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材料科学与工程(专外)Materials Science(材料科学) : involves investigating the relationships that exist between the structures and properties of materials (研究结构与性能之间的关系) Materials Engineering(材料工程): designing or engineering the structure of a material to produce a prede...

材料科学与工程(专外)
Materials Science(材料科学) : involves investigating the relationships that exist between the structures and properties of materials (研究结构与性能之间的关系) Materials Engineering(材料工程): designing or engineering the structure of a material to produce a predetermined set of properties, based on these structure-property correlations. (设计材料结构以产生预定的性能) Macroscopic(宏观) Microscopic(微观) Structure (结构) Property (性能): mechanical (机械性), electrical(电性), thermal(热性), magnetic(磁性), optical(光学性), and deteriorative(失效性) Processing and Performance(加工和性能) Classification of Materials(材料的分类): Basic: metals, ceramics, polymers Engineering materials: composites, semiconductors, biomaterials Basic Engineering materials 2.2 Basic concepts (基本概念) Crystal (晶体) It is solid. The arrangement of atoms in the crystal is periodic. In crystalline structure, the atoms display both short-range and long-range order(原子显示短程和长程有序). (metals, many ceramics, and even some polymers). Characteristic of Crystals晶体的特性 1. Geometrical shape几何形状 2. Fixed melting point and boiling point固定的熔点和沸点 3. Anisotropy (各向异性):质点在晶格各个方向排列的距离不同而形成 Lattice(点阵,晶格) An infinite array of points in space, in which each point has identical surroundings to all others (晶体点阵是晶体粒子所在位置的点在空间的排列 ). A three dimensional array of points coinciding with atom positions (or atomic sphere center). 一个三维数组与原子的位置(或原子球体中心)相吻合点。 Crystal Structure(晶体结构) It can be described by associating each lattice point with a group of atoms. 晶体结构=空间点阵+结构基元(原子,分子或集团) 2.3 Unit cells (单胞) Atomic hard sphere model. 原子硬球模型 Unit cells (单胞):The smallest component of crystal, which when stacked together with pure translational repetition reproduces the whole crystal (晶格中最小的结构重复单位) Unit Cell Dimensions (单胞参数) a, b and c are the unit cell edge lengths. α, β, and γ, are the angles α between b and c β between c and a γ between a and b 2.4 Crystal Structures (晶体结构) Three simple crystal structures are:   Face-centered cubic (面心立方)--FCC   Body-centered cubic(体心立方)--BCC Hexagonal-close-packed(六方密堆)--HCP FCC crystal structure has a unit cell of cubic geometry, with atoms located at each of the corners and centers of all the cube face. 除8个顶点外,每个面心上有一个阵点. a=b=c, α=β=γ=90o eg: Cu, Al, Au, Ag For FCC structure, a total of four atoms are assigned to a given unit cell (对FCC结构来说,每个单胞有4个完整的原子) Corner and face positions are really equivalent (顶角和面心的位置是完全相等的) The relationship between cube edge length a and the atomic radius R : Solution: The length of a face diagonal 4R,The cell edge length a For FCC, it is a cube. So, there has a right triangle on the face: a2+a2=(4R)2 Unit cell volume of FCC VC is: Coordination number (配位数) For each atom, coordination number is the number of nearest-neighbor or touching atoms. 对于每一个原子,配位数是近邻或触摸原子的数目。 The face atom , has four corner nearest-neighbor , four face atoms from behind , and other four equivalent face atoms from the front. Coordination number=4+ 4 + 4 Atomic packing factor (APF) (原子堆积系数) volume of atoms in a unit cell---原子在晶胞体积 total unit cell volume--总晶胞体积 For FCC structure, APF=0.74 Solution: BCC crystal structure has a unit cell of cubic geometry, with atoms located at eight corners and a single atom at cube center. 除8个顶点外,体心上还有一个阵点. a=b=c, α=β=γ=90o eg: Cr, a-Fe,W, Unit cell length a and atomic radius R are related as: Each BCC unit has 2 atoms: single center atom + one atom from the eight corner. 8x1/8+1x1=2 Corner and center atom positions are equivalent. 角和中心原子的位置等价的。 