Comparative evaluation of corrosion behaviour of type K thin film thermocouple and its bulk counterpart

This paper investigates the corrosion behaviour of type K thermoelements and their thin films, and compares the performance of chromel–alumel thin film thermocouple with its wire counterpart before and after exposure to 5% NaCl medium. Potentiodynamic polarisation tests reveal that chromel and alumel films are more “noble” than their respective wires. Alumel corrodes faster when coupled with chromel in films than as wires. Secondary electron micrographs and electrochemical impedance spectroscopy measurements suggest that chromel shows localised corrosion while alumel undergoes uniform corrosion. Corrosion adversely affects the thermocouple output and introduces an uncertainty in the measurement.     

Evaluation of hydroxyapatite and β-tri calcium phosphate microplasma spray coated pin intra-medullary for bone repair in a rabbit model

Here we report a comparative study of the healing kinetics of surgically created artificial defects in the tibia of New Zealand white rabbits. Comparison of the healing kinetics was made for uncoated conventional SS316L intramedullary pins, and the same pins with microplasma sprayed (MIPS) pure hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) coatings. After thorough material characterizations including XRD, FTIR, SEM, etc., MIPS coated pins were implanted to such animals. Serum biochemistry, radiology and fluorochrome labelling were used to evaluate the comparative healing kinetics of these implants in vivo. In comparison to those of the uncoated pins, the pins coated with both MIPS HAp and β-TCP showed significant increment of alkaline phosphatase up to 15th postoperative day, insignificant changes in serum phosphorus and calcium with uneventful healing of bone defect. There was development of Havarsian canals and well-defined peripherally placed osteoblasts along with evidence of angiogenesis and comparatively more new bone formation in the defect site. On a comparative scale, the performance of the β-TCP coated intramedullary pins was much better than that of the pure HAp coated pins than the uncoated intramedullary pins.     

Programmable memory in organic field-effect transistor based on lead phthalocyanine

A nonvolatile organic field-effect transistor (OFET) with a polymeric electret as gate insulator and spun cast film of lead phthalocyanine (PbPc) as semiconductor channel is reported. Hysteresis induced by gate–bias stress was exploited to study nonvolatile memory effects. The observation of the hysteresis and memory window is proposed to originate from charge storage in the polymeric electret. The on state retention time for the OFET memory device is more than 5 h and the device can reproduce continuous write–read–erase–read switching cycles.     

Dislocation processes in the deformation of nanocrystalline aluminium by molecular-dynamics simulation

The mechanical behaviour of nanocrystalline materials (that is, polycrystals with a grain size of less than 100 nm) remains controversial. Although it is commonly accepted that the intrinsic deformation behaviour of these materials arises from the interplay between dislocation and grain-boundary processes, little is known about the specific deformation mechanisms. Here we use large-scale molecular-dynamics simulations to elucidate this intricate interplay during room-temperature plastic deformation of model nanocrystalline Al microstructures. We demonstrate that, in contrast to coarse-grained Al, mechanical twinning may play an important role in the deformation behaviour of nanocrystalline Al. Our results illustrate that this type of simulation has now advanced to a level where it provides a powerful new tool for elucidating and quantifying--in a degree of detail not possible experimentally--the atomic-level mechanisms controlling the complex dislocation and grain-boundary processes in heavily deformed materials with a submicrometre grain size.     

Preparation, thermal expansion, high pressure and high temperature behavior of Al2(WO4)3

The titled compound Al₂(WO₄)₃ was synthesized by a conventional solid state reaction and characterized by powder XRD. It crystallizes in an orthorhombic (Pbcn, No. 60) lattice, with unit cell parameters as 12.582(2), 9.051(1), 9.128(2) Å, and V = 1039.5(3) (Å)³. The compound was found to show negative thermal expansion (NTE) behavior in the temperature range of 25 to 850°C. The average linear NTE coefficient (₁), in this temperature range, was –1.5 × 10^–6 K^–1. The effect of pressure at ambient temperature, was studied by a Bridgman Anvil (BA) apparatus, to reveal that there is no irreversible phase transition up to 8 GPa. The effect of high pressure and high temperature on this compound was studied by a Toroid Anvil (TA) apparatus. This compound has a limited stability under high pressure and temperature, as it undergoes a decomposition to AlWO₄ and WO_3–x with a partial oxygen loss. As an off-shoot of this work, certain new modifications of WO_3–x under pressure and temperature were observed, viz., monoclinic, tetragonal and an orthorhombic modifications at 5 GPa/1400°C, 3 GPa/900°C and 1.8 GPa/1030°C, respectively. The detailed XRD studies of the products are presented here.     

An extraction-based verification methodology for MEMS

Micromachining techniques are being increasingly used to develop miniaturized sensor and actuator systems. These system designs tend to be captured as layout, requiring extraction of the equivalent microelectromechanical circuit as a necessary step for design verification. This paper presents an extraction methodology to (re-)construct a circuit schematic representation from the layout, enabling the designer to use microelectromechanical circuit simulators to verify the functional behavior of the layout. This methodology uses a canonical representation of the given layout on which feature-based and graph-based recognition algorithms are applied to generate the equivalent extracted schematic. Extraction can be performed to either the atomic level or the functional level representation of the reconstructed circuit. The choice of level in hierarchy is governed by the trade off between simulation time and simulation accuracy of the extracted circuit. The combination of the MEMS layout extraction and lumped-parameter circuit simulation provides MEMS designers with VLSI-like tools enabling faster design cycles, and improved design productivity