先驱体法合成氮化硼研究进展

综述了无氧有机先驱体法合成氮化硼的研究进展 ,系统介绍了由硼烷、硼吖嗪、卤化硼合成氮化硼的工艺条件 ,及由这些化合物制备聚合物先驱体的合成途径及其陶瓷转化 ,概述了先驱体法待研究的问题 .     

氮化硼纳米管的研究现状

详细介绍了氮化硼纳米管自发现以来的研究情况,阐述了氮化硼纳米管的结构与性质,对目前已有的合成方法进行了归类与总结,同时分析了各自的优缺点,概述了其应用研究的进展情况,并提出了今后研究和应用的发展方向.     

Radial mechanical properties of single-walled boron nitride nanotubes

The radial mechanical properties of single-walled boron nitride nanotubes (SW-BNNTs) are investigated by atomic force microscopy. Nanomechanical measurements reveal the radial deformation of individual SW-BNNTs in both elastic and plastic regimes. The measured effective radial elastic moduli of SW-BNNTs are found to follow a decreasing trend with an increase in tube diameter, ranging from 40.78 to 1.85 GPa for tube diameters of 0.58 to 2.38 nm. The results show that SW-BNNTs have relatively lower effective radial elastic moduli than single-walled carbon nanotubes (SWCNTs). The axially strong, but radially supple characteristics suggest that SW-BNNTs may be superior to SWCNTs as reinforcing additives for nanocomposite applications.     

Mechanism of nucleation and growth of cubic boron nitride thin films

The mechanism and the crystallography of the nucleation and growth of cubic boron nitride (c-BN) films deposited on 〈100〉-oriented silicon substrate by RF bias sputtering have been studied by means of cross-sectional high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Both methods provide experimental information showing no sp²-bonded BN layer formation in the subsurface region of c-BN phase. This is clear evidence for layer-by-layer homoepitaxial growth of cubic boron nitride without graphitic monolayers in the near-surface region of the film. The turbostratic boron nitride (t-BN) consists of thin sub-layers, 0.5–2 nm thick, growing in such a way that a sub-layer normal is almost parallel to the growth direction. t-BN also comprises a large volume fraction of the grain boundaries with high interface energies. The present result and the finding by Shtansky et al. [Acta Mater. 48, 3745 (2000)], who showed that an individual sub-layer consists of parallel lamellae in both the hexagonal +h-BN) and rhombohedral (r-BN) configurations, demonstrate that high intrinsic stress in the films is due to the complex structure of sp²-bonded BN. The crystallography of c-BN films indicates heteroepitaxial nucleation of cubic phase on the graphitic BN structural precursor. The present results are consistent with stress-induced c-BN formation.     

Mechanism of nucleation and growth of cubic boron nitride thin films

The mechanism and the crystallography of the nucleation and growth of cubic boron nitride (c-BN) films deposited on 100-oriented silicon substrate by RF bias sputtering have been studied by means of cross-sectional high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Both methods provide experimental information showing no sp²-bonded BN layer formation in the subsurface region of c-BN phase. This is clear evidence for layer-by-layer homoepitaxial growth of cubic boron nitride without graphitic monolayers in the near-surface region of the film. The turbostratic boron nitride (t-BN) consists of thin sub-layers, 0.5–2 nm thick, growing in such a way that a sub-layer normal is almost parallel to the growth direction. t-BN also comprises a large volume fraction of the grain boundaries with high interface energies. The present result and the finding by Shtansky et al. [Acta Mater. 48, 3745 (2000)], who showed that an individual sub-layer consists of parallel lamellae in both the hexagonal (h-BN) and rhombohedral (r-BN) configurations, demonstrate that high intrinsic stress in the films is due to the complex structure of sp²-bonded BN. The crystallography of c-BN films indicates heteroepitaxial nucleation of cubic phase on the graphitic BN structural precursor. The present results are consistent with stress-induced c-BN formation.     

