Thermodynamic restrictions on mechanosynthesis of strontium titanate

Monteiro, J.F.; Ferreira, Antônio Alves; Antunes, I.; Fagg, Duncan P.; Frade, J.R.

doi:10.1016/j.jssc.2011.10.044

Cited by 11 publications

(10 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Chemical-potential diagrams were plotted as described elsewhere. [53][54][55] These diagrams were used as thermodynamic guidelines for the relevant ternary system ZrO 2 -BaO-O 2 (Fig. 14) to assess conditions required for reactivity.…”

Section: Thermodynamic Analysismentioning

confidence: 99%

Enhanced BaZrO₃ mechanosynthesis by the use of metastable ZrO₂ precursors

et al. 2014

Self Cite

View full text Add to dashboard Cite

The current work assesses the impact of structural differences between stable and metastable ZrO2 precursors on the mechanochemical preparation of BaZrO3. Monoclinic (m-ZrO2) and tetragonal (t-ZrO2) zirconia polymorphs were prepared without stabilizing additives by slow alkaline precipitation. High-energy milling of the individual ZrO2 precursors induced different partial transformations in each case. The as-synthesized m-ZrO2 powders showed partial conversion to the tetragonal polymorph on mechanical activation, reaching about 10% t-ZrO2 after 420 min accompanied by increases in strain. In contrast, the as synthesized t-ZrO2 powders underwent the inverse transformation to the monoclinic phase, producing about 50% m-ZrO2 after 120 min with the liberation of strain. The t-ZrO2 precursor was shown to exhibit the higher reactivity with barium peroxide, yielding significantly earlier formation of barium zirconate under room-temperature mechanosynthesis. The progress of the mechanochemical formation of BaZrO3 has been discussed with respect to the differing behaviour of the ZrO2 precursors upon mechanical activation and associated thermodynamic perspectives.

show abstract

Section: Thermodynamic Analysismentioning

confidence: 99%

Enhanced BaZrO₃ mechanosynthesis by the use of metastable ZrO₂ precursors

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…The thermodynamic analysis of Fe‐Si‐C‐O system was based on the activity diagrams as proposed by Yokokawa and applied to a variety of systems and cases, including the complex chemistry of cementitious materials, mechanosynthesis of strontium titanate, and CO 2 ‐resistance of materials for electrochemical applications . The method is based on the derivation of representative reactions for 2‐phase equilibria, and then extracting the relevant values of p(O 2 ), a Fe : a Si activity ratio, or a Fe : a Si vs p(O 2 ), from the relevant mass action constant (see Supporting Information, pages S4‐S5, for details).…”

Section: Methodsmentioning

confidence: 99%

Synthetic fayalite Fe₂SiO₄ by kinetically controlled reaction between hematite and silicon carbide

et al. 2019

View full text Add to dashboard Cite

The present work explores the preparation of fayalite α‐Fe2SiO4, the iron‐rich end‐member of the olivine solid‐solution series, as a tar removal catalyst for biomass gasification. The synthetic procedure was developed starting from the stoichiometric mixture of hematite and micrometer size silicon carbide and employing thermal treatments in controlled atmospheres at 1000‐1100°C supported by thermodynamic modeling to assess the required redox conditions. The treatments in dry and humidified inert gas yielded phase mixtures containing metallic Fe as one of the main phases, thus emphasizing a shortage of oxygen supply. XRD and TGA studies of precursor mixtures on heating in dry CO2 demonstrated a multistep mechanism of the overall reaction including (a) fast reactivity between silicon carbide and hematite at ~920°C with formation of metallic Fe and amorphous silica followed by (b) formation of fayalite involving oxygen supplied in the form of CO2 and competing with (c) over‐oxidation to thermodynamically favorable Fe3O4+SiO2 mixture. Comparative studies of reactivity in powdered and pelletized samples emphasized the importance of the kinetic factor in the formation of Fe2SiO4 while preventing further oxidation. The preferential formation of fayalite in the CO2 atmosphere is shown to be favored by shorter treatments of compacted samples at higher temperatures. The procedure was designed (2‐step heating to 1100°C in CO2 followed by fast cooling) for the preparation of pelletized fayalite α‐Fe2SiO4 catalyst with only minor traces of surface over‐oxidation which can be suppressed by adding 10 vol.% of forming gas to CO2 flow.

show abstract

“…In contrast, the STF25 materials showed phase stability, with no secondary phases detected after syngas annealing at 600 °C. The [44], [45] and apparently the Ruddlesden-Popper-like phases show superior stability in such conditions.…”

Section: Annealing Of Stcf In Syngasmentioning

confidence: 99%