Authors:F. Pavan, S. Gobbi, T. Costa, and E. Benvenutti
FTIR thermal analysis was used for a hybrid xerogel, anilinepropylsilica, obtained from three different organic precursor
amounts, using HF and NaF as catalysts in the sol–gelprocess. The aniline ring vibrational mode at 1500 cm−1 of attached aniline groups was used to obtain the relative aniline content in the xerogel materials after being submitted
to thermal treatment in the temperature range from 100 to 400C. This technique allowed to evaluate the thermal stability
of organic phase. The organic coverage on the surface and the fraction of trapped organic groups in closed pores can also
Authors:P. Melnikov, R. Rolim, A. Delben, J. Delben, A. Souza, and A. Job
Xerogels were prepared from zirconium, barium, aluminum, lanthanum and lithium acetates, corresponding to a Li containing ZBLA composition. The study of their thermal properties (DSC, TG/DTG, FT-IR) showed that they might be used as chemically stable precursors in the preparation of fluoride glasses. Hydrofluoric acid in solution was chosen as a mild fluorinating agent. This newly proposed technique of fluorinating allowed to obtain high quality ZBLALi glass which presents the advantage of higher thermal stability and homogeneity in comparison with the glass obtained using individual commercial fluorides.
Authors:J.-H. Hong, J. Min, G.-H. Guo, and K.-L. Zhang
The Eu tris(dibenzoylmethanato)phenanthroline
complex doped xerogel has been synthesized by a catalyst-free sol-gel roure.
The non-isothermal kinetic analysis is calculated by Friedman isoconversional
method and multivariate non-linear regression method. The overall decomposition
process below 600C is fitted by an Fn model (n
order reaction), corresponding to the dehydration of the matrix, and a two-step
consecutive reaction of Cn model (n order
autocatalytic reaction), corresponding to the decomposition of organic complex.
Correlation coefficient is 0.99986. The lifetime values of xerogel, defined
as the 5% decomposition of europium organic complex, indicate that the xerogel
can find application at near room temperature.
Authors:I. Oja Açik, J. Madarász, M. Krunks, K. Tõnsuaadu, D. Janke, G. Pokol, and L. Niinistö
Thermal decomposition of precursor xerogels for TiO2,
obtained by gelling of acetylacetonate-modified titanium(IV) tetraisopropoxide
(prepared at Ti-alkoxide:acetylacetone molar ratios of 1:1 (Ti-1) and 1:2
(Ti-2)) in boiling 2-methoxyethanol, was monitored by simultaneous TG/DTA/EGA-MS
and EGA-FTIR measurements. Thermal degradation processes of Ti-1 and Ti-2
in the temperature range of 30–700C consist of six mass loss steps,
the total mass loss being 46.3% and 54.4%, respectively. EGA by FTIR and MS
revealed release of H2O below 120C; followed by
evolution of acetone and acetic acid between approximately 100 and 320C,
and that of CO2 up to 560C. Acetylacetone is evolved
to a significant extent from sample Ti-2 at 120–200C.
Authors:G. Dell’Agli, G. Mascolo, M. C. Mascolo, and C. Pagliuca
Summary Mechanical mixtures containing zirconia xerogel and increasing amount of crystalline yttria up to 40 mol%, were hydrothermally treated by microwave route at 110°C for 2h. All the treatments were performed in the presence of (KOH+K2CO3) mineralizer solution at concentration 0.2 M. Amorphous and hydrated ZrO2-Y2O3 solid solutions with yttria content up to 33.3 mol% (corresponding to Zr/Y molar ratio equal to 1), resulted after the hydrothermal treatments. A remarkable reduction of the surface area has been detected at increasing yttria content of the amorphous phases with a corresponding increase of the exothermic peak of crystallization. A mechanism of reaction for the formation of the amorphous solid solutions has been proposed.
Authors:Viacheslav V. Avdin, Igor V. Krivtsov, Vitaly V. Dyachuk, and Dmitry A. Zherebtsov
zirconium oxyhydroxide and polysilicic acid upon features of phase transitions of prepared samples under thermal treatment.
The composite xerogels have been obtained as adsorbents for
Authors:Ilona Acik, J. Madarász, M. Krunks, K. Tõnsuaadu, G. Pokol, and L. Niinistö
Thermal decomposition of dried crystalline powder obtained from titanium(IV) bis(acetylacetonate) diisopropoxide (75% solution
in 2-propanol) (1) was monitored by simultaneous TG/DTA, EGA-FTIR and EGA-MS measurements and the results were compared with those of amorphous
powder obtained by gelling of acetylacetonate-modified titanium(IV) tetra-isopropoxide at molar ratio of 1:2 in boiling 2-methoxyethanol
(2). Thermal degradation of 1 in the temperature range of 25–700°C consists of 5 steps with a total mass loss of 62.5%. EGA by FTIR and MS revealed the
release of H2O below 120°C; followed by an intensive evolution of acetylacetone around 245°C. The release of acetone and acetic acid occurs
up to 270°C and that of CO and CO2 up to 530°C.
Authors:A. Kyritsis, A. Spanoudaki, C. Pandis, L. Hartmann, R. Pelster, N. Shinyashiki, J. C. Rodríguez Hernández, J. L. Gómez Ribelles, M. Monleón Pradas, and P. Pissis
spectroscopy (DRS), to follow dielectric relaxations, both the segmental (primary) α relaxation associated with the glass transition and secondary relaxations, in the dry nanocomposites (xerogels), and to conclude on effects of silica on polymer dynamics and
Authors:V. Logvinenko, V. Bakovets, and L. Trushnikova
composition Ni(OH) 2 , obtained after the isothermal dehydration at 500 K, in fact, can be attributed to two-phase xerogel (NiO + Ni(OH) 2 ·H 2 O) [ 1 ].
A quantitative description of the decomposition kinetics for
Thermal reactions of model phospho-silicate gels of simple composition has been studied. The investigations demonstrate that
the kind of compounds introducing P2O5 into the gel silicate network, H3PO4, PO(OC2H5)3, POCl3 influence the course and temperature and the xerogel formation. The amount of interstitial water and xerogel porosity is
dependent on the cations, amorphous structure modifiers (Ca, Na) used. Thermal analysis curves appear the convenient carriers
of informations about the processes in gel pores and the formation of xerogel and glass.