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Sample records for nonstoichiometric titanium carbide

  1. Low temperature study of nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Tashmetov, M.Yu.

    2005-05-01

    By low temperature neutron diffraction method was studied structure in nonstoichiometric titanium carbide from room temperature up to 12K. It is found of low temperature phase in titanium carbide- TiC 0.71 . It is established region and borders of this phase. It is determined change of unit cell parameter. (author)

  2. Microhardness and grain size of disordered nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.

    1999-01-01

    Effect of the disordered nonstoichiometric titanium carbide on its microhardness and grain size is studied. It is established that decrease in defectiveness of carbon sublattice of disordered carbide is accompanied by microhardness growth and decrease in grain size. Possible causes of the TiC y microhardness anomalous behaviour in the area 0.8 ≤ y ≤ 0.9 connected with plastic deformation mechanism conditioned by peculiarities of the electron-energetic spectrum of nonstoichiometric carbide are discussed [ru

  3. Ordering effects on structure and specific heat of nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Gusev, A.I.

    1999-01-01

    The experimental results on the change in the crystal structure and specific heat of the nonstoichiometric titanium carbide TiC y (0.5 2 C phases with cubic and trigonal symmetry and the rhombic ordered Ti 3 C 2 phase are formed in the titanium carbide at the temperature below 1000 K by the phase transitions mechanism. The temperatures and heats of the order-disorder phase transitions are determined [ru

  4. Ordering effects on the microstructure and microhardness of nonstoichiometric titanium carbide TiCy

    International Nuclear Information System (INIS)

    Zueva, L.V.; Lipatnikov, V.N.; Gusev, A.I.

    2000-01-01

    The effect of transition from the disordered state to the ordered one on the microstructure and microhardness of the nonstoichiometric titanium carbide TiC y (0.5 ≤ y ≤ 0.97) is studied. It is shown that the Ti 2 C and Ti 3 C 2 ordered phases are formed due to annealing at the temperature about 1073 K in the field of TiC 0.50 -TiC 0.70 . It is established that the grains growth by annealing leads to decrease in and ordering to increase in the TiC y carbide microhardness [ru

  5. Dependence of electrical resistance in nonstoichiometric titanium carbide TiCy on carbon vacancy concentration and distribution

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Gusev, A.I.

    1999-01-01

    Electric conductivity in nonstoichiometric titanium carbide TiC y (0.5 ≤ y ≤ 0.98) is studied depending on concentration and distribution of carbon sublattice vacancies as well as on temperature. It is established that in TiC y at y y on the one hand and by the atom-vacancy interaction on the other hand [ru

  6. High temperature evaporation of titanium, zirconium and hafnium carbides

    International Nuclear Information System (INIS)

    Gusev, A.I.; Rempel', A.A.

    1991-01-01

    Evaporation of cubic nonstoichiometric carbides of titanium, zirconium and hafnium in a comparatively low-temperature interval (1800-2700) with detailed crystallochemical sample certification is studied. Titanium carbide is characterized by the maximum evaporation rate: at T>2300 K it loses 3% of sample mass during an hour and at T>2400 K titanium carbide evaporation becomes extremely rapid. Zirconium and hafnium carbide evaporation rates are several times lower than titanium carbide evaporation rates at similar temperatures. Partial pressures of metals and carbon over the carbides studied are calculated on the base of evaporation rates

  7. Plastic deformation of particles of zirconium and titanium carbide subjected to vibration grinding

    Energy Technology Data Exchange (ETDEWEB)

    Kravchik, A.E.; Neshpor, V.S.; Savel' ev, G.A.; Ordan' yan, S.S.

    1976-12-01

    A study is made of the influence of stoichiometry on the characteristics of microplastic deformation in powders of zirconium and titanium carbide subjected to vibration grinding. The carbide powders were produced by direct synthesis from the pure materials: metallic titanium and zirconium and acetylene black. As to the nature of their elastic deformation, zirconium and titanium carbides can be considered elastic-isotropic materials. During vibration grinding, the primary fracture planes are the (110) planes. Carbides of nonstoichiometric composition are more brittle.

  8. Phase transformation order-disorder in nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Vlasov, V.A.; Karmo, Yu.S.; Kustova, L.V.

    1986-01-01

    Titanium carbide delta-phase is studied using the methods of electric conductivity and differential thermal analysis (DTA). It is shown on the Ti-C system phase diagram that two regions of TiCsub(0.46-0.60) and TiCsub(0.65-1.00) compositions, different in their properties, correspond to delta-phase. Both ordered and disordered phases exist within the TiCsub(0.046-0.60) concentration range, and in equilibrium heating or cooling one phase converts to another at 590 deg C (the first order phase transformation). Samples of the TiCsub(0.65-1.00) composition are characterized by low electric conductivity stability, that is explained by strong titanium carbide electric conductivity sensitivity to defects and impurities

  9. Ordering effects in nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.; Kottar, A.

    2000-01-01

    The effect of nonstoichiometry and ordering on crystalline structure and specific electric resistance (ρ) of TiC y (0.52≤y≤0.98) is studied within the temperature range of 300-1100 K. It is shown that the titanium carbide ordering in the areas 0.52≤y≤0.55, 0.56≤y≤0.58 and 0.62≤y≤0.68 leads to formation of the Ti 2 C cubic and trigonal ordered phase and the Ti 3 C 2 rhombic ordered phase correspondingly. Availability of hysteresis on the ρ(T) dependences in the area of the disorder-order reversible equilibrium transition points out to the fact that the TiC y ↔Ti 2 C and TiC y ↔Ti 3 C 2 transformations are the first order phase transitions [ru

  10. Features of order-disorder phase transformation in nonstoichiometric transition metals carbides

    International Nuclear Information System (INIS)

    Emel'yanov, A.N.

    1996-01-01

    Measurements of temperature and electric conductivity of nonstoichiometric transition metals carbides TiC χ and NbC χ in the area of order-disorder phase transformation are carried out. There are certain peculiarities on the temperature and electric conductivity curves of the carbides, connected with the carbon sublattice disordering. On the basis of the anomalies observed on the curves of the temperature conductivity of nonstoichiometric carbides of transition metals above the temperature of the order-disorder transition the existence of the second structural transition is supposed

  11. Atom-vacancy ordering and magnetic susceptibility of nonstoichiometric hafnium carbide

    International Nuclear Information System (INIS)

    Gusev, A.I.; Zyryanova, A.N.

    1999-01-01

    Experimental results on magnetic susceptibility of nonstoichiometric hafnium carbide HfC y (0.6 0.71 , HfC 0.78 and HfC 0.83 in the range of 870-930 K the anomalies are revealed which are associated with superstructure short-range ordering in a non-metallics sublattice. It is shown that a short-range order in HfC 0.71 and HfC 0.78 carbides corresponds to Hf 3 C 2 ordered phase, and in HfC 0.83 carbide - to Hf 6 C 5 ordered phase. HfC 0.78 carbide is found to possesses zero magnetic susceptibility in temperature range 910-980 K [ru

  12. Atomic structure of non-stoichiometric transition metal carbides

    International Nuclear Information System (INIS)

    Moisy-Maurice, Virginie.

    1981-10-01

    Different kinds of experimental studies of the atomic arrangement in non-stoichiometric transition metal carbides are proposed: the ordering of carbon vacancies and the atomic static displacements are the main subjects studied. Powder neutron diffraction on TiCsub(1-x) allowed us to determine the order-disorder transition critical temperature -Tsub(c) approximately 770 0 C- in the TiCsub(0.52-0.67) range, and to analyze at 300 K the crystal structure of long-range ordered samples. A neutron diffuse scattering quantitative study at 300 K of short-range order in TiCsub(0.76), TiCsub(0.79) and NbCsub(0.73) single crystals is presented: as in Ti 2 Csub(1+x) and Nb 6 C 5 superstructures, vacancies avoid to be on each side of a metal atom. Besides, the mean-square carbon atom displacements from their sites are small, whereas metal atoms move radially about 0.03 A away from vacancies. These results are in qualitative agreement with EXAFS measurements at titanium-K edge of TiCsub(1-x). An interpretation of ordering in term of short-range interaction pair potentials between vacancies is proposed [fr

  13. Magnetic susceptibility as a method of investigation of short-range order in strongly nonstoichiometric carbides

    International Nuclear Information System (INIS)

    Nazarova, S.Z.; Gusev, A.I.

    2001-01-01

    Magnetic susceptibility in disordered and ordered carbides of transition metals (M = Ti, Zr, Hf, Nb, Ta) was studied, the results are generalized. It was ascertained that the change in carbide susceptibility induced by deviation from stoichiometry stems from specific features of electronic spectra of the compounds. The use of magnetic susceptibility for determining structural disorder-order transitions is discussed. It is shown that change in the contribution made by orbital paramagnetism, resulting from short-range order formation, is the reason of decrease in susceptibility of nonstoichiometric carbides during the ordering. Experimentally obtained data on susceptibility permitted evaluating short- and far-range order parameters in NbC y , TaC y , TiC y and HfC y carbides [ru

  14. Nonmetal effect on ordering structures in titanium carbide

    International Nuclear Information System (INIS)

    Tashmetov, M.Yu.; Ehm, V.T.; Savenko, B.M.

    1997-01-01

    The effect of oxygen and nitrogen atoms on formation of intermediate, cubic and trigonal ordering structures in the titanium carbide is studied through the roentgenography and neutron radiography methods. Metal atoms in the TiC 0.545 O 0.08 , TiC 0.545 N 0.09 samples under study are shifted from ideal positions in the direction from vacancies to metalloid atoms. In the intermediate cubic phase the values of the titanium atoms free parameter in both samples are identical, but they differ from analogous values in the titanium carbide

  15. REVIEWS OF TOPICAL PROBLEMS: Order-disorder transformations and phase equilibria in strongly nonstoichiometric compounds

    Science.gov (United States)

    Gusev, Aleksandr I.

    2000-01-01

    Data on order-disorder phase transformations in strongly nonstoichiometric carbides and nitrides MXy (X=C, N) of Group IV and V transition metals at temperatures below 1300-1400 K are reviewed. The order-parameter functional method as applied to atomic and vacancy ordering in strongly nonstoichiometric MXy compounds and to phase equilibrium calculations for M-X systems is discussed. Phase diagram calculations for the Ti-C, Zr-C, Hf-C, V-C, Nb-C, Ta-C, Ti-N, and Ti-B-C systems (with the inclusion of the ordering of nonstoichiometric carbides and nitrides) and those for pseudobinary carbide M(1)C-M(2)C systems are presented. Heat capacity, electrical resistivity and magnetic susceptibility changes at reversible order-disorder phase transformations in nonstoichiometric carbides are considered.

  16. Microstructural Study of Titanium Carbide Coating on Cemented Carbide

    DEFF Research Database (Denmark)

    Vuorinen, S.; Horsewell, Andy

    1982-01-01

    Titanium carbide coating layers on cemented carbide substrates have been investigated by transmission electron microscopy. Microstructural variations within the typically 5µm thick chemical vapour deposited TiC coatings were found to vary with deposit thickness such that a layer structure could...... be delineated. Close to the interface further microstructural inhomogeneities were obsered, there being a clear dependence of TiC deposition mechanism on the chemical and crystallographic nature of the upper layers of the multiphase substrate....

  17. The preparation of titanium-vanadium carbide/nickel cermets. Technical report

    International Nuclear Information System (INIS)

    Precht, W.; Sprissler, B.

    1976-01-01

    Titanium/vanadium alloy carbide rods were prepared by a zone melting procedure. Wetting studies were carried out using sections of the fused rods and candidate matrix material. It was established that nickel exhibits excellent wetting of (Ti, V) C, and accordingly cermet blends were prepared and liquid phase sintered. Processing parameters are discussed as well as their effect on the final microstructure. Alternate methods for cermet preparation are offered which use as received titanium carbide and vanadium carbide powders

  18. Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water

    Directory of Open Access Journals (Sweden)

    Chen Shuei-Yuan

    2010-01-01

    Full Text Available Abstract Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.

  19. The precipitation behavior of titanium carbide on the surface of SUS 321 stainless steel

    International Nuclear Information System (INIS)

    Yoshihara, Kazuhiro; Nii, Kazuyoshi

    1982-01-01

    The surface composition of SUS 321 stainless steel at high temperatures was observed in vacuum with Auger electron spectroscopy. The precipitation of titanium carbide was found on the surface of SUS 321. The thickness of precipitated titanium carbide layer increased in proportion to the square root of annealing time and became about 0.05 μm after heated at 1100 K for 432 ks. The precipitated titanium carbide was not replaced by the most surface active element sulfur, and remained stable on the surface. The precipitated layer, however, was not even and had many holes about 1 μm in diameter. The bottom of a hole was SUS 321, on which phosphorus, oxygen and sulfur segregated. As the annealing time was prolonged, these segregants were replaced one by one in the order of the surface activity, and finally the most surface active element, sulfur, remained on the bottom of the hole. Moreover, sulfur diffused over the outside of the hole. The precipitation of titanium carbide on the surface occurred according to the following processes: (1) The titanium and carbon which had been dissolved in the bulk diffused onto the surface of the stainless steel. (2) The titanium carbide which had been precipitated in the bulk dissolved because the concentration of titanum and carbon fell under their solubility limits in the bulk. (3) The titanium and carbon diffused onto the surface which was exposed to vacuum. (4) The titanium and carbon recombined into titanium carbide and precipitated on the surface. The growth rate of the thickness of the precipitated layer was controlled by the diffusion of titanium and carbon in the precipitated titanium carbide. (J.P.N.)

  20. Study of aging and ordering processes in titanium carbide

    International Nuclear Information System (INIS)

    Arbuzov, M.P.; Khaenko, B.V.; Kachkovskaya, Eh.T.

    1977-01-01

    Aging and ordering processes in titanium carbide were investigated on monocrystals (fragments of alloys) with the aid of roentgenographic method. The sequence of phase transformations during aging was ascertained,and a monoclinic structure of the carbon atoms ordering is suggested. The microhardness of titanium carbide was studied as a function of the heat treatment of alloys and the main factors (ordering and dislocation structure) which govern the difference in the microhardness of hardened and aged (annealed) specimens were determined

  1. Evaluation of titanium carbide metal matrix composites deposited via laser cladding

    Science.gov (United States)

    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.

  2. High pressure sintering (HP-HT) of diamond powders with titanium and titanium carbide

    International Nuclear Information System (INIS)

    Jaworska, L.

    1999-01-01

    Polycrystalline diamond compacts for cutting tools are mostly manufactured using high pressure sintering (HP-HT). The standard diamond compacts are prepared by diamond powders sintering with metallic binding phase. The first group of metallic binder are metals able to solve carbon - Co, Ni. The second group of metal binders are carbide forming elements - Ti, Cr, W and others. The paper describes high pressure sintering of diamond powder with titanium and nonstoichiometry titanium carbide for cutting tool application. A type of binding phase has the significant influence on microstructure and mechanical properties of diamond compacts. Very homogeneous structure was achieved in case of compacts obtained from metalized diamond where diamond-TiC-diamond connection were predominant. In the case of compacts prepared by mechanical mixing of diamond with titanium powders the obtained structure was nonhomogeneous with titanium carbide clusters. They had more diamond to diamond connections. These compacts compared to the compact made of metallized diamond have greater wear resistance. In the case of the diamond and TiC 0.92 sintering the strong bonding of TiC diamond grains was obtained. The microstructure observations for diamond with 5% wt. Ti and diamond with 5% wt. TiC 0.92 (the initial composition) compacts were performed in transmission microscope. For two type of compacts the strong bonding phase TiC without defects is creating. (author)

  3. Comparative sinterability of combustion synthesized and commercial titanium carbides

    International Nuclear Information System (INIS)

    Manley, B.W.

    1984-11-01

    The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600 0 C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables

  4. In situ formation of titanium carbide using titanium and carbon-nanotube powders by laser cladding

    International Nuclear Information System (INIS)

    Savalani, M.M.; Ng, C.C.; Li, Q.H.; Man, H.C.

    2012-01-01

    Titanium metal matrix composite coatings are considered to be important candidates for high wear resistance applications. In this study, TiC reinforced Ti matrix composite layers were fabricated by laser cladding with 5, 10, 15 and 20 wt% carbon-nanotube. The effects of the carbon-nanotube content on phase composition, microstructure, micro-hardness and dry sliding wear resistance of the coating were studied. Microstructural observation using scanning electron microscopy showed that the coatings consisted of a matrix of alpha-titanium phases and the reinforcement phase of titanium carbide in the form of fine dendrites, indicating that titanium carbide was synthesized by the in situ reaction during laser irradiation. Additionally, measurements on the micro-hardness and dry sliding wear resistance of the coatings indicated that the mechanical properties were affected by the amount of carbon-nanotube in the starting precursor materials and were enhanced by increasing the carbon-nanotube content. Results indicated that the composite layers exhibit high hardness and excellent wear resistance.

  5. In situ formation of titanium carbide using titanium and carbon-nanotube powders by laser cladding

    Energy Technology Data Exchange (ETDEWEB)

    Savalani, M.M., E-mail: mmfsmm@inet.polyu.edu.hk [Department of Industrial and Systems Engineering, Hong Kong Polytechnic University (Hong Kong); Ng, C.C.; Li, Q.H.; Man, H.C. [Department of Industrial and Systems Engineering, Hong Kong Polytechnic University (Hong Kong)

    2012-01-15

    Titanium metal matrix composite coatings are considered to be important candidates for high wear resistance applications. In this study, TiC reinforced Ti matrix composite layers were fabricated by laser cladding with 5, 10, 15 and 20 wt% carbon-nanotube. The effects of the carbon-nanotube content on phase composition, microstructure, micro-hardness and dry sliding wear resistance of the coating were studied. Microstructural observation using scanning electron microscopy showed that the coatings consisted of a matrix of alpha-titanium phases and the reinforcement phase of titanium carbide in the form of fine dendrites, indicating that titanium carbide was synthesized by the in situ reaction during laser irradiation. Additionally, measurements on the micro-hardness and dry sliding wear resistance of the coatings indicated that the mechanical properties were affected by the amount of carbon-nanotube in the starting precursor materials and were enhanced by increasing the carbon-nanotube content. Results indicated that the composite layers exhibit high hardness and excellent wear resistance.

  6. Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

    Science.gov (United States)

    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.

  7. Friction and wear performance of diamond-like carbon, boron carbide, and titanium carbide coatings against glass

    International Nuclear Information System (INIS)

    Daniels, B.K.; Brown, D.W.; Kimock, F.M.

    1997-01-01

    Protection of glass substrates by direct ion beam deposited diamond-like carbon (DLC) coatings was observed using a commercial pin-on-disk instrument at ambient conditions without lubrication. Ion beam sputter-deposited titanium carbide and boron carbide coatings reduced sliding friction, and provided tribological protection of silicon substrates, but the improvement factor was less than that found for DLC. Observations of unlubricated sliding of hemispherical glass pins at ambient conditions on uncoated glass and silicon substrates, and ion beam deposited coatings showed decreased wear in the order: uncoated glass>uncoated silicon>boron carbide>titanium carbide>DLC>uncoated sapphire. Failure mechanisms varied widely and are discussed. Generally, the amount of wear decreased as the sliding friction decreased, with the exception of uncoated sapphire substrates, for which the wear was low despite very high friction. There is clear evidence that DLC coatings continue to protect the underlying substrate long after the damage first penetrates through the coating. The test results correlate with field use data on commercial products which have shown that the DLC coatings provide substantial extension of the useful lifetime of glass and other substrates. copyright 1997 Materials Research Society

  8. Titanium Carbides Coatings for Wear Resistant Biomedical Devices: Manufacturing and Modeling

    International Nuclear Information System (INIS)

    Contro, R.; Vena, P.; Gastaldi, D.; Masante, S.; Cavallotti, P. L.; Nobili, L.; Bestetti, M.

    2008-01-01

    Deposition of Titanium Carbide coatings on Ti6Al4V substrate, through the reactive magnetron sputtering technique is here presented. The mechanical characterization of the coatings has been carried out through a set of indentation tests at different maximum applied loads. The elastic stiffness as well as the hardness of the coating-substrate system indicate that these coatings are suitable candidates for wear resistance applications in the orthopaedic field. Numerical simulation of the indentation tests allowed the identification of the constitutive parameters of the titanium carbide. Good agreement was achieved between experimental and numerical results

  9. Process of making titanium carbide (TiC) nano-fibrous felts

    Science.gov (United States)

    Fong, Hao; Zhang, Lifeng; Zhao, Yong; Zhu, Zhengtao

    2015-01-13

    A method of synthesizing mechanically resilient titanium carbide (TiC) nanofibrous felts comprising continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix, comprising: (a) electrospinning a spin dope for making precursor nanofibers with diameters less than 0.5 J.Lm; (b) overlaying the nanofibers to produce a nanofibrous mat (felt); and then (c) heating the nano-felts first at a low temperature, and then at a high temperature for making electrospun continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix; and (d) chlorinating the above electrospun nano-felts at an elevated temperature to remove titanium for producing carbide derived carbon (CDC) nano-fibrous felt with high specific surface areas.

  10. Mechanism of protective action of surface carbide layers on titanium

    International Nuclear Information System (INIS)

    Chukalovskaya, T.V.; Chebotareva, N.P.; Tomashov, N.D.

    1990-01-01

    The protective action of surface carbide layer on titanium produced in methane atmosphere at 1000 deg C and under 6.7 kPa pressure in H 2 SO 4 solutions is studied through comparison of microsection metallographic specimens prior to and after corrosion testing (after specimen activation); through comparison of anodic characteristics after partial stripping of the layer up to its complete stripping; through analysis of the behaviour of Ti-TiC galvanic couple, and through investigation of corresponding corrosion diagrams under test conditions. It is shown that screening protective mechanism is primarily got involved in highly agressive media (high temperature and concentration of solution), and in less agressive environment the protection of titanium with carbide layer is primarily ensured by electrochemical mechanism

  11. Two-Dimensional Titanium Carbide (MXene) as Surface-Enhanced Raman Scattering Substrate

    Energy Technology Data Exchange (ETDEWEB)

    Sarycheva, Asia [Drexel Univ., Philadelphia, PA (United States); Makaryan, Taron [Drexel Univ., Philadelphia, PA (United States); Maleski, Kathleen [Drexel Univ., Philadelphia, PA (United States); Satheeshkumar, Elumalai [National Cheng Kung Univ., Tainan (Taiwan); National Institute of Technology-Trichy, Tamil Nadu (India); Melikyan, Armen [Russian-Armenian (Slavonic) State Univ., Yerevan (Armenia); Minassian, Hayk [A. Alikhanian National Science Lab., Yerevan (Armenia); Yoshimura, Masahiro [National Cheng Kung Univ., Tainan (Taiwan); Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States)

    2017-08-22

    Here, noble metal (gold or silver) nanoparticles or patterned films are typically used as substrates for surface-enhanced Raman spectroscopy (SERS). Two-dimensional (2D) carbides and nitrides (MXenes) exhibit unique electronic and optical properties, including metallic conductivity and plasmon resonance in the visible or near-infrared range, making them promising candidates for a wide variety of applications. Herein, we show that 2D titanium carbide, Ti3C2Tx, enhances Raman signal from organic dyes on a substrate and in solution. As a proof of concept, MXene SERS substrates were manufactured by spray-coating and used to detect several common dyes, with calculated enhancement factors reaching ~106. Titanium carbide MXene demonstrates SERS effect in aqueous colloidal solutions, suggesting the potential for biomedical or environmental applications, where MXene can selectively enhance positively charged molecules.

  12. Formation and characterization of titanium nitride and titanium carbide films prepared by reactive sputtering

    International Nuclear Information System (INIS)

    Sundgren, J.-E.

    1982-01-01

    Titanium has been reactively r.f. sputtered in mixed Ar-N 2 and Ar-CH 4 discharges on to substrates held at 775 K. The films obtained have been characterized by scanning electron microscopy, X-ray diffraction and by measurements of hardness and electrical resistivity. The compositions of the films have been determined using Auger electron spectroscopy. The processes occurring both on substrates and target surfaces have been studied and it is shown that the latter is of great importance for the composition and structure of deposited films. Titanium nitride films of full density and with electrical resistivity and hardness values close to those of bulk TiN were only obtained in a narrow range close to the stoichiometric composition. Titanium carbide films grown on non-biased substrates were found to have an open structure and thus a low density. A bias applied to the substrate, however, improved the quality of the films. It is also shown that the heat of formation of the compounds plays an important role in the formation of carbides and nitrides. A large value promotes the development of large grains and dense structures. (Auth.)

  13. Preparation of fiber reinforced titanium diboride and boron carbide composite bodies

    International Nuclear Information System (INIS)

    Newkirk, L.R.; Riley, R.E.; Sheinberg, H.; Valencia, F.A.; Wallace, T.C.

    1979-01-01

    A process is described for uniformly infiltrating woven carbon cloth with either titanium diboride or boron carbide at reduced pressure (15 to 25 torr). The effects of deposition temperature on the uniformity of penetration and on coating rate are described for temperatures from 750 to 1000 0 C and deposit loadings from 20 to 43 vol. %. For the boron carbides, boron composition is discussed and evidence is presented suggesting that propene is the dominant rate controlling reactant

  14. Engineering a novel material: Nanometric titanium carbide particles in a matrix of carbon nanotubes

    CERN Document Server

    BADIE, Sylvain

    2015-01-01

    New physics studies at ISOLDE are motivated by new beams available, especially beams of exotic nuclei located at the frontier of the nuclear chart. Such beams are often short lived (in the order of milliseconds) and decay before they can be extracted from the target material, where typical diffusion times are in the order of seconds or more. Novel nanostructured and nanocomposite target materials have been developed to increase the release efficiency by reducing the diffusion paths and so the diffusion times, allowing ISOLDE to deliver new and more intense beams of exotic nuclei. 35Ca (25 ms half-life) was attempted by developing a titanium carbide and carbon black nanocomposite, but such isotope could not be extracted. A different production method with different precursors - titanium oxide and multiwall carbon nanotubes - is here proposed and expected to yield a target material which will increase the release rates of such isotope. A novel material, very porous, consisting of titanium carbide particles disp...

  15. Influence of nonstoichiometry and ordering on basic structure parameter of cubic titanium carbide

    International Nuclear Information System (INIS)

    Zueva, L.V.; Gusev, A.I.

    1999-01-01

    Effect of nonstoichiometry and phase transformations of the disorder-order type on the basis (B1 type) structure period of TiC y (0.5 y titanium carbide with formation of the Ti 2 C and Ti 3 C 2 superstructures leads to growth of the basic crystal lattice period as compared to disordered carbide. The problem on trends in static atomic displacement near vacancy is discussed with an account of the lattice period change [ru

  16. Formation Energies and Electronic Properties of Vanadium Carbides Found in High Strength Steel Alloys

    Science.gov (United States)

    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.

  17. Production of titanium carbide from ilmenite

    Directory of Open Access Journals (Sweden)

    Sutham Niyomwas

    2008-03-01

    Full Text Available The production of titanium carbide (TiC powders from ilmenite ore (FeTiO3 powder by means of carbothermal reduction synthesis coupled with hydrochloric acid (HCl leaching process was investigated. A mixture of FeTiO3 and carbon powders was reacted at 1500oC for 1 hr under flowing argon gas. Subsequently, synthesized product of Fe-TiC powders were leached by 10% HCl solutions for 24 hrs to get final product of TiC powders. The powders were characterized using X-ray diffraction, scanning electron and transmission electron microscopy. The product particles were agglomerated in the stage after the leaching process, and the size of this agglomerate was 12.8 μm with a crystallite size of 28.8 nm..

  18. Synthesis and characterization of nanostructured titanium carbide for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Paviter; Singh, Harwinder; Singh, Bikramjeet; Kaur, Manpreet; Kaur, Gurpreet; Kumar, Akshay, E-mail: akshaykumar.tiet@gmail.com [Advanced Functional Material Laboratory, Department of Nanotechnology,, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140 406 Punjab (India); Kumar, Manjeet [Department of Materials Engineering, Defense Institute of Advanced Technology (DU), Pune-411 025 (India); Bala, Rajni [Department of Mathematics Punjabi University Patiala-147 002 Punjab (India)

    2016-04-13

    Titanium carbide (TiC) nanoparticles have been successfully synthesized by carbo-thermic reaction of titanium and acetone at 800 °C. This method is relatively low temperature synthesis route. It can be used for large scale production of TiC. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA) techniques. XRD analysis confirmed the formation of single phase TiC. XRD analysis confirmed that the particles are spherical in shape with an average particle size of 13 nm. DTA analysis shows that the phase is stable upto 900 °C and the material can be used for high temperature applications.

  19. Short-range order studies in nonstoichiometric transition metal carbides and nitrides by neutron diffuse scattering

    International Nuclear Information System (INIS)

    Priem, Thierry

    1988-01-01

    Short-range order in non-stoichiometric transition metal carbides and nitrides (TiN 0.82 , TiC 0.64 , TiC 0.76 , NbC 0.73 and NbC 0.83 ) was investigated by thermal neutron diffuse scattering on G4-4 (L.L.B - Saclay) and D10 (I.L.L. Grenoble) spectrometers. From experimental measurements, we have found that metalloid vacancies (carbon or nitrogen) prefer the f.c.c. third neighbour positions. Ordering interaction energies were calculated within the Ising model framework by three approximations: mean field (Clapp and Moss formula), Monte-Carlo simulation, Cluster variation Method. The energies obtained by the two latter methods are very close, and in qualitative agreement with theoretical values calculated from the band structure. Theoretical phase diagrams were calculated from these ordering energies for TiN x and TiC x ; three ordered structures were predicted, corresponding to compositions Ti 6 N 5 Ti 2 C and Ti 3 C 2 . On the other hand, atomic displacements are induced by vacancies. The metal first neighbours were found to move away from a vacancy, whereas the second neighbours move close to it. Near neighbour atomic displacements were theoretically determined by the lattice statics formalism with results in good agreement with experiment. (author) [fr

  20. Parameters optimization, microstructure and micro-hardness of silicon carbide laser deposited on titanium alloy

    CSIR Research Space (South Africa)

    Adebiyia, DI

    2016-06-01

    Full Text Available Silicon carbide (SiC), has excellent mechanical properties such as high hardness and good wear resistance, and would have been a suitable laser-coating material for titanium alloy to enhance the poor surface hardness of the alloy. However, SiC has...

  1. Ordered hierarchical mesoporous/microporous carbon derived from mesoporous titanium-carbide/carbon composites and its electrochemical performance in supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hai-Jing; Wang, Jie; Wang, Cong-Xiao; Xia, Yong-Yao [Department of Chemistry and Shanghai Key Laboratory of Molecular, Catalysis and Innovative Materials, Institute of New Energy, Fudan University, Shanghai (China)

    2011-11-15

    Novel ordered hierarchical mesoporous/microporous carbon (OHMMC) derived from mesoporous titanium-carbide/carbon composites was prepared for the first time by synthesizing ordered mesoporous nanocrystalline titanium-carbide/carbon composites, followed by chlorination of titanium carbides. The mesostructure and microstructure can be conveniently tuned by controlling the TiC contents of mesoporous TiC/C composite precursor, and chlorination temperature. By optimal condition, the OHMMC has a high surface area (1917 m{sup 2}g{sup -1}), large pore volumes (1.24 cm{sup 3}g{sup -1}), narrow mesopore-size distributions (centered at about 3 nm), and micropore size of 0.69 and 1.25 nm, and shows a great potential as electrode for supercapacitor applications: it exhibits a high capacitance of 146 Fg{sup -1} in noaqueous electrolyte and excellent rate capability. The ordered mesoporous channel pores are favorable for retention and immersion of the electrolyte, providing a more favorable path for electrolyte penetration and transportation to achieve promising rate capability performance. Meanwhile, the micropores drilled on the mesopore-walls can increase the specific surface area to provide more sites for charge storage. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. The effect of substrate bias on titanium carbide/amorphous carbon nanocomposite films deposited by filtered cathodic vacuum arc

    International Nuclear Information System (INIS)

    Zhang, Xu; Liang, Hong; Wu, Zhenglong; Wu, Xiangying; Zhang, Huixing

    2013-01-01

    The titanium carbide/amorphous carbon nanocomposite films have been deposited on silicon substrate by filtered cathodic vacuum arc (FCVA) technology, the effects of substrate bias on composition, structures and mechanical properties of the films are studied by scanning electron spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy and nano-indentation. The results show that the Ti content, deposition rate and hardness at first increase and then decrease with increasing the substrate bias. Maximum hardness of the titanium carbide/amorphous carbon nanocomposite film is 51 Gpa prepared at −400 V. The hardness enhancement may be attributed to the compressive stress and the fraction of crystalline TiC phase due to ion bombardment

  3. Cathodic stripping voltammetric determination of chromium in coastal waters on cubic Nano-titanium carbide loaded gold nanoparticles modified electrode

    Directory of Open Access Journals (Sweden)

    Haitao eHan

    2015-09-01

    Full Text Available The novel cubical nano-titanium carbide loaded gold nanoparticles modified electrode for selective and sensitive detection of trace chromium (Cr in coastal water was established based on a simple approach. Nano-titanium carbide is used as the typical cubical nanomaterial with wonderful catalytic activity towards the reduction of Cr(VI. Gold nanoparticles with excellent physical and chemical properties can facilitate electron transfer and enhance the catalytic activity of the modified electrode. Taking advantage of the synergistic effects of nano-titanium carbide and gold nanoparticles, the excellent cathodic signal responses for the stripping determination of Cr(VI can be obtained. The detection limit of this method is calculated as 2.08 μg L-1 with the linear calibration curve ranged from 5.2 to 1040 μg L-1. This analytical method can be used to detect Cr(VI effectively without using any complexing agent. The fabricated electrode was successfully applied for the detection of chromium in coastal waters collected from the estuary giving Cr concentrations between 12.48 and 22.88 μg L-1 with the recovery between 96% and 105%.

  4. The effect of fiber microstructure on evolution of residual stresses in silicon carbide/titanium aluminide composites

    Science.gov (United States)

    Pindera, Marek-Jerzy; Freed, Alan D.

    1992-01-01

    This paper examines the effect of the morphology of the SCS6 silicon carbide fiber on the evolution of residual stresses in SiC/Ti composites. A micromechanics model based on the concentric cylinder concept is presented which is used to calculate residual stresses in a SiC/Ti composite during axisymmetric cooling by a spatially uniform temperature change. The silicon carbide fiber is modeled as a layered material with five distinct transversely isotropic and orthotropic, elastic layers, whereas the titanium matrix is taken to be isotropic, with temperature-dependent elastoplastic properties. The results arc compared with those obtained based on the assumption that the silicon carbide fiber is isotropic and homogeneous.

  5. Non-oxidic nanoscale composites: single-crystalline titanium carbide nanocubes in hierarchical porous carbon monoliths.

    Science.gov (United States)

    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.

  6. Transition metal carbide and boride abrasive particles

    International Nuclear Information System (INIS)

    Valdsaar, H.

    1978-01-01

    Abrasive particles and their preparation are discussed. The particles consist essentially of a matrix of titanium carbide and zirconium carbide, at least partially in solid solution form, and grains of crystalline titanium diboride dispersed throughout the carbide matrix. These abrasive particles are particularly useful as components of grinding wheels for abrading steel. 1 figure, 6 tables

  7. Osseointegration is improved by coating titanium implants with a nanostructured thin film with titanium carbide and titanium oxides clustered around graphitic carbon

    International Nuclear Information System (INIS)

    Veronesi, Francesca; Giavaresi, Gianluca; Fini, Milena; Longo, Giovanni; Ioannidu, Caterina Alexandra; Scotto d'Abusco, Anna; Superti, Fabiana; Panzini, Gianluca; Misiano, Carlo; Palattella, Alberto; Selleri, Paolo; Di Girolamo, Nicola; Garbarino, Viola; Politi, Laura; Scandurra, Roberto

    2017-01-01

    Titanium implants coated with a 500 nm nanostructured layer, deposited by the Ion Plating Plasma Assisted (IPPA) technology, composed of 60% graphitic carbon, 25% titanium oxides and 15% titanium carbide were implanted into rabbit femurs whilst into the controlateral femurs uncoated titanium implants were inserted as control. At four time points the animals were injected with calcein green, xylenol orange, oxytetracycline and alizarin. After 2, 4 and 8 weeks femurs were removed and processed for histology and static and dynamic histomorphometry for undecalcified bone processing into methylmethacrylate, sectioned, thinned, polished and stained with Toluidine blue and Fast green. The overall bone-implant contacts rate (percentage of bone-implant contacts/weeks) of the TiC coated implant was 1.6 fold than that of the uncoated titanium implant. The histomorphometric analyses confirmed the histological evaluations. More precisely, higher Mineral Apposition Rate (MAR, μm/day) (p < 0.005) and Bone Formation Rate (BFR, μm 2 /μm/day) (p < 0.0005) as well as Bone Implant Contact (Bic) and Bone Ingrowth values (p < 0.0005) were observed for the TiC coated implants compared to uncoated implants. In conclusion the hard nanostructured TiC layer protects the bulk titanium implant against the harsh conditions of biological tissues and in the same time, stimulating adhesion, proliferation and activity of osteoblasts, induces a better bone-implant contacts of the implant compared to the uncoated titanium implant. - Highlights: • Ti implants were coated with a nanostructured film composed of C gr , TiC and TiO x . • The TiC layer stimulates adhesion, proliferation and activity of osteoblasts. • Uncoated and TiC coated titanium implants were implanted in rabbit femurs. • Bone-implant contacts of TiC coated implants were higher than that of uncoated. • Mineral Apposition Rate of TiC coated implants were higher than that of uncoated.

  8. Plasma synthesis of titanium nitride, carbide and carbonitride nanoparticles by means of reactive anodic arc evaporation from solid titanium

    International Nuclear Information System (INIS)

    Kiesler, D.; Bastuck, T.; Theissmann, R.; Kruis, F. E.

    2015-01-01

    Plasma methods using the direct evaporation of a transition metal are well suited for the cost-efficient production of ceramic nanoparticles. In this paper, we report on the development of a simple setup for the production of titanium-ceramics by reactive anodic arc evaporation and the characterization of the aerosol as well as the nanopowder. It is the first report on TiC X N 1 − X synthesis in a simple anodic arc plasma. By means of extensive variations of the gas composition, it is shown that the composition of the particles can be tuned from titanium nitride over a titanium carbonitride phase (TiC X N 1 − X ) to titanium carbide as proven by XRD data. The composition of the plasma gas especially a very low concentration of hydrocarbons around 0.2 % of the total plasma gas is crucial to tune the composition and to avoid the formation of free carbon. Examination of the particles by HR-TEM shows that the material consists mostly of cubic single crystalline particles with mean sizes between 8 and 27 nm

  9. Analysis of cobalt, tantalum, titanium, vanadium and chromium in tungsten carbide by inductively coupled plasma-optical emission spectrometry

    CSIR Research Space (South Africa)

    Archer, M

    2003-12-01

    Full Text Available Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to measure the concentrations of cobalt, tantalum, titanium, vanadium and chromium in solutions of tungsten carbide. The main advantage of the method described here lies...

  10. Crystallography and Morphology of MC Carbides in Niobium-Titanium Modified As-Cast HP Alloys

    Science.gov (United States)

    Buchanan, Karl G.; Kral, Milo V.; Bishop, Catherine M.

    2014-07-01

    The microstructures of two as-cast heats of HP alloy stainless steels modified with niobium and titanium were examined with particular attention paid to the interdendritic niobium-titanium-rich carbides formed during solidification of these alloys. Generally, these precipitates obtain a blocky morphology in the as-cast condition. However, the (NbTi)C precipitates may obtain a nodular morphology. To provide further insight to the origin of the two different morphologies obtained by the (NbTi)C precipitates in the HP-NbTi alloy, the microstructure and crystallography of each have been studied in detail using scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (EBSD, SAD, and CBED), and energy-dispersive X-ray spectroscopy.

  11. Osseointegration is improved by coating titanium implants with a nanostructured thin film with titanium carbide and titanium oxides clustered around graphitic carbon

    Energy Technology Data Exchange (ETDEWEB)

    Veronesi, Francesca [Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic Institute, Via Di Barbiano 1/10, Bologna 40136 (Italy); Giavaresi, Gianluca; Fini, Milena [Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic Institute, Via Di Barbiano 1/10, Bologna 40136 (Italy); Laboratory of Biocompatibility, Innovative Technologies and Advanced Therapies, Department Rizzoli RIT, Via Di Barbiano 1/10, Bologna 40136 (Italy); Longo, Giovanni [CNR Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Roma (Italy); Ioannidu, Caterina Alexandra; Scotto d' Abusco, Anna [Dept. of Biochemical Sciences, Sapienza University of Roma, Ple A. Moro 5, 00185 Roma (Italy); Superti, Fabiana; Panzini, Gianluca [Dept. of Technologies and Health, Istituto Superiore di Sanità, Viale Regina Elena, 299 Roma (Italy); Misiano, Carlo [Romana Film Sottili, Anzio, Roma (Italy); Palattella, Alberto [Dept. of Clinical Sciences and Translational Medicine, Tor Vergata University, Via Montpellier 1, 00133 Roma (Italy); Selleri, Paolo; Di Girolamo, Nicola [Exotic Animals Clinic, Via S. Giovannini 53, 00137 Roma (Italy); Garbarino, Viola [Dept. of Radiology, S.M. Goretti Hospital, Via G. Reni 2, 04100 Latina (Italy); Politi, Laura [Dept. of Biochemical Sciences, Sapienza University of Roma, Ple A. Moro 5, 00185 Roma (Italy); Scandurra, Roberto, E-mail: roberto.scandurra@uniroma1.it [Dept. of Biochemical Sciences, Sapienza University of Roma, Ple A. Moro 5, 00185 Roma (Italy)

    2017-01-01

    Titanium implants coated with a 500 nm nanostructured layer, deposited by the Ion Plating Plasma Assisted (IPPA) technology, composed of 60% graphitic carbon, 25% titanium oxides and 15% titanium carbide were implanted into rabbit femurs whilst into the controlateral femurs uncoated titanium implants were inserted as control. At four time points the animals were injected with calcein green, xylenol orange, oxytetracycline and alizarin. After 2, 4 and 8 weeks femurs were removed and processed for histology and static and dynamic histomorphometry for undecalcified bone processing into methylmethacrylate, sectioned, thinned, polished and stained with Toluidine blue and Fast green. The overall bone-implant contacts rate (percentage of bone-implant contacts/weeks) of the TiC coated implant was 1.6 fold than that of the uncoated titanium implant. The histomorphometric analyses confirmed the histological evaluations. More precisely, higher Mineral Apposition Rate (MAR, μm/day) (p < 0.005) and Bone Formation Rate (BFR, μm{sup 2}/μm/day) (p < 0.0005) as well as Bone Implant Contact (Bic) and Bone Ingrowth values (p < 0.0005) were observed for the TiC coated implants compared to uncoated implants. In conclusion the hard nanostructured TiC layer protects the bulk titanium implant against the harsh conditions of biological tissues and in the same time, stimulating adhesion, proliferation and activity of osteoblasts, induces a better bone-implant contacts of the implant compared to the uncoated titanium implant. - Highlights: • Ti implants were coated with a nanostructured film composed of C{sub gr}, TiC and TiO{sub x}. • The TiC layer stimulates adhesion, proliferation and activity of osteoblasts. • Uncoated and TiC coated titanium implants were implanted in rabbit femurs. • Bone-implant contacts of TiC coated implants were higher than that of uncoated. • Mineral Apposition Rate of TiC coated implants were higher than that of uncoated.

  12. Cu_2O Hybridized Titanium Carbide with Open Conductive Frameworks for Lithium-ion Batteries

    International Nuclear Information System (INIS)

    Zhang, Huang; Dong, Hui; Zhang, Xuan; Xu, Yunlong; Fransaer, Jan

    2016-01-01

    Though MXenes, a new family of 2D transition metal carbides, are generating considerable interests as electrode materials for batteries and supercapacitors, further application is hindered by their low capacities and poor rate capabilities. Here we propose a simple route for the synthesis of Cu_2O particle hybridized titanium carbide Ti_2CT_x (T = O, OH) composites via a solvothermal method. Electrodes containing Cu_2O/MXene were fabricated without carbon black, and tested as anodes for lithium ion batteries. A discharge capacity of 143 mAh g"−"1 was obtained at a discharge current density of 1000 mA g"−"1 and the capacity retention was near 100% after 200 cycles. The hybrid electrodes with open conductive frameworks exhibited significantly improved electrochemical performance, suggesting a new method for preparing MXene-based composites for energy storage application.

  13. Point defects and transport properties in carbides

    International Nuclear Information System (INIS)

    Matzke, Hj.

    1984-01-01

    Carbides of transition metals and of actinides are interesting and technologically important. The transition-metal carbides (or carbonitrides) are extensively being used as hard materials and some of them are of great interest because of the high transition temperature for superconductivity, e.g. 17 K for Nb(C,N). Actinide carbides and carbonitrides, (U,Pu)C and (U,Pu)(C,N) are being considered as promising advanced fuels for liquid metal cooled fast breeder nuclear reactors. Basic interest exists in all these materials because of their high melting points (e.g. 4250 K for TaC) and the unusually broad range of homogeneity of nonstoichiometric compositions (e.g. from UCsub(0.9) to UCsub(1.9) at 2500 K). Interaction of point defects to clusters and short-range ordering have recently been studied with elastic neutron diffraction and diffuse scattering techniques, and calculations of energies of formation and interaction of point defects became available for selected carbides. Diffusion measurements also exist for a number of carbides, in particular for the actinide carbides. The existing knowledge is discussed and summarized with emphasis on informative examples of particular technological relevance. (Auth.)

  14. Vacancy distribution in nonstoichiometric vanadium monoxide

    International Nuclear Information System (INIS)

    Gusev, A.I.; Davydov, D.A.; Valeeva, A.A.

    2011-01-01

    Graphical abstract: Display Omitted Research highlights: → A certain fraction of vanadium atoms in disordered cubic vanadium monoxide VO y and ordered tetragonal phase V 52 O 64 is located in tetrahedral positions of a basic cubic lattice. → These positions are never occupied by any atoms in other strongly nonstoichiometric carbides, nitrides and oxides. → Both disordered and ordered structures of vanadium monoxide are characterized by the presence of short-range order of displacements in the oxygen sublattice and short-range order of substitution in the metal sublattice. → The short-range order of displacement is caused by the local displacements of O atoms from V (t) atoms occupying tetrahedral positions. The short-range order of substitution appears because V (t) atoms in the tetrahedral positions are always in the environment of four vacancies □ of the vanadium sublattice. - Abstract: Structural vacancy distribution in the crystal lattice of the tetragonal V 52 O 64 superstructure which is formed on the basis of disordered superstoichiometric cubic vanadium monoxide VO y ≡V x O z is experimentally determined and the presence of significant local atomic displacements and large local microstrains in a crystal lattice of real ordered phase is established. It is shown that the relaxation of local microstrains takes place owing to the basic disordered cubic phase grain refinement and a formation of ordered phase domains. The ordered phase domains grow in the direction from the boundaries to the centre of grains of the disordered basic cubic phase. Isothermal evolution at 970 K of the average domain size in ordered VO 1.29 vanadium monoxide is established. It is shown that the short-range order presents in a metal sublattice of disordered cubic VO y vanadium monoxide. The character of the short-range order is such that vanadium atoms occupying tetrahedral positions are in the environment of four vacant sites of the vanadium sublattice. This means that the

  15. Phase equilibria, phases and compounds in the Ti-C system

    International Nuclear Information System (INIS)

    Gusev, A.I.

    2002-01-01

    The results of experimental and theoretical investigations related to the phase equilibria in the titanium-carbon system are generalized. The generalized thermodynamic characteristics of the disordered titanium carbide TiC y are given. The crystal structure of all the discovered and hypothetical compounds of titanium with carbon are considered in detail. The x-ray diffraction patterns which allow one to identify all these compounds are given. The phase diagrams of the Ti-C system constructed with allowance for atomic ordering of non-stoichiometric TiC y carbide and for the existence of the compounds Ti 8 C 12 and Ti 13 C 22 (TiC 2 ) of the molecule cluster type are discussed [ru

  16. Liquid phase sintering of carbides using a nickel-molybdenum alloy

    International Nuclear Information System (INIS)

    Barranco, J.M.; Warenchak, R.A.

    1987-01-01

    Liquid phase vacuum sintering was used to densify four carbide groups. These were titanium carbide, tungsten carbide, vanadium carbide, and zirconium carbide. The liquid phase consisted of nickel with additions of molybdenum of from 6.25 to 50.0 weight percent at doubling increments. The liquid phase or binder comprised 10, 20, and 40 percent by weight of the pressed powders. The specimens were tested using 3 point bending. Tungsten carbide showed the greatest improvement in bend rupture strength, flexural modulus, fracture energy and hardness using 20 percent binder with lesser amounts of molybdenum (6.25 or 12.5 wt %) added to nickel compared to pure nickel. A refinement in the carbide microstructure and/or a reduction in porosity was seen for both the titanium and tungsten carbides when the alloy binder was used compared to using the nickel alone. Curves depicting the above properties are shown for increasing amounts of molybdenum in nickel for each carbide examined. Loss of binder phase due to evaporation was experienced during heating in vacuum at sintering temperatures. In an effort to reduce porosity, identical specimens were HIP processed at 15 ksi and temperatures averaging 110 C below the sintering g temperature. The tungsten carbide and titanium carbide series containing 80 and 90 weight percent carbide phase respectively showed improvement properties after HIP while properties decreased for most other compositions

  17. Facile synthesis of silicon carbide-titanium dioxide semiconducting nanocomposite using pulsed laser ablation technique and its performance in photovoltaic dye sensitized solar cell and photocatalytic water purification

    Energy Technology Data Exchange (ETDEWEB)

    Gondal, M.A., E-mail: magondal@kfupm.edu.sa [Laser Research Group, Physics Department & Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Ilyas, A.M. [Laser Research Group, Physics Department & Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Baig, Umair [Laser Research Group, Physics Department & Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Center of Excellence for Scientific Research Collaboration with MIT, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2016-08-15

    Highlights: • SiC–TiO{sub 2} semiconducting nanocomposites synthesized by nanosecond PLAL technique. • Synthesized nanocomposites were morphologically and optically characterized. • Nanocomposites were applied for the photocatalytic degradation of toxic organic dye. • Photovoltaic performance was investigated in dye sensitized solar cell. - Abstract: Separation of photo-generated charge carriers (electron and holes) is a major approach to improve the photovoltaic and photocatalytic performance of metal oxide semiconductors. For harsh environment like high temperature applications, ceramic like silicon carbide is very prominent. In this work, 10%, 20% and 40% by weight of pre-oxidized silicon carbide was coupled with titanium dioxide (TiO{sub 2}) to form nanocomposite semiconductor via elegant pulsed laser ablation in liquid technique using second harmonic 532 nm wavelength of neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. In addition, the effect of silicon carbide concentration on the performance of silicon carbide-titanium dioxide nanocomposite as photo-anode in dye sensitized solar cell and as photocatalyst in photodegradation of methyl orange dye in water was also studied. The result obtained shows that photo-conversion efficiency of the dye sensitized solar cell was improved from 0.6% to 1.65% and the percentage of methyl orange dye removed was enhanced from 22% to 77% at 24 min under ultraviolet–visible solar spectrum in the nanocomposite with 10% weight of silicon carbide. This remarkable performance enhancement could be due to the improvement in electron transfer phenomenon by the presence of silicon carbide on titanium dioxide.

  18. Preliminary Investigation of the Effect of Surface Treatment on the Strength of a Titanium Carbide - 30 Percent Nickel Base Cermet

    Science.gov (United States)

    Robins, Leonard; Grala, Edward M

    1957-01-01

    Specimens of a nickel-bonded titanium carbide cermet were given the following surface treatments: (1) grinding, (2) lapping, (3) blast cleaning, (4) acid roughening, (5) oxidizing, and (6) oxidizing and refinishing. Room-temperature modulus-of-rupture and impact strength varied with the different surface treatments. Considerable strength losses resulted from the following treatments: (1) oxidation at 1600 F for 100 hours, (2) acid roughening, and (3) severe grinding with 60-grit silicon carbide abrasive. The strength loss after oxidation was partially recovered by grit blasting or diamond grinding.

  19. Carbide-reinforced metal matrix composite by direct metal deposition

    Science.gov (United States)

    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.

  20. Electronic specific heat of transition metal carbides

    International Nuclear Information System (INIS)

    Conte, R.

    1964-07-01

    The experimental results that make it possible to define the band structure of transition metal carbides having an NaCI structure are still very few. We have measured the electronic specific heat of some of these carbides of varying electronic concentration (TiC, either stoichiometric or non-stoichiometric, TaC and mixed (Ti, Ta) - C). We give the main characteristics (metallography, resistivity, X-rays) of our samples and we describe the low temperature specific heat apparatus which has been built. In one of these we use helium as the exchange gas. The other is set up with a mechanical contact. The two use a germanium probe for thermometer. The measurement of the temperature using this probe is described, as well as the various measurement devices. The results are presented in the form of a rigid band model and show that the density of the states at the Fermi level has a minimum in the neighbourhood of the group IV carbides. (author) [fr

  1. Strain-induced ordered structure of titanium carbide during depositing diamond on Ti alloy substrate

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.J., E-mail: lixj@alum.imr.ac.cn [College of Material Science and Engineering, Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun, 130012 (China); He, L.L., E-mail: llhe@imr.ac.cn [Shenyang National Lab of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Li, Y.S. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon S7N 5A9, SK (Canada); Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); Yang, Q. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon S7N 5A9, SK (Canada); Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada)

    2017-01-15

    During the deposition of diamond films on Ti alloy substrates, titanium carbide is a common precipitated phase, preferentially formed at the interfacial region. However, in this case, the precipitation of an ordered structure of titanium carbide has not been reported. In our work, a long periodic ordered structure of TiC has been observed at the deposited diamond film/Ti alloy interface by high resolution transmission electron microscopy (HRTEM). The long periodic ordered structure is identified as 6H-type. The formation mechanism is revealed by comparative studies on the different structures of TiC precipitated under different diamond deposition conditions in terms of deposition time, atmosphere and temperature. A large number of carbon vacancies in the interfacial precipitated TiC phase are verified through electron energy loss spectroscopy (EELS) quantification analysis. However, an ordered arrangement of these carbon vacancies occurs only when the interfacial stress is large enough to induce the precipitation of 6H-type TiC. The supplementary analysis by X-ray diffraction (XRD) further confirms that additional diffraction peaks presented in the XRD patterns are corresponding to the precipitation of 6H-type TiC. - Highlights: •Different structures of TiC are observed during deposited diamond on Ti alloy. •One is common NaCl structure, the other is periodic structure. •The periodic structure is identified as 6H-type by HRTEM. •Carbon vacancies are verified to always exist in the TiC phase. •The precipitation of 6H-type TiC is mainly affected by interfacial stress.

  2. Strain-induced ordered structure of titanium carbide during depositing diamond on Ti alloy substrate

    International Nuclear Information System (INIS)

    Li, X.J.; He, L.L.; Li, Y.S.; Yang, Q.; Hirose, A.

    2017-01-01

    During the deposition of diamond films on Ti alloy substrates, titanium carbide is a common precipitated phase, preferentially formed at the interfacial region. However, in this case, the precipitation of an ordered structure of titanium carbide has not been reported. In our work, a long periodic ordered structure of TiC has been observed at the deposited diamond film/Ti alloy interface by high resolution transmission electron microscopy (HRTEM). The long periodic ordered structure is identified as 6H-type. The formation mechanism is revealed by comparative studies on the different structures of TiC precipitated under different diamond deposition conditions in terms of deposition time, atmosphere and temperature. A large number of carbon vacancies in the interfacial precipitated TiC phase are verified through electron energy loss spectroscopy (EELS) quantification analysis. However, an ordered arrangement of these carbon vacancies occurs only when the interfacial stress is large enough to induce the precipitation of 6H-type TiC. The supplementary analysis by X-ray diffraction (XRD) further confirms that additional diffraction peaks presented in the XRD patterns are corresponding to the precipitation of 6H-type TiC. - Highlights: •Different structures of TiC are observed during deposited diamond on Ti alloy. •One is common NaCl structure, the other is periodic structure. •The periodic structure is identified as 6H-type by HRTEM. •Carbon vacancies are verified to always exist in the TiC phase. •The precipitation of 6H-type TiC is mainly affected by interfacial stress.

  3. Comparative study of titanium carbide and nitride coatings grown by cathodic vacuum arc technique

    International Nuclear Information System (INIS)

    Devia, D.M.; Restrepo-Parra, E.; Arango, P.J.

    2011-01-01

    Titanium nitride (TiN), titanium carbide (TiC) thin films and TiC/TiN bilayers have been deposited on AISI 304 stainless steel substrates by plasma assisted physical vapor deposition technique - reactive pulsed vacuum arc method. The coatings were characterized in terms of crystalline structure, microstructure and chemical nature by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. Tribological behavior was investigated using ball on disc technique. The average coefficient of friction was measured, showing lower values for the TiN/TiC bilayer. Dynamic wear curves were performed for each coating, observing a better wear resistance for TiN/TiC bilayers, compared to TiN and TiC monolayers. On the other hand, the TiCN formation in the TiN/TiC bilayer was observed, being attributed to the interdiffusion between TiN and TiC at the interface. Moreover, the substrate temperature influence was analysing observing a good behavior at T S = 115 °C.

  4. Fabrication and oxidation resistance of titanium carbide-coated carbon fibres by reacting titanium hydride with carbon fibres in molten salts

    International Nuclear Information System (INIS)

    Dong, Z.J.; Li, X.K.; Yuan, G.M.; Cong, Y.; Li, N.; Jiang, Z.Y.; Hu, Z.J.

    2009-01-01

    Using carbon fibres and titanium hydride as a reactive carbon source and a metal source, respectively, a protective titanium carbide (TiC) coating was formed on carbon fibres in molten salts, composed of LiCl-KCl-KF, at 750-950 o C. The structure and morphology of the TiC coatings were characterised by X-ray diffraction and scanning electron microscopy, respectively. The oxidation resistance of the TiC-coated carbon fibres was measured by thermogravimetric analysis. The results reveal that control of the coating thickness is very important for improvement of the oxidation resistance of TiC-coated carbon fibres. The oxidative weight loss initiation temperature for the TiC-coated carbon fibres increases significantly when an appropriate coating thickness is used. However, thicker coatings lead to a decrease of the carbon fibres' weight loss initiation temperature due to the formation of cracks in the coating. The TiC coating thickness on carbon fibres can be controlled by adjusting the reaction temperature and time of the molten salt synthesis.

  5. Synthesis of titanium carbide from wood by self-propagating high temperature synthesis

    Directory of Open Access Journals (Sweden)

    Sutham Niyomwas

    2010-05-01

    Full Text Available Titanium carbide (TiC particles were obtained in situ by a self-propagating high temperature synthesis (SHS of wooddust with TiO2 and Mg. The reaction was carried out in a SHS reactor under static argon gas at the pressure of 0.5 MPa. Thestandard Gibbs energy minimization method was used to calculate the equilibrium composition of the reacting species. Theeffects of increasing Mg mole ratio to the precursor mixture of TiO2 and wood dusts were investigated. XRD and SEManalyses indicate a complete reaction of the precursors to yield TiC-MgO as a product composite. The synthesized compositeswere leached with 0.1M HCl acid solution to obtain TiC particles as final products.

