The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

http://repository.ust.hk/ir/bitstream/1783.1-77094/1/acs.chemrev.5b00462_withlink.pdf

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

This review covers important advances in recent years in the physics of thin-film ferroelectric oxides, the strongest emphasis being on those aspects particular to ferroelectrics in thin-film form. The authors introduce the current state of development in the application of ferroelectric thin films for electronic devices and discuss the physics relevant for the performance and failure of these devices. Following this the review covers the enormous progress that has been made in the first-principles computational approach to understanding ferroelectrics. The authors then discuss in detail the important role that strain plays in determining the properties of epitaxial thin ferroelectric films. Finally, this review ends with a look at the emerging possibilities for nanoscale ferroelectrics, with particular emphasis on ferroelectrics in nonconventional nanoscale geometries.

/pdf/physics-of-thin-film-ferroelectric-oxides-3zmqphtpv1.pdf

Physics of thin-film ferroelectric oxides

Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics are reviewed with the aim of providing an insight into different processes which may affect the behaviour of ferroelectric devices, such as ferroelectric memories and micro-electro-mechanical systems. Taking into consideration recent advances in this field, topics such as polarization switching, polarization fatigue, effects of defects, depletion layers, and depolarization fields on hysteresis loop behaviour, and contributions of domain-wall displacement to dielectric and piezoelectric properties are discussed. An introduction into dielectric, pyroelectric, piezoelectric and elastic properties of ferroelectric materials, symmetry considerations, coupling of electro-mechanical and thermal properties, and definitions of relevant ferroelectric phenomena are provided.

https://iopscience.iop.org/article/10.1088/0034-4885/61/9/002/pdf

Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics

Quantitative measurement of displacement and strain fields from HREM micrographs

This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

Colossal carbon supersaturation in austenitic stainless steels carburized at low temperature

Present knowledge on metal-oxide interfaces is reviewed, emphasizing fundamental properties and behaviour. Methods have become available to fabricate ‘ideal’ metal-oxide interfaces with precisely controlled chemistry, special crystallography and high structural perfection. Recent experimental investigations of such model systems have advanced the understanding of adhesion, structure, mechanical behaviour and diffusion reactions at metal-oxide interfaces. In parallel, physical theories and powerful methods of computer modelling have been pushed forward to predict and to interpret the experimental observations. As an important development, recent work increasingly explores the correlation between microscopic properties of metal-oxide interfaces and their technically important macroscopic behaviour.

Metal-oxide interfaces

In a combined theoretical and experimental study, the energies and structures of σ = 3, [011] tilt boundaries in Cu were investigated. Equilibrium atomistic structures and grain-boundary energies were calculated by static energy minimization using an embedded-atom potential. Cu bicrystals of the same boundary orientations were fabricated by welding of Cu single crystals. Grain-boundary energies were measured by the thermal grooving technique. The atomistic structure of the {211} twin boundary was investigated by high-resolution transmission electron microscopy (HRTEM). The calculated grain-boundary energies γb plotted against the inclination of the boundary plane show a minimum for the {111} twin boundary and a second minimum at an inclination of about 82° to the {111} boundary. The calculated dependence of γb on inclination is confirmed by the measured energies over the entire range. Common to all calculated boundary structures is a microfaceting into {111} and {211} twin facets. The structures ...

The influence of grain boundary inclination on the structure and energy of Σ=3 grain boundaries in copper

Carbon supersaturation due to paraequilibrium carburization: Stainless steels with greatly improved mechanical properties

In a stack of vertically aligned Stranski–Krastanov grown islands, the critical thickness for planar growth for all but the initial dot layer is reduced, if the thickness of the spacer layer ts is smaller than a certain value t0. We present structural and photoluminescence results on the basis of the extensively studied lattice-mismatched material system Si/Ge.

Frank Ernst

Papers

Colossal carbon supersaturation in austenitic stainless steels carburized at low temperature

Metal-oxide interfaces

The influence of grain boundary inclination on the structure and energy of Σ=3 grain boundaries in copper

Carbon supersaturation due to paraequilibrium carburization: Stainless steels with greatly improved mechanical properties

Modified Stranski–Krastanov growth in stacked layers of self-assembled islands