Facile synthesis of boron nitride coating on carbon nanotubes

Boron nitride (BN) coating on the surface of carbon nanotubes (CNTs) was synthesized by the direct reaction of NaBH₄ and NH₄Cl in the temperature range of 500–600 °C. X-ray diffraction, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) confirm the formation of BN coating. It is revealed that the BN coating follows the shape of CNTS without damaging the surface of CNTs, and the elements B and N distribute homogenously along the whole CNTs without chemical bonds between carbon and BN layers. Besides, the oxidation resistance of the CNTs improved a lot after being coated with BN.     

Synthesis of multiwall boron nitride nanotubes dependent on crystallographic structure of boron

Synthesis and growth of multiwall boron nitride nanotubes (BNNTs) under the B and ZrO₂ seed system in the milling–annealing process were investigated. BNNTs were synthesized by annealing a mechanically activated boron powder under nitrogen environment. We explored the aspects of the mechanical activation energy transferred to milled crystalline boron powder producing structural disorder and borothermal reaction of the ZrO₂ seed particles on the synthesis of BNNTs during annealing. Under these circumstances, the chemical reaction of amorphous boron coated on the seed nanoparticles with nitrogen synthesizing amorphous BN could be enhanced. It was found that amorphous BN was crystallized to the layer structure and then grown to multiwall BNNTs during annealing. Especially, bamboo-type multiwall BNNTs were mostly produced and grown to the tail-side of the nanotube not to the round head-side. Open gaps with ∼0.3 nm of the bamboo side walls of BNNTs were also observed. Based on these understandings, it might be possible to produce bamboo-type multiwall BNNTs by optimization of the structure and shape of boron coat on the seed nanoparticles.     

Intrinsic ion transport of highly charged sub-3-nm boron nitride nanotubes

Debate regarding the transport mechanisms of water and ions in highly charged one-dimensional (1D) nanochannel continues because of a lack of available experimental data. Here, we present a nanofluidic platform consisting of ≈2.7-nm-diameter boron nitride nanotubes (BNNTs) as a model system, and report the experimental ion transport in these sub-3-nm BNNTs. We elucidate that strong electrostatic interactions between the highly charged tube walls and ions, stemming from the high surface-charge density (378 mC/m²) of BNNTs, play important roles in defining the ion transport mechanism in BNNT pores. Experimental analysis of ion transports supported by numerical the Donnan steric pore model with dielectric exclusion (DSPM-DE) and Derjaguin–Landau–Verwey–Overbeek (DLVO) model elucidate the relationship of the ionic charge density and surface-charge density of the BNNT wall to electrostatic interaction, steric, and dielectric effects. We also demonstrate that BNNTs exhibit higher NaCl separation (≈90%) than commercial reverse-osmosis (≈80%) and nanofiltration (≈60%) membranes under the same experimental conditions, despite having a larger pore size. Our results establish design criteria for developing highly efficient ion-selective membranes for various practical applications.     

Parameter spaces for the nucleation and the subsequent growth of cubic boron nitride films

The data existing in the literature about the deposition of cubic boron nitride thin films were reviewed critically in order to establish the parameter spaces of c-BN nucleation and growth. The ion energy E_i, the flux ratio F (=incoming ions/incoming boron atoms), the ion mass m_i, (or the ratio Ar/N₂, respectively), and the substrate temperature T_s, had already been identified as the decisive parameters which are, however, interdependent. Earlier data collections on c-BN deposition had shown that, irrespective of the deposition technique used, a well-defined c-BN region exists in the F/E_i parameter space, in which the deposition of c-BN is possible. Similar regions exist in the F/m_i and F/T_s parameter spaces. The present collection extends these older diagrams considerably, especially to the low energy region. From this extention it can be concluded that the momentum transfer concepts proposed in the literature fail to explain the data. Furthermore, the older collections were considered valid for nucleation and growth likewise. However, in recent years data have been published showing that the boundaries of the c-BN regions are different for nucleation and growth. After successful nucleation, subsequent growth can occur either at reduced ion bombardment (either energy or flux ratio or ion mass) and also at reduced temperatures. The existing data for this parameter reduction have been collected in this paper. It will be shown that the growth depends in a similar way as the nucleation on the (interdependent) ion bombardment parameters but no longer on temperature. This means that the nucleation and growth of c-BN are based on different, although in both cases ion-induced, mechanisms.     