  6. Neutron irradiation damage in transition metal carbides

    International Nuclear Information System (INIS)

    Matsui, Hisayuki; Nesaki, Kouji; Kiritani, Michio

    1991-01-01

    Effects of neutron irradiation on the physical properties of light transition metal carbides, TiC x , VC x and NbC x , were examined, emphasizing the characterization of irradiation induced defects in the nonstoichiometric composition. TiC x irradiated with 14 MeV (fusion) neutrons showed higher damage rates with increasing C/Ti (x) ratio. A brief discussion is made on 'cascade damage' in TiC x irradiated with fusion neutrons. Two other carbides (VC x and NbC x ) were irradiated with fission reactor neutrons. The irradiation effects on VC x were not so simple, because of the complex irradiation behavior of 'ordered' phases. For instance, complete disordering was revealed in an ordered phase, 'V 8 C 7 ', after an irradiation dose of 10 25 n/m 2 . (orig.)

  7. The valve effect of the carbide interlayer of an electric resistance plug

    International Nuclear Information System (INIS)

    Lakomskii, V.

    1998-01-01

    The welded electric resistance plug (ERP) usually contains a carbide interlayer at the plug-carbon material interface. The interlayer forms during welding the contact metallic alloy with the carbon material when the oxide films of the alloy are reduced on the interface surface by carbon to the formation of carbides and the surface layer of the plug material dissolves carbon to saturation. Subsequently, during solidification of the plug material it forms carbides with the alloy components. The structural composition of the carbide interlayer is determined by the chemical composition of the contact alloy. In alloys developed by the author and his colleagues the carbide forming elements are represented in most cases by silicon and titanium and, less frequently, by chromium and manganese. Therefore, the carbide interlayers in the ERP consisted mainly of silicon and titanium carbides

  8. Anodic solubility and electrochemical machining of hard alloys on the base of chromium and titanium carbides

    Energy Technology Data Exchange (ETDEWEB)

    Davydov, A D; Klepikov, A N; Malofeeva, A N; Moroz, I I

    1985-01-01

    The regularities of anodic behaviour and electrochemical machining (ECM) of the samples of three materials with the following compositions: 25% of Cr/sub 3/C/sub 2/, 15% of Ni, 70% of TiC, 25% of Ni, 5% of Cr, 70% of TiC, 15% of Ni, 15% of Mo are investigated. It is shown that the electrochemical method is applicable to hard alloys machining on the base of chromium and titanium carbides, the machining of which mechanically meets serious difficulties. The alloys machining rate by a mobile cathode constitutes about 0.5 mm/min.

  9. Replacing Chlorine with Hydrogen Chloride as a Possible Reactant for Synthesis of Titanium Carbide Derived Carbon Powders for High-Technology Devices

    International Nuclear Information System (INIS)

    Tallo, Indrek; Thomberg, Thomas; Jänes, Alar; Lust, Enn

    2013-01-01

    Micro- and mesoporous carbide-derived carbons were synthesized from titanium carbide (TiC) powder via gas phase reaction by using different reactants (Cl 2 and HCl) within the temperature range from 700 to 1100 °C. Analysis of XRD results show that TiC-derived carbons (TiC-CDC) consist mainly of graphitic crystallites. The first-order Raman spectra showed the graphite-like absorption peaks at ∼1577 cm 1 and the disorder-induced peaks at ∼1338 cm- 1 . The energy-related properties of supercapacitors based on 1 M (C 2 H 5 ) 3 CH 3 NBF 4 in acetonitrile and carbide-derived carbons (TiC-CDC (Cl 2 ) and TiC-CDC (HCl)) as electrode materials were also investigated using cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic charge/discharge and constant power methods. The Ragone plots for carbide-derived carbons prepared by using different reactants (Cl 2 , HCl) are quite similar and at high power loads TiC-CDC (Cl 2 ) material synthesized at 900 °C, i.e. materials with optimal porous structure, deliver higher power at constant energy

  10. Hydrogen insertion in titanium carbide based thin films (nc-TiC{sub x}/a-C:H) - comparison with bulk TiC{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Julien; Jaoul, Cédric, E-mail: jaoul@ensil.unilim.fr; Glandut, Nicolas; Lefort, Pierre

    2016-08-01

    Nanocomposites composed of titanium carbide nanosized grains embedded in an amorphous hydrogenated carbon matrix (nc-TiC{sub x}/a-C:H) are prepared by hybrid Magnetron Sputtering - PECVD process using a titanium metal target and gaseous C{sub 6}H{sub 6}. By controlling the benzene flow rate, thin films with different carbon content are obtained. The structures of nc-TiC{sub x}/a-C:H materials are analyzed by X-ray diffraction, X-ray photoelectron and Raman spectroscopic methods. The electrochemical hydrogen insertion, as studied by cyclic voltammetry, strongly depends on the carbon content in the thin films. The correlation between the hydrogen insertion ability and the structure of materials are discussed. Furthermore, we show that the hydrogen insertion in these thin films reaches values much more significant than in bulk substoichiometric titanium carbide obtained by reactive sintering. - Highlights: • nc-TiC{sub x}/a-C:H thin films are prepared hybrid Magnetron Sputtering - PECVD process. • Different carbon contents are obtained by changing the hydrocarbon flowrate. • Expanded lattice parameter of the TiC{sub x} phase and a-C:H phase are observed. • Electrochemical hydrogen insertion strongly depends on the carbon content. • The maximum insertion is 22 times more important than bulk TiC{sub x}.

  11. Fabrication of graphene/titanium carbide nanorod arrays for chemical sensor application

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Chong [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Mingji, E-mail: limingji@163.com [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Hongji, E-mail: hongjili@yeah.net [Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Cuiping; Qu, Changqing; Yang, Baohe [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2017-03-01

    Vertically stacked graphene nanosheet/titanium carbide nanorod array/titanium (graphene/TiC nanorod array) wires were fabricated using a direct current arc plasma jet chemical vapor deposition (DC arc plasma jet CVD) method. The graphene/TiC nanorod arrays were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction spectroscopy. The TiO{sub 2} nanotube array was reduced to the TiC nanorod array, and using those TiC nanorods as nucleation sites, the vertical graphene layer was formed on the TiC nanorod surface. The multi-target response mechanisms of the graphene/TiC nanorod array were investigated for ascorbic acid (AA), dopamine (DA), uric acid (UA), and hydrochlorothiazide (HCTZ). The vertically stacked graphene sheets facilitated the electron transfer and reactant transport with a unique porous surface, high surface area, and high electron transport network of CVD graphene sheets. The TiC nanorod array facilitated the electron transfer and firmly held the graphene layer. Thus, the graphene/TiC nanorod arrays could simultaneously respond to trace biomarkers and antihypertensive drugs. - Highlights: • Vertical graphene sheets were prepared with Ti as the catalyst via a CVD method. • TiO{sub 2} nanotubes were key transition layers in the formation of the TiC nanorods. • Vertical growth mechanism of graphene products was discussed. • Biomolecules were detected to be a chemical sensor. • Response mechanism for analytes at the graphene/TiC nanorod array was discussed.

  12. Fabrication of graphene/titanium carbide nanorod arrays for chemical sensor application

    International Nuclear Information System (INIS)

    Fu, Chong; Li, Mingji; Li, Hongji; Li, Cuiping; Qu, Changqing; Yang, Baohe

    2017-01-01

    Vertically stacked graphene nanosheet/titanium carbide nanorod array/titanium (graphene/TiC nanorod array) wires were fabricated using a direct current arc plasma jet chemical vapor deposition (DC arc plasma jet CVD) method. The graphene/TiC nanorod arrays were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction spectroscopy. The TiO 2 nanotube array was reduced to the TiC nanorod array, and using those TiC nanorods as nucleation sites, the vertical graphene layer was formed on the TiC nanorod surface. The multi-target response mechanisms of the graphene/TiC nanorod array were investigated for ascorbic acid (AA), dopamine (DA), uric acid (UA), and hydrochlorothiazide (HCTZ). The vertically stacked graphene sheets facilitated the electron transfer and reactant transport with a unique porous surface, high surface area, and high electron transport network of CVD graphene sheets. The TiC nanorod array facilitated the electron transfer and firmly held the graphene layer. Thus, the graphene/TiC nanorod arrays could simultaneously respond to trace biomarkers and antihypertensive drugs. - Highlights: • Vertical graphene sheets were prepared with Ti as the catalyst via a CVD method. • TiO 2 nanotubes were key transition layers in the formation of the TiC nanorods. • Vertical growth mechanism of graphene products was discussed. • Biomolecules were detected to be a chemical sensor. • Response mechanism for analytes at the graphene/TiC nanorod array was discussed.

  13. Plasma metallization of refractory carbide powders

    International Nuclear Information System (INIS)

    Koroleva, E.B.; Klinskaya, N.A.; Rybalko, O.F.; Ugol'nikova, T.A.

    1986-01-01

    The effect of treatment conditions in plasma on properties of produced metallized powders of titanium, tungsten and chromium carbides with the main particle size of 40-80 μm is considered. It is shown that plasma treatment permits to produce metallized powders of carbide materials with the 40-80 μm particle size. The degree of metallization, spheroidization, chemical and phase composition of metallized carbide powders are controlled by dispersivity of the treated material, concentration of a metal component in the treated mixtures, rate of plasma flow and preliminary spheroidization procedure

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

    International Nuclear Information System (INIS)

    Cockeram, B.V.

    1999-01-01

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

  15. Effect of Titanium on the Microstructure and Mechanical Properties of High-Carbon Martensitic Stainless Steel 8Cr13MoV

    Directory of Open Access Journals (Sweden)

    Wen-Tao Yu

    2016-08-01

    Full Text Available The effect of titanium on the carbides and mechanical properties of martensitic stainless steel 8Cr13MoV was studied. The results showed that TiCs not only acted as nucleation sites for δ-Fe and eutectic carbides, leading to the refinement of the microstructure, but also inhibited the formation of eutectic carbides M7C3. The addition of titanium in steel also promoted the transformation of M7C3-type to M23C6-type carbides, and consequently more carbides could be dissolved into the matrix during hot processing as demonstrated by the determination of extracted carbides from the steel matrix. Meanwhile, titanium suppressed the precipitation of secondary carbides during annealing. The appropriate amount of titanium addition decreased the size and fraction of primary carbides in the as-cast ingot, and improved the mechanical properties of the annealed steel.

  16. Development of a hard nano-structured multi-component ceramic coating by laser cladding

    International Nuclear Information System (INIS)

    Masanta, Manoj; Ganesh, P.; Kaul, Rakesh; Nath, A.K.; Roy Choudhury, A.

    2009-01-01

    The present paper reports laser-assisted synthesis of a multi-component ceramic composite coating consisting of aluminum oxide, titanium di-boride and titanium carbide (Al 2 O 3 -TiB 2 -TiC). A pre-placed powder mixture of aluminum (Al), titanium oxide (TiO 2 ) and boron carbide (B 4 C) was made to undergo self-propagating high-temperature synthesis (SHS) by laser triggering. Laser subsequently effected cladding of the products of SHS on the substrate. The effect of laser scanning speed on the hardness, microstructure and phase composition of the composite coating was investigated. The coating exhibited an increase in hardness and a decrease in grain size with increase in laser scanning speed. A maximum micro-hardness of 2500 HV 0.025 was obtained. X-ray diffraction (XRD) of the top surface of the coating revealed the presence of aluminum oxide (Al 2 O 3 ), titanium di-boride (TiB 2 ) and titanium carbide (TiC) along with some non-stoichiometric products of the Ti-Al-B-C-O system. Field emission gun scanning electron microscopy (FESEM) and high-resolution transmission electron microscopic (HRTEM) analysis revealed some nano-structured TiB 2 and Al 2 O 3 , which are discussed in detail.

  17. Corrosion-electrochemical characteristics of oxide-carbide and oxide-nitride coatings formed by electrolytic plasma

    International Nuclear Information System (INIS)

    Tomashov, N.D.; Chukalovskaya, T.V.; Medova, I.L.; Duradzhi, V.N.; Plavnik, G.M.

    1990-01-01

    The composition, structure, microhardness and corrosion-electrochemical properties of oxide-carbide and oxide-nitride coatings on titanium in 5n H 2 SO 4 , 50 deg, produced by the method of chemical-heat treatment in electrolytic plasma, containing saturation components of nitrogen and carbon, were investigated. It is shown that the coatings produced have increased hardness, possess high corrosion resistance in sulfuric acid solution at increased temperature, as to their electrochemcial behaviour they are similar to titanium carbide and nitride respectively. It is shown that high corrosion resistance is ensured by electrochemical mechanism of the oxide-carbide and oxide-nitride coating protection

  18. Fabrication of TiC-TiO{sub 2} composite powders by thermal plasma oxidation of titanium carbide powder; Tanka chitan funmatsu no plasma sanka hanno ni yori seiseishita TiC-TiO{sub 2} fukugo funmatsu

    Energy Technology Data Exchange (ETDEWEB)

    Ishigaki, T.; Li, Y.; Haneda, H. [National institute for Research Inorganic materials, Tsukuba (Japan); Kataoka, E. [Showa Cabot Supermetals K.K., Tokyo (Japan)

    2000-09-15

    TiC-TiO{sub 2} composite powders were prepared by in-flight oxidation of titanium carbide powder in RF induction thermal plasmas. Original titanium carbide powder of 20 - 38 {mu}m in particle size was axially injected into the center of argon-oxygen plasma. The powders were partially spheroidized and evaporated through the plasma treatment. X-ray diffraction of plasma-treated powders showed the formation of titanium dioxides, both rutile and anatase phases. The phase content of the plasma-prepared powders strongly depended on the plasma conditions, such as the plasma generating pressure and the oxygen flow rate in plasma generating gas. Especially, the increase of oxygen flow rate in plasma gas gave rise to the increase of heat transfer from plasma to powder particles, exothermic heat of oxidation reaction and cooling rate of plasma, giving the increase of spheroidization ratio, formation ratio of titanium dioxides, and content of anatase phases. (author)

  19. Fracture properties of hydrogenated amorphous silicon carbide thin films

    International Nuclear Information System (INIS)

    Matsuda, Y.; King, S.W.; Bielefeld, J.; Xu, J.; Dauskardt, R.H.

    2012-01-01

    The cohesive fracture properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films in moist environments are reported. Films with stoichiometric compositions (C/Si ≈ 1) exhibited a decreasing cohesive fracture energy with decreasing film density similar to other silica-based hybrid organic–inorganic films. However, lower density a-SiC:H films with non-stoichiometric compositions (C/Si ≈ 5) exhibited much higher cohesive fracture energy than the films with higher density stoichiometric compositions. One of the non-stoichiometric films exhibited fracture energy (∼9.5 J m −2 ) greater than that of dense silica glasses. The increased fracture energy was due to crack-tip plasticity, as demonstrated by significant pileup formation during nanoindentation and a fracture energy dependence on film thickness. The a-SiC:H films also exhibited a very low sensitivity to moisture-assisted cracking compared with other silica-based hybrid films. A new atomistic fracture model is presented to describe the observed moisture-assisted cracking in terms of the limited Si-O-Si suboxide bond formation that occurs in the films.

  20. Toward a comprehensive UV laser ablation modeling of multicomponent materials—A non-equilibrium investigation on titanium carbide

    Science.gov (United States)

    Ait Oumeziane, Amina; Parisse, Jean-Denis

    2018-05-01

    Titanium carbide (TiC) coatings of great quality can be produced using nanosecond pulsed laser deposition (PLD). Because the deposition rate and the transfer of the target stoichiometry depend strongly on the laser-target/laser-plasma interaction as well as the composition of the laser induced plume, investigating the ruling fundamental mechanisms behind the material ablation and the plasma evolution in the background environment under PLD conditions is essential. This work, which extends previous investigations dedicated to the study of nanosecond laser ablation of pure target materials, is a first step toward a comprehensive non-equilibrium model of multicomponent ones. A laser-material interaction model coupled to a laser-plasma interaction one is presented. A UV 20 ns KrF (248 nm) laser pulse is considered. Ablation depths, plasma ignition thresholds, and shielding rates have been calculated for a wide range of laser beam fluences. A comparison of TiC behavior with pure titanium material under the same conditions is made. Plasma characteristics such as temperature and composition have been investigated. An overall correlation between the various results is presented.

  1. Combined Photoemission Spectroscopy and Electrochemical Study of a Mixture of (Oxy)carbides as Potential Innovative Supports and Electrocatalysts.

    Science.gov (United States)

    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.

  2. Development of a hard nano-structured multi-component ceramic coating by laser cladding

    Energy Technology Data Exchange (ETDEWEB)

    Masanta, Manoj [Department of Mechanical Engineering, IIT Kharagpur, West Bengal 721302 (India); Ganesh, P.; Kaul, Rakesh [Laser Material Processing Division, Raja Ramanna Centre for Advanced Technology, Indore (India); Nath, A.K. [Department of Mechanical Engineering, IIT Kharagpur, West Bengal 721302 (India); Roy Choudhury, A., E-mail: roychoudhuryasimava@gmail.com [Department of Mechanical Engineering, IIT Kharagpur, West Bengal 721302 (India)

    2009-05-20

    The present paper reports laser-assisted synthesis of a multi-component ceramic composite coating consisting of aluminum oxide, titanium di-boride and titanium carbide (Al{sub 2}O{sub 3}-TiB{sub 2}-TiC). A pre-placed powder mixture of aluminum (Al), titanium oxide (TiO{sub 2}) and boron carbide (B{sub 4}C) was made to undergo self-propagating high-temperature synthesis (SHS) by laser triggering. Laser subsequently effected cladding of the products of SHS on the substrate. The effect of laser scanning speed on the hardness, microstructure and phase composition of the composite coating was investigated. The coating exhibited an increase in hardness and a decrease in grain size with increase in laser scanning speed. A maximum micro-hardness of 2500 HV{sub 0.025} was obtained. X-ray diffraction (XRD) of the top surface of the coating revealed the presence of aluminum oxide (Al{sub 2}O{sub 3}), titanium di-boride (TiB{sub 2}) and titanium carbide (TiC) along with some non-stoichiometric products of the Ti-Al-B-C-O system. Field emission gun scanning electron microscopy (FESEM) and high-resolution transmission electron microscopic (HRTEM) analysis revealed some nano-structured TiB{sub 2} and Al{sub 2}O{sub 3}, which are discussed in detail.

  3. Guidelines for Synthesis and Processing of 2D Titanium Carbide (Ti3C2Tx MXene)

    KAUST Repository

    Alhabeb, Mohamed

    2017-08-25

    Two-dimensional (2D) transition metal carbides, carbonitrides and nitrides (MXenes) were discovered in 2011. Since the original discovery, more than 20 different compositions have been synthesized by the selective etching of MAX phase and other precursors and many more theoretically predicted. They offer a variety of different properties, making the family promising candidates in a wide range of applications, such as energy storage, electromagnetic interference shielding, water purification, electrocatalysis and medicine. These solution-processable materials have the potential to be highly scalable, deposited by spin, spray or dip coating, painted or printed, or fabricated in a variety of ways. Due to this promise, the amount of research on MXenes has been increasing, and methods of synthesis and processing are expanding quickly. The fast evolution of the material can also be noticed in the wide range of synthesis and processing protocols that determine the yield of delamination, as well as the quality of the 2D flakes produced. Here we describe the experimental methods and best practices we use to synthesize the most studied MXene, titanium carbide (Ti3C2Tx), using different etchants and delamination methods. We also explain effects of synthesis parameters on the size and quality of Ti3C2Tx and suggest the optimal processes for the desired application.

  4. High temperature oxidation of carbide-carbon materials of NbC-C, NbC-TiC-C systems

    International Nuclear Information System (INIS)

    Afonin, Yu.D.; Shalaginov, V.N.; Beketov, A.R.

    1981-01-01

    The effect of titanium carbide additions on the oxidation of carbide - carbon composition NbC-TiC-C in oxygen under the pressure of 10 mm Hg and in the air at atmospheric pressure in the temperature range 800-1300 deg is studied. It is shown that the region of negative temperature coefficient during oxidation in the system NbC+C is determined by the processes of sintering and polymorphous transformation. The specific character of the oxide film, formed during oxidation of Nbsub(x)Tisub(y)C+C composites is connected with non-equilibrium nature of carbide grain in its composition. Carbon gasification takes place with the formation of carbon dioxide. Composite materials, containing titanium carbide in complex carbide up to 50-83 mol. %, are the most corrosion resisting ones [ru

  5. Highly antibacterial UHMWPE surfaces by implantation of titanium ions

    Energy Technology Data Exchange (ETDEWEB)

    Delle Side, D., E-mail: domenico.delleside@le.infn.it [LEAS, Dipartimento di Matematica e Fisica “Ennio de Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare – Sezione di Lecce, Lecce (Italy); Nassisi, V.; Giuffreda, E.; Velardi, L. [LEAS, Dipartimento di Matematica e Fisica “Ennio de Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare – Sezione di Lecce, Lecce (Italy); Alifano, P.; Talà, A.; Tredici, S.M. [Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Lecce (Italy)

    2014-07-15

    The spreading of pathogens represents a serious threat for human beings. Consequently, efficient antimicrobial surfaces are needed in order to reduce risks of contracting severe diseases. In this work we present the first evidences of a new technique to obtain a highly antibacterial Ultra High Molecular Weight Polyethylene (UHMWPE) based on a non-stoichiometric titanium oxide coating, visible-light responsive, obtained through ion implantation.

  6. Highly antibacterial UHMWPE surfaces by implantation of titanium ions

    Science.gov (United States)

    Delle Side, D.; Nassisi, V.; Giuffreda, E.; Velardi, L.; Alifano, P.; Talà, A.; Tredici, S. M.

    2014-07-01

    The spreading of pathogens represents a serious threat for human beings. Consequently, efficient antimicrobial surfaces are needed in order to reduce risks of contracting severe diseases. In this work we present the first evidences of a new technique to obtain a highly antibacterial Ultra High Molecular Weight Polyethylene (UHMWPE) based on a non-stoichiometric titanium oxide coating, visible-light responsive, obtained through ion implantation.

  7. Thermoelectric properties of non-stoichiometric lanthanum sulfides

    International Nuclear Information System (INIS)

    Shapiro, E.; Danielson, L.R.

    1983-01-01

    The lanthanum sulfides are promising candidate materials for high-efficiency thermoelectric applications at temperatures up to 1300 0 C. The nonstoichiometric lanthanum sulfides (LaS /SUB x/ , where 1.33 2 //rho/ can be chosen. The thermal conductivity remains approximately constant with stoichiometry, so a material with an optimum value of α 2 //rho/ should possess the optimum figure-of-merit. Data for the Seebeck coefficient and electrical resistivity of non-stoichiometric lanthanum sulfides is presented, together with structural properties of these materials

  8. Effect of Titanium on the Microstructure and Mechanical Properties of High-Carbon Martensitic Stainless Steel 8Cr13MoV

    OpenAIRE

    Wen-Tao Yu; Jing Li; Cheng-Bin Shi; Qin-Tian Zhu

    2016-01-01

    The effect of titanium on the carbides and mechanical properties of martensitic stainless steel 8Cr13MoV was studied. The results showed that TiCs not only acted as nucleation sites for δ-Fe and eutectic carbides, leading to the refinement of the microstructure, but also inhibited the formation of eutectic carbides M7C3. The addition of titanium in steel also promoted the transformation of M7C3-type to M23C6-type carbides, and consequently more carbides could be dissolved into the matrix duri...

  9. Spheroidization of transition metal carbides in low temperature plasma

    International Nuclear Information System (INIS)

    Klinskaya, N.A.; Koroleva, E.B.; Petrunichev, V.A.; Rybalko, O.F.; Solov'ev, P.V.; Ugol'nikova, T.A.

    1986-01-01

    Plasma process of preparation of titanium, tungsten and chromium carbide spherical powders with the main particle size 40-80 μm is considered. Spheroidization degree, granulometric and phase composition of the product are investigated

  10. Titanium Matrix Composite Pressure Vessel, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — For over 15 years, FMW Composite Systems has developed Metal Matrix Composite manufacturing methodologies for fabricating silicon-carbide-fiber-reinforced titanium...

  11. Characterization of hard nitride and carbide titanium and zirconium coatings on high-speed steel cutting tool inserts

    International Nuclear Information System (INIS)

    Fenske, G.; Kaufherr, N.; Albertson, C.; Mapalo, G.; Nielsen, R.; Kaminsky, M.

    1986-01-01

    Hard nitride and carbide coatings of titanium and zirconium deposited by reactive evaporation and reactive sputtering techniques were characterized by electron microscopy and Auger spectroscopy to determine the effect of coating process on coating composition and microstructure. Analysis of the chemical composition by Auger spectroscopy revealed the coatings were of high purity with slight differences in stoichiometry depending on the coating technique. Both techniques produced coatings with a columnar microstructure. However, the reactive sputtering technique produced coarser (shorter and wider) columnar grains than the reactive evaporation technique. Furthermore, selected area diffraction analysis of reactively sputtered ZrN coatings showed a two-phased zone (hcp Zr and fcc ZrN) near the substrate/coating interface, while TiC coatings deposited by reactive sputtering and evaporation only showed a single-phase region of fcc TiC

  12. Quantitative Analysis on Carbide Precipitation in V-Ti Microalloyed TRIP Steel Containing Aluminum

    Directory of Open Access Journals (Sweden)

    Fu Shiyu

    2016-01-01

    Full Text Available Introducing fine precipitates is an important way to enhance the properties of transformation-induced plasticity (TRIP steels. In present work, two V-Ti microalloyed TRIP steels containing aluminum with different content were compared. The average size, size distribution and numbers of vanadium-titanium carbides in samples cold rolled, quenched after being held at 800°C and quenched after intercritical annealing at 800°C and being held at bainitic isothermal transformation temperature of 400°C were investigated by using the technique of carbon extraction replica, twin jet chemical polishing thinning and transmission electron microscopy. The carbides were identified to be (Ti,VC precipitates in steel A and VC in steel B respectively, precipitated mainly from ferrites grains. The average equivalent radius was 3~6nm. Comparison of the experimental results in A and B steel revealed low carbon diffusion rate caused by aluminum inhibited the coarsening of vanadium-titanium carbides. The experimental results also showed that VC carbides dissolution occurred during the intercritical annealing at 800°C.

  13. ELASTO-PLASTIC DEFORMATION OF COMPOSITE POWDERS WITH LAYERED CARBON AND CARBIDE-FORMING ELEMENT COATING

    Directory of Open Access Journals (Sweden)

    V. N. Kovalevsky

    2012-01-01

    Full Text Available Coating structure formation under magnetron spraying of titanium and carbon cathodes and combined cathodes, namely cobalt (EP 131 – nickel, tungsten – carbon have been investigated under conditions of carbide separate synthesis within the temperature range of 650–1200 °C. Usage of cobalt and nickel particles as matrix material leads to their rapid thermal expansion under heating during sintering process in the dilatometer. Subsequent plastic deformation of sintered samples provides obtaining a composite powder material that is a composite with framing structure of cobalt, titanium and tungsten carbides in the coatings.

  14. Study of the stability of ordered phases in non-stoichiometric transition metal carbides and nitrides

    International Nuclear Information System (INIS)

    Landesman, J.P.

    1986-03-01

    After presenting the results of neutron diffraction experiments on the ordered compounds Nb 6 C 5 and Ti 2 N, we propose a classification of the ordered phases encountered in this class of compounds, and, using a tight-binding description of the electronic structure, we calculate the band energy for several ordered configurations and the disordered configuration, for a given metalloid vacancy concentration. We can then, on one hand, predict the relative stability (at O K) of the various ordered phases possible at this concentration - and these predictions are in good agreement with the experimental observations, mainly in the case of carbides - and on the other hand calculate the effective pair interactions V 1 and V 2 which appear in the Ising model and reconstruct theoretical stability maps, for any vacancy concentration, which are again in agreement with the phenomenological stability maps (overall agreement in the case of nitrides, more precise agreement in the case of carbides) [fr

  15. Structure and strength of carbide-steel cermet and their changes during heat treatment

    International Nuclear Information System (INIS)

    Dariel, M.P.; Frage, N.R.; Kaputkina, L.M.; Kaputkin, D.M.; Sverdlova, N.R.

    2004-01-01

    Both homogeneous and 'graded' materials were produced by pressing and sintering of titanium carbide TiC x (0.7 x takes place during the joining. If the titanium carbide is carbon deficient that the carbon goes from the steel binder to TiC x , and this redistribution intensity with the x decreases. So-named graded cermets were produced on controlled distribution of TiC x with different x. An additional flow of carbon from C-rich to C-poor TiC x layers was obtained in these cermets. These changes both in the steel and TiC x compositions result in changes in such processes as austenitization, carbide dissolution and precipitation, and martensitic transformation. Both general strength of the material and the gradient of properties in graded cermets can be increased using kinetic factors of element redistribution and structure changes resulted from the heat treatment. (author)

  16. Morphological evolution of primary TiC carbide in laser clad TiC reinforced FeAl intermetallic composite coating

    Institute of Scientific and Technical Information of China (English)

    陈瑶; 王华明

    2003-01-01

    The novel rapidly solidified TiC/FeAl composite coatings were fabricated by laser cladding on the substrate of 1Cr18Ni9Ti stainless steel, particular emphasis has been placed on the growth morphologies of TiC carbide and its growth mechanism under a constant solidification conditions. Results show that the growth morphology of TiC carbide strongly depends upon the nucleation process and mass transportation process of TiC forming elements in laser melt pool. With increasing amount of titanium and carbon in melt pool, the growth morphology of TiC carbide changes from block-like to star-like and well-developed dendrite. As the amount of titanium and carbon increases further, TiC carbide particles are found to be irregular polyhedral block. Although the growth morphologies of TiC are various,their advancing fronts are all faceted, illustrating that TiC carbide grows by the mechanism of lateral ledge growth.

  17. High-speed deposition of titanium carbide coatings by laser-assisted metal–organic CVD

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Yansheng [Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074 (China); Tu, Rong, E-mail: turong@whut.edu.cn [State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Goto, Takashi [Institute for Materials Research, Tohoku University, Aoba-ku, 2-1-1 Katahira, Sendai 980-8577 (Japan)

    2013-08-01

    Graphical abstract: - Highlights: • A semiconductor laser was first used to prepare wide-area LCVD-TiC{sub x} coatings. • The effect of laser power for the deposition of TiC{sub x} coatings was discussed. • TiC{sub x} coatings showed a columnar cross section and a dense surface texture. • TiC{sub x} coatings had a 1–4 order lower laser density than those of previous reports. • This study gives the possibility of LCVD applying on the preparation of TiC{sub x} coating. - Abstract: A semiconductor laser-assisted chemical vapor deposition (LCVD) of titanium carbide (TiC{sub x}) coatings on Al{sub 2}O{sub 3} substrate using tetrakis (diethylamido) titanium (TDEAT) and C{sub 2}H{sub 2} as source materials were investigated. The influences of laser power (P{sub L}) and pre-heating temperature (T{sub pre}) on the microstructure and deposition rate of TiC{sub x} coatings were examined. Single phase of TiC{sub x} coatings were obtained at P{sub L} = 100–200 W. TiC{sub x} coatings had a cauliflower-like surface and columnar cross section. TiC{sub x} coatings in the present study had the highest R{sub dep} (54 μm/h) at a relative low T{sub dep} than those of conventional CVD-TiC{sub x} coatings. The highest volume deposition rate (V{sub dep}) of TiC{sub x} coatings was about 4.7 × 10{sup −12} m{sup 3} s{sup −1}, which had 3–10{sup 5} times larger deposition area and 1–4 order lower laser density than those of previous LCVD using CO{sub 2}, Nd:YAG and argon ion laser.

  18. Chemical, mechanical, and tribological properties of pulsed-laser-deposited titanium carbide and vanadium carbide

    International Nuclear Information System (INIS)

    Krzanowski, J.E.; Leuchtner, R.E.

    1997-01-01

    The chemical, mechanical, and tribological properties of pulsed-laser-deposited TiC and VC films are reported in this paper. Films were deposited by ablating carbide targets using a KrF (λ = 248 nm) laser. Chemical analysis of the films by XPS revealed oxygen was the major impurity; the lowest oxygen concentration obtained in a film was 5 atom%. Oxygen was located primarily on the carbon sublattice of the TiC structure. The films were always substoichiometric, as expected, and the carbon in the films was identified primarily as carbidic carbon. Nanoindentation hardness tests gave values of 39 GPa for TiC and 26 GPa for VC. The friction coefficient for the TiC films was 0.22, while the VC film exhibited rapid material transfer from the steel ball to the substrate resulting in steel-on-steel tribological behavior

  19. Vaporization study on nonstoichiometric NbOsub(2+-x) by mass-spectrometric method

    International Nuclear Information System (INIS)

    Matsui, T.; Naito, K.

    1981-01-01

    The vapor pressures over nonstoichiometric NbOsub(2+-x)(s) (1.972 2 (g) and NbO(g) over nonstoichiometric NbOsub(2+-x), from which the partial molar enthalpies and entropies of oxygen were calculated as a function of O/Nb composition. The composition dependence of the partial molar enthalpy and entropy obtained suggested the existence of some kind of short-range ordering in the nonstoichiometric Nbsub(2+-x) (s) phase. The enthalpies of formation of nonstoichiometric NbOsub(2+-x) (s) were also determined as a function of composition by combining the partial molar enthalpies of oxygen with the enthalpy of formation of stoichiometric NbOsub(2.000) (s). The phase diagram around NbOsub(2+-x) at high temperatures was determined from the vaporization study. (orig.)

  20. Kinetic study of synthesis of Titanium carbide by methano thermal reduction of Titanium dioxide

    International Nuclear Information System (INIS)

    Alizadeh, R.; Ostrovski, O.

    2011-01-01

    Reduction of the Titanium dioxide, TiO 2 , by methane was investigated in this work. The thermodynamic of reaction was examined and found favorable. The reaction of titanium dioxide with methane was carried out in the temperature range 1150 d egree C to 1450 d egree C at atmospheric pressure with industrial high porosity pellets prepared from titanium dioxide powder. The evolved gas analyzing method was used for determination of the extent of reduction rate. The gas products of the reaction are mostly CO and trace amount of CO 2 and H 2 O. The synthesized product powder was characterized by X-ray diffraction for elucidating solid phase compositions. The effect of varying temperature was studied during the reduction. The conversion-time data have been interpreted by using the grain model. For first order reaction with respect to methane concentration, the activation energy of titanium dioxide reduction by methane is found to be 51.4 kcal/g mole. No detailed investigation of kinetic and mechanism of the reaction was reported in literatures.

  1. Self-propagating high-temperature synthesis of nonstoichiometric wuestite

    Energy Technology Data Exchange (ETDEWEB)

    Hiramoto, Maki [Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Okinaka, Noriyuki [Center for Advanced Research of Energy and Materials, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Akiyama, Tomohiro, E-mail: takiyama@eng.hokudai.ac.jp [Center for Advanced Research of Energy and Materials, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer The manuscript describes an SHS method of producing Fe{sub x}O. Black-Right-Pointing-Pointer Focus on the effects of nonstoichiometric Fe content and diluent addition on the phase of the SHS product. Black-Right-Pointing-Pointer Without the NaCl diluent, the lattice parameter of SHS Fe{sub 0.947}O corresponded to the theoretical lattice parameter. Black-Right-Pointing-Pointer Nonstoichiometric compounds of Fe{sub x}O (0.942 {<=} x {<=} 0.952) were obtained through SHS without additional external heating. - Abstract: This paper describes the self-propagating high-temperature synthesis (SHS) of nonstoichiometric Fe{sub x}O (x = 0.833-1), with particular focus on the effects of nonstoichiometric Fe content and diluent addition on the phase of the SHS product. In the SHS process, the raw materials Fe, NaClO{sub 4} (oxidizer), and NaCl (diluent) were thoroughly mixed in the desired ratio by ball milling, and the lower surfaces of the disk-shaped green compacts were subsequently electrically ignited to produce Fe{sub x}O through the propagation of the sustainable exothermic reaction. X-ray diffraction analysis showed that the SHS products comprised double phases of Fe{sub x}O and Fe{sub 3}O{sub 4}. The peaks of products with 0.947 {<=} x {<=} 1.00 shifted to lower angles in comparison to those of the product with x = 0.833 attributed to the lattice parameter distortion of the crystal structure because of the Fe defects. In the presence of the NaCl diluent, the raw materials were converted to high-purity Fe{sub x}O powders during the SHS process. Without the NaCl diluent, the lattice parameter of SHS Fe{sub 0.947}O corresponded to the theoretical lattice parameter. Nonstoichiometric compounds of Fe{sub x}O (0.942 {<=} x {<=} 0.952) were obtained through SHS without additional external heating.

  2. Laser deposition of carbide-reinforced coatings

    International Nuclear Information System (INIS)

    Cerri, W.; Martinella, R.; Mor, G.P.; Bianchi, P.; D'Angelo, D.

    1991-01-01

    CO 2 laser cladding with blown powder presents many advantages: fusion bonding with the substrate with low dilution, metallurgical continuity in the metallic matrix, high solidification rates, ease of automation, and reduced environmental contamination. In the present paper, laser cladding experimental results using families of carbides (tungsten and titanium) mixed with metallic alloys are reported. As substrates, low alloy construction steel (AISI 4140) (austenitic stainless steel) samples have been utilized, depending on the particular carbide reinforcement application. The coating layers obtained have been characterized by metallurgical examination. They show low dilution, absence of cracks, and high abrasion resistance. The WC samples, obtained with different carbide sizes and percentages, have been characterized with dry and rubber wheel abrasion tests and the specimen behaviour has been compared with the behaviour of materials used for similar applications. The abrasion resistance proved to be better than that of other widely used hardfacing materials and the powder morphology have a non-negligible influence on the tribological properties. (orig.)

  3. Supported molybdenum carbide for higher alcohol synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Christensen, Jakob Munkholt; Chiarello, Gian Luca

    2013-01-01

    Molybdenum carbide supported on active carbon, carbon nanotubes, and titanium dioxide, and promoted by K2CO3, has been prepared and tested for methanol and higher alcohol synthesis from syngas. At optimal conditions, the activity and selectivity to alcohols (methanol and higher alcohols) over...... carbide, while the selectivity to methanol follows the opposite trend. The effect of Mo2C loading on the alcohol selectivity at a fixed K/Mo molar ratio of 0.14 could be related to the amount of K2CO3 actually on the active Mo2C phase and the size, structure and composition of the supported carbide...... alcohols is obtained at a K/Mo molar ratio of 0.21 over the active carbon supported Mo2C (20wt%)....

  4. Neutron diffraction study of the formation of ordered antiphase domains in cubic titanium carbide TiC0.60

    International Nuclear Information System (INIS)

    Khidirov, I.; Parpiev, A. S.

    2013-01-01

    A series of superstructural reflections (described within the sp. gr. Fd3m) are found to be split into three symmetric parts in the neutron powder diffraction pattern of titanium carbide TiC 0.60 annealed at a temperature of 600°C. No splitting of superstructural reflections is observed in the neutron diffraction pattern of TiC 0.60 annealed at relatively high temperatures (780°C). This phenomenon can be explained by that fact that the ordering of carbon atoms at relatively high temperatures (780°C) is accompanied by the formation of randomly oriented rather large antiphase domains (APDs) (450 Å). At relatively low temperatures (600°C), stacking faults arise in the arrangement of partially ordered carbon atoms. In this case, relatively small ordered APDs (290 Å) are formed, along with disordered ones.

  5. Hydrogen chemisorption and oxidation of transition metal carbides

    International Nuclear Information System (INIS)

    Bethin, J.R.

    1979-01-01

    A study was made of the catalytic activity of WC, focusing on the possible influence of point defects. The chemisorption of H on WC and titanium oxycarbides was studied with differential scanning calorimetry. The catalytic activity of these materials for oxidation of H was determined by potentiostatic steady-state and potentiodynamic measurements in acid electrolyte. Compositions of WC surfaces were determined by x-ray photoemission and related to the catalytic behavior. Titanium oxycarbide surfaces were analyzed by Auger electron spectroscopy. Of the carbides tested only one WC preparation was able to chemisorb H. Both WC powders investigated catalyzed H oxidation with similar specific activities. Spectroscopic studies showed that the active surface of WC was a mixture of WO 3 and a carbon-deficient WC phase. This result indicates that carbon vacancies are the active sites in tungsten carbide. Theoretical models of a carbon vacancy surrounded by metal atoms suggested by calculations by other workers support this assignment and identify the important role of the W6s level. The measured value of the heat of chemisorption is consistent with the proposed model

  6. Multilayered and composite PVD-CVD coatings in cemented carbides manufacture

    International Nuclear Information System (INIS)

    Glushkov, V.N.; Anikeev, A.I.; Anikin, V.N.; Vereshchaka, A.S.

    2001-01-01

    Carbide cutting tools with wear-resistant coatings deposited by CVD process are widely employed in mechanical engineering to ensure a substantially longer service life of tool systems. However, the relatively high temperature and long time of the process make the substrate decarburise and, as a result, the bend strength and performance characteristics of a tool decrease. The present study suggests the problem of deteriorated strength of CVD-coated carbide tools be solved by the development of a technology that combines arc-PVD and CVD processes to deposit multilayered coatings of titanium and aluminium compounds. (author)

  7. High temperature synthesis of ceramic composition by directed reaction of molten titanium or zirconium with boron carbide

    International Nuclear Information System (INIS)

    Johnson, W.B.

    1990-01-01

    Alternative methods of producing ceramics and ceramic composites include sintering, hot pressing and more recently hot isostatic pressing (HIP) and self-propagating high temperature synthesis (SHS). Though each of these techniques has its advantages, each suffers from several restrictions as well. Sintering may require long times at high temperatures and for most materials requires sintering aids to get full density. These additives can, and generally do, change (often degrade) the properties of the ceramic. Hot pressing and hot isostatic pressing are convenient methods to quickly prepare samples of some materials to full density, but generally are expensive and may damage some types of reinforcements during densification. This paper focuses on the preparation and processing of composites prepared by the directed reaction of molten titanium or zirconium with boron carbide. Advantages and disadvantages of this approach when compared to traditional methods are discussed, with reference to specific examples. Examples of microstructure are properties of these materials are reported

  8. Characterization of Transition Metal Carbide Layers Synthesized by Thermo-reactive Diffusion Processes

    DEFF Research Database (Denmark)

    Laursen, Mads Brink; Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin

    2015-01-01

    . In this study halide-activated pack cementation techniques were used on tool steel Vanadis 6 and martensitic stainless steel AISI 420 in order to produce hard layers of titanium carbide (TiC), vanadium carbide (V8C7) and chromium carbides (Cr23C6 and Cr7C3). Surface layers were characterized by scanning......Hard wear resistant surface layers of transition metal carbides can be produced by thermo-reactive diffusion processes where interstitial elements from a steel substrate together with external sources of transition metals (Ti, V, Cr etc.) form hard carbide and/or nitride layers at the steel surface...... electron microscopy, X-ray diffraction and Vickers hardness testing. The study shows that porosityfree, homogenous and very hard surface layers can be produced by thermo-reactive diffusion processes. The carbon availability of the substrate influences thickness of obtained layers, as Vanadis 6 tool steel...

  9. Study on Microstructures and Mechanical Properties of Foam Titanium Carbide Ceramics Fabricated by Reaction Sintering Process

    Science.gov (United States)

    Ma, Yana; Bao, Chonggao; Chen, Jie; Song, Suocheng; Han, Longhao

    2018-05-01

    Foam titanium carbide (TiC) ceramics with a three-dimensional network structure were fabricated by the reaction sintering process, in which polyurethane foam was taken as the template, and TiO2 and phenolic resin were used as the reactants. Phase, microstructures and fracture morphologies of foam TiC ceramics were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that when the mass ratios of phenolic resin and TiO2 (F/T) are (0.8-1.2): 1, foam TiC ceramics with pure TiC phase can be formed. As the F/T ratios increase, crystal lattice parameters of fabricated foam TiC ceramics become bigger. When the value of F/T decreases from 1.2 to 0.8, grain size of TiC grows larger and microstructures get denser; meanwhile, the compressive strength increases from 0.10 to 1.05 MPa. Additionally, either raising the sintering temperatures or extending holding time can facilitate the completion of the reaction process and increase the compressive strength.

  10. Synthesis of carbides of refractory metals in salt melts

    International Nuclear Information System (INIS)

    Ilyushchenko, N.G.; Anfinogenov, A.I.; Chebykin, V.V.; Chernov, Ya.B.; Shurov, N.I.; Ryaposov, Yu.A.; Dobrynin, A.I.; Gorshkov, A.V.; Chub, A.V.

    2003-01-01

    The ion-electron melts, obtained through dissolving the alkali and alkali-earth metals in the molten chlorides above the chloride melting temperature, were used for manufacturing the high-melting metal carbides as the transport melt. The lithium, calcium and magnesium chlorides and the mixture of the lithium chloride with the potassium or calcium chloride were used from the alkali or alkali-earth metals. The metallic lithium, calcium, magnesium or the calcium-magnesium mixtures were used as the alkali or alkali-earth metals. The carbon black or sugar was used as carbon. It is shown, that lithium, magnesium or calcium in the molten salts transfer the carbon on the niobium, tantalum, titanium, forming the carbides of the above metals. The high-melting metal carbides are obtained both from the metal pure powders and from the oxides and chlorides [ru

  11. Study of PVD AlCrN Coating for Reducing Carbide Cutting Tool Deterioration in the Machining of Titanium Alloys.

    Science.gov (United States)

    Cadena, Natalia L; Cue-Sampedro, Rodrigo; Siller, Héctor R; Arizmendi-Morquecho, Ana M; Rivera-Solorio, Carlos I; Di-Nardo, Santiago

    2013-05-24

    The manufacture of medical and aerospace components made of titanium alloys and other difficult-to-cut materials requires the parallel development of high performance cutting tools coated with materials capable of enhanced tribological and resistance properties. In this matter, a thin nanocomposite film made out of AlCrN (aluminum-chromium-nitride) was studied in this research, showing experimental work in the deposition process and its characterization. A heat-treated monolayer coating, competitive with other coatings in the machining of titanium alloys, was analyzed. Different analysis and characterizations were performed on the manufactured coating by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDXS), and X-ray diffraction (XRD). Furthermore, the mechanical behavior of the coating was evaluated through hardness test and tribology with pin-on-disk to quantify friction coefficient and wear rate. Finally, machinability tests using coated tungsten carbide cutting tools were executed in order to determine its performance through wear resistance, which is a key issue of cutting tools in high-end cutting at elevated temperatures. It was demonstrated that the specimen (with lower friction coefficient than previous research) is more efficient in machinability tests in Ti6Al4V alloys. Furthermore, the heat-treated monolayer coating presented better performance in comparison with a conventional monolayer of AlCrN coating.

  12. Fluorine-free preparation of titanium carbide MXene quantum dots with high near-infrared photothermal performances for cancer therapy.

    Science.gov (United States)

    Yu, Xinghua; Cai, Xingke; Cui, Haodong; Lee, Seung-Wuk; Yu, Xue-Feng; Liu, Bilu

    2017-11-23

    Titanium carbide MXene quantum dots (QDs) were synthesized using an effective fluorine-free method as a biocompatible and highly efficient nanoagent for photothermal therapy (PTT) applications. In contrast to the traditional, hazardous and time-consuming process of HF pretreatment, our fluorine-free method is safe and simple. More importantly, abundant Al oxoanions were found to be modified on the MXene QD surface by the fluorine-free method, which endowed the QDs with strong and broad absorption in the NIR region. As a result, the as-prepared MXene QDs exhibited an extinction coefficient as large as 52.8 Lg -1 cm -1 at 808 nm and a photothermal conversion efficiency as high as 52.2%. Both the values are among the best reported so far. The as-prepared MXene QDs achieved simultaneous photoacoustic (PA) imaging and the remarkable PTT effect of tumors. Moreover, MXene QDs showed great biocompatibility without causing noticeable toxicity in vitro and in vivo, indicating their high potential for clinical applications.

  13. Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

    Directory of Open Access Journals (Sweden)

    Doris E. Braun

    2018-02-01

    Full Text Available The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis, gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations. Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (dehydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules and (form III differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products.

  14. Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

    Science.gov (United States)

    Braun, Doris E.; Griesser, Ulrich J.

    2018-01-01

    The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and (form III) differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products. PMID:29520359

  15. Anodic oxidation of commercially pure titanium for purification of polluted water

    Science.gov (United States)

    Benkafada, Faouzia; Kerdoud, Djahida; Bouchoucha, Ali

    2018-05-01

    Anodisation of pure titanium has been carried out in sulphuric acid solution at potentials ranging from 40 V to 5 days. We studied the parameters influencing the anodic deposition such as acid concentration and anodic periods. Anodic oxides thin films were characterized by X-ray diffraction, cyclic polarization and electrochemical impedance spectroscopy. The I-V curves and electrochemical impedance measurements were carried out in 0.1 N NaOH solution. The results indicated that although the thin films obtained by anodic oxidation are nonstoichiometric, they have an electric behaviour like n-type semiconducting material.

  16. Characterizing the Effect of Laser Power on Laser Metal Deposited Titanium Alloy and Boron Carbide

    Science.gov (United States)

    Akinlabi, E. T.; Erinosho, M. F.

    2017-11-01

    Titanium alloy has gained acceptance in the aerospace, marine, chemical, and other related industries due to its excellent combination of mechanical and corrosion properties. In order to augment its properties, a hard ceramic, boron carbide has been laser cladded with it at varying laser powers between 0.8 and 2.4 kW. This paper presents the effect of laser power on the laser deposited Ti6Al4V-B4C composites through the evolving microstructures and microhardness. The microstructures of the composites exhibit the formation of α-Ti phase and β-Ti phase and were elongated towards the heat affected zone. These phases were terminated at the fusion zone and globular microstructures were found growing epitaxially just immediately after the fusion zone. Good bondings were formed in all the deposited composites. Sample A1 deposited at a laser power of 0.8 kW and scanning speed of 1 m/min exhibits the highest hardness of HV 432 ± 27, while sample A4 deposited at a laser power of 2.0 kW and scanning speed of 1 m/min displays the lowest hardness of HV 360 ± 18. From the hardness results obtained, ceramic B4C has improved the mechanical properties of the primary alloy.

  17. Reaction of uranium and plutonium carbides with austenitic steels

    International Nuclear Information System (INIS)

    Mouchnino, M.

    1967-01-01

    The reaction of uranium and plutonium carbides with austenitic steels has been studied between 650 and 1050 deg. C using UC, steel and (UPu)C, steel diffusion couples. The steels are of the type CN 18.10 with or without addition of molybdenum. The carbides used are hyper-stoichiometric. Tests were also carried out with UCTi, UCMo, UPuCTi and UPuCMo. Up to 800 deg. C no marked diffusion of carbon into stainless steel is observed. Between 800 and 900 deg. C the carbon produced by the decomposition of the higher carbides diffuses into the steel. Above 900 deg. C, decomposition of the monocarbide occurs according to a reaction which can be written schematically as: (U,PuC) + (Fe,Ni,Cr) → (U,Pu) Fe 2 + Cr 23 C 6 . Above 950 deg. C the behaviour of UPuCMo and that of the titanium (CN 18.12) and nickel (NC 38. 18) steels is observed to be very satisfactory. (author) [fr

  18. Dilatometry of nonstoichiometric titanium carbide in the range of order-disorder phase transformation

    International Nuclear Information System (INIS)

    Karpov, A.V.; Kobyakov, V.P.; Chernomorskaya, E.A.

    1995-01-01

    Method of dilatometry was used for investigation of TiC x (0.49 x in ordered and disordered states, as well as on transformation heat were obtained. Increase of bond strength in result of carbon atom ordering in carbon sublattice was noted. 14 refs., 6 figs

  19. Interaction of titanium and vanadium with carbon dioxide under heating

    International Nuclear Information System (INIS)

    Vlasyuk, R.Z.; Kurovskij, V.Ya.; Lyapunov, V.P.; Radomysel'skij, I.D.

    1986-01-01

    The methods of gravitmetric and X-ray phase analysis as well as analysis of composition of gases in the heating chamber have been used to investigate the mechanism of titanium and vanadium interaction with carbon dioxide in the 300-1000 deg C temperature range. The analogy of mechanisms of the interaction of titanium and vanadium with carbon dioxide in oxides production on the metal surface with subsequent carbidizing treatment at temperatures above 800 deg C is shown. Temperature limits of material operation on the base of titanium or vanadium in carbon dioxide must not exceed 400 or 600 deg C, respectively

  20. Electrochemical deposition of carbon films on titanium in molten LiCl–KCl–K2CO3

    International Nuclear Information System (INIS)

    Song, Qiushi; Xu, Qian; Wang, Yang; Shang, Xujing; Li, Zaiyuan

    2012-01-01

    Electrodeposition of carbon films on the oxide-scale-coated titanium has been performed in a LiCl–KCl–K 2 CO 3 melt, which are characterized by scanning electron microscopy, Raman spectroscopy and X-ray diffraction analysis. The electrochemical process of carbon deposition is investigated by cyclic voltammetry on the graphite, titanium and oxide-scale-coated titanium electrodes. The particle-size-gradient carbon films over the oxide-scale-coated titanium can be achieved by electrodeposition under the controlled potentials for avoiding codeposition of lithium carbide. The deposited carbon films are comprised of micron-sized ‘quasi-spherical’ carbon particles with graphitized and amorphous phases. The cyclic voltammetry behavior on the graphite, titanium and oxide-scale-coated titanium electrodes shows that CO 3 2− ions are reduced most favorably on the graphite for the three electrodes. Lithium ions can discharge under the less negative potential on the electrode containing carbon compared with titanium electrode because of the formation of lithium carbide from the reaction between lithium and carbon. - Highlights: ► Carbon films are prepared on oxide-scale-coated titanium in a LiCl–KCl–K 2 CO 3 melt. ► The films comprise micron-size ‘quasi-spherical’ carbon particles. ► The films present particle-size-gradient. ► The particles contain graphitized and amorphous phases. ► The prepared carbon films are more electrochemically active than graphite.

  1. First-principles study of hydrogen storage in non-stoichiometric TiCx

    International Nuclear Information System (INIS)

    Ding, Haimin; Fan, Xiaoliang; Li, Chunyan; Liu, Xiangfa; Jiang, Dong; Wang, Chunyang

    2013-01-01

    Highlights: ► The absorption of hydrogen in non-stoichiometric TiC x is thermally favorable. ► As many as four hydrogen atoms can be trapped by a carbon vacancy. ► The diffusion of hydrogen in TiC x is difficult, especially in TiC x with high x. - Abstract: In this work, the first principles calculation has been performed to study the hydrogen storage in non-stoichiometric TiC x . It is found that hydrogen absorption in stoichiometric TiC is energetically unfavorable, while it is favorable in non-stoichiometric TiC x . This indicates that the existence of carbon vacancies is essential for hydrogenation storage in TiC x . At the same time, multiple hydrogen occupancy of the vacancy has been confirmed and it is calculated that as many as four hydrogen atoms can be trapped by a carbon vacancy. These absorbed hydrogen atoms tend to uniformly distribute around the vacancy. However, it is also found that the diffusion of hydrogen atoms in TiC x is difficult, especially in TiC x with high x.

  2. Kinetics of growing the disordered antiphase domains in titanium carbohydride TiC0.50H0.21

    International Nuclear Information System (INIS)

    Khidirov, I.; Sotvoldiev, D.I.

    2010-01-01

    For establishing formation and growth laws of the disordered nanostructures (the antiphase domains) in the nonstoichiometric titanium carbohydride with cubic NaCl type structure we quenched the titanium carbohydride TiC 0.50 H 0.21 from 1000 deg C followed by annealing at 500, 600, 700, 800 deg C with 24 hour ageing. Neutron diffraction patterns were recorded after each annealing temperature. The half-width of the superstructure (111) reflection is shown to decrease with increasing the annealing temperature that testified on the disordered nanostructure size growing with temperature. The sizes of the disordered nanostructure formed at various temperatures and their dependence D = f(T) were determined on the basis of the neutron diffraction data. (authors)

  3. Electronic structure and charge transport in nonstoichiometric tantalum oxide

    Science.gov (United States)

    Perevalov, T. V.; Gritsenko, V. A.; Gismatulin, A. A.; Voronkovskii, V. A.; Gerasimova, A. K.; Aliev, V. Sh; Prosvirin, I. A.

    2018-06-01

    The atomic and electronic structure of nonstoichiometric oxygen-deficient tantalum oxide TaO x<2.5 grown by ion beam sputtering deposition was studied. The TaO x film content was analyzed by x-ray photoelectron spectroscopy and by quantum-chemistry simulation. TaO x is composed of Ta2O5, metallic tantalum clusters and tantalum suboxides. A method for evaluating the stoichiometry parameter of TaO x from the comparison of experimental and theoretical photoelectron valence band spectra is proposed. The charge transport properties of TaO x were experimentally studied and the transport mechanism was quantitatively analyzed with four theoretical dielectric conductivity models. It was found that the charge transport in almost stoichiometric and nonstoichiometric tantalum oxide can be consistently described by the phonon-assisted tunneling between traps.

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

    International Nuclear Information System (INIS)

    Miyoshi, K.; Buckley, D.H.

    1978-04-01

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

  5. Studies on the O-polysaccharide of Escherichia albertii O2 characterized by non-stoichiometric O-acetylation and non-stoichiometric side-chain l-fucosylation.

    Science.gov (United States)

    Naumenko, Olesya I; Zheng, Han; Xiong, Yanwen; Senchenkova, Sof'ya N; Wang, Hong; Shashkov, Alexander S; Li, Qun; Wang, Jianping; Knirel, Yuriy A

    2018-05-22

    An O-polysaccharide was isolated from the lipopolysaccharide of Escherichia albertii O2 and studied by chemical methods and 1D and 2D 1 H and 13 C NMR spectroscopy. The following structure of the O-polysaccharide was established: . The O-polysaccharide is characterized by masked regularity owing to a non-stoichiometric O-acetylation of an l-fucose residue in the main chain and a non-stoichiometric side-chain l-fucosylation of a β-GlcNAc residue. A regular linear polysaccharide was obtained by sequential Smith degradation and alkaline O-deacetylation of the O-polysaccharide. The content of the O-antigen gene cluster of E. albertii O2 was found to be essentially consistent with the O-polysaccharide structure established. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. Characterization of electron beam evaporated carbon films and compound formation on titanium and silicon

    International Nuclear Information System (INIS)

    Luthin, J.; Linsmeier, C.

    2001-01-01

    The formation of carbon-based mixed materials is unavoidable on the plasma-facing components (e.g. first wall and divertor) of fusion devices when carbon is used together with other materials. On the surfaces of these components very different conditions with respect to particle and energy impact occur. To predict the mixed material formation under these conditions the precise knowledge of the fundamental mechanisms governing these interactions is essential. In this paper we present the results of carbon interaction with titanium and silicon, as model substances for metallic and covalent carbides, during thermal treatment. To perform basic studies of the reactions of carbon with different elements, thin carbon films are produced by electron beam evaporation on the different substrates under UHV conditions. All measurements for chemical analysis are performed using X-ray photoelectron spectroscopy (XPS). We discuss first the properties of the deposited carbon films. The carbon films are characterized on inert gold surfaces and are compared to bulk graphite. Annealing of the carbon films up to 970 K leads to a transition from a disordered carbon network into a graphitic structure. Preparation of carbon films at room temperature on titanium or silicon leads to a limited carbide formation at the carbon/substrate interface. Carbon deposited in excess of several monolayers is present in elementary form. Annealing of the samples leads to complete carbidization consuming the available carbon in both cases. Titanium reacts to TiC and additional substoichiometric carbide, silicon forms SiC with exact stoichiometry. (orig.)

