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Tungsten carbide

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https://www.readbyqxmd.com/read/28376618/cage-confinement-pyrolysis-route-to-ultrasmall-tungsten-carbide-nanoparticles-for-efficient-electrocatalytic-hydrogen-evolution
#1
Yan-Tong Xu, Xiaofen Xiao, Zi-Ming Ye, Shenlong Zhao, Rongan Shen, Chun-Ting He, Jie-Peng Zhang, Yadong Li, Xiao-Ming Chen
The size-controlled synthesis of ultrasmall metal-based catalysts is of vital importance for chemical conversion technologies. Here, a cage-confinement pyrolysis strategy is presented for the synthesis of ultrasmall tungsten carbide nanoclusters/nanoparticles. An RHO type zeolitic metal azolate framework MAF-6, possessing large nanocages and small apertures, is selected to confine the metal source W(CO)6. High temperature pyrolysis gives tungsten carbide nanoclusters/nanoparticles with sizes ca. 2 nm, which can serve as an excellent electrocatalyst for the hydrogen evolution reaction...
April 10, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28337857/wxc-c-nrgo-composite-derived-from-polyoxotungstate-conductive-polypyrrole-graphene-as-efficient-electrocatalyst-for-hydrogen-evolution-reaction
#2
Ya-Qian Lan, Xiao-Li Wang, Yu-Jia Tang, Wei Huang, Chun-Hui Liu, Long-Zhang Dong, Shun-Li Li
Efficient hydrogen evolution reaction (HER) from water through electrocatalysis using cost-effective materials is critical to realize the clean hydrogen production. Herein, with controlling the structure and composition of polyoxotungstate/conductive polypyrrole/graphene (PCG) precursor precisely and followed by the temperature-programmed reaction, we developed a highly active and stable catalyst WxC@C/NRGO. The composite presents splendid performance towards HER in acidic media, with a small onset overpotential of 24 mV vs...
March 23, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28318483/automated-atom-by-atom-three-dimensional-3d-reconstruction-of-field-ion-microscopy-data
#3
Michal Dagan, Baptiste Gault, George D W Smith, Paul A J Bagot, Michael P Moody
An automated procedure has been developed for the reconstruction of field ion microscopy (FIM) data that maintains its atomistic nature. FIM characterizes individual atoms on the specimen's surface, evolving subject to field evaporation, in a series of two-dimensional (2D) images. Its unique spatial resolution enables direct imaging of crystal defects as small as single vacancies. To fully exploit FIM's potential, automated analysis tools are required. The reconstruction algorithm developed here relies on minimal assumptions and is sensitive to atomic coordinates of all imaged atoms...
March 20, 2017: Microscopy and Microanalysis
https://www.readbyqxmd.com/read/28300257/electrochemical-synthesis-of-nanoporous-tungsten-carbide-and-its-application-as-electrocatalysts-for-photoelectrochemical-cells
#4
Jin Soo Kang, Jin Kim, Myeong Jae Lee, Yoon Jun Son, Juwon Jeong, Dong Young Chung, Ahyoun Lim, Heeman Choe, Hyun S Park, Yung-Eun Sung
Photoelectrochemical (PEC) cells are promising tools for renewable and sustainable solar energy conversion. Currently, their inadequate performance and high cost of the noble metals used in the electrocatalytic counter electrode have postponed the practical use of PEC cells. In this study, we report the electrochemical synthesis of nanoporous tungsten carbide and its application as a reduction catalyst in PEC cells, namely, dye-sensitized solar cells (DSCs) and PEC water splitting cells, for the first time...
