Search results for "Gravimetry"
showing 10 items of 178 documents
Organometallic complexes with biological molecules. XVII. Triorganotin(IV) complexes with amoxicillin and ampicillin.
2002
Novel triorganotin(IV) complexes of two β-lactamic antibiotics, 6-[D-(-)-β-amino-p-hydroxyphenyl-acetamido]penicillin (=amoxicillin) and 6-[D-(-)-α-aminobenzyl]penicillin (=ampicillin), have been synthesized and investigated both in solid and solution states. The complexes corresponded to the general formula R3Sn(IV)antib·H2O (R=Me, n-Bu, Ph; antib=amox=amoxicillinate or amp=ampicillinate). Structural investigations about configuration in the solid state have been carried out by interpreting experimental IR and 119Sn Mössbauer data. In particular, IR results suggested polymeric structures both for R3Sn(IV)amox·H2O and R3Sn(IV)amp·H2O. Moreover, both antibiotics appear to behave as monoanion…
Organometallic complexes with biological molecules. XVIII. Alkyltin(IV) cephalexinate complexes: synthesis, solid state and solution phase investigat…
2004
Abstract Dialkyltin(IV) and trialkyltin(IV) complexes of the deacetoxycephalo-sporin-antibiotic cephalexin [7-( d -2-amino-2-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid] (Hceph) have been synthesized and investigated both in solid and solution phase. Analytical and thermogravimetric data supported the general formula Alk 2 SnOHceph · H 2 O and Alk 3 Snceph · H 2 O (Alk=Me, n -Bu), while structural information has been gained by FT-IR, 119 Sn Mossbauer and 1 H, 13 C, 119 Sn NMR data. In particular, IR results suggested polymeric structures both for Alk 2 SnOHceph · H 2 O and Alk 3 Snceph · H 2 O. Moreover, cephalexin appears to behave as monoanionic tridentate ligand coordinating th…
Xyloglucan-based hydrogel films for wound dressing: Structure-property relationships
2017
Thin xyloglucan-based hydrogel films have been synthetized and characterized in the prospect of producing wound dressings. Polyvinyl alcohol (PVA) and glycerol (Gro) were added to have an optimal combination of softness, conformability and resilience. Physical hydrogels have been transformed into permanent covalent hydrogels by reaction with glutaraldehyde (GA). Network structure-process-property relationships are discussed on the account of the results of several complementary characterizations: FTIR, rheology, thermal analysis, morphological analysis, moisture retention and swelling measurements. Selected formulations were also subjected to preliminary in vitro cytotoxicity tests. The phy…
On the origin of the sigmoid shape in the UO2 oxidation weight gain curves
2009
International audience; Cracking and spalling are known to occur during the oxidation of UO2. However, these phenomena are not considered by the existing kinetic models of the oxidation of UO2 into U3O8. In this study the oxidation of UO2 samples of various sizes from the single crystal to nanopowders, has been followed by isothermal and isobaric thermogravimetry, environmental scanning electron microscopy and in situ X-ray diffraction at temperatures ranging from 250 to 370°C in air. It has been shown that cracking occurs once a critical layer thickness of intermediate oxide has been reached, which corresponds to the beginning of the sigmoid kinetic curve. Cracking contribution to the sigm…
Mechanism of co-pyrolysis of coal-tar pitch with polyacrylonitrile
2003
Abstract Co-pyrolysis of coal-tar pitch with polyacrylonitrile (PAN) and PAN oxidized in air at 300 °C was studied as a possible way of manufacturing of carbonaceous materials enriched in nitrogen. The thermal behaviour of components and blends was evaluated by thermogravimetry and optical microscopy of solid residues. The transformation of nitrogen functional groups on co-treatment was monitored using elemental analysis, infrared spectroscopy and X-ray photoelectron spectroscopy. Oxidized polymer behaved as an inert during co-pyrolysis. In contrast, strong interactions of unoxidized PAN with pitch could be deduced from enhanced residue yield and extensive deterioration of the optical textu…
Multicavity halloysite-amphiphilic cyclodextrin hybrids for co-delivery of natural drugs into thyroid cancer cells
2015
Multicavity halloysite nanotube materials were employed as simultaneous carriers for two different natural drugs, silibinin and quercetin, at 6.1% and 2.2% drug loadings, respectively. The materials were obtained by grafting functionalized amphiphilic cyclodextrin onto the HNT external surface. The new materials were characterized by FT-IR spectroscopy, SEM, thermogravimetry, turbidimetry, dynamic light scattering and ζ-potential techniques. The interaction of the two molecules with the carrier was studied by HPLC measurements and fluorescence spectroscopy, respectively. The release of the drugs from HNT-amphiphilic cyclodextrin, at two different pH values, was also investigated by means of…
Halloysite nanotubes/pluronic nanocomposites for waterlogged archeological wood: thermal stability and X-ray microtomography
2020
Filling a polymer with halloysite nanotubes is considered a promising strategy to generate nanocomposites with tailored physicochemical properties. We have focused our attention on pluronic block copolymer/halloysite nanocomposites prepared by melt blending. The effect of composition on thermal stability and polymer crystallinity was investigated by thermogravimetry and differential scanning calorimetry. Electron microscopy was used to monitor the nanoparticle distribution in the polymeric matrix. The pluronic thermal stability is reduced by the clay nanoparticles. Concerning the polymer crystallinity, it is slightly decreased even if the melting temperature is lowered by halloysite. Furthe…
New insight on the lithium hydride–water vapor reaction system
2018
Abstract The reaction of lithium hydride (LiH) powder with pure water vapor (H2O and D2O) was studied by thermogravimetry and in situ infrared spectroscopy at 298 K over a large pressure range. The mean particle size of LiH is around 27 μm. At very low pressure, the hydrolysis starts with the formation of lithium oxide (Li2O). Then, both Li2O and lithium hydroxide (LiOH) are formed on increasing pressure, thus, creating a Li2O/LiOH bilayer. The reaction takes place through the consumption of LiH and the formation of Li2O at the LiH/Li2O interface and through the consumption of Li2O and the formation of LiOH at the Li2O/LiOH interface. Above 10 hPa, only the monohydrate LiOH·H2O is formed. T…
High temperature oxidation of higher manganese silicides
2021
Abstract The oxidation kinetics and mechanisms of higher manganese silicides (HMS) MnSi1.75, MnSi (1.75-x)Gex, MnSi(1.75-x)Alx (with x = 0.005 and 0.01)were studied and the effects of densification methods and dopant concentration discussed. Oxidation experiments were conducted using thermogravimetry (TGA), while post characterization with X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope (SEM) showed that spark plasma sintering (SPS) is a better densification method than hot pressing (HP). Except for undoped HMS, HMS doped with 0.5at% Ge had the lowest oxidation rate. Stable formation of a SiO2 protective layer was the main reason for improved oxidation resistance in …
Electrochemically induced free solvent transfer in thin poly(3,4-ethylenedioxythiophene) films
2015
International audience; In dynamic intrinsically conducting films, counterions transfer and conformational movements stimulated by the electrochemical reactions affect the free water molecules transfer. Poly(3,4-ethylenedioxythiophene) or PEDOT is included in this category. Here, p-doping of PEDOT immersed in LiClO4 aqueous solution was explored by ac-electrogravimetry. Electrochemical impedance spectroscopy combined with mass impedance spectroscopy proves useful for species identification and kinetics. For PEDOT, new equations have been developed to analyze the ac -electrogravimetry response. Quantitatively, faster free water transfer and slower coupled View the MathML sourceClO4−/free wat…