  7. Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses

    International Nuclear Information System (INIS)

    Oliveira, Eduardo Spinelli

    2017-01-01

    Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

  8. Synthesis of Novel (Polymer Blend-Titanium Carbide Nanocomposites and Studying their Characterizations for Piezoelectric Applications

    Directory of Open Access Journals (Sweden)

    Ahmed Hashima

    2018-05-01

    Full Text Available Piezoelectric nanocomposites are very important for many applications as a pressure sensors. Fabrication of (polyvinyl alcohol - polyvinyl pyrrolidinone -titanium carbide nanocompos- ites and study their structural, electrical, dielectric and optical properties have been in- vestigated. The effect of adding the TiC nanoparticles on structural, electrical, dielectric and optical properties of polymeric blend has been studied. The results showed that the electrical conductivity of (PVA-PVP-TiC nanocomposites is increasing with the increase of TiC nanoparticles concentrations at room temperature. The FTIR analysis showed there is no interactions between (PVA- PVP polymer blend and TiC nanoparticles. The dielectric studies showed the dielectric constant and dielectric loss of nanocomposites increase with the increase of TiC nanoparticles concentrations and they decrease as frequency increased. The A.C electrical conductivity increases with the increase of TiC nanoparticles concentra- tions and frequency. The results of optical properties showed that the optical absorbance of (PVA- PVP polymer blend increases with the increase of TiC nanoparticles concentrations. The optical constants change with increase in TiC nanoparticles concentrations. The piezo- electric application results of (PVA-PVP-TiC nanocomposites showed that the electrical resistance of (PVA-PVP-TiC nanocomposites decreases with an increase of the pressure which make it is suitable for piezoelectric applications or pressure sensors.

  9. Sintering of nonstoichiometric UO2

    International Nuclear Information System (INIS)

    Susnik, D.; Holc, J.

    1983-01-01

    Activated sintering of UO 2 pellets at 1100 deg C is described. In CO 2 atmosphere is UO 2 is nonstoichiometric and pellets from active UO 2 powders sinter at 900 deg C to high density. At 1100 deg C the final sintered density is practically achieved at heating on sintering temperature. After reduction and cooling in H 2 atmosphere which is followed sintering in CO 2 the structure is identical to the structured UO 2 pellets sintered at high temperature in H 2 . Density of activated sintered UO 2 pellets is stable, even after additional sintering at 1800 deg C. (author)

  10. Nonstoichiometric defects in GaAs and the EL2 bandwagon

    Science.gov (United States)

    Lagowski, J.; Gatos, H. C.

    1985-09-01

    In the present paper, an attempt is made to formulate a common framework for a discussion of nonstoichiometric defects, especially EL2 and dislocations. An outline is provided of the most important settled and unsettled issues, taking into account not only fundamental interests, but also urgent needs in advancing IC technology. Attention is given to stoichiometry-controlled compensation, the expected role of melt stoichiometry in electrical conductivity for the basic atomic disorders, defect equilibria-dislocations and EL2, and current issues pertaining to the identification of EL2. It is concluded that nonstoichiometric defects play a critical role in the electronic properties of GaAs and its electronic applications. Very significant progress has been recently made in learning how to adjust melt stoichiometry in order to maximize its beneficial effects and minimize its detrimental ones.

  11. Thermodynamic Studies of the Phase Relationships of Nonstoichiometric Cerium Oxides at Higher Temperatures

    DEFF Research Database (Denmark)

    Sørensen, Ole Toft

    1976-01-01

    Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater-or-equal, slan......Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater...

  12. Contribution to the study of U-Ti and U-Pu-Ti carbides

    International Nuclear Information System (INIS)

    Milet, C.A.

    1968-01-01

    After having discussed the reasons to use (U,Pu) carbides as fast reactor fuel, we examine the influence of the addition of titanium to these carbides. A preliminary study has been done on the system of U-C-Ti and some properties have been measured such as: density, thermal expansion, electrical resistivity, atmospheric corrosion and compatibility with stainless steel. The systems U-Pu-C-Ti (Pu/U + Pu equal to 15 per cent) and U-C-Ti have been found to be very similar. There exists a two phases region (U,Pu)C + TiC, an eutectic between (U,Pu)C and TiC for approximately 15 at %. The solubilities of U + Pu in TiC and of Ti in (U,Pu)C is less than 1 % at. The addition of titanium does not markedly change thermal expansion coefficients of (U,Pu)C. However the resistance to atmospheric corrosion and compatibility with stainless steel is improved. Thermal conductivity, calculated from electrical resistivity, has increased. On the other side, the density of fissile material is lowered. The combination of (U,Pu)C + TiC seems to be the most promising alloy for application as nuclear fuel. (author) [fr

  13. Prediction of the wear and evolution of cutting tools in a carbide / titanium-aluminum-vanadium machining tribosystem by volumetric tool wear characterization and modeling

    Science.gov (United States)

    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

  14. Quantitative analyses of impurity silicon-carbide (SiC) and high-purity-titanium by neutron activation analyses based on k0-standardization method. Development of irradiation silicon technology in productivity using research reactor (Joint research)

    International Nuclear Information System (INIS)

    Motohashi, Jun; Takahashi, Hiroyuki; Magome, Hirokatsu; Sasajima, Fumio; Tokunaga, Okihiro; Kawasaki, Kozo; Onizawa, Koji; Isshiki, Masahiko

    2009-07-01

    JRR-3 and JRR-4 have been providing neutron-transmutation-doped silicon (NTD-Si) by using the silicon NTD process, which is a method to produce a high quality semiconductor. The domestic supply of NTD-Si is insufficient for the demand, and the market of NTD-Si is significantly growing at present. It is very important to increase achieve the production. To fulfill the requirement, we have been investigating a neutron filter, which is made of high-purity-titanium, for uniform doping. Silicon-carbide (SiC) semiconductor doped with NTD technology is considered suitable for high power devices with superior performances to conventional Si-based devices. We are very interested in the SiC as well. This report presents the results obtained after the impurity contents in the high-purity-titanium and SiC were analyzed by neutron activation analyses (NAA) using k 0 -standardization method. There were 6 and 9 impurity elements detected from the high-purity-titanium and SiC, respectively. Among those Sc from the high-purity-titanium and Fe from SiC were comparatively long half life nuclides. From the viewpoint of exposure in handling them, we need to examine the impurity control of materials. (author)

  15. Synergistic methods for the production of high-strength and low-cost boron carbide

    Science.gov (United States)

    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

  16. Creep behaviour of a casting titanium carbide reinforced AlSi12CuNiMg piston alloy at elevated temperatures; Hochtemperaturkriechverhalten der schmelzmetallurgisch hergestellten dispersionsverstaerkten Kolbenlegierung AlSi12CuNiMg

    Energy Technology Data Exchange (ETDEWEB)

    Michel, S.; Scholz, A. [Zentrum fuer Konstruktionswerkstoffe, TU Darmstadt (Germany); Tonn, B. [Institut fuer Metallurgie, TU Clausthal (Germany); Zak, H.

    2012-03-15

    This paper deals with the creep behaviour of the titanium carbide reinforced AlSi12CuNiMg piston alloy at 350 C and its comparison to the conventional AlSi12Cu4Ni2MgTiZr piston alloy. With only 0,02 vol-% TiC reinforcement the creep strength and creep rupture strength of the AlSi12CuNiMg piston alloy are significantly improved and reach the level of the expensive AlSi12Cu4Ni2MgTiZr alloy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. X-ray photoelectron spectroscopy characterization of high dose carbon-implanted steel and titanium alloys

    Science.gov (United States)

    Viviente, J. L.; García, A.; Alonso, F.; Braceras, I.; Oñate, J. I.

    1999-04-01

    A study has been made of the depth dependence of the atomic fraction and chemical bonding states of AISI 440C martensitic stainless steel and Ti-6Al-4V alloy implanted with 75 keV C + at very high doses (above 10 18 ions cm -2), by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. A Gaussian-like carbon distribution was observed on both materials at the lowest implanted dose. More trapezoidal carbon depth-profiles were found with increasing implanted doses, and a pure carbon layer was observed only on the titanium alloy implanted at the highest dose. The implanted carbon was combined with both base metal and carbon itself to form metallic carbides and graphitic carbon. Furthermore, carbon-enriched carbides were also found by curve fitting the C 1s spectra. The titanium alloy showed a higher carbidic contribution than the steel implanted at the same C + doses. A critical carbon concentrations of about 33 at.% and 23 at.% were measured for the formation of C-C bonds in Ti-6Al-4V and steel samples, respectively. The carbon atoms were bound with metal to form carbidic compounds until these critical concentrations were reached; when this C concentration was exceeded the proportion of C-C bonds increased and resulted in the growth of carbonaceous layers.

  18. Matrix-reinforcement reactivity in P/M titanium matrix composites

    International Nuclear Information System (INIS)

    Amigo, V.; Romero, F.; Salvador, M. D.; Busquets, D.

    2007-01-01

    The high reactivity of titanium and the facility of the same one to form intermetallics makes difficult obtaining composites with this material and brings the need in any case of covering the principal fibres used as reinforcement. To obtain composites of titanium reinforced with ceramic particles ins proposed in this paper, for this reason it turns out to be fundamental to evaluate the reactivity between the matrix and reinforcement. Both titanium nitride and carbide (TiN and TiC) are investigated as materials of low reactivity whereas titanium silicide (TiSi 2 ) is also studied as materials of major reactivity, already stated by the scientific community. This reactivity will be analysed by means of scanning electron microscopy (SEM) there being obtained distribution maps of the elements that allow to establish the possible influence of the sintering temperature and time. Hereby the matrix-reinforcement interactions are optimized to obtain suitable mechanical properties. (Author) 39 refs

  19. Study of the defect structure of ''pure'' and doped nonstoichiometric CeO2. Final report, January 1, 1965--May 31, 1977

    International Nuclear Information System (INIS)

    Blumenthal, R.N.

    1977-11-01

    The defect structure and transport properties of defects in nonstoichiometric oxides was studied based on their electrical and thermodynamic behavior. Similar studies were also made on doped-nonstoichiometric oxides to determine the effect of the ionic radii, valence and concentration of the dopant cation on the nonstoichiometric defect structure and the transport properties of these defects. The thermodynamic and electrical property study on ''pure'' and doped-nonstoichiometric CeO 2 /sub -x/ is reviewed. The combined study of the electrical conductivity, ionic transference, and thermodynamic measurements initiated on CaO-doped CeO 2 as a function of temperature, oxygen pressure and CaO content is discussed. The results of similar measurements on CeO 2 doped with other oxides (e.g., ThO 2 , Ta 2 O 5 , etc.) which have cations with different valences and ionic radii are also discussed. The primary objective of these studies was to determine the effect of ionic radii, valence and concentration of the dopant cation on (1) the nonstoichiometric behavior, (2) the thermodynamic quantities ΔantiH/sub O 2 / and ΔantiS/sub O 2 /, (3) the nonstoichiometric defect structure, (4) the electronic and ionic conductivities, and (5) the mobility of electrons and oxygen vacancies in doped CeO 2 /sub -x/

  20. Microscopic mapping of specific contact resistances and long-term reliability tests on 4H-silicon carbide using sputtered titanium tungsten contacts for high temperature device applications

    Science.gov (United States)

    Lee, S.-K.; Zetterling, C.-M.; Ostling, M.

    2002-07-01

    We report on the microscopic mapping of specific contact resistances (rhoc) and long-term reliability tests using sputtered titanium tungsten (TiW) ohmic contacts to highly doped n-type epilayers of 4H-silicon carbide. The TiW ohmic contacts showed good uniformity with low contact resistivity of 3.3 x10-5 Omega cm2. Microscopic mapping of the rhoc showed that the rhoc had a distribution that decreased from the center to the edge of the wafer. This distribution of the rhoc is caused by variation of the doping concentration of the wafer. Sacrificial oxidation at high temperature partially recovered inductively coupled plasma etch damage. TiW contacts with platinum and gold capping layers have stable specific contact resistance at 500 and 600 degC in a vacuum chamber for 308 h.

  1. Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals.

    Science.gov (United States)

    Lv, Yang-Yang; Zhang, Bin-Bin; Li, Xiao; Pang, Bin; Zhang, Fan; Lin, Da-Jun; Zhou, Jian; Yao, Shu-Hua; Chen, Y B; Zhang, Shan-Tao; Lu, Minghui; Liu, Zhongkai; Chen, Yulin; Chen, Yan-Feng

    2016-05-27

    Recently, the layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~10(5)%), which can be useful for magnetic memory and spintronic devices. However, the underlying mechanisms of the giant magnetoresistance are still under hot debate. Herein, we grew the stoichiometric and non-stoichiometric WTe2 crystals to test the robustness of giant magnetoresistance. The stoichiometric WTe2 crystals have magnetoresistance as large as 3100% at 2 K and 9-Tesla magnetic field. However, only 71% and 13% magnetoresistance in the most non-stoichiometry (WTe1.80) and the highest Mo isovalent substitution samples (W0.7Mo0.3Te2) are observed, respectively. Analysis of the magnetic-field dependent magnetoresistance of non-stoichiometric WTe2 crystals substantiates that both the large electron-hole concentration asymmetry and decreased carrier mobility, induced by non-stoichiometry, synergistically lead to the decreased magnetoresistance. This work sheds more light on the origin of giant magnetoresistance observed in WTe2.

  2. Benzyl Alcohol-Mediated Versatile Method to Fabricate Nonstoichiometric Metal Oxide Nanostructures.

    Science.gov (United States)

    Qamar, Mohammad; Adam, Alaaldin; Azad, Abdul-Majeed; Kim, Yong-Wah

    2017-11-22

    Nanostructured metal oxides with cationic or anionic deficiency find applications in a wide range of technological areas including the energy sector and environment. However, a facile route to prepare such materials in bulk with acceptable reproducibility is still lacking; many synthesis techniques are still only bench-top and cannot be easily scaled-up. Here, we report that the benzyl alcohol (BA)-mediated method is capable of producing a host of nanostructured metal oxides (MO x , where M = Ti, Zn, Ce, Sn, In, Ga, or Fe) with inherent nonstoichiometry. It employs multifunctional BA as a solvent, a reducing agent, and a structure-directing agent. Depending on the oxidation states of metal, elemental or nonstoichiometric oxide forms are obtained. Augmented photoelectrochemical oxidation of water under visible light by some of these nonstoichiometric oxides highlights the versatility of the BA-mediated synthesis protocol.

  3. Properties of titanium-alloyed DLC layers for medical applications

    Science.gov (United States)

    Joska, Ludek; Fojt, Jaroslav; Cvrcek, Ladislav; Brezina, Vitezslav

    2014-01-01

    DLC-type layers offer a good potential for application in medicine, due to their excellent tribological properties, chemical resistance, and bio-inert character. The presented study has verified the possibility of alloying DLC layers with titanium, with coatings containing three levels of titanium concentration prepared. Titanium was present on the surface mainly in the form of oxides. Its increasing concentration led to increased presence of titanium carbide as well. The behavior of the studied systems was stable during exposure in a physiological saline solution. Electrochemical impedance spectra practically did not change with time. Alloying, however, changed the electrochemical behavior of coated systems in a significant way: from inert surface mediating only exchange reactions of the environment in the case of unalloyed DLC layers to a response corresponding rather to a passive surface in the case of alloyed specimens. The effect of DLC layers alloying with titanium was tested by the interaction with a simulated body fluid, during which precipitation of a compound containing calcium and phosphorus - basic components of the bone apatite - occurred on all doped specimens, in contrast to pure DLC. The results of the specimens' surface colonization with cells test proved the positive effect of titanium in the case of specimens with a medium and highest content of this element. PMID:25093457

  4. Microstructure analysis and wear behavior of titanium cermet femoral head with hard TiC layer.

    Science.gov (United States)

    Luo, Yong; Ge, Shirong; Liu, Hongtao; Jin, Zhongmin

    2009-12-11

    Titanium cermet was successfully synthesized and formed a thin gradient titanium carbide coating on the surface of Ti6Al4V alloy by using a novel sequential carburization under high temperature, while the titanium cermet femoral head was produced. The titanium cermet phase and surface topography were characterized with X-ray diffraction (XRD) and backscattered electron imaging (BSE). And then the wear behavior of titanium cermet femoral head was investigated by using CUMT II artificial joint hip simulator. The surface characterization indicates that carbon effectively diffused into the titanium alloys and formed a hard TiC layer on the Ti6Al4V alloys surface with a micro-porous structure. The artificial hip joint experimental results show that titanium cermet femoral head could not only improve the wear resistance of artificial femoral head, but also decrease the wear of UHMWPE joint cup. In addition, the carburized titanium alloy femoral head could effectively control the UHMWPE debris distribution, and increase the size of UHMWPE debris. All of the results suggest that titanium cermet is a prospective femoral head material in artificial joint.

  5. Coulometric titration at low temperatures-nonstoichiometric silver selenide

    OpenAIRE

    Beck, Gesa K.; Janek, Jürgen

    2003-01-01

    A modified coulometric titration technique is described for the investigation of nonstoichiometric phases at low temperatures. It allows to obtain titration curves at temperatures where the conventional coulometric titration technique fails because of too small chemical diffusion coefficients of the mobile component. This method for indirect coulometric titration is applied to silver selenide between -100 and 100 °C. The titration curves are analyzed on the basis of a defect chemical model an...

  6. Formation of microspheres under the action of femtosecond laser radiation on titanium samples in hydrocarbons

    Science.gov (United States)

    Kochuev, D. A.; Khorkov, K. S.; Ivashchenko, A. V.; Prokoshev, V. G.; Arakelian, S. M.

    2018-01-01

    This work describes the original method of laser synthesis of microspheres which contain titanium carbide. The formation of microspheres is carried out by the action of femtosecond laser radiation on the surface of titanium in the reaction medium - the ultimate hydrocarbon. The resulting microspheres have a high surface smoothness, a narrow particle size distribution, an average size of 1-3 μm. They can be used in applications of additive engineering, powder metallurgy as the main raw material, or as an alloying additive.

  7. ENTIRELY AQUEOUS SOLUTION-GEL ROUTE FOR THE PREPARATION OF ZIRCONIUM CARBIDE, HAFNIUM CARBIDE AND THEIR TERNARY CARBIDE POWDERS

    Directory of Open Access Journals (Sweden)

    Zhang Changrui

    2016-07-01

    Full Text Available An entirely aqueous solution-gel route has been developed for the synthesis of zirconium carbide, hafnium carbide and their ternary carbide powders. Zirconium oxychloride (ZrOCl₂.8H₂O, malic acid (MA and ethylene glycol (EG were dissolved in water to form the aqueous zirconium carbide precursor. Afterwards, this aqueous precursor was gelled and transformed into zirconium carbide at a relatively low temperature (1200 °C for achieving an intimate mixing of the intermediate products. Hafnium and the ternary carbide powders were also synthesized via the same aqueous route. All the zirconium, hafnium and ternary carbide powders exhibited a particle size of ∼100 nm.

  8. Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

    Science.gov (United States)

    Latha, S.; Mathew, M. D.; Parameswaran, P.; Nandagopal, M.; Mannan, S. L.

    2011-02-01

    14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.

  9. Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Latha, S. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102 (India); Mathew, M.D., E-mail: mathew@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102 (India); Parameswaran, P.; Nandagopal, M. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102 (India); Mannan, S.L. [National Engineering College, Kovilpatti, Tamil Nadu 628 503 (India)

    2011-02-28

    14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.

  10. Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

    International Nuclear Information System (INIS)

    Latha, S.; Mathew, M.D.; Parameswaran, P.; Nandagopal, M.; Mannan, S.L.

    2011-01-01

    14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.

  11. Cemented carbide cutting tool: Laser processing and thermal stress analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia)]. E-mail: bsyilbas@kfupm.edu.sa; Arif, A.F.M. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia); Karatas, C. [Engineering Faculty, Hacettepe University, Ankara (Turkey); Ahsan, M. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia)

    2007-04-15

    Laser treatment of cemented carbide tool surface consisting of W, C, TiC, TaC is examined and thermal stress developed due to temperature gradients in the laser treated region is predicted numerically. Temperature rise in the substrate material is computed numerically using the Fourier heating model. Experiment is carried out to treat the tool surfaces using a CO{sub 2} laser while SEM, XRD and EDS are carried out for morphological and structural characterization of the treated surface. Laser parameters were selected include the laser output power, duty cycle, assisting gas pressure, scanning speed, and nominal focus setting of the focusing lens. It is found that temperature gradient attains significantly high values below the surface particularly for titanium and tantalum carbides, which in turn, results in high thermal stress generation in this region. SEM examination of laser treated surface and its cross section reveals that crack initiation below the surface occurs and crack extends over the depth of the laser treated region.

  12. Titanium Oxide/Platinum Catalysis: Charge Transfer from a Titanium Oxide Support Controls Activity and Selectivity in Methanol Oxidation on Platinum

    KAUST Repository

    Hervier, Antoine

    2011-11-24

    Platinum films of 1 nm thickness were deposited by electron beam evaporation onto 100 nm thick titanium oxide films (TiOx) with variable oxygen vacancy concentrations and fluorine (F) doping. Methanol oxidation on the platinum films produced formaldehyde, methyl formate, and carbon dioxide. F-doped samples demonstrated significantly higher activity for methanol oxidation when the TiOx was stoichiometric (TiO 2), but lower activity when it was nonstoichiometric (TiO 1.7 and TiO1.9). These results correlate with the chemical behavior of the same types of catalysts in CO oxidation. Fluorine doping of stoichiometric TiO2 also increased selectivity toward partial oxidation of methanol to formaldehyde and methyl formate, but had an opposite effect in the case of nonstoichiometric TiOx. Introduction of oxygen vacancies and fluorine doping both increased the conductivity of the TiO x film. For oxygen vacancies, this occurred by the formation of a conduction channel in the band gap, whereas in the case of fluorine doping, F acted as an n-type donor, forming a conduction channel at the bottom of the conduction band, about 0.5-1.0 eV higher in energy. The higher energy electrons in F-doped stoichiometric TiOx led to higher turnover rates and increased selectivity toward partial oxidation of methanol. This correlation between electronic structure and turnover rate and selectivity indicates that the ability of the support to transfer charges to surface species controls in part the activity and selectivity of the reaction. © 2011 American Chemical Society.

  13. Titanium nitride deposition in titanium implant alloys produced by powder metallurgy

    International Nuclear Information System (INIS)

    Henriques, V.A.R.; Cairo, C.A.A.; Faria, J.; Lemos, T.G.; Galvani, E.T.

    2009-01-01

    Titanium nitride (TiN) is an extremely hard material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve wear resistance. Electron Beam Physical Vapor Deposition (EB-PVD) is a form of deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work are presented results of TiN deposition in targets and substrates of Ti (C.P.) and Ti- 13 Nb- 13 Zr obtained by powder metallurgy. Samples were produced by mixing of hydride metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900°C up to 1400 °C, in vacuum. The deposition was carried out under nitrogen atmosphere. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure, with ideal characteristics for an adequate deposition and adherence. The film layer presented a continuous structure with 15μm. (author)

  14. Investigations on Wear Mechanisms of PVD Coatings on Carbides and Sialons

    Directory of Open Access Journals (Sweden)

    Staszuk M.

    2017-12-01

    Full Text Available The paper presents the results on the wear resistance of PVD coatings on cutting inserts made from sintered carbide and sialon ceramics. The exploitative properties of coatings in technological cutting trials were defined in the paper, which also examined the adhesion of coatings to the substrate, the thickness of the coating, and the microhardness. As a result, it was found that isomorphic coating with AlN-h phase of covalent interatomic bonds exhibits much better adhesion to the sialon substrate than isomorphic coating with titanium nitride TiN. These coatings assure the high wear resistance of the coated tools, and the high adhesion combined with the high microhardness and fine-grained structure assure an increase in the exploitative life of the coated tools. In the case of coatings on substrate made from sintered carbide, there was a significant influence on the properties of the tools coated with them as concerns the existence of the diffusion zone between the substrate and the coating.

  15. Functional group-dependent anchoring effect of titanium carbide-based MXenes for lithium-sulfur batteries: A computational study

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yuming; Zhao, Jingxiang, E-mail: xjz_hmily@163.com

    2017-08-01

    Highlights: • We have studied the anchong effects of two-dimensional Ti{sub 2}CO{sub 2} monolayer for Li-S batteries. • Ti{sub 2}CO{sub 2} monolayer can strongly interact with Li{sub 2}S{sub n} species with moderate binding strength to effectively immobilize the soluble polysulfides. • The intactness of the Li{sub 2}S{sub n} species can be well saved. - Abstract: The large-scale practical application of lithium-sulfur (Li-S) batteries cannot be relized unless the challenge of dissolving of soluble lithium polysulfides (Li{sub 2}S{sub n}) species in electrolytes can be solved. Herein, by means of density functional theory (DFT) computations, we systematically exploited the anchoring effects of various titanium carbide-based MXenes for Li-S batteries. Our results revealed that, due to the attraction between Li ions in Li{sub 2}S{sub n} species and O atoms in Ti{sub 2}CO{sub 2} and Ti{sub 3}C{sub 2}O{sub 2} monolayer, the two Mxenes can strongly interact with Li{sub 2}S{sub n} species with remarkable but not too strong binding strength to effectively immobilize the soluble polysulfides. Especially, the intactness of the Li{sub 2}S{sub n} species can be well saved, although the Li−S bonds are weakened. Therefore, Ti{sub 2}CO{sub 2} and Ti{sub 3}C{sub 2}O{sub 2} monolayers are quite promising anchoring materials with good cycling performances for Li-S batteries.

  16. Irradiation response in titanium modified austenitic stainless steels prepared by rapid solidification processing. Pt. 3. A model for the effect of titanium addition

    Energy Technology Data Exchange (ETDEWEB)

    Imeson, D.; Tong, C.H.; Parker, C.A.; Vander Sande, J.B.; Grant, N.J.; Harling, O.K. (Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Materials Science and Engineering; Massachusetts Inst. of Tech., Cambridge (USA). Nuclear Reactor Lab.)

    1984-05-01

    Titanium carbide precipitation on dislocations during irradiation and recoil-induced particle dissolution are considered. The outline analysis given indicates that complete swelling suppression may occur in favorable conditions due to a counterbalancing of the effective dislocation interstitial bias. The behavior is, however, not stable against a return to normal swelling levels for type 316 steels. A model is presented which may serve as a basis for the interpretation of some aspects of the irradiation response in this system.

  17. Efficiency of two-step solar thermochemical non-stoichiometric redox cycles with heat recovery

    International Nuclear Information System (INIS)

    Lapp, J.; Davidson, J.H.; Lipiński, W.

    2012-01-01

    Improvements in the effectiveness of solid phase heat recovery and in the thermodynamic properties of metal oxides are the most important paths to achieving unprecedented thermal efficiencies of 10% and higher in non-stoichiometric solar redox reactors. In this paper, the impact of solid and gas phase heat recovery on the efficiency of a non-stoichiometric cerium dioxide-based H 2 O/CO 2 splitting cycle realized in a solar-driven reactor are evaluated in a parametric thermodynamic analysis. Application of solid phase heat recovery to the cycling metal oxide allows for lower reduction zone operating temperatures, simplifying reactor design. An optimum temperature for metal oxide reduction results from two competing phenomena as the reduction temperature is increased: increasing re-radiation losses from the reactor aperture and decreasing heat loss due to imperfect solid phase heat recovery. Additionally, solid phase heat recovery increases the efficiency gains made possible by gas phase heat recovery. -- Highlights: ► Both solid and gas phase heat recovery are essential to achieve high thermal efficiency in non-stoichiometric ceria-based solar redox reactors. ► Solid phase heat recovery allows for lower reduction temperatures and increases the gains made possible by gas phase heat recovery. ► The optimum reduction temperature increases with increasing concentration ratio and decreasing solid phase heat recovery effectiveness. ► Even moderate levels of heat recovery dramatically improve reactor efficiency from 3.5% to 16%.

  18. Spectra of soft X-ray excitation potentials of titanium and vanadium compounds with carbon and nitrogen of a variable composition

    International Nuclear Information System (INIS)

    Brytov, I.A.; Bleher, B. Eh.; Neshpor, V.S.

    1979-01-01

    Lsub(3,2) spectra of excitation potentials (SEP) of a soft X-ray radiation of titanium and vanadium carbides and titanium nitrides in their homogeneity range, as well as solid solutions of nitrogen in α-titanium, are studied. The binding energies of electrons of the exciting levels relatively to the Fermi level are determined, adequacy of different quantomechanical calculations is experimentally proved. The observed changes in SEP at the variation of the metalloid concentration are explained by a quantitative transformation model of valent state energetic spectra when metalloid vacancies and connected with them local levels form

  19. Electrochemical studies and growth of apatite on molybdenum doped DLC coatings on titanium alloy β-21S

    International Nuclear Information System (INIS)

    Anandan, C.; Mohan, L.; Babu, P. Dilli

    2014-01-01

    Highlights: • Titanium alloy β21S was coated with Mo doped DLC. • XRD, XPS and micro Raman show that Mo is present in the form of carbide. • Mo doping facilitates apatite growth on DLC during immersion in Hanks’ solution. • Mo doped DLC sample shows better passivation behavior in Hanks’ solution. - Abstract: Titanium alloy β-21S (Ti–15Mo–3Nb–3Al–0.2Si) was coated with molybdenum doped DLC by Plasma-enhanced chemical vapor deposition and sputtering. XRD, XPS and Raman spectroscopy show that Mo is present in the form of carbide in the coating. XPS of samples immersed in Hanks’ solution shows presence of calcium, phosphorous and oxygen in hydroxide/phosphate form on the substrate and Mo-doped DLC. Potentiodynamic polarization studies show that the corrosion resistance and passivation behavior of Mo-doped DLC is better than that of substrate. Electrochemical impedance spectroscopy (EIS) studies show that Mo-doped DLC samples behave like an ideal capacitor in Hanks’ solution

  20. Electrochemical studies and growth of apatite on molybdenum doped DLC coatings on titanium alloy β-21S

    Energy Technology Data Exchange (ETDEWEB)

    Anandan, C., E-mail: canandan@nal.res.in; Mohan, L.; Babu, P. Dilli

    2014-03-01

    Highlights: • Titanium alloy β21S was coated with Mo doped DLC. • XRD, XPS and micro Raman show that Mo is present in the form of carbide. • Mo doping facilitates apatite growth on DLC during immersion in Hanks’ solution. • Mo doped DLC sample shows better passivation behavior in Hanks’ solution. - Abstract: Titanium alloy β-21S (Ti–15Mo–3Nb–3Al–0.2Si) was coated with molybdenum doped DLC by Plasma-enhanced chemical vapor deposition and sputtering. XRD, XPS and Raman spectroscopy show that Mo is present in the form of carbide in the coating. XPS of samples immersed in Hanks’ solution shows presence of calcium, phosphorous and oxygen in hydroxide/phosphate form on the substrate and Mo-doped DLC. Potentiodynamic polarization studies show that the corrosion resistance and passivation behavior of Mo-doped DLC is better than that of substrate. Electrochemical impedance spectroscopy (EIS) studies show that Mo-doped DLC samples behave like an ideal capacitor in Hanks’ solution.

  1. Tungsten carbide and tungsten-molybdenum carbides as automobile exhaust catalysts

    International Nuclear Information System (INIS)

    Leclercq, L.; Daubrege, F.; Gengembre, L.; Leclercq, G.; Prigent, M.

    1987-01-01

    Several catalyst samples of tungsten carbide and W, Mo mixed carbides with different Mo/W atom ratios, have been prepared to test their ability to remove carbon monoxide, nitric oxide and propane from a synthetic exhaust gas simulating automobile emissions. Surface characterization of the catalysts has been performed by X-ray photoelectron spectroscopy (XPS) and selective chemisorption of hydrogen and carbon monoxide. Tungsten carbide exhibits good activity for CO and NO conversion, compared to a standard three-way catalyst based on Pt and Rh. However, this W carbide is ineffective in the oxidation of propane. The Mo,W mixed carbides are markedly different having only a very low activity. 9 refs.; 10 figs.; 5 tabs

  2. Corrosion resistant cemented carbide

    International Nuclear Information System (INIS)

    Hong, J.

    1990-01-01

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

  3. Highly n-Type Titanium Oxide as an Electronically Active Support for Platinum in the Catalytic Oxidation of Carbon Monoxide

    KAUST Repository

    Baker, L. Robert

    2011-08-18

    The role of the oxide-metal interface in determining the activity and selectivity of chemical reactions catalyzed by metal particles on an oxide support is an important topic in science and industry. A proposed mechanism for this strong metal-support interaction is electronic activation of surface adsorbates by charge carriers. Motivated by the goal of using electronic activation to drive nonthermal chemistry, we investigated the ability of the oxide support to mediate charge transfer. We report an approximately 2-fold increase in the turnover rate of catalytic carbon monoxide oxidation on platinum nanoparticles supported on stoichiometric titanium dioxide (TiO2) when the TiO2 is made highly n-type by fluorine (F) doping. However, for nonstoichiometric titanium oxide (TiOX<2) the effect of F on the turnover rate is negligible. Studies of the titanium oxide electronic structure show that the energy of free electrons in the oxide determines the rate of reaction. These results suggest that highly n-type TiO2 electronically activates adsorbed oxygen (O) by electron spillover to form an active O- intermediate. © 2011 American Chemical Society.

  4. On the development of a dual-layered diamond-coated tool for the effective machining of titanium Ti-6Al-4V alloy

    International Nuclear Information System (INIS)

    Srinivasan, Balaji; Rao, Balkrishna C; Ramachandra Rao, M S

    2017-01-01

    This work is focused on the development of a dual-layered diamond-coated tungsten carbide tool for machining titanium Ti-6Al-4V alloy. A hot-filament chemical vapor deposition technique was used to synthesize diamond films on tungsten carbide tools. A boron-doped diamond interlayer was added to a microcrystalline diamond layer in an attempt to improve the interface adhesion strength. The dual-layered diamond-coated tool was employed in machining at cutting speeds in the range of 70 to 150 m min −1 with a lower feed and a lower depth of cut of 0.5 mm rev −1 and 0.5 mm, respectively, to operate in the transition from adhesion- to diffusion-tool-wear and thereby arrive at suitable conditions for enhancing tool life. The proposed tool was then compared, on the basis of performance under real-time cutting conditions, with commercially available microcrystalline diamond, nanocrystalline diamond, titanium nitride and uncoated tungsten carbide tools. The life and surface finish of the proposed dual-layered tool and uncoated tungsten carbide were also investigated in interrupted cutting such as milling. The results of this study show a significant improvement in tool life and finish of Ti-6Al-4V parts machined with the dual-layered diamond-coated tool when compared with its uncoated counterpart. These results pave the way for the use of a low-cost tool, with respect to, polycrystalline diamond for enhancing both tool life and machining productivity in critical sectors fabricating parts out of titanium Ti-6Al-4V alloy. The application of this coating technology can also be extended to the machining of non-ferrous alloys owing to its better adhesion strength. (paper)

  5. Titanium diboride ceramic fiber composites for Hall-Heroult cells

    Science.gov (United States)

    Besmann, T.M.; Lowden, R.A.

    1990-05-29

    An improved cathode structure is described for Hall-Heroult cells for the electrolytic production of aluminum metal. This cathode structure is a preform fiber base material that is infiltrated with electrically conductive titanium diboride using chemical vapor infiltration techniques. The structure exhibits good fracture toughness, and is sufficiently resistant to attack by molten aluminum. Typically, the base can be made from a mat of high purity silicon carbide fibers. Other ceramic or carbon fibers that do not degrade at temperatures below about 1000 C can be used.

  6. DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

    Directory of Open Access Journals (Sweden)

    Madhuri W.

    2017-02-01

    Full Text Available Nonstoichiometric series of Mg0.5−xCuxZn0.5Fe1.9O4−δ where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD. The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 °C and 400 °C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient α decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes.

  7. Micro-supercapacitors from carbide derived carbon (CDC) films on silicon chips

    Science.gov (United States)

    Huang, Peihua; Heon, Min; Pech, David; Brunet, Magali; Taberna, Pierre-Louis; Gogotsi, Yury; Lofland, Samuel; Hettinger, Jeffrey D.; Simon, Patrice

    2013-03-01

    Interdigitated on-chip micro-supercapacitors based on Carbide Derived Carbon (CDC) films were fabricated and tested. A titanium carbide (TiC) film was patterned and treated with chlorine to obtain a TiC derived carbon (TiC-CDC) film, followed by the deposition of two types of current collectors (Ti/Au and Al) using standard micro-fabrication processes. CDC based micro-supercapacitors were electrochemically characterized by cyclic voltammetry and impedance spectroscopy using a 1 M tetraethylammonium tetrafluoroborate, NEt4BF4, in propylene carbonate (PC) electrolyte. A capacitance of 0.78 mF for the device and 1.5 mF cm-2 as the specific capacitance for the footprint of the device was measured for a 2 V potential range at 100 mV s-1. A specific energy of 3.0 mJ cm-2 and a specific power of 84 mW cm-2 were calculated for the devices. These devices provide a pathway for fabricating pure carbon-based micro-supercapacitors by micro-fabrication, and can be used for powering micro-electromechanical systems (MEMS) and electronic devices.

  8. Solid-state interfacial reaction in molybdenum-carbide systems at high temperature-pressure, and its application to bonding technique

    International Nuclear Information System (INIS)

    Horiguchi, Akihiro; Suganuma, Katsuaki; Miyamoto, Yoshinari; Koizumi, Mitsue; Shimada, Masahiko.

    1986-01-01

    Diffusion couples of molybdenum with several carbides, i.e. SiC, B 4 C, TiC, ZrC, HfC and TaC, were heated at various temperatures ranging from 1500 to 1840 deg C under high pressures of 3 GPa and 100 MPa for up to 4 hr. The couples were then examined for the composition of reaction products, the growth rate of reaction layers, interfacial structures, and tensile strength. In case of Mo-transition metal carbides, Mo 2 C layer was mainly formed, so that the carbides, which had supplied carbon, resulted in having the nonstoichiometric composition near the interface. The activation energy for the growth of Mo 2 C layer in Mo-TiC system was 332 kJ/mol, and that in Mo-TaC system was 366 kJ/mol. In Mo-SiC system, Mo 2 C layer, the mixed phase of Mo 2 C and Mo 5 Si 3 , and Mo 5 Si 3 C layer were formed in order from the Mo side. In Mo-B 4 C system, the mixed phase of Mo 2 B and MoB, and Mo 2 BC layer appeared. The decomposed graphite from B 4 C was also observed between B 4 C and Mo 2 BC phase. The activation energy for the growth of total reaction layer in Mo-SiC system was 531 kJ/mol, and that in Mo-B 4 C system was 183 kJ/mol. It can be said that the growth of reaction layers is controlled by diffusion. The orientation of crystals was observed in all reaction products except for Mo 2 BC phase in Mo-B 4 C system and (Mo, Ta) 2 C phase in Mo-TaC system. In HIPed couples, the magnitude of tensile strength was dependent on the difference in thermal expansion coefficient between Mo and carbides. HIPed Mo-TaC couple had the best weldability among the systems examined in the present investigation. (author)

  9. Combined experimental–theoretical study of the optoelectronic properties of non-stoichiometric pyrochlore bismuth titanate

    KAUST Repository

    Noureldine, Dalal; Lardhi, Sheikha F.; Ziani, Ahmed; Harb, Moussab; Cavallo, Luigi; Takanabe, Kazuhiro

    2015-01-01

    A combination of experimental and computational methods was applied to investigate the crystal structure and optoelectronic properties of the non-stoichiometric pyrochlore Bi2−xTi2O7−1.5x. The detailed experimental protocol for both powder and thin

  10. Interaction of titanium and vanadium with carbon dioxide in heating

    International Nuclear Information System (INIS)

    Vlasyuk, R.Z.; Kurovskii, V.Y.; Lyapunov, A.P.; Radomysel'skii, I.D.

    1986-01-01

    To obtain prediction data on the change in properties of titaniumand vanadium-base powder metallurgy materials operating in a carbon dioxide atmosphere, and also to clarify the mechanism of their interaction with the gas in this work, gravimetric investigations of specimens heated at temperatures of 300-1000 C and an x-ray diffraction analysis of their surface were made and the composition of the gas in the heating chamber was studied. The results of the investigations indicate a similarity between the mechanisms of interaction of titanium and vanadium with carbon dioxide including the formation of oxides on the surface of the metal with subsequent carbidization at temperatures above 800 C. On the basis of the data obtained, it may be concluded that the operating temperature limits of titanium- or vanadium-base materials in carbon dioxide must not exceed 400 and 600 C, respectively

  11. Monolithic Carbide-Derived Carbon Films for Micro-Supercapacitors

    Science.gov (United States)

    Chmiola, John; Largeot, Celine; Taberna, Pierre-Louis; Simon, Patrice; Gogotsi, Yury

    2010-04-01

    Microbatteries with dimensions of tens to hundreds of micrometers that are produced by common microfabrication techniques are poised to provide integration of power sources onto electronic devices, but they still suffer from poor cycle lifetime, as well as power and temperature range of operation issues that are alleviated with the use of supercapacitors. There have been a few reports on thin-film and other micro-supercapacitors, but they are either too thin to provide sufficient energy or the technology is not scalable. By etching supercapacitor electrodes into conductive titanium carbide substrates, we demonstrate that monolithic carbon films lead to a volumetric capacity exceeding that of micro- and macroscale supercapacitors reported thus far, by a factor of 2. This study also provides the framework for integration of high-performance micro-supercapacitors onto a variety of devices.

  12. Laser ablation of titanium in liquid in external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Serkov, A.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); The Federal State Educational Institution of Higher Professional Education, “Moscow Institute of Physics and Technology (State University)”, 9 Institutskiy per., 141700, Dolgoprudny, Moscow Region (Russian Federation); Barmina, E.V., E-mail: barminaev@gmail.com [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31, Kashirskoye Highway, 115409 Moscow (Russian Federation); Voronov, V.V. [A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation)

    2015-09-01

    Highlights: • Ablation of a bulk Ti target by 10 ps laser pulses in liquid is experimentally studied in external DC electric field. • Applied cathodic bias leads to increase in average size of self-organized nanostructures formed upon ablation of titanium target. • Laser ablation of Ti target in external electric field results in generation of elongated titanium oxide nanoparticles. - Abstract: Ablation of a bulk Ti target by 10 ps laser pulses in water is experimentally studied in external DC electric field. It is demonstrated that both lateral size of nanostructures (NS) on Ti surface and their density depend on the electric field applied to the target. Scanning Electron Microscopy of NS reveals the shift of their size distribution function toward larger sizes with applied field (cathodic bias, 25 V DC). Density of mushroom-like NS with applied electric field amounts to 10{sup 10} cm{sup −2}. X-ray diffraction of generated nanoparticles (NPs) shows difference in the crystallographic structure of NPs of non-stoichiometric Ti oxides generated with and without electric field. This conclusion is corroborated with the optical absorption spectroscopy of obtained colloids. Transmission Electron Microscopy of NPs also shows difference in morphology of particles produced with and without cathodic bias. The results are interpreted on the basis of instability of the melt on Ti surface in the electric field.

  13. Effect of heat absorbing powder addition on cell morphology of porous titanium composite manufactured by reactive precursor method

    International Nuclear Information System (INIS)

    Kobashi, Makoto; Kamiya, Yoshinori; Kanetake, Naoyuki

    2012-01-01

    Open-cell structured porous titanium/ceramics composite was synthesized by a reactive precursor method using titanium and boron carbide (B 4 C) as reactant powders. Pore morphology was controlled by adding heat absorbing powder (titanium diboride: TiB 2 ) in the Ti+B 4 C blended powder. The effects of molar blending ratio of titanium and B 4 C and the amount of heat absorbing powder addition on the cell morphology (either open or closed) were investigated. Fine and homogeneous open-cell structure was achieved by adding appropriate amount of heat absorbing agent powder (>15 vol%), and the relative density of the specimen after the reaction became closer to that of the precursor by increasing TiB 2 volume fraction. When the volume fraction of TiB 2 addition was 20%, the open-cell fraction was maintained as 1.0 regardless of the relative density of the precursor.

  14. Study of stress relief cracking in titanium stabilized austenitic stainless steel

    International Nuclear Information System (INIS)

    Chabaud-Reytier, M.

    1999-01-01

    The heat affected zone (HAZ) of titanium stabilised austenitic stainless steel welds (AISI 321) may exhibit a serious form of intercrystalline cracking during service at high temperature. This type of cracking, called 'stress relief cracking', is known to be due to work hardening but also to ageing: a fine and abundant intragranular Ti(C,N) precipitation appears near the fusion line and modifies the mechanical behaviour of the HAZ. This study aims to better know the accused mechanism and to succeed in estimating the risk of such cracking in welded junctions of 321 stainless steel. To analyse this embrittlement mechanism, and to assess the lifetime of real components, different HAZ are simulated by heat treatments applied to the base material which is submitted to various cold rolling and ageing conditions in order to reproduce the HAZ microstructure. Then, we study the effects of work hardening and ageing on the titanium carbide precipitation, on the mechanical (tensile and creep) behaviour of the resulting material and on its stress relief cracking sensitivity. It is shown that work hardening is the main parameter of the mechanism and that ageing do not favour crack initiation although it leads to titanium carbide precipitation. The role of this precipitation is also discussed. Moreover, a creep damage model is identified by a local approach to fracture. Materials sensitive to stress relief cracking are selected. Then, creep tests are carried out on notched bars in order to quantify the intergranular damage of these different materials; afterwards, these measurements are combined with calculated mechanical fields. Finally, it is shown that the model gives good results to assess crack initiation for a compact tension (CT) specimen during relaxation tests, as well as for a notched tubular specimen tested at 600 deg. C under a steady torque. (author)

  15. On the composition of nonstoichiometric europium monoxide

    International Nuclear Information System (INIS)

    Ignat'eva, N.I.

    1990-01-01

    Consideration is given to results of of investigation into chemical composition, homogeneity region, type of disordering of nonstoichiometric europium monoxide. Precision methods of X-ray diffraction, electron-microscopic, atomic-absorption chemical analysis were used. It is shown that lattice volume reduces with increase of oxygen content in the oxide. For monocrystal of EuO 1.01 composition a=5.146 A. All samples of europium monoxide are characterized by low conductivity. Conductivity value changes by two orders (from 10 -8 to 10 -6 Θ -1 ·cm -1 ) when passing from the sample of stoichiometric composition to maximally disordered one. The disordering is considered according to the type of charged cation vacancies, leading to occurrence of equivalent number of electron defects of positive holes. 4 refs.; 1 tab

  16. Electrophoretic deposition of magnesium silicates on titanium implants: Ion migration and silicide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Afshar-Mohajer, M. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Yaghoubi, A., E-mail: yaghoubi@siswa.um.edu.my [Center for High Impact Research, University of Malaya, Kuala Lumpur 50603 (Malaysia); Ramesh, S., E-mail: ramesh79@um.edu.my [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Bushroa, A.R.; Chin, K.M.C.; Tin, C.C. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Chiu, W.S. [Low Dimensional Materials Research Center, Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia)

    2014-07-01

    Magnesium silicates (Mg{sub x}SiO{sub y}) and in particular forsterite (Mg{sub 2}SiO{sub 4}) owing to their low thermal expansion mismatch with metals are promising materials for bioactive coating of implants. Here, we report the electrophoretic deposition (EPD) of forsterite onto titanium substrates using different precursors. Unlike bulk samples which achieve full stoichiometry only beyond 1400 °C, non-stoichiometric magnesium silicate rapidly decomposes into magnesium oxide nanowires during sintering. Elemental mapping and X-ray diffraction suggest that oxygen diffusion followed by ion exchange near the substrate leads to formation of an interfacial Ti{sub 5}Si{sub 3} layer. Pre-annealed forsterite powder on the other hand shows a comparatively lower diffusion rate. Overall, magnesium silicate coatings do not exhibit thermally induced microcracks upon sintering as opposed to calcium phosphate bioceramics which are currently in use.

  17. Effect of a defect structure on the static and long-term strength of submicrocrystalline VT1-0 titanium fabricated by plastic deformation during screw and lengthwise rolling

    Czech Academy of Sciences Publication Activity Database

    Betekhtin, V. I.; Kolobov, Yu. R.; Sklenička, Václav; Kadomtsev, A. G.; Narykova, M. V.; Dvořák, Jiří; Golosov, E. V.; Kardashev, B. K.; Kuz'menko, I. N.

    2015-01-01

    Roč. 60, č. 1 (2015), s. 66-71 ISSN 1063-7842 Institutional support: RVO:68081723 Keywords : titanium * nanoporosity * carbide dispersion * thermal stability * severe plastic deformation Subject RIV: JJ - Other Materials Impact factor: 0.569, year: 2015

  18. Fabrication of uranium carbide/beryllium carbide/graphite experimental-fuel-element specimens

    International Nuclear Information System (INIS)

    Muenzer, W.A.

    1978-01-01

    A method has been developed for fabricating uranium carbide/beryllium carbide/graphite fuel-element specimens for reactor-core-meltdown studies. The method involves milling and blending the raw materials and densifying the resulting blend by conventional graphite-die hot-pressing techniques. It can be used to fabricate specimens with good physical integrity and material dispersion, with densities of greater than 90% of the theoretical density, and with a uranium carbide particle size of less than 10 μm

  19. Development and evaluation of two PVD-coated β-titanium orthodontic archwires for fluoride-induced corrosion protection.

    Science.gov (United States)

    Krishnan, Vinod; Krishnan, Anand; Remya, R; Ravikumar, K K; Nair, S Asha; Shibli, S M A; Varma, H K; Sukumaran, K; Kumar, K Jyothindra

    2011-04-01

    The present research was aimed at developing surface coatings on β titanium orthodontic archwires capable of protection against fluoride-induced corrosion. Cathodic arc physical vapor deposition PVD (CA-PVD) and magnetron sputtering were utilized to deposit thin films of titanium aluminium nitride (TiAlN) and tungsten carbide/carbon (WC/C) coatings on β titanium orthodontic archwires. Uncoated and coated specimens were immersed in a high fluoride ion concentration mouth rinse, following a specially designed cycle simulating daily use. All specimens thus obtained were subjected to critical evaluation of parameters such as electrochemical corrosion behaviour, surface analysis, mechanical testing, microstructure, element release, and toxicology. The results confirm previous research that β titanium archwires undergo a degradation process when in contact with fluoride mouth rinses. The study confirmed the superior nature of the TiAlN coating, evident as many fewer changes in properties after fluoride treatment when compared with the WC/C coating. Thus, coating with TiAlN is recommended in order to reduce the corrosive effects of fluorides on β titanium orthodontic archwires. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Preparation of nickel-coated titanium carbide particulates and their use in the production of reinforced iron matrix composites

    International Nuclear Information System (INIS)

    Yi, Danqing; Yu, Pengchao; Hu, Bin; Liu, Huiqun; Wang, Bin; Jiang, Yong

    2013-01-01

    Highlights: • Ni-coated TiC composite powders were prepared by electroless plating. • Iron-based composites reinforced by TiC particles was prepared by HIP. • Mechanical and wear properties were improved with the addition of Ni-coated TiC. • The nickel coating promotes the formation and growth of sintering neck. - Abstract: Ni-coated titanium carbide (TiC) composite powders were prepared by electroless plating (EP). Further, using hot isostatic pressing (HIP), iron matrix composites reinforced with 4 wt% Ni-coated TiC particulates with relative density close to 100% were prepared. The microstructure and phase composition of the Ni-coated powders and the composites were analyzed using X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results showed that the TiC particles were distributed uniformly in the matrix and were free of segregation or coarsening. Compared to the TiC particles without Ni coating, the reinforced iron-based composites containing the Ni-coated particles showed higher relative densities and better mechanical properties. The density, hardness, tensile strength, and elongation were enhanced to 99.98%, 243 HV, 565 MPa, and 11.7%, respectively in composites containing Ni-coated TiC particles from 99.70%, 210 HV, 514 MPa, and 10.3%, respectively in composites that were prepared using particles without Ni coating. In addition, the mass losses in the composites containing the Ni-coated particles were reduced by 32–75% in the abrasive wear test with various vertical loads. We propose that the nickel coatings on the particulates had a beneficial effect on the microstructure and properties of the reinforced iron-based composites is due to promotion of neck formation and growth between TiC and iron powders during sintering, which enhanced the density of the sintered compact and the bonding strength between the TiC particles and the iron matrix

  1. Intermetallic Nickel-Titanium Alloys for Oil-Lubricated Bearing Applications

    Science.gov (United States)

    DellaCorte, C.; Pepper, S. V.; Noebe, R.; Hull, D. R.; Glennon, G.

    2009-01-01

    An intermetallic nickel-titanium alloy, NITINOL 60 (60NiTi), containing 60 wt% nickel and 40 wt% titanium, is shown to be a promising candidate material for oil-lubricated rolling and sliding contact applications such as bearings and gears. NiTi alloys are well known and normally exploited for their shape memory behavior. When properly processed, however, NITINOL 60 exhibits excellent dimensional stability and useful structural properties. Processed via high temperature, high-pressure powder metallurgy techniques or other means, NITINOL 60 offers a broad combination of physical properties that make it unique among bearing materials. NITINOL 60 is hard, electrically conductive, highly corrosion resistant, less dense than steel, readily machined prior to final heat treatment, nongalling and nonmagnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Further, NITINOL 60 has shown remarkable tribological performance when compared to other aerospace bearing alloys under oil-lubricated conditions. Spiral orbit tribometer (SOT) tests were conducted in vacuum using NITINOL 60 balls loaded between rotating 440C stainless steel disks, lubricated with synthetic hydrocarbon oil. Under conditions considered representative of precision bearings, the performance (life and friction) equaled or exceeded that observed with silicon nitride or titanium carbide coated 440C bearing balls. Based upon this preliminary data, it appears that NITINOL 60, despite its high titanium content, is a promising candidate alloy for advanced mechanical systems requiring superior and intrinsic corrosion resistance, electrical conductivity and nonmagnetic behavior under lubricated contacting conditions.

  2. Electronic specific heat of transition metal carbides; Chaleur specifique electronique de carbures de metaux de transition

    Energy Technology Data Exchange (ETDEWEB)

    Conte, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1964-07-15

    The experimental results that make it possible to define the band structure of transition metal carbides having an NaCI structure are still very few. We have measured the electronic specific heat of some of these carbides of varying electronic concentration (TiC, either stoichiometric or non-stoichiometric, TaC and mixed (Ti, Ta) - C). We give the main characteristics (metallography, resistivity, X-rays) of our samples and we describe the low temperature specific heat apparatus which has been built. In one of these we use helium as the exchange gas. The other is set up with a mechanical contact. The two use a germanium probe for thermometer. The measurement of the temperature using this probe is described, as well as the various measurement devices. The results are presented in the form of a rigid band model and show that the density of the states at the Fermi level has a minimum in the neighbourhood of the group IV carbides. (author) [French] Les donnees experimentales permettant de preciser la structure de bandes des carbures de metaux de transition de structure NaCI sont encore peu.nombreuses. Nous avons mesure la chaleur specifique electronique de certains de ces carbures, de differentes concentrations electroniques (TiC stoechiometrique ou non, TaC et mixtes (Ti, Ta) - C). Nous donnons les principales caracteristiques (metallographie, resistivite, rayon X), de nos echantillons, et nous decrivons l'appareillage de chaleur specifique a basse temperature realise. Dans l'un nous utilisons l'helium comme gaz d'echange. L'autre est monte avec un contact mecanique. Les deux utilisent une sonde au germanium comme thermometre. La mesure de la resistance de cette sonde est decrite, ainsi que les differents montages de mesure. Les resultats, presentes dans un modele de bande rigide, font apparaitre que la densite des etats au niveau de Fermi presente un minimum au voisinage des carbures du groupe IV. (auteur)

  3. Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

    Science.gov (United States)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2009-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  4. Ion irradiation of carbides ZrC and TiC. Effects of electronic and nuclear energy losses

    International Nuclear Information System (INIS)

    Pellegrino-Chateau, Stephanie

    2015-01-01

    This study is focused on the ceramic refractory transition metals, such as titanium carbide and zirconium envisaged to their strength characteristics under extreme conditions. These ceramics are subject to various sources of radiation (neutrons, fission products, the alpha decays) in future generation reactors IV high temperature reactor and gas cooled reactor. Radiation encountered in the reactor can be simulated by external irradiation with particle accelerators, using various ions in a wide energy range. These instruments can reproduce in controlled conditions damage suffered by structural nuclear materials. (author) [fr

  5. Porous silicon carbide (SIC) semiconductor device

    Science.gov (United States)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1996-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  6. The machinability of cast titanium and Ti-6Al-4V.

    Science.gov (United States)

    Ohkubo, C; Watanabe, I; Ford, J P; Nakajima, H; Hosoi, T; Okabe, T

    2000-02-01

    This study investigated the machinability (ease of metal removal) of commercially pure (CP) titanium and Ti-6Al-4V alloy. Both CP Ti and Ti-6Al-4V were cast into magnesia molds. Two types of specimens (with alpha-case and without alpha-case) were made for CP Ti and Ti-6Al-4V. Machinability (n = 5) was evaluated as volume loss (mm3) by cutting/grinding the 3.0 mm surface using fissure burs and silicon carbide (SiC) under two machining conditions: (1) two machining forces (100 or 300 gf) at two rotational speeds (15000 or 30000 rpm) for 1 min, and (2) constant machining force of 100 gf and rotational speed of 15000 rpm for 1, 2, 5, 10, and 30 min. As controls, conventionally cast Co-Cr and Type IV gold alloys were evaluated in the same manner as the titanium. When fissure burs were used, there was a significant difference in the machinability between CP titanium with alpha-case and without alpha-case. On the other hand, there was no appreciable difference in the amount of metal removed for each tested metal when using the SiC points.

  7. Modification of the surface of metal products with carbide coatings by electrospark alloying

    Science.gov (United States)

    Koshuro, Vladimir A.; Fomina, Marina A.; Fomin, Aleksandr A.

    2018-04-01

    Electrospark alloying (ESA) technology has existed for a long time (since the middle of the 20th century) but its potential has not been exhausted yet. In the present paper it is proposed to increase the mechanical properties of steel and titanium products by doping with a hard carbide alloy based on "WC-TiC-Co" system. As a result, the hardness of coatings obtained by ESA reaches at least 18-22 GPa with a layer thickness of up to 0.5 mm. The proposed solution can improve the functional qualities of various friction surfaces that are used in engineering, as well as in friction elements.

  8. INTERMEDIATE STAGES OF REACTIONS FORMING CARBIDES OF TITANIUM, ZIRCONIUM, VANADIUM, NIOBIUM, AND TANTALIUM

    Science.gov (United States)

    intermediate and final products, and also during the calculation of approximate heat values of their formation, the passage of the reaction is confirmed...for obtaining TiC, and ZrC through the stage of intermediate oxides Ti2O3, Ti3O5, TiO and Zr2O3, ZrO, respectively and also for the reaction of...forming carbides of V (from V2O3 + 5C), of Nb and Ta (from Nb2O5 + 7C and Ta205 + 7C) through the stage of intermediate oxides VO, V4O and TaO2, Ta4O. The

  9. Joining aluminum to titanium alloy by friction stir lap welding with cutting pin

    International Nuclear Information System (INIS)

    Wei, Yanni; Li, Jinglong; Xiong, Jiangtao; Huang, Fu; Zhang, Fusheng; Raza, Syed Hamid

    2012-01-01

    Aluminum 1060 and titanium alloy Ti–6Al–4V plates were lap joined by friction stir welding. A cutting pin of rotary burr made of tungsten carbide was employed. The microstructures of the joining interface were observed by scanning electron microscopy. Joint strength was evaluated by a tensile shear test. During the welding process, the surface layer of the titanium plate was cut off by the pin, and intensively mixed with aluminum situated on the titanium plate. The microstructures analysis showed that a visible swirl-like mixed region existed at the interface. In this region, the Al metal, Ti metal and the mixed layer of them were all presented. The ultimate tensile shear strength of joint reached 100% of 1060Al that underwent thermal cycle provided by the shoulder. - Highlights: ► FSW with cutting pin was successfully employed to form Al/Ti lap joint. ► Swirl-like structures formed due to mechanical mixing were found at the interface. ► High-strength joints fractured at Al suffered thermal cycle were produced.

