- Nano Express
- Open Access
Mechanically activated catalyst mixing for high-yield boron nitride nanotube growth
© Li et al.; licensee Springer. 2012
- Received: 19 June 2012
- Accepted: 14 July 2012
- Published: 24 July 2012
Boron nitride nanotubes (BNNTs) have many fascinating properties and a wide range of applications. An improved ball milling method has been developed for high-yield BNNT synthesis, in which metal nitrate, such as Fe(NO3)3, and amorphous boron powder are milled together to prepare a more effective precursor. The heating of the precursor in nitrogen-containing gas produces a high density of BNNTs with controlled structures. The chemical bonding and structure of the synthesized BNNTs are precisely probed by near-edge X-ray absorption fine structure spectroscopy. The higher efficiency of the precursor containing milling-activated catalyst is revealed by thermogravimetric analyses. Detailed X-ray diffraction and X-ray photoelectron spectroscopy investigations disclose that during ball milling the Fe(NO3)3 decomposes to Fe which greatly accelerates the nitriding reaction and therefore increases the yield of BNNTs. This improved synthesis method brings the large-scale production and application of BNNTs one step closer.
- Boron nitride nanotube
- Mechanical milling
- Nanostructured materials
- X-ray absorption fine structure
Boron nitride nanotubes (BNNTs) are a promising nanomaterial with many fascinating properties and a wide range of applications. BNNTs have high thermal and chemical stabilities [1, 2] and can be reinforced into composites working in harsh environments. BNNTs have a wide bandgap close to 6 eV and strong deep ultraviolet light emission [3, 4], useful in fabricating optoelectronic devices at nanoscale. Transistor behaviour has been predicted from BNNTs due to their giant stark effect . In addition, BNNTs have many potential bioapplications, including drug delivery, nanofluidics and nanoscaled biosensors [6–8].
BNNTs were first produced using arc discharge and laser ablation methods [9, 10]. Later on, other synthesis routes, including ball milling and annealing [11–14], chemical vapour deposition [15–17] and other thermal chemical methods [6, 18], were demonstrated. The ball milling and annealing method has been shown to be able to produce larger quantities of BNNTs and more easily to scale up [11–13]. In this process, metal nanoparticles from repeated collisions between milling jar and balls during ball milling act as catalysts for BNNT growth [11–13]. The recent B ink process added metal nitrate (e.g. Fe(NO3)3 or Co(NO3)2) to the milled B powder in the form of ethanol solution, and the additional nitrate catalyst showed a more efficient catalytic effect and greatly boosted the growth of BNNTs [19, 20], especially in the case of the growth of BNNT thin films on different surfaces .
Here, we report an improved ball milling and annealing method for BNNT synthesis, which shows a better BNNT yield compared to the original ball milling method as well as the B ink method. The method involves ball milling of metal nitrate with B powder, and the subsequent thermal annealing of the milled powder in nitrogen-containing gases grows a high density of BNNTs.
Amorphous B powder (95% to 97%, Fluka, Sigma-Aldrich Corporation, St. Louis, MO, USA) and 10 wt.% Fe(NO3)3•9H2O (98%, Pronalys, Thermo Fisher Scientific, Waltham, MA, USA) were sealed in a stainless milling jar with several hardened steel balls. The weight ratio of ball to powder was 80:1. Dehydrated NH3 gas was filled into the jar at a pressure of 250 kPa. The ball milling was conducted on a custom-built vertical milling machine and lasted for 150 h at a speed of 110 rpm at room temperature. The milled powder was then heated up to 1,100°C in N2 + 15% H2 or 1,300°C in NH3 for 3 to 6 h to produce BNNTs.
