Mass spectrometric study of the vaporization of sodium borosilicate glasses

A mass spectrometric Knudsen effusion method has been used to study the vaporization behaviors of three sodium borosilicate glasses with the compositions of 1Na₂O-1B₂O₃-3SiO₂(Glass-1), 1Na₂O-1.5B₂O₃-3SiO₂(Glass-2) and 1.5Na₂O-1B₂O₃-3SiO₂(Glass-3) in the temperature range 915–1172 K. Vapor species of NaBO₂(g) and Na₂(BO₂)₂(g) have been identified over Glass-1 and Glass-2, in which the mole ratio of Na₂O to B₂O₃ is equal to and less than unity, respectively. Over Glass-3, in which the ratio is larger than unity, vapor species of Na(g) has been observed in addition to NaBO₂(g) and Na₂(BO₂)₂(g), and the total vapor pressure over Glass-3 is much higher as compared with those over Glass-1 and Glass-2. From the measured partial pressures of Na(g), NaBO₂(g) and Na₂(BO₂)₂(g), the activity coefficient of NaBO₂ in Glass-1, enthalpies of vaporization, enthalpies of formation and dissociation energies for the vapors have been determined.     

Mass spectrometric study of the vaporization of lithium metasilicate

The vaporization of Li₂SiO₃(c/1) has been studied by the mass spectrometric Knudsen effusion method. The vaporization process has been found to be incongruent. Partial pressures of Li(g), LiO(g), Li₂O(g), SiO(g) and Li₂SiO₃(g) over Li₂SiO₃(c/1) have been determined in the temperature range 1166–1762 K. Partial pressures of O₂(g) have also been calculated from the reaction Li₂SiO₃(1) = 2 Li(g) + SiO(g) + O₂(g). The enthalpies of formation and the atomization energies for LiO(g) and Li₂O(g) have been evaluated from the partial pressures to be ΔH^o_f0(LiO,g) = (84.5 ± 12.8)kJ/mol, ΔH^o_f0(Li₂O, g) = (?148.1 ± 15.8)kJ/mol, D₀^o(LiO) = (321.4 ± 12.8)kJ/mol and D₀^o(Li₂O) = (713.2 ± 15.8)kJ/mol, respectively. The value of D₀^o(Li₂O) is somewhat greater than twice that of D₀^o(LiO).     

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (V)

The difference in electrochemical corrosion potential of stainless steel exposed to high temperature pure water containing hydrogen peroxide (H₂O₂) and oxygen (O₂)is caused by differences in chemical form of oxide films. In order to identify differences in oxide film structures on stainless steel after exposure to H₂O₂ and O₂ environments, characteristics of the oxide films have been examined by multilateral surface analyses, e.g., X-ray diffraction (XRD), Rutherford back scattering spectroscopy (RBS), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). Preliminary characterization results of oxide films confirmed that the oxide film formed under the H2O2 environment consists mainly of hematite (α-Fe₂O₂), while that under the O₂ environment consists of magnetite (Fe₃O₄). Furthermore oxidation at the very surface of the film is much more enhanced under the H₂O₂ environment than that under the O₂ environment. It was speculated that metal hydroxide plays an important role in oxidation of stainless steel in the presence of H₂O₂. The difference in electric resistance of oxide film causes the difference in anodic polarization properties. It is recommended that several anodic polarization curves for specimens with differently oxidized films should be prepared to calculate ECP based on the Evans diagram.     

Mass spectrometric study of the evaporation of LiCrO2 as a corrosion product in the compatibility experiment of Li2O pellets with Fe-Ni-Cr alloys

A mass spectrometric Knudsen effusion study of the vaporization of LiCrO₂ in the temperature range of 1673–1873 K has shown the following: (1) The major vapor species over solid LiCrO₂ are Li(g), Cr(g), CrO(g), CrO₂(g) and LiCrO₂(g). (2) The vaporization process involves a sublimation reaction, LiCrO₂(s) = LiCrO₂(g), and a dissociation reaction, $\text{LiCrO}{}_2\text{(s) =}\text{1}\text{2}\text{Cr}{}_2\text{O}{}_3\text{(s) + Li(g) +}\text{1}\text{4}\text{O}{}_2\text{(g)}$. (3) The standard enthalpy of solid LiCrO₂ at 298 K is derived to be (?935 ± 21) and (?966 ± 18) kJ/mol from the 2nd and 3rd law treatments, respectively.     

