共查询到20条相似文献,搜索用时 0 毫秒
1.
A. S. Shulakov A. P. Braiko S. V. Bukin V. E. Drozd 《Physics of the Solid State》2004,46(10):1935-1939
The phase chemical composition of an Al2O3/Si interface formed upon molecular deposition of a 100-nm-thick Al2O3 layer on the Si(100) (c-Si) surface is investigated by depth-resolved ultrasoft x-ray emission spectroscopy. Analysis is performed using Al and Si L2, 3 emission bands. It is found that the thickness of the interface separating the c-Si substrate and the Al2O3 layer is approximately equal to 60 nm and the interface has a complex structure. The upper layer of the interface contains Al2O3 molecules and Al atoms, whose coordination is characteristic of metallic aluminum (most likely, these atoms form sufficiently large-sized Al clusters). The shape of the Si bands indicates that the interface layer (no more than 10-nm thick) adjacent to the substrate involves Si atoms in an unusual chemical state. This state is not typical of amorphous Si, c-Si, SiO2, or SiOx (it is assumed that these Si atoms form small-sized Si clusters). It is revealed that SiO2 is contained in the vicinity of the substrate. The properties of thicker coatings are similar to those of the 100-nm-thick Al2O3 layer and differ significantly from the properties of the interfaces of Al2O3 thin layers. 相似文献
2.
Takashi Iwata Taketoshi Matsumoto Sumio Terakawa Hikaru Kobayashi 《Central European Journal of Physics》2010,8(6):1015-1020
A thick Al2O3/aluminum (Al) structure has been fabricated by oxidation of Al with 68wt% and 98wt% nitric acid (HNO3) aqueous solutions at room temperature. Measurements of the Al2O3 thickness vs. the oxidation time show that reaction and diffusion are the rate-determining steps for oxidation with 68wt%
and 98wt% HNO3 solutions, respectively. Observation of transmission electron micrographs shows that the Al2O3 layer formed with 68wt% HNO3 has a structure with cylindrically shaped pores vertically aligned from the Al2O3 surface to the Al2O3/Al interface. Due to the porous structure, diffusion of HNO3 proceeds easily, resulting in the reaction-limited oxidation mechanism. In this case, the Al2O3/Al structure is considerably rough. The Al2O3 layer formed with 98wt% HNO3 solutions, on the other hand, possesses a denser structure without pores, and the Al2O3/Al interface is much smoother, but the thickness of the Al2O3 layer formed on crystalline Al regions is much smaller than that on amorphous Al regions. Due to the relatively uniform Al2O3 thickness, the leakage current density flowing through the Al2O3 layer formed with 68wt% HNO3 is lower than that formed with 98wt% HNO3. 相似文献
3.
B. S. Seplyarskii G. B. Brauer A. G. Tarasov 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(4):641-647
The results of experiments on the combustion of a powdery Fe2O3-Al-Al2O3 mixture in an argon flow are reported. The process of combustion is perturbed by a pressure drop across the batch created
by evacuating one of the end faces of the reaction cell. The effects of gasifiable additives (borax and soda) and a pressure
drop on the combustion characteristics are studied. The results obtained are interpreted within the framework of the convection-conduction
theory of combustion of heterogeneous condensed systems. 相似文献
4.
T. Yu. Kiseleva A. O. Polyakov A. A. Novakova N. N. Sysoev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(5):924-929
The structural transformations at different stages of the preparation of oxide FeAl/Al2O3 nanocomposite by mechanosynthesis with the use of a preliminarily activated FeAl precursor are studied by means of transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy. 相似文献
5.
A. Akbari Tochaei H. Arabshahi M. R. Benam A. Vatan-Khahan M. Abedininia 《Journal of Experimental and Theoretical Physics》2016,122(5):869-873
The discrete breathers in graphane in thermodynamic equilibrium in the temperature range 50–600 K are studied by molecular dynamics simulation. A discrete breather is a hydrogen atom vibrating along the normal to a sheet of graphane at a high amplitude. As was found earlier, the lifetime of a discrete breather at zero temperature corresponds to several tens of thousands of vibrations. The effect of temperature on the decay time of discrete breathers and the probability of their detachment from a sheet of graphane are studied in this work. It is shown that closely spaced breathers can exchange energy with each other at zero temperature. The data obtained suggest that thermally activated discrete breathers can be involved in the dehydrogenation of graphane, which is important for hydrogen energetics. 相似文献
6.
