- Synthesis of plate-like ZrB2 grains
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Plate-like ZrB2 grains were synthesized at 1550°C by in situ solid/liquid reaction using Zr and B powders mixed with transition metal (Mo, Nb, Ti, or W) and Si powder. The preferred growth direction of plate grains was along a- or b-axis depending on the initial content of transition metal and silicon in the mixtures. The synthesis mechanism of plate-like grain was possibly related to the catalysis of in situ formed silicides.
- Hu, Chunfeng,Zou, Ji,Huang, Qing,Zhang, Guojun,Guo, Shuqi,Sakka, Yoshio
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- Surface electronic structure of ZrB2 buffer layers for GaN growth on Si wafers
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The electronic structure of epitaxial, predominantly single-crystalline thin films of zirconium diboride (ZrB2), a lattice-matching, conductive ceramic to GaN, grown on Si(111) was studied using angle-resolved ultraviolet photoelectron spectroscopy. The existence of Zr-derived surface states dispersing along the Γ-M direction indicates a metallic character provided by a two-dimensional Zr-layer at the surface. Together with the measured work function, the results demonstrate that the surface electronic properties of such thin ZrB2 (0001) buffer layers are comparable to those of the single crystals promising excellent conduction between nitride layers and the substrate in vertical light-emitting diodes on economic substrates.
- Yamada-Takamura, Yukiko,Bussolotti, Fabio,Fleurence, Antoine,Bera, Sambhunath,Friedlein, Rainer
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- New borothermal reduction route to synthesize submicrometric ZrB 2 powders with low oxygen content
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The ZrB2 powders with submicrometric particle size and low oxygen content were synthesized by a new borothermal reduction route using ZrO2 and excess boron as raw materials. The conventional process only contained the borothermal red
- Guo, Wei-Ming,Zhang, Guo-Jun
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- ZrB2 powders synthesis by borothermal reduction
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High-purity zirconium diboride (ZrB2) powders with submicrometer particle size were synthesized by borothermal reduction of nanometric ZrO 2 powders in vacuum. The reaction process was experimentally and thermodynamically assessed. B2O3 was identified as a possible intermediate reaction product. ZrO2 completely converted to ZrB2 when thermally treated at 1000°C for 2 h in a vacuum, but the removal of residual boron-related species required a temperature above 1500°C. ZrB2 powders obtained at 1000°-1200°C showed a faceted morphology, whereas those prepared above 1500°C had a nearly spherical morphology. The particle size that was calculated from the measured surface area increased with the increasing synthesis temperature from 0.15 μm at 1000°C to 0.66 μm at 1650°C. The oxygen content of the ZrB 2 powders synthesized at 1650°C was as low as 0.43 wt%.
- Ran, Songlin,Van Der Biest, Omer,Vleugels, Jef
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- Synthesis of ZrB2 powders by carbothermal and borothermal reduction
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Zirconium diboride (ZrB2) powders were synthesized using ZrO2 + B2O3 + C (carbothermal reduction), ZrO2 + B4C (boron carbide reduction), and ZrO2 + B4C + C (combined reduction) with various compositions at 1250 °C for 1-3 h under flowing argon. ZrB2 powders synthesized using ZrO2 + B2O3 + C displayed rod shape growth. There was much residual impurity carbon in ZrB2 powders synthesized using ZrO2 + B4C + C. When synthesized using ZrO 2 + B4C, there were the residual impurity B 2O3 and little rod shape growth. Residual B 2O3 impurities were easily removed by washing with methanol. We concluded that the ZrB2 powder synthesis method using boron carbide reduction is the most desirable way to produce ZrB2 powders among the three synthesis routes. ZrB2 powders synthesized using ZrO2 + B4C have a particle size of 1.1 μm and a hexagonal shape, and low oxygen content (0.725 wt.%).
- Jung, Eun-Young,Kim, Jung-Hun,Jung, Se-Hyuk,Choi, Sung-Churl
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- Reaction processes and characterization of ZrB2 powder prepared by boro/carbothermal reduction of ZrO2 in vacuum
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The present work was concentrated mainly on the reaction processes of boro/carbothermal reduction (BCTR) of ZrO2 with B4C and carbon in vacuum, and characterization of morphology and sinterability of the obtained ZrB2 powd
- Guo, Wei-Ming,Zhang, Guo-Jun
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- Epitaxial growth of group III nitrides on silicon substrates via a reflective lattice-matched zirconium diboride buffer layer
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The growth of metallic and reflecting ZrB2 films was conducted on Si(111) substrates at 900 °C using a single-source unimolecular precursor Zr(BH4)4. The ZrB2 buffer layer on Si(111) provided a near lattice-matched template for the growth of epitaxial GaN. The reflective nature of the ZrB2 surface presented an added bonus to optoelectronic applications of the 111- nitrides.
- Tolle,Roucka,Tsong,Ritter,Crozier,Chizmeshya,Kouvetakis
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- Reactive hot pressing of ZrB2-SiC-ZrC ultra high-temperature ceramics at 1800°C
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A ZrB2-SiC-ZrC composite was prepared from a mixture of zirconium, silicon, and B4C via reactive hot pressing at a relatively low temperature (1800°C) for 60 min under 20 MPa in an argon atmosphere. The relative density was 96.8%, the micro-hardness (Hv10) was 16.7 GPa, and the fracture toughness was 5.1 MPa-m1/2. The presence of ZrC was helpful for the densification process and improved the mechanical properties of the composite. A model of the microstructure development of the composite was proposed to explain the phase distribution.