Synthesis,characterization and solubility of mixed zirconium-cerium molybdate precipitates

The reaction between fission products Mo(VI) and Zr(IV) in hot nitric acid solution during the spent fuel dissolution process leads to the formation of hydrated zirconium molybdate precipitate. This solid can include other metallic cations at the 4th oxidation state (+ IV) inside the crystal such as Pu(IV).

Precipitations in the inactive surrogate system of mixed zirconium-cerium molybdates Mo-Zr(IV)-Ce(IV) were performed all over the cerium molar percentage scale from 0 to 100%, Ce(IV) being used as a surrogate of Pu(IV). The crystal structures were identified from powder X-ray diffraction patterns and complementary investigations by SEM and elemental analyses were carried out. The solid composition pointed out two phases that are ZrMo₂O₇(OH)₂(H₂O)₂ and Ce₃Mo₆O₂₄(H₂O)₄. Each of these compounds was proved being a solid solution within which the Zr^IV and Ce^IV atoms can substitute each other.

Moreover, the influence of the cerium molar fraction on the precipitate solubility was investigated and showed a strong evolution of solubility not only with the nature of the precipitate and the Ce content, but also with the nitric acid concentration.     

Spectroscopic investigations of new metallic complexes with leucine as ligand

The [Cu(L)₂] · H₂O (1), [Co(L)₂] · 2H₂O (2) and [Zn(L)₂] · H₂O (3) complexes with leucine (L) as ligand, were synthesized in water solution and analyzed by physical-chemical and spectroscopic means (UV-VIS, FT-IR, ESR). The comparative analysis of the IR spectra for the ligand and the complexes indicate the coordination of the metallic centre to the carboxylic oxygen atom and the nitrogen atom of the amino group due to the shift of the ν_s(CO) and ν_s(NH) stretching vibrations. Spectral UV-VIS and ESR data confirmed the covalent metal-ligand bonds, the pseudotetrahedral symmetry around the copper and zinc ions and the octahedral environment for the cobalt ion.     

Dissolution Behaviors of Copper Metal in Alkaline H2O2-EDTA Solutions

Abstract

The dissolution behavior of Cu metal in hydrogen peroxide (H₂O₂)-ethylenediaminetetraacetic acid (EDTA) solution was studied through both electrochemical and chemical tests. In the electrochemical experiments, the open circuit potential (OCP) of Cu electrode at low H₂O₂concentration below 0.5wt% was determined by Cu anodic reaction and H₂O₂ cathodic reaction. On the other hand, the OCP in higher concentration above 2 w/t% of H₂O₂ approached to 70 mV vs. SCE, since the redox reaction of H₂O₂ was so dominant reaction that the Cu anodic reaction was masked. The anodic polarization curve of Cu around the OCP of 70 mV in the range between -200 and 200 mV in the solution without H₂O₂ showed the maximum Cu dissolution reaction front, while those of both carbon steel and Inconel 600 in the same potential range were situated in the passivation region. The anodic polarization behaviors of Cu in the H₂O₂ concentrations above 1 wt% were examined by a potentiostatic method along with a weight loss measurement. The anodic Cu dissolution current estimated from the weight loss measurement in the solution containing more than 1 wt% of H₂O₂ was higher than that predicted by the polarization curve of Cu in the H₂O₂-free solution. The dissolution reaction rate of Cu in the H₂O₂ solution linearly increased with H₂O₂ concentration. This result indicated that the dissolution reaction rate of Cu in the presence of H₂O₂ was enhanced by a reaction between Cu and H₂O₂, resulting in the shift of the polarization curves depending on H₂O₂ concentration. The experimental correlation equation based on the above results described well the overall dissolution reaction rate of Cu in H₂O₂ concentration ranges below 1 wt% and above 2 wt% in the EDTA solution.     

Vaporization behavior and Gibbs energy of formation of Rb2ThO3

The thermodynamic stability of rubidium thorate, Rb₂ThO₃(s), was determined from vaporization studies using the Knudsen effusion forward collection technique. Rb₂ThO₃(s) vaporized incongruently and predominantly as Rb₂ThO₃(s)=ThO₂(s) + 2Rb(g) + 1/2 O₂(g). The equilibrium constant K=p_Rb²·p_O2^1/2 was evaluated from the measurement of the effusive flux due to Rb vapor species under the oxygen potential governed by the stoichiometric loss of the chemical component Rb₂O from the thorate phase. The Gibbs energy of formation of Rb₂ThO₃ derived from the measurement and other auxiliary data could be given by the equation, Δ_fG°(Rb₂ThO₃,s)=−1794.7+0.42T ± .     

