材料科学与工程专业英语（第三版）全册课件.ppt

材料科学与工程专业英语;课程简介;主要内容和课时安排;Part 1 Introduction to materials science and engineering;Unit 1 Physical and chemical properties of materials;In general, some of the more important physical and chemical properties from an engineering material standpoint include phase transformation temperatures, density, specific gravity, thermal conductivity, linear coefficient of thermal expansion, electrical conductivity and resistivity, magnetic permeability, and corrosion resistance, and so on.;Phase Transformation Temperatures;Melting point: the phase transition temperature where a solid changes to a liquid Boiling point: the temperature at which the vapor pressure of a liquid equals 1 atm (101.3 kPa) ; Some materials, such as many polymers, do not go simply from a solid to a liquid with increasing temperature. Instead, at some temperature below the melting point, they start to lose their crystalline structure but the molecules remain linked in chains, which results in a soft and pliable material. The temperature at which a solid, glassy material begins to soften and flow is called the glass transition temperature.;Density;Mass (m) is a fundamental measure of the amount of matter. Weight (w) is a measure of the force exerted by a mass and this force is produced by the acceleration of gravity. Therefore, on the surface of earth, the mass of an object is determined by dividing the weight of an object by 9.8 m/s2 (the acceleration of gravity on the surface of the earth).;The density (r) of a material depends on the phase it is in and the temperature (the density of liquids and gases is very temperature dependent). Water in the liquid state has a density of 1 g/cm3 at 4 ℃. Ice has a density of 0.917 1 g/cm3 at 0 ℃, and it should be noted that this decrease in density for the solid phase is unusual. For almost all other substances, the density of the solid phase is greater than that of the liquid phase. Water vapor has a density of 0.051 g/cm3. ;Specific Gravity;Similarly, an obje