Search results for "thermal [radiation]"
showing 10 items of 1167 documents
Investigation of water transfer across thin layer biopolymer films by infrared spectroscopy
2011
International audience; The investigation of the apparent diffusivity of water in thin layer iota-carrageenan-based films by FTIR-ATR spectroscopy clearly evidences the fundamental role of surface properties on water transfer. Water diffusivity in iota-carrageenan based biopolymer films ranges from 0.3 to 1.3 × 10−10 m2 s−1 and is thus 10–100 times lower than that in highly hydrated carrageenan gels. The surface heterogeneity and composition when fat is added strongly influence the diffusivity by modifying the liquid water absorption at the inner surface.This study of diffusing molecules in liquid state is particularly interesting to mimic situations where direct liquid water contact occurs…
DSC study on hyaluronan drying and hydration
2011
Abstract The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning calorimetry. In the first approach the isoconversional Kissinger–Akahita–Sunose (KAS) method was applied in order to determine actual activation energies of evaporation of pure water and water from concentrated HYA solutions. Since the evaporation is a single-step process, the activation energies for pure water provided results consistent with tabulated values of evaporation enthalpies. In the course of water evaporation from hyaluronan solution a break in increasing enthalpy followed by a decrease below 0.34 g of water per 1 g of HYA was observed. This result confirmed earlier observati…
Some fundamentals of the vapor and solution growth of ZnSe and ZnO
1999
Abstract Some fundamentals of ZnSe and ZnO vapor and solution growth are investigated. Residual water present in gases or gaseous mixtures such as H 2 , Ar or H 2 +H 2 O is shown to act as a sublimation activator in the vapor-phase transport of both compounds. The processes involved in the growth by chemically activated sublimation with such gases and gas mixtures have been studied by close-spaced vapor transport (CSVT). The ZnSe growth rate is found to be constant, while in the ZnO case a high initial growth rate is followed by slower growth subsequently. Using a theoretical model, the thermodynamic constants of the transport – energies of activation, sublimation and condensation and entha…
Preparation of multi-nanocrystalline transition metal oxide (TiO2–NiTiO3) mesoporous thin films
2005
Ordered mesoporous TiO2–NiTiO3 thin films, with nickel content x < 0.5, were prepared by dip-coating an acidic solution of hydrolysed transition metal chlorides in controlled humidity, followed by a very careful annealing treatment. These latter treatments were studied by in situ SAXS-WAXS experiments involving synchrotron radiation and TEM analysis. They revealed that the walls can be composed of amorphous, single crystalline or multi crystalline nanoparticles depending on x and the conditions applied during the thermal treatment.
On the synthesis and characterization of layered antimony(III) phosphate and its interaction with moist ammonia and amines
1998
Samples of antimony(III) phosphate, a layered material, were prepared at room temperature, using the two allotropic forms of Sb2O3, layered valentinite and cubic senarmontite. The compounds were characterized by infrared spectroscopy, X-ray diffraction, and thermogravimetric–differential thermal analysis. Solids exposed to ammonia, ethylenediamine, or hydrazine vapors also were studied. The interaction between SbPO4 and the bases always led to the formation of stoichiometric amounts of Sb2O3 and hydrogen phosphate(–2) salts of the bases. With ammonia, the SbPO4 raw materials gave rise to valentinite or senarmontite, depending on which Sb2O3 allotropic form was used to prepare antimony phosp…
Determination of the first ionization potential of einsteinium by resonance ionization mass spectroscopy (RIMS)
1998
Abstract The first ionization potential of einsteinium (IP Es ) was determined by resonance ionization mass spectroscopy (RIMS) using samples with ≤10 12 atoms of 254 Es ( T 1/2 =276 days). This method is based on the measurement of photoionization thresholds as a function of applied electric field strength, followed by extrapolation to zero field strength to yield IP Es . An atomic beam of Es was created by heating a filament on which einsteinium was electrodeposited from an aqueous solution onto a tantalum backing and covered with titanium metal. Es atoms were ionized via a three-step excitation scheme, and the ions mass-selectively detected in a time-of-flight (TOF) mass spectrometer. Th…
Determination of the first ionization potential of nine actinide elements by resonance ionization mass spectroscopy (RIMS)
1998
The high sensitivity of RIMS enables the precise determination of the first ionization potential of actinide elements with a sample size of ≤1012 atoms. By multiple resonant laser excitation, the actinide atoms under investigation are ionized in the presence of an electric field, and the ions are mass-selectively detected in a time-of-flight spectrometer. The first ionization potential is obtained by scanning the wavelength of the laser used for the last excitation step across the ionization threshold Wth—indicated by a sudden increase of the ion count rate—at various electric field strengths. Extrapolation of Wth to electric field strength zero leads directly to the first ionization potent…
Thermal analyses of commercial magnesium stearate pseudopolymorphs
2005
Abstract Two commercial magnesium stearate powders in two well-characterised structural states are investigated using DSC and coupled TGA–DTA under dry nitrogen flow. They consist of either a mixture of crystalline hydrates or a poorly crystallised so-called anhydrate. Following the degassing of unbound water, 1 or 3 weight-loss peaks are observed below about 100 °C, each associated with one heat loss peak at the same temperature. The present results and a review of graphical data from literature show that the so-called anhydrate always contains a significant amount of water. At the beginning of the dehydration process, the heat loss is the same as the standard heat of vaporisation of water…
Chemical modification of porous calcium hydroxyapatite surfaces by grafting phenylphosphonic and phenylphosphite acids
2006
Abstract It is well known that the incorporation of organic molecules can provide an effective route to modify the surface properties of apatite ceramics. The present study shows that phosphonates can react with calcium ions to control the formation of the hydroxyapatite structures. The grafting of C6H5PO(OH)2 (PPOH) and C6H5PO(OH)H (PPH) was used to increase the specific surface area as well as the porosity of hydroxyapatite materials. The higher specific surface area for HAp treated by PPOH is around 267 m2/g compared to the pure HAp (140 m2/g). The phenyl (C6H5) groups are removed by thermal treatment around 500 °C. After treatment at 800 °C, organoapatites (PP-HAp) are converted to stoi…
Crystal structures and thermal behavior of bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)am…
2006
Abstract Bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr4 were crystallized from acetonitrile and/or dilute HX solutions. Five different kinds of single crystals were obtained. In the case of bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl), the acetonitrile molecules cocrystallized into the crystal structure when acetonitrile solution was used. As a result, the isomorphic structures of Bis[dibenzyldimethylammonium]CuX4·0.5 CH3CN (X=Br or Cl) in monoclinic space group P21/n were obtained. When a dilute HX solution was used, the bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl) crystallized without solvent molecules. The formed…