共查询到20条相似文献,搜索用时 46 毫秒
1.
S. I. Ashitkov M. B. Agranat G. I. Kanel’ P. S. Komarov V. E. Fortov 《JETP Letters》2010,92(8):516-520
The dynamics of the motion of the free surface of micron and submicron films under the action of a compression pulse excited
in the process of femtosecond laser heating of the surface layer of a target has been investigated by femtosecond interferometric
microscopy. The relation between the velocity of the shock wave and the particle velocity behind its front indicates the shock
compression to 9–13 GPa is elastic in this duration range. This is also confirmed by the small (≤1 ps) time of an increase
in the parameters in the shock wave. Shear stresses reached in this process are close to their estimated ultimate values for
aluminum. The spall strength determined at a strain rate of 109 s−1 and a spall thickness of 250–300 nm is larger than half the ultimate strength of aluminum. 相似文献
2.
V. P. Rotshtein Yu. F. Ivanov A. B. Markov D. I. Proskurovskii K. V. Oskomov V. V. Uglov S. N. Dub Y. Pauleau I. A. Shulepov 《Russian Physics Journal》2005,48(12):1221-1228
The surface topography, chemical composition, microstructure, nanohardness, and tribological characteristics of a Cu (film,
512 nm)-stainless steel 316 (substrate) system subjected to pulsed melting by a low-energy (20–30 keV), high-current electron
beam (2–3 μs, 2–10 J/cm2) were investigated. The film was deposited by sputtering a Cu target in the plasma of a microwave discharge in argon. To
prevent local exfoliation of the film due to cratering, the substrate was multiply pre-irradiated with 8–10 J/cm2. On single irradiation, the bulk of the film survived, and a diffusion layer containing the film and substrate components
was formed at the interface. The thickness of this layer was 120–170 nm irrespective of the energy density. The diffusion
layer consisted of subgrains of γ-Fe solid solution and nanosized particles of copper. In the surface layer of thickness 0.5–1 μm, which included the copper
film quenched from melt and the diffusion layer, the nanohardness and the wear resistance nonmonotonicly varied with energy
density, reaching, respectively, a maximum and a minimum in the range 4.3–6.3 J/cm2. As the number of pulsed melting cycles was increased to five in the same energy density range, there occurred mixing of
the film-substrate system and a surface layer of thickness ∼2 μm was formed which contained ∼20 at. % copper. Displacement
of the excess copper during crystallization resulted in the formation of two-phase nanocrystal interlayers separating the
γ-phase grains.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 6–13, December, 2005. 相似文献
3.
T. A. Alekhova V. Ya. Shklover N. A. Zagustina N. V. Shvyndina A. D. Plotnikov A. L. Vasil’ev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(5):747-753
The surfaces of AMg6 (aluminum-magnesium) alloy samples that have passed accelerated biocorrosion tests have been investigated
in a Quanta-3D scanning electron microscope. The alloy samples have been treated with the Ulocladium botrytis Preuss fungus, which is an active destructive fungus and was previously extracted on surfaces of the International Space Station.
Biocorrosion pits 2–10 μm in diameter, cavities the depths of which can reach 70–250 μm depth, and spots of modified color
are found to be the most typical defects. The surfaces of large cavities consist of faceted cubic particles that are formed
when the acid products of fungus metabolism interact with the alloy surface. The particles have an average size of 30 μm,
which is close to the size of alloy grains. The microstructure of a biocorrosion layer has been investigated in a Quanta-3D
microscope with the use of a focused Ga+ ion beam. The samples of 12-μm-wide transverse slices are obtained near large cavities and investigated in a Tecnai G230ST transmission electron microscope. The X-ray microanalysis of the defective layer has revealed the high concentration of
oxygen in this layer. Obtained images indicate that the corrosion cavity surface has a complex porous structure. 相似文献
4.
