1、Determination of temperature in the process of graphitization

　　The temperature of carbon carbon composite material graphitization is one of the most important index during the processing. For a long time,it is basically determined by experience. In the old days,people think the temperature is the higher the better,but it’s wrong. To any carbon composite material,there is always a ideal temperature,to the resin carbon,the best temperature is 2480℃,as for the CVD carbon,pitch carbon and mixed matrix carbon,the ideal temperature is influence by the relative content,mix form and the different type and property of the carbon fiber,and the application is also need to be considered. Usually, the resin carbon can be partly graphitized at about 2500℃,as for the pitch carbon,it’s easily to be graphitized,so the 2200℃ is enough.

　　2、High pressure impregnation and carbonization process

　　During the carbon carbon composite material processing,many condition need to be considered,

　　such as temperature control,pressure control,the matching between temperature and pressure,the type of pitch etc.as the production cycle is very long during the processing,and so many parameters, each parameter can have a big influence on the production structure,property. The comprehensive influence is complex.

　　3、The relationship between content, arrangement of carbon fiber and the mechanical properties

　　We can choose different types of the carbon fiber according to the pressure of the parts. In a particular direction,if the fiber content is the same,the mechanical properties will be better when the fiber distribute uniformity.

　　4、The relationship between the density and property of the carbon carbon composite.

　　All the properties of carbon carbon composite material is closely related to the density.

　　So the density is also a key point during design,production and using. People think the higher density means higher properties,but it’s not true.as for the density,there is a ideal density,if the density is higher than it,the cost and production cycle will be higher and longer,on the other hand,it may have a negative effect to the properties of carbon carbon composite material.

　　With the development of solar energy Photovoltaic industry, the traditional graphite material is difficult to meet the needs of large-scale production equipment. However the carbon carbon composite material has a good thermo physical properties,it has a great advantage over the graphite material. The carbon carbon composite insulation parts,structure parts and heating unit will be more and more important to silicon single crystal furnace and poly-silicon ingot furnace. There are also some problems to the carbon carbon composite material,now,the best way is to use the SiC coating to increase the effective and service life.

　　The carbon carbon composite material is to do some reinforce treatment on the basis of carbon fiber,it forms under the 2000~2500℃,it can withstand the high temperature of 2000 ℃,after multiple heat treatment,the strength of C/C material is 3~5times than the graphite material,the parts will not break even drop off,and it’s also easy to process,good heat resistance, corrosion resistance, friction resistance,the service like is 3 times longer than the graphite material,and the price is about 2times than the graphite material.

　　The service life of silicon single crystal furnace is about 50 times,and the service life poly-silicon ingot furnace is about 100 times,however, the service of silicon single crystal furnace with carbon carbon composite material is more than 50times.

　　The bigger size of the C/C material means the higher cost performance. It can weave any shape and size perform,then use the densification process to make the CFC material,so the bigger size the cheaper price it will be. If use the graphite material,it needs to assemble with piece by piece together,the cost from processing is also expansive.

　　The service life of the C/C material with SiC coating is longer than the material without coating. Overall consideration,no mater the cost or property,the carbon carbon composite material is better than graphite material.

　　Recently, the author is commissioned by the company to develop a kind of can meet the high performance of high-speed brakes brake piece, raw material is used in continuous filament untwisted PAN based carbon fiber T300 and its tensile strength is more than 3400 mpa, tensile modulus of 230 gpa, elongation is 115%, the density of 1175 g/cm3, carbon content over 94%, fiber diameter between 6 ~ 8 lm, count is 6 k.

　　The needled felt manufacturing process and requirements are as follows: 1.1 short carbon fiber net tire manufacturing will long carbon fiber bundle of short cut in 68 ~ 70 mm long short carbon fiber bundle, and then folded into a net shop on network, made into uniform short carbon fiber net. 1.2 needled felt manufacturing as a whole According to a layer of short carbon fiber net, a layer of long fiber without weft cloth for layer overlapping, no weft cloth layer Angle between 90 b, each lay a layer of short carbon fiber net acupuncture again, needle density [3 mm, acupuncture depth is 10 ~ 12 mm, to achieve the overall needled felt each needle density uniform, long fiber and short fiber ratio is 75/25.

