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Sample records for cemented tungsten carbides

  1. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    PubMed

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    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. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  2. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    NASA Astrophysics Data System (ADS)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    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. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  3. Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

    NASA Astrophysics Data System (ADS)

    Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

    2017-02-01

    A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V ( vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

  4. Effects of laser ablation on cemented tungsten carbide surface quality

    NASA Astrophysics Data System (ADS)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  5. Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons

    SciTech Connect

    Z. Zak Fang, H. Y. Sohn

    2009-03-10

    This report contains detailed information of the research program entitled "Development of Bulk Nanocrystalline Cemented Tungsten Carbide Materials for Industrial Applications". The report include the processes that were developed for producing nanosized WC/Co composite powders, and an ultrahigh pressure rapid hot consolidation process for sintering of nanosized powders. The mechanical properties of consolidated materials using the nanosized powders are also reported.

  6. Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Novotný, K.; Staňková, A.; Häkkänen, H.; Korppi-Tommola, J.; Otruba, V.; Kanický, V.

    2007-12-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation. Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r2 > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r2 = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

  7. Shock propagation in a cemented tungsten carbide

    NASA Astrophysics Data System (ADS)

    Appleby-Thomas, G. J.; Hazell, P. J.; Stennett, C.; Cooper, G.; Helaar, K.; Diederen, A. M.

    2009-03-01

    WC-based ceramic metal composites (cermets) are of great importance in both armor and munition design due to the combination of properties imparted by the presence of two different phases. WC-Co cermets are of interest in this area due to the hardness and strength imparted by the WC phase while the cementing Co matrix acts to increase plasticity and toughness. Here the dynamic response of G13 WC-Co manufactured by Kennametal Engineered Products B.V. was studied via a series of plate impact experiments involving both longitudinal and lateral gauges, which allowed determination of the Us-Up relationship, measurement of a Hugoniot elastic limit of 3.3±0.2 GPa, measurement of a spall strength of 4.38 GPa, and an investigation of the stress dependence of shear strength in such a strong material.

  8. Energy loss mechanics in the erosion of cemented tungsten carbide

    SciTech Connect

    Freinkel, D.M. ); Luyckx, S.B. )

    1989-05-01

    The erosion of tungsten carbide has been studied by several researchers under various conditions: the cobalt content of the cemented carbide has been varied from 4.5 to 11.3 wt % Co, the size of the WC grains varied from 0.9 to 5.1 {mu}m, the size of the erodant particles varied from 30 to 630 {mu}m, the velocity of the particles varied from 30 to 507 m/s, and particle incidence angle varied from 15{degrees} to 90{degrees}. While it is generally agreed that with increasing cobalt content and increasing particle velocity the erosion rate of WC-Co increases, there is disagreement on the effect of grain size and angle of incidence. More work was clearly required to explain this disagreement, thus the present investigation was undertaken. The present work differs from previous experimental work in that the erodant particles are 4 mm average diameter and that the present investigation does not neglect the role of plastic deformation in the erosion process and the energy lost in damage to the erodant particles. These two additional energy loss mechanisms have been found to contribute significantly to the interpretation of the present results and of the results previously reported in the literature.

  9. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    NASA Astrophysics Data System (ADS)

    Li, T.; Lou, Q.; Dong, J.; Wei, Y.; Liu, J.

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm2. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to βWC1-x, then to αW2C and CW3, and finally to W crystal. It is suggested that the undulating `hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation.

  10. Escape of carbon element in surface ablation of cobalt cemented tungsten carbide with pulsed UV laser

    NASA Astrophysics Data System (ADS)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 30 ns XeCl excimer laser. The surface phase transformation on different pulse number of laser shots has been investigated by means of XRD and microphotography as well as AES at laser fluence of 2.5 J/cm 2. The experimental results showed that the phase structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. It is suggested that the formation of non-stoichiometric tungsten carbide should result from the escaping of carbon element due to accumulated heating of surface by pulsed laser irradiation.

  11. Experimental and Analytical Investigation of Cemented Tungsten Carbide Ultra-Short Pulse Laser Ablation

    NASA Astrophysics Data System (ADS)

    Urbina, J. P. Calderón; Daniel, C.; Emmelmann, C.

    Ultra-short pulse laser processing of hard materials, such as cemented tungsten carbide, requires an accurate and agile experimental and analytical investigation to obtain adequate information and setting parameters to maximize ablation rate. Therefore, this study presents a systematic approach which, first, experimentally searches for the variables with the most significant influence on the objective using a design of experiments method; and second, analyzes by means of existing ablation theory the interaction of the material and laser taking into account the Beer-Lambert law and incubation effect.Therefore, this places a basis for future analytical-experimental validation of the examined material.

  12. Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles.

    PubMed

    Stefaniak, Aleksandr B; Virji, M Abbas; Day, Gregory A

    2009-07-01

    As many as 30,000 workers in the United States of America are exposed to cemented tungsten carbides (CTC), alloys composed primarily of tungsten carbide and cobalt, which are used in cutting tools. Inhalation of cobalt-containing particles may be sufficient for the development of occupational asthma, whereas tungsten carbide particles in association with cobalt particles are associated with the development of hard metal disease (HMD) and lung cancer. Historical epidemiology and exposure studies of CTC workers often rely only on measures of total airborne cobalt mass concentration. In this study, we characterized cobalt- and tungsten-containing aerosols generated during the production of CTC with emphasis on (1) aerosol "total" mass (n=252 closed-face 37 mm cassette samples) and particle size-selective mass concentrations (n=108 eight-stage cascade impactor samples); (2) particle size distributions; and (3) comparison of exposures obtained using personal cassette and impactor samplers. Total cobalt and tungsten exposures were highest in work areas that handled powders (e.g., powder mixing) and lowest in areas that handled finished product (e.g., grinding). Inhalable, thoracic, and respirable cobalt and tungsten exposures were observed in all work areas, indicating potential for co-exposures to particles capable of getting deposited in the upper airways and alveolar region of the lung. Understanding the risk of CTC-induced adverse health effects may require two exposure regimes: one for asthma and the other for HMD and lung cancer. All sizes of cobalt-containing particles that deposit in the lung and airways have potential to cause asthma, thus a thoracic exposure metric is likely biologically appropriate. Cobalt-tungsten mixtures that deposit in the alveolar region of the lung may potentially cause HMD and lung cancer, thus a respirable exposure metric for both metals is likely biologically appropriate. By characterizing size-selective and co-exposures as well as

  13. Corrosion resistant cemented carbide

    SciTech Connect

    Hong, J.

    1990-10-16

    This paper describes a corrosion resistant cemented carbide composite. It comprises: a granular tungsten carbide phase, a semi-continuous solid solution carbide phase extending closely adjacent at least a portion of the grains of tungsten carbide for enhancing corrosion resistance, and a substantially continuous metal binder phase. The cemented carbide composite consisting essentially of an effective amount of an anti-corrosion additive, from about 4 to about 16 percent by weight metal binder phase, and with the remaining portion being from about 84 to about 96 percent by weight metal carbide wherein the metal carbide consists essentially of from about 4 to about 30 percent by weight of a transition metal carbide or mixtures thereof selected from Group IVB and of the Periodic Table of Elements and from about 70 to about 96 percent tungsten carbide. The metal binder phase consists essentially of nickel and from about 10 to about 25 percent by weight chromium, the effective amount of an anti-corrosion additive being selected from the group consisting essentially of copper, silver, tine and combinations thereof.

  14. Nucleation and growth of diamond films on Ni-cemented tungsten carbide: Effects of substrate pretreatments

    SciTech Connect

    Polini, R.; Traversa, E. . Dipt. di Scienze e Tecnologie Chimiche); Marcheselli, G. )

    1994-08-01

    The nucleation and growth of diamond films on Ni-cemented carbide is investigated. Substrates made of WC with 6 wt% of Ni were submitted to grinding, and then to different pretreatments (scratching, etching, and/or decarburization) before diamond deposition. Diamond synthesis was carried out by hot-filament chemical vapor deposition (HFCVD) using a mixture of CH[sub 4] (1% v/v) and H[sub 2]. Depositions were performed for different lengths of time with the substrates at various temperatures. The specimens were analyzed before and after deposition by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffractometry (XRD). Raman spectra showed that the phase purity of the diamond films was not affected by the presence of nickel on the substrate surface. After wet etching pretreatments, the nucleation of diamond was enhanced, mainly at the WC grain boundaries. Continuous films were obtained on scratched and etched substrates. The decarburizing treatment led to the formation of metallic tungsten and of brittle nickel-tungsten carbide phases. These phases reacted in the early stages of diamond film formation with gaseous carbon species with a parallel process which competes with stable diamond nucleus formation. The diamond film formed after long-term deposition on these samples was not continuous.

  15. Environmental contamination by cobalt in the vicinity of a cemented tungsten carbide tool grinding plant

    SciTech Connect

    Abraham, J.L.; Hunt, A.

    1995-04-01

    Surface soil and dust samples have been collected from the vicinity of a hard metal (cemented tungsten carbide) tool grinding factory. As a result of poor waste management practices, dusts generated by the grinding operation were, for the most part, swept from the interior of the building onto open ground at the rear of the plant. The potential for contamination of the local environment with cobalt, tungsten, and other metals as a result of dust being either resuspended from the resulting uncontrolled mound of debris or emitted from the factory vents was considerable. Levels of cobalt in local soils were found to be as high as 12,700 mg kg{sup -1}; almost 2000 times higher than the average value for in the United States. Scanning electron microscopy and energy dispersive X-ray microanalysis examination of the waste dust particles revealed that the individual particles were, in general, composites containing variable quantities of tungsten, cobalt, calcium, titanium, and iron. Individual particles in soil samples collected at some distance from the plant were less heterogenous, and fewer particles contained detectable quantities of cobalt. This would suggest that a degree of disassociation had occurred in the soil environment resulting in a mobilization of the cobalt. 31 refs., 5 figs., 2 tabs.

  16. Nucleation and adhesion of diamond films on Co cemented tungsten carbide

    SciTech Connect

    Polini, R.; Santarelli, M.; Traversa, E.

    1999-12-01

    Diamond deposits were grown using hot filament chemical vapor deposition (CVD) on pretreated Co cemented tungsten carbide (WC-Co) substrates with an average grain size of 6 {micro}m. Depositions were performed with 0.5 or 1.0% methane concentration and with substrate temperatures ranging from 750 to 1,000 C. Diamond nucleation densities were measured by scanning electron microscopy. Scratched and bias-enhanced nucleation pretreated substrates showed the larger nucleation densities. Etching of the WC performed by Murakami's reagent, followed by surface-Co dissolution (MP pretreatment), led to a roughened but scarcely nucleating surface. The performance of a scratching prior to the MP pretreatment allowed one to increase the nucleation density, due scratching-induced defects, confined in the outermost layer of WC grains, which act as nucleation sites. Smaller nucleation densities were observed with increasing the substrate temperature and reducing the methane concentration, confirming that diamond nucleates via a heterogeneous process. The adhesion of continuous films was evaluated by the reciprocal of the slope of crack radius-indentation load functions. The substrate pretreatments mainly affected the film adhesion, while the influence of CVD process conditions was minor. The two main factors that improve the diamond film adhesion are the coating-substrate contact area and the surface-Co removal.

  17. Stoichiometric tungsten carbide coatings

    NASA Astrophysics Data System (ADS)

    Hirata, G. A.; Contreras, O.; Farías, M. H.; Cota-Araiza, L.

    1996-07-01

    Filament Assisted Chemical Vapor Deposition (FA-CVD) technique has been used to prepare tungsten carbide (WC) thin films. With this simple technique we obtained polycrystalline and stoichiometric WC coatings deposited on crystalline silicon and on stainless steel substrates. Tungsten carbide coatings were studied with Auger Electron Spectroscopy and Scanning Electron Microscopy.

  18. Effect of Cobalt Content on Microstructures and Wear Resistance of Tungsten Carbide-Cobalt-Cemented Carbides Fabricated by Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Ma, Renqi; Ju, Shaodong; Chen, Haiyan; Shu, Chenyang

    2017-06-01

    We researched tungsten carbide-cobalt (WC-Co)-cemented carbides without binder and with little binder and sintered by spark plasma sintering with 0 wt. %, 0.2 wt. %, 0.5 wt. % and 0.8 wt. % Co at different temperatures. The microstructures, hardness, fracture toughness and wear resistance of the WC-Co-cemented carbides were investigated by scanning electron microscopy and mechanical property tests. The wear resistance of WC-Co-cemented carbides with little to no binder is acceptable and it decreases with increase in Co content. There is no significant difference in wear resistance at 0 wt. % and 0.2 wt. % Co content. By analysing the friction and wear mechanism, it can be concluded that because the Co phase was extruded first, the stability of the WC hard base was disrupted, the WC phase desquamated and abrasion occurred. WC-cemented carbide with 0.2 wt. % Co is the most suitable material. The best results were achieved at 1680°C with 2333 HV30 and 6.82 MPa.m1/2

  19. Modified surface morphology in surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser radiation

    NASA Astrophysics Data System (ADS)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt-cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. The influence of ablation rate, surface roughness, surface micromorphology as well as surface phase structure on laser conditions including laser irradiance and pulse number have been investigated. The experimental results showed that the ablation rate and surface roughness were controlled by varying the number of pulses and laser irradiance. The microstructure and crystalline structure of irradiated surface layer varied greatly with different laser conditions. After 300 shots of laser irradiation at irradiance of 125 MW/cm 2, the surface micromorphology characterizing a uniform framework pattern of "hill-valleys". With the increment of laser shots at laser irradiance of 125 MW/cm 2, the microstructure of cemented tungsten carbide transformed from original polygon grains with the size of 3 μm to interlaced large and long grains after 300 shots of laser irradiation, and finally to gross grains with the size of 10 μm with clear grain boundaries after 700 shots. The crystalline structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. At proper laser irradiance and pulse number, cobalt binder has been selectively removed from the surface layer of hardmetal. It has been demonstrated that surface ablation with pulsed UV laser should be a feasible way to selectively remove cobalt binder from surface layer of cemented tungsten carbide hardmetal.

  20. Improved adhesion of diamond coating on cobalt-cemented tungsten carbide hardmetal by using pulsed-UV-laser substrate surface pretreatment

    NASA Astrophysics Data System (ADS)

    Tiejun, Li; Qihong, Lou; Jingxing, Dong; Yunrong, Wei; Jun, Zhou; Jingru, Liu; Zhiming, Zhang; Fanghong, Sun

    2002-06-01

    Pulsed-UV-laser surface ablation has been applied in substrate pretreatment in order to obtain good adhesion of diamond coating grown on cobalt-cemented tungsten carbide hardmetal. The dependence of diamond coating's adhesion on different shots of pulsed-UV-laser substrate pretreatment has been studied experimentally. The results were compared with diamond coating deposited by using traditional acid-etching substrate pretreatment. It was shown that adhesion of diamond coating grown on tungsten carbide hardmetal has been greatly improved by using pulsed-UV-laser substrate pretreatment. The corresponding laser pretreatment condition for the optimal adhesion of diamond coatings was finally obtained. It has been demonstrated that pulsed-UV-laser substrate pretreatment should be a feasible and effective method for improving adhesion of diamond coating on cobalt-cemented tungsten carbide hardmetal. It is the characteristic surface morphology produced by pulsed-UV-laser surface ablation that subsequently results in this improved adhesion of diamond coating grown on tungsten carbide hardmetal. The number of laser shots being used in substrate pretreatment has a great influence to the adhesion of diamond coating deposited on tungsten carbide hardmetal. One should always apply proper number of laser shots in pulsed-UV-laser substrate pretreatment when seeking for the optimal adhesion of diamond coating on tungsten carbide hardmetal. In this work, the corresponding number of laser shots for the optimal adhesion of diamond coating has found to be 300 laser shots.

  1. Study on tribological behavior and cutting performance of CVD diamond and DLC films on Co-cemented tungsten carbide substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Dongcan; Shen, Bin; Sun, Fanghong

    2010-02-01

    The tribological behaviors of diamond and diamond-like carbon (DLC) films play a major role on their machining and mechanical applications. In this study, diamond and diamond-like carbon (DLC) films are deposited on the cobalt cemented tungsten carbide (WC-Co) substrate respectively adopting the hot filament chemical vapor deposition (HFCVD) technique and the vacuum arc discharge with a graphite cathode, and their friction properties are evaluated on a reciprocating ball-on-plate tribometer with counterfaces of silicon nitride (Si 3N 4) ceramic, cemented tungsten carbide (WC) and ball-bearing steel materials, under the ambient air without lubricating condition. Moreover, to evaluate their cutting performance, comparative turning tests are conducted using the uncoated WC-Co and as-fabricated CVD diamond and DLC coated inserts, with glass fiber reinforced plastics (GFRP) composite materials as the workpiece. The as-deposited HFCVD diamond and DLC films are characterized with energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Raman spectroscopy and 3D surface topography based on white-light interferometry. Furthermore, Rocwell C indentation tests are conducted to evaluate the adhesion of HFCVD diamond and DLC films grown onto WC-Co substrates. SEM and 3D surface topography based on white-light interferometry are also used to investigate the worn region on the surfaces of diamond and DLC films. The friction tests suggest that the obtained friction coefficient curves that of various contacts exhibit similar evolution tendency. For a given counterface, DLC films present lower stable friction coefficients than HFCVD diamond films under the same sliding conditions. The cutting tests results indicate that flank wear of the HFCVD diamond coated insert is lower than that of DLC coated insert before diamond films peeling off.

  2. Chemical vapor deposition of highly adherent diamond coatings onto co-cemented tungsten carbides irradiated by high power diode laser.

    PubMed

    Barletta, M; Rubino, G; Valle, R; Polini, R

    2012-02-01

    The present investigation deals with the definition of a new eco-friendly alternative to pretreat Co-cemented tungsten carbide (WC-Co) substrates before diamond deposition by hot filament chemical vapor deposition (HFCVD). In particular, WC-5.8 wt %Co substrates were submitted to a thermal treatment by a continuous wave-high power diode laser to reduce surface Co concentration and promote the reconstruction of the WC grains. Laser pretreatments were performed both in N(2) and Ar atmosphere to prevent substrate oxidation. Diamond coatings were deposited onto the laser pretreated substrates by HFCVD. For comparative purpose, diamond coatings were also deposited on WC-5.8 wt %Co substrates chemically etched by the well-known two-step pretreatment employing Murakami's reagent and Caro's acid. Surface morphology, microstructure, and chemical composition of the WC-5.8 wt %Co substrates after the different pretreatments and the deposition of diamond coatings were assessed by surface profiler, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. Wear performance of the diamond coatings was checked by dry sliding linear reciprocating tribological tests. The worn volume of the diamond coatings deposited on the laser pretreated substrates was always found lower than the one measured on the chemically etched substrates, with the N(2) atmosphere being particularly promising.

  3. Abrasive wear of cemented carbides

    SciTech Connect

    Hawk, Jeffrey A.; Wilson, Rick D.

    2003-10-01

    Cemented carbides are used for a wide variety of applications where wear is a problem. Usually the wear of the cemented carbides is a combination of metal-to-metal and abrasion. Wear can occur at room or elevated temperatures. This research summarizes initial research to understand the abrasive wear of various cemented carbides (various grain sizes, carbide types, carbide grain sizes and binder compositions) in terms of absolute material removal rates and material removal mechanisms.

  4. Ultrasonic ranking of toughness of tungsten carbide

    NASA Technical Reports Server (NTRS)

    Vary, A.; Hull, D. R.

    1983-01-01

    The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.

  5. Hard coating of ultrananocrystalline diamond/nonhydrogenated amorphous carbon composite films on cemented tungsten carbide by coaxial arc plasma deposition

    NASA Astrophysics Data System (ADS)

    Naragino, Hiroshi; Egiza, Mohamed; Tominaga, Aki; Murasawa, Koki; Gonda, Hidenobu; Sakurai, Masatoshi; Yoshitake, Tsuyoshi

    2016-08-01

    Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were deposited on cemented carbide containing Co by coaxial arc plasma deposition. With decreasing substrate temperature, the hardness was enhanced accompanied by an enhancement in the sp3/(sp2 + sp3). Energy-dispersive X-ray and secondary ion mass spectrometry spectroscopic measurements exhibited that the diffusion of Co atoms from the substrates into the films hardly occurs. The film deposited at room temperature exhibited the maximum hardness of 51.3 GPa and Young's modulus of 520.2 GPa, which evidently indicates that graphitization induced by Co in the WC substrates, and thermal deformation from sp3 to sp2 bonding are suppressed. The hard UNCD/a-C films can be deposited at a thickness of approximately 3 μm, which is an order larger than that of comparably hard a-C films. The internal compressive stress of the 51.3-GPa film is 4.5 GPa, which is evidently smaller than that of comparably hard a-C films. This is a reason for the thick deposition. The presence of a large number of grain boundaries in the film, which is a structural specific to UNCD/a-C films, might play a role in releasing the internal stress of the films.

  6. Dissolution and reactive oxygen species generation of inhaled cemented tungsten carbide particles in artificial human lung fluids

    NASA Astrophysics Data System (ADS)

    Stefaniak, A. B.; Leonard, S. S.; Hoover, M. D.; Virji, M. A.; Day, G. A.

    2009-02-01

    Inhalation of both cobalt (Co) and tungsten carbide (WC) particles is associated with development of hard metal lung disease (HMD) via generation of reactive oxygen species (ROS), whereas Co alone is sufficient to cause asthma via solubilization and hapten formation. We characterized bulk and aerodynamically size-separated W, WC, Co, spray dryer (pre-sintered), and chamfer grinder (post-sintered) powders. ROS generation was measured in the murine RAW 264.7 cell line using electron spin resonance. When dose was normalized to surface area, hydroxyl radical generation was independent of particle size, which suggests that particle surface chemistry may be an important exposure factor. Chamfer grinder particles generated the highest levels of ROS, consistent with the hypothesis that intimate contact of metals is important for ROS generation. In artificial extracellular lung fluid, alkylbenzyldimethylammonium chloride (ABDC), added to prevent mold growth during experiments, did not influence dissolution of Co (44.0±5.2 vs. 48.3±6.4%) however, dissolution was higher (p<0.05) in the absence of phosphate (62.0±5.4 vs. 48.3±6.4%). In artificial macrophage phagolysosomal fluid, dissolution of Co (36.2±10.4%) does not appear to be influenced (p=0.30) by the absence of glycine (29.8±2.1%), phosphate (39.6±8.6%), or ABDC (44.0±10.5%). These results aid in assessing and understanding Co and W inhalation dosimetry.

  7. Review on Sintering Process of WC-Co Cemented Carbide in Metal Injection Molding Technology

    NASA Astrophysics Data System (ADS)

    Prathabrao, M.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

    2017-01-01

    The objective of this paper is to give an overview on sintering process of WC-Co cemented carbides in metal injection molding technology. Metal injection molding is an advanced and promising technology in producing cemented nanostructured carbides. Cemented tungsten carbide (WC-Co) hard metal is known for its high hardness and wear resistance in various applications. Moreover, areas include fine grained materials, alternative binders, and alternative sintering techniques has been discussed in this paper.

  8. Evidence of hydrogen embrittlement of tungsten carbide.

    PubMed

    Kennedy, G C

    1978-02-01

    Tungsten carbide vessels containing materials at high temperature and high pressure are used in many laboratories. We note that any oils at medium to high temperature which can break down and liberate hydrogen cause rapid failure of the pressure vessel, whereas perfluorated kerosenes used as lubricants inside a pressure vessel give sharply increased life of the vessel.

  9. Reactive deposition of tungsten and titanium carbides by induction plasma

    NASA Astrophysics Data System (ADS)

    Jiang, X. L.; Gitzhofer, F.; Boulos, M. I.; Tiwari, R.

    1995-05-01

    A study is reported on the use of induction plasma technology for the preparation of dense free-standing deposits of tungsten carbide and titanium carbide from metallic powders and methane. Phase analysis by X-ray diffraction indicates that primary carburization of the particles takes place in-flight giving rise to the formation of W2C and TiC(1 - x). Secondary carburization occurs in the deposits resulting in the formation of tungsten and titanium carbides. Microstructures revealed by optical and scanning electron microscopy show uniform small grains of the carbides. The reactive plasma spray-formed tungsten carbide shows transgranular fracture, while pure tungsten deposits show intergranular fracture.

  10. Microstructure Analysis of Tungsten Carbide Hardfacing on Carbon Steel Blade

    NASA Astrophysics Data System (ADS)

    Nagentrau, M.; Tobi, A. L. Mohd; Kamdi, Z.; Ismail, M. I.; Sambu, M.

    2017-05-01

    Tungsten carbide (WC) hardfacing coating is commonly used to enhance carbon steel blade performance which works in acidic and abrasive condition during production process. This paper deals with tungsten carbide (WC) hardfacing microstructure analysis on a carbon steel blade. Mixing of ilmenite ore with sulphuric acid is performed by the carbon steel blade as part of a production process. Tungsten carbide hardfacing is deposited on the carbon steel blade to enhance its wear resistance. The carbide distribution along with elemental composition analysis of the hardfaced carbon steel blade specimens is examined using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) respectively. Microstructure analysis revealed that different sizes of carbides with non-uniform distribution are found around the coating region. The carbide region is contains high percentage of tungsten (W) meanwhile, non-carbide region rich in tungsten (W) and iron (Fe).

  11. Superhard Diamond/tungsten Carbide Nanocomposites

    SciTech Connect

    Z Lin; J Zhang; B Li; L Wang; H Mao; R Hemley; Y Zhao

    2011-12-31

    We investigated the processing conditions of diamond/tungsten carbide (WC) composites using in situ synchrotron x-ray diffraction (XRD) and reactive sintering techniques at high pressure and high temperatures. The as-synthesized composites were characterized by synchrotron XRD, scanning electron microscopy, high-resolution transmission electron microscopy, and indentation hardness measurements. Through tuning of the reaction temperature and time, we produced fully reacted, well-sintered, and nanostructured diamond composites with Vickers hardness of about 55 GPa and the grain size of WC binding matrix smaller than 50 nm. A specific set of orientation relationships between WC and tungsten is identified to gain microstructural insight into the reaction mechanism between diamond and tungsten.

  12. Preparation and electrocatalytic activity of tungsten carbide and titania nanocomposite

    SciTech Connect

    Hu, Sujuan; Shi, Binbin; Yao, Guoxing; Li, Guohua; Ma, Chunan

    2011-10-15

    Graphical abstract: The electrocatalytic activity of tungsten carbide and titania nanocomposite is related to the structure, crystal phase and chemical components of the nanocomposite, and is also affected by the property of electrolyte. A synergistic effect exists between tungsten carbide and titania of the composite. Highlights: {yields} Electrocatalytic activity of tungsten carbide and titania nanocomposite with core-shell structure. {yields} Activity is related to the structure, crystal phase and chemical component of the nanocomposite. {yields} The property of electrolyte affects the electrocatalytic activity. {yields} A synergistic effect exists between tungsten carbide and titania of the composite. -- Abstract: Tungsten carbide and titania nanocomposite was prepared by combining a reduced-carbonized approach with a mechanochemical approach. The samples were characterized by X-ray diffraction, transmission electron microscope under scanning mode and X-ray energy dispersion spectrum. The results show that the crystal phases of the samples are composed of anatase, rutile, nonstoichiometry titanium oxide, monotungsten carbide, bitungsten carbide and nonstoichiometry tungsten carbide, and they can be controlled by adjusting the parameters of the reduced-carbonized approach; tungsten carbide particles decorate on the surface of titania support, the diameter of tungsten carbide particle is smaller than 20 nm and that of titania is around 100 nm; the chemical components of the samples are Ti, O, W and C. The electrocatalytic activity of the samples was measured by a cyclic voltammetry with three electrodes. The results indicate that the electrocatalytic activities of the samples are related to their crystal phases and the property of electrolyte in aqueous solution. A synergistic effect between titania and tungsten carbide is reported for the first time.

  13. Dynamic compaction of tungsten carbide powder.

    SciTech Connect

    Gluth, Jeffrey Weston; Hall, Clint Allen; Vogler, Tracy John; Grady, Dennis Edward

    2005-04-01

    The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.

  14. Dynamic SEM wear studies of tungsten carbide cermets

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined. Etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the WC and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation. The wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  15. Dynamic SEM wear studies of tungsten carbide cermets

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined. Etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the WC and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation. The wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  16. Potential application of tungsten carbides as electrocatalysts

    NASA Astrophysics Data System (ADS)

    Hwu, Henry H.; Chen, Jiangguang G.

    2003-07-01

    The reactions of methanol, water, and carbon monoxide over clean and modified tungsten carbide surfaces are studied by using temperature programmed desorption, high-resolution electron energy loss spectroscopy, and Auger electron spectroscopy. The carbide-modified W(111) surface is highly active toward the decomposition of methanol, with 55% going to complete decomposition, 31% to CO, and 14% to CH4. Additionally, the C/W(111) surface exhibits strong activity toward the dissociation of water. Furthermore, the desorption of CO from C/W(111) occurs at a relatively low temperature of ~330 K. When modified by the presence of submonolayer Pt, the decomposition pathways of methanol are significantly altered. The presence of low-coverage Pt onto C/W(111) effectively inhibits the production of CH4, an undesirable side product in direct methanol fuel cells. The Pt-modified C/W(111) surface also remains active toward the dissociative of water. When C/W(111) is modified by oxygen, the surface retains significant activity toward water and methanol, and at the same time lower the CO desorption temperature to 242 K. Finally, the investigations on carbide-modified W(110) reveal minor structure sensitivity in terms of product selectivities, while the overall activity values of methanol and water on the two C/W surfaces are nearly identical. The results on the C/W(111), Pt/C/W(111), O/C/W(111), and C/W(110) surfaces are compared to those on the Ru(0001) and Pt(111) surfaces.

  17. Toxicity of tungsten carbide and cobalt-doped tungsten carbide nanoparticles in mammalian cells in vitro.

    PubMed

    Bastian, Susanne; Busch, Wibke; Kühnel, Dana; Springer, Armin; Meissner, Tobias; Holke, Roland; Scholz, Stefan; Iwe, Maria; Pompe, Wolfgang; Gelinsky, Michael; Potthoff, Annegret; Richter, Volkmar; Ikonomidou, Chrysanthy; Schirmer, Kristin

    2009-04-01

    Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobalt-doped tungsten carbide (WC-Co) nanoparticle suspensions in an array of mammalian cells. We examined acute toxicity of WC and of WC-Co (10% weight content Co) nanoparticles in different human cell lines (lung, skin, and colon) as well as in rat neuronal and glial cells (i.e., primary neuronal and astroglial cultures and the oligodendrocyte precursor cell line OLN-93). Furthermore, using electron microscopy, we assessed whether nanoparticles can be taken up by living cells. We chose these in vitro systems in order to evaluate for potential toxicity of the nanoparticles in different mammalian organs (i.e., lung, skin, intestine, and brain). Chemical-physical characterization confirmed that WC as well as WC-Co nanoparticles with a mean particle size of 145 nm form stable suspensions in serum-containing cell culture media. WC nanoparticles were not acutely toxic to the studied cell lines. However, cytotoxicity became apparent when particles were doped with Co. The most sensitive were astrocytes and colon epithelial cells. Cytotoxicity of WC-Co nanoparticles was higher than expected based on the ionic Co content of the particles. Analysis by electron microscopy demonstrated presence of WC nanoparticles within mammalian cells. Our findings demonstrate that doping of WC nanoparticles with Co markedly increases their cytotoxic effect and that the presence of WC-Co in particulate form is essential to elicit this combinatorial effect.

  18. Toxicity of Tungsten Carbide and Cobalt-Doped Tungsten Carbide Nanoparticles in Mammalian Cells in Vitro

    PubMed Central

    Bastian, Susanne; Busch, Wibke; Kühnel, Dana; Springer, Armin; Meißner, Tobias; Holke, Roland; Scholz, Stefan; Iwe, Maria; Pompe, Wolfgang; Gelinsky, Michael; Potthoff, Annegret; Richter, Volkmar; Ikonomidou, Chrysanthy; Schirmer, Kristin

    2009-01-01

    Background Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. Objective We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobaltdoped tungsten carbide (WC-Co) nanoparticle suspensions in an array of mammalian cells. Methods We examined acute toxicity of WC and of WC-Co (10% weight content Co) nanoparticles in different human cell lines (lung, skin, and colon) as well as in rat neuronal and glial cells (i.e., primary neuronal and astroglial cultures and the oligodendro cyte precursor cell line OLN-93). Furthermore, using electron microscopy, we assessed whether nanoparticles can be taken up by living cells. We chose these in vitro systems in order to evaluate for potential toxicity of the nanoparticles in different mammalian organs (i.e., lung, skin, intestine, and brain). Results Chemical–physical characterization confirmed that WC as well as WC-Co nanoparticles with a mean particle size of 145 nm form stable suspensions in serum-containing cell culture media. WC nanoparticles were not acutely toxic to the studied cell lines. However, cytotoxicity became apparent when particles were doped with Co. The most sensitive were astrocytes and colon epithelial cells. Cytotoxicity of WC-Co nanoparticles was higher than expected based on the ionic Co content of the particles. Analysis by electron microscopy demonstrated presence of WC nanoparticles within mammalian cells. Conclusions Our findings demonstrate that doping of WC nanoparticles with Co markedly increases their cytotoxic effect and that the presence of WC-Co in particulate form is essential to elicit this combinatorial effect. PMID:19440490

  19. Some observations on uranium carbide alloy/tungsten compatibility.

    NASA Technical Reports Server (NTRS)

    Phillips, W. M.

    1972-01-01

    Results of chemical compatibility tests between both pure tungsten and thoriated tungsten run at 1800 C for up to 3300 hours with uranium carbide alloys. Alloying with zirconium carbide appeared to widen the homogeneity range of uranium carbide, making additional carbon available for reaction with the tungsten. Reaction layers were formed both by vapor phase reaction and by physical contact, producing either or both UWC2 and W2C, depending upon the phases present in the starting fuel alloy. Formation of UWC2 results in slow growth of the reaction layer with time, while W2C reaction layers grow rapidly, allowing equilibrium to be reached in less than 2500 hours at 1800 C. Neither the presence of a thermal gradient nor the presence of thoria in the tungsten clad affect the reactions observed.

  20. Surface Coating of Tungsten Carbide by Electric Exploding of Contact

    SciTech Connect

    Grigoryev, Evgeny G.

    2011-01-17

    Electric exploding of a tungsten carbide--cobalt material near-by high-speed steel surface forms on it a hardening coating. The essential structure properties of the formed coatings are determined by parameters of contact exploding electrode at the pulse current amplitude from above 106 A/cm2 and duration less than 10-4 s. The metallographic investigations of coating structures were done by microscope 'Neophot-24'. They have shown that the contact electric exploding caused the transfer of tungsten carbide and cobalt on the surface of high-speed steel. The breakdown of tungsten carbide--cobalt material took place during electrical exploding. The hardening layers of tungsten carbide and pure nanocrystalline tungsten have been formed upon the surface of high-speed steel as a result of electric exploding. Crystalline grains of tungsten have an almost spherical form and their characteristic size less than 400 nanometers. Micro hardness of the coating layers and high-speed steel structures was measured.

  1. METHOD FOR PRODUCING CEMENTED CARBIDE ARTICLES

    DOEpatents

    Onstott, E.I.; Cremer, G.D.

    1959-07-14

    A method is described for making molded materials of intricate shape where the materials consist of mixtures of one or more hard metal carbides or oxides and matrix metals or binder metals thereof. In one embodiment of the invention 90% of finely comminuted tungsten carbide powder together with finely comminuted cobalt bonding agent is incorporated at 60 deg C into a slurry with methyl alcohol containing 1.5% paraffin, 3% camphor, 3.5% naphthalene, and 1.8% toluene. The compact is formed by the steps of placing the slurry in a mold at least one surface of which is porous to the fluid organic system, compacting the slurry, removing a portion of the mold from contact with the formed object and heating the formed object to remove the remaining organic matter and to sinter the compact.

  2. Properties of tungsten-rhenium and tungsten-rhenium with hafnium carbide

    NASA Astrophysics Data System (ADS)

    Leonhardt, Todd

    2009-07-01

    Historically, tungsten-25wt.% rhenium alloy has been manufactured into wire for the thermocouple market, but recent demands for high-temperature structural components have forced the development of novel processing techniques for tungsten-rhenium and tungsten-rhenium with hafnium carbide. With a melting temperature of 3,050°C, and a recrystallization temperature near 1,900°C, tungsten-rhenium alloys are being used in aerospace, temperature measuring, and friction stir welding applications. The mechanical properties and microstructures of tungsten-25wt.% rhenium and tungsten-25wt.% rhenium with hafnium carbide are reported at ambient temperature, 1,371°C, and 1,926°C, after processing by three methods: hot isostatic pressing, swaging, and extrusion.

  3. Some observations on uranium carbide alloy/tungsten compatibility

    NASA Technical Reports Server (NTRS)

    Phillips, W. M.

    1972-01-01

    Chemical compatibility between both pure and thoriated tungsten and uranium carbide alloys was studied at 1800 C for up to 3300 hours. Alloying with zirconium carbide appeared to widen the homogeneity range of uranium carbide, making additional carbon available for reaction with the tungsten. Reaction layers were formed both by vapor phase reaction and by physical contact, producing either or both UWC2 and W2C, dependent upon the phases present in the starting fuel alloy. Formation of UWC2 results in slow growth of the reaction layer with time, while W2C reaction layers grow rapidly, allowing equilibrium to be reached in less than 2500 hours at 1800 C. The presence of a thermal gradient had no effect on the reactions observed nor did the presence of thoria in the tungsten clad.

  4. Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  5. Characteristics of deposited boron doping diamond on tungsten carbide insert by MPECVD

    NASA Astrophysics Data System (ADS)

    Kim, Jong Seok; Park, Yeong Min; Kim, Jeong Wan; Tulugan, Kelimu; Kim, Tae Gyu

    2015-03-01

    Diamond-coated cutting tools are used primarily for machining non-ferrous materials such as aluminum-silicon alloys, copper alloys, fiber-reinforced polymers, green ceramics and graphite. Because the tool life of cemented carbide cutting tool is greatly improved by diamond coating, and typically more than 10 times of the tool life is obtained. However, research of boron-doped diamond (BDD) coating tool has not been fully researched yet. In this study, we have succeeded to make boron-doped microcrystalline and nanocrystalline diamond-coated Co-cemented tungsten carbide (WC-Co) inserts. Microcrystalline BDD thin film is deposited on WC-Co insert by using microwave plasma enhanced chemical vapor deposition (MPECVD) method. Scanning electron microscope (SEM) and Raman spectroscopy are used to characterize the as-deposited diamond films.1,2

  6. Hollow microspheres with a tungsten carbide kernel for PEMFC application.

    PubMed

    d'Arbigny, Julien Bernard; Taillades, Gilles; Marrony, Mathieu; Jones, Deborah J; Rozière, Jacques

    2011-07-28

    Tungsten carbide microspheres comprising an outer shell and a compact kernel prepared by a simple hydrothermal method exhibit very high surface area promoting a high dispersion of platinum nanoparticles, and an exceptionally high electrochemically active surface area (EAS) stability compared to the usual Pt/C electrocatalysts used for PEMFC application.

  7. Tungsten-yttria carbide coating for conveying copper

    DOEpatents

    Rothman, Albert J.

    1993-01-01

    A method is provided for providing a carbided-tungsten-yttria coating on the interior surface of a copper vapor laser. The surface serves as a wick for the condensation of liquid copper to return the condensate to the interior of the laser for revolatilization.

  8. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    SciTech Connect

    Airapetov, A. A.; Begrambekov, L. B.; Buzhinskiy, O. I.; Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A.

    2015-12-15

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  9. Microstructure and properties of CVD tungsten carbide from tungsten hexafluoride and dimethyl ether

    SciTech Connect

    Skaf, D.W.; Warner, A.W.; Dollahon, N.R.; Fargo, G.H. )

    1994-12-01

    Tungsten carbide was deposited from tungsten hexafluoride, dimethyl ether, and hydrogen using a horizontal, cold-wall reactor. The effects of substrate temperature, reactor pressure, and reagent ratio on the coating growth rate, morphology, composition, and microhardness were studied. Under most conditions, the solid deposit was primarily W[sub 3]C with minor amounts of W. The tungsten carbide growth rate data fit an Arrhenius rate expression for temperatures from 425 to 550 C and had an activation energy of 24 kcal/mol at 70 mmHg total pressure and a WF[sub 6]/DME ratio of 6.3. A variety of surface morphologies and microstructures were observed. The microhardness of the coated substrates increased with coating thickness to a maximum value of 2,400 kg/mm[sup 2].

  10. Automated laser fabrication of cemented carbide components

    NASA Astrophysics Data System (ADS)

    Paul, C. P.; Khajepour, A.

    2008-07-01

    Automated Laser Fabrication (ALFa) is one of the most rapidly growing rapid-manufacturing technologies. It is similar to laser cladding at process level with different end applications. In general, laser cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn-out parts, while ALFa is capable of near net shaping the components by layer-by-layer deposition of the material directly from CAD model. This manufacturing method is very attractive for low volume manufacturing of hard materials, as near net shaping minimizes machining of hard material and subsequently brings significant savings in time and costly material. To date, many researchers have used this technology to fabricate components using various alloy steels, nickel-based alloys and cobalt-based alloys. In the present study, the work is extended to tungsten carbide cobalt (WC-Co) composites. A set of comprehensive experiments was carried out to study the effect of processing parameters during multi-layer fabrication. The process parameters were optimized for the component-level fabrication. Fabricated components were subjected to dye-penetrant testing, three-point flexural testing, hardness measurement, optical and scanning electron microscopy and X-ray diffraction analysis. The test results revealed that the laser-fabricated material was defect free and more ductile in nature. Thus, ALFa technology, not only produced the quality components, but also minimized machining of hard material and brought significant saving of time and costly WC-Co material.

  11. Femtosecond laser ablation of cemented carbides: properties and tribological applications

    NASA Astrophysics Data System (ADS)

    Dumitru, G.; Romano, V.; Weber, H. P.; Gerbig, Y.; Haefke, H.; Bruneau, S.; Hermann, J.; Sentis, M.

    Laser ablation with fs laser pulses was performed in air on cobalt cemented tungsten carbide by means of a Ti : sapphire laser (800 nm, 100 fs). Small and moderate fluences (2, 5, 10 J/cm2) and up to 5×104 pulses per irradiated spot were used to drill holes with aspect ratios up to 10. Cross-section cuts from laser-irradiated samples were produced and they were analysed with optical microscopy and SEM. EDX analyses were carried out on selected zones. Quasi-cylindrical holes were found for 2 J/cm2, whereas for 5 and 10 J/cm2 irregular shapes (lobes, bottoms wider than hole entrances) were found to occur after a given number of incident pulses. Layers with modified structure were evidenced at pore walls. SEM revealed a denser structure, while EDX analyses showed uniform and almost similar contents of W, C, and Co in these layers. As a direct application, patterning of coated WC-Co was carried out with 2 J/cm2 and 100 pulses per pore. The resulted surfaces were tribologically tested and these tests revealed an improved friction and wear behaviour.

  12. Feasibility study of fluxless brazing cemented carbides to steel

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Sievers, N.

    2017-03-01

    One of the most important brazing processes is the joints between cemented carbides and steel for the tool industry such as in rotary drill hammers or saw blades. Even though this technique has already been used for several decades, defects in the joint can still occur and lead to quality loss. Mostly, the joining process is facilitated by induction heating and the use of a flux to enhance the wetting of the filler alloy on the surface of the steel and cemented carbide in an ambient atmosphere. However, although the use of flux enables successful joining, it also generates voids within the joint, which reduces the strength of the connection while the chemicals within the flux are toxic and polluting. In this feasibility study, a fluxless brazing process is used to examine the joint between cemented carbides and steel for the first time. For this, ultrasound is applied during induction heating to enable the wetting between the liquid filler metal and the surfaces of the cemented carbide and steel. The ultrasound generates cavitations within the liquid filler metal, which remove the oxides from the surface. Several filler metals such as a silver based alloy Ag449, pure Zn, and an AlSi-alloy were used to reduce the brazing temperature and to lower the thermal residual stresses within the joint. As a result, every filler metal successfully wetted both materials and led to a dense connection. The ultrasound has to be applied carefully to prevent a damage of the cemented carbide. In this regard, it was observed that single grains of the cemented carbide broke out and remained in the joint. This positive result of brazing cemented carbides to steel without a flux but using ultrasound, allows future studies to focus on the shear strength of these joints as well as the behavior of the thermally induced residual stresses.

  13. A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

    SciTech Connect

    Kim, Young-ho; Irie, Hiroshi; Hashimoto, Kazuhito

    2008-05-05

    A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO{sub 3}) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400-530 nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO{sub 3}.

  14. Effect of surface composition on the chemisorption of hydrogen on tungsten carbide

    SciTech Connect

    Boudart, M.; Lee, J.S.; Imura, K.; Yoshida, S.

    1987-01-01

    Polymeric carbon and oxygen were detected at the surface of tungsten carbide powders by Auger electron spectroscopy and electron spin resonance. Chemisorption of dihydrogen is suppressed by polymeric carbon but enhanced by surface oxygen as some of the latter reacts in the presence of water with hydrogen spilling over from the tungsten carbide parts of the surface. 21 references.

  15. A Review of Metal Injection Molding- Process, Optimization, Defects and Microwave Sintering on WC-Co Cemented Carbide

    NASA Astrophysics Data System (ADS)

    Shahbudin, S. N. A.; Othman, M. H.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

    2017-08-01

    This article is about a review of optimization of metal injection molding and microwave sintering process on tungsten cemented carbide produce by metal injection molding process. In this study, the process parameters for the metal injection molding were optimized using Taguchi method. Taguchi methods have been used widely in engineering analysis to optimize the performance characteristics through the setting of design parameters. Microwave sintering is a process generally being used in powder metallurgy over the conventional method. It has typical characteristics such as accelerated heating rate, shortened processing cycle, high energy efficiency, fine and homogeneous microstructure, and enhanced mechanical performance, which is beneficial to prepare nanostructured cemented carbides in metal injection molding. Besides that, with an advanced and promising technology, metal injection molding has proven that can produce cemented carbides. Cemented tungsten carbide hard metal has been used widely in various applications due to its desirable combination of mechanical, physical, and chemical properties. Moreover, areas of study include common defects in metal injection molding and application of microwave sintering itself has been discussed in this paper.

  16. Tungsten carbide laser alloying of a low alloyed steel

    NASA Astrophysics Data System (ADS)

    Cojocaru, Mihai; Taca, Mihaela

    1996-10-01

    Laser alloying is a way to change the composition of metal surfaces in order to improve their corrosion-resistance, high-temperature strength and hardness. The results of a structural and phase analysis of a tungsten carbide based surface layer prepared by laser alloying of a low carbon steel substrate are presented. Structure, phase composition and microhardness of surface alloyed layers have been investigated. The surface of the samples exhibited a thin layer with a different chemical and phase composition. An increase in alloyed surface hardness and wear-resistance was observed.

  17. Tunable carbon nanotube-tungsten carbide nanoparticles heterostructures by vapor deposition

    SciTech Connect

    Xia, Min; Guo, Hongyan; Ge, Changchun; Yan, Qingzhi Lang, Shaoting

    2014-05-14

    A simple, versatile route for the synthesis of carbon nanotube (CNT)-tungsten carbide nanoparticles heterostructures was set up via vapor deposition process. For the first time, amorphous CNTs (α-CNTs) were used to immobilized tungsten carbide nanoparticles. By adjusting the synthesis and annealing temperature, α-CNTs/amorphous tungsten carbide, α-CNTs/W{sub 2}C, and CNTs/W{sub 2}C/WC heterostructures were prepared. This approach provides an efficient method to attach other metal carbides and other nanoparticles to carbon nanotubes with tunable properties.

  18. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.; Catledge, Shane A.

    2016-02-01

    Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W2CoB2 with average hardness from 23 to 27 GPa and average elastic modulus of 600-730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  19. Grain growth, densification and mechanical properties of nanocrystalline tungsten carbide-cobalt

    NASA Astrophysics Data System (ADS)

    Wang, Xu

    Over two decades, attempts to produce cemented tungsten carbide with nanocrystalline grain structure have been made to obtain dramatically improved mechanical properties to extend the lifetime and robustness of tungsten carbide tools. The attempts have shown that the conventional methods by liquid phase sintering cannot retain nanoscale grain sizes while achieving full densification because significant grain growth of WC occurs during sintering. There have been many works that focused on developing alternative techniques to liquid phase sintering, such as Microwave Sintering (MS), Spark Plasma Sintering (SPS), High Frequency Induction Heated Sintering (HFIHS), and so on. In all of these investigations, densification is accompanied by significant grain growth. The finest average grain size that is achievable until now is still approximately 100-300 nm. In this research, the challenges of sintering nanocrystalline WC-Co powders were further examined. The key challenge to the production of bulk nanocrystalline cemented tungsten carbide materials is to control the rapid grain growth during the early stage of sintering, especially during heat up stage. In order to understand the mechanisms of grain growth and densification during the early stage of sintering of nanocrystalline WC-Co powders, the sintering behaviors of nanosized WC during the early stages of sintering were studied as a function of temperature and time. The effects of other influencing factors, such as initial grain size, cobalt content, and grain growth inhibitor, were investigated. As a way to make nanocrystalline WC-Co materials, an ultrahigh pressure rapid hot consolidation process (UPRC) was developed. The effects of the UPRC process variables (including heating rate, temperature, holding time, and pressure) on grain growth and densification of the nano powders were studied. Based on the analysis of kinetics of the grain growth and densification and the microstructure evolution during sintering, the

  20. Solid-state chemistry route for supported tungsten and tungsten carbide nanoparticles

    SciTech Connect

    Hugot, N.; Desforges, A.; Fontana, S.; Mareche, J.F.; Herold, C.; Albiniak, A.

