低温烧结高性能2Y-TZP材料

通过在2Y－TZP中加入一定量的硅酸盐玻璃相添加剂，在较低的烧结温度下，制备出细晶、具有良好综合性能的2Y－TZP材料，研究了添加剂加入后，2Y－TZP材料烧结特性、显微结构及力学性能。发现加入少量的添加剂后，不但可以明显降低材料的烧结温度，而且由于结晶及相变增韧的共同作用，材料仍具有较高的抗折强度和断裂韧性。讨论了稳定剂含量对低温烧结Y－TZP力学性能的影响，发现较低稳定剂含量的2Y－TZP材料，由于临界相变尺寸小，在断裂过程中，有更多的四方相氧化锆转变成单斜相，相变增韧的效果更好，因而具有更高的断裂韧性。     

纳米3Y-TZP陶瓷粉体形貌的分形分析

为了应用分形理论确定纳米3Y－TZP粉体制备方法的优劣，采用共沸蒸馏法和醇水溶液加热法制备了纳米3Y－TZP粉体，利用TEM观察确定了粉体粒径尺寸和团聚体形貌，并运用分形理论分析了分形维数和粉体烧结性能的关系。结果表明：纳米粉体在颗粒尺寸相同的情况下，粉体分形维数越低，团聚体半径越小，烧结性能越好；对粉体TEM图像进行分形维数计算并与粉体红外光谱分析和烧结结果进行了比较，确定醇水溶液加热法制备纳米3Y－TZP粉体效果较好。     

添加剂的膨胀系数对Y-TZP力学性能的影响

通过在Y－TZP中加入不同膨胀系数的玻璃相添加剂，低温烧结得到了具有不同力学性能的试样，建立了薄晶界应力模型，定性地计算了晶界应力，讨论了添加剂的热膨胀系数对Y－TZP陶瓷晶界应力及力学性能的影响。发现小膨胀系数的添加剂使晶界获得压应力，有利于获得较高断裂韧性的Y－TZP陶瓷。     

聚乙烯亚胺在SiC粉体上的定量吸附研究

利用紫外－可见光谱研究了分散剂聚乙烯亚胺在粉体ＳｉＣ上的定量吸附情况,加入酸性ＰＥＩ后粉体ＳｉＣ表面的电性发生改变,等电点由ＰＨ－２．０移至ＰＨ＝１０．５,分散 粉体上的吸附满足Ｌａｎｇｍｕｉｒ单层吸附方程,对分散为说,单层吸附值为０．０１７２ｍｇ／ｍＬ,对分散剂ＰＥＩ－Ｈ来说,意志支吸附值为０．０２０８ｍｇ／ｍＬ,ｔｊｅｔ ｐｇｋｌｔｊｈ ｋｆ ｘａ ｑｈ ｉｑｙｕｙｇｈ ｕｐｇ ｂｐ ｔｋｈ     

低温烧结细晶Y-TZP

通过在Y－TZP中加入达量的硅酸盐玻璃添加剂，使其烧结温度明显降低，并且制备出具有细晶粒，高强度的四方相氧化锆增韧陶瓷材料，分析了添加剂含量及烧结温度与材料致密度，显微结构及力学性能的关系，发现在Y－TZP材料中加入1wt%的添加剂，可以使材料在1400℃下烧结，氧化锆晶粒尺寸约为100－200nm，其抗折强度可达950MPa。     

Tiron对纳米Al2O3悬浮液性能的影响

以1，2－二羟基苯－3，5－二磺酸钠（Tiron)为分散剂获得了平均粒径约为57nm的氧化铝粉体的稳定悬浮液。通过测定等温吸附曲线及悬浮液的Zeta电位，研究了Tiron对粉体表面特性的影响。结果表明，Tiron在Al2O3表面发生化学吸附，磺酸基的离解使胶粒表面电荷更负，显著提高颗粒表面的带电量，从而改善浆料的稳定性。FTIR研究表明：Tiron分子结构中两个相邻羟基与Al-OH形成内环结构，从而提高了吸附强度。流变测试确定了制备在含量稳定浆料在pH=8.5时所需的最佳分散剂用量为0.8wt%。     

柱状莫来石弥散强化Y-TZP复合材料高温性能研究

采用化学共沉淀法制备Y－TZP超细粉料，通过适宜的无压烧结工艺烧成莫来石Y－TZP复合材料，探索了不同的莫来石含量对Y－TZP材料的常温及高温强度的影响，并对柱状莫来石弥散强化Y－TZP复合材料的机理做了初步讨论。     

