氧化铝基纳米复合陶瓷显微结构的研究

考察了Al2O3-SiC和Al2O3-ZrO2(3Y)-SiC纳米复合陶瓷的断裂方式。由于SiC的加入,材料以穿晶断裂为主。通过透射电镜观察,研究了纳米复合陶瓷中材料SiC颗粒的分布,证明所制备的材料为晶内型纳米复合陶瓷。在Al2O3-ZrO3(3Y)-SiC纳米复合陶瓷中,小的ZrO2颗粒分布于Al2O3晶粒内,大的ZrO2晶粒位于Al2O3晶粒间,ZrO2的分布影响Al2O3晶粒的形状。通过高分辨透射电镜,观察了Al2O3-SiC和Al2O3-ZrO2(3Y)-SiC纳米复合陶瓷中Al2O3/Al2O3,Al2O3/SiC,Al2O3/ZrO2的界面。在两颗晶粒间的晶界几乎没有玻璃相的存在,证明纳米复合材料中晶界得到了加强,有利于力学性能的提高。     

ZrO2-SiC材料中原位SiC生成量预报的神经网络模型

研究了基于神经网络的ZrO2-SiC材料中原位SiC生成量预报模型,运用材料制备过程中的工艺参数,实现了SiC生成量的预报.结果表明:本模型具有良好的预报效果,人工神经网络是材料性能定量预报的一种有效方法.     

太阳能热发电用氧化铝基复相陶瓷抗热震性及EPMA分析

为了提高Al2O3陶瓷的抗热震性及强度,在Al2O3基陶瓷中添加SiC、nano-ZrO2+SiC,利用无压烧结工艺,制备了用于太阳能热发电的Al2O3-SiC及Al2O3-ZrO2(3Y)-SiC复相陶瓷。材料的EPMA分析结果表明:样品中ZrO2颗粒在室温下为以亚稳四方相存在,在裂纹尖端应力场的作用下,ZrO2粒子发生四方相→单斜相的相变吸收能量,从而提高了材料强度及断裂韧性;原料中的部分SiC颗粒发生氧化反应,反应生成莫来石,针棒状莫来石形成桥连结构,阻止热震情况下产生的微裂纹发展成危险裂纹,从而提高材料抗热震性。SEM研究显示,SiC晶粒在外力作用下发生穿晶断裂、被拔出及桥结作用。     

流延法制备ZrO2/不锈钢功能梯度材料

采用流延法制备了ZrO2/316L不锈钢功能梯度材料,利用成分分布函数设计梯度层厚度来减小各层间的残余应力,通过改变黏合剂添加量得到各梯度层中ZrO2的体积分数(φ)和黏合剂与混合粉体积比(M)的关系:M=1.029φ 1.652,并研究了烧结工艺对材料组织形貌的影响.结果表明:在真空无压条件下,1 350 ℃烧结可得到成分呈梯度变化,各梯度层界面结合良好的ZrO2/316L功能梯度材料.     

人工神经网络及其在耐火材料研究中的应用

介绍了人工神经网络的发展、特点、模型及其在材料研究中的应用现状;并以反应烧结原位ZrO2-SiC（p）材料中SiC生成量的拟合预报为例,讨论了其在耐火材料研究中的应用。     

合成低聚甘油M/ZrO2催化剂的制备及性能

为寻找一种可用于连续化生产低聚甘油的固体碱催化剂,采用共沉淀法将Na+、K+、Ca2+、Sr2+、Ba2+掺杂到ZrO2中,分别制得Na/ZrO2、K/ZrO2、Ca/ZrO2、Sr/ZrO2、Ba/ZrO2,同时将制得的催化剂用于合成低聚甘油。通过XRD、Raman、CO2-TPD等方法研究掺杂不同金属离子对催化剂结构及其表面碱度的影响。采用GC,ICP等方法研究催化剂的活性和稳定性。结果表明,Na/ZrO2,K/ZrO2为单斜相,Ba/ZrO2为四方相,Ca/ZrO2,Sr/ZrO2为立方相,且各催化剂表现出不同的碱性位点。五种催化剂中Ca/ZrO2表现出最佳的稳定性, Ca2+浸出量为0.003%,催化剂用量减半并循环4次后,甘油转化率保持在22%以上,催化剂回收率在95%以上。在Ca/ZrO2用量为1 g,甘油用量100 g,反应温度270 ℃,反应24 h的条件下,低聚甘油产率为73.05%,选择性为100%。     

