RESUMO
The electronic structure and the corresponding electrical conductive behavior of the Cu/Cr2C/TiN stack were assessed according to a newly developed first-principle model based on density functional theory. Using an additional Cr2C layer provides the metal-like characteristic of the Cu/Cr2C/TiN stack with much larger electrical conduction coefficients (i.e., mobility, diffusivity, and electrical conductivity) than the conventional Ag/Ti3C2/Pt stack due to the lower activation energy. This device is therefore capable of offering faster switching speeds, lower programming voltage, and better stability and durability than the memristor device with conventional Ti3C2 MXene.
RESUMO
The surface structures, O2 adsorption, and CO oxidation reaction properties of Ce6O12/Cu(111) have been investigated using density functional theory including on-site Coulomb corrections (DFT + U). Results show that the supported ceria nanoparticles would gain electrons from the Cu(111) surface, and the Ce4+ are reduced to Ce3+. In addition, the oxygens at the interface have been largely activated, resulting in much low formation energy of O vacancies. For the CO oxidation reaction, two possible pathways are investigated, CO reacts with the O2 molecule adsorbed on Ce3+ and the lattice O at the interface, respectively. It has been found that CO reacting with the lattice O atom gives a lower reaction barrier than that of adsorbed O2 on Ce3+. These results are important for further understanding of the role of different active sites on the inverse CeOx/Cu(111) surface structure.
RESUMO
The surface structures, CO adsorption, and oxidation-reaction properties of CuO1-x(111) with different reduction degree have been investigated by using density functional theory including on-site Coulomb corrections (DFT + U). Results indicate that the reduction of Cu has a great influence on the adsorption of CO. Electron localization caused by the reduction turns Cu(2+) to Cu(+), which interacts much stronger with CO, and the adsorption strength of CO is related to the electronic interaction with the substrate as well as the structural relaxation. In particular, the electronic interaction is proved to be the decisive factor. The surfaces of CuO1-x(111) with different reduction degree all have good adsorption to CO. With the expansion of the surface reduction degree, the amount of CO that is stably adsorbed on the surface increases, while the number of surface active lattice O decreases. In general, the activity of CO oxidation first rises and then declines.
RESUMO
Polyethylene-grafted multiwalled carbon nanotubes (PE-g-MWNT) were used to reinforce polyethylene (PE). The nanocomposites possessed not only improved stiffness and strength, but also increased ductility and toughness. The effects on the structure and morphology of composites due to pristine multiwalled carbon nanotubes (MWNT) and PE-g-MWNT were studied and compared using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The SAXS long period, crystalline layer thickness and crystallinity of polymer lamellar stacks were found to decrease significantly in MWNT composites, while the decreases were much smaller in PE-g-MWNT composites. PE-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. The SAXS crystallinity and the mechanical properties of the composites showed similar trends as a function of MWNT content. This suggested that the improvement of the interfacial strength between polymer and carbon nanotubes was a result of synergistic effects of better dispersion of the filler, better stress transfer, due to the grafting of polymer and MWNT, and the nucleation of a crystalline phase around MWNT. The latter effect was confirmed by measurements of kinetics of non-isothermal crystallization.
