New materials for micro-scale sensors and actuators: An engineering review

This paper provides a detailed overview of developments in transducer materials technology relating to their current and future applications in micro-scale devices. Recent advances in piezoelectric, magnetostrictive and shape-memory alloy systems are discussed and emerging transducer materials such as magnetic nanoparticles, expandable micro-spheres and conductive polymers are introduced. Materials properties, transducer mechanisms and end applications are described and the potential for integration of the materials with ancillary systems components is viewed as an essential consideration. The review concludes with a short discussion of structural polymers that are extending the range of micro-fabrication techniques available to designers and production engineers beyond the limitations of silicon fabrication technology.     

Regression-based CVN–KIC Models for hot work tool steels

Dies and tools used in hot metal forming (extrusion, forging, rolling, etc.) are exposed to high pressures, elevated temperatures, and thermo-mechanical fatigue. The most common mode of in-service die failure is fatigue fracture (brittle failure through crack propagation). Reliable determination of fracture toughness of the die material is thus critically important. However, as die steels have a combination of high-hardness and high-strength, and are used at elevated temperatures, standard plane-strain fracture toughness (K_IC) testing methods become impracticable. Alternate testing procedures such as the Charpy impact energy (CVN), together with empirical/semi-empirical correlations of K_IC to other data, are then more viable and economical. Experimental data (values of K_IC, CVN, and HRC) of H13 steels have been collected through an exhaustive literature search. This data set has been augmented through in-house experimentation: samples variously heat treated (different tempering temperatures and times, and both air-cooling and oil-quenching), and tested at different working temperatures. Linear and quadratic models are proposed for determination of fracture toughness, based on experimental (in-house) and published values of Charpy impact energy (CVN) and Rockwell hardness (HRC), both at room and at elevated temperatures.     

Dye degradation study by incorporating Cu-doped ZnO photocatalyst into polyacrylamide microgel

Journal of Materials Science: Materials in Electronics - In this study, Cu-doped ZnO NPs (xCZO) were formed by the coprecipitation route by changing the concentration of dopant Cu from 0 to 24%...     

The fatty acid composition of edible marine fish oils

The body oils of 13 species of marine edible fishes found around the Karachi-Makran coast were studied by gas-liquid chromatography (GLC) for their fatty acid composition. The analyses showed the presence of fatty acids with chain lengths from 10 to 24 carbon atoms and with zero to six double bonds. The oils were found to be rich in polyunsaturated acids, particularly the penta- and hexaenoic. Certain major fatty acids were found to vary widely among the species: myristic acid 2.3 to 13.7%; palmitic 11.6 to 41.2%; stearich 7.2 to 23.2%; oleic 6.9 to 29.6%; eicosapentaenoic 1.4 to 19.0%; docosapentaenoic zero to 10.2%; and docosahexaenoic zero to 36.4%. The linoleic and linolenic acids were present in small amounts in some of the fish oils, and arachidonic acid was present in all of them.     

Structural Rietveld refinement and magnetic features of prosademium (Pr) doped Cu nanocrystalline spinel ferrites

Pr doped spinel nanoferrites having following composition Cu Pr_x Fe_2-xO₄ (x?=?0, 0.25, 0.50, 0.75, 1.00) were synthesized using sol-gel route. Prosademium (Pr) which is a rare earth metal was doped to tailor the properties of the Cu spinel nanoferrites. Characterization tools such as FTIR, XRD, FESEM and VSM were employed to investigate the phase, absorption bands, structure, microstructure and magnetic properties. FTIR was used to see the absorption bands and force constants of the Pr doped Cu spinel nanoferrites. Crystallite size, lattice parameters, cell volume and micro strains were determined from XRD data. Bulk density, X-ray density and porosity of the Pr doped Cu spinel nanoferrites were also calculated. Rietveld refinement was applied to investigate the detailed structural parameters of the Pr doped Cu spinel nanoferrites. Unit cell software based on regression diagnostics was also used to determine the structural factors of the prepared nanoferrites. It was noticed that Cu nanoferrite showed the single-phase cubic structure whereas the Pr doped Cu ferrite depicted the orthorhombic structure respectively. FESEM show large amount of agglomerations at x?=?0.00 whereas irregular shape of the particles confirms the nanosized of ferrites as well. Magnetic properties were determined from VSM which elaborated the remanence, coercivity, saturation magnetization, anisotropy constant (K), initial permeability, Bohr magneton and YK (Yafet and Kittel) angles. Magnetic saturation, coercivity, remanence and anisotropy constant were decreased with Pr concentration in Cu spinel ferrite. However, YK angles were increased with Pr doping in Cu spinel nanoferrites. Microwave frequency response was evaluated which confirm the use of these Pr doped Cu spinel nanoferrites in the range of 5.2?Ghz–9.5?GHz respectively. The properties of these Pr doped Cu spinel nanoferrites suggested their used for microwave devices, memory devices and recording media applications.