A.A. Lyalin A.V. Simakin G.A. Shafeev E.N. Loubnin 《Applied Physics A: Materials Science & Processing》1999,68(3):373-376
6 H5CH3, C6H6, and C6H5CH(CH3)2) to pulsed visible laser radiation of a copper vapor laser (λ=510.6 nm). The X-ray Auger electron spectroscopy (XAES), reflection
high energy electron diffraction (RHEED), and Raman analysis are employed to characterize the deposited films. The sp3 fraction in deposited films amounts to 60–70% and depends on the precursor. The average film thickness on a glass substrate
is about 100 nm. The films show excellent adherence, are transparent in the visible and have microhardness of 50–70 GPa, as
measured by nanoindentor.
Received: 28 September 1998 / Accepted: 13 January 1999 相似文献
5.
A. S. Komolov S. A. Komolov E. F. Lazneva A. A. Gavrikov P. S. Repin 《Technical Physics》2012,57(2):256-261
The modification of the electronic structure during adsorption of ultrathin copper phthalocyanine (CuPc) and 3, 4, 9, 10 perylene-tetracarboxylic-dianhydride
(PTCDA) coatings on the surface of polycrystalline tin dioxide is traced. Auger electron spectroscopy is employed to find
changes in the atomic composition of the surface. It is found with the help of low-energy electron total current spectroscopy
using a testing beam of electrons with energies up to 30 eV that the total current spectra typical of organic films are formed
when the thickness of the coating being deposited is 2–7 nm. The formation of an interface layer 1.5–2.0 nm in thickness is
detected, in which the intensity of the structure of the total current spectra decreases and the effect of interaction of
PTCDA molecules with the SnO2 surface is manifested. 相似文献
6.
The Hugoniot elastic limit and the spall strength of aluminum and copper samples pressed from a mixture of a metallic powder and 2–5 wt % C60 fullerene powder are measured under a shock loading pressure up to 6 GPa and a strain rate of 105 s?1 by recording and analyzing full wave profiles using a VISAR laser interferometer. It is shown that a 5% C60 fullerene addition to an initial aluminum sample leads to an increase in its Hugoniot elastic limit by an order of magnitude. Mixture copper samples with 2% fullerene also exhibit a multiple increase in the elastic limit as compared to commercial-grade copper. The elastic limits calculated from the wave profiles are 0.82–1.56 GPa for aluminum samples and 1.35–3.46 GPa for copper samples depending on the sample porosity. The spall strength of both aluminum and copper samples with fullerene additions decreases approximately threefold because of the effect of high-hardness fullerene particles, which serve as tensile stress concentrators in a material under dynamic fracture. 相似文献
7.
Subthreshold photoemission from copper nanoclusters formed on the SiO2 surface has been observed under irradiation of the surface by photons in the 3.1–6.5-eV energy range. The average size of
copper nanoclusters on the silicon oxide surface is 250–500 nm. Besides the conventional photoemission from the filled Shockley
surface state (SS), strong photoemission has been recorded at incident photon energies of 0.5 eV below the work function of
the copper surface. This emission is assumed to be generated in direct electron transitions from the SS state to the unfilled
electron surface states formed by the Coulomb image potential, followed by escape from these states into vacuum. 相似文献
8.
G. A. Oganesyan I. I. Novak 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(6):962-965
The electrical properties of thermal donors formed in the bulk and near-surface regions in silicon samples with (3–9) × 1017 cm−3 oxygen concentrations under elastic tensile stress σ of about 1 GPa have been studied. The original method allowing us to
control an introduced elastic tensile stress during the thermal donor’s formation at T = 450°C by a double-crystal X-ray diffractometer has been used. The formation of thermal donors in silicon with a high oxygen
concentration of 9.3 × 1017 cm−3 under tensile stress has been found to be less effective than in silicon with a low oxygen concentration of (3–5) × 1017 cm−3. Single-charged donors are formed in silicon with a low oxygen concentration under tensile stress while double-charged donors
are formed in silicon with a high oxygen concentration. 相似文献
9.
10.
