The first direct evidence is provided for the presence of an interstitial carbide in the Fe-V cofactor of Azotobacter vinelandii vanadium nitrogenase. As for our identification of the central carbide in the Fe-Mo cofactor, we employed Fe Kβ valence-to-core X-ray emission spectroscopy and density functional theory calculations, and herein report the highly similar spectra of both variants of the...

Metal matrix composites have been widely studied in terms of abrasion resistance, but a particular material system may behave differently as particle size, morphology, composition, and distribution of the hardening phase varies. The purpose of this thesis was to understand the mechanical and microstructural effects of combining titanium carbide with 431 series stainless steel to create a unique...

Silicon carbide nanowires have been synthesized at 1400 degrees C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires....

In the production of high speed steel, the rolling a ects the micro-structure of the steel, which in turn in uences the mechanical properties. Speci cally, the distribution of carbide is essential, since cracks propagate within the carbide agglomerations. In current quality control, the properties of the steel are assessed manually by comparison with a standard chart, containing representative ...

INTRODUCTION Calcium carbide used in fruit ripening industry as a cheap alternative to natural plant hormone ethylene produces highly inflammable acetylene gas. Inadvertent ignition of this gas can cause severe ocular burn injury with unilateral or bilateral blindness. OBJECTIVE To determine the characteristics and visual outcome of ocular burn injuries from calcium carbide during mango ripen...

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating comple...

While empirical relationships between the mechanical properties of WC-Cocomposites and the carbide grain size and carbide volume fraction are qualitatively well-known, the influence of other microstructural features on the macroscopic properties hasbeen less clear. In this thesis, a comprehensive study of the effect of the interfacecharacter distribution (grain shape and misorie...

Near-isotropic pyrolytic carbon containing a small amount of co-deposited silicon carbide has been used for years as the materials from which prosthetic heart valves are fabricated [ 1 ]. Silicon carbide was introduced into this material to increase the hardness and thereby the wear resistance of the material. Silicon carbide, however, has poor thromboresistance relative to pyrolytic carbon, so...

We report the study of ultrasound tunneling in 3D phononic crystals, consisting of fcc arrays of close-packed tungsten carbide beads in water. The transmission coefficient, phase velocity, and group velocity were measured along the [111] direction, allowing us to systematically investigate the tunneling of ultrasound at frequencies in the lowest band gap. Our experimental data are interpreted u...

This paper describes the fabrication and mechanical testing of Al-Mg-boron carbide particulate composites using stir casting technique. The size of the boron carbide particulates is ranging between 30 to 100 μm. The boron carbide contents are varied from 3 and 7% by weight and are dispersed in the alloy matrix. The mechanical properties of the castings, particularly their tensile properties and...