In graphite field, impregnation is a kind of technology ,via dipping graphite product into certain kind of melted material, which can change physical or chemical condition of graphite product.

　　In general, increasing in porosity of graphite product can not only lead to decling in gravity (density),rising in resistance, decreacing in mechanical strength, but also make product become more easier to be oxidated, to be corrosion and to be immersed. To avoid those circumstance, you can use impregnation technology to control porosity of graphite product.

　　Usually, when you face following condition, you should apply impregnation .

　　1. Producing little scale graphitized electrode and Joint stock.

　　Those product are required high strength, low density and resistivity, so semi-finished products should be impregnated by coal tar pitch previously.

　　2. Producing high quality graphite anode used in diaphragm electrolyzer.

　　Normal graphite anode can only work for 5-6 months,but impregrated graphite anode can work 8-9 months, because ,after impregration,there is less porosity existing in graphite anode. Less porosity means less corrosion and less immersion. In order to improve service life of graphite anodes , drying oils (such as Tung oil, linseed oil, etc) should be used during the curse of producing, which can prolong 1/3 service life.

　　3. Producing impermeable graphite chemical .

　　Graphite products are porous materials, whose porosity can reduce by impregnating into organic resins (such as phenolic resins, Furfuryl ketone resin). At the same time,while mechanical trength was improved by this technology, thermal condition can also stay at it’s good condition.

　　4. Producing wear-resistant carbon and graphite products.

　　When the working temperature and the working media don’t allow to use lubricating oil and other liquid lubricants, using graphite and carbon materials,such as sealing rings, bearings or redirect loop is the only way to ensure the machine runs at high temperatures for long periods. This graphite or carbon wear-resisting material needs high density and hardness and wear-resistance, so this product usually impregnated by synthetic resins or low melting point metals (such as aluminum, Tin alloy, lead-bronze and babbit).

　　That is all what I want to introduce.After reading this article, you must have a superficial impression on impregnation technology.If want to learn more knowledge about graphite product, welcome to our web site:www.bjgreatwall.com. If you have any question, don’t hesitate to contact me:This email address is being protected from spambots. You need JavaScript enabled to view it..

　　The glassy carbon (GC) is a new type of carbon material ,it’s similar to glass and in the carbon structure, and it is also a new type of amorphous carbon structure material. The GC is made of biological resin carbon through high temperature pyrolyzation and carbonization . It does not contain harmful substances on the human body, high purity carbon. Glassy carbon is characterized by its high hardness and permeability due to its port morphology and structural characteristics similar to that of glass.

　　Glass carbon has high strength, hardness and elastic modulus. It can be used to make high speed typewriter wheel and record. Glass carbon has many superior properties: density is small, about 1.3g/cm3; 3800℃high temperature resistance; anti penetration; corrosion resistance. It’s widely used in chemical industry, metallurgical industry, electronic industry, biological engineering and many other fields.

　　Glass carbon can withstand 1 million 300 thousand times the atmospheric pressure, in other directions it can withstand the atmospheric pressure of 600 thousand times. It’s used in the manufacture of ultra high temperature micro electrode used as stoichiometric electrode, its diameter is below 1mm, a disc type, cylindrical, conical, used as a chemical measurement electrode used in analysis of trace components and measurement of various compounds coexisting clinical specimens, samples and raw thick liquid etc.. It can be used in medical equipment production such as tooth material and cardiac pacemaker. Glass carbon can be used for 3800 degrees heat insulation material and high heat resistant protective clothing. special glass carbon ultra high temperature crucible, ultra high temperature beaker, ultra high temperature pipe, ultra high temperature casting mold, carbon crystal wall heating, the carbon crystal heating plate, ultra high temperature electric heater, glass carbon fiber composite panel for the touch screen of computer and mobile phone , it’s also used in the manufacture of high-speed wheel typewriter and recording.

