Structure and Properties of Materials
Structure and Properties of Materials EGN 3365
University of Central Florida
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Date Created: 10/22/15
Chapter 1 ATOMIC STRUCTURE AND BONDING Notes 1 Protons Electrons Neutrons Nucleus Charge of Protons and Electrons Why these are important in Mechanical Electrical and Chemical Properties Difference between Atomic No and Atomic Wt Atomic no no of protons in the nucleus Atomic wt Mass in gms of Avogadro no Na At wt 22 11 proton 11 neutron 1 gm mole of Na Ans 22 gm of Na contains 6023 X 1023 atoms EGN 3365 Dr Seal Orbwta e ectron FIGURE 21 Schematic representation of the Bohr atom Chapter 1 ATOMIC STRUCTURE AND BONDING Electronic Structure Concept of Hydrogen Atom 1 e39 surrounding the nucleus of 1 proton Excitation of Hydrogen atom Photon can be released Energy Change transition of 1 e from level a to b relates to the photon by the Planck s eqn Concept of QM and Planck s Eq AE hv hcl h 663 x 103934joule sec Theory by Niels Bohr 1922 Nobel Prize Energy of the hydrogen e for allowed energy levels 2p2me n2h2 n principal quantum number Figure 24 Concept of Ionization Energy Energy required to remove the e39 from the atom Heisenberg s Uncertainty Principle Impossible to determine at the same time the momentum and position of a small particle EGN 3365 Dr Seal FIGURE 22 a The rst three electron energy states for the Bohr hydrogen atom b Electron energy states for the rst three shells of the wave mechanical hydrogen atom Adapted from W G Moffatt G W Pearsall and J Wulff The Structure and Properties of Materials Vol 1 Structure p 10 Copyright 1964 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc Energy eV SdX 113 3piE 35f 2 112 P 25 n l ls 71 xlO39lB ZX lO lB Energy J Chapter 1 ATOMIC STRUCTURE AND BONDING Quantum numbers oPrinciple Q no 11 main energy levels large n far away from nucleus Subsidiary quantum no l subenergy levels with probability of finding an e 1 0 1 2 3 l s p d f orbital oMagnetic Q no ml special orientation of single atomic orbital when l 1 then 3 possible values of ml 1 0 1 21 I allowed values for ml 1 s 3 p 5 d 7 f oElectron Spin Q no mS specifies 2 allowed spins 12 and 12 can 2 electrons occupy the same orbital PAULI s exclusion Principle no 2 e39 can have the same four quantum numbers 2 n2 no of electrons in shells increase in quantum no increase in atomic shell Why atomic size is important Diffusion EGN 3365 Dr Seal Energy 9 11 f d I dP 5 d g Principal quantum number n 4 FIGURE 24 Schematic representation of the relative energies of the electrons for the various shells and subshells From K M Ralls T H Courtney and J Wulff Introduction to Materials Science and Engineering p 22 Copyright 1976 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc Chapter 1 ATOMIC STRUCTURE AND BONDING Electron Configurations 1s22s22p63s23p63d10 Hund s Rule Figure Why noble gases are stable Ne Ar Kr Xe Rn s2p6 Difference in electronegative and electropositive elements EP Alkali metals Na K EN 0 Fl N Dual nature Si Ge C As Sb P Question Write a short paragraph With examples Metals vs Nonmetals EGN 3365 Dr Seal ncreasmg energy FIGURE 25 Schematic representation of the lled energy states for a sodium atom Chapter 1 ATOMIC STRUCTURE AND BONDING Types of Bonds Atomic vs Molecular Ionic Bonds large interatomic force Coloumbic Forces non directional Covalent Bonds Sharing of bonds directional Metallic Bonds Sharing of e39 in a delocalized manner to form strong nondirectional bonds What is a dipole Dipole exists due to asymmetry in its electron density distribution Criteria of Ionic Bonds oElectronegative vs Electropositive Example of NaCl EGN 3365 Dr Seal bonding in sodium chloride NaCl FIGURE 29 Schematic representation of ionic Couiombwc bonding force ion cores GQGG 990 0000 Q9 C Q Sea ofvalence electrons FIGURE 211 Schematic illustration of metallic bonding lt gt lt gt lt lt gt FIGURE 212 Schematic illustration of van der Waals bonding between two dipoles ALOFFHC or molecular dipoles FIGURE 215 Schematic representation of hydrogen lt bonding in hydrogen uoride HF w Hydrogen Chapter 1 ATOMIC STRUCTURE AND BONDING Interatomic Forces for an Ion Pair Fnet Z1Z2e241i0a2 nba 1 Attractive Repulsive 80 permittivity of