Volatile Gaseous Species Research Articles

Effect of swift heavy ions irradiation on physicochemical and dielectric properties of chitosan and chitosan-Ag nanocomposites

Self-sustained films of biodegradable chitosan (CS) and chitosan-Ag nanocomposites (CSN) were prepared by chemical route followed by C+5 and Ni+7 ions irradiation with varying fluences. The crystallite size decreased from 11.1 to 2.7 nm for CS and 17.6 to 14.2 nm for CSN with increasing ions fluence as observed from the analysis of X-ray Diffraction (XRD) spectra. ATR-FTIR spectra revealed assorted vibrational modes and degradation of polymeric chains in both, CS and CSN matrices upon irradiation. The molecular interactions between main and side-chain functional groups impeded due to nanoparticles confining effects. MeV ions yield low-molecular-weight fragments with degassing of some volatile gaseous species during irradiation. An acute amendment in absorption spectra ascribed to change in surface color and differential absorbance at the wavelength of 370 nm showing blocking of UV radiation. The formation of conjugated linkages and carbonization of CS and CSN matrices lead to decrease in bandgap. Modifications in the physicochemical properties were found to be in persuasive association with changes in frequency-dependent dielectric responses. The shape parameter was moderately decreased and indicating non-Debye relaxation. The conductivity of CS and CSN matrices enhanced and follows the universal dielectric response. The amendment in surface morphology was also revealed upon irradiation.

Analysis of Four Solvatomorphs of Betulin by TG\u2013DTA\u2013EI/PI\u2013MS System Equipped with the Skimmer-Type Interface

Betulin (BE) has exceedingly become a potential natural product, providing multiple pharmacological and biological activities, including anti-cancer, anti-viral, and anti-inflammatory benefits. Previous research indicated that the solvatomorphism of BE can easily occur through crystallization with different organic solvents. This property of BE can directly affect its extraction, isolation, and preparation process. In this study, a system of thermogravimetry (TG)–differential thermal analysis (DTA) coupled with mass spectrometry (MS) with electron ionization (EI) and photoionization (PI) capability, equipped with the skimmer-type interface (i.e., skimmer-type interfaced TG–DTA–EI/PI–MS system), as a real-time and onsite analysis technique, was employed. Then, four solvatomorphs of BE, namely, with pyridine and water (A), sec-butanol (B), n,n-dimethylformamide (DMF) (C), and isopropanol (V), were analyzed for the first time. Finally, five kinds of the main volatile gaseous species, including H2O, pyridine, sec-butanol, DMF, and isopropanol, were identified clearly. Furthermore, the multi-step desolvation processes of the four solvatomorphs of BE were revealed by this system for the first time. This system showed great potential for the rapid and accurate analysis of various solvatomorphs of natural products.Graphic

Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc.In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt.In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T < 1422 K for rhodium sesquioxide and T < 1815 K for ruthenium dioxide), the formed oxides are relatively stable. On the other hand, at high temperatures (T > 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species.A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident.The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

Fire behaviour of carbon fibre epoxy composite for aircraft: Novel test bench and experimental study

A versatile fire test has been developed with a complete set of instrumentation to investigate the fire behaviour of carbon fibre epoxy composite designed for aircraft. During a single test, both condensed and gas phases can be simultaneously studied measuring the temperature profile and the mass loss and studying the nature and quantity of volatile gaseous species. This novel test bench is compliant with two aeronautical certification fire tests: ISO2685:1998(E) and FAR25.856(b):2003. Titanium coupons have been first submitted to fire to validate the testing method. Composite coupons have been evaluated to examine completely their fire behaviour. To go further in the investigation, post-fire analyses have been performed using X-ray microtomographic images of coupons exposed to fire. Thus, the phenomena identified during the test are the apparition of cracks in the virgin material, the thermal degradation, the migration of evolved gases through the material up to both side and the thermal delamination.

Stability of rare earth oxides in a moist environment at elevated temperatures—Experimental and thermodynamic studies: Part II: Comparison of the rare earth oxides

Volatilisation tests enabled to quantify the stability of different rare earth sesquioxides, RE 2O 3 (where RE = Sc, Dy, Er, Yb) and to understand the corrosion process. These tests were carried out at temperatures ranging from 1000 to 1400 °C in moist air with 50 kPa of water at atmospheric pressure, under a flowing gas velocity of 5 cm s −1. Besides the volatilisation rate, the nature of the volatile gaseous species was determined. The proposed experimental method allowed too to assess the Gibbs free energy of formation of these gaseous volatile species. Finally, the stability of each rare earth oxide under a moist environment at high temperature was compared.

