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Tungsten carbide

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https://www.readbyqxmd.com/read/27877859/self-lubricating-low-friction-wear-resistant-al-based-quasicrystalline-coatings
#1
Bruno Alessandro Silva Guedes de Lima, Rodinei Medeiros Gomes, Severino Jackson Guedes de Lima, Diana Dragoe, Marie-Geneviève Barthes-Labrousse, Richard Kouitat-Njiwa, Jean-Marie Dubois
After gas atomization, a quasicrystalline powder based on aluminium was used to prepare a thick coating by high-velocity oxygen-fuel flame torch spraying. This layer was deposited on top of a bond-coat layer on a steel plate. A post-spraying annealing treatment turned the two layers to their stable state, a γ-brass crystal and an icosahedral quasicrystal, respectively. The projection parameters were selected in such a way that the coating behaved like a self-lubricating material, which offered very good wear resistance (duration of pin-on-disk tests superior to 5 km with negligible material loss) and low friction (µ ≤ 6% against sintered tungsten carbide), in contrast to the state of the art...
2016: Science and Technology of Advanced Materials
https://www.readbyqxmd.com/read/27877856/a-simple-synthesis-method-for-nanostructured-co-wc-carbon-composites-with-enhanced-oxygen-reduction-reaction-activity
#2
Jun Kang, Hye-Min Kim, Nagahiro Saito, Myeong-Hoon Lee
Co nanoparticles (Co NPs) and nanoscale tungsten carbide (WC) are successfully synthesized simultaneously with mesoporous structured carbon black (C) using an innovative simple method, which is known as solution plasma processing (SPP), and NPs are also loaded onto carbon black at the same time by SPP. The introduction of Co NPs led to not only superior oxygen reduction reaction (ORR) activity in terms of onset potential and peak potential, but also to a more efficient electron transfer process compared to that of pure WC...
2016: Science and Technology of Advanced Materials
https://www.readbyqxmd.com/read/27871710/microbiological-assessment-of-aerosol-generated-during-debond-of-fixed-orthodontic-appliances
#3
Michael Dawson, Valeria Soro, David Dymock, Robert Price, Helen Griffiths, Tom Dudding, Jonathan R Sandy, Anthony J Ireland
INTRODUCTION: The aims of this study were to describe bacterial load and diversity of the aerosol created during enamel cleanup after the removal of fixed orthodontic appliances and to assess the effect of a preprocedural mouth rinse. METHODS: The study involved the sampling of ambient air adjacent to the patient's mouth during adhesive removal using a slow-speed handpiece and a spiral fluted tungsten carbide bur without water irrigation. Sampling was carried out during enamel cleanup with or without a preprocedural mouth rinse of either sterile water or chlorhexidine...
November 2016: American Journal of Orthodontics and Dentofacial Orthopedics
https://www.readbyqxmd.com/read/27863130/valorization-of-lignin-to-simple-phenolic-compounds-over-tungsten-carbide-impact-of-lignin-structure
#4
Changzhi Li, Haiwei Guo, Bo Zhang, Tao Dai, Zaojuan Qi, Aiqin Wang, Tao Zhang, Jianwei Ji
Lignins isolated from representative hardwood, softwood and grass materials, were effectively hydrocracked to aromatics catalyzed by W2C/AC. The effects of botanical species and fractionation methods on lignin structure and the activity of tungsten carbide were detailed studied. GPC, FT-IR, elemental analysis, 2D HSQC NMR showed that all the extracted samples shared the basic skeleton of lignin, whereas the fractionation method significantly affected the structure. Organosolv process provided lignin with structure more similar to the native lignin, which was liable to be depolymerized by W2C/AC catalyst...
November 10, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27828342/ultrafast-particle-plasmon-enhancement-by-energy-band-modification-in-nanostructured-tungsten-carbide
#5
Xinping Zhang, Haibin Wang, Meng Wang, Yuanhai Lin, Xiaoyan Song
Ultrafast optical excitation induced transient modification on the energy-band structures in tungsten, which resulted in the expansion and shift toward the Fermi-level of d-band. This process led to enhanced interband transitions at reduced photon energies. Meanwhile, enhanced interband excitation led to increased electron density above the Fermi level, resulting in enhanced optical scattering by localized surface plasmon resonance (LSPR). These mechanisms are responsible for balancing the direct heating of bulk electrons by optical pulses...
October 3, 2016: Optics Express
https://www.readbyqxmd.com/read/27825213/fabrication-of-electrocatalytic-ta-nanoparticles-by-reactive-sputtering-and-ion-soft-landing
#6
Grant E Johnson, Trevor Moser, Mark Engelhard, Nigel D Browning, Julia Laskin
About 40 years ago, it was shown that tungsten carbide exhibits similar catalytic behavior to Pt for certain commercially relevant reactions, thereby suggesting the possibility of cheaper and earth-abundant substitutes for costly and rare precious metal catalysts. In this work, reactive magnetron sputtering of Ta in the presence of three model hydrocarbons (2-butanol, heptane, and m-xylene) combined with gas aggregation and ion soft landing was employed to prepare organic-inorganic hybrid nanoparticles (NPs) on surfaces for evaluation of catalytic activity and durability...
