Showing papers in "Transactions of The Indian Ceramic Society in 2010"

Nanometal-Glass Hybrid Nanocomposites: Synthesis, Properties and Applications

Abstract: In recent past research on nanometal-glass hybrid composites has been the centre of attention across the globe particularly in the area of nanoscience and for the future nanotechnology. In this review, with a short historical background, its preparation by various multi-step techniques, properties and applications are briefly described. In addition, recently developed single-step in situ thermochemical reduction methodology by these authors for synthesis of various nanometal-glass hybrid nanocomposites are described in detail with their significant characteristic properties, relevant theories and applications. Here Au, Ag and Bi metals are considered and the synthesized glasses are mostly based on antimony, bismuth and phosphorus oxides. Some of them are dichroic in nature, that is, they exhibit blue to green colourations in transmitted light and brown to reddish brown colourations in reflected light. The appropriate reasons for their dichroic character are still remained unsolved. Nanometal-antimony oxide glass nanocomposites have been found to enhance the photoluminescence upconversion intensities up to 11 fold when co-doped with rare earth (RE) ions due to the plasmonic induced local field as enhanced by the effects of doped metal nanoparticles. The nanometal-glass hybrid nanocomposites, therefore, seem to be very promising for various nanophotonic applications (such as nanometal enhanced rare earth luminescence, solar cell, light emitting diode, plasmonic integrated circuit, plasmon slot waveguide, etc) that have presently emerged into a major field called `plasmonics'.

Some Studies on the Synthesis and Characterization of Carbon Aerogel

Abstract: Porous carbon aerogels were synthesized from resorcinol-formaldehyde monomers using acetic acid, sodium carbonate and sodium hydroxide catalysts. The synthesized aerogels were characterized by XRD, TGA, SEM, BET and FTIR. The carbon aerogel developed by acetic acid catalyst produced a very high surface area (619.26 m2.g−1). All the different catalysis resulted in different surface morphology of the aerogels. The synthesized carbon aerogels contained significant amount of hydroxyl, carboxyl groups and different types of C-C linkages. These aerogels exhibited potential as adsorbents for removal of toxic materials and heavy metals.

Nanostructured Ceramic Materials for Chemical Sensors: Present Status and Future Prospects

Abstract: Nanocrystalline ceramic materials (semiconducting oxides, SiC, GaN, CNT), due to their excessive surface to volume ratio and large free surface energy, are one of the key focus domains for researchers in the field of chemicals sensors during the last decade. Owing to the nanocrystallinity, several promising effects on sensor parameters like operating temperature, response magnitude (S), response time (τres), recovery time (τrec) and selectivity have been studied. This article provides a comprehensive review of the current research activities that concentrate on chemical sensors based on nanocrystalline-nanoporous thin films along with the thin films consisting of nanotubes, nanorods, nanobelts, nanoribbons and nanowires, comprising the wide bandgap semiconducting oxides (like SnO2, ZnO, TiO2, In2O3 etc) and other ceramic materials like SiC, GaN, CNT. The review also predictcs about the possible directions towards future research on nanostructured chemical sensors.

Layered Double Hydroxides Based Ceramic Nanocapsules as Reservoir and Carrier of Functional Anions

Abstract: An extensive study of the intercalation of a number of commercially important anions into a range of layered double hydroxides (LDHs) has been presented. Intercalating anions include key drugs, vitamins, fragrances, dye, etc. The immense potential of LDH systems as reservoirs and carrier of different functional anions was demonstrated. The release of the guest anions was studied in representative conditions.

Lead Free Strontium Barium Niobate Ferroelctric Ceramics—A Review on Synthesis, Microstructure and Dielectric Properties

Abstract: Environmental concerns have led to a strong focus on the development of lead free materials for ever expanding electroceramics industry. Strontium barium niobate (SBN) (SrxBa1-xNb2O6, 0.20≤ x ≤ 0.80) is a promising lead free ferroelectric. Large composition range provides an opportunity to design SBN with desired properties for applications in pyroelectric, photo-refractive, electro-optic, surface acoustic wave (SAW) devices. However, abnormal grain growth, on conventional sintering, and resultant deterioration in dielectric properties have plagued the applications of this material. Many synthesis routes have been attempted to overcome this problem that are discussed here with merits and demerits. General features of ferroelectric ceramics and various synthesis routes for SBN are reviewed and form second part of the review. Finally, our strategies to suppress the abnormal grain growth through novel and modified synthesis processes and improved dielectric performance of SBN are outlined.

