Mordkovich Vladimir Z, Karaeva Aida R, Kazennov Nikita V, Mitberg Eduard B, Nasraoui Mariem, Kulnitskiy Boris A, Blank Vladimir D
Technological Institute for Superhard and Novel Carbon Materials, 7A Tsentralnaya street, Troitsk, 108840 Moscow, Russia.
Department of Electrochemistry, Faculty of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russia.
Materials (Basel). 2022 Oct 21;15(20):7377. doi: 10.3390/ma15207377.
Catalytic synthesis of carbon nanotubes (CNT) produces numerous various byproducts such as soot, graphite platelets, catalyst nanoparticles, etc. Identification of the byproduct formation mechanisms would help develop routes to more selective synthesis of better carbon-based materials. This work reports on the identification of the formation zone and conditions for rather unusual closed multishell carbon nanocapsules in a reactor for float-catalysis synthesis of longer CNT. Structural investigation of the formed nanocapsule material along with computational fluid dynamics (CFD) simulations of the reactor suggested a nanocapsule formation mechanism, in which CNT embryos are suppressed in growth by the in-reactor turbulence. By means of TEM and FFT investigation, it is found that differently oriented single crystals of γ-FeO, which do not have clear connections with each other, determine a spherical surface. The carbon atoms that seep through these joints do not form crystalline graphite layers. The resulting additional product in the form of graphene-coated (γ-Fe/FeC)/γ-FeO nanoparticles can be a lightweight and effective microwave absorber.
碳纳米管（CNT）的催化合成会产生大量各种副产物，如烟灰、石墨片、催化剂纳米颗粒等。确定副产物的形成机制将有助于开发出更具选择性的路线，以合成更好的碳基材料。这项工作报告了在用于浮动催化合成较长碳纳米管的反应器中，识别相当不寻常的封闭多壳碳纳米胶囊的形成区域和条件。对形成的纳米胶囊材料进行结构研究，并结合反应器的计算流体动力学（CFD）模拟，提出了一种纳米胶囊形成机制，即碳纳米管胚胎在反应器内的湍流作用下生长受到抑制。通过透射电子显微镜（TEM）和快速傅里叶变换（FFT）研究发现，相互之间没有明显连接的不同取向的γ-FeO单晶决定了一个球形表面。渗透过这些连接处的碳原子不会形成结晶石墨层。以石墨烯包覆的（γ-Fe/FeC）/γ-FeO纳米颗粒形式产生的额外产物可以成为一种轻质且有效的微波吸收剂。
