共查询到20条相似文献,搜索用时 78 毫秒
1.
M. Nowak M. Jesionek P. Szperlich J. Szala T. Rzycho D. Str 《Ultrasonics sonochemistry》2009,16(6):800-804
This paper presents for the first time the nanocrystalline, semiconducting ferroelectrics antimony sulfoiodide (SbSI) grown in multiwalled carbon nanotubes (CNTs). It was prepared sonochemically using elemental Sb, S and I in the presence of methanol under ultrasonic irradiation (35 kHz, 2.6 W/cm2) at 323 K for 3 h. The CNTs filled with SbSI were characterized by using techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, selected area electron diffraction, and optical diffuse reflection spectroscopy. These investigations exhibit that the SbSI filling the CNTs is single crystalline in nature and in the form of nanowires. It has indirect forbidden energy band gap EgIf = 1.871(1) eV. 相似文献
2.
Jesionek M Nowak M Szperlich P Stróż D Szala J Jesionek K Rzychoń T 《Ultrasonics sonochemistry》2012,19(1):179-185
This paper presents, for the first time, the nanocrystalline, semiconducting antimony selenoiodide (SbSeI) grown in multi-walled carbon nanotubes (CNTs). It was prepared sonochemically using elemental Sb, Se, and I in the presence of ethanol under ultrasonic irradiation (35 kHz, 2.6 W/cm2) at 323 K for 3 h. The CNTs filled with SbSeI were characterized by using techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, selected area electron diffraction, and optical diffuse reflection spectroscopy. These investigations exhibit that the SbSeI filling the CNTs is single crystalline in nature and in the form of nanowires. It has indirect allowed energy band gap EgIf = 1.61(6) eV. 相似文献
3.
F. Kokai K. Uchiyama T. Shimazu A. Koshio 《Applied Physics A: Materials Science & Processing》2010,101(3):497-502
Two types of one-dimensional (1D) nanostructures—amorphous silicon carbide (SiC) nanowires, 5–30 nm thick and 0.5–2 μm long,
and carbon nanotubes (CNTs) filled completely with crystalline SiC nanowires, 10–60 nm thick and 2–20 μm long—were synthesized
by the laser ablation of carbon-silicon targets in the presence of high-pressure Ar gas up to 0.9 MPa. All the CNTs checked
by transmission electron microscopy contained SiC, and no unfilled CNTs were produced. We discuss the growth of the two nanostructures
based on the formation of molten Si–C composite particles and their instabilities leading to the precipitation of Si and C. 相似文献
4.
L. S. Parfen’eva T. S. Orlova B. I. Smirnov I. A. Smirnov H. Misiorek A. Jezowski K. T. Faber 《Physics of the Solid State》2010,52(7):1348-1355
The thermal conductivity of composites of a new type prepared by infiltration under vacuum of melted copper into empty sap
channels (aligned with the sample length) of high-porosity biocarbon preforms of white pine tree wood has been studied in
the temperature range 5–300 K. The biocarbon preforms have been prepared by pyrolysis of tree wood in an argon flow at two
carbonization temperatures of 1000 and 2400°C. From the experimental values of the composite thermal conductivities, the fraction
due to the thermal conductivity of the embedded copper is isolated and found to be substantially lower than that of the original
copper used in preparation of the composites. The decrease in the thermal conductivity of copper in the composite is assigned
to defects in its structure, namely, breaks in the copper filling the sap channels, as well as the radial ones, also filled
by copper. A possibility of decreasing the thermal conductivity of copper in a composite due to its doping by the impurities
present in the carbon preform is discussed. 相似文献
5.
F. Kokai T. Shimazu K. Adachi A. Koshio Y. Takahashi 《Applied Physics A: Materials Science & Processing》2009,97(1):55-62
Carbon nanotubes (CNTs) filled completely with polycrystalline Cu nanowires were synthesized by laser vaporization of Cu and
graphite under high-pressure Ar gas atmosphere. Depending on the Ar gas pressure (0.1–0.9 MPa) and the Cu content (1–40 at.%)
in graphite targets for laser vaporization, various products with different morphologies were observed by scanning and transmission
electron microscopy. The ratios of the Cu-filled CNTs and carbon nanocapsules particularly increased as Ar gas pressure was
increased. The maximum ∼60% fraction of Cu-filled CNTs with outer diameter of 10–50 nm and length of 0.3–3 μm was achieved
at 0.9 MPa from graphite containing 20 at.% Cu. Most of the encapsulated Cu-nanowires were surrounded by single, double, or
triple graphitic layers. Although the yield of the Cu-filled CNTs was also dependent on the Cu content in the graphite targets,
no unfilled CNTs were produced even for low Cu content. The growth of Cu-filled CNTs is explained by the formation of molten
Cu–C composite particles with an unusually C-rich composition in a space confined by high-pressure Ar gas, followed by precipitating
Cu and C from the particles and subjecting them to phase separation. 相似文献
6.