The coordination number is 8. Atomic packing factor is 0.68= 31/2*π/8 HCP: The top and bottom faces of the unit cell consist of six atoms that form regular hexagons and surround a single atom in the center. Another plane provides three additional atoms to the unit cell. a=b≠c,a=(=90o, (=120o eg:Co Cd Mg Zn Ti Unit cell length a and atomic radius R are related as: Each HCP unit has 6 atoms: (1/6) ×12+(1/2) × 2+3 Atomic edge length c=1.633a (ideal value). →c=(2*61/2a)/3 The coordination number is 12. Atomic packing factor is 0.74. 2.5 Density Computations- Metals (金属的密度计算) ρ:Theoretical density of a metallic solid. n: number of atoms associated with each unit cell.-- 每个晶胞的原子数 A: Atomic weight.-- 原子量 VC: Volume of the unit cell.-- 晶胞体积 VA: Avogadro’s number (6.02x1023 atoms/mol) Example: To calculate the theoretical density of Cu Known parameters: Atomic radius: 0.128nm, →R= 0.128nm FCC crystal structure, :→ Atomic weight A=63.5g/mol. n=4 Solution: 2.6 Ceramic Crystal Structures (陶瓷的晶体结构) 2.7 Density Computations-Ceramics (陶瓷的密度计算) 1 Closest Packing Methods ABAB Hexagonal Closest Packing (HCP) (六方紧密堆积) ABCABC Faced Closest Packing (FCP) (面心立方紧密堆积) 2.The coordination numbers and geometries for various cation-anion radius ratio 协调各种阴阳离子半径比的数字和几何 3.Typical Ceramic Crystal Structure典型的陶瓷的晶体结构 4.Covalent Structures 2.6 Ceramic Crystal Structures 2.6.1 Cation(阳离子)and Anion(阴离子) The metallic ions, or cations,are positively charged,because they have given up their valence electrons to the nonmetallic ions,or anions, which are negatively charged. Two characteristics of the component ions In crystalline ceramic materials Cation and Anion influence the crystal structure: the magnitude of the electrical charge on each of the component ions, and the relative sizes of the cations and anions. 金属离子或阳离子,带正电荷,因为他们已放弃其价非金属离子或阴离子,带负电荷的电子。组件离子的两个特征 在晶陶瓷材料的阳离子和阴离子的影响的晶体结构:每个组件的离子电荷的大小,和阳离子和阴离子的相对大小。 2.6.2 The coordination numbers and geometries for various cation-anion radius ratio 2.6.3 Ionic Ceramic Crystal Structure AB type crystal structures AB2 type crystal structures ABO3 type crystal structures A2B3 type crystal structures AB type crystal structures: 1.Sodium Chloride structure (Rock salt structure) (氯化钠结构,食盐结构) coordination number = 6 Structure: FCC, Cl- ions at FCC positions; Na+ at the four octahedral sites. Eg: magnesium oxide (MgO), calcium oxide (CaO), iron oxide (FeO 2.Cesium Chloride Structure (氯化铯结构) (1) Coordination number Coordination number = 8 (2) Structure Simple cubic简立方, Cs+ fill cubic interstitial sites by the Cl (3) Other compounds CsBr, CsI, TiCl, NH4Cl 3.Zinc Blende Structure (ZnS)(硫化锌结构) ●S Coordination number coordination number = 4 Structure FCC, Zn cations at the normal lattice points, S anions at half of the tetrahedral sites. other compounds GaAs, Ⅲ-Ⅴ semiconductors AB2 type crystal structures Fluorite Structure(CaF2) (1) coordination number coordination number = 8 (2) other compounds ZrO2, UO2,ThO2, CeO2 ABO3 type crystal structures a) unit cell structure (b) Ca cation coordination number 12 Perovskite Structure钙钛矿结构(CaTiO3) · Structure Ca cations occupy the cube corner; 钙离子占据多维数据集的角落; Ti cations occupy cube center, 钛离子占据中心线, O anions occupy the face centers of the O阴离子占据了面部中心 Perovskite unit cell. 钙钛矿单元细胞 · Other compounds BaTiO3 (capacitors for electronic applications ) A2B3 type crystal structures Corundum Structure刚玉结构(α-Al2O3 alpha alumina) (a) crystal structure (b) close-packed model · (1) Structure Oxygen anions pack in a hexagonal arrangement, 氧负离子包在一个六角形的安排, aluminum cations occupy some of the available positions. 铝离子占据了一些可用的 · (2) application(2)应用 most widely ceramic material : 最广泛的陶瓷材料: spark plugs, refractories, electronic packaging substrates and abrasives. 火花塞,耐火材料,电子产品包装基材和磨料。 