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CVD(Chemical Vapor Deposition)
Chemical vapor deposition (CVD) is a technology in which chemical substances in gaseous or vapor state are chemically reacted to form solid deposits on the gas phase or gas-solid interface in the reactor by means of chemical reaction and various energy sources such as heating, plasma excitation or light radiation.? In short, two or more gaseous raw materials are introduced into a reaction chamber, and then they react with each other to form a new material and deposit it on the surface of the substrate.? The solid precipitated from the gas phase mainly has the following forms: thin films, whiskers and grains are formed on the solid surface, and particles are formed in the gas.
CVD technology is the deposition of solid substances from feed gas or steam through vapor phase reaction. Therefore, when CVD technology is used in Inorganic Synthesis and material preparation, it has the following characteristics:
(1) If the deposition reaction takes place on the gas-solid interface, the sediment will be coated with a thin film according to the shape of the original solid substrate (also known as substrate).
(2) The chemical composition of the coating can change with the change of gas phase composition, so as to obtain gradient deposits or mixed coatings.
(3) Using a certain base material, the sediment can be easily separated from the base after reaching a certain thickness, so that various specific shapes of free sediment can be obtained.
(4) In CVD technology, crystal or fine powder can also be deposited, or the deposition reaction can take place in the gas phase rather than on the substrate surface. In this way, the inorganic synthetic material can be very fine powder or even nano-sized particles, which is called nano ultra-fine powder.
(5) CVD process is carried out at lower pressure and temperature. It is not only used to densify carbon based materials, but also enhance the fracture strength and seismic performance of materials. It is carried out at lower pressure and temperature.
CVD technology can be divided into low pressure CVD (LPCVD), atmospheric pressure CVD (APCVD), sub atmospheric pressure CVD (sacvd), ultra-high vacuum CVD (uhcvd), plasma enhanced CVD (PECVD), high density plasma CVD (HDPCVD), fast heating CVD (RTCVD) and metal organic CVD (MOCVD) according to reaction type or pressure
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