材料科学与工程基础英文版第五版课后习题.doc

Homework 11.1 What are materials? List eight commonly encountered engineering materials. Answer1.1: Materials are substances of which something is composed or made. Steels, aluminum alloys, concrete, wood, glass, plastics, ceramics and electronic materials.1.2 What are the main classes of engineering materials? Answer1.2: Metallic, polymeric, ceramic, composite, and electronic materials are the five main classes. 1.3 What are some of the important properties of each of the five main classes of engineering materials? Answer1.3: Metallic Materials many are relatively strong and ductile at room temperature some have good strength at high temperature most have relatively high electrical and thermal conductivities Polymeric Materials generally are poor electrical and thermal conductors most have low to medium strengths most have low densities most are relatively easy to process into final shape some are transparentCeramic Materials generally have high hardness and are mechanically brittle some have useful high temperature strength most have poor electrical and thermal conductivities Composite Materials have a wide range of strength from low to very high some have very high strength-to-weight ratios (e.g. carbon-fiber epoxy materials) some have medium strength and are able to be cast or formed into a variety of sha(e.g. fiberglass-polyester materials) some have useable strengths at very low cost (e.g. wood and concrete) Electronic Materials able to detect, amplify and transmit electrical signals in a complex manner are light weight, compact and energy efficient1.8 What are nanomaterials? What are some proposed advantages of using nanomaterials over their conventional counterparts? Answer1.8: Are defined as materials with a characteristic length scale smaller than 100 nm. The length scale could be particle diameter, grain size in a material, layer thickness in a sensor, etc. These materials have properties different than that at bulk scale or at the molecular scale. These materials have often enhanced properties and characteristics because of their nano-features in comparison to their micro-featured counterparts. The structural, chemical, electronic, and thermal properties (among other characteristics) are often enhanced at the nano-scale.Homework 2 Chapter 3, Problem 4What are the three most common metal crystal structures? List five metals that have each of these crystal structures.Chapter 3, Solution 4The three most common crystal structures found in metals are: body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP). Examples of metals having these structures include the following.BCC: vanadium, tungsten, niobium, and chromium.FCC:copper, aluminum, lead, nickel, and silver.HCP:magnesium, zinc, beryllium, and cadmium.Chapter 3, Problem 5For a BCC unit cell, (a) how many atoms are there inside the unit cell, (b) what is the coordination number for the atoms, (c) what is the relationship between the length of the side a of the BCC unit cell and the radius of its atoms, and (d) APF = 0.68 or 68%Chapter 3, Solution 5(a) A BCC crystal structure has two atoms in each unit cell. (b) A BCC crystal structure has a coordination number of eight. (c) In a BCC unit cell, one complete atom and two atom eighths touch each other along the cube diagonal. This geometry translates into the relationship Chapter 3, Problem 6For an FCC unit cell, (a) how many atoms are there inside the unit cell, (b) What is the coordination number for the atoms, (c) , and (d) what is the atomic packing factor?Chapter 3, Solution 6(a) Each unit cell of the FCC crystal structure contains four atoms. (b) The FCC crystal structure has a coordination number of twelve. (d) By definition, the atomic packing factor is given as:These volumes, associated with the four-atom FCC unit cell, are andwhere a represents the lattice constant. Substituting ,The atomic packing factor then becomes,Chapter 3, Problem 7For an HCP unit cell (consider the primitive cell), (a) how many atoms are there inside the unit cell, (b) What is the coordination number for the atoms, (c) what is the atomic packing factor, (d) what is the ideal c/a ratio for HCP metals, and (e) repeat a through c considering the “larger” cell.Chapter 3, Solution 7The primitive cell has (a) two atoms/unit cell; (b) The coordination number associated with the HCP crystal structure is twelve. (c)the APF is 0.74 or 74%; (d) The ideal c/a ratio for HCP metals is 1.633; (e) all answers remain the same except for (a) where the new answer is 6.Homework 3Chapter 3, Problem 25Lithium at 20C is BCC and has a lattice constant of 0.35092 nm. Calculate a value for the atomic radius of a lithium atom in nanometers.Chapter 3, Solution 25For the lithium BCC structure, which has a lattice constant of a = 0.35092 nm, the atomic radius is,Chapter 3, Problem 27Palladium is FCC and has an atomic radius of 0.137 nm. Calculate a value for its lattice constant a in nanometers.Chapter 3, Solution 27Letting a represent the FCC unit cell edge length and R the palladium atomic radius, Chapter 3, Problem 31 Draw the following directions in a BCC unit cell and list the position coordinates of the atoms whose centers are intersected by the direction vector:(a) 100(b) 110(c) 111Chapter 3, Solution 31Error! Reference source not found.(a) Position Coordinates:(b) Position Coordinates:(c) Position Coordinates: (0, 0, 0), (1, 0, 0) (0, 0, 0), (1, 1, 0) (0, 0, 0), (1, 1, 1)Chapter 3, Problem 32Draw direction vectors in unit cells for the following cubic directions:(a) (b) (c) (d) Chapter 3, Solution 32yxzx = +1y = -1z = -1x = +1y = -1z = 0(a)(b)Dividing by 2, x = - y = 1 z = -(c)Dividing by 3, x = y = z = 1(d)Chapter 3, Problem 46A cubic plane has the following axial intercepts: . What are the Miller indices of this plane? Cha