Baoqiang Xu

Application of Molecular Interaction Volume Model for Phase Equilibrium of Sn-Based Binary System in Vacuum Distillation

Based on the molecular interaction volume model (MIVM), the activities of components of Sn-Sb, Sb-Bi, Sn-Zn, Sn-Cu, and Sn-Ag alloys were predicted. The predicted values are in good agreement with the experimental data, which indicate that the MIVM is of better stability and reliability due to its good physical basis. A significant advantage of the MIVM lies in its ability to predict the thermodynamic properties of liquid alloys using only two parameters. The phase equilibria of Sn-Sb and Sn-Bi alloys were calculated based on the properties of pure components and the activity coefficients, which indicates that Sn-Sb and Sn-Bi alloys can be separated thoroughly by vacuum distillation. This study extends previous investigations and provides an effective and convenient model on which to base refining simulations for Sn-based alloys.

Analysis of Magnesia Carbothermic Reduction Process in Vacuum

The mechanism of magnesia carbothermic reduction was investigated experimentally in a reduction reaction process in vacuum. The thermodynamic calculation results showed that the initial reduction temperature between MgO and C was 1500 K (1227 °C) at 50 Pa. Other reduction reactions did not occur between the temperature 300 K and 1900 K (27 °C and 1627 °C) and 30 to 100 Pa. Based on the analysis of experimental results, the initial reduction reaction temperature was 1553 K (1280 °C), and it matched well with the thermodynamic calculations. The gas–solid reaction between MgO and CO did not occur at 1723 K (1450 °C), 30 to 100 Pa. Therefore, the main reduction reaction was MgO(s) + C(s) = Mg(g)+ CO(g) in vacuum. This reaction belonged to the solid–solid reaction type, the condensing product was obtained in the condensation zone, and the main component of the product was metal magnesium. A little magnesia was also obtained in the condensing product due to the reverse reaction.

Study on Effect of Al-O-C Compound in Alumina Carbothermal Reduction

In this paper, The structures and properties changes for single unit cell of alumina, Al-O-C compounds and aluminium carbide were simulated by first principles method. According to theoretical calculation results, alumina carbothermal reductions with coal and charcoal separately used as reductant were carried out under vacuum. The major equations in carbonthermal reduction reduced to three general equations by reaction temperature; the sequence for each substance which formed in reductions was Al4O4C→Al2OC→Al4C3

Direct calciothermic reduction of porous calcium titanate to porous titanium

A metallurgical material integration concept, using porous calcium titanate (CaTiO3) as raw material, was put forward for preparation of metallic titanium powder and porous titanium by calciothermic reduction. Porous metallic titanium was prepared by calcium vapor reduction at 1273 K for 6 h with two types of interconnected pores in titanium samples. The interconnected macropores about 50-300 μm were inherited from porous CaTiO3, and the micropores about 5-40 μm were made by leaching removal of byproduct CaO in reduction products. Metallic porous titanium was fabricated in Ca-dissolved CaO-CaCl2 molten salt mixtures by self-sintering and had a good interconnectivity inside with thickness about 155 μm and the porosities of the porous titanium are 65-81%.

Removal of Sulfur from Copper Dross Generated by Refining Lead

Typical copper dross, the byproduct of lead bullion pyrometallurgical refining for copper removal, mainly contains Pb, Cu, S, As, Sb and Sn etc. In traditional treatment process, copper dross is transformed to be copper matte by smelting with iron scarp and iron pyrite. Here, a new treatment process of converting-vacuum distillation (CVD) was proposed and investigated. Based on this concept, the converting process was tentatively investigated in this paper. The results of element distribution of converting samples showed the sample has three layers. The upper layer is mainly sulfides of lead and copper, the middle layer is mainly copper arsenide, and the lower layer is lead arsenide and crude lead. On the condition of oxygen flow rate 400 ml/min, the converting temperature 1000 °C, the holding time 1 h, the converting time 10 min, the lead copper alloy containing 0.17% S was obtained.

Study on the Volatilization of Sb 2 S 3 in Vacuum

The thermogravimetric method was selected for investigating the evaporation of Sb2S3 in the pressure range of 50–300 Pa and in the temperature range of 823–1123 K, the gas phase diffusion was the rate-determining step for Sb2S3. The volatilization rate was related to the temperature and pressure, that the logarithm of volatilization rate yielded a line with the reciprocal of temperature and pressure. The volatilization rate for Sb2S3 was between 0–0.023 g·cm−2·s. The apparent activation energy was between 65.8 and 60.6 kJ/mol.