free space 885 X 103912 C2Nm2 Picture EGN 3365 Dr Seal Probability 4 e 7 Distance from nucleus 4i l Orbital electron Nucleus a b FIGURE 23 Comparison of the a Bohr and b wave mechanical atom models in terms of electron distribution Adapted from Z D Jastrzebski The Nature and Properties of Engineering Materials 3rd edition p 4 Copyright 1987 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc Force F Potential energy E Attraction 4 Repulslon lt Repulslon 4 Attraction lt Attractwe force FA q lnteratomlc Separation r I Repulswe force FR iNet force FN f7 Repulswe energy ER l mteratomxc separation r 7 Net energy EN Amtractwe energy EA b FIGURE 28 a The dependence of repulsive attractive and net forces on interatomic separation for two isolated atoms b The dependence of repulsive attractive and net potential energies on interatom39 separation for two isolated atoms Meta Atormc number Nonmeta Symboi Atormc we1ght intermemate 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Rare earth seHes U La Ce Pr Nd Sm Eu Go To Dy H0 Er Tm Vb Lu 13891 14012 14091 14424 145 15035 15196 15725 15892 16250 164 93 16726 16893 17304 17497 89 90 91 2 93 94 95 9 97 98 99 100 101 102 103 Acumde seHes Ac Th Pa U Np Cm BK Cf Fm M0 N0 Lw 227 23204 231 23803 Pu Am E5 237 242 243 247 247 249 254 253 256 254 257 FIGURE 26 The periodic table of the elements The numbers in parentheses are the atomic weights of the most stable or common isotopes FIGURE 27 The electronegativity values for the elements Adapted from Linus Pauling The Nature of the Chemical Bond 3rd edition Copyright 1939 and 1940 3rd edition copyright 1960 by Cornell University Used by permission of the pu lisher Cornell University Press INTRODCUTION TO PLASTICS Dr Yaw Obeng A CKNO WLED GEMEN TS Most of the Material Presented in this Talk Is Adapted form the Course Notes for CHEE390 Queens University and from Prof Joe Greene of California State University Chico OBJETIVE LOOK AT POLYMERS AND PLASTICS FOM ENGINEERING PERSPECTIVES gt Industrial Plastic Polymer Consumption gt Polymer Classification Schemes gt Material Selection Criteria Quantify Desired Characteristics gt Material Testing Methods gt Case Studies Polymer Science and Processing Technology Successful product design requires a knowledge of gt the requirements of the final product gt the behaviour of polymeric materials gt commercial polymer processing technology gt relevant cost and market factors Molecular Structure 15 Applications At the heart of polymer science and technology is molecular structure It dictates not only final product properties but polymer synthesis and processing methods Classification of Polymer Applications 1 Elastomers gt static uses gaskets hoses gt dynamic uses tires sports equipment 2 Adhesives gt structural epoxy resins gt nonstructural pressuresensitive tapes hotmelt adhesives 3 Plastics gt semicrystalline automobile exterior gt amorphous packaging films plexiglass 4 Fibres gt naturalmodified cotton rayon gt synthetic carpeting apparel 5 Coatings gt lacquers paints Material Selection Application Perspectives gt Industrial requirements for enduse and processing gt Basic testing methods gt Polymer compound formulations essential polymer properties compound additives gt Relevant engineering science Elastomers origin of elasticity Adhesives surface energy Plastics mechanical properties polymer blends Fibres crystallization Coatings oxidative thermal and chemical stability Alternate Schemes for Polymer Classification Application Specific Composition Property Specific Chemical Microstructure Chemical Functionality Polymer Architecture Thermoplastic vs Thermoset Polymer Classification Terminology AMORPHOUSGLASSUKE CRYSTALLINE FIBREFORMING PDLVHUNVLCMLOMCIYLAYE POLY TE39IRAFLUOIOE THVLENE PUL ISTVRENE POLYACIYLOIHTRILE POLVHETHVL HETHACRYLATE CHLORINAYED POLVETNVLEME POLVMNV mm cummnzs POLVWWVL CHLOMDE mum ACETATE roumnuvl ACMLATE mum aura At VLATE IRREGULAR REGULAR quotSWINE NATURAL IUTVL RUIIER IUIIER cDPO 39OLVISDBUTENE Ml IITERHOLECULAR AYIIACYIOI AND OR MOLECULAR SilFfNESS INCREASING RUBBERMKS mcnusma ntcuumv or noucuun STRUCTURE O Polymer Classification ThermoplasticThermoset One of the most practical and useful classification of polymer compounds is based on their ability to