Molybdenum

About: Molybdenum is a research topic. Over the lifetime, 30662 publications have been published within this topic receiving 412446 citations. The topic is also known as: Mo & element 42.

The Hotter the Engine, the Better

Abstract: Jet turbine engines have benefited from decades of development of nickel-based superalloys, which have allowed a steady increase in engine operating temperatures and led to improved performance and efficiency. However, operating temperatures are now reaching limits posed by the melting temperatures ( T m) of these materials. New materials, including alloys based on metals with higher melting points, such as molybdenum (Mo) and niobium (Nb) alloyed with silicon (Si), are now being seriously examined as alternatives by academic and industrial groups.

Vapor Deposition of Diamond Particles from Methane

Abstract: Microcrystalline diamond has been formed on silicon or molybdenum substrates by vapor deposition from a geseous mixture of methane and hydrogen. Cubo-octahedral or multiply-twinned crystals were obtained. The structure of the deposits was identified by electron diffraction and Raman scattering.

Molybdenum cofactors, enzymes and pathways

Abstract: The trace element molybdenum is essential for nearly all organisms and forms the catalytic centre of a large variety of enzymes such as nitrogenase, nitrate reductases, sulphite oxidase and xanthine oxidoreductases. Nature has developed two scaffolds holding molybdenum in place, the iron-molybdenum cofactor and pterin-based molybdenum cofactors. Despite the different structures and functions of molybdenum-dependent enzymes, there are important similarities, which we highlight here. The biosynthetic pathways leading to both types of cofactor have common mechanistic aspects relating to scaffold formation, metal activation and cofactor insertion into apoenzymes, and have served as an evolutionary 'toolbox' to mediate additional cellular functions in eukaryotic metabolism.

High yield exfoliation of two-dimensional chalcogenides using sodium naphthalenide

Abstract: Transition-metal dichalcogenides like molybdenum disulphide have attracted great interest as two-dimensional materials beyond graphene due to their unique electronic and optical properties. Solution-phase processes can be a viable method for producing printable single-layer chalcogenides. Molybdenum disulphide can be exfoliated into monolayer flakes using organolithium reduction chemistry; unfortunately, the method is hampered by low yield, submicron flake size and long lithiation time. Here we report a high-yield exfoliation process using lithium, potassium and sodium naphthalenide where an intermediate ternary Li(x)MX(n) crystalline phase (X=selenium, sulphur, and so on) is produced. Using a two-step expansion and intercalation method, we produce high-quality single-layer molybdenum disulphide sheets with unprecedentedly large flake size, that is up to 400 μm(2). Single-layer dichalcogenide inks prepared by this method may be directly inkjet-printed on a wide range of substrates.

Phase instabilities during high temperature exposure of 316 austenitic stainless steel

Abstract: Although Type 316 austenitic stainless steel is widely used in steam generating plants and nuclear reactors the knowledge about aging reactions, nature of precipitates, and precipitation kinetics during high temperature exposure is limited. Time-temperature-precipitation (TTP) diagrams were determined between 400° and 900°C for up to 3000 hr as a function of carbon content, solution treatment temperature, and cold work. The nucleation and growth phenomena, morphology, and composition of the various carbide (M23C6, M6C) and intermetallic phases (σ, χ, η were determined. The complex sequence of phase instabilities can be explained on the basis of the carbon content, effect of molybdenum and chromium on the carbon solubility, thermodynamic stability of the phases, and the kinetics of the various precipitation reactions.