Morden Enginering Materials-final

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MODERN ENGINEERING MATERIALS Contents: 1.Metallic glasses 2.Shape memory alloys(SMA) 3.Nano-phase materials 4.Carbon nano tubes sunny 1


INTRODUCTION The development of science and technology have paved the way for the scientists to find out new materials for high-tech applications The materials used for high tech applications are designed to have maximum performance sunny 2




METALLIC GLASSES - INTRODUCTION Metallic glasses are amorphous metallic solid which has high strength ad good magnetic properties and better corrosion resistance ad will posses both the properties of metals and glasses Properties of metals + Properties of glasses = Properties of metallic glasses sunny 4

Formation Of Metallic Glasses : 

Formation Of Metallic Glasses Metals are made into glassy state by increasing there rate of cooling to a very high level c/sec due to this the atoms are unable to arrange properly manner and form an new amorphous state These materials formed by the rapid cooling technique are called metallic glasses sunny 5

Glass Transition Temperature : 

Glass Transition Temperature The temperature at which the metals in the molten form transforms into glasses ( i.e. from liquid to solid )-glass transition temperature It is a pseudo second order phase transition sunny 6

Techniques For preparation : 

Techniques For preparation 1.Melt spinning system: Molten alloy is made to impinge on a fast rotating roller to form metallic glass 2.Twi roller system: Molten alloy is made to pass through the 2 rollers rotating in opposite direction to form metallic glass 3.Metal extracting system: Fast moving roller sweeps off molten droplet into a strip to form metallic glass 4.sputtering: The sputtering gas is ionized and the atoms are made to fly towards the substrate to form metallic glasses sunny 7


PREPARATION OF METALLIC GLASSES 1.Quenching: It means rapid cooling Atoms move freely in the liquid state When the liquid is quenched ( rapidly cooled ) it results in an irregular pattern of the metallic glasses sunny 8

2.Metal spinning : 

2.Metal spinning Effective technique Quartz tube with fine nozzle . It is placed over a cold rotor made up of copper Heating coil is wounded over quartz tube sunny 9

Types of metallic glasses : 

Types of metallic glasses sunny 10 1.metal-metalloid glasses 2.Metal-metal glasses

Properties of metallic glasses : 

Properties of metallic glasses sunny 11 1.Structural They have TCP than HCP It does not have any crystal defects 2.Mechanical They are strong in nature They have high corrosion resistance They posses malleability and ductility

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3.Magnetic They can be easily magnetized and demagnetized They have narrow hysteresis loop 4.Electrical High electrical resistance and it will not vary with temperature Low eddy current losses sunny 12

Applications of metallic glasses : 

Applications of metallic glasses Since they are malleable and ductile they are used in filament winding As they are very strong they are used to make different kinds of springs They have corrosion resistance they can be used in surgical clips and marine vessels They are highly resistance they are used to make computer memories They behave as superconductors hence they are used in production of high magnetic field They are not affected by magnetic radiation they are used in nuclear reactors sunny 13



Shape memory alloys : 

Shape memory alloys Smart metal or memory alloy or muscle wire sunny 15

Martesite : 

Martesite Interstitial super solution of carbon in - iron and it crystallizes into twinned structure They will have this type of structure only at lower temperature and it is soft in this phase sunny 16

Austenite : 

Austenite Solid solution of carbon -iron and it crystallizes to cubic structure It will attain their shapes at higher temperature and it is hard in this phase sunny 17

Processing of SMA : 

Processing of SMA Lower temperature – martensite structure On heating to higher temperature – austenite while cooling again it returns to martensite form This effect is called shape memory effect sunny 18

Twinned martesite : 

Twinned martesite sunny 19 Same size as that of austentite Macroscopically no change in shape or size between austentite and martensite Both are stable at a particular temperature range

Characteristics of SMA : 

Characteristics of SMA Transformation occurs not only at single temperature rather they occur over a range of temperatures Crystallographically the thermo-elastic martensites are reversible sunny 20

Pseudo elasticity : 