be refabricated Thermoplastic polymers that can be heatsoftened in order to process into a desired form gt Polystyrene polyethylene gt recyclable food containers Thermoset polymers whose individual chains have been chemically crosslinked by covalent bonds and therefore resist heat softening creep and solvent attack gt Phenolformaldehyde resins melamine paints gt permanent adhesives coatings Polymer Classification Chain Architecture Linear A linear polymer chain is one without branches Its actual conformation may not be linelike but varies with chain stiffness crystallinity and applied stresses Branched Chains with an appreciable number of sidechains are classified as branched These side chains may differ in composition from the polymer backbone Crosslinked A continuous network of polymer chains is a crosslinked condition In effect there is just one polymer chain of infinite molecular weight Chain architecture has a dramatic effect on properties such as viscosity elasticity and temperature stability 175 iv m LEAR BRANCH WIRED M W R Polymer Classification Chemical Microstructure Homopolymers polymers derived from a single monomer can be linear branched or crosslinked gt polyethylene polybutadiene Random copolymers two monomers randomly distributed in chain gt AABAAABBABAABBA gt polyacrylonitrileran butadiene Alternating copolymers two monomers incorporated sequentially gt ABABABABABABABAB gt polystyrene alt maleic anhydride Block copolymers linear arrangement of blocks of high mol weight gt AAAAAAAAAAABBBBBBBBBBBBBBBAAAAAAAA gt polystyreneblockpolybutadieneblockpolystyrene or polystyrene b butadieneb styrene Graft copolymers differing backbone and sidechain monomers gt polyisobutylenegraft butadiene Polymer Classification Chemical Class A popular classification scheme amongst chemists is based on polymer functionality Polyesters O gt polyethylene terephthalate Dacron g 0 Polyamides gt polycaprolactam nylon 6 If I Urethanes gt carbamate linkages through reaction of diisocyanates and diols I I Another l classification scheme again favoured by chemists is based on differences between the polymer and constituent monomers gt Condensation polymers synthesis involves elimination of some small molecule H20 in the preparation of nylon gt Addition polymer formed without loss of a small molecule ie ethylene polymerization to generate polyethylene Additive Classification Terminology It is relatively rare for an article to be made from polymer alone Most are polymer compounds consisting of a mixture of polymer and various additives These include Fillers solid additives used to modify physical properties gt Dilution talc gt Reinforcing carbon black in tires gt Toughening rubber in ABS plastic Plasticizers nonvolatile solvents added to improve flexibility gt Dialkyl phthalates in polyvinylchloride Colourants additives used to change product aesthetics gt Pigments soluble colourants gt Dyestuffs insoluble additives Antioxidants compounds that reduce polymer degradation through intervention in free radical reactions Physical Properties of Polymer Compounds The materials selection component of a part design demands careful consideration of all required properties Consider the following case studies gt electric drill casing gt automobile bumper gt aircraft tire What properties must a given material provide for each of these components We must be able to translate qualitative terms strong flexible into engineering terms for which quantitative data is available gt Understand physical testing methods that are used industrially and highlight important behavioral characteristics of polymers Polymer Material Selection Key Questions When developing a polymer compound for a given application you may ask yourself the following questions gt What are the maximum and minimum temperatures the compound will experience throughout its lifetime includes manufacturing as well as product use gt To what loads will the material be subjected and what is the frequency of load application engine mounts fishing line gt Is the part transparent translucent or opaque Colouring gt Is flame resistance necessary and to what environmental conditions will the product be exposed solvent resistance oxidative degradation Material Testing Static