The morphology and chemical composition of the products were investigated using a Supra 55VP scanning electron microscope (SEM; Carl Zeiss AG, Oberkochen, Germany) equipped with an energy dispersive X-ray spectroscopy (EDX) system. A JEOL-2100 transmission electron microscope (TEM; JEOL Ltd., Akishima, Tokyo, Japan) was used to check the structure of the nanotubes. The material phases were analysed by X-ray diffraction (XRD; PANalytical B.V., Almelo, The Netherlands). The nitriding reaction rates of different samples were compared by thermogravimetric analyses (TGA; Netzsch, Hanau, Germany) which monitored the sample weight changes up to 1,300°C (with a temperature increasing rate of 10°C/min) in a pure N2 atmosphere. A Thermo Fischer Scientific K-alpha X-ray photoelectron spectroscopy (XPS) system was used to measure the chemical compositions of the milled B powders. Pass energies of 100 and 20 eV were used in survey and high-resolution scans. All XPS data were corrected using the binding energy of C-C at 284.6 eV. The near-edge X-ray absorption fine structure (NEXAFS) measurements were performed in the ultrahigh vacuum chamber (approximately 10−10 mbar) at the undulator soft X-ray spectroscopy beamline of the Australian Synchrotron, Victoria, Australia. The raw NEXAFS data were normalized to the photoelectron current of the photon beam, measured on an Au grid.
The above analysis results reveal the following enhancing mechanism of ball milling Fe(NO3)3 with B powder. During the milling, Fe(NO3)3 was first decomposed to iron oxide under milling collisions, and the iron oxide was then reduced to Fe by either NH3 or B. These reduced Fe was much more reactive than the steel particles from the collisions between the steel milling jar and balls, due to both the more stable nature of steel and the smaller particle sizes of the chemically reduced Fe. During the heating up to 1,300°C in nitrogen-containing gases, the Fe became quasi-liquid at lower temperature than the steel particles and provides a better catalytic effect. BNNTs started to form from the BN layers precipitating on the surface of the metal particles diffused with excessive B and N atoms, following the VLS growth mechanism . As a result, a strong BN phase XRD peak was observed after the heating (Figure 5 (iv)). The Fe(NO3)3 + B milled powder showed even better BNNT yield than the B ink, possibly thanks to the 71% more N content of the Fe(NO3)3 milled powder. The amorphous B-N phase produced by milling is unstable and can directly provide N source for BNNT growth with little aid from the nitrogen-containing gas. This can reduce the temperature of BNNT formation and result in a better yield of BNNTs.
The ball milling of amorphous B powder and metal nitrate, such as Fe(NO3)3, produces a more effective precursor for BNNT production. The detailed XRD and XPS investigations reveal that during the milling of B powder and Fe(NO3)3, Fe(NO3)3 is first decomposed to iron oxide which is further reduced to Fe. The reduced Fe greatly increases the nitriding reaction of the B powder during ball milling in ammonia (NH3) atmosphere, evidenced by 71% more N content. The pre-formed amorphous BN is much more reactive than crystallined hBN and can directly provide N source for the formation of BNNTs; therefore it lowers the BNNT formation temperature and improves the nitriding rate. The homogeneously mixed additional Fe reduced from Fe(NO3)3 also acts as effective catalysts and assists the growth of BNNTs. As a result, a higher yield of BNNTs can be synthesized. Other metal nitrates, such as Mg(NO3)2 and Co(NO3)2, can also be used in this method.
We thank Dr. Bruce Cowie from Australian Synchrotron for the experimental support, and scientific and technical assistance from the XPS facility in RMIT University Part of this research was undertaken on the soft X-ray beamline at the Australian Synchrotron, Victoria, Australia. Financial support from the Australian Research Council under the centre of excellence and discovery programmes as well as Deakin University under CRGS are gratefully acknowledged.
