For more information, visit www.wileyplus.com

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Sections 107 or 108 of United States Copyright 1976. Acting without the prior written permission of the publisher, or authorization by payment of the applicable fee per copy to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, website www.copyright.com . Return instructions and a free return shipping label are available at http://www.wiley.com/go/returnlabel.

NEW/REVISED CONTENT

This is a web-based assessment program that contains questions and problems similar to those in the text; Students can visit the website to find the correct answers to the Concept Check questions in the printed textbook.

ONLINE RESOURCES

The student can use this electronic tool to go through the course material and to assess his/her mastery and understanding of the topics covered in the text. These slides (in both Adobe Acrobat® PDF and PowerPoint® formats) are virtually identical to those provided to a teacher for classroom use.

ACKNOWLEDGMENTS

List six different property classifications of materials that determine their applicability

Cite the four components that are involved in the design, production, and utilization of materials,

Cite three criteria that are important in the materials selection process

HISTORICAL PERSPECTIVE
MATERIALS SCIENCE AND ENGINEERING
WHY STUDY MATERIALS SCIENCE AND ENGINEERING?
CLASSIFICATION OF MATERIALS
Classification of Materials • 7
ADVANCED MATERIALS
MODERN MATERIALS’ NEEDS

Throughout this text we draw attention to the relationships between these four components in terms of the design, manufacture and use of materials. All of the preceding materials - metals, ceramics, polymers, composites and semiconductors - can be used as biomaterials.

Figure 1.2 Three thin-disk specimens of aluminum oxide that have been placed over a printed page in order to demonstrate their differences in light-transmittance characteristics

SUMMARY

QUESTIONS

Select one or more of the following modern items or devices and conduct an Internet search in order

List three items (in addition to those shown in Figure 1.9) made from metals or their alloys. For

List three items (in addition to those shown in Figure 1.10) made from ceramic materials. For each

List three items (in addition to those shown in Figure 1.11) made from polymeric materials. For

Each chemical element is characterized by the number of protons in the nucleus, or the atomic number (Z).2 For an electrically neutral or complete atom, the atomic number is also equal to the number of electrons. The atomic mass (A) of a specific atom can be expressed as the sum of the masses of protons and neutrons inside the nucleus.

INTRODUCTION

Some of the important properties of solid materials depend on geometric atomic arrangements and also the interactions that exist between constituent atoms or molecules. This atomic number varies in integral units from 1 for hydrogen to 92 for uranium, the highest of the natural elements.

FUNDAMENTAL CONCEPTS

The atomic weight of an element corresponds to the weighted average of the atomic masses of the atom's naturally occurring isotopes.3 The atomic mass unit (amu) can be used to calculate atomic weight. In this expression, fiM is the fractional occurrence of isotope i for element M (i.e., the percentage of occurrence divided by 100), and AiM is the atomic weight of the isotope.

ELECTRONS IN ATOMS

During the later part of the nineteenth century it was realized that many phenomena involving electrons in solids could not be explained in terms of classical mechanics. An understanding of the behavior of electrons in atoms and crystalline solids necessarily involves discussion of quantum mechanical concepts.

This quantum number is related to the size of an electron's orbital (or its average distance from the nucleus). Axes of these three orbitals are mutually perpendicular to each other like the axes of an x-y-z coordinate system; therefore, it is convenient to label these orbitals px, py, and pz (see Figure 2.5).

Figure 2.3 Comparison of the (a) Bohr and (b) wave-mechanical atom models in terms of electron distribution.

For example, the energy of a 3d state is greater than that of a 3p, which is greater than that of a 3s. Finally, there can be overlap in energy of a state in one layer with states in an adjacent layer, which is especially true for the d and f states; for example, the energy of a 3d state is generally greater than that of a 4s.

Figure 2.7 Schematic representation of the filled and lowest unfilled energy states for a sodium atom.

Here the elements are arranged, with increasing atomic number, in seven horizontal rows called periods. The elements in Group 0, the rightmost group, are the inert gases, which have filled electron shells and stable electron configurations.

THE PERIODIC TABLE

In addition to chemical behavior, the physical properties of the elements also tend to vary systematically with position in the periodic table. Mechanically, metallic elements exhibit varying degrees of ductility—the ability to be plastically deformed without fracture (eg, the ability to roll into thin sheets).

