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Tungsten carbide

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https://www.readbyqxmd.com/read/28871118/durable-and-self-hydrating-tungsten-carbide-based-composite-polymer-electrolyte-membrane-fuel-cells
#1
Weiqing Zheng, Liang Wang, Fei Deng, Stephen A Giles, Ajay K Prasad, Suresh G Advani, Yushan Yan, Dionisios G Vlachos
Proton conductivity of the polymer electrolyte membranes in fuel cells dictates their performance and requires sufficient water management. Here, we report a simple, scalable method to produce well-dispersed transition metal carbide nanoparticles. We demonstrate that these, when added as an additive to the proton exchange Nafion membrane, provide significant enhancement in power density and durability over 100 hours, surpassing both the baseline Nafion and platinum-containing recast Nafion membranes. Focused ion beam/scanning electron microscope tomography reveals the key membrane degradation mechanism...
September 4, 2017: Nature Communications
https://www.readbyqxmd.com/read/28869256/regioselective-hydrogenolysis-of-aryl-ether-c-o-bonds-by-tungsten-carbides-with-controlled-phase-compositions
#2
Huihuang Fang, Junmou Du, Chenchen Tian, Jianwei Zheng, Xinping Duan, Linmin Ye, Youzhu Yuan
Evenly dispersed tungsten carbides with controlled phase compositions that exhibit an impressive capacity to carry out the regioselective hydrogenolysis of inert aryl ether C-O bonds instead of aliphatic C-O bonds to produce aromatic compounds are reported.
September 14, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28843405/intracanal-temperature-changes-during-bone-preparations-close-to-and-penetrating-the-inferior-alveolar-canal-drills-versus-piezosurgery
#3
József Szalma, László Vajta, Edina Lempel, Ákos Tóth, Sára Jeges, Lajos Olasz
PURPOSE: The aim of this in vitro study was to investigate temperature increases in the inferior alveolar canal (IAC), when different bone preparation methods approximate and penetrate the IAC. MATERIALS AND METHODS: In pig mandible, buccal bone removals were performed until the neurovascular bundle became visible. Temperatures were registered with thermocouple probes and with infrared thermometer. Preparations were performed with diamond drills (DD), tungsten carbide drills (TCD), piezoelectric diamond sphere (PT_D) and saw (PT_S) tips, and a combined preparation method was also performed whereby the superficial three-fourths of the bone was removed with TCD and the deepest one-fourth of the bone with PT_D (TCD + PT_D_7 °C) or PT_S (TCD + PT_S_7 °C), using cooled irrigation (7 °C)...
July 27, 2017: Journal of Cranio-maxillo-facial Surgery
https://www.readbyqxmd.com/read/28832019/anisotropic-electrical-transport-of-flexible-tungsten-carbide-nanostructures-towards-nanoscale-interconnects-and-electron-emitters
#4
Bo Sun, Yong Sun, Chengxin Wang
Although hard tungsten carbide (WC) alloys are widely used for mechanical purposes, their electric properties have been seldom investigated. We report here that low-dimensional WC nanostructures can be integrated in such a way as to reveal novel electrical behavior and flexibility. From a mechanical perspective, novel dislocation migration was observed in bent nanosheets arising from local stress relaxation, which indicates the disappearance of the Peierls-Nabarro barrier. Some of these mobile dislocations were reversible,while other sessile dislocations were inclined to react with each other to cause plastic deformation...
