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Now showing items 65 - 80 of 21208

  • A comparison of the mechanically alloyed (V,W)C and (V,W)C–Co powders

    A.S. Bolokang  

    Milling was carried out in flowing argon but was interrupted at regular time intervals to take samples for X-ray diffraction (XRD). Because of exposure to air during the interruptions the powder was partly oxidized. The oxides formed did not appear in XRD patterns because they were of extremely fine grain size. As a result of the loss of V and W through oxidation, free carbon was also found in the final powder. The lattice parameter of the (V,W)C powder increased with milling time up to a maximum, then it decreased, which suggests that the amount of W in (V,W)C increased with milling time up to a maximum and then decreased. The crystallite size of the (V,W)C powder was calculated from the X-ray data and was found to be in the nm range (down to approximately 8 nm). Subsequent uninterrupted milling produced a powder which was freer from oxides and free carbon. [All rights reserved Elsevier].
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  • On some formulas for the Appell function F-3(a, a ', b, b '; c; w, z)

    Brychkov, Yu. A.   Saad, Nasser  

    New relations and transformation formulas for the Appell function F-3 (a,a',b,b';v';w;z) and the confluent Appell functions (Humbert functions) Phi(2),Phi(3), Xi(1), Xi(2) are obtained. These relations include limit formulas, integral representations, differentiation formulas. Various finite and infinite summation formulas are also derived.
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  • POLYMER COMPOSITION FOR W&C APPLICATION WITH ADVANTAGEOUS ELECTRICAL PROPERTIES

    The invention relates to power cable polymer composition which comprises a single site polyethylene (SSPE), a power cable, for example, a high voltage direct current (HV DC), a power cable polymer insulation, use of a polymer composition for producing a layer of a power cable, and a process for producing a power cable.
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  • Sputtering of Be/C/W compounds in molecular dynamics and ERO simulations

    Airila, M.I.   Bj?rkas, C.   Lasa, A.   Meinander, A.   Nordlund, K.   V?rtler, K.  

    We have implemented molecular dynamics (MD) generated sputtering data in the Monte Carlo impurity transport code ERO. The data set covers D bombardment of BeC, Be2C, Be2W, W2C and WC that are potentially formed on divertor targets in machines operating with an ITER-like wall. We see that intermediate compounds can have a sputtering yield different from that estimated from a homogeneous mixture, especially in the case of carbide formation with its characteristic strong bonding. At other stoichiometries, grain formation affect the yields. We also observe preferential sputtering of the lighter elements and molecular release. A linear interpolation method is proposed for the evaluation of the sputtering behaviour of any ternary Be/C/W composition. (C) 2013 Elsevier B.V. All rights reserved.
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  • Mechanochemical fabrication of C (matrix) + Cu + Si + W + Mo nanocomposites

    D. V. Onishchenko  

    Using magnesiothermic reduction of WO 3, MoO 3, SiO 2, and CuO through mechanochemical activation, we prepared high-purity (~99.3%) nanopowders with a particle size from 9 to 350 nm for the fabrication of functional materials and nanocomposite systems for anode electrodes of lithium ion (polymeric) batteries.
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  • Caesar's Civil Warby W. W. Batstone; C. Damon

    Review by: Aislinn Melchior  

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  • Interaction of C with vacancy in W: A first-principles study

    Liu, Yue-Lin   Zhou, Hong-Bo   Zhang, Ying   Lu, Guang-Hong   Luo, Guang-Nan  

    We provide a vacancy trapping mechanism of C in W by investigating structure, stability, and diffusion properties of C in W using a first-principles method. C easily bonds onto the internal-surface of vacancy. A monovacancy is capable of trapping as many as 4 C atoms to form C(n)V (n = 1, 2, 3, 4) complexes. Single C atom prefers to interact with neighboring W at vacancy with the trapping energy of -1.93 eV. With the C atoms added, both of them are preferred to bind with each other to form covalent-like bond despite the metallic W environment. For the C(n)V complexes, C(2)V is the major one due to its largest average trapping energy (-1.97 eV). Kinetically, formation of the C(n)V complexes can be ascribed to the interstitial mechanism due to the lower activation energy barrier of 1.46 eV for the interstitial C than 1.66 eV for the vacancy. (C) 2011 Elsevier B.V. All rights reserved.
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  • Investigation of aperiodic W/C multi-layer mirror for X-ray optics