Figure 2.9 The electronegativity values for the elements.

BONDING FORCES AND ENERGIES

The centers of the two atoms remain separated by the equilibrium distance r0, as shown in Figure 2.10a. For two isolated ions, the attractive energy EA is a function of interatomic distance.

Figure 2.10b plots attractive, repulsive, and net potential energies as a function of interatomic separation for two atoms

PRIMARY INTERATOMIC BONDS

In general, each of these three types of bonds results from the tendency of the atoms to adopt stable electron structures, such as those of the inert gases, by completely filling the outermost electron shell. It is always found in compounds consisting of both metallic and non-metallic elements, elements located at the horizontal ends of the periodic table.

Calculation of attractive and repulsive forces between two ions The atomic radii of K+ and Br− ions are 0.138 and 0.196 nm respectively. What is the repulsive force at the same separation distance. a) From equation 2.5b, the attraction between two ions is FA=dEA.

This orbital mixing is called hybridization, leading to the electron configuration shown in Figure 2.13c;. Many polymeric materials are composed of long chains of carbon atoms that are also linked together by sp3 tetrahedral bonds; these chains form a zigzag structure (Figure 4.1b) due to this 109.5° mutual bond angle.

Figure 2.12 Schematic representation of covalent bonding in a molecule of hydrogen (H 2 ).

They can be thought of as belonging to the metal as a whole or forming a "sea of electrons" or an "electron cloud". The remaining nonvalence electrons and atomic nuclei form what are called ionic nuclei, which have a net positive charge equal to the total metallic bond.

Figure 2.16 Schematic diagram that shows the formation of sp 2 hybrid orbitals in carbon

SECONDARY BONDING OR VAN DER WAALS BONDING

A dipole can be created or induced in an atom or molecule that is normally electrically symmetric—that is, the overall spatial distribution of electrons is symmetric with respect to the positively charged nucleus, as shown in Figure 2.21a. One of these dipoles can in turn produce a shift in the electron distribution of an adjacent molecule or atom, inducing the other to also become a dipole, which is then weakly attracted or bound to the first (Figure 2.21b); this is a type of van der Waals bond.

Figure 2.20 Schematic illustration of van der Waals bonding between two dipoles.

Thus, for solid ice, each water molecule participates in four hydrogen bonds, as shown in the three-dimensional diagram of Figure 2.24a; Here, hydrogen bonds are indicated by dotted lines, and each water molecule has four nearest neighbor molecules. During melting, this structure is partially destroyed, so that the water molecules are packed closer together (Figure 2.24b). At room temperature, the average number of nearest neighbor water molecules has increased to about 4.5; this leads to an increase in density.

Figure 2.24 The arrangement of water (H 2 O) molecules in (a) solid ice and (b) liquid water.

MIXED BONDING

Mixed metallic-ionic bonds are observed for compounds composed of two metals when there is a significant difference between their electronegativities. Calculate the percent ionic character (%IC) of the interatomic bond formed between carbon and hydrogen.

MOLECULES

For example, the bond between titanium and aluminum has little ionic character for the intermetallic compound TiAl3 because the electronegativities of both Al and Ti are the same (1.5; see Figure 2.9). However, a much greater degree of ionic character is present for AuCu3; the electronegativity difference for copper and gold is 0.5.

BONDING TYPE-MATERIAL CLASSIFICATION CORRELATIONS

The percent ionic character (%IC) of a bond between two elements (A and B) depends on their electronegativities (X's) according to equation 2.16. Ceramics – ionic/mixed ionic – covalent Molecular solids – van der Waals Semi-metals – mixed covalent – metallic Intermetallics – mixed metallic – ionic Mixed bond.

List of Symbols

Equation Summary

Important Terms and Concepts

QUESTIONS AND PROBLEMS

Zinc has five naturally occurring isotopes: 48.63%

Based on this graph, determine (i) the equilibrium spacing r0 between the Na+ and Cl− ions, and (ii) the magnitude of the binding energy E0 between the two ions. 2.26 (a) Calculate the %IC of the interatomic bonds for the intermetallic compound Al6Mn. b) Based on this result, what type of interatomic bond would you expect to find in Al6Mn.

