Al₅BO₉ is a promising thermal sealing material for hypersonic vehicles due to its low density, theoretically predicted low shear modulus, and low thermal conductivity. However, experimental investigations on the mechanical and thermal properties of bulk Al₅BO₉ have not been carried out. Herein, we report the mechanical and thermal properties of bulk Al₅BO₉ prepared by spark plasma sintering of solid‐state reaction synthesized Al₅BO₉ powders. The bulk (B ), shear (G ), and Young's (E ) moduli are 148 GPa, 85 GPa, and 214 GPa, respectively, which are close to the theoretical values. The Pugh's ratio G/B is 0.574, indicating its intrinsic damage tolerance, which is also revealed by Hertzian contact test. The Vickers hardness (H _v) is 10.8 GPa, being lower than mullite. The flexural strength, compressive strength, and fracture toughness are, respectively, 277 ± 35 MPa, 814 ± 75 MPa, and 2.4 ± 0.3 MPa·m^1/2, which are close to those of mullite. Al₅BO₉ has anisotropic coefficient of thermal expansion (CTE) in three crystallographic directions, ie α _a = (4.40 ± 0.21) × 10⁻⁶ K⁻¹, α _b = (7.11 ± 0.18) × 10⁻⁶ K⁻¹, α _c = (6.70 ± 0.29) × 10⁻⁶ K⁻¹ from Debye temperature to 1473 K, which are underpinned by its structural feature, ie lower α _a is resulted from the edge‐shared AlO₆ octahedron chains along the [100] direction. The average CTE is (6.05 ± 0.06) × 10⁻⁶ K⁻¹. The thermal conductivity declines with temperature as κ  = 1336.39/T + 1.97, consisting with predicted trend from Slack's model. The low thermal conductivity and low density guarantee Al₅BO₉ a promising candidate as ceramic wafer in the seal structure for hypersonic vehicles.

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轻质硼莫来石Al5BO9的机械和热性能

Al ₅ BO ₉由于其低密度，理论上预测的低剪切模量和低热导率而成为一种用于高超音速车辆的热密封材料。然而，尚未对块状Al ₅ BO ₉的机械和热性能进行实验研究。在这里，我们报告了固态反应合成的Al ₅ BO ₉粉末的火花等离子体烧结制备的块状Al ₅ BO ₉的力学和热性能。体积（B），剪切力（G）和杨氏（E的模量分别为148 GPa，85 GPa和214 GPa，接近理论值。普氏比G / B为0.574，表明其固有的损伤耐受性，这也通过赫兹接触试验揭示。维氏硬度（H _v）为10.8 GPa，低于莫来石。弯曲强度，抗压强度和断裂韧性分别为277±35MPa，814±75MPa和2.4±0.3MPa·m ^1/2，与莫来石相近。人₅ BO ₉具有在三个晶体学方向的热膨胀（CTE）的系数的各向异性，即，α_一个 =（4.40±0.21）×10 ^-6 ķ ^-1，α _b =（7.11±0.18）×10 ^-6 ķ ^-1，α _Ç  =（6.70±0.29）×10 ^-6 ķ ^-1从德拜温度到1473 K，其通过它的结构特征支撑，即降低α_一个是导致沿[100]方向从边缘共享的AlO ₆八面体链中提取。平均CTE为（6.05±0.06）×10 ^-6  K ^-1。导热系数随温度的下降而下降，κ  = 1336.39 / T + 1.97，这与Slack模型的预测趋势一致。低导热率和低密度保证了Al ₅ BO ₉ 在超音速飞行器的密封结构中作为陶瓷晶片有希望的候选者。