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排序方式: 共有96条查询结果,搜索用时 11 毫秒
1.
K. G. Vasantha Kumari P. Divya Vasu Viswanathan Kumar Thangavelu Asokan 《Journal of the American Ceramic Society》2002,85(3):703-705
Formation of spinel phases in ZnO–Sb2 O3 and ZnO–Sb2 O3 –Bi2 O3 systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn2.33 Sb0.67 O4 phase is observed in both the systems at ∼900°C. However, in these systems, at higher temperatures ( T ≥ 1100°C), formation of the inverse spinel phase Zn7 Sb2 O12 is observed. The study has been extended to understand the effect of CrO3 doping on the stability of the different spinel phases in the previously mentioned systems. Interestingly, in both the systems, samples doped with CrO3 , displayed the presence of Zn2.33 Sb0.67 O4 phase <1200°C, indicating the stabilization of the spinel phase by CrO3 . 相似文献
2.
R. Lavanya V.J. Surya I. Lakshmi K. Iyakutti V. Vasu H. Mizuseki Y. Kawazoe 《International Journal of Hydrogen Energy》2014
Hydrogen storage in titanium dioxide (TiO2) functionalized (10, 10) armchair single walled carbon nanotube (SWCNT) is investigated through first principle calculations using density functional theory (DFT). This first principles study uses Vienna Ab-initio Simulation Package (VASP) with ultrasoft pseudopotentials and local density approximation (LDA). The necessary benchmark and other systematic calculations were carried out to project the hydrogen storage capability of the designed system. Interestingly, the TiO2 molecules functionalized on the outer surface of SWCNT do not undergo any dimerization/clustering thus giving excellent stability and usable gravimetric hydrogen storage capacity of 5.7 wt.% and the value nearly fulfills the US DOE target (i.e. 6 wt.%). The band structure and density of states (DOS) plots suggest that the functionalization can lead a way to transform the nature (metallic → semiconducting) of the pristine SWCNT. The nominal values of H2 storage capacity and binding energies give much hope for using CNT functionalized with TiO2 as a practical and reversible hydrogen storage medium (HSM). 相似文献
3.
Estimating ground-level PM2.5 in the eastern United States using satellite remote sensing 总被引:1,自引:0,他引:1
Liu Y Sarnat JA Kilaru V Jacob DJ Koutrakis P 《Environmental science & technology》2005,39(9):3269-3278
An empirical model based on the regression between daily PM2.5 (particles with aerodynamic diameters of less than 2.5 microm) concentrations and aerosol optical thickness (AOT) measurements from the multiangle imaging spectroradiometer (MISR) was developed and tested using data from the eastern United States during the period of 2001. Overall, the empirical model explained 48% of the variability in PM2.5 concentrations. The root-mean-square error of the model was 6.2 microg/m3 with a corresponding average PM2.5 concentration of 13.8 microg/m3. When PM2.5 concentrations greater than 40 microg/m3 were removed, model results were shown to be unbiased estimators of observations. Several factors, such as planetary boundary layer height, relative humidity, season, and other geographical attributes of monitoring sites, were found to influence the association between PM2.5 and AOT. The findings of this study illustrate the strong potential of satellite remote sensing in regional ambient air quality monitoring as an extension to ground networks. With the continual advancement of remote sensing technology and global data assimilation systems, AOT measurements derived from satellite remote sensors may provide a cost-effective approach as a supplemental source of information for determining ground-level particle concentrations. 相似文献
4.
Low-temperature plastic flow in copper was investigated by studying its tensile and creep deformation characteristics. The
dependence of the flow stress on temperature and strain rate was used to evaluate the thermal activation energy while the
activation area was derived from the change-in-stress creep experiments. A value of 0.6 eV was obtained for the total obstacle
energy both in electrolytic and commerical copper. The activation areas in copper of three selected purities fell in the range
1200 to 100 b2. A forest intersection mechanism seems to control the temperature dependent part of the flow stress. The increase in the
athermal component of the flow stress with impurity content in copper is attributed to a change in the dislocation density.
