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911.
Manickam Sivakumar Atsuya Towata Kyuichi Yasui Toru Tuziuti Teruyuki Kozuka Masahiko Tsujimoto Ziyi Zhong Yasuo Iida 《Ultrasonics sonochemistry》2010,17(1):213-218
Fine particles of rutile TiO2 supporting nanosized particles of Pt were prepared by a simultaneous in situ sonochemical reduction and deposition method using a standing wave sonochemical reactor (SWSR). The mean diameter of sonochemically obtained Pt particles are of 2 nm. Following this sonochemical technique, rutile TiO2 was also deposited with different weight percentages of Pt. Catalytic function of the prepared composite catalysts were tested by the oxidation of CO to CO2. From the catalytic activity results, it has been found out that the catalysts prepared by the sonochemical method exhibited higher catalytic activity for CO oxidation, probably attributed to the higher Pt particle distribution achieved under sonication. Transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and diffuse reflectance spectroscopy (DRS) were employed to characterize the resulting material. 相似文献
912.
V. Jayalaskmi Rupali Rohatgi Deepa Sathian P. K. Marathe Sarala Nair G. Cyourasiya S. Kannan 《Indian Journal of Physics》2009,83(6):857-861
CR-39 (PADC) a Solid State Nuclear Track Detector., is used as a routine personnel monitor. 1800 workers are being monitored
quarterly for fast neutron using CR-39 foils. These foils procured from Pershore Mouldings, UK are very expensive and indigenous
development will make the foils cost effective. The aim of this paper is to find a suitable alternative to the imported CR-39
foils for use in personnel monitoring. The foils from three different manufacturers have been compared with the CR-39 foils
from Pershore Moulding, UK, presently in use. Out of the three, only sample no 1 is promising. It has a background and sensitivity
comparable with CR-39 presently used. The sample 2 is CR-39 being developed in India, has a relatively high background and
poor sensitivity. Efforts are being made to improve the quality of this sample. The sample 3 was a poly carbonate from local
manufacturer which produced very few tracks and the standard deviation of track counts was very large and hence not useful
for Personnel Monitoring.
相似文献
913.
A novel coating approach, based on laser shock wave generation, was employed to induce compressive pressures up to 5 GPa and compact nanodiamond (ND) powders (4-8 nm) on aluminum 319 substrate. Raman scattering indicated that the coating consisted of amorphous carbon and nanocrystalline graphite with peaks at 1360 cm−1 and 1600 cm−1 respectively. Scanning electron microscopy revealed a wavy, non-uniform coating with an average thickness of 40 μm and absence of thermal effect on the surrounding material. The phase transition from nanodiamond to other phases of carbon is responsible for the increased coating thickness. Vicker's microhardness test showed hardness in excess of 1000 kgf/mm2 (10 GPa) while nanoindentation test indicated much lower hardness in the range of 20 MPa to 2 GPa. Optical surface profilometry traces displayed slightly uneven surfaces compared to the bare aluminum with an average surface roughness (Ra) in the range of 1.5-4 μm depending on the shock wave pressure and type of confining medium. Ball-on-disc tribometer tests showed that the coefficient of friction and wear rate were substantially lower than the smoother, bare aluminum sample. Laser shock wave process has thus aided in the generation of a strong, wear resistant, durable carbon composite coating on aluminum 319 substrate. 相似文献
914.
Yogesh Kumar J. Escorcia GarciaFouran Singh S.F. Olive-MéndezV.V. Sivakumar D. KanjilalV. Agarwal 《Applied Surface Science》2012,258(7):2283-2288
Morphological, optical and transport characteristics of the RF sputtered zinc oxide (ZnO) thin films over the mesoporous silicon (PS) substrates have been studied. Effect of substrate porosity on the grain growth and transport properties of ZnO has been analyzed. Physical and optical properties of ZnO-PS structures were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy. Our experimental results indicate that on changing porosity of the PS substrates, regularity of the spatial distribution of the ZnO nanocrystallites can be controlled. While the morphology and grain size of ZnO depended strongly on the morphology and pore size of the PS substrates, the rectifying factors of the metal semiconductor junction were found to be different by a factor of 3. The deposition of semiconducting oxides on such mesoporous substrates/templates offers the possibility to control their properties and amplify their sensing response. 相似文献
915.
