Showing papers in "Transactions of The Indian Ceramic Society in 2013"

Fabrication of Biomedical Implants using Laser Engineered Net Shaping (LENS

Abstract: There has been significant research, understanding of musculoskeletal disorders, but the development of suitable bone replacement materials for load-bearing applications is still lacking. Commercially available load-bearing implants/materials differ significantly from the natural host tissues in several aspects such as macro/microstructures, mechanical, physical and chemical properties. These differences limit the effectiveness of implants’ biological repair capability and longevity. One approach to enhance the cellular response and tissue integration of metal implants is to design and fabricate novel porous biomaterials that closely resemble the architecture and properties of natural bone tissue.In this article, we review application of Laser Engineered Net Shaping (LENS™) - an additive manufacturing process developed at Sandia National Laboratories, in developing materials/structures for load bearing implant application to enhance their in vivo life time. It has been established that LENS™ process is ca...

Synthesis, Densification and Characterization of Boron Carbide

Abstract: This paper presents the experimental results on synthesis of boron carbide from its elements. Boron to carbon ratio of 4:1 and a synthesis temperature of 1850°C was found optimum to obtain stoichiometric B4C. Higher boron in charge resulted in the formation of boron rich phase B8C along with B4C but was not effective in eliminating free carbon in the product. Effect of hot pressing parameters on densification of boron carbide was investigated and the optimum operating parameters to obtain B4C pellets with a density of ≥95% TD were identified. Mechanical and thermal properties were characterized and compared with literature values.

Effects of Iron Oxide on the Crystallization Kinetics of Baiyunebo Tailing Glass-Ceramics

Abstract: Glass-ceramics in the CaO-MgO-Al2O3-SiO2 system were prepared using Baiyunebo tailing and fly ash as the main raw materials. The effects of iron oxide (Fe2O3) on the crystallization kinetics of augite-based glass-ceramics were studied by using differential thermal analysis (DTA), X-ray powder diffraction (XRD), electron backscatter diffraction (EBSD), energy dispersive spectrometer (EDS) and Raman microscopy. The results of Raman and EBSD examinations confirmed the presence of magnetite phase within the glass after nucleation treatment. Augite was the main crystal phase of the studied glass-ceramics. Our result suggested magnetite nuclei to be the starting points of augite crystallization. In addition, the activation energy of crystallization (Ec ) for augite crystal growth, obtained from Kissinger equation, first increased up to a maximum, then decreased with the increase of additional iron oxide, varying between 331 and 426 kJ.mol–1. The variation of activation energy might be related to the viscosity o...

Recent Advances of Doping of SnO2 Nanocrystals for Their Potential Applications

Abstract: SnO2 nanocrystal is a novel wide band gap n-type semiconductor which exhibits outstanding electrical, optical and electrochemical properties that can be exploited for solar cells, catalytic support materials, transparent electrodes and solid-state chemical sensors applications. The main focus of this article is to address the impacts of doping on the various properties of SnO2 nanocrystals including optical, electrical, photocatalytic and gas sensing. Recently, emphasis is given on metal ion doped SnO2 nanocrystals to enhance the electrical and optical properties. Metal ion doped SnO2 nanocrystals are found to be potential candidates for gas-sensing devices. We will begin with the description of general synthetic methodologies for designing doped SnO2 nanostructure materials. Interesting findings are that the application-based properties such as photocatalytic and gas sensing are increased manifold after doping of SnO2 nanocrystals. Finally, a tentative outlook on future developments of this research fiel...

