We uncover the fracture characteristics of a boron nitride foam (BNF): a highly promising nanomaterial with a large band gap, superelastic behavior, and high surface area. By applying tension tests to BNF samples and characterizing them using image-processing tools and detailed scanning and transmission electron microscopies, we demonstrate a transition from brittle to a ductile fracture. Complementary mechanical analyses revealed that constraints originating from the synthesis process induce significant prestresses in the BNF and that wall thickness variations explain the fracture transition. We also show that BNF has a nearly zero Poisson’s ratio and a high (>200 MPa) shear strength and that it absorbs a significant amount of energy before the fracture occurs. Thus, our findings shed light on the fundamental microscopic-scale mechanics of BNF, paving the way toward its integration into advanced applications, such as wearable electronics and energy absorbers.

中文翻译：

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3D 氮化硼泡沫的力学性能和脆性到韧性断裂转变

我们揭示了氮化硼泡沫 (BNF) 的断裂特征：这是一种非常有前途的纳米材料，具有大带隙、超弹性行为和高表面积。通过对 BNF 样品进行拉伸测试并使用图像处理工具和详细的扫描和透射电子显微镜对其进行表征，我们展示了从脆性断裂到韧性断裂的转变。补充力学分析表明，源自合成过程的约束会在 BNF 中引起显着的预应力，并且壁厚变化解释了断裂转变。我们还表明，BNF 具有几乎为零的泊松比和高 (>200 MPa) 剪切强度，并且它在断裂发生之前吸收了大量的能量。因此，我们的研究结果揭示了 BNF 的基本微观尺度力学，