微量碳对淬态Fe－Si－B非晶丝表面层结构及脆性的影响

用旋转水中熔融金属纺丝法制备了Ｆｅ－Ｓｉ－Ｂ非晶金属丝。拉伸和弯折性能表明，当合金中杂质碳原子分数含量≥０．２％时，制备态（淬态）非晶丝发生脆化。电子探针、Ａｕｇｅｒ能谱分析与透射电镜观察发现，非晶丝表面具有大约１５０－３００ｎｍ宽的富碳层且包含Ｆｅ＿（２３）（Ｃ，Ｂ）＿６相。该相是Ｆｅ－Ｓｉ－Ｂ非晶丝脆化的原因。     

矿热电炉红土矿冶炼镍铁技术概论

详细地介绍了回转-矿热炉(RKEF)红土矿冶炼镍铁工艺的各个环节,包括:红土矿的预处理,开炉,渣型的选择,并给出了2种冶炼方案.同时对电炉的供电制度、电炉参数的选定.炉衬的选择以及技术经济指标进行了阐述.并将RKEF工艺与日本大江山工艺进行了对比,对红土矿冶炼镍铁生产有一定的指导意义.     

Cr(VI) removal from aqueous solution by activated carbon coated with quaternized poly(4-vinylpyridine)

A composite sorbent (GAC-QPVP) was prepared by coating poly(4-vinylpyridine) onto a granular activated carbon, followed by cross-linking and quaternization processes. The sorbent was characterized by scanning electron microscopy, point of zero charge measurement, and BET analysis. Batch experiments with variable pH, ionic strength, and concentrations of Cr(VI), sorbent, and competing anions were conducted to evaluate the selective sorption of Cr(VI) from aqueous solutions. The results showed that Cr(VI) sorption rates could be described by a reversible second-order kinetics, and equilibrium uptake of Cr(VI) increased with decreasing pH, decreasing ionic strength, and increasing sorbent concentration. The estimated maximum equilibrium uptake of chromium was 53.7 mg/g at pH = 2.25, 30.7 mg/g at pH = 3.65, and 18.9 mg/g at pH = 6.03, much higher than the maximum capacity of PVP-coated silica gel, an adsorbent for Cr examined previously. When compared with the untreated granular activated carbon, sorption onto GAC-QPVP resulted in much less Cr(VI) reduction and subsequent release of Cr(III). The effect of phosphate, sulfate, and nitrate was minor on the selective sorption of Cr(VI). An ion exchange model that was linked with aqueous speciation chemistry described Cr(VI) sorption reasonably well as a function of pH, ionic strength, and Cr(VI) concentration. Model simulations suggested that sorbed Cr(VI) was partially reduced to Cr(III) on the sorbent when pH was less than 4. The presence of Cr(III) on the sorbent was confirmed by the X-ray photoelectron spectroscopic analysis. Overall, the study has demonstrated that GAC-QPVP can effectively remove Cr(VI) from aqueous solutions under a wide range of experimental conditions, without significant Cr(III) release associated with the virgin GAC treatment.     

Electrochemical Hydrogen Storage Performance of the Nanocrystalline and Amorphous Pr-Mg-Ni-based Alloys Synthesized by Mechanical Milling

The PrMg12-type composite alloy of PrMg₁₁Ni + x wt% Ni (x=100,200) with an amorphous and nanocrystalline microstructure were synthesized through the mechanical milling.Effects of milling duration and Ni content on the microstructures and electrochemical hydrogen storage performances of the ball-milled alloys were methodically studied.The ball-milled alloys obtain the optimum discharge capacities at the first cycle.Increasing Ni content dramatically enhances the electrochemical property of alloys.Milling time varying may obviously impact the electrochemical performance of these alloys.The discharge capacities show a significant upward trend with milling duration prolonging,but milling for a longer time more than 40 h induces a slight decrease in the discharge capacity of the x=200 alloy.As milling duration increases,the cycle stability clearly lowers,while it first declines and then augments under the same condition for the x=200 alloy.The high-rate discharge abilities of the ball-milled alloys show the optimum values with milling time varying.     

