共查询到17条相似文献,搜索用时 171 毫秒
1.
使用粉末冶金法制备了Ti B 2/Al基复合材料,使用X射线衍射仪(XRD)对复合材料进行衍射图谱分析,确定复合材料的物相组织,复合材料晶界处为增强体Ti B 2的主要分布位置,随着Ti B 2质量分数的增加,团聚现象增多。探讨了Ti B 2/Al基体的显微结构和机械性质的变化,并分析了Ti B 2粒子的加入对Ti B 2/Al基体的影响。实验发现,Ti B 2/Al与Ti B 2/Al的界面结合较好。在1 h的保温、610℃烧结、20%质量分数硼化钛的硬度最高,维氏硬度值为68.2 HV。此时的复合材料在Ti B 2质量分数15%时的综合力学性能最好,抗拉强度为153.43 MPa,比纯铝提高了19.68%。 相似文献
2.
考察B 2O 3负载量对于MoO 3/CeO 2-Al 2O 3催化剂对耐硫甲烷化活性的影响,利用BET、XRD、TEM、NH 3-TPD等手段对催化剂进行了表征。结果表明,催化剂的耐硫甲烷化活性随B 2O 3负载量增加呈现先升高后降低的变化规律;当B 2O 3负载量为0.5%时,催化剂的耐硫甲烷化活性最高,CO转化率达到55%。结合表征分析,发现添加B 2O 3会影响催化剂载体的结构和表面酸度,从而影响活性组分的分散程度,进而影响MoO 3/CeO 2-Al 2O 3催化剂的耐硫甲烷化性能。催化剂的晶化程度太高或单位面积上的强酸量太多均不利于甲烷化反应;较好的活性组分分散度有利于催化剂甲烷化活性的提高。 相似文献
3.
为提高铝基磷酸盐涂层的耐腐蚀性能和力学性能,通过在铝基磷酸盐涂料中添加 Al 2O 3溶胶,经空气喷涂与热固化得到 Al 2O 3颗粒增强铝基磷酸盐复合涂层,采用 X射线衍射仪( XRD)、扫描电镜( SEM)、胶粘拉脱法、维氏硬度、电化学腐蚀试验和模拟海水浸泡试验考察 Al 2O 3溶胶含量对复合涂层微观组织、力学性能和耐腐蚀性能的影响。结果表明: Al 2O 3溶胶在涂层 500 ℃热固化的物相演化为 Al 2O 3溶胶 -AlOOH-Al 2O 3,随 Al 2O 3溶胶含量从 0增加到(γ相)生成的 Al 2O 3颗粒在涂层呈弥散分布;4%,复合涂层的孔隙减少,致密性提高, Al 2O 3颗粒弥散强化作用得到发挥,涂层结合强度由 15 MPa提高为 25 MPa,硬度由 38 HV提高为 65 HV;添加 Al 2O 3溶胶制备得到的铝基磷酸盐复合涂层耐腐蚀性能明显提高,自腐蚀电流密度由 2. 38×10-7 A/cm2下降至 2. 79×10 -8 A/cm 2,极化电阻由 1. 95×10 4 Ω提升至 4. 73×10 5 Ω。 相似文献
4.
利用水热法将Bi 2Sn 2O 7纳米颗粒负载到CeO 2微球上制备Z型异质结光催化剂并用于光催化降解水污染物。结果表明,在光照下60 min时,优化的Bi 2Sn 2O 7/CeO 2(BSC-5)对盐酸四环素的降解效率达到88.4%(反应速率常数k=0.033 4 min -1),是CeO 2的8.25倍和Bi 2Sn 2O 7的4.71倍。Z型异质结可以形成更多暴露的活性中心,具有更好的光电子-空穴对分离效率、优异的氧化还原能力以及有效产生超氧自由基(·O -2)和羟基自由基(·OH)。此外,Bi 2Sn 2O 7/CeO 2在光催化降解实验中表现出良好的稳定性,经过5次循环后降解效率保持在85%以上。同... 相似文献
5.
