The Compositions of Materials
The compositions of materials include chemical compositions and mineral compositions which are the key factors for the properties of materials.
1. Chemical Composition
The chemical composition refers to the chemical constituents. Various chemical compositions result in different properties. For example, with the increase of carbon content, the strength, hardness and toughness of carbon steel will change; carbon steel is easy to rust, so stainless steel comes into being by adding chromium, nickel and other chemical components into steel\
2. Mineral Composition
Many inorganic non-metallic materials consist of a variety of mineral compositions. Minerals are monomers and compounds with a certain chemical components and structures. The mineral compositions are the key factors for the properties of some building materials (such as natural stone, inorganic gel and other materials). Cement reveals different characteristics because of different clinkers. For example, in Portland cement clinkers, the condensation hardening is fast and the strength is high when the content of tricalcium silicate-the clinker mineral-is high.
Structures and Constructions of Materials
The structures of materials can be divided into macro-structure, meso- structure and micro-structure, which are the key factors related to the properties of materials.
1. Macro-structure
The thick structure above millimeter that can be identified with magnifying glass or naked eyes is called as macro-structure. It can be classified into the following types: (1) Dense Structure Basically, the inner side of the material is non-porous, such as steel,
(2) Porous Structure The inside of this material has macro-pores, such as aerated concrete, foam
(3) Micro-porous Structure The inner side of this material is micro-porous which is formed by mixing plenty of water into the micro-pores, such as common fired brick, and architectural gypsum products.nonferrous metals, glass, plastic and dense natural stone. concrete, foam plastics and artificial light materials.
(4) Fibrous Structure This material has the internal organization with direction, such as wood, bamboo, glass reinforced plastic, and asbestos products
(5) Laminated or Layered Structure This material has composite structure which is layered structure formed
(6) Granular Structure This is a kind of loose granular material, such as sand, gravel, and expanded agglutinated by different sheets or anisotropic sheets pearlite.
2. Meso-structure
The micro-level structure that can be observed by optical microscope is called meso-structure or sub-microstructure. What is mainly studied in this structure are the size, shape and interface of grains and particles, and the size, shape and distribution of pores and micro-cracks. For example, the size and the metallographic structure of metal grains can be analyzed; the thickness of concrete, cement and the porous organization can be distinguished; and the wood fiber of timber, catheter, line, resin and other structures can be observed.
The micro-structure has a great influence on the mechanical properties and durability of materials. The grain refinement can improve the strength. For example, steel is mixed with titanium, vanadium, niobium and other alloying elements which can refine grains and significantly increase intensity.
3. Microstructure
The atomic and molecular structures of materials that can be studied by electron microscopy, X-ray diffractometer and other means are called micro structure. This structure can be divided into crystal and non-crystal.
(1) Crystal The solid whose particles (atoms, molecules or ions) are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions is known as crystal. It is characterised by a fixed geometric shape and anisotropy. The various mechanical properties of crystal materials are related to the arrangement pattern of particles and their bonding force (chemical bond).
Crystal can be divided into the following types by chemical bonds:
1) Atomic Crystal is formed by neutral atoms which are connected with each other by covalent bonds. The bonding force is strong. The strength, hardness, melting point and density of atomic crystal are high, such as diamond, quartz and silicon carbide.
2) Ionic Crystal is formed by cations and anions. The ions are related with each other by electrostatic attraction (Coulomb attraction) which is generally stable. The strength, hardness and melting point are high but volatile; some are soluble and density is medium. There is calcium chloride, gypsum, limestone and so on.
3) Molecular Crystal is formed by molecules which are tied to each other by molecular force (Van der Waals attraction). The bonding force is weak. The strength, hardness and melting point are low; most of them are soluble and the density is low. There is wax and some organic compounds.
4) Metal Crystal is formed by metal cations which are connected with each other by metal bonds (Coulomb attraction). The strength and hardness are volatile and the density is high. Because metal ions have free ions, the metal materials such as iron, steel, aluminum, copper and their alloys have good thermal conductivity and electrical conductivity. Of crystal materials such as asbestos, quartz and talc, only a few ones have one combination bond, and others are complex crystal materials with more than two types of combination bonds.
(2) Non-Crystal
The fuse mass with a certain chemical constituents is cooled so rapidly that the particles cannot be packed in a regular ordered pattern, and thus it is solidified into a solid, known as non-crystal or vitreous body or amorphous body. Non-crystal is characterized by no fixed geometry shape and isotropy. A large number of chemicals cannot be released because of the rapid cooling, so non-crystal materials have chemical instability, easily reacting with other substances. For example, granulated blast furnace slag, volcanic ash and fly ash can react with lime under water for hardening, which are used as building materials. Non-crystal plays the role of adhesive in products of burned clay and some natural rocks.
