IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Template free synthesis of CdSnO3 micro-cuboids for dye sensitized solar cells
No full textMesoporous transparent conducting oxide, CdSnO3 has been synthesized using ultrasonication assisted co-precipitation method. Rather employing any template or structure directing agent, the co-precipitation effect of sodium hydroxide and citric acid were able to form cuboid shaped CdSnO3 during the sonochemical treatment as investigated by a systematic X-ray diffraction and field emission scanning electron microscopy studies. An optimum 3:1 molar concentration of NaOH and citric acid leads to form cuboidal structure of CdSnO3 on calcined at 700 degrees C. Further calcination at 800 degrees C converted cuboids to nanoparticles. Comparative studies have been carried out between the cuboid and particle morphology to understand the physico-chemical properties related to the morphology using various characterization techniques. Further, the CTO cuboids and the decomposed nanoparticles have been tested as photoanode for dye sensitized solar cell applications. The cuboid based photoanode exhibited an enhanced efficiency of 3.23% with a Voc of 0.72 V than its decomposed nanoparticle which exhibited a lower efficiency of 2.67%. The electrochemical impedance and incident photon to electron conversion efficiency results also support enhanced performance of cuboid based device than particle. The overall results show the advantage of cuboidal CdSnO3 in rapid electron injection and higher light reflection leading to improved current density of the DSSC device than the decomposed nanoparticle form. The results establish the application of less explored CdSnO3 as a photoanode in DSSCs application
Thermal shock and chemical corrosion resistance of oxide bonded porous SiC ceramics prepared by infiltration technique
No full textUsing the water- and air-quenching technique, the thermal shock resistance to cooling was evaluated as a function of quenching temperatures and quenching cycles for oxide bonded porous SiC ceramics prepared by infiltration technique. It was observed that the residual strength of the quenched samples decreases with increase in the quenching temperature. However residual strength becomes independent of quenching cycles after certain cycles since the thermal shock produced by repeated cycles remained almost constant. The hot corrosions of SiC samples exposed to Na2SO4 salt were performed at 1000 degrees C. The weight loss, strength reduction and morphology evolution of the SiC specimens during corrosion were revealed and explained. The chemical and thermal shock resistance results suggest a potential advantage of porous SiC ceramics prepared by infiltration technique for several industrial applications. (C) 2018 Elsevier B.V. All rights reserved
Prediction and validation of residual stresses generated during laser metal deposition of gamma titanium aluminide thin wall structures
No full textThe focus of the current work is to predict and validate residual stresses developed during Laser Metal Deposition (LMD) of Gamma Titanium Aluminide (gamma-TiAl) alloy by using a combination of numerical modeling and experimental methods. Laser Engineered Net Shaping (LENS), which is one of the commercially available LMD techniques, was used to fabricate gamma-TiAl alloy thin wall structures at various processing conditions. These deposits are expected to develop residual stresses due to the rapid heating and cooling cycles involved in the LMD process. 3D transient thermomechanical finite element analysis was used to simulate the LMD process. Thermal gradients and residual stresses were predicted from the thermomechanical models. It was found that the magnitude of thermal gradients increases with the addition of each deposited layer. Tensile residual stresses were observed at the edges of the thin-wall, while compressive residual stresses were observed at the center of the wall as well as in regions away from the edges. Residual stresses in the deposited samples were also measured using the x-ray diffraction technique. Reasonable agreement was observed between the predicted and measured values of residual stresses
Periodicities in the roughness and biofilm growth on glass substrate with etching time: Hydrofluoric acid etchant
No full textAdherence of the microorganism to submerged solid surfaces leads to biofilm formation. Biofilm formation modifies the surfaces in favor of bacteria facilitating the survival of the bacteria under different stressed conditions. On the other hand, the formation of biofilm has a direct adverse economic impact in various industries and more importantly in medical practices. This adherence is the reason for the failure of many indwelling medical devices. Surface biofilm adhesion is the key to biofilm growth and stability. Hence this adhesion needs to be substantially lowered to inhibit biofilm stability. Both chemical and physical properties of the surface influence biofilm formation and modulating these properties can control this formation. In this study, we have investigated the effect of Hydrofluoric acid (HF), at a specific concentration as an etchant, on the surface morphology of substrates and the growth of biofilms of Pseudomonas aeruginosa. and Staphylococcus aureus. We find that the bacterial counts on the etched surfaces undergo a periodic increase and decrease. This, on one hand, shows the close correlation between the biofilm growth and the particular roughness scale, and on the other hand, explains the existing contradictory results regarding the effects of etching on substrate roughness and biofilm growth. We propose a simple model of a sequence of hole formation, hole expansion and etching away of the hole walls to form a new, comparatively smooth surface, coupled with the preferential accumulation of bacteria at the hole edges, to explain these periodicities
