Enhanced Interfacial Properties of Carbon Nanomaterial–Coated Glass Fiber–Reinforced Epoxy Composite: A Molecular Dynamics Study

The weak interfacial adhesion has significantly affected the durability, long-term reliability, and performance of glass fiber–reinforced epoxy composites. The coating of graphene and carbon nanotubes on the glass fiber can have a positive effect on the strength, toughness, and thermal insulation performance of glass fiber-reinforced composites. However, the strengthening mechanism of carbon nanomaterial coating on the interfacial adhesion between glass fiber and epoxy has not been fully explored. In this work, the effect of graphene and single-walled carbon nanotubes (SWCNTs) on the interfacial properties of the glass fiber–reinforced epoxy has been investigated at atomistic scale. The graphene and SWCNTs are sandwiched between epoxy and silica to study the debonding behavior of the sandwiched structures. It is found that the interfacial energy is significantly improved with the incorporation of graphene and SWCNTs between epoxy and silica, causing an obvious improvement in adhesion stress for graphene coating and in debonding displacement for SWCNT coating. Compared with the epoxy/silica without coatings where the silica and epoxy detach from the contact surface, the sandwiched structures display different failure modes. The sandwiched structure with graphene coating fails at the epoxy matrix close to the interface, exhibiting a cohesive failure mode because of the relatively stronger interfacial interactions. The structures with SWCNTs fail at the interface between silica and SWCNTs, representing an adhesive failure mode due to the interlocking between SWCNTs and polymer chains. This work provides a theoretical guideline to optimize the interface adhesion of coated glass fiber–reinforced epoxy via structure design and surface modification of coating materials.

Growth Properties of Carbon Nanowalls on Nickel and Titanium Interlayers

This research is conducted in order to investigate the structural and electrical characteristics of carbon nanowalls (CNWs) according to the sputtering time of interlayers. The thin films were deposited through RF magnetron sputtering with a 4-inch target (Ni and Ti) on the glass substrates, and the growth times of the deposition were 5, 10, and 30 min. Then, a microwave plasma-enhanced chemical vapor deposition (PECVD) system was used to grow CNWs on the interlayer-coated glass substrates by using a mixture of H2 and CH4 gases. The FE-SEM analysis of the cross-sectional and planar images confirmed that the thickness of interlayers linearly increased according to the deposition time. Furthermore, CNWs grown on the Ni interlayer were taller and denser than those grown on the Ti interlayer. Hall measurement applied to measure sheet resistance and conductivity confirmed that the electrical efficiency improved significantly as the Ni or Ti interlayers were used. Additionally, UV-Vis spectroscopy was also used to analyze the variations in light transmittance; CNWs synthesized on Ni-coated glass have lower average transmittance than those synthesized on Ti-coated glass. Based on this experiment, it was found that the direct growth of CNW was possible on the metal layer and the CNWs synthesized on Ni interlayers showed outstanding structural and electrical characterizations than the remaining interlayer type.

Fabrication of BaSi2 homojunction diodes on Nb-doped TiO2 coated glass substrates by aluminum-induced crystallization and two-step evaporation method

BaSi2 homojunction diodes on Nb-doped TiO2 (TiO2:Nb) coated glass substrates were fabricated using aluminum-induced crystallization (AIC) and two-step evaporation method. From Raman scattering spectra, the growth of BaSi2 on TiO2:Nb was confirmed when the thickness of poly-Si grown by AIC (AIC-Si) was more than 150 nm. The partial formation of BaSi2 diodes was confirmed from the samples prepared at temperature during AIC TAIC=475-525 oC. The long-wavelength edge of photoresponsivity of the diodes was located around 950 nm, which corresponds to the bandgap of BaSi2 of 1.3 eV, suggesting that this photocurrent is derived from BaSi2 thin films. At TAIC =500 oC, the maximum value of photoresponsivity was obtained. Since the largest grains in AIC-Si were also obtained at TAIC=500 oC, these results suggest that larger grain of AIC-Si leads to the improvement of the quality of BaSi2 thin films themselves and the performance of BaSi2 diodes.

Hydrometallurgical Treatment for the Extraction and Separation of Indium and Gallium from End-of-Life CIGS Photovoltaic Panels

This study presents experimental results for the development of a process for the recovery of indium and gallium from EoL CIGS (CuGa1−xInxSe2) panels. The process consists of a thermal treatment of the panels, followed by a hydrometallurgical treatment, where quantitative leaching of In, Ga, Mo, Cu and Zn is achieved. The elements are subsequently separated and recovered from the leachate by solvent extraction. For the development of the process, samples of EoL CIGS PV panels were used, which contained a thin film of Mo (metal base electrode), sputtered on the supporting soda-lime glass and covered by the thin film containing In, Ga, Cu and Se (1 μm). These films were detected by SEM-EDS in polished sections. The thermal treatment at 550 °C for 15 min, in excess of air, led to the successful disintegration of ethyl vinyl acetate (EVA) and delamination of the thin film-coated glass from the front protective glass. The glass fragments coated by the thin film contained the following: Se: 0.03–0.05%; In: 0.02%; Cu: 0.05%; Ga: 0.004–0.006%; and Mo: 0.04%. Following thermal treatment, thin film-coated glass fragments of about 1.5 cm × 1.5 cm were used in acid leaching experiments using HNO3, HCl and H2SO4. Quantitative leaching of Cu, Ga, In, Mo, Zn and Cu was achieved by HNO3 at ambient temperature. The effects of pulp density and acid concentration on the efficiency of metal leaching were investigated. Part of Se volatilized during the thermal treatment, whereas the rest was insoluble and separated from the solution by filtration. Finally, the separation of the elements was achieved via solvent extraction by D2EHPA.