tungsten carbide-cobalt composites: Topics by Science.gov

Sample records for tungsten carbide-cobalt composites

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.
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.
Electrochemical Synthesis of Binary Carbides of Tungsten and Iron (Nickel, Cobalt) in Halide-Oxide Melts at 823 K

NASA Astrophysics Data System (ADS)

Kushkhov, Hasbi; Adamokova, Marina; Kvashin, Vitalij; Kardanov, Anzor; Gramoteeva, Svetlana

2007-12-01

Iron, cobalt and nickel powders are used as binding components for the production of articles of tungsten carbide by the hot pressing method. This fact and the unique properties of binary carbides of tungsten-iron triad metals encouraged the search for new ways of their synthesis. In the present work, the attempt to synthezise binary tungsten-nickel (cobalt, iron) carbides in molten KCl-NaCl-CsCl at 823 K was made. As a result of voltammetry research, it was established that in eutectic KCl-NaCl-CsCl melts the deposition potentials ofWand Ni (Co, Fe) differ by 150 - 350 mV from each other, which makes their co-deposition difficult. It is possible to shift the deposition potentials of tungsten and metals of the iron triad metals towards each other by changing the acid-base properties of the melt. The products of electrolysis in these molten system were identified by X-ray analysis. They are mixtures of tungsten and nickel (cobalt, iron) carbides: Ni2W4C, W6C2.54; Co3W3C, Co6W6C, W2C, Co3C; FeW3C.
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.
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.
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.
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.
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.
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
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.
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.
Ablation properties of carbon/carbon composites with tungsten carbide

NASA Astrophysics Data System (ADS)

Yin, Jian; Zhang, Hongbo; Xiong, Xiang; Huang, Baiyun; Zuo, Jinlv

2009-02-01

The ablation properties and morphologies of carbon/carbon (C/C) composites with tungsten carbide (WC) filaments were investigated by ablation test on an arc heater and scanning electron microscopy. And the results were compared with those without tungsten carbide (WC) filaments tested under the same conditions. It shows that there is a big difference between C/C composites with and without WC filaments on both macroscopic and microscopic ablation morphologies and the ablation rates of the former are higher than the latter. It is found that the ablation process of C/C composites with WC filaments includes oxidation of carbon fibers, carbon matrices and WC, melting of WC and WO 3, and denudation of WC, WO 3 and C/C composites. Oxidation and melting of WC leads to the formation of holes in z directional carbon fiber bundles, which increases the coarseness of the ablation surfaces of the composites, speeds up ablation and leads to the higher ablation rate. Moreover, it is further found that the molten WC and WO 3 cannot form a continuous film on the ablation surface to prevent further ablation of C/C composites.
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.
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
Wear and corrosion behaviour of tungsten carbide based coatings with different metallic binder

NASA Astrophysics Data System (ADS)

Kamdi, Z.; Apandi, M. N. M.; Ibrahim, M. D.

2017-12-01

Tungsten carbide based coating has been well known as wear and corrosion resistance materials. However, less study is done on comparing the coating with different binder. Thus, in this work the wear and corrosion behaviour of high velocity oxy-fuel (HVOF) coatings, namely (i) tungsten carbide cobalt and (ii) tungsten carbide nickel will be evaluated. Both coatings were characterised using X-ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). The wear behaviour has been examined using the modified grinder machine by weight loss measurement. Two types of abrasive have been used that include 3 g by weight alumina and silica. While for the corrosion behaviour, it is monitored by three electrodes of electrochemical test and immersion test for 30 days in an acidic environment. The electrolyte used was 0.5 M sulphuric acids (H2SO4). It was found that the cobalt binder shows higher wear resistance compares to the nickel binder for both slurry types. The harder alumina compared to silica results in higher wear rate with removal of carbide and binder is about the same rate. For silica abrasive, due to slightly lower hardness compared to the carbide, the wear is dominated by binder removal followed by carbide detachment. For corrosion, the nickel binder shows four times higher wear resistance compared to the cobalt binder as expected due to its natural behaviour. These finding demonstrate that the selection of coating to be used in different application in this case, wear and corrosion shall be chosen carefully to maximize the usage of the coating.
Preparation and electrocatalytic activity of tungsten carbide and titania nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Sujuan; Shi, Binbin; Yao, Guoxing

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 andmore » 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.« less
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.
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.
Novel hard compositions and methods of preparation

DOEpatents

Sheinberg, Haskell

1983-08-23

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value. Photomicrographs show that the shapes of the grains of the alloy mixture with which the minor amount of carbide (or carbide-formers) is mixed are radically altered from large, rounded to small, very angular by the addition of the carbide. Superiority of one of these hard compositions of matter over cobalt-bonded tungsten carbide for ultra-high pressure anvil applications was demonstrated.
Novel hard compositions and methods of preparation

DOEpatents

Sheinberg, H.

1983-08-23

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value. Photomicrographs show that the shapes of the grains of the alloy mixture with which the minor amount of carbide (or carbide-formers) is mixed are radically altered from large, rounded to small, very angular by the addition of the carbide. Superiority of one of these hard compositions of matter over cobalt-bonded tungsten carbide for ultra-high pressure anvil applications was demonstrated. 3 figs.

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

2017-05-04

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.
Interaction of tungsten with tungsten carbide in a copper melt

NASA Astrophysics Data System (ADS)

Bodrova, L. E.; Goida, E. Yu.; Pastukhov, E. A.; Marshuk, L. A.; Popova, E. A.

2013-07-01

The chemical interaction between tungsten and tungsten carbide in a copper melt with the formation of W2C at 1300°C is studied. It is shown that the mechanical activation of a composition consisting of copper melt + W and WC powders by low-temperature vibrations initiates not only the chemical interaction of its solid components but also their refinement.
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
Electric Discharge Sintering and Joining of Tungsten Carbide—Cobalt Composite with High-Speed Steel Substrate

NASA Astrophysics Data System (ADS)

Grigoryev, Evgeny G.

2011-01-01

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.
Novel hard compositions and methods of preparation

DOEpatents

Sheinberg, H.

1981-02-03

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value.
Tungsten carbide: Crystals by the ton

NASA Astrophysics Data System (ADS)

Smith, E. N.

1988-06-01

A comparison is made of the conventional process of making tungsten carbide by carburizing tungsten powder and the Macro Process wherein the tungsten carbide is formed directly from the ore concentrate by an exothermic reaction of ingredients causing a simultaneous reduction and carburization. Tons of tungsten monocarbide crystals are formed in a very rapid reaction. The process is unique in that it is self regulating and produces a tungsten carbide compound with the correct stoichiometry. The high purity with respect to oxygen and nitrogen is achieved because the reactions occur beneath the molten metal. The morphology and hardness of these crystals has been studied by various investigators and reported in the listed references.
Electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal

NASA Astrophysics Data System (ADS)

Kushkhov, Kh. B.; Adamokova, M. N.; Kvashin, V. A.; Kardanov, A. L.

2010-08-01

Single and cyclic voltammetry is used to study the electrode processes that occur during electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal in tungstate and tungstate-carbonate Na2WO4-Li2WO4-Li2CO3 (5.0-22.0 wt %) melts. The conditions of bringing the electroprecipitation potentials of tungsten, carbon, and an iron triad metal into coincidence are determined.
Compatibility of buffered uranium carbides with tungsten.

NASA Technical Reports Server (NTRS)

Phillips, W. M.

1971-01-01

Results of compatibility tests between tungsten and hyperstoichiometric uranium carbide alloys run at 1800 C for 1000 and 2500 hours. These tests compared tungsten-buffered uranium carbide with tungsten-buffered uranium-zirconium carbide. The zirconium carbide addition appeared to widen the homogeneity range of the uranium carbide, making additional carbon available for reaction. Reaction layers could be formed by either of two diffusion paths, one producing UWC2, while the second resulted in the formation of W2C. UWC2 acts as a diffusion barrier for carbon and slows the growth of the reaction layer with time, while carbon diffusion is relatively rapid in W2C, allowing equilibrium to be reached in less than 2500 hours at a temperature of 1800 C.
Low Temperature Synthesis of Cobalt-Chromium Carbide Nanoparticles-Doped Carbon Nanofibers.

PubMed

Yousef, Ayman; Brooks, Robert M; Abutaleb, Ahmed; Al-Deyab, Salem S; El-Newehy, Mohamed H

2018-04-01

Electrospinning has been used to synthesize cobalt-chromium carbide nanoparticles (NPs)-doped carbon nanofibers (CNFs) (Composite). Electrospun mat comprising of cobalt acetate, chromium acetate and poly(vinyl alcohol) (PVA) has been carbonized at low temperature (850 °C) for 3 h under argon atmosphere to produce the introduced composite. The process was achieved at low temperature due to the presence of cobalt as an activator. Field emission scanning electron microscope (FE-SEM), X-ray diffractometry (XRD), and transmission electron microscopy (TEM) equipped with EDX techniques were used to determine the products characteristics. The results indicated the formation of pure cobalt (Co), Cr7C3 NPs and crystalline CNFs. The Co and Cr7C3 NPs were covered with CNFs. Overall, the proposed NFs open new avenue to prepare different metals-metal carbides-carbon NFs at low temperature and short reaction time.
Physical and Mechanical Properties of W-Ni-Fe-Co Metal Foam Modified by Titanium Tungsten Carbide Alloying

NASA Astrophysics Data System (ADS)

Ishchenko, A. N.; Tabachenko, A. N.; Afanas'eva, S. A.; Belov, N. N.; Biryukov, Yu. A.; Burkin, V. V.; D'yachkovskii, A. S.; Rogaev, K. S.; Skosyrskii, A. B.; Yugov, N. T.

2018-02-01

The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the liquid phase sintering of powder materials, including those containing tungsten nanopowders. High porosity metal foams are prepared through varying the porosity of powder specimens and the content of filling material. The penetration capability of cylinder projectiles made of new alloys is explored in this paper. It is shown that their penetration depth exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron alloy, other factors being equal.
Chemical and Phase Composition of Powders Obtained by Electroerosion Dispersion from WC - Co Alloys

NASA Astrophysics Data System (ADS)

Putintseva, M. N.

2004-03-01

The dependence of the chemical and phase composition of dispersed powders on the mode and medium of electroerosion dispersion and the content of cobalt in the initial alloy is considered. It is shown that the dissociation of carbon from tungsten carbide occurs even in dispersion in liquid hydrocarbon-bearing media (kerosene and industrial oils). The phase composition is primarily determined by the dispersion medium and the content of cobalt in the initial alloy. Compound tungsten-cobalt carbides and even a Co7W6 intermetallic are determined in all the powders.
Cobalt Doping of Semiconducting Boron Carbide Using Cobaltocene

DTIC Science & Technology

2007-03-01

COBALT DOPING OF SEMICONDUCTING BORON CARBIDE USING COBALTOCENE THESIS Lonnie Carlson, Major...DOPING OF SEMICONDUCTING BORON CARBIDE USING COBALTOCENE THESIS Presented to the Faculty Department of Engineering Physics Graduate School...DISTRIBUTION UNLIMITED AFIT/GNE/ENP/07-01 COBALT DOPING OF SEMICONDUCTING BORON CARBIDE USING COBALTOCENE Lonnie
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. Copyright © 2015 Elsevier B.V. All rights reserved.
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.
Tunable carbon nanotube-tungsten carbide nanoparticles heterostructures by vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Min; Guo, Hongyan; Ge, Changchun

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

DOE PAGES

Zheng, Weiqing; Wang, Liang; Deng, Fei; ...

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. Using 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• aremore » 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.« less
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.
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.
Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Liming; Fu, Honggang, E-mail: fuhg@vip.sina.com; Key Laboratory of Functional Inorganic Material Chemistry, Heilongjiang University, Harbin 150080

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 superiormore » 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.« less
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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Airapetov, A. A.; Begrambekov, L. B., E-mail: lbb@plasma.mephi.ru; Buzhinskiy, O. I.

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.
40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE... the production of tungsten or cobalt at secondary tungsten and cobalt facilities processing tungsten...
40 CFR 721.10600 - Calcium cobalt lead strontium titanium tungsten oxide.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium cobalt lead strontium titanium... Specific Chemical Substances § 721.10600 Calcium cobalt lead strontium titanium tungsten oxide. (a... calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS No. 1262279-30-0) is subject to...
40 CFR 721.10600 - Calcium cobalt lead strontium titanium tungsten oxide.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium cobalt lead strontium titanium... Specific Chemical Substances § 721.10600 Calcium cobalt lead strontium titanium tungsten oxide. (a... calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS No. 1262279-30-0) is subject to...
Tungsten carbide-cobalt as a nanoparticulate reference positive control in in vitro genotoxicity assays.

PubMed

Moche, Hélène; Chevalier, Dany; Barois, Nicolas; Lorge, Elisabeth; Claude, Nancy; Nesslany, Fabrice

2014-01-01

With the increasing human exposure to nanoparticles (NP), the evaluation of their genotoxic potential is of significant importance. However, relevance for NP of the routinely used in vitro genotoxicity assays is often questioned, and a nanoparticulate reference positive control would therefore constitute an important step to a better testing of NP, ensuring that test systems are really appropriate. In this study, we investigated the possibility of using tungsten carbide-cobalt (WC-Co) NP as reference positive control in in vitro genotoxicity assays, including 2 regulatory assays, the mouse lymphoma assay and the micronucleus assay, and in the Comet assay, recommended for the toxicological evaluation of nanomedicines by the French Agency of Human Health Products (Afssaps). Through these assays, we were able to study different genetic endpoints in 2 cell types commonly used in regulatory genotoxicity assays: the L5178Y mouse lymphoma cell line and primary cultures of human lymphocytes. Our results showed that the use of WC-Co NP as positive control in in vitro genotoxicity assays was conceivable, but that different parameters have to be considered, such as cell type and treatment schedule. L5178Y mouse lymphoma cells did not provide satisfactory results in the 3 performed tests. However, human lymphocytes were more sensitive to genotoxic effects induced by WC-Co NP, particularly after a 24-h treatment in the in vitro micronucleus assay and after a 4-h treatment in the in vitro Comet assay. Under such conditions, WC-Co could be used as a nanoparticulate reference positive control in these assays.
First principles study of intrinsic defects in hexagonal tungsten carbide

NASA Astrophysics Data System (ADS)

Kong, Xiang-Shan; You, Yu-Wei; Xia, J. H.; Liu, C. S.; Fang, Q. F.; Luo, G.-N.; Huang, Qun-Ying

2010-11-01

The characteristics of intrinsic defects are important for the understanding of self-diffusion processes, mechanical strength, brittleness, and plasticity of tungsten carbide, which are present in the divertor of fusion reactors. Here, we use first-principles calculations to investigate the stability of point defects and their complexes in tungsten carbide. Our results confirm that the defect formation energies of carbon are much lower than that of tungsten and reveal the carbon vacancy to be the dominant defect in tungsten carbide. The C sbnd C dimer configuration along the dense a direction is the most stable configuration of carbon interstitial defect. The results of carbon defect diffusion show that the carbon vacancy stay for a wide range of temperature because of extremely high diffusion barriers, while carbon interstitial migration is activated at lower temperatures for its considerably lower activation energy. Both of them prefer to diffusion in carbon basal plane.
Design of cemented tungsten carbide and boride-containing shields for a fusion power plant

NASA Astrophysics Data System (ADS)

Windsor, C. G.; Marshall, J. M.; Morgan, J. G.; Fair, J.; Smith, G. D. W.; Rajczyk-Wryk, A.; Tarragó, J. M.

2018-07-01

Results are reported on cemented tungsten carbide (cWC) and boride-containing composite materials for the task of shielding the centre column of a superconducting tokamak power plant. The shield is based on five concentric annular shells consisting of cWC and water layers of which the innermost cWC shield can be replaced with boride composites. Sample materials have been fabricated changing the parameters of porosity P, binder alloy fraction f binder and boron weight fraction f boron. For the fabricated materials, and other hypothetical samples with chosen parameters, Monte Carlo studies are made of: (i) the power deposition into the superconducting core, (ii) the fast neutron and gamma fluxes and (iii) the attenuation coefficients through the shield for the deposited power and neutron and gamma fluxes. It is shown that conventional Co-based cWC binder alloy can be replaced with a Fe–Cr alloy (92 wt.% Fe, 8 wt.% Cr), which has lower activation than cobalt with minor changes in shield performance. Boride-based composite materials have been prepared and shown to give a significant reduction in power deposition and flux, when placed close to the superconducting core. A typical shield of cemented tungsten carbide with 10 wt.% of Fe–8Cr binder and 0.1% porosity has a power reduction half-length of 0.06 m. It is shown that the power deposition increases by 4.3% for every 1% additional porosity, and 1.7% for every 1 wt.% additional binder. Power deposition decreased by 26% for an initial 1 wt.% boron addition, but further increases in f boron showed only a marginal decrease. The dependences of power deposited in the core, the maximum neutron and gamma fluxes on the core surface, and the half attenuation distances through the shield have been fitted to within a fractional percentage error by analytic functions of the porosity, metallic binder alloy and boron weight fractions.
Tungsten-nickel-cobalt alloy and method of producing same

DOEpatents

Dickinson, James M.; Riley, Robert E.

1977-03-15

An improved tungsten alloy having a tungsten content of approximately 95 weight percent, a nickel content of about 3 weight percent, and the balance being cobalt of about 2 weight percent is described. A method for producing said tungsten-nickel-cobalt alloy is further described and comprises (a) coating the tungsten particles with a nickel-cobalt alloy, (b) pressing the coated particles into a compact shape, (c) heating said compact in hydrogen to a temperature in the range of 1400.degree. C and holding at this elevated temperature for a period of about 2 hours, (d) increasing this elevated temperature to about 1500.degree. C and holding for 1 hour at this temperature, (e) cooling to about 1200.degree. C and replacing the hydrogen atmosphere with an inert argon atmosphere while maintaining this elevated temperature for a period of about 1/2 hour, and (f) cooling the resulting alloy to room temperature in this argon atmosphere.
Effect of fabrication process on physical and mechanical properties of tungsten carbide - cobalt composite: A review

NASA Astrophysics Data System (ADS)

Mahaidin, Ahmad Aswad; Jaafar, Talib Ria; Selamat, Mohd Asri; Budin, Salina; Sulaiman, Zaim Syazwan; Hamid, Mohamad Hasnan Abdul

2017-12-01

WC-Co, which is also known as cemented carbide, is widely used in metal cutting industry and wear related application due to their excellent mechanical properties. Manufacturing industries are focusing on improving productivity and reducing operational cost with machining operation is considered as one of the factors. Thus, machining conditions are becoming more severe and required better cutting tool bit with improved mechanical properties to withstand high temperature operation. Numerous studies have been made over the generation for further improvement of cemented carbide properties to meet the constant increase in demand. However, the results of these studies vary due to different process parameters and manufacturing technology. This paper summarizes the studies to improve the properties of WC-Co composite using different consolidation (powder size, mixing method, formulation, etc) and sintering parameters (temperature, time, atmosphere, etc).
Influence of oxygen on the carbide formation on tungsten

NASA Astrophysics Data System (ADS)

Luthin, J.; Linsmeier, Ch.

2001-03-01

As a first wall material in nuclear fusion devices, tungsten will interact with carbon and oxygen from the plasma. In this study, we report on the process of thermally induced carbide formation of thin carbon films on polycrystalline tungsten and the influence of oxygen on this process. All investigations are performed using X-ray photoelectron spectroscopy (XPS). Carbon films are supplied through electron beam evaporation of graphite. The carbidization process, monitored during increased substrate temperature, can be divided into four phases. In phase I disordered carbon converts into graphite-like carbon. In phase II significant diffusion and the reaction to W 2C is observed, followed by phase III which is dominated by the presence of W 2C and the beginning reaction to WC. Finally in phase IV only WC is present, but the total carbon amount has strongly decreased. Different mechanisms of oxygen influence on the carbide formation are proposed and measurements of the reaction of carbon on tungsten with intermediate oxide layers are presented in detail. A WO 2+ x intermediate layer completely inhibits the carbide formation, while a WO 2 layer leads to WC formation at temperatures above 1270 K.
Effect of Helmholtz Oscillation on Auto-shroud for APS Tungsten Carbide Coating

NASA Astrophysics Data System (ADS)

Jin, Younggil; Choi, Sooseok; Yang, Seung Jae; Park, Chong Rae; Kim, Gon-Ho

2013-06-01

The atmospheric-pressure plasma spray (APS) of tungsten coating was performed using tungsten carbide (WC) powder by means of DC plasma torch equipped with a stepped anode nozzle as a potential method of W coating on graphite plasma-facing component of fusion reactors. This nozzle configuration allows Helmholtz oscillation mode dominating in APS arc fluctuation, and the variation of auto-shroud effect with Helmholtz oscillation characteristics can be investigated. Tungsten coating made from WC powder has lower porosity and higher tungsten purity than that made from pure tungsten powder. The porosity and chemical composition of coatings were investigated by mercury intrusion porosimetry and x-ray photoelectron spectroscopy, respectively. The purity of tungsten coating layer is increased with the increasing frequency of Helmholtz oscillation and the increasing arc current. The modulation of Helmholtz oscillation frequency and magnitude may enhance the decarburization of WC to deposit tungsten coating without W-C and W-O bond from WC powder.
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.
[Determination of tungsten and cobalt in the air of workplace by ICP-OES].

PubMed

Zhang, J; Ding, C G; Li, H B; Song, S; Yan, H F

2017-08-20

Objective: To establish the inductively coupled plasma optical emission spectrometry (ICP-OES) method for determination of cobalt and tungsten in the air of workplace. Methods: The cobalt and tungsten were collected by filter membrane and then digested by nitric acid, inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the detection of cobalt and tungsten. Results: The linearity of tungsten was good at the range of 0.01-1 000 μg/ml with a correlation coefficient of 0.999 9, the LOD and LOQ were 0.006 7 μg/ml and 0.022 μg/ml, respectively. The recovery was ranged from 98%-101%, the RSD of intra-and inter-batch precision were 1.1%-3.0% and 2.1%-3.8%, respectively. The linearity of cobalt was good at the range of 0.01-100 μg/ml with a correlation coefficient of 0.999 9, the LOD and LOQ were 0.001 2 μg/ml and 0.044 μg/ml, respectively. The recovery was ranged from 95%-97%, the RSD of intra-and inter-batch precision were 1.1%-2.4% and 1.1%-2.9%, respectively. The sampling efficiency of tungsten and cobalt were higher than 94%. Conclusion: The linear range, sensitivity and precision of the method was suitable for the detection of tungsten and cobalt in the air of workplace.
Electrons, phonons and superconductivity in rocksalt and tungsten-carbide phases of CrC.

PubMed

Tütüncü, H M; Baǧcı, S; Srivastava, G P; Akbulut, A

2012-11-14

We present results of ab initio theoretical investigations of the electronic structure, phonon dispersion relations, electron-phonon interaction and superconductivity in the rocksalt and tungsten-carbide phases of CrC. It is found that, compared to the stable tungsten-carbide phase, the metastable rocksalt phase is characterized by a much larger electronic density of states at the Fermi level. The phonon spectra of the rocksalt phase exhibit anomalies in the dispersion curves of both the transverse and longitudinal acoustic branches along the main symmetry directions. A combination of these characteristic electronic and phonon properties leads to an order of magnitude larger value of the electron-phonon coupling constant (λ = 2.66) for the rocksalt phase compared to that for the tungsten-carbide phase (λ = 0.24). Our calculations suggest that superconducting transition temperature values of 0.01 K and 25-35 K may be expected for the tungsten-carbide and rocksalt phases, respectively.
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.
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.
Microstructure and thermal properties of copper–diamond composites with tungsten carbide coating on diamond particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Qiping; He, Xinbo, E-mail: xb_he@163.com; Ren, Shubin

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}more » 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.« less
Tribology of carbide derived carbon films synthesized on tungsten carbide

NASA Astrophysics Data System (ADS)

Tlustochowicz, Marcin

Tribologically advantageous films of carbide derived carbon (CDC) have been successfully synthesized on binderless tungsten carbide manufactured using the plasma pressure compaction (P2CRTM) technology. In order to produce the CDC films, tungsten carbide samples were reacted with chlorine containing gas mixtures at temperatures ranging from 800°C to 1000°C in a sealed tube furnace. Some of the treated samples were later dechlorinated by an 800°C hydrogenation treatment. Detailed mechanical and structural characterizations of the CDC films and sliding contact surfaces were done using a series of analytical techniques and their results were correlated with the friction and wear behavior of the CDC films in various tribosystems, including CDC-steel, CDC-WC, CDC-Si3N4 and CDC-CDC. Optimum synthesis and treatment conditions were determined for use in two specific environments: moderately humid air and dry nitrogen. It was found that CDC films first synthesized at 1000°C and then hydrogen post-treated at 800°C performed best in air with friction coefficient values as low as 0.11. However, for dry nitrogen applications, no dechlorination was necessary and both hydrogenated and as-synthesized CDC films exhibited friction coefficients of approximately 0.03. A model of tribological behavior of CDC has been proposed that takes into consideration the tribo-oxidation of counterface material, the capillary forces from adsorbed water vapor, the carbon-based tribofilm formation, and the lubrication effect of both chlorine and hydrogen.
Researches on tungsten carbide

NASA Astrophysics Data System (ADS)

1994-11-01

This paper summarizes results of the researches on tungsten carbide (WC), carried out in the 5-year period starting 1989 by the Science and Technology Agency's National Institute for Researches in Inorganic Materials. The high-frequency heating, floating zone technique, generally suited for growth of large-size, single crystals of high melting materials, is inapplicable to the hexagonal WC system, which is decomposed. This problem has been solved by adding boron to the system, to allow it to exist with the W-C-B melt at an equilibrium. The computer-aided control techniques have enabled automatic growth of the single crystals of carbides and borides. The de Haas-Van Alphen effect of the single WC crystals has been observed, to establish the Fermi surface model. The single crystals of transition metal carbides, such as WC, have been coated with the monolayer of graphite at high repeatability, to create the surface layer materials. An attempt has been done to produce the halite type structure by substituting Ti as the atom in the outermost layer of TiC by W. The new method, based on the low-speed deuterium ion scattering, has been developed to analyze the surface bonding conditions, clarifying the conditions of alkalis adsorbed on and bonded to metallic surfaces, and their surface reactivities.
Tungsten-microdiamond composites for plasma facing components

NASA Astrophysics Data System (ADS)

Livramento, V.; Nunes, D.; Correia, J. B.; Carvalho, P. A.; Mardolcar, U.; Mateus, R.; Hanada, K.; Shohoji, N.; Fernandes, H.; Silva, C.; Alves, E.

2011-09-01

Tungsten is considered as one of promising candidate materials for plasma facing component in nuclear fusion reactors due to its resistance to sputtering and high melting point. High thermal conductivity is also a prerequisite for plasma facing components under the unique service environment of fusion reactor characterised by the massive heat load, especially in the divertor area. The feasibility of mechanical alloying of nanodiamond and tungsten, and the consolidation of the composite powders with Spark Plasma Sintering (SPS) was previously demonstrated. In the present research we report on the use of microdiamond instead of nanodiamond in such composites. Microdiamond is more favourable than nanodiamond in view of phonon transport performance leading to better thermal conductivity. However, there is a trade off between densification and thermal conductivity as the SPS temperature increases tungsten carbide formation from microdiamond is accelerated inevitably while the consolidation density would rise.

Electrochemical synthesis of binary molybdenum-tungsten carbides (Mo,W)2C from tungstate-molybdate-carbonate melts

NASA Astrophysics Data System (ADS)

Kushkhov, Kh. B.; Kardanov, A. L.; Adamokova, M. N.

2013-02-01

Nanopowders of binary tungsten-molybdenum carbide are fabricated by high-temperature electrochemical synthesis. The optimum concentration relations between electrolyte components, the current density, and the quantity of electricity are determined to synthesize binary tungsten-molybdenum carbides.
Development and kinetic analysis of cobalt gradient formation in WC-Co composites

NASA Astrophysics Data System (ADS)

Guo, Jun

2011-12-01

Functionally graded cemented tungsten carbide (FG WC-Co) is one of the main research directions in the field of WC-Co over decades. Although it has long been recognized that FG WC-Co could outperform conventional homogeneous WC-Co owing to its potentially superior combinations of mechanical properties, until recently there has been a lack of effective and economical methods to make such materials. The lack of the technology has prevented the manufacturing and industrial applications of FG WC-Co from becoming a reality. This dissertation is a comprehensive study of an innovative atmosphere heat treatment process for producing FG WC-Co with a surface cobalt compositional gradient. The process exploited a triple phase field in W-C-Co phase diagram among three phases (solid WC, solid Co, and liquid Co) and the dependence of the migration of liquid Co on temperature and carbon content. WC-Co with a graded surface cobalt composition can be achieved by controlling the diffusion of carbon transported from atmosphere during sintering or during postsintering heat treatment. The feasibility of the process was validated by the successful preparations of FG WC-Co via both carburization and decarburization process following conventional liquid phase sintering. A study of the carburization process was undertaken to further understand and quantitatively modeled this process. The effects of key processing parameters (including heat treating temperature, atmosphere, and time) and key materials variables (involving Co content, WC grain size, and addition of grain growth inhibitors) on the formation of Co gradients were examined. Moreover, a carbon-diffusion controlled kinetic model was developed for simulating the formation of the gradient during the process. The parameters involved in this model were determined by thermodynamic calculations and regression-fit of simulation results with experimental data. In summary, this research first demonstrated the principle of the approach
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.
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. Copyright © 2014 Elsevier Inc. All rights reserved.
Spatial Patterns of Airborne Exposures of Tungsten and Cobalt in Fallon, Nevada, From Lichens and Surface Sediments

NASA Astrophysics Data System (ADS)

Sheppard, P. R.; Speakman, R. J.; Ridenour, G.; Glascock, M. D.; Farris, C.; Witten, M. L.

2005-12-01

This paper describes spatial patterns of airborne exposures of heavy metals in Fallon, Nevada, where a cluster of childhood leukemia has been on-going since 1997. Lichen chemistry, the measurement and interpretation of element concentrations in lichens, and surface sediment chemistry were used. Lichens were collected from within as well as from well outside of Fallon. Surface sediments were collected in a gridded spatial pattern, also within and outside of Fallon. Both the lichen and the surface sediment samples were measured chemically for a large suite of metals and other elements. Lichens indicate that Fallon itself has a high dual airborne exposure of tungsten and cobalt relative to sites well away from the town. Surface sediments samples also show high peaks of tungsten and cobalt within Fallon with nothing more than background contents away from the town. The tungsten and cobalt peaks coincide spatially with one another, with the highest values located right at a "hard-metal" facility that processes these metals. This present research confirms earlier research on total suspended particulates showing that Fallon is distinct in Nevada for its high dual exposure of airborne tungsten and cobalt and that the source of these two metals can be pinpointed to the hard-metal industry that exists just north of Highway 50 and west of Highway 95. While it is still not possible to conclude that high airborne exposure of tungsten and/or cobalt causes childhood leukemia, it can now be concluded beyond reasonable doubt that Fallon is unique environmentally due to its high airborne concentrations of tungsten and cobalt. Given that Fallon's cluster of childhood leukemia is the "most convincing cluster ever reported," it stands to reason that additional biomedical research should directly test the leukogenecity of combined airborne exposures of tungsten and cobalt.
Synthesis Functional and Constructional Nanomaterials on a Basis Carbide Tungsten, Molybdenum and Metals of a Triad of Iron in Ionic Melts

NASA Astrophysics Data System (ADS)

Kushkhov, H. B.; Adamokova, M. N.; Kvashin, V. A.; Kardanov, A. L.

2011-04-01

Single and cyclic voltammetry is used to study the electrode processes that occur during electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal in tungstate and tungstate-carbonate Na2WO4-Li2WO4-Li2CO3 (5.0-22.0 wt %) melts. The conditions of bringing the electroprecipitation potentials of tungsten, carbon, and an iron triad metal into coincidence are determined.
Numerical simulation and experiment on split tungsten carbide cylinder of high pressure apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yunfei; Li, Mingzhe, E-mail: limz@jlu.edu.cn; Wang, Bolong

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.more » 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.« less
The effect of plasma impurities on the sputtering of tungsten carbide

NASA Astrophysics Data System (ADS)

Vörtler, K.; Björkas, C.; Nordlund, K.

2011-03-01

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 WxCy molecule sputtering. We found that this molecule sputtering mechanism is of physical origin.
Genotoxic Changes to Rodent Cells Exposed in Vitro to Tungsten, Nickel, Cobalt and Iron

PubMed Central

Bardack, Stephanie; Dalgard, Clifton L.; Kalinich, John F.; Kasper, Christine E.

2014-01-01

Tungsten-based materials have been proposed as replacements for depleted uranium in armor-penetrating munitions and for lead in small-arms ammunition. A recent report demonstrated that a military-grade composition of tungsten, nickel, and cobalt induced a highly-aggressive, metastatic rhabdomyosarcoma when implanted into the leg muscle of laboratory rats to simulate a shrapnel wound. The early genetic changes occurring in response to embedded metal fragments are not known. In this study, we utilized two cultured rodent myoblast cell lines, exposed to soluble tungsten alloys and the individual metals comprising the alloys, to study the genotoxic effects. By profiling cell transcriptomes using microarray, we found slight, yet distinct and unique, gene expression changes in rat myoblast cells after 24 h metal exposure, and several genes were identified that correlate with impending adverse consequences of ongoing exposure to weapons-grade tungsten alloy. These changes were not as apparent in the mouse myoblast cell line. This indicates a potential species difference in the cellular response to tungsten alloy, a hypothesis supported by current findings with in vivo model systems. Studies examining genotoxic-associated gene expression changes in cells from longer exposure times are warranted. PMID:24619124
Effect of metallic coating on the properties of copper-silicon carbide composites

NASA Astrophysics Data System (ADS)

Chmielewski, M.; Pietrzak, K.; Teodorczyk, M.; Nosewicz, S.; Jarząbek, D.; Zybała, R.; Bazarnik, P.; Lewandowska, M.; Strojny-Nędza, A.

2017-11-01

In the presented paper a coating of SiC particles with a metallic layer was used to prepare copper matrix composite materials. The role of the layer was to protect the silicon carbide from decomposition and dissolution of silicon in the copper matrix during the sintering process. The SiC particles were covered by chromium, tungsten and titanium using Plasma Vapour Deposition method. After powder mixing of components, the final densification process via Spark Plasma Sintering (SPS) method at temperature 950 °C was provided. The almost fully dense materials were obtained (>97.5%). The microstructure of obtained composites was studied using scanning electron microscopy as well as transmission electron microscopy. The microstructural analysis of composites confirmed that regardless of the type of deposited material, there is no evidence for decomposition process of silicon carbide in copper. In order to measure the strength of the interface between ceramic particles and the metal matrix, the micro tensile tests have been performed. Furthermore, thermal diffusivity was measured with the use of the laser pulse technique. In the context of performed studies, the tungsten coating seems to be the most promising solution for heat sink application. Compared to pure composites without metallic layer, Cu-SiC with W coating indicate the higher tensile strength and thermal diffusitivy, irrespective of an amount of SiC reinforcement. The improvement of the composite properties is related to advantageous condition of Cu-SiC interface characterized by well homogenity and low porosity, as well as individual properties of the tungsten coating material.
Thermally Deposited Palladium-Tungsten Carbide and Platinum-Tungsten Carbide Counter Electrodes for a High Performance Dye-Sensitized Solar Cell Based on Organic T-/T₂ Electrolyte.

PubMed

Towannang, Madsakorn; Thiangkaew, Anongnad; Maiaugree, Wasan; Ratchaphonsaenwong, Kunthaya; Jarernboon, Wirat; Pimanpang, Samuk; Amornkitbamrung, Vittaya

2018-02-01

Tungsten carbide (WC) particles (~1 μm) were dispersed in DI water and dropped onto conductive glass. The resulting WC films were used as dye-sensitized solar cell (DSSC) counter electrodes. The performance of the WC DSSC based on the organic thiolate/disulfide (T-/T2) electrolyte was ~0.78%. The cell efficiency was greatly improved after decorating palladium (Pd) or platinum (Pt) nanoparticles on WC particles with a promising efficiency of ~2.15% for Pd-WC DSSC and ~4.62% for Pt-WC DSSC. The efficiency improvement of the composited (Pd-WC and Pt-WC) cells is attributed to co-functioning catalysts, the large electrode interfacial area and a low charge-transfer resistance at the electrolyte/counter electrode interface.
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.
Comparison of nickel, cobalt, palladium, and tungsten Schottky contacts on n-4H-silicon carbide

NASA Astrophysics Data System (ADS)

Gora, V. E.; Chawanda, A.; Nyamhere, C.; Auret, F. D.; Mazunga, F.; Jaure, T.; Chibaya, B.; Omotoso, E.; Danga, H. T.; Tunhuma, S. M.

2018-04-01

We have investigated the current-voltage (I-V) characteristics of nickel (Ni), cobalt (Co), tungsten (W) and palladium (Pd) Schottky contacts on n-type 4H-SiC in the 300-800 K temperature range. Results extracted from I-V measurements of Schottky barrier diodes showed that barrier height (ФBo) and ideality factor (n) were strongly dependent on temperature. Schottky barrier heights for contacts of all the metals showed an increase with temperature between 300 K and 800 K. This was attributed to barrier inhomogeneities at the interface between the metal and the semiconductor, which resulted in a distribution of barrier heights at the interface. Ideality factors of Ni, Co and Pd decreased from 1.6 to 1.0 and for W the ideality factor decreased from 1.1 to 1.0 when the temperature was increased from 300 K to 800 K respectively. The device parameters were compared to assess advantages and disadvantages of the metals for envisaged applications.
Tungsten carbide nanorods with zirconium dioxide composite for low cost with high efficiency Pt-free counter electrode in dye sensitized solar cell

NASA Astrophysics Data System (ADS)

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

2018-04-01

Tungsten carbide nanorods/Zirconium dioxide (WC-NRs/ZrO2) composite material was used as a counter electrode (CE) for efficient dye-sensitized solar cell (DSSC) fabrication. The prepared WC-NRs/ZrO2 (N-Methyl-2-pyrrolidone (NMP)/2-Propanol) gel is drop casted on the FTO substrate for CE. The morphological analysis was confirmed by FESEM and TEM. Nyquist plot clearly indicates that the NMP based WC-NRs/ZrO2 CE possesses high electrocatalytic activity and faster charge-transfer ability for the reduction of I3- due to the lower charge transfer resistance. The fabricated WC-NRs/ZrO2 (NMP) composite CE is demonstrated with high power conversion efficiency (PCE) of 6.63% in comparison to the WC-NRs/ZrO2 (2-propanol) CE of 2.29% under same conditions.
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.
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.
Electrochemical Dissolution of Tungsten Carbide in NaCl-KCl-Na2WO4 Molten Salt

NASA Astrophysics Data System (ADS)

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

2018-02-01

Tungsten carbide was utilized as anode to extract tungsten in a NaCl-KCl-Na2WO4 molten salt, and the electrochemical dissolution was investigated. Although the molten salt electrochemical method is a short process method of tungsten extraction from tungsten carbide in one step, the dissolution efficiency and current efficiency are quite low. In order to improve the dissolution rate and current efficiency, the sodium tungstate was added as the active substance. The dissolution rate, the anode current efficiency, and the cathode current efficiency were calculated with different contents of sodium tungstate addition. The anodes prior to and following the reaction, as well as the product, were analyzed through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The results demonstrated that the sodium tungstate could improve the dissolution rate and the current efficiency, due to the addition of sodium tungstate decreasing the charge transfer resistance in the electrolysis system. Due to the fact that the addition of sodium tungstate could remove the carbon during electrolysis, pure tungsten powders with 100 nm diameter were obtained when the content of sodium tungstate was 1.0 pct.
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.
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.
40 CFR 721.10599 - Calcium cobalt lead titanium tungsten oxide.

Code of Federal Regulations, 2013 CFR

2013-07-01

... systems). (iii) Release to water. Requirements as specified in § 721.90 (a)(4), (b)(4), and (c)(4) (Where N=8, and 8 is an aggregate of releases for the following substances: Lead strontium titanium...-271; CAS No. 1262279-31-1); Calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS...

40 CFR 721.10599 - Calcium cobalt lead titanium tungsten oxide.

Code of Federal Regulations, 2014 CFR

2014-07-01

... systems). (iii) Release to water. Requirements as specified in § 721.90 (a)(4), (b)(4), and (c)(4) (Where N=8, and 8 is an aggregate of releases for the following substances: Lead strontium titanium...-271; CAS No. 1262279-31-1); Calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS...
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.
Interdependence between electrical and magnetic properties of polycrystalline cobalt-substituted tungsten bronze multiferroic ceramics

NASA Astrophysics Data System (ADS)

Jindal, Shilpi; Devi, Sheela; Vasishth, Ajay; Batoo, Khalid Mujasam; Kumar, Gagan

Polycrystalline cobalt-substituted tungsten bronze ferroelectric ceramics with chemical composition Ba5CaTi2-xCoXNb8O30 (x=0.00, 0.02, 0.04 and 0.08) were synthesized by solid state reaction technique. X-ray diffraction (XRD) technique was used to confirm the phase formation and it revealed the formation of single phase tetragonal structure with space group P4bm. The surface morphology of the samples was studied by using the scanning electron microscopy (SEM) technique. The dielectric properties such as dielectric constant and dielectric loss have been investigated as a function of temperature and frequency. The P-E and M-H studies confirmed the coexistent of ferroelectricity and magnetism at room temperature. The P-E loop study indicated an increase in the coercive field while the M-H study depicted a decrease in the magnetization with the incorporation of cobalt ions.
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%).
Evaluation of Analysis Conditions for Laser-Pulsed Atom Probe Tomography: Example of Cemented Tungsten Carbide.

PubMed

Peng, Zirong; Choi, Pyuck-Pa; Gault, Baptiste; Raabe, Dierk

2017-04-01

Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAPTM 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAPTM 5000 XS system.
Diffusion Bonding Technology of Tungsten and SiC/SiC Composites for Nuclear Applications

NASA Astrophysics Data System (ADS)

Kishimoto, Hirotatsu; Shibayama, Tamaki; Abe, Takahiro; Shimoda, Kazuya; Kawamura, Satoshi; Kohyama, Akira

2011-10-01

Silicon carbide (SiC) is a candidate for the structural material in the next generation nuclear plants. Use of SiC/SiC composites is expected to increase the operation temperature of system over 1000 °C. For the high temperature system, refractory metals are planned to be used for several components. Tungsten is a candidate of armor on the divertor component in fusion, and is planned to be used for an upper-end plug of SiC/SiC fuel pin in a Gas cooled Fast Reactor (GFR). Joining technique of the SiC/SiC composites and tungsten is an important issue for nuclear systems in future. Nano-Infiltration and Transient Eutectoid (NITE) method is able to provide dense stable and high strength SiC/SiC composites having high resistance against pressure at elevated temperature, a diffusion bonding technique is usable to join the materials. Present research produces a NITE-SiC/SiC composite and tungsten as the similar dimension as a projected cladding tube of fuel pin for GFR using diffusion bonding, and investigated microstructure and mechanical properties.
Interface reactions between silicon carbide and interlayers in silicon carbide copper metal matrix composites

NASA Astrophysics Data System (ADS)

Köck, T.; Brendel, A.; Bolt, H.

2007-05-01

Novel copper matrix composites reinforced with silicon carbide fibres are considered as a new generation of heat sink materials for the divertor of future fusion reactors. The divertor is exposed to intense particle bombardment and heat loads of up to 15 MW m-2. This component consists of the plasma-facing material which is bonded to the actively cooled heat sink. Due to its high thermal conductivity of about 400 W m-1 K-1 copper is a promising material for the heat sink. To increase the mechanical properties of copper at working temperature (823 K), silicon carbide fibres with a diameter of 140 μm are used to reinforce the interface area between the plasma-facing material and the heat sink. Push-out tests show that the adhesion between SiC fibre and Cu matrix without any interlayer is very low. To increase the fibre-matrix bonding the fibres are coated with Cr and W with a thickness of 300-400 nm before Cu deposition by magnetron sputtering. Push-out tests on these modified fibres show a significant increase in adhesion compared to the fibres without interlayer. XRD investigations after a heat treatment at 923 K show a chromium carbide (Cr23C6, Cr3C2) formation and the absence of chromium silicides. In the case of a W interlayer a W2C formation is detected and also no tungsten silicides. Single-fibre tensile tests were performed to investigate the influence of the reaction zone on the ultimate tensile strength of the fibres. The ultimate tensile strength for fibres without interlayer remains constant at about 2200 MPa after annealing at 923 K. The fibres with chromium and tungsten interlayers, respectively, show a decrease of about 30% of the ultimate tensile strength after the heat treatment at 923 K.
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.
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.
Penetration of tungsten-alloy rods into composite ceramic targets: Experiments and 2-D simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenberg, Z.; Dekel, E.; Hohler, V.

1998-07-10

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.
Impact of temperature during He+ implantation on deuterium retention in tungsten, tungsten with carbon deposit and tungsten carbide

NASA Astrophysics Data System (ADS)

Oya, Yasuhisa; Sato, Misaki; Li, Xiaochun; Yuyama, Kenta; Fujita, Hiroe; Sakurada, Shodai; Uemura, Yuki; Hatano, Yuji; Yoshida, Naoaki; Ashikawa, Naoko; Sagara, Akio; Chikada, Takumi

2016-02-01

Temperature dependence on deuterium (D) retention for He+ implanted tungsten (W) was studied by thermal desorption spectroscopy (TDS) to evaluate the tritium retention behavior in W. The activation energies were evaluated using Hydrogen Isotope Diffusion and Trapping (HIDT) simulation code and found to be 0.55 eV, 0.65 eV, 0.80 eV and 1.00 eV. The heating scenarios clearly control the D retention behavior and, dense and large He bubbles could work as a D diffusion barrier toward the bulk, leading to D retention enhancement at lower temperature of less than 430 K, even if the damage was introduced by He+ implantation. By comparing the D retention for W, W with carbon deposit and tungsten carbide (WC), the dense carbon layer on the surface enhances the dynamic re-emission of D as hydrocarbons, and induces the reduction of D retention. However, by He+ implantation, the D retention was increased for all the samples.
High-temperature properties of joint interface of VPS-tungsten coated CFC

NASA Astrophysics Data System (ADS)

Tamura, S.; Liu, X.; Tokunaga, K.; Tsunekawa, Y.; Okumiya, M.; Noda, N.; Yoshida, N.

