Strong, heat resistant and lightweight bionic ceramic-metal composite with potentials in space and military use.
Natural nacre that consists of brittle minerals and weak organics exhibits a high fracture toughness while retaining a high strength. The exceptional mechanical performance of nacre is attributed to its hierarchical structure like a ‘brick-and-mortar’ structure, which has inspired the development of tough ceramic-based composites. However, the practical applications of biomimetic structural ceramics are hindered by limited material size, fabrication efficiency and flexibility of being molded into various shapes. We herein report the fabrication of nacre-like ceramic-metal composites based on deformable alumina microspheres coated with nickel salt. Green bodies are produced by assembling the composite microspheres in molds with different shapes. During the hot-pressing sintering of the green bodies, the microspheres are flattened into platelets under pressure and fill up the entire space without visible voids. The aligned platelets are separated by nickel that is reduced from the nickel salt on their surface, constituting a typical ‘brick-and-mortar’ structure. By tuning the microsphere sizes, the microstructures of the composites can be optimized to obtain
a high flexural strength (386 MPa at room temperature and 286.86 MPa at 600°C) and a high fracture toughness (12.76 MPa·m1/2 at room temperature and 12.99 MPa·m1/2 at 600°C) simultaneously. This strategy opens a promising avenue for the feasible mass production and all-in-one molding of nacre-like ceramic-metal composites with various shapes, sizes and raw materials.
贝类软体动物拥有坚固的保护外壳,这得益于其内部精妙的珍珠母结构。这种天然的纳米复合材料,由微米尺度的文石片(“砖”)与少量有机质(“泥”),通过“砖泥堆砌”的方式巧妙地结合而成。这种跨尺度序构特征赋予了珍珠母出色的强度和韧性,使其在受到外力时能够有效地吸收和分散能量,展现出超越其单一组分的卓越力学性能,有望应用于轻量化结构复材、防护装备等领域。然而,要实现大尺寸、形状可控的生产,并满足复杂的工程需求,仍面临诸多技术挑战。
2025年3月,《国家科学评论》(National Science Review)以“Scalable and shapable nacre-like ceramic-metal composites based on deformable microspheres”为题,刊发中国科学技术大学俞书宏院士团队最新研究成果,报道了一种基于可变形微球有序组装制备高性能仿珍珠母陶瓷—金属复合材料的新策略。该材料兼具高抗弯强度与高断裂韧性,且可通过简易工艺实现大规模、多形状定制化生产,为仿珍珠母结构复合材料走向实用化提供了新路径。
研究团队打破传统的“砖泥”分步制备思路,采用“一步乳液法”首先制备了尺寸可调的氧化铝微球,经过筛后得到粒径一致的微球并在其表面包裹镍盐层,进一步通过模具组装和热压烧结,在此过程中修饰后的复合微球被压扁成片状陶瓷,金属镍层则形成分隔结构,精准地复刻了天然珍珠母的微观“砖泥”结构(图1)。结构表征显示,该材料在多个尺度上得到了优化。在宏观层面,氧化铝陶瓷片与金属镍层交替排列(图2a)。在微观层面,镍颗粒渗入陶瓷片内部增强韧性(图2b),同时,两相界面结合紧密(图2c)。这种跨尺度协同效应使优化后的复合材料在室温下抗弯强度达到386 MPa,600°C高温下仍保持286.86 MPa(图2d)。其断裂韧性更突破至12.76 MPa·m¹/²(室温)与12.99 MPa·m¹/²(高温)(图2e)。所制备的仿珍珠母复合材料在受力发生破坏时,裂纹会沿陶瓷-金属界面发生偏转,通过能量耗散避免瞬间失效,这一特性使其在极端环境(如航天器热防护、高速冲击防护涂层)中极具应用潜力。
这项研究是继该团队实现人工合成珍珠母工作的基础上(Science2016,354,107),进一步将仿珍珠母结构设计理念拓展至陶瓷—金属复合材料体系,并与快速塑形制备技术相结合,为助力仿生结构材料从实验室走向实用化迈出了关键一步。
