The influence of O 2 , CO 2 , CO, N 2 , H 2 and CH 4 on the stability of the quantum efficiency (QE) of a negative electron affinity gallium arsenide (GaAs) photocathode activated with caesium (Cs) and oxygen (O) has been demonstrated for the first time under an extremely high vacuum condition, a base pressure of 1.5 × 10-11 mbar, where the influence of the background gas is minimized. It was found that exposure of a GaAs photocathode to N 2 , H 2 and CH 4 does not affect the QE, whereas exposure to O 2 , CO 2 and CO leads to a substantial reduction in photocathode QE. It was also found that the QE of photocathodes which have been degraded under O 2 exposure can be recovered to 95% of their initial QE level by the re-caesiation process, while those which have been degraded under exposure to CO and CO 2 can only be partly restored to 60-70% of their initial QE levels.

Radioactive Cs is a major by-product of nuclear power plants, with high radioactivity and long half-life. It is highly soluble in water and is difficult to remove. In this study, pristine graphene oxide (GO) synthesized via a Hummer's method has been demonstrated as a very efficient Cs sorbent with the maximum adsorption capacity of GO found to be 180, 465, 528 mg Cs/g sorbent at pH of 3, 7, and 12, respectively. The results from Fourier-transform infrared (FTIR) spectroscopy of GO before and after Cs sorption at various pH values reveal the mechanism of Cs sorption by GO. Several functional groups which are carboxyls, phenols, and hole defects containing multi-ether groups, are shown to play an important role in Cs capture. GO's affinity for other major cations found in seawater, namely, Na, K, and Mg was also evaluated, and the effect of these cations in competing with Cs for adsorption on GO was also studied. This reveals GO's exceptional ability in capturing Cs even in the presence of high concentrations of competitive cations and its high potential for use in Cs decontamination, as well as other heavy metal removal applications.

Fly ash (FA) and sugarcane bagasse ash (SCBA) are the wastes from lignite power plants and sugar industries, usually disposed of as landfills. In this research, these wastes were effectively utilized as a construction material, namely geopolymer. The effect of the SCBA (0–40 wt.%) addition to the FA geopolymers was investigated. The compressive strength of the FA geopolymers was reduced with the SCBA addition. The reduction was mainly due to the presence of the highly stable and non-reactive quartz (SiO₂) phase in SCBA. The SCBA was not dissolved in the alkaline activated solution and hence did not contribute to the geopolymerization process. The unreacted SCBA particles remained in the geopolymer matrix but did not provide strength. However, if the amount of SCBA was about 10 wt.% or less, the impact on the characteristics and properties of FA geopolymers was minimal. Furthermore, this research also studied the dielectric properties of the FA geopolymer/SCBA composites. The relatively large dielectric constant (ε′ = 3.6 × 10³) was found for the pristine geopolymer. The addition of SCBA decreased the ε′ slightly due to high carbon content in SCBA. Nevertheless, the variation in ε′ was mainly controlled by the geopolymerization process to form the aluminosilicate gel structure.

In this work, nanocomposites consisting of TiO₂-nanorods (TiO₂-NRs) with less than 100 nm in size and poly(vinylidene fluoride) (PVDF) were prepared using a liquid-phase assisted dispersion and hot-pressing methods. At 1 kHz and 25 °C, the high dielectric permittivity of ∼66 and loss tangent of ∼0.03 can be obtained in the nanocomposite with a filler volume fraction of 0.5, which was higher than that of a neat PVDF matrix by a factor of 6. Dielectric permittivity of TiO₂-NRs/PVDF nanocomposites not only highly increased with TiO₂-NRs, but also almost independent of the frequency range of 10²–10⁶ Hz. The significant enhancement in dielectric permittivity is mainly attributed to the interfacial polarization at the interfaces of TiO₂-NRs and PVDF, and semiconducting properties of TiO₂-NRs. Among the various models used for rationalizing the dielectric behavior, the experimental dielectric data is in close agreement with EMT (n = 0.11) and Yamada models (n = 8). Graphical Abstract