The Effect of Nanoparticle Surface State on Trap Level Distribution of Polyimide/Aluminum Nitride-montmorillonite Nanocomposite Films

The electrical properties of polyimide (PI) nanocomposites, which are widely used in microelectronic industry and electrical engineering fields, strongly depend on the surface state of nanoparticles. To explore this dependence, the aluminum nitride (AIN) nanoparticles were treated by γ-aminopropyltriethoxysilane coupling agent, while PI/MMT, PI/AlN, and PI/AlN-MMT nanocomposite films doped by 5 wt% of treated and untreated AlN nanoparticles were prepared by the in-situ polymerization process. The SEM and TEM results indicate that the untreated AlN nanoparticles are prone to accumulation in the polymer matrix, while those treated by the coupling agent are readily combined with the polyimide matrix, and their compatibility and dispersion exhibit a significant improvement. The trap level distributions of nanocomposite films were studied by the isothermal discharge current (IDC) method based on the charge decay theory linking IDC with the trap level density (TLD). The TLD and number of trapped charges of PI/AlN and PI/AlN-MMT films doped by treated AlN nanoparticles are found to be much higher than those of untreated ones. The TLD of the PI/AlN (treated) film is 6.490×1023 eV·m-3, which is about 2.27 times higher than that of pure PI film in the range of 0.9~1.1 eV, while the maximum TLD=9.370×1023 eV·m-3 is observed in the PI/AlN (treated)-MMT film

Differences and allometric relationships among assimilative branch traits of four shrubs in Central Asia

Shrubs play a major role in maintaining ecosystem stability in the arid deserts of Central Asia. During the long-term adaptation to extreme arid environments, shrubs have developed special assimilative branches that replace leaves for photosynthesis. In this study, four dominant shrubs with assimilative branches, namely Haloxylon ammodendron, Haloxylon persicum, Calligonum mongolicum, and Ephedra przewalskii, were selected as the research objects, and the dry mass, total length, node number, and basal diameter of their assimilative branches and the average length of the first three nodes were carefully measured, and the allometric relationships among five traits of four species were systematically compared. The results indicated that: (1) Four desert shrubs have different assimilative branches traits. Compared with H. persicum and H. ammodendron, C. mongolicum and E. przewalskii have longer internodes and fewer nodes. The dry mass of H. ammodendron and the basal diameter of H. persicum were the smallest; (2) Significant allometric scaling relationships were found between dry mass, total length, basal diameter, and each trait of assimilative branches, all of which were significantly less than 1; (3) The scaling exponents of the allometric relationship between four traits and the dry mass of assimilative branches of H. persicum were greater or significantly greater than those of H. ammodendron. The scaling exponents of the relationships between the basal diameter, dry mass, and total length of E. przewalskii were higher than those of the other three shrubs. Therefore, although different species have adapted to drought and high temperatures by convergence, there was great variability in morphological characteristics of assimilative branches, as well as in the scaling exponents of relationships among traits. The results of this study will provide valuable insights into the ecological functions of assimilative branches and survival strategies of these shrubs to cope with aridity and drought in desert environments

AMS measurement of 53Mn and its initial application at CIAE

The determination of cosmogenic 53Mn in terrestrial archives has important applications, such as burial ages, exposure age and erosion rates. Accelerator mass spectrometry (AMS) is the most sensitive technique to detect minute amounts of 53Mn. 53Mn measurements were developed at the China Institute of Atomic nergy (CIAE) using the DE-Q3D equipped AMS system. This approach was recently optimized with the goal to reach the sensitivity required for AMS measurements of 53Mn in deep-sea ferromanganese crust (DSFC) samples. Based on these improvements of sample preparation, current beam transmission and so on, 53Mn in two samples of DSFC was measured by AMS. The ratios of 53Mn/Mn corresponding to an age of 3.77 ± 0.42 and 13.73 ± 2.74 Ma by 129I dating method are (5.01 ± 2.15) 10 13 and (1.90 ± 0.96) 10 13. The ratios are close to the experimental reference values, deduced from the previous research. The experimental progress, performances and results are presented in this contribution.This work was mainly supported by the National Natural Science Foundations of China (NSFC), under Grant No. 11075221, and a partly supported by the National Natural Science Foundation of China under Grant Nos. 10705054, 41073044 and 11265005