- Optimization and characterization of LPCVD TiB2 for ULSI applications
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The chemical vapor deposition of TiB2 from gaseous mixtures of TiCl4, B2H6, and H2 onto various substrates was studied. A thermodynamic analysis using the SOLGASMIX computer program indicated that at an input gas ratio corresponding to the stoichiometry of TiB2, the amount of secondary-phase deposition would be considerably reduced compared to that of TiB2. For nonstoichiometric input gas mixtures, other solid phases, including oxides and silicides, are expected to result from the reaction with substrates. Experimental depositions of films were carried out in a cold wall system over a broad range of temperatures, pressures, and input gas flow rates. X-ray diffraction and x-ray photoelectron spectroscopy data indicate that the as-deposited films are very fine grained polycrystalline or amorphous, and the films RTA-annealed above 900°C are crystalline TiB2. Below 550°C, surface reactions are the dominant factor for the kinetics of TiB2 deposition, while mass transport is a limiting step for deposition above 550°C. At higher temperatures the deposition rate increases linearly with flow rate and total pressure, suggesting the deposition mechanism is reactant limited. The B/Ti ratio determined via Auger electron spectroscopy approaches the stoichiometric value of two in higher temperature films, while the presence of excess boron and chlorine was detected for low-temperature films. Stoichiometric TiB2 films were deposited over a wide range of input gas mixture B/B + Ti ratios ranging from 0.4 to 0.71. Depletion effects of input gas were observed at low flow rate and high pressure where the residence time of reactants is longer than 10 s.
- Choi,Ruggles,Osburn,Xing
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- Effect of Ni content on the products of Ni-Ti-B system via self-propagating high-temperature synthesis reaction
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The effect of Ni content on the products of Ni-Ti-B system via self-propagating high-temperature synthesis (SHS) reaction has been investigated in this research. The results show that the products of SHS reactions consist mainly of TiB2 and Ni.
- Huang,Wang,Li,Yin,Jiang
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- Chemical and electrochemical behavior of titanium diboride in cryolite-alumina melt and in molten aluminum
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Titanium diboride is the most perspective material for protection of the cathode lining of aluminum electrolysis cells. One of the possible methods for obtaining a titanium diboride coating is an electrochemical synthesis from cryolite melt containing oxides of titanium and boron. In the present paper the behavior of oxides of titanium and boron in cryolite melt is considered. Coherent coating of titanium diboride has been deposited from the molten system Na3AlF6 - Al4B2O9 - CaTiO3. (C) 2000 Academic Press.
- Devyatkin,Kaptay
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- High critical current density of MgB2 bulk superconductor doped with Ti and sintered at ambient pressure
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Ti-doped MgB2 superconductors with different doping levels were prepared by solid-state reaction at ambient pressure. The density, diamagnetic signal, and Jc of the samples change significantly with the doping level, with the best result achieved at cursive chi = 0.1. At 5 K, the Jc reaches 2 × 106 A/cm2 in the self-field and 5 × 104 A/cm2 in 5 T. At 20 K, the Jc is still as high as 1.3 × 106 A/cm2 in the self-field and 9.4 × 104 A/cm2 in 2 T. It is observed that partial melting occurs in the Ti-doped samples, resulting in an excellent grain connection and extremely high density. In addition, some fine particles (with sizes from 10 to 100 nm) of the second phases induced by Ti doping are distributed in the MgB2 matrix, and this may play an important role in flux pinning enhancement.
- Zhao,Feng,Cheng,Zhou,Wu,Machi,Fudamoto,Koshizuka,Murakami
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- Preparation of TiB2 and ZrB2. Influence of a mechano-chemical treatment on the borothermic reduction of titania and zirconia
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TiB2 and ZrB2 have been synthesized by a mechano-chemical treatment of a mixture of titania or zirconia powder and amorphous boron followed by a relatively low temperature annealing (1100°C). Both the temperature and the kinetics of the borothermic transformations are affected by the mechano-chemical treatment when the size of the particles obtained after thermal annealing of the sample milled for a short time remains in the sub-micron range. The reaction paths are different for TiB2 and ZrB2 with the formation of TiBO3 and Ti2O3 as intermediate compounds in the case of the borothermic reduction of titania, while in the zirconia/boron system a direct borothermic reduction of zirconium oxide is observed.
- Millet,Hwang
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- Low-temperature densification of TiN-TiB2 composites through reactive hot pressing with excess Ti additions
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Reactive hot pressing of Ti and BN powder mixtures is used to produce dense TiNx-TiB2 composites. The effect of excess Ti along with a small addition, ~1 wt% Ni, on the reaction and densification of the composite was investigated. A
- Rangaraj, Lingappa,Divakar, Canchi,Jayaram, Vikram
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- Processing and properties of TiB2 with MoSi2 sinter-additive: A first report
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The densification of non-oxide ceramics like titanium boride (TiB 2) has always been a major challenge. The use of metallic binders to obtain a high density in liquid phase-sintered borides is investigated and reported. However, a non-metallic sintering additive needs to be used to obtain dense borides for high-temperature applications. This contribution, for the first time, reports the sintering, microstructure, and properties of TiB 2 materials densified using a MoSi2 sinter-additive. The densification experiments were carried out using a hot-pressing and pressureless sintering route. The binderless densification of monolithic TiB2 to 98% theoretical density with 2-5 μm grain size was achieved by hot pressing at 1800°C for 1 h in vacuum. The addition of 10-20 wt% MoSi2 enables us to achieve 97%-99%ρth in the composites at 1700°C under similar hot-pressing conditions. The densification mechanism is dominated by liquid-phase sintering in the presence of TiSi2. In the pressureless sintering route, a maximum of 90%ρth is achieved after sintering at 1900°C for 2 h in an (Ar+H2) atmosphere. The hot-pressed TiB2-10 wt% MoSi2 composites exhibit high Vickers hardness (~26-27 GPa) and modest indentation toughness (~4-5 MPa·m12).