    2012-10-15

    Nanoparticles of tungsten and tungsten carbide have been prepared using solid-state chemistry methods. After the vapor phase impregnation of a tungsten hexachloride precursor on a carbon support, a temperature-programmed reduction/carburization was performed. Several parameters were investigated and the evolution of obtained samples was followed by XRD and TEM. The optimization of the reaction parameters led to the preparation of W, W{sub 2}C and WC particles well dispersed on the support. WC phase however could not be obtained alone with less than 10 nm mean size. This could be explained by the carburization mechanism and the carbon diffusion on the support. - Graphical abstract: Bright field picture of carbon-supported WC nanoparticles dispersed on the surface of the sample 1223 K in 10% CH{sub 4}/90% H{sub 2}. Highlights: Black-Right-Pointing-Pointer We aimed at the preparation of supported nanoparticulate tungsten derivatives. Black-Right-Pointing-Pointer Several parameters were investigated. Black-Right-Pointing-Pointer The evolution of obtained samples was followed by XRD and TEM. Black-Right-Pointing-Pointer The optimal preparation led to W, W{sub 2}C and WC particles dispersed on the support.

  1. Development and characterization of nickel based tungsten carbide laser cladded coatings

    NASA Astrophysics Data System (ADS)

    Rombouts, Marleen; Persoons, Rosita; Geerinckx, Eric; Kemps, Raymond; Mertens, Myrjam; Hendrix, Willy; Chen, Hong

    Laser cladded coatings consisting of various types of tungsten carbides embedded in a NiCrBSiCFe matrix are characterized. At optimal process parameters crack-free coatings with a thickness of 0.85-1 mm, excellent bonding with the substrate, carbide concentrations up to 60 wt% and a hardness in the range of 40-55 HRC are obtained. During laser cladding the carbides have partly dissolved in the matrix as indicated by the presence of dispersed carbides in the matrix and by a carbide phase growing into the matrix along the edges of the particles. The wear coefficient during sliding contact decreases logarithmically with increasing carbide concentration.

  2. Dissimilar Brazed Joints Between Steel and Tungsten Carbide

    NASA Astrophysics Data System (ADS)

    Voiculescu, I.; Geanta, V.; Binchiciu, H.; Iovanas, D.; Stefanoiu, R.

    2017-06-01

    Brazing is a joining process used to obtain heterogeneous assemblies between different materials, such as steels, irons, non-ferrous metals, ceramics etc. Some application, like asphalt cutters, require quick solutions to obtain dissimilar joints at acceptable costs, given the very short period of operation of these parts. This paper presents some results obtained during the brazing of dissimilar joints between steel and tungsten carbide by using different types of Ag-Cu system filler materials alloyed with P and Sn. The brazing techniques used were oxygen-gas flame and induction joining. The brazing behaviour was analysed in cross sections by optical and electron microscopy. The metallographic analysis enhanced the adhesion features and the length of penetration in the joining gap. The melting range of the filler materials was measured using thermal analysis.

  3. PIXE characterization of by-products resulting from the zinc recycling of industrial cemented carbides

    NASA Astrophysics Data System (ADS)

    Freemantle, C. S.; Sacks, N.; Topic, M.; Pineda-Vargas, C. A.

    2015-11-01

    By-product materials of the widely used zinc recycling process of cemented carbides have been studied. Scanning electron microscopy and micro-PIXE techniques have identified elemental concentrations, distributions and purity of by-product materials from an industrial zinc recycling plant. Cobalt surface enrichment, lamellar microstructures of varying composition, including alternating tungsten carbide (WC) grains and globular cobalt, and regions of excess zinc contamination were found in materials with incomplete zinc penetration. Liquid Co-Zn formation occurred above 72 wt.% Zn at the furnace temperature of 930 °C, and was extracted towards the surface of poorly zinc infiltrated material, primarily by the vacuum used for zinc distillation. Surface enrichment was not observed in material that was zinc infiltrated to the sample center, which was more friable and exhibited more homogeneous porosity and elemental concentrations. The result of incomplete zinc infiltration was an enriched surface zone of up to 60 wt.% Co, compared to an original sample composition of ∼10-15 wt.% Co. The impact on resulting powders could be higher or inhomogeneous cobalt content, as well as unacceptably high zinc concentrations. PIXE has proven it can be a powerful technique for solving industrial problems in the cemented carbide cutting tool industry, by identifying trace elements and their locations (such as Zn to 0.1 wt.% accuracy), as well as the distribution of major elements within WC-Co materials.

  4. Biological responses of isolated macrophages to cobalt metal and tungsten carbide-cobalt powders.

    PubMed

    Lison, D; Lauwerys, R

    1991-10-01

    A previous study from this laboratory, using morphological and biochemical (LDH release) parameters, has shown that tungsten carbide-cobalt dust exhibits a greater cytotoxicity toward isolated macrophages than cobalt metal powder alone. The present study extends this comparison by examining additional biological parameters. Glucose uptake and superoxide anion production by isolated macrophages were significantly more depressed by the tungsten carbide-cobalt mixture (WC-Co) than by cobalt alone (Co) while pure tungsten carbide (WC) had no effect or even stimulated the cells. For glucose-6-phosphate dehydrogenase and cell-associated plasminogen activator (PA) activities, no difference between Co and WC-Co dusts was observed. These observations add further evidence to our previous findings regarding the different biological reactivity of cobalt metal alone or mixed with tungsten carbide.

  5. Surface roughness analysis after machining of direct laser deposited tungsten carbide

    NASA Astrophysics Data System (ADS)

    Wojciechowski, S.; Twardowski, P.; Chwalczuk, T.

    2014-03-01

    In this paper, an experimental surface roughness analysis in machining of tungsten carbide is presented. The tungsten carbide was received using direct laser deposition technology (DLD). Experiments carried out included milling of tungsten carbide samples using monolithic torus cubic boron nitride (CBN) tool and grinding with the diamond cup wheel. The effect of machining method on the generated surface topography was analysed. The 3D surface topographies were measured using optical surface profiler. The research revealed, that surface roughness generated after the machining of tungsten carbide is affected by feed per tooth (fz) value related to kinematic-geometric projection only in a minor extent. The main factor affecting machined surface roughness is the occurrence of micro grooves and protuberances on the machined surface, as well as other phenomena connected, inter alia, with the mechanism for material removal.

  6. Preparation and investigation of ultrafine-grained tungsten carbide with high hardness and fracture toughness

    NASA Astrophysics Data System (ADS)

    Chuvil'deev, V. N.; Blagoveshchenskii, Yu. V.; Sakharov, N. V.; Boldin, M. S.; Nokhrin, A. V.; Isaeva, N. V.; Shotin, S. V.; Lopatin, Yu. G.; Smirnova, E. S.

    2015-07-01

    High-density samples of ultrafine-grained tungsten carbide with high hardness (up to 31-34 GPa) and increased fracture toughness (up to 5.2-6.4 MPa m1/2) are obtained using the technology of electropulse plasma sintering. The influence of the initial size of nanoparticles of α-WC prepared by plasmachemical synthesis on the density, structural parameters, and mechanical properties of tungsten carbide is investigated.

  7. Effect of xenon on the structural phase state of the surface layer of cemented carbide under pulsed electron-beam irradiation

    SciTech Connect

    Ovcharenko, Vladimir E.; Ivanov, Yurii F.; Mohovikov, Alexey A.; Baohai, Yu Cai, Xiaolong Zhong, Lisheng Xu, Yunhua

    2015-10-27

    A comparative analysis of the surface-layer microstructure of a tungsten-based cemented carbide modified with pulsed high-energy electron beams generated by gas-discharge plasmas and of the tool life of metal-cutting plates prepared from this alloy is performed. The choice of a plasma-forming gas providing for the emission of electrons out of the plasma-filled cathode is shown to have a profound influence both on the formation process of nano-sized structural-phase states in the surface layer of the cemented carbide and on the tool life of the metal-cutting plates prepared from this alloy.

  8. Effect of xenon on the structural phase state of the surface layer of cemented carbide under pulsed electron-beam irradiation

    NASA Astrophysics Data System (ADS)

    Ovcharenko, Vladimir E.; Ivanov, Yurii F.; Mohovikov, Alexey A.; Baohai, Yu; Cai, Xiaolong; Zhong, Lisheng; Xu, Yunhua

    2015-10-01

    A comparative analysis of the surface-layer microstructure of a tungsten-based cemented carbide modified with pulsed high-energy electron beams generated by gas-discharge plasmas and of the tool life of metal-cutting plates prepared from this alloy is performed. The choice of a plasma-forming gas providing for the emission of electrons out of the plasma-filled cathode is shown to have a profound influence both on the formation process of nano-sized structural-phase states in the surface layer of the cemented carbide and on the tool life of the metal-cutting plates prepared from this alloy.

  9. Current Status of Cemented Carbide Technology

    DTIC Science & Technology

    1958-06-01

    1100-1300 201 Q-2370 T i o2 - lampb I ack 1700-1900 309o-3q5o Zro2 - lampblack 1800-2000 3270-3630 v2o3 or v2o5 - lampblack II 00-1200 201Q-2190...is added to the powder as a solute in a solvent such as benzene or carbon-tetrachlor ide, and intensive aixing produces surface films around the...King. F. E., THIN , DUCTILE CARBIDE COATING POSSIBLE WITH NEW METHOD. Matorials and Mtthods. 40_. 112-4 (1952). Kingston. W. E.. od

  10. Creation of wear-resistant frictional surfaces by implanting materials based on tungsten carbide

    NASA Astrophysics Data System (ADS)

    Davidov, S. V.; Gorlenko, A. O.

    2017-02-01

    The influenceof the implanted tungsten carbide on the formation of wear-resistant structures, formed in the process of implementation of the combined electro-processing technology in the friction surfaces, is studied. It has been shown that during the thermal force influence in the deformation zone, there is intensive austenizationof the steel with the dissolution of the tungsten carbide powder and the subsequent formation of the composite nanostructures as a result of decomposition of the supercooled austenite, supersaturated with tungsten. The results of tribologicaltestings of cylindrical samples by the normalized method are presented.

  11. Electrochemical synthesis of nanoporous tungsten carbide and its application as electrocatalysts for photoelectrochemical cells.

    PubMed

    Kang, Jin Soo; Kim, Jin; Lee, Myeong Jae; Son, Yoon Jun; Jeong, Juwon; Chung, Dong Young; Lim, Ahyoun; Choe, Heeman; Park, Hyun S; Sung, Yung-Eun

    2017-03-16

    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. The method employed in this study involves the anodization of tungsten foil followed by post heat treatment in a CO atmosphere to produce highly crystalline tungsten carbide film with an interconnected nanostructure. This exhibited high catalytic activity for the reduction of cobalt bipyridine species, which represent state-of-the-art redox couples for DSCs. The performance of tungsten carbide even surpassed that of Pt, and a substantial increase (∼25%) in energy conversion efficiency was achieved when Pt was substituted by tungsten carbide film as the counter electrode. In addition, tungsten carbide displayed decent activity as a catalyst for the hydrogen evolution reaction, suggesting the high feasibility for its utilization as a cathode material for PEC water splitting cells, which was also verified in a two-electrode water photoelectrolyzer.

  12. Simulation study on retention and reflection from tungsten carbide under high fluence of helium ions

    NASA Astrophysics Data System (ADS)

    Ono, T.; Kawamura, T.; Kenmotsu, T.; Yamamura, Y.

    2001-03-01

    We have studied, with a Monte Carlo simulation code ACAT-DIFFUSE, the fluence-dependence of the amount of helium atoms retained in tungsten carbide at room temperature under helium ion bombardment. The retention behavior may be understood qualitatively in terms of irradiation-dependent diffusion coefficient assumed and range. The re-emission, reflection and sputtering from tungsten carbide under helium ion irradiation were derived and compared with each other. We have discussed the retention curves for incident energy of 5 keV at incident angles of 0° and 80° and of 500 eV at 0°. The energy spectra of helium atoms reflected from tungsten carbide for incident energy of 500 eV at 0° and 80° were compared with those from graphite and tungsten.

  13. Characterization of Tungsten Carbide as Diffusion Barrier for Cu Metallization

    NASA Astrophysics Data System (ADS)

    Wang, Shui Jinn; Tsai, Hao Yi; Sun, Shi Chung

    2001-04-01

    In this paper, the physical and electrical properties as well as thermal stability of the sputter-deposited tungsten carbide (WCx) film used as a diffusion barrier layer for copper metallization were investigated for the first time. It is found that the as-deposited WCx film has a nanocrystalline structure and a low electrical resistivity of approximately 227 μΩ{\\cdot}cm. According to the four-point probe technique, X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS) measurements, it is found that WCx film can preserve the integrity of the Cu(2000 Å)/WCx(600 Å)/n-Si structure without the formation of Cu3Si up to 600°C annealing in N2 for 30 min. A more sensitive diode leakage current measurement of the Cu(2000 Å){\\slash}WCx(600 Å){\\slash}p+n-Si structure shows that WCx film is effective against Cu diffusion into Si substrate up to 550°C. The failure of WCx film in preventing Cu diffusion is attributed to the Cu diffusion into the Si substrate through local defects of the WCx barrier layer. It is found that Cu diffusion is strongly enhanced by the formation of W5Si3 at the WCx/Si interface after high-temperature annealing.

  14. Porosity and wear resistance of flame sprayed tungsten carbide coatings

    NASA Astrophysics Data System (ADS)

    Winarto, Winarto; Sofyan, Nofrijon; Rooscote, Didi

    2017-06-01

    Thermal-sprayed coatings offer practical and economical solutions for corrosion and wear protection of components or tools. To improve the coating properties, heat treatment such as preheat is applied. The selection of coating and substrate materials is a key factor in improving the quality of the coating morphology after the heat treatment. This paper presents the experimental results regarding the effect of preheat temperatures, i.e. 200°C, 300°C and 400°C, on porosity and wear resistance of tungsten carbide (WC) coating sprayed by flame thermal coating. The powders and coatings morphology were analyzed by a Field Emission Scanning Electron Microscope equipped with Energy Dispersive Spectrometry (FE-SEM/EDS), whereas the phase identification was performed by X-Ray diffraction technique (XRD). In order to evaluate the quality of the flame spray obtained coatings, the porosity, micro-hardness and wear rate of the specimens was determined. The results showed that WC coating gives a higher surface hardness from 1391 HVN up to 1541 HVN compared to that of the non-coating. Moreover, the wear rate increased from 0.072 mm3/min. to 0.082 mm3/min. when preheat temperature was increased. Preheat on H13 steel substrate can reduce the percentage of porosity level from 10.24 % to 3.94% on the thermal spray coatings.

  15. EUV nanosecond laser ablation of silicon carbide, tungsten and molybdenum

    NASA Astrophysics Data System (ADS)

    Frolov, Oleksandr; Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Choukourov, Andrei; Kasuya, Koichi

    2015-09-01

    In this paper we present results of study interaction of nanosecond EUV laser pulses at wavelength of 46.9 nm with silicon carbide (SiC), tungsten (W) and molybdenum (Mo). As a source of laser radiation was used discharge-plasma driver CAPEX (CAPillary EXperiment) based on high current capillary discharge in argon. The laser beam is focused with a spherical Si/Sc multilayer-coated mirror on samples. Experimental study has been performed with 1, 5, 10, 20 and 50 laser pulses ablation of SiC, W and Mo at various fluence values. Firstly, sample surface modification in the nanosecond time scale have been registered by optical microscope. And the secondly, laser beam footprints on the samples have been analyzed by atomic-force microscope (AFM). This work supported by the Czech Science Foundation under Contract GA14-29772S and by the Grant Agency of the Ministry of Education, Youth and Sports of the Czech Republic under Contract LG13029.

  16. Spectroscopic constants and potential energy curves of tungsten carbide

    SciTech Connect

    Balasubramanian, K.

    2000-05-01

    Spectroscopic constants (R{sub e},{omega}{sub e},T{sub e},{mu}{sub e}) and potential energy curves for 40 low-lying electronic states of the diatomic tungsten carbide (WC) were obtained using the complete active space multiconfiguration self-consistent field followed by the multireference singles+doubles configuration interaction and full first- and second-order configuration interaction calculations that included up to 6.4 mil configurations. Spin-orbit effects were included through the enhanced relativistic configuration interaction method described here for 28 electronic states of WC lying below {approx}20 000 cm-1. The spin-orbit splitting of the ground state of WC was found to be very large (4394 cm-1). The ground and excited electronic states of the W atom were also computed and were found to be in good agreement with the experimental data. The nature of bonding was analyzed through the composition of orbitals, leading configurations, Mulliken populations, and dipole moments. The dissociation energy of WC was computed including spin-orbit and electron correlation effects. The recent photoelectron spectra of WC{sup -} were assigned on the basis of our computed results. (c) 2000 American Institute of Physics.

  17. Ion beam synthesis by tungsten-implantation into 6H-silicon carbide

    NASA Astrophysics Data System (ADS)

    Weishart, H.; Steffen, H. J.; Matz, W.; Voelskow, M.; Skorupa, W.

    1996-05-01

    Synthesis of a highly conductive surface layer on 6H-silicon carbide was achieved by high-dose, room temperature implantation of tungsten at 200 keV. Subsequently, the samples were annealed in two steps, namely at 500°C and 950°C. The influence of both dose and annealing on the reaction of W with SiC was investigated. Rutherford Backscattering Spectrometry (RBS), X-Ray Diffraction (XRD) and Auger Electron Spectroscopy (AES) contributed to study the structure and composition of the layer as well as the chemical states of the elements. During implantation sputtering becomes significant for doses exceeding 1.0 × 10 17 cm -2. Formation of tungsten carbide and silicide is already observed in the as-implanted state. An annealing temperature of 950°C is necessary to crystallize tungsten carbide. However, tungsten silicide remains amorphous at this temperature. Therefore, a mixture of polycrystalline tungsten carbide and amorphous tungsten silicide develops under these conditions. The resistivity of such a layer implanted with 1.0 × 10 17 W +cm -2 and annealed at 950°C is 565 μΩ cm.

  18. Effect of precursor mass on product phase composition in plasma dynamic synthesis of tungsten carbide

    NASA Astrophysics Data System (ADS)

    Shatrova, K. N.; Sivkov, A. A.; Shanenkov, I. I.; Saigash, A. S.

    2017-05-01

    An interest in WC1-x cubic tungsten carbide results from its catalytic properties similar to those of platinum group metals and the synergistic effect between WC1-x and Pt in reactions of hydrogen evolution and hydrogen oxidation. However, according to the phase diagram of the W-C system, the cubic phase WC1-x only exists in a narrow range of temperature stability (about 2798-3058 K), which makes it difficult for being obtained. To date, there are different methods for synthesizing tungsten carbide powder with a low content of cubic phase that complicates the study of WC1-x properties. A direct plasma dynamic synthesis is known as one of the promising methods to produce WC1-x. The aim of this work is to find the optimal amount of tungsten precursor to obtain cubic tungsten carbide with a high purity by plasma dynamic method. The synthesized products were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns showed that the main phase was cubic tungsten carbide with negligible content of hexagonal tungsten carbide W2C and pure tungsten W. According to a quantitative analysis of synthesized products, which were obtained using masses of initial tungsten equal to 1.0, 0.7, 0.6 and 0.5 gram, the yield of WC1-x phase was 84, 89, 95 and 92 wt%, respectively. The results of TEM displayed that the synthesized powders consist of crystallites, having the size less than 100 nm (WC1-x), and a carbon matrix. This carbon was not detected in XRD due to its presence as an amorphous phase.

  19. Characterization of Tungsten Carbide coatings deposited on AISI 1020 steel

    NASA Astrophysics Data System (ADS)

    Santos, A.; Gonzalez, C.; Ramirez, Z. Y.

    2017-01-01

    In order to determine the variation in the mechanical properties of AISI 1020 standardized steel, heat treated by a quenching and tempering process and with a Tungsten Carbide coating, was performed a microstructural and chemical characterization of the coating material through electron microscopy scanning and X-ray energy dispersive spectroscopy. The steel received a heat treatment of quenching performed by heating to 850°C, followed by cooling in water and tempering at a temperature of 450°C with air cooling. Tests of a) microhardness with a Wilson-Wolpert Tukon 2100B micro durometer and b) resistance to adhesive and abrasive wear following the ASTM G99-05 “Standard test method for wear testing with a pin-on-disk machine” and ASTM G65-04 “standard test method for measuring abrasion using dry sand and rubber Wheel” standards respectively. The results show that the microhardness of the steel do not vary with the load used to perform the test; in addition, the heat treatment of quenching and tempering improves by 5.5% the property while the coating increase it by 124.2%. Regarding the abrasive wear resistance, it is observed that the amount of material lost increases linearly with the distance covered. It was determined that the heat treatment decreased on average by 17.5% the volume of released material during the tests while the coating recued it by 66.7%. The amount volume of material lost during the adhesive wear tests increases linearly with the distance covered while the heat treatment decreased on average by 10.5% the volume of released material during the trial and the coating reduced it by 66.5%.

  20. Durability of tungsten carbide burs for the fabrication of titanium crowns using dental CAD/CAM.

    PubMed

    Hotta, Yasuhiro; Miyazaki, Takashi; Fujiwara, Toshihisa; Tomita, Shoko; Shinya, Akiyoshi; Sugai, Yasuhisa; Ogura, Hideo

    2004-06-01

    The purpose of this study was to evaluate the durability of tungsten carbide burs for the fabrication of titanium crowns using two dental CAD/CAM systems (DECSY, Digital Process, Japan and Cadim, Advance, Japan). A tungsten carbide bur in each system was examined and used without fracture to fabricate 51 titanium crowns. For both systems tiny chips were found on the bur blade at the 11th machining. These chips gradually enlarged as the number of machining times increased. At the first machining no significant difference in the average surface roughness was found on the crown between the two systems (1.6 microm for DECSY and 1.2 microm for Cadim). The cutting grooves became dull and the average surface roughness increased as the number of machining times increased. It is concluded that the tungsten carbide burs for both systems can be used to fabricate up to 51 titanium crowns.

  1. Tungsten carbide encapsulated in nitrogen-doped carbon with iron/cobalt carbides electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Chen, Jinwei; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin

    2016-12-01

    This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe3C and Co3C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe3C, and Co3C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

  2. Influence of coolant on ductile mode processing of binderless nanocrystalline tungsten carbide through ultraprecision diamond turning

    NASA Astrophysics Data System (ADS)

    Doetz, Marius; Dambon, Olaf; Klocke, Fritz; Fähnle, Oliver

    2015-08-01

    Molds made of tungsten carbide are typically used for the replicative mass production of glass lenses by precision glass molding. Consequently an ultra-precision grinding process with a subsequent fresh-feed polishing operation is conventionally applied. These processes are time consuming and have a relatively low reproducibility. An alternative manufacturing technology, with a high predictability and efficiency, which additionally allows a higher geometrical flexibility, is the single point diamond turning technique (SPDT). However, the extreme hardness and the chemical properties of tungsten carbide lead to significant tool wear and therefore the impossibility of machining the work pieces in an economical way. One approach to enlarge the tool life is to affect the contact zone between tool and work piece by the use of special cutting fluids. This publication emphasizes on the most recent investigations and results in direct machining of nano-grained tungsten carbide with mono crystal diamonds under the influence of various kinds of cutting fluids. Therefore basic ruling experiments on binderless nano grained tungsten carbide were performed, where the tool performed a linear movement with a steadily increasing depth of cut. As the ductile cutting mechanism is a prerequisite for the optical manufacturing of tungsten carbide these experiments serve the purpose for establish the influence of different cutting fluid characteristics on the cutting performance of mono crystal diamonds. Eventually it is shown that by adjusting the coolant fluid it is possible to significantly shift the transition point from ductile to brittle removal to larger depths of cut eventually enabling a SPDT of binderless tungsten carbide molds.

  3. Failure of tungsten carbide-cobalt lamination dies: A corrosion evaluation

    SciTech Connect

    Pednekar, S.P.

    1997-10-01

    Sudden failures of cemented tungsten carbide (WC)-cobalt punching dies are rare but expensive. Corrosion of the cobalt matrix, or cobalt leaching, by water-based lubricants usually is considered the cause of such failures. The validity of this mechanism was evaluated by measuring the corrosion behavior of cobalt, WC, and WC-15% Co die material in water and seven made-up lubricants. In the worst lubricant, the cobalt matrix corroded at an estimated rate of < 3 mpy. In chlorinated, chloride (Cl)-bearing (> 0.01% sodium chloride [NaCl]), aerated water of pH 7, the rate could be 80 mpy. Such a rate still was not high enough to explain die failures because of the short contact time between lubricant and sliding surfaces during punching operations. Excessive adhesive wear caused by low lubricity and resulting in removal of large wear particles may have been responsible. Such particles wedged between sliding surfaces may have exerted forces sufficient to cause breakage of the dies.

  4. Spark Plasma Sintering of high-strength ultrafine-grained tungsten carbide

    NASA Astrophysics Data System (ADS)

    Nokhrin, A. V.; Chuvil'deev, V. N.; Blagoveshchenskiy, Yu V.; Boldin, M. S.; Sakharov, N. V.; Isaeva, N. V.; Popov, A. A.; Lantcev, E. A.; Belkin, O. A.; Smirnova, E. S.

    2017-07-01

    The paper dwells on the research conducted into high-rate consolidation of pure tungsten carbide nanopowders using the Spark Plasma Sintering. Studies included the effect that the original size of WC nanoparticles and their preparation modes have on density, structure parameters, and mechanical properties of tungsten carbide. It has been found that materials that show abnormal grain growth during sintering have lower values of sintering activation energy as compared to materials the structure of which is more stable during high-rate heating. A qualitative model is proposed that explains this effect through the dependence of the grain boundary diffusion coefficient on the grain boundary migration rate.

  5. Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting.

    PubMed

    Garcia-Esparza, Angel T; Cha, Dongkyu; Ou, Yiwei; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

    2013-01-01

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C(3)N(4) (mpg-C(3)N(4)) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W(2)C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H(2) and O(2) in a stoichiometric ratio from H(2)O decomposition when supported on a Na-doped SrTiO(3) photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation.

  6. Tungsten carbide promoted Pd and Pd-Co electrocatalysts for formic acid electrooxidation

    NASA Astrophysics Data System (ADS)

    Yin, Min; Li, Qingfeng; Jensen, Jens Oluf; Huang, Yunjie; Cleemann, Lars N.; Bjerrum, Niels J.; Xing, Wei

    2012-12-01

    Tungsten carbide (WC) promoted palladium (Pd) and palladium-cobalt (Pd-Co) nanocatalysts are prepared and characterized for formic acid electrooxidation. The WC as the dopant to carbon supports is found to enhance the CO tolerance and promote the activity of the Pd-based catalysts for formic acid oxidation. Alloying of Pd with Co further improves the electrocatalytic activity and stability of the WC supported catalysts, attributable to a synergistic effect of the carbide support and PdCo alloy nanoparticles.

  7. Development of high temperature materials for solid propellant rocket nozzle applications. [tantalum carbides-tungsten fiber composites

    NASA Technical Reports Server (NTRS)

    Manning, C. R., Jr.; Honeycutt, L., III

    1974-01-01

    Evaluation of tantalum carbide-tungsten fiber composites has been completed as far as weight percent carbon additions and weight percent additions of tungsten fiber. Extensive studies were undertaken concerning Young's Modulus and fracture strength of this material. Also, in-depth analysis of the embrittling effects of the extra carbon additions on the tungsten fibers has been completed. The complete fabrication procedure for the tantalum carbide-tungsten fiber composites with extra carbon additions is given. Microprobe and metallographic studies showed the effect of extra carbon on the tungsten fibers, and evaluation of the thermal shock parameter fracture strength/Young's Modulus is included.

  8. Growth kinetics of cubic carbide free layers in graded cemented carbides

    NASA Astrophysics Data System (ADS)

    Shi, Liu-Yong; Liu, Yi-Min; Huang, Ji-Hua; Zhang, Shou-Quan; Zhao, Xing-Ke

    2012-01-01

    In order to reveal the formation mechanism of cubic carbide free layers (CCFL), graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA), respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

  9. Calibration graphs for Ti, Ta and Nb in sintered tungsten carbide by infrared laser ablation inductively coupled plasma atomic emission spectrometry.

    PubMed

    Kanický, V; Otruba, V; Mermet, J M

    2001-12-01

    Infrared laser ablation (IR-LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from +/- 3% to +/- 4% for Ti, Ta, and Nb with internal standardization by tungsten and up to +/- 5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.

  10. Surface modification of tungsten carbide by electrical discharge coating (EDC) using a titanium powder suspension

    NASA Astrophysics Data System (ADS)

    Janmanee, Pichai; Muttamara, Apiwat

    2012-07-01

    Surface modification by a titanium coating layer onto a tungsten carbide surface by electrical discharge coating (EDC) was studied by considering a titanium coating modification as well as the completeness of the tungsten carbide surface. This was carried out by electrical discharge machining (EDM). The tungsten carbide material was produced using a fluid dielectric oil, which was mixed with titanium powder. The current and duty cycles were varied resulting in a change in the titanium coating layer thickness. Also, an analysis of the chemical composition using energy dispersive spectroscopy (EDS) revealed that a titanium coating layer was formed causing the hardness of the titanium surface to be close to that of tungsten carbide. The completeness of the surface was evaluated using scanning electron microscopy (SEM) and a small number of microcracks were found on the surface since the microcracks were filled and substituted by titanium powder and carbon (a hydrocarbon) that decomposed from the dielectric that acted as a combiner (TiC). Also, the high concentration of carbon increased the amount of Ti and C combination and TiC was formed, which enhanced the surface hardness of the coated layer to 1750 HV. The surface roughness of the coated layer decreased and this reduced the formation of microcracks on the surface workpiece.

  11. Maintenance of stellite and tungsten carbide saw tips: respiratory health and exposure-response evaluations.

    PubMed Central

    Kennedy, S M; Chan-Yeung, M; Marion, S; Lea, J; Teschke, K

    1995-01-01

    OBJECTIVE--To study exposure to cobalt and chromium in saw maintenance rooms and test respiratory health among saw filers at lumber mills. Hard-metal lung disease is associated with cobalt in the manufacture of tungsten carbide tools; recently it has also been reported among tool maintenance workers. Lumber mills often use saws tipped with tungsten carbide or with a newer alloy, stellite (containing more cobalt, as well as chromium). METHODS--A cross sectional study of 118 saw filers at eight lumber mills was carried out that included a standardised questionnaire, spirometry, personal air sampling, and examination of tasks every 10 minutes (by observation). Comparison data were from a study of bus mechanics tested with similar methods. RESULTS AND CONCLUSION--Cobalt exposure was associated with tungsten carbide grinding but not with stellite grinding. Chromium exposure was associated mainly with stellite welding. Saw filers had a twofold increase in phlegm and wheeze (P < 0.01) and a threefold increase in cough, phlegm, and wheeze related to work (P < 0.001), but no increase in breathlessness. Stellite welding was associated with a significant increase in nasal symptoms and cough related to work and a small decrease in airflow (forced expiratory volume in one second/forced vital capacity (FEV1/FVC%), P < 0.05). Saw filers wet grinding with tungsten carbide had significant reductions in forced expiratory lung volumes (FEV1 and FVC, P < 0.05) and were significantly more likely to have FEV1 and FVC values in the abnormal range. Cobalt exposure (in wet grinding) and duration of work that involved tungsten carbide grinding were both associated with significant reductions in FEV1 and FVC. Average cobalt exposures in this study were about 5 micrograms/m3, well below the currently accepted permissible concentration, which suggests that the current workplace limit for cobalt may be too high. PMID:7735392

  12. In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-12-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

  13. Irradiation test of tungsten clad uranium carbide-zirconium carbide ((U,Zr)C) specimens for thermionic reactor application at conditions conductive to long-term performance

    NASA Technical Reports Server (NTRS)

    Creagh, J. W. R.; Smith, J. R.

    1973-01-01

    Uranium carbide fueled, thermionic emitter configurations were encapsulated and irradiated. One capsule contained a specimen clad with fluoride derived chemically vapor deposited (CVD) tungsten. The other capsule used a duplex clad specimen consisting of chloride derived on floride derived CVD tungsten. Both fuel pins were 16 millimeters in diameter and contained a 45.7-millimeter length of fuel.

  14. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Holá, Markéta; Otruba, Vítězslav; Kanický, Viktor

    2006-05-01

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm 3) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between ± 3% and ± 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed. The

  15. Effect of SiC Nanowhisker on the Microstructure and Mechanical Properties of WC-Ni Cemented Carbide Prepared by Spark Plasma Sintering

    PubMed Central

    Fu, Zhiqiang; Wang, Chengbiao

    2014-01-01

    Ultrafine tungsten carbide-nickel (WC-Ni) cemented carbides with varied fractions of silicon carbide (SiC) nanowhisker (0–3.75 wt.%) were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC) and tantalum carbide (TaC) as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS) Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker. PMID:25003143

  16. Effect of SiC nanowhisker on the microstructure and mechanical properties of WC-Ni cemented carbide prepared by spark plasma sintering.

    PubMed

    Ren, Xiaoyong; Peng, Zhijian; Fu, Zhiqiang; Wang, Chengbiao

    2014-01-01

    Ultrafine tungsten carbide-nickel (WC-Ni) cemented carbides with varied fractions of silicon carbide (SiC) nanowhisker (0-3.75 wt.%) were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC) and tantalum carbide (TaC) as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS) Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  17. Application of a tungsten/tungsten-carbide film to H-13 casting dies by plasma assisted deposition

    SciTech Connect

    Horswill, N.; Jetzer, W.; Fetherston, P.; Conrad, J.R.

    1995-12-31

    Die casting is used extensively to produce Al, Mg and Zn alloy parts. H-13, a widely used die material, is a medium carbon steel alloy with Cr, Mo, and Si. A problem with die casting is soldering, thermal fatigue cracking, and carbon buildup which cause degradation of the casting. Application of a metallic coating to the die has been shown to increase the resistance to thermal fatigue cracking. In this study, a tungsten/tungsten carbide thin film was deposited on a casting die of H-13 die steel by a two step Plasma Source Ion Enhanced Deposition process using an argon and methane plasmas. The film was characterized using Auger Electron Spectroscopy, Scanning Electron Microscopy and Electron Dispersive Spectroscopy. The die and representative castings (from regular intervals during the lifetime of the die) were examined for evidence of soldering, thermal fatigue cracking and carbon buildup.

  18. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  19. Nanocrystaline tungsten carbide supported Au-Pd electrocatalyst for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Nie, Ming; Shen, Pei Kang; Wei, Zidong

    Au-Pd nanobimetallic particles supported on nanocrystaline tungsten carbide as electrocatalysts for oxygen reduction were prepared by an intermittent microwave heating (IMH) method. XRD measurement revealed that AuPd alloy formed during the IMH process. We showed these novel electrocatalysts could offer the activities that surpass that of the state-of-the-art Pt-based electrocatalysts for oxygen reduction reaction. The AuPd-WC/C electrode showed an over 70 mV shift towards more positive potentials compared to Pt/C electrode for ORR. The advantage seemed to come from the novel support of tungsten carbide which itself has the catalytic activity to enhance the catalytic activity of the metal electrocatalysts.

  20. Influence of high power density plasma irradiation on the boron carbide coating on tungsten

    NASA Astrophysics Data System (ADS)

    Begrambekov, L. B.; Grunin, A. V.; Puntakov, N. A.; Sadovskiy, Ya A.; Utkov, N. S.

    2017-05-01

    The paper considers an influence of T-10 tokamak plasma disruption on boron carbide (B4C) coating on tungsten. The power density of coating irradiation reached 100 MW/m2. The relief and composition of the boron carbide coating sample areas heated up to different temperature due to influence of disruption is determined. Conclusion is made that B4C does not change integrity, when heated to temperatures of up to 2000 K. Local melting was observed in areas heated up to 2500 K. In the range of 2500-3600 K most of the coating was melted and collected into droplets. Composition rate is reduced to B:C = 1:1. In all temperature ranges the coating remained continuous and provided protection of tungsten from direct plasma irradiation.

  1. The effect of plasma impurities on the sputtering of tungsten carbide.

    PubMed

    Vörtler, K; Björkas, C; Nordlund, K

    2011-03-02

    Understanding of sputtering by ion bombardment is needed in a wide range of applications. In fusion reactors, ion impacts originating from a hydrogen-isotope-rich plasma will lead, among other effects, to sputtering of the wall material. To study the effect of plasma impurities on the sputtering of the wall mixed material tungsten carbide molecular dynamics simulations were carried out. Simulations of cumulative D cobombardment with C, W, He, Ne or Ar impurities on crystalline tungsten carbide were performed in the energy range 100-300 eV. The sputtering yields obtained at low fluences were compared to steady state SDTrimSP yields. During bombardment single C atom sputtering was preferentially observed. We also detected significant W(x)C(y) molecule sputtering. We found that this molecule sputtering mechanism is of physical origin.

  2. Dissolution of cemented carbide powders in artificial sweat: implications for cobalt sensitization and contact dermatitis.

    PubMed

    Stefaniak, Aleksandr B; Harvey, Christopher J; Virji, M Abbas; Day, Gregory A

    2010-10-06

    Skin exposure to cobalt-containing materials can cause systemic immune sensitization and upon repeat contact, elicitation of allergic contact dermatitis (ACD). Data on cobalt dissolution rates are needed to calculate uptake through skin and for development of models to understand risk of sensitization or dermatitis. The purpose of this research was to measure the dissolution kinetics of feedstock and process-sampled powders encountered in the production of hard metal alloys using artificial sweat. The physicochemical properties of each material were characterized prior to evaluation of dissolution behavior. Variations in artificial sweat solvent pH and chemistry were used to understand critical factors in dissolution. Dissolution of cobalt, tungsten, and tungsten carbide was often biphasic with the initial rapid phase being up to three orders of magnitude faster than the latter long-term phase. Artificial sweat pH did not influence dissolution of cobalt or tungsten carbide. Solvent composition had little influence on observed dissolution rates; however, vitamin E suppressed the dissolution of cobalt and tungsten carbide from sintered particles obtained from a chamfer grinder. There was no effect of particle size on dissolution of feedstock cobalt, tungsten, tungsten carbide, and admixture powders. Particle physicochemical properties influenced observed dissolution rates with more cobalt and tungsten carbide dissolving from chamfer grinder particles compared to the feedstock powders or admixture powder. Calculations using the observed dissolution rates revealed that skin exposure concentrations were similar to concentrations known to induce cobalt sensitization and elicit ACD. Observed dissolution rates for cobalt in artificial sweat indicate that dermal uptake may be sufficient to induce cobalt sensitization and allergic dermatitis.

  3. Wear Resistant Coating on Tungsten Carbide Hard Alloy

    NASA Astrophysics Data System (ADS)

    Oskolkova, T. N.

    2015-09-01

    The article reveals new knowledge about the role of zirconium in the composition of (Ti, Zr)N ion-plasma coating applied on WC10KS alloy. It is determined that when zirconium is introduced into ion-plasma coating TiN (50%) wear resistance and adhesion strength grow, nanohardness increases by 23% (up to 38500MPa), Yung's modulus rises by 67%, friction coefficient reduces to p = 0.07 and performance characteristics of a carbide alloy improve.

  4. Dry Sliding Wear behaviour of Aluminium-Red mud- Tungsten Carbide Hybrid metal matrix composites

    NASA Astrophysics Data System (ADS)

    Devi Chinta, Neelima; Selvaraj, N.; Mahesh, V.

    2016-09-01

    Red mud is an industrial waste obtained during the processing of alumina by Bayer's process. An attempt has been made to utilize the solid waste by using it as the reinforcement material in metal matrix composites. Red mud received from NALCO has been subjected for sieve analysis and milled to 42 nanometers using high energy ball mill. Red mud is used as a reinforcement material in Pure Aluminium matrix composite at 2%, 4%, and 6% weight at 100 microns level as well as 42 nano meters along with 4%Tungsten carbide by weight. Micro and Nano structured red mud powders, Tungsten carbide powder and Aluminium is mixed in a V-Blender, compacted at a pressure of 40 bar and samples are prepared by conventional sintering with vacuum as medium. In this current work, dry sliding wear characteristics at normal and heat treatment conditions are investigated with optimal combination of Aluminium, Tungsten carbide and different weight fractions of micro and nano structured red mud powder.

  5. Numerical simulation and experiment on split tungsten carbide cylinder of high pressure apparatus

    SciTech Connect

    Yang, Yunfei; Li, Mingzhe Wang, Bolong; Liu, Zhiwei

    2015-12-15

    A new high pressure device with a split cylinder was investigated on the basis of the belt-type apparatus. The belt-type die is subjected to excessive tangential tensile stress and the tungsten carbide cylinder is easily damaged in the running process. Taking into account the operating conditions and material properties of the tungsten carbide cylinder, it is divided into 6 blocks to eliminate the tangential tensile stress. We studied two forms of the split type: radial split and tangential split. Simulation results indicate that the split cylinder has more uniform stress distribution and smaller equivalent stress compared with the belt-type cylinder. The inner wall of the tangential split cylinder is in the situation that compressive stress is distributed in the axial, radial, and tangential directions. It is similar to the condition of hydrostatic pressure, and it is the best condition for tungsten carbide materials. The experimental results also verify that the tangential split die can bear the highest chamber pressure. Therefore, the tangential split structure can increase the pressure bearing capacity significantly.

  6. Durable and self-hydrating tungsten carbide-based composite polymer electrolyte membrane fuel cells.

    PubMed

    Zheng, Weiqing; Wang, Liang; Deng, Fei; Giles, Stephen A; Prasad, Ajay K; Advani, Suresh G; Yan, Yushan; Vlachos, Dionisios G

    2017-09-04

    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. Density functional theory exposes that OH• and H• radicals adsorb more strongly from solution and reactions producing OH• are significantly more endergonic on tungsten carbide than on platinum. Consequently, tungsten carbide may be a promising catalyst in self-hydrating crossover gases while retarding desorption of and capturing free radicals formed at the cathode, resulting in enhanced membrane durability.The proton conductivity of polymer electrolyte membranes in fuel cells dictates their performance, but requires sufficient water management. Here, the authors report a simple method to produce well-dispersed transition metal carbide nanoparticles as additives to enhance the performance of Nafion membranes in fuel cells.

  7. Abrasive Wear Failure Analysis of Tungsten Carbide Hard facing on Carbon Steel Blade

    NASA Astrophysics Data System (ADS)

    Tobi, A. L. Mohd; Kamdi, Z.; Ismail, M. I.; Nagentrau, M.; Roslan, L. N. H.; Mohamad, Z.; Omar, A. S.; Latif, N. Abdul

    2017-01-01

    This study investigate the abrasive wear failure of tungsten carbide hardfacing on continuous digester (CD) blade (carbon steel) in an environment of sulphuric acid and ilmenite ore mixture. Comparison being made on the hardness, thickness and microstructural of the hardfacing between unworn and 3 months old worn blade on few locations around the blade. The cross sections of the blade revealed non-uniform coverage of the hardfacing on the blade for both worn and unworn blade. The edge of the blade has the least amount of hardfacing thickness which with time acts as the point of failure during the wear process. The hardness obtained from both the unworn and worn samples are around 25% lower from the hardfacing electrode manufacturer’s hardness specification. Microstructural micrograph analysis of the hardfacing revealed non uniform size carbide with non-uniform distributed of carbide in the hardfacing layer.

  8. The Effects of Carbide Characteristics on the Performance of Tungsten Carbide-Based Composite Overlays, Deposited by Plasma-Transferred Arc Welding

    NASA Astrophysics Data System (ADS)

    Fisher, G.; Wolfe, T.; Meszaros, K.

    2013-06-01

    In Alberta, there are huge quantities of ore processed to remove bitumen from oil sands deposits. The scale of production generates very aggressive tribocorrosive conditions during the mining, extraction, and upgrading processes. It is common to apply tungsten carbide-based composite overlays to improve the reliability and extend service lives of equipment and components. The performance of the applied overlays is largely dependent on the selection of the carbide type and the wear environment. This paper will evaluate overlays containing macrocrystalline, angular eutectic, and spherical eutectic tungsten carbides and discuss the performance of the overlays with a focus on carbide properties and the interactions between the service conditions and the composite material. This discussion will demonstrate how effective selection of protective materials can improve the reliability of oil sands equipment.

  9. Tensile and stress-rupture behavior of hafnium carbide dispersed molybdenum and tungsten base alloy wires

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; Titran, Robert H.

    1993-01-01

    The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.

  10. Wear behavior and tool life of modified WC-based cemented carbides

    SciTech Connect

    Bhaumik, S.K.; Upadhyaya, G.S.; Vaidya, M.L. . Dept. of Materials and Metallurgical Engineering)

    1994-01-01

    The alloy design of WC-10 Co cemented carbides by adding hard phases like TiC/TiN and modifying the binder phase with nickel and molybdenum has been highlighted by the authors elsewhere. The present investigation was aimed at evaluating performance of such cemented carbides in steel cutting. Addition of TiC/TiN improved the crater wear resistance and tool life of WC-10 Co cemented carbide, the improvement being better with TiN additions compared with TiC. Binder phase composition was important in controlling the microstructure and mechanical properties of the tool materials, which had a direct influence on cutting performance. The results were analyzed in terms of microstructure and various properties, viz., hardness, transverse rupture strength, oxidation resistance, and thermal shock resistance, which have a bearing on tool life.

  11. Effect of WC/Co coherency phase boundaries on Fracture toughness of the nanocrystalline cemented carbides

    PubMed Central

    Xie, Hongxian; Song, Xiaoyan; Yin, Fuxing; Zhang, Yongguang

    2016-01-01

    The effect of coherency WC/Co phase boundaries on the fracture toughness of the nanocrystalline WC-Co cemented carbides is studied by MD simulation method. The simulation results show that the nanocrystalline WC-Co cemented carbides with coherency WC/Co phase boundaries has higher fracture toughness than that without coherency WC/Co phase boundaries. Moreover, the mechanism of why coherency WC/Co phase boundaries can improve the fracture toughness of the nanocrystalline cemented carbides is also investigated. It is found the fact that the separation energy of the coherent WC/Co phase boundary is larger than that of the incoherent WC/Co phase boundaries is the main reason for this excellent mechanical property. PMID:27485922

  12. Influence of WC and Co Contents in Cutting of Wear and Impact Resistant Cemented Carbides

    NASA Astrophysics Data System (ADS)

    Miyamoto, Takeshi; Heo, Sung Jung; Fujiwara, Junsuke; Hanasaki, Shinsaku

    To investigate the influence of the WC and Co contents, the cutting of five kinds of cemented carbides was carried out with the PCD tool. Moreover, one of them was the cemented carbides whose binder was Ni, and the influence of the binder was also found out. The tool wear width and the cutting forces were measured, and the worn flank was observed. Summary of results are shown as follows. (1) The tool wear didn’t always increased with increase of the Co content. (2) Not only the WC content but also the WC particle diameter influenced the tool life. (3) The adhesion could be found out in cutting every cemented carbides regardless of the content and composition. (4) The thrust forces were concerned with the flank wear.

  13. Microstructure of TiC-Based Coatings on Cemented Carbide Derived by Sol-Gel Routes

    NASA Astrophysics Data System (ADS)

    Yang, Mei; Guo, Zhixing; Qi, Kaifeng; Huang, Kun; Deng, Jianxiong; Liu, Jia

    2017-02-01

    TiC-based coating is prepared by depositing TiO2 sol on cemented carbide compact and liquid phase sintering. TiC forms due to carbothermal reduction reaction of TiO2 and then reacts with WC and transforms to TiC-based solid solution. Ti content changes the WC growth mechanism and results in the multi-stepped morphology. When sintered cemented carbide is used as substrate, WC keeps the equilibrium truncated triangle prism morphology due to the relatively weak diffusion among Ti, WC, and Co.

  14. Growth and tribological properties of diamond films on silicon and tungsten carbide substrates

    NASA Astrophysics Data System (ADS)

    Radhika, R.; Ramachandra Rao, M. S.

