https://web.njit.edu/~dave/Dry-Coating-Review.pdf

Synthesis of engineered particulates with tailored properties using dry particle coating

The growth and properties of electronic oxide thin films are reviewed. In particular, the synthesis and properties of superconducting, insulating, conducting, magnetic, and semiconducting epitaxial oxide structures are discussed. Crystal structures and functional properties common to many oxide materials are briefly reviewed. A description of film-growth techniques follows. Finally, an extensive overview of the epitaxial growth for specific oxide material systems is given. This includes the epitaxial growth of electronic oxide thin films on oxide and non-oxide substrates.

Synthesis and properties of epitaxial electronic oxide thin-film materials

Fatigue failures create enormous risks for all engineered structures, as well as for human lives, motivating large safety factors in design and, thus, inefficient use of resources. Inspired by the excellent fracture toughness of bone, we explored the fatigue resistance in metastability-assisted multiphase steels. We show here that when steel microstructures are hierarchical and laminated, similar to the substructure of bone, superior crack resistance can be realized. Our results reveal that tuning the interface structure, distribution, and phase stability to simultaneously activate multiple micromechanisms that resist crack propagation is key for the observed leap in mechanical response. The exceptional properties enabled by this strategy provide guidance for all fatigue-resistant alloy design efforts.

http://science.sciencemag.org/content/sci/355/6329/1055.full.pdf

Bone-like crack resistance in hierarchical metastable nanolaminate steels

Growth of the 2223 phase has been studied in the leaded Bi-Sr-Ca-Cu-O system. Differential thermal analysis showed that the enhanced formation of the 2223 phase occurs in the temperature range between 835°C and 869°C where partial melting occurs. The density of the pellet was found to increase by 30% at one hour and then to decrease by 40% from the highest density attained. The former is attributed to the growth of the 2223 phase with the aid of the partially melted liquid phase and the latter to the flaky shape of the resultant 2223 crystals. The effect of Pb addition for enhanced 2223 phase formation will be discussed.

Growth of the 2223 Phase in Leaded Bi-Sr-Ca-Cu-O System : Electrical Properties of Condensed Matter

The processing and properties of Ag-sheathed Bi-based superconducting tapes prepared using the powder-in-tube technique have been reviewed. Powder processing and heat treatment, among various other factors, were found to be critical to the Jc of Ag/Bi-based superconducting wires. Reactive, homogeneous, carbonate-free and incompletely reacted powders, produced by the solution route are desirable. Liquid phase sintering, which is essential to achieve intimate grain connectivity and high grain alignment, can be achieved using a short period of melt or by annealing at temperatures near the melting point of the composites. An Ag sheath has been proved to be sufficient for achieving the flexibility and stability of these tapes. The interfacial layer between Ag and oxides shows an improved strength and flexibility. The thermally activated flux creep determines the Jc at high temperature. Weak links have been largely eliminated in high-quality tapes at high temperatures but the weak-link behaviour becomes pronounced at low temperatures. The dispersed 2212 phase and defects in the Ag/2223 tapes may act as potential pinning sites. Multiprobe measurements show no accumulative grain boundary resistance for long tapes. Fabrication of long tapes shows a better reproducibility than that for the short tapes.

https://iopscience.iop.org/article/10.1088/0953-2048/6/5/001/pdf

Ag-sheathed Bi(Pb)SrCaCuO superconducting tapes

The Nb tube process has recently been developed at NRIM(Japan) for fabricating Nb3Al multifilamentary superconductors,1–3 which are characterized by the heat treatment at low temperature ( 1700°C), many attempts were made to form Nb3A1 by heat treating Nb/AI composite at high temperatures.4–6 However, rapid grain growth decreased the density of pinning center (grain boundary) in Nb3A1 and thereby degraded Jc in particular at low magnetic fields. To overcome this problem, Nb3A1 conductors fabricated through a rapid-quenching process have been studied. In this process the A15 Nb3A1 phase with fine grain structure can be precipitated from the supersaturated Nb-Al bcc phase by aging at ~800°C. However, no attempt was made to fabricate a practical-structure conductor such as a long multifilamentary wire through continuous rapid-quenching and subsequent annealing (post annealing) process.

