纳米氮化镁的合成

在制备高硬度、高热导、耐磨、耐腐蚀、耐高温的新兴陶瓷材料氧化硼、氮化硅的固相反应中，氮化镁是不可缺少的烧结助剂［‘，’j．同时，氮化镁还可用于制备发泡合金和回收核废料等领域．目前氮化镁的制备方法有：镁粉直接与氮气反应法［‘，‘1、镁在氮等离子流中与氮反应法＊‘、在氮气气氛下镁线圈爆炸法‘’‘和低压化学气相沉积法［’j．在上述方法中，有些方法需要复杂和昂贵的设备．有些方法得到氮化镁的产率较低．镁粉直接与氮气反应是具有工业生产价值的方法一然而，这种方法需要SOO”C到gOO”C的高温．我们曾经报道过利用温和…     

Hygrometric Determination of Water Activities, Osmotic and Activity Coefficients, and Excess Gibbs Energy of the System MgSO4–K2SO4–H2O

Ternary aqueous solutions of MgSO₄ and K₂SO₄ have been studied by the hygrometric method at 25°C. The relative humidity of this system is measured at total molalities from 0.35 mol-kg^–1 to about saturation for three ionic-strength fractions (y = 0.25, 0.50, and 0.80 of MgSO₄. The data allow calculation of water activities and osmotic coefficients. From these measurements, the Pitzer ionic mixing parameters are determined and used to predict the solute activity coefficients in the mixture. The results are used to calculate the excess Gibbs energy at total molalities for ionic-strength fraction y.     

Cathodic materials for lithium-ion batteries based on spinels Li x Mn2−y Me y O4: Synthesis, phase composition, and structure of Li x Mn2−y Cr y O4 at x = 1.0−1.2 and y = 0−0.5

Extralithiated chromium-doped finely divided lithium-manganese spinels are synthesized as a result of a two-step solid-phase process with use made of the fusion-saturation method. The spinels are intended for application as cathodic materials in lithium-ion batteries. The phase composition and structural characteristics of samples of cathodic materials of the type Li _x Mn_2?y Cr _y O₄ are studied. The samples with x = 1.0?1.2 and y = 0?0.5 are characterized by phase purity and cubic syngony with parameter a = 0.817?0.823 nm and a disperseness equal to 1–2 nm. The maximum content of chromium and lithium in Li _x Mn_2?y Cr _y O₄ that does not lead to violation of cubic syngony is determined. Lithium excess in the cathodic material that does not exceed 0.2 formula units may be used for compensating the irreversible capacity. Replacing some manganese atoms by chromium may facilitate retention of the structures’s integrity in the course of cycling.     

Investigation of Glass-Like Sol-Gel Coatings for Corrosion Protection of Stainless Steel Against Liquid and Gaseous Attack

Glass-like sol-gel coatings have been investigated as corrosion protective coatings on stainless steel. Magnesium- and borosilicate coatings with thickness of about 100–700 nm and methyl-modified SiO2 coatings with a thickness of about 2 m were deposited on stainless steel plates by dip-coating. The coatings were densified between 400°C and 500°C in different atmospheres (N2, air) for 1 h. The corrosion protection against gaseous attack was investigated by accelerated corrosion tests, at 800°C in air for 1 h. A corrosion protection factor was calculated from the relation Fe/Fe2O3, determined by XRD on the surface of coated and uncoated samples. Methyl-modified SiO2 coatings showed a protection factor, which was 2 orders of magnitude higher than for the other coatings. Electrochemical investigations were performed on samples submerged in a NaCl solution for 200 h. The corrosion propagation, polarization resistance and impedance vector were measured. For accelerated corrosion tests, polarization intensity curves were determined for high potentials of up to 1 V. Again excellent results were obtained for the methyl-modified SiO2 coatings, which remained passive for 200 h. Results of the salt spray corrosion test, however, showed no corrosion protection by the sol-gel coatings. After 2000 h in the salt spray chamber the steel was corroded and the coatings peeled off. It is concluded that for the further development of these coatings an improved interfacial passivation will be required.     

游离氧化钙,氧化镁连续测定的电导法研究

研究了乙二醇对氧化钙，氧化镁的提取条件，利用乙二醇提取氧化钙后在催化剂存在下继续提取氧化镁，建立了电导法连续测定ＣａＯ，ＭｇＯ分析方法，可用于水泥熟料中游离氧化钙，氧化镁的测定。     