Si－C－O－N系统相稳定性及反应烧结制备原位SiC（p）复合ZAS材料

给制了Ｓｉ－Ｃ－Ｏ－Ｎ系统平衡状态下相稳定性与Ｎ２分压和Ｏ２分压以及相稳定性与Ｎ２分压和ＳｉＯ分压的关系图；以此为指导，将原位复合引入到反应烧结锆莫来石（ＺＡＳ）材料中，制备了含原位（ｉｎ－ｓｉｔｕ）ＳｉＣ（ｐ）的ＺｒＯ２ＳｉＣ（ｐ）、ＺｒＯ２－３Ａｌ２Ｏ３·ＺＳｉＯ２－ＳｉＣ（ｐ）－ＳｉＣ（ｐ）复合材料。研究了烧结温度、时间、碳添加量、成型压力等工艺因素对烧结ＺｒＳｉＯ４－Ｃ体系中原位ＳｉＣ生成量的影响，并观察了试样的显微结构。     

β-SiC粉体中常见金属杂质的亚临界水热去除工艺

高纯β-SiC粉体作为原料,广泛应用于半导体晶圆、半导体窑具、半导体芯片设备用陶瓷器件等产品。高温高压可以促进水热反应,采用亚临界水热法可去除工业合成β-SiC粉体中的金属杂质。研究不同酸体系下β-SiC粉体中常见金属杂质的去除效果。利用电感耦合等离子原子发射光谱仪(ICP-OES)检测微量元素的含量,通过X射线衍射仪(XRD)和扫描电镜(SEM)对β-SiC粉体的物相组成和微观结构进行表征。结果表明,对于Cr和Zr去除效果较好的是HCl体系,对于Ca、Fe、Mg和Ti去除效果较好的是HCl+HF+HNO₃体系,对于Al和K去除效果较好的是H₂SO₄+(NH₄)₂SO₄体系。采用HCl体系处理的最佳反应温度为200 ℃,采用HCl+HF+HNO₃体系处理的最佳反应温度是220 ℃,采用H₂SO₄+(NH₄)₂SO₄体系处理的最佳反应温度是200 ℃。其中,H₂SO₄+(NH₄)₂SO₄体系可将β-SiC粉体中常见金属杂质含量降低至最少(杂质总含量为920.31 mg/L),因此该体系为β-SiC粉体除杂的最优方案。     

MgO/ZrO_2的制备表征及催化合成碳酸二异辛酯

分别采用物理研磨、浸渍和共沉淀3种方法制备了负载型固体碱MgO/ZrO2催化剂,并将其用于催化碳酸二甲酯与异辛醇的酯交换反应合成碳酸二异辛酯。结果表明,催化剂的活性在焙烧温度为973 K时达到最佳,合成产物的收率分别为67.00%,51.00%,59.93%。催化剂的X射线衍射、CO2程序升温脱附、FTIR表征表明,催化剂的活性及稳定性取决于MgO/ZrO2的结构。四方氧化锆晶相对催化活性有积极的影响,当单斜氧化锆晶相明显时,催化活性显著下降。用物理研磨法制备的催化剂,由于MgO均匀分散于载体表面而使其显示高催化活性。用共沉淀法制备的催化剂,由于Mg2+进入Zr4+的晶格形成MgO/ZrO2固溶体结构,使其显示了高的稳定性和活性。     

溶胶-凝胶法在SiC纤维表面制备ZrO2界面层的研究

采用溶胶凝胶法(sol-gel)在SiC纤维表面制备氧化锆(ZrO2)界面层,考察了前驱体溶胶和烧结温度对界面层的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等测试手段对ZrO2界面层的晶体结构和表观形貌进行了分析。结果表明:当烧结温度为1 000℃,Zr4+金属离子浓度为1.0 mol/L,聚乙烯醇(polyvinylalcohol,PVA)质量分数为30%时,能够制备出完整致密的ZrO2界面层。     

