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排序方式: 共有108条查询结果,搜索用时 15 毫秒
21.
Parakkulam Ramaswamy Aravind Palantavida Shajesh Sashidharan Smitha Poothayil Mukundan Krishna Gopakumar Warrier 《Journal of the American Ceramic Society》2008,91(4):1326-1328
Silica–alumina mixed oxide aerogels, with 5, 10, 15, 20, and 25 wt% of alumina in silica, have been synthesized by a hybrid sol–gel technique followed by subcritical drying. The gelation has been carried out under pH values of 3 and 5. pH is a decisive parameter that affects the rate of hydrolysis and condensation of alkoxides. Moreover, it also influences the surface area and porosity features of the final material. The gelation time has been found to be much longer for gels that were gelled at pH 3. Nitrogen sorption studies of the aerogels calcined at 500°C indicate that the mixed oxide aerogels are mesoporous in nature and the gels prepared under a gelation pH of 3 have been found to have higher surface area than the pH 5 counterpart. Transmission electron microscopy and X-ray diffraction analysis have been performed to verify the homogeneity of the mixed oxide aerogel. 相似文献
22.
K Sasikumar G Suresh KA Thomas Reji John V Natarajan T Mukundan RMR Vishnubhatla 《Bulletin of Materials Science》2006,29(6):637-640
Magnetically active elastomer materials were prepared by incorporating nickel powder in synthetic elastomeric matrices, polychloroprene
and nitrile rubber. Cure characteristics, mechanical, electrical and magnetic properties were experimentally determined for
different volume fractions of magnetoactive filler. The cure time decreases sharply for initial filler loading and the decrease
is marginal for additional loading of filler. The tensile strength and modulus at 100% strain was found to increase with increase
in the volume fraction of nickel due to reinforcement action. The magnetic impedance and a.c. conductivity are found to increase
with increase in volume fraction of nickel as well as frequency. 相似文献
23.
24.
Shiny Nair R. Rajeswari V. Natarajan T. Mukundan 《Journal of Experimental Nanoscience》2014,9(10):982-993
Polyaniline nanowires with entangled network structures were synthesised through an electropolymerisation route using a step galvanostatic method on titanium substrate. The morphology of the synthesised polyaniline was investigated by scanning electron microscopy and transmission electron microscopy. The dependence of morphology on the concentration and duration of synthesis has also been studied. Structural characterisation has been done by UV–VIS spectroscopy and Fourier transform infrared spectroscopy. The concentration of the monomer and the duration of synthesis affect the morphology as well as the amount of nanowires deposited. 相似文献
25.
Praveen K. Sekhar Eric.L. Brosha Rangachary Mukundan Hanna Mekonen Boris Farber Cortney Kreller Fernando H. Garzon 《International Journal of Hydrogen Energy》2012
In this article, testing of an electrochemical, potentiometric hydrogen safety sensor is reported within a proposed packaging scheme. Device packaging under static and flow testing conditions are presented. During the static volume sensor testing, the sensors response is compared against a calibrated Gas Chromatography (GC) measurement. Also, a commercial H2 sensor is incorporated into the test chamber to act as a benchmark for the sensor prototype. In the testing phase, H2 selectivity is demonstrated using pulsed discharge technique. 相似文献
26.
The operation of induction motors under unbalanced supply conditions is well documented. Because of the resulting unbalanced currents, there is an increase in losses and consequent overheating of the windings. IEC Standard 34-1-1996 and NEMA Standard MG-1-1993 stipulate that a motor should be able to withstand continuous operation with 1% negative sequence voltage without derating. Where motors are continuously subjected to unbalance beyond this, the effects become significant and derating the motor becomes essential. Where an unbalance in the supply cannot be easily corrected, the general method adopted is to use a motor of larger rating. Although this solves the problem of the motor getting overheated, the performance parameters of the motor (viz., power factor, efficiency, starting current, etc.) deteriorate. In fact, the negative sequence currents in the supply lines increase, causing additional losses and requiring larger capacity supply cables. Thus, although simpler to implement, use of a larger size motor does not lead to the desirable solution (viz., reduction of unbalance in the motor winding currents). This letter studies the feasibility of modifying the machine in order to minimize the unbalance in the currents of a motor subjected to unbalanced supply voltages 相似文献
27.