2004-08-01

Tungsten coated carbon fiber composite (CFC) is a candidate material for the high heat flux components in fusion reactors. In order to investigate the high-temperature properties at the joint interface of coating, heat load experiments by using electron beam were performed on VPS-tungsten coated CX-2002U samples. After the heat load test for 3.6 ks at 1400 °C, tungsten-rhenium multilayer (diffusion barrier for carbon) at the joint interface of coating was observed clearly. But, at the temperatures above 1600 °C, the multilayer was disappeared and a tungsten carbide layer was formed in the VPS-tungsten coating. At the temperatures below 1800 °C, the thickness of this layer logarithmically increased with increasing its loading time. At 2000 °C, the growth of the tungsten carbide layer was proportional to the square root of loading time. These results indicate that the diffusion barrier for carbon is not expected to suppress the carbide formation at the joint interface of the VPS-tungsten coating above 1600 °C.
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.
Gleeble Testing of Tungsten Samples

DTIC Science & Technology

2013-02-01

as a diffusion barrier to prevent the tungsten samples from fusing to the tungsten carbide inserts at elevated temperatures. After the anvils were...anvils with removable tungsten carbide inserts. The inserts were 19.05 mm (0.75 in) in diameter and 25.4 mm (1 in) long; they were purchased from...rhenium are shown in tables 6 and 7 and figure 7. The sample tested at 1300 °C, T4, partially embedded into the tungsten carbide (WC) inserts during
Molecular dynamics simulations of hydrogen bombardment of tungsten carbide surfaces

NASA Astrophysics Data System (ADS)

Träskelin, P.; Juslin, N.; Erhart, P.; Nordlund, K.

2007-05-01

The interaction between energetic hydrogen and tungsten carbide (WC) is of interest both due to the use of hydrogen-containing plasmas in thin-film manufacturing and due to the presence of WC in the divertor of fusion reactors. In order to study this interaction, we have carried out molecular dynamics simulations of the low-energy bombardment of deuterium impinging onto crystalline as well as amorphous WC surfaces. We find that prolonged bombardment leads to the formation of an amorphous WC surface layer, regardless of the initial structure of the WC sample. Loosely bound hydrocarbons, which can erode by swift chemical sputtering, are formed at the surface. Carbon-terminated surfaces show larger sputtering yields than tungsten-terminated surfaces. In both cumulative and noncumulative simulations, C is seen to sputter preferentially. Implications for mixed material erosion in ITER are discussed.
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.
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.
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.
First principles study of hydrogen behaviors in hexagonal tungsten carbide

NASA Astrophysics Data System (ADS)

Kong, Xiang-Shan; You, Yu-Wei; Liu, C. S.; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.

2011-11-01

Understanding the behaviors of hydrogen in hexagonal tungsten carbide (WC) is of particular interest for fusion reactor design due to the presence of WC in the divertor of fusion reactors. Here, we have used first principles calculations to study the hydrogen behavior in WC. It is found that the most stable interstitial site for the hydrogen atom is the projection of the octahedral interstitial site on tungsten basal plane, followed by the site near the projection of the octahedral interstitial site on carbon basal plane. The binding energy between two interstitial hydrogen atoms is negative, suggesting that hydrogen itself is not capable of trapping another hydrogen atoms to form hydrogen molecule. The calculated results on the interaction between hydrogen and vacancy indicate that hydrogen atom is preferably trapped by vacancy defects and hydrogen molecule can not be formed in mono-vacancy. In addition, the hydrogen atom bound to carbon is only found in tungsten vacancy. We also study the migrations of hydrogen in WC and find that the interstitial hydrogen atom prefers to diffuse along the c-axis. Our studies provide some explanations for the results of the thermal desorption process of energetic hydrogen ion implanted into WC.
Ductilisation of tungsten (W): Tungsten laminated composites

DOE PAGES

Reiser, Jens; Garrison, Lauren M.; Greuner, Henri; ...

2017-08-02

Here we elucidate the mechanisms of plastic deformation and fracture of tungsten laminated composites. Furthermore our results suggest that the mechanical response of the laminates is governed by the plastic deformation of the tungsten plies. In most cases, the impact of the interlayer is of secondary importance.

Characteristics of ZrC/Ni-UDD coatings for a tungsten carbide cutting tool

NASA Astrophysics Data System (ADS)

Chayeuski, V. V.; Zhylinski, V. V.; Rudak, P. V.; Rusalsky, D. P.; Višniakov, N.; Černašėjus, O.

2018-07-01

This work deals with the features of the structure of combined ZrC/Ni-ultradisperse diamonds (UDD) coating synthesized by electroplating and cathode arc evaporation physical vapor deposition (CAE-PVD) techniques on the tungsten carbide WC - 2 wt% Co on cutting inserts to improve tool life. The microstructure, phase composition, and micro-scratch test analysis of the ZrC/Ni-UDD coating were studied. The ZrC/Ni-UDD coating consists of separate phases of zirconium carbide ZrC, α-Ni, and Ni-UDD phase. The surface morphology of the coating shows a pattern with pits, pores, and particles. Separated nanodiamond particles are present in the pores of the combined coating. Therefore, the structure of the bottom layer of Ni-UDD affects the morphology of the surface of the ZrC/Ni-UDD coating. The obtained value of the critical loads on the scratch track of the coating in 26 N proves a sufficiently high value of the adhesion strength of the intermediate Ni-UDD-layer with hard alloy of WC-Co substrate. Due to their unique structure ZrC/Ni-UDD-coatings can be used to increase the durability period of a wood-cutting milling tool for cutting chipboard by CNC machines.
M(2)C Carbide Precipitation in Martensitic Cobalt - Steels.

NASA Astrophysics Data System (ADS)

Montgomery, Jonathan Scott

1990-01-01

M_2C carbide precipitation was investigated in martensitic Co-Ni steels, including the commercial AF1410 steel and a series of higher-strength model alloys. Results of TEM (from both thin foils and extraction replicas) and X-ray diffraction were combined with results of collaborative SANS and APFIM studies to determine phase fractions, compositions, and lattice parameters throughout precipitation, including estimation of carbide initial critical nucleus properties. The composition dependence of the M_2C lattice parameters was modelled to predict the composition-dependent transformation eigen-strains for coherent precipitation; this was input into collaborative numerical calculations of both the coherent carbide elastic self energy and the dislocation interaction energy during heterogeneous precipitation. The observed overall precipitation behavior is consistent with theoretically-predicted behavior at high supersaturations where nucleation and coarsening compete such that the average particle size remains close to the critical size as supersaturation drops. However, the coarsening in this system follows a t^{1over 5} rate law consistent with heterogeneous precipitation on dislocations. Initial precipitation appears to be coherent, the carbides tending toward a rod shape with major axis oriented along the minimum principal strain direction. At initial nucleation, particles are Fe-rich and C-deficient, diminishing the transformation eigenstrains to a near invariant-line strain condition. The observed relation between carbide volume fraction and the shape -dependent capillarity parameter partialS/ partialV implies a coherency loss transition in AF1410 reached at 8hr tempering at 510 ^circC. The precipitation in AF1410 at 510^ circC exhibits a "renucleation" phenomenon in which a second stage of nucleation occurs beyond the precipitation half-completion time (1-2hrs). It appears that the carbide composition during precipitation follows a trajectory of increasing
Superficial roughness on composite surface, composite-enamel and composite-dentin junctions after different finishing and polishing procedures. Part II: roughness with diamond finishing and differences between enamel composite vs body composite.

PubMed

Ferraris, Federico; Conti, Alessandro

2014-01-01

The following study asks three principle questions relative to composite finishing and composite polishing: 1) Will the superficial roughness of different restoration surfaces have different values, utilizing the same polishing system (multistep), after finishing with the tungsten carbide or diamond bur? 2) Under the same conditions of finishing and polishing sequences, will the composite surfaces (C), the composite-enamel (CE) and composite-dentin (CD) interfaces show different roughness values? 3) Will the surface roughness of composites of different translucency in the various phases of finishing and polishing, and on different interfaces, have different results? The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations when polishing, after finishing with tungsten carbide or diamond burs. Furthermore, the null hypothesis is that there are no significant differences on roughness between polishing on composite surface, composite-enamel and composite-dentin interfaces, and finally there are no differences on roughness after finishing and polishing of two composite with different translucency. For the study, 56 class V cavities were prepared on extracted teeth. Restorations were done in nanofilled composite Filtek XTE (3M Espe) in a standard fashion, and then finished and polished. The 28 buccal cavities were restored on the surface with composite enamel and the 28 palatals with composite body. Finishing was done with fine toothing burs in tungsten carbide (16 blades) or fine grit diamond burs (46 μm), and made by the same manufacturer (Komet). The second phase of finishing was done with burs (with the same form as already mentioned) ultrafine toothing tungsten carbide (30 blades) or with extra and ultrafine grit diamond (25 and 8 μm). The polishing phase for both of the earlier sequences was done with the application of three rubber tips with decreasing abrasiveness and an application with a
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.
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.
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.m^1/2. 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.
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.
Irradiation effects in tungsten-copper laminate composite

DOE PAGES

Garrison, L. M.; Katoh, Yutai; Snead, Lance L.; ...

2016-09-19

Tungsten-copper laminate composite has shown promise as a structural plasma-facing component as compared to tungsten rod or plate. The present study evaluated the tungsten-copper composite after irradiation in the High Flux Isotope Reactor (HFIR) at temperatures of 410–780 °C and fast neutron fluences of 0.02–9.0 × 10 25 n/m 2, E > 0.1 MeV, 0.0039–1.76 displacements per atom (dpa) in tungsten. Tensile tests were performed on the composites, and the fracture surfaces were analyzed with scanning electron microscopy. Before irradiation, the tungsten layers had brittle cleavage failure, but the overall composite had 15.5% elongation at 22 °C. After only 0.0039more » dpa this was reduced to 7.7% elongation, and no ductility was observed after 0.2 dpa at all irradiation temperatures when tensile tested at 22 °C. In conclusion, tor elevated temperature tensile tests after irradiation, the composite only had ductile failure at temperatures where the tungsten was delaminating or ductile.« less
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.
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.
Changes of composition and microstructure of joint interface of tungsten coated carbon by high heat flux

NASA Astrophysics Data System (ADS)

Tokunaga, K.; Matsubara, T.; Miyamoto, Y.; Takao, Y.; Yoshida, N.; Noda, N.; Kubota, Y.; Sogabe, T.; Kato, T.; Plöchl, L.

2000-12-01

Tungsten coatings of 0.5 and 1 mm thickness were successfully deposited by the vacuum plasma spraying (VPS) technique on carbon/carbon fiber composite (CFC), CX-2002U and isotropic fine grained graphite, IG-430U. High heat flux experiments by irradiation of electron beam with uniform profile were performed on the coated samples in order to prove the suitability and load limit of such coating materials. The cross-sectional composition and structure of the interface of VPS-W and carbon material samples were investigated. Compositional analyses showed that the Re/W multi-layer acts as diffusion barrier for carbon and suppresses tungsten carbide formation in the VPS-W layer at high temperature about 1300°C. Microstructure of the joint interface of the sample changed in the case of a peak temperature of about 2800°C. The multi-layer structure completely disappeared and compositional distribution was almost uniform in the interface of the sample after melting and resolidification. The diffusion barrier for carbon is not expected to act in this stage.
Dispersion of Cobalt Nanoparticles on Nanowires Grown on Silicon Carbide-Alumina Nanocomposites.

PubMed

Kim, Inho; Seo, Kyeong Won; Ahn, Byoung Sung; Moon, Dong Ju; Kim, Sang Woo

2017-04-01

Silicon carbide-alumina nanocomposite supports including a nanowire architecture for a high dispersion of cobalt nanocatalysts were fabricated using a modified sol–gel process and paste extrusion process to form cylindrical shape beads, followed by thermal treatment. Well-developed aluminosilicate nanowires were formed on a nanoporous support, which are grown from a catalytic metal seed at the nanowire growth tips during heat treatment at 1,100 °C for 1 h under nitrogen gas flow. Cobalt oxide precursors were highly dispersed on the nanowires grown on the surface of the nanoporous bodies through a supercritical carbon dioxide fluid-assisted wet-impregnation process. The highly-dispersed Co nanoparticles with size of less than 10 nm were finally obtained on the nanowires via phase transitions from Co₃O₄ to CoO and from CoO to Co during the thermal reduction.
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.
Armor-Piercing Shot Processed from Molybdenum Bearing Tungsten Carbide

DTIC Science & Technology

1959-03-01

study were of the same contour aa WC cores employed in all previous scale model terminal ballistic studies of the effect of core composition on...Pennsylvania, by cold pressing and sintering techniques from their composition WS12. This composition is reduced from low grade western ores without the...removal of Mo and results in a product of the following composition after the tungsten is carburized and the binder is added: WC 87.4% Co. 12% Mo
Frictional Performance Assessment of Cemented Carbide Surfaces Textured by Laser

NASA Astrophysics Data System (ADS)

Fang, S.; Llanes, L.; Klein, S.; Gachot, C.; Rosenkranz, A.; Bähre, D.; Mücklich, F.

2017-10-01

Cemented carbides are advanced engineering materials often used in industry for manufacturing cutting tools or supporting parts in tribological system. In order to improve service life, special attention has been paid to change surface conditions by means of different methods, since surface modification can be beneficial to reduce the friction between the contact surfaces as well as to avoid unintended damage. Laser surface texturing is one of the newly developed surface modification methods. It has been successfully introduced to fabricate some basic patterns on cemented carbide surfaces. In this work, Direct Laser Interference Patterning Technique (DLIP) is implemented to produce special line-like patterns on a cobalt (Co) and nickel (Ni) based cemented tungsten carbide grade. It is proven that the laser-produced patterns have high geometrical precision and quality stability. Furthermore, tribology testing using a nano-tribometer unit shows that friction is reduced by the line-like patterns, as compared to the polished one, under both lubricated and dry testing regimes, and the reduction is more pronounced in the latter case.
Occupational Exposure to Cobalt and Tungsten in the Swedish Hard Metal Industry: Air Concentrations of Particle Mass, Number, and Surface Area

PubMed Central

Bryngelsson, Ing-Liss; Pettersson, Carin; Husby, Bente; Arvidsson, Helena; Westberg, Håkan

2016-01-01

Exposure to cobalt in the hard metal industry entails severe adverse health effects, including lung cancer and hard metal fibrosis. The main aim of this study was to determine exposure air concentration levels of cobalt and tungsten for risk assessment and dose–response analysis in our medical investigations in a Swedish hard metal plant. We also present mass-based, particle surface area, and particle number air concentrations from stationary sampling and investigate the possibility of using these data as proxies for exposure measures in our study. Personal exposure full-shift measurements were performed for inhalable and total dust, cobalt, and tungsten, including personal real-time continuous monitoring of dust. Stationary measurements of inhalable and total dust, PM2.5, and PM10 was also performed and cobalt and tungsten levels were determined, as were air concentration of particle number and particle surface area of fine particles. The personal exposure levels of inhalable dust were consistently low (AM 0.15mg m−3, range <0.023–3.0mg m−3) and below the present Swedish occupational exposure limit (OEL) of 10mg m−3. The cobalt levels were low as well (AM 0.0030mg m−3, range 0.000028–0.056mg m−3) and only 6% of the samples exceeded the Swedish OEL of 0.02mg m−3. For continuous personal monitoring of dust exposure, the peaks ranged from 0.001 to 83mg m−3 by work task. Stationary measurements showed lower average levels both for inhalable and total dust and cobalt. The particle number concentration of fine particles (AM 3000 p·cm−3) showed the highest levels at the departments of powder production, pressing and storage, and for the particle surface area concentrations (AM 7.6 µm2·cm−3) similar results were found. Correlating cobalt mass-based exposure measurements to cobalt stationary mass-based, particle area, and particle number concentrations by rank and department showed significant correlations for all measures except for particle
Assessment of Erosion Resistance of Coated Polymer Matrix Composites for Propulsion Applications

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

2004-01-01

The erosion behavior of tungsten carbide-cobalt (WC-Co) coated and uncoated polymer matrix composites (PMCs) was examined with solid particle impingement using air jets. Erosion tests were conducted with Arizona road dust impinging at 20 degrees, 60 degrees, and 90 degrees angles at a velocity of 229 meters per second at both 294 and 366 K. Noncontact optical profilometry was used to measure the wear volume loss. Results indicate that the WC-Co coating enhanced erosion resistance and reduced erosion wear volume loss by a factor of nearly 2. This should contribute to longer wear lives, reduced related breakdowns, decreased maintenance costs, and increased product reliability.
Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, Joachim H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1450.degree. C. for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.
Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOEpatents

Schneibel, J.H.

1997-06-10

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.
Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, J.H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Silicon nitride/silicon carbide composite densified materials prepared using composite powders

DOEpatents

Dunmead, S.D.; Weimer, A.W.; Carroll, D.F.; Eisman, G.A.; Cochran, G.A.; Susnitzky, D.W.; Beaman, D.R.; Nilsen, K.J.

1997-07-01

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.
Method of making metal matrix composites reinforced with ceramic particulates

DOEpatents

Cornie, James A.; Kattamis, Theodoulos; Chambers, Brent V.; Bond, Bruce E.; Varela, Raul H.

1989-01-01

Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys.
Method of making metal matrix composites reinforced with ceramic particulates

DOEpatents

Cornie, J.A.; Kattamis, T.; Chambers, B.V.; Bond, B.E.; Varela, R.H.

1989-08-01

Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys. 2 figs.
Development and characterization of powder metallurgically produced discontinuous tungsten fiber reinforced tungsten composites

NASA Astrophysics Data System (ADS)

Mao, Y.; Coenen, J. W.; Riesch, J.; Sistla, S.; Almanstötter, J.; Jasper, B.; Terra, A.; Höschen, T.; Gietl, H.; Bram, M.; Gonzalez-Julian, J.; Linsmeier, Ch; Broeckmann, C.

2017-12-01

In future fusion reactors, tungsten is the prime candidate material for the plasma facing components. Nevertheless, tungsten is prone to develop cracks due to its intrinsic brittleness—a major concern under the extreme conditions of fusion environment. To overcome this drawback, tungsten fiber reinforced tungsten (Wf/W) composites are being developed. These composite materials rely on an extrinsic toughing principle, similar to those in ceramic matrix composite, using internal energy dissipation mechanisms, such as crack bridging and fiber pull-out, during crack propagation. This can help Wf/W to facilitate a pseudo-ductile behavior and allows an elevated damage resilience compared to pure W. For pseudo-ductility mechanisms to occur, the interface between the fiber and matrix is crucial. Recent developments in the area of powder-metallurgical Wf/W are presented. Two consolidation methods are compared. Field assisted sintering technology and hot isostatic pressing are chosen to manufacture the Wf/W composites. Initial mechanical tests and microstructural analyses are performed on the Wf/W composites with a 30% fiber volume fraction. The samples produced by both processes can give pseudo-ductile behavior at room temperature.
Micro/nano composited tungsten material and its high thermal loading behavior

NASA Astrophysics Data System (ADS)

Fan, Jinglian; Han, Yong; Li, Pengfei; Sun, Zhiyu; Zhou, Qiang

2014-12-01

Tungsten (W) is considered as promising candidate material for plasma facing components (PFCs) in future fusion reactors attributing to its many excellent properties. Current commercial pure tungsten material in accordance with the ITER specification can well fulfil the performance requirements, however, it has defects such as coarse grains, high ductile-brittle transition temperature (DBTT) and relatively low recrystallization temperature compared with its using temperature, which cannot meet the harsh wall loading requirement of future fusion reactor. Grain refinement has been reported to be effective in improving the thermophysical and mechanical properties of W. In this work, rare earth oxide (Y2O3/La2O3) and carbides (TiC/ZrC) were used as dispersion phases to refine W grains, and micro/nano composite technology with a process of "sol gel - heterogeneous precipitation - spray drying - hydrogen reduction - ordinary consolidation sintering" was invented to introduce these second-phase particles uniformly dispersed into W grains and grain-boundaries. Via this technology, fine-grain W materials with near-full density and relatively high mechanical properties compared with traditional pure W material were manufactured. Preliminary transient high-heat flux tests were performed to evaluate the thermal response under plasma disruption conditions, and the results show that the W materials prepared by micro/nano composite technology can endure high-heat flux of 200 MW/m2 (5 ms).
Method for producing silicon nitride/silicon carbide composite

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.

1996-07-23

Silicon carbide/silicon nitride composites are prepared by carbothermal reduction of crystalline silica powder, carbon powder and optionally crsytalline silicon nitride powder. The crystalline silicon carbide portion of the composite has a mean number diameter less than about 700 nanometers and contains nitrogen.
Qualification of tungsten coatings on plasma-facing components for JET

NASA Astrophysics Data System (ADS)

Maier, H.; Neu, R.; Greuner, H.; Böswirth, B.; Balden, M.; Lindig, S.; Matthews, G. F.; Rasinski, M.; Wienhold, P.; Wiltner, A.

2009-12-01

This contribution summarizes the work that has been performed to establish the industrial production of tungsten coatings on carbon fibre composite (CFC) for application within the ITER-like Wall Project at JET. This comprises the investigation of vacuum plasma-sprayed coatings, physical vapour deposited tungsten/rhenium multilayers, as well as coatings deposited by combined magnetron-sputtering and ion implantation. A variety of analysis tools were applied to investigate failures and oxide and carbide formation in these systems.
Cobalt carbide nanoprisms for direct production of lower olefins from syngas

NASA Astrophysics Data System (ADS)

Zhong, Liangshu; Yu, Fei; An, Yunlei; Zhao, Yonghui; Sun, Yuhan; Li, Zhengjia; Lin, Tiejun; Lin, Yanjun; Qi, Xingzhen; Dai, Yuanyuan; Gu, Lin; Hu, Jinsong; Jin, Shifeng; Shen, Qun; Wang, Hui

2016-10-01

Lower olefins—generally referring to ethylene, propylene and butylene—are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The ‘Fischer-Tropsch to olefins’ (FTO) process has long offered a way of producing lower olefins directly from syngas—a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.
Engineering Transition-Metal-Coated Tungsten Carbides for Efficient and Selective Electrochemical Reduction of CO2 to Methane.

PubMed

Wannakao, Sippakorn; Artrith, Nongnuch; Limtrakul, Jumras; Kolpak, Alexie M

2015-08-24

The design of catalysts for CO2 reduction is challenging because of the fundamental relationships between the binding energies of the reaction intermediates. Metal carbides have shown promise for transcending these relationships and enabling low-cost alternatives. Herein, we show that directional bonding arising from the mixed covalent/metallic character plays a critical role in governing the surface chemistry. This behavior can be described by consideration of individual d-band components. We use this model to predict efficient catalysts based on tungsten carbide with a sub-monolayer of iron adatoms. Our approach can be used to predict site-preference and binding-energy trends for complex catalyst surfaces. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Development and Performance of Boron Carbide-Based Smoke Compositions

DTIC Science & Technology

2013-03-06

DOI: 10.1002/prep.201200166 Development and Performance of Boron Carbide -Based Smoke Compositions Anthony P. Shaw,*[a] Jay C. Poret,[a] Robert A...volatilized and recondense to give smoke. Boron carbide was recognized as a pyrotechnic fuel many years ago, but it has since been overlooked. A 1961...Abstract : Pyrotechnic smoke compositions for visual ob- scuration containing boron carbide , potassium nitrate, po- tassium chloride, and various lubricants
Bearing-Foreign Material Deposition on Retrieved Co-Cr Femoral Heads: Composition and Morphology

PubMed Central

Tikekar, Nishant M.; Heiner, Anneliese D.; Baer, Thomas E.; Kruger, Karen M.; Callaghan, John J.; Brown, Thomas D.; Lannutti, John J.

2015-01-01

Bearing-foreign material deposition onto a femoral head can occur from contact with an acetabular shell due to dislocation, reduction, or subluxation. The purpose of this study was to comprehensively characterize deposit regions on retrieved cobalt-chrome femoral heads from metal-on-polyethylene total hip arthroplasties that had experienced such adverse events. The morphology, topography, and composition of deposition regions were characterized using macrophotography, optical profilometry, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. The deposit areas were relatively large, they were much rougher than the surrounding undamaged clean areas, and they displayed several distinct morphologies. Titanium alloy elements were the predominant constituents. Calcium and phosphorous were also detected within the deposit areas, in a composition that could nucleate abrasive hydroxyapatite. In addition, tungsten-rich particles, likely present as tungsten carbide, were observed on top of the titanium deposits. The increased roughness associated with these deposition features would be expected to accelerate damage and wear of the opposing liner and hence accelerate the development of osteolysis. PMID:26236744
Molybdenum disilicide composites reinforced with zirconia and silicon carbide

DOEpatents

Petrovic, John J.

1995-01-01

Compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.
Carbide coated fibers in graphite-aluminum composites

NASA Technical Reports Server (NTRS)

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1975-01-01

The study of protective-coupling layers of refractory metal carbides on the graphite fibers prior to their incorporation into composites is presented. Such layers should be directly wettable by liquid aluminum and should act as diffusion barriers to prevent the formation of aluminum carbide. Chemical vapor deposition was used to uniformly deposit thin, smooth, continuous coats of ZrC on the carbon fibers of tows derived from both rayon and polyacrylonitrile. A wet chemical coating of the fibers, followed by high-temperature treatment, was used, and showed promise as an alternative coating method. Experiments were performed to demonstrate the ability of aluminum alloys to wet carbide surfaces. Titanium carbide, zirconium carbide and carbide-coated graphite surfaces were successfully wetted. Results indicate that initial attempts to wet surfaces of ZrC-coated carbon fibers appear successful.
Rate & Microstructure Influence on Fracture of WC-Co/Ni Composites

NASA Astrophysics Data System (ADS)

Lamberson, Leslie

2017-06-01

Tungsten carbide metal matrix composites contain ceramic grains of tungsten carbide within a binder of cobalt (Co) or nickel (Ni), allowing the material to have advantageous properties of both metals and ceramics including higher resistance to fracture than most structural ceramics, and higher resistance to permanent deformation than most engineering metals. Due to these performance advantages, WC composites are of interest in drilling, manufacturing tools, and defense penetrator applications, to name a few. Under quasi-static conditions, these hardmetals have been shown to generally exhibit an increase in fracture toughness with an increase in mean free path in the binder phase, and an increase in hardness and wear resistance with a decrease in WC grain size; yet relatively little is known in regards to their dynamic response. Here we present the fracture behavior of WC metal matrix composites under three extreme loading conditions: (1) a single-strike acceleration loading to characterize classical dynamic crack tip energetics via stress intensity factors (SIFs) (2) the impact fatigue, or sub-catastrophic repetitive strikes to failure, and (3) the dynamic crack interactions with normal impact over 1 km/s using an in-house combustionless two-stage light-gas gun. All investigations are conducted using ultra high-speed imaging with full-field measurements from digital image correlation (DIC), and post-mortem scanning electron microscopy. Preliminary results for (1) show that the dynamic fracture toughness increases by a factor of 1.22 to 1.65 over quasi-static, regardless of the binder or grain size investigated. Supported by the American Chemical Society Petroleum Research Fund No. 55860-ND10.
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.
Recent advances and issues in development of silicon carbide composites for fusion applications

NASA Astrophysics Data System (ADS)

Nozawa, T.; Hinoki, T.; Hasegawa, A.; Kohyama, A.; Katoh, Y.; Snead, L. L.; Henager, C. H., Jr.; Hegeman, J. B. J.

2009-04-01

Radiation-resistant advanced silicon carbide (SiC/SiC) composites have been developed as a promising candidate of the high-temperature operating advanced fusion reactor. With the completion of the 'proof-of-principle' phase in development of 'nuclear-grade' SiC/SiC composites, the R&D on SiC/SiC composites is shifting toward the more pragmatic phase, i.e., industrialization of component manufactures and data-basing. In this paper, recent advances and issues in (1) development of component fabrication technology including joining and functional coating, e.g., a tungsten overcoat as a plasma facing barrier, (2) recent updates in characterization of non-irradiated properties, e.g., strength anisotropy and chemical compatibility with solid lithium-based ceramics and lead-lithium liquid metal breeders, and (3) irradiation effects are specifically reviewed. Importantly high-temperature neutron irradiation effects on microstructural evolution, thermal and electrical conductivities and mechanical properties including the fiber/matrix interfacial strength are specified under various irradiation conditions, indicating seemingly very minor influence on the composite performance in the design temperature range.
Molybdenum disilicide composites reinforced with zirconia and silicon carbide

DOEpatents

Petrovic, J.J.

1995-01-17

Compositions are disclosed consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.
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.
Feasibility of producing cast-refractory metal-fiber superalloy composites

NASA Technical Reports Server (NTRS)

Mcintyre, R. D.

1973-01-01

A study was conducted to evaluate the feasibility of direct casting as a practical method for producing cast superalloy tungsten or columbium alloy fiber composites while retaining a high percentage of fiber strength. Fourteen nickel base, four cobalt, and three iron based matrices were surveyed for their degree of reaction with the metal fibers. Some stress-rupture results were obtained at temperatures of 760, 816, 871, and 1093 C for a few composite systems. The feasibility of producing acceptable composites of some cast nickel, cobalt, and iron matrix alloys with tungsten or columbium alloy fibers was demonstrated.
The relation of the yield stress of high-pressure anvils to the pressure attained at yielding and the ultimate attainable pressure

NASA Technical Reports Server (NTRS)

Panda, P. C.; Ruoff, A. L.

1979-01-01

A sensitive microprofilometer was used to determine the onset of yielding in the anvils of a supported opposed anvil device for the case of 3% cobalt-cemented tungsten carbide as the anvil material. In addition, it is shown how the commencement of yielding in boron carbide pistons, the yield strength being known, can be used to obtain the transition pressure to a conducting phase in gallium phosphide. The transition pressures of bismuth and gallium phosphide are obtained and it is found that these transitions are extremely close to the maximum attainable pressure in, respectively, a maraging steel and a 3% cobalt-cemented tungsten carbide.

Method of making silicon carbide-silicon composite having improved oxidation resistance

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

2002-01-01

A Silicon carbide-silicon matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is provided. A method is given for sealing matrix cracks in situ in melt infiltrated silicon carbide-silicon matrix composites. The composite cracks are sealed by the addition of various additives, such as boron compounds, into the melt infiltrated silicon carbide-silicon matrix.
Method for making hot-pressed fiber-reinforced carbide-graphite composite

DOEpatents

Riley, Robert E.; Wallace Sr., Terry C.

1979-01-01

A method for the chemical vapor deposition of a uniform coating of tantalum metal on fibers of a woven graphite cloth is described. Several layers of the coated cloth are hot pressed to produce a tantalum carbide-graphite composite having a uniformly dispersed, fine grained tantalum carbide in graphite with compositions in the range of 15 to 40 volume percent tantalum carbide.
TUNGSTEN BRONZE RELATED NON-NOBLE ELECTROCATALYSTS.

DTIC Science & Technology

FUEL CELLS, *CATALYSTS), (*OXYGEN, *ELECTRODES), (* SILICIDES , ELECTRODES), (*CARBIDES, ELECTRODES), (*TUNGSTEN COMPOUNDS, *ELECTROCHEMISTRY...CATALYSTS, TITANIUM COMPOUNDS, ZIRCONIUM COMPOUNDS, VANADIUM COMPOUNDS, NIOBIUM COMPOUNDS, TUNGSTEN COMPOUNDS, TANTALUM COMPOUNDS, MOLYBDENUM COMPOUNDS, SULFURIC ACID, CRYSTAL GROWTH, SODIUM COMPOUNDS
Hertzian indentation of colloidally processed titanium carbide-nickel aluminide composites

NASA Astrophysics Data System (ADS)

Collier, R. Bradley

Advanced cermets based on titanium carbide (TiC), with a ductile nickel aluminide (Ni3Al) binder, have shown significant promise for use in a variety of demanding wear environments, due to a combination of high strength and good corrosion behaviour. A unique feature of TiC-Ni3Al cermets is that they show increasing strength from room temperature up to ˜1,000°C, while current materials such as tungsten carbide/cobalt (WC/Co) show significant strength degradation above ˜500°C. In this thesis, aqueous colloidal forming methods have been applied to process TiC preforms. The mechanisms and effectiveness of suspension stabilization were examined using methods such as zeta potential analysis, rheological measurements, and sedimentation trials for two common dispersants; an ammonium salt of polymethacrylate (PMA-NH 4) and two molecular weights (l,800 and 10,000) of polyethylenimine (PEI). TiC preforms were prepared by slip casting suspensions of up to 50 vol. % solids content. After drying, the TiC-based cermets were processed by melt infiltration with the Ni3Al alloy (IC-50) at 1475°C.Ni 3Al content was varied between 20 and 50 vol. % using this approach, resulting in final densities that exceeded 98% of theoretical. These samples were subjected to Hertzian indentation testing with loads ranging from 250 -- 2000 N, using WC-Co spheres with sizes ranging from 1.191 to 2.38 mm. Indentation stress-strain curves were produced from the indentation data and compared to the calculated elastic Hertzian response. The bonded interface method was used to examine the subsurface deformation of the material under load. Significant deformation of the binder and the eventual fracture of the TiC grains were observed. The nature of the quasi-plasticity of TiC-Ni 3Al and the effects of binder content on surface and subsurface deformation is examined.
Versatile Boron Carbide-Based Visual Obscurant Compositions for Smoke Munitions

DTIC Science & Technology

2015-04-17

Versatile Boron Carbide-Based Visual Obscurant Compositions for Smoke Munitions Anthony P. Shaw,*,† Giancarlo Diviacchi,‡ Ernest L. Black,‡ Jared D...have been demonstrated to produce thick white smoke clouds upon combustion. These compositions use powdered boron carbide (B4C) as a pyrotechnic...ignition and are safe to handle. KEYWORDS: Smoke, Obscurants, Pyrotechnics, Boron carbide, Sustainable chemistry ■ INTRODUCTION Visible obscuration
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.
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.
Three-component fermions with surface Fermi arcs in tungsten carbide

NASA Astrophysics Data System (ADS)

Ma, J.-Z.; He, J.-B.; Xu, Y.-F.; Lv, B. Q.; Chen, D.; Zhu, W.-L.; Zhang, S.; Kong, L.-Y.; Gao, X.; Rong, L.-Y.; Huang, Y.-B.; Richard, P.; Xi, C.-Y.; Choi, E. S.; Shao, Y.; Wang, Y.-L.; Gao, H.-J.; Dai, X.; Fang, C.; Weng, H.-M.; Chen, G.-F.; Qian, T.; Ding, H.

2018-04-01

Topological Dirac and Weyl semimetals not only host quasiparticles analogous to the elementary fermionic particles in high-energy physics, but also have a non-trivial band topology manifested by gapless surface states, which induce exotic surface Fermi arcs1,2. Recent advances suggest new types of topological semimetal, in which spatial symmetries protect gapless electronic excitations without high-energy analogues3-11. Here, using angle-resolved photoemission spectroscopy, we observe triply degenerate nodal points near the Fermi level of tungsten carbide with space group P 6 ¯m 2 (no. 187), in which the low-energy quasiparticles are described as three-component fermions distinct from Dirac and Weyl fermions. We further observe topological surface states, whose constant-energy contours constitute pairs of `Fermi arcs' connecting to the surface projections of the triply degenerate nodal points, proving the non-trivial topology of the newly identified semimetal state.
Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regmi, Yagya N.; Roy, Asa; King, Laurie A.

Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. Here, to identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide–phosphide composite prevents catalyst dissolution in acid electrolyte.more » Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Lastly, our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support.« less
Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

DOE PAGES

Regmi, Yagya N.; Roy, Asa; King, Laurie A.; ...

2017-10-19

Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. Here, to identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide–phosphide composite prevents catalyst dissolution in acid electrolyte.more » Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Lastly, our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support.« less
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.
Selection criteria for wear resistant powder coatings under extreme erosive wear conditions

NASA Astrophysics Data System (ADS)

Kulu, P.; Pihl, T.

2002-12-01

Wear-resistant thermal spray coatings for sliding wear are hard but brittle (such as carbide and oxide based coatings), which makes them useless under impact loading conditions and sensitive to fatigue. Under extreme conditions of erosive wear (impact loading, high hardness of abrasives, and high velocity of abradant particles), composite coatings ensure optimal properties of hardness and toughness. The article describes tungsten carbide-cobalt (WC-Co) systems and self-fluxing alloys, containing tungsten carbide based hardmetal particles [NiCrSiB-(WC-Co)] deposited by the detonation gun, continuous detonation spraying, and spray fusion processes. Different powder compositions and processes were studied, and the effect of the coating structure and wear parameters on the wear resistance of coatings are evaluated. The dependence of the wear resistance of sprayed and fused coatings on their hardness is discussed, and hardness criteria for coating selection are proposed. The so-called “double cemented” structure of WC-Co based hardmetal or metal matrix composite coatings, as compared with a simple cobalt matrix containing particles of WC, was found optimal. Structural criteria for coating selection are provided. To assist the end user in selecting an optimal deposition method and materials, coating selection diagrams of wear resistance versus hardness are given. This paper also discusses the cost-effectiveness of coatings in the application areas that are more sensitive to cost, and composite coatings based on recycled materials are offered.
Carbide-reinforced metal matrix composite by direct metal deposition

NASA Astrophysics Data System (ADS)

Novichenko, D.; Thivillon, L.; Bertrand, Ph.; Smurov, I.

Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.
Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Godec, Matjaz, E-mail: matjaz.godec@imt.si; Batic, Barbara Setina; Mandrino, Djordje

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 carbidesmore » 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.« less
Multi-Energy Processing for Novel Coating Technologies

DTIC Science & Technology

2014-12-18

tungsten carbide (WC) substrate (BS-6S, Basic Carbide Corp.) with a dimension of 25.4 x 25.4 x 1.6 mm^ and a cobalt composition of 6% was placed on a...as dopant sources. (a) No NH3 + No laser (b) NH3 added, No laser (c) 10.591 ^m Figure 4.4 SEM micrographs of the diamond films deposited using...typed 37 diamond. Nitrogen was widely used as n-typed dopant . Nitrogen-containing additives in CVD diamond growth led to severe deterioration of the
Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Levine, S. R.

1995-01-01

A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.
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.
Tungsten fiber reinforced copper matrix composites: A review

NASA Technical Reports Server (NTRS)

Mcdanels, David L.

1989-01-01

Tungsten fiber reinforced copper matrix (W/Cu) composites have served as an ideal model system with which to analyze the properties of metal matrix composites. A series of research programs were conducted to investigate the stress-strain behavior of W/Cu composites; the effect of fiber content on the strength, modulus, and conductivity of W/Cu composites; and the effect of alloying elements on the behavior of tungsten wire and of W/Cu composites. Later programs investigated the stress-rupture, creep, and impact behavior of these composites at elevated temperatures. Analysis of the results of these programs as allows prediction of the effects of fiber properties, matrix properties, and fiber content on the properties of W/Cu composites. These analyses form the basis for the rule-of-mixtures prediction of composite properties which was universally adopted as the criteria for measuring composite efficiency. In addition, the analyses allows extrapolation of potential properties of other metal matrix composites and are used to select candidate fibers and matrices for development of tungsten fiber reinforced superalloy composite materials for high temperature aircraft and rocket engine turbine applications. The W/Cu composite efforts are summarized, some of the results obtained are described, and an update is provided on more recent work using W/Cu composites as high strength, high thermal conductivity composite materials for high heat flux, elevated temperature applications.
Silicon carbide-silicon composite having improved oxidation resistance and method of making

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

1999-01-01

A Silicon carbide-silicon matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is provided. A method is given for sealing matrix cracks in situ in melt infiltrated silicon carbide-silicon matrix composites. The composite cracks are sealed by the addition of various additives, such as boron compounds, into the melt infiltrated silicon carbide-silicon matrix.
FP-LAPW calculations of equation of state and elastic properties of α and β phases of tungsten carbide at high pressure

NASA Astrophysics Data System (ADS)

Mishra, Vinayak; Chaturvedi, Shashank

2013-03-01

Tungsten carbide is used in high pressure devices therefore knowledge of its elastic properties and their pressure dependence is of utmost practical importance. In this paper we present first principles results of equation of state and elastic properties of α and β phases of tungsten carbide and compare our results with the available reported experimental results. These calculations have been performed using the FPLAPW method within the framework of density functional theory. Enthalpies of α and β phases of WC have been compared up to 350 GPa to investigate possibility of structural transformation. Density-dependent Grüneisen parameter has been deduced from P-V isotherm using the well-known Slater's formula. High pressure elastic constants of α and β phases of WC have been calculated by applying various distortions to the original crystal structure. The elastic properties such as bulk, shear and Young's moduli have been derived from the calculated elastic constants. Pressure-dependent longitudinal velocity, shear velocity, Debye temperature and melting temperature have been deduced from the elastic properties. These calculated properties are in good agreement with the available experimental results.

Ceramic composites reinforced with modified silicon carbide whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1990-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.
A Magnetorheological Polishing-Based Approach for Studying Precision Microground Surfaces of Tungsten Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

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.
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.
Evaluation of silicon carbide fiber/titanium composites

NASA Technical Reports Server (NTRS)

Jech, R. W.; Signorelli, R. A.

1979-01-01

Izod impact, tensile, and modulus of elasticity were determined for silicon carbide fiber/titanium composites to evaluate their potential usefulness as substitutes for titanium alloys or stainless steel in stiffness critical applications for aircraft turbine engines. Variations in processing conditions and matrix ductility were examined to produce composites having good impact strength in both the as-fabricated condition and after air exposure at elevated temperature. The impact strengths of composites containing 36 volume percent silicon carbide (SiC) fiber in an unalloyed (A-40) titanium matrix were found to be equal to unreinforced titanium-6 aluminum-4 vanadium alloy; the tensile strengths of the composites were marginally better than the unreinforced unalloyed (A-70) matrix at elevated temperature, though not at room temperature. At room temperature the modulus of elasticity of the composites was 48 percent higher than titanium or its alloys and 40 percent higher than that of stainless steel.
Cobalt-Free Permanent Magnet Alloys.

DTIC Science & Technology

1984-10-01

carbide co- UC CbC lumbium carbide M003 Uranium carbide - tho- UC 2 25ThC rium carbide ZrO2 MgO WOs Use of this Process for MnAlC As indicated in the...cobalt. Free World Cobal Consumption Estimated Breakdown by End Uses Magnetic alloys 20% Cemented carbides - 5% 30 SuPerolloy _ 15% Other steels and...would normally result in the formation of binary alloy of TbFe 2 and preventing the formation of amorphous alloy (Fe-B) contain- ing Tb. The
Synthesis and structural characterization of polyaniline/cobalt chloride composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asha, E-mail: arana5752@gmail.com; Goyal, Sneh Lata; Kishore, Nawal

2016-05-23

Polyaniline (PANI) and PANI /cobalt chloride composites were synthesized by in situ chemical oxidative polymerization of aniline with CoCl{sub 2}.6H{sub 2}O using ammonium peroxidisulphate as an oxidant. These composites were characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The XRD study reveals that both PANI and composites are amorphous. The XRD and SEM results confirm the presence of cobalt chloride in the composites.
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.
Carbide coated fibers in graphite-aluminum composites

NASA Technical Reports Server (NTRS)

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1975-01-01

The NASA-supported program at the Los Alamos Scientific Laboratory (LASL) to develop carbon fiber-aluminum matrix composites is described. Chemical vapor deposition (CVD) was used to uniformly deposit thin, smooth, continuous coats of TiC on the fibers of graphite tows. Wet chemical coating of fibers, followed by high-temperature treatment, was also used, but showed little promise as an alternative coating method. Strength measurements on CVD coated fiber tows showed that thin carbide coats can add to fiber strength. The ability of aluminum alloys to wet TiC was successfully demonstrated using TiC-coated graphite surfaces. Pressure-infiltration of TiC- and ZrC-coated fiber tows with aluminum alloys was only partially successful. Experiments were performed to evaluate the effectiveness of carbide coats on carbon as barriers to prevent reaction between alluminum alloys and carbon. Initial results indicate that composites of aluminum and carbide-coated graphite are stable for long periods of time at temperatures near the alloy solidus.
Evaluation of Shielding Performance for Newly Developed Composite Materials

NASA Astrophysics Data System (ADS)

Evans, Beren Richard

This work details an investigation into the contributing factors behind the success of newly developed composite neutron shield materials. Monte Carlo simulation methods were utilized to assess the neutron shielding capabilities and secondary radiation production characteristics of aluminum boron carbide, tungsten boron carbide, bismuth borosilicate glass, and Metathene within various neutron energy spectra. Shielding performance and secondary radiation data suggested that tungsten boron carbide was the most effective composite material. An analysis of the macroscopic cross-section contributions from constituent materials and interaction mechanisms was then performed in an attempt to determine the reasons for tungsten boron carbide's success over the other investigated materials. This analysis determined that there was a positive correlation between a non-elastic interaction contribution towards a material's total cross-section and shielding performance within the thermal and epi-thermal energy regimes. This finding was assumed to be a result of the boron-10 absorption reaction. The analysis also determined that within the faster energy regions, materials featuring higher non-elastic interaction contributions were comparable to those exhibiting primarily elastic scattering via low Z elements. This allowed for the conclusion that composite shield success within higher energy neutron spectra does not necessitate the use elastic scattering via low Z elements. These findings suggest that the inclusion of materials featuring high thermal absorption properties is more critical to composite neutron shield performance than the presence of constituent materials more inclined to maximize elastic scattering energy loss.
Diamond-silicon carbide composite and method

DOEpatents

Zhao, Yusheng [Los Alamos, NM

2011-06-14

Uniformly dense, diamond-silicon carbide composites having high hardness, high fracture toughness, and high thermal stability are prepared by consolidating a powder mixture of diamond and amorphous silicon. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPam.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness.
Evaluation of titanium carbide metal matrix composites deposited via laser cladding

NASA Astrophysics Data System (ADS)

Cavanaugh, Daniel Thomas

Metal matrix composites have been widely studied in terms of abrasion resistance, but a particular material system may behave differently as particle size, morphology, composition, and distribution of the hardening phase varies. The purpose of this thesis was to understand the mechanical and microstructural effects of combining titanium carbide with 431 series stainless steel to create a unique composite via laser cladding, particularly regarding wear properties. The most predominant effect in increasing abrasion resistance, measured via ASTM G65, was confirmed to be volume fraction of titanium carbide addition. Macrohardness was directly proportional to the amount of carbide, though there was an overall reduction in individual particle microhardness after cladding. The reduction in particle hardness was obscured by the effect of volume fraction carbide and did not substantially contribute to the wear resistance changes. A model evaluating effective mean free path of the titanium carbide particles was created and correlated to the measured data. The model proved successful in linking theoretical mean free path to overall abrasion resistance. The effects of the titanium carbide particle distributions were limited, while differences in particle size were noticeable. The mean free path model did not correlate well with the particle size, but it was shown that the fine carbides were completely removed by the coarse abrasive particles in the ASTM G65 test. The particle morphology showed indications of influencing the wear mode, but no statistical reduction was observed in the volume loss figures. Future studies may more specifically focus on particle morphology or compositional effects of the carbide particles.
Protective coating for alumina-silicon carbide whisker composites

DOEpatents

Tiegs, Terry N.