Ni-ZrO2复合镀层形成过程的研究

采用复合电沉积技术制备出了Ｎｉ－ＺｒＯ２复合镀层,并利用正交设计对影响复合电沉积过程的有关因素进行了系统研究,镀液中ＺｒＯ２微粒表面荷电状况的分析表明,ＺｒＯ２微粒表面由于吸附子溶液中的Ｎｉ＾２＋而荷正电。     

Cobalt catalysts for Fischer–Tropsch synthesis: The effect of support,precipitant and pH value

In this report,Co-based catalysts supported on ZnO,Al_2O_3 and ZrO_2 as well as the ZrO_2 derived from different precipitants and different pH values were prepared by co-precipitation method.Their catalytic Fischer–Tropsch synthesis(FTS)performance was investigated in a fixed-bed reactor.The results revealed that Co catalyst supported on ZrO_2 exhibited better FTS catalytic performance than that supported on ZnO or Al_2O_3.For the Co/ZrO_2catalyst,different precipitants showed the following an activity order of NaOHNa_2CO_3NH_4OH,and the best pH value is 13.The catalysts were characterized by N_2adsorption–desorption,XRF,XRD,H_2-TPR,H_2-TPD and TEM.It was found that the main factor affecting the CO conversion of the catalyst was the amounts of low-temperature active adsorption sites.Moreover,the selectivity of C_5~+hydrocarbons had a positive relationship with the peak temperature of the weak hydrogen adsorption sites.The higher the peak temperature,the higher the C_5~+selectivity is.     

引入硅对固体超强酸催化合成萘齐聚物的影响

研究了 Si O2 的引入对固体超强酸催化剂 SO42 -/Zr O2 性能的影响 ,并将 SO42 -/Zr O2 -Si O2 应用到萘齐聚反应中以制备中间相沥青 .用热台偏光显微镜观察了固体超强酸 SO42 -/Zr O2及 SO42 -/Zr O2 - Si O2 在焙烧过程中形态结构变化及晶相转变过程 .另外发现 ,适量 Si O2 的引入提高了固体超强酸 SO42 -/Zr O2 晶相转变的温度 ,催化剂中 SO42 -的分解温度有较大提高 ,催化剂的TG- DTG曲线也有所变化 .固体超强酸焙烧温度、引入 Si O2 比例对催化剂的性质以及萘齐聚反应都会产生影响 ,对萘齐聚物的结构进行了初步分析 .     

液体在固体表面上的铺展动力学

Based on assuming that there is the precursor film in the front of the apparent contact line （ACL）, a model was proposed to understand the dynamic wetting process and associated dynamic contact angle. The present model indicated that a new dimensionless characteristic parameter, 2, attects the dynamic wetting process and associated dynamic contact angle as well. However, the previous model suggested that the dynamic contact angle is dependent＇on the capillary number and static contact angle only. An experimental investigation was conducted to measure the dynamic wetting behavior of silicon oil moving over glass, aluminum and stainless steel surfaces. It concluded that when the value of 2 was selected as 0.07, 0.16 and 0.35 for glass, aluminum and stainless steel, respectively, the experimental results were in good accordance with the prediction of the model. Furthermore, the comparison of the model with Strom＇s experimental data showed that 2 is independent on the species of liquids. Apparently, 2 should be interpreted as the effect of the solid surface properties on the dynamic wetting process.Meanwhile, it is found in the present experiment that the Hoffman-Voinov-Tanner law, which is valid at very low capillary number （Ca 〈〈 1 or 80〈 10°） recommend by Cazabat, still holds for higher contact angles, even up to 70°-80°. This is explained by （he present model very well.     

Scanning Tunneling Microscopy of Cubic Silicon Carbide Surfaces

Scanning tunneling microscopy is used to study β-SiC(001) surfaces. The β-SiC(001) single crystals were epitaxially grown by a two-steep chemical vapor deposition process on Si(001) wafer substrates. The overall surface topography of β-SiC is generally much rougher than that of Si wafers. Atomically resolved images corresponding to 3 × 2 and c (2 × 2) geometries of the β-SiC(001) surface are presented. Our results agree with models constructed from Si dimers for these structures. The larger-scale images show that the surface is under compressive stress and exhibits high density of defects, e.g., antiphase boundaries (APB's), in some areas. Images with unusual superstructures are also shown.     