The investigation also revealed that thermal activation of some attractive junctions also takes place during low-temperature
creep. The model of attractive junction formation on a stress decrement during creep, yields a value of 45±10 ergs cm−2 for the stacking fault energy in copper. 相似文献
5.
Response of materials as a function of grinding angle on friction and transfer layer formation 总被引:1,自引:1,他引:0
Pradeep L. Menezes Kishore Satish Vasu Kailas Michael R. Lovell 《The International Journal of Advanced Manufacturing Technology》2010,49(5-8):485-495
Surface texture influences friction and transfer layer formation during sliding contact. In the present investigation, basic studies were conducted using an inclined pin-on-plate sliding apparatus to understand the effect of grinding mark directionality on the coefficient of friction and transfer layer formation. In the experiments, 080 M40 steel plates were ground to attain different surface roughness with unidirectional grinding marks. Pins consisting of soft materials (pure Al, pure Mg, and Al–4Mg alloy) were then slid against the prepared steel plates. The grinding angle (angle between direction of sliding and grinding marks) was varied between 0° and 90° in the tests. The experiments were conducted under both dry and lubricated conditions in an ambient environment. It was observed that the transfer layer formation and the coefficient of friction depend primarily on the directionality of the plate grinding marks. For the case of pure Mg pins, a stick-slip friction phenomenon was observed for all grinding angles under dry conditions and for grinding angles over 25° under lubricated conditions. In the case of Al pins, the stick-slip phenomenon was observed only under lubricated conditions for angles exceeding 25°. The stick-slip phenomena did not occur in any of the conditions studied with Al–4Mg alloy pins. Based on the results, it was concluded that the magnitudes of the friction and the stick-slip motion amplitude (for Al and Mg pins) were primarily controlled by changes in the level of plowing friction. 相似文献
6.
Pulipparambil Vasu Divya Divakaran Ambika Dhanya Krishnan Kalathil Sivanandan Viswanathan Kumar 《International Journal of Applied Ceramic Technology》2009,6(2):231-235
Ferroelectric glass–ceramics of composition 0.90 (Ba0.7 Sr0.3 ) TiO3 –0.10(B2 O3 :SiO2 ) (0.90 BST:0.10 BS) synthesized by sol–gel method have been used for the preparation of dielectric thick-film inks. The particle dispersion of the glass–ceramic powders in the thick-film ink formulations have been studied through rheological measurements for fabricating thick-film capacitors by screen printing technique. The thick films derived from such glass–ceramics are found to sinter at considerably lower temperatures than the pure ceramic, and exhibit good dielectric characteristics with a tunability of 32% at 1 MHz under a dc bias field of 35 kV/cm. 相似文献
7.
Bian Da Liu Yaxuan Aradhyula Thirumala Vasu Guo Yongxin Tang Hao Zhao Yongwu Wang Yongguang 《Ceramics International》2021,47(11):15722-15731
To enhance the tribocorrosion properties of chemically bonded phosphate ceramic coating (CBPCC), GO-ZnO was prepared and added into CBPCC. And the tribocorrosion behaviour of CBPCC was investigated. Results show that, with the introduction of GO-ZnO, the open circuit potential of CBPCC shifts in a positive direction and corrosion current density decreases. In addition, the total material loss, the total mechanical wear loss and the total electrochemical corrosion loss of CBPCC all decrease with the increase of GO-ZnO. The wear track of CBPCC after tribocorrosion without GO-ZnO is rough and porous, while the wear track becomes smooth and dense with the incorporation of GO-ZnO. The material in wear track is anchored by GO-ZnO due to the strong bond between GO-ZnO and CBPCC, which decreases the wear loss. Because of the extra force from the tribocorrosion experiment, the material anchored by GO-ZnO forms to a dense structure which prevents electrolyte diffusion into CBPCC. Moreover, GO-ZnO can block the electrolyte diffusion pathway and make it more tortuous. The resistance to the electrolyte diffusion decreases the corrosion current density and the increased wear loss due to electrochemical corrosion. 相似文献
8.
