排序方式: 共有147条查询结果,搜索用时 245 毫秒
1.
M. Olivares-Marín C. Fernández-González V. Gómez-Serrano 《Applied Surface Science》2006,252(17):5980-5983
Using cherry stones, the preparation of activated carbon has been undertaken in the present study by chemical activation with potassium hydroxide. A series of KOH-activated products was prepared by varying the carbonisation temperature in the 400-900 °C range. Such products were characterised texturally by gas adsorption (N2, −196 °C), mercury porosimetry, and helium and mercury density measurements. FT-IR spectroscopy was also applied. The carbons prepared as a rule are microporous and macroporous solids. The degree of development of surface area and porosity increases with increasing carbonisation temperature. For the carbon heated at 900 °C the specific surface area (BET) is 1624 m2 g−1, the micropore volume is 0.67 cm3 g−1, the mesopore volume is 0.28 cm3 g−1, and the macropore volume is 1.84 cm3 g−1. 相似文献
2.
Manuel María Mahamud 《Applied Surface Science》2007,253(14):6019-6031
In this paper two series of active carbons obtained at different flow rates of the activating agent, CO2, are characterized in order to establish the different mechanisms of pore development during the activation step. This study complements previous works on textural development during the different steps in the process of obtaining active carbons: coal oxidation, coal pyrolysis and char gasification. As the characteristics of the original and intermediate materials are of capital importance in the pore development of active carbons, the properties of the active carbons, precursor chars and coals were considered and analyzed together. Mercury porosimetry and helium picnometry were used to determine classical textural parameters as well as to perform a more detailed study of the pore volume generation during the different conditions of the activation step. Data obtained from the mercury porosimetry determinations was also employed for fractal determinations according to the methodologies proposed by Friesen and Mikula, Zhang and Li and the procedure of Neimark. Average surface fractal dimensions as well as fractal profiles and local surface fractal dimensions were calculated. The use of different flow rates during the activation step produces changes not only in the ordinary textural parameters but also in the fractal characteristics of the active carbons. Activation at higher flow rates leads to smoother fractal profiles and also to lower values of the average surface fractal dimensions of the active carbons. 相似文献
3.
I. Heller S. Chatoor J. Mnnik M. A. G. Zevenbergen C. Dekker S. G. Lemay 《固体物理学:研究快报》2009,3(6):190-192
We present an experimental and theoretical comparison of the weak and strong gate‐coupling regimes that arise for carbon nanotube (CNT) and graphene field‐effect transistors (FETs) in back‐gated and liquid‐gated configuration, respectively. We find that whereas the back‐gate efficiency is suppressed for a liquid‐gated CNT FET, the back gate is still effective in case of a liquid‐gated graphene FET. We calculate the gate‐induced Fermi‐level shifts and induced charge densities. In both strong and weak coupling regimes, nonlinearities occur in the gate dependence of these parameters, which can significantly influence the electronic transport. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
J. Barzola-Quiquia R. Höhne M. Rothermel A. Setzer P. Esquinazi V. Heera 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):127-130
In this work we have investigated the changes of the magnetic
properties of highly oriented pyrolytic graphite samples after
irradiation either with ~3×1014 protons or 3.5×1013 ... 3.5×1014 iron ions with energies in
the MeV range. Our results show that iron and proton irradiations can
produce similar paramagnetic contributions depending on the
implantation temperature. However, only protons induce a
ferromagnetic effect. 相似文献
5.
A. Ganchev 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):173-175
The invertible objects in a tensor category form a subcategory the Grothendieck ring of which is the group ring of an abelian
group. This abelian fusion ring acts on the objects of the initial category and one can in principle determine all 6j-symbols that contain the lable of an invertible object.
Received 1st October 2001 / Received in final form 12 April 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: ganchev@inrne.bas.bg 相似文献
6.
A. Vollkopf O. Rudow M. Müller-Wiegand G. Georgiev E. Oesterschulze 《Applied Physics A: Materials Science & Processing》2003,76(6):923-926
The thermal oxidation of structured silicon surfaces was successfully used to reproducibly define apertures of approximately
100 nm in silicon dioxide tips at reduced oxidation temperatures. In this paper we theoretically investigate the oxidation
process in more detail, describing the rheological behavior of silicon dioxide as a Maxwell fluid with non-linear viscosity.
For this purpose numerical calculations of the oxidation process of trench-like silicon structures were performed. Contrary
to former assumptions, our theoretical results indicate that oxide-growth retardation is more effective at raised oxidation
temperatures. This is experimentally confirmed in the case of trench structures. The more pronounced oxide retardation at
elevated temperatures is exploited to obtain apertures in silicon dioxide tips of 60 nm for oxidation temperatures of 1100 °C.
Received: 8 April 2002 / Accepted: 11 April 2002 / Published online: 4 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-561/804-4136, E-mail: oester@physik.uni-kassel.de 相似文献
7.
Field emitters of vertical carbon fibers on a silicon substrate are fabricated by catalytic chemical vapor deposition. After an ageing process of 150 min, field emission measurement of the fibers is carried out in a vacuum chamber with a base pressure of 5.0 × 10−4 Pa. The experimental results display that field emission performance of the carbon fibers depends strongly on the vacuum level during the experiments. After the field emission measurement, damage to the carbon fiber field emitters is observed from the scanning electron microscopic images. 相似文献
8.
Ion scattering spectrometry (ISS) with time of flight (TOF) analysis is employed to measure the ion fraction of positively charged hydrogen (H+) projectiles scattered from a well characterized highly oriented pyrolitc graphite (HOPG) surface at a 45° scattering angle, various ingoing/outgoing angles and two different incoming energies (4 and 5 keV). In the theoretical approach, the negative ionization probability is calculated by employing a Green's function formalism to solve the dynamic collisional process. Both theoretical and experimental results are analyzed and contrasted. The theoretical negative ion fraction evolution during the collisional process is described in detail. 相似文献
9.
Indium-tin oxide (ITO) films deposited on heated and non-heated glass substrates by a pulsed Nd:YAG laser at 355 nm and ∼2.5 J/cm2 were used in the fabrication of simple organic light-emitting diodes (OLEDs), ITO/(PVK + Alq3 + TPD)/Al. The ITO was deposited on heated glass substrates which possessed resistivity as low as ∼3 × 10−4 Ω cm, optical transmission as high as ∼92% and carrier concentration of about ∼5 × 1020 cm−3, were comparable to the commercial ITO. Substrate heating transformed the ITO microstructure from amorphous to polycrystalline, as revealed by the XRD spectrum. While the polycrystalline ITO produced higher OLED brightness, it was still lower than that on the commercial ITO due to surface roughness. A DLC layer of ∼1.5 nm deposited on this ITO at laser fluence of >12.5 J/cm2 improved its device brightness by suppressing the surface roughness effect. 相似文献
10.
Effects of Radius and Orientation of Single-Walled Carbon Nanotubes on Their Nonlinear Tensile Deformation Behaviour 下载免费PDF全文
By capturing the atomic information and reflecting the behaviour governed by a nonlinear potential function, an analytical molecular mechanics approach is applied to establish the constitutive relation for single-walled carbon nanotubes (SWCNTs). The nonlinear tensile deformation curves of zigzag and armchair nanotubes with different radii are predicted, and the elastic properties of these SWCNTs are obtained. A conclusion is made that the nanotube radius has little effect on the mechanical behaviour of SWCNTs subject to simple tension, while the nanotube orientation has larger influence. 相似文献