CHEMISTRY OF ADVANCED MATERIALS

NANO MATERIALS

The materials like metals, ceramics, polymeric materials or composite materials with dimensions and tolerances in the range of 1 nm to 100 nm are called nanomaterials. A nanometer (nm) ion one billionth (10-9) of a meter is a unit of measurement. One meter is equal to 39 inches or 3 feet, of a meter is called centimeter (cm),   of a meter is called millimeter (mm),  of a meter is called micron or micrometer, which is a scale of most integrated circuits and microelectromechanical systems.  of a meter (one billionth of a meter) is called nanometer (nm) which is a scale of size of a single small molecules.
Nanometer is used to measure the objects which are very small in size. For eg. the size of hydrogen atom is 0.1 nm, water molecule is less than one nanometer, RBC is 5000 nm and human hair is 50,000 nm. The limit of human eye’s visibility is 10,000 nm. The diameter of a carbon nanotube is 1.3 nm.
The significance of nanomaterials is due to their small size. They exhibit unique properties (different from those observed in bulk materials) like melting point reactivity, reaction rates, electrical conductivity, colour, transparency etc. Nanomaterials may be biological,          inorganic or organic by their origin. A nanoparticle is defined as a small object that behaves as a whole unit in terms of its transport and properties and exhibit a number of special properties relative to bulk materials.

General Methods of Preparation 

There are basically two major types of approach for the preparation of nanomaterials.
1. Top-down approach : In this method bulk materials are converted to powder and then to nanoparticles by making use of lithographic methods. This method is used in the microelectronic industry.

Top-down Approach
2. Bottom up approach : In this method very small particles like individual                molecules or atoms are assembled to get clusters which in turn are aggregated to  get nanoparticles. This method is used to prepare a new class of nanomaterials.          Eg: Fullerenes and polymer nano composites are prepared by this method.

Bottom up Approach

Properties of Nanomaterials

Nanoparticles are specific in their behaviour because the physical behaviour of              particles change with decreasing size of the particle. The particles are always aggregated due to high energetic adhesive forces close to the surface, hence the surface of a nanoparticle is never naked.
The following are some of the important properties of  nanomaterials.
1. Properties based on size of the particles :
By varying the size of the material, properties like melting point, solubility, colour, transparency and catalytic behaviour of nanomaterials vary. Let us consider a material which is not nanomaterial exhibit ordered electronic spin on the surface and disordered electronic spin inside because the number of atoms inside is more than outside the material. When the material is reduced to smaller nanosize, the number of atoms on the surface increases when compared to number of atoms inside the material, thereby increasing the ordered electronic spins inside the nanomaterial. Nanoparticles or nanocrystals possess ordered electronic spins inside and outside the material exhibiting magnetism.
a) The magnetic properties increase with decrease in size of the materials due to              increased orderly electronic spins.
b) Melting point of the nanomaterials increases, when compared with other material depending on the size of the particles.
c) Solubility of nanomaterials is more than other materials due to the decreased size.
d) Colour : The physical property colour is again size dependant. As the size of the particle decreases the colour of the material changes. For eg. bulk gold looks                 yellow but 12 nm nanosized gold particle looks red, due to the decreased size of the particle and inturn different scattering of light.
e) Transparency : Transparency of nanomaterials is more than the other materials due to decreased size of the particles and increased transmission of light.
f) Catalytic behaviour : Due to increased surface area, the catalytic activity of the nanomaterials is more than other materials.
2. Properties based on composition of nanomaterials :
The composition effects of the nanomaterials influence both physical and chemical properties of nanomaterials as given below.
a) Colloidal properties : The colloidal nanoparticles are called coercing colloids. The colloidal properties of coercing colloids is more than the colloidal solutions like optical properties, electrical, magnetic and gel properties.
b) Chemical reactivity : Nanomaterials possess high chemical reactivity than other materials.
c) Reaction rates : High reaction rates were observed with nanomaterials when compared with other materials.
3. Properties due to surface of nanomaterials :
The surface of nanomaterials is always agglomerated with particles due to high energetic adhesive forces due to the properties like dispersibility, conductivity, optical properties and catalytic behaviour.
a) Dispersibility : The nanomaterials exhibit good dispersibility.
b) Conductivity : The energy gap between the valence band and conducting band in a semiconductor is proportional to the inverse of the square of the size due to quantum confinement where the spatial domain of the electronic wave function is about the size of the nanoparticle. Hence discrete energy states exist instead of continuous energy bands as that of bulk semiconductors resulting in the absorption of wavelengths characteristic of the composition and size of the nanoparticle. The nanomaterials can be used as good conducting, semiconducting and insulating             depending on the structure of nanomaterial.
c) Catalytic behaviour : The nanomaterials possess very good catalytic activity due to increased surface area of contact than other materials. In crystalline particles, the place where two faces of a crystal are in contact is called edge and the place where two or more faces come together is called a point. These edges and points are the seat of pronounced catalytic activity. Because the crystalline nanoparticles contain enormous number of edges and points, their catalytic activity is maximum.

 Engineering Applications of Nanomaterials

 Nanomaterials are an emerging field of material science technology, where vast engineering applications of these nanomaterials in a wide range of  fields. Some of these engineering applications are listed below.
1. Electronics :  A variety of applications of nanomaterials in the field of electronics are there. Some of them are mentioned below.
a) Commercial digital switching devices, integrated in 1012 devices on a single chip are fabricated.
b) High sensitivity and high selectivity environmental sensors to sense gaseous chemicals like CO, NO, NO2 and O3 in high traffic environments are fabricated.
c) The nanomaterials find good application in making light emitted electroluminescence devices, which find application in flat panel display technologies like T.V., Computer monitor, Colour changing fabrics etc.
2. Magnetic applications : Newly synthesised magnetic nanoparticles from iron and palladium, have been found to self-arrange automatically and these materials are extensively used in the manufacture of magnetic storage devices producing tetrabyte storage capabilities.
3. Biomedical applications : The following are the applications of nanomaterials in biomedical field.
a) Drug delivery of biomedical drugs which are bounded to magnetic nanocrystals to the region of body where the drug is required is carried out. For example, rare tumour causing cells can be targeted by nanocrystals, then captured and removed from blood stream.
b) Medical diagnostics is a field which extensively use nanocrystals silica coated iron oxide nanocrystals with embedded magnetic colloidal particles are sent into bloodstream where the antibody reacts and binds with the target hormone and move rapidly which can be separated and detected from blood sample. DNA detection through colorimetric technique by using oligonucleotide functionalised gold nanocrystals is developed.
c) Structural and mechanical material applications are as follows :
    i) Coating nanocrystals of metals with ceramics is carried nanostructuring by getting the benefits of ceramics (corrosion resistant, hard and wear resistant) and metals (ambient ductility). These coatings are superior coatings.
      ii) Fabrication of ceramic components is easier through nanostructuring. By nanoscale distribution of tungsten in the matrix containing tungsten               carbide improves the life and performance of cutting tool materials.
d) Industrial catalysts should contain high surface area and capacity to make any material attach to their surface. Cerium oxide, platinum, gold, molybdenum, nickel nanoparticles are extensively used as catalysts.
e) Because of high tensile strength, light weight and flexible nature some nanomaterials like CNT (Carbon Nano Tubes) are extensively used in aircraft industry.
f) Nanomaterials like fullerenes are used extensively in making consumer goods like sports goods, cleaning products and fabrics etc.
g) Agriculture is another field where nanomaterials find their use in delivery of genes and drugs to animals for health and genetic improvement and in delivery the biodegradable chemical for plant nourishment is adopted.
Applications of Nanomaterials can be summed up as follows :

Applications of Nanomaterials

Fullerenes 

A fullerene is any molecule composed entirely of carbon in the form of a hollow sphere, ellipsoid or tube. Spherical fullerenes are also called buckyballs as they resemble the balls used in football (soccer). Fullerenes are similar in structure to graphite which is composed of stacked graphene sheets of linked hexagonal rings, may also contain pentagonal or heptagonal.
The first fullerene molecule was prepared in 1985 by Richard Smalley etal at Rice University, USA. They were awarded Noble prize in 1996 for their work. The name fullerene was given as a homage to Buckminster Fuller, whose geodesic domes the molecule               resembles.
Types of fullerene :
Due to structural variations fullerenes exist in the following different types.
a. Buckyball clusters : The smallest is C20 (unsaturated version of dodecahedrane) and most common is C60.
b. Carbon nanotubes : Hollow tubes of very small dimensions having single or multiple walls. Potential applications in electronic industry.
c. Megatubes : Larger in diameter than nanotubes and prepared with walls of different thickness. Potentially used for the transport of a variety of molecules of different sizes.
d. Polymers : Chain, two dimensional and three dimensional polymers are formed under high-pressure, high temperature conditions.
e. Nano ‘onions’ : Spherical particles based on multiple layers surrounding a buckball core. Proposed for lubricants.
f. Linked ball and chain dimers : Two buckballs linked by a carbon chain. The           different individual fullerenes based on composition is listed below.
i. Buckminster Fullerene is the smallest fullerene molecule containing pentagonal and hexagonal rings (Fig. 6.1) in which two pentagons share an edge. It is naturally occurring fullerene found in soot. The structure of C60 is called truncated icosahedron which resembles football containing twenty hexagons and twelve pentagons with a carbon atom at the vertices of each polygon. The vander Waals diameter of C60 is 1.1 nm and its average bond length is 1.4Å. Silicon bucky balls have been created around metal ions.
                                       
                 (a) Fullerene/buckyball (b) C20  fullerene (dodecahedral graph)
ii. Boron buckyballs : A type of buckyball which uses boron atoms instead of a carbon atom is discovered in 2007. The B80 structure with each atom forming 5 or 6 bonds is more stable than C60 buckyballs.
The smallest fullerene is dodecahedral (C20).
Metallofullerenes are a class of novel nanoparticles, comprises 80 carbon atom (C80) forming a sphere which encloses a complex of three metal atoms and one nitrogen atom, and they find potential use in diagnostics, therapeutics and organic solar cells.
Preparation of fullerenes :
A common method used to produce fullerenes is to send a large current between two nearby graphite electrodes in an innert atmosphere. The resulting carbon plasma arc between the electrodes cools into sooty residue from which many fullerenes can be isolated. The fullerenes are extracted from soot using multi step procedure.
Properties : Fullerenes are stable with sp2 hybridized carbon atoms. The reactivity of fullerenes is increased by attaching active groups in their surfaces. The characteristic reaction of fullerenes is electrophilic addition at 6-6 double bonds which reduce the angle strain by changing sp2 hybridised carbon to sp3 hybridised carbon. When other atoms tapped inside fullerenes to form inclusion compounds is known as endohedral fullerenes                                            
Eg : Tb3NeC84 (egg shaped fullerene).
When a metal is used as an inclusion compound it is called metallo fullerene. For                  eg: steel.
Solubility : Fullerenes are sparingly soluble in many solvents. Common solvents for fullerenes are toluene, CS2.
Quantum mechanics : Wave-particle duality is exhibited by fullerenes as a result           several sculptures symbolizing wave-particle duality are created.
Chirality : Some fullerenes are inherently chiral because they are D2–symmetric and have been successfully resolved.
Hydrogenation : C60 exhibits a small degree of aromatic character, undergoes addition with hydrogen to polyhydro fullerenes.
Halogenation : Addition of F, Cl and Br occur for C60 under various conditions,           produce a vast number of halogenated derivatives. For ex. C60 Br8 and C60 Br24.
Addition of oxygen : C60 can be oxygenated to epoxide C60O and ozonisation of C60  in orthoxylene at 257K gives ozonide C60O3 which can be decomposed into 2 forms of C60O and the same decomposition at 296 K gives epoxide.
Free radical reaction : When C60 is mixed with a disulphide, the radical C60SR is  formed spontaneously, whose stability depends on steric factors.
Metal complexes were produced with C60 fullerenes by using metals Mo, W, Pa, IG and Ti.
C60+M(CO)6M(n25C60)6+ CO (M = Mo, W)
Applications
1. As a fuel : Buckyballs are efficient medium to make hydrogen fuel.
2. Medicine : Buckminster fullerene inhibit the HIV virus. C60 inhibits a key enzyme in the human immunodeficiency virus known as HIV-1 protease which could inhibit the reproduction of HIV virus in immune cells. When impregnated with He, C60 buckyballs can be used as chemical tracers in human body.
3. Solar cells : The optical absorption properties of C60 match solar spectrum, hence finds its application in solar cells.