March 16, 2017: Nanoscale
https://www.readbyqxmd.com/read/28296306/a-novel-phantom-and-procedure-providing-submillimeter-accuracy-in-daily-qa-tests-of-accelerators-used-for-stereotactic-radiosurgery
#5
Ivan A Brezovich, Richard A Popple, Jun Duan, Sui Shen, Xingen Wu, Sidi Benhabib, Mi Huang, Rex A Cardan
Stereotactic radiosurgery (SRS) places great demands on spatial accuracy. Steel BBs used as markers in quality assurance (QA) phantoms are clearly visible in MV and planar kV images, but artifacts compromise cone-beam CT (CBCT) isocenter localization. The purpose of this work was to develop a QA phantom for measuring with sub-mm accuracy isocenter congruence of planar kV, MV, and CBCT imaging systems and to design a practical QA procedure that includes daily Winston-Lutz (WL) tests and does not require computer aid...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28289759/thermal-imaging-of-the-pulp-during-residual-adhesive-removal
#6
Gökmen Kurt, Nisa Gül, Özgür Er, Gülşen Çakmak, Emre Bendeş, Veysel Aslantaş
OBJECTIVE: The aim of this study was to evaluate the temperature changes of the pulpal area during different adhesive clean-up procedures. MATERIALS AND METHODS: A total of 80 freshly extracted adult maxillary premolar teeth were divided into four groups. Adhesive clean-up was performed with 6- and 12-fluted tungsten carbide burs (TCB) using low- and high-speed handpieces with air or water cooling after bracket debonding. The temperature changes and cool down times were evaluated with a thermal camera...
March 13, 2017: Journal of Orofacial Orthopedics, Fortschritte der Kieferorthopädie
https://www.readbyqxmd.com/read/28257737/evaluation-of-enamel-surface-roughness-after-orthodontic-bracket-debonding-with-atomic-force-microscopy
#7
Shadi Mohebi, Hassan-Ali Shafiee, Nazila Ameli
INTRODUCTION: Achieving a smooth enamel surface after orthodontic bracket debonding is imperative. In this study, we sought to compare the enamel surface roughness values after orthodontic bracket debonding and resin removal using a white stone bur, a tungsten carbide bur, and a tungsten carbide bur under loupe magnification. METHODS: Thirty sound premolars were randomly divided into 3 groups, and their buccal surfaces were subjected to atomic force microscopy to measure initial surface roughness...
March 2017: American Journal of Orthodontics and Dentofacial Orthopedics
https://www.readbyqxmd.com/read/28240393/circular-graphene-platelets-with-grain-size-and-orientation-gradients-grown-by-chemical-vapor-deposition
#8
Xing Xin, Zeyuan Fei, Teng Ma, Long Chen, Mao-Lin Chen, Chuan Xu, Xitang Qian, Dong-Ming Sun, Xiu-Liang Ma, Hui-Ming Cheng, Wencai Ren
Monolayer circular graphene platelets with a grain structure gradient in the radial direction are synthesized by chemical vapor deposition on immiscible W-Cu substrates. Because of the different interactions and growth behaviors of graphene on Cu and tungsten carbide, such substrates cause the formation of grain size and orientation gradients through the competition between Cu and tungsten carbide in graphene growth.
February 27, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28198415/quick-and-inexpensive-paraffin-embedding-method-for-dynamic-bone-formation-analyses
#9
Amy Porter, Regina Irwin, Josselyn Miller, Daniel J Horan, Alexander G Robling, Laura R McCabe
We have developed a straightforward method that uses paraffin-embedded bone for undemineralized thin sectioning, which is amenable to subsequent dynamic bone formation measurements. Bone has stiffer material properties than paraffin, and therefore has hereforto usually been embedded in plastic blocks, cured and sectioned with a tungsten carbide knife to obtain mineralized bone sections for dynamic bone formation measures. This process is expensive and requires special equipment, experienced personnel, and time for the plastic to penetrate the bone and cure...
