Ganfeng Tu

Rapid recovery of polycrystalline silicon from kerf loss slurry using double-layer organic solvent sedimentation method

The rapid development of photovoltaic (PV) industries has led to a shortage of silicon feedstock. However, more than 40% silicon goes into slurry wastes due to the kerf loss in the wafer slicing process. To effectively recycle polycrystalline silicon from the kerf loss slurry, an innovative double-layer organic solvent sedimentation process was presented in the paper. The sedimentation velocities of Si and SiC particles in some organic solvents were investigated. Considering the polarity, viscosity, and density of solvents, the chloroepoxy propane and carbon tetrachloride were selected to separate Si and SiC particles. It is found that Si and SiC particles in the slurry waste can be successfully separated by the double-layer organic solvent sedimentation method, which can greatly reduce the sedimentation time and improve the purity of obtained Si-rich and SiC-rich powders. The obtained Si-rich powders consist of 95.04% Si, and the cast Si ingot has 99.06% Si.

Study on nanostructures induced by high-current pulsed electron beam

Four techniques using high-current pulsed electron beam (HCPEB) were proposed to obtain surface nanostructure of metal and alloys. The first method involves the distribution of several fine Mg nanoparticles on the top surface of treated samples by evaporation of pure Mg with low boiling point. The second technique uses superfast heating, melting, and cooling induced by HCPEB irradiation to refine the primary phase or the second phase in alloys to nanosized uniform distributed phases in the matrix, such as the quasicrystal phase Mg30Zn60Y10 in the quasicrystal alloy Mg67Zn30Y3. The third technique involves the refinement of eutectic silicon phase in hypereutectic Al-15Si alloys to fine particles with the size of several nanometers through solid solution and precipitation refinement. Finally, in the deformation zone induced by HCPEB irradiation, the grain size can be refined to several hundred nanometers, such as the grain size of the hypereutectic Al-15Si alloys in the deformation zone, which can reach ∼400nm after HCPEB treatment for 25 pulses. Therefore, HCPEB technology is an efficient way to obtain surface nanostructure.

Effect of CaO on Fluorine in the Decomposition of REFCO3

Abstract Influence of CaO on thermal decomposition of REFCO 3 was studied. The results showed that CaO did not affect significantly the decomposition ratio of REFCO 3 . The XRD experiment showed that there was a great deal of CaF 2 in the roasting production, the gas chromatographic analysis on the gas of REFCO 3 decomposed, and the 70% content of fluorine in the gas of REFCO 3 added 15% CaO was reduced. CaO could absorb the fluorine from the decomposition of REFCO 3 , and the environmental pollution of the fluorine was greatly alleviated.

Study on the Corrosion Mechanism of Zn-5Al-0.5Mg-0.08Si Coating

A new type of hot-dip Zn-5Al-0.5Mg-0.08Si and Zn-5Al alloy coatings was performed on the cold rolled common steel. The hot-dip process was executed by self-made hot-dip galvanising simulator. SEM and EDS test results demonstrated that Mg was mainly distributed in crystal boundaries. XRD test results showed that the corrosion product of Zn-5Al-0.5Mg-0.08Si alloy coating was almost Zn5(OH)8C12⋅H2O. The features of Zn5(OH)8C12⋅H2O are low electric conductivity, insolubility and good adhesion.The corrosion resistance of alloy-coated steels was detected by neutral salt spray test. The microstructural characterization of the coating surface after neutral salt spray test and removing the corrosion products revealed that the corrosion process of Zn-5Al-0.5Mg-0.08Si coating was uniform and the coating surface was almost flat. As a result, the corrosion resistance of Zn-5Al-0.5Mg-0.08Si coating has a remarkable improvement with a factor of 9.2 compared with that of Zn-5Al coating.

Deposition behavior of TiB2 by microwave heating chemical vapor deposition (CVD)

Abstract Microwave heating chemical vapor deposition (CVD) is used to deposit titanium diboride (TiB2) films on graphite substrate using a gas mixture of TiCl4, BCl3, H2 and Ar. The influences of microwave power and the growth rate of TiB2 are studied by using X-ray diffraction, field emission scanning electron microscopy (FESEM) and energy dispersive spectrometer (EDS). In the range of experimental conditions, the TiB2 film’s micro-hardness evaluated by using a computer controlled micro-hardness tester increases with increasing deposition temperature and microwave power. The grain size and the growth rate of TiB2 film are also improved with increasing microwave power at a fixed gas flow ratio of TiCl4 and BCl3, and the bulk TiB2 is obtained at a higher hardness.