  10. Plasma spraying of zirconium carbide – hafnium carbide – tungsten cermets

    Czech Academy of Sciences Publication Activity Database

    Brožek, Vlastimil; Ctibor, Pavel; Cheong, D.-I.; Yang, S.-H.

    2009-01-01

    Roč. 9, č. 1 (2009), s. 49-64 ISSN 1335-8987 Institutional research plan: CEZ:AV0Z20430508 Keywords : Plasma spraying * cermet coatings * microhardness * zirconium carbide * hafnium carbide * tungsten * water stabilized plasma Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  11. Metal Carbides for Biomass Valorization

    Directory of Open Access Journals (Sweden)

    Carine E. Chan-Thaw

    2018-02-01

    Full Text Available Transition metal carbides have been utilized as an alternative catalyst to expensive noble metals for the conversion of biomass. Tungsten and molybdenum carbides have been shown to be effective catalysts for hydrogenation, hydrodeoxygenation and isomerization reactions. The satisfactory activities of these metal carbides and their low costs, compared with noble metals, make them appealing alternatives and worthy of further investigation. In this review, we succinctly describe common synthesis techniques, including temperature-programmed reaction and carbothermal hydrogen reduction, utilized to prepare metal carbides used for biomass transformation. Attention will be focused, successively, on the application of transition metal carbide catalysts in the transformation of first-generation (oils and second-generation (lignocellulose biomass to biofuels and fine chemicals.

  12. Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

    International Nuclear Information System (INIS)

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

    2011-01-01

    The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

  13. Irradiation response in titanium modified austenitic stainless steels prepared by rapid solidification processing. Pt. 3

    International Nuclear Information System (INIS)

    Imeson, D.; Tong, C.H.; Parker, C.A.; Vander Sande, J.B.; Grant, N.J.; Harling, O.K.; Massachusetts Inst. of Tech., Cambridge

    1984-01-01

    Titanium carbide precipitation on dislocations during irradiation and recoil-induced particle dissolution are considered. The outline analysis given indicates that complete swelling suppression may occur in favorable conditions due to a counterbalancing of the effective dislocation interstitial bias. The behavior is, however, not stable against a return to normal swelling levels for type 316 steels. A model is presented which may serve as a basis for the interpretation of some aspects of the irradiation response in this system. (orig.)

  14. Combined experimental–theoretical study of the optoelectronic properties of non-stoichiometric pyrochlore bismuth titanate

    KAUST Repository

    Noureldine, Dalal

    2015-10-27

    A combination of experimental and computational methods was applied to investigate the crystal structure and optoelectronic properties of the non-stoichiometric pyrochlore Bi2−xTi2O7−1.5x. The detailed experimental protocol for both powder and thin-film material synthesis revealed that a non-stoichiometric Bi2−xTi2O7−1.5x structure with an x value of ∼0.25 is the primary product, consistent with the thermodynamic stability of the defect-containing structure computed using density functional theory (DFT). The approach of density functional perturbation theory (DFPT) was used along with the standard GGA PBE functional and the screened Coulomb hybrid HSE06 functional, including spin–orbit coupling, to investigate the electronic structure, the effective electron and hole masses, the dielectric constant, and the absorption coefficient. The calculated values for these properties are in excellent agreement with the measured values, corroborating the overall analysis. This study indicates potential applications of bismuth titanate as a wide-bandgap material, e.g., as a substitute for TiO2 in dye-sensitized solar cells and UV-light-driven photocatalysis.

  15. Superhard PVD carbon films deposited with different gradients with and without additions of titanium and silicon

    International Nuclear Information System (INIS)

    Bauer, C.

    2003-10-01

    This work focusses on thin carbon-based films, deposited by magnetron sputtering with additional argon ion bombardment (0 eV to 800 eV) without extra adhesive layer on hard metal inserts. As one possibility of increasing the reduced adherence of hard carbon films the deposition of films with additions of titanium and silicon is studied. The aim of this work is to examine the influence of a modification of the transition between substrate and film by realizing three different types of deposition gradients. The pure carbon films are amorphous, the dominant network of atoms is formed by sp 2 bonded atoms. The amount of sp 3 bonded atoms is up to 30% and is influenced by the bombarding argon ion energy. Carbon films with additions of silicon are amorphous, only in films with a high amount of titanium (approx. 20 at%) nanocomposites of titanium carbide crystals with diameters of less than 5 nm in an amorphous carbon matrix were found. The mechanical properties and the behavior of single layer carbon films strongly depend on the argon ion energy. An increase of this energy leads to higher film hardness and higher residual stress and results in the delamination of superhard carbon films on hard metal substrates. The adhesion of single layer films for ion energies of more than 200 eV is significantly improved by additions of titanium and silicon, respectively. The addition of 23 at% silicon and titanium, respectively leads to a high reduction of the residual stress. In a non-reactive PVD process thin films were deposited with a continuously gradient in chemical composition. The results of the investigations of the films with two different concentrations of titanium and silicon, respectively show that carbon-based films with a good adhesion could be deposited. The combination of the two gradients in structure and properties and in chemical composition leads in the system with carbon and silicon carbide to hard and very adhesive films. Especially for carbon films with a high

  16. Dispersion toughened ceramic composites and method for making same

    Science.gov (United States)

    Stinton, D.P.; Lackey, W.J.; Lauf, R.J.

    1984-09-28

    Ceramic composites exhibiting increased fracture toughness are produced by the simultaneous codeposition of silicon carbide and titanium disilicide by chemical vapor deposition. A mixture of hydrogen, methyltrichlorosilane and titanium tetrachloride is introduced into a furnace containing a substrate such as graphite or silicon carbide. The thermal decomposition of the methyltrichlorosilane provides a silicon carbide matrix phase and the decomposition of the titanium tetrachloride provides a uniformly dispersed second phase of the intermetallic titanium disilicide within the matrix phase. The fracture toughness of the ceramic composite is in the range of about 6.5 to 7.0 MPa..sqrt..m which represents a significant increase over that of silicon carbide.

  17. How does the composition of quasi-stoichiometric titanium diboride affect its wetting by molten Cu and Au?

    International Nuclear Information System (INIS)

    Aizenshtein, M.; Froumin, N.; Barth, P.; Shapiro-Tsoref, E.; Dariel, M.P.; Frage, N.

    2007-01-01

    The poor wetting in non-oxide ceramic/metal (M = Au or Cu) systems is usually attributed to the lack of chemical interaction at the solid/liquid interface. In contrast, sessile drop experiments on two non-stoichiometric titanium diboride substrates (TiB 1.9 and TiB 1.95 ) displayed a surprisingly good wetting. The experimental results are well accounted for by the thermodynamic analysis of the Me-Ti-B systems. According to this analysis, some limited boride dissolution and altering of the substrate composition takes place at the TiB x /Me interface. These changes are more substantial, the stronger the departure from stoichiometry of the initial substrate composition. Minor composition changes are sufficient for improving wetting. Based on the results of the thermodynamic analysis and the wetting experiments, a novel method for the fabrication of Cu infiltrated composites is put forward

  18. Milling Machinability of TiC Particle and TiB Whisker Hybrid Reinforced Titanium Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    Huan Haixiang; Xu Jiuhua; Su Honghua; Ge Yingfei; Liang Xinghui

    2017-01-01

    The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination.Polycrystalline diamond (PCD) tools with different grain sizes and geometries,and carbide tools with and without coatings were used in the experiments.Milling forces,milling temperatures,tool lifetimes,tool wear,and machined surface integrities were investigated.The PCD tool required a primary cutting force 15 % smaller than that of the carbide tool,while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiAlN-coated tool.A cutting force of 300 N per millimeter of the cutting edge (300 N/mm) was measured.This caused excessive tool chipping.The cutting temperature of the PCD tool was 20%-30% lower than that of the carbide tool,while that of the TiAlN-coated tool was 12% lower than that of the uncoated carbide tool.The cutting temperatures produced when using water-based cooling and minimal quantity lubrication (MQL) were reduced by 100 ℃ and 200 ℃,compared with those recorded with dry cutting,respectively.In general,the PCD tool lifetimes were 2-3 times longer than the carbide tool lifetimes.The roughness Ra of the machined surface was less than 0.6μm,and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached.The PCD tool with a 0.8 mm tool nose radius,0° rake angle,10° flank angle,and grain size of (30+2)μm exhibited the best cutting performance.For this specific tool,a lifetime of 16 min can be expected.

  19. Study of non-stoichiometric BaSrTiFeO3 oxide dedicated to semiconductor gas sensors

    International Nuclear Information System (INIS)

    Fasquelle, D.; Verbrugghe, N.; Deputier, S.

    2016-01-01

    Developing instrumentation systems compatible with the European RoHS directive (restriction of hazardous substances) to monitor our environment is of great interest for our society. Our research therefore aims at developing innovating integrated systems of detection dedicated to the characterization of various environmental exposures. These systems, which integrate new gas sensors containing lead-free oxides, are dedicated to the detection of flammable and toxic gases. We have firstly chosen to study semiconductor gas sensors implemented with lead-free oxides in view to develop RoHS devices. Therefore thick films deposited by spin-coating and screen-printing have been chosen for their robustness, ease to realize and ease to finally obtain cost-effective sensors. As crystalline defects and ionic vacancies are of great interest for gas detection, we have decided to study a non-stoichiometric composition of the BaSrTiFeO 3 sensible oxide. Nonstoichiometric BaSrTiFeO 3 lead-free oxide thick films were deposited by screen-printing on polycrystalline AFO 3 substrates covered by a layer of Ag-Pd acting as bottom electrode. The physical characterizations have revealed a crystalline structure mainly composed of BaTiO 3 pseudo-cubic phase and Ba 4 Ti 12 O 27 monoclinic phase for the powder, and a porous microstructure for the thick films. When compared to a BSTF thick film with a stoichiometric composition, a notable increase in the BSTF dielectric constant value was observed when taking into account of a similar microstructure and grain size. The loss tangent mean value varies more softly for the non-stoichiometric BaSrTiFeO 3 films than for the perovskite BSTF film as tanδ decreases from 0.45 to 0.04 when the frequency increases from 100 Hz to 1 MHz. (paper)

  20. Titanium

    Science.gov (United States)

    Woodruff, Laurel G.; Bedinger, George M.; Piatak, Nadine M.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Titanium is a mineral commodity that is essential to the smooth functioning of modern industrial economies. Most of the titanium produced is refined into titanium dioxide, which has a high refractive index and is thus able to impart a durable white color to paint, paper, plastic, rubber, and wallboard. Because of their high strength-to-weight ratio and corrosion resistance, titanium metal and titanium metal alloys are used in the aerospace industry as well as for welding rod coatings, biological implants, and consumer goods.Ilmenite and rutile are currently the principal titanium-bearing ore minerals, although other minerals, including anatase, perovskite, and titanomagnetite, could have economic importance in the future. Ilmenite is currently being mined from two large magmatic deposits hosted in rocks of Proterozoic-age anorthosite plutonic suites. Most rutile and nearly one-half of the ilmenite produced are from heavy-mineral alluvial, fluvial, and eolian deposits. Titanium-bearing minerals occur in diverse geologic settings, but many of the known deposits are currently subeconomic for titanium because of complications related to the mineralogy or because of the presence of trace contaminants that can compromise the pigment production process.Global production of titanium minerals is currently dominated by Australia, Canada, Norway, and South Africa; additional amounts are produced in Brazil, India, Madagascar, Mozambique, Sierra Leone, and Sri Lanka. The United States accounts for about 4 percent of the total world production of titanium minerals and is heavily dependent on imports of titanium mineral concentrates to meet its domestic needs.Titanium occurs only in silicate or oxide minerals and never in sulfide minerals. Environmental considerations for titanium mining are related to waste rock disposal and the impact of trace constituents on water quality. Because titanium is generally inert in the environment, human health risks from titanium and titanium

  1. Helium diffusion in irradiated boron carbide

    International Nuclear Information System (INIS)

    Hollenberg, G.W.

    1981-03-01

    Boron carbide has been internationally adopted as the neutron absorber material in the control and safety rods of large fast breeder reactors. Its relatively large neutron capture cross section at high neutron energies provides sufficient reactivity worth with a minimum of core space. In addition, the commercial availability of boron carbide makes it attractive from a fabrication standpoint. Instrumented irradiation experiments in EBR-II have provided continuous helium release data on boron carbide at a variety of operating temperatures. Although some microstructural and compositional variations were examined in these experiments most of the boron carbide was prototypic of that used in the Fast Flux Test Facility. The density of the boron carbide pellets was approximately 92% of theoretical. The boron carbide pellets were approximately 1.0 cm in diameter and possessed average grain sizes that varied from 8 to 30 μm. Pellet centerline temperatures were continually measured during the irradiation experiments

  2. Effect of Non-Stoichiometric Solution Chemistry on Improving the Performance of Wide-Bandgap Perovskite Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Kai [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Yang, Mengjin [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Kim, Donghoe [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Li, Zhen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Reid, Obadiah G [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Yu, Yue [University of Toledo; Song, Zhaoning [University of Toledo; Zhao, Dewei [University of Toledo; Wang, Changlei [University of Toledo; Li, Liwei [ENN Energy Research Institute; ENN Solar Energy Co., Ltd.; Meng, Yuan [ENN Energy Research Institute; ENN Solar Energy Co., Ltd.; Guo, Ted [ENN Energy Research Institute; ENN Solar Energy Co., Ltd.; Yan, Yanfa [University of Toledo

    2017-10-18

    A high-efficiency wide-bandgap (WBG) perovskite solar cell is critical for developing perovskite-related (e.g., all-perovskite, perovskite/Si, or perovskite/Cu(In,Ga)Se2) tandem devices. Here, we demonstrate the use of non-stoichiometric precursor chemistry with excess methylammonium halides (MAX; X = I, Br, or Cl) for preparing high-quality ~1.75-eV FA0.83Cs0.17Pb(I0.6Br0.4)3 perovskite solar cells. Among various methylammonium halides, using excess MABr in the non-stoichiometric precursor exhibits the strongest effect on improving perovskite crystallographic properties and device characteristics without affecting the perovskite composition. In contrast, using excess MAI significantly reduces the bandgap of perovskite due to the replacement of Br with I. Using 40% excess MABr, we demonstrate a single-junction WBG perovskite solar cell with stabilized efficiency of 16.4%. We further demonstrate a 20.3%-efficient 4-terminal tandem device by using a 14.7%-efficient semi-transparent WBG perovskite top cell and an 18.6%-efficient unfiltered (5.6%-efficient filtered) Si bottom cell.

  3. Shock Response of Boron Carbide

    National Research Council Canada - National Science Library

    Dandekar, D. P. (Dattatraya Purushottam)

    2001-01-01

    .... The present work was undertaken to determine tensile/spall strength of boron carbide under plane shock wave loading and to analyze all available shock compression data on boron carbide materials...

  4. Calcium carbonate hybrid coating promotes the formation of biomimetic hydroxyapatite on titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, Marcos Antônio E.; Ruiz, Gilia C.M. [Departamento de Química-Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14040-901, SP (Brazil); Faria, Amanda N. [Departamento de Química-Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14040-901, SP (Brazil); Departamento de Bioquímica e Imunologia-Faculdade de Medicina de Ribeirão Preto Universidade de São Paulo, Ribeirão Preto, SP (Brazil); Zancanela, Daniela C.; Pereira, Lourivaldo S.; Ciancaglini, Pietro [Departamento de Química-Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14040-901, SP (Brazil); Ramos, Ana P., E-mail: anapr@ffclrp.usp.br [Departamento de Química-Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14040-901, SP (Brazil)

    2016-05-01

    Graphical abstract: - Highlights: • CaCO{sub 3} continuous films were deposited on titanium discs using a biomimetic approach. • The coatings origin hydroxyapatite when immersed in simulated body fluid. • The wettability and the free energy of the surfaces were increased after the treatment. • The coated titanium discs are bioactive and non-toxic to osteoblasts. - Abstract: CaCO{sub 3} particles dispersed in liquid media have proven to be good inductors of hydroxyapatite (HAp) growth. However, the use of CaCO{sub 3} deposited as thin films for this propose is unknown. Here, we report the growth of CaCO{sub 3} continuous films on Langmuir–Blodgett (LB) modified titanium surfaces and its use as HAp growth inductor. The Ti surfaces were modified with two, four, and six layers of dihexadecylphosphate (DHP)-LB films containing Ca{sup 2+}, exposed to CO{sub 2} (g) for 12 h. The modified surfaces were immersed in simulated body fluid (SBF) at 37 °C for 36 h and submitted to bioactivity studies. This procedure originates bioactive coatings composed by non-stoichiometric HAp as evidenced by Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). The presence of the CaCO{sub 3} film as pre-coating diminished the time necessary to growth continuous and homogeneous HAp films using a biomimetic approach. The surface properties of the films regarding their roughness, composition, charge, wettability, and surface free energy (γ{sub s}) were accessed. The presence of HAp increased the wettability and γ{sub s} of the surfaces. The coatings are not toxic for osteoblasts as observed for cell viability assays obtained after 7 and 14 days of culture. Moreover, the CaCO{sub 3} thin films promote the recovery of the osteoblasts viability more than the Ti surfaces themselves.

  5. Calcium carbonate hybrid coating promotes the formation of biomimetic hydroxyapatite on titanium surfaces

    International Nuclear Information System (INIS)

    Cruz, Marcos Antônio E.; Ruiz, Gilia C.M.; Faria, Amanda N.; Zancanela, Daniela C.; Pereira, Lourivaldo S.; Ciancaglini, Pietro; Ramos, Ana P.

    2016-01-01

    Graphical abstract: - Highlights: • CaCO 3 continuous films were deposited on titanium discs using a biomimetic approach. • The coatings origin hydroxyapatite when immersed in simulated body fluid. • The wettability and the free energy of the surfaces were increased after the treatment. • The coated titanium discs are bioactive and non-toxic to osteoblasts. - Abstract: CaCO 3 particles dispersed in liquid media have proven to be good inductors of hydroxyapatite (HAp) growth. However, the use of CaCO 3 deposited as thin films for this propose is unknown. Here, we report the growth of CaCO 3 continuous films on Langmuir–Blodgett (LB) modified titanium surfaces and its use as HAp growth inductor. The Ti surfaces were modified with two, four, and six layers of dihexadecylphosphate (DHP)-LB films containing Ca 2+ , exposed to CO 2 (g) for 12 h. The modified surfaces were immersed in simulated body fluid (SBF) at 37 °C for 36 h and submitted to bioactivity studies. This procedure originates bioactive coatings composed by non-stoichiometric HAp as evidenced by Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). The presence of the CaCO 3 film as pre-coating diminished the time necessary to growth continuous and homogeneous HAp films using a biomimetic approach. The surface properties of the films regarding their roughness, composition, charge, wettability, and surface free energy (γ s ) were accessed. The presence of HAp increased the wettability and γ s of the surfaces. The coatings are not toxic for osteoblasts as observed for cell viability assays obtained after 7 and 14 days of culture. Moreover, the CaCO 3 thin films promote the recovery of the osteoblasts viability more than the Ti surfaces themselves.

  6. Joining elements of silicon carbide

    International Nuclear Information System (INIS)

    Olson, B.A.

    1979-01-01

    A method of joining together at least two silicon carbide elements (e.g.in forming a heat exchanger) is described, comprising subjecting to sufficiently non-oxidizing atmosphere and sufficiently high temperature, material placed in space between the elements. The material consists of silicon carbide particles, carbon and/or a precursor of carbon, and silicon, such that it forms a joint joining together at least two silicon carbide elements. At least one of the elements may contain silicon. (author)

  7. The use of cutting temperature to evaluate the machinability of titanium alloys.

    Science.gov (United States)

    Kikuchi, Masafumi

    2009-02-01

    This study investigated the machinability of titanium, two commercial titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) and free-cutting brass using the cutting temperature. The cutting temperature was estimated by measuring the thermal electromotive force of the tool-workpiece thermocouple during cutting. The thermoelectric power of each metal relative to the tool had previously been determined. The metals were slotted using a milling machine and carbide square end mills under four cutting conditions. The cutting temperatures of Ti-6Al-4V and Ti-6Al-7Nb were significantly higher than that of the titanium, while that of the free-cutting brass was lower. This result coincided with the relationship of the magnitude of the cutting forces measured in a previous study. For each metal, the cutting temperature became higher when the depth of cut or the cutting speed and feed increased. The increase in the cutting speed and feed was more influential on the value than the increase in the depth of cut when two cutting conditions with the same removal rates were compared. The results demonstrated that cutting temperature measurement can be utilized to develop a new material for dental CAD/CAM applications and to optimize the cutting conditions.

  8. Method of fabricating porous silicon carbide (SiC)

    Science.gov (United States)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1995-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  9. Laser-induced oxidation of titanium substrate: Analysis of the physicochemical structure of the surface and sub-surface layers

    Energy Technology Data Exchange (ETDEWEB)

    Antończak, Arkadiusz J., E-mail: arkadiusz.antonczak@pwr.edu.pl [Laser and Fiber Electronics Group, Faculty of Electrical Engineering, Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw (Poland); Skowroński, Łukasz; Trzcinski, Marek [Institute of Mathematics and Physics, University of Technology and Life Sciences, Kaliskiego 7, 85-789 Bydgoszcz (Poland); Kinzhybalo, Vasyl V. [Wroclaw Research Centre EIT+, Stabłowicka 147, 54-066 Wrocław (Poland); Institute of Low Temperature and Structure Research, Okólna 2, 50-422 Wrocław (Poland); Łazarek, Łukasz K.; Abramski, Krzysztof M. [Laser and Fiber Electronics Group, Faculty of Electrical Engineering, Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw (Poland)

    2015-01-15

    Highlights: • Chemical structure of the films induced by laser on titanium surface was analyzed. • It was shown that outer layer of this films consist of oxides doped with nitrogen. • The optical properties of the laser-induced oxynitride films were characterized. • We found that the films demonstrated significant absorption in the band of 300–580 nm. • The morphology of the layers as a function of the laser fluence was investigated. - Abstract: This paper presents the results of the analysis of the complex chemical structure of the layers made on titanium in the process of the heating of its surfaces in an atmospheric environment, by irradiating samples with a nanosecond-pulsed laser. The study was carried out for electroplated, high purity, polycrystalline titanium substrates using a Yb:glass fiber laser. All measurements were made for samples irradiated in a broad range of accumulated fluence, below the ablation threshold. It has been determined how the complex index of refraction of both the oxynitride layers and the substrate vary as a function of accumulated laser fluence. It was also shown that the top layer of the film produced on titanium, which is transparent, is not a pure TiO{sub 2} as had been supposed before. The XPS and XRD analyses confirmed the presence of nitrogen compounds and the existence of nonstoichiometric compounds. By sputtering of the sample's surface using an Ar{sup +} ion gun, the changes in the concentration of individual elements as a function of the layer's cross-section were determined. Lastly, an analysis of the surface morphology has also been carried out, explaining why the layers crack and exfoliate from their substrate.

  10. Characterization of Nanometric-Sized Carbides Formed During Tempering of Carbide-Steel Cermets

    Directory of Open Access Journals (Sweden)

    Matus K.

    2016-06-01

    Full Text Available The aim of this article of this paper is to present issues related to characterization of nanometric-sized carbides, nitrides and/or carbonitrides formed during tempering of carbide-steel cermets. Closer examination of those materials is important because of hardness growth of carbide-steel cermet after tempering. The results obtained during research show that the upswing of hardness is significantly higher than for high-speed steels. Another interesting fact is the displacement of secondary hardness effect observed for this material to a higher tempering temperature range. Determined influence of the atmosphere in the sintering process on precipitations formed during tempering of carbide-steel cermets. So far examination of carbidesteel cermet produced by powder injection moulding was carried out mainly in the scanning electron microscope. A proper description of nanosized particles is both important and difficult as achievements of nanoscience and nanotechnology confirm the significant influence of nanocrystalline particles on material properties even if its mass fraction is undetectable by standard methods. The following research studies have been carried out using transmission electron microscopy, mainly selected area electron diffraction and energy dispersive spectroscopy. The obtained results and computer simulations comparison were made.

  11. Opportunities in the electrowinning of molten titanium from titanium dioxide

    CSIR Research Space (South Africa)

    Van Vuuren, DS

    2005-10-01

    Full Text Available used, the following forms of titanium are produced: titanium sponge, sintered electrode sponge, powder, molten titanium, electroplated titanium, hydride powder, and vapor-phase depos- ited titanium. Comparing the economics of alter- native...-up for producing titanium via the Kroll process is approximately as follows: ilmenite ($0.27/kg titanium sponge); titanium slag ($0.75/kg titanium sponge); TiCl4 ($3.09/kg titanium sponge); titanium sponge raw materials costs ($5.50/kg titanium sponge); total...

  12. The influence of Mn on the crystallography and electrochemistry of nonstoichiometric AB5-type hydride-forming compounds

    International Nuclear Information System (INIS)

    Notten, P.H.L.; Latroche, M.; Percheron-Guegan, A.

    1999-01-01

    To design Co-free, low-pressure, hydride-forming compounds for application in rechargeable nickel metal hydride batteries, nonstoichiometric AB x materials were investigated. The influence of both the Mn content and the degree of nonstoichiometry on the crystallography, electrochemical cycling stability, and electrode morphology were studied. The investigated composition was in the range of La(Ni 1-z Mn z ) x with 5.0 le x le 6.0 and 0 le xz le 2.0. The annealing temperature was essential in preparing homogeneous compounds. In agreement with geometric considerations, both the a and c axis of the hexagonal unit cell increase with increasing Mn content. In contrast, the a axis decreases with increasing degree of nonstoichiometry. As proved by neutron-diffraction experiments, the introduction of dumbbell pairs of Ni or Mn atoms on the La positions in the crystal lattice is responsible for this behavior. The electrochemical cycling stability is found to be strongly dependent on both the chemical and nonstoichiometric composition. Electrochemically stable materials are characterized by the absence of a significant particle-size reduction upon electrode cycling, reducing the overall oxidation rate. Unstable materials suffer from severe mechanical cracking through which the oxidation rate is increased. The improved mechanical stability is attributed to the reduced discrete lattice expansion. The most stable compound has a partial hydrogen pressure of only 0.1 bar, which matches well with that desirable in practical NiMH batteries. Neutron-diffraction experiments confirmed the hypothesis that La atoms are replaced by dumbbell pairs of Ni, in the case of the binary LaNi 5.4 , and by Mn atoms in the case of the mn-containing nonstoichiometric compounds. Electron-probe microanalyses and density measurements support the dumbbell hypothesis

  13. Diffraction study on the nonstoichiometric α-U2N3+x phase

    International Nuclear Information System (INIS)

    Serizawa, H.; Fukuda, K.; Ishii, Y.; Funahashi, S.; Katsura, M.

    1993-01-01

    X-ray and neutron diffraction studies were performed on nonstoichiometric α-U 2 N 3+ x having a composition range 1.68 2 N 3+x in this composition range was distorted Mn 2 O 3 -type. Structure parameters of U and N atoms were determined. The results showed that positions of U atoms varied continuously with nitrogen content. No evidence of the modification from bcc to fcc could be obtained. Interatomic distances of U-U and U-N were determined. The position parameter of N atoms showed that N atoms were slightly deviated from the tetrahedral site. (author)

  14. Attenuation of Neutron and Gamma Radiation by a Composite Material Based on Modified Titanium Hydride with a Varied Boron Content

    Science.gov (United States)

    Yastrebinskii, R. N.

    2018-04-01

    The investigations on estimating the attenuation of capture gamma radiation by a composite neutron-shielding material based on modified titanium hydride and Portland cement with a varied amount of boron carbide are performed. The results of calculations demonstrate that an introduction of boron into this material enables significantly decreasing the thermal neutron flux density and hence the levels of capture gamma radiation. In particular, after introducing 1- 5 wt.% boron carbide into the material, the thermal neutron flux density on a 10 cm-thick layer is reduced by 11 to 176 factors, and the capture gamma dose rate - from 4 to 9 times, respectively. The difference in the degree of reduction in these functionals is attributed to the presence of capture gamma radiation in the epithermal region of the neutron spectrum.

  15. Rare-earth-free luminescent non-stoichiometric phases formed in SrO-HfO.sub.2./sub. ternary compositions

    Czech Academy of Sciences Publication Activity Database

    Boháček, Pavel; Trunda, Bohumil; Beitlerová, Alena; Drahokoupil, Jan; Jarý, Vítězslav; Studnička, Václav; Nikl, Martin

    2013-01-01

    Roč. 580, Dec (2013), s. 468-474 ISSN 0925-8388 R&D Projects: GA AV ČR KAN300100802 Institutional support: RVO:68378271 Keywords : solid state sintering * nonstoichiometric phase * SrHfO3 * X-ray phosphor * luminescence Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.726, year: 2013

  16. New Icosahedral Boron Carbide Semiconductors

    Science.gov (United States)

    Echeverria Mora, Elena Maria

    Novel semiconductor boron carbide films and boron carbide films doped with aromatic compounds have been investigated and characterized. Most of these semiconductors were formed by plasma enhanced chemical vapor deposition. The aromatic compound additives used, in this thesis, were pyridine (Py), aniline, and diaminobenzene (DAB). As one of the key parameters for semiconducting device functionality is the metal contact and, therefore, the chemical interactions or band bending that may occur at the metal/semiconductor interface, X-ray photoemission spectroscopy has been used to investigate the interaction of gold (Au) with these novel boron carbide-based semiconductors. Both n- and p-type films have been tested and pure boron carbide devices are compared to those containing aromatic compounds. The results show that boron carbide seems to behave differently from other semiconductors, opening a way for new analysis and approaches in device's functionality. By studying the electrical and optical properties of these films, it has been found that samples containing the aromatic compound exhibit an improvement in the electron-hole separation and charge extraction, as well as a decrease in the band gap. The hole carrier lifetimes for each sample were extracted from the capacitance-voltage, C(V), and current-voltage, I(V), curves. Additionally, devices, with boron carbide with the addition of pyridine, exhibited better collection of neutron capture generated pulses at ZERO applied bias, compared to the pure boron carbide samples. This is consistent with the longer carrier lifetimes estimated for these films. The I-V curves, as a function of external magnetic field, of the pure boron carbide films and films containing DAB demonstrate that significant room temperature negative magneto-resistance (> 100% for pure samples, and > 50% for samples containing DAB) is possible in the resulting dielectric thin films. Inclusion of DAB is not essential for significant negative magneto

  17. Reactive laser-induced ablation as approach to titanium oxycarbide films

    International Nuclear Information System (INIS)

    Jandova, V.; Fajgar, R.; Dytrych, P.; Kostejn, M.; Drinek, V.; Kupcik, J.

    2015-01-01

    The IR laser-induced reactive ablation of frozen titanium ethoxide target was studied. The method involves the laser ablation of titanium ethoxide at − 140 °C in gaseous methane (4–50 Pa) atmosphere. This process leads to reactions of the ablative species with hydrocarbon in the gaseous phase. During the ablation of the frozen target excited species interact with methane molecules. The reactive ablation process leads to the formation of a smooth thin film. The thickness of prepared films depends on the number of IR pulses and their composition depends on the pressure of gaseous methane. This reactive IR ablation proceeds as a carbidation process providing nanostructured films with good adhesion to various substrates (glass, metals, KBr) depending on the carbon content in prepared films. Particles are also stabilized by layer preventing their surface oxidation in the atmosphere. The described results are important in the general context for the synthesis of reactive particles in the gas phase. The final products are characterized by spectroscopic, microscopic and diffraction techniques: SEM/EDX, HRTEM, electron diffraction, Raman spectroscopy and XPS. - Highlights: • IR laser ablation of frozen target of titanium ethoxide leads to a reduction in the gaseous methane (4-50 Pa). • Films deposited in methane have Ti/O/C stoichiometry and are oxidized in the atmosphere. • Layers deposited in methane are reduced and have less O in the topmost layers

  18. Reactive laser-induced ablation as approach to titanium oxycarbide films

    Energy Technology Data Exchange (ETDEWEB)

    Jandova, V., E-mail: jandova@icpf.cas.cz; Fajgar, R.; Dytrych, P.; Kostejn, M.; Drinek, V.; Kupcik, J.

    2015-09-01

    The IR laser-induced reactive ablation of frozen titanium ethoxide target was studied. The method involves the laser ablation of titanium ethoxide at − 140 °C in gaseous methane (4–50 Pa) atmosphere. This process leads to reactions of the ablative species with hydrocarbon in the gaseous phase. During the ablation of the frozen target excited species interact with methane molecules. The reactive ablation process leads to the formation of a smooth thin film. The thickness of prepared films depends on the number of IR pulses and their composition depends on the pressure of gaseous methane. This reactive IR ablation proceeds as a carbidation process providing nanostructured films with good adhesion to various substrates (glass, metals, KBr) depending on the carbon content in prepared films. Particles are also stabilized by layer preventing their surface oxidation in the atmosphere. The described results are important in the general context for the synthesis of reactive particles in the gas phase. The final products are characterized by spectroscopic, microscopic and diffraction techniques: SEM/EDX, HRTEM, electron diffraction, Raman spectroscopy and XPS. - Highlights: • IR laser ablation of frozen target of titanium ethoxide leads to a reduction in the gaseous methane (4-50 Pa). • Films deposited in methane have Ti/O/C stoichiometry and are oxidized in the atmosphere. • Layers deposited in methane are reduced and have less O in the topmost layers.

  19. Stable carbides in transition metal alloys

    International Nuclear Information System (INIS)

    Piotrkowski, R.

    1991-01-01

    In the present work different techniques were employed for the identification of stable carbides in two sets of transition metal alloys of wide technological application: a set of three high alloy M2 type steels in which W and/or Mo were total or partially replaced by Nb, and a Zr-2.5 Nb alloy. The M2 steel is a high speed steel worldwide used and the Zr-2.5 Nb alloy is the base material for the pressure tubes in the CANDU type nuclear reactors. The stability of carbide was studied in the frame of Goldschmidt's theory of interstitial alloys. The identification of stable carbides in steels was performed by determining their metallic composition with an energy analyzer attached to the scanning electron microscope (SEM). By these means typical carbides of the M2 steel, MC and M 6 C, were found. Moreover, the spatial and size distribution of carbide particles were determined after different heat treatments, and both microstructure and microhardness were correlated with the appearance of the secondary hardening phenomenon. In the Zr-Nb alloy a study of the α and β phases present after different heat treatments was performed with optical and SEM metallographic techniques, with the guide of Abriata and Bolcich phase diagram. The α-β interphase boundaries were characterized as short circuits for diffusion with radiotracer techniques and applying Fisher-Bondy-Martin model. The precipitation of carbides was promoted by heat treatments that produced first the C diffusion into the samples at high temperatures (β phase), and then the precipitation of carbide particles at lower temperature (α phase or (α+β)) two phase field. The precipitated carbides were identified as (Zr, Nb)C 1-x with SEM, electron microprobe and X-ray diffraction techniques. (Author) [es

  20. Rotationally resolved state-to-state photoionization and photoelectron study of titanium carbide and its cation (TiC/TiC⁺).

    Science.gov (United States)

    Luo, Zhihong; Huang, Huang; Chang, Yih-Chung; Zhang, Zheng; Yin, Qing-Zhu; Ng, C Y

    2014-10-14

    Titanium carbide and its cation (TiC/TiC(+)) have been investigated by the two-color visible (VIS)-ultraviolet (UV) resonance-enhanced photoionization and pulsed field ionization-photoelectron (PFI-PE) methods. Two visible excitation bands for neutral TiC are observed at 16,446 and 16,930 cm(-1). Based on rotational analyses, these bands are assigned as the respective TiC((3)Π1) ← TiC(X(3)Σ(+)) and TiC((3)Σ(+)) ← TiC(X(3)Σ(+)) transition bands. This assignment supports that the electronic configuration and term symmetry for the neutral TiC ground state are …7σ(2)8σ(1)9σ(1)3π(4) (X(3)Σ(+)). The rotational constant and the corresponding bond distance of TiC(X(3)Σ(+); v″ = 0) are determined to be B0″ = 0.6112(10) cm(-1) and r0″ = 1.695(2) Å, respectively. The rotational analyses of the VIS-UV-PFI-PE spectra for the TiC(+)(X; v(+) = 0 and 1) vibrational bands show that the electronic configuration and term symmetry for the ionic TiC(+) ground state are …7σ(2)8σ(1)3π(4) (X(2)Σ(+)) with the v(+) = 0 → 1 vibrational spacing of 870.0(8) cm(-1) and the rotational constants of B(e)(+) = 0.6322(28) cm(-1), and α(e)(+) = 0.0085(28) cm(-1). The latter rotational constants yield the equilibrium bond distance of r(e)(+) = 1.667(4) Å for TiC(+)(X(2)Σ(+)). The cleanly rotationally resolved VIS-UV-PFI-PE spectra have also provided a highly precise value of 53 200.2(8) cm(-1) [6.5960(1) eV] for the adiabatic ionization energy (IE) of TiC. This IE(TiC) value along with the known IE(Ti) has made possible the determination of the difference between the 0 K bond dissociation energy (D0) of TiC(+)(X(2)Σ(+)) and that of TiC(X(3)Σ(+)) to be D0(Ti(+)-C) - D0(Ti-C) = 0.2322(2) eV. Similar to previous experimental observations, the present state-to-state PFI-PE study of the photoionization transitions, TiC(+)(X(2)Σ(+); v(+) = 0 and 1, N(+)) ← TiC((3)Π1; v', J'), reveals a strong decreasing trend for the photoionization cross section as |ΔN(+)| = |N

  1. Pulsed ion beam-assisted carburizing of titanium in methane discharge

    International Nuclear Information System (INIS)

    Shafiq, M.; Shahzad, K.; Zakaullah, M.; Hassan, M.; Qayyum, A.; Ahmad, S.; Rawat, R. S.

    2010-01-01

    The carburizing of titanium (Ti) is accomplished by utilizing energetic ion pulses of a 1.5 kJ Mather type dense plasma focus (DPF) device operated in methane discharge. X-ray diffraction (XRD) analysis confirms the deposition of polycrystalline titanium carbide (TiC). The samples carburized at lower axial and angular positions show an improved texture for a typical (200)TiC plane. The Williamson–Hall method is employed to estimate average crystallite size and microstrains in the carburized Ti surface. Crystallite size is found to vary from ∼ 50 to 100 nm, depending on the deposition parameters. Microstrains vary with the sample position and hence ion flux, and are converted from tensile to compressive by increasing the flux. The carburizing of Ti is confirmed by two major doublets extending from 300 to 390 cm −1 and from 560 to 620 cm −1 corresponding to acoustic and optical active modes in Raman spectra, respectively. Analyses by scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS) have provided qualitative and quantitative profiles of the carburized surface. The Vickers microhardness of Ti is significantly improved after carburizing. (nuclear physics)

  2. Microsegregation in Nodular Cast Iron with Carbides

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2012-12-01

    Full Text Available In this paper results of microsegregation in the newly developed nodular cast iron with carbides are presented. To investigate the pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The distribution of linear elements on the eutectic cell radius was examined. To investigate the microsegregation pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen.The linear distribution of elements on the eutectic cell radius was examined. Testing of the chemical composition of cast iron metal matrix components, including carbides were carried out. The change of graphitizing and anti-graphitizing element concentrations within eutectic cell was determined. It was found, that in cast iron containing Mo carbides crystallizing after austenite + graphite eutectic are Si enriched.

  3. Microsegregation in Nodular Cast Iron with Carbides

    Directory of Open Access Journals (Sweden)

    Pietrowski S.

    2012-12-01

    Full Text Available In this paper results of microsegregation in the newly developed nodular cast iron with carbides are presented. To investigate the pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The distribution of linear elements on the eutectic cell radius was examined. To investigate the microsegregation pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The linear distribution of elements on the eutectic cell radius was examined. Testing of the chemical composition of cast iron metal matrix components, including carbides were carried out. The change of graphitizing and anti-graphitizing element concentrations within eutectic cell was determined. It was found, that in cast iron containing Mo carbides crystallizing after austenite + graphite eutectic are Si enriched.

  4. Rotationally resolved state-to-state photoionization and photoelectron study of titanium carbide and its cation (TiC/TiC+)

    International Nuclear Information System (INIS)

    Luo, Zhihong; Huang, Huang; Chang, Yih-Chung; Zhang, Zheng; Ng, C. Y.; Yin, Qing-Zhu

    2014-01-01

    Titanium carbide and its cation (TiC/TiC + ) have been investigated by the two-color visible (VIS)-ultraviolet (UV) resonance-enhanced photoionization and pulsed field ionization-photoelectron (PFI-PE) methods. Two visible excitation bands for neutral TiC are observed at 16 446 and 16 930 cm −1 . Based on rotational analyses, these bands are assigned as the respective TiC( 3 Π 1 ) ← TiC(X 3 Σ + ) and TiC( 3 Σ + ) ← TiC(X 3 Σ + ) transition bands. This assignment supports that the electronic configuration and term symmetry for the neutral TiC ground state are …7σ 2 8σ 1 9σ 1 3π 4 (X 3 Σ + ). The rotational constant and the corresponding bond distance of TiC(X 3 Σ + ; v″ = 0) are determined to be B 0 ″ = 0.6112(10) cm −1 and r 0 ″ = 1.695(2) Å, respectively. The rotational analyses of the VIS-UV-PFI-PE spectra for the TiC + (X; v + = 0 and 1) vibrational bands show that the electronic configuration and term symmetry for the ionic TiC + ground state are …7σ 2 8σ 1 3π 4 (X 2 Σ + ) with the v + = 0 → 1 vibrational spacing of 870.0(8) cm −1 and the rotational constants of B e + = 0.6322(28) cm −1 , and α e + = 0.0085(28) cm −1 . The latter rotational constants yield the equilibrium bond distance of r e + = 1.667(4) Å for TiC + (X 2 Σ + ). The cleanly rotationally resolved VIS-UV-PFI-PE spectra have also provided a highly precise value of 53 200.2(8) cm −1 [6.5960(1) eV] for the adiabatic ionization energy (IE) of TiC. This IE(TiC) value along with the known IE(Ti) has made possible the determination of the difference between the 0 K bond dissociation energy (D 0 ) of TiC + (X 2 Σ + ) and that of TiC(X 3 Σ + ) to be D 0 (Ti + −C) − D 0 (Ti−C) = 0.2322(2) eV. Similar to previous experimental observations, the present state-to-state PFI-PE study of the photoionization transitions, TiC + (X 2 Σ + ; v + = 0 and 1, N + ) ← TiC( 3 Π 1 ; v′, J′), reveals a strong decreasing trend for the photoionization cross

  5. Method to manufacture a nuclear fuel from uranium-plutonium monocarbide or uranium-plutonium mononitride

    International Nuclear Information System (INIS)

    Krauth, A.; Mueller, N.

    1977-01-01

    Pure uranium carbide or nitride is converted with plutonium oxide and carbon (all in powder form) to uranium-plutonium monocarbide or mononitride by cold pressing and sintering at about 1600 0 C. Pure uranium carbide or uranium nitride powder is firstly prepared without extensive safety measures. The pure uranium carbide or nitride powder can also be inactivated by using chemical substances (e.g. stearic acid) and be handled in air. The sinterable uranium carbide or nitride powder (or also granulate) is then introduced into the plutonium line and mixed with a nonstoichiometrically adjusted, prereacted mixture of plutonium oxide and carbon, pressed to pellets and reaction sintered. The surface of the uranium-plutonium carbide (higher metal content) can be nitrated towards the end of the sinter process in a stream of nitrogen. The protective layer stabilizes the carbide against the water and oxygen content in air. (IHOE) [de

  6. Spontaneous polarization of a nonstoichiometric ferroelectric NaNO2 at low temperatures

    Science.gov (United States)

    Matyjasik, S.; Shaldin, Yu.

    2017-10-01

    We report measurements of the temperature dependence of the pyroelectric charge in a nonstoichiometric z-cut sample of sodium nitrite in the temperature range 4.2-300 K. The obtained data are supplemented by the measurements of thermally stimulated depolarization (TSD) in electric fields of different magnitudes and polarities. All the experimental results serve as the basis for constructing the temperature dependence of the spontaneous polarization ΔPs(T,U) and the pyroelectric coefficient γ(U,T) for fixed external stimuli. It is found that the value of ΔPs in the sample of sodium nitrite is negligible at low temperatures, up to 40 K. This indicates (for known experimental values of the linear expansion coefficients) a minor contribution of the sample piezoelectricity to the spontaneous polarization in this temperature range. Starting from T = 75 K, an exponential increase in the contribution to the total charge of the TSD is found only in the defect subsystem of the crystal. Based on the data of physical studies, a crystal-physics model is proposed, which differs from the model presented by Lines and Glass. Due to the splitting of ion positions in all three sublattices upon the transition to the paraelectric phase, NaNO2 crystals can be assigned to the three-dimensional type of ferroelectrics, according to the classification by Abrahams and Keve. This agrees with the estimate of the spontaneous polarization Ps ˜ 0.01 C/m2 given in the paper. This value is significantly different from the data obtained by repolarization of nonstoichiometric samples in strong electric fields up to the phase transition temperature.

  7. Metal Matrix Composite Material by Direct Metal Deposition

    Science.gov (United States)

    Novichenko, D.; Marants, A.; Thivillon, L.; Bertrand, P. H.; Smurov, I.

    Direct Metal Deposition (DMD) is a laser cladding process for producing a protective coating on the surface of a metallic part or manufacturing layer-by-layer parts in a single-step process. The objective of this work is to demonstrate the possibility to create carbide-reinforced metal matrix composite objects. Powders of steel 16NCD13 with different volume contents of titanium carbide are tested. On the base of statistical analysis, a laser cladding processing map is constructed. Relationships between the different content of titanium carbide in a powder mixture and the material microstructure are found. Mechanism of formation of various precipitated titanium carbides is investigated.

  8. Fine-scale precipitation and mechanical properties of thin slab processed titanium-niobium bearing high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Z. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70503 (United States); Misra, R.D.K., E-mail: dmisra@louisiana.edu [Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70503 (United States); O' Malley, R. [Nucor Steel Decatur, LLC, 4301 Iverson Blvd., Trinity, AL 35673 (United States); Jansto, S.J. [CBMM-Reference Metals Company, 1000 Old Pond Road, Bridgeville, PA 15017 (United States)

    2011-08-25

    Highlights: {yields} Precipitation and mechanical behavior of Ti-Nb and Ti-Nb-Mo-V steels were elucidated. {yields} Distribution of precipitates was analyzed with microscopy and diffraction pattern. {yields} During austenite-ferrite transformation, interface precipitation of NbC was observed. {yields} Epitaxial precipitation of NbC on TiC surface results in mixed precipitates Ti(Nb)C. - Abstract: We describe here the precipitation behavior and mechanical properties of 560 MPa Ti-Nb and 770 MPa Ti-Nb-Mo-V steels. The precipitation characteristics were analyzed in terms of chemistry and size distribution of precipitates, with particular focus on the crystallography of precipitates through an analysis of electron diffraction patterns. In addition to pure carbides (NbC, TiC, Mo{sub 2}C, and VC), Nb containing titanium-rich carbides were also observed. These precipitates were of a size range of 4-20 nm. The mechanism of formation of these Ti-rich niobium containing carbides is postulated to involve epitaxial nucleation of NbC on previously precipitated TiC. Interface precipitation of NbC was an interesting observation in compact strip processing which is characterized by an orientation relationship of [0 0 1]{sub NbC}//[0 0 1]{sub {alpha}-Fe}, implying that the precipitation of NbC occurred during austenite-ferrite transformation.

  9. Fine-scale precipitation and mechanical properties of thin slab processed titanium-niobium bearing high strength steels

    International Nuclear Information System (INIS)

    Jia, Z.; Misra, R.D.K.; O'Malley, R.; Jansto, S.J.

    2011-01-01

    Highlights: → Precipitation and mechanical behavior of Ti-Nb and Ti-Nb-Mo-V steels were elucidated. → Distribution of precipitates was analyzed with microscopy and diffraction pattern. → During austenite-ferrite transformation, interface precipitation of NbC was observed. → Epitaxial precipitation of NbC on TiC surface results in mixed precipitates Ti(Nb)C. - Abstract: We describe here the precipitation behavior and mechanical properties of 560 MPa Ti-Nb and 770 MPa Ti-Nb-Mo-V steels. The precipitation characteristics were analyzed in terms of chemistry and size distribution of precipitates, with particular focus on the crystallography of precipitates through an analysis of electron diffraction patterns. In addition to pure carbides (NbC, TiC, Mo 2 C, and VC), Nb containing titanium-rich carbides were also observed. These precipitates were of a size range of 4-20 nm. The mechanism of formation of these Ti-rich niobium containing carbides is postulated to involve epitaxial nucleation of NbC on previously precipitated TiC. Interface precipitation of NbC was an interesting observation in compact strip processing which is characterized by an orientation relationship of [0 0 1] NbC //[0 0 1] α-Fe , implying that the precipitation of NbC occurred during austenite-ferrite transformation.

  10. Cell Attachment Following Instrumentation with Titanium and Plastic Instruments, Diode Laser, and Titanium Brush on Titanium, Titanium-Zirconium, and Zirconia Surfaces.

    Science.gov (United States)

    Lang, Melissa S; Cerutis, D Roselyn; Miyamoto, Takanari; Nunn, Martha E

    2016-01-01

    The aim of this study was to evaluate the surface characteristics and gingival fibroblast adhesion of disks composed of implant and abutment materials following brief and repeated instrumentation with instruments commonly used in procedures for implant maintenance, stage-two implant surgery, and periimplantitis treatment. One hundred twenty disks (40 titanium, 40 titaniumzirconium, 40 zirconia) were grouped into treatment categories of instrumentation by plastic curette, titanium curette, diode microlaser, rotary titanium brush, and no treatment. Twenty strokes were applied to half of the disks in the plastic and titanium curette treatment categories, while half of the disks received 100 strokes each to simulate implant maintenance occurring on a repetitive basis. Following analysis of the disks by optical laser profilometry, disks were cultured with human gingival fibroblasts. Cell counts were conducted from scanning electron microscopy (SEM) images. Differences in surface roughness across all instruments tested for zirconia disks were negligible, while both titanium disks and titaniumzirconium disks showed large differences in surface roughness across the spectrum of instruments tested. The rotary titanium brush and the titanium curette yielded the greatest overall mean surface roughness, while the plastic curette yielded the lowest mean surface roughness. The greatest mean cell counts for each disk type were as follows: titanium disks with plastic curettes, titanium-zirconium disks with titanium curettes, and zirconia disks with the diode microlaser. Repeated instrumentation did not result in cumulative changes in surface roughness of implant materials made of titanium, titanium-zirconium, or zirconia. Instrumentation with plastic implant curettes on titanium and zirconia surfaces appeared to be more favorable than titanium implant curettes in terms of gingival fibroblast attachment on these surfaces.

  11. Investigations of niobium carbide contact for carbon-nanotube-based devices

    International Nuclear Information System (INIS)

    Huang, L; Chor, E F; Wu, Y; Guo, Z

    2010-01-01

    Single-walled carbon nanotube (SWCNT) field effect transistors (FETs) with Nb contacts have been fabricated and upon annealing in vacuum at 700 deg. C for 1 h, niobium carbide (Nb 2 C) is formed at the Nb/SWCNT interface. The Nb 2 C/SWCNT contacts demonstrate a very small Schottky barrier height of ∼ 18 meV (decreased by > 80% relative to that of pristine Nb/SWCNT contact of ∼ 98 meV) to p-type transport. This is attributed to the higher work function of Nb 2 C (∼5.2 eV) than Nb (∼4.3 eV) and better bonding between Nb 2 C and SWCNTs. The performance of Nb 2 C-contacted SWCNT FETs is as follows: the p-channel ON current is as high as 0.5 μA at V DS = 0.1 V, the I ON /I OFF ratio is up to ∼ 10 5 and the subthreshold slope is ∼ 550 mV/dec, which is as good as that of titanium carbide (TiC-) and Pd-contacted SWCNT FETs. Compared with TiC, Nb 2 C contacts yield more unipolar p-type SWCNT FETs, as a result of the Nb 2 Cs higher work function. More importantly, Nb 2 C contacts can form near-ohmic contacts to both large-(≥1.6 nm) and small-diameter (∼1 nm) SWCNTs, while Pd can only form near-ohmic contacts for large-diameter SWCNTs. Moreover, the Nb 2 C contacts demonstrate good stability in air.

  12. Tribological Characteristics of Tungsten Carbide Reinforced Arc Sprayed Coatings using Different Carbide Grain Size Fractions

    Directory of Open Access Journals (Sweden)

    W. Tillmann

    2017-06-01

    Full Text Available Tungsten carbide reinforced coatings play an important role in the field of surface engineering to protect stressed surfaces against wear. For thermally sprayed coatings, it is already shown that the tribological properties get mainly determined by the carbide grain size fraction. Within the scope of this study, the tribological characteristics of iron based WC-W2C reinforced arc sprayed coatings deposited using cored wires consisting of different carbide grain size fractions were examined. Microstructural characteristics of the produced coatings were scrutinized using electron microscopy and x-ray diffraction analyses. Ball-on-disk test as well as Taber Abraser and dry sand rubber wheel test were employed to analyze both the dry sliding and the abrasive wear behavior. It was shown that a reduced carbide grain size fraction as filling leads to an enhanced wear resistance against sliding. In terms of the Taber Abraser test, it is also demonstrated that a fine carbide grain size fraction results in an improved wear resistant against abrasion. As opposed to that, a poorer wear resistance was found within the dry sand rubber wheel tests. The findings show that the operating mechanisms for both abrasion tests affect the stressed surface in a different way, leading either to microcutting or microploughing.

  13. Precipitation behavior of carbides in high-carbon martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao; Shi, Chang-min [University of Science and Technology, Beijing (China). State Key Laboratory of Advanced Metallurgy; Li, Ji-hui [Yang Jiang Shi Ba Zi Group Co., Ltd, Guangdong (China)

    2017-01-15

    A fundamental study on the precipitation behavior of carbides was carried out. Thermo-calc software, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, X-ray diffractometry and high-temperature confocal laser scanning microscopy were used to study the precipitation and transformation behaviors of carbides. Carbide precipitation was of a specific order. Primary carbides (M7C3) tended to be generated from liquid steel when the solid fraction reached 84 mol.%. Secondary carbides (M7C3) precipitated from austenite and can hardly transformed into M23C6 carbides with decreasing temperature in air. Primary carbides hardly changed once they were generated, whereas secondary carbides were sensitive to heat treatment and thermal deformation. Carbide precipitation had a certain effect on steel-matrix phase transitions. The segregation ability of carbon in liquid steel was 4.6 times greater that of chromium. A new method for controlling primary carbides is proposed.

  14. Heat treated 9 Cr-1 Mo steel material for high temperature application

    Science.gov (United States)

    Jablonski, Paul D.; Alman, David; Dogan, Omer; Holcomb, Gordon; Cowen, Christopher

    2012-08-21

    The invention relates to a composition and heat treatment for a high-temperature, titanium alloyed, 9 Cr-1 Mo steel exhibiting improved creep strength and oxidation resistance at service temperatures up to 650.degree. C. The novel combination of composition and heat treatment produces a heat treated material containing both large primary titanium carbides and small secondary titanium carbides. The primary titanium carbides contribute to creep strength while the secondary titanium carbides act to maintain a higher level of chromium in the finished steel for increased oxidation resistance, and strengthen the steel by impeding the movement of dislocations through the crystal structure. The heat treated material provides improved performance at comparable cost to commonly used high-temperature steels such as ASTM P91 and ASTM P92, and requires heat treatment consisting solely of austenization, rapid cooling, tempering, and final cooling, avoiding the need for any hot-working in the austenite temperature range.

  15. Structure and stability of nonstoichiometric cubic phase δ-NbN1.2(O,C)

    International Nuclear Information System (INIS)

    Shalaeva, E.V.; Mitrofanov, B.V.; Shveikin, G.P.

    1996-01-01

    The nonstoichiometric δ-niobium nitride with surplus content of nitrogen atoms and the NaCl-type structure (a=0.439 nm), i.e. δ-NbN 1.2 (O, C), is stabilized in epitaxial deposited films. The diffraction patterns of these films display intensive diffuse scattering with regular intensity vanishings in the form of plane regions in the vicinity of structural and superstructural reciprocal space points of the δ-phase and in the form of spherical surfaces in the neighbourhood of structural points. The analysis performed shows that this scattering can be associated with the presence of mixed-nature short-range order regions in the nonstoichiometric δ-NbN 1.2 (O, C) phase which are characterized by longitudinal uncorrelated atomic displacement waves, as well as by concentration-type waves. The ordered oxycarbonitride phase (X-phase) described in the first approximation by the cubic lattice with parameter a=0.392 nm is found to precipitate when annealing the films at T=873 K. It has been established that the diffuse scattering occurring in δ-NbN 1.2 (O, C) and the structure of short-range order regions exhibit certain correlation with the structure of the precipitated ordered phase - G 100 x ∼1.1G 100 δ = K 1 ; G 010 x ∼1.1G 010 δ = K 2 (where K 1 and K 2 are wave vectors of longitudinal atomic displacement waves characterizing short-range order). (orig.)

  16. Tungsten--carbide critical assembly

    International Nuclear Information System (INIS)

    Hansen, G.E.; Paxton, H.C.

    1975-06-01

    The tungsten--carbide critical assembly mainly consists of three close-fitting spherical shells: a highly enriched uranium shell on the inside, a tungsten--carbide shell surrounding it, and a steel shell on the outside. Ideal critical specifications indicate a rather low computed value of k/sub eff/. Observed and calculated fission-rate distributions for 235 U, 238 U, and 237 Np are compared, and calculated leakage neutrons per fission in various energy groups are given. (U.S.)

  17. Characterization of TiN, TiC and Ti(C,N) in titanium-alloyed ferritic chromium steels focusing on the significance of different particle morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Michelic, S.K., E-mail: susanne.michelic@unileoben.ac.at [Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Loder, D. [Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Reip, T.; Ardehali Barani, A. [Outokumpu Nirosta GmbH, Essener Straße 244, 44793 Bochum (Germany); Bernhard, C. [Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria)

    2015-02-15

    Titanium-alloyed ferritic chromium steels are a competitive option to classical austenitic stainless steels owing to their similar corrosion resistance. The addition of titanium significantly influences their final steel cleanliness. The present contribution focuses on the detailed metallographic characterization of titanium nitrides, titanium carbides and titanium carbonitrides with regard to their size, morphology and composition. The methods used are manual and automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy as well as optical microscopy. Additional thermodynamic calculations are performed to explain the precipitation procedure of the analyzed titanium nitrides. The analyses showed that homogeneous nucleation is decisive at an early process stage after the addition of titanium. Heterogeneous nucleation gets crucial with ongoing process time and essentially influences the final inclusion size of titanium nitrides. A detailed investigation of the nuclei for heterogeneous nucleation with automated Scanning Electron Microscopy proved to be difficult due to their small size. Manual Scanning Electron Microscopy and optical microscopy have to be applied. Furthermore, it was found that during solidification an additional layer around an existing titanium nitride can be formed which changes the final inclusion morphology significantly. These layers are also characterized in detail. Based on these different inclusion morphologies, in combination with thermodynamic results, tendencies regarding the formation and modification time of titanium containing inclusions in ferritic chromium steels are derived. - Graphical abstract: Display Omitted - Highlights: • The formation and modification of TiN in the steel 1.4520 was examined. • Heterogeneous nucleation essentially influences the final steel cleanliness. • In most cases heterogeneous nuclei in TiN inclusions are magnesium based. • Particle morphology provides important information

  18. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first...... example of a cationic terminal carbide complex, [RuC(Cl)(CH3CN)(PCy3)2]+, is described and characterized by NMR, MS, X-ray crystallography, and computational studies. The experimentally observed irregular variation of the carbide 13C chemical shift is shown to be accurately reproduced by DFT, which also...... demonstrates that details of the coordination geometry affect the carbide chemical shift equally as much as variations in the nature of the auxiliary ligands. Furthermore, the kinetics of formation of the sqaure pyramidal dicyano complex, trans-[RuC(CN)2(PCy3)2], from RuC has been examined and the reaction...

