A. K. Suri

Electro-extraction of molybdenum from Mo2C-type carbide

A process for the preparation of molybdenum from molybdenum carbide was investigated.It involved fused salt electrolysis of the carbide in an inert atmosphere electrolytic cell using a KCl-K3MoCl6 electrolyte. The preferred conditions for electrolysis carried out in a 0.075 m (3 in.) diam cell were: voltage 0.2 to 0.5 V; cathode current density 8000 A/m2 (720 amp/f2);bath temperature 1203 K; and electrolyte composition 7.5 pct molybdenum. Under these conditions, electrolysis in a 0.15 m (6 in.) diam cell charged with 1.5 kg of the carbide yielded a total metal recovery of 71 pct at an average current efficiency of 60 pct. The metal purity was better than 99.9 pct. The electron beam melt hardness for the electro-extracted molybdenum was in the range of 150 to 160 DPH.

Formation of Silicide Based Oxidation Resistant Coating Over Mo-30 wt% W Alloy

Studies were carried out to develop silicide based oxidation resistant coatings over Mo-30W alloy substrate employing halide activated pack cementation coating process. Effect of activator content and temperature on coating was studied. Coated samples were characterized for phase and microstructure evaluation by SEM and EDS. Cyclic oxidation tests on coated alloy were performed at 1000°C up to 50 h. The coating provided enough protection from oxidation.

Thermal analysis on conversion of MoO3 to MoO2 and its silicothermic reduction

The present paper deals with differential thermal analysis studies conducted to find out the onset temperature for silicothermic reduction of MoO2 to Mo. The reaction kinetics of Si–MoO2 system has been analyzed by a model-free Kissinger method. X-ray diffraction analysis has confirmed the formation of Mo metal and SiO2 as the slag phase after silicothermic reduction of MoO2. The activation energy for silicothermic reduction of MoO2 to Mo was evaluated to be 309xa0kJxa0mol−1.

Electrolytic recovery of molybdenum from molybdic oxide and molybenum sesquisulfide

An electrolytic process for molybdenum extraction in a KCl−K3MoCl4 electrolyte (containing approximately 7.5 wt pct molybdenum) was investigated using three types of anode feed —namely, molybdic oxide-graphite, molybdenum sesquisulfide-graphite, and molybdenum sesquisulfide without graphite. In the case of molybdic oxide-graphite anode, a maximum current efficiency of 99 pct was achieved at an operating voltage of 0.35V, a cathode current density of 5000 A/m2 (450 A/f2) and a bath temperature of 1223 K. Electrolysis with molybdenum sesquisulfide-graphite, at an operating voltage of 1.2V, a cathode current density of 13,900 A/m2 (1250 A/f2) and a bath temperature of 1173 K, yielded a maximum current efficiency of 84 pct. Electrolysis of molybdenum sesquisulfide without graphite incorporation, yielded under almost similar conditions, a maximum current efficiency of 87 pct. Extended electrolysis was carried out using molybdic oxide-graphite and molybdenum sesquisulfide cell charges and yielded metal with purity over 99.9 pct.

Kinetics of Alkaline Leaching of UO2 and FeS2 in Co-existing System

The dissolution of uranium dioxide under oxidative alkaline conditions is critically influenced by iron pyrite (FeS2), which is a gangue mineral commonly found in uranium ores. This paper makes an effort in understanding the kinetics of dissolution of UO2 in a co-existing system of UO2 and FeS2 under the lixiviant combination of Na2CO3 and NaHCO3–O2 at elevated temperature and pressure. Dissolution experiments were carried out in a laboratory batch autoclave reactor using synthetic mixtures of minerals consisting of UO2, FeS2 (reactive gangue—varied from 1 to 6xa0%), silica (inert gangue) and calcite (inert gangue). The kinetic profiles indicated that the rate of dissolution of UO2 increased with initial increase in FeS2 content in the feed and decreased when the FeS2 weight increased beyond 3xa0%. The dissolution phenomenon was analysed using scanning electron microscopy and X-ray diffraction studies.