Showing papers in "Transactions of The Indian Ceramic Society in 2016"
TL;DR: In this article, the effects of partial substitution of K2O for Na2O on the sintering and crystallization of a SiO2-CaO-K2O-Na2O -CaF2 glass have been studied.
Abstract: In this work, the effects of partial substitution of K2O for Na2O on the sintering and crystallization of a SiO2-CaO-K2O-Na2O-CaF2 glass have been studied. This glass composition was close to the glass-forming composition of fluorocanasite miner al. T he glass-cer amics were made v ia sintering with concurr ent crystallization of glass-powder compacts. The samples were characterized by hot stage micr oscopy, dif fer ential t hermal analy sis, X- r ay diff r action and scanning electron microscopy. CaF2 precipitated as a primary crystal in all studied glasses and crystallizat ion was predominant between 625° and 1000°C . All glasses showed the best sinterability at 1000°C. By increasing the K2O content from 7 to 13 mol% (at the expense of Na2O), the crystallization peaks shifted to higher t emper at ur es and the main cr yst alline phases at t he best sintering temperature were fluorocanasite, cuspidine, xonotlite and wollastonite. Vickers microhar dness, 3- point bending str ength, f ract ure t ou...
24 citations
TL;DR: In this article, an activated carbon adsorbent was synthesized from waste tire rubber through pyrolytic technique and characterized by CHNS elemental analysis, XRD, FESEM-EDX and FTIR spectra.
Abstract: The activated carbon adsorbent was synthesized from waste tire rubber through pyrolytic technique and characterized by CHNS elemental analysis, BET, XRD, FESEM-EDX and FTIR spectra. The adsorption of Cr(VI) and Mn(II) ions on thus obtained adsorbent was investigated separately by varying experimental parameters, such as pH, adsorbent dose, contact time, adsorbate ion concentration and temperature. The adsorption processes were found to be the best fitted in Langmuir adsorption isotherm model controlled by pseudo-second-order kinetics. The Cr(VI) and Mn(II) ions adsorption capacity of AC were 14.45 and 3.04 mg.g–1, respectively. The rate constants for the adsorptions of Cr(VI) and Mn(II) ions were 5.88×10–1 and 3.95×10–1 g.mg–1.min–1, respectively. The thermodynamic study revealed the adsorption processes to be spontaneous.
16 citations
TL;DR: In this article, the basic principles of DSSCs along with essential characteristics of working electrode, photoanode and other major components, namely photosensitizers, electrolytes and counter electrodes, are concisely highlighted in this review.
Abstract: Dye sensitized solar cells (DSSCs), the third generation solar cell devices have been designed to produce large-scale, inexpensive, environmentally benign solar power devices having promising efficiency and lifetime. Albeit, perfect commercialization of the devices has not been possible worldwide so far, research in this area is immensely growing with promising future. Basic principles of DSSCs along with essential characteristics of working electrode, photoanode and other major components, namely photosensitizers, electrolytes and counter electrodes, which are essential to fabricate an efficient device, are concisely highlighted in this review. In addition, successive propagation of research based on the semiconducting oxides as photoanode for the DSSC device starting from binary to ternary oxides, the perspectives, selection strategies and the status with respect to performance has also been highlighted. In an effort to introduce newer oxides as appropriate alternatives to the pioneer TiO2, ZnO-...
16 citations
TL;DR: In this paper, an attempt has been made to evaluate the mechanical behaviour and wear properties of Al6061-9 wt% B4Cp composite prepared by stir casting.