- Wu, Wen-Wen,Zhang, Guo-Jun,Kan, Yan-Mei,Wang, Pei-Ling
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- Thermal Properties of Hf-Doped ZrB2 Ceramics
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The effect of Hf additions on the thermal properties of ZrB2 ceramics was studied. Reactive hot pressing of ZrH2, B, and HfB2 powders was used to synthesize (Zr1-x,Hfx)B2 ceramics with Hf contents ranging from x = 0.0001 (0.01 at.%) to 0.0033 (0.33 at.%). Room-temperature heat capacity values decreased from 495 J·(kg·K)-1 for a Hf content of 0.01 at.% to 423 J·(kg·K)-1 for a Hf content of 0.28 at.%. Thermal conductivity values decreased from 141 to 100 W·(m·K)-1 as Hf content increased from 0.01 to 0.33 at.%. This study revealed, for the first time, that small Hf contents decreased the thermal conductivity of ZrB2 ceramics. Furthermore, the results indicated that reported thermal properties of ZrB2 ceramics are affected by the presence of impurities and do not represent intrinsic behavior.
- Lonergan, Jason M.,McClane, Devon L.,Fahrenholtz, William G.,Hilmas, Gregory E.
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- Aerospace application on Al 2618 with reinforced – Si3N4, AlN and ZrB2in-situ composites
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In this study, the Al 2618 aluminium alloy is reinforced with Si3N4(Silicon Nitride), AlN (Aluminium Nitride) & ZrB2(Zirconium Boride) in wt. % of (0,2,4,6,8) by stir casting process. The tribological and mechanical proper
- Mathan Kumar,Senthil Kumaran,Kumaraswamidhas
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- Morphology evolution of ZrB2 nanoparticles synthesized by solgel method
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Zirconium diboride (ZrB2) nanoparticles were synthesized by solgel method using zirconium n-propoxide (Zr(OPr)4), boric acid (H3BO3), sucrose (C12H22O 11), and acetic acid (AcOH). Clearly, it was a non-aqueous solution system at the very beginning of the reactions. Here, AcOH was used as both chemical modifier and solvent to control Zr(OPr)4 hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C12H 22O11 was selected, since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. Furthermore, we investigated the influence of the gelation temperature on the morphology of ZrB2 particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 °C to a particle chain at 75 °C, and then form rod-like particles at 85 °C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB2 were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB2 related to the gelation temperature obeyed the oriented attachment mechanism of crystallography.
- Zhang, Yun,Li, Ruixing,Jiang, Yanshan,Zhao, Bin,Duan, Huiping,Li, Junping,Feng, Zhihai
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- Mechanosynthesis of Hf1-xZrxB2 solid solution and Hf1-xZrxB2/SiC composite powders
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The synthesis of solid solutions in the HfB2-ZrB2 system was conducted by mechanically induced self-sustaining reaction (MSR) processes under an inert atmosphere from elemental mixtures of Hf, Zr, and B. The stoichiometry of the Hf1-xZrxB2 solid solution phase was controlled by adjusting the Hf/Zr/B atomic ratio in the starting mixture. Composite materials with SiC were achieved by adding the required amount of SiC to the Hf/Zr/B reactant mixture. The presence of up to 20 vol% of SiC did not inhibit the MSR process. Longer milling times were required to ignite the mixture. Small amounts of the refractory phases ZrC or HfC were observed in the composite powders. The chemical composition, structure, and microstructure of products were studied by X-ray diffraction, scanning and transmission electron microscopy, electron diffraction, and energy-dispersive X-ray spectroscopy. This complete characterization confirmed the formation of P6/mmm hexagonal diboride phases with a submicrometric microstructure. The determination of the chemical composition and lattice parameters ascertained the formation of solid solutions with good chemical homogeneity in the HfB 2-ZrB2 system.
- Aviles, Miguel A.,Cordoba, Jose M.,Sayagues, Maria J.,Alcala, Maria D.,Gotor, Francisco J.
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- Formation of zirconium diboride (ZrB2) by room temperature mechanochemical reaction between ZrO2, B2O3 and Mg
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A mixture of magnesium, boric oxide and zirconium dioxide were mechanically milled under argon for up to 15 h in a laboratory scale ball mill. X-ray diffraction showed that there was an increasing conversion of ZrO2 to ZrB2 with milling time with >98% reaction after 15 h. Differential thermal analysis revealed there were multiple, overlapping reactions all of which seemed to be formation of ZrB2. The energy evolved decreased with milling time and the sample after 15 h milling showed no thermal reaction. After milling, separation of the ZrB2 from the coproduct MgO was easily achieved by a mild acid leaching leaving essentially pure ZrB2 with a crystallite size of ～75 nm.
