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1.
The sorption of n-alkanes, viz. hexane, heptane and octane by cross-linked natural rubber/poly(ethylene-co-vinyl acetate) (NR/EVA) blends has been studied at 28, 38, 48 and 58°C, with special reference to the effects of EVA content,
cross-linking systems, penetrant nature and temperature. The solvent transport was found to decrease with increase in EVA
content in the blends. The effects of blend ratio on the transport characteristics have been correlated with the phase morphology
of the blends, using scanning electron micrographs and optical micrographs. Among the three vulcanising systems, viz. sulphur
(S), dicumyl peroxide (DCP) and a mixed system (S + DCP) employed for the matrix, the DCP cross-linked blends exhibited the
lowest solvent uptake. Octane has been found to show higher interaction with the blends than hexane and heptane, probably
owing to the closer solubility parameter values. The computed transport coefficients, viz. diffusion coefficient and permeability
coefficient, were found to decrease with increase in EVA content in the blends. At room temperature, the mechanism of diffusion
was found to deviate slightly from the regular Fickian trend for all blend systems. The blend–solvent interaction parameter
and the activation energy for transport were also determined from the sorption data. 相似文献
2.
Sujith Vijayan Praveen Wilson Remani Sreeja Kuttan Prabhakaran 《Journal of the American Ceramic Society》2016,99(12):3866-3873
Open cellular SiC foams with low densities were prepared by thermo‐foaming and setting (130°C–150°C) of silicon powder dispersions in molten sucrose followed by pyrolysis and reaction sintering at 1500°C. The bubbles generated in the dispersion by water vapor produced by the –OH condensation was stabilized by the adsorption of silicon particles on the air‐molten sucrose interface. The composition of a sucrose‐silicon powder mixture for producing SiC foam without considerable unreacted carbon was optimized. The sucrose in the thermo‐foamed silicon powder dispersion leaves 24 wt% carbon during the pyrolysis. The sintering additives such as alumina and yttria promoted the silicon‐carbon reaction. SiC nanowires with diameters in the range of 35–55 nm and length >10 μm observed on the cell walls as well as in the fractured strut region were grown by both vapor–liquid–solid and vapor–solid mechanisms. Large SiC foam bodies without crack could be prepared as the total shrinkage during pyrolysis and reaction sintering was only ~30 vol%. The relatively low compressive strength (0.06–0.41 MPa) and Young's modulus (14.9–24.2 MPa) observed was due to the large cell size (1.1–1.6 mm) and high porosity (93%–96%). 相似文献
3.
Pranab Dey Kinsuk Naskar Golok B. Nando Biswaranjan Dash Sujith Nair G. Unnikrishnan 《应用聚合物科学杂志》2014,131(23)
Thermoplastic vulcanizates (TPVs), which are a special class of elastomer alloy, prepared by dynamic vulcanization possess unique morphology of finely dispersed micron‐size cross‐linked elastomeric particles in a continuous thermoplastic matrix. The present study investigates the microstructure formation of elastomeric phase and its associated morphological changes during reprocessing of TPVs based on poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] triblock co‐polymer (S‐EB‐S) and solution polymerized styrene butadiene elastomer (S‐SBR) by scanning electron microscopy and atomic force microscopy. Semi‐efficient and efficient sulfur‐based curing systems have been adopted to cure the elastomeric phase and a comparative study has been made to demonstrate and explain the effect of reprocessing on the melt rheology and dynamic viscoelasticity of the TPVs. The present work also provides a better insight and guidance to control the microstructure of the cross‐linked elastomeric phase to prepare selectively co‐continuous or dispersed phase morphology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41182. 相似文献
4.