2.6.4 Covalent Structures (1) Diamond Cubic Structure (金刚石结构) · Diamond Cubic Structure is a variant of the zinc blende. · Carbons occupy both Zn and S positions. · Carbon (in its diamond form) are bonded by four covalent bonds and produce a tetrahedron. · Coordination · The coordination number for each silicon atom is only four, because of the nature of the covalent bonding. · other matters · ⅣA (silicon, germanium etc) (2) Graphite Structure(石墨结构) · The graphite structure is composed of layers of the hexagonally arranged carbon atoms. · 六角排列的碳原子层石墨结构组成。 · Within the layers, each carbon atom is bonded to three coplanar neighbor atoms by strong covalent bonds. · 每个碳原子层内,保税三个共面的近邻原子的强共价键。 · The fourth bonding electron participates in a weak Vander Waals type of bond between the layers. 第四个价电子参与弱范德华层之间的粘结类型。 2.7 Density computation -ceramic计算陶瓷密度 It is possible to compute the theoretical density of a crystalline ceramic material它是可以计算的结晶陶瓷材料的理论密度 From unit cell data in a manner similar to metals. 从晶胞数据的方式类似金属 General density Equation一般密度方程 · ρ:theoretical density of a crystalline ceramic material. 结晶陶瓷材料的理论密度 · n: number of atoms associated with each unit cell. 每个晶胞的原子数 · ∑Ac: the sum of the atomic weights of all cations in the formula unit. 公式中的单位所有阳离子的原子量的总和 · ∑AA: the sum of the atomic weights of all anions in the formula unit. 公式中的单位所有阴离子的原子量的总和。 · V: volume of the unit cell. 晶胞的体积 · NA: Avogadro’s number (6.02×1023 atoms/mol) Problem: · On the basis of crystal structure ,calculate the theoretical density for sodium chloride. How does this compare with its measured density? 在晶体结构的基础上,计算氯化钠的理论密度。这是如何比较其测得的密度? · rNa+ = 0.102nm rCl- = 0.181nm Solution: Both sodium and chloride ions form FCC lattices. The number of NaCl units per unit cell is 4. · ∑Ac=ANa =22.99g/mol · ∑Aa:= ACl =35.45g/mol · Since the unit cell is cubic, V=a3, a being the unit cell edge length. For the face of the cubic unit cell shown below a=2rNa+ +2rCl- · V=a3=(2rNa+ +2rCl-)3 This compares very favorably with the experimental value of 2.16g/cm3 Example 2: Illustrating a Crystal structure and Calculating Density说明晶体结构和计算密度 Show that MgO has the sodium chloride crystal structure氯化钠晶体结构and calculate the density of MgO rMg+2 =0.066nm ro-2 =0.132nm the atomic mass of Mg =24.312g/mol, the atomic mass of Oxygen =16g/mol rMg+2/ ro-2=0.066/0.132=0.5 since 0.414<0.50<0.732, the coordination number for each is 6,and the sodium chloride structure is possible. The ions touch along the edge of the cube, so a0=2 rMg+2+2 ro-2= =2×0.066+2×0.132=0.396nm=3.96×10-8cm ρ =(4Mg+2)(24.312)+(4O-2)(16)/(3.96x10-8cm)3(6.02x1023) =4.31g/cm3 Problem: · Would you expect CsBr to have the sodium chloride (NaCl), zinc blende(ZnS), fluorite(CaF2), or cesium chloride(CsCl) structure ? · rCs+=0.167nm, rBr-=0.196nm · Based on your answer, determine · (a) the lattice parameter; · (b) the density; and (c) the packing factor Solution: · Cesium chloride · (a) 0.41916nm · (b) 4.8g/cm3 (c) 0.693 2.8 Polymer Structures (聚合物结构) 2.8.1 Introduction · Hydrocarbons(烃) Hydrocarbons are composed of hydrogen and carbon. The intramolecular bonds are covalent.共价键连接 · Types of covalent bond in hydrocarbons: Single covalent bond(单键) Example: Saturated hydrocarbons (饱和烃); Alkane/ paraffin(烷烃) Double covalent bond (双键) Example:Alkene/olefin(烯烃) Triple covalent bond (三键) Example: Alkyne/Alkine(炔烃) Covalent Bond 1)Saturated (饱和) All bonds are single ones and no new atoms may be joined without the removal of others that are already bonded. paraffin family石蜡家庭: methane (CH4), ethane (C2H6), propane (C3H8) etc. 2)Unsaturated(不饱和) Molecules that have double and triple covalent bonds are termed unsaturated 有双重和三重共价键的分子,被称为不饱和 Alkene family烯烃家庭: ethene (C2H4), propene (C3H6) etc. Alkyne family炔家庭: ethyne (C2H2), propyne (C3H4) etc. 2.8.2 Naming of Polymer (聚合物命名) · Naming of Monomer · Postfix of some organic compounds -ane Alkane( 烷烃) -ene Alkene (烯烃) -yne Alkyne (炔烃) -ol Alcohols(醇类) -ether Ether (醚类) -acid Acid (酸类) -ate Ester (酯类) · Prefix of some organic compounds Methyl-,甲基; Ethyl-,乙基; propyl-,丙基; Butyl-, 