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Tungsten carbide

Igor Konyashin, Alexander Zaitsev, Alexander Meledin, Joachim Mayer, Pavel Loginov, Evgeny Levashov, Bernd Ries
Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established...
March 9, 2018: Materials
Nana Han, Ke R Yang, Zhiyi Lu, Yingjie Li, Wenwen Xu, Tengfei Gao, Zhao Cai, Ying Zhang, Victor S Batista, Wen Liu, Xiaoming Sun
Tungsten carbide is one of the most promising electrocatalysts for the hydrogen evolution reaction, although it exhibits sluggish kinetics due to a strong tungsten-hydrogen bond. In addition, tungsten carbide's catalytic activity toward the oxygen evolution reaction has yet to be reported. Here, we introduce a superaerophobic nitrogen-doped tungsten carbide nanoarray electrode exhibiting high stability and activity toward hydrogen evolution reaction as well as driving oxygen evolution efficiently in acid. Nitrogen-doping and nanoarray structure accelerate hydrogen gas release from the electrode, realizing a current density of -200 mA cm-2 at the potential of -190 mV vs...
March 2, 2018: Nature Communications
P Huntsman, J M Skeaff, M Pawlak, R Beaudoin
The transformation/dissolution protocol (T/DP) for metals and sparingly soluble metal compounds was applied to determine the transformation/dissolution (T/D) characteristics of yellow tungsten trioxide, WO3; blue tungsten oxide, WOx (x taken as 2.9); tungsten disulphide, WS2; tungsten metal, W; three samples of tungsten carbide, WC; sodium tungstate, Na2WO4 · 2H2O; ammonium paratungstate (APT), (NH4)10(H2W12O42) · 4H2O; and ammonium metatungstate (AMT), (NH4)6(H2W12O40) · 3H2O. The T/D data were used to derive aquatic hazard classification outcomes under the UN GHS and EU CLP schemes by comparing the data with selected acute and chronic ecotoxicity reference values (ERVs) of 31 and 3...
February 21, 2018: Integrated Environmental Assessment and Management
Madsakorn Towannang, Anongnad Thiangkaew, Wasan Maiaugree, Kunthaya Ratchaphonsaenwong, Wirat Jarernboon, Samuk Pimanpang, Vittaya Amornkitbamrung
Tungsten carbide (WC) particles (~1 μm) were dispersed in DI water and dropped onto conductive glass. The resulting WC films were used as dye-sensitized solar cell (DSSC) counter electrodes. The performance of the WC DSSC based on the organic thiolate/disulfide (T-/T2) electrolyte was ~0.78%. The cell efficiency was greatly improved after decorating palladium (Pd) or platinum (Pt) nanoparticles on WC particles with a promising efficiency of ~2.15% for Pd-WC DSSC and ~4.62% for Pt-WC DSSC. The efficiency improvement of the composited (Pd-WC and Pt-WC) cells is attributed to co-functioning catalysts, the large electrode interfacial area and a low charge-transfer resistance at the electrolyte/counter electrode interface...
February 1, 2018: Journal of Nanoscience and Nanotechnology
Aditya Jetly, Ivan U Vakarelski, Sigurdur T Thoroddsen
We investigate the effect of thin air layers naturally sustained on superhydrophobic surfaces on the terminal velocity and drag force of metallic spheres free falling in water. The surface of 20 mm to 60 mm steel or tungsten-carbide spheres is rendered superhydrophobic by a simple coating process that uses a commercially available hydrophobic agent. By comparing the free fall of unmodified spheres and superhydrophobic spheres in a 2.5 meter tall water tank, it is demonstrated that even a very thin air layer (∼1-2 μm) that covers the freshly dipped superhydrophobic sphere can reduce the drag force on the spheres by up to 80%, at Reynolds numbers from 105 to 3 × 105, owing to an early drag crisis transition...
February 7, 2018: Soft Matter
Alaa Daud, Gordon Gray, Christopher D Lynch, Nairn H F Wilson, Igor R Blum
OBJECTIVES: The aim of this study was to evaluate theeffects of different finishing and polishing techniques on the surface roughness of microhybrid and nanofilled resin composites. METHODS: The resin composites included were Filtek Z250 (a universal microhybrid resin composite) and Filtek Supreme XTE (a universal nanofill resin composite). Ninety cylindrical-shaped specimens were prepared for each composite resin material. The polishing methods used included tungsten carbide bur (TC); diamond bur (Db); Sof-Lex discs (S); Enhance PoGo discs (PG); TC + S; Db + S; TC + PG; Db + PG...
January 19, 2018: Journal of Dentistry
Mikael T Ekvall, Jonas Hedberg, Inger Odnevall Wallinder, Lars-Anders Hansson, Tommy Cedervall
As the production and usage of nanomaterials are increasing so are the concerns related to the release of the material into nature. Tungsten carbide (WC) is widely used for its hard metal properties, although its use, in for instance tyre studs, may result in nano-sized particles ending up in nature. Here, we evaluate the potential long-term exposure effects of WC nanoparticles on a pelagic (Daphnia magna) and a benthic (Asellus aquaticus) organism. No long-term effects were observed in the benthic system with respect to population dynamics or ecosystem services...