- Murthy,Basu,Balasubramaniam,Suri,Subramanian,Fotedar
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- Determination of the thermodynamic stability of TiB2
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The standard free energy of formation of titanium boride (TiB2) was measured by the Electro Motive Force (EMF) method (by using yttria doped thoria (YDT) as the solid electrolyte). Two galvanic cells viz. Cell (I): Pt, TiB2 (s), TiO
- Jain, Ashish,Pankajavalli,Anthonysamy,Ananthasivan,Babu,Ganesan,Gupta
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- Effect of KCl, NaCl and CaCl2 mixture on volume combustion synthesis of TiB2 nanoparticles
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Preparation of titanium diboride (TiB2) nanoparticles was carried out by volume combustion synthesis. TiO2, B2O 3 and elemental Mg were mixed with 0-60% salt mixture of KCl, NaCl and CaCl2 with increment of 15% as a low melting temperature diluent. Compressed samples were synthesized in a tubular furnace at a constant heating rate under argon atmosphere. Thermal analysis of the process showed that the addition of the low melting temperature salts mixture led to a significant decrease in ignition and combustion temperatures. Synthesized samples were then leached by nitric and hydrochloric acids to remove impurities. The samples were examined by XRD, SEM and DLS analysis. The results showed the formation of fine deagglomerated particles with the addition of the salts mixture. The results revealed that 45% salts mixture had the smallest average particle size of about 90 nm.
- Nekahi, Atiye,Firoozi, Sadegh
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- Mechanochemical synthesis and pressureless sintering of TiB2-AlN composites
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TiB2-AlN composites have been fabricated by the pressureless sintering of a mechanochemically processed Ti, Al, and BN powder mixture. TiB2-AlN powder was obtained from the mixture of Ti, Al, and BN, which had a composition corresponding to 45.7 wt% TiB2-54.3 wt% AlN, after mechanochemical processing for longer than 24 h. X-ray diffraction and transmission electron microscopy analysis showed that the powder subjected to mechanochemical processing for 60 h consisted of crystallites less than 300 nm in size with a disordered crystal structure. TiB2-AlN composites with 95% relative density, a flexural strength of 172 MPa, a fracture toughness of 4.6 MPa·m1/2, a hardness of 12.0 GPa, and an electrical resistivity of 1488 μΩ·cm were obtained by pressureless sintering at 1700°C for 2 h of the powder subjected to mechanochemical processing for 60 h.
- Kim, Hyung-Jong,Choi, Heon-Jin,Lee, June-Gunn
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- Compositional and structural changes in TiB2 films induced by bias, in situ and post-deposition annealing, respectively
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Structural changes in TiB2 films were induced at relatively low temperatures by the application of bias and in situ annealing or by post-deposition heat treatment of samples subjected to bias with simultaneous in situ annealing. In situ annealing by itself evoked only partial crystallization. Application of bias by itself only modified the composition of the as deposited film. A simple model is presented to explain the variation of the composition when RF bias is applied to a cold substrate. The crystallized films had a (0 0 0 1) texture. A model has been suggested to explain the observed preferred orientation, based on the contribution of surface and strain energies. Both, the surface energy and strain energy are direction dependent. These were evaluated for two film orientations reported in the literature, namely, the (0 0 0 1) and ( 1 0 over(1, -) 1 )orientations. The preferred orientation of the film is determined by the lowest overall free energy resulting from the competition between the surface energy and the strain energy on different lattice planes. The surface energy is not film thickness dependent while the strain energy is thickness dependent and increases with it. For small film thickness, as in this work, the surface energy term is significant and (0 0 0 1) orientation with a minimum surface energy is preferred. At large film thicknesses the strain energy becomes dominant and the ( 1 0 over(1, -) 1 ) preferred orientation is observed. Under certain experimental conditions strain energy effects may tip the preferred orientation to ( 1 0 over(1, -) 1 ). The elastic moduli in the (0 0 0 1) and ( 1 0 over(1, -) 1 ) directions were determined as 435 and 538 GPa, respectively.
- Pelleg, Joshua,Sade,Sinder,Mogilyanski
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- Sn-flux syntheses, characterizations and bonding analyses of OsB and TiB2
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Single-phase crystalline powder of the technologically important TiB2 and powder of OsB have been successfully synthesized at moderate temperature (900 °C) using metallic tin as a melting agent. The structural relationship between both phases is discussed. COHP bonding analyses show strong B-B interactions in TiB2 but no such in OsB. The bonding situation in both phases is also compared with that of Ti1.6Os2.4B2 and Ti1.6Os1.4RuB2 phases. TiB2 and OsB are metallic conductors according to DOS curves.
- Fokwa, Boniface P.T.,Misse, Patrick R.N.,Gille?en, Michael,Dronskowski, Richard
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- Ball milling-induced combustion in powder mixtures containing titanium, zirconium, or hafnium
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Ball milling induces self propagating high temperature reactions in many highly exothermic powder mixtures. This phenomenon has been studied in a variety of reactions with titanium, zirconium, and hafnium. Several oxides (CuO, Cu2O, NiO, Fe3O4, and ZnO) were reduced with Ti, Zr, and Hf and the borides, carbides, silicides, and sulfides of these metals were prepared from elemental mixtures. The ignition time is much shorter with Zr than with either Ti or Hf whenever oxygen or sulfur is involved in the reaction, but no similar variation is observed for the formation of borides, carbides, and silicides. It is suggested that the fast diffusion of oxygen in ZrO2 and very likely of sulfur in ZrS2 are responsible for this behavior.
- Takacs
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- A convenient solid-state reaction route to nanocrystalline TiB2
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Nanocrystalline titanium diboride (TiB2) powders were successfully synthesized at 650°C by using TiCl4, Mg and MgB 2 as the reactants. Transmission electron microscopy images show that typical TiB2 crystallites are composed of uniform particles with the average grain size of about 40 nm.
- Shi, Liang,Gu, Yunle,Chen, Luyang,Yang, Zeheng,Ma, Jianhua,Qian, Yitai
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- Influence of stearic acid on mechanochemical reaction between Ti and BN powders
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The influence of stearic acid as a process control agent on the mechanochemical reaction between Ti and BN to form TiN/TiB2 nanocomposite powder by high energy ball milling has been investigated. A powder mixture of pure Ti and hexagonal BN powders with a molar ratio of 3:2 was milled for up to 40 h with up to 1.75 wt.% of stearic acid. The XRD analysis shows that an intimate mixture of TiN and TiB2 crystalline powders was formed during milling by a displacement reaction. It has been observed by monitoring the temperature of the vial surface during the milling process that the addition of over 1.5 wt.% of stearic acid changed the reaction mode from a mechanically induced self-propagating reaction (MSR) to a gradual reaction. It has also been found by XRD and TEM analyses that the MSR produces TiN and TiB2 particles initially of sub-micron size, which are reduced gradually by further milling. However, there still remain some coarse TiB2 particles larger than a few hundred nanometers even after 16-h milling due to their extremely high hardness. On the other hand, the gradual reaction induced by stearic acid successfully inhibits the formation of coarse TiB2 particles and eventually decreases the crystallite size of the products below 40 nm after 16 h of milling.
