Nonequilibrium solidification of undercooled melt of Ag-Cu alloy entrained in the primary phase

The solidification structure of undercooled melt of Ag-Cu alloy, entrained in its primary Cu-rich phase, has been investigated. The undercooling procedure consisted of equilibration of a Cu-13 pct Ag alloy in the two-phase liquid-solid region, followed by repeated thermal cycling of the liquid. Slow cooling of the sample in the present work established the ability to undercool the melt up to 70 K below the eutectic temperature of this alloy. The microstructure of the undercooled alloy indicated a complete absence of eutectic reaction on subsequent quenching of the melt directly from the equilibration temperature. The compositional analysis of the constituent phases by electron probe microanalysis (EPMA) technique provided evidence for the massive diffusionless solidification of the undercooled liquid. The X-ray diffraction study and electron microscopic examination indicated evidence for the spinodal transformation of the metastable solid solution phase. The composition of the phases formed on decomposition matched well with the calculated coherent spinodal boundaries in this system. The evolution of the metastable microstructure in the mushy-state quenching process of this alloy is discussed.     

Changes in Zeta Potential During Hydration of C3S With and Without CaCl2 Additions

C₃S and C₃S+2% CaCl₂ were hydrated for varied times; the degree of hydration and zeta potential were determined. In the absence of CaCl₂, the duration of the induction period was 5 h, whereas when CaCl₂ was added, an induction period of 1 h was observed. The zeta potential was positive, maximum, and constant during induction .     

Exact solution for wind tunnel interference using the panel method

Wind tunnel wall interference effects on lifting and non-lifting bodies are computed here for incompressible two-dimensional flows. The flows around bodies under consideration are computed by a panel method using linearly varying vortex distributions. The method is regarded as an exact numerical method. Also to exactly compensate for the wind tunnel wall, we use the method of images of the complete body in the wind tunnel. The image system consists of two cascades which extend infinitely on both sides of the wind tunnel. Thus, the exact wind tunnel wall interference effects are obtained for circular and elliptic cylinders, NACA 23012, NACA 64A010 and NACA 0010 airfoils. The velocity distributions and lift coefficient variations are presented for different blockages. The effects of airfoil incidences and the relative proximity of the two walls are also investigated. The present analysis has given rise to some results which otherwise would not have been possible by earlier existing very approximate methods. Wind tunnel walls are found to change the circulation around the body in the wind tunnel. This effect is further accentuated if we either change the incidence or change the relative proximity of the wind tunnel walls.     

A competitive progression perspective of JIT systems: evidence from early US implementations

This study investigates the holistic implementation of just-in-time (JIT) manufacturing. We contend that the most important elements of holistic JIT systems – focused factory, reduced setup times, group technology, total productive maintenance, multifunction employees, uniform workload, just-in-time purchasing, Kanban, total quality control and quality circles – should be implemented in a sequential manner for a firm to reap sustainable operational gains. The right sequence of implementation of JIT practices is derived using the theory of competitive progression and based on four JIT practice bundles – conformance quality related practices, delivery reliability related practices, volume flexibility related practices and low cost related practices. Data collected in a cross-sectional field study of US manufacturers are used to test the suggested implementation sequence of JIT practices and the impact of the JIT practice bundles on improvement in non-value added performance. The results indicate that implementations of JIT management practices should be in the order – first, conformance quality related practices; second, delivery reliability related practices; third, volume flexibility related practices and; finally low cost related practices. In addition, significant improvement in operational performance, as reflected in improvement of non-value added performance, is achieved via the cumulative capability building.     

Filter performance of reduced sized defect photonic crystals based on single‐negative materials

Single‐ and multiple‐channeled filters based on single‐negative (SNG) photonic crystals with inversion defects have been demonstrated theoretically. Omnidirectional filters with wide angular apertures and multiple‐channeled filters at normal incidence have been reported. Sharp, high transmission peaks with frequencies lying within the SNG range are obtained. By variation of the structural parameters these structures can also be made to function as tunable or polarizing filters, though the frequencies of the transmission modes in these two cases will lie outside the SNG range. A significant feature of all the filter types discussed is the drastic reduction in size of the proposed structures in comparison to those reported earlier. This implies easier fabrication methods and lower cost. Improved performance of devices has been achieved by proper placement of defects.     

