IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Effect of bulk and surface modification of SnO2 thin films with PdO catalyst on CO gas sensing characteristics prepared by vacuum evaporation process
No full textWe have investigated various approaches of PdO addition on to SnO2 thin films for efficient detection of CO gas molecules. Bulk-doped and surface-decorated PdO/SnO2 thin films were prepared by the thermal oxidation of vacuum evaporated metal films in ambient air. For bulk-doping, Pd and Sn metals were co-evaporated followed by thermal oxidation. PdO surface-decoration was done by thermal oxidization of either Pd/Sn metal bilayer or Pd/SnO2 films. The SnO2 thin films are characterized with rutile crystalline structure and porous surface morphology. X-ray photoelectron spectroscopy confirms the dominant presence of PdO on SnO2 surface for the doped films. Pristine SnO2 film exhibited a maximum sensitivity of about 13% for 915 ppm of calibrated CO molecules in nitrogen gas with a response/recovery time of 69/49 s. The PdO bulk-doping in SnO2 film marginally increased the CO sensitivity, whereas, two to four-fold increase is achieved for PdO surface-decorated SnO2 thin films. It is also found that the Pd film thickness plays a critical role in determining the CO sensitivity and is optimized to be 4 nm. A maximum CO sensitivity of 52% with a lowest response/recovery time of 34/46 s is obtained for PdO/SnO2 structure formed through direct oxidation of Pd metal on SnO2 films. A possible gas sensing mechanism based on PdO/SnO2 hetero-junction is discussed. (C) 2020 Elsevier B.V. All rights reserved
Novel barium hexaferrite based highly selective and stable trace ammonia sensor for detection of renal disease by exhaled breath analysis
No full textExhaled human breath bears the fingerprints of multifarious pathophysiological conditions, and diseases. In this paper we report for the first time a highly sensitive, selective, and stable barium hexaferrite based sensor for the detection of trace ammonia vapor in exhaled human breath, the biomarker for renal diseases. Barium hexaferrite nanoparticles were synthesized by a facile solid-state reaction route. The as prepared nanopowder and the sensor film were well characterized by using XRD, FESEM, TEM, EDX, XPS, BET, and I-V measurements. The fabricated sensor delineates p-type behavior and the capability to detect ammonia down to 0.2 ppm with reasonably high response of similar to 1.46 folds. Further, the sensor showed remarkable response of similar to 2.34 folds towards 1 ppm ammonia. The sensor is practically insensitive towards similar concentrations of other major interfering breath volatiles, viz. acetone, ethanol, and saturated moisture. Also, the sensor exhibited fast response (similar to 2.88 s), and recovery (similar to 39.4 s) times ensuring real time breath analysis. Finally, long-term stability of the sensor for more than three months renders it suitable for commercial applications
Atomic Layer Deposition Seeded Growth of Rutile SnO2 Nanowires on Versatile Conducting Substrates
No full textExtended and oriented rutile nanowires (NWs) hold great promise for numerous applications because of their various tunable physicochemical properties in air and/or solution media, but their direct synthesis on a wide range of conducting substrates remains a significant challenge. Their device performance is governed by relevant NW geometries that cannot be fully controlled to date by varying bulk synthetic conditions. Herein, orientation engineering of rutile SnO2 NWs on a variety of conducting substrates by atomic layer deposition (ALD) seeding has been investigated. The seeded growth controls the nucleation event of the NW, and thicknesses and crystallographic properties of seed layers are the key parameters toward tuning the NW characteristics. The seed layers on carbon cloth produce NWs with highly enhanced electrochemically active surface area, which would show efficient electrochemical CO2 reduction. In addition, the hierarchical architecture resulted from the seeded growth of NWs on SnO2 nanosheets allows thin layers of BiVO4, forming a heterojunction photoanode, which shows a record charge separation efficiency of 96.6% and a charge-transfer efficiency of 90.2% at 1.23 V versus the reversible hydrogen electrode among, to date, the reported BiVO4-based photoanodes for water oxidation. Our study illustrates that such a versatile interfacial engineering effort by the ALD technique would be promising for further wide range of practical applications
Nanoparticle Induced Morphology Modulation in Spin Coated PS/PMMA Blend Thin Films
