Dissolution mechanism and solubility of hemimorphite in NH3-(NH4)2SO4-H2O system at 298.15 K简

The dissolution mechanism of hemimorphite in NH3-（NH4）2SO4-H2O system at 298.15 K was investigated by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS） analysis. The results show that hemimorphite is soluble in NH3-（NH4）2SO4-H2O system and its residue exists in the form of an amorphous SiO2 layer on the hemimorphite surface. The XPS data also indicate that the Si 2p3/2 and O ls spectra of the hemimorphite are broadened and shift to higher binding energies and their binding energies are closer to silica with an increase of total ammonia and time. Solubility of hemimorphite in NH3-（NH4）2SO4-H2O system was measured by means of isothermal solution method at 298.15 K based on the study of the dissolution mechanism of hemimorphite. The results show that the solubility of zinc in solution increases firstly and then decreases with the increase of cr（NH3） （total ammonia concentration） at different NH3/NH4^＋ ratios. The solubility of silicon in solution decreases from 0.0334 mol/kg in ct（NH3）-4.1245 mol/kg NH3-（NH4）2SO4-H2O solution to 0.0046 mol/kg in cT（NH3）=7.6035 mol/kg NH3-（NH4）2SO4-H2O solution.     

Effects of Al and Sn on electrochemical properties of Mg-6%Al-1%Sn （mass fraction） magnesium alloy as anode in 3.5%NaCl solution

Mg-6%Al-1%Sn（mass fraction） alloy is a newly developed anode material for seawater activated batteries. The electrochemical properties of Mg-1%Sn, Mg-6%Al and Mg-6%Al-1%Sn alloys are measured by galvanostatic and potentiodynamic tests. Scanning electron microscopy（SEM） with energy dispersive spectrometry（EDS） is used to characterize the microstructures of the experimental alloys. The results show that the Mg-6%Al-1%Sn alloy obtains more negative discharge potential（-1.38 V（vs SCE）） in hot-rolled condition. This is attributed to the fine dynamically recrystallized grains during the hot rolling process. After the experimental alloys are annealed at 473 K for 1 h, the discharge potentials of Mg-6%Al-1%Sn alloy are more negative than those of Mg-6%Al alloy under different current densities. After annealing at 673 K, the discharge potentials of Mg-6%Al-1%Sn alloy become more positive than those of Mg-6%Al alloy. Such phenomenon is due to the coarse grains and the second phase Mg2 Sn. The discharge potentials of Mg-1%Sn shift positively obviously in the discharge process compared with Mg-6%Al-1%Sn alloy. This is due to the corrosion products pasting on the discharge surface, which leads to anode polarization.     

胜利褐煤二硫化碳-丙酮萃取物的超临界醇解物的GC/MS分析

胜利褐煤经CS2-丙酮混合溶剂(V/V=1 1)萃取获得萃取物EM,EM在300℃的甲醇中热溶2 h获得热溶物ET.对EM和ET进行了气相色谱/质谱联用(GC/MS)分析,在EM中有43种GC/MS可检测组分,而在ET中检测到了132种有机化合物,其中包括32种在EM中未检测到的甲酯类化合物(MAs)和16种酚类化合物.分析了MAs和酚类化合物的形成机理,得出了胜利褐煤CS2-丙酮可溶大分子化合物中可能存在的4种结构单元.本文提供了一种研究煤中可溶大分子化合物的有效方法,弥补了GC/MS在检测大分子化合物时的不足.     

基于表面反应和扩散迁移控制的灰岩单裂隙渗流—溶解模型及其数值模拟

针对碳酸盐类可溶岩地区水电站坝址流场、化学场以及固相介质属性等随时间发生改变,从而对工程安全运行造成不利影响等问题,研究了灰岩地区地下水运移过程中各物理场间的相互作用,分析了影响灰岩溶解速率的两个因素,即表面反应控制和扩散迁移控制。在此基础上,建立了单裂隙中的渗流—溶解耦合模型,并进行数值求解。模拟结果表明,在垂直裂隙延伸方向,其溶蚀锋面为非齐整平面,而是呈似“虫洞”状非均一变化,而沿裂隙延伸方向即自上游侧向下游方向溶蚀程度逐渐减轻;而通过裂隙的流量呈现随时间逐渐增大的趋势,但变幅不大;根据流量求得的等效水力隙宽,其增幅和增长速率均小于实际平均隙宽;同时,化学场中Ca2+浓度的分布与裂隙开度变化具有相似性,不同时刻下上游侧反应速率R均大于下游侧。就反应机制而言,在初期均受表面反应控制,而随反应进行,位于上游补给区部位转为受扩散迁移控制,但在下游位置仍受表面反应控制。     

