V. Š. Fajnor

Differential thermal analysis of montmorillonite

The paper provides an overview of publications on the DTA of montmorillonites (in the temperature range 20–1100°C), starting with the first experiments of Le Chatelier (1887) and ranging up to the present. Consideration is given to the dehydration, dehydroxylation, amorphization and rehydration of montmorillonite (42 references).

Thermal Stability of Clay/organic Intercalation Complexes

The comparison of thermal stabilities of different organoclay intercalation complexes is presented in this work. Montmorillonite/monomer and montmorillonite/polymer intercalation complexes with similar basal spacings show a pronounced difference in changes of d001 values after 30 min heating. The hydrophilic and/or organophilic surface modification of the starting montmorillonite is an important factor affecting the intercalated amount of organic material and thus the expansion of the sheet silicate structure.

Vavilov-Cherenkov radiation emitted by heavy ions near the threshold

Abstract The Vavilov–Cherenkov radiation (VChR) emitted by the heavy ions 79 Au was studied by the photography method. The photographs of the radiation near and below the VChR threshold are published for the first time.

Effect of degradation of montmorillonite by vibration grinding on the dTA curves in the range 20–1500°C

The effect of vibration grinding on the DTA curves of montmorillonite isolated from the most important locality of bentonite in the Slovak Republic (Jelšovy potok, Middle Slovakia) was studied in the temperature range 20–1500°C. Interpretation is offered for 6 endothermic and 3 exothermic peaks. vibration grinding modified the course of dehydration of the mineral, suppresses the “dehydroxylation’ peak at 700°C, enables the crystallization of high-temperature quartz, cristobalite and cordierite at lower temperatures in comparison with unground natural montmorillonite. Vibration griding slows down the crystallization of mullite which—unlike quartz, cristobalite and cordierite—does not belong to high-temperature phases of Cheto-montmorillonite. The order in which these high-temperature phases occur is not influenced by vibration grinding.ZusammenfassungIm Temperaturbereich 20–1500°C wurde der Effekt von Vibrationsmahlen auf DTA-Kurven von Montmorillonit untersucht, welches aus den bekanntesten Bentonit-Vorkommen der Slowakischen Republik (Jelšovy potok, Mittelslowakei) isoliert wurde. Für 6 endotherme und 3 exotherme Peaks wurde eine Interpretation vorgeschlagen. Vibrationsmahlen verändert den Weg der Dehydratation des Minerals, unterdrückt im Vergleich zu ungemahlenem natürlichen Montmorillonit den “Dehydroxylierungs”-Peak bei 700°C und ermöglicht die Kristallisation von Hochtemperatur-Quarz, Cristobalit und Kordierit bei niedrigeren Temperaturen. Vibrationsmahlen verlangsamt die Kristallisation von Mullit, welches—im Gegensatz zu Quarz, Cristobalit und Kordierit—nicht zu den Hochtemperatur-Phasen von Cheto-Montmorillonit gehört. Die Reihenfolge, in der diese Hochtemperatur-Phasen vorkommen, wird durch Vibrationsmahlen nicht beeinflußt.

Calcination of SiO2-AEROGEL in oxidizing atmosphere

Differences in mass loss occurring in the course of dynamic and isothermal heating of SiO2-aerogel and changes of specific surface and hydrophylicity during calcination were studied by thermal analysis. SiO2-aerogel was prepared from tetramethoxysilane (TMOS) hydrolyzed by ammonia solution at 0°C with molar ratio TMOS: H2O:NH4OH 4:1:0.01. Differences are caused mainly by oxidation of organic matter and by diffusion of products of the oxidation. Heat transfer has none or little effect on the differences. Samples calcined at temperatures about 300°C reach maximum hydrophilicity though they still contain small amounts of residual organic matter.

About the synthesis and thermal stability of SiO2-aerogel

Aerogels are extremely porous high-tech materials based on inorganic oxides, especially silica. The paper describes synthesis and properties of SiO2-aerogel, and changes occurring during heating of SiO2-aerogel in the temperature range from 20 to 1000°C. Four thermoanalytical methods were used: Thermodilatometry, Differential thermal analysis, Thermogravimetry and Derivative thermogravimetry.

