Electrospining Machine: Ceramic aerogel with super thermal insulation performance at 1700 °C constructed by reactive electrospinning of self-crosslinked nanofiber networks

Background

In key technical fields such as national defense, military industry, aerospace, etc., the extreme working conditions of thermal insulation materials such as complex thermomechanical stress forms, large temperature conversion gradients, and high thermal shock frequencies require materials to have reliable structural stability and excellent thermal insulation capabilities. Ceramic aerogels have attracted much attention due to their structural properties, such as small pore size and high porosity, which greatly limit the heat transfer of gas molecules, and have low thermal conductivity comparable to air and excellent fire resistance and corrosion resistance. However, due to the inherent brittleness of strong chemical bonds and low dislocation slip systems, ceramic aerogels are prone to sudden and catastrophic structural collapse under high-frequency large external forces. Especially in extremely high temperature environments (above 1500°C), the malignant increase in grain size may cause irreversible damage to the structure of ceramic aerogels, thereby accelerating this process and greatly increasing the probability of catastrophic accidents. Therefore, the preparation of ceramic aerogels with excellent structural stability and thermal stability is the key to obtaining reliable thermal protection materials for extreme high temperature environments.

The main point of this paper

Research progress in structural engineering:

Researchers have improved the mechanical properties of ceramic aerogels by fiber reinforcement, three-dimensional reconstruction of nanofibers, and layer-by-layer stacking of nanofiber membranes

Limitations of organic fiber reinforcement:

Organic fiber reinforcement can improve mechanical strength, but is not resistant to high temperatures, and has weak interface interactions with ceramic particles, resulting in instability at high temperatures

One-dimensional nanofiber ceramic aerogels:

It has flexibility and can form a flexible honeycomb structure, which can be used at temperatures up to 1300°C, but cannot withstand huge loads

Application of two-dimensional ceramic nanofiber membranes:

Replace one-dimensional ceramic nanofibers, improve load resistance through surface contact mode and arch bridge formation, and recover under 90% compression deformation

Challenges of thermal insulation performance:

The large mesh structure leads to poor thermal insulation performance. Researchers have tried to Improved by interlacing silica nanoparticle aerogel, but the use temperature is reduced to 1100℃

Component design avoids mechanical and thermal mutual exclusion problems:

Integrated molding of ceramic nanofiber aerogels with twin crystal structures and amorphous components can initially withstand 1500°C, but microstructure design is challenging

Application of highly active long-chain inorganic molecules (PP-HAIM):

Design of PP-HAIM, whose sol can form a two-dimensional ceramic nanofiber membrane (CNF-CNNS) with a cross-linked nanofiber network structure through reactive electrospinning, ensuring structural stability at 1700℃

Characteristics of CNF-CNNS:

It has excellent flexibility, and is bonded to the interface of SiO2 particle aerogel to form a semi-closed pore structure, used as the upper part of the ceramic aerogel, and chemical cross-linking ensures network stability

Thermal insulation breakthrough in extreme environments: ceramic gas gel with ultra-low thermal conductivity

Thermal insulation challenges:

The material needs to withstand complex thermomechanical stresses, gradient temperature transitions, and high-frequency thermal shocks.

Limitations of ceramic aerogels:

The thermal insulation capacity and thermomechanical stability are limited in extremely high temperature environments above 1500°C.

Design of new ceramic aerogels:

A cross-linked nanofiber network is constructed through a reactive electrospinning strategy to ensure thermomechanical stability and super insulation under extreme conditions.

Ultra-low thermal conductivity:

Ceramic aerogels have an ultra-low thermal conductivity of 0.027 W m⁻¹ K⁻¹.

Performance in high temperature environments:

In a high temperature environment of 1700°C, the cold surface temperature is only 303°C.

Mechanical durability:

After a significant gradient temperature transition from liquid nitrogen to a 1700°C flame, it can still withstand thousands of mechanical actions such as shearing, bending, and compression.

Structural stability:

Under extreme temperatures and mechanical actions, ceramic aerogels will not collapse structurally

Summarize

Ceramic aerogel has excellent thermal protection performance and is expected to become a key material for the preparation of long-term and reliable extreme environment thermal protection systems. The binary synergistic structure composed of nanofiber-nanoparticle aerogel provides ceramic aerogel with super thermal insulation performance, while the cross-linked nanofiber network structure gives the material excellent structural stability, so that ceramic aerogel can be used for a long time in a wide temperature range. We have elaborated in depth the design principle of ceramic aerogel and the logic of coping with complex and changing environments. This design concept can provide reference and new theoretical insights for the preparation of thermal insulation materials in extreme high temperature environments. The raw materials we use are inexpensive and the process is simple. If we can solve the problem of uniform loading of silica aerogel particles during batch preparation, we can realize the industrial production of ceramic aerogel.