Effective atomic numbers of some composite mixtures including borax

Effective atomic numbers for (PbO and Na₂B₄O₇10H₂O) and (UO₂(NO₃)₂, and Na₂B₄O₇10H₂O) mixtures against changing contents of PbO, Na₂B₄O₇10H₂O, and UO₂(NO₃)₂ were measured in the X-ray energy range from 25.0 to 58.0 keV. The gamma rays emitted by a ²⁴¹Am annular source have been sent on the absorbers which emits their characteristic X-rays to be used in transmission arrangement. The X-rays were counted by a Si(Li) detector with a resolution of 146 eV at 5.90 keV. The changing compositions of the compounds were assigned to be 0, 0.167, 0.333, 0.500, 0.666, 0.833 and total masses of the mixtures were adjusted to be identical. Also, the total effective atomic numbers of each mixture were estimated by using the mixture rule. The measured values were compared with estimated values for the mixtures.     

PL and XPS study of radiation damage created by various slow highly charged heavy ions on GaN epitaxial layers

Photoluminescence (PL) spectrum, in conjunction with X-ray photoelectron spectroscopy (XPS) is used to evaluate the surface damage of GaN layer by highly-charged Xe^q+ (18 ? q ? 30), Ar^q+ (6 ? q ? 16) and Pb^q+ (q = 25,35) ions. The intensity of PL emission of GaN layer, including near band-edge peak and yellow luminescence, decreases with increasing fluence and charge state of the incident ions. Finally the PL emission is completely quenched after irradiation to high fluences at high charge state. A new peak at 450 nm appeared in PL spectra of the specimens irradiated with Xe¹⁸⁺, Ar⁶⁺ and Ar¹¹⁺, indicating that radioactive recombination within donor-acceptor pairs (DAPs) during irradiation. After irradiation, XPS spectra show N deficient or Ga rich on GaN surface and XPS spectra of Ga3d core levels indicate spectral peak evidently shifts from a Ga-N to Ga-Ga and Ga-O bond. The relative content of Ga-N bond decreases and the content of Ga-Ga bond increases with the increase of ion fluence and ion charge state. The binding energy of Ga3d_5/2 electron corresponding to Ga-Ga bond of the irradiated GaN film is found to be smaller than that of metallic Gallium (Ga⁰), which can be attributed to irradiation damage.     

Nuclear tracks in garnets studied by means of Rutherford backscattering and X-ray diffraction

(Y, La)₃(Fe, Ga)₅O₁₂ epitaxial garnet films on (111) Gd₃Ga₅O₁₂ substrates irradiated with ²³⁸U ions of 1.4 MeV/u specific energy in the dose range 10¹⁰ cm^?2 to 3 × 10¹¹ cm^?2 were measured by means of Rutherford backscattering and double-crystal X-ray diffraction before and after thermal annealing in oxygen. The nuclear track diameter of 10 nm confining a cylindrical volume of highly disordered material caused by each ion impact has been deduced from the comparison of the backscattering spectra of the irradiated and unirradiated film areas. The fraction of randomly backscattered ions due to the irradiation-induced damage as well as the lattice expansion perpendicular to the crystal surface caused by irradiation-induced lateral compressive stress are proportional to the ion dose. After thermal annealing the comparison of the almost identical backscattering yield of the irradiated areas and the unirradiated film regions demonstrates a nearly perfect recrystallization of the damaged track volumes.     

Localised modifications of anatase TiO2 thin films by a Focused Ion Beam

A Focused Ion Beam (FIB) has been used to implant micrometer-sized areas of polycrystalline anatase TiO₂ thin films with Ga⁺ ions using fluencies from 10¹⁵ to 10¹⁷ ions/cm². The evolution of the surface morphology was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the chemical modifications of the surface were followed by X-ray photoelectron spectroscopy (XPS). The implanted areas show a noticeable change in surface morphology as compared to the as-deposited surface. The surface loses its grainy morphology to gradually become a smooth surface with a RMS roughness of less than 1 nm for the highest ion fluence used. The surface recession or depth of the irradiated area increases with ion fluence, but the rate with which the depth increases changes at around 5 × 10¹⁶ ions/cm². Comparison with implantation of a pre-irradiated surface indicates that the initial surface morphology may have a large effect on the surface recession rate. Detailed analysis of the XPS spectra shows that the oxidation state of Ti and O apparently does not change, whereas the implanted gallium exists in an oxidation state related to Ga₂O₃.     