　　In order to enhance the oxidation resistance of graphite mould and prolong its service life, it is necessary to reduce the gasification reaction rate of graphite material at high temperature. Under normal circumstances, there are three factors affecting the gasification reaction of graphite materials:

　　(1) graphitization degree of carbon graphite material increased, the activity of gas decreased, gasification reaction rate was slow. The higher the heat treatment temperature of carbon materials, the higher the temperature of the starting oxidation.

　　(2) the state of the surface of the structure is loose and porous carbon graphite material, easy to react with the gas, and the surface of carbon graphite material, not easy to react with gas. For example, after 3200 degrees of heat treatment of the surface of the dense pyrolytic graphite, starting in the air temperature of up to 850 degrees C.

　　(3) the impurities impurities in the catalysis of carbon materials have great influence on the gasification reaction, such as oxidation of iron, lead, manganese, copper and other elements of carbon materials have a catalytic effect to reduce the impurity content of carbon graphite materials, can improve its antioxidant properties.

　　Therefore, to make use of carbon graphite products raw material of ultrafine particle size, and try to improve the graphitization temperature, can greatly reduce the porosity of carbon graphite products rate, stomatal aperture and impurity content, improve the graphitization degree, so as to improve the anti oxidative properties of carbon graphite products, reduce the oxidation speed.

　　Flow battery is to achieve large-scale renewable energy application of new green secondary battery two, the performance of electrode materials has important significance for the practical application of the flow battery, PAN based graphite felt electrode material is the preferred flow battery, in order to further improve the hydrophilicity and electrochemical activity of the modified Shi Mozhan electrode materials, graphite related research in recent years the carpet has become a hot spot.

　　Energy storage technology is very conducive to the balance between energy production and consumption between the control in power, plays an important role in the integration of renewable energy and other areas, as one of the electrochemical energy storage technology flow battery, the redox flow battery, with current conversion capability, flexible structure design, reasonable cost, operation simple, is a new type of green two battery suitable for large scale electricity storage.

　　Carbon fiber, also called graphite felt, is made of carbon fiber after pre oxidation by lapping process of acupuncture, felt body made of carbonization process, graphite felt is a low strength carbon fiber products, has the advantages of low density, low linear expansion coefficient, low thermal capacity, small thermal conductivity, high temperature resistance thermal shock resistance, strong resistance, chemical corrosion resistance and excellent high temperature, is widely used in industry, energy industry, auto industry, chemical and environmental protection.

　　Graphite felt is the first choice of electrode material for liquid flow battery, but its electrochemical activity and hydrophilicity can not fully meet the requirements of liquid flow battery.

　　The electrochemical activity of graphite felt is not high and the poor hydrophilicity, so graphite felt modification has become an important means to improve the properties of electrode materials, the modified method is mainly to increase the graphite felt surface oxygen and deposited on the Shi Mozhan surface catalytic material, and surface morphology of carbon felt, produce different effects of chemical composition and electrochemical performance, and improve the properties of liquid flow battery.

　　Graphite is charactered by good conductivity, good heat conduction and rust-resistance, but graphite contains many pores during their manufacturing process inevitably. H2 and O2 will be mixed if the graphite bipolar plates which contain pores are used in PEMFC ( proton exchange membrane fuel cell) , and the performance of fuel cell is low . Graphite bipolar plates were impregnated by thick Na2SiO3 solution in vacuum and pressure. Na2SiO3 in graphite plate was turned into SiO2 after being reacted with acid and heated. Porosity of graphite plate dropped to 3. 3 %from 18. 2%.No H2 leakage occurred at the pressure of 0 . 3 MPa.The resistance of graphite plate after impregnation did not rise. The voltage of fuel cell used the graphite plates added 40 mV at the same current density.

