Search Results
Abstract
The interactions of CO with a high specific surface area tin dioxide was investigated by FTIR spectroscopy and thermogravimetric analysis. FTIR study of CO interactions have shown that CO can adsorb on cus (coordinatively unsaturated sites) Sn4+ cation sites (band at 2201 cm-1). In addition, CO reacts with surface oxygen atoms. This leads to the partial reduction of SnO2 surface and to the formation of ionised oxygen vacancies together with the release of free electrons, which are responsible for the loss of transmission. Formed CO2 can chemisorb on specific surface sites: on basic sites to form carbonates species and on acidic sites (Sn4+-CO2 species) which is in competition with the formation of Sn4+-CO species. TG experiment have shown that the reduction of SnO2 by CO at 400°C occurs in two steps. First, the reduction of SnO2 surface, which is a quick phenomenon. This has allowed to evaluate that more than 12% of reducible surface oxygens can react with CO, essentially because of the presence of a large amount of surface hydroxyl groups. The second step of the reduction of SnO2 would be the progressive reduction of SnO2 bulk by the slow diffusion of oxygen atoms from the bulk to the surface.
Summary
The Iron Age ceramic technology used in the manufacturing of cooking pots was studied by thermo-FTIR spectroscopy analysis. The pottery was excavated at Tel Hadar on the eastern shore of the Sea of Galilee. The results demonstrate that the cooking pots were manufactured using noncalcareous or slightly calcareous raw material proceeds from soil. The firing was at about 750-850C and the cementation to ceramic was obtained by low temperature sintering of the clay. The use of soil raw material composed of smectitic (montmorillonitic) clay enabled the low temperature sintering. The clay from soil is relatively poorly crystallized and rich in natural iron oxide, both of which induce earlier sintering. Most of the cooking pots were tempered with broken pieces of large calcite crystals that were added to the clayey raw material from an additional source. Alternative tempering with limestone particles composed of polycrystalline calcite is inappropriate as it brings about earlier and intense decarbonation during the firing, which causes defects in the pots.
been found. Furthermore, the crystallisation process detected using FTIR spectroscopy was observed to be sharper than the corresponding exotherm observed using DSC. This observation was interpreted in terms of reduced thermal lag in the ATR cell due to
Partial thermal reduction of ammonium paratungstate tetrahydrate
Evolved gas analysis (TG/DTA-MS) and solid state studies (XRD, FTIR)
Abstract
Thermal decomposition of ammonium paratungstate tetrahydrate, (NH4)10[H2W12O42]4H2O has been followed by simultaneous TG/DTA and online evolved gas analysis (TG/DTA-MS) in flowing 10% H2/Ar directly up to 900C. Solid intermediate products have been structurally evaluated by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained exothermic heat effect has been detected at 700–750C. On the basis of TG/DTA as well as H2O and NH3 evolution curves and XRD patterns, it has been assigned to the formation and crystallization heat of γ-tungsten-oxide (WO2.72/W18O49) from β-tungsten-oxide (WO2.9/W20O58) and residual ammonium tungsten bronze.
Chemically modified acidic alumina T stationary phases have been prepared by organosilylation with the trifunctional organosilicon compounds n -octadecyltrichlorosilane, 3-mercaptopropyltri-methoxysilane, and N -(2-aminoethyl)-3-aminopropyltrimethoxysilane. These chemically modified phases were characterized by elemental analysis, measurement of specific surface area, FTIR spectroscopy, 13 C CP/MAS NMR spectroscopy, mass spectrometry, and thermal analysis. The TLC behavior of unmodified and chemically modified acidic alumina T has been tested by separation and identification of some dyes and benzo[ a ]pyrene derivatives.
Abstract
This work describes the experimental determination of sucrose hydrolysis kinetics using a heterogeneous catalyst. We used an Amberlite IR-120 strong acidic cation-exchange resin. The experiments were performed under previously determined optimal process conditions: sucrose mass concentration, γ S = 50 g L−1, catalyst mass concentration, γ C = 180 g L−1, rotational frequency of the stirrer f m = 180 min−1, and temperature ϑ = 79 °C. The parameters of the supposed kinetic model were determined using experimental data. The kinetics of sucrose hydrolysis over Amberlite IR-120 has not been reported to date. Therefore, we could not directly compare the calculated values of kinetic parameters with those from the literature. However, the calculated values are within the range of values determined by other types of catalysts. Furthermore, we investigated the influence of catalyst mass concentration γ C on the reaction rate constant k′.
Abstract
A series of calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials were prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C–S–H from aqueous solution. The as-synthesized C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The XRD analysis of C–S–HPN materials suggest the intermediate organizations presenting intercalation of PAA within C–S–H and exfoliation of C–S–H. The SEM micrographs of C–S–H, PAA and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. The effect of the material’s composition on the thermal stability of a series of C–S–HPN materials along with PAA and C–S–H were studied by TG, DTA and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.
Abstract
Several calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials have been prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C-S-H from aqueous solution. The synthetic C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS), thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC). The XRD peaks of C–S–HPN materials suggest the intermediate organizations presenting both intercalation of PAA and exfoliation of C–S–H. The SEM images of C–S–H and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. Effects of the material compositions on the thermal stability of series of C–S–HPN materials along with PAA and C–S–H has been studied by TG, DTG and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.
TG curves of ( a ) Cu-MMT, ( b ) Ca-MMT, ( c ) Co-MMT FTIR spectroscopy FTIR spectral data of the cation exchanged-montmorillonites are summarized in Table 2 . Several peaks was
Summary Inclusion complexation between dimethyl-β-cyclodextrin and a very poorly water-soluble serum lipid-regulating agent, gemfibrozil, was studied. Products were prepared by several methods (physical mixing, kneading, spray-drying and ultrasonic treatment) in four different molecular ratios (2:1, 1:1, 1:2 and 1:3). The possibility of complex formation between the drug and the host molecule was studied by thermal analysis. Supplementary techniques, such as Fourier transformation-infrared spectroscopy and X-ray diffractometry, were also applied to interpret the results of thermal study of the products.
