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Vol 63, No 14 (2018)
- Year: 2018
- Articles: 4
- URL: https://journal-vniispk.ru/0036-0236/issue/view/10317
Article
Manganese Pnictides MnP, MnAs, and MnSb are Ferromagnetic Semimetals: Preparation, Structure, and Properties (a Survey)
Abstract
Manganese pnictides MnP, MnAs, and MnSb are ferromagnetic semimetals and have some unique properties, namely, high Curie points, considerable magnetic anisotropy, and giant magnetocaloric effect. Experimental and theoretical studies showed that these compounds can enter a superconducting state under high external pressures. Manganese pnictides are widely used in design of hybrid structures, such as spin diodes and transistors, in combination with semiconductors. The survey focuses on the design and properties of such the structures.
1753-1763
Structural Features of Monomeric Octahedral Monooxo d2-Rhenium(V) Complexes [ReO(Ltrin)(Lmono)2] and [ReO(Ltrin)(Lbim)] with Oxygen Atoms of Tridentate Chelating (O, N, O) Ligands (Ltrin) (Review)
Abstract
Structural features of 22 mononuclear octahedral monooxo d2-Re(V) complexes with tridentate chelating (О, N, О) ligands (Ltrin)—[ReO(Ltrin)(Lmono)2] and [ReO(Ltrin)(Lbim)] (Lmono is a monodentate ligand, is a bidentate ligand)—have been considered. Conditions for selecting ligands that can be located trans to the multiply bonded O(oxo) ligand are discussed.
1764-1771
ZrB2/HfB2–SiC Ultra-High-Temperature Ceramic Materials Modified by Carbon Components: The Review
Abstract
The review has been made of recent publications on modification of ZrB2/HfB2–SiC ultra-hightemperature ceramic composite materials (UHTC) by carbon components: amorphous carbon, graphite, graphene, fibers, and nanotubes. Available data have been presented on some aspects of oxidation of such materials at temperatures ≥1500°C and both at the atmospheric pressure and at the reduced oxygen partial pressure; structural features of the formed multilayer oxidized regions have been noted. It has been considered how the type and content of the carbon component and the conditions (first of all, temperature) of UHTC production affect the density, flexural strength, hardness, fracture toughness, and thermal and oxidation resistance of the modified ceramic composites.
1772-1795
Crystal Chemistry of Lithium Intermetallic Compounds: A Survey
Abstract
The structural chemistry of lithium intermetallic compounds that are formed in Li–М binary systems where М = Ca, Sr, Ba, Mg, Zn, Cd, and Hg is surveyed. It is for the first time that the crystal structures of intermetallic compounds are classified in terms of polyhedral precursor metal clusters (in the program package ToposPro). The precursor metal clusters of crystal structures are identified using the algorithms of partitioning structural graphs into cluster structures and via the design of the basal 3D network of the structure in the form of a graph whose nodes correspond to the positions of the centers of precursor clusters. Tetrahedral precursor metal clusters M4 are identified for the crystal structures LiZn3-oC4, LiMg3-hP2, LiCd3-hP2, LiHg3-hP8, (LiMg3)(Li2Mg2)-tI16, Li2Zn2-cF16, Li2Cd2-cF16, Li2Hg2-cP2, Li3Cd-cF4, and Li3Hg-cF16; tetrahedral metal clusters M4 are found for the framework structures with spacer atoms Sr(Li2Sr2)-tP20, Ca2(Li4)-cF24, and Ca2(Li4)-cP12; tetrahedral metal clusters M4 and rings M6, for framework structures Ba3Li2(Li10)-hP30 and Ba3Li2(Li4In6)-hP30; icosahedral metal clusters M13 for the framework structure Li(Zn13)-cF112; bilayer tetrahedral metal clusters 0@М4@M22 for the framework structure Li23Sr6-cF116; and deltahedra М17 and deltahedra М30, for framework structures Sr4Li14 [Sr(Sr4Li12)] [(Sr2 (Sr8Li18)]-tI252 and Ba4Li14 [Ba(Ba4Li12)][(Ba2 (Ba8Li18)]-tI252. The scenario of crystal structure self-assembly from precursor metal clusters S30 in intermetallic compounds is reconstituted as: primary chain S31→ microlayer S32→ microframework S33.
1796-1811