共查询到20条相似文献,搜索用时 15 毫秒
1.
I. L. Deryagina E. N. Popova E. P. Romanov E. A. Dergunova A. E. Vorob’eva S. M. Balaev 《The Physics of Metals and Metallography》2012,113(4):391-405
The effect of diffusion annealing on the structure of superconducting layers of the Nb3Sn phase and the extent of transformation of niobium filaments of multifilamentary Nb/Cu-Sn superconductors obtained using
the bronze process has been investigated by scanning and transmission electron microscopy. The samples differed in the titanium
concentration and method of alloying. It has been shown that the thickness of layers of the Nb3Sn phase grows with an enhancement in the titanium concentration in Nb filaments and that it is composites with the alloyed
bronze matrix that exhibit the most favorable structure and morphology from the viewpoint of reaching the maximum current-carrying
capacity of the conductor in all of the regimes of diffusion annealing under study. 相似文献
2.
B. A. Aleksashin A. V. Soloninin A. V. Korolev V. P. Dyakina E. N. Popova E. P. Romanov S. V. Sudareva 《The Physics of Metals and Metallography》2007,104(1):59-66
The paper presents the results of measurements of the temperature dependence of the shape of the NMR lines of 93Nb and of the real part of the dynamic magnetic ac susceptibility χ′(T) for multifilamentary superconducting Nb3Sn-based composites with various geometry of niobium filaments (ordinary cylindrical, paired cylindrical, and ringlike (tubular)) produced by the bronze technology. In all the composites studied, a superconducting (SC) transition was observed in diffusional Nb3Sn layers at T c ~ 17 K. Its width is ΔT c ≈ 3 K and is independent of the composite design. The difference in the absolute value of χ′(T) in the composites of ordinary assembly and with paired filaments is less by a factor of 1.5 than that of a composite with ring filaments. In the experimental NMR spectra of 93Nb, subspectra of different intensities have been distinguished, whose number is three in ordinary assemblies and in assemblies with paired filaments, and two in composites with ring filaments. Estimates of the intensities of each subspectrum in each experimental spectrum of the composites studied has been correlated with a definite diffusional layer of Nb3Sn; thus, the number of grains of a corresponding layer in each composite has been estimated. In addition, it has been established that in the first two composites the shape of the NMR line of 93Nb is asymmetric, which indicates the existence of an anisotropy of the Knight shift in Nb3Sn layers in both the normal and superconducting states, whereas in the composite with ring filaments the line is symmetric and the Knight shift is isotropic. The magnitude of the anisotropic Knight shift in composites with isolated and paired cylindrical filaments is 93 K an ≈ 0.02%. The anisotropy in them appears to be due to the different character and magnitude of interaction of grains of the Nb3Sn layers with the bronze matrix and the residual Nb, which leads to different shifts of the subspectrum frequencies and, correspondingly, to the shape asymmetry of the NMR line of 93Nb. At the same time, in a composite with ring filaments the interaction of the Nb3Sn layer with the bronze matrix occurs on both sides, is, apparently, of the same character and is compensated in magnitude. In this case, in the first two composites the tin distribution across the diffusional layers of Nb3Sn is nonuniform and a significant deviation from the stoichiometric composition is observed. 相似文献
3.
M. A. Borovkova R. S. Il’yasov N. V. Fedorova E. P. Elsukov A. V. Zagainov G. N. Konygin O. M. Nemtsova 《The Physics of Metals and Metallography》2009,107(3):245-253
Double electromagnetic acoustic transformation method was used to study dynamic magnetoelastic properties of the Fe73.7Cu1.0Nb3.2Si12.7B9.4 amorphous alloy subjected to crystallization annealing at different temperatures. Anomalous variations in the differential magnetostriction and ultrasound damping and velocity were found. According to Mössbauer spectroscopy data, they are related to the formation of a component of magnetic moments that is perpendicular to the ribbon surface. 相似文献
4.
