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Preparation and characterization of titania powders obtained via hydrolysis of titanium tetraisopropoxide

Grzeskowiak M, Wrobel R. J., Grzechulska J., Przepiorski J

Materials Science Poland

2014

Vol. 32, No. 1

71--79

TiO2 powders were prepared through the hydrolysis of titanium isopropoxide followed by calcination at temperatures of 200 °C to 600 °C. The obtained powders were characterized by N2 adsorption-desorption and X-ray powder diffraction. The results confirmed strong dependence between specific surface area of the TiO2 powders and both the conditions of the hydrolysis process and the calcination temperature. While calcination temperature strongly affected crystallinity of the product, no significant influence of the hydrolysis conditions on this parameter was observed. TiO2 powders prepared at various conditions were examined as catalysts for photodegradation of Acid Red 18 in water. Photoactivities of the prepared powders were influenced by both the amount of water used to hydrolyze the TiO2 precursor and the temperature of calcination process. TiO2 samples calcined at 500 °C appeared to be the most active and the photocatalytic activities of the prepared materials increased along with the amount of water used for the hydrolysis process.

Explosion Hazard of Aromatic Organic Compounds Containing One or Two Nitrogroups

Kozak G. D., Vasin A. Y., Dyachkova A. V.

Central European Journal of Energetic Materials

2008

Vol. 5, nr 2

49-55

Aromatic compounds containing one or two nitrogroups use in chemical industry commercially, in the first place there are mono- and di- nitroderivatives of benzene and toluene. Some industrial incidents at heat selfignition of them, and explosive properties of them were discussed in literature. This investigation deals with explosion hazard of less investigated in this regard class nitrocompounds - azo-dyes. All azo-dyes contain azo or amino groups, two benzene circles with substituents. Some of them contain one or two nitrogroups. Nitro- and azo- groups can give explosion hazard to organic substance. Temperature of fast decomposition beginning at heating and kinetic parameters of slow decomposition were experimentally measured for nine of them. The enthalpies of formation were measured experimentally, and explosion parameters were calculated for three of them. These results gave an opportunity to calculate the temperatures of heat explosion on a base of fundamental theory of heat explosion at convection heat transfer with environment. It was found that calculated temperatures of heat explosion agreed with experimental temperatures of fast decomposition beginning at heating, the divergence was 4.5% on average. Thus it was shown that investigated azo-dyes were the weak explosives, and theory of heat explosion could be quite applied to them.

Spectroscopic investigations of azo-dyes covalently linked to polymers

Łukasiewicz J., Hanyż I., Siejak A., Apostoluk A. A., Wróbel D.

Scientific Bulletin. Physics / Lodz University of Technology

2006

Vol. 26

107-113

In this work an azo-dye and the azo-dye covalently linked to polymers dissolved in dimethylsulfoxide were investigated. Absorption, fluorescence, phosporescence, photoacustic and time-resolved photothermal studies were used. The fluorescence quantum yields estimated for all investigated samples were extremely low and phosphorescence was not observed. It suggests that deactivation of excitation energy in radiative processes is unlike. The results of the photoacustic study show that a large part of absorbed energy is changed into heat by fas relaxation processes occurring with singlet states participation. The influence of the polymers presence on the dye ground and excited states was observed.

Przeprowadzono badania absorpcyjne, fluorescencyjne/fosforescencyjne i fototermiczne barwnika azowego DR1 kowalencyjnie przyłączonego do polimerów polimetakrylanu lub polifenylovinylu. Pokazana wpływ obecności polimeru na właściwości stanu podstawowego i wzbudzonego barwnika. Niska wydajność kwantowa fluorescencji barwnika azowego i nieobserwalna fosforescencja wskazywały na brak udziałów procesów promienistych w dezaktywacji stanów wzbudzonych. Pokazana również, że energia wzbudzenia jest dezaktywowana w szybkich procesach cieplnych bez udziału stanu trypletowego barwnika.