Testing of Polymers and Polymer nmnnllnrls I Stressstrain analysis is the most widely used mechanical test However it is only a rough guide as to how a material will behave in a given application Test specimens are prepared in the form of dog bones whose dimensions are known accurately T HH W0 A static test involves deformation of the saqomple at a steady rate usually with one end fixed and the other pulled at a constant rate of elongation tensile testing The retractive force of the material is recorded as a function of the elongation and the engineering stress 6 is calculated as a function of the engineering strain a F 8 AL Pa 6 A0 LO Static Testing of Polymers and Polymer annnnnrlc We will soon see that observed polymer properties are strongly dependent on temperature and the applied rate of deformation Under some conditions an elastomer can behave like a brittle plastic and viceversa A Three typical behaviors are Brittle lastic Illustrated here p Tough plastic Often cited sample properties 6 A Ultimate tensile stress Pa and elongation at break El B Yield tensile stress Pa asmme39 Toughness Area under 6 a curve Compression and Shear vs Tensile Tests Stressstrain curves are very dependent on the test method A modulus determined under compression is generally higher than one derived from a tensile experiment as shown below for polystyrene MVS39IVRENE Tensile testing is most sensitive to material flaws and microscopic cracks Compression tests tend to be characteristic ofthe polymer while tension tests are more characteristic of sample flaws smsss PSI x loquot Note also that flexural and shear test modes are commonly employed I5 20 STRAIN m Static Testing of Polymers and Polymer nmnm mrle I Shown is a representative stressstrain curve for a polymer undergoing brittle failure initial An often quoted material modulu5 property is the tensile or Young s modulus E a E g e m which relates strain to retractive stress over the linear region E Pa Copper 121O11 Polystyrene 3O1O9 Soft Rubber 2O1O6 oh 51 failure I quot 1 sccant I modulus I39 proportional I v hmlt 001 Strain Mechanical Properties of Representative Bolymers Elastic Yield Ultimate Elongation Modulus Strength Strength to Break GPa MPa MPa Polypropylene 1016 23 2438 200600 Polystyrene 2835 3855 125 Polytetrafluoroethylene 041 1014 1428 100350 Polymethyl methacrylate 2428 4862 4869 210 Nylon 38 800 25 Polyethylenelowdensity 0103 6914 1017 400700 Note that these values depend on temperature and strain rate gt We will see that behaviour is highly influenced by temperature when we examine factors such as degree of crystallinity glass transitions and melt viscosity Transient Testing Creep Tests Creep tests can be made under all load conditions and provide data needed to design products that sustain loads for long periods gt A constant stress 60 is applied with the strain a varying with time Creep behaviour arises from the viscoelastic properties of polymers and their compounds 0 E A 8 B E c Applied quot0 load C 5 00 quot 7 0 E Time 1 Time 1 I Time Time Above are illustrated the response of different idealized materials to step changes in applied stress A Elastic B Viscous C Viscoelastic Impact Testing Impact tests are highspeed fracture tests that measure the energy required to break a specimen Izod and Charpy shown to right impact tests use a weighted pendulum to measure the loss of kinetic energy associated with specimen fracture Agreement between different methods can be poor and results are not material constants but dependent on sample geometry notching and size Impact strength units vary but notched tests are de ned in terms of energy per unit length of notch kJm Heat Distortion Temperature The maximum temperature at which a polymer can be used in rigid material applications is called the softening or heat distortion temperature HDT A typical test plastic sheeting involves application of a static load and heating at a rate of 2 C per min The HDT is defined as the temperature at which the elongation becomes 2 6 A Rigid polyvinyl chloride A c 50 psi load B Lowdensity polyethylene 50 psi load C Polystyrenecoacrylonitrile 25 psi load D Cellulose acetate Plasticized 25 psi load a u PE RCEMT ELONGATION i i u 75 W 5 5quot TEMPERATURE 0c WOEIvNmZ Static