Pseudo elasticity 3. Temperature greater than Af the load is absorbed by the Martensite when the load is applied But when the load is removed martensite transforms to austensite temperature still above Af sunny 21

Slide 22: 

sunny 22 4. The SMA which have its change at constant room temperature are called super-elastic SMA and that effect is called super-elasticity At a single temperature when the load is applied it will have new shape (deformed martensite ) and when the load is removed it regains to its original shape (twinned martensite ) i.e pressing a rubber or a spring Super elasticity:

Hysteresis : 

Hysteresis sunny 23 5. During cooling process martensite starts (Ms) and ends (Mf) During cooling process austensite starts (As) and ends (Af)

Types of SMA : 

Types of SMA sunny 24

Types of SMA : 

Types of SMA One way shape memory alloys Though there is some change in the temperature the SMA remains in the same phase Two way shape memory alloys When the temperature is increased the martensite becomes austenite and the condition is vice-verse sunny 25

Properties of SMA : 

Properties of SMA High shape memory strain[8.5%] Density of 6.45 gm/cm3 More flexibility High melting point [1300] High thermal stability High corrosion resistance Thermal conductivity 8.5-martesite 18-austenite Transformation temperature-200-110 High yield strength 70-140Mps-martensite 200-700Mps - austenite sunny 26

Applications of SMA : 

Applications of SMA Eye glass frames – bed back and froth and can regain its original shape – Nickel Titanium Alloy Toys can be made using SMA – more flexible and movable Lifetime of helicopter blades can be improved using SMA Blood clot filter when it is cooled sent into the body through vein it controls the blood flow rate according to our body temperature sunny 27

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To control and prevent the fire and toxic gases when the fire occurs due to rise in temperature the fire safety valves ( SMA) changes its shape and shuts the fire In the coffee makers Ni-Ti alloys are used to release the hot milk and ingredients for a certain period of time Circuit edge connector- connected or disconnected based on temperature depending on the variation of the temperature sunny 28

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Preventing and controlling the cracks Used in relay and activators Used to correct the irregularities in teeth sunny 29

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Advantages Compact in nature Safe and smart material They are flexible They are no corrosive Disadvantages Cost is high Efficiency is low Transformation occurs over a range of temp Structural arrangements may get deformed sunny 30

Nano phase materials : 

Nano phase materials sunny 31

Introduction : 

Introduction These atoms do not move away from each other ah have their size about 1-100 nm Examples : Zno,Cu-Fealloys,Ni,Pd,Pt. sunny 32

Synthesis of nano phase materials : 

Synthesis of nano phase materials Top down approach: bulk materials-broken-nano sizes Bottom down approach: nano materials are made by building atom by atom sunny 33

Techniques of preparation of nanophase materials : 

Techniques of preparation of nanophase materials sunny 34

Plasma arching : 

Plasma arching sunny 35 They are produced using the radio frequency heating coil The starting metal is placed in the metal container RF coil is switched on and produces heat radiation Evaporation occurs Helium gas is allowed to pass through it The nano particles are collected in the collector rod

Chemical vapour deposition : 

Chemical vapour deposition Used to prepare nano powder Metal - heated - to form gas-allowed to deposit on solid surface under vacuum- forms nano powder For coating an object with nano powder it can be introduced into the CVD Examples ; 1.nano powder of oxides and carbides 2.pure metal nano powders sunny 36

Sol - gel technique : 

Sol - gel technique Used to prepare nano powder and nano particle Sol-colloid suspended in liquid Gel-pores filled with the liquid Based on hydrolysis of liquid precursors and formation of colloidal solutions Hydrodynamic cavitations technique is used often sunny 37

Slide 38: 

Sol-gel is taken in the drying chamber and mixed thoroughly and high pressure and temperature It creates the hydrodynamic bubbles And it under nucleation ,growth forms nano particles sunny 38 Hydrodynamic cavitations technique

Electro-deposition : 

Electro-deposition Electro plate an material Using current it reduces the cations of desired metal from a solution and coat a conductive object with a thin layer of the material sunny 39

