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Current Materials Used for Neutron Detection
Published in Alan Owens, Semiconductor Radiation Detectors, 2019
Boron nitride (BN) is a refractory compound of boron and nitrogen, which crystallizes in three allotropic modifications. Like carbon, the hexagonal form (h-BN) is the most stable and consists of layers of tiny platelets similar to graphite. The cubic variety (c-BN) is analogous to diamond, and while it is softer (it is the second hardest material known), its thermal and chemical stability properties are superior. Cubic-BN has an indirect bandgap of 6.4 eV at room temperature and has in fact the largest indirect bandgap of the diamond-like semiconductors. However it is metastable at standard conditions and converts to h-BN when heated to 1700 K in vacuum. A third wurtzite modification also exists (w-BN) although it is metastable at all conditions in the solid state.
General Information About Electrical Heating Elements
Published in Thor Hesborn, Integrating Electrical Heating Elements in Appliance Design, 2017
Boron nitride, BN, has low thermal expansion and high thermal conductivity. This results in high thermal shock resistance. Its mechanical strength is low, and it can be used only at low temperatures in air. It is used as an additive to other ceramics to increase the thermal conductivity.
Selection and Application of Solid Lubricants as Friction Modifiers
Published in Leslie R. Rudnick, Lubricant Additives, 2017
A reaction process generates boron nitride. Boric oxide and urea are reacted at temperatures from 800°C to 2000°C to create the ceramic material. Two chemical structures are available: cubic and hexagonal boron nitride. As one might expect, the hexagonal boron nitride is the lubricating version. Cubic boron nitride is a very hard substance used as an abrasive and cutting tool component. Cubic boron nitride does not have any lubrication value. The hexagonal version of boron nitride is analogous to graphite and molybdenum disulfide. The structure consists of hexagonal rings of boron and nitrogen, which are connected to each other, forming a stack of planar hexagonal rings. As with graphite, boron nitride exhibits a platelet structure.
On the effect of local torsion on the electromechanical properties of armchair boron nitride nanoribbons
Published in Molecular Physics, 2022
R. Sadeghi, M. Yaghobi, M. R. Niazian, M. A. Ramzanpour
In recent years, caused by the attractive chemical and physical properties of the fullerene, a spherical allotrope of carbon, several research groups have investigated the properties of fullerene-like structures which are made from other atoms, including the members of the groups III, IV and V of the periodic table [1,2]. These attractive properties have resulted in finding different applications for these fullerene-like structures [3]. Similarly, physical and chemical properties of two-dimensional (2D) graphene-like nanostructures have also been considered for investigation [4]. Boron nitride (BN) is an inorganic compound with equal numbers of boron and nitrogen atoms which is isoelectronic to a similarly structured carbon lattice and exists in various crystalline forms. Among the BN polymorphs, the hexagonal form which is similar to the graphite is the softest and most stable structure [5].
Latest trends for structural steel protection by using intumescent fire protective coatings: a review
Published in Surface Engineering, 2020
Muhammad Yasir, Faiz Ahmad, Puteri Sri Melor Megat Yusoff, Sami Ullah, Maude Jimenez
Wang et al. [210,211] studied the incorporation of nano-boron nitride in a waterborne multilayer IC. 3% of micron-sized or nano-sized particles were added in the system. The multilayered structure of the boron nitride made it highly chemical resistant and thermally stable. The dispersion of nano-sized boron nitride was much easier as compared to micron-sized particles, indicating sedimentation properties. Due to the uniform foam formation by the nano-boron nitride particles, they showed thermal resistance as compared to micron-sized boron nitride. The multilayered structure of the nano-boron nitride precluded the transfer of the hydrophilic flame retardants into the coating formulation after weathering test. Due to this, the thermal resistance of the nano-boron nitride enhanced after aging.
The application of nanogenerators and piezoelectricity in osteogenesis
Published in Science and Technology of Advanced Materials, 2019
Fu-Cheng Kao, Ping-Yeh Chiu, Tsung-Ting Tsai, Zong-Hong Lin
Boron nitride nanotubes (BNNTs) have shown great potential for practical use in many areas due to their excellent intrinsic properties, including superior mechanical strength, high thermal conductivity, electrically insulating behavior, piezoelectric property, neutron shielding capability, and oxidation resistance [90]. The piezoelectric property of BNNT is superior to that of piezoelectric polymers, with a d33 coefficient of 0.3 pC/N [91]. Over the last few years, BNNT has gained increasing attention in the field of osteogenesis, owing to its favorable biocompatibility, large specific surface area, and superior mechanical properties [92]. BNNT composite scaffolds have been shown to have a positive influence on osteogenesis and osteoinductive properties, owing to more calcium deposition and up-regulated expression levels of osteoblast markers, as presented in the study by Shuai et al [93]. (Figure 11). Xia Li et al. also presented similar results indicating that a BNNT layer could promote the attachment and growth of mesenchymal stem cells and enhance ALP activity, a marker of osteogenic differentiation [94]. Moreover, the positive influence on cell proliferation and attachment to BNNT seems to be exclusively related to osteoblasts, but not on chondrocytes, fibroblasts, or smooth muscle cells [95]. Therefore, BNNT is potentially useful for bone regeneration and orthopedic applications.