High-Purity Composite Briquette for Direct UMG-Si Production in Arc Furnaces

In metallurgical grade Si (MG-Si), the coal (B) and charcoal (P) contents are on average above 30 ppm as the carbon reduction materials used in the arc furnace are either rich in B or in P. A decrease of both impurities by a factor of 3 using purer raw materials would allow for the direct production of the upgraded metallurgical grade (UMG).This would significantly improve the efficiency of the resulting photovoltaic (PV) cells made with the refined solar grade silicon (SoG-Si) or massively decrease the costs of Si purification by shortening the number of steps needed for reaching B and P contents below 1 ppm requested for the SoG-Si used for the PV cells. A composite C/SiO₂ briquette fulfilling the purity targets for the direct production of UMG-Si in the arc furnace was developed. The composite contains several carbon materials with different levels of reactivities and quartz sand. The raw materials aspects, the paste and briquette preparation, as well as the final carbonization step are discussed. The finished briquettes are free of volatiles and are mechanically and thermally very stable, thus, ensuring stable arc furnace charges with minimum losses of dust and SiO gas. Semi-industrial trials including the downstream purification steps for the production of SoG-Si by a metallurgical low-cost route are contemplated.     

太阳能晶体硅切割废料中高纯硅的提取(英文)

研究从太阳能晶体硅切割废料中制取高纯硅。分析切割废料的组成、粒度分布等,利用物理沉降法对废料中的硅粉进行富集,然后经酸洗除杂。研究酸洗工艺参数如酸洗时间、温度、固液比等对提纯效率的影响,并优化工艺参数。最后将酸洗除杂的硅富集料进行真空高温熔炼获得含99.96%Si、1.1×10-6B及4.0×10-6P(质量分数)的高纯硅。结果表明:从晶体硅切割废料中回收太阳能多晶硅是未来的一个重要发展方向。     

The combustion synthesis of Ni-Ti shape memory alloys

Combustion synthesis is a new and promising method of producing Ni-Ti series shape memory alloys. It has the advantage of both time and energy savings compared with the conventional melting or powder metallurgy approaches. The value of the ratio ΔH°_?,298/ C_p,298 plays a key role in this method, especially if a liquid product is required. Solidified products made by the combustion synthesis process were hot rolled into plates exhibiting the shape memory effect. It was discovered that shape memory transition temperatures can be tailored over a wide temperature range (from ?78 to 460°C) by substituting a third element, such as palladium or iron, for nickel. This approach should greatly extend the application of such alloys.     

Simulation of grain coarsening in two dimensions by cellular-automaton

This paper presents a computer simulation model, namely Cellular Automaton (CA), which aims at investigating the behaviour of normal grain coarsening in 2D that corresponds well to the described physical model. The CA model takes into account the following: the energy barrier of cellular transition depends on the energy of the grain boundary; the energy of boundaries depends on the misorientation of the grains and the energy of the cells follows the Maxwell–Boltzmann distribution. The model was tested on both simple geometrical configurations and on real structures. The effect of temperature, orientation difference, activation energy, and boundary energy for the kinetics of grain coarsening were analysed and discussed. The optimal orientation value, q_max, was greater than 64, and at smaller q_max values non-real structures develop. The rate and kinetics of coarsening depend on a q_max value up to 64, the energy barrier and the boundary energy. The rate of coarsening cannot be described by only one exponential function over a wide temperature range.     

天然气管道环焊缝缺陷部位的腐蚀沉淀机理

为了深入分析天然气管道的“梗阻”现象,采用金相法和能谱仪对靖边某气田典型的有大量沉积物管道进行了焊缝和沉积物结构及成分分析.结果表明,焊缝缺陷处的腐蚀和沉淀机理为管内发生CO₂腐蚀、缝隙腐蚀和H₂S腐蚀,产生了氧化物、氯化物和硫化物等腐蚀产物.随着腐蚀产物的逐渐堆积,其阻隔了管子材料与腐蚀性介质,使得腐蚀速率减慢,沉积物转为以粉尘为主.沉积物堆积到一定高度时,天然气的流向改变,管道顶部的腐蚀变为冲刷腐蚀,腐蚀速率加快,管道壁厚严重减薄,危害管道的正常安全运行.     

