Full-field strain around propagating shear bands and von mises criteria for metallic glasses

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Size effect in polymer-supported ultrathin metallic glass films

Although metallic glasses (MGs) exhibit a unique combination of mechanical and chemical properties, their application as structural or functional materials is hindered by the lack of ductility which leads to catastrophic brittle-like fracture. When the size of a MG sample is reduced below some critical value, typically of the order of a few hundred nanometers, then considerable ductility can be observed. However, this size effect was demonstrated so far mostly by nanomechanical testing inside a transmission electron microscope using samples prepared by focused ion beam (FIB) milling. Whether the ductile-like behavior of submicrometer-sized metallic glasses is a real “intrinsic” size effect or it is rather caused by extrinsic factors like sample shape, ion beam effect or parameters of the testing setup is currently a subject of extensive discussions in the community. In this contribution the tensile properties of thin film Pd82Si18 MGs grown by sputter deposition on a polymer substrate are considered. The integrity of the MG films during stretching was monitored by in-situ measurements of the electrical resistance. An overview of electro-mechanical behavior of considered films is demonstrated in Fig. 1.The 250, 100, and 60 nm thick films fail in a brittle manner at 2% strain through propagation of long cracks perpendicularly to the straining direction. The rapid crack propagation in these films results in rapid increase of in-situ resistance signal. The size effect on the deformation behavior appears when the film thickness drops below 15 nm. The 7 nm thick films with the same composition show a crack-free deformation up to a strain of 7%. Even at higher strains no brittle-like failure but rather short and isolated cracks are observed. Cyclic tensile loading revealed extreme fracture resistance of ultrathin amorphous films showing no cracks after 30000 stretching cycles with a strain amplitude of 3%. Since all tests are performed at ambient conditions on films deposited using an industrially scalable process, the demonstrated size effect can be directly utilized for applications, such as protective coatings, nanoelectromechanical devices or half-transparent conductive layers for flexible electronics. Please click Additional Files below to see the full abstract

Role of film microstructure on interface stability: in-situ and ex-situ investigations

Thin film adhesion is an important measure to quantify the stability of thin film – substrate interfaces. Film thickness, film microstructure, residual stresses as well as chemical reactions at the interface determine this value and it is often difficult to decouple each individual factor to study their influence on interface adhesion. In the following study the role of grain size on the interface stability was investigated for a model system at constant film thickness with comparable residual stresses. Therefore, 100 nm thin Cu films were sputtered on glass substrates. The film microstructure was tuned by a change of Argon pressure during deposition and by isothermal heat treatments post-deposition. To quantify the adhesion of the obtained Cu films, 500 nm thick, highly stressed Mo overlayers were deposited on the films leading to a spontaneous delamination at the Cu-glass interface in the shape of straight and telephone cord buckles. The model of Hutchinson & Suo could then be extended to a bilayer problem, allowing to determine adhesion for each Cu-glass system. The small grained films revealed improved adhesion compared to the large grained films. Detailed characterizations of the Cu film microstructures as well as the particular interfaces were conducted by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Finally, to study the plasticity mechanisms upon delamination, cyclic bending experiments were conducted in-situ in the TEM to observe the crack propagation towards the Cu-glass interface as a function of the film microstructure. Please click Additional Files below to see the full abstract

Synthesis of bulk reactive Ni-Al composites using high pressure torsion

17 USC 105 interim-entered record; under review.The article of record as published may be found at http://dx.doi.org/10.1016/j.jallcom.2020.157503Self-propagating exothermic reactions, for instance in the nickel-aluminum (Ni-Al) system, have been widely studied to create high performance intermetallic compounds or for in-situ welding. Their easy ignition once the phase spacing is reduced below the micron scale, makes top-down methods like high energy ball milling, ideal to fabricate such reactive nanostructures. A major drawback of ball milling is the need of a sintering step to form bulk pieces of the reactive material. However, this is not possible, as the targeted reactions would already proceed. Therefore, we investigate the ability of high pressure torsion as an alternative process, capable to produce bulk nanocomposites from powder mixtures. Severe straining of powder mixtures with a composition of 50 wt% Ni and 50 wt% Al enables fabrication of self reactive bulk samples with microstructures similar to those obtained from ball milling or magnetron sputtering. Samples deformed at ambient temperature are highly reactive and can be ignited signifi cantly below the Al melting point, finally predominantly consisting of Al3Ni2 and Al3Ni, independent of the applied strain. Although the reaction proceeds first at the edge of the disk, the strain gradient present in the disks does not prevent reaction of the whole sample.COMETAustrian Federal MinistriesDepartment of Energy National Nuclear Security AdministrationERC Advanced Grant INTELHYBCOMET programERC-2013-ADG-340025DENA0002377Project No 859480DE-AC02-06CH1135