丁基; pentyl-,戊基; hexyl-, 己基; Heptyl-, 庚基; octyl-, 辛基; nonyl-,壬基; Decyl-, 癸基 · Naming of Polymer Poly+name of monomer PE聚乙烯 PVC聚氯乙烯 PTFE聚四氟乙烯 PP聚丙烯 PS聚苯乙烯 PMMA聚甲基丙烯酸甲脂 Bakelite酚醛树脂 尼龙66 PET聚对苯二甲酸乙二酯 聚碳酸酯 Mer (单体单元,结构单元): Structural entities, originates from the Greek word meros, which means part. Polymer: poly: 聚,多聚;Polymer was coined to mean many mers. A compound consisting of long-chain molecules, each molecule made up of repeating units connected together long-chain molecules:长链分子 chain链 repeating units: 重复单元 · Macromolecules (polymer) These molecules are in the form of long and flexible chains, the backbone of which is a string of carbon atoms. · Monomer (单体) A stable molecule from which a polymer is synthesized, such as ethylene. 2.8.4 The Characteristics of Polymer General Characteristics(一般性质)  Extremely light (质轻) Insulation(绝缘) High Elasticity (高弹性) Easy molding(易加工) High Toughness (高韧性) Transparency(透明) Chemical resistance (化学惰性) Colorability (易着色) Origin of the Characteristics(特性根源) ① High molecular weight, molecular weight distribution:104---107, Mn, Mw, (高分子量,分子量分布) ② Polymer chain has various morphologies; (高分子链的多种形态) ③ Intermolecular: mainly Vander Waals bonding, partially chemical bonding Intramolecular: covalent bonding. (分子链间力:范氏力为主,部分化学键;分子内:共价键) ④ Multi levels of structure(结构的多层次性 ) 2.8.5 The Family of Polymer(聚合物家族) Polymer :Plastics(塑料) Rubber(橡胶) Fiber (纤维) Coating(涂料) Adhesive(胶粘剂) Elastomer(弹性体)、 Functional Polymer(功能高分子) 2.8.6 Polymer Structure 1)Polymer ChainStructure(分子链结构) (1)Short-range Structure(近程结构):Compositon(组成),Constitution(构造),Sequence structure (序列结构),Configuration(构型) (2)Long-distance Structure(远程结构):Size( 高分子的大小), Molecular weight and distribution(分子量及分布) 2)Condensed Structure(凝聚态结构) Crystalline (晶态) Non—crystalline非晶态(Amorphous/无定形) Orientatim (取向态) Liquid crystals(液晶态) Texture(织态) Compositon (组成) Backbone(主链) Side-branch chain(支链) End group (端基) Side group(侧基) Architechture/Constitution (构造) (1) Linear Polymers(线型聚合物) Linear polymers are those in which the mer units are joined together end to end in single chains. These long chains are flexible and may be thought of as a mass of spaghetti (2) Branched Polymers(支化聚合物) Polymers may be synthesized in which side-branch chains are connected to the main ones. (3) Cross-linked Polymers(交联聚合物) Adjacent linear chains are joined one to another at various positions by covalent bonds. (4) Network Polymers(网状聚合物) Trifunctional mer units, having three active covalent bonds, form three-dimensional networks Sequence structure (序列结构) · Homopolymer(均聚物) When all the repeating units along a chain are of the same type, the resulting polymer is called a homopolymer. · Copolymer(共聚物) When the chains may be composed of two or more different mer units, the resulting polymer are termed copolymers. · Random Copolymer(无规共聚物) The two different units are randomly dispersed along the chain in what is termed a random copolymer · Alternating Copolymer (交替共聚物) An alternating copolymer is one in which the two mer units alternate chain positions. · Block Copolymer(嵌段共聚物) A block copolymer is one in which identical mers are clustered in blocks along the chain. · Graft Copolymer(接枝共聚物) A graft copolymer is one in which homopolymer side branches of one type may be grafted to homopolymer main chains that are composed of a different mer. Configuration (构型) Isomerism (异构) same composition, different atomic arrangements成分相同,不同的原子排列 Example: Pentane (戊烷) (3 isomers) Normal Pentane (正戊烷,b.p 36.1℃) Isopentane(异戊烷b.p 28 ℃ ) Neopentane(新戊烷 b.p 9.5℃ ) Stereoisomers(立体异构) · Isotactic (等规/全同) · Syndiotactic (间规/间同) · Atactic (无规) Geometrical Isomers(几何异构/顺反异构) cis (顺式) trans(反式) Size(molecular weight)(分子量) · The characteristics of polymer molecular weight 1)High molecular weight 103-107(高分子量) 2)Polydispersity(多分散性) Macromolecules are synthesized from smaller molecules, not allpolymer chains grow to the same length; this results in a distribution of chain lengths or molecular weights,an average molecular weight is specified. Average molecular weight平均分子量 1) number-average molecular weight数均分子量--- Mn Mi represents the mean (middle) molecular weight of size range i, and xi is the fraction of the total number of chains within the corresponding size range. 