中国高潜水位沉陷区采煤废弃物复垦农田的土壤特征(英文)

为了研究充填介质对中国东部高潜水位采煤塌陷区复垦土壤特征的影响,对采用煤矸石或粉煤灰作为充填介质形成的复垦土壤化学和微生物指标进行分析。结果表明,充填介质粉煤灰的存在能显著提高复垦土壤中pH值和含水率;在0~10 cm、10~20 cm、20~50 cm土壤层,采用粉煤灰形成的复垦土壤MBC、MBN、MBC/TOC的比率高于采用煤矸石形成的复垦土壤;采用煤矸石作为充填介质形成的复垦土壤中,重金属As和Cr含量、土壤微生物碳氮比、呼吸熵等高于对照土壤和粉煤灰充填形成的复垦土壤;主成分分析表明,充填土壤中重金属含量、土壤微生物量和土壤酶活性能代表大部分复垦土壤特征。     

Structural, optical and chemical analysis of zinc sulfide thin film deposited by RF-mganetron sputtering and post deposition annealing

Zinc sulfide (ZnS) thin films were deposited by radio-frequency (RF) magnetron sputtering. The effects of the process parameters such as deposition time and RF-power, as well as of post deposition annealing under oxygen containing atmospheres, on the material properties of ZnS films have been investigated. X-ray diffraction analysis reveals out that the as-deposited ZnS films preferred (002) hexagonal wurtzite and (111) cubic zinc blend (111) at 28.60°, while a thicker ZnS film has additional hexagonal wurtzite (100), (110), and (200) planes coexisting with the preferred oriented-planes, suggesting that the thickness is dependent on the growth of ZnS. After annealing, ZnO phases were detected, indicating island-like grain growth on the surface of the ZnS film. By increasing the deposition time and the RF power, the optical band gap energy (E_g) of the ZnS film changes from 4.13 to 3.87 eV, indicating the presence of lower E_g with thicker ZnS film. The lower E_g (～3.27 eV) value of the annealed films is attributed to the ZnO transition. Unlike bulk ZnS material (Zn/S～1.08), deposited ZnS thin film has Zn-rich and S-deficient composition (Zn/S～1.28). However, the Zn/S ratio is closer to the ideal value when there is a longer deposition time or higher RF-power.     

稀土添加对30Mn钢奥氏体化过程的影响

采用差示扫描量热仪分别对未添加稀土和添加稀土的30Mn钢进行连续加热实验,利用Kissinger和JMA方程计算了材料的相变激活能和动力学因子。结果表明,添加0.2%(质量分数)的稀土硅铁合金使30Mn钢奥氏体化的起始温度A_(c1)和结束温度A_(c3)提高,相变激活能增加了186 k J/mol,相变动力学因子n值减小。未添加稀土和添加稀土的30Mn钢的奥氏体化过程均可分为2个阶段,并且不同阶段具有不同的晶粒长大机制。     

Adhesion characteristics of copper thin film deposited on PET substrate by electron cyclotron resonance-metal organic chemical vapor deposition

The adhesion characteristics of Cu/C:H films on the pretreated PET (polyethylene terephthalate) substrate prepared by ECR-MOCVD with a periodic DC bias system were investigated in the aspect of surface energy, surface morphology, roughness, and adhesion force. For a chromo-sulfuric acid pretreatment, the surface roughness of PET substrate was increased up to a maximum value at 60 min of acid-soaking time, followed by a gradual decrease for longer acid-soaking times. The changes of surface energy by various pretreatment methods (such as Ar-ion implantation, O₂ plasma, chromo-sulfuric acid, and sandblasting) barely affected on the adhesion force because the pretreated PET was changed into hydrophobic surface through ECR-plasma polymerization of hfac (1,1,1,5,5,5-hexafluoro-2,4-pentandione) ligand of copper precursor. The acid pretreatment followed by ECR-deposition was confirmed as an effective method for the good adhesion of copper thin film on PET substrate at room temperature. The adhesion force of deposited metallic films primarily depended on the surface roughness of the pretreated substrate, and there was no strong correlation between the surface energy of the pretreated PET and the adhesion force of deposited Cu/C:H films.     

