Abrasive water jet machining and mechanical behavior of banyan tree saw dust powder loaded polypropylene green composites

Banyan tree saw dust powder (BSD) filled Polypropylene (PP) green composites have been fabricated with varying amounts viz., 0%, 20%, and 40% of BSD particulate filler by using a co‐rotating twin screw extruder followed by injection molding. The mechanical properties such as surface hardness, tensile behavior, and impact strength of the fabricated PP/BSD green composites have been studied in order to standardize the composites. Abrasive water jet (AWJ) machining has been reported mainly for ceramics, concrete, and glass but not much literature is available on AWJ machining of polymer composites. This research is aimed at examining the AWJ machining of green polymer composites. The effect of BSD loading on the AWJ machining behavior of the PP/BSD green composites has been investigated. Furthermore, the effect of addition of 4% maleic anhydride grafted PP (coupling agent) and 4% talc (mineral filler) on the machining behavior of PP/BSD composites has also been evaluated. Surface roughness and optical micrographs of the AWJ cut composite specimens were examined to assess the effect of BSD content, AWJ traverse speed and pressure on the machining behavior of the composites. In order to probe the mechanism of AWJ machining behavior of PP/BSD composites, the kerf width and taper have been measured and results are correlated. POLYM. COMPOS., 37:1754–1764, 2016. © 2014 Society of Plastics Engineers     

Efficient conversion of light paraffinic naphtha to aromatics over metal-modified Mo/MFI catalysts

Journal of Porous Materials - The transformation of light naphtha to value-added aromatic compounds is gaining momentum in the petrochemical industry. In this work, a series of metal modified...     

Synthesis and Properties of MoSi2–MoB–SiC Ceramics

MoB and SiC particulate reinforced MoSi₂ matrix composites were synthesized in situ from Mo, Si, and B₄C powder mixtures by self‐propagating high‐temperature synthesis (SHS). The SHS MoSi₂–MoB–SiC products were vacuum hot‐pressed (HPed) at 1400°C for 90 min to fabricate high‐density (> 97.5% relative density) bulk composites. Microstructure refinement and improvements in the Vickers hardness and fracture toughness of the HPed composites were observed with increasing B₄C content in the reaction mixture. The HPed composite of composition MoSi₂–0.4MoB–0.1SiC exhibited grain size of 1–5 μm, Vickers hardness of 12.5 GPa, bending strength of 537 MPa, and fracture toughness of 3.8 MPa.m^1/2. These excellent mechanical properties indicate that MoB and SiC particulate reinforced MoSi₂ composites could be promising candidates for structural applications.     

N-3 Polyunsaturated Fatty Acids Modulate In-Vitro T Cell Function in Type I Diabetic Patients

In this work, we assessed the in-vitro effects of eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) (final concentration, 15 microM) on T cell blastogenesis, interleukin-2 and -4 (IL-2, IL-4) secretion, fatty acid composition and intracellular oxidative status in type I diabetic patients with or without complications. Con A stimulated lymphocyte proliferation, glucose uptake, intracellular reduced glutathione levels and catalase activity were lower in diabetics as compared to controls, regardless to the presence of complications. EPA and DHA diminished T-lymphocyte proliferation and IL-2 production but enhanced IL-4 secretion in both diabetic and control groups. No changes in the levels of reduced glutathione and in the activities of catalase and SOD were observed in control T cells cultured in the presence of EPA and DHA. However, in diabetic patients, addition of n-3 PUFA to culture induced an increase in T cell levels of reduced glutathione and hydroperoxide, and in activities of catalase and SOD. Low levels of arachidonic acid (C20:4n-6) were found in plasma membrane phospholipids of lymphocytes from diabetic patients compared to controls. Incubation of lymphocytes with EPA and DHA was associated with an incorporation of these fatty acids in membrane phospholipids. In conclusion, the beneficial effects of n-3 PUFA on T cell functions in type I diabetes could be attributed to their suppressive action and modulation of cytokine secretion, and to the improvement of intracellular oxidative status.     