- Setoudeh,Welham
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- Effect of carbon and titanium carbide on sintering behaviour of zirconium diboride
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Systematic sintering studies on the ZrB2 powder were carried out with the addition of carbon (C) in the range of 0 x 10 (x = wt.%) and (titanium carbide) TiC in the range of 0 y 30 (y = wt.%). Zirconium diboride powder made by different
- Mishra,Pathak
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- Pressureless densification of zirconium diboride with boron carbide additions
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Zirconium diboride (ZrB2) was densified (>98% relative density) at temperatures as low as 1850°C by pressureless sintering. Sintering was activated by removing oxide impurities (B2O3 and ZrO2) from particle surfaces. Boron oxide had a high vapor pressure and was removed during heating under a mild vacuum (～150 mTorr). Zirconia was more persistent and had to be removed by chemical reaction. Both WC and B4C were evaluated as additives to facilitate the removal of ZrO2. Reactions were proposed based on thermodynamic analysis and then confirmed by X-ray diffraction analysis of reacted powder mixtures. After the preliminary powder studies, densification was studied using either as-received ZrB2 (surface area ～1 m2/g) or attritionmilled ZrB2 (surface area ～ 7.5 m2/g) with WC and/or B4C as a sintering aid. ZrB2 containing only WC could be sintered to ～95% relative density in 4 h at 2050°C under vacuum. In contrast, the addition of B4C allowed for sintering to >98% relative density in 1 h at 1850°C under vacuum.
- Zhang,Hilmas,Fahrenholtz
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- Epitaxial semimetallic HfxZr1-xB2 templates for optoelectronic integration on silicon
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High quality heteroepitaxial Hfx Zr1-x B2 (x=0-1) buffers were grown directly on Si(111). The compositional dependence of the film structure and ab initio elastic constants were used to show that hexagonal Hfx Zr1-x B2 possess tensile in-plane strain (0.5
- Roucka, Radek,An, YuJin,Chizmeshya, Andrew V. G.,Tolle, John,Kouvetakis, John,D'Costa, Vijay R.,Menendez, Jose,Crozier, Peter
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- Fabrication of UHTCs by conversion of dynamically consolidated Zr+B and Hf+B powder mixtures
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Mixtures of Zr+B and Hf+B were shock compacted into bulk samples possessing relative densities above 95.5% and were subsequently converted to ZrB 2 and HfB2 ceramic components by a heat treatment. The conversion temperature was varied between 1600° and 2000°C. The conversion temperature was found to have no effect on the final density of the ceramics. Theoretical densities of 72% and 62% were obtained for the converted ZrB2 and HfB2 ceramics, respectively. Increasing the heat-treatment temperature promoted grain growth rather than densification for the ZrB2 samples. The grain size increased from 1.8±0.6 to 5.6±1.3 to 8.5±3.3 μm, for heat treatments at 1600°, 1800°, and 2000°C, respectively. No grain growth was observed for the HfB2 system, which exhibited a grain structure of 5.0±1.6, 3.3±1.5, and 4.4±2.2 μm for the same temperature range studied. Microhardness values for the ZrB2 decreased from 19.4±0.4 to 17.2±0.6 down to 13.7±0.6 GPa, while similar hardness results of 19.1±0.8, 17.1±1.0, and 17.8±0.5 GPa were observed for the HfB2 samples.
- Brochu, Mathieu,Gauntt, Bryan,Zimmerly, Tony,Ayala, Alicia,Loehman, Ronald
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- Synthesis of ZrB2 and ZrB2-SiC powders using a sucrose-containing system
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ZrB2 and ZrB2-SiC powders are synthesized by a sol-gel method from zirconium n-propoxide, tetraethyl orthosilicate (only for ZrB2-SiC), boric acid, and sucrose. After reduction at 1550 °C, both ZrB2 and ZrB2-SiC are unconsolidated, soft gray powders. The ZrB2-SiC particles have an equiaxed shape with a diameter of about 800 nm and a uniform size distribution. The SiC may be very finely distributed, because we barely find SiC among ZrB2 particles when using energy dispersive X-ray spectroscopy (EDS), although both ZrB2 and SiC are identified by X-ray diffractometry (XRD).
- Wang, Tingyu,Zhang, Yun,Li, Junping,Zhao, Bin,Li, Ruixing,Yin, Shu,Feng, Zhihai,Sato, Tsugio,Cai, Hongnian
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- Microstructure and properties of spark plasma-sintered ZrO 2-ZrB2 nanoceramic composites
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In a recent work,1 we have reported the optimization of the spark plasma sintering (SPS) parameters to obtain dense nanostructured 3Y-TZP ceramics. Following this, the present work attempts to answer some specific issues: (a) whether ZrO2-based composites with ZrB2 reinforcements can be densifled under the optimal SPS conditions for TZP matrix densiflcation (b) whether improved hardness can be obtained in the composites, when 30 vol% ZrB2 is incorporated and (c) whether the toughness can be tailored by varying the ZrO2-matrix stabilization as well as retaining finer ZrO2 grains. In the present contribution, the SPS experiments are carried out at 1200° C for 5 min under vacuum at a heating rate of 600 K/min. The SPS processing route enables retaining of the finer f-ZrO2 grains (100-300 nm) and the ZrO2-ZrB2 composite developed exhibits optimum hardness up to 14 GPa. Careful analysis of the indentation data provides a range of toughness values in the composites (up to 11 MPa-m 1/2), based on Y2O3 stabilization in the ZrO2 matrix. The influence of varying yttria content, t-ZrO 2 transformability, and microstructure on the properties obtained is discussed. In addition to active contribution from the transformation-toughening mechanism, crack deflection by hard second phase brings about appreciable increment in the toughness of the nanocomposites.
