【作者】 吕晓棠；

【导师】 王子忱； 肖平；

【作者基本信息】 吉林大学 ， 物理化学， 2010， 博士

【摘要】 本论文主要以化学控制方法为主要手段,研究制备稳定化纳米氧化锆粉体和复合材料,利用各种有效控制方法和新的合成路线,探讨了其合成和原位分散技术,并进一步探讨了氧化锆做为陶瓷材料的应用性能。首先,采用新的方法,在液相中以氧氯化锆和硝酸钇作为锆源和钇源,以氢氧化钠水溶液作为沉淀剂和晶化反应的液相环境,合成钇稳定化氧化锆纳米晶体。讨论了反应过程中,液相中的各种离子、碱度和时间对于反应的影响,并且讨论和计算了,此种反应条件下氧化锆的反应机理和反应的活化能。接下来,以氧氯化锆和氯化镁作为锆源和镁源,利用此液相晶化方法又成功的制备了镁稳定化纳米氧化锆晶粒粉体,产物经XRD检测为立方相镁稳定化氧化锆。这种制备方法,避免了传统高温焙烧制备方法中产生的不可避免的纳米晶粒粉体的团聚现象,以及湿化学法制备所需时间较长的缺陷,有效缩短了反应时间短,并具有低能耗,高产率的特点,有利于今后的工业化推广。其次,以氧氯化锆和硝酸钇作为锆源和钇源,采用原位分散合成法,结合纳米碳酸钙合成过程中的化学和电化学特性,以纳米碳酸钙的前驱体氢氧化钙溶液为沉淀剂,利用生成的纳米碳酸钙作为干燥和高温焙烧过程中纳米氧化锆的阻聚剂,制备出了分散性良好的纳米钇稳定化氧化锆粉体。此方法的反应机理为液相中不同种粒子的表面电位正负电性不同,带有电负性的氧化锆前驱体吸附在具有正电性的纳米碳酸钙表面,从而有效的避免了干燥和焙烧过程中产物颗粒的团聚和生长,从而获得分散性良好的产品。最后,采用无水溶胶凝胶法与电泳沉积法相结合,以正丙醇锆和钇稳定化氧化锆粉体为锆源,以乙酰丙酮为介质,在金属基板上沉积钇稳定化氧化锆陶瓷粉体和氧化锆凝胶,经过高温烧结后获得微米/纳米复合氧化锆陶瓷涂层材料。由于引入无水溶胶凝胶方法控制纳米氧化锆在钇稳定化氧化锆粉体颗粒的沉积,使得获得的陶瓷涂层厚度有显著提高,并且通过微米压痕仪的检测证明,涂层的机械性能也得到大大提升。这种湿化学与电化学法的结合,使得电泳沉积的产品性能有了大幅度提高,为今后的应用推广打下良好基础。更多还原

【Abstract】 The preparation of stabilized zirconia nanomarterials has been studied by chemical control strategies, in which all synthesis, reaction procedure, dispersion and application properties have been investigated.At first, we successfully synthesized tetragonal/cubic yttria stabilized zirconia and cubic magnesia stabilized zirconia particles in aqueous solution at low temperature. On YSZ, nanocrystalline particles were prepared in alkaline aqueous solution at temperature of 50-90 oC. The average crystal size of the YSZ particles is 3.7 nm. In this crystallization process, combination of Na+ and OH- is the most effective in promotion of YSZ crystallization, in comparison with the effect K+ and CO32+. With decrease in reaction temperature from 90 to 50 oC, complete crystallization time in the NaOH solution increased from 30 minutes to 7 days. The activation energy for crystallization of YSZ in the NaOH solution has been obtained as 145±10 kJ/mol, which is verified by the reaction at 50 oC for 7 days one, which YSZ product crystallized within the time fitted the calculated results.In case of MSZ, nanocrystalline particles were prepared in alkaline aqueous solution at temperature of 95 oC. The average crystal size of 20MSZ particles is 4.3 nm. [OH-] plays the key role on crystallization for MSZ as MSZ crystallized faster in higher [OH-] solution, which is the same in that of YSZ. The synthesized 5MSZ, 10MSZ, 12MSZ and 15MSZ are all exhibit cubic phase without independent MgO occurred. This aqueous phase synthesis method is a low costing on energy and substance, promising to be expanded on prepare more nano materials to obtain better properties and functions.Second, In this work, we successfully synthesized YSZ nanoparticles with in situ dispersion method, in which CaCO3 nano particles acted as disperser. The particle size of obtained YSZ is 6.3 nm, with a standard deviation of 1.4 nm from TEM image, and the average grain size of as prepared YSZ is 6.6 nm from XRD. This YSZ has well dispersion stability in water and the suspension is homogeneous. In two weeks, the sedimentation phenomenon of this suspension is too light to be observed. This in situ dispersion method is advancer than previous one on preparing smaller and homogenous dispersed particles. Investigation on influence of calcination temperature indicates 600 oC is the optimal heating condition for the crystallization of this YSZ nanoparticle. The proportion of 1:5 (wt.) for YSZ: CaCO3 is the best for a well dispersion state of YSZ particles. The mechanism of this preparation process is investigated and discussed with theory of electrostatic force and double layer. The dynamic of this in situ dispersion is the electrostatic force, which makes a tight connection between opposite charged YSZ and CaCO3 particles in the whole preparing procedure.At last, using Zr(n-OPr)4, ZrO2 nanoparticles was prepared in acetylacetone by nonaqueous sol-gel method. Smaller ZrO2 particles derived from Zr(n-OPr)4 can be induced in EPD coating and the small ZrO2 particles combined with YSZ particles and transform to tetragonal phase in heat treatment process. The properties of the suspension showed the YSZ particle with a main size of 1μm agglomerated with Zr(n-OPr)4 in suspension, and the sedimentation results indicted the agglomeration is loose. Theζ-potential, electrical conductivity and current all increased with the addition of Zr(n-OPr)4 dramatically as the surface property of YSZ particle was changed with zirconium propyl-hydroxide adhered on the particle surface. The addition of Zr(n-OPr)4 in EPD suspension helps on making thicker and crack free coating. The mechanical properties detected by microhardness indicated the Young’s modulus of the EPD coatings is affected by Zr(n-OPr)4 addition, the hardness was improved as well. It shows a promising application of this wet-chemical and electric-chemical combined ways for further fabrication of functional materials.更多还原