Photoconductivity, photovoltaic effect and photoluminescence in chemically deposited films of (Cd0.95–Pb0.05)S:CdCl2,Gd

Results of XRD, optical absorption spectra, photoconductivity, photovoltaic effect and photoluminescence are reported for (Cd_0.95–Pb_0.05)S:CdCl₂,Gd films prepared by chemical deposition technique at 60 °C and room temperature (RT). The XRD studies show prominent diffraction lines of CdS and PbS. Optical absorption spectra show direct bandgap nature with decreasing value due to addition of PbS. The saturated photocurrent (I_pc) to dark current (I_dc) ratios 10⁷ are found in films prepared at 60 °C and 10⁴ in films prepared at RT. Photoluminescence is found to be brighter in films prepared at RT. Photovoltaic efficiency 5% has been observed in such films.     

Counterfeit capacitors in the supply chain

Counterfeit electronic components have become a significant concern in the electronic parts supply chain. Original equipment manufacturers in particular are concerned about counterfeit components as there have been several recent reports of counterfeit parts entering the supply chain of the US military. This paper presents a case study of multilayer ceramic capacitors for use in a printed circuit assembly in an electronic system on a military aircraft. The capacitors failed during a high temperature screening test. Upon failure analysis it was revealed that the capacitors were not made to the correct specifications and were suspected to be counterfeit and not the authentic military grade capacitors manufactured by Kemet. Further investigation revealed that the suspect multilayered ceramic capacitors had entered into the electronics parts supply chain and were sold as authentic Kemet capacitors that met the higher military-specified requirements. The manufacturing and distribution of the counterfeit capacitors were traced to locations where, according to Kemet, its authentic capacitors are neither manufactured nor distributed.     

First application of calorimetric low-temperature detectors in accelerator mass spectrometry

For the first time, calorimetric low-temperature detectors were applied in accelerator mass spectrometry, a well-known method for determination of very small isotope ratios with high sensitivity. The aim of the experiment was to determine with high accuracy the isotope ratio of ²³⁶U/²³⁸U for several samples of natural uranium, ²³⁶U being known as a sensitive monitor for neutron flux. Measurements were performed at the VERA tandem accelerator at Vienna, Austria. The detectors consist of sapphire absorbers and superconducting transition edge thermometers operated at T≈ 1.5 K. The relative energy resolution obtained for 17.39 MeV ²³⁸U is ΔE/E=4–9×10⁻³, depending on the experimental conditions. This performance enabled to substantially reduce background from neighbouring isotopes and to increase the detection efficiency. Due to the high sensitivity achieved, a value of ²³⁶U/²³⁸U=6.5×10⁻¹² could be obtained, representing the smallest ²³⁶U/²³⁸U ratio measured until now.     

Cation exchange applications of synthetic tobermorite for the immobilization and solidification of cesium and strontium in cement matrix

Immobilization and solidification of hazardous cations like Cs¹³⁷ and Sr⁹⁰ are required while handling the radioactive waste of nuclear power plants. Efforts are on to find a fail proof method of safe disposal of nuclear wastes. In this context, various materials like borosilicate glass, zeolites, cements and synthetic rocks have been tried by several workers. This communication deals with the synthesis, characterization, cesium uptake capacity and leaching behaviour of synthetic alumina-substituted calcium silicate hydroxy hydrate, which are close to that obtained for the natural mineral,11 Å tobermorite. The synthetic mineral show cation selectivity for Cs⁺ in presence of500–1000 times concentrated solutions of Na⁺, K⁺, Mg⁺, Ca²⁺, Ba²⁺ and Sr²⁺. Although the ordinary portland cement (OPC) which is often used in waste management operations alone holds negligible amounts of Cs⁺ and Sr²⁺, the addition of alumina-substituted tobermorite to OPC enhances the retention power of cement matrix by drastically lowering the leach rate of cations     

Photocatalytic removal of hazardous dye cyanosine from industrial waste using titanium dioxide

In this paper, photocatalytic degradation studies of a hazardous water soluble xanthene dye cyanosine in aqueous suspensions of titanium dioxide under a variety of conditions, viz., catalyst concentration, substrate concentration, pH, temperature and electron acceptor hydrogen peroxide (H2O2) have been reported. It was observed that photocatalytic degradation by TiO2 is an effective, economic and faster mode of removing cyanosine from aqueous solution. The optimum conditions for the degradation of the dye was dye concentration 1x10(-4)M, pH 8, catalyst concentration 0.04g/L and temperature +/-30 degrees C. Chemical oxygen demand and dye absorbance of the photodegraded dye solution substantially decreased.