 Carbon Nanotubes (CNT) 

Carbon nanotubes are sheets of graphite about 0.4 nm in diameter rolled up to make a tube of few nm in diameter. Carbon nanotubes are otherwise called buckytubes.

Preparation of CNT : CNT was observed in 1991 in the carbon soot of graphite electrodes during arc discharge. First production CNT was 1992 by arc discharge at Funda-mental Research Laboratory, USA. Carbon nanotubes are prepared by the following methods :
1. Arc discharge : By arc discharge of graphite electrodes in presence of ionised gas to reach high temperatures and by using a current of 100 amps CNT was produced. During this process, the carbon contained in the negative electrode sublimates because of high-discharge temperature. This method has been widely used method of CNT synthesis. The yield is 30% and produces both single and multi-walled nanotube with lengths of upto 50 micrometers with few structural defects.
2. Laser ablation : This method was developed by Dr. Richard Smalley at Rice          University, USA. In this process a pulsed laser vaporises a graphite target, in a high temperature reactor. While an innert gas is bled into the chamber, Nanotube develops on the cooler surface of the reactor as the vaporised carbon condenses. A water cooled surface is used in the process to collect nanotubes. To improve the yield a composite of graphite, metal catalyst particles (Co and Ni mixture) was used to synthesise single walled CNT. The yield of this process is 70%. The reaction temperature determines the diameter of the single walled CNT. However this method is more expensive than arch discharge or chemical vapour deposition.
3. Plasma torch method : Single walled CNT was prepared by this method in 2005 at National Research Council of Canada. The method is similar to arc discharge in that both make use of ionised gas to reach high temperature necessary to vaporise carbon and the nanotube growth takes place. A metal catalyst is used. In thermal plasma torch method high frequency oscillating currents in a coil in flowing innert gas was fed with a feedstock of carbon black and catalyst particles and then cooled down to get single walled nanotubes. This method produces 2gms of CNT per minute.
4. Chemical vapor deposition (CVD) : This method was developed in 2007 at university of Cincinnati, USA. During chemical vapour deposition process a substrate was prepared with a layer of metal catalyst nanoparticles (Ni or Co). The substrate is heated to 700 oC and a mixture of nitrogen and carbon containing acetylene or ethylene or ethanol or methane was passed. The CNT grows at the surface of the catalyst particle where the carbon containing gas is broken and carbon is transported to the edges of the particle where it forms CNT. Fluidised bed red reactor is most widely used for CNT production. CVD method is most promisable for industrial production CNT because of its low cost and direct growth on the catalyst surface.
Properties of CNT :
The following are the properties of CNT :
1. Strength : CNTs are the strongest and stiffest materials in terms of tensile strength, which is due to covalent sp2 bonds between the individual carbon atoms. CNT possess strength upto 100 gigapascals (GPa).
2. Hardness : Standard single walled CNT withstands a pressure upto 25GPa without deformation.
3. Kinetic properties : Multiwalled CNT are multiple concentric nanotubes nested within one another which exhibit a striking telescoping property whereby the inner nanotube may slide without friction within its outer nanotube; this property is utilised to create a smallest rational motor and gigahertz mechanical oscillator.
4. Electrical properties : Because of symmetry and unique electronic structure of graphene, CNT is semiconducting with a very small band gap between valence band and conducting band. Because the electrons propagate only along the tube  axis and involves quantum effects, CNT is referred as one-dimensional conductor. The electrical conductance of a single walled CNT is 2G0, where G0 = 2e2/h.
5. Optical properties : The optical properties of CNT is due to the absorption of Photoluminiscene and Raman spectroscopy which allows the quick and reliable characterisation of this nanotube quality in terms of non-tubular carbon content.
6. Electromagnetic wave absorption : CNT possesses microwave absorption characteristic which is useful for military radars and to better the stilth characteristics of aircrafts.
7. Thermal properties : CNT are very good thermal conductor and exhibit a property called ballistic condition. Single walled CNT at room temperature has thermal             conductivity 3500 WM–1K–1 which is more than Cu metal (385 W M– K–). The temperature stability of CNT is 2800 0C in vacuum and 750 0C in air.
8. Toxicity : CNT possess toxicity. Under certain conditions CNT can cross the membrane barriers and reach organs which induces harmful effects like inflammatory, fibrotic (toxicological changes in lungs) reaction and can cause cell death.
Applications of CNT :
1. Because of the superior mechanical properties CNTs are used to make space elevators, stab-proof, bullet-proof clothing.
2. Carbon nanotubes are used for producing CNT field effect transistors provided with digital switching using a single electron, semiconducting nanotubes.
3. CNT is also used recently for making nano-tube polymers composites which are used for making electrical cables and wires because of their high conductivity.
4. Paper batteries : A paper battery is a battery engineered to use a paper-thin sheet of cellulose infused with CNT. Here CNT acts as electrodes allowing storage devices to conduct electricity which can provide steady power output comparable to a conventional battery.
5. Solar cells : One of the promising application of CNT is their use in solar panels due to their strong UV/Vis-NIR absorption characteristic. The solar cell developed at NIIT, New Jersey, USA contain a mixture of CNT and buckballs (Fullerenes).
6. Hydrogen storage : CNT can store hydrogen to be used as a fuel source.
7. Medical : Single walled CNT is inserted around cancerous cells and excited with radiowaves which causes them to heat up and kill the surrounding cells and CNT is a suitable scaffold materials for bone cell proliferation and bone formation.
8. Textile : CNT is used for coating and absorption on the surface fibre for manufacturing fabric which is antibacterial, electric conductive, flame retardant and with electromagnetic absorbance properties.
9. Optical power detectors : A spray-on mixture of CNT and ceramic coating gives uprecedented ability to resist damage while absorbing laser light.
6.2 Liquid Crystals (lcs)
Liquid crystals (LCs) are matter in a state that has properties between those of conventional liquid and those of solid crystals. For example, a LC may flow like a liquid, but its molecules may be oriented in a crystal like way (Fig. 6.3). There are many different types of LC phases which can be distinguished by their optical properties. Liquid crystals can be found naturally and in technological applications. Many proteins, cell membranes and              tobacco virus are the natural LCs. Most contemporary electronic displays, solutions of soap and various related detergents are synthetic LCs.
LC behaviour was first observed by Friendrich Reinitzer at Charles university, prague in derivatives of cholesterol which now belong to cholesteric liquid crystals. The name            ‘liquid crystal’ was coined by Otto Lehman in 1904. Later liquid crystals became a topic of research into the development of flat panel electronic displays to replace the cathode ray vacuum tube in televisions from 1962 onwards.

Fig. 6.3 Positional and orientational order in solids, liquid crystal and liquids

 Types of Liquid Crystals

LCs can be divided into three types :
1. Thermotropic LCs exhibit a phase transition into LC phase as the temperature is changed.
2. Lyotropic LCs exhibit a phase transition into LC phase when both temperature and concentration of LC molecules in solvent changes.
3. Metallotropic LCs are constituted by both organic and inorganic molecules. They exhibit phase transition into LC phase when temperature, concentration, and           organic-inorganic composition ratio changes.
6.2.2 Thermotropic Liquid Crystals
Thermotropic phases are those that occur in a certain temperature range. If temperature is too high thermal motion may destroy the ordering of LC phase; pushing the material into a conventional isotropic liquid phase. The following are some of the phases as the temperature is changed. The liquid crystalline phase of thermotropic crystals can be observed by carefully lowering or raising the temperature of liquids and solids respectively. Thermotropic liquid crystals are formed from organic molecules with rod-like shape, rigid and planar ring structures.
Examples of thermotropic liquid crystalline substances are cholesteryl benzoate, exhibit liquid crystalline state at 145.5–178.5 0C, P-azoxyanisole at 116–135 0C, and P-azoxy phenetole at 137–167 0C.
There are three distinct phases in which thermotropic crystals exist.
a) Nematic phase
b) Cholesteric phase
c) Smectic phase
a) Nematic liquid phases : Nematic in Greek means thread like. Nematic liquid crystals are less ordered, they point in the same direction, characterised by the total loss of positional order and a near normal flow behaviour similar to its liquid phase with simple structure as shown below (Fig. 6.4(a)) ywhere                         x = azo (–N=N–], azoxy (–N=], ester  and Schiffs bases (-CH=N–).                        y and y” are smaller groups.
                       
                (a) Nematic                             (b) Helical structure
b) Cholesteric liquid crystals : The name of these liquid crystals originated from the fact that many derivatives of cholesterol form this structure and the molecules are chiral. The structure of these crystals are similar to nematic liquid crystals, but each plane of the molecules is twisted slightly in relation to plane above and below. The molecules are aligned parallel to a preferred direction as in nematic phase. When proceeding in a direction normal to the plane, the preferred direction rotates continuously, the result is helical structure (Fig. 6.4(b))
c) Smectic liquid crystals : In Greek smectic means soap. The substances that form smectic phase are soap like. In smectic LCs there is a small amount of orientational as well as positional order. The molecules form planes perpendicular to the axes of the molecules and they tend to point along the director. There are three types of smectic phases based on the orientation of the director.

