Search results for "Analytical"
showing 10 items of 9586 documents
The measurement of impurities in silicon for solar cell production
2012
The power conversion efficiency of solar cells is largely dependent on impurity levels in silicon. In the current investigations two sample preparation methods of silicon had been used before analysis - acid dissolution at atmospheric pressure and pressured microwave assisted technique. Quantification of impurities in solar silicon was done by inductively coupled plasma mass spectrometry and electrothermal atomic spectrometry. Microwave assisted dissolution of solar silicon was more effective compared to the traditional dissolution method on the hot plate, but complete dissolution of impurities and silicon matrix was achieved with a nitric and hydrofluoric acid mixture. The mass of solar si…
Study by static SIMS, XPS and UPS of the adsorption of cyanogen on (100) Ni surfaces
2000
Abstract The interaction of cyanogen with (100) Ni surfaces at room temperature was studied using secondary ion mass spectrometry in a static mode, and photoemission spectroscopies (XPS and UPS). It has been shown that cyanogen is adsorbed on this nickel surface in a dissociative mode: atomic carbon and nitrogen are present on the surface as well as CN fragments. These adsorbed species have been characterized by XPS and UPS. Increasing the temperature in the 400 K range increases the rate of the dissociation reaction of CN into atomic carbon and nitrogen. Moreover carbon is found to dissolved into the bulk for temperatures as low as 475 K. No evidence has been found of a polymerized form of…
Trace Analysis of Plutonium and Technetium by Resonance Ionization Mass Spectrometry Using an Atomic Beam and a Laser Ion Source
1990
A method for low level detection of plutonium and technetium is described with a detection limit of less than 107 atoms. Plutonium is a very toxic element due to its radioactive decay as well as its chemical behaviour. It was released to the environment in large amounts during the fifties and sixties of his century, principally by nuclear-weapon tests and some accidents. As a result about 0.4 − 4 mBq per gram 239Pu(T1/2 = 24390 y), corresponding to 4 × 108 − 4 × 109 atoms, can be found in the Northern Hemisphere in soil samples.
Adsorption and desorption surface dynamics of gaseous adsorbate on silicate-1 by molecular dynamics simulation
2013
The dynamics of adsorption and desorption of gaseous molecules on the external surface of a crystal and a membrane of zeolite silicate-1 is investigated by molecular dynamics simulation. The gases ...
Determination of toxic elements by cathodic-stripping-voltammetry
1981
The DPCSV determination of arsenic, selenium and tellurium in the sub-ng/ml range is discussed. After electrolytic deposition of the elements as intermetallic compounds with copper on the electrode surface, the determination is carried out by cathodic stripping. The simultaneous determination of selenium and tellurium or of selenium and arsenic is possible. Problems which occur in the application of these methods are discussed.
A surface EXAFS study of thin nickel deposits on (110) TiO2 surfaces
1997
Abstract The first stages of nickel deposition on a clean (110) TiO 2 surface were studied using surface extended X-ray absorption fine structure (EXAFS). Experiments were performed on two kinds of nickel deposits, one of 0.8 equivalent monolayers and another of 1.6 equivalent monolayers. Depositions were performed on well characterized TiO 2 (110)-p(1 × 1) surfaces. The correlation of Auger experiments with EXAFS results showed that no islands were present on the surface; only two-dimensional growth of nickel was observed. Moreover, it was shown, in the case of the thinner deposit, that a model with nickel atoms forming chains in the channels determined by oxygen atoms on the surface is co…
Modeling of surface vs. bulk ionic conductivity in fixed charge membranes
2003
A two-region model for describing the conductivity of porous fixed charge membranes is proposed. In the surface region, the conductivity is due to the mobile positive ions (counterions) around the negative fixed charges. In the pore center region, the conductive properties resemble those of the external electrolyte solution because the fixed charges are assumed to be effectively neutralized by the counterions in the surface region. Activation energies and surface diffusion coefficients are estimated by assuming that the counterion jump from a fixed charge group is the rate limiting process for surface transport. The barrier energy for this jump is calculated using a simple electrostatic mod…
Determination of the Absolute Density of Fe3+ and Ni2+ Ions in Langmuir-Blodgett Films
1996
By means of the Langmuir–Blodgett (LB) technique, mono- and multilayers of Ni2+ and Fe3+ containing fatty acid salts are transferred onto silicon wafers. After thermal treatment, oxidic layers can be produced. The absolute amounts of Fe3+ and Ni2+ ions per monolayer of LB film were measured and calculated by three different methods. In the case of nickel, the amount expected from theory and preparation conditions was obtained experimentally. In contrast, about twice the number of Fe3+ ions as expected is transferred. An explanation can be given by the presence of hydroxide groups bound to iron. The mean film thickness of the oxidic layers after thermal treatment was estimated where the thic…
Mass spectrometric studies on pyridine-piperazine-containing ligands and their complexes with transition metals formed in solution.
2001
Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) methods were used to study open-chain piperazine-containing ligands (L) and their complexes formed with transition-metal salts. ESI and MALDI measurements were performed with a Fourier transform ion cyclotron resonance (FT-ICR) and a time-of-flight (TOF) mass spectrometer, respectively. Only singly charged complexes, between one ligand and one or several metal ions, were formed in the ESI measurements. Because the net charge was always one, one or several counterions were attached to the complex. Under ESI conditions, the complexes formed between the ligands and metal (Co, Ni, Cu, and Cd) salts were [L + M…
A M�ssbauer and ESR study of LiNbO3-Fe2O3 for low Fe2O3 concentrations
1989
Samples of the system LiNbO3-Fe2O3 prepared by water quenching and by the double-roller quenching method in the range up to 24 mol% Fe2O3 were investigated by Mossbauer and ESR spectroscopy. In the water quenched samples up to 11 mol% Fe2O3 only the Fe3+ and the Fe2+ valence states could be detected. The Fe2+ concentration decreased with increasing Fe2O3 content. Above 11 mol% Fe2O3 magnetically split Mossbauer spectra indicated the presence of Fe2O3 clusters. The isomer shift values of Fe3+ as a function of Fe2O3 concentration showed jumps at 6 and 11 mol% Fe2O3, whereas no significant changes could be detected in the quadrupole splitting values. The ESR data already exhibited the existenc…