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采用高温熔融法制备了不同Pr2O3掺量的SiO2-B2O3-Al2O3-BaO玻璃,利用DTA,XRD,TEM以及IR等手段研究了稀土氧化物掺入量对玻璃热稳定性、析晶行为、玻璃结构的影响。结果表明:当稀土掺入量逐渐增加时,玻璃的热稳定性递减;在高于Tx的温度下进行热处理,玻璃析晶产物逐渐由PrAl2.03(B4O10)O0.54向PrBO3转变;Pr^3+填充在[SiO4],[BO4]和[BO3]等结构单元组成的混合网络的空隙之中,网络中间离子Al^3+随稀土氧化物的增加,发生从网络变性离子向网络形成离子的转变。 相似文献
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通过不同的工艺制备了稀土氧化物-钼(RE2O3-Mo)阴极材料的次级发射体,测定了材料的次级发射性能,采用SEM和能谱分析等手段研究了材料的微观结构。实验结果表明,影响材料次级发射性能的因素有:材料的化学成分、掺杂方式、烧结方法、热激活温度等。所有利于提高材料表面稀土氧化物含量的因素均可以提高材料的次级发射性能,这是因为稀土氧化物中的自由电子比较少,由一次电子激发出的二次电子在离开材料时,与材料体内自由电子碰撞的机会就小,而提高材料的次级发射性能。 相似文献
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研究了在ZnO压敏材料组分中以溶液方式加入稀土氧化物Pr6O11后其微观结构的变化。结果表明,Pr6O11的加入改变了ZnO尖晶石相的生成途径,使该材料在低于700℃时生成大量焦绿石相(Bi3Zn2Sb3O14)。当烧成温度高于900℃时,焦绿石相分解生成细小的二次尖晶石相(Zn7Sb2O12)。这种二次生成的细小尖晶石使材料晶粒尺寸减小,分布均匀;此外,Pr6O11的引入能生成含Pr物相,以及Pr氧化物相也有利于材料的晶粒细化。晶粒细化结果改善了ZnO压敏材料的压敏电压和非线性特性,与掺杂前相比,压敏电压提高了约60%。 相似文献
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稀土掺杂对锂离子电池正极材料LiMn2O4结构及电性能的影响 总被引:19,自引:5,他引:19
利用微波加热技术合成稀土掺杂基锂离子电池正极材料LiMn2-xRExO4(RE=Y,Nd,Gd,Ce),通过XRD、循环伏安及恒电漉充放电测试研究了稀土掺杂离子对合成正极材料结构及电化学性能的影响。XRD测试结果表明,合适的掺杂量可以起到扩展锂离子脱嵌通道和稳定骨架结构的作用,稀土离子的引入可以部分取代原有的三价锰离子,由于稀土离子的离子半径较三价锰离子大,因此稀土掺杂锰酸锂材料的晶胞参数比未掺杂材料大,在一定程度上扩充了锂离子迁移的三维通道,更有利于锂离子的嵌入与脱嵌;循环伏安及恒电漉充放电测试结果表明稀土掺杂有效提高了LiMn2O4材料的电化学循环可逆性及循环稳定性。 相似文献
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稀土红色长余辉发光材料研究进展 总被引:16,自引:0,他引:16
综述了稀土元素掺杂红色长余辉发光材料的研究进展,总结了硫化物、钛酸盐、硫氧化物、硅酸盐、氧化物和磷酸盐等基质体系的红色长余辉发光,并指出硫氧化物和磷酸盐等基质是最具有发展前景的红色长余辉发光体系,讨论了Eu^2 在硫化物、Pr^3 在钛酸盐以及Eu^3 和Sm^3 等稀土离子在硫氧化物和硅酸盐等体系中的红色长余辉发光机制。介绍了传统的高温固相法以及溶胶.凝胶法、微波合成法等稀土红色长余辉材料的制备技术。提出了从基质材料、制备技术和稀土离子发光机制入手是稀土红色长余辉发光材料今后研究与开发的发展方向。 相似文献
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稀土氧化物对连铸保护渣粘度的影响 总被引:1,自引:1,他引:1
通过实验室自配渣研究了稀土氧化物对保护渣粘度的影响。研究表明,稀土氧化物提高了保护渣粘度,特别是当其含量大于10%后最为明显;稀土氧化物导致保护渣粘度升高的原因是生成的高熔点物相随温度降低析出;稀土氧化物在保护渣中具有一定溶解度,当稀土氧化物在保护渣中出现过饱和时,未溶解的固态质点使保护渣粘度随之升高;Li2O,B2O3和BaO可以降低液态保护渣粘度,同时可以提高保护渣溶解吸收稀土氧化物的能力,但是其加入量应控制在合理的范围之内。稀土氧化物可以显著提高保护渣凝固温度,这对铸坯.结晶器之间的传热和润滑非常不利。 相似文献
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研究了稀土氧化物Ce2O3在采用氟盐法制备铝合金用Al-Ti-C细化剂的作用,通过OM,XRD,SEM及EDAX等研究手段对细化剂的组织进行了研究。结果表明,稀土氧化物Ce2O3制备Al-Ti-C细化剂过程中,可以提高反应物氟钛酸钾与碳粉反应速度,在铝液中产生激烈的翻腾作用,从而在制备过程中对铝熔体产生强烈搅拌作用,这样可以不采用物理搅拌方法就能使合金中的组织分布均匀,此外通过环境扫描电镜(ESEM)观察发现,稀土氧化物Ce2O3反应后的稀土元素是一种强烈的表面活化元素,可以吸附在Al-Ti-C细化剂中的Al3Ti相上,形成新的稀土化合相[AlTiCe],并提高产生TiC粒子的反应速率,促进TiC粒子生成。 相似文献
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A rapid and solvent free substitution reaction of a fluorine atom in perfluorooctane sulfonyl fluoride (PFOSF) with a hydroxyl radical is reported. Under irradiation of ultraviolet laser on semiconductor nanoparticles or metal surfaces, hydroxyl radicals can be generated through hole oxidization. Among all fluorine atoms of PFOSF, highly active hydroxyl radicals specifically substitute the fluorine of sulfonyl fluoride functional group. Resultant perfluorooctane sulfonic acid is further ionized through capture of photo-generated electrons that switch the neutral molecules to negatively charged odd electron hypervalent ions. The unpaired electron subsequently initiates α O-H bond cleavage and produces perfluorooctane sulfonate negative ions. Hydroxyl radical substitution and molecular dissociation of PFOSF have been confirmed by masses with high accuracy and resolution. It has been applied to direct mass spectrometric imaging of PFOSF adsorbed on surfaces of plant leaves. 相似文献
