Electrical conductivity of boron carbide from ∼5 to ∼2100 K in the whole homogeneity range

Werheit, H.; Herstell, Bernhard; Winkelbauer, Walter; Pristáš, G.; Gabáni, S.; Flachbart, К.; Shalamberidze, Sulkhan

doi:10.1016/j.solidstatesciences.2022.106987

Cited by 8 publications

(6 citation statements)

References 33 publications

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“…The activation energies obtained from the electrical conductivity are displayed in Figure 7, showing that at ~B8C, the homogeneity range is divided into two parts with significantly different electronic characteristics. The activation energy at about 80 meV found in both regions is uncertain as obtained in that range of temperature, where a continuous transition from thermal excitation to variable-range hopping takes place (see [37]). Former theoretical studies on boron carbide were not very helpful in understanding the complex interactions between structural details and electronic properties [45][46][47][48][49][50][51], as they were based on idealized structure models deviating more or less considerably from the real structures.…”

Section: Phase Transition Near the Compound B8cmentioning

confidence: 79%

“…The activation energies obtained from the electrical conductivity are displayed in Figure 7, showing that at ~B8 C, the homogeneity range is divided into two parts with significantly different electronic characteristics. The activation energy at about 80 meV found in both regions is uncertain as obtained in that range of temperature, where a continuous transition from thermal excitation to variable-range hopping takes place (see [37]). It is expected that this phase transition is correlated with a structural change.…”

Section: Phase Transition Near the Compound B 8 Cmentioning

confidence: 79%

“…Reliable information on the electronic structure of more boron-rich boron carbide is obtained from electrical conductivity, measured between 5 and 2100 K by Werheit et al [37], by Wood [38,39] and by Aselage et al [40]. Results obtained by Amulele et al [41] up to 9 GPa pressure are compatible.…”

Section: Phase Transition Near the Compound B8cmentioning

confidence: 94%

“…High-quality B 4.3 C single crystals were used in References [10,35,36]. Figure 4 shows a collection of transition energies, consistently obtained from optical absorption such as those shown in Figure 5, indicating interband transitions at 2.09 and 2.41 eV and from electrical transport measurements (see [37][38][39][40][41] and references cited therein). [3,4,42].…”

Section: Electronic Structure Of B 43 C At Ambient Conditionsmentioning

confidence: 99%

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Phase Transitions in Boron Carbide

Werheit

2023

Materials

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The idealized rhombohedral unit cell of boron carbide is formed by a 12-atom icosahedron and a 3-atom linear chain. Phase transitions are second order and caused by the exchange of B and C sites or by vacancies in the structure. Nevertheless, the impact of such minimal structural changes on the properties can be significant. As the X-ray scattering cross sections of B and C isotopes are very similar, the capability of X-ray fine structure investigation is substantially restricted. Phonon spectroscopy helps close this gap as the frequency and strength of phonons sensitively depend on the bonding force and mass of the vibrating atoms concerned. Phase transitions known to date have been identified due to significant changes of properties: (1) The phase transition near the chemical composition B8C by clear change of the electronic structure; (2) the endothermic temperature-dependent phase transition at 712 K according to the change of specific heat; (3) the high-pressure phase transition at 33.2 GPa by the drastic change of optical appearance from opacity to transparency. These phase transitions affect IR- and Raman-active phonons and other solid-state properties. The phase transitions at B~8C and 712 K mean that a well-defined distorted structure is converted into another one. In the high-pressure phase transition, an apparently well-defined distorted structure changes into a highly ordered one. In all these cases, the distribution of polar C atoms in the icosahedra plays a crucial role.

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Section: Phase Transition Near the Compound B8cmentioning

confidence: 79%

“…The activation energies obtained from the electrical conductivity are displayed in Figure 7, showing that at ~B8 C, the homogeneity range is divided into two parts with significantly different electronic characteristics. The activation energy at about 80 meV found in both regions is uncertain as obtained in that range of temperature, where a continuous transition from thermal excitation to variable-range hopping takes place (see [37]). It is expected that this phase transition is correlated with a structural change.…”

Section: Phase Transition Near the Compound B 8 Cmentioning

confidence: 79%

Section: Phase Transition Near the Compound B8cmentioning

confidence: 94%

Section: Electronic Structure Of B 43 C At Ambient Conditionsmentioning

confidence: 99%

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Phase Transitions in Boron Carbide

Werheit

2023

Materials

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“…Because of the better bonding structure, it was accumulated while doing so metal matrix composites. It leads to improving the upgraded system to achieve the exceptional mechanical-based characteristics in the nano-processed metal matrix composites [14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Tribological Behavior on Stir-Casted Metal Matrix Composites of Al8011 and Nano Boron Carbide Particles

Vinayaka¹,

Christiyan

Shreepad³

et al. 2023

Journal of Nanomaterials

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The aluminum metal matrix composites were broadly exploited in the applications of automotive, aerospace, and other defense with functionally graded materials-related application. Above applications definitely required excellent mechanical characteristics. Therefore, in this way, the major attempt was made on the nano-based composites with aluminum alloy utilization. In this research, aluminum alloy AA8011 and the ceramic-based reinforcement particles of nano boron carbide (B4C) were selected for producing the metal matrix composites by the liquefying process or stir casting route. The weight percentage of nano boron carbide particles having 15 wt% was subjected to add into the aluminum alloy during the stir casting process. Then, processed nano boron carbide and AA8011 specimens were prepared to conduct tribological behaviors with various processing conditions like sliding velocity, setting wear temperature, and applied load by the tribometer setup. The scanning electron microscope was employed to examine the processed composites samples and worn-out surface samples. Finally, the multiobjective optimization was used to measure the individual performances of the tribological parameters by the gray relational technique.

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