On the Modification of Hydration Resistance of CaO with ZrO2 Additive

Various ZrO₂/CaO samples were fabricated by cold isostatic pressing and sintered at 1750°C for 4 h. It was observed that the sample with 12% ZrO₂ additive possessed the good hydration resistance and had the lowest apparent porosity of about 0.75%; its weight additive stored after 56 days was less than 0.6 wt%, and it contributed to the occurrence of CaZrO₃ on the surface of CaO. The CaO crucible with 12 mol% ZrO₂ additive did not react with titanium melt during melting TiNi alloy. This provides a support for searching a new refractory with the good hydration resistance for induction melting titanium alloys.     

Pd/Ce0.6Zr0.4O2/Al2O3 as advanced materials for three-way catalysts: Part 1. Catalyst characterisation, thermal stability and catalytic activity in the reduction of NO by CO

Pd-loaded Ce_0.6Zr_0.4O₂ solid solutions supported on Al₂O₃ are investigated as catalysts for the reduction of NO by CO. The attention is focused on the role of the Ce_0.6Zr_0.4O₂ and of the Pd dispersion on the catalytic activity. The system shows a very high activity below 500 K, which is almost independent on the Pd dispersion. The high activity is attributed to a promoting effect of the Ce_0.6Zr_0.4O₂ on the NO conversion. Investigation of the influence of high temperature treatments disclosed a thermal stabilisation of both Ce_0.6Zr_0.4O₂ and Al₂O₃ in the Ce_0.6Zr_0.4O₂/Al₂O₃ system.     

Active sites in Cu/ZnO/ZrO2 catalysts for methanol synthesis from CO/H2

Among various Cu/ZnO/ZrO₂ catalysts with the Cu/Zn ratio of 3/7, the one with 15 wt.% of ZrO₂ obtains the best activity for methanol synthesis by hydrogenation of CO. The TPR, TPO and XPS analyses reveal that a new copper oxide phase is formed in the calcined Cu/ZnO/ZrO₂ catalysts by the dissolution of zirconium ions in copper oxide. In addition, the Cu/ZnO/ZrO₂ catalyst with 15 wt.% of ZrO₂ turns out to contain the largest amount of the new copper oxide phase. When the Cu/ZnO/ZrO₂ catalysts is reduced, the Cu²⁺ species present in the ZrO₂ lattice is transformed to Cu⁺ species. This leads to the speculation that the addition of ZrO₂ to Cu/ZnO catalysts gives rise to the formation of Cu⁺ species, which is related to the methanol synthesis activity of Cu/ZnO/ZrO₂ catalyst in addition to Cu metal particles. Consequently, the ratio of Cu⁺/Cu⁰ is an important factor for the specific activity of Cu/ZnO/ZrO₂ catalyst for methanol synthesis.     

添加物对MgO-ZrO2-C材料性能的影响

研究了Al和Si添加物对镁锆炭砖碳化烧成后膨胀性能的影响及机理。结果表明 :Al和Si在高温下氧化成Al2 O3和SiO2 ,继而与CaZrO3或用于稳定氧化锆的稳定剂反应 ,生成铝酸钙、MA、C2 S和M2 S,另外 ,C2 S和ZrO2 还发生了晶型转变。这一系列反应使试样产生很大的体积膨胀 ,从而破坏了制品结构。因此 ,与镁炭砖不同 ,Al和Si不但不能增强镁锆炭砖 ,而且使其结构破坏和耐侵蚀性降低。     

ZrO2-8mol%Dy2O3固体电解质燃料电池性能

将强碱介质中用水热法合成的立方相ZrO2-8mol％Dy2O3纳米晶在较低的温度（1400℃）下烧结,制得了导电性固体电解质陶瓷样品。以该陶瓷作为固体电解质,Pt作电极材料组成氢．空气燃料电池,测定了不同pH介质中水热反应产物纳米晶的陶瓷样品在800～1000℃下的燃料电池性能。结果表明,该系列陶瓷样品的燃料电池均具有稳定的放电性能,燃料电池的短路电流密度随着水热反应介质pH值的减小而增大。在该系列陶瓷中,水热反应介质pH=9．95的陶瓷样品的燃料电池性能最高,在1000℃下,其短路电流密度为320mA／cm^2。     

Isomerization of n-hexane over mono- and bimetallic Pd–Pt catalysts supported on ZrO2–Al2O3–WOx prepared by sol–gel

