【作者】 王楠；

【导师】 张健；

【作者基本信息】 山东大学 ， 无机化学， 2022， 硕士

【摘要】 氧化物纤维是一种具有较大的比表面积、较大的长径比以及良好柔韧性的一种纤维材料,在航空航天、军事、民用等领域都有很大的应用价值。其中,氧化铝纤维由于高模量、高强度、低热导率的特点,在众多领域发挥着不可或缺的作用。此外,以氧化镥为代表的倍半氧化物也是一类性质优异的材料,具有物理化学性质稳定、熔点高等优势,近年来逐渐成为科研工作者的研究热点。国内对于氧化镥纤维的研究较少,而对氧化铝的研究较久,由于氧化镥与氧化铝同属于金属倍半氧化物,金属原子具有相似的价态,氧化物具有相似的性质,所以氧化铝纤维的制备过程对于氧化镥纤维的制备具有重要的参考意义。本论文先制备出性质较为稳定的氧化铝纤维,希望以此作为参考来制备氧化镥纤维。首先以异丙醇铝和乙酰丙酮作为反应物原料,通过控制反应温度(80℃)和反应物摩尔比(1:1)条件,合成了具有稳定性的氧化铝前驱体,并对前驱体的热分解过程进行了测试。将制备的氧化铝前驱体采用前驱体热分解法制备了一种多孔氧化铝材料,并对该材料进行了形貌结构、理化性质以及吸-脱附性能的测试。利用静电纺丝法以及热处理工艺制备了氧化铝纤维,对纤维的形貌结构、柔性、相变规律、热力学性质进行了测试。针对氧化镥前驱体的合成路径进行了探索,对合成产物进行基本表征,利用静电纺丝法进行氧化镥前驱体纤维制备尝试。具体内容包括以下五章:第一章主要综述了氧化物纤维的研究背景,介绍了几种氧化物纤维的制备方法,并介绍了氧化物纤维在应用方面的研究。最后基于上述总结,提出了本论文的选题意义,主要研究内容和研究目的。第二章主要介绍了氧化铝前驱体的制备过程、以及多孔氧化铝材料的制备方法及流程,并对前驱体和多孔材料的性质进行表征。氧化铝前驱体的制备过程包括合成路线以及讨论影响前驱体性质的因素,包括反应温度和反应物配比。采用前驱体热分解法成功制备了一种多孔氧化铝材料,对材料的微观结构进行了表征,800和900℃温度下制备的材料表面没有气孔,1000℃之后,材料表面开始出现孔隙,多孔材料的氮气吸附-脱附曲线也从一方面表明,800、900℃与1000℃之后结构的不同,800℃和900℃符合H2型磁滞回线的Ⅳ型等温线,而1000℃之后的等温线则符合H3型的磁滞回线,这是由于1000℃热处理后晶粒的尺寸过大,结构疏松形成孔状结构所导致的。多孔材料的一些理化性质测试结果表明,随着温度的升高,材料的表面积逐渐变小,孔体积也逐渐变小,从表面积的角度看主要是因为,随着温度的升高,晶粒的生长以及结晶度的提高导致表面积的减小,从孔体积的角度来看,随着热处理温度的升高,高温造成的氧化铝的结构较为疏松发生了孔隙间的塌陷,从而结构变得紧凑,孔体积变小。第三章本论文主要介绍了氧化铝纤维的制备过程、氧化铝纤维相变、热力学性质的研究。SEM测试结果显示纤维的直径在300-400 nm之间,表面结构致密,无气孔和裂纹。XRD图谱显示了 700-1200℃温度区间内的相变情况,可分为3个阶段:700℃为无定形态的氧化铝,800℃开始出现γ相的衍射峰,900℃时衍射峰强度增强,此时主要为γ晶相,1000℃时转化为热稳定状态的α-Al2O3。较低的相变温度可以避免晶粒长大现象的发生,避免由于晶粒的聚集而影响纤维的性能。对于纤维的隔热性能进行测试,并与一些隔热材料进行的热导率进行对比发现,氧化铝纤维在一些温度下的热导率小于这些材料的值,说明本实验制备的氧化铝纤维在隔热方面具有一定的优势,在航空航天、高温隔热、工业材料等领域具有潜在的应用价值在第四章中,本论文主要叙述了针对氧化镥前驱体的制备为中心展开。主要选择异丙醇镥、乙酸镥和碳酸镥作为镥源,采用不同的配体进行反应。其中异丙醇镥和乙酸镥作原料时,由于反应条件的限制和反应物反应活性等因素的影响,导致未能得到理想的氧化镥前驱体。以碳酸镥作为镥源,柠檬酸为配体参与反应,得到了质量较好的氧化镥前驱体,并且探究了不同溶剂对实验产物的影响,对制备的氧化镥前驱体进行了基本性质表征,通过静电纺丝制备氧化镥前驱体,但是由于其性质的不稳定,出现纤维之间的缩聚现象。第五章对本论文的实验成果进行了总结、对工作的创新点和后续有待进行的工作进行了阐述。更多还原

【Abstract】 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.更多还原