    2016-11-01

    Hot filament chemical vapor deposition technique was used to deposit microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films on silicon (Si) and tungsten carbide (WC-6Co) substrates. Friction coefficient of larger diamond grains deposited on WC-6Co substrate shows less value approximately 0.2 while this differs marginally on films grown on Si substrate. The study claims that for a less friction coefficient, the grain size is not necessarily smaller. However, the less friction coefficient (less than 0.1 saturated value) in MCD and NCD deposited on Si is explained by the formation of graphitized tribolayer. This layer easily forms when diamond phase is thermodynamically unstable.

  15. Solid state synthesis of tungsten carbide nanorods and nanoplatelets by a single-step pyrolysis.

    PubMed

    Shanmugam, Sangaraju; Jacob, David S; Gedanken, Aharon

    2005-10-20

    We report a simple and efficient single-step synthesis of tungsten carbide nanorods and nanoplatelets by direct pyrolysis of a hybrid composite material of 12-tungstophosphoric acid and hexadecyltrimethylammonium bromide in a closed Swagelok cell at 1000 degrees C. The product was characterized by XRD, TGA, SEM, TEM, XPS, and CV. The diameter of the nanorods is 30-50 nm, and the length varies from 200 to 500 nm. The size of the platelets is around 55 nm. The WC exhibits an interesting structural surface with kinks, steps, and terraces which is evidenced by HRTEM studies.

  16. Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

    NASA Astrophysics Data System (ADS)

    De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

    2012-09-01

    Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

  17. Magnetic field imaging of a tungsten carbide film by scanning nano-SQUID microscope

    NASA Astrophysics Data System (ADS)

    Shibata, Yusuke; Nomura, Shintaro; Ishiguro, Ryosuke; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Nago, Yusuke; Takayanagi, Hideaki

    2016-10-01

    We present the results of magnetic field imaging by scanning nano-superconducting quantum interference device (SQUID) microscopy on a tungsten carbide (W-C) film fabricated using focused-ion-beam chemical vapor deposition. We have investigated magnetic field change by a W-C film in an external magnetic field using a scanning nano-SQUID microscope system. We have found that the reduction of the magnetic field above the W-C film was 0.9%, indicating the penetration of vortices in the W-C at an external magnetic field of 0.171 mT.

  18. Tungsten carbide production from ore concentrates by molten salt-natural gas sparging treatment

    SciTech Connect

    Carnahan, T.G.; Kazonich, G.; Raddatz, A.E.

    1988-01-01

    The U.S. Bureau of Mines conducted a bench-scale study to delineate the important parameters in a three-step process to produce commercial-quality tungsten carbide (WC) directly from tungsten minerals. In the process, tungsten concentrates of wolframite or wolframite and scheelite are decomposed at 1,050{sup 0}C in a molten mixture of NcCl and Na{sub 2}SiO{sub 3} that forms two immiscible phases. Tungsten, as sodium tungstate, reports to the halide phase and is separated from the gangue constituents, which report to the silicate phase. After decanting to separate the two phases, natural gas is sparged into the molten halide phase a 1,070{sup 0}C. Submicrometer crystals of WC are initially produced. These crystals grow into thin triangular-shaped plates up to 100 {mu}m on a side or into popcorn-shaped conglomerates. Sparged WC was examined for its suitability for use in sintered carbide products. In physical evaluations, sparged WC ground to an average particle size of 1.52 {mu}m and compacted with 10 pct Co binder into standard 6-by 22-mm test bars had a density of 14.35 and a Rockwell A hardness of 89.6. This compared favorably with 14.39 and 89.7 respectively, for test bars made from a standard commercial 1.52-{mu}m WC powder. Test bars made from Bureau of Mines WC had no C'' porosity or eta phase.

  19. Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils.

    PubMed

    Ishii, T; Shi, L; Huang, R; Tsujino, N; Druzhbin, D; Myhill, R; Li, Y; Wang, L; Yamamoto, T; Miyajima, N; Kawazoe, T; Nishiyama, N; Higo, Y; Tange, Y; Katsura, T

    2016-02-01

    We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5) high heating efficiency.

  20. Metal modified tungsten carbide (WC) for catalytic and electrocatalytic applications

    NASA Astrophysics Data System (ADS)

    Mellinger, Zachary J.

    One of the major challenges in the commercialization of proton exchange membrane fuel cells (PEMFC) is the cost, and low CO tolerance of the anode electrocatalyst material. The anode typically requires a high loading of precious metal electrocatalyst (Pt or Pt--Ru) to obtain a useful amount of electrical energy from the electrooxidation of methanol (CH3OH) or ethanol (C2H5OH). The complete electro--oxidation of methanol or ethanol on these catalysts produces strongly adsorbed CO on the surface, which reduces the activity of the Pt or Pt--Ru catalysts. Another major disadvantage of these electrocatalyst components is the scarcity and consequently high price of both Pt and Ru. Tungsten monocarbide (WC) has shown similar catalytic properties to Pt, leading to the utilization of WC and metal modified WC as replacements to Pt and Pt--Ru. In this thesis we investigated WC and Pt--modified WC as a potentially more CO--tolerant electrocatalysts as compared to pure Pt. These catalysts would reduce or remove the high loading of Pt used industrially. The binding energy of CO, estimated using temperature programmed desorption, is weaker on WC and Pt/WC than on Pt, suggesting that it should be easier to oxidize CO on WC and Pt/WC. This hypothesis was verified using cyclic voltammetry to compare the electro--oxidation of CO on WC, Pt/WC, and Pt supported on carbon substrates, which showed a lower voltage for the onset of oxidation of CO on WC and Pt/WC than on Pt. After observing these improved properties on the Pt/WC catalysts, we decided to expand our studies to investigate Pd--modified WC as Pd is less expensive than Pt and has shown more ideal properties for alcohol electrocatalysis in alkaline media. Pd/WC showed a lower binding energy of CO than both its parent metal Pd as well as Pt. Then, density functional theory (DFT) calculations were performed to determine how the presence of Pd affected the bonding of methanol and ethanol on the WC surface. The DFT studies showed

  1. HVOF and HVAF Coatings of Agglomerated Tungsten Carbide-Cobalt Powders for Water Droplet Erosion Application

    NASA Astrophysics Data System (ADS)

    Tarasi, F.; Mahdipoor, M. S.; Dolatabadi, A.; Medraj, M.; Moreau, C.

    2016-12-01

    Water droplet erosion (WDE) is a phenomenon caused by impingement of water droplets of several hundred microns to a few millimeters diameter at velocities of hundreds of meters per second on the edges and surfaces of the parts used in such services. The solution to this problem is sought especially for the moving compressor blades in gas turbines and those operating at the low-pressure end of steam turbines. Thermal-sprayed tungsten carbide-based coatings have been the focus of many studies and are industrially accepted for a multitude of wear and erosion resistance applications. In the present work, the microstructure, phase analysis and mechanical properties (micro-hardness and fracture toughness) of WC-Co coatings are studied in relation with their influence on the WDE resistance of such coatings. The coatings are deposited by high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes. The agglomerated tungsten carbide-cobalt powders were in either sintered or non-sintered conditions. The WDE tests were performed using 0.4 mm water droplets at 300 m/s impact velocity. The study shows promising results for this cermet as WDE-resistant coating when the coating can reach its optimum quality using the right thermal spray process and parameters.

  2. Tungsten carbide nanotubes supported platinum nanoparticles as a potential sensing platform for oxalic acid.

    PubMed

    Maiyalagan, Thandavarayan; Kannan, Palanisamy; Jönsson-Niedziolka, Martin; Niedziolka-Jönsson, Joanna

    2014-08-05

    Supported tungsten carbide is an efficient and vital nanomaterial for the development of high-performance, sensitive, and selective electrochemical sensors. In this work, tungsten carbide with tube-like nanostructures (WC NTs) supported platinum nanoparticles (PtNPs) are synthesized and explored as an efficient catalyst toward electrochemical oxidation of oxalic acid for the first the time. The WC NTs supported PtNPs modified glassy carbon (GC) electrode is highly sensitive toward the electrochemical oxidation of oxalic acid. A large decrease in the oxidation overpotential (220 mV) and significant enhancement in the peak current compared to unmodified and Pt/C modified GC electrodes have been observed without using any redox mediator. Moreover, WC NTs supported PtNPs modified electrode possessed wide linear concentration ranges from 0 to 125 nM and a higher sensitivity toward the oxidation of oxalic acid (80 nA/nM) achieved by the amperometry method. The present modified electrode showed an experimentally determined lowest detection limit (LOD) of 12 nM (S/N = 3). Further, WC NTs supported PtNPs electrode can be demonstrated to have an excellent selectivity toward the detection of oxalic acid in the presence of a 200-fold excess of major important interferents. The practical application of WC NTs supported PtNPs has also been demonstrated in the detection of oxalic acid in tomato fruit sample, by differential pulse voltammetry under optimized conditions.

  3. Surface morphology and bond characterization of nanocrystalline diamonds grown on tungsten carbide via hot filament chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hamzah, E.; Yong, T. M.; Mat Yajid, M. A.

    2013-06-01

    Nanocrystalline diamonds (NCDs) were deposited on chemically prepared tungsten carbide substrates via hot filament chemical vapor deposition. The surface morphology of the NCDs was examined using field emission scanning electron microscopy. The NCDs formed a ballas morphology evenly across the tungsten carbide surface. Overetching affected the diamond deposition by causing the ballas to form aggregations. Cross-sectional fragmentation using a diamond wafering blade caused the nanocrystalline diamond to fragment at overetched boundaries, and delamination only occurred 30-50 µm off the edge and revealed that the thickness of the diamond film was 6 µm. Grazing XRD is an effective method to identify diamonds even at the nanoscale. The crystallite size was calculated to be 18.4 nm by modeling. Cross-sectional TEM analysis indicated that the diamond grain size was approximately 10-30 nm near the interface. Amorphous carbon, an embedded diamond and voids were also observed. TEM also revealed that the tungsten carbide surface undulates. The nanocrystalline diamonds nucleated and grew on the tungsten carbide (100) planes in the <111> direction, forming (111) planes, as observed from HRTEM, d-spacing measurements, SAD and FFT analyses for a FIB-prepared sample.

  4. Effect of bond coat and preheat on the microstructure, hardness, and porosity of flame sprayed tungsten carbide coatings

    NASA Astrophysics Data System (ADS)

    Winarto, Winarto; Sofyan, Nofrijon; Rooscote, Didi

    2017-06-01

    Thermally sprayed coatings are used to improve the surface properties of tool steel materials. Bond coatings are commonly used as intermediate layers deposited on steel substrates (i.e. H13 tool steel) before the top coat is applied in order to enhance a number of critical performance criteria including adhesion of a barrier coating, limiting atomic migration of the base metal, and corrosion resistance. This paper presents the experimental results regarding the effect of nickel bond coat and preheats temperatures (i.e. 200°C, 300°C and 400°C) on microstructure, hardness, and porosity of tungsten carbide coatings sprayed by flame thermal coating. Micro-hardness, porosity and microstructure of tungsten carbide coatings are evaluated by using micro-hardness testing, optical microscopy, scanning electron microscopy, and X-ray diffraction. The results show that nickel bond coatings reduce the susceptibility of micro crack formation at the bonding area interfaces. The percentage of porosity level on the tungsten carbide coatings with nickel bond coat decreases from 5.36 % to 2.78% with the increase of preheat temperature of the steel substrate of H13 from 200°C to 400°C. The optimum hardness of tungsten carbide coatings is 1717 HVN in average resulted from the preheat temperature of 300°C.

  5. Pump/probe Microwave-Optical Double Resonance (ppmodr) Study of Tungsten Carbide (wc) and Platinum Carbide (PtC)

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Steimle, Timothy C.

    2012-06-01

    Gas-phase metal-containing molecules serve as ideal venues for testing computational methodologies being developed to predict chemical properties of simple molecules. The most accurate determination of molecular properties comes from the analysis of pure rotational spectra, which for metal containing molecules can be difficult to obtain. One powerful method for recording pure rotational spectrum is to use the PPMODR technique which couples the sensitivity of optical detection with the precision of molecular beam microwave spectroscopy. Here we report on the application of PPMODR to the study of tungsten carbide, WC, and platinum carbide, PtC. The J=1→2 pure rotational transitions in the X^3Δ_1(v=0) state of ^1^8^6W^1^2C and ^1^8^4W^1^2C reveal a small splitting, an analysis of which provides accurate determination of the rotational and Ω-doubling parameters for the X^3Δ_1(v=0) state, which are critical to the proposed electron electric dipole moment experiments (eEDM). The implications for the proposed eEDM measurements will be presented. We also report on the J=0→1 and J=1→2 rotational transitions of PtC for the X^1Σ^+(v=0) state. The ^1^9^5Pt(I=1/2) nuclear spin-rotation interaction parameter, C_I^e^f^f , was determined to be 0.138(6) MHz. A comparison with other Pt-containing molecules and a proposed molecular orbital correlation diagram is given. W. J. Childs, Physics Reports 211, No. 3 (1991). F. Wang and T. C. Steimle, J. Chem. Phys. 136, 044312 (2012). J. Lee, E. R. Meyer, R. Paudel, J. L. Bohn and A. E. Leanhardt, J. Mod. Opt. 56 2005, (2009). F. Wang and T. C. Steimle, J. Chem. Phys. 134, 201106 (2011). F. Wang and T. C. Steimle, J. Chem. Phys. 135, 104313 (2011).

  6. Application of Deep Cryogenic Treatment to Uncoated Tungsten Carbide Inserts in the Turning of AISI 304 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Özbek, Nursel Altan; Çİçek, Adem; Gülesİn, Mahmut; Özbek, Onur

    2016-12-01

    This study investigated the effects of deep cryogenic treatment (DCT) on the wear performance of uncoated tungsten carbide inserts. AISI 304 austenitic stainless steel, widely used in industry, was selected as the workpiece material. Cutting experiments showed that the amount of wear significantly increased with increasing cutting speed. In addition, it was found that DCT contributed to the wear resistance of the turning inserts. The treated turning inserts were less worn by 48 and 38 pct in terms of crater wear and notch wear, respectively, whereas they exhibited up to 18 pct superior wear performance in terms of flank wear. This was attributed to the precipitation of new and finer η-carbides and their homogeneous distribution in the microstructure of the tungsten carbide material after deep cryogenic treatment. Analyses via image processing, hardness measurements, and SEM observations confirmed these findings.

  7. Expansion into vacuum of a shocked tungsten carbide-epoxy mixture.

    SciTech Connect

    Reinhart, William Dodd; Thornhill, Tom Finley, III; Vogler, Tracy John; Alexander, C. Scott

    2009-03-01

    The behavior of a shocked tungsten carbide / epoxy mixture as it expands into a vacuum has been studied through a combination of experiments and simulations. X-ray radiography of the expanding material as well as the velocity measured for a stood-off witness late are used to understand the physics of the problem. The initial shock causes vaporization of the epoxy matrix, leading to a multi-phase flow situation as the epoxy expands rapidly at around 8 km/s followed by the WC particles moving around 3 km/s. There are also small amounts of WC moving at higher velocities, apparently due to jetting in the sample. These experiments provide important data about the multi-phase flow characteristics of this material.

  8. Pulsed laser deposition of tungsten carbide thin films on silicon (100) substrate

    NASA Astrophysics Data System (ADS)

    Suda, Y.; Nakazono, T.; Ebihara, K.; Baba, K.

    1997-01-01

    A method of synthesizing tungsten carbide (WC) thin films by a pulsed YAG laser deposition is investigated. WC thin films are deposited on silicon (100) substrates by using WC5%Co alloy targets. Glancing angle X-ray diffraction shows that the strong peaks of W 2C appear at the substrate temperature of 500°C. Beside the strong peaks of W 2C, weak peaks of WC and W 3Co 3C appear at the substrate temperature of 650°C. Auger electron spectroscopy shows that the almost stoichiometric WC films are deposited at the methane gas pressure of 1.0 Pa. Morphological features of the samples have been obtained by employing the technique of scanning electron microscopy. X-ray photoelectron spectroscopy has been used to obtain structural and compositional information about the samples.

  9. Diffusion barrier performance of pulsed laser deposited amorphous tungsten carbide films

    NASA Astrophysics Data System (ADS)

    Ghaisas, Smita

    1991-12-01

    The performance of pulsed laser deposited tungsten carbide films as diffusion barriers between a <100> Si substrate and an Al overlayer has been investigated. Four-point probe measurement of resistance is employed to monitor the electrical stability of the Al/WC/Si metallization schemes upon thermal annealing in a vacuum for 30 min in a temperature range from 100 to 500 °C. The Glancing angle x-ray diffraction technique has been used to characterize the as-deposited as well as annealed samples. To study the metallurgical interaction between Al overlayer and the barrier film, experiments on isothermal annealings are carried out. The data obtained have been used to estimate the activation energy for the formation of the intermetallic compound WAl12. Morphological features of the annealed samples have been obtained by employing the technique of scanning electron microscopy.

  10. Chemical vapor deposited tungsten with dispersed carbides for Space Shuttle check valves

    NASA Technical Reports Server (NTRS)

    Williams, G. E.

    1980-01-01

    A chemical vapor deposited tungsten with dispersed carbides was selected as the material for Space Shuttle Orbital Maneuvering and Reaction Control Systems check valve poppets and seats. The selection followed a NASA-sponsored prototype check valve development program utilizing the cutter-seal shell poppet concept. The poppet material is deposited as a coating approximately 0.9 mm thick and fabricated into a shell as a free standing body. The seat material is deposited as a coating 1.1 mm thick on a seat blank, and the cutter seal is machined in the coating. Module tests demonstrated that the material could be ground and lapped to very sharp edges and could cut through typical system contaminants without excessive damage to the sealing surfaces. The material was also determined to be unaffected by exposure to a strongly oxidizing storable propellant.

  11. Analysis of tungsten carbide coatings by UV laser ablation inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Kanicky, V.; Otruba, V.; Mermet, J.-M.

    2000-06-01

    Tungsten carbide coatings (thickness 0.1-0.2 mm) containing 8.0, 12.2, 17.2 and 22.9% Co were studied with laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES). Composition of these plasma sprayed deposits on steel disks was determined using X-ray fluorescence spectrometry and electron microprobe energy/wavelength dispersive X-ray spectrometry. The coatings were ablated by means of a Q-switched Nd:YAG laser at 266 nm (10 Hz, 10 mJ per shot) coupled to an ICP echelle-based spectrometer equipped with a segmented charge-coupled device detector. Non-linear dependences of cobalt lines intensities on the Co percentage were observed both at a single spot ablation and at a sample translation. This behaviour could be attributed to a complex phase composition of the system W-C-Co. However, employing tungsten as internal standard the linear calibration was obtained for studied analytical lines Co II 228.616 nm, Co II 230.786 nm, Co II 236.379 nm and Co II 238.892 nm.

  12. Reactive ion etching of sputtered silicon carbide and tungsten thin films for device applications. Final report

    SciTech Connect

    Pan, W.S.; Steck, A.J.

    1989-01-01

    For high-temperature processing and device applications, refractory materials, such as silicon carbide (SiC) and tungsten (W), are actively considered or evaluated as the basic semiconductor and metallization materials for future generations of integrated circuits. In order to pattern fine lines in SiC and W thin films, a selective and anisotropic etching technique needs to be developed for future device applications. Therefore, the etching process including basic mechanisms and process requirement have been chosen as the overall research goals of this project. Reactive ion etching (RIE) of SiC thin films in a variety of fluorinated gas plasmas, such as SF{sub 6}, CBrF{sub 3} and CHF{sub 3} mixed with oxygen was investigated in depth. The best anisotropic profile was observed by using CHF{sub 3} gas in the RIE mode. A typical DC bias, -300V, is concluded from etching experiments to determine the dependence of SiC etch rate and physical reaction under RIE mode. Reactive ion etching of tungsten (W) thin film was also investigated by using the different fluorinated gas plasmas, such as CF{sub 4}, SF{sub 6}, CBrF{sub 3} and CHF{sub 3} mixed with oxygen. The obtaining of anisotropic etching profiles in W etching was suggested and the mechanisms were also studied.

  13. Laser cladding of tungsten carbides (Spherotene ®) hardfacing alloys for the mining and mineral industry

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Alvarez, J. C.; Lamas, J.; Yáñez, A.

    2009-03-01

    The abrasive nature of the mechanical processes involved in mining and mineral industry often causes significant wear to the associated equipment and derives non-negligible economic costs. One of the possible strategies to improve the wear resistance of the various components is the deposition of hardfacing layers on the bulk parts. The use of high power lasers for hardfacing (laser cladding) has attracted a great attention in the last decade as an alternative to other more standard methods (arc welding, oxy-fuel gas welding, thermal spraying). In laser cladding the hardfacing material is used in powder form. For high hardness applications Ni-, Co- or Fe-based alloys containing hard phase carbides at different ratios are commonly used. Tungsten carbides (WC) can provide coating hardness well above 1000 HV (Vickers). In this respect, commercially available WC powders normally contain spherical micro-particles consisting of crushed WC agglomerates. Some years ago, Spherotene ® powders consisting of spherical-fused monocrystaline WC particles, being extremely hard, between 1800 and 3000 HV, were patented. Very recently, mixtures of Ni-based alloy with Spherotene powders optimized for laser processing were presented (Technolase ®). These mixtures have been used in our study. Laser cladding tests with these powders were performed on low carbon steel (C25) substrates, and results in terms of microstructure and hardness will be discussed.

  14. Precision grinding of tungsten carbide mold insert for molding of sub-millimeter glass aspheric lenses

    NASA Astrophysics Data System (ADS)

    Chao, Choung-Lii; Chang, Chia-Jung; Chen, Chun-Chieh; Chou, Wen-Chen; Ma, Kung-Jeng

    2013-06-01

    As the demand for precision optical components with sub-millimeter feature size steadily increasing, numerous efforts have been made in developing new techniques and in improving the existing approaches to efficiently and economically produce those components. Glass molding process (GMP) is one of these methods to enable mass production of precision glass optical components in recent years. One of the key issues in GMP is precision mold insert fabrication. Since the mould are normally made of hard and brittle materials such as tungsten carbide (WC) and silicon carbide (SiC), precision diamond grinding is by far the principal choice used to machine the GMP mould. As the feature size of optical component gets smaller, the size of mould and grinding wheel used to fabricate the mould gets smaller too. This makes the grinding process a very time consuming and expensive task. This research aimed to improve the small mold fabrication processes by developing an effective way of producing small diamond wheels and in-process monitoring wheel profile. Diamond wheels of around 0.2mm to 0.5mm in diameter after truing and WC aspheric mold insert of form accuracy around 0.47μm were successfully produced in this research.

  15. [Study on the Interface Characteristics of Cemented Carbide after Stripping Ti Department Coatings].

    PubMed

    Yan, Qiang; Liang, Zheng; Song, Hui-jin; Wu, Tao; Wu, Jun

    2015-04-01

    TiAlN Coatings were stripped by chemical method, which were deposited on Y WZ Alloy by arc ion plating. The surface morphology and composition of the cemented carbide after stripping TiAlN coatings by chemistry method were analyzed. It was found that TiA1N coatings on the cemented carbide substrates could be removed by being taken in 30% of hydrogen peroxide and potassium oxalate in alkaline mixed solution (V(NaOH so1ution):V(3O%H2O2):V(COOK solution) = 1:1:1) at 45 °C for 45 minutes. The surface of the cemented carbide substrate was bright, and the color was the same as that before depositing TiA1N coatings. The surface of the substrate after removing was studied by X-ray photoelectron spectrum (XPS). The results showed that binding energies of the W element and the main peak of N element on the substrate surface were much close to the criterion binding energy in the XPS data-base; and the valence of the element on the YW2 alloy changed little. The Al, Ti and N elements diffusing into the superficial zone of the sample during the coating depositing process made their contents increase and the band energy location offset after stripping the coating. TiN and A1N were formed, which benefit to increase the film-substrate cohesion during re-preparing coatings. The influence of stripping solution on the corrosion degree of cemented carbide substrate was small.

  16. Effects of Implant Copper Layer on Diamond Film Deposition on Cemented Carbides

    NASA Astrophysics Data System (ADS)

    Ma, Zhi-bin; Wang, Jian-hua; Wu, Qin-chong; Wang, Chuan-xin

    2001-02-01

    The deposition of high-quality diamond films and their adhesion on cemented carbides are strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing Co content on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leading to a mechanical weak surface often causes a poor adhesion. In this paper we adopted an implant copper layer prepared by vaporization to improve the mechanical properties of the Co-leached substrate. The diamond films were grown by microwave plasma chemical vapor deposition from CH4:H2 gas mixture. The cross section and the morphology of the diamond film were characterized by scanning electron microscopy (SEM). The non-diamond content in the film was analyzed by Raman spectroscopy. The effects of pretreatment on the concentrations of Co and Cu near the interfacial region were examined by energy dispersive spectrum (EDS) equipped with SEM. The adhesion of the diamond on the substrate was evaluated with a Rockwell-type hardness tester. The results indicate that the diamond films prepared with implant copper layer have a good adhesion to the cemented carbide substrate due to the recovery of the mechanical properties of the Co-depleted substrate after the copper implantation and the formation of less amorphous carbon between the substrate and the diamond film.

  17. Comparison Between Cemented Carbide and PCD Tools on Machinability of a High Silicon Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Soares, R. B.; de Jesus, A. M. P.; Neto, R. J. L.; Chirita, B.; Rosa, P. A. R.; Reis, A.

    2017-08-01

    The high content of silicon of aluminum casting alloys challenges the tool life of conventional cemented carbide inserts, and polycrystalline diamond (PCD) tools appear as an interesting material to machine these alloys because they improve substantially the durability of cutting tools and consequently the productivity of machining. However, the surface roughness, cutting forces and chip morphology are equally important factors in machining evaluation. Therefore, an experimental study is performed aiming at comparing the performance of cemented carbide and PCD tools taking into account cutting forces, surface roughness and chip morphology, under dry longitudinal turning, performed for the AlSi9Cu3 alloy produced by permanent mold casting process. Different chip breaker geometries were also considered, and their influence on the referred parameters was also investigated. Analysis of variance was employed to study the different contributions of inserts, cutting speed, feed rate, depth of cut and their interactions in machinability performance. The results show low cutting forces and better results for surface roughness for uncoated cemented carbide tools, with simpler chip breakers and flat rake face PCD tool, but an efficient chip control was obtained for inserts with small grooves with high cutting forces and power consumption. Nevertheless, the feed rate and depth of cut have the highest influence on the machinability performance of the alloy under investigation.

  18. Core-Shell-Structured Tungsten Carbide Encapsulated within Nitrogen-Doped Carbon Spheres for Enhanced Hydrogen Evolution.

    PubMed

    Han, Lei; Xu, Miao; Han, Yujie; Yu, You; Dong, Shaojun

    2016-10-06

    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. Benefited from the unique structure and morphology, the resultant TCNC spheres exhibit high electrocatalytic activity and excellent stability toward HER in both acidic and alkaline solutions. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Electric Discharge Sintering and Joining of Tungsten Carbide--Cobalt Composite with High-Speed Steel Substrate

    SciTech Connect

    Grigoryev, Evgeny G.

    2011-01-17

    Simultaneous electro discharge sintering of high strength structure of tungsten carbide-cobalt composite and connection it with high-speed steel substrate is investigated and suitable operating parameters are defined. Tungsten carbide-cobalt and high-speed steel joining was produced by the method of high voltage electrical discharge together with application of mechanical pressure to powder compact. It was found that the density and hardness of composite material reach its maximum values at certain magnitudes of applied pressure and high voltage electrical discharge parameters. We show that there is an upper level for the discharge voltage beyond which the powder of composite material disintegrates like an exploding wire. Due to our results it is possible to determine optimal parameters for simultaneous electro discharge sintering of WC-Co and bonding it with high-speed steel substrate.

  20. Pressure generation to 50 GPa in Kawai-type multianvil apparatus using newly developed tungsten carbide anvils

    NASA Astrophysics Data System (ADS)

    Kunimoto, Takehiro; Irifune, Tetsuo; Tange, Yoshinori; Wada, Kouhei

    2016-04-01

    A pressure generation test for Kawai-type multianvil apparatus (KMA) has been made using second-stage anvils of a newly developed ultra-hard tungsten carbide composite. Superb performance of the new anvil with significantly less plastic deformation was confirmed as compared to those commonly used for the KMA experiments. A maximum pressure of ∼48 GPa was achieved using the new anvils with a truncation edge length (TEL) of 1.5 mm, based on in situ X-ray diffraction measurements. Further optimization of materials and sizes of the pressure medium/gasket should lead to pressures even higher than 50 GPa in KMA using this novel tungsten carbide composite, which may also be used for expansion of the pressure ranges in other types of high pressure apparatus operated in large volume press.

  1. Study of the Influence of Cutting Regime Parameters on Grinding Forces in Processing Tungsten Carbide Dk460uf

    NASA Astrophysics Data System (ADS)

    Vulc, Silvia

    2014-12-01

    This paper presents a study on grinding tungsten carbide DK460UF, through experimental investigation using diamond grinding wheel with 54 μm grain size. Different sets of experiments were performed to study the effects of the independent grinding parameters such as grinding wheel speed, feed and depth of cut on cutting forces. Test results showed that the feed and depth of cut influence significantly the cutting forces. The research was lead to optimize the process parameters for reducing cutting forces. In this way, for different parameters of cutting regime, it were measured the values of the components of the grinding force, tangential component, Ft and normal component Fn. The results of the experiment showed that it is better to use great speeds and small feed rate and depth of cut in grinding tungsten carbides, such as DK460UF

  2. Some aspects of machining cast Al-SiCp composites with conventional high speed steel and tungsten carbide tools

    NASA Astrophysics Data System (ADS)

    Narahari, P.; Pai, B. C.; Pillai, R. M.

    1999-10-01

    An attempt was made to evaluate machining of eutectic Al-Si (LM6) and hypoeutectic Al-Si (LM25) alloys reinforced with 10, 15, and 20% SiCp of two particle sizes using conventional high-speed steel (HSS) and tungsten carbide (WC) tools by varying cutting speed, feed, depth of cut, and environment. Machining of metal matrix composites (MMCs) is a difficult task using HSS and WC tools. The tool life of both these conventional tools was observed to decrease with increasing percentage and coarseness of SiCp in the composites. Tungsten carbide tools had a longer tool life than HSS under all the different conditions studied. Contrary to the known phenomenon of enhanced tool life in machining monolithic alloys with the use of cutting fluid, the tool life of WC/HSS tool in machining composites with cutting fluid was only 10 to 20% of that without cutting fluid.

  3. Determination of emissivity coefficient of heat-resistant super alloys and cemented carbide

    NASA Astrophysics Data System (ADS)

    Kieruj, Piotr; Przestacki, Damian; Chwalczuk, Tadeusz

    2016-12-01

    This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples' temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.

  4. Morphology of powders of tungsten carbide used in wear-resistant coatings and deposition on the PDC drill bits

    NASA Astrophysics Data System (ADS)

    Zakharova, E. S.; Markova, I. Yu; Maslov, A. L.; Polushin, N. I.; Laptev, A. I.

    2017-05-01

    Modern drill bits have high abrasive wear in the area of contact with the rock and removed sludge. Currently, these bits have a protective layer on the bit body, which consists of a metal matrix with inclusions of carbide particles. The research matrix of this coating and the wear-resistant particles is a prerequisite in the design and production of drill bits. In this work, complex investigation was made for various carbide powders of the grades Relit (tungsten carbide produced by Ltd “ROSNAMIS”) which are used as wear-resistant particles in the coating of the drill bit body. The morphology and phase composition of the chosen powders as well as the influence of a particle shape on prospects of their application in wear-resistance coating presented in this work.

  5. Microstructure and thermal properties of copper–diamond composites with tungsten carbide coating on diamond particles

    SciTech Connect

    Kang, Qiping; He, Xinbo Ren, Shubin; Liu, Tingting; Liu, Qian; Wu, Mao; Qu, Xuanhui

    2015-07-15

    An effective method for preparing tungsten carbide coating on diamond surfaces was proposed to improve the interface bonding between diamond and copper. The WC coating was formed on the diamond surfaces with a reaction medium of WO{sub 3} in mixed molten NaCl–KCl salts and the copper–diamond composites were obtained by vacuum pressure infiltration of WC-coated diamond particles with pure copper. The microstructure of interface bonding between diamond and copper was discussed. Thermal conductivity and thermal expansion behavior of the obtained copper–diamond composites were investigated. Results indicated that the thermal conductivity of as-fabricated composite reached 658 W m{sup −} {sup 1} K{sup −} {sup 1}. Significant reduction in coefficient of thermal expansion of the composite compared with that of pure copper was obtained. - Highlights: • WC coating was successfully synthesized on diamond particles in molten salts. • WC coating obviously promoted the wettability of diamond and copper matrix. • WC coating greatly enhanced the thermal conductivity of Cu–diamond composite. • The composites are suitable candidates for heat sink applications.

  6. Decontamination of viable Streptococcus mutans from orthodontic tungsten carbide debonding burs. An in vitro microbiological study.

    PubMed

    Sheriteh, Zahra; Hassan, Tasnim; Sherriff, Martyn; Cobourne, Martyn; Cobourne, Martin; Riley, Peter

    2010-09-01

    To investigate the effectiveness of currently recommended decontamination procedures on tungsten carbide debonding burs (TCDBs). In vitro microbiological study. St George's Hospital NHS Trust, UK. A total of 240 extracted tooth surfaces were bonded with orthodontic brackets, debonded to leave residual composite and artificially contaminated with Streptococcus mutans. Sterilized TCDBs in a slow handpiece were used to remove this composite before random allocation into one of six different decontamination groups of 40 burs each. These included a control group that was not decontaminated and a further five that underwent different methods of presterilization cleaning within the decontamination process (none, manual, ultrasonic, washer disinfector and enzyme soak) followed by sterilization in a vacuum phase autoclave at 134 degrees C for 3 min. The burs were placed in brain heart infusion (BHI) broths, incubated for 48 h. Following this the broths were inspected for turbidity and microbiological analysis was carried out to detect viable bacterial growth. Data were analysed using the Kruskal-Wallis test for single ordered data. S. mutans was recovered from 39 out of 40 burs in the control group and no burs from the decontamination groups, which was statistically significant (P = 0.001). No differences were found between decontamination groups (P = 0.271). However, skin flora contamination was noted in 17 broths. The five methods of decontaminating TCDBs investigated in this study were effective in removing viable S. mutans. Other investigations are required to determine if TCDBs can be successfully cleaned of blood and protein residue prior reuse.

  7. Magnetotransport properties of the triply degenerate node topological semimetal tungsten carbide

    NASA Astrophysics Data System (ADS)

    He, J. B.; Chen, D.; Zhu, W. L.; Zhang, S.; Zhao, L. X.; Ren, Z. A.; Chen, G. F.

    2017-05-01

    We report the magnetoresistance (MR), Hall effect, and de Haas-van Alphen (dHvA) effect studies of single crystals of tungsten carbide, WC, which is predicted to be a new type of topological semimetal with triply degenerate nodes. With the magnetic field rotated in the plane perpendicular to the current, WC shows a field induced metal-to-insulator-like transition and large nonsaturating quadratic MR at low temperatures. As the magnetic field parallel to the current, a pronounced negative longitudinal MR only can be observed for a certain direction of current flow. The Hall effect indicates WC is a perfect compensated semimetal, which may be related to the large nonsaturating quadratic MR. The analysis of dHvA oscillations reveals that WC is a multiband system with small cross-sectional areas of Fermi surface and light cyclotron effective masses. Our results indicate that WC is an ideal platform to study the recently proposed "new fermions" with triply degenerate crossing points.

  8. Erosion and Corrosion Behavior of Laser Cladded Stainless Steels with Tungsten Carbide

    NASA Astrophysics Data System (ADS)

    Singh, Raghuvir; Kumar, Mukesh; Kumar, Deepak; Mishra, Suman K.

    2012-11-01

    Laser cladding of tungsten carbide (WC) on stainless steels 13Cr-4Ni and AISI 304 substrates has been performed using high power diode laser. The cladded stainless steels were characterized for microstructural changes, hardness, solid particle erosion resistance and corrosion behavior. Resistance of the clad to solid particle erosion was evaluated using alumina particles according to ASTM G76 and corrosion behavior was studied by employing the anodic polarization and open circuit potential measurement in 3.5% NaCl solution and tap water. The hardness of laser cladded AISI 304 and 13Cr-4Ni stainless steel was increased up to 815 and 725Hv100 g, respectively. The erosion resistance of the modified surface was improved significantly such that the erosion rate of cladded AISI 304 (at 114 W/mm2) was observed ~0.74 mg/cm2/h as compared to ~1.16 and 0.97 mg/cm2/h for untreated AISI 304 and 13Cr-4Ni, respectively. Laser cladding of both the stainless steels, however, reduced the corrosion resistance in both NaCl and tap water.

  9. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties

    PubMed Central

    Sun, Hongfang; Li, Zishanshan; Bai, Jing; Ali Memon, Shazim; Dong, Biqin; Fang, Yuan; Xu, Weiting; Xing, Feng

    2015-01-01

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills. PMID:28787963

  10. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties.

    PubMed

    Sun, Hongfang; Li, Zishanshan; Bai, Jing; Memon, Shazim Ali; Dong, Biqin; Fang, Yuan; Xu, Weiting; Xing, Feng

    2015-02-13

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)₂, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

  11. Tungsten Carbide Grain Size Computation for WC-Co Dissimilar Welds

    NASA Astrophysics Data System (ADS)

    Zhou, Dongran; Cui, Haichao; Xu, Peiquan; Lu, Fenggui

    2016-06-01

    A "two-step" image processing method based on electron backscatter diffraction in scanning electron microscopy was used to compute the tungsten carbide (WC) grain size distribution for tungsten inert gas (TIG) welds and laser welds. Twenty-four images were collected on randomly set fields per sample located at the top, middle, and bottom of a cross-sectional micrograph. Each field contained 500 to 1500 WC grains. The images were recognized through clustering-based image segmentation and WC grain growth recognition. According to the WC grain size computation and experiments, a simple WC-WC interaction model was developed to explain the WC dissolution, grain growth, and aggregation in welded joints. The WC-WC interaction and blunt corners were characterized using scanning and transmission electron microscopy. The WC grain size distribution and the effects of heat input E on grain size distribution for the laser samples were discussed. The results indicate that (1) the grain size distribution follows a Gaussian distribution. Grain sizes at the top of the weld were larger than those near the middle and weld root because of power attenuation. (2) Significant WC grain growth occurred during welding as observed in the as-welded micrographs. The average grain size was 11.47 μm in the TIG samples, which was much larger than that in base metal 1 (BM1 2.13 μm). The grain size distribution curves for the TIG samples revealed a broad particle size distribution without fine grains. The average grain size (1.59 μm) in laser samples was larger than that in base metal 2 (BM2 1.01 μm). (3) WC-WC interaction exhibited complex plane, edge, and blunt corner characteristics during grain growth. A WC ( { 1 {bar{{1}}}00} ) to WC ( {0 1 1 {bar{{0}}}} ) edge disappeared and became a blunt plane WC ( { 10 1 {bar{{0}}}} ) , several grains with two- or three-sided planes and edges disappeared into a multi-edge, and a WC-WC merged.

  12. Tungsten

    SciTech Connect

    1996-08-01

    The name tungsten, derived from the Swedish words {open_quotes}tung{close_quotes} and {open_quotes}sten{close_quotes}, meaning heavy stone, was first applied to a tungsten-containing mineral in 1755. The mineral, itself, was subsequently identified by C.W. Scheele in 1781, and named scheelite. Metallic tungsten was first isolated from the mineral wolframite in 1783, and given the German name {open_quotes}wolfram,{close_quotes} which remains an alternative name for the element. Ultimately, the English word, tungsten, became the official name, while W remains the element`s chemical symbol. This article discusses the geology, exploitation, applications, and market overview of tungsten.

  13. Experimental analysis about the evaluation of tungsten carbide-bur, piezoelectric and laser osteotomies.

    PubMed

    De Santis, D; Gerosa, R; Zanotti, G; Cigikov, N; Cenzi, A; Chiarini, L; Rossetto, A; Nocini, P F; Bertossi, D

    2013-08-01

    Aim: Osteotomies are performed in oral surgery with five kinds of cutting instruments: 1) burs (Tungsten carbide cylindric burs), 2-3) ultrasound Piezosurgery (type I and II), 4-5) and lasers (Er:YAG; Er,Cr:YSGG). This study compares the quality of cutting of every single instruments, evaluating accuracy (length, thickness, depth and morphology), velocity (number of passages and time) and entity of damage. Methods: In vitro experiments with ten osteotomies were performed on one-hundred of cow ribs with each instrument. In vivo surgery was performed on New Zealand white rabbit: two osteotomies are made with all instruments on the mandible and on the shinbone, totalizing four osteotomies for each instrument. Samples are processed to be evaluated through histological exam at stereomicroscopy Discussion: Results show a statistically significant variability on "thickness" (p value=0.001), "time" (p value=0.001), "depth" and penetration speed (p-value=0.001; p-value=0.001) and the "number of passages" (p-value=0.001). No differences have been observed in "length" (p-value=0.078). Histological analysis reveals that osteotomy performed with laser and Piezosurgery II generates major damage to osteocytes near cutting surfaces. Conclusion: Currently, purchase and management elevated costs, minor versatility of use, and long training times for equipments such as Piezosurgery and laser limit their general use, but remain advantageous in case of risky interventions near noble structures. Choice of device depends on experience maturated by operator in time, characteristics of operation and patient's clinical conditions.

  14. Valorization of Lignin to Simple Phenolic Compounds over Tungsten Carbide: Impact of Lignin Structure.

    PubMed

    Guo, Haiwei; Zhang, Bo; Qi, Zaojuan; Li, Changzhi; Ji, Jianwei; Dai, Tao; Wang, Aiqin; Zhang, Tao

    2017-02-08

    Lignins isolated from representative hardwood, softwood, and grass materials were effectively hydrocracked to aromatics catalyzed by tungsten carbide over activated carbon (W2 C/AC). The effects of botanical species and fractionation methods on lignin structure and the activity of W2 C/AC were studied in detail. Gas permeation chromatography (GPC), FTIR, elemental analysis, and 2 D HSQC NMR showed that all the extracted samples shared the basic skeleton of lignin, whereas the fractionation method significantly affected the structure. The organosolv process provided lignin with a structure more similar to the native lignin, which was labile to be depolymerized by W2 C/AC. Softwood lignins (i.e., spruce and pine) possessed higher molecular weights than hardwood lignins (i.e., poplar and basswood); whereas corn stalk lignin that has noncanonical subunits and exhibited the lowest molecular weight owing to its shorter growth period. β-O-4 bonds were the major linkages in all lignin samples, whereas softwood lignins contained more resistant linkages of β-5 and less β-β than corn stalk and hardwood lignins; as a result, lowest hydrocracking efficiency was obtained in softwood lignins, followed by corn stalk and hardwood lignins. 2 D HSQC NMR spectra of lignin and the liquid oil as well as the solid residue showed that W2 C/AC exhibited high activity not only in β-O-4 cleavage, but also in deconstruction of other ether linkages between aromatic units, so that high yield of liquid oil was obtained from lignin. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Influence of Grain Refinement on Microstructure and Mechanical Properties of Tungsten Carbide/Zirconia Nanocomposites

    NASA Astrophysics Data System (ADS)

    Nasser, Ali; Kassem, Mohamed A.; Elsayed, Ayman; Gepreel, Mohamed A.; Moniem, Ahmed A.

    2016-11-01

    WC-W2C/ZrO2 nanocomposites were synthesized by pressure-less sintering (PS) and spark plasma sintering (SPS) of tungsten carbide/yttria-stabilized tetragonal zirconia, WC/TZ-3Y. Prior to sintering, WC/TZ-3Y powders were totally ball-milled for 20 and 120 h to obtain targeted nano (N) and nano-nano (N-N) structures, indicated by transmission electron microscopy and powder x-ray diffraction (PXRD). The milled powders were processed via PS at temperatures of 1773 and 1973 K for 70 min and SPS at 1773 K for 10 min. PXRD as well as SEM-EDS indicated the formation of WC-W2C/ZrO2 composites after sintering. The mechanical properties were characterized via Vicker microhardness and nanoindentation techniques indicating enhancements for sufficiently consolidated composites with high W2C content. The effects of reducing particle sizes on phase transformation, microstructure and mechanical properties are reported. In general, the composites based on the N structure showed higher microhardness than those for N-N structure, except for the samples PS-sintered at 1773 K. For instance, after SPS at 1773 K, the N structure showed a microhardness of 18.24 GPa. Nanoindentation measurements revealed that nanoscale hardness up to 22.33 and 25.34 GPa and modulus of elasticity up to 340 and 560 GPa can be obtained for WC-W2C/ZrO2 nanocomposites synthesized by the low-cost PS at 1973 K and by SPS at 1773 K, respectively.

  16. Kinetics of carbide formation in the molybdenum-tungsten coatings used in the ITER-like Wall

    NASA Astrophysics Data System (ADS)

    Maier, H.; Rasinski, M.; von Toussaint, U.; Greuner, H.; Böswirth, B.; Balden, M.; Elgeti, S.; Ruset, C.; Matthews, G. F.

    2016-02-01

    The kinetics of tungsten carbide formation was investigated for tungsten coatings on carbon fibre composite with a molybdenum interlayer as they are used in the ITER-like Wall in JET. The coatings were produced by combined magnetron sputtering and ion implantation. The investigation was performed by preparing focused ion beam cross sections from samples after heat treatment in argon atmosphere. Baking of the samples was done at temperatures of 1100 °C, 1200 °C, and 1350 °C for hold times between 30 min and 20 h. It was found that the data can be well described by a diffusional random walk with a thermally activated diffusion process. The activation energy was determined to be (3.34 ± 0.11) eV. Predictions for the isothermal lifetime of this coating system were computed from this information.

  17. Effect of Powder-Feeding Modes During Plasma Spray on the Properties of Tungsten Carbide Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhong, Yi-ming; Du, Xiao-dong; Wu, Gang

    2017-05-01

    A WC-reinforced composite coating was fabricated on the surface of 45 steel samples by plasma, cladding process with WC powder added to the molten pool synchronously or in the tail of the molten pool. The microstructure, phase composition, and element distribution in the coating were analyzed. The results show that the undissolved WC particles and crystallized carbide (WC, W2C) were distributed uniformly in the sub-eutectic matrix in both cases. Fewer of the WC particles are dissolved in the matrix when they are injected into the tail of the molten pool. There are fewer needle-like tungsten carbide formations seen in the composite coating fabricated by back-feeding process than in that formed by synchronous feeding. The former results in a finer microstructure and a higher concentration gradient of elements near the interface between the WC particles and the coating matrix.

  18. Permanent Electron Electric Dipole Moment Search in the X^3Δ_1 Ground State of Tungsten Carbide Molecules

    NASA Astrophysics Data System (ADS)

    Lee, Jeongwon; Chen, Jinhai; Leanhardt, Aaron

    2011-06-01

    We are developing an experiment to search for the permanent electric dipole moment (EDM) of the electron using the valence electrons in the X^3Δ_1 ground state of Tungsten Carbide (WC) molecules. Currently, we are detecting the molecules by Laser Induced Fluorescence spectroscopy at ˜75cm downstream of a pulsed ablation beam source. We have a detection rate of ˜10 182W12C molecules/second in X^3Δ_1, v"=0, J"=1 state with geometric detection efficiency of 0.004. A continuous WC molecular beam is under development. Additionally, preliminary measurements of the 183W12C hyperfine structure will be presented.

  19. Atomic Force Microscopy Study of an Ideally Hard Contact: The Diamond{bold (}111{bold )}/Tungsten Carbide Interface

    SciTech Connect

    Enachescu, M.; van den Oetelaar, R.J.; Carpick, R.W.; Ogletree, D.F.; Flipse, C.F.; Salmeron, M.

    1998-08-01

    A comprehensive nanotribological study of a hydrogen-terminated diamond(111)/tungsten carbide interface has been performed using ultrahigh vacuum atomic force microscopy. Both contact conductance, which is proportional to contact area, and friction have been measured as a function of applied load. We demonstrate for the first time that the load dependence of the contact area in UHV for this extremely hard single asperity contact is described by the Derjaguin-M{umlt u}ller-Toporov continuum mechanics model. Furthermore, the frictional force is found to be directly proportional to the contact area. {copyright} {ital 1998} {ital The American Physical Society}

  20. Investigation of atypical molten pool dynamics in tungsten carbide-cobalt during laser deposition using in-situ thermal imaging

    SciTech Connect

    Xiong Yuhong; Schoenung, Julie M.; Hofmeister, William H.; Smugeresky, John E.; Delplanque, Jean-Pierre

    2012-01-16

    An atypical ''swirling'' phenomenon observed during the laser deposition of tungsten carbide-cobalt cermets by laser engineered net shaping (LENS) was studied using in-situ high-speed thermal imaging. To provide fundamental insight into this phenomenon, the thermal behavior of pure cobalt during LENS was also investigated for comparison. Several factors were considered as the possible source of the observed differences. Of those, phase difference, material emissivity, momentum transfer, and free surface disruption from the powder jets, and, to a lesser extent, Marangoni convection were identified as the relevant mechanisms.