    Wang, Zhanshan   Cheng, Xinbin   Zhu, Jingtao   Huang, Qiushi   Zhang, Zhong   Chen, Lingyan  

    Design, fabrication and characterization of aperiodic tungsten/carbon (W/C) multi-layer mirror were studied. W/C multi-layer was designed as a broad-angle reflective supermirror for Cu-K alpha line (lambda = 0.154 nm) in the grazing incident angular range (0.9-1.1 degrees) using simulated annealing algorithm. To deposit the W/C depth-graded multi-layer mirror accurately, we introduce an effective layer growth rate as a function of layer thickness. This method greatly improves the reflectivity curve compared to the conventional multi-layer mirror prepared with constant growth rate. The deposited multi-layer mirror exhibits an average reflectivity of 19% over the grazing incident angle range of 0.88-1.08 degrees which mainly coincides with the designed value. Furthermore, the physical mechanisms were discussed and the re-sputtering process of light-atom layers is accounted for the modification of layer thicknesses which leads to the effective growth rates. Using this calibration method, the aperiodic multi-layer mirrors can be better fabricated for X-ray optics. (C) 2011 Elsevier B.V. All rights reserved.
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  • French Romantic Travel Writing: Chateaubriand to Nerval, by C. W. Thompson

    Yee, Jennifer  

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  • Elements of Adaptive Testing edited by van der Linden, W. J., & Glas, C. A. W.

    Ying Cheng  

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  • Microstructure and mechanical properties of nanolayered W/W–C thin films

    K. Abdelouahdi   C. Legrand-Buscema and P. Aubert  

    The present study reports on the mechanical and structural properties of W/W–C multilayered thin films with bilayer periods Λ ranging from 2.5 to 100 nm. Films were grown by reactive sputtering radio frequency on Si (100) substrate. X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXRD) and X-ray reflectivity were used to globally characterise the multilayers structure. Hardness and Young modulus have been determined using nanoindentation with a Berkovich tip. The XRD and the GIXRD diagrams revealed the presence of three phases: WC1−x randomly oriented, W2C with (100) preferred orientation and W with (110) preferred orientation. An increase in hardness is observed with decreasing period Λ, reaching a maximum value of ~26 GPa at Λ = 2.5 nm.
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  • Nicht wie eine Toiletten-Lektüre – C.?W. Hufeland und sein Verleger Brockhaus

    Hansen   W.  

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  • Terrae-Rarae-Preis: P.?C. Junk und P.?W. Roesky / Preis der Bau-Familie: H. Xu

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  • Terrae-Rarae-Preis: P. C. Junk und P. W. Roesky / Preis der Bau-Familie: H. Xu

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  • Characterization of WC-(W,V)C-Co made from pre-alloyed (W,V)C

    Hashe, Nobom Gretta   Norgren, Susanne M.   Andren, Hans-Olof   Neethling, Johannes H.  

    Large (W,V)C cubic carbides in WC-VC-Co cemented carbides are undesirable as their presence is one of the causes for poor properties in the material. Earlier attempts to reduce the (W,V)C cubic carbide grain sizes in the WC-VC-Co cemented carbide have been published before. The present investigation strives to reduce the cubic carbide grain size by using a pre-alloyed (W,V)C powder in the place of VC, to reduce the driving force for the formation of (W,V)C during sintering. This should in turn reduce the possibility of forming large (W,V)C grains. WC-VC-Co was prepared using WC, (W,V)C, and Co powders. The compositions were 8.1 wt% V and 12 wt% Co, with the balance comprising W and C. XRD diffraction patterns confirmed that the bulk of WC-(W,V)C-Co contains WC grains, cubic (W,V)C grains, and a Co-rich binder phase. SEM-EDS measurements yielded an average composition of (W(0.31)V(0.69))C(x). TEM-EDS of the cubic carbide was in good agreement with the SEM-EDS measurement, yielding the average composition of (W(0.30)V(0.70))C(x) The average grain size of the cubic carbide of WC-(W,V)C-Co material after sintering had grown to only the same size as that of the starting powder, 1.4 mu m. (C) 2008 Elsevier Ltd. All rights reserved.
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  • Caesar\"s Civil Warby W. W. Batstone; C. Damon

    Review by: Aislinn Melchior  

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