Ning Wei , Ph.D, Associate Professor of Engineering Mechanics  

Google Scholar Profile: http://scholar.google.com.hk/citations?user="wdbvXKgAAAAJ

Dr. Ning Wei   received his Ph.D (2012) from Xiamen University. After working at Tsinghua University (2012-2014), he came to Northwest A&F University as an associate professor in year 2014. His current research interests include physics of synthetic materials (e.g. bio-nano interfaces, mechanics and microscale fluid-structure interactions, as well as their applications).

Research interests:

Mechanical properties

Carbon nanotube (CNT) and graphene are new materials whose structures consist of a single layer of carbon atoms packed in a honeycomb crystal lattice. They have attracted widespread interest for both their novel electronic, thermal and mechanical properties. Besides, CNT and graphene are the thinnest and the strongest materials ever synthesized [1, 2]. Therefore, they are considered to be the ideal candidates to manufacture the super-strong cables for suspension bridge and space elevator. Though mechanical properties of graphene and carbon nanotube have been well studied by various approaches, there still remains some interesting topics, such as,      

●Anomalous strength characteristics of tilt grain boundaries in graphene

Grantab et al found that graphene sheets with large-angle tilt boundaries that have a high density of defects are as strong as the pristine material and, unexpectedly, are much stronger than those with low-angle boundaries having fewer defects [3]. That is important to nanodesign about welding CNTs and graphene sheets together.

●Morphological structure effects on mechanical properties

Mechanical properties of graphene with various configurations, such as self-folding, bending and scrolling, have not been well studied, which can affect their stability and mechanical characters.

● Stability of nano-structure consists of graphene and CNT

New nanostructures are designed using graphene and CNTs. For instance, pillared graphene [4] was proposed in 2008 and attract much attention for its potential usage in energy storage. However, the stabilities and mechanical properties of these novel nanostructures have not been studied systematically.

Thermal properties

CNT and graphene are outstanding thermal conductors. (for CNTs 3000 W m−1 K−1 [5] and monolayer graphene 5300 W m−1 K−1 [6]), with many potential applications in thermal management and energy technology. There are important and interesting topics on thermal properties of graphene and CNT:

● Strain effects on the thermal conductivity

Applying stressrain on a material provides a mechanism to tune the thermal conductivity of materials dynamically or on demand, which can be applied to thermomutability.

Unlike in three dimensional solids, single-walled carbon nanotube and graphene are low-dimensional materials and composed of atomic monolayers. When the structure is compressed, the intrinsic in-plane elastic deformation can be released by transverse deflection of CNT and graphene. Therefor, their thermal conductivity can be compromised under both compressive and tensile strain.

● Thermal rectification in asymmetric structure

The heat flux runs preferentially along the direction of decreasing width, Which can be applied to thermal logic gate and thermal memory. The asymmetric structures can be made by tailoring graphene sheet, welding CNTs with different radius and jointing graphene nanoribbon and CNT together.

Our studies are mainly focused on the following topics:

(1) Mechanical/thermal properties of pristine and defective carbon nanotubes and graphene nanoribbons

(2) Mechanical/thermal properties of jointed carbon nanotubes or/and graphene nanoribbons

(3) Mechanical/thermal properties of hierarchial structures of carbon nanotubes or/and graphene nanoribbons

Pulications:                                                                                  

[1] Wei N, Xu L, Wang H Q, et al. Strain engineering of thermal conductivity in graphene sheets and nanoribbons: a demonstration of magic flexibility[J]. Nanotechnology, 2011, 22(10): 105705.(IF = 3.842)

[2] Wei N, Fan Z, Xu L Q, et al. Knitted graphene-nanoribbon sheet: a mechanically robust structure[J]. Nanoscale, 2012, 4(3): 785-791. (IF = 6.7)

[3] Wei N, Wang H Q, Zheng J C. Nanoparticle manipulation by thermal gradient[J]. Nanoscale research letters, 2012, 7(1): 1-9.(IF = 2.524)

