Application status of natural microcrystalline graphite

Natural microcrystalline graphite has the characteristics of high temperature resistance, chemical corrosion resistance, conductivity, heat conduction and self-lubrication and other characteristics. It is widely used in metallurgy, electrical, refractory, battery materials and other fields. The ultra high power graphite electrode detailed information.

• 1 Application in metallurgical field

  Natural microcrystalline graphite is widely used in the field of metallurgy as carburizing agent, heating agent and release agent. Fu Jingchun uses industrial waste and microcrystalline graphite to prepare steel mold casting protective slag. Microcrystalline graphite has been popularized to replace pig iron for carburization in 5 t and 25 t EAFs in Jiangxi steel plant. Yan Hongyan et al. Studied the carburizing effect of microcrystalline graphite raw ore at 1600 ℃ and its effect on the mass fraction of elements such as S, N and O and other elements in steel. The results show that the carburizing effect of microcrystalline graphite is equivalent to that of other carburizing agents, and has little effect on S, N and O in steel. In the electrolytic aluminum industry, before the anode carbon block and steel claw are assembled, it is necessary to spray or dip graphite at a certain height of the steel claw leg to prevent high-temperature phosphorus pig iron from excessively eroding the steel claw leg, so that the phosphorus pig iron ring is easy to separate from the surface of the steel claw leg. In China, the mixture of kerosene and microcrystalline graphite or the mixture of water and microcrystalline graphite is widely used to dip the anode steel claw.

   

• 2 Application in grounding field

  In order to prevent damage caused by lightning attack and ensure personal and property safety, some parts of transmission line towers, substations and high-rise buildings need to be connected to the ground, which is called grounding. Graphite is an ideal grounding material because of its conductivity, thermal conductivity and good chemical stability. Wu Shaopeng et al. prepared conductive concrete by adding an appropriate amount of microcrystalline graphite to asphalt concrete. Some domestic enterprises press microcrystalline graphite into grounding resistance reduction module. Liu Dezhou et al. used microcrystalline stone ink reducing agent to improve grounding resistance. Practice has proved that the method of spreading microcrystalline graphite to reduce the soil resistivity in high resistivity areas such as deserts and arid and rainless mountainous areas has a significant effect on reducing the grounding resistance of the grounding grid.

   

  

• 3 Application in refractory field

  In order to improve the thermal shock resistance and slag erosion resistance of refractories, a certain amount of large flake graphite is usually added in traditional production ingredients. In recent years, with the needs of special steel smelting, the development and application of low carbon refractory materials have been widely concerned. In order to ensure the uniform distribution of a small amount of graphite in the products, it is necessary to reduce the particle size of the graphite used. Microcrystalline graphite itself has fine crystal and is easier to make ultrafine powder. It has become a development trend to use microcrystalline graphite to gradually replace flake graphite to prepare low-carbon refractories. Wang Tongsheng et al. added ultra-fine microcrystalline graphite to the carbon brick. The results showed that the addition of microcrystalline graphite promoted the formation of silicon carbide whiskers in the material, significantly improved the compressive strength and thermal conductivity of the carbon brick, and increased the volume ratio of ultrafine pores below 1 μm. Liang Xiong and others introduced microcrystalline graphite as an activated carbon source into the preparation of aluminum carbon refractories containing metal aluminum powder, silicon powder and silica powder. The results show that natural microcrystalline graphite has higher reaction activity than flake graphite. The introduction of microcrystalline graphite can promote the formation of aluminum nitride and silicon carbide whiskers in the material matrix and improve the mechanical properties of aluminum carbon materials.

  
  

• 4 Applications in the field of battery materials

  Using natural microcrystalline stone ink as aggregate and coal pitch as binder, the carbon rod for dry battery was prepared by mixing and kneading-extrusion forming-baking-grinding-wax dipping, which has a long production history. Hunan Changning Carbon Co., Ltd. and Chenzhou Yongfa graphite products Co., Ltd. have an annual output of more than 20,000 tons of carbon rods for various microcrystalline graphite based dry batteries, accounting for more than 60% of the global output, which improves the application value of natural microcrystalline stone ink to a certain extent. Natural microcrystalline graphite has small grains and different orientations, which is beneficial to absorb the deformation energy generated by the lithium ion embedment and release. It has good structural stability and magnification performance, and has a good application prospect in the field of lithium ion power battery cathode material. In recent years, natural microcrystalline graphite based cathode materials for lithium ion batteries have been studied more and more. He Ming et al. coated microcrystalline graphite with core-shell structure was prepared by coating a layer of resin carbon on the surface of microcrystalline graphite, which reduced the first irreversible capacity of microcrystalline graphite. He Yuide et al. coated resin carbon on the surface of spherical microcrystalline graphite particles by liquid-phase impregnation process to improve their electrochemical properties. For the first time, the coulomb efficiency was increased from 81.0% to 92.7%. Lin Zhengyu et al. used microcrystalline graphite as conductive aggregate and thermosetting resin as binder to prepare microcrystalline graphite/resin composite bipolar plates for proton exchange membrane fuel cells by molding process. Using bisphenol a vinyl resin with content of 18% ~ 20% as binder and microcrystalline graphite powder with particle size of 200 mesh ~ 250 mesh as conductive aggregate, the properties of bipolar plate prepared under the molding conditions of curing temperature 140 ~ 145 ℃, molding pressure 15 ~ 20 MPa and molding time 18 ~ 22 min are as follows: bending strength>25 MPa, conductivity>100 s/cm and gas permeability<3×10-5  mL/(s·cm²)。

