Integration of Ceramics Research with the Development of a Microsystem

Rapid implementation of new materials into engineering systems may require a paradigm shift in our approach to materials research. One option is to obtain fundamental material properties from experimental systems that can also serve as devices. This concept is applied to the measurement of Young's modulus of a novel ceramic, a polymer-derived silicon carbonitride (SiCN), directly from the performance of a microelectromechanical system (MEMS) device. The device is an electrostatic actuator. The flexure resistance of the arms of the actuator is measured and analyzed for the elastic modulus of SiCN. The comparison between theory and experiment yields a value for Young's modulus in the range 130–155 GPa.     

Effects of the pH,concentration, and solvents on the ultrasonic degradation of poly(vinyl alcohol)

The ultrasonic degradation of poly(vinyl alcohol) was investigated at different pHs of the solvent, in different water/solvent binary mixtures, and at different polymer concentrations. The samples were analyzed with gel permeation chromatography. The degradation rate coefficients were determined with a continuous distribution model. A higher degradation rate was obtained at pH extremes, in better solvents, and at lower polymer concentrations. The results are explained and discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4888–4892, 2006     

Studies on some trace and minor elements in blood. A survey of the Kalpakkam (India) population. Part I: Standardization of analytical methods using ICP-MS and AAS

Blood is one of the widely used specimens for biological trace element research because of its biological significance and ease of sampling. We have conducted a study of the blood of the Kalpakkam township population for trace and minor elements. For this purpose, analytical methods have been developed and standardized in our laboratory for the elemental analysis of blood plasma and red cells. Inductively coupled plasma-mass spectrometry (ICP-MS), a relatively new technique, has been applied for the analysis of trace elements. Details regarding spectral interference and matrix interference encountered in the analysis of blood and the methods of correcting them have been discussed. Flame atomic absorption spectrometry (AAS)/atomic emission spectrometry (AES) has been applied for the determination of minor elements. Precision and accuracy of these methods have also been discussed.     

Polyaniline Salts and Complexes as Catalyst in Bisindole Synthesis

Polyaniline salts are prepared by doping of polyaniline base with different Bronsted acids (H₂SO₄, HNO₃ and H₃PO₄), organic acid — p-toluene sulfonic acid (PTSA) and Iodine (I₂). Polyaniline complexes are also prepared using Lewis acids (BF₃, AlCl₃ and SnCl₂). Polyaniline salts and polyaniline complexes are characterized by physical, electrical and spectral methods. Polyaniline salts and polyaniline complexes are used as catalyst for the first time in bisindole synthesis. Bisindole (3,3′-bis(indolyl)phenylmethane) is obtained in excellent yields with simple and more environmental benign procedure. The use of polyaniline catalysts are feasible because of their easy preparation, easy handling, stability, easy recovery, reusability, good activity and eco-friendly.     

Combined influence of throughflow and Soret effect on the onset of Marangoni convection

The onset of Marangoni convection with throughflow and the Soret effect in a top-free and bottom-rigid horizontal fluid layer is studied using the normal mode method for different types of thermal and solutal boundary combinations. The bottom surface is either conducting or insulating to temperature and solute concentration perturbations. The resulting eigenvalue problem is solved exactly by assuming that stationary convection is exhibited at the neutral state. It is found that the destabilizing behavior of a small amount of throughflow described by Nield (J Fluid Mech 185:353–360, 1987) becomes more significant in the presence of Soret effect for some boundary combinations. The results are consistent with the existing results in the literature.     

CdS microflowers and interpenetrated nanorods grown on Si substrate: Structural,optical properties and growth mechanism

CdS semiconductor with different morphologies have been achieved by simple thermal evaporation of CdS powder at 1050 °C in a flowing Ar atmosphere. The products were characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy and Photoluminescence. microflowers and interpenetrative nanorods of CdS were formed on catalyst free Si wafers at a temperature of 700 °C and 600 °C respectively. The flower like structures are composed of many interleaving nanorods which have the uniform diameter of about 700 nm and a well crystalline structure with [0001] as growth direction. The interpenetrative nanorods are found to be bounded with six side facets. X-ray diffraction studies revealed the hexagonal structure in both the products. The formation mechanism of microflowers and interpenetrated nanorods was discussed on the basis of nucleation growth kinetics. Room temperature photoluminescence spectra showed a strong green emission band (at ∼510 nm) from the CdS flower like structures, but on the other hand a red emission shoulder along with strong green emission band was observed for interpenetrative nanorods. These CdS micro/nanostructures with abundant morphologies may find applications in various micro/nanodevices, and the kinetics-driven morphology might be exploited to synthesize similar structures of other functional II–VI semiconductors.     

