Characterization of Pd–Cu membranes fabricated by surfactant induced electroless plating (SIEP) for hydrogen separation

Pd–Cu composite membranes on microporous stainless steel (MPSS) substrate were fabricated using surfactant induced electroless plating (SIEP). In the SIEP method, dodecyl trimethyl ammonium bromide (DTAB), a cationic surfactant, was used in Pd- and Cu-baths for the sequential deposition of metals on MPSS substrates. The SIEP Pd–Cu membrane performance was compared with membranes fabricated by conventional electroless plating (CEP). The pre- and post-annealing characterizations of these membranes were carried out by SEM, XRD, EDX and AFM studies. The SEM images showed a significant improvement of the membrane surface morphology, in terms of metal grain structures and grain agglomeration compared to the CEP membranes. The SEM images and helium gas-tightness studies indicated that dense and thinner films of Pd–Cu can be produced with shorter deposition time using SIEP method. From XRD, cross-sectional SEM and EDS studies, alloying of Pd–Cu was confirmed at an annealing temperature of 773 K under hydrogen environment. These membranes were also studied for H₂ perm-selectivity as a function of temperature and feed pressure. SIEP membranes had significantly higher H₂ perm-selectivity compared to CEP membranes. Under thermal cycling (573 K – 873 K – 573 K), the SIEP Pd–Cu membrane was stable and retained hydrogen permeation characteristics for over three months of operation.     

Template-assisted synthesis of high packing density SrLi2Ti6O14 for use as anode in 2.7-V lithium-ion battery

SrLi₂Ti₆O₁₄ has been prepared by using mesoporous TiO₂ brookite as a template and reactant. The prepared particles retained the rounded shape of the precursor, leading to high dispersivity and high packing density. The material has been further electrochemically characterized in both half and full cells. It shows good cycling stability and rate capability. A 2.7-V cell has been built by combining a SrLi₂Ti₆O₁₄ anode with a 4-V spinel cathode of LiMn₂O₄. This cell has a higher voltage compared to the 2.5-V LiMn₂O₄/Li₄Ti₅O₁₂ system.     

Characterization of HAZ of API X70 Microalloyed Steel Welded by Cold-Wire Tandem Submerged Arc Welding

High-strength low-carbon microalloyed steels may be adversely affected by the high-heat input and thermal cycle that they experience during tandem submerged arc welding. The heat-affected zone (HAZ), particularly the coarse-grained heat-affected zone (CGHAZ), i.e., the region adjacent to the fusion line, has been known to show lower fracture toughness compared with the rest of the steel. The deterioration in toughness of the CGHAZ is attributed to the formation of martensite-austenite (M-A) constituents, local brittle zones, and large prior austenite grains (PAG). In the present work, the influence of the addition of a cold wire at various wire feed rates in cold-wire tandem submerged arc welding, a recently developed welding process for pipeline manufacturing, on the microstructure and mechanical properties of the HAZ of a microalloyed steel has been studied. The cold wire moderates the heat input of welding by consuming the heat of the trail electrode. Macrostructural analysis showed a decrease in the CGHAZ size by addition of a cold wire. Microstructural evaluation, using both tint etching optical microscopy and scanning electron microscopy, indicated the formation of finer PAGs and less fraction of M-A constituents with refined morphology within the CGHAZ when the cold wire was fed at 25.4 cm/min. This resulted in an improvement in the HAZ impact fracture toughness. These improvements are attributed to lower actual heat introduced to the weldment and lower peak temperature in the CGHAZ by cold-wire addition. However, a faster feed rate of the cold wire at 76.2 cm/min adversely affected the toughness due to the formation of slender M-A constituents caused by the relatively faster cooling rate in the CGHAZ.     

Thermochromic composite fibres containing liquid crystals formed via melt extrusion

A three-layered composite fibre has been generated via a modified wire-coating melt co-extrusion process. The continuous fibre consists of a thermochromic liquid crystalline (TLC) layer encapsulated between a transparent polypropylene outer sheath and a black polyether ether ketone inner core. The fibres exhibit clear thermochromic behaviour consistent with the behaviour of unincorporated TLCs, and have been formed into a textile. The presence of the black inner core was found to be the key for the clear retention of colour within the fibres against both white and black backgrounds. The temperature-sensitive fibres and textiles can be applied to a variety of thermal mapping applications, such as in the medical and engineering fields, due to the tunable nature of TLCs.     

Physicochemical Properties of Sb, Sn, Zn, and Sb–Sn System

The physicochemical properties, viscosity, density, and surface tension, were measured using the discharge crucible method (DC) on five alloys of Sb–Sn. The performance of the DC method was demonstrated with measurements on pure metals Sb, Sn, Zn, and comparisons with the corresponding literature data. The results reported in this study are for Sb–Sn alloys containing (10, 20, 25, 50, and 75) at% of Sb at 550 K to 850 K. The results show that all the physicochemical properties decrease with decreasing temperature and increase with increasing Sb content in the alloy. The experimentally measured surface-tension values are compared with the Butler model. Several models for viscosity are compared and discussed.     

Effect of Processing Parameters on the Mechanical Properties of Injection Molded Thermoplastic Polyolefin (TPO) Cellular Foams

In this study, the effects of processing parameters on the mechanical properties of injection molded thermoplastic polyolefin (TPO) foams are investigated. Closed cell TPO foams were prepared by injection molding process. The microstructure of these foamed samples was controlled by carefully altering the processing parameters on the injection molding machine. The foam morphologies were characterized in terms of skin thickness, surface roughness, and relative foam density. Tensile properties and impact resistance of various injection molded TPO samples were correlated with various foam morphologies. The findings show that the mechanical properties are significantly affected by foam morphologies. The experimental results obtained from this study can be used to predict the microstructure and mechanical properties of cellular injection molded TPO foams prepared with different processing parameters.

     

Novel Thermally Conductive Thermoplastic/Ceramic Composite Foams

Multifunctional materials that are lightweight and thermally conductive but electrically insulating are important for modern electronics, computer, and telecommunication technologies. Here, a novel foam structure of a polymer/matrix composite filled with ceramic platelets with improved thermal conductivity is reported. Such improvement is caused by the stress‐induced alignment of thermally conductive fillers in the cell wall of the plastic foam. The foam structure is very promising for use as a lightweight electronic packaging material owing to its light weight, thermal conduction ability, electrical insulation, and good processability.