ZnAl2O4-Based Microwave Dielectric Ceramics as GPS Patch Antenna: A Review

Abstract: This paper describes the potentials of zinc aluminate (ZnAl2O4) based microwave dielectric ceramics as patch antenna for GPS applications. Nowadays the GPS operating frequencies has been shifted from microwave technology to millimeter-wave technology. Various microwave dielectric ceramics (MDC) have been explored and widely used in telecommunication industries. Among the most interesting materials of that kind, zinc aluminate (ZnAl2O4) is recognized as one of the most promising non-metals and offers many advantages as GPS patch antenna. By modifying ZnAl2O4 compound with other materials, it is found to have high quality factor (Q>5,000), low dielectric constant (er<20), and near zero temperature coefficient of resonant frequency (τf∼0). The studies also evidence the typical value of er for GPS patch antenna and microwave substrate in the range of 4

Large Area Deposition of Polycrystalline Diamond Coatings by Microwave Plasma CVD

Abstract: Polycrystalline diamond (PCD) films have been grown over 100 mm diameter silicon (100) substrate, using microwave plasma chemical vapour deposition (MPCVD) technique. The deposition was carried out inside a 15 cm diameter quartz chamber with microwave power of 15 kW at 915 MHz frequency. Uniform substrate surface temperature of 1050°C with plasma heating was maintained with simultaneous cooling arrangement. The pressure was 110 Torr and the microwave incident power was 8.5 kW. Temperature uniformity and plasma geometry over the substrate are the key parameters for producing uniformly thick MPCVD diamond films of high quality. Thickness uniformity of as-deposited films is ±10% across 100 mm diameters with a growth rate of 1 µm.h–1. The grown PCD was characterized by X-ray diffractometry (XRD), Raman spectrometry, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and bright field imaging technique. Experimental results indicate columna...

Functional Anode Materials for Solid Oxide Fuel Cell – A Review

Abstract: Solid oxide fuel cells (SOFC) have received wide interest due to the associated advantages of environment friendly alternate energy source. Owing to the capability of efficient power generation from a broad spectrum of practical fuels, viz. hydrogen, bio fuels, etc, SOFC finds potential applications in portable, mobile and stationary markets. Presence of multi components, viz. anode, cathode, electrolyte, etc in single cell demands the maintenance of mutual compatibility in SOFC. The present review describes the research work related to the development of anode component. In addition, the present context also highlights the research work at CSIR-CGCRI, Kolkata, India, focussed towards the development of planar anode-supported SOFC. Under this on-going activity, novel electroless technique is employed to prepare nickel (Ni)-8 mol% yttria stabilized zirconia (YSZ) anode. Optimized processing parameters of electroless technique impinge certain interesting features in the cermet, by the virtue of which major ...

Sol-Gel Combustion Synthesis of Nanocrystalline Wollastonite by Using Glycine as a Fuel and Its in vitro Bioactivity Studies

Abstract: Nanocrystalline wollastonite was produced by sol-gel combustion method by using glycine as a fuel. The obtained powders were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The functional groups were identified by FTIR spectra and the XRD pattern reveals the formation of pure wollastonite phase. The SEM images reveal that the wollastonite particles are agglomerated and possess porous flakes-like morphology. The average particle size of the wollastonite particle observed from SEM images is found to be in the range of 44-111 nm. In vitro bioactivity characteristics of wollastonite were studied by immersing the prepared wollastonite scaffold in simulated body fluid (SBF) solution and the results indicate good bioactivity of wollastonite.

Study of the Structural and Electrical Behaviour of Ca Doped LaInO3 Electrolyte Material

Abstract: LaInO3 has been doped with CaO to study the structural changes that lead to variation in properties of the electrolyte. It has been observed that LaInO3 is orthorhombic in nature, but with addition of Ca above certain value, it gets distorted from its orthorhombic symmetry. The electrical conductivity of the material has also been studied. The ac impedance plots have been used to analyze the electrical properties of the doped sample. The plots clearly indicate that the replacement of La by Ca enhances ionic conductivity of the system, whereas substitution of Ca at In site is rather difficult due to large difference in the ionic radii. The conductivity observed is of the order of 10–4 S.cm–1 at 800°C for 10 mol% doped Ca in LaInO3.

