Oxygen-containing Ions Research Articles

Insights into vanadium removal performance and mechanism in aqueous solution by one-step pyrolysis prepared Phytolacca acinosa biochar composite

Iron-loaded biochar (FBC) was synthesized via the dry-mixed co-pyrolysis of Phytolacca acinosa, Fe2(SO4)3 and NaOH and then used to remove aqueous vanadium (V (V)). FBC demonstrated the optimal adsorption performance for V (V) (57.67 mg/g) due to the loading of iron oxide, which increased the number of oxygen-containing functional groups. The adsorption of V (V) on FBC was pH-dependent, and the adsorption rate was high in the pH range of 2–8. Common cations and anions in water did not affect the adsorption of V (V) onto FBC, while NH4+, Na+, Ca2+, and Cd2+ can promoted its adsorption. The adsorption mechanism of FBC mainly included chemical adsorption, electrostatic adsorption, oxygen-containing functional group complexation and ion exchange. The easy preparation method, high adsorption capacity and adaptability makes FBC an ideal material for removing V (V) from wastewater.

On the evolution and formation of discharge morphology in pulsed dielectric barrier discharge

The discharge morphology of pulsed dielectric barrier discharge (PDBD) plays important roles in its applications. Here, we systematically investigated the effects of the voltage amplitude, discharge gap, and O2 content on the PDBD morphology, and revealed the possible underlying mechanism of the U-shaped formation. First, the morphological evolution under different conditions was recorded. A unique U-shaped region appears in the middle edge region when the gap is larger than 2 mm, while the entire discharge region remains columnar under a 2 mm gap in He PDBD. The width of the discharge and the U-shaped region increase with the increase in voltage, and decrease with the increase of the gap and O2 content. To explain this phenomenon, a two-dimensional symmetric model was developed to simulate the spatiotemporal evolution of different species and calculate the electric thrust. The discharge morphology evolution directly corresponds to the excited-state atomic reduction process. The electric thrust on the charged particles mainly determines the reaction region and strongly influences the U-shaped formation. When the gap is less than 2 mm, the electric thrust is homogeneous throughout the entire region, resulting in a columnar shape. However, when the gap is larger than 2 mm or O2 is added, the electric thrust in the edge region becomes greater than that in the middle, leading to the U-shaped formation. Furthermore, in He PDBD, the charged particles generating electric thrust are mainly electrons and helium ions, while in He/O2 PDBD those that generate electric thrust at the outer edge of the electrode surface are mainly various oxygen-containing ions.

Utilization of local rich banana straw bioresource to solve Cd2+ pollution problem in major non-ferrous metal production areas of Southwest China

The development of non-ferrous metal resources has caused serious cadmium pollution problem in Southwest China. Meanwhile, these areas are rich in bioresources like banana straw. With the assistance of microwave radiation, biomass may accomplish thermal breakdown and carbonization processes efficiently and quickly. In this work, banana straw was used as bioresource to synthesize biochar by microwave pyrolysis for the removal of Cd2+ from aqueous solution. The experiment result showed that the maximum Cd2+ adsorption capacity was 244.43 mg/g. The Elovich kinetic model and the Langmuir isotherm could well fit the adsorption process of Cd2+. Furthermore, the adsorption of Cd2+ by banana straw biochar is achieved through the synergistic effects of mineral precipitation, complexation with oxygen-containing functional groups (OFGs), ion exchange and Cd-π interaction, which accounted for the contribution of 86.57 %, 0.15 %, 3.73 % and 9.55 %, respectively. This study provides an innovative solution of cadmium pollution problem relying on local rich banana straw bioresource.

Does deprotonated benzoic acid lose carbon monoxide in collision-induced dissociation?

Decarboxylation is known to be the major fragmentation pathway for the deprotonated carboxylic acids in collision-induced dissociation (CID). However, in the CID mass spectrum of deprotonated benzoic acid (m/z 121) recorded on a Q-orbitrap mass spectrometer, the dominant peak was found to be m/z 93 instead of the anticipated m/z 77. Based on theoretical calculations, 18 O-isotope labeling and MS3 experiments, we demonstrated that the fragmentation of benzoate anion begins with decarboxylation, but the initial phenide anion (m/z 77) can react with trace O2 in the mass analyzer to produce phenolate anion (m/z 93) and other oxygen-containing ions. Thus oxygen adducts should be considered when annotating the MS/MS spectra of benzoic acids.

