Podcast Beta
Questions and Answers
The compositions of materials include ______ compositions and mineral compositions.
chemical
The ______ composition refers to the chemical constituents.
chemical
With the increase of ______ content, the strength, hardness and toughness of carbon steel will change.
carbon
Stainless steel comes into being by adding ______, nickel and other chemical components into steel.
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Many inorganic materials consist of a variety of ______ compositions.
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The ______ compositions are the key factors for the properties of some building materials.
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Cement reveals different characteristics because of different ______.
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The structures of materials can be divided into ______-structure, meso-structure and micro-structure.
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The thick structure above ______ that can be identified with magnifying glass or naked eyes is called as macro-structure.
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The ______ level refers to the macro-structure.
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Atoms, the building block of ______, consist of a nucleus surrounded by a cloud of orbiting electrons.
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At the ______ level, the total material is considered as continuous and homogeneous and average properties are assumed throughout the whole volume of the material body.
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The nucleus consists of positively charged ______ and neutral neutrons, and so has a net positive charge.
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The minimum scale that must be considered is governed by the size of the ______ cell, which is the minimum volume of the material that represents the entire material system.
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Atoms tend to arrange themselves in the most stable patterns possible, which means that they have a tendency to complete or fill their outermost ______ orbits.
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Ionic bonding involves a transfer of an ______, so one atom gains an electron while one atom loses an electron.
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If the properties are the same in all directions, then the material is ______ and the representative cell is a cube.
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A covalent bond involves the sharing of ______ between two atoms.
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The micro-level structure that can be observed by optical microscope is called ______ or sub-microstructure.
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What is mainly studied in this structure are the size, shape and interface of ______ and particles, and the size, shape and distribution of pores and micro-cracks.
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The simplest model of metallic bonding is the ______ of electrons model.
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The material consists of ______ such as aggregates distributed in a matrix such as hydrated cement or bitumen.
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Metal ions have free ______, the metal materials such as iron, steel, aluminum, copper and their alloys have good thermal conductivity and electrical conductivity.
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The strength, hardness, and melting point of atomic crystal are high, such as ______, quartz and silicon carbide.
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The dimensions of the ______ differ considerably, from the wall thickness of a wood cell at 5 × 10 -6 m to the length of a brick at 0.225 m.
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The bonding force in covalent bond is ______.
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The atomic and molecular structures of materials that can be studied by electron microscopy, X- ray diffractometer and other means are called ______.
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An obvious limitation of the ionic bond is that it can only occur between atoms of different ______.
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The material is considered as a composite of different ______, which interact to realize the behavior of the total material.
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If the properties can only be described with reference to ______, the material is anisotropic.
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Study Notes
Materials Composition and Structure
- Materials composition includes chemical composition and mineral composition, which are key factors for the properties of materials.
- Chemical composition refers to the chemical constituents, and varying chemical compositions result in different properties.
- For example, increasing carbon content in carbon steel changes its strength, hardness, and toughness, making it prone to rust, which can be addressed by adding chromium, nickel, and other chemical components to create stainless steel.
Mineral Composition
- Many inorganic materials consist of various mineral compositions, which are key factors for the properties of some building materials (e.g., natural stone, inorganic gel, and other materials).
- Cement exhibits different characteristics due to different clinkers.
Structure of Materials
- The structures of materials can be divided into macro-structure, meso-structure, and micro-structure, which are key factors related to the properties of materials.
Macro-structure
- Macro-structure refers to the thick structure above millimeter that can be identified with a magnifying glass or naked eyes.
- At the engineering level, the total material is considered, and it is normally taken as continuous and homogeneous, with average properties assumed throughout the whole volume of the material body.
- The minimum scale that must be considered is governed by the size of the representative cell, which varies from 10^(-3) m for metals to 0.1 m for concrete and 1 m for masonry.
Meso-structure
- Meso-structure refers to the micro-level structure that can be observed by optical microscope.
- It includes the size, shape, and interface of grains and particles, and the size, shape, and distribution of pores and micro-cracks.
- The material is considered as a composite of different phases, which interact to realize the behavior of the total material.
Microstructure
- Microstructure refers to the atomic and molecular structures of materials that can be studied by electron microscopy, X-ray diffractometer, and other means.
- Atoms consist of a nucleus surrounded by a cloud of orbiting electrons, and the nucleus consists of positively charged protons and neutral neutrons.
Bonding of Atoms
- Atoms tend to arrange themselves in the most stable patterns possible, which means they have a tendency to complete or fill their outermost electron orbits.
- Ionic bonding involves a transfer of an electron, resulting in high strength, hardness, and melting point, but also volatility and medium density.
- Covalent bonding involves the sharing of electrons between two atoms, resulting in strong bonding force, high strength, hardness, melting point, and density.
- Metallic bonding involves sharing electrons, resulting in volatile strength and hardness, high density, and good thermal and electrical conductivity.
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Description
Learn about the chemical and mineral composition of materials and how they affect their properties. Understand how varying compositions result in different properties and characteristics.
