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1.
A new model of the activated recrystallization of molybdenum under the diffusion action of a nickel coating is proposed. In
the context of this model, dependences of the thickness of the recrystallized layer and of the velocity of motion of the recrystallization
front on the annealing time have been derived analytically. It has been revealed that an increase in nickel concentration
on the surface increases, whereas an increase in average size of recrystallized grains decreases the recrystallization velocity
in molybdenum. A temperature dependence of the thickness of the recrystallized molybdenum layer has also been derived.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 50–55, November, 2007. 相似文献
2.
Marina Tikhonova Yuliya Kuzminova Xiaoying Fang Weiguo Wang Rustam Kaibyshev 《哲学杂志》2013,93(36):4181-4196
The effect of processing and annealing temperatures on the grain boundary characters in the ultrafine-grained structure of a 304-type austenitic stainless steel was studied. An S304H steel was subjected to multidirectional forging (MDF) at 500–800°C to total strains of ~4, followed by annealing at 800–1,000°C for 30 min. The MDF resulted in the formation of ultrafine-grained microstructures with mean grain sizes of 0.28–0.85 μm depending on the processing temperature. The annealing behaviour of the ultrafine-grained steel was characterized by the development of continuous post-dynamic recrystallization including a rapid recovery followed by a gradual grain growth. The post-dynamically recrystallized grain size depended on both the deformation temperature and the annealing temperature. The recrystallization kinetics was reduced with an increase in the temperature of the preceding deformation. The grain growth during post-dynamic recrystallization was accompanied by an increase in the fraction of Σ3n CSL boundaries, which was defined by a relative change in the grain size, i.e. a ratio of the annealed grain size to that evolved by preceding warm working (D/D0). The fraction of Σ3n CSL boundaries sharply rose to approximately 0.5 in the range of D/D0 from 1 to 5, which can be considered as early stage of continuous post-dynamic recrystallization. Then, the rate of increase in the fraction of Σ3n CSL boundaries slowed down significantly in the range of D/D0 > 5. A fivefold increase in the grain size by annealing is a necessary condition to obtain approximately 50% Σ3n CSL boundaries in the recrystallized microstructure. 相似文献
3.
The kinetics of microstructure transformations are studied during annealing of deformed single crystals of KCl and KCl:0.05wt
%Sr2+ at temperatures of (0.35–0.55)T
m (where T
m is the melting temperature) and during storage at room temperature. The effect of deformation rates ranging from 0.01 mm/min
to 0.1 mm/min at a deformation temperature T
d=0.5T
m on the crystal structure and on the recrystallization kinetics is noted. It is found experimentally that the incubation period
for static recrystallization in single-crystal KCl:0.05wt%Sr2+ is shortened and recrystallization takes place at room temperature after deformation in this temperature range. Here, during
the new recrystallization grains have a twinned orientation with respect to the initial single crystal during the first stage
and to the subgrains of the deformed crystal. As the annealing temperature is raised, the stage in which twins grow in KCl:0.05wt%Sr2+ crystals is shortened and it is displaced by recrystallization through migration of high-angle grain boundaries of the common
type. Deformation conditions which ensure prolonged (at least three months) stability of the post-deformation hardening of
single crystals are found experimentally for Sr2+-doped deformed single crystals.
Fiz. Tverd. Tela (St. Petersburg) 41, 259–264 (February 1999) 相似文献
4.
D. A. Romanov E. A. Budovskikh V. E. Gromov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(6):1112-1117
The surface topography and structure of copper layers exposed to multiphase plasma jets of products of electrical explosion
of molybdenum and copper foils are studied using profilometry and scanning electron and light microscopy. Such treatment allows
deposition of either layered coatings or alloyed composite layers. It is found that the surface layer roughness parameter
is R
a
= 3.2−4.0 μm. The thickness of some copper and molybdenum layers of coatings is 15–20 μm. Electroexplosive alloying produces
layers 25 μm thick. Sizes of copper inclusions in the molybdenum matrix near the surface of such layers vary from 30 nm to
1–2 μm. 相似文献
5.