Microstructure and hardness studies of the electron beam welded zone of Hastelloy C-276

Electron beam welding (EBW) technique is becoming popular in nuclear, chemical and aerospace industries due to its high penetration depth and fast cooling rate. Samples of Hastelloy C-276 have been welded by electron beam (EB). A scanning electron microscope (SEM) having the attachment of an energy dispersive system (EDS) has been employed to study the resulting microstructure and micro-eutectic phases. The microstructure of the molten zone (MZ) is found to be of fine lamellar type. The hardness of the MZ is found to be 35% higher compared to as-received alloy. The micro-eutectoids are rich in Mo and W. The X-ray diffraction patterns of the MZ show shifting of peaks towards higher angle compared to the diffraction pattern of the as-received alloy. Broadening of the peaks is also observed in the diffraction pattern of the MZ. Formation of the μ-phase was observed in the MZ after a tempering treatment at 950 °C.     

Structural,rheological, and mechanical properties of ternary blends of PEN,PET, and liquid crystalline polymer

Structural, rheological, and mechanical properties of ternary blends of a liquid crystalline copolyester (LCP) composed of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, poly(ehtylene naphthalate)(PEN), and poly(ethylene terephtalate) (PET) were investigated using capillary rheometry, tensile testing, scanning electron microscopy, and X-ray diffraction. Viscosity-shear rate behavior of the ternary blends is very similar to that of pure polymers and their binary blends. The activation energy of flows of the ternary blends was smaller than those of PEN and PET. Tensile modulus and strength of extruded strands of the blends increased with increasing LCP content. The extruded strands of the blends consist of a crystalline and oriented LCP phase and an amorphous and unoriented PEN/PET blended phase. Tensile mechanical properties and structures of the ternary blends were discussed.     

RF electro-thermal modeling of LDMOSFETs for power-amplifier design

A new approach for the electro-thermal modeling of LDMOSFETs for power-amplifier design that bypasses pulsed-IVs and pulsed-RF measurements is presented in this paper. The existence of low-frequency dispersion in LDMOSFETs is demonstrated by comparing pulsed IVs with iso-thermal IVs. The modeling technique uses iso-thermal IV and microwave measurements to obtain the temperature dependence of small-signal parameters. Optimized tensor-product B-splines, which distribute knots to minimize fitting errors, are used to represent the small-signal parameters and extract the large-signal model as a function of voltages and temperature. The model is implemented on ADS and is verified by simulating and measuring the power harmonics and IMD large-signal performance of a power amplifier. The impact on the model of temperature-dependent drain and gate charge is investigated. The presented model is found to compare well and, in some cases, exceed the existing MET model for LDMOSFETs     

Structural stability of silver under single-chamber solid oxide fuel cell conditions

In the present study, structural stability of silver under single-chamber conditions has been examined. Micro-tubular cells made of conventional solid oxide fuel cell materials (Ni-YSZ/YSZ/LSM) with silver paste and silver current-collecting wires (for both electrodes) were prepared. The cells were operated with methane/air mixture of 25/60 mL min⁻¹, furnace temperature of 750 °C, and at an operating voltage of 0.5 V. The results showed increasing porosity in the current-collecting silver wire with time, leading to rupture, finally. It is postulated that the porosity formation could be due to the formation of silver oxide which is highly unstable (volatile) at operating temperature considered in this study. Furthermore, vaporization and melting of silver due to cell overheating under mixed-reactant conditions is expected. Based on experimental evidences, it is concluded that silver may not be a good choice to be employed under the above specified operating conditions, as it lacks long-term structural stability.     

Three Dimensional Conceptualisation of Hydrogeological Environment to Underpin Groundwater Management in Irrigation Area

Australian irrigated agriculture utilises about 70?% of all water used in the country, 21?% of which is derived from groundwater. Sustainability for irrigated agriculture also depends on keeping the watertables at a safe level below the rootzone to avoid salinisation and reduction in crop yields. There is a vital need to understand groundwater and aquifer systems and their roles in the sustainability of irrigated agriculture in order to manage groundwater properly. This study builds on the previous hydrogeological and groundwater investigations of the Coleambally Irrigation Area (CIA) in New South Wales of Australia. It presents a new approach which systematically characterises regional hydrogeological environment using a three-dimensional (3-D) conceptual framework developed in ArcGIS. The 3-D hydrological conceptualisation of the CIA has integrated disparate sources of data into a coherent knowledge base for a better visualisation of hydrogeological characteristics and a comprehensive analysis of groundwater flow and aquifers. As an application example, the model was used to develop cross-sectional models of the area and to estimate regional-scale net recharge. The results have provided a basis for the numerical modelling and added values to procedures which underpin irrigation system management investment decisions through improving the understanding of hydrogeology underlying the area and creating an action-oriented dialogue among stakeholders.