Thermal hysteresis in a simulated Al2O3 system has been
investigated using a Molecular Dynamics (MD) method. Simulations were done
in the basic cube under periodic boundary conditions containing 3000 ions
with Born-Mayer type pair potentials. The system was cooled down from 7000 K
to 0 K and heated up from 0 K to 7000 K by the same cooling/heating rate of
1.7178×1014 K/s. The temperature dependence of the system density
upon cooling and heating shows thermal hysteresis. The differences between
structure and dynamics of the models obtained by cooling (MOBC) and heating
(MOBH) at three different temperatures of 2100 K, 3500 K and 5600 K have been
detected. Calculations show that the differences in the dynamics of the
systems are more pronounced than those in the structure. Furthermore,
dynamical heterogeneities in MOBC and MOBH at the temperature of 2100 K have
been studied through a non-Gaussian parameter and comparison of partial
radial distribution functions (PRDFs) for the 10% most mobile or immobile
particles with their corresponding mean ones. Cluster size distributions of
the 10% most mobile or immobile particles in MOBC and MOBH at the
temperature of 2100 K have been obtained. Calculations show that differences
in dynamical heterogeneities are pronounced. 相似文献
7.
Samples of oriented aerogel based on aluminum oxide are studied by the electron paramagnetic resonance (EPR) technique under steady-state and pulse conditions. At least two types of paramagnetic centers interacting with Al nuclei on the surface of aerogel are revealed. Their spectra are characterized by the presence or absence of superhyperfine structure in the EPR spectra, respectively. The X-ray irradiation at room temperature gives rise to the formation of additional long-lived paramagnetic centers of the second kind. Their characteristic decay times for the “fast” and “slow” processes are determined. The interaction of induced paramagnetic centers with protons located on the surface of aerogel is revealed. 相似文献
8.
Al<Subscript>2</Subscript>O<Subscript>3</Subscript> plasma production during pulsed laser deposition
F. Caridi L. Torrisi A. M. Mezzasalma G. Mondio A. Borrielli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):467-472
A Nd:YAG laser operating in second harmonic (532 nm), 3 ns pulse duration, 150 mJ pulse energy, and 10 Hz repetition rate,
is employed to irradiate Al2O3 target placed in high vacuum. The produced plasma is investigated by an ion collector used in time-of-flight configuration
and by a mass quadrupole spectrometer, in order to determine the equivalent plasma temperature and the atomic and molecular
composition. Pulsed laser deposition technique has been used to produce thin films on different substrates placed close to
the target. Different surface analyses, such as energy dispersive X-ray fluorescence (EDXRF), X-ray photoelectron spectroscopy
(XPS) and surface profilometry are employed to characterize the produced films. Measurements of ablation yield, plasma equivalent
temperature, acceleration voltage and characterization of grown thin films are presented and discussed. 相似文献
9.
S. V. Gorbunov A. F. Zatsepin V. A. Pustovarov S. O. Cholakh V. Yu. Yakovlev 《Physics of the Solid State》2005,47(4):733-737
A time-resolved cathodo-and photoluminescence study of nanostructural modifications of Al2O3 (powders and ceramics) excited by heavy-current electron beams, as well as by pulsed synchrotron radiation, is reported. It was found that Al2O3 nanopowders probed before and after Fe+ ion irradiation have the same phase composition (the γ-phase/δ-phase ratio is equal to 1), an average grain size equal to ~17 nm, and practically the same set of broad cathodoluminescence (CL) bands peaking at 2.4, 3.2, and 3.8 eV. It was established that Al2O3 nanopowders exhibit fast photoluminescence (PL) (a band at 3.2 eV), whose decay kinetics is described by two exponential stages (τ1 = 0.5 ns, τ2 = 5.5 ns). Three bands, at 5.24, 6.13, and 7.44 eV, were isolated in the excitation spectrum of the fast PL. Two alternate models of PL centers were considered, according to which the 3.2-eV luminescence either originates from radiative relaxation of the P? centers (anion-cation vacancy pairs) or is due to the formation of surface analogs of the F+ center (F S + -type centers). In addition to the fast luminescence, nano-Al2O3 was found to produce slow luminescence in the form of a broad band peaking at 3.5 eV. The excitation spectrum of the 3.5-eV luminescence obtained at T = 13 K exhibits two doublet bands with maxima at 7.8 and 8.3 eV. An analysis of the luminescent properties of nanostructural and single-crystal Al2O3 suggests that the slow luminescence of nanopowders at 3.5 eV is due to radiative annihilation of excitons localized near structural defects. 相似文献
10.