V. K. Voronkova R. T. Galeev L. V. Mingalieva G. Novitchi 《Applied magnetic resonance》2008,33(1-2):73-84
For the first time the exchange interaction between copper and non-Kramers Tb3+ ions was studied by means of electron paramagnetic resonance (EPR). Features of the manifestation of this interaction in
the EPR spectra of dimer fragments Cu–Tb and pentanuclear fragments Cu–Tb–Cu–Tb–Cu are analyzed. The possibility to determine
the sign and value of this interaction from EPR spectra for the case when the lowest states of Tb3+ are the states |0〉, | ± 1〉 is shown. The exchange interaction between copper and trivalent terbium ions in the studied pentanuclear
complex is ferromagnetic.
Authors' address: Violeta K. Voronkova, Kazan Physical-Technical Institute, Russian Academy of Sciences, Sibirsky trakt 10/7,
Kazan 420029, Russian Federation 相似文献
11.
V. V. Uglov N. T. Kvasov Yu. A. Petukhov R. S. Kudaktin N. N. Koval’ Yu. F. Ivanov A. D. Teresov V. M. Astashinskii A. M. Kuz’mitskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(2):296-302
Structural phase changes in a titanium-silicon system treated by low-energy high-current electron beams (HCEBs) and compression
plasma flows (CPFs) with the duration 100 μs and the energy density 12–15 J/cm2 are studied. Scanning electron microscopy, X-ray diffraction and electron microprobe analysis are used in this work. The
formation of a titanium-doped silicon layer 10–25 μm thick, titanium silicides (TiSi2 under HCEBs and Ti5Si3 under CPF treatment), silicon dendrites, and needle-like eutectics (typical size of precipitates is about 50 nm) is revealed.
It is shown via the results of numerical simulation that the thickness of the metal-doped layer is mainly controlled by the
power density value and the surface nonuniformity of the heat flow over the target surface. The thermodynamic regularities
of phase formation are discussed, taking into account heat transfer between the silicide nuclei and solid silicon. 相似文献
12.
V. D. Glukhodedov S. I. Kirshanov T. S. Lebedeva M. A. Mochalov 《Journal of Experimental and Theoretical Physics》1999,89(2):292-298
The following quantities of shock-compressed liquid krypton are measured behind a plane shock front at pressures up to 90
GPa: compressibility up to densities of 7 g/cm3, brightness (color) temperatures of 6000–24000 K, and electrical conductivities of 40–60000 (Ω·m)−1. X-t diagram methods are used to estimate sound speeds of up to 5.5 km/s at pressures of 30–75 GPa. The optical absorption coefficients
in the violet and red (30–300 cm−1) are measured at pressures of 20–90 GPa from the rise in brightness of the shock front luminosity. The optical reflection
coefficient of the shock front (∼13%) at a pressure of 76.1 GPa is measured for the first time.
Zh. éksp. Teor. Fiz. 116, 551–562 (August 1999) 相似文献
13.
The method of nitriding of metals in an electron beam plasma is used to change the current density and energy of nitrogen
ions by varying the electron beam parameters (5–20 A, 60–500 eV). An electron beam is generated by an electron source based
on a self-heated hollow cathode discharge. Stainless steel 12Kh18N10T is saturated by nitrogen at 500°C for 1 h. The microhardness
is measured on transverse polished sections to obtain the dependences of the nitrided layer thickness on the ion current density
(1.6–6.2 mA/cm2), the ion energy (100–300 eV), and the nitrogen-argon mixture pressure (1–10 Pa). The layer thickness decreases by 4–5 μm
when the ion energy increases by 100 V and increases from 19 to 33 μm when the ion current density increases. The pressure
dependence of the layer thickness has a maximum. These results are in conflict with the conclusions of the theory of the limitation
of the layer thickness by ion sputtering, and the effective diffusion coefficient significantly exceeds the well-known reported
data. 相似文献
14.