BaTiO3颗粒对分散剂PMAA-NH4的吸附机制研究

通过ζ电位测量及PTIR分析，研究了BaTiO3颗粒对阴离子型分散剂PMAA－NH4的吸附机制。结果表明，加入PMAA－NH4后，由于BaTiO3颗粒表面上存在Ba-OH2^ 的正电荷中心，从而吸附了分散剂的阴离子，使BaTiO3表面带电特性改变，等电点由pH＝5.1移至pH=3.5，当pH=10，PMAA－NH4的加入量为0．8wt％时，BaTiO3颗粒表面吸附达到饱和，可以得到稳定性好的BaTiO3悬浮体。     

聚丙烯酸铵在纳米氮化钛上的定量吸附研究

研究了聚丙烯酸铵在纳米氮化钛粉体上的定量吸附及其影响因素，实验结果表明，纳米氮化钛的等电点在pH=3.8左右，加入分散剂PAA－NH4后，等电点移至pH=2附近，PAA－NH4在纳米氮化钛上的吸附量随吸附时间的增加而增加，同时溶液的酸碱性也影响吸附量，扫描俄歇分析结果表明：PAA－NH4吸附在纳米氮化钛颗粒表面上。     

聚电解质分散剂对Y-TZP悬浮液性能的影响

通过聚电解质聚丙烯酸铵（ＮＨ４ＰＡＡ）和聚甲基丙烯酸铵（ＮＨ４ＰＭＡＡ）的合成与在Ｙ－ＴＺＰ粉体上的等温吸附实验及红外分析发现,悬浮微粒的表面状态由于聚电解质的吸附而得到改变;ζ电位测定表明,阴离子型分散剂使粉体的等电点（ＩＥＰ）降低,浆料的流变性能也因为分散剂的加入而有明显的改善。     

抗水性AlN粉体的电动特性研究

通过测量粉体在水溶液中的Ｚｅｔａ电位和颗粒尺寸,研究了引入不同的分散剂时抗水性ＡｌＮ粉体的电动特性。结果表明,溶液的ｐＨ值和引入不同的分散剂均会导致抗水性ＡｌＮ粉体的表面荷电状况及其在水溶液中的分散状况发生变化。ＮＨ４ＰＡ是一种适合抗水性ＡｌＮ粉体水基流延用的有效分散剂,在碱性条件下添加该分散剂有利于抗水性ＡｌＮ粉体在水溶液中的稳定分散。     

超长侧链型聚羧酸梳形共聚物对水泥早期水化的影响

选用了一组超长侧链型聚羧酸梳形共聚物作为水泥体系的分散剂,通过水化热测定、强度试验和扫描电镜等表征手段,研究了超长侧链型聚羧酸梳形共聚物分散剂对水泥早期水化的影响.研究发现,超长侧链型聚羧酸梳形共聚物比普通聚羧酸梳形共聚物具有加速水泥水化、提高水泥基材料强度的作用.扫描电镜得到的形貌结果发现,超长侧链型聚羧酸梳形共聚物的掺入改变了水化产物的形貌,并且侧链越长,呈絮状的C-S-H凝胶和呈针状的钙矾石晶体明显增加.这说明超长侧链型聚羧酸加速了C-S-H凝胶和钙矾石晶体的形成,促进了水泥混凝土体系早期强度的形成.     

钡铁氧体磁粉在液相中的分散性能

为了提高分散作用效果,选用聚乙二醇-20000(PEG-20000)、十二烷基硫酸钠(SDS)及二者组成的复配分散剂,利用机械球磨与添加分散剂相结合的分散方法制备了钡铁氧体浆料,通过考察分散剂的用量、浆料的pH值、zeta电位对分散性的影响,根据红外光谱分析,研究了分散剂的分散效果及作用机理,并测定了分散前后磁场成型各向异性钡铁氧体材料的磁性能。结果表明:加入分散剂可以改善钡铁氧体的分散效果,且SDS和PEG-20000的用量为钡铁氧体质量的1%和2%时,分散效果最好。SDS和PEG-20000均为静电和空间位阻稳定作用。分散后磁场成型各向异性钡铁氧体材料的磁性能得到提高。     

铜金粉在水性体系中的分散性研究

采用涂-4粘度计、扫描电镜和光泽度仪对4种不同类型分散剂对铜金粉在水性介质中的润湿和分散行为进行了研究,并分析分散剂的作用机理。实验结果表明,分散剂通过改变铜金粉的表面特性、降低水性介质的表面张力而影响铜金粉在水性介质的分散性和印金光泽度,4种润湿分散剂均提高铜金粉的分散性,其中以全氟辛基磺酸钠(PSOS)的效果最好。用SEM照片分析进一步证明了分散效果,确定了分散剂的最佳用量。     

