The equilibrium phase boundary between hexagonal and cubic boron nitride

Fukunaga, Osamu

doi:10.1016/s0925-9635(99)00188-0

Cited by 47 publications

(63 citation statements)

References 19 publications

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“…The phase diagram and atomistic computational modeling have shown that the free‐energy of cBN is slightly lower than that of hBN in STP conditions and should be the most stable phase. The cBN to hBN transformation occurs at ~1400°C and is pushed to higher temperatures as pressure increases . Nevertheless, hBN is the most common phase found under STP conditions and the transformation to cBN requires high temperature and high pressures (>7.7 GPa) to occur.…”

Section: Introductionmentioning

confidence: 99%

High hardness cubic boron nitride with nanograin microstructure produced by high‐energy milling

Semenic

Kräemer

et al. 2018

J Am Ceram Soc

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High‐energy shaker milling of hexagonal boron nitride (hBN) powders was used to produce powders rich in sp3 bonding. The powders contained up to 68% sp3 bonding and were found to nucleate nanosize cBN grains during consolidation at 5.5 GPa and 1400°C. The effect of hBN starting particle size, milling time, and powder‐to‐milling ball ratio were studied. The amount of sp3 bonding for milled hBN powders was determined, using 11B solid‐state NMR. The milled material was also analyzed by XRD, Raman spectroscopy, and HRTEM. The results indicate that the material has a nanosized microstructure comprised of a disordered hBN matrix and cBN nuclei in the form of sp3‐rich domains. Eight different milled powders were produced and consolidated at pressures of either 5.5 or 6.5 GPa and temperatures of either 1400°C or 1450°C into 12 mm diameter and 5 mm thick pellets. Consolidated pellets formed from milled hBN with 68% sp3 bonding had Vickers hardness of 42 ± 1 GPa and fracture toughness 3.8 ± 0.1 MPa.m1/2. Vickers hardness of 49 ± 1 GPa and fracture toughness of 4.6 ± 0.1 MPa.m1/2 was achieved with a precursor that contained milled hBN and 50 vol. % of 0.5 μm diameter cBN crystals.

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Section: Introductionmentioning

confidence: 99%

High hardness cubic boron nitride with nanograin microstructure produced by high‐energy milling

Semenic

Kräemer

et al. 2018

J Am Ceram Soc

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“…8). In these characterizations, no change could be identified between the initial state and after treatment at 2200 K. This stability at high temperature, and the absence of phase change, was provided by the stability of boron nitride in the hexagonal form at low pressure and high temperature [16,17]. Besides high-temperature tests, the MEDIASE facility was also used to investigate the behavior of the pBN coating under VUV radiation and proton bombardment at high temperature.…”

Section: Experimental Results On Candidate Materials For Solar Prmentioning

confidence: 99%

Emissivity of Boron Nitride and Metals for the Solar Probe Plus Mission

Brodu

Balat‐Pichelin

2016

Journal of Spacecraft and Rockets

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“…Portanto, os dados obtidos testemunham a favor do que foi estabelecido no trabalho do autor acima citado, com relação ao diagrama de equilíbrio. A relação obtida por FUKUNAGA [12], onde p(GPa)=T(°C)/465+0,79, está localizada em uma posição intermediária entre as dependências de equilíbrio hBN↔cBN apresentadas por CORREGAN [5] e SOLOZHENKO [13]. Isto pode significar a não existência de uma linha de equilíbrio, mas sim de uma faixa.…”

Section: Resultsunclassified

Transformação do nitreto hexagonal de boro em nitreto cúbico de boro com o catalisador magnésio

2008

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RESUMOA importância do Nitreto cúbico de Boro (cBN) reside em processos de usinagem de metais ferrosos de elevada dureza. Apesar do cBN ser superado pelo diamante em termos de dureza, ele é mais resistente a oxidação provocada pelo ferro sob altas temperaturas em torno de 700 o C. Os cristais de cBN podem ser obtidos pela síntese a partir da mistura de Nitreto hexagonal de Boro (hBN), aplicando altas pressões e altas temperaturas (HPHT), durante um determinado tempo. Para facilitar os processos de transformação do hBN em cBN, podem ser utilizados um ou mais catalisadores, tais como o magnésio, lítio e bário e outros. No presente trabalho o magnésio na forma de partículas de até 53μm foi utilizado como catalisador nas tentativas de síntese de cBN. Com o objetivo de identificar os parâmetros de síntese (HPHT) que possibilitam a obtenção de partículas de cBN, foram feitas calibrações de temperatura e pressão na prensa hidráulica de 630 toneladas utilizada nos experimentos. As sínteses foram realizadas, utilizando a mesma temperatura para quatro pressões de 5,0; 6,0; 7,0; e 8,0 GPa, durante 5 minutos. E logo após as sínteses foram obtidas imagens por microscopia eletrônica de varredura (MEV) de cada amostra fraturada, o que mostrou algumas formações de cBN.Palavras chaves: nitreto cúbico de boro, síntese, altas pressões, altas temperaturas. Transformation of Hexagonal Boron Nitride in Cubic Boron Nitride with Catalytic Magnesium ABSTRACTThe importance of the cubic Boron Nitride (cBN) lies in processes of machining of ferrous metals of raised hardness, where it substitutes the diamond. Despite the cBN being surpassed by the diamond in hardness terms, it has more oxidation resistance provoked by the iron under high temperatures around 700 o C. The cBN crystals can be gotten by the synthesis through the hexagonal boron nitride (hBN) applying High Pressures and High Temperatures (HPHT), during determined time. To facilitate the transformation of hBN to cBN, there can be applied one or more catalytic, such as magnesium, lithium, barium and others. In this work the magnesium in the particle form of until 53μm was used as catalytic in the attempts of cBN synthesis. With the objective to identify the synthesis parameters (HPHT) that they make possible the cBN particle attainment, calibrations of temperature and pressure in the hydraulic press of 630 ton used in the experiments had been made. Synthesis was carried out with the same temperature and four different values of pressure 5.0; 6.0; 7.0 and 8.0 GPa, for 5 minutes. After the synthesis, images had been gotten for Scanning Electron Microscope (SEM) of each broken sample, what it showed some formations of cBN.

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The equilibrium phase boundary between hexagonal and cubic boron nitride

Cited by 47 publications

References 19 publications

High hardness cubic boron nitride with nanograin microstructure produced by high‐energy milling

High hardness cubic boron nitride with nanograin microstructure produced by high‐energy milling

Emissivity of Boron Nitride and Metals for the Solar Probe Plus Mission

Transformação do nitreto hexagonal de boro em nitreto cúbico de boro com o catalisador magnésio

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