K. Dasthaiah B. Robert Selvan A. S. Suneesh M. P. Antony R. L. Gardas 《分离科学与技术》2017,52(14):2308-2317
Aliquat-336-based strongly hydrophobic ionic liquid, tri-n-octylmethylammonium diglycolamate ([A336]+[DGA]?), was prepared and impregnated in Amberlite XAD-7 (abbreviated as [A336]+[DGA]?/XAD-7) for studying the extraction behavior of Am(III) and Eu(III) from nitric acid medium. The distribution ratio of Am(III) and Eu(III) in [A336]+[DGA]?/XAD-7 decreased with an increase in the concentration of nitric acid and the mechanism of trivalent metal ion extraction in the resin phase was elucidated. The uptake of Am(III) and Eu(III) in [A336]+[DGA]?/XAD-7 followed a second order and from the Langmuir adsorption model the apparent europium extraction capacity was determined. The conditions needed for efficient separation of Am(III) from Eu(III) was optimized. 相似文献
9.
Varma HM Vasu RM Nandakumaran AK 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(10):3089-3099
We present an optical tomographic reconstruction method to recover the complex refractive index distribution from boundary measurements based on intensity, which are the logarithm of intensity and normal derivative of intensity. The method, which is iterative, repeatedly implements the forward propagation equation for light amplitude, the Helmholtz equation, and computes appropriate sensitivity matrices for these measurements. The sensitivity matrices are computed by solving the forward propagation equation for light and its adjoint. The results of numerical experiments show that the data types ln(I) and partial differential I/ partial differential n reconstructed, respectively, the imaginary and the real part of the object refractive index distribution. Moreover, the imaginary part of the refractive index reconstructed from partial differential I/ partial differential n and the real part from ln(I) failed to show the object's inhomogeneity. The value of the propagation constant, k, used in our simulations was 50, and this value resulted in smoothing of the reconstructed inhomogeneities. Thus we have shown that it is possible to reconstruct the complex refractive index distribution directly from the measured intensity without having to first find the light amplitude, as is done in most of the currently available reconstruction algorithms of diffraction tomography. 相似文献
10.
Shivakumar Nagavelly Vasu Velagapudi N. Narasaiah 《Transactions of the Indian Institute of Metals》2017,70(8):2155-2163
ZA-27 alloy is a lightest alloy which offers excellent bearing and mechanical properties in automobile and industrial applications. In this study, the MoS2 particles with 0.5, 1 and 1.5 (wt%) weight percentages were reinforced in ZA-27 alloy to form composites, which were fabricated by using ultrasonic assisted stir casting method. The ZA-27/MoS2 composite specimens were examined for chemical composition with the aid of XRD technique and EDS. Microstructure analysis of the ZA-27/MoS2 composites was studied using SEM. Tests were conducted for mechanical properties such as tensile strength and hardness on ZA-27/MoS2 composites samples as per ASTM standards. Dry sliding wear behavior of the composites was tested at various operating conditions by using pin-on-disc apparatus. Microstructural images of the ZA-27 composites reveal that there is a uniform dispersion of the MoS2 particles in the base material. From the results it is observed that the mechanical properties increases with ZA-27 reinforced with 0.5 wt% MoS2 composite and further decreases with increase in the filler content. The enhanced wear resistance is observed in ZA-27 reinforced MoS2 composites as compared to the unreinforced alloy. The wear rate of the ZA-27 composites decreases with the increase in filler content, further the worn surfaces as examined using SEM reveals the wear mechanism explaining the improved wear resistance of the particulate composites. 相似文献