  1. Investigation of atypical molten pool dynamics in tungsten carbide-cobalt during laser deposition using in-situ thermal imaging

    NASA Astrophysics Data System (ADS)

    Xiong, Yuhong; Hofmeister, William H.; Smugeresky, John E.; Delplanque, Jean-Pierre; Schoenung, Julie M.

    2012-01-01

    An atypical "swirling" phenomenon observed during the laser deposition of tungsten carbide-cobalt cermets by laser engineered net shaping (LENS®) was studied using in-situ high-speed thermal imaging. To provide fundamental insight into this phenomenon, the thermal behavior of pure cobalt during LENS was also investigated for comparison. Several factors were considered as the possible source of the observed differences. Of those, phase difference, material emissivity, momentum transfer, and free surface disruption from the powder jets, and, to a lesser extent, Marangoni convection were identified as the relevant mechanisms.

  2. Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells.

    PubMed

    Ding, M; Kisin, E R; Zhao, J; Bowman, L; Lu, Y; Jiang, B; Leonard, S; Vallyathan, V; Castranova, V; Murray, A R; Fadeel, B; Shvedova, A A

    2009-12-15

    Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-kappaB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P(+)). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P(+) cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-kappaB more efficiently in JB6(+/+) cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6(+/+) cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

  3. Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells

    SciTech Connect

    Ding, M.; Kisin, E.R.; Zhao, J.; Bowman, L.; Lu, Y.; Jiang, B.; Leonard, S.; Vallyathan, V.; Castranova, V.; Murray, A.R.; Fadeel, B.; Shvedova, A.A.

    2009-12-15

    Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-kappaB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P{sup +}). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P{sup +} cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-kappaB more efficiently in JB6{sup +/+} cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6{sup +/+} cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

  4. Superficial roughness on composite surface, composite enamel and composite dentin junctions after different finishing and polishing procedures. Part I: roughness after treatments with tungsten carbide vs diamond burs.

    PubMed

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The aim of this study is to investigate different instruments for finishing composite restorations, as well as examining different surfaces and interfaces of the same restoration. The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations finishing between tungsten carbide and diamond burs, furthermore the null hypothesis is that there are no significant differences on roughness between finishing on composite surfaces (C), compositeenamel (CE) and composite-dentin (CD) interfaces. The study was performed on 28 teeth, and class V cavities were prepared on the extracted teeth. Restorations were done in Filtek XTE nanofilled composite (3M Espe) in a standardized method, to then be finished. A comparison was made in the phase 1 between tungsten carbide burs (16 blades), diamond burs (46 μm), with a similar shape by the same manufacturer (Komet). Each surface received 5 bur applications. Consequently, an analysis with a profilometer was performed. Phase 2 involved further confrontation of ulterior finishing with ultrafine tungsten carbide burs (30 blades) and with extra and ultrafine diamond burs (25 and 8 μm) (the same shape as previously mentioned). A second analysis was then performed with a profilometer. All measurements were taken on C surfaces, CE and CD interfaces. Statistical analyses were carried out with c2 test (a = 0.05). The finishing procedures with fine grit or toothing burs gave a better smoothness with tungsten carbide burs compared to diamond burs. While with the ultrafine grit no significant differences were noted between tungsten carbide and diamond burs on the CE and CD interfaces, the diamond bur left less superficial roughness on the C surfaces. With regards to the superficial roughness of the different areas of restoration, it can be concluded that: minor roughness was detected on C surfaces, while the CD interface had the most superficial roughness, regardless of whether the

  5. Structural and chemical phase transitions in tungsten carbide films evidenced by the analysis of their stiffness tensors

    SciTech Connect

    Wittkowski, T.; Jung, K.; Hillebrands, B.; Comins, J. D.

    2006-10-01

    Brillouin light scattering (BLS) is used to provide a comprehensive study of thin tungsten carbide films deposited on single crystal silicon substrates whose distinctive nature depends critically on the deposition parameters. The use of stepped films in these slow-on-fast systems provides enhanced data sets and allows the velocity dispersion of the observed surface excitations, including the discrete Rayleigh and Sezawa modes to be studied in detail. Comprehensive and powerful methods of data analysis and interpretation including the recently developed Monte Carlo (MC) method, the surface Green's function, and classical approaches are applied to extract the effective elastic constants and density of each of the films. The MC and Green's function methods are used to remove ambiguities in Sezawa mode assignments and to identify a mode-crossing event. Auger electron spectroscopy and x-ray diffraction investigations confirm conclusions about chemical composition and microstructure obtained by BLS including a structural phase transition, thus leading to a consistent description of elastic, structural, and chemical properties of tungsten carbide films as a function of their deposition conditions. The anisotropic elastic tensors of the various films are employed for an analysis of the angular dependent Young's modulus and the shear modulus, suggesting implications for the film performance in wear protection. Finally, an estimate of the elastic anisotropy of the {alpha}-W{sub 2}C single crystal is provided on the basis of the effective elastic constants of a nanocrystalline W{sub 2}C film.

  6. Structural and chemical phase transitions in tungsten carbide films evidenced by the analysis of their stiffness tensors

    NASA Astrophysics Data System (ADS)

    Wittkowski, T.; Jung, K.; Hillebrands, B.; Comins, J. D.

    2006-10-01

    Brillouin light scattering (BLS) is used to provide a comprehensive study of thin tungsten carbide films deposited on single crystal silicon substrates whose distinctive nature depends critically on the deposition parameters. The use of stepped films in these slow-on-fast systems provides enhanced data sets and allows the velocity dispersion of the observed surface excitations, including the discrete Rayleigh and Sezawa modes to be studied in detail. Comprehensive and powerful methods of data analysis and interpretation including the recently developed Monte Carlo (MC) method, the surface Green's function, and classical approaches are applied to extract the effective elastic constants and density of each of the films. The MC and Green's function methods are used to remove ambiguities in Sezawa mode assignments and to identify a mode-crossing event. Auger electron spectroscopy and x-ray diffraction investigations confirm conclusions about chemical composition and microstructure obtained by BLS including a structural phase transition, thus leading to a consistent description of elastic, structural, and chemical properties of tungsten carbide films as a function of their deposition conditions. The anisotropic elastic tensors of the various films are employed for an analysis of the angular dependent Young's modulus and the shear modulus, suggesting implications for the film performance in wear protection. Finally, an estimate of the elastic anisotropy of the α-W2C single crystal is provided on the basis of the effective elastic constants of a nanocrystalline W2C film.

  7. Wear Analysis of Cemented Carbide during Turning of Cast Iron Considering Economical Machining Speed

    NASA Astrophysics Data System (ADS)

    Znojkiewicz, Natalia; Korzeniewski, Dariusz; Wiciak, Martyna

    2017-01-01

    The purpose of this paper is to find economical machining speed during turning of grooves for piston rings with various feeds. In the first part of the paper, literature analysis concerning durability of cutting tools is presented. Next, the wear of cemented carbide cutting tools during turning of cast iron is researched. The research has been done for seven cutting tools. During conducted turning trials, angular speed has been altered from n=530rev/min to n=710rev/min and feeds from f=0.007mm/rev to f=0.105mm/rev. On the basis of Taylor's equation, which relates cutting speed to tool life, the economical cutting speed is established with the application of two various methods.

  8. Effects of pretreatment on the performance of diamond-coated cemented carbide cutting tools

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Zhang, Qing; Wang, S. G.; Yoon, S. F.; Ahn, J.; Zhao, Biaoqin; Tang, W. Z.; Miao, J. Q.; Lu, F. X.

    2003-11-01

    We studied the cutting performance of diamond-coated cemented carbide cutting tools pretreated using acid etching, Murakami reagent etching, interlayer addition, and boronization techniques. The Rockwell indentation test indicates that the best adhesion is obtained from the diamond-coated cutting tool pretreated using boronization by forming a boronized cobalt compound layer composed of CoW2B2, CoWB, and CoB. The end-milling test shows that this sample exhibits the longest lifetime among diamond-coated cutting tools, 26-times longer than that of the uncoated cutting tool. The wearing mechanism of the cutting tools used is also discussed. During the milling period, the failure of the diamond-coated tool pretreated by boronization was dominated by how the diamond grains were gradually removed from the diamond coating by the workpiece scraps, instead of the peeling off of the diamond coating. This also reveals that the diamond coating exhibits good adhesion and cutting performance.

  9. PLD deposition of tungsten carbide contact for diamond photodiodes. Influence of process conditions on electronic and chemical aspects

    NASA Astrophysics Data System (ADS)

    Cappelli, E.; Bellucci, A.; Orlando, S.; Trucchi, D. M.; Mezzi, A.; Valentini, V.

    2013-08-01

    Tungsten carbide, WC, contacts behave as very reliable Schottky contacts for opto-electronic diamond devices. Diamond is characterized by superior properties in high-power, high frequency and high-temperature applications, provided that thermally stable electrode contacts will be realized. Ohmic contacts can be easily achieved by using carbide-forming metals, while is difficult to get stable Schottky contacts at elevated temperatures, due to the interface reaction and/or inter-diffusion between metals and diamond. Novel type of contacts, made of tungsten carbide, WC, seem to be the best solution, for their excellent thermal stability, high melting point, oxidation and radiation resistance and good electrical conductivity. Our research was aimed at using pulsed laser deposition for WC thin film deposition, optimizing experimental parameters, to obtain a final device characterized by excellent electronic properties, as a detector for radiation in deep UV or as X-ray dosimeter. We deposited our films by laser ablation from a target of pure WC, using different reaction conditions (i.e., substrate heating, vacuum or reactive atmosphere (CH4/Ar), RF plasma activated), to optimize both the stoichiometry of the film and its structure. Trying to obtain a material with the best electronic response, we used also two sources of laser radiation for target ablation, i.e., nano-second pulsed excimer laser ArF, and ultra-short fs Ti:Sapphire laser. The structure and chemical aspects have been evaluated by Raman and X-ray photoelectron spectroscopy (XPS), while the dosimeter photodiode response has been tested by the I-V measurements, under soft X-ray irradiation.

  10. Comparison of Mechanical Properties and Calculation of Cutting Force Between Uncoated Tungsten Carbide & ti Coated Tip Tungsten Carbide with the Help of Lathe Tool Dynamometer

    NASA Astrophysics Data System (ADS)

    Mehra, Deepak; Rakhecha, Khushwant

    The keyword for manufacturers of cutting tools and coatings for cutting tools is productivity: a 30%; reduction of tool costs, or a 50%; increase in tool lifetime results only in a 1%; reduction of manufacturing costs. But an increase in cutting data by 20%; reduces manufacturing costs by 15%;. In order to achieve higher productivity different approaches - High Performance Cutting (HPC) and High Speed Cutting (HSC) can be chosen. The performance of Carbide tools was studied to investigate the tool life and wear behavior at various machining parameters. This study presents tool wear characterization of carbide cutting tool inserts coated with titanium nitride (TiN) on a single point turning operation on copper, aluminum. A set of experiments with conditions of cutting speed, depth of cut and feed rate were performed on a lathe machine. Force analysis is done on Lathe Tool Dynamometer. From the result, cutting speed was found to be the main factor to have significant effect on surface roughness. At the end of this study, optimization was made by suggesting the most suitable sets of parameter settings to produce minimum surface roughness. Suggestion on parameter settings to obtain minimum surface roughness made.

  11. Investigation on the Tribological Behavior of Arc-Sprayed and Hammer-Peened Coatings Using Tungsten Carbide Cored Wires

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Hagen, L.; Schröder, P.

    2017-01-01

    Due to their outstanding properties, WC-W2C iron-based cermet coatings are widely used in the field of wear protection. Regarding commonly used WC-W2C reinforced coating systems, it has been reported that their tribological behavior is mainly determined by the carbide grain size fraction. Although the manufacturing route for arc-sprayed WC-W2C cermet coatings is in an advanced state, there is still a lack of knowledge concerning the performance of cored wires with tungsten carbides as filling material and their related coating properties when post-treatment processes are used such as machine hammer peening (MHP). A major objective was to characterize WC-W2C FeCMnSi coatings, deposited with different carbide grain size fractions as a filling using cored wires, with respect to their tribological behavior. Moreover, deposits derived from cored wires with a different amount of hard phases are investigated. According to this, polished MHP surfaces are compared to as-sprayed and polished samples by means of metallographic investigations. With the use of ball-on-disk and dry rubber wheel tests, dry sliding and rolling wear effects on a microscopic level are scrutinized. It has been shown that the MHP process leads to a densification of the microstructure formation. For dry sliding experiments, the MHP coatings obtain lower wear resistances, but lower coefficients of friction than the conventional coatings. In view of abrasion tests, the MHP coatings possess an improved wear resistance. Strain hardening effects at the subsurface area were revealed by the mechanical response using nanoindentation. However, the MHP process has caused a cracking of embedded carbides, which favor breakouts, leading to advanced third-body wear.

  12. Role of Silicon Carbide in Phase-Evolution and Oxidation Behaviors of Pulse Electrodeposited Nickel-Tungsten Coating

    NASA Astrophysics Data System (ADS)

    Sribalaji, M.; Asiq Rahman, O. S.; Arun Kumar, P.; Suresh Babu, K.; Wasekar, Nitin P.; Sundararajan, G.; Keshri, Anup Kumar

    2017-01-01

    Silicon carbide (SiC) was reinforced in the pulse electrodeposited nickel-tungsten (Ni-W) coatings deposited on the steel substrate, and isothermal oxidation test was performed at 1273 K (1000 °C) for 24 hours. Addition of just 2 vol pct of SiC showed 26 pct increase in the relative oxidation resistance of Ni-W coating. The increased oxidation resistance was attributed to the phase evolution (SiO2, Cr2O3, CrSi2, Ni2SiO4, Cr7C3, Cr3C2, and Cr3Si), which suppressed the spallation of the oxide scale in Ni-W-2 vol pct SiC. The presence of Fe2O3 phase in the oxidized Ni-W coating was mainly responsible for the major multiple spallations at the interface and in the bulk, which resulted in the degradation of oxidation resistance.

  13. Tungsten carbide cobalt nanoparticles exert hypoxia-like effects on the gene expression level in human keratinocytes

    PubMed Central

    2010-01-01

    Background Tungsten carbide (WC) and tungsten carbide cobalt (WC-Co) nanoparticles are of occupational health relevance because of the increasing usage in hard metal industries. Earlier studies showed an enhanced toxic potential for WC-Co compared to WC or cobalt ions alone. Therefore, we investigated the impact of these particles, compared to cobalt ions applied as CoCl2, on the global gene expression level in human keratinocytes (HaCaT) in vitro. Results WC nanoparticles exerted very little effects on the transcriptomic level after 3 hours and 3 days of exposure. In contrast, WC-Co nanoparticles caused significant transcriptional changes that were similar to those provoked by CoCl2. However, CoCl2 exerted even more pronounced changes in the transcription patterns. Gene set enrichment analyses revealed that the differentially expressed genes were related to hypoxia response, carbohydrate metabolism, endocrine pathways, and targets of several transcription factors. The role of the transcription factor HIF1 (hypoxia inducible factor 1) is particularly highlighted and aspects of downstream events as well as the role of other transcription factors related to cobalt toxicity are considered. Conclusions This study provides extensive data useful for the understanding of nanoparticle and cobalt toxicity. It shows that WC nanoparticles caused low transcriptional responses while WC-Co nanoparticles are able to exert responses similar to that of free cobalt ions, particularly the induction of hypoxia-like effects via interactions with HIF1α in human keratinocytes. However, the enhanced toxicity of WC-Co particles compared to CoCl2 could not be explained by differences in gene transcription. PMID:20105288

  14. High surface area synthesis, electrochemical activity, and stability of tungsten carbide supported Pt during oxygen reduction in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Chhina, H.; Campbell, S.; Kesler, O.

    The oxidation of carbon catalyst supports to carbon dioxide gas leads to degradation in catalyst performance over time in proton exchange membrane fuel cells (PEMFCs). The electrochemical stability of Pt supported on tungsten carbide has been evaluated on a carbon-based gas diffusion layer (GDL) at 80 °C and compared to that of HiSpec 4000™ Pt/Vulcan XC-72R in 0.5 M H 2SO 4. Due to other electrochemical processes occurring on the GDL, detailed studies were also performed on a gold mesh substrate. The oxygen reduction reaction (ORR) activity was measured both before and after accelerated oxidation cycles between +0.6 V and +1.8 V vs. RHE. Tafel plots show that the ORR activity remained high even after accelerated oxidation tests for Pt/tungsten carbide, while the ORR activity was extremely poor after accelerated oxidation tests for HiSpec 4000™. In order to make high surface area tungsten carbide, three synthesis routes were investigated. Magnetron sputtering of tungsten on carbon was found to be the most promising route, but needs further optimization.

  15. Analysis of tungsten carbide coatings by infrared laser-induced argon spark with inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Kanický, V.; Otruba, V.; Mermet, J.-M.

    2000-10-01

    Infrared laser ablation was studied for application to the analysis of plasma-sprayed tungsten carbide/cobalt coatings. The potential of the laser induced argon-spark (LINA-Spark™), as a sample introduction device in inductively coupled plasma atomic emission spectrometry was studied. The use of an IR laser along with defocusing led to laser-induced microplasma-based ablation. The mass ablation rate, represented by the ICP emission intensity per laser beam unit area, exhibited a flat increase in the irradiance range 2-250 GW/cm 2. A low slope (0.5) of this dependence in log-log scale gave evidence of plasma shielding. The steep increase in the measured acoustic signal when focused in front of the sample, i.e. in argon, indicated a breakdown of argon. Consequently, considerably lower ICP emissions were observed within the same range of irradiance. The cobalt/tungsten line intensity ratio in the ICP was practically constant from 1.5 up to at least 250 GW/cm 2. Acceptable precision (R.S.D.<5%) was obtained without internal standardization for irradiance between 2 and 8 GW/cm 2. Optimization of the laser pulse energy, repetition rate, beam focusing and sample displacement during interaction led to the linearization of dependences of signal vs. cobalt percentage, at least up to the highest studied value of 23% Co.

  16. The abrasive wear of plasma sprayed nanoscale tungsten carbide-cobalt (WC-Co)

    NASA Astrophysics Data System (ADS)

    Tewksbury, Graham Alfred

    Thermal spray coatings composed of a variety of carbide sizes and cobalt contents were sprayed with a high energy plasma spray system. The size of the carbides used fell into three rough groupings, micrometer scale carbides (1--2 mum), submicrometer (700--300 nm), and nanoscale (≈100 nm). The feedstock powder was evaluated in terms of their size distribution, external morphology, internal morphology, and initial carbide size. Two different fixtures were used in spraying to evaluate the effect of cooling rate on the wear resistance of the coatings. The microstructures of the sprayed coatings were examined using optical metallography, SEM, FESEM, TEM, XRD and chemical analysis. The coatings were evaluated in low stress abrasive wear by the ASTM G-65 Dry Sand Rubber Wheel test. Furthermore, the porosity and hardness of the coatings were evaluated. The cobalt content was found to be the predominant influence on the wear rate of the coatings. The decrease in the carbide size was not found to effect the wear rate of the coatings. Coatings sprayed on the 'hot' fixture were found to have slightly improved wear resistance as compared to coatings sprayed on the 'cold' fixture. The wear rates of the coatings were found to be a function of the WC/Co volume ratio.

  17. Ultraviolet-Diode Pump Solid State Laser Removal of Titanium Aluminium Nitride Coating from Tungsten Carbide Substrate

    NASA Astrophysics Data System (ADS)

    See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

    2017-09-01

    This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

  18. Biomass-Derived Porous Fe3C/Tungsten Carbide/Graphitic Carbon Nanocomposite for Efficient Electrocatalysis of Oxygen Reduction.

    PubMed

    Ma, Ming; You, Shijie; Wang, Wei; Liu, Guoshuai; Qi, Dianpeng; Chen, Xiaodong; Qu, Jiuhui; Ren, Nanqi

    2016-11-30

    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. The nanocomposite is characterized by a porous structure consisting of uniform Fe3C nanoparticles encased by graphitic carbon (GC) layers with highly dispersed nanosized WC. The Fe3C provides the active sites for ORR, while the graphitic layers and WC nanoparticles can stibilize the Fe3C surface, preventing it from dissociation in the electrolyte. The Fe3C/WC/GC nanocomposite is highly active, selective, and stable toward four-electron ORR in pH-neutral electrolyte, which results in a 67.82% higher power density than that of commercial Pt/C and negligible voltage decay during a long-term phase of a 33 cycle (2200 h) operation of a microbial fuel cell (MFC). The density functional theory (DFT) calculations suggest high activity for splitting the O-O bond of molecular oxygen on the surface of Fe3C.

  19. Ultraviolet-Diode Pump Solid State Laser Removal of Titanium Aluminium Nitride Coating from Tungsten Carbide Substrate

    NASA Astrophysics Data System (ADS)

    See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

    2017-07-01

    This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

  20. Measurements of nanoparticle size distribution produced by laser ablation of tungsten and boron-carbide in N 2 ambient

    NASA Astrophysics Data System (ADS)

    Bereznai, Miklós; Heszler, Péter; Tóth, Zsolt; Wilhelmsson, Ola; Boman, Mats

    2006-04-01

    Nanoparticles (NPs) were produced by ablating tungsten and boron-carbide (B 4C) target materials in atmospheric pressure nitrogen ambient using ArF excimer laser pulses. The size distributions of the NPs formed during the ablation were monitored—within a 7-133 nm size window—by a condensation particle counter connected to a differential mobility analyzer. The laser repetition rate was varied between 1-50 Hz, and the fluence was systematically changed in the range of 0.5-15 J/cm 2, for both materials, allowing a comparative study in an extended laser parameter regime. The multishot ablation threshold ( Φth) of B 4C was determined to be ˜1.9 J/cm 2 for the laser used (ArF excimer, λ = 193 nm). Similarly to earlier studies, it was shown that the size distributions consist of mainly small nanoparticles (<˜20 nm) attributed to a non-thermal ablation mechanism below Φth. An additional broad peak appears (between 20 and 40 nm) above Φth as a consequence of the thermally induced macroscopic ablation. Chemical composition of deposited polydisperse nanoparticles was studied by X-ray photoelectron spectroscopy showing nitrogen incorporation into the boron-carbide.

  1. Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

    SciTech Connect

    Jiang, Liming; Fu, Honggang; Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong

    2014-01-01

    Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: • The WC/PC composite with high specific surface area was prepared by a simple way. • The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. • The current density for methanol electro-oxidation is as high as 595.93 A g{sup −1} Pt. • The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. • The performance of Pt/WC/PC is superior to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 °C, exhibited a specific surface area (S{sub BET}) of 457.92 m{sup 2} g{sup −1}. After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g{sup −1} Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance.

  2. Effect of Decreasing of Cobalt Content in Properties for Diamond/Cemented Carbide Tools

    NASA Astrophysics Data System (ADS)

    Waratta, A.; Hamdi, M.; Ariga, T.

    2010-03-01

    Powder metallurgy plays a role in manufacturing such as automotive and cutting tool applications. Diamond/cemented carbide tools are also made from this technique. Diamond particle and other matrix materials were employed in this study. The purpose is to investigate the physical and mechanical properties of different Cobalt (Co) content samples by using Taguchi's method. The materials used in the experiments were mixed by using a ball-mill machine. The mixed powders were pressed by conventional method. Then the green samples were sintered in a vacuum furnace. After reaching 500° C, the samples were sintered with Argon (Ar) gas. The sintered samples were investigated density by immersion method, porosity by water saturation method, and hardness by Vicker hardness tester. It was found that with 59.5% Co content, plain diamond type, sintering temperature of 950° C, sintering time of 40 minutes, and pressure of 625 MPa, density, porosity, and hardness got the best result in this study. From the Taguchi's analysis, the significant factors effected the performance were composition, sintering temperature, and sintering time.

  3. Effect of Decreasing of Cobalt Content in Properties for Diamond/Cemented Carbide Tools

    SciTech Connect

    Waratta, A.; Hamdi, M.; Ariga, T.

    2010-03-11

    Powder metallurgy plays a role in manufacturing such as automotive and cutting tool applications. Diamond/cemented carbide tools are also made from this technique. Diamond particle and other matrix materials were employed in this study. The purpose is to investigate the physical and mechanical properties of different Cobalt (Co) content samples by using Taguchi's method. The materials used in the experiments were mixed by using a ball-mill machine. The mixed powders were pressed by conventional method. Then the green samples were sintered in a vacuum furnace. After reaching 500 deg. C, the samples were sintered with Argon (Ar) gas. The sintered samples were investigated density by immersion method, porosity by water saturation method, and hardness by Vicker hardness tester. It was found that with 59.5% Co content, plain diamond type, sintering temperature of 950 deg. C, sintering time of 40 minutes, and pressure of 625 MPa, density, porosity, and hardness got the best result in this study. From the Taguchi's analysis, the significant factors effected the performance were composition, sintering temperature, and sintering time.

  4. Elastic-Plastic Constitutive Equation of WC-Co Cemented Carbides with Anisotropic Damage

    NASA Astrophysics Data System (ADS)

    Hayakawa, Kunio; Nakamura, Tamotsu; Tanaka, Shigekazu

    2007-05-01

    Elastic-plastic constitutive equation of WC-Co cemented carbides with anisotropic damage is proposed to predict a precise service life of cold forging tools. A 2nd rank symmetric tensor damage tensor is introduced in order to express the stress unilaterality; a salient difference in uniaxial behavior between tension and compression. The conventional framework of irreversible thermodynamics is used to derive the constitutive equation. The Gibbs potential is formulated as a function of stress, damage tensor, isotropic hardening variable and kinematic hardening variable. The elastic-damage constitutive equation, conjugate forces of damage, isotropic hardening and kinematic hardening variable is derived from the potential. For the kinematic hardening variable, the superposition of three kinematic hardening laws is employed in order to improve the cyclic behavior of the material. For the evolution equation of the damage tensor, the damage is assumed to progress by fracture of the Co matrix — WC particle interface and by the mechanism of fatigue, i.e. the accumulation of microscopic plastic strain in matrix and particles. By using the constitutive equations, calculation of uniaxial tensile and compressive test is performed and the results are compared with the experimental ones in the literature. Furthermore, finite element analysis on cold forward extrusion was carried out, in which the proposed constitutive equation was employed as die insert material.

  5. Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser

    NASA Astrophysics Data System (ADS)

    Dobrzański, L. A.; Bonek, M.; Hajduczek, E.; Klimpel, A.

    2005-07-01

    The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented.

  6. Ablation of carbide materials with femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Sentis, Marc; Marine, Wladimir

    2003-01-01

    The response of cemented tungsten carbide and of titanium carbonitride was investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of significant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2. The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions.

  7. Study of the mechanism responsible for the elective toxicity of tungsten carbide-cobalt powder toward macrophages.

    PubMed

    Lison, D; Lauwerys, R

    1992-04-01

    We have previously demonstrated that tungsten carbide-cobalt powder (WC-Co) is more toxic toward murine macrophages in vitro than pure cobalt metal particles and that the cellular uptake of cobalt is enhanced when the metal is present in the form of WC-Co mixture. The present study was undertaken to assess the possible mechanism(s) of this interaction. We found that solubilization of cobalt in the extracellular milieu was increased in the presence of WC. This phenomenon, however, is not the critical factor explaining the greater toxicity of the WC-Co mixture since increasing the amount of solubilized cobalt in the extracellular medium in the absence of WC did not result in increased toxicity. Moreover, the amount of cobalt solubilized from a toxic dose of WC-Co was insufficient to affect by itself macrophage viability. A toxic effect was only observed when the WC-Co mixture came directly in contact with the cells. The elective toxicity of WC-Co can also not be explained by stimulation of phagocytosis of cobalt metal particles due to the simultaneous presence of other particles (WC) in the extracellular fluid since stimulation of phagocytosis by latex beads or zymosan particles did not amplify the toxicity of cobalt metal particles. These results indicate that the toxicity of the WC-Co mixture does not simply result from an enhanced bioavailability of its cobalt component. This suggests that hard metal dust behaves as a specific toxic entity.

  8. Effects of Process Parameters on the Deposition Rate, Hardness, and Corrosion Resistance of Tungsten Carbide Coatings Deposited by Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Park, Yunkyu; Lim, Jongmin; Lee, Chongmu

    2005-05-01

    The reactive sputter deposition of tungsten carbide (WCx) films as an alternative to chromium electroplating was studied. The effects of rf power, pressure, sputtering gas composition, and substrate temperature on the deposition rate of the WCx coatings were investigated. The effects of rf power and sputtering gas composition on the hardness and corrosion resistance of the WCx coatings were also investigated. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) analyses were performed to determine the structures and compositions of the films, respectively. The hardnesses of the films were measured using a nanoindenter. The microstructures of the films were observed by scanning electron microscopy. The corrosion resistances of the films were evaluated using a salt-spray test. The deposition rate of the films was proportional to rf power and inversely proportional to the CH4 content of the sputtering gas. The deposition rate increased linearly with increasing chamber pressure. The hardness of the WCx coatings increased as rf power increased. The highest hardness was obtained at a CH4 concentration of 10 vol.% in the sputtering gas. The hardness of the WCx film deposited under optimal conditions was much higher than that of the electroplated chromium film, although the corrosion resistance of the former was slightly lower than that of the latter.

  9. Application of the laser spallation technique to the measurement of the adhesion strength of tungsten carbide coatings on superalloy substrates

    NASA Astrophysics Data System (ADS)

    Boustie, M.; Auroux, E.; Romain, J.-P.

    2000-10-01

    High power pulsed lasers are used to induce shock waves in Hastelloy X targets coated with tungsten carbide of 70 μm and 50 μm thickness. In suitable irradiation conditions, a debonding of the substrate/coating interface due to the generation of tensile stresses is observed. Experimental results are analyzed with the use of numerical simulations yielding the stress history at interface and its dependence on laser pulse intensity up to 600 GW/cm2 with 1 ns and 3 ns durations under direct irradiation, and 23 ns with water confinement. As a consequence of shock decay during the propagation through the substrate, a strong variation of incident intensity results in a small variation of tensile stress. This allows an accurate determination of the debonding threshold which is found in the range of 1.0 to 1.3 GPa for short laser pulses (1 and 3 ns) and 0.5 to 0.6 GPa for long laser pulses (23 ns confined).

  10. Genotoxicity of tungsten carbide-cobalt (WC-Co) nanoparticles in vitro: mechanisms-of-action studies.

    PubMed

    Moche, Hélène; Chevalier, Dany; Vezin, Hervé; Claude, Nancy; Lorge, Elisabeth; Nesslany, Fabrice

    2015-02-01

    We showed previously that tungsten carbide-cobalt (WC-Co) nanoparticles (NP) can be used as a nanoparticulate positive control in some in vitro mammalian genotoxicity assays. Here, we investigate the mechanisms of action involved in WC-Co NP genotoxicity in L5178Y mouse lymphoma cells and primary human lymphocytes, in vitro. Data from the micronucleus assay coupled with centromere staining and from the chromosome-aberration assay show the involvement of both clastogenic and aneugenic events. Experiments with the formamidopyrimidine DNA glycosylase (FPG)-modified comet assay showed a slight (non-significant) increase in FPG-sensitive sites in the L5178Y mouse lymphoma cells but not in the human lymphocytes. Electron paramagnetic resonance spin-trapping results showed the presence of hydroxyl radicals (•OH) in WC-Co NP suspensions, with or without cells, but with time-dependent production in the presence of cells. However, a significant difference in •OH production was observed between human lymphocytes from two different donors. Using H2O2, we showed that WC-Co NP can participate in Fenton-like reactions. Thus, •OH might be produced either via intrinsic generation by WC-Co NP or through a Fenton-like reaction in the presence of cells.

  11. Functional Multi-Nanolayer Coatings of Amorphous Carbon/Tungsten Carbide with Exceptional Mechanical Durability and Corrosion Resistance.

    PubMed

    Nemati, Narguess; Bozorg, Mansoor; Penkov, Oleksiy V; Shin, Dong-Gap; Sadighzadeh, Asghar; Kim, Dae-Eun

    2017-09-06

    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 modulus, excellent wear resistance, and minimal susceptibility to corrosive and caustic media could be acquired. The structural and mechanical properties of the optimized coatings were studied in detail using a variety of analytical techniques. Furthermore, finite element method simulations indicated that the stress generated due to contact against a steel ball was distributed well within the coating, which allowed the stresses to be lower than the yield threshold of the coating. Thus, an ultralow wear rate of ∼10(-12)mm(3)/N mm could be achieved in dry sliding conditions under relatively high Hertzian contact pressures of ∼0.4-0.9 GPa. The amorphous and pinhole-free structure of the individual layers, sufficient number of pairs, and the relatively dense stacked layers resulted in significant polarization resistance (Z″ = 5.5 × 10(6) Ω cm(2)) and increased the corrosion resistance of the coating by 10-fold compared to that of recently reported corrosion-resistant coatings.

  12. Structural Evaluation and Mechanical Properties of Aluminum/Tungsten Carbide Composites Fabricated by Continual Annealing and Press Bonding (CAPB) Process

    NASA Astrophysics Data System (ADS)

    Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Drummen, G. P. C.

    2014-12-01

    In the present work, a novel technique is introduced called continual annealing and press bonding (CAPB) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol pct tungsten carbide particles (Al/WCp composite). The microstructural evolution and mechanical properties of the Al/WCp composite during various CAPB cycles were examined by scanning electron microscopy (SEM), wavelength dispersive X-ray spectroscopy (WDX), and tensile testing. The microstructure of the fabricated composite after fourteen cycles of CAPB showed homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. According to WDX analysis, the manufactured Al/WCp composite did not evidence the presence of additional elements. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of the fourteenth cycle, which was 1.6 times higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB process, it increased significantly during the final cycles. SEM observation of fracture surfaces showed that the rupture mode in the CAPB-processed Al/WCp composite was of the shear ductile rupture type.

  13. Paste development and co-sintering test of zirconium carbide and tungsten in freeze-form extrusion fabrication

    NASA Astrophysics Data System (ADS)

    Li, Ang

    Ultra-high temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as oxidation resistance, at temperatures above 2000°C. However, their brittle properties make them susceptible to thermal shock failure. Components fabricated as functionally graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal by fabricating graded composites. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGMs parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and W were developed and utilized in the FEF process to fabricate test bars graded from 100%ZrC to 50%W-50%ZrC (volume percent). Following FEF processing the test bars were co-sintered at 2300°C and characterized to determine their resulting density and micro-structure. Four-point bending tests were performed to assess the strength of test bars made using the FEF process, compared to test bars prepared using conventional powder processing and isostatic pressing techniques, for five distinct ZrC-W compositions. Scanning electron microscopy (SEM) was used to verify the inner structure of composite parts built using the FEF process.

  14. Tungsten Carbide-Cobalt Nanoparticles Induce Reactive Oxygen Species, AKT, ERK, AP-1, NF-κB, VEGF, and Angiogenesis.

    PubMed

    Liu, Ling-Zhi; Ding, Min; Zheng, Jenny Z; Zhu, Yingxue; Fenderson, Bruce A; Li, Bingyun; Yu, Jing J; Jiang, Bing-Hua

    2015-07-01

    Powder mixtures of tungsten carbide and metallic cobalt (WC-Co) are widely used in various products. Nanoparticles are engineered structures with at least one dimension of 100 nm or smaller. WC-Co is known to be associated with lung injury and diseases. Angiogenesis is a key process during vasculature, carcinogenesis, recovery of injury, and inflammatory diseases. However, the cellular effects of WC-Co nanoparticles on angiogenesis remain to be elucidated. In this study, we investigated angiogenic response and relative mechanisms after exposure to WC-Co nanoparticles. Our results showed that WC-Co nanoparticles at 5 μg/cm(2) induced ROS production which activated AKT and ERK1/2 signaling pathways in lung epithelial cells by reactive oxygen species (ROS) staining and immunoblotting; WC-Co treatment also increased transcriptional activation of AP-1, NF-κB, and VEGF by reporter assay. Further studies demonstrated that ROS are upstream molecules of AKT and ERK signaling pathways; the activation of AP-1, NF-κB, and VEGF was through ROS generation, AKT and ERK1/2 activation. In addition, WC-Co nanoparticles affected the cells to induce angiogenesis by chicken chorioallantoic membrane (CAM) assay. These results illustrate that exposure to WC-Co nanoparticles induces angiogenic response by activating ROS, AKT, and ERK1/2 signaling pathways and the downstream molecules and elucidate the potential molecular mechanisms during this process. This information may be useful for preventing potential damage from nanoparticle exposure in the future.

  15. Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

    NASA Astrophysics Data System (ADS)

    Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

    2015-10-01

    Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to produce carbon monoxide and methane. Furthermore, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.

  16. Research into preparation and properties of graded cemented carbides with face center cubic-rich surface layer

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Deng, Xin; Gong, Manfeng; Liu, Wei; Wu, Shanghua

    2016-09-01

    This paper systematically investigated a set of functionally graded WC-TiC-Mo-Co cemented carbides with modified surface layer (called fcc-rich surface layer in this study), which is mainly composed of fcc phases (Ti(CN) and TiN) and WC. Nitridation at liquid phase sintering temperature is the key process making this fcc-rich surface layer. The functionally graded WC-TiC-Mo-Co cemented carbides synthesized in this study show 3 layer structure: the outer layer, i.e. the fcc-rich surface layer; the intermediate layer, which is characterized by abnormally large WC and high Co content; and the inner layer. It was found that TiC is the most critical component for the formation of fcc-rich surface layer. The higher content of TiC results in the thicker fcc-rich outer layer, higher (Ti(CN) and TiN) content in the outer layer, and higher hardness of the fcc-rich outer layer. The formation of this fcc-rich surface layer is mainly due to the nitridation process between Ti and N, which leads to the diffusion of Ti outwards (from the inside of the sample to the surface) and the subsequent migration of liquid cobalt inwards (from surface to the inside of the sample). The three-layer structure developed in this study provides the excellent combination of high wear resistance and high toughness, which is favorable for some applications.

  17. Atomic layer deposited nanocrystalline tungsten carbides thin films as a metal gate and diffusion barrier for Cu metallization

    SciTech Connect

    Kim, Jun Beom; Kim, Soo-Hyun; Han, Won Seok; Lee, Do-Joong

    2016-07-15

    Tungsten carbides (WC{sub x}) thin films were deposited on thermally grown SiO{sub 2} substrates by atomic layer deposition (ALD) using a fluorine- and nitrogen-free W metallorganic precursor, tungsten tris(3-hexyne) carbonyl [W(CO)(CH{sub 3}CH{sub 2}C ≡ CCH{sub 2}CH{sub 3}){sub 3}], and N{sub 2} + H{sub 2} plasma as the reactant at deposition temperatures between 150 and 350 °C. The present ALD-WC{sub x} system showed an ALD temperature window between 200 and 250 °C, where the growth rate was independent of the deposition temperature. Typical ALD characteristics, such as self-limited film growth and a linear dependency of the film grown on the number of ALD cycles, were observed, with a growth rate of 0.052 nm/cycle at a deposition temperature of 250 °C. The ALD-WC{sub x} films formed a nanocrystalline structure with grains, ∼2 nm in size, which consisted of hexagonal W{sub 2}C, WC, and nonstoichiometric cubic β-WC{sub 1−x} phase. Under typical deposition conditions at 250 °C, an ALD-WC{sub x} film with a resistivity of ∼510 μΩ cm was deposited and the resistivity of the ALD-WC{sub x} film could be reduced even further to ∼285 μΩ cm by further optimizing the reactant pulsing conditions, such as the plasma power. The step coverage of ALD-WC{sub x} film was ∼80% on very small sized and dual trenched structures (bottom width of 15 nm and aspect ratio of ∼6.3). From ultraviolet photoelectron spectroscopy, the work function of the ALD-WC{sub x} film was determined to be 4.63 eV. Finally, the ultrathin (∼5 nm) ALD-WC{sub x} film blocked the diffusion of Cu, even up to 600 °C, which makes it a promising a diffusion barrier material for Cu interconnects.

  18. Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

    DOE PAGES

    Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

    2015-03-27

    Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to producemore » carbon monoxide and methane. In addition, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.« less

  19. Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

    SciTech Connect

    Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

    2015-03-27

    Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to produce carbon monoxide and methane. In addition, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.

  20. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel-tungsten composite coatings

    NASA Astrophysics Data System (ADS)

    Singh, Swarnima; Sribalaji, M.; Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G.; Singh, Raghuvir; Keshri, Anup Kumar

    2016-02-01

    Silicon carbide (SiC) reinforced nickel-tungsten (Ni-W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni-W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni-W-5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni-W-5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, Ecorr) compared to Ni-W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni-W-5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2.

  1. Wear resistance and electrical property of infrared processed copper/tungsten carbide composites

    NASA Astrophysics Data System (ADS)

    Deshpande, Pranav K.

    Copper matrix composites with 53 vol% of WC particle reinforcements have been prepared with an infrared infiltration technique. The process produced fully dense composite owing to excellent wetting between copper and WC. The microhardness values of completely infiltrated Cu/WC composites were in the range of 360-370 HV which is significantly higher than the microhardness of pure copper, 65 HV. The electric conductivity of these composites, as determined by a four-point-probe method, is similar to commercially available Cu/W composites containing 52 vol% of tungsten. The wear behavior of Cu/WC composites has been determined with a pin-on-disk technique against a sintered SiC abrasive disk. The wear rate as a function of a normal wear stress and composite porosity was investigated. Results have shown that up to a normal load of around 9 N (or 0.55 MPa pressure), the wear rate of fully dense Cu/WC composites increases linearly with the applied pressure. Results also show that porosity in the Cu/WC composite increases wear. A model of wear, taking into account various wear mechanisms, was developed. This model successfully predicts the wear behavior of dense Cu/WC composites. Owing to its significantly better wear resistance, as compared to Cu/W composites, the composition of Cu/53 vol% WC composite was varied by an innovative technique to improve the electrical conductivity of these composites without much compensation on its wear resistance. The technique of composition variation also helped in overcoming the shortcomings of pressure-less infiltration technique.

  2. Effect of composition of titanium in silver-copper-titanium braze alloy on dissimilar laser brazing of binder-less cubic boron nitride and tungsten carbide

    NASA Astrophysics Data System (ADS)

    Sechi, Yoshihisa; Nagatsuka, Kimiaki; Nakata, Kazuhiro

    2014-08-01

    Laser brazing with Ti as an active element in silver-copper alloy braze metal has been carried out for binder-less cubic boron nitride and tungsten carbide, using silver-copper- titanium braze alloys with titanium content that varied between 0.28 mass% and 1.68 mass%. Observations of the interface using electron probe microanalysis and scanning acoustic microscopy show that efficient interface adhesion between binder-less cubic boron nitride and the silver-copper-titanium braze alloy was achieved for the braze with a titanium content of 0. 28 mass%.

  3. Robot based deposition of WC-Co HVOF coatings on HSS cutting tools as a substitution for solid cemented carbide cutting tools

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Schaak, C.; Biermann, D.; Aßmuth, R.; Goeke, S.

    2017-03-01

    Cemented carbide (hard metal) cutting tools are the first choice to machine hard materials or to conduct high performance cutting processes. Main advantages of cemented carbide cutting tools are their high wear resistance (hardness) and good high temperature strength. In contrast, cemented carbide cutting tools are characterized by a low toughness and generate higher production costs, especially due to limited resources. Usually, cemented carbide cutting tools are produced by means of powder metallurgical processes. Compared to conventional manufacturing routes, these processes are more expensive and only a limited number of geometries can be realized. Furthermore, post-processing and preparing the cutting edges in order to achieve high performance tools is often required. In the present paper, an alternative method to substitute solid cemented carbide cutting tools is presented. Cutting tools made of conventional high speed steels (HSS) were coated with thick WC-Co (88/12) layers by means of thermal spraying (HVOF). The challenge is to obtain a dense, homogenous, and near-net-shape coating on the flanks and the cutting edge. For this purpose, different coating strategies were realized using an industrial robot. The coating properties were subsequently investigated. After this initial step, the surfaces of the cutting tools were ground and selected cutting edges were prepared by means of wet abrasive jet machining to achieve a smooth and round micro shape. Machining tests were conducted with these coated, ground and prepared cutting tools. The occurring wear phenomena were analyzed and compared to conventional HSS cutting tools. Overall, the results of the experiments proved that the coating withstands mechanical stresses during machining. In the conducted experiments, the coated cutting tools showed less wear than conventional HSS cutting tools. With respect to the initial wear resistance, additional benefits can be obtained by preparing the cutting edge by means

  4. The effects of Ti carbonization on the nucleation and oriented growth of diamond films on cemented carbide.

    PubMed

    Yu, Xiang; Zhao, Xi-an; Liu, Ya-yun; Hua, Meng; Jiang, Xin

    2014-04-09

    To better understand the influence of carbonization of the Ti interlayer on diamond nucleation and growth, a series of Ti/diamond composite films were deposited on cemented carbide (WC:Co) substrates using a two-step deposition technique. The microstructural properties of the composite films were then characterized by scanning electron microscopy, X-ray diffractometry, and Raman spectroscopy, and their tribological properties were evaluated using a ball-on-disc tester and a metalloscope. The results showed that differences in carbonization for five Ti interlayers of different thicknesses led to variations in the preferred orientations of the TiC layers and in the subsequent nucleation and oriented growth of diamond. This suggests that Ti carbonization significantly influences the nucleation and growth of diamond and subsequently causes variations in the tribological properties of the produced diamond films.

  5. Microstructure and Wear Behavior of High-Cr WCI Matrix Surface Composite Reinforced with Cemented Carbide Rods

    NASA Astrophysics Data System (ADS)

    Hou, Shuzeng; Bao, Chonggao; Zhang, Zhiyun; Bai, Yaping

    2013-07-01

    The present article reports a new superior wear resistance surface composite prepared by a vacuum evaporative pattern casting-in process. This surface composite was constructed with reinforcing cemented carbide rod (CCR) array within high-Cr white cast iron (WCI) matrix. Three reaction zones that formed around the CCRs were characterized and established the good metallurgical bonding between CCRs and matrix. In addition, some compound carbide containing Fe, Cr, W, and Co elements were formed in the reaction zones, owing to the partial dissolution of the CCRs and the resulting interdiffusion of elements such as W, Co, C, Fe, and Cr. The wear behavior of the composite was evaluated and compared with unreinforced high-Cr WCI by means of a three-body abrasive wear tester. The results showed that the wear resistance of the composite was significantly higher than that of the unreinforced high-Cr WCI. The exciting wear resistance can be ascribed to protective effect introduced by the CCRs during wear process and the good metallurgical bonding between CCRs and matrix.

  6. Microstructural analyses and wear behavior of the cemented carbide tools after laser surface treatment and PVD coating

    NASA Astrophysics Data System (ADS)

    Neves, Davi; Diniz, Anselmo Eduardo; Lima, Milton Sérgio Fernandes

    2013-10-01

    Adhesion is one of the most important characteristics of coating on cutting tools. Poor coating adhesion on the tool favors fragmentation and release of hard abrasive particles between the tool and the workpiece. These particles interact with the surfaces of the tool, accelerating its wear and decreasing tool life. One possible solution is the use of laser texturing prior to coating in order to achieve a desired surface topography with enhanced adhesion properties. In the texturing, a high-frequency short-pulse laser changes surface characteristics, generating resolidified material and selective vaporization. This work evaluated the effectiveness of laser texturing in improving the substrate-coating adhesion of PVD coated cemented carbide tools. To this end, the substrates were textured with a Nd:YAG laser, in four different intensities, and then coated with a PVD TiAlN film. To ascertain the effectiveness of laser texturing, Rockwell C indentation and turning experiments were performed on both textured tools and conventional unlasered tools. The PVD coated laser-textured tool showed better performance in the indentation and turning tests than the standard tools. A comparative evaluation of tool wear mechanisms indicated that texturing did not change the wear mechanisms, but altered their importance to tool wear. The anchoring provided by the higher roughness of the textured surface increased the adhesion of the coating on the substrate, thus increasing tool life. Additionally, the chemical modification of the carbide grains due to the laser heating might be responsible for an enhanced adhesion between coating and substrate.

  7. Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal

    NASA Astrophysics Data System (ADS)

    Zhang, X. Z.; Liu, G. W.; Tao, J. N.; Shao, H. C.; Fu, H.; Pan, T. Z.; Qiao, G. J.

    2017-02-01

    The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers.

  8. Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal

    NASA Astrophysics Data System (ADS)

    Zhang, X. Z.; Liu, G. W.; Tao, J. N.; Shao, H. C.; Fu, H.; Pan, T. Z.; Qiao, G. J.

    2016-12-01

    The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers.

  9. Active wear and failure mechanisms of TiN-coated high speed steel and TiN-coated cemented carbide tools when machining powder metallurgically made stainless steels

    SciTech Connect

    Jiang, L.; Haenninen, H.; Paro, J.; Kauppinen, V.