Thermal research of montmorillonite synthetized from the oxides SiO2-Al2O3-MgO-CaO

The thermal behaviour of synthetic montmorillonite of relatively simple chemical composition has been studied and interpreted. Montmorillonite was prepared by hydrothermal synthesis at 300° and 8.8 MPa during 165 hours. With the methods of DTA, DTG, TG, X-ray diffraction analysis, infrared spectroscopy and electron microscopy it was proved that the synthetic montmorillonite is a monomineral sample and no differences from natural montmorillonite were observed.ZusammenfassungDas thermische Verhalten synthetischer Montmorillonite verhältnismässig einfacher chemischer Zusammensetzung wurde untersucht und gedeutet. Montmorillonit wurde durch hydrothermische Synthese bei 300°C und 8.8 MPa in 165 Stunden hergestellt. Durch die Methoden der DTA, DTG, TG, Röntgendiffraktionsanalyse, Infrarotspektroskopie und Elektronenmikroskopie wurde erwiesen, daß synthetische Montmorillonit eine monominerale Probe ist und keine Abweichungen von natürlichem Montmorillonit beobachtet werden konnten.РезюмеИзучено и объяснено т ермическое поведени е синтетического монт мориллонита относительно просто го химического соста ва. Монтмориллонит был п лучен гидротермич еским синтезом в тече нии 165 часов при 300° и давл ении 8.8 МПа. Методами ДТА, ДТГ, ТГ, рентгенодифракци онного анализа, ИК спе ктроскопии и электронной микрос копии доказано, что синтети ческий монтмориллон ит является мономинералом и не от личается от природного.

THERMAL ANALYSIS OF THE SYNTHETIC ZEOLITE ZSM5 AND ITS SILVER IODIDE FORM

TG, DTG and DTA measurements were used to study the thermal properties of the synthetic zeolite ZSM5, its silver form (Ag-ZSM5) and a zeolitic product containing silver iodide (K-ZSM5/AgI). Thermoanalytical measurements were supplemented by morphology studies.

High-temperature phases of montmorillonite synthetized from the oxides SiO2-Al2O3-MgO-CaO

The high-temperature (950–1500°) changes in synthetic montmorillonite of relatively simple chemical composition, studied by X-ray diffraction analysis, infrared spectroscopy and electron microscopy, are described. It was found that this montmorillonite belongs to the Wyoming type and the high-temperature phases involve cristobalite, mullite, anorthite and spinel. Only mullite crystallized from this sample on heating for two hours at 1500°.ZusammenfassungDie durch Röntgendiffraktionsanalyse, Infrarotspektroskopie und Elektronenmikroskopie untersuchten Hochtemperatur (950–1500°) — Änderungen in synthetischem Montmorillonit verhältnismässig einfacher chemischer Zusammensetzung werden beschrieben. Es wurde gefunden, daß dieser Montmorillonit dem Typ Wyoming angehört und, daß die Hochtemperaturphasen Cristobalit, Mullit, Anorthit und Spinell enthalten. Aus dieser Probe kristalliesierte bei zweistündigem Erhitzen auf 1500°C nur Mullit.РезюмеС помощью рентгеноди фракционного анализ а, ИК спектроскопии и элек тронн ой микроскопии изуче ны высокотемператур ные изменения (950–1500°) синтет ического монтмориллонита отн осительно простого х имического состава. Найдено, что э тот монтм ориллонит относится к типу Вайоминг, а его высокотемпературны е фазы включают кристобалит, муллит, а нортит и шпинель. При н агревании монтмориллонита в те чении 2 часов при 1500° кристалл изуется только мулли т.

Calcination of SiO2-Aerogel in Inert Atmosphere

Thermal treatment of SiO2-aerogel in inert atmosphere, in contrary to oxidizing atmosphere, yields a series of gas products with great range of mole masses (12–154 g mol−1) and every product has specific way of evolving. These substances are represented by CO, CO2, CH4, CH3OH, C2H6, C2H4 and aromates. Part of evolving products, which are formed during catalytic condensation, is trapped under the surface and after carbonisation it causes opacity of surface layer of aerogel.