- Golberg D, Bando Y, Kurashima K, Sato T: Synthesis and characterization of ropes made of BN multiwalled nanotubes. Scr Mater 2001, 44: 1561–1565. 10.1016/S1359-6462(01)00724-2View ArticleGoogle Scholar
- Chen Y, Zou J, Campbell SJ, Le Caer G: Boron nitride nanotubes: pronounced resistance to oxidation. Appl Phys Lett 2004, 84: 2430–2432. 10.1063/1.1667278View ArticleGoogle Scholar
- Blase X, Rubio A, Louie SG, Cohen ML: Stability and band gap constancy of boron nitride nanotubes. Europhys Lett 1994, 28: 335–340. 10.1209/0295-5075/28/5/007View ArticleGoogle Scholar
- Li LH, Chen Y, Lin MY, Glushenkov AM, Cheng BM, Yu J: Single deep ultraviolet light emission from boron nitride nanotube film. Appl Phys Lett 2010, 97: 141104. 10.1063/1.3497261View ArticleGoogle Scholar
- Ishigami M, Sau JD, Aloni S, Cohen ML, Zettl A: Observation of the giant stark effect in boron-nitride nanotubes. Phys Rev Lett 2005, 94: 056804.View ArticleGoogle Scholar
- Zhi C, Bando Y, Tan C, Golberg D: Effective precursor for high yield synthesis of pure BN nanotubes. Solid State Commun 2005, 135: 67–70. 10.1016/j.ssc.2005.03.062View ArticleGoogle Scholar
- Hilder TA, Gordon D, Chung S-H: Boron nitride nanotubes selectively permeable to cations or anions. Small 2009, 5: 2870–2875. 10.1002/smll.200901229View ArticleGoogle Scholar
- Wu J, Yin L: Platinum nanoparticle modified polyaniline-functionalized boron nitride nanotubes for amperometric glucose enzyme biosensor. ACS Appl Mater Interfaces 2011, 3: 4354–4362. 10.1021/am201008nView ArticleGoogle Scholar
- Chopra NG, Luyken RJ, Cherrey K, Crespi VH, Cohen ML, Louie SG, Zettl A: Boron nitride nanotubes. Science 1995, 269: 966–967. 10.1126/science.269.5226.966View ArticleGoogle Scholar
- Golberg D, Bando Y, Eremets M, Takemura K, Kurashima K, Yusa H: Nanotubes in boron nitride laser heated at high pressure. Appl Phys Lett 1996, 69: 2045–2047. 10.1063/1.116874View ArticleGoogle Scholar
- Chen Y, Fitz Gerald J, Williams JS, Bulcock S: Synthesis of boron nitride nanotubes at low temperatures using reactive ball milling. Chem Phys Lett 1999, 299: 260–264. 10.1016/S0009-2614(98)01252-4View ArticleGoogle Scholar
- Li YJ, Zhou JE, Zhao K, Tung SM, Schneider E: Synthesis of boron nitride nanotubes from boron oxide by ball milling and annealing process. Mater Lett 2009, 63: 1733–1736. 10.1016/j.matlet.2009.05.005View ArticleGoogle Scholar
- Kim J, Lee S, Uhm YR, Jun J, Rhee CK, Kim GM: Synthesis and growth of boron nitride nanotubes by a ball milling–annealing process. Acta Mater 2011, 59: 2807–2813. 10.1016/j.actamat.2011.01.019View ArticleGoogle Scholar
- Wen G, Zhang T, Huang XX, Zhong B, Zhang XD, Yu HM: Synthesis of bulk quantity BN nanotubes with uniform morphology. Scr Mater 2010, 62: 25–28. 10.1016/j.scriptamat.2009.09.018View ArticleGoogle Scholar
- Lourie OR, Jones CR, Bartlett BM, Gibbons PC, Ruoff RS, Buhro WE: CVD growth of boron nitride nanotubes. Chem Mater 2000, 12: 1808–1810. 10.1021/cm000157qView ArticleGoogle Scholar
- Huang Y, Lin J, Tang CC, Bando Y, Zhi CY, Zhai TY, Dierre B, Sekiguchi T, Golberg D: Bulk synthesis, growth mechanism and properties of highly pure ultrafine boron nitride nanotubes with diameters of sub-10 nm. Nanotechnology 2011, 22: 145602. 10.1088/0957-4484/22/14/145602View ArticleGoogle Scholar
- Sartinska LL: Catalyst-free synthesis of nanotubes and whiskers in an optical furnace and a gaseous model for their formation and growth. Acta Mater 2011, 59: 4395–4403. 10.1016/j.actamat.2011.03.063View ArticleGoogle Scholar
- Tang CC, Ding XX, Huang XT, Gan ZW, Qi SR, Liu W, Fan SS: Effective growth of boron nitride nanotubes. Chem Phys Lett 2002, 356: 254–258. 10.1016/S0009-2614(02)00325-1View ArticleGoogle Scholar