2－取代亚胺基－3－［N－（2－氯乙基）］氨甲酰四氢噻唑类化合物的质谱研究

介绍十三种新的２－取代亚胺基－３－［Ｎ－（２－氯乙基）］氨甲酰四氢噻唑化合物的电子轰击（ＥＩ）质谱及其分子离子峰。它们的特征峰为ｍ／ｚ［Ｍ—１０５］＋，［Ｍ—４９］＋，［Ｍ—３５］＋，１０５，５６等。其中Ｍ—１０５碎片的强度较大（大多为基峰）。据此，提出了它们经电子轰击断裂的可能途径──麦克拉弗蒂重排（ＭｃＬａｆｆｅｒｔｙＲｅａｒｒａｎｇｅｍｅｎｔ）。     

N—取代—2—氨基—2—噻唑啉的质谱研究

报导了十四种N-取代-2-氨基-2-噻唑啉类化合物的质谱及其分子离子峰,其中化合物(1~13)的特征峰为:M/Z[M-28]~+、[M-43]~+、[M-101]~+、101等;化合物14为官能团化合物,其特征峰为[M-101]~+、101等。据此,提出了它们经电子轰击断裂的可能途径。     

Quaternized Poly(4-Vinylpyridine) Coated Activated Carbon: Diffusion Controlled Sorption of Chromium(VI)

Quaternized poly(4-vinylpyridine) coated activated carbon has been proven to be successful in removal and recovery of Cr(VI) from aqueous solution. However, the key component of the mass transfer operations and the diffusion coefficient has not been determined. In this study, adsorption of Cr(VI) was investigated at different initial concentrations. A finite bath diffusion control model with changing bulk concentrations was derived analytically, and a constant related to radius of the absorbent particle and the fractional attainment of adsorption was first introduced into this model. Results indicated that the adsorbent provided fast adsorption kinetics and the modified diffusion-control model fitted the experimental data well. The observed sorption kinetics was consistent with the finite bath diffusion, with an average value of 4.10×10?6?cm2/s for the product of the distribution coefficient and the effective diffusivity in the adsorption of Cr(VI) on the quaternized poly(4-vinylpyridine) coated activated carbon.     

Modifying activated carbon with hybrid ligands for enhancing aqueous mercury removal

In an effort to enhance mercury (Hg) removal from the aqueous solution, activated carbon (AC) was modified by a combined treatment of nitric acid and thionyl chloride, followed by the reaction with ethylenediamine, to introduce N-, S-, and Cl-containing functional groups. The modified activated carbon (MAC) was characterized by SEM-EDS, FT-IR, XPS, elemental analyzer, and potentiometry. Kinetics and equilibrium isotherms of Hg sorption by MAC were determined in batch experiments. Characterization indicated that additions of the organic-inorganic ligands onto AC surface by treatment were effective, likely through the acyl chloride-carbon reactions. Potentiometric titration showed that the modifications introduced more negative surface charges favoring cation sorption. Kinetics and isotherm studies demonstrated that the Hg sorption by MAC was faster (<30 min) and higher (>200%) than that by AC, suggesting a high affinity of MAC for Hg ions. The sorption by MAC occurred in a wider pH range (4-10 vs. 5-7), and low ionic strength appeared to enhance Hg sorption. The sorption isotherms were best described by Freundlich model, and enhanced Hg sorption by MAC was primarily accomplished by the coordinations of ligand atoms (O, N and S) with Hg ions through the mechanisms of surface complexation, reduction, and ion exchange.     

死区模式对双极性PWM调速系统的影响

在双极性PWM调制方式中,为了防止桥臂的直通需要在互补的上下桥臂驱动信号上设置死区。利用硬件电路设置死区的方式具有设置简单、可靠性高的优点,常被应用在集成驱动模块中,然而不同的死区模式会对逆变器输出电压产生不同的影响。本文针对一种硬件死区设置方式在特定占空比附近输出电压跃变而造成电机转速非线性的问题进行分析,并给出了改进硬件电路和软件补偿两种解决措施。仿真和实验结果表明这两种方法都能够很好的解决在特定占空比附近输出电压跃变的问题,使转速能够在占空比改变时平稳变化。     

过碳酸钠的生产现状及发展前景

本文阐述了国内外过碳酸钠的生产现状、应用范围及今后的发展前景。