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微波水热合成ZrO2-8%Y2O3纳米粉体 总被引:5,自引:0,他引:5
以Zr(OH)4和Y(OH)3的共沉淀为前驱体,在碱性介质中用微波水热法合成摩尔分数为8%的氧化钇稳定氧化锆(yttria stabilized cubic zirconia,YSZ)纳米粉体。通过X射线粉末衍射仪、透射电镜和等离子发射光谱等表征粉体的性能。研究了微波水热法的反应温度、时间和前驱物浓度对反应产物形貌、粒度等的影响。获得了制备具有纳米立方相结构的YSZ粉体的最佳工艺参数:粉体粒度为5~10nm,产物纯度为99%。结果表明:温度为200℃时,产物粒径较小且均匀。微波水热制备YSZ的最佳反应时间为20~40min。前驱物中Zr^4+的最佳浓度为0.2mol/l。增大碱性介质KOH的浓度对产物的晶型和粒度影响不大。 相似文献
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超细氧化钇合成与表征 总被引:2,自引:1,他引:1
以硝酸钇为原料,氨水、碳酸铵、酒石酸铵为沉淀剂,聚乙二醇、十二烷基苯磺酸钠、十六烷基三甲基溴化铵为表面活性剂,在水溶液中制备氧化钇前驱体,在空气中焙烧制备氧化钇粉体;用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(IR)对样品进行表征,用激光粒度仪分析样品的晶粒团聚度.结果表明,使用氨水、碳酸铵、酒酸铵为沉淀剂所得前驱体在673 K焙烧2 h,均获得立方晶相氧化钇粉体,一级晶粒直径分别为13,40,63 nm;用小分子有机醇回流处理氧化钇前驱体(氢氧化钇),团聚体粒径为58.8 nm,焙烧后的氧化钇团聚体粒径为423 nm,说明有机醇回流处理阻止了粒子团聚. 相似文献
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以氧化锆(ZrO2)、硼酸(H3 BO3)和碳(C)粉为原料,研究了不同碳粉(活性炭、石墨)与前驱体粒度、温度及保温时间对碳热还原法制备硼化锆(ZrB2)粉体的影响.通过X射线衍射(XRD)分析合成粉体物相,扫描电镜(SEM)观察合成粉体形貌,并通过化学方法分析了合成粉体中的C、O含量.结果表明:以活性炭为碳源合成的粉体形貌呈条棒状,以石墨为碳源合成的粉体形貌呈规则的块状;合成粉体的粒度随前驱体粒度减小而减小,形貌由规则的块状逐渐转变为圆滑的不规则形貌,合成ZrB2粉体最小平均粒度约为1.69μm,产物中C含量随前驱体粒度减小而减少,O含量随前驱体粒度减小而增加,氧含量最低为0.54wt%;碳热还原法合成ZrB2粉体在1500℃下是可行的,但直到1900℃碳热还原反应合成ZrB2才进行完全;碳热还原反应合成ZrB2粉体最佳的反应条件为1900℃保温30 min. 相似文献
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以尿素为沉淀剂,硝酸钇为钇源,十六烷基三甲基溴化铵为分散剂,采用均相沉淀法制备球形纳米氧化钇粉体,研究了反应物浓度比、表面活性剂用量、反应时间、搅拌转速、反应温度对氧化钇形貌及粒径的影响。通过激光粒度分析、X射线衍射(XRD)分析、扫描电镜(SEM)分析、傅里叶红外光谱(FTIR)分析等手段对样品进行表征。结果表明,反应物浓度比、反应时间、搅拌转速、反应温度会影响粉体的尺寸,适量CTAB的加入可显著降低氧化钇的粒径;在最佳工艺条件下,可制得粒径大小为110~130 nm的球形氧化钇粉体。 相似文献
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用聚合物前驱体法低温合成铌酸锂纳米粉体 总被引:1,自引:0,他引:1
用聚合物前驱体法,以柠檬酸为配位剂.乙二醇为酯化剂.水为溶剂合成纳米铌酸锂(LiNbO3)粉体。研究发现:当柠檬酸和金属离子的摩尔比(下同)为3:1,柠檬酸和乙二醇的为1:2时,可形成稳定的Li-Nb前驱体溶液和凝胶。用差热-热重分析研究凝胶前驱体的热分解历程。用X射线衍射分析和红外光谱分析研究凝胶前驱体及其不同温度下煅烧所得粉体的相组成和结构。结果表明:Li-Nb凝胶前驱体在加热过程中分解形成LizCO3相.Li2CO3与Nb2O3发生固相反应生成LiNbO3。凝胶前驱体经800℃煅烧2h可以制备纯钙钛矿型的纳米LiNbO3粉体。 相似文献
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研究以结晶氯化铝和碳酸氢铵为原料,采用室温固相反应制备尺寸均一、颗粒细小分散的包含有少量纳米晶γ-AIOOH的碱式碳酸铝钱前驱体。用XRD、Zeta电位及粒度分析仪表征,研究了起声分散、聚乙二醇聚合度及其加入量和pH值等对制备起细前驱体的影响。结果表明:在起声分散及酸性条件下,PEG为不同分子量匹配得到的前驱体.在水中的分散和稳定性最好,并制备出比表面高达66.32m^2/g(1100℃煅烧)的纳米α-Al2O3粉体。 相似文献
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F. M. T. Mendes C. A. Perez R. R. Soares F. B. Noronha M. Schmal 《Catalysis Today》2003,78(1-4):449-458
Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation of x% Nb2O5/Al2O3 (x=5, 10, 20 and 30 wt.%) samples. Catalysts with the same Nb2O5 contents were also prepared from the traditional niobium oxalate/oxalic acid aqueous solution. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), infrared spectroscopy of chemisorbed pyridine and X-ray photoelectron spectroscopy (XPS). A comparison with the preparation method using the niobium oxalate salt was performed. The results showed that the niobium precursor influence the species growing leading to phases with different reducibility. The XPS revealed the presence of multilayers of niobium oxide on the Nb2O5/Al2O3 samples prepared by using niobium ammonium oxalate complex, while the ones obtained from niobium oxalate led to Nb2O5 particles islands. The addition of niobium oxide decreased the fraction of Lewis acid sites and increased the fraction of Brønsted acid sites, independent of the precursor salt. However, the creation of BAS was more pronounced on the Nb2O5/Al2O3 samples prepared from niobium oxalate. 相似文献
