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881.
Asok K. Sarkar Gregory Kozlowski Iman Maartense 《Journal of the American Ceramic Society》1990,73(10):3110-3112
A bulk density of 85% of the theoretical density was achieved by sintering a powder compact of YBa2 Cu4 O8 (124) at 850°C in flowing oxygen at 1 atm (≅105 Pa). This value is very close to that obtained by the hot isostatic pressure technique (90%). The superconducting properties of the sample were characterized by magnetization and ac susceptibility techniques. The magnetization critical current density at 20 K in zero field was determined to be ∼5 × 104 A/cm2 , and the superconducting transition temperatures were found to be 77 K for the bulk material and 82 K for the granular phase. The powder X-ray diffraction and ac susceptibility studies revealed the sintered 124 material to be single phase. 相似文献
882.
Jaydeep Sarkar Tien-Heng Huang Lih-Ping Wang Peter H. McDonald Chi-Fung Lo Paul S. Gilman 《中国科学E辑(英文版)》2009,52(1):79-87
In this study we have used a combinatorial approach for producing binary and ternary alloy thin film libraries using a lab-scale RF co-sputtering system. Initially we used two elemental sputtering targets, i.e. aluminum (Al) target and neodymium (Nd) target, to produce a film library of varying composition and successfully identified a suitable composition range (1.95―2.38 at% Nd) in which resistance to hillock formation and resistivity of the film spots were found to be satisfactory in annealed state (350℃, 30 min). In another case, in order to form ternary alloy composition library we have used two sputtering targets, i.e. an Al-0.5 at% Nd alloy target and an elemental Ni target. Though, co-sputtered Al-0.6 at% Nd-0.9 at% Ni alloy films showed satisfactory resistance to hillock formation and low resistivity after annealing, film deposited from a ternary alloy target with the same composition failed to show satis- factory resistance to hillock formation during annealing. In case of Al-0.6 at% Nd-0.9 at% Ni alloy target, 250 nm thick film showed poor resistance to hillock formation than the 500 nm thick film. This clearly showed thickness-dependent hillock performance of Al-0.6 at% Nd-0.9 at% Ni alloy. In this study it was found that, in addition to the process variables, metallurgical microstructure of the alloy sputtering targets had significant effect on the film properties which was not obvious from the results of films deposited using co-sputtering of the individual elemental targets. 相似文献
883.
In the present paper, design of a flow control loop using a thyristor driven pump as final control element has been described. In this technique, the load current of a thyristor driven pump motor has been utilized as a mass flow sensing parameter of a fluid passing through a pipeline. This thyristor driven pump has been utilized as a final control element of a flow control loop and the speed of the pump has been selected as the manipulated variable. The non-linearity between the thyristor input signal and pump output has been eliminated by using a modified PID control technique with inverse derivative control action. Thus without using any conventional flow meter and control valve only the thyristor driven pump has been utilized both as the final control element and flow indicating device by using the proposed technique. The whole system has been designed, fabricated and tested by using tap water as the flowing liquid through a pipe line. The experimental results along with the theoretical analysis are compared and reported in the paper. 相似文献
884.
Biswajit Sarkar B. K. Jha Vinod Kumar S. K. Chaudhuri Sudhaker Jha 《Journal of Materials Engineering and Performance》2005,14(2):219-223
Ferrite grain sizes of the order of 1 to 2 μm were obtained by optimizing the strain, strain rate, the stage of cooling, as
well as the cooling rate during hot rolling of 0.15C-0.92Mn-0.01Si-0.036S-0.04P-0.013Nb steel. It was found that in single-pass
rolling of a 10 mm plate to a thickness of 3.5 mm with an entry temperature of 800 °C, and early-stage water cooling, very
fine grains of ferrite (1–2 μm) were formed at the surface and in subsurface regions. It was also found that the threshold
level of reduction during rolling, which is required for the refinement of ferrite grains, is >50%. The 3.5 mm thermomechanically
processed plate was found to possess very attractive mechanical properties in terms of the yield strength (485 MPa), the ultimate
tensile strength (UTS) (763 MPa), and particularly the yield strength to ultimate tensile strength (YS/UTS) ratio (0.63).
This combination of properties can be explained on the basis of the composite microstructure consisting of ferrite and bainite
that was obtained as a result of the thermomechanical processing. 相似文献
885.