1989-01-01

Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.
40 CFR 421.314 - Standards of performance for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of 7.5 to 10.0 at all times. (b) Tungsten leaching acid. NSPS for the Secondary Tungsten and Cobalt....570 30.850 pH (1) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Tungsten post-leaching wash... times. (e) Tungsten carbide leaching wet air pollution control. NSPS for the Secondary Tungsten and...
40 CFR 421.314 - Standards of performance for new sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... of 7.5 to 10.0 at all times. (b) Tungsten leaching acid. NSPS for the Secondary Tungsten and Cobalt....570 30.850 pH (1) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Tungsten post-leaching wash... times. (e) Tungsten carbide leaching wet air pollution control. NSPS for the Secondary Tungsten and...
40 CFR 421.314 - Standards of performance for new sources.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of 7.5 to 10.0 at all times. (b) Tungsten leaching acid. NSPS for the Secondary Tungsten and Cobalt....570 30.850 pH (1) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Tungsten post-leaching wash... times. (e) Tungsten carbide leaching wet air pollution control. NSPS for the Secondary Tungsten and...
40 CFR 421.314 - Standards of performance for new sources.

Code of Federal Regulations, 2013 CFR

2013-07-01

... of 7.5 to 10.0 at all times. (b) Tungsten leaching acid. NSPS for the Secondary Tungsten and Cobalt....570 30.850 pH (1) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Tungsten post-leaching wash... times. (e) Tungsten carbide leaching wet air pollution control. NSPS for the Secondary Tungsten and...
40 CFR 421.314 - Standards of performance for new sources.

Code of Federal Regulations, 2012 CFR

2012-07-01

... of 7.5 to 10.0 at all times. (b) Tungsten leaching acid. NSPS for the Secondary Tungsten and Cobalt....570 30.850 pH (1) (1) 1 Within the range of 7.5 to 10.0 at all times. (c) Tungsten post-leaching wash... times. (e) Tungsten carbide leaching wet air pollution control. NSPS for the Secondary Tungsten and...
Low Temperature Processing of Boron Carbide Cement Composite for Tough, Wear Resistant Structures

DTIC Science & Technology

1997-12-15

TITLE AND SUBTITLE Low Temperature Processing of Boron Carbide Cement Composite for Tough, Wear Resistant Structures 6. AUTHOR(S) Kristen J. Law...project has developed a low temperature polymer ceramic composite consisting of boron carbide layers bonded by cement, laminated with polymer...composite have been shown to compare favorably to those of partially sintered boron carbide. Applications for this material have been identified in
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.
Residual Stresses and Thermo-Mechanical Behavior of Metal-Matrix Composites

DTIC Science & Technology

1984-01-01

necessary and identify by block number) ELO I GROUP I Sue. GR. I Metal-matrix composites Silicon -carbide/Aluminum Graphite/Alumimun Cross-plied laminate I...aluminum, tungsten/aluminum and silicon -carbide aluminum composites . For the graphite/aluminum material a parametric study was carried out on the...PROPERTIES AS GIVEN IN TABLE 2.1. 5 3.1 CALCULATED THERUMOELASTIC PROPERTIES OF A TUNG- STEN /AL 2024 COMPOSITE 54 5.1 INPUT ELASTIC CONSTANTS FOR FIBER AND

Carbide/fluoride/silver self-lubricating composite

NASA Technical Reports Server (NTRS)

Sliney, Harold E. (Inventor)

1988-01-01

A self-lubricating, friction and wear reducing composite material for use over a wide temperature spectrum from cryogenic temperature to about 900.degree. C. in a chemically reactive environment comprising silver, barium fluoride/calcium fluoride eutectic, and metal bonded chromium carbide.
Diamond-Silicon Carbide Composite And Method For Preparation Thereof

DOEpatents

Qian, Jiang; Zhao, Yusheng

2005-09-06

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.multidot.m.sup.1/2. 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.
Carbide-fluoride-silver self-lubricating composite

NASA Technical Reports Server (NTRS)

Sliney, Harold E. (Inventor)

1987-01-01

A self-lubricating, friction and wear reducing composite material is described for use over a wide temperature spectrum from cryogenic temperature to about 900 C in a chemically reactive environment comprising silver, barium fluoride/calcium fluoride eutectic, and metal bonded chromium carbide.
Synergistic effect of tungsten carbide and palladium on graphene for promoted ethanol electrooxidation.

PubMed

Yang, Jun; Xie, Ying; Wang, Ruihong; Jiang, Baojiang; Tian, Chungui; Mu, Guang; Yin, Jie; Wang, Bo; Fu, Honggang

2013-07-24

The synergistic effect of WC and Pd has large benefit for ethanol electrooxidation. The small-sized Pd nanoparticles (NPs) decorated tungsten carbide on graphene (Pd-WC/GN) will be a promising anode catalyst for the direct ethanol fuel cells. The density functional theory (DFT) calculations reveal that the strong interaction exists at the interface between Pd and WC, which induces the electron transfer from WC to Pd. Fortunately, the nanoscale architecture of Pd-WC/GN has been successfully fabricated in our experiments. X-ray photoelectron spectrum further confirms the existence of electron transfer from WC to Pd in a Pd-WC/GN nanohybrid. Notably, electrochemical tests show that the Pd-WC/GN catalyst exhibits low onset potential, a large electrochemical surface area, high activity, and stability for ethanol electrooxidation in alkaline solution compared with Pd/graphene and Pd/commercial Vulcan 72R carbon catalysts. The enhancement can be attributed to the synergistic effect of Pd and WC on graphene. At the interface between Pd and WC, the electron transfer from WC to Pd leads to the increased electron densities of surface Pd, which is available for weakening adsorption of intermediate oxygen-containing species such as CO and activating catalyst. Meanwhile, the increased tungsten oxide induced by electron transfer can facilitate the effective removal of intermediate species adsorbed on the Pd surface through a bifunctional mechanism or hydrogen spillover effect.
Near Net-Shape, Ultra High Melting, Erosion Resistant Carbide/Metal Composites with Tailored Fibrillar Microstructures via the Displacive Compensation of Porosity Process

DTIC Science & Technology

2006-11-26

vapor species, formed over tungsten trioxide powder, is 1.25xl0Ŗ atm at 1400°C and 1 atm total pressure (assuming an oxygen partial pressure greater...with CO(g). ■19- These hollow tungsten fibers were then carburized via reaction with CO(g) to generate the polycrystalline WC-based fibers shown in...of tungsten carbide via reaction with a hafnium-copper melt," Ada Mater., 57(13), 3924-3931 (2009).) The kinetic mechanism of incongruent reduction
Influence of Chemical Composition on Rupture Properties at 1200 Degrees F. of Forged Chromium-Cobalt-Nickel-Iron Base Alloys in Solution-Treated and Aged Condition

NASA Technical Reports Server (NTRS)

Reynolds, E E; Freeman, J W; White, A E

1951-01-01

The influence of systematic variations of chemical composition on rupture properties at 1200 degrees F. was determined for 62 modifications of a basic alloy containing 20 percent chromium, 20 percent nickel, 20 percent cobalt, 3 percent molybdenum, 2 percent tungsten, 1 percent columbium, 0.15 percent carbon, 1.7 percent manganese, 0.5 percent silicon, 0.12 percent nitrogen and the balance iron. These modifications included individual variations of each of 10 elements present and simultaneous variations of molybdenum, tungsten, and columbium. Laboratory induction furnace heats were hot-forged to round bar stock, solution-treated at 2200 degrees F., and aged at 1400 degrees F. The melting and fabrication conditions were carefully controlled in order to minimize all variable effects on properties except chemical composition. Information is presented which indicates that melting and hot-working conditions play an important role in high-temperature properties of alloys of the type investigated.
Nonequilibrium Diamond Growth during the High-Temperature High-Pressure Synthesis of a Composite Material Made of a Mixture of Cobalt and Fullerene Powders

NASA Astrophysics Data System (ADS)

Bulienkov, N. A.; Zheligovskaya, E. A.; Chernogorova, O. P.; Drozdova, E. I.; Ushakova, I. N.; Ekimov, E. A.

2018-01-01

A composite material (CM) reinforced by diamond particles is fabricated from a mixture of cobalt and 10 wt % C60 powders at a pressure of 8 GPa and a temperature of 1200-1300°C, which is close to the melting temperature of the metastable Co-C eutectic. The results of X-ray diffraction, Raman spectroscopy, and electron-probe microanalysis demonstrate that the CM consists of diamond and the Co3C carbide. Diamond crystals are shown to grow as plates parallel to a {100} plane according to the mechanism of nonequilibrium normal growth during liquid-phase CM synthesis. The diamond particles have a hardness of 82 GPa at an elastic recovery of 95%. The structure of the synthesized cobalt-based CM with diamond inclusions ensures its ultrahigh wear resistance and antifriction properties.
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.
Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

NASA Astrophysics Data System (ADS)

Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

2016-03-01

Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.
Experimental investigation of grain boundaries misorientations and nano twinning induced strengthening on addition of silicon carbide in pulse electrodeposited nickel tungsten composite coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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{supmore » −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.« less
Heat of combustion of tantalum-tungsten oxide thermite composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes, Octavio G.; Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616; Kuntz, Joshua D.

2010-12-15

The heat of combustion of two distinctly synthesized stoichiometric tantalum-tungsten oxide energetic composites was investigated by bomb calorimetry. One composite was synthesized using a sol-gel (SG) derived method in which micrometric-scale tantalum is immobilized in a tungsten oxide three-dimensional nanostructured network structure. The second energetic composite was made from the mixing of micrometric-scale tantalum and commercially available (CA) nanometric tungsten oxide powders. The energetic composites were consolidated using the spark plasma sintering (SPS) technique under a 300 MPa pressure and at temperatures of 25, 400, and 500 C. For samples consolidated at 25 C, the density of the CA compositemore » is 61.65 {+-} 1.07% in comparison to 56.41 {+-} 1.19% for the SG derived composite. In contrast, the resulting densities of the SG composite are higher than the CA composite for samples consolidated at 400 and 500 C. The theoretical maximum density for the SG composite consolidated to 400 and 500 C are 81.30 {+-} 0.58% and 84.42 {+-} 0.62%, respectively. The theoretical maximum density of the CA composite consolidated to 400 and 500 C are 74.54 {+-} 0.80% and 77.90 {+-} 0.79%, respectively. X-ray diffraction analyses showed an increase of pre-reaction of the constituents with an increase in the consolidation temperature. The increase in pre-reaction results in lower stored energy content for samples consolidated to 400 and 500 C in comparison to samples consolidated at 25 C. (author)« less
Selective Production of Renewable para-Xylene by Tungsten Carbide Catalyzed Atom-Economic Cascade Reactions.

PubMed

Dai, Tao; Li, Changzhi; Li, Lin; Zhao, Zongbao Kent; Zhang, Bo; Cong, Yu; Wang, Aiqin

2018-02-12

Tungsten carbide was employed as the catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA). This intermediate is the product of the Diels-Alder reaction between the two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization-hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W 2 C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio-based building blocks, thus potentially providing a petroleum-independent solution to valuable aromatic compounds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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.
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.
Composition optimization of self-lubricating chromium-carbide-based composite coatings for use to 760 C

NASA Technical Reports Server (NTRS)

Dellacorte, Chris; Sliney, Harold E.

1987-01-01

This paper describes new compositions of self-lubricating coatings that contain chromium carbide. A bonded chromium carbide was used as the base stock because of the known excellent wear resistance and the chemical stability of chromium carbide. Additives were silver and barium fluoride/calcium fluoride eutectic. The coating constituents were treated as a ternary system consisting of: (1) the bonded carbide base material, (2) silver, and (3) the eutectic. A study to determine the optimum amounts of each constituent was performed. The various compositions were prepared by powder blending. The blended powders were then plasma sprayed onto superalloy substrates and diamond ground to the desired coating thickness. Friction and wear studies were performed at temperatures from 25 to 760 C in helium and hydrogen. A variety of counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications such as piston ring/cylinder liner couples for Stirling engines.
Reactive Fusion Welding for Ultra-High Temperature Ceramic Composite Joining

DTIC Science & Technology

2015-03-16

Titanium diboride TiC-Titanium carbide C-Carbon SiC - Silicon carbide B4C-Boron carbide 67 W-Tungsten WC-Tungsten carbide ZrB2-20ZrC-ZrB2...ceramics with a nominal carbide content of 20 vol% were prepared. Starting powders were mechanically mixed by ball milling ZrB2 (H.C. Starck; Grade B...0.50 wt%, or ~1.5 vol%. Milling was carried out in acetone for 2 hours using tungsten carbide media. After milling, the powder slurry was dried
Synthesis, Consolidation and Characterization of Sol-gel Derived Tantalum-Tungsten Oxide Thermite Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes, O

2010-06-01

Energetic composite powders consisting of sol-gel (SG) derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the SG derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The SG derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO3) energetic composite was consolidated to a density of 9.17 g·cm-3more » or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy.« less
Microstructure Changes of Plasma Spraying Tungsten Coatings on Cfc after Different Temperature Annealing

NASA Astrophysics Data System (ADS)

Liu, X.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.

2003-06-01

Thermal behaviors of tungsten coating of 0.5 mm thick with multi-layers interface of tungsten (W) and rhenium (Re) coated on CFC (CX-2002U) substrate by vacuum plasma spraying (VPS) technique were examined by annealing with an electron beam thermal load facility between 1200 °C and 2000 °C. Change of the microstructure was observed and its chemical composition was analyzed by EDS after annealing. It was observed that remarkable recrystallization of VPS-W occurred above 1400 °C. The structure of the multi-layers of W and Re become obscure by the mutual diffusion of W, Re and C above 1600°C and finally disappeared after annealing at 2000 °C for one hour. Very hard tungsten carbides are formed at the interface above 1600 °C and they were broadening with increasing annealing temperature and time.
Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

NASA Astrophysics Data System (ADS)

Ponomarev, V. I.; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.

2015-09-01

Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide В15- х С х , (1.5 ≤ x ≤ 3) and its magnesium derivative C4B25Mg1.42. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from В12.9С2.1 to В12.4С2.6.
Carcinogenicity of Embedded Tungsten Alloys in Mice

DTIC Science & Technology

2011-03-01

year carcinogenicity (Aim 1) and serial euthanasia (Aim 2) studies were analyzed for metal content using inductively coupled-plasma mass spectrometry...inductively coupled- plasma mass spectrometer (PQ ExCell ICPMS System, ThermoElemental, Franklin, MA) equipped with a Cetac ASX500 Autosampler. High...Metal analysis using inductively coupled-plasma mass spectrometry showed that both the tungsten/nickel/cobalt and tungsten/nickel/iron

Composition optimization of self-lubricating chromium carbide-based composite coatings for use to 760 deg C

NASA Technical Reports Server (NTRS)

Dellacorte, C.; Sliney, H. E.

1986-01-01

This paper describes new compositions of self-lubricating coatings that contain chromium carbide. A bonded chromium carbide was used as the base stock because of the known excellent wear resistance and the chemical stability of chromium carbide. Additives were silver and barium fluoride/calcium fluoride eutectic. The coating constituents were treated as a ternary system consisting of: (1) the bonded carbide base material, (2) silver, and (3) the eutectic. A study to determine the optimum amounts of each constituent was performed. The various compositions were prepared by powder blending. The blended powders were then plasma sprayed onto superalloy substrates and diamond ground to the desired coating thickness. Friction and wear studies were performed at temperatures from 25 to 760 C in helium and hydrogen. A variety of counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications such as piston ring/cylinder liner couples for Stirling engines.
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.
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.
Effective load transfer by a chromium carbide nanostructure in a multi-walled carbon nanotube/copper matrix composite

NASA Astrophysics Data System (ADS)

Cho, Seungchan; Kikuchi, Keiko; Kawasaki, Akira; Kwon, Hansang; Kim, Yangdo

2012-08-01

Multi-walled carbon nanotube (MWCNT) reinforced copper (Cu) matrix composites, which exhibit chromium (Cr) carbide nanostructures at the MWCNT/Cu interface, were prepared through a carbide formation using CuCr alloy powder. The fully densified and oriented MWCNTs dispersed throughout the composites were prepared using spark plasma sintering (SPS) followed by hot extrusion. The tensile strengths of the MWCNT/CuCr composites increased with increasing MWCNTs content, while the tensile strength of MWCNT/Cu composite decreased from that of monolithic Cu. The enhanced tensile strength of the MWCNT/CuCr composites is a result of possible load-transfer mechanisms of the interfacial Cr carbide nanostructures. The multi-wall failure of MWCNTs observed in the fracture surface of the MWCNT/CuCr composites indicates an improvement in the load-bearing capacity of the MWCNTs. This result shows that the Cr carbide nanostructures effectively transferred the tensile load to the MWCNTs during fracture through carbide nanostructure formation in the MWCNT/Cu composite.
Characterization of SiC Fiber (SCS-6) Reinforced-Reaction-Formed Silicon Carbide Matrix Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Dickerson, R. M.

1996-01-01

Silicon carbide fiber (SCS-6) reinforced-reaction-formed silicon carbide matrix composites were fabricated using a reaction-forming process. Silicon-2 at.% niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bimodal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon, and silicon. Fiber pushout tests on these composites determined a debond stress of approximately 67 MPa and a frictional stress of approximately 60 MPa. A typical four-point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pullout.
Powder Processing of Amorphous Tungsten-bearing Alloys and Composites

DTIC Science & Technology

2015-03-01

8725 John J. Kingman Road, MS-6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-14-73 Powder Processing of Amorphous Tungsten...Technology, Boise State University, Army Research Laboratory Project Title: Powder Processing of Amorphous Tungsten-bearing Alloys and Composites...Our year 3 tasks, as laid out in the project proposal, were to 1) Consolidate amorphous or nanocrystalline powder blends 2) Mechanical testing
Decomposition Mechanism and Decomposition Promoting Factors of Waste Hard Metal for Zinc Decomposition Process (ZDP)

NASA Astrophysics Data System (ADS)

Pee, J. H.; Kim, Y. J.; Kim, J. Y.; Seong, N. E.; Cho, W. S.; Kim, K. J.

2011-10-01

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc steam pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 hrs at 650 °C, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of γ-β1 phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at 1000 °C. The small amount of zinc remaining in the tungsten carbide-cobalt powder which was completely decomposed was fully removed by using phosphate solution which had a slow cobalt dissolution speed.
Room temperature humidity sensor based on polyaniline-tungsten disulfide composite

NASA Astrophysics Data System (ADS)

Manjunatha, S.; Chethan, B.; Ravikiran, Y. T.; Machappa, T.

2018-05-01

Polyaniline-tungsten disulfide (PANI-WS2) composite was synthesized using in situ polymerization technique by adding finely grinded powder of WS2 during the polymerization of aniline. Field emission scanning electron microscopy (FESEM) images showed the granular morphology with porous nature. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of carbon, nitrogen, chlorine of PANI, tungsten and sulfur elements of WS2. Humidity sensing property of the composite was investigated by plotting change in its resistance with different relative humidity environments ranging from 10 to 97% RH. Decrease in resistance of the composite was observed with increase in relative humidity. Maximum sensing response of the composite was found to be 88.46%. Response and recovery times of the composite at 97%RH were fair enough to fabricate a sensor based on it. Stability of the composite with respect to the humidity sensing behavior was observed to be unchanged even after two months.
Hard metal composition

DOEpatents

Sheinberg, H.

1983-07-26

A composition of matter having a Rockwell A hardness of at least 85 is formed from a precursor mixture comprising between 3 and 10 wt % boron carbide and the remainder a metal mixture comprising from 70 to 90% tungsten or molybdenum, with the remainder of the metal mixture comprising nickel and iron or a mixture thereof. The composition has a relatively low density of between 7 and 14 g/cc. The precursor is preferably hot pressed to yield a composition having greater than 100% of theoretical density.
Characterization of SiC (SCS-6) Fiber Reinforced Reaction-Formed Silicon Carbide Matrix Composites

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Dickerson, Robert M.

1995-01-01

Silicon carbide (SCS-6) fiber reinforced-reaction formed silicon carbide matrix composites were fabricated using NASA's reaction forming process. Silicon-2 at a percent of niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bi-modal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon and silicon. Fiber push-out tests on these composites determined a debond stress of approx. 67 MPa and a frictional stress of approx. 60 MPa. A typical four point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pull out.
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.
Carbide coated fibers in graphite-aluminum composites

NASA Technical Reports Server (NTRS)

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1975-01-01

Thin, uniform coats of titanium carbide, deposited on graphite fibers by chemical vapor deposition with thicknesses up to approximately 0.1 microns were shown to improve fiber strength significantly. For greater thicknesses, strength was degraded. The coats promote wetting of the fibers and infiltration of the fiber yarns with aluminum alloys, and act as protective barriers to inhibit reaction between the fibers and the alloys. Chemical vapor deposition was used to produce silicon carbide coats on graphite fibers. In general, the coats were nonuniform and were characterized by numerous surface irregularities. Despite these irregularities, infiltration of these fibers with aluminum alloys was good. Small graphite-aluminum composite samples were produced by vacuum hot-pressing of aluminum-infiltrated graphite yarn at temperatures above the metal liquidus.
Cobalt as chemical modifier to improve chromium sensitivity and minimize matrix effects in tungsten coil atomic emission spectrometry.

PubMed

Silva, Sidnei G; Donati, George L; Santos, Luana N; Jones, Bradley T; Nóbrega, Joaquim A

2013-05-30

Cobalt is used as chemical modifier to improve sensitivity and minimize matrix effects in Cr determinations by tungsten coil atomic emission spectrometry (WCAES). The atomizer is a tungsten filament extracted from microscope light bulbs. A solid-state power supply and a handheld CCD-based spectrometer are also used in the instrumental setup. In the presence of 1000 mg L(-1) Co, WCAES limit of detection for Cr (λ=425.4 nm) is calculated as 0.070 mg L(-1); a 10-fold improvement compared to determinations without Co modifier. The mechanism involved in such signal enhancement is similar to the one observed in ICP OES and ICP-MS determinations of As and Se in the presence of C. Cobalt increases the population of Cr(+) by charge transfer reactions. In a second step, Cr(+)/e(-) recombination takes place, which results in a larger population of excited-state Cr atoms. This alternative excitation route is energetically more efficient than heat transfer from atomizer and gas phase to analyte atoms. A linear dynamic range of 0.25-10 mg L(-1) and repeatability of 3.8% (RSD, n=10) for a 2.0 mg L(-1) Cr solution are obtained with this strategy. The modifier high concentration also contributes to improving accuracy due to a matrix-matching effect. The method was applied to a certified reference material of Dogfish Muscle (DORM-2) and no statistically significant difference was observed between determined and certified Cr values at a 95% confidence level. Spike experiments with bottled water samples resulted in recoveries between 93% and 112%. Copyright © 2013 Elsevier B.V. All rights reserved.
Comparison of W-VC-C composites against Co-60, Se-75 and Sb-125 for gamma radioisotope sources

NASA Astrophysics Data System (ADS)

Demir, Ertugrul; Tugrul, A. Beril; Buyuk, Bulent; Yilmaz, Ozan; Ovecoglu, Lutfi

2018-02-01

Tungsten based materials are considered to be the promising materials for nuclear applications due to the good properties. The tungsten composite materials have so many advantages in nuclear technological applications especially fusion reactor systems. In this paper, Tungsten-Vanadium carbide-Graphite (W-VC-C) which include 93% tungsten (W), 6% vanadium carbide (VC) and 1% graphite (C) also which has three different alloying time (6-12-24 hours) were produced by mechanical alloying method. Co-60, Se-75 and Sb-125 gamma radioisotopeswere used as a gamma sources in order to determine behavior of gamma attenuation properties of the composite materials. The experimental results were compared with each other to clarify effects of varying gamma energies on the tungsten based composite materials. The mass attenuation coefficients of the samples were obtained by using XCOM computer code and compared with experimental data. The gamma linear attenuation, the mass attenuation coefficients and half value thickness (HVL) of the samples were evaluated and compared with Co-60, Se-75 and Sb-125 for gamma radioisotopes. Results showed that gamma attenuation coefficients of the samples depend on gamma energies and mechanical alloying time has negatively effect on the gamma shielding properties for the all studied W-VC-C.
Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

PubMed Central

Feng-Chen, Siyuan; Aldalbahi, Ali; Feng, Peter Xianping

2015-01-01

We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670
Tantalum-tungsten oxide thermite composites prepared by sol-gel synthesis and spark plasma sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuntz, Joshua D.; Gash, Alexander E.; Cervantes, Octavio G.

2010-08-15

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and the results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High-Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta-WO{sub 3}) energetic composite was consolidated to a density of 9.17 g cm{sup -3}more » or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy. (author)« less
Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes, O; Kuntz, J; Gash, A

2009-02-13

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17more » g.cm{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.« less
Boron-carbide-aluminum and boron-carbide-reactive metal cermets

DOEpatents

Halverson, Danny C.; Pyzik, Aleksander J.; Aksay, Ilhan A.

1986-01-01

Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.
Mechanical intermixing of components in (CoMoNi)-based systems and the formation of (CoMoNi)/WC nanocomposite layers on Ti sheets under ball collisions

NASA Astrophysics Data System (ADS)

Romankov, S.; Park, Y. C.; Shchetinin, I. V.

2017-11-01

Cobalt (Co), molybdenum (Mo), and nickel (Ni) components were simultaneously introduced onto titanium (Ti) surfaces from a composed target using ball collisions. Tungsten carbide (WC) balls were selected for processing as the source of a cemented carbide reinforcement phase. During processing, ball collisions continuously introduced components from the target and the grinding media onto the Ti surface and induced mechanical intermixing of the elements, resulting in formation of a complex nanocomposite structure onto the Ti surface. The as-fabricated microstructure consisted of uniformly dispersed WC particles embedded within an integrated metallic matrix composed of an amorphous phase with nanocrystalline grains. The phase composition of the alloyed layers, atomic reactions, and the matrix grain sizes depended on the combination of components introduced onto the Ti surface during milling. The as-fabricated layer exhibited a very high hardness compared to industrial metallic alloys and tool steel materials. This approach could be used for the manufacture of both cemented carbides and amorphous matrix composite layers.
Hard metal composition

DOEpatents

Sheinberg, Haskell

1986-01-01

A composition of matter having a Rockwell A hardness of at least 85 is formed from a precursor mixture comprising between 3 and 10 weight percent boron carbide and the remainder a metal mixture comprising from 70 to 90 percent tungsten or molybdenum, with the remainder of the metal mixture comprising nickel and iron or a mixture thereof. The composition has a relatively low density of between 7 to 14 g/cc. The precursor is preferably hot pressed to yield a composition having greater than 100% of theoretical density.

Relative SHG measurements of metal thin films: Gold, silver, aluminum, cobalt, chromium, germanium, nickel, antimony, titanium, titanium nitride, tungsten, zinc, silicon and indium tin oxide

NASA Astrophysics Data System (ADS)

Che, Franklin; Grabtchak, Serge; Whelan, William M.; Ponomarenko, Sergey A.; Cada, Michael

We have experimentally measured the surface second-harmonic generation (SHG) of sputtered gold, silver, aluminum, zinc, tungsten, copper, titanium, cobalt, nickel, chromium, germanium, antimony, titanium nitride, silicon and indium tin oxide thin films. The second-harmonic response was measured in reflection using a 150 fs p-polarized laser pulse at 1561 nm. We present a clear comparison of the SHG intensity of these films relative to each other. Our measured relative intensities compare favorably with the relative intensities of metals with published data. We also report for the first time to our knowledge the surface SHG intensity of tungsten and antimony relative to that of well known metallic thin films such as gold and silver.
Pressure-enhanced superconductivity in quasi-1D cobalt carbide Sc3CoC4

NASA Astrophysics Data System (ADS)

Wang, Enyu; Zhu, Xiyu; Wen, Hai-Hu

2016-07-01

We have successfully synthesized the quasi-1D cobalt carbide Sc3CoC4 by using the arc-melting technique which is similar to that of the previous reports. An incomplete superconducting transition is detected at ambient pressure. In addition, two anomalies have been observed at 72 K and 143 K both from resistivity and magnetic susceptibility measurements. According to previous studies, it was argued that they correspond to the 1D Peierls-type distortion and charge-density-wave transitions, respectively. By applying a pressure, the transition at about 72 K is quickly suppressed, which is accompanied by the occurrence of a complete superconducting transition at about 4.5 K. Moreover, the DC magnetic susceptibility under high pressures also reveals the enhancement of superconductivity. We attribute this enhancement of superconductivity to the suppression of the Peierls-type distortion at about 72 K and probably together with the promoted Josephson coupling between the [CoC4] ∞ one-dimensional ribbons.
Exploration on Wire Discharge Machining Added Powder for Metal-Based Diamond Grinding Wheel on Wire EDM Dressing and Truing of Grinding Tungsten Carbide Material

NASA Astrophysics Data System (ADS)

Chow, H. M.; Yang, L. D.; Lin, Y. C.; Lin, C. L.

2017-12-01

In this paper, the effects of material removal rate and abrasive grain protrusion on the metal-based diamond grinding wheel were studied to find the optimal parameters for adding powder and wire discharge. In addition, this kind of electric discharge method to add powder on the metal-based diamond grinding wheel on line after dressing and truing will be applied on tungsten carbide to study the grinding material removal rate, grinding wheel wear, surface roughness, and surface micro-hardness.
The erosion performance of cold spray deposited metal matrix composite coatings with subsequent friction stir processing

NASA Astrophysics Data System (ADS)

Peat, Tom; Galloway, Alexander; Toumpis, Athanasios; McNutt, Philip; Iqbal, Naveed

2017-02-01

This study forms an initial investigation into the development of SprayStir, an innovative processing technique for generating erosion resistant surface layers on a chosen substrate material. Tungsten carbide - cobalt chromium, chromium carbide - nickel chromium and aluminium oxide coatings were successfully cold spray deposited on AA5083 grade aluminium. In order to improve the deposition efficiency of the cold spray process, coatings were co-deposited with powdered AA5083 using a twin powder feed system that resulted in thick (>300 μm) composite coatings. The deposited coatings were subsequently friction stir processed to embed the particles in the substrate in order to generate a metal matrix composite (MMC) surface layer. The primary aim of this investigation was to examine the erosion performance of the SprayStirred surfaces and demonstrate the benefits of this novel process as a surface engineering technique. Volumetric analysis of the SprayStirred surfaces highlighted a drop of approx. 40% in the level of material loss when compared with the cold spray deposited coating prior to friction stir processing. Micro-hardness testing revealed that in the case of WC-CoCr reinforced coating, the hardness of the SprayStirred material exhibits an increase of approx. 540% over the unaltered substrate and 120% over the as-deposited composite coating. Microstructural examination demonstrated that the increase in the hardness of the MMC aligns with the improved dispersion of reinforcing particles throughout the aluminium matrix.
Structural Assessment of Tungsten-Epoxy Bonding in Spacecraft Composite Enclosures with Enhanced Radiation Protection

NASA Astrophysics Data System (ADS)

Kanerva, M.; Koerselman, J. R.; Revitzer, H.; Johansson, L.-S.; Sarlin, E.; Rautiainen, A.; Brander, T.; Saarela, O.

2014-06-01

Spacecraft include sensitive electronics that must be protected against radiation from the space environment. Hybrid laminates consisting of tungsten layers and carbon- fibre-reinforced epoxy composite are a potential solution for lightweight, efficient, and protective enclosure material. Here, we analysed six different surface treatments for tungsten foils in terms of the resulting surface tension components, composition, and bonding strength with epoxy. A hydrofluoric-nitric-sulfuric-acid method and a diamond-like carbon-based DIARC® coating were found the most potential surface treatments for tungsten foils in this study.
Method of preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals

DOEpatents

Peng, Yu-Min; Wang, Jih-Wen; Liue, Chun-Ying; Yeh, Shinn-Horng

1994-01-01

A method for preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals includes the steps of washing the silicon carbide particles with an organic solvent; washing the silicon carbide particles with an inorganic acid; grinding the silicon carbide particles; and heating the silicon carbide particles in a nickel-containing solution at a boiling temperature for a predetermined period of time.
Infiltrated W–Cu composites with combined architecture of hierarchical particulate tungsten and tungsten fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Shuhua, E-mail: liangsh@xaut.edu.cn; Shaanxi Province Key Laboratory for Electrical Materials and Infiltration Technology, Xi'an 710048; Chen, Long

In this article, novel W–Cu composites reinforced with topologically-inserted tungsten fibers (W{sub f}) have been fabricated by hot-press sintering and infiltration method. By pre-sputtering of ~ 100 nm thick chromium layer onto the surface of W{sub f}, the contiguity or connectivity between W{sub f} and neighboring tungsten particles (W{sub p}) or Cu after sintering and infiltration was enhanced. Combined SEM, TEM and STEM techniques confirmed that the intact interfaces of W{sub f}/W{sub p} and W{sub f}/Cu free from precipitates, impurities and porosities would provide desirable strength and ductility. Further mechanical tests also validated its superior compressive strength and plasticity atmore » various temperatures, together with significantly improved tensile strength (by 23.6%) and hardness (by 9.3%) for the W–Cu composite after reinforcement with Cr-coated W{sub f}, which promotes the engineering application of the composite greatly. - Highlights: • W-fibers reinforced W–Cu composites were fabricated by sintering and infiltration. • The sputtered Cr onto W{sub f} has dissolved into adjacent W{sub f} and W{sub p} during fabrication. • The intact interfaces of W{sub f}/W{sub p} and W{sub f}/Cu confer enhanced strength and ductility. • Tensile strength and hardness improve by 23.6% and 9.3% after interface tuning.« less
Bulk metallic glass matrix composites: Processing, microstructure, and application as a kinetic energy penetrator

NASA Astrophysics Data System (ADS)

Dandliker, Richard B.

The development of alloys with high glass forming ability allows fabrication of bulk samples of amorphous metal. This capability makes these materials available for applications which require significant material thickness in all three dimensions. Superior mechanical properties and advantages in processing make metallic glass a choice candidate as a matrix material for composites. This study reports techniques for making composites by melt-infiltration casting using the alloy Zrsb{41.2}Tisb{13.8}Cusb{12.5}Nisb{10.0}Besb{22.5} (VitreloyspTM 1) as a matrix material. Composite rods 5 cm in length and 7 mm in diameter were made and found to have a nearly fully amorphous matrix; there was less than 3 volume percent crystallized matrix material. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed samples were made with uniaxially aligned tungsten and carbon steel continuous wire reinforcement; the majority of the analysis presented is of these samples. The measured porosity was typically less than 3%. The results also indicate necessary guidelines for developing processing techniques for large scale production, new reinforcement materials, and other metallic glass compositions. Analysis of the microstructure of the tungsten wire and steel wire reinforced composites was performed by x-ray diffraction, scanning electron microscopy, scanning Auger microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The most common phase in the crystallized matrix is most likely a Laves phase with the approximate formula Besb{12}Zrsb3TiNiCu. In tungsten-reinforced composites, a crystalline reaction layer 240 nm thick of tungsten nanocrystals in an amorphous matrix formed. In the steel reinforced composites, the reaction layer was primarily composed of a mixed metal carbide, mainly ZrC. One promising application of the metallic glass matrix composite is as a kinetic
Wrought cobalt- base superalloys

NASA Astrophysics Data System (ADS)

Klarstrom, D. L.

1993-08-01

Wrought cobalt-base superalloys are used extensively in gas turbine engines because of their excellent high-temperature creep and fatigue strengths and resistance to hot corrosion attack. In addition, the unique character of the oxide scales that form on some of the alloys provides outstanding resistance to high-temperature sliding wear. This article provides a review of the evolutionary development of wrought cobalt-base alloys in terms of alloy design and physical metallurgy. The topics include solid-so-lution strengthening, carbide precipitation characteristics, and attempts to introduce age hardening. The use of PHACOMP to enhance thermal stability characteristics and the incorporation of rare-earth ele-ments to improve oxidation resistance is also reviewed and discussed. The further development of cobalt-base superalloys has been severely hampered by past political events, which have accentuated the strategic vulnerability of cobalt as a base or as an alloying element. Consequently, alternative alloys have been developed that use little or no cobalt. One such alternative, Haynes® 230TMalloy, is discussed briefly.
Tool wear mechanisms in turning titanium-aluminum-vanadium using tungsten carbide and polycrystalline diamond inserts

NASA Astrophysics Data System (ADS)

Schrock, David James

The objective of this work is to identify some of the tool wear mechanisms at the material level for the machining of titanium and to provide some understanding of these mechanisms for use in physics based tool wear models. Turning experiments were conducted at cutting speeds of 61m/min, 91m/min, and 122m/min on Ti-6Al-4V, an alloy of titanium, using two different grades of tungsten carbide cutting inserts and one grade of polycrystalline diamond inserts. Three-dimensional wear data and two-dimensional wear profiles of the rake face were generated using Confocal Laser Scanning Microscopy to quantify the tool wear mechanisms. Additionally, the microstructure of the deformed work material (chip) and un-deformed parent material (work piece) were studied using Orientation Imaging Microscopy (OIM). Observations from tool wear studies on the PCD inserts revealed the presence of two fundamentally different wear mechanisms operating at the different cutting speeds. Microstructural analyses of the chip and the work material showed phase dependent tool wear mechanisms for machining titanium. There is a high likelihood of phase change occurring in the work material during machining, with a transformation from the alpha phase to the beta phase. The observed dramatic increase in wear is attributed to a combination of increased diffusivity in the beta phase of the titanium alloy in conjunction with a higher degree of recrystallization of the prior beta phase upon cooling. Results of other observations such as the influence of carbide grain size on tool wear are also discussed.
Method of making carbide/fluoride/silver composites

NASA Technical Reports Server (NTRS)

Sliney, Harold E. (Inventor); Dellacorte, Christopher (Inventor)

1991-01-01

A composition containing 30 to 70 percent chromium carbide, 5 to 20 percent soft noble metal, 5 to 20 percent metal fluorides, and 20 to 60 percent metal binder is used in a powdered metallurgy process for the production of self-lubricating components, such as bearings. The use of the material allows the self-lubricating bearing to maintain its low friction properties over an extended range of operating temperatures.
Scalable and Tunable Carbide-Phosphide Composite Catalyst System for the Thermochemical Conversion of Biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regmi, Yagya; Rogers, Bridget; Labbe, Nicole

We have prepared composite materials of hexagonal nickel phosphide and molybdenum carbide (Mo2C) utilizing a simple and scalable two-stage synthesis method comprised of carbothermic reduction followed by hydrothermal incubation. We observe the monophasic hexagonal phosphide Ni2P in the composite at low phosphide-to-carbide (P:C) ratios. Upon increasing the proportion of P:C, the carbide surface becomes saturated, and we detect the emergence of a second hexagonal nickel phosphide phase (Ni5P4) upon annealing. We demonstrate that vapor-phase upgrading (VPU) of whole biomass via catalytic fast pyrolysis is achievable using the composite material as a catalyst, and we monitor the resulting product slates usingmore » pyrolysis gas chromatography/mass spectrometry. Our analysis of the product vapors indicates that variation of the P:C molar ratio in the composite material affords product slates of varying complexity and composition, which is indicated by the number of products and their relative proportions in the product slate. Our results demonstrate that targeted vapor product composition can be obtained, which can potentially be utilized to tune the composition of the bio-oil downstream.« less
Scalable and Tunable Carbide-Phosphide Composite Catalyst System for the Thermochemical Conversion of Biomass

DOE PAGES

Regmi, Yagya; Rogers, Bridget; Labbe, Nicole; ...

2017-07-13

We have prepared composite materials of hexagonal nickel phosphide and molybdenum carbide (Mo2C) utilizing a simple and scalable two-stage synthesis method comprised of carbothermic reduction followed by hydrothermal incubation. We observe the monophasic hexagonal phosphide Ni2P in the composite at low phosphide-to-carbide (P:C) ratios. Upon increasing the proportion of P:C, the carbide surface becomes saturated, and we detect the emergence of a second hexagonal nickel phosphide phase (Ni5P4) upon annealing. We demonstrate that vapor-phase upgrading (VPU) of whole biomass via catalytic fast pyrolysis is achievable using the composite material as a catalyst, and we monitor the resulting product slates usingmore » pyrolysis gas chromatography/mass spectrometry. Our analysis of the product vapors indicates that variation of the P:C molar ratio in the composite material affords product slates of varying complexity and composition, which is indicated by the number of products and their relative proportions in the product slate. Our results demonstrate that targeted vapor product composition can be obtained, which can potentially be utilized to tune the composition of the bio-oil downstream.« less
Pressure generation to 65 GPa in a Kawai-type multi-anvil apparatus with tungsten carbide anvils

NASA Astrophysics Data System (ADS)

Ishii, Takayuki; Yamazaki, Daisuke; Tsujino, Noriyoshi; Xu, Fang; Liu, Zhaodong; Kawazoe, Takaaki; Yamamoto, Takafumi; Druzhbin, Dmitry; Wang, Lin; Higo, Yuji; Tange, Yoshinori; Yoshino, Takashi; Katsura, Tomoo

2017-10-01

We have expanded the pressure ranges at room and high temperatures generated in a Kawai-type multi-anvil apparatus (KMA) using tungsten carbide (WC) anvils with a high hardness of Hv = 2700 and a Young's modulus of 660 GPa. At room temperature, a pressure of 64 GPa, which is the highest pressure generated with KMA using WC anvils in the world, was achieved using 1°-tapered anvils with a 1.5-mm truncation. Pressures of 48-50 GPa were generated at high temperatures of 1600-2000 K, which are also higher than previously achieved. Tapered anvils make wide anvil gaps enabling efficient X-ray diffraction. The present pressure generation technique can be used for studying the upper part of the Earth's lower mantle down to 1200 km depth without sintered diamond anvils.
Fabrication of tungsten wire reinforced nickel-base alloy composites

NASA Technical Reports Server (NTRS)

Brentnall, W. D.; Toth, I. J.

1974-01-01

Fabrication methods for tungsten fiber reinforced nickel-base superalloy composites were investigated. Three matrix alloys in pre-alloyed powder or rolled sheet form were evaluated in terms of fabricability into composite monotape and multi-ply forms. The utility of monotapes for fabricating more complex shapes was demonstrated. Preliminary 1093C (2000F) stress rupture tests indicated that efficient utilization of fiber strength was achieved in composites fabricated by diffusion bonding processes. The fabrication of thermal fatigue specimens is also described.
Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1991-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.
Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

DOEpatents

Tiegs, T.N.; Lindemer, T.B.

1991-02-19

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.
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 properties 1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family 3. 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 superconductivity 4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour depositionmore » with a high crystallinity and very low defect concentration.« less
Effect of rolling on the high temperature tensile and stress-rupture properties of tungsten fiber-superalloy composites

NASA Technical Reports Server (NTRS)

Petrasek, D. W.

1974-01-01

An investigation was conducted to determine the effects of mechanical working on the 1093 C (2000 F) tensile and stress-rupture strength of tungsten alloy/superalloy composites. Hot pressed composites containing either conventional tungsten lamp filament wire or tungsten-1% ThO2 wire and a nickel base alloy matrix were hot rolled at 1093 C (2000 F). The hot pressed and rolled composite specimens were then tested in tension and stress-rupture at 1093 C (2000 F). Rolling decreased the degree of fiber-matrix reaction as a function of time of exposure at 1093 C (2000 F). The stress-rupture properties of the rolled composites were superior to hot pressed composites containing equivalent diameter fibers. Rolling did not appreciably affect the 1093 C (2000 F) ultimate tensile strength of the composites.
Base-metal saturation of refractory carbide coatings produced by enhanced ceramic jets in electrothermally exploded powder spray

NASA Astrophysics Data System (ADS)

Tamura, Hideki; Itaya, Masanobu

2000-09-01

Tungsten carbide and tantalum carbide were sprayed onto substrates of mild steel by the electrothermally exploded powder spray (ELTEPS) process. High-speed x-ray radiography revealed that tungsten-carbide jets of molten particles guided inside a nozzle exhibited denser flow than unguided jets at the substrate. The velocity of the jet was approximately 800 m/s at the early stage of jetting. The ceramic coatings obtained from the guided spray consisted of carbides of a few to tens of micrometers in size, which were saturated by the base metal up to the top of the coating. The coatings exhibited diffusion of the sprayed ceramics and base metal at the interface of the deposit and substrate. The enhancement of the jet flow formed a microstructure of the ceramic coating, which was saturated by the base metal even without post heat treatment.

Microstructural analysis of W-SiCf/SiC composite

NASA Astrophysics Data System (ADS)

Yoon, Hanki; Oh, Jeongseok; Kim, Gonho; Kim, Hyunsu; Takahashi, Heishichiro; Kohyama, Akira

2015-03-01

Continuous silicon carbide fiber-reinforced silicon carbide (SiCf/SiC) composites are promising structure candidates for future fusion power systems such as gas coolant fast channels, extreme high temperature reactor and fusion reactors, because of their intrinsic properties such as excellent mechanical properties, high thermal conductivity, good thermal-shock resistance as well as excellent physical and chemical stability in various environments under elevated temperature conditions. In this study, bonding of tungsten and SiCf/SiC was produced by hot-press method. Microstructure analyses were performed using SEM and TEM.
Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

DOEpatents

Lillo, Thomas M.; Chu, Henry S.; Harrison, William M.; Bailey, Derek

2013-01-22

Methods of forming composite materials include coating particles of titanium dioxide with a substance including boron (e.g., boron carbide) and a substance including carbon, and reacting the titanium dioxide with the substance including boron and the substance including carbon to form titanium diboride. The methods may be used to form ceramic composite bodies and materials, such as, for example, a ceramic composite body or material including silicon carbide and titanium diboride. Such bodies and materials may be used as armor bodies and armor materials. Such methods may include forming a green body and sintering the green body to a desirable final density. Green bodies formed in accordance with such methods may include particles comprising titanium dioxide and a coating at least partially covering exterior surfaces thereof, the coating comprising a substance including boron (e.g., boron carbide) and a substance including carbon.
Composites comprising silicon carbide fibers dispersed in magnesia-aluminate matrix and fabrication thereof and of other composites by sinter forging

DOEpatents

Panda, Prakash C.; Seydel, Edgar R.; Raj, Rishi

1989-10-03

A novel ceramic-ceramic composite of a uniform dispersion of silicon carbide fibers in a matrix of MgO.multidot.nAl.sub.2 O.sub.3 wherein n ranges from about 1 to about 4.5, said composite comprising by volume from 1 to 50% silicon carbide fibers and from 99 to 50% MgO.multidot.nAl.sub.2 O.sub.3. The composite is readily fabricated by forming a powder comprising a uniform dispersion of silicon carbide fibers in poorly crystalline phase comprising MgO and Al.sub.2 O.sub.3 in a mole ratio of n and either (a) hot pressing or preferably (b) cold pressing to form a preform and then forging utilizing a temperature in the range of 1100.degree. C. to 1900.degree. C. and a strain rate ranging from about 10.sup.-5 seconds .sup.-1 to about 1 seconds .sup.-1 so that surfaces cracks do not appear to obtain a shear deformation greater than 30%.
Non-oxidic nanoscale composites: single-crystalline titanium carbide nanocubes in hierarchical porous carbon monoliths.