　　Overall needled felt volume density in 0160 ~ 0163 g/cm3, layer density of between 12 ~ 13 units/cm. Made of carbon fiber needled felt through the test, has high strength and good antistatic performance, can satisfy the requirement of high-speed buffer braking.

　　The carbon carbon composite material which used in the medical domain,is made of 3D carbon fiber perform and impregnated furfural resin, carbonization, chemical vaporized infiltration(CVI). It has all the good properties of carbon material,and also has a good biocompatibility and the similar modulus of elasticity as human skeleton,stable chemical property,high strength,light weight etc. but the disadvantage of carbon carbon composite material used for human skeleton is that the surface carbon particles of the CFC material will fall off,it’s not a small problem.the small partical will assimilated by macrophage or lymphocyte,however,the bigger particle will flow with the body fluid,and will be deposition at the body surface,and this situation will lead to the “black skin”. So it’s very important to produce and design the CFC material as per requirements for clinical applications to reduce the pollution to the body and increase the stability.

　　In general, scholars use SEM and Shore hardness tester to observe the micro morphology and test the surface hardness. They also need to do plant experiment in animal to research the CFC biological property,and study the feasibility of human bone tissue replacement.

　　Carbon carbon composite material as a new type carbon material,the material has an apparent similarity with the human bone. Traditional bone repair materials,such as metal, macromolecule, ceramic etc. to a certain extent,it can meet the effect of bone repair,but because of limitations of a single material,it hard to solve the patient suffering.

　　Compared with the metal material,the surface hardness and modulus of elasticity is better than the metal ones. Now the problem is to solve the biological activity of the surface and carbon partical falling off. And the process optimization of carbon carbon composite material producing and surface modification are also important issues to be solved.

　　Carbon carbon composite material can be used in the national defense industry and aerospace industry.

　　C/C composite material is made of PAN pre-oxidized fiber,use CVI and resin impregnation processing.it has a high specific strength,erosion resistance, thermal shock resistance,high temperature resistance,etc. After analogue simulation to the CVI processing of carbon carbon composite material and optimization of CVI processing,we could meet Computer automatic control of CVI processing and carbonization process,and reach the international advanced level.

　　In the early days,the solid rocket motor nozzle is made of graphite material and high strength steel or aluminium alloy,the weight of them increased costs and reduce the working efficienfy of the engine.with the rapid development of composite materials,the carbon carbon composite material replace the graphite material. The C/C composite material is light in weight and high strength,high temperature resistance,the developing trend in future is to make full carbon nozzle which means using carbon carbon composite material as integration structure material of the nozzle.

　　The throat is the main part of solid motor nozzle,the structure of it is sample,however,it’s the key parts. Among all the nozzle parts,the throat is in the worst environment,so the throat is easiest to be erosion. At present, high performance, large solid rocket motor nozzle general use carbon carbon composite material to make the throat.

　　The carbon carbon composite throat is now used in apogee kick rocket engine, medium range missile engine and II stage engine of long-range strategic missile,after the developing of multi direction weaving C/C composite throat,the I and III stage engine of long-range strategic missile can also made of it.

　　The failure behavior of carbon carbon composite throat is also important,the main factors include thermal contact resistance and ablation boundary, under the action of thermal stress, the fracture of the throat is broken.

　　　Carbon fiber cloth, also known as carbon fiber cloth, carbon fiber, carbon fiber woven cloth, carbon fiber pre dipped cloth, cloth reinforced by carbon fibre, carbon cloth, carbon fiber fabric, carbon fiber, carbon fiber sheet, prepreg. Carbon fiber cloth is a kind of unidirectional carbon fiber reinforced carbon fiber products, 12K is often used for weaving. [1]

　　Can provide two kinds of thickness: 0.111mm (200g) and 0.167mm (300g). Variety of widths: 100mm, 150mm, 200mm, 300mm, 500mm, and other special width required for engineering. With the continuous development of carbon fiber cloth industry, more and more industries and enterprises to use carbon fiber cloth, but also a sector enterprises to enter the carbon fiber cloth industry and development.