A. T. Burkov S. V. Novikov B. I. Smirnov I. A. Smirnov Cz. Sulkovski A. Jezowski 《Physics of the Solid State》2010,52(11):2340-2344
The thermopower S(T) of the composites prepared by filling empty sap channels in high-porosity biocarbon preforms of white pine wood by melted
copper in vacuum and the thermopower S(T) of these preforms have been measured in the temperature range 5–300 K. The biocarbon preforms have been obtained by pyrolysis
of pine wood in an argon flow at two carbonization temperatures, 1000 and 2400°C. An analysis of the experimental data has
demonstrated that the thermopower of the composites is determined by the contribution related to the copper filling the channels
of the biocarbon preform and exhibits a characteristic temperature dependence with a deep minimum close to 20 K. This suggests
that copper in the preform channels is essentially a Kondo alloy with the iron and manganese impurities entering into it from
the carbon preform in the course of infiltration of melted copper. 相似文献
7.
8.
Y. T. Lee S. Shanmugan D. Mutharasu 《Applied Physics A: Materials Science & Processing》2014,114(4):1145-1152
Vertically aligned carbon nanotubes (VACNTs) were synthesized over copper substrate. The diameter and length of the CNTs were 100 nm and 2–3 μm, respectively. Synthesis of CNTs was confirmed by Raman spectrum and verified by TEM as multi walled CNTs. SEM images showed the vertically aligned CNTs over Cu substrate. Strengthening of CNTs was performed by filling with Cu and SU-8 epoxy sealant in gap between the CNTs. The observed density was high for epoxy sealed CNTs. The bending ability of CNTs was checked and observed as low for epoxy sealed CNTs. The thermal resistance of the samples was measured by JESD51-2 standard for various loads. The observed resistance was low (0.277 cm2?K/W) for epoxy sealed CNTs at 1100 kPa. The calculated resistance of CNTs alone was 0.097 cm2?K/W for epoxy sealed at 900 kPa. 相似文献
9.
We have investigated the electronic and magnetic properties of Fe, Co, and Ni nanowires encapsulated in carbon nanotubes (CNTs) using spin polarized ab initio calculation. The incorporated systems with hollow region between the nanowire and the C shell have the enhanced magnetic moments compared to the ferromagnetic nanowires tightly wrapped by CNTs. The Co nanowire encapsulated in CNTs is a strong ferromagnet and has high spin polarization regardless of the distance between the nanowire and the C shell. The results show that the Co-filled CNTs are useful for spin polarized transport nanodevice. 相似文献
10.
J. Cheng X.P. Zou G. Zhu M.F. Wang Y. Su G.Q. Yang X.M. Lü 《Solid State Communications》2009,149(39-40):1619-1622
Iron-filled carbon nanotubes (CNTs) were synthesized using a floating catalyst chemical vapor deposition method with a great excess of ferrocene (more than 30 mg/min of vaporization rate) at 800 C. The amount of ferrocene is more than that in previous reports. The ferrocene was employed as both catalyst precursor and an iron source. Our observations indicate that the CNTs were more than 10 micrometer in length, with an outer diameter of 20–100 nm and inner diameter of 10–30 nm. The inner cavity of the CNTs was partial filled with iron nanowires. Magnetic property measurements reveal that the iron-filled CNTs exhibit an average coercivity of about 257.05 G. 相似文献
11.
G. A. Bukhtiyarova M. A. Shuvaeva O. A. Bayukov S. S. Yakushkin O. N. Martyanov 《Journal of nanoparticle research》2011,13(10):5527-5534
An approach is suggested to synthesize the ε-Fe2O3 particles supported on silica with the mean size of few nanometers, narrow size distribution and no admixture of any other
iron oxide polymorphs. The facile synthesis is based on the pore filling impregnation method by iron sulfate (II) water solution
with the following annealing procedure at ~1173 K. It is shown that the ε-Fe2O3 nanoparticles obtained are stable up to ~1173 K and possess superparamagnetic behavior up to ~870 K. 相似文献
12.
