Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统乳浊釉的研究

对Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统釉进行了较全面的正交试验研究,找到了影响该系统釉乳浊及釉面质量的主次因素,获得了性能良好的乳浊釉及其较优乳浊釉配方.     

SiO_2-ZrO2-Na_2O玻璃中SiO_2、TiO_2、ZrO_2受碱侵蚀的研究

吴正明等在1986年曾报道(76-x)SiO_2·XZrO_2·6 TiO_2·5CaO·10.4Na_O·2.6K_2O(氧化物前的系数为重量百分数,X为引入ZrO_2的重量百分数)玻璃随ZrO_2含量的变化受碱侵蚀前后试样失重百分数的变化.为进一步查明在上述系列玻璃中,当以ZrO_2代替等重量的SiO_2后,系统中各主要氧化物(SiO_2,TiO_2,ZrO_2)受碱侵蚀的变化,特开展了本次试验.     

H_2O_2的新制法

<正> 据(日)《化学工业时报》1988.3.25报道,美国杜邦公司开发出制造过氧化氢的新方法,与现行的蒽醌法相比较,建设费用可削减50％。新制法是在铂族金属催化剂和卤离子存在下,使氢与氧反应。采用Pd/C催化剂和2％(重)以上的非有机化合物水溶液时,可提高收率,尤其是在氯化氢存在下,可生成13％以上浓度的过氧化氢。反应温度在-10℃以下,压力35～176kg/cm~2。生成物的浓度随操作压力的提高而增高。本     

MgF2基催化剂合成CH2F2的研究

用混合法制备了一系列含Cr3＋和过渡金属助剂的MgF2基催化剂。考察了助剂对CrF3/ MgF2 催化剂氟化CH2Cl2的催化性能，结果表明，在Cr3＋/ MgF2中添加一定的Co2＋和Ni2＋能提高催化剂稳定性，延长使用寿命；Zn2＋能提高CH2F2的选择性；Fe3＋和Cu2＋对Cr3＋/ MgF2的活性有抑制作用。讨论了配料比、空速和温度等反应条件对催化剂性能的影响。     

电沉积Cu2xIn2—2xSe2薄膜的光电化学研究

用电沉积法制得Ｃｕ２ｘＩｎ２－２ｘＳｅ２（铜铟硒）（０＜ｘ＜１）薄膜＾［１］并用ＥＤＡＸ对其组成进行分析。对薄膜电极的光电化学性能、光谱响应、能隙与ｘ的依赖关系进行了研究。借助于现场微区扫描光电流谱观察了热处理、薄膜厚度、光极化对薄膜电极的光电性能影响。研究了Ｐｂ（ＮＯ３）２有效的浸渍对簿膜光电性能的影响。     

MgO-Al_2O_3-SiO_2-TiO_2-CeO_2微晶玻璃的相转变

通过DTA ,XRD ,TEM ,SEM和EDS等测试手段 ,研究了MgOAl2 O3SiO2 TiO2 CeO2 微晶玻璃的相转变过程。研究结果表明 :退火后的原始玻璃已存在液相分离结构。在热处理过程中硅钛铈矿 (Ce2 Ti2 Si2 O1 1 )首先在 840℃从富含Ti4 ,Ce4 的孤立液滴相中析出。金红石 (TiO2 )晶核于 95 0℃开始形成。α堇青石相在 114 0℃左右从富含Si4 ,Al3 的玻璃相中大量生成。当温度升高到 12 0 5℃时 ,部分硅钛铈矿分解并与残余玻璃相反应生成金红石和新相氧化铈。通过控制晶化得到的MgOAl2 O3SiO2 TiO2 CeO2 微晶玻璃 ,其晶相由硅钛铈矿、金红石、α堇青石及少量氧化铈构成     

Na_2O-K_2O-RO-SiO_2-Al_2O_3生料颜色釉的研究

选用单一或复合的钙、镁、钡、锌、锶氧化物作为RO,制备了Na_2O-K_2O-RO-SiO_2-Al_2O_3系统生料釉。在此基础上,研究了Fe_2O_3、MnO_2、Co_2O_3、NiO、V_2O_5、SnO_2、TiO_2中任意两种配合,在CaO-ZnO、CaO-SrO、MgO-ZnO碱土釉中的显色效果。结果表明:(1)不同成分及比例的RO对釉面效果影响显著,钙碱土往往可以搭配其它RO而形成质量良好的釉面;(2)复合离子型着色剂易在Na_2O-K_2O-CaO-ZnO-SiO_2-Al_2O_3系统中产生复杂的"窑变"现象而使釉面产生花色效果,当ZnO全部被SrO置换后,有明显的降低釉面花色趋势,且使釉面效果单一、颜色加深;(3)镁锌釉中,复合离子型着色剂往往会使釉面产生一定的斑点效果,但由于高温黏度大,釉面质量一般,并会产生一定的鼓泡和气孔缺陷。     

