Hydrogen reduction of complex oxides—a novel route toward the production of nanograined alloys and intermetallics

Abstract

One of the major obstacles in the incorporation of nanomaterials in high technology is the lack of new processes for the bulk production of the materials with compositions tailored to suit the application. Oxides can potentially be reduced to metals, intermetallics or alloys by hydrogen or natural gas. The formation of homogeneous alloys and intermetallics by this method has been confirmed by a number of experimental studies. The kinetics of hydrogen reduction of pure oxides of transition metals as well as complex tungstates, molybdates, titanates, aluminates and chromate were investigated by thermogravimetry. The formation of homogeneous alloys and intermetallics was confirmed by these studies. Arrhenius activation energies of the reduction reactions could be linked to the stabilities of the complex oxides. The products were found to have nanograin structure. Bulk processing through hydrogen reduction route was examined in the case of iron molybdate using a fluidized bed reactor.

Chemical Synthesis and Characterization of Nickel Powder

“…The reduction in a hydrogen atmosphere to produce high-purity nanoparticles from fine metal oxides is significant. [25][26][27][28][29][30][31] Regarding the application, the synthesis of particles with a definite shape, tailor-made size, and narrow size distribution may be the main goal with a definite composition either as a crystal or amorphous phase.…”

Fabrication of Sub‐10 nm Metallic Lines of Low Line‐Width Roughness by Hydrogen Reduction of Patterned Metal–Organic Materials

“…In this work, we report on an alternative strategy of using hydrogen reduction of an electron beam‐exposed metal naphthenate resist film to form patterned metal lines of good integrity at the sub‐10 nm size scale. Although the reduction of metal oxides to the base metals (such as Ni, Co, Fe, Cu, Mo, and W) using hydrogen is well known,13–18 there have been no attempts to use this process in the fabrication of metal nanostructures. It has previously been observed, in studies of oxide‐hydrogen reaction kinetics, that nanometer‐scale‐grained pure metal and alloy films can be produced successfully 13.…”

“…Although the reduction of metal oxides to the base metals (such as Ni, Co, Fe, Cu, Mo, and W) using hydrogen is well known,13–18 there have been no attempts to use this process in the fabrication of metal nanostructures. It has previously been observed, in studies of oxide‐hydrogen reaction kinetics, that nanometer‐scale‐grained pure metal and alloy films can be produced successfully 13. The reduction of metal oxides to their respective metals by hydrogen is best understood by studying the principles of extractive metallurgy, and in particular, the Ellingham diagram of oxides 19.…”

Reduction Kinetics of the Nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98-y(EtOH)y]

“…The reduction of iron-molybdenum oxides has been previously studied; however, the literature reports varied kinetic results, indicating the importance of analysis methods and experimental conditions [44][45][46][47][48]. Table 3 shows the apparent activation energies (E a ) reported in literature with the corresponding temperature range, experimental conditions, kinetic analysis methods, and proposed reaction mechanisms.…”