IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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High-Pressure Phase Transitions of Morphologically Distinct Zn2SnO4 Nanostructures
Get PDFMany aspects of nanostructured materials at high pressures are still unexplored. We present here, high-pressure structural behavior of two Zn2SnO4 nanomaterials with inverse spinet type, one a particle with size of similar to 7 nm zero dimensional (0-D)] and the other with a chain-like one dimensional (1-D)] morphology. We performed in situ micro-Raman and synchrotron X-ray diffraction measurements and observed that the cation disordering of the O-D nanoparticle is preserved up to similar to 40 GPa, suppressing the reported martensitic phase transformation. On the other hand, an irreversible phase transition is observed from the 1-D nanomaterial into a new and dense high-pressure orthorhombic CaFe2O4-type structure at similar to 40 GPa. The pressure-treated 0-D and 1-D nanomaterials have distinct diffuse reflectance and emission properties. In particular, a heterojunction between the inverse spinet and quenchable orthorhombic phases allows the use of 1-D Zn2SnO4 nanomaterials as efficient photocatalysts as shown by the degradation of the textile pollutant methylene blue
Spark plasma sintering of nano magnesia: Processing parameters influencing optical properties
No full textDensification of laboratory-made nanocrystalline magnesium oxide powder synthesized by gel combustion method was performed through spark-plasma-sintering using both pulsed and unpulsed DC. Grain growth in post-sintered microstructure limited within 200 nm. Photoluminescence study through Gaussian splitting of broad band emission spectra reveals that SPS-processing enhances luminescence in bulk specimens because of oxygen vacancies generated under reducing atmosphere during sintering. Influence of heat treatment on the defect-induced photoluminescence behaviour was investigated. Decrease in emission intensity with post-sintering annealing temperature, caused by decreasing concentration of colour centres due to oxygen recombination process, has been found to be related to the improvement in transmittance property
Spark plasma sintering of Ti-diamond composites
No full textLaser melting of Ti-diamond powders have been found to enhance the mechanical properties of technologically important material like titanium matrix composite (TMC). However, there is a tendency for the diamond to graphitise during the laser melting process. In order to overcome this fallacy, an alternate processing route, namely, spark plasma sintering (SPS) was adopted for fabricating the TMC's. A wide range of powder compositions varying from 5 to 50 wt percentage of diamond (0.25 mu m) was added to titanium and the as-sintered compacts were investigated by X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDAX). In-situ phase changes were observed with increase in diamond content in the composition. Addition of diamond upto 15% led to formation of a mixed Ti and TiC phase in the matrix. Interestingly there was no trace of metallic titanium with 20% diamond in the composition and a TiC-only phase was observed, corroborated by an abrupt increase in hardness to 1076 Hv. At even higher diamond percentages there was trace of unreacted carbon along with TiC. This work indicates, for the first time, the use of SPS as an alternate route for fabricating in-situ TMCs with enhanced mechanical properties
Correlation between Raman spectroscopy and mechanical properties of As-Sb-S-I chalcogenide glasses
No full textPresent investigation explores the structural changes that occur in glass network as a function of compositional variation through Raman spectra of As-Sb-S-I chalcogenide glasses and correlated with their bulk mechanical properties. In this study, a series of six glasses are prepared by melt quenching technique. The glass without iodine (G1) is assigned as base glass. The rest of the glass compositions are designed with iodine content either at 10 or 20 mol% and simultaneously varying the As/Sb mol% ratio. The effects of iodine variation in the glass matrix are clearly evident from their Raman spectra as well as bulk mechanical properties which are further validated by theoretical estimated average coordination number . Raman spectra analysis indicates that the peak around 150 cm(-1) corresponding to Sb-S bonds increases in amplitude and appearance of peak around 233 cm(-1) of As-S bonds in antimony and arsenic rich glasses, respectively. In addition, an intense peak around 490-495 cm(-1) and weak peak around 233 cm(-1) which are attributed to stretching vibrations S-S and As-S bonds respectively in As2S3 units can be seen only in arsenic rich glasses. The elastic modulus values denote the dependence on antimony content while Vickers hardness values are decreasing with an increase in iodine content. The Raman spectra of raw materials used in glass preparation are also analysed to compare the bonds present in crystalline raw materials to that of amorphous structure in the prepared glasses