FE Which of the following electron configurations is for an inert gas?

It should be noted that the hexagonal symmetry of the close-packed hexagonal crystal structure of magnesium [shown in (c)] is indicated by the diffraction spot pattern that was created. Also, the direction perpendicular to this plane is a [0001] direction. e) Photo of a mag wheel—a lightweight automotive wheel made of magnesium.

WHY STUDY Structures of Metals and Ceramics?

Describe the difference in atomic/molecular structure between crystalline and noncrystalline

Draw unit cells for face-centered cubic, body-centered cubic, and hexagonal close-

Derive the relationships between unit cell edge length and atomic radius for face-centered cubic

Compute the densities for metals having face- centered cubic and body-centered cubic crystal

Sketch/describe unit cells for sodium chloride, cesium chloride, zinc blende, diamond cubic,

Given the chemical formula for a ceramic compound and the ionic radii of its

Given three direction index integers, sketch the direction corresponding to these indices within

Specify the Miller indices for a plane that has been drawn within a unit cell

Describe how face-centered cubic and hexagonal close-packed crystal structures may be generated

Distinguish between single crystals and polycrystalline materials

INTRODUCTION
FUNDAMENTAL CONCEPTS
UNIT CELLS
Metallic Crystal Structures • 51
METALLIC CRYSTAL STRUCTURES
Metallic Crystal Structures • 53
Ceramic Crystal Structures • 57
DENSITY COMPUTATIONS—METALS
CERAMIC CRYSTAL STRUCTURES
Density Computations—Ceramics • 63
DENSITY COMPUTATIONS—CERAMICS
SILICATE CERAMICS
Silicate Ceramics • 65
Silicate Ceramics • 67
CARBON
Crystal Systems • 69 (layers or sheets), sp 2 hybrid orbitals bond each carbon atom to three other adjacent and
POLYMORPHISM AND ALLOTROPY
CRYSTAL SYSTEMS
Crystal Systems • 71
POINT COORDINATES
Point Coordinates • 73 EXAMPLE PROBLEM 3.8
Crystallographic Directions • 75

Both the total atomic and unit cell volumes can be calculated in terms of the atomic radius R. AA= the sum of the atomic weights of all anions in the formula unit VC= the unit cell volume.

Figure 3.1 For the face-centered cubic crystal structure, (a) a hard-sphere unit cell representation, (b) a reduced- reduced-sphere unit cell, and (c) an aggregate of many atoms.

If necessary, these three numbers are multiplied or divided by a common factor to reduce them to the smallest integer values

CRYSTALLOGRAPHIC DIRECTIONS
Crystallographic Planes • 81

Conversion from the three-index system (using the coordinate axes a1–a2–z of Figure 3.22b) to the four-index system as. The first thing we need to do is determine the indices U, V and W for the vector referred to in the three-axis scheme shown in the sketch; this is possible using equations 3.13a to 3.13c.

Figure 3.22 Coordinate axis systems for a hexagonal unit cell: (a) four-axis Miller–Bravais; (b) three-axis.

If the plane passes through the selected origin, either another parallel plane must be constructed within the unit cell by an appropriate translation, or a new origin

Again, the unit cell is the basis with a triaxial coordinate system, as shown in Figure 3.19. If the plane passes through the selected origin, another parallel plane or a new origin must be constructed within the unit cell with an appropriate displacement.

At this point, the crystallographic plane either intersects or parallels each of the three axes. The coordinate for the intersection of the crystallographic plane with each of

The reciprocals of these numbers are taken. A plane that parallels an axis is con- sidered to have an infinite intercept and therefore a zero index

If necessary, these three numbers are changed to the set of smallest integers by multiplication or by division by a common factor. 8

CRYSTALLOGRAPHIC PLANES
Linear and Planar Densities • 87
LINEAR AND PLANAR DENSITIES
CLOSE-PACKED CRYSTAL STRUCTURES
Close-Packed Crystal Structures • 89
Close-Packed Crystal Structures • 91
SINGLE CRYSTALS
POLYCRYSTALLINE MATERIALS
ANISOTROPY
Anisotropy • 93

In the unit cell shown in (b) the intersection locations for this plane are marked. If one of the indices is zero [as with (110)], the plane will be a parallelogram, having two sides coinciding with the edges of opposite unit cells (or the edges of adjacent unit cells) (according to Figure 3.24b) .