Filler-matrix thermal boundary resistance of diamond-copper composite with high thermal conductivity 总被引:1,自引:0,他引:1
A composite material with a high thermal conductivity is obtained by capillary infiltration of copper into a bed of diamond
particles of 400 μm size, the particles having been pre-coated with tungsten. The measured thermal conductivity of the composite
decreases from 910 to 480 W m−1 K−1 when the coating thickness is increased from 110 to 470 nm. Calculations of the filler/matrix thermal boundary resistance
R and the thermal conductivity of the coating layer λ
i
using differential effective medium, Lichtenecker’s and Hashin’s models give similar numerical values of R and λ
i
≈ 1.5 W m−1 K−1. The minimal thickness of the coating h ∼ 100 nm necessary for ensuring production of a composite while maximizing its thermal conductivity, is of the same order
as the free path of the heat carriers in diamond (phonons) and in copper (electrons). The heat conductance of the diamond/tungsten
carbide coating/copper interface when h is of this thickness is estimated as (0.8–1) × 108 W m−2 K−1 and is at the upper level of values characteristic for perfect dielectric/metal boundaries. 相似文献
15.
E. F. Dudarev A. B. Markov G. P. Bakach A. N. Tabachenko S. D. Polevin N. V. Girsova O. A. Kashin M. F. Zhorovkov V. P. Rotshtein 《Russian Physics Journal》2009,52(3):239-244
Experimental data are presented on the fracture mechanism and plastic deformation and thickness of the spalled layer obtained
on irradiation of targets made from coarse- and fine-grained fcc metals (copper and aluminum) by a nanosecond high-current
relativistic beam. The general and special features inherent in the modification of the microstructure of the spalled layer
and near the surface of the spall fracture are discussed for the coarse- and fine-grained materials of the targets. Possible
reasons for the varying extent to which the characteristics of the spall fracture of the copper and aluminum targets are affected
by the grain size are suggested.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 20–24, March, 2009. 相似文献
16.
Ceria supported copper catalysts were synthesized by laser vaporization and controlled condensation method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX) and temperature programmed reduction (TPR). The catalytic activity of the nanopowders for CO oxidation reaction was tested in a fixed bed flow tube reactor in Ar–20%O2–4%CO mixture. Irrespective of the copper content, the catalytic activity of the nanopowders is similar in the initial CO test, and the catalytic activity improves (i.e. the light-off temperature decreases) during a subsequent run. The lowest light-off temperature during the second run is recorded in the material with 20% copper. TEM studies on 20%Cu–CeO2 sample in the as-prepared condition and after CO test exhibit two types of ceria particles namely, polygonal particles 3–5 nm in size and spherical particles of 15–20 nm in size. Rapid cooling of the nanoparticles formed during the laser ablation results in incorporation of a large amount of copper within the ceria as solid solution. Presence of solid solution of copper is confirmed by EDAX and electron diffraction analyses. In addition, copper-rich surface layer of Cu2O is found over the spherical particles. The cerium oxide components are essentially identical before and after CO test, except that the polygonal CeO2 particles contain newly formed fine crystals of CuO. TPR results reveal two reduction peaks, which further supports, the presence of two different copper species in the material. The shift in light-off temperature during the second run is attributed to the synergistic interaction between newly formed CuO crystals with the CeO2 matrix. 相似文献
17.
A. D. Korotaev D. P. Borisov V. Yu. Moshkov S. V. Ovchinnikov K. V. Oskomov Yu. P. Pinzhin V. M. Savostikov A. N. Tymentsev 《Russian Physics Journal》2007,50(10):969-979
Electron microscopy, x-ray diffraction analysis, and micro-and nanohardness measurements were used to investigate the interrelations
between the fine structure and the variations in strength properties of nanostructured and nanocomposite Ti-Si-B-N coatings with high oxygen and carbon contents. It has been shown that under the conditions of low-temperature (T = 200°C)
coating deposition, a two-level grain structure forms with {200} texture and grains 0.1–0.3 μm in size fragmented into subgrains
15–20 nm in size. As the silicon content is increased, textureless coatings with the crystal phase grain size less than 15
nm and high amorphous component or coatings of amorphous-crystalline structure are produced. At coating deposition temperatures
of 400–450°C, a nanocomposite structure with a grain size d = 10–15 nm and no texture is observed. For all test compositions
and conditions of coating production, a Ti
1−x
Si
x
N crystal phase with the lattice parameter a = (0.416–0.420) ± 0.001 nm has been detected. For optimum coating compositions
and synthesis conditions, the hardness is over 40–50 GPa. It has been supposed that superhardness can be attained with multiphase
grain-boundary interlayers of thickness more than 1 nm.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 13–23, October, 2007. 相似文献
18.