  19. Modeling of composite synthesis in conditions of controlled thermal explosion

    Science.gov (United States)

    Kukta, Yaroslav; Knyazeva, Anna

    2017-12-01

    The paper proposes the model for the titanium-based composite synthesis from powders of titanium and carbon of non-stoichiometric composition. The model takes into account the mixture heating from chamber walls, the dependence of liquidus and solidus temperatures on the composition of reacting mixture and the formation of possible irreversible phases. The reaction retardation by the reaction product is taken into consideration in kinetic laws. As an example, the results of temperature and conversion level calculation are presented for the system Ti-C with the summary reaction for different temperatures of chamber walls heating. It was revealed that the reaction retardation being the reaction product can be the cause of incomplete conversion in the thermal explosion conditions. Non-stoichiometric composition leads to the conditions of degenerated mode when some additional heating is necessary to complete the reaction.

  20. Crystallization of nodular cast iron with carbides

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2008-12-01

    Full Text Available In this paper a crystallization process of nodular cast iron with carbides having a different chemical composition have been presented. It have been found, that an increase of molybdenum above 0,30% causes the ledeburutic carbides crystallization after (γ+ graphite eutectic phase crystallization. When Mo content is lower, these carbides crystallize as a pre-eutectic phase. In this article causes of this effect have been given.

  1. Effect of nanometer scale surface roughness of titanium for osteoblast function

    Directory of Open Access Journals (Sweden)

    Satoshi Migita

    2017-02-01

    Full Text Available Surface roughness is an important property for metallic materials used in medical implants or other devices. The present study investigated the effects of surface roughness on cellular function, namely cell attachment, proliferation, and differentiation potential. Titanium (Ti discs, with a hundred nanometer- or nanometer-scale surface roughness (rough and smooth Ti surface, respectively were prepared by polishing with silicon carbide paper. MC3T3-E1 mouse osteoblast-like cells were cultured on the discs, and their attachment, spreading area, proliferation, and calcification were analyzed. Cells cultured on rough Ti discs showed reduced attachment, proliferation, and calcification ability suggesting that the surface inhibited osteoblast function. The findings can provide a basis for improving the biocompatibility of medical devices.

  2. Preparation and Fatigue Properties of Functionally Graded Cemented Carbides

    International Nuclear Information System (INIS)

    Liu Yong; Liu Fengxiao; Liaw, Peter K.; He Yuehui

    2008-01-01

    Cemented carbides with a functionally graded structure have significantly improved mechanical properties and lifetimes in cutting, drilling and molding. In this work, WC-6 wt.% Co cemented carbides with three-layer graded structure (surface layer rich in WC, mid layer rich in Co and the inner part of the average composition) were prepared by carburizing pre-sintered η-phase-containing cemented carbides. The three-point bending fatigue tests based on the total-life approach were conducted on both WC-6wt%Co functionally graded cemented carbides (FGCC) and conventional WC-6wt%Co cemented carbides. The functionally graded cemented carbide shows a slightly higher fatigue limit (∼100 MPa) than the conventional ones under the present testing conditions. However, the fatigue crack nucleation behavior of FGCC is different from that of the conventional ones. The crack nucleates preferentially along the Co-gradient and perpendicular to the tension surface in FGCC, while parallel to the tension surface in conventional cemented carbides

  3. Study of the defect structure of ''pure'' and doped nonstoichiometric CeO2

    International Nuclear Information System (INIS)

    Blumenthal, R.N.

    1975-09-01

    Electrical conductivity and thermogravimetric measurements were made on Ta 2 O 5 -doped nonstoichiometric CeO 2 (i.e. Ce/sub 1-y/Ta/sub y/O/sub 2-x/ ) as a function of temperature and oxygen partial pressure. Over a limited range of temperature and nonstoichiometry, the isothermal dependence of the electrical conductivity on nonstoichiometry may be described by the equation sigma = A + Bx, where A is the electronic conductivity associated with the electronic defects produced by doping CeO 2 with Ta 2 O 5 . The electronic conductivity resulting from the nonstoichiometric defect reaction O/sup x/ + 2Ce/sub Ce//sup x/ = V 0 + 2Ce'sub Ce/ + 1 / 2 O 2 (g) is equal to Bx. The ionic conductivity may be described by the relation sigma/sub i/ = B[y+x]eμ'/sub V 0 / exp (--E/sub i//kT), and the electronic conductivity by the isothermal expressions sigma/sub e/ proportional to P/sub O 2 //sup -1/4/ and sigma/sub e/ proportional to x; x less than 3 x 10 -2 . These results are consistent with defect models involving doubly ionized oxygen vacancies. An empirical expression (i.e. Δ anti H/sub O 2 / proportional to y/2 or z/4) was obtained relating the dependence of Δ anti H/sub O 2 / on the dopant concentration of lower valent foreign cations (e.g. y/2 for Ce/sub 1-y/M/sub y/O/sub 2-y-x/ and z/4 for Ce/sub 1-z/M/sub z/O/sub 2-z/2-x/ where M = Ca, Sr and M' = Y, La). (auth)

  4. HCl removal using cycled carbide slag from calcium looping cycles

    International Nuclear Information System (INIS)

    Xie, Xin; Li, Yingjie; Wang, Wenjing; Shi, Lei

    2014-01-01

    Highlights: • Cycled carbide slag from calcium looping cycles is used to remove HCl. • The optimum temperature for HCl removal of cycled carbide slag is 700 °C. • The presence of CO 2 restrains HCl removal of cycled carbide slag. • CO 2 capture conditions have important effects on HCl removal of cycled carbide slag. • HCl removal capacity of carbide slag drops with cycle number rising from 1 to 50. - Abstract: The carbide slag is an industrial waste from chlor-alkali plants, which can be used to capture CO 2 in the calcium looping cycles, i.e. carbonation/calcination cycles. In this work, the cycled carbide slag from the calcium looping cycles for CO 2 capture was proposed to remove HCl in the flue gas from the biomass-fired and RDFs-fired boilers. The effects of chlorination temperature, HCl concentration, particle size, presence of CO 2 , presence of O 2 , cycle number and CO 2 capture conditions in calcium looping cycles on the HCl removal behavior of the carbide slag experienced carbonation/calcination cycles were investigated in a triple fixed-bed reactor. The chlorination product of the cycled carbide slag from the calcium looping after absorbing HCl is not CaCl 2 but CaClOH. The optimum temperature for HCl removal of the cycled carbide slag from the carbonation/calcination cycles is 700 °C. The chlorination conversion of the cycled carbide slag increases with increasing the HCl concentration. The cycled carbide slag with larger particle size exhibits a lower chlorination conversion. The presence of CO 2 decreases the chlorination conversions of the cycled carbide slag and the presence of O 2 has a trifling impact. The chlorination conversion of the carbide slag experienced 1 carbonation/calcination cycle is higher than that of the uncycled calcined sorbent. As the number of carbonation/calcination cycles increases from 1 to 50, the chlorination conversion of carbide slag drops gradually. The high calcination temperature and high CO 2

  5. Influence of uranium dioxide nonstoichiometric oxygen on the work function of Mo(110) single crystal

    International Nuclear Information System (INIS)

    Bekmukhabetov, E.S.; Dzhajmurzin, A.A.; Imanbekov, Zh.Zh.

    1985-01-01

    The influence of the uranium dioxide nonstoichiometric oxygen on the work function of a Mo(110) single crystal has been studied. When the surface diffusion of oxygen on the tested surface takes place, the work function is shown to decrease and, subsequently, to increase until it becomes stable. The dependence of the work function on the temperature of the specimen in the range of 1600-1900 K with a minimum at 1730 K has been found. The minimum is attributed to the dipole layer formation

  6. Titanium ; dream new material

    International Nuclear Information System (INIS)

    Lee, Yong Tae; Kim Seung Eon; Heoon, Yong Taek; Jung, Hui Won

    2001-11-01

    The contents of this book are history of Titanium, present situation of Titanium industry, property of Titanium alloy, types of it, development of new alloy of Titanium smelting of Titanium, cast of Titanium and heat treatment of Titanium, Titanium alloy for plane, car parts, biological health care, and sport leisure and daily life, prospect, and Titanium industrial development of Titanium in China.

  7. Boron-carbide-aluminum and boron-carbide-reactive metal cermets. [B/sub 4/C-Al

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jie; Chen, Jinwei, E-mail: jwchen@scu.edu.cn; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin, E-mail: rl.wang@scu.edu.cn

    2016-12-15

    Graphical abstract: A hybrid catalyst was prepared via a quite green and simple method to achieve an one-pot synthesis of the N-doping carbon, tungsten carbides, and iron/cobalt carbides. It exhibited comparable electrocatalytic activity, higher durability and ability to methanol tolerance compared with commercial Pt/C to ORR. - Highlights: • A novel type of hybrid Fe/Co/WC@NC catalysts have been successfully synthesized. • The hybrid catalyst also exhibited better durability and methanol tolerance. • Multiple effective active sites of Fe{sub 3}C, Co{sub 3}C, WC, and NC help to improve catalytic performance. - Abstract: 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 Fe{sub 3}C and Co{sub 3}C 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, Fe{sub 3}C, and Co{sub 3}C. 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.

  9. Composition and properties tailoring in Mg.sup.2+./sup. codoped non-stoichiometric LuAG:Ce,Mg scintillation ceramics

    Czech Academy of Sciences Publication Activity Database

    Liu, S.; Mareš, Jiří A.; Babin, Vladimir; Hu, C.; Kou, H.; D'Ambrosio, C.; Li, J.; Pan, Y.; Nikl, Martin

    2017-01-01

    Roč. 37, č. 4 (2017), s. 1689-1694 ISSN 0955-2219 R&D Projects: GA ČR GA16-15569S Institutional support: RVO:68378271 Keywords : non-stoichiometric ceramic s * LuAG:Ce * Mg scintillator * Mg 2+ codopant * antisite defects * afterglow Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.411, year: 2016

  10. Preparation of aluminum nitride-silicon carbide nanocomposite powder by the nitridation of aluminum silicon carbide

    NARCIS (Netherlands)

    Itatani, K.; Tsukamoto, R.; Delsing, A.C.A.; Hintzen, H.T.J.M.; Okada, I.

    2002-01-01

    Aluminum nitride (AlN)-silicon carbide (SiC) nanocomposite powders were prepared by the nitridation of aluminum-silicon carbide (Al4SiC4) with the specific surface area of 15.5 m2·g-1. The powders nitrided at and above 1400°C for 3 h contained the 2H-phases which consisted of AlN-rich and SiC-rich

  11. Three-dimensional nanometer scale analyses of precipitate structures and local compositions in titanium aluminide engineering alloys

    Science.gov (United States)

    Gerstl, Stephan S. A.

    Titanium aluminide (TiAl) alloys are among the fastest developing class of materials for use in high temperature structural applications. Their low density and high strength make them excellent candidates for both engine and airframe applications. Creep properties of TiAl alloys, however, have been a limiting factor in applying the material to a larger commercial market. In this research, nanometer scale compositional and structural analyses of several TiAl alloys, ranging from model Ti-Al-C ternary alloys to putative commercial alloys with 10 components are investigated utilizing three dimensional atom probe (3DAP) and transmission electron microscopies. Nanometer sized borides, silicides, and carbide precipitates are involved in strengthening TiAl alloys, however, chemical partitioning measurements reveal oxygen concentrations up to 14 at. % within the precipitate phases, resulting in the realization of oxycarbide formation contributing to the precipitation strengthening of TiAl alloys. The local compositions of lamellar microstructures and a variety of precipitates in the TiAl system, including boride, silicide, binary carbides, and intermetallic carbides are investigated. Chemical partitioning of the microalloying elements between the alpha2/gamma lamellar phases, and the precipitate/gamma-matrix phases are determined. Both W and Hf have been shown to exhibit a near interfacial excess of 0.26 and 0.35 atoms nm-2 respectively within ca. 7 nm of lamellar interfaces in a complex TiAl alloy. In the case of needle-shaped perovskite Ti3AlC carbide precipitates, periodic domain boundaries are observed 5.3+/-0.8 nm apart along their growth axis parallel to the TiAl[001] crystallographic direction with concomitant composition variations after 24 hrs. at 800°C.

  12. Three-dimensional studies of intergranular carbides in austenitic stainless steel.

    Science.gov (United States)

    Ochi, Minoru; Kawano, Rika; Maeda, Takuya; Sato, Yukio; Teranishi, Ryo; Hara, Toru; Kikuchi, Masao; Kaneko, Kenji

    2017-04-01

    A large number of morphological studies of intergranular carbides in steels have always been carried out in two dimensions without considering their dispersion manners. In this article, focused ion beam serial-sectioning tomography was carried out to study the correlation among the grain boundary characteristics, the morphologies and the dispersions of intergranular carbides in 347 austenitic stainless steel. More than hundred intergranular carbides were characterized in three dimensions and finally classified into three different types, two types of carbides probably semi-coherent to one of the neighboring grains with plate-type morphology, and one type of carbides incoherent to both grains with rod-type morphology. In addition, the rod-type carbide was found as the largest number of carbides among three types. Since large numbers of defects, such as misfit dislocations, may be present at the grain boundaries, which can be ideal nucleation sites for intergranular rod-type carbide precipitation. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved.For permissions, please e-mail: journals.permissions@oup.com.

  13. Graphite and boron carbide composites made by hot-pressing

    International Nuclear Information System (INIS)

    Miyazaki, K.; Hagio, T.; Kobayashi, K.

    1981-01-01

    Composites consisting of graphite and boron carbide were made by hot-pressing mixed powders of coke carbon and boron carbide. The change of relative density, mechanical strength and electrical resistivity of the composites and the X-ray parameters of coke carbon were investigated with increase of boron carbide content and hot-pressing temperature. From these experiments, it was found that boron carbide powder has a remarkable effect on sintering and graphitization of coke carbon powder above the hot-pressing temperature of 2000 0 C. At 2200 0 C, electrical resistivity of the composite and d(002) spacing of coke carbon once showed minimum values at about 5 to 10 wt% boron carbide and then increased. The strength of the composite increased with increase of boron carbide content. It was considered that some boron from boron carbide began to diffuse substitutionally into the graphite structure above 2000 0 C and densification and graphitization were promoted with the diffusion of boron. Improvements could be made to the mechanical strength, density, oxidation resistance and manufacturing methods by comparing with the properties and processes of conventional graphites. (author)

  14. Effect of metallic coating on the properties of copper-silicon carbide composites

    Science.gov (United States)

    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.

  15. Joining of boron carbide using nickel interlayer

    International Nuclear Information System (INIS)

    Vosughi, A.; Hadian, A. M.

    2008-01-01

    Carbide ceramics such as boron carbide due to their unique properties such as low density, high refractoriness, and high strength to weight ratio have many applications in different industries. This study focuses on direct bonding of boron carbide for high temperature applications using nickel interlayer. The process variables such as bonding time, temperature, and pressure have been investigated. The microstructure of the joint area was studied using electron scanning microscope technique. At all the bonding temperatures ranging from 1150 to 1300 d eg C a reaction layer formed across the ceramic/metal interface. The thickness of the reaction layer increased by increasing temperature. The strength of the bonded samples was measured using shear testing method. The highest strength value obtained was about 100 MPa and belonged to the samples bonded at 1250 for 75 min bonding time. The strength of the joints decreased by increasing the bonding temperature above 1250 d eg C . The results of this study showed that direct bonding technique along with nickel interlayer can be successfully utilized for bonding boron carbide ceramic to itself. This method may be used for bonding boron carbide to metals as well.

  16. Surface metallurgy of cemented carbide tools

    International Nuclear Information System (INIS)

    Chopra, K.L.; Kashyap, S.C.; Rao, T.V.; Rajagopalan, S.; Srivastava, P.K.

    1983-01-01

    Transition metal carbides, owing to their high melting point, hardness and wear resistance, are potential candidates for specific application in rockets, nuclear engineering equipment and cutting tools. Tungsten carbide sintered with a binder (either cobalt metal or a mixture of Co + TiC and/or TaC(NbC)) is used for cutting tools. The surface metallurgy of several commercially available cemented carbide tools was studied by Auger electron spectroscopy and X-ray photoelectron spectroscopy techniques. The tool surfaces were contaminated by adsorbed oxygen up to a depth of nearly 0.3 μm causing deterioration of the mechanical properties of the tools. Studies of fractured samples indicated that the tool surfaces were prone to oxygen adsorption. The fracture path passes through the cobalt-rich regions. The ineffectiveness of a worn cutting tool is attributed to the presence of excessive iron from the steel workpiece and carbon and oxygen in the surface layers of the tool. The use of appropriate hard coatings on cemented carbide tools is suggested. (Auth.)

  17. A hybrid Taguchi-artificial neural network approach to predict surface roughness during electric discharge machining of titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sanjeev; Batish, Ajay [Thapar University, Patiala (India); Singh, Rupinder [GNDEC, Ludhiana (India); Singh, T. P. [Symbiosis Institute of Technology, Pune (India)

    2014-07-15

    In the present study, electric discharge machining process was used for machining of titanium alloys. Eight process parameters were varied during the process. Experimental results showed that current and pulse-on-time significantly affected the performance characteristics. Artificial neural network coupled with Taguchi approach was applied for optimization and prediction of surface roughness. The experimental results and the predicted results showed good agreement. SEM was used to investigate the surface integrity. Analysis for migration of different chemical elements and formation of compounds on the surface was performed using EDS and XRD pattern. The results showed that high discharge energy caused surface defects such as cracks, craters, thick recast layer, micro pores, pin holes, residual stresses and debris. Also, migration of chemical elements both from electrode and dielectric media were observed during EDS analysis. Presence of carbon was seen on the machined surface. XRD results showed formation of titanium carbide compound which precipitated on the machined surface.

  18. Importance of Fuel Cell Tests for Stability Assessment—Suitability of Titanium Diboride as an Alternative Support Material

    Directory of Open Access Journals (Sweden)

    Christina Roth

    2014-06-01

    Full Text Available Carbon corrosion is a severe issue limiting the long-term stability of carbon-supported catalysts, in particular in the highly dynamic conditions of automotive applications. (Doped oxides have been discussed as suitable alternatives to replace carbon, but often suffer from poor electron conductivity. That is why non-oxide ceramics, such as tungsten carbide and titanium nitride, have been discussed recently. Titanium diboride has also been proposed, due to its promising activity and stability in an aqueous electrochemical cell. In this work, Pt nanoparticles were deposited onto μm-sized TiB2 particles with improved grain size, manufactured into porous gas diffusion electrodes and tested in a realistic polymer electrolyte membrane (PEM fuel cell environment. In contrast to the model studies in an aqueous electrochemical cell, in the presence of oxygen and high potentials at the cathode side of a real fuel cell, TiB2 becomes rapidly oxidized as indicated by intensely colored regions in the membrane-electrode assembly (MEA. Moreover, already the electrode manufacturing process led to the formation of titanium oxides, as shown by X-ray diffraction measurements. This demonstrates that Cyclic Voltammetry (CV measurements in an aqueous electrochemical cell are not sufficient to prove stability of novel materials for fuel cell applications.

  19. Tribology of carbide derived carbon films synthesized on tungsten carbide

    Science.gov (United States)

    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.

  20. Titanium Oxide/Platinum Catalysis: Charge Transfer from a Titanium Oxide Support Controls Activity and Selectivity in Methanol Oxidation on Platinum

    KAUST Repository

    Hervier, Antoine; Baker, L. Robert; Komvopoulos, Kyriakos; Somorjai, Gabor A.

    2011-01-01

    formaldehyde, methyl formate, and carbon dioxide. F-doped samples demonstrated significantly higher activity for methanol oxidation when the TiOx was stoichiometric (TiO 2), but lower activity when it was nonstoichiometric (TiO 1.7 and TiO1.9). These results

  1. Improved hardness of laser alloyed X12CrNiMo martensitic stainless steel

    CSIR Research Space (South Africa)

    Adebiyi, DI

    2011-07-01

    Full Text Available The improvement in hardness of X12CrNiMo martensitic stainless steel laser alloyed with 99.9% pure titanium carbide, stellite 6 and two cases of premixed ratio of titanium carbide and stellite 6 [TiC (30 wt.%)- stellite 6 (70 wt.%) and TiC (70 wt...

  2. Natural precursor based hydrothermal synthesis of sodium carbide for reactor applications

    Science.gov (United States)

    Swapna, M. S.; Saritha Devi, H. V.; Sebastian, Riya; Ambadas, G.; Sankararaman, S.

    2017-12-01

    Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.

  3. Vanadium carbide coatings: deposition process and properties

    International Nuclear Information System (INIS)

    Borisova, A.; Borisov, Y.; Shavlovsky, E.; Mits, I.; Castermans, L.; Jongbloed, R.

    2001-01-01

    Vanadium carbide coatings on carbon and alloyed steels were produced by the method of diffusion saturation from the borax melt. Thickness of the vanadium carbide layer was 5-15 μm, depending upon the steel grade and diffusion saturation parameters. Microhardness was 20000-28000 MPa and wear resistance of the coatings under conditions of end face friction without lubrication against a mating body of WC-2Co was 15-20 times as high as that of boride coatings. Vanadium carbide coatings can operate in air at a temperature of up to 400 o C. They improve fatigue strength of carbon steels and decrease the rate of corrosion in sea and fresh water and in acid solutions. The use of vanadium carbide coatings for hardening of various types of tools, including cutting tools, allows their service life to be extended by a factor of 3 to 30. (author)

  4. Reactor irradiation effect on the physical-mechanical properties of zirconium carbides and niobium carbides

    International Nuclear Information System (INIS)

    Andrievskij, R.A.; Vlasov, K.P.; Shevchenko, A.S.; Lanin, A.G.; Pritchin, S.A.; Klyushin, V.V.; Kurushin, S.P.; Maskaev, A.S.

    1978-01-01

    A study has been made of the effect of the reactor radiation by a flux of neutrons 1.5x10 20 n/cm 2 (E>=1 meV) at radiation temperatures of 150 and 1100 deg C on the physico-mechanical properties of carbides of zirconium and niobium and their equimolar hard solution. A difference has been discovered in the behaviour of the indicated carbides under the effect of radiation. Under the investigated conditions of radiation the density of zirconium carbide is being decreased, while in the niobium carbide no actual volumetric changes occur. The increase of the lattice period in ZrC is more significant than in NbC. The electric resistance of ZrC is also changed more significantly than in the case of NbC, while for the microhardness a reverse relationship is observed. Strength and elasticity modulus change insignificantly in both cases. Resistance to crack formation shows a higher reduction for ZrC than for NbC, while the thermal strength shows an approximately similar increase. The equimolar hard solution of ZrC and NbC behaves to great extent similar to ZrC, although the change in electric resistance reminds of NbC while thermal strength changes differently. The study of the microstructure of the specimens has shown that radiation causes a large number of etching patterns-dislocations in NbC which are almost absent in ZrC

  5. Joining of porous silicon carbide bodies

    Science.gov (United States)

    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.

  6. Conceptual design study of LMFBR core with carbide fuel

    International Nuclear Information System (INIS)

    Tezuka, H.; Hojuyama, T.; Osada, H.; Ishii, T.; Hattori, S.; Nishimura, T.

    1987-01-01

    Carbide fuel is a hopeful candidate for demonstration FBR(DFBR) fuel from the plant cost reduction point of view. High thermal conductivity and high heavy metal content of carbide fuel lead to high linear heat rate and high breeding ratio. We have analyzed carbide fuel core characteristics and have clarified the concept of carbide fuel core. By survey calculation, we have obtained a correlation map between core parameters and core characteristics. From the map, we have selected a high efficiency core whose features are better than those of an oxide core, and have obtained reactivity coefficients. The core volume and the reactor fuel inventory are approximately 20% smaller, and the burn-up reactivity loss is 50% smaller compared with the oxide fuel core. These results will reduce the capital cost. The core reactivity coefficients are similar to the conventional oxide DFBR's. Therefore the carbide fuel core is regarded as safe as the oxide core. Except neutron fluence, the carbide fuel core has better nuclear features than the oxide core

  7. Microstructural studies of carbides in MAR-M247 nickel-based superalloy

    Science.gov (United States)

    Szczotok, A.; Rodak, K.

    2012-05-01

    Carbides play an important role in the strengthening of microstructures of nickel-based superalloys. Grain boundary carbides prevent or retard grain-boundary sliding and make the grain boundary stronger. Carbides can also tie up certain elements that would otherwise promote phase instability during service. Various types of carbides are possible in the microstructure of nickel-based superalloys, depending on the superalloy composition and processing. In this paper, scanning electron and scanning transmission electron microscopy studies of carbides occurring in the microstructure of polycrystalline MAR-M247 nickel-based superalloy were carried out. In the present work, MC and M23C6 carbides in the MAR-M247 microstructure were examined.

  8. Compressor Impeller Erosion Resistant Surface Treatment

    National Research Council Canada - National Science Library

    Riley, Michael

    2000-01-01

    ...). Coatings based on tungsten carbide tantalum carbide. titanium carbide all with a cobalt matrix were evaluated for high velocity particle erosion in conventional wear test studies as well as wind tunnel testing...

  9. Processes and applications of silicon carbide nanocomposite fibers

    International Nuclear Information System (INIS)

    Shin, D G; Cho, K Y; Riu, D H; Jin, E J

    2011-01-01

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and γ-Al 2 O 3 . Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200deg. C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  10. Processes and applications of silicon carbide nanocomposite fibers

    Energy Technology Data Exchange (ETDEWEB)

    Shin, D G; Cho, K Y; Riu, D H [Nanomaterials Team, Korea Institute of Ceramic Engineering and Technology, 233-5 Gasan-dong, Guemcheon-gu, Seoul 153-801 (Korea, Republic of); Jin, E J, E-mail: dhriu15@seoultech.ac.kr [Battelle-Korea Laborotary, Korea University, Anamdong, Seongbuk-gu, Seoul (Korea, Republic of)

    2011-10-29

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and {gamma}-Al{sub 2}O{sub 3}. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200deg. C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  11. Processes and applications of silicon carbide nanocomposite fibers

    Science.gov (United States)

    Shin, D. G.; Cho, K. Y.; Jin, E. J.; Riu, D. H.

    2011-10-01

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and γ-Al2O3. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200°C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  12. Fabrication of chamfered uranium-plutonium mixed carbide pellets

    International Nuclear Information System (INIS)

    Arai, Yasuo; Iwai, Takashi; Shiozawa, Kenichi; Handa, Muneo

    1985-10-01

    Chamfered uranium-plutonium mixed carbide pellets for high burnup irradiation test in JMTR were fabricated in glove boxes with purified argon gas. The size of die and punch in a press was decided from pellet densities and dimensions including the angle of chamfered parts. No chip or crack caused by adopting chamfered pellets was found in both pressing and sintering stages. In addition to mixed carbide pellets, uranium carbide pellets used as insulators were also successfully fabricated. (author)

  13. Carbides in Nodular Cast Iron with Cr and Mo

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2007-07-01

    Full Text Available In these paper results of elements microsegregation in carbidic nodular cast iron have been presented. A cooling rate in the centre of the cross-section and on the surface of casting and change of moulding sand temperature during casting crystallization and its self-cooling have been investigated. TDA curves have been registered. The linear distribution of elements concentration in an eutectic grain, primary and secondary carbides have been made. It was found, that there are two kinds of carbides: Cr and Mo enriched. A probable composition of primary and secondary carbides have been presented.

  14. Sealing glasses for titanium and titanium alloys

    Science.gov (United States)

    Brow, Richard K.; McCollister, Howard L.; Phifer, Carol C.; Day, Delbert E.

    1997-01-01

    Barium lanthanoborate sealing-glass compositions are provided comprising various combinations (in terms of mole-%) of boron oxide (B.sub.2 O.sub.3), barium oxide (BaO), lanthanum oxide (La.sub.2 O.sub.3), and at least one other oxide selected from the group consisting of aluminum oxide (Al.sub.2 O.sub.3), calcium oxide (CaO), lithium oxide (Li.sub.2 O), sodium oxide (Na.sub.2 O), silicon dioxide (SiO.sub.2), or titanium dioxide (TiO.sub.2). These sealing-glass compositions are useful for forming hermetic glass-to-metal seals with titanium and titanium alloys having an improved aqueous durability and favorable sealing characteristics. Examples of the sealing-glass compositions are provided having coefficients of thermal expansion about that of titanium or titanium alloys, and with sealing temperatures less than about 900.degree. C., and generally about 700.degree.-800.degree. C. The barium lanthanoborate sealing-glass compositions are useful for components and devices requiring prolonged exposure to moisture or water, and for implanted biomedical devices (e.g. batteries, pacemakers, defibrillators, pumps).

  15. Determination of free carbon content in boron carbide ceramic powders

    International Nuclear Information System (INIS)

    Castro, A.R.M. de; Lima, N.B. de; Paschoal, J.O.A.

    1990-01-01

    Boron carbide is a ceramic material of technological importance due to its hardness and high chemical and thermal stabilities. Free carbon is always found as a process dependent impurity in boron carbide. The development of procedures for its detection is required because its presence leads to a degradation of the boron carbide properties. In this work, several procedures for determining free carbon content in boron carbide specimens are reported and discussed for comparison purposes. (author) [pt

  16. Surface modification of titanium and titanium alloys by ion implantation.

    Science.gov (United States)

    Rautray, Tapash R; Narayanan, R; Kwon, Tae-Yub; Kim, Kyo-Han

    2010-05-01

    Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, to improve the biological, chemical, and mechanical properties, surface modification is often performed. In view of this, the current review casts new light on surface modification of titanium and titanium alloys by ion beam implantation. (c) 2010 Wiley Periodicals, Inc.

  17. Gentamicin-Eluting Titanium Dioxide Nanotubes Grown on the Ultrafine-Grained Titanium.

    Science.gov (United States)

    Nemati, Sima Hashemi; Hadjizadeh, Afra

    2017-08-01

    Titanium (Ti)-based materials is the most appropriate choices for the applications as orthopedic and dental implants. In this regard, ultrafine-grained (UFG) titanium with an enhanced mechanical properties and surface energy has attracted more attention. Titanium dioxide (TiO 2 ) nanotubes grown on the titanium could enhance bone bonding, cellular response and are good reservoirs for loading drugs and antibacterial agents. This article investigates gentamicin loading into and release from the TiO 2 nanotubes, grown on the UFG compared to coarse-grained (CG) titanium substrate surfaces. Equal Channel Angular Pressing (ECAP) was employed to produce the UFG structure titanium. TiO 2 nanotubes were grown by the anodizing technique on both UFG and CG titanium substrate surfaces. Scanning electron microscopy (SEM) imaging confirmed TiO 2 nanotube growth on the surface. The UV-vis spectroscopy analysis results show that the amount of gentamicin load-release in the anodized UFG titanium sample is higher than that of CG one which can be explained in terms of thicker TiO 2 nanotube arrays layer formed on UFG sample. Moreover, the anodized UFG titanium samples released the drug in a longer time than CG (1 day for the UFG titanium vs. 3 h for the CG one). Regarding wettability analysis, anodized UFG titanium sample showed more enhanced hydrophilicity than CG counterpart. Therefore, the significantly smaller grain size of pure titanium provided by the ECAP technique coupled with appropriate subsequent anodization treatment not only offers a good combination of biocompatibility and adequate mechanical properties but also it provides a delayed release condition for gentamicin.

  18. Ti3SiC2 Synthesis by Powder Metallurgical Methods

    OpenAIRE

    Kero, Ida; Antti, Marta-Lena; Odén, Magnus

    2007-01-01

    Titanium silicon carbide MAX phase was synthesised by a powder metallurgical method from ball milled TiC/Si powders of two different compositions, with TiC/Si ratios of 3:2 and 3:2.2 respectively. The cold pressed samples were analysed by dilatometry under flowing argon or sintered under vacuum for different times. The sintered samples were evaluated using x-ray diffraction (XRD). This study showed that titanium carbide was always present as a secondary phase and silicon carbide accompanied t...

  19. Carbides crystalline structure of AISI M2 high-speed steel

    International Nuclear Information System (INIS)

    Serna, M.M.; Galego, E.; Rossi, J.L.

    2005-01-01

    The aim of this study was to identify the crystallographic structure of the extracted carbides of AISI M2 steel spray formed The structure determination of these carbides. The structure determination of these carbides is a very hard work. Since these structures were formed by atom migration it is not possible to reproduce them by a controlled process with a determined chemical composition. The solution of this problem is to obtain the carbide by chemical extraction from the steel. (Author)

  20. Ternary carbide uranium fuels for advanced reactor design applications

    International Nuclear Information System (INIS)

    Knight, Travis; Anghaie, Samim

    1999-01-01

    Solid-solution mixed uranium/refractory metal carbides such as the pseudo-ternary carbide, (U, Zr, Nb)C, hold significant promise for advanced reactor design applications because of their high thermal conductivity and high melting point (typically greater than 3200 K). Additionally, because of their thermochemical stability in a hot-hydrogen environment, pseudo-ternary carbides have been investigated for potential space nuclear power and propulsion applications. However, their stability with regard to sodium and improved resistance to attack by water over uranium carbide portends their usefulness as a fuel for advanced terrestrial reactors. An investigation into processing techniques was conducted in order to produce a series of (U, Zr, Nb)C samples for characterization and testing. Samples with densities ranging from 91% to 95% of theoretical density were produced by cold pressing and sintering the mixed constituent carbides at temperatures as high as 2650 K. (author)

  1. Structure and thermal expansion of NbC complex carbides

    International Nuclear Information System (INIS)

    Khatsinskaya, I.M.; Chaporova, I.N.; Cheburaeva, R.F.; Samojlov, A.I.; Logunov, A.V.; Ignatova, I.A.; Dodonova, L.P.

    1983-01-01

    Alloying dependences of the crystal lattice parameters at indoor temperature and coefficient of thermal linear exspansion within a 373-1273 K range are determined for complex NbC-base carbides by the method of mathematical expemental design. It is shown that temperature changes in the linear expansion coefficient of certain complex carbides as distinct from NbC have an anomaly (minimum) within 773-973 K caused by occurring reversible phase transformations. An increase in the coefficient of thermal linear expansion and a decrease in hardness of NbC-base tungsten-, molybdenum-, vanadium- and hafnium-alloyed carbides show a weakening of a total chemical bond in the complex carbides during alloying

  2. Tantalum and niobium carbides obtention by carbothermic reduction of columbotantalite ores

    International Nuclear Information System (INIS)

    Gordo, E.; Garcia-Carcedo, F.; Torralba, J.M.

    1998-01-01

    Tantalum and niobium carbides are characterized by its high hardness and chemical corrosion resistance. Both carbides, but mainly TaC, are used in hard metals (sintered carbides), together with their carbides, to manufacture cutting tools and dies in special machining applications involving mechanical shock at high temperature. Its use as reinforcement of wear resistant materials through powder metallurgy techniques are being investigated. However, the use of TaC is usually limited because of its high cost. Therefore tantalum carbide with niobium content, which is cheaper, is used. In this work the obtention of complex tantalum and niobium carbides from a Spanish columbotantalite ore is studied through relatively cheap and simple process as it is carbothermic reduction. Concentration of the ore, its reduction and the characterization of products are described. (Author) 11 refs

  3. Extreme-Environment Silicon-Carbide (SiC) Wireless Sensor Suite

    Science.gov (United States)

    Yang, Jie

    2015-01-01

    Phase II objectives: Develop an integrated silicon-carbide wireless sensor suite capable of in situ measurements of critical characteristics of NTP engine; Compose silicon-carbide wireless sensor suite of: Extreme-environment sensors center, Dedicated high-temperature (450 deg C) silicon-carbide electronics that provide power and signal conditioning capabilities as well as radio frequency modulation and wireless data transmission capabilities center, An onboard energy harvesting system as a power source.

  4. Oxide film assisted dopant diffusion in silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Tin, Chin-Che, E-mail: cctin@physics.auburn.ed [Department of Physics, Auburn University, Alabama 36849 (United States); Mendis, Suwan [Department of Physics, Auburn University, Alabama 36849 (United States); Chew, Kerlit [Department of Electrical and Electronic Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur (Malaysia); Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin [Physical Technical Institute, Uzbek Academy of Sciences, 700084 Tashkent (Uzbekistan); Atabaev, Bakhtiyar [Institute of Electronics, Uzbek Academy of Sciences, 700125 Tashkent (Uzbekistan); Adedeji, Victor [Department of Chemistry, Geology and Physics, Elizabeth City State University, North Carolina 27909 (United States); Rusli [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore)

    2010-10-01

    A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.

  5. Oxide film assisted dopant diffusion in silicon carbide

    International Nuclear Information System (INIS)

    Tin, Chin-Che; Mendis, Suwan; Chew, Kerlit; Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin; Atabaev, Bakhtiyar; Adedeji, Victor; Rusli

    2010-01-01

    A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.

  6. Qualification testing and full-scale demonstration of titanium-treated zeolite for sludge wash processing

    Energy Technology Data Exchange (ETDEWEB)

    Dalton, W.J.

    1997-06-30

    Titanium-treated zeolite is a new ion-exchange material that is a variation of UOP (formerly Union Carbide) IONSIV IE-96 zeolite (IE-96) that has been treated with an aqueous titanium solution in a proprietary process. IE-96 zeolite, without the titanium treatment, has been used since 1988 in the West Valley Demonstration Project`s (WVDP) Supernatant Treatment System (STS) ion-exchange columns to remove Cs-137 from the liquid supernatant solution. The titanium-treated zeolite (TIE-96) was developed by Battelle-Pacific Northwest Laboratory (PNL). Following successful lab-scale testing of the PNL-prepared TIE-96, UOP was selected as a commercial supplier of the TIE-96 zeolite. Extensive laboratory tests conducted by both the WVDP and PNL indicate that the TIE-96 will successfully remove comparable quantities of Cs-137 from Tank 8D-2 high-level radioactive liquid as was done previously with IE-96. In addition to removing Cs-137, TIE-96 also removes trace quantities of Pu, as well as Sr-90, from the liquid being processed over a wide range of operating conditions: temperature, pH, and dilution. The exact mechanism responsible for the Pu removal is not fully understood. However, the Pu that is removed by the TIE-96 remains on the ion-exchange column under anticipated sludge wash processing conditions. From May 1988 to November 1990, the WVDP processed 560,000 gallons of liquid high-level radioactive supernatant waste stored in Tank 8D-2. Supernatant is an aqueous salt solution comprised primarily of soluble sodium salts. The second stage of the high-level waste treatment process began November 1991 with the initiation of sludge washing. Sludge washing involves the mixing of Tank 8D-2 contents, both sludge and liquid, to dissolve the sulfate salts present in the sludge. Two sludge washes were required to remove sulfates from the sludge.

  7. Study on the performance of fuel elements with carbide and carbide-nitride fuel

    International Nuclear Information System (INIS)

    Golovchenko, Yu.M.; Davydov, E.F.; Maershin, A.A.

    1985-01-01

    Characteristics, test conditions and basic results of material testing of fuel elements with carbide and carbonitride fuel irradiated in the BOR-60 reactor up to 3-10% burn-up at specific power rate of 55-70 kW/m and temperatures of the cladding up to 720 deg C are described. Increase of cladding diameter is stated mainly to result from pressure of swelling fuel. The influence of initial efficient porosity of the fuel on cladding deformation and fuel stoichiometry on steel carbonization is considered. Utilization of carbide and carbonitride fuel at efficient porosity of 20% at the given test modes is shown to ensure their operability up to 10% burn-up

  8. Formation mechanism of spheroidal carbide in ultra-low carbon ductile cast iron

    Directory of Open Access Journals (Sweden)

    Bin-guo Fu

    2016-09-01

    Full Text Available The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.

  9. Synthesis of highly non-stoichiometric Cu{sub 2}ZnSnS{sub 4} nanoparticles with tunable bandgaps

    Energy Technology Data Exchange (ETDEWEB)

    Hamanaka, Yasushi, E-mail: hamanaka@nitech.ac.jp; Oyaizu, Wataru; Kawase, Masanari [Nagoya Institute of Technology, Department of Materials Science and Engineering (Japan); Kuzuya, Toshihiro [Muroran Institute of Technology, College of Design and Manufacturing Technology (Japan)

    2017-01-15

    Non-stoichiometric Cu{sub 2}ZnSnS{sub 4} nanoparticles with average diameters of 4–15 nm and quasi-polyhedral shape were successfully synthesized by a colloidal method. We found that a non-stoichiometric composition of Zn to Cu in Cu{sub 2}ZnSnS{sub 4} nanoparticles yielded a correlation where Zn content increased with a decrease in Cu content, suggesting formation of lattice defects relating to Cu and Zn, such as a Cu vacancy (V{sub Cu}), antisite with Zn replacing Cu (Zn{sub Cu}), and/or defect cluster of V{sub Cu} and Zn{sub Cu}. The bandgap energy of Cu{sub 2}ZnSnS{sub 4} nanoparticles systematically varies between 1.56 and 1.83 eV depending on the composition ratios of Cu and Zn, resulting in a wider bandgap for Cu-deficient Cu{sub 2}ZnSnS{sub 4} nanoparticles. These characteristics can be ascribed to the modification in electronic band structures due to formation of V{sub Cu} and Zn{sub Cu} on the analogy of ternary copper chalcogenide, chalcopyrite CuInSe{sub 2}, in which the top of the valence band shifts downward with decreasing Cu contents, because much like the structure of CuInSe{sub 2}, the top of the valence band is composed of a Cu 3d orbital in Cu{sub 2}ZnSnS{sub 4}.

  10. Crystal structure of non-stoichiometric copper selenides studied by neutron scattering and X-ray diffraction

    International Nuclear Information System (INIS)

    Bikkulova, N.N.; Yagafarova, Z.A.; Asylguzhina, G.N.; Danilkin, S.A.; Fuess, H.; Skomorokhov, A.N.; Yadrovskii, E.L.; Beskrovnyi, A.I.

    2003-01-01

    Structural characteristics of non-stoichiometric copper selenides were studied by the elastic neutron and X-ray scattering techniques. Rietveld analysis was used to refine the structure of the high-temperature β-phase of the Cu 1.75 Se, Cu 1.78 Se, and Cu 1.83 Se samples. The homogeneity ranges of the cubic phase were determined. The modification of the crystal structure accompanying the β-α phase transition was studied for Cu 1.75 Se and Cu 1.98 Se compounds within the 443-10 K temperature range. It was shown that the phase transition is accompanied by distortions of the fcc lattice and the ordering of copper ions

  11. Highly thermal conductive carbon fiber/boron carbide composite material

    International Nuclear Information System (INIS)

    Chiba, Akio; Suzuki, Yasutaka; Goto, Sumitaka; Saito, Yukio; Jinbo, Ryutaro; Ogiwara, Norio; Saido, Masahiro.

    1996-01-01

    In a composite member for use in walls of a thermonuclear reactor, if carbon fibers and boron carbide are mixed, since they are brought into contact with each other directly, boron is reacted with the carbon fibers to form boron carbide to lower thermal conductivity of the carbon fibers. Then, in the present invention, graphite or amorphous carbon is filled between the carbon fibers to provide a fiber bundle of not less than 500 carbon fibers. Further, the surface of the fiber bundle is coated with graphite or amorphous carbon to suppress diffusion or solid solubilization of boron to carbon fibers or reaction of them. Then, lowering of thermal conductivity of the carbon fibers is prevented, as well as the mixing amount of the carbon fiber bundles with boron carbide, a sintering temperature and orientation of carbon fiber bundles are optimized to provide a highly thermal conductive carbon fiber/boron carbide composite material. In addition, carbide or boride type short fibers, spherical graphite, and amorphous carbon are mixed in the boron carbide to prevent development of cracks. Diffusion or solid solubilization of boron to carbon fibers is reduced or reaction of them if the carbon fibers are bundled. (N.H.)

  12. Design, Fabrication and Performance of Boron-Carbide Control Elements

    International Nuclear Information System (INIS)

    Brammer, H.A.; Jacobson, J.

    1964-01-01

    A control blade design, incorporating boron-carbide (B 4 C) in stainless-steel tubes, was introduced into service in boiling water reactors in April 1961. Since that time this blade has become the standard reference control element in General Electric boiling-water reactors, replacing the 2% boron-stainless-steel blades previously used. The blades consist of a sheathed, cruciform array of small vertical stainless-steel tubes filled with compácted boron-carbide powder. The boron-carbide powder is confined longitudinally into several independent compartments by swaging over ball bearings located inside the tubes. The development and use of boron-carbide control rods is discussed in five phases: 1. Summary of experience with boron-steel blades and reasons for transition to boron-carbide control; 2. Design of the boron-carbide blade, beginning with developmental experiments, including early measurements performed in the AEC ''Control Rod Material and Development Program'' at the Vallecitos Atomic Laboratory, through a description of the final control blade configuration; 3. Fabrication of the blades and quality control procedures; 4. Results of confirmatory pre-operational mechanical and reactivity testing; and 5. Post-operational experience with the blades, including information on the results of mechanical inspection and reactivity testing after two years of reactor service. (author) [fr

  13. Elastic modulus and fracture of boron carbide

    International Nuclear Information System (INIS)

    Hollenberg, G.W.; Walther, G.

    1978-12-01

    The elastic modulus of hot-pressed boron carbide with 1 to 15% porosity was measured at room temperature. K/sub IC/ values were determined for the same porosity range at 500 0 C by the double torsion technique. The critical stress intensity factor of boron carbide with 8% porosity was evaluated from 25 to 1200 0 C

  14. Spontaneous and continuous anti-virus disinfection from nonstoichiometric perovskite-type lanthanum manganese oxide

    Directory of Open Access Journals (Sweden)

    Ding Weng

    2015-06-01

    Full Text Available Viral pathogens have threatened human being׳s health for a long time, from periodically breakout flu epidemics to recent rising Ebola virus disease. Herein, we report a new application of nonstoichiometric Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9 compounds in spontaneous and continuous disinfection of viruses. Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9 is well-known for their catalytic properties involving oxidization reactions, which are usually utilized as electrodes in fuel cells. By utilizing superb oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9, amino acid residues in viral envelope proteins are oxidized, thus envelope proteins are denatured and infectivity of the virus is neutralized. It is of great importance that this process does not require external energy sources like light or heat. The A/PR/8/34H1N1 influenza A virus (PR8 was employed as the sample virus in our demonstration, and high-throughput disinfections were observed. The efficiency of disinfection was correlated to oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9 by EPR and H2-TPR results that La0.9MnO3 had the highest oxidative ability and correspondingly gave out the best disinfecting results within three nonstoichiometric compounds. Moreover, denaturation of hemagglutinin and neuraminidase, the two key envelope proteins of influenza A viruses, was demonstrated by HA unit assay with chicken red blood cells and NA fluorescence assay, respectively. This unique disinfecting application of La0.9MnO3 is considered as a great make up to current sterilizing methods especially to photocatalyst based disinfectants and can be widely applied to cut-off spread routes of viruses, either viral aerosol or contaminated fluid, and help in controlling the possibly upcoming epidemics like flus and hemorrhagic fever.

  15. Iron Carbides in Fischer–Tropsch Synthesis: Theoretical and Experimental Understanding in Epsilon-Iron Carbide Phase Assignment

    International Nuclear Information System (INIS)

    Liu, Xing-Wu; Cao, Zhi; Zhao, Shu; Gao, Rui

    2017-01-01

    As active phases in low-temperature Fischer–Tropsch synthesis for liquid fuel production, epsilon iron carbides are critically important industrial materials. However, the precise atomic structure of epsilon iron carbides remains unclear, leading to a half-century of debate on the phase assignment of the ε-Fe 2 C and ε’-Fe 2.2 C. Here, we resolve this decades-long question by a combining theoretical and experimental investigation to assign the phases unambiguously. First, we have investigated the equilibrium structures and thermal stabilities of ε-Fe x C, (x = 1, 2, 2.2, 3, 4, 6, 8) by first-principles calculations. We have also acquired X-ray diffraction patterns and Mössbauer spectra for these epsilon iron carbides, and compared them with the simulated results. These analyses indicate that the unit cell of ε-Fe 2 C contains only one type of chemical environment for Fe atoms, while ε’-Fe 2.2 C has six sets of chemically distinct Fe atoms.

  16. Reduction of metal oxides in metal carbide fusion superheated with plasma

    Energy Technology Data Exchange (ETDEWEB)

    Hedai, L

    1981-01-01

    A significant part of metals is capable of binding a high quantity of carbon in the form of carbide. The carbide fusion produced as a result of smelting and superheating, metal carbides with the use of plasma might be a medium to be utilized for the reduction of different metal oxides, whilst also the original carbide structure of the metal carbides will be reduced to metallic structure. The experiments conducted by making use of plasma equipment, of 20, 55 and 100 kW performances are described. On the basis of the results of the experiments performed, the following statements are to be made. The oxide reductions taking place in the metal carbide fusion might also be carried out in open-hearth furnaces, because reducing atmosphere is not necessitated during this procedure. The quantity of energy required is basically defined by the energy needed for smelting and superheating the metal carbide. The method for producing the metal described may be mainly applied for the allied production of high-purity steels as well as for that of ferro-alloys.

  17. Production of silicon carbide bodies

    International Nuclear Information System (INIS)

    Parkinson, K.

    1981-01-01

    A body consisting essentially of a coherent mixture of silicon carbide and carbon for subsequent siliconising is produced by casting a slip comprising silicon carbide and carbon powders in a porous mould. Part of the surface of the body, particularly internal features, is formed by providing within the mould a core of a material which retains its shape while casting is in progress but is compressed by shrinkage of the cast body as it dries and is thereafter removable from the cast body. Materials which are suitable for the core are expanded polystyrene and gelatinous products of selected low elastic modulus. (author)

  18. High yield silicon carbide prepolymers

    International Nuclear Information System (INIS)

    Baney, R.H.

    1982-01-01

    Prepolymers which exhibit good handling properties, and are useful for preparing ceramics, silicon carbide ceramic materials and articles containing silicon carbide, are polysilanes consisting of 0 to 60 mole% (CH 3 ) 2 Si units and 40 to 100 mole% CH 3 Si units, all Si valences being satisfied by CH 3 groups, other Si atoms, or by H atoms, the latter amounting to 0.3 to 2.1 weight% of the polysilane. They are prepared by reducing the corresponding chloro- or bromo-polysilanes with at least the stoichiometric amount of a reducing agent, e.g. LiAlH 4 . (author)

  19. Iron Carbides and Nitrides: Ancient Materials with Novel Prospects.

    Science.gov (United States)

    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.

  20. HCP to FCT + precipitate transformations in lamellar gamma-titanium aluminide alloys

    Science.gov (United States)

    Karadge, Mallikarjun Baburao

    Fully lamellar gamma-TiAl [alpha2(HCP) + gamma(FCT)] based alloys are potential structural materials for aerospace engine applications. Lamellar structure stabilization and additional strengthening mechanisms are major issues in the ongoing development of titanium aluminides due to the microstructural instability resulting from decomposition of the strengthening alpha 2 phase. This work addresses characterization of multi-component TiAl systems to identify the mechanism of lamellar structure refinement and assess the effects of light element additions (C and Si) on creep deformation behavior. Transmission electron microscopy studies directly confirmed for the first time that, fine lamellar structure is formed by the nucleation and growth of a large number of basal stacking faults on the 1/6 dislocations cross slipping repeatedly into and out of basal planes. This lamellar structure can be tailored by modifying jog heights through chemistry and thermal processing. alpha 2 → gamma transformation during heating (investigated by differential scanning calorimetry and X-ray diffraction) is a two step process involving the formation of a novel disordered FCC gamma' TiAl [with a(gamma') = c(gamma)] as an intermediate phase followed by ordering. Addition of carbon and silicon induced Ti2AlC H-type carbide precipitation inside the alpha2 lath and Ti 5(Al,Si)3 zeta-type silicide precipitation at the alpha 2/gamma interface. The H-carbides preserve alpha2/gamma type interfaces, while zeta-silicide precipitates restrict ledge growth and interfacial sliding enabling strong resistance to creep deformation.

  1. Analysis of Minimum Quantity Lubrication (MQL for Different Coating Tools during Turning of TC11 Titanium Alloy

    Directory of Open Access Journals (Sweden)

    Sheng Qin

    2016-09-01

    Full Text Available The tool coating and cooling strategy are two key factors when machining difficult-to-cut materials such as titanium alloy. In this paper, diamond coating was deposited on a commercial carbide insert as an attempt to increase the machinability of TC11 alloy during the turning process. An uncoated carbide insert and a commercial Al2O3/TiAlN-coated tool were also tested as a comparison. Furthermore, MQL was applied to improve the cutting condition. Cutting performances were analyzed by cutting force, cutting temperate and surface roughness measurements. Tool wears and tool lives were evaluated to find a good matchup between the tool coating and cooling strategy. According to the results, using MQL can slightly reduce the cutting force. By applying MQL, cutting temperatures and tool wears were reduced by a great amount. Besides, MQL can affect the tool wear mechanism and tool failure modes. The tool life of an Al2O3/TiAlN-coated tool can be prolonged by 88.4% under the MQL condition. Diamond-coated tools can obtain a good surface finish when cutting parameters and lubrication strategies are properly chosen.

  2. Active carbon supported molybdenum carbides for higher alcohols synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Chiarello, Gian Luca; Christensen, Jakob Munkholt

    This work provides an investigation of the high pressure CO hydrogenation to higher alcohols on K2CO3 promoted active carbon supported molybdenum carbide. Both activity and selectivity to alcohols over supported molybdenum carbides increased significantly compared to bulk carbides in literatures...

  3. Growth and structure of carbide nanorods

    International Nuclear Information System (INIS)

    Lieber, C.M.; Wong, E.W.; Dai, H.; Maynor, B.W.; Burns, L.D.

    1996-01-01

    Recent research on the growth and structure of carbide nanorods is reviewed. Carbide nanorods have been prepared by reacting carbon nanotubes with volatile transition metal and main group oxides and halides. Using this approach it has been possible to obtain solid carbide nanorods of TiC, SiC, NbC, Fe 3 C, and BC x having diameters between 2 and 30 nm and lengths up to 20 microm. Structural studies of single crystal TiC nanorods obtained through reactions of TiO with carbon nanotubes show that the nanorods grow along both [110] and [111] directions, and that the rods can exhibit either smooth or saw-tooth morphologies. Crystalline SiC nanorods have been produced from reactions of carbon nanotubes with SiO and Si-iodine reactants. The preferred growth direction of these nanorods is [111], although at low reaction temperatures rods with [100] growth axes are also observed. The growth mechanisms leading to these novel nanomaterials have also been addressed. Temperature dependent growth studies of TiC nanorods produced using a Ti-iodine reactant have provided definitive proof for a template or topotactic growth mechanism, and furthermore, have yielded new TiC nanotube materials. Investigations of the growth of SiC nanorods show that in some cases a catalytic mechanism may also be operable. Future research directions and applications of these new carbide nanorod materials are discussed

  4. Thermionic emission of cermets made of refractory carbides

    International Nuclear Information System (INIS)

    Samsonow, G.W.; Bogomol, I.W.; Ochremtschuk, L.N.; Podtschernjajewa, I.A.; Fomenko, W.S.

    1975-01-01

    In order to improve the resistance to thermal variations of refractory carbides having good behavior for thermionic emission, they have been combined with transition metals d. Thermionic emission was studied with cermets in compact samples. Following systems were examined: TiC-Nb, TiC-Mo, TiC-W, ZrC-Nb, ZrC-Mo, ZrC-W, WC-Mo with compositions of: 75% M 1 C-25% M 2 , 50%M 1 C-50%M 2 , 25%M 1 C-75%M 2 . When following the variation of electron emission energy phi versus the composition, it appears that in the range of mixed crystals (M 1 M 2 )C, phi decreases and the resistance to thermal variations of these phases is higher than that of individual carbides. The study of obtained cermets shows that their resistance to thermal variations is largely superior to the one of starting carbides; TiC and ZrC carbides, combined with molybdenum and tungsten support the highest number of thermic cycles

  5. Silicon carbide microsystems for harsh environments

    CERN Document Server

    Wijesundara, Muthu B J

    2011-01-01

    Silicon Carbide Microsystems for Harsh Environments reviews state-of-the-art Silicon Carbide (SiC) technologies that, when combined, create microsystems capable of surviving in harsh environments, technological readiness of the system components, key issues when integrating these components into systems, and other hurdles in harsh environment operation. The authors use the SiC technology platform suite the model platform for developing harsh environment microsystems and then detail the current status of the specific individual technologies (electronics, MEMS, packaging). Additionally, methods

  6. Highly efficient transition metal and nitrogen co-doped carbide-derived carbon electrocatalysts for anion exchange membrane fuel cells

    Science.gov (United States)

    Ratso, Sander; Kruusenberg, Ivar; Käärik, Maike; Kook, Mati; Puust, Laurits; Saar, Rando; Leis, Jaan; Tammeveski, Kaido

    2018-01-01

    The search for an efficient electrocatalyst for oxygen reduction reaction (ORR) to replace platinum in fuel cell cathode materials is one of the hottest topics in electrocatalysis. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites made by pyrolysis of cheap materials are the most promising with control over the porosity and final structure of the catalyst a crucial point. In this work we show a method of producing a highly active ORR catalyst in alkaline media with a controllable porous structure using titanium carbide derived carbon as a base structure and dicyandiamide along with FeCl3 or CoCl2 as the dopants. The resulting transition metal-nitrogen co-doped carbide derived carbon (M/N/CDC) catalyst is highly efficient for ORR electrocatalysis with the activity in 0.1 M KOH approaching that of commercial 46.1 wt.% Pt/C. The catalyst materials are also investigated by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to characterise the changes in morphology and composition causing the raise in electrochemical activity. MEA performance of M/N/CDC cathode materials in H2/O2 alkaline membrane fuel cell is tested with the highest power density reached being 80 mW cm-2 compared to 90 mW cm-2 for Pt/C.

  7. Titanium metal: extraction to application

    Energy Technology Data Exchange (ETDEWEB)

    Gambogi, Joseph (USGS, Reston, VA); Gerdemann, Stephen J.

    2002-09-01

    In 1998, approximately 57,000 tons of titanium metal was consumed in the form of mill products (1). Only about 5% of the 4 million tons of titanium minerals consumed each year is used to produce titanium metal, with the remainder primarily used to produce titanium dioxide pigment. Titanium metal production is primarily based on the direct chlorination of rutile to produce titanium tetrachloride, which is then reduced to metal using the Kroll magnesium reduction process. The use of titanium is tied to its high strength-to-weight ratio and corrosion resistance. Aerospace is the largest application for titanium. In this paper, we discuss all aspects of the titanium industry from ore deposits through extraction to present and future applications. The methods of both primary (mining of ore, extraction, and purification) and secondary (forming and machining) operations will be analyzed. The chemical and physical properties of titanium metal will be briefly examined. Present and future applications for titanium will be discussed. Finally, the economics of titanium metal production also are analyzed as well as the advantages and disadvantages of various alternative extraction methods.