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Y2O3-CeO2-doped ZrO2 ceramics were prepared from coprecipitated oxalate precursor material. The thermal decomposition behaviour of the oxalates was studied to find proper conditions for conversion to the oxides. The properties of the calcined oxide powders were measured and sintering conditions to prepare ceramic specimen were investigated. The mechanical properties of the sintered bodies are reported and their relations to composition and sintering conditions will be discussed. 相似文献
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SiC/Si3N4 composites with rare earth oxide additions have been prepared by glass encapsulated hot isostatic pressing at 1850 °C and 200 MPa pressure. Mechanical properties and microstructures of the sintered samples have been studied. It is shown that different molar ratios of La2O3 to Y2O3 and the total amount of La2O3 and Y2O3 additions can affect the mechanical properties significantly. With 3 wt% La2O3 + Y2O3 additions, lower La2O3/Y2O3 molar ratio exhibits higher bending strength and median fracture toughness, but relatively lower Vickers hardness. For addition of 6 wt% La2O3 + Y2O3, the higher bending strength, Vickers hardness and fracture toughness correspond to a certain La2O3/Y2O3 molar ratio of 1.5, 1.0 and 0.5, respectively. SEM observation shows that the SiC matrix composite with fine grain size and homogeneous microstructure can be obtained. 相似文献
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Na-oyoshi Iwasaki Takanori Miyake Eriko Yagasaki Toshimitsu Suzuki 《Catalysis Today》2006,111(3-4):391-397
Attention has been increasingly paid to the partial oxidation of lower alkanes to synthesis gas, due to its intrinsic energy saving process. We studied the partial oxidation of ethane (POE) on Co loaded on various supports. The POE performance varied as follows: Y2O3, CeO2, ZrO2, La2O3 SiO2, Al2O3, TiO2 > MgO. Comparing Y2O3 and CeO2, the carbon deposition during the POE was negligible on CeO2 and therefore CeO2 was the most preferable support. By changing space velocity and O2 partial pressure, reaction mechanism of POE was studied and it was revealed that two-step mechanism was prevailing; combustion of ethane to H2O and CO2 and subsequent reforming of ethane with H2O and CO2 to synthesis gas. Co/CeO2 catalyst exhibited high and stable catalytic activity for 10 h; high ethane conversion of 18% (maximum ethane conversion 20% at O2/C2H6 = 0.2) with H2 and CO selectivities of 93 and 84%, respectively. 相似文献
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针对磁力搅拌器制备纳米材料时存在粒径分布宽、分散不均匀的问题,采用撞击流-旋转填料床结合化学共沉淀法,以Fe(NO3)3·9H2O、Co(NO3)2·6H2O、NaOH为原料制备CoFe2O4纳米颗粒。研究了转速、液体流量、NaOH浓度以及晶化时间对CoFe2O4纳米颗粒粒径的影响;并与磁力搅拌器制备的CoFe2O4纳米颗粒在磁性能方面进行了对比。采用X射线衍射仪(XRD)、傅里叶红外光谱仪(FTIR)、透射电镜(TEM)、纳米粒度仪及振动样品磁强计(VSM)对产物的粒径形貌及磁性能进行表征。结果表明:CoFe2O4纳米颗粒的粒径随转速、液体流量和NaOH浓度的增加而减小,但随晶化时间的增加而增大。最佳工艺条件为:转速900r/min,液体流量60L/h,NaOH浓度3mol/L,晶化时间6h。此条件下制备的CoFe2O4纳米颗粒的粒径约为20nm,饱和磁化强度为75.43emu/g,较磁力搅拌器提高40%。 相似文献
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对多因素的复杂实验体系,均匀设计法能在不降低交互作用敏感性分析的前提下,可通过较少的实验次数获得可靠的数学模型,高效优化出最佳工艺条件。本文采用优化组合的U12+(6^6)均匀设计试验方案,考察了微乳液法制备纳米氧化铝前体的工艺条件,获得了氧化铝粉体的粒径与铝盐浓度、沉淀剂浓度、反应温度、表面活性剂与助表面活性剂的体积比、油相与表面活性剂的体积比5个关键因素之间的数学模型。利用该数学模型优化出的最佳制备工艺条件,制备出了氧化铝前体,该前体经1180℃焙烧,转晶为α-Al2O3粉体。α-Al2O3的一次粒子形状为棒状,一次粒子的Scherrer粒径为30nm左右,二次粒子的粒径D50为760nm。 相似文献
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《Journal of the European Ceramic Society》2001,21(16):1061-2801
