Superfunctional high-entropy alloys and ceramics by severe plastic deformation

High-entropy alloys and ceramics containing at least five principal elements have received high attention in recent years for various mechanical and functional applications. The application of severe plastic deformation (SPD), particularly the high-pressure torsion (HPT) method combined with the CALPHAD and first-principles calculations, resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials. This article reviews the recent advances in the application of SPD to achieving superfunctional high-entropy materials. These superfunctional properties include (i) ultrahigh hardness levels in high-entropy alloys which are comparable to ceramics, (ii) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys; (iii) high strength, low elastic modulus, and high biocompatibility in high-entropy alloys, (iv) fast and reversible hydrogen storage in high-entropy alloys and corresponding hydrides, (v) photovoltaic performance and photocurrent generation on high-entropy semiconductors, (vi) photocatalytic oxygen and hydrogen production on high-entropy oxides and oxynitrides from water splitting, and (vii) CO2 photoreduction on high-entropy ceramics. These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to synthesize novel high-entropy materials with superior properties compared with conventional engineering materials

Orientations of galaxies and their distribution in space

Distributions of angular momenta of galaxies can be used to test theories of galaxy origin. The observational problems are discussed in detail. Previously, interpretations have been hampered by physical and physiological selection effects that operate on visual measurements. With the COSMOS machine and the deep Schmidt plates many of these problems should be overcome. Before investigating the COSMOS data, two visual sets of measures, were examined. Firstly, Brown's original uncorrected catalogue of position angles was studied. Previous investigators claim remarkable anisotropies exist in this data, and indeed there are some histograms showing peaks significant at the 4б-level. Further examination reveals little reason for considering these excesses to be physical, and, taking into consideration the number of histograms possible (by splitting the data with various parameters), the anisotropies are too insignificant to use in theoretical arguments. Secondly, a set of visual measurements made on a deep UK Schmidt plate recording both position angles and axis ratios was examined. The position angles are consistent with that expected for a random distribution, except for the smallest galaxies where some selection effect may be involved. There is no evidence for a correlation between position angles of adjacent galaxies. When the quantization effects are taken into account the axial ratio distributions are consistent with a random 3-dimensional orientation of a mixture of 83% spirals and 17% ellipticals. A comparison of the distribution of nearest neighbour separations with that expected for a random distribution of galaxies; on the sky shows that there is clustering. When combined with an estimate of the size of clusters from a covariance analysis a mean number of 6.5 galaxies per cluster is obtained. Using COSMOS coarse mode measurements of a portion of plate R1049, galaxy axial ratio distributions have been obtained. The results can not be explained by any mixture of galaxy types. To check COSMOS, the plate was scanned by eye and an assessment of the machine is provided. At the intermediate sizes l00√m< 2a<200√m the identifications are satisfactory, but for larger images there are unexplained errors in the COSMOS data. For both sizes the agreement between the axial ratios from COSMOS and those measured, by eye is disappointing. It is concluded that further work of this nature must be performed only using the fine-mode facilities of the machine

Superfunctional materials by ultra-severe plastic deformation

Superfunctional materials are defined as materials with specific properties being superior to the normal functions of engineering materials. Numerous studies introduced severe plastic deformation (SPD) as an effective process to improve the functional and mechanical properties of various metallic and non-metallic materials. Moreover, the concept of ultra-SPD - introducing shear strains over 1,000 to reduce the thickness of sheared phases to levels comparable to atomic distances - was recently utilized to synthesize novel superfunctional materials. In this article, after a brief review of the recent advances in the SPD field, the application of ultra-SPD for controlling atomic diffusion and phase transformation and achieving superfunctional properties is discussed. The main properties achieved by ultra-SPD include (i) high-temperature thermal stability in new immiscible age-hardenable aluminum alloys, (ii) room-temperature superplasticity for the first time in magnesium and aluminum alloys, (iii) high strength and high plasticity in nanograined intermetallics, (iv) low elastic modulus and high hardness in biocompatible binary and high-entropy alloys, (v) superconductivity and high strength in the Nb-Ti alloys, (vi) room-temperature hydrogen storage for the first time in magnesium alloys, and (vii) superior photocatalytic hydrogen production, oxygen production, and carbon dioxide conversion on high-entropy oxides and oxynitrides as a new family of photocatalysts

Holographic non-relativistic fermionic fixed point and bulk dipole coupling

Inspired by the recently discovered non-relativistic fermionic fixed points, we investigate how the presence of bulk dipole coupling modifies the spectral function at one of these novel fixed points. As a result, although the infinite flat band is always visible in the presence of the bulk dipole coupling as well as chemical potential, the band is modified in a remarkable way at small momenta up to the order of magnitude of bulk dipole coupling. On the other hand, like a phoenix, a new Fermi surface sprouts from the formed gap when the bulk dipole coupling is pushed up further such as to overshadow the charge parameter, which is obviously different from what is found at the relativistic fixed points.Comment: JHEP style, 1+17 pages, 9 figures, 1 table, typos corrected, references added, version to appear in JHE