  8. Flexural strength of proof-tested and neutron-irradiated silicon carbide

    Science.gov (United States)

    Price, R. J.; Hopkins, G. R.

    1982-08-01

    Proof testing before service is a valuable method for ensuring the reliability of ceramic structures. Silicon carbide has been proposed as a very low activation first-wall and blanket structural material for fusion devices, where it would experience a high flux of fast neutrons. Strips of three types of silicon carbide were loaded in four-point bending to a stress sufficient to break about a third of the specimens. Groups of 16 survivors were irradiated to 2 × 10 26n/ m2 ( E>0.05 MeV) at 740°C and bend tested to failure. The strength distribution of chemically vapor-deposited silicon carbide (Texas Instruments) was virtually unchanged by irradiation. The mean strength of sintered silicon carbide (Carborundum Alpha) was reduced 34% by irradiation, while the Weibull modulus and the truncated strength distribution characteristic of proof-tested material were retained. Irradiation reduced the mean strength of reaction-bonded silicon carbide (Norton NC-430) by 58%, and the spread in strength values was increased. We conclude that for the chemically vapor-deposited and the sintered silicon carbide the benefits of proof testing to eliminate low strength material are retained after high neutron exposures.

  9. Study of stress relief cracking in titanium stabilized austenitic stainless steel; Etude de la fissuration differee par relaxation d'un acier inoxydable austenitique stabilise au titane

    Energy Technology Data Exchange (ETDEWEB)

    Chabaud-Reytier, M

    1999-07-01

    The heat affected zone (HAZ) of titanium stabilised austenitic stainless steel welds (AISI 321) may exhibit a serious form of intercrystalline cracking during service at high temperature. This type of cracking, called 'stress relief cracking', is known to be due to work hardening but also to ageing: a fine and abundant intragranular Ti(C,N) precipitation appears near the fusion line and modifies the mechanical behaviour of the HAZ. This study aims to better know the accused mechanism and to succeed in estimating the risk of such cracking in welded junctions of 321 stainless steel. To analyse this embrittlement mechanism, and to assess the lifetime of real components, different HAZ are simulated by heat treatments applied to the base material which is submitted to various cold rolling and ageing conditions in order to reproduce the HAZ microstructure. Then, we study the effects of work hardening and ageing on the titanium carbide precipitation, on the mechanical (tensile and creep) behaviour of the resulting material and on its stress relief cracking sensitivity. It is shown that work hardening is the main parameter of the mechanism and that ageing do not favour crack initiation although it leads to titanium carbide precipitation. The role of this precipitation is also discussed. Moreover, a creep damage model is identified by a local approach to fracture. Materials sensitive to stress relief cracking are selected. Then, creep tests are carried out on notched bars in order to quantify the intergranular damage of these different materials; afterwards, these measurements are combined with calculated mechanical fields. Finally, it is shown that the model gives good results to assess crack initiation for a compact tension (CT) specimen during relaxation tests, as well as for a notched tubular specimen tested at 600 deg. C under a steady torque. (author)

  10. Titanium disilicide formation by sputtering of titanium on heated silicon substrate

    Science.gov (United States)

    Tanielian, M.; Blackstone, S.

    1984-09-01

    We have sputter deposited titanium on bare silicon substrates at elevated temperatures. We find that at a substrate temperature of about 515 °C titanium silicide is formed due to the reaction of the titanium with the Si. The resistivity of the silicide is about 15 μΩ cm and it is not etchable in a selective titanium etch. This process can have applications in low-temperature, metal-oxide-semiconductor self-aligned silicide formation for very large scale integrated

  11. Nonmetallic inclusions in JBK-75 stainless steel

    International Nuclear Information System (INIS)

    Brewer, A.W.; Krenzer, R.W.; Doyle, J.H.; Riefenberg, D.H.

    1977-01-01

    Stainless steel alloys that are chemically complex, such as A-286 or JBK-75, are designed to improve such high-temperature properties as strength. This is accomplished by precipitating secondary phases during aging. Such multicomponent systems, however, can also produce undesirable phases that are detrimental to forgeability and final mechanical properties. Cast segregation and numerous nonmetallic inclusions can have a degrading influence on the toughness and ductility of the alloy. Several different heats of A-286 and JBK-75 were studied, and titanium carbide and/or molybdenum carbide [(Ti, Mo)C] plus titanium carbide and/or titanium carbonitride Ti(C,N)-type phases were qualitatively identified as the major nonmetallic constituent in these alloys. The common procedure for rating the microcleanliness of steels does not classify such carbide or carbonitride phases and thus does not provide an appropriate means of controlling in-process inspection. The results of this study are discussed in terms of alternative methods for evaluating the microcleanliness of superalloys

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

    Science.gov (United States)

    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.

  13. Advanced technologies of production of cemented carbides and composite materials based on them

    International Nuclear Information System (INIS)

    Bondarenko, V.; Pavlotskaya, E.; Martynova, L.; Epik, I.

    2001-01-01

    The paper presents new technological processes of production of W, WC and (Ti, W)C powders, cemented carbides having a controlled carbon content, high-strength nonmagnetic nickel-bonded cemented carbides, cemented carbide-based composites having a wear-resistant antifriction working layer as well as processes of regeneration of cemented carbide waste. It is shown that these technological processes permit radical changes in the production of carbide powders and products of VK, TK, VN and KKhN cemented carbides. The processes of cemented carbide production become ecologically acceptable and free of carbon black, the use of cumbersome mixers is excluded, the power expenditure is reduced and the efficiency of labor increases. It becomes possible to control precisely the carbon content within a two-phase region -carbide-metal. A high wear resistance of parts of friction couples which are lubricated with water, benzine, kerosene, diesel fuel and other low-viscosity liquids, is ensured with increased strength and shock resistance. (author)

  14. Diamond dispersed cemented carbide produced without using ultra high pressure equipment

    International Nuclear Information System (INIS)

    Moriguchi, H.; Tsuzuki, K.; Ikegaya, A.

    2001-01-01

    We have developed a composite material of dispersed diamond particles in cemented carbide without using ultra high pressure equipment. The developed diamond dispersed cemented carbide combines the excellent properties of cemented carbide with diamond and also provides 1.5 times improved fracture toughness over that of cemented carbide. They also show 10 times higher wear resistance over that of cemented carbide in a wear resistance test against bearing steel, and 5 times greater grindability than diamond compacts. Because ultra high pressure equipment is not used to produce the developed material, large compacts over 100 mm in diameter can be manufactured. The developed material showed 10-25 times higher wear resistance in real use as wear-resistant tools such as centerless blades and work-rests. (author)

  15. Fission product phases in irradiated carbide fuels

    International Nuclear Information System (INIS)

    Ewart, F.T.; Sharpe, B.M.; Taylor, R.G.

    1975-09-01

    Oxide fuels have been widely adopted as 'first charge' fuels for demonstration fast reactors. However, because of the improved breeding characteristics, carbides are being investigated in a number of laboratories as possible advanced fuels. Irradiation experiments on uranium and mixed uranium-plutonium carbides have been widely reported but the instances where segregate phases have been found and subjected to electron probe analysis are relatively few. Several observations of such segregate phases have now been made over a period of time and these are collected together in this document. Some seven fuel pins have been examined. Two of the irradiations were in thermal materials testing reactors (MTR); the remainder were experimental assemblies of carbide gas bonded oxycarbide and sodium bonded oxycarbide in the Dounreay Fast Reactor (DFR). All fuel pins completed their irradiation without failure. (author)

  16. Present status of uranium-plutonium mixed carbide fuel development for LMFBRs

    International Nuclear Information System (INIS)

    Handa, Muneo; Suzuki, Yasufumi

    1984-01-01

    The feature of carbide fuel is that it has the doubling time as short as about 13 years, that is, close to one half as compared with oxide fuel. The development of the carbide fuel in the past 10 years has been started in amazement. Especially in the program of new fuel development in USA started in 1974, He and Na bond fuel attained the burnup of 16 a/o without causing the breaking of cladding tubes. In 1984, the irradiation of the assembly composed of 91 fuel pins in the FFTF is expected. On the other hand in Japan, the fuel research laboratory was constructed in 1974 in the Oarai Laboratory, Japan Atomic Energy Research Institute, to carry out the studies on carbide fuel. In the autumn of 1982, two carbide fuel pins with different chemical composition have been successfully made. Accordingly, the recent status of the development is explained. The uranium-plutonium mixed carbide fuel is suitable to liquid metal-cooled fast breeder reactors because of large heat conductivity and the high density of nuclear fission substances. The thermal and nuclear characteristics of carbide fuel, the features of the reactor core using carbide fuel, the chemical and mechanical interaction of fuel and cladding tubes, the selection of bond materials, the manufacturing techniques for the fuel, the development of the analysis code for fuel behavior, and the research and development of carbide fuel in Japan are described. (Kako, I.)

  17. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    Laterite obtained from Ikpayongo was stabilized with 2-10 % cement and 2-10 % Calcium Carbide waste, for use .... or open dumping which have effect on surface and ... Table 1: Chemical Composition of Calcium Carbide Waste and Cement.

  18. Corrosion behavior of porous chromium carbide in supercritical water

    International Nuclear Information System (INIS)

    Dong Ziqiang; Chen Weixing; Zheng Wenyue; Guzonas, Dave

    2012-01-01

    Highlights: ► Corrosion behavior of porous Cr 3 C 2 in various SCW conditions was investigated. ► Cr 3 C 2 is stable in SCW at temperature below 420–430 °C. ► Cracks and disintegration were observed at elevated testing temperatures. ► Degradation of Cr 3 C 2 is related to the intermediate product CrOOH. - Abstract: The corrosion behavior of highly porous chromium carbide (Cr 3 C 2 ) prepared by a reactive sintering process was characterized at temperatures ranging from 375 °C to 625 °C in a supercritical water environment with a pressure of 25–30 MPa. The test results show that porous chromium carbide is stable in SCW environments at temperatures under 425 °C, above which disintegration occurred. The porous carbide was also tested under hydrothermal conditions of pressures between 12 MPa and 50 MPa at constant temperatures of 400 °C and 415 °C, respectively. The pressure showed little effect on the stability of chromium carbide in the tests at those temperatures. The mechanism of disintegration of chromium carbide in SCW environments is discussed.

  19. Precipitation behavior during thin slab thermomechanical processing and isothermal aging of copper-bearing niobium-microalloyed high strength structural steels: The effect on mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Misra, R.D.K., E-mail: dmisra@louisiana.edu [Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70503 (United States); Jia, Z. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70503 (United States); O' Malley, R. [Nucor Steel Decatur, LLC Sheet Mill, 4301, Iverson Blvd., Trinity, AL 35673 (United States); Jansto, S.J. [CBMM-Reference Metals Company, 1000 Old Pond Road, Bridgeville, PA 15017 (United States)

    2011-11-15

    Highlights: {yields} Copper does not significantly influence toughness. {yields} Copper precipitation during aging occurs at dislocations. {yields} Precipitation of copper and carbides is mutually exclusive. - Abstract: We describe here the precipitation behavior of copper and fine-scale carbides during thermo-mechanical processing and isothermal aging of copper-bearing niobium-microalloyed high strength steels. During thermo-mechanical processing, precipitation of {epsilon}-copper occurs in polygonal ferrite and at the austenite-ferrite interface. In contrast, during isothermal aging, nucleation of {epsilon}-copper precipitation occurs at dislocations. In the three different chemistries investigated, the increase in strength associated with copper during aging results only in a small decrease in impact toughness, implying that copper precipitates do not seriously impair toughness, and can be considered as a viable strengthening element in microalloyed steels. Precipitation of fine-scale niobium carbides occurs extensively at dislocations and within ferrite matrix together with vanadium carbides. In the presence of titanium, titanium carbides act as a nucleus for niobium carbide formation. Irrespective of the nature of carbides, copper precipitates and carbides are mutually exclusive.

  20. Precipitation behavior during thin slab thermomechanical processing and isothermal aging of copper-bearing niobium-microalloyed high strength structural steels: The effect on mechanical properties

    International Nuclear Information System (INIS)

    Misra, R.D.K.; Jia, Z.; O'Malley, R.; Jansto, S.J.

    2011-01-01

    Highlights: → Copper does not significantly influence toughness. → Copper precipitation during aging occurs at dislocations. → Precipitation of copper and carbides is mutually exclusive. - Abstract: We describe here the precipitation behavior of copper and fine-scale carbides during thermo-mechanical processing and isothermal aging of copper-bearing niobium-microalloyed high strength steels. During thermo-mechanical processing, precipitation of ε-copper occurs in polygonal ferrite and at the austenite-ferrite interface. In contrast, during isothermal aging, nucleation of ε-copper precipitation occurs at dislocations. In the three different chemistries investigated, the increase in strength associated with copper during aging results only in a small decrease in impact toughness, implying that copper precipitates do not seriously impair toughness, and can be considered as a viable strengthening element in microalloyed steels. Precipitation of fine-scale niobium carbides occurs extensively at dislocations and within ferrite matrix together with vanadium carbides. In the presence of titanium, titanium carbides act as a nucleus for niobium carbide formation. Irrespective of the nature of carbides, copper precipitates and carbides are mutually exclusive.

  1. Leaching of Titanium and Silicon from Low-Grade Titanium Slag Using Hydrochloric Acid Leaching

    Science.gov (United States)

    Zhao, Longsheng; Wang, Lina; Qi, Tao; Chen, Desheng; Zhao, Hongxin; Liu, Yahui; Wang, Weijing

    2018-05-01

    Acid-leaching behaviors of the titanium slag obtained by selective reduction of vanadium-bearing titanomagnetite concentrates were investigated. It was found that the optimal leaching of titanium and silicon were 0.7% and 1.5%, respectively. The titanium and silicon in the titanium slag were firstly dissolved in the acidic solution to form TiO2+ and silica sol, and then rapidly reprecipitated, forming hydrochloric acid (HCl) leach residue. Most of the silicon presented in the HCl leach residue as floccules-like silica gel, while most of the titanium was distributed in the nano-sized rod-like clusters with crystallite refinement and intracrystalline defects, and, as such, 94.3% of the silicon was leached from the HCl leach residue by alkaline desilication, and 96.5% of the titanium in the titanium-rich material with some rutile structure was then digested by the concentrated sulfuric acid. This provides an alternative route for the comprehensive utilization of titanium and silicon in titanium slag.

  2. Mixed Uranium/Refractory Metal Carbide Fuels for High Performance Nuclear Reactors

    International Nuclear Information System (INIS)

    Knight, Travis; Anghaie, Samim

    2002-01-01

    Single phase, solid-solution mixed uranium/refractory metal carbides have been proposed as an advanced nuclear fuel for advanced, high-performance reactors. Earlier studies of mixed carbides focused on uranium and either thorium or plutonium as a fuel for fast breeder reactors enabling shorter doubling owing to the greater fissile atom density. However, the mixed uranium/refractory carbides such as (U, Zr, Nb)C have a lower uranium densities but hold significant promise because of their ultra-high melting points (typically greater than 3700 K), improved material compatibility, and high thermal conductivity approaching that of the metal. Various compositions of (U, Zr, Nb)C were processed with 5% and 10% metal mole fraction of uranium. Stoichiometric samples were processed from the constituent carbide powders, while hypo-stoichiometric samples with carbon-to-metal (C/M) ratios of 0.92 were processed from uranium hydride, graphite, and constituent refractory carbide powders. Processing techniques of cold uniaxial pressing, dynamic magnetic compaction, sintering, and hot pressing were investigated to optimize the processing parameters necessary to produce high density (low porosity), single phase, solid-solution mixed carbide nuclear fuels for testing. This investigation was undertaken to evaluate and characterize the performance of these mixed uranium/refractory metal carbides for high performance, ultra-safe nuclear reactor applications. (authors)

  3. Properties of cemented carbides alloyed by metal melt treatment

    International Nuclear Information System (INIS)

    Lisovsky, A.F.

    2001-01-01

    The paper presents the results of investigations into the influence of alloying elements introduced by metal melt treatment (MMT-process) on properties of WC-Co and WC-Ni cemented carbides. Transition metals of the IV - VIll groups (Ti, Zr, Ta, Cr, Re, Ni) and silicon were used as alloying elements. It is shown that the MMT-process allows cemented carbides to be produced whose physico-mechanical properties (bending strength, fracture toughness, total deformation, total work of deformation and fatigue fracture toughness) are superior to those of cemented carbides produced following a traditional powder metallurgy (PM) process. The main mechanism and peculiarities of the influence of alloying elements added by the MMT-process on properties of cemented carbides have been first established. The effect of alloying elements on structure and substructure of phases has been analyzed. (author)

  4. Medium temperature reaction between lanthanide and actinide carbides and hydrogen

    International Nuclear Information System (INIS)

    Dean, G.; Lorenzelli, R.; Pascard, R.

    1964-01-01

    Hydrogen is fixed reversibly by the lanthanide and actinide mono carbides in the range 25 - 400 C, as for pure corresponding metals. Hydrogen goes into the carbides lattice through carbon vacancies and the total fixed amount is approximately equal to two hydrogen atoms per initial vacancy. Final products c.n thus be considered as carbo-hydrides of general formula M(C 1-x , H 2x ). The primitive CFC, NaCl type, structure remains unchanged but expands strongly in the case of actinide carbides. With lanthanide carbides, hydrogenation induces a phase transformation with reappearance of the metal structure (HCP). Hydrogen decomposition pressures of all the studied carbo-hydrides are greater than those of the corresponding di-hydrides. (authors) [fr

  5. On the carbide formation in high-carbon stainless steel

    International Nuclear Information System (INIS)

    Mujahid, M.; Qureshi, M.I.

    1996-01-01

    Stainless steels containing high Cr as well as carbon contents in excess of 1.5 weight percent have been developed for applications which require high resistance erosion and environmental corrosion. Formation of carbides is one of important parameters for controlling properties of these materials especially erosion characteristics. Percent work includes the study of different type of carbides which from during the heat treatment of these materials. It has been found that precipitation of secondary carbides and the nature of matrix transformation plays an important role in determining the hardness characteristics of these materials. (author)

  6. Titanium and titanium alloys: fundamentals and applications

    National Research Council Canada - National Science Library

    Leyens, C; Peters, M

    2003-01-01

    ... number of titanium alloys have paved the way for light metals to vastly expand into many industrial applications. Titanium and its alloys stand out primarily due to their high specific strength and excellent corrosion resistance, at just half the weight of steels and Ni-based superalloys. This explains their early success in the aerospace and the...

  7. Sintering of nano crystalline α silicon carbide by doping with boron ...

    Indian Academy of Sciences (India)

    Sinterable nano silicon carbide powders of mean particle size (37 nm) were prepared by attrition milling and chemical processing of an acheson type alpha silicon carbide having mean particle size of 0.39 m (390 nm). Pressureless sintering of these powders was achieved by addition of boron carbide of 0.5 wt% together ...

  8. Synthesis mechanism of an Al-Ti-C grain refiner master alloy prepared by a new method

    Science.gov (United States)

    Zhang, B. Q.; Lu, L.; Lai, M. O.; Fang, H. S.; Ma, H. T.; Li, J. G.

    2003-08-01

    The mechanisms of in-situ synthesis of an Al-Ti-C grain-refiner master alloy, prepared by adding a powder mixture of potassium titanium fluoride and carbon into an aluminum melt, have been systematically studied. It was found that vigorous reactions occurred at the initial stage of reaction and then slowed down. After about 20 minutes, the reactions, which led the formation of blocky titanium aluminides and submicron titanium carbides in the aluminum matrix, appeared to reach completion. Potassium titanium fluoride reacted with aluminum and carbon at 724 °C and 736 °C, respectively, resulting in the formation of titanium aluminides and titanium carbides in the aluminum matrix as well as in the formation of a low-melting-point slag of binary potassium aluminofluorides. The reaction between potassium titanium fluoride and carbon is believed to be the predominant mechanism in the synthesis of TiC by this method.

  9. Synthesis of Titanium Oxycarbide from Titanium Slag by Methane-Containing Gas

    Science.gov (United States)

    Dang, Jie; Fatollahi-Fard, Farzin; Pistorius, Petrus Christiaan; Chou, Kuo-Chih

    2018-02-01

    In this study, reaction steps of a process for synthesis of titanium oxycarbide from titanium slag were demonstrated. This process involves the reduction of titanium slag by a methane-hydrogen-argon mixture at 1473 K (1200 °C) and the leaching of the reduced products by hydrofluoric acid near room temperature to remove the main impurity (Fe3Si). Some iron was formed by disproportionation of the main M3O5 phase before gaseous reduction started. Upon reduction, more iron formed first, followed by reduction of titanium dioxide to suboxides and eventually oxycarbide.

  10. Recovery of pure slaked lime from carbide sludge: Case study of ...

    African Journals Online (AJOL)

    Adaobi

    Carbide sludge is the by-product of reaction between calcium carbide and water in the production of ... soluble in water. The optimum percentage yield was 78.2% at a ratio of 1:1000(w/v) of sludge to water held for 24 h at room temperature. Key words: Carbide, recovery, ..... calcium carbonate and other calcium products.

  11. Thermodynamic analysis of thermal plasma process of composite zirconium carbide and silicon carbide production from zircon concentrates

    International Nuclear Information System (INIS)

    Kostic, Z.G.; Stefanovic, P.Lj.; Pavlovic; Pavlovic, Z.N.; Zivkovic, N.V.

    2000-01-01

    Improved zirconium ceramics and composites have been invented in an effort to obtain better resistance to ablation at high temperature. These ceramics are suitable for use as thermal protection materials on the exterior surfaces of spacecraft, and in laboratory and industrial environments that include flows of hot oxidizing gases. Results of thermodynamic consideration of the process for composite zirconium carbide and silicon carbide ultrafine powder production from ZrSiO 4 in argon thermal plasma and propane-butane gas as reactive quenching reagents are presented in the paper. (author)

  12. Dilatometry Analysis of Dissolution of Cr-Rich Carbides in Martensitic Stainless Steels

    Science.gov (United States)

    Huang, Qiuliang; Volkova, Olena; Biermann, Horst; Mola, Javad

    2017-12-01

    The dissolution of Cr-rich carbides formed in the martensitic constituent of a 13 pct Cr stainless steel was studied by dilatometry and correlative electron channeling contrast examinations. The dissolution of carbides subsequent to the martensite reversion to austenite was associated with a net volume expansion which in turn increased the dilatometry-based apparent coefficient of thermal expansion (CTEa) during continuous heating. The effects of carbides fraction and size on the CTEa variations during carbides dissolution are discussed.

  13. Titanium by design: TRIP titanium alloy

    Science.gov (United States)

    Tran, Jamie

    Motivated by the prospect of lower cost Ti production processes, new directions in Ti alloy design were explored for naval and automotive applications. Building on the experience of the Steel Research Group at Northwestern University, an analogous design process was taken with titanium. As a new project, essential kinetic databases and models were developed for the design process and used to create a prototype design. Diffusion kinetic models were developed to predict the change in phase compositions and microstructure during heat treatment. Combining a mobility database created in this research with a licensed thermodynamic database, ThermoCalc and DICTRA software was used to model kinetic compositional changes in titanium alloys. Experimental diffusion couples were created and compared to DICTRA simulations to refine mobility parameters in the titanium mobility database. The software and database were able to predict homogenization times and the beta→alpha plate thickening kinetics during cooling in the near-alpha Ti5111 alloy. The results of these models were compared to LEAP microanalysis and found to be in reasonable agreement. Powder metallurgy was explored using SPS at GM R&D to reduce the cost of titanium alloys. Fully dense Ti5111 alloys were produced and achieved similar microstructures to wrought Ti5111. High levels of oxygen in these alloys increased the strength while reducing the ductility. Preliminary Ti5111+Y alloys were created, where yttrium additions successfully gettered excess oxygen to create oxides. However, undesirable large oxides formed, indicating more research is needed into the homogeneous distribution of the yttrium powder to create finer oxides. Principles established in steels were used to optimize the beta phase transformation stability for martensite transformation toughening in titanium alloys. The Olson-Cohen kinetic model is calibrated to shear strains in titanium. A frictional work database is established for common alloying

  14. An Investigation into the Effects of Process Conditions on the Tribological Performance of Pack Carburized Titanium with Limited Oxygen Diffusion

    Science.gov (United States)

    Bailey, R.; Sun, Y.

    2018-04-01

    In the present study, a new pack carburization technique for titanium has been investigated. The aim of this treatment is to produce a titanium carbide/oxycarbide layer atop of an extended oxygen diffusion zone [α-Ti(O)]. The effects of treatment temperature and pack composition have been investigated in order to determine the optimal conditions required to grant the best tribological response. The resulting structural features were investigated with particular interest in the carbon and oxygen concentrations across the samples cross section. The optimization showed that a temperature of 925 °C with a pack composition of 1 part carbon to 1 part energizer produced surface capable of withstanding a contact pressure of ≈ 1.5 GPa for 1 h. The process resulted in TiC surface structure which offers enhanced hardness (2100 HV) and generates a low friction coefficient (μ ≈ 0.2) when in dry sliding contact with an alumina (Al2O3) ball. The process also produced an extended oxygen diffusion zone that helps to improve the load bearing capacity of the substrate.

  15. Carbide Transformation in Haynes 230 during Long-term Exposure at High Temperature

    International Nuclear Information System (INIS)

    Lee, Ho Jung; Kim, Hyunmyung; Hong, Sunghoon; Jang, Changheui

    2014-01-01

    Long-term aging behaviors of a solid solution hardened Ni-base superalloy, Haynes 230 at high temperature have not been fully investigated yet. In this study, long-term aging tests of Haynes 230 was carried out to evaluate microstructure changes especially in carbide evolution. In addition, its consequential effects on tensile property such as tensile strength and elongation were discussed. In Haynes 230, a nucleation of the secondary carbides was dominant at 800 .deg. C ageing while growth at 900 .deg. C ageing. In addition, after aging at 800 .deg. C, transition of primary W-rich M 6 C carbides (break down) were observed and it showed high W content (up to 70 at.% W) compared to un-aged W-rich M 6 C carbides (around 30 at.% W). Coarsened Cr- and Ni-rich phase surrounded by carbide depleted region and high W-rich M 6 C carbide along the grain boundary were formed only at 900 .deg. C after long-term exposure above 10000 h. Tensile strength of aged Haynes 230 increased at 800 .deg. C while decreased at 900 .deg. C due to the formation of secondary carbide within the grains at 800 .deg. C. Decrease in elongation would be resulted from the coarsened and continuous carbides at the grain boundary as well as Cr- and Ni-rich phase along the grain boundary

  16. Microstructural evaluation of the NbC-20Ni cemented carbides during sintering

    International Nuclear Information System (INIS)

    Rodrigues, D.; Cannizza, E.

    2016-01-01

    Full text: Fine carbides in a metallic matrix (binder) form the microstructure of the cemented carbides. Grain size and binder content are the main variables to adjust hardness and toughness. These products are produced by Powder Metallurgy, and traditional route involves mixing carbides with binder by high energy milling, pressing and sintering. During sintering, a liquid phase promotes densification, and a final relative density higher than 99% is expected. Sintering is carried out at high temperatures, and dissolution of the carbides changes the chemical composition of the binder. To control grain growth of the main carbide, which reduces hardness, small quantities of secondary carbides are used. These additives limit dissolution and precipitation of the main carbides reducing the final grain size. This paper focused the structural and chemical evolution during sintering using NbC-20Ni cermets. Mixtures of very fine NbC carbides and carbonyl Ni powders were produce by intense milling. These mixtures were pressed using uniaxial pressures from 50 to 200MPa. Shrinkage was evaluated using dilatometric measurements under an atmosphere of dynamic argon. Samples were also sintered under vacuum in high temperature industrial furnace. The sintered samples were characterized in terms of density hardness, toughness and microstructure. DRX was the main tool used to evaluate the structural evolution of the binder. In situ chemical analysis helped to understand the dissolution mechanisms. (author)

  17. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    the stabilization of soil will ensure economy in road construction, while providing an effective way of disposing calcium carbide waste. KEYWORDS: Cement, Calcium carbide waste, Stabilization, Ikpayongo laterite, Pavement material. INTRODUCTION. Road building in the developing nations has been a major challenge to ...

  18. Wear resistance and electronic structure of cutting tool materials on a basis carbides of tungsten and titanium

    International Nuclear Information System (INIS)

    Ryzhkin, A.A.; Ilyasov, V.V.; Lyulko, A.V.

    2001-01-01

    The tool materials durability problem, in particular shock and wear resistance, has allowed to formulate a set of requirements and also to stablish the dependence between physical properties and wear. However, for understanding the nature of the process, for example determining the tribological property of the cutting tool, it is necessary to consider the atom interactions in a crystal. A theoretical study of the physical properties of cutting tool materials (W-Ti-C) with varying concentration of titanium is presented. Total and partial local electronic density for each atom in such hard solutions were calculated. (nevyjel)

  19. Corrosion of titanium and titanium alloys in spent fuel repository conditions - literature review

    International Nuclear Information System (INIS)

    Aho-Mantila, I.; Haenninen, H.; Aaltonen, P.; Taehtinen, S.

    1985-03-01

    The spent nuclear fuel is planned to be disposed in Finnish bedrock. The canister of spent fuel in waste repository is one barrier to the release of radionuclides. It is possible to choose a canister material with a known, measurable corrosion rate and to make it with thickness allowing corrosion to occur. The other possibility is to use a material which is nearly immune to general corrosion. In this second category there are titanium and titanium alloys which exhibit a very high degree of resistance to general corrosion. In this literature study the corrosion properties of unalloyed titanium, titanium alloyed with palladium and titanium alloyed with molybdenum and nickel are reviewed. The two titanium alloys own in addition to the excellent general corrosion properties outstanding properties against localized corrosion like pitting or crevice corrosion. Stress corrosion cracking and corrosion fatique of titanium seem not to be a problem in the repository conditions, but the possibilities of delayed cracking caused by hydrogen should be carefully appreciated. (author)

  20. Calculation of vapour pressures over mixed carbide fuels

    International Nuclear Information System (INIS)

    Joseph, M.; Mathews, C.K.

    1988-01-01

    Vapour pressure over the uranium-plutonium mixed carbide (Usub(l-p) Pusub(p C) was calculated in the temperature range of 1300-9000 for various compositions (p=0.1 to 0.7). Effects of variation of the sesquicarbide content were also studied. The principle of corresponding states was applied to UC and mixed carbides to obtain the equation of state. (author)

  1. Development of Gradient Cemented Carbides Through ICME Strategy

    Science.gov (United States)

    Du, Yong; Peng, Yingbiao; Zhang, Weibin; Chen, Weimin; Zhou, Peng; Xie, Wen; Cheng, Kaiming; Zhang, Lijun; Wen, Guanghua; Wang, Shequan

    An integrated computational materials engineering (ICME) including CALPHAD method is a powerful tool for materials process optimization and alloy design. The quality of CALPHAD-type calculations is strongly dependent on the quality of the thermodynamic and diffusivity databases. The development of a thermodynamic database, CSUTDCC1, and a diffusivity database, CSUDDCC1, for cemented carbides is described. Several gradient cemented carbides sintered under vacuum and various partial pressures of N2 have been studied via experiment and simulation. The microstructure and concentration profile of the gradient zones have been investigated via SEM and EPMA. Examples of ICME applications in design and manufacture for different kinds of cemented carbides are shown using the databases and comparing where possible against experimental data, thereby validating its accuracy.

  2. Three-point bending fatigue behavior of WC–Co cemented carbides

    International Nuclear Information System (INIS)

    Li, Anhai; Zhao, Jun; Wang, Dong; Gao, Xinliang; Tang, Hongwei

    2013-01-01

    Highlights: ► Mechanical fatigue tests were conducted on a specific designed jig. ► Three-point bending fatigue behavior of WC–Co cemented carbides was studied. ► Fatigue mechanisms of WC–Co cemented carbides with different WC grain sizes and Co binder contents were revealed. -- Abstract: WC–Co cemented carbides with different WC grain sizes and Co binder contents were sintered and fabricated. The three-point bending specimens with a single edge notch were prepared for tests. In the experiments, the mechanical properties of materials were investigated under static and cyclic loads (20 Hz) in air at room temperature. The fatigue behaviors of the materials under the same applied loading conditions are presented and discussed. Optical microscope and scanning electron microscopy were used to investigate the micro-mechanisms of damage during fatigue, and the results were used to correlate with the mechanical fatigue behavior of WC–Co cemented carbides. Experimental results indicated that the fatigue fracture surfaces exhibited more fracture origins and diversification of crack propagation paths than the static strength fracture surfaces. The fatigue fracture typically originates from inhomogeneities or defects such as micropores or aggregates of WC grains near the notch tip. Moreover, due to the diversity and complexity of the fatigue mechanisms, together with the evolution of the crack tip and the ductile deformation zone, the fatigue properties of WC–Co cemented carbides were largely relevant with the combination of transverse rupture strength and fracture toughness, rather than only one of them. Transverse rupture strength dominated the fatigue behavior of carbides with low Co content, whilst the fatigue behavior of carbides with high Co content was determined by fracture toughness.

  3. Stress in tungsten carbide-diamond like carbon multilayer coatings

    NARCIS (Netherlands)

    Pujada, B.R.; Tichelaar, F.D.; Janssen, G.C.A.M.

    2007-01-01

    Tungsten carbide-diamond like carbon (WC-DLC) multilayer coatings have been prepared by sputter deposition from a tungsten-carbide target and periodic switching on and off of the reactive acetylene gas flow. The stress in the resulting WC-DLC multilayers has been studied by substrate curvature.

  4. Graphitic carbon in a nanostructured titanium oxycarbide thin film to improve implant osseointegration

    International Nuclear Information System (INIS)

    Zanoni, R.; Ioannidu, C.A.; Mazzola, L.; Politi, L.; Misiano, C.; Longo, G.; Falconieri, M.; Scandurra, R.

    2015-01-01

    A nanostructured coating layer on titanium implants, able to improve their integration into bones and to protect against the harsh conditions of body fluids, was obtained by Ion Plating Plasma Assisted, a method suitable for industrial applications. A titanium carbide target was attached under vacuum to a magnetron sputtering source powered with a direct current in the 500–1100 W range, and a 100 W radio frequency was applied to the sample holder. The samples produced at 900 W gave the best biological response in terms of overexpression of some genes of proteins involved in bone turnover. We report the characterization of a reference and of an implant sample, both obtained at 900 W. Different micro/nanoscopic techniques evidenced the morphology of the substrates, and X-ray Photoelectron Spectroscopy was used to disclose the surface composition. The layer is a 500 nm thick hard nanostructure, composed of 60% graphitic carbon clustered with 15% TiC and 25% Ti oxides. - Highlights: • Nanostructured TiC protective layers were produced on Ti samples for prostheses. • Ion Plating Plasma-Assisted Deposition from TiC targets was used on Ti samples. • A model of the surface layer has been drawn from XPS, Raman, AFM, FIB/SEM, TEM. • The layer is mainly composed of graphitic carbon in addition to TiC and Ti oxides

  5. Graphitic carbon in a nanostructured titanium oxycarbide thin film to improve implant osseointegration

    Energy Technology Data Exchange (ETDEWEB)

    Zanoni, R., E-mail: robertino.zanoni@uniroma1.it [Dipartimento di Chimica, Università di Roma ‘La Sapienza’ p.le Aldo Moro 5, 00185 Rome (Italy); Ioannidu, C.A.; Mazzola, L.; Politi, L. [Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, p.le Aldo Moro 5, 00185 Rome (Italy); Misiano, C. [Romana Film Sottili, Anzio, Rome (Italy); Longo, G. [Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome (Italy); Ecole Polytechnique Fédérale de Lausanne, SB IPSB LPMV, BSP 409 (Cubotron UNIL), R.te de la Sorge, CH-1015 Lausanne (Switzerland); Falconieri, M. [ENEA, Unità Tecnica Applicazioni delle Radiazioni, via Anguillarese 301, 00123 Rome (Italy); Scandurra, R. [Dipartimento di Scienze Biochimiche, Università di Roma ‘La Sapienza’, p.le Aldo Moro 5, 00185 Rome (Italy)

    2015-01-01

    A nanostructured coating layer on titanium implants, able to improve their integration into bones and to protect against the harsh conditions of body fluids, was obtained by Ion Plating Plasma Assisted, a method suitable for industrial applications. A titanium carbide target was attached under vacuum to a magnetron sputtering source powered with a direct current in the 500–1100 W range, and a 100 W radio frequency was applied to the sample holder. The samples produced at 900 W gave the best biological response in terms of overexpression of some genes of proteins involved in bone turnover. We report the characterization of a reference and of an implant sample, both obtained at 900 W. Different micro/nanoscopic techniques evidenced the morphology of the substrates, and X-ray Photoelectron Spectroscopy was used to disclose the surface composition. The layer is a 500 nm thick hard nanostructure, composed of 60% graphitic carbon clustered with 15% TiC and 25% Ti oxides. - Highlights: • Nanostructured TiC protective layers were produced on Ti samples for prostheses. • Ion Plating Plasma-Assisted Deposition from TiC targets was used on Ti samples. • A model of the surface layer has been drawn from XPS, Raman, AFM, FIB/SEM, TEM. • The layer is mainly composed of graphitic carbon in addition to TiC and Ti oxides.

  6. Morphology study of refractory carbide powders

    International Nuclear Information System (INIS)

    Vavrda, J.; Blazhikova, Ya.

    1982-01-01

    Refractory carbides were investigated using JSM-U3 electron microscope of Joelco company at 27 KV accelerating voltage. Some photographs of each powder were taken with different enlargements to characterise the sample upon the whole. It was shown that morphological and especially topographic study of powders enables to learn their past history (way of fabrication and treatment). The presence of steps of compact particle fractures and cracks is accompanied by occurence of fine dispersion of carbides subjected to machining after facrication. On the contrary, the character of crystallographic surfaces and features of surface growth testify to the way of crystallization

  7. Model of the thermodynamic properties and structure of the non-stoichiometric plutonium and cerium oxides

    International Nuclear Information System (INIS)

    Manes, L.; Mari, C.; Ray, I.

    1979-01-01

    The tetrahedral defect consisting of one oxygen vacancy bonded to two reduced cations - is an important concept, which, as shown in the present work, can explain both the thermodynamic properties and the structures of the phases of the PuO 2 -x and CeO 2 -x systems. Based on this concept a statistical thermodynamic model has been developed and this model is described along with some preliminary calculations. A relatively good agreement with experimental thermodynamic data was obtained in this calculation. Using the exclusion principle, defect complexes each containing one tetrahedral defect are derived and it is shown that a systematic packing of these gives a good description both of the non-stoichiometric and the ordered phases observed for these oxide systems. (orig.) [de

  8. Separation of Nuclear Fuel Surrogates from Silicon Carbide Inert Matrix

    International Nuclear Information System (INIS)

    Baney, Ronald

    2008-01-01

    The objective of this project has been to identify a process for separating transuranic species from silicon carbide (SiC). Silicon carbide has become one of the prime candidates for the matrix in inert matrix fuels, (IMF) being designed to reduce plutonium inventories and the long half-lives actinides through transmutation since complete reaction is not practical it become necessary to separate the non-transmuted materials from the silicon carbide matrix for ultimate reprocessing. This work reports a method for that required process

  9. Optimization of cutting parameters in CNC turning of stainless steel 304 with TiAlN nano coated carbide cutting tool

    Science.gov (United States)

    Durga Prasada Rao, V.; Harsha, N.; Raghu Ram, N. S.; Navya Geethika, V.

    2018-02-01

    In this work, turning was performed to optimize the surface finish or roughness (Ra) of stainless steel 304 with uncoated and coated carbide tools under dry conditions. The carbide tools were coated with Titanium Aluminium Nitride (TiAlN) nano coating using Physical Vapour Deposition (PVD) method. The machining parameters, viz., cutting speed, depth of cut and feed rate which show major impact on Ra are considered during turning. The experiments are designed as per Taguchi orthogonal array and machining process is done accordingly. Then second-order regression equations have been developed on the basis of experimental results for Ra in terms of machining parameters used. Regarding the effect of machining parameters, an upward trend is observed in Ra with respect to feed rate, and as cutting speed increases the Ra value increased slightly due to chatter and vibrations. The adequacy of response variable (Ra) is tested by conducting additional experiments. The predicted Ra values are found to be a close match of their corresponding experimental values of uncoated and coated tools. The corresponding average % errors are found to be within the acceptable limits. Then the surface roughness equations of uncoated and coated tools are set as the objectives of optimization problem and are solved by using Differential Evolution (DE) algorithm. Also the tool lives of uncoated and coated tools are predicted by using Taylor’s tool life equation.

  10. Hydrotreatment activities of supported molybdenum nitrides and carbides

    Energy Technology Data Exchange (ETDEWEB)

    Dolce, G.M.; Savage, P.E.; Thompson, L.T. [University of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering

    1997-05-01

    The growing need for alternative sources of transportation fuels encourages the development of new hydrotreatment catalysts. These catalysts must be active and more hydrogen efficient than the current commercial hydrotreatment catalysts. Molybdenum nitrides and carbides are attractive candidate materials possessing properties that are comparable or superior to those of commercial sulfide catalysts. This research investigated the catalytic properties of {gamma}-Al{sub 2}O{sub 3}-supported molybdenum nitrides and carbides. These catalysts were synthesized via temperature-programmed reaction of supported molybdenum oxides with ammonia or methane/hydrogen mixtures. Phase constituents and compositions were determined by X-ray diffraction, elemental analysis, and neutral activation analysis. Oxygen chemisorption was used to probe the surface properties of the catalysts. Specific activities of the molybdenum nitrides and carbides were competitive with those of a commercial sulfide catalyst for hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodeoxygenation (HDO). For HDN and HDS, the catalytic activity on a molybdenum basis was a strong inverse function of the molybdenum loading. Product distributions of the HDN, HDO and HDS of a variety of heteroatom compounds indicated that several of the nitrides and carbides were more hydrogen efficient than the sulfide catalyst. 35 refs., 8 figs., 7 tabs.

  11. Influence of nanometric silicon carbide on phenolic resin composites ...

    Indian Academy of Sciences (India)

    Abstract. This paper presents a preliminary study on obtaining and characterization of phenolic resin-based com- posites modified with nanometric silicon carbide. The nanocomposites were prepared by incorporating nanometric silicon carbide (nSiC) into phenolic resin at 0.5, 1 and 2 wt% contents using ultrasonication to ...

  12. Synthesis, characterization and thermoelectric properties of metal borides, boron carbides and carbaborides; Synthese, Charakterisierung und thermoelektrische Eigenschaften ausgewaehlter Metallboride, Borcarbide und Carbaboride

    Energy Technology Data Exchange (ETDEWEB)

    Guersoy, Murat

    2015-07-06

    detected. Furthermore boron carbide/metal boride-composites were investigated concerning their high-temperature thermoelectric properties up to 1073 K. In some cases selected thermoelectric properties were optimized compared to boron carbide (example: Seebeck coefficients of ca. 240 μV . K{sup -1} for a boron carbide/titanium diboride-composite), but such systems still remain to be optimized concerning their homogeneity and overall thermoelectric performance.

  13. Chitosan patterning on titanium alloys

    OpenAIRE

    Gilabert Chirivella, Eduardo; Pérez Feito, Ricardo; Ribeiro, Clarisse; Ribeiro, Sylvie; Correia, Daniela; González Martin, María Luisa; Manero Planella, José María; Lanceros Méndez, Senentxu; Gallego Ferrer, Gloria; Gómez Ribelles, José Luis

    2017-01-01

    Titanium and its alloys are widely used in medical implants because of their excellent properties. However, bacterial infection is a frequent cause of titanium-based implant failure and also compromises its osseointegration. In this study, we report a new simple method of providing titanium surfaces with antibacterial properties by alternating antibacterial chitosan domains with titanium domains in the micrometric scale. Surface microgrooves were etched on pure titanium disks at i...

  14. Electrocatalysis on tungsten carbide

    International Nuclear Information System (INIS)

    Fleischmann, R.

    1975-01-01

    General concepts of electrocatalysis, the importance of the equilibrium rest potential and its standardization on polished WC-electrodes, the influence of oxygen in the catalysts upon the oxidation of hydrogen, and the attained results of the hydrogen oxidation on tungsten carbide are treated. (HK) [de

  15. Structure and single-phase regime of boron carbides

    International Nuclear Information System (INIS)

    Emin, D.

    1988-01-01

    The boron carbides are composed of twelve-atom icosahedral clusters which are linked by direct covalent bonds and through three-atom intericosahedral chains. The boron carbides are known to exist as a single phase with carbon concentrations from about 8 to about 20 at. %. This range of carbon concentrations is made possible by the substitution of boron and carbon atoms for one another within both the icosahedra and intericosahedral chains. The most widely accepted structural model for B 4 C (the boron carbide with nominally 20% carbon) has B/sub 11/C icosahedra with C-B-C intericosahedral chains. Here, the free energy of the boron carbides is studied as a function of carbon concentration by considering the effects of replacing carbon atoms within B 4 C with boron atoms. It is concluded that entropic and energetic considerations both favor the replacement of carbon atoms with boron atoms within the intericosahedral chains, C-B-C→C-B-B. Once the carbon concentration is so low that the vast majority of the chains are C-B-B chains, near B/sub 13/C 2 , subsequent substitutions of carbon atoms with boron atoms occur within the icosahedra, B/sub 11/C→B/sub 12/. Maxima of the free energy occur at the most ordered compositions: B 4 C,B/sub 13/C 2 ,B/sub 14/C. This structural model, determined by studying the free energy, agrees with that previously suggested by analysis of electronic and thermal transport data. These considerations also provide an explanation for the wide single-phase regime found for boron carbides

  16. Single-Event Effects in Silicon Carbide Power Devices

    Science.gov (United States)

    Lauenstein, Jean-Marie; Casey, Megan C.; LaBel, Kenneth A.; Ikpe, Stanley; Topper, Alyson D.; Wilcox, Edward P.; Kim, Hak; Phan, Anthony M.

    2015-01-01

    This report summarizes the NASA Electronic Parts and Packaging Program Silicon Carbide Power Device Subtask efforts in FY15. Benefits of SiC are described and example NASA Programs and Projects desiring this technology are given. The current status of the radiation tolerance of silicon carbide power devices is given and paths forward in the effort to develop heavy-ion single-event effect hardened devices indicated.

  17. On the use of titanium hydride for powder injection moulding of titanium-based alloys

    International Nuclear Information System (INIS)

    Carrenoo-Morelli, E.; Bidaux, J.-E.

    2009-01-01

    Full text: Titanium and titanium-based alloys are excellent materials for a number of engineering applications because of their high strength, lightweight, good corrosion resistance, non magnetic characteristic and biocompatibility. The current processing steps are usually costly, and there is a growing demand for net-shape solutions for manufacturing parts of increasing complexity. Powder injection moulding is becoming a competitive alternative, thanks to the advances in production of good quality base-powders, binders and sintering facilities. Titanium hydride powders, have the attractiveness of being less reactive than fine titanium powders, easier to handle, and cheaper. This paper summarizes recent advances on PIM of titanium and titanium alloys from TiH2 powders, including shape-memory NiTi alloys. (author)

  18. Estimation of sesqui-carbide fraction for MARK-I fuel

    International Nuclear Information System (INIS)

    Vana Varamban, S.; Ananthasivan, K.

    2016-01-01

    Sesqui-carbide content of FBTR bi-phasic mixed carbide is specified as 5-20 wt.%. For each batch of fuel production, the sesqui-carbide (M2C3) content is being determined by a K-ratio method using XRD information. There is a need to evolve an alternate method for qualitative determination of M2C3 content for a fabricated FBTR fuel pellet. Two independent approaches resulted in a correlation between overall carbon content and the M2C3 phase fraction. The thermodynamic calculations agree well with the stoichiometric correlation between the overall carbon content and the M2C3 phase fraction in FBTR MARK I fuel

  19. Carbide coated fibers in graphite-aluminum composites

    Science.gov (United States)

    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.

  20. Effect of carbides on the creep properties of a Ni-base superalloy M963

    International Nuclear Information System (INIS)

    He, L.Z.; Zheng, Q.; Sun, X.F.; Guan, H.R.; Hu, Z.Q.; Tieu, A.K.; Lu, C.; Zhu, H.T.

    2005-01-01

    Effect of carbides on the creep properties of a cast Ni-base superalloy M963 tested at 800 and 900 deg. C over a broad stress range has been investigated. Correlation between the carbides and creep properties of the alloy is enabled through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). During high temperature creep tests, the primary MC carbide decomposes sluggishly and a large amount of secondary carbides precipitate. The cubic and acicular M 6 C carbide precipitates at the dendritic core region. Extremely fine chromium-rich M 23 C 6 carbide precipitates preferentially at grain boundaries. The M 6 C and M 23 C 6 carbides are found to be beneficial to the creep properties of the alloy. At lower temperature (800 deg. C), the interface of MC carbide with matrix is one of the principal sites for crack initiation. At higher temperature (900 deg. C), the oxidation and the precipitation of μ phase are the main factors for significant loss in creep strength of the alloy

  1. Rheological Characteristics of 2D Titanium Carbide (MXene) Dispersions: A Guide for Processing MXenes.

    Science.gov (United States)

    Akuzum, Bilen; Maleski, Kathleen; Anasori, Babak; Lelyukh, Pavel; Alvarez, Nicolas Javier; Kumbur, E Caglan; Gogotsi, Yury

    2018-03-27

    Understanding the rheological properties of two-dimensional (2D) materials in suspension is critical for the development of various solution processing and manufacturing techniques. 2D carbides and nitrides (MXenes) constitute one of the largest families of 2D materials with >20 synthesized compositions and applications already ranging from energy storage to medicine to optoelectronics. However, in spite of a report on clay-like behavior, not much is known about their rheological response. In this study, rheological behavior of single- and multilayer Ti 3 C 2 T x in aqueous dispersions was investigated. Viscous and viscoelastic properties of MXene dispersions were studied over a variety of concentrations from colloidal dispersions to high loading slurries, showing that a multilayer MXene suspension with up to 70 wt % can exhibit flowability. Processing guidelines for the fabrication of MXene films, coatings, and fibers have been established based on the rheological properties. Surprisingly, high viscosity was observed at very low concentrations for solutions of single-layer MXene flakes. Single-layer colloidal solutions were found to exhibit partial elasticity even at the lowest tested concentrations (<0.20 mg/mL) due to the presence of strong surface charge and excellent hydrophilicity of MXene, making them amenable to fabrication at dilute concentrations. Overall, the findings of this study provide fundamental insights into the rheological response of this quickly growing 2D family of materials in aqueous environments as well as offer guidelines for processing of MXenes.

  2. Classification of titanium dioxide

    International Nuclear Information System (INIS)

    Macias B, L.R.; Garcia C, R.M.; Maya M, M.E.; Ita T, A. De; Palacios G, J.

    2002-01-01

    In this work the X-ray diffraction (XRD), Scanning Electron Microscopy (Sem) and the X-ray Dispersive Energy Spectroscopy techniques are used with the purpose to achieve a complete identification of phases and mixture of phases of a crystalline material as titanium dioxide. The problem for solving consists of being able to distinguish a sample of titanium dioxide being different than a titanium dioxide pigment. A standard sample of titanium dioxide with NIST certificate is used, which indicates a purity of 99.74% for the TiO 2 . The following way is recommended to proceed: a)To make an analysis by means of X-ray diffraction technique to the sample of titanium dioxide pigment and on the standard of titanium dioxide waiting not find differences. b) To make a chemical analysis by the X-ray Dispersive Energy Spectroscopy via in a microscope, taking advantage of the high vacuum since it is oxygen which is analysed and if it is concluded that the aluminium oxide appears in a greater proportion to 1% it is established that is a titanium dioxide pigment, but if it is lesser then it will be only titanium dioxide. This type of analysis is an application of the nuclear techniques useful for the tariff classification of merchandise which is considered as of difficult recognition. (Author)

  3. Modeling of cryogenic frictional behaviour of titanium alloys using Response Surface Methodology approach

    International Nuclear Information System (INIS)

    El-Tayeb, N.S.M.; Yap, T.C.; Venkatesh, V.C.; Brevern, P.V.

    2009-01-01

    The potential of cryogenic effect on frictional behaviour of newly developed titanium alloy Ti-5Al-4V-0.6Mo-0.4Fe (Ti54) sliding against tungsten carbide was investigated and compared with conventional titanium alloy Ti6Al4V (Ti64). In this study, four models were developed to describe the interrelationship between the friction coefficient (response) and independent variables such as speed, load, and sliding distance (time). These variables were investigated using the design of experiments and utilization of the response surface methodology (RSM). By using this method, it was possible to study the effect of main and mixed (interaction) independent variables on the friction coefficient (COF) of both titanium alloys. Under cryogenic condition, the friction coefficient of both Ti64 and Ti54 behaved differently, i.e. an increase in the case of Ti64 and decrease in the case of Ti54. For Ti64, at higher levels of load and speed, sliding in cryogenic conditions produces relatively higher friction coefficients compared to those obtained in dry air conditions. On contrary, introduction of cryogenic fluid reduces the friction coefficients of Ti54 at all tested conditions of load, speed, and time. The established models demonstrated that the mixed effect of load/speed, time/speed, and load/time consistently decrease the COF of Ti54. However this was not the case for Ti64 whereas the COF increased up to 20% when the Ti64 was tested at higher levels of load and sliding time. Furthermore, the models indicated that interaction of loads and speeds was more effective for both Ti-alloy and have the most substantial influence on the friction. In addition, COF for both alloys behaved linearly with the speed but nonlinearly with the load.

  4. Corrosion behaviour of porous chromium carbide/oxide based ceramics in supercritical water

    International Nuclear Information System (INIS)

    Dong, Z.; Xin, T.; Chen, W.; Zheng, W.; Guzonas, D.

    2011-01-01

    Porous chromium carbide with a high density of open pores was fabricated by a reactive sintering method. Chromium oxide ceramics were obtained by re-oxidizing the porous chromium carbides formed. Some samples were added with yttria at 5 wt. %, prior to reactive sintering to form porous structures. Corrosion tests in SCW were performed at temperatures ranging from 375 o C to 625 o C with a fixed pressure at around 25∼30 MPa. The results show that chromium carbide is stable in SCW environments at temperatures up to 425 o C, above which disintegration of carbides through oxidation occurs. Porous chromium oxide samples show better corrosion resistance than porous chromium carbide, but disintegrate in SCW at around 625 o C. Among all the samples tested, chromium oxide ceramics with added yttria exhibited much better corrosion resistance compared with the pure chromium carbide/oxides. No evidence of weight change or disintegration of porous chromium oxides with 5 wt % added yttria was observed after exposure at 625 o C in SCW for 600 hours. (author)

  5. Colloidal characterization of ultrafine silicon carbide and silicon nitride powders

    Science.gov (United States)

    Whitman, Pamela K.; Feke, Donald L.

    1986-01-01

    The effects of various powder treatment strategies on the colloid chemistry of aqueous dispersions of silicon carbide and silicon nitride are examined using a surface titration methodology. Pretreatments are used to differentiate between the true surface chemistry of the powders and artifacts resulting from exposure history. Silicon nitride powders require more extensive pretreatment to reveal consistent surface chemistry than do silicon carbide powders. As measured by titration, the degree of proton adsorption from the suspending fluid by pretreated silicon nitride and silicon carbide powders can both be made similar to that of silica.

  6. Corrosion behaviour and galvanic coupling of titanium and welded titanium in LiBr solutions

    International Nuclear Information System (INIS)

    Blasco-Tamarit, E.; Igual-Munoz, A.; Garcia Anton, J.; Garcia-Garcia, D.

    2007-01-01

    Corrosion resistance and galvanic coupling of Grade 2 commercially pure titanium in its welded and non-welded condition were systematically analyzed in LiBr solutions. Galvanic corrosion was evaluated through two different methods: anodic polarization (according to the Mixed Potential Theory) and electrochemical noise (using a zero-resistance ammeter). Samples have been etched to study the microstructure. The action of lithium chromate as corrosion inhibitor has been evaluated. Titanium and welded titanium showed extremely low corrosion current densities and elevated pitting potential values (higher than 1 V). The results of both methods, anodic polarization and electrochemical noise, showed that the welded titanium was always the anodic element of the pair titanium-welded titanium, so that its corrosion resistance decreases due to the galvanic effect

  7. Electrowinning molten titanium from titanium dioxide

    CSIR Research Space (South Africa)

    Van Vuuren, DS

    2005-10-01

    Full Text Available the Manufacturing and Materials Industry in it quest for global competitiveness CSIR Manufacturing and Materials Technology 3 Rationale – Titanium Cost Build-up Material Cost Ilmenite $0.27/kg Ti sponge Titanium slag $0.75/kg Ti Sponge TiCl4 and TiO2 $3....10/kg Ti Sponge Ti Sponge raw materials costs $5.50/kg Ti Sponge Total Ti Sponge cost $9-$11/kg Ti Sponge Ti ingot $15-17/kg Ti Aluminium $1.7/kg Al Supporting the Manufacturing and Materials Industry in its quest for global competitivenessorting...

  8. The impact of the presence on global markets of calcium carbide originating from China on other industry role players: the case of sa calcium carbide (PTY LTD

    Directory of Open Access Journals (Sweden)

    Royce Sitshonile Mazo

    2017-12-01

    Full Text Available This research assesses how the presence of calcium carbide originating from China has impacted on the operations of other role players in the industry. SA Calcium Carbide (Pty Ltd. located in Newcastle, South Africa, was used as a case study. The study spanned all markets where the company has a footprint meaning domestically, regionally and internationally. The aim of the study was to discern the extent to which companies like SA Calcium Carbide have been affected by the presence of products from China on the global market with special focus being put on the competitiveness in terms of pricing of products. The study used a survey strategy, and was exploratory in nature. The choice of the survey strategy was motivated by the need to collect both quantitative and qualitative data in order to meet the research objectives. The data was gathered, with an 80 percent response rate, using a questionnaire method from more than 70 current SA Calcium Carbide customers both from the domestic and the export side of the business. In order to consider the different perspectives of the whole scenario, 10 companies involved in either manufacturing or trading of Chinese manufactured calcium carbide were interviewed, some face to face and some telephonically. The study revealed that current customers, who are predominantly from the African continent, buy product from SA Calcium Carbide primarily because of its high quality. It also evident from the results that the export volumes of SA Calcium Carbide were on a gradual downward trend due to loss of market share to Chinese companies

  9. Nanocharacterisation of precipitates in austenite high manganese steels with advanced techniques: HRSTEM and DualEELS mapping

    International Nuclear Information System (INIS)

    Bobynko, J; Craven, A J; McGrouther, D; MacLaren, I; Paul, G

    2014-01-01

    To achieve optimal mechanical properties in high manganese steels, the precipitation of nanoprecipitates of vanadium and niobium carbides is under investigation. It is shown that under controlled heat treatments between 850°C and 950°C following hot deformation, few-nanometre precipitates of either carbide can be produced in test steels with suitable contents of vanadium or niobium. The structure and chemistry of these precipitates are examined in detail with a spatial resolution down to better than 1 nm using a newly commissioned scanning transmission electron microscope. In particular, it is shown that the nucleation of vanadium carbide precipitates often occurs at pre-existing titanium carbide precipitates which formed from titanium impurities in the bulk steel. This work will also highlight the links between the nanocharacterisation and changes in the bulk properties on annealing

  10. Preparation of hafnium carbide by chemical vapor deposition

    International Nuclear Information System (INIS)

    Hertz, Dominique.