The electrophysical properties and structure of the nonstoichiometric high-temperature superconductor YBa2Cu3O
y
restored at T = 930–950°C after low-temperature decomposition (T = 200°C) into phases different in the oxygen content have been studied. It has been shown that, unlike heat treatments at
T ≤ 900°C, the superconducting properties are almost completely restored for 3–5 h during grain recrystallization, which is
impossible at lower temperatures. After short-term annealing at T = 930–950°C (for 1–2 h), the ceramic material still contains a significant number of structural defects, most likely, in
cation sublattices. These defects can contribute to the pinning of magnetic vortices, which substantially increases the critical
current density in magnetic fields up to 2 T as compared to ceramic materials produced by the conventional technology. 相似文献
6.
V. Ya. Shur S. A. Negashev A. L. Subbotin D. V. Pelegov E. A. Borisova E. B. Blankova S. Trolier-McKinstry 《Physics of the Solid State》1999,41(2):274-277
The recrystallization kinetics of amorphous lead zirconate-titanate films prepared by sol-gel technology are investigated
experimentally using elastic scattering of light. Sequences of elastic dependences of the scattered light intensity are recorded
directly during thermal annealing. The evolution of the morphology of the film surface during annealing is described in terms
of the variation of their fractal dimensionalities D
s. The experimental dependences D
s(t) are compared with the results of a computer simulation of the phase transition kinetics in a thin plate (film).
Fiz. Tverd. Tela (St. Petersburg) 41, 306–309 (February 1999) 相似文献
7.
Crespillo M. L. Caballero-Calero O. Joco V. Rivera A. Herrero P. Olivares J. Agulló-López F. 《Applied Physics A: Materials Science & Processing》2011,104(4):1143-1152
The thermal annealing of amorphous tracks of nanometer-size diameter generated in lithium niobate (LiNbO3) by Bromine ions at 45 MeV, i.e., in the electronic stopping regime, has been investigated by RBS/C spectrometry in the temperature
range from 250°C to 350°C. Relatively low fluences have been used (<1012 cm−2) to produce isolated tracks. However, the possible effect of track overlapping has been investigated by varying the fluence
between 3×1011 cm−2 and 1012 cm−2. The annealing process follows a two-step kinetics. In a first stage (I) the track radius decreases linearly with the annealing
time. It obeys an Arrhenius-type dependence on annealing temperature with activation energy around 1.5 eV. The second stage
(II) operates after the track radius has decreased down to around 2.5 nm and shows a much lower radial velocity. The data
for stage I appear consistent with a solid-phase epitaxial process that yields a constant recrystallization rate at the amorphous-crystalline
boundary. HRTEM has been used to monitor the existence and the size of the annealed isolated tracks in the second stage. On
the other hand, the thermal annealing of homogeneous (buried) amorphous layers has been investigated within the same temperature
range, on samples irradiated with Fluorine at 20 MeV and fluences of ∼1014 cm−2. Optical techniques are very suitable for this case and have been used to monitor the recrystallization of the layers. The
annealing process induces a displacement of the crystalline-amorphous boundary that is also linear with annealing time, and
the recrystallization rates are consistent with those measured for tracks. The comparison of these data with those previously
obtained for the heavily damaged (amorphous) layers produced by elastic nuclear collisions is summarily discussed. 相似文献
8.
B. M. Ayupov S. A. Prokhorova M. L. Kosinova Yu. M. Rumyantsev 《Optics and Spectroscopy》2012,112(2):201-205
The optical characteristics of nickel films deposited on Si(100) substrates by vacuum thermal evaporation have been studied.
The thickness and optical constants of the films are determined using monochromatic zero ellipsometry, while the inverse problems
are solved within the three-layer optical model of the samples. It is shown that thermal annealing leads to a change in the
optical constants of nickel films in the heating-temperature range of 500–900°C. Boron carbonitride layers deposited on silicon
substrates with a nickel sublayer are analyzed within multilayer optical models, which make it possible to determine the refractive
index and absorption coefficient distributions along the thickness of the synthesized Si(100)/Ni/BC
x
N
y
structure. 相似文献
9.