Effect of Zirconia Content and Powder Processing on Mechanical Properties of Gelcasted ZTA Composite

Abstract: Addition of fine zirconia particles in the alumina matrix in order to produce ZTA composite is a well-known method for improving the mechanical properties of alumina ceramics such as flexural strength and fracture toughness. Increasing homogeneity and reducing alumina grain size are two key factors for achieving proper mechanical properties in this ceramic matrix composite. In this work two batches of ZTA powder precursor were prepared through mixing of alumina and zirconia by ball milling and in situ synthesis of ZTA composite via solution combustion method. The bending strength testing samples were fabricated through gel-casting process. The effects of different powder processing methods as well as zirconia contents on microstructural homogeneity and mechanical properties of ZTA composites were investigated. The samples produced by solution combustion synthesized powder yielded higher homogeneity, finer microstructure and higher flexural strength. Results showed an upswing in the fracture toughness for ...

Lithium Disilicate based Glass-Ceramics for Dental Applications

Abstract: Glass-ceramics are used in dentistry for various applications such as dental inlays, onlays, crowns, veneers, bridges, etc. Especially lithium disilicate glass-ceramics, because of their excellent aesthetics, supreme mechanical properties and ease of shaping into final restoration, are becoming a compelling material in dental prosthetics. The present work is aimed at synthesizing lithium disilicate glass-ceramics for their application as a dental restorative material. In this, effects of composition and heat treatment schedule on microstructure and phase content are investigated.

Electrochemical Performance of Cathode LiVOPO4 Doped with Mo and W

Abstract: Molybdenum (Mo) and tungsten (W) substituted LiV0.99X0.01OPO4 (X = Mo and W) compounds were synthesized by impregnation method. The structures of samples were characterized by X-ray diffraction, and their electrochemical properties were studied by using charge-discharge in galavanostatic mode versus Li+/Li. The electrical conductivity of the samples was estimated by using impedance spectroscopy measurement with 2 point probe method at room temperature. Phosphates of composition LiV0.99X0.01OPO4 with 1% Mo and W content in the structure exhibits high intercalation potential of 3.95 V versus Li/Li+. It was found that the electrical conductivity of Mo and W substituted samples at room temperature was improved to 4.8 × 10–6 and 1.5 × 10–5 S.cm–1, respectively. Discharge capacity was also observed for the W doped sample with good retention performance up to 20 cycles at high current density of C/5 (0.4 mA.cm–2).

ZnCl2 Modified Physical and Optical Properties of Barium Tellurite Glasses

Abstract: The optical properties of tellurite based glass systems are composition dependent. For this purpose glass samples of the composition 70TeO2-(30–x)BaO-xZnCl2 with x = 5, 10, 15, 20 and 25 have been synthesized by rapid melt quenching technique. Glassy nature has been confirmed by X-ray diffraction pattern. The physical properties like density, molar volume and crystalline volume have been estimated and found that density decreases while the molar volume increases with increase in ZnCl2 content. The glass transition temperature decreases with increase in halide content due to increase in the non-bridging oxygen contribution. Direct allowed optical transitions are favourable in these glasses and the optical band gap energy (Eopt) has been observed to increase with increase in ZnCl2 content. The value of Urbach energy of these glasses shows increasing behaviour with ZnCl2 concentration indicating the breaking of weak bonds into defects. Metallization criterion for these materials shows that these glasses may ...

Synthesis of Cordierite Powder from Blast Furnace Slag

Abstract: We report a new process of synthesizing cordierite powder from blast furnace (BF) slag developed by using sol-gel route. The phase transformation of dried gel calcined under different temperatures was investigated by XRD and FTIR. It was found that one complicated silicic acid-sulphuric solutions system containing cations of Al3+ and Mg2+ was formed as the precursor of the cordierite by acid treatment of the slag. Cordierite powders with α-cordierite as the main crystalline phase can be obtained when dried gel was calcined in the 1200°-1300°C temperature range. A viable technology to recover the major constituents from BF slag was provided.

Formation of Silicide Based Oxidation Resistant Coating Over Mo-30 wt% W Alloy

Abstract: Studies were carried out to develop silicide based oxidation resistant coatings over Mo-30W alloy substrate employing halide activated pack cementation coating process. Effect of activator content and temperature on coating was studied. Coated samples were characterized for phase and microstructure evaluation by SEM and EDS. Cyclic oxidation tests on coated alloy were performed at 1000°C up to 50 h. The coating provided enough protection from oxidation.

