RESUMO
The electrical tree in grafted polypropylene (PP) is inhibited compared with that of pure PP. To understand the free radicals that are generated during the treeing process, we study the electron paramagnetic resonance (EPR) spectra. Additionally, to provide a clearer explanation of the suppression of electrical trees, this research uses electroluminescence (EL) and excitation computation. These methods help us to observe the movement of electrons and to understand the geometric and electronic structures involved. In pure PP, the energy required to excite the electrons is approximately the same as the band gap of PP while electrons are easier to be excited in grafted PP than in pure PP, because the band gap is narrower. As a result, though the electrical tree length is shorter in PP-g-MMA, the EPR signal is more intense because of the uneven distribution of electrons.
RESUMO
Polymer dielectrics need to operate at high temperatures to meet the demand of electrostatic energy storage in modern electronic and electrical systems. The polymer nanocomposite approach, an extensively proved strategy for performance improvement, encounters a bottleneck of reduced energy density and poor discharge efficiency beyond 150 °C. In this work, a polymer/metal oxide cluster composite prepared based on the "site isolation" strategy is reported. Capitalizing on the quantum size effect, the bandgap and surface defect states of the ultrasmall inorganic clusters (2.2 nm diameter) are modulated to markedly differ from regular-sized nanoparticles. Experimental results in conjunction with computational simulation demonstrate that the presence of ultrasmall inorganic clusters can introduce more abundant, deeper traps in the composite dielectric with respect to conventional polymer/nanoparticle blends. Unprecedented high-temperature capacitive performance, including colossal energy density (6.8 J cm-3 ), ultrahigh discharge efficiency (95%) and superior stability at different electric field frequencies, are achieved in these polymer/cluster composites up to 200 °C. Along with the advantages in material preparation (inexpensive precursors and one-pot synthesis), such polymer/inorganic cluster composite approach is promising for high-temperature dielectric energy storage in practical power apparatus and electronic devices.
RESUMO
Understanding the Sichuan potted landscapes, one of the five types of traditional Chinese potted landscapes, is important for exploring the development of Sichuan landscape architecture in Southwest China. In this study, we analyzed the shape and aesthetic characteristics of the traditional regular bonsai of the Sichuan style according to trunk features, branch patterns, tree shape, branch arrangement, and branch and plate numbers. Studies have shown that the flat-branch-type branch plate slopes downward and the bottom rises, and the number of branch plates is 2n + 1 (where n is the number of layers of the branch plate, n > 4), which is a proportional sequence. The ratio of the main pile height to the footplate is approximately 1.5:1−2:1, the pot:footplate ratio is <1:1, and the maximum bend:trunk ratio is <1:2. There were extremely significant differences between the length of the foot plate and its adjacent branch and plate length and the distance between the branch and plate. Interestingly, the rolling branch-type plants are characterized by vertical curved branches, oblique curved branches, and curved branches, reflecting the beauty of harmony and symmetry. Overall, the regular-style Sichuan tree potted landscape is mainly characterized by the beauty of rhythm and symmetry.