   

• 5 Application of rubber filler and other fields

  A large number of fillers with different functions are often added to the rubber formula to realize its use value. At present, carbon black is the most important rubber reinforcing filler, accounting for about 40% ~ 50% of the total mass. Although carbon black has excellent performance, it has the disadvantages of high processing pollution, high energy consumption and easy flying when adding, therefore, the rubber industry has been looking for alternative materials of carbon black. LV Jiaping et al. studied the effect of microcrystalline graphite partially replacing carbon black N550 on the properties of ethylene acrylate rubber (AEM) compound. The results showed that after microcrystalline graphite partially replacing carbon black N550, the vulcanization time of AEM compound was greatly shortened, and the heat generation and raw material cost were reduced before the heat aging resistance and oil resistance were maintained. Wu Jiangtao et al. studied the influence of natural microcrystalline graphite in different mining areas on the properties of natural rubber (NR). The results show that microcrystalline graphite improves the physical properties of NR compound to a certain extent, but the influence of microcrystalline graphite in different mining areas on the physical properties of NR compound is quite different. The particle size of microcrystalline graphite has a great influence on the physical properties of NR compound when the particle size is greater than 5μm, the amount of microcrystalline graphite in NR compound has a critical value and precipitation phenomenon. The above research shows that microcrystalline graphite has similar chemical composition and microstructure to carbon black, so it is possible to partially replace carbon black for rubber reinforcing filler. Microcrystalline graphite has the characteristics of good chemical stability, heat conduction and lubrication. It is easy to disperse in the rubber matrix after ultrafine grinding, which is conducive to improving the performance of rubber products. Therefore, natural microcrystalline graphite as a new rubber reinforcing filler has excellent potential application value.

   

• 6 Application in the field of electric carbon products

  Natural microcrystalline graphite has the advantages of high graphitization degree, good conductivity, heat conduction and lubricity, and strong adhesion with asphalt, resin and other adhesives. It has good application value in the field of electric carbon products. The final performance of carbon graphite products largely depends on the interaction between binder asphalt and aggregate particles in the kneading process. Duan Shengzhi studied the preparation of copper/carbon composites by powder metallurgy with natural microcrystalline graphite and copper powder as main raw materials. The effects of microcrystalline graphite purity and ratio on the microstructure, conductivity, flexural strength, hardness and friction and wear properties of the composites were studied, results show that with increasing microlite ink purity, copper/carbon composite material main performance index showed a trend of increase.  When the proportion of microcrystalline graphite is 7.5%, the conductivity and friction and wear properties of copper/carbon composites are relatively optimal. The lubricity of microcrystalline graphite to copper/carbon composites is slightly less than that of flake graphite, but the wear rate of composites can be reduced.

  
  

• 7 Applications in other new material fields

  Yang Xing et al. synthesized nano diamond by pulsed laser bombarding suspended graphite particles in circulating water, and studied the synthetic process, purification process, formation mechanism of nano diamond and the effects of carbon particle size and phase structure on the synthesis. The results show that the microcrystalline graphite with fine particles is easier to synthesize nano diamond than the flake graphite with large particles. Wei Linyin et al. studied the transformation process and law of sodium tungstate and microcrystalline graphite in high temperature argon atmosphere with sodium tungstate as tungsten source and natural microcrystalline graphite as carbon source. The results show that the samples mixed with sodium tungstate and microcrystalline graphite in different proportions can produce different tungsten carbon compounds after high temperature treatment in argon atmosphere. Vlastimil Vyskocil et al. have developed a new voltammetric DNA biosensor based on natural microcrystalline graphite polystyrene composite membrane, which is used to study the model carcinogen 2-aminofluorene (the most widely studied aromatic amine carcinogen) and calf thymus double stranded DNA. Dana Deylová et al. studied the voltammetric behavior of two genotoxic nitro compounds, 2-amino-6-nitrobenzothiazole and 5-nitrobenzoimidazole, using natural microcrystalline graphite polystyrene composite sensor and improved p-ag SAE electrode. The practical applicability of the new method was verified on drinking water and river water model samples by DC voltammetry (DCV) and differential pulse voltammetry. Xie Wei et al. prepared natural microcrystalline graphite/low density polyethylene (MG/LDPE) composites by extrusion calensioning method, and studied their electromagnetic absorption properties. It was found that when the thickness was 2.0 ~ 2.1 mm, there were two absorption peaks at low frequency and high frequency, and the content and particle size of microcrystalline graphite had a great influence on the electromagnetic absorption properties of MG/LDPE Composites. It shows that MG/LDPE Composites have good application prospects in the field of electromagnetic absorption.

An in-depth and comprehensive understanding of the basic structure and characteristics of natural microcrystalline graphite is the key to guide the development of microcrystalline graphite industry. Therefore, the basic research of microcrystalline graphite should be further strengthened. At the same time, it is necessary to further strengthen the development of efficient, environment-friendly, low-cost purification technology, particle shaping, surface modification and other technologies, encourage independent innovation and product research and development, and promote the industrialization of relevant scientific research achievements. With the continuous development of relevant new theories, new technologies and new equipment, natural microcrystalline graphite will be widely used in the fields of new refractories, new energy materials and advanced composites, and will have a far-reaching impact, to get the related technical information from us.