PubMed

Sonnenburg, Kirstin; Smarsly, Bernd M; Brezesinski, Torsten

2009-05-07

We report the preparation of nanoscale carbon-titanium carbide composites with carbide contents of up to 80 wt%. The synthesis yields single-crystalline TiC nanocubes 20-30 nm in diameter embedded in a hierarchical porous carbon matrix. These composites were generated in the form of cylindrical monoliths but can be produced in various shapes using modern sol-gel and nanocasting methods in conjunction with carbothermal reduction. The monolithic material is characterized by a combination of microscopy, diffraction and physisorption. Overall, the results presented in this work represent a concrete design template for the synthesis of non-oxidic nanoscale composites with high surface areas.
Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

NASA Astrophysics Data System (ADS)

Ambrosio, E. P.; Abdul Karim, M. R.; Pavese, M.; Biamino, S.; Badini, C.; Fino, P.

2017-05-01

Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.
Computational-Experimental Processing of Boride/Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C

DTIC Science & Technology

2015-09-16

AFRL-AFOSR-VA-TR-2015-0314 Computational -Experimental Processing of Boride /Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C...Computational -Experimental Processing of Boride /Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C 5a. CONTRACT NUMBER 5b. GRANT...with a packed bed of B4C to form boride - carbide precipitates. Although the ultimate goal of the research endeavor is to enhance significantly the
Inorganic fullerene-like tungsten disulfide nanocoating for friction reduction of nickel-titanium alloys.

PubMed

Samorodnitzky-Naveh, Gili R; Redlich, Meir; Rapoport, Lev; Feldman, Yishay; Tenne, Reshef

2009-12-01

To fabricate a friction-reducing coating onto different nickel-titanium (NiTi) substrates using inorganic fullerene-like tungsten disulfide (IF-WS(2)) nanoparticles and to estimate in vitro friction reducing extent of the coating. Different NiTi substrates were coated with cobalt and IF-WS(2) nanoparticles film by the electrodeposition procedure. Coating composition analyses was made by scanning-electron microscopy, energy dispersive x-ray spectroscopy, x-ray powder diffractometry and x-ray photoelectron spectroscopy. Friction evaluation was carried out using standard tribological tests and an Instron system. Stable and well-adhered cobalt + IF-WS(2) coating of the NiTi substrates was obtained. Friction tests presented up to 66% reduction of the friction coefficient. NiTi alloy is widely used for many medical appliances; hence, this unique friction-reducing coating could be implemented to provide better manipulation and lower piercing rates.
SEM Evaluation of Surrounding Enamel after Finishing of Composite Restorations- Preliminary Results

NASA Astrophysics Data System (ADS)

Iovan, G.; Stoleriu, S.; Solomon, S.; Ghiorghe, A.; Sandu, A. V.; Andrian, S.

2017-06-01

The purpose of this study was to analyze the surface characteristics of the enamel adjacent to composite resin after finishing the restoration with different diamond and tungsten carbide burs. The topography of enamel was observed by using a scanning electron microscope. Finishing with extra-/ultra-fine carbide burs, and extra-fine diamond burs resulted in smooth surfaces. In few areas some superficial scratches with no clinical relevance were observed. Deep grooves were observed on the surface of enamel when fine diamond burs were used. Finishing of composite restorations with coarse burs should be avoided when there is a high risk of touching and scratching adjacent enamel during the procedure.
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.
Effects of cobalt in nickel-base superalloys

NASA Technical Reports Server (NTRS)

Tien, J. K.; Jarrett, R. N.

1983-01-01

The role of cobalt in a representative wrought nickel-base superalloy was determined. The results show cobalt affecting the solubility of elements in the gamma matrix, resulting in enhanced gamma' volume fraction, in the stabilization of MC-type carbides, and in the stabilization of sigma phase. In the particular alloy studied, these microstructural and microchemistry changes are insufficient in extent to impact on tensile strength, yield strength, and in the ductilities. Depending on the heat treatment, creep and stress rupture resistance can be cobalt sensitive. In the coarse grain, fully solutioned and aged condition, all of the alloy's 17% cobalt can be replaced by nickel without deleteriously affecting this resistance. In the fine grain, partially solutioned and aged condition, this resistance is deleteriously affected only when one-half or more of the initial cobalt content is removed. The structure and property results are discussed with respect to existing theories and with respect to other recent and earlier findings on the impact of cobalt, if any, on the performance of nickel-base superalloys.
3D-WOVEN FIBER-REINFORCED COMPOSITE FOR CAD/CAM DENTAL APPLICATION

PubMed Central

Petersen, Richard; Liu, Perng-Ru

2016-01-01

Three-dimensional (3D)-woven noncrimp fiber-reinforced composite (FRC) was tested for mechanical properties in the two principal directions of the main XY plane and compared to different Computer-Aided-Design/Computer-Aided-Machining (CAD/CAM) Dental Materials. The Dental Materials included ceramic with Vitablock Mark II®, ProCAD®, InCeram® Spinel, InCeram® Alumina and InCeram® Zirconia in addition to a resin-based 3M Corp. Paradigm® particulate-filled composite. Alternate material controls included Coors 300 Alumina Ceramic and a tungsten carbide 22% cobalt cermet. The 3D-woven FRC was vacuum assisted resin transfer molding processed as a one-depth-thickness ~19-mm preform with a vinyl-ester resin and cut into blocks similar to the commercial CAD/CAM Dental Materials. Mechanical test samples prepared for a flexural three-point span length of 10.0 mm were sectioned for minimum-depth cuts to compare machinability and fracture resistance between groups. 3D-woven FRC improved mechanical properties with significant statistical differences over all CAD/CAM Dental Materials and Coors Alumina Ceramic for flexural strength (p<0.001), resilience (p<0.05), work of fracture (p<0.001), strain energy release (p<0.05), critical stress intensity factor (p<0.001) and strain (p<0.001). PMID:27642198
3D-WOVEN FIBER-REINFORCED COMPOSITE FOR CAD/CAM DENTAL APPLICATION.

PubMed

Petersen, Richard; Liu, Perng-Ru

2016-05-01

Three-dimensional (3D)-woven noncrimp fiber-reinforced composite (FRC) was tested for mechanical properties in the two principal directions of the main XY plane and compared to different Computer-Aided-Design/Computer-Aided-Machining (CAD/CAM) Dental Materials. The Dental Materials included ceramic with Vitablock Mark II®, ProCAD®, InCeram® Spinel, InCeram® Alumina and InCeram® Zirconia in addition to a resin-based 3M Corp. Paradigm® particulate-filled composite. Alternate material controls included Coors 300 Alumina Ceramic and a tungsten carbide 22% cobalt cermet. The 3D-woven FRC was vacuum assisted resin transfer molding processed as a one-depth-thickness ~19-mm preform with a vinyl-ester resin and cut into blocks similar to the commercial CAD/CAM Dental Materials. Mechanical test samples prepared for a flexural three-point span length of 10.0 mm were sectioned for minimum-depth cuts to compare machinability and fracture resistance between groups. 3D-woven FRC improved mechanical properties with significant statistical differences over all CAD/CAM Dental Materials and Coors Alumina Ceramic for flexural strength (p<0.001), resilience (p<0.05), work of fracture (p<0.001), strain energy release (p<0.05), critical stress intensity factor (p<0.001) and strain (p<0.001).
Nitrogen anion-decorated cobalt tungsten disulfides solid solutions on the carbon nanofibers for water splitting.

PubMed

Wan, Meng; Li, Jiang; Li, Tao; Zhu, Han; Wu, Weiwei; Du, Mingliang

2018-06-28

A facile method to prepared nitrogen anion-decorated cobalt tungsten disulfides solid solutions retaining ultra-thin WS2-like nanosheet structures (The N-CoxW1-xS2) anchored on carbon nanofibers is developed. The synergistic effect of the WS2 nanosheets provides a secure framework for stabilizing the amorphous Co-S clusters, carbon nanofibers (CNFs) substrate and nitrogen anion-decoration significantly enhances the inherent conductivity of the catalyst, resulting in a significantly promoted hydrogen evolution reaction (HER) activity and stable performance compared to pure Co9S8 nanoparticles or ultra-thin WS2 nanosheets. The N-CoxW1-xS2 electrode demonstrates the excellent electrocatalytic performance, with current density of 10 mA cm-2 at a low overpotential of 93 mV and Tafel slope of 85 mV dec-1, as well as the long-term stability in acid electrolyte. The present investigation may provide a feasible strategy for incorporating other heteroatoms into transitional metal disulfides (TMDs) materials to design catalysts with highly active and stable performance for water splitting. © 2018 IOP Publishing Ltd.
Processing and Properties of Silicon Carbide Reinforced Reaction Bonded Silicon Nitride Composites

DTIC Science & Technology

1992-11-30

work as well as of polymer derived and composite parts will be discussed. 3. Mechanical Behavior of a Continuous SiC Fiber Reinforced RBSN, S.V...Silicon carbide paniculate composites exhibited improved fracture toughnesses and evidence of R-Curve behavior. Composites made with SiC (w...i£L LIST OF TABLES Page No. 1. Summary of mechanical properties measured for RBSN and RBSN/ SiC 7 composites 2. Summary of characteristics for
Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

2004-01-01

Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.
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.
Fracture and fatigue of discontinuously reinforced copper/tungsten composites

NASA Technical Reports Server (NTRS)

Harris, B.; Ramani, S. V.

1975-01-01

The strength, toughness and resistance to cyclic crack propagation of composites consisting of copper reinforced with short tungsten wires of various lengths have been studied and the results compared with the behavior of continuously reinforced composites manufactured by the same method, i.e., by vacuum hot-pressing. It has been found that whereas the resistance to fatigue crack growth of continuously reinforced composites is very similar to that of continuous Al/stainless steel composites reported elsewhere, the addition of short fibers completely changes the mode of fracture, and no direct comparisons are possible. In effect, short fibers inhibit single crack growth by causing plastic flow to be distributed rather than localized, and although these composites are much less strong than continuous fiber composites, they nevertheless have much greater fatigue resistance.
Boron-carbide-aluminum and boron-carbide-reactive metal cermets. [B/sub 4/C-Al

DOEpatents

Halverson, D.C.; Pyzik, A.J.; Aksay, I.A.

1985-05-06

Hard, tough, lighweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidated step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modules of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi..sqrt..in. These composites and methods can be used to form a variety of structural elements.
Tungsten fiber reinforced superalloy composite high temperature component design considerations

NASA Technical Reports Server (NTRS)

Winsa, E. A.

1982-01-01

Tungsten fiber reinforced superalloy composites (TFRS) are intended for use in high temperature turbine components. Current turbine component design methodology is based on applying the experience, sometimes semiempirical, gained from over 30 years of superalloy component design. Current composite component design capability is generally limited to the methodology for low temperature resin matrix composites. Often the tendency is to treat TFRS as just another superalloy or low temperature composite. However, TFRS behavior is significantly different than that of superalloys, and the high environment adds consideration not common in low temperature composite component design. The methodology used for preliminary design of TFRS components are described. Considerations unique to TFRS are emphasized.
Combined Photoemission Spectroscopy and Electrochemical Study of a Mixture of (Oxy)carbides as Potential Innovative Supports and Electrocatalysts.

PubMed

Calvillo, Laura; Valero-Vidal, Carlos; Agnoli, Stefano; Sezen, Hikmet; Rüdiger, Celine; Kunze-Liebhäuser, Julia; Granozzi, Gaetano

2016-08-03

Active and stable non-noble metal materials, able to substitute Pt as catalyst or to reduce the Pt amount, are vitally important for the extended commercialization of energy conversion technologies, such as fuel cells and electrolyzers. Here, we report a fundamental study of nonstoichiometric tungsten carbide (WxC) and its interaction with titanium oxycarbide (TiOxCy) under electrochemical working conditions. In particular, the electrochemical activity and stability of the WxC/TiOxCy system toward the ethanol electrooxidation reaction (EOR) and hydrogen evolution reaction (HER) are investigated. The chemical changes caused by the applied potential are established by combining photoemission spectroscopy and electrochemistry. WxC is not active toward the ethanol electrooxidation reaction at room temperature but it is highly stable under these conditions thanks to the formation of a passive thin film on the surface, consisting mainly of WO2 and W2O5, which prevents the full oxidation of WxC. In addition, WxC is able to adsorb ethanol, forming ethoxy groups on the surface, which constitutes the first step for the ethanol oxidation. The interaction between WxC and TiOxCy plays an important role in the electrochemical stability of WxC since specific orientations of the substrate are able to stabilize WxC and prevent its corrosion. The beneficial interaction with the substrate and the specific surface chemistry makes tungsten carbide a good electrocatalyst support or cocatalyst for direct ethanol fuel cells. However, WxC is active toward the HER and chemically stable under hydrogen reduction conditions, since no changes in the chemical composition or dissolution of the film are observed. This makes tungsten carbide a good candidate as electrocatalyst support or cocatalyst for the electrochemical production of hydrogen.

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.
Progress toward a tungsten alloy wire/high temperature alloy composite turbine blade

NASA Technical Reports Server (NTRS)

Ritzert, F. J.; Dreshfield, R. L.

1992-01-01

A tungsten alloy wire reinforced high temperature alloy composite is being developed for potential application as a hollow turbine blade for advanced rocket engine turbopumps. The W-24Re-HfC alloy wire used for these composite blades provides an excellent balance of strength and wire ductility. Preliminary fabrication, specimen design, and characterization studies were conducted by using commercially available W218 tungsten wire in place of the W-24Re-Hfc wire. Subsequently, two-ply, 50 vol pct composite panels using the W-24Re-HfC wire were fabricated. Tensile tests and metallographic studies were performed to determine the material viability. Tensile strengths of a Waspaloy matrix composite at 870 C were 90 pct of the value expected from rule-of-mixtures calculations. During processing of this Waspaloy matrix composite, a brittle phase was formed at the wire/matrix interface. Circumferential wire cracks were found in this phase. Wire coating and process evaluation efforts were performed in an attempt to solve the reaction problem. Although problems were encountered in this study, wire reinforced high temperature alloy composites continue to show promise for turbopump turbine blade material improvement.
Pendulum impact resistance of tungsten fiber/metal matrix composites.

NASA Technical Reports Server (NTRS)

Winsa, E. A.; Petrasek, D. W.

1972-01-01

The impact properties of copper, copper-10 nickel, and a superalloy matrix reinforced with tungsten fibers were studied. In most cases the following increased composite impact strength: increased fiber or matrix toughness, decreased fiber-matrix reaction, increased test temperature, hot working and heat treatment. Notch sensitivity was reduced by increasing fiber or matrix toughness. The effect of fiber content depended on the relative toughness of the fibers and matrix. Above 530 K a 60 volume per cent superalloy matrix composite had a greater impact strength than a turbine blade superalloy, whereas below 530 K a hot worked 56 volume per cent composite had a greater impact strength than the superalloy.
Silicon carbide/calcium aluminosilicate: A notch-insensitive ceramic-matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cady, C.M.; Mackin, T.J.; Evans, A.G.

Tension experiments performed on a 0/90 laminated silicon carbide/calcium aluminosilicate composite at room temperature establish that this material is notch insensitive. Multiple matrix cracking is determined to be the stress redistribution mechanism. This mechanism is found to provide a particularly efficient means for creating local inelastic strains, which eliminate stress concentrations.
Initial Considerations of a Dust Dispenser for Injecting Tungsten Particles in Space

DTIC Science & Technology

2014-09-26

INTRODUCTION We began to learn how to work with tungsten particles as fine as corn starch , which must be ejected as individual particles. Several designs...purchased a quantity of tungsten carbide spheres, with diameters in our desired range, because of their shape and improved resistance to oxidation... resistance . When ignoring air resistance the only force acting on the particle after it leaves the dispenser is gravity. The particle motion can be
Preparation and Dynamic Mechanical Properties at Elevated Temperatures of a Tungsten/Glass Composite

NASA Astrophysics Data System (ADS)

Gao, Chong; Wang, Yingchun; Ma, Xueya; Liu, Keyi; Wang, Yubing; Li, Shukui; Cheng, Xingwang

2018-03-01

Experiments were conducted to prepare a borosilicate glass matrix composite containing 50 vol.% tungsten and examine its dynamic compressive behavior at elevated temperatures in the range of 450-775 °C. The results show that the homogenous microstructure of the tungsten/glass composite with relative density of 97% can be obtained by hot-pressing sintering at 800 °C for 1 h under pressure of 30 MPa. Dynamic compressive testing was carried out by a separate Hopkinson pressure bar system with a synchronous device. The results show that the peak stress decreases and the composite transforms from brittle to ductile in nature with testing temperature increasing from 450 to 750 °C. The brittle-ductile transition temperature is about 500 °C. Over 775 °C, the composite loses load-bearing capacity totally because of the excessive softening of the glass phase. In addition, the deformation and failure mechanism were analyzed.
Carbide Coatings for Nickel Alloys, Graphite and Carbon/Carbon Composites to be used in Fluoride Salt Valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagle, Denis; Zhang, Dajie

2015-10-22

The focus of this research was concerned with developing materials technology that supports the evolution of Generation IV Advanced High Temperature Reactor (AHTR) concepts. Specifically, we investigate refractory carbide coatings for 1) nickel alloys, and 2) commercial carbon-carbon composites (CCCs). Numerous compelling reasons have driven us to focus on carbon and carbide materials. First, unlike metals, the strength and modulus of CCCs increase with rising temperature. Secondly, graphite and carbon composites have been proven effective for resisting highly corrosive fluoride melts such as molten cryolite [Na₃AlF₆] at ~1000°C in aluminum reduction cells. Thirdly, graphite and carbide materials exhibit extraordinary radiationmore » damage tolerance and stability up to 2000°C. Finally, carbides are thermodynamically more stable in liquid fluoride salt than the corresponding metals (i.e. Cr and Zr) found in nickel based alloys.« less
Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

NASA Technical Reports Server (NTRS)

Poindexter, A. M.

1967-01-01

Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.
Deuterium retention in tungsten in dependence of the surface conditions

NASA Astrophysics Data System (ADS)

Ogorodnikova, O. V.; Roth, J.; Mayer, M.

2003-03-01

The paper reviews hydrogen isotope retention and migration in tungsten (W). Due to a large scatter of the deuterium (D) retention database, new measurements of ion-driven D retention in polycrystalline W foil have been performed to clarify the mechanism of hydrogen isotope inventory in W. Deuterium retention has been investigated as a function of ion fluence, implantation temperature, incident energy and surface conditions. Special attention has been given on the investigation of D retention in thin films of tungsten carbide and tungsten oxide which can be formed on W surface in a fusion device. Such kinds of films increase the D retention in W. Several points are reviewed: (i) inventory in pure W, (ii) inventory in W pre-implanted by carbon ions and (iii) inventory in tungsten oxide.
A study of lubrication, processing conditions, and material combinations that affect the wear of micro-textured-carbide coated cobalt-chromium-molybdenum alloy surfaces used for artificial joints implants

NASA Astrophysics Data System (ADS)

Ettienne-Modeste, Geriel A.

Total joint replacement remains one of the most successful treatments for arthritis. The most common materials used for artificial joints are metals (e.g., cobalt-chrome alloys or titanium alloys), which articulate against ultra-high molecular weight polyethylene. Wear related failures of artificial joints may be reduced with the use of novel micro-textured carbide surfaces. The micro-textured carbide surfaces were deposited on a CoCrMo alloy using microwave plasma-assisted chemical vapor deposition. Wear tests were conducted to determine wear mechanisms and properties of the micro-textured surfaces. The research presented in this thesis addresses: (1) rheolgoical behavior of bovine calf serum with and without antibacterial agents to determine whether they can be used as appropriate models for synovial fluid, (2) the wear behavior of the micro-textured CoCrMo surface system, and (3) the mechanical and material properties of the micro-textured CoCrMo alloy surface relevant to wear performance. The rheological studies showed that the apparent viscosity of bovine calf serum increased with an increase in concentration before and after the serum was used for wear testing. The wear analysis showed that the processing conditions (2hr deposition vs. 4hr deposition times) affected the wear properties. The 2hr carbide-on-carbide lubricated in 50% BCS produced the lowest wear factor and rate for the five wear couple systems containing the carbide disk or plate material. Greater wear was produced in serum without penicillin/streptomycin (P/S) compared to the serum containing P/S. A greater carbide coating thickness 10 (micrometers) was produced during the 4hr deposition time than for the 2hr deposition (˜3mum). The nano-hardness value was higher than the micro-hardness for both the 4hr and 2hr carbide surfaces. The micro-hardness results of the worn carbide surfaces showed that an increase in BCS concentration from 0% to 100% increased the micro-hardness (HV) for carbide
Study on drilling induced delamination of woven kenaf fiber reinforced epoxy composite using carbide drills

NASA Astrophysics Data System (ADS)

Suhaily, M.; Hassan, C. H. Che; Jaharah, A. G.; Azmi, H.; Afifah, M. A.; Khairusshima, M. K. Nor

2018-04-01

In this research study, it presents the influences of drilling parameters on the delamination factor during the drilling of woven kenaf fiber reinforced epoxy composite laminates when using the carbide drill bits. The purpose of this study is to investigate the influence of drilling parameters such as cutting speed, feed rate and drill sizes on the delamination produced when drilling woven kenaf reinforced epoxy composite using the non-coated carbide drill bits. The damage generated on the woven kenaf reinforced epoxy composite laminates were observed both at the entrance and exit surface during the drilling operation. The experiments were conducted according to the Box Behnken experimental designs. The results indicated that the drill diameter has a significant influence on the delamination when drilling the woven kenaf fiber reinforced epoxy composites.
Preparation and microwave absorbing properties of carbon/cobalt ferromagnetic composites.

PubMed

Li, Wangchang; Qiao, Xiaojing; Zhao, Hui; Wang, Shuman; Ren, Qingguo

2013-02-01

Carbon/cobalt ferromagnetic light composites with high performance of microwave absorbing properties were prepared by hydrothermal method using starch and hollow cobalt ferrites. It was concluded that after carbonization the spinel structure ferrites changed to Co3Fe7 alloys and the temperature of graphitization was significantly decreased for the catalytic of CoFe2O4/Co3Fe7. The increase of carbon content, and exist of CoFe2O4/Co3Fe7 heightened the microwave absorbing properties. Electromagnetic parameters were tested with 40% of the titled materials and 60% of paraffin wax composites by using HP8722ES vector network analyzer. The reflection was also simulated through transmission line theory. The microwave absorbers exhibited a maximum reflection loss -43 dB and the electromagnetic wave absorption less than -10 dB was found to exceed 3.0 GHz between 11.6 GHz and 15 GHz for an absorber thickness of 2 mm.
Wear behavior of carbide tool coated with Yttria-stabilized zirconia nano particles.

NASA Astrophysics Data System (ADS)

Jadhav, Pavandatta M.; Reddy, Narala Suresh Kumar

2018-04-01

Wear mechanism takes predominant role in reducing the tool life during machining of Titanium alloy. Challenges of wear mechanisms such as variation in chip, high pressure loads and spring back are responsible for tool wear. In addition, many tool materials are inapt for machining due to low thermal conductivity and volume specific heat of these materials results in high cutting temperature during machining. To confront this issue Electrostatic Spray Coating (ESC) coating technique is utilized to enhance the tool life to an acceptable level. The Yttria Stabilized Zirconia (YSZ) acts as a thermal barrier coating having high thermal expansion coefficient and thermal shock resistance. This investigation focuses on the influence of YSZ nanocoating on the tungsten carbide tool material and improve the machinability of Ti-6Al-4V alloy. YSZ nano powder was coated on the tungsten carbide pin by using ESC technique. The coatings have been tested for wear and friction behavior by using a pin-on-disc tribological tester. The dry sliding wear test was performed on Titanium alloy (Ti-6Al-4V) disc and YSZ coated tungsten carbide (pin) at ambient atmosphere. The performance parameters like wear rate and temperature rise were considered upon performing the dry sliding test on Ti-6Al-4V alloy disc. The performance parameters were calculated by using coefficient of friction and frictional force values which were obtained from the pin on disc test. Substantial resistance to wear was achieved by the coating.
Composites based on SiO2 micrograins and cobalt-containing nanoparticles: Synthesis, structure, and magnetic properties

NASA Astrophysics Data System (ADS)

Yurkov, G. Yu.; Kozinkin, A. V.; Koksharov, Yu. A.; Ovchenkov, E. A.; Volkov, A. N.; Kozinkin, Yu. A.; Vlasenko, V. G.; Popkov, O. V.; Ivicheva, S. N.; Kargin, Yu. F.

2013-05-01

Cobalt-containing particles are synthesized on the surface of silicon dioxide micrograins prepared by the Stöber-Fink method. The composition and structure of nanoparticles are determined by transmission electron microscopy, X-ray diffraction analysis, and EXAFS. The average size of cobalt nanoparticles in the samples is found to be 14 ± 5 nm. The resulting composites are shown to be ferromagnetics with low specific magnetization values.
Investigation of iron adsorption on composite transition metal carbides in steel by first-principles calculation

NASA Astrophysics Data System (ADS)

Xiong, Hui-Hui; Gan, Lei; Tong, Zhi-Fang; Zhang, Heng-Hua; Zhou, Yang

2018-05-01

The nucleation potential of transition metal (TM) carbides formed in steel can be predicted by the behavior of iron adsorption on their surface. Therefore, Fe adsorption on the (001) surface of (A1-xmx)C (A = Nb, Ti, m = Mo, V) was investigated by the first-principles method to reveal the initialization of Fe nucleation. The Mulliken population and partial density of state (PDOS) were also calculated and analyzed in this work. The results show that Fe adsorption depends on the composition and configuration of the composite carbides. The adsorption energy (Wads) of Fe on most of (A1-xmx)C is larger than that of Fe on pure TiC or NbC. The maximum Wads is found for Fe on (Nb0.5Mo0.5)C complex carbide, indicating that this carbide has the high nucleation capacity at early stage. The Fe adsorption could be improved by the segregation of Cr and Mn atoms on the surfaces of (Nb0.5Mo0.5)C and (Ti0.5Mo0.5)C. The PDOS analysis of (Cr, Mn)-doped systems further explains the strong interactions between Fe and Cr or Mn atoms.
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.
Preservation of Earth-forming events in the tungsten isotopic composition of modern flood basalts.

PubMed

Rizo, Hanika; Walker, Richard J; Carlson, Richard W; Horan, Mary F; Mukhopadhyay, Sujoy; Manthos, Vicky; Francis, Don; Jackson, Matthew G

2016-05-13

How much of Earth's compositional variation dates to processes that occurred during planet formation remains an unanswered question. High-precision tungsten isotopic data from rocks from two large igneous provinces, the North Atlantic Igneous Province and the Ontong Java Plateau, reveal preservation to the Phanerozoic of tungsten isotopic heterogeneities in the mantle. These heterogeneities, caused by the decay of hafnium-182 in mantle domains with high hafnium/tungsten ratios, were created during the first ~50 million years of solar system history, indicating that portions of the mantle that formed during Earth's primary accretionary period have survived to the present. Copyright © 2016, American Association for the Advancement of Science.
Anisotropic electrical transport of flexible tungsten carbide nanostructures: towards nanoscale interconnects and electron emitters

NASA Astrophysics Data System (ADS)

Sun, Bo; Sun, Yong; Wang, Chengxin

2017-11-01

Due to the coexistence of metal- and ionic-bonds in a hexagonal tungsten carbide (WC) lattice, disparate electron behaviors were found in the basal plane and along the c-axial direction, which may create an interesting anisotropic mechanical and electrical performance. To demonstrate this, low-dimensional nanostructures such as nanowires and nanosheets are suitable for investigation because they usually grow in single crystals with special orientations. Herein, we report the experimental research regarding the anisotropic conductivity of [0001] grown WC nanowires and basal plane-expanded nanosheets, which resulted in a conductivity of 7.86 × 103 Ω-1 · m-1 and 7.68 × 104 Ω-1 · m-1 respectively. This conforms to the fact that the highly localized W d state aligns along the c direction, while there is little intraplanar directional bonding in the W planes. With advanced micro-manipulation technology, the conductivity of a nanowire was tested to be approximately constant, even under a considerable bending state. Moreover, the field electron emission of WC was evaluated based on large area emission and single nanowire (nanosheet) emission. A single nanowire exhibits a stable electron emission performance, which can output emission currents >3 uA before fusing. These results provide useful references to assess low-dimensional WC nanostructures as electronic materials in flexible devices, such as nanoscale interconnects and electron emitters.
Silver-hafnium braze alloy

DOEpatents

Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

2003-12-16

A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.
Development of high toughness, high strength aluminide-bonded carbide ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becher, P.F.; Plucknett, K.P.; Tiegs, T.N.

1997-04-01

Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that aremore » retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.« less

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.
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.
Investigation of the fracture mechanics of boride composites

NASA Technical Reports Server (NTRS)

Kaufman, L.; Clougherty, E. V.; Nesor, H.

1971-01-01

Fracture energies of WC-6Co, Boride 5 (ZrB2+SiC), Boride 8(ZrB2+SiC+C) and Boride 8-M2(ZrB2+SiC+C) were measured by slow bend and impact tests of notched charpy bars. Cobalt bonded tungsten carbide exhibited impact energies of 0.76 ft-lb or 73.9 in-lb/square inch. Boride 5 and the Boride 8 exhibit impact energies one third and one quarter of that observed for WC-6Co comparing favorably with measurements for SiC and Si3N4. Slow bend-notched bar-fracture energies for WC-6Co were near 2.6 in-lb/square inch or 1/20 the impact energies. Slow bend energies for Boride 8-M2, Boride 8 and Boride 5 were 58%, 42% and 25% of the value observed for WC-6Co. Fractograph showed differences for WC-6Co where slow bend testing resulted in smooth transgranular cleavage while samples broken by impact exhibited intergranular failures. By contrast the boride fractures showed no distinction based on testing method. Fabrication studies were conducted to effect alteration of the boride composites by alloying and introduction of graphite cloth.
Addition of a Second Metal (Co) to Molybdenum Carbide: Effect of the Doping Route.

PubMed

Araujo, C P B; Frota, A V V M; Souza, C P de; Souto, M V M; Barbosa, C M

2018-03-01

Molybdenum carbide is an interesting and versatile material, which has important applications in the metal matrix industry as a reinforcement material, as well as in the catalytic field. Though many papers suggest different methodologies for adding cobalt to the carbide structure aiming either to increase catalytic activity or enhancing mechanical proprieties such as ductility, etc. no straightforward evaluation is available. In the present paper two doping methodologies were studied: via solid state mixture of powders and via wet impregnation. Ammonium molybdate [(NH4)2MoO4] and cobalt nitrate [Co(NO3)2·6H2O] were used as starting materials and the doping process was carried out before carburization reaction. Those materials were characterized by FT-IR, SEM, XRF and XRD. The carbo-reduction products' were evaluated on XRD and XRF basis. Doped precursors' evaluation showed that the wet impregnated doped materials presented smaller particle sizes, were more homogeneous and retained more cobalt than the solid state doped ones. However, final products' assessment indicated that the solid state methodology was able to retain a greater dopant percentage according to XRF evaluation, and XRD data indicated a more intrinsic addition of the dopant to the carbide structure. In addition, no significant changes on particle size could be attributed to any of the methodologies, both producing Mo2C of approximately 30 nm.
A quantitative analysis of aerosols inside an armored vehicle perforated by a kinetic energy penetrator containing tungsten, nickel, and cobalt.

PubMed

Gold, Kenneth; Cheng, Yung Sung; Holmes, Thomas D

2007-04-01

These tests were conducted to develop a database that could be used to assess risks to soldiers from exposure to aerosolized metallic particulates when the crew compartment of an Abrams tank is perforated by a kinetic energy penetrator. Quantitative data are reported for aerosols produced by kinetic energy penetrators containing tungsten, nickel, and cobalt. The following are addressed: (1) concentrations and rates of particle settling inside the vehicle, (2) particle size distribution, (3) inhalable and respirable particulates, (4) distribution of aerosol particles by mass, and (5) particle shapes. The scenario described in this report simulates a rare occurrence. The lessons learned, however, highlight a requirement for developing protocols for analyses of metals in body fluids and urine as soon as practical, and also for implementing targeted postdeployment medical surveillance programs that monitor both body burden for respired metals and pulmonary function.
Bimetallic iron and cobalt incorporated MFI/MCM-41 composite and its catalytic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Baoshan, E-mail: bsli@mail.buct.edu.cn; Xu, Junqing; Li, Xiao

2012-05-15

Graphical abstract: The formation of FeCo-MFI/MCM-41 composite is based on two steps, the first step of synthesizing the MFI-type proto-zeolite unites under hydrothermal conditions. The second step of assembling these zeolite fragment together new silica and heteroatom source on the CTAB surfactant micelle to synthesize the mesoporous product with hexagonal structure. Highlights: Black-Right-Pointing-Pointer Bimetallic iron and cobalt incorporated MFI/MCM-41 composite was prepared using templating method. Black-Right-Pointing-Pointer FeCo-MFI/MCM-41 composite simultaneously possessed two kinds of meso- and micro-porous structures. Black-Right-Pointing-Pointer Iron and cobalt ions incorporated into the silica framework with tetrahedral coordination. -- Abstract: The MFI/MCM-41 composite material with bimetallic Fe andmore » Co incorporation was prepared using templating method via a two-step hydrothermal crystallization procedure. The obtained products were characterized by a series of techniques including powder X-ray diffraction, N{sub 2} sorption, transmission electron microscopy, scanning electron microscope, H{sub 2} temperature programmed reduction, thermal analyses, and X-ray absorption fine structure spectroscopy of the Fe and Co K-edge. The catalytic properties of the products were investigated by residual oil hydrocracking reactions. Characterization results showed that the FeCo-MFI/MCM-41 composite simultaneously possessed two kinds of stable meso- and micro-porous structures. Iron and cobalt ions were incorporated into the silicon framework, which was confirmed by H{sub 2} temperature programmed reduction and X-ray absorption fine structure spectroscopy. This composite presented excellent activities in hydrocracking of residual oil, which was superior to the pure materials of silicate-1/MCM-41.« less
Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

2016-01-01

The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.
A plasma-sprayed valve coating

NASA Technical Reports Server (NTRS)

Brennan, A.; Olmore, A. B.

1980-01-01

Need to reduce wear on nickel alloy seats and poppets for Space Shuttle main engine led to fused cobalt/tungsten carbide coating. Coating, which is dense, wear-resistant, and nonporous, can be applied in controlled amounts to various substrate configurations. Ease of application to parts with intricate shapes and contours should make coating useful in automotive and aircraft manufacturing.
LIQUID PHASE SINTERING OF METALLIC CARBIDES

DOEpatents

Hammond, J.; Sease, J.D.

1964-01-21

An improved method is given for fabricating uranium carbide composites, The method comprises forming a homogeneous mixture of powdered uranium carbide, a uranium intermetallic compound which wets and forms a eutectic with said carbide and has a non-uranium component which has a relatively high vapor pressure at a temperature in the range 1200 to 1500 deg C, and an organic binder, pressing said mixture to a composite of desired green strength, and then vacuum sintering said composite at the eutectic forming temperature for a period sufficient to remove at least a portion of the non-uranium containing component of said eutectic. (AEC)
Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Yongqiang; Luo, Heng; Zhang, Haibin, E-mail: hbzhang@caep.cn, E-mail: pengshuming@caep.cn

2016-03-15

Lightweight graphene nanoplatelet (GNP)/boron carbide (B{sub 4}C) composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI) shielding effectiveness (SE) has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B{sub 4}C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ∼ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high dielectric loss as well as multiple reflections by aligned GNPs inside the composite. The GNP/B{sub 4}C composite is demonstratedmore » to be promising candidate of high-temperature microwave EMI shielding material.« less
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
Characterization of failure processes in tungsten copper composites under fatigue loading conditions

NASA Technical Reports Server (NTRS)

Kim, Yong-Suk; Verrilli, Michael J.; Gabb, Timothy P.

1989-01-01

A fractographic and metallographic investigation was performed on specimens of a tungsten fiber reinforced copper matrix composite (9 vol percent), which had experienced fatigue failures at elevated temperatures. Major failure modes and possible failure mechanisms, with an emphasis placed on characterizing fatigue damage accumulation, were determined. Metallography of specimens fatigued under isothermal cyclic loading suggested that fatigue damage initiates in the matrix. Cracks nucleated within the copper matrix at grain boundaries, and they propagated through cavity coalescence. The growing cracks subsequently interacted with the reinforcing tungsten fibers, producing a localized ductile fiber failure. Examinations of interrupted tests before final failure confirmed the suggested fatigue damage processes.
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.
Plasma-induced damage of tungsten coatings on graphite limiters

NASA Astrophysics Data System (ADS)

Fortuna, E.; Rubel, M. J.; Psoda, M.; Andrzejczuk, M.; Kurzydowski, K. J.; Miskiewicz, M.; Philipps, V.; Pospieszczyk, A.; Sergienko, G.; Spychalski, M.; Zielinski, W.

2007-03-01

Vaccum plasma sprayed tungsten coatings with an evaporated sandwich Re-W interlayer on graphite limiter blocks were studied after the experimental campaign in the TEXTOR tokamak. The coating morphology was modified by high-heat loads and co-deposition of species from the plasma. Co-deposits contained fuel species, carbon, boron and silicon. X-ray diffractometer phase analysis indicated the coexistence of metallic tungsten and its carbides (WC and W2C) and boride (W2B). In the Re-W layer the presence of carbon was detected in a several micrometres thick zone. In the overheated part of the limiter, the Re-W layer was transformed into a sigma phase.
Gas metal arc welding in refurbishment of cobalt base superalloys

NASA Astrophysics Data System (ADS)

Shahriary, M. S.; Miladi Gorji, Y.; Kolagar, A. M.

2017-01-01

Refurbishments of superalloys which are used in manufacturing gas turbine hot components usually consists of removing cracks and other defects by blending and then repair welding in order to reconstruct damaged area. In this study, the effects of welding parameters on repair of FSX-414 superalloy, as the most applicable cobalt base superalloy in order to manufacture gas turbine nozzles, by use of Gas Metal Arc Welding (GMAW) technic were investigated. Results then were compared by Gas Tungsten Arc Welding (GTAW). Metallographic and SEM studies of the microstructure of the weld and HAZ showed that there are no noticeable defects in the microstructure by use of GMAW. Also, chemical analysis and morphologies of carbide in both methods are similar. Hardness profile of the GM AW structure then also compared with GTAW and no noticeable difference was observed between the profiles. Also, proper tensile properties, compared with GTAW, can be achieved by use of optimum parameters that can be obtained by examining the current and welding speed. Tensile properties of optimized condition of the GMAW then were compared with GTAW. It was seen that the room and high temperature tensile properties of the GMAW structure is very similar and results confirmed that changing the technic did not have any significant influence on the properties.
Structural models of increasing complexity for icosahedral boron carbide with compositions throughout the single-phase region from first principles

NASA Astrophysics Data System (ADS)

Ektarawong, A.; Simak, S. I.; Alling, B.

2018-05-01

We perform first-principles calculations to investigate the phase stability of boron carbide, concentrating on the recently proposed alternative structural models composed not only of the regularly studied B11Cp (CBC) and B12(CBC), but also of B12(CBCB) and B12( B4 ). We find that a combination of the four structural motifs can result in low-energy electron precise configurations of boron carbide. Among several considered configurations within the composition range of B10.5C and B4C , we identify in addition to the regularly studied B11Cp (CBC) at the composition of B4C two low-energy configurations, resulting in a new view of the B-C convex hull. Those are [B12 (CBC)]0.67[B12(B4)] 0.33 and [B12 (CBC)]0.67[ B12 (CBCB)]0.33, corresponding to compositions of B10.5C and B6.67C , respectively. As a consequence, B12(CBC) at the composition of B6.5C , previously suggested in the literature as a stable configuration of boron carbide, is no longer part of the B -C convex hull. By inspecting the electronic density of states as well as the elastic moduli, we find that the alternative models of boron carbide can provide a reasonably good description for electronic and elastic properties of the material in comparison with the experiments, highlighting the importance of considering B12(CBCB) and B12( B4 ), together with the previously proposed B11Cp (CBC) and B12(CBC), as the crucial ingredients for modeling boron carbide with compositions throughout the single-phase region.
High Temperature Joining and Characterization of Joint Properties in Silicon Carbide-Based Composite Materials

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2015-01-01

Advanced silicon carbide-based ceramics and composites are being developed for a wide variety of high temperature extreme environment applications. Robust high temperature joining and integration technologies are enabling for the fabrication and manufacturing of large and complex shaped components. The development of a new joining approach called SET (Single-step Elevated Temperature) joining will be described along with the overview of previously developed joining approaches including high temperature brazing, ARCJoinT (Affordable, Robust Ceramic Joining Technology), diffusion bonding, and REABOND (Refractory Eutectic Assisted Bonding). Unlike other approaches, SET joining does not have any lower temperature phases and will therefore have a use temperature above 1315C. Optimization of the composition for full conversion to silicon carbide will be discussed. The goal is to find a composition with no remaining carbon or free silicon. Green tape interlayers were developed for joining. Microstructural analysis and preliminary mechanical tests of the joints will be presented.
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.
Creep resistant high temperature martensitic steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6 carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followedmore » by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.« less
Creep resistant high temperature martensitic steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, copper, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followedmore » by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.« less

Modified silicon carbide whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1991-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.
Modified silicon carbide whiskers

DOEpatents

Tiegs, T.N.; Lindemer, T.B.

1991-05-21

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.
A Model for the Oxidation of Carbon Silicon Carbide Composite Structures

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

2004-01-01

A mathematical theory and an accompanying numerical scheme have been developed for predicting the oxidation behavior of carbon silicon carbide (C/SiC) composite structures. The theory is derived from the mechanics of the flow of ideal gases through a porous solid. The result of the theoretical formulation is a set of two coupled nonlinear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The nonlinear differential equations are cast into matrix equations by applying the Bubnov-Galerkin weighted residual method, allowing for the solution of the differential equations numerically. The numerical method is demonstrated by utilizing the method to model the carbon oxidation and weight loss behavior of C/SiC specimens during thermogravimetric experiments. The numerical method is used to study the physics of carbon oxidation in carbon silicon carbide composites.
Ductile-Phase-Toughened Tungsten for Plasma-Facing Materials

NASA Astrophysics Data System (ADS)

Cunningham, Kevin Hawkins

A variety of processing approaches were employed to fabricate ductile-phase-toughened (DPT) tungsten (W) composites. Mechanical testing and analytical modeling were used to guide composite development. This work provides a basis for further development of W composites to be used in structural divertor components of future fusion reactors. W wire was tested in tension, showing significant ductility and strength. Coatings of copper (Cu) or tungsten carbide (WC) were applied to the W wire via electrodeposition and carburization, respectively. Composites were fabricated using spark plasma sintering (SPS) to consolidate W powders together with each type of coated W wire. DPT behavior, e.g. crack arrest and crack bridging, was not observed in three-point bend testing of the sintered composites. A laminate was fabricated by hot pressing W and Cu foils together with W wires, and subsequently tested in tension. This laminate was bonded via hot pressing to thick W plate as a reinforcing layer, and the composite was tested in three-point bending. Crack arrest was observed along with some fiber pullout, but significant transverse cracking in the W plate confounded further fracture toughness analysis. The fracture toughness of thin W plate was measured in three-point bending. W plates were brazed with Cu foils to form a laminate. Crack arrest and crack bridging were observed in three-point bend tests of the laminate, and fracture resistance curves were successfully calculated for this DPT composite. An analytical model of crack bridging was developed using the basis described by Chao in previous work by the group. The model uses the specimen geometry, matrix properties, and the stress-displacement function of a ductile reinforcement ("bridging law") to calculate the fracture resistance curve (R-curve) and load-displacement curve (P-D curve) for any test specimen geometry. The code was also implemented to estimate the bridging law of an arbitrary composite using R-curve data
Thermodynamic Considerations of Contamination by Alloying Elements of Remelted End-of-Life Nickel- and Cobalt-Based Superalloys

NASA Astrophysics Data System (ADS)

Lu, Xin; Matsubae, Kazuyo; Nakajima, Kenichi; Nakamura, Shinichiro; Nagasaka, Tetsuya

2016-06-01

Cobalt and nickel are high-value commodity metals and are mostly used in the form of highly alloyed materials. The alloying elements used may cause contamination problems during recycling. To ensure maximum resource efficiency, an understanding of the removability of these alloying elements and the controllability of some of the primary alloying elements is essential with respect to the recycling of end-of-life (EoL) nickel- and cobalt-based superalloys by remelting. In this study, the distribution behaviors of approximately 30 elements that are usually present in EoL nickel- and cobalt-based superalloys in the solvent metal (nickel, cobalt, or nickel-cobalt alloy), oxide slag, and gas phases during the remelting were quantitatively evaluated using a thermodynamic approach. The results showed that most of the alloying elements can be removed either in the slag phase or into the gas phase. However, the removal of copper, tin, arsenic, and antimony by remelting is difficult, and they remain as tramp elements during the recycling. On the other hand, the distribution tendencies of iron, molybdenum, and tungsten can be controlled by changing the remelting conditions. To increase the resource efficiency of recycling, preventing contamination by the tramp elements and identifying the alloying compositions of EoL superalloys are significantly essential, which will require the development of efficient prior alloy-sorting systems and advanced separation technologies.
The influence of CO adsorption on the surface composition of cobalt/palladium alloys

NASA Astrophysics Data System (ADS)

Murdoch, A.; Trant, A. G.; Gustafson, J.; Jones, T. E.; Noakes, T. C. Q.; Bailey, P.; Baddeley, C. J.

