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UNIT VI

UNIT VI. 1. DTEL. 1. UNIT-VI SPECIFIC OBJECTIVE / COURSE OUTCOME. The student will be able to understand:. The significance of Advanced materials in technological applications. 1. Science behind the advanced engineering materials so as to use them in innovative products in future. 2.

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UNIT VI

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  1. UNIT VI 1 DTEL 1

  2. UNIT-VI SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to understand: The significance of Advanced materials in technological applications 1 Science behind the advanced engineering materials so as to use them in innovative products in future 2 DTEL 2

  3. UNIT VI SYLLABUS Introduction to Advanced Materials (8 hrs) New materials Nanomaterials: Definition of nanomaterials, nano scale. Carbon nano tubes: Different Types of CNT ; applications of nanomaterials in medicine, environment and electronics. Threats of Nanomaterials. Shape memory alloys: Definition, Properties, general applications. Specific properties and applications of Nitinol. Composite materials: Introduction , Classification and their industrial applications. Advanced Polymeric materials Biodegradable polymers. Conducting polymers- types of doping, Polyacetylene and Polyaniline, Liquid crystals and liquid crystal polymers (thermotropic and lyotropic),phases of thermotropic polymers: nematic, smectic, cholesteric; advantages, disadvantages and applications 3 DTEL 3

  4. Nanomaterials LECTURE 1-NANOMATERIALS What are nano materials? • A nanometer is one billionth of a meter(10-9) • The span of nanotechnology lies between 1 and 100nm which is more than atomic length and less than micrometer. • Materials whose at least one dimension is confining to nanoscale are called as nanomaterials. • Materials at nanoscale are different from the properties of macro or bulk material 4 DTEL 4

  5. LECTURE 1-NANOMATERIALS The transition from micro particle to nano particle can lead a number of changes in their physical properties such as : An opaque substance like copper becomes transparent.  Inert metals like platinum and gold become catalyst.  Insulators like silicon becomes conductor.  An ordinary magnet becomes super magnet  5 DTEL 5

  6. Nanotechnology LECTURE 1-NANOMATERIALS Basically, nanotechnology is the ability to design & control the structure of an object at nano-scale. Materials when reduced to nano-scale behave differently because of Large surface- interface to volume ratio, Quantum Mechanical Behavior. Size effect 6 DTEL 6

  7. LECTURE 1-NANOMATERIALS Discovery of Fullerenes Fullerenes or Buckey balls Discovered by Robert Smalley & group while studying artificial red giant stars Stable clusters of carbon with 12 pentagons and six hexagons resembling dome designed by Buckminster fullerene Could withstand tremendous heat and pressure 7 DTEL 7

  8. Graphite & Graphene LECTURE 1-NANOMATERIALS Graphene is a single layer of carbon atoms densely packed into a benzene ring structure (Fig.2b). It is the 2D counterpart of 3D graphite Graphite Graphene Because of its 2 dimensional structure and the lateral availability of the carbon, graphene is now known to be the most reactive form of carbon. 8 DTEL 8

  9. Carbon nanotubes LECTURE 1-NANOMATERIALS Straight, hollow tubes of carbon that appear to consist of graphene layers of carbon separated by the same spacing as the planar layers of graphite were called as CARBON NANOTUBES. It was as if a graphene sheet rolled up into a tube with capped end. CARBON NANOTUBES(CNT) SINGLE WALLED (SWNT) MULTIWALLED (MWNT) Further classification depending on angle of rolling of CNT’s: Zigzag,Chiral,Nematic 9 DTEL 9

  10. CNT LECTURE 1-NANOMATERIALS Unique Properties of Carbon Nanotube: • A CNT can conduct, semiconduct or insulate electrons. • CNTs emit electrons without resistance at lower voltage than conventional electrodes • CNTs are suitable for microelectronics because they have high current capacity, high thermal conductivity, mechanical stability and resistance not dependent on length. • As a composite show a unique combination of stiffness, strength, and tenacity compared to other fiber materials • Thermal and electrical conductivity are also very high, and comparable to other conductive materials. • High aspect ratio , high strength with light weight, stiffness, low density, regular structure, good heat conductance 10 DTEL 10