　　Graphite plates are widely used as bipolar plates for proton exchange membrane fuel cells because of their good electrical conductivity, thermal conductivity and corrosion resistance. But as a result of the graphite plate in the process of burning coal tar as the binder will be oxidized or volatile, are caused by the size of the holes graphite products, the porosity is about 18.2% ~ 24.3%, such a high rate of stomata use graphite plate. At present, more and more researchers in the world are using organic materials such as phenol resin, paraffin, asphalt, and so on to fill the hole of graphite plate, which can reduce the porosity and achieve the purpose of sealing graphite plate. The advantages of organic matter are large molecular weight, long molecular chain and good deformation performance. However, due to the organic matter seems to penetrate into the graphite plate hole, and even penetrate into the graphite layer, forming a composite material, thus increasing the graphite plate body resistance and surface resistance. The theory of voltage of single proton exchange membrane fuel cell is only 1.229 V, the greater the material resistance of the battery, the output power is small, therefore, most of the organic material is not suitable for the impregnation of proton exchange membrane fuel cell with graphite bipolar plate.

　　Tiled arrangement of carbon felt and carbon fiber unidirectional arrangement of absorbing microwave absorbing properties of the composites, polyacrylonitrile based carbon fiber unidirectional arrangement is closely related to the suction arrangement spacing and wave properties of fiber and fiber content. Suction arrangement of carbon felt greatly influence the flat wave properties with carbon fiber content.

　　At present, the negative effect of electromagnetic radiation has affected all aspects of human life. It is an effective way to reduce or eliminate electromagnetic wave pollution by absorbing materials. Graphite felt is one of the most commonly used structural absorbing materials, and has been widely used.

　　By changing the cross section of the carbon fiber in the graphite felt, the surface modification of the fiber or the change of the electromagnetic parameters of the fiber by reducing the carbonization temperature of the carbon fiber were used to prepare the absorbing material for graphite felt.With the increase of carbon fiber content, the reflection attenuation of the sample decreases, and the absorbing property of the material decreases obviously.

　　In the graphite felt in the fiber, the duty ratio is about 5% to 8.6%, and third in the direction of vertical or inclined distribution of fiber. In this way, the carbon felt is not completely covered by the matrix with high viscosity in the composite with the epoxy resin, but forms a certain low filling net". If the graphite felt is compounded with other high density powder or particles, it can not only prevent the precipitation of the filler, but also help to obtain the composite material with uniform distribution.

　　The bipolar plate used therein are required to achieve higher electrical conductivity due to the requirements for redox flow batteries have become more and more stringent in recent years.and thus A bipolar plate composed of an electrically conductive composite achieves a higher electrical conductivity by increasing the conductive filler content in the material.

　　Graphite was used as one of the main bipolar plate material in redox flow batteries due to its high electrical conductivity ,low weight and good chemical stability in the past.Graphite blocks were produced by sintering process and plates were machined to desired sizes.The main limitation of this method was the porosity of produced graphite plates.

　　At present, our company provides a bipolar plate for a redox flow battery , the bipolar late including an electrically conductive composite prepared by mixing a thermoplastic resin ,a carbonaceous material selected from graphite and carbon black ,and a carbon nano-tube.

　　Our current business is extended from the overall solution of the material to the manufacture of bipolar plates, and thus provides the following three VRB assembly services:

　　1).The bipolar plate (we can provide punch service. The thickness of the bipolar plate now can be processed are 0.6/0.8/1.0 /1.2/1.3mm.

　　2).The composite of the bipolar plate and the electrode, the advantage is that the electrode felt is fully combined with the felt in the plate, it greatly reduces the theoretical value of the contact resistance to the felt.

　　3).The bipolar plate ,the electrode and outline border. Three in one frame after embedding flow

　　box (precision injection), it’s the way which improve the reliability greatly compared with the above 1 and 2.

　　The graphite crucibles were prepared with flake graphite, silicon carbide, silica and kaolin. The influence factors on the properties of samples were investigated. The results show that, with the increase of the silicon carbide content, the volume density of samples increases, the porosity decreases, the weight loss rate of the sample reduces and the antioxidant activity improves. Elevating the oxidation temperature and prolonging the oxidation time increase the weight loss rate of the sample, decrease the antioxidant activity. The microstructure analysis show that the compactness of the samples rises when the silicon carbide content and the sintering temperature increase.