Morphology and electrical contact properties of electrical connection materials in corrosive atmosphere

The impact mechanism of environmental factors, such as corrosive atmosphere, on connector materials was investigated, and the porosity of gold plating was tested. Series of inspections and analytical research methods were introduced in this article. The surface morphology of specimens after corrosion was observed by stereoscopic microscope and scanning electron microscope. Chemical constitution was examined by X-ray energy spectrum. The contact resistances were measured by four-point method. The experiment results show that after exposure to certain environment, the corrosion products, such as Cu2O, Cu(NO3)2·3H2O, and NiO, are observed on the surface of the specimens without gold coatings, whereas the corrosion products appear to have circle-shaped spots on gold-plating surface after corrosion test, which indicate that the gold plating has good corrosion protection. The porosity is increased with the increase of corrosion time for every kind of specimens gold plated, and the corrosion degree of goldplating specimens is decreased with the increase of the thickness of gold coatings. The static contact resistances of circle-shaped spots appear higher contact resistance than normal value, which can reach to 2,000 mX nearly. It is found that the high and unstable contact resistance of the pore and products is more likely to cause contact failure.     

A new mixed-valent iron arsenate black crystal

Scorodite (FeAsO₄·2H₂O) is the most popular phase for arsenic (As) immobilization while the reductive dissolution of Fe(III) to Fe(II) will promote As release. In the present study, an equilibrium between Fe(III) and Fe(II) was achieved in scorodite preparation system by introducing certain alcohol (methanol, ethanol, isopropanol or tert-butanol), and thus a new mixed-valent iron arsenate black crystal formulated as Fe(II)_5.2Fe(III)_8.8(HAsO₄)₄(AsO₄)₈·H₂O was prepared. In comparison with scorodite, the black crystal has higher As content (36.4%, mass fraction) and lower crystal water content (0.73%, mass fraction). Additionally, the leaching concentration of As can be lower than the threshold value (5 mg/L) regulated by identification standards for hazardous wastes of China (GB 5080.3–2007). Therefore, this new mixed-valent iron arsenate crystal could be classified as a non-hazardous and promising As-bearing phase in environmental applications.     

Experimental investigation of the dynamic elastic modulus and vibration damping in MoSi2-30%Si3N4 as a function of temperature

The dynamic elastic modulus, E, and vibration damping of molybdenum disilicide (MoSi₂) with 30% volume addition of silicon nitride (Si₃N₄) were measured at varying temperatures using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The value of the elastic modulus of the composite was observed to decrease as temperature, T, was increased. The value of dE/dT of MoSi₂ was determined to be −0.03 GPa/K. The vibration damping of MoSi₂-30%Si₃N₄ increased as temperature was increased, with an effective activation energy of 0.076 eV/atom. This was an average over the entire temperature range, but two distinct slopes were observed in the plot of damping versus inverse temperature.     

一种新型回转式电力推进空气动力艇的设计分析

针对湿地旅游、保护和开发的需求,提出了一种采用超级电容和锂电池组复合储能、具有太阳能光伏发电装置辅助供能、以回转式电力推进装置替代传统燃油发动机进行推进的新型空气动力艇的设计方案.分析了其基本结构与原理、关键技术及优势.研究发现:该艇不仅可实现绿色供能,以降低污染排放,而且操纵灵活、机动性强,能更好适应障碍物多、水面情况复杂的湿地环境,具有较高的应用价值和广阔的发展前景.     

A dislocation model for the minimum grain size obtainable by milling

Primary among the processing techniques that are now available for synthesizing bulk nanocrystalline materials is ball milling, which produces nanostructures by the structural decomposition of large-grained structures as the result of severe cyclic deformation. It is well-documented that during milling, the grain size decreases with milling time, reaching a minimum grain size, d_min, which is a characteristic of each metal. In this paper, a dislocation model that predicts the value of d_min as a function of material parameters, such as hardness, melting temperature, and stacking fault energy, has been developed. The model is based on the concept that d_min is governed by a balance between the hardening rate introduced by dislocation generation and the recovery rate arising from dislocation annihilation and recombination. It is demonstrated that the model provides possible explanations for several recent observations regarding the characteristics of d_min.     

Metal Recovery from Scrap and Waste

The depletion of high grade ores and accumulation of huge quantities of metallic scrap and metallurgical wastes have generated significant interest in their processing. In this paper, both pyrometallurgical, as well as hydrometal-lurgical, methods for metal recovery from scrap and wastes (viz., slag, dusts, aqueous effluents, sludge and residues) are reviewed. Scrap recycling and the processing of metallurgical wastes will pollute the environment to a lesser extent and consume less energy compared to the primary metal production. Reprocessing metallurgical waste (viz., slag, red mud, etc.) serves a social objective and ensures raw materials conservation. Research trends reveal that hydrometallurgy may play a dominant role in the waste treatment. Recently developed processes like continuous ion exchange and fluidized bed electrolysis may be used in the future for recovering metals from dilute solutions.     

