Advanced Materials Research Vols. 554-556

Abstract: A research study has been undertaken to develop the fundamentals of a method for the direct dissolution of Metal Platinum. At room temperature and pressures, the reaction between sodium cyanide and platinum group metals (PGMs) does not occur because of poor kinetics. However, at elevated temperatures between 20°C and 180°C, PGMs can be dissolved by sodium cyanide like the reaction of gold. In this work, the dissolution of Platinum was measured in pressure clear cyanide solution. The data at different cyanide concentrations, different temperature and different oxygen pressure are obtained. With increasing cyanide concentration and oxygen pressure, the dissolution first increased to a maximum value and then decreased. With increasing temperature the dissolution is increased. The dissolution was found to have a relation of the cyanide and oxygen level. The dissolution was independent of rotation speed for oxygen-saturated solutions and cyanide concentrations above 5 mol.m-3 and was well below chemical reaction-limited for cyanide and oxygen.

Abstract: With the development of powder metallurgy industry, the fine-metal-powder classification becomes one of the vital techniques in powder technology. A pneumatic classifier without screen and mechanical moving parts is designed and developed. Theoretical analysis and experiments of Pneumatic-Classification was conducted. The oversize ratio in fine powder can be reduced to less than 5% and the undersize ratio in coarse powder less than 15% when the air flow is suitable. The classification effect is satisfactory for the customers.

Abstract: This paper did the research on Interaction mechanism between Ce and P added in high-carbon steel.with the use of QUANTA-400 SEM and EDS, the morphology of Ce-P-O inclusions were observed.By the Ce，O，P，S surface scanning observation of the inclusion, the inclusions were sured to be Ce-P or Ce-P-O compounds.furthermore,Ce-P compounds were irregular spherical , mainly in the grain. Ce-P-O compounds were long strip, mainly along the grain boundaries.

Abstract: Ionic liquids (ILs) as “green solvents” provided an effective and efficient procedure for Knoevenagel condensation reactions. It is applicable for a large range of aldehydes, ketones with active methylene compounds. ILs can significantly promote the reaction rates. High yields and selectivity of products have been observed. ILs can be recycled and reused. In this paper, the recent achievements of Knoevenagel condensation reactions promoted by ILs are reviewed.

Abstract: The residual rich SiO₂ slag was obtained for MgO and B₂O₃ was leached from the boromagnesite by ammonium sulfate. The SiO₂ was leached from the residual slag by sodium hydroxide. The effect of the roasting time, calcination temperature and the ratio of sodium hydroxide to the residual slag on the leaching efficiency of SiO₂ in the residual slag were also studied. The reasonable technical condition as follow : the roasting time is 60 min, the calcination temperature is 550°C, the ratio of the sodium hydroxide to the residual slag is 3.0:1. The SiO₂ leached rate can be stabilized about 85% under this condition.The residual rich SiO

Abstract: The solidification microstructure and the microhardness of Al-11Mg-4.5Zn alloy under high pressure were researched by optical microscope, scanning electron microscope (SEM), X-ray diffraction(XRD) and microhardness tester. The results revealed that high pressure solidification refined the dendrite structure, and made the primary dendrite arms grow long. The alloy all consisted of α-Al phase and Mg₃₂(Al, Zn)₄₉ phase whether under normal pressure or high pressure solidification conditions. However, the morphology of the Mg₃₂(Al, Zn)₄₉ phases changed from fork-like of normal pressure to the graininess of high pressure, the size of them reduced, and that of the amount decreased. Furthermore, the solid solubility of Mg and Zn in α-Al phase increased comparing with those of normal pressure, and they were the largest at 4GPa high pressure, reaching 11.37% and 4.15%, respectively. The microhardness of Al-Mg-Zn alloy had an increment with the pressure increasing.

Abstract: With the growing demand of phosphoric fertilizer a great quantity of phosphogypsum (PG) was produced in China.To utilization of PG in an energy-saving way,the phase transition of PG from DH to α-HH in CaCl₂ solution under atmospheric pressure was conducted, the reaction time of phase transition was significantly shortened by higher reaction temperature and CaCl₂ content of the mixtures. The suitable temperature and CaCl₂ addition of the mixture were 95 °C and 24 wt.% respectively, morphology of the corresponding dehydration product phase is rod-like shape. Preparation of α-HH from PG in hot CaCl₂ solution at atmospheric pressure was based on dissolution- crystallization mechanism. The increasing addition of CaCl₂ in solution makes the solubility of CaSO₄ decrease due to the common ion effect.

Abstract: The preparation of different morphological basic magnesium carbonate particles with hollow rod-like, hull of peanut and leaf from the pyrogenation of magnesium carbonate trihydrate were described. The morphology, crystal phase and purity of basic magnesium carbonate were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectrometer (ICP-AES). The results indicated that the formation of three morphological basic magnesium carbonates were obtained via platelike particles of magnesium carbonate trihydrate under certain conditions where the temperature and stirring rate were properly controlled. The length of the hollow rod means up to 6～7µm, and its diameter means up to 1～2µm.

Abstract: Under ultrasonic wave and using aminopropyltriethoxysilane as modifier and acid catalyst, hydrophobic SiO₂ aerogel was prepared through fractional hydrophobic modification and ambient pressure drying of the raw material, tetraethoxysilane (TEOS), in the process of sol-gel and acid-base catalysis.SiO₂ aerogels were analyzed and compared using scanning electron microscopy, Brunauer-Emmett-Teller analysis method, Fourier transform infrared spectroscopy. The results indicate that modifiering by the ultrasonic wave and aminopropyltriethoxysilane, the temperature tolerance of the SiO₂ aerogels was 407°C.the specific surface area of the SiO₂ aerogels was 877.17m²/g. Pore distribution in micro -pore range was 0.5～1nm. Pore distribution in meso -pore range was 1.8～2.5nm. Thermal stability of the hydrophobic SiO₂ aerogels prepared through fractional modification assisted by the ultrasonic wave method was increased with the hydrophobic angle at160°, which showed super hydrophobicity.

Abstract: Nowadays in China, excessive import of boron isotope has always been the bottleneck to its industrial applications in nuclear, mechanical, steel and electronic fields. To pull the boron industry out of the mire of import, it is prerequisite to study the enriching and refining of boron isotope. In this work, we present an experimental setup of boron isotope separation by chemical exchange distillation with focus on pyrolysis reaction. After repeated tests, the optimal temperature of pyrolysis reaction (i.e., 140oC) had been found and the best enrichment of 10B (i.e., 34.4%) could be achieved when the reaction continued to the 8th day. These results indicate that the more completely the pyrolysis reaction performs, the better enrichment of 10B arrives.