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A series of coprecipitates of basic cobalt carbonate and hydrated titanium oxide were investigated by TG and DTA up to 1000°. In the absence of water and CO2, an oxide system is obtained consisting of Co3O4 and TiO2, from which cobalt metatitanate is first formed; from the latter, depending on the presence of TiO2 or Co3O4 in the system, the dititanate or the orthotitanate is formed. IR absorption and X-ray spectra and TG and DTA curves prove that the double oxides of cobalt and titanium are obtained in this manner at temperatures lower than in other methods; this gives them useful properties for practical applications.

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Journal of Thermal Analysis and Calorimetry
Authors:
E. Jóna
,
K. Nemčeková
,
A. Plško
,
D. Ondrušová
, and
P. Šimon

Abstract  

To evaluate the thermal stability of oxide glasses, various criteria have been used. Not only the simple parameters, as characteristic temperatures and values of activation energy and enthalpy changes, but also the combined criteria E/RTp and kf(T) have been taken into account. Three glasses with the composition of Li2O·2SiO2 (a), Li2O·2SiO2·0.03TiO2 (b) and Li2O·2SiO2·0.1TiO2 (c) were prepared and the validity of the criteria was tested by applying them to these glasses. The results indicate that the sequence thermal stability of the studied glass system vs. crystallization depends not only on their composition but also on the used criteria.

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Summary  

Modification of the physico-chemical properties of hydrous titanium dioxide (TiO2) was conducted by using binding polyacrylonitrile (PAN) for the preparation of larger size particles having higher granular strength. The thermal behavior of the obtained composite has been studied by thermogravimetric and differential thermal analysis (TG/DTA). Sorption behavior of the TiO2-PAN composite for removal of some hazardous radionuclides has been studied at different conditions such as, pH, contact time, ion concentrations and reaction temperature as well as the drying temperature. The effects of interfering ions as well as some complexing agents on the distribution ratio of the sorption process have been determined. As a result of the obtained data the optimum conditions for the removal of the studied radionuclides were recommended.

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Abstract  

Synthesis of potassium bismuth titanate ferroelectric by heating of mixtures prepared using oxide precursors, i.e. Bi2O3, TiO2 and K2CO3 was investigated. DTA, TG, XRD and SEM methods were used to study the formation of intermediate compounds and the final product. Usage of associated homogenization and grinding of precursors mixture permits to decrease the temperature of formation of K0.5Bi0.5TiO3.

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Abstract  

Emanation Thermal Analysis (ETA) was used to characterize microstructure changes of hydrous ruthenia and hydrous ruthenia-titania as precursors for preparation of RuO2 and (RuO2)0.9-(TiO2)0.l by heating in the temperature range of 20–600C in argon. A good agreement was found between ETA, TG and DTA results, X-ray diffraction patterns and surface area measurements of intermediate products of the thermal treatment.

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Abstract  

Radiation treatment with gamma-rays was used to improve the biodegradability of EDTA that is known to be a non-biodegradable substance. The effect of metal ions and catalysts on the treatment of EDTA was studied first. The removal of EDTA was definitely decreased in the presence of metal ions such as Cr(III), Cd(II), Pb(II) and Cu(II) at doses greater than 3 kGy. The addition of a TiO2

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Abstract  

PET with 68Ga from the TiO2- or SnO2- based 68Ge/68Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity (68Ge vs. 68Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of 68Ge activity is produced by eluting the 68Ge/68Ga generators and residues from PET chemistry. Since clearance level of 68Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce 68Ge activity in solution from >10 kBq/g to <10 Bq/g; which implies the solution can be discarded as regular waste. Most efficient method to reduce the 68Ge activity is by sorption of TiO2 or Fe2O3 and subsequent centrifugation. The required 10 Bq per mL level of 68Ge activity in waste was reached by Fe2O3 logarithmically, whereas with TiO2 asymptotically. The procedure with Fe2O3 eliminates ≥90% of the 68Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate 68Ge activity sorption on TiO2, Fe2O3 or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore 68Ge activity containing waste could directly be used without further interventions. 68Ge activity containing liquid waste at different HCl concentrations (0.05–1.0 M HCl), was recirculated at 1 mL/min. With Zeolite in the recirculation system, 68Ge activity showed highest sorption.

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Abstract  

The interactions between titanium dioxide, niobium pentoxide and tantalum pentoxide and 55 elements have been studied by batch experiments in nitric acid. The variation of the distribution ccefficients with nitric acid concentration is presented and discussed. The adsorption mechanism for some ions has also been investigated. Column experiments have been carried out to check the practical use of the investigated oxides in radiochemical separations. A99mTc generator based on the use of TiO2 is also presented.

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Thermal properties of oxide glasses

Part II. Activation energy as a criterion of thermal stability of Li2O·2SiO2·nTiO2 glass systems against crystallization

Journal of Thermal Analysis and Calorimetry
Authors:
E. Jóna
,
P. Šimon
,
K. Nemčeková
,
V. Pavlík
,
G. Rudinská
, and
E. Rudinská

Abstract  

Three glasses with the composition of Li2O⋅2SiO2 (a), Li2O⋅2SiO2⋅0.03TiO2 (b) and Li2O⋅2SiO2⋅0.1TiO2 (c) were prepared and the relationship between structural and kinetic parameters of thermal stability vs. crystallization has been studied by X-ray diffraction, IR spectra and thermal analysis. The XRD patterns proved the presence of lithium metasilicate as a primary crystalline phase which subsequently transformed to lithium disilicate where the transformation is supported by the presence of TiO2. The order of thermal stability vs. crystallization of studied glass systems based on the results of XRD is (a)<(b)<(c). The same order was obtained from the values of activation energy. It has been shown that the values of activation energies obtained from the Ozawa and Kissinger methods are equivalent and that the Kissinger method should be used to obtain the activation energy from the dependence of the maximum peak temperature on the heating rate. It has been discussed that the activation energy represents only an incomplete description of the kinetics of the crystallization process.

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Abstract  

The hydroxide, oxalate and citrate precursors of the metal oxides such as γ-Fe2O3, (MnZn)Fe2O4, Cu(K)Fe2O4, BaTiO3, La(Sr)MnO3, La(Sr)AlO3, La/Gd(Ca/Ba/Sr)CoO3, and anatase TiO2 on modifications with the hydrazine decompose at low temperatures give single phase oxides of superior properties, while the complexes without such modification require higher temperatures for achieving the phases. The hydrazine released at lower temperatures reacts with the oxygen in the atmosphere, N2H4+O2→N2+2H2O; ΔH=−625 kJ mol−1, and liberates enormous energy that is sufficient for the oxidative decomposition of the complexes now devoid of hydrazine. Such extra energy is not available in the case of the precursors without such modifications. The reaction products of hydrazine oxidation provide desired partial pressure of moisture needed for the stabilization of γ-Fe2O3. Also, the nitrogen that is formed in the reaction of hydrazine with oxygen gets trapped in the lattice of TiO2 giving yellow color nitrogen doped TiO2−xNx photocatalyst. Thus, hydrazine method of preparation has many advantages in the preparation of metal oxides of superior properties.

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