A Raman spectroscopic study of arsenite and thioarsenite species in aqueous solution at 25°C

The Raman spectra of thioarsenite and arsenite species in aqueous solution were obtained at room temperature. Solutions at constant ΣAs + ΣS of 0.1 and 0.5 mol kg(-1 )were prepared with various ΣS/ΣAs ratios (0.1–9.0) and pH values (~7–13.2). Our data suggest that the speciation of As under the conditions investigated is more complicated than previously thought. The Raman measurements offer evidence for at least six separate S-bearing As species whose principal bands are centered near 365, 385, 390, 400, 415 and 420 cm(-1). The data suggest that at least two different species may give rise to bands at 385 cm(-1), bringing the probable minimum number of species to seven. Several additional species are possible but could not be resolved definitively. In general, the relative proportions of these species are dependent on total As concentration, ΣS/ΣAs ratio and pH. At very low ΣS/ΣAs ratios we also observe Raman bands attributable to the dissociation products of H(3)AsO(3)(aq). Although we were unable to assign precise stoichiometries for the various thioarsenite species, we were able to map out general pH and ΣS/ΣAs conditions under which the various thioarsenite and arsenite species are predominant. This study provides a basis for more detailed Raman spectroscopic and other types of investigations of the nature of thioarsenite species

Temperature Effects on Gas Sensing Properties of Electrodeposited Chlorine Doped and Undoped n-Type Cuprous Oxide Thin Films

Abstract As one of the most widely used domestic fuels, the detection of possible leakages of Liquefied Petroleum (LP) gas from production plants, from cylinders during their storage, transport and usage is of utmost importance. This article discusses a study of the response of undoped and chlorine doped electrodeposited n-type Cuprous Oxide (Cu 2 O) films to of LP gas. Undoped n-type Cu 2 O films were fabricated in an electrolyte bath containing a solution of sodium acetate and cupric acetate whereas n-type chlorine doped Cu 2 O thin films were prepared by adding a 0.02 M cuprous chloride (CuCl 2 ) into an electrolyte solution containing lactic acid, cupric sulfate and sodium hydroxide. The n-type conductivity of the deposited films was determined using spectral response measurements. The structural and morphological properties of the fabricated films were monitored using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Due to doping, the overall conductivity of the chlorine doped n-type Cu 2 O films increased by several orders of magnitude. The temperature dependent gas responses of both the undoped and chlorine doped n-type Cu 2 O thin films to the LP gas was monitored by measuring the electrical resistance (R), and using the contact probe method at a constant gas flow rate of 0.005 ml/s. Upon exposure to gases, both doped and undoped films showed a good response to the gas by increasing/decreasing the electrical resistance by ΔR. The undoped n-type Cu 2 O thin films showed a negative response (ΔR < 0) at all temperatures resulting in a maximum response around 85˚C. However, the chlorine doped n-type Cu 2 O thin films initially showed a positive response (ΔR > 0) to the LP gas which then reversed its sign to give a negative response which peaked at 52˚C. The positive response shown by the chlorine doped Cu 2 O films vanished completely at 42˚C. N. Bandara et al. 12

Glancing angle x-ray study of crystallization of amorphous Ge at the Ge-Al interface

The amorphous to crystalline transformations of Ge in Al/Ge thin film couples has been studied using glancing angle EXAFS, x-ray reflectivity and diffraction. It was found that crystallization occurs at a much lower temperature (118--150{degrees}C) than for bulk Ge, and initiates at the Al/Ge interface. X-ray diffraction studies were made at 152{degrees}C to study the kinetics of the reaction. After an initial period we find good agreement with a square root dependence of the time, characteristic of a diffusion limited reaction

Critical Analysis of Lean Construction Maturity Models: A Systematic Literature Review

Lean construction (LC) is becoming prevalent, and assessment of the level of LC implementation is vital for organizations to realize their full potential. In meeting that need, lean construction maturity models (LCMMs) play a key role. However, there is less evidence of critical reviews in spite of the significant number of LCMMs available. Therefore, this study was initiated with the aim of systematically reviewing the literature on existing lean-construction-related maturity models (MMs) through a critical review. The study adopted the PRISMA method to review 24 such models using manual content analysis. The study revealed the most common attributes among the models, along with their key strengths and weaknesses. The findings of this study can be directly used to develop more robust LCMMs and enhance the knowledge base on theoretical underpinnings. From an industry perspective, the findings assist organizations to more effectively assess LC maturity. The study invites further research on the area of LC maturity and advocates for developing new MMs addressing these areas identified for improvement

Study of annealing effects of cuprous oxide grown by electrodeposition technique

Low temperature electrochemical deposition of cuprous oxide from aqueous solutions has been investigated. X-ray diffraction, scanning electron microscopy, optical absorption, and photo-response of liquid/cuprous oxide junctions have been used to study the deposits' crystallographic, morphological, optical, and electrical properties. Effects of annealing in air have been studied using the above mentioned methods. As-deposited cuprous oxide exhibits a direct band gap of 2.0 eV, and shows an n-type behaviour when used in an liquid/solid junction. Annealing below 300 degrees C enhances the n-type photocurrent produced by the junction. Type conversion occurs after heat treatments in air at temperatures above 300 degrees C. No apparent bulk structure changes have been observed during annealing below this temperature, but heat treatments above this temperature produce darker films containing cupric oxide and its complexes with water

Electrodeposition and characterisation of CuInSe2 for applications in thin film solar cells

Copper indium diselenide (CuInSe2) layers have been grown at room temperature by electrochemical deposition technique in an aqueous medium. Resulting thin films have been characterised using XRD, XRF, XPS, GDOES and SEM for structural, stoichiometric and morphological properties. A considerable influence of the deposition potential on the atomic composition of In and Se present in the film was observed. Cu composition remains the same within the deposition potentials used in this investigation. The deposited layers are polycrystalline and annealing at 350 degreesC for 30 min improves the crystallinity. The film quality deteriorates due to dissociation when annealed at temperatures above 350 degreesC. Excessive annealing results in a surface which is depleted in Cu and rich in In and Se. (C) 2001 Elsevier Science B.V. All rights reserved