[4] Wei N, et al. Properties of Zr hypernuclei in deformed Skyrme Hartree—Fock approach[J]. Chinese Physics C, 2009, 33(S1): 116.(IF = 0.338)

[5] Wei N, et al. Breakdown of fast water transport in graphene oxides [J]. Physical Review E, 2013, 89, 012113. (IF = 2.313)

[6] Wei N, et al. Mechanotunable monatomic metal structures at graphene edges[J]. Physical Chemistry Chemical Physics, 2014, 16,10295 (IF = 3.829)

[7] Wei N, et al. Understanding Water Permeation in Graphene Oxide Membranes [J].Applied Materials & Interfaces, 2014, 6,5877 (IF = 5.90)

[8] Wei N, et al. Wetting of Graphene Oxide: A Molecular Dynamics Study[J].Langmuir, 2014, 30, 3572 (IF = 4.384)

[9] Huang H, Song Z, Wei N, et al., Ultrafast viscous water flow through nanostrand-channeled graphene oxide membranes, Nature Communications, 2013, 4, 2979.(IF="10.01)"

[10] Zhang Y, Wei N*, et al. Quasi-analytical solution for the stable system of the multi-layer folded graphene wrinkles, Journal of Applied Physics, 2013, 114(6): 063511-063511-8. (IF = 2.21)

[11] Xu L, Wei N*, Zheng Y. Mechanical properties of highly defective graphene: from brittle rupture to ductile fracture[J]. Nanotechnology, 2013, 24, 505703. (IF = 3.842)

[12] Zhao J, Wei N*, Fan Z, et al. The mechanical properties of three types of carbon allotropes[J]. Nanotechnology, 2013, 24(9): 095702.(IF = 3.842)

[13] Xu L, Wei N, Xu X, et al. Defect-activated self-assembly of multilayered graphene paper: a mechanically robust architecture with high strength[J]. Journal of Materials Chemistry A, 2013, 1(6): 2002-2010.

[14] Xu L, Wei N, Zheng Y, et al. Graphene-nanotube 3D networks: intriguing thermal and mechanical properties[J]. Journal of Materials Chemistry, 2012, 22(4): 1435-1444.(IF = 5.97)

[15] Zheng Y, Wei N, Fan Z, et al. Mechanical properties of grafold: a demonstration of strengthened graphene[J]. Nanotechnology, 2011, 22(40): 405701.(IF = 3.842)

[16] Zhou X, Cui J, Wei N, Nonrelativistic mean-field description of the deformation of Λ hypernuclei[J]. Science in China Series G, 2009, 52, 1548. (IF = 1.413)

[17] Zhang Y, Zhao J, Wei N, et al. Effects of the dispersion of polymer wrapped two neighbouring single walled carbon nanotubes (SWNTs) on nanoengineering load transfer[J]. Composites Part B: Engineering, 2012.(2.143)

[18] Zhao J, Jiang J W, Wei N, et al. Thermal conductivity dependence on chain length in amorphous polymers[J]. Journal of Applied Physics, 2013, 113(18): 184304-184304-4.(IF = 2.21)

[19] Zheng Y, Xu L, Fan Z, Wei N, et al. Mechanical Properties of Graphene Nanobuds: A Molecular Dynamics Study[J]. Current Nanoscience, 2012, 8(1): 89-96.

[20] Zheng Y, Xu L, Fan Z, Wei N, et al. A molecular dynamics investigation of the mechanical properties of graphene nanochains[J]. Journal of Materials Chemistry, 2012, 22(19): 9798-9805.(IF = 5.97)

[21] Zhang Y, Zhao J, Jia Y, Mabrouki T, Gong Y, Wei N, et al. An analytical solution on interface debonding for large diameter carbon nanotube-reinforced composite with functionally graded variation interphase[J]. Composite Structures, 2013.(IF="2.550)

Contact:  Email: nwei@nwsuaf.edu.cn