Banana stem and leaf biochar as an effective adsorbent for cadmium and lead in aqueous solution

Lead (Pb) and cadmium (Cd) are toxic heavy metals commonly found in aqueous environments. Biochar as a green adsorbent generated from biomass feedstock may be used for effective removal of these heavy metals. This study investigated the adsorption kinetics and isotherms of Pb2+ and Cd2+ in aqueous solutions at different pH by biochar prepared from banana stem and leaf (BSL-BC) at 400 °C. Characterizations using scanning electron microscope, X-ray diffraction, and Fourier-transform infrared spectroscopy showed that the synthesized BSL-BC had rough surface, porous structure, and oxygen-containing functional groups. The adsorption of Pb2+ and Cd2+ onto BSL-BC reached equilibrium in 8 h and 200 min, respectively, with faster adsorption attained at higher pH and the optimum pH occurred at 5 (Pb2+) and 8 (Cd2+). All adsorption kinetic data followed the pseudo-second-order rate model. The adsorption isotherm data of Pb2+ and Cd2+ could be well-described by the Langmuir and Freundlich models, respectively, whereas neither the Temkin or Dubinin–Radushkevich models provided satisfactory fitting results. The maximum adsorption capacities for Pb2+ and Cd2+ were 302.20 and 32.03 mg/g, respectively. The calculated mechanism contributions showed that complexation with oxygen-containing functional groups, ion exchange, mineral precipitation, and Pb2+/Cd2+-π coordination accounted for 0.1%, 8.4%, 88.8%, and 2.6% to Pb2+ adsorption, and 0.4%, 6.3%, 83.0%, and 10.4% to Cd2+ adsorption, respectively. Therefore, mineral precipitation was likely the major mechanism responsible for adsorption of both Pb2+ and Cd2+ by BSL-BC. The results suggest that the synthesized BSL-BC has great potential for adsorption of Pb2+ and Cd2+ from aqueous solutions.

Raman spectroscopy and quantum theory calculations on complexes in the KF-AlF3-Al2O3 system

The ionic structure of the KF-AlF3-Al2O3 system was studied using in situ high-temperature Raman spectroscopy and quantum mechanics calculations. The complexes in the KF-AlF3-Al2O3 system with different molar ratios of KF to AlF3 were AlF63−, AlF52−, AlF4−, Al2OF4, Al2OF84−, Al2OF62−, and Al2O2F42−. The structures of Al2OF4, Al2OF84−, Al2OF62−, and Al2O2F42− were optimized considering that the counterion K+, Al2OF4 exhibits D2d point group symmetry, K4Al2OF8 and K2Al2OF6 exhibit C2v point group symmetry, and K2Al2O2F4 exhibits C2h point group symmetry. The experimental main Raman bands of Al2OF84−, Al2OF62−, and Al2O2F42− were at 495 cm−1, 465 cm−1, and 410 cm−1, respectively, after comparing their theoretical Raman spectra. The forms and contents of the oxygen-containing complex ions in the system were related to the molar ratio of KF to AlF3 and to the concentration of alumina. AlF63−, AlF52−, AlF4−, and Al2OF4 were found in the molten KF-AlF3-Al2O3 system with a KF-to-AlF3 molar ratio of 1.22 at a temperature of 1003 K. In the KF-AlF3-Al2O3 system with a KF-to-AlF3 molar ratio of 2 at a temperature of 1273 K, when the alumina concentration was less than or equal to 10 wt%, it contained AlF63−, AlF52−, AlF4−, Al2OF4, and Al2OF84−, and when the alumina concentration reached 12 wt%, Al2OF62− and Al2O2F42− appeared. In the KF-AlF3-Al2O3 system with a KF-to-AlF3 molar ratio of 3 at a temperature of 1273 K, when the alumina concentration was less than or equal to 10 wt%, the system contained AlF63−, AlF52−, AlF4−, Al2OF4, and Al2OF84−. When the alumina concentration increased to 14 wt%, Al2OF62− and Al2O2F42− began to appear but AlF4− disappeared. As the concentration of alumina increased, the contents of Al2OF62− and Al2O2F42− increased. The ionic reactions that formed the various oxygen-containing complexes were obtained. The occurrence of these chemical reactions was related to the molar ratio of KF to AlF3 in the system and the alumina concentration. When the KF-AlF3-Al2O3 molten system with KF-to-AlF3 molar ratios of 1.22, 2 and 3 were used as the aluminum electrolytes, the ion discharged at the anode was Al2OF84−(except for the system with a KF-to-AlF3 molar ratio of 1.22 in which the Al2OF4 was discharged at the anode), and the ion discharged at the cathode was Al2OF4 according to wave function analyses.