Vaporization study on UO2 and (U1−yNby)O2+x by mass-spectrometric method

The vapor pressures over UO_2.000 and (U_1?yNb_y)O_2+x (y = 0.01, 0.05, x = 0.000–0.022) were measured by the mass-spectrometric method in the temperature range 2025–2343 K. The main gas species over UO_2.000 were observed to be UO₃(g) and UO₂(g) and those over (U_1?yNb_y)O_2+x were NbO₂(g), NbO(g), UO₃(g) and UO₂(g). The partial vapor pressures of almost all gas species over (U_1?yNb_y)O_2+x increased with increasing O/M (M = U + Nb) ratio. With increasing Nb content in (U_1?yNb_y)O_2.000, the partial vapor pressures of UO₂(g) and UO₃(g) decreased and those of NbO(g) and NbO₂(g) increased. The congruently vaporizing composition in the (U_1?yNb_y)O_2+x phase was estimated to be ($\text{U}{}_{\mathrm{0.985\pm 0.005}}\text{Nb}{}_{\mathrm{0.015\pm 0.005}}\text{)O}{}_{2.000}$ from the compositional dependence of the total vapor pressures. The partial molar enthalpy and entropy of oxygen of (U_1?yNb_y)O_2+x calculated from the partial pressures of gaseous species NbO₂(g) and NbO(g) were in fairly good agreement with those previously obtained by the present authors with a thermobalance.     

Deposition of Nickel and Cobalt Ions on Heated Surface under Nucleate Boiling Condition

The depositionof Ni and Co ions on a heated surface of simulating fuel rods has been studied in water at atmospheric and 70 atm pressures during nucleate boiling.

The effects of various factors, including heat flux of the heated surface, concentration of coexisting iron oxide (αFe₂O₃ and concentration of Ni and Co ions, on their deposition rate have been investigated. The model for iron oxide deposition which is based on microlayer evaporation and drying out phenomena in the nucleate boiling bubble was shown to be applicable to the deposition of Ni and Co ions. That is, dW/dt=K.Q.C/L, where dW/dt is the deposition rate, K the deposition rate coefficient, Q the heat flux, C the ion concentration, and L the latent heat of vaporization. The K value of Ni ion is about 0.1 and independent of iron oxide concentration. On the hand, the K value of Co ion increases with iron oxide concentration and seems to approach that of iron oxide concentration and seems to approach that of iron oxide (0.3). The Co ion deposited with iron oxide forms Co ferrite. Solubility of Co ferrite is small compared with that of Co deposits without iron oxide (CoO or Co(OH)₂). The increase in the K value of Co ion with iron oxide concentration is attributed to the change in chemical form of Co deposits into more stable species not favoring Co release.     

Electronic sputtering of Gd3Ga5O12 and Y3Fe5O12 garnets: Yield, stoichiometry and comparison to track formation

The results of present paper have shown that sputtering of yttrium iron garnet (Y₃Fe₅O₁₂) under swift heavy ions in the electronic energy loss regime is non-stoichiometric. Here we are presenting additional experimental results for gadolinium gallium garnet (Gd₃Ga₅O₁₂) as target. The irradiations were performed with different ions (⁵⁰Cr (589 MeV), ⁸⁶Kr (195 MeV) and ¹⁸¹Ta (400 MeV)) impinging perpendicularly to the surface. As earlier, the sputtering yield was determined by collecting the emitted gadolinium and gallium atoms on a thin aluminium foil, placed upstream above the target and analyzing the Al catcher by Rutherford backscattering. Also for Gd₃Ga₅O_12, the emission of Gd and Ga is non-stoichiometric. Sputtering appears above a critical electronic stopping power of S_th = 11.6 ± 1.5 keV/nm, which is larger than the threshold for track formation, in agreement with other amorphisable materials. In addition, the angular distribution of the sputtered species was measured for Y₃Fe₅O₁₂ and Gd₃Ga₅O₁₂ using 200 MeV Au ions impinging the surface at 20° relatively to the surface. For the two garnets the ratio of Y/Fe (and Gd/Ga) varies with the angle of emitted species and the stoichiometry seems to be preserved only for an emission perpendicular to the surface.     