- Byun, Jung-Soo,Shim, Jae-Hyeok,Cho, Young Whan
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- Effects of TiC doping on the upper critical field of MgB2 superconductors
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TiC doped MgB2 bulks were fabricated by two-step reaction method. The sample with a nominal compositions of Mg(B0.95(TiC)0.05)4 was first sintered at 1000 °C for 0.5 h. An appropriate amount of Mg was added to reach the stoichiometry of Mg(B0.95(TiC)0.05)2, which was sintered at 750 °C for 2 h. The Hc2 for the micro-TiC doped MgB2 reached 12 T at 20 K. And Jc is 5.3 × 104 A/cm2 at 20 K and 1 T. The results indicate that the two-step reaction method could effectively introduce the carbon in TiC into the MgB2 crystalline lattice, and therefore improve the upper critical field.
- Yan,Zhou,Yan,Lu
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- Mechanism of the cathode process in the electrochemical synthesis of TiB2 in molten salts. I. The synthesis in an all-fluoride electrolyte
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The mechanism of the cathode process in the electrochemical synthesis of titanium diboride in molten LiF-KF supporting electrolyte containing potassium hexafluorotitanate and tetrafluoroborate as electrochemically active components has been determined by
- Makyta,Matiasovsky,Taranenko
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- Properties of titanium and zirconium diborides obtained by self-propagated high-temperature synthesis
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Self-propagated high-temperature synthesis (SHS) of TiB2 and ZrB2 is carried out in a steel reactor under Ar. The SHS is initiated by a current pulse of 60 A and 40 V. It is shown that the interparticle contacts play a significant role in the successful proceeding of the synthesis reactions. The products obtained have similar morphology. X-ray data show the presence of welt-crystallized phases of TiB2 and ZrB2. Chemical analyses indicate a high boron content in the products. The properties of TiB2 powders synthesized from the same initial titanium and boron reagents by both SHS and mechanochemical synthesis are compared.
- Radev,Marinov
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- In situ synthesis of ceramic composite materials in the Ti-B-C-N system by a mechanically induced self-sustaining reaction
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The synthesis of multicomponent ceramic materials in the titanium-diboride-carbide-nitride-carbonitride system by the mechanochemical process known as the mechanically induced self-sustaining reaction (MSR) was investigated. Ceramic composite powders containing TiB2and TiC, TiN or TiCxN1-xwere prepared from a blended mixture of the elements by exploiting the highly exothermic nature of the formation reactions. The synthesis of the composite materials was made possible by the ability of the MSR to simultaneously induce independent self-sustaining reactions, generating a mixture of ceramic phases. The composition of the ceramic composites was designed using the initial atomic ratio of the reactants, and the achieved microstructure was characterized by TiB2particles in the micrometric range, surrounded by submicrometric and nanometric TiC, TiN, or TiC xN1-xcrystals.
- Aviles, Miguel A.,Chicardi, Ernesto,Cordoba, Jose M.,Sayagues, Maria J.,Gotor, Francisco J.
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- Properties of TiB2 powders obtained in a mechanochemical way
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Mechanochemical synthesis of TiB2 powders was achieved in a planetary mill. The product obtained, whose physical and chemical properties were investigated, was a single-phase powder, possessing submicronic particle size. Microstrain of the lattice was registered by X-ray studies. The amount of combined boron was comparatively high. These properties were preconditioned for high activity of the substances obtained, especially during sintering. A mechanism for the synthesis is proposed.
- Radev,Klisurski
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- The effect of surface oxides during hot pressing of TiB2
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Hot pressing of TiB2 has been investigated with particular emphasis on the evolution of secondary phases originating from the initial surface oxide layer on the TiB2 powders. Carbothermal reduction of the surface oxides during sinter
- Jensen, Morten Sundheim,Einarsrud, Mari-Ann,Grande, Tor
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- Simultaneous spark plasma synthesis and densification of TiC-TiB 2 composites
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The simultaneous synthesis and densification of dense TiC-TiB2 composite has been investigated starting from Ti, B4C, and C as reactants, and using the spark plasma sintering (SPS) technique. The optimal conditions for complete conversion of the reactants to the composite were determined for different applied DC current levels. A kinetic investigation performed allows us to conclude that solid-state diffusion is the mechanism governing the synthesis process. It is seen that TiC is the first phase formed, while TiB2 formation occurs afterward. Two intermediate boride phases, i.e. TiB and Ti3B4, are also formed but, as the SPS holding time was augmented, they were gradually and completely converted to TiB2. Moreover, it is found that in order to reach relatively high dense products, an electric current needs to be applied for time intervals longer than those required for obtaining complete conversion. A pure dense product (relative density ~98%) was obtained when an electric pulsed current of 1100 A and a mechanical pressure of 20 MPa were applied for about 4 min.
- Locci, Antonio M.,Orru, Roberto,Cao, Giacomo,Munir, Zuhair A.
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- A reduction-boronation route to nanocrystalline titanium diboride
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Nanocrystalline titanium diboride (TiB2) has been prepared through a reduction-boronation route by using Ti powders and BBr3 as titanium and boron sources, and metallic sodium as reductant at 400 °C. X-ray powder diffraction (XRD) pattern can be indexed as hexagonal TiB 2 with the lattice constants of a=3.028 and c=3.223A?. Transmission electron microscopy images show particle morphology with average size of 15 nm. Selected area electron diffraction patterns confirm the preparation of the hexagonal TiB2.
- Chen, Luyang,Gu, Yunle,Shi, Liang,Yang, Zeheng,Ma, Jianhua,Qian, Yitai
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- In situ synthesis and properties of Ti3AlC2/TiB 2 composites
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In order to improve the mechanical properties of Ti3AlC 2, near-fully dense Ti3AlC2/TiB2 composites were synthesized using Ti, Al, graphite, and B4C powders as the initial materials. Compared with monolithic Ti3AlC 2, the composites exhibit a much higher strength (for the compressive strength, from initial 723 MPa to maximal 2205 MPa; for flexural strength, from initial 340 MPa to maximal 861 MPa), and the strengthening effect can be held at least up to 1100°C. Moreover, besides the enhancement of the elastic modulus and hardness of Ti3AlC2, the introduction of a TiB2 phase makes a positive contribution to its electrical conductivity.
