The microencapsulation of essential oils can provide their evaporation and oxidation protection, flavor retention or/and masking of unpleasant taste. The microencapsulation process involves emulsions preparation and drying of the obtained emulsion droplets. The aim of this study is the determination of optimal conditions for preparation of the stable O/W emulsions containing juniper berry essential oil with minimal droplet size, as a preparatory stage for microcapsule formation. As the first step for pre-emulsions preparation, homogenization at 10000 rpm for 5 min. was chosen, which gave emulsions with droplet size between 1.82 and 2.51µm, depending on concentrations of the surfactant (Tween 20) and encapsulated essential oil. The second step was ultrasound emulsification during 5 minutes at a frequency of 99%, using pulsed 10:10 s (ON/OFF) ultrasound treatment, which was chosen as an optimal, creating emulsions of droplet sizes of 320 nm in diameter (for 5% essential oil and 1% Tween 20). The addition of wall material changed the size and stability of emulsions, which depends on type of biopolymer and its surface competition with used surfactant. The maltodextrin (MD), gum arabic (GA) and their mixture in equal ratio were used. GA emulsions can be singled out as the most stable without used surfactant, with D 4,3 = 1.11 ± 0.003 µm. Using MD as a wall material requires addition of surfactant (1% w/v) to form stable emulsions. The mixture of MD/GA can be used with or without surfactant. The addition of Tween 20 (1% w/v) decreases droplet size from 14.86 to 0.99 µm, while utilization of the ultrasound contributes to the droplet size decrease and emulsions stability.
The influence of different processing parameters and various Ba
2+
addition (up to 10 mol%) on the structure and dielectric properties of Bi
0.5
Na
0.5
TiO
3
-BaTiO
3
(BNT-BT) ceramics was investigated. The powders were hydrothermally synthesized in the alkaline environment at 180°C for different time periods. X-ray diffraction confirmed the presence of dominant rhombohedral Bi
0.5
Na
0.5
TiO
3
phase and a small amount of secondary pyrochlore Bi
2
Ti
2
O
7
phase in the pure BNT powders. In addition, one-dimensional Na
2
Ti
2
O
7
structure was also observed in the powder hydrothermally treated for a long time (i.e. 48 h). The amount of secondary pyrochlore phase in the BNT-BT powders increases with the increase of Ba
2+
content. The synthesized powders were pressed into pellets and finally sintered at various temperatures up to 1150°C. High density (more than 90%TD) was obtained in all BNT-BT sintered samples. Optimal sintering parameters were chosen in order to obtain dense ceramics with the optimal phase composition. The temperature dependence of dielectric properties for the BNT-BT ceramics was also studied. Relaxor behaviour of BNT-based ceramics and broad transition peaks are evident in all samples. Dielectric constant up to 400 as well as an acceptable low dielectric loss at temperatures lower than 200°C were obtained in BNT-BT ceramics.
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