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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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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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采用柠檬酸凝胶法制备锰-镍-铁基前驱体,在300℃煅烧干燥的前驱体得到纳米粒度粉末,压制成圆片坯体后在1100~1300℃烧结得到负温度系数(negative temperature coefficient,NTC)热敏陶瓷样品。研究了粉体和烧结样品的相结构、微观形貌、电性能和热敏特性。结果表明:合成粉体的纳米颗粒为单相Mn1/3Ni2/3Fe2O4尖晶石,粉体具有高化学均匀性。烧结的Mn1/3Ni2/3Fe2O4陶瓷样品具有均匀的微观结构,陶瓷样品的烧结密度和材料敏感指数β随着烧结温度的增加而增加。测量温度为50~150℃范围时,1300℃烧结的Mn1/3Ni2/3Fe2O4样品,其β可高达4300K。 相似文献
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Zhihui Yin Xiaomin Zhong Yajie Zhang Jinghua Yin 《Polymer-Plastics Technology and Engineering》2013,52(3):393-401
Melt mixing of nylon 8 with neodymium oxide particles was carried out with a single-screw extruder. The crystal behaviors of plain nylon 6 and the neodymium oxide filled nylon 6 mixture were studied by means of isothermal crystallization kinetic analysis. Isothermal crystallization thermograms obtained by differential scanning calorimetry (DSC) were analyzed based on the Avrami equation. The neodymium oxide particles acted as a nucleating agent in the mixture. The overall rate of di-isothermal crystallization of the neodymium oxide filled nylon 6 mixture is higher than that of plain nylon 6. The mechanism and modes of plain nylon 6 were the same as those of neodymium oxide filled PA6 mixture. 相似文献
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İbrahim Uslu Arda Aytimur Mustafa Kemal Öztürk Serhat Koçyiğit 《Ceramics International》2012,38(6):4943-4951
In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the hybrid polymers solution of their composite precursor was put forward. Calcined and sintered nanopowders were characterized by FT-IR, XRD, BET, SEM, and AFM techniques. According to the XRD analysis, the obtained powders are single phase and independent of the dopant concentration in the range investigated. The crystallite sizes were calculated using Scherrer equation. Moreover, lattice parameters, dislocation densities and microstrain values were calculated. BET results show that the increase of the neodymium doped content decrease the surface area of the composite powders, confirming the highly ordered micro and mesostructure. SEM and AFM results show that the samples have spherical grains. According to the surface roughness measurements, the increase in the amount of neodymium and the decrease in the amount of cerium decreased the surface roughness. 相似文献
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以硝酸锌为锌源,分别以碳酸钠和碳酸氢铵为沉淀剂,采用热分解碱式碳酸锌工艺制备纳米氧化锌。通过热重分析、晶型测试、平均粒径测试、微观形貌观察等系列对比,分析了以两种碳酸盐为沉淀剂制备氧化锌的过程,建立了生长动力学方程,对比了微观形貌和分散状态。实验结果表明,以碳酸氢铵为沉淀剂制备的前驱体在煅烧温度为200 ℃后直接生成纳米氧化锌,而以碳酸钠为沉淀剂制备的前驱体在煅烧温度为200~250 ℃时先生成碳酸锌然后在300 ℃时完全转变为氧化锌;两种沉淀剂制备纳米氧化锌的生长过程符合不同指数方程生长关系,以碳酸钠为沉淀剂制备纳米氧化锌的生长满足方程y=2.775 04e0.004 76x,而以碳酸氢铵为沉淀剂制备纳米氧化锌的生长满足方程y=5.152 96e0.002 85x,对比来看以碳酸氢铵为沉淀剂制备纳米氧化锌在相同温度下得到的晶粒尺寸要小;从粒度分布和透射电镜观察分析,在相同温度下也是以碳酸氢铵为沉淀剂制备的纳米氧化锌的粒径较小。 相似文献
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Faisal Alahmadi Anastasiya Bavykina Daria Poloneeva Adrian Ramirez Robert Schucker Jorge Gascon 《American Institute of Chemical Engineers》2023,69(4):e17959
