硫酸亚铁铵滴定法测定铬青铜中的铬

以稀硝酸溶解试样,加入硫磷混酸加热蒸发冒烟至试样完全溶解;以硝酸银为催化剂,过硫酸铵为氧化剂,将Cr3+氧化至Cr6+;以N—苯代邻氨基苯甲酸为指示剂,用硫酸亚铁铵标准溶液滴定还原Cr6+为Cr3+,以此计算试样中铬的百分含量。方法的测定结果准确,相对标准偏差(RSD)<2.01%。     

二溴对甲基偶氮磺褪色光度法测定铬青铜中铬

基于0.6 mol/L硝酸介质中,显色剂二溴对甲基偶氮磺与铬(Ⅵ)的褪色反应,建立了测定铬青铜中铬(Ⅵ)含量的褪色光度分析方法。讨论了吸收光谱、酸度、试剂用量、时间、络合物组成、干扰离子等因素的影响,确定了反应的最佳条件。在25 mL溶液中,铬(Ⅵ)量在0.8~12μg范围内符合比尔定律,表观摩尔吸光系数为4.34×104L.mol-1.cm-1。方法可用于直接测定铬青铜中铬(Ⅵ)的含量,结果与二苯基碳酰二肼光度法(DPC)相符,其相对标准偏差(RSD)在0.97%~1.02%之间。     

再生铝合金熔炼工艺探讨

分析了再生铝合金熔炼过程中环境影响因素及工艺技术特点,引导企业结合自身的生产实际,因地制宜,制定出适合本企业实际的工艺技术操作方法。     

热处理对自力型整体式W-Cu/QCr0.5电触头材料组织与性能的影响

用烧结熔渗法制备W-Cu／QCr0．5自力型整体电触头材料，采用扫描电镜(SEM)和X射线衍射仪(XRD)分析固溶时效处理前后的组织与性能的变化。结果表明，固溶时效热处理后，伴随着铜尾电导率和硬度的明显提高，钨铜合金头的组织分布更加均匀、致密，两者的结合强度也得到改善。     

Fe-0.5Mn-0.5C预混合钢粉性能及粘结剂作用机制

设计4种不同有机粘结剂,分别对合金元素Mn、石墨进行粘结处理,制备Fe-0.5Mn-0.5C预混合钢粉。研究4种粘结剂对预混合钢粉合金元素与石墨的粘结率、预混合钢粉的流动性、松装密度、压坯密度的影响。并通过对粉末表面基团的表征,研究高分子粘结剂与铁基体间的相互作用方式。结果表明:以丙烯酸类树脂制备的预混合钢粉工艺性能最好,其流动速率为24.3 s/50 g松装密度为24.3 s/50 g,在600 MPa压力下的压坯密度为3.03~3.23 g/cm3粘结剂中的极性基团与铁基粉末通过氢键作用相吸附。     

锂离子电池正极材料LixNi0.5Mn0.5O2电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理超软贋势平面波法,对LixNi0.5Mn0.5O2的几何结构进行优化,并计算相应的电子结构和平均嵌锂电压.结果表明：x=1时,费米能级上分布着Ni、Mn d轨道电子和部分O2p轨道电子,层状LiNi0.5Mn0.5O2是电子的良导体;O2p轨道与Ni、Mn形成较强的共价键, Ni-O与Mn-O具有相近的键长,抑制了LiNiO2与m-LiMnO2中的因Jahn-Teller效应导致的八面体扭曲,且Mn-O键长在充放电过程中保持不变,材料具有稳定的结构;Li在晶胞中以主要离子态的形式存在,有利于脱嵌与传输.随着锂离子的脱出,材料的带隙增加,导电性能变差.     