M. A. Mikhailov S. G. Mamontova S. Z. Zelentcov T. V. Demina O. Yu. Belozerova L. A. Bogdanova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2018,12(4):756-760
The joint crystallization of the stable phase (a number of solid solutions of chromium-containing beryllian indialite) and metastable phases (crystalline modifications) of the compound with β-quartz structure (Si0.64Al0.28Mg0.21Be0.09)IVO2 ~ Mg1.89Be0.81Al2.52Si5.76O18 admixed with Cr2O3 phases of khmaralite Mg1.21Cr0.01Be0.46Al1.78Si3.38O20 and spinel {(Mg0.95Be0.045Si0.005)IV(Al1.31Cr0.67Mg0.02)VI}O4 is performed using melted chromium–beryllian indialite preliminarily obtained by solid-phase synthesis as a precursor. Simultaneously, the residual X-ray amorphous melt of composition Mg1.83Cr0.01Be1.04Al2.64Si5.57O18 is hardened. Thus, a reconstructive transition from the beryllian indialite melt to a phase with the β-quartz structure is implemented, and the chemical similarity of these compounds is demonstrated. The rate of change in the crystallization isotherm of 2°С/h and increased heat outflow through the highly heat-conducting walls of the Pt–Rh crucible (taper) contribute to this process. 相似文献
11.
In this study, FeNi3/Al2O3 core-shell
nanocomposites, where individual FeNi3 nanoparticles were coated with a
thin layer of alumina, were fabricated by a modified sol-gel method. Several physical characterizations were performed on the samples of FeNi3/Al2O3 nanocomposites with different thickness of Al2O3 shell. The encapsulation of FeNi3 nanoparticles with
alumina stops FeNi3 agglomeration during heat treatment, and prevents
interaction among the closely spaced magnetic FeNi3 nanoparticles. The
Al2O3 insulating shell improves the soft magnetic properties of FeNi3. The study of the complex permeability of the samples shows that the real part μ’ of the permeability of the sample with Al molar content of 20% (Al/(Fe+Ni)) is as high as 12, and independent of frequency up to at least 1 GHz. The tunneling magnetoresistance arising from the presence of the Al2O3 shell have also been studied. 相似文献
12.
This paper reports on an atomic-force microscopy study of the surface of α-Al2O3 single crystals irradiated by Bi ions with energies of 710, 557, 269, and 151 MeV. The shape of the radiation defects produced by single ions was established to depend on the ionization energy loss. The threshold ionization density above which the surface topography is observed to change lies in the 27–35 keV/nm interval. Possible mechanisms of defect formation in the thermal-spike model, namely, a phase transition and the creation of thermoelastic stresses in the high-energy ion track, are considered. 相似文献
13.
A trilayer carbon nanotube (CNT)/Al2O3/polypropylene (PP) separator is prepared by means of simple tape casting of Al2O3 and CNT layers onto a commercial PP separator, respectively. The electrochemical performance of the trilayer separator in the lithium-sulfur batteries is compared with those of the PP and the Al2O3/PP separator. The CNT/Al2O3/PP separator exhibits the best electrochemical performance, including the cycling performance and rate capability. The CNT component in the trilayer separator acts as a matrix for capturing the polysulfide species and suppressing the migration of polysulfides to the lithium anode side and also reduces the charge transfer resistance of sulfur cathodes significantly. Meanwhile, the Al2O3 layer in the trilayer separator not only has the advantages on thermal stability and electrolyte intake but also can provide the strong shield for CNT from penetrating the separator. 相似文献
14.
V. S. Dneprovskii E. A. Zhukov V. L. Lyaskovskii M. V. Ryzhkov I. V. Tolpeikin A. I. Shatalin 《Physics of the Solid State》2004,46(9):1755-1760
Nonlinear dependence of the CdSe/Al2O3 quantum wire luminescence intensity on the photoexcitation level and an asymmetric broadening of luminescence spectra accompanied by a high-frequency shift of the maximum are observed and explained in terms of the dominant filling of exciton phase space in wires with different cross sections. 相似文献
15.