- Li LH, Chen Y, Glushenkov AM: Synthesis of boron nitride nanotubes by boron ink annealing. Nanotechnology 2010, 21: 105601. 10.1088/0957-4484/21/10/105601View ArticleGoogle Scholar
- Li LH, Li CP, Chen Y: Synthesis of boron nitride nanotubes, bamboos and nanowires. Physica E 2008, 40: 2513–2516. 10.1016/j.physe.2007.06.065View ArticleGoogle Scholar
- Li LH, Chen Y, Glushenkov AM: Boron nitride nanotube films grown from boron ink painting. J Mater Chem 2010, 20: 9679–9683. 10.1039/c0jm01414aView ArticleGoogle Scholar
- Huo KF, Hu Z, Fu JJ, Xu H, Wang XZ, Chen Y, Lü YN: Microstructure and growth model of periodic spindle-unit BN nanotubes by nitriding Fe-B nanoparticles with nitrogen/ammonia mixture. J Phys Chem B 2003, 107: 11316–11320. 10.1021/jp035375wView ArticleGoogle Scholar
- Barth J, Kunz C, Zimkina TM: Photoemission investigation of hexagonal BN: band structure and atomic effects. Solid State Commun 1980, 36: 453–456. 10.1016/0038-1098(80)90932-1View ArticleGoogle Scholar
- Petravic M, Peter R, Kavre I, Li LH, Chen Y, Fan LJ, Yang YW: Decoration of nitrogen vacancies by oxygen atoms in boron nitride nanotubes. Phys Chem Chem Phys 2010, 12: 15349–15353.View ArticleGoogle Scholar
- Franke R, Bender S, Hormes J, Pavlychev AA, Fominych NG: A quasi-atomic treatment of chemical and structural effects on K-shell excitations in hexagonal and cubic BN crystals. Chem Phys 1997, 216: 243–257. 10.1016/S0301-0104(96)00374-6View ArticleGoogle Scholar
- Jimenez I, Gago R, Albella JM, Terminello LJ: Identification of ternary boron-carbon-nitrogen hexagonal phases by x-ray absorption spectroscopy. Appl Phys Lett 2001, 78: 3430–3432. 10.1063/1.1376428View ArticleGoogle Scholar
- Wong SS, Hemraj-Benny T, Banerjee S, Sambasivan S, Fischer DA, Han WQ, Misewich JA: Investigating the structure of boron nitride nanotubes by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Phys Chem Chem Phys 2005, 7: 1103–1106.View ArticleGoogle Scholar
- Niibe M, Miyamoto K, Mitamura T, Mochiji K: Identification of B-K near edge x-ray absorption fine structure peaks of boron nitride thin films prepared by sputtering deposition. J Vac Sci Technol A 2010, 28: 1157–1160. 10.1116/1.3474913View ArticleGoogle Scholar
- Caretti I, Jimenez I: Point defects in hexagonal BN, BC(3) and BC(x)N compounds studied by x-ray absorption near-edge structure. J Appl Phys 2011, 110: 023511. 10.1063/1.3602996View ArticleGoogle Scholar
- Yu J, Li BCP, Zou J, Chen Y: Influence of nitriding gases on the growth of boron nitride nanotubes. J Mater Sci 2007, 42: 4025–4030. 10.1007/s10853-006-0381-4View ArticleGoogle Scholar
- Khadilkar B, Borkar S: Silica gel supported ferric nitrate: a convenient oxidizing reagent. Synth Commun 1998, 28: 207–212.View ArticleGoogle Scholar
- Wieczorek-Ciurowa K, Kozak A: The thermal decomposition of Fe(NO3)3•9H2O. J Therm Anal Calorim 1999, 58: 647–651. 10.1023/A:1010112814013View ArticleGoogle Scholar
- Sen S, Ozbek I, Sen U, Bindal C: Mechanical behavior of borides formed on borided cold work tool steel. Surf CoatTechnol 2001, 135: 173–177. 10.1016/S0257-8972(00)01064-1View ArticleGoogle Scholar
- Ruuskanen P, Heczko O: Mechanically alloyed Fe-B, Fe-Si and Fe-B-Si powders. Key Eng Mater 1993, 81–3: 159–168.View ArticleGoogle Scholar
- Kaupp G: Reactive milling with metals for environmentally benign sustainable production. CrystEngComm 2011, 13: 3108–3121. 10.1039/c1ce05085kView ArticleGoogle Scholar
- Arabczyk W, Zamlynny J: Study of the ammonia decomposition over iron catalysts. Catal Lett 1999, 60: 167–171. 10.1023/A:1019007024041View ArticleGoogle Scholar
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