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991.
Using sol-gel method, mesoporous and photoluminescent silica nanocomposites of soluble starch have been synthesized and characterized. Different ratios of H2O, TEOS and EtOH were used at fixed template (soluble starch) and catalyst (NH4OH) concentrations to obtain materials of different performances in terms of heavy metal binding from a solution which has been monitored using Cd(II) as representative divalent heavy metal ion. Optimum material was obtained when H2O, TEOS and EtOH were used in 14:1:2 ratio. This sample was not only an efficient metal ion adsorbent but also had an intense luminescence in ultra-violet region and potentially may be used in silicon-based UV-emitting devices. Metal binding by the material was further enhanced after calcination (at 800 °C in air) while its luminescence had a multipeak profile in UV-visible region. In a batch adsorption study, calcined hybrid composite (0.25 g/L) could remove 98.5% Cd(II) from 100 mg/L Cd(II) solution in 2 h. The chemical, structural and textural characteristics of the synthesized materials have been investigated using Fourier Transform Infrared Spectroscopy (FTIR), X-rays Diffraction (XRD), Thermal Analysis (TGA/DTA), Photoluminescence (PL), Brunauer-Emmett-Teller Analysis (BET) and Scanning Electron Microscopy (SEM). 相似文献
992.
Devraj Singh Dharmendra K. Pandey Pramod K. Yadawa 《Central European Journal of Physics》2009,7(1):198-205
The ultrasonic attenuation in thulium monochalcogenides TmX (X=S, Se and Te) has been studied theoretically with a modified Mason’s approach in the temperature and range 100 K to 300 K
along 〈100〉, 〈110〉 〈111〉 crystallographic directions. The thulium monochalcogenides have attracted a lot of interest due to
their complex physical and chemical characteristics. TmS, TmSe and TmTe are trivalent metal, mixed valence state, and divalent
semiconductor, respectively. Coulomb and Born-Mayer potential is applied to evaluate the second- and third-order elastic constants.
These elastic constants are used to compute ultrasonic parameters such as ultrasonic velocities, thermal relaxation time,
and acoustic coupling constants that, in turn, are used to evaluate ultrasonic attenuation. A comparison of calculated ultrasonic
parameters with available theoretical/experimental physical parameters gives information about classification of these materials.
相似文献
993.
Divya Singh Amit Saxena Shri Prakash Pandey Sandeep Kumar Tomar K. Asokan D. Kanjilal Ranvir Kumar Bhaskar Bhattacharya 《Macromolecular Symposia》2009,277(1):8-13
In this paper, we report the ion beam interaction with a well explored ion conducting polymer electrolyte, viz., polyethylene oxide complexed with sodium iodide (PEO:NaI). Li3+ ions at 50 MeV were bombarded on the film at different flux. The conductivity modulation of the films has been reported due to interaction at different fluence. The increase in the total conductivity is explained in terms of the change in the number of charge carriers and the dielectric constant of the polymer electrolyte films. 相似文献
994.
Results are presented on the evolution of subsequent yield surfaces with finite deformation in a very high work hardening annealed 1100 aluminum alloy. In Part I [Khan, A.S., Kazmi, R., Stoughton, T., Pandey, A., 2009a. Evolution of subsequent yield surfaces and elastic constants with finite plastic deformation. Part 1: a very low work hardening aluminum alloy (Al-6061–T6511) 25, 1611–1625.] of this paper, similar results are presented for a very low work hardening aluminum alloy. Those results were very different from the present ones, and all the results were for proportional loading paths. The subsequent yield surfaces are determined in tension, free end torsion and combined tension–torsion proportional and non-proportional loading paths, using 10 με deviation from linearity definition of yield. Yield surfaces are also determined after linear, bi-linear, and non-linear unloading paths after finite deformation under tension, free end torsion, and combined tension–torsion loading. The initial yield surface is closer to the von-Mises surface and the subsequent yield surfaces show distortion, expansion, positive cross-effect, and “nose” in the loading direction. Additionally, the subsequent yield surfaces after non-proportional loading paths show shrinkage and compounded distortion. The yield surfaces after unloading depict strong anisotropy, positive cross-effect and exhibits different proportion of distortion in each loading conditions. The Young’s and shear modulus decrease with plastic deformation and this decrease is much less than those reported in the published literature. 相似文献
995.
