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Lu Hua Li, Ying Chen and Alexey M. Glushenkov
Journal of Materials Chemistry 20 (2010) 9679-9683
Abstract: The growth of nanotube films can have important applications in building nanoscale functional devices or solving interfacial and heat problems. We report that high-density boron nitride nanotube (BNNT) films with any desired pattern can be grown on complicated surfaces using a B ink process. The special B ink, a mixture of nanosized B particles, metal nitrate and ethanol, is first painted, sprayed or inkjet printed at desired location with required pattern, and then the ink layer is annealed in a nitrogen-containing atmosphere to form BNNT film. This is the first method capable of growing BNNTs on complex non-flat surfaces, which greatly broadens the potential application of BNNTs. For example, it is demonstrated here that a BNNT coated steel mesh can separate water and oil on a microlitre scale; a needle given an internal BNNT coating could greatly enhance microfluidic transport; and a coated screw could be used to minimize wear at the interface.
Xiujuan J Dai*, Ying Chen, Zhiqiang Chen, Peter R Lamb, Lu Hua Li, Johan du Plessis, Dougal G McCulloch and Xungai Wang
Nanotechnology 22 (2011) 245301 [DOI: 10.1088/0957-4484/22/24/245301]
Abstract: Controlled surface modification of boron nitride nanotubes has been achieved by gentle plasma treatment. Firstly, it was shown that an amorphous surface layer found on the outside of the nanotubes can be removed without damaging the nanotube structure. Secondly, it was shown that an oxygen plasma creates nitrogen vacancies that then allow oxygen atoms to be successfully substituted onto the surface of BNNTs. The percentage of oxygen atoms can be controlled by changing the input plasma energy and by the Ar plasma pre-treatment time. Finally, it has been demonstrated that nitrogen functional groups can be introduced onto the surface of BNNTs using an N2 + H2 plasma. The N2 + H2 plasma also created nitrogen vacancies, some of which led to surface functionalization while some underwent oxygen healing.
Mladen Petravic, Robert Peter, Ivna Kavre, Lu Hua Li, Ying Chen, Liang-Jen Fan and Yaw-Wen Yang
Physical Chemistry Chemical Physics 12 (2010) 15349-15353
Abstract: Decoration of nitrogen vacancies by oxygen atoms has been studied by near-edge X-ray absorption fine structure (NEXAFS) around B K-edge in several boron nitride (BN) structures, including bamboo-like and multi-walled BN nanotubes. Breaking of B-N bonds and formation of nitrogen vacancies under low-energy ion bombardment reduces oxidation resistance of BN structures and promotes an efficient oxygen-healing mechanism, in full agreement with some recent theoretical predictions. The formation of mixed O-B-N and B-O bonds is clearly identified by well-resolved peaks in NEXAFS spectra of excited boron atoms.
Luhua Li and Ying Chen
Langmuir 26 (2010) 5135-5140
Abstract: Superhydrophobicity is highly desirable for numerous applications. Here, we found that a semi-erect but non-aligned boron nitride nanotube (BNNT) film showed superhydrophobicity with contact angle above 170° and a small contact angle hysteresis. This superhydrophobicity was stable over a large range of drop sizes, and the measured critical transition pressure was about 10 kPa. The drop retraction behaviour during evaporation, the pressure effect on contact angle, the critical transition pressure, the drop impact behaviour, and the self-cleaning efficiency were systematically investigated.
Lu Hua Li, Ying Chen, Meng-Yeh Lin, Alexey M. Glushenkov, Bing-Ming Cheng and Jun Yu
Applied Physics Letters 97 (2010) 141104
Abstract: Light in deep ultraviolet (DUV) region has a wide range of applications and the demand for finding DUV light emitting materials at nanoscale is increasingly urgent as they are vital for building miniaturized optic and optoelectronic devices. We discover that boron nitride nanotubes (BNNTs) with a well-crystallized cylindrical multiwall structure and diameters smaller than 10 nm can have single DUV emission at 225nm (5.51eV). The measured BNNTs are grown on substrate in the form of a thin film. This study suggests that BNNTs may work as nanosized DUV light sources for various applications.
Hua Chen , Ying Chen, Yun Liu, Lan Fu, Cheng Huang, David Llewellyn
Chemical Physics Letters 463 (2008) 130 - 133
Abstract: Over 1.0 mm boron nitride nanotubes (BNNTs) were successfully synthesized by an optimized ball milling and annealing method. The annealing temperature of 1100 C is crucial for the growth of the long BNNTs because at this temperature there is a fast nitrogen dissolution rate in Fe and the B/N ratio in Fe is 1. Such long BNNTs enable a reliable single tube configuration for electrical property characterization. These BNNTs are promising insulators for three dimensional microelectromechanical system.
Luhua Li, Ying Chen and Alexey M Glushenkov
Nanotechnology 21 (2010) 105601 (5pp)
Abstract: Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). This method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.
Figure (a) SEM image of the BNNTs produced with Co(NO3)2 in NH3 gas at 1300 ·C; (b) TEM image revealing the small diameter and cylindrical structure of the nanotubes.