Stability of rare earth oxides in a moist environment at high temperatures—Experimental and thermodynamic studies. Part I: The way to assess thermodynamic parameters from volatilisation rates

A methodology based on a weight loss measurement was used to quantify the volatility of yttria in high temperature water vapor. This method was first assessed on silica. Sintered materials with a shape of pellets were exposed at temperatures between 1000 and 1400 °C in air with 50 kPa of water at atmospheric pressure, under a flowing gas velocity of 5 cm s −1. Besides the volatilisation rate, the nature of the volatile gaseous species was determined using a kinetic study. Knowing the nature of flows in the furnace, partial pressures of yttrium (oxy-)hydroxide in equilibrium over Y 2O 3 were calculated, and used to assess the enthalpies of formation of YO(OH) and Y(OH) 3.

Water to atmosphere fluxes of 131I in relation with alkyl-iodide compounds from the Seine Estuary (France)

This study presents an original work on measurements of stable and radioactive iodinated species in the Seine estuary (France), with estimates fluxes of volatile gaseous species from water to the atmosphere. Various iodinated compounds were identified in water and air in particular 131I in water, what is unusual. Concentrations and behaviour of iodinated elements in the Seine estuary seem similar to what has been observed in other European estuaries. MeI (Methyl Iodide) and Total Volatile Iodine (TVI) fluxes from water to air vary between 392 and 13949 pmol m −2 d −1 and between 1279 and 16484 pmol m −2 d −1, respectively. Water to air flux of TVI for the Seine river was estimated in the range 4–46 kg y −1. Measurements of 131I in water varying between 0.4 and 11.9 Bq m −3. Fluxes of 131I from water to atmosphere are in the range 2.4 × 10 5–1.3 × 10 7 Bq y −1, close to an annual discharge of 131I by a nuclear reactor.

Thermodynamic treatment of uranium dioxide based nuclear fuel

Abstract Many projects involving nuclear fuel rest on a quantitative understanding of the co-existing phases at various stages of burnup. Since the fission products have considerably different abilities to chemically associate with oxygen, and the metal-to-oxygen molar ratio is necessarily increasing, the chemical potential of oxygen is a function of burnup. Concurrently, well-recognized small fractions of new phases such as inert gas, noble metals, zirconates, etc. also develop. To further complicate matters, the dominant UO2 fuel phase may be non-stoichiometric and most of the minor phases themselves have a variable composition dependent on temperature and possible contact with the coolant in the event of a sheathing breach. A thermodynamic database has been in development to predict the phases in partially burned CANDU (CANada Deuterium Uranium) nuclear fuel containing the major fission products. The building blocks are the standard Gibbs energies of formation of the many possible compounds expressed as a function of temperature. To these data are added mixing terms associated with the appearance of the component species in particular phases. In operational terms, the treatment rests on the ability to minimize the Gibbs energy in a multicomponent system using the algorithms developed by Eriksson. The treatment, considered applicable in the range 300 to 2000 °C, is capable of handling non-stoichiometry in the UO2 fluorite phase, dilute solution behaviour of significant solute oxides, noble metal inclusions, a second metal solid solution U(Pd – Rh – Ru)3, zirconate, molybdate, and uranate solutions as well as other minor solid phases, and volatile gaseous species. The paper highlights the current capability of an ongoing project.

Refinement of the vapour pressures in equilibrium with InP and InAs by mass spectrometry

The vapour phase in equilibrium with the compounds InP and InAs has been analysed by mass spectrometry. A new ionization source directly frozen with liquid nitrogen has been built in conjunction with narrow molecular-beam sampling to avoid any parasitic evaporations coming mainly from the highly volatile gaseous species P 4 and As 4. The evolution with temperature of the ionization efficiencies for the ions P 2 + and As 2 + is explained by the dissociative ionization contributions of the P 4 and As 4 molecules. This contribution is quantitatively evaluated as respectively (21 ± 2) per cent and (17 ± 2) per cent by measurements of the vapour phase over pure amorphous red phosphorus and pure arsenic. The partial pressures measured in equilibrium with the compounds are optimized together with previous selected phase diagrams and thermodynamic quantities. Enthalpies of formation and entropies for these compounds are deduced: Δ f H m o(InP, cr, 298.15 K)/(kJ · mol −1) = −(61.3 ± 2.0), Δ f H m o(InAs, cr, 298.15 K)/(kJ · mol −1) = −(58.8 ± 2.0), S m o(InP, cr, 298.15 K)/(J · K −1 · mol −1) = (59.0 ± 0.8), and S m o(InAs, cr, 298.15 K)/(J · K −1 · mol −1) = (75.9 ±1.3).