Effect of small amounts of additives on the sintering of high-purity Y-TZP

Superfine Y-TZP powders of high purity were prepared by using clean-room facilities. The effects of several kinds of minute or small amounts of additives on the densification and microstructural development of the Y-TZP powder were investigated. It was found that ≤1 wt% ferric or calcium oxides did not affect the densification of the Y-TZP powder compacts, while the addition of sodium oxides retarded the densification and that of copper oxide accelerated it, and these effects are most obvious at an additive level of 1 wt%. The retardation of the densification by sodium oxide was found to result from the agglomeration effect of the powder, and the formation of the eutectic liquid phase between zirconia and copper oxides promoted the densification and grain growth during sintering of copper oxide-doped powder. In addition, sodium and copper oxides both destabilize the tetragonal Y-TZP and lead to the formation of monoclinic phase. This revised version was published online in November 2006 with corrections to the Cover Date.     

Optimization of barium titanate nanopowder slip for tape casting

Dispersion of barium titanate nano powder of average particle size ∼30 nm in different solvent systems of tape casting (toluene–ethanol, methyl ethyl ketone–ethanol, xylene–ethanol) along with Triton x-100 or phosphate ester as dispersants has been studied using sedimentation experiments. The influence of different parameters such as type of solvent system, dispersant and concentration of dispersant on BaTiO₃ slip dispersion, viscosity and the properties of green tape were studied. The optimal concentration of dispersant was determined from the minimum slip viscosity. Xylene–ethanol with phosphate ester was found to be the best solvent and dispersant system for tape casting. Defect free, denser and smooth green tapes are formed with this system.     

Covalently bonded organosilicon and organoaluminium dispersants for silicon carbide

Covalently bonded organosilicon and organoaluminium compounds were used as dispersants for SiC powder and whiskers in hexane. The improved dispersion resulted in a threefold increase in whisker packing density in sedimented compacts. Comparison experiments with organosilanes having the formulas RSi (OCH₃)₃ and RSiCl₃ showed that the chlorosilanes were much more effective than their alkoxy counterparts in dispersing SiC powder. The aluminium alkoxy carboxylate aluminiumsec-butoxide stearate was also a much more effective dispersant for SiC than the alkoxysilanes. Fourier transform infrared spectroscopy and solid-state¹³C nuclear magnetic resonance were used to characterize the organometallic dispersants grafted to the surface of the SiC.     

Characterisation of aqueous suspensions of fumed aluminium oxide in presence of two Dolapix dispersants

The stability of a fumed aluminium oxide nano powder suspended in water has been assessed through measurement of zeta potential and streaming current, using the fact that the particles exhibit maximum repulsion at high magnitude of charge. Two commercial dispersants belonging to a Dolapix series have been tested. Dolapix CE 64 has shown a better deflocculating action than Dolapix A 88. The iso electric point of the powder suspension has been found close to pH 9. A notable shift in the pH of iso electric point when Dolapix CE 64 was present, indicating that the interaction between particles and dispersant has involved chemical sorption. It has been found out, that at the relative low solids loading studied and within the limits of the pH measurement accuracy, a dispersant supplied in dose levels from 12 to 24 mg/g, has confined the pH of iso electric point to a relatively narrow range. A capillary suction time technique has been tried for evaluation of suspension fluidity as function of dispersant concentration and pH. For the dispersant stabilised suspensions, a correlation between their capillary suction time and pH of iso electric point has been documented.     

Mechanical and magnetic properties of nickel-dispersed tetragonal zirconia nanocomposites

Effects of Ni dispersions on microstructure and mechanical properties have been studied for Y2O3-stabilized tetragonal zirconia (Y-TZP)/Ni nanocomposites with Ni dispersion up to 10 vol%. Composites were successfully fabricated by reducing and hot-pressing Y-TZP/NiO powder mixtures. Fracture strength was significantly improved from 1.5 GPa for monolithic Y-TZP to 1.9 GPa for nanocomposites with a small addition of Ni (1-2 vol%). Magnetic properties of Y-TZP/Ni nanocomposites were also investigated. Magnetization curves of Y-TZP/Ni nanocomposites showed typical hysteresis loops of soft magnetic materials, whereas coercivity was much larger than that of pure Ni metal. A new function arising from magnetomechanical effects of metallic Ni is also discussed for the present nanocomposites.