Sunflower oil‐based HBTPU/Ag and LTPU/Ag nanocomposites have been prepared by in situ catalytic reduction of a silver salt. The virgin polymer and their nanocomposites are soluble in various polar organic solvents and amenable for both solution‐casting and hot pressing. XRD, TEM, and UV spectroscopic analyses ascertained well‐dispersed, narrow‐sized Ag nanoparticles. Tensile testing, dynamic mechanical, thermogravimetric, and DSC analyses showed desirable mechanical and thermal features with improvement upon incorporation of Ag nanoparticles and the presence of a hyperbranched component in the nanocomposites. RSM has been used to evaluate the catalytic efficacy of the nanocomposites.
Two types of stoving paints have been prepared from Mesua ferrea L. seed oil (MFLSO) modified poly(urethane ester) (PUE) binder systems. One stoving paint system was prepared from partially butylated melamine formaldehyde (MF) resin modified MFLSO-based PUE (70:30 weight ratio) and other one comprised of bisphenol-A-based epoxy resin modified with MFLSO-based PUE (50:50 weight ratio). Paints made with these two resin systems as binders were evaluated against the standard paint system. The physical properties of the paint systems viz. non-volatile content, specific gravity, viscosity, drying time, flexibility, adhesion, scratch hardness, gloss, etc. and chemical properties such as corrosion resistance, salt spray resistance, UV resistance, etc. were measured as per the standard methods and were compared. Thermal stability and surface morphology of the paints were also studied by using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively. The performance characteristics of both the test paints were found to be comparable with the corresponding industrial standard paints. Out of the two test paints, the epoxy modified PUE-based stoving paint has been found to be preferred. 相似文献
An epoxidized vegetable oil of Mesua ferrea L. seed was prepared and used as a reactive diluent for commercial BPA-based epoxy resin at different compositions for the first time. The prepared epoxidized oil (ENO100) was characterized by determination of physical properties like epoxy equivalent, viscosity, hydroxyl value, saponification value, iodine value, acid value, etc. and FTIR study. The morphology and rheological characteristics of the ENO100 modified commercial epoxy systems have been studied by SEM and rheometer. The performance of poly(amido amine) cured above resin systems have been investigated by the measurement of drying time, tensile strength, elongation at break, adhesive strength, impact resistance, scratch hardness, gloss and chemical resistance studies. The results indicate that the epoxidized oil not only reduces the viscosity of the BPA-based epoxy resin but it also enhances the performance of the cured resin. The performance of this system (50 wt.% dilution) was further enhanced by formation of nanocomposites using ex-situ technique with organically modified nanoclay at different dose levels (1–5 wt.%).The formation of nanocomposites was confirmed by XRD, SEM and FTIR studies. The studies of above performance indicate the enhancement of properties compared to pristine system. As naturally renewable diluent is used in the above studies, so the resultant nanocomposites are green high performance materials with zero VOC. 相似文献
Superior antimicrobial activity of 2 wt.% Pt-dispersed TiO2 thin film was observed in photokilling Gram-negative Escherichia coli bacteria within 5 min irradiation (640 μW cm−2, λ > 340 nm) from UV torch than bare TiO2 film. Severe disruption of cell membrane has occurred over illuminated Pt-TiO2 catalysts films coated with 100–300 μg powders per 5 cm2 areas over sterilized glass slides. The Pt dispersion onto TiO2 by impregnation–hydrogen reduction always exhibited better photokilling effect than Pt photodeposition, irrespective of Pt–TiO2 dose and light exposure time. Similar trend in photoactivity difference between two Pt–TiO2 catalysts is also observed in aqueous slurry because of the unlike surface structure of TiO2 due to different annealing temperatures, size and nature of Pt particles dispersion onto TiO2 photocatalysts. 相似文献
A new technique is reported for the transformation of smooth nonpolar ZnO nanowire surfaces to zigzagged high‐index polar surfaces using polycrystalline ZnO thin films deposited by atomic layer deposition (ALD). The c‐axis‐oriented ZnO nanowires with smooth nonpolar surfaces are fabricated using vapor deposition method and subsequently coated by ALD with a ZnO particulate thin film. The synthesized ZnO–ZnO core–shell nanostructures are annealed at 800 °C to transform the smooth ZnO nanowires to zigzagged nanowires with high‐index polar surfaces. Ozone sensing response is compared for all three types of fabricated nanowire morphologies, namely nanowires with smooth surfaces, ZnO–ZnO core–shell nanowires, and zigzagged ZnO nanowires to determine the role of crystallographic surface planes on gas response. While the smooth and core–shell nanowires are largely non‐responsive to varying O3 concentrations in the experiments, zigzagged nanowires show a significantly higher sensitivity (ppb level) owing to inherent defect‐rich high‐index polar surfaces. 相似文献
Two different ionic liquids have been tested in the electrochemical fabrication of anodic porous alumina in an aqueous solution
of oxalic acid. It was found that during galvanostatic anodization of the aluminum at a current density of 200 mA/cm2, addition of 0.5% relative volume concentration of 1-butyl-3-methylimidazolium tetrafluoborate resulted in a three-fold increase
of the growth rate, as compared to the bare acidic solution with the same acid concentration. This ionic liquid was also used
successfully for an assessment of the wettability of the outer surface of the alumina, by means of liquid contact angle measurements.
