共查询到19条相似文献,搜索用时 140 毫秒
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La0.6Sr0.4Co1-yFeyO3(y=0.2,0.8)复合氧化物混合导电性能研究 总被引:2,自引:0,他引:2
采用甘氨酸-硝酸盐(GNP)法制备了La0.6Sr0.4Co1-yFeyO3(y=0.2,0.8)g合氧化物,研究了材料的结构、电子-离子混合导电性能及其相关性。结果表明,La0.6Sr0.4Co1-yFeyO3(y=0.2,0.8)合成粉料的颗粒细小均匀(~100nm),陶瓷形成菱形六面体钙钛矿结构。与La0.6Sr0.4Co0.2Fe0.8O3(y=0.8)陶瓷相比,La0.6Sr0.4Co0.8Fe0.2O3(y=0.2)陶瓷的晶粒尺寸大、致密度较高。在La0.6Sr0.4Co0.8Fe0.2O3(y=0.2)陶瓷中观察到Co^3+离子歧化对电子导电性能的影响。与La0.6Sr0.4Co0.2Fe0.8O3(y=0.8)陶瓷相比,La0.6Sr0.4Co0.8Fe0.2O3(y=0.2)陶瓷具有更优异的电子-离子混合导电性能,材料在混合导电性能上的差异与其电子结构和显微结构紧密相关。 相似文献
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采用柠檬酸络合法制备B位掺杂的纳米钙钛矿复合氧化物La0.8Sr0.2Mn1-xCoxO3(x=0,0.3,0.5,1.0)。应用X射线衍射法(XRD)进行结构的测定与分析,并结合扫描电镜(SEM)和热磁曲线(M-T曲线)的实验结果,研究这4种样品的结构和磁性之间的关系。X射线衍射实验分析表明4个样品均属六方晶系,M-T曲线得出的1/χ-T曲线表明:La0.8Sr0.2MnO3是铁磁性,La0.8Sr0.2Mn0.7Co0.3O3和La0.8Sr0.2Mn0.5Co0.5O3是亚铁磁性,而La0.8Sr0.2CoO3是反铁磁性的。利用电镜观察到前3种样品均为颗粒状,颗粒之间首尾相接形成链状结构,并进一步由链状结构支起一个个的空间网状结构,最后一种样品为较为分散的颗粒。 相似文献
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硼掺杂对K2La2Ti3O10光催化分解水制氢活性的影响 总被引:2,自引:0,他引:2
通过溶胶-凝胶法制备了层状钙钛矿复合氧化物K2La2Ti3O10 及B掺杂的K2La2Ti3O10, 并采用X射线衍射和紫外-可见漫反射光谱等对制得样品进行了表征. 以I-为电子给体,分别在紫外和可见光辐射下研究了所制得样品光催化分解水的产氢活性; 采用第一性原理,计算了B掺杂对K2La2Ti3O10 半导体能带结构和态密度的影响,从电子结构的变化揭示了掺杂引起光催化活性差异的原因. 结果表明, B的掺入能够提高K2La2Ti3O10 的光解水产氢活性且存在合适的B掺杂浓度. 当B与Ti的摩尔比为0.01∶1时,紫外光催化分解水产氢速率为151.7 μmol/(L·h), 比未掺杂B的K2La2Ti3O10 产氢速率提高166%; 当B与Ti的摩尔比为0.02∶1时,可见光催化分解水产氢速率为85.2 μmol/(L·h), 为未掺杂B的K2La2Ti3O10 产氢速率的5.2倍. 相似文献
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采用柠檬酸络合法制备出具有不同原子比(La+Co/La+Co+Ce)的La-Co-Ce-O系列复合氧化物,并采用XRD、XPS和H2-TPR等方法对样品进行了表征测试.XRD结果表明,样品中的活性相为高分散的Co3O4纳米微晶(20~50nm)和少量的LaCoO3相,与浸渍法相比,柠檬酸络合法制得的样品具有更高的组分分散度和更小的晶粒度.CO氧化活性测试结果表明,柠檬酸络合法制得的样品比传统浸渍法制得的样品起燃温度降低约40℃,但样品的氧化活性与活性相Co3O4的多少及其晶粒度并不呈顺变关系.TPR和XPS的结果表明,样品中CeO2含量及可还原氧物种的多少与活性有直接关联,样品表面La、Co和Ce的原子百分数接近时,协同效应最佳,活性最好. 相似文献
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采用低温燃烧合成技术制备了La1-xSrxCu0.9Fc0.1O2.5-δ(x=0.1-0.4)粉体。利用X-射线衍射(XRD)和差热分析(DTA)技术对粉体的性能进行了表征。XRD结果表明,经800℃焙烧的La0.9Sr0.1Cu0.9Fe0.1O2.5-δ粉体的对称性较低,未形成钙钛矿结构,其余La1-xSrxCu0.9Fe0.1O2.5-δ(x=0.2-0.4)粉体为四方钙钛矿结构,晶体结构参数之间满足关系式a=b≈2√2c。DTA结果证明La1-xSrxCu0.9Fe0.1O2.5-δ在800℃以下是热力学稳定的,不会发生分解反应。采用直流四电极法测试了La1-xSrxCu0.9Fe0.1O2.5-δ试样在100-800℃之间的电导率。试样的电导率^ln(σT)与1/T之间呈很好的线性关系,说明La1-xSrxCu0.9Fe0.1O2.5-δ在测试温度范围内服从小极化子导电机制。Sr掺杂量对试样的电导率和电导活化能有着明显的影响,当Sr掺杂量为0.3时,La1-xSrxCu0.9Fe0.1O2.5-δ的电导率最高,电导活化能最小。 相似文献
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用固相法制备了新型固体电解质La2Mo2O9, 用热膨胀仪、 X射线衍射仪和Raman光谱分析了La2Mo2O9相的形成过程. 用交流阻抗谱和热膨胀仪对合成样品的电学和热学性能进行了研究, 分析了热处理温度对La2Mo2O9相的形成过程和电学性能的影响, 确定了样品获得高电学性能的最佳条件. 研究结果表明: 600 ℃时样品中开始形成La2Mo2O9相, 700 ℃以上烧结的样品可获得具有完整氧空位的La2Mo2O9相. 900 ℃烧结10 h可获得具有高密度和高电导率的La2Mo2O9氧离子导体. 样品的电学性能随烧结温度的升高而增大, 900 ℃时烧结的样品在800 ℃时的电导率为0.067 S·cm-1, 远高于同温度下YSZ的电导率, 与晶粒电阻相比, 晶界电阻非常小. 用热膨胀仪测得La2Mo2O9在555 ℃时有一个一级相变, 对应α-La2Mo2O9到β-La2Mo2O9的相变. 相似文献
