RESUMEN
Thin films of Poly (ethylene-co-vinyl acetate)/tin chloride different weight (w/w) ratios were prepared using a spin-coating method. The diameter, height, grain size, and other morphological and structural features of the prepared thin films were studied using atomic force microscope (AFM) system. Moreover, the maximum surface roughness and average diameter of the prepared thin films were reported to weight ratio of 0.3%Sn Also, the shielding properties of adding tin chloride inside the polymer matrix were investigated. In addition, the impact of adding the tin-dopant to the targeted polymer on the attenuation parameters, including the linear attenuation coefficient (µ), half-value layer (HVL), screening ratios, and the mean free path, were theoretically calculated. The results show that the properties of the prepared thin films can be improved significantly by introducing a small amount of tin chloride to the host polymer promoting the crystallinity of the produced material and enhancing the shielding property for gamma-rays. The better linear attenuation coefficient of the produced thin films was reported to the weight ratio of 0.3% Sn. The produced Poly (ethylene-co-vinyl acetate)/tin chloride thin films can be suggested as one of the significant shielding materials to be used in a wide range of applications in the field of radiation.
RESUMEN
The mechanical properties of engineered van der Waals (vdW) 2D materials and heterostructures are critically important for their implementation into practical applications. Using a non-destructive Raman spectroscopy approach, this study investigates the strain evolution of single-layer graphene (SLGr) and few-layered boron nitride/graphene (FLBN/SLGr) heterostructures. The prepared 2D materials are synthesized via chemical vapor deposition (CVD) method and then transferred onto flexible polyethylene terephthalate (PET) substrates for subsequent strain measurements. For this study, a custom-built mechanical device-jig is designed and manufactured in-house to be used as an insert for the 3D piezoelectric stage of the Raman system. In situ investigation of the effects of applied strain in graphene detectable via Raman spectral data in characteristic bonds within SLGr and FLBN/SLGr heterostructures is carried out. The in situ strain evolution of the FLBN/SLGr heterostructures is obtained in the range of (0-0.5%) strain. It is found that, under the same strain, SLG exhibits a higher Raman shift in the 2D band as compared with FLBN/SLGr heterostructures. This research leads to a better understanding of strain dissipation in vertical 2D heterostacks, which could help improve the design and engineering of custom interfaces and, subsequently, control lattice structure and electronic properties. Moreover, this study can provide a new systematic approach for precise in situ strain assessment and measurements of other CVD-grown 2D materials and their heterostructures on a large scale for manufacturing a variety of future micro- and nano-scale devices on flexible substrates.
RESUMEN
A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D-1D and 1D-2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method was utilized to ensure high-quality materials' synthesis and scalable production of different architectures. Iron-based universal compound molecular ink was used as a catalyst in both processes (a) to form a monolayer of horizontally defined networks of SWCNTs interfaced with vertically oriented ZnO NWs and (b) to grow densely packed ZnO NWs directly on a graphene surface. We show here that our universal compound molecular ink is efficient and selective in the direct synthesis of ZnO NWs/CNTs and ZnO NWs/Gr heterostructures. Heterostructures were also selectively patterned through different fabrication techniques and grown in predefined locations, demonstrating an ability to control materials' placement and morphology. Several characterization tools were employed to interrogate the prepared heterostructures. ZnO NWs were shown to grow uniformly over the network of SWCNTs, and much denser packed vertically oriented ZnO NWs were produced on graphene thin films. Such heterostructures can be used widely in many potential applications, such as photocatalysts, supercapacitors, solar cells, piezoelectric or thermal actuators, as well as chemical or biological sensors.