August 23, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28821121/reductive-mineralization-of-cellulose-with-vanadium-iron-and-tungsten-chlorides-and-access-to-mxoy-metal-oxides-and-mxoy-c-metal-oxide-carbon-composites
#5
Aurélien Henry, Peter Hesemann, Johan G Alauzun, Bruno Boury
MxOy and MxOy/C composites (M=V, Fe and W) were obtained by mineralization of cellulose with several metal chlorides. Cellulose was used both as a templating agent and as an oxygen and a carbon source. Soluble chloride molecules (VOCl3 and WCl6) and a poorly soluble ionic chloride compound (FeCl3) were chosen as metal oxide precursors. In a first time, primary metal oxide/cellulose composites were obtained via a thermal treatment by reacting urea impregnated filter paper with the corresponding metal chlorides in an autoclave at 150°C after 3days...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28808462/temperature-rises-in-the-pulp-chamber-with-different-techniques-of-orthodontic-adhesive-removal
#6
Maurício Barbieri Mezomo, Juliana Abreu, Juliana Weber, Renato Dalla Porta Garcia, José Antônio Poli Figueiredo, Eduardo Martinelli de Lima
INTRODUCTION: The aim of this in vitro study was to compare the temperature rises in the pulp chamber and time spent with different techniques for orthodontic resin adhesive removal. METHODS AND MATERIALS: Adhesive removal was performed in 20 extracted human maxillary second premolars with five techniques: high-speed tungsten carbide burs with water-cooling (BurH-cool) and without cooling (BurH), low-speed carbide burs (BurL), low-speed aluminum-oxide discs (DiscL), and low-speed fiberglass burs (BurFGL)...
2017: Iranian Endodontic Journal
https://www.readbyqxmd.com/read/28803468/functional-multi-nanolayer-coatings-of-amorphous-carbon-tungsten-carbide-with-exceptional-mechanical-durability-and-corrosion-resistance
#7
Narguess Nemati, Mansoor Bozorg, Oleksiy V Penkov, Dong-Gap Shin, Asghar Sadighzadeh, Dae-Eun Kim
A novel functional multilayer coating with periodically stacked nanolayers of amorphous carbon (a:C)/ tungsten carbide (WC) and an adhesion layer of chromium (Cr) was deposited on 304 stainless steel using a dual magnetron sputtering technique. Through process optimization, highly densified coatings with high elasticity and shear moduli, excellent wear resistance, as well as minimal susceptibility to corrosive and caustic media could be acquired. The structural and mechanical properties of the optimized coatings were studied in detail by a variety of techniques...
August 14, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28774124/fabrication-of-fe-based-diamond-composites-by-pressureless-infiltration
#8
Meng Li, Youhong Sun, Qingnan Meng, Haidong Wu, Ke Gao, Baochang Liu
A metal-based matrix is usually used for the fabrication of diamond bits in order to achieve favorable properties and easy processing. In the effort to reduce the cost and to attain the desired bit properties, researchers have brought more attention to diamond composites. In this paper, Fe-based impregnated diamond composites for drill bits were fabricated by using a pressureless infiltration sintering method at 970 °C for 5 min. In addition, boron was introduced into Fe-based diamond composites. The influence of boron on the density, hardness, bending strength, grinding ratio, and microstructure was investigated...
December 12, 2016: Materials
https://www.readbyqxmd.com/read/28765598/synthesis-and-multi-scale-tribological-behavior-of-wc-co-nanodiamond-nanocomposites
#9
Andy Nieto, Lin Jiang, Jaekang Kim, Dae-Eun Kim, Julie M Schoenung
Nanodiamonds (ND) present a unique combination of desirable mechanical, functional, and chemical characteristics that are ideally suited for reinforcing and enhancing the wear resistance of carbide based materials. Tungsten carbide cobalt (WC-Co) matrix nanocomposites reinforced with varying amounts of ND (2 - 10 vol.%) were synthesized here by spark plasma sintering. The rapid thermal consolidation route enabled attainment of dense samples with a significant retention of the metastable diamond phase. NDs affected the microstructural evolution, chemistry, and mechanical properties of WC-Co...
August 1, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28747641/evolution-of-phase-microstructure-and-zrc-lattice-parameter-in-solid-solution-treated-w-zrc-composite
#10
Peng Jia, Lei Chen, Jiancun Rao, Yujin Wang, Qingchang Meng, Yu Zhou
Zirconium carbide (ZrC) reinforced tungsten (W) composite was hot-pressed at 2200 °C for 1 h in vacuum, which was subsequently heat treated in the temperature range of 2200 to 2500 °C for 1.5 or 2 h. The relative ratios of ZrC phase were 21.0, 23.3 and 25.9 mol.% for the mixture of starting powders, composites sintered for 1 h and solid-solution treated at 2500 °C for 1.5 h, respectively. The solid solubility of W in ZrC increased with the increment in heat-treating temperature and time to a maximum value of 18...
