Authors:M. Bernardi, S. Rojas, M. Andreeta, A. de Rastelli, A. Hernandes, and V. Bagnato
The structural and thermal properties of three different dental composite resins, Filtek™ Supreme XT, Filtek™ Z-250 and TPH®3 were investigated in this study. The internal structures of uncured and cured resins with blue light-emitting diodes (LEDs)
were examined by Micro-Raman spectroscopy. Thermal analysis techniques as DSC, TG and DTG methods were used to investigate
the temperature characteristics, as glass transition (Tg), degradation, and the thermal stability of the resins. The results showed that the TPH®3 and Filtek™ Supreme XT presented very similar Tg values, 48 and 50°C, respectively, while the Filtek™ Z-250 composite resin presented a higher one, 58°C. AFM microscope was
utilized in order to analyze the sample morphologies, which possess different fillers. The composed resin Filtek™ Z-250 has
a well interconnected more homogeneous morphology, suggesting a better degree of conversion correlated to the glass phase
transition temperature. The modes of vibration of interest in the resin were investigated using Raman spectroscopy. It was
possible to observe the bands representative for the C=C (∼1630 cm−1) and C=O(∼1700 cm−1) vibrations were studied with respect to their compositions and polymerization. It was observed that the Filtek™ Z -250 resin
presents the best result related to the thermal properties and polymerization after light curing among the other resins.
Authors:N. Buzás, M. Pujar, L. Nagy, A. Vértes, E. Kuzmann, and H. Mehner
Dibenzyltin(IV) complexes of carbohydrate derivatives were prepared and studied by Mössbauer and FTIR spectroscopy and by thermogravimetry. The Mössbauer studies indicated that the reaction between dibenzyltin(IV)-dichloride and sugar-type ligands led to reaction products containing tin(IV)-oxide. beside the dibenzyltin(IV) sugar complex. These two type of species were shown to be in weak interaction. Comparison of the experimental quadrupole splitting values with those calculated on the basis of the partial quadrupole splitting concept revealed the steric arrangements of the coordination sphere of tin(IV) in the sugar complexes.
Authors:Cynthia Ferrari, Maria Baccia, A. Ibanez, and A. Hernandes
Pure Er:YAB (Er:YAl3(BO3)4) nanometer-sized crystalline powder was produced from low cost chemical route, the polymeric precursor method. The initial
homogeneous solutions were heat treated from 200 to 700°C under oxygen atmosphere and the unique crystalline phase was synthesized
at around 1150°C. The thermal treatments and the initial stoichiometry play a very important role on the Er:YAB preparation.
The thermal events of amorphous precursor resins and the crystallization process up to phase formation were investigated.
Zirconium phosphate-phosphite have various structure belonging to the drying heat of the sample. While sample dried above sat. NaCl solution had interlayer distance of 1.30 nm (result fromd1=0.74 nm andd2=0.56 nm for phosphite layer), the sample dried under IR lamp on air having interlayer spacingd=0.74 nm charactderistic for -Zr(HPO4)2·H2O containing little amount of phosphite groups. The composition of the first sample can be characterized by chemical formula, as Zr(HPO4)0.7(HPO3)1.3· ·0.5H2O. The X-ray powder diffraction data ofn-butylamine intercalate suggest that in the process take place only the phosphate region of zirconium phosphate-phosphite (ZrPP).
The pseudobinary systems ACl−FeCl3 (A=Na, K, Rb, Cs) were reinvestigated by means of differential thermal analysis and X-ray powder diffraction. The existence
of the compounds AFeCl4 (A=Na−Cs) and Cs3Fe2Cl9 could be confirmed; Cs3Fe2Cl9 is a stable compound which decomposes to CsCl and CsFeCl4 above 270°C. Additionally, two Rb-compounds—Rb3FeCl6 and Rb3Fe2Cl9—were found, which decompose, when heated, in the solid state. Rb3Fe2Cl9 is isotypic with the analogous Cs-compound; Rb3FeCl6 has the Cs3BiCl6 structure. Cs3FeCl6 is isotypic with Cs3CrCl6, a recently found orthorhombic variant of the elpasolite type.
Authors:D. Tsotcheva, T. Tsanov, L. Terlemezyan, and S. Vassilev
Structural studies of powdered polyaniline (PANI) prepared in aqueous medium by the oxidative polymerization of aniline in the presence of dodecylbenzenesulfonic acid(DBSA) were performed by means of DSC and WAXS. The influence of the alkyl side-chains on the structure and crystallinity of the as-synthesized PANI—DBSA and on the structural transitions taking place in PANI upon washing and heating were investigated. It was found that DBSA induces crystallinity in the rigid matrix of PANI, and residual crystalline phases were also observed after the deprotonation of PANI—DBSA. For the first time, a melting peak and a relaxation transition of non-cross-linked PANI were registered.
Authors:M. Niculescu, N. Vaszilcsin, M. Bîrzescu, P. Budrugeac, and E. Segal
The results of an investigation concerning there action between 1,2-propanediol and Co(NO3)2⋅ 6H2O, leading to a complex containing the lactate anion (L) as ligand are presented. The obtained solid homopolynuclear coordination compound[Co2(OH)2L2(H2O)2⋅0.5H2O]n, has been investigated by thermal analysis, electronic and IR spectroscopy and magnetic methods. Cobalt oxide obtained by
thermal decomposition of this coordinative compound was characterized by IR and X-ray spectroscopy.