PTC material production process and flow of PTC heater
1. Ingredients
At present, most domestic and foreign manufacturers use solid-phase synthesis technology. The raw materials used are BaCO3, SrCO3, Pb3O4, TiO2, Nb2O5, MnCO3, SiO2 and other powders, and the purity should generally be above 99.5%. The purity of the raw materials, the variety and content of impurities, the chemical activity of the raw materials, etc. all have a great impact on the function of the PTC final product. The accuracy of the ingredients also has a great influence on the performance of the product.
2. Ball mill destroys and removes water
Put several weighed raw material powder, grinding balls, and pure water into the ball mill and destroy them, and mix them evenly. The ball-milled raw materials can be simply put into an oven for drying, or they can be dried after dewatering using filtration, centrifugal separation, vacuum filtration and other techniques.
Three, solid phase synthesis
Solid-phase synthesis is also called pre-sintering, which is to put the mixed raw materials into a high-temperature furnace for reaction to form a uniform solid solution. The general formula of the solid solution can be written as (Bax, Sry, Pbz)TiO3, where x+y+z=1 , The temperature of solid-phase synthesis is selected according to the material and the ratio between 1000~1250℃, and the holding time is 2~4 hours.
Fourth, the second ball mill
After solid-phase synthesis, the materials agglomerate and certain crystal grains grow up, which need to be destroyed by ball milling to facilitate firing. The technique of secondary ball milling is similar to that of ball milling before synthesis.
Five, forming
PTC materials can be made into a variety of styles, such as: round, square, honeycomb and so on. The sheet-like components are formed by dry pressing, and a viscous PVA solution is added to the material. Then the sheet is granulated by the sieving method or spray drying method, and then press-formed on the punching machine. The honeycomb elements are formed by extrusion techniques.
Six, firing
Put the formed green sheet into a high-temperature furnace, and according to the necessary firing premise, fire the semiconductor ceramic with the required PTC characteristics. The firing curve and firing air have a great influence on the function of the product, so it must be strictly controlled in production to improve the product function and product rate.