Effect of Poly(vinyl pyrrolidone) on Antifouling Properties of Asymmetric Poly(ethylene‐co‐vinyl alcohol) Membranes 下载免费PDF全文
Poly(ethylene‐co‐vinyl alcohol)/poly(vinyl pyrrolidone) (EVAL/PVP) blend membranes with antifouling properties were prepared by nonsolvent induced phase separation. Residual PVP in the sample was calculated by infrared spectroscopic data and confirmed by thermogravimetric analysis. The effect of residual PVP on hydrophilicity and permeation characteristics of the membranes was evaluated. Porosity and equilibrium water content of the membranes were influenced by the addition of PVP. The effect of protein fouling on flux using bovine serum albumin as a model system was studied in detail. The residual PVP content could enhance the antifouling property of the membrane. All membranes proved to have sufficient mechanical strength to withstand pressure‐driven filtrations. 相似文献
5.
Sujith Vengayil M. Vanathi Anita Panda Sudharshan Khokhar 《Contact lens & anterior eye》2008,31(3):161-163
PURPOSE: To report a case of retained Descemet's membrane after penetrating keratoplasty for congenital hereditary endothelial dystrophy (CHED) documented by anterior segment optical coherence tomography and review of literature. METHODS: Case report and review of literature. RESULTS: A 14-year-old boy underwent penetrating keratoplasty for CHED. A retained host Descemet's membrane was detected with a supernumerary anterior chamber on the first postoperative day. The retained Descemet's membrane was documented using slit lamp adapted anterior segment optical coherence tomography (SLOCT). Surgical intervention for the Descemet's membrane removal was done in the third postoperative week. The complete removal of the membrane was confirmed on SLOCT. CONCLUSION: Inadvertent retention of the host Descemet's membrane is a rare but possible complication in penetrating keratoplasty for CHED. Proper anticipation, early detection and removal will help in preventing any undue risk of graft failure. 相似文献
6.
M. Vanathi Geeta Behera Sujith Vengayil Anita Panda S. Khokhar 《Contact lens & anterior eye》2008,31(3):164-166
PURPOSE: To report a case of acute hydrops in pellucid marginal corneal degeneration (PMCD) documented with anterior segment optical segment tomography and successfully treated with sulphur hexafluoride (SF6) intracameral injection. METHODS: A 47-year-old female patient presented with spontaneous onset of pain, redness and decreased vision in her left eye. Clinical evaluation revealed bilateral PMCD with evidence of acute hydrops in the left eye. Anterior segment Slit lamp Adapted Optical Coherence Tomography (SL-OCT) examination revealed intrastromal clefts with Descemet's membrane detachment in the left eye. She was managed with descemetopexy with 0.2ml injection of iso-expansile SF6 (18%) intracameral. RESULTS: The patient showed excellent early resolution of the stromal edema with reattachment of the Descemet's membrane. CONCLUSION: Prompt intervention in acute hydrops in PMCD cases helps in achieving early good visual results and prevents potentially serious complications such as perforation. Newer imaging modalities like SL-OCT helps in better visualisation and also in monitoring the response to treatment. 相似文献
7.
This study investigates the characteristics of fuel NOx formation resulting from the combustion of producer gas derived from biomass gasification using different feedstocks. Common industrial burners are optimized for using natural gas or coal-derived syngas. With the increasing demand in using biomass for power generation, it is important to develop burners that can mitigate fuel NOx emissions due to the combustion of ammonia, which is the major nitrogen-containing species in biomass-derived gas. In this study, the combustion process inside the burner is modeled using computational fluid dynamics (CFD) with detailed chemistry. A reduced mechanism (36 species and 198 reactions) is developed from GRI 3.0 in order to reduce the computation time. Combustion simulations are performed for producer gas arising from different feedstocks such as wood gas, wood + 13% DDGS (dried distiller grain soluble) gas and wood + 40% DDGS gas and also at different air equivalence ratios ranging from 1.2 to 2.5. The predicted NOx emissions are compared with the experimental data and good levels of agreement are obtained. It is found out that NOx is very sensitive to the ammonia content in the producer gas. Results show that although NO–NO2 interchanges are the most prominent reactions involving NO, the major NO producing reactions are the oxidation of NH and N at slightly fuel rich conditions and high temperature. Further analysis of results is conducted to determine the conditions favorable for NOx reduction. The results indicate that NOx can be reduced by designing combustion conditions which have fuel rich zones in most of the regions. The results of this study can be used to design low NOx burners for combustion of gas mixtures derived from gasification of biomass. One suggestion to reduce NOx is to produce a diverging flame using a bluff body in the flame region such that NO generated upstream will pass through the fuel rich flame and be reduced. 相似文献
8.