Effectiveness of an additional individualized multi-component complementary medicine treatment on health-related quality of life in breast cancer patients: a pragmatic randomized trial

The aim of this study was to evaluate the effectiveness of an additional, individualized, multi-component complementary medicine treatment offered to breast cancer patients at the Merano Hospital (South Tyrol) on health-related quality of life compared to patients receiving usual care only. A randomized pragmatic trial with two parallel arms was performed. Women with confirmed diagnoses of breast cancer were randomized (stratified by usual care treatment) to receive individualized complementary medicine (CM group) or usual care alone (usual care group). Both groups were allowed to use conventional treatment for breast cancer. Primary endpoint was the breast cancer-related quality of life FACT-B score at 6 months. For statistical analysis, we used analysis of covariance (with factors treatment, stratum, and baseline FACT-B score) and imputed missing FACT-B scores at 6 months with regression-based multiple imputation. A total of 275 patients were randomized between April 2011 and March 2012 to the CM group (n = 136, 56.3 ± 10.9 years of age) or the usual care group (n = 139, 56.0 ± 11.0). After 6 months from randomization, adjusted means for health-related quality of life were higher in the CM group (FACT-B score 107.9; 95 % CI 104.1-111.7) compared to the usual care group (102.2; 98.5-105.9) with an adjusted FACT-B score difference between groups of 5.7 (2.6-8.7, p < 0.001). Thus, an additional individualized and complex complementary medicine intervention improved quality of life of breast cancer patients compared to usual care alone. Further studies evaluating specific effects of treatment components should follow to optimize the treatment of breast cancer patients

Effects of Place of Articulation Changes on Auditory Neural Activity: A Magnetoencephalography Study

In casual speech, phonemic segments often assimilate such that they adopt features from adjacent segments, a typical feature being their place of articulation within the vocal tract (e.g., labial, coronal, velar). Place assimilation (e.g., from coronal /n/ to labial /m/: rainbow→*raimbow) alters the surface form of words. Listeners' ability to perceptually compensate for such changes seems to depend on the phonemic context, on whether the adjacent segment (e.g., the /b/ in “rainbow”) invites the particular change. Also, some assimilations occur frequently (e.g., /n/→/m/), others are rare (e.g., /m/→/n/). We investigated the effects of place assimilation, its contextual dependency, and its frequency on the strength of auditory evoked mismatch negativity (MMN) responses, using pseudowords. Results from magnetoencephalography (MEG) revealed that the MMN was modulated both by the frequency and contextual appropriateness of assimilations

The Roles of Impurities and Surface Area on Thermal Stability and Oxidation Resistance of BN Nanoplatelets

This study considers the influence of purity and surface area on the thermal and oxidation properties of hexagonal boron nitride (h-BN) nanoplatelets, which represent crucial factors in hightemperature oxidizing environments. Three h-BN nanoplatelet-based materials, synthesized with different purity levels and surface areas (~3, ~56, and ~140 m2/g), were compared, including a commercial BN reference. All materials were systematically analyzed by various characterization techniques, including gas pycnometry, scanning electron microscopy, X-ray diffraction, Fouriertransform infrared radiation, X-ray photoelectron spectroscopy, gas sorption analysis, and thermal gravimetric analysis coupled with differential scanning calorimetry. Results indicated that the thermal stability and oxidation resistance of the synthesized materials were improved by up to ~13.5% (or by 120 ◦C) with an increase in purity. Furthermore, the reference material with its high purity and low surface area (~4 m2/g) showed superior performance, which was attributed to the minimized reactive sites for oxygen diffusion due to lower surface area availability and fewer possible defects, highlighting the critical roles of both sample purity and accessible surface area in h-BN thermooxidative stability. These findings highlight the importance of focusing on purity and surface area control in developing BN-based nanomaterials, offering a path to enhance their performance in extreme thermal and oxidative conditions