The compositions of materials include chemical compositions and mineral compositions which are the key factors for the properties of materials.
1. Chemical Composition
The chemical composition refers to the chemical constituents. Various chemical compositions result in different properties. For example, with the increase of carbon content, the strength, hardness and toughness of carbon steel will change; carbon steel is easy to rust, so stainless steel comes into being by adding chromium, nickel and other chemical components into steel\
2. Mineral Composition
Many inorganic non-metallic materials consist of a variety of mineral compositions. Minerals are monomers and compounds with a certain chemical components and structures. The mineral compositions are the key factors for the properties of some building materials (such as natural stone, inorganic gel and other materials). Cement reveals different characteristics because of different clinkers. For example, in Portland cement clinkers, the condensation hardening is fast and the strength is high when the content of tricalcium silicate-the clinker mineral-is high.
Structures and Constructions of Materials
The structures of materials can be divided into macro-structure, meso- structure and micro-structure, which are the key factors related to the properties of materials.
1. Macro-structure
The thick structure above millimeter that can be identified with magnifying glass or naked eyes is called as macro-structure. It can be classified into the following types: (1) Dense Structure Basically, the inner side of the material is non-porous, such as steel,
(2) Porous Structure The inside of this material has macro-pores, such as aerated concrete, foam
(3) Micro-porous Structure The inner side of this material is micro-porous which is formed by mixing plenty of water into the micro-pores, such as common fired brick, and architectural gypsum products.nonferrous metals, glass, plastic and dense natural stone. concrete, foam plastics and artificial light materials.
(4) Fibrous Structure This material has the internal organization with direction, such as wood, bamboo, glass reinforced plastic, and asbestos products
(5) Laminated or Layered Structure This material has composite structure which is layered structure formed
(6) Granular Structure This is a kind of loose granular material, such as sand, gravel, and expanded agglutinated by different sheets or anisotropic sheets pearlite.
2. Meso-structure
The micro-level structure that can be observed by optical microscope is called meso-structure or sub-microstructure. What is mainly studied in this structure are the size, shape and interface of grains and particles, and the size, shape and distribution of pores and micro-cracks. For example, the size and the metallographic structure of metal grains can be analyzed; the thickness of concrete, cement and the porous organization can be distinguished; and the wood fiber of timber, catheter, line, resin and other structures can be observed.
The micro-structure has a great influence on the mechanical properties and durability of materials. The grain refinement can improve the strength. For example, steel is mixed with titanium, vanadium, niobium and other alloying elements which can refine grains and significantly increase intensity.
3. Microstructure
The atomic and molecular structures of materials that can be studied by electron microscopy, X-ray diffractometer and other means are called micro structure. This structure can be divided into crystal and non-crystal.
(1) Crystal The solid whose particles (atoms, molecules or ions) are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions is known as crystal. It is characterised by a fixed geometric shape and anisotropy. The various mechanical properties of crystal materials are related to the arrangement pattern of particles and their bonding force (chemical bond).
Crystal can be divided into the following types by chemical bonds:
1) Atomic Crystal is formed by neutral atoms which are connected with each other by covalent bonds. The bonding force is strong. The strength, hardness, melting point and density of atomic crystal are high, such as diamond, quartz and silicon carbide.
2) Ionic Crystal is formed by cations and anions. The ions are related with each other by electrostatic attraction (Coulomb attraction) which is generally stable. The strength, hardness and melting point are high but volatile; some are soluble and density is medium. There is calcium chloride, gypsum, limestone and so on.
3) Molecular Crystal is formed by molecules which are tied to each other by molecular force (Van der Waals attraction). The bonding force is weak. The strength, hardness and melting point are low; most of them are soluble and the density is low. There is wax and some organic compounds.
4) Metal Crystal is formed by metal cations which are connected with each other by metal bonds (Coulomb attraction). The strength and hardness are volatile and the density is high. Because metal ions have free ions, the metal materials such as iron, steel, aluminum, copper and their alloys have good thermal conductivity and electrical conductivity. Of crystal materials such as asbestos, quartz and talc, only a few ones have one combination bond, and others are complex crystal materials with more than two types of combination bonds.
(2) Non-Crystal
The fuse mass with a certain chemical constituents is cooled so rapidly that the particles cannot be packed in a regular ordered pattern, and thus it is solidified into a solid, known as non-crystal or vitreous body or amorphous body. Non-crystal is characterized by no fixed geometry shape and isotropy. A large number of chemicals cannot be released because of the rapid cooling, so non-crystal materials have chemical instability, easily reacting with other substances. For example, granulated blast furnace slag, volcanic ash and fly ash can react with lime under water for hardening, which are used as building materials. Non-crystal plays the role of adhesive in products of burned clay and some natural rocks.