    1996-09-01

    In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

  10. Active wear and failure mechanisms of TiN-Coated high speed steel and tin-coated cemented carbide tools when machining powder metallurgically made stainless steels

    NASA Astrophysics Data System (ADS)

    Jiang, Laizhu; Hänninen, Hannu; Paro, Jukka; Kauppinen, Veijo

    1996-09-01

    In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

  11. Tungsten carbide nanorods with titanium dioxide composite counter electrode: Effect of NMP to enhanced efficiency in dye sensitized solar cell (DSSC)

    NASA Astrophysics Data System (ADS)

    Vijayakumar, P.; Pandian, M. Senthil; Ramasamy, P.

    2017-05-01

    Tungsten carbide Nanorods / Titanium dioxide (WC NRs/TiO2) composite material was successfully prepared and used as a counter electrode (CE) in DSSC. The N-Methyl pyrrolidone (NMP) played a crucial role in determining the efficiency of a resultant counter eelctrode material. The structural and morphological analysis were confirmed by XRD and FESEM with EDS. The photovoltaic performance was evaluated under the simulated conditions AM 1.5 light intensity (100 mW/cm2). DSSC fabricated using WC NRs/TiO2 with NMP showed an efficiency (η) of 4.7%, which is compared with WC NRs/TiO2 with 2-propanol based DSSC (η =2.9%). The results concluded NMP is the suitable organic binder for counter electrode preparation.

  12. Laser-induced breakdown spectroscopy for on-line control of selective removal of cobalt binder from tungsten carbide hardmetal by pulsed UV laser surface ablation

    NASA Astrophysics Data System (ADS)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-09-01

    Laser-induced breakdown spectroscopy (LIBS) was successfully used in on-line control of selective removal of cobalt from tungsten carbide hardmetal by pulsed UV laser surface ablation. The dependence of LIBS on number of laser shots was investigated at different laser fluences. The optimal laser fluence of 2.5 J/cm 2 suited for selective removal of cobalt from surface layer of hardmetal was confirmed. The result sample was also subject to different post-examinations to evaluate the feasibility of the application of LIBS in this laser ablation process. It was demonstrated that, monitoring of the emission intensity of cobalt lines could be used as a control parameter for selective removal of cobalt from surface layer of hardmetal by pulsed UV laser. The on-line implementation of the spectroscopic technique LIBS to the surface-ablation process provided important information about the optimal-ablation parameters.

  13. An Experimental Study of the Corrosion Behavior of Nickel Tungsten Carbide in Some Water-Glycol Hydraulic Fluids for Subsea Applications

    NASA Astrophysics Data System (ADS)

    Zheng, Lei; Neville, Anne; Gledhill, Andrew; Johnston, David

    2010-02-01

    Corrosion failures of components in electro-hydraulic control systems can have serious consequences for the operation of an entire subsea oil recovery system, especially in water depths more than 150 m (Fleming, Meas. Control, 2000, 33(7), p 207-213). An acceptable reason for this is that seawater ingress can have a great effect on stainless steel 316L, the most commonly used material for the failed components of the direction control valves, since chloride irons destabilize the passive film [Malik et al., Corros. Sci., 1992, 33(11), p 1809-1827; Desalination, 1994, 97(1-3), p 189-197; Al-Malahy and Hodgkiess, Desalination, 2003, 158(1-3), p 35-42]. Other materials, claimed to be seawater tolerant, are starting to be used in this system. However, problems can still exist due to the complex factors relating to the corrosion process and how the environmental parameters affect the corrosion mechanisms. In this work, the corrosion behavior of a nickel tungsten carbide cermet, one of the proposed materials, is compared with stainless steel 316L, in four different water-glycol hydraulic fluids and 50% hydraulic fluid/50% seawater solutions using an electrochemical test methodology. Systematic fluid analysis, which includes GC-MS for organic components and ICP-MS analysis for ionic content, and surface analysis of the material are carried out to assess the corrosion mechanisms. Detailed conclusions are then made to summarize the advantages and disadvantages of nickel tungsten carbide being used in this system. The effects of each factor on the corrosion rates and mechanisms are discussed.

  14. Atom probe tomography of a Ti-Si-Al-C-N coating grown on a cemented carbide substrate.

    PubMed

    Thuvander, M; Östberg, G; Ahlgren, M; Falk, L K L

    2015-12-01

    The elemental distribution within a Ti-Si-Al-C-N coating grown by physical vapour deposition on a Cr-doped WC-Co cemented carbide substrate has been investigated by atom probe tomography. Special attention was paid to the coating/substrate interface region. The results indicated a diffusion of substrate binder phase elements into the Ti-N adhesion layer. The composition of this layer, and the Ti-Al-N interlayer present between the adhesion layer and the main Ti-Si-Al-C-N layer, appeared to be sub-stoichiometric. The analysis of the interlayer showed the presence of internal surfaces, possibly grain boundaries, depleted in Al. The composition of the main Ti-Al-Si-C-N layer varied periodically in the growth direction; layers enriched in Ti appeared with a periodicity of around 30 nm. Laser pulsing resulted in a good mass resolution that made it possible to distinguish between N(+) and Si(2+) at 14 Da. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Nanostructured TaxC interlayer synthesized via double glow plasma surface alloying process for diamond deposition on cemented carbide

    NASA Astrophysics Data System (ADS)

    Rong, Wolong; Hei, Hongjun; Zhong, Qiang; Shen, Yanyan; Liu, Xiaoping; Wang, Xin; Zhou, Bing; He, Zhiyong; Yu, Shengwang

    2015-12-01

    The aim in this work was to improve the adhesion of diamond coating with pre-deposition of a TaxC interlayer on cemented carbide (WC-Co) substrate by double glow plasma surface alloying technique. The following deposition of diamond coating on the interlayer was performed in a microwave plasma chemical vapor deposition (MPCVD) reactor. TaxC interlayer with an inner diffusion layer and an outer deposition layer was composed of Ta2C and TaC nanocrystalline, and it exhibited a special compact surface morphology formed of flower-shaped pits. As the gradual element distributions existed in the diffusion layer, the interlayer displayed a superior adherence to the substrate with significantly enhanced surface microhardness to the original substrate. After CVD process, the preferred orientation of TaC changed from (2 2 2) to (2 0 0) plane, and a uniform and tense diamond coating with adhesion referred to class HF 2 at least (Verein Deutscher Ingenieure 3198 norm) was obtained on the interlayered substrate. It indicated that the diffusion of Co was effectively inhibited by the formation of TaxC diffusion-deposition interlayer. The TaxC interlayer is most likely to improve the performance of diamond coatings used in cutting tools.

  16. Comparison of tungsten carbide and stainless steel ball bearings for grinding single maize kernels in a reciprocating grinder

    USDA-ARS?s Scientific Manuscript database

    Reciprocating grinders can grind single maize kernels by shaking the kernel in a vial with a ball bearing. This process results in a grind quality that is not satisfactory for many experiments. Tungesten carbide ball bearings are nearly twice as dense as steel, so we compared their grinding performa...

  17. Influence of artificial gastric juice composition on bioaccessibility of cobalt- and tungsten-containing powders.

    PubMed

    Stefaniak, Aleksandr B; Virji, M Abbas; Harvey, Christopher J; Sbarra, Deborah C; Day, Gregory A; Hoover, Mark D

    2010-03-01

    The dissolution of metal-containing particles in the gastric compartment is poorly understood. The purpose of this study was to elucidate the influence of artificial gastric juice chemical composition on bioaccessibility of metals associated with ingestion-based health concerns. Dissolution rates were evaluated for well-characterized feedstock cobalt, tungsten metal, and tungsten carbide powders, chemically bonded pre-sintered (spray dryer material) and post-sintered (chamfer grinder) cemented tungsten carbide materials, and an admixture of pure cobalt and pure tungsten carbide, prepared by mechanically blending the two feedstock powders. Dissolution of each study material was evaluated in three different formulations of artificial gastric juice (from simplest to most chemically complex): American Society of Testing Materials (ASTM), U.S. Pharmacopoeia (USP), and National Institute for Occupational Safety and Health (NIOSH). Approximately 20% of cobalt dissolved in the first dissolution phase (t(1/2) = 0.02 days) and the remaining 80% was released in the second long-term dissolution phase (t(1/2) = 0.5 to 1 days). Artificial gastric juice chemical composition did not influence dissolution rate constant values (k, g/cm(2)day) of cobalt powder, either alone or as an admixture. Approximately 100% of the tungsten and tungsten carbide that dissolved was released in a single dissolution phase; k-values of each material differed significantly in the solvents: NIOSH > ASTM > USP (p<0.05). The k-values of cobalt and tungsten carbide in pre- and post-sintered cemented tungsten carbide powders were significantly different from values for the pure feedstock powders. Solvent composition had little influence on oral bioaccessibility of highly soluble cobalt and our data support consideration of the oral exposure route as a contributing pathway to total-body exposure. Solvent composition appeared to influence bioaccessibility of the low soluble tungsten compounds, though

  18. Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry.

    PubMed

    Holá, Markéta; Kanický, Viktor; Mermet, Jean-Michel; Otruba, Vítezslav

    2003-12-01

    The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO2 as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm(-2). Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from +/- 6% to +/- 11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from +/- 9% to +/- 14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.

  19. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro.

    PubMed

    Armstead, Andrea L; Arena, Christopher B; Li, Bingyun

    2014-07-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause "hard metal lung disease" but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure.

  20. Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

    NASA Astrophysics Data System (ADS)

    Kartal, Muhammet; Uysal, Mehmet; Gul, Harun; Alp, Ahmet; Akbulut, Hatem

    2015-11-01

    A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55-65%).

  1. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

    PubMed Central

    Armstead, Andrea L.; Arena, Christopher B.; Li, Bingyun

    2014-01-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggests that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. PMID:24746988

  2. Spark Plasma Sintering of Aluminum-Magnesium-Matrix Composites with Boron Carbide and Tungsten Nano-powder Inclusions: Modeling and Experimentation

    NASA Astrophysics Data System (ADS)

    Dvilis, E. S.; Khasanov, O. L.; Gulbin, V. N.; Petyukevich, M. S.; Khasanov, A. O.; Olevsky, E. A.

    2016-03-01

    Spark-plasma sintering (SPS) is used to fabricate fully-dense metal-matrix (Al/Mg) composites containing hard ceramic (boron carbide) and refractory metal (tungsten) inclusions. The study objectives include the modeling (and its experimental verification) of the process of the consolidation of the composites consisted of aluminum-magnesium alloy AMg6 (65 wt.%), B4C powder (15 wt.%), and W nano-powder (20 wt.%), as well as the optimization of the composite content and of the SPS conditions to achieve higher density. Discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders is utilized for the determination of the powder compositions rendering maximum mixture packing densities. Two models: a power-law creep model of the high temperature deformation of powder materials, and an empirical logarithmic pressure-temperature-relative density relationship are successfully applied for the description of the densification of the aluminum-magnesium metal matrix powder composite subjected to spark-plasma sintering. The elastoplastic properties of the sintered composite samples are assessed by nanoindentation.

  3. Evaluation of dioxins and dioxin-like compounds from a cement plant using carbide slag from chlor-alkali industry as the major raw material.

    PubMed

    Zhao, Yuyang; Zhan, Jiayu; Liu, Guorui; Zheng, Minghui; Jin, Rong; Yang, Lili; Hao, Liwei; Wu, Xiaolin; Zhang, Xian; Wang, Pu

    2017-05-15

    Carbide slag produced from chlor-alkali industry contains high amounts of calcium compounds and can potentially be used as raw material for cement production; however, it contains large amounts of chlorine so it is essential to evaluate the emissions of chlorinated organic pollutants, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs). A field study of the emission profiles of these pollutants in a cement plant using such slag was performed. The average concentrations of PCDD/Fs, PCBs, and PCNs in stack gases collected at the kiln back end were 6.31, 1.07, and 31.89pg TEQ m(-3), respectively. PCDFs dominated over PCDDs in particulate samples. Di- to pentachlorinated biphenyls were dominant homologs in the particulate samples. MonoCBs were the dominant homolog in stack gases from the kiln back end, and homolog concentrations decreased with increasing chlorine numbers. Mono- and diCNs accounted for 48-98% of PCNs. The estimated toxic equivalents of stack gas emissions of PCNs, classified as new persistent organic pollutants under Stockholm Convention, were unexpectedly higher than those of PCDD/Fs and PCBs. A mass balance indicated that all of the toxic equivalents were reduced by this cement kiln system. The highest 2,3,7,8-PCDD/F output is with clinker.

  4. Synthesis of Tungsten Carbides by Temperature-Programmed Reaction with CH 4-H 2 Mixtures. Influence of the CH 4 and Hydrogen Content in the Carburizing Mixture

    NASA Astrophysics Data System (ADS)

    Giraudon, J.-M.; Devassine, P.; Lamonier, J.-F.; Delannoy, L.; Leclercq, L.; Leclercq, G.

    2000-11-01

    The influence of the composition of a carburizing CH4-H2 gas mixture on the process of reduction-carburization over WO3 has been studied. Bulk tungsten carbide synthesis has been carried out from WO3 in different CH4-H2 mixtures (CH4-H2=1/1-3/1; CH4-N2=1/1; pure CH4) at atmospheric pressure by temperature-programmed reduction-carburization (TPRC). The composition of the reaction products has been monitored and quantified by gas chromatography analysis (GCA) and the results have been compared to those obtained for a reference sample WC20 (CH4-H2=1/4). The solids have been characterized by elemental analysis, XRD, XPS, and BET surface area measurements. The overall process is complex. Considering first the reduction, both H2 and CH4 act as oxides reducing agents and are converted respectively into H2O, CO, and to a less extent CO2. If the reduction steps follow the same sequence observed under pure H2, WO3→W20O58→WO2→W, with the strong difference that W metal is detected only at the surface to be rapidly carburized, the overall reduction process can be accomplished under CH4-H2 mixtures at temperatures all the lower than PCH4/PH2 increases. Prereduction of WO3 into bulk WO2 allows an easier reduction in practically pure CH4 (95% (v/v) CH4-H2) as reduction with CH4 increases the rate of the WO2→W transformation. Studies of the carburization suggest that CH4 decomposes on a metallic surface into C (or CHx) species before bulk WO2 reduction followed by surface carburization. Then carbon diffuses into the bulk of the solid to give first α-W2C whose formation occurs rapidly. α-W2C transformation into WC is slower and seems to be very much influenced by the ratio PCH4/PH2 which controls the rate of carbon deposit at the surface of the solid. The best surface area carbide of 27 m2.g-1 consisting of a core of α-W2C covered with α-WC has been obtained by using WO2 as starting material.

  5. The effect of resin cement type and cleaning method on the shear bond strength of resin cements for recementing restorations.

    PubMed

    Koodaryan, Roodabeh; Hafezeqoran, Ali; Khakpour Maleki, Amin

    2017-04-01

    This laboratory study assessed the effect of different dentin cleaning procedures on shear bond strength of resin cements for recementing prosthesis. 4 × 4 flat surface was prepared on the labial surface of 52 maxillary central incisors. Metal frames (4 × 4 × 1.5 mm) were cast with nickel-chromium alloy. All specimens were randomly divided into 2 groups to be cemented with either Panavia F2.0 (P) or RelyX Ultimate (U) cement. The initial shear bond strength was recorded by Universal Testing Machine at a crosshead speed of 0.5 mm/min. Debonded specimens were randomly allocated into 2 subgroups (n = 13) according to the dentin cleaning procedures for recementation. The residual cement on bonded dentin surfaces was eliminated with either pumice slurry (p) or tungsten carbide bur (c). The restorations were rebonded with the same cement and were subjected to shear test. Data failed the normality test (P < .05), thus were analyzed with Mann Whitney U-test, Wilcoxon signed rank test, and two-way ANOVA after logarithmic transformation (α = .05). The initial shear bond strength of group P was significantly higher than group U (P = .001). Pc and Uc groups presented higher bond strength after recementation compared to the initial bond strength. However, it was significant only in Pc group (P = .034). The specimens recemented with Panavia F2.0 provided higher bond strength than RelyX Ultimate cement. Moreover, a tungsten carbide bur was a more efficient method in removing the residual resin cement and increased the bond strength of Panavia F2.0 cement after recementation.

  6. The effect of resin cement type and cleaning method on the shear bond strength of resin cements for recementing restorations

    PubMed Central

    Koodaryan, Roodabeh; Khakpour Maleki, Amin

    2017-01-01

    PURPOSE This laboratory study assessed the effect of different dentin cleaning procedures on shear bond strength of resin cements for recementing prosthesis. MATERIALS AND METHODS 4 × 4 flat surface was prepared on the labial surface of 52 maxillary central incisors. Metal frames (4 × 4 × 1.5 mm) were cast with nickel-chromium alloy. All specimens were randomly divided into 2 groups to be cemented with either Panavia F2.0 (P) or RelyX Ultimate (U) cement. The initial shear bond strength was recorded by Universal Testing Machine at a crosshead speed of 0.5 mm/min. Debonded specimens were randomly allocated into 2 subgroups (n = 13) according to the dentin cleaning procedures for recementation. The residual cement on bonded dentin surfaces was eliminated with either pumice slurry (p) or tungsten carbide bur (c). The restorations were rebonded with the same cement and were subjected to shear test. Data failed the normality test (P < .05), thus were analyzed with Mann Whitney U-test, Wilcoxon signed rank test, and two-way ANOVA after logarithmic transformation (α = .05). RESULTS The initial shear bond strength of group P was significantly higher than group U (P = .001). Pc and Uc groups presented higher bond strength after recementation compared to the initial bond strength. However, it was significant only in Pc group (P = .034). CONCLUSION The specimens recemented with Panavia F2.0 provided higher bond strength than RelyX Ultimate cement. Moreover, a tungsten carbide bur was a more efficient method in removing the residual resin cement and increased the bond strength of Panavia F2.0 cement after recementation. PMID:28435620

  7. Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials.

    PubMed

    Holá, Markéta; Mikuska, Pavel; Hanzlíková, Renáta; Kaiser, Jozef; Kanický, Viktor

    2010-03-15

    A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm. The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 microm) and particle size distribution in the range of 0.25-17 microm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS). The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials. The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  8. Experimental investigation of grain boundaries misorientations and nano twinning induced strengthening on addition of silicon carbide in pulse electrodeposited nickel tungsten composite coating

    SciTech Connect

    Rahman, O.S. Asiq; Wasekar, Nitin P.; Sundararajan, G.; Keshri, Anup Kumar

    2016-06-15

    Nanoindentation was performed on silicon carbide (SiC) reinforced pulse electrodeposited nickel-tungsten (Ni-W) composite coating. Addition of 5 vol.% of SiC in Ni-W coating increased the hardness from 10.31 ± 0.65 GPa to 14.32 ± 0.63 GPa and elastic modulus from 119.74 ± 3.15 GPa to 139.26 ± 2.09 GPa. Increased hardness and elastic modulus directly translates to the improved strengthening in the coating. An experimental investigation of strengthening mechanism was carried out in Ni-W-5 vol.% SiC alloy. Two simultaneous phenomena viz. grain refinement and increased internal strain was observed, which increased the dislocation density from 5.51 × 10{sup 18} m{sup −2} to 1.346 × 10{sup 19} m{sup −2} on reinforcement of 5 vol.% of SiC in Ni-W coating. Increased dislocation density promoted the formation of grain boundary misorientations and nano twinning. Low angle grain boundary, high angle grain boundary and nano twinning were identified using high resolution transmission electron microscope (HR-TEM) image and their role in strengthening mechanism was discussed in details. - Highlights: • SiC reinforced pulse electrodeposition Ni-W coating was deposited on steel. • Nanoindentation showed the increased mechanical properties on addition of SiC. • Grain refinement and increased internal strain was observed in Ni-W-SiC coating. • Dislocation density increased on reinforcement of SiC in Ni-W coating. • Increased dislocation density triggered grain boundary misorientation and twinning.

  9. Induction of miR-21-PDCD4 signaling by tungsten carbide-cobalt nanoparticles in JB6 cells involves ROS-mediated MAPK pathways.

    PubMed

    Hou, Lichao; Bowman, Linda; Meighan, Terence G; Shi, Xianglin; Ding, Min

    2013-01-01

    Tungsten carbide-cobalt (WC-Co) nanoparticle composites have wide applications because of their hardness and toughness. WC-Co was classified as "probably carcinogenic" to humans by the International Agency for Research on Cancer (IARC) in 2003. It is believed that the toxicity and carcinogenesis of WC-Co is associated with particle size. Recent studies demonstrated that the tumor suppressor gene programmed cell death 4 (PDCD4) and its upstream regulator miR-21 have been considered as oncogenes for novel cancer prevention or anticancer therapies. The present study examined the effects of WC-Co nanoparticles on miR-21-PDCD4 signaling in a mouse epidermal cell line (JB6 P+). The results showed that (i) exposure of JB6 cells to WC-Co stimulated a increase of miR-21 generation; (ii) WC-Co also caused inhibition of PDCD4, a tumor suppressor protein and downstream target of miR-21, expression in JB6 cells; (iii) inhibition of ERKs with ERK inhibitor U0126 significantly reversed WC-Cominus;induced PDCD4 inhibition, but inhibition of p38 with p38 inhibitor SB203580 did not; and (iv) ROS scavengers, N-acetyl-L-cysteine and catalase, blocked the inhibitory effect of WC-Co on PDCD4 expression, while superoxide dismutase promoted the inhibitory effect. These findings demonstrate that WC-Co nanoparticles induce miR-21 generation, but inhibit PDCD4 production, which may be mediated through ROS, especially endogenous H2O2, and ERK pathways. Unraveling the complex mechanisms associated with these events may provide insights into the initiation and progression of WC-Co-induced carcinogenesis.

  10. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

    SciTech Connect

    Armstead, Andrea L.; Arena, Christopher B.; Li, Bingyun

    2014-07-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. - Highlights: • Hard metal (WC-Co) particle toxicity was established in lung epithelial cells. • Nano-WC-Co particles caused greater toxicity than micro-WC-Co particles. • Nano- and micro-WC-Co particles were capable of inducing cellular apoptosis. • Nano-WC-Co particles were internalized by lung epithelial cells. • WC-Co particle internalization was mediated by actin dynamics.

  11. Microstructure and Mechanical Properties of Nano-Size Zirconium Carbide Dispersion Strengthened Tungsten Alloys Fabricated by Spark Plasma Sintering Method

    NASA Astrophysics Data System (ADS)

    Xie, Zhuoming; Liu, Rui; Fang, Qianfeng; Zhang, Tao; Jiang, Yan; Wang, Xianping; Liu, Changsong

    2015-12-01

    W-(0.2, 0.5, 1.0)wt% ZrC alloys with a relative density above 97.5% were fabricated through the spark plasma sintering (SPS) method. The grain size of W-1.0wt% ZrC is about 2.7 μm, smaller than that of pure W and W-(0.2, 0.5)wt% ZrC. The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature, higher tensile strength at high temperature, and a lower ductile to brittle transition temperature (DBTT) than pure W. The tensile strength and total elongation of W-0.5wt% ZrC alloy at 700 °C is 535 MPa and 24.8%, which are respectively 59% and 114% higher than those of pure W (337 MPa, 11.6%). The DBTT of W-(0.2, 0.5, 1.0)wt% ZrC materials is in the range of 500°C-600°C, which is about 100 °C lower than that of pure W. Based on microstructure analysis, the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening. supported by the Innovation Program of Chinese Academy of Sciences (No. KJCX2-YW-N35), the National Magnetic Confinement Fusion Science Program of China (No. 2011GB108004), National Natural Science Foundation of China (Nos. 51301164, 11075177, 11274305), and Anhui Provincial Natural Science Foundation of China (No. 1408085QE77)

  12. Measurements of Total Hemispherical Emissivity of Several Stably Oxidized Nickel-Titanium Carbide Cemented Hard Metals from 600 F to 1,600 F

    NASA Technical Reports Server (NTRS)

    Wade, William R.; Casey, F. W., Jr.

    1959-01-01

    The total hemispherical emissivity of several nickel-titanium carbide cemented hard metals have been measured over a temperature range from 600 F to l,600 F. A variety of cemented hard metals were obtained from the Kennametal Corporation. A brief discussion of the apparatus employed and the procedures used for this investigation is included. The results of the tests of specimens in the as-received and polished states indicate a nearly constant emissivity for each material tested over the temperature range considered and only slight differences in emissivity values for the different materials. Values obtained on the stably oxidized specimens range from 0.90 to 0.94 at 6000 F and o.88 to 0.92 at 1,600 F for the as-received specimens and from 0.82 to 0.89 at 600 F and 0.85 to 0.87 at 1,600 F for the polished specimens. The surface analysis of the oxidized materials as obtained by X-ray diffraction methods and metallographic techniques are presented as an aid to reproducing the surface on which these measurements were made.

  13. Agglomeration of tungsten carbide nanoparticles in exposure medium does not prevent uptake and toxicity toward a rainbow trout gill cell line.

    PubMed

    Kühnel, Dana; Busch, Wibke; Meissner, Tobias; Springer, Armin; Potthoff, Annegret; Richter, Volkmar; Gelinsky, Michael; Scholz, Stefan; Schirmer, Kristin

    2009-06-28

    Due to their increased production and use, engineered nanoparticles are expected to be released into the aquatic environment where particles may agglomerate. The aim of this study was to explore the role of agglomeration of nanoparticles in the uptake and expression of toxicity in the rainbow trout (Oncorhynchus mykiss) gill cell line, RTgill-W1. This cell line was chosen as model because it is known to be amenable to culture in complete as well as greatly simplified exposure media. Nano-sized tungsten carbide (WC) with or without cobalt doping (WC-Co), two materials relevant in the heavy metal industry, were applied as model particles. These particles were suspended in culture media with decreasing complexity from L15 with 10% fetal bovine serum (FBS) to L15 to L15/ex, containing only salts, galactose and pyruvate of the complete medium L15. Whereas the serum supplement in L15 retained primary nanoparticle suspensions, agglomerates were formed quickly in L15 and L15/ex. Nevertheless, scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) elemental analysis revealed an uptake of both WC and WC-Co nanoparticles into RTgill-W1 cells irrespective of the state of agglomeration of nanoparticles. The localisation seemed to be restricted to the cytoplasm, as no particles were observed in the nucleus of cells. Moreover, reduction in cell viability between 10 and 50% compared to controls were observed upon particle exposure in all media although the pattern of impact varied depending on the medium and exposure time. Short-term exposure of cells led to significant cytotoxicity at the highest nominal particle concentrations, irrespective of the particle type or exposure medium. In contrast, long-term exposures led to preferential toxicity in the simplest medium, L15/ex, and an enhanced toxicity by the cobalt-containing WC nanoparticles in all exposure media. The composition of the exposure media also influenced the toxicity of the cobalt ions, which may

  14. Microchemical and microstructural changes of Co cemented WC induced by ion implantation

    NASA Astrophysics Data System (ADS)

    Lin, W. L.; Sang, J. M.; Ding, X. J.; Xu, J.; Yuan, X. M.

    2002-04-01

    Changes in the microchemistry and microstructure of cobalt cemented tungsten carbide (WC-Co) hard alloy which were implanted with energetic Ta ions, with and without an additional C ion beam, have been investigated. Ion implantation was carried out at room temperature using a metal vapor vacuum arc source ion implanter. The extraction voltage and average current density of the ion beam was 45 kV and 50 μA/cm 2, respectively. The concentration depth profiles and microstructure of implanted the WC-Co alloy were analyzed by Rutherford backscattering spectroscopy, Auger electron spectroscopy, and glancing angle X-ray diffraction, respectively. The results showed that as compared with the control, there were no significant microstructural changes in the tungsten carbide phase of implanted WC-Co alloy substrate; both Ta implantation and Ta+C dual implantation induced a transformation from a metastable cubic form to a stable hcp form of cobalt binder phase.

  15. Handbook of refractory carbides and nitrides: Properties, characteristics, processing and applications

    SciTech Connect

    Pierson, H.O.

    1997-12-31

    This reference work provides a complete review of the structure properties, processing and applications of refractory carbides and nitrides. The contents include: the refractory carbides; interstitial carbides, structure and composites; titanium, zirconium, and hafnium carbides; vanadium, niobium and tantalum carbides; chromium, molybdenum, and tungsten carbides; covalent carbides--structure and composition; characteristics and properties of silicon carbide and boron carbide; the refractory nitrides; interstitial nitrides--structure and composition; interstitial nitrides--properties and general characteristics; covalent nitrides--composition and structure; covalent nitrides--properties and general characteristics; processing of refractory carbides and nitrides and applications of refractory carbides and nitrides.

  16. Progress in development of coated indexable cemented carbide inserts for machining of iron based work piece materials

    NASA Astrophysics Data System (ADS)

    Czettl, C.; Pohler, M.

    2016-03-01

    Increasing demands on material properties of iron based work piece materials, e.g. for the turbine industry, complicate the machining process and reduce the lifetime of the cutting tools. Therefore, improved tool solutions, adapted to the requirements of the desired application have to be developed. Especially, the interplay of macro- and micro geometry, substrate material, coating and post treatment processes is crucial for the durability of modern high performance tool solutions. Improved and novel analytical methods allow a detailed understanding of material properties responsible for the wear behaviour of the tools. Those support the knowledge based development of tailored cutting materials for selected applications. One important factor for such a solution is the proper choice of coating material, which can be synthesized by physical or chemical vapor deposition techniques. Within this work an overview of state-of-the-art coated carbide grades is presented and application examples are shown to demonstrate their high efficiency. Machining processes for a material range from cast iron, low carbon steels to high alloyed steels are covered.

  17. A TEM study of CVD TiC x /Ti(C, N) x coating on WC-Co cemented carbide

    NASA Astrophysics Data System (ADS)

    Liao, J.; Li, Jian Chun; Kuo, K. H.

    1989-02-01

    The cross-sectional microstructure of TiC x /Ti(C,N) x (0< x<1) coating deposited on WC-8 wt pct Co-4 pct TaC-6 wt pct TiC cemented carbide by chemical vapor deposition (CVD) has been investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopic analysis (EELS), and the interfacial structures between TiC x coating and the substrate were emphasized. TEM studies showed that a multilayer structure can be delineated in the coating. Selected area electron diffraction (SAED) and EELS analysis revealed that it consists mainly of a TiC x layer and a Ti(C,N) x layer. Additionally, two sublayers were found, one between the TiC x and Ti(C,N) x layers and the other between the substrate and the TiC x layer. A <111> preferred orientation formed in the TiC x layer, whereas <100> preferred orientation formed in the Ti(C,N) x layer. Grains in the sublayers, in general, oriented randomly. The changes in composition of the coating were measured qualitatively by the EELS analysis. Microelectron diffraction (γ-Diff) analysis and centered dark-field (CDF) technique were used to investigate the interfacial structure between the TiC x and the γ-phase (TaC or TiC in the substrate), and two kinds of coherent structure were revealed. According to these findings, the formation of the CVD TiC x coating is possibly affected by the carbon supply from the component phases in the substrate.

  18. Tungsten toxicity.

    PubMed

    Witten, Mark L; Sheppard, Paul R; Witten, Brandon L

    2012-04-05

    There is emerging evidence that tungsten has toxic health effects. We summarize the recent tungsten toxicity research in this short review. Tungsten is widely used in many commercial and military applications because it has the second highest melting temperature of any element. Consequently, it is important to elucidate the potential health effects of tungsten.

  19. Development of refractory armored silicon carbide by infrared transient liquid phase processing

    NASA Astrophysics Data System (ADS)

    Hinoki, Tatsuya; Snead, Lance L.; Blue, Craig A.

    2005-12-01

    Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m 2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m 2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing.

  20. HIP Joining of Cemented Carbides

    SciTech Connect

    Derby, B.; Miodownik, M.

    1999-04-01

    Hot Isostatic Pressing (HIP) is investigated as a technique for joining the cermet WC-15% Co to itself. Encapsulation of the specimens prior to HIPing was carried out using steel encapsulation, glass encapsulation and self encapsulation. The bonds were evaluated using a four point bend method. It is shown that the glass and steel encapsulation methods have a number of inherent problems which make them inappropriate for near net shape processing. In contrast the novel self encapsulation method, described for the first time in this communication, is both simple and effective, producing joined material with bulk strength. The concept of self encapsulation is potentially widely applicable for joining composite materials.

  1. Depth profile analysis of various titanium based coatings on steel and tungsten carbide using laser ablation inductively coupled plasma--"time of flight" mass spectrometry.

    PubMed

    Bleiner, D; Plotnikov, A; Vogt, C; Wetzig, K; Günther, D

    2000-01-01

    A homogenized 193 nm ArF* laser ablation system coupled to an inductively coupled plasma-"Time of Flight"-mass spectrometer (LA-ICP-TOFMS) was tested for depth profiling analysis on different single-layer Ti based coatings on steel and W carbides. Laser parameters, such as repetition rate, pulse energy and spatial resolution were tested to allow optimum depth related calibration curves. The ablation process using a laser repetition rate of 3 Hz, 120 microm crater diameter, and 100 mJ output energy, leads to linear calibration curves independent of the drill time or peak area used for calibrating the thickness of the layer. The best depth resolution obtained (without beam splitter) was 0.20 microm per laser shot. The time resolution of the ICP-TOFMS of 102 ms integration time per isotope was sufficient for the determination of the drill time of the laser through the coatings into the matrix with better than 2.6% RSD (about 7 microm coating thickness, n = 7). Variation of the volume of the ablation cell was not influencing the depth resolution, which suggests that the depth resolution is governed by the ablation process. However, the application on the Ti(N,C) based single layer shows the potential of LA-ICP-TOFMS as a complementary technique for fast depth determinations on various coatings in the low to medium microm region.

  2. Interaction between tungsten monocarbide and an iron-based metallic melt

    NASA Astrophysics Data System (ADS)

    Chumanov, I. V.; Anikeev, A. N.

    2015-12-01

    A technique and results of investigation of compacted tungsten carbide substrates by scanning microscopy are reported. Samples are prepared in the course of studies of the wettability of tungsten carbide substrates with the iron melt, which are performed in accordance with the sessile drop method using two different heating strategies, namely, contact and noncontact heating of metal.

  3. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  4. Carbides composite surface layers produced by (PTA)

    SciTech Connect

    Tajoure, Meloud; Tajouri, Ali E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar E-mail: dr.mokhtarphd@yahoo.com; Akreem, Mosbah

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  5. Tin-tungsten mineralizing processes in tungsten vein deposits: Panasqueira, Portugal

    NASA Astrophysics Data System (ADS)

    Lecumberri-Sanchez, P.; Pinto, F.; Vieira, R.; Wälle, M.; Heinrich, C. A.

    2015-12-01

    Tungsten has a high heat resistance, density and hardness, which makes it widely applied in industry (e.g. steel, tungsten carbides). Tungsten deposits are typically magmatic-hydrothermal systems. Despite the economic significance of tungsten, there are no modern quantitative analytical studies of the fluids responsible for the formation of its highest-grade deposit type (tungsten vein deposits). Panasqueira (Portugal) is a tungsten vein deposit, one of the leading tungsten producers in Europe and one of the best geologically characterized tungsten vein deposits. In this study, compositions of the mineralizing fluids at Panasqueira have been determined through combination of detailed petrography, microthermometric measurements and LA-ICPMS analyses, and geochemical modeling has been used to determine the processes that lead to tungsten mineralization. We characterized the fluids related to the various mineralizing stages in the system: the oxide stage (tin and tungsten mineralization), the sulfide stage (chalcopyrite and sphalerite mineralization) and the carbonate stage. Thus, our results provide information on the properties of fluids related with specific paragenetic stages. Furthermore we used those fluid compositions in combination with host rock mineralogy and chemistry to evaluate which are the controlling factors in the mineralizing process. This study provides the first quantitative analytical data on fluid composition for tungsten vein deposits and evaluates the controlling mineralization processes helping to determine the mechanisms of formation of the Panasqueira tin-tungsten deposit and providing additional geochemical constraints on the local distribution of mineralization.

  6. Spinodal decomposition of tungsten-containing phases in functional coatings obtained via high-energy implantation processes

    NASA Astrophysics Data System (ADS)

    Davydov, S. V.; Petrov, E. V.

    2017-08-01

    We have studied structural and phase transformations in tungsten-containing functional coatings of carbon steels obtained during the high-energy processes of implanting tungsten carbide micropowders by the method of complex pulse electromechanical processing and micropowders of tungsten by technology of directed energy of explosion based on the effect of superdeep penetration of solid particles (Usherenko effect). It has been shown that, during thermomechanical action, intensive steel austenization occurs in the deformation zone with the dissolution of tungsten carbide powder, the carbidization of tungsten powder, and the subsequent formation of composite gradient structures as a result of the decay of supercooled austenite supersaturated by tungsten according to the diffusion mechanism and the mechanism of spinodal decomposition. Separate zones of tungsten-containing phases of the alloy are in the liquid-phase state, as well as undergo spinodal decomposition with the formation of highly disperse carbide phases of globular morphology.

  7. Route to transition metal carbide nanoparticles through cyanamide and metal oxides

    SciTech Connect

    Li, P.G. Lei, M.; Tang, W.H.

    2008-12-01

    We have designed an efficient route to the synthesis of transition metal carbide nanoparticles starting from an organic reagent cyanamide and transition metal oxides. Four technologically important metal carbide nanoparticles such as tungsten carbide, niobium carbide, tantalum carbide and vanadium carbide were synthesized successfully at moderate temperatures. It is found that cyanamide is an efficient carburization reagent and that the metal oxides are completely transmitted into the corresponding carbide nanoparticles. A possible mechanism is proposed to explain the results of the reaction between cyanamide and the metal oxides.

  8. Damage and Reliability of Y-TZP after Cementation Surface Treatment

    PubMed Central

    Guess, P.C.; Zhang, Y.; Kim, J.-W.; Rekow, E.D.; Thompson, V.P.

    2010-01-01

    Zirconia-based restorations are widely used in prosthetic dentistry, but their susceptibility to post-sintering cementation surface treatments remains controversial. We hypothesized that grinding (600-grit) and alumina abrasion (50 µm, 5 sec, 0.5 MPa) affect the damage modes and reliability of zirconia core material. Monolithic CAD/CAM-machined and sintered Y-TZP plates (0.5 mm thickness) were adhesively cemented to dentin-like composite substrates. Uni-axial mouth-motion cyclic contact was applied through a tungsten carbide spherical indenter (r = 3.18 mm). Results showed that zirconia core ceramic is vulnerable to lower surface radial fracture after grinding or alumina abrasion, while the as-received control chiefly fractured from load-application surface cone fracture. Significantly lower reliability of ground and alumina-abraded compared with the as-received zirconia core ceramic can be attributed to damage induced on the cementation surface. Clinical relevance concerning surface treatment protocols for zirconia framework materials prior to cementation is addressed. PMID:20354231

  9. Damage and reliability of Y-TZP after cementation surface treatment.

    PubMed

    Guess, P C; Zhang, Y; Kim, J-W; Rekow, E D; Thompson, V P

    2010-06-01

    Zirconia-based restorations are widely used in prosthetic dentistry, but their susceptibility to post-sintering cementation surface treatments remains controversial. We hypothesized that grinding (600-grit) and alumina abrasion (50 microm, 5 sec, 0.5 MPa) affect the damage modes and reliability of zirconia core material. Monolithic CAD/CAM-machined and sintered Y-TZP plates (0.5 mm thickness) were adhesively cemented to dentin-like composite substrates. Uni-axial mouth-motion cyclic contact was applied through a tungsten carbide spherical indenter (r = 3.18 mm). Results showed that zirconia core ceramic is vulnerable to lower surface radial fracture after grinding or alumina abrasion, while the as-received control chiefly fractured from load-application surface cone fracture. Significantly lower reliability of ground and alumina-abraded compared with the as-received zirconia core ceramic can be attributed to damage induced on the cementation surface. Clinical relevance concerning surface treatment protocols for zirconia framework materials prior to cementation is addressed.

  10. Influence of the matrix structure and properties on the crack resistance of sintered carbides

    SciTech Connect

    Novikov, N.V.; Devin, L.N.; Mitlikin, M.D.; Ul'yanenko, A.P.

    1985-05-01

    This paper presents the results of an automatic analysis of the structure of tungsten-cobalt sintered carbides with 6-25% weight of the binder phase and shows the possibility of their practical use for improvement of the mechanical properties of the materials. The authors conclude that accurate determination of the structural parameters of sintered carbides has made it possible to establish the yield strengths of the matrix material of different types of tungsten-cobalt sintered carbides and to determine those for which an increase in crack resistance is possible. The effect of the increase in fracture toughness of sintered carbides with an increase in loading rate is also explained.

  11. Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel

    SciTech Connect

    Godec, Matjaz; Batic, Barbara Setina; Mandrino, Djordje; Nagode, Ales; Leskovsek, Vojteh; Skapin, Sreco D.; Jenko, Monika

    2010-04-15

    A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M{sub 6}C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V{sub 6}C{sub 5}, while the tungsten-rich carbides were M{sub 6}C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.

  12. Surface texture of resin-modified glass ionomer cements: effects of finishing/polishing time.

    PubMed

    Yap, A U J; Ong, S B; Yap, W Y; Tan, W S; Yeo, J C

    2002-01-01

    This study compared the surface texture of resin-modified glass ionomer cements after immediate and delayed finishing with different finishing/polishing systems. Class V preparations were made on the buccal and lingual/palatal surfaces of 64 freshly extracted teeth. The cavities on each tooth were restored with Fuji II LC (GC) and Photac-Fil Quick (3M-ESPE) according to manufacturers' instructions. Immediately after light-polymerization, gross finishing was done with 8-fluted tungsten carbide burs. The teeth were then randomly divided into four groups of 16 teeth. Half of the teeth in each group were finished immediately, while the remaining half were finished after one-week storage in distilled water at 37 degrees C. The following finishing/polishing systems were employed: (a) Robot Carbides; (b) Super-Snap system; (c) OneGloss and (d) CompoSite Polishers. The mean surface roughness (microm; n=8) in vertical (RaV) and horizontal (RaH) axis was measured using a profilometer. Data was subjected to ANOVA/Scheffe's tests and Independent Samples t-test at significance level 0.05. Ra values were generally lower in both vertical and horizontal axis with delayed finishing/polishing. Although significant differences in RaV and RaH values were observed among several systems with immediate finishing/polishing, only one (Fuji II LC: RaH - Super-Snap < Robot Carbides) was observed with delayed finishing.

  13. Thermal shock and erosion resistant tantalum carbide ceramic material

    NASA Technical Reports Server (NTRS)

    Honeycutt, L., III; Manning, C. R. (Inventor)

    1978-01-01

    Ceramic tantalum carbide artifacts with high thermal shock and mechanical erosion resistance are provided by incorporating tungsten-rhenium and carbon particles in a tantalum carbide matrix. The mix is sintered by hot pressing to form the ceramic article which has a high fracture strength relative to its elastic modulus and thus has an improved thermal shock and mechanical erosion resistance. The tantalum carbide is preferable less than minus 100 mesh, the carbon particles are preferable less than minus 100 mesh, and the tungsten-rhenium particles are preferable elongate, having a length to thickness ratio of at least 2/1. Tungsten-rhenium wire pieces are suitable as well as graphite particles.

  14. [Murine peritoneal neutrophil activation upon tungsten nanoparticles exposure in vivo].

    PubMed

    Martinova, E A; Baranov, V I

    2014-01-01

    Two examples of tungsten carbide nanoparticles (d = 15 nm, 50 nm) and tungsten carbide nanoparticles with 8% cobalt (d = 50 nm) have been found to induce the neutrophil activation 3 h and 36 h after intraperitoneal administration in the doses 0.005; 0.025; 0.05; 0.25; 0.5; 1; 2.5 and 5 microgram per 1 gram body weight to FVB mice. Neutrophil activation was calculated based on the CD11b and S100 antigen expression. Effect of nanoparticles is bimodal for all tested examples.

  15. DEVELOPMENT OF ADVANCED DRILL COMPONENTS FOR BHA USING MICROWAVE TECHNOLOGY INCORPORATING CARBIDE, DIAMOND COMPOSITES AND FUNCTIONALLY GRADED MATERIALS

    SciTech Connect

    Dinesh Agrawal; Rustum Roy

    2000-11-01

    The main objective of this program was to develop an efficient and economically viable microwave processing technique to process cobalt cemented tungsten carbide with improved properties for drill-bits for advanced drilling operations for oil, gas, geothermal and excavation industries. The program was completed in three years and successfully accomplished all the states goals in the original proposal. In three years of the program, we designed and built several laboratory scale microwave sintering systems for conducting experiments on Tungsten carbide (WC) based composites in controlled atmosphere. The processing conditions were optimized and various properties were measured. The design of the system was then modified to enable it to process large commercial parts of WC/Co and in large quantities. Two high power (3-6 kW) microwave systems of 2.45 GHz were built for multi samples runs in a batch process. Once the process was optimized for best results, the technology was successfully transferred to our industrial partner, Dennis Tool Co. We helped them to built couple of prototype microwave sintering systems for carbide tool manufacturing. It was found that the microwave processed WC/Co tools are not only cost effective but also exhibited much better overall performance than the standard tools. The results of the field tests performed by Dennis Tool Co. showed remarkable advantage and improvement in their overall performance. For example: wear test shows an increase of 20-30%, corrosion test showed much higher resistance to the acid attack, erosion test exhibited about 15% better resistance than standard sinter-HIP parts. This proves the success of microwave technology for WC/Co based drilling tools. While we have successfully transferred the technology to our industrial partner Dennis Tool Co., they have signed an agreement with Valenite, a world leading WC producer of cutting and drilling tools and wear parts, to push aggressively the new microwave technology in

  16. The effect of a weak W/SiC interface on the strength of sigma silicon carbide monofilament

    PubMed

    Dyos; Shatwell

    1999-11-01

    Fractography studies have shown that the strength-determining flaws in silicon carbide monofilaments are generally at the core/silicon carbide interface or in the vicinity of the outside, carbon-based coating. In tungsten-cored monofilaments like DERA Sigma, the W/SiC flaws primarily determine the strength. Fracture is accompanied by brittle failure of the tungsten. The crack propagates simultaneously outwards through the silicon carbide, inwards through the tungsten and also around the W/SiC interface before being deflected into the tungsten or out through the silicon carbide. Experiments depositing boundary layers between the tungsten and silicon carbide have resulted in significantly different fracture behaviour. The tungsten fails in a ductile manner and the strength-determining flaws are located predominantly at the outside surface of the silicon carbide. This behaviour is discussed in terms of models proposed by E. Martin and W. Curtin. It is thought that the work will ultimately lead to a significantly stronger, tungsten-based monofilament.

  17. Creep behavior of uranium carbide-based alloys

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wright, T. R.; Moak, D. P.

    1975-01-01

    The present work gives the results of experiments on the influence of zirconium carbide and tungsten on the creep properties of uranium carbide. The creep behavior of high-density UC samples follows the classical time-dependence pattern of (1) an instantaneous deformation, (2) a primary creep region, and (3) a period of steady-state creep. Creep rates for unalloyed UC-1.01 and UC-1.05 are several orders of magnitude greater than those measured for carbide alloys containing a Zr-C and/or W dispersoid. The difference in creep strength between alloyed and unalloyed materials varies with temperature and applied stress.

  18. Creep behavior of uranium carbide-based alloys

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wright, T. R.; Moak, D. P.

    1975-01-01

    The present work gives the results of experiments on the influence of zirconium carbide and tungsten on the creep properties of uranium carbide. The creep behavior of high-density UC samples follows the classical time-dependence pattern of (1) an instantaneous deformation, (2) a primary creep region, and (3) a period of steady-state creep. Creep rates for unalloyed UC-1.01 and UC-1.05 are several orders of magnitude greater than those measured for carbide alloys containing a Zr-C and/or W dispersoid. The difference in creep strength between alloyed and unalloyed materials varies with temperature and applied stress.

  19. Effects of cementation surface modifications on fracture resistance of zirconia.

    PubMed

    Srikanth, Ramanathan; Kosmac, Tomaz; Della Bona, Alvaro; Yin, Ling; Zhang, Yu

    2015-04-01

    To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Effects of cementation surface modifications on fracture resistance of zirconia

    PubMed Central

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  1. The diffusion bonding of silicon carbide and boron carbide using refractory metals

    SciTech Connect

    Cockeram, B.V.

    1999-10-01

    Joining is an enabling technology for the application of structural ceramics at high temperatures. Metal foil diffusion bonding is a simple process for joining silicon carbide or boron carbide by solid-state, diffusive conversion of the metal foil into carbide and silicide compounds that produce bonding. Metal diffusion bonding trials were performed using thin foils (5 {micro}m to 100 {micro}m) of refractory metals (niobium, titanium, tungsten, and molybdenum) with plates of silicon carbide (both {alpha}-SiC and {beta}-SiC) or boron carbide that were lapped flat prior to bonding. The influence of bonding temperature, bonding pressure, and foil thickness on bond quality was determined from metallographic inspection of the bonds. The microstructure and phases in the joint region of the diffusion bonds were evaluated using SEM, microprobe, and AES analysis. The use of molybdenum foil appeared to result in the highest quality bond of the metal foils evaluated for the diffusion bonding of silicon carbide and boron carbide. Bonding pressure appeared to have little influence on bond quality. The use of a thinner metal foil improved the bond quality. The microstructure of the bond region produced with either the {alpha}-SiC and {beta}-SiC polytypes were similar.

