2022-11-23
2023-08-28The factors that affect the impregnation effect include: firstly, the impregnation process conditions (such as temperature and pressure), and secondly, the physicochemical properties of the impregnation.Influence of process conditions(1) Temperature (product preheating temperature, impregnation tank temperature, impregnation agent temperature), depending on the impregnation process: 1. The product is preheated too high and is prone to oxidation; The temperature is too low, and when it comes out of the preheating box, it quickly cools down and enters the impregnation tank. When the impregnating agent encounters cold products, its viscosity increases and its fluidity deteriorates, resulting in poor impregnation effect. 2. If the tank temperature is too high, asphalt is prone to oxidation condensation reaction, viscosity will also increase, and flowability will deteriorate; The tank temperature is too low, the fluidity of asphalt is also poor, and the impregnation effect is not ideal.(2)
2023-08-25The so-called carbon materials such as artificial graphite molded products are polycrystalline materials with extremely complex structures, and the basic structure of graphite crystallization has strong anisotropy. Therefore, the macroscopic thermal conductivity of carbon materials, apart from relying on empirical data, is almost unpredictable. The factors that have a significant impact on thermal conductivity include:(1) The differences in the basic properties of the initial raw materials;(2) The manufacturing process - macroscopic anisotropy;(3) Heat treatment temperature - the growth degree of graphite microcrystals;(4) Apparent density, distribution of holes, etc.
2023-08-25(1) Degree of graphitization: As the degree of graphitization of carbon materials increases, their activity towards gases decreases. The higher the final heat treatment temperature of carbon materials, the higher the temperature at which they begin to oxidize, so graphite products have a higher starting oxidation temperature than carbon products.(2) Structural state: Carbon materials with loose and porous surfaces are prone to react with gases. For example, the surface dense pyrolytic graphite treated at 3200 ℃ begins to oxidize in air at a temperature of 850 ℃, while the porous and loose charcoal on the surface begins to burn at 360 ℃.(3) Catalytic effect of impurities: Carbon materials contain impurities that have a significant impact on their gasification reaction, with varying catalytic effects. For example, iron, cobalt, nickel, copper, manganese, etc. are catalysts for the oxidation of carbon materials, while impurities such as boron, titanium, and tungsten have inhibitory effec
2023-08-25Carbon materials are chemically inert in non oxidizing media. Under normal temperature and pressure, no chemical changes will occur. Except for long-term immersion in nitric acid, hydrofluoric acid, or in fluorine, bromine, and other strong oxidizing atmospheres, interlayer compounds will slowly form. It is not corroded by other acids, bases, and salts, and does not interact with any organic compounds. There is no significant oxidation phenomenon of graphite within 450 ℃ in the air. It only reacts with water vapor above 700 ℃ and with CO and CO2 above 900 ℃. The temperature at which graphite produces carbides with certain metal and oxide powders is mostly above 1000 ℃.The chemical reactions of carbon materials can be divided into the following three types:(1) Gasification reaction and high-temperature oxidation reaction;(2) Solid solid reactions with metals, ceramics, etc;(3) Formation reaction of interlayer compounds.
2023-08-24Artificial graphite is not necessarily a good conductor of electricity, but structurally belongs to the so-called polycrystalline graphite. Polycrystalline graphite is a carbon material with good graphitization performance obtained by heating at high temperatures. Carbon materials are generally obtained by treating organic matter in a reducing atmosphere, inert atmosphere, or vacuum. The carbon material obtained by heating below 1000 ℃ is not called carbonized material, but rather considered as an insulator. Only by heating the carbonized material above 1000 ℃ can the specific resistance rapidly decrease and become a good conductor of electricity. The polycrystalline graphite obtained by this method is still a carbon material in a sense, and artificial graphite requires temperature treatment above 2500 ℃ under atmospheric pressure. The change in electrical properties of carbon materials and carbides during simultaneous heating treatment is a very interesting and profound issue.A solid
2023-08-24Testing of graphitized blanks and machined products:(1) The detection of mechanical processing quality mainly involves the detection of dimensional accuracy and surface roughness.(2) Detection of chemical composition analysis, analysis of components and their elements, and analysis of sulfur, phosphorus, barium, nickel, titanium, and other trace elements based on different products.(3) General physical performance measurement, including measurement of bulk density, true density, porosity, pore size distribution, and pore size distribution.(4) The detection of structural analysis mainly includes metallographic microscopy, X-ray diffraction, electron microscopy, and graphitization degree measurement.(5) Mechanical performance testing includes the determination of compressive strength, bending resistance, tensile strength, elastic modulus, and hardness. In addition, there are measurements of friction coefficient and wear amount.(6) Electromagnetic performance testing mainly includes the
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