In order to assess the role of carbon with respect to the grain boundary chemistry of Si3N4-based ceramics model experiments were performed. Y2O3–SiO2 glass systems with various amount of carbon (from 1 to 30 wt.%) were prepared by high-temperature treatment in a graphite furnace. High carbon activity of the furnace atmosphere was observed. EDX analysis proved the formation of SiC by the carbothermal reduction of SiO2 either in the melt or in the solid state. The melting temperature of the Y2O3–SiO2 system is strongly dependent on the amount of reduced SiO2. XRD analysis of the products documented the presence of Y2Si2O7, Y2SiO5 and Y2O3 crystalline phases in that order with an increasing amount of free C in the starting mixture. The reduction of Y2O3 was not confirmed. 相似文献
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Al2O3 hollow fibre membranes were prepared by a combined phase-inversion and sintering method. An organic binder solution (dope) containing suspended aluminium oxide (Al2O3) powders, either in mono size or a distributed size, is spun to a hollow fibre precursor, which is then sintered at elevated temperatures. In spinning the hollow fibre precursor, polyethersulfone (PESf), N-methyl-2-pyrrolidone (NMP) and polyvinyl pyrrolidone (PVP) were used as a polymer binder, a solvent and an additive, respectively. The Al2O3 hollow fibre membranes prepared were characterized using a scanning electron microscope (SEM) and gas permeation techniques. Effects of Al2O3 particle size and size distribution, the sintering temperature and Al2O3/PESf ratio on the structure and performance of the resulting membranes were studied extensively. The prepared Al2O3 hollow fibre membranes retains its asymmetric structure (mainly resulted from the phase inversion technique) even after the sintering process. Preparation of the Al2O3 hollow fibre membrane with a high mechanical strength and moderate permeation characteristics is feasible if the Al2O3 powders with a distributed particle size in the spinning (dope) solution is employed. 相似文献
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以废弃CRT荧光粉为原料,在前期稀盐酸预处理工艺的基础上,通过进一步深入研究,开发出从废弃CRT荧光粉中提取稀土的完整工艺路线。结果表明:稀酸预处理后,盐酸酸浸剩余荧光粉固体的最佳浓度为5 mol·L-1,最佳反应温度为80℃;酸浸后稀土浸出液净化除杂的pH控制为5.5,DDTC最佳用量比为6:1;稀土净化液经草酸沉淀后煅烧的最佳温度为900℃。从废弃CRT荧光粉中提取到稀土产物Y2O3和Eu2O3的总含量为99.2%,其晶粒由若干片状晶体密实堆积成多面体结构,晶粒之间相互嵌入,呈镶嵌式接触。 相似文献
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Matilda Zemanov Emmanuel Lecomte Pavol
ajgalík Ralf Riedel 《Journal of the European Ceramic Society》2002,22(16):2963-2968
The pyrolised polysilazanes poly(hydridomethyl)silazane NCP 200 and poly(urea)silazane CERASET derived Si–C–N amorphous powders were used for preparation of micro/nano Si3N4/SiC composites by hot pressing. Y2O3–Al2O3 and Y2O3–Yb2O3 were used, as sintering aids. The resulting ceramic composites of all compositions were dense and polycrystalline with fine microstructure of average grain size <1 μm of both Si3N4 and SiC phases. The fine SiC nano-inclusions were identified within the Si3N4 micrograins. Phase composition of both composites consist of , β modifications of Si3N4 and SiC. High weight loss was observed during the hot pressing cycle, 12 and 19 wt.% for NCP 200 and CERASET precursors, respectively. The fracture toughness of both nanocomposites (NCP 2000 and CERASET derived) was not different. Indentation method measured values are from 5 to 6 MPa m1/2, with respect to the sintering additive system. Fracture toughness is slightly sensitive to the SiC content of the nanocomposite. Hardness increases with the content of SiC in the nanocomposite. The highest hardness was achieved for pyrolysed CERASET precursor with 2 wt.% Y2O3 and 6 wt.% Yb2O3, HV 23 GPa. This is a consequence of the highest SiC content as well as the chemical composition of additives. 相似文献