  11. Applications of CNT LECTURE 1-NANOMATERIALS Conductive plastics • Structural composite materials • Flat-panel displays • Gas storage • Antifouling paint • Micro- and nano-electronics(miniaturization of IC’s) • Radar-absorbing coating • Technical textiles • Atomic Force Microscope (AFM) tips • Batteries with improved lifetime • Biosensors for harmful gases Extra strong fibers • • 11 DTEL 11

  12. Applications of CNT LECTURE 1-NANOMATERIALS DTEL 12

  13. Difference between SWNT& MWNT LECTURE 1-NANOMATERIALS S.No. SWCNT MWCNT These consist of a layer of graphite, a single atom thick, called graphene, which is rolled into a seamless cylinder. Multiple graphene layers either in the form of a coaxial assembly of SWNT or as a single sheet of graphite rolled into the shape of a scroll. Can be produced without catalyst Bulk synthesis is easy The diameters of MWNT are in the range of 5 nm to 50 nm. High purity Chance of defect is less but once occurred is difficult to improve 1 Catalyst required for synthesis Bulk synthesis is difficult Most SWNT typically have a diameter of close to 1 nm. Purity is poor A chance of defect during functionalization (grafting of chemical functional group at the surface)is more Characterization and evaluation is easy Can be easily twisted, flattened, and bent into small circles or round sharp bends without breaking for better performance SWNT are more workable yet harder to make than MWNT. Hence the prices of SWNT currently remain higher than MWNT. 2 3 4 5 6 Complex because of complex structure Cannot be easily twisted. The structure of MWNT is less well understood because of its greater complexity and variety. Since bulk synthesis is easy they are less costlier than SWNT. However, the prices of both are very high for common use. 7 8 9 13 DTEL 13

  14. Applications of Nanomaterials -Medicene LECTURE 1-NANOMATERIALS The major application is in CANCER TREATMENT since nanomedicine identifies & destroys the cancerous cells without harming healthy non- cancerous cells. Beside cancer treatment, nanotech have following medical applications : Tissue engineering : To repair or reproduce damaged tissues which is far better than conventional organ-transplantation or artificial implantation. Synthetic Bone : Nano-particulated synthetic bones are as efficient as natural bones. Diagnosis and surgery : Nanotubes, Nanoshells, BioMEMS..etc in diagnosis, treatment, surgery in medical field. 1) 2) 3) 14 DTEL 14

  15. Applications of Nanomaterials -Environment LECTURE 1-NANOMATERIALS ENVIRONMENT: • In renewable energy technologies such as photovoltaic or solar cells, hydrogen fuel cell • CNT membranes during desalination • Nanofilters to clean up water or automobile tailpipes, chimneys • Nanosensors to detect waterborne contaminants and pathogens accurately and quickly; to detect toxic gas leak even at very low concentration • Surface coatings that act as a permanent air purifier on exterior walls of buildings • Nanosized iron treatment for groundwater treatment Nanotech devised solar cells are much more efficient than today's conventional solar cells which are at the most 40% efficient. 15 DTEL 15

  16. Applications of Nanomaterials -Electronics LECTURE 1-NANOMATERIALS ELECTRONICS: • Improving display screens on electronics devices for reduction inces power consumption and the weight and thickness of the screens. Increasing the density of the memory chips • Reducing the size of the transistors used in the Ics • Using electrodes made from nanowires that would enable flat panel displays to be flexible as well as thinner than current flat panel displays • Using CNTs to direct electrons to illuminate pixels, resulting in a lightweight display panel for high clarity • 16 DTEL 16

  17. Threats of Nanomaterials LECTURE 1-NANOMATERIALS • Loss of jobs in the traditional farming and manufacturing industry. • Lowering of the value of oil due to the possibility of developing alternative more efficient sources of energy Lowering of the value of diamonds since these could be synthesized using nanotechnology. • • Atomic weapons can now be more accessible and made to be more powerful and more destructive • Since these particles are very small, problems can actually arise from the inhalation of these minute particles, much like the problems a person gets from inhaling minute asbestos particles. • Presently, nanotechnology is very expensive and developing it can cost a lot of money. It is also pretty difficult to manufacture, which is probably why products made with nanotechnology are more expensive. 17 DTEL 17

