•As-cast and annealed high entropy alloys FeCrCoNiMnxVy (x, y=0, 1) were studied.•V turned CoCrFeNiMnx single FCC phase structure to σ phase matrix with FCC particles.•No effect of annealing on the ...phase composition of the alloys was observed.•Formation of σ phase resulted in considerable strengthening and loss in ductility.
Microstructure and mechanical properties of equimolar composition alloys FeCrCoNi, FeCrCoNiV, FeCrCoNiMn and FeCrCoNiMnV were studied in as-solidified and annealed conditions. The FeCrCoNi and FeCrCoNiMn alloys were single-phase FCC solid-solutions in both conditions. However, the FeCrCoNiV and FeCrCoNiMnV alloys consisted of the intermetallic σ-phase matrix with a tetragonal crystal lattice and precipitates of a disordered FCC phase. The crystal structures of these alloys were found to be not affected by annealing. A number of criteria were considered to explain phase composition of the studied alloys. It was shown that poor compatibility of V with other alloying elements caused significant distortions of FCC solid solution and thus promoted formation of the σ phase. Tensile and compressive properties of these alloys together with their microhardness were determined. Significant strengthening accompanied by the loss of ductility due to formation of the σ phase was demonstrated in the V containing alloys. The characteristics of the microstructure formation in the studied alloys were discussed.
Ni
Mn
In
(close to 2-1-1 system) Heusler alloy was studied by magnetization measurement dependence on the temperature in magnetic fields of up to 13.5 T. The magnetocaloric effect measured by the ...direct method in quasi-adiabatic conditions showed a maximum value of ∆T
= -4.2 K at a temperature T = 212 K in a magnetic field of 10 T in the region of martensitic transformation. The structure of the alloy was studied by transmission electron microscopy (TEM) as a function of the temperature and the thickness of the sample foil. In the temperature range from 353 to 215 K, at least two processes were established. The results of the study indicate that the concentration stratification occurs according to the mechanism of spinodal decomposition (conditionally spinodal decomposition) into nanoscale regions. At a temperature of 215 K and lower, martensitic phase with 14 M modulation is observed in the alloy at thicknesses greater than 50 nm. Some austenite is also observed. In foils with thickness of less than 50 nm in a temperature range from 353 to 100 Km only the initial austenite, which has not transformed, was found.
We have developed a deep generative model, generative tensorial reinforcement learning (GENTRL), for de novo small-molecule design. GENTRL optimizes synthetic feasibility, novelty, and biological ...activity. We used GENTRL to discover potent inhibitors of discoidin domain receptor 1 (DDR1), a kinase target implicated in fibrosis and other diseases, in 21 days. Four compounds were active in biochemical assays, and two were validated in cell-based assays. One lead candidate was tested and demonstrated favorable pharmacokinetics in mice.
Abstract The harmonic modulation of coherent systems gives rise to a wealth of physical phenomena, e.g., the AC-Stark effect and Mollow triplets, with important implications for coherent control and ...frequency conversion. Here, we demonstrate a novel regime of temporal coherence in oscillators harmonically driven at extreme energy modulation amplitudes relative to the modulation quantum. The studies were carried out by modulating a confined exciton-polariton Bose-Einstein condensate (BEC) by an acoustic wave. Features of the new regime are the appearance, in the spectral domain, of a comb of resonances termed acceleration beats with energy spacing tunable by the modulation amplitude and, in the time domain, of temporal correlations at time scales much shorter than the acoustic period, which also depend on the modulation amplitude. These features are quantitatively accounted for by a theoretical framework, which associates the beats with accelerated energy-change rates during the harmonic cycle. These observations are underpinned by the high sensitivity of the BEC energy to the acoustic driving, which simultaneously preserves the BEC’s temporal coherence. The acceleration beats are a general feature associated with accelerated energy changes: analogous features are thus also expected to appear under highly accelerated motion e.g., in connection with Cherenkov and Hawking radiation.
An ever growing demand for efficient energy conversion, for instance in luminescent lamps, flexible screens and solar cells, results in the current significant growth of research on functionalized ...nanomaterials for these applications. This paper reviews recent developments of a new class of optically active nanostructured materials based on glasses doped with luminescent Ag nanoclusters consisting of only a few Ag atoms, suitable for mercury-free white light generation and solar down-shifting. This new approach, based solely on Ag nanocluster doped glasses, is compared to other alternatives in the field of Ag and rare-earth ion co-doped materials.
► Radiation-protective composites were fabricated by solid state intermixing and thermal pressing. ► The composites based on UHMWPE contain В4С and W nanopowders as fillers. ► The mechanical and ...γ-radiation protective properties of the polymer-matrix nanocomposites were determined experimentally. ► For composites containing 12% B4C and 12% W the mechanical properties were studied prior to and after the irradiation with fast neutrons.
UHMWPE-based nanostructured composites containing B4C and W nanopowders were fabricated and studied. The mechanical and γ-radiation protective properties of the polymer-matrix nanocomposites were determined experimentally. For selected composites the mechanical properties were studied prior to and after the irradiation.
Polariton-driven phonon laser Chafatinos, D. L.; Kuznetsov, A. S.; Anguiano, S. ...