- Li, Chao,Li, Meishuan,Zhou, Yanchun,Zhang, Jie,He, Lingfeng
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- Effect of Cu content on the reaction behaviors of self-propagating high-temperature synthesis in Cu-Ti-B4C system
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The SHS reaction behaviors of the Cu-Ti-B4C system with various Cu content were investigated. Theoretical calculation of the adiabatic temperatures reveals that the reaction in the Cu-Ti-B4C system is self-sustainable for the presence of 0-72.22 wt.% Cu in the reactants without any preheat. With the increase of Cu content, the adiabatic temperatures, combustion temperatures and wave velocity decrease greatly, while the ignition time shows first a remarkable decrease and then an increase with the minimum value at 20 wt.% Cu. Moreover, with the increase of Cu content, the sizes of the TiC and TiB2 grains decrease considerably.
- Liang,Wang,Yang,Zhao,Jiang
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- Morphology and deposition rates of TiB2 prepared by chemical vapour deposition of TiCl4 + B2H6 system
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Titanium diboride (TiB2) is a promising new material in applications to cutting tools, letdown valves for coal conversion reactors and the cathodes of aluminium smelting cells due to its superior wear and corrosion resistance. TiB2 i
- Mukaida,Goto,Hirai
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- A facile one-step route to nanocrystalline TiB2 powders
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Nanocrystalline titanium diboride (TiB2) has been prepared by the reaction of TiCl4 with NaBH4 in the temperature range of 500-700°C in an autoclave. X-ray powder diffraction (XRD) patterns can be indexed as hexagonal TiB2 with the lattice constants of a=3.032 and c=3.229A?. Transmission electron microscopy (TEM) image shows particle morphology, with average size of 15nm for the powder obtained at 600°C. Selected area electron diffraction (SAED) pattern confirms the prepared hexagonal TiB2. The oxidation behavior of TiB2 is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA).
- Chen, Luyang,Gu, Yunle,Qian, Yitai,Shi, Liang,Yang, Zeheng,Ma, Jianhua
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- PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION OF TITANIUM DIBORIDE FILMS.
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Thin films of titanium borides were deposited at temperatures from 480 to 650 degree C using a glow discharge and feed gases of TiCl//4, BCl//3, and H//2. High quality films have been obtained that are smooth, shiny, and crack-free; they have as-deposited
- Williams
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- Structure of TiB2 produced by dynamic ion mixing
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The technique of dynamic ion mixing is based on the use of a high energy ion beam to homogenize at the atomic scale and to improve the adherence of a growing film on any substrate. TiB2 films of stoichiometric composition were produced either by co-evaporation or by dynamic ion mixing using 100 keV Ar+ ions. The characterization of the films was performed by transmission electron spectroscopy (TEM). The ion mixing of the growing film has a crucial importance with regard to the resulting microstructural state. Amorphous TiB2 films are produced by conventional co-evaporation although crystalline TiB2 films of hexagonal structure are produced by dynamic ion mixing. The TiB2 amorphous phase appears to be very stable since crystallization starts only at about 1170 K, and complete transformation into the hexagonal crystalline structure is obtained at 1280 K. Relatively thick TiB2 coatings have been prepared with e=1 μm and studied by TEM on cross-sectional preparations. The microhardness of crystalline TiB2 films is about 2800 kgf mm-2 and is in good agreement with the value reported for bulk TiB2.
- Riviere,Guesdon,Delafond,Denanot
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- Synthesis of nano-sized titanium diboride in a melt of anhydrous sodium tetraborate
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X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, and elemental analysis were used to study the interaction of titanium powder with finely powdered boron of particle size 10-20 μm in Na2B4O7 ionic melt, in the temperature range 973-1088 K, at the 5-10 h contact duration. The TiB2 formation was shown to occur at the temperatures 1018 K or above, that is, at the borax melting temperature. According to the scanning electron microscopy, theTiB 2 powder consists of the 70-75 nm particles, and its coherent scattering region calculated from the XRD data amounts to 55 nm.
- Volkova,Shulga,Shilkin
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- Electrochemical deposition of TiB2 in high temperature molten salts
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The electrochemical deposition of TiB2 out of a NaCl-KCl-NaF-KBF4-K2TiF6 electrolyte at 600 °C was tested on steel and molybdenum substrates using various current programs. The characterisation of the deposited layers has been carried out by X-ray diffraction methods, scanning electron microscopy and microhardness measurements. The pulse sequences and the current densities used influence in a significant way the homogeneity of the layers deposited, the crystal size, the texture and other physical properties like electrical and thermal conductivity. The microhardness range was up to 2900 HV, smooth and dense layers were prepared at a pulse frequency of 100 Hz.
- Fastner,Steck,Pascual,Fafilek,Nauer
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- Effect of titanium carbide addition on the thermoelectric properties of B4C ceramics
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TiB2/B4C composite ceramics are prepared via hot pressing, in which the TiB2 particles are formed by introducing TiC0.78 and through the reaction between B4C and TiC0.78. The electrical and thermal conductivities and Seebeck coefficient of samples containing 0, 12.5 and 25.4 vol% TiB2 are measured from room temperature up to 1200 K. The results show that the transport properties of the samples vary with the TiB2 content. The transport properties of a 12.5 vol% TiB2/B4C sample are dominated by the B4C matrix as in undoped B4C ceramics, whilst the transport properties of a 25.4 vol% TiB2/B4C sample are dominated by TiB2 particles. The figure of merit of the 25.4 vol% TiB2/B4C sample is higher than that of the undoped B4C ceramic sample between room temperature and about 700 K, which indicates that it is possible to improve the thermoelectric properties by selecting an optimum combination of different materials.
- Cai,Nan,Paderno,McLachlan
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- Preparation of titanium diboride nanopowder
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We have studied the reaction between NaBH4 and TiCl4 at elevated temperatures in the range 570-1020 K and pressures of up to 10 MPa, with no solvent. The results indicate that nanoparticulate tita- nium diboride forms at temperatures
- Kravchenko,Torbov,Shilkin
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- Reactive hot pressing of titanium nitride-titanium diboride composites at moderate pressures and temperatures
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Dense composites in the Ti-B-N system have been produced by reactive hot pressing of titanium and BN powders. The effect of the addition of a small amount of nickel (1-3 wt%) on the reaction kinetics and densification of TiN-TiB2 (40 vol%) composite has been studied. Composites of ~99% of theoretical density have been produced at 1600°C under 40 MPa for 30 min with 1% nickel. The hardness and fracture toughness of these composites are 24.5 ± 0.97 GPa and 6.53 ± 0.27 MPa·m1/2, respectively. The microstructural studies on samples produced at lower temperatures indicate the formation of a transient liquid phase, which enhances the kinetics of the reaction and densification of the composite.