High temperature dephosphorus behavior of Baotou mixed rare earth concentrate with carbon

Abstract Based on the carbothermal reduction technology applied in industry, the dephosphorization behavior of Baotou mixed rare earth concentrate (Baotite) with carbon at high temperature was investigated. The experimental results showed that both the charred coal and the coking coal were effective carbonaceous reductants for the dephosphorization of the Baotite. Among them, the charred coal was more suitable for the dephosphorus due to its high carbon content and lower volatile and ash. When the rare earth pellets, made by pressing the mixture of the Baotite, charred coal and water in mould, were roasted at 1500 °C for 2 h, its dephosphorus rate was as high as 98%. Roasting temperature was a main factor for the dephosphorus rate, and roast time was the second one. The size of both charred coal and coking coal also had influence on the dephosphorus, and was better less than 150 μm.

The Microstructure of Nanocrystalline TiB2 Films Prepared by Chemical Vapor Deposition

Nanocrystalline titanium diboride (TiB2) ceramics films were prepared on a high purity graphite substrate via chemical vapor deposition (CVD). The substrate was synthesized by a gas mixture of TiCl4, BCl3, and H2 under 1000 °C and 10 Pa. Properties and microstructures of TiB2 films were also examined. The as-deposited TiB2 films had a nano-sized grain structure and the grain size was around 60 nm, which was determined by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Further research found that a gas flow ratio of TiCl4/BCl3 had an influence on the film properties and microstructures. The analyzed results illustrated that the grain size of the TiB2 film obtained with a TiCl4/BCl3 gas flow ratio of 1, was larger than the grain size of the as-prepared TiB2 film prepared with a stoichiometric TiCl4/BCl3 gas flow ratio of 0.5. In addition, the films deposited faster at excessive TiCl4. However, under the condition of different TiCl4/BCl3 gas flow ratios, all of the as-prepared TiB2 films have a preferential orientation growth in the (100) direction.

Glass-forming ability and mechanical properties of a Zr52.8Cu29.1Ni7.3Al9.8Y1 bulk metallic glass prepared by hereditary process

Abstract Zr-based bulk metallic glass possesses the highest potential as a structural material among metallic glasses. However, the production conditions have a great effect on its glass-forming ability (GFA) and mechanical characteristics. In this paper, an attempt was made to find the effect of a hereditary structure on the GFA and mechanical properties of a solid Zr52.8Cu29.1Ni7.3Al9.8Y1 bulk metallic glass in order to evaluate a novel process of using binary alloys as precursors, which have a hereditary relation to the aim metallic glass (MGs). When the quenching temperature is below the threshold overheating temperature, the hereditary process can improve the GFA and compressive strength obviously. At a quenching temperature of 1523 K, the hereditary process can improve the supercooled liquid region ΔTx from 33 K to 55 K and the compressive strength from 1555 MPa to 1652 MPa.

Simulation Method Based on Equivalent Circuit to Investigate the Circuit Characteristics in Aluminum Reduction Cell

In this paper, on the basis of simulation on the electric field of aluminum reduction cell, the simulation signals of cell voltage (CV) and anode currents were obtained through simulating the cell equivalent circuit which was established using Matlab/Simulink software. Several cell conditions, including potline current fluctuation, anode changing, low anode–cathode distance, metal pad contacting with anode surface and local anode effect, were simulated using this model. These obtained simulation data were analyzed comprehensively by time domain, frequency domain, and other statistical methods, such as skewness, and kurtosis. This study further demonstrates that the individual anode current can provide more information on local cell conditions. Different cell conditions produce different characteristics of CV and anode current in time domain or frequency domain, skewness and kurtosis are more sensitive to the change of signals.

Effect of Lime Addition on the Predesilication and Digestion Properties of a Gibbsitic Bauxite

The effect of lime addition on the predesilication and digestion properties of a gibbsitic bauxite in industrial Bayer liquor at different temperatures was investigated in the present paper. Lime increases the desilication efficiency of gibbsitic bauxite during the predesilication process, which promotes the conversion of sodalite and cancrinite to hydrogarnet in the presence of CO32−. Lime slightly decreases the alumina digestion rate of gibbsitic bauxite at both 145 °C and 245 °C when the lime dosage is 2 wt%. However, the soda consumption during the digestion process is decreased due to lime addition, especially at the higher temperature. Lime can also promote the conversion of aluminogoethite to hematite during the digestion process, which improves the digestion property of aluminogoethitic alumina in the gibbsitic bauxite.