Zirconia (ZrO2) nanoparticles with nonstabilized monoclinic and sodium‐stabilized cubic phase were produced from zircon sand using the ball mill‐aided precipitation route. Characterization and a comprehensive study of nanocrystalline ZrO2 particles were expressed by X‐ray diffraction, particle size distribution (PSD), Fourier transform infrared spectroscopy, thermal analysis, Brunauer–Emmett–Teller surface area and pore size analysis, X‐ray fluorescence spectrometry, scanning electron microscopy, and transmission electron microscopy. In this article, the influence of the processing parameters on the crystalline phase, particle size, PSD, aggregation, and morphology are reported. The experimental results prove that the precipitation leads to aggregated particles, which are disaggregated by the ball‐milling process. The ball‐milling process strongly influences the formation of uniform‐sized spherical particles with a high surface area. Fully crystalline monoclinic ZrO2 nanoparticles with an average particle size of 64 nm (d50) and the specific surface area of 126 m2/g were obtained. In addition, the sodium‐stabilized cubic ZrO2 nanoparticles with an average particle size of 39 nm (d50) and the specific surface area of 227 m2/g were obtained with the help of the ball‐milling process. In the present process, a simple reaction scheme is developed for the large‐scale production of stabilized and nonstabilized ZrO2 nanoparticles using inexpensive precursor obtained from zircon sand.
Nanosized TiO2 was obtained using a simple chemical route from natural ilmenite available in Tamilnadu, India. The nano‐TiO2 particles obtained were comprehensively characterized by X‐ray diffraction, FTIR, BET surface area, particles size, and transmission electron microscopic analysis. The results observed reveal that the nano‐TiO2 show a rutile crystal structure with an average particle size of 50 nm and a specific surface area of 112.64 m2/g with spherical morphology. Different proportions of nanotitania were added in silica brick composition to determine out the amount of tridymite phase transformation. It was observed that the addition of 0.5 wt% nano‐TiO2 leads to highest amount of tridymite phase formation. The effect of incorporation of nano‐TiO2 in silica refractory was explored in terms of refractory properties such as bulk density, apparent porosity, cold crushing strength, refractoriness under load, creep in compression, and reversible thermal expansion.
Anode baking furnaces is an integral part of aluminium industry. In this furnace, anodes are baked to use in electrolytic reduction. Depending on the design either open top or closed top furnaces are employ ed. Till date, alumino-silicate refractories are the choicest material due to low cost, low creep under compression, high resistance to thermal cycle, carbon monoxide disintegration and alkali attack. This paper deals with failure mechanism of such type of refractories. Used samples from a Reid Hammer bake oven have been studied to find out the reasons of failure. The failure has occurred due to thermomechanical, pyro-chemical stresses and alkali attack in reducing condition. Out of different reasons of failure, alkali attack in reducing condition is found to be the prime cause for failure.[Keywords : Alumino-silicate, Alkali attack, Aluminium industry] IntroductionAnodes are required for pot lining furnaces where alumina is reduced to metallic aluminium. These anodes are made of petroleum coke along with spent anode bonded with pitch which is formulated at high pressure for baking in furnace before use. The anodes are baked at a temperature range of 1150 o -1200 o C. In the electrolytic pot cryolite (NaAlF 6 ) is being added as electrolyte. During the process the anode absorbs alkali oxide and comes in the spent anode. 1 Alumino-silicate refractories with alumina content ranging from 45-50% are generally used in these types of furnace. For getting higher life, the proper selection of refractory is of paramount importance to refractory manufacturers and users. 2 In the present study, attempts have been made to understand the failure mechanism of refractory used in a Reid Hammer bake oven with future action to augment the furnace life.A number of literatures are available on the study of failure mechanism of alumino-silicate refractories in anode baking furnace. However, till now, significant studies have not been carried out to assess the failure due to alkali attack on the refractory. 3 The present study is attempted to understand the mechanism of refractory attack by alkali.
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