Thermal expansion of boron and boron carbide

Tsagareishvili, G.V.; Nakashidze, T.G; Jobava, J.Sh; Lomidze, G.P; Khulelidze, D.E.; Tsagareishvili, D. Sh.; Tsagareishvili, Otar

doi:10.1016/0022-5088(86)90025-1

Cited by 63 publications

(26 citation statements)

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“…The average coefficients of linear expansion for the a and c axes were 4.9x10 -6 K -1 , and 5.3x10 -6 K -1 , respectively from 25°C to 850°C. There was some anisotropy between the axes, with a 10% difference in the coefficient of thermal expansion for the a and c axis, which is similar to the 16.2% difference Wu et al [16] reported for B 12 As 2 compression in a diamond anvil, and that reported for boron carbide [10][11][12]. This anisotropy is significant because it shows the fundamental difference in properties that exists in these two different directions in the B 12 As 2 crystal structure.…”

Section: Resultssupporting

confidence: 75%

“…The thermal expansion in the two main directions, parallel to the a and c axes of the hexagonal unit cell, are calculated from equations 5 and 6 [10], where a and c are the lattice constants.…”

Section: Introductionmentioning

confidence: 99%

“…Tsagareishvili et al [10], Rice [11] and Yakel [12] completed thorough investigations of the coefficient of thermal expansion of boron carbide, reporting an average CTE for the a direction of 5.73x10 -6 K -1 (25-940°C), 5.29x10 -6 K -1 (25-600°C) and for the c direction of 5.65x10 -6 K -1 (25-940°C), and 6.25x10 -6 K -1 (25-600°C) [11]. Anisotropy in boron carbide of up to 15% can be explained by the differences in the a and c directions of the hexagonal structure [10][11][12]. The strong covalent bonds of the icosahedra should show less flexibility than the bonds between the carbon atoms parallel to the c axis.…”

Section: Introductionmentioning

confidence: 99%

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The coefficients of thermal expansion of boron arsenide (B12As2) between 25°C and 850°C

Whiteley

Kirkham

Edgar

2013

Journal of Physics and Chemistry of Solids

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Section: Resultssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The coefficients of thermal expansion of boron arsenide (B12As2) between 25°C and 850°C

Whiteley

Kirkham

Edgar

2013

Journal of Physics and Chemistry of Solids

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“…9 was confirmed by X-ray diffractometry as well [33]. But neither some additional weaker anomalies at lower and at higher temperatures nor particularly the strong anisotropy stated by these authors [33] have been confirmed by our own results or by those of other authors to be discussed. The softening of the structure in the temperature range around 500 to 600 K is additionally confirmed by the temperature dependent internal friction (typical curves reproduced from [34] and [35] in Fig.…”

Section: Discussionsupporting

confidence: 78%

“…The strong anomaly of the thermal expansion coefficient close to 600 K in Fig. 9 was confirmed by X-ray diffractometry as well [33]. But neither some additional weaker anomalies at lower and at higher temperatures nor particularly the strong anisotropy stated by these authors [33] have been confirmed by our own results or by those of other authors to be discussed.…”

Section: Discussionsupporting

confidence: 77%

Interband and Gap State Related Transitions in β‐Rhombohedral Boron

Werheit

Laux

Kuhlmann

1993

Physica Status Solidi (b)

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The anisotropy of the electronic interband transitions of 0-rhombohedra1 boron is determined by optical absorption measurements. The band gaps (indirect allowed transitions) are 1.32(1) and 1.50(1) eV for E 11 c, respectively, 1.29(1) and 1.46(1) eV for E I c (extrapolated to T = 0 K). At low temperatures these gaps decrease, while the thermal equilibrium develops. The temperature dependence of the gap isattributed to the thermaldisorder caused byphonons of 121.9(E 11 c)and 94.1 meV(E I c) representing the most prominent intraicosahedral vibrations. Six intrinsic trapping levels for electrons in distances between 0.17 and 1.15 eV from the conduction band edge are determined, the closer ones in agreement with different photo effects. The trapping levels are attributed to distortion states of the icosahedra due to a dynamical Jahn-Teller effect. This conception allows the interpretation of other physical properties like internal friction, discontinuities of thermal expansion, and electrical conductivity, of the temperature dependence of the ESR linewidth, and of the density of paramagnetic centers (spin density and magnetic susceptibility).Die Anisotropy der elektronischen Interbandubergange des P-rhomboedrischen Bors wurde aus der optischen Absorption bestimmt. Die Bandabstande (indirekt erlaubte Ubergange) betragen, extrapoliert auf T = 0 K, 1,32(1) und 1,50(l)eV fur E 11 c bzw. 1,29(1) und 1,46(l)eV fur E l c. Bei tiefen Temperaturen nehmen die Bandabstande im Verlauf der Einstellung des thermischen Gleichgewichtes ab. Der Temperaturgang der Bandabstande wird der temperaturbedingten Fehlordnung des Gitters durch die thermische Anregung der starksten intraikosaedrischen Phononen bei 121.9 ( E 1) c) und 94,l meV ( E i c) zugeordnet. Sechs intrinsische Haftniveaus fur Elektronen in Ahtanden zwischen 0,17 und 1,15 eV vom Leitungsband werden nachgewiesen, die bandnahen sind in Ubereinstimmung mit verschiedenen Photoeffekten. Die Haftniveaus werden Verzerrungszustanden der Ikosaeder infolge eines dynamischen Jahn-Teller-Effektes zugeschrieben. Diese Konzeption erlaubt die Erklirung anderer physikalischer Eigenschaften wie der inneren Reibung, der Diskontinuitaten der thermischen Dilatation und der elektrischen Leitfahigkeit, der Temperaturabhangigkeit der ESR-Linienbreite sowie der Konzentration lokalisierter paramagnetischer Zentren (Spindichte und magnetische Suszeptibilitat).

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Thermal Conductivity of ZrB₂SiCB₄C from 25 to 2000 °C

et al. 2013

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The thermal diffusivities of ZrB2–SiC (10.7, 21.9, or 48.7 vol% SiC) with B4C sintering aid were measured over 25–2000 °C using laser flash. The composition with the highest SiC showed the highest thermal conductivity (k) at 25 °C, but the lowest above ≈400 °C, because of the greater k temperature sensitivity of the SiC phase. Finite difference calculations of k, using selected literature data for the individual phases, and the concentration of phases from microstructures, correctly predicted temperature and phase concentration dependencies, but were lower than experimental results. The k of pure ZrB2 and SiC as a function of temperature were back‐calculated from the experimental results for the multi‐phase materials; they were in good agreement with specific literature values.

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Thermal expansion of boron and boron carbide

Cited by 63 publications

References 1 publication

The coefficients of thermal expansion of boron arsenide (B12As2) between 25°C and 850°C

The coefficients of thermal expansion of boron arsenide (B12As2) between 25°C and 850°C

Interband and Gap State Related Transitions in β‐Rhombohedral Boron

Thermal Conductivity of ZrB₂SiCB₄C from 25 to 2000 °C

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Thermal expansion of boron and boron carbide

Cited by 63 publications

References 1 publication

The coefficients of thermal expansion of boron arsenide (B12As2) between 25°C and 850°C

The coefficients of thermal expansion of boron arsenide (B12As2) between 25°C and 850°C

Interband and Gap State Related Transitions in β‐Rhombohedral Boron

Thermal Conductivity of ZrB2SiCB4C from 25 to 2000 °C

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Thermal Conductivity of ZrB₂SiCB₄C from 25 to 2000 °C