Showing papers in "Transactions of The Indian Ceramic Society in 2009"
TL;DR: In this paper, the authors extracted silica aerogel from rice husk ash as sodium silicate by boiling it in sodium hydroxide solution and neutralized with nitric acid to form silica gel.
Abstract: Silica aerogel was prepared from rice husk ash by sol-gel process followed by ambient pressure drying. Silica was extracted from ash as sodium silicate by boiling it in sodium hydroxide solution. Sodium silicate was neutralized with nitric acid to form silica gel. To prepare aerogel, first the pore water of the gel was exchanged by ethanol and then surface modification was done by aging alcogel in tetraethylorthosilicate (TEOS)/ethanol solution. Before drying, TEOS/ethanol solvent was exchanged with n-heptane. Capillary stress and shrinkages were greatly reduced due to the low surface tension of n-heptane. The prepaid aerogel was a light and crack-free solid, with bulk de nsity cf 0.67 g.cm−3, porosity of about 80%, total pore volume of 3.1 cm3.g−1 and specific surface area of about 273 m2.g−1. The nature of surface modification and thermal stability of the aerogel was studied by FTIR and DSC/TG respectively.
55 citations
TL;DR: In this article, a review of recent developments in research on the stability, enhancement of thermal conductivities, viscosity and heat transfer characteristics of nanofluids is presented.
Abstract: The ability of conventional fluids to conduct heat is significantly inferior to solids. The motivation to increase fluid thermal characteristics is not a novel idea. Initial experiments involved adding solid particles with more desirable properties to the base fluid under the hypothesis that the overall mixture's thermal behaviour would be more favourable. The recent advance in materials technology has made it possible by producing nanofluids. These are produced by suspending metallic or nonmetallic nanometer-sized solid particles in base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. The aim of this review is to summarize recent developments in research on the stability, enhancement of thermal conductivities, viscosity and heat transfer characteristics of nanofluids. As is evident in this report, extensive research has been carried out in Alumina-water and CuO-water systems besides few reports in Cu-water, and carbon nanotube (CNT) based systems. ...
49 citations
TL;DR: The UV-visible spectra of undoped and nominally transition metals (Ti→Cu) doped lead borate glasses have been measured from 200 to 1000 nm before and after various doses of gamma-ray irradiation as discussed by the authors.
Abstract: The UV-visible spectra of undoped and nominally transition metals (Ti→Cu) doped lead borate glasses have been measured from 200 to 1000 nm before and after various doses of gamma-ray irradiation. In the undoped lead borate glass, strong charge transfer ultraviolet absorption bands are observed which are related mostly to trace iron impurities and the possible sharing of Pb2+ ions. In transition metal (TM) doped glasses, characteristic absorption bands are recorded due to each specific TM ion which may interfere with that due to iron impurities. Gamma (γ-ray) irradiation reveals significant changes depending on the TM ion and some of the ions show retardation effect as observed in the induced bands. The responses of the undoped and TM-doped glasses to γ-ray irradiation are related to the formation of induced colour centers associated with the intrinsic or extrinsic defects in the glasses. The rates of formation or growth behaviour of the various induced defects are believed to approach saturation with prol...
42 citations
TL;DR: In this article, the authors reviewed previous works and recent achievements by different researchers on various CO2 selective ceramic membranes with reference to other type of membranes, like polymeric, hybrid and mixed matrix type.
Abstract: The separation and sequestration of CO2 produced from the combustion of fossil fuels is the need of the day to encounter ‘Greenhouse Effect’ and ‘Global Warming’. Again, it is quite important also for improving the calorific value of natural gas and for reutilization of flue gas. Membrane technology has the potential to play a crucial role in this regard. Compared to other traditional techniques for the separation and sequestering of CO2, membrane technology, particularly ceramic membrane, is still in relatively developing stage. But it has tremendous potential to emerge as a successful technology to meet the requirement in future. This article reviews previous works and recent achievements by different researchers on various CO2 selective ceramic membranes with reference to other type of membranes, like polymeric, hybrid and mixed matrix type. It also discusses various gas transport mechanism in membranes, different features of ceramic membranes, parameters that affect the gas separation in ceramic membr...
14 citations
TL;DR: Carbon nanotubes have revolutionalized various areas of science and technology as discussed by the authors and can be subdivided into two classes: the single walled and multi-walled carbon nanotube (MWNT) classes.