  18. Smart materials LECTURE2 :SHAPE MEMORY ALLOYS Smart materials : Materials that have one or more properties that can be significantly changed in a controlled fashion by very small external force, such as stress, temperature, moisture, electric or magnetic fields e.g. shape memory alloys and shape memory polymers, piezoelectric, pH-sensitive, self healing and many more materials. 18 DTEL 18

  19. Shape memory alloy as a smart material LECTURE 2 :SHAPE MEMORY ALLOYS Shape memory alloy (SMA) : • Mixture of two or more metals that has the special ability to memorize a certain shape and return to that shape even after being deformed usually by application of heat. They are particularly useful because at lower temperatures they have a rubbery feel due to martensitic crystal structure and can be deformed by a small force • at the high temperature they behave like normal alloys or metals due to Austenitic crystal structure. • The change is very fast, often within seconds. Super elasticity and Shape memory are remarkable properties of SMA which normal alloys do not exhibit • 19 DTEL 19

  20. Shape memory effect LECTURE 2 :SHAPE MEMORY ALLOYS The properties of SMAs are entirely an outcome of its dynamic heat sensitive crystalline structure. 20 DTEL 20

  21. Shape memory effect LECTURE 2 :SHAPE MEMORY ALLOYS Four characteristic temperatures defining a thermo elastic martensitic transformation; (1)the martensite start temperature, Ms(2)the martensite finish temperature, Mf (3)the austenite start temperature on heating, As, (4)the austenite finish temperature, Af. Above Af, the specimen is in the original undistorted state. 21 DTEL 21

  22. One way training of SMA LECTURE 2 :SHAPE MEMORY ALLOYS 22 Remembering the shape only on heating(1way training) DTEL 22

  23. Two way training of an SMA LECTURE 2 :SHAPE MEMORY ALLOYS Remembering the shape on heating and cooling( 2 way training) 23 DTEL 23

  24. Nitinol-An important SMA LECTURE 2 :SHAPE MEMORY ALLOYS The alloy of Ni and titanium having shape memory effect is called as Nitinol. Ni- Ti alloys are excellent SMAs and the most useful of all SMAs. The transition temperature varies for different compositions from about -50 ° C to 166 ° C. Salient features of Nitinol: • Low Density: 6.45gms/cc • High Melting Temperature: 1240-1310° C • Low electrical Resistivity (hi-temp and low-temp) • Good corrosion resistance • Nonmagnetic nature • High fatigue strength, hardness and impact toughness • Machinability. • Excellent damping • Heat-resistance • Good Tensile Strength 24 DTEL 24

  25. Nitinol-Applications LECTURE 2 :SHAPE MEMORY ALLOYS MILITARY AND AEROSPACE APPLICATIONS Nitinol couplers in F-14 fighter planes to join hydraulic lines tightly • to insulate the spacecraft from vibration which can be a major issue during launch. • In Helicopter blades • 25 DTEL 25

  26. Nitinol-An important SMA LECTURE 2 :SHAPE MEMORY ALLOYS MEDICAL APPLICATIONS: Salient features favouring Medical applications • Flexibility, • large recoverable deformations, • good fatigue life, • bio-compatibility and outstanding • superelastic behavior at or around the body temperature NITINOL HOOKS 26 DTEL 26

  27. Nitinol-An important SMA LECTURE 2 :SHAPE MEMORY ALLOYS Medical applications: • Mending of broken bones • Reinforcement for Arteries and Veins Dental wires Vascular stents Tweezers to remove foreign objects through small incisions • anchors with Nitinol hooks for shoulder surgery • to locate and mark tumors so that surgery can be more exact and less invasive • in robotics actuators and micromanipulators to simulate human muscle motion. • Superelastic Nitinol tubings as a surgical (guide) catheters through blood vessels due to better flexibility and access todifficult areas of the human body. 27 DTEL 27