　　Carbon fiber cloth is used for structural members with tensile, shear and seismic strengthening. This material is used as carbon fiber composite material. It can be used as a carbon fiber composite material, which can be used to increase the load of buildings.

　　The advantages of the carbon fiber cloth

　　High strength, small density, thin thickness, basic does not increase the weight and cross-sectional size of the reinforced members. Wide range of application, widely used in building bridge tunnel and other structural types, structural shape of the reinforcement and repair and seismic strengthening and joint structure of the joints. Construction is convenient, without the need of large-scale machinery and equipment, wet operations, without flare, without fixed site facilities, construction takes up less space, construction efficiency. High durability, due to not rust, is very suitable for high acid, alkali, salt and atmospheric corrosion environment.

　　Applicable to a variety of structural types and various structural parts of the repair and strengthening, such as beams, plates, columns, roof trusses, piers, bridges, a barrel body, a casing, etc., structure. For port engineering and water conservancy and hydropower projects, such as concrete structure, masonry structure, wood structure and seismic reinforcement, especially suitable for complex forms such as curved surface and joints. The strength of the concrete is not less than C15. Construction environment temperature in the range of 5 ~ 35, the relative humidity is not more than 70%.

　　The carbon carbon composite material has a big difference to the superalloy and ceramic materials. Under inert conditions,even the temperature reach 20000C,the strength of the C/C material can still remain unchanged situation,the strength will not reduce.

　　The carbon carbon composite material have a good resistance to thermal shocks and excellent mechanical properties. However, the fatal weakness of CFC material is the low oxidation resistance.although the C/C material has a high specific strength, high specific stiffness and high temperature stability,as one attractive structure material,when the temperature reach 4000C,the carbon carbon composite material start to oxidize. So the most researches on the C/C composite is how to avoid or reduce the degree of oxidation,and also many researches on the processing of the material,structure and the activity, quantitative relationship and the comparison between the C/C with protective layer and without protective layer. One of the most important results is that the physical properties have a big influence to the carbon carbon composite material activity.

　　The flow chart of C/C material below：

　　The different processing between carbon cloth and carbon felt can lead to the different C/C composite material,although they have the similar structure and graphitization degree and same heating treatment,they still have the different properties,the main reason is the oxidation direction,as the two different carbon fiber,they have the different surface area and pore volume.

　　So before using the carbon cloth or carbon felt to make C/C composite material,it’s also important to research the different fiber physical property.

　　C/C composite material is carbon matrix reinforced by carbon fiber. The whole system is made up of carbon element. So the carbon structure which is formed by carbon element will have a big influence on the mechanical properties, thermal performance, friction and wear properties of the composite material.the degree of graphitization is one of the most important indexes to characterize the carbon carbon composite material.most researches show that the higher degree of graphitization which has a better combination properties to the carbon carbon composite material.

　　According to the different kinds of raw materials,the carbon fiber can be divided into three kinds: polyacrylonitrile base(PAN) fiber,pitch base fiber and rayon base fiber. Generally speaking,the PAN base fiber is harder to be graphitization than pitch base,the rayon base is easier to be graphitizatioin than ordinary pitch base fiber.the difficult degree of graphitization is affected by the presoma.

　　The technology of matrix carbon mainly includes pyrolytic carbon,resin carbon,pitch carbon, in general,the pitch carbon is easier to be graphitization,and the resin carbon is hard to be graphitization,the difficult degree of pyrolytic carbon is depanding on the different structure,the rough laminar is easiest to be graphitization,the smooth laminar is harder than the RL,and the isotropic is the most difficult to be graphitization of all.

　　Under the right temperature (>1600C0),the carbon will transform into the graphite,and the changing process will be finished until the temperature reach 3000C0.