Nb3Al Multifilamentary Wires Continuously Fabricated by Rapid-Quenching

Strain effects on critical current densities have been examined for conductors containing nearly stoichiometric Nb3Al filaments with fine grains. The Nb3Al phase in these multifilamentary conductors are prepared by phase transformation from supersaturated Nb(Al) bcc solid solution and show high-field critical current densities much larger than those for conventionally prepared Nb3Al conductors, where the Nb3Al phase is known to be off-stoichiometric. The degradation of critical current densities with −0.7% intrinsic strain is ca. 20% at 12 T, comparable with those for conventional Nb3Al conductors of high strain tolerance.

Strain effects in Nb3Al multifilamentary conductors prepared by phase transformation from bcc supersaturated-solid solution

Improvements in superconducting properties and workability have been achieved both in V 2 (Hf,Zr) and in V 2 (Hf,Nb), through the effects of additional elements. The V 2 (Hf,Zr) can be fabricated into a conductor form by a composite diffusion process in which a composite of vanadium sheath and Zr-Hf alloy core is cold-worked and then heat treated. The addition of hafnium to the vanadium sheath considerably improves the critical current density J c , and moreover it makes the fabrication of the composite easier by reducing the difference in workability between the sheath and the core. The multifilamentary V-(1-2)at%Hf/Zr-25at%Hf wire may be practically useful for generating magnetic fields up to 15T. The V 2 (Hf,Nb) ternary alloys containing hafnium less than 17at% can be fabricated by direct plastic deformation at room temperature. The titanium addition to the V 2 (Hf,Nb) significantly improves both the superconducting properties and the workability. In the cold-rolled V-19at%Hf-6at%Ti-8.3at%Nb, transition temperature T c of 9.9K, upper critical field H c2 (4.2K) of about 22T and overall J c (4.2K) of 1 × 104A/cm2at 13T are obtained.

Some improvements in laves phase high-field superconductors

A sheet-conductor fabrication method has been developed for Cu-Ag alloys containing 6-24 mass% Ag. Both the strength and the conductivity of the sheet were improved remarkably by the repetition of heat treatment combined with cold working. The intermediate heat treatments were repeated 3 times at 400-450/spl deg/C for 1-2 h at appropriate stages of cold rolling. The optimized Cu-24 mass% Ag alloy sheet with a 96% reduction ratio showed a ultimate tensile strength of 1050 MPa and an electrical conductivity of 75% IACS at room temperature. Anisotropy in the strength with respect to the rolling direction was less than 10% and no anisotropy in the electrical conductivity were observed. The sheets fabricated by this method are promising as conductors for high-field Bitter magnet coils. >

High-strength and high-conductivity Cu-Ag alloy sheets: new promising conductor for high-fieId Bitter coils

We fabricated a Bi2Sr2CaCu2Ox/Ag pancake coil by applying a dip‐coating process, which was used as an insert coil of conventional superconducting magnet system. The critical current of the insert coil at saturated superfluid helium temperature (1.8 K) in the bias field of 20.8 T, was 275 A, and the field generated at this current was 0.7 T. As a result, we could achieve the field generation of 21.5 T at the center of the magnet system which was the highest field obtained by the full superconducting state.

Kiyoshi Inoue

Papers

Nb3Al Multifilamentary Wires Continuously Fabricated by Rapid-Quenching

Strain effects in Nb3Al multifilamentary conductors prepared by phase transformation from bcc supersaturated-solid solution

Some improvements in laves phase high-field superconductors

High-strength and high-conductivity Cu-Ag alloy sheets: new promising conductor for high-fieId Bitter coils

Generation of 21.5 T by a superconducting magnet system using a Bi2Sr2CaCu2Ox/Ag coil as an insert magnet