Preparation Of Alumina-based Fibers By Sol-gel Process

Alumina fiber is a high performance new inorganic fiber.Its main component is Al₂O₃,and contains a certain amount of additives,such as silica,iron oxide,zirconia,boron nitride and magnesium oxide.Alumina fiber is a high performance ceramic fiber,with high tensile strength and elastic modulus,good electrical insulation and oxidation resistance,and can be oxidized or reduced atmosphere to maintain good chemical stability,It also has the advantages of low thermal conductivity,low thermal expansion coefficient and good resistance to thermal shock.It is mainly used in refractory materials,structural reinforcement materials and environmental recycling.With aluminum powder,crystalline aluminum chloride,silica sol and nano-silica as raw materials prepare the aluminum-based fibers with good spinning properties by sol-gel method.The effects of different silicon sources on the structure and properties of mullite fibers,and the effects of different silica additions on the structure and properties of alumina fibers were studied.The drying process of the fibers was studied.The fiber forming process of mullite was studied by continuous spinning and centrifugal spinning.To reduce the fiber cracks in the use of continuous spinning machine fiber,In order to reduce the defects of fiber cracks,the sol was evacuated to remove the gas in the sol liquid before the fibers were prepared while using a continuous spinning machine to form fibers.The results show that using aluminum powder and hexahydrate aluminum chloride as raw material,distilling and reacting 4 h to prepare polyaluminum chloride sol,According to the proportion of silicon in mullite,adding silica sol and nano silicon oxide,When nanosilica is added,the sol spinning performance decreases;When all the silica sols are added,the spinning performance is best,and the gel fiber length is more than 500 cm.Different silica gel fibers calcined at 1200?,the main phase is mullite.When nano-silica?7 nm and 15 nm?was added,sillimanite was formed after calcination at 1600?.When nano silicon dioxide is added as the silicon source,the density of fibers is significantly increased,the crystal grains are refined,and the porosity is reduced.The silica sol was added in a proportion of 0%,10%,20%,and 30%of SiO2 in Al₂O₃.The incorporation of different amounts of SiO₂ had little effect on the spinning performance of the sol,and the length of the gel fibers obtained was greater than 500cm.No silicon source mixed gel fibers calcined at 1200?,the main phase was sillimanite.When the main crystal phase of the gel mixed with 10%,20%,30%SiO₂was sillimanite and mullite.With the increase in the amount of SiO2,the more compact fiber structure,the more uniform grain size.Through the study of the drying process,it was found that when the fibers were dried at 60?,80?and 100?,the defects of the fibers increased as the temperature increased,and the fiber quality gradually deteriorated.By comparing directly drying in an oven or drying in a dryer,it was found that the quality of the directly dried fiber was better than in the dryer.The silica sol was added in the proportion of silicon in mullite,and mullite fiber was prepared using a continuous spinning machine.When the solid content of the sol was 30%,the fiber diameter obtained was a minimum of 16?m.With the same solid content of the sol,the evacuated sol is denser with fibers obtained using a continuous spinning machine.Fibers were prepared by centrifugal spinning.When the speed reached 7000r/min,the diameter of the fiber was 7?m,and at the speed of 5000 r/min,6000 r/min and 7000 r/min,the diameter of the fiber became smaller with the increase of the speed.