Carbon nanotubes growth on silicon nitride substrates

Carbon nanotubes were synthesized on silicon nitride substrates by thermal chemical vapour deposition using an iron precursor catalyst. The nanotubes were characterized by AFM, FESEM, TEM and micro-Raman spectroscopy. The surface topography of the substrate, dense and flat or porous and rough, controlled the catalyst distribution and carbon nanotubes growth. Flat surfaces led to the synthesis of single-walled carbon nanotubes, whereas the porous ones promoted the growth of multi-walled carbon nanotubes of 60 nm diameter. These nanotubes preferentially grew on the porous sites, exhibiting a good substrate-nanotube interface.     

Facile synthesis of cubic boron nitride nanoparticles from amorphous boron by triple thermal plasma jets at atmospheric pressure

Cubic boron nitride (c-BN) is a superhard material, with hardness value comparable to that of diamond. c-BN is used in a wide range of industrial applications, including tool, abrasives, and refractory. The hardness of c-BN can be improved by decreasing the particle size to the nanoscale; however, the simultaneous application of high pressure (～8 GPa) and temperature (>2,500 K) is required to synthesize the c-BN crystal structure. In this study, we effectively synthesized c-BN nanoparticles from amorphous boron using a triple direct current (DC) thermal plasma jet system at atmospheric pressure. The injection of nitrogen as plasma forming gas generated reactive nitridation species. The average particle size of the synthesized c-BN was 22 nm, and the major crystal structure is the (1 1 1) cubic phase. We carried out a numerical simulation for a thermal fluid, to confirm the high temperature and velocity fields of the plasma jets that formed inside the reactor as the flow rate of plasma forming gas was adjusted. A high production yield of 51% was achieved using amorphous boron at a feed rate of 190 mg/min and the c-BN nanoparticles exhibited high crystallinity without requiring pre-and post-processing.     

Structural evolution of boron nitride films grown on diamond buffer-layers

Boron nitride films on diamond buffer layers of varying grain size, surface roughness and crystallinity are deposited by the reaction of B₂H₆ and NH₃ in a mixture of H₂ and Ar via microwave plasma-assisted chemical vapor deposition. Various forms of boron nitride, including amorphous α-BN, hexagonal h-BN, turbostratic t-BN, rhombohedral r-BN, explosion E-BN, wurzitic w-BN and cubic c-BN, are detected in the BN films grown on different diamond buffer layers at varying distances from the interface of diamond and BN layers. The c-BN content in the BN films is inversely proportional to the surface roughness of the diamond buffer layers. Cubic boron nitride can directly grow on smooth nanocrystalline diamond films, while precursor layers consisting of various sp²-bonded BN phases are formed prior to the growth of c-BN film on rough microcrystalline diamond films.     

Thin films of boron nitride grown by CVD

For the first time, thin films of boron nitride were deposited by chemical vapour deposition on to polished silicon and other metal substrates using the inorganic compound H₃BNH₃ (aminodiborane) and ammonia as carrier gas. The substrate temperature was varied from 400 to 600°C. The films were chemically inert and adherent to the substrates. The FTIR spectrum of the film showed B-N-B absorption at 800 cm⁻¹, B-N stretching at 1056 cm⁻¹, and also a weak absorption at 1340cm⁻¹ corresponding to B-N-B bending vibration. Deposited films also exhibited X-ray diffraction pattern with interplanar spacing with (002) plane of hexagonal boron nitride.     

Molecular dynamics study of deposition mechanism of cubic boron nitride

We have performed molecular dynamics simulations of bombardment of graphitic boron nitride (gBN) by energetic boron and nitrogen particles in order to examine the roles of ion bombardment in ion/plasma-assisted deposition of cubic boron nitride (cBN) thin films. We have found that the interaction of the energetic particles with gBN creates four-fold coordinated local structures (sp³-formation) inside gBN. We have also found that clusters of sp³-formations are created as a result of successive bombardment, some of which have cBN-like structures. On the basis of these results, we propose an atomic-scale model of cBN nucleation in which successive sp³-formation converts gBN into cBN.     