Kamlesh Pandey Mrigank Mauli Dwivedi Sharda Sundaram Sanjay Nidhi Asthana 《Ionics》2017,23(1):113-120
To develop porous polymeric membrane, we have used poly(vinylidene-co-hexafluoropropylene) (P(VdF-HFP)) as a host matrix and the ionic liquid 1-ethyl-3-methylimidazolium tosylate as salt for the source of charge carriers in the polymer electrolyte system. Appropriate weight of mica (muscovite) has been added to the highest conducting polymer–salt electrolyte. The composite membrane has been prepared by breath figure method through controlling evaporation time and then tested this membrane for water filtration. The composite polymeric membrane has been characterized by X-ray diffraction, FTIR spectrometry, SEM, and electrochemical impedance spectroscopy. The pore volume in the mica-based film has been calculated, and it is found to be 64.3 % in the filler-dispersed membrane. 相似文献
996.
We have developed a compact, robust adaptive optics (AO) scanning laser ophthalmoscope using a microelectromechanical (MEMS) deformable mirror (DM). Facilitated with a Shack-Hartmann wavefront sensor, the MEMS-DM-based AO operates a closed-loop modal wave aberration correction for the human eye and reduces wave aberrations in most eyes to below 0.1 microm rms. Lateral resolution is enhanced, and images reveal a clear cone mosaic near the foveal center. The significant increase in throughput allows for a confocal pinhole whose diameter is less than the Airy disc of the collection lens, thereby fully exploiting the axial resolution capabilities of the system. 相似文献
997.
Shiv Chand Anand Kumar Pandey Rahul Singh Saurabh Kumar Krishna Nand Singh 《化学:亚洲杂志》2019,14(24):4712-4716
An operationally simple Eosin Y catalyzed sulfenylation of hydrazones has been realized to afford a range of thioethers under visible light. The methodology provides high yields of thioethers under ambient conditions employing readily available and inexpensive starting materials. The reaction has broad substrate scope and is compatible with various functional groups. 相似文献
998.
Prashant K. Sharma Ranu K. Dutta Avinash C. Pandey 《Journal of magnetism and magnetic materials》2009,321(20):3457-3461
The ZnO:Ni2+ nanoparticles of mean size 2-12 nm were synthesized at room temperature by the simple co-precipitation method. The crystallite structure, morphology and size were determined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The wurtzite structure of ZnO gradually degrades with the increasing Ni doping concentration and an additional NiO-associated diffraction peak was observed above 15% of Ni2+ doping. The change in magnetic behavior of the nanoparticles of ZnO with varying Ni2+ doping concentration was investigated using a vibrating sample magnetometer (VSM). Initially, these nanoparticles showed strong ferromagnetic behavior, however, at higher doping percentage of Ni2+, the ferromagnetic behavior was suppressed and paramagnetic nature was observed. The enhanced antiferromagnetic interaction between neighboring Ni-Ni ions suppressed the ferromagnetism at higher doping concentrations of Ni2+. 相似文献
999.
Prashant K. Sharma Ranu K. Dutta Prashant K. Singh Avinash C. Pandey 《Journal of luminescence》2009,129(6):605-950
Surface effects significantly influence the functionality of semiconductor nanocrystals. In the current work we present synthesis of ZnO quantum dots (QD) vis-a-vis symmetrically dispersed ZnO quantum dots embedded in SiO2 matrix and discussed their optical properties to understand the role of the surface effects. These nanomaterials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared (FTIR), absorption (UV-visible) and photoluminescence (PL) spectroscopy. TEM studies confirm the formation of ZnO nanophosphors inside the SiO2 matrix in highly symmetrical manner. These symmetrically dispersed ZnO@SiO2 nanophosphors exhibited enhanced stable emission over uncoated sample and would permit the conjugation of the nanocrystals to biological entities after functionalization. Furthermore, the mechanism behind the formation of symmetrically dispersed ZnO quantum dots embedded in SiO2 matrix was discussed in detail. 相似文献
1000.
In this paper, we are presenting an analytical study of the effect of curvature of the spiral shape on the modal dispersion characteristics of the waveguide whose core cross-section is bounded by two involuted spirals of the form 1/r=ξθ, where ξ is a constant and represents the curvature of the spiral taken to design the waveguide into consideration. This study has been done under the weak guidance approximation. Analyzing the dispersion curves for different curvature we found that this waveguide supports only the single mode, and their cutoff value decreases as the the curvature of the spiral increases. 相似文献