高比表面积介孔网状氧化镁的制备、表征及对废水中Pb(Ⅱ)的吸附性能和机理

以天然水菱镁矿为原料，通过"煅烧-水化-煅烧"的简单方法制备了高比表面积介孔网状MgO，且实验过程中无须加入任何试剂。系统性研究了氧化镁用量、吸附时间、吸附温度及pH对氧化镁吸附模拟废水中铅离子吸附性能的影响，揭示了吸附机理，并考察了氧化镁对多种离子的吸附效果。结果表明：该氧化镁吸附剂具有188 m²·g^-1的高比表面积和0.85 cm³·g^-1的高孔体积，平均孔径为12.33 nm，其吸附动力学和等温线数据与伪二级模型和Langmuir模型高度吻合，表明重金属离子在氧化镁上为单层化学吸附。MgO介孔网状结构表现出对Pb（Ⅱ）的高吸附性能，最大吸附量为7 431.5 mg·g^-1，该数值远高于其他报道的基于MgO吸附剂的数值，铅去除率高达99.8%以上。介孔网状MgO的吸附机理主要是羟基官能团以及Mg（Ⅱ）与MgO表面重金属离子之间的离子交换所致。另外，该氧化镁可同时吸附多种离子，对Cd、Cr、Ni、As、Co、P、Se、Be、Bi、Cu、Fe、Mn、V、Zn、Al离子均具有优异的吸附性能。     

溶胶-凝胶法制备纳米氢氧化铝溶胶

研究了利用铝酸钠溶液碳酸化产生的沉淀, 经胶溶作用制备出纳米氢氧化铝溶胶的过程. 分析了铝酸钠溶液滴加到大量碳酸氢钠溶液中时发生的反应. X射线衍射研究结果表明, 在纳米氢氧化铝溶胶制备过程中, 从无定形氢氧化铝沉淀到拟薄水铝石的晶型转变过程是氢氧化铝沉淀胶溶时溶解再析出的过程. 将碳酸氢钠加入到苛性比为1.7的铝酸钠溶液中, 中和至苛性比为1.3后, 溶液诱导期中的紫外光谱显示270 nm处的Al(OH)3-6吸收增强. 经与含铝原子六配位的晶体紫外光谱对比后表明, 在铝酸钠分解生成氢氧化铝的过程中, 其铝的配位结构从四配位转化为六配位. 拟薄水铝石溶胶粒子的形貌与胶溶所用的酸和分散剂有关.     

尖晶石构造LiCu0.5Mn1.5O4的合成及其在水溶液中对Li^＋的抽出／嵌入反应

尖晶石构造ＬｉＣｕ０．５Ｍｎ１．５Ｏ４的合成及其在水溶液中对Ｌｉ＋的抽出／嵌入反应董殿权钟杰柳敦雷刘亦凡＊（青岛化工学院化学工程系青岛２６６０４２）关键词尖晶石，Ｌｉ－Ｃｕ－Ｍｎ复合氧化物，合成，锂离子交换１９９７－０９－１７收稿，１９９７－１２－２...     

Structural disorder in Ba0.6Sr0.4Al2O4

The structural disorder in Ba_0.6Sr_0.4Al₂O₄ (space group P6₃22) was investigated by X-ray powder diffraction and selected-area electron diffraction (SAED). The initial structural model was determined using direct methods, and it was further modified by the combined use of Rietveld method and maximum-entropy method (MEM). MEM-based pattern fitting method was subsequently applied, resulting in the final reliability indices of R_wp=9.61%, R_p=6.96%, R_B=1.40% and S=1.25. The electron density distribution was satisfactorily expressed by the split-atom model in which the strontium/barium and oxygen atoms were split to occupy the lower symmetry sites. The diffuse scattering in SAED was mainly attributable to the positional disorder of oxygen atoms.     

Kristallstrukturen von MgCr2O4-Typ Li2VCl4 und Spinell-Typ Li2MgCl4 und Li2CdCl4

Crystal Structures of MgCrO₄-type Li₂VCl₄ and Spinel-type Li₂MgCl₄ and Li₂CdCl₄ The crystal structures of the ternary lithium chlorides Li₂MCl₄ (M = Mg, V, Cd) have been determined firstly by X-ray single-crystal experiments. Li₂MgCl₄ and Li₂CdCl₄ crystallize in an inverse spinel structure (space group Fd3 m, Z = 8, a = 1 040.1(2) and 1 062.06(9) pm, structural parameters u = 0.25699(2) and 0.2550(1), R = 1.7 and 3.7% for 218 and 211 unique reflections). The Li? Cl distances of the tetrahedrally coordinated Li⁺ ions are significantly greater than calculated with Shannon's crystal radii ( > 238 ± 1 instead of 233 pm). Contrary to the results of X-ray powder data reported in the literature, Li₂VCl₄ crystallizes in the distorted spinel structure of MgCr₂O₄ type (space group F4 3m, Z = 8, a = 1 037.49(2) pm, R = 5.9% for 217 unique reflections). The decrease of the site symmetry of the octahedrally coordinated ions (V²⁺, Li⁺) from 3 m to 3m resulting in contracted and widened tetrahedral M₄ entities of the spinel structure is obviously caused by V? V metal—metal bonds (shortest V? V distance 366.2(7) pm).