July 26, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28688246/compact-shielding-design-of-a-portable-241-am-be-source
#11
Feng Zhang, He Wu, Xinguang Wang, Guoli Wu, Wenbao Jia, Yongzhou Ti
A compact shielding tank for portable (241)Am-Be neutron source, which is used in nuclear well logging, was designed according to the Monte Carlo simulation. From inner to outer, the proposed tank has two shielding layers to shield the high- and low-energy neutrons. In this study, the shielding properties of several materials were evaluated. Tungsten was selected as the neutron moderator to build the inner layer. The thermal neutron absorber in the outer layer was made of polyethylene containing 1.2% boron carbide...
June 23, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28665836/mortality-among-hardmetal-production-workers-a-retrospective-cohort-study-in-the-austrian-hardmetal-industry
#12
Peter Wallner, Michael Kundi, Hanns Moshammer, Sarah D Zimmerman, Jeanine M Buchanich, Gary M Marsh
OBJECTIVE: This study retrospectively investigates causes of death among workers of a hardmetal plant in Austria. METHODS: A retrospective cohort was formed of 1965 workers still employed in or after 1970. Follow-up was until end of 2014 based on national databases. Cobalt exposure was assessed through industrial hygiene data and urine analyses. Cox proportional hazards models were calculated for selected causes of death. RESULTS: During 45,598 years of observation in total 177 deaths were observed...
June 29, 2017: Journal of Occupational and Environmental Medicine
https://www.readbyqxmd.com/read/28644384/characterisation-of-the-chemical-composition-and-structural-features-of-novel-antimicrobial-nanoparticles
#13
Yuen-Ki Cheong, Jesus Calvo-Castro, Lena Ciric, Mohan Edirisinghe, Elaine Cloutman-Green, Upulitha Eranka Illangakoon, Qiang Kang, Suntharavathanan Mahalingam, Rupy Kaur Matharu, Rory M Wilson, Guogang Ren
Three antimicrobial nanoparticle types (AMNP0, AMNP1, and AMNP2) produced using the Tesima(TM) thermal plasma technology were investigated and their compositions were determined using a combination of analytical methods. Scanning electron micrographs provided the morphology of these particles with observed sizes ranging from 10 to 50 nm, whilst FTIR spectra confirmed the absence of polar bonds and organic impurities, and strong Raman active vibrational bands at ca. 1604 and 1311 cm(-1) ascribed to C-C vibrational motions were observed...
June 23, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28622725/self-supported-biocarbon-fiber-electrode-decorated-with-molybdenum-carbide-nanoparticles-for-highly-active-hydrogen-evolution-reaction
#14
Jian Xiao, Yan Zhang, Zheye Zhang, Qiying Lv, Feng Jing, Kai Chi, Shuai Wang
Devising and facilely synthesizing an efficient noble metal-free electrocatalyst for the acceleration of the sluggish kinetics in the hydrogen-evolution reaction (HER) is still a big challenge for electrolytic water splitting. Herein, we present a simple one-step approach for constructing self-supported biocarbon-fiber cloth decorated with molybdenum carbide nanoparticles (BCF/Mo2C) electrodes by a direct annealing treatment of the Mo oxyanions loaded cotton T-shirt. The Mo2C nanoparticles not only serve as the catalytic active sites toward the HER but also enhance the hydrophilicity and conductivity of resultant electrodes...
July 12, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28614933/-study-on-the-establishment-of-hmld-model-and-the-expression-of-kl-6-tgf-beta-in-rat
#15
Z S Zhang, Y F Zhao, L Tang, H K Xie, D Y Sun
Objective: To establish an animal model of hard metal lung disease (HMLD) in rats, and to screen the indications for diagnosis of HMLD. Methods: The rats were randomly divided into 5 groups, each group included 8 rats: saline group, pure cobalt group, pure tungsten carbide group, silica group and hard metal (HM) group. 10 mg subjects were administered in each group by using the pulmonary endotracheal tube. After 8 week, the lung CT scan and lung tissue pathology were observed, the serum and bronchoalveolar lavage fluid (BALF) were collected for KL-6, TGF-beta1 and TGF-beta2...
