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1.
Investigations on CVD boron nitride films on fibres by means of photoelectron and X-ray spectroscopy resulted in B/N ratios
above the stoichiometric value 1 and oxygen contents up to 25 at%. Compared to the hydrolytic rate of the films an apparent
dependence was found on the deposition rate and some evidence of the oxygen concentration. CVD fibre coatings exhibit a hexagonal
turbostratic structure with extremely small atomic layer plane dimensions, which was proved by transmission electron microscopy.
Corresponding to oxygen concentrations in pyrolytic carbon films with similar structure a model is proposed, where the small
atomic layers with dimensions of some nanometers cause a relatively high oxygen concentration in the boron nitride films.
The oxygen atoms saturate the dangling bonds. Moreover the B/N ratio extents the expected stoichiometric ratio due to the
oxygen atoms at nitrogen sites.
Received: 15 July 1997 / Revised: 29 January 1998 / Accepted: 2 February 1998 相似文献
2.
Cubic boron nitride (c-BN) coatings produced by PVD and PECVD techniques usually exhibit very high compressive stresses and poor adhesion due to intense ion bombardments of the growing surface that are mandatory during the formation of the cubic phase. Our previous investigations indicate, however, that a controlled addition of oxygen during film deposition can lead to a drastic reduction of the detrimental stress, yet having minor effect on the cubic phase content in the resulting low-stress, oxygen-containing c-BN:O coatings (as already confirmed by various analytical methods like X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and electron diffraction, and Fourier transform infra-red spectroscopy (FTIR)). This stress-reduction technique makes possible the deposition of well-adhered, superhard c-BN:O layer about 2 μm thick through magnetron sputtering on top of an adhesion-promoting base layer and via a compositional-graded nucleation process. In the present paper, we report on the atomic bonding structure relating in particular to the incorporated oxygen within such a thick c-BN:O coating using X-ray photoelectron spectroscopy (XPS). The c-BN:O top layer was found to consist of about 49.8 at% boron, 42.2 at% nitrogen, 5.5 at% oxygen, as well as small amounts of carbon (1.4 at%) and argon (1.1 at%). Because of the low oxygen concentration, it was difficult to categorize the bonding state of oxygen according to the XPS spectra of B 1s and N 1s elemental lines. However, the detailed results in terms of the O 1s spectrum strongly indicated that the lattice nitrogen of c-BN was partially replaced by the added oxygen. 相似文献
3.
Guoxin Chen Huanming Lu Junfeng Cui Haitao Yu Bo Wang Yan Liu He Li Nan Jiang 《中国化学快报》2019,30(7):1401-1404
The real time analysis structure evolution of BNNT with compression showed that the formation of V-shape in the post-buckling before BNNT fracture was reversible. 相似文献
4.
Structural characterizations and electronic properties of boron nitride nanotube crystalline bundles
The structural characterizations and electronic properties of aligned armchair single-walled boron nitride nanotube (BNNT) bundles are theoretically investigated. In the spontaneous bundling process, the cylindrical shapes of bundled BNNTs are preserved all along, whereas their diameters expand, then shrink, and return back to the initial dimensions. Owing to the nonuniform distribution of positive and negative charges among BNNTs, the multipole interaction in bundles is completely dependent upon the chirality of each BNNT and the arrangement of bundled BNNTs. The effect of intertube coupling on the dispersions of BNNT bundles is demonstrated. Our systematical simulations might be helpful for the understanding of potential applications of BNNT bundles in the nanometer manufacturing techniques such as doping, adsorption, and derivative synthesis. 相似文献
5.
Origins of thermodynamically stable superhydrophobicity of boron nitride nanotubes coatings 总被引:1,自引:0,他引:1
Boinovich LB Emelyanenko AM Pashinin AS Lee CH Drelich J Yap YK 《Langmuir : the ACS journal of surfaces and colloids》2012,28(2):1206-1216
Superhydrophobic surfaces are attractive as self-cleaning protective coatings in harsh environments with extreme temperatures and pH levels. Hexagonal phase boron nitride (h-BN) films are promising protective coatings due to their extraordinary chemical and thermal stability. However, their high surface energy makes them hydrophilic and thus not applicable as water repelling coatings. Our recent discovery on the superhydrophobicity of boron nitride nanotubes (BNNTs) is thus contradicting with the fact that BN materials would not be hydrophobic. To resolve this contradiction, we have investigated BNNT coatings by time-dependent contact angle measurement, thermogravimetry, IR spectroscopy, and electron microscopy. We found that the wettability of BNNTs is determined by the packing density, orientation, length of nanotubes, and the environmental condition. The origins of superhydrophobicity of these BNNT coatings are identified as (1) surface morphology and (2) hydrocarbon adsorbates on BNNTs. Hydrocarbon molecules adsorb spontaneously on the curved surfaces of nanotubes more intensively than on flat surfaces of BN films. This means the surface energy of BNNTs was enhanced by their large curvatures and thus increased the affinity of BNNTs to adsorb airborne molecules, which in turn would reduce the surface energy of BNNTs and make them hydrophobic. Our study revealed that both high-temperature and UV-ozone treatments can remove these adsorbates and lead to restitution of hydrophilic BN surface. However, nanotubes have a unique capability in building a hydrophobic layer of adsorbates after a few hours of exposure to ambient air. 相似文献
6.