Ionic polymer‐metal composites made from radiation grafted FEP‐g‐styrene‐SO3H membranes

Ionic polymer‐metal composites have been made from radiation grafted fluorinated ethylene propylene (FEP) membranes. Membranes have been synthesized by grafting of styrene on FEP films followed by sulfonation. These membranes were then used to fabricate IPMCs. Chemical plating of silver has been done to form the microelectrodes. Influence of degree of grafting on actuation, surface resistance, and tensile properties of the IPMC have been evaluated. It has been observed that on increasing the degree of grafting surface resistance, tensile strength, and elongation of IPMC decrease while degree of actuation and modulus increase. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A comparative analysis of woven jute/glass hybrid polymer composite with and without reinforcing of fly ash particles

The objective of this research article is to compare the mechanical and tribological properties of jute‐glass‐fiber‐reinforced epoxy (J‐G‐E) hybrid composites with and without fly ash particulate filler. A dry hand lay‐up technique is used to fabricate all the laminates. The properties including flexural strength, tensile strength, flexural modulus, and erosion behavior of all the composites are evaluated as per American Society for Testing and Materials (ASTM) standards. The fly ash particulate‐filled hybrid composite shows a better mechanical and tribological property. The maximum flexural strength and flexural modulus are obtained for GJGJ+ 5 wt% fly ash filler epoxy composites. Whereas the maximum tensile strength is obtained for GJJG+ 10 wt% fly ash filler epoxy composites. Scanning Electron Microscopy (SEM) analysis also has been carried out to categorize mechanical and tribological behavior of composites. POLYM. COMPOS. 37:658–665, 2016. © 2014 Society of Plastics Engineers     

Effect of Hydrophobic Modification on the Properties of Polymer‐Blended Microemulsion Gels

Phase behavior of sodium oleate (NaOl)/isoamyl alcohol‐based lamellar gel phase in cedar oil/water medium in the presence of the nonionic polymer hydroxyethyl cellulose (HEC) and its hydrophobic modified product (HMHEC) is investigated for the development of polymer‐embedded surfactant gels. HMHEC is more soluble in oil‐in‐water (o/w) microemulsions, but nonionic HEC shows limited solubility in the lamellar microemulsion (o/w type). Quantitative estimation of rate of adsorption of the polymer on lamellae bilayers can be easily done by Sudan solubilization and methylene blue complexation methods. Addition of HMHEC to the lamellar gel phase increases the polymer solubilization limit of lamellar gels as well as the viscoelasticity and thermal stability. The polymer‐embedded microemulsion gel acts as a “clean gel” since it exhibits good solubilization in different hydrocarbon media at ambient conditions. Elastic modulus of the polymer‐embedded gel influences directly the suspension performance of gels at high temperature and yields a reasonable sand‐settling velocity acceptable according to fracturing standards. The thermal characteristics and viscoelastic properties of polymer‐embedded gel were found to be suitable for moderate‐temperature reservoir stimulation where the bottom hole temperature is in the range 70–75 °C. Already a large amount of experimental data on pure microemulsions (without polymer) exists. Our studies indicate that the developed polymer‐embedded microemulsion gel has great potential as a model system for the study of polymer–microemulsion interactions.     

Effect of polymer concentration on porosity and pore size characteristics of alumina membrane substrates prepared by gelcasting

The effect of urea–formaldehyde (UF) polymer concentration on porosity and average pore size of alumina membrane substrates prepared by gelcasting has been studied. The soluble UF oligomers formed in the initial stages of polymerization act as steric stabilizer for alumina particles in the suspension. The porosity and average pore size of the substrate samples decreased with both the decrease of amount of polymer in the gelcast body and the increase of sintering temperature. Membrane substrates obtained by sintering of gelcast bodies containing UF polymer concentrations from 24.3 to 15.6 wt% at temperatures from 1250 to 1450 °C showed porosity and average pore size of 62.5–27 vol% and 0.43–0.20 μm, respectively. The membrane substrates prepared by the gelcasting method had narrow pore size distribution.     

Supplementary Networking of Interpenetrating Polymer System (SNIPSy) Strategy to Develop Strong & High Water Content Ionic Hydrogels for Solid Electrolyte Applications

To synthesize hydrogels that possess tensile strength and modulus together in MPas along with extensibility at high equilibrium water content (≥90 wt%) is challenging but important from the application perspective. Especially, such hydrogel compositions are useful for fabricating flexible electronics devices for subsea applications, where underwater risk-free implementation and optimum device performance at low temperature (≈0 °C) and high hydrostatic pressure (≤20 bar) conditions is desirable. The high water content of hydrogel is necessary to facilitate ion transportation, and mechanical strength is desirable to maintain a stable electrode–electrolyte interface under load. In this study, supplementary networking of an interpenetrating polymer system strategy is utilized to develop ionic hydrogels with tensile strength and Young's modulus values up to 2 and 1.67 MPa, respectively, at high equilibrium water content value up to 96%. Cost-effective, durable, rechargeable, and flexible batteries are fabricated using the Zn & Li ion soaked hydrogel as solid electrolyte without barrier. These batteries display minimal loss in capacity when immersed in water, deformed, exposed to flame, put under high load, and operated under low-temperature conditions suggesting the viability for subsea application.