Study of ZnO-CNT Nanocomposites in High-Pressure Conditions

Abstract

Recently, carbon nanotubes (CNTs) have been used extensively to develop new materials and devices due to their specific morphology and properties. The reinforcement of different metal oxides such as zinc oxide (ZnO) with CNT develops advanced multifunctional materials with improved properties. Our aim is to obtain ZnO-CNT nanocomposites by in situ hydrothermal method in high-pressure conditions. Various compositions were tested. The structure and morphology of ZnO-CNT nanocomposites were analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry—thermogravimetry (DSC-TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). These analyses showed the formation of complex ZnO-CNT structures. FT-IR spectra suggest possible interactions between CNT and ZnO. DSC-TG analysis also reveals the formation of some physical bonds between ZnO and CNT, through the appearance of endothermic peaks which could be assigned to the decomposition of functional groups of the CNT chain and breaking of the ZnO-CNT bonds. XRD characterization demonstrated the existence of ZnO nanocrystallites with size around 60 nm. The best ZnO:CNT composition was further selected for preliminary investigations of the potential of these nanocomposite powders to be processed as pastes for extrusion-based 3D printing.

Development of 3D ZnO-CNT Support Structures Impregnated with Inorganic Salts

“…Two important processes with mass loss (Figure 8a) and endothermic effects (Figure 8b) can be observed in the case of the first heating cycle of printed 3D support structures with a total mass loss of ~1.4% with maximum rates at 55 and 240 • C, respectively. While the first process can be assigned with solvent/water losses, the second one can be associated with the multi-stage transformation/decomposition of the CNT carboxyl functional groups (195-240 • C) [61]. The heat flow curve (Figure 8b) confirms two main steps decomposition process in the interval of 160-240 • C.…”

“…As was revealed by the DSC-TGA techniques, significant differences between the first and the next four heating cycles can be observed. The characteristic endothermic peaks of this hybrid material at about 240 • C, assigned to structural transformations of CNTs carboxyl functional groups of 3D structure [61] no longer appear in subsequent cycles. In the curves corresponding to cycles two to five, no irreversible processes were observed (Figure 9b).…”

“…The working parameters were cube-like structure with 10 × 10 × 5 mm 3 in size, 1.3 mm strand distance, nozzle diameter of 400µm, angle between layers of 90 • and the printing speed of 9-10 mm/s. More details about 3D printing process of ZnO-CNT structures are presented in [61].…”

“…Thermogravimetric analysis results for PCM impregnated structures are presented in Table 4. CNTs carboxyl functional groups of 3D structure [61] no longer appear in subsequent cycles. In the curves corresponding to cycles two to five, no irreversible processes were observed (Figure 9b).…”

Statistical Simulation of the Switching Mechanism in ZnO-Based RRAM Devices

“…Various materials have been used to demonstrate resistive switching (RS) behaviors. Among them, ZnO material has been studied extensively and shown to be promising [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. In RRAM design, ZnO has been established as one of the suitable materials for RRAM devices and has been identified as a multifunctional device that exhibits a significant amount of oxygen vacancy (Vo), which helps in the conductive filament (CF) formation [ 12 , 13 ].…”