The Structure of Crystalline Solids | Chapter 3 - Materials Science & Engineering (10th Edition)

Описание: Chapter 3 of Materials Science & Engineering explores the ordered atomic arrangements that define crystalline materials and how these structures dictate material properties. The chapter begins by distinguishing crystalline from noncrystalline (amorphous) solids, emphasizing long-range order as the defining feature of crystalline materials. Fundamental concepts such as the atomic hard-sphere model, unit cells, and lattices are introduced, showing how repeating structural units describe entire crystals. Metallic crystal structures are detailed with the three most common types: face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP). For each, coordination number, atomic packing factor (APF), and edge length relationships are derived, linking geometry to density and packing efficiency. Students learn how to calculate theoretical density from unit cell parameters and atomic weight, with worked examples for copper and other metals.

The chapter then addresses polymorphism and allotropy, where materials such as iron and carbon can exist in multiple crystal structures depending on temperature and pressure. A case study on tin’s white-to-gray transformation (tin disease) illustrates real-world consequences of allotropy. Crystal systems are classified into seven types—cubic, tetragonal, hexagonal, orthorhombic, rhombohedral, monoclinic, and triclinic—based on lattice parameters and interaxial angles. Crystallographic points, directions, and planes are indexed using Miller indices, with step-by-step procedures for determining [uvw] directions and (hkl) planes. The hexagonal Miller–Bravais four-index scheme is introduced for convenience in hexagonal crystals, while concepts of equivalent directions and families of planes are clarified.

Linear density and planar density calculations demonstrate how atomic packing along directions and planes influences slip and deformation mechanisms. Close-packed structures are examined through stacking sequences: ABAB… for HCP and ABCABC… for FCC. The discussion extends to crystalline versus noncrystalline materials, introducing single crystals, polycrystalline materials, grains, and grain boundaries. Anisotropy and isotropy are defined, highlighting how properties such as modulus and conductivity can vary with crystallographic direction. Finally, the chapter covers x-ray diffraction as the primary experimental method for determining crystal structures, explaining Bragg’s law, interplanar spacing calculations, reflection rules, and diffraction patterns. The chapter concludes with amorphous solids, like glasses and some polymers, which lack long-range order. By the end, students see how crystallography, density, anisotropy, and diffraction form the basis of modern materials characterization and design.

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Materials Science & Engineering Chapter 3 summary, crystalline solids explained, unit cells and lattices, FCC BCC HCP crystal structures, atomic packing factor APF calculations, coordination number in metals, theoretical density of copper example, polymorphism and allotropy iron carbon tin disease, seven crystal systems cubic tetragonal hexagonal, crystallographic directions and Miller indices, Miller–Bravais hexagonal indexing, linear density and planar density calculations, slip systems and close-packed planes, single crystals vs polycrystals, grain boundaries anisotropy isotropy, x-ray diffraction Bragg’s law explained, diffraction patterns powder method, crystalline vs amorphous solids glass polymers