- Basu, Bikramjit,Venkateswaran,Kim, Doh-Yeon
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- Nanocarbon-dependent synthesis of ZrB2 in a binary ZrO 2 and boron system
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Thermodynamically, ZrO2 may react with boron to form B 2O3/B2O2 and ZrB2 at room temperature. However, this reaction is incomplete at temperatures lower than 1550 °C, even with the use of m
- Li, Ruixing,Lou, Haijie,Yin, Shu,Zhang, Yun,Jiang, Yanshan,Zhao, Bin,Li, Junping,Feng, Zhihai,Sato, Tsugio
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- Synthesis of ZrB2 powders by molten-salt participating silicothermic reduction
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A novel molten-salt silicothermic reduction method was developed to prepare ZrB2 powders from raw materials of ZrO2, Na2B4O7 and silicon powders with the assistance of sodium orthosilicate in the reaction system. The influences of reaction temperature and quantity of silicon on the phase composition and morphology of final products were investigated. The results showed that the silicothermic reduction reaction for synthesizing ZrB2 was initiated at the temperature as low as 800 °C, and the reaction completed at 1200 °C for 3 h. Only ZrB2 was detected by X-ray diffractormeter in the final products prepared at only 1000 °C for 3 h with addition of excessive 20 wt% Si powders in the reaction system. Moreover, the sheet-like ZrB2 particles were observed by SEM and TEM, which were homogeneously distributed at the samples.
- Li, Mengrui,Ke, Changming,Zhang, Jinhua
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- Synthesis and thermal stability of Zr(BH4)4 and Zr(BD4)4 produced by mechanochemical processing
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Zirconium tetrahydroborate Zr(BH4)4 and its deuteride compound Zr(BD4)4 were successfully synthesized by mechanochemical reaction between NaBH4 or NaBD4 and ZrCl4, reaching yield
- Gennari,Fernández Albanesi,Rios
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- An investigation on the formation mechanism of nano ZrB2 powder by a magnesiothermic reaction
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Nanocrystalline zirconium diboride (ZrB2) powder was produced by mechanochemistry from the magnesiothermic reduction in the Mg/ZrO 2/B2O3 system. The use of high-energy milling conditions was essential to induce a mechanically induced self-sustaining reaction (MSR) and significantly reduce the milling time required for complete conversion. Under these conditions, it was found that the ignition time for ZrB2 formation was only about a few minutes. In this study, the mechanism for the formation of ZrB2 in this system was determined by studying the relevant sub-reactions, the effect of stoichiometry, and the thermal behavior of the system.
- Jalaly,Bafghi, M.Sh.,Tamizifar,Gotor
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- Synthesis and microstructure of zirconium diboride formed from polymeric precursor pyrolysis
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Zirconium diboride was synthesized by pyrolysis of a novel polymeric precursor. Phase compositions and microstructures of the formed ceramic were characterized. It was found that a precursor with B/Zr molar ratio of 2 can completely transform into zirconium diboride by heating in an inert atmosphere with temperatures above 1500°C. However, the initial formation temperature of zirconium diboride was as low as 1300°C whereas zirconium oxide was also produced from the precursor at 1100°C, the mixture was finally transformed into pure zirconium diboride at the elevated temperature. Zirconium diboride particles, dispersed relatively uniformly with characteristic dimension less than 100 nm, were found to be formed following a liquid phase reaction mechanism.
- Xie, Changming,Chen, Mingwei,Wei, Xi,Ge, Min,Zhang, Weigang
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- ZIRCONIUM BOROHYDRIDE AS A ZIRCONIUM BORIDE PRECURSOR.
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Synthesis of zirconium boride, ZrB//2, from zirconium borohydride has been explored by a variety of methods, including chemical vapor deposition (CVD) in a hot tube, laser CVD with both continuous-wave (cw) and pulsed lasers, and cw-laser synthesis of fine powders. In all cases, ZrB//2 was the only crystalline product identified. Products made at high temperature contained excess boron, while those made at low temperature were boron-deficient.
- Rice,Woodin
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- Boron Carbide-Zirconium Boride in Situ Composites by the Reactive Pressureless Sintering of Boron Carbide-Zirconia Mixtures
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The heating of B4C-YTZP (where YTZP denotes yttriastabilized zirconia polycrystals) mixtures, under an argon atmosphere, generates B4C-ZrB2 composites, because of a low-temperature (4C that has been fired under the same conditions. Firing to ～2160 °C (1 h dwell) generates specimens with a bulk density of ≥91% of the theoretical density (TD) for cases where the initial mixture includes ≥15% YTZP. Mixtures that include 30% YTZP allow a fired density of >97.5% TD to be attained. The behavior of the B4C-YTZP system is similar to that of the B4C-TiO2 system. Dense B4C-ZrB2 composites attain a hardness (Vickers) of 30-33 GPa.
