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排序方式: 共有494条查询结果,搜索用时 15 毫秒
61.
Aiswarya Dash Sumit Kumar Pal Indranil Banerjee Subhabrata Chakraborty 《International Journal of Applied Ceramic Technology》2018,15(1):223-231
Rare‐earth‐doped upconversion nano‐phosphor shows new possibilities in the field of bioimaging because of its unique properties like higher penetration depth, low signal to noise ratio (SNR), good photo stability, and zero auto fluorescence. The oxyfluoride glass system is the combination of both fluoride and oxide where fluoride host offers high optical transparency due to low phonon energy and oxide network offers high physical stability. Thus, in the present work, an attempt has been made to synthesize 1 mol% Er3+ doped SiO2‐CaF2 glass ceramic nano‐particles through sol‐gel route. The synthesized glass ceramic particles were heat treated at 4 different temperatures starting from 600°C to 900°C.The X‐ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) analysis confirmed the formation of CaF2 nano‐crystals in the matrix which is 20‐30 nm in size. The vibrational spectroscopic analysis of the glass ceramics sample has been investigated by Fourier transform infrared (FTIR) spectroscopy. The UV‐Visible‐NIR spectroscopy analysis was carried out to analyze the absorption intensity in the near infrared region. Upon 980 nm excitation, the sample shows red emission corresponds to 4F9/2→4I15/2 energy level transition. The prepared nano‐particles showed excellent biocompatibility when tasted on MG‐63 osteoblast cells. 相似文献
62.
63.
Ionization rate coefficients and saturation drift velocities for electrons and holes are the vital material parameters in determining the performance of an IMPATT diode. We have performed a sensitivity analysis of the millimeter wave characteristics of 4H-SiC and 6H-SiC IMPATT diodes with reference to the above mentioned material data and an operating frequency of 220 GHz. The effect of a small variation in the ionization rate and drift velocity on the device characteristics like break down voltage, efficiency, noise measure and power output has been presented here. 相似文献
64.
Optical and mechanical properties of diamond like carbon films deposited by microwave ECR plasma CVD
S. B. Singh M. Pandey N. Chand A. Biswas D. Bhattacharya S. Dash A. K. Tyagi R. M. Dey S. K. Kulkarni D. S. Patil 《Bulletin of Materials Science》2008,31(5):813-818
Diamond like carbon (DLC) films were deposited on Si (111) substrates by microwave electron cyclotron resonance (ECR) plasma
chemical vapour deposition (CVD) process using plasma of argon and methane gases. During deposition, a d.c. self-bias was
applied to the substrates by application of 13·56 MHz rf power. DLC films deposited at three different bias voltages (−60
V, −100 V and −150 V) were characterized by FTIR, Raman spectroscopy and spectroscopic ellipsometry to study the variation
in the bonding and optical properties of the deposited coatings with process parameters. The mechanical properties such as
hardness and elastic modulus were measured by load depth sensing indentation technique. The DLC film deposited at −100 V bias
exhibit high hardness (∼ 19 GPa), high elastic modulus (∼ 160 GPa) and high refractive index (∼ 2·16–2·26) as compared to
films deposited at −60 V and −150 V substrate bias. This study clearly shows the significance of substrate bias in controlling
the optical and mechanical properties of DLC films. 相似文献
65.
A two dimensional (2D) analytical drain current model has been developed for a delta-doped tunnel field-effect transistor (D-TFET) that can address the ON-current issues of the conventional TFET. Insertion of a highly doped delta layer in the source region paves the way for improved tunneling volume and thus provides high drain current as compared with TFETs. The present model takes into account the effects of the distance between the delta-doping region and the source–channel interface on the subthreshold swing (SS), current ratio, and ON-current performance. The D-TFET is predicted to have a higher current ratio \(\left( {\frac{I_\mathrm{ON} }{I_\mathrm{OFF} }\cong 10^{11}} \right) \) compared with TFETs \(\left( {\frac{I_\mathrm{ON} }{I_\mathrm{OFF} }\cong 10^{10}} \right) \) with a reasonable SS \(\left( {{\sim }52\,\mathrm{mV/dec}} \right) \) and \(V_\mathrm{th}\) performance at an optimal position of 2 nm from the channel. The surface potential, electric field, and minimum tunneling distance have been derived using the solution of the 2D Poisson equation. The accuracy of the D-TFET model is validated using the technology computer aided design (TCAD) device simulator from Synopsys. 相似文献
66.