  2. Evaluation of Heat Transfer to the Implant-Bone Interface During Removal of Metal Copings Cemented onto Titanium Abutments.

    PubMed

    Cakan, Umut; Cakan, Murat; Delilbasi, Cagri

    2016-01-01

    The aim of this investigation was to measure the temperature increase due to heat transferred to the implant-bone interface when the abutment screw channel is accessed or a metal-ceramic crown is sectioned buccally with diamond or tungsten carbide bur using an air rotor, with or without irrigation. Cobalt-chromium copings were cemented onto straight titanium abutments. The temperature changes during removal of the copings were recorded over a period of 1 minute. The sectioning of coping with diamond bur and without water irrigation generated the highest temperature change at the cervical part of the implant. Both crown removal methods resulted in an increase in temperature at the implant-bone interface. However, this temperature change did not exceed 47°C, the potentially damaging threshold for bone reported in the literature.

  3. Tungsten and tungsten-alloy powder metallurgy: Powder production and applications-excluding lamps. November 1971-July 1989 (Citations from the US Patent data base). Report for November 1971-July 1989

    SciTech Connect

    Not Available

    1989-10-01

    This bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys including various applications of these materials. The hydrogen reduction of tungsten compounds together with alloying-element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of various cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography. (Contains 60 citations fully indexed and including a title list.)

  4. Systematic studies of the nucleation and growth of ultrananocrystalline diamond films on silicon substrates coated with a tungsten layer

    SciTech Connect

    Chu, Yueh-Chieh; Jiang, Gerald; Tu, Chia-Hao; Chang Chi; Liu, Chuan-pu; Ting, Jyh-Ming; Lee, Hsin-Li; Tzeng, Yonhua; Auciello, Orlando

    2012-06-15

    We report on effects of a tungsten layer deposited on silicon surface on the effectiveness for diamond nanoparticles to be seeded for the deposition of ultrananocrystalline diamond (UNCD). Rough tungsten surface and electrostatic forces between nanodiamond seeds and the tungsten surface layer help to improve the adhesion of nanodiamond seeds on the tungsten surface. The seeding density on tungsten coated silicon thus increases. Tungsten carbide is formed by reactions of the tungsten layer with carbon containing plasma species. It provides favorable (001) crystal planes for the nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the density of diamond seeds/nuclei. UNCD films grown at different gas pressures on tungsten coated silicon which is pre-seeded by nanodiamond along with heteroepitaxially nucleated diamond nuclei were characterized by Raman scattering, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy.

  5. Silicon carbide

    SciTech Connect

    Ault, N.N.; Crowe, J.T. )

    1991-05-01

    This paper reports that, since silicon carbide (SiC) does not occur in nature, it must be synthesized by a high-temperature chemical reaction. The first commercial production began at the end of the 19th century when Acheson developed a process of reacting sand and coke in a resistance furnace. This process is still the basic SiC manufacturing process used today. High-quality silica sand (99.5% SiO{sub 2}), low-sulfur petroleum coke, and electricity (23.8 MJ/kg) are the major ingredients in the production of SiC. The reaction takes place in a trough-like furnace with a removable refractory side (or some similar configuration) and with permanent refractory ends holding carbon electrodes. When the furnace is started, the carbon electrodes are joined by the graphite core laid the length of the furnace near the center of the mixture which fills the furnace.

  6. Ion beam synthesis by tungsten-implantation into 6H-SiC

    SciTech Connect

    Weishart, H.; Schoeneich, J.; Steffen, H.J.; Matz, W.; Skorupa, W.

    1995-12-31

    The authors studied high-dose implantation of tungsten into 6H-silicon carbide in order to synthesize a highly conductive surface layer. Implantation was performed at 200 keV at room temperature. Subsequently, the samples were annealed in two steps at 500 C and 700 C or 950 C, respectively. The influence of dose and annealing temperature on the reaction of W with SiC was investigated. Rutherford Backscattering Spectrometry (RBS), X-Ray Diffraction (XRD) and Auger Electron Spectroscopy (AES) contributed to study structure and composition of the layer as well as chemical states of the elements. During implantation sputtering became significant at a dose exceeding 1.0 {times} 10{sup 17} W{sup +}cm{sup {minus}2}. Formation of tungsten carbide and silicide was observed already in the as-implanted state. An annealing temperature of 950 C was necessary to crystallize tungsten carbide. However, tungsten silicide remained amorphous at this temperature. Therefore, a mixture of polycrystalline tungsten carbide and amorphous tungsten silicide evolved under these conditions. The resistivity of such a layer implanted with 1.0 {times} 10{sup 17} W{sup +} cm{sup {minus}2} and annealed at 950 C is 565 {micro}{Omega}cm.

  7. Bone cement

    PubMed Central

    Vaishya, Raju; Chauhan, Mayank; Vaish, Abhishek

    2013-01-01

    The knowledge about the bone cement is of paramount importance to all Orthopaedic surgeons. Although the bone cement had been the gold standard in the field of joint replacement surgery, its use has somewhat decreased because of the advent of press-fit implants which encourages bone in growth. The shortcomings, side effects and toxicity of the bone cement are being addressed recently. More research is needed and continues in the field of nanoparticle additives, enhanced bone–cement interface etc. PMID:26403875

  8. Chemical vapour deposition: Transition metal carbides go 2D

    DOE PAGES

    Gogotsi, Yury

    2015-08-17

    Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a highmore » crystallinity and very low defect concentration.« less

  9. Chemical vapour deposition: Transition metal carbides go 2D

    SciTech Connect

    Gogotsi, Yury

    2015-08-17

    Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a high crystallinity and very low defect concentration.

  10. Tungsten materials as durable catalyst supports for fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Perchthaler, M.; Ossiander, T.; Juhart, V.; Mitzel, J.; Heinzl, C.; Scheu, C.; Hacker, V.

    2013-12-01

    Durable platinum catalyst support materials, e.g. tungsten carbide (WC), tungsten oxide (WOx) and self-synthesized tungsten oxide (WOxs) were evaluated for the use in High-Temperature Proton Exchange Fuel Cells (HT-PEM) based on phosphoric acid doped polybenzimidazole as electrolyte. The support materials and the catalyst loaded support materials were characterized ex-situ by cyclic voltammetry in HClO4, potential cycling, CO-stripping, electron microscopy and X-ray diffraction measurements. The tungsten oxide and tungsten carbide based supported catalysts were compared to High Surface Area Carbon (HSAC), each coated with platinum via the same in-house manufacturing procedures. The in-house manufacturing procedures resulted in catalyst particle sizes on HSAC of 3-4 nm with a uniform distribution. The in-situ Potential Cycling experiments of WOx or WOxs supported catalysts showed much lower degradation rates compared to High Surface Area Carbons. The formation of WOx species on WC was proven by ex- and in-situ cyclic voltammetric studies and thermogravimetric analyses. X-ray diffraction, ex-situ cyclic voltammetry and in-situ cyclic voltammetry showed that WOx is formed from WC as starting material under oxidizing conditions. Finally a 1000 h durability test with WOx as catalyst support material on the anode was done in a HT-PEM fuel cell with reformed methanol on the anode.

  11. Surface texture of resin-modified glass ionomer cements: effects of finishing/polishing systems.

    PubMed

    Yap, Adrian U J; Tan, W S; Yeo, J C; Yap, W Y; Ong, S B

    2002-01-01

    This study investigated the surface texture of two resin-modified glass ionomer cements (RMGICs) in the vertical and horizontal axis after treatment with different finishing/polishing systems. Class V preparations were made on the buccal and lingual/palatal surfaces of freshly extracted teeth. The cavities on each tooth were restored with Fuji II LC (GC) and Photac-Fil Quick (ESPE) according to manufacturers' instructions. Immediately after light-polymerization, gross finishing was done with 8-flute tungsten carbide burs. The teeth were then randomly divided into four groups and finished/polished with (a) Robot Carbides (RC); (b) Super-Snap system (SS); (c) OneGloss (OG) and (d) CompoSite Points (CS). The sample size for each material-finishing/polishing system combination was eight. The mean surface roughness (microm) in vertical (RaV) and horizontal (RaH) axis was measured using a profilometer. Data was subjected to ANOVA/Scheffe's tests and Independent Samples t-test at significance level 0.05. Mean RaV ranged from 0.59-1.31 and 0.83-1.52, while mean RaH ranged from 0.80-1.43 and 0.85-1.58 for Fuji II LC and Photac-Fil, respectively. Results of statistical analysis were as follows: Fuji II LC: RaV-RC, SScarbides (RC) and one-step rubber abrasive system (OG) for finishing/polishing of RMGICs is not recommended. Graded abrasive disk (SS) or two-step rubber abrasive (CS) systems should be used instead.

  12. Synthesis and characterization of monometallic niobium carbides and bimetallic niobium carbides using hafnium, titanium, and tantalum

    NASA Astrophysics Data System (ADS)

    Watts, Cassandra Jean

    As fossil fuels are rapidly depleting there is an enormous push for the development of new forms of energy based on renewable resources. Proton Exchange Membrane (PEM) fuel cells are one possible solution, but are constrained by the necessity of the platinum catalyst to initiate the oxygen reduction reaction (ORR). Transition metal carbides, like tungsten and molybdenum carbide, have shown catalytic properties that resemble platinum. This project seeks to synthesize through a low temperature solid state method with a LiCl:KCl:KF salt flux monometallic niobium carbides (NbC, Nb4C3, and Nb2C) and the bimetallic niobium carbides HfNbC, TiNbC, and TaNbC. The synthesized materials are characterized using XRD, SEM, and EDS. The results showed that a pure single phase of NbC and Nb4C 3, and a semi alloyed phase of TiNbC2 are obtainable. The remaining systems yielded phase separated carbide systems and are dominated by irreproducibility or oxidization.

  13. Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

    NASA Technical Reports Server (NTRS)

    Douglas, F. C.; Paradis, E. L.; Veltri, R. D.

    1973-01-01

    A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed.

  14. Preparation of crystalline tungsten oxide films from organometallic precursors

    SciTech Connect

    Meda, L.; Kirss, R.U.

    1995-12-31

    Thin films of tungsten oxide, WO{sub 3}, are of interest in the preparation of electrochromic display devices. Chemical vapor deposition experiments using tetra(allyl)tungsten, W({eta}{sup 3}-C{sub 3}H{sub 5}){sub 4}, led to the deposition of dark, reflective, amorphous carbon rich tungsten/tungsten carbide films on SiO{sub 2} glass between 250 and 450{degrees}C. When {approx}0.25 {mu} thick films were annealed at 400{degrees}C under oxygen, conversion to transparent, nearly colorless, crystalline WO{sub 3} was observed. The films were characterized by x-ray diffraction, SEM and ESCA. Shorter reaction times and lower temperatures yielded dark blue, amorphous films characteristic of WO{sub 3-n} films. The smooth blue films were characterized by SEM and ESCA. While the crystalline WO{sub 3} films were found to be electrically insulating, the blue films were found to be electrically conductive. Preliminary results on the conversion of the WO{sub 3} films to tungsten sulfide and tungsten selenide films will be discussed.

  15. SILICON CARBIDE FOR SEMICONDUCTORS

    DTIC Science & Technology

    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  16. Silicon Carbide Shapes.

    DTIC Science & Technology

    Free-standing silicon carbide shapes are produced by passing a properly diluted stream of a reactant gas, for example methyltrichlorosilane, into a...reaction chamber housing a thin walled, hollow graphite body heated to 1300-1500C. After the graphite body is sufficiently coated with silicon carbide , the...graphite body is fired, converting the graphite to gaseous CO2 and CO and leaving a silicon carbide shaped article remaining.

  17. Structural and phase changes in carbides of the high-speed steel upon heat treatment

    NASA Astrophysics Data System (ADS)

    Chaus, A. S.

    2016-07-01

    The effect of austenitizing temperature on structural and phase changes in carbides of the tungsten-molybdenum high-speed steel has been studied. The results of metallographic analysis and energy dispersive microanalysis have been discussed. It has been shown that an increase in austenitizing temperature from 1180 to 1260°C causes structural transformations in carbide particles of eutectic origin crushed upon hot plastic deformation, which are related to their dissolution and coalescence, and changes in the phase composition of the carbides themselves.

  18. Tungsten Filament Fire

    ERIC Educational Resources Information Center

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  19. Materials Survey: Tungsten

    DTIC Science & Technology

    1956-12-01

    arsenopyrite, in places with muscovite, tourmaline , and France fluorite, are associated with the wolfram- ite. A small amount of tungsten has been The...scheelite, tourmaline , muscovite, arseno- wolframite to scheelite is 3:2. pyrite, and pyrrhotite. The veins are in A total of 53 productive tungsten mines

  20. Tungsten filament fire

    NASA Astrophysics Data System (ADS)

    Ruiz, Michael J.; Perkins, James

    2016-05-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent light bulb is being replaced by compact fluorescent and LED lamps.

  1. Tungsten Filament Fire

    ERIC Educational Resources Information Center

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  2. Squeeze cementing

    SciTech Connect

    Ewert, D.P.; Kundert, D.P.; Dahl, J.A.; Dalrymple, E.D.; Gerke, R.R.

    1992-06-16

    This patent describes a method for terminating the flow of fluid from a portion of a subterranean formation into a wellbore. It comprises: placing within the wellbore adjacent the portion a volume of a slurry of hydraulic cement, permitting the volume to penetrate into the portion; and maintaining the slurry in the portion for a time sufficient to enable the slurry to form a rigid mass of cement in the portion.

  3. Influence of the Third Invariant in the Ballistic Impact of Silicon Carbide

    DTIC Science & Technology

    2010-08-06

    tensile and compressive plate-impact tests, long-rod penetration of prestressed targets, long-rod penetration of confined targets, long-rod penetration...10 3.3 Prestressed Long-Rod Penetration...11 Figure 6. Results of tungsten long-rod impacts with thick prestressed silicon- carbide targets from tests [12

  4. Silicon carbide ceramic production

    NASA Technical Reports Server (NTRS)

    Suzuki, K.; Shinohara, N.

    1984-01-01

    A method to produce sintered silicon carbide ceramics in which powdery carbonaceous components with a dispersant are mixed with silicon carbide powder, shaped as required with or without drying, and fired in nonoxidation atmosphere is described. Carbon black is used as the carbonaceous component.

  5. Silicon Carbide Photoconductive Switches

    DTIC Science & Technology

    1994-09-01

    The optoelectronic properties of p-type 6-H silicon carbide (6H-SiC) have been investigated in an experiment that used lateral and vertical...and the bandgap was determined to be approximately 3.1 eV. 6H-SiC, Photoconductive, Photovoltaic, Absorption coefficient, Switch, Silicon carbide

  6. SILICON CARBIDE DATA SHEETS

    DTIC Science & Technology

    These data sheets present a compilation of a wide range of electrical, optical and energy values for alpha and beta- silicon carbide in bulk and film...spectrum. Energy data include energy bands, energy gap and energy levels for variously-doped silicon carbide , as well as effective mass tables, work

  7. Friction and metal transfer for single-crystal silicon carbide in contact with various metals in vacuum

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted with single-crystal silicon carbide in contact with transition metals (tungsten, iron, rhodium, nickel, titanium, and cobalt), copper, and aluminum. Results indicate the coefficient of friction for a silicon carbide-metal system is related to the d bond character and relative chemical activity of the metal. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to the surface of silicon carbide in sliding. The chemical activity of metal to silicon and carbon and shear modulus of the metal may play important roles in metal transfer and the form of the wear debris. The less active and greater resistance to shear the metal has, with the exception of rhodium and tungsten, the less transfer to silicon carbide.

  8. Exposure assessment in the hard metal manufacturing industry with special regard to tungsten and its compounds

    PubMed Central

    Kraus, T; Schramel, P; Schaller, K; Zobelein, P; Weber, A; Angerer, J

    2001-01-01

    OBJECTIVES—To assess the exposure to tungsten, cobalt, and nickel in a plant producing hard metals. The main components of hard metals are tungsten carbide and cobalt metal. According to recent studies, these two components may be responsible for both fibrogenic and carcinogenic effects.
METHODS—87 workers were investigated (86 male, one female) with a median age of 42 (range 22-58) and a mean duration of exposure of 13 years (range 1-27 years). Stationary and personal air sampling, and biological monitoring were carried out.
RESULTS—Ambient monitoring yielded maximum tungsten concentrations of 417 µg/m3 in the production of heavy alloys. A maximum cobalt concentration of 343 µg/m3 and a maximum nickel concentration of 30 µg/m3 were found at the sintering workshop. The highest urinary cobalt concentrations were found in the powder processing department. The mean concentration was 28.5 µg/g creatinine and the maximum value was 228 µg/g creatinine. The maximum nickel concentration in urine of 6.3 µg/g creatinine was detected in the department producing heavy alloys. The highest tungsten concentrations excreted in urine were found in grinders and had a mean value of 94.4 µg/g creatinine and a maximum of 169 µg/g creatinine. Due to the different solubility and bioavailability of the substance, there was no correlation between the tungsten concentrations in air and urine on a group basis.
CONCLUSIONS—Despite its low solubility, tungsten carbide is bioavailable. The different bioavailability of tungsten metal and tungsten compounds has to be considered in the interpretation of ambient and biological monitoring data in the hard metal producing industry. The bioavailability increases in the order: tungsten metal, tungsten carbide, tungstenate. Only if both monitoring strategies are considered in combination can a valid and effective definition of high risk groups be derived.


Keywords: tungsten; cobalt; biological monitoring PMID

  9. Microwave sintering of boron carbide

    DOEpatents

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  10. KISMET tungsten dispersal experiment

    SciTech Connect

    Wohletz, K.; Kunkle, T.; Hawkins, W.

    1996-12-01

    Results of the KISMET tungsten dispersal experiment indicate a relatively small degree of wall-rock contamination caused by this underground explosive experiment. Designed as an add-on to the KISMET test, which was performed in the U-1a.02 drift of the LYNER facility at Nevada Test Site on 1 March 1995, this experiment involved recovery and analysis of wall-rock samples affected by the high- explosive test. The chemical, high-explosive blast drove tungsten powder, placed around the test package as a plutonium analog, into the surrounding wall- rock alluvium. Sample analyses by an analytical digital electron microscope (ADEM) show tungsten dispersed in the rock as tiny (<10 {mu}m) particles, agglomerates, and coatings on alluvial clasts. Tungsten concentrations, measured by energy dispersive spectral analysis on the ADEM, indicate penetration depths less than 0.1 m and maximum concentrations of 1.5 wt % in the alluvium.

  11. Cement Burns

    PubMed Central

    Alam, Munir; Moynagh, M.; Lawlor, C.

    2007-01-01

    Objective: Cement burns account for relatively few admissions to a burn unit; however, these burns deserve separate consideration because of special features of diagnosis and management. Cement burns, even though potentially disabling, have rarely been reported in literature. Methods: A retrospective review was performed of all patients admitted with cement burns injuries to the national burns unit at the St James's Hospital in Dublin, Ireland, over a 10-year period for the years 1996–2005. Results: A total of 46 patients with cement burns were admitted. The majority of patients were aged 16–74 years (mean age = 32 years). Eighty-seven percent of injuries occurred in an industrial and 13% in a domestic setting. The upper and lower extremities were involved in all the patients, and the mean total body surface area affected was 6.5%. The mean length of hospital stay was 21 days with a range of 1–40 days. Thirty-eight (82%) were surgically managed involving debridement and split-thickness skin graft (SSG) and four (9%) were conservatively managed. A further four did not have data available. Conclusion: Widespread inexperience in dealing with this group of cement burns patients and delays in referral to burns unit highlights the potential for greater levels of general awareness and knowledge in both prevention and treatment of these burns. As well, early debridement and split-thickness skin grafting at diagnosis constitutes the best means of reducing the high socioeconomic costs and allows for early return to work. PMID:18091981

  12. Simple preparation of tungsten supported carbon nanoreactors for specific applications: Adsorption, catalysis and electrochemical activity

    NASA Astrophysics Data System (ADS)

    Mayani, Vishal J.; Mayani, Suranjana V.; Kim, Sang Wook

    2015-08-01

    Porous carbon supported tungsten carbide nanoreactors, two sizes (∼25 and 170 nm), were designed using economical petroleum pitch residue followed by tungsten (W) doping. X-ray diffractions showed both carbon tungsten composites (CTC-25 and CTC-170) contained tungsten subcarbide (W2C) and monocarbide (WC) as the major and minor crystalline phases, respectively. The present study provides a multiple perspective of carbon tungsten composites (CTCs) for methanol oxidation (as an electrode), adsorption (as an adsorbent) and degradation (as a solid catalyst) of methylene blue (MB). The operational electrodes were designed from both CTCs and used as a catalyst in an electrocatalysis process. The electrocatalysts exhibited high and stable catalytic performance (CTCE-25 > CTCE-170) in methanol electro-oxidation. The newly synthesized W-doped carbon nanoreactors were used successfully as an adsorbent for MB and a heterogeneous catalyst for MB oxidation. Ordered CTC-25 and CTC-170 exhibited dynamic MB adsorption within 15 min and complete oxidation of MB in 25-40 min. A synergetic effect between tungsten carbide and the carbon cage framework was noted.

  13. Nanoengineering Applied to Tungsten

    DTIC Science & Technology

    2006-05-01

    and R. Z. Valiev ARL-RP- 123 May 2006 A reprint from the Proceedings of the Sixth International Conference on Tungsten, Refractory...Ground, MD 21005-5066 ARL-RP- 123 May 2006 Nanoengineering Applied to Tungsten Q. Wei University of North Carolina-Charlotte B. E...ORGANIZATION REPORT NUMBER ARL-RP- 123 10. SPONSOR/MONITOR’S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 11. SPONSOR

  14. Tensile behavior of tungsten and tungsten-alloy wires from 1300 to 1600 K

    NASA Technical Reports Server (NTRS)

    Hee, Man Yun

    1988-01-01

    The tensile behavior of a 200-micrometer-diameter tungsten lamp (218CS-W), tungsten + 1.0 atomic percent (a/o) thoria (ST300-W), and tungsten + 0.4 a/o hafnium carbide (WHfC) wires was determined over the temperature range 1300 t0 1600 K at strain rates of 3.3 X 10 to the -2 to 3.3 X 10 to the -5/sec. Although most tests were conducted on as-drawn materials, one series of tests was undertaken on ST300-W wires in four different conditions: as-drawn and vacuum-annealed at 1535 K for 1 hr, with and without electroplating. Whereas heat treatment had no effect on tensile properties, electropolishing significantly increased both the proportional limit and ductility, but not the ultimate tensile strength. Comparison of the behavior of the three alloys indicates that the HfC-dispersed material possesses superior tensile properties. Theoretical calculations indicate that the strength/ductility advantage of WHfC is due to the resistance to recrystallization imparted by the dispersoid.

  15. Effect of atmospheric plasma versus conventional surface treatments on the adhesion capability between self-adhesive resin cement and titanium surface

    PubMed Central

    Kilicarslan, Mehmet Ali; Deniz, Sule Tugba; Mumcu, Emre; Ozkan, Pelin

    2015-01-01

    PURPOSE The aim of this study was to evaluate the effects of atmospheric plasma (APL) versus conventional surface treatments on the adhesion of self-adhesive resin cement to Ti-6Al-4V alloy. MATERIALS AND METHODS Sixty plates of machined titanium (Ti) discs were divided into five groups (n=12): 1) Untreated (CNT); 2) Sandblasted (SAB); 3) Tribochemically treated (ROC); 4) Tungsten CarbideBur (TCB); 5) APL treated (APL). SEM analysis and surface roughness (Ra) measurements were performed. Self-adhesive resin cement was bonded to the Ti surfaces and shear bond strength (SBS) tests, Ra and failure mode examinations were carried out. Data were analyzed by one-way analysis of variance and chi-squared test. RESULTS The lowest SBS value was obtained with CNT and was significantly different from all other groups except for APL. The ROC showed the highest SBS and Ra values of all the groups. CONCLUSION It was concluded that the effect of APL on SBS and Ra was not sufficient and it may not be a potential for promoting adhesion to titanium. PMID:26140177

  16. Laser irradiation of carbon-tungsten materials

    NASA Astrophysics Data System (ADS)

    Marcu, A.; Avotina, L.; Marin, A.; Lungu, C. P.; Grigorescu, C. E. A.; Demitri, N.; Ursescu, D.; Porosnicu, C.; Osiceanu, P.; Kizane, G.; Grigoriu, C.

    2014-09-01

    Carbon-tungsten layers deposited on graphite by thermionic vacuum arc (TVA) were directly irradiated with a femtosecond terawatt laser. The morphological and structural changes produced in the irradiated area by different numbers of pulses were systematically explored, both along the spots and in their depths. Although micro-Raman and Synchrotron-x-ray diffraction investigations have shown no carbide formation, they have shown the unexpected presence of embedded nano-diamonds in the areas irradiated with high fluencies. Scanning electron microscopy images show a cumulative effect of the laser pulses on the morphology through the ablation process. The micro-Raman spatial mapping signalled an increased percentage of sp3 carbon bonding in the areas irradiated with laser fluencies around the ablation threshold. In-depth x-ray photoelectron spectroscopy investigations suggested a weak cumulative effect on the percentage increase of the sp2-sp3 transitions with the number of laser pulses just for nanometric layer thicknesses.

  17. MECHANICAL PROPERTIES OF WROUGHT TUNGSTEN

    DTIC Science & Technology

    Mechanical properties of wrought tungsten vol. II. Creep rupture test data from 1500 to 5000 F, and tensile test data from room temperature to 5000 F at various strain rates for tungsten sheet material.

  18. Development of Tungsten Based Composites

    DTIC Science & Technology

    1992-02-01

    Watertown, MA, July 1991. - 59 - 9. Williams , B.E. et al, "CVD Coated Tungsten Powder Composites, Part I: Powder Processing and Characterization...34, Tungsten and Tungsten Alloys - Recent Advances, TMS, Warrendale, PA c1991. 10. Williams , B.E. et al, "CVD Coated Tungsten Powder Composites, Part II: Powder...MIAC/ CINDAS , Purdue University, 2595 Yeager Road, West Lafayette, IN 47905 Commander, Army Research Office, P.O. Box 12211, Research Triangle Park, NC

  19. Plasma deposition of tungsten

    SciTech Connect

    Greenberg, K.E.

    1986-12-01

    Tungsten films were plasma-deposited using an abnormal glow discharge through a mixture of tungsten hexafluoride, hydrogen, and argon. The films adhered well to silicon, silicon dioxide, gallium arsenide, and aluminum substrates placed directly on the discharge cathode. Typical deposition rates were on the order of 160 Angstroms/minute with as-deposited film resistivities of 40 to 70 microohm-cm. The tungsten was analyzed using a number of techniques including x-ray diffraction, scanning electron microscopy, and Auger spectroscopy. Low-resistivity (<10 microohm-cm) films that adhered well to silicon dioxide were obtained with a two-step process utilizing plasma deposition and conventional chemical vapor deposition.

  20. Lunar cement

    NASA Technical Reports Server (NTRS)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  1. Cryogenics with cement microscopy redefines cement behavior

    SciTech Connect

    Mehta, S.; Jones, R. ); Caveny, B. )

    1994-10-03

    Cement microscopy (CM), cryogenics, environmental scanning microscopy (ESM), scanning electron microscopy (SEM), and other technologies are leading investigators to change their views on cement gelation, hydration, and retardation. Cement samples frozen in a nitrogen slush and viewed with an SEM present a more accurate picture of the setting process. Observations made through this technique have revolutionized ARCO Exploration and Production Technology's and Halliburton Energy Services' oil field cement procurement and slurry design. Findings from this joint study are expected to lead to: optimized waiting on cement (WOC) times; reduced planning and design time; optimized slurry retarder additions; optimized gel times to fit given situations; especially applicable to squeeze operations; improved cement selection (from vendors) for peak performance; and improved cement manufacture. The paper discusses the measuring methods and the findings on the following: cement voids, cement gelation, and retardation mechanisms. It also briefly discusses the impact these discoveries have on operations.

  2. Simulation of Ballistic Impact of a Tungsten Carbide Sphere on a Confined Silicon Carbide Target

    DTIC Science & Technology

    2009-06-01

    AUTODYN – tensile crack softening and stochastic failure - were varied to study their influence on the simulated crack patterns. Comparisons with the...Johnson-Holmquist model parameters along with modifications incorporated to brittle damage models included in AUTODYN – tensile crack softening and...using the nonlinear analysis software AUTODYN . Using the geometry detailed above, the projectile and the SiC target were discretized using Smooth

  3. Sculpting with Cement.

    ERIC Educational Resources Information Center

    Olson, Lynn

    1983-01-01

    Cement offers many creative possibilities for school art programs. Instructions are given for sculpting with fiber-cement and sand-cement, as well as for finishing processes and the addition of color. Safety is stressed. (IS)

  4. Sculpting with Cement.

    ERIC Educational Resources Information Center

    Olson, Lynn

    1983-01-01

    Cement offers many creative possibilities for school art programs. Instructions are given for sculpting with fiber-cement and sand-cement, as well as for finishing processes and the addition of color. Safety is stressed. (IS)

  5. Chemical downstream etching of tungsten

    SciTech Connect

    Blain, M.G.; Jarecki, R.L.; Simonson, R.J.

    1998-07-01

    The downstream etching of tungsten and tungsten oxide has been investigated. Etching of chemical vapor deposited tungsten and e-beam deposited tungsten oxide samples was performed using atomic fluorine generated by a microwave discharge of argon and NF{sub 3}. Etching was found to be highly activated with activation energies approximated to be 6.0{plus_minus}0.5thinspkcal/mol and 5.4{plus_minus}0.4thinspkcal/mol for W and WO{sub 3}, respectively. In the case of F etching of tungsten, the addition of undischarged nitric oxide (NO) directly into the reaction chamber results in the competing effects of catalytic etch rate enhancement and the formation of a nearly stoichiometric WO{sub 3} passivating tungsten oxide film, which ultimately stops the etching process. For F etching of tungsten oxide, the introduction of downstream NO reduces the etch rate. {copyright} {ital 1998 American Vacuum Society.}

  6. Silicon carbide thyristor

    NASA Technical Reports Server (NTRS)

    Edmond, John A. (Inventor); Palmour, John W. (Inventor)

    1996-01-01

    The SiC thyristor has a substrate, an anode, a drift region, a gate, and a cathode. The substrate, the anode, the drift region, the gate, and the cathode are each preferably formed of silicon carbide. The substrate is formed of silicon carbide having one conductivity type and the anode or the cathode, depending on the embodiment, is formed adjacent the substrate and has the same conductivity type as the substrate. A drift region of silicon carbide is formed adjacent the anode or cathode and has an opposite conductivity type as the anode or cathode. A gate is formed adjacent the drift region or the cathode, also depending on the embodiment, and has an opposite conductivity type as the drift region or the cathode. An anode or cathode, again depending on the embodiment, is formed adjacent the gate or drift region and has an opposite conductivity type than the gate.

  7. Carbide and carbonitride surface treatment method for refractory metals

    DOEpatents

    Meyer, G.A.; Schildbach, M.A.

    1996-12-03

    A carbide and carbonitride surface treatment method for refractory metals is provided, in steps including, heating a part formed of boron, chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten or zirconium, or alloys thereof, in an evacuated chamber and then introducing reaction gases including nitrogen and hydrogen, either in elemental or water vapor form, which react with a source of elemental carbon to form carbon-containing gaseous reactants which then react with the metal part to form the desired surface layer. Apparatus for practicing the method is also provided, in the form of a carbide and carbonitride surface treatment system including a reaction chamber, a source of elemental carbon, a heating subassembly and a source of reaction gases. Alternative methods of providing the elemental carbon and the reaction gases are provided, as well as methods of supporting the metal part, evacuating the chamber with a vacuum subassembly and heating all of the components to the desired temperature. 5 figs.

  8. Gas tungsten arc welder

    DOEpatents

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  9. Diffusion of tungsten hexafluoride

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of tungsten hexafluoride

  10. High purity tungsten targets

    NASA Technical Reports Server (NTRS)

    1975-01-01

    High purity tungsten, which is used for targets in X-ray tubes was considered for space processing. The demand for X-ray tubes was calculated using the growth rates for dental and medical X-ray machines. It is concluded that the cost benefits are uncertain.

  11. High purity tungsten targets

    NASA Technical Reports Server (NTRS)

    1975-01-01

    High purity tungsten, which is used for targets in X-ray tubes was considered for space processing. The demand for X-ray tubes was calculated using the growth rates for dental and medical X-ray machines. It is concluded that the cost benefits are uncertain.

  12. Utilization of geothermal energy in the mining and processing of tungsten ore. Quarterly report

    SciTech Connect

    Lane, C.K.; Erickson, M.V.; Lowe, G.D.

    1980-02-01

    The status of the engineering and economic feasibility study of utilizing geothermal energy for the mining and processing of tungsten ore at the Union Carbide-Metals Division Pine Creek tungsten complex near Bishop, Calfironia is reviewed. Results of geophysical data analysis including determination of assumed resource parameters are presented. The energy utilization evaluation identifies potential locations for substituting geothermal energy for fossil fuel energy using current technology. Preliminary analyses for local environmental and institutional barriers to development of a geothermal system are also provided.

  13. Penetration of tungsten-alloy rods into composite ceramic targets: Experiments and 2-D simulations

    NASA Astrophysics Data System (ADS)

    Rosenberg, Z.; Dekel, E.; Hohler, V.; Stilp, A. J.; Weber, K.

    1998-07-01

    A series of terminal ballistics experiments, with scaled tungsten-alloy penetrators, was performed on composite targets consisting of ceramic tiles glued to thick steel backing plates. Tiles of silicon-carbide, aluminum nitride, titanium-dibroide and boron-carbide were 20-80 mm thick, and impact velocity was 1.7 km/s. 2-D numerical simulations, using the PISCES code, were performed in order to simulate these shots. It is shown that a simplified version of the Johnson-Holmquist failure model can account for the penetration depths of the rods but is not enough to capture the effect of lateral release waves on these penetrations.

  14. Indication of worn WC/C surface locations of a dry-running twin-screw rotor by the oxygen incorporation in tungsten-related Raman modes

    NASA Astrophysics Data System (ADS)

    Debus, J.; Schindler, J. J.; Waldkirch, P.; Goeke, S.; Brümmer, A.; Biermann, D.; Bayer, M.

    2016-10-01

    By comparing the worn and untouched locations of a tungsten-carbide/carbon surface of a dry-running twin-screw rotor, we demonstrate that tungsten-oxide Raman modes become observable only at worn locations and the integral intensity of the Raman line at 680 cm-1, which is related to the incipient oxidation of the tungsten-carbide stretching mode, is enhanced. Its frequency and width moreover change significantly, thus indicating the mechanical distortion of the bonding that has been occurred during the wearing process. The shape of the tungsten-oxide Raman lines, resembling the Voigt function, hints at a surface morphology that is a characteristic for an amorphous solid environment. Our Raman scattering results may be exploited to characterize the degree of wear of coated surfaces and to identify signatures of a tribological layer.

  15. Diamond Growth on Carbide Surfaces Using a Selective Etching Technique

    DTIC Science & Technology

    1993-07-01

    nucleation when utilizing hexafluoroethane (C2F6 ) (b), perfluoropropane ( C3F8 ) (c), and octafluorocyclobutane (C4F8 ) (d). Carbon-fluorine atomic ratios...and roughen WC particles SiC: No modification Feed Gases: CF 4, C2F6, C3F8 , or C4F8 all at 1/2% - 3%, 1% 02, balance H2 Total Flow Rate: 200 sccm...1/2% CF 4, (b) 1/2% C2F6, (c) 1/2% C3F8 , and (d) 1/2% C4F8. Figure 6. Growth of diamond on tungsten carbide / 6% cobalt using various fluorocarbon

  16. Auger electron spectroscopy and mass spectroscopy studies on hydrogenation of graphite in the presence of nickel and tungsten

    SciTech Connect

    Bliznakov, G.M.; Kiskinova, M.P.; Surnev, L.N.

    1983-05-01

    Hydrogenation of polycrystalline graphite in the presence of nickel and tungsten was studied by means of Auger electron spectroscopy and mass spectroscopy at temperatures up to 850K and a hydrogen pressure ranging from 1.10/sup -8/ to 5.10/sup -6/ Torr. The changes in the carbon Auger lineshape with increasing metal surface concentration revealed a tendency to formation of a carbide phase, the latter being much stabler in the case of tungsten. The mass spectrometric studies of the interaction of hydrogen with the metal graphite systems showed the formation of CH/sub 4/ methane at temperatures higher than 750K. The electronic and adsorption properties of the metal-graphite systems and the formation of active surface carbide carbon were considered in explaining the different catalytic activites of nickel and tungsten. 6 figures.

  17. The interaction of cobalt metal with different carbides and other mineral particles on mouse peritoneal macrophages.

    PubMed

    Lison, D; Lauwerys, R

    1995-06-01

    Chronic inhalation of hard metal particles can produce an interstitial lung disease (hard metal disease). Recent studies on rats and on isolated alveolar and peritoneal macrophages have demonstrated that this disorder can be explained by an interaction between cobalt metal (Co) and tungsten carbide (WC) particles, which represent the main constituents of hard metal. The exact mechanism of this interaction is still undefined. The present study was undertaken to assess in vitro whether a similar interaction also occurs between cobalt and other metallic carbide particles which may also be incorporated in hard metals depending on the desired applications. When tested separately, Co and metallic carbide particles did not affect the cell integrity. In contrast, TiC, NbC and Cr(3)C(2) exerted a synergistic effect with Co (interactive carbides) while TaC, Mo(2)C and SiC did not (non-interactive carbides). The interaction did not simply result from an increased cobalt bioavailability since cobalt uptake by the macrophages was increased 4-7-fold in the presence of interactive as well as non-interactive carbides. The interactive effect appeared dependent on the size of the carbide particles, which suggests that a physicochemical reaction taking place at the interface between certain carbides and cobalt particles may be responsible for the toxicity of the Co-carbide mixture. Other non-carbide particles (Fe, diamond, crystalline silica) did not produce a similar interaction with cobalt. This observation may contribute to the better delineation of the pathogenesis of hard metal disease.

  18. Carbide fuel pin and capsule design for irradiations at thermionic temperatures

    NASA Technical Reports Server (NTRS)

    Siegel, B. L.; Slaby, J. G.; Mattson, W. F.; Dilanni, D. C.

    1973-01-01

    The design of a capsule assembly to evaluate tungsten-emitter - carbide-fuel combinations for thermionic fuel elements is presented. An inpile fuel pin evaluation program concerned with clad temperture, neutron spectrum, carbide fuel composition, fuel geometry,fuel density, and clad thickness is discussed. The capsule design was a compromise involving considerations between heat transfer, instrumentation, materials compatibility, and test location. Heat-transfer calculations were instrumental in determining the method of support of the fuel pin to minimize axial temperature variations. The capsule design was easily fabricable and utilized existing state-of-the-art experience from previous programs.

  19. Gas-phase photofragmentation of tris(methyl vinyl ketone) tungsten(0) and the relationship to laser-assisted CVD of tungsten oxide thin films.

    PubMed

    Bitner, Theodore W; Zink, Jeffrey I

    2002-02-25

    The gas-phase laser-induced photofragmentation of tris(methyl vinyl ketone) tungsten(0) is studied, and the photoproducts are identified by time-of-flight mass spectroscopy. The initially populated excited electronic state of the complex is attributed to metal-to-ligand charge transfer by analysis of the electronic and preresonance Raman spectra. The major metal-containing photofragmentation products are W(+) and WO(+); smaller amounts of WC(+) and W(C(2)H(2))(+) are also observed. Intramolecular ligand coupling occurs, and dimeric products and their fragments are identified. Reaction pathways that explain the observed products are proposed. Thin films on silicon substrates are produced by laser-assisted chemical vapor deposition. The films consist of polycrystalline tungsten oxide with less than 10% tungsten carbide and are characterized by X-ray diffraction, SEM, and Auger electron spectroscopy. Relationships between the composition of the gas-phase photofragments and that of the solid films are discussed.

  20. Cementing multilateral wells with latex cement

    SciTech Connect

    1997-08-01

    A multilateral well is a well with one or more branches or lateral sections extending from its main wellbore. The laterals can be openhole or cased hole. When laterals are cased hole, the cement integrity for casing support and zonal isolation is very important. When cementing the lateral sections of multilateral wells, it is important to use a cement with high strength and durability to support the liner throughout the life of the well and to support the lateral section. The cement column is subjected to various stresses when the cemented inner stub is cut. High tensile strength, flexural strength, and crack resistance are required. These properties are necessary to make a clean cut through the cement sheath that does not induce cracks in the cement column. Latex cement is commonly used for its gas-migration-control property.

  1. Silicon carbide reinforced silicon carbide composite

    NASA Technical Reports Server (NTRS)

    Lau, Sai-Kwing (Inventor); Calandra, Salvatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    2001-01-01

    This invention relates to a process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  2. Expansive Cements

    DTIC Science & Technology

    1970-10-01

    sulfate (C), and free lime (C) as well as other known portland cement compounds. 9. Etiite (C6AS3H3 2 ) is the phase formed during the hydration of...hydroxide (CH), required for chemical combination originates by hydration of alite (C3 S), belite (C2 S), and hydration of free lime in both the... shrinkage was also observed when the specimens were moist cured to full exparn-on for a pericd of 33 days. The data regarding the effect of aggregate size on

  3. Non-selective tungsten CVD using tungsten hexacarbonyl

    SciTech Connect

    Creighton, J.R.

    1987-01-01

    We have used tungsten hexacarbonyl to deposit thin (<1000 A) non-selective tungsten films on silicon and silicon dioxide at 550/sup 0/C. Thicker (approx. =1 micron) tungsten films were then deposited using conventional H/sub 2/ reduction of WF/sub 6/ at 470/sup 0/C using the non-selective film as an adhesion layer. Films grown in this manner have excellent adhesion to SiO/sub 2/, essentially 100% step coverage, and good resistivity. Samples could be transferred under vacuum from the deposition chamber to a uhv chamber equipped with Aguer spectroscopy, thus allowing surface and interface properties of the tungsten films to be studied at the initial stages of growth. No evidence was found for a stoichiometric tungsten oxide or tungsten silicide at the W/SiO/sub 2/ interface. 13 refs., 4 figs.

  4. Improved toughness of silicon carbide

    NASA Technical Reports Server (NTRS)

    Palm, J. A.

    1975-01-01

    Several techniques were employed to apply or otherwise form porous layers of various materials on the surface of hot-pressed silicon carbide ceramic. From mechanical properties measurements and studies, it was concluded that although porous layers could be applied to the silicon carbide ceramic, sufficient damage was done to the silicon carbide surface by the processing required so as to drastically reduce its mechanical strength. It was further concluded that there was little promise of success in forming an effective energy absorbing layer on the surface of already densified silicon carbide ceramic that would have the mechanical strength of the untreated or unsurfaced material. Using a process for the pressureless sintering of silicon carbide powders it was discovered that porous layers of silicon carbide could be formed on a dense, strong silicon carbide substrate in a single consolidation process.

  5. Silicon Carbide Metallization

    NASA Astrophysics Data System (ADS)

    Lescoat, F.; Tanguy, F.; Durand, P.

    2016-05-01

    A study has been done to assess the feasibility of metallization of Silicon Carbide (SiC) in order to simplify design and mounting of one or more ground reference rail needed to provide an electrical reference for electronics mounted on an SiC structure.

  6. Composition Comprising Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  7. Characterization of Silicon Carbide.

    DTIC Science & Technology

    The various electrical and structural measurement techniques for silicon carbide are described. The electrical measurements include conductivity, resistivity, carrier concentration, mobility, doping energy levels, and lifetime. The structural measurements include polytype determination and crystalline perfection. Both bulk and epitaxial films are included.

  8. Synthesis of Tungsten Nitrene Complexes as Precursors for Tungsten Nitride

    DTIC Science & Technology

    1994-06-16

    AND DATES COVERED 6/16/94 IFinal Report 5/1/91 - 4/30/94 - ... 5. FUNDING NUMBERS Synthesis of Tungsten Nitrene Complexes as Precursors for Tungsten...deposition using organometallic precursors (MOCVD) provides a method for the preparation of thin films. Low valent tungsten nitrene complexes were...involved the tungsten(IV) imido (or nitrene ) complexes (CO)2I2LWwNPh, which were prepared by oxidation of the zwitterionic species (CO)5WNPhNPhC(OMe)Ph with

  9. Selective formation of tungsten nanowires

    PubMed Central

    2011-01-01

    We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions. PMID:21970543

  10. Selective formation of tungsten nanowires.

    PubMed

    Bien, Daniel Cs; Saman, Rahimah Mohd; Badaruddin, Siti Aishah Mohamad; Lee, Hing Wah

    2011-10-04

    We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

  11. A Magnetorheological Polishing-Based Approach for Studying Precision Microground Surfaces of Tungsten Materials

    SciTech Connect

    Shafrir, S.N.; Lambropoulos, J.C.; Jacobs, S.D.

    2007-03-23

    Surface features of tungsten carbide composites processed by bound abrasive deterministic microgrinding and magnetorheological finishing (MRF) were studied for five WC-Ni composites, including one binderless material. All the materials studied were nonmagnetic with different microstructures and mechanical properties. White-light interferometry, scanning electron microscopy, and atomic force microscopy were used to characterize the surfaces after various grinding steps, surface etching, and MRF spot-taking.

  12. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  13. Cement design based on cement mechanical response

    SciTech Connect

    Thiercelin, M.J.; Dargaud, B.; Baret, J.F.; Rodriquez, W.J.

    1998-12-01

    The disappearance of cement bond log response as a result of variations of downhole conditions has been observed in numerous wells. This observation has led to concern about the loss of proper zonal isolation. Stresses induced in the cement, through deformation of the cemented casing resulting from the variation of downhole conditions, are the cause of this damage. The authors present an analysis of the mechanical response of set cement in a cased wellbore to quantify this damage and determine the key controlling parameters. The results show that the thermo-elastic properties of the casing, cement, and formation play a significant role. The type of failure, either cement debonding or cement cracking, is a function of the nature of the downhole condition variations. This analysis allows one to propose appropriate cement mechanical properties to avoid cement failure and debonding. The authors show that the use of high compressive strength cement is not always the best solution and, in some cases, flexible cements are preferred.

  14. Helium bubble bursting in tungsten

    SciTech Connect

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  15. Mineral resource of the month: tungsten

    USGS Publications Warehouse

    Shedd, Kim B.

    2012-01-01

    The article offers information on tungsten. It says that tungsten is a metal found in chemical compounds such as in the scheelite and ore minerals wolframite. It states that tungsten has the highest melting point and it forms a compound as hard as diamond when combined with carbon. It states that tungsten can be used as a substitute for lead in fishing weights, ammunition, and hunting shot. Moreover, China started to export tungsten materials and products instead of tungsten raw materials.

  16. Tungsten coating for improved wear resistance and reliability of microelectromechanical devices

    DOEpatents

    Fleming, James G.; Mani, Seethambal S.; Sniegowski, Jeffry J.; Blewer, Robert S.

    2001-01-01

    A process is disclosed whereby a 5-50-nanometer-thick conformal tungsten coating can be formed over exposed semiconductor surfaces (e.g. silicon, germanium or silicon carbide) within a microelectromechanical (MEM) device for improved wear resistance and reliability. The tungsten coating is formed after cleaning the semiconductor surfaces to remove any organic material and oxide film from the surface. A final in situ cleaning step is performed by heating a substrate containing the MEM device to a temperature in the range of 200-600 .degree. C. in the presence of gaseous nitrogen trifluoride (NF.sub.3). The tungsten coating can then be formed by a chemical reaction between the semiconductor surfaces and tungsten hexafluoride (WF.sub.6) at an elevated temperature, preferably about 450.degree. C. The tungsten deposition process is self-limiting and covers all exposed semiconductor surfaces including surfaces in close contact. The present invention can be applied to many different types of MEM devices including microrelays, micromirrors and microengines. Additionally, the tungsten wear-resistant coating of the present invention can be used to enhance the hardness, wear resistance, electrical conductivity, optical reflectivity and chemical inertness of one or more semiconductor surfaces within a MEM device.

  17. The asquenched microstructure and tempering behavior of rapidly solidified tungsten steels

    NASA Astrophysics Data System (ADS)

    Rayment, J. J.; Cantor, B.

