High-Throughput Electrospinning System| 3D self-supportive structures ofmicro /nanofiber assembliesconstructed in situ in air turbulentflow fields for thermal protection atextreme conditions

Professor Long Yunze & Associate Professor Zhang Jun from Qingdao University: In-situ Construction of 3D Micro/Nanofiber Aerogels for Thermal Insulation under Extreme Conditions in Turbulent Fields
The development of cutting-edge fields such as aerospace, national defense, and civil industry demands thermal-resistant, lightweight, and structurally stable thermal insulation materials. Ceramic aerogels show promising applications in high-temperature environments due to their high heat resistance and low thermal conductivity. Solution blow spinning (SBS) is a simple method for producing 3D ceramic aerogel fiber assemblies by utilizing air turbulence to construct and stack fluffy fiber layers. However, existing research lacks exploration of the formation and assembly mechanisms of 3D fiber assemblies.

Recently, the team of Professor Long Yunze and Associate Professor Zhang Jun from Qingdao University published their latest research 成果 in the journal Chemical Engineering Journal, titled "3D self-supportive structures of micro/nanofiber assemblies constructed in situ in air turbulent flow fields for thermal protection at extreme conditions". The researchers proposed a self-supporting assembly strategy based on SBS to in-situ prepare 3D fiber assemblies under high-speed air flow impact. They revealed the assembly mechanism of 3D fiber assemblies in air turbulent flow fields through in-situ observation by high-speed cameras and finite element analysis. Using this technology, they successfully prepared zirconia ceramic nanofiber aerogels (ZCFAs) with a layered structure, ultra-low density (9.5 mg·cm⁻³), and extremely low thermal conductivity (0.0254 W·m⁻¹·K⁻¹). ZCFAs exhibit recoverable compressibility at up to 90% strain and high compression fatigue resistance with 1000 cycles at 50% strain. Additionally, the aerogel has the same tensile breaking strain (approximately 23.5%) at 1300 °C as at room temperature. This work is of great significance for the development, large-scale production, and application of high-performance 3D fiber aerogels.

Figure 1: Self-supporting assembly for preparing fiber assemblies.

Based on PVA/TEOS solutions, the team achieved the transition of fiber assemblies from 2D to 3D by controlling solution viscosity and air flow velocity without changing the spinning and collection devices. They also identified an air flow velocity-solution viscosity region for stable assembly of 3D fiber assemblies, termed the "3D region". The study indicates that sufficient solution viscosity is necessary to enhance fiber rigidity and resistance to air flow impact, which is crucial for stably constructing 3D self-supporting structures. Moreover, the interaction between air flow velocity and solution viscosity is critical for effectively regulating the structure of the obtained fibers. These two parameters must be maintained within the "3D region", as too low or too high air flow velocity or solution viscosity will hinder the in-situ construction of 3D fiber assemblies.

Figure 2: Material properties of ZCFAs.

Based on the above results, ZCFAs with low density and high porosity (99.4%) were obtained by adjusting the spinning solution viscosity and air flow velocity within the "3D region" and calcination. ZCFAs exhibit a layered structure with smooth fiber surface morphology. The ceramic fibers consist of ZrO₂ nanoparticles embedded in an amorphous matrix, which enhances the flexibility of ZCFAs. 

Figure 3: Mechanical properties of ZCFAs.

ZCFAs have high thermal stability (1300 °C) and the same high tensile breaking strain (~23.5%) at 1300 °C as at room temperature. The layered ZCFAs show a recoverable compressive strain of up to 90%, high compression fatigue resistance with 1000 cycles at 50% strain, and stable viscoelastic properties across a wide temperature range.

Figure 4: Thermal insulation properties of ZCFAs.