Characterisation of diamond coatings with different morphologies by Raman spectroscopy using various laser wavelengths 总被引:1,自引:0,他引:1
Since the beginning of low-pressure diamond synthesis, Raman spectroscopy has been widely used to identify and characterise
the quality of diamonds. The diamond crystal is characterised by a Raman peak at about 1,332 cm-1. Other peaks are associated with miscellaneous carbon structures, e.g. graphite and amorphous phases. In recent years, both
well-faceted crystalline diamonds and nanocrystalline and ultrananocrystalline diamonds have been investigated. For these
fine-grained materials, the diamond peak at 1,332 cm-1 disappears and the intensities of peaks at other wavelengths increase. To study the influence of the Raman laser wavelength,
three lasers were used (472.681 nm, blue; 532.1 nm, green; 632.81 nm, red). For well-faceted diamonds, the Raman spectra with
blue and green laser light were similar. A shift of the peak maxima and different intensities were observed. With use of the
red laser, a strong luminescence peak and low peak intensities for the various carbon-related peaks occurred. When the diamond
morphology changes from well-faceted to fine-grained ballas diamond, the spectra are similar for all three lasers. 相似文献
7.
Improved techniques are described for the determination of boron and nitrogen in pure boron nitride. Controlled fusion of boron nitride with sodium carbonate in a muffle furnace is followed by a potentiometric titration of the boric acid. A special quartz vessel is described for the determination of nitrogen. The boron nitride is fused with sodium hydroxide and the resulting ammonia is swept into a receiver and titrated with standard hydrochloric acid. Boron and nitrogen values with their standard deviation are given for a typical pure boron nitride. 相似文献
8.
The electronic energy structure of boron nitride with ZnS (c-BN) and wurtzite (w-BN) type crystal lattices is calculated by
the local coherent potential (LCPA) method in a multiple scattering approximation. The local partial 2p states of boron with
c-BN and w-BN are compared with the boron K emission spectra in the corresponding compounds. Fine structure is first obtained
in the region of the top of the valence band.
Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1083–1087, November–December, 1998. 相似文献
9.
10.
The aim of this work is the investigation of the haemocompatibility properties of homogeneous and amorphous boron nitride (a-BN) thin films, through the adsorption of two basic blood plasma proteins, human serum albumin (HSA) and fibrinogen (Fib). The a-BN thin films were grown onto c-Si(100) substrates under different values of substrate bias voltage, employing the radio frequency (RF) magnetron sputtering technique. For the consideration of the optical, compositional and structural properties of the films, Spectroscopic Ellipsometry (SE) in the Vis–UV spectral region was used, while for the study of surface topography and surface charge distribution as well as of the wetting properties of the a-BN thin films, Atomic Force Microscopy (AFM), Electric Force Microscopy (EFM) and Contact Angle measurements were additionally employed. The properties of the thin films were correlated with their haemocompatibility, through the estimation of the ratio of HSA/Fib surface concentration. The sp3 content of the samples does not seem to correlate with the haemocompatibility of the a-BN thin films. However, the surface properties determine the thrombogenicity potential of the studied samples. More precisely, the a-BN films with a less negatively charged surface exhibit the smallest possibility of clot formation, possibly due to the interactions between the charged chains of the Fib molecules and the a-BN surface, while slight changes in the surface roughness do not affect their haemocompatibility properties. The wetting properties determine the thickness of the adsorbed Fib as well as the ratio of HSA/Fib surface concentration. 相似文献
11.
R. Reiche S. Oswald D. Hofman J. Thomas K. Wetzig 《Analytical and bioanalytical chemistry》1999,365(1-3):76-82
For further evaluation of photoemission properties of argon ion bombarded rhenium-silicon thin films pure element Re(21 nm)
/ Si(39 nm) / Re(21 nm) layer sandwiches were investigated on Si(111) substrates. TEM cross sectioning revealed abrupt interfaces
between the polycrystalline Re layers and the amorphous Si layer in the as-deposited sample. In XPS sputter depth profiling
the interfaces were severely broadened. This is not just a result of the finite electron escape depth together with atomic
mixing and preferential sputtering which was demonstrated with the dynamic Monte Carlo simulation program T-DYN, but mainly
caused by topographic effects and silicide formation. Factor analysis of XPS spectra results in two Re-Si principal components
which can be ascribed to silicide bonding. Accordingly the valence band changes are caused by different bonding configurations.