G. E. Abrosimova A. S. Aronin I. I. Zver’kova A. F. Gurov Yu. V. Kir’yanov 《Physics of the Solid State》1998,40(1):8-13
Radiography, differential scanning calorimetry, luminescence and high-resolution electron microscopy are used to study the
production, nanocrystalline structure, stability, and microhardness of alloys from the Ni-Mo-B system containing from 27 at.
% to 31.5 at. % Mo and 10 at. % B. All studies of these alloys indicated that annealing at 600 °C leads to the creation of
a granular phase consisting of FCC nanocrystallites with average grain sizes of 15–25 nm, depending on the chemical composition
of the alloy. Annealing these nanocrystalline samples isothermally at a temperature of 600 °C has no appreciable effect on
the grain size. Structurally, the nanocrystalline phase consists of grains of an FCC solid solution of Mo and B in Ni, dispersed
in an amorphous matrix that isolates them from one another. The lattice parameters of the FCC nanocrystallites depend on the
alloy composition and the duration of their isothermal anneal. Within this latter time, molybdenum and boron atoms diffuse
from the FCC solid-solution lattice into the surrounding amorphous matrix. The stability of the nanocrystalline structure
is determined by the thermal stability of the amorphous matrix, whose crystallization temperature increases with the isothermal
annealing time due to enrichment by boron and molybdenum. As the structure forms, the alloy becomes harder as the nanocrystalline
grains grow in size. This relation between hardness and grain size, which is opposite to the Hall-Petch law, is explained
by hardening of the amorphous matrix due to changes in its chemical composition.
Fiz. Tverd. Tela (St. Petersburg) 40, 10–16 (January 1998) 相似文献
10.
M. F. Al-Kuhaili S. M. A. Durrani I. A. Bakhtiari 《Applied Physics A: Materials Science & Processing》2010,98(3):609-615
Thin films of molybdenum oxide were deposited in vacuum by pulsed laser ablation using a xenon fluoride (351 nm) and a krypton
fluoride (248 nm) excimer lasers. The films were deposited on unheated substrates and were post-annealed in air in the temperature
range 300–500°C. The structural, morphological, chemical, and optical properties of the films were studied. As-deposited films
were found to be dark. The transparency of the films was improved with annealing in air. The films were polycrystalline with
diffraction peaks that belong to the orthorhombic phase of MoO3. The surface morphology of the films showed a layered structure. Both the grain size and surface roughness increased with
annealing temperature. The stoichiometry of the films improved upon annealing in air, with the best stoichiometry of MoO2.95 obtained for films deposited by the XeF laser and annealed at 400°C. Similarly, the best transparency, with a transmittance
exceeding 80%, was obtained with the films annealed in the temperature range 400–450°C. 相似文献
11.
The mechanism of the transport of nickel along a Si(111) surface in the presence of adsorbed cobalt atoms is established by
LEED and Auger electronic spectroscopy. The mechanism consists of diffusion of nickel atoms through the bulk and segregation
of the atoms on the surface during annealing. This mechanism of nickel transport plays the governing role at temperatures
below 700°C, where nickel transport along clean silicon surfaces is not observed. It is found that the nickel segregation
factor is what determines the lowest temperature at which nickel transport is observed on clean silicon surfaces.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 6, 423–425 (25 March 1999) 相似文献
12.
The phase transformations occurring in the Ni70Mo10B20 alloy in the course of heating above the glass transition temperature are investigated using x-ray diffraction, transmission electron microscopy, high-resolution electron microscopy, and differential scanning calorimetry. It is shown that annealing of the alloy above the glass transition temperature leads to segregation of the amorphous phase into regions enriched with and depleted in molybdenum and/or boron. An increase in the temperature or time of annealing is accompanied by primary crystallization in regions of each type. Crystallization of the regions enriched with molybdenum results in the formation of face-centered cubic crystals of a molybdenum solid solution in nickel (phase 2). Nickel boride crystallizes in the regions enriched with boron. The face-centered cubic phase (phase 1), which is similar to pure nickel, crystallizes in the regions depleted in molybdenum and boron. Nanocrystals of phase 1 are free of defects. Nanocrystals of phase 2 with larger sizes contain a great number of defects. 相似文献
13.
