聚乙二醇为碳源合成0.7LiFePO_4·0.3Li_3V_2(PO_4)_3/C复合正极材料及性能研究

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。     

有机／无机层状类钙钛矿（C12H25NH3）2PbI4晶体及薄膜的制备与结构表征

介绍了有机／无机类钙钛矿（C12H25NH3）2PbI4的晶体和薄膜的制备，并采用了XRD、SEM、AFM和PL表征材料的结构、形貌及光学特性等。XRD实验表明制备的（C12H25NH3）2PbI4晶体结晶度高。探索旋涂法制备工艺参数对薄膜结构的影响．在薄膜XRD中几乎只能观察到（0021）晶面的衍射峰．表明有机／无机类钙钛矿层沿平行与基片方向择优生长，SEM和AFM表明薄膜致密性较好，表面粗糙度较小。     

快速水热法制备铝掺杂羟基磷灰石

利用CaCl2、NH4H2PO4、NH3·H2O和Al（NO3）3溶液为原料,在高温、高压条件下快速水热制取羟基磷石灰,并用红外（IR）、X射线衍射（XRD）分析和表征羟基磷灰石晶体的结构及其结晶度。结果表明,用该法制备的羟基磷石灰晶体有较好的结晶度,且该法制备过程简单、制备时间短。     

LiFePO4/C复合正极材料的固相法合成

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.     

CaMoO_4:Eu~(3+)红色荧光粉化学共沉淀合成与表征

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.     

二钼酸铵的热分解行为研究

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↑。     

Mn4+-掺杂锂钒氧化物的合成及其电化学性能

以LiOH·H2O、NH4VO3和Mn(CH3COO)2·4H2O为原料,以柠檬酸(C6H8O7·H2O)为络合剂,用凝胶溶胶法按xLiV3O8·yLiMn2O4(x∶y=1∶0,4∶1,8∶l,12∶1,16∶1)合成出锂离子电池正极材料Mn4+-LiV3O8,并对其结构和电化学性能进行了研究.结果表明,用该法制备的...     

[（C6H5）2NH2]3[PWl2PO40]·4H2O的合成与表征

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。     

固相法制备LiMnPO4/C及其电化学性能的研究

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。     

纳米ZnFe2O4的低温固相合成及其电磁损耗特性

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.     

Quaternary system Li2MoO4-Na2MoO4-CaMoO4-BaMoO4

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.     

Superconducting and normal state properties of ErRh4B4 and LuRh4B4

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.     

10Cr4Ni4Mo4V钢和Cr4Mo4V钢的特性与断裂行为

对１０Ｃｒ４Ｎｉ４Ｍｏ４Ｖ钢和Ｃｒ４Ｍｏ４Ｖ钢的特性与断裂行为进行了试验研究。结果表明,１０Ｃｒ４Ｎｉ４Ｍｏ４Ｖ钢经微氮渗碳热处理后,其表面硬度、残余应力、断裂韧性及裂纹扩展速率均优于Ｃｒ４Ｍｏ４Ｖ钢的。     

Itinerant electron magnetism in the Mo4 tetrahedral cluster compounds GaMo4S8, GaMo4Se8, and GaMo4Se4Te4

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.     

Dielectric properties of Bi4(GeO4)3 and Bi4(SiO4)3

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.     

球形NH4FePO4·H2O的制备

以柠檬酸铵作络合剂通过控制结晶法制备了的球形NH4FePO4·H2O,用扫描电镜观察了颗粒的形貌和分布.通过研究加料方式、反应温度、滴加速度、搅拌速度、反应物浓度等对颗粒形态的影响,得到了制备球形NH4FePO4·H2O的最佳工艺条件.     

Nano-phases of NaBH4 and KBH4

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.     

5d-4f and 4f-4f emissions in Ln-doped sesquioxide ceramics

In this study, various lanthanide and mixed lanthanide oxides (Ln₂O₃ with Ln = La, Lu, Lu_0.5Gd_0.5) 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.     

LiZnPO4-LnPO4体系离子导电性的研究

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.