The current-voltage characteristics of a porous superconductor Bi
2
Sr
2
Ca
2
Cu
3
O
x
(Bi2223) have been measured at temperatures in the range from 10 to 90 K in magnetic fields of 0–80 kOe. The ...experimental dependences have been analyzed within the model allowing for pinning by clusters of a normal phase with fractal boundaries, as well as the model taking into account phase transformations of vortex matter. It has been found that the electrical resistance of the superconductor material significantly increases at temperatures of 60–70 K over the entire range of magnetic fields under consideration without changing in the sign of the curvature of the dependence
R
(
I
). It has been assumed that this behavior is associated with the specific feature of the pinning in a highly porous high-temperature superconductor, which lies in the fractality of the distribution of pinning centers in a wide range of self-similarity scales. The studied material at the aforementioned temperatures is characterized by the melting of the vortex structure.
The study of electrolytic-plasma jet polishing process was made using a high-speed camera. The process visualization allowed us to find optimization methods. Electrolytic-plasma jet polishing ...capabilities are demonstrated in terms of processing the additively manufactured gas turbine engine components with a high level of initial surface roughness and with internal cavities and channels.
Zinc stearate additions have been used to increase the remanence of sintered Nd-Fe-B magnets produced by the powder metallurgy without powder pressing. Zinc stearate acts as an internal lubricant, ...i.e., it decreases the friction forces between the particles and favors an increase in the degree of texture of the powders, which is induced by the magnetic field. It is shown that the density and the magnetic hysteresis characteristics of sintered magnets produced using additions of 0.15 wt % zinc stearate exceeds the corresponding values obtained for magnets produced without this addition at a filling density of powders in containers of more than 2.9 and 3.0 g/cm
3
in dry and wet states, respectively. Using additions of zinc stearate in the amount of 0.15% with respect to the weight of the powder, magnets with a density of 7.55 g/cm
3
,
B
r
= 14.02 kG,
H
c
= 7.91 kOe, and (
BH
)
max
= 46.1 MG Oe have been produced.
The fractal dimension of the boundaries of clusters formed by pores and granules in polycrystalline materials is shown to be determined by the sample density and crystallite sizes. The dependence of ...the fractal dimension on the density has a maximum. It is shown that the maximum diamagnetic response can be obtained in a porous high-temperature superconductor with a porosity of 50–60% and small crystallite sizes.
The effective application of a biocatalyst based on recombinant enzyme preparations obtained using
Penicillium verruculosum
is studied for the modification of marketable bleached sulfate hardwood ...cellulose. The effect of treatment with cellulase complex on the structure, morphology, and surface state of cellulose fibers is evaluated. After biocatalytic exposure, cellulose is shown to have an improved capacity for beating and the formation of bonds in paper sheets, along with greater strength than the initial cellulose. Application of the enzymatic modification of cellulose in the paper industry during biotechnological processes allows a range of problems in the efficient use of energy and resources to be solved.
The temperature and field dependences of the magnetization, the electrical resistivity, and the magnetostriction of bilayer lanthanum manganite La
1.4
Sr
1.6
Mn
2
O
7
single crystals and cobalt-doped ...La
1.4
Sr
1.6
(Mn
0.9
Cu
0.1
)
2
O
7
are measured. The magnetostriction of the cobalt-doped compound increases as compared to the initial La
1.4
Sr
1.6
Mn
2
O
7
compound, and the magnetization and the magnetoresistance of the former compound change substantially. Powder and single-crystal neutron diffraction patterns are used to detect ferromagnetic ordering in La
1.4
Sr
1.6
(Mn
0.9
Co
0.1
)
2
O
7
at a temperature below
T
C
~ 45(2) K, and this ordering coexists with antiferromagnetic correlations, which develop at temperatures below
T
C
~ 80(5) K.
In this report, we prepared for the first time the orthorhombic Dy{sub 1−x}Ho{sub x}MnO{sub 3} single crystals with x = 0, 0.1, 0.2, 0.3, and 0.4 using the flux technique. The post-growth processing ...and chemical and structural characterization of the synthesized samples were performed. Also, we examined the samples obtained by their magnetic properties and the magnetic anisotropy in wide ranges of temperatures and magnetic fields.
Composite materials fabricated by annealing of nonsuperconducting ceramics La{sub 2}CuO{sub 4} and La{sub 1.56}Sr{sub 0.44}CuO{sub 4} at 910 °C during various time are investigated. Areas of ...superconducting La{sub 1.85}Sr{sub 0.15}CuO{sub 4} phase arises at boundaries of contacting nonsuperconducting granules. The volume fraction of the superconducting phase increases with increasing annealing time. A model describing the magnetic and transport properties of the samples at low magnetic fields is constructed. The magnetotransport characteristics of obtained samples at low magnetic fields (∼ 100 Oe) are defined by weak links network formed by superconducting areas. At high fields, behavior of the system is defined by a magnetization of the disconnected superconducting islands. The average size of the superconducting areas has been estimated from an extended critical state model.
We report on the magnetostriction of hexagonal HoMnO{sub 3} and YMnO{sub 3} single crystals in a wide range of applied magnetic fields (up to H = 14 T) at all possible combinations of the mutual ...orientations of magnetic field H and magnetostriction ΔL/L. The measured ΔL/L(H, T) data agree well with the magnetic phase diagram of the HoMnO{sub 3} single crystal reported previously by other authors. It is shown that the nonmonotonic behavior of magnetostriction of the HoMnO{sub 3} crystal is caused by the Ho{sup 3+} ion; the magnetic moment of the Mn{sup 3+} ion parallel to the hexagonal crystal axis. The anomalies established from the magnetostriction measurements of HoMnO{sub 3} are consistent with the phase diagram of these compounds. For the isostructural YMnO{sub 3} single crystal with a nonmagnetic rare-earth ion, the ΔL/L(H, T) dependences are described well by a conventional quadratic law in a wide temperature range (4–100 K). In addition, the magnetostriction effect is qualitatively estimated with regard to the effect of the crystal electric field on the holmium ion.
The temperature and field dependences of the magnetization, the electrical resistivity, and the magnetostriction of bilayer lanthanum manganite La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7} single crystals ...and cobalt-doped La{sub 1.4}Sr{sub 1.6}(Mn{sub 0.9}Cu{sub 0.1}){sub 2}O{sub 7} are measured. The magnetostriction of the cobalt-doped compound increases as compared to the initial La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7} compound, and the magnetization and the magnetoresistance of the former compound change substantially. Powder and single-crystal neutron diffraction patterns are used to detect ferromagnetic ordering in La{sub 1.4}Sr{sub 1.6}(Mn{sub 0.9}Co{sub 0.1}){sub 2}O{sub 7} at a temperature below T{sub C} ~ 45(2) K, and this ordering coexists with antiferromagnetic correlations, which develop at temperatures below T{sub C} ~ 80(5) K.
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