Synthesis of Norbergite Fe3BO6 of Single Crystallites from a Borate Glass

Abstract: Iron oxyborate Fe3BO6 is one of the important ceramics of the norbergites useful for electrodes in lithium ion batteries, gas sensors and biological probes. A facile biofriendly method of rapid cooling of a borate glass-melt (starting composition 40Fe2O3-60 B2O3), after an isothermal heating for 30 min at ∼1220°C in air, is explored in view of producing Fe3BO6 single crystallites. The method is feasible to scale-up for high yield. Scanning electron microscopic images of as-cooled rectangular bars or laminates of Fe3BO6 crystallites measure 1–2 μm length, 0.51 μm width and ∼45 nm thickness. A single phase compound, Fe3BO6, as analyzed from the X-ray diffractogram, shows an orthorhombic crystal structure (Pnma space group), with lattice parameters a = 1.0048 nm, b = 0.8531 nm, c = 0.4466 nm, and density 44.76 g.cm−3. It is highly stable in air unless heating above 700°C. At room temperature these Fe3BO6 crystallites behave as the surface modified antiferromagnet, showing a nearly linearly increasing magneti...

Effect of Process Variations on Anticancerous Drug Intercalation in Ceramic Based Delivery System

Abstract: Two methods have been attempted to intercalate an anionic anticancerous drug methotrexate (MTX) into Mg-Al layered double hydroxide (LDH): a) anion exchange method (sample A′) and b) in situ coprecipitation method followed by a soft hydrothermal treatment (sample A″) to form a biohybrid material. Both the materials obtained were characterized by powdered sample X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), thermogravimetric-differential thermal analysis (TG-DTA), particle size distribution (PSD) analysis and field emission scanning electron microscopy (FE-SEM). High performance liquid chromatography (HPLC) was used to determine the integrity of the MTX and to quantify the drug loading in the materials. HPLC data of sample A′ confirms the integrity of the MTX moiety in the interlayer space of Mg-Al-LDH which has been further verified by XRD and FTIR spectroscopy and drug loading in the hybrid system was found to be 20.22 mg.g−1. However, the HPLC data of sample A″ supports that under...

Nanosize SnO2 Based Tubular Resistive Gas Sensor for Hydrogen and Acetone Vapour

Abstract: Tin oxide films were deposited on cylindrical alumina substrates using dip coating technique. These films were subsequently dried and sintered at 500°C for development of microstructure having nanoparticles of SnO2 and adhesion with the substrate. These resistive gas sensors were tested for H2 of concentration range 7–3900 ppm at the operating temperature of 260°C. The sensors also showed good response to acetone vapour (11–5500 ppm) at operating temperature of 200°C. These sensors showed good temperature sensor selectivity. The structural and microstracural analyses of the films were carried out using X-ray diffractometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM).

A Short Review on the Pulsed Laser Deposition of Er3+ Ion Doped Oxide Glass Thin Films for Integrated Optics

Abstract: Short pulsed (ns) excimer laser was employed as a technique for the deposition of more than 2 μm thick glassy films from phosphorous pentoxide and tungsten lanthanum modified tellurite bulk glasses. High quality glass thin films with measured propagation loss less than 0.15, 0.71 and 2.3 dB.cm−1 were obtained after optimization of deposition parameters for silica, siloxane and semiconductor substrates. The optical, spectroscopic and microstructural properties of deposited thin films were compared with bulk glass materials for demonstrating the differences in the properties, which must be optimized for device engineering. Channel waveguides were fabricated after using reactive ion etching technique, up to 2 μm thickness by using CHF3 and Ar gas mixture.

Synthesis of Strontium Hexaferrite Using D-Fructose as a Fuel

Abstract: Strontium hexaferrite (SrFe12O19) powder was synthesized by sol-gel based combustion technique. In this technique, strontium and iron nitrates were used as the source nitrates and D-fructose as the fuel. The phase formation, thermal properties, particle morphology and surface morphology of the sintered pellets were analyzed by X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG-DTA) and high-resolution scanning electron microscope (HR-SEM). Crystalline particles obtained by the calcinations of the precursor powder at 900°C, showed the crystalline diffraction pattern with the corresponding major angles, 30.41°, 31.02°, 32.37°, 34.24°, 35.81°, 37.21°, 40.47° and 42.60° respectively. HR-SEM studies have revealed that the structure of calcined particles is a mixed hexagonal and nearly plate like hexagonal, and the surface of the sintered pellets results in hexagonal structure with good magnetic properties.