November 7, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/27791336/tungsten-carbide-a-remarkably-efficient-catalyst-for-the-selective-cleavage-of-lignin-c-o-bonds
#7
Haiwei Guo, Bo Zhang, Changzhi Li, Chang Peng, Tao Dai, Haibo Xie, Aiqin Wang, Tao Zhang
A remarkably effective method for the chemoselective cleavage of the C-O bonds of typical β-O-4 model compounds and the deconstruction of lignin feedstock was developed by using tungsten carbide as the catalyst. High yields of C-O cleavage products (up to 96.8 %) from model compounds and liquid oils (up to 70.7 %) from lignin feedstock were obtained under low hydrogen pressure (0.69 MPa) in methanol. The conversion efficiency was determined to a large extent by solvent effects and was also affected by both the electronic and steric effects of the lignin model compounds...
November 23, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27761343/effect-of-orthodontic-debonding-and-residual-adhesive-removal-on-3d-enamel-microroughness
#8
Joanna Janiszewska-Olszowska, Robert Tomkowski, Katarzyna Tandecka, Piotr Stepien, Tomasz Szatkiewicz, Katarzyna Sporniak-Tutak, Katarzyna Grocholewicz
BACKGROUND: Termination of fixed orthodontic treatment is associated with bracket debonding and residual adhesive removal. These procedures increase enamel roughness to a degree that should depend on the tool used. Enamel roughening may be associated with bacterial retention and staining. However, a very limited data exists on the alteration of 3D enamel roughness resulting from the use of different tools for orthodontic clean-up. AIMS: 1. To perform a precise assessment of 3D enamel surface roughness resulting from residual adhesive removal following orthodontic debonding molar tubes...
2016: PeerJ
https://www.readbyqxmd.com/read/27736967/accuracy-of-gypsum-casts-after-different-impression-techniques-and-double-pouring
#9
Stephania Caroline Rodolfo Silva, Aion Mangino Messias, Filipe de Oliveira Abi-Rached, Raphael Freitas de Souza, José Maurício Dos Santos Nunes Reis
This study evaluated the accuracy of gypsum casts after different impression techniques and double pouring. Ten patients were selected and for each one it was obtained 5 partial putty/wash impressions with vinyl polysiloxane (VPS) material from teeth #13 to #16 with partial metal stock trays. The following techniques were performed: (1) one-step; two-step relief with: (2) PVC film; (3) slow-speed tungsten carbide bur and scalpel blade, (4) small movements of the tray and (5) without relief-negative control...
2016: PloS One
https://www.readbyqxmd.com/read/27722059/microindentation-hardness-and-calcium-phosphorus-ratio-of-dentin-following-excavation-of-dental-caries-lesions-with-different-techniques
#10
Gunseli Katirci, R Banu Ermis
BACKGROUND: The aim of this in vitro study was to evaluate the microindentation hardness and chemical composition of residual dentin left at the cavity bottom following removal of carious dentin using the Carisolv chemomechanical and Er:YAG laser caries excavation methods in comparison with the conventional tungsten-carbide bur excavation. METHODS: Sixty-nine extracted permanent teeth with occlusal dentin caries were assigned into three groups according to caries removal technique...
2016: SpringerPlus
https://www.readbyqxmd.com/read/27718543/a-robust-versatile-hybrid-electrocatalyst-for-the-oxygen-reduction-reaction
#11
Kun Wang, Yi Wang, Yexiang Tong, Zhangweihao Pan, Shuqin Song
Identifying non-precious-metal catalysts with desirable over-all performance for oxygen reduction reaction (ORR) in either acidic or basic media is still a bottleneck. Here, a hybrid material is reported, in which tungsten carbide (WC) and ferberite (FeWO4) are attached to the Fe and N dual-doped ordered mesoporous carbon (WC-FeWO4@FeN-OMC), as a superior performance catalyst for the ORR in either acidic or basic media. In comparison with the frequently used Pt/C ORR catalyst (20 wt.%), our hybrid materials exhibit comparable electrocatalytic activity mainly via a 4e ORR process, better stability, and totally tolerance to methanol in either acidic or basic media...
October 10, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27666123/lasers-for-caries-removal-in-deciduous-and-permanent-teeth
#12
Alessandro Montedori, Iosief Abraha, Massimiliano Orso, Potito Giuseppe D'Errico, Stefano Pagano, Guido Lombardo
BACKGROUND: Despite considerable improvements in oral health, dental caries continue to be a public health issue. The most frequently used, and universally accepted technique, to remove caries is through mechanical ablation of decayed tissues by means of rotating drills (diamond or tungsten carbide, or both). In the past few decades, the introduction of adhesive filling materials (resin composites) has affected cavity filling procedures by reducing its retention needs, with advantages for dental tissue conservation...
