2016年4月13日星期三

What Is Graphite ?

Graphite, also called plumbago or black lead. Graphite has a layered structure that consists of rings of six carbon atoms arranged in widely spaced horizontal sheets. Graphite thus crystallizes in the hexagonal system, in contrast to the same element crystallizing in the octahedral or tetrahedral system as diamond. Such dimorphous pairs usually are rather similar in their physical properties, but not so in this case. Graphite is dark gray to black, opaque, and very soft (with a hardness of 1 1/2 on the Mohs scale), while diamond may be colourless and transparent and is the hardest naturally occurring substance. Graphite has a greasy feel and leaves a black mark, thus the name from the Greek verb graphein, “to write.” For detailed physical properties of graphite, see native element (table).
Graphite is formed by the metamorphosis of sediments containing carbonaceous material, by the reaction of carbon compounds with hydrothermal solutions or magmatic fluids, or possibly by the crystallization of magmatic carbon. It occurs as isolated scales, large masses, or veins in older crystalline rocks, gneiss, schist, quartzite, and marble and also in granites, pegmatites, and carbonaceous clay slates. Small isometric crystals of graphitic carbon (possibly pseudomorphs after diamond) found in meteoritic iron are called cliftonite.
Graphite is used in pencils, lubricants, crucibles, foundry facings, polishes, arc lamps, batteries, brushes for electric motors, and cores of nuclear reactors.Graphite products such as graphite rods, graphite blocks, graphite plates etc. It is mined extensively in China, India, Brazil, North Korea, and Canada.
Graphite was first synthesized accidentally by Edward G. Acheson while he was performing high-temperature experiments on carborundum. He found that at about 4,150 °C (7,500 °F) the silicon in the carborundum vaporized, leaving the carbon behind in graphitic form. Acheson was granted a patent for graphite manufacture in 1896, and commercial production started in 1897. Since 1918 petroleum coke, small and imperfect graphite crystals surrounded by organic compounds, has been the major raw material in the production of 99 to 99.5 percent pure graphite.

Graphite Industry Moves Toward The High-end 

2016年4月10日星期日

Graphite Industry Moves Toward The High-end

Development of low-end of chinese graphite industry is seriously hurt resource protection and industrial upgrading. with the rapid development of modern science and technology and the country's new materials, the field of new energy broaden continuously, graphite industry is facing the same fate with rare earth: due to the low threshold which leads to over-exploitation of resources, the low end of the industry, low deep processing technology, a few companies monopoly control, lack of unified planning and regulation, and all these situation restrict the healthy development of graphite industry.
According to the records of Bureau of Customs, datas show that China graphite is major exporting to japan, south Korea, the united states, india, russia, japan and south korea import large quantities of graphite material from china, the price per ton only a few thousand dollars, after its purification process re-export to china, the price per ton of 10 million -20 million.
In Inner Mongolia, Shandong, Heilongjiang, Hubei, Hunan and other places of rich graphite, graphite industry is basically still in the process of mining the primary stage of the production of raw materials, graphite products, quality and technical level are all backward, so as to form a waste of resources, environmental pollution , and the cycle of low efficiency, and lack of funds, lack of information, lack of talent is also fatal factors to these graphite companies, china graphite companies are most are still at a loss.

Advantages Of Carbon-Carbon Composite Material 

2016年4月6日星期三

Advantages Of Carbon-Carbon Composite Material

Carbon-carbon composite material is a material made of high strength carbon fiber and carbon matrix after the process of graphitization, it can be widely used in various types of structures, heaters and containers under high temperature environments.
Compared to graphite materials and other materials,What are the main advantages of carbon-carbon composites material?
1)High intensity (five times stronger than steel);
2)High temperature resistance (still maintain excellent mechanical and electrical properties at 2000 ℃);
3) Thermal shock resistance;
4) Low thermal expansion coefficient;
5) Small heat capacity;
6) Low density (1.7);
7) Excellent corrosion resistance and radiation performance.
It can be mainly used in industries such as aerospace、auto industry、chemical, textile and machinery manufacturing and medical field etc.

The Graphite Material of Photovoltaic Industry