Hua Chen, Hongzhou Zhang, Lan Fu, Ying Chen, James S. Williams, Chao Yu, and Dapeng Yu
Appl. Phys. Lett. 92, 243105 (2008); DOI:10.1063/1.2943653
Abstract: This letter reports the electrical and field-emission properties of Au-decorated bamboo boron nitride nanotubes (Au-BNNTs). The insulating BNNTs become metallic after Au coating as the Au coverage exceeds a critical value. The Au decoration modifies the work function of the BNNTs and, as a consequence, the field-emission current densities of Au-BNNTs are significantly enhanced. Correspondingly, the turn-on field of the Au-BNNTs is reduced to one third and the emission current density is increased by four orders in contrast to pure BNNTs. The experimental results demonstrate that such Au-BNNTs are promising electron field emitters.
Feng Li, Zhonghua Zhu, Xiangdong Yao, Gaoqing Lu, Mingwen Zhao, Yueyuan Xia, and Ying Chen
APPLIED PHYSICS LETTERS 92, 102515 (2008)
Abstract: Ab initio calculations were conducted to investigate the electronic structures and magnetic properties of fluorinated boron nitride nanotube. It was found that the chemisorption of F atoms on the B atoms of BNNT can induce spontaneous magnetization, whereas no magnetism can be produced when the B and N atoms are equally fluorinated. This provides a different approach to tune the magnetic properties of BNNTs as well as a synthetic route toward metal-free magnetic materials.
Yongjun Chen, Lan Fu,, Ying Chen,* Jin Zou, Jia Li and Wen Hui Duan
Abstract: Boron nitride (BN) nanotubes with electric conductivities from semiconducting to metallic have been achieved by controlled Au doping, demonstrating a promising approach in tailoring of BN nanotube conductivities with the application potential in electronics, chemical catalysts, and sensing.
Hua Chen, Ying Chen,* Chi Pui Li, Hongzhou Zhang, James S. Williams, Yun Liu, Zongwen Liu, and Simon P. Ringer
Advanced Materials 2007, 19, 1845 - 1848
Abstract: A broad and tunable visible light emission, excited by electrons, from Eu doped BN nanotubes has been realized for the first time. The special broad light emission is due to the insertion of Eu2+ ions into nanotube walls via in-situ Eu doping during nanotube growth instead of a common post-synthesis doping process.
Hua Chen, Ying Chen, Yun Liu, Chao-Nan Xu and Jim S. Williams
Abstract: Photoluminescent (PL) and optical absorption spectra of high-yield multi-wall BN nanotubes (BNNTs) were systematically investigated at room temperature in comparison with commercial hexagonal BN (h-BN) powder. The direct band gap of the BNNTs was determined to be 5.75 eV, just slightly narrower than that of h-BN powder (5.82 eV). Two Frenkel excitons with the binding energy of 1.27 and 1.35 eV were also determined. However, they were not a distinctive characteristic of the BNNTs as reported previously. Observed broad UV-visible-NIR light emission demonstrates the potential of the BNNTs as a nano light source.
Jun Yu, Ying Chen, Robert G. Elliman, and Mladen Petravic
Advanced Materials, 2006, 18, 2157-2160
Abstract: Isotopically enriched 10BN nanotubes have been produced for the first time. SIMS analysis has confirmed a high content of 10B in the nanotubes. The 10BN nanotubes have light weight, excellent mechanical properties, a stronger resistance to oxidation and a better radiation shielding property, which offer a multifunctional material with promising aerospace applications.
Jun Yu, Ying Chen, Richard Wuhrer, Zongwen Liu, and Simon P. Ringer
Chemistry of Material, 2005, 17, 5172-5176
Abstract: High-yield multiwalled boron nitride (BN) nanotubes have been produced using a ball milling-annealing method. The BN nanotubes with a diameter less than 10 nm and a well-crystallized multiwalled structure were formed via an in situ nitriding reaction. The systematic investigation of the formation process at different annealing temperatures and for different times suggested that the formation of the unique multiwalled structure was attributed by a two-dimensional growth of the BN phase and a nonmetal catalytic growth.
Ying Chen, Jin Zou, Stewart J. Campbell and Gerard Le Caer
Appl. Phys. Lett, 84(13) (2004) p. 2430-2432.
Abstract: Boron nitride (BN) nanotubes have the same nanostructure as carbon nanotubes but are found to exhibit significant resistance to oxidation at high temperatures. Our systematic study has revealed that BN nanotubes are stable at 700 °C in air and that some thin nanotubes (diameter less than 20 nm) with perfect multiwalled cylindrical structure can survive up to 900 °C. Thermogravimetric analysis reveals an onset temperature for oxidation of BN nanotubes of 800 °C compared with only 400 °C for carbon nanotubes under the same conditions. This more pronounced resistance of BN nanotubes to oxidation is inherited from the hexagonal BN and also depends on the nanocrystalline structure. This high level of resistance to oxidation allows promising BN nanotube applications at high temperatures.