Preparation of zinc phosphide

Journal of Materials Science Letters -     

Synthesis of single phase Tl-2223 superconductors: How much thallium do we really need?

This paper describes the synthesis and microwave absorption studies of single phase Tl-2223 compound, withT _c=(129 ± 1) K. The single phase compound has been synthesized using a precursor matrix method. It has been found that Tl-deficient starting composition gives the best results.     

Preparation and characterisation of silver particulate films on softened polystyrene substrates

The preparation of silver particulate films on softened polystyrene (PS) substrates and their characterisation using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and optical absorption spectroscopy is reported in this paper. Silver films of 150 nm thickness were vacuum deposited onto PS coated glass substrates held at temperatures in the range 415–475 K at different deposition rates of 4 to 12 Å/s. SEM studies indicate that films deposited at 415 K are close to a semicontinuous structure and the structure is discontinuous at higher temperatures. The film morphology is strongly dependent on the deposition rate at any given substrate temperature. The film agglomeration increases with increasing rate of deposition. In the XPS studies, considerable attenuation of the signal corresponding to silver is observed at lower electron take of angles (ETOAs). This indicates that Ag is formed beneath the PS surface. Optical absorption studies showed an interesting red shift of the plasmon resonance wavelength for lower deposition rates again indicating that a sub-surface particulate structure is formed at lower deposition rates. These results are consistent with reported observations.     

Optimal soft starting of voltage-controller-fed IM drive based onvoltage across thyristor

AC voltage controllers are used as induction motor starters in fan or pump drives and the crane hoist drives. This paper presents a method of identifying the end of soft start of an AC voltage controller-fed induction motor (IM) drive based on the voltage across the nonconducting thyristor through a dynamic simulation of the whole drive system. A two point current minimization technique is adopted to operate the drive system at the required optimal voltage under all operating conditions. This minimizes the motor losses. Graphic modeling of the whole drive system is done in a modular format using Design Star and dynamic simulation is done using SABER. The dynamic simulation results of the whole drive system are supported with experimental data     

Electrical properties of vacuum annealed CdS films

Cadmium sulphide (CdS) films were evaporated in vacuum on glass substrates maintained at room temperature. These films were later annealed in vacuum at temperatures in the range 30 to 300° C. The variation of d.c. electrical conductivity was studied in the temperature range 100 to 300 K. While the conductivity data in the range 100 to 150 K were observed to follow Mott's variable range hopping process, the conductivity in the high-temperature region (150 to 300 K) could be explained by Seto's model.     

Thermodynamics of acrylic esters containing binary liquid mixtures. I. Excess volumes and isentropic compressibilities of alkyl methacrylates +n-hexane, +n-heptane, + carbon tetrachloride, + chlorobenzene,ando-dichlorobenzene at 303.15 K

Excess volumes and isentropic compressibilities of 15 binary liquid mixtures containing methyl methacrylate (MMA). ethyl methacrylate (EMA), and butyl methacrylate (BM) andn-Hexane,n-heptane, carbon tetrachloride chlorobenzene ando-dichlorobenzene are derived from the measured densities and speeds of sound at 303.15 K. The dependence of the excess volumes and the isentropic compressibilities both on the alkyl chain length and on the nature of the solvent shots the dominance of dispersing interactions in the mixtures of aliphatic hydrocarbons and specific interactions im the chlorinated solvent mixtures. The speeds of sound of binary mixtures of MMA were found to be reasonably predicted by free length and collision factor theories. An attempt is also made to estimate the individual contributions of interactional. free volume andP ^* effects to the overall excess volumes of binary mixtures containing MMA. The results indicate that the three factors are equally responsible for the observed values.     

Subcritical crack-growth under sustained load in Ti-6AI-6V-2Sn

The subcritical sustained-load cracking (SLC) behavior of beta annealed, recrystallization annealed, and solution-treat-and-aged Ti-6Al-6V-2Sn was studied in dry argon and moist air. The effects of microstructure, internal hydrogen concentration, specimen orientation, and specimen thickness on threshold stress-intensity and crack-growth rate were determined under increasing stress-intensity conditions using wedge-opening load (WOL) specimens, and the fracture morphologies were studied by scanning electron microscopy. The SLC threshold stress intensities are lower and crack growth rates are higher in solution-treatand-aged condition than in beta-annealed and recrystallization conditions. The plane strain conditions increase the susceptibility to SLC. The texture effects on SLC are intensified when the cracking plane is close to the basal plane. For low interstitial-hydrogen concentrations ≈10 ppm, sustained-load crack growth is controlled by creep at the crack tip. Increased hydrogen concentration results in enhanced cleavage, lower threshold stress-intensity, and accelerated crack-growth. Of the possible mechanisms for hydrogen-assisted SLC in Ti-6Al-6V-2Sn, the most likely is that involving preferential segregation of hydrogen to beta phase, leading to fracture by α-β interface separation. Formerly with McDonnell Douglas Research Laboratories.