Modulus of Amorphous PS T K A Glassy I5 I I 9 Leathery 7 c Rubbery I quot3 5 39 Polystyrene 1 l A 30 370 410 lCDE r Stress applied at x and removed at y Heat Capacity Changes at Tg Specific heat capacity Cp plotted against temperature for atactic polypropylene showing the glass transition in the region of 260 K 20 CpJ Kquotgquot Factors Influencing Tg Polymers whose structures are flexible do not provide for strong intermolecular attraction and do not pack well are those with relatively low Tg s Four factors are generally believed to affect Tg 1 Internal chain mobility rotational freedom along the chain as influenced by side chains 2 Free volume volume of the material that is not occupied by polymer molecules 3 Attractive forces hydrogen bonding dipole association 4 Chain length shorter chains have greater relative free volume Thermal Transition Points of Select D n I m a re Polymer Repealing Unit T C TI quotC Polydimethylsiloxanc OSiCH1 127 40 Polyelhylene CHCH m 137 Polyoxymelhylenc 7 82 181 Natural rubber polyisoprenc CHCCHCHCH1 v 73 28 Pol isobul lene 4CH2CCH32 73 44 Polyelhylenc oxide CH1CH20 741 66 Polyvinylidene uoride CH1CF1 40 185 Polypm Iene c11CHCH s 17o Polyvinyl uoride 4CH1CHF 41 200 Polyvinylidene chloride CH1CC12 18 200 Polyvinyl acetate vcnzcmococng 32 Polychlomtri uom cth lene 2 220 Polyeczpmlaclam CI123CONH 52 223 Yulyhexamclhylene adipamide NHCHBNHCOCH2CO 50 265 Pubethylene lerephlhalale ocmc11ococo 51 270 Polyvinyl chluride CH1CHCI 8 273 Polystyrene c11CH 100 250 Polymethyl methacrylalc CHCCHC02CH 105 200 Cellulose lriacetat CHZOAc 306 0 AcO 0A Polyletra uoroelhylene CF2CF1 117 327 Differential Scanning Calorimetry DSC E A DSC instrument controls the energy input 5m to sample and reference so they remain at l i l the same T throughout a programmed temperature rise ABM A DSC trace is a plot of energy AHHsampleHref as a function of T DSC trace of polyethylene terephthalatecopoxbenzoate quenched reheated cooled at 05 Klmin through the glass transition and reheated for measurement at IOKImin Tg is taken at the temperature at which halfthe increase in heat capacity has occurred The width of the transition is indicated by AT Temperature Thermal Expansion lfa part is to be produced Within a close dimensional tolerance careful consideration ofthermal expansioncontraction must be made Parts are produced in the melt state and solidify to amorphous or semicrystalline states Changes in density must be taken into account when designing the mold om I r I I r I I 011 M39lll IIq CASE STUDY 1 THERMOSETS Thermoset Definition Thermoset materials are polymers that under go a chemical reaction to build molecular weight and viscosity Thermosets are set or crosslinked with heat and can not be reheated for forming repeated forming lllustration of a Thermoset gtStandard epoxy is based on bisphenol A and epichlorohydrin gtCuring can occur at room temperature with the use of 2 component systems Curing at elevated temperature with use of onecomponent Thermoset Definition i Thermosetting resin hot solid cold solid 11 can be liquid or easily Thermoset quot quot melted solid V Liquids I Thermoplastic hot liquid Temperature rgt Figure 81 Viscositytemperature behavior for thermoplastic and thermosetting resins Applications for Thermosets Epoxy gt Protective coatings gt Bonding and adhesives gt Molding casting and tooling Laminating and composites gt Building and construction Polyester gt Boat hulls gt Recreation vehicles automotive body panels floor pans SMC gt Soft tooling patterns gt Cultured marble buttons corrosion resistant tanks and parts gt Corrugated and flat paneling Polyurethane gt Rigid foams gt Semiflexible foam gt Flexible foam gt Packaging gt Microcellular foam gt Nonfoam cast elastomers gt Coatings binders thermoplastic elastomers sealants paints Mechanical Properties of Thermosets Epoxy Polyester PET Thermoplastic Polyurethane Density gcc 111140 104 146 129140 103 115 Tensile Strength psi 4000 13000 600 13000 7000 10500 175 10000 Tensile Modulus psi 350K 300K 640K 400K 600K 10K 100K Tensile Elongation 36 2 6 30 300 3 6 Impact Strength ft 020 1 0 02 04 025 070 25 to no break lbin CLTE 4565 55 100 65 100 200 106 mmmrnC HDT 264 psi 115F550F 140F 400F 70F 100F 70F 150F Advantages of Thermosets