MgO-Al2O3-SiO2-TiO2-CeO2微晶玻璃的相转变

通过DTA，XRD，TEM，SEM和EDS等测试手段，研究了MgO—Al2O3一SiO2一TiP2-CeO2微晶玻璃的相转变过程。研究结果表明：退火后的原始玻璃已存在液相分离结构。在热处理过程中硅钛铈矿(Ce2Ti2Si2O11)首先在840℃从富含Ti^4 ，Ce^4 的孤立液滴相中析出。金红石(TiO2)晶核于950℃开始形成。α堇青石相在1140℃左右从富含Si^4 ，Al^3 的玻璃相中大量生成。当温度升高到1205℃时，部分硅钛铈矿分解并与残余玻璃相反应生成金红石和新相氧化铈。通过控制晶化得到的MgO—Al2O3-SiO2-TiO2—CeO2微晶玻璃，其晶相由硅钛铈矿、金红石、α堇青石及少量氧化铈构成。     

Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统乳浊釉的乳浊机理研究

本文对Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统乳浊釉的乳浊机理进行了研究.借助于XRD分析,发现该系统乳浊釉为熔析乳浊釉,主要乳浊相是α-CaSiO3,晶相和CaSiO3晶相.     

Na2O-Li2O-Al2O3-SiO2-P2O5玻璃的结构与性能的分子动力学模拟

磷硅酸盐玻璃因有着良好的生物活性和光学性能,已广泛用于生物材料、光纤等领域。运用分子动力学模拟方法研究Li₂O含量对Na₂O–Al₂O₃–SiO₂–P₂O₅玻璃的微观结构以及扩散性能影响,着重讨论了其微观结构与维氏硬度,扩散系数之间的关系。结果表明:玻璃的磷网络聚合度（Q^p）随着Li₂O逐渐替代Na₂O而增加,硬度随着Q^p的增加而增大。体系中Li⁺的自扩散系数比Na⁺大,即Li⁺比Na⁺更易扩散。Li⁺的势垒随着Li₂O增加而逐渐变小,Li₂O对Na₂O取代有益于Li⁺扩散。     

钛酸镍水基浓悬浮体的制备及流变特性研究

测定了超细NiTiO3粉体的ζ-电位,并研究了分散剂聚甲基丙烯酸铵(NH4PAA)的用量对NiTiO3悬浮体粘度的影响。结果表明:超细NiTiO3粉体在水中的等电点约为5.0;悬浮体的粘度与分散剂的用量有关,并得出最佳用量约为粉体质量的0.4wt%;研究了不同水基浓悬浮体的流变特性,成功地制备出体积分数为60vol%的低粘度(0.75Pa·S,剪切速率为50S-1)悬浮体。     

Dispersion behaviour of laser-synthesized nanometric SiC powders in aqueous medium with ammonium polyacrylate

The dispersion behaviour of laser-synthesized nanometric SiC powders in water using ammonium polyacrylate (molecular WEIGHT=10,000) as dispersant was investigated. The influence of oxidation, presoaking time, ammonium polyacrylate (NH₄PA) concentration, and pH on suspension stability and coagulation rate of aggregates was determined. The stabilization mechanism is discussed. Excellent dispersion stability was obtained for oxidized (500 °C) powders containing 2.45 wt.% NH₄PA at pH 9.25 after a lengthy aging treatment.     

YAG ceramic processed by slip casting via aqueous slurries

Stable YAG (Y₃Al₅O₁₂) aqueous slurry with ammonium polyacrylate (NH₄PAA) polyelectrolytes as dispersant was prepared by ball mill method. The effects of polyelectrolyte concentration and pH value on the stability of the suspension is described here, and the stability maps are constructed at different pH value and polymer concentration. The rheological behavior of YAG slips of different solid loading (60–70%) has been studied by measuring their viscosity and shear stress as a function of shear rate and pH of the slurry. An optimal amount of dispersant and pH value for the suspension was found. YAG suspension displays a maximum in zeta potential values and a minimum viscosity in pH range of 9–11. Slips behaved as near Newtonian at the pH value up to a solid loading of 60 wt% and as non-Newtonian with thixotropic behaviors above this solid loading value. The density and the green as well as sintered microstructure of the cast products bear a direct relationship to the state of this slips induced by the alternation in the pH and the concentration of the dispersant as well as solid loading.     

Effect of varied powder processing routes on the stabilizing performance and coordination type of polyacrylate in alumina suspensions

The influence of initial pH and energy input during suspension homogenization on the stabilizing performance and coordination type of commercial available polyacrylate dispersant were studied. Additionally to widely used rheology and electroacoustic measurement techniques the alumina suspensions were analysed with centrifugal separation and in situ ATR-FTIR to study the impact of varied powder processing in detail. In contrast to zeta potential analysis and viscosity measurements only the determination of sedimentation properties by centrifugal separation shows the effect of macroscopic changes in powder processing. A combination of positively charged alumina surface and a high shear homogenization leads to the most stable suspension. Accordingly ATR-FTIR results show a correlation between improved suspension stability and inner-sphere coordination of polyacrylate. Moreover it was possible to determine an optimal pH range for inner-sphere adsorption. It can be shown that macroscopic changes in powder processing influence the coordination of dispersant and thus the suspension stability.     