The results have been discussed and interpreted with the aid of atomic force microscopy. The observed wetting property allowed
to use the ionic liquid for protection of the pores during a test removal of the oxide barrier layer. 相似文献
Heat transfer measurement using thin film gauges (TFG) is the most prevalently used technique for determination of surface heat flux. They are best suited for short duration transient surface temperature measurements and typically used in the applications where convection is a dominant mode of heat transfer such as gas turbine engines, high speed flights etc. However, in few interdisciplinary research areas, there are practical issues and difficulties in exposing the gauges for convection based measurements. These present investigations are aimed at exploring the possibility of using thin film gauges for short duration conduction based transient measurements with pure conduction mode of heat transfer. A simple calibration set-up has been used to supply known heat flux of different magnitudes to the thin film gauges that are fabricated in-house with platinum as sensing element and pyrex as an insulating substrate. Experimentally recorded temperature signals from the gauges are compared with simulated temperature histories obtained through finite element analysis. Convoluted integral of one-dimensional heat conduction equation is used to predict the surface heat flux and compared with input heat loads. The presently developed calibration setup is seen to be very useful for conduction based measurements of thin film gauges. 相似文献
Nickel-based superalloys have served as the most competitive high temperature structural materials under highly stressed and aggressive operating conditions in a variety of applications for more than 60 years. The most demanding among all the applications has been the gas turbine aerofoil castings of modern aero-engines. These turbine parts operate in extremely aggressive environment of high velocity hot combustion gas-air mixture carrying highly corrosive ingredients at high pressure. Gas turbine aerofoil materials should therefore possess adequate resistance to creep, fatigue and aggressive environment. Materials design for such application therefore has been extremely challenging, particularly since the engine designers always aim at higher turbine entry temperature (TET) in order to achieve greater engine thrust and better fuel efficiency. In spite of enormous efforts made in the recent past towards developing ceramics and their composites, Ni-based superalloys continue to be most reliable blade and vane materials offering always the highest TET. This has been possible through better alloy design, improved blade cooling schemes, protective coatings and directional solidification (DS) of either columnar grains or single crystals (SC) along the most favorable 〈001〉 texture. During the last six decades, TET has gone up by about 500K. This article covers recent advances in cast Ni-based superalloys, including our own efforts in this direction. Extensive research at DMRL has led to the development of new generation Ni-based superalloys, designated as DMD-4 and DMS-4 for DS and SC processing, respectively. Simultaneously, expertise has been developed to cast DS and SC components for aero-engines. Technology has also been established for pilot scale production of these components. 相似文献
ABSTRACT: Bubble inclusion is one of the fastest growing operations practiced in the food industry. A variety of aerated foods is currently available in supermarkets, and newer products are emerging all the time. This paper aims to combine knowledge on chocolate aeration with studies performed on bubble formation and dispersion characteristics. More specifically, we have investigated bubble formation induced by applying vacuum. Experimental methods to determine gas hold-up (volume fraction of air), bubble section distributions along specific planes, and chocolate rheological properties are presented. This study concludes that decreasing pressures elevate gas hold-up values due to an increase in the number of bubble nuclei being formed and release of a greater volume of dissolved gases. Furthermore, bubbles are observed to be larger at lower pressures for a set amount of gas because the internal pressure needs to be in equilibrium with the surrounding pressures. Temperature-induced changes to the properties of the chocolate have less of an effect on bubble formation. On the other hand, when different fats and emulsifiers are added to a standard chocolate recipe, milk fat was found to increase, significantly, the gas hold-up values and the mean bubble-section diameters. It is hypothesized that this behavior is related to the way milk fats, which contain different fatty acids to cocoa butter, crystallize and influence the setting properties of the final product. It is highlighted that apparent viscosity values at low shear rate, as well as setting behavior, play an important role in terms of bubble formation and entrainment. 相似文献