共查询到20条相似文献,搜索用时 99 毫秒
1.
2.
本试验以工业氧化铝、工业钛白粉为主要原料,通过添加SnO2、Y2O3等添加剂,采用一步烧结法合成了含钛酸铝90%以上的陶瓷材料,经1100℃左右保温10小时分解试验,保持较好的稳定性。 相似文献
4.
用传统熔融冷却法制得SiO_2-B2O3-Bi3O_2系统玻璃,采用差热分析法研究了玻璃的结构和玻璃的特征温度Tg和Tf,测试了玻璃的密度、热膨胀系数、介电常数等性能。结果表明,在SiO_2-B_2O_3-Bi_3O_2系统玻璃中,当ZnO含量增加,ZnO/SnO_2质量比上升时,玻璃的热膨胀系数、密度和摩尔体积均呈下降趋势,玻璃的转化温度Tg和软化温度Tf变化不大,析晶温度Ts则有明显的上升。 相似文献
5.
以氯氧化锆、硝酸铈、硝酸铝为原料,按n(Ce)∶n(Zr)=0.7∶0.3的比例,采用化学共沉淀法与有机物共沸蒸馏法,将CeO2、ZrO2分散到γ-Al2O3表面上使其形成Ce0.7Zr0.3O2/γ-Al23固溶体。用XRD考察纳米固溶体在不同温度下焙烧后的相结构。结果表明:Ce0.7Zr0.3O2/γ-Al2O3纳米固溶体为立方晶型,且随着焙烧温度的升高,样品的衍射峰依次变强,峰宽变窄。 相似文献
6.
7.
8.
用传统熔融冷却法制备ZnO-B_2O_3-Bi_2O_3,系统玻璃,采用X射线衍射法和差热分析法研究了玻璃的结构和玻璃的特征温度T_g和T_f,测试了玻璃的密度、热膨胀系数和介电常数等性能。结果表明,在ZnO-B_2O_3-Bi_2O_3系统玻璃中,当用B_2O_3逐步取代Bi_2O_3时,玻璃的特征温度T_g和T_f呈现逐渐升高的趋势,玻璃热膨胀系数由11.13×10~(-6)/℃减小至6.22×10~(-6)/℃,玻璃的密度由5.920 g/cm~3减小至4.114 g/cm~3,同时,玻璃的介电常数也有一定程度的下降。 相似文献
10.
γ-Al_2O_3转化为α-Al_2O_3的热力学分析 总被引:1,自引:0,他引:1
γ-Al2O3和α-Al2O3都是氧化铝的重要存在形式,都是催化剂的常用载体。γ-Al2O3在热力学上是不稳定的,经高温焙烧或研磨等可以转化为α-Al2O3。采用业界公认的热力学数据,首次对γ-Al2O3转化为α-Al2O3的热力学进行了分析。结果表明,在298.15~1000K范围内,这种相转变属于放热反应,且随温度升高,放热量增大;同时其自由能变化小于0,但随温度升高,自由能负值越来越小。这是因为这一相变反应为熵减过程。 相似文献
11.
The phase diagram of the Al2O3–ZrO2–Nd2O3 system was constructed in the temperature range 1250–2800 °C. The liquidus surface of the phase diagram reflects the preferentially eutectic interaction in the system. Two new ternary and one new binary eutectics were found. The minimum melting temperature is 1675 °C and it corresponds to the ternary eutectic Nd2O3·11Al2O3 + F-ZrO2 + NdAlO3. The solidus surface projection and the schematic of the alloy crystallization path confirm the preferentially congruent character of phase interaction in the ternary system. The polythermal sections present the complete phase diagram of the Al2O3–ZrO2–Nd2O3 system. No ternary compounds or regions of remarkable solid solution were found in the components or binaries in this ternary system. 相似文献
12.
The mixed oxide catalyst (Mn2O3 + SnO2) prepared by the coprecipitation method has been impregnated with Pd metal and it's catalytic behaviour for CO oxidation reaction has been investigated. In the coprecipitated material, Mn2O3 and SnO2 were found to crystallise at 875 K and 1175 K, respectively, which are significantly higher than the crystallisation temperatures of individual oxides prepared under similar conditions. Results of catalytic oxidation of CO, carried out using the pulse method for the mixed oxide system and the individual oxides, suggest significant synergistic effects between these two oxides. The impregnation of palladium metal facilitated CO oxidation and the catalyst Pd/(Mn2O3 + SnO2) was found to be quite effective for CO oxidation even at room temperature. Further, the CO disproportionation has been observed on palladium sites in the temperature range 350 to 400 K for the individual oxide systems. 相似文献
13.
Yanmei Kan Guojun Zhang Peiling Wang Omer Van der Biest Jef Vleugels 《Journal of the European Ceramic Society》2006,26(16):3607-3612
A suspension stabilizer-coating technique was employed to prepare x mol% Yb2O3 (x = 1.0, 2.0, 3.0 and 4.0) and 1.0 mol% Y2O3 co-doped ZrO2 powder. A systematic study was conducted on the sintering behaviour, phase assemblage, microstructural development and mechanical properties of Yb2O3 and Y2O3 co-doped zirconia ceramics. Fully dense ZrO2 ceramics were obtained by means of pressureless sintering in air for 1 h at 1450 °C. The phase composition of the ceramics could be controlled by tuning the Yb2O3 content and the sintering parameters. Polycrystalline tetragonal ZrO2 (TZP) and fully stabilised cubic ZrO2 (FSZ) were achieved in the 1.0 mol% Y2O3 stabilised ceramic, co-doped with 1.0 mol% Yb2O3 and 4.0 mol% Yb2O3, respectively. The amount of stabilizer needed to form cubic ZrO2 phase in the Yb2O3 and Y2O3 co-doped ZrO2 ceramics was lower than that of single phase Y2O3-doped materials. The indentation fracture toughness could be tailored up to 8.5 MPa m1/2 in combination with a hardness of 12 GPa by sintering a 1.0 mol% Yb2O3 and 1.0 mol% Y2O3 ceramic at 1450 °C for 1 h. 相似文献
14.
