Polishing of zirconia ceramics by chemically-induced micro-nano bubbles

This study introduces micro-nano bubbles (MNBs) in the process of polishing zirconia ceramics through sodium borohydride hydrolysis to assist in polishing yttria-stabilized zirconia (YSZ). Compared with conventional silica sol, the material removal rate using this MNB-assisted technology is increased by 261.4%, and a lower surface roughness of 1.28 nm can be obtained. Raman, X-ray diffraction, and X-ray photoelectron spectroscopy are used to study the structural changes and phase stability of the YSZ during different polishing periods. The results show that MNBs are the key factor promoting the transformation from the tetragonal phase to the monoclinic phase on the surface of the YSZ during polishing. The H₂O molecules (or OH^? ions) on the surface of the YSZ are driven by the thermal kinetic energy of the micro-jets formed by the collapse of micro-bubbles, and they permeate to occupy more oxygen vacancies in the crystal lattice. Atomic force microscopy and nano-indentation tests show that the micro-protrusions on the surface of the YSZ preferentially undergo phase transformation, and their hardness decreases. This promotes abrasives to preferentially remove rough spots on the surface and achieve more efficient polishing. We believe this work adds valuable insights regarding low-temperature degradation and ultra-precise machining of YSZ ceramic materials.     

负载型复合载体及其镍基催化剂的性能

采用溶胶-凝胶法制备了负载型ZrO_2/Al_2O_3和ZrO_2/Al_2O_3-SiO_2复合载体,研究了不同复合载体对Ni基催化剂CO_2重整甲烷反应和性能的影响,并用XRD、IR、TPR、TPD和BET等方法对复合载体及催化剂进行了表征。结果表明,ZrO_2负载在基载体后比表面积、碱性、活性组分Ni的分散度和Ni与ZrO_2的相互作用增大。NiO在复合载体表面的分散容量与ZrO_2的负载量有关,ZrO_2的负载量为37．5%时NiO的分散容量达最高值(24．0%)。与Ni/ZrO_2相比,Ni/ZrO_2/Al_2O_3-SiO_2和Ni/ZrO_2/Al_2O_3催化剂对CO_2的吸附能力增大,CO_2吸附量增加,酸强度降低,CO_2重整CH_4反应活性提高,其中以Ni/ZrO_2/Al_2O_3催化剂的活性最好。     

ZrSiO4/α-Al2O3反应烧结过程中非晶态物质的形成与演化

采用XRD和TEM等技术研究了ZrSiO4/α-Al2O3反应烧结过程中非晶态物质的形成及演化。结果表明，1400℃莫来石开始形成时体系中的液相是富Al2O3的，随着温度的升高，ZrSiO4分解速率加快及富Al2O3莫来石的形成，液相逐渐向富SiO2方向演化，液相的形成及其演化与莫来石的形成密切相关。     

纳米ZrO2等离子涂层的结构,性能和工艺特点

采用大气等离子喷涂技术(APS)，制备了常规氧化锆和纳米结构氧化锆两种涂层．利用扫描电镜(SEM)对涂层的显微结构进行了观察．对两种涂层的沉积效率、表面粗糙度和显微硬度作了对比研究．结果表明，粉末原料的显微结构、粒度、形态、喷涂工艺参数(喷涂功率和距离)对涂层的显微结构有较大的影响．等离子喷涂造粒纳米氧化锆粉制备的涂层沉积效率高而稳定，其显微结构与喷涂功率和距离密切相关．与常规氧化锆涂层相比，纳米结构氧化锆涂层具有较高的显微硬度和较低的表面粗糙度．     

Sulfated zirconia catalysts: Are Brønsted acid sites the source of the activity?

The thermal decomposition products of pyridinium sulfate differ from those of pyridinium sulfate supported on zirconia which in turn differs from that of pyridine adsorbed on a sulfated zirconia. Unsupported pyridinium sulfate decomposes to produce pyridine and sulfuric acid, and these subsequently react to produce oxides of carbon and sulfur. Zirconia that is sulfated and then exposed to pyridine does not release detectable amount of pyridine during heating in an inert gas; rather the pyridine undergoes oxidation reduction reactions simultaneously to release CO₂ and sulfur compounds. Pyridinium sulfate supported on zirconia decomposes upon heating to release pyridine and sulfuric acid, which reacts with the zirconia. The desorption of pyridine in one case and only CO₂/SO_x in the other case suggests that sulfated zirconia does not contain Brønsted acidity that can form pyridinium sulfate.     

SiC（w）／TZP＋mullite陶瓷复合材料界面和组成设计与力学性能

本文从理论上分析了ＳｉＣ（ｗ）ＴＺＰ＋ｍｕｌｌｉｔｅ（ｐ）复合材料界面残余热应力及其在基质内的分布规律。提出在ＳｉＣ（ｗ）表面涂复Ａｌ２Ｏ３和在ＰＺＴ中加入ｍｕｌｌｉｔｅ（ｐ）联合作用来降低晶须／基质界面残余热应力的界面设计方案，导出ＳｉＣ（ｗ）和ｍｕｌｌｉｔｅ（ｐ）协同补强ＰＺＴ的匹配条件。制备了ＳｉＣ（ｗ）／ＴＺＰ＋ｍｕｌｌｉｔｅ（ｐ）复合材料并了ＳｉＣ（ｗ）表面涂层Ａｌ２Ｏ３厚度和ＳｉＣ（ｗ     

Revised Model of Strain in Ceria–Zirconia-Encapsulated Precious-Metal Particles

A previously proposed model of strain in ceria–zirconia-encapsulated precious-metal particles is revised to reflect several new observations: encapsulation of unstrained Pt particles, quantitative relation between partial reduction and the change in ceria–zirconia cell parameters, temperature/time dependence of strain relaxation/imposition in encapsulated Pd and Rh particles, and strained PdO. According to the revised model, the main cause of strain is partial oxidation of the precious metal (rather than the change in oxygen content of ceria–zirconia, as originally suggested).     

β″－Al_2O_3陶瓷的强化和韧化

研究了稳定ＺｒＯ＿２和部份稳定ＺｒＯ＿２对β″－Ａｌ＿２Ｏ＿３陶瓷的强化和韧化作用，观察了不同种类、不同含量的ＺｒＯ＿２对β″－Ａｌ＿２Ｏ＿３陶瓷的显微结构、力学性能和电导率的影响，探讨了β″－Ａｌ＿２Ｏ＿３的韧化机理。     

Hydrodechlorination of 3-chloropyridine and chlorobenzene in methanol solution over alkali-modified zirconia-supported palladium catalysts

The liquid-phase hydrodechlorination of 3-chloropyridine and chlorobenzene has been studied over alkali-modified zirconia-supported palladium catalysts. The modification of the ZrO₂ with alkali metal carbonates improves the catalytic activity of the final palladium catalyst. Therefore, the larger the ionic radii (Li⁺ < Na⁺ < K⁺), the greater the catalytic activity (TOF) of the palladium catalyst. For 3-chloropyridine, hydrodechlorination proceeds without catalyst deactivation. This is explained as the result of the interaction of reaction products (pyridine and HCl) forming pyridinium chloride, thus avoiding the detrimental effect of HCl on the palladium particles. Catalytic hydrodechlorination of chlorobenzene over Pd catalysts exhibits an initial catalytic activity (TOF) much lower than that of 3-chloropyridine and the Pd catalysts deactivate as the reaction proceeds. Finally, chlorobenzene hydrodehalogenation has also been carried out in the presence of an equimolecular amount of pyridine resulting in a decrease in the initial reaction rate on the one hand, but also in an increase in final conversion on the other.