Smectic A : The long axes of the molecules are parallel to a preferred direction which may be normal to the planes. Fig. 6.5(b).
Ex : Diethyl 4, 4’ – azoxydibenzoate.
Smectic B : The director is perpendicular to the smectic plane with the molecules arranging themselves into a network of hexagones within the layer Fig. 6.5(c)
Ex : N, N’ – Terepthalylidene-bis-(4-n butylaniline) (TBBA)
Smectic C : The long axes of the molecules are disordered and parallel to a preferred direction which may be tilted by a certain angle. Fig. 6.5 (d).
Ex :  4, 4’–di–n–dodecyloxy-azoxybenzene.

Lyotropic Liquid Crystals 

Some compounds are transformed to a liquid crystal phase, when mixed with other substance (solvent) or when the concentration of one component is increased. Such compounds which exhibit liquid crystallinity on mixing with a solvent or changing its concentration are called lyotropic liquid crystals. Lyotropic liquid crystals are amphiphilic in nature as they contain both lyophilic (solvent attracting) and lyophobic (solvent repelling) parts in the same molecule (Fig. 6.6(a)). When treated with a solvent the lyophobic ends come closer whereas the lyophilic ends are directed away forming micelle. The micelle are formed only at a particular concentration critical micelle concentrate (CMC). Beyond CMC, when the solution is heated to a particular temperature, the size of micelle increases, collapses and separates out as a liquid crystal. Thus the solvent-solute interactions play a vital role in such systems. Lyotropic liquid crystals are two types broadly 1. Lamellar phases and 2. Hexogonal phases.
1. Lamellar lyotropic liquid crystals : These are characterised by layers of well defined thickness but no order within the layers (Fig. 6.6(b)) and water is sandwiched between. Lamellar phase is called neat phase or G-phase.
2. Hexagonal lyotropic liquid crystals possess hexagonal arrays like upforming             cylinders with the water molecule by the formation of polar heads as outer shell                    (Fig. 6.6(c)). Sometimes inverted hexagonal phases are formed with tails point away from the centres of the hexagons.

General & Engineering Applications of LCs

1. Liquid Crystal Display : Liquid crystals find wide use in liquid crystal displays which rely on optical properties of certain liquid crystall substances in the presence and absence of electric field. In a typical device, a liquid crystal layer (typically 10 mm thick) sits between two polarizers that are crossed (oriented at 900 to one another). (Fig. 6.7) The liquid crystal alignment is chosen so that its relaxed phase is twisted one. This twisted phase reorients light that has passed through the first polarizer, allowing its transmission through the second polariser (and reflected back to the observer if a reflector is provided). The device thus appears transparent when electric field is applied to the LC layer. In this state the LC molecules do not reorient light, so that light polarised at first polariser is absorbed at the second polariser and the device loses transparency with increasing voltage. In this way the electric field can be used to make a pixel switch between transparent or opaque on command color LCD systems also use the same technique with color filters used to generate red, green and blue pixels. Similar principles can be used to other LC based optical devices.

LC tunable filters are used as electro optical devices and in hyperspectral imaging.
2. Thermotropic chiral LC vary their pitch with change in temperature as a result the colour of the material changes as the temperature changes. They are used as thermometer for aquarium, swimming pools and infant baths and also to look for hot spots for failure analysis in semiconducting industry.
3. Liquid crystal lasers are used in casing medium for stable monochromatic emission.
4. When the temperature of cholesteric liquid crystal is changed over a particular range, these LCs exhibit colour change from red to violet. This important property is utilised in thermography (for measuring surface temperature), to indicate temperature variation by using colour differences, for following thermal diffusion, thermal mapping (like integrated circuits) and aerodynamic testing.
5. Medical applications of liquid crystals are for studying circulatory system, detection of tumours, skin and breast cancers.
6. Liquid crystals are also used in finding the efficiency of heat engines and testing of radiations.

Fibre Reinforced Plastics

Fibre reinforced plastics are produced by reinforcing a plastic matrix with a high strength fibre materials such as glass, graphite, alumina, carbon, boron, beryllium and aromatic polyamide. Natural fibres such as sisal, asbestos are also used for reinforcement. Depending on the desired properties of the final reinforced composite, the nature of the fibre used is decided. Glass fibre is the most extensively used reinforced fibre because of durability, acid proof, water proof, and fire proof nature of glass.
Glass is drawn into threads or fibres in the form of filaments fine than cotton or silk thread. Then the filaments are woven in the form of mats. The fibre material is suitably bonded with plastic materials to be reinforced. The common plastic resins used are polyesters, epoxy, silicone, malamine, vinyl derivatives and polyamides. The following are the various processing techniques adopted.
1) Matched metal die molding : This is the most efficient and economical method for mass production of high strength parts. It is press moulding under a temperature of 235 - 260 0F and 200 - 300 psi pressure. The upper mould containing the resin and reinforcing fibres is pressed on to the lower mould.
2) Injection moulding : This method is for reinforced thermoplastics. A mix of short fibres and resin are forced by a screw or plunger through a nozzle into the heated mould and allowed to curve.
3) Hand - lay - up : Mostly used for thermoset plastic resins the reinforcing mat fibre is cut to fit in a mould and saturated with resin by hand using a brush, roller or spray gun. Layer built up gives the thickness of the article.
4) Continuous lamination : Reinforcing mats or fabrics are impregnated with resin, run through laminating rolls between cellophane sheets to control the thickness and resin continent. They are then cured in heating chamber.
5) Centrifugal casting : Chopped fibres and resin are placed inside a mandrel and uniformly distributed as mandrel is rotated inside an oven.
6) Spray up : Short length of reinforcement and resin are projected by a specially designed spray gun so that they are deposited simultaneously on the surface of the mould. Curing is done with a catalyst at room temperature.
6.3.1 Properties of Fibre Reinforced Plastics
The properties of fibre reinforced plastics (FRP) is governed by
a) Properties of constituent materials like fibre material and plastic matrix
b) Relative concentrations of the constituent materials
c) The distribution and orientation, shape, size, distribution etc. of constituent materials.
d) Strength of the interfacial bond between the fibre and the matrix phases.
1. The frp are very strong, tough materials. Their strength depends on the critical fibre length (lC) which is given by

where = Ultimate fibre strength
d  = diameter of the fibre
 TC = fibre matrix strength
The efficiency of continuous fibres is more than discontinuous fibres.
2. The frp materials possess lower densities, high impact strength and excellent chemical and corrosion resistance.
3. Possess good lustre, abrasion resistance, inflammability and dielectric constant. The limitations of frp are
a. Limited service temperature because of polymeric matrices.
b. frp materials possess less rigidity and stiffness when used for structural components.
6.3.2 Applications of FRP
The fibre reinforced plastics find extensive use in the following ways :
a) In automobiles : For making door handles, battery cases, engine cooling fans etc.
b) In defence : For making nose cones, pistol grips and rifle bullets.
c) In textile  industry : For making shuttle (Nylon 6 as polymer matrix).
d) In electronic/electrical industry : For making exhaust fans, computer tapes,                         insulators, wires (malamine in frp), switch gear parts, spools.
e) In consumer goods : For making door and window hinges, chair shells, camera housing etc.
f) Other uses of frp are for making seat coverings, tubings, chemical pump housings etc.

 Advantages of FRP

The fibre reinforced plastics have the following advantages.
1. Low efficiency of thermal expansion.
2. High dimensional stability.
3. Low cost of production.
4. Good tensile strength.
5. Low dielectric constant.
6. Non inflammability and corrosion and chemical resistance.
6.3.4 Fibre Glass (Glass Fibre Reinforced Composite)
Fibre glass is produced by drawing glass in the form of fine threads/filaments more fine than cotton or silk and then woven in the form of mats. The fabric material is suitably bonded with polyester/nylon polymeric material/matrix to be reinforced.
Properties :
Fibre glass properties possesses lower densities, high tensile strength, high impact resistance and excellent chemical and corrosion resistance. The fibre glass materials possess less service temperature, stiffness and rigidity.
Applications :
1. Automotive parts and storage tanks are made from fibre glass.
2. It is used for making industrial floorings, plastic pipes.
3. It is used for making transport vehicles to reduce vehicle weight and boost fuel efficiency.
6.4  Biodegradable polymers
Biodegradability is defined as the ability of being chemical transformation by enzymatic action of bacteria which are capable of further degradation.
Polymers are popular materials as they are not attacked by environmental conditions including biological attack. To some extent polymers are degraded slowly by oxidation, u.v. radiation etc., but not by bacteria. This property creates difficulty in disposing the polymer wastes. Biodegradation of polymers not only aimed at eliminating landfills but also compostable bags for the collection of leaf and yard waste. Those polymers which degrade by the enzymatic action of naturally occurring microorganisms and bacteria are called biodegradable polymers. Biodegradable polymers were used in the times of Romans where they used catgut for sutures which slowly degrades as the wound heals.
The basic requirements of the biodegradable polymers should be (a) Production of non-toxic products (b) Capable of maintaining good mechanical integrity until degradation and (c) Controlled rates of degradation.
The factors controlling the rate of degradation include (a) Percentage of crystallinity of polymer, (b) Molecular weight of polymer, (c) Hydrophobicity of polymer and (d) The environment surrounding the polymer.
The biodegradable polymers are classified as naturally occurring and synthesised polymers.
(a) Naturally occurring biodegradable polymers
There is a belief that anything that comes from nature goes back to nature. Hence it is assumed that these natural polymers are "beautiful for environmental degradation". The rate of degradation and the formation of metabolites depend very much on the structural complexity of material and the environmental conditions selected for degradation. There are four groups of naturally occurring biodegradable polymers.
1. Polysaccharides - Eg : Starch and Cellulose
2. Proteins - Eg : Gelatin, Casein, Silk, Wool
3. Polyesters - Eg : Polyhydroxy alkanoates
4. Others - Eg : Lignin, Shellac, Natural rubber etc.
In many quarters these polymers were not known as biodegradable polymers and ignored.
(b) Synthetic biodegradable polymers
These polymers are produced from chemicals or biological sources that are biodegradable. The following are some types of synthetic biodegradable polymers.
1. Polyhydroxy Alkanoates (PHA) BIPOL :
These are linear polyesters produced by bacterial fermentation of sugars or lipids and sold under the trade name biopol. These are produced by the bacteria to store carbon and energy. More than 150 monomers can be polymerised to give materials with extremely different properties. These biopols are used in the production of bioplastics. The following are some biopols produced.










Biosynthesis : To produce PHA, a culture of microorganisms such as alkaligenes entrophys is placed in a suitable medium along with appropriate nutrients. Once the population of bacteria reached a substantial level, the nutrient composition is changed to synthesise PHA. The yield of PHA obtained from intracellular inclusions can be as high as 80% of the organism's dry weight. The PHA is deposited in the form of highly refractive granules in the cells which were disrupted to recover PHA granules. Industrially PHA is produced by microbial fermentation of sugar or glucose. PHA is processed mainly by injection moulding and extrusion moulding into films and hollow bodies.
Properties :
i) PHA polymers are thermoplastic.
ii) Stable to u.v. radiation.
iii) The crystallinity lie in the range of 70%.
iv) Good resistance to moisture, aroma barrier properties are possessed by the PHA.
v) PHBV possesses good elasticity.
Applications of PHA :
The potential application of PHA is in the medical and pharmaceutical industries, like fixation and orthopedic application including sutures, suture fasteners, miniscus repair devices, rivets, tacks, staples, bone plating systems, surgical meshs etc. Skin substitutes, bone graft substitutes, bone dowels, dressing and lemostats are produced from PHA.
Polylactic acid / polylactide (PLA) : This is a biodegradable thermoplastic polyester  belonging to the class of polyhydroxy alkanoates, derived from renewable sources such as starch, topioca or sugarcane possess the following structure.