February 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28196769/nanoparticles-of-wc-co-wc-co-and-cu-of-relevance-for-traffic-wear-particles-particle-stability-and-reactivity-in-synthetic-surface-water-and-influence-of-humic-matter
#10
Yolanda S Hedberg, Jonas F Hedberg, Sara Isaksson, Nanxuan Mei, Eva Blomberg, Susanna Wold, Inger Odnevall Wallinder
Studded tyres made of tungsten carbide cobalt (WC-Co) are in the Northern countries commonly used during the winter time. Tungsten (W)-containing nano- and micron-sized particles have been detected close to busy roads in several European countries. Other typical traffic wear particles consist of copper (Cu). The aims of this study were to investigate particle stability and transformation/dissolution properties of nanoparticles (NPs) of WC-Co compared with NPs of tungsten carbide (WC), cobalt (Co), and Cu. Their physicochemical characteristics (primarily surface oxide and charge) are compared with their extent of sedimentation and metal release in synthetic surface water (SW) with and without two different model organic molecules, 2,3- and 3,4-dihydroxybenzoic acid (DHBA) mimicking certain sorption sites of humic substances, for time periods up to 22 days...
February 11, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28153158/assessing-adhesive-remnant-removal-and-enamel-damage-with-ultraviolet-light-an-in-vitro-study
#11
Alexandre Antonio Ribeiro, Layene Figueiredo Almeida, Lidia Parsekian Martins, Renato Parsekian Martins
INTRODUCTION: Our objective was to assess the amounts of adhesive remnant and enamel damage when removing composite under conventional lighting and ultraviolet (UV) light. METHODS: Thirty-eight premolars were divided into 2 groups according to the lighting used for adhesive removal. A multifluted tungsten-carbide bur at low speed was used for this process in both groups. The UV group received conventional lighting associated with UV light, and the conventional group received conventional lighting only...
February 2017: American Journal of Orthodontics and Dentofacial Orthopedics
https://www.readbyqxmd.com/read/28093092/evaluation-of-analysis-conditions-for-laser-pulsed-atom-probe-tomography-example-of-cemented-tungsten-carbide
#12
Zirong Peng, Pyuck-Pa Choi, Baptiste Gault, Dierk Raabe
Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition...
January 17, 2017: Microscopy and Microanalysis
https://www.readbyqxmd.com/read/28068063/porous-iron-tungsten-carbide-electrocatalyst-with-high-activity-and-stability-toward-oxygen-reduction-reaction-from-the-self-assisted-synthetic-mechanism-to-its-active-species-probing
#13
Li Song, Tao Wang, Yilin Wang, Hairong Xue, Xiaoli Fan, Hu Guo, Wei Xia, Hao Gong, Jianping He
We synthesized a novel nonprecious metal electrocatalyst by pyrolysis of a colloid mixture consisting of a tungsten source and phenolic resin, with the simultaneous addition of ferric salt. The rationally designed electrocatalyst has a unique structure, with nanosized WC and Fe3W3C uniformly dispersed in a three-dimensional porous carbon framework. WC, which was thought difficult to produce, is successfully prepared at a relatively low temperature of about 750 °C at an inert atmosphere. XRD studies demonstrate the self-assisted effect of Fe, which accelerates the formation of WC, getting around the pathway of direct carbonaceous reduction of tungsten by carbon...
February 1, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28040908/low-temperature-system-for-a-large-volume-multi-anvil-press
#14
Richard A Secco, Wenjun Yong
A new custom-designed system for a 3000 ton multi-anvil press has been developed to reach temperatures below room temperature at high pressures. The system was designed to remove heat selectively and conductively from the sample volume through six of the eight tungsten carbide (WC) cubes in direct contact with the octahedral pressure cell. The key components of the system include Cu cooling fins sandwiched between neighboring cube faces and the connected Cu heat exchange chamber through which liquid nitrogen flows...
December 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28025444/histological-evaluation-of-three-techniques-for-caries-removal
#15
Etienne Medioni, Jean-Paul Rocca, Carlo Fornaini, Elisabetta Merigo
A number of concepts and devices have been proposed for caries removal. Among these, the Er:YAG laser is a potential alternative to conventional mechanical treatment. This study compared the effectiveness of the Er:YAG laser with that of low-speed rotary instruments for removal of carious tissue in 26 extracted human molars and premolars with severe decay (i.e., large occlusal or proximal decay but no pulpal contact). The teeth were divided into three groups of eight teeth, and two teeth were used as controls...
