The infrared infiltration and joining of advanced material

JOM - Infrared processing is a newly developed technique for materials processing. Key features include rapid processing, simplicity, and low cost. Because of the rapid processing, very little...     

Tribological Behavior of Micrometer- and Submicrometer-Size Cenosphere Particulate-Filled Glass Fiber–Reinforced Vinylester Composites Under Dry and Water-Lubricated Sliding Conditions

In this work, the tribological behavior of micrometer and submicrometer cenosphere particulate–filled E-glass fiber–reinforced vinylester composites have been investigated on a pin-on-disc tester under dry sliding and water-lubricated sliding conditions. Three different uniform sizes of cenosphere particles (2 μm, 900 nm, 400 nm) were used as fillers in the glass fiber–reinforced vinylester composites. The weight fraction of cenosphere particles has been varied in the ranges from 5, 10, 15, to 20 wt%. The experimental results show that all of the composites exhibited lower coefficient of friction and lower wear resistance under water-lubricated sliding conditions than under dry sliding. It has been noted that the submicrometer size (400 nm) cenosphere particulates as fillers contributed significantly to improve the wear resistance. It has also been noted that 10 wt% of the cenosphere particles is the most effective in reducing the wear rate and coefficient of friction. Effects of various wear parameters such as applied normal loads, sliding speeds, particle size, and particle content on the tribological behavior were also discussed. In order to understand the wear mechanism, the morphologies of the worn surface were analyzed by means of scanning electron microscopy (SEM) for composite specimens under both dry and water-lubricated sliding conditions.     

Mechanical,thermal, and microwave properties of conducting composites of polypyrrole/polypyrrole‐coated short nylon fibers with acrylonitrile butadiene rubber

Pyrrole was polymerized in the presence of anhydrous ferric chloride as oxidant and p‐toluene sulfonic acid as dopant. Polypyrrole‐coated short nylon fibers were prepared by polymerizing pyrrole in the presence of short nylon fibers. The resultant polypyrrole (PPy) and PPy‐coated nylon fiber (F‐PPy) were then used to prepare rubber composites based on acrylonitrile butadiene rubber (NBR). The cure pattern, direct current (DC) conductivity, mechanical properties, morphology, thermal degradation parameters, and microwave characteristics of the resulting composites were studied. PPy retarded the cure reaction while F‐PPy accelerated the cure reaction. Compared to PPy, F‐PPy was found to be more effective in enhancing the DC conductivity of NBR. The tensile strength and modulus values increased on adding PPy and F‐PPy to NBR, suggesting a reinforcement effect. Incorporation of PPy and F‐PPy improved the thermal stability of NBR. The absolute value of the dielectric permittivity, alternating current (AC) conductivity, and absorption coefficient of the conducting composites prepared were found to be much greater than the gum vulcanizate. PPy and F‐PPy were found to decrease the dielectric heating coefficient and skin depth significantly. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Parameter estimation in multiple contact CO2 miscibility simulation with uncertain experimental core flooding data

CO₂ flooding, which is an efficient method of enhanced oil recovery, is a very complicated process involving phase behavior. To understand the performance of CO₂ flooding and provide accurate data for designing reservoir development, a comprehensive investigation of the phase behavior of CO₂ miscible flooding and an accurate compositional reservoir simulation needs to be conducted. In PVT modeling, an effective and more physically reasonable equation of state model was achieved and the feasibility of CO₂ miscible flooding was determined by multiple contact minimum miscibility pressure (MCMMP) calculation. Furthermore, compositional reservoir simulation studies for predicting CO₂ miscible performance were designed and constructed with core flooding data. By matching with laboratory core flooding data, we can estimate parameters with uncertainty. The objective of this study was to find a work flow for parameter estimation in CO₂ miscible flooding process that can be used to design and optimize field CO₂ miscible floods.     

Synthesis and characterization of novel citric acid-based polyester elastomers

In this paper we report successful simple synthesis of unique elastic polyesters by carrying out catalyst-free polyesterification of multifunctional non-toxic monomers: 1,8-octanediol (OD), citric acid (CA) and sebacic acid (SA). The chemical, physical, and surface chemical properties of the resulting copolyester polyoctanediol citrate/sebacate [p(OCS)] have been investigated. This new material was characterized by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), thermal analysis (TA), mechanical tests, photo-acoustic Fourier-transform infrared spectroscopy (PA-FTIR), X-ray photoelectron spectroscopy (XPS) and swelling experiments. We demonstrate that the chemical structure, morphology, physical integrity and surface chemistry of the synthesized co-polymer can be controlled by simply varying the initial acid concentration (CA/SA) in the pre-polymer. This novel p(OCS) polymer exhibits versatility in mechanical properties, hydration and hydrolytic degradation as determined by the chemical structure of the polyester elastomer.     

Asymmetrically loaded annular ring antenna

A numerical model for resonant frequency using asymmetric loading is presented using cavity model. In asymmetric loaded antenna, the posts are not equispaced on annular ring antenna and resonant frequency is independent of the angular location of posts. The posts are located away from the centre of patch. The diameter of post is thin as compared to the diameter of annular ring antenna. The first few dominant modes calculated for asymmetric loading are compared to symmetric loading where the posts are to be located at specific angular locations. The theoretical model is compared to the simulated results of IE3D based on Method of Moments. The numerical model developed can also be verified further by the full wave analysis.     

Stress analysis & life prediction of a cryogenic rocket engine thrust chamber considering low cycle fatigue, creep and thermal ratchetting

The paper deals with stress analysis, cyclic and creep life prediction of a cryogenic rocket engine thrust chamber, being used in one of the satellite launch vehicles of ISRO. The thrust chamber is of double walled construction wherein high conductivity copper alloy is used for the inner wall and stainless steel for the outer. Regenerative cooling of the chamber is achieved by passing the fuel through rectangular coolant passages milled on outer surface of the inner wall. The inner and outer walls are bonded together by brazing at high temperature. Failure of a double walled chamber occurs due to thinning of the inner wall and bulging into the chamber due to three mechanisms viz. (i) low cycle fatigue (ii) thermal ratchetting and (iii) creep. To capture the structural behaviour of the chamber in a complete sequence of operation of the engine, axisymmetric modeling and cyclic stress analysis is carried out using the ANSYS finite element analysis software package. High temperature mechanical properties, low cycle fatigue and creep properties of copper are characterised. Results of creep tests conducted at various temperatures are utilized for evaluating creep constants of Norton secondary creep model available in ANSYS. Analysis is performed in a seven load step sequence simulating one complete hot test of the engine. Life prediction is done using the cumulative damage accumulation methodology, considering the above three damage mechanisms. Allowable number of hot runs permissible is then arrived at after assigning suitable factors of safety for each damage mode.     

Investigation of the Applicability of Ion Exchange Resins as a Sustained Release Drug Delivery System Forpropranolol Hydrochloride

The purpose of this study was to investigate the application of six strongly acidic cation exchange resins as a sustained release drug delivery system. Propranolol hydrochloride was chosen as the model drug to study the in vitro adsorption and desorption characteristics of the resins because of its chemical structure and pharmacokinetie properties which make it a good candidate for a sustained release formulation. The exchange rate constants and diffusion coefficients for the adsorption and desorption experiments were determined for each resin using the equations derived by Boyd, Adamson and Myers. Only one cation exchange resin showed potential as a sustained release drug delivery system for propranolol hydrochloride.