共查询到20条相似文献,搜索用时 62 毫秒
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论述了碳酸盐共沉淀法制备多层陶瓷电容器(MLCC)用钛酸钡超微粉的新工艺.原料采用TiCl4和BaCl2,以(NH4)2CO3+NH3·H2O作为沉淀剂,对TiCl4浓度、沉淀反应温度、反应物钡钛比、煅烧温度等因素对钛酸钡超细粉理化指标的影响进行了系统研究,并将所制粉体用于制备X7R型MLCC瓷料.结果表明在控制(NH4)2CO3/BaCl2(摩尔比)=1.2、体系终点pH>9、TiCl4/BaCl2(摩尔比)=1~1.02,TiCl4浓度为0.6 mol/L、沉淀温度为20℃、煅烧温度为1020℃、煅烧时间为1.5h的条件下,可以制得粒径在0.1μm~0.3μm之间的钛酸钡超细粉,所制备X7R型MLCC瓷料的瓷片介电性能为ε25=3200~3700,tgδ=0.7×10-2,△C/C(-55℃~125℃)≤14%,ρ≥1012Ω·cm. 相似文献
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高纯纳米氧化钽的制备 总被引:3,自引:0,他引:3
以自制高纯乙醇钽为原料,通过水解、干燥与煅烧生产粒度约35nm的高纯Ta2O5纳米粉。研究了水解过程中乙醇钽浓度、温度、加料时间对产品粒度的影响以及煅烧温度与时间对Ta2O5晶形的影响。选取水解最佳条件为:乙醇钽浓度1.0mol/L,水解温度50℃左右,加料时间约15min。加完后,搅拌5min,接着加入氨水溶液调节pH值到8~9,同时升温至80℃-85℃保温30min;煅烧温度800℃,时间2h。得到的Ta2O5产品粒度约35nm,纯度〉99.997%。 相似文献
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以ZrO(NO3)2·2H2O、Ce(NO3)·6H2O和La2O3为原料,采用柠檬酸法制备了La2Ce2O7粉体,研究了pH值、乙二醇及柠檬酸用量、煅烧温度等工艺参数对La2Ce2O7粉体的影响。结果表明,采用该方法能够制备纯净的La2Ce2O7粉体,最佳实验条件是pH值为5,乙二醇、柠檬酸与金属离子的摩尔比分别是1.8和2,煅烧温度为400℃。 相似文献
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以分析纯的NH4Al(SO4)2和NH4HCO3为原料,选择合适的溶液浓度、分散剂及pH值,在合适的工艺条件下,得到NH4Al(OH)2CO3前驱体化合物.前驱体在1100℃下煅烧1h,得到粒径为80~100nm的超细α-Al2O3,Al2O3颗粒基本上呈球形,粒度均匀.研究了溶液浓度、分散剂及pH值对前驱体化合物颗粒细度的影响,用XRD法对前驱体化合物及其煅烧产物进行了表征,并研究了热处理过程中的相变化,对Al2O3多晶转变与热处理温度之间的关系进行了讨论.用SEM对Al2O3粉体的形貌、大小进行了表征.该方法工艺简单,原料易得便宜,综合成本较低,易实现工业化生产. 相似文献
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采用溶剂热结晶法制备工艺,以硫酸亚铁(FeSO4)为原料,聚乙二醇为溶剂,NH3H2O为沉淀剂,制备纳米氧化铁.然后利用XRD和SEM等分析手段,对样品进行表征,研究结果如下:当pH由6升高到10时,反应时间由90min可以缩短到30 min,氧化铁的晶体形态从粒状逐渐向片状晶过渡,颜色加深;当反应温度由140℃升高到170℃时,反应时间由90 min缩短到45 min,晶体的平均粒度由50 nm增加到800 nm,均匀性降低,晶体形态由球晶向针状晶过渡,颜色逐渐变红.在本实验条件下,最佳的pH=7,最佳的水热温度为160 ℃,最佳的水热时间为60 min. 相似文献
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采用柠檬酸法制备了固体氧化物燃料电池钙钛矿型阴极粉体La_(1-x)Sr_xMnO_(3-δ)(0.1<x<0.5),研究了pH值、络合剂量、煅烧温度等各工艺参数对络合效果的影响.结果表明:pH值是关键因素,最佳pH值为3.乙二醇能很好地促进柠檬酸络合金属离子,同时适当增加柠檬酸量有利于金属离子的络合.制备阴极粉体La_(1-x)Sr_xMnO_(3-δ)的最佳实验条件为:pH值为3,添加乙二醇,柠檬酸与金属离子的摩尔比为2,煅烧温度为1000 ℃. 相似文献
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Edward Ghali Wolfgang Dietzel Karl-Ulrich Kainer 《Journal of Materials Engineering and Performance》2004,13(1):7-23
Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative
applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure
and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general,
localized and metallurgically influenced corrosion, which are the main challenges for their use. Exposure to humid air with
∼65% relative humidity during 4 days gives 100–150 nm thickness. The film is amorphous and has an oxidation rate less than
0.01 μm/y. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film; however above
11.5 a passive stable layer is observed. The poor corrosion resistance of many Mg alloys can be due to the internal galvanic
corrosion caused by second phases or impurities. Agitation or any other means of destroying or preventing the formation of
a protective film leads to increasing corrosion kinetics. The pH changes during pitting corrosion can come from two different
reduction reactions: reduction of dissolved oxygen (O) and that of hydrogen (H) ions. Filiform corrosion was observed in the
uncoated AZ31, while general corrosion mainly occurred in some deposition coated alloys. Crevice corrosion can probably be
initiated due to the hydrolysis reaction. Exfoliation can be considered as a type of intergranular attack, and this is observed
in unalloyed Mg above a critical chloride concentration. 相似文献
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New development of anodizing process of magnesium alloys 总被引:1,自引:1,他引:0
Magnesium alloy, a kind of environment-friendly material with promising and excellent properties, is a good choice for a number of applications. The research and development of anodizing on magnesium alloys and its application situation are reviewed, and the anodizing development trend on magnesium alloys is summarized. 相似文献
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镁及镁合金阳极氧化技术 总被引:22,自引:4,他引:22
镁是目前最轻的金属结构材料之一,具有优良的物理和力学性能,应用日益受到关注,但耐蚀性差却制约了其应用范围,寻找一种合适的表面处理方法已成为必然。简要评述了镁及镁合金的各种阳极氧化处理方法,包括Dow17、HAE、Anomag、Magoxid—coat、Tagnite氧化方法,以及已见于报道的、但仍处于实验室研究阶段的各种阳极氧化处理方法。 相似文献
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用失重、线性电位扫描、交流阻抗、恒流放电等多种方法研究了AZ镁合金在1.0 mol/L Mg(ClO4)2溶液中的电化学行为,考察了它们作为镁电池负极材料的性能。浸泡与伏安实验结果表明,AZ21的自腐蚀比AZ31和AZ61严重;AZ21和AZ31的电化学活性优于AZ61,表现为阳极极化小,开路电位负。交流阻抗结果表明AZ21、AZ31、AZ61的Rct值逐渐增加。恒电流放电发现,AZ31的放电电位负且稳定;电流效率为82%,高于AZ21和AZ61;滞后时间2 s,小于AZ21和AZ61。可望用于Mg电池。 相似文献
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