Strain Profiling of a Ferritic‐Martensitic Stainless Steel Sheet — Comparing Synchrotron with Conventional X‐Ray Diffraction

To improve the fatigue resistance of stainless steel sheet, it is a common practice to induce compressive residual stress in the surface through shot‐peening or tumbling. Stress depth profiles obtained by tumbling of thin stainless steel tensile rods were analysed using laboratory and synchrotron X‐Ray Diffraction (XRD). Both the non‐destructive synchrotron and the laboratory XRD etch‐depth profile gave similar results: a residual stress profile decaying over a depth not exceeding 50 µm into the material.     

X‐Ray Absorption Spectroscopy Characterizations on PGM‐Free Electrocatalysts: Justification,Advantages, and Limitations

Transition metals embedded in nitrogen‐doped carbon matrices (denoted as M‐N‐C) are the leading platinum group metal (PGM)‐free electrocatalysts for the oxygen reduction reaction (ORR) in acid, and are the most promising candidates for replacing platinum in practical devices such as fuel cells. Two of the long‐standing puzzles in the field are the nature of active sites for the ORR and the reaction mechanism. Poor understanding of the structural and mechanistic basis for the exceptional ORR activity of M‐N‐C electrocatalysts impedes rational design for further improvements. Recently, synchrotron‐based X‐ray absorption spectroscopy (XAS) has been successfully implemented to shed some light on these two issues. In this context, a critical review is given to detail the contribution of XAS to the advancement of the M‐N‐C electrocatalysis to highlight its advantages and limitations.     

In‐Situ Synchrotron X‐Ray Microtomography Studies of Microstructure and Damage Evolution in Engineering Materials

In materials science X‐ray microtomography has evolved as an increasingly utilized technique for characterizing the 3D microstructure of materials. The fundamentals of X‐ray microtomography experimental methods and the reconstruction and data evaluation processes are briefly described. A review of in‐situ synchrotron X‐ray microtomography studies in literature is given. Examples of recent work include in‐situ microtomography investiagtions of metallic foams, in‐situ studies of the sintering of copper particles, and in‐situ investigations of creep damage evolution in composites. Future perspectives of in‐situ X‐ray microtomography studies in materials science are outlined.     

Rapid,High‐Temperature,In Situ Microwave Synthesis of Bulk Nanocatalysts

Carbon‐black‐supported nanoparticles (CNPs) have attracted considerable attention for their intriguing catalytic properties and promising applications. The traditional liquid synthesis of CNPs commonly involves demanding operation conditions and complex pre‐ or post‐treatments, which are time consuming and energy inefficient. Herein, a rapid, scalable, and universal strategy is reported to synthesize highly dispersed metal nanoparticles embedded in a carbon matrix via microwave irradiation of carbon black with preloaded precursors. By optimizing the amount of carbon black, the microwave absorption is dramatically improved while the thermal dissipation is effectively controlled, leading to a rapid temperature increase in carbon black, ramping to 1270 K in just 6 s. The whole synthesis process requires no capping agents or surfactants, nor tedious pre‐ or post‐treatments of carbon black, showing tremendous potential for mass production. As a proof of concept, the synthesis of ultrafine Ru nanoparticles (≈2.57 nm) uniformly embedded in carbon black using this microwave heating technique is demonstrated, which displays remarkable electrocatalytic performance when used as the cathode in a Li–O₂ battery. This microwave heating method can be extended to the synthesis of other nanoparticles, thereby providing a general methodology for the mass production of carbon‐supported catalytic nanoparticles.     

YBCO超导薄膜进氧脱氧过程的原位X射线衍射研究

用原位X射线衍射法研究了磁控溅射c取向YBa2 Cu3 O6+x/SrTiO3 (YBCO/STO)优质超导外延膜在 3 2 5℃氧气中的进氧过程和氮气中的脱氧过程。研究表明 ,薄膜的进氧和脱氧过程快慢相当 ,进脱氧过程都由氧扩散控制。     

Quantitative High‐Dynamic‐Range Electron Diffraction of Polar Nanodomains in Pb2ScTaO6

Highly B‐site ordered Pb₂ScTaO₆ crystals are studied as a function of temperature via dielectric spectroscopy and in situ high‐dynamic‐range electron diffraction. The degree of ordering is examined on the local and macroscopic scale and is determined to be 76%. Novel analysis of the electron diffraction patterns provides structural information with two types of antiferroelectric displacements determined to be present in the polar structure. It is then found that a low‐temperature transition occurs on cooling at ≈210 K that is not present on heating. This phenomenon is discussed in terms of the freezing of dynamic polar nanodomains where a high density of domain walls creates a metastable state.