CO2-laser photoacoustic spectroscopy of deuterated ammonia

Photoacoustic (PA) coincidence absorption spectra of ammonia and its deuterated forms with carbon-dioxide laser emission were obtained. In addition, a simple isotope synthesis procedure was developed for that purpose. The strongest coincidence for the NH, molecule was found with laser line 9R(30) at 1084.628 cm(-1). Laser PA spectra of samples with different deuterium content indicate that coincidences with laser lines 10R(14) and 10R(30) at 971.93 and 982.10 cm(-1) respectively, correspond to NH2D, while one with 10R(20) at 975.93 cm(-1) is attributed to NHD2. The data obtained are discussed in relation to their uses in isotope chemistry and analysis. They are in agreement with results published by other authors. (C) 1997 Elsevier Science B.V

A simplified approach to the vibrational self-relaxation of simple molecules through convolution of their velocities

A theoretical approach has been developed for computing collisional self-relaxation probabilities of the first excited level in the lowest vibrational mode of simple molecules. The bending (nu(2)) vibration in triatomic molecules, in which the average translational and rotational velocities are of the same order of magnitude, was examined. The approach was based on the assumption that both the velocities should be taken into account as a convolution of the corresponding Maxwells distribution functions. The model was checked for the SO2 molecule in the temperature range from 130-1100 K. The calculated temperature dependence curve (the Landau-Teller plot) exhibits a minimum at about 150 K. The data obtained is discussed in I elation to some experimental results. The comparison indicates that the problem was treated in con ect manner: Some additional aspects of the relaxation, like intermolecular interactions and the steric factor, are also briefly considered. It is believed that this approach offers guile a good basis for further improvements of theoretical treatments.12th Yugoslav Conference on General and Applied Spectroscopy, Oct, 1999, Belgrade, Yugoslavi

Electrochemical H/D isotope separation efficiency along a hypo-hyper-d-electronic (Ti-Ni) phase diagram

Intermetallic phases (stable and meta-stable) along the Ti-Ni phase diagram, together with the pure constituents (TI, Ni), have been investigated as cathode materials for separation of hydrogen isotopes (protium and deuterium, HID) by water electrolysis from alkaline solutions. The H/.D separation factors, obtained using these electrodes, were compared with their hydridic and electrocatalytic features significant for the hydrogen evolution reaction (HER), the enthalpies of intermetallic formation, and their electronic work function. As with the similar behavior of transition elements along the Periodic Table, close correlations were found amongst them. The Ti-Ni intermetallic phases obey typical volcanic plots for all the mutually compared properties along their phase diagram. The TiNi3 alloy with an average d(8)-electronic configuration has maximal electrocatalytic activity for both hydrogen evolution and H/D electrochemical separation processes, the highest value of electronic work function, as well as maximal enthalpy of formation. Intermetallic phases Ti2Ni and TiNi, with an average electronic configuration between d(4) and d(5), exhibit lower values on each of these specific curves. The similarity between the mentioned features suggests that the average electronic configuration of these intermetallic phases determine overall electrode process kinetics, isotope separation efficiency, bond strength, electronic work function, and other physical and chemical properties

An efficient small scale TEA CO2 laser for material surface modification

An efficient small scale TEA (Transversely Excited Atmospheric) CO2 laser has been considered, The laser was a low flowing, UV preionized, pulsed system. Specific design of the head as well as the electrical circuit ensure the laser operation with high efficiency and reliability. Nonconventional CO2/Y, Y = N-2/H-2; H-2/He and H-2 gas mixtures showed relatively high energy output. CO2/N-2/H-2 mixture as the most superior one produces output energy and peak power of 220 mJ and 1.40 MW, respectively. High-energy output of the laser was employed for surface modification of austenitic stainless steel AISI 3 16 and titanium nitride (TiN) coating deposited on the same steel substrate. Used laser peak power densities of 100 and 170 MW/cm(2) have induced the morphology changes of AISI 316 steel and TiN coating, respectively.Proceedings of the Society of Photo-Optical Instrumentation Engineers (SPIE), International Conference on Atomic and Molecular Pulsed Lasers IV, Sep 10-14, 2001, Tomsk, Russi

Detection of malathion by the CO2 laser: Potentials and limitations

Possibilities of on-line non-contact detection of the vapour of the commercially available pesticide malathion by the CO2 laser were investigated, using a photoacoustic technique developed in our laboratory. A set of laser/vapour spectral coincidences in the usual range of CO2 laser wavelengths were obtained, the samples being: the commercial product Etiol available on the market, solvent, emulsifiers, and neat malathion, all with air added to a mid-pressure of about 100 mbar and to atmospheric pressure. Relative contributions of the components in the product are discussed. A detection limit of 0.002 vol.% of the product in air was estimated. (c) 2005 Elsevier B.V. All rights reserved