Coagulation of electrosterically dispersed concentrated alumina suspensions for paste production

The effect of salt induced coagulation of concentrated alumina suspensions initially electrosterically dispersed with ammonium polyacrylate (NHPA) has been investigated. Addition of ammonium chloride caused enhanced adsorption of the NHPA onto the alumina surface. In terms of suspension characteristics minimum viscosity and minimum sediment height coincided with the attainment of complete surface coverage of the dispersing agent (3.7 mg g⁻¹). Coagulation resulted in a reduction in the degree of sample homogeneity in all samples. Coagulation of suspensions initially dispersed with NHPA levels below that needed for complete surface coverage under coagulated conditions (1.4 mg g⁻¹) produced viscous pastes with a yield stress suitable for processing by extrusion. At 70 wt% solids the green densities could not be distinguished from corresponding flocculated samples. Significantly, however, at 80 wt% solids a small degree of homogeneity was retained upon coagulation resulting in a higher green density than those prepared by a flocculated route. The approach of initial dispersion followed by coagulation is therefore of potential benefit in the processing of viscous, pastes such that higher degrees of homogeneity can be achieved compared to those prepared by a flocculated route.     

Rheological properties of nanosized barium titanate prepared by HGRP for aqueous tape casting

The conditions for the preparation of stable nanosized barium titanate suspensions with high solids content for the production of aqueous tape casting are identified. The rheological behavior of colloidal barium titanate suspension with Ammonium polyacrylate (NH₄-PAA) as a dispersant to aid the powder dispersion has been investigated. Nanosized barium titanate powder was synthesized by a continuous high-gravity reactive preparation (HGRP) technique, and then annealed at 900 °C for 2 h. Measuring the zeta potential, the particle size distributions and ball-milling time, assessed the optimum conditions of the suspension with low viscosity and stability. An isoelectric point (IEP) at pH = 2.8 was found. Particle size distribution tests identified an optimum pH value about 10 and an optimum dispersant addition about 1.2 wt.% (based on the dry powder weight). As the ball-milling time was longer than 8 h, the amount NH₄-PAA adsorbed on the barium titanate reached to saturation. The maximum solid content attained during this work was 45 vol.% at pH of 10, with dispersant addition 1.2 wt.%. High green density value (up to ∼55.4% of the theoretical density) in BaTiO₃ sheet was achieved with a solid content 40 vol.%. After sintering at 1200 °C for 2 h a final density of 95% is reached.     

Effect of Green Density on the Subsequent Densification and Grain Growth of Ultrafine SnO2 Powder during Isochronal Sintering

An ultrafine powder of SnO₂ has been synthesized by a gas flow condensation method. The average particle size of the powder was about 40 nm. The effect of the green density on the subsequent densification and grain growth of the ultrafine SnO₂ during sintering has been studied. A loose green compact consolidated under 500 MPa (green MC) showed rapid densification as well as rapid grain growth at relatively low sintering temperatures. A dense green compact fabricated under 4.5 GPa (green GC) exhibited a slow increase in the density and almost no grain growth even at high sintering temperatures.     

Centrifugal Casting of Tubular Perovskite Membranes

Dense tubular membranes were produced by centrifugal casting of an aqueous suspension, containing powder particles of the mixed-conducting perovskite La_0.5Sr_0.5CoO_3−δ and a dispersant. The resulting green bodies were dried and sintered to produce tubes with a maximum length of 12 cm, having a relative density higher than 92%. The particle morphology, the amount of dispersant and its burnout appeared to influence the quality of the final product. Oxygen permeation measurements were conducted in the temperature range 850°–950°C in Air/He gradients. Results were found to be consistent with data reported for disk-type membranes.     

高强高密石墨材料的制备研究现状

讨论了高强高密石墨材料的性能和应用,从原料选择和工艺强化两个方面进行了分析。重点讨论了超细石墨粉、生焦粉、中间相炭微球、"二次焦"、COPNA树脂等原料制备高强高密石墨材料的优点和实际应用中的不足,对现行的高压成型、加压焙烧、加压成型焙烧、多次浸渍再焙烧进行了分析总结。     

Improvement of the deflocculating power of polyacrylates in ceramic slips by small additions of quaternary ammonium salts

In this work, we examine the effect of small additions of cationic quaternary ammonium salts (QAS) of different molecular weight on the rheology of an industrial ceramic suspension deflocculated with sodium polyacrylate and sodium metasilicate. The observed shear thinning behaviors obey the typical power law of fluid rheology. In order to characterize the rheological behavior of these slurries, three new parameters are introduced: a low shear rate consistency index and two transient viscosities, distant from the equilibrium, after increasing and decreasing the shear rates. These parameters vary with polyacrylate molecular weight and on additions of small quantities of QAS, which we found to be useful for decreasing the slurry viscosity.