The catalytic performance of mono- and bimetallic Pd (0.6, 1.0 wt.%)–Pt (0.3 wt.%) catalysts supported on ZrO₂ (70, 85 wt.%)–Al₂O₃ (15, 0 wt.%)–WO_x (15 wt.%) prepared by sol–gel was studied in the hydroisomerization of n-hexane. The catalysts were characterized by N₂ physisorption, XRD, TPR, XPS, Raman, NMR, and FT-IR of adsorbed pyridine. The preparation of ZrW and ZrAlW mixed oxides by sol–gel favored the high dispersion of WO_x and the stabilization of zirconia in the tetragonal phase. The Al incorporation avoided the formation of monoclinic-WO₃ bulk phase. The catalysts increased their S_BET for about 15% promoted by Al₂O₃ addition. Various oxidation states of WO_x species coexist on the surface of the catalysts after calcination. The structure of the highly dispersed surface WO_x species is constituted mainly of isolated monotungstate and two-dimensional mono-oxotungstate species in tetrahedral coordination. The activity of Pd/ZrW catalysts in the hydroisomerization of n-hexane is promoted both with the addition of Al to the ZrW mixed oxide and the addition of Pt to Pd/ZrAlW catalysts. The improvement in the activity of Pd/ZrAlW catalysts is ascribed to a moderated acid strength and acidity, which can be correlated to the coexistence of W⁶⁺ and reduced-state WO_x species (either W⁴⁺ or W⁰). The addition of Pt to the Pd/ZrAlW catalyst does not modify significantly its acidic character. Selectivity results showed that the catalyst produced 2MP, 3MP and the high octane 2,3-dimethylbutane (2,3-DMB) and 2,2-dimethylbutane (2,2-DMB) isomers.     

Al对ZrO_2增韧Si_3N_4烧结体的相变及性能的影响

在高温 (140 0℃ )、超高压 (4.2GPa)条件下制备了Al ZrO2 (Y2 O3 ) Si3 N4 烧结体。采用XRD分析及力学强度测试等方法 ,研究了Al对ZrO2 相变能力及ZrO2 增韧烧结体作用的影响。结果表明 :在烧结体中加入 2 %Al,利用Al与N反应生成AlN可阻止Zr O N化合物生成 ,避免ZrO2 在Si3 N4 基体中被N稳定生成不可相变t′ ZrO2 ,提高ZrO2 的t→m相变能力 ,使ZrO2 起到增韧氮化硅烧结体的作用 ;当Y2 O3 含量为 2 %～ 2 .5 % (摩尔分数 )时 ,烧结体抗压强度及断裂韧性均较高 ,ZrO2 相变增韧作用最大。     

激光悬浮区熔定向凝固Al2O3/YAG/ZrO2三元过共晶合金的微观组织

利用自行研制的激光悬浮区熔设备制备了Al₂O₃/YAG/ZrO₂三元过共晶自生复合材料.在过共晶成分下获得了不含初生相的全共晶层片状组织.详细分析了固/液界面形貌形成原因,并由界面形貌出发阐述了Al₂O₃/YAG/ZrO₂三元过共晶组织织构化趋势.结果表明,低凝固速率下,三元过共晶成分下层片间距大于三元共晶成分下层片间距,而在高凝固速率下则相反,这主要是由于ZrO₂的加入影响了体系的传热及传质条件,通过经典非规则共晶模型综合分析了传输条件对层片间距的影响.过共晶平均层片间距(λ_av)与凝固速率（V）满足λ_avV^0.5=14.7μm^1.5·s^-0.5,符合JH模型.对于激光加工中经常出现的带状组织形成机理也进行了讨论.     

复合纳米固体超强酸SO4^2-／ZrO2-Al2O3-SiO2的制备及催化合成乙酸戊酯的研究

制备了纳米级复合固体超强酸SO4^2-／ZrO2-Al2O3-SiO2催化剂,研究了其对乙酸和正戊醇酯化反应的催化作用,确定了反应的最佳条件：复合氧化物中n（Zr）：n（AD：n（Si）=1：4：1,浸渍液（NH4）2SO4浓度为2mol/L,600℃焙烧3h,n（酸）：n（醇）=1：1．4,催化剂用量为反应物料总质量的4．4％,在130℃下反应6h,乙酸戊酯的收率为89．13％。并通过XRD、IR、流动Hammer指示剂法以及TEM法对催化剂进行了表征,该催化剂的酸强度为-12．70〈Ho≤-11．99。     

Oxidative dehydrogenation of ethylbenzene to styrene with CO2 over SnO2–ZrO2 mixed oxide nanocomposite catalysts

SnO₂–ZrO₂ nanocomposite catalysts with different compositions ranging from 0 to 100% of SnO₂ were prepared at room temperature by co-precipitation method using aqueous ammonia as a hydrolyzing agent. X-ray diffraction, transmission electron microscopic characterization revealed the SnO₂–ZrO₂ nanocomposite behavior. Acid–base properties of these catalysts were ascertained by temperature-programmed desorption (TPD) of NH₃ and CO₂. Both acidic and basic sites distribution of the nanocomposite catalysts is quite different from those of respective single oxides (SnO₂ or ZrO₂). Catalytic activity of these nanocomposite catalysts for ethylbenzene dehydrogenation (EBD) to styrene in the presence of excess CO₂ was evaluated. The change in the acid–base bi-functionality of the nanocomposite catalysts in comparison with single oxides had profound positive influence in enhancing the catalytic activity.