scispace - formally typeset
Search or ask a question

Showing papers in "Transactions of The Indian Ceramic Society in 2008"


Journal ArticleDOI
TL;DR: In this article, the 3D transition metals-doped sodium borate host have been measured before and after successive gamma-irradiation, and the traditional and induced spectral data are analyzed and interpreted on the basis of current views on the effect of ionizing irradiation on glass.
Abstract: UV-visible and infrared absorption spectra of 3d transition metals-doped sodium borate host have been measured before and after successive gamma-irradiation. Transition metals are known to exhibit characteristic absorption bands. Infrared absorption spectra of the prepared samples exhibit characteristic bands indicating the coexistence of 3- and 4-coordinated boron groups. Transition metals reveal varying response in the UV-visible spectra to the effect of successive gamma irradiation while minor effect is obvious in the infrared spectra. The traditional and induced spectral data are analyzed and interpreted on the basis of current views on the effect of ionizing irradiation on glass.

32 citations


Journal ArticleDOI
TL;DR: The effects of diminishing size of crystalline particles in the nanodimensional regime on their properties are well known and in certain cases well understood as discussed by the authors, which has led to various ideas relating to its dependence on size.
Abstract: The effects of diminishing size of crystalline particles in the nanodimensional regime on their properties are well known and in certain cases well understood. Melting is a property that has been looked at from different viewpoints through more than a century, which has led to various ideas relating to its dependence on size. Two very important papers by P. Pawlow and F. A. Lindemann, written separately about one hundred years ago, supporting earlier classical indications of the important role of surface of crystalline solids have led to important advancements in this area. The present overview makes a brief summary of this advancement.

14 citations


Journal ArticleDOI
TL;DR: In this article, the authors present an overview of glass-ceramics-based sealants for planar anode-supported solid oxide fuel cell (SOFC) applications.
Abstract: One of the major challenges for the commercialization of planar anode-supported solid oxide fuel cell (SOFC) is the development of suitable high temperature sealant. The sealants must maintain gas-tightness between the anode and the cathode compartments to avoid intermixing of fuel and oxidant at high operating temperature (700°-800°C), be an electrical insulator and chemically non-reactive with the stack components. Due to the high commercial importance of such sealants, very few sealing compositions are available in the open literature and have to be developed by the individual SOFC developer. In this context the present article gives an overview on such sealant development with particular emphasis on glass-ceramics based sealants. Other than glass-based sealants, very recent approaches such as compressive and self healing seals also show some potential as SOFC sealants. The review of literature is followed by description of the progress of work related to development of glass based sealant at our Insti...

13 citations


Journal ArticleDOI
TL;DR: In this paper, a review of the development in the growth process of device grade ZnO nanowires, nanobelts and their possible technological applications for the realization of smart gas sensors usable in environmental, automotive, chemical industries and health care fields is presented.
Abstract: The review covers up-to-date developments in the growth process of device grade ZnO nanowires, nanobelts and their possible technological applications for the realization of smart gas sensors usable in environmental, automotive, chemical industries and health care fields. The gas sensing mechanism in bulk ZnO as well as in ZnO nanowires and nanobelts for a wide variety of industrial gases like oxygen, hydrogen, carbon monoxide, nitrogen oxide, hydrogen sulphide, ethanol, etc are addressed. In addition, the design aspects, sensitivity and limitations of various types of ZnO nano gas sensors are also discussed.

7 citations


Journal ArticleDOI
TL;DR: In this paper, the performance of Ferroelectric materials of Ba0.95 RE0.05TiO3 and LiNb 0.95 Nb0.5O3 was investigated by measuring excitation and emission spectra of the prominent emission bands, luminescence performance of these optical materials was investigated.
Abstract: Ferroelectric materials of Ba0.95RE0.05TiO3 and LiNb0.95RE0.05O3 (RE3+ = Eu3+, Sm3+, Dy3+ and Pr3+) have been prepared by a conventional solid state sintering method. By measuring excitation and emission spectra of the prominent emission bands, luminescence performance of these optical materials has been investigated. In addition, structural analysis of these powder materials has also been carried out by using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, characteristic transition scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Lifetime measurements of RE3+ have also been carried out to evaluate emission performance of these ceramic powders.