Polylactic acid / polylactide (PLA)
Properties :
i) The glass transition temperature of PLA is 60 - 65°C
ii) PLA possess melting point 173 - 178°C
iii) PLA is a Chiral compound existing as poly l - lactic acid (PLLA).
iv) PLA possess good biocompatibility, processability as well as high strength and modulus can be processed as thermoplastic fibre.
Applications of PLA :
i) Medical implants like anchors, screws, pins, mesh etc.
ii) For making compostable packing materials, disposable garments, diapers, food packaging, 3D printers etc.
2. Mater Bi :
An innovative bioplastic is a starch based resin containing 60% starch and 40% modified biodegradable complexing agent. It is produced in granular form and can be processed by most common techniques. Its properties are similar and sometimes better than traditional plastics. As the polymer is starch based such as corn starch which has come from nature, it can be easily degraded by bacteria. It is commercially produced in granular form and processed.
Properties : Mater bi is a strong, tough bioplastic, resistant to abrasion and possess viscible solubility. This is permeable to water, easy to print and quick to seal.
Applications : Mater bi possesses diversified applications as given below.
a) Agriculture : Mulching films are produced from Mater bi which minimise environmental impact with efficient control of weeds and reduction of greenhouse effect by reducing the amount of CO2 evolution.
b) Waste management : Compostable plastics are made from mater bi.
c) Catering : Disposable tableware like cutlery, plates, cups, boxes for transporting food etc. are made from Mater bi.
d) Large scale retail productions : Mater bi is used in nappies ensuring comfort to babies, sanitary towels, panty liners etc.
e) Industrial applications : Mater bi is used in the foamed packing materials, compostable films for packing finished agricultural products, shopping bags. Now a days Mater-Bi is used for making cotton buds,  rigid or semi-rigid drinking straws, flexible agricultural tubes.
Mater Bi is used for making a range of objectives such as pens, rubbers, pencil sharpeners, gadgets, toys, plant pots and objects for pets to play.
Mater Bi is used as an additive in the manufacture of tyres.
3. Polyvinyl acetate (PVA) :
Polyvinyl acetate is a water soluble and biodegradable polymer; possessing excellent mechanical properties and compatibility with starch. The structure of PVA is




PVA is another class of innovative biodegradable polymer produced from starch which is totally biodegradable in a wide variety of environment as it can be hydrolysed to glucose by microorganisms or enzymes and then metabolised to CO2 and H2O. Biodegradable PVA is produced from acetic acid and acetaldehyde produced from molasses by fermentation.
Properties :
1. It belongs to the class of vinyl polymers.
2. It is water soluble.
3. Possesses excellent mechanical properties.
4. It is compatible with starch. i.e. starch mole can be introduced into the backbone for quick biodegradability.
Application :
1. Polyvinyl acetate is used in food industry as a packing materials, food storage and catering, mailing compost bags.
2. Polyvinyl acetate is used as adhesive for wood, paper & cloth for book binding, envelopes, wall paper etc.
6.5 Conducting polymers
Those polymers which conduct electricity are called conducting polymers. The conduction of the polymers may be due to unsaturation or due to the presence of externally added ingredients in them. The conducting polymers can be classified in the following way.

Intrinsic conducting polymers :
These polymers are characterised by intensive conjugation of double bonds in their structure i.e. the backbone of the polymer. Again intrinsic conducting polymers are two types as given below.
1) Conducting polymers having conjugation :  Such polymers having conjugated double bonds in the backbone possess their conductivity due toelectrons. Inbonding the overlapping of the orbitals is lateral over the entire backbone resulting in the formation of lower energy valence bands and higher energy conducting bands which were separated by a significant fermi energy gap. The electrical conductivity takes place only after thermal or photolytic activation of the electrons, which give them sufficient energy to jump the gap and reach into conduction band.
Examples :



All the above polymers possess conductivities around 10–10 Scm–1 which is sufficient for their use in any engineering applications.
2) Doped conducting polymers : The conducting polymers having  electrons in their backbone can easily be oxidised or reduced because they possess low ionisation potential and high electron affinities. Hence their conductance can be increased by introducing a positive charge or negative charge on polymer backbone by oxidation or reduction. This process is similar to semiconductor technology and is called doping. Doping is again two types.
1. Creating a positive site on polymer backbone called p-doping
2. Creating a negative site on the polymer backbone called n-doping.
p - doping : p - doping is done by oxidation of a conducting polymer like polyacetylene with a Lewice acid or iodine vapour. This is also called oxidative doping.


During oxidation process the removal of  electron from polymer backbone lead to the formation of a delocalised radical ion called polaron having a hole in between valence band and conducting band as shown below.

                                                                              polaron is a delocalised radical ion
The second oxidation of the polaron results in two positive charge carriers in each chain called bipolaron, which are mobile because of delocalisation. These delocalised charge carriers are responsible for conductance when placed in electric field.


n - Doping : n - Doping is carried out by reduction process by the addition of an electron to polymer backbone by using reducing agents like sodium naphthalide Na+(C10H8)–. Formation of polaron, bipolaron takes place in two steps, followed by recombination of radicals, which yields two charge carriers on the polyacetylene chain responsible for conduction as shown below.

The electron added to polyacetylene by reductive doping does not go into the conducting band but goes into an intermediate electronic state within the bandgap of radical anion (polaron).
      +e–, Na+(C6 H8)

Bipolaron contains electrons in the energy levels residing in the band gap.
The Bianion lowers its energy by segregating into two negative solitrons at the midgap energy levels. The presence of holes in the band gap allows facile jumps of electrons from valence band into the conduction band. This leads to the generation of conduction pathways. As a consequence the conductivity increases significantly.
In general doping increases the surface conductivity of a polymer to a large extent. The following are conductivities of conducting polymers.
   S. No.  Conducting Polymer    Dopants           Conductance (s, cm–1)
1.   Trans polyacetylene         I2, Na, Br2, Li, ASF5 10,000
2.   Polyaniline                  HCl  1,000
3.   Poly pyrrole             BF4+ ClO4+         500 - 7500
Polyanilines exist in several oxidation states as far as electrical conductivities are concerned varying from 10–11 S/cm, to > 105 S/cm, only one form called emeraldine salt is electrically conducting. The flexible dark blue films of conducting polyaniline is made by protonic doping i.e. protonation of imine nitrogen atoms in the backbone. Doping is a reversible process, deprotination can also be done by treatment with alkali Emeraldine salt also known as synthetic metal because it possess metallic conductivity, metallic lusture and metallic sound.

They have got poor mechanical strength, less strength and storage ability.
Extrinsically Conducting Polymers :
The conductivity of these polymers is due to the presence of externally added ingredients in them. Again the extrinsically conducting polymers are two types.
1) Conducting element filled polymers :
The polymer acting as a binder to hold the conducting element such as carbon black, metallic fibres, metallic oxides etc. Minimum concentration of conducting filler is added so that the polymer starts conducting. This minimum concentration of conductive filler is called percolation threshold. At this concentration of filler, a conducting path is formed in polymeric material. The most preferred filler is the special conducting grade C - black has very high surface area, more porosity and more of filamentous properties.
Advantages of conducting element filled polymers :
1. These polymers are low cost polymers.
2. They are light in weight and mechanically durable.
3. These polymers are strong with good bulk conductivity.
4. They are fabricated very easily to any design.
Applications of conducting element filled polymers : These are used in hospitals and operation theatres. The disadvantage of the conducting element filled polymers is that addition of 10% carbon black will drastically decrease the tensile strength, elongation strength and impact strength of the polymer.
2) Blended conducting polymers :
The conventional polymer is blended with a conducting polymer to improve physical, chemical, electrical and mechanical properties along with the processing properties.
Examples : 40% of polypyrrole in a conventional polymer give higher impact strength. These blended polymers are used in electromagnetic shielding.
Applications of  conducting polymers :
1. The conducting polymers are used in rechargeable batteries, small in size (button size), producing current density upto 50 mA/cm2.
2. Conducting polymers are also used for making analytical sensors for pH, O2, NOx, SO2, NH3 and glucose.
3. The conducting polymers are used for making ion exchangers. These membranes made of conducting polymers show selective permeability for ions and gases hence they are used for control release of drug.
4. The conducting polymers are used in making electronic displays and optical fibres.
5. They are used for electron beam lithography.
6. The conducting polymers are applicable in photovoltaic devices.
Factors influencing the conductivity of organic polymers :
The conductivity of organic polymers is influenced by various factors, listed below.
1) Conjugation length of the polymer chain : The conductivity of a polymer increases with increase in chain length or conjugation.
2) Doping level : The conductivity increases with increase in doping level, but after some time, it becomes saturated.
3) Temperature : The conductivity of conducting polymers increase with increase in temperature. At some high temperature, conductivity becomes constant.
4) Frequency of current : The conductivity of these materials also depend on the frequency of current, because doping is the transport mechanism of these materials.
Advantages of intrinsic conducting polymers :
The following are the advantages of the intrinsic conducting polymers.
1. These polymers possess good conductivity.
2. They can store a charge.
3. Ion - exchange is possible with these polymers.
4. They absorb visible light to give coloured products.
5. They are transparent to x-rays.
6. They can be easily processed with product stability and efficient recycling.
Disadvantages of intrinsic conducting polymers :
Their conductivities are inferior to metal conductivities.
For example : The conductivity of polyacetylene is 400,000 S cm–1 whereas the conductivity of Cu is 600,000 S cm–1.
6.6 Solar cells or photovoltaic cells
Solar energy is a renewable ecofriendly energy. As the conventional sources of other electrical devices are going to extinct, much attention is paid to solar energy. A solar cell is an electrical device that converts the energy of light directly into electricity by photovoltaic effect. Solar cell is a form of photoelectric cell, which when exposed to light, can generate and support an electric current without being attached to any external voltage source.
6.6.1 Photovoltaic Cells
The term photovoltaic comes from greek word ‘phos’ meaning light and volt is the unit of emf which was named after inventer of the battery, an Italian physicist Alessandro Volta. This term photo-voltaic is in use since 1849.
Photovoltaic is a field related to practical application of photovoltaic cells, producing electricity from light and it is often used specifically to refer to the generation of electricity from sun light, lamp light  or artificial light. When the source of light is not sunlight it is used as a photodetector (Ex: Infrared detectors) and also to detect electromagnetic radiation near the visible range and measuring light intensity.
6.6.1.1 Working of Solar Cells
A solar photovoltaic cell works on the following steps :
1. Photon in sunlight hits the panel and absorbed by semiconducting material such as silicon.
2. The electrons present in the material are delocalised allowing to flow through the material to produce electricity. Due to the special composition of solar cells the electrons are allowed to move in a single direction.
3. An array of solar cells converts solar energy into the direct current which can be used.
When the photon hits the semiconducting material, a) photon can pass through the semiconducting material b) photon can be reflected c) photon can be absorbed by the material. When a photon is absorbed its energy is given to an electron in the crystal lattice in the valence band and the electron gets excited and jumps to conduction band. Where it is free to move around in the semiconductor as there are no covalent bonds which tightly bound with neighbouring atoms thus creating a hole. Later this hole is filled by another neighbouring electron, creating another a hole there, which results in movement of hole through the lattice. A photon should possess more energy than fermi energy of the band gap. Usually the photon coming from sun possess more energy than the fermi energy gap and the difference of energy is given out in the form of heat via lattice vibrations inturn the unusable electric energy. (Fig. 6.8)

