Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties^1,2. Due to its important applications in technology, amorphous carbon with sp² or mixed sp²–sp³ hybridization has been explored and prepared^3,4, but synthesis of bulk amorphous carbon with sp³ concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties⁵. Here, we successfully synthesized millimetre-sized samples—with volumes 10³–10⁴ times as large as produced in earlier studies—of transparent, nearly pure sp³ amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 ± 2.3 GPa), elastic modulus (1,182 ± 40 GPa) and thermal conductivity (26.0 ± 1.3 W m⁻¹ K⁻¹) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids.

非晶材料从相应的晶体继承了短程和中程有序，因此保留了它的一些特性，同时仍然表现出新的特性^1,2。由于其在技术上的重要应用，已经探索和制备了具有sp ²或混合sp ² – sp ^{3杂化的无定形碳3,4}，但是合成具有接近 100% sp ^{3浓度的块状无定形碳仍然是一个挑战。}这些材料继承了金刚石的中短程顺序，也应继承其优越的性能⁵。在这里，我们成功合成了毫米大小的样本——体积为 10³ –10 ⁴倍于早期研究中产生的透明、几乎纯的sp ³无定形碳，通过在接近笼坍塌边界的压力下加热富勒烯。合成的材料由许多具有类金刚石短程/中程有序的随机取向簇组成，具有最高的硬度（101.9 ± 2.3 GPa）、弹性模量（1,182 ± 40 GPa）和热导率（26.0 ± 1.3 W m ^{- 1} 千^-1) 在任何已知的无定形材料中观察到。它还展示了从 1.85 eV 到 2.79 eV 可调谐的光学带隙。这些发现有助于我们了解先进的无定形材料和通过高压和高温技术合成大块无定形材料，并可能使无定形固体的新应用成为可能。