SrZr1−x
Y
x
O3 coatings were co-sputtered from metallic Zr–Y (84–16 at.%) and Sr targets in the presence of a reactive argon–oxygen gas
mixture. The structural and chemical features of the film have been assessed by X-ray diffraction and scanning electron microscopy.
The electrical properties have been investigated for different substrates by Complex Impedance Spectroscopy as a function
of crystalline state, temperature and atmosphere. The as-deposited coatings are amorphous and crystallise after annealing
at 673 K for 2 h under air. The stabilisation of the perovskite structure is a function of the nominal composition. The films
are dense and present a good adhesion on different substrates. Crystallisation and mechanical stresses are detected by alternating
current (AC) impedance spectroscopy. Significant ionic conductivity in the 473–823 K temperature range is evidenced in air.
Two different conduction regimes in the presence of steam are attributed to a modification of the charge carrier nature. In
spite of low conductivity values (σ ~10−6 S.cm−1 at 881 K), the activation energies are in agreement with that of Y-doped strontium zirconate ceramics (~0.7 eV in air). 相似文献
14.
Tina Nestler Kay Potzger Hartmut St?cker Barbara Abendroth Ralph Strohmeyer Robert Zierer Dirk C. Meyer 《Applied Physics A: Materials Science & Processing》2011,105(1):103-109
Electrical properties of SrTiO3 single crystal samples treated by an anisotropic surface annealing technique under reducing conditions have been investigated
in the temperature range of 35 K–300 K. Optical and atomic force microscopy show that annealing gives rise to polycrystallization
and the formation of colored dendritic structures. Carrier concentrations and mobilities determined by Hall measurements as
well as resistivities detected by van der Pauw measurements show the expected metallic behavior due to oxygen vacancy doping.
Moreover, the temperature dependent resistivities indicate a cubic-to-tetragonal phase transition, which to our knowledge
has not been reported before. Additionally, the transition occurred up to 53 K above the known bulk transition temperature
T
C
at 105 K with a hysteresis up to a temperature of 220 K. Both phenomena possibly arise from dislocations and associated strain
fields introduced by surface annealing that are assumed to lower the free energy of the tetragonal phase and simultaneously
pin tetragonal domains. Thus, microregions of the tetragonal phase persist above T
C
causing the hysteresis in resistivity up to ∼12%. This effect possibly provides new chances for future oxide based non-volatile
data-storage devices. 相似文献
15.
The initial fine-grained structure of superplastic alloys is attained by rather complicated thermomechanical treatment. Various processes can take place during annealing of such materials due to the release of deformation energy stored in specimens in the course of their preparation. This paper deals with the measurements of the electrical resistivity annealing curves of the superplastic Zn-0·25 wt. % Cd alloy. The pronounced electrical resistivity drop due to the recrystallization was observed between 320 and 360 K. The value of kinetic exponentn from Avrami's equation was found to be 1<n<2;n increases with increasing temperature of annealing. The influence of superplastic deformation on the electrical resistivity annealing curves was investigated. Due to the softening during superplastic deformation the recrystallization becomes less pronounced and shifts to higher temperatures. The kinetic exponentn decreases to unity and its temperature dependence disappears. The attempt was made to explain these results on the ground of literature findings on the kinetics of recrystallization after preceding hot deformation. 相似文献
16.
K. Schouteden P. Lievens C. Van Haesendonck 《Applied Physics A: Materials Science & Processing》2009,96(2):409-413
The structural stability of rapidly solidified (about 104 K/s) Sn–3.7Ag–0.9Zn eutectic solder was explored by high-temperature annealing. For the as-cast solders, the applied fast
cooling rate had a significant influence on the microstructure of the solders. The faster the applied cooling rates, the smaller
the β-Sn dendrites. After annealing at 473 K for 20 and 50 h, β-Sn dendrites congregated together into bulk ones for minimizing the interfacial energy, and Ag3Sn intermetallic compounds (IMCs) as well as ternary Ag–Zn–Sn IMCs segregated on the grain boundary of the β-Sn dendrites. It seems that the coarsening of the β-Sn dendrites in the rapidly solidified specimen brought a significant softening during annealing of the explored Sn–Ag–Zn
alloy. Finally, the β-Sn dendrites vanished gradually with increase of the annealing period, which leads to a kind of softening. 相似文献
17.