Epoxy gtExcellent chemical and corrosion resistance gtExcellent thermal properties and low creep gtHigh stiffness and modulus properties Polyester gt Rigid resilient to chemical and environmental exposures corrosion resistant and flame retardant gtEasily processed in low cost equipment Polyurethane gtHigh strength to weight ratios resistance to flame spread excellent thermal insulation low cost easily processed Disadvantages of Thermosets Epoxy gtMoisture absorption toxicity not recyclable gtCost Polyester gtMoisture absorption toxicity not recyclable gtStyrene emmisions Polyurethane gtMoisture absorption toxicity not recyclable Temperature Thermoset Reacting Polymers Process Window gtTemperature and pressure must be set to produce chemical reaction without excess ash too low a viscosity short shot too high a viscosity degradation too much heat Thermal Degradation Fully cured pal s Tempermum Short shot quotI Melting Tlme Pmsum Caco3 BMC Resin fiber and filler gtBMC stands for Bulk Molding Compound gtcompression molded under high temperature and pressure gtBMC has a solid uniform constitution By changing the blend design the characteristics can be altered to meet a wide range of applications Polyester Molding Operations Polyester Use with RTM RTM Resin Transfer Molding gtThe process of injecting a liquid resin trough a glass mat while in a heated mold gtMaterials Polyester Vinyl ester Epoxies Prefo rm Tool Injection Cure Demold mm SCRIMP Process Used for polyester vinyl ester and epoxies SCRIMP SYSTEM SCHEMATIGS Ena t Hul Manufacture ieurm illlunnlinn um Hardcom DuPunt tampoiltw PI39DCBEE develnped and patented by Seamann39s Cum pnsi tes 439 Sing lieaid ad reeling Injectimn achieved thmugh higI39rlznnermreealzni i151r surface layer t0 cause thm ughetheethickneaa aw Polyurethane Chemistry Reaction between isocyanate and alcohol polyol Crosslinking occurs between isocyanate groups NCO and the polyol s hydroxyl endgroups OH Thermoplastic PU TPU have some crosslinking but purely by physical means These bonds can be broken reversibly by raising the material s temperature as in molding or extrusion Ratio between the two give a range of properties between a flexible foam some crosslinking to a rigid urethane high degree of crosslinking Foams are produced by chemical blowing agents Catalyst are used to initiate reaction RIM process is used to produce fenders and bumper covers Polyurethane Chemistry Figure 87 Basic reaction to form polyurethanes indicating f39 i ll the flexibility possible through H 0 R 0 H C N R39 N C different choices of the sub r A diisocyanate stituent groups R and R39 39 ii til i 0 R 0C N R39 N C A polyurethane Note R is usually a multifunctionalpolyether or polyester but can also be a small organic group R39 is usually a large aromatic group Polyurethane Processing Polyurethane can be processed by gtCasting painting foaming gtReaction Injection Molding RIM mcm mmn hm mpamm A campnnmi a Structural RIM Fiber preform is placed into mold Polyol and Isocyanate liquids are injected into a closed mold and reacted to form a urethane Suns Mnlur Suvmyiinz 7 7 Malawi Fishquot m1 mammlion pump Ogtmm mCUlt N mltgtum OOUOltltmNm ELVAX Elvax resins are copolymers of ethylene and vinyl acetate available from Dupont Commercial grades range in vinyl acetate content from 9 to 40 and in melt index from 03 to 500 dgmin Elvax is inherently flexible resilient tough and show excellent resistance to ozone and environmental stress cracking Depending on the needs Elvax can be opigmented ofilled ofoamed ocrosslinked ELVAX Flexibility resilience toughness and transparency increase with increasing vinyl acetate content Flexibility inherent in their molecular structure excels in critical applications requiring repeated flexing over a broad temperature range okesilience excellent recovery under repeated instantaneous load Toughness Tensile impact values show exceptional toughness at low 20 CI4 F as well as moderate 23 C73 F temperatures iii dugL 335 H k lf l HEW WEIR ML m m m m m quotJ E E l in an a 3 a m l 4m I ED 5 g F u mmmmmmm mmmmmm mm 335 tnIt EE BEE emu Ems iniu i ailg my mm m m mm a a a y R EMU ia wining H 3I JIM l lh l F3535 1 m Typical Applications Flexible hose and tubing Cap liners Footwear components