Enhanced thermal shock response of Al₂O₃–graphite composites through a layered architectural design

Abstract

The use of ceramics such as alumina in moving components often requires the addition of low friction materials such as graphite. A new strategy for improving toughness, strength, and thermal‐shock resistance of Al2O3–graphite self‐lubricating composites was proposed in this study. Alumina layers embedded between Al2O3–graphite layers were fabricated and tested after thermal shock conditions ranging between 500 °C and 800 °C maximum temperature. Retained strength and apparent fracture toughness after the tests were compared to room temperature values. Results show that compressive residual stresses generated in the outer Al2O3–graphite layers during cooling down from sintering improve the failure resistance of the materials. The introduction of heat‐resistant particles (Al2O3 particles) into graphite layers combined with a layered architecture can greatly decrease the oxidation degradation of the materials below 500 °C. In addition, the retained strength and toughness in the layered architectures after thermal shock between 550 °C and 800 °C remains constant, thus indicating that the new‐developed Al2O3/Al2O3–graphite laminated composites may be reliable candidates for self–lubricating applications also for elevated temperatures.

Development and Prospects of High Strength Pre-stressed Ceramics

“…分层铺叠, 按相互平行的层面配置增强相, 各层之 间通过基体材料连接, 主要利用增强层与陶瓷基体材 料的热膨胀系数的差异来提供预压应力。Song 等 [47] 利用膨胀系数为 8. [47] Fig.…”

“…分层铺叠, 按相互平行的层面配置增强相, 各层之 间通过基体材料连接, 主要利用增强层与陶瓷基体材 料的热膨胀系数的差异来提供预压应力。Song 等 [47] 利用膨胀系数为 8. [47] Fig. 4 Schematic diagram of the laminated composites (a), microstructures of different structural composites (b-g) and mechanical properties of different laminate samples (h) [47] ( 而提出的金属紧凑型约束预应力陶瓷(Pre-stressed ceramics) [43] , 即利用金属熔体包裹陶瓷, 在冷却中 Fig.…”

Bioinspired alumina/reduced graphene oxide fibrous monolithic ceramic and its fracture responses

“…They also present much lower density than most structural materials, and have great potential applications in aviation, aerospace, and other high‐stress, high‐temperature operating conditions . However, their strong covalent bonds also completely prevent the ductile behavior of ceramics, and this feature has become its most prominent inferiority . Their lack of plasticity makes ceramic materials unpredictable and catastrophic failure occur once they are destroyed by external stress, thereby greatly limiting their extensive applications as structural components .…”

“…1,2 However, their strong covalent bonds also completely prevent the ductile behavior of ceramics, and this feature has become its most prominent inferiority. 3,4 Their lack of plasticity makes ceramic materials unpredictable and catastrophic failure occur once they are destroyed by external stress, thereby greatly limiting their extensive applications as structural components. 5 Therefore, reducing the brittleness of ceramics and improving their ductile behavior have become crucial toward developing damage-resistant ceramics.…”

Fibrous monolithic ceramic with a single alumina phase: Fracture and high‐temperature tribological behaviors

“…However, since the fiber cells and boundaries are different materials, they have notably different physical and chemical properties, such as thermal expansion and oxidation resistance. Therefore, when subjected to elevated temperatures or high/low‐temperature alternating environments, the boundaries of the ceramic composites tend to be oxidized, and the fibers and boundaries to be prone to exfoliation because of due to the large residual stresses, which severely limits their wider applicability . Moreover, multiphase composites have become more resource dependent and more costly.…”