Search Results
Abstract
Reaction of recoild38Cl atoms with o-dichlorobenzene in the presence of carbon tetrachloride or iodine has been studied by using radio-high performance liquid chromatography. The major products were detected by a 4-channel-wavelengths spectrophotometric detector. The radioactivity of38Cl compounds including minor products was measured with a NaI(T1) scintillation detector. The main products found were38Cl labeled HCl/Cl2, CHCl3, CCl4, o-, p-, m-C6H6Cl2 and polymer, whereas only minor products such as HCl/Cl2, CHCl3, C2Cl6, C6H3Cl3, and polymer were found in the radio-chromatogram. The reaction mechanisms of recoil38Cl atom are briefly described.
Abstract
The complexes of yttrium and lanthanide with 1,1-cyclobutanedicarboxylic acid of the formula: Ln2(C6H6O4)3⋅nH2O, where n=4 for Y, Pr–Tm, n=5 for Yb,Lu, n=7 for La, Ce have been studied. The solid complexes have colours typical of Ln3+ ions. During heating in air they lose water molecules and then decompose to the oxides, directly (Y, Ce, Tm, Yb) or with intermediate formation. The thermal decomposition is connected with released water (313–353 K), carbon dioxide, hydrocarbons(538–598 K) and carbon oxide for Ho and Lu. When heated in nitrogen they dehydrate to form anhydrous salt and next decompose to the mixture of carbon and oxides of respective metals. IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating.
Abstract
This paper describes first the application of neutron depth profiling (NDP) for measuring the distribution of6Li in LiAlO2 ceramics. Using a surface barrier detector for detecting3H produced in6Li(n, 
)3H,6Li was profiled to a depth of 14 
m in the ceramics. Secondly, a new methodology is presented for NDP with enhanced capabilities based on measuring the energy of recoiling nuclei from (n, p) and (n, ) reactions by time-of-flight mass spectrometry. The scope of recoil nucleus time-of-flight mass spectrometry (RN-TOF-MS) includes profiling of10B,14N,17O,33S,35Cl,40K. Probe depths may be of a few tens nanometers. RN-TOF-MS complements and refines NDP based on charged particle (p or ) spectrometry.
Caracterisation par analyse calorimetrique differentielle des complexes entre LiAlH4 et les ethers-couronnes 12-C-4, 15-C-5, dicyclohexano-18-C-6
Comportement thermique des phases solides et de certains de leurs solvates avec le benzène
The thermal behaviour of complexes [Li+-EC](AlH4)− withEC=12-C-4, 15-C-5, DC 18-C-6 (cis-anti-cis andcis-syn-cis isomers) was investigated by Differential Scanning Calorimetry (DSC). These complexes were prepared as solids from benzene solutions. Pure EC and several solvated species [Li+-EC](AlH4)−·nC6H6 (EC=15-C-5, DC 18-C-6syn) were also studied. DSC has revealed various phenomena. Solid-solid transitions were observed before melting for [Li+-EC](AlH4)− withEC=12-C-4 and 15-C-5. They are probably explained by small molecular modifications strongly dependent on the thermal history of the sample. A glass-transition was found for the pure crown-ether DC 18-C-6anti, the complex [Li+-EC](A1H4)− withEC=DC-18-C-6anti and the two solvates mentioned above.
Abstract
Polyether-urethane samples were irradiated at the dose range from 10 to 2000 kGy by 2 MeV electron beams. Volatile species from the polymer degradation were analyzed quantitatively and qualitatively with GC/MS. Thermal properties and micro-phase separation of the samples were examined by TG and the morphology was studied by TEM and SEM. The results show that the irradiated polyether-polyurethane evolves CO2, H2, CH4 and C2H6, etc. The thermal stabilities between the hard and soft segments in the irradiated samples are different. At high doses, the phase separation in the sample is predominant and the hard segment of sample is more stable. The dose rate affects the soft segment of the irradiated sample much more.
