As a key material in the high-temperature industrial field, the thermal shock resistance of refractory matter resin powder directly affects the equipment life and production efficiency.
The porosity of refractory matter resin powder needs to be controlled in the range of 13%-20%. Appropriate porosity can form a "maze effect" of crack propagation, complicating the thermal stress release path. For example, under high-temperature thermal shock conditions, the cross network of short cracks can absorb more elastic strain energy and avoid catastrophic fracture. The pore structure can be regulated by adding hollow microspheres or pore-forming agents to the formula, while ensuring the uniformity of pore distribution to maintain the overall strength of the material.
The introduction of large-particle aggregates (such as corundum and silicon carbide) can significantly improve thermal shock resistance. The difference in elastic modulus between aggregates and matrix forms a "bridge effect", which causes cracks to turn around large particles instead of penetrating directly. Studies have shown that when the critical aggregate size is controlled at 1-3mm, the crack propagation path can be extended by more than 30%. In addition, the addition of rod-shaped or flaky aggregates can further enhance the crack turning ability and improve toughness through nonlinear fracture mechanisms.
The interface bonding strength between aggregate and matrix needs to achieve dynamic balance through interface design. If the bonding is too strong, cracks are easy to penetrate directly; if the bonding is too weak, the material strength is insufficient. Optimization strategies include: using pre-treated aggregate to form a transition layer, or introducing a depolymerized phase (such as a silicate glass phase) to form an energy dissipation mechanism at the interface. For example, in the alumina-spinel system, the formation of a magnesium-aluminum spinel layer through interfacial reaction can improve the interface toughness by 20%-30%.
Adding phases with low coefficient of thermal expansion (CTE) (such as cordierite and zircon) to the matrix can introduce controllable microcracks. When the material is heated, the low CTE phase and the matrix produce thermal mismatch and form a microcrack network. However, the addition amount needs to be strictly controlled (usually not more than 5%) to avoid microcrack aggregation and strength loss. For example, adding 3% cordierite to the mullite matrix can improve thermal shock stability by 40%.
Uniformly dispersed fibrous reinforcements (such as steel fibers and silicon carbide whiskers) can significantly improve fracture energy. The fiber absorbs energy through bridging, pull-out and fracture mechanisms, making the material exhibit nonlinear fracture characteristics. Studies have shown that when the fiber volume fraction is 2%-5%, the fracture toughness can be increased by more than 50%. In addition, in-situ generated whiskers (such as tetragonal whiskers generated by ZrO2 phase transformation) can further enhance the crack diversion ability.
Adding plastic components (such as alumina sol) or using high-viscosity liquid phases formed during calcination (such as ZrO2-SiO2 glass phase) can significantly improve the toughness of the material. The plastic phase absorbs elastic strain energy through viscous flow. For example, in the zircon-zirconia system, the ZrO2 grains formed after calcination work synergistically with the SiO2 glass phase to increase the toughness by 2-3 times.
A breakthrough in thermal shock resistance is achieved through multiphase synergy. For example, the combination of low CTE phase, fiber reinforcement and plastic phase can simultaneously reduce thermal stress, enhance crack diversion ability and energy absorption capacity. A study has improved the thermal shock stability by 70% by adding 3% cordierite, 2% steel fiber and 5% alumina sol to the alumina matrix, while keeping the strength loss below 15%.
The optimization of thermal shock resistance of refractory matter resin powder needs to start with the coordinated design of material microstructure and macro properties. Through strategies such as pore network, particle grading, interface regulation, and functional phase introduction, multiple mechanisms of thermal stress release, crack deflection and energy absorption can be achieved.
