ternary boron carbonitride ( b  c  n ) nanotubes have recently attracted much attention because of their excellent mechanical properties , electrical properties , and anti - oxidant capacities . in addition , theoretical studies have revealed that the band gaps of b  c  n nanotubes can be tailored over a wide range by simply varying the chemical composition rather than by geometrical structure [ 3 - 7 ] , which is superior to their carbon and boron nitride ( bn ) counterparts .
this gives b  c  n nanotubes potential for use in electronics , electrical conductors , high temperature lubricants , and novel composites .
compared with the very extensive study about carbon and bn nanotubes , however , very little work was reported about b 
 n nanotubes in 1994 , several methods have been devoted to the synthesis of b  c  n nanotubes , such as arc - discharge , laser ablation , chemical vapor deposition ( cvd ) , template route , and pyrolysis techniques . particularly , single - walled b
n nanotubes have been recently synthesized by wang et al .   via a bias - assisted hot - filament method .
however , most of them usually used risky reagents such as diborane ( b2h2)/ammonia ( nh3 ) , or produced nanotubes with low purity and high - cost and encountered the phase separation problem of bn and c. thus , it is of great significance to explore novel and simple routes to prepare b 
the current work reports a relatively safe and effective approach for growing high - purity b  c  n nanotubes directly on commercial stainless steel foil , by using simple raw materials of boron , zinc oxide ( zno ) , and ethanol absolute .
the reaction of boron and zno at high temperature produces boron oxide vapor that is the source of b , while ethanol absolute and nitrogen provide the source of c and n , respectively .
it is interesting that the stainless steel foil is not only the support substrate but also the catalyst for the growth of the nanotubes .
the obtained nanotubes have an average diameter of about 90 nm and the b , c , and n elements are found to be homogeneously distributed in the nanotubes .
the growth mechanism of the nanotubes is also investigated in this study . to the best of our knowledge , it is the first time to report the synthesis of ternary b 
the growth of nanotubes was carried out in a conventional tube furnace . an alumina boat loaded with about 1.0 g mixture of hexagonal zno and amorphous b powder ( with a zno : b molar ratio of 1.5:1 )
commercial stainless steel-304 foil with a thickness of 0.05 mm was inserted into the quartz tube as the substrate .
prior to heating , the chamber was flushed with high - purity n2flow to eliminate the residual air .
then the furnace was heated to 1150 c under a mixture gas flow of n2(60 ml min ) and h2(40 ml min ) .
ethanol absolute ( ar grade ) was introduced into the chamber when the furnace temperature reached at 1150 c , which was carried by another n2flow with a rate of 20 ml min .
finally , the furnace was cooled naturally to ambient temperature under the protection of n2flow .
after taken from the furnace , the stainless steel substrate was found to be covered with white  gray deposit in the temperature range of 10001100 c .
the product was characterized by field - emission scanning electron microscopy ( fe - sem , hitachi s5500 ) , high - resolution transmission microscopy ( hrtem , jem-2010f ) , x - ray energy dispersive spectrometer ( eds ) , and electron energy loss spectroscopy ( eels ) , respectively .
figure 1shows the sem images of the product grown on the surface of stainless steel substrate .
1a ) indicates a high production of one - dimensional ( 1d ) nanostructures was synthesized .
1a is a high - magnification cross - sectional image of some 1d nanostructures , illustrating the hollow structure of the product .
figure 1b clearly reveals that the nanotubes are shaped in bamboo consisting of a number of compartments .
the surfaces of the nanotubes are very clean and no impurities can be observed , which indicates the high purity of the nanotubes .
the diameters of the nanotubes are approximately 60120 nm , with an average value of about 90 nm .
furthermore , it can also be found that nanoparticles are attached at the ends of nanotubes , which could be regarded as a typical symbol of vapor  liquid  solid ( vls ) growth model .
figure 1c and d are the secondary electron and back scattering electron ( bse ) images of the same area of the product .
it can be seen that the attached particles ( bright particles ) are distinguished clearly in the bse image , which further confirms the vls growth mechanism of the nanotubes .
alow - magnification sem image of the product , showing the large quantity of the 1d product grown on the stainless steel substrate .
the inset is the high - magnification cross - sectional image of some nanotubes , illustrating the hollow structure.bhigh-magnification image ofa , indicating the bamboo - like structure and high purity of the nanotubes.canddthe secondary electron and back scattering electronic ( bse ) sem images of the same area of the product the tem images of the product are shown in fig .
the bamboo structure of the nanotubes with clean surface and uniform diameter along the nanotube length can be clearly seen ( fig .
2a is the edx result , which shows the dominating peaks of b , c , and n with a low level of o , cu , and si . the existence of cu peak should be caused by the copper tem grid , while the si peak might come from the stainless steel substrate .
furthermore , quantitative analysis gives the b : c : n atomic ratio of about 0.45:0.31:0.24 .
n nanotubes . in figure 2b , a particle attached at the end of the nanotube
the edx spectrum indicates that the particle is mainly composed of fe with a small amount of ni , cr , cu , and c ( inset in fig .
