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     

B2O3—Y2O3添加剂对AlN陶瓷显微结构及性能的影响

研究了以Ｂ２Ｏ３－Ｙ２Ｏ３作为助烧结剂的ＡｌＮ陶瓷的烧结特性及显微结构。结果表明，晶界处存在ＹＡｌＯ３，Ｙ４Ａｌ２Ｏ３及Ｙ３Ａｌ５Ｏ１２等各种铝酸钇结晶物，Ｂ２Ｏ３可固溶到铝酸钇中形成固溶体。     

添加Al2O2对ZrO2（Y2O3）粉末性能的影响

采用化学共沉淀法制备了ＺｒＯ２（Ｙ２Ｏ３）和ＺｒＯ２（Ｙ２Ｏ３）／Ａｌ２Ｏ３超细粉末，研究了添加Ａｌ２Ｏ３对粉末性能的影响。添加Ａｌ２Ｏ３提高了ｔ－ＺｒＯ２的结晶化温度，抑制了ＺｒＯ２－ｍ－ＺｒＯ２相变。Ａｌ２Ｏ３相变。Ａｌ２Ｏ３添加量超过２０ｗｔ％时，粉末烧结活性降低，烧结温度提高。     

溶胶—凝胶法制备莫来石先驱粉末的烧结特性及材料的显微结构变化

对用溶胶－凝胶法制备的莫来石先驱粉末的晶化及烧结行为为进行了研究，先驱粉末在１０００℃煅烧１ｈ形成少量尖晶石，在更高的高度由这种尖晶石相及无定形ＳｉＯ２相形成莫来石，煅烧后的粉末具有很高的活性，在１５５０℃烧成０．５ｈ，烧结体相对密度达到９８．７％，陶瓷显微结构由细小等轴莫来石晶粒构成，随着烧成时间的延长或烧成温度的升高，烧结体中柱状莫来石晶粒变得越来越多。     

95Al2O3瓷烧成制度的研究

通过利用影像式烧结点仪对９５Ａｌ２Ｏ３瓷的烧成制度进行了初步研究，探讨了９５Ａｌ２Ｏ３瓷在烧结过程中的收缩变化情况及不同的烧成制度对９５Ａｌ２Ｏ３瓷显微结构的影响。研究发现，采用低温阶段快速升温、中温阶段缓慢升温、高温阶段快速升温和短时间保温的烧成制度有利于制度９５Ａｌ２Ｏ３的瓷的致密度，改善其显微结构。     

Si3N4—MgAl2O4—Al2O3系材料无压烧结的研究

本文对Ｓｉ３Ｎ４－ＭｇＡｌ２Ｏ４－Ａｌ２Ｏ３系复合材料的无压烧结进行了研究，讨论了Ａｌ２Ｏ３含量对材料性能的影响及烧结工艺对材料性能和显微结构的相互关系。实验表明：两段法烧结可以得到性能良好的Ｓｉ３Ｎ４－ＭｇＡｌ２Ｏ４－Ａｌ２Ｏ３复合材料。     

B_2O_3－Y_2O_3添加剂对AlN陶瓷显微结构及性能的影响

研究了以Ｂ_２Ｏ_３－Ｙ_２Ｏ_３作为助烧结剂的ＡｌＮ陶瓷的烧结特性及显微结构。结果表明，晶界处存在ＹＡｌＯ_３，Ｙ_４Ａｌ_２Ｏ_９及Ｙ_３Ａｌ_５Ｏ_（１２）等各种铝酸钇结晶物，Ｂ_２Ｏ_３可固溶到铝酸钇中形成固溶体。随烧结温度变化，第二相的种类、数量和分布不同，从而影响ＡｌＮ的热导率。在１８５０℃下，可获得热导率为１８９Ｗ／ｍ·Ｋ的ＡｌＮ陶瓷。     

Si_2ON_2-SiC复合材料制备研究

通过Ｓｉ粉、ＳｉＯ２微粉及ＳｉＣ,经氮化反应制备了Ｓｉ２ＯＮ２－ＳｉＣ复合材料,研究了烧结助剂、硅加入量、氮化制度对复合材料性能的影响,并对其进行强度、ＸＲＤ和ＳＥＭ分析后认为材料性能随烧结助剂、硅加入量变化而变化,氮化制度对材料的物相和显微结构有重要影响。     

化学共沉淀法制备微晶PSZ陶瓷的显微结构与力学性能

采用化学共沉淀法制备ＺｒＯ２－ＭｇＯ－Ｙ２Ｏ３系和ＺｒＯ２－ＭｇＯ－Ｙ２Ｏ３系均匀超细活性粉末，经化学组成和显微结构设计，获得了固溶湿度小于等于１５５０℃且致密烧结的微晶ＰＳＺ复相陶瓷，其常温抗弯强度为７６６ＭＰａ，断裂韧性Ｋ１ｃ为１２．５ＭＰａ·ｍ＾１／２。研究了ＭｇＯ和Ａｌ２Ｏ３以及１１００℃热处理时间对材料显微结构、相组成和力学性能的影响。     

