Research On The Effective Construction And Application Of Electrostatic Blown Alumina Fibers With Special-shaped Structures

Alumina fiber is a kind of high-performance inorganic fiber with high strength,high temperature resistance,chemical corrosion resistance,low thermal conductivity,high modulus and low cost.It is widely used in aerospace,composite reinforcement,catalysis and environmental protection.In particular,special-shaped alumina fibers have more excellent properties due to the change of the structure.In this paper,aluminum chloride,aluminum metal powder,polytetrafluoroethylene（PTFE）emulsion,etc.were used as raw materials,and electro-blowing spinning（EBS）technology was adopted,through regulating the composition of sol-gel spinning solution and combination with heat treatment process.The special-shaped ultra-fine alumina fiber with multi-stage pores or spiny structure was constructed and its related application research was carried out.The main research contents include the following aspects:（1）Alumina sol（PTFE content of sol accounted for 22%）was prepared by using aluminum metal powder,aluminum chloride,etc.as raw materials,water as solvent,PTFE nanoparticle emulsion as pore-forming agent,and using EBS technology combined with heat treatment process,ultrafine alumina fibers with multi-stage pore structure were successfully constructed.The effects of different calcination temperatures（500°C,800°C and 1100°C）on the morphology and structure of multi-stage porous alumina fibers were systematically investigated.The results have shown that the calcination temperature has a significant effect on the morphology and structure of alumina fibers.The alumina fiber prepared at 800°C（HPAF-800）has a pore size distribution at 3.5 nm and 64.5 nm.It has a distinct multi-stage pore structure,good fiber continuity and a specific surface area of 67 m² g^-1.At the same time,HPAF-800showed excellent adsorption performance for methylene blue（MB）dye contaminants,and the dye removal rate reached 97.65%within 30 minutes at room temperature.Adsorption kinetics studies showed that the adsorption process of HPAF-800 on MB follows a quasi-secondary kinetic model.（2）The single factor control variable method was used to systematically study the effects of different PTFE additions（0 wt%,22 wt%and 36 wt%）,different calcination temperatures（700°C,900°C and 1100°C）and different heating rates(2℃min^-1,5℃min^-1 and 10℃min^-1)on the morphology and structure of alumina fiber.The results have shown that by adjusting the amount of PTFE added and the calcination temperature,different structural alumina fibers such as smooth,multi-stage porous and spiny alumina fibers can be obtained.When the amount of PTFE added is 36 wt%,the calcination temperature is 1100°C,and the heating rate is 5°C min^-1,the well-formed spiny alumina fiber can be obtained,and the specific surface area is 96 m² g^-1.The spiny fiber is used as the catalyst carrier for a copper oxide（Cu O）catalyst to selectively oxidize 5-hydroxymethyl furaldehyde（HMF）to 2,5-furandicarboxylic acid（FDCA）,needle-like structure can well avoid agglomeration of the Cu O active particles.When the Cu O loading was 76 wt%,the FDCA yield of the spiny Cu O/Al₂O₃ fiber catalyst was 98.6%,and only slightly decreased after 5 repeated uses.