Strain localization during plastic deformation drastically reduces the shear band stability in metallic glasses, ultimately leading to catastrophic failure. Therefore, improving the plasticity of ...metallic glasses has been a long-standing goal for several decades. In this regard, nanoglass, a novel type of metallic glass, has been proposed to exhibit differences in short and medium range order at the interfacial regions, which could promote the formation of shear transformation zones. In the present work, by introducing heterogeneities at the nanoscale, both crystalline and amorphous, significant improvements in plasticity are realized in micro-compression tests. Both amorphous and crystalline dispersions resulted in smaller strain bursts during plastic deformation. The yield strength is found to increase significantly in Cu–Zr nanoglasses compared to the corresponding conventional metallic glasses. The reasons for the mechanical behavior and the importance of nanoscale dispersions to tailor the properties is discussed in detail.
Graphic Abstract
Clusters with diverse structures and functions have been used to create novel cluster‐assembled materials (CAMs). Understanding their self‐assembly process is a prerequisite to optimize their ...structure and function. Herein, two kinds of unlike organo‐functionalized inorganic clusters are covalently linked by a short organic tether to form a dumbbell‐shaped Janus co‐cluster. In a mixed solvent of acetonitrile and water, it self‐assembles into a crystal with a honeycomb superstructure constructed by hexagonal close‐packed cylinders of the smaller cluster and an orderly arranged framework of the larger cluster. Reconstruction of these structural features via coarse‐grained molecular simulations demonstrates that the cluster crystallization and the nanoscale phase separation between the two incompatible clusters synergistically result in the unique nano‐architecture. Overall, this work opens up new opportunities for generating novel CAMs for advanced future applications.
How to pack dumbbells: The size asymmetry and Janus characteristics of a dumbbell‐shaped co‐cluster synergistically define its self‐assembly in solution into crystals with a filled‐honeycomb superstructure. The Janus co‐cluster consists of a POM (purple sphere) and a POSS (green sphere) linked by an organic tether.
4D-STEM-PDF is implemented as a new approach to image the phase distribution in organic nanocomposites including information on the short- and medium range order in each phase enabling atomic level ...structural analysis.
Abstract
Imaging the phase distribution of amorphous or partially crystalline organic materials at the nanoscale and analyzing the local atomic structure of individual phases has been a long-time challenge. We propose a new approach for imaging the phase distribution and for analyzing the local structure of organic materials based on scanning transmission electron diffraction (4D-STEM) pair distribution function analysis (PDF). We show that electron diffraction based PDF analysis can be used to characterize the short- and medium-range order in aperiodically packed organic molecules. Moreover, we show that 4D-STEM-PDF does not only provide local structural information with a resolution of a few nanometers, but can also be used to image the phase distribution of organic composites. The distinct and thickness independent contrast of the phase image is generated by utilizing the structural difference between the different types of molecules and taking advantage of the dose efficiency due to use of the full scattering signal. Therefore, this approach is particularly interesting for imaging unstained organic or polymer composites without distinct valence states for electron energy loss spectroscopy. We explore the possibilities of this new approach using 6,6-phenyl-C61- butyric acid methyl ester (PC61BM) and poly(3-hexylthiophene-2,5-diyl) (P3HT) as the archetypical and best-investigated semiconductor blend used in organic solar cells, compare our phase distribution with virtual dark-field analysis and validate our approach by electron energy loss spectroscopy.
We report the preparation of monodisperse silicon nanocrystals (ncSi) by size-separation of polydisperse alkyl-capped ncSi using organic density gradient ultracentrifugation. The ncSi were ...synthesized by thermal processing of trichlorosilane-derived sol-gel glasses followed by HF etching and surface passivation with alkyl chains and were subsequently fractionated by size using a self-generating density gradient of 40 wt % 2,4,6-tribromotoluene in chlorobenzene. The isolated monodisperse fractions were characterized by photoluminescence spectroscopy and high-angle annular dark-field scanning transmission electron microscopy and determined to have polydispersity index values between 1.04 and 1.06. The ability to isolate monodisperse ncSi will allow for the quantification of the size-dependent structural, optical, electrical, and biological properties of silicon, which will undoubtedly prove useful for tailoring property-specific optoelectronic and biomedical devices.
