Purification of metallurgical grade silicon by electrorefining in molten salts

Electrochemical studies on silicon deposition were performed in molten salt electrolytes. Purification of metallurgical grade silicon by electrorefining was carried out in molten Si-chloride salts at temperatures from 973 K to 1223 K. It was found that the use of a liquid alloy anode of silicon and copper was beneficial in molten CaCl2 with NaCl, CaO and dissolved Si. ICP-AES analysis results showed efficient removal of metal impurities, such as titanium, aluminum and iron, which are present in significant quantities in the feedstock. The contents of boron and phosphorus in the silicon after electrorefining were reduced from 36×10-6 and 25×10-6 to 4.6×10-6 and 2.8 ×10-6, respectively. The energy consumption of electrorefining was estimated to be about 9.3 kW?h/kg.

Characterization of microstructure and strain response in Ti-6Al-4V plasma welding deposited material by combined EBSD and in-situ tensile test

Additive layer manufacturing （ALM） of aerospace grade titanium components shows great promise in supplying a cost-effective alternative to the conventional production routes. Complex microstructures comprised of columnar remnants of directionally solidifiedβ-grains, with interior inhabited by colonies of finerα-plate structures, were found in samples produced by layered plasma welding of Ti-6Al-4V alloy. The application of in-situ tensile tests combined with rapid offline electron backscatter diffraction （EBSD） analysis provides a powerful tool for understanding and drawing qualitative correlations between microstructural features and deformation characteristics. Non-uniform deformation occurs due to a strong variation in strain response between colonies and across columnar grain boundaries. Prismatic and basal slip systems are active, with the prismatic systems contributing to the most severe deformation through coarse and widely spaced slip lines. Certain colonies behave as microstructural units, with easy slip transmission across the entire colony. Other regions exhibit significant deformation mismatch, with local build-up of strain gradients and stress concentration. The segmentation occurs due to the growth morphology and variant constraints imposed by the columnar solidification structures through orientation relationships, interface alignment and preferred growth directions. Tensile tests perpendicular to columnar structures reveal deformation localization at columnar grain boundaries. In this work connections are made between the theoretical macro- and microstructural growth mechanisms and the observed microstructure of the Ti-6Al-4V alloy, which in turn is linked to observations during in-situ tensile tests.

Microstructure of a Mo-Si-C-N multi-layered anti-oxidation coating on carbon/carbon composites by fused slurry

A Mo-Si-C-N multi-layered anti-oxidation coating was in-situ fabricated by introducing nitrogen atmosphere during the fused sintering of Mo-Si slurry pre-layer on carbon/carbon composites. The phase composition and microstructure of the Mo-Si-C-N coating were characterized by X-ray diffractometry, optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Mo-Si-C-N coating exhibited a three-layered structure. Besides the MoSi2/Si main-layer and the SiC bonding-layer, a surface layer of about 10 μm in thickness was synthesized on the coating surface. The surface layer mainly consisted of SiC nanowires and contained some Si3N4 and Si phases. SiC nanowires of 10 to 200 nm in diameter presented a terrace and distortion structure. Transmission electron microscopy indicated that the SiC nanowires grew along the preferred 〈111〉 direction. During oxidation test, SiC nanowires transmuted into SiO2 glass, which can play an important role in improving the oxidation resistance of C/C composites.

Effects of simulated on-fire processing conditions on the microstructure and mechanical performance of Q345R steel

A series of simulated on-fire processing experiments on Q345R steel plates was conducted, and the plates＇ Brinell hardness, ten- sile strength, and impact energy were tested. Microstructure morphologies were systematically analyzed using a scanning electron micro- scope with the aim of investigating the effect of the steel＇s microstructure on its performance. All examined performance parameters exhib- ited a substantial decrease in the cases of samples heat-treated at temperatures near 700℃. However, although the banded structure decreased with increasing treatment temperature and holding time, it had little effect on the performance decline in fact. Further analysis revealed that pearlite degeneration near 700℃, which was induced by the interaction of both subcritical annealing and conventional spherical annealing, was the primary reason for the degradation behavior. Consequently, some nonlinear mathematical models of different mechanical perform- ances were established to facilitate processing adjustments.

Morphology Characterization and Kinetics Evaluation of Pitting Corrosion of Commercially Pure Aluminium by Digital Image Analysis

The pit morphology and growth kinetics of commercially pure aluminium in naturally aerated NaCl solutions were studied using an image processing method based on reflected light microscopy. In order to distinguish between pits and pre-existing cavities, metallographic examination and statistical analysis were carried out before and after corrosion testing. The results show that the pit shapes and sizes are more dependent on the immersion time than the chloride concentration. Pits are predominantly hemispherical, but they undergo reasonable geometric transitions associated with increased immersion time and occur without significant depth variation. The role of chloride ions is more closely associated with the pit nucleation phenomenon.

Electromagnetic Characterization of Recyclable Polymer Nanofibers Based on PSU/Carbonyl Iron

This study investigated and defined the optimal processing parameters for the electrospinning of polysulfone polymer solutions with N,N-dimethylacetamide.Variation of parameters such as solute concentration,electrical voltage,and working distance were correlated with the quality of the obtained nanofibers using morphological characterization via scanning electron microscopy(SEM).Carbonyl iron additive was dispersed in the polymer solutions,using ultrasonic tip,and the material processed via electrospinning with aforementioned parameters defined.Nanofibers with the property of interaction with electromagnetic waves were obtained.The dispersion of different concentrations of the additive and electromagnetic characterizations in the X-band of microwaves(8.2 and 12.4 GHz),using vector network analyzer(VNA)and rectangular waveguide,allowed the identification of the materials electromagnetic behaviors.Scattering parameters allowed the calculation of reflected and transmitted energy by the material.