Preparation of Fine Ceramics by Soft Chemistry

Abstract: Nanostructured ceramic oxides exhibit novel and appreciable mechanical, electrical and magnetic properties in comparison with the bulk counterparts and therefore offer many industrial applications. Most of the research in the field of nanoscience in the past two decades has been dedicated to the synthesis routes of the fine particles. This review presents an overview of the generally followed methods for the synthesis of fine ceramic oxides with special focus on the methods suitable for bulk production of fine ceramics, particularly on the methods developed by the authors. The method developed by the authors basically involves evaporation/flame pyrolysis of a precursor solution constituting the desired metal ions dispersed in a polymeric reagent (polyhydroxy-organics). Afterward the process has been improved involving metal ions complexed with a chelating agent (diethanolamine triethanolamine, inorganic acids such as citric/oxalic/tartaric acid, EDTA, etc) and simple polyhydroxy organic compound. These re...

Synthesis, Characterization and Magnetic Properties of Nickel Ferrite by Soft Chemical Method

Abstract: Synthesis of nanosized nickel ferrite by a template method where tartaric acid is used as a ligand and nitric acid as an oxidant is described. The synthesized powders were characterized by TGA, XRD, FTIR, TEM, BET, VSM and SQUID studies. The average crystallite size of the phase pure material was of 30 nm and the surface area was found to be 20.37 m(2).g(-1). Magnetic measurements of the phase pure powder were carried out at room temperature by VSM at a magnetic field of 1 Tesla, and by SQUID at a magnetic field of 6 Tesla. High saturation magnetization of 31.43 emu.g(-1) is observed in case of VSM and 43.36 emu.g(-1) is observed for SQUID measurements. Comparative analysis of M(s) values synthesized by different routes are compared.

Combustible Gas Sensing Characteristics of Chemical Solution Synthesized Nanocrystalline Magnesium Ferrite Spinel Particles

Abstract: In the present work we have synthesized nanocrystalline magnesium ferrite powders using an economic wet chemical synthesis route. The phase formation behaviour, microstructure evolution and surface area of the synthesized powder have been investigated using infrared spectroscopy in conjunction with X-ray diffraction, electron microscopy and Brunauer-Emmett-Teller (BET) adsorption isotherm analyses. The structural characteristics of these ferrite powders are correlated with their room temperature magnetic properties. These low temperature synthesized magnesium ferrite nanoparticles are investigated in terms of hydrogen and carbon monoxide gas sensing properties. A gas sensing reactor, equipped with automated gas flow controllers and data acquisition system, are used to evaluate the gas sensing characteristics of the synthesized materials under dynamic flow of gases.

Influence of SiO 2 and Al 2 O 3 Fillers on Thermal and Dielectric Properties of Barium Zinc Borate Glass Microcomposites for Barrier Rib of Plasma Display Panels (PDPs)

Abstract: In a lead-free low temperature sinterable multicomponent barium zinc borate glass system, BaO-ZnO-B(2)O(3)- SiO(2)-Li(2)O-Na(2)O (BZBSLN), the influence of SiO(2) (amorphous) and Al(2)O(3) (crystalline, a-alumina) ceramic fillers on the softening point (T(s)), glass transition temperature (T(g)), coefficient of thermal expansion (CTE), and dielectric constant (epsilon(r)) has been investigated with a view to its use as the barrier ribs of plasma display panels (PDPs). The interaction of fillers with glass which occurred during sintering at 570 degrees C has also been studied by XRD and FTIR spectroscopic analyses. It is observed that the filler has partially dissolved in the glass at the sintering temperature leaving some residual filler which results in ceramic-glass microcomposites. The distribution of fillers in the glass matrix and microstructures of the composites have been analyzed by SEM images. It has been seen that the T(s), T(g), CTE and epsilon(r) slightly increased with the increase of Al(2)O(3) content. In the case of SiO(2) filler, the T(s) and T(g) gradually, increased whereas CTE and epsilon(r) gradually decreased along with the addition or SiO(2). These experimentally measured properties have also been compared with the theoretically predicted values. Both the experimental and theoretical predictions of these properties with added filler contents have been found to be correlated very well. In consideration of the desired properties of barrier rib of PDPs with respect to use on PD200 glass substrates, the addition of Al(2)O(3) filler to BZBSLN glass has been found to be more preferable than SiO(2) filler.

Functional Ceramic Tiles

Abstract: The ceramic industries in India have made a quantum jump in last couple of years. The tile industry in India is about 100 years old and is now forming a sizable industrial base. The production of ceramic tiles in the year 2008–09 has reached a record high of about 450 million m2 in India as against about 9000 million m2 in the world. The growth rate of industry has gone up to 12% per annum as compared to the preceding year. In particular reference, H & R Johnson (India) Ltd (HRJ) being the leader in the ceramic tiles has developed number of special types of new generation functional ceramic tiles like anti bacterial, anti static, anti skid, water repellent, photo-luminescent tiles, easy clean, etc. Work is also in progress to develop other functional tiles.

