RESUMEN
The synthesis of ZnO comprising different ratios of zinc acetate (ZA) and zinc nitrate (ZN) from the respective zinc precursor solutions was successfully completed via a simple precipitation method. Zinc oxide powders with different mole ratios of ZA/ZN were produced-80/1, 40/1, and 20/1. The crystallinity, microstructure, and optical properties of all produced ZnO powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis-NIR spectrophotometry. The average agglomerated particle sizes of ZnO-80/1, ZnO-40/1, and ZnO-20/1 were measured at 655, 640, and 620 nm, respectively, using dynamic light scattering (DLS). The optical properties of ZnO were significantly affected by the extreme ratio differences in the zinc precursors. ZnO-80/1 was found to have a unique coral-sheet structure morphology, which resulted in its superior ability to reflect near-infrared (NIR) radiation compared to ZnO-40/1 and ZnO-20/1. The NIR-shielding performances of ZnO were assessed using a thermal insulation test, where coating with ZnO-80/1 could lower the inner temperature by 5.2 °C compared with the neat glass substrate. Due to the synergistic effects on morphology, ZnO-80/1 exhibited the property of enhanced NIR shielding in curtailing the internal building temperature, which allows for its utilization as an NIR-reflective pigment coating in the construction of building envelopes.
RESUMEN
In this work, the novel natural rubber latex (NRL) mixing was approached. The mixing process was carried out by using n-hexane as the dispersed phase of silica aerogel which acted as thermal insulation filler prior to NRL mixing. The silica aerogel/NR composites were prepared with different silica aerogel contents of 20, 40, 60, 80, and 100 parts per hundred rubber (phr). The morphology of the 40 phr composite showed the NR macropore formation with silica aerogel intercalated layers. The optimal content of silica aerogels and n-hexane were the key to obtaining the NR macropore. The thermal insulation performance of silica aerogel/NR composites was investigated because of their porous structures. The thermal conductivity of the composites were lower than that of the neat NR sheet and decreased from 0.081 to 0.055 W m-1·K-1 with increasing silica aerogel content. The lower densities of the composites than that of the NR sheet were revealed noticeably. In addition, the silica aerogel/NR composites exhibited a higher heat retardant ability than that of the NR sheet, and the comparable glass transition temperatures (Tg) of the composites and the neat NR indicated the maintained flexibility at ambient temperature or higher, which can benefit various temperature applications. The overall results demonstrated that the silica aerogel/NR composites from the novel NRL mixing preparation could be a promising technique to develop the porous materials and be utilised as thermal insulation products and building constructions.
RESUMEN
Oxide nanowire arrays were studied for their applications to solar cells. It was demonstrated that the nanowires could provide direct pathways for electron transport in dye-sensitized solar cells and therefore, while forming photoelectrode films, they offered better suppression of charge recombination than nanoparticles. However, the photoelectron films consisting of nanowires suffered a disadvantage in giving large surface area for dye adsorption. Such a shortcoming of nanowires had been exemplified in this paper illustrating that it could be well compensated by incorporating with nanoparticles to form a nanoparticle-nanowire array hybrid photoelectrode film. The oxide nanowires were also demonstrated to be able to enhance the performance of inverted structure polymer solar cells as a cathode buffer layer by establishing a large interface with the polymers so as to facilitate the transport of photogenerated electrons from the polymer to the electron collecting electrode. Such an enhancement effect could be further boosted while the nanowires were replaced with nanotubes; the latter may build up larger interface with the polymers than the former and therefore facilitates the electron transport more efficiently.