April 20, 2017: Chinese Journal of Industrial Hygiene and Occupational Diseases
https://www.readbyqxmd.com/read/28594463/ultralarge-bending-strain-and-fracture-resistance-investigation-of-tungsten-carbide-nanowires
#16
Yong Sun, Yanmao Chen, Hao Cui, Jing Wang, Chengxin Wang
Hard tungsten carbide (WC) with brittle behavior is frequently applied for mechanical purposes. Here, ultralarge elastic bending deformation is reported in defect-rare WC [0001] nanowires; the tested bending strain reaches a maximum of 20% ± 3.33%, which challenges the traditional understanding of this material. The lattice analysis indicates that the dislocations are confined to the inner part of the WC nanowires. First, the high Peierls-Nabarro barrier hinders the movement of the locally formed dislocations, which causes rapid dislocation aggregation and hinders long-range glide, resulting in a dense distribution of the dislocation network...
June 8, 2017: Small
https://www.readbyqxmd.com/read/28544178/transition-metal-nitride-core-noble-metal-shell-nanoparticles-as-highly-co-tolerant-catalysts
#17
Aaron Garg, Maria Milina, Madelyn Ball, Daniela Zanchet, Sean T Hunt, James A Dumesic, Yuriy Román-Leshkov
Core-shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core-shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO...
May 25, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28521771/cancer-incidence-among-finnish-male-cobalt-production-workers-in-1969-2013-a-cohort-study
#18
Riitta Sauni, Panu Oksa, Jukka Uitti, Asko Linna, Raimo Kerttula, Eero Pukkala
BACKGROUND: There is inadequate evidence for the carcinogenicity of cobalt and cobalt compounds in humans. Consequently, the International Agency for Research on Cancer (IARC) has evaluated cobalt metal without tungsten carbide as possibly carcinogenic to humans (Group 2B). The aim of the study was to assess the risk of cancer among workers employed in a Finnish cobalt plant since the beginning of production in 1968. METHODS: The study cohort consisted of all males employed by the Finnish cobalt plant for at least a year during 1968-2004...
May 18, 2017: BMC Cancer
https://www.readbyqxmd.com/read/28512535/evaluation-of-surface-roughness-of-enamel-after-various-bonding-and-clean-up-procedures-on-enamel-bonded-with-three-different-bonding-agents-an-in-vitro-study
#19
Amit Goel, Atul Singh, Tarun Gupta, Ramandeep-Singh Gambhir
BACKGROUND: The purpose of this study was to analyze and compare the enamel surface roughness before bonding and after debonding, to find correlation between the adhesive remnant index and its effect on enamel surface roughness and to evaluate which clean-up method is most efficient to provide a smoother enamel surface. MATERIAL AND METHODS: 135 premolars were divided into 3 groups containing 45 premolars in each group. Group I was bonded by using moisture insensitive primer, Group II by using conventional orthodontic adhesive and Group III by using self-etching primer...
May 2017: Journal of Clinical and Experimental Dentistry
https://www.readbyqxmd.com/read/28500790/accuracy-evaluation-of-a-six-degree-of-freedom-couch-using-cone-beam-ct-and-isocal-phantom-with-an-in-house-algorithm
#20
Qinghui Zhang, Joseph Driewer, Shuo Wang, Sicong Li, Xiaofeng Zhu, Dandan Zheng, Yijian Cao, Jiaju Zhang, Abolghassem Jamshidi, Brett W Cox, Jonathan P S Knisely, Louis Potters, Eric E Klein
PURPOSE: The accuracy of a six degree of freedom (6DoF) couch was evaluated using a novel method. METHODS: Cone beam CT (CBCT) images of a 3D phantom (IsoCal) were acquired with different, known combinations of couch pitch and roll angles. Pitch and roll angles between the maximum allowable values of 357 and 3 degrees were tested in one degree increments. A total of 49 combinations were tested at 0 degrees of yaw (couch rotation angle). The 3D positions of 16 tungsten carbide ball bearings (BBs), each 4 mm in diameter and arranged in a known geometry within the IsoCal phantom, were determined in the 49 image sets with in-house software...
August 2017: Medical Physics
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