Mahima Goel Marie Siegert Gert Krauss John Mohanraj Adrian Hochgesang David C. Heinrich Martina Fried Jens Pflaum Mukundan Thelakkat 《Advanced materials (Deerfield Beach, Fla.)》2020,32(43):2003596
Unlike the conventional p-doping of organic semiconductors (OSCs) using acceptors, here, an efficient doping concept for diketopyrrolopyrrole-based polymer PDPP[T]2-EDOT (OSC-1) is presented using an oxidized p-type semiconductor, Spiro-OMeTAD(TFSI)2 (OSC-2), exploiting electron transfer from HOMOOSC-1 to HOMOOSC-2. A shift of work function toward the HOMOOSC-1 upon doping is confirmed by ultraviolet photoelectron spectroscopy (UPS). Detailed X-ray photoelectron spectroscopy (XPS) and UV–vis–NIR absorption studies confirm HOMOOSC-1 to HOMOOSC-2 electron transfer. The reduction products of Spiro-OMeTAD(TFSI)2 to Spiro-OMeTAD(TFSI) and Spiro-OMeTAD is also confirmed and their relative amounts in doped samples is determined. Mott–Schottky analysis shows two orders of magnitude increase in free charge carrier density and one order of magnitude increase in the charge carrier mobility. The conductivity increases considerably by four orders of magnitude to a maximum of 10 S m−1 for a very low doping ratio of 8 mol%. The doped polymer films exhibit high thermal and ambient stability resulting in a maximum power factor of 0.07 µ W m−1 K−2 at a Seebeck coefficient of 140 µ V K−1 for a very low doping ratio of 4 mol%. Also, the concept of HOMOOSC-1 to HOMOOSC-2 electron transfer is a highly efficient, stable and generic way to p-dope other conjugated polymers. 相似文献
28.
Christoph Jonda Andrea B. R. Mayer Mukundan Thelakkat Hans‐Werner Schmidt Andreas Schreiber Dietrich Haarer David Terrell 《Advanced functional materials》1999,9(3):117-128
The performance of organic light‐emitting devices (OLEDs) is strongly influenced by the electronic properties of the employed materials. In order to determine the effect of these materials' parameters, several different hole‐transporting 1,3,5‐tris(4‐diphenylaminophenyl)benzenes (TDAPBs) were synthesised. These TDAPBs contained different substituents, different numbers of substituents and different positions of theses substituents. For the evaluation of the electronic properties, cyclic voltammetry was employed in order to determine the HOMO values, and time‐of‐flight (TOF) measurements to obtain the hole mobilities. OLEDs were prepared consisting of the TDAPBs blended in a polymer matrix, and of Alq3 as electron‐conducting and light‐emitting layer. These devices were investigated regarding their current density/voltage characteristics, efficiencies, onset voltages for electroluminescence, and lifetimes. For hole‐transporting blend systems an exponential relationship between the current density and the HOMO levels of the TDAPBs was found. However, even though the HOMO values cover a range from −5.09 to −5.35 eV, no effects on the performance of the OLEDs were detected for electroluminescent two‐layer systems. In this case the initial voltage seems to be a determining parameter for the behaviour of the devices during operation. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
29.
30.
Studies on salts of 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4,6-trinitroanilino benzoic acid (TABA): potential energetic ballistic modifiers 总被引:2,自引:0,他引:2
Kulkarni PB Reddy TS Nair JK Nazare AN Talawar MB Mukundan T Asthana SN 《Journal of hazardous materials》2005,123(1-3):54-60
The Co/Cu/Ni/Fe salts of 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4,6-trinitroanilino benzoic acid (TABA) were prepared and characterized during this work. All the salts exhibited exothermic decomposition in DSC. The FT-IR spectra of the gaseous products evolved during TGA of NTO salts indicated the release of NO2 and cleavage of NTO ring during the course of decomposition. Thermal decomposition of TABA salts also produced NO2 on decomposition. The transition metal salts enhanced the burning rates of AP-HTPB composite propellant evaluated during this work. The best catalytic effect was obtained with Fe-NTO salt which increased the burning rate to the extent of approximately 80% as well as brought down the pressure index (n) to 0.18 (2-9MPa). 相似文献