- Goldstein, Adrian,Geffen, Ygal,Goldenberg, Ayala
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- Synthesis and characterization of a novel precursor-derived ZrC/ZrB 2 ultra-high-temperature ceramic composite
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ZrC and ZrB2, two valuable members of ultra-high-temperature ceramics (UHTCs), are potentially useful as structural materials in aerospace engineering and hypersonic flight vehicles. This work focused on the preparation of ZrC/ZrB2 U
- Wang, Hao,Chen, Xingbo,Gao, Bo,Wang, Jun,Wang, Yingde,Chen, Shugang,Gou, Yanzi
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- Mechanochemical processing of nanocrystalline zirconium diboride powder
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Nanocrystalline ZrB2 powder was prepared by mechanochemical processing of a zirconium (II) dihydride-boron mixture with subsequent annealing from 800°C to 1200°C. The crystallite size and morphology of the synthesized ZrB2 powders were characterized by X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. The effects of annealing temperature on powder particle size and morphology were assessed. At 900°C or above, pure ZrB2 powder was obtained without trace quantities of residual ZrH2. The synthesized ZrB2 powder particles were spherically shaped, with a crystallite size between 5 and 40 nm. The crystallite size increased with increase of annealing temperature.
- Guo, Shuqi,Hu, Chunfeng,Kagawa, Yutaka
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- Thermal Expansion of Micro- and Nanocrystalline ZrB2 Powders
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Abstract—: Nano- and microcrystalline ZrB2 powders have been studied by high-temperature X-ray diffraction in the temperature range 300–1400 K, and their unit-cell parameters have been measured as functions of temperature. The thermal expansion coefficient (TEC) of ZrB2 has been shown to be a linear function of temperature, and its thermal expansion has been shown to be anisotropic: in the temperature range 300–600 K, both the micro- and nanocrystalline ZrB2 powders have anisotropic thermal expansion, with αa c. Above 640 K, the a-axis TEC of ZrB2 exceeds its c-axis TEC. The thermal expansion of the nanocrystalline ZrB2 powder has been shown to be considerably smaller than that of the microcrystalline ZrB2. The anomalously small thermal expansion of the nanocrystalline ZrB2 is tentatively attributed to the effect of a boric anhydride layer on the surface of the nanoparticles.
- Kalinnikov, G. V.,Khomenko, N. Yu.,Konovalikhin, S. V.,Korobov, I. I.,Kovalev, D. Yu.,Kravchenko, S. E.,Shilkin, S. P.
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- Low-temperature synthesis of nanocrystalline ZrB2 via co-reduction of ZrCl4 and BBr3
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Nanocrystalline zirconium diboride (ZrB2) has been synthesized via a sodium co-reduction of ZrCl4 and BBr3 at 400 °C. The XRD patterns can be indexed as hexagonal ZrB2 with the lattice constants a = 3.167 and c = 3.527 A. The TEM image indicates the product has particle morphology, with size of about 20 nm.
- Chen, Luyang,Gu, Yunle,Shi, Liang,Ma, Jianhua,Yang, Zeheng,Qian, Yitai
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- Preparation of zirconium boride powder
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An intermediate reaction in the synthesis of ZrB2 powder by the reduction of ZrO2 with B4C and carbon was confirmed through both thermodynamical calculation and experimental results. Because the intermediate product B
- Zhao,He,Jin
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- Reaction chemistry during self-propagating high-temperature synthesis (SHS) of H3BO3-ZrO2-Mg system
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In the present investigation, the ZrB2 powder is produced by SHS of mixture containing H3BO3, ZrO2 and Mg. The thermal analysis and XRD study reveal the reaction mechanism of ZrB2 formation by SHS process. Synthesis of H3BO3-Mg system results in formation of Mg3(BO3)2 and MgB4 phases, whereas ZrO2 is partially reduced to Zr3O and Zr during synthesis of ZrO2-Mg system. The reaction between elemental Zr and MgB4 results in ZrB2 formation. The particle size of ZrB2 is found to decrease with the addition of SHS diluent.
- Khanra
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- Preparation and microstructure of a ZrB2-SiC composite fabricated by the spark plasma sintering-reactive synthesis (SPS-RS) method
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A mixture of Zr, B4C, and Si powders was adopted to synthesize a ZrB2-SiC composite using the spark plasma sintering-reactive synthesis (SPS-RS) method. SPS treatments were carried out in the temperature range of 1350°-1500°C under a varying pressure of 20-65 MPa with a 3-min holding time. A dense (～98.5%) ZrB2-SiC composite was successfully fabricated at 1450°C for 3 min under 30 MPa. The microstructure of the composite was investigated. The in situ formed ZrB2 and SiC phases dispersed homogeneously on the whole. The grain size of ZrB2 and SiC was A number of in situ formed ultrafine SiC particles were observed entrapped in the ZrB2 grains.
- Zhao, Yuan,Wang, Lian-Jun,Zhang, Guo-Jun,Jiang, Wan,Chen, Li-Dong
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- Electronic transport in MgB2, AlB2 and ZrB2 - A comparative study
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We report on the temperature dependence of the resistivity (ρ) and the absolute thermopower (S) of the polycrystalline title materials and of AlB2 single crystals. For all samples ρ(T) exhibits a Bloch-Gru?neisen-like temperature dependence, with large characteristic temperatures θR (≈θD - the Debye temperature). At high temperatures the thermopower S(T) for ZrB2 (n-type) is almost the mirror image of S(T) for MgB2 (p-type) while S(AlB2) is very small for all temperatures. The density of states distribution N(E) around EF seems to play a dominant role in determining S(T) of these materials. ln(T) terms in the low-temperature ρ(T) and S(T) of ZrB2 samples bear evidence for weak localization in 2D.