Laser surface melting of Mg-Zn-Dy alloy for better wettability and corrosion resistance for biodegradable implant applications
No full textIn order to improve the performance of magnesium (Mg) for resorbable implant applications, Mg-1Zn-2Dy alloy was developed and the surface of the alloy has been modified by melting using lasers. Laser melted samples, at different laser energy density, were then subjected to microstructural, hardness, wettability and in-vitro degradation assessment. The microstructure of the Mg-Zn-Dy alloy mainly consisted of alpha-Mg and eutectic phase (Mg8ZnDy). The melted region of the alloy surface evolved with fine grain microstructure at the near surface region and columnar grains near to the liquid solid substrate. The degree of grain size refinement obtained at the melted zone in the order of 1-2 mu m. The cross sectional microhardness of the modified zone was measured by Vickers microhardness tester. Due to these microstructural refinements and solid solution strengthening the surface hardness of laser treated alloy increased by two-fold. It was found that as the energy density increased the surface roughness along with the surface energy also increased. The wetting behaviour of the surface was estimated through measuring the contact angle by dropping the polar and non-polar liquid. Results showed that the surface energy is also found to change with LSM due to changes in the surface morphology, microstructure and chemical composition of the material. The detailed degradation study was carried out by immersing the samples in hanks balances salt solution (HBSS). The improvement in the degradation behaviour followed by laser surface melting is related to the microstructural refinement as a result of rapid heating and cooling of the melted zone
Ferroelectric and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 films in 200 nm thickness range
No full textLead-free piezoelectric Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCZT) thin films were fabricated on Si/SiO2/TiO2/Pt (100) substrates following chemical solution deposition technique. Microstructure of the nano-sized BCZT particles crystallized in the thin film was thoroughly characterized. Ferroelectric, dielectric and piezoelectric properties of the films were investigated in detail. The BCZT films annealed at 800 degrees C temperature exhibited high remanent polarization of 25 +/- 1 C/cm(2), energy density of 17 J/cm(3), dielectric constant of 1550 +/- 50 and dielectric tunability of 50%. Converse piezoelectric coefficients (d(33)) obtained from piezo-response force microscopy (PFM) measurements on BCZT grains of different grain size (20-100 nm) distributed on the BCZT 700 film varied widely from 90 to 230 pm/V. The same for BCZT 800 measured on different grain size (30-130 nm) varied from 120 to 295 pm/V. These BCZT thin films with high dielectric, ferroelectric, and piezoelectric properties might be good alternative to the PZT films for thin film piezoelectric device applications
Structural and phase analysis of multi-ion doped hydroxyapatite for biomedical applications
No full textMulti-ion doping in synthetic HA was carried out using high energy planetary ball milling followed by calcination at 1250 degrees C for 2 h. The influence of Sr+2, Zn+2, Ag+, and F- ion doping on crystallinity and crystallite size was analyzed using Taguchi design of experiments (DOE) and optimal concentration of different dopants has been identified to achieve desired crystallinity and crystallite size. The doped HA samples have been characterized using X-ray diffraction and Fourier transform infrared spectroscopy to determine their phase purity, degree of crystallinity, crystallite size and functional groups. Standard Analysis of variance (ANOVA) showed relatively high contribution of Sr+2 and Zn+2 doping in changing the crystallinity and crystal size of HA compared to the effect of Ag+ and F- doping. Our analysis demonstrated strong interaction between dopants at binary level doping, while ternary and quaternary doping