Superficial modifications in TiO2 and Al2O3 ceramics

Abstract

The properties of hydrophilicity or hydrophobicity of materials are defined mainly, though not exclusively, by their composition, morphology and surface energy. In this work, titanium dioxide (TiO2) and aluminum oxide-alumina (Al2O3) ceramics prepared by uniaxial pressing were studied in terms of surface energy. The surfaces of these ceramics were treated with nitrogen plasma, using a stainless steel reactor excited by a 13,6 MHz radio frequency operating at 50 W input power and 13 Pa nitrogen pressure. The surface morphology was investigated by scanning electron microscopy (SEM) analysis. Surface energy and contact angle measurements were taken using a RAMÉ-HART goniometer. These measurements were taken as function of time, over a 21-day period. The contact angle and surface energy values were found to change by almost 34% in comparison to their initial values immediately following plasma treatment. Nonetheless, the hydrophilic character of the Al2O3 and TiO2 remained constant throughout the test period

Particulate Nanoinsecticides: A New Concept in Insect Pest Management

“…Above Particulate Nanoinsecticides: A New Concept in Insect Pest Management http://dx.doi.org/10.5772/intechopen.72448 the critical value, the capillary forces are the predominant forces [87]. Due to the different contact angles, hydrophilic substances as DE [88,89] are more exposed to the influence of moisture than hydrophobic materials (synthesized Al 2 O 3 ; [90]). In addition, water adsorption also affects the surface energy of the particles [91].…”

Tortuosity of Aligned Channels in Alumina Membranes Produced by Vacuum-Induced Surface Directional Freezing

“…Note that the validity of Washburn in such fine channels (down to 3 µm radius) has been demonstrated with water [19]. The contact angle of water on sintered alumina compacts, θ ls , is 37° [20]. For an assumed tortuosity of τ = 1 the calculated value for $\hat{t}$ using Equation (2) is 50 ms. For an assumed τ = 5, the $\hat{t}$ lengthens to 0.86 s and for assumed τ = 10 to 4.5 s. It is, therefore, clear that capillarity through the very fine aligned channels in the membrane is rapid.…”

Sorption and hydration effects on liquid carbon dioxide transport through mesoporous γ-alumina and titania membranes

“…Hysteresis was not observed in the 5 nm ␥-alumina membrane (Fig. 5), which may reflect the greater water capacity relative to titania [29]. Non-linear flux behavior and hysteresis was attributed to the presence of physisorbed water on pore surfaces, which led to a reduction in the effective pore diameter.…”

“…This analysis shows that the 1 kDa and 5 kDa titania membranes exhibit the same degree of pore blockage, while that of ␥-alumina is nearly two-fold greater. Comparatively, Santos et al [29] have reported that the water adsorption capacity for ␥-alumina is twice that of titania, which can be attributed to the higher sorption capacity of surface hydroxyl sites on ␥-alumina. These hydroxyl sites can also chemisorb carbon dioxide (discussed in Section 4.3).…”