- Fisher,Chashka,Patlagan,Reisner
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- Thermal and electrical transport properties of spark plasma-sintered HfB2 and ZrB2 ceramics
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The thermal and electrical transport properties of various spark plasma-sintered HfB2- and ZrB2-based polycrystalline ceramics were investigated experimentally over the 298-700 K temperature range. Measurements of thermal diffusivity, electrical resistivity, and Hall coefficient are reported, as well as the derived properties of thermal conductivity, charge carrier density, and charge carrier mobility. Hall coefficients were negative confirming electrons as the dominant charge carrier, with carrier densities and mobilities in the 3-5 × 1021 cm -3 and 100-250 cm2·(V·s)-1 ranges, respectively. Electrical resistivities were lower, and temperature coefficients of resistivity higher, than those typically reported for HfB 2 and ZrB2 materials manufactured by the conventional hot pressing. A Wiedemann-Franz analysis confirms the dominance of electronic contributions to heat transport. The thermal conductivity was found to decrease with increasing temperature for all materials. Results are discussed in terms of sample morphology and compared with data previously reported in the scientific literature.
- Zhang, Luning,Pejakovic, Dusan A.,Marschall, Jochen,Gasch, Matthew
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- New route to synthesize ultra-fine zirconium diboride powders using inorganic-organic hybrid precursors
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Ultra-fine zirconium diboride (ZrB2) powders have been synthesized using inorganic-organic hybrid precursors of zirconium oxychloride (ZrOCl2 · 8H2O), boric acid, and phenolic resin as sources of zirconia, boron oxide, and carbon, respectively. The reactions were substantially completed at a relatively low temperature (～1500°C). The synthesized powders had a smaller average crystallite size (a larger specific surface area (～32 m2/g), and a lower oxygen content (2 powders. The thermodynamic change in the ZrO2-B 2O3-C system was mainly studied by thermogravimetric and differential thermal analysis. The crystallite size and morphology of the synthesized powders were characterized by transmission electron microscopy and scanning electron microscopy.
- Yan, Yongjie,Huang, Zhengren,Dong, Shaoming,Jiang, Dongliang
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- The effect of starting precursors on size and shape modification of ZrB2 ceramic nanoparticles
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The formation of ZrB2 nanoparticles through reaction of Zr(n-PrO)4 with H3BO3 and carbon has been studied with different ligands by carbothermal reduction at 1500 °C. In the first step, by introducing N,N′-bis (salicylidene)-1,3-diaminopropane (H2salpn) or salicylaldehyde (Hsal) species into reaction mixture, the reaction of the zirconium alkoxide using citric acid and boric acid yielded the zirconium diboride (ZrB2) sol-gel precursors. In the second step, the mixture was heated by introducing the reactant compact into an argon furnace held at 1500 °C for 2 h to obtain the final pure phase ZrB2 nanocrystallites with a diameter of about 50 nm. The kind of chelating agent used in the preparation of ZrB2 nanoparticles plays the predominant role on the final product size. This demonstrates that the proper kind of donor atom and a very specific ligand structure are necessary for the reaction of Zr4+ complexes.
- Amirsardari, Zahra,Aghdam, Rouhollah Mehdinavaz,Salavati-Niasari, Masoud,Jahannama, Mohammad Reza
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- ZrB2- SiC nano-powder mixture prepared using ZrSi2 and modified spark plasma sintering
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ZrB2-SiC nano-powder mixture was synthesized using ZrSi 2 source material and a modified spark plasma sintering apparatus. The particle size of ZrB2 and SiC was about 80 and 20 nm, respectively. The molecular-level homogeneity of Zr/Si source and fast heating/cooling rate by SPS caused the formation of homogeneously intermixed nano-powders. A strong exothermal reaction occurred at around 860°C, which caused strong agglomeration and growth of the synthesized powder mixture. The rapid reaction could be controlled by adding 20 wt% of NaCl, which acted as an inert filler.
- Lee, Sea-Hoon,Choi, Si-Young,Kim, Hai-Doo
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- Reactive hot pressing of ZrB2-SiC-ZrC composites at 1600°C
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A ZrB2-SiC-ZrC ceramic was produced by reactive hot pressing using Zr, Si, and B4C as raw materials. The kinetics of the reaction process was studied. The reduction of powders by ball milling is of crucial importance for the sintering. The self-propagating high-temperature synthesis reaction between the raw powders can be ignited by controlling the sintering conditions, which leads to a sintering temperature as low as 1600°C, the lowest sintering temperature reported thus far. The relative density is 97.3%, with an open porosity of 0.6%, and the mechanical properties are comparable to the composites that sintered at higher temperatures. The depletion of oxygen impurities during the sintering was discussed.
- Wu, Wen-Wen,Zhang, Guo-Jun,Kan, Yan-Mei,Wang, Pei-Ling
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- Improved oxidation resistance of zirconium carbide at 1500°C by lanthanum hexaboride additions
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Addition of LaB6 is adopted to improve the oxidation resistance of ZrC at 1500°C. Mixed powder of ZrC-25 vol% LaB6 is reactively hot pressed at 1900°C for 30 min under vacuum with an applied pressure of 25 MPa. The LaB6 reacts with ZrC to form ZrB2 and a layered La-containing phase. ZrB2 improves the oxidation resistance of ZrC in static air. The La-containing phase is beneficial to increasing the relative density of oxide scale during oxidation and in enhancing the oxide scale stability during exposure to thermal cycles.