6.8 Band diagram of silicon solar cell under short circuit conditions
Charge carrier separation is carried out mainly by two ways :
1. Drift of carriers - driven by an electric field established across the device.
2. Diffusion of carriers is due to their random thermal motion until they are captured by electric fields existing at the edge of the active region.
The most commonly known solar cell is constituted by a p-n junction made from silicon, which is a layer of n-type silicon in direct contact with p-type silicon. The p-n-junction of solar cells are made by diffusing n-type dopant into one side of the p-type wafer or vice-versa. If a piece of p-type silicon is placed in intimate contact with a piece of n-type silicon, the diffusion of electrons occurs from the region of high electron concentration to the region of low electron concentration. As the electrons diffuse across the p-n junction they recombine with holes on the p-type side. The charge build up on either side of the junction create an electric field, which creates a diode that promotes charge flow known as drift current which eventually, balance the diffusion of electrons and holes. The region where electrons and holes diffused across the junction is called depletion region and also as space charge region.
The current produced by a solar cell is equal to the current produced by the source, minus the current flows through the diode minus current flows through the shunt resistor.
I = IL – ID – ISh
Where     I   = Output current in amperes
IL = Photogenerated current in amperes
ID = Diode current in amperes
ISh = Shunt current in amperes.
The amount of photogenerated current (IL) increases slightly with increase in temperature.
6.6.1.2 Materials used for making Solar Cells
Many currently available solar cells are made from bulk materials that are cut into wafers of 180–240 mm thick. The following is the list of materials :
a) Crystalline silicon is one of the most important material also known as solar grade silicon. The monocrystalline silicon, poly crystalline silicon and ribbon silicon are the other types of silicon material used for solar cells.
b) Cadmium Telluroide (CdTe) photovoltaic devices in the form of thin films is used to absorb and convert sunlight to electricity.
c) Copper Indium Gellium Selenide (CIGS) is a direct band gap material with highest efficiency (~20%) among the film materials.
d) Gallium Arsedide multijunction (GaAs) material is developed for special application such as satellites and space exploration. Multi junction cells consist of multiple thin films.
e) Dye-sensitized solar cells are made from Ruthium melallo organic dye (Ru-centered) in the form of monolayer of light-absorbing material and mesoporous layer of nanoparticulate titanium dioxide, which greatly amplifies the surface area.
f) Quantum dot solar cells are based on Gratzel cell or dye sensitized solar cell. The quantum dot used are CdS, CdSe, Sb2S3, Pbs etc.
g) Organic polymer solar cells are made from organic semiconductors like polyphenylene vinylene, carbon fullerenes.
6.6.1.3 Applications of Solar Cells
1. The main application of solar cells is to generate large scale or  small scale electricity from sun light.
2. Solar photovoltaic cells are often electrically connected and encapsuled as a module which are connected in series to create additive voltage and to yield high        current.
3. To make use of solar generated energy, the current is fed into electricity grid using inverters in stand alone systems and batteries to store energy.
4. Solar panels can be used for making power or rechange the portable devices and heating water etc.
5. Solar panels can be used for solar street lighting, home lighting systems and          lanterns.
6. Solar cells are majorly used in electronic industry for calculators, components, solar flash light etc.
7. Solar power not only helps preserving the environment but also a good economic renewable energy source.
6.6.2 Solar Heaters
Solar heating systems comprise several innovations and renewable energy technologies and widely used in Australia, China, Greece, Austria, India, Japan and Turkey.
The solar water heater consists of a storage tank horizontally mounted above the solar collectors on the roof. No pumping is required as the hot water naturally rises into tank through thermosiphon flow. A circulating pump moves water or heat transfer fluid between the tank and collectors. In winter sometimes the solar heaters are not efficient due to  insufficient sunlight. The solar heaters are also used for heating of swimming pools.
There are different types of solar heating systems like direct and indirect system, passive and active systems, passive direct systems, active direct systems etc.

6.9 Active close loop solar water heater
6.6.3 Solar Reflectors
Solar thermal systems use the sun’s heat to produce electricity. Mirrored surfaces concentrate sunlight into a receiver that super heats a liquid. The energy from the scalding liquid is either used to produce steam or is converted into mechanical energy. In both the cases the final product is electricity.
The solar reflectors are classified by how they collect solar energy. The most common types are
a) Parabolic troughs
b) Parabolic dishes
c) Power towers
Parabolic troughs and dishes use mirrors shaped like parabolas to focus incoming radiant energy onto a fluid filled pipe that runs down the centre of the trough. Heat from the fluid is used to boil water in a steam generator to produce electricity. A parabolic reflector collects or project energy such as light, sound or radiowaves. A parabolic reflector functions due to the geometric properties of the paraboloidal shape, any incoming ray of light that is parallel to the axis of dish will be reflected to a central point called focus hence parabolic reflectors are used to collect and concentrate energy entering the reflector at a particular angle. The energy radiating from the focus to the dish can be transmitted outward in a beam that is parallel to the axis of the dish (Fig. 6.10).

Fig. 6.10 Parallel rays coming into a parabolic mirror are focused at a point F.
The vertex is V, the axis of symmetry passes through V and F
Applications of solar reflectors :
1. The major application of solar reflectors is in the generation of solar power.
2. The most common modern application of solar reflectors is in satellite dishes,      reflecting telescopes, radio telescopes, parabolic microphones, solar cookers and many lighting devices like spotlights, car headlights, PAR lamps and LED housings.
3. The Olympic Flame is traditionally lit at Olympia, Greece by using a parabolic reflector concentrating sunlight.
Solar reflectors are used for creating optical illusions, display products such as mirage, liquid mirror telescopes, rotating furnaces etc.
6.7 GreeN house concepts
The green house is about designing and operating better places for people, places that let us touch natural materials and understand where everyday things come from and taste fresh food straight from the garden. The green house aims to harness the growing understanding of human beings to other alternative solutions that find a balance between functionality, sustainability and beuty. Some of the concepts of green house can be listed below :
1. Use recycled or recyclable materials.
2. Avoid the use of chemicals that are harmful or harmful treatments on the surfaces or in the materials.
3. Minimise ecological footprint through careful consideration of source materials, their lifecycle and operation.
4. In designing buildings, encourage a new perspective idea giving a productive place in the building that can harvest food, water and energy and improve the local environment for people and animals rather than exploiting it. The building designed must be warm (created by floorplan), smart (cost effective), and green (sunlight, plants and access to outdoor).
5. To establish treatment plants for the disposal of waste from industries, which should not produce hazardous waste. For this the production must be carried out with non-hazardous materials by taking care not to produce hazardous byproducts which create the hazardous waste.
6. A proper technical designing is required by all the industries which use minimum or no hazardous materials for production.
7. In agriculture also hazardous pesticides, chemicals, hormones etc must not be used. The use of chemical fertilisers must be minimised and in its place natural manures must be used.
8. In dairy farms also use of hormones to activate the milk and growing of flesh of animal must be prevented.
6.7.1 Green Chemistry
Green chemistry is called sustainable chemistry, is a philosophy of chemical research and engineering that encourages the design of products and processes that minimise the use  and generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product including design, manufacture and use.
The green chemistry technologies provide a number of benefits listed below.
1. Reduce waste, eliminating the costly treatments.
2. Produce safer products.
3. Reduce the use of energy and resources.
4. Improves competitiveness of the chemical manufacturers and their customers.
5. Use of feedstock and reagents that are less hazardous to human health and environment.
6. Use of feedstock derived from annually renewable resources or from abundant waste.
7. Reuse or recycle chemicals.
8. Treat chemicals to render them less hazardous.
9. Dispose chemicals properly.
10. Design the chemical products to be less hazardous to environment and human health. These chemicals must be less toxic to organisms and ecosystem not persistent or bio-accumulative in organisms or in the environment and safer to handling and use.
Hence we can define the green chemistry as the invention, design and application of chemical products and processes to reduce or to eliminate the use and generation of hazardous substances.
The term hazard is not restricted to physical hazards such as explosiveness, flammability and corrosibility but also includes acute and chronic toxicity, carcinogenicity and ecological toxicity. Hence we can say that the product of hazard and exposure is risk.
Risk = Hazardexposure
If the product of hazard and exposure increases risk also increases.
6.7.2 Methods for Green Synthesis
Green synthesis is a chemical synthesis that involve the preparation of new compounds by using non-hazardous chemicals to environment and human health and producing non-hazardous byproducts. The green synthesis users reagents that are less toxic or reagents and catalysts that can be recycled easily.
The following are some of important aspects of green synthetic methods.
1. Develop new method for green chemical synthesis, including the use of microwave reactors to minimise energy needs and use of micro fluid reactors to minimise solvent waste.
2. As far as possible making use of water an environmentally-friendly solvent.
3. The waste production in the green synthesis must be negligible as calculated by E-factor which is defined as the ratio of mass of waste (kg) per unit of product in kgs.
E - factor =
Green synthetic methods are the essential tools in the field of synthetic chemistry. The following are some of the important green synthetic methods.
6.7.2.1  Applications of Green Synthesis
1. Green solvent methods : The role of a solvent is very crucial in green synthesis. An ideal solvent facilitates the mass transfer but does not dissolve. In addition a desirable green solvent should be natural, non-toxic, cheap and readily available with additional benefits of aiding the reaction, separation or catalyst recycling. An other important aspect of green solvent is maximising the atom efficiency so that efficient chemical reaction takes place.
% atom utilisation =
Eg : Acetanilide is synthesised by conventional method as well as green synthesis method as given below.
i) Conventional method


ii) Green synthesis method

Both the methods give the desired product, but by applying green synthetic method
1. We can avoid the use of acetic anhydride and formation of by product CH3COOH which is hazardous to human health and environment.
2. The atom economy obtained for green synthesis is in the range of 72-82% which is more than conventional method (69%) i.e. yield of acetanilide is more by green          synthesis.
3. The atom economy indicates the complete use of chemicals. Hence the green synthetic method is superior over the conventional method.
An alternative is use of microfluid reactor to minimise solvent waste
2. Green synthesis by selecting reagents that are eco-friendly : By selecting                            eco-friendly chemicals, reduction of number of steps between initial and final products, and avoiding the byproduct production, green synthesis of drugs chemicals and polymers can be achieved. For example, the synthesis of Iboprofen a non-steroidal, anti inflammatory drug with high sales was performed in six steps with the production of byproducts and waste conventionally with poor atom economy (40% yields). By green synthetic method Iboprofen is synthesised in three steps with increased yields (90%) minimised waste. For conventional and green synthesis the starting chemical is 2-methyl propyl benzene, produced in the petrochemical industry. In the greener method Raney Ni was used which can be recycled and reused. In the conventional method AlCl3 was used which was thrown into waste. The energy requirement of green method is very less.
The new green synthetic method for Iboprofen is a classic example of green chemistry.