Morphology of alumina in NaF-AlF3 systems determined by Raman spectroscopy and quantum mechanical calculations

In-situ Raman spectroscopy and quantum mechanical calculations were used to study the forms of oxygen-containing complexes in molten NaF-AlF3 systems. The molar ratios of NaF to AlF3 were varied at 1.22, 1.9, and 2.7 at temperatures of 1023 K, 1223 K, and 1283 K, respectively. Upon adding alumina to molten NaF-AlF3 systems, oxygen-containing complexes, Al2OF4, Al3O2F83−, Al2OF84−, and Al2O2F42−, were formed. The structures of Al2OF4 and Na4Al2OF8 belong to the D2d and C2v point groups, respectively, while Na3Al3O2F8 and Na2Al2O2F4 structures belong to the C1 point group. The main bands in the experimental Raman spectra of Al2OF4, Al3O2F83−, Al2OF84−, and Al2O2F42− were located at 460 cm−1, 530 cm−1, 505 cm−1, and 400 cm−1, respectively. The types and contents of the oxygen-containing complex ions in the system were related to the NaF-to-AlF3 molar ratio and the concentration of alumina. In the molten NaF-AlF3-Al2O3 system, with a NaF-to-AlF3 molar ratio of 1.22, only Al2OF4 formed. When the molar ratio was increased to 1.9, the oxygen-containing entities generated were Al2OF4 and Al3O2F83−. The content of the two oxygen-containing entities was low when the alumina content was below 6 wt%. As the concentration of alumina was 6 wt% or more, Al3O2F83− gradually became the main oxygen-containing entity. For the system with a NaF-to-AlF3 molar ratio of 2.7, when the alumina concentration was less than 6 wt%, the main oxygen-containing entities were Al2OF4, Al3O2F83−, and Al2OF84−, but with low concentrations. The concentrations of Al3O2F83− and Al2OF84− ions increased considerably as the alumina content approached 6 wt%. Al2O2F42− was formed when the alumina concentration reached 10 wt%. The reaction equations occurring after adding alumina to molten NaF-AlF3 systems were also determined herein.

Effect of Activation Time on the Performance and Mechanism of CO2-Activated Wheat Straw Char for the Removal of Cd2+

The removal behavior and characteristic of cadmium (Cd2+) on wheat straw char activated by CO2 were investigated in this study. The equilibrium, kinetics, and removal isotherms were studied. The results of batch experiments revealed that the removal of Cd2+ was described well by pseudo-second-order and Langmuir models. The increase in activation time improved the removal of Cd2+, especially for the activation time of 84 min. The results suggested that chemisorption of Cd2+ on activated carbon was the main reaction mechanism. The maximum removal capacity of Cd2+ onto activated WSC-84 was 75.55 mg/g, which was much higher than other three samples activated by CO2 with other amounts of time. According to the results of SEM, XPS, and FT-IR, complexation with surface oxygen-containing functional groups, ion exchange, and precipitation were the possible mechanisms of the removal process. It is suggested that the experimental results will enhance the comprehensive understanding of the activation of biomass and its utilization in the restoration of Cd-contaminated soil.

Local Anodic Oxidation of Thin GeO Films and Formation of Nanostructures Based on Them

The process of local anodic oxidation of thin GeO films has been studied using an atomic force microscope. The electron-probe microanalysis showed that oxidized areas of a GeO film were germanium dioxide. The effect of the voltage pulse duration applied to the probe–substrate system and the atmospheric humidity on the height of the oxide structures has been studied. The kinetics of the local anodic oxidation (LAO) in a semi-contact mode obeys the Cabrera–Mott model for large times. The initial growth rate of the oxide (R0) significantly increases and the time of starting the oxidation (t0) decreases as the atmospheric humidity increases by 20%, which is related to an increase in the concentration of oxygen-containing ions at the surface of the oxidized GeO film. It was shown that nanostructures in thin GeO layers can be formed by the LAO method.