Wire and cable compounding Toys and athletic goods Bearing pads FIGURE Twodimensional representations of a vacancy and a self interstitial Adapted from W G Moffatt G W Pearsall and J Wulff The Structure and Properties of Materials Vol 1 Structure p 77 Copyright 1964 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc Schematic representations of cation and anion vacancies and a cation interstitial From W G Moffatt G W Pearsall and J Wulff The Structure and Properties of Materials Vol 1 Structure p 78 Copyright 1964 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc TWT a lmbtt can FtpUM Schematic diagram showing Frenkel and Schottky defects in ionic solids From W G Moffatt G W Pearsall and J Wulff The Structure and Properties of Materials Vol 1 Structure p 78 Copyright 1964 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc Interstitial impurity atom Ft SURE Two dimensional schematic representations of substitutional and interstitial impurity atoms Adapted from W G Moffatt G W Pearsall and J Wulff The Structure and Properties of Materials Vol 1 Structure p 77 Copyright 1964 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc gt393 939 i J 3 i J Interstitial impurity atom 24 Substitutional impurity ions t J J J J l J J J J 39 FIGURE 56 Schematic representations of interstitial anionisubstitutional and cationisubstitutional impurity atoms in an ionic compound Adapted from W G Moffatt G W Pearsall and J Wulff The Structure and Properties of Materials Vol 1 Structure p 78 Copyright 1964 by John Wiley amp Sons New York Reprinted by permission of John Wiley amp Sons Inc Edge dwsiocauon Mme Burgers vector b FIGURE 57 The atom positions around an edge dislocation extra halfiplane of atoms shown in perspective Adapted from A G Guy Essentials of Materials Science McGrawiHill Book Company New York 1976 p 153 Edge dwsiocauon Mme Burgers vector b FIGURE 57 The atom positions around an edge dislocation extra halfiplane of atoms shown in perspective Adapted from A G Guy Essentials of Materials Science McGrawiHill Book Company New York 1976 p 153 FIGURE 58 a A screw dislocation within a crystal b The screw dislocation in a as Viewed from above The dislocation line extends along line AB Atom positions above the slip plane are designated by open circles those below by solid circles Figure b from W T Read Jr Dislocations in Crystals McGrawiHill Book Company New York 1953 AEEECEEEIISE DHCCCCCCECC Q iiiiiiiiii Iiiiiiiiiiim Iiiiiiiiiiii kasdxss tntnmeeeuk Wtfaewbnmonamhae hhgbrkomoo aohxeco 0 ie eettdJmo 5 11r1htt1dwr xeexs 09 mnmmvin awaie ene 0 BY 9e csP ch th1 draW 1 oh P 0 5100 eet m u H hitd P lwr e e eCw 5cm nhmPhbes ubemlxmaR we Smma WmsmwdwpmmmeGmeN U e Kb oednem shv TS m mmwmmmdmmmnmwmmmmmmw F rloareeehnei coarW Ga P sehtvosAng ltc acP em awooSo u e mcsmc m 55 um pmpmm dmdomMo r mba mmmo mm g C em P PF c D FIGURE 510 A transmission electron micrograph of a titanium alloy in which the dark lines are dislocations 51450gtlt Courtesy of M R Plichta Michigan Technological University Angie of misangnrnent FIGURE 511 Schematic diagram showing low and highiangle grain boundaries and the adjacent atom positions ngnrangie grain boundary ngie grain boundary Angie of misangnrnent FIGURE 5 12 Demonstration of how a tilt boundary having an angle of misorientation 9 results from an alignment of edge dislocations Twm mane boundary FIGURE 513 Schematic diagram showing a twin plane or boundary and the adjacent atom positions dark circles a Microscope b Polished and etched surface FIGURE 515 a Polished and etched grains as they might appear when Viewed with an optical microscope b Section taken through these grains showing how the etching characteristics and resulting surface texture vary from grain to grain because of orientation 6 Photomicrograph of a polycrystalline brass specimen gtlt Photomicrograph courtesy of J E Burke General Electric Co We did 333quot mm myquot mundmsavwrdaw 39 39 m x mmmmpmmymc Sn amc BMYJMNamndBmmu m msmaamwsmqmnncy CLAS Manage 6 56m 3366 wad f s HATERMLS 0LyCR5ML MGM GEL8714 CZocH RALSKI SIN E 6275744 Hm am am jrow f m s C3901 3 NHAT ls TH E NVICLEATIN J V IENT wqx 51mg CRjSTALS erE IMPQRTANT2 IMPmmzegi 1017210quot3 mp9ng moms a an modem 01 Cubicmev er may Sinr Cidj cchQ my Offer