               2-methyl propyl benzene

                             2-methyl propyl benzene
Another example is the green synthetic method of adipic acid, a starting material for the production of Nylon 6:6
In the conventional method benzene was used as a starting material which is carcinogenic (causes lukemia). For oxidation purpose Nitric acid was used which produces toxic fumes of nitrous oxide which is not eco friendly and yields are low (55.7%).
In the green synthetic method the starting material is cyclohexane and its oxidation was performed by 30% H2O2, an effective and environmentally benine oxidising agent. A Tungsten catalyst is used. In green synthesis greener oxidising agents are used, the reaction can be run without organic solvents. The products produced are in high yields (90%).


Thus green synthetic methods should have the following characteristics.
1. High efficiency
2. Low waste
3. Low energy requirement
4. Environmentally benine reagents, catalysts, byproducts and solvents should be       involved
5. High atom efficiency so that high yields should be produced
6. High quality with no contaminations.
6.8 Cement
Cement is most widely used non-metallic material in construction of buildings, dams, bridges, highways, runways for the aircrafts etc. The essential bonding material which binds sand and rock when mixed with water in concrete is cement.
Cement is a dirty greenish heavy powder used as a building material. Cement possesses adhesive and cohesive properties to bind rigid masses like stones, bricks, building blocks etc. Cement is hydraulic in nature i.e. it possesses the property of setting and hardening in the presence of water. Further the essential constituents of cement used for constructional purpose are compounds of calcium (calcarious) and aluminium silicon (argillaceous) materials.
Based on different chemical compositions, cement is classified into four types. They are :
1) Natural cement
2) Puzzolana cement
3) Slag cement and
4) Portland cement
6.8.1 Setting and Hardening of Cement
Portland cement on mixing with water, changes to a plastic mass called cement paste, which slowly loses its plasticity and becomes a stiff and ultimately a rockymass is obtained. This process is known as setting. After hydration, anhydrated compounds become hydrated, which have less solubility. Hence they are precipitated as insoluble gels or crystals. These have the ability to surround sand, crushed stones, other inert materials and bind them very strongly.
The physical changes occurring in the setting and hardening of cement may be                 summarized in a flow chart (Fig. 6.11) as follows :

Fig. 6.11 Schematic diagram of setting and hardening of cement
Hardening of cement can be explained on the basis of two theories :
a) Crystalline theory (given by Le-chatlier) : According to this theory, constitutional compounds after hydration form crystalline products. These crystalline products undergo interlocking which is responsible for hardening of cement.
b) Colloidal theory (given by Michaelis) : According to this theory, during hydration silicate gels  are formed  which undergo hardening and are responsible for the hardening of cement. Thus, it can be concluded that setting and hardening of             cement  is due to the formation of interlocking crystals reinforced by the rigid gels formed by the hydration and hydrolysis of the constitutional compounds. Most portland cements exhibit initial set in about 3 hours and final set in about 7 hours. Setting can be tested by a standard needle (vicat needle). If the needle does not penetrate into the paste beyond a certain limit, then it has reached the initial setting stage. Further if the needle does not penetrate at all, the cement is said to have reached final setting stage.
Reactions involved in setting and hardening of cement
The basic chemical compounds in the portland cement are :
        Name Chemical formula                Abbreviation
Tricalcium silicate 3CaO. SiO2 C3S
Dicalcium silicate 2CaO. SiO2 C2S
Tricalcium aluminate 3CaO. Al2O3 C3A
Tetracalcium alumino ferrite 4CaO. Al2O3 Fe2O3 C4AF
The behaviour of the cement can be altered by modifying the relative percentages of these compounds.
When cement is mixed with water, the paste becomes quite rigid within a short time which is known as initial set or flash set. This is due to C3A which hydrates rapidly as follows :
3CaO. Al2O3 + 6H2O   3CaO. Al2O3.6H2O
     (crystals)
These crystals prevent the hydration reactions of other constitutional compounds forming barrier over them. In order to retard this flash set, gypsum is added during the pulverization of cement clinkers. Gypsum retards the dissolution of C3A by interacting with it forming insoluble complex of sulfoaluminate which does not have quick hydrating property.
3CaO. Al2O3 + x H2O + y CaSO4 . 2H2O  3CaO. Al2O3. y CaSO4.zH2O
The tetracalcium alumino ferrite (C4AF) then reacts with water forming both gels and crystalline compounds as follows :
4 CaO. Al2O3.Fe2O3 + 7 H2O  3CaO. Al2O3. 6H2O + CaO. Fe2O3. H2O
                   crystals                gels                              
These gels shrink with passage of time and leave some capillaries for the water to come in contact with C3S and C2S to undergo further hydration and hydrolysis reactions enabling the development of greater strength over a length of time.
Final setting and hardening of cement paste is due to the formation of tobermonite gel plus crystallization of calcium hydroxide and hydrated tricalcium aluminate.
2 CaO.SiO2 + x H2O  2CaO.SiO2. xH2O
       gels    
2 (3CaO.SiO2) + 6H2O  3CaO.SiO2. 3H2O
                   Tobermonite gel + 3 Ca (OH)2
During the setting and hardening of portland cement, some amount of heat is liberated due to hydration and hydrolysis reactions. On an average, the quantity of heat evolved during complete hydration of cement is of the order of 500 kJ / kg.  The heats of hydration of the different constitutional compounds are in the following order :
C3A   >   C3S    >  C4AF  >  C2S
         878       502         418        251   kJ / kg
Therefore, where ever large masses of concrete are used (i.e., construction of dams), it is essential to dissipate the heat generated during hydration as quickly as possible, to prevent shrinkage cracks on setting and hardening.
Steps during setting and hardening of cement
When water is added to cement, at first hydration of tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF) takes place.

Next, hydration of tricalcium silicate (C3S) begins within 24 hours and gets completed in 7 days. The gel of aluminate begins to crystallize and at the same time, dicalcium silicate (C2S) begins to hydrate in 7 to 28 days.
Hence, the initial setting of cement is due to hydration of aluminate. Hydration of tricalcium silicate and further hydration of aluminate leads to the development of early strength between 1 to 7 days. Further hydration of dicalcium silicate and continued hydration of tricalcium silicate between 7 to 28 days, is responsible for the increase of strength of cement.
Specifications for cement
In order to maintain the quality of cement, various tests are conducted. Therefore specifications for ordinary portland cement as per Indian Standard : 269 – 1967 are given below :
1) Lime saturation factor  = = 0.66 to 1.02
2) The ratio of  shall not be less than 0.66.
3)   Insoluble residue should not exceed 2%.
4) The weight of magnesia (MgO) should not exceed 6%.
5) Total sulphur contents calculated as SO3 should be not more than 2.75%.
6) Loss on ignition should not exceed 4%.
7) Fineness should not exceed 10% after sieving the residue on B.S. 170 mesh     test sieve.
8) Setting times : Initial = 30 minutes
                            Final = 10 hrs
9)  Heat of hydration :
     After seven days : < 65 cal / gm
     After twenty eight days : < 75 cal / gm
10) Compressive strength :
    After three days : > 1600 lb / sq. inch
    After seven days : > 2500 lb / sq. inch
11) Soundness :
     By autoclave method  : expansion not more than 0.8%
     By Lechatlier method  : unaerated cement : max 10 mm
                                           aerated cement : max 5 mm
6.8.2  Deterioration of Cement Concrete
Deterioration of cement concrete takes place due to attack of salty water and other acidic solutions. The rate of attack will be minimised by the impermeable surface. On long exposure to salty water and acidic environment, the structure can be weakened. The rate of attack increases with decreasing pH (increase in acidity). The acidic environment is mainly due to chemical action of dissolved CO2 and other organic and inorganic acids. Due to the action of CO2 leaching out of free lime from cement concrete takes place.
Ca(OH)2 + CO2CaCO3 + H2O
CaCO3 + H2O + CO2Ca(HCO3)2
Ca(OH)2 + Ca(HCO3)2 2CaCO3+2H2O
Initially insoluble CaCO3 is formed, which on further reaction with CO2 and water             produces soluble calcium bicarbonate, which again reacts with calcium hydroxide produces calcium carbonate which again reacts with CO2 and H2O. The cycle is repeated causing deterioration of cement concrete. Hydrolysis of silicates and aluminates also cause deterioration of cement. Ex : Concrete pipes carrying sewage.
Prevention of deterioration : By making use of a surface coating with epoxy resin paint deterioration is minimised by the fact that coating makes the concrete surface impermeable to acidic environment. To prevent the hydrolysis of silicates coating the surface with SiF4 which forms CaF2 which is insoluble resistant to hydrolysis is carried out.