    1981-09-01

    Transmission electron microscopy, and microhardness testing were used to examine the as-quenched structure and mechanical properties of a series of rapidly solidified (RS) iron-tungsten-carbon-alloys ranging from 6 to 23 pct tungsten with a constant W:C atomic ratio of 2:1, and Tl high speed tool steel. The RS iron-tungsten-carbon alloys were found to exhibit a significant change in microstructure and hardness as the tungsten and carbon content was increased. The change in morphology was from lath martensite in the lower tungsten alloys to a solidification structure of δ-ferrite cells surrounded by austenite and M6C carbide, in the higher tungsten alloys. A model is proposed to explain the morphologicl change. In addition, the tempering behaviors of RS Fe-6.2 wt pct W-0.21 wt pct C, Fe-23 wt pct W-0.75 wt pct C and Tl high speed tool steel were examined and compared to those observed for the conventional solution-treated and quenched alloys. A discussion is also included on the microstructural dependence upon cooling rate of RS high speed tool steels.

  18. Synthesis of Tungsten Nitrene Complexes as Precursors to Tungsten Nitride.

    DTIC Science & Technology

    1995-01-17

    Chemical vapor deposition using organometallic precursors (MOCVD) provides a method for the preparation of thin films. Low valent tungsten nitrene ...Later synthetic work involved the tungsten(IV) imido (or nitrene ) complexes (CO) 2I2LW equivalent NPh, which were prepared by oxidation of the

  19. An x-ray diffraction investigation of heat-treated WC-Co sintered carbides

    SciTech Connect

    Aleksandrova, L.I.; Gorbacheva, T.B.; Loshak, M.G.; Varaksina, A.V.

    1986-10-01

    This work presents the results of an x-ray diffraction investigation of the microstructure of WC-Co sintered carbides after hardening under different conditions. The materials studied were medium grain alloys with 6.15 and 25 wt. % cobalt. A portion of the specimens was hardened under different conditions differing in temperature and hold time. The heating was done in a salt bath. The specimens were annealed in vacuum at 1373 K for 2 h. Hardening of sintered carbides from 1300 K and more may lead to a change in the phase composition of the alloy under conditions of long holds at the hardening temperature. With an increase in hardening temperature there is an increase in the solubility of tungsten in the binder phase and an increase in stresses in the carbide and cobalt phases. The optimum heat-treatment cycle for sintered carbides corresponds to the maximum solubility of tungsten in cobalt with the minimum change in phase composition and stressed state of the phase. Tables are included.

  20. Properties and Tribological Performance of Vanadium Carbide Coatings on AISI 52100 Steel Deposited by Thermoreactive Diffusion

    NASA Astrophysics Data System (ADS)

    Strahin, B. L.; Shreeram, D. D.; Doll, G. L.

    2017-07-01

    Vanadium carbide coatings were formed on AISI 52100 steel specimens by thermoreactive diffusion and characterized using nanoindentation, x-ray diffraction, and chemical analysis. The deposition process formed a 4-µm coating of vanadium carbide (V4C3) with an average grain size of 33 nm and a [200] crystallographic texture. The hardness and elastic modulus of the coatings were determined to be 35 ± 7.5 GPa and 334 ± 67 GPa, respectively. Friction and wear of the coatings were examined in reciprocating sliding contact against tungsten carbide (WC) balls in dry and in an abrasive environment. It was determined that in the abrasive environment, the V4C3 coating provided wear protection comparable to WC.

  1. Preparation of tungsten oxide

    DOEpatents

    Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee

    2009-09-22

    Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

  2. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, Cressie E.; Morrow, Marvin S.

    1993-01-01

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  3. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  4. Evaluation of adhesive and compressive strength of glass ionomer cements.

    PubMed

    Ramashanker; Singh, Raghuwar D; Chand, Pooran; Jurel, Sunit Km; Tripathi, Shuchi

    2011-12-01

    The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11, Japan), MR dental (MR dental suppliers Pvt Ltd, England). (B) Ceramometal alloy (Ni-Cr: Wiron 99; Bego, Bremen, Germany). (C) Cold cure acrylic resin. (E) Temperature cum humidity control chamber. (F) Instron Universal Testing Machine. Four different types of Glass ionomer cements were used in the study. From each type of the Glass ionomer cements, 15 specimens for each were made to evaluate the compressive strength and adhesive strength, respectively. The 15 specimens were further divided into three subgroups of five specimens. For compressive strength, specimens were tested at 2, 4 and 12 h by using Instron Universal Testing Machine. To evaluate the adhesive strength, specimens were surface treated with diamond bur, silicone carbide bur and sandblasting and tested under Instron Universal Testing Machine. It was concluded from the study that the compressive strength as well as the adhesive bond strength of MR dental glass ionomer cement with a ceramometal alloy was found to be maximum compare to other glass ionomer cements. Sandblasting surface treatment of ceramometal alloy was found to be comparatively more effective for adhesive bond strength between alloy and glass ionomer cement.

  5. Cement mixing with vibrator

    SciTech Connect

    Allen, T.E.

    1991-07-09

    This patent describes a method of cementing a casing string in a bore hole of a well. It comprises introducing water and dry cement material into a mixing vessel; mixing the water and dry cement material in the mixing vessel to form a cement slurry, the slurry including lumps of the dry cement material, the mixing including steps of: agitating the slurry; and while agitating the slurry, transmitting vibrational energy into the slurry and thereby aiding disintegration and subsequent wetting of the lumps of the dry cement material in the slurry; and pumping the slurry into an annulus between the casing string and the bore hole.

  6. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  7. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  8. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service. [ 74 FR 16143, Apr. 9,...

  9. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  10. High strength uranium-tungsten alloy process

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1990-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  11. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  12. High strength uranium-tungsten alloys

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1991-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  13. Synthesis of Nanostructured Tungsten and Tungsten - Phases

    NASA Astrophysics Data System (ADS)

    Angastiniotis, Nicos Costa

    Reductive decomposition of spray dried ammonium metatungstate gives rise to nanocrystalline alpha -W (bcc structure) or nanocrystalline beta -W (A15 structure), depending on the specifics of the processing conditions. By controlling the reaction rate of the high surface area alpha-W and beta -W phases with oxygen at low temperatures ( <=300^circC) it is possible to transform both phases to an amorphous tungsten oxide. Furthermore, reduction of the amorphous oxide in hydrogen at <=400 ^circC yields gamma -W (amorphous structure), in which all or nearly all of the oxygen atoms are removed. The high surface area alpha -W and beta-W phases show striking differences in susceptibility to gas-solid reactions. Reaction of beta-W with ammonia at low temperatures (100^circ-300^ circC) results in the formation of an intermediate amorphous delta-WN_ {rm x} phase, which decomposes at higher temperatures (>=650 ^circC) into nanocrystalline rm W_2N_{x} phase. On the other hand, if nitridation is initiated at room temperature and continues as the temperature gradually increases to 300^circC, another amorphous phase (gamma-WN_{ rm x}) is formed. A similar behavior occurs when beta -W is reacted with carbon monoxide at low temperatures, starting at room temperature and continuing as the temperature gradually increases to 300^circC. The resulting amorphous phase delta- rm WC_{x}O_{y } is exceptionally stable. Only upon heating to 800^circC in carbon monoxide does it decompose to rm WC_{x }.. The unusual chemical activity of high surface area beta-W led to speculation concerning its susceptibility to solid-solid reactions, in addition to the gas-solid reactions noted above. Tests on the W -Cu system, in which both elements are mutually insoluble in the solid state, clearly showed that Cu can be diffused into beta-W to form a metastable solid solution. Some diffusional disordering evidently occurs because of the disappearance of the high order peaks of beta-W. However, the disordering

  14. Silicon Carbide Integrated Circuit Chip

    NASA Image and Video Library

    2015-02-17

    A multilevel interconnect silicon carbide integrated circuit chip with co-fired ceramic package and circuit board recently developed at the NASA GRC Smart Sensors and Electronics Systems Branch for high temperature applications. High temperature silicon carbide electronics and compatible packaging technologies are elements of instrumentation for aerospace engine control and long term inner-solar planet explorations.

  15. Asphalt cement poisoning

    MedlinePlus

    ... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

  16. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-10-31

    The objective of this project is to develop an improved ultra- lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries.

  17. Silicon carbide sewing thread

    NASA Technical Reports Server (NTRS)

    Sawko, Paul M. (Inventor)

    1995-01-01

    Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

  18. Fabrication of (U, Zr) C-fueled/tungsten-clad specimens for irradiation in the Plum Brook Reactor Facility

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Fuel samples, 90UC - 10 ZrC, and chemically vapor deposited tungsten fuel cups were fabricated for the study of the long term dimensional stability and compatibility of the carbide-tungsten fuel-cladding systems under irradiation. These fuel samples and fuel cups were assembled into the fuel pins of two capsules, designated as V-2E and V-2F, for irradiation in NASA Plum Brook Reactor Facility at a fission power density of 172 watts/c.c. and a miximum cladding temperature of 1823 K. Fabrication methods and characteristics of the fuel samples and fuel cups prepared are described.

  19. METHOD OF MAKING TUNGSTEN FILAMENTS

    DOEpatents

    Frazer, J.W.

    1962-12-18

    A method of making tungsten filaments is described in which the tungsten is completely free of isotope impurities in the range of masses 234 to 245 for use in mass spectrometers. The filament comprises a tantalum core generally less than 1 mil in diameter having a coating of potassium-free tantalum-diffused tungsten molecularly bonded thereto. In the preferred process of manufacture a short, thin tantalum filament is first mounted between terminal posts mounted in insulated relation through a backing plate. The tungsten is most conveniently vapor plated onto the tantalum by a tungsten carbonyl vapor decomposition method having a critical step because of the tendency of the tantalum to volatilize at the temperature of operntion of the filament. The preferred recipe comprises volatilizing tantalum by resistance henting until the current drops by about 40%, cutting the voltage back to build up the tungsten, and then gradually building the temperature back up to balance the rate of tungsten deposition with the rate of tantalum volatilization. (AEC)

  20. Fabrication of a tantalum-clad tungsten target for LANSCE

    NASA Astrophysics Data System (ADS)

    Nelson, A. T.; O'Toole, J. A.; Valicenti, R. A.; Maloy, S. A.

    2012-12-01

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 °C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta2O5 surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO2, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  1. RECOVERY OF URANIUM FROM TUNGSTEN

    DOEpatents

    Newnam, K.

    1959-02-01

    A method is presented for the rccovery of uranium which has adhered to tungsten parts in electromagnetic isotope separation apparatus. Such a tungsten article is dissolved electrolytically in 20% NaOH by using the tungsten article as the anode. The resulting solution, containing soluble sodium lungstate and an insoluble slime, is then filtered. The slime residue is ignited successively with sodium nitrate and sodium pyrosulfate and leashed, and the resulting filtrates are combined with the original filtrate. Uranium is then recovered from the combined flltrates by diuranate precipitation.

  2. Tungsten resources of Brazil

    USGS Publications Warehouse

    White, Max Gregg

    1974-01-01

    Brazilian tungsten production, 85 percent of which is exported, comes almost entirely from scheelite-bearing tactites in northeast Brazil, and has reached an annual rate of about 2,000 metric tons (2,200 short tons) of scheelite concentrate with 70 percent WO3. Scheelite ore reserves, located principally in the State of Rio Grande do Norte, are estimated to be as high as 8,300,000 tons (9,100,000 short tons) containing 0.7 percent WO3. Minor deposits (or those about which only minimal information is available) of wolframite, with which some cassiterite is associated, are located in Sao Paulo, Santa Catarina, and Rio Grande do Sul. Both the scheelite and the wolframite deposits are considered . to be late Precambrian A (620 to 900 m.y.) or early Cambrian in age.

  3. Tungsten Toxicity in Plants

    PubMed Central

    Adamakis, Ioannis-Dimosthenis S.; Panteris, Emmanuel; Eleftheriou, Eleftherios P.

    2012-01-01

    Tungsten (W) is a rare heavy metal, widely used in a range of industrial, military and household applications due to its unique physical properties. These activities inevitably have accounted for local W accumulation at high concentrations, raising concerns about its effects for living organisms. In plants, W has primarily been used as an inhibitor of the molybdoenzymes, since it antagonizes molybdenum (Mo) for the Mo-cofactor (MoCo) of these enzymes. However, recent advances indicate that, beyond Mo-enzyme inhibition, W has toxic attributes similar with those of other heavy metals. These include hindering of seedling growth, reduction of root and shoot biomass, ultrastructural malformations of cell components, aberration of cell cycle, disruption of the cytoskeleton and deregulation of gene expression related with programmed cell death (PCD). In this article, the recent available information on W toxicity in plants and plant cells is reviewed, and the knowledge gaps and the most pertinent research directions are outlined. PMID:27137642

  4. PREPARATION AND PURIFICATION OF SILICON CARBIDE.

    DTIC Science & Technology

    the materials were divided into two parts. Part I covers problems of silicon carbide preparation and the growing of silicon carbide single crystals...and thin films for semiconductor devices. Part II treats problems of purity, including the purification and chemical analysis of silicon carbide and of starting materials for silicon carbide preparation.

  5. Methods of producing continuous boron carbide fibers

    SciTech Connect

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  6. Heated die facilitates tungsten forming

    NASA Technical Reports Server (NTRS)

    Chattin, J. H.; Haystrick, J. E.; Laughlin, J. C.; Leidy, R. A.

    1966-01-01

    Tungsten forming in a press brake employs a bottom die assembly with a heating manifold between two water-cooled die sections. The manifold has hydrogen-oxygen burners spaced along its length for even heat during forming.

  7. Hydrogen-silicon carbide interactions

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Jacobson, Nathan S.; Misra, Ajay K.; Humphrey, Donald L.

    1989-01-01

    A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamic maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of Region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicon carbide is the single stable solid phase in Region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4, and SiH. Analysis of the kinetics of reaction for Region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to Regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

  8. Hydrogen-silicon carbide interactions

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Misra, Ajay K.; Humphrey, Donald L.; Jacobson, Nathan S.

    1990-01-01

    A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamics maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicone carbide is the single stable solid phase in region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4 and SiH. Analyses of the kinetics of reaction for region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

  9. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-04-15

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  10. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-04-29

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, and shear bond. Testing to determine the effect of temperature cycling on the shear bond properties of the cement systems was also conducted. In addition, the stress-strain behavior of the cement types was studied. This report discusses a software program that is being developed to help design ULHS cements and foamed cements.

  11. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-10-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that will be performed for analyzing the alkali-silica reactivity of ULHS in cement slurries, as well as the results of Field Tests 1 and 2.

  12. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-07-18

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job.

  13. Effects of tungsten on environmental systems.

    PubMed

    Strigul, Nikolay; Koutsospyros, Agamemnon; Arienti, Per; Christodoulatos, Christos; Dermatas, Dimitris; Braida, Washington

    2005-10-01

    Tungsten is a metal with many industrial and military applications, including manufacturing of commercial and military ammunition. Despite its widespread use, the potential environmental effects of tungsten are essentially unknown. This study addresses environmental effects of particulate and soluble forms of tungsten, and to a minor extent certain tungsten alloy components, present in some munitions formulations. Dissolution of tungsten powder significantly acidifies soils. Tungsten powder mixed with soils at rates higher than 1% on a mass basis, trigger changes in soil microbial communities resulting in the death of a substantial portion of the bacterial component and an increase of the fungal biomass. It also induces the death of red worms and plants. These effects appear to be related with the soil acidification occurring during tungsten dissolution. Dissolved tungsten species significantly decrease microbial yields by as much as 38% for a tungsten media concentration of 89 mg l(-1). Soluble tungsten concentrations as low as 10(-5) mg l(-1), cause a decrease in biomass production by 8% which is possibly related to production of stress proteins. Plants and worms take up tungsten ions from soil in significant amounts while an enrichment of tungsten in the plant rhizosphere is observed. These results provide an indication that tungsten compounds may be introduced into the food chain and suggest the possibility of development of phytoremediation-based technologies for the cleanup of tungsten contaminated sites.

  14. A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides.

    PubMed

    Esposito, Daniel V; Hunt, Sean T; Kimmel, Yannick C; Chen, Jingguang G

    2012-02-15

    This work explores the opportunity to substantially reduce the cost of hydrogen evolution reaction (HER) catalysts by supporting monolayer (ML) amounts of precious metals on transition metal carbide substrates. The metal component includes platinum (Pt), palladium (Pd), and gold (Au); the low-cost carbide substrate includes tungsten carbides (WC and W(2)C) and molybdenum carbide (Mo(2)C). As a platform for these studies, single-phase carbide thin films with well-characterized surfaces have been synthesized, allowing for a direct comparison of the intrinsic HER activity of bare and Pt-modified carbide surfaces. It is found that WC and W(2)C are both excellent cathode support materials for ML Pt, exhibiting HER activities that are comparable to bulk Pt while displaying stable HER activity during chronopotentiometric HER measurements. The findings of excellent stability and HER activity of the ML Pt-WC and Pt-W(2)C surfaces may be explained by the similar bulk electronic properties of tungsten carbides to Pt, as is supported by density functional theory calculations. These results are further extended to other metal overlayers (Pd and Au) and supports (Mo(2)C), which demonstrate that the metal ML-supported transition metal carbide surfaces exhibit HER activity that is consistent with the well-known volcano relationship between activity and hydrogen binding energy. This work highlights the potential of using carbide materials to reduce the costs of hydrogen production from water electrolysis by serving as stable, low-cost supports for ML amounts of precious metals.

  15. Silicon Carbide Electronic Devices

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.

    2001-01-01

    The status of emerging silicon carbide (SiC) widebandgap semiconductor electronics technology is briefly surveyed. SiC-based electronic devices and circuits are being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot function. Projected performance benefits of SiC electronics are briefly illustrated for several applications. However, most of these operational benefits of SiC have yet to be realized in actual systems, primarily owing to the fact that the growth techniques of SiC crystals are relatively immature and device fabrication technologies are not yet sufficiently developed to the degree required for widespread, reliable commercial use. Key crystal growth and device fabrication issues that limit the performance and capability of high-temperature and/or high-power SiC electronics are identified. The electrical and material quality differences between emerging SiC and mature silicon electronics technology are highlighted.

  16. Silicon Carbide Electronic Devices

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.

    2001-01-01

    The status of emerging silicon carbide (SiC) widebandgap semiconductor electronics technology is briefly surveyed. SiC-based electronic devices and circuits are being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot function. Projected performance benefits of SiC electronics are briefly illustrated for several applications. However, most of these operational benefits of SiC have yet to be realized in actual systems, primarily owing to the fact that the growth techniques of SiC crystals are relatively immature and device fabrication technologies are not yet sufficiently developed to the degree required for widespread, reliable commercial use. Key crystal growth and device fabrication issues that limit the performance and capability of high-temperature and/or high-power SiC electronics are identified. The electrical and material quality differences between emerging SiC and mature silicon electronics technology are highlighted.

  17. Silicon Carbide Technology

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    2006-01-01

    Silicon carbide based semiconductor electronic devices and circuits are presently being developed for use in high-temperature, high-power, and high-radiation conditions under which conventional semiconductors cannot adequately perform. Silicon carbide's ability to function under such extreme conditions is expected to enable significant improvements to a far-ranging variety of applications and systems. These range from greatly improved high-voltage switching for energy savings in public electric power distribution and electric motor drives to more powerful microwave electronics for radar and communications to sensors and controls for cleaner-burning more fuel-efficient jet aircraft and automobile engines. In the particular area of power devices, theoretical appraisals have indicated that SiC power MOSFET's and diode rectifiers would operate over higher voltage and temperature ranges, have superior switching characteristics, and yet have die sizes nearly 20 times smaller than correspondingly rated silicon-based devices [8]. However, these tremendous theoretical advantages have yet to be widely realized in commercially available SiC devices, primarily owing to the fact that SiC's relatively immature crystal growth and device fabrication technologies are not yet sufficiently developed to the degree required for reliable incorporation into most electronic systems. This chapter briefly surveys the SiC semiconductor electronics technology. In particular, the differences (both good and bad) between SiC electronics technology and the well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are highlighted for several large-scale applications. Key crystal growth and device-fabrication issues that presently limit the performance and capability of high-temperature and high-power SiC electronics are identified.

  18. Process Of Bonding Copper And Tungsten

    DOEpatents

    Slattery, Kevin T.; Driemeyer, Daniel E.; Davis, John W.

    2000-07-18

    Process for bonding a copper substrate to a tungsten substrate by providing a thin metallic adhesion promoting film bonded to a tungsten substrate and a functionally graded material (FGM) interlayer bonding the thin metallic adhesion promoting film to the copper substrate. The FGM interlayer is formed by sintering a stack of individual copper and tungsten powder blend layers having progressively higher copper content/tungsten content, by volume, ratio values in successive powder blend layers in a lineal direction extending from the tungsten substrate towards the copper substrate. The resulting copper to tungsten joint well accommodates the difference in the coefficient of thermal expansion of the materials.

  19. Polarographic determination of tungsten in rocks

    USGS Publications Warehouse

    Reichen, L.E.

    1954-01-01

    This work was undertaken to develop a simpler and faster method than the classical gravimetric procedure for the determination of tungsten in rocks and ores. A new polarographic wave of tungsten is obtained in a supporting electrolyte of dilute hydrochloric acid containing tartrate ion. This permits the determination of tungsten both rapidly and accurately. No precipitation of the tungsten is necessary, and only the iron need be separated from the tungsten. The accuracy is within the limits of a polarographic procedure; comparison of polarographic and gravimetric results is given. The method reduces appreciably the amount of time ordinarily consumed in determination of tungsten.

  20. Global Tungsten Demand and Supply Forecast

    NASA Astrophysics Data System (ADS)

    Dvořáček, Jaroslav; Sousedíková, Radmila; Vrátný, Tomáš; Jureková, Zdenka

    2017-03-01

    An estimate of the world tungsten demand and supply until 2018 has been made. The figures were obtained by extrapolating from past trends of tungsten production from1905, and its demand from 1964. In addition, estimate suggestions of major production and investment companies were taken into account with regard to implementations of new projects for mining of tungsten or possible termination of its standing extraction. It can be assumed that tungsten supply will match demand by 2018. This suggestion is conditioned by successful implementation of new tungsten extraction projects, and full application of tungsten recycling methods.

  1. Low-chromium reduced-activation chromium-tungsten steels

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J.

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  2. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15} cm{sup −2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960 °C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

  3. Improvement of casing cementation of deep and ultradeep wells. Part 2: Oilfield cements and cement additives

    NASA Astrophysics Data System (ADS)

    Arens, K. H.; Akstinat, M.

    1982-07-01

    Oilfield cements and cement additives were investigated in order to improve the casing cementation of deep and ultradeep wells. Characterization and evaluation of the main oil field cements commercially available were studied. The testing was carried out according to American Petroleum Institute API standards and nonstandardized test methods (dynamic modulus of elasticity, expansion/shrinkage), especially the rheology, thickening time and the influence of pressure, temperature and water-cement ratio, were considered. The main emphasis in the field of cement additives was on the evaluation of cement retarders for high temperatures, accelerators, and additives for cement expansion. Furthermore oil field cements were tested, and their properties are described.

  4. Abyssal seep site cementation

    SciTech Connect

    Neumann, A.C.; Paull, C.K.; Commeau, R.; Commeau, J.

    1988-01-01

    The deepest submarine cements known so far occur along the 3,300-m deep base of the Florida escarpment and are associated with methane-bearing brine seeps, which emanate there. These deep Holocene carbonates, which occur as surficial and buried crusts, burrow fillings, and friable horizons, were sampled via ALVIN. The carbonates form irregular halos extending up to 20 m from seeps colonized by chemosynthetic fauna. Mussels, gastropods, and clams, the carbonate components of the community, produce a shell hash that is locally cemented by coarsely crystalline low-Mg calcite. Halos of palisade calcite are reminiscent of ancient examples of marine cements. Also present are carbonate hemipelagics cemented by micrite into crusts and burrow fillings. The degree of cementation varies from pervasive to light. Slabs of cemented crust up to 30 cm thick contrast with typical shallow crusts and exhibit irregular tops and smooth bottoms indicating different chemical gradients and pathways.

  5. Cementation of indirect restorations: an overview of resin cements.

    PubMed

    Stamatacos, Catherine; Simon, James F

    2013-01-01

    The process of ensuring proper retention, marginal seal, and durability of indirect restorations depends heavily on effective cementation. Careful consideration must be made when selecting an adhesive cement for a given application. This article provides information on resin cements that can guide clinicians in determining which type of cement is best suited to their clinical needs regarding cementation of indirect restorations. Emphasis is placed on successful cementation of all-ceramic restorations.

  6. Fabrication techniques developed for small- diameter, thin-wall tungsten and tungsten alloy tubing

    NASA Technical Reports Server (NTRS)

    Brillhart, D. C.; Burt, W. R.; Karasek, F. J.; Mayfield, R. M.

    1968-01-01

    Report describes methods for the fabrication of tungsten and tungsten alloys into small-diameter, thin-wall tubing of nuclear quality. The tungsten, or tungsten alloy tube blanks are produced by double extrusion. Plug-drawing has emerged as an excellent secondary fabrication technique for the reduction of the overall tube dimensions.

  7. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-01-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. DOE joined the Materials Management Service (MMS)-sponsored joint industry project ''Long-Term Integrity of Deepwater Cement under Stress/Compaction Conditions.'' Results of the project contained in two progress reports are also presented in this report.

  8. Physical, Mechanical, and Dry Sliding Wear Properties of Fe-Cr-W-C Hardfacing Alloys Under Different Tungsten Addition

    NASA Astrophysics Data System (ADS)

    Hajihashemi, Mahdi; Shamanian, Morteza; Azimi, Ghasem

    2015-04-01

    In this study, the effects of tungsten on microstructure and wear performance of Fe-Cr-C claddings were evaluated. In this regard, tungsten inert gas surfacing process was employed to deposit Fe-Cr-C and Fe-Cr-C-W hardfacing alloys on plain carbon steel substrate using preplaced powders. Phase composition, microstructure, and wear behavior of clad layers were investigated using X-ray diffraction analysis, optical and scanning electron microscopy, and reciprocating wear tests, respectively. The claddings were well bonded to the substrate and showed a uniform microstructure. Cr7C3 and WC carbides were detected in the deposited layers. Further investigations indicated that the hardness and wear resistance can be improved by adding tungsten into Fe-Cr-C hardfacing alloys.

  9. Processing of boron carbide

    NASA Astrophysics Data System (ADS)

    Cho, Namtae

    The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although the relative densities of pressureless sintered specimens were lower than that of commercially produced hot-pressed B4C, their (Vickers) hardness values were comparable. For 4.45 cm dia. 1.35 cm height disk-shaped specimens, pressureless sintered to at least 93.0% relative density, post-hot isostatic pressing resulted in vast increases in relative densities (e.g. 100.0%) and hardness values significantly greater than that of commercially produced hot-pressed B 4C. The densification behavior of 20-40nm graphite-coated B4C nano-particles was studied using dilatometry, x-ray diffraction and electron microscopy. The higher than expected sintering onset from a nano-scale powder (˜1500°C) was caused by remnant B2O3 not removed by methanol washing, keeping particles separated until volatilization, and the carbon coatings, which imposed particle to particle contact of a substance more refractory than B4C. Solid state sintering (1500-1850°C) was followed by an arrest in contraction attributed to formation of eutectic liquid droplets of size more than 10X the original nano-particles. These droplets, induced to form well below known B4C-graphite eutectic temperatures by the high surface energy of nanoparticles, are interpreted to have quickly solidified to form a vast number of voids in particle packing, which in turn, impeded continued solid state sintering. Starting at 2200°C, a permanent liquid phase formed which facilitated a rapid measured contraction by liquid phase sintering and/or compact slumping.

  10. Palladium interaction with silicon carbide

    NASA Astrophysics Data System (ADS)

    Gentile, M.; Xiao, P.; Abram, T.

    2015-07-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC-5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  11. Accurate pointing of tungsten welding electrodes

    NASA Technical Reports Server (NTRS)

    Ziegelmeier, P.

    1971-01-01

    Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.

  12. Wettability of boron carbide

    SciTech Connect

    Torvund, T.; Akselsen, O.M.; Ulvensoeen, J.H.; Grong, O.

    1994-12-31

    The wettability of boron carbide has been examined by means of the sessile drop method, using the following candidate alloys: (96wt%AG-4wt%Ti), (Ag-26.5wt%Cu-3wt%Ti), (Sn-10wt%Ag-4wt%Ti), Sn(99.95wt%) and Al(99.99wt%). The results show that B{sub 4}C is completely wetted by the Ag-based alloys. Sn-10wt%Ag-4wt%Ti alloy and pure Al partly wet the B{sub 4}C surface, while pure Sn does not wet B{sub 4}C at all. For all the alloys used, except pure Sn, a reaction layer was observed at the interface between the ceramic part and the metal drop. Although the spreading kinetics of the Al-drop was much slower compared with the Ti-containing alloys, the reaction rate was considerably higher in the former case. This suggests that aluminium is an attractive candidate material for brazing of B{sub 4}C. Formation of the low melting B{sub 2}O{sub 3} at the B{sub 4}C surface may cause oxidation of the filler metal during joining, which, in turn, leads to a low bond strength.

  13. Silicon carbide photoconductive switches

    NASA Astrophysics Data System (ADS)

    Saddow, Stephen E.

    1994-09-01

    The optoelectronic properties of p-type 6-H silicon carbide (6H-SiC) have been investigated in an experiment that used lateral and vertical photoconductive (PC) switches. Both photovoltaic and photoconductive effects are reported, which were observed on switches using both geometries and measured at several wavelengths near the 6H-SiC absorption edge. PC techniques were employed to measure the surface and bulk carrier lifetimes of 40 and 200 ns, respectively. The switches displayed a high-speed photovoltaic response to picosecond laser excitations in the UV and visible spectral regions. In particular, efficient subnanosecond optical absorption processes were observed in the visible region. The photovoltage was measured as a function of both laser wavelength (and hence absorption depth) and laser beam position within the switching gap. The switch response to picosecond laser pulses in the UV, violet, green, and red spectral regions was shown to have subnanosecond photovoltaic response times. Finally, since the optical absorption coefficient had not been well established for device-grade 6H-SiC, the optical absorption coefficient near the 6H-SiC bandgap energy (Eg) was also measured, and the bandgap was determined to be approximately 3.1 eV.

  14. Silicon Carbide Growth

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Andrew Trunek has focused on supporting the Sic team through the growth of Sic crystals, making observations and conducting research that meets the collective needs and requirements of the team while fulfilling program commitments. Cancellation of the Ultra Efficient Engine Technology (UEET) program has had a significant negative impact on resources and research goals. This report highlights advancements and achievements made with this cooperative agreement over the past year. NASA Glenn Research Center (GRC) continues to make advances in silicon carbide (SiC) research during the past year. Step free surfaces were used as substrates for the deposition of GaN epilayers that yielded very low dislocation densities. Defect free 3C- SiC was successfully nucleated on step free mesas and test diodes were fabricated. Web growth techniques were used to increase the usable surface area of dislocation free SiC by approximately equal to 40%. The greatest advancement has been attained on stepped surfaces of SiC. A metrology standard was developed using high temperature etching techniques titled "Nanometer Step Height Standard". This development culminated in being recognized for a 2004 R&D100 award and the process to produce the steps received a NASA Space Act award.

  15. Method of synthesizing tungsten nanoparticles

    SciTech Connect

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  16. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  17. Carbide and carbonitride surface treatment method for refractory metals

    DOEpatents

    Meyer, Glenn A.; Schildbach, Marcus A.

    1996-01-01

    A carbide and carbonitride surface treatment method for refractory metals is provided, in steps including, heating a part formed of boron, chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten or zirconium, or alloys thereof, in an evacuated chamber and then introducing reaction gases including nitrogen and hydrogen, either in elemental or water vapor form, which react with a source of elemental carbon to form carbon-containing gaseous reactants which then react with the metal part to form the desired surface layer. Apparatus for practicing the method is also provided, in the form of a carbide and carbonitride surface treatment system (10) including a reaction chamber (14), a source of elemental carbon (17), a heating subassembly (20) and a source of reaction gases (23). Alternative methods of providing the elemental carbon (17) and the reaction gases (23) are provided, as well as methods of supporting the metal part (12), evacuating the chamber (14) with a vacuum subassembly (18) and heating all of the components to the desired temperature.

  18. Physical vapor deposition synthesis of tungsten monocarbide (WC) thin films on different carbon substrates

    SciTech Connect

    Weigert, E. C.; Humbert, M. P.; Mellinger, Z. J.; Ren, Q.; Beebe, T. P. Jr.; Bao, L.; Chen, J. G.

    2008-01-15

    The synthesis of tungsten monocarbide (WC) thin films has been performed by physical vapor deposition on various substrates including glassy carbon, carbon fiber sheet, carbon foam, and carbon cloth. The WC and W{sub 2}C phase contents of these films have been evaluated with bulk and surface analysis techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. These characterization techniques were also used to determine the effects of synthesis by nonreactive and reactive sputtering. The synthesis of WC particles supported on the carbon fiber substrate has also been accomplished using the temperature programmed reaction method. Overall, the results demonstrate that the phase purity of tungsten carbides can be controlled by the deposition environment and annealing temperatures.

  19. Laser melting of uranium carbides

    NASA Astrophysics Data System (ADS)

    Utton, C. A.; De Bruycker, F.; Boboridis, K.; Jardin, R.; Noel, H.; Guéneau, C.; Manara, D.

    2009-03-01

    In the context of the material research aimed at supporting the development of nuclear plants of the fourth Generation, renewed interest has recently arisen in carbide fuels. A profound understanding of the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents. In this context, the main goal of the present paper is to demonstrate the feasibility of laser induced melting experiments on stoichiometric uranium carbides; UC, UC1.5 and UC2. Measurements were performed, at temperatures around 3000 K, under a few bars of inert gas in order to minimise vaporisation and oxidation effects, which may occur at these temperatures. Moreover, a recently developed investigation method has been employed, based on in situ analysis of the sample surface reflectivity evolution during melting. Current results, 2781 K for the melting point of UC, 2665 K for the solidus and 2681 K for the liquidus of U2C3, 2754 K for the solidus and 2770 K for the liquidus of UC2, are in fair agreement with early publications where the melting behaviour of uranium carbides was investigated by traditional furnace melting methods. Further information has been obtained in the current research about the non-congruent (solidus-liquidus) melting of certain carbides, which suggest that a solidus-liquidus scheme is followed by higher ratio carbides, possibly even for UC2.

  20. Porous silicon carbide (SIC) semiconductor device

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1996-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  1. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2004-01-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries.

  2. Biomass-derived high-performance tungsten-based electrocatalysts on graphene for hydrogen evolution

    DOE PAGES

    Meng, Fanke; Hu, Enyuan; Zhang, Lihua; ...

    2015-08-05

    We report a new class of highly active and stable tungsten-based catalysts to replace noble metal materials for the hydrogen evolution reaction (HER) in an acidic electrolyte. The catalyst is produced by heating an earth-abundant and low-cost mixture of ammonium tungstate, soybean powder and graphene nanoplatelets (WSoyGnP). The catalyst compound consists of tungsten carbide (W₂C and WC) and tungsten nitride (WN) nanoparticles decorated on graphene nanoplatelets. The catalyst demonstrates an overpotential (η₁₀, the potential at a current density of 10 mA cm⁻²) of 0.105 V, which is the smallest among tungsten-based HER catalysts in acidic media. The coupling with graphenemore » significantly reduces the charge transfer resistance and increases the active surface area of the product, which are favorable for enhancing the HER activity. Therefore, the approach of employing biomass and other less expensive materials as precursors for the production of catalysts with high HER activity provides a new path for the design and development of efficient catalysts for the hydrogen production industry.« less

  3. Biomass-derived high-performance tungsten-based electrocatalysts on graphene for hydrogen evolution

    SciTech Connect

    Meng, Fanke; Hu, Enyuan; Zhang, Lihua; Sasaki, Kotaro; Muckerman, James T.; Fujita, Etsuko

    2015-08-05

    We report a new class of highly active and stable tungsten-based catalysts to replace noble metal materials for the hydrogen evolution reaction (HER) in an acidic electrolyte. The catalyst is produced by heating an earth-abundant and low-cost mixture of ammonium tungstate, soybean powder and graphene nanoplatelets (WSoyGnP). The catalyst compound consists of tungsten carbide (W₂C and WC) and tungsten nitride (WN) nanoparticles decorated on graphene nanoplatelets. The catalyst demonstrates an overpotential (η₁₀, the potential at a current density of 10 mA cm⁻²) of 0.105 V, which is the smallest among tungsten-based HER catalysts in acidic media. The coupling with graphene significantly reduces the charge transfer resistance and increases the active surface area of the product, which are favorable for enhancing the HER activity. Therefore, the approach of employing biomass and other less expensive materials as precursors for the production of catalysts with high HER activity provides a new path for the design and development of efficient catalysts for the hydrogen production industry.

  4. 500 C SILICON CARBIDE RECTIFIER PROGRAM.

    DTIC Science & Technology

    Efforts were continued on the development of 500 degree C silicon carbide rectifiers. The growth rate of silicon carbide crystals prepared by the...as obtained from a simple model. All values agree within a factor of five. The use of molten borax as an etchant for silicon carbide was studies...is possible. Details are given on the life and storage tests which were successfully passed by two silicon carbide rectifiers. An open tube-flowing

  5. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  6. Mechanical Property Comparison of the Soviet BS-41 and the US M993 Armor-Penetrating Cores

    DTIC Science & Technology

    2016-11-23

    41 and US M993 armor-penetrating cores is made. The BS-41 core is composed of coarse-grained tungsten carbide (WC) cemented in nickel, while the M993...core is a fine-grained WC cemented in cobalt. The M993 core was determined to have superior hardness and indentation toughness. The superior...Introduction Tungsten carbide (WC) has high hardness and good wear resistance, but low toughness. The toughness can be greatly increased by cementing it in a

  7. Silicon Carbide Semiconductor Device Fabrication and Characterization

    DTIC Science & Technology

    1990-02-08

    SPACE ADMINISTRATION For Grant NAG 3-782 S- 1 entitled SILICON CARBIDE SEMICONDUCTOR DEVICE FABRICATION AND CHARACTERIZATION For the Period 10 February...NUMBERS Silicon Carbide ..Semiconductor Device Fabrication and PR# 335820 Characterization __________________________________________________ APP# 505-62-01...also been demonstrated. _________ 14. SUBJECT TERMS 15. NuMBER OF PACiES -~- Silicon carbide , Ysemiconductor devices, ion implantation aseeI4i

  8. Method of Fabricating Silicon Carbide Articles.

    DTIC Science & Technology

    The patent relates to a method for fabricating silicon carbide articles which comprises hot pressing a homogeneous mixture of carbonaceous particles...and silicon carbide powder. The presence of the carbon limits grain growth so that a silicon carbide product having greatly improved physical

  9. Process Of Bonding Copper And Tungsten

    DOEpatents

    Slattery, Kevin T.; Driemeyer, Daniel E.

    1999-11-23

    Process for bonding a copper substrate to a tungsten substrate by providing a thin metallic adhesion promoting film bonded to a tungsten substrate and a functionally graded material (FGM) interlayer bonding the thin metallic adhesion promoting film to the copper substrate. The FGM interlayer is formed by thermal plasma spraying mixtures of copper powder and tungsten powder in a varied blending ratio such that the blending ratio of the copper powder and the tungsten powder that is fed to a plasma torch is intermittently adjusted to provide progressively higher copper content/tungsten content, by volume, ratio values in the interlayer in a lineal direction extending from the tungsten substrate towards the copper substrate. The resulting copper to tungsten joint well accommodates the difference in the coefficient of thermal expansion of the materials.

  10. Process development for cladding APT tungsten targets

    SciTech Connect

    Horner, M H; Barber, R; Dalder, E

    2000-11-27

    This report describes development of processes for cladding APT Target tungsten components with a thin layer (0.127-mm) of Alloy 718, Alloy 600 or 316L stainless steel alloy. The application requires that the cladding be thermally bonded to the tungsten in order to transfer heat generated in the tungsten volume to a surrounding coolant. High temperature diffusion bonding using the hot isostatic processing (HIP) technique was selected as the method for creating a metallurgical bond between pure tungsten tubes and rods and the cladding materials. Bonding studies using a uniaxially loaded vacuum hot press were conducted in preliminary experiments to determine acceptable time-temperature conditions for diffusion bonding. The results were successfully applied in cladding tungsten rods and tubes with these alloys. Temperatures 800-810 C were suitable for cladding tungsten with Alloy 600 and 316L stainless steel alloy, whereas tungsten was clad with Alloy 718 at 1020 C.

  11. Fabrication of tungsten wire needles

    SciTech Connect

    Roder, A.

    1983-02-01

    Fine point needles for field emissoin are conventionally produced by electrolytically or chemically etching tungsten wire. Points formed in this manner have a typical tip radius of about 0.5 microns and a cone angle of some 30 degrees. The construction of needle matrix detector chambers has created a need for tungsten needles whose specifications are: 20 mil tungsten wire, 1.5 inch total length, 3 mm-long taper (resulting in a cone angle of about 5 degrees), and 25 micron-radius point (similar to that found on sewing needles). In the process described here for producing such needles, tungsten wire, immersed in a NaOH solution and in the presence of an electrode, is connected first to an ac voltage and then to a dc supply, to form a taper and a point on the end of the wire immersed in the solution. The process parameters described here are for needles that will meet the above specifications. Possible variations will be discussed under each approprite heading.

  12. Mineral of the month: tungsten

    USGS Publications Warehouse

    Shedd, Kim B.

    2006-01-01

    Tungsten has the highest melting point of all metals, one of the highest densities and, when combined with carbon, is almost as hard as diamond. These and other properties make it useful in a wide variety of important commercial, industrial and military applications.

  13. Vacuum Gas Tungsten Arc Welding

    NASA Technical Reports Server (NTRS)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  14. Desulfurization chemistry on tungsten surfaces

    SciTech Connect

    Benziger, J.B.; Preston, R.E.

    1985-01-01

    Desulfurization on tungsten surfaces was studied by Auger spectroscopy, temperature programmed desorption, and infrared spectroscopy. Aliphatic compounds reacted by electrophilic interaction of sulfur with the surface. On sulfided surfaces adsorption occurred by disulfide linkages, but C-S bond scission required vacant metal sites. Thiophene underwent electrophilic attack on the ring at the ..cap alpha..-carbon by metal sites.

  15. Gleeble Testing of Tungsten Samples

    DTIC Science & Technology

    2013-02-01

    North American Carbide in Orchard Park, New York. The anvils were anchored in place in two jaws; the left jaw is mobile and the right one is... automatically adjusted to achieve the programmed temperature in 3 min. During testing, force, temperature, and displacement (both across the machine

  16. Tungsten coil atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Rust, Jennifer A.; Nóbrega, Joaquim A.; Calloway, Clifton P.; Jones, Bradley T.

    2006-02-01

    A tungsten coil atomic emission spectrometer is described and evaluated. The system employs a single tungsten coil as a combined atomizer and excitation source for the determination of metals by atomic emission spectrometry. The tungsten coil is extracted from a 150 W, 15 V commercial slide projector light bulb. A simple, laboratory constructed, computer-controlled power supply provides a constant current to the coil. A high-resolution Czerny-Turner monochromator with a charge coupled device detector completes the system. Simultaneous, multi-element analyses are possible within a 4 nm spectral window. Eleven test elements are used to characterize the system: Al (396.1 nm), Co (353.0 nm), Cr (427.1 nm), Dy (404.6 nm), Ga (403.3 nm), K (404.4 nm), Mn (403.1 nm), Pb (405.8 nm), Rb (420.2 nm), Sc (404.8 nm), and Yb (398.7 nm). Tungsten coil atomic emission detection limits are reported for these elements for the first time: 0.02 ng Al, 0.7 ng Co, 0.003 ng Cr, 0.01 ng Dy, 0.7 ng Ga, 0.3 ng K, 0.04 ng Mn, 10 ng Pb, 0.07 ng Rb, 1 ng Sc, and 0.003 ng Yb. The precision for the new technique is better than 13% relative standard deviation for all metals at concentrations two orders of magnitude above the detection limit. Aluminum, Cr, Mn, and K are determined in a standard reference material (trace elements in water) after simple dilution with water, and found values varied from certified values by up to 26%. The average tungsten coil lifetime was found to be 265 heating cycles. The elimination of the external radiation source needed for atomic absorption measurements results in an emission system that could be quite portable.

  17. Timing of syntaxial cement

    SciTech Connect

    Perkins, R.D.

    1985-02-01

    Echinodermal fragments are commonly overgrown in ancient limestones, with large single crystals growing in optical continuity over their skeletal hosts (i.e., syntaxial overgrowths). Such syntaxial cements are usually considered to have precipitated from meteoric pore waters associated with a later stage of subaerial exposure. Although several examples have been reported from ancient carbonates where petrographic relationships may indicate an early submarine formation of syntaxial cement, no occurrences have been noted in Holocene submarine-cemented rocks. Syntaxial cements of submarine origin have been found in Bermuda beachrock where isopachous high-magnesian calcite cements merge with large optically continuous crystals growing on echinodermal debris. Examination of other Holocene sediments cemented by magnesian calcite indicates that echinodermal fragments are not always overgrown syntaxially, but may be rimmed by microcrystalline calcite. The reason for this difference is not clear, although it may be a function of the spacing of nucleation sites and rates of crystal growth. A review of syntaxial cements from several localities in ancient carbonate sequences reveals that many are best interpreted as having formed in the submarine setting, whereas it is more clear that others formed from meteoric precipitation. These occurrences suggest that care should be exercised in inferring meteoric diagenesis from syntaxial overgrowths and that the possibility of submarine formation should be considered.

  18. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-07-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. Laboratory testing during the eleventh quarter focused on evaluation of the alkali-silica reaction of eight different cement compositions, four of which contain ULHS. This report provides a progress summary of ASR testing. The original laboratory procedure for measuring set cement expansion resulted in unacceptable erosion of the test specimens. In subsequent tests, a different expansion procedure was implemented and an alternate curing method for cements formulated with TXI Lightweight cement was employed to prevent sample failure caused by thermal shock. The results obtained with the modified procedure showed improvement over data obtained with the original procedure, but data for some compositions were still questionable. Additional modification of test procedures for compositions containing TXI Lightweight cement were implemented and testing is ongoing.

  19. Anisotropic Tribological Properties of Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1980-01-01

    The anisotropic friction, deformation and fracture behavior of single crystal silicon carbide surfaces were investigated in two categories. The categories were called adhesive and abrasive wear processes, respectively. In the adhesive wear process, the adhesion, friction and wear of silicon carbide were markedly dependent on crystallographic orientation. The force to reestablish the shearing fracture of adhesive bond at the interface between silicon carbide and metal was the lowest in the preferred orientation of silicon carbide slip system. The fracturing of silicon carbide occurred near the adhesive bond to metal and it was due to primary cleavages of both prismatic (10(-1)0) and basal (0001) planes.

  20. Cement and concrete

    NASA Technical Reports Server (NTRS)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  1. Stage cementing apparatus

    SciTech Connect

    Blamford, D.M.; Easter, J.H.

    1988-06-21

    A stage cementing apparatus for selectively passing cement from the interior passage of a casing to the annulus between the exterior of the casing and borehole, the casing having an upper portion and a lower portion, is described comprising: a barrel secured to the upper portion of the casing; a mandrel secured to the lower portion of the casing, and a stage cementing tool having a generally cylindrical configuration adapted for attachment to the lower end of the barrel about a portion of the mandrel.

  2. Ablation study of tungsten-based nuclear thermal rocket fuel

    NASA Astrophysics Data System (ADS)

    Smith, Tabitha Elizabeth Rose

    The research described in this thesis has been performed in order to support the materials research and development efforts of NASA Marshall Space Flight Center (MSFC), of Tungsten-based Nuclear Thermal Rocket (NTR) fuel. The NTR was developed to a point of flight readiness nearly six decades ago and has been undergoing gradual modification and upgrading since then. Due to the simplicity in design of the NTR, and also in the modernization of the materials fabrication processes of nuclear fuel since the 1960's, the fuel of the NTR has been upgraded continuously. Tungsten-based fuel is of great interest to the NTR community, seeking to determine its advantages over the Carbide-based fuel of the previous NTR programs. The materials development and fabrication process contains failure testing, which is currently being conducted at MSFC in the form of heating the material externally and internally to replicate operation within the nuclear reactor of the NTR, such as with hot gas and RF coils. In order to expand on these efforts, experiments and computational studies of Tungsten and a Tungsten Zirconium Oxide sample provided by NASA have been conducted for this dissertation within a plasma arc-jet, meant to induce ablation on the material. Mathematical analysis was also conducted, for purposes of verifying experiments and making predictions. The computational method utilizes Anisimov's kinetic method of plasma ablation, including a thermal conduction parameter from the Chapman Enskog expansion of the Maxwell Boltzmann equations, and has been modified to include a tangential velocity component. Experimental data matches that of the computational data, in which plasma ablation at an angle shows nearly half the ablation of plasma ablation at no angle. Fuel failure analysis of two NASA samples post-testing was conducted, and suggestions have been made for future materials fabrication processes. These studies, including the computational kinetic model at an angle and the

  3. Characterization and modeling of tungsten source during DIII-D tungsten ring experiments

    NASA Astrophysics Data System (ADS)

    Guterl, J.; Abrams, T.; Elder, D.; Guo, H. Y.