　　The numerical simulation results show that the electromagnetic force and the flow distribution induced by the melt surface are significantly different when the coil position is different. When the coil is located at the upper side of the melt side, the induced electromagnetic force and flow are mainly concentrated in the upper part of the melt, and in the actual production and experiment, it is easy to appear the splash of liquid droplets, and increase the risk. The top of the air and the side mold respectively the heat conduction rate of the melt during solidification process are different. Therefore, when the coil is located at the upper side of the melt side, the precipitation of the grains on the top and side of the melt will occur in time, and the effect of the magnetic oscillation will be affected. And the free grains will move to a long distance to form the solidification structure and increase the possibility of melting the high temperature melt. The coil is located in the side of the lower part of the melt, induction of electromagnetic force and flow distribution in the melt can lower precipitation oscillation impact melt grain side and the bottom of the mold and the heat conduction and the bottom side of the melt rate, grain precipitation at the same time will be better vibration shock effect, nucleation rate get increased significantly. In addition, with the flow of the grain can be directly deposited on the bottom of the melt solidification structure refinement, reduce the high temperature melt melted in free process, the grain refinement effect will be better than in the upper part of the side of the coil.

　　Although the density of carbon fiber is lower than that of aluminum, its strength is higher than that of steel. Carbon fiber is not only the inherent "hard" characteristic of carbon materials, but also the machinability of textile fiber.

　　A carbon fiber woven graphite felt has good conductivity, mechanical properties, electrochemical reaction activity, acid resistance, corrosion resistance and oxidation resistance, is a good electrode material, compared with metal, graphite powder and various electrode materials, more suitable for the electrode storage battery.

　　At present, the domestic production of graphite felt is mainly used to make thermal insulation material, and its conductivity and electrochemical activity can not meet the requirements of the use of battery electrode materials, therefore, the need for carbon fiber felt surface treatment. The commonly used surface treatment methods include heat treatment, acid treatment and electrochemical oxidation treatment.

　　The operation of heat treatment in air atmosphere, and after the heat treatment,the conductive ability of graphite felt has been improved, in the heat treatment of graphite felt, if the temperature is too low, resulting in electrochemical active graphite felt low, unable to meet the requirements of use as electrode materials; but if the heat treatment temperature is too high, it will cause the graphite felt surface etching, serious excessive oxidation, fiber breakage and breakage, resulting in the the electrical conductivity and mechanical properties decreased sharply, seriously affecting their life.

　　With the heat treatment temperature increased gradually from 450 degrees to 600 degrees Celsius, the impurities of graphite felt surface are gradually disappear, with the further oxidation of the holes, grooves and other defects; carbon fiber structure with the oxidation degree also changed gradually from the turbostratic structure of two dimensional ordered structure transformation three.

　　The high thermal conductivity graphite sheet has good thermal conductivity of 800-1900W/MK, it is perfect heat conduction material , it’s made from the new film materials after 3500 degrees Celsius high temperature sintering , it’s light and it’s 1/3-3/4 times of aluminum, 1/5-1/4 times of copper , these high thermal conductivity graphite sheet is easy to processing, it can be bent repeatedly and cut to any shapes.

　　The properties of high thermal conductivity graphite sheet : high thermal conductivity, 1900W/m-K (X-Y axis), 15W/m-K (Z axis); high forming temperature , stable and reliable performance, no aging problem; good flexibility performance, easy to cutting, installation and use; it’s flexible and has light weight and high EMI shielding effectiveness; it meet the EU Rohs instructions and the requirements of no the halogen content and other harmful substances.

　　High thermal conductivity graphite sheet is a revolutionary breakthrough in the thermal conductivity material application field, it has a wide range of application areas, it’s the perfect thermal conductivity of electronic mobile intelligent products. This product can be used in PDP, LCD TV, set-top boxes, notebook computers, projectors, mobile phones, handheld devices and automotive electronics and other fields.

　　Our standard high thermal conductivity graphite sheet size: 210mmX250mm, 225mmX225mm, 260mmX260MM, 260mmX800mm, 300mmX300mm, we also can customize the different thickness and size according to the requirements of our customers.