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Currently, MgB2 wires made by the powder-in-tube (PIT) method are most often used in the construction and design of superconducting devices. In this work, we investigated the impact of heat treatment under both low and high isostatic pressures on the formation of a layered structure in PIT MgB2 wires manufactured using the Mg coating method. The microstructure, chemical composition, and density of the obtained superconductive wires were investigated using scanning electron microscopy (SEM) with an energy-dispersive X-ray spectroscopy (EDS) analyzer and optical microscopy with Kameram CMOS software (version 2.11.5.6). Transport measurements of critical parameters were made by using the Physical Property Measurement System (PPMS) for 100 mA and 19 Hz in a perpendicular magnetic field. We observed that the Mg coating method can significantly reduce the reactions of B with the Fe sheath. Moreover, the shape, uniformity, and continuity of the layered structure (cracks, gaps) depend on the homogeneity of the B layer before the synthesis reaction. Additionally, the formation of a layered structure depends on the annealing temperature (for Mg in the liquid or solid-state), isostatic pressure, type of boron, and density of layer B before the synthesis reaction. [ABSTRACT FROM AUTHOR]

In our paper, we present the results of the structural, morphological and critical parameters of MgB 2 cylindrical materials doped with Dy 2 O 3 , Tb 2 O 3 , Er 2 O 3 , Eu 2 O 3 and Sm 2 O 3. The materials were annealed under low and high isostatic pressures at 800 °C for 1 h in an argon atmosphere. Our results show that the HIP process significantly increases the density of MgB 2 materials modified by the RE 2 O 3 additive from 1.05 to 2.4 g/cm3. Scanning electron microscope (SEM) images indicate that the HIP process removes voids from the MgB 2 material. The results indicate that the HIP process slightly affects the formation of REB 4 and REB 6 and does not affect the process of RE substitution for Mg. Further SEM results show that the morphologies of samples annealed at low isostatic pressure with Dy 2 O 3 , Tb 2 O 3 and Er 2 O 3 doping are completely different from those of samples with Eu 2 O 3 and Sm 2 O 3 doping. The magnetic measurements indicate that RE 2 O 3 doping and annealing under low isostatic pressure slightly increases the critical temperature (T c) and decreases the irreversible magnetic field (B irr). On the other hand, thermal treatment under high isostatic pressure with an admixture of RE 2 O 3 lead to a greater increase in T c and a decrease in B irr. Further magnetic measurements show that RE 2 O 3 doping and annealing under low isostatic pressure mainly increase the magnetic critical current density (J mc) at 4.2 K–30 K in low magnetic fields. Additional results indicate that high isostatic-pressure annealing of the RE 2 O 3 -doped MgB 2 material significantly increases J mc in low magnetic fields and decreases J mc in high magnetic fields. Our results indicate that the Eu 2 O 3 admixture most effectively increases T c and J mc and creates the large amount of the REB 6 phase. It is as the only admixture that increases B irr after the HIP process and yields the smallest MgB 2 grains. [ABSTRACT FROM AUTHOR]

Currently, MgB2 wires made by the powder-in-tube (PIT) method are most often used in the construction and design of superconducting devices. In this work, we investigated the impact of heat treatment under both low and high isostatic pressures on the formation of a layered structure in PIT MgB2 wires manufactured using the Mg coating method. The microstructure, chemical composition, and density of the obtained superconductive wires were investigated using scanning electron microscopy (SEM) with an energy-dispersive X-ray spectroscopy (EDS) analyzer and optical microscopy with Kameram CMOS software (version 2.11.5.6). Transport measurements of critical parameters were made by using the Physical Property Measurement System (PPMS) for 100 mA and 19 Hz in a perpendicular magnetic field. We observed that the Mg coating method can significantly reduce the reactions of B with the Fe sheath. Moreover, the shape, uniformity, and continuity of the layered structure (cracks, gaps) depend on the homogeneity of the B layer before the synthesis reaction. Additionally, the formation of a layered structure depends on the annealing temperature (for Mg in the liquid or solid-state), isostatic pressure, type of boron, and density of layer B before the synthesis reaction.

