Showing papers in "Transactions of The Indian Ceramic Society in 2006"
TL;DR: In the last two decades, various researchers have worked with a variety of traditional and advanced ceramics such as alumina, zirconia, etc. as mentioned in this paper reported substantial improvements in their properties over conventional products, as well as enhancements in the diffusion and reaction kinetics.
Abstract: Though microwaves have been in use for many applications for over 60 years, their application in ceramic processing involving synthesis, sintering, melting, joining, surface modifications, etc, has developed only in the last twenty years. Microwave materials processing is recognized for many advantages, namely, substantial reduction in cycle time resulting in large energy savings, selective and volumetric heating, providing fine microstructures, improved mechanical properties, and eco-friendliness. In the last two decades, various researchers have worked with a variety of traditional and advanced ceramics such as alumina, zirconia. hydroxyapatites, transparent ceramics, electroceramics, ceramic superconductors, glass-ceramics, non-oxide ceramics including Si3N4, AIN, SiC and WC/Co, etc. In all of these materials, substantial improvements in their properties over conventional products, as well as enhancements in the diffusion and reaction kinetics, were reported. Recently, microwave melting of glasses has ...
147 citations
TL;DR: In this article, microwave energy was utilized for the development of oxide coatings on blocks of commercial aluminium of various geometrical shapes, and the results revealed that the geometric term, i.e., the volume to surface ratio, had a dominant influence on the microwave induced oxidation behavior of the samples.
Abstract: Microwave processing is an energy-efficient advanced technique to prepare materials with finer microstructure and better mechanical properties. In the present paper, microwave energy was utilized for the development of oxide coatings on blocks of commercial aluminium of various geometrical shapes. Experimental results revealed that the geometrical term, i.e. the volume to surface ratio had a dominant influence on the microwave induced oxidation behaviour of the samples. In all the cases, coating thickness and its density progressively increased with increasing microwave exposure time. The coating phase was found out to be α-Al2O3 by XRD analysis. The coating microstructure and elemental analysis as examined by SEM and EDAX respectively have been discussed in detail. Adhesion of coatings was studied by using the scratch test.
16 citations
TL;DR: In this paper, three dicotyledonous wood of local origin (mango (Mangifera indica), jackfruit (Artocarpus integrifolia) and teak (Tectona grandis)) were transformed by pyrolysis into carbonaceous preforms and subsequently converted into microcellular Si/SiC ceramics by liquid Si-infiltration under vacuum.
Abstract: Three dicotyledonous woods of local origin (mango (Mangifera indica), jackfruit (Artocarpus integrifolia) and teak (Tectona grandis)) were transformed by pyrolysis into carbonaceous preforms and subsequently converted into microcellular Si/SiC ceramics by liquid Si-infiltration under vacuum. The pyrolyzed mango, jackfruit and teak were characterized in terms of pyrolysis weight loss, shrinkages, bulk density and microstructures. The end ceramics were found to be 91-98% dense with respect to theoretical densities (T.D.) with porosities in the range of 0.1-4.8%. SEM (in back scattered electron (BSE) mode) imaging confirmed the preservation of microcellular tissue anatomy of the precursor wood structure in the morphologies of the final ceramics. The microcellular Si/SiC ceramics from mango, jackfruit and teak exhibited excellent oxidation resistance during heating to 1350oC in flowing air, showing a marginal weight gain at the highest temperature. Si/SiC-mango was also characterized in terms of flexural strength, Young’s modulus and hardness. These biostructural microcellular Si/SiC ceramics possess application potential in various structural ceramic sectors (e.g. mechanical pump seals, wear inserts, kiln support structures, heat exchangers etc).
4 citations
TL;DR: The effect of polyvinyl pyrrolidone (PVP) addition in the ordinary cement and mortar mixes on the properties such as setting time, heat of hydration, compressive and tensile strength has been studi... as mentioned in this paper.
Abstract: The effect of polyvinyl pyrrolidone (PVP) addition in the ordinary cement and mortar mixes on the properties such as setting time, heat of hydration, compressive and tensile strength has been studi...
4 citations
TL;DR: In this article, the ability of sodium polymethacrylates with various molecular weights (1200 to 30000) to deflocate concentrated aqueous suspensions (56 wt%) of two Indian ball clays was investigated.