Abstract: An attempt has been made to evaluate the mechanical behaviour and wear properties of Al6061-9 wt% B4Cp composite prepared by stir casting. During the preparation of composites, K2TiF6 salt is used as flux to increase wettability of B4Cp at low temperature and also two step introduction of the mixture containing B4Cp and K2TiF6 flux (ratio of 0.3) is adopted to achieve better dispersion. Characterization of the prepared composites is done using XRD/SEM/EDS studies. Microstructural characterization has revealed fairly uniform dispersion of B4Cp in Al6061 matrix with clustering at few places. X-ray diffraction pattern taken on the prepared composite clearly reveals the presence of α-Al, B4C, Ti compound layer (Al3Ti/TiB2), AlB2 and Al3BC. Mechanical properties of the prepared composites such as hardness, UTS and specific strength have been improved by 115.3%, 38.8% and 42.8% respectively in comparison with matrix alone. Further, fractography studies conducted on the tensile specimens revealed both du...
15 citations
TL;DR: ZnWO4 nanopowder photocatalyst has been successfully prepared by a simple solution combustion synthesis using Zn(NO3)2.6H2O as oxidizer, sucrose as reducing agent and peroxo tungstic acid as tungsten source.
Abstract: ZnWO4 nanopowder photocatalyst has been successfully prepared by a simple solution combustion synthesis using Zn(NO3)2.6H2O as oxidizer, sucrose as reducing agent and peroxo tungstic acid as tungsten source. The as prepared nanopowder was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) techniques. The PXRD analysis revealed the formation of pure ZnWO4 monoclinic phase. The crystallite sizes calculated using Scherrer equation are in the range 20–30 nm. SEM images exhibit highly porous nature of the product. BET surface area analysis of ZnWO4 nanopowder shows large specific surface area of 19.20 m2 .g–1. Photocatalytic activities of as synthesized powder were investigated by the degradation of methylene blue (MB) solution under UV light irradiation.
14 citations
TL;DR: In this article, the structural, thermal and dielectric properties of MgO-B2O3-SiO2 (MBS) glass-ceramics, with and without TiO2 as additive, have been prepared by sintering at 900oC.
Abstract: MgO-B2O3-SiO2 (MBS) glass-ceramics, with and without TiO2 as additive, has been prepared by sintering at 900oC and their structural, thermal and dielectric properties have been studied. The XRD and SEM studies show that the crystallization increases with addition of nucleating agent TiO2. The per cent thermal expansion decreases as TiO2 content increases. The value of dielectric constant increases with increasing wt% of TiO2 in MHz and GHz frequency range. The dielectric constant values lie in between 3 and 5 in the frequency range of 13.5–18 GHz and in between 9 and 11 at 1 MHz frequency. The microwave dielectric constants of the specimen have been found to be strongly dependent on TiO2 content. Due to low dielectric constant and low sintering temperature, this glass-ceramics is an attractive material for low temperature co-fired ceramics (LTCC) application.
12 citations
TL;DR: In this paper, the preparation of cobalt oxide doped 45S5 bioactive glass and glass-ceramics has been reported, which is used widely because of their bonding capability with hard and soft tissues.
Abstract: 45S5 bioactive glass and glass-ceramics have been used widely because of their bonding capability with hard and soft tissues. One of their major applications is as artificial bone graft. Therefore, they are promising materials in the field of biomedical application. They have inferior mechanical properties in comparison to cortical bone. The present paper reports preparation of cobalt oxide doped 45S5 bioactive glass. Doping of Co2+ ion from 0-2.0 wt% CoO was done to replace Si4+ ion and yield a non charge balanced bioglass. Addition of Co2+ ion was expected to form Si-O-Co and P-O-Co linkages in the bioglass. Tg of bioglasses were determined by differential thermal analysis. Bioactive glassceramics were processed through controlled crystallization of glasses. The crystalline phases in bioactive glass-ceramics were identified using X-ray difractometry. Density, compressive and bending strengths were determined. Ultrasonic wave velocities of bioactive glass and glass-ceramics were measured to study...
11 citations
TL;DR: In this article, a review of recent progress on development of rare-earth (RE) doped glass host based optical fiber materials with special emphasis on large mode area fibers for efficient laser and amplifier is presented.