- Rangaraj, Lingappa,Divakar, Canchi,Jayaram, Vikram
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- Preparation of TiB2 sintered compacts by hot pressing
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A sintered compact of titanium diboride (TiB2) was prepared by hot pressing of synthesized TiB2 powder which was obtained by a solid-state reaction between TiN and amorphous boron. Densification occurred at 20 MPa and 1800°C for 5 to
- Itoh, Hideaki,Naka, Shigeharu,Matsudaira, Tsuneaki,Hamamoto, Hiroshi
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- Electrochemical synthesis of TIB2 layers out of FLiNaK electrolyte in the presence of TaCl5 additive
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TiB2 coatings on Mo substrates were electrodeposited out of a FLiNaK electrolyte in the presence of TaCl5 additive. The results show that a low concentration of TaCl5 in the melt changes significantly the chemical composition and consequently, the properties of the coatings. The energy-dispersive X-ray analysis indicates up to 10 atom % Ta in the TiB2 coatings. X-ray phase analysis demonstrates the changes in the texture of TiB2 in the 〈 001 〉 direction. Codeposition of TaB2 in a TiB2 layer decreases the grain size and improves the smoothness of the layer. Addition of TaCl5 in the electrolyte permits to obtain TiB2 - TaB2 layers of high quality and makes the process reproducible. In addition, the individual electrochemical behavior of the starting compounds, K2 TiF 6, KBF4, and TaCl5, as well as their mixtures was investigated in the FLiNaK electrolyte by means of cyclic voltammetry.
- Rybakova,Babushkina,Artner,Nauer
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- Low temperature electrical resistivity studies and search for superconductivity in Ti-B system
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Resistivity of TiBx alloy has been measured for three different compositions. The alloys contain the three known phases TiB2, TiB and Ti3B4 and unknown phase/phases. Resistivity measurements between room temperature and 77 K show that there is no superconducting transition in this range of temperature contrary to some recent reports. Resistivity shows a small anomaly at low temperature which is attributed to the unknown phase.
- Kutty,Pillai,Karunakaran,Vaidya
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- Effect of HCl concentration on TiB2 separation from a self-propagating high-temperature synthesis (SHS) product
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This paper presents a synthesis of TiB2 powder via self-propagating high-temperature synthesis (SHS) method using a mixture of TiO2, B2O3 and Mg followed by acid leaching. In the acid leaching step, the MgO content in the SHS product was leached in different HCl concentrations. X-ray diffraction (XRD) analysis showed that when 9.3 M HCl was used, the leached SHS product was found similar to that of the commercial TiB2 powder. However, scanning electron microscopy (SEM) and BET surface area analysis revealed that the leached product was agglomerated and exhibited very high surface area.
- Demircan, Umut,Derin, Bora,Yücel, Onuralp
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- Formation of titanium nitride by mechanical milling and isothermal annealing of titanium and boron nitride
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The formation of titanium nitride with rock salt structure (δ-TiNx) was studied by mechanical milling of a mixture of Ti and hexagonal boron nitride (h-BN) powders and isothermal annealing of the mixture after milling for 70 h under argon atmosphere. The mole ratio of Ti to h-BN is 22:78. In the milling process, an amorphous Ti-N alloy was formed firstly by a diffusion reaction between Ti and BN, and then the amorphous Ti-N alloy transformed into δ-TiNx driven by mechanical milling. However, in the annealing process, a Ti(N) solid solution was formed firstly by incorporation of N into Ti, and the N content in the Ti(N) increased with increasing annealing temperature. When the N content exceeded the solubility limit of the Ti(N) at some annealing temperature, the Ti(N) decomposed into δ-TiNx and Ti(N) with the solubility limit. No self-sustaining reaction occurs in the present work. No TiB2 is observed to form in the two processes. The thermodynamic and kinetic mechanisms of formation of the δ-TiNx are discussed.
- Ding,Yao,Qiu,Bai,Guo,Xue,Wang,Zhou,Su
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- Acid leaching of SHS produced magnesium Oxide/titanium diboride
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The stoichiometric self-propagating high-temperature synthesis (SHS) thermite reaction involving magnesium (Mg), titanium dioxide (TiO2), and boron oxide (B2O3) forms MgO and titanium diboride (TiB2) as final pr
- Lok, Jonathan Y.,Logan, Kathryn V.,Payyapilly, Jairaj J.
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- Consolidation of combustion-synthesized titanium diboride-based materials
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The quasi-static consolidation in uniaxial compression of combustion-synthesized TiB2-based materials was investigated. Consolidation was carried out in insulated containers upon completion of the combustion reaction, while the porous reaction products were ductile. Since the consolidation is not an isothermal process, the temperature change during consolidation was monitored and recorded. The effect of the addition of metallic elements to the elemental powders was established, and it was found that nickel and chromium provide the best compact integrity. The partial densification is sufficient to show significant differences between the effects of metallic additives. A phenomenological (not based on the micromechanisms of densification) constitutive model was applied to the hot and porous reaction products incorporating the temperature dependence of flow stress. The activation energy for the temperature dependence of the flow stress is established and indicates that, in addition to diffusion-induced plastic deformation, other processes occur, such as fracturing of ligaments.
- Hoke,Meyers
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- Synthesis of ultrafine titanium diboride particles by rapid carbothermal reduction in a particulate transport reactor
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Ultrafine TiB2 powders were synthesized by rapid carbothermal reduction in a vertical tubular reactor through which the particles fell freely. The starting materials were TiO2, H3BO3 and cornstarch, which were mixed and calcined at 400°C for 1 h. The calcined precursor was milled, sieved and then fed into the top of the reactor. The reduction was carried out between 1786-1791°C in a downward flow of argon. Product particles were recovered at the bottom of the reactor. When the precursor molar composition ratio was TiO2:B2O3:C = 1:2:5.5, the carbon content in the product was 5 wt % and the crystallite size was 80 nm. The carbon content in the product was reduced to 2.9 wt % by a heat treatment in an H2 atmosphere for 9 h.
- Saito, Takeyasu,Fukuda, Tomoyuki,Maeda, Hideaki,Kusakabe, Katsuki,Morooka, Shigeharu
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- Synthesis of TiB2 by electric discharge assisted mechanical milling
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In this study, synthesis of titanium diboride from elemental powders of Ti and B by electric discharge assisted mechanical milling technique was investigated. This recently developed technique has the following advantages: rapid reaction rate, controlled
- Calka,Oleszak
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- Reaction control of TiB2 formation from titanium metal and amorphous boron
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TiB2 powder was synthesized by a controlled formation reaction from titanium metal and amorphous boron. Precursory TiB2 formed by the pretreatment of the mixed powder (mole ratio: B/Ti = 2.0) at 600°C for 60 min in an argon stream. H
- Itoh,Matsudaira,Naka,Hamamoto
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- A mild solvothermal route to nanocrystalline titanium diboride
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Titanium diboride (TiB2) has been synthesized via a benzene-thermal reaction of metallic sodium with amorphous boron powder and titanium tetrachloride at 400°C in an autoclave; the temperature was much lower than that of traditional methods. The X-ray diffraction (XRD) pattern can be indexed with the hexagonal cell of TiB2 and the lattice constants a = 3.027 and c = 3.228 A?. X-ray photoelectron spectroscopy (XPS) results show the mole ratio of Ti:B as 1:1.766. Transmission electron microscope (TEM) images indicate that the average particle size is in the range of 15-40 nm in diameter.
