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1.
采用高温热解法在860℃分别制备出了碳、碳氮和硼碳氮纳米管,提纯后利用丝网印刷工艺分别将它们制备成薄膜,并测试了它们的场发射性能.结果表明:碳纳米管、碳氮纳米管和硼碳氮纳米管薄膜的开启电场分别为2.22,1.1和4.4V/μm,当电场增加到5.7V/μm时,它们的电流密度分别达到1400,3000μA/cm2和小于50μA/cm2.碳和碳氮纳米管薄膜的场增强因子分别为10062和11521.可见,碳氮纳米管的场发射性能优于碳纳米管,而硼碳氮纳米管的场发射性能比前两者要差.解释了这三种纳米管场发射性能差别的原因.
关键词:
碳纳米管
碳氮纳米管
硼碳氮纳米管
场发射 相似文献
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The oxidation of vanadium nitride (VN) and titanium nitride (TiN) coatings in ultra-high vacuum has been investigated in situ by X-ray photoelectron spectroscopy. On the VN coatings mixed oxide layers containing V3+ and V4+ species form at elevated temperatures (?600°C) and at high oxygen exposures, which cover completely the VN surface. Under similar oxidation conditions the TiN surface oxidises partially to a mixture of TiO2 and Ti oxynitride (TiOxNy) phases. This oxidation behaviour has been correlated to the tribological properties of the VN and TiN coatings investigated recently. 相似文献
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P. P. George A. Gedanken Shirly Ben-David Makhlouf I. Genish A. Marciano Riam Abu-Mukh 《Journal of nanoparticle research》2009,11(4):995-1003
TiN, NbN, and TaN nanocrystals have been selectively prepared through a simple, solvent-free, and convenient reaction under
autogenic pressure at moderate temperature (RAPET) process at 350 °C for 12 h, reacting transition metal chlorides and sodium
azide. The nanostructures obtained are characterized by powder X-ray diffraction (PXRD), transmission electron microscopy
(TEM), and scanning electron microscopy (SEM). A reaction mechanism is suggested based on the experimental results. These
rapid reactions produce nanocrystals of TiN, NbN, and TaN with average sizes of approximately 30, 28, and 27 nm, respectively
(as calculated from X-ray line broadening). An octahedral inorganic fullerene was detected among the various structures of
the TiN. 相似文献
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Translated from Zhurnal Prikladnoii Spektroskopii, Vol. 55, No. 5, pp. 861–863, November, 1991. 相似文献
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T. S. Bartnitskaya G. S. Oleinik A. V. Pokropivnyi V. V. Pokropivnyi 《JETP Letters》1999,69(2):163-168
The structure and mechanism of formation and growth are investigated for two forms of BN nanotubes produced by carbothermal
synthesis.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 145–150 (25 January 1999) 相似文献
7.
Using the DFT-B3LYP calculations we investigate the adsorption of Li atom on CNT, BNNT, AlNNT and SiCNT. We found that Li atom can be chemisorbed on zig-zag SiCNT with binding energy of −2.358 eV and charge transfer of 0.842 |e|, which are larger than the results of other nanotubes. The binding energy of Li on SiCNT is foun to be stronger than activation energy barrier indicating that Li metal could be well dispersed on SiCNTs. Furthermore, the average voltage caused by the lithium adsorption on SiCNT demonstrated that SiCNTs could exhibit as a stable anode similar to the lithium metal anode. The binding nature has been rationalized by analyzing the electronic structures. Our findings demonstrate that Li-BNNT, Li-SiCNT and Li-AlNNT systems exhibit spin polarized behaviors and can fascinating potential application in future spintronics. Also, Li-SiCNT system with rather small band gap might be a promising material for optical applications and active molecule in its environment. 相似文献
8.
