Tungsten

About: Tungsten is a research topic. Over the lifetime, 35225 publications have been published within this topic receiving 456213 citations. The topic is also known as: W & element 74.

Si nanowire growth with ultrahigh vacuum scanning tunneling microscopy

Abstract: Using a scanning tunneling microscope (STM), Si nanowires were grown by applying a voltage at a constant current between a Si substrate and a gold STM tip. Silicon atoms were deposited onto a gold tip by field evaporation. The field evaporation rate of silicon atoms was activated by heating the substrate. Silicon nanowire was grown on the gold tip at a substrate temperature of 700 °C. Nanowires could not be grown on a clean tungsten tip when using a gold-free Si substrate. The presence of gold atoms is important for the growth of silicon. Apparently, gold atoms deposited on the silicon substrate by field evaporation reduce the activation energy of field evaporation by attacking Si–Si bonds.

The Surface Energy of Solid Metals

Abstract: Published solid/vapour surface-energy data for pure metals are collected and appraised. Preferred values at the melting point are related to heat of sublimation in conformity with the simplest theoretical predictions. Except for surface energies higher than expected for chromium and zinc and lower values for beryllium, molybdenum, tin, and tungsten, the results fit a relation corresponding within error to that for liquid/vapour surface energies. This correspondence is consistent with the expected increment in solid/vapour over liquid/vapour surface energy at the melting point.

Thermal stability and mechanical properties of Ni–W–P electroless deposits

Abstract: The ternary Ni–W–P alloy coatings were deposited by electroless plating on 420 stainless steel to evaluate the thermal property and related mechanical characteristics of the coating assemblies. The thermal stability of electroless Ni–W–P deposits, analyzed by differential scanning calorimetry (DSC), could be enhanced by the co-deposition of tungsten as compared to binary electroless Ni–P films. The phase and composition of Ni–W–P and Ni–P were evaluated by X-ray diffraction technique and electron probe microanalysis, respectively. The co-deposition of tungsten enabled the deposits to exhibit an amorphous structure with lower phosphorus content. Adhesion strength of the deposits on the substrates were assessed by a scratch test. The introduction of the tungsten in the Ni–P coating effectively reduced the linear crack length and delayed the cracking formation. Surface hardness of binary alloy coating could be modified with the introduction of the tungsten element.