Abstract: Recent advances of development of rare-earth (RE) doped optical fibers have become increasingly important due to their applications in various optoelectronic devices such as high power optical fiber amplifiers, fiber lasers, etc. We present a review of recent progress on development of RE-doped glass host based optical fiber materials with special emphasis on large mode area fibers for efficient laser and amplifier. The challenging task is to manage high power inside the active core otherwise output power instability would affect the beam quality. Best solution is to use suitable dopants in addition to active elements during the process of fabrication. Modified chemical vapour deposition (MCVD) process combined with solution doping technique is deployed to develop RE-doped nano-engineered glass based optical fibers through suitable thermal annealing of optical preforms. The developed doped fibers are characterized by DTA, TEM, XRD, XAS, EPMA and EXAFS to assess the structural parameters. This new ...
11 citations
TL;DR: In this paper, the effect of cleaning of the FTO substrates on efficiency of the DSSC was shown by two methods, bath sonication and heat treatment, and it was found that heat treatment effectively removed organics compared to the non heat treated process.
Abstract: Cleaning of the FTO substrate is being done to remove the debris present on the substrate during the fabrication of dye sensitized solar cells (DSSC’s). Sonication of FTO substrates by keeping it in soap solution, ethanol and distilled water followed by drying at 100°C has been reported by researchers. Some researchers have mentioned the use of ultr aviolet ozonization (UV-O3) processes to remove the organic contamination over FTO substrates. The present work shows the effect of cleaning of the FTO substrates on efficiency of the DSSC. Cleaning of FTOs was done by two methods – one by only bath sonication and other by bath sonication followed by heat treatment. It was found that heat treatment effectively removed organics compared to the non heat treated process. Heat treatment improved the performance of DSSC’s by enhancing the adhesion of titania film to the FTO substrate.
10 citations
TL;DR: In this article, the authors investigated flash sintering behavior of several zirconia-alumina formulations under a range of DC electric fields up to 700V and found that at low alumina contents (75 wt%) the effectiveness of field assisted Sintering drops off.
Abstract: Flash and field assisted sintering techniques (FAST) have been demonstrated in many singular ceramic systems. However, little has been done to thoroughly investigate this phenomenon in binary systems. Zirconia-alumina composites are of interest because of their widespread use in demanding situations for health care, petrochemical and energy applications. The prospect of minimizing grain growth associated with FAST whilst achieving maximum densification is vital for the above applications to improve performance. Flash sintering behaviour of several zirconia-alumina formulations was investigated under a range of DC electric fields up to 700V.cm–1. At low alumina contents ( 75 wt%) the effectiveness of field assisted sintering drops off. These pointers allowed to gain further insight into the mechanisms of flash sintering and will help to deve...
10 citations
TL;DR: In this article, the effect of sintering temperature and duration on single phase formation and structural properties of Pb0.9Bi0.45O3 (PBFNO) solid solution was investigated.
Abstract: Effect of sintering temperature and duration on single phase formation and structural properties of Pb0.9Bi0.1Fe0.55Nb0.45O3 (PBFNO) solid solution was investigated. The single step solid state reaction method was adopted to achieve the pure perovskite phase. Calcination was carried out at 700oC for 2 h and sintering at different temperatures as 800o, 850o, 900o, 950o, 1000o and 1050oC for 1 h and also at 800oC for 1-5 h to achieve the single phase in PBFNO solid solution. From the X-ray diffraction studies, it was found that sintering at 800oC for 3 h was optimum for achieving single phase and all the other conditions showed an impurity phase. Rietveld refinement was carried out on single phase PBFNO solid solution by using FullProf Suite, which confirmed the monoclinic structure with Cm space group and the obtained refinement parameters were Rp=15.7; Rw p=20.7, Rexp=16.72, χ2(Chi2)=1.54. The lattice parameters were: a=5.666(3) A, b=5.667(4) A, c=4.017(2) A and α=γ=90o, β=89.943(4)o. Scanning ele...