- Zhao, Liyou,Jia, Dechang,Duan, Xiaoming,Yang, Zhihua,Zhou, Yu
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- Nanosized zirconium diboride: Synthesis and properties
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The thermolysis of Zr(BH4)4 vapor at 573 and 623 K in a vacuum of 1.33 × 10-1 Pa was studied. Nanosized zirconium diboride was produced as an X-ray amorphous powder and a crystalline film. According to electron microscopy data, the X-ray amorphous zirconium diboride powder obtained at 573 or 623 K consists of spherical particles 30-40 nm in diameter, which is in quite a good agreement with the equivalent particle diameter (～35 nm) calculated from the specific surface area of ZrB 2. After annealing at 1273 K, the X-ray amorphous zirconium diboride powder crystallizes into a hexagonal lattice with the unit cell parameters a = 0.3159 nm and c = 0.3527 nm. The coherent scattering length D hkl is ～27 nm. The zirconium diboride film produced at 573 or 623 K crystallizes into a hexagonal lattice with the unit cell parameters a = 0.3163-0.3168 nm and c = 0.3524-0.3531 nm. The coherent scattering length D hkl is ～14 nm. The thickness of the ZrB2 film on quartz, glass ceramics, and stainless steel is 5-7 μm. The microhardness of the film on a stainless steel substrate under a load of 20 g is 17.8 GPa.
- Kravchenko,Torbov,Shilkin
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- Fully dense ZrB2 ceramics by borothermal reduction with ultra-fine ZrO2 and solid solution
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The effects of ZrO2 particle size (55?nm and 113?nm) and borothermal reduction routes (borothermal reduction with water-washing (BRW) and in situ 5?mol% TaB2 solid solution, BRS) on synthesis and densification of ZrB2 were
- Xu, Liang,Guo, Wei-Ming,Liu, Qiu-Yu,Zhang, Yan,Wu, Li-Xiang,You, Yang,Lin, Hua-Tay
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p. 3133 - 3140
(2022/01/19)
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- Super-hardening and localized plastic deformation behaviors in ZrB2 –TaВ2 ceramics
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A systematic study of the Zr-Ta-B system was performed using thermodynamic and ab initio modeling, nanoindentation, and high-resolution TEM and XRD experiments. The phase diagram (convex hull) of the Zr-Ta-B system was constructed at 0 K, and phase stability, lattice parameters, and mechanical properties of ZrB2-TaB2 solid solutions were ascertained in silico. Dense ceramics were manufactured by the combination of combustion synthesis and hot pressing techniques. As opposed to theoretically predicted complete solubility in the ZrB2-TaB2 solid solution series, the highest experimentally attained Ta content in the ZrB2-based solution was 25–27 at%, suggesting that at higher Ta contents a non-equilibrium phase composition is formed during combustion synthesis and inherited during hot pressing. Single-phase ZrB2-TaB2 solid solutions displayed a super-hardness up to 70 GPa and coefficient of elastic recovery as high as 99.7%, which surpasses wurtzite and cubic boron nitride and rivals polycrystalline diamonds. In the non-equilibrium samples with multiple solid solutions, a “pop-in” (localized plastic deformation) effect was discovered and attributed to the formation of shearing bands, microtwins, and dislocation loops. The composition-dependent switching between super-hardened and locally plastic mechanical behavior allows the creation of a new generation of ultra-high temperature ceramic composites.
- Klechkovskaya, V. V.,Kurbatkina, V. V.,Levashov, E. A.,Lobova, T. A.,Loginov, P. A.,Patsera, E. I.,Sidnov, K.,Sviridova, T. A.,Vorotilo, S.
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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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- ZrB2as an earth-abundant metal diboride catalyst for electroreduction of dinitrogen to ammonia
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ZrB2 is first explored as an earth-abundant metal diboride catalyst for highly efficient nitrogen reduction reaction (NRR). The synthesized ZrB2 nanocubes exhibited a highly attractive NRR performance with an NH3 yield of 37.7 μg h-1 mg-1 and a Faradaic efficiency 18.2% at -0.3 V (RHE). Theoretical calculations unraveled that active Zr centers enabled the effective activation of the N2 molecule via a unique tetranuclear side-on mode and concurrently impeded hydrogen evolution by restricting H+ adsorption. This journal is
- Cheng, Yonghua,Chu, Ke,Guo, Yali,Li, Qingqing,Li, Xiaotian
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supporting information
p. 13009 - 13012
(2020/11/07)
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- Synthesis and Characterization of Single-Phase Metal Dodecaboride Solid Solutions: Zr1- xYxB12 and Zr1- xUxB12
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Single-phase metal dodecaboride solid solutions, Zr0.5Y0.5B12 and Zr0.5U0.5B12, were prepared by arc melting from pure elements. The phase purity and composition were established by powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and 10B and 11B solid-state nuclear magnetic resonance (NMR) spectroscopy. The effects of carbon addition to Zr1-xYxB12 were studied and it was found that carbon causes fast cooling and as a result rapid nucleation of grains, as well as "templating" and patterning effects of the surface morphology. The hardness of the Zr0.5Y0.5B12 phase is 47.6 ± 1.7 GPa at 0.49 N load, which is ～17% higher than that of its parent compounds, ZrB12 and YB12, with hardness values of 41.6 ± 2.6 and 37.5 ± 4.3 GPa, respectively. The hardness of Zr0.5U0.5B12 is ～54% higher than that of its UB12 parent. The dodecaborides were confirmed to be metallic by band structure calculations, diffuse reflectance UV-vis, and solid-state NMR spectroscopies. The nature of the dodecaboride colors - violet for ZrB12 and blue for YB12 - can be attributed to charge-transfer. XPS indicates that the metals are in the following oxidation states: Y3+, Zr4+, and U5+/6+. The superconducting transition temperatures (Tc) of the dodecaborides were determined to be 4.5 and 6.0 K for YB12 and ZrB12, respectively, as shown by resistivity and superconducting quantum interference device (SQUID) measurements. The Tc of the Zr0.5Y0.5B12 solid solution was suppressed to 2.5 K.