, the cu and c peaks should come from the carbon film - coated copper grid . while the existence of fe , ni , and cr in the particle should originate from the stainless steel substrate .
hence , we believe that the stainless steel substrate play a catalyst role during the vls growth of the nanotubes . atem image of a nanotube .
the inset is the edx spectrum of the nanotube.btem image shows a catalyst particle attached at the end of a nanotube .
the inset is the edx spectrum of the particle figure 3a shows the hrtem image of the edge part of the nanotube wall .
it can be seen that the lattice fringes are well - defined , which suggests that the nanotube wall has a high degree of crystalline perfection .
the interlayer spacing is approximately 0.348 nm , corresponding to the ( 002 ) plane of hexagonal system of b  c  n crystal ( jcpds no .
35 - 1292 ) . the spots in the fast fourier - transformed ed ( fft ed ) pattern can be indexed as the ( 002 ) basal planes of the b 
figure 3b is the hrtem image of the joint , showing the tight connection between nanotube wall and compartment .
the compartment is also well - crystallized with the identical lattice spacing of about 0.343 nm , which also corresponds to the ( 002 ) plane of b  c  n crystal . the fft ed pattern ( inset in fig .
3b ) is also indexed as the ( 002 ) planes of b  c  n crystal .
figure 3c shows a representative eels spectrum taken from a segment of the nanotube wall , which demonstrates that the distinct absorption peaks of b , c , and n characteristic k - edges at 188 , 201 , and 401 ev , respectively .
the k - edge signals show a discernible  * peak , as well as an  * band , indicating that the b , c , and n atoms are in the sp - hybridized state . the eels spectrum of the compartment shown in fig .
3d also indicates the distinct absorption features of k - edges of b , c , and n atoms .
furthermore , the elemental maps reveal that b , c , and n elements are homogeneously distributed in the nanotube ( fig .
therefore , it can be concluded that the product is composed of ternary compound b 
ahrtem image of nanotube wall and the corresponding fft ed pattern ( inset).bhrtem image of a joint between the wall and compartment and the corresponding fft ed pattern ( inset).canddeels spectra taken from the nanotube wall and the compartment , respectively , revealing the dominating composition of b , c , and n elements in the wall and compartment elemental maps of a nanotube , implying the uniform distribution of the b , c , and n species in the nanotube as described above , a simple approach to synthesize b  c 
n nanotubes was proposed by involving an additional role of catalyst of the stainless steel substrate . and based on the above results , vls model is believed to be responsible for the growth of the current nanotubes .
similar to the literatures reported about bn nanotubes and nanowires [ 17 - 19 ] , fig .
firstly , the reaction of b and zno generates zn and boron oxide ( b2o2 ) vapor at high temperature ( 1150 c ) .
meanwhile , the surface of the stainless steel may partially melt at this temperature assisted by the erosion of n2 and h2 . and
thus liquid alloy droplets with main composition of fe  cr  ni are formed on the surface , as are verified by the edx result . then the liquid droplets adsorb the growth species from the surrounding vapors of b2o2 , c2h5oh , n2 , and h2 ( fig .
5a ) . the involving species of b and c could lead to the further decrease of the melting temperature of stainless steel and promotes the formation of liquid droplets .
the reactions among these vapors produce b / c / n atoms , which diffuse through fe  cr  ni alloy droplets . when the concentrations of species are greater than the saturation threshold , b 
n crystals begin to precipitate and initially form the cap on the liquid droplets , as is shown in fig .
, the cap will be lift from the droplet due to the stress under the curvature and then the hollow tip forms . at the same time , due to the diffusion of b / c / n atoms through the surface and bulk , the b 
when the nanotube wall grows , the b / c / n atoms also precipitate inside the nanotube and result in the formation of compartment layer .
the compartment layers connect with the wall and grow together for a period , and finally depart from the droplet due to the stress accumulated under the curved compartment layers ( fig .
moreover , the flowing character of b2o2 , c2h5oh , n2 , and h2 vapors could lower their partial pressures in the chamber , which is also favorable for the formation of 1d nanotubes . it should be noted that the produced zn vapor is transported by the carrier gas to a much lower temperature zone ( below the melting point of zn ) , where it deposits on the substrate in the form of zn products .
in addition , it is found that the hydrogen in the mixture gas is essential for the growth of b  c  n nanotubes . if only pure n2 flow is introduced , no b
n nanotubes can be obtained , adding weight to the proposed mechanism and suggesting that hydrogen plays an important role during the growth of the b 
n nanotubes directly onto commercial stainless steel foil is demonstrated by using raw materials of boron powder , zinc oxide powder , and ethanol absolute .
the nanotubes are pure with bamboo - like morphology and an average diameter of about 90 nm . during the formation process
, the stainless steel foil plays a catalyst role additionally besides the substrate role for the b 
the authors acknowledge financial support from the national natural science foundation of china ( nsfc , grant no .
208106 ) , tsinghua university state key laboratory of new ceramics & fine processing and guangxi university ( grant no .
 in this study , a novel and facile approach for the synthesis of ternary boron carbonitride ( b  c  n ) nanotubes was reported . 
 growth occurred by heating simple starting materials of boron powder , zinc oxide powder , and ethanol absolute at 1150 c under a mixture gas flow of nitrogen and hydrogen . 
 as substrate , commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes . 
 the nanotubes were characterized by sem , tem , edx , and eels . 
 the results indicate that the synthesized b  
 c  
 n nanotubes exhibit a bamboo - like morphology and b , c , and n elements are homogeneously distributed in the nanotubes . a catalyzed vapor  liquid  
 solid ( vls ) mechanism was proposed for the growth of the nanotubes . 