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Number of results: 4
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Abstract

The amount of waste from washing dolomite aggregates increases continuously. Aggregates are washed to remove clayey pollutants.They consist of a large amount of clay minerals and carbonates. Their properties and amount depends on the type of raw material and type of washing technology. Utilization of waste from washing aggregates is common problem and has not been sought out yet. Their usage as the raw material in ceramics might be environmentally friendly way to utilize them. This paper presents technological properties, phase composition and microstructure analysis of materials made of waste sludge from washing dolomite aggregates. Research was divided into three parts: technological properties analysis, phase composition analysis and microstructure analysis. Samples made of waste dolomite sludge were formed in laboratory clay brick vacuum extruder and fired at 900, 1000 and 1100°C. For final materials, apparent density, open porosity, water absorption, compressive strength and durability were examined. Results of technological research suggest the possibility of the application of the waste sludge from washing aggregates in building ceramics technology as bricks materials. Waste sludge from washing dolomite aggregates can be used as the main raw material of building ceramics masses. Without any additional technological operations (e.g. drying or grinding), the material with satisfactory properties was obtained. According to durability results all obtained materials can be used for masonry protected against water penetration and without contact with soil and ground water and also for masonry subjected to passive exposure (F0 – according to the standard EN 771-1).
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Abstract

The paper presents the test results for the microstructure of ZnO varistors comprising high voltage gapless surge arresters. The tests were performed on varistors produced in different periods and by various manufacturers. The research was inspired by different characteristics of changes in values of current flowing through surge arresters as a function of changes in values of system voltage in a 220 kV substation, and the temperature in a multi-year cycle. Furthermore, the effects of varistor microstructure degradation following a failure of an unsealed surge arrester were investigated. The results provided the grounds for assessment of ZnO varistor microstructure parameters in terms of their durability and resistance to degradation processes.
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Abstract

The article discusses the process of copper production in a slurry furnace and in a converter, with the indication of corrosion effects of the extractor. The furnace shaft and settling furnace of the flash furnace were analyzed. The basic factors determining the choice of singlestage technology of copper smelting in relation to the exploitation of refractory materials were indicated. The effects of dissolving the furnace lining material through slag have been presented. Structural analysis results using a scanning microscope are also included. The kinetics of destruction of ceramic materials under the influence of copper slag were evaluated. It has been shown that detailed analyzes are necessary in order to extend the time of furnace extensibility of furnaces in copper processes. The surface layer of the crucible softens due to saturation with slag reagents and is then washed out and moves in the solid form to the slag. The research in the article indicate not only the possibility of dissolution of the ceramic material in the molten slag, but also possibility of erosive activity of the slag on that material.
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Abstract

The paper presents investigations of microstructure of varistors of damaged surge arrester counters. A similar ZnO varistor, not subjected before to operation, was a point of reference in this research. The results of investigations of the ZnO varistors show an untypical phase composition of their material, which was characterized by unsatisfying homogeneity and cohesion. The degradation processes of varistor material in the subsequent stages were recognized and described. A harmful impact of humidity inside the untight surge arrester counter on its operation and its ZnO varistors was proved. Some conclusions being the result of the operation checking of surge arrester counters were presented too.
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