2)Weight-average molecular weight质均分子量 It is based on the weight fraction of molecules within the various size ranges Mi is the mean molecular weight within a size range, whereas wi denotes the weight fraction of molecules within the same size interval. 3)Z-average molecular weight Z均分子量 4)Viscosity-average molecular weight粘均分子量 Degree of polymerization n (聚合度) Another way of expressing average chain size of polymer. It represents the average number of mer units in a chain. · Number-average(nn) degree of polymerization m is the mer molecular weight Weight-average(nw) degree of polymerization: EXAMPLE PROBLEM 4.1: Assume that the molecular weight distributions shown in figure are for PVC. For this material, compute (a) the number-average molecular weight; (b) the number-average degree of polymerization; and (c) the weight average molecular weight. Solution: a) b) nn=Mn/m (1) Compute the mer molecular weight of PVC (2) Compute the number-average degree of polymerization of PVC c) The step of computing the weight-average molecular weight is the same as a) Molecular Weight Distribution分子量分布 Polydispersity coefficient(多分散系数):to express dispersing degree. 表达的分散程度。 Condensation polymerization product(缩聚产物) d=2 Radical product(自由基产物) d=3~5 Side-branch d=25~30(PE) Crystallinity结晶 · Polymer crystal(聚合物晶体) The packing of molecular chains so as to produce an ordered atomic array. · Degree of crystallinity(结晶度) %Crystallinity=ρc(ρs-ρa)/ρs(ρc-ρa) ρs :the density of a specimen ρa :the density of the totally amorphous polymer ρc : the density of the perfectly crystalline polymer. Factors effecting degree of crystallinity结晶影响程度的因素 · The chain structure(分子链结构) Chemical regular(化学规整) Stereoisomer regular(立构规整) · The temperature(温度) · The rate of cooling (冷却速度) Polymer crystal shape(聚合物的结晶形态) Single crystals(单晶):Grown from dilute solutions(0.01%~0.1%) Spherulites(球晶): Grown from concentrated solutions or melt Structure models(结构模型) 1)Fringed-micelle model(樱状胶束模型) 2)Chain-folded model (折叠链模型) 2.8.7 Thermoplastic and Thermosetting Polymers · Thermoplastics(热塑性聚合物) Thermoplastics soften when heated (and eventually liquefy) and harden when cooled—processes that are totally reversible and may be repeated. · Thermosetting (热固性聚合物) Thermosetting polymers become permanently hard when heat is applied and do not soften upon subsequent heating. 3.1 Introduction The mechanical behavior of a material reflects the relationship between its response of deformation to an applied load or force. 材料力学行为反映了其应用负载或力的变形响应之间的关系。 Examples of designing materials based on their characteristics: the aluminum alloy from which an airplane wing (机翼) is constructed and the steel in an automobile axle (车轴). Factors to be considered as design of materials: the nature of the applied load and its duration, as well as the environmental conditions材料设计要考虑的因素:应用负载的性质,其持续时间,以及环境条件 Examples: · It is possible for the load to be tensile (拉伸), compressive (压缩), or shear (剪切), and its magnitude may be constant with time or it may fluctuate continuously. · Application time may be only a fraction of a second, or it may extend over a period of many years. · Service temperature may be an important factor. Mechanical properties机械性能 Strength (强度) Hardness (硬度) Ductility (塑性) Stiffness (韧度) The testing techniques of these mechanical properties have been standardized( 标准 excel标准偏差excel标准偏差函数exl标准差函数国标检验抽样标准表免费下载红头文件格式标准下载 化) in order to have consistency
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