WC/Co tool used in the turning of Ti-alloys are subject to rapid crater wear due to chemical processes at the tool chip interface in the form of dissolution/diffusion. It has been observed that a thin layer of bcc W forms on the outermost WC grains in contact with the Ti workpiece meaning that C has diffused away from the WC. The rates involved in this process are of interest for formulating a theory of how wear progresses during turning of Ti-alloys. In this work we investigate the rates involved in this diffusion process by means of classical MD simulations on 6 different WC/W interfaces, 3 with a basal WC surface and 3 with a prismatic WC surface, as a function of C depletion in the outermost WC layer. The results show that all interfaces are stable and that principally no diffusion events of C occur at temperatures below 1373 K for C depletion levels below 30 at.%. At 50 at.% depletion, C diffusion starts occurring regularly and at 70 at.% depletion and above the majority of the C atoms are diffusing except at the lowest temperatures. Additionally, any difference in diffusion rate observed between the basal and prismatic interfaces in their pristine states have vanished at the point of 50 at.% depletion. This all points to a process which is initially slow for each layer of the WC but which increases in speed substantially as C atoms are removed.
New relations and transformation formulas for the Appell function F-2 (a, b, b; c, c; w, z) and confluent Appell functions (Humbert functions) (1), (2) are obtained. These relations include limit formulas, integral representations, differentiation and recurrence formulas. Summation formulas for F-2, (1), and (2) are derived.
The effect of ball milling on microstructural change of (Ti,W)C solid solution was investigated. In addition to the particle size reduction with milling time, detailed studies using the X-ray diffraction line profiles were carried out to evaluate the microstructural parameters, including lattice parameter, crystallite size and microstrain. Nelson Riley extrapolation and Williamson-Hall method are employed. The results suggest lattice expansion, with the lattice parameter increasing from 43212 A to 43241 A. The defects and surface stress generated during ball milling are deemed to be responsible for the increased d-spacing of (Ti,W)C solid solution with milling time. The crystallite size displays a diminishing trend with increasing milling time, which is consistent with the SEM observation. However, the microstrain developed is tensile in nature and firstly increases with up to 36 h milling, and then the strain reduces for further milling perhaps due to the strain relaxation by the formation of dislocations. (C) 2017 Elsevier Ltd. All rights reserved.
The retention of hydrogen (H) isotope in plasma-facing materials (PFMs) is an important issue for next step fusion device. We used density functional theory (DFT) to study the chemical bonds of H in tungsten-carbon (W-C) mixed layers of tungsten surface, aiming to explore the retention behaviour of H in PFMs. The solubility of C in W was first calculated for revealing the phase components in W-C mixed layers. It was found that C has low solubility in W, which prefers to be segregated on the W surface. Vacancies can enhance the solution of C in W. This makes C appear somewhat carbide feature. Thus, W-C mixed layers should contain multiple phase components. H retention strongly depends on the phase components in the W-C mixed layers. The solution of C will suppress the retention of H in W no matter whether neighbouring vacancies are present, or not. Hydrocarbon precursors, which were observed in desorption experiments, prefer to form by means of H binding to C atoms in C amorphous, or in precipitators in the W-C mixed layers, while not in tungsten carbide phase or in W bulk. Our investigation reasonably explains the experimental results.
The process pp -> W(-)c produces polarized charm quarks. The polarization is expected to be partly retained in Lambda(c) baryons when those form in the c-quark hadronization. We argue that it will likely be possible for ATLAS and CMS to measure the Lambda(c) polarization in the W+c samples in Run 2 of the LHC. This can become the first measurement ever of a longitudinal polarization of charm quarks. Its results will provide a unique input to the understanding of polarization transfer in fragmentation. They will also allow applying the same measurement technique to other (e.g., new physics) samples of charm quarks in which the polarization is a priori unknown. The proposed analysis is similar to the ATLAS and CMS measurements of the W+c cross section in the 7TeV run that used reconstructed D-meson decays for charm tagging.
Microstructures of as-cast 28 wt%Cr-2.6 wt.%C irons containing (0-10)wt.%W with the Cr/C ratio about 10 were studied and related to their hardness. The experimental irons were cast into dry sand molds. Microstructural investigation was performed by light microscopy, X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectrometry. It was found that the irons with 1 to 10 wt%W addition was hypereutectic containing large primary M7C3, whereas the reference iron without W addition was hypoeutectic. The matrix in all irons was austenite, partly transformed to martensite during cooling. The volume fractions of primary M7C3 and the total carbides increased, but that of eutectic carbides decreased with increasing the W content of the irons. W addition promoted the formation of W-rich M7C3, M6C and M23C6. At about 4 wt%W, two eutectic carbides including M7C3 and M6C were observed together with primary M7C3. At 10 wt.%W, multiple carbides including primary M7C3, fish-bone M23C6, and M6C were observed. MC where x = 3 or less has not been found due possibly to the high M/C ratio in the studied irons. W distribution to all carbides has been determined increasing from ca. 0.3 to 0.8 in mass fraction as the W content in the irons was increased. W addition led to an increase in Vickers macro-hardness of the irons up to 671 kgf/(mm)(2) (HV30/15) obtained from the iron with 10 wt%W. The formation of primary M7C3 and aggregates of M6C and M23C6 were the main reasons for hardness increase, indicating potentially improved wear performance of the as-cast irons with W addition. (C) 2014 Elsevier Inc. All rights reserved.
Lukashenko, S Y; Komissarenko, F E; Mukhin, I S; Lysak, V V; Averkiev, D A; Sapozhnikov, I D; Golubok, A O
Nanomechanical system (NMS) based on amorphous carbon nanowhiskers localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope (SEM) chamber using focused electron beam technique. The manipulation of SiO2 and TiO2 nanospheres was provided in SEM by means of dielectrophoretic force. Oscillation trajectories and amplitude-frequency characteristic of the oscillator were visualized at low pressure using a scanning electron microscope. The estimation of mass sensitivity of NMS was conducted.
Satterfield, Benjamin A.
Cross, Robert W.
Fenton, Karla A.
Agans, Krystle N.
Deer, Daniel J.
Basler, Christopher F.
Mire, Chad E.
Nipah virus (NiV) is a highly lethal paramyxovirus that recently emerged as a causative agent of febrile encephalitis and severe respiratory disease in humans. The ferret model has emerged as the preferred small-animal model with which to study NiV disease, but much is still unknown about the viral determinants of NiV pathogenesis, including the contribution of the C protein in ferrets. Additionally, studies have yet to examine the synergistic effects of the various P gene products on pathogenesis in animal models. Using recombinant NiVs (rNiVs), we examine the sole contribution of the NiV C protein and the combined contributions of the C and W proteins in the ferret model of NiV pathogenesis. We show that an rNiV void of C expression resulted in 100% mortality, though with limited respiratory disease, like our previously reported rNiV void of W expression; this finding is in stark contrast to the attenuated phenotype observed in previous hamster studies utilizing rNiVs void of C expression. We also observed that an rNiV void of both C and W expression resulted in limited respiratory disease; however, there was severe neurological disease leading to 60% mortality, and the surviving ferrets demonstrated sequelae similar to those for human survivors of NiV encephalitis.
A gallium antimonide-based semiconductor disk laser (SDL) emitting 17 W of continuous wave output power at a heat sink temperature of 20 degrees C and an emission wavelength of 2.02 m are presented. This high-output power is achieved by optimising the thermal management and reducing the quantum deficit of the SDL structure.