In the current study, results of the milled and sintered V, W, C, Co powders are presented. Analytical techniques such as SEM equipped with EDS and XRD were used to study microstructure and phase evolution, respectively. In addition to B1 (VW)C solid solution, a rhombohedral V2O3 and new τ-type (Cr23C6) carbide were formed after sintering. The possible formation mechanisms behind detected phases are discussed. It is evident that complete MA process depends strongly on the starting compositions of pure elements, their lattice coherency according to Hume-Rothery rules on crystal structure and atomic size, and enough milling time that provides adequate kinetics.
In the current study, results of the milled and sintered V, W, C, Co powders are presented. Analytical techniques such as SEM equipped with EDS and XRD were used to study microstructure and phase evolution, respectively. In addition to B1 (VW)C solid solution, a rhombohedral V2O3 and new τ-type (Cr23C6) carbide were formed after sintering. The possible formation mechanisms behind detected phases are discussed. It is evident that complete MA process depends strongly on the starting compositions of pure elements, their lattice coherency according to Hume-Rothery rules on crystal structure and atomic size, and enough milling time that provides adequate kinetics.
K. Nordlund, C. Bjö
rkas, K. Vö
rtler, A. Mein,er, A. Lasa, M. Mehine, A.V. Krasheninnikov
Current and future tokamak-like fusion reactors include the three elements Be, C, and W as the plasma-facing materials. During reactor operation, also mixtures of all these elements will form. Hence it is important to understand the atom-level mechanisms of physical and chemical sputtering in these materials. We have previously shown that athermal low-energy sputtering of pure C and Be can be understood by the swift chemical sputtering mechanism, where an incoming H (or D or T) ion enters between two atoms and pushes them apart. In the current article, we examine the model system of D impacting on a single dimer to determine the detailed mechanism of bond breaking and its probability for the Be2, C2, W2, WC, BeW, and BeC dimers. The results are found to correlate well with recent experiments and simulations of sputtering of the corresponding bulk materials during prolonged H isotope bombardment.
A. Novinrooz
S. Moniri
M. Asadi Asadabad
A. Hojabri
The precipitate particles formed during several heat treatments consisting of solution, air-cooling, and high-temperature tempering in reduced activation Fe – Cr – W – V – C alloy were investigated. The morphology and structure of the precipitate particles formed in the matrix of the alloy were evaluated by means of metallography, transmission electron microscopy (TEM), x-ray diffraction (XRD), and scanning electron microscopy (SEM) after tempering at 600°C for 5 and 20 h. Hardness measurements of the specimens were also done. The combination of these techniques provided new insights into how different precipitate morphologies may form during different heat treatments. The results showed that two types of particles were mainly precipitated, M7C3and M23C6, were in spherical and blocky shapes.
Nordlund, K.
Bjorkas, C.
Vortler, K.
Meinander, A.
Lasa, A.
Mehine, M.
Krasheninnikov, A. V.
Current and future tokamak-like fusion reactors include the three elements Be, C, and W as the plasma-facing materials. During reactor operation, also mixtures of all these elements will form. Hence it is important to understand the atom-level mechanisms of physical and chemical sputtering in these materials. We have previously shown that athermal low-energy sputtering of pure C and Be can be understood by the swift chemical sputtering mechanism, where an incoming H (or D or T) ion enters between two atoms and pushes them apart. In the current article, we examine the model system of D impacting on a single dimer to determine the detailed mechanism of bond breaking and its probability for the Be(2), C(2), W(2), WC, BeW, and BeC dimers. The results are found to correlate well with recent experiments and simulations of sputtering of the corresponding bulk materials during prolonged H isotope bombardment. (C) 2010 Elsevier B.V. All rights reserved.
This paper presents design of a high-precision curvature-compensated bandgap reference (BGR) circuit implemented in a 0.35 mu m CMOS technology. The circuit delivers an output voltage of 1.09 V and achieves the lowest reported temperature coefficient of similar to 3.1 ppm/degrees C over a wide temperature range of [-20 degrees C/+100 degrees C] after trimming, a power supply rejection ratio of -80 dB at 1 kHz and an output noise level of 1.43 mu V root Hz p at 1 kHz. The BGR circuit consumes a very low current of 37 mu A at 3 V and works for a power supply down to 1.5 V. The BGR circuit has a die size of 980 mu m x 830 mu m.
The combustion synthesis reaction was combined with liquid phase sintering to fabricate net-shape TiC-Ni and TiC-WC-Ni composites in a single processing operation. When Ti and C powders used for in situ production of TiC-Ni cermet, the final product was porous and had low strength. By the addition of fine W powder with W/Ti = 1 molar ratio, the product contained (Ti,W)C, W 2C and mix compounds of type Ni 2W 4C. Using W with W/Ti = 2 molar ratio results in a dense high strength product containing (Ti,W)C and WC. [All rights reserved Elsevier].