Ag(Nb0.8Ta0.2)O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and di-electric properties of Ag(Nb0.8Ta0.2)O3 ceramics was investigated. The addition of CaF2 led the ceramics to a larger grain size and distortion of lattice. With the addition of 4.5 wt.% CaF2, the permittivity of the ceramics increased from 442 to 1028, the dielectric loss decreased sharply from 6.12 × 10-3 to 8.6 × 10-4, and the temperature coefficient of capacitance decreased from 1834 ppm/°C to-50 ppm/°C (at 1 MHz). These results indicated that the high permittivity was related with a large grain size, a low grain boundary density, and the weak Ta-O or Nb-O bond strength caused by the addition of CaF2. 相似文献
5.
M. A. Eremina S. F. Lomaeva S. N. Paranin S. L. Demakov E. P. Elsukov 《The Physics of Metals and Metallography》2016,117(5):510-517
Cu + Cr3C2 composites have been produced using the mechanical alloying of the elemental components, followed by severe plastic deformation by torsion, magnetic-pulse pressing, and electric-pulse plasma sintering. The composites are studied using X-ray diffraction and light and electron microscopy, as well as measurements of the hardness, density, and electric conductivity. Magnetic-pulse pressing at a temperature of 500°C makes it possible to produce volume nanocomposites with a homogeneous distribution of dispersed carbides over the copper matrix, which has a density of 96%, a Vickers microhardness of 4.6 GPa, a Rockwell hardness of 69 HRA, and an electric conductivity of 19% IACS units. Using electric-pulse plasma sintering at a temperature of 700°C, composites with the nanostructured copper matrix, which contains carbide inclusions and consists of domains surrounded by a layer of nearly pure copper, have been produced. These composites have a density of 88%, a Vickers microhardness of 4.0 GPa, a Rockwell hardness of 58 HRA, and electric conductivity of 26% IACS units. 相似文献
6.
A. K. Shikov V. I. Panstsyrnyi A. V. Vorob’eva E. A. Dergunova S. V. Sud’ev K. A. Mareev N. A. Belyakov I. M. Abdyukhanov V. V. Sergeev 《Metal Science and Heat Treatment》2004,46(11-12):504-513
Results of a study of promising Nb3Sn superconductors fabricated with the use of a “bronze” method and a method of “internal source of tin” for toroidal coils of the magnet system of the international thermonuclear experimental reactor (ITER) are presented. The main structural parameters and factors of the process of manufacturing technical superconductors based on Nb3Sn, which determine the superconducting properties, are analyzed. The current-carrying capacity and the losses to hysteresis are determined for conductors with various diameters. The structure of the layer of superconducting Nb3Sn compound is studied, and the relation between the structural parameters and the superconducting properties of the developed conductors is described. Examples of Nb3Sn superconductors with a reinforcing element from a nanocomposite alloy Cu - 18% Nb are presented. Strength characteristics of the reinforced conductors are studied. Prospects of further enhancement of superconducting properties of Nb3Sn superconductors obtained by both methods are estimated. 相似文献
7.
Shi Hong Zhang Ming Xi Li Tong Yul Cho Jae Hong Yoon Wei Fang Yun Kon Joo Jin Ho Kang Chan Gyu Lee 《Metals and Materials International》2008,14(3):315-319
The effects on the microstructures and phases of coating layers by the addition of micron-sized (m) and nano-sized (n) (m&n)
Sm2O3 powders were investigated. The coating materials, which were prepared by means of 2.0 kW CO2 laser cladding, consist of a powder mixture of m Ni-based alloy (NBA) powders comprising 1.5 wt.% m Sm2O3 and 3.0% n Sm2O3 powders. The results indicate that γ-Ni, Cr23C6 and Ni3B are the primary phases of the NBA coatings. The Fe7Sm and Ni3Si phases are highlighted by the addition of m&n Sm2O3 powders. From the substrate, planar crystal layers are first grown in all NBA and m&n Sm2O3/NBA coatings. The dendrite growth then occurs as a result of the addition of the m Sm2O3 powder, and the equiaxed dendrite growth occurs as a result of the addition of the n Sm2O3. With the addition of a rare earth oxide such as Sm2O3 powder, the width of the planar crystal becomes smaller than that of the NBA coating. 相似文献
8.