Exercise

I. Short answer questions :

1. What are nanomaterials?

2. Why nanomaterials are good catalysts?

3. How are nanomaterials useful in electronics?

4. What are buckytubes?

5. What is fullerene?

6. What are buckyballs?

7. Which are called ‘nano onions’?

8. What are metallo fullerene?

9. Explain the optical properties of CNT.

10. What are endohedral fullerenes?

11. Define liquid crystals.

12. What are the distinguishing features of liquid crystals?

13. Name the different types of liquid crystals.

14. What are thermotropic liquid crystals?

15. Define lyotropic liquid crystals.

16. Explain metallotropic liquid crystals.

17. What are nematic liquid phases?

18. Why are cholesteric liquid crystals called so?

19. What is meant by smectic liquid crystals?

20. Explain smectic A liquid crystals.

21. What is the characteristic feature of smectic B liquid crystals?

22. Which are called smectic C liquid crystals?

23. Define lamellar lyotropic liquid crystals.

24. Explain the hexagonal lyotropic crystals.

25. Mention any two applications of liquid crystals.

26. Which materials are called fibre reinforced plastics?

27. Name any materials used for reinforcing.

28. Why glass fibre is extensively used as a reinforscing material?

29. What are the common plastics resins used for reinforcement?

30. Write any three advantages of fibre reinforced plastics.

31. What are biodegradable polymers?

32. What are the basic requirements of biodegradable polymers?

33. Explain the factors influencing biodegradable polymers.

34. Write an account on naturally occurring biodegradable polymers.

35. Write the composition of biopols.

36. What is Mater Bi? How is it produced?

37. What are conducting polymers?

38. Explain intrinsic conducting polymers and their types.

39. Define extrinsic conducting polymers and their types.

40. Which are called doped polymers?

41. What is meant by p-doping?

42. Explain n-doping.

43. What are blended conducting polymers?

44. What is a bipolaron?

45. What is meant by percolation threshold?

46. Which polymer is called ‘synthetic metal’? Why?

47. How do temperature influence the conductivity of a polymer?

48. What is the disadvantage of intrinsic conducting polymers?

49. Which dopants added to trans-polyacetylene?

50. Why the conducting polymers are easily oxidised or reduced?

51. What is a solar cell?

52. What is photovoltaic effect?

53. What is the function of a photodetector?

54. How do you calculate the current produced by a solar cell?

55. What is wafer?

56. Mention any three types of solar heaters.

57. What is a solar reflector?

58. What is meant by green chemistry?

59. Explain the green house concept in the field of agriculture.

60. What is green synthesis?

61. How is deterioration of cement takes place due to hydrolysis?

62. What is meant by setting of cement?

63. Why cements are called hydraulic cements?

64. What is meant by leaching out of free lime?

65. How is the deterioration of cement by CO2 prevented?

II. Essay type questions :

1. a) Which materials are called nanomaterials? Why are they called nanomaterials?

b) Give an account of the properties of nanomaterials.

2. Give an account of the following :

a) Properties of nanomaterials based on surface.

b) What are the engineering applications of nanomaterials?

c) Explain the chemical reactivity of fullerenes.

3. a) What are carbon nanotubes?

b) How is CNT prepared by the following methods : 

i) Arc discharge       ii) Laser ablation       iii) Chemical vapour deposition

4. Give an account of the properties of the following nanomaterials.

a) CNT b) Fullerenes

5. a) Which fullerenes are called buckyballs?

b) Give an account of the different types of fullerenes.

c) Write a brief account on Buckminster fullerene.

6. a) Write an account on the different physical and chemical properties of fullerenes.

b) Explain the kinetic, optical and thermal properties of fullerenes.

7. Explain the applications of the following in electronic, medical and chemical fields.

a) CNT b) Buckballs

8. Give an account of 

a) The preparation of CNT 

b) Properties of nanomaterials based on size

c) Application of CNT.

9. Write short notes on the following :

a) Properties of nanomaterials based on composition 

b) Properties of fullerenes.

10. a) What are Fullerenes? Why are they called Fullerenes?

b) Give an account of the different types of Fullerenes based on structure and composition.

c) Write a detailed account on the properties of CNT.

11. a) What are liquid crystals and their distinguishing features?

b) Explain with suitable examples lyotropic liquid crystals.

12. a) What are thermotropic liquid crystals?

b) Explain the following phases in thermotropic liquid crystals with examples.

i. Nematic liquid crystal phase.

ii. Cholesteric liquid crystal phase.

13. a) With the help of neat diagrams, explain the different types of smectic liquid crystal with suitable examples.

b) Give an account of the applications of liquid crystals in medical field.

14. a) What are liquid crystals? How do you differentiate the liquid crystals from solids and liquids?

b) Give an account of the different types of liquid crystals with suitable examples.

15. Write a detailed account on the applications of liquid crystals in engineering with a special mention about the application in LCD.

16. Write a brief account on the following :

a) Metallotropic liquid crystals.

b) Lyotropic liquid crystals.

17. Differentiate the following with suitable examples.

a) Lyotropic liquid crystals from thermotropic liquid crystal.

b) Smectic A phase from Smectic C phase.

18. Give a comparative account on the following : 

a) Nematic liquid crystal phases and cholesteric liquid crystal phases

b) Smectic A phase and Smectic C phase.

19. a) Why do liquid crystals find extensive use in electronic industry as LCDs?

b) Explain the lamellar liquid crystals.

20. Give an account of the applications of liquid crystals.

21. a) Which materials are called fibre reinforced plastics?

b) Name some reinforcing materials and plastics resins used for preparation of fibre reinforced plastics.

c) Give an account of the advantages and applications of fibre-reinforced plastics.

22. Write an account on the different types of processing techniques adopted for fibre- reinforced plastics.

23. a) What is fibre glass? How is it made?

b) Give an account of the properties and applications of fibre reinforced plastics.

24. Write short notes on the following :

a) Fibre glass         b) Applications and advantages of fibre reinforced plastics

c) Properties of fibre reinforced plastics.

25. Give an account of the following processing techniques for the fabrication of reinforced plastics.

a) Matched metal die moulding

b) Injection moulding

c) Continuous lamination

d) Spray up.

26. a) What are biodegradable polymers? What are their basic requirements?

b) Give an account of the preparation, properties and applications of polyhydroxy alkanoates.

27. a) How are biodegradable polymers classified?

b) What are the factors influencing biodegradation?

c) Explain the preparation, properties and applications of polylactic acid.

28. How are the following polymers produced by biosynthesis? Mention their properties and uses.

a) Biopol b) Mater Bi c) Polyvinyl acetate

29. Give an account of applications and properties of the following.

a) Polylactic acid

b) Polyhydroxy alkonoate

c) Polyvinyl acetate.

30. a) Give an account of naturally occurring biodegradable polymers by quoting suitable examples.

b) Why biodegradable polymers undergo biological degradation?

c) What are the factors controlling rate of degradation?

31. Write an account of the following :

a) classification of conducting polymers.

b) p-doping of conducting polymers.

c) conducting element filled polymers.

32. Give a detailed account with suitable examples of doped conducting polymers.

33. Write short notes on the following :

a) Emraldine b) Poly acetylene

34. Present an account on the conducting polymers having conjugation and their applications.

35. a) What are the factors influencing conductivity of organic polymers?

b) Give an account of the applications of conducting polymers.

36. What are intrinsic conducting polymers? How are they produced? Give an account of the advantages and disadvantages of intrinsic conducting polymers.

37. a) Explain the working of solar cells.

b) Give an account of any two materials for making solar cells.

38. Write a brief account on the following :

a) Materials used for making solar cells.

b) Applications of solar cells.

39. a) Explain the solar water heater with the help of a neat diagram.

b) What are solar reflectors? How are they classified? Explain the applications of solar reflectors.

40. a) Write an account on paraboloid solar reflectors and their applications.

b) Give an account of green house concepts.

41. a) What is green chemistry? What are the benefits of green chemistry?

b) Explain the applications of green synthesis.

42. a) Explain any two methods of green synthesis and its advantages.

b) What are the advantages of green synthesis?

43. a) Explain the setting of cement with chemical reaction involved in it.

b) How is the deterioration of cement takes place?

44. Write short notes on the following :

a) Photovoltaic cells

b) Green house concepts

45. Write a brief account on the following :

a) Solar reflectors b) Setting of cement

46. a) Explain the green synthesis and its applications 

b) Give an account of solar water heaters.

III. Multiple Choice Questions :

1. A nanometer is 

a) 10–6 of a meter b) 10–8 of a meter 

c) 10–9 of a meter d) 10–7 of a meter

2. The diameter of carbon nanotube is

a) 1.5 nm b) 1.6 nm c) 1.8 nm d) 1.3 nm

3. The size of the nanoparticle is responsible for one of the following property.

a) colour b) chemical reactivity

c) dispersibility d) conductivity

4. Environmental sensors are used to detect one of the following gases :

a) He b) H2

c) Ar d) CO

5. CNT is prepared by one of the following methods

a) arc discharge b) electrolysis

c) heating in presence of air d) oxidation

6. One of the following nanomaterials undergo electrophilic addition.

a) CNT b) Bucktubes

c) Buckballs d) Composites

7. The spherical nanomaterials based on multiple layers surrounding a buckball core are called

a) Nano onions b) Megatubes

c) Buckyball clusters d) Metallo fullerenes

8. One of the following aromatic compound is used as a solvent for fullerenes

a) benzene b) toluene c) water d) naphtha

9. Fullerenes form complexes with one of the following metals.

a) Zn b) Fe c) W d) Na

10. On hydrogenation fullerenes produce

a) Dihydrofullerene b) Trihydrofullerene

c) Tetrahydrofullerene d) Polyhydrofullerene

11. The matter in a state that has properties in between conventional liquids and solids is called

a) liquid crystals b) crystalloids

c) colloids d) gel

12. Those materials that exhibit a phase transition to liquid crystalline phase as the temperature changes.

a) lyotropic b) metallotropic

c) thermotropic d) crystallotropic

13. One of the following liquid crystal type is constituted by both organic and inorganic composition.

a) Thermotropic b) Metallotropic c) Lyotropic d) Nematic

14. One of the following material is naturally occurring liquid crystal

a) Derivatives of cholesterol b) Proteins

c) P-azoxy anisole d) Diethyl 4,4’-azoxydibenzoate

15. The orientation of long axes of the molecules are parallel to a preferred direction, which may be tilted by certain angle in one of the following phases.

