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以Li OH·H2O、Fe C2O4·2H2O、NH4VO3和NH4H2PO4为原料,分别以不同聚合度的聚乙二醇(PEG-200、PEG-600、PEG-1000、PEG-2000、PEG-6000)为碳源,通过高温固相法合成0.7Li Fe PO4·0.3Li3V2(PO4)3/C复合正极材料(LFVP/C)。用X射线衍射、拉曼光谱和扫描电镜对材料的结构和形貌进行了表征。充放电测试表明,在电压范围为2.0~4.3 V时,PEG-200为碳源的LFVP/C的复合正极材料具有较高的比容量、优良的循环性能和倍率特性。10C条件下其放电容量可以保持120 m Ah/g。 相似文献
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以LiOH·H2O、FeC2O4·2H2O、NH4H2PO4和C6H12 O6·H2O为原料,采用一步固相法在氮气氛下合成了LiFePO4/C复合正极材料.采用XRD、SEM和电池性能测试仪对合成产物进行了表征.研究了煅烧温度、煅烧时间、葡萄糖用量和锂过量对合成产物结构和电化学性能的影响.实验结果表明,采用一步固相法合成LiFePO4/C的最佳务件为:将经过高能球磨的前驱体在氮气氛下于650℃煅烧18h,葡萄糖用量为其它原料总质量的10%,锂过量10%(摩尔分数).在此条件下合成的LiFeP(4/C具有单一的橄榄石型结构和良好的电化学性能,0.1C的首次放电容量达到154.87mAh/g,30次循环后放电容量仍保持138.97mAh/g. 相似文献
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《无机材料学报》2010,(10)
以NH4HCO3-NH3·H2O为混合沉淀剂,采用化学共沉淀法制备CaMoO4:Eu3+红色荧光粉.通过TG-DTA和XRD研究CaMoO4:Eu3+前驱体的热分解和晶相形成过程;采用SEM和PL表征了该荧光粉的表面形貌和发光性能,并与NH4HCO3沉淀剂、NH3·H2O沉淀剂合成的CaMoO4:Eu3+荧光粉以及高温固相法制备的荧光粉进行对比.结果表明,煅烧温度700℃时,前驱体能够完全转换成单一CaMoO4:Eu3+白钨矿结构;煅烧温度900℃制备的荧光粉发光强度达到最大值;采用混合沉淀剂制备的荧光粉大小均匀、无团聚、呈类球型,平均粒径0.9μm.与高温固相法比较,其激发光谱中的Eu-O电荷迁移带向长波方向微小移动,而7F0→5L6(394nm)和7F0→5D2(465nm)的强电子吸收能有效改善红色荧光粉使用性能;与单独的NH4HCO3或NH3·H2O沉淀剂或高温固相法相比,该荧光粉发光性能显著改善,发光强度为传统固相法的2倍. 相似文献
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采用DTA、TG和XRD等检测手段研究了二钼酸铵的热分解行为,结果表明:二钼酸铵的热分解经历了两个阶段,所对应的反应温度分别在180℃左右及300℃左右,二钼酸铵热分解反应第一步为:4(NH4)2MO2O7→180℃ (NH4)4MO8O26+4NH3↑+2H2O↑;第二步为(NH4)4MO8O26→300℃ 8MoO3+4NH3↑+2H2O↑。 相似文献
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以12-钨磷酸和二苯胺为原料合成了一种电荷转移盐。通过元素分析确定其组成为[(C6H5)2NH2]3[PW12O40]·4H2O,各元素的质量分数分别为(括号内为理论值)C 12.91%(13.08%),H 1.304%(1.344%),N 1.793%(1.793%),采用红外光谱、紫外.可见分光光度法、X射线粉末衍射等测试技术对该化合物进行了分析表征。结果表明:所合成的新型电荷转移化合物的杂多阴离子保持Keggin结构特征。 相似文献
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分别采用传统高温固相法、以表面活性剂辅助所制NH4MnPO4·H2O为前驱体的高温固相法合成了LiMnPO4/C材料,运用XRD、SEM、充放电测试、电化学交流阻抗频谱(EIS)等表征手段考察了不同制备方法对材料结构与性能的影响。结果表明,以表面活性剂辅助所制NH4MnPO4·H2O前驱体来合成LiMnPO4/C材料,可以显著减小初始晶粒尺寸至约30nm。表面活性剂种类对二次颗粒的形貌、结构和电性能有显著影响。以P123为辅助表活剂时,所制材料确保了小晶粒与低团聚的结构特性,有利于其与锂盐高温反应时得到相更纯、晶面生长更优、晶化度更高、与电解液接触面积更大、锂离子扩散更容易、电性能更优的LiMnPO4/C材料。该材料0.2C容量达116.6mAh/g,5C放电容量达79.8mAh/g,且在各倍率下均保持优良循环稳定性。 相似文献
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纳米ZnFe2O4的低温固相合成及其电磁损耗特性 总被引:5,自引:1,他引:4
以Fe(NO3)3·9H2O,Zn(NO3)2·6H2O和H2C2O4·2H2O为原料通过低温固相反应合成了ZnFe2O4纳米粉.利用XRD、TG-DTA和SEM对产物的物相、热分解特性和微观结构进行了表征,表明粉体平均粒径为60nm;同时测定了产物的介电常数和磁导率,发现该复合氧化物在高频带具有较大的损耗系数,适宜用作高频下的磁性吸波材料. 相似文献
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The Li2MoO4-Na2MoO4-CaMoO4-BaMoO4 quaternary system was studied by differential thermal analysis and direct visual observation. Three invariant points, two
peritectic and one eutectic, were located. 相似文献
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L. D. Woolf D. C. Johnston H. B. MacKay R. W. McCallum M. B. Maple 《Journal of Low Temperature Physics》1979,35(5-6):651-669
Detailed heat capacity measurements of the ternary compounds ErRh4B4 and LuRh4B4 have been performed between 0.5 and 36 K and in magnetic fields up to 4 kG, yielding new information on crystal field effects in these materials and on the influence of externally applied magnetic fields on the coupled superconducting-ferromagnetic reentrant transition in ErRh4B4. Static magnetic susceptibility data on LuRh4B4 are presented which allow qualitative conclusions to be drawn regarding the magnitude of exchange enhancement and orbital paramagnetic effects in the RERh4B4 compounds. The electrical resistivity of ErRh4B4 has also been determined between 4 K and room temperature.This research was supported by the Department of Energy under Contract Number Ey-76-S-03-0034-PA227-3 (LDW, HBM, RWM, MBM) and by the National Science Foundation under Grant Number NSF/DMR77-08469 (DCJ). One of us (RWM) thanks the National Science Foundation for a postdoctoral fellowship. 相似文献