Abstract: Carbon nanotubes have revolutionalized various areas of science and technology. Conceptually, carbon nanotubes can be thought of as all sp2 carbons arranged in graphene sheets, which have been rolled up to form a seamless hollow tube. The tubes can be capped at the ends by a fullerene type hemisphere and can have lengths ranging from tens of nanometers to several microns. They can be subdivided into two classes: the single walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT). SWNT, as the name suggests, consists of a single hollow tube with diameters between 0.4 and 2 nm while MWNTs are composed of multiple concentric nanotubes ∼0.34 nm apart where the final MWNT has diameters of 2–100 nm. The present review will describe the types of carbon nanotubes, methods of synthesis, properties and some of the applications having commercial importance emphasizing biomedical applications.
9 citations
TL;DR: In this paper, a 3-6 nm cerium oxide single crystal was synthesized by ammonia precipitation in alcohol-water mixed solvent, which was estimated by photon correlation spectroscopy (PCS), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM).
Abstract: Uniform nanosized 3–6 nm cerium oxide single crystals have been synthesized by ammonia precipitation in alcohol-water mixed solvent. The size was estimated by photon correlation spectroscopy (PCS), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). The surface area of CeO2 nanocrystals were measured by Brunauer-Emmett-Teller (BET) technique. The nanoparticles synthesized were mono-dispersed with a narrow size distribution with low polydispersity index (PDI). The size of the ceria nanocrystals synthesized was found to decrease with decrease in the ϵ of the solvent. The crystals precipitated from isopropyl alcohol were highly crystalline. The smallest CeO2 crystals were obtained using ethylene glycol/water medium whereas lowest PDI was obtained from IPA/water system.
9 citations
TL;DR: In this article, the provenance and source materials of a group of Late-Hittite ceramics were studied by mineralogical analyses, showing that they were products of a mixture of local raw materials such as basalts and soils developed on olivine basalts.
Abstract: The firing temperature and production technology together with the provenance and source materials of a group of the Domuztepe (Cilicia, Turkey) Late-Hittite ceramics were studied by mineralogical analyses. The mineralogical (presence of basaltic minerals and the formation of forsterite and tridymite as high temperature minerals) results revealed that this group of Late-Hittite ceramics were products of a mixture of local raw materials such as basalts (10–15%) and soils developed on olivine basalts (70–75%). Evidence demonstrated that the potters of that period were highly aware of achieving temperatures well around 1000°C, despite the lack of proficiency or unwillingness to sustain prolonged firing durations, that later became the norm of cultures in Asia Minor.
6 citations
TL;DR: In this article, the authors present a scenario of the happenings in this area, list up some of the common features of the candidate species (as a guideline for identification of poss...
Abstract: Transition of a crystalline substance from one kind of structural arrangement of atoms to another as a function of external actions like pressure and/or temperature without any change in composition, described as polymorphism, is a very well-known phenomenon. Similar transitions in case of amorphous solids or the corresponding melts (currently called “polyamorphism”), as also possibilities of such transitions have been indicated in various reports in historically early, intermediate and new literature. Recent endeavours have led to systematic studies on a series of liquids and solids, yielding clear proof of first order transition in several cases (e.g. liquid water and silicon, as also specific glassy aluminates), and indications of such isochemical transformations in various other liquid or solid substances. The plan of the present article is to offer a current scenario of the happenings in this area, list up some of the common features of the candidate species (as a guideline for identification of poss...
6 citations
TL;DR: In this article, the authors describe the fabrication of porous LSM cathode by gelcasting process and show the suitability of the gelcast generated L SM cathodes for SOFC applications.
Abstract: Solid oxide fuel cells (SOFCs) are devices that offer high efficiency power output with negligible emissions. Cathode supported tubular SOFCs consist of porous cathode tubes made up of strontium doped lanthanum manganite, La1-xSrxMnO3 (LSM) that work as functional component as well as structural support for the rest of the cell components. Gelcasting is one of the most suitable methods for the fabrication of porous ceramics. This paper describes the fabrication of porous LSM cathode by gelcasting process. Gelcasting parameters such as monomer concentration, powder volume fraction, pH of the slurry, etc were optimized. Slow drying of green specimens minimized warpage and cracking. Sintered specimens with controlled porosity were obtained by the use of suitable pore-forming agents. The coefficient of thermal expansion (CTE) of sintered specimens was measured, which was found matching with the CTE values of cell components reported in the literature. These results have shown the suitability of the gelcast generated LSM cathodes for SOFC applications.
