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Abstract—The possibility of low-temperature in situ synthesis of (Ti, W)C using plasma-chemical WC nanopowders and industrial micron TiC powders is demonstrated. Sintering/synthesis of WC–(25, 50, and 75) wt % TiC is carried out by electric pulsed ("spark") plasma sintering (SPS) by heating powders in a vacuum at a rate of 50°C/min to a temperature of more than 1200°C under conditions of applying a stress of 70 MPa. It is established that the synthesis proceeds most efficiently in nanopowders with an addition of 50 and 75 wt % TiC. It is shown that the joint use of plasma-chemical synthesis of nanopowders and SPS makes it possible to obtain fine-grained (with a grain size of less than 1 μm) samples with increased density and satisfactory mechanical properties (Vickers hardness is 17–18 GPa, and minimum Palmquist crack resistance coefficient is ~3 MPa m1/2). [ABSTRACT FROM AUTHOR]

The sintering mechanisms of WC–Al2O3 nanopowder compositions with different contents of al-umina particles (1, 3, and 5 wt %) have been studied. The samples of WC–Al2O3 ceramics are obtained by electropulse (spark) plasma sintering (SPS) in vacuum by heating to a temperature of 1450°C at a rate of 50°C/min under a uniaxial stress of 70 MPa. Plasma-chemical nanopowders of tungsten monocarbide and submicron powders of alumina are used to fabricate the ceramics. The density, microstructure, phase composition, microhardness (HV), and crack resistance (KIC) of the ceramics have been studied. It has been shown that the use of SPS enables the production of WC-Al2O3 ceramics with a high relative density (95.4–98.1%) and a homogeneous microstructure with the ultrafine grain size (0.1–0.2 μm). The X-ray phase analysis has shown that during the SPS of WC–Al2O3 ceramics the formation of undesirable W2C phase occurs which results in a decrease in the crack resistance. To reduce the intensity of formation of W2C particles, free carbon in the form of colloidal graphite (0.1, 0.2, and 0.3 wt %) is introduced into the WC–Al2O3 ceramic. Using the Young–Cutler model and the model of diffusion resorption of pores it has been shown that the main mechanism behind the SPS of WC–Al2O3 ceramics is a grain-boundary diffusion. It has been found that the introduction of graphite leads to a decrease in the activation energy of SPS of the WC–Al2O3 ceramics, which is probably due to a reduction in the W2C particle content to 0.5 wt %. [ABSTRACT FROM AUTHOR]

The paper is based on the results of a study of secondary school principal decision-making styles conducted in eight regions of the Russian Federation (one per federal district) in 2014 using the methodological approach developed by Alan J. Rowe. The study aimed to assess the reformist potential of Russian school principals. We believe that this potential is determined in the present context by a leadership style that involves teachers in decision-making processes and the delegation of responsibilities to them in uncertain situations that require them to solve extremely complex tasks. Using the two-factor leadership model proposed by B. Bass, we suggest that either the transformational or transactional leadership style may prove to be effective depending on a given school's individual circumstances. Consequently, two types of leaders may be the most effective in terms of their ability to enact reforms: (1) principals who mainly exhibit a conceptual decision-making style and secondarily make recourse to an analytical style; (2) principals who mainly exhibit an analytical decision-making style and secondarily make resource to a conceptual style. The article establishes that only 12% of school principals apply the conceptual decision-making style while relying on an analytical style to a secondary degree. These are the principals who we classify as transformational leaders. Only 11% are effectively prepared to implement changes given a specific environment. These are the transactional leaders who are likely to change their leadership style for a transformational one. [This article was translated by Kenneth Cargill.]

Low-temperature synthesis of ceramics and cemented carbides based on plasma-chemical tungsten and titanium carbides nanopowders and micron-sized commercial titanium carbide powders has been investigated. Compact samples were prepared by spark plasma sintering (SPS), which consists in high-speed heating of powders at a rate of 50°C/min in vacuum under pressure up to 70 MPa. Compact samples with high density were obtained in a narrow temperature region above 1000. Phase evolution of double carbide having FCC lattice is considered based upon XRD data. A model for calculating the theoretical density of this phase is proposed, the calculated values agree with the experimental data. [ABSTRACT FROM AUTHOR]