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3,137 results on '"Kang Feiyu"'

9. Proton Collective Quantum Tunneling Induces Anomalous Thermal Conductivity of Ice under Pressure

Author

Wang, Yufeng, Luo, Ripeng, Chen, Jian, Zhou, Xuefeng, Wang, Shanmin, Wu, Junqiao, Kang, Feiyu, Yu, Kuang, and Sun, Bo

Subjects
Physics - Chemical Physics, Condensed Matter - Materials Science
Abstract

Proton tunneling is believed to be non-local in ice but has never been shown experimentally. Here we measured thermal conductivity of ice under pressure up to 50 GPa and found it to increase with pressure until 20 GPa but decrease at higher pressures. We attribute this anomalous drop of thermal conductivity to the collective tunneling of protons at high pressures, supported by large-scale quantum molecular dynamics simulations. The collective tunneling loops span several picoseconds in time and are as large as nanometers in space, which match the phonon periods and wavelengths, leading to strong phonon scattering at high pressures. Our results show direct evidence of collective quantum motion existing in high-pressure ice and provide a new perspective to understanding the coupling between phonon propagation and atomic tunneling.

Published
2023

10. Synthesis and Enhanced Field-Emission of Thin-Walled, Open-Ended, and Well-Aligned N-Doped Carbon Nanotubes

Author

Hu Qiang, Wang Kunlin, Wu Dehai, Cui Tongxiang, Lv Ruitao, Kang Feiyu, and Gu Jialin

Subjects
Carbon nanotubes, Thin-walled open-ended and aligned, Thin-walled index, Bamboo-shaped carbon nanotubes, Field emission, Free-standing, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

Abstract Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs) on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT). The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780–860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 105, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm2 free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.

Published
2010
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12. Roadmap for rechargeable batteries: present and beyond

Author

Xin, Sen, Zhang, Xu, Wang, Lin, Yu, Haijun, Chang, Xin, Zhao, Yu-Ming, Meng, Qinghai, Xu, Pan, Zhao, Chen-Zi, Chen, Jiahang, Lu, Huichao, Kong, Xirui, Wang, Jiulin, Chen, Kai, Huang, Gang, Zhang, Xinbo, Su, Yu, Xiao, Yao, Chou, Shu-Lei, Zhang, Shilin, Guo, Zaiping, Du, Aobing, Cui, Guanglei, Yang, Gaojing, Zhao, Qing, Dong, Liubing, Zhou, Dong, Kang, Feiyu, Hong, Hu, Zhi, Chunyi, Yuan, Zhizhang, Li, Xianfeng, Mo, Yifei, Zhu, Yizhou, Yu, Dongfang, Lei, Xincheng, Zhao, Jianxiong, Wang, Jiayi, Su, Dong, Guo, Yu-Guo, Zhang, Qiang, Chen, Jun, and Wan, Li-Jun

Published
2024
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19. Incoherent phonon transport dominates heat conduction across van der Waals superlattices

Author

Zhao, Lu, Zhang, Lijuan, Song, Houfu, Du, Hongda, Wang, Renshaw X., Wu, Junqiao, Kang, Feiyu, and Sun, Bo

Subjects
Condensed Matter - Materials Science
Abstract

Heat conduction mechanisms in superlattices could be different across different types of interfaces. Van der Waals superlattices are structures physically assembled through weak van der Waals interactions by design, and may host properties beyond the traditional limits of lattice matching and processing compatibility, offering new types of interfaces. In this work, natural van der Waals (SnS)1.17(NbS2)n superlattices are synthesized, and their thermal conductivities are measured by time-domain thermoreflectance as a function of interface density. Our results show that heat conduction of (SnS)1.17(NbS2)n superlattices is dominated by interface scattering when the coherent length of phonons is larger than the superlattice period, indicating incoherent phonon transport dominates cross-plane heat conduction in van der Waals superlattices even when the period is atomically thin and abrupt. Moreover, our result suggests that the widely accepted heat conduction mechanism for conventional superlattices that coherent phonons dominate when the period is short, is not applicable due to symmetry breaking in most van der Waals superlattices. Our findings provide new insight for understanding the thermal behavior of van der Waals superlattices, and devise approaches for effective thermal management of superlattices depending on the distinct types of interfaces., Comment: 31 pages, 7 figures

Published
2022
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36. Inelastic phonon transport across atomically sharp metal/semiconductor interfaces

Author

Li, Qinshu, Liu, Fang, Hu, Song, Song, Houfu, Yang, Susu, Jiang, Hailing, Wang, Tao, Koh, Yee Kan, Zhao, Changying, Kang, Feiyu, Wu, Junqiao, Gu, Xiaokun, Sun, Bo, and Wang, Xinqiang

Subjects
Engineering, Physical Sciences, Condensed Matter Physics
Abstract

Understanding thermal transport across metal/semiconductor interfaces is crucial for the heat dissipation of electronics. The dominant heat carriers in non-metals, phonons, are thought to transport elastically across most interfaces, except for a few extreme cases where the two materials that formed the interface are highly dissimilar with a large difference in Debye temperature. In this work, we show that even for two materials with similar Debye temperatures (Al/Si, Al/GaN), a substantial portion of phonons will transport inelastically across their interfaces at high temperatures, significantly enhancing interface thermal conductance. Moreover, we find that interface sharpness strongly affects phonon transport process. For atomically sharp interfaces, phonons are allowed to transport inelastically and interface thermal conductance linearly increases at high temperatures. With a diffuse interface, inelastic phonon transport diminishes. Our results provide new insights on phonon transport across interfaces and open up opportunities for engineering interface thermal conductance specifically for materials of relevance to microelectronics.

Published
2022

41. Effect of sulfur on enhancing nitrogen-doping and magnetic properties of carbon nanotubes

Author

Wang Kunlin, Wu Dehai, Cui Tongxiang, Lv Ruitao, Huang Zheng-hong, and Kang Feiyu

Subjects
Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

Abstract Sulfur (S) is introduced as an additive in the growth atmosphere of carbon nanotubes (CNTs) in the range of 940-1020°C. CNT products with distorted sidewalls can be obtained by S-assisted growth. Moreover, many fascinating CNT structures can also be found in samples grown with S addition, such as bamboo-like CNTs, twisted CNTs, arborization-like CNTs, and bead-like CNTs. Compared with CNTs grown without S, more nitrogen-doping content is achieved in CNTs with S addition, which is beneficial for the properties and applications of nitrogen-doped CNTs. In addition, S can also enhance the encapsulation of ferromagnetic materials and thus improve the soft magnetic properties of CNTs, which is favorable to the applications of CNTs in the electromagnetic wave-absorbing and magnetic data storage areas.

Published
2011

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