Search results for "Melting-point depression"

showing 3 items of 3 documents

Microscopic evidence of a flat melting curve of tantalum

2010

International audience; New data on the high-pressure melting curve of Ta up to 48GPa are reported. Evidence of melting from changes in sample texture was found in five different experiments using scanning electron microscopy. The obtained melting temperatures are in excellent agreement with earlier measurements using x-ray diffraction or the laser-speckled method but are in contrast with several theoretical calculations. The results are also compared with shock-wave data. These findings are of geophysical relevance because they confirm the validity of earlier experimental techniques that resulted in low melting slopes of the transition metals measured in the diamond-anvil cell, including i…

Diffractionlaser-heatingMaterials sciencehigh-pressurePhysics and Astronomy (miscellaneous)Scanning electron microscope62.50.-p64.70.djTantalumAnalytical chemistrychemistry.chemical_element02 engineering and technology01 natural sciencesdiamond-anvil cellDiamond anvil cellMelting curve analysistransition metalsTransition metal0103 physical sciencesTexture (crystalline)010306 general physics62.50.EfAstronomy and Astrophysics021001 nanoscience & nanotechnologyCrystallographyGeophysicsmelting curvechemistrySpace and Planetary Science0210 nano-technologyMelting-point depression
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Small-angle x-ray scattering studies of melting

1980

The course of melting of melt-crystallized polyethylene fractions and of a poly(ethylene oxide)-polystyrene-poly(ethylene oxide) triblock copolymer has been followed by small-angle x-ray scattering (SAXS). Changes in the intensity and shape of the SAXS curves indicated that both surface melting and melting over the full crystallite thickness (full-strand melting) take place. Full strand melting is the final, irreversible process. Comparison with an analytical model indicates that in the earlier stages of the irreversible, full-strand process the crystallites melt out randomly throughout the bulk. Later stages may occur by the simultaneous melting of a larger stack of crystallites.

Materials scienceEthylene oxideScatteringSmall-angle X-ray scatteringGeneral EngineeringAnalytical chemistryPolyethyleneIrreversible processchemistry.chemical_compoundCrystallographychemistryCopolymerCrystalliteMelting-point depressionJournal of Polymer Science: Polymer Physics Edition
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Comparative Study of Different Methods for the Prediction of Drug–Polymer Solubility

2015

In this study, a comparison of different methods to predict drug-polymer solubility was carried out on binary systems consisting of five model drugs (paracetamol, chloramphenicol, celecoxib, indomethacin, and felodipine) and polyvinylpyrrolidone/vinyl acetate copolymers (PVP/VA) of different monomer weight ratios. The drug-polymer solubility at 25 °C was predicted using the Flory-Huggins model, from data obtained at elevated temperature using thermal analysis methods based on the recrystallization of a supersaturated amorphous solid dispersion and two variations of the melting point depression method. These predictions were compared with the solubility in the low molecular weight liquid ana…

Vinyl CompoundsRecrystallization (geology)PolymersChemistry PharmaceuticalIndomethacinAnalytical chemistryPharmaceutical ScienceFlory–Huggins solution theorychemistry.chemical_compoundDrug StabilityDrug DiscoveryVinyl acetatemedicineSolubilityThermal analysisAcetaminophenSupersaturationChromatographyCalorimetry Differential ScanningFelodipinePolyvinylpyrrolidonePovidonePyrrolidinonesChloramphenicolSolubilitychemistryCelecoxibThermodynamicsMolecular MedicineCrystallizationMelting-point depressionmedicine.drugMolecular Pharmaceutics
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