Naslov
Evolved gas analysis of sol-gel derived precursors for ZnAl2O4 synthesis

Autori
Mandić, Vilko ; Tkalčec, Emilija, Kurajica, Stanislav ; Schmauch, Joerg, Brnardić, Ivan

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Hrvatski skup kemičara i kemijskih inženjera: Knjiga sažetaka / Tomašić, Vesna ; Maduna Vlakaj, Karolina - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI) ; Hrvatsko kemijsko drustvo, 2011

ISBN
987-953-6894-38-3

Skup
XXII. Hrvatski skup kemičara i kemijskih inženjera

Mjesto i datum
Zagreb, Hrvatska, 13.02.2011. - 16.02.2011

Vrsta sudjelovanja
Poster

Vrsta recenzije
Domaća recenzija

Ključne riječi
Evolved gas analysis; TG/DTA-MS; TG/DTA-FTIR; Zn/Al layered double hydroxide; XRD; ZnAl2O4

Sažetak
Thermally evolved gases released from precursors used for gahnite (ZnAl2O4) synthesis were monitored by simultaneous thermogravimetry and differential thermal analysis coupled online with mass spectrometer (TG/DTA-EGA-MS) and FTIR spectroscopic gas cell (TG/DTA-EGA-FTIR), respectively, up to 1000 °C. Al-sec-butoxide [Al(OsBu)3], as the source of aluminum and Zn(NO3)2•6H2O as the source of zinc, were used as starting materials. The dry gels and thermally treated samples were characterized by X-ray diffraction analysis (XRD). The course of thermal reaction is dominated by initial formation of layered double hydroxides (Zn-Al-NO3/LDH), followed by intermediate Zn(NO3)(OH)•H2O phase and gahnite at as low as 300°C. According to online coupled mass spectrometry, the decomposition of LDH starts with an evolution of water (m/z=18) and CO2 (m/z= 44) above 90 °C. The evolution rate of CO2 reveals its maximum at 233 °C and 333 °C. Nitrate anion is revealed by ion fragment of m/z=30 at 273 °C and 573 °C. Residuals of butoxide groups were revealed by ion fragment m/z=56. In order to gain a deeper understanding in the mechanism of the sample decomposition, TG/DTA-EGA-FTIR analysis was applied. Four small molecular gaseous species were identified by their characteristic absorbance: CO2, (νC=O 2400 cm-1), CO (νC=O 2266 cm-1), H2O (νO-H 3000-3700 cm-1, δO-H 1250-1770 cm-1) and NO2 (1670 cm-1 and 1540 cm-1). The change in intensity ratios of gaseous species at about 300 °C was due to the decomposition of LDH and formation of a faint crystalline Zn(NO3)(OH)•H2O and ZnAl2O4.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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