氧化铝粉体的压滤成型工艺初探

研究了两种氧化铝粉体的压滤成型行为及其影响因素，无硬团聚体的粉料在分散良好时可以获得比干压成型（５５％，３００ＭＰａ）的较高的素坯密度（６３％，４５ＭＰａ）和小的气孔尺寸分布，硬团聚的粉体无论是压滤成型还是干压成型，素坯密度都远低于无团聚粉体，此外还讨论了引起密度差别的原因。     

Al2O3粉模压成型与烧结尺寸变化的研究

采用Ａｌ２Ｏ３粉末加入石蜡和不加石蜡作对比,研究不同压力下金属模压成型的Ａｌ２Ｏ３生坯的密度变化和烧结后的变化。结果表明,添加石蜡的Ａｌ２Ｏ３生坯密度提高,试样上下部分的密度减小;成型压力为１５０Ｍｐａ,添加石蜡４．５ｗｔ％,Ａｌ２Ｏ３生坯上下部分的密度差最小;密度差最小的生坯烧结尺寸收缩均匀,烧结后尺寸精度提高。     

纳米ZrO_2－Al_2O_3复合粉末注浆成型与烧结行为研究

平均粒径为２０ｎｍ的ＺｒＯ_２添加５～１５ｖｏｌ％的粒径为２００ｎｍ的Ａｌ_２Ｏ_３粉末注浆成型与烧结特性表现出与普通微米及亚微米级粉末不同的特性：浆料具有较低的含固量，粘度为５厘泊时为５５ｗｔ％；浆料呈微弱触变性：生坯具有较低相对密度，仅为理论值的３５．５％；少量Ａｌ_２Ｏ_３（５～１０ｖｏｌ％）促进复合材料的烧结，但也伴随着Ａｌ_２Ｏ_３晶粒异常长大。上述现象归因于纳米粉末具有非常高的比表面，粉末表面吸附大量紧吸附水不能被石膏模所排除，而粉末巨大的表面能促进了烧结过程中的质点扩散。     

纳米级ZrO2（Y2O3）／Al2O3粉末的制备及其烧结性能

本文采用化学共沉淀凝胶法制备了２ｍｏｌ％Ｙ２Ｏ３－ＺｒＯ２－２０ｗｔ％Ａｌ２Ｏ３纳米级超细复合的陶瓷粉末，在常压下对该粉末进行了不同温度下的烧结试验，利用ＸＲＤ分析了粉末的相组成；用ＸＲＤ－ＢＬ法计算了粉晶尺寸，用ＴＥＭ研究了粉末的形貌，大小及其分布，用Ａｒｃｈｉｍｅｄｅｓ法测定了烧结体的体积密度，用ＳＥＭ观察测定了烧结体的显微结构，结果表明，该法制备的粉末尺寸分布范围窄，分散性好，粉体烧结活性高     

纳米ZrO2—Al2O3复合粉末注浆成型与烧结行为研究

平均粒径为２０ｎｍ的ＺｒＯ２添加５－１５ｖｏｌ％的粒径为２００ｎｍ的Ａｌ２Ｏ３粉末注浆成型与烧结特性表现出与普通微米及亚微米级粉末不同的特性浆料具有较低的含固量，粘度为５厘泊为５５ｗｔ％；浆料呈微弱触变性；生坯具有较低相对密度，仅为理论值的３５．５％，少量Ａｌ２Ｏ３促进复合材料的烧结，但也伴随着Ａｌ２Ｏ３晶粒异常长大。     

粉末固含量对ZTA陶瓷注射成型的影响

本论文采用注射成型技术制备氧化锆增韧氧化铝(ZTA)陶瓷,系统分析了粉末固含量对注射成型喂料流变性能及陶瓷坯体的烧结和力学性能的影响.结果表明:随着粉末固含量的增加,喂料的粘度和非牛顿指数都有所增加,尤其当固含量达到65vol％时,喂料的粘度急剧增大;注射生坯的密度也随着固含量增加有所提高,但烧结收缩率反而相应降低了,特别是65vol％固含量时,烧结收缩率明显下降,这是由于坯体内存在较大的无法排除的气孔缺陷,所以导致最终烧结坯体的密度只略微增加;坯体的抗弯强度随着固含量增加到60vol％时达到最大.综上,喂料中60vol％粉末固含量是最适宜ZTA陶瓷注射成型工艺的.     

