carbon nanoscrolls
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Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4075
Author(s):  
Casey Sugie ◽  
Alexandra Navrotsky ◽  
Stefan Lauterbach ◽  
Hans-Joachim Kleebe ◽  
Gabriela Mera

Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp2 hybridized carbon, tetrahedrally coordinated SiO4, and tetrahedrally coordinated silicon with carbon substitution for oxygen, called “mixed bonds.” Here we synthesize two preceramic polymers possessing both phenyl substituents as unique organic groups. In one precursor, the phenyl group is directly bonded to silicon, resulting in a SiOC polymer-derived ceramic (PDC) with mixed bonding. In the other precursor, the phenyl group is bonded to the silicon through Si-O-C bridges, which results in a SiOC PDC without mixed bonding. Radial breathing-like mode bands in the Raman spectra reveal that SiOC PDCs contain carbon nanoscrolls with spiral-like rolled-up geometry and open edges at the ends of their structure. Calorimetric measurements of the heat of dissolution in a molten salt solvent show that the SiOC PDCs with mixed bonding have negative enthalpies of formation with respect to crystalline components (silicon carbide, cristobalite, and graphite) and are more thermodynamically stable than those without. The heats of formation from crystalline SiO2, SiC, and C of SiOC PDCs without mixed bonding are close to zero and depend on the pyrolysis temperature. Solid state MAS NMR confirms the presence or absence of mixed bonding and further shows that, without mixed bonding, terminal hydroxyls are bound to some of the Si-O tetrahedra. This study indicates that mixed bonding, along with additional factors, such as the presence of terminal hydroxyl groups, contributes to the thermodynamic stability of SiOC PDCs.


Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1372
Author(s):  
Shih-Yang Lin ◽  
Sheng-Lin Chang ◽  
Cheng-Ru Chiang ◽  
Wei-Bang Li ◽  
Hsin-Yi Liu ◽  
...  

How to form carbon nanoscrolls with non-uniform curvatures is worthy of a detailed investigation. The first-principles method is suitable for studying the combined effects due to the finite-size confinement, the edge-dependent interactions, the interlayer atomic interactions, the mechanical strains, and the magnetic configurations. The complex mechanisms can induce unusual essential properties, e.g., the optimal structures, magnetism, band gaps and energy dispersions. To reach a stable spiral profile, the requirements on the critical nanoribbon width and overlapping length will be thoroughly explored by evaluating the width-dependent scrolling energies. A comparison of formation energy between armchair and zigzag nanoscrolls is useful in understanding the experimental characterizations. The spin-up and spin-down distributions near the zigzag edges are examined for their magnetic environments. This accounts for the conservation or destruction of spin degeneracy. The various curved surfaces on a relaxed nanoscroll will create complicated multi-orbital hybridizations so that the low-lying energy dispersions and energy gaps are expected to be very sensitive to ribbon width, especially for those of armchair systems. Finally, the planar, curved, folded, and scrolled graphene nanoribbons are compared with one another to illustrate the geometry-induced diversity.


2021 ◽  
Vol 542 ◽  
pp. 148639
Author(s):  
Hai-zhen Zhang ◽  
Halidan Maimaiti ◽  
Pei-shuai Zhai ◽  
Shi-Xin Wang ◽  
Bo Xu

2021 ◽  
Author(s):  
Binhong He ◽  
Yangyang Chen ◽  
Da Hu ◽  
Ziyan Wen ◽  
Minjie Zhou ◽  
...  

Rational design of oxygen reduction reaction (ORR) electrocatalysts is essential for promoting the development of clean energy conversion devices. Herein, we report an in–situ sacrificial template strategy combining with external...


Author(s):  
Sonia Saini ◽  
Reshmi S ◽  
Girish Gowda ◽  
Kuntala Bhattacharjee

: Carbon nanoscrolls (CNS), a one dimensional (1D) helical form of carbon have received enormous attention recently due to their unique structure, superior properties and potential applications. In this work,...


2020 ◽  
Vol 31 (31) ◽  
pp. 315707
Author(s):  
Taewoo Uhm ◽  
Jeonghyeon Na ◽  
Jae-Ung Lee ◽  
Hyeonsik Cheong ◽  
Sang Wook Lee ◽  
...  

2019 ◽  
Vol 126 (1) ◽  
pp. 014301 ◽  
Author(s):  
Anping Hua ◽  
Yixuan Xue ◽  
Rumeng Liu ◽  
Ning Wei ◽  
Junhua Zhao

2018 ◽  
Vol 29 (22) ◽  
pp. 18891-18904 ◽  
Author(s):  
Hongdong Liu ◽  
Tao Le ◽  
Lei Zhang ◽  
Maowen Xu
Keyword(s):  

ACS Nano ◽  
2018 ◽  
Vol 12 (8) ◽  
pp. 8456-8466 ◽  
Author(s):  
Zhaomeng Liu ◽  
Jue Wang ◽  
Hongbo Ding ◽  
Suhua Chen ◽  
Xinzhi Yu ◽  
...  
Keyword(s):  

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