Production and Characterization of Glasses and Glass-Ceramics from Egyptian Iron Slag Waste

Abstract: Trials were made for reprocessing Egyptian blast furnace slag with and without additives or commercial batches to produce glasses. X-ray diffraction studies were done to identify the crystallization phases separated by two steps regime for controlled crystallization. The corrosion behaviours of the prepared glasses and corresponding glass-ceramics by different leaching solutions were done at both room temperature for 1 and 2 months and at 95°C for 1 h through the grain method. A further corrosion test inside a gamma-irradiation chamber was carried out for both the reference vitrified slag and the highly promising glass and glass-ceramic samples under direct gamma irradiation facility. Infrared absorption spectra of the prepared samples were measured to identify their structural building units. Scanning electron microscope was used to study the morphology of the prepared samples after corrosion and irradiation. X-ray diffraction studies indicate the separation of gehlenite and akermanite as major phases in...

Drying Behaviour of Gelcast Green Alumina Parts Utilizing PEG Solution

Abstract: In this work, gelcast alumina green parts were dried by utilizing polyethylene glycol (PEG) solution as the liquid desiccant medium. The parts lost about 30–40 wt% of internal water in a reasonable period of time, i.e. 2–3 h and accomplished most of the shrinkage uniformly, then the part could continue drying in air at the room conditions. Finally, a defect-free porous part could be obtained after the process of the binder burnout at 900oC. The results show that the green part loses more weight at a higher rate while drying in the PEG6000 solution than in the other PEG solutions with different PEG molecular weight. The solid loading of the alumina slurry and the concentration of PEG solution also affect the drying process significantly.

Supercontinuum Generation in Microstructured Silica Optical Fibers: The Formation of Artificial White Light

Abstract: The inherent feature of nonlinear optics is the modification of the optical properties of the medium due to the interaction of the propagating high intensity light with the medium ultimately leading to the generation of new frequencies. An ultra-short optical pulse experiences spectral broadening when it is passed through a nonlinear medium such as high purity silica fiber and eventually generates artificial white light with unique spectral properties, controlled time duration and high spectral brightness. Owing to its wide and continuous spectra, such phenomenon is generally called supercontinuum (SC) generation. A variety of nonlinear processes governed by the associated pulse duration are involved in such spectral broadening. For femtosecond pump pulses, soliton dynamics plays a pivotal role whereas self-phase modulation (SPM), four wave mixing (FWM) etc are important for wider pump pulses. The generation of white light is an interesting physical phenomenon and it opens up new possibilities in the fiel...

Thermally Stable Ultrafine Au Nanoparticles Embedded in an Anatase Matrix

Abstract: A novel method has been developed to form Au-TiO2 composites where the sizes of the Au nanoparticles (NP) are maintained below 5 nm along with a high level of loading. Specifically, an optimized TiO2 reactive sol was hydrolyzed in the presence of pre-fabricated 2.2 ± 1.4 nm CTAB capped Au NPs to form combined Au-TiO2 composites. It was found that the embedded Au NPs did not undergo any growth or aggregation even when the composites were heated up to 500°C. X-ray diffraction patterns of the as-synthesized and annealed products indicate that there was no bulk deposition of Au on the surface of the composite, concomitantly anatase phase of TiO2 formed and the Au NP sizes were maintained at 3.2 ± 1.0 nm. These were well dispersed within the anatase matrix and characterization of the products was done using transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD).

A Hybrid Approach of Partial Least Squared Analysis and Artificial Neural Networks for Predictive Control of a Ceramic Process

Abstract: Artificial neural networks (ANNs) have been widely used in modelling and control of many practical industrial nonlinear processes. However, most of them have focused on a general approach for input selection. In this paper, a hierarchical hybrid approach of partial least squared (PLS) analysis and ANNs has been applied for predictive control of a real drying process in ceramic tile manufacturing. This approach is employed in order to promote the reliability of neural network model via reduction of the input set dimension. First, PLS analysis is done to arrive at the significant factors that influence the spray drying quality the most. Also, the significant factors are used to construct the predictive neural network model so called the Focus-NN model. Next, the reliability of the Focus-NN model is compared with the ANN model. In order to develop a predictive-control strategy using a more reliable model, i.e. the Focus-NN model, several scenarios as an accurate, fast running and inexpensive method are deplo...