On the strength of polycrystals of boron nitride dense modifications

An analytical algorithm for the calculation of stresses in polycrystals of boron nitride dense modifications has been described. The relations established between the tensile and compression strength have been based on the Griffith fracture hypothesis for a biaxial stressed state. The effect has been taken into account of technological residual thermal stresses, which are formed in wurtzitic boron nitride (wBN) grains in sintering at the stage of cooling because of the thermal expansion anisotropy, on the strength of wBN.     

Synthesis of boron carbon nitride oxide (BCNO) from urea and boric acid

A solid state synthesis of boron carbon nitride oxide (BCNO) material was carried out starting from urea and boric acid treated at 600°C. The X-ray diffraction pattern corresponded to amorphous BCNO with an interlayer distance of 3.49 Å. The material had a layered structure similar to that of graphite and hexagonal boron nitride (h-BN). Infrared spectroscopy (IR) showed bands which were similar to those typical of BN and carbon nitride. The presence of boron was also confirmed by energy dispersive spectroscopy in an amount compatible with the IR spectrum. The spectra obtained by X-ray photoelectron spectroscopy (XPS) corresponded to those of a BCNO family with a considerable content of oxygen too. The optical band gap was estimated to be 3.22 eV, typical of a wide band-gap semiconductor. The particle size was very dispersed from micro to nanosize. The material dispersed in polar solvents formed stable suspensions due to the presence of hydroxyl groups.     

Cubic boron nitride based metastable coatings and nanocomposites

Various PVD and plasma-assisted CVD methods presently used for the deposition of cubic boron nitride (c-BN) thin films demand adequate conditions relating to ion bombardment of growing films, growth temperature, film stoichiometry, etc. The deposition conditions, often appearing rather apparatus-dependent, can be well categorized according to the fundamental parameters of bombarding ions as well as condensing neutral particles, including their energy and flux ratio, and a few of others like ion mass and incident angle. According to these parameters, various surface kinetic processes and their consequences are discussed particularly in connection with the resulting film phases and stress. Typical c-BN films are known for their extremely high compressive stress and poor adhesion as a result of intensive ion bombardment during deposition. Individual measures attempting to relieve this detrimental stress are briefly summarized. The present paper focuses on magnetron-sputtered, c-BN-based metastable films and nanocomposite films with considerably reduced internal stress in comparison to the usual “pure” c-BN films. Two examples will be shown, namely c-BN/a-C nanocomposite and c-BN:O metastable films, including their deposition details, structure and composition characterization, and mechanical properties. Also illustrated is a growth scheme tailored for the deposition of thick, adhered, cubic-phase dominated, superhard c-BN:O films above 2 µm on silicon substrates.     

水热条件下氮化硼枝蔓晶的形成

利用水热方法合成了氮化硼枝蔓晶,根据X射线衍射(XRD),傅立叶红外吸收(FTIR)测试确定了产物的物相组成,X射线能谱仪(XPS)也证明了枝蔓晶的立方氮化硼成分,同时,利用透射电镜(TEM)和选取电子衍射(SAED)的测试结果分析了枝蔓晶的形貌和表面特征,另外,本文结合负离子配位多面体理论探讨了枝蔓晶的形成机理.     

Oxygen-suppressed selective growth of monolayer hexagonal boron nitride on copper twin crystals

Controlled growth of hexagonal boron nitride (h-BN) with desired properties is essential for its wide range of applications.Here,we systematically carried out the chemical vapor deposition of monolayer h-BN on Cu twin crystals.It was found that h-BN nucleated and grew preferentially and simultaneously on the narrow twin crystal strips present in the Cu substrates.The density functional theory calculations revealed that the introduction of oxygen could efficiently tune the selectivity.This is because of the reduction in the dehydrogenation barrier of the precursor molecules by the introduction of oxygen.Our findings throw light on the direct growth of functional h-BN nanoribbons on nano-twinned crystal strips and switching of the growth behavior of h-BN films by oxygen.     

Third order elastic constants of hexagonal boron nitride

Third order elastic constants of hexagonal Boron Nitride have been evaluated using the Lannard-Jones potential. The results obtained are presented and compared with the only available measurement ofC ₃₃₃ for this material.