Foamed glass-ceramic materials based on oil shale by-products

The feasibility and features of the production of foamed glass-ceramic materials based on oil shale ash were investigated. The optimal regime of synthesis found involved the following steps: glass fusion at 1400 °C, preparation of the glass powders and blending with the foaming agent. The foaming was carried out at 900 to 920 °C with a further one-stage crystallization at 790 to 820 °C. It was noted that the admixture of calcium carbonate, as a foaming agent, changed the phase composition of the resulting glass-ceramics by an increased rate of the crystallization process and the intensive formation of gehlenite simultaneously with diopside

Cyclic cocycles on twisted convolution algebras

We give a construction of cyclic cocycles on convolution algebras twisted by gerbes over discrete translation groupoids. For proper \'etale groupoids, Tu and Xu provide a map between the periodic cyclic cohomology of a gerbe-twisted convolution algebra and twisted cohomology groups which is similar to a construction of Mathai and Stevenson. When the groupoid is not proper, we cannot construct an invariant connection on the gerbe; therefore to study this algebra, we instead develop simplicial techniques to construct a simplicial curvature 3-form representing the class of the gerbe. Then by using a JLO formula we define a morphism from a simplicial complex twisted by this simplicial curvature 3-form to the mixed bicomplex computing the periodic cyclic cohomology of the twisted convolution algebras. The results in this article were originally published in the author's Ph.D. thesis.Comment: 39 page

Groupoids and an index theorem for conical pseudo-manifolds

We define an analytical index map and a topological index map for conical pseudomanifolds. These constructions generalize the analogous constructions used by Atiyah and Singer in the proof of their topological index theorem for a smooth, compact manifold $M$. A main ingredient is a non-commutative algebra that plays in our setting the role of $C_0(T^*M)$. We prove a Thom isomorphism between non-commutative algebras which gives a new example of wrong way functoriality in $K$-theory. We then give a new proof of the Atiyah-Singer index theorem using deformation groupoids and show how it generalizes to conical pseudomanifolds. We thus prove a topological index theorem for conical pseudomanifolds

Wastewater Treatment from Lead and Strontium by Potassium Polytitanates: Kinetic Analysis and Adsorption Mechanism

The reduction of heavy and radioactive metal pollution of industrial wastewater remains a vital challenge. Due to layered structure and developed surface, potassium polytitanate had potential in becoming an effective sorbent for metal extraction from wastewater in the presented paper. On the basis of the different sorption models, this paper studied the mechanism of Pb2+ and Sr2+ cation extraction from aqueous solution by non-crystalline potassium polytitanate produced by molten salt synthesis. The ion exchange during metal extraction from model solutions was proven by kinetic analysis of ion concentration change, electronic microscopy, and X-ray fluorescence analysis of sorbent before and after sorption, as well as by theoretical modeling of potassium, lead, and strontium polytitanates. The sorption was limited by the inner diffusion in the potassium polytitanate (PPT) interlayer space, as was shown using the Boyd diffusion model. The sorption processes can be described by Ho and McKay’s pseudo-second-order model compared to the Lagergren pseudo-first-order model according to kinetic analysis. It was found that the ultimate sorption capacity of synthesized sorbent reached about 714.3 and 344.8 (ions mg/sorbent grams) for Pb2+ and Sr2+ ions, respectively, which was up to four times higher than sorption capacity of the well-known analogues. Therefore, the presented study showed that potassium polytitanate can be considered as a promising product for industry-scaled wastewater purification in practice

Computer modelling of nonisothermal transfer of moisture during drying of wood with the use of the computing environment mathcad

This study explores the features of process of drying internal heat and mass transfer in wood in the conditions of essentially noniso-thermal transfer of moisture. The process of capillary conductivity of wood is analyzed on the model of colloidal capillary-porous solid. The density of moisture flows caused by the phenomenon of thermal and hydraulic conductivity is determined. Previously experimentally established fact of influence on the process of moisture removal of the current moisture content of wood is analytically confirmed. De-pendences of the phase transition criterion taking into account the direction of the temperature gradient and wood moisture are analytically obtained. Recommendations are given to determine the thermogradient coefficient taking into account the asymmetry of moisture flows depending on the direction of the temperature gradient, and also for the correction in the entry form of the equation of moisture transfer with the influence of the effect of thermal and hydraulic conductivity. © 2018 CEUR-WS. All rights reserved

Strong and chemically inert sinter crystallised glass ceramics based on Estonian oil shale ash

In heat and power production, oil shale combustion forms substantial amounts of solid waste, including fly ash. The present paper is dedicated to the manufacturing of frit derived glass ceramics from melting high amounts of this waste (65\u201367 wt-%) combined with inexpensive minerals, such as rhyolite (33\u201335 wt-%). Owing to a surface mechanism of crystallisation, fine powders led to glass ceramics with high strength and reliability, even for rapid treatments (fast heating, at a rate of 40uC min21, followed by 30 min holding stage). To minimise the presence of pressing and demoulding induced defects, the tiles were prepared by incorporating binders, i.e. polyethylene glycol or kaolin, to the frit mixtures. Finally, the stabilising effect of recycled borosilicate glass powders, mixed with waste derived glass powders, was also investigated with promising results for the production of a chemically stable material

Overview of current trends in SOFC materials

Because of their potential to reduce the environmental impact and geopolitical consequences of the use of fossil fuels, fuel cells have emerged as sustainable power generation systems. Like a combustion engine, a fuel cell uses a chemical fuel as its energy source; but like a battery, the chemical energy is directly converted into electrical energy. In addition to high efficiency and low emissions, fuel cells are attractive for their modular and distributed nature, and zero noise pollution. SOFC single cells and stack systems are multilayer structures consisting of ceramic and metallic materials with different well defined electrical transport properties. All components have to show well-adjusted thermal expansion behaviour, chemical compatibility of material interfaces and chemical stability in the prevailing temperature and gas atmosphere. Performance and long-term stability improvements at affordable costs can be obtained by lowering the operating temperature. This goal requires drastic reduction of electrodes polarisation resistance as well as highly-conducting electrolyte materials. The use of new and nanostructured material and the application of appropriate technologies for the production of optimized microstructure becomes essential for highly efficient SOFCs operating in the medium and low temperature range. A review of state-of-art materials is given together with a perspective presentation of innovative materials and technologies for new types of SOFC