Flexible, hybrid nanogenerator based on Zinc Ferrite nanorods incorporated poly(vinylidene fluoride-co-hexafluoropropylene) nanocomposite for versatile mechanical energy harvesting
No full textHerein, an efficient, low-cost, scalable in-situ poled fabrication strategy to construct a large area, highly sensitive, flexible piezocomposite nanogenerator comprising of rod shaped Zinc Ferrite (ZF-R) and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was developed. ZF-R with an average length of 330 nm was synthesized via a facile two-pot hydrothermal method and its PVDF-HFP-based composites with different weight ratio were prepared. Fabricated 3 wt% ZF-R incorporated PVDF-HFP flexible piezocomposite (3H) was used as an effective nanogenerator which could generate an output voltage of 8.5 V and current density similar to 0.5 mu A/cm(2) upon repetitive mechanical stresses. The generated power could enlighten 21 commercial light emitting diodes (LEDs). Furthermore, 3H demonstrated the capability to monitor height with level of accuracy upto +/- 3 cm. Moreover, this flexible hybrid film can scavenge environmental sensations such as air flow (maximum 3.2 V peak to peak voltage) and muscular vibration when integrated with arm, wrist and finger in conjunction with superior integratebility and nontoxicity. Thus, this nanocomposite can be explored for application as ultrasensitive height monitor, mechanical energy scavenger and effective power source for driving portable electronics and wearable devices
TiO2 hollow microspheres impregnated with biogenic gold nanoparticles for the efficient visible light-induced photodegradation of phenol
No full textIn this study, titania hollow microspheres were prepared via sol-gel process followed by autoclaving at 180 degrees C for 20 h using titanium (IV) oxysulfate and ammonium fluoride. Different amounts of Au in a water-dispersible sol obtained from carambola fruit extract at room temperature were incorporated into the synthesized TiO2 to prepare Au/TiO2 nanocomposite. The physicochemical properties of the synthesized products were studied by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, N(2 )adsorption-desorption analysis, ultraviolet-diffuse reflectance spectroscopy, photoluminescence spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The prepared Au/TiO2 nanocomposite was applied to study the photocatalytic degradation of phenol (a toxic organic pollutant) under irradiation by visible light. The Au/TiO2 nanocomposite containing 5 wt% Au had the smallest band gap energy of 2.24 eV and the maximum photocatalytic efficiency (95%), where it decomposed 97.5% of the organic pollutant after irradiation by visible light for 1 h
Mega-Hertz repetition rate broadband nano-second pulses from an actively mode-locked Yb-fiber laser
No full textThis work demonstrates an actively mode-locked all-normal dispersion Yb-fiber ring laser, delivering pulses of few nano-seconds (ns) to sub-ns duration at a 4 MHz repetition rate. Employing a filterless cavity architecture and different, long-length intra-cavity nonlinear fibers; a broadband output spectrum in the 1060-1140 nm wavelength region was obtained. With an increasing pump power, the pulse width reduced along with the appearence of new pulses, resulting into a muti-pulsing output. For a fixed pump power, the number of pulses and the amount of spectral broadening varied for different non-linear fibers. In the multi-pulsing state, the pulses were found to be located seperately in both time and wavelength, where Raman stokes corresponding to individual pulses could also be observed. The maximum output pulse energy achieved in a single pulse state was around 8.7 nJ, which increased to 14.5 nJ in a multi-pulse state. To the best of the authors' knowledge, this is the first demonstration of a filterless active mode-locked fiber ring laser producing high-repetition rate broadband nano-second pulses in single and multi-pulse states at 1 mu m
Poly (m-amino benzene sulfonic acid)-based composites on plastic substrates: A simple and cost effective approach towards low ppm ammonia detection at room temperature and kinetic analysis
No full textBecause of intimidating toxicity of ammonia, development of ultra-sensitive, as well as portable and energy efficient ammonia sensor is of paramount importance. Here, we report a simple as well as cost-effective synthesis protocol of graphite- poly-amino benzene sulfonic acid (Graphite -PABS) nanocomposite via an in-situ chemical oxidative polymerization pathway. The ammonia sensing characteristics of graphite - PABS composite based sensors on low cost plastic substrate has been investigated in the concentration range of 10-100 ppm of ammonia in air at room temperature. While the sensitivity for sensors comprising only PABS is about 136.38%, the graphite -PABS nanocomposites demonstrated an appreciably high value of about 282.5% towards 100 ppm of ammonia. The sensors have not only demonstrated high sensitivity, selectivity and fast recovery; they are operable at room temperature and hence consume considerably low power compared to the conventional metal-oxide sensors. Furthermore, we have fitted the response and recovery transients of conductance of graphite/ PABS based cost effective sensor using two sites Langmuir adsorption kinetics to explain the plausible ammonia sensing mechanism of graphite loaded PASS sensor. Low concentration ammonia sensing characteristics of this newly synthesized graphite/PABS composite on the plastic substrate is first demonstrated by our group