What is the material?

1.Introduction to materials

1.1 Classification of materials

1. Natural materials: stone, wood, etc.

2.Produced materials: pottery and various metals

3.Synthetic materials: alloy resin, composite materials and other artificial materials

1.2 Classification of structures Structures can be classified according to size:

1. Subatomic structure: Including electrons in a single atom, their energy interacts with the atomic nucleus

2. Atomic structure (Atomic structurc): related to the organization of atoms, molecules or crystals 3. Nanostructure (Nanostructure): the structure of objects between the molecular and micron scales

4. Microstructure (Microstructurre): Microstructure is the extremely small-scale structure of the material, which is defined as the structure of the surface of the material, as shown by an optical microscope with a magnification of more than 25 times.

5. Macrostructure: Structural elements that can be observed with the naked eye (scale range between a few millimeters and one meter)

2. Material properties (Properties) are the way materials respond to the environment and external forces.

2.1 Physical properties Physical properties are those properties that can be observed without changing the properties of matter. The general properties of a substance, such as color, density, and hardness, are physical properties.

2.2 Chemical properties Properties that describe how a substance transforms into a completely different substance are called chemical properties. Flammability, corrosion resistance, and oxidation resistance are chemical properties. Generally speaking, from the perspective of engineering materials, some of the more important properties include phase change temperature, density, specific gravity, thermal conductivity, thermal expansion linear coefficient, electrical conductivity and resistivity, magnetic permeability efficiency and corrosion resistance, etc.

2.3 Categories of Solid Materials Almost all important properties of solid materials can be divided into six different categories to induce different reactions:

1. Mechanical properties: relate deformation to applied load or force; for example, elastic modulus Strength (stiffness), strength and fracture resistance

2. Electrical properties (Electrical properties): An electric field is applied; typical properties include conductivity and dielectric constant

3. Thermal properties (Thermal properties): Related to material temperature or temperature gradient Related to changes in temperature; examples of thermal properties include thermal expansion and heat capacity

4. Magnetic properties: the response of materials to magnetic fields; common magnetic properties include magnetic susceptibility and magnetization intensity

5. Optical properties: external electromagnetic radiation Or optical radiation; refractive index and reflectivity index are representative optical properties

6. Deteriorative characteristics: related to the chemical reactivity of the material; for example, the corrosion resistance of metals.

2.4 Classification of materials

---------------------------------------------------------------------------------------------------------------Reprinted from Zhihu-Eternal East(知乎-永恒的东风).