2016-04-01

Segregation induced by the adsorption of gas phase species can strongly influence the composition of bimetallic surfaces and can therefore play an important role in influencing heterogeneous catalytic reactions. The addition of palladium to cobalt catalysts has been shown to promote Fischer Tropsch catalysis. We investigate the adsorption of CO onto bimetallic CoPd surfaces on Pd{111} using a combination of reflection absorption infrared spectroscopy and medium energy ion scattering. The vibrational frequency of adsorbed CO provides crucial information on the adsorption sites adopted by CO and medium energy ion scattering probes the surface composition before and after CO exposure. We show that cobalt segregation is induced by CO adsorption and rationalise these observations in terms of the strength of adsorption of CO in various surface adsorption sites.
Carbon nanotubes/cobalt sulfide composites as potential high-rate and high-efficiency supercapacitors

NASA Astrophysics Data System (ADS)

Chen, Chia-Ying; Shih, Zih-Yu; Yang, Zusing; Chang, Huan-Tsung

2012-10-01

We have prepared carbon nanotube (CNT)/cobalt sulfide (CoS) composites from cobalt nitrate, thioacetamide, and CNTs in the presence of poly(vinylpyrrolidone). CNT/CoS composites are deposited onto fluorine-doped tin oxide glass substrates and then subjected to simple annealing at 300 °C for 0.5 h to fabricate CNT/CoS electrodes. Data collected from Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and d-spacing reveal the changes in the CoS structures and crystalline lattices after annealing. Cyclic voltammetry results reveal that the annealed CNT/CoS composite electrodes yield values of 2140 ± 90 and 1370 ± 50 F g-1 for specific capacitance at scan rates of 10 and 100 mV s-1, respectively. To the best of our knowledge, the annealed CNT/CoS composite electrodes provide higher specific capacitance relative to other reported ones at a scan rate of 100 mV s-1. CNT/CoS composite electrodes yield a power density of 62.4 kW kg-1 at a constant discharge current density of 217.4 A g-1. With such a high-rate capacity and power density, CNT/CoS composite supercapacitors demonstrate great potential as efficient energy storage devices.
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.
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.
Spark plasma sintering of tantalum carbide and graphene reinforced tantalum carbide composites

NASA Astrophysics Data System (ADS)

Kalluri, Ajith Kumar

Tantalum carbide (TaC), an ultra-high temperature ceramic (UHTC), is well known for its exceptional properties such as high hardness (15-19 GPa), melting point (3950 °C), elastic modulus (537 GPa), chemical resistance, and thermal shock resistance. To make TaC to be the future material for hypersonic vehicles, it is required to improve its thermal conductivity, strength, and fracture toughness. Researchers have previously reinforced TaC ceramic with carbides of silicon and boron as well as carbon nanotubes (CNTs), however, these reinforcements either undergo chemical changes or induce defects in the matrix during processing. In addition, these reinforcements exhibit a very minimal improvement in the properties. In the present work, we attempted to improve TaC fracture toughness by reinforcing with graphene nano-platelets (GNPs) and processing through spark plasma sintering at high temperature of 2000 °C, pressure of 70 MPa, and soaking time of 10 min. In addition, we investigated the active densification mechanism during SPS of TaC powder and the effect of ball milling time on mechanical properties of sintered TaC. A relative density of >96% was achieved using SPS of monolithic TaC (<3 μm). Ball milling improved the sintering kinetics and improved the mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness). Activation energy (100 kJ/mol) and stress exponent (1.2) were obtained using the analytical model developed for power-law creep. Grain boundary sliding is proposed as active densification mechanism based on these calculations. Reinforcing GNPs (2-6 vol.% ) in the TaC matrix improved relative density (99.8% for TaC-6 vol.% GNP). Also ˜150% and ˜180% increase in flexural strength and fracture toughness, respectively, was observed for TaC-6 vol.% GNP composite. The significant improvement in these properties is attributed to improved densification and toughening mechanisms such as sheet pull-out and crack
Stability of the tungsten diselenide and silicon carbide heterostructure against high energy proton exposure

NASA Astrophysics Data System (ADS)

Walker, Roger C.; Shi, Tan; Jariwala, Bhakti; Jovanovic, Igor; Robinson, Joshua A.

2017-10-01

Single layers of tungsten diselenide (WSe2) can be used to construct ultra-thin, high-performance electronics. Additionally, there has been considerable progress in controlled and direct growth of single layers on various substrates. Based on these results, high-quality WSe2-based devices that approach the limit of physical thickness are now possible. Such devices could be useful for space applications, but understanding how high-energy radiation impacts the properties of WSe2 and the WSe2/substrate interface has been lacking. In this work, we compare the stability against high energy proton radiation of WSe2 and silicon carbide (SiC) heterostructures generated by mechanical exfoliation of WSe2 flakes and by direct growth of WSe2 via metal-organic chemical vapor deposition (MOCVD). These two techniques produce WSe2/SiC heterostructures with distinct differences due to interface states generated during the MOCVD growth process. This difference carries over to differences in band alignment from interface states and the ultra-thin nature of the MOCVD-grown material. Both heterostructures are not susceptible to proton-induced charging up to a dose of 1016 protons/cm2, as measured via shifts in the binding energy of core shell electrons and a decrease in the valence band offset. Furthermore, the MOCVD-grown material is less affected by the proton exposure due to its ultra-thin nature and a greater interaction with the substrate. These combined effects show that the directly grown material is suitable for multi-year use in space, provided that high quality devices can be fabricated from it.
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 (W 2 C/AC). The effects of botanical species and fractionation methods on lignin structure and the activity of W 2 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 W 2 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 W 2 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.
Joining of porous silicon carbide bodies

DOEpatents

Bates, Carl H.; Couhig, John T.; Pelletier, Paul J.

1990-05-01

A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.
Attenuated effect of tungsten carbide nanoparticles on voltage-gated sodium current of hippocampal CA1 pyramidal neurons.

PubMed

Shan, Dehong; Xie, Yongling; Ren, Guogang; Yang, Zhuo

2013-02-01

Nanomaterials and relevant products are now being widely used in the world, and their safety becomes a great concern for the general public. Tungsten carbide nanoparticles (nano-WC) are widely used in metallurgy, aeronautics and astronautics, however our knowledge regarding the influence of nano-WC on neurons is still lacking. The aim of this study was to investigate the impact of nano-WC on tetrodotoxin (TTX)-sensitive voltage-activated sodium current (I(Na)) of hippocampal CA1 pyramidal neurons. Results showed that acute exposure of nano-WC attenuated the peak amplitudes of I(Na) in a concentration-dependent manner. The minimal effective concentration was 10(-5)g/ml. The exposure of nano-WC significantly decreased current amplitudes of the current-voltage curves of I(Na) from -50 to+50 mV, shifted the steady-state activation and inactivation curves of I(Na) negatively and delayed the recovery of I(Na) from inactivation state. After exposure to nano-WC, the peak amplitudes, overshoots and the V-thresholds of action potentials (APs) were markedly reduced. These results suggested that exposure of nano-WC could influence some characteristics of APs evoked from the hippocampal CA1 neurons by modifying the kinetics of voltage-gated sodium channels (VGSCs). Copyright © 2012 Elsevier Ltd. All rights reserved.
Optimizing the vacuum plasma spray deposition of metal, ceramic, and cermet coatings using designed experiments

NASA Astrophysics Data System (ADS)

Kingswell, R.; Scott, K. T.; Wassell, L. L.

1993-06-01

The vacuum plasma spray (VPS) deposition of metal, ceramic, and cermet coatings has been investigated using designed statistical experiments. Processing conditions that were considered likely to have a significant influence on the melting characteristics of the precursor powders and hence deposition efficiency were incorporated into full and fractional factorial experimental designs. The processing of an alumina powder was very sensitive to variations in the deposition conditions, particularly the injection velocity of the powder into the plasma flame, the plasma gas composition, and the power supplied to the gun. Using a combination of full and fractional factorial experimental designs, it was possible to rapidly identify the important spraying variables and adjust these to produce a deposition efficiency approaching 80 percent. The deposition of a nickel-base alloy metal powder was less sensitive to processing conditions. Generally, however, a high degree of particle melting was achieved for a wide range of spray conditions. Preliminary experiments performed using a tungsten carbide/cobalt cermet powder indicated that spray efficiency was not sensitive to deposition conditions. However, microstructural analysis revealed considerable variations in the degree of tungsten carbide dissolution. The structure and properties of the optimized coatings produced in the factorial experiments are also discussed.
Functionally gradient hard carbon composites for improved adhesion and wear

NASA Astrophysics Data System (ADS)

Narayan, Roger Jagdish

A new approach is proposed for fabricating biomedical devices that last longer and are more biocompatible than those presently available. In this approach, a bulk material is chosen that has desirable mechanical properties (low modulus, high strength, high ductility and high fatigue strength). This material is coated with corrosion-resistant, wear-resistant, hard, and biocompatible hard carbon films. One of the many forms of carbon, tetrahedral amorphous carbon, consists mainly of sp3-bonded atoms. Tetrahedral amorphous carbon possesses properties close to diamond in terms of hardness, atomic smoothness, and inertness. Tetrahedral amorphous carbon and diamond films usually contain large amounts of compressive and sometimes tensile stresses; adhesive failure from these stresses has limited widespread use of these materials. This research involves processing, characterization and modeling of functionally gradient tetrahedral amorphous carbon and diamond composite films on metals (cobalt-chromium and titanium alloys) and polymers (polymethylmethacrylate and polyethylene) used in biomedical applications. Multilayer discontinuous thin films of titanium carbide, titanium nitride, aluminum nitride, and tungsten carbide have been developed to control stresses and graphitization in diamond films. A morphology of randomly interconnected micron sized diamond crystallites provides increased toughness and stress reduction. Internal stresses in tetrahedral amorphous carbon were reduced via incorporation of carbide forming elements (silicon and titanium) and noncarbide forming elements (copper, platinum, and silver). These materials were produced using a novel target design during pulsed laser deposition. These alloying atoms reduce hardness and sp3-bonded carbon content, but increase adhesion and wear resistance. Silver and platinum provide the films with antimicrobial properties, and silicon provides bioactivity and aids bone formation. Bilayer coatings were created that couple
Neutron shielding behavior of thermoplastic natural rubber/boron carbide composites

NASA Astrophysics Data System (ADS)

Mat Zali, Nurazila; Yazid, Hafizal; Megat Ahmad, Megat Harun Al Rashid

2018-01-01

Many shielding materials have been designed against the harm of different types of radiation to the human body. Today, polymer-based lightweight composites have been chosen by the radiation protection industry. In the present study, thermoplastic natural rubber (TPNR) composites with different weight percent of boron carbide (B4C) fillers (0% to 30%) were fabricated as neutron shielding through melt blending method. Neutron attenuation properties of TPNR/B4C composites have been investigated. The macroscopic cross section (Σ), half value layer (HVL) and mean free path length (λ) of the composites have been calculated and the transmission curves have been plotted. The obtained results show that Σ, HVL and λ greatly depend on the B4C content. Addition of B4C fillers into TPNR matrix were found to enhance the macroscopic cross section values thus decrease the mean free path length (λ) and half value layer (HVL) of the composites. The transmission curves exhibited that the neutron transmission of the composites decreased with increasing shielding thickness. These results showed that TPNR/B4C composites have high potential for neutron shielding applications.
Silicon Carbide as a tritium permeation barrier in tungsten plasma-facing components

NASA Astrophysics Data System (ADS)

Wright, G. M.; Durrett, M. G.; Hoover, K. W.; Kesler, L. A.; Whyte, D. G.

2015-03-01

The control of tritium inventory is of great importance in future fusion reactors, not only from a safety standpoint but also to maximize a reactor's efficiency. Due to the high mobility of hydrogenic species in tungsten (W) one concern is the loss of tritium from the system via permeation through the tungsten plasma-facing components (PFC). This can lead to loss of tritium through the cooling channels of the wall thereby mandating tritium monitoring and recovery methods for the cooling system of the first wall. The permeated tritium is then out of the fuel cycle and cannot contribute to energy production until it is recovered and recycled into the system.
Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

NASA Technical Reports Server (NTRS)

Lineback, L. D.; Manning, C. R.

1971-01-01

Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.
Electrocatalysis using transition metal carbide and oxide nanocrystals

NASA Astrophysics Data System (ADS)

Regmi, Yagya N.

Carbides are one of the several families of transition metal compounds that are considered economic alternatives to catalysts based on noble metals and their compounds. Phase pure transition metal carbides of group 4-6 metals, in the first three periods, were synthesized using a common eutectic salt flux synthesis method, and their electrocatalytic activities compared under uniform electrochemical conditions. Mo2C showed highest hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) activities among the nine metal carbides investigated, but all other metal carbides also showed substantial activities. All the metal carbides showed remarkable enhancement in catalytic activities as supports, when compared to traditional graphitic carbon as platinum support. Mo2C, the most active transition metal carbide electrocatalyst, was prepared using four different synthesis routes, and the synthesis route dependent activities compared. Bifunctional Mo 2C that is HER as well as oxygen evolution reaction (OER) active, was achieved when the carbide was templated on a multiwalled carbon nanotube using carbothermic reduction method. Bimetallic carbides of Fe, Co, and Ni with Mo or W were prepared using a common carbothermic reduction method. Two different stoichiometries of bimetallic carbides were obtained for each system within a 60 °C temperature window. While the bimetallic carbides showed relatively lower electrocatalytic activities towards HER and ORR in comparison to Mo2C and WC, they revealed remarkably higher OER activities than IrO2 and RuO2, the state-of-the-art OER catalysts. Bimetallic oxides of Fe, Co, and Ni with Mo and W were also prepared using a hydrothermal synthesis method and they also revealed OER activities that are much higher than RuO2 and IrO2. Additionally, the OER activities were dependent on the degree and nature of hydration in the bimetallic oxide crystal lattice, with the completely hydrated, as synthesized, cobalt molybdate and nickel

Fabrication of Lightweight Radiation Shielding Composite Materials by Field Assisted Sintering Technique (FAST)

NASA Technical Reports Server (NTRS)

Prasad, Narasimha; Trivedi, Sudhir; Chen, Henry; Kutcher, Susan; Zhang, Dajie; Singh, Jogender

2017-01-01

Advances in radiation shielding technologies are needed to protect humans and electronic components from all threats of space radiation over long durations. In this paper, we report on the use of the innovative and novel fabrication technology known as Field Assisted Sintering Technology (FAST) to fabricate lightweight material with enhanced radiation shielding strength to safeguard humans and electronics suitable for next generation space exploration missions. The base materials we investigated were aluminum (Al), the current standard material for space hardware, and Ultra-High Molecular Weight Polyethylene (UHMWPE), which has high hydrogen content and resistance to nuclear reaction from neutrons, making it a good shielding material for both gamma radiation and particles. UHMWPE also has high resistance to corrosive chemicals, extremely low moisture sensitivity, very low coefficient of friction, and high resistance to abrasion. We reinforced the base materials by adding high density (ie, high atomic weight) metallic material into the composite. These filler materials included: boron carbide (B4C), tungsten (W), tungsten carbide (WC) and gadolinium (Gd).
Influence of adding strong-carbide-formation elements multiply on particle-reinforced Fe-matrix composite layer produced by laser cladding

NASA Astrophysics Data System (ADS)

Ma, Mingxing; Liu, Wenjin; Zhong, Minlin; Zhang, Hongjun; Zhang, Weiming

2005-01-01

In the research hotspot of particle reinforced metal-matrix composite layer produced by laser cladding, in-situ reinforced particles obtained by adding strong-carbide-formation elements into cladding power have been attracting more attention for their unique advantage. The research has demonstrated that when adding strong-carbide-formation elements-Ti into the cladding powder of the Fe-C-Si-B separately, by optimizing the composition, better cladding coating with the characters of better strength and toughness, higher wear resistance and free of cracks. When the microstructure of cladding coating is hypoeutectic microstructure, its comprehensive performance is best. The research discovered that, compositely adding the strong-carbide-formation elements like Ti+V, Ti+Zr or V+Zr into the cladding coating is able to improve its comprehensive capability. All the cladding coatings obtained are hypoeutectic microstructure. The cladding coatings have a great deal of particulates, and its average microhardness reaches HV0.2700-1400. The research also discovered that the cladding coating obtained is of less cracking after adding the Ti+Zr.
Controlled synthesis of Co2C nanochains using cobalt laurate as precursor: Structure, growth mechanism and magnetic properties

NASA Astrophysics Data System (ADS)

Zhang, Yajing; Zhu, Yuan; Wang, Kangjun; Li, Da; Wang, Dongping; Ding, Fu; Meng, Dan; Wang, Xiaolei; Choi, Chuljin; Zhang, Zhidong

2018-06-01

Cobalt carbides (Co2C and Co3C) nanocomposites exhibit interesting hard magnetic property, controlled synthesis of individual phase facilitates to clarify the magnetism of each, but it is difficult to obtain the single phase. We present a new approach to address this issue via a polyol refluxing process, using cobalt laurate as the precursor. The single phase Co2C magnetic nanochains self-assembled by nanoparticles are synthesized. The precursor is the key factor for controlling the growth kinetics of the Co2C nanochains. Cobalt, instead of cobalt carbides, is produced if cobalt chloride, acetate and acetylacetonate replace cobalt laurate as the precursor, respectively. The evolution of the growth process has been studied. In the formation of Co2C, first fcc-Co produces, then it transforms into Co2C by carbon diffusion process, and the produced carbon first exists in disordered state and then a small amount of them transforms into graphite. Saturation magnetization (Ms) of Co2C nanochains obtained at 300 °C for 20, 60, and 180 min are 27.1, 18.9, and 10.9 emu g-1, respectively. The decrease of Ms caused by increasing carbon content, and the carbon content are much larger than the stoichiometric ratio value of Co2C (9.2 wt%). The Co2C nanochains have mesoporous pore of 3.8 nm and the specific surface area of 48.6 m2 g-1.
Preparation and characterization of high performance NBR/cobalt (II) chloride coordination composites

NASA Astrophysics Data System (ADS)

Shang, Peng; Shao, Chengli; Li, Qiqing; Wu, Chifei

2018-02-01

Acrylonitrile-butadiene rubber (NBR) composites filled with Cobalt (II) Chloride (CoCl2) particles were prepared by a solvent dispersion method. Acetone was selected as solvent for NBR and CoCl2. To directly enhance the interaction between NBR and CoCl2, a coordination reaction was generated by hot pressing at 200 °C. Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), and x-ray photoelectron spectroscopy (XPS) were employed to investigate the coordination reaction. Results showed that the coordination reaction occurred between the nitrile groups (-CN) of NBR and cobalt ions (Co2+) of CoCl2. Compared with the properties of pure NBR, the tensile strength of NBR/CoCl2 composites filled with 10 parts per hundreds of rubber (phr) CoCl2 increased 2200%. Scanning electron microscopy (SEM) indicated that the CoCl2 particles were dispersed in the NBR matrix homogeneously. The indistinguishable interface between CoCl2 particles and NBR matrix indicated good compatibility. Additionally, thermogravimetric analysis (TGA) showed that coordination reaction improved heat resistance of NBR matrix.
Effects of cobalt on the microstructure of Udimet 700. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Engel, M. A.

1982-01-01

Cobalt, a critical and "strategic" alloying element in many superalloys, was systematically substituted by nickel in experimental alloys Udimet 700 containing 0.1, 4.3, 8.6, 12.8 and the standard 17.0 wt.% cobalt. Electrolytic and chemical extraction techniques, X-ray diffraction, scanning electron and optical microscopy were used for the microstructural studies. The total weight fraction of gamma' was not significantly affected by the cobalt content, although a difference in the size and quantities of the primary and secondary gamma' phases was apparent. The lattice parameters of the gamma' were found to increase with increasing cobalt content while the lattice mismatch between the gamma matrix and gamma' phases decreased. Other significant effects of cobalt on the weight fraction, distribution and formation of the carbide and boride phases as well as the relative stability of the experimental alloys during long-time aging are also discussed.
Hydrogen permeation properties of plasma-sprayed tungsten*1

NASA Astrophysics Data System (ADS)

Anderl, R. A.; Pawelko, R. J.; Hankins, M. R.; Longhurst, G. R.; Neiser, R. A.

1994-09-01

Tungsten has been proposed as a plasma-facing component material for advanced fusion facilities. This paper reports on laboratory-scale studies that were done to assess the hydrogen permeation properties of plasma-sprayed tungsten for such applications. The work entailed deuterium permeation measurements for plasma-sprayed (PS) tungsten coatings, sputter-deposited (SP) tungsten coatings, and steel substrate material using a mass-analyzed, 3 keV D 3+ ion beam with fluxes of ˜6.5 × 10 19 D/m 2 s. Extensive characterization analyses for the plasma-sprayed tungsten coatings were made using Auger spectrometry and scanning electron microscopy (SEM). Observed permeation rates through composite PS-tungsten/steel specimens were several orders of magnitude below the permeation levels observed for SP-tungsten/steel composite specimens and pure steel specimens. Characterization analyses indicated that the plasma-sprayed tungsten coating had a nonhomogeneous microstructure that consisted of splats with columnar solidification, partially-melted particles with grain boundaries, and void regions. Reduced permeation levels can be attributed to the complex microstructure and a substantial surface-connected porosity.
Enhanced optical and electrochemical properties of polyaniline/cobalt oxide nano composite

NASA Astrophysics Data System (ADS)

Niranjana, M.; Yesappa, L.; Ashokkumar, S. P.; Vijeth, H.; Basappa, M.; Devendrappa, H.

2018-05-01

Polyaniline and its composites at different wt. % of Cobalt oxide nano (PDC1, PDC2 and PDC5) were prepared by in-situ chemical reaction method The optical property was carried out using UV-Vis. Absorption Spectroscopy. The electrochemical property like cyclic voltammetry and galvonostatic charging-discharging was carried out for PANI and PDC nanocomposite electrode materials. A specific capacitance of 212.08 F/g and 336.41 F/g with scan rates 100 and 200 mV/s at 0.4 A/g current density respectively. These results are suggesting PDC composite is a prominent candidate for supercapacitor properties applications.
Persistence of tungsten oxide particle/fiber mixtures in artificial human lung fluids

PubMed Central

2010-01-01

Background During the manufacture of tungsten metal for non-sag wire, tungsten oxide powders are produced as intermediates and can be in the form of tungsten trioxide (WO3) or tungsten blue oxides (TBOs). TBOs contain fiber-shaped tungsten sub-oxide particles of respirable or thoracic size. The aim of this research was to investigate whether fiber-containing TBOs had prolonged biodurability in artificial lung fluids compared to tungsten metal or WO3 and therefore potentially could pose a greater inhalation hazard. Methods Dissolution of tungsten metal, WO3, one fiber-free TBO (WO2.98), and three fiber-containing TBO (WO2.81, WO2.66, and WO2.51) powders were measured for the material as-received, dispersed, and mixed with metallic cobalt. Solubility was evaluated using artificial airway epithelial lining fluid (SUF) and macrophage phagolysosomal simulant fluid (PSF). Results Dissolution rates of tungsten compounds were one to four orders of magnitude slower in PSF compared to SUF. The state of the fiber-containing TBOs did not influence their dissolution in either SUF or PSF. In SUF, fiber-containing WO2.66 and WO2.51 dissolved more slowly than tungsten metal or WO3. In PSF, all three fiber-containing TBOs dissolved more slowly than tungsten metal. Conclusions Fiber-containing TBO powders dissolved more slowly than tungsten metal and WO3 powders in SUF and more slowly than tungsten metal in PSF. Existing pulmonary toxicological information on tungsten compounds indicates potential for pulmonary irritation and possibly fibrosis. Additional research is needed to fully understand the hazard potential of TBOs. PMID:21126345
Metallic transfer between metals in sliding contact examined by auger emission spectroscopy

NASA Technical Reports Server (NTRS)

Pepper, S. V.

1972-01-01

Metallic transfer between polycrystalline metals in sliding contact was examined. Hemispherical riders of iron, nickel, and cobalt were slid on tungsten, tantalum, niobium, and molybdenum disks in ultrahigh vacuum. Auger emission spectroscopy was used to monitor the elemental composition of the disk surfaces. Iron, nickel, and cobalt transferred to tungsten, whereas only cobalt transferred to tantalum, niobium, and molybdenum. The results of this investigation are discussed in terms of the cohesive energy and strain hardening characteristics of the specimen materials.
Critical aspect ratio for tungsten fibers in copper-nickel matrix composites

NASA Technical Reports Server (NTRS)

Jech, R. W.

1975-01-01

Stress-rupture and tensile tests were conducted at 816 C (1500 F) to determine the effect of matrix composition on the minimum fiber length to diameter ratio (critical aspect ratio) below which fibers in a tungsten fiber/copper-nickel alloy matrix composite could not be stressed to their ultimate load carrying capability. This study was intended to simulate some of the conditions that might be encountered with materials combinations used in high-temperature composites. The critical aspect ratio for stress-rupture was found to be greater than for short-time tension, and it increased as the time to rupture increased. The increase was relatively slight, and calculated fiber lengths for long service appear to be well within practical size limits for effective reinforcement and ease of fabrication of potential gas turbine components.
Methanol electro-oxidation on platinum modified tungsten carbides in direct methanol fuel cells: a DFT study.

PubMed

Sheng, Tian; Lin, Xiao; Chen, Zhao-Yang; Hu, P; Sun, Shi-Gang; Chu, You-Qun; Ma, Chun-An; Lin, Wen-Feng

2015-10-14

In exploration of low-cost electrocatalysts for direct methanol fuel cells (DMFCs), Pt modified tungsten carbide (WC) materials are found to be great potential candidates for decreasing Pt usage whilst exhibiting satisfactory reactivity. In this work, the mechanisms, onset potentials and activity for electrooxidation of methanol were studied on a series of Pt-modified WC catalysts where the bare W-terminated WC(0001) substrate was employed. In the surface energy calculations of a series of Pt-modified WC models, we found that the feasible structures are mono- and bi-layer Pt-modified WCs. The tri-layer Pt-modified WC model is not thermodynamically stable where the top layer Pt atoms tend to accumulate and form particles or clusters rather than being dispersed as a layer. We further calculated the mechanisms of methanol oxidation on the feasible models via methanol dehydrogenation to CO involving C-H and O-H bonds dissociating subsequently, and further CO oxidation with the C-O bond association. The onset potentials for the oxidation reactions over the Pt-modified WC catalysts were determined thermodynamically by water dissociation to surface OH* species. The activities of these Pt-modified WC catalysts were estimated from the calculated kinetic data. It has been found that the bi-layer Pt-modified WC catalysts may provide a good reactivity and an onset oxidation potential comparable to pure Pt and serve as promising electrocatalysts for DMFCs with a significant decrease in Pt usage.
Study of the reaction of tungsten carbide in molten alkali metal nitrates. Syntheses of divalent (s and d blocks) metal tungstates

NASA Astrophysics Data System (ADS)

Deloume, Jean-Pierre; Marote, Pedro; Sigala, Catherine; Matei, Cristian

2003-08-01

WC is tested as precursor to synthesize metal tungstates by reaction in molten alkali metal nitrates. This constitutes a complex redox system with two reducing agents, W and C, and an oxidizer having several oxidation states. The mass loss due to the evolution of gases reveals the reaction steps. The infrared analyses of the gas phase show what kind of reaction develops according to the temperature. WC produces a water-soluble alkali metal tungstate. The reaction of a mixture of WC and a divalent metal chloride (Mg, Ca, Ba, Ni, Cu, Zn) leads to water-insoluble metal tungstates. As the reactivity of the cations increases in the order Zn, Ni, Cu, the reaction of WC is modified by their presence. The physico-chemical characterizations of the products show that some of them are contaminated either by WC or by metal oxide. Some others are rather pure products. These differences, in relationship with the other analyses, allow to propose first reaction pathways of the tungsten carbide in molten salts.
The interface in tungsten fiber reinforced niobium metal-matrix composites. Final Report Ph.D. Thesis - Case Western Reserve Univ., Cleveland, OH

NASA Technical Reports Server (NTRS)

Grobstein, Toni L.

1989-01-01

The creep resistance of tungsten fiber reinforced niobium metal-matrix composites was evaluated. The interface region between the fiber and matrix was characterized by microhardness and electron probe microanalysis measurements which indicated that its properties were between those of fiber and matrix. However, the measured properties of the composite exceeded those calculated by the rule of mixtures even when the interface zone was assumed to retain all the strength of the fiber. The composite structure appeared to enhance the strengths of both the fibers and the matrix above what they exhibited in stand-alone tests. The effect of fiber orientation and matrix alloy composition on the fiber/matrix interface were also evaluated. Small alloying additions of zirconium and tungsten to the niobium matrix affected the creep resistance of the composites only slightly. A decrease in the creep resistance of the composite with increasing zirconium content in the matrix was ascribed to an increase in the diffusion rate of the fiber/matrix interdiffusion reaction, and a slight increase in the creep resistance of the composite was observed with an addition of 9 w percent tungsten to the matrix. In addition, Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending on the fiber orientation relative to the stress axis.
High-temperature brazing for reliable tungsten CFC joints

NASA Astrophysics Data System (ADS)

Koppitz, Th; Pintsuk, G.; Reisgen, U.; Remmel, J.; Hirai, T.; Sievering, R.; Rojas, Y.; Casalegno, V.

2007-03-01

The joining of tungsten and carbon-based materials is demanding due to the incompatibility of their chemical and thermophysical properties. Direct joining is unfeasible by the reason of brittle tungsten carbide formation. High-temperature brazing has been investigated in order to find a suitable brazing filler metal (BFM) which successfully acts as an intermediary between the incompatible properties of the base materials. So far only low Cr-alloyed Cu-based BFMs provide the preferential combination of good wetting action on both materials, tolerable interface reactions, and a precipitation free braze joint. Attempts to implement a higher melting metal (e.g. Pd, Ti, Zr) as a BFM have failed up to now, because the formation of brittle precipitations and pores in the seam were inevitable. But the wide metallurgical complexity of this issue is regarded to offer further joining potential.
Presence of Tungsten-Containing Fibers in Tungsten Refining and Manufacturing Processes

PubMed Central

Mckernan, John L.; Toraason, Mark A.; Fernback, Joseph E.; Petersen, Martin R.

2009-01-01

In tungsten refining and manufacturing processes, a series of tungsten oxides are typically formed as intermediates in the production of tungsten powder. The present study was conducted to characterize airborne tungsten-containing fiber dimensions, elemental composition and concentrations in the US tungsten refining and manufacturing industry. During the course of normal employee work activities, seven personal breathing zone and 62 area air samples were collected and analyzed using National Institute for Occupational Safety and Health (NIOSH) fiber sampling and counting methods to determine dimensions, composition and airborne concentrations of fibers. Mixed models were used to identify relationships between potential determinants and airborne fiber concentrations. Results from transmission electron microscopy analyses indicated that airborne fibers with length >0.5 μm, diameter >0.01 μm and aspect ratios ≥3:1 were present on 35 of the 69 air samples collected. Overall, the airborne fibers detected had a geometric mean length ≈3 μm and diameter ≈0.3 μm. Ninety-seven percent of the airborne fibers identified were in the thoracic fraction (i.e. aerodynamic diameter ≤ 10 μm). Energy dispersive X-ray spectrometry results indicated that airborne fibers prior to the carburization process consisted primarily of tungsten and oxygen, with other elements being detected in trace quantities. Based on NIOSH fiber counting ‘B’ rules (length > 5 μm, diameter < 3 μm and aspect ratio ≥ 5:1), airborne fiber concentrations ranged from below the limit of detection to 0.085 fibers cm−3, with calcining being associated with the highest airborne concentrations. The mixed model procedure indicated that process temperature had a marginally significant relationship to airborne fiber concentration. This finding was expected since heated processes such as calcining created the highest airborne fiber concentrations. The finding of airborne tungsten-containing fibers in
Abrasive wear of resin composites as related to finishing and polishing procedures.

PubMed

Turssi, Cecilia P; Ferracane, Jack L; Serra, Mônica C

2005-07-01

Finishing and polishing procedures may cause topographical changes and introduce subsurface microcracks in dental composite restoratives. Since both of these effects may contribute toward the kinetics of wear, the purpose of this study was to assess and correlate the wear and surface roughness of minifilled and nanofilled composites finished and polished by different methods. Specimens (n=10) made of a minifilled and a nanofilled composite were finished and polished with one of the four sequences: (1) tungsten carbide burs plus Al(2)O(3)-impregnated brush (CbBr) or (2) tungsten carbide burs plus diamond-impregnated cup (CbCp), (3) diamond burs plus brush (DmBr) or (4) diamond burs plus cup (DmCp). As a control, abrasive papers were used. After surface roughness had been quantified, three-body abrasion was simulated using the OHSU wear machine. The wear facets were then scanned to measure wear depth and post-testing roughness. All sets of data were subjected to ANOVA and Tukey's tests (alpha=0.05). Pearson's correlation test was applied to check for the existence of a relationship between pre-testing roughness and wear. Significantly smoother surfaces were attained with the sequences CbBr and CbCp, whereas DmCp yielded the roughest surface. Regardless of the finishing/polishing technique, the nanofilled composite exhibited the lowest pre-testing roughness and wear. There was no correlation between the surface roughness achieved after finishing/polishing procedures and wear (p=0.3899). Nano-sized materials may have improved abrasive wear resistance over minifilled composites. The absence of correlation between wear and surface roughness produced by different finishing/polishing methods suggests that the latter negligibly influences material loss due to three-body abrasion.
Development and characterization of (Ti, Mo)C carbides reinforced Fe-based surface composite coating produced by laser cladding

NASA Astrophysics Data System (ADS)

Wang, Xinhong; Zhang, Min; Qu, Shiyao

2010-09-01

In this study, in situ multiple carbides reinforced Fe-based surface composite coatings were fabricated successfully by laser cladding a precursor mixture of graphite, ferrotitanium (Fe-Ti) and ferromolybdenum (Fe-Mo) powders. The results showed that (Ti, Mo)C particles with flower-like and cuboidal shapes were in situ formed during the solidification and most shapes of (Ti, Mo)C particles were diversiform according to different contents of Fe-Mo powder in the Fe-Ti-Mo-C system. The growth morphology of the reinforcing (Ti, Mo)C carbide has typically faceted features, indicating that the lateral growth mechanism is still predominant growth mode under rapid solidification conditions. Increasing the amount of Fe-Mo in the reactants led to a decrease of carbide size and an increase of volume fraction of carbides. The coatings had good cracking resistance when the amounts of Fe-Mo were controlled within a range of 15 wt%.
Microstructure and orientation effects on properties of discontinuous silicon carbide/aluminum composites

NASA Technical Reports Server (NTRS)

Mcdanels, D. L.; Hoffman, C. A.

1984-01-01

Composite panels containing up to 40 vol % discontinuous silicon carbide SiC whisker, nodule, or particulate reinforcement in several aluminum matrices are commercially fabricated and the mechanical properties and microstructual characteristics are evaluated. The yield and tensile strengths and the ductility are controlled primarily by the matrix alloy, the temper condition, and the reinforcement content. Particulate and nodule reinforcements are as effective as whisker reinforcement. Increased ductility is attributed to purer, more uniform starting materials and to more mechanical working during fabrication. Comparing mechanical properties with those of other aluminum alloys shows that these low cost, lightweight composites demonstrate very good potential for application to aerospace structures.
Interface control and mechanical property improvements in silicon carbide/titanium composites

NASA Technical Reports Server (NTRS)

Brewer, W. D.; Unnam, J.

1982-01-01

Several composite systems made of titanium matrix reinforced with silicon carbide fiber were investigated to obtain a better understanding of composite-degradation mechanisms and to develop techniques to minimize loss of mechanical properties during fabrication and in service. Emphasis was on interface control by fiber or matrix coatings. X-ray diffraction studies on planar samples showed that the formation of titanium silicides was greatly inhibited by the presence of aluminum or Ti3A1 layers at the fiber-matrix interface, with the Ti3A1 being more effective in reducing the reactions. Fiber studies showed that coating the fiber with a 1-micron-thick layer of aluminum improved the as-fabricated strength of a stoichiometric SiC fiber and reduced the fiber degradation during exposure to composite-fabrication conditions. Applying an interfacial barrier by coating the matrix foils instead of the fibers was found to be an effective method for improving composite strength. Reducing the fabrication temperature also resulted in significant improvements in composite strengths. Good-quality, well-consolidated composites were fabricated at temperatures well below those currently used for SiC-Ti composite fabrication.
Synchrotron-radiation-based X-ray micro-computed tomography reveals dental bur debris under dental composite restorations.

PubMed

Hedayat, Assem; Nagy, Nicole; Packota, Garnet; Monteith, Judy; Allen, Darcy; Wysokinski, Tomasz; Zhu, Ning

2016-05-01

Dental burs are used extensively in dentistry to mechanically prepare tooth structures for restorations (fillings), yet little has been reported on the bur debris left behind in the teeth, and whether it poses potential health risks to patients. Here it is aimed to image dental bur debris under dental fillings, and allude to the potential health hazards that can be caused by this debris when left in direct contact with the biological surroundings, specifically when the debris is made of a non-biocompatible material. Non-destructive micro-computed tomography using the BioMedical Imaging & Therapy facility 05ID-2 beamline at the Canadian Light Source was pursued at 50 keV and at a pixel size of 4 µm to image dental bur fragments under a composite resin dental filling. The bur's cutting edges that produced the fragment were also chemically analyzed. The technique revealed dental bur fragments of different sizes in different locations on the floor of the prepared surface of the teeth and under the filling, which places them in direct contact with the dentinal tubules and the dentinal fluid circulating within them. Dispersive X-ray spectroscopy elemental analysis of the dental bur edges revealed that the fragments are made of tungsten carbide-cobalt, which is bio-incompatible.

Electrochemical Study of Cobalt in Urea and Choline Chloride

NASA Astrophysics Data System (ADS)

Li, Min; Shi, Zhongning; Wang, Zhaowen; Reddy, Ramana G.

The nucleation mechanism of Co(II) in urea-choline chloride-CoCl2 melt at 373 K was studied using chronoamperometry. Chronoamperometry experiments confirm that the electrodeposition of cobalt on tungsten electrode is governed by three-dimensional (3D) progressive nucleation and diffusion-controlled growth mechanisms. The average diffusion coefficient of Co(II) in the melt at 373 K is 1.1 × 10-6 cm2 s-1, which is in good agreement with the estimated value obtained from cyclic voltammetry data. Characterization of the Co electrodeposit using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) techniques indicate that the electrodeposit obtained at -0.75 V and 373 K contain dense and compact surface formed from pure cobalt metal.
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
High temperature tension-compression fatigue behavior of a tungsten copper composite

NASA Technical Reports Server (NTRS)

Verrilli, Michael J.; Gabb, Timothy P.

1990-01-01

The high temperature fatigue of a (O)12 tungsten fiber reinforced copper matrix composite was investigated. Specimens having fiber volume percentages of 10 and 36 were fatigued under fully-reversed, strain-controlled conditions at both 260 and 560 C. The fatigue life was found to be independent of fiber volume fraction because fatigue damage preferentially occurred in the matrix. Also, the composite fatigue lives were shorter at 560 C as compared to 260 C due to changes in mode of matrix failure. On a total strain basis, the fatigue life of the composite at 560 C was the same as the life of unreinforced copper, indicating that the presence of the fibers did not degrade the fatigue resistance of the copper matrix in this composite system. Comparison of strain-controlled fatigue data to previously-generated load-controlled data revealed that the strain-controlled fatigue lives were longer because of mean strain and mean stress effects.
Dynamics of tungsten hexacarbonyl, dicobalt octacarbonyl, and their fragments adsorbed on silica surfaces.

PubMed

Muthukumar, Kaliappan; Valentí, Roser; Jeschke, Harald O

2014-05-14

Tungsten and cobalt carbonyls adsorbed on a substrate are typical starting points for the electron beam induced deposition of tungsten or cobalt based metallic nanostructures. We employ first principles molecular dynamics simulations to investigate the dynamics and vibrational spectra of W(CO)6 and W(CO)5 as well as Co2(CO)8 and Co(CO)4 precursor molecules on fully and partially hydroxylated silica surfaces. Such surfaces resemble the initial conditions of electron beam induced growth processes. We find that both W(CO)6 and Co2(CO)8 are stable at room temperature and mobile on a silica surface saturated with hydroxyl groups (OH), moving up to half an Angström per picosecond. In contrast, chemisorbed W(CO)5 or Co(CO)4 ions at room temperature do not change their binding site. These results contribute to gaining fundamental insight into how the molecules behave in the simulated time window of 20 ps and our determined vibrational spectra of all species provide signatures for experimentally distinguishing the form in which precursors cover a substrate.
Silicon Carbide Monofilament Reinforced Titanium Composites For Space Structures: A New Material Option

NASA Astrophysics Data System (ADS)

Kyle-Henney, Stephen; Flitcroft, Stephen; Shatwell, Robert; Gibbon, David; Voss, Gary; Harkness, Patrick

2012-07-01

Silicon carbide fibre reinforced titanium composite material has been in development since the 1980s initially for high temperature structures on hypersonic vehicles (HOTOL, NASP). Since then development has focused on military and civil aircraft. Development in the European Union has reached a level of maturity where it is again being considered for space applications. Current activities include pressure vessels and studies for launch vehicles and satellite applications. The paper provides background to the technology key performance characteristics current application work and future activities. The renewed interest in hypersonic vehicles has also picked up on the potential for lightweight metallic composites.
Rhodamine B removal on A-rGO/cobalt oxide nanoparticles composite by adsorption from contaminated water

NASA Astrophysics Data System (ADS)

Alwan, Salam H.; Alshamsi, Hassan A. Habeeb; Jasim, Layth S.

2018-06-01

Cobalt oxide nanoparticles@rGO composite is prepared by using graphene oxide (GO) as a supporting substance. GO is first treated with ascorbic acid to form rGO. Finally, cobalt oxide nanoparticles reaction with rGO sheets and using as the adsorbent to removal Rh.B dye from wastewater. The morphology and chemical structure of prepared samples were characterized by FTIR, X-ray spectroscopy, SEM-EDX, TEM, AFM and TGA. The adsorption of Rh.B dye on the A-rGO/Co3O4 composite was accomplished under different conditions that are equilibrium time, pH solution, ionic strength, and temperature. The adsorption isotherms of Rh.B dye on the A-rGO/Co3O4 composite could be illustrated well by the Langmuir, Freundlich and Tempkin model. The thermodynamic factors (ΔHo, ΔSo, and ΔGo) estimated from the temperature-dependent isotherms revealed that the adsorption reaction of Rh.B dye on the A-rGO/Co3O4 composite was an endothermic and spontaneous process.
Effect of negative bias on the composition and structure of the tungsten oxide thin films deposited by magnetron sputtering

NASA Astrophysics Data System (ADS)

Wang, Meihan; Lei, Hao; Wen, Jiaxing; Long, Haibo; Sawada, Yutaka; Hoshi, Yoichi; Uchida, Takayuki; Hou, Zhaoxia

2015-12-01

Tungsten oxide thin films were deposited at room temperature under different negative bias voltages (Vb, 0 to -500 V) by DC reactive magnetron sputtering, and then the as-deposited films were annealed at 500 °C in air atmosphere. The crystal structure, surface morphology, chemical composition and transmittance of the tungsten oxide thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometer. The XRD analysis reveals that the tungsten oxide films deposited at different negative bias voltages present a partly crystallized amorphous structure. All the films transfer from amorphous to crystalline (monoclinic + hexagonal) after annealing 3 h at 500 °C. Furthermore, the crystallized tungsten oxide films show different preferred orientation. The morphology of the tungsten oxide films deposited at different negative bias voltages is consisted of fine nanoscale grains. The grains grow up and conjunct with each other after annealing. The tungsten oxide films deposited at higher negative bias voltages after annealing show non-uniform special morphology. Substoichiometric tungsten oxide films were formed as evidenced by XPS spectra of W4f and O1s. As a result, semi-transparent films were obtained in the visible range for all films deposited at different negative bias voltages.
Method for forming fibrous silicon carbide insulating material

DOEpatents

Wei, G.C.

1983-10-12

A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.
Method for forming fibrous silicon carbide insulating material

DOEpatents

Wei, George C.

1984-01-01

A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.
Investigation on the diffusion bonding of tungsten and EUROFER97

NASA Astrophysics Data System (ADS)

Basuki, Widodo Widjaja; Aktaa, Jarir

2011-10-01

Due to its advantages, tungsten is selected as armor and structural material for use in future fusion power plants. To apply tungsten as structural material, a joint to EUROFER97 is foreseen in current divertor design for which the diffusion bonding is considered in this work. The joining must have acceptable strength and ductility without significant change in microstructures. So far, numerous diffusion bonding experiments without and with post bonding heat treatment (PBHT) are performed at 1050 °C for various bonding duration. For the bonding processes without PBHT, the bonding seams obtained are defect free and have a very high tensile strength. However they are brittle due to a thin layer of FeW intermetallic phase and metal carbides. For the bonding processes with PBHT, the bonding specimens fail at the bonding seam.
Effect of reinforcement phase on the mechanical property of tungsten nanocomposite synthesized by spark plasma sintering

DOE PAGES

Lee, Jin -Kyu; Kim, Song -Yi; Ott, Ryan T.; ...

2015-07-15

Nanostructured tungsten composites were fabricated by spark plasma sintering of nanostructured composite powders. The composite powders, which were synthesized by mechanical milling of tungsten and Ni-based alloy powders, are comprised of alternating layers of tungsten and metallic glass several hundred nanometers in size. The mechanical behavior of the nanostructured W composite is similar to pure tungsten, however, in contrast to monolithic pure tungsten, some macroscopic compressive plasticity accompanies the enhanced maximum strength up to 2.4 GPa by introducing reinforcement. As a result, we have found that the mechanical properties of the composites strongly depend on the uniformity of the nano-grainedmore » tungsten matrix and reinforcement phase distribution.« less
Multifunctional Ceramic Nanostructured Coatings

DTIC Science & Technology

2010-12-01

silicon carbide composites // J. Europ. Cer. Soc. − 2004. − Vol. 24. − P. 2169−2179. 22. Yu. P. Udalov, E. E. Valova, S. S. Ordanian. Fabrication and...by the titanium and tungsten borides and carbides . The analysis was done using the X-ray and electron-optical methods. This information expands our...coating compositions should be based on limited solubility materials. Such systems include carbides , nitrides, borides and silicides based on
The Flexural Strength and Fracture Toughness of TC4-Based Laminated Composites Reinforced with Ti Aluminide and Carbide

PubMed Central

Fei, Yanhan; Ai, Taotao; Niu, Qunfei; Li, Wenhu; Yuan, Xinqiang; Jing, Ran; Dong, Hongfeng

2017-01-01

TiC–Ti–Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti3Al, Ti2AlC, and Ti3AlC2 phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti2AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m1/2, respectively. PMID:29027949
The Flexural Strength and Fracture Toughness of TC4-Based Laminated Composites Reinforced with Ti Aluminide and Carbide.

PubMed

Fei, Yanhan; Ai, Taotao; Niu, Qunfei; Li, Wenhu; Yuan, Xinqiang; Jing, Ran; Dong, Hongfeng

2017-10-13

TiC-Ti-Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti₃Al, Ti₂AlC, and Ti₃AlC₂ phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti₂AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m 1/2 , respectively.
Diallyl disulphide as natural organosulphur friction modifier via the in-situ tribo-chemical formation of tungsten disulphide

NASA Astrophysics Data System (ADS)

Rodríguez Ripoll, Manel; Totolin, Vladimir; Gabler, Christoph; Bernardi, Johannes; Minami, Ichiro

2018-01-01

The present work shows a novel method for generating in-situ low friction tribofilms containing tungsten disulphide in lubricated contacts using diallyl disulphide as sulphur precursor. The approach relies on the tribo-chemical interaction between the diallyl disulphide and a surface containing embedded sub-micrometer tungsten carbide particles. The results show that upon sliding contact between diallyl disulphide and the tungsten-containing surface, the coefficient of friction drops to values below 0.05 after an induction period. The reason for the reduction in friction is due to tribo-chemical reactions that leads to the in-situ formation of a complex tribofilm that contains iron and tungsten components. X-ray photoelectron spectroscopy analyses indicate the presence of tungsten disulphide at the contact interface, thus justifying the low coefficient of friction achieved during the sliding experiments. It was proven that the low friction tribofilms can only be formed by the coexistence of tungsten and sulphur species, thus highlighting the synergy between diallyl disulphide and the tungsten-containing surface. The concept of functionalizing surfaces to react with specific additives opens up a wide range of possibilities, which allows tuning on-site surfaces to target additive interactions.
Nanocrystalline ordered vanadium carbide: Superlattice and nanostructure

NASA Astrophysics Data System (ADS)

Kurlov, A. S.; Gusev, A. I.; Gerasimov, E. Yu.; Bobrikov, I. A.; Balagurov, A. M.; Rempel, A. A.