Vigneashwari B Dash S Tyagi AK Parameswaran P Ravichandran V Sunthathiraraj SA 《Journal of nanoscience and nanotechnology》2007,7(6):2087-2091
Semiconductor nanoparticles of Indium Sulphide were synthesized by a hydrothermal method using InCl3 and Na2S. Powder X-ray Diffraction analysis confirmed that the product obtained was nanocrystals of single-phase beta-In2S3. The crystallite size distribution was obtained from the diffraction profile and the average size was approximately 5 nm. The compositional analyses performed on the as-prepared powder showed that the material was devoid of any impurity with an In:S ratio very close to 2:3. A colloid of very fine In2S3 particles was obtained from the as-prepared powder by suspending them in acetonitrile. The optical absorption of this colloid showed evidence of strong quantum confinement of excitons and as a result the particles yielded intense photoluminescence in the violet-blue region. These colloidal particles were then electrophoretically driven on to a transparent conducting substrate to assemble into a nanostructure. A Grazing Incidence X-ray Diffraction analysis of the deposited layer revealed that the preferred orientation noticed in the native powder was removed in the deposit. The surface morphology of the deposit studied using SEM and AFM displayed an inherent ordering behaviour in the clusters organized into a two-dimensional film. The locus of the cluster lines tend to form closed circles, at the nanoscopic as well as microscopic scales, indicative of certain strong neighborhood correlations. Such structures may be expected to exhibit novel correlated properties also. 相似文献
67.
Tyagi AK Mangamma G Kamruddin M Dash S Raj B 《Journal of nanoscience and nanotechnology》2007,7(6):2005-2009
A novel methodology based on a hybrid approach has been evolved for synthesizing nearly monodisperse nanocrystalline oxides. The approach basically involves precipitation of gelatinous hydroxide in liquid phase hydrolysis and subsequent temperature programmed calcination to obtain nanocrystalline oxide. Cr2O3 and ZrO2 have been synthesized through this route. This paper describes synthesis procedures giving details of temperature windows required for this synthesis. In addition, solid state analytical technique like X-Ray Diffraction (XRD) and Photoluminescence (PL) have been used to characterize these materials. Especially PL was used to derive information on confinement effect. Transmission Electron Microscope (TEM), Scanning Probe Microscope (SPM), and Scanning Near Field Optical Microscope (SNOM) were used to derive morphology. 相似文献
68.
69.
Improvement of surface finish and material removal has been quite a challenge in a finishing operation such as abrasive flow machining (AFM). Factors that affect the surface finish and material removal are media viscosity, extrusion pressure, piston velocity, and particle size in abrasive flow machining process. Performing experiments for all the parameters and accurately obtaining an optimized parameter in a short time are difficult to accomplish because the operation requires a precise finish. Computational fluid dynamics (CFD) simulation was employed to accurately determine optimum parameters. In the current work, a 2D model was designed, and the flow analysis, force calculation, and material removal prediction were performed and compared with the available experimental data. Another 3D model for a swaging die finishing using AFM was simulated at different viscosities of the media to study the effects on the controlling parameters. A CFD simulation was performed by using commercially available ANSYS FLUENT. Two phases were considered for the flow analysis, and multiphase mixture model was taken into account. The fluid was considered to be a Newtonian fluid and the flow laminar with no wall slip. 相似文献
70.
S. Gayathri R. Krishnan T.R. Ravindran S. Tripura Sundari S. Dash A.K. Tyagi Baldev Raj M. Sridharan 《Materials Research Bulletin》2012,47(3):843-849
The hydrogen-free diamond-like carbon (DLC) films with transition metal (TM = Cr, Ag, Ti, Ni) interlayer (bilayer and multilayer) were deposited on to stainless steel and silicon substrates using pulsed laser deposition technique. Secondary ion mass spectroscopy (SIMS) confirmed that the films were hydrogen free. Incorporation of chromium inter layer reduced the stress value by about 3 GPa as determined by micro Raman spectroscopy. Incorporation of the TM inter layer enhanced the photoluminescence (PL) intensity as compared to the monolithic DLC films. The optical band gap determined by spectroscopic ellipsometry for DLC/TM films was found to be in the range of 1.56–1.67 eV. 相似文献