不同工艺制备ZrO2—Al2O3复合陶瓷超细粉体的研究

采用正滴定工艺，反滴定工艺和水解工艺来制备ＺｒＯ２－Ａｌ２Ｏ３系复合陶瓷超细粉体。研究了制备工艺对水合氧化锆凝胶的包裹状态，煅烧后粉体中ＺｒＯ２颗粒的弥散状态以及烧结体显微结构的影响。结果表明采用水解工艺，ＺｒＯ２颗粒能均匀弥散在Ａｌ２Ｏ３颗粒周围，最终获得均匀细晶的陶瓷烧结体；在反滴定工艺中，虽然水合氧化锆凝胶能较好包裹Ａｌ２Ｏ３颗粒，但由于Ａｌ２Ｏ３颗粒本身得不到有效分散，因此在烧结体中出现了     

基于高岭土制备轻量微孔莫来石骨料结构与性能研究

以高岭土细粉和α-Al2O3微粉为主要原料,采用原位分解法制备轻量微孔莫来石骨料,研究了铝硅摩尔比及热处理温度对轻量微孔莫来石骨料结构与性能的影响.结果表明:经过1400～1600℃热处理后,富铝莫来石试样中除主要物相莫来石相外,还残余一定量刚玉相,接近理论莫来石组成试样及富硅试样均仅检测到莫来石相;所制备的轻量骨料孔径分布主要集中于0.1 ～4 μm范围,均具有微孔结构;随着热处理温度的升高,骨料的体积密度上升,显气孔率下降,耐压强度上升;经1500℃热处理后,富铝试样体积密度为2.49 g/cm3、显气孔率为25.6％、耐压强度为146 MPa;接近理论莫来石组成试样及富硅试样体积密度均小于1.95 g/cm3、显气孔率大于38.0％,1000℃时导热系数均小于0.77 W/(m·K).     

Sintering and Microstructure of Mullite Aerogels

Mullite (3Al₂O₃·2SiO₂) was prepared by a sol-gel process and dried by supercritical extraction with CO₂. The aerogel (<0.05 of the theoretical density of mullite) experienced a shrinkage of up to 0.6 and reached a density of only ∼0.5 of theoretical after 1 h at 1350°C Mechanically compacted aerogels, however, sintered to nearly theoretical density below 1200°C. This density is somewhat higher than those of gels prepared by conventional drying (i.e., exposure to the atmosphere) and is considerably higher than mullite prepared from mixed powders at higher temperatures. Although the X-ray diffraction pattern of the sintered gels was almost identical to that of mullite, transmission electron microscopy and energy-dispersive microanalysis showed two types of grain structure. Elongated grains with an Al/Si atomic ratio corresponding to that of stoichiometric mullite were surrounded by equiaxed grains with a lower Al/Si ratio.     

工业用高温热电偶瓷管材料烧结行为的研究

为制备工业用高温热电偶瓷管,本实验依据原位反应的原理,配制了不同Ａｌ２Ｏ３含量的试样,主要研究了以Ａｌ２Ｏ３作为第二相增韧增强的ｍｕｌｌｉｔｅ基复相陶瓷材料的烧结行为。     

莫来石结合Al2O3-SiC浇注料的显微结构特征

借助SEM和EDAX研究了莫来石结合Al2O3 -SiC浇注料的显微结构特征。结果表明 :在莫来石结合Al2 O3 -SiC浇注料中 ,莫来石相与填充在其间隙的玻璃相形成连续基质 ;刚玉颗粒与基质中SiO2 反应生成的二次莫来石与基质中的原生莫来石交错存在 ,构成网状结构 ;SiC颗粒表面高温氧化生成的SiO2 膜 ,改善了SiC颗粒与基质的润湿性 ,是其与基质直接结合的媒介。     

ρ-Al2O3添加量对原位反应结合碳化硅膜支撑体性能的影响

以黑色碳化硅为骨料,添加不同含量的ρ-Al2O3,在1430℃、无压条件下,用碳化硅表面氧化产生的SiO2与Al2O3反应制备多孔碳化硅膜支撑体,研究了ρ-Al2O3添加量对碳化硅支撑体粘结相组成及性能的影响。结果表明,ρ-Al2O3添加量由3wt%增加到15wt%时,试样烧结后粘结相中莫来石相增多,石英相减少但不能完全消除,支撑体的显气孔率降低,孔径减小,透气度由1127.8 m3?cm/(m2?h?kPa)下降到210.4 m3?cm/(m2?h?kPa);支撑体抗弯强度先增大后降低,ρ-Al2O3添加量为9wt%时,支撑体抗弯强度为25.1 MPa,透气度为372.7 m3?cm/(m2?h?kPa),支撑体的综合性能满足高温含尘气体过滤的要求。     