采用共沉淀法制备CeO 2-MnO x和La 2O 3-CeO 2-MnO x催化剂,再用沉积-沉淀法制备La 2O 3/CeO 2-MnO x催化剂,并对催化剂的氯苯催化氧化反应活性进行检测。结果表明,La的加入可以显著提高催化剂催化氧化氯苯的活性。XRD和TPR表征结果表明,La的加入抑制CeO 2晶粒尺寸的长大,增强CeO 2的晶格应变,并促进Mn进入CeO 2的晶相,形成较好的MnCeO x固溶体。催化剂的热稳定性评价结果表明,La的加入有效提高CeO 2-MnO x催化剂的热稳定性。 相似文献
6.
以B 2O 3为助催化剂,采用研磨混合法改性Na 2CO 3催化剂,在固定床反应器中催化甲醇脱氢制备无水甲醛,考察催化剂的组成和反应条件等对催化反应的影响,采用XRD、TG-DTG、N 2吸附-脱附、SEM和CO 2-TPD等对催化剂进行表征。结果表明,以B 2O 3为助催化剂采用机械研磨混合法改性的Na 2CO 3催化剂,增加了催化剂的比表面积,在(10~30) nm增加了大量的孔道,平均孔径达18.44 nm,比表面积为1.65 m 2·g -1,且B 2O 3分布均匀,改性后的催化剂碱性降低,在催化甲醇脱氢制备无水甲醛的反应中,催化活性明显高于Na 2CO 3催化剂,表明B 2O 3改性Na 2CO 3催化剂能提高甲醇转化率和甲醛选择性。在B 2O 3/Na 2CO 3催化剂中B 2O 3质量分数为30%、甲醇进料质量分数为26%、反应温度为650 ℃和甲醇重时空速为2.94 h -1条件下,甲醇转化率达59.97%,甲醛选择性达83.28%。 相似文献
7.
利用搪瓷涂层的制备工艺在Q235A钢表面制备Al2O3-瓷釉复合陶瓷涂层,研究了瓷釉粒度、Al2O3陶瓷颗粒的粒度和体积分数对复合涂层耐冲蚀磨损性能的影响。结果表明:过渡层原料瓷釉粒度为16μm时获得涂搪性较好;硬质耐磨相的加入可显著提高复合涂层的耐冲蚀性能;本实验中在45°冲蚀角、15 MPa冲蚀气压、2.2 kg冲砂量的冲蚀实验条件下Al2O3粒度为50μm、体积分数为30%时涂层具有很好的耐冲蚀性,是无硬质相搪瓷层的4倍。 相似文献
8.
为了提高碳材料的抗烧蚀性能,以石墨块作为基体,SiC(d 50=10μm)、B 4C(d 50=50μm)、TaC(d 50=3μm)为主要原料,采用料浆法结合反应熔渗Si在石墨材料表面制备了Si-SiC和Si-SiC-TaB 2涂层,研究了涂层的物相组成、显微结构和元素分布,考察了Si-SiC-TaB 2复合涂层在室温至1 600℃的抗热震性能,并通过等离子火焰烧蚀试验(2 350℃分别烧蚀120和1 980 s)测试了涂层对石墨材料高温下的抗烧蚀防护性能。结果表明:Si-SiC-TaB 2复合涂层结构致密,涂层中SiC和TaB 2陶瓷颗粒与Si无明显界面;在1 600℃热震循环20次后,涂层试样的质量基本逐渐增加,具有良好的抗热震性能;Si-SiC-TaB 2复合涂层试样烧蚀1 980 s后质量增加,表面覆盖了含有Ta 2O 5和SiO 2的Ta... 相似文献
9.
多孔竹炭为无定形碳,具有丰富的孔结构,孔径分布在1~6 nm之间,且具有较大的孔体积(1.21 cm 3/g)。本文以多孔竹炭为载体,采用溶胶-凝胶法制得B 2O 3-SnO 2/C复合材料。SEM和TEM结果显示SnO 2和B 2O 3均匀分布在多孔竹炭表面。多孔竹炭和B 2O 3有效缓冲SnO 2可逆反应的体积变化,提高SnO 2的循环稳定性。将B 2O 3-SnO 2/C复合材料作为负极组装成锂离子半电池,进行电化学性能测试,在1 C(1 C=372 mA/g)倍率下充放电循环200次结束后仍然保留649.9 mAh/g的放电比容量,放电比容量保留率为58.6%。B 2O 3-SnO 2/C复合材料充放电过程受扩散和电容两种行为控制,电容控制的贡献率随着扫描速率的增大而增大。 相似文献
10.
