tailieunhanh - Structure of Solids

Effects of Structure on Properties Physical properties of metals, ceramics, and polymers, such as ductility, thermal expansion, heat capacity, elastic modulus, electrical conductivity, and dielectric and magnetic properties, are a direct result of the structure and bonding of the atoms and ions in the | PART 1 MATERIALS AND MECHANICAL DESIGN CHAPTER 1 STRUCTURE OF SOLIDS Charles H. Drummond III Department of Materials Science and Engineering Ohio State University Columbus Ohio INTRODUCTION 3 Alloys 13 Effects of Structure on Noncrystalline Metals 13 Properties 3 Atomic Structure 3 CERAMICS 14 Bonding 4 Crystalline Ceramics 14 Simple Structures 4 Noncrystalline Ceramics 14 Crystallography 5 Glass-Ceramics 15 States of Matter 7 Polymorphism 8 POLYMERS 15 Defects 8 COMPOSITES AND COATINGS 15 METALS 12 Fiberglass 15 Structures 12 Coatings 15 INTRODUCTION Effects of Structure on Properties Physical properties of metals ceramics and polymers such as ductility thermal expansion heat capacity elastic modulus electrical conductivity and dielectric and magnetic properties are a direct result of the structure and bonding of the atoms and ions in the material. An understanding of the origin of the differences in these properties is of great engineering importance. In single crystals a physical property such as thermal expansion varies with direction reflecting the crystal structure whereas in polycrystalline and amorphous materials a property does not vary with direction reflecting the average property of the individual crystals or the randomness of the amorphous structure. Most engineering materials are polycrystalline composed of many grains and thus an understanding of the properties requires not only a knowledge of the structure of the single grains but also a knowledge of grain size and orientation grain boundaries and other phases present that is a knowledge of the microstructure of this material. Atomic Structure Atoms consist of electrons protons and neutrons. The central nucleus consists of positively charged protons and electrically neutral neutrons. Negatively charged electrons are in orbits about the nucleus in different energy