Using molecular dynamics simulations, we studied the morphologies of Lennard-Jones liquid encapsulated in carbon nanotubes (CNTs) for a wide range of liquid–CNT interaction, system size and temperature. The morphology of liquid is found to be sensitive to the filling ratio of liquid (a ratio of liquid volume to the available volume of CNT pore) and the liquid–CNT interaction. The ‘phase diagram’, namely by the morphologies versus the liquid–CNT interaction and the filling ratio, is obtained. In most cases, the liquid inside CNTs forms a thin liquid shell attached to a carbon wall when the filling ratio is small. With the increasing of the filling ratio, liquid tends to form droplet. As the filling ratio increases further, liquids form a cylinder with finite length. Finally, the whole inner space of CNT was filled with liquid when the filling ratio is large enough. Current studies could shed light on the adsorption and flow of liquid inside CNTs. 相似文献
13.
采用基于密度泛函理论的第一性原理方法研究了β-碳化硅/(15, 0) 碳纳米管和β-碳化硅/(16, 0)碳纳米管核壳结构的电子结构特性. 结果表明, 两种核壳异质结构都呈现出金属性, 它们的金属性主要是由碳纳米管和碳化硅纳米线表面的原子所贡献的. 碳化硅纳米线表面呈现的金属性由其结构本身决定, 而对于金属性的 (15, 0) 和半导体性的 (16, 0) 碳纳米管在填充碳化硅纳米线之后都表现出金属性, 主要是由于碳纳米管和碳化硅纳米线之间的电荷转移导致的, 而并不是由于碳纳米管形变造成的.
关键词:
核壳结构
电子结构
第一性原理 相似文献
14.
Carbon nanotube (CNT)/europium hydroxide core-shell nanowires were prepared easily on a large scale under the boiling reflux of water assisted by the surfactant, sodium polystyrenesulfonate (SPS). The core-shell nanowires are characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectrum. A possible formation mechanism has been suggested as follows: The phenyl rings of SPS can react with the carbon ring of CNTs to form the π-π noncovalent bond, which makes the SPS cover the surface of CNTs entirely, and thus the surface of modified CNTs is negatively charged, which repel with each other resulting in the good dispersion. In addition, the negatively charged surface of CNTs adsorbs europium ions (positive). The adsorbed europium ions in situ react with OH− ions to create europium hydroxide nanoparticles, and subsequently, the nanoparticles fuse together to form a dense coating layer on CNTs. 相似文献
15.
《中国物理 B》2019,(3)
Carbon nanotubes(CNTs) have the ideal structure to be used as templates for nanomaterials, especially for nanowires,and the tungsten nanowire is an important nanomaterial that is used as a strengthening phase. Therefore, we have proposed to apply mesoporous CNT(mCNT) as a template to prepare tungsten nanowires. However, the tungsten precursor should fill the hollow tube of mCNT firstly, and very few related studies have been reported. In this paper, we have systematically studied the filling process of ammonium metatungstate(AMT) aqueous solution. The results reveal that owing to the mesopores in the mCNT sidewall, the AMT can be encapsulated into the tube at room temperature(RT) and we can fully fill it without destroying the structure. In addition, vibration and solute concentration are also important factors. Besides,the mesoporous sidewall and hollow tubular core structure of mCNT are prerequisites to realize full filling. Furthermore,tungsten nanowires have been obtained after reduction of AMT in mCNTs. 相似文献
16.
N. Demoncy O. Stéphan N. Brun C. Colliex A. Loiseau H. Pascard 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):147-157
Various filled carbon nanotubes have recently been successfully produced by the arc-discharge method by doping a 99.4% graphite
anode with a transition metal like Cr, Ni, a rare earth like Yb, Dy, or a covalent element like S, Ge. In this work, the structural
characteristics of these encapsulated nanowires were studied by High Resolution Transmission Electron Microscopy and their
chemical composition was investigated using Electron Energy-Loss Spectroscopy with high spatial resolution: this analysis
mode provides elemental concentration profiles across or along the filled nanotubes. Except in the case of Ge for which only
pure Ge fillings were identified, surprising amounts of sulfur, which was present as an impurity ( 0.25%) in the graphite rods, were found within numerous filling materials. When using high purity carbon rods, no filled
nanotube was obtained. We chose the case of Cr to clearly evidence that the addition of sulfur in catalytic quantity is responsible
for the formation of filled nanotubes, including sulfur free encapsulated nanowires. A growth mechanism based on a catalytic
process involving three elements, i.e. carbon, a metal and sulfur, and taking into account the experimental results is proposed.
Received: 20 January 1998 / Received in final form and accepted: 9 April 1998 相似文献
17.