Structure and Properties of Nanoglasses Ivanisenko, Yulia; Kübel, Christian; Nandam, Sree Harsha ...
Advanced engineering materials,
December 2018, Letnik:
20, Številka:
12
Journal Article
Recenzirano
Nanoglasses represent a novel structural modification of amorphous materials, exhibiting properties and structural details that are markedly different from those observed in metallic glasses prepared ...by rapid quenching. In this review, the synthesis method and the techniques used for charactering the structure of nanoglasses are described together with our current understanding of their salient microstructural features. It is believed that the structure of nanoglasses consists of two distinct amorphous regions give rise to mechanical, thermal, and magnetic properties that are significantly different from those observed in rapidly quenched (RQ) metallic glasses. Nanoglasses, therefore, constitute a distinct new class of amorphous materials and thus opening up new opportunities for their potential use in a number of structural and functional applications.
Nanoglasses constitute a distinct new class of amorphous materials exhibiting a range of novel properties, not present in metallic glasses prepared by rapid quenching. Nanoglasses exhibit internal structural features on the length scale of a few nanometers, and therefore their microstructure can be tailored which opens up the opportunity for their potential use as structural and functional materials.
The development of competitive rechargeable Mg batteries is hindered by the poor mobility of divalent Mg ions in cathode host materials. In this work, we explore the dual cation co-intercalation ...strategy to mitigate the sluggishness of Mg
in model TiS
material. The strategy involves pairing Mg
with Li
or Na
in dual-salt electrolytes in order to exploit the faster mobility of the latter with the aim to reach better electrochemical performance. A combination of experiments and theoretical calculations details the charge storage and redox mechanism of co-intercalating cationic charge carriers. Comparative evaluation reveals that the redox activity of Mg
can be improved significantly with the help of the dual cation co-intercalation strategy, although the ionic radius of the accompanying monovalent ion plays a critical role on the viability of the strategy. More specifically, a significantly higher Mg
quantity intercalates with Li
than with Na
in TiS
. The reason being the absence of phase transition in the former case, which enables improved Mg
storage. Our results highlight dual cation co-intercalation strategy as an alternative approach to improve the electrochemical performance of rechargeable Mg batteries by opening the pathway to a rich playground of advanced cathode materials for multivalent battery applications.
In this work, the thermal stability of the strongly elongated and textured ultrafine-grained microstructure of a high-strength low-alloy steel processed by linear flow splitting is investigated. The ...annealing behavior is studied for α- and γ-fiber orientations, which are dominant in the rolling type texture of the material and are known for their differences in stored energy in conventionally cold rolled steels. Electron backscatter diffraction is used to assess contributions from curvature-driven boundary migration while the contribution of strain-induced migration is investigated by comparing the annealing behavior of prerecovered to non-prerecovered samples. The exact nature of the coarsening process is studied using in situ TEM heat treatments and complementary ACOM analysis. The results show that the observed preferred growth of α-fiber grains can be fully described by curvature-driven grain boundary migration and that there is no indication for the relevance of gradients in dislocation density.
A method for the fabrication of flexible electrical circuits on polyaramid substrates is presented based on laser-induced carbonization followed by copper electroplating. Locally carbonized flexible ...sheets of polyaramid (Nomex), by laser radiation, create rough and highly porous microstructures that show a higher degree of graphitization than thermally carbonized Nomex sheets. The found recipe for laser-induced carbonization creates conductivities of up to ∼45 S cm
, thereby exceeding that observed for thermally pyrolyzed materials (∼38 S cm
) and laser carbon derived from Kapton using the same laser wavelength (∼35 S cm
). The electrical conductivity of the carbonized tracks was further improved by electroplating with copper. To demonstrate the electrical performance, fabricated circuits were tested and improvement of the sheet resistance was determined. Copper films exhibit antimicrobial activity and were used to fabricate customized flexible antibacterial coatings. The integration of laser carbonization and electroplating technologies in a polyaramid substrate points to the development of customized circuit designs for smart textiles operating in high-temperature environments.
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