The Study on Sintering Capabilities of High Purity Metal Vanadium Powder

High purity metal vanadium powder was milled by high energy ball milling, and the grain size and morphology of vanadium powder was observed by electron probe, and the stress-strain curve was measured by CMT5305 universal testing machine for research of the mechanical property. In order to investigate the effect of sintering process on the property of product, the vanadium powder was sintered by the hot pressing sintering process and the cold isostatic pressing with vacuum sintering process respectively. The experimental results show that for the cold isostatic pressing with vacuum sintering process, the density of raw compact increases with the increase of pressing pressure. When the pressure increases to 280 MPa, the density and relative density of raw compact are 3.99 g·cm-3 and 66.94% respectively, the density and relative density of product after sintering are 5.28 g·cm-3 and 88.59% respectively. With the pressure increasing from 80 MPa to 200 MPa, the compressive strength increases significantly from 0.4 MPa to 6.0 MPa, the pressure increases to 280 MPa, the compressive strength slowly increases to 7.4 MPa. For the hot pressing sintering process, the relative density of product is higher than that of cold isostatic pressing with vacuum sintering process, and the density and relative density reach to 5.51 g·cm-3 and 92.91% respectively under 280 MPa pressure.

Direct AMS 14C Analysis of Carbonate

ABSTRACTWe have investigated the possibility of direct accelerator mass spectrometry radiocarbon (AMS 14C) measurement of carbonate samples at ANSTO using the STAR 2 MV tandem accelerator. Each carbonate sample was powdered, mixed with metal powder and pressed into an aluminum cathode for direct carbonate measurement by AMS 14C. Of the three high-purity metal powders (Fe, Nb, and Ag) used in our investigation, Nb was found to be the best metal, which delivered higher carbon beam currents and lower background. Beam currents for targets containing the optimal carbonate mass of 1.5–2.0 mg were ∼8% of those obtained from graphite targets of standard size (>0.5 mg C). Typical measured blank for Carrara marble (IAEA-C1) of ∼40 ka was obtained. Background-corrected 14C values of carbonate targets agreed well with their associated values obtained from high-precision analysis of graphite targets within 2σ uncertainties. Typical precision of this rapid AMS analysis was ∼1% for samples <8 ka. Despite lower precision for carbonate target ages (compared to standard graphite target ages), these ages are useful for palaeobiological applications where a large number of dates are required, such as time-averaging studies.

Preparation of High-Purity Alumina by Hydrolyzing High-Purity Metal Aluminum

This paper puts forward a new method for the preparation of 99.999% high-purity alumina used for the LED underlay sapphire, which has above 99.999% high-purity aluminum atomized the active aluminum powder by the supersonic multistage cooling way, then makes the powder form the hydrate of the alumina through the hydrolyzing reaction, and finally gets 99.999% high-purity alumina by means of the calcinations and the follow-up granularity treatment. By the processing way, the reactant is only aluminum and water, and there is no other additive, which profitably keeps the product pure and completely satisfies the requirements of synthetic crystals while tested.