The physical and mechanical properties of pyrolytic graphite plate depend on its preparation method. Although the material prepared at 2100 – 2400C has high strength, the pyrolytic graphite plate prepared at low temperature has the highest strength. The oxidation resistance of pyrolytic graphite is very strong, and it is more stable along the deposition direction. The experimental results show that the reaction rate of the industrial graphite is almost 2 / 3 slower in the hot gas flow at 2500C | C. It is the performance of carbon film that determines the reaction speed, which is more effective than density, because the reaction speed of low density (1.34g / cm3) deposited carbon is much lower than that of high density (1.68g / cm3) industrial graphite. In industrial practice and in the process of graphite material densification technology, as well as in the deposition (covering) of a variety of other surface carbon films, various equipment are used. However, all the equipment can be divided into two categories: the equipment for pyrolysis of hydrocarbon in vacuum and the equipment used under atmospheric pressure. Recently, a new method of increasing bulk density of graphite plate, boiling layer method, is being studied.
This method is expensive but widely used. The characteristics of vacuum equipment are more complicated than that of atmospheric equipment in structure and operation because it can make pyrolytic graphite plate have higher density and uniformity. The main equipment in the device is a reaction furnace with a certain specification and reaction volume. In the furnace, another part to be treated will be heated to a specified temperature. If there is a vacuum device, the reaction furnace shall be equipped with special equipment that can reach a certain degree of vacuum. The process of health and strictness is intermittent. The reactor is electrically heated (usually resistance furnace) and sometimes high frequency. Provide the reaction volume of the reaction furnace with the prepared quantitative gas: the port of hydrocarbon (reaction gas) and inert gas (diluent) can use argon and helium as inert gas, and nitrogen is more often used. In some units, the possibility of supplying nitrogen to the furnace is also considered. In order to enhance the density of graphite materials, a variety of hydrocarbon gases can be used: methane, benzene, heptane and other methane. Methane is most suitable and clean.
Methane is the smallest molecule, which has great significance for filling micropores. Put the materials to be compacted into the reaction volume of the reaction furnace, cover the furnace cover after the completion of charging, start heating and input inert gas at the same time. Once the necessary temperature is reached, input inert gas containing quantitative hydrocarbon gas into the furnace immediately, and continue to input inert gas to cool the furnace after the completion of the compaction process. Check the compaction process with instruments. The instrument shall indicate the temperature, negative pressure value, quantity and concentration of input gas in the reaction volume. After compaction, the other parts shall be checked for air tightness and weight gain. When operating with natural gas, the symbiotic gas harmful to the reaction process in natural gas must be removed, such as C02. Therefore, a device with alkali lime and silica gel is installed on the pipe network line: the former is to absorb C02, and the latter is to dry the gas. When nitrogen is used, a small amount of oxygen impurities that are always in nitrogen must still be removed. Some physical properties of pyrolytic graphite plate and the process of increasing density are mainly these, hoping to be useful to customers.