Abstract: The ability of sodium polymethacrylates salts with various molecular weights (1200 to 30000) to deflocculate concentrated aqueous suspensions (56 wt%) of two Indian ball clays was investigated. The ball clays were one from Bikaner, Rajasthan and the other from Bhimandole, Andhra Pradesh, which are widely used in Indian sanitaryware and tile industry. The clays were characterized for their chemical analysis, cation exchange capacity (methylene blue index test) and for particle size distribution. The clay slips were prepared with distilled water and water containing calcium ions (0 to 60 ppm) using sodium polymethacrylates as deflocculant. All the slurries showed non-Newtonian behaviour. Polymethacrylates with low molecular weights (1200 to 2500) were found to be the most efficient deflocculants for these clay suspensions. The salts acted by an essentially electrosteric stabilization mechanism in combination with a high sequestering ability towards flocculating cations (calcium ion binding power values of 7...
3 citations
TL;DR: In this article, the hardness, fracture toughness, flexural strength and diametrical tensile strength for compacts containing variable amounts of calcium oxide were studied. But, there was a slight decrease in the density and hardness with increase in calcia content.
Abstract: Boehmite sol was prepared by hot water hydrolysis of aluminium iso-propoxide using nitric acid as the catalyst. Calcium nitrate to yield 5 to 20 vol% of calcium oxide was added to the boehmite sol. The sol was precipitated in ammonia, dried at 120°C and calcined at 500°C for 3 h. The calcined powder was milled at 230 rpm for 6 h. The powder was compacted into cylindrical pellets using a uni-axial press at 180 MPa and sintered at temperatures ranging from 1400° to 1600°C for 6 h. Mechanical properties such as hardness, fracture toughness and diametrical tensile strength for compacts containing variable amounts of calcium oxide were studied. There was a slight decrease in the density and hardness with increase in calcia content. Increase in the mechanical properties such as fracture toughness, flexural strength and diametrical tensile strength was observed with increase in calcia content.
3 citations
TL;DR: A broad spectrum of the fundamental principles of ceramic monoliths as supports in different applications based on catalytic reactions is presented in this article, where the importance of selecting right ceramic structure, carrier materials etc has been discussed in detail focusing on several major studies performed since ‘50s till date.
Abstract: A broad spectrum of the fundamental principles of ceramic monoliths as supports in different applications based on catalytic reactions is presented in this review. Importance of selecting right ceramic structure, carrier materials etc has been discussed in detail focusing on several major studies performed since ‘50s till date. The large array of preparation technology using various incorporation techniques of active phase on the support meeting suitable characteristics of a good monolithic catalyst has also been illustrated at length. The choice of a suitable ceramic catalyst for a particular application strongly depends on emphasizing the physical properties of the catalyst, i.e. active surface area, adhesion properties, pore volume and particle size. The significance of these properties have also been reviewed in this article. Ceramic monoliths are especially well-known due to their cost-effectiveness, low pressure drop and requisite high mechanical strength for the long run harsh conditions encountere...
2 citations
TL;DR: In this paper, the use of systematic DMAIC methodology (Define, Measure, Analyze, and Explain) for low-cost technologies is presented in a rigorous manner.
Abstract: Development of appropriate specifications for low cost technologies is not often done in a rigorous manner. This paper presents the use of systematic DMAIC methodology (Define, Measure, Analyze, Im...
2 citations
TL;DR: Refractories are part and parcel of modern civilization as discussed by the authors and are the most essential ingredient of all high temperature processes such as producing metals, glass etc. Significant developments have been made in this area.
Abstract: Refractories are part and parcel of modern civilization. It is the most essential ingredient of all high temperature processes such as producing metals, glass etc. Significant developments have tak...
2 citations
TL;DR: A multielement program for trace impurity analysis of silica sand has been developed in this paper, where the accuracy of overall analysis was first estimated by the analysis of three certified reference materials, and good agreement between measured and reference values has been found for all the elements.
Abstract: Determination of trace impurities in silica sand is simplified by the introduction of automated inductively coupled plasma atomic emission spectrometer (ICP AES). Due to high sensitivity and wide linear concentration range most of the elements are possible to be determined directly using ICP AES in one sample solution. The instrument has been optimized using silica sand matrix considering radio frequency (RF) power, nebulizer pressure, auxiliary flow rate and pump speed. A multielement programme for trace impurity analysis of silica sand has been developed. The accuracy of overall analysis was first estimated by the analysis of three certified reference materials, and good agreement between measured and reference values has been found for all the elements. As the second way of determining accuracy, results obtained from independent analytical techniques ICP AES and AAS have been compared by analyzing real samples.
2 citations
TL;DR: In this article, the double exchange interaction theory is used to analyze the correlation between metallic charge conduction and ferromagnetism and hence a sizable magnetoresistivity observed in a series of transition metal oxides with different crystallographic structures.
