Jae-Won Lim

Preparation method of Ti powder with oxygen concentration of <1000 ppm using Ca

Abstract To reduce the high oxygen concentration of commercial Ti powder and to obtain Ti powder with the oxygen concentration of <1000 ppm, we utilised two types of deoxidation pots to conduct deoxidation experiments: below the melting point of Ca using a contact deoxidation pot (experiment A), and above its melting point using a non-contact deoxidation pot (experiment B). To obtain Ti in powder form even after deoxidation above the melting point of Ca, we developed a new non-contact deoxidation pot in the experiments. In experiment A, the oxygen concentration in the Ti powder decreased down to 50% compared with the initial stage (2200 ppm). In experiment B, the oxygen concentration reduced to ∼63% at the deoxidation temperature of 1000°C. As a result, Ti powder with 820 ppm of oxygen concentration could be prepared using the non-contact deoxidation pot with Ca.

Mechanical Properties and Fabrication of Nanostructured 1.5TiAl-Al2O3 Composite by Pulsed Current Activated Sintering

Nano-powders of 1.5TiAl and Al2O3 were synthesized from 1.5TiO2 and 3Al powders by high energy ball milling. Nanocrystalline Al2O3 reinforced composite was consolidated by pulsed current activated sintering within 2 minutes from mechanochemically synthesized powders of Al2O3 and 1.5TiAl. The relative density of the composite was 99.5%. The average hardness and fracture toughness values obtained were 1250 kg/mm and 10 MPa ·m, respectively. (Received September 5, 2011)

New method for preparation of low oxygen Mo powder by reduction of MoO3 using Ca

Abstract A new method for the reduction of MoO3 using Ca as a reducing agent was developed. A low oxygen Mo powder can thus be prepared by two-step reduction process: the first step reduction involves a contact type method while the second step reduction uses a non-contact type method involving Ca vapour followed by additional deoxidation. The oxygen concentration in the resultant Mo powder was ∼2800 ppm, which was much lower than that of commercial Mo powder (>4400 ppm).