Since its discovery in 1982, oxidative coupling of methane (OCM) has been considered one of the most promising approaches for the on-purpose synthesis of ethylene. The development of more selective catalysts is essential to improve process economics. In this work, undoped neodymium oxide as well as neodymium oxide doped with high (20%) and low (2.5%) levels of strontium were tested in a high-throughput fashion covering a wide range of operating conditions. The catalysts were shown to be able to achieve greater than 18% C2+ yield. Space velocity was shown to play a significant role in C2+ selectivity. For a methane to oxygen feed ratio of 3.5, selectivity increased with increasing space velocity, reaching a maximum of 62% at a methane conversion of 30% at an optimal space velocity of ~250,000 ml/h/g. The difference in activity between the three samples was linked to the contribution of different oxygen centers. 相似文献
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以七水硫酸锌、碳酸氢铵为原料,通过液相沉淀法合成纳米氧化锌前体,并焙烧获得纳米氧化锌。本文采用XRD、TG-DSC、TEM、BET等测试手段对纳米氧化锌及其前体进行表征,研究了焙烧温度对所制备氧化锌形貌、晶型及脱硫活性的影响,结果表明:所获得的碱式碳酸锌为不规则纳米晶,晶粒尺寸约为2~10nm;在不同的焙烧温度下所获得的纳米氧化锌的综合性能存在较大差异,其中在焙烧温度300℃处理所得纳米氧化锌综合性能较高,其晶粒尺寸为5~10nm之间,结晶度较完整,比表面积为41.41m2/g,在220℃脱硫活性较高,穿透硫容>25%;随着焙烧温度的提高,纳米氧化锌的晶化程度加大,表面性质被破坏,比表面积急剧下降,颗粒团聚严重;焙烧温度太低,则纳米氧化锌前体分解不完全,影响其纯度。 相似文献
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文章通过沉淀法合成了体相掺杂镁元素的球形钴酸锂正极材料前驱体。通过SEM形貌、密度测量、粒度表征等手段研究了共沉淀工艺对合成体相掺杂镁元素钴酸锂前驱体的影响,并通过EDS及ICP测试表征了镁元素掺杂的均匀性。研究结果表明:共结晶的反应时间对颗粒密度、颗粒形貌、粒度大小及分布有较大的影响,随着时间延长密度逐渐增加,颗粒形貌变好,粒度变大且趋于集中;共结晶体相掺杂镁的钴酸锂前驱体,镁元素能达到原子级混合均匀的要求;掺杂镁后,钴酸锂前驱体四氧化三钴物相未发生变化。掺镁钴酸锂前驱体在高压实密度钴酸锂得到了广阔的应用。 相似文献
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Total oxidation of methane over doped nanophase cerium oxides 总被引:7,自引:0,他引:7
The formation of solid solutions of cerium oxide with the oxides of calcium, manganese, or neodymium enhances the catalytic
activity of cerium oxide for the total oxidation of methane, whereas solid solutions with lead oxide showed an opposite effect.
Reasons for this are discussed in terms of oxygen vacancy concentrations and mobilities, local structure configurations, number
of oxidation states of dopant, and electron transfer properties. The effects of increased oxygen ion mobility and a more beneficial
local structure support the increased catalytic activity for the calcium- and neodymium-doped cerium oxide samples. In addition,
a reduced energy for charge transfer from oxygen to cerium supports a higher activity for the calcium-doped sample. The activity
data were fitted to an Arrhenius equation, and the apparent activation energies were found to be between 110 and 130 kJ/mol.
The particle sizes and the BET areas of the samples were only little affected by the reactor runs, and none of the samples
were subjected to phase changes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Nanocrystalline silicon carbide was synthesized from the precursor prepared by spray drying slurry of water glass and carbon black. The effect of process parameters, such as reaction temperature, reaction time and carbon content, on phase evolution, crystallite size and specific surface of the resulting samples were characterized by XRD, SEM and BET. The results show the powder produced in this process has a very fine crystallite size and high specific area and the reaction can be completed at 1550 °C for 2 h when the C/Si ratio is 5 or larger. In addition, the powder is of high purity, because sodium oxide in the precursor can be eliminated by the escape of sodium at high temperature. It is a simple and cost-efficient method to synthesize nanocrystalline silicon carbide using cheap and abundant water glass as silicon source. 相似文献
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稀土氧化钕填充尼龙6体系的流变行为研究 总被引:3,自引:1,他引:3
用锥板粘度仪测试仪测试了稀土氧化钕填充尼龙6体系的流变行为,填充体系的熔融粘度明显低于空白尼龙6,体系的粘度随稀土氧化物含量的增加而降低,填充后试样具有良好的流动性和加工稳定性。 相似文献