2016-02-01

The crystal structure, micro- and nanostructure of coarse- and nanocrystalline powders of ordered vanadium carbide V8C7 have been examined by X-ray and neutron diffraction and electron microscopy methods. The synthesized coarse-crystalline powder of ordered vanadium carbide has flower-like morphology. It was established that the real ordered phase has the composition V8C7-δ (δ ≅ 0.03) deviating from perfect stoichiometric composition V8C7. The vanadium atoms forming the octahedral environment □V6 of vacant sites in V8C7-δ are displaced towards the vacancy □. The presence of carbon onion-like structures was found in the vanadium carbide powders with a small content of free (uncombined) carbon. The nanopowders of V8C7-δ carbide with average particle size of 20-30 nm produced by high-energy milling of coarse-crystalline powder retain the crystal structure of the initial powder, but differ in the lattice deformation distortion anisotropy.
Ultrafine-grained Aluminm and Boron Carbide Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Vogt, Rustin

Cryomilling is a processing technique used to generate homogenously distributed boron carbide (B4C) particulate reinforcement within an ultrafine-grained aluminum matrix. The motivation behind characterizing a composite consisting of cryomilled aluminum B4C metal matrix composite is to design and develop a high-strength, lightweight aluminum composite for structural and high strain rate applications. Cryomilled Al 5083 and B4C powders were synthesized into bulk composite by various thermomechanical processing methods to form plate and extruded geometries. The effects of processing method on microstructure and mechanical behavior for the final consolidated composite were investigated. Cryomilling for extended periods of time in liquid nitrogen has shown to increase strength and thermal stability. The effects associated with cryomilling with stearic acid additions (as a process-control agent) on the degassing behavior of Al powders is investigated and results show that the liberation of compounds associated with stearic acid were suppressed in cryomilled Al powders. The effect of thermal expansion mismatch strain on strengthening due to geometrically necessary dislocations resulting from quenching is investigated and found not to occur in bulk cryomilled Al 5083 and B 4C composites. Previous cryomilled Al 5083 and B4C composites have exhibited ultrahigh strength associated with considerable strain-to-failure (>14 pct.) at high strain rates (>103/s) during mechanical testing, but only limited strain-to-failure (˜0.75 pct.) at quasi-static strain rates (10-3/s). The increased strain to failure at high strain rates is attributed to micro-flaw developments, including kinking, extensive axial splitting, and grain growth were observed after high strain rate deformation, and the significance of these mechanisms is considered.
Stress-rupture strength and microstructural stability of tungsten-hafnium-carbon-wire reinforced superalloy composites

NASA Technical Reports Server (NTRS)

Petrasek, D. W.; Signorelli, R. A.

1974-01-01

Tungsten-hafnium-carbon - superalloy composites were found to be potentially useful for turbine blade applications on the basis of stress-rupture strength. The 100- and 1000-hr rupture strengths calculated for 70 vol. % fiber composites based on test data at 1090C (2000F) were 420 and 280 MN/m2 (61,000 and 41,000 psi, respectively). The investigation indicated that, with better quality fibers, composites having 100- and 1000-hr rupture strengths of 570 and 370 MN/m2 (82,000 and 54,000 psi, respectively), may be obtained. Metallographic studies indicated sufficient fiber-matrix compatibility for 1000 hr or more at 1090C (2000F).
Effect of cobalt content on wear and corrosion behaviors of electrodeposited Ni-Co/WC nano-composite coatings.

PubMed

Amadeh, A; Ebadpour, R

2013-02-01

Metal-ceramic composite coatings are widely used in automotive and aerospace industries as well as micro-electronic systems. Electrodeposition is an economic method for application of these coatings. In this research, nickel-cobalt coatings reinforced by nano WC particles were applied on carbon steel substrate by pulse electrodeposition from modified Watts bath containing different amounts of cobalt sulphate as an additive. Saccharin and sodium dodecyl sulphate (SDS) were also added to electroplating bath as grain refiner and surfactant, respectively. The effect of cobalt content on wear and corrosion behavior of the coatings was investigated. Wear and corrosion properties were assessed by pin-on-disk and potentiodynamic polarization methods, respectively. Phase analysis was performed by X-ray diffraction (XRD) using CuK(alpha) radiation and the worn surfaces were studied by means of Scanning Electron Microscopy (SEM). The results showed that the addition of cobalt improved the wear resistance of the coatings. In the presence of 18 g/L cobalt in electrodeposition bath, the wear rate of the coating decreased to 0.002 mg/m and the coefficient of friction reduced to 0.695 while they were 0.004 mg/m and 0.77 in the absence of cobalt, respectively. This improvement in wear properties can be attributed to the formation of hcp phase in metallic matrix. Meanwhile, the corrosion resistance of the coatings slightly reduced because cobalt is more active metal with respect to nickel.
Synthesis of microsphere silicon carbide/nanoneedle manganese oxide composites and their electrochemical properties as supercapacitors

NASA Astrophysics Data System (ADS)

Kim, Myeongjin; Yoo, Youngjae; Kim, Jooheon

2014-11-01

Synthesis of microsphere silicon carbide/nanoneedle MnO2 (SiC/N-MnO2) composites for use as high-performance materials in supercapacitors is reported herein. The synthesis procedure involves the initial treatment of silicon carbide (SiC) with hydrogen peroxide to obtain oxygen-containing functional groups to provide anchoring sites for connection of SiC and the MnO2 nanoneedles (N-MnO2). MnO2 nanoneedles are subsequently formed on the SiC surface. The morphology and microstructure of the as-prepared composites are characterized via X-ray diffractometry, field-emission scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The characterizations indicate that MnO2 nanoneedles are homogeneously formed on the SiC surface in the composite. The capacitive properties of the as-prepared SiC/N-MnO2 electrodes are evaluated using cyclic voltammetry, galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy in a three-electrode experimental setup using a 1-M Na2SO4 aqueous solution as the electrolyte. The SiC/N-MnO2(5) electrode, for which the MnO2/SiC feed ratio is 5:1, displays a specific capacitance as high as 273.2 F g-1 at 10 mV s-1.

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.
Laser-Induced Molybdenum Carbide-Graphene Composites for 3D Foldable Paper Electronics.

PubMed

Zang, Xining; Shen, Caiwei; Chu, Yao; Li, Buxuan; Wei, Minsong; Zhong, Junwen; Sanghadasa, Mohan; Lin, Liwei

2018-05-15

Versatile and low-cost manufacturing processes/materials are essential for the development of paper electronics. Here, a direct-write laser patterning process is developed to make conductive molybdenum carbide-graphene (MCG) composites directly on paper substrates. The hierarchically porous MCG structures are converted from fibrous paper soaked with the gelatin-mediated inks containing molybdenum ions. The resulting Mo 3 C 2 and graphene composites are mechanically stable and electrochemically active for various potential applications, such as electrochemical ion detectors and gas sensors, energy harvesters, and supercapacitors. Experimentally, the electrical conductivity of the composite is resilient to mechanical deformation with less than 5% degradation after 750 cycles of 180° repeated folding tests. As such, the direct laser conversion of MCGs on papers can be applicable for paper-based electronics, including the 3D origami folding structures. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effect of interfacial interactions on the thermal conductivity and interfacial thermal conductance in tungsten–graphene layered structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jagannadham, K., E-mail: jag-kasichainula@ncsu.edu

2014-09-01

Graphene film was deposited by microwave plasma assisted deposition on polished oxygen free high conductivity copper foils. Tungsten–graphene layered film was formed by deposition of tungsten film by magnetron sputtering on the graphene covered copper foils. Tungsten film was also deposited directly on copper foil without graphene as the intermediate film. The tungsten–graphene–copper samples were heated at different temperatures up to 900 °C in argon atmosphere to form an interfacial tungsten carbide film. Tungsten film deposited on thicker graphene platelets dispersed on silicon wafer was also heated at 900 °C to identify the formation of tungsten carbide film by reaction of tungstenmore » with graphene platelets. The films were characterized by scanning electron microscopy, Raman spectroscopy, and x-ray diffraction. It was found that tungsten carbide film formed at the interface upon heating only above 650 °C. Transient thermoreflectance signal from the tungsten film surface on the samples was collected and modeled using one-dimensional heat equation. The experimental and modeled results showed that the presence of graphene at the interface reduced the cross-plane effective thermal conductivity and the interfacial thermal conductance of the layer structure. Heating at 650 and 900 °C in argon further reduced the cross-plane thermal conductivity and interface thermal conductance as a result of formation nanocrystalline tungsten carbide at the interface leading to separation and formation of voids. The present results emphasize that interfacial interactions between graphene and carbide forming bcc and hcp elements will reduce the cross-plane effective thermal conductivity in composites.« less
Synergistic methods for the production of high-strength and low-cost boron carbide

NASA Astrophysics Data System (ADS)

Wiley, Charles Schenck

2011-12-01

Boron carbide (B4C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B4C make it a nearly ideal material for personnel and vehicular armor. B4C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B4C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B4C powders. The boron carbide powder examined in this study was a sub-micron (0.6 mum median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form of phenolic resin, and titanium additives in the form of 32 nm and 0.9 mum TiO2 powders were selected. Parametric studies of
Method of preparing copper-dendritic composite alloys for mechanical reduction

DOEpatents

Verhoeven, John D.; Gibson, Edwin D.; Schmidt, Frederick A.; Spitzig, William A.

1988-01-01

Copper-dendritic composite alloys are prepared for mechanical reduction to increase tensile strength by dispersing molten droplets of the composite alloy into an inert gas; solidifying the droplets in the form of minute spheres or platelets; and compacting a mass of the spheres or platelets into an integrated body. The spheres preferably have diameters of from 50 to 2000 .mu.m, and the platelets thicknesses of 100 to 2000 .mu.m. The resulting spheres or platelets will contain ultra-fine dendrites which produce higher strengths on mechanical reduction of the bodies formed therefrom, or comparable strengths at lower reduction values. The method is applicable to alloys of copper with vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron and cobalt.
Mirrorlike pulsed laser deposited tungsten thin film.

PubMed

Mostako, A T T; Rao, C V S; Khare, Alika

2011-01-01

Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10(-5) Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness ∼782 nm.
Tungsten oxide--fly ash oxide composites in adsorption and photocatalysis.

PubMed

Visa, Maria; Bogatu, Cristina; Duta, Anca

2015-05-30

A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite's crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau - BB and Bemacid Rot - BR) and one heavy metal ion-Cu(2+), and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate. Copyright © 2015 Elsevier B.V. All rights reserved.
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.
Two-component end mills with multilayer composite nano-structured coatings as a viable alternative to monolithic carbide end mills

NASA Astrophysics Data System (ADS)

Vereschaka, Alexey; Mokritskii, Boris; Mokritskaya, Elena; Sharipov, Oleg; Oganyan, Maksim

2018-03-01

The paper deals with the challenges of the application of two-component end mills, which represent a combination of a carbide cutting part and a shank made of cheaper structural material. The calculations of strains and deformations of composite mills were carried out in comparison with solid carbide mills, with the use of the finite element method. The study also involved the comparative analysis of accuracy parameters of machining with monolithic mills and two-component mills with various shank materials. As a result of the conducted cutting tests in milling aluminum alloy with monolithic and two-component end mills with specially developed multilayer composite nano-structured coatings, it has been found that the use of such coatings can reduce strains and, correspondingly, deformations, which can improve the accuracy of machining. Thus, the application of two-component end mills with multilayer composite nano-structured coatings can provide a reduction in the cost of machining while maintaining or even improving the tool life and machining accuracy parameters.
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.
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.
Friction stir weld tools having fine grain structure

DOEpatents

Grant, Glenn J.; Frye, John G.; Kim, Jin Yong; Lavender, Curt A.; Weil, Kenneth Scott

2016-03-15

Tools for friction stir welding can be made with fewer process steps, lower cost techniques, and/or lower cost ingredients than other state-of-the-art processes by utilizing improved compositions and processes of fabrication. Furthermore, the tools resulting from the improved compositions and processes of fabrication can exhibit better distribution and homogeneity of chemical constituents, greater strength, and/or increased durability. In one example, a friction stir weld tool includes tungsten and rhenium and is characterized by carbide and oxide dispersoids, by carbide particulates, and by grains that comprise a solid solution of the tungsten and rhenium. The grains do not exceed 10 micrometers in diameter.
Carbide factor predicts rolling-element bearing fatigue life

NASA Technical Reports Server (NTRS)

Chevalier, J. L.; Zaretsky, E. V.

1973-01-01

Analysis was made to determine correlation between number and size of carbide particles and rolling-element fatigue. Correlation was established, and carbide factor was derived that can be used to predict fatigue life more effectively than such variables as heat treatment, chemical composition, and hardening mechanism.
Tungsten Isotopic Compositions in Stardust SiC Grains from the Murchison Meteorite: Constraints on the s-process in the Hf-Ta-W-Re-Os Region

NASA Astrophysics Data System (ADS)

Ávila, Janaína N.; Lugaro, Maria; Ireland, Trevor R.; Gyngard, Frank; Zinner, Ernst; Cristallo, Sergio; Holden, Peter; Buntain, Joelene; Amari, Sachiko; Karakas, Amanda

2012-01-01

We report the first tungsten isotopic measurements in stardust silicon carbide (SiC) grains recovered from the Murchison carbonaceous chondrite. The isotopes 182,183,184,186W and 179,180Hf were measured on both an aggregate (KJB fraction) and single stardust SiC grains (LS+LU fraction) believed to have condensed in the outflows of low-mass carbon-rich asymptotic giant branch (AGB) stars with close-to-solar metallicity. The SiC aggregate shows small deviations from terrestrial (= solar) composition in the 182W/184W and 183W/184W ratios, with deficits in 182W and 183W with respect to 184W. The 186W/184W ratio, however, shows no apparent deviation from the solar value. Tungsten isotopic measurements in single mainstream stardust SiC grains revealed lower than solar 182W/184W, 183W/184W, and 186W/184W ratios. We have compared the SiC data with theoretical predictions of the evolution of W isotopic ratios in the envelopes of AGB stars. These ratios are affected by the slow neutron-capture process and match the SiC data regarding their 182W/184W, 183W/184W, and 179Hf/180Hf isotopic compositions, although a small adjustment in the s-process production of 183W is needed in order to have a better agreement between the SiC data and model predictions. The models cannot explain the 186W/184W ratios observed in the SiC grains, even when the current 185W neutron-capture cross section is increased by a factor of two. Further study is required to better assess how model uncertainties (e.g., the formation of the 13C neutron source, the mass-loss law, the modeling of the third dredge-up, and the efficiency of the 22Ne neutron source) may affect current s-process predictions.
Fabrication of Fe-Based Diamond Composites by Pressureless Infiltration

PubMed Central

Li, Meng; Sun, Youhong; Meng, Qingnan; Wu, Haidong; Gao, Ke; Liu, Baochang

2016-01-01

A metal-based matrix is usually used for the fabrication of diamond bits in order to achieve favorable properties and easy processing. In the effort to reduce the cost and to attain the desired bit properties, researchers have brought more attention to diamond composites. In this paper, Fe-based impregnated diamond composites for drill bits were fabricated by using a pressureless infiltration sintering method at 970 °C for 5 min. In addition, boron was introduced into Fe-based diamond composites. The influence of boron on the density, hardness, bending strength, grinding ratio, and microstructure was investigated. An Fe-based diamond composite with 1 wt % B has an optimal overall performance, the grinding ratio especially improving by 80%. After comparing with tungsten carbide (WC)-based diamond composites with and without 1 wt % B, results showed that the Fe-based diamond composite with 1 wt % B exhibits higher bending strength and wear resistance, being satisfactory to bit needs. PMID:28774124
Adhesion and friction of transition metals in contact with nonmetallic hard materials

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1981-01-01

Sliding friction experiments were conducted with the metals yttrium, titanium, tantalum, zirconium, vanadium, neodymium, iron, cobalt, nickel, tungsten, platinum, rhenium, ruthenium, and rhodium in sliding contact with single crystal diamond, silicon carbide, pyrolytic boron nitride, and ferrite. Auger electron spectroscopy analysis was conducted with the metals and nonmetals to determine the surface chemistry and the degree of surface cleanliness. The results of the investigation indicate the adhesion and friction of the transition metals in contact with diamond, silicon carbide, boron nitride, and ferrite are related to the relative chemical activity of the metals. The more chemically active the metal, the higher the coefficient of friction and the greater amount of transfer to the nonmetals.
Fabrication and Characterization of Silicon Carbide Epoxy Composites

NASA Astrophysics Data System (ADS)

Townsend, James

Nanoscale fillers can significantly enhance the performance of composites by increasing the extent of filler-to-matrix interaction. Thus far, the embedding of nanomaterials into composites has been achieved, but the directional arrangement has proved to be a challenging task. Even with advances in in-situ and shear stress induced orientation, these methods are both difficult to control and unreliable. Therefore, the fabrication of nanomaterials with an ability to orient along a magnetic field is a promising pathway to create highly controllable composite systems with precisely designed characteristics. To this end, the goal of this dissertation is to develop magnetically active nanoscale whiskers and study the effect of the whiskers orientation in a polymer matrix on the nanocomposite's behavior. Namely, we report the surface modification of silicon carbide whiskers (SiCWs) with magnetic nanoparticles and fabrication of SiC/epoxy composite materials. The magnetic nanoparticles attachment to the SiCWs was accomplished using polyelectrolyte polymer-to-polymer complexation. The "grafting to" and adsorption techniques were used to attach the polyelectrolytes to the surface of the SiCWs and magnetic nanoparticles. The anchored polyelectrolytes were polyacrylic acid (PAA) and poly(2-vinylpyridine) (P2VP). Next, the SiC/epoxy composites incorporating randomly oriented and magnetically oriented whiskers were fabricated. The formation of the composite was studied to determine the influence of the whiskers' surface composition on the epoxy curing reaction. After curing, the composites' thermal and thermo-mechanical properties were studied. These properties were related to the dispersion and orientation of the fillers in the composite samples. The obtained results indicated that the thermal and thermo-mechanical properties could be improved by orienting magnetically-active SiCWs inside the matrix. Silanization, "grafting to", adsorption, and complexation were used to modify
Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling

NASA Astrophysics Data System (ADS)

Travessa, Dilermando Nagle; Silva, Marina Judice; Cardoso, Kátia Regina

2017-06-01

Aluminum and its alloys are key materials for the transportation industry as they contribute to the development of lightweight structures. The dispersion of hard ceramic particles in the Al soft matrix can lead to a substantial strengthening effect, resulting in composite materials exhibiting interesting mechanical properties and inspiring their technological use in sectors like the automotive and aerospace industries. Powder metallurgy techniques are attractive to design metal matrix composites, achieving a homogeneous distribution of the reinforcement into the metal matrix. In this work, pure aluminum has been reinforced with particles of niobium carbide (NbC), an extremely hard and stable refractory ceramic. Its use as a reinforcing phase in metal matrix composites has not been deeply explored. Composite powders produced after different milling times, with 10 and 20 vol pct of NbC were produced by high-energy ball milling and characterized by scanning electron microscopy and by X-ray diffraction to establish a relationship between the milling time and size, morphology, and distribution of the particles in the composite powder. Subsequently, an Al/10 pct NbC composite powder was hot extruded into cylindrical bars. The strength of the obtained composite bars is comparable to the commercial high-strength, aeronautical-grade aluminum alloys.
Wear resistance and mechanisms of composite hardfacings at abrasive impact erosion wear

NASA Astrophysics Data System (ADS)

Surzhenkov, A.; Viljus, M.; Simson, T.; Tarbe, R.; Saarna, M.; Casesnoves, F.

2017-05-01

Tungsten carbide based hardmetal containing sprayed and melted composite hardfacings are prospective for protection against abrasive wear. For selection of abrasive wear resistant hardfacings under intensive impact wear conditions, both mechanical properties (hardness, fracture toughness, etc.) and abrasive wear conditions (type of abrasive, impact velocity, etc.) should be considered. This study focuses on the wear (wear rate and mechanisms) of thick metal-matrix composite hardfacings with hardmetal (WC-Co) reinforcement produced by powder metallurgy technology. The influence of the hardmetal reinforcement type on the wear resistance at different abrasive impact erosion wear (AIEW) conditions was studied. An optimal reinforcement for various wear conditions is described. Based on wear mechanism studies, a mathematical model for wear prediction was drafted.
Chemical-Vapor Deposition Of Silicon Carbide

NASA Technical Reports Server (NTRS)

Cagliostro, D. E.; Riccitiello, S. R.; Ren, J.; Zaghi, F.

1993-01-01

Report describes experiments in chemical-vapor deposition of silicon carbide by pyrolysis of dimethyldichlorosilane in hydrogen and argon carrier gases. Directed toward understanding chemical-kinetic and mass-transport phenomena affecting infiltration of reactants into, and deposition of SiC upon, fabrics. Part of continuing effort to develop method of efficient and more nearly uniform deposition of silicon carbide matrix throughout fabric piles to make improved fabric/SiC-matrix composite materials.

The resistance of selected high strength alloys to embrittlement by a hydrogen environment. [iron and cobalt base alloys

NASA Technical Reports Server (NTRS)

Benson, R. B., Jr.

1974-01-01

Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.
Production and Characterization of WC-Reinforced Co-Based Superalloy Matrix Composites

NASA Astrophysics Data System (ADS)

Özgün, Özgür; Dinler, İlyas

2018-05-01

Cobalt-based superalloy matrix composite materials were produced through the powder metallurgy technique using element powders at high purity and nano-sized wolfram carbide (WC) reinforcement in this study. An alloy that had the same chemical composition as the Stellite 6 alloy but not containing carbon was selected as the matrix alloy. The powder mixtures obtained as a result of mixing WC reinforcing member and element powders at the determined ratio were shaped by applying 300 MPa of pressure. The green components were sintered under argon atmosphere at 1240 °C for 120 minutes. The densities of the sintered components were determined by the Archimedes' principle. Microstructural characterization was performed via X-ray diffraction analysis, scanning electron microscope examinations, and energy-dispersive spectrometry. Hardness measurements and tensile tests were performed for determining mechanical characteristics. The relative density values of the sintered components increased by increasing the WC reinforcement ratio and they could almost reach the theoretical density. It was determined from the microstructural examinations that the composite materials consisted of fine and equiaxed grains and coarse carbides demonstrating a homogeneous dispersion along the microstructure at the grain boundaries. As it was the case in the density values, the hardness and strength values of the composites increased by increasing the WC ratio.
Production and Characterization of WC-Reinforced Co-Based Superalloy Matrix Composites

NASA Astrophysics Data System (ADS)

Özgün, Özgür; Dinler, İlyas

2018-07-01

Cobalt-based superalloy matrix composite materials were produced through the powder metallurgy technique using element powders at high purity and nano-sized wolfram carbide (WC) reinforcement in this study. An alloy that had the same chemical composition as the Stellite 6 alloy but not containing carbon was selected as the matrix alloy. The powder mixtures obtained as a result of mixing WC reinforcing member and element powders at the determined ratio were shaped by applying 300 MPa of pressure. The green components were sintered under argon atmosphere at 1240 °C for 120 minutes. The densities of the sintered components were determined by the Archimedes' principle. Microstructural characterization was performed via X-ray diffraction analysis, scanning electron microscope examinations, and energy-dispersive spectrometry. Hardness measurements and tensile tests were performed for determining mechanical characteristics. The relative density values of the sintered components increased by increasing the WC reinforcement ratio and they could almost reach the theoretical density. It was determined from the microstructural examinations that the composite materials consisted of fine and equiaxed grains and coarse carbides demonstrating a homogeneous dispersion along the microstructure at the grain boundaries. As it was the case in the density values, the hardness and strength values of the composites increased by increasing the WC ratio.
Salt flux synthesis of single and bimetallic carbide nanowires

NASA Astrophysics Data System (ADS)

Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

2016-07-01

Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ˜15-20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.
The Effect of Time, Temperature and Composition on Boron Carbide Synthesis by Sol-gel Method

NASA Astrophysics Data System (ADS)

Hadian, A. M.; Bigdeloo, J. A.

2008-02-01

To minimize free carbon residue in the boron carbide (B4C) powder, a modified sol-gel process is performed where the starting materials as boric acid and citric acid compositions are adjusted. Because of boron loss in the form of B2O2(g) during the reduction reaction of the stoichiometric starting composition, the final B4C powders contain carbon residues. Thus, an excess H3BO3 is used in the reaction to compensate the loss and to obtain stoichiometric powders. Parameters of production have been determined using x-ray diffraction analysis and particle size analyses. The synthesized B4C powder using an excess boric acid composition shows no trace of carbon.
Pulmonary toxicity after exposure to military-relevant heavy metal tungsten alloy particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roedel, Erik Q., E-mail: Erik.Roedel@amedd.army.mil; Cafasso, Danielle E., E-mail: Danielle.Cafasso@amedd.army.mil; Lee, Karen W.M., E-mail: Karen.W.Lee@amedd.army.mil

2012-02-15

Significant controversy over the environmental and public health impact of depleted uranium use in the Gulf War and the war in the Balkans has prompted the investigation and use of other materials including heavy metal tungsten alloys (HMTAs) as nontoxic alternatives. Interest in the health effects of HMTAs has peaked since the recent discovery that rats intramuscularly implanted with pellets containing 91.1% tungsten/6% nickel/2.9% cobalt rapidly developed aggressive metastatic tumors at the implantation site. Very little is known, however, regarding the cellular and molecular mechanisms associated with the effects of inhalation exposure to HMTAs despite the recognized risk of thismore » route of exposure to military personnel. In the current study military-relevant metal powder mixtures consisting of 92% tungsten/5% nickel/3% cobalt (WNiCo) and 92% tungsten/5% nickel/3% iron (WNiFe), pure metals, or vehicle (saline) were instilled intratracheally in rats. Pulmonary toxicity was assessed by cytologic analysis, lactate dehydrogenase activity, albumin content, and inflammatory cytokine levels in bronchoalveolar lavage fluid 24 h after instillation. The expression of 84 stress and toxicity-related genes was profiled in lung tissue and bronchoalveolar lavage cells using real-time quantitative PCR arrays, and in vitro assays were performed to measure the oxidative burst response and phagocytosis by lung macrophages. Results from this study determined that exposure to WNiCo and WNiFe induces pulmonary inflammation and altered expression of genes associated with oxidative and metabolic stress and toxicity. Inhalation exposure to both HMTAs likely causes lung injury by inducing macrophage activation, neutrophilia, and the generation of toxic oxygen radicals. -- Highlights: ► Intratracheal instillation of W–Ni–Co and W–Ni–Fe induces lung inflammation in rats. ► W–Ni–Co and W–Ni–Fe alter expression of oxidative stress and toxicity genes. ► W�
Impact resistance and energies of intermetallic bonded diamond composites and polycrystalline diamond compacts and their comparison

NASA Astrophysics Data System (ADS)

Gorla, Sai Prasanth

Chemistry of intermetallic bonded diamond is studied. The impact resistance and energies of intermetallic bonded diamond is compared to current poly crystalline diamond compacts. IBD's are found to have high standards of hardness and have more impact energies absorbed. Intermetallic bonded diamond composite comprises of diamond particles dispersed in Tungsten carbide using Nickel aluminide (Ni3Al) as binder. In previous research conducted on IBD's, diamonds are successfully dispersed in intermetallic alloy of nickel aluminide and processed at 1350°C such that diamond particles remain intact without forming graphite. Composites are formed by milling, pressing the intermetallic binder and diamond particles and sintering at high temperature conditions.
Characterization of thin film deposits on tungsten filaments in catalytic chemical vapor deposition using 1,1-dimethylsilacyclobutane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Yujun, E-mail: shiy@ucalgary.ca; Tong, Ling; Mulmi, Suresh

Metal filament plays a key role in the technique of catalytic chemical vapor deposition (Cat-CVD) as it serves as a catalyst in dissociating the source gas to form reactive species. These reactive species initiate the gas-phase reaction chemistry and final thin film and nanostructure formation. At the same time, they also react with the metal itself, leading to the formation of metal alloys and other deposits. The deposits on the tungsten filaments when exposed to 1,1-dimethylsilacyclobutane (DMSCB), a single-source precursor for silicon carbide thin films, in the process of Cat-CVD were studied in this work. It has been demonstrated thatmore » a rich variety of deposits, including tungsten carbides (W{sub 2}C and WC), tungsten silicide (W{sub 5}Si{sub 3}), silicon carbide, amorphous carbon, and graphite, form on the W filament surfaces. The structural and morphological changes in the tungsten filaments depend strongly on the DMSCB pressure and filament temperature. At 1000 and 2000 °C, the formation of WC and W{sub 2}C dominates. In addition, a thin amorphous carbon layer has been found at 1500 °C with the 0.12 and 0.24 Torr of DMSCB and a lower temperature of 1200 °C with the 0.48 Torr of DMSCB. An increase in the DMSCB sample pressure gives rise to higher Si and C contents. As a result, the formation of SiC and W{sub 5}Si{sub 3} has been observed with the two high-pressure DMSCB samples (i.e., 0.24 and 0.48 Torr). The rich decomposition chemistry of DMSCB on the W surfaces is responsible for the extensive changes in the structure of the W filament, providing support for the close relationship between the gas-phase decomposition chemistry and the nature of alloy formation on the metal surface. The understanding of the structural changes obtained from this work will help guide the development of efficient methods to solve the filament aging problem in Cat-CVD and also to achieve a controllable deposition process.« less
Novel fabrication of silicon carbide based ceramics for nuclear applications

NASA Astrophysics Data System (ADS)

Singh, Abhishek Kumar

Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These materials include refractory alloys based on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as SiC--SiCf; carbon--carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor components is necessary for improved efficiency. Improving thermal conductivity of the fuel can lower the center-line temperature and, thereby, enhance power production capabilities and reduce the risk of premature fuel pellet failure. Crystalline silicon carbide has superior characteristics as a structural material from the viewpoint of its thermal and mechanical properties, thermal shock resistance, chemical stability, and low radioactivation. Therefore, there have been many efforts to develop SiC based composites in various forms for use in advanced energy systems. In recent years, with the development of high yield preceramic precursors, the polymer infiltration and pyrolysis (PIP) method has aroused interest for the fabrication of ceramic based materials, for various applications ranging from disc brakes to nuclear reactor fuels. The pyrolysis of preceramic polymers allow new types of ceramic materials to be processed at relatively low temperatures. The raw materials are element-organic polymers whose composition and architecture can be tailored and varied. The primary focus of this study is to use a pyrolysis based process to fabricate a host of novel silicon carbide-metal carbide or oxide composites, and to synthesize new materials based on mixed-metal silicocarbides that cannot be processed using conventional techniques. Allylhydridopolycarbosilane (AHPCS), which is an organometal polymer, was used as the precursor for silicon carbide. Inert gas pyrolysis of AHPCS produces near-stoichiometric amorphous
A multiscale microstructural approach to ductile-phase toughened tungsten for plasma-facing materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Henager, Jr., Charles H.; Overman, Nicole R.

Increasing fracture toughness and modifying the ductile-brittle transition temperature of a tungsten-alloy relative to pure tungsten has been shown to be feasible by ductile-phase toughening (DPT) of tungsten for future plasma-facing materials for fusion energy. In DPT, a ductile phase is included in a brittle tungsten matrix to increase the overall work of fracture for the material. This research models the deformation behavior of DPT tungsten materials, such as tungsten-copper composites, using a multiscale modeling approach that involves a microstructural dual-phase (copper-tungsten) region of interest where the constituent phases are finely discretized and are described by a continuum damage mechanicsmore » model. Large deformation, damage, and fracture are allowed to occur and are modeled in a region that is connected to adjacent homogenized elastic regions to form a macroscopic structure, such as a test specimen. The present paper illustrates this multiscale modeling approach to analyze unnotched and single-edge notched (SENB) tungsten-copper composite specimens subjected to three-point bending. The predicted load-displacement responses and crack propagation patterns are compared to the corresponding experimental results to validate the model. Furthermore, such models may help design future DPT composite configurations for fusion materials, including volume fractions of ductile phase and microstructural optimization.« less
A multiscale microstructural approach to ductile-phase toughened tungsten for plasma-facing materials

DOE PAGES

Nguyen, Ba Nghiep; Henager, Jr., Charles H.; Overman, Nicole R.; ...

2018-05-23

Increasing fracture toughness and modifying the ductile-brittle transition temperature of a tungsten-alloy relative to pure tungsten has been shown to be feasible by ductile-phase toughening (DPT) of tungsten for future plasma-facing materials for fusion energy. In DPT, a ductile phase is included in a brittle tungsten matrix to increase the overall work of fracture for the material. This research models the deformation behavior of DPT tungsten materials, such as tungsten-copper composites, using a multiscale modeling approach that involves a microstructural dual-phase (copper-tungsten) region of interest where the constituent phases are finely discretized and are described by a continuum damage mechanicsmore » model. Large deformation, damage, and fracture are allowed to occur and are modeled in a region that is connected to adjacent homogenized elastic regions to form a macroscopic structure, such as a test specimen. The present paper illustrates this multiscale modeling approach to analyze unnotched and single-edge notched (SENB) tungsten-copper composite specimens subjected to three-point bending. The predicted load-displacement responses and crack propagation patterns are compared to the corresponding experimental results to validate the model. Furthermore, such models may help design future DPT composite configurations for fusion materials, including volume fractions of ductile phase and microstructural optimization.« less
Process for preparing metal-carbide-containing microspheres from metal-loaded resin beads

DOEpatents

Beatty, Ronald L.

1976-01-01

An improved method for treating metal-loaded resin microspheres is described which comprises heating a metal-loaded resin charge in an inert atmosphere at a pre-carbide-forming temperature under such conditions as to produce a microsphere composition having sufficient carbon as to create a substantially continuous carbon matrix and a metal-carbide or an oxide-carbide mixture as a dispersed phase(s) during carbide-forming conditions, and then heating the thus treated charge to a carbide-forming temperature.
An in vitro study of the effect of different restorative materials on the reliability of a veneering porcelain.

PubMed

Anderson, Matthew R; Chung, Kwok-Hung; Flinn, Brian D; Raigrodski, Ariel J

2013-12-01

Implant-supported, porcelain veneered restorations experience a greater rate of porcelain fracture than tooth-supported restorations. For completely edentulous patients, one approach to minimizing porcelain fracture is to use acrylic resin in the mandible, although its efficacy is unknown. The purpose of this study was to evaluate the reliability of a veneering porcelain fatigued with different restorative materials in vitro. Fifty-nine veneering porcelain disk specimens were fabricated by layering veneering porcelain on nickel-chromium base metal alloy disks. Four groups of different indenter materials fatigued the porcelain specimens: group WC, tungsten carbide served as a control; group FC, pressed leucite glass ceramic; group NHC, nanohybrid composite resin denture tooth; and group AR, unfilled acrylic resin denture tooth. Porcelain specimens were randomly divided into 4 groups (n=14). A step-stress accelerated life-testing model was used. Use-level probability Weibull plots were generated, and the reliability of each group was estimated for a theoretical completion of 50 000 cycles at 150 N. Nanohybrid composite resin and unfilled acrylic resin denture tooth groups had higher reliability than tungsten carbide and leucite glass ceramic groups. No significant differences existed between the reliability of the tungsten carbide and leucite glass ceramic groups and the nanohybrid composite resin and acrylic resin denture tooth groups. Veneering porcelain disk specimens fatigued with the unfilled acrylic resin and nanohybrid composite resin denture tooth indenters exhibited higher reliability than the specimens fatigued with either the tungsten carbide or leucite glass ceramic indenters. All of the veneering porcelain disk specimens failed with the same mode of fracture, although the surface posttest exhibited different fracture characteristics among specimens fatigued with the 4 different materials. Copyright © 2013 Editorial Council for the Journal of
Dynamic Modulus and Damping of Boron, Silicon Carbide, and Alumina Fibers

NASA Technical Reports Server (NTRS)

Dicarlo, J. A.; Williams, W.

1980-01-01

The dynamic modulus and damping capacity for boron, silicon carbide, and silicon carbide coated boron fibers were measured from-190 to 800 C. The single fiber vibration test also allowed measurement of transverse thermal conductivity for the silicon carbide fibers. Temperature dependent damping capacity data for alumina fibers were calculated from axial damping results for alumina-aluminum composites. The dynamics fiber data indicate essentially elastic behavior for both the silicon carbide and alumina fibers. In contrast, the boron based fibers are strongly anelastic, displaying frequency dependent moduli and very high microstructural damping. Ths single fiber damping results were compared with composite damping data in order to investigate the practical and basic effects of employing the four fiber types as reinforcement for aluminum and titanium matrices.
Underwater explosive compaction-sintering of tungsten-copper coating on a copper surface

NASA Astrophysics Data System (ADS)

Chen, Xiang; Li, Xiaojie; Yan, Honghao; Wang, Xiaohong; Chen, Saiwei

2018-01-01

This study investigated underwater explosive compaction-sintering for coating a high-density tungsten-copper composite on a copper surface. First, 50% W-50% Cu tungsten-copper composite powder was prepared by mechanical alloying. The composite powder was pre-compacted and sintered by hydrogen. Underwater explosive compaction was carried out. Finally, a high-density tungsten-copper coating was obtained by diffusion sintering of the specimen after explosive compaction. A simulation of the underwater explosive compaction process showed that the peak value of the pressure in the coating was between 3.0 and 4.8 GPa. The hardness values of the tungsten-copper layer and the copper substrate were in the range of 87-133 and 49 HV, respectively. The bonding strength between the coating and the substrate was approximately 100-105 MPa.
Tribological composition optimization of chromium-carbide-based solid lubricant coatings for foil gas bearings at temperatures to 650 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher

1988-01-01

The determination of the tribilogically optimum composition of chromium-carbide-based solid lubricant coatings using a foil gas bearing test apparatus is described. The coatings contain a wear resistant chromium carbide `base stock' with the lubricant additives silver and BaF2-CaF2 eutectic. The coating composition is optimized for air-lubricated foil gas bearings at temperatures ranging from 25 to 650 C. The various compositions were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized Ni-Cr alloy foils, and the test bearings were subjected to repeated start-stop cycles under a bearing unit of 14 kPa. Sliding contact between the coated journal and the smooth foil occurs during bearing start-up before lift-off or hydrodynamic lubrication by the air film and during bearing coast-down. The bearings were tested for 9000 start-stop cycles or until specimen reached a predetermined failure level.
Method of preparing copper-dendritic composite alloys for mechanical reduction

DOEpatents

Verhoeven, J.D.; Gibson, E.D.; Schmidt, F.A.; Spitzig, W.A.

1988-09-13

Copper-dendritic composite alloys are prepared for mechanical reduction to increase tensile strength by dispersing molten droplets of the composite alloy into an inert gas; solidifying the droplets in the form of minute spheres or platelets; and compacting a mass of the spheres or platelets into an integrated body. The spheres preferably have diameters of from 50 to 2,000 [mu]m, and the platelets thicknesses of 100 to 2,000 [mu]m. The resulting spheres or platelets will contain ultra-fine dendrites which produce higher strengths on mechanical reduction of the bodies formed therefrom, or comparable strengths at lower reduction values. The method is applicable to alloys of copper with vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron and cobalt. 3 figs.
Fabrication of thorium bearing carbide fuels

DOEpatents

Gutierrez, Rueben L.; Herbst, Richard J.; Johnson, Karl W. R.

1981-01-01

Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750.degree. C. and 2000.degree. C. were used during the reduction cycle. Sintering temperatures of 1800.degree. C. and 2000.degree. C. were used to prepare fuel pellet densities of 87% and >94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproducibility of chemicals and phase composition. Methods employing liquid techniques that form carbide microspheres or alloying-techniques which form alloys of thorium-uranium or thorium-plutonium suffer from limitation on the quantities processed of because of criticality concerns and lack of precise control of process conditions, respectively.
3D WO3 /BiVO4 /Cobalt Phosphate Composites Inverse Opal Photoanode for Efficient Photoelectrochemical Water Splitting.

PubMed

Zhang, Haifeng; Zhou, Weiwei; Yang, Yaping; Cheng, Chuanwei

2017-04-01

A novel 3D WO 3 /BiVO 4 /cobalt phosphate composite inverse opal is designed for photoeletrochemical (PEC) water splitting, yielding a significantly improved PEC performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Breaking the icosahedra in boron carbide

PubMed Central

Xie, Kelvin Y.; An, Qi; Sato, Takanori; Breen, Andrew J.; Ringer, Simon P.; Goddard, William A.; Cairney, Julie M.; Hemker, Kevin J.

2016-01-01

Findings of laser-assisted atom probe tomography experiments on boron carbide elucidate an approach for characterizing the atomic structure and interatomic bonding of molecules associated with extraordinary structural stability. The discovery of crystallographic planes in these boron carbide datasets substantiates that crystallinity is maintained to the point of field evaporation, and characterization of individual ionization events gives unexpected evidence of the destruction of individual icosahedra. Statistical analyses of the ions created during the field evaporation process have been used to deduce relative atomic bond strengths and show that the icosahedra in boron carbide are not as stable as anticipated. Combined with quantum mechanics simulations, this result provides insight into the structural instability and amorphization of boron carbide. The temporal, spatial, and compositional information provided by atom probe tomography makes it a unique platform for elucidating the relative stability and interactions of primary building blocks in hierarchically crystalline materials. PMID:27790982

Structure and mechanical properties of a multilayer carbide-hardened niobium composite material fabricated by diffusion welding

NASA Astrophysics Data System (ADS)

Korzhov, V. P.; Ershov, A. E.; Stroganova, T. S.; Prokhorov, D. V.

2016-04-01

The structure, the bending strength, and the fracture mechanism of an artificial niobium-based composite material, which is fabricated by high-pressure diffusion welding of multilayer stacks assembled from niobium foils with a two-sided carbon coating, are studied. The microstructure of the composite material is found to consist of alternating relatively plastic layers of the solid solution of carbon in niobium and hardening niobium carbide layers. The room-temperature proportional limit of the developed composite material is threefold that of the composite material fabricated from coating-free niobium foils using the proposed technology. The proportional limit of the developed composite material and the stress corresponding to the maximum load at 1100°C are 500 and 560 MPa, respectively. The developed material is considered as an alternative to Ni-Al superalloys.
Fabrication of thorium bearing carbide fuels

DOEpatents

Gutierrez, R.L.; Herbst, R.J.; Johnson, K.W.R.

Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750/sup 0/C and 2000/sup 0/C were used during the reduction cycle. Sintering temperatures of 1800/sup 0/C and 2000/sup 0/C were used to prepare fuel pellet densities of 87% and > 94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproductibility of chemical and phase composition.
Fabrication and tribological response of aluminium 6061 hybrid composite reinforced with bamboo char and boron carbide micro-fillers

NASA Astrophysics Data System (ADS)

Chethan, K. N.; Pai, Anand; Keni, Laxmikant G.; Singhal, Ashish; Sinha, Shubham

2018-02-01

Metal matrix composites (MMCs) have a wide scope of industrial applications and triumph over conventional materials due to their light weight, higher specific strength, good wear resistance and lower coefficient of thermal expansion. The present study aims at establishing the feasibility of using Bamboo charcoal particulate and boron carbide as reinforcements in Al-6061 alloy matrix and to investigate their effect on the wear of composites taking into consideration the interfacial adhesion of the reinforcements in the alloy. Al-6061 alloy was chosen as a base metallic alloy matrix. Sun-dried bamboo canes were used for charcoal preparation with the aid of a muffle furnace. The carbon content in the charcoal samples was determined by EDS (energy dispersive spectroscopy). In present study, stir casting technique was used to prepare the samples with 1%, 2%, and 3% weight of bamboo charcoal and boron carbide with Al-6061. The fabricated composites were homogenised at 570°C for 6 hours and cooled at room temperature. Wear studies were carried out on the specimens with different speed and loads. It was found that wear rate and coefficient of friction decreased with increase in the reinforcement content.
Development of an Extreme High Temperature n-type Ohmic Contact to Silicon Carbide

NASA Technical Reports Server (NTRS)

Evans, Laura J.; Okojie, Robert S.; Lukco, Dorothy

2011-01-01

We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 -cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 C while potentially extending operations to 1000 C. Introduction Silicon Carbide (SiC) is widely recognized as one of the materials of choice for high temperature, harsh environment sensors and electronics due to its ability to survive and continue normal operation in such environments [1]. Sensors and electronics in SiC have been developed that are capable of operating at temperatures of 600 oC. However operating these devices at the upper reliability temperature threshold increases the potential for early degradation. Therefore, it is important to raise the reliability temperature ceiling higher, which would assure increased device reliability when operated at nominal temperature. There are also instances that require devices to operate and survive for prolonged periods of time above 600 oC [2, 3]. This is specifically needed in the area of hypersonic flight where robust sensors are needed to monitor vehicle performance at temperature greater than 1000 C, as well as for use in the thermomechanical characterization of high temperature materials (e.g. ceramic matrix composites). While SiC alone can withstand these temperatures, a major challenge is to develop reliable electrical contacts to the device itself in order to facilitate signal extraction
Measurements of Erosion Wear Volume Loss on Bare and Coated Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Mondry, Richard J.; Bowman, Cheryl; Ma, Kong; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

2003-01-01

An investigation was conducted to examine the erosion behavior of uncoated and coated polymer matrix composite (PMC) specimens subjected to solid particle impingement using air jets. The PMCs were carbon-Kevlar (DuPont, Wilmington, DE) fiber-epoxy resin composites with a temperature capability up to 393 K (248 F). Tungsten carbide-cobalt (WC-Co) was the primary topcoat constituent. Bondcoats were applied to the PMC substrates to improve coating adhesion; then, erosion testing was performed at the University of Cincinnati. All erosion tests were conducted with Arizona road-dust (ARD), impinging at angles of 20 and 90 on both uncoated and two-layer coated PMCs at a velocity of 229 m/s and at a temperature of 366 K (200 F). ARD contains primarily 10-m aluminum oxide powders. Vertically scanning interference microscopy (noncontact, optical profilometry) was used to evaluate surface characteristics, such as erosion wear volume loss and depth, surface topography, and surface roughness. The results indicate that noncontact, optical interferometry can be used to make an accurate determination of the erosion wear volume loss of PMCs with multilayered structures while preserving the specimens. The two-layered (WC-Co topcoat and metal bondcoat) coatings on PMCs remarkably reduced the erosion volume loss by a factor of approximately 10. The tenfold increase in erosion resistance will contribute to longer PMC component lives, lower air friction, reduced related breakdowns, decreased maintenance costs, and increased PMC reliability. The decrease in the surface roughness of the coated vanes will lead to lower air friction and will subsequently reduce energy consumption. Eventually, the coatings could lead to overall economic savings.
The Role of the Component Metals in the Toxicity of Military-Grade Tungsten Alloy

PubMed Central

Emond, Christy A.; Vergara, Vernieda B.; Lombardini, Eric D.; Mog, Steven R.; Kalinich, John F.