Исследование процесса локального анодного окисления тонких пленок GeO и создание наноструктур на их основе

AbstractThe process of local anodic oxidation of thin GeO films has been studied using an atomic force microscope. The electron-probe microanalysis showed that oxidized areas of a GeO film were germanium dioxide. The effect of the voltage pulse duration applied to the probe–substrate system and the atmospheric humidity on the height of the oxide structures has been studied. The kinetics of the local anodic oxidation (LAO) in a semi-contact mode obeys the Cabrera–Mott model for large times. The initial growth rate of the oxide ( R _0) significantly increases and the time of starting the oxidation ( t _0) decreases as the atmospheric humidity increases by 20%, which is related to an increase in the concentration of oxygen-containing ions at the surface of the oxidized GeO film. It was shown that nanostructures in thin GeO layers can be formed by the LAO method.

Group Additivity Determination for Oxygenates, Oxonium Ions, and Oxygen-Containing Carbenium Ions

Bio-oil produced from biomass fast pyrolysis often requires catalytic upgrading to remove oxygen and acidic species over zeolite catalysts. The elementary reactions in the mechanism for this process involve carbenium and oxonium ions. In order to develop a detailed kinetic model for the catalytic upgrading of biomass, rate constants are required for these elementary reactions. The parameters in the Arrhenius equation can be related to thermodynamic properties through structure–reactivity relationships, such as the Evans–Polanyi relationship. For this relationship, enthalpies of formation of each species are required, which can be reasonably estimated using group additivity. However, the literature previously lacked group additivity values for oxygenates, oxonium ions, and oxygen-containing carbenium ions. In this work, 71 group additivity values for these types of groups were regressed, 65 of which had not been reported previously and six of which were newly estimated based on regression in the context of...

Transition temperature of poly(methyl methacrylate) determined by time-of-flight secondary ion mass spectrometry and contact angle measurements

The surface chain conformations of poly(methyl methacrylate) (PMMA) at different temperatures were extensively studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Similar to our previous experimental studies on polystyrene (PS) and poly(2, 3, 4, 5, 6-pentafluorostyrene) (5FPS), a transition temperature (TT) could be identified through the principal component analysis (PCA) of the ToF-SIMS spectra obtained from the PMMA samples annealed at different temperatures. Interestingly, our results show that the TT depended on molecular weight and was about 50–60˚C below the bulk glass transition temperature (Tg) and therefore could possibly be related to the surface glass transition temperature (TgS). These results were confirmed by contact angle measurements. ToF-SIMS results showed higher peak intensities of several low-mass oxygen-containing positive ions, hydrocarbon positive ions and OCH3− negative ion at higher temperatures, which can be interpreted by a higher surface concentration of methoxy groups at the surface.

Electrolytic Production of Aluminium Using Gas Anode Supplied with Methane

Mitigation of carbon emissions from the aluminium electrolysis cell is one of the main research topics of the aluminium industry. Prolonged research on inert anode candidates has not led to a commercial product yet. Another approach is to apply a reducing gas, e.g. methane, to the bath through porous anodes; where it reacts with oxygen-containing ions of the bath. When the gas (methane) replaces the consumable anode in reacting with the bath, the amount of generated CO2is reduced substantially. However, if the porous anode is made of carbon, the anode itself also takes part in the anodic reaction to some extent. Therefore, the consumption of the reducing gas and the anode occur simultaneously. Aluminium electrolysis experiments were carried out using porous graphite electrodes supplied with methane. The potential and weight changes of the anode together with the off gas analyses were done to study the effect of methane supply. It was found that the supply of methane during electrolysis led to decreased consumption of the graphite anode. But at the same time, the level of HF in the off gas showed a noticeable rise, which was expected due to the formation of water from methane oxidation. Provided that the share of the methane in the anodic reaction increases, the anode will be consumed less and a smaller amount of CO2is generated. Different grades of graphite were tested. Moreover, experimental parameters such as current density and anode gas composition were varied. Figure below: Anode potential plotted against time during aluminium electrolysis for two experiments where in one (top) only N2 and in the other (below) N2 + CH4 were flushed through the porous anodes. The anode was made of isotropic graphite. i = 0.4 A.cm-2, T = 970°C. The values in the figure are flow of the gas in ml.min-1. Figure 1

