Multifunctional Thermal Barrier Application Composite with SiC Nanowires Enhanced Structural Health Monitoring Sensitivity and Interface Performance.

Carbon fiber (CF)-reinforced ceramic composites show the attractive potential for next generation thermal protection materials because of their outstanding reliability and excellent high-temperature resistance but are facing great challenges in the combination of the engineering practicality and versatility. Herein, it is demonstrated that silicon carbide nanowires can be grown on the surface of CF to create a multifunctional thermal barrier application composite. The embedding of the silicon carbide nanowires in the interface of CF and ceramic matrix significantly increased the structural health monitoring sensitivity and interface strength of the composites. Compared to the conventional CF/ZrC composites, the structural health monitoring sensitivity of the composites with SiC nanowires is greatly elevated with a 14-fold improvement. Additional investigations revealed that the multifunctional SiCnws-CF/ZrC nanocomposites enjoyed a low thermal conductivity of 0.49 W/(m·K), a light weight (0.76-1.85 g/cm3), and a relative high compressive strength of 23.64 MPa, which is favorite in applying as a thermal barrier material. Furthermore, the interface design strategy could be extended as a universal method in fabricating various fiber-reinforced composites for a wide range of other applications.

Significantly enhanced mechanical properties in AlN helix.

To safely and reliably use aluminum nitride (AlN) helices in the fabrication of novel micro/nanodevices, it is very important to know their mechanical properties. Herein, we investigate the mechanical properties of individual AlN helices using an in situ tensile-bending test. Tensile tests reveal that an AlN helix has an average ε of ∼4.7 ± 0.8% elastic deformation before a typical brittle fracture occurs. The bending test shows a two-step mechanical feature-linear-elastic followed by an elastic-plastic process-with an average ε bent of ∼54.5 ± 0.6%. Our results provide direct cognition about the mechanical properties of AlN helices and their benefit to the design of AlN-based flexible micro/nanodevices.

Enhanced mechanical, thermal, and electric properties of graphene aerogels via supercritical ethanol drying and high-temperature thermal reduction.

Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels' applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stability and electric conductivities via hydrothermal reduction and supercritical ethanol drying. Annealing at 1500 °C resulted in slightly increased thermal conductivity and further improvement in mechanical properties, oxidation temperature and electric conductivity of the graphene aerogel. The large BET surface areas, together with strong mechanical properties, low thermal conductivities, high thermal stability and electrical conductivities made these graphene aerogels feasible candidates for use in a number of fields covering from batteries to sensors, electrodes, lightweight conductor and insulation materials.

Ordered Silica Nanoparticles Grown on a Three-Dimensional Carbon Fiber Architecture Substrate with Siliconborocarbonitride Ceramic as a Thermal Barrier Coating.

Hierarchical structure consisting of ordered silica nanoparticles grown onto carbon fiber (CF) has been fabricated to improve the interfacial properties between the CFs and polymer matrix. To improve the reactivity of CFs, their surface was modified using poly(1,4-phenylene diisocyanate) (PPDI) via in situ polymerization, which also resulted in the distribution of numerous isocyanate groups on the surface of CFs. Silica nanoparticles were modified on the interface of CF-PPDI by chemical grafting method. The microstructure, chemical composition, and interfacial properties of CFs with ordered silica nanoparticles were comprehensively investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Results indicated an obvious increase in the interfacial shear strength, compared to that of CF precursor, which was attributed to silica nanoparticles interacting with the epoxy resin. Furthermore, siliconborocarbonitride (SiBCN) ceramic was used as thermal barrier coating to enhance 3D CF architecture substrate antioxidant and ablation properties. Thermogravimetric results show that the thermal stability of the CF with SiBCN ceramic layer has a marked increase at high temperature.