通过球磨混合法,制备TiO 2、SiO 2和TiO 2+SiO 2掺杂的Al 2O 3粉体,经不同温度煅烧后进行X射线衍射(XRD)测试,比较研究这三种掺杂对Al 2O 3粉体相转变温度的影响。研究结果表明,TiO 2、SiO 2掺杂对γ-Al 2O 3向α-Al 2O 3的相转变均有促进作用。在掺杂质量分数为0.5%的情况下,二者可分别使γ-Al 2O 3完全转变为α-Al 2O 3的温度降低100 ℃和125 ℃。而TiO 2+SiO 2复合掺杂对γ-Al 2O 3向α-Al 2O 3相转变的促进作用优于TiO 2、SiO 2单独掺杂。TiO 2、SiO 2的质量分数均为0.3%时,复合掺杂可使γ-Al 2O 3完全转变为α-Al 2O 3的温度降低150 ℃。此外,还对TiO 2、SiO 2和TiO 2+SiO 2掺杂促进Al 2O 3粉体相转变的机理作了简单分析。 相似文献
12.
Ni catalysts supported on γ-Al 2O 3, CeO 2 and CeO 2–Al 2O 3 systems were tested for catalytic CO 2 reforming of methane into synthesis gas. Ni/CeO 2–Al 2O 3 catalysts showed much better catalytic performance than either CeO 2- or γ-Al 2O 3-supported Ni catalysts. CeO 2 as a support for Ni catalysts produced a strong metal–support interaction (SMSI), which reduced the catalytic activity and carbon deposition. However, CeO 2 had positive effect on catalytic activity, stability, and carbon suppression when used as a promoter in Ni/γ-Al 2O 3 catalysts for this reaction. A weight loading of 1–5 wt% CeO 2 was found to be the optimum. Ni catalysts with CeO 2 promoters reduced the chemical interaction between nickel and support, resulting in an increase in reducibility and stronger dispersion of nickel. The stability and less coking on CeO 2-promoted catalysts are attributed to the oxidative properties of CeO 2. 相似文献
13.
Sodium polyphosphate-modified Class F fly ash/calcium aluminate blend (SFCB) cements were prepared at room temperature and their resistance to hot acid erosion was evaluated by submerging them in H 2SO 4 solution (pH 1.6) at 90°C. Sodium polyphosphate preferentially reacted with calcium aluminate cement (CAC) to form amorphous Ca(HPO 4).xH 2O and Al 2O 3.xH 2O gel, rather than fly ash. These amorphous reaction products, which bound the partially reacted and unreacted CAC and fly ash particles into a coherent mass, were responsible for strengthening and densifying the SFCB specimens at room temperature, playing an essential role in mitigating their acid erosion. In these cements, the extent of acid erosion depended primarily on the ratio of fly ash/CAC; namely, those with a higher ratio underwent a severe erosion. This effect was due to the formation of a porous structure, which allowed acid to permeate the cement easily, diminishing the protective activity of Ca(HPO 4).xH 2O and Al 2O 3.xH 2O gel against H 2SO 4. 相似文献
14.