Effect of MgO addition and sintering parameters on mullite formation through reaction sintering kaolin and alumina

Abstract

In the present work, the influence of MgO addition and sintering parameters on the formation and densification of mullite was investigated. The morphology of powders and the microstructure of the sintered samples were characterised by means of a scanning electron microscope. X-ray diffraction was used to characterise phases formed in sintered samples. The density of sintered samples was measured using a densimeter and quantified according to the Archimedes principle. MgO was added at 1, 2, 3, 4, 5 and 6 wt-% to kaolin and alumina and the powders were ball milled for 5 h then uniaxially compacted at 75 MPa and finally sintered at 1500, 1550, 1600 and 1650°C for 2, 4, 6 and 8 h. It was found that addition of MgO not only affected mullite formation but also promoted grain growth. For samples containing 0, 1 and 2 wt-%MgO only mullite was formed. While, in addition to mullite, Al₂O₃ was present in sample containing 3 wt-%MgO. At higher MgO content (4, 5 and 6 wt-%), three phases, i.e. mullite, Al₂O₃ and spinel, were formed. Addition of 1 wt-%MgO increased the density of all samples for all sintering times and higher densities corresponded to higher sintering temperatures. At higher MgO content, higher temperatures led to lower densities and lower temperatures led to higher densities for almost all sintering times.     

Al2O3/SiC复合陶瓷的反应烧结

在空气中于1600℃对Al2O3/0.78%SiC纳米复合体进行2h的反应烧结,制得Al2O3/5%莫来石复合陶瓷,其中的莫来石分为两类,即3Al2O3·2SiC和Al5.65Si0.35O9.175。采用SEM和TEM研究Al2O3/莫来石复全陶瓷的微观结构。对Al2O3/莫来石复合陶瓷的密度和力学性能如杨氏模量、泊松比、硬度、韧性和强度进行了研究。     

氧化锆基纳米复相陶瓷研磨介质的研制与应用

用Y-TZP作为基础相,采用成功的粉体制作工艺,复合AlCl3·6H2O进行化学法混合,然后加入自制的纳米莫来石A3S2和纳米SiO2进行混磨,制备了纳米氧化锆复相陶瓷ZTC。利用Y-TZP材料优良的室温力学性能,同时加入适量的添加剂SiO2和Al2O3,促进莫来石材料的形成,提高其在较高温度下抗水解、抗老化、硬度高的性能。所制得的ZTC材料,既保留了TZP材料优良的室温耐磨性,同时又避免了在水热蒸汽下温度高于60℃时TZP材料较易水解老化的问题,与TZP、Al2O3磨介相比,其性能价格比最优,铝球的价格低、锆球的质量好,使材料的应用领域得到扩展。     

Effects of SiO2/Al2O3 ratio of H-mordenite on encapsulated products inside the pores in shape-selective isopropylation of biphenyl

The effects of SiO2/Al2O3 ratio of H-mordenite on the selectivity of encapsulated products in the pores and of bulk products were investigated in the isopropylation of biphenyl. The selectivity of 4,40 -diisopropylbiphenyl (4,40 -DIPB) of bulk products was varied with SiO2/Al2O3 ratio. Highly dealuminated H-mordenite gave a selectivity higher than 80%, whereas the selectivity was low for H-mordenite with SiO2/Al2O3 ratio of 10-20. On the other hand, the selectivity of 4,40 -DIPB in encapsulated DIPB isomers was higher than 85% for all H-mordenites regardless of SiO2/Al2O3 ratio. These results show that all H-mordenites catalyze the isopropylation of biphenyl with high shape-selectivity inside the pore. The low selectivity of 4,40 -DIPB in bulk products for H-mordenites with low SiO2/Al2O3 ratio was not due to a lack of shape-selectivity of the H-mordenites, but to non-regioselective isopropylation at the external acid sites. Non-regioselective catalysis over H-mordenite with low SiO2/Al2O3 ratio could be induced by choking pores by coke deposition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Algerian kaolinite used for mullite formation

In the present study, mullite was synthesized through reaction sintering of Algerian kaolinite and high purity alumina. The raw powders were wet ball milled in a planetary ball mill. Powders' morphology and the microstructure of the sintered samples were characterized by means of a scanning electron microscope. An X-ray diffractometer equipped with a heating facility and a differential thermal analyzer were used to follow mullite formation. Cylindrical specimens were produced by uniaxial cold compaction at a pressure of 75 MPa and sintered at different sintering temperatures for different sintering times. The heating rate was 10 °C/min. It was found that Algerian kaolinite was suitable for mullite production through reaction sintering with pure Al₂O₃. Formation of complete mullite occurred at 1550 °C. A relative density of 94% (of the theoretical density) was achieved at a relatively low sintering temperature of 1600 °C and a sintering time of 4 h.