12045-64-6Relevant articles and documents
Synthesis of plate-like ZrB2 grains
Hu, Chunfeng,Zou, Ji,Huang, Qing,Zhang, Guojun,Guo, Shuqi,Sakka, Yoshio
, p. 85 - 88 (2012)
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.
New borothermal reduction route to synthesize submicrometric ZrB 2 powders with low oxygen content
Guo, Wei-Ming,Zhang, Guo-Jun
, p. 3702 - 3705 (2011)
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
Synthesis of ZrB2 powders by carbothermal and borothermal reduction
Jung, Eun-Young,Kim, Jung-Hun,Jung, Se-Hyuk,Choi, Sung-Churl
, p. 164 - 168 (2012)
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.%).
Epitaxial growth of group III nitrides on silicon substrates via a reflective lattice-matched zirconium diboride buffer layer
Tolle,Roucka,Tsong,Ritter,Crozier,Chizmeshya,Kouvetakis
, p. 2398 - 2400 (2003)
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.
Thermal Properties of Hf-Doped ZrB2 Ceramics
Lonergan, Jason M.,McClane, Devon L.,Fahrenholtz, William G.,Hilmas, Gregory E.
, p. 2689 - 2691 (2015)
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.
Morphology evolution of ZrB2 nanoparticles synthesized by solgel method
Zhang, Yun,Li, Ruixing,Jiang, Yanshan,Zhao, Bin,Duan, Huiping,Li, Junping,Feng, Zhihai
, p. 2047 - 2052 (2011)
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.
Formation of zirconium diboride (ZrB2) by room temperature mechanochemical reaction between ZrO2, B2O3 and Mg
Setoudeh,Welham
, p. 225 - 228 (2006)
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.
Pressureless densification of zirconium diboride with boron carbide additions
Zhang,Hilmas,Fahrenholtz
, p. 1544 - 1550 (2006)
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.
Fabrication of UHTCs by conversion of dynamically consolidated Zr+B and Hf+B powder mixtures
Brochu, Mathieu,Gauntt, Bryan,Zimmerly, Tony,Ayala, Alicia,Loehman, Ronald
, p. 2815 - 2822 (2008)
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.
Microstructure and properties of spark plasma-sintered ZrO 2-ZrB2 nanoceramic composites
Basu, Bikramjit,Venkateswaran,Kim, Doh-Yeon
, p. 2405 - 2412 (2006)
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.
Synthesis of ZrB2 powders by molten-salt participating silicothermic reduction
Li, Mengrui,Ke, Changming,Zhang, Jinhua
, (2020)
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.
An investigation on the formation mechanism of nano ZrB2 powder by a magnesiothermic reaction
Jalaly,Bafghi, M.Sh.,Tamizifar,Gotor
, p. 36 - 41 (2014)
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.
ZIRCONIUM BOROHYDRIDE AS A ZIRCONIUM BORIDE PRECURSOR.
Rice,Woodin
, p. c181-c183 (1988)
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.
Synthesis and characterization of a novel precursor-derived ZrC/ZrB 2 ultra-high-temperature ceramic composite
Wang, Hao,Chen, Xingbo,Gao, Bo,Wang, Jun,Wang, Yingde,Chen, Shugang,Gou, Yanzi
, p. 79 - 84 (2013)
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
Thermal Expansion of Micro- and Nanocrystalline ZrB2 Powders
Kalinnikov, G. V.,Khomenko, N. Yu.,Konovalikhin, S. V.,Korobov, I. I.,Kovalev, D. Yu.,Kravchenko, S. E.,Shilkin, S. P.
, p. 258 - 264 (2020)
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.
Preparation of zirconium boride powder
Zhao,He,Jin
, p. 2534 - 2536 (1995)
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
Preparation and microstructure of a ZrB2-SiC composite fabricated by the spark plasma sintering-reactive synthesis (SPS-RS) method
Zhao, Yuan,Wang, Lian-Jun,Zhang, Guo-Jun,Jiang, Wan,Chen, Li-Dong
, p. 4040 - 4042 (2007)
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.
Thermal and electrical transport properties of spark plasma-sintered HfB2 and ZrB2 ceramics
Zhang, Luning,Pejakovic, Dusan A.,Marschall, Jochen,Gasch, Matthew
, p. 2562 - 2570 (2011)
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.
Wayda, A. L.,Schneemeyer, L. F.,Opila, R. L.
, p. 361 - 363 (1988)
ZrB2- SiC nano-powder mixture prepared using ZrSi2 and modified spark plasma sintering
Lee, Sea-Hoon,Choi, Si-Young,Kim, Hai-Doo
, p. 1051 - 1054 (2013)
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.
Improved oxidation resistance of zirconium carbide at 1500°C by lanthanum hexaboride additions
Zhao, Liyou,Jia, Dechang,Duan, Xiaoming,Yang, Zhihua,Zhou, Yu
, p. 3648 - 3650 (2011)
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.
Fully dense ZrB2 ceramics by borothermal reduction with ultra-fine ZrO2 and solid solution
Xu, Liang,Guo, Wei-Ming,Liu, Qiu-Yu,Zhang, Yan,Wu, Li-Xiang,You, Yang,Lin, Hua-Tay
, p. 3133 - 3140 (2022/01/19)
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
New criteria for the applicability of combustion synthesis: The investigation of thermodynamic and kinetic processes for binary Chemical Reactions
Tan, Xiaoming,Su, Xianli,Yan, Yonggao,Uher, Ctirad,Zhang, Qingjie,Tang, Xinfeng
supporting information, (2021/01/07)
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.