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可控粒径纳米Fe_3O_4的制备及其磁性研究 总被引:2,自引:0,他引:2
本文用空气氧化法,在可见光作用下,添加配合剂(EDTA、柠檬酸、酒石酸、谷氨酸)在室温进行了不同粒径纳米Fe3O4的制备及其磁性能研究。结果表明:在可见光作用下,随EDTA、柠檬酸、酒石酸、谷氨酸等配合剂的添加,得到纳米Fe3O4的粒径有所减小、分散性有所提高;配合剂及可见光共存时,体系反应速率得到提高,高的反应速率使纳米Fe3O4晶粒减小;控制适当的光照度和添加剂的量,室温可得到11.8~29.6nm的Fe3O4颗粒。不同粒径纳米Fe3O4分别呈现出超顺磁性、铁磁性特征。 相似文献
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The distribution coefficients between the cation- and anion-exchangers Dowex 50 and Dowex 1, and aqueous solutions containing nitric or hydrochloric acid and organic solvents with or without amines or complexing agents, have been obtained for a number of metals including uranium, thorium, cerium, iron, copper, and nickel. The organic solvents were methanol, acetone and dimethylformamide; the amines were tributylamine and tribenzylamine, and the complexing agents EDTA and citric acid. Both batch and column methods were used. 相似文献
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A survey of the literature regarding the composition of mixed wastes originating from the clean ups of spills of radioactive solutions shows that (1) the mixtures obtained in studies of the X-ray and -ray radiolysis, and of the UV-photolysis of organics in aqueous solutions have very similar composition provided the photolysis is carried out with UV beams with wavelengths below 242 nm; (2) the composition of the organic fraction of mixed wastes containing initially EDTA, NTA, and/or citric acid is complex. The mass recoveries are between 20 and 60%; and (3) the UV-photolysis of complexing agents gives much more complex mixtures at high pH than at low pH, because carbonyl compounds are formed, and these compounds undergo complex series of reactions in strongly alkaline solutions. The mixed wastes considered have a high pH due to the necessity of complexing strongly the heavy metals involved in spills. These results are confirmed by an investigation of the properties of the products of the UV-irradiation of EDTA, citric acid and some of their binary mixtures. The products of the esterification by BF3/BuOH are only partly soluble in methylene chloride. Much better yields are obtained by using BF3/BuOH as the reagent.13C NMR illustrates the composition of the mixture, without requiring a separation and is useful to follow the fate of compounds during their methylene chloride extraction after esterification. 相似文献
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LaFeO_3的光催化性 总被引:1,自引:0,他引:1
LaFeO3属钙钛矿(ABO3)型复合氧化物.其结构、磁性和导电性都已有许多报道[1~3],但对其光催化性报道很少.目前普遍采用的光催化剂TiO2具有光、化学稳定性好、无毒、催化活性高、氧化能力强等优点.由于TiO2禁带宽度(Eg)较宽(约为3.2eV),太阳能的利用率低[4].对钙钛矿(ABO3)型复合氧化物的光催化活性的研究发现,禁带宽度与A—O,B—O的电负性差值有关.如,A—O电负性差值较小的PbO(1.6eV)与B—O电负性差值较大的TiO2(2.0eV)合成的PbTiO3的Eg为2.7eV,正好处在1.77~3.09eV之间(可见光波长700~400nm对应光子的能量范围)吸收可见光… 相似文献