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T. A. Lastovina A. L. Bugaev S. P. Kubrin E. A. Kudryavtsev A. V. Soldatov 《Journal of Structural Chemistry》2016,57(7):1444-1449
Magnetic nanoparticles and those doped with rare-earth metal ions having spinel structure were synthesized, possessing the average particles size of 11.3-13.4 nm. According to Mössbauer spectroscopy data it can be concluded that prepared iron oxide nanoparticles are γ-Fe2O3. For materials containing rare-earth elements the decrease of octahedral component surface was observed in comparison to non-doped material, what can be explained by Eu3+, Sm3+ и Gd3+ ions occupying the octahedral position. 相似文献
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A. R. Tenchurina A. K. Sal’keeva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(3):688-690
The thermal treatment of sodium sulfate was found to affect its optical and luminescent properties when activated with trivalent rare-earth ions. The influence of crystal water molecules on radiation processes in sodium sulfate was studied. The interactions of atomic hydrogen with ions and radicals were calculated by the semiempirical MNDO quantum-chemical method. The hydrogen atom was found to form stable complexes with all ions and radicals. The ions and radicals of the sulfate subsystem play the role of traps for hydrogen atoms and escape recombination, giving rise to recombination luminescence at 150 K during UV excitation of the crystalline hydrate. 相似文献
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Demirev PA 《Rapid communications in mass spectrometry : RCM》2000,14(9):777-781
An efficient technique for generation of H* (D*) radicals in Fourier transform ion cyclotron resonance (FTICR) mass spectrometry is described. The method allows the probing of the reactivity of gas-phase H* radicals towards various ions isolated in the cell of an FTICR mass spectrometer. Results on interactions of H* and D* radicals with trapped positive or negative C60 fullerene ions, as well as singly charged peptide ions, are presented. Hydrogen radical addition or H/D-exchange reactions between trapped ions and free H* (D*) radicals were observed. Potential implementation of the technique for probing the gas-phase three-dimensional structures of polyatomic ions is discussed as well. 相似文献
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介绍了一种利用离子束外延(Ion-beam Epitaxy, IBE)技术制备生长高纯稀土功能薄膜的新方法. 以纯度要求不高的低成本稀土氯化物为原材料来产生大束流稀土元素离子, 通过准确控制双束合成或单束浅结注入掺杂的同位素纯低能离子的能量、束斑形状、沉积剂量与配比及生长温度, 在超高真空生长室内实现了稀土功能薄膜的高纯生长和低温优质外延. 文中除了对新方法的技术特点、实施方式和应注意的关键技术进行了阐述, 还结合CeO2, Gd2O3, GdxSi1-x等薄膜的制备研究, 讨论了离子的束流密度、剂量配比、能量和生长温度等生长参数对成膜质量的影响. 相似文献
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Zinc oxide (ZnO) nanoparticles have been produced using precipitation methods from ethanolic solution. Rare-earth metal doping was performed, and the effect of lithium codoping on the luminescence properties of the rare-earth doped products was assessed. The resulting particles were characterized using cathodoluminescence and scanning electron microscopy. It was found that lithium significantly enhanced the cathodoluminescence signal from the rare-earth ions, which has been attributed to the increased integration of the rare-earth ions into the ZnO structure. The nanophase ZnO products were also annealed in argon, hydrogen, and oxygen, with hydrogen being the most successful for removing the broad defect emission present in as-grown samples and enhancing the ZnO near band edge emission. 相似文献