Figure 3.24 Representations of a series each of the (a) (001), (b) (110), and (c) (111) crystallographic planes.

Ray Diffraction and Bragg’s Law

X-RAY DIFFRACTION: DETERMINATION OF CRYSTAL STRUCTURES
Noncrystalline Solids • 99
NONCRYSTALLINE SOLIDS
Cobalt (Co) has an HCP crystal structure, an atomic radius of 0.1253 nm, and a c/a ratio of
Which of the cations in Table 3.4 would you pre- dict to form fluorides having the cesium chloride
Calculate the theoretical density of NiO, given that it has the rock salt crystal structure
From the data in Table 3.4, compute the theo- retical density of CaF 2 , which has the fluorite
A hypothetical AX type of ceramic material is known to have a density of 2.10 g/cm 3 and a unit
In terms of bonding, explain why silicate materi- als have relatively low densities
Compute the theoretical density of diamond, given that the C—C distance and bond angle are
Compute the theoretical density of ZnS, given that the Zn—S distance and bond angle are 0.234 nm
Sketch an orthorhombic unit cell, and within that cell indicate locations of the 0 1 2 1 and 13 14 14 point
Using the Molecule Definition Utility found in both
SS For an x-ray diffraction pattern (having all peaks plane-indexed) of a metal that has a unit
FE A hypothetical metal has the BCC crystal structure, a density of 7.24 g/cm 3 , and an atomic
INTRODUCTION
HYDROCARBON MOLECULES
Describe a typical polymer molecule in terms of its chain structure and, in addition, how the
Draw repeat units for polyethylene, poly(vinyl chloride), polytetrafluoroethylene, polypropyl-
Calculate number-average and weight-average molecular weights and degree of polymerization
Name and briefly describe
Cite the differences in behavior and molecular structure for thermoplastic and thermosetting
Briefly describe the crystalline state in polymeric materials
Briefly describe/diagram the spherulitic structure for a semicrystalline polymer

Hydrocarbon Molecules • 117 participate in covalent bonding, whereas every hydrogen atom has only one bonding
The Chemistry of Polymer Molecules • 119
THE CHEMISTRY OF POLYMER MOLECULES
POLYMER MOLECULES
Molecular Weight • 123
MOLECULAR WEIGHT
Molecular Weight • 125 An alternative way of expressing average chain size of a polymer is as the degree of
MOLECULAR SHAPE
Molecular Shape • 127
MOLECULAR STRUCTURE
Molecular Configurations • 129
MOLECULAR CONFIGURATIONS
THERMOPLASTIC AND THERMOSETTING POLYMERS
Copolymers • 133 Thermoplastics soften when heated (and eventually liquefy) and harden when cooled—
COPOLYMERS
POLYMER CRYSTALLINITY
Polymer Crystallinity • 135
Polymer Crystallinity • 137
POLYMER CRYSTALS
Polymer Crystals • 139 electron micrograph in chapter-opening photograph (d) for this chapter and in the
Compute repeat unit molecular weights for the following
The following table lists molecular weight data for a polytetrafluoroethylene material. Compute
Molecular weight data for some polymer are tabulated here. Compute the following
Is it possible to have a poly(vinyl chloride) homopolymer with the following molecular weight
High-density polyethylene may be chlorinated by inducing the random substitution of chlorine
For a linear, freely rotating polymer molecule, the total chain length L depends on the bond length
The density and associated percent crystallinity for two poly(ethylene terephthalate) materials
SS For a specific polymer, given at least two den- sity values and their corresponding percent crys-

One of the most important applications of X-ray diffractometry is to determine crystal structure. Calculate the atomic radius for Mg. Calculate the volume of the unit cell for Co. 3.22.

Figure 3.36 (a) Demonstration of how two waves (labeled 1 and 2) that have the same wavelength λ and remain in phase after a scattering event (waves 1′ and 2′) constructively interfere with one another

WHY STUDY Imperfections in Solids?

