Composition,structure and electrical properties of DC reactive magnetron sputtered Al2O3 thin films

Thin films of alumina (Al₂O₃) were deposited over Si 〈1 0 0〉 substrates at room temperature at an oxygen gas pressure of 0.03 Pa and sputtering power of 60 W using DC reactive magnetron sputtering. The composition of the as-deposited film was analyzed by X-ray photoelectron spectroscopy and the O/Al atomic ratio was found to be 1.72. The films were then annealed in vacuum to 350, 550 and 750 °C and X-ray diffraction results revealed that both as-deposited and post deposition annealed films were amorphous. The surface morphology and topography of the films was studied using scanning electron microscopy and atomic force microscopy, respectively. A progressive decrease in the root mean square (RMS) roughness of the films from 1.53 nm to 0.7 nm was observed with increase in the annealing temperature. Al–Al₂O₃–Al thin film capacitors were then fabricated on p-type Si 〈1 0 0〉 substrate to study the effect of temperature and frequency on the dielectric property of the films and the results are discussed.     

The stability of direct carbon fuel cells with molten Sb and Sb–Bi alloy anodes

The long‐term stability of direct carbon fuel cells, based on solid oxide fuel cells with molten Sb and Sb–Bi anodes, was examined for operation with activated charcoal, rice starch, and bio‐oil fuels at 973 K. With intermittent stirring of the fuel–metal anode interface, the anode performance was stable, and reasonable power densities (～250 mW/cm²) were achieved for periods up to 250 h. With Sc‐stabilized zirconia, severe thinning of the electrolyte occurred in regions of high current flow. No electrolyte thinning was observed with yttria‐stabilized zirconia as the electrolyte operating at the same current densities. © 2012 American Institute of Chemical Engineers AIChE J, 59: 3342–3348, 2013     

CuInxGa1−xSe2 thin films prepared by electron beam evaporation

CuIn_xGa_1−xSe₂ bulk compound of three different compositions x=0.75, 0.80 and 0.85 have been prepared using individual elements of copper, indium, gallium and selenium. Thin films of CuIn_xGa_1−xSe₂ have been deposited using the prepared bulk by electron beam evaporation method. The structural studies carried on the deposited films revealed that films annealed at 400 °C are crystalline in nature exhibiting chalcopyrite phase. The position of the (1 1 2) peak in the X-ray diffractogram corresponding to the chalcopyrite phase has been found to be dependent on the percentage of gallium in the films. The composition of the prepared bulk and thin films has been identified using energy dispersive X-ray analysis. The photoluminescence spectra of the CuIn_xGa_1−xSe₂ films exhibited sharp luminescence peaks corresponding to the band gap of the material.     

Acoustic Emission Study on Effect of Stress Triaxiality on Damage Micromechanisms in Near Alpha Titanium Alloy

Acoustic Emission (AE) studies have been performed on smooth and notched specimens of a near alpha titanium alloy under monotonic loading condition to study the effect of stress triaxiality on damage micromechanisms. The damage in the notched specimen was found to be of cleavage type as against the ductile type of damage in smooth specimen. This difference was distinguished in the AE energy evolution with notched specimen producing higher energy rate with lower total energy than that of smooth specimen.     

Characterisation of Microstructures,Deformation, and Fatigue Damage in Different Steels Using Magnetic Barkhausen Emission Technique