Abstract: The phenomenon of magnetoresistivity is known since the days of Michael Faraday when he observed nearly 1-2% change in electrical resistivity under a magnetic field in glassy materials. Over the years, while new materials with varying degrees of magnetoresistivity have been developed, the quest for unearthing the mechanism, side by side, led to the formulation of new theories for more complex materials with complicated electronic band structure courtsey local magnetic interaction and strong correlation. Following Kramer's concept of indirect magnetic exchange interaction, the formulation of double exchange interaction theory in the 1950s, by Zener, Anderson, and de Gennes, created a perspective for analyzing the correlation between metallic charge conduction and ferromagnetism and hence a sizable magnetoresistivity—observed in a series of transition metal oxides with different crystallographic structures. During the last one and a half decade, a series of unusual and unexpected observations have been made...
TL;DR: In this paper, a series of solid solutions containing NdO1.5 in ThO2 were prepared by co-precipitation method and their bulk and theoretical densities were determined by immersion and X-ray techniques respectively.
Abstract: Thorium dioxide dissolves considerable amounts of rare earth oxides forming FCC fluorite-type solid solution. In the present study a series of solid solutions containing NdO1.5 in ThO2 were prepared by co-precipitation method. These solid solutions were characterized for their composition by standard wet-chemical analysis. Their bulk and theoretical densities were determined by immersion and X-ray techniques respectively. The extent of solubility of NdO1.5 in ThO2 matrix was determined using powder X-ray diffraction at 1473 K. The measured solubility of NdO1.5, was found to be in the range 45.7 to 46.2 mol%.
TL;DR: In this paper, a comparison of two different techniques, namely, capillary suction time (CST) and flow point measurements for determination of maximum achievable solids loading in slurries is presented.
Abstract: This paper presents the comparison of two different techniques, namely, capillary suction time (CST) and flow point measurements for determination of maximum achievable solids loading in slurries. Good agreement was observed between the two techniques for Al2O3 and Y2O3. The shift in isoelectric points (iep) of the powders in presence of a dispersant was determined through zeta potential measurements on dilute suspensions. Specific free energy of interaction between oxides and dispersants was also calculated by using a model based on the electrical double layer theory of surfactant adsorption through shift in isoelectric points. The specific free energy of interaction was found to be higher for Al2O3 (-ΔGoSP = 7.5016) compared to Y2O3 (-ΔGoSP= 6.856), suggesting greater electrical double layer repulsion and hence, better dispersion and solids loading. It has been concluded that the measurement of CST and flow point are two simple but useful techniques for rapid evaluation of a required amount of dispersan...
TL;DR: In this article, small-angle neutron scattering (SANS) was used to study the sintering behavior and evolution of pore morphology in sintered compacts of titania and ceria by varying the Sintering temperature/time.
Abstract: Titania powder was prepared by a solution based hydroxide precipitation technique using the tetrachloride precursor and ammonia as the precipitating agent. Ceria powder was prepared by homogeneous precipitation method using cerium nitrate and hexamethylenetetramine. The particle size distribution of titania and ceria powders was measured by laser light scattering. The powder particles were found to follow a log-normal size distribution and the average size of the particles for both the powders was ∼0.7 microns. Small-angle neutron scattering (SANS) was used to study the sintering behaviour and evolution of pore morphology in sintered compacts of titania and ceria by varying the sintering temperature/time. The SANS profiles were analyzed in the light of poly-disperse spherical pore model using log-normal size distribution. The pore sizes in both the ceramic compacts varied from 10 to 1000 nm and the mean value of the distribution shifted from a lower, 50 nm to a higher, 350 nm size. This trend could be att...
TL;DR: In this article, a 70 : 30 mix of common clay and fly ash was used to study the physicico-mechanical properties of different types of kaolinitic clays.
Abstract: Kaolinitic clays of different varieties were progressively added to a 70 : 30 mix of common clay and fly ash. The improvement in physico-mechanical properties upon heating in the temperature range of 1050° to 1200°C was studied by evaluating their linear shrinkage, water absorption, flexural strength and phase content. Incorporation of clay I produced better ceramic properties than that of clay II. It was observed that incorporation of kaolinitic clay up to 10% of the total batch improved the physico-mechanical properties and beyond this limit the properties, particularly fired strength, remained unchanged or marginally decreased. Microstructural features were also studied using SEM technique.
TL;DR: In this article, the effect of diaspore grinding on the thermal behavior of dehydration and α-transformation was examined by means of differential thermal analysis (DTA), thermogravimetry (TG) techniques.
Abstract: The natural diaspore from Jhansi, India was ground in a pot mill in different conditions (dry and wet). The wet grinding was carried out in different media (acidic, basic and neutral) and with deflocculated aqueous diaspore suspension (60 wt%). The sodium polymethacrylate salt (mol. wt. 1200 g.mol−1) was used as the dispersant. The range of particle size of diaspore at which a limit of the grindability exists was also investigated. The effect of grinding on the thermal behaviour of dehydration and α-transformation was examined by means of differential thermal analysis (DTA), thermogravimetry (TG) techniques.
