Several previous studies demonstrated that defect-free faceted nanocrystals of face-centered cubic metals (such as Au, Ni, and Pd) exhibit extraordinarily high mechanical strength approaching the ...theoretical strength of the respective metals. In the present work, we have studied the compressive strength of Pt nanoparticles fabricated by the solid-state dewetting method optimized for producing nanoparticles with a variety of shapes and sizes. The particles exhibit a well-pronounced size effect on strength, with the smallest particles achieving the highest compressive strength of 9.5 GPa corresponding to the lower limit of the theoretical strength of Pt. However, the average strength of the Pt particles normalized by the respective shear modulus is significantly lower than that of Au and Ni nanoparticles fabricated by a similar dewetting method. We have also established a correlation between the particles strength and shape described by the ratio of the particle top facet and projected diameters. Smaller values of this ratio correlate with higher compressive strength. Based on the experimental data obtained, we formulate a power law describing the combined effect of the particle size and shape on its strength. Our results are in qualitative agreement with previous computational studies demonstrating that the theoretical strength of Pt normalized by its shear modulus is significantly lower than that of other face-centered cubic metals.
Graphical abstract
In this study, one of the severe plastic deformation (SPD) techniques, Equal Channel Angular Pressing (ECAP) has been successfully applied to the Al-Cu-Li alloy AA2195 at 250 °C and the development ...of microstructure, texture and mechanical properties has been studied. A systematic analysis has been carried out by using EBSD and TEM to understand the microstructural features, and the nature of different precipitates presence in the alloy AA2195. Microstructural features indicate considerable grain refinement leading to an average grain size of 2.8 ± 0.7 μm after 4 ECAP passes. Continuous dynamic recrystallization (CDRX) has been identified as the mechanism that leads to the formation of fine grain structure in the alloy AA2195 during the warm ECAP process. TEM results confirm the distribution of strengthening precipitates δ′(Al3Li), β(Al3Zr) and T1(Al2CuLi) in the alloy. The overall texture has become weak after ECAP processing and has been simulated using Visco-plastic self-consistent simulation (VPSC). The evaluation of mechanical properties indicates a substantial increment in hardness, strength properties with a minor reduction of ductility after 4 passes. Low mechanical property anisotropy is expected in the processed AA2195 alloy due to its weak texture.
•Significant grain refinement is achieved in AA2195 alloy after four ECAP passes.•Continuous dynamic recrystallization occurs during ECAP processing at 250 °C.•ECAP leads to overall weakening of texture.•Improvement in strength is achieved after ECAP.
In the present study, the evolution of microstructure, crystallographic texture and their influence on mechanical properties of the Al–Li alloy, AA2195 has been studied. A novel hybrid processing ...route involving warm multi-axial forging (MAF) and subsequent warm rolling was employed. Different rolling procedures were followed to obtain optimal microstructure and properties. The processing conditions significantly influenced the course of evolution of microstructure and texture. A variation in tensile properties as a function of angle from RD for the differently processed samples was noticed. The tensile properties were closer to isotropic case for the samples deformed using a combination of MAF with cross rolling. By controlling grain size and texture through optimal processing, it was possible to achieve isotropic tensile properties in the AA2195 alloy. The processing conditions have also led to enhancement in strength, which has been attributed to grain boundary strengthening, precipitation strengthening and dislocation strengthening.
•A hybrid of severe plastic deformation and rolling leads to optimal microstructure and texture in the alloy AA2195.•The hybrid processed alloy exhibits a better combination of strength and ductility.•The hybrid processed alloy exhibit isotropy in mechanical behaviour.•Hybrid of severe plastic deformation and rolling renders the alloy AA2195 amenable to improved forming.
Longitudinal control signals used to keep gravitational wave detectors at a stable operating point are often affected by modulations from test mass misalignments leading to an elevated noise floor ...ranging from 50 to 500 Hz. Nonstationary noise of this kind results in modulation sidebands and increases the number of glitches observed in the calibrated strain data. These artifacts ultimately affect the data quality and decrease the efficiency of the data analysis pipelines looking for astrophysical signals from continuous waves as well as the transient events. In this work, we develop a scheme to subtract one such bilinear noise from the gravitational wave strain data and demonstrate it at the GEO 600 observatory. We estimate the coupling by making use of narrow-band signal injections that are already in place for noise projection purposes and construct a coherent bilinear signal by a two-stage system identification process. We improve upon the existing filter design techniques by employing a Bayesian adaptive directed search strategy that optimizes across the several key parameters that affect the accuracy of the estimated model. The scheme takes into account the possible nonstationarities in the coupling by periodically updating the involved filter coefficients. The resulting postoffline subtraction leads to a suppression of modulation sidebands around the calibration lines along with a broadband reduction of the midfrequency noise floor. The observed increase in the astrophysical range and a reduction in the occurrence of nonastrophysical transients suggest that the above method is a viable data cleaning technique for current and future generation gravitational wave observatories.
In the present work, attempts have been made to control the yield strength anisotropy in an Al–Cu-Li alloy by implementing a novel processing route combining multi-axial forging (MAF) and rolling ...with an aim to weaken the texture. It has been observed that continuous destabilization of deformation texture during MAF results in weakening of texture. Further weakening of texture could be achieved upon post MAF cold cross rolling, which has been attributed to (i) the geometry induced shear in the roll gap, and (ii) the change in strain path during rolling. Such a weak texture is in contrast to strong Brass-type texture, generally observed in these alloys. Further annealing in the solution treatment regime led to even more weakening of texture. Uniaxial tensile tests along different directions of the as-processed sheets confirmed the weak dependency of yield strength on orientation of tensile axis.