Micro-channel plates with dimension of 1 mm × 0.3 mm × 48 mm were prepared by chemical etching of stainless steel plates followed by wash coating of CeO 2 and Al 2O 3 on the channels. After coating the support on the plate, Pt, Co, and Cu were added to the plate by incipient wetness method. Reaction experiments of a single reactor showed that the micro-channel reactor coated with CuO/CeO 2 catalyst was highly selective for CO oxidation while the one coated with Pt-Co/Al 2O 3 catalyst was highly active for CO oxidation. The 7-layered reactors coated with two different catalysts were prepared by laser welding and the performances of each reactor were tested in large scale of PROX conditions. The multi-layered reactor coated with Pt-Co/Al 2O 3 catalyst was highly active for PROX and the outlet concentration of CO gradually increased with the O 2/CO ratio due to the oxidation of H 2 which maintained the reactor temperature. The multi-layered reactor coated with CuO/CeO 2 showed lower catalytic activity than that coated with Pt catalyst, but its selectivity was not changed with the increase of O 2/CO ratios due to the high selectivity. In order to combine advantages (high activity and high selectivity) of the two individual catalysts (Pt-Co/Al 2O 3, CuO/CeO 2), a serial reactor was prepared by connecting the two multi-layered micro-channel reactors with different catalysts. The prepared serial reactor exhibited excellent performance for PROX. 相似文献
15.
Co 3O 4/CeO 2 composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co 3O 4) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co 3O 4 and CeO 2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out. An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co3O4 in correspondence of Co3O4–CeO2 containing 30% by weight of Co3O4. The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co3O4 phase and promoting the efficiency of the Co3+–Co2+ redox couple. The presence in the sample Co3O4(30 wt.%)–CeO2 of a high relative amount of Ce3+/(Ce4+ + Ce3+) as detected by XPS confirms the enhanced oxygen mobility. The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co3O4 phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750 °C for 7 h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co3O4 and Co3O4(30 wt.%)–CeO2, performing the tests in the presence of 5 vol.% H2O. A methane oxidation test upon hydrothermal ageing (flowing at 600 °C for 16 h a mixture 5 vol.% H2O + 5 vol.%O2 in He) of the Co3O4(30 wt.%)–CeO2 sample was also performed. All the results confirm the superiority of this composite oxide. 相似文献
16.
采用溶胶-凝胶法,制备了铈硅包覆金红石型钛白粉,通过正交实验考察了浆液浓度、分散剂用量和两种包膜剂含量对铈硅包覆金红石型钛白粉性能的影响。采用Nano-ZS型粒度仪、扫描电镜(SEM)、透射电镜(TEM)和能谱(EDS)等测试手段,对金红石型钛白粉的Zeta电位、表面形貌和元素进行了表征。结果表明:在水浴温度为80 ℃左右、转速为600 r/min、浆液质量浓度为400 g/L、分散剂质量分数为0.1%、二氧化铈质量分数为3%、二氧化硅质量分数为4%的条件下,金红石型钛白粉表面包覆了两层均匀而致密的二氧化硅和二氧化铈膜;罗丹明B光催化降解实验证实,铈硅包覆明显改善了金红石型钛白粉的光催化屏蔽性。 相似文献
17.
This work investigates performances of supported transition-metal oxide catalysts for the catalytic reduction of SO 2 with C 2H 4 as a reducing agent. Experimental results indicate that the active species, the support, the feed ratio of C 2H 4/SO 2, and pretreatment are all important factors affecting catalyst activity. Fe 2O 3/γ-Al 2O 3 was found to be the most active catalyst among six γ-Al 2O 3-supported metal oxide catalysts tested. With Fe 2O 3 as the active species, of the supports tested, CeO 2 is the most suitable one. Using this Fe 2O 3/CeO 2 catalyst, we found that the optimal Fe content is 10 wt.%, the optimal feed ratio of C 2H 4/SO 2 is 1:1, and the catalyst presulfidized by H 2+H 2S exhibits a higher performance than those pretreated with H 2 or He. Although the feed concentrations of C 2H 4:SO 2 being 3000:3000 ppm provide a higher conversion of SO 2, the sulfur yield decreases drastically at temperatures above 300 °C. With higher feed concentrations, maximum yield appears at higher temperatures. The C 2H 4 temperature-programmed desorption (C 2H 4-TPD) and SO 2-TPD desorption patterns illustrate that Fe 2O 3/CeO 2 can adsorb and desorb C 2H 4 and SO 2 more easily than can Fe 2O 3/γ-Al 2O 3. Moreover, the SO 2-TPD patterns further show that Fe 2O 3/γ-Al 2O 3 is more seriously inhibited by SO 2. These findings may properly explain why Fe 2O 3/CeO 2 has a higher activity for the reduction of SO 2. 相似文献
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