TL;DR: Porous alumina-based ceramics were fabricated by injection method, where alumina powders were used as raw materials and solvent silicone resin was used as binder as discussed by the authors, and the increase of heating temperature promoted the formation of mullite phase when the temperature was higher than 1500°C.
Abstract: Porous alumina based ceramics were fabricated by injection method, where alumina powders were used as raw materials and solvent silicone resin was used as binder. During the heat treatment process, an organic-inorganic transformation occurred in silicone resin. The increase of heating temperature promoted the formation of mullite phase when the temperature was higher than 1500°C. The weight loss of porous alumina based ceramics was maintained at 5.7∼5.9%. When the heating temsperature was 1500°C, porous alumina based ceramics showed the biggest shrinkage rate, lowest apparent porosity and highest bending strength.
TL;DR: In this article, the authors obtained a maximum at 2.44, close to the critical coordination number =2.40 optimized for maximum stability of glassy matrix, which follows Phillips-Thorpe constraint theory where the maximum stability is just obtained if the percolation threshold limit is reached.
Abstract: Ge42–xPbxSe58 (9≤×≤20) glassy alloys have been prepared using melt quenching technique. The samples were then subjected to differential scanning calorimetry (DSC) for recording the phase transformation occurring in the samples as a function of temperature. The characteristic temperatures of transformation, i.e. glass transition temperature, Tg, and crystallization temperature, Tc, were extracted from the DSC scans. The values of Tg and Tc were further used to ascertain thermal stability of the prepared glassy samples using Dietzel (ΔT) stability parameter. The variations of Tg with average coordination number, , were specified. It was found that ΔT exhibited a maximum at =2.44, close to the critical coordination number =2.40 optimized for maximum stability of glassy matrix. Thus, the obtained result follows Phillips-Thorpe constraint theory where the maximum stability of the network is just obtained if the percolation threshold limit is reached. The overall mean bond energies of the gl...
TL;DR: Fused silica ceramics with high flexural strength, and low warpage and shrinkage were casted using gelcasting, a near net shape fabrication technique as discussed by the authors, where Methylacrylamide and N,N-methylenebisac...
Abstract: Fused silica ceramics with high flexural strength, and low warpage and shrinkage were casted using gelcasting, a near net shape fabrication technique. Methylacrylamide (MAM) and N,N-methylenebisac...
TL;DR: In this paper, a surfactant-free solvothermal treatment approach using carbamide as nitrogen precursor was used to obtain N-doped urchin-like TiO2 (NUT) with enhanced photocatalytic properties.
Abstract: N-doped urchin-like TiO2 (NUT) with enhanced photocatalytic properties was prepared through a surfactant-free solvothermal treatment approach using carbamide as nitrogen precursor. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-Vis diffuse reflectance spectroscopy. Effects of different carbamide contents on the crystal phase and the photocatalytic performance of the prepared samples were discussed. XPS results showed that N doping into TiO2 formed Ti-N-O structure. SEM results showed the change of morphology after superfluous doping. N doping can form a new impurity energy level in TiO2 forbidden band and provide a favourable nucleation for TiO2 catalyst. In addition, 0.1 M NUT showed the highest photocatalytic activity among all the prepared samples upon degradation of rhodamine B under sunlight irradiation. The mechanism of organic pollutants degradation on the surface of prepared phtocatalytic...
TL;DR: In this article, a novel TBC system with multiple layers of ceramics: top layer, intermediate layer, bond coat over a suitable metal substrate has been proposed, and an elaborate design methodology has been evolved to constrain the temperature of each layer within their operational limit and minimization of thermal mismatch.
Abstract: Thermal barrier coating (TBC) is essential for scramjet structure to protect the metallic structure from melting or developing high stress. In this perspective, a novel TBC system with multiple layers of ceramics: top layer, intermediate layer, bond coat over a suitable metal substrate has been proposed. First, material selection for TBC system has been carried out based on their thermal conductivity and maximum operational temperature. Then, an elaborate design methodology has been evolved to constrain the temperature of each layer within their operational limit and minimization of thermal mismatch. Different design parameters have been identified and iterative finite element based thermo-structural analyses have been carried out to optimize them and hence, limit metal substrate temperature within 1250 K and the maximum interfacial shear stress within 80 MPa, when exposed to heat flux as high as 1.5 MW/m(2) and pressure greater than 1.3 bars.