    1974-01-01

    Hard, adhesive coatings of single-phase hafnium carbide were obtained by chemical vapor reaction in an atmosphere containing hafnium tetrachloride, methane and a large excess of hydrogen. By varying the gas phase composition and temperature the zones of formation of the different solid phases were studied and the growth of elementary hafnium and carbon deposits evaluated separately. The results show that the mechanism of hafnium carbide deposition does not hardly involve phenomene of homogeneous-phase methane decomposition or tetrachloride reduction by hydrogen unless the atmosphere is very rich or very poor in methane with respect to tetrachloride. However, hydrogen acting inversely on these two reactions, affects the stoichiometry of the substance deposited. The methane decomposition reaction is fairly slow, the reaction leading to hafnium carbide deposition is faster and that of tetrachloride reduction by hydrogen is quite fast [fr

  11. Kinematics and thermodynamics of non-stoichiometric oxidation phase transitions in spent fuel

    International Nuclear Information System (INIS)

    Stout, R.B.; Kansa, E.J.; Wijesinghe, A.M.

    1993-01-01

    At low temperatures ( 2 lattice to a U 4 O 9 lattice but with an oxygen-to-uranium (O/U) ratio of ∼2.4. Also, the weight gain time response has a plateau as the O/U approaches 2.4. Part of this response results from a geometrical dependency as a U 4 O 9 oxidation front propagates into grain volumes Of UO 2 It may also be indicative of a metastable, non-stoichiometric U 4 O 9 phase whose existence may inhibit the transition kinetics to the next expected phase Of U 3 O 8 . To gain a mechanistic understanding and to plan future oxidation tests, lattice kinematic and thermodynamic models are developed for lattice deformations and energetics of lattice phase changes (UO 2 → U 4 O 9 → U 3 0 7 → U 3 O 8) that include zeroth order influences on oxidation kinetics due to interstitial oxygen atoms and vacancies plus interstitial and substitutional actinides and fission decay products in spent fuel

  12. The growth mechanism of grain boundary carbide in Alloy 690

    International Nuclear Information System (INIS)

    Li, Hui; Xia, Shuang; Zhou, Bangxin; Peng, Jianchao

    2013-01-01

    The growth mechanism of grain boundary M 23 C 6 carbides in nickel base Alloy 690 after aging at 715 °C was investigated by high resolution transmission electron microscopy. The grain boundary carbides have coherent orientation relationship with only one side of the matrix. The incoherent phase interface between M 23 C 6 and matrix was curved, and did not lie on any specific crystal plane. The M 23 C 6 carbide transforms from the matrix phase directly at the incoherent interface. The flat coherent phase interface generally lies on low index crystal planes, such as (011) and (111) planes. The M 23 C 6 carbide transforms from a transition phase found at curved coherent phase interface. The transition phase has a complex hexagonal crystal structure, and has coherent orientation relationship with matrix and M 23 C 6 : (111) matrix //(0001) transition //(111) carbide , ¯ > matrix // ¯ 10> transition // ¯ > carbide . The crystal lattice constants of transition phase are c transition =√(3)×a matrix and a transition =√(6)/2×a matrix . Based on the experimental results, the growth mechanism of M 23 C 6 and the formation mechanism of transition phase are discussed. - Highlights: • A transition phase was observed at the coherent interfaces of M 23 C 6 and matrix. • The transition phase has hexagonal structure, and is coherent with matrix and M 23 C 6 . • The M 23 C 6 transforms from the matrix directly at the incoherent phase interface

  13. Boron carbide nanostructures: A prospective material as an additive in concrete

    Science.gov (United States)

    Singh, Paviter; Kaur, Gurpreet; Kumar, Rohit; Kumar, Umesh; Singh, Kulwinder; Kumar, Manjeet; Bala, Rajni; Meena, Ramovatar; Kumar, Akshay

    2018-05-01

    In recent decades, manufacture and ingestion of concrete have increased particularly in developing countries. Due to its low cost, safety and strength, concrete have become an economical choice for protection of radiation shielding material in nuclear reactors. As boron carbide has been known as a neutron absorber material makes it a great candidate as an additive in concrete for shielding radiation. This paper presents the synthesis of boron carbide nanostructures by using ball milling method. The X-ray diffraction pattern, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope analysis confirms the formation of boron carbide nanostructures. The effect of boron carbide nanostructures on the strength of concrete samples was demonstrated. The compressive strength tests of concrete cube B4C powder additives for 0 % and 5 % of total weight of cement was compared for different curing time period such as 7, 14, 21 and 28 days. The high compressive strength was observed when 5 wt % boron carbide nanostructures were used as an additive in concrete samples after 28 days curing time and showed significant improvement in strength.

  14. Friction and wear of stainless steel, titanium and aluminium with various surface treatments, ion implantation and overlay hard coatings

    International Nuclear Information System (INIS)

    Bunshah, R.F.

    1979-01-01

    This paper deals with the evaluation of the wear properties of 304 stainless steel, commercial grade titanium and commercial grade aluminium without and with different surface treatments, i.e., ion implantation of boron and nitrogen, and overlay coating of superhard materials, titanium carbide and nitride by the Biased Activated Reactive Evaporation (BARE) process. Wear properties were evaluated in adhesive, erosive and abrasive modes of wear. In the case of adhesive wear, ion implantation resulted in an improved wear behaviour in lubricated conditions but had no beneficial effect in dry wear conditions. Overlay coatings on the other hand resulted in improved wear behaviour for both the dry and lubricating conditions. In the case of erosive wear with SiC particles at high velocities, overlay coatings showed higher erosion rates (typical of brittle materials in normal impingement) whereas ion implanted materials behaved similarly as untreated materials; i.e., a lower wear rate than the specimens with overlay coatings. In the case of abrasive wear, it was again observed that the wear rates of overlay coatings is far lower than the wear rates of untreated or ion implanted materials. (author)

  15. The structure and function of supported molybdenum nitride and molybdenum carbide hydrotreating catalysts

    Science.gov (United States)

    Dolce, Gregory Martin

    1997-11-01

    A series of gamma-Alsb2Osb3 supported molybdenum nitrides and carbides were prepared by the temperature programmed reaction of supported molybdates with ammonia and methane/hydrogen mixtures, respectively. In the first part of this research, the effects of synthesis heating rates and molybdenum loading on the catalytic properties of the materials were examined. A significant amount of excess carbon was deposited on the surface of the carbides during synthesis. The materials consisted of small particles which were very highly dispersed. Oxygen chemisorption indicated that the nitride particles may have been two-dimensional. The dispersion of the carbides, however, appeared to decrease as the loading increased. The catalysts were evaluated for hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodeoxygenation (HDO). The molybdenum loading had the largest effect on the activity of the materials. For the nitrides, the HDN and HDS activities were inverse functions of the loading. This suggested that the most active HDN and HDS sites were located at the perimeter of the two-dimensional particles. The HDN and HDS activities of the carbides followed the same trend as the oxygen uptake. This result suggested that oxygen titrated the active sites on the supported carbides. Selected catalysts were evaluated for methylcarbazole HDN, dibenzothiophene HDS, and dibenzofuran HDO. The activity and selectivity of the nitrides and carbides were competitive with a presulfided commercial catalyst. In the second part of this work, a series of supported nitrides and carbides were prepared using a wider range of loadings (5-30 wt% Mo). Thermogravimetric analysis was used to determine the temperature at which excess carbon was deposited on the carbides. By modifying the synthesis parameters, the deposition of excess carbon was effectively inhibited. The dispersions of the supported nitrides and carbides were constant and suggested that the materials consisted of two

  16. Plasmonic Titanium Nitride Nanostructures via Nitridation of Nanopatterned Titanium Dioxide

    DEFF Research Database (Denmark)

    Guler, Urcan; Zemlyanov, Dmitry; Kim, Jongbum

    2017-01-01

    Plasmonic titanium nitride nanostructures are obtained via nitridation of titanium dioxide. Nanoparticles acquired a cubic shape with sharper edges following the rock-salt crystalline structure of TiN. Lattice constant of the resulting TiN nanoparticles matched well with the tabulated data. Energy...

  17. All-MXene (2D titanium carbide) solid-state microsupercapacitors for on-chip energy storage

    KAUST Repository

    Peng, You-Yu

    2016-08-01

    On-chip energy storage is a rapidly evolving research topic, opening doors for integration of batteries and supercapacitors at microscales on rigid and flexible platforms. Recently, a new class of two-dimensional (2D) transition metal carbides and nitrides (so-called MXenes) has shown great promise in electrochemical energy storage applications. Here, we report the fabrication of all-MXene (Ti3C2Tx) solid-state interdigital microsupercapacitors by employing a solution spray-coating, followed by a photoresist-free direct laser cutting method. Our prototype devices consisted of two layers of Ti3C2Tx with two different flake sizes. The bottom layer was stacked large-size MXene flakes (typical lateral dimensions of 3-6 μm) serving mainly as current collectors. The top layer was made of small-size MXene flakes (~1 μm) with a large number of defects and edges as the electroactive layer responsible for energy storage. Compared to Ti3C2Tx micro-supercapacitors with platinum current collectors, the all-MXene devices exhibited much lower contact resistance, higher capacitances and better rate-capabilities. The areal and volumetric capacitances of ~27 mF cm-2 and ~337 F cm-3, respectively, at a scan rate of 20 mV s-1 were achieved. The devices also demonstrated their excellent cyclic stability, with 100% capacitance retention after 10,000 cycles at a scan rate of 50 mV s-1. This study opens up a plethora of possible designs for high-performance on-chip devices employing different chemistries, flake sizes and morphologies of MXenes and their heterostructures.

  18. All-MXene (2D titanium carbide) solid-state microsupercapacitors for on-chip energy storage

    KAUST Repository

    Peng, You-Yu; Akuzum, Bilen; Kurra, Narendra; Zhao, Meng-Qiang; Alhabeb, Mohamed; Anasori, Babak; Kumbur, Emin Caglan; Alshareef, Husam N.; Ger, Ming-Der; Gogotsi, Yury

    2016-01-01

    On-chip energy storage is a rapidly evolving research topic, opening doors for integration of batteries and supercapacitors at microscales on rigid and flexible platforms. Recently, a new class of two-dimensional (2D) transition metal carbides and nitrides (so-called MXenes) has shown great promise in electrochemical energy storage applications. Here, we report the fabrication of all-MXene (Ti3C2Tx) solid-state interdigital microsupercapacitors by employing a solution spray-coating, followed by a photoresist-free direct laser cutting method. Our prototype devices consisted of two layers of Ti3C2Tx with two different flake sizes. The bottom layer was stacked large-size MXene flakes (typical lateral dimensions of 3-6 μm) serving mainly as current collectors. The top layer was made of small-size MXene flakes (~1 μm) with a large number of defects and edges as the electroactive layer responsible for energy storage. Compared to Ti3C2Tx micro-supercapacitors with platinum current collectors, the all-MXene devices exhibited much lower contact resistance, higher capacitances and better rate-capabilities. The areal and volumetric capacitances of ~27 mF cm-2 and ~337 F cm-3, respectively, at a scan rate of 20 mV s-1 were achieved. The devices also demonstrated their excellent cyclic stability, with 100% capacitance retention after 10,000 cycles at a scan rate of 50 mV s-1. This study opens up a plethora of possible designs for high-performance on-chip devices employing different chemistries, flake sizes and morphologies of MXenes and their heterostructures.

  19. Artefacts in multimodal imaging of titanium, zirconium and binary titanium-zirconium alloy dental implants: an in vitro study.

    Science.gov (United States)

    Smeets, Ralf; Schöllchen, Maximilian; Gauer, Tobias; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

    2017-02-01

    To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium-zirconium alloy dental implants. Zirconium, titanium and titanium-zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line-distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. While titanium and titanium-zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium-zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium-zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium-zirconium alloy induced more severe artefacts than zirconium and titanium. MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium-zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting.

  20. Determination of free and combined carbon in boron carbide

    International Nuclear Information System (INIS)

    Shankaran, P.S.; Kulkarni, Amit S.; Pandey, K.L.; Ramanjaneyulu, P.S.; Yadav, C.S.; Sayi, Y.S.; Ramakumar, K.L.

    2009-01-01

    A simple, sensitive and fast method for the determination of free and combined carbon in boron carbide samples, based on combustion in presence of oxygen at different temperatures, has been developed. Method has been standardized by analyzing mixture of two different boron carbide samples. Error associated with the method in the determination of free carbon is less than 5%. (author)

  1. Structure-Property Relationship in Metal Carbides and Bimetallic Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jingguan [University of Delaware

    2014-03-04

    The primary objective of our DOE/BES sponsored research is to use carbide and bimetallic catalysts as model systems to demonstrate the feasibility of tuning the catalytic activity, selectivity and stability. Our efforts involve three parallel approaches, with the aim at studying single crystal model surfaces and bridging the “materials gap” and “pressure gap” between fundamental surface science studies and real world catalysis. The utilization of the three parallel approaches has led to the discovery of many intriguing catalytic properties of carbide and bimetallic surfaces and catalysts. During the past funding period we have utilized these combined research approaches to explore the possibility of predicting and verifying bimetallic and carbide combinations with enhanced catalytic activity, selectivity and stability.

  2. Bainite obtaining in cast iron with carbides castings

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2010-01-01

    Full Text Available In these paper the possibility of upper and lower bainite obtaining in cast iron with carbides castings are presented. Conditions, when in cast iron with carbides castings during continuous free air cooling austenite transformation to upper bainite or its mixture with lower bainte proceeds, have been given. A mechanism of this transformation has been given, Si, Ni, Mn and Mo distribution in the eutectic cell has been tested and hardness of tested castings has been determined.

  3. Effect of Cement Replacement with Carbide Waste on the Strength of Stabilized Clay Subgrade

    Directory of Open Access Journals (Sweden)

    Muntohar A.S.

    2016-03-01

    Full Text Available Cement is commonly used for soil stabilization and many other ground improvement techniques. Cement is believed to be very good to improve the compressive and split-tensile strength of clay subgrades. In some application cement could be partly or fully replaced with carbide waste. This research is to study the effectiveness of the cement replacement and to find the maximum carbide waste content to be allowed for a clay subgrade. The quantities of cement replaced with the carbide waste were 30, 50, 70, 90, and 100% by its mass. The results show that replacing the cement with carbide waste decreased both the compressive and split tensile strength. Replacing cement content with carbide waste reduced its ability for stabilization. The carbide waste content should be less than 70% of the cement to provide a sufficient stabilizing effect on a clay subgrade.

  4. Influence of Ti, C and N concentration on the intergranular corrosion behaviour of AISI 316Ti and 321 stainless steels

    International Nuclear Information System (INIS)

    Pardo, A.; Merino, M.C.; Coy, A.E.; Viejo, F.; Carboneras, M.; Arrabal, R.

    2007-01-01

    Intergranular corrosion behaviour of 316Ti and 321 austenitic stainless steels has been evaluated in relation to the influence exerted by modification of Ti, C and N concentrations. For this evaluation, electrochemical measurements - double loop electrochemical potentiokinetic reactivation (DL-EPR) - were performed to produce time-temperature-sensitization (TTS) diagrams for tested materials. Transmission (TEM) and scanning electron microscopy (SEM) were used to determine the composition and nature of precipitates. The addition of Ti promotes better intergranular corrosion resistance in stainless steels. The precipitation of titanium carbides reduces the formation of chromium-rich carbides, which occurs at lower concentrations. Also, the reduction of carbon content to below 0.03 wt.% improves sensitization resistance more than does Ti content. The presence of Mo in AISI 316Ti stainless steel reduces chromium-rich carbide precipitation; the reason is that Mo increases the stability of titanium carbides and tends to replace chromium in the formation of carbides and intermetallic compounds, thus reducing the risks of chromium-depletion

  5. Effect of lead content on nonstoichiometric Bi2-xPbySr2Ca2Cu3Oδ ceramic superconductors

    International Nuclear Information System (INIS)

    Diaz-Valdes, E.; Pacheco-Malagon, G.; Contreras-Puente, G.; Mejia-Garcia, C.; Andrade-Garay, G.; Ortiz-Lopez, J.; Conde-Gallardo, A.; Falcony, C.

    1993-01-01

    Ceramic superconducting samples of the type Bi 2-x Pb y Sr 2 Ca 2 Cu 3 O δ were processed with a nonstoichiometric content of Bi and Pb (x≠y) with respect to the 2223 phase in this system. The resistance vs. temperature characteristics and the presence of the 2223 and 2212 phases as a function of the sample preparation conditions and the lead content (Bi/Pb ratio) are reported. The growth of unwanted phases such as PbO was observed for those samples with a high content of Pb (y=0.9) and Bi (x=0.1). (orig.)

  6. Reactivation properties of carbide slag as a CO{sub 2} sorbent during calcination/carbonation cycles

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yingjie; Sun, Rongyue; Liu, Hongling; Lu, Chunmei [Shandong Univ., Jinan (China). School of Energy and Power Engineering

    2013-07-01

    The carbide slag from polyvinyl chloride production as industry hazardous wastes was proposed as CO{sub 2} sorbent at high temperature in calcium looping cycle. The cyclic CO{sub 2} capture behavior and the microstructure characteristics of the carbide slag as one of the typical calcium-based industrial wastes during the multiple calcination/carbonation cycles. Also, the comparisons between the carbide slag and the natural limestone in cyclic CO{sub 2} capture behavior were made. XRD analysis demonstrates that the predominating constituent of the carbide slag is Ca(OH){sub 2}. The carbonation temperature ranging from 650 to 700 C is favourable to cyclic carbonation of the carbide slag. The cyclic carbonation conversions of the carbide slag is lower than that of the limestone before a certain time, but the situation is converse after that time in a thermogravimetric analyzer. The carbide slag has better cyclic CO{sub 2} capture capacity. The carbonation conversion of the carbide slag retains 0.28 after 100 calcination/carbonation cycles, while the two limestones achieve 0.08 and 0.14 respectively at the same reaction conditions in a dual fixed-bed reactor. The microstructure of the carbide slag by SEM reveals the reason why it possesses better CO{sub 2} capture capacity.

  7. Influence of structures on fracture and fracture toughness of cemented tungsten carbides

    International Nuclear Information System (INIS)

    Zhao, W.; Zhang, X.

    1987-01-01

    A study was made of the influence of structures on fracture and fracture toughness of cemented tungsten carbides with different compositions and grain sizes. The measurement of the fracture toughness of cemented tungsten carbide was carried out using single edge notched beam. The microstructural parameters and the proportion for each fracture mode on the fracture surface were obtained. The brittle fracture of the alloy is mainly due to the interfacial decohesion fracture following the interface of the carbide crystals. It has been observed that there are localized fractures region ahead of the crack tip. The morphology of the crack propagation path as well as the slip structure in the cobalt phase of the deformed region have been investigated. In addition, a study of the correlation between the plane strain fracture toughness and microstructural parameters, such as mean free path of the cobalt phase, tungsten carbide grain size and the contiguity of tungsten carbide crystals was also made

  8. TEM investigation of aluminium containing precipitates in high aluminium doped silicon carbide

    International Nuclear Information System (INIS)

    Wong-Leung, J.; FitzGerald, J.D.

    2002-01-01

    Full text: Silicon carbide is a promising semiconductor material for applications in high temperature and high power devices. The successful growth of good quality epilayers in this material has enhanced its potential for device applications. As a novel semiconductor material, there is a need for studying its basic physical properties and the role of dopants in this material. In this study, silicon carbide epilayers were grown on 4H-SiC wafers of (0001) orientation with a miscut angle of 8 deg at a temperature of 1550 deg C. The epilayers contained regions of high aluminium doping well above the solubility of aluminium in silicon carbide. High temperature annealing of this material resulted in the precipitation of aluminium in the wafers. The samples were analysed by secondary ion mass spectrometry and transmission electron microscopy. Selected area diffraction studies show the presence of aluminium carbide and aluminium silicon carbide phases. Copyright (2002) Australian Society for Electron Microscopy Inc

  9. Tool steel for cold worck niobium carbides

    International Nuclear Information System (INIS)

    Goldenstein, H.

    1984-01-01

    A tool steel was designed so as to have a microstructure with the matrix similar a cold work tool steel of D series, containing a dispersion of Niobium carbides, with no intention of putting Niobium in solution on the matrix. The alloy was cast, forged and heat treated. The alloy was easily forged; the primary carbide morfology, after forging, was faceted, tending to equiaxed. The hardness obtained was equivalent to the maximum hardness of a D-3 sttel when quenched from any temperature between 950 0 C, and 1200 0 , showing a very small sensitivy to the quenching temperature. (Author) [pt

  10. Hydrogen evolution activity and electrochemical stability of selected transition metal carbides in concentrated phosphoric acid

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Jensen, Jens Oluf; Bjerrum, Niels J.

    2014-01-01

    phosphoric acid were investigated in a temperature range from 80 to 170°C. A significant dependence of the activities on temperature was observed for all five carbide samples. Through the entire temperature range Group 6 metal carbides showed higher activity than that of the Group 5 metal carbides......Alternative catalysts based on carbides of Group 5 (niobium and tantalum) and 6 (chromium, molybdenum and tungsten) metals were prepared as films on the metallic substrates. The electrochemical activities of these carbide electrodes towards the hydrogen evolution reaction (HER) in concentrated...

  11. Plasma spraying process of disperse carbides for spraying and facing

    International Nuclear Information System (INIS)

    Blinkov, I.V.; Vishnevetskaya, I.A.; Kostyukovich, T.G.; Ostapovich, A.O.

    1989-01-01

    A possibility to metallize carbides in plasma of impulsing capacitor discharge is considered. Powders granulation occurs during plasma spraying process, ceramic core being completely capped. X-ray phase and chemical analyses of coatings did not show considerable changes of carbon content in carbides before and after plasma processing. This distinguishes the process of carbides metallization in impulsing plasma from the similar processing in arc and high-frequency plasma generator. Use of powder composites produced in the impulsing capacitor discharge, for plasma spraying and laser facing permits 2-3 times increasing wear resistance of the surface layer as against the coatings produced from mechanical powders mixtures

  12. Broadband antireflective silicon carbide surface produced by cost-effective method

    DEFF Research Database (Denmark)

    Argyraki, Aikaterini; Ou, Yiyu; Ou, Haiyan

    2013-01-01

    A cost-effective method for fabricating antireflective subwavelength structures on silicon carbide is demonstrated. The nanopatterning is performed in a 2-step process: aluminum deposition and reactive ion etching. The effect, of the deposited aluminum film thickness and the reactive ion etching...... conditions, on the average surface reflectance and nanostructure landscape have been investigated systematically. The average reflectance of silicon carbide surface is significantly suppressed from 25.4% to 0.05%, under the optimal experimental conditions, in the wavelength range of 390-784 nm. The presence...... of stochastic nanostructures also changes the wetting properties of silicon carbide surface from hydrophilic (47°) to hydrophobic (108°)....

  13. Silver diffusion through silicon carbide in microencapsulated nuclear fuels TRISO

    International Nuclear Information System (INIS)

    Cancino T, F.; Lopez H, E.

    2013-10-01

    The silver diffusion through silicon carbide is a challenge that has persisted in the development of microencapsulated fuels TRISO (Tri structural Isotropic) for more than four decades. The silver is known as a strong emitter of gamma radiation, for what is able to diffuse through the ceramic coatings of pyrolytic coal and silicon carbide and to be deposited in the heat exchangers. In this work we carry out a recount about the art state in the topic of the diffusion of Ag through silicon carbide in microencapsulated fuels and we propose the role that the complexities in the grain limit can have this problem. (Author)

  14. Simulations of Proton Implantation in Silicon Carbide (SiC)

    Science.gov (United States)

    2016-03-31

    Simulations of Proton Implantation in Silicon Carbide (SiC) Jonathan P. McCandless, Hailong Chen, Philip X.-L. Feng Electrical Engineering, Case...of implanting protons (hydrogen ions, H+) into SiC thin layers on silicon (Si) substrate, and explore the ion implantation conditions that are...relevant to experimental radiation of SiC layers. Keywords: silicon carbide (SiC); radiation effects; ion implantation ; proton; stopping and range of

  15. Carbon-coated tungsten and molybdenum carbides for electrode of electrochemical capacitor

    International Nuclear Information System (INIS)

    Morishita, Takahiro; Soneda, Yasushi; Hatori, Hiroaki; Inagaki, Michio

    2007-01-01

    New electrode materials for electrochemical capacitor, tungsten carbide WC and molybdenum carbide Mo 2 C coated by porous carbon, were prepared through a simple heat treatment of the mixture of K 2 WO 4 and K 2 MoO 4 , respectively, with hydroxy propyl cellulose. Carbide changed to hydroxide during the 1st charge-discharge cycle in H 2 SO 4 aqueous electrolyte, which showed redox reaction in further charge-discharge cycles, in addition to electric double layers of the carbon formed on its surface. The carbon-coated carbide gave a high capacitance in 1 mol L -1 H 2 SO 4 electrolyte, as about 350 F cm -3 for carbon-coated WC and 550-750 F cm -3 for carbon-coated Mo 2 C. Coating of carbon inhibits the growth of carbide particles during their formation, of which the small particle size make possible to complete transformation to hydroxides during the 1st charge-discharge cycle, and also disturbs the agglomeration of tungsten and molybdenum hydroxides during charge-discharge cycles, as well as porous carbon coated act as electrode material for electric double layers of electrolyte ions

  16. Influence of Heat Treatment on Content of the Carbide Phases in the Microstructure of High-Speed Steel

    Directory of Open Access Journals (Sweden)

    Jaworski J.

    2017-09-01

    Full Text Available This article presents the results of investigations of the effect of heat treatment temperature on the content of the carbide phase of HS3-1-2 and HS6-5-2 low-alloy high-speed steel. Analysis of the phase composition of carbides is carried out using the diffraction method. It is determined that with increasing austenitising temperature, the intensification of dissolution of M6C carbide increases. As a result, an increase in the grain size of the austenite and the amount of retained austenite causes a significant reduction in the hardness of hardened steel HS3-1-2 to be observed. The results of diffraction investigations showed that M7C3 carbides containing mainly Cr and Fe carbides and M6C carbides containing mainly Mo and W carbides are dissolved during austenitisation. During austenitisation of HS3-1-2 steel, the silicon is transferred from the matrix to carbides, thus replacing carbide-forming elements. An increase in a degree of tempering leads to intensification of carbide separation and this process reduce the grindability of tested steels.

  17. Rough surfaces of titanium and titanium alloys for implants and prostheses

    International Nuclear Information System (INIS)

    Conforto, E.; Aronsson, B.-O.; Salito, A.; Crestou, C.; Caillard, D.

    2004-01-01

    Titanium and titanium alloys for dental implants and hip prostheses were surface-treated and/or covered by metallic or ceramic rough layers after being submitted to sand blasting. The goal of these treatments is to improve the surface roughness and consequently the osteointegration, the fixation, and the stability of the implant. The microstructure of titanium and titanium alloys submitted to these treatments has been studied and correlated to their mechanical behavior. As-treated/covered and mechanically tested surfaces were characterized by scanning electron microscopy (SEM). Structural analyses performed by transmission electron microscopy (TEM), mainly in cross-section, reveal the degree of adherence and cohesion between the surface layer and the substrate (implant). We observed that, although the same convenient surface roughness was obtained with the two types of process, many characteristics as structural properties and mechanical behavior are very different

  18. Effect of carbides on erosion resistance of 23-8-N steel

    Indian Academy of Sciences (India)

    8-N nitronic steel, carbides present in the form of bands are observed to accelerate the erosion rate. Coarse ... lar carbides, precipitating at random boundaries, were more likely to ... 23-8-N nitronic steel is basically austenitic stainless steel.

  19. Sintering of nano crystalline α silicon carbide by doping with boron ...

    Indian Academy of Sciences (India)

    Unknown

    tions, they concluded that either reaction sintering or liquid phase .... α-6H silicon carbide single crystal by three different laboratories ... silicon carbide particles by the overall reaction .... layer displacement is likely to occur in such a manner as.

  20. Loss-of-flow transient characterization in carbide-fueled LMFBRs

    International Nuclear Information System (INIS)

    Rothrock, R.B.; Morgan, M.M.; Baars, R.E.; Elson, J.S.; Wray, M.L.

    1985-01-01

    One of the benefits derived from the use of carbide fuel in advanced Liquid Metal Fast Breeder Reactors (LMFBRs) is a decreased vulnerability to certain accidents. This can be achieved through the combination of advanced fuel performance with the enhanced reactivity feedback effects and passive shutdown cooling systems characteristic of the current 'inherently safe' plant concepts. The calculated core response to an unprotected loss of flow (ULOF) accident has frequently been used as a benchmark test of these designs, and the advantages of a high-conductivity fuel in relation to this type of transient have been noted in previous analyses. To evaluate this benefit in carbide-fueled LMFBRs incorporating representative current plant design features, limited calculations have been made of a ULOF transient in a small ('modular') carbide-fueled LMFBR

  1. Carbide precipitation kinetics in austenite of a Nb-Ti-V microalloyed steel

    International Nuclear Information System (INIS)

    Jung, Jae-Gil; Park, June-Soo; Kim, Jiyoung; Lee, Young-Kook

    2011-01-01

    Highlights: → Carbide precipitation kinetic was fastest at 950 deg. C and accelerated by strain. → Nucleation sites for (Nb,Ti)C above 950 deg. C were mainly undissolved (Ti,Nb)(C,N). → Strain enabled (Nb,Ti)C to nucleate on all sides of (Ti,Nb)(C,N) above 950 deg. C. → Strain changed nucleation sites from (Ti,Nb)(C,N) to dislocations below 900 deg. C. → Strain also accelerated the change in particle composition to equilibrium one. - Abstract: The isothermal precipitation kinetics of carbides in both strain-free and strained austenite (γ) of a microalloyed steel were quantitatively investigated through the electrical resistivity and transmission electron microscopy. The (Nb,Ti)C carbides at the interfaces of the undissolved (Ti,Nb)(C,N) carbonitrides were observed at all temperatures in strain-free γ. However, for strain-induced precipitation, above 950 deg. C, the precipitation of (Nb,Ti)C carbides near the undissolved (Ti,Nb)(C,N) carbonitrides was predominant due to the recrystallization of strained γ. Meanwhile, the fine (Nb,Ti,V)C carbides were homogeneously precipitated in non-recrystallized γ at 850 deg. C and 900 deg. C, as well as near the undissolved (Ti,Nb)(C,N) particles. The electrical resistivity method was successfully used to quantitatively measure the isothermal precipitation kinetics of carbides in both strain-free and strained γ. The precipitation-time-temperature diagrams of the carbide in strain-free and strained γ, with nose temperatures of 950 deg. C, were generated and the precipitation kinetics were greatly accelerated by the applied strain.

  2. Rapid PMR determination of hydrogen in titanium hydride and dehydrogenated titanium powders

    International Nuclear Information System (INIS)

    Il'enko, V.S.; Demidenko, L.M.

    1987-01-01

    Proton magnetic resonance (PMR) enables determining hydrogen quantitatively in titanium hydride and dehydrogenated titanium powders without destroying the specimen and is also more informative than high-temperature extraction methods. PMR provides data on the electron-nuclear interactions and the activation energies for hydrogen diffusion while also providing conclusions on the forms and positives of the hydrogen in the lattice and the binding to the metal atoms. The authors have developed a rapid method for determining hydrogen in titanium hydride and dehydrogenated titanium powders which reduces the analysis time and improves the metrological characteristics. The authors use a YaMR-5535 spectrometer working at 40 MHz upgraded for use with hydrogen in solids. The authors used specimens of mass about 2 g ground to 0.1 mm powder

  3. Investigations on the conditions for obtaining high density boron carbide by sintering

    International Nuclear Information System (INIS)

    Kislyj, P.S.; Grabtschuk, B.L.

    1975-01-01

    The results of investigations on kinetics of condensation and mechanisms of mass transfer in the process of sintering of technical, chemically pure and synthesized boron carbide are generalized. Laws on boron carbide densification depending upon temperature, time of isothermic endurance, thermal speed, size of powder particles and variable composition in homogeneity are determined. From the results obtained on condensation kinetics and special experiments on studying the changes in properties after heating under different conditions, the role of dislocation and diffusion processes in mass transfer during boron carbide sintering is exposed. The properties of sintered boron carbide are 15-20% lower than the properties of high-pressed one, that is conditioned by intercrystallite distortion of the first one and transcrystallite of the second one

  4. Process for the preparation of fine grain metal carbide powders

    International Nuclear Information System (INIS)

    Gortsema, F.P.

    1976-01-01

    Fine grain metal carbide powders are conveniently prepared from the corresponding metal oxide by heating in an atmosphere of methane in hydrogen. Sintered articles having a density approaching the theoretical density of the metal carbide itself can be fabricated from the powders by cold pressing, hot pressing or other techniques. 8 claims, no drawings

  5. Hafnium carbide formation in oxygen deficient hafnium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Rodenbücher, C. [Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-7), JARA-FIT, 52425 Jülich (Germany); Hildebrandt, E.; Sharath, S. U.; Kurian, J.; Komissinskiy, P.; Alff, L. [Technische Universität Darmstadt, Institute of Materials Science, 64287 Darmstadt (Germany); Szot, K. [Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-7), JARA-FIT, 52425 Jülich (Germany); University of Silesia, A. Chełkowski Institute of Physics, 40-007 Katowice (Poland); Breuer, U. [Forschungszentrum Jülich GmbH, Central Institute for Engineering, Electronics and Analytics (ZEA-3), 52425 Jülich (Germany); Waser, R. [Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-7), JARA-FIT, 52425 Jülich (Germany); RWTH Aachen, Institute of Electronic Materials (IWE 2), 52056 Aachen (Germany)

    2016-06-20

    On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO{sub 2−x}) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfC{sub x}) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfC{sub x} surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO{sub 2} thin films prepared and measured under identical conditions, the formation of HfC{sub x} was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.

  6. Mechanical stability and adhesion of ceramic coatings deposited on steels

    International Nuclear Information System (INIS)

    Ignat, M.; Armann, A.; Moberg, L.; Sibieude, F.

    1991-01-01

    This paper presents the results of two sorts of deformation experiment performed on coating/substrate systems. The coating/substrate systems were constituted by coatings of titanium nitride and chromium carbide, deposited in both cases on steel substrates. The formation experiments were cyclic bending tests on macroscopic samples with chromium carbide coatings, and straining experiments performed in a scanning electron microscope on samples with titanium nitride coatings. By the analysis of our experimental results we develop an attempt to correlate the mechanical stability of the systems with the interfacial adhesion, by taking into account the internal residual stresses as an adhesion parameter. For the samples with chromium carbide coatings, the evolution of internal stresses is detected from X-ray diffractometry and discussed in terms of the observed induced damaging mechanisms, in the cyclic tests. For the samples with titanium nitride coatings, we discussed the adhesion from the microstructural observations and from the critical parameters determined during the in-situ straining experiments. (orig.)

  7. Present status of uranium-plutonium mixed carbide fuel development for LMFBR

    International Nuclear Information System (INIS)

    Handa, Muneo; Suzuki, Yasufumi.

    One Oarai characteristic of a carbide fuel is that its doubling time is about 13 years which is only about half as long as that of an oxide fuel. The development of carbide fuels in the past ten years has been truly remarkable. Especially, through the new fuel development program initiated in 1974 in the United States, success has been achieved with respect to He- and Na-bond fuels in obtaining a 16 a/o burning rate without damage to cladding tubes. In 1984 at FFTF, a radiation of a fuel assembly consisting 91 fuel pins is contemplated. On the other hand, in Japan, in 1974, a Fuel Research Wing specializing in the study of carbide fuels was constructed in the Oarai Laboratory of the Atomic Energy Research Institute and in the fall of 1982, was successful in fabricating two carbide fuel pins having different chemical compositions

  8. APS- and XPS-investigations of vanadium, vanadium carbide and graphite

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, A M; Krause, U [Technische Univ. Muenchen (F.R. Germany). Inst. fuer Physikalische Chemie und Theoretische Chemie

    1975-11-01

    Soft X-ray appearance potential spectroscopy (APS) and X-ray photoelectron spectroscopy (XPS) have been used to study vanadium, vanadium carbide, and graphite. The chemical shifts for vanadium carbide with respect to metallic vanadium and graphite are compared for the two methods. The Csub(K) structure in APS and the valence band in XPS for vanadium carbide show good agreement with the band structure calculations of Neckel and co-workers. Using the band structure calculations of Painter et al. it is also shown how the multi-peak structure in the APS spectrum of graphite is possibly due to density of states effects. It would therefore appear that plasmon coupling plays only a minor role.

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

    Science.gov (United States)

    Cakan, Umut; Cakan, Murat; Delilbasi, Cagri

    2016-01-01

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

  10. Carbides precipitated from the melt in a Zr-2.5 Nb alloy

    International Nuclear Information System (INIS)

    Piotrkowski, R.; Garcia, E.A.; Vigna, G.L.; Bermudez, S.E.

    1993-01-01

    An experimental method is presented which leads to the formation of carbides similar in size (3 to 8 microns) and composition to those observed in some pressure tubes of CANDU type reactors. The method is based on melting the Zr-2.5 Nb alloy in a graphite crucible, where isothermal C diffusion in the Zr-Nb melt took place. It can be inferred that the carbides observed in pressure tubes could be originated in high temperature stages of the manufacture process. Otherwise, they could have been incorporated in the Zr sponge. As a result of the diffusion couple Liquid Zr-2.5 Nb/Solid Graphite, a carbide layer, up to 100μm thick, grew attached to the crucible wall, together with carbide particles whose size was in the some microns range. The smallest particles were arranged in rows determined by the prior β phase grains. The main carbide phase detected was the cubic MC 1-x ; the hexagonal M 2 C was also detected; M for metal. (Author)

  11. Effect of Titanium Inoculation on Tribological Properties of High Chromium Cast Iron

    Directory of Open Access Journals (Sweden)

    Siekaniec D.

    2017-12-01

    Full Text Available The present investigation focuses on the study of the influence of titanium inoculation on tribological properties of High Chromium Cast Iron. Studies of tribological properties of High Chromium Cast Iron, in particularly the wear resistance are important because of the special application of this material. High Chromium Cast Iron is widely used for parts that require high wear resistance for example the slurry pumps, brick dies, several pieces of mine drilling equipment, rock machining equipment, and similar ones. Presented research described the effects of various amounts of Fe-Ti as an inoculant for wear resistance. The results of wear resistance were collated with microstructural analysis. The melts were conducted in industrial conditions. The inoculation was carried out on the stream of liquid metal. The following amount of inoculants have been used; 0.17% Fe-Ti, 0.33% Fe-Ti and 0.66% Fe-Ti. The tests were performed on the machine type MAN. The assessment of wear resistance was made on the basis of the weight loss. The experimental results indicate that inoculation improve the wear resistance. In every sample after inoculation the wear resistance was at least 20% higher than the reference sample. The best result, thus the smallest wear loss was achieved for inoculation by 0.66% Fe-Ti. There is the correlation between the changing in microstructure and wear resistance. With greater amount of titanium the microstructure is finer. More fine carbides do not crumbling so quickly from the matrix, improving the wear resistance.

  12. The chemical vapor deposition of zirconium carbide onto ceramic substrates

    International Nuclear Information System (INIS)

    Glass A, John Jr.; Palmisiano, Nick Jr.; Welsh R, Edward

    1999-01-01

    Zirconium carbide is an attractive ceramic material due to its unique properties such as high melting point, good thermal conductivity, and chemical resistance. The controlled preparation of zirconium carbide films of superstoichiometric, stoichiometric, and substoichiometric compositions has been achieved utilizing zirconium tetrachloride and methane precursor gases in an atmospheric pressure high temperature chemical vapor deposition system

  13. Helium generation and diffusion in graphite and some carbides

    International Nuclear Information System (INIS)

    Holt, J.B.; Guinan, M.W.; Hosmer, D.W.; Condit, R.H.; Borg, R.J.

    1976-01-01

    The cross section for the generation of helium in neutron irradiated carbon was found to be 654 mb at 14.4 MeV and 744 mb at 14.9 MeV. Extrapolating to 14.1 MeV (the fusion reactor spectrum) gives 615 mb. The diffusion of helium in dense polycrystalline graphite and in pyrographite was measured and found to be D = 7.2 x 10 -7 m 2 s -1 exp (-80 kJ/RT). It is assumed that diffusion is primarily in the basal plane direction in crystals of the graphite. In polycrystalline graphite the path length is a factor of √2 longer than the measured distance due to the random orientation mismatch between successive grains. Isochronal anneals (measured helium release as the specimen is steadily heated) were run and maximum release rates were found at 200 0 C in polycrystalline graphite, 1000 0 C in pyrographite, 1350 0 C in boron carbide, and 1350 0 and 2400 0 C (two peaks) in silicon carbide. It is concluded that in these candidates for curtain materials in fusion reactors the helium releases can probably occur without bubble formation in graphites, may occur in boron carbide, but will probably cause bubble formation in silicon carbide. 7 figures

  14. Effect of electroslag remelting on carbides in 8Cr13MoV martensitic stainless steel

    Science.gov (United States)

    Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao

    2015-11-01

    The effect of electroslag remelting (ESR) on carbides in 8Cr13MoV martensitic stainless steel was experimentally studied. Phases precipitated from liquid steel during solidification were calculated using the Thermo-Calc software. The carbon segregation was analyzed by original position analysis (OPA), and the carbides were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy- dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that more uniform carbon distribution and less segregation were obtained in the case of samples subjected to the ESR process. After ESR, the amount of netty carbides decreased significantly, and the chromium and vanadium contents in the grain-boundary carbides was reduced. The total area and average size of carbides were obviously smaller after the ESR process. In the sample subjected to ESR, the morphology of carbides changed from lamellar and angular to globular or lump, whereas the types of carbides did not change; both M23C6 and M7C3 were present before and after the ESR process.

  15. Chemical changes of titanium and titanium dioxide under electron bombardment

    Directory of Open Access Journals (Sweden)

    Romins Brasca

    2007-09-01

    Full Text Available The electron induced effect on the first stages of the titanium (Ti0 oxidation and titanium dioxide (Ti4+ chemical reduction processes has been studied by means of Auger electron spectroscopy. Using factor analysis we found that both processes are characterized by the appearance of an intermediate Ti oxidation state, Ti2O3 (Ti3+.

  16. The Mechanical and Tribology Properties of Sputtered Titanium Aluminum Nitride Coating on the Tungsten Carbide Insert Tool in the Dry Turning of Tool Steel

    Directory of Open Access Journals (Sweden)

    Esmar Budi

    2015-02-01

    Full Text Available The effect of the sputtering parameters on the mechanical tribology properties of Titanium Aluminum Nitride coating on the tungsten cabide insert tool in the dry turning of tool steel has been investigated. The coating was deposited using a Direct Current magnetron sputtering system with various substrate biases (-79 to -221 V and nitrogen flow rates (30 to 72 sccm. The dry turning test was carried out on a Computer Numeric Code machine using an optimum cutting parameter setting. The results show that the lowest flank wear (~0.4 mm was achieved using a Titanium Aluminum Nitride-coated tool that was deposited at a high substrate bias (-200 V and a high nitrogen flow rate (70 sccm. The lowest flank wear was attributed to high coating hardness.

  17. Titanium fasteners. [for aircraft industry

    Science.gov (United States)

    Phillips, J. L.

    1972-01-01

    Titanium fasteners are used in large quantities throughout the aircraft industry. Most of this usage is in aluminum structure; where titanium structure exists, titanium fasteners are logically used as well. Titanium fasteners offer potential weight savings to the designer at a cost of approximately $30 per pound of weight saved. Proper and least cost usage must take into consideration type of fastener per application, galvanic couples and installation characteristics of protective coatings, cosmetic appearance, paint adhesion, installation forces and methods available and fatigue performance required.

  18. Titanium for salt water service

    International Nuclear Information System (INIS)

    Gadiyar, H.S.; Shibad, P.R.

    1980-01-01

    Titanium has potential as major material of construction in desalination plants, in condensers and heat exchangers, in view of its excellent corrosion resistance to salt water upto at least 120deg C. The advantages of titanium in such applications are brought out. The various specific problems such as pitting, crevice and galvanic corrosion and the preventive methods, for adopting titanium have been discussed. The hydriding problem can be overcome by suitably controlling the operating parameters such as temperature and surface preparation. A case has been made to prove the economic viability of titanium in comparison to Al-brass and Cu-Ni alloy. The future of titanium seems to be very promising in view of the negligible tube failures and outages. (auth.)

  19. [The surface roughness analysis of the titanium casting founding by a new titanium casting investment material].

    Science.gov (United States)

    Liang, Qin-ye; Wu, Xia-yi; Lin, Xue-feng

    2012-04-01

    To investigate the surface roughness property of the titanium castings cast in a new investment for titanium casting. Six wax patterns (20 mm × 20 mm × 0.5 mm) were invested using two investments: three in a new titanium investment material and three in the control material (Rematitan Plus). Six titanium specimens were obtained by conventional casting. After casting, surface roughness of the specimens were evaluated with a surface profilometer. The surface roughness of the specimens cast in new titanium investment material was (1.72 ± 0.08) µm, which was much smaller than that from Rematitan Plus [(1.91 ± 0.15) µm, P cast using these two investment materials are both smooth enough to fulfill the demand of the titanium precision-casting for prosthodontic clinical use.

  20. Pilot production of 325 kg of uranium carbide

    International Nuclear Information System (INIS)

    Clozet, C.; Dessus, J.; Devillard, J.; Guibert, M.; Morlot, G.

    1969-01-01

    This report describes the pilot fabrication of uranium carbide rods to be mounted in bundles and assayed in two channels of the EL 4 reactor. The fabrication process includes: - elaboration of uranium carbide granules by carbothermic reduction of uranium dioxide; - electron bombardment melting and continuous casting of the granules; - machining of the raw ingots into rods of the required dimensions; finally, the rods will be piled-up to make the fuel elements. Both qualitative and quantitative results of this pilot production chain are presented and discussed. (authors) [fr

  1. Nanofibre growth from cobalt carbide produced by mechanosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Barriga-Arceo, L [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, Colonia San Bartolo Atepehuacan, Mexico DF, 07730 (Mexico); Orozco, E [Instituto de Fisica UNAM, Apartado Postal 20-364 CP 01000, DF (Mexico); Garibay-Febles, V [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, Colonia San Bartolo Atepehuacan, Mexico DF, 07730 (Mexico); Bucio-Galindo, L [Instituto de Fisica UNAM, Apartado Postal 20-364 CP 01000, DF (Mexico); Mendoza Leon, H [FM-UPALM, IPN, Apartado Postal 75-395 CP 07300, DF (Mexico); Castillo-Ocampo, P [UAM-Iztapalapa, Apartado Postal 55-334 CP 09340, DF (Mexico); Montoya, A [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, Colonia San Bartolo Atepehuacan, Mexico DF, 07730 (Mexico)

    2004-06-09

    Mechanical alloying was used to prepare cobalt carbide. Microstructural characterization of samples was performed by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy methods. In order to produce carbon nanotubes, the cobalt carbide was precipitated after heating at 800 and 1000 deg. C for 10 min. Nanofibres of about 10-50 nm in diameter, 0.04-0.1 {mu}m in length and 20-200 nm in diameter and 0.6-1.2 {mu}m in length were obtained after heating at 800 and 1000 deg. C, respectively, by means of this process.

  2. Nanofibre growth from cobalt carbide produced by mechanosynthesis

    International Nuclear Information System (INIS)

    Diaz Barriga-Arceo, L; Orozco, E; Garibay-Febles, V; Bucio-Galindo, L; Mendoza Leon, H; Castillo-Ocampo, P; Montoya, A

    2004-01-01

    Mechanical alloying was used to prepare cobalt carbide. Microstructural characterization of samples was performed by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy methods. In order to produce carbon nanotubes, the cobalt carbide was precipitated after heating at 800 and 1000 deg. C for 10 min. Nanofibres of about 10-50 nm in diameter, 0.04-0.1 μm in length and 20-200 nm in diameter and 0.6-1.2 μm in length were obtained after heating at 800 and 1000 deg. C, respectively, by means of this process

  3. A novel plastification agent for cemented carbides extrusion molding

    International Nuclear Information System (INIS)

    Ji-Cheng Zhou; Bai-Yun Huang

    2001-01-01

    A type of novel plastification agent for plasticizing powder extrusion molding of cemented carbides has been developed. By optimizing their formulation and fabrication method, the novel plastification agent, with excellent properties and uniform distribution characters, were manufactured. The thermal debinding mechanism has been studied, the extruding rheological characteristics and debinding behaviors have been investigated. Using the newly developed plastification agent, the cemented carbides extrusion rods, with diameter up to 25 mm, have been manufactured. (author)

  4. Hard metal - a wear resistant material. Hartmetall - ein verschleissbestaendiger Werkstoff

    Energy Technology Data Exchange (ETDEWEB)

    Kolaska, J.; Dreyer, K. (Krupp Widia GmbH, Essen (Germany, F.R.))

    1989-01-01

    The article provides a survey of the various types of alloys of presently used carbides, their production processes and properties. Cermets (alloys with a high content of titanium carbide) are in the foreground here. With an eye on the future, advancements of further improved carbide materials are described, which feature at the same time a high resistance to wear and tenacity. (orig.).

  5. Phase equilibria, phases and compounds in the Ti-C system

    International Nuclear Information System (INIS)

    Gusev, Aleksandr I

    2002-01-01

    The results of experimental and theoretical investigations of the phase equilibria in the titanium-carbon system are generalised. The generalised thermodynamic characteristics of disordered titanium carbide TiC y , are reported. Peculiarities of the crystal structures of all the known and hypothetical compounds of titanium with carbon are considered in detail. The X-ray diffraction patterns which allow identification of all these compounds are presented. The phase diagrams of the Ti-C system constructed with allowance for atomic ordering of non-stoichio metric carbide, TiC y , and for the existence of the molecular cluster-like compounds Ti 8 C 12 and Ti 13 C 22 (TiC 2 ) are discussed. The bibliography includes 142 references.

  6. Recent observations of particulates in Nitinol

    International Nuclear Information System (INIS)

    Shabalovskaya, S.; Anderegg, J.; Humbeeck, J. van

    2008-01-01

    In spite of 40 years of history of Nitinol, the issues regarding its inclusions have been poorly explored. In our brief studies, conducted within the projects on surface design using Auger, energy-dispersive X-ray spectroscopy and scanning electrons microscopy, we discovered that particulates in NiTi medical alloys were always based on Ti: either ∼Ti 2 NiO oxide, titanium dioxide, titanium carbide or oxidized titanium carbide. Nonmetallic particles were rather brittle, had various shapes and sizes, and revealed different solubility in chemical solutions. The matrix material surrounding inclusions showed a tendency to localized corrosion. It was hypothesized that release of inclusion debris in the human body due to corrosion might compromise biocompatibility of Nitinol

  7. Structure-performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

    NARCIS (Netherlands)

    Stellwagen, D.R.; Bitter, J.H.

    2015-01-01

    This work demonstrates for the first time that carbide particle size is a critical factor for the activity and stability of carbon supported tungsten- and molybdenum carbide catalysts in (hydro-)deoxygenation reactions. The stability of the catalyst was shown to increase for larger particles due to

  8. Fracture and Residual Characterization of Tungsten Carbide Cobalt Coatings on High Strength Steel

    National Research Council Canada - National Science Library

    Parker, Donald S

    2003-01-01

    Tungsten carbide cobalt coatings applied via high velocity oxygen fuel thermal spray deposition are essentially anisotropic composite structures with aggregates of tungsten carbide particles bonded...

  9. Effect of composition and heat treatment on carbide phases in Ni-Mo alloys

    International Nuclear Information System (INIS)

    Svistunova, T.V.; Tsvigunov, A.N.; Stegnukhina, L.V.; Sakuta, N.D.

    1984-01-01

    The investigation results of vanadium, iron, carbon and silicon effect and heat treatment regime on the type and composition of carbides in Ni-(26...31)%Mo alloys are presented. It is shown that type, composition and quantity of carbide phases forming in alloys are determined not only by molybdenum and carbon content, but presence of other elements (V, Fe), admixtures (C, Si) and reducers as well as by regime of thermal treatment. In the alloy, containing 26...31% Mo, 0.01...0.03% C ( 12 C type with a=1.083...1.089 nm lattice parameter, in which V and Ti, Fe and Si are presented besides Mo and Ni. In the temperature range of 600-800 deg C high dispersed carbides segregate on grain boundaries. Silicon initiates segregation of the carbide phases among them by grain boundaries at the temperatures of 800 deg C as well as regulates carbide of M 12 C type with a=1.094...1.098 nm lattice parameter

  10. Mössbauer study of iron carbide nanoparticles produced by laser ablation in alcohols

    Energy Technology Data Exchange (ETDEWEB)

    Amagasa, S., E-mail: B115608@ed.tus.ac.jp; Nishida, N. [Tokyo University of Science, Department of Chemistry (Japan); Kobayashi, Y. [The University of Electro-Communications, Graduate School of Informatics and Engineering (Japan); Yamada, Y. [Tokyo University of Science, Department of Chemistry (Japan)

    2016-12-15

    Iron carbide nanoparticles were synthesized by laser ablation of iron in alcohols (methanol and ethanol). A new cell, designed to allow the ablation to be conducted in a flowing solvent, enabled separation and collection of the nanoparticles immediately after production, thus preventing further photochemical reactions of the colloids. The nanoparticles were investigated using Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. In methanol, they consisted of α-iron, γ-iron, iron carbide, and amorphous paramagnetic iron carbides, whereas in ethanol they consisted of iron carbides and amorphous paramagnetic iron carbides. The difference in products depending on the alcohol was attributed to the different carbon supplies for methanol and ethanol. For both solvents, the average particle size was found to be 16 nm, and the nanoparticles were dispersed in amorphous carbon. We also examined the effect of further laser irradiation of the colloids using stagnant solvent, and the particle size was found to increase and a very small amount of carbonization was observed.

  11. Nonstoichiometric control of tunnel-filling order, thermal expansion, and dielectric relaxation in tetragonal tungsten Bronzes Ba0.5-xTaO3-x.

    Science.gov (United States)

    Pan, Fengjuan; Li, Xiaohui; Lu, Fengqi; Wang, Xiaoming; Cao, Jiang; Kuang, Xiaojun; Véron, Emmanuel; Porcher, Florence; Suchomel, Matthew R; Wang, Jing; Allix, Mathieu

    2015-09-21

    Ordering of interpolated Ba(2+) chains and alternate Ta-O rows (TaO)(3+) in the pentagonal tunnels of tetragonal tungsten bronzes (TTB) is controlled by the nonstoichiometry in the highly nonstoichiometric Ba0.5-xTaO3-x system. In Ba0.22TaO2.72, the filling of Ba(2+) and (TaO)(3+) groups is partially ordered along the ab-plane of the simple TTB structure, resulting in a √2-type TTB superstructure (Pbmm), while in Ba0.175TaO2.675, the pentagonal tunnel filling is completely ordered along the b-axis of the simple TTB structure, leading to a triple TTB superstructure (P21212). Both superstructures show completely empty square tunnels favoring Ba(2+) conduction and feature unusual accommodation of Ta(5+) cations in the small triangular tunnels. In contrast with stoichiometric Ba6GaTa9O30, which shows linear thermal expansion of the cell parameters and monotonic decrease of permittivity with temperature within 100-800 K, these TTB superstructures and slightly nonstoichiometric simple TTB Ba0.4TaO2.9 display abnormally broad and frequency-dependent extrinsic dielectric relaxations in 10(3)-10(5) Hz above room temperature, a linear deviation of the c-axis thermal expansion around 600 K, and high dielectric permittivity ∼60-95 at 1 MHz at room temperature.

  12. Survey of post-irradiation examinations made of mixed carbide fuels

    International Nuclear Information System (INIS)

    Coquerelle, M.

    1997-01-01

    Post-irradiation examinations on mixed carbide, nitride and carbonitride fuels irradiated in fast flux reactors Rapsodie and DFR were carried out during the seventies and early eighties. In this report, emphasis was put on the fission gas release, cladding carburization and head-end gaseous oxidation process of these fuels, in particular, of mixed carbides. (author). 8 refs, 16 figs, 3 tabs

  13. Numerical assessment of bone remodeling around conventionally and early loaded titanium and titanium-zirconium alloy dental implants.

    Science.gov (United States)

    Akça, Kıvanç; Eser, Atılım; Çavuşoğlu, Yeliz; Sağırkaya, Elçin; Çehreli, Murat Cavit

    2015-05-01

    The aim of this study was to investigate conventionally and early loaded titanium and titanium-zirconium alloy implants by three-dimensional finite element stress analysis. Three-dimensional model of a dental implant was created and a thread area was established as a region of interest in trabecular bone to study a localized part of the global model with a refined mesh. The peri-implant tissues around conventionally loaded (model 1) and early loaded (model 2) implants were implemented and were used to explore principal stresses, displacement values, and equivalent strains in the peri-implant region of titanium and titanium-zirconium implants under static load of 300 N with or without 30° inclination applied on top of the abutment surface. Under axial loading, principal stresses in both models were comparable for both implants and models. Under oblique loading, principal stresses around titanium-zirconium implants were slightly higher in both models. Comparable stress magnitudes were observed in both models. The displacement values and equivalent strain amplitudes around both implants and models were similar. Peri-implant bone around titanium and titanium-zirconium implants experiences similar stress magnitudes coupled with intraosseous implant displacement values under conventional loading and early loading simulations. Titanium-zirconium implants have biomechanical outcome comparable to conventional titanium implants under conventional loading and early loading.

  14. Microstructure Characteristics of Fe-Matrix Composites Reinforced by In-Situ Carbide Particulates

    Science.gov (United States)

    Huang, Xiaodong; Song, Yanpei

    2017-10-01

    Carbide particulates reinforced iron-matrix composites were prepared by in-situ synthesis reaction between Ti, V and C on liquid alloys surface. The microstructure of the composite was characterized by SEM, TEM and OM. The results showed that the main phases were α-Fe, carbide particulate; besides, there were small amounts of γ-Fe and graphite (G) in the composite. The carbides were TiVC2 and VC in the shape of short bar and graininess. The matrix consisted of martensite and small amounts of retained austenite.

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

    KAUST Repository

    Garcia Esparza, Angel T.

    2012-12-17

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    KAUST Repository

    Garcia Esparza, Angel T.; Cha, Dong Kyu; Ou, Yiwei; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

    2012-01-01

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Sulfide phase in the Fe-Ti-S and Fe-C-Ti-S alloys

    International Nuclear Information System (INIS)

    Malinochka, Ya.N.; Balakina, N.A.; Shmelev, Yu.S.