磷酸溶解尿素的反应动力学

为了开发适合我国湿法磷酸生产磷酸脲的技术,以磷酸溶解尿素来研究磷酸脲制取的反应动力学,实验在消除液相扩散影响下,研究了尿素的溶解反应时间,考察了反应温度、尿素粒度及磷酸浓度对溶解反应的影响,经分析和实验数据处理,建立了磷酸溶解尿素的反应动力学式,得出反应为近似一级反应,求取了有关参数,结果为进一步研究和工业化奠定良好基础。     

Effects of molten aluminum on H13 dies and coatings

The effects of molten aluminum casting alloy A390 on a commercially heat treated H13 die steel and two wear-resistant coatings, Cr₂₃C₆ and TiN, were investigated by an accelerated corrosion test. The H13 steel suffered severe corrosion due to the rapid formation of intermetallic compounds. The formation of multilayer intermetallic compounds and the simultaneous dissociation of the intermetallic compound τ6 (Al₄FeSi) were attributed to the fast dissolution of H13 steels into the melt. This dissolution of the H13 steel was accelerated dramatically by turbulence and an increase in melt temperature. Significant improvement in corrosion resistance was achieved for the H13 steel coated by Cr₂₃C₆ via a pack cementation process.     

初生硅在熔体中的溶解动力学

研究了初生硅在熔体中的溶解特性，并以原子扩散为模型，考虑界面反应等因素的影响，建立了初生硅在过热熔体中的溶解动力学模型。同时以Al-17%Si合金为研究对象，采用等温液淬技术，对所建立的模型进行了实验验证。结果表明，初生硅在熔体中的溶解机制不是单纯受扩散控制的，而是由扩散、界面反应共同作用的结果，文中所建立的初生硅溶解模型可以较好地描述初生硅在不同温度过热熔体中的溶解特性。     

Dissolution mechanism of solid nickel in liquid zinc saturated with Fe

The dissolution behavior of solid nickel in static liquid zinc saturated with Fe at 723 K was studied. The results show that when immersing solid Ni in liquid Zn saturated with Fe, the intermetallic compound layers consisted of γ and δ phases are formed on nickel substrate, which is the same as that in liquid pure zinc. However, some F2 particles are formed in the liquid near the solid/liquid interface. These Г2 particles can easily heterogeneously nucleate on （particles and grow fast. The dissolution process is governed by diffusion of nickel atom across a concentration boundary layer in liquid Zn saturated with Fe, and is different from a mixed control mechanism of nickel in liquid pure zinc. The participation of Г2 particles makes the dissolution of solid Ni in the liquid accelerated.     

镍硫化物阳极溶解的电化学研究

研究了合成镍硫化物的阳极过程。Ni_3S_2,Ni_7S_6和NiS的活性溶解伴随着生成表面产物层,其反应机理与电极电位有关。根据三种不同类型产物层生成规律的电化学研究,Ni溶出表观电子数的测定,以及产物层相组成分析和相的元素分析,认为存在三组平行反应:直接生成HSO_4~-或SO_(4-)~2的反应,生成中间硫化物的反应及生成元素硫的反应,每组反应具有不同的优势发展电位区。NiS_2阳极溶解时,基本上为生成HSO_(4-)或SO_(4-)~2的反应。     

BEHAVIOUR AND MECHANISM OF STRESS CORROSION CRACKING FOR Al-Li-Cu-Mg ALLOY

Studies were made of the influence of aging conditions and applied potentials on thestress corrosion carcking(SCC)susceptibility for an Al-Li-Cu-Mg alloy by slow strainrate technique.The relationship between the relative hydrogen content on specimensurface,the applied potentials and elapsed time has also been examined.The SCCsusceptibility was found to be dependent on aging conditions in which the peak agedcondition gave the worst SCC resistance and the natural aged condition had the best one.The SCC susceptibility and surface hydrogen content relates to the applied potentials.The anodic potentials increase SCC susceptibility,while the cathodic ones below thecritical potential accelerate SCC.It is considered that both the anodic dissolution and