a) smectic A b) smectic B

c) nematic d) smectic C

16. The lyotropic liquid crystals have the following nature.

a) Lyophilic b) Lyophobic

c) Amphiphilic d) Hydrophobic

17. The liquid crystals find extensive use as

a) LCD b) Chemical diagnosis

c) power generator d) fuel

18. The material that possesses orientational order but no positional order is called

a) solid b) liquid

c) crystalloid d) liquid crystal

19. Cholesteric liquid crystals possess one of the following property.

a) chirality b) insulation

c) lustrous d) ductility

20. One of the following factor plays vital role in lyotropic liquid crystals.

a) nature of solute b) nature of solvent

c) solute-solvent interaction d) nature of solution

21. One of the following is an example of fibre-reinforced plastic.

a) fibre glass b) kevular

c) mater bi d) silicones

22. The most extensively used fibre for reinforcement of fibre reinforced plastics is

a) silk b) cotton

c) nylon d) glass fibre

23. One of the following plastics resin is used for making fibre reinforced plastics.

a) polyester b) polyacetylene

c) polyamide d) polybutylene

24. Malaminine fibre reinforced plastics is used for 

a) industrial fibre b) tyres

c) insulation d) making footwear

25. Fibre reinforced plastics are fabricated by one of the following technique.

a) extrusion moulding b) centrifugal casting

c) slush casting d) blowing

26. The properties of fibre reinforced plastics materials depend on 

a) only matrix b) only fibre used

c) both matrix and fibre d) fabrication technique

27. One of the following is a naturally occurring biodegradable polymer 

a) petroleum b) coal

c) natural gas d) natural rubber

28. The feed stock for the production of majority of biodegradable polymers are from

a) chemicals b) biological sources

c) petro chemicals d) agricultural products

29. Mulching films used in agriculture are produced from

a) PVA b) Mater Bi

c) Biopol d) Polylactic acid

30. The rate of biodegradation is controlled by

a) molecular weight of polymer b) carbon present in polymer

c) hydrogen present in the polymer d) functional groups in the polymer chain

31. One of the following is an example of conducting polymer

a) poly pyrrole b) mater bi

c) vectra d) poly isoprene

32. Filled polymers hold a conducting element like

a) poly pyrrole b) carbon black

c) copper d) NOx

33. n-doping is carried out by using a reducing agent like 

a) Zinc naphthalide b) Sodium anilide

c) Sodium naphthide d) Lewice acid

34. Polaron is a

a) localised radical ion b) radical ion

c) radical d) delocalised radical ion

35. The conducting polymers are also used for making analytical sensors for

a) pH b) CH4

c) CO2 d) CO

36. The conductivity of trans polyacetylene when I2 iodine vapour is used as dopant is

a) 100 S, cm–1 b) 10,000 S, cm–1

c) 1000 S, cm–1 d) 7500 S, cm–1

37. Solar cells convert solar energy to electricity by one of the following effect

a) photovoltaic effect b) photochemical effect

c) photosynthesis d) photosensitive effect

38. One of the following is a material used for making solar cells.

a) Gallium b) Indium

c) Tellurium d) Cadmium Telluride

39. Solar reflectors contain

a) metal surfaces b) wooden surfaces

c) mirrored surfaces d) non-metal surfaces

40. One of the following is a green house concept

a) use of chemicals that are harmful

b) improper technical designing

c) production of byproducts in large amounts

d) use of recycled or recyclable products

41. Green chemistry is called

a) sustainable chemistry b) unsustainable chemistry

c) developing chemistry d) conceptual chemistry

42. Due to action of CO2 on cement, one of the following takes place. 

a) Leaching out of free lime b) Bleaching out of free lime

c) Leaching out Iron d) Leaching out of silica

43. The initial setting of cement is due to

a) Hydration of calcium b) hydration of aluminate

c) hydration of silicate d) hydration of dicalcium

44. To prevent hydrolysis of silicates from concrete coating the surface of the material with one of the following

a) SiF b) SiCl4

c) SiF4 d) SiCl2

IV. Fill in the blanks with suitable words : 

1. The catalytic activity of nanomaterials is due _____ and _____ in the crystalline structure.

2. The nanomaterials find good application in making light emitted ______ devices.

3. The magnetic properties of nanomaterials increase with ___________ orderly             electronic spins.

4. The bottom up approach is used for the synthesis of ______ and ____.

5. Plasma torch method is used for the synthesis of _______.

6. A paper battery is a battery engineered to use a paper, a thin sheet of cellulose infused with ______.

7. The nanomaterial that resembles the balls used in football (soccer) is called ______.

8. A fullerene, larger in diameter than nanotubes and prepared with walls of different thickness is called _______.

9. A smallest fullerene is ______.

10. When other atoms tapped inside fullerenes to form inclusion compounds is known as ______.

11. Fullerenes are inherently ________.

12. On hydrogenation fullerenes give _________________.

13. The ozonide with composition C60O3 decomposes at 296k to produce ____.

14. Buckminster fullerene inhibit the ______.

15. The carbon nanotubes are otherwise called _____.

16. The strength of CNT is upto __________.

17. CNT is considered as _____ conductor.

18. Nanotube polymer composites are used for making _____ and ____.

19. Because of superior mechanical properties ____ is used to make stab-proof and bullet proof clothings.

20. The structure of fullerenes is composed of ______.

21. The micelle in lyotropic liquid crystals are formed at _____.

22. Lyotropic liquid crystals are _________.

23. Diethyl 4,4’ – azoxy benzoate is an example of ______.

24. Tobacco virus is an example of _____ liquid crystal.

25. The materials which exhibit liquid crystal phase with change in temperature is called ______.

26. P-azoxy anisole exhibit liquid crystallinity at _____ temperature.

27. Cholesteric liquid crystals possess ______ structure.

28. Lamellar phase is called ______.

29. The efficiency of heat engines is found out by making use of _______.

30. _______ liquid crystals are utilised in thermography.

31. By reinforcing plastic matrix with high strength fibre materials ____________ are             produced.

32. ______ is produced by drawing glass in the form of fibres and suitably bonded with plastics materials.

33. In _______ a mix of short fibres and resin are forced by a plunger through a nozzle into the heated mould.

34. Natural fibre like _______ and _______ is used for making fibre reinforced plastics.

35. Fibre reinforced plastics possess ______ dielectric constant.

36. In textile industry frp is used for making _____.

37. The strength of fibre reinforced plastics depends on _____.

38. Biopol has the composition ______.

39. ______ are the examples of naturally occurring, biodegradable polyester.

40. Those polymers which degrade by the enzymatic action of naturally occurring micro organisms and bacteria are called _______.

41. Polyvinyl acetate is widely used because of its solubility in _______.

42. The application of biodegradable polymers in waste management is as _____.

43. _____ is used as a dopant for polyaniline.

44. The conducting polymer that possess metallic lustre is ______.

45. The conductance of intrinsic conducting polymer is due to ______ present in the backbone of the polymer.

46. Creating a positive site on polymer backbone is called _____.

47. The polaron is mobile because of ______

48. n-doping is carried out by ______ process.

49. Emraldine salt is also known as _____.

50. Conducting polymers are used for _____ lithography.

51. The minimum concentration of a conductive filler is called _____.

52. The conductivity of a conducting polymer increases with _______ in temperature.

53. Solar cells convert solar energy to _______ energy. 

54. When the source of light is not sunlight, photovoltaic cell is used as a ______.

55. Charge carrier separation in photovoltaic cells is carried out by _____ and ______ of carriers.

56. ___________ solar cells are used in satellites and space exploration.

57. ________ are used for creating optical illusions.

58. Green chemistry is called _______ chemistry.

59. ______ is defined as the ratio of mass of waste in kgs per unit of product in kgs.

60. Acidic solutions can cause ______ of cement concrete. 

61. The constituent of cement having least setting time is _______.

62. The final setting product of cement is mainly due to ________ formation along with ___________.

63. The colloidal nanoparticles are also called __________.

V.  Indicate TRUE OR FALSE for the following :

1. One billionth of a meter is called nanometer. [ T / F ]

2. The physical properties of particles change with change in size of the particle. 

[ T / F ]

3. The magnetic properties of the nanoparticles increase with decrease in size of the particles.          [ T / F ]

4. The colloidal nanoparticles are called coercing colloids. [ T / F ]

5. The nanoparticles are not used as environmental sensors. [ T / F ]

6. Buckminster fullerene contains pentagonal and hexagonal rings. [ T / F ]

7. Endohedral fullerenes do not contain other atoms tapped inside the structure.    [ T / F ]

8. Carbon nanotubes are otherwise called bucktubes. [ T / F ]

9. Chemical vapor deposition method is used for the preparation of CNT. [ T / F ]

10. One of the promising application of CNT is their use in solar panels. [ T / F ]

11. Liquid crystals possess orientational order but no positional order. [ T / F ]

12. Thermotropic liquid crystal exhibit phase transition due to solvent changes.   [ T / F ]

13. Smectic liquid crystals are soap like. [ T / F ]

14. The liquid crystal displays do not rely on optical properties. [ T / F ]

15. Cholesteric liquid crystals exhibit colour change from red to violet. [ T / F ]

16. Glass fibre is an extensively used fibre reinforced plastic. [ T / F ]

17. The strength of the FRP does not depend on critical fibre length. [ T / F ]

18. The fibre reinforced plastics are used for making shuttle in textile industry.     [ T / F ]

19. Natural rubber is a naturally occurring biodegradable polymer. [ T / F ]

20. Bipol is produced from sugar by chemical reaction. [ T / F ]

21. Mater Bi is used as an additive in the manufacture of tyres. [ T / F ]

22. Extrinsic conducting polymers contains double bonds responsible for conductance.

[ T / F ]

23. Creating a positive site on polymer is called n-doping. [ T / F ]

24. Conducting polymers are used for electronic beam lithography. [ T / F ]

25. Photovoltaic cell produces electricity from light. [ T / F ]

26. The amount of photogenerated current increases slightly with decreasing temperature.

[ T / F ]

27. Solar heaters comprise non-renewable energy technology. [ T / F ]

28. The Olympic flame is lit by using parabolic reflector concentrating sunlight.  [ T / F ]

29. Green synthesis reduces the use of energy and resources. [ T / F ]

30. Initial setting of cement is due to hydration of aluminate. [ T / F ]

Answers

III. Multiple Choice Questions :

1) c 2) d 3) a 4) d 5) a 6) c 7) a 8) b 9) c 10) d

11) a 12) c 13) b 14) b 15) d 16) c 17) a 18) d 19) a 20) c

21) a 22) d 23) a 2 4) c 25) b  26) c 27) d 28) d 29) b   30) a

31) a 32) b 33) c 34) d 35) a 36) b 37) a 38) d 39) c  40) d 41) a 42) a 43) b 44) c

IV. FILL IN THE BLANKS :

   1) edges and points  2) electroluminescence  3) increased

 4) fullerenes and polymer nanocomposites

 5) carbon nanotubes (CNT)  6) CNT   7) buckballs

 8) megatubes

 9) dodecahedral C20 or buckminster fullerene

10) endohedral fullerenes 11) chiral 12) polyhydrofullerene

13) epoxide 14) HIV virus 15) bucktubes

16) 100GPa 17) one dimensional

18) electric cables and wires 19) CNT

20) stacked graphene

21) Critical micelle concentration (cmc) 22) amphiphilic

23) smectic A liquid crystal 24) natural 25) Thermotropic liquid crystal

26) 116–135 0C 27) helical 28) neat phase or G-phase

29) Liquid crystals 30) Cholesteric

31) fibre reinforced plastics 32) Fibre glass 33) injection moulding

34) sisal and asbestos 35) low 36) shuttle

37) critical fibre length 38) polyhydroxy alkanoate

39) Polyhydroxy alkanoates 40) biodegradable polymers

41) H2O 42) compost bags 43) HCl

44) emraldine 45) p electrons 46) p-doping

47) delocalisation 48) reduction 49) synthetic metal

50) electron beam 51) percolation threshold

52) increase 53) electric 54) photodetector

55) drift and diffusion 56) Gallium arsenide multijunction

57) Solar reflectors 58) sustainable 59) E-factor

60) deterioration 61) tricalcium aluminate

62) Tobermonite gel, calcium hydroxide  

63) coercing colloids 

V.  TRUE OR FALSE QUESTIONS :

 1) T   2) T  3) T  4) T 5) F 6) T  7) F  8) T  9) T   10) T

11)  T 12) F 13) T 14) F 15) T 16) T 17) F 18) T 19) T 20) F

21) T 22) F 23) F 24) T 25) T 26) F 27) F 28) T 29) T 30) T