acme 0 Add IWI war 539 501MJC J AolcP 601M 501M gtV jgjgmm No new 50W 5 x ngg m39 am SONW t d ww39 W 2nd Hmm 5 695 dew 40 e gubgapm39m Lahrs Ha K1416 a follow r U Abme 913a adrorx Diszwce CHEMVic rod ltilg I 7 5 Mew plwage L2 Cmng 9M0uml Ma 46 ba 6W6 139 le dKszfIACE 1 rkmw MAMEW L6 Elecm mamaZ I L4 Vowma Nair Um Woe a mwce A Wadng w Wm 6mm 90 4 WWW KMu f My 5 Mam W hmg 7 4 2 W W De ects zmm VOtCmvm cg 2 WM 14144 SIAMw k 5 Ch 01 J D s gmmz 7X50 Cahb39w m s s FVaxt a i a fcah39o n Mam2s an r5 6 x an Mfers w AZ FM MCQ WOW tr mmrj Mr N Mtg 0mm 4 Cahmwcc ampvzackam 9142ng 4 jam1 a dzjacj Vaccwcj Hamid an M 2 W M 9 QW Hm Wigwa Kz 801brvxm J 56mm 5mm devices T9 me w ae fw6quot EMA644 4 GHQ Ari Allaj lt2 M 612AM39 x100 DYG Cgmo 04 i AM 39 Ml39m2 DRS OCurCO39M 11 A f OWIia Wsm airax E0136 Disloca cm a W smaJ c 074 M1 Lac727 Dianne a pHam 50mg 4amp2 2332 Q Wite YWMOL M a 035 73i foca1 1 o39m We 0 0 o 0 J 0 6 a 0 o 0 7 O U Cowse locah ged O o O O dquotsorm4 0 0 CD 0 a o 0 0 I 1 fastm 0 one M br 33 shear w cams9 6945th hacec Grow C 141e oasloCah K Screw 0M9 panama Ch SEM provides topographical and elemental information at magni cations of 10x to 100000x with virtually unlimited depth of eld Applications include Materials evaluation Grain size Surface roughness Porosity Particle size distributions Material homogeneity Intermetallic distribution and diffusion Failure analysis Contamination location Mechanical damage assessment Electrostatic discharge effects Microcrack location Quality Control screening quotGoodquot to quotbadquot sample comparison Film and coating thickness determination Dimension veri cation Gate width measurement Mil Std screening Principle of Operation A nely focused electron beam scanned across the surface of the sample generates secondary electronsbackscattered electrons and characteristic Xrays These signals are collected by detectors to form images of the sample displayed on a cathode ray tube screen Secondary Electron Imaging shows the topography of surface features a few nm across Films and stains as thin as 20 nm produce adequatecontrast images Materials are Viewed at useful magni cations up t0100000X without the need for extensive sample preparation and without damaging the sample Data Output is generated in real time on the CRT monitor Hard copies are photographed from this high resolution 2000 line pairs display onto Polaroid film withnegatives available for later production of multiple copies Transmission Electron Microscope TEM TEMs are patterned after Transmission Light Microscopes and will yield similar information Morphology The size shape and arrangement of the particles which make up the specimen as well as their relationship to each other on the scale of atomic diameters Crystallographic Information The arrangement of atoms in the specimen and their degree of order detection of atomicscale defects in areas a few nanometers in diameter Compositional Information if so equipped The elements and compounds the sample is composed of and their relative ratios in areas a few nanometers in diameter A TEM works much like a slide projector A projector shines a beam of light through transmits the slide as the light passes through it is affected by the structures and objects on the slide These effects result in only certain parts of the light beam being transmitted through certain parts of the slide This transmitted beam is then projected onto the Viewing screen forming an enlarged image of the slide TEMs work the same way except that they shine a beam of electrons like the light through the specimenlike the slide Whatever part is transmitted is projected onto a phosphor screen for the user to see A more technical explanation of a typical TEMs workings is as follows refer to the diagram below V1 rtus1 Souroe F139rst Condenser Lens Incident e 39 Beam f aoksoattered e Iiirays Esthodslumlnesoenoe is I As 13 M 562de 6 7 W7 i 7 WWW Seoond Condenser Lens Condenser Aperture lllll EEI II Ssmote Dojeottve Lens fill TLI39ll k your a l l Seteoted res aperture q Irrelsstrtelo39 attered e 39 Flashaha oust t rud e unseattered 39 F1 rst lntermedtate Lens Transmitted Electrons Seco nd Inte r medtate Le n3 Frojeotor Lens Metn Soreen phosphor
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