Experimental Study on the Reversion Reaction Between Magnesium and CO Vapor in the Carbothermic Reduction of Magnesia Under Vacuum

The mechanism of magnesia production was investigated experimentally in reversion reaction process in vacuum. Condensation temperature and temperature gradient which effected on the condensation of the magnesium vapor produced by magnesia carbothermic reduction in vacuum have been investigated by Mg recovery efficiency, XRD, SEM and EDS. The results show that the higher recovery efficiency was obtained when the condensing temperature which is closer to the dew point of magnesium in the constant temperature gradient. Under the condition of appropriate condensation temperature, the lower the temperature gradient is, the better the crystallization of magnesium vapor is. The XRD patterns of the profile and undersurface of the condensation product of 1873 K show that the profile of the condensation contains Mg only and the purity of the metal magnesium is high. But the undersurface of the condensation contains Mg and MgO. The SEM and EDS images of the profile and undersurface of condensation indicate that the microstructure of the undersurface of condensation is largely flocculent structure and irregular arrangement and the crystal morphology was poor and particles were also tiny. This is due to magnesium vapor reacted with CO vapor at cooling phase, MgO and C obtained covered the undersurface and stopped magnesium vapor condensing.

A comparison of the thermal decomposition mechanism of wurtzite AlN and zinc blende AlN

The sublimation route is one of the primary and most significant methods for the synthesis of an aluminum nitride (AlN) single crystal. Its long synthesis time and high reaction temperature, however, limit the production of its commercial product. In this work, we applied HSC Chemistry 6 software, ab initio molecular dynamics, and X-ray diffraction to investigate the thermal decomposition of AlN. We calculated the decomposition temperatures of AlN under vacuum and simulated the decomposition mechanism of AlN by the ab initio molecular dynamics method. According to the thermodynamic calculations, the decomposition temperature of AlN decreased following a decrease in the system pressure. The ab initio molecular dynamics results indicated that wurtzite-type AlN (w-AlN) was decomposed by the layer-by-layer mechanism and followed a decomposition reaction equation of AlN → Al(g) + 0.29N2(g) + 0.42N(g), which originated from the inequality sp3 hybridization. The zinc-type AlN (z-AlN) decomposed from the surface to interior of the structure because of the equality of the sp3 hybridization, and the z-AlN decomposition reaction equation followed AlN → Al(g) + 0.5N2(g). The AlN decomposition experiments further verified that Al(g) was the product of the wurtzite-type AlN thermal decomposition. This work can provide valuable information for the preparation of the AlN single crystal.

The Density Functional Theory Investigation on the Structural, Relative Stable and Electronic Properties of Bimetallic PbnSbn (n = 2–12) Clusters

Recently, bimetallic clusters have attracted a great deal of attention from research community because clusters yield intriguing properties ranging from the molecular and the bulk materials, which have extensive applications in nanomaterials. Clusters with tailored properties are governed by cluster size, geometrical structures, and elemental composition. Motivated by that we systematically investigated the structural, relative stable, and electronic properties of PbnSbn (n = 2–12) clusters by means of density functional theory. In this paper, the ground state structures, average binding energies, fragmentation energies, HOMO–LUMO gaps, and density of states were theoretically calculated. The results demonstrate that the large clusters adopt distorted ellipsoid structures with no symmetry. The average binding energies tend to be stable when cluster size n ≥ 4. Pb5Sb5 and Pb9Sb9 clusters are more chemically stable compared with the neighboring PbnSbn clusters, which may serve as the cluster assembled materials. The density of states of PbnSbn (n = 2–12) clusters moving toward more negative energy levels with the growing cluster size n, which also becoming more nonlocalized as the clusters size n increasing.

Theoretical insights into the structural, relative stable, electronic, and gas sensing properties of PbnAun (n = 2–12) clusters: a DFT study

Recently, Au-based clusters have been provoking great interest due to their potential applications in nanotechnology. Herein, the structural, relative stable, electronic, and gas sensing properties of PbnAun (n = 2–12) clusters were systematically investigated using density functional theory together with scalar relativistic pseudopotential. The ground state structures, average binding energies, dissociation energies, second order energy differences, HOMO–LUMO gaps, and average Mulliken charges of PbnAun (n = 2–12) clusters were calculated. The results revealing that the PbnAun (n = 4, 6, and 8) clusters are more relatively stable than their neighboring clusters. Furthermore, charges are always transferred from the Pb atoms to Au atoms based on Mulliken charge analysis. Furthermore, through the investigations of CO or NO molecule adsorption onto PbnAun (n = 4, 6, and 8) clusters, it is found that CO or NO molecule can chemisorb on those clusters with high sensitivity, and the charges are transferred from PbnAun (n = 4, 6, and 8) clusters to the gas molecules. According to the analysis of the electric conductivity, PbnAun (n = 4, 6, and 8) clusters can be served as potential gas sensors in CO and NO molecules detection.