Search results for "Thermogravimetry"
showing 10 items of 150 documents
Study of the thermal decomposition of bromazepan complexes with Co(II), Ni(II), Cu(II) and Zn(II)
1984
Abstract The thermal behaviour of complexes of bromazepan with Co(II), Ni(II), Cu(II) and Zn(II) was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The complexes decompose in two steps: dehydration and decomposition. A correlation between the dehydration temperatures of MB2Xn and the coordinating ability of X is observed.
3D polylactide-based scaffolds for studying human hepatocarcinoma processes in vitro
2012
We evaluated the combination of leaching techniques and melt blending of polymers and particles for the preparation of highly interconnected three-dimensional polymeric porous scaffolds for in vitro studies of human hepatocarcinoma processes. More specifically, sodium chloride and poly(ethylene glycol) (PEG) were used as water-soluble porogens to form porous and solvent-free poly(L,D-lactide) (PLA)-based scaffolds. Several characterization techniques, including porosimetry, image analysis and thermogravimetry, were combined to improve the reliability of measurements and mapping of the size, distribution and microarchitecture of pores. We also investigated the effect of processing, in PLA-ba…
Novel silicon microparticles to improve sunlight stability of raw polypropylene
2015
Oxidation of polyolefins by ultraviolet/visible irradiation is a significant limitation for their use in several technological applications. The use of high-tech additives such as silicon microparticles becomes a compositing strategy that can improve the performance of these materials at long-term service conditions. Silicon particles were added to non-additivated raw polypropylene (PP) prepared by hot melt extrusion and subjected to accelerated sunlight irradiation tests. The stability of thermal properties, mechanical performance and thermal decomposition behaviour of composites was evaluated by differential scanning calorimetry, dynamic mechanical thermal analysis and thermogravimetry. T…
Monolacunary Keggin polyoxometalates connected to ten 4d or 4f metal atoms.
2013
The rational self-assembly of mono-lacunary Keggin clusters with 4d and 4f metal salts via a conventional method has yielded two novel polyoxometalate-based 4d-4f heterometallic compounds containing lacunary Keggin anions connected to ten metal atoms: {[Ag{Ag2(H2O)4}{Ln(H2O)6}2H ⊂ {SiW11Ln(H2O)4O39}2]·nH2O (Ln = Ce and n = 7 for 1, Ln = Pr and n = 3 for 2). Their structures were determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. A structural feature in 1 and 2 is that each [SiW11O39](8-) cluster (SiW11) is connected to ten metals (five Ag(+) and five Ln(3+) cations), representing the highe…
Sponge biosilica formation involves syneresis following polycondensation in vivo.
2011
Syneresis is a process observed during the maturation/aging of silica gels obtained by sol-gel synthesis that results in shrinkage and expulsion of water due to a rearrangement and increase in the number of bridging siloxane bonds. Here we describe how the process of biosilica deposition during spicule ("biosilica" skeleton of the siliceous sponges) formation involves a phase of syneresis that occurs after the enzyme-mediated polycondensation reaction. Primmorphs from the demosponge Suberites domuncula were used to study syneresis and the inhibition of this mechanism. We showed by scanning electron microscopy that spicules added to primmorphs that have been incubated with manganese sulfate …
A comparative study of the surface and bulk properties of lanthanum-strontium-manganese oxides La1âxSrxMnO3±δ as a function of Sr-content, oxygen…
1999
Abstract The properties of the perovskite-type La 1− x Sr x MnO 3± δ oxides (0≤ x ≤1) are related to the reversible redox reaction of manganese ions Mn 3+ ↔Mn 4+ . This reaction plays an essential role both in the interfacial transfers and transport properties and depends on relative cation concentrations and experimental conditions. In this paper we present experimental investigations aiming to determine, to compare and to control some of the surface and bulk properties of these oxides. The bulk and surface Mn 4+ contents were investigated by thermogravimetry analysis (TGA) in hydrogen and X-ray photo-electron spectroscopy (XPS) respectively. With a finely divided La 0.8 Sr 0.2 MnO 3 powde…
Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition p…
2010
The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition…
Halloysite nanotubes filled with salicylic acid and sodium diclofenac: effects of vacuum pumping on loading and release properties
2021
AbstractIn this work, we investigated the effects of the vacuum pumping on both the loading efficiencies and the release kinetics of halloysite nanotubes filled with drug molecules dissolved in ethanol. As model drugs, salicylic acid and sodium diclofenac were selected. For comparison, the loading of the drug molecules was conducted on platy kaolinite to explore the key role of the hollow tubular morphology on the filling mechanism of halloysite. The effects of the pressure conditions used in the loading protocol were interpreted and discussed on the basis of the thermodynamic results provided by Knudsen thermogravimetry, which demonstrated the ethanol confinement inside the halloysite cavi…
Adsorption of m-Xylene on Prehydrated Zeolite BaX: Correlation between Temperature-Programmed Desorption and Low-Temperature Neutron Powder Diffract…
1999
Adsorption of m-xylene on partially hydrated zeolite BaX is studied by thermogravimetry, mass spectrometry, temperature-programmed desorption and neutron diffraction for different m-xylene loadings of the zeolite. Macroscopic and microscopic measurements, for both molecules, were correlated and relationships were found between the crystallographic positions of the adsorbed molecules on the zeolite and macroscopic properties such as the number and the area of the peaks in the desorption spectra for m-xylene or water. The influence of water molecules on the adsorption phenomenon of m-xylene on BaX zeolite was characterized. In particular, it was shown that the increase of the filling of the p…
Pyrolysis study of sol-gel derived TiO2powders
2004
An amorphous TiO2 gel was obtained by hydrolysing titanium(IV) isopropoxide with a stoichiometric amount of water using SnCl2 as catalyst. In these operative conditions, a TiO2 gel matrix containing a lower fraction of organic residual was obtained with respect to samples prepared by previously modifying the titanium alkoxide precursor with chelating ligands. Dried gel powders were characterized by N2 adsorption analyses, FT-IR and XRD measurements. Thermogravimetric (TG) and differential thermal analysis (DTA) coupled with mass spectrometric (MS) and gas chromatographic (GC) measurements were performed in order to identify the organic products released from TiO2 gel pyrolysis. The Tg-MS se…