Preparation of Silicon Carbide/Aluminum Nitride Ceramics Using Organometallic Precursors

Solid solutions of 2H -SiC/AlN can be prepared at temperatures less than 1600°C by rapid pyrolysis ("hot drop") of mixtures of [(Me₃Si)_0.80((CH₂=CH)MeSi)_1.0(MeHSi)_0.35] _n (VPS) or [MeHSiCH₂] _n (MPCS) with [R₂AlNH₂]₃, where R=Et, i -Bu or simply by slow pyrolysis of the precursor mixture in the case of [Et₂AlNH₂]₃. In contrast, slow pyrolysis of mixtures of VPS or MPCS with [ i -Bu₂AlNH₂]₃ yields a composite of 2 H -AlN and 3 C -SiC at 1600°C, which transforms into a single 2 H -SiC/AlN solid solution on heating to 2000°C. The influences of the nature of the precursor and processing conditions on the structure, composition, and purity of the SiC/AlN materials are discussed.     

Low temperature synthesis of β-SiC by a metal vapor vacuum arc ion source

β-SiC surface layers were synthesized by implantation of C⁺ into Si substrates at a comparatively low temperature of 400°C with a metal vapour vacuum arc ion source. X-ray diffraction patterns showed that these layers had a strong (111) preferred orientation. The amount of β-SiC formed increased significantly with the rise of the implantation dose, but the crystallinity of the layers formed relied little on the implantation dose. Both the broad X-ray diffraction peaks and the scanning electron microscopy photograph showed that the grain size of the sample with a dose of 7×10¹⁷ cm⁻² is relatively small.     

Corrosion Resistance of Ceramic Coating on Steel Substrate

Fe/Al2O3 ceramic coating was made by spraying and sol-gel. The corrosion resistance between Fe/Al2O3 ceramic coating and steel 45# was studied. By microscope and X-ray diffraction, the binding and the composition of the interface were also analyzed. The results showed that Fe/Al2O3 ceramic coating had dense struc- ture, less porosity and better binding with the substrate which was effective to prevent erosive liquor immersing into the inside of ceramic coating. Some substances that distributed homogeneously in Fe/Al2O3 ceramic coating, such as α-Al2O3, FeAlO3 and Fe3Al, could improve the corrosion resistance of this material.     

均匀设计在沉淀法制备纳米二氧化锆中的应用

用氨水作沉淀剂与氯氧化锆进行反应生成的胶体沉淀再焙烧制备出纳米二氧化锆。利用均匀设计考察了反应物量比、反应物浓度、焙烧温度和焙烧时间对产品平均粒径、分散性和晶形状态的影响。粒径由TEM测出 ,分散性和晶形状态由人为评分给出。研究表明反应物量比、氯氧化锆浓度和焙烧温度对产品性质影响较大。本实验优化的制备条件是 :n(氨水 )∶n(氯氧化锆 ) =3∶1;c(氯氧化锆 ) =0 .1mol/L ;c(氨水 ) =0 .5mol/L ;焙烧温度为 6 0 0℃ ;焙烧时间为 1h ,在此条件下可获得均匀分散的纳米二氧化锆 ,收率为 95 .4%。XRD分析结果表明 ,此产品主要为单斜晶形     

氧化锆负载硝酸盐固体碱催化剂的制备与表征

氧化锆分别用NaNO3、KNO3、Ca(NO3)2浸渍,经高温焙烧制得Na2O/ZrO2、K2O/ZrO2、CaO/ZrO2固体碱催化剂,将其用于碳酸二甲酯和异辛醇酯交换合成碳酸二异辛酯的反应。通过XRD、FT-IR、BET等表征手段,分析了催化剂的物相结构、硝酸盐与载体的相互作用及焙烧温度对催化剂活性的影响。结果表明,Na2O/ZrO2、K2O/ZrO2、CaO/ZrO2固体碱催化剂分别在600,500,700℃达到各自活性的最大值。Na2O/ZrO2具有高活性和高稳定性,K2O/ZrO2活性高,但是稳定性较差。