7 citations


Journal ArticleDOI
TL;DR: In this paper, the failure mechanism of anode baking furnaces has been investigated and the failure has occurred due to thermomechanical, pyro-chemical stresses and alkali attack in reducing condition.
Abstract: 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 employed. 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.

6 citations


Journal ArticleDOI
TL;DR: In this article, a detailed review of the process of making oxide ceramic foams of porosity more than 70% with pore sizes in the range of 0.1-4 mm is presented.
Abstract: Processing routes to make oxide ceramic foams of porosity more than 70% with pore sizes in the range of 0.1–4 mm are reviewed. Microstructures and mainly characteristics of pores produced by incorporation of fugitives, infiltration through 3D-preforms, direct casting of foams are compared. Emphasis has been given to the versatile processes with use of natural additives, which allow in controlling microstructural features while improving the desired mechanical property. The critical step in setting of ceramic foam through direct casting foaming process, i.e. stabilization of bubbles during consolidation, is being highlighted emphatically with use of water soluble additives.

6 citations


Journal ArticleDOI
TL;DR: In this paper, X-ray diffraction (XRD) patterns of the samples showed the presence of sodium calcium silicate Na2Ca2Si3O9 as the main crystalline phase.
Abstract: Silicate bioglass-ceramics with incorporation of small TiO2 and MgO were prepared using an appropriate two-step heat treatment for controlled crystallization defined by differential thermal analysis (DTA). Identification and quantification of crystalline phases precipitated from the silicate glasses were done by X-ray diffraction. The X-ray diffraction (XRD) patterns of the samples showed the presence of sodium calcium silicate Na2Ca2Si3O9 as the main crystalline phase. The evolution of the XRD peaks with the addition of MgO and TiO2 showed the formation of a new crystalline calcium phosphate phase, Ca4P2O9. Investigation of in vitro bioactivity of the prepared glass-ceramics was done by the infrared reflection spectra of the samples after immersion in simulated body fluid (SBF) for different periods at 37°C. The results showed that an apatite layer was formed on the surface of the sample containing MgO while samples containing TiO2 did not form the apatite layer.

5 citations


Journal ArticleDOI
TL;DR: In this article, microwave and conventional heat treatment processes were utilized to achieve adequate crystallization in MgO-Al2O3-TiO2 based glass coatings with identical compositions.
Abstract: Microwave and conventional heat treatment processes were utilized to achieve adequate crystallization in MgO-Al2O3-TiO2 based glass coatings with identical compositions. The processed coatings were evaluated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and image analysis. XRD analysis showed that the misfit strain in the lattice of conventionally heat treated coating was higher than that in the corresponding microwave processed coating. SEM investigation along with image analysis confirmed that microwave heating generated finer crystallites in the glass coating than those obtained in the coating processed by conventional heating.

5 citations


Journal ArticleDOI
TL;DR: In this paper, graphite powders have been coated with Magnesio-Aluminate Hydrate (MAH), and the coated powders were characterized by TGA/DTGA, DTA and calcinations at 1000°C to study their oxidation loss.
Abstract: Graphite has extraordinary properties, viz. high corrosion resistance against liquid metals and slags, good spalling resistance and impact on reduction of porosity and finer pore size distribution in oxides—carbon composite refractories. However, it has poor oxidation resistance which restricts its use in pyrometallurgical operation and gives poor campaign life. Different antioxidants such as Al, Si, Al/Mg, B4C, SiC, etc have been used in commercial production of carbon bearing composite refractories for improvement of their oxidation resistance. Coating of graphite with oxides such as Al2O3, SiO2, TiO2, ZrO2, etc has been the recent trend of R & D work to improve the oxidation resistance of graphite in composite refractories. In the present investigation, graphite powders have been coated with Magnesio-Aluminate Hydrate (MAH). The coated powders were characterized by TGA/DTGA, DTA and calcinations at 1000°C to study their oxidation loss. Liquid resin was also specially treated with MAH. Both MAH treated ...