TL;DR: MoSi2-10 vol% SiC composites have been prepared in situ by self propagating combustion synthesis from three different composite systems: Mo-Si-C, MoSi-Mo2C and Mo- Si-SiC as discussed by the authors.
Abstract: MoSi2-10 vol% SiC composites have been prepared in situ by self propagating combustion synthesis from three different composite systems: Mo-Si-C, Mo-Si-Mo2C and Mo-Si-SiC. The combustion synthesis temperatures were all above 1800 K and the products were composed of MoSi2, SiC and trace Mo5Si3. MoSi2 and MoSi2-10 vol% SiC composites were consolidated by vacuum hot-pressing at 1400°C to produce monoliths with high density. A uniform dispersion of SiC particles was obtained in MoSi2 matrix composites. MoSi2-10 vol% SiC composites prepared by Mo-Si-SiC raw materials exhibited excellent mechanical properties: Vickers hardness 12.21 GPa, bending strength 773.4 MPa and fracture toughness 3.65 MPa m1/2.
TL;DR: In this article, the physical, structural and optical properties of some semiconducting V2O5-MoO3-ZnO glass-nanocomposites using density, molar volume, X-ray diffraction (XRD), field effect scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectra and UV-VIS absorption spectra have been analyzed.
Abstract: The present work points to highlight the physical, structural and the optical properties of some semiconducting V2O5-MoO3-ZnO glass-nanocomposites using density, molar volume, X-ray diffraction (XRD), field effect scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV-VIS absorption spectra. We have observed that addition of V2O5 increases (or decreases) the density (or molar volume) of the glassy system due to structural changes. Distribution of Zn3V2MoO11, Zn2.5VMoO8 and Zn2V2O7 nanoparticles has been confirmed from FESEM and XRD studies. It has been observed from FTIR spectra that the network structure depends upon isolated strongly deformed M oO4 polyhedra and VO4 metavanadate chains. Vibrations of MoO6 octahedra, Zn2V2O6, Zn2V2O7, Zn3V2MoO11 and VO2 are observed from the Raman spectroscopic studies. The fundamental UV-VIS absorption spectra have been analyzed, which indicates indirect transitions.
TL;DR: In this article, two types of kaolin clay samples of different origins were studied using X-ray diffraction, Xray fluorescence spectroscopy, scanning electron microscopy and thermogravimetric/differential thermal analysis.
Abstract: Two types of kaolin clay samples of different origins were studied using X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy and thermogravimetric/differential thermal analysis. Mineralogical and morphological characteristics of die-pressed kaolin samples were investigated. Kaolinite was identified as the major mineral phase; however, other minerals, e.g. illite and quartz were also present as subordinates. The transformation heats during heating were quantified from DTA measurements and phase changes were followed by XRD analyses. The present results indicated a series of phase transformations as the kaolin was fired at elevated temperatures. The formation of mullite was detected by XRD at a temperature as low as 1100°C. Microstructural evolution investigations showed that mullite needles were formed within the powder compacts during sintering. Size and aspect ratio of the mullite grains increased with the increase of firing temperature. The powder compacts showed ani...
TL;DR: In this article, the effects of sintering temperature on linear shrinkage rate (LSR), bulk density, apparent porosity, cold crushing strength (CCS), mean pore diameter and thermal conductivity of the porous mullite ceramics were investigated.