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采用交流伏安法、电化学阻抗谱(EIS)和Mott-Schottky 分析技术研究了无锡钢电镀液中氟离子电化学行为. 结果表明, 在氧化还原过程中氟离子抑制铬离子化学状态转变, 降低铅合金和铅氧化物阳极的氧化电流密度, 改变铅合金和铅氧化物阳极的氧化还原历程. EIS 结果表明电场作用下溶液中铬氧离子团发生聚合, 在铅合金阳极表面形成感抗现象. 含氟溶液中铬氧离子团在阳极表面的感抗现象消失, 溶液导电性提高. Mott-Schottky 曲线显示氟离子提高阳极材料的载流子密度, 铅合金阳极和铅氧化物阳极均为n 型半导体. 相似文献
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Voinov MA Sosa Pagán JO Morrison E Smirnova TI Smirnov AI 《Journal of the American Chemical Society》2011,133(1):35-41
Emerging applications of nanosized iron oxides in nanotechnology introduce vast quantities of nanomaterials into the human environment, thus raising some concerns. Here we report that the surface of γ-Fe(2)O(3) nanoparticles 20-40 nm in diameter mediates production of highly reactive hydroxyl radicals (OH(?)) under conditions of the biologically relevant superoxide-driven Fenton reaction. By conducting comparative spin-trapping EPR experiments, we show that the free radical production is attributed primarily to the catalytic reactions at the nanoparticles' surface rather than being caused by the dissolved metal ions released by the nanoparticles as previously thought. Moreover, the catalytic centers on the nanoparticle surface were found to be at least 50-fold more effective in OH(?) radical production than the dissolved Fe(3+) ions. Conventional surface modification methods such as passivating the nanoparticles' surface with up to 935 molecules of oleate or up to 18 molecules of bovine serum albumin per iron oxide core were found to be rather ineffective in suppressing production of the hydroxyl radicals. The experimental protocols developed in this study could be used as one of the approaches for developing analytical assays for assessing the free radical generating activity of a variety of nanomaterials that is potentially related to their biotoxicity. 相似文献
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在新陈代谢过程中,机体会产生大量以自由基为主要形式的氧化活性物质,而抗氧化剂可以通过电子转移的方式捕获并中和自由基,从而有效抵御自由基引起的细胞损害,以保障和维护人体健康.食品作为人体外源性抗氧化剂的重要来源可以有效补充因体内代谢及体液排出而损失的抗氧化物质,因此对食品中抗氧化物质消除自由基的能力即抗氧化能力的测定和评价具有重要意义.光电化学技术作为一种简单快捷、低成本、低背景且高灵敏度的测定方法,能够有效克服光学法、色谱法和电化学法等传统测试手段在抗氧化容量分析中的不足.本文综述了基于半导体及其复合材料的光电化学传感平台的构建及食品体系抗氧化容量分析的研究进展,评论了多种检测体系的特点并对其研究前景进行了展望. 相似文献
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Sajjad Dadashi‐Silab Abdullah Mohamed Asiri Sher Bahadar Khan Khalid A. Alamry Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2014,52(10):1500-1507
Photoinduced free radical polymerization of vinyl monomers by using semiconductor inorganic nanoparticles (NPs) is investigated. Zinc oxide and iron‐doped zinc oxide were used as photosensitive compounds to initiate the polymerization of acrylamide as a water‐soluble monomer in aqueous environment and methyl methacrylate as an oil‐soluble monomer in organic media under UV‐light irradiation. The method uses photochemically generated electrons and holes from the NPs to form initiating hydroxyl radicals in aqueous media, while tertiary amines and iodonium salt served as coinitiator in organic media. The initiation mechanism in organic media involves hydrogen abstraction or reduction processes via charge carriers, respectively. The kinetic of the polymerization in both environments was studied by means of a photo‐differential scanning calorimetry. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1500–1507 相似文献