- Gu, Yunle,Qian, Yitai,Chen, Luyang,Zhou, Fu
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- Homogeneous TiB2 ceramics achieved by electric current-assisted self-propagating reaction sintering
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Using spark plasma sintering techniques, homogeneous microstructures of titanium diboride (TiB2) ceramics were obtained by sintering of boron and titanium powder mixtures. The results show that an additional electric current is essential for achieving a large number of evenly distributed ignition points that ensure that the self-propagating reaction simultaneously takes place within the entire volume. The effects of the electric current, the use of Mg additions, and the heating rates on the resulting TiB2 ceramic densities and microstructures are discussed.
- Salamon, David,Eriksson, Mirva,Nygren, Mats,Shen, Zhijian
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- New criteria for the applicability of combustion synthesis: The investigation of thermodynamic and kinetic processes for binary Chemical Reactions
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Combustion synthesis is a novel technique that utilizes the exothermic heat of a chemical reaction to maintain the reaction and to rapidly prepare materials. But, hitherto, none of unified criterion for the validation of combustion synthesis has been proposed. Herein, we proposed the conditions need to be met. In terms of kinetics, at the adiabatic temperature (Tad), the diffusion distance of atoms (lTad) within 0.1 s should be larger than the particle size of the reactants(d), that is, lTad≥d. For systems that satisfy Tad/Tm,L≥1(where Tm,L is the melting point of the low-melting point component of the reactants), the presence of a liquid phase significantly increases the atomic diffusion distance from nanometers to tens of microns, making the criterion lTad≥d simplified to Tad/Tm,L≥1 in most situations. In terms of thermodynamics, the system needs to ensure that the reaction components are in an activated state, that is, Tad/Tm,H ≥0.7, where Tm,H is the melting point of the high-melting point component. The criteria for the SHS reactions proposed in this study further improve the theoretical understanding of SHS reactions, and provide guidance for exploring the ultra-fast synthesis of binary and multicomponent compounds.
- Tan, Xiaoming,Su, Xianli,Yan, Yonggao,Uher, Ctirad,Zhang, Qingjie,Tang, Xinfeng
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supporting information
(2021/01/07)
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- Novel sustainable silicothermic synthesis of phase-pure TiB2 fine powder
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Phase pure TiB2 powder of 100–400 nm was synthesized at 1100 °C via a novel sustainable silicothermic reduction technique using TiO2, Na2B4O7 and Si powders as starting materials. By introducing sodium salts as source of Na2O into the reactant mixture, the original water-insoluble byproduct SiO2, which is hard eliminated from resultant product in the conventional silicothermic reduction process, was transformed into water-soluble Na2Si2O5, making it much easy to remove it from the reacted mass via simple hot water washing. Consequently, a ‘‘post reduction’’ leaching process with a strong acid, generally required by the conventional metallothermic processes, was successfully avoided, and the relevant environmental concerns could be alleviated. Moreover, the aqua Na2Si2O5 could be readily recycled and used as a precursor for preparing many other types of valuable materials. Evaporation loss of silicon in the reduction process was dominated by SiO (g) resultant from the interactions between Si, SiO2 and Na2Si2O5 at test temperatures. By using 5 wt% excessive Si, TiO2 and Na2B4O7 were completely converted into TiB2 at 1100 °C.
- Ke, Changming,Ni, Yue'e,Qin, Zhi,Wang, Jingran,Zhang, Jinhua
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- Sequence of phase evolution during mechanically induced self-propagating reaction synthesis of TiB and TiB2via magnetically controlled ball milling of titanium and boron powders
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Mechanically induced self-propagating reaction synthesis of titanium boride and diboride was investigated for elemental mixtures of titanium and amorphous boron in starting atomic ratios of Ti50B50and Ti34B66. Samples were milled for different periods leading up to and after an ignition point which was determined by in-situ monitoring of the mill temperature. Methods of X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy were used to determine product evolution. For both compositions, a partial crystallisation of amorphous boron commences during the early stages of milling and progresses through to the ignition point. At later stages and prior to ignition, HRTEM combined with electron diffraction revealed the formation of nanocrystalline titanium diboride, which was confirmed by Raman spectroscopy to be of an off-stoichiometric, boron-lean composition; TiB2-x.This phase is believed to have formed by solid-state reaction at the interface of the heavily deformed Ti and amorphous B via a mechanism which parallels the formation of nanocrystalline off-stoichiometric Ti1+xC1-xprior to the self-propagating synthesis of TiC from Ti and graphite. After ignition, the product for Ti34B66comprised relatively large facetted grains of TiB2, liquid phase sintered by thin regions of unreacted Ti which had melted due to high heat of reaction. In contrast, the product of Ti50B50comprised platelike TiB particles, and spheroidal dispersions of TiB2in unreacted Ti and B. Likely mechanisms for the different product evolution routes for the two compositions are proposed and discussed.
- Oghenevweta,Wexler,Calka
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p. 380 - 391
(2017/02/05)
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- Densification, characterization and oxidation studies of novel TiB2+EuB6compounds
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TiB2+EuB6ceramic samples with different EuB6contents were fabricated using hot -pressing technique. The introduction of EuB6promoted the sinterability, fracture toughness and oxidation resistance of TiB2. 98.7% TD achieved by adding 2.5% EuB6to TiB2by hot pressing at a relatively low temperature of 1750?°C, 35?MPa, 1h. Formation of complete solid solution of TiB2+EuB6observed for all the samples by XRD, EDS and EBSD. Hardness of all samples is measured in the range of 24–27?GPa ~50% higher fracture toughness value of 5.2?MPa?m1/2was obtained in the 2.5% EuB6contained sample compared to monolithic TiB2. Enhancement of oxidation resistance of TiB2was observed by EuB6addition due to the formation of EuBO3and Eu2O3. Oxidized cross section of TiB2+EuB6sample was measured as 340?μm, which is ~35% less than that of monolithic TiB2(520?μm), after oxidation at 1400?°C for 8h.