5 citations


Journal ArticleDOI
TL;DR: In this paper, an alumina-mullite composites with various mole ratios of Al2O3 and SiO2 were generated by interacting fly ash with bauxite.
Abstract: In the present investigation alumina-mullite composites with various mole ratios of Al2O3 and SiO2 were generated by interacting fly ash with bauxite. The magnitude of sintering was examined by exa...

Journal ArticleDOI
TL;DR: In this paper, a new model for design of multilayer ceramic composite (MLC) with both high failure energy and fracture toughness is developed, based on changes in stored elastic energy as well as compliance of the MLC beam as a function of crack growth process.
Abstract: A new model for design of multilayer ceramic composite (MLC) with both high failure energy and fracture toughness is developed in the present work. The model considers, for the sake of simplicity, the failure process under three point bend loading for a notched MLC beam comprised of N number of matrix layers separated by (N-1) very thin interfacial layers. The theory is developed on the basis of changes in stored elastic energy as well as compliance of the MLC beam as a function of crack growth process. Finally, the model predicts the interfacial toughness and the amount of energy consumed per unit volume, E-con MLC, during controlled propagation of interfacial cracks and through thickness cracks in the IVILC beam. The predictions of the model for an optimally designed MLC beam comprised of 20 number of 150 pm thick alumina matrix layers separated by 19 number of very thin (7 mu m) lanthanum phosphate interface layers compared favourably with experimental data from literature as well as our own work. Further, it is illustrated that working with our proposed model, the optimally designed MLC beam can achieve significant toughening. The influence of material properties and the fabrication process design parameters on failure energy and fracture toughness is also considered for designing MLC beam.

Journal ArticleDOI
TL;DR: In this paper, the effect of grain size on the microwave dielectric properties of ZST is discussed, and the unloaded quality factors (Q) are effectively promoted by Sm2O3 additions.
Abstract: (Zr0.8, Sn0.2)TiO4 ceramics containing ZnO and Sm2O3 as sintering aids are prepared by the conventional solid-state reaction. The effects of sintering parameters such as sintering temperature, sintering time and increasing Sm2O3 concentration on structural and dielectric properties are investigated. A secondary phase is not observed for the levels of 0.5–1.5 wt% Sm2O3 additions. Crystallite size of the sintered ZST ceramics ranges between 20 and 55 nm. The dielectric constant (er) and temperature coefficient of the resonance frequency (τf) are not significantly affected. The unloaded quality factors (Q) are effectively promoted by Sm2O3 additions. A er value of 39.3 and Qxfo of 63,850 (at 11.94 GHz) have been obtained for 1 wt% ZnO added (Zr0.8, Sn0.2)TiO4 ceramics with 1 wt% Sm2O3. The increase in Qxfo is attributed to the increase in grain size. The effect of grain size on the microwave dielectric properties of ZST is discussed.

Journal ArticleDOI
TL;DR: In this paper, factors influencing the behavior of an alumina/aluminium interpenetrating phase composite during wire-cut electrical discharge machining were studied, and the results showed that the machining process affects the surface quality of the machined composite.
Abstract: Factors influencing the behaviour of alumina/aluminium interpenetrating phase composite during wire-cut electrical discharge machining (WEDM) are studied. Machining performance in terms of material removal rate (mm(3)center dot min(-1)) and surface roughness (R-a) were compared under different machining conditions. Results show that the machining process affects the surface quality of the machined composite. Under the conditions of the present study, the cutting rate and surface roughness are inter-dependent and vary between 5 and 8 mm(3)center dot min(-1) and 3 and similar to 4 mu m, respectively. WEDM cutting gives rise to the formation of a heat-affected surface layer containing pores and a few cracks. The results are analyzed using the prevailing concepts of electro-discharge machining.

