Microstructure-Based Thermochemical Ablation Model of Carbon/Carbon-Fiber Composites.

The microstructure of carbon fiber-reinforced carbon-matrix composites (carbon/carbon composites) has important effects on its ablation performance. However, the traditional macro-ablation methods have underestimated the ablation recession rate and ignored the influence of microstructure. To simulate the ablation of large-sized structures while accounting for the influence of microstructure, it is necessary to modify these methods. In this work, a thermochemical ablation model for carbon/carbon composites is proposed based on the evolution behavior of their microstructure. The ablation recession rate and surface temperature predicted by this model are in good agreement with the experimental results. Through numerical analysis, we found that the ablation recession rate of the material without carbon fibers is much greater than that of the material containing carbon fibers. The ablation recession rate is influenced by the fiber orientation due to the change in thermal conductivity. The anti-ablation efficiency of carbon/carbon composites can be improved by increasing their fiber radius, radiation coefficient, specific heat capacity, interphase density, and thermal conductivity coefficient. The thermochemical ablation model provides a guide for the design of better anti-ablation carbon/carbon composites.

A Smart Fluorescent Probe Based on Salicylaldehyde Schiff's Base with AIE and ESIPT Characteristics for the Detections of N2H4 and ClO.

Smart and versatile salicylaldehyde Schiff's bases have been proved their excellent performances including large shocks shift, dual emission wavelengths and sensitive to environment for fluorescence analysis. Herein, a simple salicylaldehyde Schiff's base molecular (PBAS) with aggregation-induced emission (AIE) and the excited-state intramolecular proton-transfer (ESIPT) effects was constructed for detecting N2H4 and ClO-. The highly specific and sensitive response to N2H4 was witnessed by the fast turn-on of the strong blue fluorescence and to ClO- was observed by the rapid turn off of the weak green fluorescence simultaneous decomposing of the probe. The results of mass spectrum analysis showed that probe PBAS decomposed under the influence of N2H4, whereas probe PBAS can complex with ClO- and prevent effective ESIPT process. Benefiting from its high properties, this fluorescence molecular provides an effective tool for probing N2H4 and ClO- in live cells.