Nanocomposites and nanomaterials

Adsorption-desorption processes 
in nanostructured MgAl2O4 ceramics 
H. Klym1, I. Hadzaman2, I. Vasylchyshyn1, I. Karbovnyk3

1 Lviv Polytechnic National University, Bandery str., 12, Lviv-79013, Ukraine 
E-mail: halyna..klym@lpnu.ua; klymha@yahoo.com  
2 Drohobych State Pedagogical University,
I. Franko str., 24, Drohobych-82100, Ukraine
3 Department of Electronics and Computer Technologies, Ivan Franko National University of Lviv, 107, Tarnavskogo Str., Lviv, 79000, Ukraine

Nanoporous MgAl2O4 ceramics is obtained by the traditional method of ceramic technology. By selecting the raw materials are obtained by mechanical, physical, chemical or physical-chemical methods and by modifying the temperature-time modes of sintering, it is possible to obtain the necessary microstructure of humidity-sensitive ceramics. The aim of this work is investigation of electrical (exploitative electrophysical) properties of nanostructured MgAl2O4 ceramics sintered at different temperatures and durations in adsorption-desorption cycles.
It is established that exploitative electrophysical properties of nanostructured MgAl2O4 ceramics sintered at maximal temperatures of 1100, 1200, 1300 and 1400 oC for 2 h and 1300 and 1400 oC for 5 and 9 h were studied at 50 oC and frequency of 500 Hz [1]. Investigation in adsorption-desorption cycles were performed for MgAl2O4 ceramics after sintering, after ageing test at 40 oC and relative humidity of 95 % and after natural physical ageing in natural conditions (for ceramics sintered at 1200, 1300 and 1400 oC for 2 h). It is shown that ceramics prepared at 1100-1400 oC are slightly sensitive in the region of higher relative humidity. After ageing test these samples lose sensitivity in the region of low relative humidity. After ageing test humidity sensitivity of ceramics sintered at 1300 and 1400 oC for 2, 5 and 9 h are improved. Natural physical ageing results in slight changes in dependences of electrical resistance from relative humidity and narrowing of hysteresis of characteristics.
1.	Klym H., Hadzaman I., Shpotyuk O. Influence of sintering temperature on pore structure and electrical properties of technologically modified MgO-Al2O3 ceramics // Materials Science, 2015, 21(1), pp. 92-95, 2015.