Anodic Processes under Extraction Tellurium from Oxihalide Melts

There was investigated kinetic of processes on graphite anode in oxidative melt on the base of eutectic CsCl–KCl–NaCl with additives TeO2 and NaF at temperature 600 °C. There were researched relationships between limiting current of ions tellurium’s overcharge and limiting current of discharge of oxygen-containing ions and content of TeO2 and NaF. Excess of these currents leads to chlorine evolution in oxychloride melts and freons in oxychloride-fluoride melts. There was offered mechanism of TeO2 dissolution in chloride and chloride-fluoride melts with generation and subsequent dissociation of tellurium oxychloride with forming of O2–, TeCl6 2–, and [TeO2Cl]–. Its availability in electrolyte was confirmed by method of infrared spectroscopy, and explains high rate of discharge of oxygenated ions at the anode.

Anodic processes during recovery of tellurium from oxyhalogenide melts

The process kinetics on a graphite anode in oxyhalide melts based on the CsCl–KCl–NaCl eutectic with TeO2 and NaF additives is investigated at 600°C. Dependences of limiting recharge currents of tellurium atoms and residual discharge currents of oxygen-containing ions on the TeO2 and NaF contents are investigated. Exceeding these currents leads to chlorine liberation in oxychloride melts and liberation of freons in chloride–fluoride melts. The dissolution mechanism of TeO2 in chloride and chloride–fluoride melts through the formation and subsequent dissociation of tellurium oxychloride with the formation of O2–, TeCl62-, and [TeO2Cl]– ions is proposed. The presence of these ions in the electrolyte is confirmed by infrared spectroscopy and explains high discharge rates of oxygen-containing ions at the anode.

Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres

The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al+ regardless of the background gas species, whereas Cr2+ ions were dominating in Ar and N2 and Cr+ in O2 atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ions that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O2 atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings.

Enhanced characterization of oil sands acid-extractable organics fractions using electrospray ionization-high-resolution mass spectrometry and synchronous fluorescence spectroscopy.

The open pit oil sands mining operations north of Fort McMurray, Alberta, Canada, are accumulating tailings waste at a rate approximately equal to 4.9 million m(3) /d. Naphthenic acids are among the most toxic components within tailings to aquatic life, but structural components have largely remained unidentified. In the present study, electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and synchronous fluorescence spectroscopy (SFS) were used to characterize fractions derived from the distillation of an acid-extractable organics (AEO) mixture isolated from oil sands process-affected water (OSPW). Mean molecular weights of each fraction, and their relative proportions to the whole AEO extract, were as follows: fraction 1: 237 Da, 8.3%; fraction 2: 240 Da, 23.8%; fraction 3: 257 Da, 26.7%; fraction 4: 308 Da, 18.9%; fraction 5: 355 Da, 10.0%. With increasing mean molecular weight of the AEO fractions, a concurrent increase occurred in the relative abundance of nitrogen-, sulfur-, and oxygen-containing ions, double-bond equivalents, and degree of aromaticity. Structures present in the higher-molecular-weight fractions (fraction 4 and fraction 5) suggested the presence of heteroatoms, dicarboxyl and dihydroxy groups, and organic acid compounds with the potential to function as estrogens. Because organic acid compositions become dominated by more recalcitrant, higher-molecular-weight acids during natural degradation, these findings are important in the context of oil sands tailings pond water remediation.

Molybdenum(V) Species in Alkali Chloride Melts: An Electronic Absorption Spectroscopy Study