V. V. Ovchinnikov F. F. Makhin’ko N. V. Gushchina A. V. Stepanov A. I. Medvedev Yu. N. Starodubtsev V. A. Kataev V. S. Tsepelev V. Ya. Belozerov 《The Physics of Metals and Metallography》2017,118(2):150-157
The effect of accelerated Ar+ ions on the crystallization process and magnetic properties of nanocrystalline Fe72.5Cu1Nb2Mo1.5Si14B9 alloy has been studied using X-ray diffraction analysis, transmission electron microscopy, thermomagnetic analysis, and other magnetic methods. Irradiation by Ar+ ions with an energy of 30 keV and a fluence of 3.75 × 1015 cm–2 at short-term heating to a temperature of 620 K (which is 150 K below the thermal threshold of crystallization) leads to the complete crystallization of amorphous alloy, which is accompanied by the precipitation of the α-Fe(Si) solid solution crystals (close in composition to Fe80Si20), Fe3Si stable phase, and metastable hexagonal phases. The crystallization caused by irradiation leads to an increase in the grain size and changes the morphology of grain boundaries and volume fraction of crystalline phases, which is accompanied by changes in the magnetic properties. 相似文献
9.
I. B. Bobylev N. A. Zyuzeva M. V. Degtyarev E. G. Gerasimov Yu. S. Ponosov V. P. Pilyugin 《The Physics of Metals and Metallography》2016,117(9):870-875
The influence of water vapors and plastic deformation on the structure and electrophysical properties of YBa2Cu3O6.9 (123) has been studied. It has been established that, at T = 200°C, the introduction of water into the structure of YBa2Cu3O6.9 leads to its transition into a defect tetragonal phase of the 124 type as a result of the formation of planar stacking faults. After annealing at T = 930°C, these defects are partially retained and are efficient centers of pinning in the magnetic fields applied perpendicularly to the c axis, which makes it possible to increase (by an order of magnitude) the critical current density in the high-textured ceramics at 77 K in the external magnetic field of 5–10 T. The plastic deformation of the hydrated ceramics favors the reverse transition of the arising 124 phase to the 123 phase at T = 930°C and is accompanied by a recrystallization of the material, which leads to the appearance of a texture and an increase the critical current density. 相似文献
10.
Geun Woo Kim Shalendra Kumar Yong Jun Seo Kai Wang Chan Gyu Lee Bon Heun Koo 《Metals and Materials International》2010,16(5):807-811
The (La0.7Ca0.3MnO3)1x
/(NiFe2O4)
x
(x = 0 to 0.09) composites were prepared using a conventional solid state reaction method. The structural, magnetic properties,
and electrical properties of LCMO/NFO composites were investigated using X-ray diffraction, scanning electron microscopy,
field cooled DC magnetization, and magnetoresistance (MR) measurements. The resistivity measured as a function temperature
demonstrates that the pure LCMO and x = 0.01 samples display metal to semiconductor transitions. However, the composites of x > 0.03 samples clearly present the electrical behavior as an insulator/semiconductor type behavior. It was observed that
the resistivity of the samples increased systemically with an increase of the NFO content. From the MR measurements, it was
found that the MR effect is enhanced for x = 0.01 with a NFO composition. In all, the spin-polarized tunneling and the spin-dependent scattering may be beneficial for
an improved low-field magnetoresistance effect. These phenomena can be explained by the segregation of a new phase related
to NFO at the grain boundaries or surfaces of the LCMO grains. 相似文献
11.