Characterization and Stability of La0.5Sr0.5CoO2.91 Perovskite-Type Oxide

Compositely doped oxide La0.5Sr0.5CoO2.91 （LSC） was synthesized using solid state reaction and citric acid-nitrate low temperature self-propagating combustion methods. The crystal structure and the particle size micrograph of LSC powders synthesized by different methods were investigated with XRD and SEM. The experimental results show that the single perovskite phase of LSC can be synthesized by solid state reaction method, but LaSrCoO4 phase appears in LSC powder synthesized by citric acid-nitrate low temperature self-propagating combustion method. The LSC particle by citric acid-nitrate low temperature self- propagating combustion method has smaller size. To analyze the character of cathode material based on Ceo.gGdo.101.95（GDC） electrolyte, two types of cathode wafers were fabricated with the two kinds of LSC and GDC powders at the mass rate of 6：4, respectively. The electrical conductivity of the sintered samples was measured by four probe DC method from 300 to 800 ℃. The cathode with LSC particle by citric acid- nitrate low temperature self-propagating combustion method has higher electrical conductivity. In order to investigate the stability, the two samples were put into the muffle furnace to heat up in air at 800℃for 800 h. To analysis the reason for reduced electrical conductivity, the crystal structure and the particle micrograph of the cathode wafers before and after an exposure were investigated with XRD and SEM. The result shows that new crystal structure appears in both the two kinds of cathode wafers and crystal micrographs change a lot.     

Preparation and Electrical Transport Properties of Perovskite Oxide Ln0.5Sr0.5CoO3

The superfine powders of Ln0.5 Sr0.5 CoO3 （Ln = La, Pr, Nd, Sm, Eu） were obtained by solid state reactions. The crystal structure and electrical transport properties of samples doped with different rare earth elements as well as the forming process of the Perovskite structure were studied. The result shows that when the temperature reaches 1200 ℃, the samples will become a steady and unitary Perovskite phase by solid state reactions. The conductive behavor at low temperature is consistent with small polaron mechanism （i. e., localized electronic carriers having a thermally activated mobility）. However, the maximum of conductivity appears at about 700 ℃, and the conductivity of La0.5Sr0.5CoO3 is the biggest in the intermediate-temperature （600 - 850 ℃ ）, so it is fit for cathode material of intermediate-temperature solid oxide fuel cells.     

Growth and Spectral Properties of Crystal Er3+:Y0.5Gd0.5VO4

Er3 :Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er3 ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.     

加强冶炼工艺措施减少轧后废品

采用控制转炉过氧化、调节钢中氧含量、优选最佳工艺以数及杜绝高温挂罐等一系列质量管理措施,降低了轧后废品,使钢锭质量合格率大幅度提高,达到了提高降耗的目的。     

Magnetic and Transport Properties of La0.5-x Ndx Ba0.5 CoO3 Compounds

Substituting effects of Nd for La in La0.5Ba0.5CoO3 compounds were studied systematically. The results show that Nd doping does not change the itinerant properties of the Co3d electrons. The molecular magnetic moment of the mate-rials decreases monotonically with increasing Nd dopant. When Nd content x ≥0.45, a magnetic phase separation appears in the materials. When x ≤0.45, the Curie temperature decreases monotonically with increasing Nd dopant. This is due to the size effects of the rare earth ions. The electric resistance measurements show that in the studied temperature range, the conduction of the materials belongs to the thermo-diffusion conduction below the Curie temperature, while it belongs to the variable range hopping conduction of polarons over the Curie temperature.     

0.5Li3VO4-0.5Li4TiO4的溶胶-凝胶法合成及其离子导电性

用非醇盐溶胶凝胶法合成了组成和粒度均匀的锂离子导体０．５Ｌｉ３ＶＯ４０．５Ｌｉ４ＴｉＯ４超细粒子。用Ｘ射线衍射、ＴＥＭ及交流阻抗等方法对产物进行了表征。产物中两相的相纯度各为５０％,粒径在０３μｍ以下,室温下的离子电导率为７１０×１０－６ｓ·ｃｍ－１。     

Substituting Effect of Y in La0.5Ba0.5 CoO3

La0.5-xYxBa0.5CoO3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically. The results indicate that substitution of Y induces two effects. Firstly, the charge transfer from Y to 3d orbital of Co happens. This causes the molecular magnetic moment to decrease. Secondly, the antiferromagnetic exchange interaction of Co ions appears. When the content of Y is less than or equal to 30%, the non-colinear structure of spins in materials is observed. When the content of Y is greater than 30%, the materials transit from predominant ferromagnetic state to predominant antiferromagnetic one. The conductive mechanism for the materials with different content of Y belongs to the variable range hopping conduction of polarons.The resistivity of materials increases sharply with increasing Y content.