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A. K. Rastogi A. Berton J. Chaussy R. Tournier M. Potel R. Chevrel M. Sergent 《Journal of Low Temperature Physics》1983,52(5-6):539-557
The specific heat and magnetic properties of GaMo4X8 (X=S, Se, SeTe) between 1.4 and 290 K are reported. Our measurements tend to demonstrate that these compounds have a very high density of states, leading to a Stoner magnetic instability of conduction electrons at low temperatures. The linear temperature-dependent term in the specific heat is enhanced by electron-phonon coupling and spin fluctuation effects. These compounds could indicate an electron-phonon contribution to the Stoner enhancement factor. 相似文献
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Dielectric constant, dielectric loss and conductivity of Bi4(GeO4)3 and Bi4(SiO4)3 single crystals have been measured as a function of frequency and in the temperature range from liquid nitrogen temperature
to 400° C. The values of the static dielectric constant at room temperature are 16·4 and 13·7 for Bi4(GeO4)3 and Bi4(SiO4)3 respectively. The plots of log (σ) against reciprocal temperature at different frequencies of these crystals merge into a straight line beyond 250°C and the
activation energies calculated in this region are found to be 0·95 eV and 1·2 eV for Bi4(GeO4)3 and Bi4(SiO4)3 respectively. 相似文献
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Phase stability and chemical bonding of beta-NaBH4 and beta-KBH4 derived nano-structures and possible low energy surfaces of them from thin film geometry have been investigated using ab initio projected augmented plane wave method. Structural optimizations based on total energy calculations predicted that, for beta-NaBH4 and beta-KBH4 phases, the (011) and (101) surfaces are more stable among the possible low energy surfaces. The predicted critical size of the nano-cluster for beta-NaBH4 and beta-KBH4 is 1.35 and 1.8 nm, respectively. The corresponding critical diameter for the nano-whisker is 2.6 and 2.8 nm respectively for beta-NaBH4 and beta-KBH4. Structural optimization based on total energy calculations show that the bond distances in the surfaces of nano-whisker are found to be higher than that in the bulk material and the calculated H site energies and bond overlap population analysis suggesting that it is considerably easier to remove hydrogen from the surface of the clusters and nano-whiskers than that from the bulk crystals. 相似文献
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In this study, various lanthanide and mixed lanthanide oxides (Ln2O3 with Ln = La, Lu, Lu0.5Gd0.5) powders have been synthesized by a coprecipitation method. The luminescence properties and/or the quenching mechanisms of different dopants (europium, cerium, praseodymium) have been studied. Luminescence mechanisms of Ce:Ln2O3 and Pr:Ln2O3, are closely related to the 5d and 4f energy levels positions of the dopant versus materials bandgap and crossing effect between dopant energy levels. Energy level positions have been analyzed through optical spectroscopy and their effect on the luminescence is presented. Eu:Lu2O3 and Eu:LuGdO3 have also been prepared as transparent ceramics and radioluminescence properties are presented. 相似文献
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LiZnPO4-LnPO4体系离子导电性的研究 总被引:2,自引:0,他引:2
采用柠檬酸盐溶胶-凝胶法制备了低温相α-LiZnPO4和以LiZnPO4为基质稀土磷酸盐(LnPO4)掺杂的(LiZnPO4)1-x-(LnPO4)x(Ln3+=Nd3+、Sm3+、Er3+、X=0.1;Ln3+=La3+,X=0.1、0.2、0.4、0.6)的超细粉体并对它们进行DTA、TG和XRD的表征.讨论了室温下不同比例、不同稀土磷酸盐的掺杂对基质LiZnPO4离子导电率的影响.测试结果表明,LiZnPO4-LnPO4体系是由α-LiZnPO4和LnPO4两相组成;由于α-LiZnPO4烧结体的相对密度(d=58)极小,室温下样品几乎不显示导电性,而适量的非导电相LnPO4的掺入有助于提高烧结体的相对密度,增大体系的晶界电导率. 相似文献