Sol-Gel Synthesis and Characterization of Gels with Compositions Relevant to Hydrated Glass Alteration Layers

Characterisation of Holographic Recording in Environmentally Stable Photopolymerisable Glass

Photopolymerisable glasses are holographic recording materials which provide good recording capability, improved dimensional stability, and negligible shrinkage. Recently, a novel photopolymerisable hybrid sol-gel (PHSG) for holographic recording of volume gratings has been reported. The PHSG has significantly improved gelation time and high water resistance, both of which make it an attractive material for mass production of holographic optical elements (HOEs) with no sensitivity to ambient humidity. In order to achieve full control over the performance of the material and further improve its properties, a study of grating formation under holographic patterning is essential. This paper reports characterisation of the grating recording in PHSG. The approach is based on the analysis of grating parameters during exposure and post-recording dark processes. The obtained results suggest that photopolymerisation of the methacrylate groups is the main contributor to the creation of refractive index modulation during exposure. During the dark process, the enhancement of the refractive index modulation is observed, probably due to further polycondensation. The observations made facilitate controlled and predictable diffraction efficiency of gratings recorded on the PHSG, thereby furthering the prospect of the development of HOEs with customisable specification.

Controlling resistive switching behavior in the solution processed SiO2-x device by the insertion of TiO2 nanoparticles

The resistive switching behavior of the solution processed SiO_x device was investigated by inserting TiO₂ nanoparticles (NPs). Compared to the pristine SiO_x device, the TiO₂ NPs inserted SiO_x (SiO_x@TiO₂ NPs) device achieves outstanding switching characteristics, namely a higher ratio of SET/RESET, lower operating voltages, improved cycle-to-cycle variability, faster switching speed, and multiple-RESET states. Density functional theory calculation (DFT) and circuit breaker simulation (CB) were used to detail the origin of the outstanding switching characteristic of the SiO_x@TiO₂ NPs. The improvement in resistive switching is mainly based on the difference in formation/rupture of the conductive path in the SiO₂ and SiO₂@TiO₂ NPs devices. In particular, the reduction of resistance and lower switching voltage of TiO₂ NPs control the formation and rupture of the conductive path to achieve more abrupt switching between SET/RESET with higher on/off ratio. This method of combined DFT calculation and CB offers a promising approach for high-performance non-volatile memory applications.

Environmental Remediation with Functional Aerogels and Xerogels

Several different types of aerogels and xerogels are demonstrated as effective sorbents for the capture and/or immobilization of radionuclides and other contaminants in gaseous form [e.g., Hg(g), I2(g), Xe, Kr] as well as ionic form (e.g., Cd2+, Ce4+, Cs+, Cu2+, Fe2+, Hg2+, I-, IO3 -, Kr, Pb2+, Rb+, Sr2+, 99Tc7+, U6+, Zn2+). These sorbents have unique properties, which include high specific surface areas, high pore volumes, a range of pore sizes, and functionalities that provide methods for binding radionuclides and other contaminants, generally through physisorption, chemisorption, or a combination thereof. This combination of properties and functionalities makes these types of materials ideal for use as sorbents for capturing radionuclides. The primary base materials that will be discussed in this paper include Ag0-functionalized silica aerogels, Ag+-impregnated aluminosilicate aerogels, Ag0-functionalized aluminosilicate aerogels, metal-impregnated (non-Ag) aluminosilicate aerogels and xerogels, sulfide-based aerogels, and carbon-based aerogel composites. For the capture of I2(g), the materials reported herein show some of the highest iodine loadings ever reported for inorganic sorbents. For the capture of ionic species, these materials also show promise as next-generation materials for active radionuclide remediation. This progress report describes materials fabrication, general properties, and environmental remediation applications.