Iron powder

About: Iron powder is a research topic. Over the lifetime, 8429 publications have been published within this topic receiving 45711 citations.

Sonochemical synthesis of amorphous iron

Abstract: AMORPHOUS metallic alloys ('metallic glasses') lack long-range crystalline order and have unique electronic, magnetic and corrosion-resistant properties1–3. Their applications include use in power-transformer cores, magnetic storage media, cryothermometry and corrosion-resistant coatings. The production of metallic glasses is made difficult, however, by the extremely rapid cooling from the melt that is necessary to prevent crystallization. Cooling rates of about 105 to 107 K s−1 are generally required; for comparison, plunging red-hot steel into water produces cooling rates of only about 2,500 K s−1. Metallic glasses can be formed by splattering molten metal on a cold surface using techniques such as gun, roller or splat quenching4,5. Acoustic cavitation is known to induce extreme local heating in otherwise cold liquids, and to provide very rapid cooling rates6–11. Here we describe the synthesis of metallic-glass powders using the microscopically extreme (yet macroscopically mild) conditions induced by high-intensity ultrasound. The sonolysis of iron pentacarbonyl, a volatile organometallic compound, produces nearly pure amorphous iron. This amorphous iron powder is a highly active catalyst for the Fischer–Tropsch hydrogenation of carbon monoxide and for hydrogenolysis and dehydrogenation of saturated hydrocarbons.

Remediation of Cr(VI) and Pb(II) aqueous solutions using supported, nanoscale zero-valent iron

Abstract: Borohydride reduction of an aqueous iron salt in the presence of a support material gives supported zero-valent iron nanoparticles that are 10−30 nm in diameter. The material is stable in air once it has dried and contains 22.6% iron by weight. The supported zero-valent iron nanoparticles (“Ferragels”) rapidly separate and immobilize Cr(VI) and Pb(II) from aqueous solution, reducing the chromium to Cr(III) and the Pb to Pb(0) while oxidizing the Fe to goethite (α-FeOOH). The kinetics of the reduction reactions are complex and include an adsorption phase. About 10% of the iron in the material appears to be located at active surface sites. Once these sites have been saturated, the reduction process continues but at a much lower rate, which is likely limited by mass transfer. Rates of remediation of Cr(VI) and Pb(II) are up to 30 times higher for Ferragels than for iron filings or iron powder on a (Fe) molar basis. Over 2 months, reduction of Cr(VI) was 4.8 times greater for Ferragels than for an equal weigh...

Effects of laser sintering processing parameters on the microstructure and densification of iron powder

Abstract: The densification behavior and the attendant microstructural features of iron powder processed by direct laser sintering were investigated. The effects of processing parameters such as laser power, scan rate, scan line spacing, thickness of layer, scanning geometry and sintering atmosphere were studied. A specific energy input (ψ) was defined using the “energy conservation” rule to explore the effects of the processing condition on the density and the attendant microstructure of laser sintered iron. It was found that the sintered density increased sharply with increasing the specific energy input until a critical energy input had been reached (ψ∼0.2 kJ mm−3). The microstructure consists of large pores (>0.5 mm) and elongated ferrite grains parallel to the building direction. The increase in the sintered density was followed with further increasing the specific energy, but at slower rate. Intensifying the energy input over 0.8 kJ mm−3 leads to the formation of horizontally elongated pores while the sintered density remains almost constant. The inter-agglomerates are fully dense and consist of elongated ferrite grains which are oriented parallel to the building direction. The iron powder was used as a model material so the outcomes are generic and can be applied to other material systems with congruent melting point or systems which melting/solidification approach is the mechanism feasible for the rapid bonding of metal powders in direct laser sintering.