МНОГОФАЗНО-ОДНОФАЗНыЕ РЕВЕРСИВНыЕ ЭЛЕКТРОМАШИННО-ВЕНТИЛЬНыЕ ПРЕОБРАЗОВАТЕЛИ БЕСКОНТАКТНыХ МАШИН ДВОЙНОГО ПИТАНИЯ

Розглянуто процеси в багатофазно-однофазних реверсивних електромашинно-вентильних перетворю- вачах безконтактних машин подвійного живлення. Рассмотрены процессы в многофазно-однофазных реверсивных электромашинно-вентильных преобра- зователях бесконтактных машин двойного питания

Potential ultra-incompressible material ReN: first-principles prediction

The structural, elastic and electronic properties of ReN are investigated by first-principles calculations based on density functional theory. Two competing structures, i.e., CsCl-like and NiAs-like structures, are found and the most stable structure, NiAs-like, has a hexagonal symmetry which belongs to space group P63/mmc with a=2.7472 and c=5.8180 \AA. ReN with hexagonal symmetry is a metal ultra-incompressible solid and has less elastic anisotropy. The ultra-incompressibility of ReN is attributed to its high valence electron density and strong covalence bondings. Calculations of density of states and charge density distribution, together with Mulliken atomic population analysis, show that the bondings of ReN should be a mixture of metallic, covalent, and ionic bondings. Our results indicate that ReN can be used as a potential ultra-incompressible conductor. In particular, we obtain a superconducting transition temperature T$_c$=4.8 K for ReN.Comment: 21 pages, 6 figures, 3 table

Pharaoh's Serpents: New Insights into a Classic Carbon Nitride Material

The combustion of mercury(II) thiocyanate to form "Pharaoh's serpents" is a spectacular reaction first described nearly two centuries ago. The large volume of distinctive yellow branches that grow from a tiny quantity of flaming reactants makes this an enchanting demonstration, often used to depict the magic of chemistry. In recent years several videos of this bizarre process have "gone viral" online. Formally, the reaction should yield a carbon nitride with the ideal formula C 3 N 4 along with HgS. However, since early characterization attempts there has been little further study of the materials produced. Herein we apply modern characterization techniques to reinvestigate the nature of the carbon nitride and its intimate relationship to the HgS produced. The HgS phase forms nanoparticles that decorate the surfaces of a C 3 N 4 foam matrix. Both of these compounds are important wide-gap semiconductors and we propose that the "Pharaoh's serpents reaction" could be used to produce a potentially important heterojunction nanocomposite materials that could be useful optoelectronic and photocatalytic applications

Carbon nitrides: synthesis and characterization of a new class of functional materials

Carbon nitride compounds with high N[thin space (1/6-em)]:[thin space (1/6-em)]C ratios and graphitic to polymeric structures are being investigated as potential next-generation materials for incorporation in devices for energy conversion and storage as well as for optoelectronic and catalysis applications. The materials are built from C- and N-containing heterocycles with heptazine or triazine rings linked via sp2-bonded N atoms (N(C)3 units) or –NH– groups. The electronic, chemical and optical functionalities are determined by the nature of the local to extended structures as well as the chemical composition of the materials. Because of their typically amorphous to nanocrystalline nature and variable composition, significant challenges remain to fully assess and calibrate the structure–functionality relationships among carbon nitride materials. It is also important to devise a useful and consistent approach to naming the different classes of carbon nitride compounds that accurately describes their chemical and structural characteristics related to their functional performance. Here we evaluate the current state of understanding to highlight key issues in these areas and point out new directions in their development as advanced technological materials.Our work on carbon nitride materials has been supported by the EPSRC (EP/L017091/1) and the EU Graphene Flagship grant agreement No. 696656 - GrapheneCore1. Additional support to advance the science and technology of these materials was also received from the UCL Enterprise Fund and the Materials Innovation Impact Acceleration funding enabled by the UK EPSRC

Synthese und Eigenschaften von Kohlenstoffnitriden

In der hier vorliegenden Arbeit über die „Synthese und Eigenschaften von Kohlenstoffnitriden“ wird im ersten Teil über die Synthese, die Strukturaufklärung, thermische Stabilität und die optischen Eigenschaften von Tri-s-triazin Derivaten (Cyamelurate, Melonate, Melem usw.) berichtet. Weil sich molekulare und polymere Tri-s-triazin Derivaten relativ einfach in reiner Form darstellen lassen, wurden sie als Precursoren zur Herstellung von harten Kohlenstoffnitriden ausgewählt. Im zweiten Teil werden die in der Diamantstempel-Hochdruckaparatur (DAC) durchgeführten Hochdrucksynthesen und die Charakterisierung der CN-Hochdruckphasen dargestellt. HT-HP-Umwandlungsversuche, die mit aromatischen Verbindungen wie Melon und Melem durchgeführt wurden, bildeten keine kristallinen Produkte. Jedoch führten die HT-HP-Experimente mit Dicyandiamid unter gleichen Herstellungsbedingungen teilweise zu kristallinen CN-Phasen. In den Proben, die bei Drücken zwischen 27-40 GPa und bei Temperaturen zwischen 1700-2400 °C synthetisiert wurden, ließ sich mit in situ Raman-Untersuchungen und teilweise mit Elektronenbeugung das Vorliegen kristalliner Bereiche nachweisen. Mittels EELS-Untersuchungen wurde die Zusammensetzung der Probenbereiche bestimmt (N:C Verhältnis zwischen 0,33 und 1,33) und die Abwesenheit von Sauerstoff belegt. Der Wasserstoffgehalt wurde mit Hilfe von Nano-SIMS-Untersuchungen bestimmt. Eine Röntgenstrukturanalyse der kristallinen Phase ist aufgrund der geringen Probemenge nicht gelungen, weshalb auch keine eindeutige Strukturlösung gefunden werden konnte. Dennoch konnte anhand der Elektonenbeugungsbilder ein Strukturvorschlag in der kubischen I213 Raumgruppe vorgestellt werden