Abstract: In this research, green porous mullite ceramics with high porosity, high strength and low thermal conductivity were fabricated by using insulator waste as the main raw material. The effects of sintering temperature on linear shrinkage rate (LSR), bulk density, apparent porosity, cold crushing strength (CCS), mean pore diameter and thermal conductivity of the porous mullite ceramics were investigated. As the sintering temperature increased from 1300o to 1500oC at intervals of 50oC, the LSR initially decreased from 1300o to 1400oC, and then increased from 1400o to 1500oC, while CCS and thermal conductivity increased constantly from 3.2 to 8.5 MPa and from 0.187 to W.m–1.K–1 respectively. Meanwhile, the crystallization and morphology of the mullite grains were optimiz ed wit h t he incr easing sintering temperature. Comprehensive properties of specimens can be adjusted by changing the sintering temperature.
TL;DR: In this paper, the ratio between fine and coarse β-Si3N4 powders in a strong magnetic field of 6T and subsequent pressureless sintering was used to obtain textured porosity and anisotropic bending strength.
Abstract: Textured porous Si3N4 ceramics with fine and coarse β-Si3N4 powders as the raw materials were prepared by gel casting in a strong magnetic field of 6T and subsequent pressureless sintering. These results showed that highly textured porous Si3N4 ceramics could be obtained by adjusting the ratio between fine and coarse β-Si3N4 powders in 6T. The Lotgering orientation factor in green bodies showed the value of 0.72∼0.74 with the increase of coarse powder content. The sintering process promoted texture development of the samples by Ostwald ripening owing to the big difference in the β-Si3N4 initial powder size. After sintering at 1800oC for 2 h, the degree of texture (Lotgering orientation factor) in the sample, prepared with fine and coarse powders at the ratio of 1:1, reached the maximum value (0.91), and it had relatively high density (66.91%) and low apparent porosity (34.51%). The crystallographic texture in porous Si3N4 ceramics led to the anisotropic bending strength. The method combined with g...
TL;DR: In this article, an asymmetric supercapacitor was fabricated using manganese oxide-multi-walled carbon nanotubes (MnO2-MWCNTs) nanocomposite as positive electrode and functionalized multilayer carbon nanotsubes as negative electrode.
Abstract: An asymmetric supercapacitor device (ASD) was fabricated using manganese oxide- multiwalled carbon nanotubes (MnO2-MWCNTs) nanocomposite as positive electrode and functionalized multiwalled carbon nanotubes (f-MWCNTs) as negative electrode. This ASD demonstrated a specific capacitance (Cs) of 47 F.g−1 at a scan rate of 2 mV.s−1 in a wide operating potential of 0-2V in 1 M Na2SO4. The energy density of the device was 14.3 Wh.kg−1 at 1 A.g−1 current density. The maximum power density obtained for the ASD was found to be 5.9 kW.kg−1 with a corresponding energy density of 7.3 Wh kg−1. The device was subjected to 20,000 galvanostatic charge-discharge cycles at a high current density of 25 A.g−1 to test its stability. The ASD retained 65% of the initial capacitance with 82% coulombic efficiency even at 20,000th cycle. Further, electrochemical impedance spectroscopic (EIS) studies indicated the charge transfer resistance (Rct) of the device as 2.6 Ω, with a phase angle of –72o, which confirmed its good c...
TL;DR: In this article, a carbon-opacified silica aerogel (COSA) was used to synthesize water glass and activated carbon and the results showed that COSA is thermally stable up to 495°C and is therefore suitable for use in thermal insulation at high temperature.
Abstract: Opacification of silica aerogel to reduce its thermal conductivity is normally done by using carbon. The motivation of this work is to use bamboo leaf as a single source to synthesize water glass and activated carbon. These precursors were then used to synthesize carbon-opacified silica aerogel (COSA). Because bamboo leaf is an agriculture waste, it provides a low-cost source to synthesize COSA. The properties of COSA were compared with other aerogels, including aerogel opacified with carbon black and synthesized from alkoxide. The results indicate that COSA have a bulk density of 0.069±0.0014 g.cm–3, a porosity of 97.9%, a BET specific surface area of 330.5±3.7 m2.g–1, a total pore volume of 1.38±0.07cm3.g–1 and a thermal conductivity of 0.0311±0.009 W.m–1.K–1. The TGA results show that COSA is thermally stable up to 495°C and is therefore suitable for use in thermal insulation at high temperature.