Nature communications,
09/2020, Letnik:
11, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Efficient generation of phonons is an important ingredient for a prospective electrically-driven phonon laser. Hybrid quantum systems combining cavity quantum electrodynamics and ...optomechanics constitute a novel platform with potential for operation at the extremely high frequency range (30–300 GHz). We report on laser-like phonon emission in a hybrid system that optomechanically couples polariton Bose-Einstein condensates (BECs) with phonons in a semiconductor microcavity. The studied system comprises GaAs/AlAs quantum wells coupled to cavity-confined optical and vibrational modes. The non-resonant continuous wave laser excitation of a polariton BEC in an individual trap of a trap array, induces coherent mechanical self-oscillation, leading to the formation of spectral sidebands displaced by harmonics of the fundamental 20 GHz mode vibration frequency. This phonon “lasing” enhances the phonon occupation five orders of magnitude above the thermal value when tunable neighbor traps are red-shifted with respect to the pumped trap BEC emission at even harmonics of the vibration mode. These experiments, supported by a theoretical model, constitute the first demonstration of coherent cavity optomechanical phenomena with exciton polaritons, paving the way for new hybrid designs for quantum technologies, phonon lasers, and phonon-photon bidirectional translators.
We report here for the first time a fabrication of betavoltaic battery prototype consisting of 200 single conversion cells based on Schottky barrier diamond diodes which have been vertically stacked ...with ~24% 63Ni radioactive isotope. The maximum electrical output power of about 0.93 μW was obtained in total volume of 5 × 5 × 3.5 mm3. We used the ion-beam assisted lift-off technique to obtain conversion cells of minimal thickness comparable with the characteristic penetration length of beta-particles emitted by 63Ni isotope. The obtained value of 15 μm was limited by the mechanical strength of produced structures and process reliability. To check the performance of thin diamond based conversion cells we carried out IV-curves measurements at electron beam irradiation in SEM. We found that the sacrificial layer for the splitting of such thin conversion cell from HPHT diamond substrate did not cause a considerable degradation of device charge collection efficiency. As a result, the fabricated prototype provided the output power density of about 10 μW/cm3, that is the best known value for nuclear batteries based on 63Ni radioisotope. Moreover, the long half-life of 63Ni isotope gives the battery specific energy of about 3300 mWh/g that is an order of magnitude higher than the typical value of commercial chemical cells.
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•We successfully used ion-beam assisted lift-off technique to fabricate 15 μm thick diamond-based energy conversion cells.•The energy conversion efficiency (~5-6 %) of produced cells was limited by relatively low open-circuit voltage (~1.1 V).•For produced conversion cells the charge collection efficiency >90% was demonstrated.•Compact (~90 mm3, 0.35 g) ~1 μW nuclear battery was developed and fabricated by using of 200 cells combined with ~24% 63Ni foil.•The battery power density of 10 μW/cm3 and specific energy of 3300 mWh/g were achieved due to cell thickness decreasing.
Lattices of exciton-polariton condensates represent an attractive platform for the study and implementation of non-Hermitian bosonic quantum systems with strong non-linear interactions. The ...possibility to actuate on them with a time dependent drive could provide for example the means to induce resonant inter-level transitions, or to perform Floquet engineering or Landau-Zener-Stückelberg state preparation. Here, we introduce polaromechanical metamaterials, two-dimensional arrays of μm-sized traps confining zero-dimensional light-matter polariton fluids and GHz phonons. A strong exciton-mediated polariton-phonon interaction induces a time-dependent inter-site polariton coupling J(t) with remarkable consequences for the dynamics. When locally perturbed by continuous wave optical excitation, a mechanical self-oscillation sets-in and polaritons respond by locking the energy detuning between neighbor sites at integer multiples of the phonon energy, evidencing asynchronous locking involving the polariton and phonon fields. These results open the path for the coherent control of dissipative quantum light fluids with hypersound in a scalable platform.
The most urgent problems in meso-, micro- and nano-technological productions are controlling wetting of metals and alloys and liquid spreading over engineering surfaces after their hardware abrasive ...processing. Nowadays, there is a lack in theoretical basis and comprehensive experimental studies to predict the texture formation and change of the functional surface properties (including wetting) of metals and alloys after abrasive processing. In this study, based on the analysis of the three dimensional roughness parameters (amplitude, hybrid and feature) and elemental composition of the near-surface layer, the features of texture formation, changes in the surface free energy and wettability of copper and steel surfaces that are widely used in industry were established after their hardware abrasive processing. The use of abrasive material with an average grit size of up to 100 μm was found to significantly change the surface roughness. The abrasive processing significantly modifies the polar component in the surface free energy, while not influencing its dispersed component. The texture parameters allowing one to control both the growth and decrease of the polar component in the surface free energy were determined. It is shown that the abrasive processing directly influences the wettability properties and allows varying the contact angles in a sufficiently wide range of from 54.0° to 108.2° (for copper surfaces) and from 71.6° to 89.5° (for steel surfaces).
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•To change the roughness of metals, abrasives with a grit size of up to 100 μm must be used.•The polar component of the SFE depends on the surface roughness.•The roughness parameters predicting the change in the SFE and wetting were established.
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