No full textThe influence of adding nanoparticles on the ascast morphology of spin coated immiscible polystyrene/poly(methyl methacrylate) (PS/PMMA) thin films of different thickness (h(E)) and composition (R-B, volume ratio of PS to PMMA) has been explored in this article. To understand the precise effect of nanoparticle addition, the morphology of PS/PMMA thin blend films spin cast from toluene on a native oxide covered silicon wafer substrate was first investigated. It is seen that in particle free films, the generic morphology of the films remains nearly unaltered with increase in h(E), for R-B = 3:1 and 1:3. In contrast, strong h(E) dependent morphology transformation is observed in films with R-B = 1:1. Subsequently, thiol-capped gold nanoparticles (AuNP) containing films with different particle concentrations (C-NP) were cast from the same solvent along with the polymer mixture. We observe that addition of AuNPs barely alters the generic morphology of the films with R-B = 3:1. In contrast, the presence of the particles significantly influences the morphology of the films with R-B = 1:1 and 1:3, particularly at higher C-NP (approximate to 10.0%). X-ray photoelectron spectroscopy and X-ray reflectivity of some samples reveal that the AuNPs tend to migrate to the free surface through the PS phase, thereby stabilizing this layer partially or fully (depending on C-NP) against dewetting over a surface of adsorbed PMMA layer and influencing the ascast morphology as a function of C-NP. The work is fundamentally important in understanding largely overlooked implications of nanoparticle addition on the morphology of PS/PMMA blend thin films which forms the fundamental basis for future interesting studies involving dynamics of nanoparticles within the blend thin films
Understanding the role of post-indentation recovery on the hardness of glasses: Case of silica, borate, and borosilicate glasses
No full textHardness is an important property of glasses, which depends strongly on the method of measurement. Herein, we estimate the hardness of three oxide glasses, namely, pure silica (0B), borosilicate (37B), and sodium borate (75B) glass samples at micro and nanoscale. We observe that annealing of these glass samples, after polishing, has little effect on their hardness and modulus. Interestingly, we observe that the nanoindentation is unable to capture the full extent of elastic recovery, thereby underestimating the hardness of these glasses. We show that the post-indentation elastic recovery is highly dependent on the chemical composition of glass. Combining nanoindentation and atomic force microscopy (AFM) imaging, we accurately capture the complete elastic recovery of glass samples, thereby calculating the true hardness values from indentation depth profiles. Overall, we show that post-indentation elastic recovery plays a crucial role in determining the hardness of glasses
Passively Q-switched fiber laser utilizing new hafnium-bismuth-erbium co-doped fiber as saturable absorber
No full textA stable all-fiber passively Q-switched erbium-doped fiber laser emitting at 1559 nm is proposed and demonstrated using an 8-cm-long hafnium-bismuth-erbium co-doped fiber (HBEDF) as a saturable absorber (SA). The HBEDF is fabricated in-house and has a linear absorption of around 5.2 dB at the laser operating wavelength of 1559 nm. The Q-switching pulses are obtained with an input pump power ranging from 50 to 121 mW. It has the pulse repetition rate of 81.57 kHz, the shortest pulse width of 3.31 ls, output power of 10 mW, pulse energy of 123 nJ and peak power of 37.3 mW at the maximum pump power of 121 mW. The corresponding signal-to-noise ratio of the electrical spectrum is measured to be around 70 dB, which indicates the stability of the laser. To the best of our knowledge, this is the first demonstration of the deployment of HBEDF SA in generating a robust and steady pulsed laser in 1.5-micron region
The study of Magnetic and Room Temperature Magnetoelectric Properties of Fe2Te0.95Ta0.05O6