球磨过程对α－Al_2O_3注浆成形的影响

对平均粒径为１．４μ的α－Ａｌ_２Ｏ_３以ＰＡＡ为分散剂，以石膏为模具，进行了注浆成形，并在１６００℃下烧结３小时。料浆的球磨过程对生坯的相对密度，烧结体的收缩率及其抗弯强度有很大影响。烧结体的抗弯强度为２３０－３５０ＭＰａ。实验表明：当料浆中ＰＡＡ含量为０．２ｗｔ％（以Ａｌ_２Ｏ_３干基为准），ｐＨ值为８．８时素坯相对密度最大，其值为４９．３％。料浆中颗粒的充分分散有助于提高素坯的相对密度及烧结体的抗弯强度。建议在浇注前对料浆进行充分球磨。     

共沉淀-超临界流体干燥法合成CaO-ZrO_2复合氧化物超微粉体及其烧结性能研究(Ⅱ)粉体的烧结性能

用共沉淀－超临界流体干燥法合成ＣａＯ－ＺｒＯ２（１５ｍｏｌ．％ＣａＯ）复合氧化物超微粉末，并对粉末的烧结性能进行了研究。实验表明，该法合成的粉末具有很高的烧结活性，能在较低的温度及较短的时间内完成致密化过程。４００℃，２ｈ煅烧的粉体加压成型后于１１００℃下保温０．５ｈ，其体积密度可达理论值的９８．２％，开口气孔仅为０．０００８ｃｍ３／ｇ。     

溶胶－凝胶法合成纳米级PbTiO_3超细粉末

采用钛酸丁酯和醋酸铅作为原料，通过溶胶－凝胶（Ｓｏｌ－Ｇｅｌ）方法合成了纳米级ＰｂＴｉＯ３超细粉末。实验结果表明：采用Ｓｏｌ－Ｇｅｌｌ方法可以制得纯度为含ＰｂＴｉＯ３，９９．６７ｗｔ％，平均粒径为６０ｎｍ的高纯、超细、粒径分布范围窄的ＰｂＴｉＯ３粉末。ＰｂＴｉＯ４干凝胶在４００℃下热处理２ｈ后，可以得到结晶程度很高的纳米级ＰｂＴｉＯ３超细粉末。同时通过对醋酸铅（Ｐｂ（Ａｃ）２·３Ｈ２Ｏ）脱水方法的探讨，得出在１９０℃下加热数小时可以有效地脱去醋酸铅中的结晶水。     

热解前驱体制备AlN粉末

以硝酸铝、尿素、蔗糖为原料低分解得到均匀分散的前驱身粉末,对前驱体粉末的碳热的过程研究表明：不存在γ－ＡＩ２Ｏ３→α－ＡＩ２Ｏ３晶型转变,因而ＡＩＮ粉末的合成温度降低合成的ＡＩＮ粉末粒径约８０～１２０ｎｍ,比表面积１９．２ｍ＾２／ｇ,脱碳后的ＡＩＮ粉末氮的质量分数为３２．３％,氧的质量分数为２．１％,碳的质量分数为０．２％。     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

用两个形状指数表征粉煤灰颗粒形貌的研究

引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。     

典型煤碳燃烧特性研究和数值模拟

本文以三种典型煤的碳燃烧为研究对象，分别采用简单一维沉降燃烧方式和等温加热燃烧方式，实验研究了煤在快速加热条件下，其碳的初期和中，后期燃烧过程。以实验为基础，建立了煤的碳燃烧模型，变工况数值模拟了煤的碳燃烧过程，揭示了煤不同条件下的单颗粒碳燃烧特性。     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.     

环氧树脂羟基值测定方法的研究

利用乙酸酐、吡啶和浓硫酸混合的乙酰化试剂测定环氧树脂中羟基值含量的方法具有操作简便、滴定终点明显和分析结果误差小等优点。     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

剪力对梁变形影响的分析

本文用材料力学的分析方法,导出了一个计入剪力时梁的挠曲线的微分方程式。为了估计剪力对梁变形的影响,在集中力作用下梁内剪力用一个单值连续的反三角函数表示。由能量法确定了截面因子数值之后,定量地给出计入剪力时梁变形的分析结果。其结果和弹性力学的结来是一致的。