Search results for "gravimetric"
showing 10 items of 272 documents
A novel oxovanadate structural type – Synthesis, single crystal structure and magnetic properties of a mixed-valence polyoxovanadate formed by {V17O4…
2007
Abstract A novel polyoxovanadate structural type, with an average nuclearity of V16, formed by a mixture of two different polyoxovananadates: {V15O36(Cl)} and{V17O40(Cl)} has been synthesized and characterized. The title compound, formulated as [Ni(phen)3]2{[V15O36(Cl)]0.5[V17O40(Cl)]0.5} · H2O (1) (phen = 1,10′-phenanthroline), presents two different polyoxovanadate architectures: {V15O36(Cl)} and {V17O40(Cl)}, with the last one representing a new framework type in polyoxovanadate chemistry. Here, we present the synthesis of this novel polyoxovanadate under hydrothermal conditions and its characterization by IR and XPS spectroscopies, elemental and thermogravimetric analysis, redox titrati…
Iron(II) Spin Transition Complexes with Dendritic Ligands, Part I
2008
The ligands G1- and G2-oligo (benzyl ether) (PBE) dendrons and their iron(II) complexes [Fe(Gn-PBE)3]A2·xH2O (with n = 1, 2 and A = triflate, tosylate) were prepared. The magnetic properties of the complexes were investigated by a SQUID magnetometer. All complexes exhibit gradual spin transition below room temperature. At very low temperatures the magnetic behaviour reflects zero-field splitting (ZFS) effects. 57Fe-Mossbauer spectroscopy was performed to distinguish between ZFS of high spin species and spin state conversion into the low spin state. Further characterisation was carried out by thermogravimetric analysis (TGA) and FT-IR spectroscopy. Structural features have been determined by…
Tin(II) Derivatives of 2,3-Dihydroxynaphthalene
1983
Abstract The reaction of aqueous solutions of tin(II) chloride and 2,3-dihydroxynaphthalene (H2A) gives a white precipitate of SnA. This compound has been characterized by chemical analysis, IR spectra and thermogravimetric analysis. A spectrophotometric study of tin(II) and H2A in DMF shows the formation of two species with stoichiometric ratios Sn:H2A 1:1 and 1:2.
Monitoring the carburization of molybdenum bimetallic nitrides and oxynitrides with CH4/H2/Ar mixtures: identification of a new carbonitride.
2008
A new carbonitride Ni2Mo3(CxNy) has been synthesized by temperature-programmed carburization of the Ni2Mo3N precursor with a CH4/H2/Ar gas mixture at 923 K. This compound has been characterized by X-ray diffraction, elemental analysis, Auger electron spectroscopy, laser Raman spectroscopy, thermogravimetric analysis and field-emission scanning electron microscopy. Ni2Mo3(CxNy) crystallizes in the cubic space group P4(1)32, with a lattice parameter of a=6.64575(3) A, corresponding to the unusual filled beta-Mn structure. Its formation occurs by partial substitution of N by C via a topotactic and pseudomorphic reaction and its stability in air is higher that of Ni2Mo3N. A two-phase mixture wi…
Thermal desorption gas chromatography with mass spectrometry study of outgassing from polymethacrylimide foam (Rohacell®)
2015
Polymethacrylimide foams are used as light structural materials in outer-space devices; however, the foam closed cells contain volatile compounds that are outgassed even at low temperatures. These compounds ignite as plasmas under outer-space radiation and the intense radio-frequency fields used in communications. Since plasmas may cause spacecraft fatal events, the conditions in which they are ignited should be investigated. Therefore, qualitative and quantitative knowledge about polymethacrylimide foam outgassing should be established. Using thermogravimetric analysis, weight losses reached 3% at ca. 200°C. Thermal desorption gas chromatography with mass spectrometry detection was used to…
The comparison of seven different methods to quantify the amorphous content of spray dried lactose
2006
The purpose of this work was to verify the usefulness, advantages and disadvantages of seven methods that are widely used to detect, and quantify the amorphous contents in pharmaceutical solids. Here, StepScan DSC, a type of modulated temperature calorimetry method, was applied for the first time to quantify amorphicity. The comparison of the analytical methods was undertaken with real (non-artificial) test samples, i.e. spray-dried lactose samples with various degrees of crystallinity. In these samples, it was essential that the amorphous and the crystalline portions are not present as separate particles, which is the case when physical (artificial) mixtures of totally amorphous and totall…
Synthesis, characterization and study of covalently modified triazole LAPONITE® edges
2020
Abstract LAPONITE® (Lap) clay mineral was successful functionalized by triazole groups in a two steps procedure. First, the Lap edges were modified with 3-azidopropyltrimethoxysilane by traditional heating and microwave irradiation. Microwave irradiation allowed us to obtain high loading onto the Lap edges in lower times compared to those obtained through conventional method. Afterwards, the triazole moieties were obtained by reaction between azido functionalized Lap and propargyl alcohol. The successful functionalization of Lap was proved by thermogravimetric analysis, FT-IR spectroscopy, dynamic light scattering and ζ-potential measurements. Finally, the effects of the surface modificatio…
Why does vacuum drive to the loading of halloysite nanotubes? The key role of water confinement.
2019
The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the…
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…
Tuning of the Mg Alloy AZ31 Anodizing Process for Biodegradable Implants
2021
Coatings were grown on the AZ31 Mg alloy by a hard anodizing process in the hot glycerol phosphate-containing electrolyte. Anodizing conditions were optimized, maximizing corrosion resistance estimated by impedance measurements carried out in Hank's solution at 37 °C. A post anodizing annealing treatment (350 °C for 24 h) allowed us to further enhance the corrosion resistance of the coatings mainly containing magnesium phosphate according to energy-dispersive X-ray spectroscopy and Raman analyses. Gravimetric measurements revealed a hydrogen evolution rate within the limits acceptable for application of AZ31 in biomedical devices. In vitro tests demonstrated that the coatings are biocompati…