  28. Nitinol- Some more applications LECTURE 2 :SHAPE MEMORY ALLOYS Miscellaneous Applications Safety Devices • Anti scalding • Spectacle frames • Fire security and Protection systems • Cellular phone antennas • Clothing • Dampening 28 DTEL 28

  29. LECTURE 3 :COMPOSITE MATERIALS Definition and classification A system created by combination of two or more materials referred to as ‘phases’, which are mutually insoluble, differing in form and/ or composition so as to enhance the properties like strength, toughness, corrosion resistance of the desired material. Main constituents of composite • MATRIX + FILLER OR REINFORCEMENT • A continuous material and a major component or bulk material mainly Polymers, Metals and Ceramics MATRIX • The material impregnated in the matrix to lend its advantage to the composite e.g. carbon fiber, glass bead, sand, or ceramic FILLER OR REINFORCEMENT 29 DTEL 29

  30. Need for composites LECTURE 3 :COMPOSITE MATERIALS Certain engineering applications like Modern day aircrafts, spacecrafts, automobiles, racing cars, Gas turbines, high temperature reactors, supersonic aircrafts, and missiles require very specialised materials. • Materials should be lightweight as well as strong enough to withstand harsh conditions, including high temperature and incredible stress and strain. • Such materials are either not available or are too costly to be commonly used. • A single material may not have all the required characteristics. • Under such conditions a physical combination of two or more materials called as ‘Composite materials.’ are used • 30 DTEL 30

  31. Advantages of composite materials LECTURE 3 :COMPOSITE MATERIALS Incredibly light weight Highly elastic High Specific strength COMPOSITE MATERIALS Resistant to chemicals Non- conductive Resistant to corrosion Low cost 31 DTEL 31

  32. LECTURE 3 :COMPOSITE MATERIALS Properties Properties of composite materials depend upon Properties of phases Geometry of dispersed phases Amount of phases 32 DTEL 32

  33. Classification of composites LECTURE 3 :COMPOSITE MATERIALS COMPOSITE MATERIALS PARTICULATE STRUCTURAL FIBRES 33 DTEL 33

  34. LECTURE 3:COMPOSITE MATERIALS Classification of composites • particles of different size and shape of one material in a matrix of another material either in liquid form or powder form Particulate composites • Concrete-(cement+water+aggregates • Tungsten–thoria as lamp filaments, metal ceramic composites used in cutting tools (cermets). • Reinforced rubber -rubber with 20- 50 nm carbon-black particles used in tyres Examples of Particulate composites 34 DTEL 34

  35. Classification of composites LECTURE 3 : COMPOSITE MATERIALS Structural Composites:- The properties depend on geometry of fillers in form of thin sheets Laminar e.g. Plywood e.g. Sandwich Alclad sheets 35 DTEL 35

  36. Classification of composites LECTURE 3 :COMPOSITE MATERIALS Fibers( l/d>1) Long fiber Short fiber l/d≈∞ carbon fibers in polymer matrix used in spacecrafts, launch vehicles l/d≈100 glass fibers in polymer matrix used in boat panels 36 DTEL 36

  37. Importance in aircraft building LECTURE 3 :COMPOSITE MATERIALS 37 DTEL 37

  38. Definition LECTURE 4 :CONDUCTING POLYMERS An organic polymer with highly delocalized pi-electron systems, having electrical conductance of the order of a conductor is called a conducting polymer. Chemical structures of some conductive polymers polyacetylene; polyphenylene vinylene; polypyrrole (X = NH) and polythiophene (X = S); and polyaniline (X = NH/N) and polyphenylene sulfide (X = S 38 DTEL 38

  39. Classification of conducting polymers LECTURE 4 :CONDUCTING POLYMERS Conductive element filled conducting polymers • Conjugated pi-electron conducting polymers • Doped conducting polymers • Co-ordination conducting polymers • Blended conducting polymers • 39 DTEL 39

  40. Doped conducting polymers LECTURE 4 :CONDUCTING POLYMERS Oxidation doping (p-type):- • Removal of electron or electrons from the valence bond is done by the oxidizing agent, leaving the polymer with a +ve charge. • Doping(oxidizing) agents used : I2,Br2, AsS5, H2SO4, HClO4 • Reduction doping (n-type):- • Done by donation of an electron by a reducing agent(electron rich species). • Doping occurs when alkaloid components like Li,Na,K,Cs,Rb in naphthalene or anthracene are used in a proper solvent over the immersed polymer. 40 DTEL 40