INTRODUCTION

The necessity of the existence of vacancies is explained by applying the principles of thermodynamics; essentially, the presence of vacancies increases the entropy (ie randomness) of the crystal. The equilibrium number of vacancies Nυ for a given amount of material (usually per cubic meter) depends on temperature and increases with temperature accordingly.

POINT DEFECTS IN METALS

The simplest of the point defects is a vacancy, or empty lattice site, one that is normally occupied but where an atom is missing (Figure 5.1). For most metals, the fraction of vacancies Nυ/N just below the melting temperature is on the order of 10−4—that is, one lattice site in 10,000 will be empty.

POINT DEFECTS IN CERAMICS

Non-stoichiometry can occur for some ceramic materials in which two wave (or ionic) states exist for one of the ion types. The formation of an Fe3+ ion disrupts the electroneutrality of the crystal by introducing an excess +1 charge, which must be compensated by a defect type.

Figure 5.2 Schematic representations of cation and anion vacancies and a cation interstitial.

Now, plugging this value into equation 5.4 leads to the following value for Ns: Ns=Nexp(−Qs . 2kT). Solvent is the element or component that is present in the largest amount; sometimes, solvent atoms are also called host atoms.

IMPURITIES IN SOLIDS

The addition of impurity atoms to a metal results in the formation of a solid solution and/or a new second phase, depending on the types of impurities, their concentrations and the temperature of the alloy. The current discussion is about the idea of a solid solution; the consideration of the formation of a new phase is postponed to chapter 10.

Consequently, the atomic diameter of an interstitial impurity must be significantly smaller than that of the host atoms. Calculate the radius r of an impurity atom that fits only in a BCC octahedral site in terms of the atomic radius R of the host atom (without introducing lattice strains).

If electroneutrality is to be maintained, at which point defects are possible in NaCl when a Ca2+. Electroneutrality is maintained when a single positive charge is eliminated or another single negative charge is added.

POINT DEFECTS IN POLYMERS

SPECIFICATION OF COMPOSITION

Sometimes it is necessary to switch from one composition scheme to another, for example from weight percent to atomic percent. In addition, we occasionally want to determine the density and atomic weight of a binary alloy given its composition in terms of weight percent or atomic percent.

DISLOCATIONS—LINEAR DEFECTS

In addition, the nature of a dislocation (that is, edge, screw, or mixed) is determined by the relative orientations of the dislocation line and the Burgers vector. At an edge they are perpendicular (Figure 5.9), at a screw they are parallel (Figure 5.10); they are neither perpendicular nor parallel for a mixed dislocation.

As we note in Section 8.3, the permanent deformation of most crystalline materials occurs through the motion of dislocations. One of the most obvious boundaries is the outer surface, along which the crystal structure ends.

INTERFACIAL DEFECTS

In addition, the Burgers vector is an element of the theory that has been developed to explain this type of deformation. Interfacial defects are boundaries that are two-dimensional and usually separate areas of materials that have different crystal structures and/or crystallographic orientations.

Annealing twins can be observed in the photomicrograph of the polycrystalline copper sample shown in Figure 5.19c. The twins correspond to those regions with relatively straight and parallel sides and a different visual contrast than the untwinned regions of the grains within which they Figure 5.14 Demonstration of.

Figure 5.15 Schematic diagram showing a twin plane or boundary and the adjacent atom positions (colored circles).

ATOMIC VIBRATIONS

BULK OR VOLUME DEFECTS

Several types of surface defects, shown schematically in Figure 5.16, include ledges, bends, terraces, vacancies, and individual adatoms (i.e., atoms adsorbed on the surface). Individual atoms are resolved in this micrograph, as well as some of the defects shown in Figure 5.16.

Figure 5.16 Schematic representations of surface defects that are potential adsorption sites for catalysis

BASIC CONCEPTS OF MICROSCOPY

Contrasts in the produced image are due to differences in reflectivity of the different areas of the microstructure. Normally, careful and painstaking surface preparations are required to reveal the important details of the microstructure.

MICROSCOPIC TECHNIQUES

With optical microscopy, light microscopy is used to study the microstructure; Optical and lighting systems are its basic elements. The chemical reactivity of the grains of some single-phase materials depends on the crystallographic orientation.