Structural and Optical Investigation of Rare Earth Doped Oxyfluoride Glasses

Abstract: UV-Vis and FTIR analyses have been performed on an aluminosilcate base glass doped with two different rare earths (Dy3+ and Eu3+) with varying concentrations. The glasses were prepared by conventional melt quenching technique. While the absorption intensity of the observed bands was found to increase with increase of RE concentration, the RE doping did not cause any new structural unit and the FTIR spectra practically remained unchanged.

Effect of Process Parameters and Binder Concentration on Mechanical Properties of Phosphate Bonded Alumina

Abstract: Alumina and alumina matrix composites typically require sintering temperature in excess of 1550°C. Utilization of aluminium phosphate bonding provides process flexibility and significantly lowers sintering temperature (500° to 1280°C). While phosphate bonded alumina (PBA) may have a lower sintering temperature, its limitations include the presence of porosity in pressure less sintered samples leading to lowered strength and phase instability above approximately 1200°C. The present study describes the effect of processing routes and binder concentration on density, hardness, Young's modulus and transverse rupture strength (TRS) of PBA. In this study, ultra fine Al2O3 (particle size ≈0.5 µm) was reacted with H3PO4 to yield phosphate bond in a matrix of tabular Al2O3 (particle size ≈0.5 µm) after final sintering at 1280°C for 6 h. Green samples were compacted at pressures in the range of 96-290 MPa. The effect of aluminium phosphate binder concentration on mechanical properties of the PBA samples was measure...

The Spectroscopic Properties of Mo5+ in ZnO-ZnF2-B2O3 Glasses

Abstract: The system of glass samples ZnO-ZnF2-B2O3 containing different concentrations of MoO3 (ranging from 1.0-7.0 mol%) were prepared. The glasses were characterized by optical absorption, ESR, FTIR and Raman spectral studies. The analyses of the results of the optical absorption and ESR studies indicated that the molybdenum ions coexisted in Mo5+ state with Mo6+ state in these glasses, whereas the results of the FTIR and Raman spectral studies indicated that there was an increasing degree of disorder in the glass network with increase in the concentration of MoO3.

Heating Transformations, Technical Properties and Ceramic Suitability of Clays

Abstract: Heating transformations of calcareous chloritic-illitic and carbonate-free kaolinitic-illitic raw clays, and their mixes were investigated in the range of 700°-1060°C using X-ray diffraction, thermal analyses and scanning electron microscopy. Moreover, changes of bending strength, shrinkage and water absorption versus temperature and clay content were followed. The results showed that plagioclase and sanidine together with spinel formed and persisted in fired calcareous and non-calcareous clays respectively. In fired clay mixtures only plagioclase occurred. Formation of the latter phase was discussed using CaO-SiO2-Al2O3 equilibrium diagram. The intensification of the neoformation processes due to the increase of temperature together with melt formation mainly in carbonate-free clay improved the ceramic properties to certain extent. Improvement of the mechanical strength was also observed for mixture of clays. The reported diagrams, involving grain size distribution and chemical composition, showed that b...

High Strength Lightweight Glass-Ceramics Sintered from Fly Ash: A Potential Proppant Material

Abstract: High strength lightweight glass-ceramics were sintered with fly ash as the main raw material. The effects of utilization rate of fly ash, nucleating agents, sintering temperature and heating rate were studied. The optimum utilization rate was found to be 60%. The nucleating agents enhanced the properties of the proppant in the order: Fe2O3 > TiO2 > MnO2 > Cr2O3. The enhancement was much pronounced with the use of 6 wt% Fe2O3 or 5 wt% Fe2O3 along with 1 wt% TiO2. The sample sintered at 1400°C for 30 min at a heating rate of 5°C.min–1 showed optimum properties, viz. high strength (120.97-125.45 MPa), low water absorption (0.57-0.82%) and low density (1.32-1.56 g.cm–3). The fabricated glass-ceramics may be assumed to be a promising proppant material for hydaulic fracturing production of petroleum.