  41. Examples of conducting polymers LECTURE 4 :CONDUCTING POLYMERS Polyacetylene: - It can be doped by oxidation with a halogen (iodine) called as p-doping or by reduction with alkali metals (Na) called n-doping. The conductivity increases from10-5S/cm to 103to 105S/cm. Polyaniline: - In a polyaniline molecule there are conjugated pi-bonds .To make it electrically conductive, doping is done with the help of oxidation or p-type doping during manufacture itself by protonation with HCl It can also be doped by using a reducing agent which creates a polaron i.e.radical ion. The conductivity increases by approximately 9-10 times. 41 DTEL 41

  42. Applications LECTURE 4 :CONDUCTING POLYMERS • Conductivity based applications • To avoid build up of static electricity under inflammable or explosive conditions • Conductive adhesive used to stick conducting objects together • Coating the inside of the plastic casing of computers with a • conductive surface to absorb harmful radiations. • In printed circuit boards • (v)As artificial nerves due to the biocompatibility (vi)By coating light weight modern planes with a conducting polymer, to save any damage from lightning bolts. • 42 DTEL 42

  43. Applications LECTURE 4 : CONDUCTING POLYMERS Electroactivity based applications Biosensor to measure glucose concentration in blood • In light weight rechargeable batteries. • Gas sensors • Electromechanical actuators which directly convert small voltages into mechanical energy • 43 DTEL 43

  44. Definition & classification LECTURE 5 :LIQUID CRYSTAL POLYMERS A liquid crystal is a substance that flows like a liquid but maintains some of the ordered structure characteristic of crystals in between a certain temperature. The liquid crystalline state is a very interesting state since the molecules in some of the phases react to light or small voltages changing their orientation & are useful as display devices. 44 DTEL 44

  45. LECTURE 5 : LIQUID CRYSTAL POLYMERS What can form meso phases? Organic molecules long and thin ;rod-like, disc-like and banana shaped, not very symmetrical can exist in liquid crystalline phases also called as meso phases e.g. CH3-O-C6H5-CH=N-C6H5- CH2CH2CH2CH3 Generally the following type of molecules form liquid crystalline phases where R is mostly alkyl, alkoxy etc.; A & B are phenyl group; Z is linking group like ester, azo etc while X is a chain termination group mostly an alkyl group. - - -X Z R- A B 45 DTEL 45

  46. Classification LECTURE 5: LIQUID CRYSTAL POLYMERS Nematic Smectic THERMOTROPIC LIQUID CRYSTALS Cholestric LYOTROPIC 46 DTEL 46

  47. Classification LECTURE 5: LIQUID CRYSTAL POLYMERS Lyotropic liquid crystals are those, which change into liquid crystal phase with change in concentration in a solution. Thermotropic crystals are formed from organic molecules with rod shape, change phases with temperature, will react to changes in temperature or, in some cases, temperature and pressure. 47 DTEL 47

  48. Sub classification LECTURE :LIQUID CRYSTAL POLYMERS Nematic:The molecules tend to have the same alignment but their positions are not correlated Smectic: The molecules are arranged in layers and exhibit some correlations in their positions as well as orientation. Cholestric (Chiral or twisted nematic)the molecules twist slightly from one layer to the next, resulting in a spiral formation. 48 DTEL 48

  49. Definition LECTURE 5 :LIQUID CRYSTAL POLYMERS LIQUID CRYSTAL POLYMERS : Polymeric liquid crystals are basically the polymer versions of the monomers containing vinyl group, Kevlar(aramids) or polypeptide chain. These are a class of chemically complex materials that have useful properties of polymers and those of liquid crystals. These are needed for different technological applications of use properties of liquid crystals. 49 DTEL 49

  50. Examples LECTURE 5 : LIQUID CRYSTAL POLYMERS Some Liquid Crystal Polymers 50 DTEL 50

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