胶体五氧化二锑胶粒大小与分布的影响因素及其稳定性

选择3种有机物作为稳定剂,采用双氧水回流氧化法制备胶体五氧化二锑,探讨了影响胶体粒子大小及分布的主要因素,并从Zeta电位的观点研究了胶体的稳定性.结果表明:稳定剂的种类及用量、反应温度、双氧水的用量及加入方式、反应物的固液比是影响胶体粒子大小及分布的主要因素.2号稳定剂的吸附作用、静电斥力作用及空间位阻效应导致胶体能稳定存放1 a以上,等电点从pH=1.85向更酸性区移动,Zeta电位从-30mV变为-60 mV.     

THE ELECTROCHEMICAL BEHAVIOUR OF Sb ELECTROWINNING IN Na_2S-NaOH SOLUTION

本文是湿法炼Sb的物理化学研究中的一部分。 当用Na_2S-NaOH溶液浸出复杂的Pb-Sb精矿时,Sb以SbS_3~(3-)离子形态进入溶液。精矿中的Sn和As部分溶解,而Pb则留在残渣中与Sb分离,SbS_3~(3-)离子与空气接触时,部分氧化成SbS_4~(3-)离子。 用稳态法测定了极化曲线,确定了在硫化碱溶液中Sb(Ⅲ).Sn(Ⅳ),As(Ⅲ),Sb(Ⅴ)和H~+离子的放电电位。其相应数值如下:-0.92,-1.04,-0.81,-0.68和-1.12V。这些数值分别用纯化学试剂配制的溶液和工业电解液进行了比较测定,并用热力学计算结果进行核对。Sb(Ⅴ)的放电电位还通过计时电位法核对。 将所得极化曲线进行浓差极化修正后获得了Tafel直线,由此计算出有关的电极动力学参数。 应用计时电位法,探讨了SbS_3~(3-)和SbS_4~(3-)离子的阴极放电机理。结果表明:SbS_3~(3-)离子放电前经历一个前置转化步骤,即: SbS_3~(3)→SbS~++2S~(2-) (1)生成的中间产物SbS~+按下列反应 SbS~++3e→Sb+S~(2-) (2)还原为金属Sb。 SbS_4~(3-)离子在阴极上放电过程分两步进行,首先,SbS_4~(3-)离子按下式还原为SbS_3~(3-)离子, SbS_4~(3-)+2e→SbS_3~(3-)+S~(2-) (3)生成的中间产物SbS_3~(3-)离子再按反应(1)和(2)式还原为金属Sb。     

Electrodeposition of chromium from trivalent chromium urea bath containing sulfate and chloride

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｏｏｂｔａｉｎｃｈｒｏｍｉｕｍｃｏａｔｉｎｇｂｙｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｐｒｏｃｅｄｕｒｅ，ｅｌｅｃｔｒｏｄｅｐｏｓｉｔｉｏｎｆｒｏｍｅｎｖｉｒｏｎｍｅｎｔａｌｌｙｆｒｉｅｎｄｌｙＣｒ（Ⅲ）ｂａｔｈｉｓｍｏｒｅａｃｃｅｐｔａｂｌｅｔｈａｎｔｈａｔｆｒｏｍｔｏｘｉｃＣｒ（Ⅺ）（ｃｈｒｏｍｉｕｍａｃｉｄ）ｂａｔｈ．Ｎｕｍｅｒｏｕｓａｔｔｅｍｐｔｓｈａｖｅｂｅｅｎｍａｄｅｔｏｄｅｐｏｓｉｔｃｈｒｏｍｉｕｍｆｒｏｍｉｔｓｔｒｉｖａｌｅｎｔｓｔａｔｅ，ｈｏｗｅｖｅ…     

火焰原子吸收光谱法测定铅碲渣中碲

建立了空气-乙炔火焰原子吸收光谱法测定铅碲渣中碲,研究了各项实验条件。在王水(φ=5%)-酒石酸(30 g/L)介质中测定碲,不必分离干扰元素。方法线性范围为1~16μg/mL,相关系数为0.999 9,检出限0.09μg/mL。用于铅碲渣样中碲的测定,加标回收率为98.0%~102.3%,相对标准偏差≤0.8%。     

Corrosion leaking of preheater weldment in alumina factories

Stress corrosion cracking （SCC） and anticorrosion measures of TU42C weld-joint were studied by constant load experiments and pickling experiments. The results show that in 40% （mass fraction） NaOH solution at 110℃, caustic SCC occurs in TU42C weld-joints at the applied potential of —1020 mV（vs SCE） for 3 d while at the potential of—950 mV（vs SCE） for 10 d. All the cracks are intergranular. In the 10% sulfuric acid, the cracks have the most negative self-corrosion potential —432.5 mV（vs SCE） and are active to be further corroded by the acid. Because of the same corrosion behaviour as the lab weldment, preheater＇s cracking in alumina factories is attributed to the combining actions of previous caustic SCC in Bayer solutions and continuous acid corrosion by pickling with the addition of RD. The following measures are effective to prevent the corrosion failure of preheater, such as postweld heat treatment at 620 ℃ to relax the residual weld stress, addition of CC3 and L826 as the corrosion inhibitors to improve the pickling and cleaning by the high pressure water instead of by pickling.     

Zn2+离子掺杂对负载TiO2薄膜光催化活性的影响

以钛酸丁酯和ZnSO₄·7H₂O为原料，采用溶胶-凝胶法在钛片、玻璃、釉面瓷砖、陶瓷、不锈钢和铝片六种载体上制备了Zn²⁺掺杂TiO₂薄膜，讨论了不同Zn²⁺掺杂浓度下不同载体表面上制备的TiO₂薄膜对甲基橙脱色率的影响。结果表明，Zn²⁺对TiO₂薄膜的掺杂效果与载体的类型密切相关，并且不同载体其Zn²⁺掺杂的最佳浓度也不同。Zn²⁺掺杂后，TiO₂薄膜光催化活性提高最大的是釉面瓷砖，其次是钛片、玻璃、陶瓷。不锈钢和铝片上TiO₂薄膜的光催化活性不但没有升高，反而降低了。     

铝活塞的磷化工艺

研究了铝活塞的锰系磷化工艺.以外观和耐磨性为定量指标,讨论了主要成分、添加剂、温度和时间对磷化膜质量的影响,确定了最佳磷化工艺.结果表明:该磷化工艺稳定,维护简单.所得磷化膜为灰黑色,均匀光亮,耐蚀性、耐磨性和耐热性优良.由磷化机理分析表明,磷化膜的组成为AlPO4和Mn3(PO4)2.     

Synthesis of Ni-Zn ferfite and its microstructure and magnetic properties

Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.