January 15, 2018: Nanotoxicology
Changzhi Li, Tao Dai, Lin Li, Zongbao Kent Zhao, Bo Zhang, Yu Cong, Aiqin Wang
Tungsten carbide was employed as a catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA), the product of Diels-Alder reaction between two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization-hydrodeoxygenation cascade pathway via intramolecular hydrogen transfer without involving any external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W2C surface...
January 8, 2018: Angewandte Chemie
Kai Zhang, Gong Zhang, Jiuhui Qu, Huijuan Liu
Phase tuning during crystal phase transformation is an important but challenging step toward the development of effective hydrogen evolution reaction (HER) catalysts. Herein, we report on a feasible approach to achieve effective polycrystalline molybdenum carbides during transformation from α-phase to β-phase through the regulation of additive (tungsten) amount. Benefiting from the optimal Mo-C bond lengths and abundant active sites, molybdenum carbide prepared with a moderate addition of tungsten enhanced electrocatalytic activity and stability compared with pure α-phase and β-phase Mo2C in the HER, and only required an overpotential of 148 and 93 mV to drive 20 mA cm-2 of current density in 0...
January 3, 2018: ACS Applied Materials & Interfaces
V N Lednev, P A Sdvizhenskii, M Ya Grishin, V V Cheverikin, A Ya Stavertiy, R S Tretyakov, M V Taksanc, S M Pershin
Three-dimensional multi-elemental mapping of composite wear-resistant coatings by laser-induced breakdown spectroscopy has been demonstrated for the first time, to the best of our knowledge. Individual clads of 1560 nickel alloy reinforced with tungsten carbide were synthesized by a co-axial laser cladding technique. Electron energy dispersive x-ray spectroscopy revealed elemental maps for major elements (W, Ni, Co, Cr, Fe) but failed to measure silicon and carbon. Laser-induced breakdown spectroscopy was utilized for elemental mapping of carbon and all other elements of interest...
December 10, 2017: Applied Optics
João Vitor de Queiroz, José Cavalcante Souza Vieira, Izabela da Cunha Bataglioli, Alis Correia Bittarello, Camila Pereira Braga, Grasieli de Oliveira, Cilene do Carmo Federici Padilha, Pedro de Magalhães Padilha
This paper presents a slurry sampling method for total mercury determination by graphite furnace atomic absorption spectrometry (GFAAS) in tissue of fish from the Amazon. The tissue samples were lyophilized and macerated, and then the slurry samples were prepared by putting 20 mg of tissue, added to a solution containing Triton X-100, Suprapur HNO3 , and zirconium nitrate directly in sampling vials of a spectrometer. Mercury standard solutions were prepared under the same conditions as the slurry samples. The slurry samples and the mercury standard solutions were sonicated for 20 s...
December 2, 2017: Biological Trace Element Research
Yan Zhang, Yanhui Wang, Chan Han, Shaopei Jia, Shuyu Zhou, Jianbing Zang
Herein, tungsten-coated nano-boron carbide (W-WB4 -WCx /B4 C) particles were prepared by heating a mixture of B4 C and W powder using a spark plasma coating (SPC) method. During the discharge treatment process, metal W in the mixture is activated and reacts with B4 C to form WCx , WB4 , and graphite nanoribbons. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance of W-WB4 -WCx /B4 C is tested in an alkaline solution, and the results show that the W-WB4 -WCx /B4 C composite electrocatalyst exhibits a low overpotential of 0...
December 14, 2017: Nanoscale
Ayam A Taha, Robert G Hill, Padhraig S Fleming, Mangala P Patel
OBJECTIVES: To develop a novel, bioactive glass for removing residual orthodontic adhesive via air-abrasion, following bracket debonding, and to evaluate its effectiveness against a proprietary bioactive glass 45S5(Sylc™)-air-abrasion, and a slow-speed tungsten carbide (TC) bur. MATERIALS AND METHODS: Three glasses were prepared and their bioactivity was proved. One novel glass (QMAT3) was selected due to its appropriate hardness, lower than that of enamel/45S5(Sylc™)...