Madeneni Madhava Naidu P. V. Sujith Kumar B. N. Shyamala Guruguntla Sulochanamma Maya Prakash M. S. Thakur 《Food and Bioprocess Technology》2012,5(2):527-532
Vanilla planifolia Andrews is a perennial tropical vine and is an orchid grown for its pleasant flavor. There is an increasing trend world over
for using natural flavors. Vanilla being an important food flavoring ingredient, the demand for natural vanilla extract is
increasing. Hence, the aim of the present study was to prepare vanilla extract from green beans without going through the
elaborate and time-consuming conventional curing process. Vanilla beans after size reduction were mixed in a suitable proportion
with tea leaf enzyme extract (TLEE) and incubated to facilitate action of enzymes on vanilla flavor precursors. The beans
mix was squeezed, and the filtrate was treated with ethanol to extract the vanilla flavor. TLEE-treated extracts had higher
vanillin content (4.2%) compared to Viscozyme extract (2.4%). Also, it had higher intensity of vanilla flavor, sweet, and
floral notes. Further, electronic nose analysis confirmed the discrimination between extracts. It was concluded that the use
of TLEE is very much useful to obtain higher yield of vanilla extract and superior quality vanilla flavor, which avoids the
traditional laborious and time-consuming curing process. 相似文献
9.
Sujith Vijayan Rajaram Narasimman Kuttan Prabhakaran 《Journal of the American Ceramic Society》2013,96(9):2779-2784
Highly concentrated alumina powder suspensions have been prepared in aqueous urea solutions of concentrations in the range 200–360 g/100 mL using an ammonium poly(acrylate) dispersant at 80°C. The dispersant concentration for the suspension viscosity minimum in the urea solutions is higher than that in water due to the higher processing temperature. The urea solutions having higher dielectric constant than that of water offer higher interparticle potential that resulted in better dispersion of the powder as evidenced from the lower viscosity and yield stress of the suspensions. The decrease in temperature increased the suspension viscosity and the suspension formed a strong gel when cooled to room temperature due to the crystallization of urea. The minimum urea solution concentration for a 55 vol% alumina suspension to form a dimensionally stable gel is 240 g/100 mL. The compressive strength and Young's modulus of the gels increased with the increase in urea solution concentration. The alumina ceramics prepared by the urea removal followed by sintering at 1500°C had porosity in the range 28–36 vol% with the rectangular rod‐shaped aligned pores. 相似文献
10.
Unni Santhosh Yasser Gowayed Greg Ojard Imelda Smyth Sujith Kalarikkal George Jefferson 《Journal of Nondestructive Evaluation》2018,37(2):37
Thermography is one of the Non-Destructive Evaluation methods used to qualitatively estimate the amount of porosity in as-manufactured ceramic matrix composite (CMC) parts. Through-transmission (TT) thermography allows for comparison of thermal diffusivity caused by differences in material density and porosity at different locations in the part. In this study, volume fraction of pores and its distribution in CMC samples containing different amounts of porosity was quantified using optical microscopy and X-ray computed tomography scans. TT thermography was done on the same specimens and images were analyzed to determine the distribution of thermal diffusivity. Comparison of porosity measurements and thermal diffusivity images shows an inverse correlation. A simple two-phase analytical model describing this relationship is derived for composites and its solution is shown to compare favorably with experimental data. In the absence of porosity data, the model can be used to estimate porosity directly from thermal diffusivity data. 相似文献