Diamond can be amorphous: from scenario to reality

AUGUST 22, 2017 — A team led by HPSTAR scientist, Dr. Zhidan Zeng synthesizes a new form of carbon—“amorphous diamond”—under high pressure and temperature (HPHT). This bulk amorphous diamond obtained under HPHT can be maintained to ambient conditions for potential applications, realizing possible the hardest amorphous (glass) material ever discovered. This work is recently published as an article by Nature Communications (Synthesis of quenchable amorphous diamond. Nature Communications, 2017).

金刚石是天然存在的硬度最高的材料，同时还具有最高的弹性模量（体模量），最高的原子密度、最高的热导率等优异性质。这些优异性能和其特殊结构有关。本研究采用玻璃碳（glassy carbon）作为起始材料，利用高压原位激光加温技术首次成功合成了块体状的100% sp3 共价键的新型非晶态碳材料。通过同步辐射x 射线衍射、高分辨电子显微镜及电子能量损失谱等多种实验手段，一致证明这种新型碳材料具有典型非晶态结构，且材料内部所有碳原子间的共价键都是sp3 键，因而是真正的“非晶态金刚石”。非晶态金刚石的合成说明金刚石并不是唯一的全部碳原子都以sp3 键结合的碳材料，改变了我们对碳材料的传统认知。“非晶态金刚石”由于其无序的原子结构而具备非晶材料各向同性的特点，且材料内部不存在晶界、位错等传统晶体缺陷，又因高强度sp3 共价键的存在而很可能具备接近甚至超越单晶金刚石的优异性能（高压原位同步辐射x 射线衍射实验已经证实其体模量高于金刚石），作为一种新型的超硬材料，可能在众多科学技术领域取得重要应用。

Lithiation-inducedstress in Li-ion batteries from micro-Raman Spectroscopy

Stress is along standing challenge for the applications of silicon(Si) anodesin lithium(Li)ion batteries. Using in situ micro Raman spectroscopy, a team ofscientists led by Dr. Zhidan Zeng at the Center for High Pressure Science &Technology Advanced Research (HPSTAR) measured the stress in siliconnanoparticles in a working Li-ion battery for the first time. This new studywould be helpful in understanding how the nanostructured silicon anodesfracture during battery operation, and therefore provide guidance for theirfuture design.