4 citations
TL;DR: Magnesium aluminate spinel aggregate was prepared by reaction sintering technique from its constituent oxides in a single firing process and the aggregate was used to develop alumina spinel castable as discussed by the authors.
Abstract: Magnesium aluminate spinel aggregate was prepared by reaction sintering technique from its constituent oxides in a single firing process and the aggregate was used to develop alumina spinel castable. Different compositions were studied with variation in spinel content between 16 and 20 wt%. Other constituents used were WTA aggregates, bauxite aggregates, high alumina cements and additives. Developed castable was characterized for various properties both at dried and fired conditions.
2 citations
TL;DR: In this paper, the incorporation of 5 wt% of nano silica particles in the form of colloidal silica resulted in 97.2% increase in dry flexural strength.
Abstract: Silica nanoparticles in the form of colloidal silica was incorporated in a standard porcelain body and influence of its addition on the dry as well as thermo-mechanical properties, vitrification behaviour and microstructure have been investigated. The incorporation of 5 wt% of nano silica particles in the form of colloidal silica resulted in 97.2% increase in dry flexural strength. Fired properties showed that 2 wt% addition was found to be better due to higher flexural strength, bulk density and lower porosity compared to the standard.
TL;DR: In this paper, a new method was developed for the evaluation of kinetic parameters of solid state reactions using Gauss's quardature rule with Radau integration with a computer program, applied to determine the kinetic parameters for the decomposition reactions of MgCO3 and CaCO3 from non-isothermal thermogravimetric study.
Abstract: The existing methods for the determination of kinetic parameters of solid state reactions from non-isothermal thermoanalytical data suffer from some limitations due to inexact solution of the Arrhenius temperature integral and non-consideration of the temperature dependence of pre-exponential factor. In the present paper a new method was developed for the evaluation of kinetic parameters of solid state reactions using Gauss's quardature rule with Radau integration with a computer programme. The method was applied to determine the kinetic parameters for the decomposition reactions of MgCO3 and CaCO3 from non-isothermal thermogravimetric study.
TL;DR: In this article, the authors used X-ray diffraction analysis to identify the phases formed while SEM studies have been used to get an idea about the microstructure of the castable matrix.
Abstract: Activated alumina is prepared by thermal dehydration (300°-600°C) of chemically pure aluminium hydroxide. The prepared materials have been characterized by residual water content, BET surface area and hydraulic activity. These aluminas are incorporated in cement free castable batch. Important properties like bulk density, apparent porosity, linear change, cold compressive strength, strength retainment after thermal shock have been studied. X-ray diffraction analysis has been performed to identify the phases formed while SEM studies have been used to get an idea about the microstructure of the castable matrix.
TL;DR: In this article, the occurrence of residual carbon during carbothermal reduction synthesis of B4C was investigated using boric oxide (B2O3) and carbon black (C) reaction mixtures with less than stoichiometric carbon.
Abstract: The occurrence of residual carbon during carbothermal reduction synthesis of B4C was investigated using boric oxide (B2O3) and carbon black (C) reaction mixtures with less than stoichiometric carbon (with B: C molar ratios of 4: 2.66, 4: 2.0 and 4: 0.833). The reaction was studied in 1 atm argon in a temperature range of 1300° to 1625°C for 0.5 h. The reaction mixture with B: C = 4: 2.66 was also found to form residual free carbon. Addition of a small quantity of K2CO3 to reactant mixture was found to decrease the free residual carbon. No peak, corresponding to free carbon, was observed in B4C formed with boron and carbon in the ratio of 4: 2. When the carbon content in the reactant mixture was decreased to a very low value (B: C = 4: 0.833), no B4C could be formed and the B2O3 was found lost totally. The B4C powder was found to have uniform size and needle like shape which was also observed to be influenced by K2CO3 addition to the reaction mixture.
TL;DR: In this paper, a systematic study on leachability of iron ions from binary and ternary phosphate glasses having molar composition (40+X)FeO., 60-X P2O5 and (55-X) FeO.