Upadhyay J Sharma ML Navathe CP Toley MA Shinde SJ Nadkarni SA Sarkar SK 《The Review of scientific instruments》2012,83(2):024709
A high-voltage pulse-slicer unit with variable pulse duration has been developed and integrated with a 7 MeV linear electron accelerator (LINAC) for pulse radiolysis investigation. The pulse-slicer unit provides switching voltage from 1 kV to 10 kV with rise time better than 5 ns. Two MOSFET based 10 kV switches were configured in differential mode to get variable duration pulses. The high-voltage pulse has been applied to the deflecting plates of the LINAC for slicing of electron beam of 2 μs duration. The duration of the electron beam has been varied from 30 ns to 2 μs with the optimized pulse amplitude of 7 kV to get corresponding radiation doses from 6 Gy to 167 Gy. 相似文献
886.
Rodenhausen KB Kasputis T Pannier AK Gerasimov JY Lai RY Solinsky M Tiwald TE Wang H Sarkar A Hofmann T Ianno N Schubert M 《The Review of scientific instruments》2011,82(10):103111
Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing. 相似文献
887.
We have designed, fabricated, and made operational an ex situ cantilever beam magnetometer (CBM), which is versatile in the sense that it can measure most of the magnetic properties of a material in all probable shapes. The working principle of a CBM is discussed considering the magnetic torque into the beam theory. The individual components of the instrument are described in details and experiments were performed on the bulk materials, pellets of nanoparticles, ribbon samples, and thin films, and the magnetization, magnetostriction, and magnetocrystalline anisotropy were studied. This magnetometer is inexpensive, but versatile and would be suitable for the research as well as teaching laboratories. 相似文献
888.
Pal SS Mondal SK Tiwari U Swamy PV Kumar M Singh N Bajpai PP Kapur P 《The Review of scientific instruments》2011,82(9):095107
We propose a novel refractive index sensor based on multimode microfiber knot-type loop (NL) interferometer. The middle portion (~5 cm) of a 15 cm long multimode fiber is etched in 48% hydrofluoric acid to reduce its diameter to ~12 μm. A NL of diameter <1 mm is made from the etched fiber. The ends of etched fiber are spliced with single-mode fibers for launching and detecting light from the NL interferometer. The NL introduces path differences to produce interferometric spectra with free spectral range ~16 nm. The spectrum shifts as the surrounding refractive index of the loop is changed by adding chemicals. We observe the highest sensitivity of the NL interferometer ~172 nm/RIU (refractive index unit) at a refractive index value 1.370 as obtained experimentally using commonly available chemicals. The design could be used as simple, low cost, and highly sensitive biological and chemical sensor. 相似文献
889.
Binary melts of AlSi alloys were cast into bars 6.25 mm in diameter which were slid against hard steel bushes on a pin-bush machine. Surfaces, subsurfaces and wear debris were examined with a scanning electron microscope. Simulated studies were also carried out using model asperities in wax. The topographies from sliding were compared with those on cutting tools after machining aluminium. The surfaces of wax models were studied for comparison with machined and slid surfaces. Wear rates were measured. Techniques such as X-ray diffraction analysis were used to identify the nature of the surface and subsurface. Heavy loads produce a topography which has the appearance of roof tiles and these indicate near-seizure conditions. The bulk of the wear debris is produced by craze cracking. It is evident that transfer and back transfer of material occur across the sliding interface throughout a wear run. A critical number of layers build up on both members of the friction couple. Wear particles are produced once this number is exceeded. The wear rates of the AlSi alloys are not linear with load and a near-eutectic alloy is the ideal material from the point of view of wear and load-carrying capacity. 相似文献
890.
Implementing statistical modeling approach towards development of ultrafine grained bioceramics: Case of ZrO2‐toughened Al2O3 下载免费PDF全文
Debasish Sarkar Bhimavarapu Sambi Reddy Bikramjit Basu 《Journal of the American Ceramic Society》2018,101(3):1333-1343
The application of statistical modeling approach with the predictive capability of sinter density and grain size is perceived as a central theme in the development of next generation ceramics. Such computationally intensive method can be equally significant, if the predicted process conditions can be adapted experimentally to develop complex shaped ceramics with variable sizes. In the first ever attempt to address such issues for the ceramics, we have, in the present work, considered a range of factors and levels from relevant process variables (sintering temperature, sintering time) and material variables (sinter‐aid addition and reinforcement content) as input parameters to formulate data‐driven, high throughput analytical assays by response surface method (RSM). Using ZrO2 toughened Al2O3 (ZTA) as a model system, the adopted RSM approach has been used to quantitatively predict independent and interactive role of process and material variables on sinter density and grain size. 相似文献