Foamed Geopolymer Composites with the Addition of Glass Wool Waste

This study examines foamed geopolymer composites based on fly ash from the Skawina coal-fired power plant in Poland. The paper presents the effect of adding 3% and 5% by weight of glass wool waste on selected properties of foamed geopolymers. The scope of the tests carried out included density measurements, compressive and bending strength tests, measurements of the heat conduction coefficient, and the results of measurements of changes in thermal radiation in samples subjected to a temperature of 800 °C. The obtained results indicate that glass wool waste can be successfully used to lower the density and heat conduction coefficient of foamed geopolymer composites with a fly ash matrix. In addition, the results of changes in thermal radiation in the samples subjected to the temperature of 800 °C showed a positive effect of the addition of glass wool waste. Moreover, the introduction of the addition of glass wool waste made it possible to increase the compressive strength of the examined foamed geopolymers. For the material modified with 3% by weight of mineral wool, the increase in compressive strength was about 10%, and the increase in fibers in the amount of 5% by weight resulted in an increase of 20% concerning the base material. The obtained results seem promising for future applications. Such materials can be used in technical constructions as thermal insulation materials.

Investigation of the effect of B4C amount and sintering temperature on the thermal properties of the material in Al 1070–B4C composites

Today, the usage area of metal matrix and ceramic reinforced composites is increasing and researches in this field are increasing. However, majority of the studies conducted are constituted of studies on investigation of mechanical features of composites. One of the reasons why composite materials are preferred is because these materials have improved thermal property. With this experimental study, it is aimed to contribute to the literature in the area of investigating features of thermal properties. In this study, composite materials were produced at 500 °C, 550 °C and 600 °C sintering temperatures by adding 4%, 8% and 16% B4C to Al 1070 quality aluminium by powder metallurgy technique. Firstly, the microstructures of the composites were investigated. Then, experiments were conducted to determine the specific heat of composite materials at different ambient temperatures together with thermal conductivity measurements. With the data obtained from the experiments, finite-element modelling was done and the thermal properties of the composite structure were optimised. In the microstructure studies, it was determined that with the increase in the B4C reinforcement ratio, the reinforcement agglomeration and porosity in the composite structure were found. As a result of the thermal experiments, it was observed that the thermal conductivity values of the composites were inversely proportional to the amount of B4C reinforcement and as the reinforcement ratio increased, the thermal conductivity values decreased. Besides, it was determined that the sintering temperature has an effect on the thermal conductivity value and that it increases the thermal conductivity of the composites with increasing sintering temperature. The highest heat conduction coefficient was obtained at 4% B4C reinforcement ratio and 600 °C sintering temperature. It was observed that the finite-element models prepared to determine the heat conduction coefficient effectively were consistent with the experimental results.

ANALYTICAL MODEL OF WETTING THE POROUS MEDIUM

The purpose of this article is to develop an analytical model for determining the weakening of the thermal insulation capacity of porous materials - mineral wool and polystyrene because of increased water content. In the dry state, it was assumed that the sample consists of a skeleton and air-filled pores without process moisture content. In the second shot, however, dry material skeleton and pores with dry air and moisture content were taken into account. In addition, the results of tests involving the process of absorbing moisture in different moisturizing environments for both types of materials were presented. Based on the adopted calculation model, the value of the heat conduction coefficient in the dry state was determined based on the sum of the products of the volume shares of individual components of the material sample, i.e. the apparent volume of the sample material skeleton and the volume of air pores contained. The results of the thermal conductivity coefficient λ obtained in this way are consistent with those obtained from measurements during the experiment. This allowed to determine the validation of the adopted calculation model. Key words: humidity in porous materials, heat transfer coefficient, moisturizing

Effect of foam glass granules fillers modification of lime-sand products on their microstructure

Silicate products are products made exclusively from natural raw materials. A relatively high value of the heat transfer coefficient is still considered a fault. This property adversely affects the thermal insulation of buildings and energy consumption, so you should look for materials with a low heat conduction coefficient. One of the ways of obtaining such products can be the use of light, porous fillers in the mass of lime-sand products.Due to the above, particular attention was paid to white foam glass in the form of granules, which is a product of recycling glass cullet. The research was carried out with a granulate size of 0.25-0.5 mm, share of which in the tested samples ranged from 5 to 30%. The obtained results were referred to the tests carried out on basic (lime-sand) sample.The aim of the article is to determine the correctness of the formation of selected usable properties of modified lime-sand products, taking into account changes in their microstructure. The article describes the results of volume density and compressive strength tests of basic samples and the samples modified by using the expanded glass granulate as well as the results of their observations by using of SEM and tests of phase composition obtained from XRD.

Non-linear unsteady inverse boundary problem for heat conduction equation

Direct and inverse problems for unsteady heat conduction equation for a cylinder were solved in this paper. Changes of heat conduction coefficient and specific heat depending on the temperature were taken into consideration. To solve the non-linear problem, the Kirchhoff’s substitution was applied. Solution was written as a linear combination of Chebyshev polynomials. Sensitivity of the solution to the inverse problem with respect to the error in temperature measurement and thermocouple installation error was analysed. Temperature distribution on the boundary of the cylinder, being the numerical example presented in the paper, is similar to that obtained during heating in the nitrification process.

Preparation and Properties of Lightweight, High-Strength Insulation Materials Using Fly Ash Floating Beads

In our paper, to save energy conservation and environmental protection, and in view of waste fly ash floating bead with excellent properties such as light and refractory, lightweight insulation materials was prepared using fly ash floating beads as the main materials. Firstly, two different fly ash floating bead contents on the properties of the light and refractory material were investigated. Then, on the basis of the optimum fly ash floating bead content, effects of various different particle sizes and firing temperature on the bulk density, compressive strength and the heat conduction coefficients of the samples were studied. The microstructure of the light-weight refractory materials was characterized by XRD and SEM. The heat conduction coefficient (λ') of the samples were also measured by the self-made test instrument. The experimental results showed that the properties of the as-prepared sample using 80% fly ash floating beads was superior to that of 95 % fly ash floating beads. The optimal volume density of 0.60-1.04 g/cm3, compressive strength of 10.6-39.5 MPa and the heat conduction coefficient of 0.183-0.25 °C·g/ min·cm2 were achieved in the presence of 80% fly ash floating beads with 120-160 particle size at 1200°C-1300°C, which has the potential application in lightweight insulation materials.

The limit to rarefaction wave with vacuum for 1D compressible fluids with temperature-dependent transport coefficients

In this paper, we study the zero dissipation limit of the one-dimensional full compressible Navier–Stokes equations with temperature-dependent viscosity and heat-conduction coefficient. It is proved that given a rarefaction wave with one-side vacuum state to the full compressible Euler equations, we can construct a sequence of solutions to the full compressible Navier–Stokes equations which converge to the above rarefaction wave with vacuum as the viscosity and the heat-conduction coefficient tend to zero. Moreover, the uniform convergence rate is obtained. The main difficulty in our proof lies in the degeneracies of the density, the temperature and the temperature-dependent viscosities at the vacuum region in the zero dissipation limit.