This article reports the influence of isostatic pressure (from 0.1 MPa to 1.1 GPa), low annealing temperature of 570 ∘C, and annealing time for the formation of high-field pinning centers in 2% C-doped MgB2 wires. Measurements indicate that 1.1 GPa pressure significantly increases the density of high-field pinning centers below 20 K. However, lower pressure (0.6 GPa) slightly increases the density of high-field pinning centers. Increasing the annealing time from 120 to 210 min leads to a reduction of critical temperature (Tc), irreversibility field (Birr), critical current density (Jc), and upper critical field (Bc2), suggesting that a long annealing time leads to a reduction of high-field pinning center density and the number of connections between superconducting grains. The high pressures and low annealing temperature lead to a high critical current density of 1000 A/mm2 in 7.2 T and 100 A/mm2 in 12.5 T at 4.2 K in MgB2 wires. [ABSTRACT FROM AUTHOR]

We show for the first time the results for small coils, which were wound with unreacted magnesium diboride (MgB 2) wires with nano-amorphous isotopic boron (11B) by using combined internal magnesium (Mg) diffusion (IMD) and hot isostatic pressing (HIP) techniques. The small coils with a diameter of 20 mm or 10 mm were annealed under low (0.1 MPa) and high (1.1 GPa) isostatic pressure. The 10 mm coils annealed under high isostatic pressure of 1.1 GPa had significantly increased critical temperature (T c), irreversible magnetic field (B irr) and transport critical current density (J tc), with significantly accelerated Mg diffusion and improved homogeneity of the Mg11B 2 material. Moreover, our findings show for the first time that the bending of the unreacted IMD Mg11B 2 wires significantly affects the synthesis reaction under the low and high isostatic pressure. Our findings also show for the first time that diffusion of Mg during heat treatment under high isostatic pressure is completely different than during heating under low isostatic pressure. Mg diffusion under low isostatic pressure annealing is mainly dependent on the heat treatment temperature, bending diameter and 11B layer density. This Mg diffusion is related to the simultaneous formation of the superconducting phase. However, the diffusion of Mg under high isostatic pressure heat treatment is mainly dependent on the isostatic pressure, 11B layer density and Mg state (liquid or solid). Our results indicate that liquid Mg is first pushed into the 11B layer by high isostatic pressure and then a superconducting phase is formed. • The bend with 20 mm diameter and heat treatment under 0.1 MPa does not accelerate the diffusion of Mg. • The bend with 10 mm diameter and heat treatment under 0.1 MPa accelerate the diffusion of Mg in outer part. • The bend with 10 mm diameter and heat treatment under 1.1 GPa accelerate the diffusion of Mg. • The density of the layer 11B significantly influences the diffusion of Mg. • HIP process increase B irr and J c in IMD Mg11B 2 wires. [ABSTRACT FROM AUTHOR]

We present our research on the influence of pressure on the synthesis of the MgB 2 phase and, consequently, on the superconducting properties of the MgB 2 system. We investigated undoped, C-doped, and double-doped, i.e. C and Re 2 O 3 Re = Sm, Eu, Er), MgB 2 samples. We conducted comparative studies of critical temperature, irreversibility field, critical current and pinning force for ceramic samples annealed at ambient pressure and 1 GPa. Heat treatment under high isostatic pressing (HIP) of 1 GPa reduced the volume of the undoped MgB 2 cylinder by 40%. This significantly increases the density, homogeneity and number of connections between the grains, and also eliminates voids in the undoped material. However, we did not observe any reduction in the volume of C-doped and double-doped MgB 2 cylinders. Our research shows that the critical parameters of the MgB 2 superconductor can be increased more effectively by doping C and the HIP process than by double doping C with Er, Sm or Eu and the HIP process. The HIP process improved the efficiency of pinning centers created by magnetic admixtures with a low magnetic moment (Sm and Eu), but on the other hand, reduced this efficiency for admixture with a high magnetic moment (Er). ● Doping of carbon encapsulated boron and high pressure most strongly increases J c at 4.2 K and 20 K. ● The high pressure allows to obtain the highest J c in undoped MgB 2 material at 30 K. ● Doping of carbon encapsulated boron, erbium, samarium and europium oxides reduce the critical temperature. ● Rare earth metals made it difficult to substitute carbon for boron in the MgB2 structure. [ABSTRACT FROM AUTHOR]