A. G. Rousskikh A. V. Shishlov A. S. Zhigalin V. I. Oreshkin S. A. Chaikovsky R. B. Baksht 《Technical Physics》2010,55(11):1619-1627
The results of the experiments on the formation of a plasma emitter with small spatial dimensions for pulsed radiography in
the soft X-ray spectral range are presented. Emitting hot plasma was formed as a result of compression of the plasma jet by
a current pulse with amplitude I
m
= 215 kA and rise time T
fr = 200 ns. For the jet formation, we used a plasma gun based on the arc discharge (I
m
= 8.5 kA and T
fr = 6 μs) initiated by breakdown over the surface of a dielectric in vacuum. The experiments were carried out with aluminum,
tin, copper, and iron plasma jets. A single emitter, i.e., point Z-pinch (PZ-pinch), was formed when an interelectrode gap of a high current generator of 1.3–1.5 mm was used. The smallest spatial dimensions
of the emitting region were obtained with the use of aluminum and tin. For a tin jet, the diameter of the emitting region
was 7 ± 2 μm and its height was 17 ± 2 μm. The emission pulse duration at half-height was 2–3 ns. The total emission yield
per pulse in the spectral range 1.56–1.90 keV was 30–50 mJ for the aluminum pinch and 10–30 mJ for the tin pinch. The developed
method makes it possible to carry out radiographic examination of microobjects (including biological ones) 1–1000 μm in thickness,
with spatial (10–20 μm) and time (2–3 ns) resolution. 相似文献
19.
G. G. Zakharova E. G. Astafurova M. S. Tukeeva E. V. Naidenkin G. I. Raab S. V. Dobatkin 《Russian Physics Journal》2011,54(4):416-422
Using the method of equal-channel angular pressing (ECAP), submicrocrystalline structure is formed in lowcarbon Fe–Mn–V–Ti–C
steel with the average grain size 260 nm in the ferrite-perlite state and 310 nm in the martensitic state. It is established
that the ECAP treatment gives rise to improved mechanical properties (Hμ = 2.9 GPa, σ0 = 990 MPa in the ferrite-perlite and Hμ = 3.7 GPa, σ0 = 1125 MPa in martensitic states), decreased plasticity, and results in plastic flow localization under tensile loading.
The high strength properties formed by the ECAP are shown to sustain up to the annealing temperature 500°C. 相似文献
20.
Organic–inorganic composite microspheres with PS as a core and CeO2 as a shell were synthesized by in situ chemical precipitation method. The size of PS core was 117, 163, 206, and 241 nm,
respectively, and the shell thickness was about 10 nm. The CeO2 shell was composed of a large number of nanoparticles, of which the size was 4–6 nm. Atomic force microscopy was employed
to probe the mechanical properties of core–shell structured ceria-coated polystyrene (PS/CeO2) composite microspheres. On the basis of Hertz’s theory of contact mechanics, compressive moduli were measured by the analysis
of force–displacement curves captured on the microsphere samples. For a fixed CeO2 shell thickness, the Young’s modulus of composite microspheres increased with an increase of PS core size. The calculated
Young’s moduli (E) values of composites for 136, 185, 242, and 261 nm in diameter were 5.78 ± 0.9, 7.23 ± 1.3, 11.46 ± 1.7, and 14.54 ± 1.4 GPa,
respectively. The results revealed the effect of the CeO2 shell on the elastic deformation of the PS core. This approach will provide fundamental insights into the actual role of
organic/inorganic core/shell composite abrasives in chemical mechanical polishing. 相似文献