Pre-martensitic phenomena in Ti40.7Hf9.5Ni44.8Cu5 shape memory alloy

Pre-martensitic phenomena such as abnormal resistivity growth, diffusion scattering, “tweed” contrast and internal friction peak were observed in Ti_40.7Hf_9.5Ni_44.8Cu₅ alloy prior to the forward martensitic transformation on cooling. It was shown that all the observed phenomena were due to the formation of quasi-static strain nanodomains in the B2 phase prior to the forward martensitic transformation. This led to accumulation of the elastic energy before the phase transition and resulted in the variation in thermodynamic balance for the forward martensitic transformation and, as a result, influenced the parameters of the phase transition. The appearance of elastic energy prior to the forward transformation caused a decrease in the forward and reverse martensitic transformations' start temperatures, a widening of the temperature range of the reverse transformation and an increase in the hysteresis of the transformation.     

Microstructures and electrical responses of pure and chromium-doped CaCu3Ti4O12 ceramics

Pure and chromium-doped CCTO (CaCu₃Ti₄O₁₂) ceramics were prepared by a conventional solid-state reaction method, and the effects of chromium doping on the microstructures and electrical properties of these ceramics were investigated. Efficient crystalline phase formation accompanied by dopant-induced lattice constant expansion was confirmed through X-ray diffraction studies. Scanning electron microscopy (SEM) results show that doping effectively enhanced grain growth or densification, which should increase the complex permittivity. The dielectric constant reached a value as high as 20,000 (at 1 kHz) at a chromium-doping concentration of 3%. The electrical relaxation and dc conductivity of the pure and chromium-doped CCTO ceramics were measured in the 300-500 K temperature range, and the electrical data were analyzed in the framework of the dielectric as well as the electric modulus formalisms. The obtained activation energy associated with the electrical relaxation, determined from the electric modulus spectra, was 0.50-0.60 eV, which was very close to the value of the activation energy for dc conductivity (0.50 ± 0.05 eV). These results suggest that the movement of oxygen vacancies at the grain boundaries is responsible for both the conduction and relaxation processes. The short-range hopping of oxygen vacancies as “polarons” is similar to the reorientation of the dipole and leads to dielectric relaxation. The proposed explanation of the electric properties of pure and chromium-doped CCTO ceramics is supported by the data from the impedance spectrum.     

Detection of breakaway oxidation with Acoustic Emission during titanium oxide scale growth

Extensive in-situ analysis of high temperature breakaway oxidation of titanium metal has been performed using the Acoustic Emission (AE) technique. Depending on temperature and oxidising atmosphere, different model cases were examined: with breakaway (900 °C/O₂), without breakaway (750 °C/O₂ and 900 °C/H₂O). Two specific population of AE hits were observed before and after breakaway. Contrary to the pre-breakaway population, the post-breakaway population exhibited low AE activity characterised by high values of energy. A critical energy value of E = 3 fJ was determined as a frontier between signals resulting from oxide parabolic growth and signals resulting from rapid linear growth.     

Thermodynamics of chemisorption of sulfur from thiocyanate on nickel during electrochemical passivation

The effect of potassium thiocyanate content in an aqueous H₂SO₄ solution on the activation potential of a passive film formed on the nickel surface is studied. Based on the results, a thermodynamic model of chemisorption in electrochemical passivation of nickel in an aqueous H₂SO₄ solution containing surface-active KSCN thiocyanate additive is proposed. In the model, the formation of a NiO-NiS film is considered as a result of the equilibrium processes at the interfaces of the Ni|NiO-NiS|H₂O, SCN^? system. The total Gibbs energy of the chemisorptive phase formation of NiO-NiS solid solution is determined by partial chemisorptive formation energies of NiO and NiS. In turn, partial formation energy of either component is estimated as a sum of the Gibbs energy of the chemical formation of the component and the surface Gibbs energy of nickel, which depends on the KSCN concentration in the solution in the case of NiS formation. The system can be controlled due to the relation between the Gibbs energy and Flade electrode potential. As was experimentally found, the latter value determines the quantitative NiO: NiS ratio in the passive film.