Bombardment-induced silicide formation is proved by TEM investigations of a selected cross-sectioned sandwich. Due to preferential
bombardment-induced effects Re2Si is formed at the Re/Si interfaces in contrast to the ReSi2 growth on thermal heating. This is discussed in terms of the interface composition and the effective heat of formation (EHF)
model.
Received: 6 September 1998 / Revised: 17 December 1998 / Accepted: 31 January 1999 相似文献
12.
Zhang Y Ago H Yumura M Komatsu T Ohshima S Uchida K Iijima S 《Chemical communications (Cambridge, England)》2002,(23):2806-2807
Crystalline boron nanowires with tetragonal structure have been synthesized based on laser ablation of a B/NiCo target; the nanowires are sometimes single crystals and have a droplet at one end of the nanowire; the droplet contains B, Ni and Co elements, which indicates that the vapor-liquid-solid (VLS) mechanism may play a key role in the growth of the boron nanowires. 相似文献
13.
14.
Modification of siloxane coatings of protective materials with boron (boric acid, boric anhydride, triethyl borate) and aluminum
(aluminum butylate, oxide, hydroxide) compounds was studied with the aim to enhance the fireproofing and physicomechanical
properties of the materials. 相似文献
15.
不同材料表面纳米复合化学镀层镍-磷-硅酸锌的XPS和AES分析 总被引:1,自引:0,他引:1
对Q235碳钢片和D310硅钢片表面表面镍-磷-硅酸锌纳米复合化学镀层,用SEM观察外貌,称重法测定厚度;10%NaCl、1%H2S加速腐蚀试验,10%CuSO4溶液点滴试验循环伏安(CV)、抗粘性及抗高温氧化试验等测定其性能。用X-射线电子谱(XPS)及俄歇电子能谱(AES)测定其价态及组成。结果表明其性能优镍-磷镀层和其它微米复合化学镀层,表面的镀层Q235碳钢片优于D310硅钢片表面的镀层,镀层的原子百分组成为:D235碳钢片:Ni79.00,P10.06,Zn2.01,Si1.88,O5.87,C1.18;D310硅钢片:Ni80.50,P10.67,Zn1.70,Si1.52,O4.83,C0.78. 相似文献
16.
Nanocrystalline boron nitride (BN) with needle-like and hollow spherical morphology has been synthesized by nitriding of MgB2 with NH4Cl and NH4Cl-NaN3, respectively. The amount of NaN3 has an obvious effect on the size of the hollow spheres. The samples were characterized by X-ray powder diffraction, Fourier transformation infrared spectroscopy, X-ray photoelectron spectra, and transmission electron microscopy. The possible mechanism of morphology control is also discussed. 相似文献
17.
Graphite is exfoliated into graphene by shearing vortex fluidic films of N-methyl-pyrrolidone (NMP), as a controlled process for preparing oxide free graphene, and for exfoliating the corresponding boron nitride sheets. 相似文献
18.
Simple synthesis of mesoporous boron nitride with strong cathodoluminescence emission 总被引:1,自引:0,他引:1
Mesoporous BN was prepared at 550 °C for 10 h or so via a simple reaction between NaBH4 and CO(NH2)2. X-ray diffraction demonstrates the formation of t-BN with lattice constants a=2.46 and c=6.67 Å. High-resolution transmission electron microscopy displays a lot of porous films in the product, which possesses a high surface area of 219 m2 g−1 and a pore size primarily around 3.8 nm tested by nitrogen adsorption-desorption method. The mesoporous BN exhibits a strong luminescence emission around 3.41 eV in the cathodoluminescence spectra, a high stability in both morphology and structure, and good oxidation resistance up to 800 °C. The byproducts generated during the reaction are responsible for the formation of the mesoporous BN. 相似文献
19.
Boron nitride nanotube (BNNT) films were synthesized by combining ball milling and thermal chemical vapor deposition (CVD) using nano-Fe3O4 as a catalyst. The as-produced BNNTs have a bamboo-like structure and have a diameter in the range of 50~200 nm with an average length of more than 40 mm. Moreover, BNNT nanojunction structures were synthesized. The structure and morphology of the BNNTs were characterized by XRD, SEM, TEM and HRTEM. The possible growth mechanism of BNNTs and BNNT nanojunction structures were proposed. Though the BNNT films were observed, out of our expectation, BNNTs with thin tube wall and small average diameter have not been achieved, and this could be mainly ascribed to the aggregation of the nanoparticle catalyst, resulting in greater catalyst particles during the process of BNNT growth. This result will provide a promising approach to obtain the desired shape of BNNTs and produce branched junctions of BNNTs. 相似文献
20.
Petravic M Peter R Kavre I Li LH Chen Y Fan LJ Yang YW 《Physical chemistry chemical physics : PCCP》2010,12(47):15349-15353
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. 相似文献