The thermal degradation of H6TeO6 in air has been evaluated critically. Evidence is presented for a decomposition mechanism involving step-wise dehydration of H6TeO6 via non-stoichiometric amorphous solids to polymetatelluric acid and up to a composition corresponding to pyrotelluric acid. No morphological changes were observed during these structural variations and no evidence was found for the formation of allotelluric acid. Further dehydration is accompanied by reduction, which, depending upon the experimental conditions accounts for the considerable variety of results reported previously. Crystalline Te(VI)-Te(IV) oxides are obtained at about 550‡ from which TeO2 is formed by additional calcination at about 620‡.
4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III)
Thermal, spectral and magnetic behaviour
Abstract
4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III) were obtained as mono-, di-, tri-or tetrahydrates with metal to ligand ratio of 1:3 and general formula Ln(C8H6ClO3)3·nH2O, where n=1 for Ln=Er, n=2 for Ln=Tb, Dy, Tm, Y, n=3 for Ln=Ho and n=4 for Yb and Lu. The complexes were characterized by elemental analysis, FTIR spectra, TG, DTA and DSC curves, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate chelating ligand. All complexes are polycrystalline compounds. The values of enthalpy, ΔH, of the dehydration process for analysed complexes were also determined. The solubilities of heavy lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10−4 mol dm−3. The magnetic moments were determined over the range of 76–303 K. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.
Abstract
Selenium nuclides are available from thermal neutron induced nuclear fission of 235U at the gas-jet facility at the Swiss spallation neutron source (SINQ) at Paul Scherrer Institute, Switzerland. The formation of stable selenium compounds, their transport yields using the gas-jet system and their relative thermal decomposition temperature were investigated under oxidizing and reducing conditions in the target chamber. Using O2, H2, CO, and propene as additional gases, the selenium isotopes are suggested to form H2SeO3, H2Se, COSe, and C3H6Se, respectively, with overall 84Se yields of 1.5%, 4.7%, 6.3%, and 21.9%, respectively. Adsorption enthalpy, vapour pressure, solubility and acidity data for these species were collected from the literature or estimated from other known thermochemical properties. Carrier free bromine isotopes (84Br, 86Br) in the form of HOBr were obtained by thermally decomposing H2SeO3 and retaining elemental Se under oxygen rich conditions on quartz at 400 K.
Abstract
The order of extraction of Mo(VI) from 1M acid solutions by 5% (v/v) LIX 622 (HL) in benzene is HCl>HNO3>HClO4>H2SO4, and extraction decreases with increasing concentration of HCl and H2SO4, and increases slightly with increasing concentration of HNO3 and HClO4. The extracted species is shown to be MoO2L2 as established by IR data of organic extracts and the extracted species in the solid form. Extraction is almost quantitative at and above 10% LIX 622, and is found to be independent of [Mo(VI)] in the range of 10–4 to 10–3 M. The diluents CCl4, CHCl3 and C6H6 are found to be superior to solvents of high dielectric constant for extraction of Mo(VI). Extraction of uranium(VI) by 10% (v/v) LIX 622 in benzene was found to increase with increasing equilibrium pH (3.0 to 6.0), and becomes quantitative at pH 5.9. Tributyl phosphate acts as a modifier up to 2% (v/v). Thorium(IV) is almost not extracted by LIX 622 or its mixture. Separation of Mo(VI) and U(VI) is feasible.
Abstract
We studied the extraction of phosphomolybdic acid labelled with99Mo and32P and of other species extracted. From the influence of the acidity and of the concentration of excess molybdenum on the distribution coefficient of phosphorus, we propose the following equilibrium for the formation of phosphomolybdate in our experimental conditions
free
molybdenum has been shown. It can be eliminated by washing the organic phase with a 5M HNO3 solution. Subsequently we test a method using radioactive molybdenum, proposed by J. E. KENNEY and M. P. MENON1 for the titration of phosphorus in steels. Because of the presence of interfering elements (Nb, Zr, Ti, V, Si, etc.) specific conditions for the extraction of phosphomolybdic acid have to be found for the application of this method to steels.