18.
Rakesh Malik S. Annapoorni S. Lamba S. Mahmood R. S. Rawat 《Applied Physics A: Materials Science & Processing》2011,105(1):233-238
Nickel ferrite thin films were deposited by a pulsed laser deposition (PLD) technique on silicon substrate at room temperature
in a vacuum of 5×10−5 mbar. The films were subjected to different annealing temperatures from 300–900°C and were also exposed to single shot energetic
hydrogen ions using a Dense Plasma Focus (DPF) device. The changes induced in the films exposed at different distances from
the top of the anode were investigated. The structural, morphological and magnetic properties of the annealed and exposed
samples were investigated. X-ray diffraction (XRD) studies reveal the presence of a single phase of nickel ferrite after annealing.
SEM micrographs indicate an increase in the grain size, both on annealing as well as on exposure to hydrogen ions. Annealing
and hydrogen ion irradiation induced an enhancement in the magnetic moments. Laser droplets which are inherent in films deposited
by laser ablation were found to be dispersed as a result of single shot hydrogen ion irradiation from the DPF. 相似文献
19.
The experimental setup is described and results are presented for measuring average boiling-up lag time for superheated n-hexane mixed with solid structures (activated coal, cellulose, silica gel) as function of temperature under atmospheric pressure.
The “aging” of the cell with the filler was carried out before measurements: this was about 600–1000 boiling events. We developed
a new method for analysing of “aging” procedure: comparison of average flux (frequency) of boiling-up events (processing of
experimental data) and the frequency of nucleation obtained from exponential model. By the end of aging of the cell with silica
gel the average empirical flux reduces by factor of four relative to the “exponential” value. But for activated coal and cellulose
the difference in these fluxes is about 20 %. In all experiments, the event flux was nonstationary. For n-hexane in tested
systems, the margin of superheating was T
n/T
cr ≅ 0.873–0.875, although it was T
n/T
cr ≅ ≅ 0.883 for n-pentane in systems filled by nickel powder (sintered porous nickel with grains of 1.5 or 5.0 micron size) and in the presence
of a smooth copper plate. The average time of boiling-up lag in n-hexane at low normalized temperatures was also smaller than
for n-pentane. For all systems, the lag time is almost the same for the temperature range T
n/T
cr ≅ 0.860–0.874 (plateau). Thus, a smaller amount of superheated liquid or its division into smaller liquid elements does not
result in longer liquid lifetime for superheat liquid and the maximal superheat temperature, as one could expect from the
classical theory of homogeneous nucleation.
Research was supported by the RF Presidential Foundation (NS-905.2003.2) and Russian Foundation for Basic Research (Grant
No. 04-02-16285). 相似文献
20.
An investigation is made of the diffusion of antimony through the bulk and along grain boundaries in copper bicrystals containing
a symmetric 〈100〉 misorientation boundary with misorientation angles from 20 to 37.2°. The bicrystals are grown by the method
of horizontal zone recrystallization. The temperature range for these studies is 480–580 °C, where the solubility of Sb in
Cu is about 6 atomic % and practically temperature-independent. The concentration profiles are obtained by x-ray spectral
microanalysis, and the grain-boundary diffusion parameters are computed by the method of Whipple and Suzuoka. The orientation
dependence of the triple product P=sδD
b
(where s is the segregation coefficient, δ the width of the grain boundary, and D
b
the grain-boundary diffusion coefficient) is nonmonotonic, with a maximum for the special ∑5 misorientation boundary (36.9°).
The effective activation energy for grain-boundary diffusion ranges from ∼70 kJ/mol for ∑5 to140 kJ/mol for general boundaries.
Fiz. Tverd. Tela (St. Petersburg) 39, 1153–1157 (July 1997) 相似文献