September 26, 2016: Cochrane Database of Systematic Reviews
https://www.readbyqxmd.com/read/27664322/testing-in-artificial-sweat-is-less-more-comparison-of-metal-release-in-two-different-artificial-sweat-solutions
#13
Klara Midander, Anneli Julander, Jolinde Kettelarij, Carola Lidén
Metal release from materials immersed in artificial sweat can function as a measure of potential skin exposure. Several artificial sweat models exist that, to various degree, mimic realistic conditions. Study objective was to evaluate metal release from previously examined and well characterized materials in two different artificial sweat solutions; a comprehensive sweat model intended for use within research, based on the composition of human sweat; and the artificial sweat, EN1811, intended for testing compliance with the nickel restriction in REACH...
November 2016: Regulatory Toxicology and Pharmacology: RTP
https://www.readbyqxmd.com/read/27642198/3d-woven-fiber-reinforced-composite-for-cad-cam-dental-application
#14
Richard Petersen, Perng-Ru Liu
Three-dimensional (3D)-woven noncrimp fiber-reinforced composite (FRC) was tested for mechanical properties in the two principal directions of the main XY plane and compared to different Computer-Aided-Design/Computer-Aided-Machining (CAD/CAM) Dental Materials. The Dental Materials included ceramic with Vitablock Mark II®, ProCAD®, InCeram® Spinel, InCeram® Alumina and InCeram® Zirconia in addition to a resin-based 3M Corp. Paradigm® particulate-filled composite. Alternate material controls included Coors 300 Alumina Ceramic and a tungsten carbide 22% cobalt cermet...
May 2016: SAMPE Journal
https://www.readbyqxmd.com/read/27609195/reinforcement-of-tungsten-carbide-grains-by-nanoprecipitates-in-cemented-carbides
#15
Xingwei Liu, Xiaoyan Song, Haibin Wang, Chao Hou, Xuemei Liu, Xilong Wang
In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales...
October 14, 2016: Nanotechnology
https://www.readbyqxmd.com/read/27573186/core-shell-structured-tungsten-carbide-encapsulated-within-nitrogen-doped-carbon-spheres-for-enhanced-hydrogen-evolution
#16
Lei Han, Miao Xu, Yujie Han, You Yu, Shaojun Dong
It is highly desirable and remains a great challenge to develop alternative hydrogen evolution reaction (HER) electrocatalysts that are low-cost, highly efficient, and exhibit excellent stability. In this work, we report the synthesis of tungsten carbide nanocrystallites encapsulated within nitrogen-doped carbon (TCNC) spheres through in situ polymerization of dopamine with metatungstate followed by carburization under an inert atmosphere. During the in situ and confined carburization process, very small tungsten carbide nanocrystallites are obtained and uniformly dispersed in the simultaneously generated carbon matrix...
October 6, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27506268/2d-nanostructures-for-water-purification-graphene-and-beyond
#17
REVIEW
Saoirse Dervin, Dionysios D Dionysiou, Suresh C Pillai
Owing to their atomically thin structure, large surface area and mechanical strength, 2D nanoporous materials are considered to be suitable alternatives for existing desalination and water purification membrane materials. Recent progress in the development of nanoporous graphene based materials has generated enormous potential for water purification technologies. Progress in the development of nanoporous graphene and graphene oxide (GO) membranes, the mechanism of graphene molecular sieve action, structural design, hydrophilic nature, mechanical strength and antifouling properties and the principal challenges associated with nanopore generation are discussed in detail...
August 18, 2016: Nanoscale
https://www.readbyqxmd.com/read/27455506/a-novel-phantom-and-procedure-providing-submillimeter-accuracy-in-daily-qa-tests-of-accelerators-used-for-stereotactic-radiosurgery
#18
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...
2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/27399154/combined-photoemission-spectroscopy-and-electrochemical-study-of-a-mixture-of-oxy-carbides-as-potential-innovative-supports-and-electrocatalysts
#19
Laura Calvillo, Carlos Valero-Vidal, Stefano Agnoli, Hikmet Sezen, Celine Rüdiger, Julia Kunze-Liebhäuser, Gaetano Granozzi
Active and stable non-noble metal materials, able to substitute Pt as catalyst or to reduce the Pt amount, are vitally important for the extended commercialization of energy conversion technologies, such as fuel cells and electrolyzers. Here, we report a fundamental study of nonstoichiometric tungsten carbide (WxC) and its interaction with titanium oxycarbide (TiOxCy) under electrochemical working conditions. In particular, the electrochemical activity and stability of the WxC/TiOxCy system toward the ethanol electrooxidation reaction (EOR) and hydrogen evolution reaction (HER) are investigated...
August 3, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27370464/alternating-current-calorimeter-for-specific-heat-capacity-measurements-at-temperatures-below-10-k-and-pressures-up-to-10-gpa
#20
Kazunori Umeo
A developed alternating current calorimeter for measuring the absolute value of specific heat C of a very small sample under a pressure up to 10 GPa and low temperature below 10 K is described. A Bridgman anvil cell made of tungsten carbide with a top diameter of 3 mm is used. A hollow at the top prevents expansion of the sample space over the anvil top. Two chip resistors, which act as a thermometer and a heater, are mounted on the outer part of a copper-beryllium gasket with a frying pan-like shape. Thus, the thermometer is not pressurized...
June 2016: Review of Scientific Instruments
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