Plasma spray coatings for producing next-generation supported membranes

Ceramic systems as membranes play a critical role in synthesis gas production as well as gas separation technologies. This paper presents, the potential for thermal spray technology in natural gas-related programs, with a special emphasis on the production of ceramic membranes for oxygen gas separation processes. Yttria-stabilized zirconia (YSZ) coatings were deposited under different environments (air and vacuum) resulting in altered pore and crack distributions introduced during the spray process. We report on the characterization of these coatings using small-angle neutron scattering (SANS) and ultrasmall-angle X-ray scattering (USAXS) to explain the different pore structures observed for the two coating conditions. A quantitative representation of the microstructural features in these coatings is presented in terms of porosity, anisotropic void surface area and pore size distribution. Also, thermal and mechanical properties, complemented with impedance spectroscopy measurements, help understand coating behavior. Such comprehensive characterization, coupled with property measurements of the coatings, successfully demonstrates the potential of thermal spray technology in membrane production.*To whom correspondence should be addressed. E-mail: hherman@ms.cc.sunysb.edu     

Theoretical and Numerical Aspects in the Thermo-Viscoelastic Material Behaviour of Rubber-Like Polymers

Most current models for finite deformation thermo-viscoelasticity are restricted to linear evolution laws for the viscous behaviour and to thermorheologically simple materials. In this paper, we extend a model for finite deformation viscoelasticity that utilizes a nonlinear evolution law to include thermal effects. In particular, we present a thermodynamically consistent framework for the model and give a detailed form for then on-equilibrium Helmholtz free energy of the material in terms of the isothermal free energy function. The use of the model in a computational setting is addressed and it is shown that an efficient predictor-correct oralgorithm can be used to integrate the evolution equation of the proposed constitutive model. The integration algorithm makes crucial use of the exponential map as has been done previously in elastoplasticity. Numerical examples are presented to show some interesting features of the new model. This revised version was published online in July 2006 with corrections to the Cover Date.     

Minimizing total tardiness on a batch processing machine with incompatible job families

Motivated by an application in semiconductor manufacturing, we study the problem of minimizing total tardiness on a batch processing machine with incompatibl8e job families, where all jobs of the same family have identical processing times and jobs of different families cannot be processed together. We present a dynamic programming algorithm which has polynomial time complexity when the number of job families and the batch machine capacity are fixed. We also examine various heuristic solution procedures which can provide near optimal solutions in a reasonable amount of computation time.     

Experimental study on thermo-chemical phenomena during interaction of limestone concrete with liquid sodium under inert atmosphere

Sodium leak in fast breeder reactor, either from pipe in inert equipment cells or inside the reactor cavity may come in contact with the limestone sacrificial layer on structural concrete. Experimental studies are carried out to investigate thermal and chemical impact of sodium on the limestone concrete under different test conditions. Sodium pool is maintained at different temperature on the test blocks placed in leak tight test chamber. The temperatures at different locations, pressure, release of hydrogen and oxygen gas are monitored online during the experiments. On-set time and residence period for energetic thermal transients (ETT) along with peak and average heat generation rates are evaluated. Chemical parameters such as rate and extent of water release from concrete, sodium consumption, sodium hydroxide production and sodium emission into argon atmosphere are also elucidated. Preliminary analysis of test results revealed that when hot sodium at 500 °C reacts on cold concrete block, it monotonically cools down with low degree of interaction. However, supply of external heat to sodium pool triggers considerable reaction with or without occurrence of ETT phase.     

Optimization of photoelectrochemical solar cells based on polycrystalline CdTe film photoanode

Polycrystalline films of CdTe were electroplated onto titanium substrates from acidic baths. When surface treated, these layers show good photoelectrochemical behaviour in a polysulphide electrolyte with high conversion efficiencies and stability. The solid state parameters of the films annealed are calculated and compared with those of unannealed film based cells. Donor densities are found to be in the range of 1014 cm⁻³. Chemical etching improves the short-circuit current and fill factor and also results in Fermi level pinning of the photoanode, whereas photoelectrochemical etching improves the stability of the photoanode in polysulphide electrolyte.     

Mechanism of Toughening in Rubber Toughened Polyolefin—A Review

The recent advances and theories in the studies of the toughening mechanism have been reviewed to explain the effect of rubber particles in different rubber modified Polyolefin materials. To elucidate toughening effect, major theories e.g., critical particle distance, particle size, micro deformation by stress field of rubber, shear yielding and crazing phenomena has been reviewed. Based on these theories, variety of blends of rubber modified Polyolefin materials has been compared but no one of these provided adequate information to be considered as total theory of toughening. To achieve the objective of toughening, it is important to maintain critical particle size, uniform particle distribution and good interfacial adhesion by inclusion of suitable compatibilizer in the matrix. Particular attention has been paid to study the type of morphology and bimodal distribution of rubber particles to elucidated toughening effect. Rubber particle cavitation, which comes from micro-voids and rubber phase interface are then further discussed.     

Influence of compatibilizer on mechanical,morphological and rheological properties of PP/ABS blends

The objective of this work was to study the compatibilizer effect on polypropylene (PP) and acrylonitrile butadiene styrene (ABS) blends. The blends were coextruded and injection molded in various ratios of ABS with and without compatibilizers. Universal testing machine was employed to analyze the tensile properties of basic PP/ABS binary blends. From the mechanical testing, the impact and tensile properties of PP/ABS blend were optimized at 80/20 weight ratio. Various compatibilizers such as PP-g-MAH, SEBS-g-MAH and ethylene α-olefin copolymer were used and their comparative performance on binary blend was enumerated. Hybrid compatibilization effect was also studied and reported. However, the addition of compatibilizers showed the maximum increase in impact strength attributed to rubber toughening effect of ABS. The effect of compatibilizers on morphological properties was examined using scanning electron microscopy (SEM). SEM micrographs depicted the more efficient dispersion of ABS particles in PP matrix with the addition of compatibilizers. Further, interparticle distance analysis was carried out to evaluate the rubber toughening effect. The ABS droplet size in compatibilized PP/ABS blend was brought to minimum of 3.2 μm from 9.9 μm with the addition of compatibilizers. The melt rheology of PP/ABS blend systems was investigated through parallel plate arrangement in frequency sweep. Linear viscoelastic properties like storage (G′) and loss (G″) modulus and complex viscosity (η*) have been reported with reference to the virgin materials. It is understood that the combination of compatibilizers (hybrid compatibilizer) had a considerable effect on the overall blend properties.