工学]材料科学基础英文版.pptVIP

Chapter 1 Atomic Structure and Interatomic Bonding 1. Introduction Some of the important properties of solid materials depend on geometrical atomic arrangements. The properties of materials are controllable and can be tailored to the needs of a given application by controlling their structure and composition. We can examine and describe the structure of materials at different levels. Subatomic level: Electronic structure of individual atoms that defines interaction among atoms (interatomic bonding). Atomic level: Arrangement of atoms in materials. Nanostructure: the structure of material at a length-scale of ?100nm. Microstructure: the structure of material at a length-scale of ~10 to 1000nm. Macrostructure: the structure of a material at a macroscopic level where the length-scale is ~?1000,000 nm. Length-scales Angstrom = 1? = 1/10,000,000,000 meter = 10-10 m Nanometer = 10 nm = 1/1,000,000,000 meter = 10-9 m Micrometer = 1μm = 1/1,000,000 meter = 10-6 m Millimeter = 1mm = 1/1,000 meter = 10-3 m Interatomic distance ~ a few ? A human hair is ~ 50 μm Elongated bumps that make up the data track on CD are ~ 0.5 μm wide, minimum 0.83 μm long, and 125 nm high This micrograph, which represents the surface of a gold specimen, was taken with a atomic force microscope (AFM). Individual atoms for this (111) crystallographic surface plane are resolved. Amorphous: lack a long-range ordering of atoms or ions. Crystalline: exhibit periodic arrangements of atoms or ions. The long-range atomic order is in the form of atoms or ions arranged in a three dimensional pattern that repeats over much larger distances (from ~100 nm to up to few cm). Short-range atomic arrangements: the atoms of ions show a particular order only over relatively short distances. 2. Atomic Structure Atomic structure influences how atoms are bonded together. An understanding of this helps categorize material as metals, semiconductors, ceramics, or polymers. Charges: Electrons and protons have negative