Physical and Barrier Properties of Polylactic Acid/Halloysite Nanotubes-Titanium Dioxide Nanocomposites

In this study, PLA/TiO2 and PLA/HNTs-TiO2 nanocomposites films were fabricated via solution casting method. By testing the film density, solubility, water contact angle and water vapor permeability, the PLA nanocomposite films, the comprehensive performances of the nanocomposites were analysed. The outcomes demonstrated that maximum film density of PLA/TiO2 and PLA/HNTs-TiO2 nanocomposites films increased gradually with the increasing of nanofiller loadings. Moreover, the incorporation of TiO2 and HNTs-TiO2 significantly decreased the water vapor transmittance rate of the nanocomposite films with a slight priority to the addition of HNTs-TiO2, the water solubility was significantly improved with the addition of both nanofillers. Furthermore, the barrier properties were developed with the addition of both TiO2 and HNTs-TiO2 especially after the addition of low nanofiller loadings. Overall, the performance of the PLA/HNTs-TiO2 nanocomposite films was better than that PLA/TiO2 film. Nevertheless, both of the PLA nanocomposite samples achieved the requests of food packaging applications.

Enhancing the Photocatalytic Activity of SnO2-TiO2 and ZnO-TiO2 Tandem Structures Toward Indoor Air Decontamination

ZnO-TiO2 and SnO2-TiO2 tandem structures were developed using the doctor blade technique. It was found that by employing organic hydrophilic and hydrophobic as additives into the precursor it is possible to tailor the film density and morphology with direct consequences on the photocatalytic activity of the tandem structures. The highest photocatalytic efficiency corresponds to ZnO-TiO2 and can reach 74.04% photocatalytic efficiency toward acetaldehyde when a hydrophilic additive is used and 70.93% when a hydrophobic additive is employed. The snO2-TiO2 tandem structure presents lower photocatalytic properties (61.35 % when the hydrophilic additive is used) with a constant rate reaction of 0.07771 min−1.

Simple Non-Destructive Method of Ultrathin Film Material Properties and Generated Internal Stress Determination Using Microcantilevers Immersed in Air

Recent progress in nanotechnology has enabled to design the advanced functional micro-/nanostructures utilizing the unique properties of ultrathin films. To ensure these structures can reach the expected functionality, it is necessary to know the density, generated internal stress and the material properties of prepared films. Since these films have thicknesses of several tens of nm, their material properties, including density, significantly deviate from the known bulk values. As such, determination of ultrathin film material properties requires usage of highly sophisticated devices that are often expensive, difficult to operate, and time consuming. Here, we demonstrate the extraordinary capability of a microcantilever commonly used in a conventional atomic force microscope to simultaneously measure multiple material properties and internal stress of ultrathin films. This procedure is based on detecting changes in the static deflection, flexural and torsional resonant frequencies, and the corresponding quality factors of the microcantilever vibrating in air before and after film deposition. In contrast to a microcantilever in vacuum, where the quality factor depends on the combination of multiple different mechanical energy losses, in air the quality factor is dominated just by known air damping, which can be precisely controlled by changing the air pressure. Easily accessible expressions required to calculate the ultrathin film density, the Poisson’s ratio, and the Young’s and shear moduli from measured changes in the microcantilever resonant frequencies, and quality factors are derived. We also show that the impact of uncertainties on determined material properties is only minor. The validity and potential of the present procedure in material testing is demonstrated by (i) extracting the Young’s modulus of atomic-layer-deposited TiO2 films coated on a SU-8 microcantilever from observed changes in frequency response and without requirement of knowing the film density, and (ii) comparing the shear modulus and density of Si3N4 films coated on the silicon microcantilever obtained numerically and by present method.