2016: Journal of Oral Science
https://www.readbyqxmd.com/read/28025073/nano-and-microstructured-model-carrier-surfaces-to-alter-dry-powder-inhaler-performance
#16
Niklas Renner, Hartwig Steckel, Nora Urbanetz, Regina Scherließ
The present study investigates the effect of different carrier surface modifications on the aerosolisation performance and on the effective carrier payload of interactive blends for inhalation. Two different active pharmaceutical ingredients (APIs) were used: Formoterol fumarate dihydrate (FF) and budesonide (BUD). Blends were prepared with glass beads as model carriers which have been subjected to mechanical surface modifications in order to introduce surface roughness via treatment with hydrofluoric acid (HF) and/or milling with tungsten carbide (TC)...
December 23, 2016: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/27998144/electronic-structure-and-band-gap-of-fullerenes-on-tungsten-surfaces-transition-from-a-semiconductor-to-a-metal-triggered-by-annealing
#17
Ehsan Monazami, John B McClimon, James Rondinelli, Petra Reinke
The understanding and control of molecule-metal interfaces is critical to the performance of molecular electronics and photovoltaics devices. We present a study of the interface between C60 and W, which is a carbide-forming transition metal. The complex solid-state reaction at the interface can be exploited to adjust the electronic properties of the molecule layer. Scanning tunneling microscopy/spectroscopy measurements demonstrate the progression of this reaction from wide band gap (>2.5 eV) to metallic molecular surface during annealing from 300 to 800 K...
December 21, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27942214/nanotoxicity-emerging-concerns-regarding-nanomaterial-safety-and-occupational-hard-metal-wc-co-nanoparticle-exposure
#18
REVIEW
Andrea L Armstead, Bingyun Li
As the number of commercial and consumer products containing engineered nanomaterials (ENMs) continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no "standardized" approach used to assess ENM toxicity in the research community...
2016: International Journal of Nanomedicine
https://www.readbyqxmd.com/read/27933842/biomass-derived-porous-fe3c-tungsten-carbide-graphitic-carbon-nanocomposite-for-efficient-electrocatalysis-of-oxygen-reduction
#19
Ming Ma, Shijie You, Wei Wang, Guoshuai Liu, Dianpeng Qi, Xiaodong Chen, Jiuhui Qu, Nanqi Ren
The oxygen-reduction reaction (ORR) draws an extensive attention in many applications, and there is a growing interest to develop effective ORR electrocatalysts. Iron carbide (Fe3C) is a promising alternative to noble metals (e.g., platinum), but its performances need further improvement, and the real role of the Fe3C phase remains unclear. In this study, we synthesize Fe3C/tungsten carbide/graphitic carbon (Fe3C/WC/GC) nanocomposites, with waste biomass (i.e., pomelo peel) serving as carbon source, using a facile, one-step carbon thermal-reduction method...
November 30, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27925316/functional-species-encapsulated-in-nitrogen-doped-porous-carbon-as-a-highly-efficient-catalyst-for-the-oxygen-reduction-reaction
#20
Li Song, Tao Wang, Yiou Ma, Hairong Xue, Hu Guo, Xiaoli Fan, Wei Xia, Hao Gong, Jianping He
The scarcity, high cost, and poor stability of precious metal-based electrocatalysts have stimulated the development of novel non-precious metal catalysts for the oxygen reduction reaction (ORR) for use in fuel cells and metal-air batteries. Here, we fabricated in situ a hybrid material (Co-W-C/N) with functional species (tungsten carbide and cobalt nanoparticles) encapsulated in an N-doped porous carbon framework, through a facile multi-constituent co-assembly method combined with subsequent annealing treatment...
December 7, 2016: Chemistry: a European Journal
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