- Murthy, T.S.R.Ch.,Sonber,Vishwanadh,Nagaraj,Sairam,Bedse,Chakravartty
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- Influence of friction stir processing on microstructure and properties of AA7075/TiB2 in situ composite
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Friction stir processing (FSP) is a novel solid state method to homogenize the distribution of particles in aluminum matrix composites (AMCs). AA7075/TiB2 AMCs were prepared by the in situ reaction of inorganic salts K2TiF6 and KBF4 with molten aluminum. The microstructure, before and after FSP, was studied using optical and scanning electron microscopy. TiB2 particles were segregated and clustered at the grain boundaries. The fabricated composite was subjected to single pass FSP using a friction stir welding machine. FSP changed the distribution of TiB2 particles to be intragranular. TiB2 particles fragmented during FSP and were rounded due to the abrading action of the rotating tool. FSP significantly enhanced the mechanical and wear properties of the composite. The details of fracture morphology, worn surface and wear debris are also presented in this paper.
- Rajan, H.B. Michael,Dinaharan,Ramabalan,Akinlabi
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p. 250 - 260
(2015/11/09)
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- Low-temperature synthesis of nanosized metal borides through reaction of lithium borohydride with metal hydroxides or oxides
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In this study, we report a novel and facile synthesis approach of boron-rich transition metal borides such as LaB6 and TiB2 through reaction of lithium borohydride (LiBH4) with corresponding metal hydroxide or oxide at temperatures below 600 °C. A fast endothermic reaction occurred at around 350 °C in the ball milled mixture of 6LiBH4 + La(OH)3 or 12LiBH4 + La2O3, efficiently producing crystalline LaB6 nanoparticles of a size smaller than 100 nm. In comparison, the reaction of LiBH4 with TiO2 proceeded within a wide temperature range from 120 °C to 500 °C, resulting in the formation of nanocrystalline TiB2 of only a few nanometers. This synthesis method proved to be a facile and general route to fabricate nanosized transition metal borides.
- Pan, Wei Yuan,Bao, Qian Wen,Mao, Yang Jun,Liu, Bin Hong,Li, Zhou Peng
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p. 666 - 672
(2015/09/07)
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- Microstructure characterization and mechanical properties of (TiC-TiB2)-Ni/TiAl/Ti functionally gradient materials prepared by FAPAS
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The composite ceramics TiC-TiB2 with Ni as the binder were successfully fabricated and bonded with Ti using TiAl as the transitional layer. (TiC-TiB2)-Ni composite ceramics were prepared in-situ through the combustion synthesis process using titanium, nickel and B4C powders as raw materials. Interfacial investigations of (TiC-TiB2)-Ni/TiAl and TiAl/Ti showed that the three layers were bonded together very well. The TiC and TiB2 particles of the synthesized composite ceramics were fine and homogeneously dispersed in the matrix. The shear strength increased as the applied current and pressure increased, with the maximum shear strength of the joint reaching 85.78 MPa. The fracture morphology investigated by SEM indicated that the fracture occurred in the (TiC-TiB2)-Ni/TiAl interface. The friction coefficient and the loss rate of the ceramic (TiC-TiB2)-Ni decreased as the testing temperature increased. The lubrication films of Fe2O3, TiO2, and B2O3 formed at an elevated temperature resulted in a smaller mass loss and friction coefficient.
- Hu, Lifang,Chen, Daming,Meng, Qingsen,Zhang, Hua
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p. 298 - 303
(2015/03/30)
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- High catalytic efficiency of amorphous TiB2 and NbB2 nanoparticles for hydrogen storage using the 2LiBH4-MgH2 system
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LiBH4-MgH2 system in a 2:1 molar ratio constitutes a representative reactive hydride composite (RHC) for hydrogen storage. However, sluggish kinetics and poor reversibility hinder the practical applications. To ease these problems, amorphous TiB2 and NbB2 nanoparticles were synthesized and employed as catalysts for the 2LiBH4-MgH 2 system. Isothermal de-/rehydrogenation and temperature programmed mass spectrometry (MS) measurements show that amorphous TiB2 and NbB2 nanoparticles can significantly improve the hydrogen storage performance of the 2LiBH4-MgH2 system. 9 wt% hydrogen can be released within only 6 min for nanoTiB2-doped 2LiBH 4-MgH2, while for the undoped composite limited hydrogen of 3.9 wt% is released in 300 min at 400 °C. The dehydrogenation activation energies for the first and second steps are dramatically reduced by 40.4 kJ mol-1 and 35.2 kJ mol-1 after doping with nanoTiB 2. It is believed that TiB2 and NbB2 nanoparticles can first catalyze the dehydrogenation of MgH2, and then induce the decomposition of LiBH4 and meanwhile act as nucleation agents for MgB2, thereby greatly enhancing the kinetics of dehydrogenation. The present study gives clear evidence for the significant performance of transition metal boride species in doped RHCs, which is critically important for understanding the mechanism and further improving the hydrogen storage properties of RHCs.
- Fan, Xiulin,Xiao, Xuezhang,Chen, Lixin,Wang, Xinhua,Li, Shouquan,Ge, Hongwei,Wang, Qidong
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p. 11368 - 11375
(2013/09/23)
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- The unexpected formation of MB2 layers (M = refractory metal) on metal surfaces
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The reactions between refractory metals (Ti, Zr, V, Nb, Ta, Mo, W) and BCl3 vapour at high temperatures have been studied. For this purpose, the metal wires were heated up by an electrical current in a BCl3 atmosphere for a couple of hours. Optical and X-ray diffraction methods were used to analyze the solid products, whereas mass spectrometry was used to study the gas phase composition. In the reactions with Ti, Zr, V, Nb and Ta, we observed the formation of MB2 layers on the metal surfaces. Molybdenum reacted with formation of MoB, with tungsten no reaction was observed at all. This is contrary to the thermodynamic expectations. The mechanism of the coating process is discussed from a thermodynamic viewpoint. In the course of reactions between refractory metals (Ti, Zr, V, Nb, Ta) with boron(III) chloride at temperatures of about 1500 K, layers of the diborides of these metals are formed. The coexistence of the refractory metal with its diboride is impossible from a thermodynamic viewpoint. The formation of metal diborides in the presence of the metal is discussed. Copyright
- Friedhoff, Wibke,Milke, Edgar,Binnewies, Michael
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p. 3398 - 3402
(2011/11/30)
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- Effect of Zn doping on improving crystal quality and thermoelectric properties of borosilicides
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Transition-metal (Mo, Mn, Fe, Rh, Ti, Cu, Zn) doping was carried out on the borosilicide compound REB44Si2 (RE = rare earth). REB44Si2 compounds exhibit Seebeck coefficients greater than 200 V K-1 at high temperatures and unlike most compounds, the figure of merit shows a steep increase at T > 1000 K making them promising high-temperature thermoelectric materials. Although zinc itself does not remain in the final product, zinc doping was found to improve the crystal quality, which has been a long-standing problem for the borosilicides. As a result, a significant increase of the thermoelectric power factor by more than 30% was achieved.
