Enhancing the high-temperature energy storage properties of PEI dielectrics by constructing trap-rich covalently cross-linked networks via POSS-functionalized BNNS.

Polymer films are ideal dielectric materials for energy storage capacitors due to their light weight and flexibility, but lower energy density and poor heat resistance greatly limit their application in high-temperature energy storage. Unlike the traditional method of solely adding wide-bandgap inorganic fillers to enhance energy density, in this study we constructed trap-rich hybrid covalently cross-linked networks in polyetherimide (PEI) via reactive polyhedral oligomeric silsesquioxane (POSS)-functionalized boron nitride nanosheets (BNNS@POSS), which not only serve as interfacial layers for dielectric transitions and insulating barriers but also create deeper traps and higher energy barriers in the region of cross-linked chains. This strategy based on the co-modulation of interfaces and traps achieved the compatibility of high polarization and high breakdown strength and improved energy storage performance. Therefore, the composite film BNNS@POSS/PEI with the addition of 5 wt% BNNS@POSS achieved a maximum discharge energy density and charge-discharge efficiency at 150 °C of 6.16 J cm-3 and 89.92%, and maintained high values at 200 °C of 4.12 J cm-3 and 88.38%, respectively. Moreover, the glass transition temperature (Tg) of the composite dielectrics increased by 20.2 °C. This work provides a promising candidate material and development directions for research in the field of high-temperature energy storage capacitors.

Experimental and theoretical studies on stability of new stabilizers for N-methyl-P-nitroaniline derivative in CMDB propellants.

Although N-methyl-P-nitroaniline (MNA) was a quite effective stabilizer in composite modified double base (CMDB) propellants, it undergoes crystallization easily from nitroglycerin (NG) during storage. In order to improve its solubility in nitroglycerin (NG) and the stability in propellants, several new stabilizers including N-ethyl-p-nitroaniline (ENA), N-n-propyl-p-nitroaniline (n-PNA), N-i-propyl-p-nitroaniline (i-PNA), N-n-butyl-p-nitroaniline (n-BNA) and N-t-butyl-p-nitroaniline (t-BNA) were designed and synthesized to replace MNA by increasing the carbon chain length. The interaction between NG and different stabilizers was simulation by Materials Studio 5.5 and the stability and the high temperature stability performance of those new stabilizers in propellants were calculated by Gaussian 09. It was found that both the solubility of new stabilizers in NG and the stability and the high temperature stability performance of those in propellants were improved when the carbon chain length of substitution groups on nitrogen atom was increased. Thus, the n-BNA was a most potential stabilizer. Then all properties of the stabilizers were studied experimentally, which was agreement well with the theoretical analysis.