- Akopov, Georgiy,Mak, Wai H.,Koumoulis, Dimitrios,Yin, Hang,Owens-Baird, Bryan,Yeung, Michael T.,Muni, Mit H.,Lee, Shannon,Roh, Inwhan,Sobell, Zachary C.,Diaconescu, Paula L.,Mohammadi, Reza,Kovnir, Kirill,Kaner, Richard B.
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p. 9047 - 9062
(2019/06/13)
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- Bulk monolithic zirconium and tantalum diborides by reactive and non-reactive spark plasma sintering
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Monolithic ZrB2 and TaB2 were produced starting from the precursors through Self-propagating High temperature Synthesis followed by Spark Plasma Sintering (SHS-SPS) and by means of Reactive Spark Plasma Sintering (RSPS). Both methods enabled to achieve almost fully dense ceramics with mean grain size typical of pure bulks. ZrB2 materials displayed significant differences in the final mean grain size of the products obtained by the two routes, while a satisfactory homogeneity was reached in both cases. This was confirmed by good mechanical strength values, about 400 MPa at room temperature, basically maintained up to 1200°C. On the other hand, TaB2 sintered materials were quite diverse, in particular TaB2/RSPS showed a dual distribution of mean grain size, along with an almost no residual porosity, whilst TaB2/SHS-SPS had more homogeneous grain size distribution and diffused trapped porosity which corrupted the mechanical and oxidation performances.
- Licheri, Roberta,Musa, Clara,Orrù, Roberto,Cao, Giacomo,Sciti, Diletta,Silvestroni, Laura
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p. 351 - 359
(2016/01/09)
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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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- Fabrication and characterization of ZrB2-based ceramic using synthesized ZrB2-LaB6 powder
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ZrB2-LaB6 powder was obtained by reactive synthesis using ZrO2, La2O3, B4C, and carbon powders. Then ZrB2-20 vol% SiC-10 vol% LaB6 (ZSL) ceramics were prepared from co
- Spring, Alex,Guo, Wei-Ming,Zhang, Guo-Jun,Wang, Pei-Ling,Krstic, Vladimir D.
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p. 2763 - 2765
(2009/02/06)
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- Solution-based synthesis of submicrometer ZrB2 and ZrB 2-TaB2
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Zirconium diboride and a zirconium diboride/tantalum diboride mixture were synthesized by solution-based processing. Zirconium n-propoxide was refluxed with 2,4-pentanedione to form zirconium diketonate. This compound hydrolyzed in a controllable fashion to form a zirconia precursor. Boria and carbon precursors were formed via solution additions of phenol-formaldehyde and boric acid, respectively. Tantalum oxide precursors were formed similarly as zirconia precursors, in which tantalum ethoxide was used. Solutions were concentrated, dried, pyrolyzed (800°-1100°C, 2 h, flowing argon), and exposed to carbothermal reduction heat treatments (1150°-1800°C, 2 h, flowing argon). Spherical particles of 200-600 nm for pure ZrB2 and ZrB 2-TaB2 mixtures were formed.
- Xie, Yanli,Sanders Jr., Thomas H.,Speyer, Robert F.
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p. 1469 - 1474
(2009/01/30)
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- High-temperature electrochemical synthesis of zirconium diboride in halide melts
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Conditions for the joint electrolytic reduction of zirconium and boron complexes, composition, shape, and the mechanism of formation and discharge of electrochemically active species during high-temperature electrochemical synthesis of zirconium diboride were studied.
- Uskova,Sarychev,Malyshev,Shapoval
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p. 1531 - 1537
(2007/10/03)
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- Reaction Kinetics in the System Al2O3-Glass-Ceramic Coating
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The kinetics of reactions between alumina and a glass-ceramic coating were studied. Reaction of alumina with the aluminoborosilicate melt at 1400°C in air for 100 h was found to yield mullite. Reaction of zirconium silicate and silicon boride yields zirconium boride. These processes ensure good adhesion of the coating to the substrate and high thermal stability of the system.
- Ban'kovskaya,Lapshin
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p. 1281 - 1284
(2008/10/08)
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