- Mori, Takao,Berthebaud, David,Nishimura, Toshiyuki,Nomura, Akiko,Shishido, Toetsu,Nakajima, Kazuo
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p. 1027 - 1030
(2010/04/01)
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- Interaction between BNc and titanium in vacuum
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The thermal stability of cubic boron nitride in vacuum at temperatures up to 1470 K in contact with titanium is studied by means of the differential thermal, X-ray phase, and chemical analyses. It is found that, in the system Ti-BNc, the reverse phase transition of boron nitride from the cubic to hexagonal structure, followed by formation of titanium borides and nitrides, is observed.
- Korzun,Ignatenko,Lebedev
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p. 626 - 630
(2011/03/21)
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- Electronic structure and magnetic properties of transition metal diborides
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The temperature dependencies of the magnetic susceptibility χ and its anisotropy Δ χ = χ{norm of matrix} - χ⊥ were measured for the hexagonal single crystalline TB2 compounds (T = Sc, Ti, Zr, Hf, V and Cr) in the temperatu
- Grechnev,Fedorchenko,Logosha,Panfilov,Svechkarev,Filippov,Lyashchenko,Evdokimova
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- Formation of TiB2 by volume combustion and mechanochemical process
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Titanium diboride was produced both by volume combustion synthesis (VCS) and by mechanochemical synthesis (MCP) through the reaction of TiO2, B2O3 and Mg. VCS products, expected to be composed of TiB2 and MgO, were found to contain also side products such as Mg2TiO4, Mg3B2O6, MgB2 and TiN. HCl leaching was applied to the reaction products with the objective of removing MgO and the side products. Formation of TiN could be prevented by conducting the VCS under an argon atmosphere. Mg2TiO4 did not form when 40% excess Mg was used. Wet ball milling of the products before leaching was found to be effective in removal of Mg3B2O6 during leaching in 1 M HCl. When stoichiometric starting mixtures were used, all of the side products could be removed after wet ball milling in ethanol and leaching in 5 M HCl when pure TiB2 was obtained with a molar yield of 30%. Pure TiB2 could also be obtained at a molar yield of 45.6% by hot leaching of VCS products at 75 °C in 5 M HCl, omitting the wet ball milling step. By MCP, products containing only TiB2 and MgO were obtained after 15 h of ball milling. Leaching in 0.5 M HCl for 3 min was found to be sufficient for elimination of MgO. Molar yield of TiB2 was 89.6%, much higher than that of VCS. According to scanning electron microscope analyses, the TiB2 produced had average grain size of 0.27 ± 0.08 μm.
- Bilgi, Eda,?amurlu, H. Erdem,Akgün, Bari?,Topkaya, Yavuz,Sevin?, Naci
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p. 873 - 881
(2008/10/09)
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- Advances in manufacturing boron carbide-aluminum composites
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An infiltration method for preparing a boron carbide-aluminum (B4C-Al) composite was modified so as to reduce the processing temperature and time. Titanium metal and titanium-based compounds were added to B4C powders to enhance the wettability of the liquid aluminum on boron carbide skeletons. As expected, the time required for infiltration was significantly reduced on using the additives. Of these additives titanium metal was the most effective in facilitating aluminum infiltration. Another method, involving the heat treatment of boron carbide compacts at 1300°C for 1 h before infiltration, was attempted, and a significant improvement was gained. These findings show that the treatment modified the surface condition of boron carbide powders via the removal of oxides. An additional attempt was made to increase the boron carbide content of the system by using a bimodal powder mixture. A maximum green density of 78% was achieved by mixing fine particle size and coarse particle size powders. The infiltrated boron carbide composites prepared using a bimodal powder with a preinfiltration heat treatment of the compacts exhibited promising mechanical properties, such as a Vickers hardness (Hv) of 11 Gpa and an indentation toughness (KIC) in the range of 5-7.5 MPa·m1/2.
- Jung, Jinkwan,Kang, Shinhoo
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- Simultaneous synthesis and densification of titanium nitride/titanium titanium diboride composites by high nitrogen pressure combustion
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Composites of TiN/TiB2 were synthesized by a combustion process of BN, Ti in a nitrogen atmosphere. The effect of the BN/Ti ratio and the nitrogen gas pressure on the synthesis of these composites was investigated. Dense TiN/TiB2 composites with relatively high hardness and toughness were fabricated by combustion synthesis from Ti and BN under a nitrogen pressure of 4.0 MPa. The Vickers microhardness of the products obtained from reactants with a BN/Ti mole ratio of 0.11 increased with an increase in nitrogen pressure and had a maximum value of ~25 GPa. Fracture toughness, KIC, of the products increased from 3.1 to 5.9 MPa·m1/2 as the BN/Ti ratio increased from 0.11 to 0.20. However, products formed under nitrogen pressures higher than 6.0 MPa exhibited circumferential macrocracks due to thermal shock.
- Shibuya, Masachika,Ohyanagi, Manshi,Munir, Zuhir A.
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p. 2965 - 2970
(2008/10/08)
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- Reactivity of MgB2 with common substrate and electronic materials
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The reactivity of MgB2 with powdered forms of common substrate and electronic materials is reported. Reaction temperatures between 600 and 800°C, encompassing the range commonly employed in thin-film fabrication, were studied. The materials tes
- He,Cava,Rowell, John M.
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p. 291 - 293
(2008/10/08)
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- Formation of nanometric TiB2 from TiO2
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Titanium diboride can be produced by ball-milling a mixture of TiO2, B2O3, and Mg metal for between 10 and 15 h. The reaction was found to be completed during the milling with no evidence of residual Mg. The unwanted phase, MgO, was readily removed by leaching in acid. The leached powder obtained after 15 h milling had a particle size of 200 nm and was highly faceted. The particle size decreased to approx. 50 nm after 100 h milling and seemed to be relatively nondisperse. Scherrer calculation of the crystallite size showed that the product particles were probably single crystal.
- Welham, Nicholas J.
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p. 1290 - 1292
(2008/10/08)
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