Physicochemical Characterization and Valorization of Tunisian Olive Oil Mill Wastewater Sludge in Ceramic Product

Abstract: This study describes the introduction of the effluent olive mill wastewater sludge (OMWS) with a grain size lower than 1 mm into the fired laboratory produced clay bricks. In Tunisia, a set of olive oil production factories produce OMWS in large quantities. Currently, in Sfax (Tunisia), the OMWS has been stored into basin of storage, even though presenting a high toxicity which causes pollution to the environment. After characterization, the Tunisian OMWS was introduced into the clay bricks with mass percentages of 0, 3, 6, 8 and 10. The samples prepared with OMWS were found to be comparable in properties and performance to a control product, without OMWS, as adjuvant. The prepared samples were undergone physico-chemical, mechanical and environmental tests. The obtained results showed that with 6% OMWS, the clay-bricks successfully satisfied the standard requirements. Introduction of OMWS in clay-bricks can be considered as a promising solution to valorize this effluent (OMWS).

Spectroscopic Studies on Er3+ doped Boro-Tellurite Glasses

Abstract: Er3+ doped boro-tellurite glasses with the chemical composition (40–x)B2O3+30TeO2+10Na2O+10ZnO+5Li2O+5CaO+xEr2O3 (where x = 0.01, 0.1, 1, 2 and 3 wt%) were prepared by conventional melt quenching technique. The spectroscopic analyses were made through absorption and luminescence measurements. From the absorption spectra, bonding parameters, oscillator strengths and Judd-Ofelt (JO) parameters were calculated. Through the luminescence spectra the various lasing parameters such as stimulated emission cross-section (σP), branching ratios ( ) and radiative lifetime (τcal) were calculated for the transition and the results were presented.

Na2S-P2S5 Based Super-Ionic Glasses for Solid Electrolytes

Abstract: Melt quenched sulphide glass of system Na2S-P2S5 has been synthesized by taking equimolar quantities of Na2S and P2S5. The glass sample was characterized by XRD, DTA/TG, dilatometery and impedance ...

Fluorescence Features of Samarium Ion in PbO-B2O3-SiO2-Al2O3 Glass System

Abstract: The glasses of the composition 30PbO-65B2O3-0.5SiO2-(4.5–x)Al2O3-xSm2O3 with x varying from 0 to 2 mol% have been synthesized. Optical absorption and photoluminescence spectra in the spectral range 300-2200 nm and 450-700 nm, respectively, were studied at ambient temperature. The Judd-Ofelt theory was applied to characterize these spectra. The analysis of the results indicated that the glasses containing maximum concentration of Al3+ ions in octahedral positions is preferable for achieving the highest luminescence efficiency.

Effect of Polyethylene Glycol in Porous Alumina Based Thin Film Capacitive Humidity Sensor and Its Modelling

Abstract: Present work deals with the development of a capacitive humidity sensor using porous thin film of aluminium oxide on the interdigitated gold electrodes. We describe the effect of polyethylene glycol (PEG) addition to pure sol solution of γ-Al2O3 on the humidity sensing characteristics of the sensor. The film was fabricated by dip coating of sol solution obtained from the sol-gel method. To compare the response characteristics, three different sensors such as pure alumina sol, 0.125 g and 1 g PEG added in pure sol have been fabricated. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. The sensor so obtained was found to be sensitive in humidity range of 1 to 90%. Addition of fixed amount of PEG in pure alumina sol improved the response characteristics significantly. The response time of the 0.125 g PEG added sensor was very low, about 10 s and the recovery time was about 3 s. The behaviour of the most sensitive sensor has been modelled with a view to minimize...

