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Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the "Reduction-Sintering" process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H-2, CH4 and N-2 were used for simultaneous reduction, carburization and nitridation, respectively. Different techniques have been utilized. A thermogravimetric analyzer was used to accurately control the process conditions and obtain reaction kinetics. The fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method. These efforts end up with a successful preparation of nanograined intermetallics like Fe-Mo and Ni-W. In addition, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures in single step., QC 20161124

The reduction kinetics of MoO3 shallow powder beds by hydrogen was investigated by isothermal and non-isothermal thermogravimetric technique. The isothermal reduction was carried out in the temperature range 823 to 973 K, whereas in the case of non-isothermal experiments, the reduction was studied by heating the sample from room temperature up to 1073 K with temperature ramps from 8 to 15 K/min. A mathematical expression based on the chemical reaction control was used to evaluate the activation energy from the non-isothermal experimental data. It was found that the chemical reaction was the rate-controlling step at the beginning of the reduction process. The activation energy for this step evaluated from the isothermal data was found to be 175 kJ/mol, which is in an excellent agreement with the value obtained from the non-isothermal data, 172 kJ/mol., QC 20100525