Advanced Materials Research Vol. 548

Abstract: Scandium is concentrated in the dust during TiO2 chlorization. The dust can be used as a raw material from which Scandium is extracted. Scandium leaching conditions such as leaching acid concentration , liquid-solid ratio , leaching temperature and leaching time is investigated with chemical analysis through the orthogonal experiment. The results show that the optimum leaching conditions is: chloride dust particle size is 44 μ m, leaching acid concentration is 15%, liquid-solid ratio is 2:1, leaching temperature is 28 °C, leaching time is 1 h.

Abstract: In order to decrease the consumption of lixiviant, study on dissolution of pure gold and middle-refractory gold ore using a novel thiosulfate leaching system with ferricyanide as oxidant was carried out. The results showed that the advantage of the novel system is that the thiosulfate consumption is negligible though the potential of ferricyanide is much higher than that of traditional cupric ammine complex. And compared to the ferric oxalate system, novel system could be used at relatively high pH condition which benefit to the stability of thiosulfate because ferricyanide can’t transfer to iron hydroxide in base solution. It is unlikely that very high dissolution rate of gold can be obtained using an air saturated thiosulfate- ferricyanide system without thiourea catalyst. However gold dissolution rate was increased with the increasing of concentration of ferricyanid in 5 mmol/L to 30mmol/L. When 0.1mmol/L thiourea was presented, the dissolution of gold approximately 1.5 times faster than that of in the absence of thiourea. Leaching of middle-refractory gold ore show that both of the consumption of thiosulfate and leaching rate was decreased compare to the traditional copper–ammonia thiosulfate system. Thiourea is not stable in base solution, but it was found that gold dissolution rates can be increased with a little thiourea ,the mechanism is still unclear.

Abstract: The effects of heat treatment on the microstructure and mechanical properties of Mg-3Sn-2Ca alloy were investigated. The results indicate that after solutionized at 500 °C for more than 24 h, the morphology of the CaMgSn phase in the alloy changes from the continuous and/or quasi-continuous nets to the particle-like shape. Furthermore, after solutionized at 500 °C for 24 h, for a given aging temperature of 285 °C, with prolonging aging time the matrix hardness of the alloy increases, and attains the maximum at 32 h of aging time and beyond that it decreases. In addition, it is preliminarily inferred that heat treatment would give a beneficial effects on the tensile and creep properties of Mg-3Sn-2Ca alloy due to the modification of the CaMgSn phase.

Abstract: The as-cast microstructures and solidification behaviours of Mg-Zn-Al ternary magnesium alloys with different Zn/Al mass ratios were investigated and compared. The results indicate that, when the Zn/Al mass ratio is less than 2, the alloys are composed of a-Mg and Mg₃₂(Al,Zn)₄₉ phases, and with the increase of the Zn/Al mass ratio, the amount of the second phase gradually decreases and its distribution changes from continuous net to quasti-continuous net. However, when the Zn/Al mass ratio is more than 2, the alloys are composed of a-Mg, Mg₃₂(Al,Zn)49 and MgZn phases, and with the increase of the Zn/Al mass ratio, the amount of the second phase gradually increases and its distribution changes from quasti-continuous net to uniform particles. In addition, the onset and the peak temperatures of the second phase transformation for the alloys with the Zn/Al mass ratio of less than 2, are higher than that of the alloys with the Zn/Al mass ratio of more than 2, which results in the different reactions during the second phase transformation and the different types of the second phase.

Abstract: Microstructure of the arc-melted Cr-20at%Nb alloy solidified in different positions was investigated using optical microscope (OM) and scanning electron microscope (SEM). The results show that fully coupled eutectic was developed at the bottom of the ingot and then the eutectic experienced a columnar to equiaxed transition due to the decrease of G/V ratio (G the thermal gradient and V the solidification rate) with increasing the solidification distance. A novel lamellar structure was observed in the middle side of the arc-melted ingot, which may form by means of the eutectoid reaction of C14-Cr₂Nb→C15-Cr₂Nb+Crss. With the increase of the solidification distance from the middle side to the top side, the primary Cr₂Nb phase underwent a nonfaceted to faceted transition.

Abstract: A series of ferroelectric BIT ceramics with various V₂O₅ dopants were prepared by conventional solid-state route. The influence of V2O5 dopant on microstructural and electrical properties of BIT ceramic were investigated in detail, which were examined by XRD, Raman spectra and P-E hysteresis loops, etc. X-ray Photoelectron Spectroscopy was used to examine the chemical state of the vanadium ions inside the BIT ceramics. Vanadium added to the BIT system can enhance the ferroelectric property due to the decrease of the concentration of space charge occurred during calcinations and weaken the polarization property due to the decrease of grain size and the change of chemical valence for vanadium ion. The BIT ceramic with 3 mol% V₂O₅ dopant exhibits a remnant polarization 2Pr of 25.6 μC/cm², and coercive field Ec of 47.4 KV/cm. Besides, the conductivity of BTV was obviously lower than that of the undoped BIT, which was accord with donor dopants decreasing the conductivity of a material with a p-type mechanism.

Abstract: The compounds of Fe substitution of Al in nanotructured Sr₂Fe_1-x Al _xMoO₆ (0≤x≤0.2) double perovskite have been prepared by sol-gel method. The x-ray diffraction patterns of the samples show that the samples are in nanometer range. The Curie temperature and thesaturation magnetization of the samples decrease with the increasing of Al substitution. And the magnetoresistance of the samples increase with the increasing of x.

Abstract: The growth of {111}-oriented CVD diamond film under a two-step model was simulated at atomic scale by using revised KMC method. The simulation was conducted at various substrate temperature (1100K-1400K), CH3 radical concentration (0.01%-0.03%) and atomic hydrogen concentration (0.005%-0.3%). The results showed that: Substrate temperature (Ts), the concentration of CH3 ([CH3]) and the concentration of atomic H ([H]) can produce important effects on the film deposition rate and surface roughness.

Abstract: Some azeotropic entrainers in the process of acetic acid dehydration could extract acetic acid from its dilute solution; this text would observe the ability of extraction about these entrainers mentioned in the literatures. By using the EXTRACT module in Aspen Plus, it is found that isopropyl acetate was the most effective extracting agent. The process of acetic acid dehydration via extraction combined with azeotropic distillation by using isopropyl acetate was established. Acetic acid was first extracted from its dilute solution and then was distilled in the azeotropic column, finally acetic acid having 99.8%(weight percent) purity was obtained. This process avoided evaporating a lot of water from the solution, and the entrainer’s existence effectively enhanced the relative volatility between acetic acid and water. The simulation result indicated that when dealing with the acetic acid solution used in this research, the total heat exhaustion was reduced from 11.73MW to 2.98MW and the number of theoretical plates needed in the distillation was also reduced from 65 to 34 compared with simple distillation.

Abstract: To research the mechanical performance and vibration modes of current longitudinal thrust rod of rear axle, the finite element model of original thrust rod is established and analyzed with NASTRAN codes. The simulation results demonstrate: the maximum stress of original thrust rod of dump truck is in the limit of the yield strength of material, which satisfies with the design requirements; the first step modal frequency of the component under free conditions is greater than upper limits value of the excited frequency of roads, which can evade the resonance excited by irregular roads. But there is structural stress concentration area in the thrust rod, so the structure of thrust rod is modified to ameliorate the stress state of this area. The maximum structural stress is reduced by 35.1% on the basis of reduction by 4.7% in total weight, which indicates the modification improves the mechanical and modal performance greatly. The research above has significant reference values for mechanical performance analysis and lightweight design of complicated automotive components.