To date the strategy for inducing pinning in REBa2Cu3O7−x (REBCO where RE = rare-earth) coated conductors has largely been empirical. Hence, we are not yet at a point where we can dial-in the compositions and process parameters to optimise pinning for particular applications having specific temperature, field, and field angle requirements. In this review, we cover the critical materials science aspects which enable the understanding, design and engineering of desired pinning centre morphologies. Our main emphasis is on in in situ epitaxial growth of REBCO films by vapour deposition. We review the optimal pinning centre morphologies which have been determined to be effective for different operation regimes. We also highlight how the interplay of thermodynamics (including epitaxial effects), film-particle interfacial strain, and kinetics determine pinning morphologies. Finally, we also briefly cover pinning in rapid ex situ, liquid assisted growth which is likely to be a necessary universal approach for applications where low cost is critical.

Highly crystalline graphene nanosheets were reproducibly generated by the electrochemical exfoliation of graphite electrodes in molten LiCl containing protons. The graphene product has been successfully applied in several applications. This paper discusses the effect of molten salt produced graphene on the microstructures and mechanical properties of alumina articles produced by slip casting and pressureless sintering, which is one of the most convenient methods for the commercial production of alumina ceramics. In addition to graphene, graphite powder and multi-walled carbon nanotubes (CNTs) were also used to prepare alumina articles for comparative purposes. A graphene strengthening effect was realized through microstructural refinement and by influencing the formation of alumina nanorods during the sintering of α-Al2O3 articles. The fracture toughness of the sintered alumina articles increased to an impressive value of 6.98 MPa m(1/2) by adding 0.5 wt% graphene nanosheets. This was attributed to the unique microstructure obtained, comprised of micrometer sized alumina grains separated by alumina nanorods.

A long-term goal for superconductors is to increase the superconducting transition temperature, TC. In cuprates, TC depends strongly on the out-of-plane Cu-apical oxygen distance and the in-plane Cu-O distance, but there has been little attention paid to tuning them independently. Here, in simply grown, self-assembled, vertically aligned nanocomposite thin films of La2CuO4+δ + LaCuO3, by strongly increasing out-of-plane distances without reducing in-plane distances (three-dimensional strain engineering), we achieve superconductivity up to 50 K in the vertical interface regions, spaced ~50 nm apart. No additional process to supply excess oxygen, e.g., by ozone or high-pressure oxygen annealing, was required, as is normally the case for plain La2CuO4+δ films. Our proof-of-concept work represents an entirely new approach to increasing TC in cuprates or other superconductors.

Structural and transport properties of YBa 2 Cu 3 O 7-x films grown by pulsed laser deposition with mixed 2.5 mol.% Ba 2 YTaO 6 (BYTO) and 2.5 mol.% Ba 2 YNbO 6 (BYNO) double-perovskite secondary phases are investigated in an extended film growth rate, R = 0.02 -1.8 nm/s. The effect of R on the film microstructure analyzed by TEM techniques shows an evolution from sparse and straight to denser, thinner and splayed continuous columns, with mixed BYNO+BYTO (BYNTO) composition, as R increases from 0.02 nm/s to 1.2 nm/s. This microstructure results in very efficient flux pinning at 77 K leading to a remarkable improvement of the J c behaviour, with the maximum of the pinning force density F p (Max) = 13.5 GN/m 3 and the irreversibility field in excess of 11 T. In this range, the magnetic field values at which the F p , is maximized varies from 1 T to 5 T being related to the BYNTO columnar density. The film deposited with R = 0.3 nm/s exhibits the best performances over the whole temperature and magnetic field ranges achieving F p (Max) = 900 GN/m 3 at 10 K and 12 T. At higher rates, R > 1.2 nm/s, BYNTO columns show a meandering nature and are prone to form short nanorods. In addition, in the YBCO film matrix a more disordered structure with a high density of short stacking faults is observed. From the analysis of the F p (H, T) curves it emerges that in films deposited at the high R limit, the vortex pinning is no longer dominated by BYNTO columnar defects, but by a new mechanism showing the typical temperature scaling law. Even though this microstructure produces a limited improvement at 77 K, it exhibits a strong J c improvement at lower temperature with F p = 700 GN/m 3 at 10 K, 12 T and 900 GN/m 3 at 4.2 K, 18 T.

In self-assembled vertically aligned nanocomposite (VAN) thin films of La2CuO4+δ + LaCuO3, we find from DC magnetic susceptibility measurements, weak signatures of superconductivity at ∼120 K.