Toshitada Shimozaki Je-hyun Lee Chan-Gyu Lee 《Journal of Phase Equilibria and Diffusion》2017,38(1):17-29
Reactive diffusion in the Cu-Sn binary system has been studied by using pure Cu/electrically plated Sn with 0.1-0.2 mm thicknesses diffusion couples (EP-couples) at 473 K. The interdiffusion coefficients, \(\tilde{D}\), of the Cu3Sn and Cu6Sn5 diffusion phase layers were determined at the center of these layers by supposing linear concentration (\(C_{\text{i}}\))-distance (X) curves in these layers and by neglecting the interdiffusion in the Sn terminal solution (IDS) as the previous researchers have neglected it. By using \(\tilde{D}\) thus determined, the phase boundary concentrations for the layers obtained in this work and these parameters for the Cu terminal solution chosen appropriately, \(C_{\text{i}}\)-X curves were determined numerically for various values of interdiffusion coefficient, \(\tilde{D}_{\text{in Sn}}\), and the solubility limit of Cu mole fractions, \(N_{\text{Cu}}^{\text{in Sn}}\), in the Sn terminal solution by our method reported previously taking the molar volume change effect into account. The \(C_{\text{i}}\)-X curves obtained experimentally could be reproduced numerically well by neglecting IDS. This result, on the other hand, suggests a large influence of IDS in the semi-infinite diffusion couples (S-couples) or the diffusion couples used by the previous researchers. The quantitative evaluation of the influence in S-couples revealed that it makes the widths of the diffusion layers thinner than those in the present EP-couples in which the influence on the widths is negligibly small. The evaluation of the influence in the diffusion couples used by the previous researchers indicates larger values of \(N_{\text{Cu}}^{\text{in Sn}}\) than those reported as the value of the equilibrium phase diagram. 相似文献
12.
Su Jung Woo Hyeon Jeong Cho Eun Kyoung Cho Mansig Kim Keun Yong Sohn Won-Wook Park 《Metals and Materials International》2008,14(4):511-514
Fe-based nanocrystalline powder sheets with dielectric TiO2 powder additives were investigated to improve the characteristics of electromagnetic (EM) wave absorption. The amorphous
ribbons of Fe73Si16B7Nb3Cu1 (at.%) alloys were prepared by a planar flow casting (PFC) process, and the ribbons were pulverized using an attrition mill.
Fe-based flake powder crystallized at 550°C for 1h was mixed with a nano-sized and a micro-sized TiO2 powder. The powder mixtures were then tape-cast with binders to become EM wave-absorbing sheets. The absorbing properties
of the fabricated sheet sample, such as complex permittivity and permeability, were measured by a network analyzer. The properties
of EM wave absorption improved with the increase of TiO2 powder in the mixture. The mixture with micro-sized TiO2 powder was a little more effective in causing power loss of EM waves than the mixture with nano-sized TiO2 powder. 相似文献
13.
V. S. Tsepelev Yu. N. Starodubtsev V. A. Zelenin V. A. Kataev V. Ya. Belozerov V. V. Konashkov 《The Physics of Metals and Metallography》2017,118(6):553-557
The process of the nanocrystallization of magnetically soft Fe72.5Cu1Nb2Mo1.5Si14B9 alloy has been studied using dilatometry and thermomagnetic analysis, together with structural investigations. It has been shown that the amount of nanocrystalline phase precipitated upon heating of the amorphous precursor is in good agreement with a shortening of the ribbon length in the course of crystallization. Thermal expansion at the different stages of heating and cooling depends on the structural and phase states, as well as on the magnetic state of the alloy. The numerical value of the coefficient of linear thermal expansion decreases with an increase in the fraction of the ferromagnetic crystalline phase. 相似文献
14.
Yu. V. Blinova L. A. Cherepanova T. P. Krinitsina E. I. Kuznetsova S. V. Sudareva S. G. Titova S. V. Pryanichnikov M. V. Degtyarev E. P. Romanov 《The Physics of Metals and Metallography》2016,117(2):151-159
The crystal structure of the high-temperature Y1–xCaxBa2Cu3O6.8 superconductor has been studied in a temperature range of 80–300 K using low-temperature X-ray diffraction analysis; its microstructure has been studied by scanning and transmission electron microscopy. Changes of the bond length in the structure of principal phase and precipitation topology of impurity phases and their compositions have been analyzed. An addition of calcium was shown to increase the environmental tolerance of the principal Y123 phase and its microhardness and ensures the low unchanged coefficient of thermal expansion. All of the facts indicate that the material can be used to manufacture composite superconducting articles. 相似文献
15.
Yttria (Y) dispersed ferrum (Fe) films were prepared by a double-target magnetron co-sputtering method. Vacuum annealing and
xenon ion irradiation were conducted to investigate the influence on the magnetic and mechanical properties of the films.
The crystal grain growth mechanism and second phase precipitation mechanism were conducted simultaneously in the vacuum annealing
process. These two effects led to an opposite variation of nano-hardness and coercivity in the films. Xenon ion irradiation
played a role in rapid annealing, which also affected the magnetic performance of the yttria dispersed ferrum films. 相似文献
16.
