University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

&nbsp;

The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

&nbsp;

It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

A newer class of spinel-alumina castable was fabricated by incorporating 8.0 wt.% of modified spinel additives synthesized via sol-gel and coprecipitation methods. These additives prepared by cheaper ingredients after optimum grinding and calcination, were characterized in terms of particle size distribution, infrared spectra and X-ray diffraction patterns. The properties of those spinel-alumina castables, with another prepared by the same amount of commercial preformed spinel fine, were studied and compared. Cold crushing strength, apparent porosity, hot modulus of rupture, pore size distribution, scanning electron microscopy, energy dispersive spectral analysis, thermal shock and slag corrosion resistance tests of selected samples were done to identify the immense prospect of sol-gel additive. Transmission electron microscope (with SAED facility) was also utilized to establish the nanocrystalline feature of the sol-gel additive. © 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

World University root node

Chemical Technology

Ceramics International

Influence of gel-derived nanocrystalline spinel in a high alumina castable: Part 1

Magnesium aluminate gel precursor has been synthesized by rapid co precipitation technique at a relatively low temperature. This gel exhibits the evolution of spinel phase at significantly lower temperature than solid state sintering; however it is associated with secondary phase like corundum and periclase at higher temperature. The gel has been incorporated in different concentration 0.5-4.0 wt.% to a high alumina based castable to fabricate in situ spinel-alumina monolithic refractory. Uncontrolled agglomeration and an enormous amount of-OH,-NH2 and C= 0 groups associated with the precursor gel indicates a serious apprehension about the performance of the castable. Nevertheless an optimum amount of 2.0 wt. % of spinel gel renders a satisfactory role towards the physical properties of the castable. The microsilica content of the original batch should be reduced to eliminate the detrimental CaO-Al2O3-SiO2 phase generated in the matrix.

Ceramics - Silikaty

The properties of a low cement castable containing chemically prepared hydrous spinel

Two types of magnesium-aluminate spinels, one commercially available as preformed powder and the other prepared from cheaper precursors by the sol-gel route as a semidried reactive mass, were characterized in terms of particle size distribution, XRD phase evolution and chemical composition. These two were incorporated in a high alumina based refractory castable in different concentrations and fired at elevated temperatures. Those preformed and in situ spinel bonded castables were characterized in terms of bulk density, apparent porosity, cold crushing strength, thermal shock resistance, volume shrinkage, flexural strength, XRD, SEM, EDS and slag corrosion resistance test to understand the effect of both kinds of spinel in the castable composition. © 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.

GENERAL

Effect of preformed and in situ spinels on microstructure and properties of a low cement refractory castable

Synthesis and sintering of dense cordierite ceramics, prepared from magnesium and aluminium ions precipitated in dispersed silica have been reported and phase evolution at 1200°C been studied by XRD. Densification of compacted precursor powder at 1200°C has been substantiated by SEM and it was found that the dielectric properties of cordierite ceramics prepared by this route are good enough for substrate application. © 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Sintering and crystallisation behaviour of chemically prepared cordierite for application in electronic packaging

Modified in situ spinel-alumina castables were prepared by using 8.0 wt.% of calcined hydrated magnesium aluminate additives synthesized via facile sol gel and coprecipitation routes. These additives were characterized by particle size analysis and transmission electron microscopy. The castables prepared by them were compared in terms of bulk density, apparent porosity, cold crushing strength and spalling resistance to identify the excellent performance of the sol gel additive having nanocrystalline feature. The quality of castable was illustrated again by comparing it with the same prepared by commercially available spinel fines having well established performance. Scanning electron microscopy, energy dispersive spectroscopy, pore size distribution and X-ray diffraction analysis were used to examine selected fired samples. It appeared that the spinel-alumina castable prepared by the sol gel additive can be a potential candidate for application in steel plants.

Modified in situ spinel-alumina castables

Synthetic commercial MgAl2O4 spinel and chemically prepared coprecipitated spinels were characterized by XRD, IR, particle size distribution, chemical analysis and utilized as additives in a refractory castable composition. The qualities of those two types of spinel bonded castables were examined in terms of bulk density, apparent porosity, cold crushing strength, spalling resistance and flexural strength. XRD, SEM and slag corrosion tests were also carried out to evaluate the performance of these spinel additives at aggressive atmosphere.

Industrial Ceramics

Presintered and coprecipitated spinels as additives in a low moisture castable - Part 2

The microstructures of refractory castables prepared with sol-gel additives were studied. Several kinds of inorganic sol and gel materials were applied to high alumina based low and ultra low cement refractory castable compositions and these were fired at elevated temperature. A scanning electron microscope (SEM) study of the fired specimens was also performed.

Microstructures of refractory castables prepared with sol-gel additives

Alumina and silica sols prepared from cheap precursors have been characterized with respect to viscosity, zeta potential and differential thermal analysis. It has been observed that silica sol possesses higher viscosity and zeta potential values than those of alumina sol. The effect of these sols on high alumina based ULC castables has been investigated by comparing their bulk density, apparent porosity, cold crushing strength, flexural strength, slag corrosion and thermal shock resistance properties. XRD and SEM studies have been carried out on fired samples to explain the effect of sols on the fired strength and homogeneity in structure. © 2003 Taylor and Francis Group, LLC.

