The Preparation And Characterization Of Continuous Ceramic Fiber Containing Boron Alumina

Alumina fiber has excellent properties such as high strength,high modulus,wear resistance and high temperature oxidation resistance.It can be combined with other materials to form many excellent composite materials.Boron is an important component of ceramic materials.Hence,adding B2O3 into fibers to improve the physical properties and properties of fibers has becoming a research trend.Therefore,domestic researchers have been exploring new spinning systems and processes to prepare boron based alumina ceramic continuous fibers with finer diameter.In this paper,two kinds of boron based alumina based ceramic continuous fibers were prepared by sol-gel process and dry spinning process.The preparation of fiber precursor sol,the process of ceramic fiber,the mechanical properties of fibers,the crystalline phase of fibers,and the surface and internal structure of fibers were studied and characterized.The preparation of boron containing alumina fibers makes up for the shortage of domestic boron containing alumina based ceramic continuous fibers and breaks the monopoly of alumina based ceramic continuous fibers in Europe and the United States and other European countries.1.Preparation and characterization of high boron content(14 wt%)alumina based ceramic continuous fibersIn this experiment,inorganic aluminum salt,calcium salt,boric acid and glacial acetic acid were used as raw materials to prepare boron-bearing aluminum sol.As aluminum source and boron source,silica sol was used as silicon source.The continuous gel fiber with high boron content alumina base was prepared by sol-gel method and dry spinning process.With 27Al NMR TG-DSC,TG-MS,XRD,IR,tensile strength tester,SEM,TEM and other analytical methods,preparation of precursor sol,the ceramic process,the mechanical properties,the crystalline phase and the surface and internal structure of the fibers were studied and characterized.The experimental results show that the diameter shrinkage rate of gel fiber is higher after heat treatment,and it needs slower heating rate at low temperature stage.Sintering at high temperature stage can obtain continuous ceramic fibers with high strength,high modulus,fine grain size and dense inner structure,and enhance the mechanical properties of fibers.SiO2 and B2O3 can inhibit grain growth,and the alumina ceramics with high boron content are continuous.The diameter of the fiber is 14?16 pm,the tensile strength of the single fiber reaches 1.346 GPa,the modulus is 81.76 GPa,the main crystal phase of the fiber is mullite phase and amorphous phase,but the gel fiber is brittle and the diameter is coarse,so the experimental scheme and spinning process need further optimization.This high strength and high modulus ceramic fiber is widely used in aerospace,automobile,machinery and other fields.2.Preparation and characterization of low boron content(2 wt%)alumina based ceramic continuous fibersIn this experiment,alumina based continuous fiber containing low boron was prepared by sol-gel method combined with dry spinning with aluminum salt,aluminum powder,silica sol and boric acid as raw material and polyvinyl alcohol as spinning auxiliary.Using TG-DSC,XRD,IR,tensile strength test,SEM,TEM and other analytical methods,the ceramic process,the mechanical properties of fibers,the crystalline phase of fibers and the surface and internal structure of fibers were studied.The experimental results show that the precursor sol with excellent properties can be obtained by selecting suitable raw materials,and several thousand kilometer long alumina based gel continuous fibers with low boron content can be prepared and calcined at high temperature to obtain high strength,high modulus,fine and soft alumina based ceramic continuous fibers.The diameter of the fiber is 5?8 ?m,the highest intensity is 2.0 GPa,the modulus is 149 GPa,and the main crystalline phase of the fiber is ?-Al2O3 and amorphous phase.The experimental material is easy to obtain,so that industrialization can be realized.