16.
W. J. Nellis 《The European physical journal. Special topics》2011,196(1):121-130
Dynamic compression has been used to synthesize liquid metallic hydrogen at 140 GPa (1.4 million bar) and experimental data
and theory predict Al2O3 might be a metallic glass at ∼ 300 GPa. The mechanism of metallization in both cases is probably a Mott-like transition.
The strength of sapphire causes shock dissipation to be split differently in the strong solid and soft fluid. Once the 4.5-eV
H-H and Al-O bonds are broken at sufficiently high pressures in liquid H2 and in sapphire (single-crystal Al2O3), electrons are delocalized, which leads to formation of energy bands in fluid H and probably in amorphous Al2O3. The high strength of sapphire causes shock dissipation to be absorbed primarily in entropy up to ∼400 GPa, which also causes
the 300-K isotherm and Hugoniot to be virtually coincident in this pressure range. Above ∼400 GPa shock dissipation must go
primarily into temperature, which is observed experimentally as a rapid increase in shock pressure above ∼400 GPa. The metallization
of glassy Al2O3, if verified, is expected to be general in strong oxide insulators. Implications for Super Earths are discussed. 相似文献
17.
A. A. Dedyukhin P. N. Krylov N. V. Kostenkov R. M. Zakirova I. V. Fedotova 《Technical Physics》2016,61(4):569-573
The ZnSe/Al2O3 nanocomposite films synthesized by laser evaporation followed by heat treatment are studied. X-ray diffraction and electron-microscopic investigations of the as-deposited films demonstrate the presence of ZnSe crystallites in an Al2O3 amorphous matrix. Annealing changes the structures of ZnSe and Al2O3, increases the ZnSe crystallite size, and causes the appearance of the ZnSeO4 phase. The presence of aluminum oxide layers decreases the phase transformation temperature of zinc selenide. 相似文献
18.
D. A. Zatsepin V. M. Cherkashenko É. Z. Kurmaev S. N. Shamin V. V. Fedorenko N. A. Skorikov S. V. Plastinin N. V. Gavrilov A. I. Medvedev S. O. Cholakh 《Physics of the Solid State》2004,46(11):2134-2138
Valence states of metal ions and the phase composition of nanocrystalline Al2O3 (of the original oxide and the oxide irradiated by high-energy Fe+ ions) are studied by using x-ray emission Al L2, 3 and O Kα spectra. It is established that the shape of the Al L2, 3 spectra strongly changes as one goes from the original (bulk) Al2O3 to nanocrystalline oxide, while the O Kα spectra remain practically unchanged. Moreover, irradiation by high-energy Fe+ ions results in slight additional changes in the x-ray spectral characteristics of the aluminum oxides under study. The obtained experimental data are compared with the results of theoretical calculations of the electronic structure of α and γ phases of Al2O3 performed using the LDA formalism. Using the results of x-ray spectral studies, electronic structure calculations, and x-ray diffraction analysis, it is shown that the revealed spectral differences between the nanocrystalline state of aluminum oxide and the bulk material can be interpreted as a phase transition from the α phase to the γ phase of Al2O3 with an addition of bayerite. 相似文献
19.
We have studied the transmission of bulk Al2O3 ceramic used as heat shields for the working chamber of a turbine. We have established that radiation scattered from such
an object has a pronounced speckle structure, while the scattering indicatrix is the same as the indicatrix for an ideal scatterer.
We show that existing highpower semiconductor laser sources make it possible to penetrate sufficiently deeply into such materials,
and the small transmission coefficient is not the limiting factor for development of optical methods for inspecting the quality
of ceramic shielding blocks.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 237–240, March–April, 2007. 相似文献
20.
V. N. Kolobanov V. V. Mikhailin N. N. Petrovnin D. A. Spasskii Yu. V. Zorenko 《Moscow University Physics Bulletin》2007,62(1):34-36
The luminescence spectra of single-crystal films and bulk crystals of yttrium-aluminum garnet Y3Al5O12 and Ce3+-activated Y3Al5O12 were investigated. It was shown that the room-temperature luminescence intensity of the Ce3+-free single-crystal Y3Al5O12 film was considerably lower than that of the bulk crystals, while the luminescence intensity of the Ce3+ ions in the Y3Al5O12:Ce films was considerably higher than that one for the corresponding bulk crystal. 相似文献