Low-temperature magnetostriction and distortions in the rare-earth Laves phases

The effects of partial substitution of dysprosium in Tb0.2Dy0.8Co2 by terbium and gadolinium on the structure and magnetic properties have been studied. Two compositions, Tb0.3Dy0.7Co2 and Tb0.2Dy0.7Gd0.1Co2 have been synthesized. Their crystal structure, in contrast to the structure of the original compound, has both tetragonal distortions and rhombohedral distortions at lower temperatures. Anomalies of magnetostriction and magnetocaloric effect near the observed magnetic phase transitions have been studied. The sign-alternating temperature dependences of the longitudinal and transverse magnetostrictions associated with various types of crystal structure distortions of the alloys are revealed

The influence of changes in the project on the reliability of heat power systems during construction and installation works

However, during the construction and reconstruction of existing heat networks, cases that lead to unstable operation of newly laid or replaced areas arise. An important task is to minimize the reasons that can cause damage to replaced areas. Factors that negatively affect the reliability include: laying pipelines without design documentation, non-compliance of the regulatory requirements for their laying by installation organizations. The assumptions of design engineers developing the project and installers laying the heating main can lead to negative consequences, including a decrease in the reliability of the facilities functioning. Physical deterioration, coupled with the above factors, leads to a large number of failures of heat networks. Breakthroughs reduce the reliability of the entire heat supply system, worsen the quality of the supplied coolant and lead to an increase in the cost of maintenance of heat networks by operating organizations. The paper considers the influence of changes in the project during the construction and installation works on the reliability of the heat supply system. Document type: Articl

Synthesis and characterisation of the vibrational and electrical properties of antiferromagnetic 6L-Ba2CoTeO6 ceramics

Optimal processing conditions for fabrication of dense single-phase 6L-Ba2CoTeO6 ceramics via the solid-state reaction method were determined. These ceramics possess a room-temperature crystal structure described by the centrosymmetric P[3 with combining macron]m1 space group. Polarized Raman spectroscopy enabled the observation of all the 25 predicted Raman modes and assignment of their symmetries. On cooling, BCTO ceramics exhibit two antiferromagnetic transitions at 3 K and 12.5 K, in broad agreement with a recent single-crystal study [P. Chanlert, N. Kurita, H. Tanaka, D. Goto, A. Matsuo and K. Kindo, Phys. Rev. B: Condens. Matter Mater. Phys., 2016, 93, 094420]. Low temperature Fourier-transform infrared reflectivity analyses suggest the antiferromagnetic phase transitions to be driven by small distortions of the CoO6 octahedra, lowering locally their C3v symmetry. This causes splitting of the associated vibrational modes, but without a long-range structural change. AC impedance spectroscopy revealed BCTO ceramics to be leaky insulators with an activation energy for conduction of ∼0.15−0.25 eV, which suggests electron hopping between mixed oxidation states of Co

Yttria co-doping of scandia-zirconia electrolytes for SOFCs

Scandia stabilised zirconias offer much better performance than the conventional yttria stabilised materials and now it seems that availability and cost may not be hugely problematic. This offers a very important way forward to fuel cell manufacturing. It is shown here that a small addition of 2 mol% yttria to scandia stabilised zirconia results in formation of the cubic phase and so avoids major phase changes in scandia only substituted zirconia, which we believe is likely to be detrimental to long term electrolyte stability. This addition of yttria can be achieved without significant impairment of the electrical conductivity of the scandia stabilised zirconia. Samples which are cubic throughout the studied temperature range, i.e. either effectively quenched scandia only or yttria co-doped show two linear conductivity regions in Arrhenius conductivity plots. Importantly the low temperature activation energy decreases and the high temperature activation energy increases as yttrium content increases and scandium content decreases. This correlates with shortrange order effects observed by neutron diffraction. Thus we have identified a new range of composition for use in solid oxide fuel cell electrolytes, which exhibits a good compromise between phase stability and electrical properties.</p

The impact of monitoring the state of heating networks on their effectiveness

© Published under licence by IOP Publishing Ltd. The tasks of improving the efficiency and reliability of the operation of heat and power equipment are associated with the renewal of fixed production assets and a reduction in the cost of carrying out repair and restoration activities. The increase in the cost of repair and maintenance, spare parts, installation and emergency repair work in the context of a shortage of funds dictates the need to develop and implement new maintenance technologies. In this regard, scientific developments aimed at improving the methods and means of assessing the technical condition of thermal power equipment are relevant