The authors’ endeavors over the last few years with respect to boron nitride (BN) nanotube metal filling are reviewed. Mo
clusters of 1–2 nm in size and FeNi Invar alloy (Fe ∼60 at. %; Ni ∼40 at. %) or Co nanorods of 20–70 nm in diameter were embedded
into BN nanotube channels via a newly developed two-stage process, in which multi-walled C nanotubes served as templates for
the BN multi-walled nanotube synthesis. During cluster filling, low-surface-tension and melting-point Mo oxide first filled
a C nanotube through the open tube ends, followed by fragmentation of this filling into discrete clusters via O2 outflow and C→BN conversion within tubular shells at high temperature. During nanorod filling, C nanotubes containing FeNi
or Co nanoparticles at the tube tips were first synthesized by plasma-assisted chemical vapor deposition on FeNi Invar alloy
or Co substrates, respectively, and, then, the nanomaterial was heated to the melting points of the corresponding metals in
a flow of B2O3 and N2 gases. During this second stage, simultaneous filling of nanotubes with a FeNi or Co melt through capillarity and chemical
modification of C tubular shells to form BN nanotubes occurred. The synthesized nanocomposites were analyzed by scanning and
high-resolution transmission electron microscopy, electron diffraction, electron-energy-loss spectroscopy and energy-dispersive
X-ray spectroscopy. The nanostructures are presumed to function as ‘nanocables’ having conducting metallic cores (FeNi, Co,
Mo) and insulating nanotubular shields (BN) with the additional benefit of excellent environmental stability.
Received: 10 October 2002 / Accepted: 25 October 2002 / Published online: 10 March 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/51-6280, E-mail: golberg.dmitri@nims.go.jp 相似文献
18.
Haiping Hong Dustin Thomas Andy Waynick Wenhua Yu Pauline Smith Walter Roy 《Journal of nanoparticle research》2010,12(2):529-535
A stable and homogeneous grease based on carbon nanotubes (CNTs, single-wall and multi-wall) in polyalphaolefin oil has been
produced without using a chemical surfactant. For example, for a 11 wt% (7 vol%) single-wall CNT (diameter 1–2 nm, length
0.5–40 μm) loading, the thermal conductivity (TC) of the grease shows a 60–70% increase compared to that for no nanotube loading.
In addition, the grease is electrically conductive, has a high dropping point, good temperature resistance, and does not react
with copper at temperatures up to 177 °C. The performance of carbon nanotube grease could be much better with the improvement
of nanotube quality and purity. A possible explanation for these results is that of a high loading of CNTs (>10 wt%), they
become associated with each other by van der Waals forces in the grease to form three-dimensional percolation networks. Time-dependent
magnetic results demonstrate that, even under the influence of a strong outside magnetic field, the TC value remains constant.
This phenomenon can be attributed to the existence of networks that makes magnetic alignment of nanotubes impossible. 相似文献
19.
A simple controllable method is reported for the coating of ZnO nanowires with Ag nanoparticles and ZnO/carbon nanotubes (CNTs) composite. It has been achieved through DC electrophoresis AgNO3 electrolyte and CNTs in the presence of isopropanol dispersion of ZnO nanowires. In the present work, the influence of Ag nanoparticles and CNTs on the field emission properties of the composite materials is studied. The results of this research demonstrate a remarkable enhancement of field emission current of ZnO nanowires in case of CNTs mixture and Ag nanoparticles coating. 相似文献
20.
采用乙酰丙酮铜为原料, 通过化学气相沉积大批量制备出Cu/C核/壳纳米颗粒和纳米线. 研究结果表明, 通过控制沉积温度可对Cu/C核/壳纳米材料的形貌和结构进行很好的控制. 比如, 沉积温度为400 ℃时可获得直径约200 nm的Cu/C核/壳纳米线, 沉积温度为450 ℃ 时可获得直径约200 nm的Cu/C核/壳纳米颗粒和纳米棒的混合产物, 沉积温度为600 ℃时可获得直径约22 nm的Cu/C核/壳纳米颗粒. 获得的Cu/C核/壳纳米结构是由一个新颖的凝聚机理形成的, 而这种机理不同于著名的溶解-析出机理. 紫外-可见光谱和荧光光谱分析结果表明: Cu/C核/壳纳米线和纳米颗粒均在225 nm处出现Cu的吸收峰, 同时在620 和616 nm处分别出现了纳米线和纳米颗粒的表面等离子共振吸收峰. Cu/C核/壳纳米线在312 和348 nm处、 Cu/C核/壳纳米颗粒在304 和345 nm处出现荧光发射谱峰.
关键词:
Cu/C核/壳结构
纳米线
纳米颗粒
光学性能 相似文献