本文采用基于密度泛函理论的第一性原理平面波赝势和局域密度近似方法,优化了立方和六方氮化硼的几何结构,系统地研究了零温高压下立方和六方氮化硼的几何结构、力学、电学以及光学性质.结构与力学性质研究表明:立方氮化硼的结构更加稳定,两种结构的氮化硼均表现出一定的脆性,而六方氮化硼的热稳定性则相对较差;电学性质研究表明:立方氮化硼和六方氮化硼均为间接带隙半导体,且立方氮化硼比六方氮化硼局域性更强;光学性质结果显示:立方氮化硼和六方氮化硼对入射光的通过性都很好,在高能区立方氮化硼对入射光的表现更加敏感.此外,还研究了高温高压下立方氮化硼的热力学性质,并得到其热膨胀系数、热容、德拜温度和格林艾森系数随温度和压力的变化关系.本文的理论研究阐述了高压下立方氮化硼和六方氮化硼的相关性质,为今后的实验研究提供了比较可靠的理论依据. 相似文献
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B. I. Smirnov Yu. A. Burenkov B. K. Kardashev D. Singh K. C. Goretta A. R. de Arellano-López 《Physics of the Solid State》2001,43(11):2094-2098
A study is reported on the effect of temperature and elastic vibration amplitude on Young’s modulus E and internal friction in Si3N4 and BN ceramic samples and Si3N4/BN monoliths obtained by hot pressing of BN-coated Si3N4 fibers. The fibers were arranged along, across, or both along and across the specimen axis. The E measurements were carried out under thermal cycling within the 20–600°C range. It was found that high-modulus silicon-nitride specimens possess a high thermal stability; the E(T) dependences obtained under heating and cooling coincide well with one another. The low-modulus BN ceramic exhibits a considerable hysteresis, thus indicating evolution of the defect structure under the action of thermoelastic (internal) stresses. Monoliths demonstrate a qualitatively similar behavior (with hysteresis). This behavior of the elastic modulus is possible under microplastic deformation initiated by internal stresses. The presence of microplastic shear in all the materials studied is supported by the character of the amplitude dependences of internal friction and the Young’s modulus. The experimental data obtained are discussed in terms of a model in which the temperature dependences of the elastic modulus and their features are accounted for by both microplastic deformation and nonlinear lattice-atom vibrations, which depend on internal stresses. 相似文献
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X.C. Wang 《Applied Surface Science》2009,255(7):4005-4010
The structure and mechanical properties of the multilayers consisting of 5-73 nm thick titanium nitride (TiN) and 4.6 nm thick carbon nitride (CN) have been investigated. It has been found that the CN layers are amorphous and the TiN layers thinner than 17 nm are amorphous. The TiN layers become crystallized as the thickness is increased to 30 nm or thicker. The hardness from the composite response of the multilayered films and their substrates determined using continuous stiff measurement is smaller than the film-only hardness (without substrate effects) calculated using Bhattacharya-Nix empirical equation. The hardness increases with raising the thickness of TiN layers. With the crystallization of the TiN layer, the multilayers become even harder than that calculated based on the rule of mixtures. However, no enhancement in hardness has been observed when the TiN layers are amorphous. 相似文献
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Boron nitride (BN) nanohorns were synthesized by arc-melting YB6 powders. Method, and atomic structure models for BN nanohorns encaging Y@B36N36 were proposed from high-resolution electron microscopy. The molecular mechanics calculation indicated that BN clusters with metal atoms would be stabilized by being encaged in double-walled BN nanohorns. 相似文献
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Abstract Recent advances on the preparation technique of sintered diamond and cubic boron nitride containing small amount of sintering additives having superior thermal and mechanical properties is reviewed. Sintered diamond of lower metallic content (1–5 vol%) shows high hardness (100–150 GPa) and high electrical resistivity (108 ohm-cm) at room temperature. Reaction sintered cubic boron nitride contained 1–3 mole % of magnesium boron nitride shows high thermal conductivity. (7 watt/cm K at RT) 相似文献
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P. I. Ignatenko 《Technical Physics》2011,56(2):264-268
The influence of the relative supersaturation, elastic strain energy of the growing phase, and adhesion energy on the morphology and orientation of boride, nitride, and silicide coatings is estimated using X-ray diffraction, electron microscopy, and secondary-ion mass spectrometry data. A diagram is constructed from which growth conditions for phases with given morphology and structural perfection can be found. 相似文献
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R. Franchy G. Schmitz P. Gassmann F. Bartolucci 《Applied Physics A: Materials Science & Processing》1997,65(6):551-566
At 300 K, an amorphous Al-oxide film is formed on NiAl(001) upon oxygen adsorption. Annealing of the oxygen-saturated NiAl(001)
surface to 1200 K leads to the formation of thin well-ordered θ-Al2O3 films. At 300 K, and low-exposure oxygen atoms are chemisorbed on CoGa(001) on defects and on step edges of the terraces.
For higher exposure up to saturation, the adsorption of oxygen leads to the formation of an amorphous Ga-oxide film. The EEL
spectrum of the amorphous film exhibits two losses at ≈400 and 690 cm-1. After annealing the amorphous Ga-oxide films to 550 K thin, well-ordered β-Ga2O3 films are formed on top of the CoGa(001) surface. The EEL spectrum of the β-Ga2O3 films show strong Fuchs-Kliewer (FK) modes at 305, 455, 645, and 785 cm-1. The β-Ga2O3 films are well ordered and show (2×1) LEED pattern with two domains, oriented perpendicular to each other. The STM study
confirms the two domains structure and allows the determination of the two-dimensional lattice parameters of β-Ga2O3. The vibrational properties and the structure of β-Ga2O3 on CoGa(001) and θ-Al2O3 on NiAl(001) are very similar.