No full textThe polycrystalline Fe2Te0.95Ta0.05O6 possessing tetragonal trirutile structure with P4(2)/mnm space group is synthesized via solid state reaction route. Phase confirmation and structural parameter calculation are done by the Rietveld refinement of XRD data. We demonstrate the temperature and magnetic field dependent magnetic property and room temperature magnetoelectric (ME) behavior of the material. The temperature dependent magnetic susceptibility confirms the antiferromagnetic transition at 210K along with a broad transition prior to it due to presence of short range magnetic ordering. The typical temperature response of magnetic susceptibility like Fe2TeO6 parent material differ at 18K as it shows a transitional anomaly due to Ta doping. MH hysteresis measured at 300K and 2K shows an apparent linear behavior. A hysteretic ferromagnetic induction in low field region at 300K is observed due to doping induced modification in exchange interaction mechanisms. Presence of linear ME effect is confirmed through ME voltage measurement wit ME coefficients a/d approximate to 0.23 mV cm(-1) Oe(-1), beta/d approximate to -3.47 x 10(-4) mV cm(-1) Oe(-2), obtained by linear fit to M. Ferroelectric hysteresis loop is obtained by PE loop measurement using remanent polarization measurement with value approximate to 2.5 nC/cm(2)
Short-term corrosion behavior of Indian RAFM steel in liquid Pb-Li: Corrosion mechanism and effect of alloying elements
No full textThe compatibility of RAFM steels in liquid lead-lithium (Pb-Li) is a major area of concern for the development of Pb-Li cooled fusion reactor blankets. In order to establish the corrosion mechanism during the short term exposure (i.e. Incubation Period) when the protective oxide layers are present over the RAFM surface, the dissolution behavior of Indian RAFM steel (IN RAFMS) has been studied in liquid Pb-Li under static conditions at 773 K for 1, 000 h of exposure. Pure chromium and plain carbon steel (as a substitute for pure iron) have also been exposed along with IN RAFMS under similar conditions for understanding the effect of alloying elements over the corrosion process. The dissolution rate of pure chromium in Pb-Li was found to be the highest among all materials although iron dissolution was the rate controlling step for IN RAFMS corrosion. It was established that Pb-Li attack over RAFM steels during exposures up to 1, 000 h was associated with non-uniform dissolution of oxide scales and grain boundary penetration which can also dislodge the grain boundary carbides. The dissolution of constituent elements into the grain boundary channels of Pb-Li governed the depth of elemental depletion from the exposed surface. However, dissolution of oxide scales was found to be the major factor behind weight loss during short term exposures. An attempt has been made to theoretically model the depletion of chromium from IN RAFMS surface which was a result of its slower diffusivity in the steel matrix. (C) 2019 Elsevier B.V. All rights reserved
Rogue waves in a linear cavity Yb-fiber laser through spectral filtering induced pulse instability
No full textIn this Letter, experimental observation of dissipative rogue waves (DRWs) due to spectral filtering induced pulse instabilities in a mode-locked ytterbium (Yb) fiber laser has been presented. A semiconductor saturable absorber mirror was used to mode-lock the linear cavity laser and a chirped fiber Bragg grating (CFBG) was used for dispersion management, which also acted as a spectral filter and output coupler. Under stable conditions, the cavity delivered dispersion managed dissipative solitons of 447 fs duration and 0.69 nJ pulse energy at 10.19 MHz repetition rate with uniform intensity distribution over a long time span. As the spectral width increased with pump power, random intensity fluctuations were observed in the pulse train due to the filtering effect of the CFBG. Employing a dispersive Fourier transform by stretching the output pulse train in time allowed the existence of DRWs more than 4 times stronger than the significant wave height to be observed. Further increments of pump power led to a stable multi-pulsing state. (C) 2019 Optical Society of Americ
Custard apple-shaped NaX zeolite with a large surface area derived from rice husk ash by a single-step template-free process
No full textCustard apple-shaped NaX zeolite with a large surface area was synthesized from rice husk ash without use of a templating agent via a single-step autoclave process at 90 degrees C/6h. The crystallinity of the particles was confirmed by XRD. An FTIR study shows the characteristic bands at 560 cm(-1) for a double 6-membered ring (D6R), while a Raman shift at around 500 cm(-1) indicates the bending mode of 4-membered ring fragments of NaX zeolite. The total BET surface area of the product was found to be 703 m(2)g(-1) comprising a micrpore surface area of 623 m(2)g(-1) and a mesopore surface area of 80 m(2)g(-1). A hierarchical porous structure with micropores in the range of 0.72-1.76nm and mesopores centred at 3.5nm was obtained. FESEM and TEM images of NaX zeolite show a custard apple-like morphology (1-2 mu m) of secondary particles which was formed by self-assembly of nanometer-sized (50-100nm) primary particles. A proposed formation mechanism was illustrated