Investigation on Slag Resistance of Magnesia Based Castable Containing SiC

Abstract: Corrosion of four magnesia based castables with different SiC contents by ladle slag was conducted using the static crucible test. Effect of SiC content on the slag resistance of castables was investigated by XRD, SEM, EDAX. The reactions between refractories and slag were simulated through FactSage® thermochemical software. It has been found that SiC can increase the penetration resistance of magnesia based castables, not decreasing their corrosion resistance. With increasing the content of SiC, the SiO2 content and the viscosity of penetrated slag increase. The lower wettability of slag to SiC and the higher viscosity of penetrated slag affect the penetration resistance of magnesia based castables, whereas the reactions between slag and castables affect the corrosion resistance of magnesia based castables. The thermochemical simulation helps to understand the reaction mechanism.

New Trends in Bioactive Glasses: The Importance of Mesostructure

Abstract: A new generation templated mesoporous bioactive glasses (MBGs) with alkali oxide has been synthesized for biomedical applications with different compositions by sol-gel method. The sol-gel route involves the evaporation induced self assembly (EISA) process using non-ionic block copolymer as structure directing agent. In vitro bioactivity test on the obtained glasses after immersion in simulated body fluid has been carried out for various time durations. With the aid of four different glass systems, the role of calcium and phosphorus on in vitro bioactivity of silicate glasses has been investigated. Several analytical techniques have been used to characterize the MBG samples before and after soaking in the simulated body fluid (SBF) to establish correlation between composition, porosity and bioactivity. The quaternary glasses have been found to show rapid hydroxycarbonate apatite (HCA) formation and crystallization than ternary and binary glasses independent of Na2O/CaO content. Based on the obtained resul...

Formulation of Specialty Glass Frit and Its Use for Decontamination of Joule Melter Employed for Vitrification of High Level Radioactive Liquid Waste

Abstract: Advanced vitrification system at TWMP Tarapur was used for successful vitrification of large volume of high level radioactive liquid waste (HLW) stored in PREFRE waste tank farm. After completion of the operational life of the Joule melter, dismantling was planned. Prior to dismantling, the holdup inventory of active glass product from the melter was flushed out using specially formulated inactive glass frit to reduce the air activity buildup in the cell during dismantling operations. The properties of the specialty glass frit prepared were comparable with those of the regular product glass. More than 94% of holdup activity was flushed out from the Joule melter prior to dismantling of the melter.

Development and Characterization of Porous Silicon Nitride Tubes

Abstract: As the porous aluminous porcelain diaphragm tubes in the electrolytic cells, employed in the aqueous reprocessing of spent nuclear fuels, undergo leaching in concentrated nitric acid, corrosion resistant 600 mm long silicon nitride tubes were developed indigenously by reaction bonding of pre-formed silicon green tubes in nitrogen atmosphere. The process parameters for the fabrication were optimized to produce tubes with density, porosity and liquid permeability in the range 2.2-2.5 kg.dm–3, 20-25% and 10–5-10–6 cm.s–1 respectively. The performance of the fabricated tubes was evaluated by using them as the diaphragm tubes in the electrolytic destruction of 4 M nitric acid and the efficiency of the process was compared with that for a cell in which a commercially available silicon nitride tube was used as the diaphragm material. Though performance of both the tubes was comparable, the resistance offered by the indigenous tube to the flow of current through it was much lower than that of the other tube.

Effect of Addition of Talc on the Properties of Feldspar-Kaolinitic Clay Blends during Heating

Abstract: Effects of low addition of talc (up to 8 wt%) on thermal transformations of feldspar-kaolinitic clay blends were investigated by X-ray diffraction, scanning electron microscope and Fourier-transform infrared spectroscopy. The variations of some properties (firing shrinkage, water absorption, density and bending strength) versus talc additions were measured. It was found that talc additions did not affect the presence of neoformed phases (mullite, spinel and glassy phase) but markedly influenced their contents. With up to 4 wt% talc addition, the amount of the formed phases increased with the increase of talc content; consequently shrinkage increased along with strength and density. Apparently, talc derivative oxide (MgO) facilitated the sintering process. For >4 wt% talc, the effect of alkali fluxes reduced because of the abundance of MgO, and consequently the glassy phase content decreased. Therefore, the variations of properties changed except for water absorption and total porosity, which manifested a ...