Precipitation of Thorium or Uranium(VI) Complex Ion with Cobalt(III) or Chromium(III) Complex Cation, (II)

The precipitations of thorium and uranium(VI) sulfito complex ions with hexammine cobalt(III) chloride as the precipitant have been studied.

The orange-colored uranium(VI) precipitate obtained is [Co(NH₃)₆]₄[UO₂(SO₃)₃]₃22H₂O, which is in the form of square bipyramid, about 4 μm across in a cubic symmetry of the diamond type with a=10.40Å It decomposes to an oxide mixture of Co₃O₄ and U₃O₈ above 850°C in the air through a sulfate mixture of CoSo₄ and UO₂SO₄.

Composition of the thorium precipitate varies with the precipitation conditions. Therefore, it is considered that the thorium precipitate contains thorium hydroxide and basic thorium sulfite.     

Calorimetric and thermodynamic analysis of palladium-deuterium electrochemical cells

An analysis is made of the chemical heats liberated from a palladium-deuterium electrochemical cell operating inside a calorimeter. It is important, in such an analysis, to carefully identify the chemical and electrochemical sources of heat, before any “excess heats” can be ascribed to non-chemical reactions.⁽¹⁾ The calorimeter measures the enthalpy (ΔH _r ) of the reaction; whereas, the electrochemical voltage of the cell reflects the free energy (ΔG _r ) of the reaction within the Pd-D electrolysis cell. The heat energy from the calorimeter cell therefore doesnot equal the electrical energy supplied to the cell, as might initially be expected. The magnitudes of the differing calorimetric and electrochemical energies were found to be related through the “thermoneutral potential” (ξ_H) of the electrochemical reaction. The chemical heat theoretically expected from the calorimeter is given by (1) I(ξ_L-ξ_H), the cell current (I), multiplied by the difference between the operating cell voltage (ξ_L) and the thermoneutral potential (ξ_H), rather than (2) Iξ_L, the electrical input power. This was verified empirically using a freon vaporization calorimeter, which operates on the principle of accurate measurement of the vaporization rate of liquid freon which completely surrounds the electrochemical cell. The calorimetrically-measured heats observed from a Pt/D₂O, 0.1M LiOD/Pd electrochemical cell were within 2% of the thermoneutral potential predicted value, I(ξ_L-ξ_H); but were found to be 15–30% less than the electrical work supplied to the cell, Iξ_L. Measurements of D₂O consumed by the cell reactions also verified that essentially no significant recombination of D₂ and O₂ gases occurred within the cell. No “excess heats” were observed from this Pd cell during the 36 days of its electrolytic operation. Likewise, no increase in the neutron flux around the cell was found, using three³He radiation detectors.     

Characterization of solidified melt among materials of UO2 fuel and B4C control blade

To predict the fundamental phase relationships in the solidified core melt of the Fukushima Daiichi Nuclear Power Plant, solidified melt samples of the various core materials [B₄C, stainless steel, Zr, ZrO₂, (U,Zr)O₂] were prepared by arc melting. Phases and compositions in the samples were determined by means of X-ray diffraction, microscopy, and elemental analysis. With various compositions, the only oxide phase formed was (U,Zr)O₂. After annealing, the stable metallic phases were an Fe-Cr-Ni alloy and an Fe₂Zr-type (Fe,Cr,Ni)₂(Zr,U) intermetallic compound. The borides, ZrB₂ and Fe₂B-type (Fe,Cr,Ni)₂B, were solidified in the metallic part. Annealing at 1773 K under an oxidizing atmosphere (Ar-0.1%O₂) resulted in the oxidation of U and Zr in the alloy and in ZrB₂, and consequently the (Fe,Cr,Ni)₂B and Fe-Cr-Ni alloy became dominant in the metallic part. The experimental phase relationships in the metallic part agreed reasonably with the thermodynamic evaluation of equilibrium phases in a simplified B₄C–Fe–Zr system. The metallic Zr content in the melt was found to be a key factor in determining the phase relationships. As a basic mechanical property, the microhardness of each phase was measured. The borides, especially ZrB₂, showed notably higher hardness than any other oxide or metallic phases.