Hydrogen generation from water electrolysis - possibilities of energy saving

Hydrogen production via electrolysis of water from alkaline aqueous electrolytes is a well-established conventional technology. However, due to high energy requirements of about 4.5-5 kWh/m(n)(3) H-2 in most industrial electrolysers, the cost of hydrogen produced in such a way is n high. This is a limiting factor for the use of this method on a large scale, except in countries where the electricity is very cheap. There were various attempts to improve this process, like zero-gap cell geometry, developmentof new diaphragm materials, development of new electrocatalytic materials for electrodes, etc. We tried here to use ionic activators to reduce energy consumption. Two types of activators, both ethylenediamine complexes of cobalt, were used separately or in combination with some molybdates. The activation energies were significantly decreased in the presence of single ionic activators. However, the best results regarding the activation energy reduction were obtained when combinations with the molybdate were used. On the basis of the results of our experiments there is a strong indication that the activation with ionic activators reduces energy needs per mass unit of hydrogen produced for more than 10% in some cases, compared to those of non-activated electrolytes. (C) 2003 Elsevier Science B.V. All rights reserved.Conference on Scientific Advances in Fuel Cell Systems, Sep 25-26, 2002, Amsterdam, Netherland

Conditioning of the filament for diamond deposition by hot-filament chemical vapour deposition method

A tungsten filament, 0.12 mm in diameter, was conditioned by heating in a mixture of methane and hydrogen of three different concentration ratios. The filament was heated by an electric current. The procedure was carried out stepwise keeping either the voltage or the temperature of the filament constant. Changes in the filament material were monitored by resistance and temperature measurements. The chemical composition was checked using X-ray diffraction (XRD) analysis. The final state of the filament was investigated and photographed using the scanning-electron microscopy (SEM) technique

Ionic activators in the electrolytic production of hydrogen - cost reduction-analysis of the cathode

As recent technology progress makes hydrogen a realistic long-term energy option with little or no pollution, development of new methods for its production and improvement of conventional technology is important. In spite of the fact that, among overall world technologies for hydrogen production today, only 4% is produced by electrolysis, this is the most promising method in the future as a consequence of the high existing water supply. The limitation factor for its use on the large scale is well known-high energy consumption. In this work, methods for increasing efficiency and lowering the energy consumption in the electrolytic hydrogen production are presented. The stability of ionic activators, as an indicator of capital cost, are also shown, as are an analysis of composition, structure and morphology characteristic of cathode, formed in the presence as ionic activators. (C) 2004 Elsevier B.V. All rights reserved.8th Grove Fuel Cell Symposium, Sep 24-26, 2003, London, Englan

Electrochemical H/D isotope separation efficiencies on Ti-Ni intermetallic phases and alloys in relation to their hydridic and catalytic properties

Single Ti and Ni metals, their intermetallic phases (stable and unstable) and alloys along the Ti-Ni phase diagram, have been investigated as cathode materials for separation of hydrogen isotopes (protium and deuterium, H/D) by water electrolysis from alkaline solutions. The HID separation factors obtained were compared with the hydridic features and electrocatalytic properties for the hydrogen evolution (HER), enthalpies of intermetallic formation, and in common with similar behavior of transition elements along the Periodic Table, therefrom a close correlation amongst them resulted. The Ti-Ni intermetallic phases, as hypo-hyper-d-electronic combination of transition metals, obey typical volcano plots for all the mutually compared properties along their phase diagram. The TiNi3 alloy with an average d(8)-electronic configuration creates maximal electrocatalytic activity for both hydrogen evolution and HID electrochemical separation processes, as well as maximal enthalpy of formation. At the same time the best hydridic intermetallic phases (Ti2Ni and TiNi) and alloys (between d(4) and d(5)) exhibit lower values upon each specific curve. The similarity between those properties suggests that, alike along individual transition series, there exist the same electronic configuration causes which correlate them and determine the whole electrode kinetics. (C) 2000 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved

Comparison of different electrode materials - Energy requirements in the electrolytic hydrogen evolution process

Hydrogen is one of the most widely produced commodities in the world economy. The basic technologies for producing hydrogen via the electrolysis of water have long been known. However, there are disadvantages when using this process. Two-thirds of the operation costs of the electrolyzers are electricity costs. The challenge, addressed.by numerous companies and researchers in the last few years, is the cost cutting by increasing efficiency of the process. The aim of this work was the attempt to optimize the electrolytic hydrogen production from alkaline solution, through the variation of cathode materials and use of ionic activators. The part of our results shows the better electrocatalytic activity of intermetallic phases and the energy consumption is decreased when compared with the industrial data (4.5-5 kWh m(-3) H-2). The role of ionic activator used is also very significant. These results give the opportunity for further research of cumulative effect of the intermetallic electrodes and ionic activators on industrial level. (c) 2005 Elsevier B.V. All rights reserved.9th Grove Fuel Cell Symposium, Oct 04-06, 2005, London, Englan