The characterization of microstructures, mechanical properties, deformation, damage initiation, and growth by Non-Destructive Evaluation (NDE) techniques is assuming a vital role in various industries because of the growing awareness of the benefits that can be derived by using NDE techniques for assessing the performance of various components. NDE is widely applied for assessment of material degradation, where investment in new plants is not cost-effective and safe operational life of existing plants needs to be extended. In recent years, various advanced NDE techniques have been successfully employed for characterization of defects and microstructural features such as grain size, texture, nucleation and growth of second phases, assessment of tensile, creep and fatigue properties, deformation, and damage. With the advent of fracture mechanics concepts, microstructure, defects as well as stresses must be quantitatively characterized to have reliable and fail-safe materials and components. Any alteration in the microstructure, which reduces the life or performance, should be predicted sufficiently in advance in order to ensure safe, reliable, and economic operation of the components. This is possible when one realizes that the interaction of the nondestructive probing medium with the material depends on the substructural/microstructural features such as point defects, dislocations, voids, micro and macro cracks, secondary phases, texture, residual stress, etc. In this paper, use of Magnetic Barkhausen Emission technique for characterization of microstructures, deformation, and fatigue damage in different steels would be discussed. When a ferromagnetic material is subjected to a varying magnetic field, the magnetic flux densidy during magnetization varies in discrete steps as the magnetic domain walls have to overcome various types of obstacles during their movement. The discrete changes in magnetization induce electric voltage pulses in pickup coil placed near the surface of ferromagnetic materials. This noise like voltage pulses were, firstly observed by Barkhausen in 1919 and this phenomenon is named as magnetic Barkhausen Noise (MBN) or magnetic Barkhausen emission (MBE). Based on the two stage magnetization process modeled by the authors, the size of the grain/lath and carbides in ferritic steels could be correlated with MBE parameters. The influence of morphology of cementite (lamellar and spheroidized) on the MBE behaviour has been understood. Various stages of tensile deformation, viz. (i) perfectly elastic, (ii) micro-plastic yielding, (iii) macroyielding, and (iv) progressive plastic deformation in ferritic steels could be identified using the MBE parameters. The hardening depth and its quality with respect to the microstructure in induction hardened specimens could also be established using the MBE technique. MBE is found to be highly sensitive in detection of stress induced martensite in stainless steels with metastable austenite phase. Different stages of fatigue damage in 9Cr-1Mo steel, viz. (i) cyclic hardening, (ii) softening, (iii) saturation, and (iv) crack initiation could be identified using the MBE parameters.     

Improvements and systolic implementation of the hough transformation for straight line detection

Hough Transformation (HT) is an efficient method to detect straight lines in digital pictures. In the conventional HT, pixel contiguity is not taken into account, and this leads to the following drawbacks: (1) actual length of line segments cannot be computed; (2) colinear line segments cannot be distinguished; and (3) very often, false lines are detected and short lines go undetected. This paper proposes a modified Hough Transformation which performs contiguity check in a simple and efficient way. A systolic architecture that implements this modified transform is presented. The systolic array takes the bit-map of the binary picture as input and processes one row/column of pixels concurrently. The area-time complexity of the proposed architecture is shown to be superior to the conventional sequential algorithm. Preliminary simulation results are presented.     

Of insects and eggs: a case report

A middle aged woman presented with delusions of infestation and multimodal hallucinations due to an underlying glioma of the corpus callosum. After surgery, the phenomena in question changed and finally disappeared. A recurrence of the tumour caused dementia.     

A novel surface-active peptide derivative exhibits in vitro inhibition of platelet aggregation

A tetrapeptide corresponding to a region of the N-terminal portion of lactotransferrin with hydrophobic alkyl groups at the terminal ends was synthesized and its physicochemical properties as well as its effect on thrombin-stimulated platelet aggregation were examined. The tetrapeptide derivative, in the aggregated state, produced inhibitory effect on platelet aggregation. The concentration dependent activity of the peptide was analyzed in the light of micelle formation, with the micellar aggregate comprising four tetrapeptide units. The unique action of this peptide derivative on the inhibition of platelet aggregation might be useful in the development of potent antithrombotic drugs.     

Analysis of Drought from Humid,Semi-Arid and Arid Regions of India Using DrinC Model with Different Drought Indices

The study aims at evaluating the various drought indices for the humid, semi-arid and arid regions of India using conventional indices, such as rainfall anomaly index, departure analysis of rainfall and other indices such as Standard Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) that were analyzed using the DrinC software. In SPI, arid region has seven drought years, whereas humid and semi-arid regions have four. In case of RDI, the humid and semi-arid regions have 11 drought years, whereas arid regions have 10 years. The difference in SPI and RDI was due to the fact that RDI considered potential evapotranspiration, and hence, correlation with plants would be better in case of RDI. Humid region showed a decreasing trend in initial value of RDI during the drought as compared to semiarid and arid regions and indicated possible climate change impact in these regions. Among all the indices, RDI was considered as an effective indicator because of implicit severity and high prediction matches with the actual drought years. SPI and RDI were found to be well correlated with respect to 3 months rainfall data and SPI values led to prediction of annual RDI. The results of our study established that this correlation could be used for developing disaster management plan well in advance to combat the drought consequences.

     

Damage Assessment of 2.5D C/SiC Ceramic Matrix Composite: Effect of Fibre Off-Axis Orientation

Transactions of the Indian Institute of Metals - 2.5D C/SiC ceramic matrix composite is widely used for thermal protection and hot sections of gas turbine engines. The fibre axis in these...