R. RamakrishnanS. Kalaivani J. Amala Infant JoiceT. Sivakumar 《Applied Surface Science》2012,258(7):2515-2521
TiO2 although considered a promising photocatalyst for the degradation of aqueous pollutants, it suffers from poor absorption in the visible region and hence requires ultraviolet (UV) light for activation. To make TiO2 a visible active photocatalyst, multielement (C, N, B, and F) doping has been done. The synthesised CNBF/TiO2 catalysts were calcined at different temperatures and characterized by XRD, BET surface area, UV DRS, XPS, HRSEM-EDAX, and TEM techniques. These catalysts found to show less band gap values when compared to bare TiO2. These catalysts were tested for their catalytic activity towards the degradation of a textile dye - congo red (CR) under different reaction conditions. It was found that the photocatalytic activity was dependent on both doping of multielement and the calcination temperature of CNBF/TiO2. The co-doped catalysts which were calcined at 400 °C and 600 °C (100% intensity in anatase phase) were found to be the best catalysts (100% decolourisation of CR in 21/2 h and 2 h respectively). TOC analysis carried out for the samples at the reaction time of 5 h showed very high percentage (83%) degradation of CR over CNBF/TiO2 catalysts calcined at 600 °C when compared to the other catalysts calcined at different temperatures. CNBF/TiO2 (1000 °C) showed very less photocatalytic activity due to the formation of rutile phase. 相似文献
916.
917.
918.
Sivakumar M Towata A Yasui K Tuziuti T Kozuka T Iida Y Maiorov MM Blums E Bhattacharya D Sivakumar N Ashok M 《Ultrasonics sonochemistry》2012,19(3):652-658
In the present investigation, synthesis of manganese zinc ferrite (Mn0.5Zn0.5Fe2O4) nanoparticles with narrow size distribution have been prepared using ultrasound assisted emulsion (consisting of rapeseed oil as an oil phase and aqueous solution of Mn2+, Zn2+ and Fe2+ acetates) and evaporation processes. The as-prepared ferrite was nanocrystalline. In order to remove the small amount of oil present on the surface of the ferrite, it was subjected to heat treatment at 300 °C for 3 h. Both the as-prepared and heat treated ferrites have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) techniques. As-prepared ferrite is of 20 nm, whereas the heat treated ferrite shows the size of 33 nm. In addition, magnetic properties of the as-prepared as well as the heat treated ferrites have also been carried out and the results of which show that the spontaneous magnetization (σs) of the heat treated sample (24.1 emu/g) is significantly higher than that of the as-synthesized sample (1.81 emu/g). The key features of this method are avoiding (a) the cumbersome conditions that exist in the conventional methods; (b) usage of necessary additive components (stabilizers or surfactants, precipitants) and (c) calcination requirements. In addition, rapeseed oil as an oil phase has been used for the first time, replacing the toxic and troublesome organic nonpolar solvents. As a whole, this simple straightforward sonochemical approach results in more phase pure system with improved magnetization. 相似文献
919.
Sepioni M Nair RR Rablen S Narayanan J Tuna F Winpenny R Geim AK Grigorieva IV 《Physical review letters》2010,105(20):207205
We have studied magnetization of graphene nanocrystals obtained by sonic exfoliation of graphite. No ferromagnetism is detected at any temperature down to 2?K. Neither do we find strong paramagnetism expected due to the massive amount of edge defects. Rather, graphene is strongly diamagnetic, similar to graphite. Our nanocrystals exhibit only a weak paramagnetic contribution noticeable below 50?K. The measurements yield a single species of defects responsible for the paramagnetism, with approximately one magnetic moment per typical graphene crystallite. 相似文献
920.
The dynamics of an F center created by an oxygen vacancy on the TiO?(110) rutile surface has been investigated using ab initio molecular dynamics. These simulations uncover a truly complex, time-dependent behavior of fluctuating electron localization topologies in the vicinity of the oxygen vacancy. Although the two excess electrons are found to populate preferentially the second subsurface layer, they occasionally visit surface sites and also the third subsurface layer. This dynamical behavior of the excess charge explains hitherto conflicting interpretations of both theoretical findings and experimental data. 相似文献