Ammonia adsorption at 80 K on NiAl(111) and NiAl(001) and subsequent thermal decomposition at elevated temperatures leads
to the formation of AlN. Well-ordered and homogeneous AlN thin films can be prepared by several cycles of ammonia adsorption
and annealing to 1250 K. The films render a distinct LEED pattern with hexagonal [AlN/NiAl(111)] or pseudo-twelve-fold [AlN/NiAl(001)]
symmetry. The lattice constant of the grown AlN film is determined to be aAlN= 3.11 Å. EEL spectra of AlN films show a FK phonon at 865 cm-1. The electronic gap is determined to be Eg= 6.1±0.2 eV. GaN films are prepared by using the same procedure on the (001) and (111) surfaces of CoGa. The films are characterized
by a FK phonon at 695 cm-1 and an electronic band gap Eg= 3.5±0.2 eV.
NO adsorption at 75 K on NiAl(001) and subsequent annealing to 1200 K leads to the formation of aluminium oxynitride (AlON).
An oxygen to nitrogen atomic ratio of ≈2:1 was estimated from the analysis of AES spectra. The AlON films shows a distinct
(2×1) LEED pattern and the EEL spectrum exhibits characteristic Fuchs-Kliewer modes. The energy gap is determined to be Eg= 6.6±0.2 eV. The structure of the AlON film is derived from that of θ-Al2O3 formed on NiAl(001).
Received: 21 March 1997/Accepted: 12 August 1997 相似文献
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The development of novel structure, fabrication methods, formation mechanisms, and versatile applicability of boron nitride (BN) nanomaterials is still one of the research hotspots. In this report, we developed a novel two dimensional cubic boron nitride nanosheets (2D c-BNNSs) based on the first principles calculations. This structure is converted from hexagonal BN (h-BN) bilayers induced by hydroxyl (OH) radical and fluoride (F) atom codoping. The geometrical, electronic, and optical properties of the novel 2D OH radical and F atom codoped c-BNNSs (OH-F-c-BNNSs) have been systematically investigated. The results reveal that the unpaired electrons appear due to the electronegativity difference between OH radical and F atoms, resulting in the excellent electrical and magnetic properties of OH-F-c-BNNSs. In addition, OH-F-c-BNNSs also exhibit a strong response to the visible light with an absorption range covering the whole visible light region. More importantly, when the doping positions of OH radical and F atom are exchanged (F-OH-c-BNNSs), the F-OH-c-BNNS will have only electrical conductivity, which will make us to regulate the intrinsic properties of c-BNNSs for different applications only by adjusting the element doping positions. This work can provide a theoretical and experimental basis/support for designing and fabricating new types of 2D c-BN nanomaterials for different applications. 相似文献
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Electrical and optical measurements were carried out on tiny crystals of cubic boron nitride. The dark current iD was found to change exponentially with T, with activation energies in the range 0·2–0·4 eV. A red electroluminescence, of intensity iEL. proportional to iD was observed. Upon illumination at low temperatures a photocurrent ip proportional to the square root of the excitation intensity appeared. It varied exponentially with T, with an activation energy of 0.05 ± 0.01 eV. The crystals exhibited a red thermoluminescence with several unresolved peaks covering the temperature range 100–400K, and having activation energies in the range 0·15–0·40 eV. 相似文献
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In this research it was studied vanadium nitride (VN) and hafnium nitride (HfN) film, which were deposited onto silicon (Si (100)) and AISI 4140 steel substrates via r.f. magnetron sputtering technique in Ar/N2 atmosphere with purity at 99.99% for both V and Hf metallic targets. Both films were approximately 1.2±0.1 µm thick. The crystallography structures that were evaluated via X-ray diffraction analysis (XRD) showed preferential orientations in the Bragg planes VN (200) and HfN (111). The chemical compositions for both films were characterized by EDX. Atomic Force Microscopy (AFM) was used to study the morphology; the results reveal grain sizes of 78±2 nm for VN and 58±2 nm for HfN and roughness values of 4.2±0.1 nm for VN and 1.5±0.1 nm for HfN films. The electrochemical performance in VN and HfN films deposited onto steel 4140 were studied by Tafel polarization curves and impedance spectroscopy methods (EIS) under contact with sodium chloride at 3.5 wt% solution, therefore, it was found that the corrosion rate decreased about 95% in VN and 99% for HfN films in relation to uncoated 4140 steel, thus demonstrating, the protecting effect of VN and HfN films under a corrosive environment as function of morphological characteristics (grain size). 相似文献
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Atomistic mechanisms of fracture accompanying structural phase transformation (SPT) in AlN ceramic under hypervelocity impact are investigated using a 209 x 10(6) atom molecular-dynamics simulation. The shock wave generated by the impact splits into an elastic wave and a slower SPT wave that transforms the wurtzite structure into the rocksalt phase. The interaction between the reflected elastic wave and the SPT wave front generates nanovoids and dislocations into the wurtzite phase. Nanovoids coalesce into mode I cracks while dislocations give rise to kink bands and mode II cracking. 相似文献