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By means of simultaneous DTA-, TG- and DTG-technique, the silicate gels and the MFI crystals obtained from these gels have been investigated. The gels have been prepared in presence and in absence of tetrapropylammonium cation (TPA+) and with Li+, Na+, NH4 + and K+ fluorides. In absence of TPA+ no thermal effects have been observed in Li+- and Na+-gels. The effects observed in the NH4 + -gel stem from a decomposition and release of inorganic phases: SiF4, NH4F, NH3. The DTA/DTG effects in the TPA+ containing gels and in the MFI crystals of monodisperse size are attributed to the decomposition of TPA+ cation. It can be concluded from these effects that the interaction between the gels and the TPA+ cation is rather weak. The interaction between TPA+ and MFI crystals obtained in fluoride medium is stronger than the interaction with crystals obtained from alkaline media. Similar thermal effects are obtained after grinding the long crystals to those having a large distribution of crystal sizes.

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Abstract  

A non-destructive activation analytical method developed for the determination of the axial concentration distributions of Al, Si and K residual additives in sintered tungsten rods is briefly described. A 14 MeV neutron generator is used to produce the reactions27Al(n, p)27Mg,28Si(n, p)28Al and39K(n, 2n)38K and the activities are compared with standards. A weighted least-squares fitting program is used for peak area determination of the scintillation spectra. A scheme of the irradiating and measuring arrangement with a pneumatic sample-transfer system is presented. The system is applicable to large-scale routine analysis and lends itself well to automation. The results of preliminary measurements with this arrangement are given.

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Summary The ETS-10 is a newly formed titano-silicate the structure of which was resolved thanks to the XRD, EDS, HREM and mass NMR. The ETS-10 is a potentially good catalyst. The aim of this research is to study the physicochemical properties of ET(Zr)S-10 obtained from a gel containing different amounts of Zr. The analyses used are XRD, thermal analysis (TG-DSC), SEM, and 29Si NMR.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
A. Szorcsik
,
L. Nagy
,
B. Gyurcsik
,
Gy. Vankó
,
R. Krämer
,
A. Vértes
,
T. Yamaguchi
, and
K. Yoshida

Abstract  

A number of dibutyltin(IV) complexes of polyhydroxyalkyl carboxylic acids (O donor atoms) and amino acids (O,N donor atoms) were prepared in the solid state. The binding sites of the ligands were determined by means of FT-IR, Raman and 13C NMR spectroscopy. Partial quadrupole splitting calculations were utilized to determine the coordination geometry around the Sn(IV) centre by means of Mössbauer measurements. The results showed that in the solid state oligomeric complexes are formed, with the -COO- groups as bridges between the organometallic cations. The {Sn} atoms are mostly in trigonal bipyramidal surroundings. The Sn-O and Sn-C bond distances were determined by EXAFS measurements to be 207-234 and 295 pm, respectively. Evaluation of the pH-metric and NMR titration curves in Me2Sn(IV)-D-gluconic acid system revealed that the equilibria in aqueous solution are fairly complicated. In acidic solution, the formation of 1 : 1 and 1 : 2 -COO- coordinated species predominate, but deprotonation of the alcoholic -OH groups also starts at very low pH. In the pH range 5-9, NMR provides experimental evidence of ligand-exchange reactions without pH-metrically detectable proton release. In alkaline solution, further deprotonation processes occur, resulting in either alkoxo or mixed hydroxo complexes. The carboxylate coordination is expected for the amino acid ligands but the shift of the νN-H stretching vibrations in the FT-IR spectra demonstrated that the ammine group also binds to the metal ion in the solid Bu2Sn(IV)complexes.

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Abstract  

Solvent and melt techniques were used to obtain molecular dispersion of the poorly soluble spironolactone (SPIR) model drug enhancing its dissolution rate. DSC study of the interaction between SPIR and hydroxypropyl-β-cyclodextrin confirmed the need for molecular dispersion if their complexation is required. Solvent-free twin-screw extrusion was suitable for forming inclusion complex significantly below the melting temperature of the SPIR. According to DSC, Raman and XRPD results fine dispersion of both components was achieved in a hydrophilic polymer. The molecules of the active ingredient are separated from each other in the polymer and the lack of the lattice energy causes faster dissolution.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
E. Tóth
,
F. Deák
,
Cs. Gyurkócza
,
Zs. Kasztovszky
,
R. Kuczi
,
G. Marx
,
B. Nagy
,
S. Oberstedt
,
L. Sajó-Bohus
,
Cs. Sükösd
,
G. Tóth
, and
N. Vajda

Abstract  

For the public, indoor radon is the main source of exposure from ionizing radiation. Radon gas originates from the radioactive decay chain of uranium deposited in rocks or in building materials. In the reviews mostly a rather steady radon exhalation has been assumed. In a village of North-East Hungary, however, high radon concentrations have been measured, differing strongly in neighbouring houses and varying in time, due to the interplay of several geochemical phenomena.

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