Sponges, metallic

TiH2 is prepared on an industrial scale by dkect combination of hydrogen and the metal (sponge, ingot, scrap, etc) at 200—650°C, followed by cooling in an H2 atmosphere. An alternative method is the reduction of the oxide using calcium hydride under hydrogen ... 

Hafnium Carbide. The need of pure zirconium [7440-67-7] for nuclear reactors prompted the large-scale separation of hafnium [7440-58-6] from zirconium. This in turn made sufficient quantities of hafnium dioxide [12055-23-17, Hf02, or Hf metal sponge available for production of HfC for use in cemented carbides (see Hafniumand hafnium compounds). 

A significant volume of literature relates to our work. Concerning choice of support, Montassier et al. have examined silica-supported catalysts with Pt, Co, Rh Ru and Ir catalysts.However, these systems are not stable to hydrothermal conditions. Carbon offers a stable support option. However, the prior art with respect to carbon-supported catalysts has generally focused on Ru and Pt as metals.Additionally, unsupported catalysts have also been reported effective including Raney metals (metal sponges).Although the bulk of the literature is based on mono-metallic systems, Maris et al. recently reported on bimetallic carbon-supported catalysts with Pt/Ru and Au/Ru. In contrast, our work focuses primarily on the development of a class of rhenium-based carbon supported catalysts that have demonstrated performance equal to or better than much of the prior art. A proposed reaction mechartism is shown in Figure 34.2 °l... 

Colloidal metals, metallic sponges or blacks, skeletal metals, metal powders, evaporated metal films, electrodeposited films, wires, foils, gauzes... 

Metallic sponges (or blacks) are coagulated colloids formed from the reduction of a salt in an alkaline solution with formaldehyde. 

Skeletal catalysts were first discovered in the 1920s by Murray Raney [1,2], In recognition of their inventor, the catalysts are often referred to as Raney catalysts, although this trademark is now owned by the Davison division of W.R. Grace Co., who supply a range of catalysts for industrial use. Another common name is metal sponge, which refers to the porous structure of the catalysts. 

Thermal reduction processes have been apphed successfully in making the metal from salts. In one such process, potassium fluotantalate is reduced with sodium metal at high temperatures to form tantalum powder of high purity and small particle size. Also, tantalum oxide can be reduced at high temperatures in vacuum with aluminum, silicon, or tantalum carbide. When the oxide is reduced by tantalum carbide, a metal sponge is obtained which can be embrittled with hydrogen to form powder metal. 

Highly porous metal sponges can be made in aqueous solutions by dissolution of aluminium alloys by a strong base. The metal sponges are typically used for hydrogenation in laboratory syntheses. 

Figure4.8 The Raney process, in which a metal/aluminum alloy is prepared by fusion, and subsequently the aluminum is dissolved by aqueous NaOH, leaving a metallic sponge. ...

This unique micro structure can be described as an intermediate stage between a supported catalyst and a bulk metallic sponge or skeletal Raney-type catalyst. It enables a reasonably high dispersion of Cu and exposure of many Cu-ZnO interfaces at a high total Cu content. The specific Cu surface area (SACu) of methanol catalysts can be determined by reactive N20 titration [59, 60], which causes surface oxidation of the Cu particles and allows calculation of SAcu from the amount of evolved N2. The SACu of state-of-the-art methanol synthesis catalysts measured by this method... 

Surfactant-based synthesis of mesoporous metal oxides and metal sulfides emerged about four years after the initial report of MCM-41 [21-36]. High surface area and thermally robust mesoporous metal oxides and sulfides represent a new class of materials with diverse opportunities for the development of improved fuel and solar cells, batteries, membranes, chemical delivery vehicles, heavy metal sponges, sensors, magnetic devices and new catalysts. All of these applications could benefit from tailorable Bronsted and Lewis acidity and basicity, flexible oxidation states, and tunable electronic, optical and magnetic properties. 

The most important commercial methods of production of metalhc zirconium and hafnium are based on furnace reduction, either of MCI4 with magnesium or a Na-Mg mixture (the KroU process), yielding a metal sponge, or of metal fluorides with Ca at 2000 °C to give an ingot. The... 

Assemble the apparatus shown in Figs. 6 and 7. The fractionating column is packed with one-fourth to one-third of a metal sponge. The column should be perfectly vertical and it should be insulated with glass wool covered with aluminum foil with the shiny side in. However, in order to observe what is taking place within the column, insulation is omitted for this experiment. 

The reduction occurs by direct oxygen removal from the solid oxides (solid-state diffusion). The basic underlying mechanism is not known (diffusion of O, OH, H2O) and is likely to vary for different for different phase transitions. On the final reduction the metal remains pseudomorphous to the starting oxide, forming a polycrystalline metal sponge. Solid-state reactions are characteristic for low reduction temperatures (<750 °C) and the early WO3 - WO2 9 transition ( crystallographic shear transition). 

Zinc Process [11.1,11.2,11.5,11.6]. In this process, cemented carbide scrap is treated in molten zinc or zinc vapor, which reacts with the binder to form intermetallic phases and a zinc-cobalt alloy. These reactions lead to a volume expansion of the binder and bloat the scrap. After vacuum distillation of zinc, the material is liiable and can be readily disintegrated. The condensed Zn can be re-used. The reclaimed carbide/metal sponge contains less than 50 ppm Zn. 

C. San Marchi and A. Mortensen, Chapter 2.6 Infiltration and the Replication Process for Producing Metal Sponges , in Handbook of Cellular Materials - Production, Processing, Applications (Ed. H.P. Degischer), Wiley-VCH, Weinheim, 2002, pp. 44-56. 

Cellular solids are a class of materials with low densities and novel physical, mechanical, thermal, electrical, and acoustic properties. Low-density cellular metals can feature a wide variety of topologies to include open-cell foam, closed-cell foam, hollow-sphere foam, periodic/optimized truss structures, and honeycomb. Metallic foams consist of air dispersed in a solid matrix, similar to polymer foams such as polystyrene or food foams such as whipped cream. Closed-cell foams feature solid faces such that each cell is independently sealed from its neighboring cells, whereas open-cell foams (also known as porous metals, metal sponges and truss-type materials) do not contain cell walls they only have cell edges. Hollow-sphere foams consist of an assembly of individual hollow spheres. 

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