Preparation And Study Of Alumina And Lutetium Oxide Fibers By Precursor Method

Oxide fiber is a kind of fiber material with large specific surface area,large aspect ratio and good flexibility,which has great application value in aerospace,military and civilian fields.People’s demand for high performance oxide materials is increasing,especially for fiber materials with various excellent properties.There is little research on lutetium oxide fiber in China,and the research on alumina has been long.As lutetium oxide and alumina belong to metal sesquioxides,the valence states of metal atoms are similar and the properties of oxides are similar,the preparation technology of alumina fiber has important reference significance for the preparation of lutetium oxide fiber.Firstly,the stable alumina fiber was prepared in this paper,and it was hoped that it could be used as a reference for preparing lutetium oxide fiber.In this paper,aluminum isopropoxide and acetylacetone were used as reactants,and the stable alumina precursor was synthesized.The synthetic route of lutetium oxide precursor was explored,the synthesized products was basically characterized,and lutetium oxide fiber was explored by electrospinning method.The paper include the following five chapters:In the first chapter,the research background of oxide fiber is summarized,several preparation methods of oxide fiber are introduced,and the application research of oxide fiber is introduced.At last,on the basis of the above summary,we put forward the research significance,main research contents and research purposes in this paper.In second chapter,the preparation technology of alumina precursor,the preparation method and technology of porous alumina material are introduced,and the properties of precursor and porous material are characterized.The preparation process of alumina precursor includes the synthesis route and the factors that affect the performance of the precursor,including reaction temperature and reactant ratio.The results show that the precursor with stable properties can be obtained at the molar ratio of 1:1 at 80℃.A kind of porous alumina material was prepared by thermal decomposition of precursor.The micrographs after heat treatment at different temperatures showed that there are no obvious pores on the surface of the material at 800 and 900℃,and pores begin to appear after 1000℃.The nitrogen adsorption-desorption curves of porous materials also show that the structural differences at 800℃,900℃ and 1000℃.800℃ and 900℃ conform to the type Ⅳ isotherm of H2 hysteresis loop,while the isotherm after 1000℃ accords with the type H3 hysteresis loop,which is caused by the larger grain size and porous structure after heat treatment at 1000℃.Some physical and chemical performance test results of porous materials show that the surface area and pore volume of porous alumina gradually decrease with the increase of temperature.From the surface area point,the grains grow and the crystallinity increase with the increase of temperature,while the surface area decrease.From the point of view of pore volume,with the increase of heat treatment temperature,the structure of alumina becomes loose and the pores collapse,thus the structure becomes dense.In the third chapter,we mainly introduce the preparation process,phase transformation and thermodynamic properties of alumina fiber.Alumina fibers was prepared by electrospinning,setting appropriate parameters and heat treatment.SEM test results show that the diameter of the fiber is 300-400 nm,and the surface structure is compact,without pores and cracks.XRD spectrum shows that the phase transition occurs in the temperature range of 7001200℃,it is amorphous alumina at 700℃,it begins to show the diffraction peak of γphase at 800℃,completely transforms into γ phase at 900℃,and 1000℃ completely transforms into a thermally stable α-Al2O3.Lower phase transition temperature can avoid grain growth and grain aggregation,thus avoiding the degradation of fiber properties.The thermal insulation performance of this fiber is tested and compared with the thermal conductivity of some thermal insulation materials,it is found that the thermal conductivity of alumina fiber at some temperatures is lower than that of these materials,which indicates that the alumina fiber prepared in this experiment has certain advantages in heat insulation and has potential application value in the fields of aerospace,high-temperature heat insulation and industrial materials.In the fourth chapter,we made a series of explorations on the preparation of lutetium oxide precursor.In this paper,lutetium isopropoxide,lutetium acetate and lutetium carbonate were selected as lutetium sources,and different ligands were used to react.When lutetium isopropoxide and lutetium acetate were used as raw materials,the ideal precursor of lutetium oxide could not be obtained due to the limitation of reaction conditions and the influence of the reactivity of reactants.Using lutetium carbonate as lutetium source and citric acid as ligand,a precursor of lutetium oxide with good quality was obtained.The effects of different solvents on the experimental products were investigated,and the basic properties of lutetium oxide precursor were characterized.When the precursor fibers are prepared by electrospinning,fibrous lutetium oxide precursor fibers could appear,but due to the instability of properties,condensation polymerization reaction will also occur between fibers.The fifth chapter summarizes the experimental results of this paper,and expounds the innovation of this paper and the work for further research to be completed.