S. A. Gridnev Yu. E. Kalinin A. V. Kalgin E. S. Grigor’ev 《Protection of Metals and Physical Chemistry of Surfaces》2009,45(5):583-587
The magnetoelectric (ME) effect in two- and three-layered composites made up of polarized ceramic plates of lead zirconate-titanate
PbZr0.53Ti0.47O3 (PZT) and manganese-zinc ferrite Mn0.4Zn0.6Fe2O4 (MZF) has been studied. Dependences of the transverse ME voltage coefficient (α31) on the magnetostrictive layer thickness and the magnetic field intensity and frequency have been established. The mechanical
coupling coefficient of the composite plates has been estimated. Results obtained for two-layered PZT-MZF structures have
been analyzed using the method of efficient medium parameters. 相似文献
17.
Xianhui Wang Shuhua Liang Ping Yang Zikang Fan 《Journal of Materials Engineering and Performance》2010,19(9):1330-1336
Al2O3/Cu composites were prepared by external addition of Al2O3, and the effect of Al2O3 content on microstructure, density, hardness, electrical conductivity and vacuum electrical breakdown properties was studied.
The results show that with increasing Al2O3 addition, the density of Al2O3/Cu composite significantly decreases, the hardness sharply increases and then slowly decreases, but the electrical conductivity
invariably decreases. The vacuum breakdown test shows that with increasing Al2O3 addition, the breakdown strength first sharply increases and then decreases when the Al2O3 content exceeds 1.2 wt.%; the chopping current always exhibits a decreasing trend and the arc life first increases and then
decreases. According to the morphology of arc erosion and analysis, the arc erosion resistance increases and then decreases
sharply. In the range of experiments, the optimal arc erosion resistance of Al2O3/Cu composite can be obtained with the addition of 1.2 wt.% Al2O3. 相似文献
18.
L. Lâallam A. Jouaiti A. Barroug S. El Allali J. Berthet R. Tenu J. J. Counioux 《Journal of Phase Equilibria and Diffusion》2011,32(6):543-550
The phase diagram of the H2O-Zn(NO3)2-Al(NO3)3-Cu(NO3)2 quaternary system at 30 °C has been established by using the conductivity measurements. The solid-liquid equilibria of the
H2O-Zn(NO3)2-Al(NO3)3, H2O-Zn(NO3)2-Cu(NO3)2, H2O-Al(NO3)3-Cu(NO3)2 ternary systems and two isoplethic sections were determined experimentally. The solid phases in equilibrium with the saturated
solution are the tri- and hemipentahydrate of copper nitrate, the hexahydrate α and β of the zinc nitrate and the nonahydrate
of aluminum nitrate. The copper and zinc nitrates are relatively soluble in opposition to the aluminum nitrate which presents
some important precipitation domains. 相似文献
19.
Amorphous (Nd,Pr)13Fe80Nb1B6 ribbons were crystallized at 670–730°C for 5–25 min to study the effects of isothermal crystallization on their behavior
and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700,
and 730°C, respectively. High coercivities, with the maximum value of i
H
c = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons.
This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but
also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics
of the furnace that the authors designed. 相似文献
20.
Sun-Gyu Park Seong-Rae Lee Won Il Cho Byung Won Cho 《Metals and Materials International》2010,16(1):93-98
We studied the dependence of Al2O3 coating thickness and annealing conditions on the surface morphology and electrochemical properties of Al2O3 coated LiCoO2 films. The optimum coating thickness allowing for the highest capacity retention was about 24 nm. A sample consisting of
Al2O3 coated on annealed LiCoO2 film with additional annealing at 400 °C had a uniform coating layer between the coating materials and cathode films. This
sample showed the best capacity retention of ∼91 % with a charge-cut off of 4.5 V after 30 cycles, while the bare cathode
film showed a capacity retention of ∼32 % under the same conditions. The formation of second phases such as Co-Al-O was observed
in the coating films by X-ray photoelectron spectroscopy (XPS). The Co-Al-O containing samples showed a higher initial capacity
because of their smaller grain size, but less capacity retention than the Al2O3 containing samples. 相似文献