•Novel processing route of multiaxial forging and rolling is proposed for texture weakening of Al-Cu-Li alloys.•Texture weakening is due to continuous change in reference frame during multiaxial forging.•Further weakening of texture occurs due to geometric induced shear and change in strain path imposed during rolling.•Highly isotropic mechanical properties are obtained via the proposed processing method.
Shock-induced plasticity in FCC crystals has been demonstrated in many experimental and numerical simulation studies. Even though some theories have been proposed with regard to dislocation ...nucleation, the phenomenon occurring in the elastically shock-compressed region and the elastic–plastic transition region, which might be the origin region for dislocation nucleation, is largely unexplored. In this work, we present a molecular dynamics simulation of the shock compression of a Cu single crystal along the 〈110〉 direction specifically focusing on the mechanisms observed in the elastically compressed and the elastic–plastic transition regions. A distribution of planes of high and low atomic volume is observed in the elastically compressed region near the shock front, but the distribution becomes random as the elastic–plastic transition regime is approached. Density variations are also observed. It is observed that the formation of the defects initiates through local atomic shuffling/rearrangement. Shear stress distribution shows values greater than those required for homogeneous nucleation, and Shockley partials are observed at a certain region behind the shock front. Potential energy variations are also observed in these regions, explaining the mechanisms leading to dislocation nucleation. The present findings shed new insight into the mechanism of dislocation nucleation in shock-induced single-crystal FCC metals.
Conducting polymers have recently been employed with metal derivative macromolecules that have led to great improvement in the field of supercapacitor materials. The current work reports on the ...synthesis of a novel class of haemoglobin/polyindole composites (HPCs) through doping of haemoglobin (Hb) into a polyindole (PIN) matrix. HPCs with enhanced electrocapacitive performance were prepared through a cationic surfactant-assisted dilute solution polymerization of indole (IN) in the presence of Hb at various concentrations ranging from 10 to 30% (w/w) and ferric chloride (
FeCl
3
) as an oxidant. The HPCs were characterized through Fourier transform infrared spectra, scanning electron microscopy and simultaneous thermogravimetric analysis. Electrochemical capacitance (
C
s
,
F
g
-
1
) of graphite-based electrodes fabricated from HPCs over stainless steel in the presence of sulphonated polysulphone as a binder has been investigated in KOH solution (1.0 M) with reference to Ag/AgCl at a scan rate (
V
s
-
1
) ranging from 0.001 to 0.2. HPCs with 30% (w/w) of Hb have shown the highest
C
s
of 294.00 as compared with 112.00 for pure PIN at a scan rate of
0.001
V
s
-
1
. Successive scans of HPC electrodes show a capacitive decline of
∼
2
%
during the first 1000 cycles at a scan rate of
0.1
V
s
-
1
in KOH (1.0 M), which indicates the appreciable electrochemical cyclic stability of the HPCs over PIN. Thus, the fabricated HPCs may serve as potential electrode material for development of electrochemical supercapacitors.
SUMMARY
The International Haemovigilance Network (IHN) defines haemovigilance as ‘a set of surveillance procedures covering the whole transfusion chain (from the collection of blood and its ...components to the follow‐up of recipients), intended to collect and assess information on unexpected or undesirable effects resulting from the therapeutic use of labile blood products, and to prevent their occurrence or recurrence’. IHN, the International Society of Blood Transfusion and World Health Organization work together to support both developing and established haemovigilance systems.
Haemovigilance systems provide valuable data on a range of adverse events related to blood donation and clinical transfusion, from donor syncopal events to transfusion‐transmitted infections, immunological complications and the impact of human errors. Harmonised definitions for most adverse reactions have been developed and validated internationally. Definitions of pulmonary complications are again under review.
Haemovigilance data have resulted in changes in policy, products and practice, and can complement and inform clinical audit and research, leading to improved blood donor safety, optimised product use and better clinical outcomes after transfusion.
However, more work is needed. Not all countries have haemovigilance systems in place. More robust data and careful analysis are required to improve the understanding of the causes, occurrence and clinical outcomes of these events. Wider dissemination of results will facilitate health policy development internationally, and implementation of haemovigilance recommendations will support further important progress in blood safety.
Large scale laser interferometric gravitational wave detectors (GWDs), such as GEO 600 require high quality optics to reach their design sensitivity. The inevitable surface imperfections, ...inhomogeneities, and light-absorption induced thermal lensing in the optics, can convert laser light from the fundamental mode to unwanted higher order modes, and pose challenges to the operation and sensitivity of the GWDs. Here we demonstrate the practical implementation of a thermal projection system which reduces those unwanted effects via targeted spatial heating of the optics. The thermal projector consists of 108 individually addressable heating elements which are imaged onto the beam splitter of GEO 600. We describe the optimization of the spatial heating profile and present the obtained results.
Beam alignment is an important practical aspect of the application of squeezed states of light. Misalignments in the detection of squeezed light result in a reduction of the observable squeezing ...level. In the case of squeezed vacuum fields that contain only very few photons, special measures must be taken in order to sense and control the alignment of the essentially dark beam. The GEO 600 gravitational wave detector employs a squeezed vacuum source to improve its detection sensitivity beyond the limits set by classical quantum shot noise. Here, we present our design and implementation of an alignment sensing and control scheme that ensures continuous optimal alignment of the squeezed vacuum field at GEO 600 on long time scales in the presence of free-swinging optics. This first demonstration of a squeezed light automatic alignment system will be of particular interest for future long-term applications of squeezed vacuum states of light.
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