六硼化镧纳米粉末制备技术的研究

发布时间：2018-04-04 20:54

  本文选题：六硼化镧　切入点：纳米粉末　出处：《电子科技大学》2015年硕士论文

【摘要】：六硼化镧(La B6)具有电导率高、热蒸发率低、发射电流密度大和良好的热稳定性等优异性能。本论文旨在研究高纯度、小颗粒、粒度分布均匀且具有优异电子发射性能的纳米LaB6粉末的制备工艺,用于改善PDP的显示性能。本论文采用固相合成法进行LaB6纳米粉末的制备,借助X射线衍射图谱分析、沉降分析、扫描电子显微镜等分析技术研究了LaCl3和KBH4为原料的固相合成反应的机理,对合成制备工艺参数进行了优化,同时还研究了合成产物的清洗和分散技术,并对制备的LaB6纳米粉末进行了组织形貌表征和性能测试。通过自然沉降分析和扫描电镜观察分析了LaB6纳米粉末分散体系的稳定性,探索LaB6纳米粉末的有效的分散方法及粒度的分析手段。不同分散剂和分散方法对LaB6纳米粉末的分散效果有明显的差异,PEI阳离子型表面活性剂对其分散作用不明显,非离子型的表面活性剂PEG2000一定程度上起到了分散作用,但不够稳定,DBS阴离子型表面活性剂配制的分散液稳定性良好,但在过滤烘干后仍然不利于形貌观测;磷酸对La B6纳米粉末的改性效果明显,稳定性优于DBS,在过滤并干燥处理后,颗粒团聚情况明显优于未分散的颗粒。通过对不同温度下反应产物的成分分析探索反应机理。该反应的主要产物除LaB6外,还有大量的KCl和少量的LaBO3、La3BO6。600℃时开始产生LaB6,700℃时反应得到充分的进行,800℃时产物中的KCl开始熔融并蒸发,随着温度的继续升高,900℃时有单质K析出,在温度升高到1000℃以后,KCl和LaBO3等杂质气化和分解殆尽,产物为较纯净的LaB6。借助XRD、扫描电镜和沉降分析等方法,对制备工艺参数进行探索研究。结果表明,反应温度越高,生成的LaB6晶粒越大,保温时间越长,越有助于LaB6的生成和晶粒的长大,提高B元素的配料比有助于LaB6的生成,但生成物的团聚状况严重,加入反应助剂Mg后可以有效的避免B元素和La元素与O的结合。对LaB6纳米粉末进行精细组织表征和性能测试。固相合成的LaB6纳米粉末结晶良好,颗粒分散均匀,晶粒尺寸在10~50nm的范围内,优化工艺参数后制备出了纯度约为97.52%的LaB6纳米粉末,其平均晶粒尺寸为D=19.53nm,晶格常数a=4.153?,通过理查森直线法算得其逸出功为2.45eV。
[Abstract]:Lanthanum hexaboride (La B 6) has excellent properties such as high conductivity, low thermal evaporation rate, high emission current density and good thermal stability.The purpose of this paper is to study the preparation process of high purity, small particle size, uniform particle size distribution and excellent electron emission properties of nano-sized LaB6 powder, which can be used to improve the display performance of PDP.In this paper, solid state synthesis method was used to prepare LaB6 nanometer powder. The mechanism of solid state synthesis of LaCl3 and KBH4 was studied by means of X-ray diffraction pattern analysis, sedimentation analysis and scanning electron microscope.The preparation process parameters were optimized, the cleaning and dispersion techniques of the synthesized products were studied, and the microstructure and properties of the prepared LaB6 nano-powders were characterized.The stability of LaB6 nano-powder dispersion system was analyzed by natural sedimentation analysis and scanning electron microscope, and the effective dispersion method and particle size analysis method of LaB6 nano-powder were explored.The dispersion effects of different dispersants and methods on LaB6 nano-powders were obviously different. The dispersion effect of LaB6 cationic surfactants was not obvious, and that of non-ionic surfactants PEG2000 played a dispersing role to some extent.However, the dispersion prepared by DBS anion surfactant has good stability, but it is not good for morphology observation after filtration and drying, the modification effect of phosphoric acid on La B6 nanometer powder is obvious, the stability is better than that of DBS, and after filtration and drying, the dispersion is better than DBS.The agglomeration of particles is better than that of undispersed particles.The reaction mechanism was explored by analyzing the composition of the reaction products at different temperatures.In addition to LaB6, a large number of KCl and a small amount of LaBO _ 3B _ 3BO _ (6.600 鈩，

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