Journal ArticleDOI
TL;DR: In this article, the effect of vinyl acetate addition to the ordinary cement on its properties like heat of hydration, setting time, compressive and tensile strength has been studied by adding 0.1 to 5.0 per cent additive by weight of cement.
Abstract: Effect of vinyl acetate addition to the ordinary cement on its properties like heat of hydration, setting time, compressive and tensile strength has been studied by adding 0.1 to 5.0 per cent additive by weight of cement. It was observed that the compressive and tensile strengths, hardness, toughness and corrosion resistance increase up to 3.0 per cent vinyl acetate addition in the ordinary Portland cement. Polymeric phase is interspersed in the cement and causes decrease in the water absorption/open porosity of the modified cement products. The chemical interaction between functional group of organic material and hydrating cement phases causes the formation of new phases which cause additional bond formation in addition to cement bonds leading to the increase in strength.

Journal ArticleDOI
TL;DR: In this paper, a trivalent Cr-doped Bi4V2-xMexO11-5 (Me = CrIII) has been prepared by solid state reaction technique and three phases (α, β, γ) are observed in the unsubstituted compound.
Abstract: Solid electrolyte materials based on bismuth vanadate (Bi4V2O11) exhibit 50–100 times more ionic conductivity than any other solid electrolyte materials which are in use in solid oxide fuel cell. Partially substituted trivalent Cr-doped Bi4V2-xMexO11-5 (Me = CrIII) has been prepared by solid state reaction technique. Three phases (α, β, γ) are observed in the unsubstituted compound. Alpha (α) is the low conducting room temperature phase and gamma (γ) is the high conducting phase observed at higher temperature. Stabilization of α, β and γ phases at room temperature depends on the Bi:V ratio and the nature of the dopant. These phases have been characterized by X-ray diffraction analysis. All the substituted phases (0≤x≤0.4) retain the low conducting α-phase. AC conductivity measurement of all the samples in the temperature range of 200°-700°C has been done. The change of slopes observed in the Arrhenius plots is in agreement with the phase transitions for all the studied compositions.

Journal ArticleDOI
TL;DR: In this paper, the magnetic properties of strontium hexaferrite (SrFe12O19) have been examined with respect to its structural morphology, including particle shape, size, orientation, lattice parameters and phase formation.
Abstract: In this study strontium hexaferrite (SrFe12O19) has been prepared from celestite (natural mineral of strontium) and blue dust (iron ore fines) at different mole ratios SrO.nFe2O3 (n = 5.0 to 5.9) with variation in calcination and sintering temperatures. Its magnetic properties with respect to its structural morphology have been examined. Structural properties like particle shape, size, orientation, lattice parameters and phase formation were measured. The effect of each parameter on magnetic properties in correlation with phase formation has been discussed in the present study. It was found that magnetic properties of strontium hexaferrite prepared from processed ore are strongly dependent on mole ratio, calcination and sintering temperature, density, particle shape, size and its orientation. It was observed that at a mole ratio (SrO/Fe2O3) of 5.0 the (BH)max value is 3.58 kJ.m−3, whereas at the mole ratio of 5.9 the value drops to 1.12 kJ.m−3. Similarly the remenence value is maximum (150 mT) at the mole...

Journal ArticleDOI
TL;DR: In this paper, the development of a Mn-Zn ferrite material suitable for power applications with core losses amounting to 529 and 296 kW, respectively, has been reported.
Abstract: The present work reports the development of a Mn-Zn ferrite material suitable for power applications with core losses amounting to 529 and 296 kW.m−3 at the operating frequency of 100 kHz and a driving flux density of 200 mT at 25° and 100°C respectively. Power loss values below 400 kW.m−3 in a wide temperature range above 65°C make it the most promising candidate for regular switching power supplies, as well as in the main transformers of DC-DC converters for automotive applications.