Molybdenum in chloride melts can form chloro-species containing the metal in the oxidation states +3, +4 and +5. In the highest oxidation state, +6, molybdenum can form oxygen-containing ions. Amongst the molybdenum chloro-species those of the higher oxidation states (+5 and +4) are the least studied. In the present work the behavior of Mo(V) chloride was studied in a range of alkali chloride melts employing electronic absorption spectroscopy. The experiments were performed in LiCl-KCl, NaCl-CsCl, NaCl-KCl-CsCl eutectics and NaCl-KCl equimolar mixture between 450 and 750 oC, depending on the melt composition. Molybdenum(V) ions were introduced into the melt by feeding MoCl5vapor using the procedure described earlier (1). Analysis of the melt samples taken after the experiments showed that the mean oxidation state of molybdenum in the salt phase was +5.Electronic absorption spectra recorded upon dissolution of MoCl5 in an alkali chloride melt contained a broad band with a maximum around 13000 cm-1 (770 nm). Resolution of the spectra into individual bands, however, showed that this band represents a superposition of two bands with maxima around 15500 and 12500 cm-1, Fig. 1. The ratio between the intensities of these two component bands depends on temperature. At low temperatures the spectrum contains essentially one band (marked as 1 in Fig. 1) around 767 nm (13100 cm-1) corresponding to 2T2g→2Eg transition in the octahedral MoCl6 - ion. The energy of this transition agrees with that observed for WCl6 - ion, isoelectronic with MoCl6 - (2). On increasing temperature the second band (marked as 2 in Fig. 1) around 650 nm (15500 cm-1) becomes more prominent. The ratio of intensities of bands 1 and 2 changes with temperature, e.g. in LiCl-KCl melt it decreases from 1 : 0.2 at 450 oC to 1 : 2.6 at 850 oC.The band around 650 nm corresponds to the absorption of molecular MoCl5 (3). In the present study the absorption spectra of gaseous MoCl5 were measured at various temperatures and an example is shown in Fig. 2. Resolution of the spectrum of gaseous MoCl5 into individual bands, Fig. 3, shows that in the visible region there are two bands, a very intense one above 17000 cm-1 and a medium intensity band around 15000 cm-1. These bands can account for the changes in the spectra of Mo(V) solutions in the chloride melts occurring upon increasing temperature. Analysis of the spectroscopic data therefore shows that there are two species present in alkali chloride melts containing the products of MoCl5 dissolution, MoCl6 - and MoCl5. Most likely that these species are present in the equilibrium:MoCl6 - ↔ MoCl5 + ½ Cl2 and this equilibrium is shifted to the right with temperature.1. V. A. Volkovich, I. B. Polovov, R. V. Kamalov, B. D. Vasin and T. R. Griffiths, in Molten Salts Chemistry and Technology, M. Gaune-Escard and G. M. Haarberg, Editors, p. 489, John Wiley & Sons Inc., Hoboken (2014).2. V. A. Volkovich, D. A. Danilov, I. B. Polovov, B. D. Vasin, T. R. Griffiths, D. E. Aleksandrov, O. A. Tropin and D. V. Tsarevskii, ECS Transactions, 3(35), 555 (2007).3. R. F. W. Bader and A. D. Westland, Can. J. Chem., 39, 2306 (1961).

Excitation and ionic fragmentation of the carvone molecule (C10H14O) around the O 1s edge

The electronic excitation and associated ionic dissociation of the carvone molecule have been studied around the oxygen 1s edge, using synchrotron radiation and time-of-flight techniques. Photoabsorption spectrum (total ion yield) and mass spectra have been obtained in the range between 520 and 545eV. For the sake of comparison, carvone mass spectra have also been obtained following valence (21.21eV) and core (carbon 1s) ionization. Fragmentation of the molecule is seen to be greatly enhanced following core excitation. Around the oxygen 1s edge, we observe an extensive fragmentation of the molecular skeleton, as exemplified by the appearance of several previously unreported ions: H+, H2+, CH+, CH2+ and CH3+, which are not formed at low energies. A maximum is observed at 536eV photon energy in the relative intensity of the oxygen-containing ions O+, O2+ and OH+, as an evidence for the existence of site-selective fragmentation of the carvone molecule excited around the O 1s edge. Absolute values for the photoionization and photodissociation cross sections were estimated using the molecular additive rule.

A Mechanism of Anodic Film Formation in Molten Melts Using Preformed Porous Film Formed in 0.6 M Oxalic Acid Electrolyte

Direct interpretation of the results of the two stage anodizing procedure suggests that the film formed in the molten salt developed both at the film/electrolyte interface by aluminum ion egress and at the film/substrate interface by oxygen-containing species, O2- and/or OH-, ingress. Either at the high current density or within the geometrically high field strength region, i.e. the pore base of the preformed porous film, sulphate ions migrate inwards into the film and move in the direction normal to the film/substrate interface. The thin preformed porous film formed in aqueous electrolyte can be employed as a marker to obtain the apparent transport numbers of aluminum and oxygen-containing ions during anodizing in the molten salt.