2015-01-01

Tungsten-based composites have been recommended as a suitable replacement for depleted uranium. Unfortunately, one of these mixtures composed of tungsten (W), nickel (Ni) and cobalt (Co) induced rhabdomyosarcomas when implanted into the leg muscle of laboratory rats and mice to simulate a shrapnel wound. The question arose as to whether the neoplastic effect of the mixture could be solely attributed to one or more of the metal components. To investigate this possibility, pellets with one or two of the component metals replaced with an identical amount of the biologically-inert metal tantalum (Ta) were manufactured and implanted into the quadriceps of B6C3F1 mice. The mice were followed for two years to assess potential adverse health effects. Implantation with WTa, CoTa or WNiTa resulted in decreased survival, but not to the level reported for WNiCo. Sarcomas in the implanted muscle were found in 20% of the CoTa-implanted mice and 5% of the WTa- and WCoTa-implanted rats and mice, far below the 80% reported for WNiCo-implanted mice. The data obtained from this study suggested that no single metal is solely responsible for the neoplastic effects of WNiCo and that a synergistic effect of the three metals in tumor development was likely. PMID:29051474
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.
Effects of long-time elevated temperature exposures on hot-isostatically-pressed power-metallurgy Udimet 700 alloys with reduced cobalt contents

NASA Technical Reports Server (NTRS)

Hart, F. H.

1984-01-01

Because almost the entire U.S. consumption of cobalt depends on imports, this metal has been designated "strategic'. The role and effectiveness of cobalt is being evaluated in commercial nickel-base superalloys. Udiment 700 type alloys in which the cobalt content was reduced from the normal 17% down to 12.7%, 8.5%, 4.3%, and 0% were prepared by standard powder metallurgy techniques and hot isostatically pressed into billets. Mechanical testing and microstructural investigations were performed. The mechanical properties of alloys with reduced cobalt contents which were heat-treated identically were equal or better than those of the standard alloy, except that creep rates tended to increase as cobalt was reduced. The effects of long time exposures at 760 C on mechanical properties and at 760 C and 845 C on microstructures were determined. Decreased tensile properties and shorter rupture lives with increased creep rates were observed in alloy modifications. The exposures caused gamma prime particle coarsening and formation of sigma phase in the alloys with higher cobalt contents. Exposure at 845 C also reduced the amount of MC carbides.
Prediction of the wear and evolution of cutting tools in a carbide / titanium-aluminum-vanadium machining tribosystem by volumetric tool wear characterization and modeling

NASA Astrophysics Data System (ADS)

Kuttolamadom, Mathew Abraham

being carried away by the rubbing action of the chips -- this left behind a smooth crater surface predominantly of tungsten and cobalt as observed from EDS analysis. Also, at high surface speeds, carbon from the tool was found diffused into the adhered titanium layer to form a titanium carbide (TiC) boundary layer -- this was observed as instances of TiC build-up on the tool edge from EDS analysis. A complex wear mechanism interaction was thus observed, i.e., titanium adhered on top of an earlier worn out crater trough, additional carbon diffused into this adhered titanium layer to create a more stable boundary layer (which could limit diffusion-rates on saturation), and then all were further worn away by dissolution wear as temperatures increased. At low and medium feeds, notch discoloration was observed -- this was detected to be carbon from EDS analysis, suggesting that it was deposited from the edges of the passing chips. Mapping the dominant wear mechanisms showed the increasing dominance of dissolution wear relative to adhesion, with increasing grain size -- this is because a 13% larger sub-micron grain results in a larger surface area of cobalt exposed to chemical action. On the macro-scale, wear quantification through topology characterization elevated wear from a 1D to 3D concept. From investigation, a second order dependence of volumetric tool wear (VTW) and VTW rate with the material removal rate (MRR) emerged, suggesting that MRR is a more consistent wear-controlling factor instead of the traditionally used cutting speed. A predictive model for VTW was developed which showed its exponential dependence with workpiece stock volume removed. Also, both VTW and VTW rate were found to be dependent on the accumulated cumulative wear on the tool. Further, a ratio metric of stock material removed to tool volume lost is now possible as a tool efficiency quantifier and energy-based productivity parameter, which was found to inversely depend on MRR - this led to a more
An electrical conductivity inspection methodology of polycrystalline diamond cutters

NASA Astrophysics Data System (ADS)

Bogdanov, G.; Wiggins, J.; Bertagnolli, K.; Ludwig, R.

2012-05-01

The polycrystalline diamond cutter (PDC) is widely used in oil and gas drilling operations. It is manufactured by sintering diamond powder onto a tungsten carbide substrate at 6 GPa and 1500 C. During sintering, molten cobalt from the substrate infiltrates the diamond table. The residual metal content correlates with cutter performance. We present an instrument that employs electrical impedance tomography capable of imaging the 3D metal content distribution in the diamond table. These images can be used to predict cutter performance as well as detect flaws.
Microwave-Assisted Curing of Silicon Carbide-Reinforced Epoxy Composites: Role of Dielectric Properties

NASA Astrophysics Data System (ADS)

Pal, Ranu; Akhtar, M. J.; Kar, Kamal K.

2018-05-01

In this work, the dielectric properties of epoxy-based composites are significantly improved with the help of the silicon carbide (SiC) filler at an operating frequency of 2.45 GHz to make them ideal candidates for microwave curing. The improvement is due to enhancement of the interfacial polarization because of the presence of the SiC filler. The dielectric properties are measured using the microwave cavity perturbation method. The cavity structure is simulated using the COMSOL@Multiphysics software to verify the measured data in terms of the resonant frequency. Finally, all the SiC-based composites including the neat epoxy resin are heated in the 2.45 GHz microwave oven at 300 W for 20 min. The thermal and mechanical properties of all the cured composites are measured, and the data are compared with their room temperature pre-cured counterparts. The dielectric properties of composite samples using SiC as a reinforcing agent in the epoxy are found to be substantially improved compared with those of the pure epoxy sample, which actually leads to better curing of these composite using the 2.45 GHz microwave system.
High temperature fatigue behavior of tungsten copper composites

NASA Technical Reports Server (NTRS)

Verrilli, Michael J.; Kim, Yong-Suk; Gabb, Timothy P.

1989-01-01

The high temperature fatigue behavior of a 9 vol percent, tungsten fiber reinforced copper matrix composite was investigated. Load-controlled isothermal fatigue experiments at 260 and 560 C and thermomechanical fatigue (TMF) experiments, both in phase and out of phase between 260 and 560 C, were performed. The stress-strain response displayed considerable inelasticity under all conditions. Also, strain ratcheting was observed during all the fatigue experiments. For the isothermal fatigue and in-phase TMF tests, the ratcheting was always in a tensile direction, continuing until failure. The ratcheting during the out-of-phase TMF test shifted from a tensile direction to a compressive direction. This behavior was thought to be associated with the observed bulging and the extensive cracking of the out-of-phase specimen. For all cases, the fatigue lives were found to be controlled by damage to the copper matrix. Grain boundary cavitation was the dominant damage mechanism of the matrix. On a stress basis, TMF loading reduced lives substantially, relative to isothermal cycling. In-phase cycling resulted in the shortest lives, and isothermal fatigue at 260 C, the longest.
The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Zheng, Liping; Wang, Ying; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie; Guo, Jia

Calcium carbide (CaC 2)-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N 2 sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g -1 measured by cyclic voltammetry at 1 mV s -1. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles.
Microstructural, dielectric and magnetic properties of multiferroic composite system barium strontium titanate – nickel cobalt ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pahuja, Poonam, E-mail: poonampahuja123@gmail.com; Tandon, R. P., E-mail: ram-tandon@hotmail.com

2015-05-15

Multiferroic composites (1-x) Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3} + (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4} (where x = 0.1, 0.2, 0.3, 0.4) has been prepared by solid state reaction method. X-ray diffraction analysis of the composite samples confirmed the presence of both barium strontium titanate (BST) and nickel cobalt ferrite (NCF) phases. FESEM images indicated the well dispersion of NCF grains among BST grains. Dielectric constant and loss of the composite samples decreases with increase in frequency following Maxwell-Wagner relaxation mechanism. Composite sample with highest ferrite content possesses highest values of remanent and saturation magnetization.
Development and Processing of Nickel Aluminide-Carbide Alloys

NASA Technical Reports Server (NTRS)

Newport, Timothy Scott

1996-01-01

With the upper temperature limit of the Ni-based superalloys attained, a new class of materials is required. Intermetallics appear as likely candidates because of their attractive physical properties. With a relatively low density, high thermal conductivity, excellent oxidation resistance, high melting point, and simple crystal structure, nickel aluminide (NiAl) appears to be a potential candidate. However, NiAl is limited in structural applications due to its low room temperature fracture toughness and poor elevated temperature strength. One approach to improving these properties has been through the application of eutectic composites. Researchers have shown that containerless directional solidification of NiAl-based eutectic alloys can provide improvement in both the creep strength and fracture toughness. Although these systems have shown improvements in the mechanical properties, the presence of refractory metals increases the density significantly in some alloys. Lower density systems, such as the carbides, nitrides, and borides, may provide NiAl-based eutectic structure. With little or no information available on these systems, experimental investigation is required. The objective of this research was to locate and develop NiAl-carbide eutectic alloys. Exploratory arc-melts were performed in NiAl-refractory metal-C systems. Refractory metal systems investigated included Co, Cr, Fe, Hf, Mo, Nb, Ta, Ti, W, and Zr. Systems containing carbides with excellent stability (i.e.,HfC, NbC, TaC, TiC, and ZrC) produced large blocky cubic carbides in an NiAl matrix. The carbides appeared to have formed in the liquid state and were randomly distributed throughout the polycrystalline NiAl. The Co, Cr, Fe, Mo, and W systems contained NiAl dendrites with a two-phase interdendritic microconstituent present. Of these systems, the NiAl-Mo-C system had the most promising microstructure for in-situ composites. Three processing techniques were used to evaluate the NiAl-Mo-C system
Article and method for making complex shaped preform and silicon carbide composite by melt infiltration

NASA Technical Reports Server (NTRS)

Corman, Gregory S. (Inventor); Steibel, James D. (Inventor); Schikner, Robert C. (Inventor); Szweda, Andrew (Inventor)

2001-01-01

Small diameter silicon carbide-containing fibers are provided in a bundle such as a fiber tow that can be formed into a structure where the radii of curvature is not limited to 10-20 inches. An aspect of this invention is directed to impregnating the bundles of fibers with the slurry composition to substantially coat the outside surface of an individual fiber within the bundle and to form a complex shaped preform with a mass of continuous fibers.
Article and method for making complex shaped preform and silicon carbide composite by melt infiltration

NASA Technical Reports Server (NTRS)

Szweda, Andrew (Inventor); Corman, Gregory S. (Inventor); Steibel, James D. (Inventor); Schikner, Robert C. (Inventor)

2000-01-01

Small diameter silicon carbide-containing fibers are provided in a bundle such as a fiber tow that can be formed into a structure where the radii of curvature is not limited to 10-20 inches. An aspect of this invention is directed to impregnating the bundles of fibers with the slurry composition to substantially coat the outside surface of an individual fiber within the bundle and to form a complex shaped preform with a mass of continuous fibers.
Silicon carbide-free graphene growth on silicon for lithium-ion battery with high volumetric energy density

PubMed Central

Son, In Hyuk; Hwan Park, Jong; Kwon, Soonchul; Park, Seongyong; Rümmeli, Mark H.; Bachmatiuk, Alicja; Song, Hyun Jae; Ku, Junhwan; Choi, Jang Wook; Choi, Jae-man; Doo, Seok-Gwang; Chang, Hyuk

2015-01-01

Silicon is receiving discernable attention as an active material for next generation lithium-ion battery anodes because of its unparalleled gravimetric capacity. However, the large volume change of silicon over charge–discharge cycles weakens its competitiveness in the volumetric energy density and cycle life. Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation. The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers. When paired with a commercial lithium cobalt oxide cathode, the silicon carbide-free graphene coating allows the full cell to reach volumetric energy densities of 972 and 700 Wh l−1 at first and 200th cycle, respectively, 1.8 and 1.5 times higher than those of current commercial lithium-ion batteries. This observation suggests that two-dimensional layered structure of graphene and its silicon carbide-free integration with silicon can serve as a prototype in advancing silicon anodes to commercially viable technology. PMID:26109057
The effect of thermal cycling on the structure and properties of a Co, Cr, Ni-TaC directionally solidified eutectic composite

NASA Technical Reports Server (NTRS)

Dunlevey, F. M.; Wallace, J. F.

1973-01-01

The effect of thermal cycling on the structure and properties of a cobalt, chromium, nickel, tantalum carbide directionally solidified eutectic composite is reported. It was determined that the stress rupture properties of the alloy were decreased by the thermal cycling. The loss in stress rupture properties varied with the number of cycles with the loss in properties after about 200 cycles being relatively high. The formation of serrations and the resulting changes in the mechanical properties of the material are discussed.
Thermal conductivity behavior of boron carbides

NASA Technical Reports Server (NTRS)

Wood, C.; Zoltan, A.; Emin, D.; Gray, P. E.

1983-01-01

Knowledge of the thermal conductivity of boron carbides is necessary to evaluate its potential for high temperature thermoelectric energy conversion applications. The thermal diffusivity of hot pressed boron carbide B/sub 1-x/C/sub x/ samples as a function of composition, temperature and temperature cycling was measured. These data in concert with density and specific heat data yield the thermal conductivities of these materials. The results in terms of a structural model to explain the electrical transport data and novel mechanisms for thermal conduction are discussed.

Processing and consolidation of copper/tungsten

DOE PAGES

Chen, Ching-Fong; Pokharel, Reeju; Brand, Michael J.; ...

2016-09-27

Here, we developed a copper/tungsten (Cu/W) composite for mesoscale Materials Science applications using the novel High-Energy Diffraction Microscopy (HEDM) technique. Argon-atomized copper powder was selected as the starting raw powder and screened to remove the extremely large particle fraction. Tungsten particles were collected by milling and screening the -325 mesh tungsten powder between 500 and 635 mesh sieves. Hot pressing of screened Cu powder was performed at 900 °C in Ar/4 %H 2 atmosphere. XRD and ICP results show that the hot-pressed Cu sample consists of about 5 vol% Cu 2O, which is caused by the presence of oxygen onmore » the surface of the starting Cu powder. Hot pressing the copper powder in a pure hydrogen atmosphere was successful in removing most of the surface oxygen. Our process was also implemented for hot pressing the Cu/W composite. The density of the Cu/W composites hot pressed at 950 °C in pure hydrogen was about 94 % of the theoretical density (TD). The hot-pressed Cu/W composites were further hot isostatic pressed at 1050 °C in argon atmosphere, which results in 99.6 % of the TD with the designed Cu grain size and W particle distribution. Tensile specimens with D-notch were machined using the wire EDM method. Furthermore, the processing and consolidation of these materials will be discussed in detail. The HEDM images are also showed and discussed.« less
Design and development of solid carbide step drill K34 for machining of CFRP and GFRP composite laminates

NASA Astrophysics Data System (ADS)

Rangaswamy, T.; Nagaraja, R.

2018-04-01

The Study focused on design and development of solid carbide step drill K34 to drill holes on composite materials such as Carbon Fiber Reinforced Plastic (CFRP) and Glass Fiber Reinforced Plastic (GFRP). The step drill K34 replaces step wise drilling of diameter 6.5mm and 9 mm holes that reduces the setup time, cutting speed, feed rate cost, delamination and increase the production rate. Several researchers have analyzed the effect of drilling process on various fiber reinforced plastic composites by carrying out using conventional tools and machinery. However, this process operation can lead to different kind of damages such as delamination, fiber pullout, and local cracks. To avoid the problems encountered at the time of drilling, suitable tool material and geometry is essential. This paper deals with the design and development of K34 Carbide step drill used to drill holes on CFRP and GFRP laminates. An Experimental study carried out to investigate the tool geometry, feed rate and cutting speed that avoids delamination and fiber breakage.
Insensitive high-energy energetic structural material of tungsten-polytetrafluoroethylene-aluminum composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Liu; Liu, Jinxu, E-mail: liujinxu@bit.edu.cn; Zhang, Xinbo

2015-11-15

Energetic structural material is a kind of materials that are inert under normal conditions but could produce exothermic chemical reaction when subjected to impact. This report shows a kind of energetic structural material of tungsten (W)-polytetrafluoroethylene (PTFE)-aluminum (Al) with density of 4.12 g/cm{sup 3}, excellent ductility and dynamic compressive strength of 96 MPa. Moreover, 50W-35PTFE-15Al (wt%) can exhibit a high reaction energy value of more than 2 times of TNT per unit mass and 5 times of TNT per unit volume, respectively, but with excellent insensitivity compared with traditional explosives. Under thermal conditions, the W-PTFE-Al composite can keep stable atmore » 773 K. Under impact loading, when the strain rate up to ∼4820 s{sup −1} coupled with the absorbed energy per unit volume of 120 J/cm{sup 3}, deflagration occurs and combustion lasts for 500 μs. During impact compressive deformation, the PTFE matrix is elongated into nano-fibers, thus significantly increases the reaction activity of W-PTFE-Al composites. The nano-fiber structure is necessary for the reaction of W-PTFE-Al composites. The formation of PTFE nano-fibers must undergo severe plastic deformation, and therefore the W-PTFE-Al composites exhibit excellent insensitivity and safety. Furthermore, the reaction mechanisms of W-PTFE-Al composites in argon and in air are revealed.« less
Perspectives of SiC-Based Ceramic Composites and Their Applications to Fusion Reactors 5.Development of Evaluation and Application Techniques of SiC⁄SiC Composites for Fusion Reactors

NASA Astrophysics Data System (ADS)

Hinoki, Tatsuya

Evaluation techniques and mechanical properties of silicon carbide composites (SiC⁄SiC composites) reinforced with highly crystalline fibers are reviewed for fusion applications. The SiC⁄SiC composites used were fabricated by means of the CVI method. The evaluation includes in-plane tensile strength by in-plane tensile test, transthickness tensile strength by transthickness tensile test and diametral compression test and shear strength by compression test using double-notched specimen. All tests were successfully conducted using small specimens for neutron irradiation experiment. As application technique, the novel tungsten(W) coating technique on SiC is reviewed. The W powder melted by high power lamp in a few seconds and formed coating on SiC. No thick reaction layers of WC and W5Si3, which are formed by the other coating methods, were formed by this method.
Plasma Processing Systems for the Manufacture of Refractory Metals and their Alloys for Military Needs

DTIC Science & Technology

1978-10-09

melting point is around 4000*K. An exceedingly interesting feature of these solidification composites is the formation of fibrous MC type carbide ...the matrix could be refractory metal binary alloys with copper or uranium and the eutectic phase could be carbide of tungsten, * molybdenum, tantalum or...42 Accs -n or - *DTTI Tf Avn ! -7ll ’ i CrDi t , l’’*i,;. LIST OF FIGURES FIG. 1 Flow Diagram of Cemented Carbide Manufacture
Rovibronically selected and resolved two-color laser photoionization and photoelectron study of cobalt carbide cation.

PubMed

Huang, Huang; Chang, Yih Chung; Luo, Zhihong; Shi, Xiaoyu; Lam, Chow-Shing; Lau, Kai-Chung; Ng, C Y

2013-03-07

We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization efficiency and pulsed field ionization-photoelectron (PFI-PE) study of gaseous cobalt carbide (CoC) near its ionization onset in the total energy range of 61,200-64,510 cm(-1). The cold gaseous CoC sample was prepared by a laser ablation supersonically cooled beam source. By exciting CoC molecules thus generated to single N' rotational levels of the intermediate CoC∗((2)Σ(+); v') state using a VIS dye laser prior to UV laser photoionization, we have obtained N(+) rotationally resolved PFI-PE spectra for the CoC(+)(X(1)Σ(+); v(+) = 0 and 1) ion vibrational bands free from interference by impurity species except Co atoms produced in the ablation source. The rotationally selected and resolved PFI-PE spectra have made possible unambiguous rotational assignments, yielding accurate values for the adiabatic ionization energy of CoC(X(2)Σ(+)), IE(CoC) = 62,384.3 ± 0.6 cm(-1) (7.73467 ± 0.00007 eV), the vibrational frequency ωe (+) = 985.6 ± 0.6 cm(-1), the anharmonicity constant ωe (+)χe (+) = 6.3 ± 0.6 cm(-1), the rotational constants (Be (+) = 0.7196 ± 0.0005 cm(-1), αe (+) = 0.0056 ± 0.0008 cm(-1)), and the equilibrium bond length re (+) = 1.534 Å for CoC(+)(X(1)Σ(+)). The observation of the N(+) = 0 level in the PFI-PE measurement indicates that the CoC(+) ground state is of (1)Σ(+) symmetry. Large ΔN(+) = N(+) - N' changes up to 6 are observed for the photoionization transitions CoC(+)(X(1)Σ(+); v(+) = 0-2; N(+)) ← CoC∗((2)Σ(+); v'; N' = 6, 7, 8, and 9). The highly precise energetic and spectroscopic data obtained in the present study have served as a benchmark for testing theoretical predictions based on state-of-the-art ab initio quantum calculations at the CCSDTQ∕CBS level of theory as presented in the companion article.
Cobalt

USGS Publications Warehouse

Slack, John F.; Kimball, Bryn E.; Shedd, Kim B.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Cobalt is a silvery gray metal that has diverse uses based on certain key properties, including ferromagnetism, hardness and wear-resistance when alloyed with other metals, low thermal and electrical conductivity, high melting point, multiple valences, and production of intense blue colors when combined with silica. Cobalt is used mostly in cathodes in rechargeable batteries and in superalloys for turbine engines in jet aircraft. Annual global cobalt consumption was approximately 75,000 metric tons in 2011; China, Japan, and the United States (in order of consumption amount) were the top three cobalt-consuming countries. In 2011, approximately 109,000 metric tons of recoverable cobalt was produced in ores, concentrates, and intermediate products from cobalt, copper, nickel, platinum-group-element (PGE), and zinc operations. The Democratic Republic of the Congo (Congo [Kinshasa]) was the principal source of mined cobalt globally (55 percent). The United States produced a negligible amount of byproduct cobalt as an intermediate product from a PGE mining and refining operation in southeastern Montana; no U.S. production was from mines in which cobalt was the principal commodity. China was the leading refiner of cobalt, and much of its production came from cobalt ores, concentrates, and partially refined materials imported from Congo (Kinshasa).The mineralogy of cobalt deposits is diverse and includes both primary (hypogene) and secondary (supergene) phases. Principal terrestrial (land-based) deposit types, which represent most of world’s cobalt mine production, include primary magmatic Ni-Cu(-Co-PGE) sulfides, primary and secondary stratiform sediment-hosted Cu-Co sulfides and oxides, and secondary Ni-Co laterites. Seven additional terrestrial deposit types are described in this chapter. The total terrestrial cobalt resource (reserves plus other resources) plus past production, where available, is calculated to be 25.5 million metric tons. Additional resources of
Additive Manufacturing of Silicon Carbide-Based Ceramic Matrix Composites: Technical Challenges and Opportunities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Halbig, Michael C.; Grady, Joseph E.

2016-01-01

Advanced SiC-based ceramic matrix composites offer significant contributions toward reducing fuel burn and emissions by enabling high overall pressure ratio (OPR) of gas turbine engines and reducing or eliminating cooling air in the hot-section components, such as shrouds, combustor liners, vanes, and blades. Additive manufacturing (AM), which allows high value, custom designed parts layer by layer, has been demonstrated for metals and polymer matrix composites. However, there has been limited activity on additive manufacturing of ceramic matrix composites (CMCs). In this presentation, laminated object manufacturing (LOM), binder jet process, and 3-D printing approaches for developing ceramic composite materials are presented. For the laminated object manufacturing (LOM), fiber prepreg laminates were cut into shape with a laser and stacked to form the desired part followed by high temperature heat treatments. For the binder jet, processing optimization was pursued through silicon carbide powder blending, infiltration with and without SiC nano powder loading, and integration of fibers into the powder bed. Scanning electron microscopy was conducted along with XRD, TGA, and mechanical testing. Various technical challenges and opportunities for additive manufacturing of ceramics and CMCs will be presented.
Electronic structure and mechanical properties of osmium borides, carbides and nitrides from first principles

NASA Astrophysics Data System (ADS)

Liang, Yongcheng; Zhao, Jianzhi; Zhang, Bin

2008-06-01

The stabilities, mechanical properties and electronic structures of osmium boride (OsB), carbide (OsC) and nitride (OsN), in the tungsten carbide (WC), rocksalt (NaCl), cesium chloride (CsCl) and zinc blende (ZnS) structures respectively, are systematically predicted by calculations from first-principles. Only four phases, namely, OsB(WC), OsB(CsCl), OsC(WC), and OsC(ZnS), are mechanically stable, and none is a superhard compound, contrary to previous speculation. Most importantly, we find that the changing trends of bulk modulus and shear modulus are completely different for OsB, OsC and OsN in same hexagonal WC structure, which indicates that the underlying sources of hardness and incompressibility are fundamentally different: the former is determined by bonding nature while the latter is closely associated with valence electron density.
The tungsten isotopic composition of the Earth's mantle before the terminal bombardment.

PubMed

Willbold, Matthias; Elliott, Tim; Moorbath, Stephen

2011-09-07

Many precious, 'iron-loving' metals, such as gold, are surprisingly abundant in the accessible parts of the Earth, given the efficiency with which core formation should have removed them to the planet's deep interior. One explanation of their over-abundance is a 'late veneer'--a flux of meteorites added to the Earth after core formation as a 'terminal' bombardment that culminated in the cratering of the Moon. Some 3.8 billion-year-old rocks from Isua, Greenland, are derived from sources that retain an isotopic memory of events pre-dating this cataclysmic meteorite shower. These Isua samples thus provide a window on the composition of the Earth before such a late veneer and allow a direct test of its importance in modifying the composition of the planet. Using high-precision (less than 6 parts per million, 2 standard deviations) tungsten isotope analyses of these rocks, here we show that they have a isotopic tungsten ratio (182)W/(184)W that is significantly higher (about 13 parts per million) than modern terrestrial samples. This finding is in good agreement with the expected influence of a late veneer. We also show that alternative interpretations, such as partial remixing of a deep-mantle reservoir formed in the Hadean eon (more than four billion years ago) or core-mantle interaction, do not explain the W isotope data well. The decrease in mantle (182)W/(184)W occurs during the Archean eon (about four to three billion years ago), potentially on the same timescale as a notable decrease in (142)Nd/(144)Nd (refs 3 and 6). We speculate that both observations can be explained if late meteorite bombardment triggered the onset of the current style of mantle convection.
The Particle Shape of WC Governing the Fracture Mechanism of Particle Reinforced Iron Matrix Composites.

PubMed

Li, Zulai; Wang, Pengfei; Shan, Quan; Jiang, Yehua; Wei, He; Tan, Jun

2018-06-11

In this work, tungsten carbide particles (WC p , spherical and irregular particles)-reinforced iron matrix composites were manufactured utilizing a liquid sintering technique. The mechanical properties and the fracture mechanism of WC p /iron matrix composites were investigated theoretically and experimentally. The crack schematic diagram and fracture simulation diagram of WC p /iron matrix composites were summarized, indicating that the micro-crack was initiated both from the interface for spherical and irregular WC p /iron matrix composites. However, irregular WC p had a tendency to form spherical WC p . The micro-cracks then expanded to a wide macro-crack at the interface, leading to a final failure of the composites. In comparison with the spherical WC p , the irregular WC p were prone to break due to the stress concentration resulting in being prone to generating brittle cracking. The study on the fracture mechanisms of WC p /iron matrix composites might provide a theoretical guidance for the design and engineering application of particle reinforced composites.
Characterization and in-situ formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

NASA Astrophysics Data System (ADS)

Wang, Mi-qi; Zhou, Ze-hua; Wu, Lin-tao; Ding, Ying; Wang, Ze-hua

2018-04-01

The precursor carbonization method was first applied to prepare W-C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W-C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M7C3 carbides. Moreover, net-like structures were confirmed as mixtures of M23C6 and α-Fe; these structures were transformed from M7C3. The coarse herringbone M6C carbides did not only derive from the decomposition of M7C3 but also partly originated from the chemical reaction at the α-Fe/M23C6 interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M7C3 → M23C6 + M6C.
Friction and wear of plasma-sprayed coatings containing cobalt alloys from 25 deg to 650 deg in air

NASA Technical Reports Server (NTRS)

Sliney, H. E.; Jacobson, T. P.

1979-01-01

Four different compositions of self-lubricating, plasma-sprayed, composite coatings with calcium fluoride dispersed throughout cobalt alloy-silver matrices were evaluated on a friction and wear apparatus. In addition, coatings of the cobalt alloys alone and one coating with a nickel alloy-silver matrix were evaluated for comparison. The wear specimens consisted of two, diametrically opposed, flat rub shoes sliding on the coated, cylindrical surface of a rotating disk. Two of the cobalt composite coatings gave a friction coefficient of about 0.25 and low wear at room temperature, 400 and 650 C. Wear rates were lower than those of the cobalt alloys alone or the nickel alloy composite coating. However, oxidation limited the maximum useful temperature of the cobalt composite coating to about 650 C compared to about 900 C for the nickel composite coating.
Iron Carbides and Nitrides: Ancient Materials with Novel Prospects.

PubMed

Ye, Zhantong; Zhang, Peng; Lei, Xiang; Wang, Xiaobai; Zhao, Nan; Yang, Hua

2018-02-07

Iron carbides and nitrides have aroused great interest in researchers, due to their excellent magnetic properties, good machinability and the particular catalytic activity. Based on these advantages, iron carbides and nitrides can be applied in various areas such as magnetic materials, biomedical, photo- and electrocatalysis. In contrast to their simple elemental composition, the synthesis of iron carbides and nitrides still has great challenges, particularly at the nanoscale, but it is usually beneficial to improve performance in corresponding applications. In this review, we introduce the investigations about iron carbides and nitrides, concerning their structure, synthesis strategy and various applications from magnetism to the catalysis. Furthermore, the future prospects are also discussed briefly. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Incendivity of some coal-cutter materials by impact-abrasion in air-methane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blickensderfer, R.; Deardorff, D.K.; Kelley, J.E.

1974-01-01

Test equipment that simulated frictional impacts between coal-cutter bits and mineral inclusions at a coal face during operation of a continuous coal mining machine was used to study the incendivity of impacts between various rocks, metals, and hard-metal alloys in an explosive mixture of air-7 pct natural gas. Quartzitic sandstone was found to be the most incendive of several rocks tested. Limestone concretions from a coal seam, known locally as ''sulfur balls,'' sparked furiously but were not incendive. Among the metals tested, the type of steel used in commercial coal-cutter tools was the most incendive material tested. A 17-4PH stainlessmore » steel was less incendive and appears to be the most promising high-strength steel alloy, reasonably economical, for use in coal-cutter bits. Some hard-metal alloys, primarily titanium and zirconium diboride composites, were also evaluated as possible replacements for the conventional cobalt-bonded tungsten carbide used in the tip of coal-cutter bits. The metal-bonded diborides were generally less incendive (but more brittle) than the conventional tungsten carbide. Carbonitride coatings on tool bits were also tested but found to have no advantage. The source of ignition during frictional impact between metal and rock was studied. Immediately after impact, a yellow flash was observed and a smear of metal near its melting point occurred on the rock. This hotspot on the rock, rather than the yellow flash or sparks or metal fragments, was observed to be the cause of the ignition.« less
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
Processing and characterization of boron carbide-hafnium diboride ceramics

NASA Astrophysics Data System (ADS)

Brown-Shaklee, Harlan James

Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB2 sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB2 powder in part by removing oxides at the HfB2 surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB2 by 150°C compared to carbon, which reduced the hot pressing temperature by ˜50°C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated. Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB2. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB2. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B6.5 C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB2, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 2000°C suggested that the stoichiometry of the boron carbide additives did not significantly affect kth of HfB2-BxC composites. The improved sinterability and the high kth (˜110 W/m-K at 300K and ˜90 W/m-K at 1000°C ) of HfB2-BxC ceramics make them excellent candidates for isotopically enriched reactor control materials.
The material performance of HSS (high speed steel) tools and its relation with chemical composition and carbide distribution

NASA Astrophysics Data System (ADS)

Darmawan, B.; Kusman, M.; Hamdani, R. A.

2016-04-01

The study aims to compare the performance of two types of material HSS (High Speed Steel) are widely used. It also will be the chemical composition and distribution of carbide particles therein. Two types of HSS are available in the market: HSS from Germany (Bohler) and HSS from China. This research employed the pure experimental design. It consists of two stages. The first, aims to test/operate lathe machines to determine the lifetime and performance of tools based on specified wear criteria. The second, characterization of microstructure using SEM-EDS was conducted. Firstly, grinding of toolss was done so that the toolss could be used for cutting metal in the turning process. Grinding processes of the two types of toolss were done at the same geometry, that is side rake angle (12°-18°), angle of keenness (60°-68°), and side relief angle (10°-12°). Likewise, machining parameters were set in the same machining conditions. Based on the results of the tests, it is found that to reach 0.2 mm wear point, toolss made of HSS from Germany needed 24 minutes, while toolss made of HSS from China needed 8 minutes. Next, microstructure tests using SEM/EDS were done. The results of the SEM tests indicate that the carbide particles of HSS from Germany were more evenly distributed than the carbide particles of HSS from China. Carbide compounds identified in HSS from China were Cr23C6 and Fe4Mo2C. Oxide impurity of Al2O3 was also found in the material. On the other hand, in HSS from Germany, no impurity and other carbide compounds were identified, except Cr23C6 and Fe4Mo2C, also Fe4W2C, and VC or V4C3.
New Structural Materials

DTIC Science & Technology

1989-03-25

3887) Tantalum Carbide (TaC) 4150 (3877) Niobium Carbide 4023 (3750) Carbon (Graphite) 3970 (3697) Zirconium Carbide 3805 (3532) Tungsten 3643 3643...process. Some fibers, especially those made of tungsten , silicon carbide, and zirconia, survived the reaction conditions. However, the ceramic bodies...displayed cracks and voids. Examination by SEM of cross’sections of the reacted parts made with tungsten fibers disclosed the presence of "whiskers
Self-Supported Biocarbon-Fiber Electrode Decorated with Molybdenum Carbide Nanoparticles for Highly Active Hydrogen-Evolution Reaction.

PubMed

Xiao, Jian; Zhang, Yan; Zhang, Zheye; Lv, Qiying; Jing, Feng; Chi, Kai; Wang, Shuai

2017-07-12

Devising and facilely synthesizing an efficient noble metal-free electrocatalyst for the acceleration of the sluggish kinetics in the hydrogen-evolution reaction (HER) is still a big challenge for electrolytic water splitting. Herein, we present a simple one-step approach for constructing self-supported biocarbon-fiber cloth decorated with molybdenum carbide nanoparticles (BCF/Mo 2 C) electrodes by a direct annealing treatment of the Mo oxyanions loaded cotton T-shirt. The Mo 2 C nanoparticles not only serve as the catalytic active sites toward the HER but also enhance the hydrophilicity and conductivity of resultant electrodes. As an integrated three-dimensional HER cathode catalyst, the BCF/Mo 2 C exhibits outstanding electrocatalytic performance with extremely low overpotentials of 88 and 115 mV to drive a current density of 20 mA cm -2 in alkaline and acidic media, respectively. In addition, it can continuously work for 50 h with little decrease in the cathodic current density in both alkaline and acidic solutions. Even better, self-supported tungsten carbide and vanadium carbide based electrodes also can be prepared by a similar synthesis process. This work will illuminate an entirely new avenue for the preparation of various self-supported three-dimensional electrodes made of transition-metal carbides for various applications.

Deposition and properties of cobalt- and ruthenium-based ultra-thin films

NASA Astrophysics Data System (ADS)

Henderson, Lucas Benjamin

Future copper interconnect systems will require replacement of the materials that currently comprise both the liner layer(s) and the capping layer. Ruthenium has previously been considered as a material that could function as a single material liner, however its poor ability to prevent copper diffusion makes it incompatible with liner requirements. A recently described chemical vapor deposition route to amorphous ruthenium-phosphorus alloy films could correct this problem by eliminating the grain boundaries found in pure ruthenium films. Bias-temperature stressing of capacitor structures using 5 nm ruthenium-phosphorus film as a barrier to copper diffusion and analysis of the times-to-failure at accelerated temperature and field conditions implies that ruthenium-phosphorus performs acceptably as a diffusion barrier for temperatures above 165°C. The future problems associated with the copper capping layer are primarily due to the poor adhesion between copper and the current Si-based capping layers. Cobalt, which adheres well to copper, has been widely proposed to replace the Si-based materials, but its ability to prevent copper diffusion must be improved if it is to be successfully implemented in the interconnect. Using a dual-source chemistry of dicobaltoctacarbonyl and trimethylphosphine at temperatures from 250-350°C, amorphous cobalt-phosphorus can be deposited by chemical vapor deposition. The films contain elemental cobalt and phosphorus, plus some carbon impurity, which is incorporated in the film as both graphitic and carbidic (bonded to cobalt) carbon. When deposited on copper, the adhesion between the two materials remains strong despite the presence of phosphorus and carbon at the interface, but the selectivity for growth on copper compared to silicon dioxide is poor and must be improved prior to consideration for application in interconnect systems. A single molecule precursor containing both cobalt and phosphorus atoms, tetrakis(trimethylphosphine)cobalt
Micromechanical analysis of a hybrid composite—effect of boron carbide particles on the elastic properties of basalt fiber reinforced polymer composite

NASA Astrophysics Data System (ADS)

Krishna Golla, Sai; Prasanthi, P.

2016-11-01

A fiber reinforced polymer (FRP) composite is an important material for structural application. The diversified application of FRP composites has become the center of attention for interdisciplinary research. However, improvements in the mechanical properties of this class of materials are still under research for different applications. The reinforcement of inorganic particles in a composite improves its structural properties due to their high stiffness. The present research work is focused on the prediction of the mechanical properties of the hybrid composites where continuous fibers are reinforced in a micro boron carbide particle mixed polypropylene matrix. The effectiveness of the addition of 30 wt. % of boron carbide (B4C) particle contributions regarding the longitudinal and transverse properties of the basalt fiber reinforced polymer composite at various fiber volume fractions is examined by finite element analysis (FEA). The experimental approach is the best way to determine the properties of the composite but it is expensive and time-consuming. Therefore, the finite element method (FEM) and analytical methods are the viable methods for the determination of the composite properties. The FEM results were obtained by adopting a micromechanics approach with the support of FEM. Assuming a uniform distribution of reinforcement and considering one unit-cell of the whole array, the properties of the composite materials are determined. The predicted elastic properties from FEA are compared with the analytical results. The results suggest that B4C particles are a good reinforcement for the enhancement of the transverse properties of basalt fiber reinforced polypropylene.
Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum

NASA Astrophysics Data System (ADS)

Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.

2017-01-01

Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.
Elastic Moduli and Damping of Vibrational Modes of Aluminum/Silicon Carbide Composite Beams

NASA Technical Reports Server (NTRS)

Leidecker, Henning

1996-01-01

Elastic and shear moduli were determined for two aluminum matrix composites containing 20 and 40 volume percent discontinuous silicon carbide, respectively, using transverse, longitudinal, and torsional vibrational modes of specimens prepared as thin beams. These moduli are consistent with those determined from stress-strain measurements. The damping factors for these modes were also determined. Thermal properties are used to show that part of the damping of transverse modes is caused by the transverse thermal currents discussed by C. Zener (thermo-elastic damping); this damping is frequency-dependent with a maximum damping factor of approximately 0.002. The remaining damping is frequency-independent, and has roughly similar values in transverse, longitudinal, and torsional modes: approximately 0.0001.
Effects of Electric Discharge Plasma Treatment on the Thermal Conductivity of Polymer-Metal Nitride/Carbide Composites

NASA Astrophysics Data System (ADS)

Parali, Levent; Kurbanov, Mirza A.; Bayramov, Azad A.; Tatardar, Farida N.; Sultanakhmedova, Ramazanova I.; Xanlar, Huseynova Gulnara

2015-11-01

High-density polymer composites with semiconductor or dielectric fillers such as aluminum nitride (AIN), aluminum oxide (Al2O3), titanium carbide (TiC), titanium nitride (TiN), boron nitride (BN), silicon nitride (Si3N4), and titanium carbonitride (TiCN) were prepared by the hot pressing method. Each powder phase of the composites was exposed to an electric discharge plasma process before composite formation. The effects of the electric discharge plasma process and the filler content (volume fraction) on the thermal conductivity, volt-ampere characteristics, thermally stimulated depolarization current, as well as electrical and mechanical strength were investigated. The results of the study indicate that, with increasing filler volume fraction, the thermal conductivity of the samples also increased. Furthermore, the thermal conductivity, and electrophysical and mechanical properties of the high-density polyethylene + 70% BN composite modified using the electric discharge plasma showed improvement when compared with that without electric discharge plasma treatment.
Coating effects on thermal properties of carbon carbon and carbon silicon carbide composites for space thermal protection systems

NASA Astrophysics Data System (ADS)

Albano, M.; Morles, R. B.; Cioeta, F.; Marchetti, M.

2014-06-01

Many are the materials for hot structures, but the most promising one are the carbon based composites nowadays. This is because they have good characteristics with a high stability at high temperatures, preserving their mechanical properties. Unfortunately, carbon reacts rapidly with oxygen and the composites are subjected to oxidation degradation. From this point of view CC has to be modified in order to improve its thermal and oxidative resistance. The most common solutions are the use of silicon carbide into the carbon composites matrix (SiC composites) to make the thermal properties increase and the use of coating on the surface in order to protect the composite from the space plasma effects. Here is presented an experimental study on coating effects on these composites. Thermal properties of coated and non coated materials have been studied and the thermal impact on the matrix and surface degradation is analyzed by a SEM analysis.
Methods for Producing High-Performance Silicon Carbide Fibers, Architectural Preforms, and High-Temperature Composite Structures

NASA Technical Reports Server (NTRS)

Yun, Hee-Mann (Inventor); DiCarlo, James A. (Inventor)

2014-01-01

Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties tier each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.
Formation Energies and Electronic Properties of Vanadium Carbides Found in High Strength Steel Alloys

NASA Astrophysics Data System (ADS)

Limmer, Krista; Medvedeva, Julia

2013-03-01

Carbide formation and stabilization in steels is of great interest owing to its effect on the microstructure and properties of the Fe-based alloys. The appearance of carbides with different metal/C ratios strongly depends on the carbon concentration, alloy composition as well as the heat treatment. Strong carbide-forming elements such as Ti, V, and Nb have been used in microalloyed steels; with VC showing an increased solubility in the iron matrix as compared with TiC and NbC. This allows for dissolution of the VC into the steel during heating and fine precipitation during cooling. In addition to VC, the primary vanadium carbide with cubic structure, a wide range of non-stoichiometric compositions VCy with y varying from 0.72 to 0.88, has been observed. This range includes two ordered compounds, V8C7 and V6C5. In this study, first-principles density functional theory (DFT) is employed to examine the stability of the binary carbides by calculating their formation energies. We compare the local structures (atomic coordination, bond distances and angles) and the density of states in optimized geometries of the carbides. Further, the effect of alloying additions, such as niobium and titanium, on the carbide stabilization is investigated. We determine the energetically preferable substitutional atom location in each carbide and study the impurity distribution as well as its role in the carbide formation energy and electronic structure.
Cobalt.

PubMed

Fowler, Joseph F

2016-01-01

Cobalt has been a recognized allergen capable of causing contact dermatitis for decades. Why, therefore, has it been named 2016 "Allergen of the Year"? Simply put, new information has come to light in the last few years regarding potential sources of exposure to this metallic substance. In addition to reviewing some background on our previous understanding of cobalt exposures, this article will highlight the recently recognized need to consider leather as a major site of cobalt and the visual cues suggesting the presence of cobalt in jewelry. In addition, a chemical spot test for cobalt now allows us to better identify its presence in suspect materials.
Phase and composition controllable synthesis of cobalt manganese spinel nanoparticles towards efficient oxygen electrocatalysis.

PubMed

Li, Chun; Han, Xiaopeng; Cheng, Fangyi; Hu, Yuxiang; Chen, Chengcheng; Chen, Jun

2015-06-04

Spinel-type oxides are technologically important in many fields, including electronics, magnetism, catalysis and electrochemical energy storage and conversion. Typically, these materials are prepared by conventional ceramic routes that are energy consuming and offer limited control over shape and size. Moreover, for mixed-metal oxide spinels (for example, Co(x)Mn(3-x)O4), the crystallographic phase sensitively correlates with the metal ratio, posing great challenges to synthesize active product with simultaneously tuned phase and composition. Here we report a general synthesis of ultrasmall cobalt manganese spinels with tailored structural symmetry and composition through facile solution-based oxidation-precipitation and insertion-crystallization process at modest condition. As an example application, the nanocrystalline spinels catalyse the oxygen reduction/evolution reactions, showing phase and composition co-dependent performance. Furthermore, the mild synthetic strategy allows the formation of homogeneous and strongly coupled spinel/carbon nanocomposites, which exhibit comparable activity but superior durability to Pt/C and serve as efficient catalysts to build rechargeable Zn-air and Li-air batteries.
Improved Ablation Resistance of Silicone Rubber Composites by Introducing Montmorillonite and Silicon Carbide Whisker.

PubMed

Zhang, Guangwu; Wang, Fuzhong; Huang, Zhixiong; Dai, Jing; Shi, Minxian

2016-08-24

Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite's char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance.
Tungsten fiber reinforced FeCralY: A first generation composite turbine blade material

NASA Technical Reports Server (NTRS)

Petrasek, D. W.; Winsa, E. A.; Westfall, L. J.; Signorelli, R. A.

1979-01-01

Tungsten-fiber/FeCrAlY (W/FeCrAlY) was identified as a promising aircraft engine, first generation, turbine blade composite material. Based on available data, W/FeCrAlY should have the stress-rupture, creep, tensile, fatigue, and impact strengths required for turbine blades operating from 1250 to 1370 K. It should also have adequate oxidation, hot corrosion, and thermal cycling damage resistance as well as high thermal conductivity. Concepts for potentially low cost blade fabrication were developed. These concepts were used to design a first stage JT9D convection cooled turbine blade having a calculated 50 K use-temperature advantage over the directionally solidified superalloy blade.
Effect of Cutting Parameters on Thrust Force and Surface Roughness in Drilling of Al-2219/B4C/Gr Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Ravindranath, V. M.; Basavarajappa, G. S. Shiva Shankar S.; Suresh, R.

