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The article presents experimental data, based on which the influence of various factors on the strength and thermophysical characteristics of porous heat-insulating materials was studied. Porous bodies in thermal power engineering are used for thermal protection of power plants, various aggregates, in thermal insulation structures of buildings and technological networks. The properties of these materials and the field of use depend on their chemical composition and method of production. The task of this research is to obtain a raw material mixture for heat-insulating material of the closed-cell type with increased thermal resistance and porosity by optimizing its qualitative and quantitative composition. The goal is also to improve the method of obtaining porous heat-insulating material by changing the temperature and time regimes in order to improve the physical, mechanical and operational characteristics, which will allow the material to be used in a wider temperature range. Based on the dependences of strength and thermophysical properties on the density of the finished material obtained in the work, it was concluded that the best characteristics are the samples of the porous material with the lowest density, which are formed at the maximum humidity of the raw material. Kinetics of drying and heat treatment of the raw material mixture, thermal regimes are the main factors that determine the porosity, strength and thermal conductivity of the finished heat-insulating material. Performed laboratory studies of the material proposed in the paper allow choosing the required temperature regimes of heat treatment. Thus, the task of further research is to choose a method of organizing effective heat and mass exchange, modeling these processes, experimental testing of the obtained data, and creating a method for determining the main technological and structural parameters of the method of obtaining a new material. The performed experimental studies made it possible to determine the conditions for the implementation of new technologies for the production of porous materials with the possibility of predictive determination of their properties., У статті наводяться експериментальні дані, на підставі яких вивчено вплив різних чинників на міцнісні та теплофізичні характеристики пористих теплоізоляційних матеріалів. Виконані лабораторні дослідження запропонованого у роботі матеріалу дозволяють підібрати потрібні температурні режими термообробки. Таким чином, завданням подальших досліджень є вибір методу організації ефективного тепломасообміну, моделювання цих процесів, експериментальна апробація отриманих даних та створення методу визначення основних технологічних та конструктивних параметрів способу отримання нового матеріалу. Виконані експериментальні дослідження дозволили визначити умови реалізації нових технологій одержання пористих матеріалів із можливістю прогнозного визначення їх властивостей.

The field of ceramics as well as the flexibility of the material class has been expanding rapidly in the last decades. Application wise, porosity is one of the most important parameters for modern ceramic materials, whether the materials in question are solid state conductive ceramics for energy conversion and storage, self-standing photo- and electrocatalyst materials, thermoelectric materials or macro-microporous bioceramics which utilize both macro- and micropores to help repair or replace damaged bone tissue. In this workshop, we will try to present both conventional (sacrificial templating) as well as state-of-the-art (supercritical drying, lithography) techniques to obtain open porous bioceramic bodies and try to elucidate on the issues regarding porosity control, sample preparation and experimental setup. We will cover the basics of precursors synthesis and what type of porosity can be controlled from which aspect. We also comment on the compressive strength trade off as a consequence of achieving high porosity.

Phosphate-based geopolymers (PGP) are a new type of geopolymers that have recently been studied due to the unresolved formation mechanism, as-achieved (micro)structure and possible applications. Thanks to their non-alkaline environment, PGPs have many advantages over alkaline analogues such as lack of efflorescence and better thermal properties. PGPs resemble to human bones and teeth (whose main constituents are calcium phosphates) stressing out their biocompatible application. PGP are usually obtained by mixing an aluminosilicate precursor with an acidic source of phosphate. In this work, we investigated the feasibility of preparing porous PGP from metakaolin and phosphoric acid via replica shaping. Polyurethane (PU) template was infiltrated by the geopolymer paste until a homogeneous green body was achieved. Green bodies were cured in a sealed vessel at 60 ℃ for 24 h in order to solidify their shape, while thereafter porous geopolymer ceramics were obtained by heat treatment to 600 °C at a rate of 1 ℃ min-1 enabling PU burnout. Samples were characterized through their porosity and morphology (SEM and adsorption behaviour) and chemical structure (XRD and ATR-FTIR). Consequently, with all of the aforementioned advantages, PGPs porous bodies were shown worthy of further investigation for fostering biomedical application.

We have studied theoretical and experimental methods of methanol adsorption in micropores of aluminum oxide agglomerates obtained by gas-dispersion synthesis. It is shown that the necessity to use strict equations based on the theory of volume filling of micropores, which implies a physical and formal analogy between the volume filling of micropores and capillary condensation, for qualitative and quantitative description of adsorption equilibrium in open slit-like micropores. The applicability of the proposed equations for the description of adsorption equilibrium in such systems is demonstrated on the example of experimental methanol adsorption/desorption isotherm on the aluminum oxide, which possesses a microporous structure.

Bioactive glass 45S5 foams were produced using a powder technology process developed by The National Research Council Canada-Industrial Materials Institute. NRC-IMI's proprietary process, combining powder technology and polymer foam technique, allows the production of materials having different structures and properties. It can be used to produce components into various forms, such as fully porous bodies or coatings on solid structures. During foaming, the foaming agent is decomposed and expands the binder-bioactive glass suspension. Then, the binder is burnt out by heating the sample at 500°C and finally the bioactive glass particle network is sintered to consolidate the material. Foams sintered at various temperatures were characterized from a microstructural and mechanical point of view. The foam structure and properties are affected by the sintering temperature when it is varied between 950°C and 1025°C. Foams exhibited open porosity (64%-79%) and pore size (335-530 μm) optimal for bone ingrowth. In all cases, the glass crystallized during sintering and the material was mostly composed of Na6Ca 3Si6O18 and Na2Ca 4(PO4)2SiO4 phases. The mechanical strength increased from 1.7 to 5.5 MPa while the density of the material increased from 0.56 to 0.97 g/cm3. © 2012 The American Ceramic Society.

A finite element method employing Galerkin's approach is developed to analyze free convection heat transfer in axisymmetric fluid saturated porous bodies. The method is used to study the effect of aspect ratio and radius ratio on Nusselt number in the case of a porous cylindrical annulus. Two cases of isothermal and convective boundary conditions are considered. The Nusselt number is always found to increase with radius ratio and Rayleigh number. It exhibits a maximum when the aspect ratio is around unity; maximum shifts towards lesser aspect ratios as Rayleigh number increases. Results are compared with those in the literature, wherever available, and the agreement is found to be good.