of elements did not exhibit any interaction in influencing the crystallinity and crystallite size of HA. In general, multi-ion doping in HA found to decrease its crystallinity from 92% to 72% (max.), but enhance the hardness, depending on the type and concentration of doping element. Similarly, a minimum crystallite size of 31 nm was achieved with some binary compositions and other combinations resulted in crystallite sizes up to 59 nm. The compositions that ensure desired crystallinity and crystallite size can also provide high hardness. Our results can be used to tailor the composition of HA in achieving desired functional properties, dependent on crystallinity and crystallite size, such as strength, bioactivity and degradation to suit variety of implant applications
Polyaniline-Layered Rutile TiO2 Nanorods as Alternative Photoanode in Dye-Sensitized Solar Cells
No full textIn this paper, dye-sensitized solar cell (DSSC) performance of the less explored polymorph of TiO2, rutile, has been explored, and its performance has been modified with polyaniline (PANI) wrapping on the surface. For this purpose, highly crystalline rutile nanorods have been synthesized without any growth-directing substrates, employing a hydrothermal treatment. Further, to understand the phase composition and morphology, the synthesized nanorods and PANI-layered nanorods have been characterized through various physicochemical methods. The synthesized rods were implemented as photoanode material for DSSCs which exhibited a photoelectric conversion efficiency (PCE) of 4.28% with a high open-circuit voltage (V-OC) of 0.84 V which is highly superior to DSSC with Degussa P25 (PCE = 3.95%) TiO2 nanoparticles. The resultant PCE of the nanorods was further enhanced to 6.23% on in situ deposition of PANI which acts as an electron-transporting layer. Introduction of conducting PANI over the rutile rod was explored as a new concept to improve the performance of photoanode material besides conventional TiCl4 treatment or scattering layer deposition
All-circular hole microstructured fiber with ultra-high birefringence and reduced confinement loss
No full textAll-circular hole microstructured fiber with ultra high birefringence in the order of similar to 10(-2) with reduced confinement loss is proposed. The increased birefringence is achieved by introducing an axial anisotropy in the geometry of the fiber, using a modified arrangement of circular holes. The vital properties of the microstructure fiber like birefringence, confinement loss, dispersion and walk-off parameter has been studied by employing numerical solution through finite element method. These finding should be useful for the fabrication of the proposed microstructure optical fiber. (C) 2019 Elsevier Ltd. All rights reserved
Preparation and in vivo biocompatibility studies of different mesoporous bioactive glasses
No full textA new generation of nanostructured glasses called mesoporous bioactive glasses (MBGs) exhibit superior surface texture, porosity and bioactive characteristics. The present study is carried out to develop and detailed characterize of ternary SiO2-CaO-P2O5 MBG structure, fabricated by three different variations using different surfactants, e.g., hexadecyltrimethylammonium bromide (CTAB), poly-ethylene glycol,(PEG) and Pluronic P123. After thorough physico-chemical characterization, MBG granules were investigated for in vivo bone regeneration in animal bone defect model (rabbit) where standard S53P4 bioactive glass was used as control. All the synthesized MBG powders showed nano-range median particle size of 80-120 nm (MBG-CTAB), 50-70 nm (MBG-PEG and MBG-P123) while their specific surface area as 473.2, 52.2 and 169.3 m(2)/g respectively. All MBGs showed mesoporous nature corroborating transmission electron microscopy (TEM) observation as well. Bone regeneration property was measured after 45 and 90 days post-implantation at distal epiphysis of rabbit femur by radiography, histology, fluorochrome labeling, micro computed tomography (micro-CT) and vital organ histology. Results from in vivo studies indicated that the MBG materials produce minimal toxicity to the body. Furthermore, the biocompatibility and biodegradability of the implant makes them more suitable for application in bone tissue engineering. Among various implants, MBG fabricated using suitable surfactant (CTAB) shown the best result compared to other implants. Nonetheless, all the materials are suitable for application in bone tissue engineering and have potential for bone regeneration and healing