Dry Machining Tool Design via Chlorine Ion Implantation

Dry machining has become a key issue to significantly reduce the wastes of used lubricants and cleaning agents and to improve the environmental consciousness for medical and food applications of special tooling. Since the tools and metallic works are in direct contact in dry, severe adhesive wear and oxidation are thought to occur even at the presence of hard protective coatings. Self-lubrication mechanism with use of lubricous oxide films is found to be effective for dry machining. Through the chlorine ion implantation to tools, titanium base oxides are in-situ formed on the tool surface. This oxide deforms elasto-plastically so that both friction coefficient and wear volume are reduced even in the high-speed cutting.

Effect of Compression with Oscillatory Torsion Processing on Structure and Properties of Cu

The results presented in this study were concerned with microstructures and mechanical properties of poly- crystalline Cu subjected to plastic deformation by a compression with oscillatory torsion process. Different deformation parameters of the compression with oscillatory torsion process were adopted to study their effects on the microstructure and mechanical properties. The deformed microstructure was characterized quantitatively by electron backscattered diffraction （EBSD） and scanning transmission electron microscopy （STEM）. Mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. From the experimental results, processes performed at high compression speed and high torsion frequency are recommended for refining the grain size. The size of structure elements, such as average grain size （D） and subgrain size （d）, reached 0.42 μm and 0.30 μm, respectively, and the fraction of high angle boundaries was 35% when the sample was deformed at a torsion frequency f = 1.6 Hz and compression rate v= 0.04 mm/s. These deformation parameters led to an improvement in the strength properties. The material exhibited an ultimate tensile strength （UTS） of 434 MPa and a yield strength （YS） of 418 MPa. These values were about two times greater than those of the initial state.

A thermodynamic description of the Si-rich Si-Fe system

Phase equilibria in the Si-rich domain of the Si-Fe system have been reassessed based on the recent DTA experimental results. Thermodynamic properties of liquid phase have been reassessed using the associated solution model. The properties of DIA- MOND_A4 mixture phase have been added in order to evaluate the phase equilibria for the pure silicon materials. The assessed system is able to reproduce the experi- mental values in the whole composition range of the Si-Fe system.

Crystal Boundary of Chemical Vapor Deposited Diamond Films

CVD diamond films were synthesized by the chemical vapor deposition method.The crystal boundary was investigated using transmission electron microscopy and scan electron microscopy.The second grains facilitate the more compact film formation.No micro-holes are seen among diamond grains in the films but there are micro-holes in the interface of film/substrate.The second grain and the primary grain would keep the twin relationship of<110/70.5°.A lot of micro-twins are observed in fivefold twin grains but there is a zone of non twins which is like a strip along the fivefold twin boundary.Two microtwins keep the twin relationship of<110/70.5° with the fivefold twin matrix.The width and length of microtwins are about 3 nm and 32 nm,respectively.

Electronic Structure and Electron-transport Properties of Peanut-shaped C_(60) Polymers with a Negative Gauss Curvature

1 Results When a C60 film was irradiated with electron-beam (EB) with an incident energy of 3 kV, a peanut-shaped C60 polymer with metallic properties was formed[1], as shown in Fig.1. To elucidate the origin of the metallic properties of the peanut-shaped polymer, we examined the valence photoelectron spectra of the polymer using in situ high-resolution photoelectron spectroscopy and found that the electronic states of the polymer came across the Fermi level (EF)[2]. Interestingly, the spectral shape i...

Formability Investigations of High-Strength Dual-Phase Steels

Car manufacturing is always regarded as the key industry behind sheet metal forming, and thus, the requirements of and developments in car manufacturing play a decisive role in the development of sheet metal forming. The automotive industry is faced with contradictory demands and requirements： better performance with lower consumption and less harmful emissions, more safety and comfort; these are extremely difficult to supply simultaneously with conventional materials and conventional manufacturing processes. The fulfillment of these often contradictory requirements is one of the main driving forces in the automotive industry and thus in the material and process developments in sheet metal forming, as well. In recent years, significant developments can be observed in the application of high-strength steels. In this respect, the application of various dual-phase steels is one of the best examples. However, the application of these highstrength steels often leads to formability and manufacturing problems. One formability problem is the springback occurring after sheet metal forming. In the current research, we have dealt mainly with advanced high-strength steels, primarily with dual-phase steels. When applying them, the springback phenomenon is one of the most critical issues. To reduce the tremendous amount of experimental work needed, we also applied numerical simulation using isotropic–kinematic hardening rules. The isotropic–kinematic hardening behavior of a given material in the applied Auto Form numerical package may be characterized with three independent material parameters c, v and K（a detailed explanation of their meaning will be given in the main part of this paper）. However, we found that the material data included in simulation packages for these new high-strength steels are not fully adequate. For the determination of more reliable material parameters and to achieve better simulation results, a new testing device was developed. Numerical simulations were performed using the material parameters determined by the new device to show the sensitivity of springback behavior to these material parameters.