    2016-10-01

    Two tungsten toroidal rings in the DIII-D divertor region were recently exposed to H-mode plasmas. During these experiments, the gross erosion rate of tungsten was spectroscopically monitored for various ELMy H-mode conditions to characterize the tungsten source in the divertor region (see e.g.). However, only a small fraction of tungsten eroded particles eventually exits the divertor region because of the large tungsten local redeposition. Tungsten local redeposition and migration in the vicinity of the tungsten tiles are simulated using the ERO-OEDGE code package to link the effective tungsten source to the measured gross erosion rates between and during ELMs. It is shown that the energy and angular distributions of sputtered tungsten particles strongly affect the ratio of locally redeposited particles and thus the effective tungsten source. Effects of carbon deposition on tungsten tiles between ELMs on the tungsten erosion rate are also discussed. Preliminary studies of divertor screening on long-range tungsten transport in the SOL between ELMs are also presented. Work supported in part by the US Department of Energy under DE-AC05-06OR23100 and DE-FC02-04ER54698.

  4. Environmentally compatible spray cement

    SciTech Connect

    Loeschnig, P.

    1995-12-31

    Within the framework of a European research project, Heidelberger Zement developed a quickly setting and hardening binder for shotcrete, called Chronolith S, which avoids the application of setting accelerators. Density and strength of the shotcrete produced with this spray cement correspond to those of an unaccelerated shotcrete. An increased hazard for the heading team and for the environment, which may occur when applying setting accelerators, can be excluded here. Owing to the special setting properties of a spray cement, the process engineering for its manufacturing is of great importance. The treatment of a spray cement as a dry concrete with kiln-dried aggregates is possible without any problems. The use of a naturally damp pre-batched mixture is possible with Chronolith S but requires special process engineering; spray cement and damp aggregate are mixed with one another immediately before entering the spraying machinery.

  5. Thermodynamics and cement science

    SciTech Connect

    Damidot, D.; Lothenbach, B.; Herfort, D.; Glasser, F.P.

    2011-07-15

    Thermodynamics applied to cement science has proved to be very valuable. One of the most striking findings has been the extent to which the hydrate phases, with one conspicuous exception, achieve equilibrium. The important exception is the persistence of amorphous C-S-H which is metastable with respect to crystalline calcium silicate hydrates. Nevertheless C-S-H can be included in the scope of calculations. As a consequence, from comparison of calculation and experiment, it appears that kinetics is not necessarily an insuperable barrier to engineering the phase composition of a hydrated Portland cement. Also the sensitivity of the mineralogy of the AFm and AFt phase compositions to the presence of calcite and to temperature has been reported. This knowledge gives a powerful incentive to develop links between the mineralogy and engineering properties of hydrated cement paste and, of course, anticipates improvements in its performance leading to decreasing the environmental impacts of cement production.

  6. Tungsten foil laminate for structural divertor applications - Joining of tungsten foils

    NASA Astrophysics Data System (ADS)

    Reiser, Jens; Rieth, Michael; Möslang, Anton; Dafferner, Bernhard; Hoffmann, Jan; Mrotzek, Tobias; Hoffmann, Andreas; Armstrong, D. E. J.; Yi, Xiaoou

    2013-05-01

    This paper is the fourth in our series on tungsten laminates. The aim of this paper is to discuss laminate synthesis, meaning the joining of tungsten foils. It is obvious that the properties of the tungsten laminate strongly depend on the combination of (i) interlayer and (ii) joining technology, as this combination defines (i) the condition of the tungsten foil after joining (as-received or recrystallised) as well as (ii) the characteristics of the interface between the tungsten foil and the interlayer (wettability or diffusion leading to a solid solution or the formation of intermetallics). From the example of tungsten laminates joined by brazing with (i) an eutectic silver copper brazing filler, (ii) copper, (iii) titanium, and (iv) zirconium, the microstructure will be discussed, with special focus on the interface. Based on our assumptions of the mechanism of the extraordinary ductility of tungsten foil we present three syntheses strategies and make recommendations for the synthesis of high temperature tungsten laminates.

  7. Laser cleaning of tungsten ribbon

    NASA Astrophysics Data System (ADS)

    Kumar, Aniruddha; Sonar, V. R.; Das, D. K.; Bhatt, R. B.; Behere, P. G.; Afzal, Mohd.; Kumar, Arun; Nilaya, J. P.; Biswas, D. J.

    2014-07-01

    Removal of a thin oxide layer from a tungsten ribbon was achieved using the fundamental, second and third harmonic radiation from a Q- switched Nd-YAG laser. It was found that beyond the threshold, oxide removal was achieved at all wavelengths for a wide range of fluence values. The removal mechanism of the oxide layer was found to be critically dependent on both wavelength and fluence of the incident radiation and has been identified as ejection or sublimation. The un-cleaned and cleaned surfaces were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and atomic force microscopy (AFM). Laser cleaned tungsten ribbons were used in a thermal ionization mass spectrometer (TIMS) to determine isotopic composition of Neodymium atoms.

  8. Does speciation matter for tungsten ecotoxicology?

    PubMed

    Strigul, Nikolay

    2010-09-01

    Tungsten is a widely used transition metal that has not been thoroughly investigated with regards to its ecotoxicological effects. Tungsten anions polymerize in environmental systems as well as under physiological conditions in living organisms. These polymerization/condensation reactions result in the development of several types of stable polyoxoanions. Certain chemical properties (in particular redox and acidic properties) differentiate these polyanions from monotungstates. However, our current state of knowledge on tungsten toxicology, biological and environmental effects is based entirely on experiments where monotungstates were used and assumed by the authors to be the form of tungsten that was present and that produced the observed effect. Recent discoveries indicate that tungsten speciation may be important to ecotoxicology. New results obtained by different research groups demonstrate that polytungstates develop and persist in environmental systems, and that polyoxotungstates are much more toxic than monotungstates. This paper reviews the available toxicological information from the standpoint of tungsten speciation and identifies knowledge gaps and pertinent future research directions.

  9. Silicon carbide semiconductor technology for high temperature and radiation environments

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.

    1993-01-01

    Viewgraphs on silicon carbide semiconductor technology and its potential for enabling electronic devices to function in high temperature and high radiation environments are presented. Topics covered include silicon carbide; sublimation growth of 6H-SiC boules; SiC chemical vapor deposition reaction system; 6H silicon carbide p-n junction diode; silicon carbide MOSFET; and silicon carbide JFET radiation response.

  10. Ultrasonic characterization of microwave joined silicon carbide/silicon carbide

    SciTech Connect

    House, M.B.; Day, P.S.

    1997-05-01

    High frequency (50--150 MHz), ultrasonic immersion testing has been used to characterize the surface and interfacial joint conditions of microwave bonded, monolithic silicon carbide (SiC) materials. The high resolution ultrasonic C-scan images point to damage accumulation after thermal cycling. Image processing was used to study the effects of the thermal cycling on waveform shape, amplitude and distribution. Such information is useful for concurrently engineering material fabrication processes and suitable nondestructive test procedures.

  11. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  12. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  13. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  14. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  15. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  16. Diamond-silicon carbide composite

    DOEpatents

    Qian, Jiang; Zhao, Yusheng

    2006-06-13

    Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=5–8 GPa, T=1400K–2300K) to form composites having high fracture toughness. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPa.dot.m1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness. X-ray diffraction patterns and Raman spectra indicate that amorphous silicon is partially transformed into nanocrystalline silicon at 5 GPa/873K, and nanocrystalline silicon carbide forms at higher temperatures.

  17. Microwave processing of silicon carbide

    SciTech Connect

    Akerman, M.A.; Baity, F.W. Jr.; Caughman, J.B.; Forrester, S.C.; Kass, M.D.; Morrow, M.S.; Holcombe, C.E. Jr.; Moyer, M.W.; Dews, T.W.

    1994-12-31

    Reaction-bonded silicon carbide ({alpha}-SiC) armor tiles were annealed at 2100{degree}C using microwave radiation at 2.45 GHz. Ultrasonic velocity measurements showed that the longitudinal and shear velocities, acoustic impedances, and acoustic moduli of the post-annealed tiles were statistically higher than for the unannealed tiles. However, the exposed surfaces of the annealed tiles experienced slight degradation, which was attributed to the high annealing temperatures.

  18. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  19. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  20. Formation mechanism of a silicon carbide coating for a reinforced carbon-carbon composite

    NASA Technical Reports Server (NTRS)

    Rogers, D. C.; Shuford, D. M.; Mueller, J. I.

    1975-01-01

    Results are presented for a study to determine the mechanisms involved in a high-temperature pack cementation process which provides a silicon carbide coating on a carbon-carbon composite. The process and materials used are physically and chemically analyzed. Possible reactions are evaluated using the results of these analytical data. The coating is believed to develop in two stages. The first is a liquid controlled phase process in which silicon carbide is formed due to reactions between molten silicon metal and the carbon. The second stage is a vapor transport controlled reaction in which silicon vapors react with the carbon. There is very little volume change associated with the coating process. The original thickness changes by less than 0.7%. This indicates that the coating process is one of reactive penetration. The coating thickness can be increased or decreased by varying the furnace cycle process time and/or temperature to provide a wide range of coating thicknesses.

  1. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, E.L.

    1984-11-29

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  2. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, Edward L.

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  3. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-10-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; Preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; Summary of pertinent information from Russian ultra-lightweight cement literature review; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  4. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-06-16

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. Laboratory testing during the tenth quarter focused on evaluation of the alkali-silica reaction of eight different cement compositions, four of which contain ULHS. The original laboratory procedure for measuring set cement expansion resulted in test specimen erosion that was unacceptable. A different expansion procedure is being evaluated. This report provides a progress summary of ASR testing. The testing program initiated in November produced questionable initial results so the procedure was modified slightly and the testing was reinitiated. The results obtained with the modified procedure showed improvement over data obtained with the original procedure, but questionable data were obtained from several of the compositions. Additional modification of test procedures for compositions containing TXI Lightweight cement are being implemented and testing is ongoing.

  5. Silicon carbide fibers and articles including same

    DOEpatents

    Garnier, John E; Griffith, George W

    2015-01-27

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  6. Methods for producing silicon carbide fibers

    DOEpatents

    Garnier, John E.; Griffith, George W.

    2016-03-01

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  7. METHOD OF JOINING CARBIDES TO BASE METALS

    DOEpatents

    Krikorian, N.H.; Farr, J.D.; Witteman, W.G.

    1962-02-13

    A method is described for joining a refractory metal carbide such as UC or ZrC to a refractory metal base such as Ta or Nb. The method comprises carburizing the surface of the metal base and then sintering the base and carbide at temperatures of about 2000 deg C in a non-oxidizing atmosphere, the base and carbide being held in contact during the sintering step. To reduce the sintering temperature and time, a sintering aid such as iron, nickel, or cobait is added to the carbide, not to exceed 5 wt%. (AEC)

  8. Oxygen and Potassium Adsorption on a Carbide-Modified STEPPED-W(100) in Contact with the Carbon Solid Solution:. AN Aes and WF Study at 300 K and at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Foulias, S. D.; Perdikis, A.; Vlachos, D.

    The adsorption of oxygen and potassium on the two-phase system: carbide-modified stepped-W(100) surface (CMT) in contact with the solid solution of carbon in bulk tungsten, was investigated by AES and WF measurements. The CMT surface shows metallic behavior judging from its interaction with K. The expected dissociative adsorption of oxygen appears to occur with 1 - θ kinetics, possibly via a molecularly chemisorbed state. The "dispersed phase — two-phase" model is clearly applicable when oxygen adsorbs on the K-pre-covered carbide. The initial sticking coefficient of oxygen increases drastically from the dispersed to the condensed phase, at least four-fold with respect to s0 on the clean carbide. It is proposed that this two-phase carbon system can be advantageous compared with the bulk carbide since it can easily regenerate the surface if the latter is depleted from carbon.

  9. Mechanical alloying of ODS tungsten heavy alloys and microstructure development of intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Liang; Huang, Chun-Lin

    2013-09-01

    Oxide dispersion strengthened tungsten heavy alloys have been used in a wide variety of industrial and military applications due to their high density, strength and stiffness. These alloys have been produced by mechanical alloying, which can provide uniform distribution of nano-oxide particles and an extremely fine grain structure, resulting in the reduction of the sintering temperature. However, the high-energy ball-milling process could introduce iron contamination from the vial and milling media during the procedure. In this study, the W-Ni-Y2O3 alloy was investigated as a function of milling time. The results show that the increase of the Fe/Ni ratio has a significant influence on the microstructural development and material properties. The XRD data reveal considerable solid solubility extension in these powders. The tungsten carbide and iron rich intermetallic compounds were formed after long milling times, which can change the relative density and hardness of the alloy. It is essential that we understand the role of intermetallic phases in the ODS tungsten heavy alloy which determine the material properties and the control of microstructural development.

  10. Small-particle-size cement

    SciTech Connect

    Ewert, D.P.; Almond, S.W.; Blerhaus, W.M. II )

    1991-05-01

    Successful remedial cementing has historically been difficult in wells with large-interval, multizone, gravel-packed completions. The reason is the inability of conventional oilfield cements to penetrate gravel packs adequately. Small-particle-size cement (SPSC) was developed to penetrate gravel packs and to provide the zonal isolation required. This paper details the laboratory work, job design, and field implementation of this new cement.

  11. Tungsten - Tungsten Trioxide Electrodes for the Long-term Monitoring of Corrosion Processes in Highly Alkaline Media and Concrete-based Materials.

    PubMed

    Kolar, Mitja; Doliška, Aleš; Svegl, Franc; Kalcher, Kurt

    2010-12-01

    The determination of pH in highly alkaline solutions and concrete materials is extremely important for monitoring or predicting the corrosion processes of reinforced concrete structures and to follow the hydration process of Portland cement, fly-ash, micro silica and other materials used in concrete manufacturing. The corrosion of reinforced concrete structures and the hydration of pozzolanic materials are long-term processes, which means, that appropriate durable, and resilient pH electrodes are needed, for direct implantation regarding solid concrete bodies. The purpose of this work was to characterise the potentiometric and surface properties of tungsten electrodes after exposure to extreme alkaline solutions. The tungsten wire surface was activated at 800 °C for 30 min within an oxygen flow. The formation of homogenous and compact multiple layers of WO3 crystals was observed using X-ray diffraction and scanning electron microscopy. X-ray diffraction of those tungsten electrodes exposed to saturated calcium hydroxide solution or the pore-water of cement-based materials during 10 months, indicated partly dissolved WO3. Two new compounds appeared on the electrodes surfaces; pure tungsten and CaWO4. The presence of tungsten was affecting any potentiometric response in acidic pH region (2-5) but in pH 5-12 region the response still remained linear with a slope of 42 ± 2 mV/pH unit. The W/WO3 electrode was suitable for the long-term monitoring of corrosion processes in concrete-based materials according to the pH changes as it has stable and repeatable responses to alkaline solutions (pH > 12). All the tested interferring ions had no significant influence on electrode potential. The W/WO3 electrode is simple, robust, inexpensive, and temperature resistant and can be applied in potentiometric titrations as well as in batch and flow-injection analysis. The prepared electrode is a highly promising pH sensor for the monitoring of pH changes in highly alkaline capillary

  12. Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition.

    PubMed

    Walock, Michael J; Rahil, Issam; Zou, Yujiao; Imhoff, Luc; Catledge, Shane A; Nouveau, Corinne; Stanishevsky, Andrei V

    2012-06-01

    Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.

  13. Deuterium retention in TiC and TaC doped tungsten at high temperatures

    NASA Astrophysics Data System (ADS)

    Zibrov, M.; Mayer, M.; Gao, L.; Elgeti, S.; Kurishita, H.; Gasparyan, Yu.; Pisarev, A.

    2015-08-01

    Samples made of tungsten doped either with titanium carbide (W-1.1TiC) or tantalum carbide (W-3.3TaC) were either exposed to D2 gas at a pressure of 100 kPa at 800-963 K or irradiated by 38 eV/D ions at 800 K. The deuterium (D) inventory in the samples was examined by nuclear reaction analysis and thermal desorption spectroscopy. The D bulk concentration and total retention in W-3.3TaC were comparable in all cases to that in pure polycrystalline W. The D bulk concentration in W-1.1TiC was more than one order of magnitude higher than that in pure W after exposure to D2 gas, and was also several times higher than that in W-1.1TiC after irradiation at 800 K. It is suggested that D trapping inside the carbide precipitates in W-1.1TiC becomes essential at high temperatures.

  14. Tungsten deposition by hydrogen-atom reaction with tungsten hexafluoride

    SciTech Connect

    Lee, W.W.

    1991-01-01

    Using gaseous hydrogen atoms with WF[sub 6], tungsten atoms can be produced in a gas-phase reaction. The atoms then deposit in a near-room temperature process, which results in the formation of tungsten films. The W atoms (10[sup 10]-10[sup 11]/cm[sup 3]) were measured in situ by atomic absorption spectroscopy during the CVD process. Deposited W films were characterized by Auger electron spectroscopy, Rutherford backscattering, and X-ray diffraction. The surface morphology of the deposited films and filled holes was studied using scanning electron microscopy. The deposited films were highly adherent to different substrates, such as Si, SiO[sub 2], Ti/Si, TiN/Si and Teflon. The reaction mechanism and kinetics were studied. The experimental results indicated that this method has three advantages compared to conventional CVD or PECVD: (1) film growth occurs at low temperatures; (2) deposition takes place in a plasma-free environment; and (3) a low level of impurities results in high-quality adherent films.

  15. Novel properties of Tungsten ditelluride

    NASA Astrophysics Data System (ADS)

    Liu, Huimei; National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Cent Collaboration

    Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 Tesla. By using density functional theory calculations, we qualitatively reproduced the observed spin texture. Since the spin texture would forbid back scatterings that are directly involved in the resistivity, we suggest that the SOC and the related spin and orbital angular momentum textures may play an important role in the anomalously large magnetoresistance of WTe2. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we also boost the electronic properties by applying a high pressure, and introduce superconductivity successfully.

  16. The electron affinity of tungsten

    NASA Astrophysics Data System (ADS)

    Lindahl, A. O.; Andersson, P.; Diehl, C.; Forstner, O.; Klason, P.; Hanstorp, D.

    2010-11-01

    The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm-1 by observing the onset of the process when W- ions in the 5d^56s^2 6S5/2 ground state are photodetached producing neutral W atoms in the 5d^46s^2 5D0 ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W-.

  17. Reducing cement's CO2 footprint

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  18. High temperature lightweight foamed cements

    DOEpatents

    Sugama, Toshifumi.

    1989-10-03

    Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed. 3 figs.

  19. Cement Mason's Curriculum. Instructional Units.

    ERIC Educational Resources Information Center

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  20. High temperature lightweight foamed cements

    DOEpatents

    Sugama, Toshifumi

    1989-01-01

    Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed.

  1. Cement Mason's Curriculum. Instructional Units.

    ERIC Educational Resources Information Center

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  2. Strengthening mechanisms of tungsten powder reinforced uranium

    SciTech Connect

    Lewis, M.A.K.; Hill, M.A.; Rollett, A.D.; Dunn, P.S.; Mortensen, A.; Massachusetts Inst. of Tech., Cambridge, MA )

    1989-01-01

    Tungsten powder reinforced uranium exhibits a three-fold increase in yield strength due to precipitation hardening. The tungsten-rich interphase precipitates form at moving phase boundaries during slow cooling. Further increases in yield strength, attained with increasing tungsten content, are due to composite strengthening; this is verified by increasing elastic modulus with increasing tungsten content. Age hardening behavior is observed, with strengthening occurring at aging temperatures low in the alpha phase. Aging higher in alpha gives initial strengthening followed by rapid overaging. Beta phase aging results in a very soft structure with precipitates visible optically. Wrought material exhibits significant strain hardening as well as composite strengthening due to elongation of the tungsten particles. 7 refs., 15 figs., 4 tabs.

  3. Cementing a wellbore using cementing material encapsulated in a shell

    DOEpatents

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael

    2017-03-14

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  4. Cementing a wellbore using cementing material encapsulated in a shell

    DOEpatents

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  5. Synthesis of metastable chromium carbide nanomaterials and their electrocatalytic activity for the hydrogen evolution reaction.

    PubMed

    Schmuecker, Samantha M; Clouser, Dale; Kraus, Theodore J; Leonard, Brian M

    2017-10-10

    Transition metal carbides including chromium, molybdenum, and tungsten are of particular interest as renewable energy catalysts due to their low cost and abundance. While several single metal carbide systems form multiple phases with different compositions and crystal structures, most of these materials are not as well studied due to their limited synthetic approaches and instability. By taking advantage of a low temperature salt flux synthetic method, these unique phases can be more easily synthesized and separated as phase pure materials. As an example, Chromium carbide forms five different crystal structures including three common phases, Cr3C2, Cr7C3, and Cr23C6, and two less studied phases, Cr2C and CrC. All five compounds were synthesized using the salt flux method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrocatalytic testing for the hydrogen evolution reaction (HER). This low temperature method allows for routine access to multiple compounds in complex phase diagrams and separation of each phase synthetically. This represents a significant step forward in synthesizing rare phases like rocksalt CrC and hexagonal Cr2C and allows for investigation into their potential catalytic properties and future applications.

  6. Reactions of methanol and water over carbide-modified Mo( 1 1 0 )

    NASA Astrophysics Data System (ADS)

    Hwu, Henry H.; Chen, Jingguang G.

    2003-06-01

    The reactions of methanol and water over clean and carbide-modified Mo(1 1 0) have been studied using temperature-programmed desorption, high-resolution electron energy loss spectroscopy, and Auger electron spectroscopy. The product selectivity of methanol on unmodified Mo(1 1 0) is 84% toward complete decomposition and 16% toward the production of CO. After the Mo(1 1 0) surface is modified by carbon, the complete decomposition pathway decreases to 63%, with the remaining methanol dissociating to produce CO. The absence of a reaction pathway to produce methane on the C/Mo(1 1 0) surface is distinctly different from that on the C/W(1 1 1) and C/W(1 1 0) surfaces. On Mo(1 1 0), the amount of H 2O undergoing dissociation is determined to be 0.25 molecules per Mo atom. Upon carbon modification, the activity of water decreases slightly to 0.20 molecules per Mo atom. These results indicate that the C/Mo(1 1 0) surface is more active toward the dissociation of H 2O than either C/W(1 1 1) or C/W(1 1 0). Overall, the comparison of the current study to our previous investigations on C/W(1 1 1) and C/W(1 1 0) provides insights into the possible role of molybdenum carbides as promoters for tungsten carbide electrocatalysts in methanol fuel cell applications.

  7. Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

    NASA Astrophysics Data System (ADS)

    Riesch, J.; Han, Y.; Almanstötter, J.; Coenen, J. W.; Höschen, T.; Jasper, B.; Zhao, P.; Linsmeier, Ch; Neu, R.

    2016-02-01

    For the next step fusion reactor the use of tungsten is inevitable to suppress erosion and allow operation at elevated temperature and high heat loads. Tungsten fibre-reinforced composites overcome the intrinsic brittleness of tungsten and its susceptibility to operation embrittlement and thus allow its use as a structural as well as an armour material. That this concept works in principle has been shown in recent years. In this contribution we present a development approach towards its use in a future fusion reactor. A multilayer approach is needed addressing all composite constituents and manufacturing steps. A huge potential lies in the optimization of the tungsten wire used as fibre. We discuss this aspect and present studies on potassium doped tungsten wire in detail. This wire, utilized in the illumination industry, could be a replacement for the so far used pure tungsten wire due to its superior high temperature properties. In tensile tests the wire showed high strength and ductility up to an annealing temperature of 2200 K. The results show that the use of doped tungsten wire could increase the allowed fabrication temperature and the overall working temperature of the composite itself.

  8. Polycrystalline silicon on tungsten substrates

    NASA Technical Reports Server (NTRS)

    Bevolo, A. J.; Schmidt, F. A.; Shanks, H. R.; Campisi, G. J.

    1979-01-01

    Thin films of electron-beam-vaporized silicon were deposited on fine-grained tungsten substrates under a pressure of about 1 x 10 to the -10th torr. Mass spectra from a quadrupole residual-gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. During separate silicon depositions, the atomically clean substrates were maintained at various temperatures between 400 and 780 C, and deposition rates were between 20 and 630 A min. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry before and after cleaning, deposition, and annealing. Auger depth profiling, X-ray analysis, and SEM in the topographic and channeling modes were utilized to characterize the samples with respect to silicon-metal interface, interdiffusion, silicide formation, and grain size of silicon. The onset of silicide formation was found to occur at approximately 625 C. Above this temperature tungsten silicides were formed at a rate faster than the silicon deposition. Fine-grain silicon films were obtained at lower temperatures.

  9. Polycrystalline silicon on tungsten substrates

    NASA Technical Reports Server (NTRS)

    Bevolo, A. J.; Schmidt, F. A.; Shanks, H. R.; Campisi, G. J.

    1979-01-01

    Thin films of electron-beam-vaporized silicon were deposited on fine-grained tungsten substrates under a pressure of about 1 x 10 to the -10th torr. Mass spectra from a quadrupole residual-gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. During separate silicon depositions, the atomically clean substrates were maintained at various temperatures between 400 and 780 C, and deposition rates were between 20 and 630 A min. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry before and after cleaning, deposition, and annealing. Auger depth profiling, X-ray analysis, and SEM in the topographic and channeling modes were utilized to characterize the samples with respect to silicon-metal interface, interdiffusion, silicide formation, and grain size of silicon. The onset of silicide formation was found to occur at approximately 625 C. Above this temperature tungsten silicides were formed at a rate faster than the silicon deposition. Fine-grain silicon films were obtained at lower temperatures.

  10. Fracture behaviour of polycrystalline tungsten

    NASA Astrophysics Data System (ADS)

    Gaganidze, Ermile; Rupp, Daniel; Aktaa, Jarir

    2014-03-01

    Fracture behaviour of round blank polycrystalline tungsten was studied by means of three point bending Fracture-Mechanical (FM) tests at temperatures between RT and 1000 °C and under high vacuum. To study the influence of the anisotropic microstructure on the fracture toughness (FT) and ductile-to-brittle transition (DBT) the specimens were extracted in three different, i.e. longitudinal, radial and circumferential orientations. The FM tests yielded distinctive fracture behaviour for each specimen orientation. The crack propagation was predominantly intergranular for longitudinal orientation up to 600 °C, whereas transgranular cleavage was observed at low test temperatures for radial and circumferentially oriented specimens. At intermediate test temperatures the change of the fracture mode took place for radial and circumferential orientations. Above 800 °C all three specimen types showed large ductile deformation without noticeable crack advancement. For longitudinal specimens the influence of the loading rate on the FT and DBT was studied in the loading rate range between 0.06 and 18 MPa m1/2/s. Though an increase of the FT was observed for the lowest loading rate, no resolvable dependence of the DBT on the loading rate was found partly due to loss of FT validity. A Master Curve approach is proposed to describe FT vs. test temperature data on polycrystalline tungsten. Fracture safe design space was identified by analysis compiled FT data.

  11. Analysis and Comparison of Aluminum Alloy Welded Joints Between Metal Inert Gas Welding and Tungsten Inert Gas Welding

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Guan, Yingchun; Wang, Qiang; Cong, Baoqiang; Qi, Bojin

    2015-09-01

    Surface contamination usually occurs during welding processing and it affects the welds quality largely. However, the formation of such contaminants has seldom been studied. Effort was made to study the contaminants caused by metal inert gas (MIG) welding and tungsten inert gas (TIG) welding processes of aluminum alloy, respectively. SEM, FTIR and XPS analysis was carried out to investigate the microstructure as well as surface chemistry. These contaminants were found to be mainly consisting of Al2O3, MgO, carbide and chromium complexes. The difference of contaminants between MIG and TIG welds was further examined. In addition, method to minimize these contaminants was proposed.

  12. Titanium Carbide Bipolar Plate for Electrochemical Devices

    SciTech Connect

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    1998-05-08

    Titanium carbide comprises a corrosion resistant, electrically conductive, non-porous bipolar plate for use in an electrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  13. Titanium carbide bipolar plate for electrochemical devices

    DOEpatents

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    2000-07-04

    A corrosion resistant, electrically conductive, non-porous bipolar plate is made from titanium carbide for use in an eletrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  14. Silicon nitride/silicon carbide composite powders

    DOEpatents

    Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

    1996-06-11

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  15. 500 C SILICON CARBIDE RECTIFIER PROGRAM

    DTIC Science & Technology

    Silicon carbide crystals of the hexagonal type were grown in a Kroll-type furnace by the sublimation technique. Both homogeneous and grown junction...feasibility of vapor-phase chemical reaction methods was investigated for the controlled growth of silicon carbide platelets and sheets. The growth of

  16. Graphene Nanoplatelet Reinforced Tantalum Carbide

    DTIC Science & Technology

    2015-08-27

    reinforced metals: copper/tungsten and copper/molybdenum. J Mech Phys Solids 1965;13:329–50. [27] Lourie O, Cox DM, Wagner HD . Buckling and collapse of...embedded carbon nanotubes. Phys Rev Lett 1998;81:1638. [28] Wagner HD , Lourie O, Feldman Y, Tenne R. Stress-induced fragmentation of multiwall carbon...nanotubes in a polymer matrix. Appl Phys Lett 1998;72:188. [29] Filleter T, Bernal R, Li S, Espinosa HD . Ultrahigh strength and stiffness in cross-linked

  17. Surface science and electrochemical studies of metal-modified carbides for fuel cells and hydrogen production

    NASA Astrophysics Data System (ADS)

    Kelly, Thomas Glenn

    Carbides of the early transition metals have emerged as low-cost catalysts that are active for a wide range of reactions. The surface chemistry of carbides can be altered by modifying the surface with small amounts of admetals. These metal-modified carbides can be effective replacements for Pt-based bimetallic systems, which suffer from the drawbacks of high cost and low thermal stability. In this dissertation, metal-modified carbides were studied for reactions with applications to renewable energy technologies. It is demonstrated that metal-modified carbides possess high activity for alcohol reforming and electrochemical hydrogen production. First, the surface chemistry of carbides towards alcohol decomposition is studied using density functional theory (DFT) and surface science experiments. The Vienna Ab initio Simulation Package (VASP) was used to calculate the binding energies of alcohols and decomposition intermediates on metal-modified carbides. The calculated binding energies were then correlated to reforming activity determined experimentally using temperature programmed desorption (TPD). In the case of methanol decomposition, it was found that tungsten monocarbide (WC) selectively cleaved the C-O bond to produce methane. Upon modifying the surface with a single layer of metal such as Ni, Pt, or Rh, the selectivity shifted towards scission of the C-H bonds while leaving the C-O bond intact, producing carbon monoxide (CO) and H2. High resolution energy loss spectroscopy (HREELS) was used to examine the bond breaking sequence as a function of temperature. From HREELS, it was shown that the surfaces followed an activity trend of Rh > Ni > Pt. The Au-modified WC surface possessed too low of a methanol binding energy, and molecular desorption of methanol was the most favorable pathway on this surface. Next, the ability of Rh-modified WC to break the C-C bond of C2 and C3 alcohols was demonstrated. HREELS showed that ethanol decomposed through an acetaldehyde

  18. Process for making silicon carbide reinforced silicon carbide composite

    NASA Technical Reports Server (NTRS)

    Lau, Sai-Kwing (Inventor); Calandra, Salavatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    1998-01-01

    A process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  19. Cement composition and sulfate attack

    SciTech Connect

    Shanahan, Natalya; Zayed, Abla . E-mail: zayed@eng.usf.edu

    2007-04-15

    Four cements were used to address the effect of tricalcium silicate content of cement on external sulfate attack in sodium sulfate solution. The selected cements had similar fineness and Bogue-calculated tricalcium aluminate content but variable tricalcium silicates. Durability was assessed using linear expansion and compressive strength. Phases associated with deterioration were examined using scanning electron microscopy and X-ray diffraction. Mineralogical phase content of the as-received cements was studied by X-ray diffraction using two methods: internal standard and Rietveld analysis. The results indicate that phase content of cements determined by X-ray mineralogical analysis correlates better with the mortar performance in sulfate environment than Bogue content. Additionally, it was found that in cements containing triclacium aluminate only in the cubic form, the observed deterioration is affected by tricalcium silicate content. Morphological similarities between hydration products of high tricalcium aluminate and high tricalcium silicate cements exposed to sodium sulfate environment were also observed.

  20. Preparation of silicon carbide fibers

    DOEpatents

    Wei, G.C.

    1983-10-12

    Silicon carbide fibers suitable for use in the fabrication of dense, high-strength, high-toughness SiC composites or as thermal insulating materials in oxidizing environments are fabricated by a new, simplified method wherein a mixture of short-length rayon fibers and colloidal silica is homogenized in a water slurry. Water is removed from the mixture by drying in air at 120/sup 0/C and the fibers are carbonized by (pyrolysis) heating the mixture to 800 to 1000/sup 0/C in argon. The mixture is subsequently reacted at 1550 to 1900/sup 0/C in argon to yield pure ..beta..-SiC fibers.

  1. Damage kinetics in silicon carbide

    NASA Astrophysics Data System (ADS)

    Pickup, I. M.; Barker, A. K.

    1998-07-01

    Three silicon carbides of similar density and grain size but manufactured via different routes (reaction bonded, pressureless sintered and pressure assisted densification) have been investigated. High speed photography in conjunction with Hopkinson pressure bar compression tests has revealed that not only does the manufacturing route confer a significant difference in failure kinetics but also modifies the phenomenology of failure. Plate impact experiments using lateral and longitudinal manganin stress gauges have been used to study shear strength behaviour of damaged material. Failure waves have been observed in all three materials and characteristically different damaged material shear strength relationships with pressure have been observed.

  2. Damage kinetics in silicon carbide

    SciTech Connect

    Pickup, I. M.; Barker, A. K.

    1998-07-10

    Three silicon carbides of similar density and grain size but manufactured via different routes (reaction bonded, pressureless sintered and pressure assisted densification) have been investigated. High speed photography in conjunction with Hopkinson pressure bar compression tests has revealed that not only does the manufacturing route confer a significant difference in failure kinetics but also modifies the phenomenology of failure. Plate impact experiments using lateral and longitudinal manganin stress gauges have been used to study shear strength behaviour of damaged material. Failure waves have been observed in all three materials and characteristically different damaged material shear strength relationships with pressure have been observed.

  3. Environmental fate of tungsten from military use.

    PubMed

    Clausen, Jay L; Korte, Nic

    2009-04-01

    This manuscript describes the distribution, fate and transport of tungsten used in training rounds at three small arms ranges at Camp Edwards on the Massachusetts Military Reservation (MMR), USA. Practice with tungsten/nylon rounds began in 2000 subsequent to a 1997 US Environmental Protection Agency ban on training with lead. Training with the tungsten rounds was halted in 2005 because of concerns regarding tungsten's environmental mobility and potential toxicity. This study, therefore, examines how tungsten partitions in the environment when fired on a small arms training range. Soil sampling revealed surface soil concentrations, highest at the berm face, up to 2080 mg/kg. Concentrations decreased rapidly with depth--at least by an order of magnitude by 25 cm. Nonetheless, tungsten concentrations remained above background to at least 150 cm. Pore-water samples from lysimeters installed in berm areas revealed a range of concentrations (<1-400 mg/L) elevated with respect to background although there was no discernable trend with depth. Groundwater monitoring well samples collected approximately 30 m below ground surface showed tungsten (0.001-0.56 mg/L) attributable to range use.

  4. New cement formulation helps solve deep cementing problems

    SciTech Connect

    Brothers, L.E.; DeBlanc, F.X.

    1989-06-01

    Invert-emulsion muds are used in most deep, hot wells. The internal aqueous phase of these muds frequently contains high concentrations of salts. It is desirable to complete these wells with a cement slurry containing salt concentrations up to and including saturation to minimize compatibility problems between cement slurry and mud. Above their effective temperature range, however, saturated salt cements - though still considered desirable for their other properties - pose design difficulties regarding thickening time, fluid loss, and rheology. High salt concentrations tend to decrease the effectiveness of most common cement additives - e.g., retarders, fluid-loss additives, and dispersants. At high temperatures, concentrations of these additives can become unacceptably large, while the additives themselves are not as effective under these conditions. Development of and field experience with a new cementing formulation for deep, high-temperature, saturated-salt applications have helped resolve the cement design problems encountered in south Texas and southern and offshore Louisiana. A single synthetic-polymer additive provides cement retardation, fluid-loss control, and dispersant properties with normal design considerations as opposed to the lengthy design requirements of other cement systems. A particular benefit derived from use of the new cement system involves cementing of long liners. Such liners frequently require squeeze cementing at the liner top because the cement is designed for conditions at the bottom of the liner and is thus frequently over-retarded for the cooler temperatures encountered at the top of the liner. This over-retardation tendency is alleviated greatly by use of the new saturated-salt cement additive.

  5. Fabrication and properties of tungsten heavy metal alloys containing 30% to 90% tungsten

    SciTech Connect

    Gurwell, W.E.; Nelson, R.G.; Dudder, G.B.; Davis, N.C.

    1984-09-01

    In 1983, Pacific Northwest Laboratory conducted a survey of tungsten heavy metal alloys having lower-than-normal (<90%) tungsten content. The purpose of the work was to develop tougher, more impact-resistant high-density alloys for applications benefitting from improved mechanical properties. Tungsten heavy metal alloys of 30 to 90% tungsten content were fabricated and their mechanical properties measured. Although ultimate strength was essentially independent of tungsten content, lower tungsten-content alloys had lower yield stress, hardness, and density, and decidedly higher elongations and impact energies. Cold work was effective in raising strength and hardness but detrimental to elongation and impact energies. Precipitation hardening and strain aging raised hardness effectively but had less influence on other mechanical properties. 34 figures, 7 tables.

  6. Non-selective tungsten chemical-vapor deposition using Tungsten hexacarbonyl

    SciTech Connect

    Creighton, J.R.

    1988-09-15

    We have used tungsten hexacarbonyl to deposit thin (<1000 A) non-selective tungsten films on silicon and silicon dioxide at 550/sup 0/C. Thicker (greater than or equal to1 micron) tungsten films were then deposited using film as an adhesion layer. Films grown in this manner have excellent adhesion to SiO/sub 2/, essentially 100% step coverage, and good resistivity (7.5--14 ..mu cap omega..-cm). Samples could be transferred under vacuum from the deposition chamber to a UHV chamber equipped with Auger spectroscopy, thus allowing surface and interface properties of the tungsten films to be studied at the initial stages of growth. No evidence was found for a stoichiometric tungsten oxide or tungsten silicide at the W/SiO/sub 2/ interface.

  7. High strength and density tungsten-uranium alloys

    DOEpatents

    Sheinberg, Haskell

    1993-01-01

    Alloys of tungsten and uranium and a method for making the alloys. The amount of tungsten present in the alloys is from about 55 vol % to about 85 vol %. A porous preform is made by sintering consolidated tungsten powder. The preform is impregnated with molten uranium such that (1) uranium fills the pores of the preform to form uranium in a tungsten matrix or (2) uranium dissolves portions of the preform to form a continuous uranium phase containing tungsten particles.

  8. Processes and applications of silicon carbide nanocomposite fibers

    NASA Astrophysics Data System (ADS)

    Shin, D. G.; Cho, K. Y.; Jin, E. J.; Riu, D. H.

    2011-10-01

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and γ-Al2O3. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200°C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  9. Ultrafast laser-triggered emission from hafnium carbide tips

    NASA Astrophysics Data System (ADS)

    Kealhofer, Catherine; Foreman, Seth M.; Gerlich, Stefan; Kasevich, Mark A.

    2012-07-01

    Electron emission from hafnium carbide (HfC) field emission tips induced by a sub-10-fs, 150-MHz repetition rate Ti:sapphire laser is studied. Two-photon emission is observed at low power with a moderate electric bias field applied to the tips. As the bias field and/or laser power is increased, the average current becomes dominated by thermally enhanced field emission due to laser heating: both the low thermal conductivity of HfC and the laser's high repetition rate can lead to a temperature rise of several hundred Kelvin at the tip apex. The contribution of current from a thermal transient at times shorter than the electron-phonon coupling time is considered in the context of the two-temperature model (TTM). Under the conditions of this experiment, the integrated current from the thermal transient is shown to be negligible in comparison with the two-photon emission. A finite element model of the laser heating and thermal conduction supports these conclusions and is also used to compare the nature of thermal effects in HfC, tungsten, and gold tips.

  10. Mineral resource of the month: hydraulic cement

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2012-01-01

    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

  11. Composition of CVD tungsten silicides

    SciTech Connect

    Hara, T.; Takahashi, H.; Ishizawa, Y.

    1987-05-01

    The composition of tungsten silicide (WSi/sub x/) deposited by chemical vapor deposition on silicon and silicon dioxide substrates was studied. The composition x changed from 2.7 to 2.2 with varying WF/sub 6/ flow rate from 6 to 20 cm/sup 3//min in the deposition on silicon. When annealing was performed at 1000C, the dissociation of excess silicon occurred from the nonstoichiometric silicide in the layer on the silicon. As a result, the composition of each layer, which was different when deposited, tended toward the same composition of around 2.1. This result indicated the formation of near-stoichiometric silicide as a result of annealing.

  12. Tungsten wire for incandescent lamps

    SciTech Connect

    Walter, J.L.; Briant, C.L. )

    1990-09-01

    Tungsten wire for incandescent lamp filaments must operate at high temperatures and for long times. To meet these requirements, the grain morphology of the wire must be controlled to reduce the propensity for grain boundary sliding. The morphology is a function of the distribution of very small pockets of potassium in the wire and the mechanical processing from ingot to wire. The behavior of the filament is directly related to the grain morphology. This paper describes the mechanism by which the potassium is incorporated into and distributed in the ingot. The elongation and spheroidization of the bubbles during hot rolling and swaging is also examined and related to the grain morphology of wire. Some indications of the relationship between grain morphology and filament behavior are also given.

  13. Viscosity of liquid undercooled tungsten

    NASA Astrophysics Data System (ADS)

    Paradis, Paul-François; Ishikawa, Takehiko; Yoda, Shinichi

    2005-05-01

    Knowledge of the viscosity and its temperature dependence is essential to improve metallurgical processes as well as to validate theoretical and empirical models of liquid metals. However, data for metals with melting points above 2504K could not be determined yet due to contamination and containment problems. Here we report the viscosity of tungsten, the highest melting point metal (3695K), measured by a levitation technique. Over the 3350-3700-K temperature range, which includes the undercooled region by 345K, the viscosity data could be fitted as η(T )=0.108exp[1.28×105/(RT)](mPas). At the melting point, the datum agrees with the proposed theoretical and empirical models of liquid metals but presents atypical temperature dependence, suggesting a basic change in the mechanism of momentum transfer.

  14. Properties of tungsten and tungsten disilicide layers on Si(100) substrates

    NASA Astrophysics Data System (ADS)

    Cros, A.; Pierrisnard, R.; Pierre, F.; Layet, J. M.; Meyer, F.

    1989-09-01

    Tungsten layers have been evaporated on Si(100) surfaces under ultra high vacuum conditions. The tungsten is in the α phase. Before the disilicide formation (at ˜ 700°C), a low temperature (400°C) reaction has been observed. Si atoms segregate at the surface and do not form crystalline WSI 2 while the tungsten layer stays in the α phase. It is suggested that this low temperature reaction plays an important role in the roughness and the adhesion properties of the tungsten disilicide subsequently grown.

  15. Cement from magnesium substituted hydroxyapatite.

    PubMed

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

    2005-05-01

    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  16. Dependence of implantation temperature on chemical behavior of energetic deuterium implanted into tungsten carbide

    NASA Astrophysics Data System (ADS)

    Igarashi, E.; Nishikawa, Y.; Nakahata, T.; Yoshikawa, A.; Oyaidzu, M.; Oya, Y.; Okuno, K.

    2007-06-01

    Dependence of implantation temperature on chemical behavior of energetic deuterium implanted into WC was investigated by TDS and XPS. 1.0 keV D2+ ions were implanted into WC samples at the implantation temperature range of 323-873 K. It was found that the deuterium retention decreased as the implantation temperature increased. Above 573 K, most of the retained deuterium was bound to C, which was less than 20% of the total D retention after D2+ implantation at 323 K. Above 673 K, C was segregated on the WC surface and some of the implanted deuterium was retained in the segregated carbon layer. Additionally, it can be said that the D retention in WC was much less than that in other carbon-related materials, such as graphite and SiC. Hydrogen isotope retention can be reduced significantly when WC is formed on a divertor surface as a redeposited layer.

  17. Mechanical and tribological properties of thermally sprayed tungsten carbide-cobalt coatings

    NASA Astrophysics Data System (ADS)

    Qiao, Yunfei

    Since previous work in our laboratory has shown that very fine microstructures increase the hardness and the resistance to sliding and abrasive wear of bulk, sintered, WC/Co composites, it was decided to explore whether similar benefits can be obtained in coatings of this material deposited by the Thermal Spray Method. The research was a collaborative effort in which a number of companies and universities prepared feedstock powders by a number of methods and deposited coatings by Plasma Spray and High Velocity Oxy Fuel spray techniques. Our role was to study the resistance of these coatings to abrasion and to wear in unlubricated sliding, to relate our findings to the microstructure of the coatings and to the properties of the powder and the parameters of deposition. The results were then used by our partners in the program to modify their processes in order to obtain the best possible performance. The thesis consists of four parts. In the first, we review the literature on WC/Co coatings and present the results of our survey of 45 coatings. This shows that the details of the thermal spray technique determine the tribological performance of the coatings much more than the size of the WC grains in the starting powder. It also shows that abrasive and sliding wear respond differently to the material properties. The remainder of the thesis describes a systematic variation of powders and deposition techniques, based on our earlier findings. In the second part, we describe the microstructures, hardness and toughness of nine coatings deposited by A. Dent at SUNY Stony Brook, with three different powders and three different flame chemistries. We find that the hardness is determined mainly by the flame temperature; hardness is decreased by porosity on the 50-nm size range, and this porosity is produced by insufficient melting of the Co binder. High temperatures and certain powder morphologies cause extensive decarburization, and the latter reduces the adhesion between the deposited material splats. In the third and fourth sections, we examine the abrasive wear resistance of these nine samples. Abrasive wear occurs on a small scale and depends mainly on the adhesion between the WC grains and the Co binder phase. Sliding wear, which occurs chiefly by the removal of entire splats by fatigue, is more sensitive to decarburization. The technological result is that WC/Co coatings made of "multimodal" powders that consist of a mixture of micrometer and nanometer-sized WC are to be preferred for abrasion resistance, and coatings made of a very fine powder with an additive that retards grain growth and decarburization is preferred for sliding wear resistance.

  18. Metal and Metal Carbide Nanoparticle Synthesis Using Electrical Explosion of Wires Coupled with Epoxide Polymerization Capping.

    PubMed

    Abdelkader, Elseddik M; Jelliss, Paul A; Buckner, Steven W

    2015-06-15

    In this study, metal-containing nanoparticles (NPs) were produced using electrical explosion of wires (EEW) in organic solvents. The explosion chamber was constructed from Teflon to withstand the shockwave, allow growth and reaction of the incipient NPs in various organic solvents containing dissolved ligands, and allow a constant flow of argon to maintain an inert environment. A survey of different transition d-block metals was conducted with metals from groups 4-8, affording metal carbide NPs, while metals from groups 9-12 gave elemental metallic NPs. Tungsten carbide phase WC1-x, which has not been previously isolated as a single-phase material, was exclusively formed during EEW. We used polymerization initiation by electron-rich metallic nanoparticles (PIERMEN) as a capping technique for the nascent NPs with an alkyl epoxide employed as the monomers. Transmission electron microscopy showed spherical particles with the metallic core embedded in a polymer matrix with predominantly smaller particles (<50 nm), but also a broad size distribution with some larger particles (>100 nm). Powder X-ray diffraction (PXRD) was used to confirm the identity of the metallic NPs. The capping agents were characterized using ATR-FTIR spectroscopy. No evidence is observed for the formation of crystalline oxides during EEW for any metals used. Differential scanning calorimetry/thermal gravimetric analysis was used to study the NP's behavior upon heating under an air flow up to 800 °C with the product oxides characterized by PXRD. The bifurcation between metal-carbide NPs and metal NPs correlates with the enthalpy of formation of the product carbides. We observed PIERMEN capping of elemental metal NPs only when the metal has negative standard electrode potentials (relative to a bis(biphenyl) chromium(I)/(0) reference electrode).

  19. Foamed well cementing compositions and methods

    SciTech Connect

    Bour, D.L.; Childs, J.D.

    1992-07-28

    This patent describes a method of cementing a well penetrating a salt containing subterranean formation. It comprises: forming a foamed cement composition; placing the foamed cement composition in contact with the salt containing formation; and permitting the foamed cement composition to set in contact with the salt containing formation to form a hardened mass of cement.

  20. US cement industry

    SciTech Connect

    Nisbet, M.A.

    1997-12-31

    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.