Transactions of the Indian Ceramic Society

Alumina and silica sols as binders in a typical ULC castable

This paper deals with the preparation and characterization of two types of in situ spinel bonded low cement high alumina based castable refractories. Semidried magnesium aluminate mass was prepared from cheaper precursors via coprecipitation and sol-gel routes for application in a refractory castable composition in different concentrations. The pH, average particle size, solid content, DTG analysis and XRD patterns of those two additives were observed. After being fired at elevated temperatures those two kinds of in situ spinel bonded castables were characterized and compared in terms of bulk density, apparent porosity, cold crushing strength, flexural strength, volume shrinkage, spalling resistance, and XRD phase analysis. Scanning electron microscopy of some selected fired samples was done to analyse the mode of interaction of in situ spinel bonds in castable microstructure. The corrosion resistance of the castables was estimated by heating with blast furnace and converter slags. © 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.

In situ spinel bonded refractory castable in relation to co-precipitation and sol-gel derived spinel forming agents

This paper deals with the preparation of colloidal suspensions of mullite and magnesium-aluminate spinel via a cheaper precursor of alumina sol. Viscosity, pH, solid content, DTA, TGA and XRD studies at different temperatures were performed to characterize those two sols. These mullite and spinel sols were used separately as bonding agents in a high-alumina based ultra low cement castable composition prepared by simple tapping technique and their performances have been compared in terms of bulk density, apparent porosity, cold crushing strength, flexural strength, slag corrosion, thermal shock, XRD and SEM reports. The results confirm that the mullite sol excels while the spinel sol degrades the refractory castable quality. © 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.

Easy-to-use mullite and spinel sols as bonding agents in a high-alumina based ultra low cement castable

Sillimanite sand, a by-product generated during the extraction of rare earth compounds, can be utilised to develop various types of refractories. This paper systematically describes various uses of sillimanite sand in the field of refractories. Sillimanite sand may even be used in the high-temperature ceramic fibre industries in future. It was found that the use of sillimanite sand in refractories not only reduces production costs but also improves the high-temperature properties of the products.

InterCeram: International Ceramic Review

Utilisation of Sillimanite beach sand minerals for the development of new generation refractories

This paper deals with the performance of basic castables with different in situ spinel-forming agents. The physical properties of these castable compositions are compared. The results indicate that an optimum amount of magnesia-aluminate hydrogel additive appears to be effective for spinel formation. All results obtained by applying SEM, DTA, TGA and XRD analysis also corroborate this feature.

Spinel-bonded basic castables in relation to spinel-forming agents

Two kinds of commercially available preformed magnesia alumina spinels, characterized through chemical analysis and X-ray diffraction methods, were utilized in different concentrations in a high alumina based refractory castable composition. After being fired at elevated temperatures, those two types of spinel bonded castables were characterized and compared with regard to bulk density, apparent porosity, cold crushing strength, spalling resistance, volume shrinkage, and flexural strength. XRD-phase analysis and SEM studies of some selected heat-treated samples were done to understand the interaction of spinel fines in the microstructure of the castables. The performance of these two types of castables was also verified by slag corrosion resistance test. © 2002 Taylor and Francis Group, LLC.

Role of preformed magnesia-alumina spinel additives on the properties of high alumina castable

Polymeric monolithic doped zirconia and zirconia-alumina stiff gels (via stable zirconia and zirconia-alumina sols respectively), derived from Zr-n-propoxide, acetyl acetone, aluminium chloride, di-methyl formamide etc with judicious time-temperature-pH selection, have been prepared by controlled hydrolysis and polycondepsation, and subsequently subjected to heat treatment at 1300°C. The crystallization behaviour of the gels was studied by X-ray powder diffraction and differential thermal analysis. For the dried (25°C) composite gels pore size distributions were estimated. FTIR spectra (at 25° and 200°C) and scanning electron microscopy (at 25° and 1300°C) of both types of gels revealed that low temperature sintering is influenced by the addition of alumina sol in doped zirconia sol matrix to result in a better monolithicity. The microhardness of the fired composite gel was also determined. © 2001 Taylor and Francis Group, LLC.

Crystallization Behaviour of Monolithic Doped Zirconia and Zirconia-Alumina Composite Gels

This paper deals with the performance of alumina sol, prepared from a cheaper precursor and used as a bonding agent in no-cement refractory castables fabricated by simple tapping technique. The physical properties of sol-bonded-castables indicate a significant improvement at elevated temperatures. The beneficial role of sol was confirmed by XRD and SEM studies when compared with similar compositions of castables cast with cement and water. It was also observed that complete rejection of cement in sol-bonded castables degrades the green strength of the materials. © 2001 Taylor and Francis Group LLC.

Effect of alumina sol in no-cement refractory castables

This paper deals with the performance of alumina bearing sol, prepared through sol-gel route, when used as a bonding agent in low cement refractory castable composition. The physical properties of the samples prepared by different processing technique (tapping and vibration) are compared. The results indicate that the simple tapping technique may be a cost-effective solution in order to achieve desired high temperature properties. Also the increase in solid content by heat treatment of a particular sol upgrades its reactivity and improves the properties of a castable at elevated temperatures. XRD and SEM studies confirm the presence of corundum as a major phase and mullite as a minor. © 2000 Taylor and Francis Group, LLC.

Role of alumina sol on the physical properties of low cement castables

The method of preparation of alumina sol by two different routes from simple precursor (hydrated aluminium nitrate and chloride) are described. Viscosity, solid content, particle size distribution and morphology of particles are studied to characterize the sols. DTA and XRD techniques have been applied for phase identification and their changes during heating. The effect of these sols in high alumina refractory castables have also been studied and discussed in this paper.