    1976-01-01

    The nature of the sulfide phases in Fe-Ti-S and Fe-C-Ti-S alloys was studied. The carbide and the sulfide phase were identified the aid of X-ray spectral microanalysis. It was established that for a small content of titanium and sulfur in ternary Fe-Ti-S alloys the solidification of the γ-solution on the boundaries of dendritic branches is accompanied, along with the precipitation of a sulfide rich in iron of the (Fe, Ti) S type where a small quantity of titanium is dissolved, by the formation of a titanium-bearing sulfide eutectic γ + TiS. The amount of the sulfide eutectic increases with the contents of titanium and sulfur until a purely eutectic alloy is formed. Both carbides and sulfides may be formed in the solidification of quaternary alloys Fe-C-Ti-S

  18. Synthesis and phase transformation mechanism of Nb{sub 2}C carbide phases

    Energy Technology Data Exchange (ETDEWEB)

    Vishwanadh, B., E-mail: visubathula@gmail.com [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India); Murthy, T.S.R.Ch. [Materials Processing Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India); Arya, A.; Tewari, R.; Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India)

    2016-06-25

    In the present work, Niobium carbide samples were prepared through powder metallurgy route using spark plasma sintering technique. Some of these samples were heat treated at 900 °C up to 7 days. In order to investigate the phase transformation in Nb{sub 2}C carbide, the as-prepared and heat treated samples were characterized by X-ray diffraction, scanning electron microscopy and electron back scattered diffraction (EBSD) and transmission electron microscopy techniques. EBSD could index the same area of the sample in terms of any of the three allotropes of Nb{sub 2}C carbide phases (γ-Nb{sub 2}C, β-Nb{sub 2}C and α-Nb{sub 2}C) with good confidence index. From the EBSD patterns orientation relationships (OR) among γ, β and α-Nb{sub 2}C have been determined. Based on this OR when crystals of the three allotropes were superimposed, it has revealed that the basic Nb metal atom lattice (hcp lattice) in all the Nb{sub 2}C phases is same. The only difference exists in the carbides is the ordering of carbon atoms and vacancies in the octahedral positions of the hcp Nb metal atom lattice. Crystallographic analysis showed that for the transformation of γ-Nb{sub 2}C → β-Nb{sub 2}C → α-Nb{sub 2}C, large movement of Nb atoms is not required; but only by ordering of carbon atoms ensues the phase transformation. Literature shows that in the Nb–C system formation of the α-Nb{sub 2}C is not well established. Therefore, first principle calculations were carried out on these carbides. It revealed that the formation energy for α-Nb{sub 2}C is lower than the β and γ-Nb{sub 2}C carbides which indicate that the formation of α-Nb{sub 2}C is thermodynamically feasible. - Highlights: • Nb{sub 2}C carbide was produced by Spark Plasma Sintering in a single process. • Phase transformation mechanism of different Nb{sub 2}C carbide phases is studied. • In all the three Nb{sub 2}C carbides (γ, β, α), the base Nb lattice remains same. • Among γ, β and α-Nb{sub 2}C

  19. On change of vanadium carbide state during 20Kh3MVF steel heat treatment

    International Nuclear Information System (INIS)

    Gitgarts, M.I.; Maksimenko, V.N.

    1975-01-01

    The Xray diffraction study of vanadium carbide MC has been made in the steel-20KH3MVF quenched from 970 and 1040 deg and tempered at 660 deg for 210 hrs. It has been found that the constant of the MC crystal lattice regularly varies with the temperature of isothermal hold-up. In the steel tempered after quenching two vanadium carbides of different content could co-exist simultaneously: carbide formed in the quenching process and carbide formed during tempering. The discovered effect of the temperature dependence of the MC content is, evidently, inherent also to other steels containing vanadium

  20. Seebeck effect of some thin film carbides

    International Nuclear Information System (INIS)

    Beensh-Marchwicka, G.; Prociow, E.

    2002-01-01

    Several materials have been investigated for high-temperature thin film thermocouple applications. These include silicon carbide with boron (Si-C-B), ternary composition based on Si-C-Mn, fourfold composition based on Si-C-Zr-B and tantalum carbide (TaC). All materials were deposited on quartz or glass substrates using the pulse sputter deposition technique. Electrical conduction and thermoelectric power were measured for various compositions at 300-550 K. It has been found, that the efficiency of thermoelectric power of films containing Si-C base composition was varied from 0.0015-0.034 μW/cmK 2 . However for TaC the value about 0.093 μW/cmK 2 was obtained. (author)

  1. On possibility of fabrication of monolith composite materials on niobium carbide base

    International Nuclear Information System (INIS)

    Ploshkin, V.V.; Ul'yanina, I.Yu.; Filonenko, V.P.

    1984-01-01

    An attempt was made to fabricate the composite material on niobium carbide base possessing the elevated heat resistance, erosion and chemical resistance in special media, as well as capable of withstanding sufficient thermal shocks. Powder of niobium carbide of 10 μm fraction was used as base material, the powder of pure copper of 10...12 μm fraction - as binder. It was shown that samples of composite mateiral on niobium carbide base fabricated by the method of hydrostatic pressing possessed the minimal porosity as compared to samples fabricated by usual methods of powder metallurgy. The basic phases of composite material-copper and niobium carbide - distribute uniformly over sample cross-section and don't interact with each other under any conditions. The fabricated composite material possesses sufficient thermal shock resistance and isn't subjected to brittle fracture

  2. A study on the formation of uranium carbide in an induction furnace

    International Nuclear Information System (INIS)

    Song, In Young; Lee, Yoon Sang; Kim, Eung Soo; Lee, Don Bae; Kim, Chang Kyu

    2005-01-01

    Uranium is a typical carbide-forming element. Three carbides, UC, U 2 C 3 and UC 2 , are formed in the uranium-carbon system. The most important of these as fuel is uranium monocarbide UC. It is well known that Uranium carbides can be obtained by three basic methods: 1) by reaction of uranium metal with carbon; 2) by reaction of uranium metal powder with gaseous hydrocarbons; 3) by reaction of uranium oxides with carbon. The use of uranium monocarbide, or materials based on it, has great prospects as fuel for nuclear reactors. It is quite possible that uranium dicarbide UC 2 may also acquire great importance as a fuel, particularly in dispersion fuel elements with graphite matrix. In the present study, uranium carbides are obtained by direct reaction of uranium metal with graphite in a high frequency induction furnace

  3. Anodic growth of titanium dioxide nanostructures

    DEFF Research Database (Denmark)

    2010-01-01

    Disclosed is a method of producing nanostructures of titanium dioxide (TiO 2 ) by anodisation of titanium (Ti) in an electrochemical cell, comprising the steps of: immersing a non-conducting substrate coated with a layer of titanium, defined as the anode, in an electrolyte solution...... an electrical contact to the layer of titanium on the anode, where the electrical contact is made in the electrolyte solution...

  4. Catalytic activity of metall-like carbides in carbon oxide oxidation reaction

    International Nuclear Information System (INIS)

    Kharlamov, A.I.; Kosolapova, T.Ya.; Rafal, A.N.; Kirillova, N.V.

    1980-01-01

    Kinetics of carbon oxide oxidation upon carbides of hafnium, niobium, tantalum, molybdenum, zirconium and chromium is studied. Probable mechanism of the catalysts action is suggested. The established character of the change of the carbide catalytic activity is explained by the change of d-electron contribution to the metal-metal interaction

  5. Evolution of secondary-phase precipitates during annealing of the 12Kh18N9T steel irradiated with neutrons to a dose of 5 DPA

    Science.gov (United States)

    Tsai, K. V.; Maksimkin, O. P.; Turubarova, L. G.

    2007-03-01

    The formation and evolution of thermally-induced secondary precipitates in an austenitic stainless steel 12Kh18N9T irradiated in the core of a laboratory reactor VVR-K to a dose of 5 dpa and subjected to post-radiation isochronous annealings for 1 h in a temperature range from 450 to 1050°C have been studied using transmission electron microscopy (TEM) and microhardness measurements. It has been shown that the formation of stitch (secondary) titanium carbides and M 23C6 carbides at grain and twin boundaries after annealing at 1050°C is preceded by a complex evolution of fineparticles of secondary phases (titanium carbides and nitrides) precipitated at dislocation loops and dislocations during annealing at temperatures above 750°C.

  6. Additive-assisted synthesis of boride, carbide, and nitride micro/nanocrystals

    International Nuclear Information System (INIS)

    Chen, Bo; Yang, Lishan; Heng, Hua; Chen, Jingzhong; Zhang, Linfei; Xu, Liqiang; Qian, Yitai; Yang, Jian

    2012-01-01

    General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB 2 , ZrB 2 , NbB 2 , CeB 6 , PrB 6 , SmB 6 , EuB 6 , LaB 6 ), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN 2 , VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN 3 with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to ∼850 °C, once the autoclave was heated to 100 °C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds. - Graphical abstract: An additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S. Highlights: ► An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. ► The reaction mechanism is demonstrated by the case of SiC nanowires. ► The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.

  7. Toughness behaviour of tungsten-carbide-cobalt alloys

    International Nuclear Information System (INIS)

    Sigl, L.S.

    1985-05-01

    In the present work the mechanisms of crack propagation in technically important WC-Co alloys are investigated and a model describing the influence of microstructural parameters and of the mechanical properties of the constituents is developed. An energy concept is used for modelling fracture toughness. The energies dissipated in the four crack-paths (trans- and intergranular carbide fracture, fracture across the binder-ligaments, fracture in the binder close to the carbide/binder interface) are summed up using the experimentally determined area-fractions of the crack-paths, the specific energy of brittle fracture in the carbide and of ductile fracture is calculated by integrating the energy to deform a volume element over the plastically deformed region. In contrast to all earlier models, this concept describes fracture toughness of WC-Co alloys only with physically meaningful parameters. The excellent agreement with experimental toughness values and with qualitative observations of crack propagation show that the new model includes all effects which influence toughness. As demonstrated with WC-based hardmetals with a cobalt-nickel binder, the results open new possibilities for optimizing the toughness of composites in which a small amount of a tough phase is embedded in a brittle matrix. (Author, shortened by G.Q.)

  8. Non-pressurized sintered silicon carbide with titanium carbide reinforcement

    International Nuclear Information System (INIS)

    Adler, J.

    1992-01-01

    A non-pressurized compression of SiC-TiC composite materials can be achieved via liquid phase sintering by the application of oxidic additives. Materials with TiC proportions up to 40% by volume of TiC and densities of 97 to 98% TD were produced at sintering temperatures around 1875 C. With SiC sintered in the liquid phase an increase of toughness at fracture of 80% compared with conventionally non-pressurized sintered SiC was achieved with B/C additive. No further increase could be achieved by the addition of TiC particles. However, the oxidation resistance at 1200 C was worsened. (orig.) [de

  9. Morphological variants of carbides of solidification origin in the rapidly solidified powder particles of hypereutectic iron alloy

    International Nuclear Information System (INIS)

    Kusy, M.; Grgac, P.; Behulova, M.; Vyrostkova, A.; Miglierini, M.

    2004-01-01

    The paper deals with the analysis of the morphological variants of solidification microstructures and vanadium rich M 4 C 3 carbide phases in the rapidly solidified (RS) powder particles from hypereutectic Fe-C-Cr-V alloy prepared by the nitrogen gas atomisation. Five main types of solidification microstructures were identified in RS particles: microstructure with globular carbides, microstructure with globular and star-like carbides, microstructure with primary carbides in the centres of eutectic colonies, microstructure with eutectic colonies without primary carbides and microstructure with eutectic spherulites. Based on the morphological features of carbide phases and the thermal history of RS particles, the microstructures were divided into two groups - microstructures morphologically affected and non-affected during the post-recalescence period of solidification. Thermophysical reasons for the morphologically different M 4 C 3 carbide phases development in the RS powder particles are discussed

  10. The effects of carbide column to swelling potential and Atterberg limit on expansive soil with column to soil drainage

    Science.gov (United States)

    Muamar Rifa'i, Alfian; Setiawan, Bambang; Djarwanti, Noegroho

    2017-12-01

    The expansive soil is soil that has a potential for swelling-shrinking due to changes in water content. Such behavior can exert enough force on building above to cause damage. The use of columns filled with additives such as Calcium Carbide is done to reduce the negative impact of expansive soil behavior. This study aims to determine the effect of carbide columns on expansive soil. Observations were made on swelling and spreading of carbides in the soil. 7 Carbide columns with 5 cm diameter and 20 cm height were installed into the soil with an inter-column spacing of 8.75 cm. Wetting is done through a pipe at the center of the carbide column for 20 days. Observations were conducted on expansive soil without carbide columns and expansive soil with carbide columns. The results showed that the addition of carbide column could reduce the percentage of swelling by 4.42%. Wetting through the center of the carbide column can help spread the carbide into the soil. The use of carbide columns can also decrease the rate of soil expansivity. After the addition of carbide column, the plasticity index value decreased from 71.76% to 4.3% and the shrinkage index decreased from 95.72% to 9.2%.

  11. METHOD FOR PRODUCING CEMENTED CARBIDE ARTICLES

    Science.gov (United States)

    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.

  12. Novel fabrication of silicon carbide based ceramics for nuclear applications

    Science.gov (United States)

    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

  13. The vapour phase deposition of boron on titanium by the reaction between gaseous boron trichloride and titanium metal. Final report

    International Nuclear Information System (INIS)

    Cameron, D.J.; Shelton, R.A.J.

    1965-03-01

    The reaction, between boron trichloride vapour and titanium has been investigated in the temperature range 200 - 1350 deg. C. It has been found that an initial reaction leads to the formation of titanium tetrachloride and the deposition of boron on titanium, but that except for reactions between 900 and 1000 deg. C, the system is complicated by the formation of lower titanium chlorides due to secondary reactions between the titanium and titanium tetrachloride

  14. Reaction of uranium and plutonium carbides with austenitic steels; Reaction des carbures d'uranium et de plutonium avec des aciers austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Mouchnino, M [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1967-07-01

    The reaction of uranium and plutonium carbides with austenitic steels has been studied between 650 and 1050 deg. C using UC, steel and (UPu)C, steel diffusion couples. The steels are of the type CN 18.10 with or without addition of molybdenum. The carbides used are hyper-stoichiometric. Tests were also carried out with UCTi, UCMo, UPuCTi and UPuCMo. Up to 800 deg. C no marked diffusion of carbon into stainless steel is observed. Between 800 and 900 deg. C the carbon produced by the decomposition of the higher carbides diffuses into the steel. Above 900 deg. C, decomposition of the monocarbide occurs according to a reaction which can be written schematically as: (U,PuC) + (Fe,Ni,Cr) {yields} (U,Pu) Fe{sub 2} + Cr{sub 23}C{sub 6}. Above 950 deg. C the behaviour of UPuCMo and that of the titanium (CN 18.12) and nickel (NC 38. 18) steels is observed to be very satisfactory. (author) [French] La reaction des carbures d'uranium et de plutonium avec des aciers austenitiques a ete etudiee entre 650 deg. C et 1050 deg. C a partir de couples de diffusion UC, acier et (UPu)C, acier. Les aciers sont du type CN 18.10 avec ou sans addition de molybdene. Les carbures utilises sont hyper-stoechiometriques. En outre on a fait des essais avec UCTi, UCMo, UPuCTi, UPuCMo. Jusqu'a 800 deg. C on ne detecte pas de diffusion sensible du carbone dans l'acier inoxydable. Entre 800 et 900 deg. C il y a diffusion dans l'acier du carbone provenant de la decomposition des carbures superieurs. A partir de 900 deg. C il y a decomposition du monocarbure selon une reaction que l'on ecrit schematiquement: (U,PuC) + (Fe, Ni, Cr) {yields} (U,Pu)Fe{sub 2} + Cr{sub 23}C{sub 6}. Nous notons a 950 deg. C le bon comportement de UPuCMo ainsi que celui des aciers au titane (CN 18. 12) et au nickel (NC 38.18). (auteur)

  15. Vapor pressure and evaporation rate of certain heat-resistant compounds in a vacuum at high temperatures

    Science.gov (United States)

    Bolgar, A. S.; Verkhoglyadova, T. S.; Samsonov, G. V.

    1985-01-01

    The vapor pressure and evaporation rate of borides of titanium, zirconium, and chrome; and of strontium and carbides of titanium, zirconium, and chrome, molybdenum silicide; and nitrides of titanium, niobium, and tantalum in a vacuum were studied. It is concluded that all subject compounds evaporate by molecular structures except AlB sub 12' which dissociates, losing the aluminum.

  16. Microstructural studies and wear assessments of Ti/TiC surface composite coatings on commercial pure Ti produced by titanium cored wires and TIG process

    Energy Technology Data Exchange (ETDEWEB)

    Monfared, A., E-mail: amirmonfared25@yahoo.com [Department of Materials Science and Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Kokabi, A.H.; Asgari, S. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2013-01-15

    Tungsten Inert Gas (TIG) process and titanium cored wires filled with micro size TiC particles were employed to produce surface composite coatings on commercial pure Ti substrate for wear resistance improvement. Wire drawing process was utilized to produce several cored wires from titanium strips and titanium carbide powders. Subsequently, these cored wires were melted and coated on commercial pure Ti using TIG process. This procedure was repeated at different current intensities and welding travel speeds. Composite coating tracks were found to be affected by TIG heat input. The microstructural studies using optical and scanning electron microscopy supported by X-ray diffraction showed that the surface composite coatings consisted of {alpha} Prime -Ti, spherical and dendritic TiC particles. Also, greater volume fractions of TiC particles in the coatings were found at lower heat input. A maximum microhardness value of about 1100 HV was measured which is more than 7 times higher than the substrate material. Pin-on-disk wear tests exhibited a better performance of the surface composite coatings than the untreated material which was attributed to the presence of TiC particles in the microstructure. -- Highlights: Black-Right-Pointing-Pointer Ti/TiC composite coatings were produced on the CP-Ti. Black-Right-Pointing-Pointer Titanium cored wire and TIG process were employed for production of the coatings. Black-Right-Pointing-Pointer Decreasing heat input, increased the volume fraction of TiC in the coatings. Black-Right-Pointing-Pointer The maximum microhardness obtained in the lowest heat input. Black-Right-Pointing-Pointer The wear resistance of the coatings improved due to the formation of TiC particles.

  17. Square lattice honeycomb tri-carbide fuels for 50 to 250 KN variable thrust NTP design

    International Nuclear Information System (INIS)

    Anghaie, Samim; Knight, Travis; Gouw, Reza; Furman, Eric

    2001-01-01

    Ultrahigh temperature solid solution of tri-carbide fuels are used to design an ultracompact nuclear thermal rocket generating 950 seconds of specific impulse with scalable thrust level in range of 50 to 250 kilo Newtons. Solid solutions of tri-carbide nuclear fuels such as uranium-zirconium-niobium carbide. UZrNbC, are processed to contain certain mixing ratio between uranium carbide and two stabilizing carbides. Zirconium or niobium in the tri-carbide could be replaced by tantalum or hafnium to provide higher chemical stability in hot hydrogen environment or to provide different nuclear design characteristics. Recent studies have demonstrated the chemical compatibility of tri-carbide fuels with hydrogen propellant for a few to tens of hours of operation at temperatures ranging from 2800 K to 3300 K, respectively. Fuel elements are fabricated from thin tri-carbide wafers that are grooved and locked into a square-lattice honeycomb (SLHC) shape. The hockey puck shaped SLHC fuel elements are stacked up in a grooved graphite tube to form a SLHC fuel assembly. A total of 18 fuel assemblies are arranged circumferentially to form two concentric rings of fuel assemblies with zirconium hydride filling the space between assemblies. For 50 to 250 kilo Newtons thrust operations, the reactor diameter and length including reflectors are 57 cm and 60 cm, respectively. Results of the nuclear design and thermal fluid analyses of the SLHC nuclear thermal propulsion system are presented

  18. The effect of precipitated carbides on the pitting corrosion of 304 stainless steel

    International Nuclear Information System (INIS)

    Kwak, Jai-Hyun; Kim, Kwan-Hun

    1985-01-01

    In order to investigate the relation between the pitting corrosion and precipitated carbides, the heat treatment of specimens was carried out in two ways: Solution treatment and carbides precipitation treatment. The experiment was focused on the polarization curves of specimens immersed in HCL solution and on the microscopic analysis of the corroded specimens through a potentiodynamic method. It was found out that the intergranular and pitting corrosion occurred remarkably in 0.1N and 1N KCL solution when carbides were precipitated around the grain boundary of the 304 stain steel. The intergranular corrosion was noticed in the region of passivation and the pitting was prominent in the region of passivation break-down. The distribution of pits on the solution treated 304 stainless steel was random, while that of pits on carbides precipitated specimen was concentrated around the grain boundary in 0.1N and 1N HCL solution. It was ascertained that the pitting resistance of the solution treated 304 stainless steel was better than that of carbides precipitated specimen. (Author)

  19. Gravimetric determination of carbon in uranium-plutonium carbide materials

    International Nuclear Information System (INIS)

    Kavanaugh, H.J.; Dahlby, J.W.; Lovell, A.P.

    1979-12-01

    A gravimetric method for determining carbon in uranium-plutonium carbide materials was developed to analyze six samples simultaneously. The samples are burned slowly in an oxygen atmosphere at approximately 900 0 C, and the gases generated are passed through Schuetze's oxidizing reagent (iodine pentoxide on silica gel) to assure quantitative oxidation of the CO to CO 2 . The CO 2 is collected on Ascarite and weighed. This method was tested using a tungsten carbide reference material (NBS-SRM-276) and a (U,Pu)C sample. For 42 analyses of the tungsten carbide, which has a certified carbon content of 6.09%, an average value of 6.09% was obtained with a standard deviation of 0.01 7 % or a relative standard deviation of 0.28%. For 17 analyses of the (U,Pu)C sample, an average carbon content of 4.97% was found with a standard deviation of 0.01 2 % or a relative standard deviation of 0.24%

  20. Metallographic detection of carbides in the steel X 41 CrMoV 51 after different austenizing processes

    International Nuclear Information System (INIS)

    Fleer, R.; Rickel, J.; Draugelates, U.

    1979-01-01

    The etchant most suitable for clearly revealing the carbide particles in the developed hardened structure was determined by comparative structural investigations with several etchants in order to be able to undertake the metallographic detection of finely distributed carbides in the structure of the high alloy ultra-high strength steel X 41 CrMoV 51. The characteristic distribution and number of carbides could be revealed as well as the ferrite pearlite matrix. The picric-hydrochloric acid solution which, on a comparative basis, was the most effective, revealed the dependence of the carbide dissolution and structural formation on the temperature. The carbide components of the structure dissolved to an increasing extent at temperatures above 1100 0 C. All carbides up to the large volume mixed carbides appeared to dissolve in the segregation zone after annealing for one hour at 1200 0 C. Considerable grain growth also occurred. (orig./RW) [de

  1. Structural stability, electronic structure and mechanical properties of actinide carbides AnC (An = U, Np)

    International Nuclear Information System (INIS)

    Manikandan, M.; Santhosh, M.; Rajeswarapalanichamy, R.

    2016-01-01

    Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of actinide carbides AnC (An=U, Np) for three different crystal structures, namely NaCl, CsCl and ZnS. Among the considered structures, NaCl structure is found to be the most stable structure for these carbides at normal pressure. A pressure induced structural phase transition from NaCl to ZnS is observed. The electronic structure reveals that these carbides are metals. The calculated elastic constants indicate that these carbides are mechanically stable at normal pressure.

  2. Platinum group metal nitrides and carbides: synthesis, properties and simulation

    International Nuclear Information System (INIS)

    Ivanovskii, Alexander L

    2009-01-01

    Experimental and theoretical data on new compounds, nitrides and carbides of the platinum group 4d and 5d metals (ruthenium, rhodium, palladium, osmium, iridium, platinum), published over the past five years are summarized. The extreme mechanical properties of platinoid nitrides and carbides, i.e., their high strength and low compressibility, are noted. The prospects of further studies and the scope of application of these compounds are discussed.

  3. Process for making a titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition

    Science.gov (United States)

    Holcombe, C.E.; Dykes, N.L.

    1992-04-28

    A ceramic composition is described. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to about 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1--A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2--The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3--The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness. No Drawings

  4. Effect of nonthermal plasma treatment on surface chemistry of commercially-pure titanium and shear bond strength to autopolymerizing acrylic resin

    Energy Technology Data Exchange (ETDEWEB)

    Vechiato-Filho, Aljomar José, E-mail: aljomarvechiatoflo@gmail.com [Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ. Estadual Paulista — UNESP, Aracatuba, Sao Paulo (Brazil); Silva Vieira Marques, Isabella da [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sao Paulo (Brazil); Santos, Daniela Micheline dos [Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ. Estadual Paulista — UNESP, Aracatuba, Sao Paulo (Brazil); Oliveira Matos, Adaias [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sao Paulo (Brazil); Rangel, Elidiane Cipriano; Cruz, Nilson Cristino da [Laboratory of Technological Plasmas (LaPTec), Engineering College, Univ. Estadual Paulista — UNESP, Sorocaba, Sao Paulo (Brazil); Barão, Valentim Adelino Ricardo [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sao Paulo (Brazil)

    2016-03-01

    The effect of nonthermal plasma on the surface characteristics of commercially pure titanium (cp-Ti), and on the shear bond strength between an autopolymerizing acrylic resin and cp-Ti was investigated. A total of 96 discs of cp-Ti were distributed into four groups (n = 24): Po (no surface treatment), SB (sandblasting), Po + NTP and SB + NTP (methane plasma). Surface characterization was performed through surface energy, surface roughness, scanning microscopy, energy dispersive spectroscopy, and X-ray diffraction tests. Shear bond strength test was conducted immediately and after thermocycling. Surface treatment affected the surface energy and roughness of cp-Ti discs (P < .001). SEM–EDS showed the presence of the carbide thin film. XRD spectra revealed no crystalline phase changes. The SB + NTP group showed the highest bond strength values (6.76 ± 0.70 MPa). Thermocycling reduced the bond strength of the acrylic resin/cp-Ti interface (P < .05), except for Po group. NTP is an effective treatment option for improving the shear bond strength between both materials. - Highlights: • We tested the bond strength between two widely used materials in dentistry (acrylic and titanium). • We performed an innovative surface treatment with nonthermal plasma. • Increasing adhesion will avoid complications of full-arch implant-retained prostheses.

  5. Tribological behaviors of graphite sliding against cemented carbide in CaCl2 solution

    International Nuclear Information System (INIS)

    Guo, Fei; Tian, Yu; Liu, Ying; Wang, Yuming

    2015-01-01

    The tribological behaviors of graphite sliding against cemented carbide were investigated using a standard tribological tester Plint TE92 in a ring-on-ring contact configuration in both CaCl 2 solution and deionized water. An interesting phenomenon occurred: as the CaCl 2 solution concentration increased, the friction coefficient firstly decreased and was lower than that in the deionized water, and then gradually increased, exceeding the friction coefficient in the deionized water. The wear rate of the ,graphite also presented the same variation trend. According to the polarization curves of cemented carbide, contact angle measurements, Raman spectrum analysis and scanning electron microscope (SEM) images analysis, the above friction and wear behaviors of graphite sliding against cemented carbide were attributed to the graphite surface wettability and the cemented carbide surface corrosion property. (paper)

  6. Carbide Precipitation in 2.25 Cr-1 Mo Bainitic Steel: Effect of Heating and Isothermal Tempering Conditions

    Science.gov (United States)

    Dépinoy, Sylvain; Toffolon-Masclet, Caroline; Urvoy, Stéphane; Roubaud, Justine; Marini, Bernard; Roch, François; Kozeschnik, Ernst; Gourgues-Lorenzon, Anne-Françoise

    2017-05-01

    The effect of the tempering heat treatment, including heating prior to the isothermal step, on carbide precipitation has been determined in a 2.25 Cr-1 Mo bainitic steel for thick-walled applications. The carbides were identified using their amount of metallic elements, morphology, nucleation sites, and diffraction patterns. The evolution of carbide phase fraction, morphology, and composition was investigated using transmission electron microscopy, X-ray diffraction, as well as thermodynamic calculations. Upon heating, retained austenite into the as-quenched material decomposes into ferrite and cementite. M7C3 carbides then nucleate at the interface between the cementite and the matrix, triggering the dissolution of cementite. M2C carbides precipitate separately within the bainitic laths during slow heating. M23C6 carbides precipitate at the interfaces (lath boundaries or prior austenite grain boundaries) and grow by attracting nearby chromium atoms, which results in the dissolution of M7C3 and, depending on the temperature, coarsening, or dissolution of M2C carbides, respectively.

  7. 40 CFR 180.1195 - Titanium dioxide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Titanium dioxide. 180.1195 Section 180.1195 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS... Titanium dioxide. Titanium dioxide is exempted from the requirement of a tolerance for residues in or on...

  8. Advances in cost effective processing of titanium

    International Nuclear Information System (INIS)

    Nelson, O.E.

    1993-01-01

    Recently an industry expert pointed out that one of the greatest hindrances to the growth of titanium usage has been the low percentage of material usable in the final product. Due to the extensive processing, forming, and machining operations typically performed on titanium, yield losses are high. This is especially true in aerospace applications where most titanium is used. In engine components, the start to finish ratio, known as the buy to fly ratio, is often as high as 7 to 1. This can be illustrated by looking at the use of titanium in Pratt and Whitney engines. In the JT-8D-217 used on Boeing's 737-200, the titanium buyweight is 5,385 pounds, whereas the finished titanium, flyweight is just 758 pounds. This start to finish ratio is 7.1:1, giving titanium 17.0% of total engine weight. (orig.)

  9. Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses; Ablação seletiva de um filme de nitreto de titânio em substrato de carboneto de tungstênio utilizando laser de pulsos ultracurtos

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Eduardo Spinelli

    2017-07-01

    Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

  10. The determining impact of coiling temperature on the microstructure and mechanical properties of a titanium-niobium ultrahigh strength microalloyed steel: Competing effects of precipitation and bainite

    Energy Technology Data Exchange (ETDEWEB)

    Natarajan, V.V.; Challa, V.S.A. [Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, 500 W. University Avenue, University of Texas at El Paso, El Paso, TX 79968 (United States); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, 500 W. University Avenue, University of Texas at El Paso, El Paso, TX 79968 (United States); Sidorenko, D.M.; Mulholland, M.D.; Manohar, M.; Hartmann, J.E. [ArcelorMittal Global R& D Center, 3001 East Columbus Drive, East Chicago, IN 46312 (United States)

    2016-05-17

    We elucidate here the influence of coiling temperature on the microstructure and mechanical properties, in an ultrahigh strength titanium-niobium microalloyed steel. The objective was to underscore the impact of coiling temperature on the nature and distribution of microstructural constituents (including different phases, precipitates, and dislocation structure) that significantly contributed to differences in the yield and tensile strength of these steels. Depending on the coiling temperature, the microstructure consisted of either a combination of fine lath-type bainite and polygonal ferrite or polygonal ferrite together with the precipitation of microalloyed carbides of size ~2–10 nm in the matrix and at dislocations. The microstructure of steel coiled at lower temperature predominantly consisted of bainitic ferrite with lower yield strength compared to the steel coiled at higher temperature, and the yield to tensile strength ratio was 0.76. The steel coiled at higher temperature consisted of polygonal ferrite and extensive precipitation of carbides and was characterized by higher yield strength and with yield strength/tensile strength ratio of 0.936. The difference in the tensile strength was insignificant for the two coiling temperatures. The observed microstructure was consistent with the continuous cooling transformation diagram.

  11. Electron beam melting of sponge titanium

    International Nuclear Information System (INIS)

    Kanayama, Hiroshi; Kusamichi, Tatsuhiko; Muraoka, Tetsuhiro; Onouye, Toshio; Nishimura, Takashi

    1991-01-01

    Fundamental investigations were done on electron beam (EB) melting of sponge titanium by using 80 kW EB melting furnace. Results obtained are as follows: (1) To increase the melting yield of titanium in EB melting of sponge titanium, it is important to recover splashed metal by installation of water-cooled copper wall around the hearth and to decrease evaporation loss of titanium by keeping the surface temperature of molten metal just above the melting temperature of titanium without local heating. (2) Specific power consumption of drip melting of pressed sponge titanium bar and hearth melting of sponge titanium are approximately 0.9 kWh/kg-Ti and 0.5-0.7 kWh/kg-Ti, respectively. (3) Ratios of the heat conducted to water-cooled mould in the drip melting and to water-cooled hearth in the hearth melting to the electron beam input power are 50-65% and 60-65%, respectively. (4) Surface defects of EB-melted ingots include rap which occurs when the EB output is excessively great, and transverse cracks when the EB output is excessively small. To prevent surface defects, the up-down withdrawal method is effective. (author)

  12. Nonstoichiometric complex of gramicidin D with KI at 0.80 (angstrom) resolution

    International Nuclear Information System (INIS)

    Olczak, A.; Glowka, M.L.; Szczesio, M.; Bojarsk, J.; Duax, W.L.; Burkhart, B.M.; Wawrzak, Z.

    2007-01-01

    The crystal structure of a nonstoichiometric complex of gramicidin D (gD) with KI has been determined at 100 K using synchrotron radiation. The final R factor was 0.106 for 83 988 observed reflections (Friedel pairs were not merged) collected to 0.80 (angstrom). The structure consists of four independent pentadecapeptides and numerous solvent molecules and salt ions. The general architecture of the antiparallel double-stranded gramicidin dimers in the crystal (a right-handed antiparallel DSβH R form) closely resembles that of previously published cation complexes of gD. However, a significantly different mixture of gramicidin isomers is found in the crystal of the KI complex, including partial occupancy of phenylalanine at position 11. Only three sites in each of the two crystallographically independent channels are partially occupied by potassium cations instead of the commonly observed seven sites. The sum of the partial occupancies of K + (1.10 per two dimers) is consistent with the sum of the iodide occupancies (1.095 over eight sites), which is also confirmed by the anomalous signal of the iodide. There was a significant asymmetry of the distribution and occupancies of cations in the crystallographically independent gramicidin channels, in contrast to the distribution found in the rubidium chloride complex with gD.

  13. Production of titanium tetrachloride

    International Nuclear Information System (INIS)

    Perillo, P.M.; Botbol, O.

    1990-01-01

    This report presents a summary of results from theoperation of a laboratory scale for the production in batches of approximately 100 gs of titanium tetrachloride by chlorination with chloroform and carbon tetrachloride between 340 deg C and 540 deg C. Chlorination agent vapors were passed through a quartz column reacting with titanium oxide powder agglomerated in little spheres. Obtained titanium tetrachloride was condensed in a condenser, taken in a ballon and then purified by fractional distillation. Optimun temperature for chloroform was 400 deg C with 74 % yield and for carbon tetrachloride was 500 deg C with 69 % yield. (Author) [es

  14. Multi-criteria methodology to design a sodium-cooled carbide-fueled Gen-IV reactor

    International Nuclear Information System (INIS)

    Stauff, N.

    2011-01-01

    Compared with earlier plant designs (Phenix, Super-Phenix, EFR), Gen IV Sodium-cooled Fast Reactor requires improved economics while meeting safety and non-proliferation criteria. Mixed Oxide (U-Pu)O 2 fuels are considered as the reference fuels due to their important and satisfactory feedback experience. However, innovative carbide (U-Pu)C fuels can be considered as serious competitors for a prospective SFR fleet since carbide-fueled SFRs can offer another type of optimization which might overtake on some aspects the oxide fuel technology. The goal of this thesis is to reveal the potentials of carbide by designing an optimum carbide-fueled SFR with competitive features and a naturally safe behavior during transients. For a French nuclear fleet, a 1500 MW(e) break-even core is considered. To do so, a multi-physic approach was developed taking into account neutronics, fuel thermo-mechanics and thermal-hydraulic at a pre-design stage. Simplified modeling with the calculation of global neutronic feedback coefficients and a quasi-static evaluation was developed to estimate the behavior of a core during overpower transients, loss of flow and/or loss of heat removal transients. The breakthrough of this approach is to provide the designer with an overall view of the iterative process, emphasizing the well-suited innovations and the most efficient directions that can improve the SFR design project.This methodology was used to design a core that benefits from the favorable features of carbide fuels. The core developed is a large carbide-fueled SFR with high power density, low fissile inventory, break-even capability and forgiving behaviors during the un-scrammed transients studied that should prevent using expensive mitigate systems. However, the core-peak burnup is unlikely to significantly exceed 100 MWd/kg because of the large swelling of the carbide fuel leading to quick pellet-clad mechanical interaction and the low creep capacity of carbide. Moderate linear power fuel

  15. Reference of Temperature and Time during tempering process for non-stoichiometric FTO films

    Science.gov (United States)

    Yang, J. K.; Liang, B.; Zhao, M. J.; Gao, Y.; Zhang, F. C.; Zhao, H. L.

    2015-10-01

    In order to enhance the mechanical strength of Low-E glass, Fluorine-doped tin oxide (FTO) films have to be tempered at high temperatures together with glass substrates. The effects of tempering temperature (600 °C ~ 720 °C) and time (150 s ~ 300 s) on the structural and electrical properties of FTO films were investigated. The results show all the films consist of non-stoichiometric, polycrystalline SnO2 without detectable amounts of fluoride. 700 °C and 260 s may be the critical tempering temperature and time, respectively. FTO films tempered at 700 °C for 260 s possesses the resistivity of 7.54 × 10-4 Ω•cm, the average transmittance in 400 ~ 800 nm of ~80%, and the calculated emissivity of 0.38. Hall mobility of FTO films tempered in this proper condition is mainly limited by the ionized impurity scattering. The value of [O]/[Sn] at the film surface is much higher than the stoichiometric value of 2.0 of pure crystalline SnO2.

  16. Contribution to the study of zirconium self-diffusion in zirconium carbide

    International Nuclear Information System (INIS)

    An, Chul

    1972-01-01

    The objective of this research thesis is to determine experimental conditions allowing the measurement of the self-diffusion coefficient of zirconium in zirconium carbide. The author reports the development of a method of preparation of zirconium carbide samples. He reports the use of ion implantation as technique to obtain a radio-tracer coating. The obtained results give evidence of the impossibility to use sintered samples with small grains because of the demonstrated importance of intergranular diffusion. The self-diffusion coefficient is obtained in the case of zirconium carbide with grains having a diameter of few millimetres. The presence of 95 Nb from the disintegration of 95 Zr indicates that these both metallic elements have very close diffusion coefficients at 2.600 C [fr

  17. Coal-Based Reduction and Magnetic Separation Behavior of Low-Grade Vanadium-Titanium Magnetite Pellets

    Directory of Open Access Journals (Sweden)

    Gongjin Cheng

    2017-05-01

    Full Text Available Coal-based reduction and magnetic separation behavior of low-grade vanadium-titanium magnetite pellets were studied in this paper. It is found that the metallization degree increased obviously with an increase in the temperature from 1100 °C to 1400 °C. The phase composition transformation was specifically analyzed with X-ray diffraction (XRD. The microscopic examination was carried out with scanning electron microscopy (SEM, and the element composition and distribution were detected with energy dispersive spectroscopy (EDS. It is observed that the amounts of metallic iron particles obviously increased and the accumulation and growing tendency were gradually facilitated with the increase in the temperature from 1100 °C to 1400 °C. It is also found that the titanium oxides were gradually reduced and separated from ferrum-titanium oxides during reduction. In addition, with increasing the temperature from 1200 °C to 1350 °C, silicate phases, especially calcium silicate phases that were transformed from calcium ferrite at 1100 °C, were observed and gradually aggregated. However, at 1400 °C some silicate phases infiltrated into metallic iron, as it appears that the carbides, especially TiC, could probably contribute to the sintering phenomenon becoming serious. The transformation behavior of valuable elements was as follows: Fe2VO4 → VO → V → VC; FeTiO3 (→ FeTi2O5 → TiO2 → TiC; FeCr2O4 → Cr → CrC; FeTiO3 (→ FeTi2O5 → Fe0.5Mg0.5Ti2O5; (Fe3O4/FeTiO3→ FeO → Mg0.77Fe0.23O. Through the magnetic separation of coal-based reduced products, it is demonstrated that the separation of Cr, V, Ti, and non-magnetic phases can be preliminarily realized.

  18. Uranium fluorides analysis. Titanium spectrophotometric determination

    International Nuclear Information System (INIS)

    Anon.

    Titanium determination in uranium hexafluoride in the range 0.7 to 100 microgrammes after transformation of uranium fluoride in sulfate. Titanium is separated by extraction with N-benzoylphenylhydroxylamine, reextracted by hydrochloric-hydrofluoric acid. The complex titanium-N-benzoylphenylhydroxylamine is extracted by chloroform. Spectrophotometric determination at 400 nm [fr

  19. 21 CFR 73.2575 - Titanium dioxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.2575 Section 73.2575 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity and specifications to the requirements...

  20. Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

    International Nuclear Information System (INIS)

    Venkatesh, L.; Samajdar, I.; Tak, Manish; Doherty, Roger D.; Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S.V.

    2015-01-01

    Highlights: • Microstructural development during laser cladding has been studied. • In this multi component system Cr 7 C 3 is found to be the stable carbide phase. • Phases were identified by EBSD since XRD results were not conclusive. • Increase in laser power and/or scanning speed reduced the carbide content. • Hardness seems to depend on phase content as well as microstructure. - Abstract: Microstructural development in laser clad layers of Chromium carbide (Cr x C y )-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr 3 C 2 and Cr 7 C 3 , the clad layers showed only the presence of Cr 7 C 3 . Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr 7 C 3 with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr 7 C 3 is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ 2 ) of the Cr 7 C 3 dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

  1. Effects of silicon carbide on the phase developments in mullite-carbon ceramic composite

    Directory of Open Access Journals (Sweden)

    Fatai Olufemi ARAMIDE

    2017-12-01

    Full Text Available The effects of the addition of silicon carbide and sintering temperatures on the phases developed, in sintered ceramic composite produced from kaolin and graphite was investigated. The kaolin and graphite of known mineralogical composition were thoroughly blended with 4 and 8 vol % silicon carbide. From the homogeneous mixture of kaolin, graphite and silicon carbide, standard samples were prepared via uniaxial compaction. The test samples produced were subjected to firing (sintering at 1300°C, 1400°C and 1500°C. The sintered samples were characterized for the developed phases using x‐ray diffractometry analysis, microstructural morphology using ultra‐high resolution field emission scanning electron microscope (UHRFEGSEM. It was observed that microstructural morphology of the samples revealed the evolution of mullite, cristobalite and microcline. The kaolinite content of the raw kaolin undergoes transformation into mullite and excess silica, the mullite and the silica phases contents increased with increased sintering temperature. It is also generally observed that the graphite content progressively reduced linearly with increased sintering temperature. It is concluded that silicon carbide acts as anti-oxidant for the graphite, this anti-oxidant effect was more effective at 4 vol % silicon carbide.

  2. The effect of manganese content on mechanical properties of high titanium microalloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaolin, E-mail: lixiaolinwork@163.com [Shougang Research Institute of Technology, Beijing 100041 (China); Li, Fei; Cui, Yang; Xiao, Baoliang [Shougang Research Institute of Technology, Beijing 100041 (China); Wang, Xuemin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-11-20

    In this work, in order to achieve an optimum combination of high strength, ductility and toughness of high Ti microalloyed steel, extensive research efforts were exerted to study the effect of soaking temperature, manganese and sulfur content on properties of titanium steels. Precipitation hardening of Ti-bearing steels has been found to vary with different soaking temperature. Higher strength was achieved in these steels at higher soaking temperature due to dissolution of more TiC, Ti{sub 4}S{sub 2}C{sub 2} and little TiN, which lead to re-precipitation of fine carbides with greater volume fraction. The results of transmission electron microscope (TEM)analysis indicates that there were more and finer TiC precipitates coherent or semi-coherent with the ferrite matrix in the high manganese content steel than in low manganese content steel. The marked improvement in strength is also associated with low sulfur content. TiC particles smaller than 20 nm in 8Ti-8Mn steel help enhance strength to higher than 302 MPa compared with 8Mn steel.

  3. Mechanism of the electrochemical hydrogen reaction on smooth tungsten carbide and tungsten electrodes

    International Nuclear Information System (INIS)

    Wiesener, K.; Winkler, E.; Schneider, W.

    1985-01-01

    The course of the electrochemical hydrogen reaction on smooth tungsten-carbide electrodes in hydrogen saturated 2.25 M H 2 SO 4 follows a electrochemical sorption-desorption mechanism in the potential range of -0.4 to +0.1 V. At potentials greater than +0.1 V the hydrogen oxidation is controlled by a preliminary chemical sorption step. Concluding from the similar behaviour of tungsten-carbide and tungsten electrodes after cathodic pretreatment, different tungsten oxides should be involved in the course of the hydrogen reaction on tungsten carbide electrodes. (author)

  4. Titanium oxide nanocoating on a titanium thin film deposited on a glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS, National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS, National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Cummings, F.R. [University of the Western Cape, Electron Microscopy Unit, Physics Department, Bellville 7535, Cape Town (South Africa); Turco, S. Lo; Ntwaeaborwa, O.M. [Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Milano, Italy Via Giovanni Pascoli, 70/3, 20133 Milano (Italy); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)-CNR, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS, National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa)

    2016-03-31

    Thin films of titanium were deposited on a glass substrate using electron beam evaporator. Femtosecond laser pulses were focused on the surface of the films, and the samples were scanned while mounted on the motorized computer-controlled motion stage to produce an areal modification of the films. X-ray diffraction of the laser-patterned samples showed evidence of the formation of a γ-Ti{sub 3}O{sub 5} with a monoclinic phase. Rutherford backscattering spectrometry simulation showed that there is an increase in the oxygen concentration as the average laser fluence is increased. Time of flight secondary ions mass spectrometry analysis showed an even distribution of the titanium and oxygen ions on the sample and also ionized molecules of the oxides of titanium were observed. The formation of the oxide of titanium was further supported using the UV–Vis-NIR spectroscopy, which showed that for 0.1 J/cm{sup 2} fluence, the laser-exposed film showed the electron transfer band and the d–d transition peak of titanium was observed at lower wavelengths. - Highlights: • γ-Ti{sub 3}O{sub 5} formed using femtosecond laser. • Fluence and oxygen relation were studied. • Nanoflakes of γ-Ti{sub 3}O{sub 5} were observed under HRSEM.

  5. 21 CFR 73.1575 - Titanium dioxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.1575 Section 73.1575 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in identity and specifications to the requirements...

  6. Adhesive-Bonded Tab Attaches Thermocouples to Titanium

    Science.gov (United States)

    Cook, C. F.

    1982-01-01

    Mechanical strength of titanium-alloy structures that support thermocouples is preserved by first spotwelding thermocouples to titanium tabs and then attaching tabs to titanium with a thermosetting adhesive. In contrast to spot welding, a technique previously used for thermocouples, fatigue strength of the titanium is unaffected by adhesive bonding. Technique is also gentler than soldering or attaching thermocouples with a tap screw.

  7. Erosion wear of boron carbide ceramic nozzles by abrasive air-jets

    International Nuclear Information System (INIS)

    Deng Jianxin

    2005-01-01

    Boron carbide nozzles were produced by hot pressing. The erosion wear of this nozzle caused by abrasive particle impact was investigated by abrasive air-jets. Silica, silicon carbide and alumina powders with different hardness were used as the erodent abrasive particles. Results showed that the hardness of the erodent particles played an important role with respect to the erosion wear of the boron carbide nozzles. As the hardness of the erodent particles increases, there is a dramatic increase in erosion rate of the nozzles. The nozzle entrance area suffered from severe abrasive impact under large impact angles, and generated maximum tensile stresses. The wear mechanisms of boron carbide nozzle at this area appeared to be entirely brittle in nature with the evidence of large scale-chipping, and exhibited a brittle fracture induced removal process. While at the nozzle center wall section, most of the particles traveled parallel to the nozzle wall, and showed minimum tensile stresses. The wear mode in this area of the nozzle changed from impact to sliding erosion, and the wear mechanisms appeared to be the lateral cracking owing to a surface fatigue fracture mechanism

  8. Stability of MC Carbide Particles Size in Creep Resisting Steels

    Directory of Open Access Journals (Sweden)

    Vodopivec, F.

    2006-01-01

    Full Text Available Theoretical analysis of the dependence microstructure creep rate. Discussion on the effects of carbide particles size and their distribution on the base of accelerated creep tests on a steel X20CrMoV121 tempered at 800 °C. Analysis of the stability of carbide particles size in terms of free energy of formation of the compound. Explanation of the different effect of VC and NbC particles on accelerated creep rate.

  9. Criterion of titanium aviation alloy application

    International Nuclear Information System (INIS)

    Stasyunas, O.P.

    1976-01-01

    The most significant statistic mechanical characteristics are presented of titanium as compared with those of aluminium and steel. Based on these data one can draw conclusions as to the advantages and disadvantages of titanium. High chemical activity and diffusivity of titanium place limitations on the use of its alloys. Despite the promising features of a needle-like structure, specifications still keep relying on a globular structure, which is explained by the easeiness of the production. Titanium is expensive, sometimes its cost may by a factor of 20 exceed that of other aviation materials

  10. Advances in carbide fuel element development for fast reactor application

    International Nuclear Information System (INIS)

    Dienst, W.; Kleykamp, H.; Muehling, G.; Reiser, H.; Steiner, H.; Thuemmler, F.; Wedermeyer, H.; Weimar, P.

    1977-01-01

    The features of the carbide fuel development programme are reviewed and evaluated. Single pin and bundle irradiations are carried out under thermal, epithermal and fast flux conditions, the latter in the DFR and KNK-II reactors. Several fuel concepts in the region of representative SNR clad temperatures are compared by parameter and performance tests. A conservative concept is based on He-bonded 8 mm pins with (U,Pu)C pellets and a smear density of 75% TD, operating at 800 W/cm rod power and burnup to 70 MWd/kg. The preparation of mixed carbide fuels is carried out by carbothermic reduction of the oxides in different methods supported by equivalent carbon content, grain size and phase distribution analysis. The fuel for subassembly performance tests is produced in a pilot plant of 0,5 t/year capacity. Compatibility studies reveal that cladding carburization is the only chemical interaction with carbide fuels. This effect leads to a reduction in ductility of the stainless steel. Fission products apparently play no role in the compatibility behaviour. Comprehensive studies lead to reliable information on the chemical and thermodynamic state of the fuel under irradiation. The swelling of carbide fuels and the fission gas release are examined and analysed. Cladding plastic strain by fuel swelling occurs during steady-state operation because the irradiation creep is rather slow compared to oxide fuels. The cladding strain observed depends on the fuel porosity and the cladding strength. The development of carbide fuel pins is complemented by the application of comprehensive computer models. In addition to the steady-state tests power cycling and safety tests are under performance. Up to 1980 the results are summarized for the final design and specification. The development target of the present program is to fabricate several subassemblies for test operation in the SNR 300 by 1981

  11. Identification of stacking faults in silicon carbide by polarization-resolved second harmonic generation microscopy.

    Science.gov (United States)

    Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Polychroniadis, Efstathios K; Stanciu, George A

    2017-07-07

    Although silicon carbide is a highly promising crystalline material for a wide range of electronic devices, extended and point defects which perturb the lattice periodicity hold deep implications with respect to device reliability. There is thus a great need for developing new methods that can detect silicon carbide defects which are detrimental to device functionality. Our experiment demonstrates that polarization-resolved second harmonic generation microscopy can extend the efficiency of the "optical signature" concept as an all-optical rapid and non-destructive set of investigation methods for the differentiation between hexagonal and cubic stacking faults in silicon carbide. This technique can be used for fast and in situ characterization and optimization of growth conditions for epilayers of silicon carbide and similar materials.

  12. 21 CFR 73.575 - Titanium dioxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.575 Section 73.575 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Foods § 73.575 Titanium dioxide. (a) Identity. (1) The color additive titanium dioxide is synthetically prepared TiO2, free from admixture with other substances. (2) Color...

  13. 21 CFR 73.3126 - Titanium dioxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Titanium dioxide. 73.3126 Section 73.3126 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No. 13463-67-7), Color Index No. 77891, shall...

  14. Effect of magnetic field on the carbide precipitation during tempering of a molybdenum-containing steel

    International Nuclear Information System (INIS)

    Hou, T.P.; Li, Y.; Zhang, J.J.; Wu, K.M.

    2012-01-01

    The influence of a high magnetic field on the carbide precipitation during the tempering of an Fe–2.8C–3.0Mo(wt%) steel was investigated. As-quenched steels were tempered at 200 °C for various times with and without the presence of 12-T magnetic field. The applied field effectively promoted the precipitation of the relatively high-temperature monoclinic χ-Fe 5 C 2 carbide, compared to the usual ε-Fe 2 C and η-Fe 2 C carbides precipitated without magnetic field. It is believed that the effect of applying a magnetic field is due to the reduction in the Gibbs free energy of the relatively higher magnetization phase. The denser distributions of the metastable carbides are attributed to the increased nucleation rate due to additional transformation force. The dispersed precipitation strengthening compensated for the decrease of hardness due to the loss of supersaturation of carbon atoms in the matrix. - Highlights: ► Applied field promoted the precipitation of χ-Fe 5 C 2 carbide. ► Promotion of the transition carbide was attributed to its higher magnetization. ► Increase in hardness was counterbalanced by the reduction in carbon content.

  15. Effect of Ion Beam Irradiation on Silicon Carbide with Different Microstructures

    International Nuclear Information System (INIS)

    Park, Kyeong Hwan; Park, Ji Yeon; Kim, Weon Ju; Jung, Choong Hwan; Ryu, Woo Seog

    2006-01-01

    SiC and SiC/SiC composites are one of promising candidates for structural materials of the next generation energy systems such as the gas-cooled reactors and fusion reactors. This anticipation yields many material issues, and radiation effects of silicon carbide are recognized as an important research subject. Silicon carbide has diverse crystal structures (called polytypes), such as α-SiC (hexagonal structure), β-SiC (cubic structure) and amorphous SiC. Among these polytypes, β-SiC has been studied as matrix material in SiC/SiC composites. Near-stoichiometric β-SiC with high crystallinity and purity is considered as suitable material in the next generation energy system and matrix material in SiC/SiC composites because of its excellent radiation resistance. Highly pure and crystalline β-SiC and SiC/SiC composites could be obtained by the chemical vapor deposition (CVD) and Infiltration (CVI) process using a gas mixture of methyltrichlorosilane (CH 3 SiCl 3 , MTS) and purified H 2 . SiC produced by the CVD method has different grain size and microstructural morphology depended on the process conditions such as temperature, pressure and the input gas ratio. In this work, irradiation effects of silicon carbide were investigated using ion beam irradiation with emphasis on the influence of grain size and grain boundary. MeV ion irradiation at low temperature makes amorphous phase in silicon carbide. The microstructures and mechanical property changes of silicon carbide with different structures were analyzed after ion beam irradiation

  16. Preparation and microstructural characterization of TiC and Ti0.6W0.4/TiC0.6 composite thin films obtained by activated reactive evaporation

    International Nuclear Information System (INIS)

    Montes de Oca, J. A.; LePetitcorps, Y.; Manaud, J.-P.; Vargas Garcia, J. R.

    2008-01-01

    Titanium carbide-based coatings were deposited on W substrates at a high coating growth rate by activated reactive evaporation at 500 and 600 deg. C in a L560 Leybold system using propene as reactive atmosphere. The crystal structure, lattice parameter, preferred orientation, and grain size of the coatings were determined by x-ray diffraction technique using Cu Kα. The analysis of the coating morphology was performed by scanning electron microscopy (SEM), and the composition of the films was analyzed by Auger electron spectroscopy and electron-probe microanalysis. Experimental results suggested that temperature was one of the most important parameters in the fabrication of stoichiometric TiC coatings. Thus, TiC coatings were obtained at 600 deg. C, whereas TiC 0.6 nonstoichiometric coatings codeposited with a free Ti phase were obtained at 500 deg. C, giving rise to the formation of a composite thin film. After annealing at 1000 deg. C, the stoichiometric films remained stable, but a crack pattern was formed over the entire coating surface. In addition, Ti 0.6 W 0.4 /TiC 0.6 composite thin coatings were obtained for the films synthesized at 500 deg. C. The formation of a Ti 0.6 W 0.4 ductile phase in the presence of a TiC 0.6 phase was responsible to avoid the coating cracking

  17. Welding and Joining of Titanium Aluminides

    Science.gov (United States)

    Cao, Jian; Qi, Junlei; Song, Xiaoguo; Feng, Jicai

    2014-01-01

    Welding and joining of titanium aluminides is the key to making them more attractive in industrial fields. The purpose of this review is to provide a comprehensive overview of recent progress in welding and joining of titanium aluminides, as well as to introduce current research and application. The possible methods available for titanium aluminides involve brazing, diffusion bonding, fusion welding, friction welding and reactive joining. Of the numerous methods, solid-state diffusion bonding and vacuum brazing have been most heavily investigated for producing reliable joints. The current state of understanding and development of every welding and joining method for titanium aluminides is addressed respectively. The focus is on the fundamental understanding of microstructure characteristics and processing–microstructure–property relationships in the welding and joining of titanium aluminides to themselves and to other materials. PMID:28788113

  18. Pipe bend wear - is tungsten carbide the answer?

    International Nuclear Information System (INIS)

    Freinkel, D.

    1988-01-01

    The purpose of the investigation was to compare the relative wear resistance of various grades of sintered tungsten carbide liners against a mild steel standard in a full-scale pneumatic conveying testing rig. Speciments ranging in cobalt content from 6 to 30 per cent and in grain size from 0,56 to 2,98 microns, including a mild steel standard, were placed on a specially designed holder which fitted into a tee type 100 mm diameter bend. The specimens were tested under various operating conditions, ie air velocity ranging from 28m/s to 52m/s, impact angles of 30 0 to 70 0 mass flow rates of 35kg/min to 83kg/min and phase densities of 1,2 to 2,9, using a 4 mm nominal size crushed granite rock. The experimental results show that the ultrafine-grained, low cobalt (6 per cent) tungsten carbide displays little sensitivity to varying velocities, impact angles, mass flow rates or phase densities, and consistently gave the best wear resistance under all testing conditions. It consistently showed the least wear resistance under all testing conditions and performed only slightly better than mild steel. The effect of the carbide grain size was found to be small, although the finer grain sizes displayed greater wear resistance than the coarse grains. The effect of cobalt content was such that the lower cobalt specimens (6 per cent range) consistently performed better than the higher cobalt contents (10 per cent, 15 per cent, 30 per cent) under all testing conditions; the wear resistance decreasing with increasing cobalt content. An empirical model for the prediction of wear for each type of material tested has been proposed, given the particular operating conditions. Microstructurally it has been shown that there is a definite relationship between erosion resistance and the inverse of the magnetic coercivity of the tungsten carbide alloys

  19. Microstructure of reactive synthesis TiC/Cr18Ni8 stainless steel bonded carbides

    Institute of Scientific and Technical Information of China (English)

    Jiang Junsheng; Liu Junbo; Wang Limei

    2008-01-01

    TiC/Cr18Ni8 steel bonded carbides were synthesized by vacuum sintering with mixed powders of iron, ferrotitanium, ferrochromium, colloidal graphite and nickel as raw materials. The microstructure and microhardness of the steel bonded carbides were analyzed by scanning electron microscope (SEM),X-ray diffraction (XRD) and Rockwell hardometer. Results show that the phases of steel bonded carbides mainly consist of TiC and Fe-Cr-Ni solid solution. The synthesized TiC particles are fine. Most of them are not more than 1 μm With the increase of sintering temperature, the porosity of TiC/Cr18Ni8 steel bonded carbides decreases and the density and hardness increase, but the size of TiC panicles slightly increases. Under the same sintering conditions, the density and hardness of steel bonded carbides with C/Ti atomic ratio 0.9 are higher than those with C/Ti atomic ratio 1.0.The TiC particles with C/Ti atomic ratio 0.9 are much finer and more homogeneous.

  20. Gelcasting of SiC/Si for preparation of silicon nitride bonded silicon carbide

    International Nuclear Information System (INIS)

    Xie, Z.P.; Tsinghua University, Beijing,; Cheng, Y.B.; Lu, J.W.; Huang, Y.

    2000-01-01

    In the present paper, gelcasting of aqueous slurry with coarse silicon carbide(1mm) and fine silicon particles was investigated to fabricate silicon nitride bonded silicon carbide materials. Through the examination of influence of different polyelectrolytes on the Zeta potential and viscosity of silicon and silicon carbide suspensions, a stable SiC/Si suspension with 60 vol% solid loading could be prepared by using polyelectrolyte of D3005 and sodium alginate. Gelation of this suspension can complete in 10-30 min at 60-80 deg C after cast into mold. After demolded, the wet green body can be dried directly in furnace and the green strength will develop during drying. Complex shape parts with near net size were prepared by the process. Effects of the debindering process on nitridation and density of silicon nitride bonded silicon carbide were also examined. Copyright (2000) The Australian Ceramic Society