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氧化镁表面修饰稀土催化材料的制备和气敏性能 总被引:1,自引:0,他引:1
本文采用湿化学过程的柠檬酸络合法、可控化学沉淀法和溶胶-凝胶法合成了纳米复合金属氧化物LaFeO3,利用各种分析方法对材料的物性和结构进行了分析和表征;并测定了材料对氧化性气体和还原性气体的气敏性能.研究结果表明LaFeO3复合物对NO2在350℃灵敏度高达127.83,特别通过添加MgO对基材进行表面修饰灵敏度提高到845.37,约添加前的70倍.本文还进一步考察了添加质和添加量对基材的结构和气敏性能的影响,并通过研究材料表面对气体的吸脱附性能和元素电子结合能的变化对敏感作用机制进行了深入分析和探讨. 相似文献
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Selective extraction-separation of yttrium(III) from heavy lanthanides into 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)mim][PF(6)]) containing Cyanex 923 was achieved by adding a water-soluble complexing agent (EDTA) to aqueous phase. The simple and environmentally benign complexing method was proved to be an effective strategy for enhancing the selectivity of [C(n)mim][PF(6)]/[Tf(2)N]-based extraction system without increasing the loss of [C(n)mim](+). 相似文献
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Transport of tervalent REEs — Sc, Y, Ce, Eu, Gd, Tm, Yb — from nitrate medium through a liquid membrane containing TBP in n-dodecane, impregnated on a flat-sheet nucleoporous support, has been studied as a function of time and initial metal concentration, salting-out agent concentration and pH of the feed phase. Influences of various complexing agents dissolved in the strip phase was investigated, too. Adding a suitable amount of EDTA into the feed phase, separation of binary mixtures of REEs was experimentally achieved. 相似文献
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M. Motta C. V. Deimling M. J. Saeki P. N. Lisboa-Filho 《Journal of Sol-Gel Science and Technology》2008,46(2):201-207
Several routes and procedures have been used in these last years as an effort to achieve single-phase mesoscopic-size superconducting
samples. In this paper, the effects of using citric acid (CA), tartaric acid (TA) and ethylenediaminetetraacetic acid (EDTA)
as chelating agents and ethylene-glycol (EG) as polyhydroxy alcohol were studied in order to establish conditions to avoid
the occurrence of BaCO3 undesirable secondary phase in YBa2Cu3O7−δ (YBCO). Thermal evolution of intermediate compounds formed during the calcinations process by the use of different chelating
agents was traced using thermogravimetric and spectroscopic methods. The obtained results indicated that the polymer breakdown
of samples prepared using EDTA occurs at higher temperatures than others chelating agents and also reduces the occurrence
of BaCO3 secondary phase as studied by X-ray diffraction measurements. Furthermore, the magnetic response of the mesoscopic-size YBCO
specimens obtained was verified showing that samples present different superconducting response. 相似文献