We show transport results of the critical temperature ( T c ), irreversible magnetic field ( B irr ), upper critical field ( B c2 ), critical current density ( J c ) and the pinning force ( F p ) for undoped MgB 2 wires without barriers. The results of SEM show that the hot isostatic pressure process increases the density and uniformity of MgB 2 materials. Hot isostatic pressure allows for obtaining small grains and increasing the number of connections between the grains, accelerated reaction rate and limits the diffusion of Fe atoms into MgB 2 material from the adjacent sheath. The pressure of 1.1 GPa increases T c quite significantly in high magnetic field range of 6–12 T, improves the B irr and B c2 and increase the J c at 4.2 K and 20 K of about three times. Our results may be important for this field since many MgB 2 wires are made from big grains of boron greater than 1 μm. Moreover, our research can be important for the production of MgB 2 wires for the International Thermonuclear Experimental Reactor with boron 11 B. [ABSTRACT FROM AUTHOR]

Abstract: In the engineering design activity of international thermonuclear experimental reactor (ITER), stainless steels are being considered as candidates materials for several module type structures. Hot isostatic pressing (HIP) technique is expected for the fabrication of these modules. Stainless steel powders are simultaneously consolidated as mono-material block or/and joined in bi-material module. This paper reviews the manufacturing stages, non-destructive examination and the developments of the HIP bonded joints of 316L SS (powder and solid) for application to the ITER shield blanket. It is well known that the powder surface oxidation negatively influences the impact toughness of raw material and joints consolidated by this way. In order to get acceptable mechanical properties of materials, a study on the effect of reducing the powder oxygen content has been launched. To evaluate susceptibility to the oxygen content of HIPed joint specimens, tensile and toughness tests have been performed. From this study, optimal conditions of HIP were fitted and the influence of oxygen was mastered to obtain good mechanical properties of the consolidated powder material as well as for HIPed junction. [Copyright &y& Elsevier]

An ultrasonic self-calibrating technique for the characterization of a ceramic which was fabricated by change pressing time during the HIP process has been applied by using the ratio of the reflection and transmission coefficients of normal incidence longitudinal waves. The ratio is self-compensated, in that it is independent of the characteristics for transmission and reception of ultrasound by the transducer and the condition of the couplant. The insensitive direction in parameter space is defined as the direction in which the variation of the ratio to changes of two parameters vanishes. For inverse problem the distribution of minima in an error surface is investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • High heating temperature and long heating time create a dense layer structure. • The dense layer structure form more number and better of connections between grains. •HIP process allows to obtain more dense longitudinal layers. In this work, we show the transport current results and structural analysis for Mg11B 2 wires for the first time made with high purity, nano-size and amorphous boron 11 (11B). Irradiation has a weak effect on the MgB 2 material made of 11B. Therefore, it is important for future applications to fusion reactors. This type of reactor will produce clean and cheap energy. We report for first time that high-fields pinning centers and dense layered structure lead to high transport critical current density (J tc) in high magnetic fields. This allows to obtain highest J tc value in the world (100 A/mm2 at 4.2 K and 8.5 T). We show that lack of dense layered structure and high-fields pinning centers lead to lower J tc in high magnetic fields. Our research shows that high isostatic pressure (HIP) promotes high-field pinning centers. [ABSTRACT FROM AUTHOR]