2016-09-01

In aluminium matrix composites, reinforcement of hard ceramic particle present inside the matrix which causes tool wear, high cutting forces and poor surface finish during machining. This paper focuses on effect of cutting parameters on thrust force, surface roughness and burr height during drilling of MMCs. In the present work, discuss the influence of spindle speed and feed rate on drilling the pure base alloy (Al-2219), mono composite (Al- 2219+8% B4C) and hybrid composite (Al-2219+8%B4C+3%Gr). The composites were fabricated using liquid metallurgy route. The drilling experiments were conducted by CNC machine with TiN coated HSS tool, M42 (Cobalt grade) and carbide tools at various spindle speeds and feed rates. The thrust force, surface roughness and burr height of the drilled hole were investigated in mono composite and hybrid composite containing graphite particles, the experimental results show that the feed rate has more influence on thrust force and surface roughness. Lesser thrust force and discontinuous chips were produced during machining of hybrid composites when compared with mono and base alloy during drilling process. It is due to solid lubricant property of graphite which reduces the lesser thrust force, burr height and lower surface roughness. When machining with Carbide tool at low feed and high speeds good surface finish was obtained compared to other two types of cutting tool materials.
Composition optimization of chromium carbide based solid lubricant coatings for foil gas bearings at temperatures to 650 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher

1987-01-01

A test program to determine the optimum composition of chromium carbide based solid lubricant coatings for compliant gas bearings is described. The friction and wear properties of the coatings are evaluated using a foil gas bearing test apparatus. The various coatings were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized nickel-chromium alloy foils. The test bearings were subjected to repeated start/stop cycles under a 14 kPa (2 psi) bearing unit load. The bearings were tested for 9000 start/stop cycles or until the specimen wear reached a predetermined failure level. In general, the addition of silver and eutectic to the chromium carbide base stock significantly reduced foil wear and increased journal coating wear. The optimum coating composition, PS212 (70 wt% metal bonded Cr3C2, 15 wt% Ag, 15% BaF2/CaF2 eutectic), reduced foil wear by a factor of two and displayed coating wear well within acceptable limits. The load capacity of the bearing using the plasma-sprayed coating prior to and after a run-in period was ascertained and compared to polished Inconel 718 specimens.
X-Ray photoelectron spectroscopy study of radiofrequency-sputtered titanium, carbide, molybdenum carbide, and titanium boride coatings and their friction properties

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1977-01-01

Radiofrequency sputtered coatings of titanium carbide, molybdenum carbide and titanium boride were tested as wear resistant coatings on stainless steel in a pin on disk apparatus. X-ray photoelectron spectroscopy (XPS) was used to analyze the sputtered films with regard to both bulk and interface composition in order to obtain maximum film performance. Significant improvements in friction behavior were obtained when properly biased films were deposited on deliberately preoxidized substrates. XPS depth profile data showed thick graded interfaces for bias deposited films even when adherence was poor. The addition of 10 percent hydrogen to the sputtering gas produced coatings with thin poorly adherent interfaces. Results suggest that some of the common practices in the field of sputtering may be detrimental to achieving maximum adherence and optimum composition for these refractory compounds.
Elemental profiling of laser cladded multilayer coatings by laser induced breakdown spectroscopy and energy dispersive X-ray spectroscopy

NASA Astrophysics Data System (ADS)

Lednev, V. N.; Sdvizhenskii, P. A.; Filippov, M. N.; Grishin, M. Ya.; Filichkina, V. A.; Stavertiy, A. Ya.; Tretyakov, R. S.; Bunkin, A. F.; Pershin, S. M.

2017-09-01

Multilayer tungsten carbide wear resistant coatings were analyzed by laser induced breakdown spectroscopy (LIBS) and energy dispersive X-ray (EDX) spectroscopy. Coaxial laser cladding technique was utilized to produce tungsten carbide coating deposited on low alloy steel substrate with additional inconel 625 interlayer. EDX and LIBS techniques were used for elemental profiling of major components (Ni, W, C, Fe, etc.) in the coating. A good correlation between EDX and LIBS data was observed while LIBS provided additional information on light element distribution (carbon). A non-uniform distribution of tungsten carbide grains along coating depth was detected by both LIBS and EDX. In contrast, horizontal elemental profiling showed a uniform tungsten carbide particles distribution. Depth elemental profiling by layer-by-layer LIBS analysis was demonstrated to be an effective method for studying tungsten carbide grains distribution in wear resistant coating without any sample preparation.
Microstructural evolution and thermal stability after aging of a cobalt-containing martensitic bearing steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Shaohong, E-mail: uniquelsh@163.com

The microstructural changes and thermal stability of a cobalt-containing martensitic heat resistance bearing steel have been investigated in this paper. The hardness variation showed a progressive hardness decrease associated with coarsening of fine carbides at elevated temperatures. The precipitation of secondary phases during tempering at 500 °C for 10 h and 100 h has been characterized and identified in detail using transmission electron microscopy. The results revealed that the aging treatment induced very fine secondary M{sub 6}C precipitates which were responsible for the secondary hardening peak when tempered at 500 °C for 30 h. But the hardness gradually decreased duemore » to the coarsening of M{sub 6}C carbide and other secondary phases (such as μ phase, σ phase, and χ phase) precipitation when the samples were tempered over 30 h at 500 °C. - Highlights: •Retained austenite fraction was reduced after cryogenic treatment. •Secondary hardening was responsible for M{sub 6}C precipitates. •TEM study to investigate different phases characteristics •Coarsening of carbides during aging has a significant effect on mechanical properties.« less
Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

NASA Astrophysics Data System (ADS)

Gaballa, Osama Gaballa Bahig

Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering
MC carbide structures in M(lc2)ar-M247. M.S. Thesis - Final Report

NASA Technical Reports Server (NTRS)

Wawro, S. W.

1982-01-01

The morphologies and distribution of the MC carbides in Mar-M247 ingot stock and castings were investigated using metallographic, X-ray diffraction and energy-dispersive X-ray analysis techniques. The MC carbides were found to form script structures during solidification. The script structures were composed of three distinct parts. The central cores and elongated arms of the MC carbide script structures had compositions (Ti, Cr, Hf, Ta, W)C and lattice parameters of 4.39 A. The elongated script arms terminated in enlarged, angular "heads". The heads had compositions (Ti, Hf, Ta, W)C and lattice parameters of approximately 4.50 A. The heads had a higher Hf content than the cores and arms. The size of the script structures, as well as the relative amount of head-type to core and arm-type MC carbide, was found to be determined by solidification conditions. No carryover of the MC carbides from the ingot stock to the remelted and cast material was observed.
Exhaled Breath Condensate as a Suitable Matrix to Assess Lung Dose and Effects in Workers Exposed to Cobalt and Tungsten

PubMed Central

Goldoni, Matteo; Catalani, Simona; De Palma, Giuseppe; Manini, Paola; Acampa, Olga; Corradi, Massimo; Bergonzi, Roberto; Apostoli, Pietro; Mutti, Antonio

2004-01-01

The aim of the present study was to investigate whether exhaled breath condensate (EBC), a fluid formed by cooling exhaled air, can be used as a suitable matrix to assess target tissue dose and effects of inhaled cobalt and tungsten, using EBC malondialdehyde (MDA) as a biomarker of pulmonary oxidative stress. Thirty-three workers exposed to Co and W in workshops producing either diamond tools or hard-metal mechanical parts participated in this study. Two EBC and urinary samples were collected: one before and one at the end of the work shift. Controls were selected among nonexposed workers. Co, W, and MDA in EBC were analyzed with analytical methods based on mass spectrometric reference techniques. In the EBC from controls, Co was detectable at ultratrace levels, whereas W was undetectable. In exposed workers, EBC Co ranged from a few to several hundred nanomoles per liter. Corresponding W levels ranged from undetectable to several tens of nanomoles per liter. A parallel trend was observed for much higher urinary levels. Both Co and W in biological media were higher at the end of the work shift in comparison with preexposure values. In EBC, MDA levels were increased depending on Co concentration and were enhanced by coexposure to W. Such a correlation between EBC MDA and both Co and W levels was not observed with urinary concentration of either element. These results suggest the potential usefulness of EBC to complete and integrate biomonitoring and health surveillance procedures among workers exposed to mixtures of transition elements and hard metals. PMID:15345342

Improved Ablation Resistance of Silicone Rubber Composites by Introducing Montmorillonite and Silicon Carbide Whisker

PubMed Central

Zhang, Guangwu; Wang, Fuzhong; Huang, Zhixiong; Dai, Jing; Shi, Minxian

2016-01-01

Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite’s char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance. PMID:28773846
Controllable synthesis of hierarchical nickel cobalt sulfide with enhanced electrochemical activity

NASA Astrophysics Data System (ADS)

Tie, Jinjin; Han, Jiaxi; Diao, Guiqiang; Liu, Jiwen; Xie, Zhuopeng; Cheng, Gao; Sun, Ming; Yu, Lin

2018-03-01

The composition of nickel cobalt sulfide has great influence on its electrochemical performance. Herein, the nickel cobalt sulfide with different composition and mixed phase were synthesized by one-step solvothermal method through changing the molar ratio of Ni to Co in the reaction system. The electrochemical measurements showed that the nickel cobalt sulfide with a theoretical molar ratio of Ni/Co to be 1.5:1.5 (NCS-2) demonstrates the superior pseudocapacitive performance with a high specific capacitance (6.47 F cm-2 at 10 mA cm-2) and a favorable Coulombic efficiency (∼99%). Whereas, when applied as the catalyst for hydrogen evolution reaction in 1 M KOH aqueous electrolyte, the nickel cobalt sulfide with a theoretical molar ratio of Ni/Co is 1:2 (NCS-1) displays better catalytic activity, and it requires a relatively lower overpotential of 282 mV to deliver the current density of 10 mA cm-2.
Direct laser metal deposition of WC/Co/Cr powder by means of the functionally graded materials strategy

NASA Astrophysics Data System (ADS)

Angelastro, A.; Campanelli, S. L.

2017-12-01

One of the many applications of direct laser metal deposition (DLMD) is the realization of multilayer thick coatings having particular mechanical characteristics, such as high hardness. The objective of this work was to obtain a thick, very hard and wear resistant coating, containing a high percentage of tungsten carbide (WC), on an AISI 304 stainless steel substrate. In order to achieve this result, a tungsten carbide-cobalt-chrome (WC/Co/Cr) powder was processed by the DLMD method. WC/Co/Cr is a composite widely used as a wear-resistant material for cutting tools, molds, coatings and other severe applications. Because of its high hardness, poor ductility and low thermal expansion coefficient, depositing this material directly on the stainless steel substrate is very difficult. In order to overcome this problem, the strategy of functionally graded materials (FGM) was used. Colmonoy 227-F nickel alloy was chosen for this purpose in order to generate a mixture with the WC/Co/Cr powder. Four different materials were deposited, layer by layer, by mixing Colmonoy 227-F with an increasing amount of WC/Co/Cr powders, until obtaining a thick surface coating with a maximum amount of WC of 77.4 wt%. For each powder mixture, a mathematical model was applied to calculate optimal values of translation speed and overlap percentages. A metallographic examination was performed in order to detect macro- and micro-structures of the different materials. Finally, Vickers micro-hardness was measured at various locations along the transverse section to appreciate the gradual increase of the FGM hardness, starting from the substrate and culminating at the top surface of the last deposited material.
Drilling of CFRP and GFRP composite laminates using one shot solid carbide step drill K44

NASA Astrophysics Data System (ADS)

Nagaraja, R.; Rangaswamy, T.

2018-04-01

Drilling is a very common machining operation to install fasteners for assembly of laminates Drilling of Carbon Fiber Reinforced Plastic (CFRP) and Glass Fiber Reinforced Plastic (GFRP) composite laminate materials are different from that of convention materials that causes excessive tool wear and edge delamination. This paper reports on the tool geometry, cutting speed and feed rate. In this work two composite materials CFRP-G926 and Glass-7781 composite materials of varying thickness are drilled to investigate the effect of feed rate, and cutting speed. The study mainly focused on drilling laminates specimen of varying thickness 9 mm, 9.6 mm and 12 mm by using a single shot solid carbide step drill K44. The drilling is performed from lower to higher feed rate and cutting speed to investigate the hole quality, bottom top edge delamination, fiber breakages and local cracks. The work performed shows that a proper combination of tool geometry, cutting speed and feed rate can help to reduce the occurrence of delamination.
Tungsten nanoparticles influence on radiation protection properties of polymers

NASA Astrophysics Data System (ADS)

Gavrish, V. M.; Baranov, G. A.; Chayka, T. V.; Derbasova, N. M.; Lvov, A. V.; Matsuk, Y. M.

2016-02-01

In the presented article the results of the study of metal-polymer composites based on the ultra-high molecular weight polyethylene GUR 4122 with the addition of superdispersed tungsten nanopowders with 5, 10, 20, 40, and 50 mass percent content levels are given, their thermophysical, radiation-shielding, and mechanical properties are shown, and the influence of content levels of tungsten superdispersed nanopowders on these properties is analyzed. The conducted studies have shown the increase in the listed properties depending on the content level of tungsten superdispersed and nanopowders in the ultra-high molecular weight polyethylene GUR 4122. Owing to their properties, the obtained materials may be used in various fields, such as aviation, space technologies, mechanical engineering, etc.
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.
High dose neutron irradiations of Hi-Nicalon Type S silicon carbide composites, Part 1: Microstructural evaluations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perez-Bergquist, Alex G.; Nozawa, Takashi; Shih, Chunghao Phillip

Over the past decade, significant progress has been made in the development of silicon carbide (SiC) composites, composed of near-stoichiometric SiC fibers embedded in a crystalline SiC matrix, to the point that such materials can now be considered nuclear grade. Recent neutron irradiation studies of Hi-Nicalon Type S SiC composites showed excellent radiation response at damage levels of 30-40 dpa at temperatures of 300-800 °C. However, more recent studies of these same fiber composites irradiated to damage levels of >70 dpa at similar temperatures showed a marked decrease in ultimate flexural strength, particularly at 300 °C. Here, electron microscopy ismore » used to analyze the microstructural evolution of these irradiated composites in order to investigate the cause of the degradation. While minimal changes were observed in Hi-Nicalon Type S SiC composites irradiated at 800 °C, substantial microstructural evolution is observed in those irradiated at 300° C. Furthermore, carbonaceous particles in the fibers grew by 25% compared to the virgin case, and severe cracking occurred at interphase layers.« less
Crystal structure and phase stability of tungsten borides

NASA Astrophysics Data System (ADS)

Li, Quan; Zhou, Dan; Ma, Yanming; Chen, Changfeng

2013-03-01

We address the longstanding and controversial issue of ground-state structures of technically important tungsten borides using a first-principles structural search method via a particle-swarm optimization (PSO) algorithm. We have explored a large set of stable chemical compositions (convex hull) and clarified the ground-state structures for a wide range of boron concentrations, including W2B, W3B2,WB,W2B3, WB2,W2B5, WB3, and WB4. We further assessed relative stability of various tungsten borides and compared the calculated results with previously reported experimental data. The phase diagram predicted by the presented calculations may serve as a useful guide for synthesis of a variety of tungsten borides. This work was supported by DOE Grant No. DE-FC52-06NA26274.
Dimensional Analysis and Extended Hydrodynamic Theory Applied to Long-Rod Penetration of Ceramics

DTIC Science & Technology

2016-07-01

thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron carbide. Test...of confined thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron ...since the mid 20th century. Popular candidate ceramics for such systems include alumina, aluminum nitride, boron carbide, silicon carbide, and titanium
High heat flux properties of pure tungsten and plasma sprayed tungsten coatings

NASA Astrophysics Data System (ADS)

Liu, X.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.; Yang, L.; Xu, Z.

2004-08-01

High heat flux properties of pure tungsten and plasma sprayed tungsten coatings on carbon substrates have been studied by annealing and cyclic heat loading. The recrystallization temperature and an activation energy QR=126 kJ/mol for grain growth of tungsten coating by vacuum plasma spray (VPS) were estimated, and the microstructural changes of multi-layer tungsten and rhenium interface pre-deposited by physical vapor deposition (PVD) with anneal temperature were investigated. Cyclic load tests indicated that pure tungsten and VPS-tungsten coating could withstand 1000 cycles at 33-35 MW/m 2 heat flux and 3 s pulse duration, and inert gas plasma spray (IPS)-tungsten coating showed local cracks by 300 cycles but did not induce failure by further cycles. However, the failure of pure tungsten and VPS-tungsten coating by fatigue cracking was observed under higher heat load (55-60 MW/m 2) for 420 and 230 cycles, respectively.
Solid Oxide Membrane (SOM) Process for Facile Electrosynthesis of Metal Carbides and Composites

NASA Astrophysics Data System (ADS)

Zou, Xingli; Chen, Chaoyi; Lu, Xionggang; Li, Shangshu; Xu, Qian; Zhou, Zhongfu; Ding, Weizhong

2017-02-01

Metal carbides (MCs) and composites including TiC, SiC, TaC, ZrC, NbC, Ti5Si3/TiC, and Nb/Nb5Si3 have been directly electrosynthesized from their stoichiometric metal oxides/carbon (MOs/C) mixture precursors by an innovative solid oxide membrane (SOM)-assisted electrochemical process. MOs/C mixture powders including TiO2/C, SiO2/C, Ta2O5/C, ZrO2/C, Nb2O5/C, TiO2/SiO2/C, Nb2O5/SiO2 were pressed to form porous pellets and then served as cathode precursors. A SOM-based anode, made from yttria-stabilized zirconia (YSZ)-based membrane, was used to control the electroreduction process. The SOM electrochemical process was performed at 1273 K (1000 °C) and 3.5 to 4.0 V in molten CaCl2. The oxygen component contained in the MOs/C precursors was gradually removed during electroreduction process, and thus, MOs/C can be directly converted into MCs and composites at the cathode. The reaction mechanism of the electroreduction process and the characteristics of the obtained MCs and composites products were systematically investigated. The results show that the electrosynthesis process typically involves compounding, electroreduction, dissolution-electrodeposition, and in situ carbonization processes. The products can be predesigned and controlled to form micro/nanostructured MCs and composites. Multicomponent multilayer composites (MMCs) have also been tried to electrosynthesize in this work. It is suggested that the SOM-assisted electroreduction process has great potential to be used for the facile and green synthesis of various MCs and composites.
Method for Forming Fiber Reinforced Composite Bodies with Graded Composition and Stress Zones

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay (Inventor); Levine, Stanley R. (Inventor); Smialek, James A. (Inventor)

1999-01-01

A near-net, complex shaped ceramic fiber reinforced silicon carbide based composite bodies with graded compositions and stress zones is disclosed. To provide the composite a fiber preform is first fabricated and an interphase is applied by chemical vapor infiltration, sol-gel or polymer processes. This first body is further infiltrated with a polymer mixture containing carbon, and/or silicon carbide, and additional oxide, carbide, or nitride phases forming a second body. One side of the second body is spray coated or infiltrated with slurries containing high thermal expansion and oxidation resistant. crack sealant phases and the other side of this second body is coated with low expansion phase materials to form a third body. This third body consisting of porous carbonaceous matrix surrounding the previously applied interphase materials, is then infiltrated with molten silicon or molten silicon-refractory metal alloys to form a fourth body. The resulting fourth body comprises dense composites consisting of fibers with the desired interphase which are surrounded by silicon carbide and other second phases materials at the outer and inner surfaces comprising material of silicon, germanium, refractory metal suicides, borides, carbides, oxides, and combinations thereof The resulting composite fourth body has different compositional patterns from one side to the other.
Understanding the interdiffusion behavior and determining the long term stability of tungsten fiber reinforced niobium-base matrix composite systems

NASA Technical Reports Server (NTRS)

Tien, John K.

1990-01-01

The long term interdiffusional stability of tungsten fiber reinforced niobium alloy composites is addressed. The matrix alloy that is most promising for use as a high temperature structural material for reliable long-term space power generation is Nb1Zr. As an ancillary project to this program, efforts were made to assess the nature and kinetics of interphase reaction between selected beryllide intermetallics and nickel and iron aluminides.
Asymmetric supercapacitor based on flexible TiC/CNF felt supported interwoven nickel-cobalt binary hydroxide nanosheets

NASA Astrophysics Data System (ADS)

Zhou, Gangyong; Xiong, Tianrou; He, Shuijian; Li, Yonghong; Zhu, Yongmei; Hou, Haoqing

2016-06-01

Nanostructured nickel-cobalt binary hydroxide (NiCosbnd BH) is widely investigated as supercapacitor electrode material. However, the aggregation and poor electrical conductivity of NiCosbnd BH limit its practical application as a supercapacitor. In this work, a flexible free-standing hierarchical porous composite composed of NiCosbnd BH nanosheets and titanium carbide-carbon nanofiber (NiCosbnd BH@TiC/CNF) is fabricated through electrospinning and microwave assisted method. The as-prepared composites exhibit desirable electrochemical performances, including high specific capacitance, cycling stability, and rate capability. In particular, the NiCosbnd BH41@TiC/CNF composite electrode exhibits a maximum specific capacitance of 2224 F g-1 at the current density of 0.5 A g-1 and excellent cyclic stability of 91% capacity retention after 3000 cycles at 5.0 A g-1. To expand its practical application, an asymmetric supercapacitor (ASC) is fabricated using the NiCosbnd BH41@TiC/CNF composite as the positive electrode and active carbon as the negative electrode. The ASC exhibits a prominent energy density of 55.93 Wh kg-1 and a high power density of 18,300 W kg-1 at 5.0 A g-1. The superior electrochemical property is attributed to the uniform dispersion of NiCosbnd BH nanosheets on the TiC/CNF felt matrix. The TiC/CNF felt with uniformed TiC nanoparticles makes the fiber surface more suitable for growing NiCosbnd BH nanosheets and simultaneously enhances the conductivity of electrode.
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
The Compressive Failure of Aluminum Nitride Considered as a Model Advanced Ceramic

DTIC Science & Technology

2012-06-01

and fragmentation of hot-pressed silicon carbide under uniaxial compression. Acta Materialia 52 (2), 355–367. Xia, Q., Xia, H., Ruoff, A.L., 1993...Orphal et al., 1996) both as a standalone material and as part of ceramic composites (particularly with SiC ). Much of the literature on bulk...compression experiments. Tungsten carbide platens jacketed by the Ti-6Al-4V titanium alloy were used to protect the loading surfaces of the testing
Fuel Retention Improvement at High Temperatures in Tungsten-Uranium Dioxide Dispersion Fuel Elements by Plasma-Spray Cladding

NASA Technical Reports Server (NTRS)

Grisaffe, Salvatore J.; Caves, Robert M.

1964-01-01

An investigation was undertaken to determine the feasibility of depositing integrally bonded plasma-sprayed tungsten coatings onto 80-volume-percent tungsten - 20-volume-percent uranium dioxide composites. These composites were face clad with thin tungsten foil to inhibit uranium dioxide loss at elevated temperatures, but loss at the unclad edges was still significant. By preheating the composite substrates to approximately 3700 degrees F in a nitrogen environment, metallurgically bonded tungsten coatings could be obtained directly by plasma spraying. Furthermore, even though these coatings were thin and somewhat porous, they greatly inhibited the loss of uranium dioxide. For example, a specimen that was face clad but had no edge cladding lost 5.8 percent uranium dioxide after 2 hours at 4750 dgrees F in flowing hydrogen. A similar specimen with plasma-spray-coated edges, however, lost only 0.75 percent uranium dioxide under the same testing conditions.
Microstructure characteristics of Ni/WC composite cladding coatings

NASA Astrophysics Data System (ADS)

Yang, Gui-rong; Huang, Chao-peng; Song, Wen-ming; Li, Jian; Lu, Jin-jun; Ma, Ying; Hao, Yuan

2016-02-01

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr7C3/Cr23C6, CrB, and Ni+Ni3Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.
Impedance spectroscopy studies in cobalt ferrite-reduced graphene oxide nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Supriya, Sweety, E-mail: sweety@iitp.ac.in; Kumar, Sunil, E-mail: sunil.pph13@iitp.ac.in; Kar, Manoranjan, E-mail: mano@iitp.ac.in

2016-05-06

(1-x)Cobalt ferrite-(x)reduced graphene oxidenanocomposites with x=0, 0.1, 0.2 and 0.3 were prepared by the ultrasonic method. The crystal symmetry modification due to reduced graphene oxide and cobalt ferrite interaction has been studied by employing the X-ray diffraction technique. Morphology of the samples was studied by the Field emission scanning electron microscopy (FE-SEM). Study on electrical properties of the cobalt ferrite-reduced graphene oxide nanocomposites explores the possible application of these composites as anode material. Impedance decreases with an increase in frequency as well as temperature, which supports an increase in ac electrical conductivity. The modified Debye relaxation model can explain themore » behavior of impedance in cobalt ferrite-reduced graphene oxide nanocomposites.« less
MC Carbide Characterization in High Refractory Content Powder-Processed Ni-Based Superalloys

NASA Astrophysics Data System (ADS)

Antonov, Stoichko; Chen, Wei; Huo, Jiajie; Feng, Qiang; Isheim, Dieter; Seidman, David N.; Sun, Eugene; Tin, Sammy

2018-04-01

Carbide precipitates in Ni-based superalloys are considered to be desirable phases that can contribute to improving high-temperature properties as well as aid in microstructural refinement of the material; however, they can also serve as crack initiation sites during fatigue. To date, most of the knowledge pertaining to carbide formation has originated from assessments of cast and wrought Ni-based superalloys. As powder-processed Ni-based superalloys are becoming increasingly widespread, understanding the different mechanisms by which they form becomes increasingly important. Detailed characterization of MC carbides present in two experimental high Nb-content powder-processed Ni-based superalloys revealed that Hf additions affect the resultant carbide morphologies. This morphology difference was attributed to a higher magnitude of elastic strain energy along the interface associated with Hf being soluble in the MC carbide lattice. The composition of the MC carbides was studied through atom probe tomography and consisted of a complex carbonitride core, which was rich in Nb and with slight Hf segregation, surrounded by an Nb carbide shell. The characterization results of the segregation behavior of Hf in the MC carbides and the subsequent influence on their morphology were compared to density functional theory calculations and found to be in good agreement, suggesting that computational modeling can successfully be used to tailor carbide features.

MC Carbide Characterization in High Refractory Content Powder-Processed Ni-Based Superalloys

NASA Astrophysics Data System (ADS)

Antonov, Stoichko; Chen, Wei; Huo, Jiajie; Feng, Qiang; Isheim, Dieter; Seidman, David N.; Sun, Eugene; Tin, Sammy

2018-06-01

Carbide precipitates in Ni-based superalloys are considered to be desirable phases that can contribute to improving high-temperature properties as well as aid in microstructural refinement of the material; however, they can also serve as crack initiation sites during fatigue. To date, most of the knowledge pertaining to carbide formation has originated from assessments of cast and wrought Ni-based superalloys. As powder-processed Ni-based superalloys are becoming increasingly widespread, understanding the different mechanisms by which they form becomes increasingly important. Detailed characterization of MC carbides present in two experimental high Nb-content powder-processed Ni-based superalloys revealed that Hf additions affect the resultant carbide morphologies. This morphology difference was attributed to a higher magnitude of elastic strain energy along the interface associated with Hf being soluble in the MC carbide lattice. The composition of the MC carbides was studied through atom probe tomography and consisted of a complex carbonitride core, which was rich in Nb and with slight Hf segregation, surrounded by an Nb carbide shell. The characterization results of the segregation behavior of Hf in the MC carbides and the subsequent influence on their morphology were compared to density functional theory calculations and found to be in good agreement, suggesting that computational modeling can successfully be used to tailor carbide features.
Two-Dimensional Titanium Carbide/RGO Composite for High-Performance Supercapacitors.

PubMed

Zhao, Chongjun; Wang, Qian; Zhang, Huang; Passerini, Stefano; Qian, Xiuzhen

2016-06-22

Ti3C2Tx, a 2D titanium carbide in the MXenes family, is obtained from Ti3AlC2 through selective etching of the Al layer. Due to its good conductivity and high volumetric capacitance, Ti3C2Tx is regarded as a promising candidate for supercapacitors. In this paper, the fabrication of Ti3C2Tx/RGO composites with different proportions of Ti3C2Tx and RGO is reported, in which RGO acts as a conductive "bridge" to connect different Ti3C2Tx blocks and a matrix to alleviate the volume change during charge/discharge process. In addition, RGO nanosheets can serve as a second nanoscale current collector and support as well for the electrode. The electrochemical performance of the as-fabricated Ti3C2Tx/RGO electrodes, characterized by CV, GCD, and EIS, are also reported. A highest specific capacitance (Cs) of 154.3 F/g at 2 A/g is obtained at the Ti3C2Tx: RGO weight ratio of 7:1 combined with an outstanding capacity retention (124.7 F/g) after 6000 cycles at 4 A/g.
Space processing of composite materials

NASA Technical Reports Server (NTRS)

Steurer, W. H.; Kaye, S.

1975-01-01

Materials and processes for the testing of aluminum-base fiber and particle composites, and of metal foams under extended-time low-g conditions were investigated. A wetting and dispersion technique was developed, based on the theory that under the absence of a gas phase all solids are wetted by liquids. The process is characterized by a high vacuum environment and a high temperature cycle. Successful wetting and dispersion experiments were carried out with sapphire fibers, whiskers and particles, and with fibers of silicon carbide, pyrolytic graphite and tungsten. The developed process and facilities permit the preparation of a precomposite which serves as sample material for flight experiments. Low-g processing consists then merely in the uniform redistribution of the reinforcements during a melting cycle. For the preparation of metal foams, gas generation by means of a thermally decomposing compound was found most adaptable to flight experiments. For flight experiments, the use of compacted mixture of the component materials limits low-g processing to a simple melt cycle.
Demonstration of Minimally Machined Honeycomb Silicon Carbide Mirrors

NASA Technical Reports Server (NTRS)

Goodman, William

2012-01-01

Honeycomb silicon carbide composite mirrors are made from a carbon fiber preform that is molded into a honeycomb shape using a rigid mold. The carbon fiber honeycomb is densified by using polymer infiltration pyrolysis, or through a reaction with liquid silicon. A chemical vapor deposit, or chemical vapor composite (CVC), process is used to deposit a polishable silicon or silicon carbide cladding on the honeycomb structure. Alternatively, the cladding may be replaced by a freestanding, replicated CVC SiC facesheet that is bonded to the honeycomb. The resulting carbon fiber-reinforced silicon carbide honeycomb structure is a ceramic matrix composite material with high stiffness and mechanical strength, high thermal conductivity, and low CTE (coefficient of thermal expansion). This innovation enables rapid, inexpensive manufacturing. The web thickness of the new material is less than 1 millimeter, and core geometries tailored. These parameters are based on precursor carbon-carbon honeycomb material made and patented by Ultracor. It is estimated at the time of this reporting that the HoneySiC(Trademark) will have a net production cost on the order of $38,000 per square meter. This includes an Ultracor raw material cost of about $97,000 per square meter, and a Trex silicon carbide deposition cost of $27,000 per square meter. Even at double this price, HoneySiC would beat NASA's goal of $100,000 per square meter. Cost savings are estimated to be 40 to 100 times that of current mirror technologies. The organic, rich prepreg material has a density of 56 kilograms per cubic meter. A charred carbon-carbon panel (volatile organics burnt off) has a density of 270 kilograms per cubic meter. Therefore, it is estimated that a HoneySiC panel would have a density of no more than 900 kilograms per cubic meter, which is about half that of beryllium and about onethird the density of bulk silicon carbide. It is also estimated that larger mirrors could be produced in a matter of weeks
Finite Element Analysis of Surface Residual Stress in Functionally Gradient Cemented Carbide Tool

NASA Astrophysics Data System (ADS)

Su, Chuangnan; Liu, Deshun; Tang, Siwen; Li, Pengnan; Qiu, Xinyi

2018-03-01

A component distribution model is proposed for three-component functionally gradient cemented carbide (FGCC) based on electron probe microanalysis results obtained for gradient layer thickness, microstructure, and elemental distribution. The residual surface stress of FGCC-T5 tools occurring during the fabrication process is analyzed using an ANSYS-implemented finite element method (FEM) and X-ray diffraction. A comparison of the experimental and calculated values verifies the feasibility of using FEM to analyze the residual surface stress in FGCC-T5 tools. The effects of the distribution index, geometrical shape, substrate thickness, gradient layer thickness, and position of the cobalt-rich layer on residual surface stress are studied in detail.
Investigation of Carbide Precipitation Process and Chromium Depletion during Thermal Treatment of Alloy 690

NASA Astrophysics Data System (ADS)

Jiao, S. Y.; Zhang, M. C.; Zheng, L.; Dong, J. X.

2010-01-01

For the purpose of studying the effect of heat treatment on carbide morphology and chromium concentration distribution, which are critical to the resistance of alloy 690 to stress corrosion cracking (SCC), a series of thermal treatments was performed. A model taking into account the intercorrelated dynamic process between the carbide precipitation and chemical diffusion of the chromium atom from matrix to grain boundary (GB) was constructed on the basis of classical nucleation theory, Kolmogorov-Johnson-Mehl-Avrami law, and diffusion theory. The validity of this model was evaluated by comparing the simulated results of the carbide average size and chromium concentration near the GB with the corresponding measured results. A discontinuous factor was introduced based on the relation linking the interdistance between the carbides and the carbide average size; thus, the carbide morphology and chromium concentration could be predicted by this model. According to the results of the experiments and simulations, a carbide discontinuous factor smaller than 2.2 together with the chromium concentration at the GB higher than a critical value (21 wt pct) were essential for the corrosion resistance ability of the alloy, and then some proper heat-treatment conditions were obtained through predicting the value of the two variables. In addition, the effects of the grain size and composition variation on the carbide discontinuous factor and chromium concentration profile were simulated. The results indicated that an intermediate grain size of approximately 31.8 to ~63.5 μm was beneficial for effectively improving the resistance of the alloy to SCC. Simultaneously, the carbon content should be adjusted near 0.02 pct, and the chromium content should be the highest possible in its chemical composition scale.
High temperature surface effects of He + implantation in ICF fusion first wall materials

NASA Astrophysics Data System (ADS)

Zenobia, Samuel J.; Radel, R. F.; Cipiti, B. B.; Kulcinski, Gerald L.

2009-06-01

The first wall armor of the inertial confinement fusion reactor chambers must withstand high temperatures and significant radiation damage from target debris and neutrons. The resilience of multiple materials to one component of the target debris has been investigated using energetic (20-40 keV) helium ions generated in the inertial electrostatic confinement device at the University of Wisconsin. The materials studied include: single-crystalline, and polycrystalline tungsten, tungsten-coated tantalum-carbide 'foams', tungsten-rhenium alloy, silicon carbide, carbon-carbon velvet, and tungsten-coated carbon-carbon velvet. Steady-state irradiation temperatures ranged from 750 to 1250 °C with helium fluences between 5 × 10 17 and 1 × 10 20 He +/cm 2. The crystalline, rhenium alloyed, carbide foam, and powder metallurgical tungsten specimens each experienced extensive pore formation after He + irradiation. Flaking and pore formation occurred on silicon carbide samples. Individual fibers of carbon-carbon velvet specimens sustained erosion and corrugation, in addition to the roughening and rupturing of tungsten coatings after helium ion implantation.
Materials for Advanced Turbine Engines (MATE). Project 4: Erosion resistant compressor airfoil coating

NASA Technical Reports Server (NTRS)

Rashid, J. M.; Freling, M.; Friedrich, L. A.

1987-01-01

The ability of coatings to provide at least a 2X improvement in particulate erosion resistance for steel, nickel and titanium compressor airfoils was identified and demonstrated. Coating materials evaluated included plasma sprayed cobalt tungsten carbide, nickel carbide and diffusion applied chromium plus boron. Several processing parameters for plasma spray processing and diffusion coating were evaluated to identify coating systems having the most potential for providing airfoil erosion resistance. Based on laboratory results and analytical evaluations, selected coating systems were applied to gas turbine blades and evaluated for surface finish, burner rig erosion resistance and effect on high cycle fatigue strength. Based on these tests, the following coatings were recommended for engine testing: Gator-Gard plasma spray 88WC-12Co on titanium alloy airfoils, plasma spray 83WC-17Co on steel and nickel alloy airfoils, and Cr+B on nickel alloy airfoils.
Superhard Rhenium/Tungsten Diboride Solid Solutions.

PubMed

Lech, Andrew T; Turner, Christopher L; Lei, Jialin; Mohammadi, Reza; Tolbert, Sarah H; Kaner, Richard B

2016-11-02

Rhenium diboride (ReB 2 ), containing corrugated layers of covalently bonded boron, is a superhard metallic compound with a microhardness reaching as high as 40.5 GPa (under an applied load of 0.49 N). Tungsten diboride (WB 2 ), which takes a structural hybrid between that of ReB 2 and AlB 2 , where half of the boron layers are planar (as in AlB 2 ) and half are corrugated (as in ReB 2 ), has been shown not to be superhard. Here, we demonstrate that the ReB 2 -type structure can be maintained for solid solutions of tungsten in ReB 2 with tungsten content up to a surprisingly large limit of nearly 50 atom %. The lattice parameters for the solid solutions linearly increase along both the a- and c-axes with increasing tungsten content, as evaluated by powder X-ray and neutron diffraction. From micro- and nanoindentation hardness testing, all of the compositions within the range of 0-48 atom % W are superhard, and the bulk modulus of the 48 atom % solid solution is nearly identical to that of pure ReB 2 . These results further indicate that ReB 2 -structured compounds are superhard, as has been predicted from first-principles calculations, and may warrant further studies into additional solid solutions or ternary compounds taking this structure type.
Ultrathin fiber poly-3-hydroxybutyrate, modified by silicon carbide nanoparticles

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Krutikova, A. A.; Goldshtrakh, M. A.; Staroverova, O. V.; Iordanskii, A. L.; Ischenko, A. A.

2016-11-01

The article presents the results of studies the composite fibrous material based on poly-3-hydroxybutyrate (PHB) and nano-size silicon carbide obtained by the electrospinning method. Size distribution of the silicon carbide nanoparticles in the fiber was estimated by X-ray diffraction technique. It is shown that immobilization of the SiC nanoparticles to the PHB fibers contributes to obtaining essentially smaller diameter of fibers, high physical-mechanical characteristics and increasing resistance to degradation in comparison with the fibers of PHB.
Facile preparation and electrochemical characterization of cobalt oxide/multi-walled carbon nanotube composites for supercapacitors

NASA Astrophysics Data System (ADS)

Lang, Junwei; Yan, Xingbin; Xue, Qunji

A series of cobalt oxide/multi-walled carbon nanotube (Co 3O 4/MWCNT) composites are successfully synthesized by a facile chemical co-precipitation method followed by a simple thermal treatment process. The morphology and structure of as-obtained composites are characterized by X-ray diffraction, scanning electron microscopy, and N 2-adsorption/desorption measurements, and the electrochemical properties are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). For all Co 3O 4/MWCNT composites, MWCNTs are well dispersed in the loosely packed Co 3O 4 nanoparticles. Among them, the Co 3O 4-5%MWCNT composite exhibits the highest specific surface area of 137 m 2 g -1 and a mesoporous structure with a narrow distribution of pore size from 2 to 10 nm. Because of the synergistic effects coming from Co 3O 4 nanoparticles and MWCNTs, the electrochemical performances of pure Co 3O 4 material are significantly improved after adding MWCNTs. The Co 3O 4-5%MWCNT composite shows the largest specific capacitance of 418 F g -1 at a current density of 0.625 A g -1 in 2 M KOH electrolyte. Furthermore, this composite exhibits good cycling stability and lifetime. Therefore, based on the above investigation, such Co 3O 4/MWCNT composite could be a potential candidate for supercapacitors.
INS studies of Cobalt-Copper Catalyst for the Conversion of Syngas to Higher Oxygenates

NASA Astrophysics Data System (ADS)

Sprunger, Phillip; Wang, Zi; Patterson, Matthew; Kurtz, Richard; Spivey, James

Cobalt-copper catalysts have been proposed for the synthesis of ethanol and higher oxygenates as a substitute of Rh and other high-cost noble metal catalysts. Two types of sites with atomic proximity are needed to form higher oxygenates: one to dissociate CO and a second to insert CO to the intermediates to form the CHxCO intermediate. Metallic cobalt is responsible for CO dissociation, while the nature of the site for CO insertion is still under study. We have utilized inelastic neutron scattering (INS) at the VISION beamline at SNS to probe intermediate surface species of this cobalt-copper catalyst. This unique technique allows for elucidation of mechanistic details of the CO insertion and subsequent CHxCO intermediate formation on the metal surfaces (Co0, Co2C and/or Cu0) . In addition to XRD and EXAFS which show a unique surface Co-C carbide formation, a combination of both INS and computational modeling indicate that the active site for CHxCO intermediates. Sponsored through the Louisiana Consortium for Neutron Scattering, DOE No. DE-SC0012432 with additional support from the LA BOR; also ORNL's Spallation Neutron Source (VISION Beamline), DOE-BES under Contract No. DE-AC0500OR22725.
Creep-fatigue of low cobalt superalloys

NASA Technical Reports Server (NTRS)

Halford, G. R.

1982-01-01

Testing for the low cycle fatigue and creep fatigue resistance of superalloys containing reduced amounts of cobalt is described. The test matrix employed involves a single high temperature appropriate for each alloy. A single total strain range, again appropriate to each alloy, is used in conducting strain controlled, low cycle, creep fatigue tests. The total strain range is based upon the level of straining that results in about 10,000 cycles to failure in a high frequency (0.5 Hz) continuous strain-cycling fatigue test. No creep is expected to occur in such a test. To bracket the influence of creep on the cyclic strain resistance, strain hold time tests with ore minute hold periods are introduced. One test per composition is conducted with the hold period in tension only, one in compression only, and one in both tension and compression. The test temperatures, alloys, and their cobalt compositions that are under study are given.
Tungsten-reinforced tantalum

NASA Technical Reports Server (NTRS)

Bacigalupi, R. J.; Breitwieser, R.

1972-01-01

Method is described for producing tungsten-reinforced tantalum, a material possessing the high temperature strength of tungsten and room temperature ductility and weldability of tantalum. This material is produced by bonding together and overlaying structure of tungsten wires with chemical vapor deposited tantalum.
Tungsten-rhenium thin film thermocouples for SiC-based ceramic matrix composites

NASA Astrophysics Data System (ADS)

Tian, Bian; Zhang, Zhongkai; Shi, Peng; Zheng, Chen; Yu, Qiuyue; Jing, Weixuan; Jiang, Zhuangde

2017-01-01

A tungsten-rhenium thin film thermocouple is designed and fabricated, depending on the principle of thermal-electric effect caused by the high temperature. The characteristics of thin film thermocouples in different temperatures are investigated via numerical analysis and analog simulation. The working mechanism and thermo-electric features of the thermocouples are analyzed depending on the simulation results. Then the thin film thermocouples are fabricated and calibrated. The calibration results show that the thin film thermocouples based on the tungsten-rhenium material achieve ideal static characteristics and work well in the practical applications.
Enhanced thermal conductivity of uranium dioxide-silicon carbide composite fuel pellets prepared by Spark Plasma Sintering (SPS)

NASA Astrophysics Data System (ADS)

Yeo, S.; Mckenna, E.; Baney, R.; Subhash, G.; Tulenko, J.

2013-02-01

Uranium dioxide (UO2)-10 vol% silicon carbide (SiC) composite fuel pellets were produced by oxidative sintering and Spark Plasma Sintering (SPS) at a range of temperatures from 1400 to 1600 °C. Both SiC whiskers and SiC powder particles were utilized. Oxidative sintering was employed over 4 h and the SPS sintering was employed only for 5 min at the highest hold temperature. It was noted that composite pellets sintered by SPS process revealed smaller grain size, reduced formation of chemical products, higher density, and enhanced interfacial contact compared to the pellets made by oxidative sintering. For given volume of SiC, the pellets with powder particles yielded a smaller grain size than pellets with SiC whiskers. Finally thermal conductivity measurements at 100 °C, 500 °C, and 900 °C revealed that SPS sintered UO2-SiC composites exhibited an increase of up to 62% in thermal conductivity compared to UO2 pellets, while the oxidative sintered composite pellets revealed significantly inferior thermal conductivity values. The current study points to the improved processing capabilities of SPS compared to oxidative sintering of UO2-SiC composites.
Converting a carbon preform object to a silicon carbide object

NASA Technical Reports Server (NTRS)

Levin, Harry (Inventor)

1990-01-01

A process for converting in depth a carbon or graphite preform object to a silicon carbide object, silicon carbide/silicon object, silicon carbide/carbon-core object, or a silicon carbide/silicon/carbon-core object, by contacting it with silicon liquid and vapor over various lengths of contact time in a reaction chamber. In the process, a stream comprised of a silicon-containing precursor material in gaseous phase below the decomposition temperature of said gas and a coreactant, carrier or diluent gas such as hydrogen is passed through a hole within a high emissivity, thin, insulating septum into the reaction chamber above the melting point of silicon. The thin septum has one face below the decomposition temperature of the gas and an opposite face exposed to the reaction chamber. Thus, the precursor gas is decomposed directly to silicon in the reaction chamber. Any stream of decomposition gas and any unreacted precursor gas from the reaction chamber is removed. A carbon or graphite preform object placed in the reaction chamber is contacted with the silicon. The carbon or graphite preform object is recovered from the reactor chamber after it has been converted to a desired silicon carbide, silicon and carbon composition.
Magnetic cobalt ferrite composite as an efficient catalyst for photocatalytic oxidation of carbamazepine.

PubMed

He, Yongzhen; Dai, Chaomeng; Zhou, Xuefei

2017-01-01

A magnetic spinel cobalt ferrite nanoparticle composite (CFO) was prepared via an ultrasonication-assisted co-precipitation method. The morphological structure and surface composition of CFO before and after reaction were investigated by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, and Fourier transform infrared spectroscopy, indicating the consumption of iron oxide during photodegradation. X-ray photoelectron spectroscopy and vibrating sample magnetometry confirm the preparation of the ferrite nanoparticle composite and its magnetic properties. The prepared CFO was then used for the photocatalytic degradation of carbamazepine (CBZ) as an example of pharmaceuticals and personal care products (PPCPs) from aqueous solution. The effects of the nanocomposite dosage, contact time, and solution pH on the photodegradation process were investigated. More than 96% of the CBZ was degraded within 100 min at 0.2 g·L -1 CFO in the presence of UV light. The reactive species for CBZ degradation in the CFO/UV system was identified as hydroxyl radicals by the methanol scavenging method. Combined with the detection of leached iron ions during the process, the CBZ degradation mechanism can be presumed to be heterogeneous and homogeneous photocatalytic degradation in the CFO/UV system. Furthermore, iminostilbene and acridine were detected as intermediate products by GC-MS.
Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

DOEpatents

Halverson, Danny C.; Landingham, Richard L.

1988-01-01

A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.
Nickel cobalt oxide nanowire-reduced graphite oxide composite material and its application for high performance supercapacitor electrode material.

PubMed

Wang, Xu; Yan, Chaoyi; Sumboja, Afriyanti; Lee, Pooi See

2014-09-01

In this paper, we report a facile synthesis method of mesoporous nickel cobalt oxide (NiCo2O4) nanowire-reduced graphite oxide (rGO) composite material by urea induced hydrolysis reaction, followed by sintering at 300 degrees C. P123 was used to stabilize the GO during synthesis, which resulted in a uniform coating of NiCo2O4 nanowire on rGO sheet. The growth mechanism of the composite material is discussed in detail. The NiCo2O4-rGO composite material showed an outstanding electrochemical performance of 873 F g(-1) at 0.5 A g(-1) and 512 F g(-1) at 40 A g(-1). This method provides a promising approach towards low cost and large scale production of supercapacitor electrode material.

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