Effect of additives, In2O3, SnO2, CoO, CuO and Ag, on the catalytic performance of Ga2O3–Al2O3 prepared by sol–gel method for the selective reduction of NO with propene in the presence of oxygen was studied. As for the reaction in the absence of H2O, CoO, CuO and Ag showed good additive effect. When H2O was added to the reaction gas, the activity of CoO-, CuO- and Ag-doped Ga2O3–Al2O3 was depressed considerably, while an intensifying effect of H2O was observed for In2O3- and SnO2-doped Ga2O3–Al2O3. Of several metal oxide additives, In2O3-doped Ga2O3–Al2O3 showed the highest activity for NO reduction by propene in the presence of H2O. Kinetic studies on NO reduction over In2O3–Ga2O3–Al2O3 revealed that the rate-determining step in the absence of H2O is the reaction of NO2 formed on Ga2O3–Al2O3 with C3H6-derived species, whereas that in the presence of H2O is the formation of C3H6-derived species. We presumed the reason for the promotional effect of H2O as follows: the rate for the formation of C3H6-derived species in the presence of H2O is sufficiently fast compared with that for the reaction of NO2 with C3H6-derived species in the absence of H2O. Although the retarding effect of SO2 on the activity was observed for all of the catalysts, SnO2–Ga2O3–Al2O3 showed still relatively high activity in the lower temperature region. 相似文献
15.
Chunlei Shi Arden B. Walters M. Albert Vannice 《Applied catalysis. B, Environmental》1997,14(3-4):175-188
Dispersing La2O3 on δ- or γ-Al2O3 significantly enhances the rate of NO reduction by CH4 in 1% O2, compared to unsupported La2O3. Typically, no bend-over in activity occurs between 500° and 700°C, and the rate at 700°C is 60% higher than that with a Co/ZSM-5 catalyst. The final activity was dependent upon the La2O3 precursor used, the pretreatment, and the La2O3 loading. The most active family of catalysts consisted of La2O3 on γ-Al2O3 prepared with lanthanum acetate and calcined at 750°C for 10 h. A maximum in rate (mol/s/g) and specific activity (mol/s/m2) occurred between the addition of one and two theoretical monolayers of La2O3 on the γ-Al2O3 surface. The best catalyst, 40% La2O3/γ-Al2O3, had a turnover frequency at 700°C of 0.05 s−1, based on NO chemisorption at 25°C, which was 15 times higher than that for Co/ZSM-5. These La2O3/Al2O3 catalysts exhibited stable activity under high conversion conditions as well as high CH4 selectivity (CH4 + NO vs. CH4 + O2). The addition of Sr to a 20% La2O3/γ-Al2O3 sample increased activity, and a maximum rate enhancement of 45% was obtained at a SrO loading of 5%. In contrast, addition of SO=4 to the latter Sr-promoted La2O3/Al2O3 catalyst decreased activity although sulfate increased the activity of Sr-promoted La2O3. Dispersing La2O3 on SiO2 produced catalysts with extremely low specific activities, and rates were even lower than with pure La2O3. This is presumably due to water sensitivity and silicate formation. The La2O3/Al2O3 catalysts are anticipated to show sufficient hydrothermal stability to allow their use in certain high-temperature applications. 相似文献
16.
An In2O3/Al2O3 catalyst shows high activity for the selective catalytic reduction of NO with propene in the presence of oxygen. The presence of SO2 in feed gas suppressed the catalytic activity dramatically at high temperatures; however it was enhanced in the low temperature range of 473–573 K. In TPD and FT-IR studies, the formation of sulfate species on the surface of the catalyst caused an inhibition of NOX adsorption sites, and the absorbance ability of NO was suppressed by the presence of SO2, and the amount of ad-NO3− species decreased obviously. This leads to a decrease of catalytic activity at higher temperatures. However, addition of SO2 enhanced the formation of carboxylate and formate species, which can explain the promotional effect of SO2 at low temperature, because active C3H6 (partially oxidized C3H6) is crucial at low temperature. 相似文献
17.
Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu2O, Bi2O3 and ZnMn2O4 are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu2O/TiO2 and Bi2O3/TiO2 by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed. 相似文献
18.
对柠檬醛-乙酸乙酯溶液中柠檬醛在La2O3/γ-Al2O3催化剂上等温吸附行为进行了研究。结果表明,30 ℃柠檬醛在La2O3/γ-Al2O3催化剂上的吸附动力学符合准二阶吸附动力学模型,吸附动力学方程为:1/qt=2.350/t+0.063 3(R2=0.998 5)。(30~65) ℃柠檬醛在La2O3/γ-Al2O3催化剂上的等温吸附符合Langmuir方程,温度升高使柠檬醛的饱和吸附量增加,吸附热为32.19 kJ·mol-1。 相似文献
19.