TL;DR: In this article, a silica aerogel/snSb/CNTs composite was successfully synthesized from a simple sol-gel process and chemical reduction method, which revealed a high reversible capacity of 448 mAh and stable cyclic retention at 50th cycle.
Abstract: A silica aerogel/SnSb/CNTs composite was successfully synthesized from silica aerogel (SA) modification of SnSb/CNTs by a simple sol-gel process and chemical reduction method. Microstructure, morphology and electrochemical properties of these materials were characterized by X-ray diffraction, scanning electron microscopy and constant current charge/discharge tests, respectively. The results showed that the aggregation of the nanoparticles was greatly reduced by the modification of silica aerogel to SnSb/ CNTs composites. The SA/SnSb/CNTs nanocomposites revealed a high reversible capacity of 448 mAh.g–1 and stable cyclic retention at 50th cycle. The improvement of reversible capacity and cyclic performance of the SA/SnSb/CNTs composites is mainly attributed to the unique structure of SA/SnSb/CNTs, and this structure fully realizes the complementary advantages of three kinds of materials. Modification of SnSb/CNTs by the addition of silica aerogel is a potential method to prepare anode material for ...
TL;DR: In this paper, the chemical stability of Ba0.8Ce0.35Zr0.5Tb0.15O3-δ has been studied in dry 5% H2/Ar, wet 5% HC and dry CO2 atmosphere at higher temperature.
Abstract: The chemical stability of Ba0.8Ce0.85-xZrxTb0.15O3-δ (0.1≤×≤0.5) has been studied in dry 5% H2/Ar, wet 5% H2/Ar and dry CO2 atmosphere at higher temperature. These materials are promising candidates for mixed ionic electronic conductor based H2 separation membr ane. The materials are prepared by combustion synthesis technique successively followed by calcination at 1100°C and sintering at 1550°C in air. The stabilization mechanism of sintered specimens in various atmospheres is explained with respect to the combined effect of zirconium oxide and zinc oxide as stabilizing agent and sintering aid respectively. Zr4+ introduction into Ce4+ site of doped bar ium cerate perovskite enhances the chemical stability of these materials, particularly for the composition with x>0.3. The stable sintered material is obtained with total electrical conductivity of 0.0189 S.cm−1 for the composition Ba0.8Ce0.35Zr0.5Tb0.15O3-δ in moist reducing atmosphere at 900°C. So, in the present work, we report a composition whi...
TL;DR: In this paper, the authors reported improvement in chemical resistance of glazed wall tile by solgel derived TiO2-Fe2O3 thin film coatings on the glazed surface.
Abstract: Present study reports improvement in chemical resistance of glazed wall tile by solgel derived TiO2-Fe2O3 thin film coatings on the glazed surface. Effect of firing temperature on the chemical resistance of the coating was estimated after firing at different temperatures (600°, 700° and 800°C). The chemical durability of the coated substrate in comparison to the uncoated was tested against acidic attack by immersing them in 3% (v/v) hydrochloric acid solution and 10 wt% citric acid solution and basic attack by immersing them in 20 wt% potassium hydroxide solution in accordance with IS: 13630 (Part 8): 2006 standard. Further, the coated surface was also tested against basic attack in 1 N sodium hydroxide and 2.5 wt% detergent solution for seven days. The chemical durability was quantitatively estimated by measuring gloss at the surface at regular time intervals. Acid resistance was found to be good for coated substrate fired at all test temperatures. The coated substrate fired at 800°C showed high ...
TL;DR: In this article, the effect of two different types of Al2O3 precursor powders (namely, Al 2O3-M and Al O3-N with average particle size of 4.2 µm and 75 nm, respectively) on phase evolution and stability was studied.