TL;DR: Fired sanitary scrap after fine grinding has been incorporated in a standard vitreous sanitaryware body and the influence of its addition on the rheological and thermo-mechanical properties, vitrification behaviour and microstructure has been investigated as mentioned in this paper.
Abstract: Fired sanitary scrap after fine grinding has been incorporated in a standard vitreous sanitaryware body and the influence of its addition on the rheological and thermo-mechanical properties, vitrification behaviour and microstructure has been investigated. The incorporation of 5-10 wt% scrap resulted in about 8% increase in flexural strength, reduction in vitrification temperature by ∼30°C and broadening of vitrification range of body by 40°to 90°C. This has also resulted in significant improvement of rheological properties of the casting slip at a reduced electrolyte demand without altering the unfired strength of body mixes.
TL;DR: In this paper, high temperature compression experiments were carried out on high purity alumina based composites containing second phases of spinel (MgAI2O4), YAG (yttrium aluminium garnet, Y3AI5O12) and zirconia (t-ZrO2) at a temperature range of 1623-1723 K, stress range of 10-200 MPa and a grain size range of ∼ 1-10 μm.
Abstract: High temperature compression experiments were carried out on high purity alumina based composites containing second phases of spinel (MgAI2O4), YAG (yttrium aluminium garnet, Y3AI5O12) and zirconia (t-ZrO2) at a temperature range of 1623-1723 K, stress range of 10-200 MPa and a grain size range of ∼1-10 μm. It was observed that 5 vol% of these second phases had no significant influence on the creep rate of alumina. The stress exponent of ∼1.0 and the inverse grain size exponent of ∼3.0 suggested no change in the creep mechanism of pure alumina with 5% second phase addition. Deformation enhanced grain growth, which was prominent in pure alumina, was not observed in the composites. The creep behaviour of the composites was discussed based on ionic radii and ionic charge, room temperature mechanical properties and grain size of individual phases. A new model was developed which took into account the creep rate of the second phase while calculating the creep rate of the composite.
TL;DR: In this paper, the elastic properties of dense, pore-free interpenetrating phase Al2O3/Al composites were determined by an ultrasonic technique and compared between the experimental data and analytical theoretical models of Voigt-Reuss (V-R) and Hashin-Shtrikman (H-S).
Abstract: Dense, pore-free interpenetrating phase Al2O3/Al composites were synthesized by a condensed phase displacement reaction between silica and aluminium, and their elastic costants were determined by an ultrasonic technique. Comparisons are made between the experimental data and analytical theoretical models of Voigt-Reuss (V-R) and Hashin-Shtrikman (H-S). Young's moduius of these composites obey both the V-R and H-S bounds but is better predicted by the Hashin-Shtrikman model. The H-S bounds for the bulk and shear moduli are very narrow and the experimental values are close to the limit calculated on the basis of alumina as the matrix phase. The microstructural features of these composites, namely, a limited variation in the phase content and somewhat larger range of contiguity values seem not to have any significant influence on the elastic behaviour of the composites. Poisson's ratio is essentially constant in these composites. Within a small range of phase composition used in this study, it can still be deduced from the results that the contiguity of the Al2O3, phase influences the elastic properties to an extent.
TL;DR: In this paper, an attempt has been made to detail out the characteristics of these new binders, improved properties obtained from the finished products after their application and finally the effect of the same in the performance.
Abstract: In recent years, process changes that have taken place in refractories as well as ceramic industries call for use of materials which can sustain stringent conditions and provide increased life during use at minimum cost. Introduction of higher grade of special binders with the existing grade of raw materials may be a possible solution. Work has been carried out successfully to develop a number of binders, namely, calcium dialuminate cement, barium aluminate cement, magnesia based cement and develop applications of these binders along with siliceous sol, aluminium hydrate, etc. In this paper, an attempt has been made to detail out the characteristics of these new binders, improved properties obtained from the finished products after their application and finally the effect of the same in the performance.
TL;DR: In this paper, the electrical discharge machining (EDM) behavior of sintered Ni3AI was carried out with different process variables, and the metal removal rates were found to increase with the applied current and pulse on-time.
Abstract: The electrical discharge machining (EDM) behaviour of sintered Ni3AI was carried out with different process variables. The metal removal rates were found to increase with the applied current and pulse on-time. The surface roughness of Ni3AI increased with pulse on-time. Cracks were formed on Ni3AI surface during the EDM operation due to generation of high thermal stress. No phase changes were found on the machined surface due to the EDM operation. The debris analysis showed solidification of liquid materials into non-crystalline spheres.