Effect of nanometric zirconia-mullite precursor on the properties of low cement castables

Abstract: Nanometric zirconia-mullite precursors are synthesized through sol-gel route. Incorporation of these precursors in low cement castable refractories improves the bulk density, compressive strength and thermal shock resistance through formation of integrated matrix of castable at high temperature. In the present investigation, white tabular alumina aggregate, calcium aluminate cement bond material, microsilica, microfine alumina and nanometric zirconia-mullite precursors are used in the formulation. The important properties like bulk density, apparent porosity, linear change, cold crushing strength before and after thermal spalling of castables are studied. Phases are identified by X-ray diffraction analysis. SEM study has been used to analyze the integrated matrix of the castables.

Effect of Different Solvents on the Synthesis of δ-Vanadyl Phosphate and Its Performance as Cathode for Li-ion Battery

Abstract: In the present work δ-vanadyl phosphate (VOPO4) was synthesized in the presence of different solvents like water, ethanol, diethyl ketone and 2-propanol. Role of these solvents on the Li-intercalation behaviour of synthesized δ-VOPO4 has been studied. The solvents affected significantly the size of the crystallites and the level of impurities in the synthesized material. δ-VOPO4 synthesized using water as solvent, possessed a significant Li-intercalation capacity ca., 124 mAh.g−1 at 3.7 V corresponding to 75% of its theoretical capacity. Among the organic solvents used, sample prepared using ethanol exhibited the highest Li intercalation capacity. Small amount of β-phase was observed in the synthesized δ-VOPO4 (with phosphate/vanadium ratio of 2) using ethanol and Li-intercalation capacity of this phase was about 137 mAh.g1, corresponding to 85% of the theoretical capacity. The capacity was found to be almost stable at 110 mAh.g−1 over 100 cycles.

Preparation of Yttria Stabilized Zirconia Precursor Hydroxy Hydrogel through Co-precipitation and Study of Sintering Process of Calcined Hydrogel

Abstract: Synthetic process of making yttria stabilized sub-micron zirconia powder was studied by co-precipitation technique at room temperature using zirconyl chloride solution of different concentrations. The effect of concentration on particle agglomeration and sinterability of powder mixed with yttrium nitrate solution as a source of Y(2)O(3) and ammonia as precipitating agent was investigated. Hydrogels of different batches obtained by precipitation reaction were characterized by characterizing particle size and specific surface area, SEM, XRD, TGA and DTA analyses. Hydrogel obtained from low concentrated ZrOCl(2) solution showed large particle size and low specific surface area due to hard agglomerate of fine particles and poor sintering behaviour of calcined powder compared to powder obtained from high concentrated solution. Sintering temperature of 1400 degrees C was found to be suitable for optimum densification (96.8% theoretical density) as also optimum flexural strength (similar to 345 MPa) that was achieved (in case of the calcined gel of agglomerate size 3.7 mu m) for powder precipitated from 30 wt% zirconyl chloride solution sintered at 1400 degrees C. This was attributed to small particle size and high specific surface area (compared to other stock solution) of hydrogel precipitated from 30 wt% stock solution. SEM of sintered sample showed fine grained structure with absence of pore.

Development of a Pneumatic Transport System for Bulk Transfer of Metal Grade Uranium Oxide Powder

Abstract: Uranium oxide powder is a commonly handled ceramic powder in nuclear industries. Design of the powder transfer system is an important aspect because of some of its typical characteristics. Pneumatic transport system has been widely used in transferring powder from one place to another. A pneumatic transport system using vacuum has been presented in the paper. This is used for bulk transfer of UO3 powder. The system consists of a cyclone separator and filter cloth at the top of the cyclone separator. The pneumatic transfer system provides high efficiency with sustainable performance and it is a compact, robust, handy and moveable unit. No degradation of the powder quality has been observed during transfer. The system provides highly efficient, easy and safe transfer of radioactive powder, better working environment for the operator.

Advances in Aerogels made by Sonocatalysis

Abstract: High power ultrasound applied to liquids produces cavities. When an alkoxide/water mixture is sonicated, the cavities, which attain very high temperatures and pressures, act as nanoreactors, where ...

Role of Iron Diffusion in Oxynitride Glass—a Mossbauer and EPR Study

Abstract: Oxynitride glass appears at the grain boundary of dense silicon nitride based ceramics sintered with metal oxides. Iron diffusion in oxynitride glass, similar in composition to that formed at the grain boundary of such ceramics, is studied. In order to know the mechanism of iron diffusion and valancy and coordination state of iron, findings of Mossbauer and EPR spectroscopies are corroborated in terms of possible occupancy of iron in such glasses. Tetravalency of iron or ferric [Fe3+]tet is indicated, though a straightway conclusion cannot be forwarded in favour of any of them right now.