Abstract: With a view to using glasses as a source of iron, which is one of the micronutrients required by plants, a systematic study on leachability of iron ions from binary and ternary phosphate glasses having molar composition (40+X)FeO.(60-X)P2O5 and (55-X)FeO. XR2O.45P2O5 (where X = 0–9 mol% and R = Li, Na, K) was carried out. Leaching of iron ions has been studied as a function of pH and the results show that leaching increases with increasing pH of the solutions. The concentration of iron ions in the leachate decreases with increasing bond strength between non-bridging oxygen ions and the cations in glasses. The leaching of iron ions enhances with increase in leaching time as well as an increase in the concentration of P2O5 in the glass. It decreases further with an increase in particle size of glasses.
TL;DR: In this paper, the potential of fly ash, a solid waste generated in huge amount from thermal power plant (TPP), to act as an adsorbent for removal of 2-nitrophenol (2-NP) from water has been investigated.
Abstract: The potential of fly ash, a solid waste generated in huge amount from thermal power plant (TPP), to act as an adsorbent for removal of 2-nitrophenol (2-NP) from water has been investigated. The operational parameters and extent of uptake was determined in standardized batch operation. The process is optimized in terms of initial solute concentration, pH and temperature of the solution, dose and particle size of the adsorbent, agitation time and speed. The sorption characteristics defined mainly by its capacity as well as low cost recommend the use of fly ash as a potential and alternative sorbent for 2-NP removal from aqueous environment.
TL;DR: In this paper, suspensions of 8 mol% yttria stabilized zirconia (YSZ) were prepared with ethanol as the dispersing medium and the suspensions were stabilized by a dispersant composed of fixed ratios of citric acid and triethylamine.
Abstract: Suspensions of 8 mol% yttria stabilized zirconia (YSZ) were prepared with ethanol as the dispersing medium. The suspensions were stabilized by a dispersant composed of fixed ratios of citric acid and triethylamine. Different quantities of the dispersants were used for a given amount of solid loading and the optimal amount was determined by measuring their zeta potential. Suspension stabilized by using the optimal dispersant amount was used for deposition on stainless steel substrates at different voltages for varying times. The optimal voltage and time was determined by observing obtained microstructures under SEM. Similar studies were then done for a lanthanum strontium manganite (LSM) substrate. The optimal composition of suspensions and the used parameters made it possible to obtain coatings with uniform thickness.
TL;DR: In this article, the authors reported on the synthesis of Mn 0.5Zn0.5Fe2O4 using iron ore fines as one of the constituents required for the synthesis.
Abstract: Mn-Zn ferrites find their application in several electronic devices in electronic industries for different applications. The better magnetic properties of nano sized Mn-Zn ferrite offers to develop technology for low power loss with miniature design of components. This will not only bring revolution in industry but is also a process which will offer high quality product. Synthesis of Mn-Zn ferrite nano powders are done through different processing routes using high purity chemicals. The cost of the product powder can be reduced if it is synthesized using the ore or mineral of any one constituent of the salt required in their synthesis. The present work is a reporting on the synthesis of Mn0.5Zn0.5Fe2O4 using iron ore fines as one of the constituents required for the synthesis of Mn-Zn nano powders.
TL;DR: In this article, three different bonds were prepared by mixing talc, China clay and calcined alumina in different proportions, 50% of each bond was mixed with 50 percent of clay grog to obtain three oxide compositions of 11%MgO.37%Al2O3.48%SiO2.
Abstract: Studies were carried out to develop cordierite kiln furniture of high hot strength with a view to get longer life. Selection of raw materials was based on lowest possible iron impurities. Three different bonds were prepared by mixing talc, China clay and calcined alumina in different proportions. 50% of each bond was mixed with 50% of clay grog to obtain three oxide compositions of 11%MgO.37%Al2O3.48%SiO2 (N-1), 8%MgO.39%Al2O3.48%SiO2 (N-2) and 5%MgO.37%Al2O3.50%SiO2 (N-3). Test bars were fired at 1250°, 1300° and 1360°C for 2 h soaking time. The decrease in MgO from 11 to 8% gave highest hot MOR (105 kg.cm−2) and lowest thermal expansion (3.0 × 10−6//°C) due to better formation of cordierite and mullite phases.