Influence of Fe catalytic doping on the properties of TiO2 nanoparticles synthesized by microwave method

The present work focus on the development of an effective process for undoped and Fe doped TiO₂ powders production by microwave technique. The influence of Fe doping on the structure, phase, vibrational bands and optical properties of TiO₂ were discussed. The X-ray diffraction patterns of nanoparticles revealed a preferentially oriented (101) anatase phase for TiO₂ and transforms to rutile TiO₂ with Fe doping. Fourier transform infrared spectra analysis confirmed the phase transformation from anatase to rutile TiO₂ with Fe doping. The UV–visible spectra showed the increase in absorption band with Fe doping when compared with undoped TiO₂ nano particles, and optical band gap decreased slightly with Fe doping. SEM micrographs revealed spherical shaped grains of TiO₂ with high homogeneity, with a subsequent reduction in the agglomeration of particles with Fe doping suggesting its potential application for better photo catalytic activity.     

Influence of oxygen pressure on structural,optical and magnetic properties of pure ZnO films

In this paper, we study the influence of oxygen pressure on structural, optical and magnetic properties of pure ZnO films. The chemical compositions and thickness of the film were estimated by Rutherford backscattering spectrometry measurements. X-ray diffraction patterns show all the films are in single phase and preferred along (002) orientation. With an increase of oxygen pressure, grain growth and average root mean square roughness is found to be increased. It is found that the intensity of UV emission peak increases whereas visible emission peak decreases in intensity with an increase of oxygen pressure. From the magnetization measurements, it is observed that ZnO film grown without oxygen pressure shows an enhanced ferromagnetic behaviour than that of the films grown with oxygen pressure of 0.05 and 0.1 mbar.     

Solubility of Mn stabilized cubic zirconia nanostructures

Mn-stabilized cubic zirconia nanostructures (Zr_1?xMn_xO₂, x = 0.10, x = 0.15 and x = 0.20) have been prepared using chemical precipitation method for different doping concentrations. The prepared powders have been characterized by X-ray diffractometer for structural analysis, vibrating sample magnetometer for analyzing magnetic properties, scanning electron microcopy–elemental compositional analysis using X-ray for morphological and elemental compositional analysis. Room temperature ferromagnetism has been found at around x = 0.15. For high doping effect of Mn impurity at host lattice, secondary phase has been detected at around x = 0.20 when exceeding the solubility limit of cubic zirconia. Due to ferromagnetic behavior, Mn doped ZrO₂ nanostructures can be considered as good candidates for spintronics applications within their solubility limit.     

Texture evolution in an Al–Cu alloy during equal channel angular pressing: the effect of starting microstructure

In this article, the effect of initial microstructure on the texture evolution in 2014 Al alloy during equal channel angular pressing (ECAP) through route A has been reported. Three heat treatment conditions were chosen to generate the initial microstructures, namely (i) the recrystallization anneal (as-received), (ii) solution treatment at 768 K for 1 h, and (iii) solution treatment (768 K for 1 h) plus aging at 468 K for 5 h. Texture analyses were performed using orientation distribution function (ODF) method. The texture strength after ECAP processing was different for the three samples in the order, solutionised > solutionised plus aged condition > as-received. The prominent texture components were A _E /[`(A)]<sub>E</sub> \bar{A}_{E} and B <sub>E</sub> /[`(B)]_E \bar{B}_{E} in addition to several weaker components for the three materials. The strong texture evolution in solutionised condition has been attributed to higher strain hardening of the matrix due to higher amount of solute. In case of the as-received as well as solutionised plus aged alloy, the weaker texture could be due to the strain scattering from extensive precipitate fragmentation and dissolution during ECAP.