　　The graphitization processing of carbon carbon composite material takes advantage of heating to activate the amorphous carbon into graphite,so the degree of graphitization is not only depanding on the material structure but the heating temperature,pressure,the time of atomic rearrangement.

　　The graphite gasket be made By pure graphite plate or metal (teeth plate, plate, mesh) reinforced graphite plate cutting or punching, with many outstanding sealing performance, such as: thermal stability, self lubrication, corrosion resistance, aging, not brittle, etc., in the harsh conditions of the conditions can be used for a long time, very few need to maintain. Lining material can be different with different metal plate. Typeoptionalwithoutedge, inneredge, outsourcing side, inside and outside wrapping.

　　Graphite cut gasket is from pure graphite plate punching or cutting into the, it has good corrosion resistance, resistant high / low temperature, good compression elasticity and high strength, a variety of circular complex geometric gasket is widely used in pipes, valves, pumps, pressure vessels, heat exchanger, condenser and generator, air compressor, exhaust pipe, a refrigerating machine.

　　Raw materials

　　Expandable graphite (flexible graphite) by pure natural graphite by chemical treatment and 1000 degrees of high temperature treatment, this material provides excellent heat resistance and chemical resistance, can be very good to make gasket with high elasticity and low ductility characteristics.

　　Second, characteristics: 1, in the extremely low temperature to 400 DEG C temperature range of sealing performance remained almost unchanged 2, almost of all of the liquid has excellent chemical resistance, strong oxidizing acids except) 3, as a result of the cold deformation and ductility is very small, install tight gasket has no effect.

　　Graphite gasket to stone line materials, warp knitting and shaping. Graphite gasket used for high temperature, high pressure, strong corrosive medium under the work of all kinds of valves, pumps, reaction kettle and other equipment of the stuffing box sealing.

　　1、Density is small, light quality. Mainly depends on the density of carbon fiber carbonization temperature, PAN based carbon fiber after 1000 E processing is 117 g/cm3 density, the temperature is above 2300 E processing, generally is 210 ~ 210 g/cm3 density, type and E glass fiber density of 2155 g/cm3, metal steel fiber density of 7180 g/cm3.

　　2、High modulus (200 ~ 700 gpa), good rigidity, fatigue resistance, self-lubrication, small friction coefficient, wear-resisting performance is good. High modulus carbon fiber is also called the graphite fiber (GRF), generally between 92% ~ 96%, the carbon content PAN fiber M70J cornerstone ink for the theoretical value of modulus of 1020 gpa) (6717%, made in mitsubishi company recently K13C20 modulus # # 39 Beijing textile 22 (6) 900 gpa, 8812% of the theoretical value, the graphite fiber modulus continues to improve. Tests show that in the copper mixed with 25% of the carbon fiber can make its attrition rate down to the original l / 100, and add in plastic products, the attrition rate could be reduced to 1/1000 of the original.

　　3、Thermal conductivity (10 to 213-1 K - 1), no heat, small thermal expansion coefficient (10-6 K - 1-111 @), dimension stability, especially in an inert atmosphere of excellent heat resistance. Thermal conductivity of carbon fiber with the temperature rising and falling, in 1500 when e is only when the room temperature of 15% ~ 30%. Its coefficient of thermal expansion anisotropy, parallel to the axial thermal expansion coefficient of fiber was much lower than perpendicular to the fiber axial, this defect with the epoxy resin composite and composite material is easy to produce cracks.

　　4、Excellent conductivity (5 ~ 17 l8m), a non-magnetic, has the function of shielding electromagnetic wave at the same time of X-ray permeability is good. In addition, the carbon fiber also has to vibration absorption, is excellent for vibration attenuation function. 215 they can withstand oil, acid, corrosion resistant performance is good, good compatibility with biological performance. In addition to the strong oxidizer, generally such as concentrated hydrochloric acid, 30% sulfuric acid, and base on the doesn't work. The corrosion resistance of carbon fiber is better than glass fiber. 216 low axial shear modulus, breaking elongation is small, the impact resistance is poor, and after processing more difficult.