Ball milling (mechanical crushing) : 

Ball milling (mechanical crushing) Used for the preparation of metal oxide nano crystals Small balls are allowed inside a drum They are made to fall on a solid with high force which crushes into nano crystals Examples ;Ni and AL bases nanocrystals sunny 40

Properties of nano materials : 

Properties of nano materials Physical property As they are close to each other their inter particle distance is less These particles cannot divide further, they have high strength and hardness Melting is very les for these materials Electronic property Energy bands are narrow Ionization potential is higher More molecular bonds when prepared from bulk materials Capable of storing hydrogen atom sunny 41

Slide 42: 

Magnetic properties Exhibit spontaneous magnetization at smaller sizes due to large magnetic moment Ferro-magnetic ,anti-ferromagnetic has an GMR(giant magnetic resistance) effect Large no of atoms less coordination number posses magnetic moment Mechanical properties Hardness varies from material to material Exhibit super plastic behavior sunny 42

Applications : 

Applications Mechanical engineering –vacuum seals,giant magneto resistance and to make hard materials In computer science engineering used in mobiles and laptops to store data in smaller chips In biomedical and chemical engineering they are used in production of DNA chip and as a catalyst in solar cells sunny 43

Carbon nano tubes : 

Carbon nano tubes sunny 44

Carbon nano tubes : 

Japanese scientist Sumio Iijima discovered carbon nanotubes in 1991. CNTs are allotropes of carbon. Each carbon atom is bonded to 3 other carbon atoms by strong covalent bonds. It forms a lattice in the shape of hexagons. They are stiffest and strongest fibers sunny 45 Carbon nano tubes

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sunny 46 One layer of carbon Greater tendency to align into ordered bundles Used in test theory of nano tubes Consist of 2 or more layers of carbon Tend to form unordered clumps

Structure of carbon nano tubes : 

Structure of carbon nano tubes sunny 47 Single walled carbon nanotubes (SWCNTs) Some SWNTs with different chiralities. a) armchair structure b) zigzag structure c) chiral structure

Pulsed laser deposition : 

Pulsed laser deposition It uses the Ruby laser,Nd-YAG laser CO2 lasers The intense laser beam is made to focus on the graphite target It is heated by the furnace up to 1200c The argon gas is filled around the graphite in the quartz tube The cold copper collector collects the CNT’s sunny 48

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Carbon arc method : 

Carbon arc method It is similar to that of the electro deposition technique The liquid helium of 500 torr pressure is applied The carbon deposited from E1-E2 by supplying it an 20- 25 volts From this the MWNT’s can be obtained sunny 50

Chemical vapour deposition : 

Chemical vapour deposition Hydro carbon gas – methane heated to 1100 c The gas decomposes to the carbon atoms These atoms are deposited over cooler substrate containing iron as the catalyst sunny 51

Properties of CNT’s : 

Properties of CNT’s It is sp2 carbon- carbon bond gives hardness to the CNT’s Young’s modulus is 5 times greater than the steel Tensile strength is 50 times greater than steel They have very high conductivities than that of copper sunny 52

Applications of CNT’s : 

Applications of CNT’s They are very light weight and very strong-used in aero space Constructing in nanoscale electronic device CNT’s battery fuel cells CNT’s are used in flat panel displays of screens Plastic composites of CNT’s are used as light weight shielding materials Semiconducting nano tubes are used as chemical sensors to sense various gases They are also used as a catalyst sunny 53

Slide 54: 

They are used in displays of cell phones monitors PDA’s and ATM They are used in the air filtering process filters it also kills bacteria CNT’s of 2 different diameters end to end can act as a diode Optical ignition: 29 % of iron with SWCNT’s placed on top of the explosive material such as PETN can be ignited with a regular camera flash sunny 54

By : T.J.Sundeep R.Prasanth E&I’B’ My sincere thanks to : 1.T.Vijay kumar 2.N.Ramkeerthi 3.N.Shivakanth 4.B.Sudharshan masthan sunny 55 THANK ’U’