Effect of cobalt powder morphology on the properties of WC-Co hard alloys

The effect of cobalt powder morphology on the microstructure of WC-Co hard alloys produced by sintering cobalt + tungsten carbide powder mixtures has been studied using X-ray diffraction, laser diffraction, scanning electron microscopy, density measurements, and Vickers microhardness tests. The results indicate that, under identical sintering conditions, the densest and most homogeneous microstructure is formed in hard alloys sintered using cobalt powders consisting of rounded particles. The use of cobalt powders with dendritic morphologies impedes the homogenization of Co + WC powder mixtures and preparation of pore-free WC-Co hard alloys. © 2013 Pleiades Publishing, Ltd

Uncertainty as the substratum of entrepreneurship

© 2015, Mediterranean Center of Social and Educational Research. All rights reserved. The article addressed the stochastic issues of modern business environment, the content of the concepts of uncertainty and risk. The basis of the concept of business initiatives are defined through the prism of ontology of venture activities. It is proved that the risk enhances the capabilities of a subject and increases its adaptive capacity due to the timely actions. That is why the risk becomes the property of a particular resource that can improve the sustainability of a business entity acting in the face of uncertainty. The sources of uncertainty and risk are shown, being conditional to the implementation of particular subject activity in the business sector. From the standpoint of this study, risk is considered as an attribute of entrepreneurship, which is sure to arise in situations where alternatives are possible, realized in many outcomes. There is uncertainty about a particular outcome, and at least one of the outcomes is harmful. In a broad sense, the risk is understood as a solution associated with the choice of a wide variety of complementary or alternative options, the result of which is internally and unavoidably inherent with uncertainty. Thus, the risk is a characteristic of solutions made by the subject, reflecting the uncertainty of achieving the objectives of its activities. Uncertainty, acting as a substrate of entrepreneurship, is implemented in various alternative ways of achieving subjective goals. Under these conditions, the venture of business activity is manifested most clearly, and the risk is acquiring attribute qualities as an immanent feature of the modern business environment

Innovation infrastructure development trends of the Russian Federation

The role of innovations in formation of the effective infrastructure is unfolded in the article. The theoretical aspects of a concept disclosure, an input of foreign and domestic scientists are considered. System elements of the infrastructure environment are analysed

Innovation infrastructure development trends of the Russian Federation

The role of innovations in formation of the effective infrastructure is unfolded in the article. The theoretical aspects of a concept disclosure, an input of foreign and domestic scientists are considered. System elements of the infrastructure environment are analysed

Microstructure and phase composition of hard alloys produced from nanocrystalline powder mixture WC–6wt.%Co with C, Al and ZrC additives

A large specific surface area of WC nanopowder determines its high chemical activity and makes it very sensitive to various impurities, among which oxygen is most harmful and unavoidable. During heating, oxygen interacts with carbon of WC being removed in the form of CO/CO2, which finally leads to the appearance of embrittling η-phases in the hard alloy, abnormal growth of WC grains, and formation of a porous microstructure. To prevent heavy decarburization of WC during vacuum sintering of hard alloy from a nanocrystalline powder mixture WC–6wt.%Co, in this work we compared three methods: addition of extra carbon to compensate for carbon loss as a result of decarburization; addition of Al to bind impurity oxygen into Al2O3 before it interacts with carbon of WC; and addition of ZrC to compensate for carbon loss and bind impurity oxygen into ZrO2. Nanocrystalline powder mixtures based on WC–6 wt.%Co with and without additions of C, Al, and ZrC were prepared from microcrystalline powders of WC, Co, Al, ZrC, and carbon black by high-energy milling, then they were compacted in a cylindrical mold by uniaxial pressing at a pressure of ~460 MPa and sintered in graphite crucibles for 15 min at 1380 °C in vacuum of ~10–2 Pa. The heating rate to the temperature of sintering was 10 °C/min. The initial powders, powder mixtures prepared therefrom, and sintered hard alloys were certified using X-ray diffraction, chemical analysis, scanning electron microscopy, BET adsorption method, helium pycnometry, and Vickers method. The studies performed showed that the average particle size in all the prepared powder mixtures does not exceed 100 nm, and the content of impurity oxygen in them varies from 3.3 to 4.3 wt.% depending on the additives. It was established that only a part of oxygen contained in the powder mixtures is in the chemisorbed state and takes part in the decarburization of WC during vacuum sintering. The Al additive is completely oxidized during milling of the powder mixture and transforms into nanocrystalline Al2O3, which only aggravates carbon loss during sintering and results in the formation of a multiphase and relatively porous microstructure of the hard alloy. On the contrary, using carbon and ZrC additives we managed to prevent the decarburization of WC during sintering of the hard alloy and to form a less porous microstructure in it. It was shown that the presence of ZrO2 inclusions does not impede intensive growth of WC grains during sintering, but rather promotes it. Carbon deficit slightly suppresses intensive WC grain growth during sintering of hard alloy leading to the formation of η-phases and to an increase in the density and microhardness, but the presence of oxide inclusions Al2O3 and ZrO2 in the microstructure reduces the values of these properties. © 2023 Russian Neurological Journal. All rights reserved.Ural Branch, Russian Academy of Sciences, UB RAS: AAAA-A19-119031890029-7the study was carried out within the framework of the state assignment of the Institute of Solid State Chemistry of the Ural Branch of the Russian Academy of Sciences No. AAAA-A19-119031890029-7. The authors kindly acknowledge the assistance of O.V. Makarova in the density measurements and of L.Yu. Buldakova and D.A.Danilov in the determination of carbon and oxygen content in powders

Conformal symmetry in quasi-free Markovian open quantum systems

Conformal symmetry governs the behavior of closed systems near second-order phase transitions, and is expected to emerge in open systems going through dissipative phase transitions. We propose a framework allowing for a manifest description of conformal symmetry in open Markovian systems. The key difference from the closed case is that both conformal algebra and the algebra of local fields are realized on the space of superoperators. We illustrate the framework by a series of examples featuring systems with quadratic Hamiltonians and linear jump operators, where the Liouvillian dynamics can be efficiently analyzed using the formalism of third quantization. We expect that our framework can be extended to interacting systems using an appropriate generalization of the conformal bootstrap.Comment: 15 pages, supplementary Wolfram Mathematica notebook available at https://github.com/idnm/third_quantization v2: minor revision (references added, typos corrected) v2: Minor revisions done and typos correcte

К вопросу о технологиях непрерывной математической подготовки бакалавров технического направления

The mechanism of the development and introduction in educational process of didactic ensure continuous mathematical education of bachelors technical direction. It is shown that the continuous updating of mathematical knowledge is a necessary condition for the formation of the students required today abilities to the solution of professional tasks.Предложен механизм разработки и внедрения в учебный процесс, дидактического обеспечения непрерывной математической подготовки бакалавров технического направления. Показано, что непрерывная актуализация математических знаний является необходимым условием формирования у студентов требуемых сегодня способностей к решению профессиональных задач

EFFECT OF Al ADDITION ON THE PHASE COMPOSITION, MICROSTRUCTURE, AND MICROHARDNESS OF NANOCRYSTALLINE WC CERAMICS

Nanocrystalline WC and WC-Al powders were prepared by high energy ball milling and mixing in a planetary ball mill. The phase composition, microstructure and microhardness of ceramics sintered from these powders have been investigated