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Том 61, № 13 (2016)
- Год: 2016
- Статей: 3
- URL: https://journal-vniispk.ru/0036-0236/issue/view/10185
Article
Structure, physicochemical properties, and reactivity of the [B9H9]2– anion
Аннотация
Data on the structure, properties, and reactivity of one of the least studied 3D aromatic clusters—nonahydro-closo-nonaborate anion [B9H9]2–—have been systematized. It has been shown that the key aspects of its reactivity are related to structural flexibility, which essentially distinguishes the [B9H9]2– anion from the higher representatives of closo-borate anions.
1629-1648
Preparation of MB2/SiC and MB2/SiC-MC (M = Zr or Hf) powder composites which are promising materials for design of ultra-high-temperature ceramics
Аннотация
This survey shows the prospects of studies targeted at preparing MB2/SiC and MB2/SiC-MC (M = Zr or Hf) nanosized composite powders for use in the manufacture of ultra-high-temperature ceramics (UHTCs) and antioxidant protective coatings on Cf/C and Cf/SiC composites. The survey considers the specifics of various preparation methods, including sol-gel technology or precipitation followed by borothermic/ carbothermic reduction, self-propagating high-temperature synthesis (SHS), specifically variants combined with mechanochemical activation or spark plasma sintering (SPS), chemical modification of ZrB2(HfB2) powders with polycarbosilane followed by pyrolysis, and dispersion of appropriate ceramics with the stabilization of the slurry. The elemental and phase compositions, particle sizes, microstructures, and some other characteristics of the products reported in the related literature are summarized.
1649-1676
Quantum-chemical modeling of lithiation–delithiation of infinite fibers [SinCm]k (k = ∞) for n = 12–16 and m = 8–19 and small silicon clusters
Аннотация
In the framework of the search for promising anode materials for lithium-ion batteries and with the aim of studying the behavior of silicon–carbon composites during cycling, quantum-chemical modeling of the structure, stability, and electronic properties of silicon-coated carbon fibers has been performed. Calculations of loose infinite nanofibers [SinCm]k (k = ∞) for n = 12–16 and m = 8–19 have been performed by the density functional theory method with inclusion of gradient correction and periodic boundary conditions. It has been demonstrated that infinite nanofibers SinCm have a large number of voids, promising for the accumulation of lithium without noticeable changes in lattice parameters, and a near-zero gap. The lithiation–delithiation of the Si21 cluster and infinite nanofibers [Si16C19] for Li: Si = 1: 1, 2: 1, 3: 1, and 4: 1 has been modeled.
1677-1687