November 28, 2017: Clinical Oral Investigations
M Jacinta Santos, Heleine Maria Chagas Rêgo, Leticia Linares, Amin S Rizkalla, Gildo C Santos
OBJECTIVE: To compare the effect of surface finishing and polishing protocols on the surface roughness (Ra) of methacrylate-based and silorane-based resin composites. METHODS AND MATERIALS: Fifty specimens (5 mm x 2 mm) of each composite material were prepared using a split mold: Filtek™ Supreme Ultra (3M ESPE), Tetric EvoCeram® (Ivoclar Vivadent), Tetric Ceram™ HB (Ivoclar Vivadent), and Filtek™ LS Low Shrink (3M ESPE). Specimens were divided into five groups (n = 10) according to the following procedures: G1 - 15-µm fine diamond bur (FDB); G2 - 15-µm FDB followed by a 20-fluted tungsten carbide bur; G3 - 15-µm FDB followed by diamond-impregnated micropolishing points (D-FINE Double Diamond Polishing System, Clinician's Choice); G4 - 15-µm FDB followed by diamond-impregnated micropolishing points (Flame Point Pre-polisher and Shine, Brassseler USA); and G5 - 15-µm FDB followed by the application of a surface sealer (PermaSeal®, Ultradent Products, Inc...
November 2017: Compendium of Continuing Education in Dentistry
Xin Tang, Kit H Bowen, Florent Calvo
Tungsten oxide cluster anions (WO3 )3 - produced from a magnetron source were soft-landed on highly oriented pyrolytic graphite (HOPG) surfaces at different temperatures, and the structures formed upon deposition were analyzed using ex situ atomic force microscopy. Under liquid nitrogen cooling conditions of 100 K, the clusters form small branched nanostructures extending over a few nanometers with a height not exceeding 1 nm. At 673 K, nanowires approximately 100 nm long and less than 10 nm in diameter are observed...
November 29, 2017: Physical Chemistry Chemical Physics: PCCP
Prashanthi Sampath Madhyastha, Shreya Hegde, N Srikant, Ravindra Kotian, Srividhya Sriraman Iyer
Background: Surface roughness associated with improper finishing/polishing of restorations can result in plaque accumulation, gingival irritation, surface staining, and poor esthetic of restored teeth. The study aimed to evaluate the efficiency of various finishing and polishing systems and time using various procedures on surface roughness of some esthetic restorative materials. Materials and Methods: In this in vitro study, samples of two composite materials, compomer and glass ionomer cement (GIC) materials, were fabricated...
September 2017: Dental Research Journal
Stiven Forti, Antonio Rossi, Holger Büch, Tommaso Cavallucci, Francesco Bisio, Alessandro Sala, Tevfik Onur Menteş, Andrea Locatelli, Michele Magnozzi, Maurizio Canepa, Kathrin Müller, Stefan Link, Ulrich Starke, Valentina Tozzini, Camilla Coletti
This work reports an electronic and micro-structural study of an appealing system for optoelectronics: tungsten disulfide (WS2) on epitaxial graphene (EG) on SiC(0001). The WS2 is grown via chemical vapor deposition (CVD) onto the EG. Low-energy electron diffraction (LEED) measurements assign the zero-degree orientation as the preferential azimuthal alignment for WS2/EG. The valence-band (VB) structure emerging from this alignment is investigated by means of photoelectron spectroscopy measurements, with both high space and energy resolution...
November 2, 2017: Nanoscale
Jiaqing Xie, Tianfeng Zhou, Benshuai Ruan, Yifei Du, Xibin Wang
To study the effects of the interface thermal resistance on surface morphology evolution in precision glass molding (PGM) for microlens array with different mold materials, including Tungsten carbide and heat-resistant stainless steel, the glass-mold interface thermal resistance is calculated, and heat-transfer simulation of PGM based on an interface thermal resistance model at the heating stage is conducted correspondingly. The effect of flattening behavior on the glass-mold interface is explained. Then, experiments evaluating the relationship between heating time and glass surface roughness are carried out, and the glass adhesion phenomenon appearing on the heat-resistant stainless steel mold is observed and analyzed...
August 10, 2017: Applied Optics
Samar Reda Al-Sayed Ali, Abdel Hamid Ahmed Hussein, Adel Abdel Menam Saleh Nofal, Salah Elden Ibrahim Hasseb Elnaby, Haytham Abdelrafea Elgazzar, Hassan Abdel Sabour
Laser cladding process was performed on a commercial Ti-6Al-4V (α + β) titanium alloy by means of tungsten carbide-nickel based alloy powder blend. Nd:YAG laser with a 2.2-KW continuous wave was used with coaxial jet nozzle coupled with a standard powder feeding system. Four-track deposition of a blended powder consisting of 60 wt % tungsten carbide (WC) and 40 wt % NiCrBSi was successfully made on the alloy. The high content of the hard WC particles is intended to enhance the abrasion resistance of the titanium alloy...
October 15, 2017: Materials
Gregory W Wilson, Alex E Hay
The short-pulse acoustic backscatter amplitude calibration technique of Dragonette, Numrich, and Frank [(1981), J. Acoust. Soc. Am. 69, 1186-1189] is evaluated for MHz frequency systems, as are used to measure environmental suspended sediment concentration. The technique involves measuring backscatter from a short transmit pulse reflected by a solid spherical target, and treating the first received reflection as equivalent to that from a perfectly rigid sphere. In this implementation, the target sphere is 16 mm diameter tungsten carbide...
September 2017: Journal of the Acoustical Society of America
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