Abstract: Al2TiO5 (AT) powder was prepared by solid-state method using Al2O3 and TiO2 precursor powders. Effect of two different types of Al2O3 precursor powder (namely, Al2O3-M and Al2O3-N with average particle size of 4.2 µm and 75 nm, respectively) on phase evolution and stability was studied. In the case of large particle Al2O3 precursor powder, AT phase was formed at 1500°C with a yield of 97%. Whereas, using nano-Al2O3 precursor powder, AT phase was formed at 1350°C with a yield of 91% and almost phase pure powder can be prepared at 1500°C. The stability of the AT pellet (sintered at 1500°C) was investigated by keeping the powder at 1150°C/6 h. It was observed from the XRD analysis that only 40% AT phase was retained in samples prepared with micron-size Al2O3. But in the case of the sample prepared using nano-size Al2O3, 93% AT phase was retained.
TL;DR: In this article, the effect of machining parameters, viz. cutting speed, feed rate and depth of cut on the cutting force components, namely, feed force, radial force, cutting force (Fc) and surface roughness, was investigated.
Abstract: Aluminium matrix composites are of great interest for researchers in recent years because of their excellent combinations of engineering properties over traditional materials. The machinability of these aluminium matrix composites has become vital for manufacturing industries. During machining of aluminium matrix composites, the cutting forces and surface roughness are dependent on machining parameters (feed rate, cutting speed and depth of cut) and manufacturing parameters (size of the particles, volume fraction, porosity, hardness). With this backdrop, the present work is aimed at investigating the effect of machining parameters, viz. cutting speed, feed rate and depth of cut on the cutting force components, namely, feed force (Ff), radial force (Fd), cutting force (Fc) and surface roughness. The experiments were performed on 0, 5, 7 and 9 wt% B4C particulate of 88 µm size reinforced composite specimens. The prepared specimens were subjected to turning operation on a conventional lathe machine u...
TL;DR: In this paper, chemical analysis of Indian magnesites from Salem and Almora regions were selected for the present study, which confirmed that Salem region magnesite (SM) contains CaO and SiO2, whereas Almoras origin magnesitic (AM) shows higher amount of Fe2O3 and CaO as major impurities.
Abstract: Indian magnesites from Salem and Almora regions were selected for the present study. Chemical analysis of these magnesites confirmed that Salem region magnesite (SM) contains CaO and SiO2, whereas Almora origin magnesite (AM) shows higher amount of Fe2O3 and CaO as major impurities. Crystalline phases developed in sintered Salem magnesite are periclase, forsterite and monticellite, while magnesioferrite and monticellite are found in sintered Almora magnesite apart from periclase as major phase. Microstructural analyses reveal that sintered SM has lower grain size than sintered AM . Although, no significant difference was noticed at room temperature flexural strengths of both the sintered samples, but sintered AM samples exhibit better flexural strength at elevated temperature (1200°C).
TL;DR: In this article, phase compositions and properties of the Al2O3-MgAl2O4 composite were studied by adding different MgO contents as additive, which resulted in an increase of compressive strength.
Abstract: Alumina (Al2O3)-magnesium aluminate (MgAl2O4) composite was prepared from powders of magnesia (MgO) and Al2O3 by pressureless sintering. Phase compositions and properties of the Al2O3-MgAl2O4 composite were studied by adding different MgO contents as additive. Sintered products were subsequently characterized in terms of phase and microstructure analysis, densification study and compressive strength test. The results show that introduction of MgO is beneficial in forming MgAl2O4 reinforcement phase by solid state reaction between Al2O3 and MgO. Average particle size of Al2O3-MgAl2O4 composite decreases gradually with the increase of MgO content. Bulk density of the composite decreases from 2.48 to 2.40 g.cm–3 with the addition of MgO from 2 to 10 wt%, whereas compressive strength increases from 13 to 40 MPa. Reduction of particle size and the increase of MgAl2O4 bonding phase have resulted in increase of compressive strength of the Al2O3-MgAl2O4 composite.