Equiatomic, face-centered-cubic, high- and medium-entropy alloys were arc melted, hot-rolled to produce recrystallized sheets, and tensile tested. The alloys having the compositions CrMnFeCoNi and ...CrFeCoNi exhibited a strong temperature-dependent decrease in strength with increasing temperature from −196 °C to 1000 °C, and a relatively weak strain-rate dependence (at 10−3 and 10−1 s−1). Ductility did not vary inversely with yield strength; rather, when strength doubled as the test temperature was decreased from room temperature to −196 °C, elongation to fracture increased by a factor of 1.5 to >60%. A high degree of work hardening, possibly due to deformation-induced nanotwinning, postpones the onset of necking and may be the reason for the ductility increase.
•First report of tensile properties of high- and medium-entropy alloys.•Strong temperature dependent yield strength unlike in pure FCC metals.•Ductility does not exhibit the usual inverse relationship with strength.•As strength doubles from 300 to 77 K, elongation increases by 1.5× to >60%.•High work hardening postpones necking instability and enhances ductility.
In this Letter, the photoinduced switching of the single nitrogen-vacancy (NV) center between two different charge states, negative (NV(-)) and neutral (NV(0)), is studied under resonant excitation ...at liquid helium temperature. We show that resonant conversion of NV(0) to NV(-) significantly improves spectral stability of the NV(-) defect and allows high fidelity initialization of the spin qubit. Based on density functional theory calculations a novel mechanism involving an Auger ionization of NV(-) and charge transfer of an electron from the valence band to NV(0) is discussed. This study provides further insight into the charge dynamics of the NV center, which is relevant for quantum information processing based on an NV(-) defect in diamond.
This study investigates the corrosion resistance and wear behaviour of aluminium matrix composites (AMCs) manufactured through the ultrasonic-assisted stir-casting technique. These composites were ...synthesized by introducing titanium carbide (TiC) and nickel (Ni) into aluminium alloys (AA6061). The X-ray diffraction results confirmed the presence of α-Al, TiC and Al
3
Ni phases within the composites. Microstructural examination demonstrated an uniform dispersion of TiC particles and dispersion of Al
3
Ni along grain boundaries. To evaluate the corrosion behaviour, samples were subjected to immersion tests and electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), in a 3.5 wt% NaCl solution. Immersion tests indicated that the composites exhibited slower dissolution rates than base AA6061 alloys. Potentiodynamic polarization results revealed that the inclusion of TiC and Ni reinforcements enhanced corrosion resistance, with TiC having a more pronounced influence. The EIS tests suggested that the composites had higher charge-transfer resistance than AA6061 alloys. After conducting corrosion tests, scanning electron microscope (SEM) images of the base AA6061 alloys unveiled the presence of deep pits but the inclusion of reinforcements resulted in the shallow pits. In addition, Vickers hardness tests and pin-on-disc wear tests were conducted to investigate hardness and wear properties. Notably, hybrid composites containing 3% TiC and 3% Ni exhibited a substantial 42.18% increase in hardness as compared to the base alloy. These hybrid composites also demonstrated superior wear resistance, with a wear rate that was 58.6% lower compared to AA6061 alloy and 41% less than that of the 3% Ni-reinforced composite.
Over the past few years, single-photon generation has been realized in numerous systems: single molecules, quantum dots, diamond colour centres and others. The generation and detection of single ...photons play a central role in the experimental foundation of quantum mechanics and measurement theory. An efficient and high-quality single-photon source is needed to implement quantum key distribution, quantum repeaters and photonic quantum information processing. Here we report the identification and formation of ultrabright, room-temperature, photostable single-photon sources in a device-friendly material, silicon carbide (SiC). The source is composed of an intrinsic defect, known as the carbon antisite-vacancy pair, created by carefully optimized electron irradiation and annealing of ultrapure SiC. An extreme brightness (2×10(6) counts s(-1)) resulting from polarization rules and a high quantum efficiency is obtained in the bulk without resorting to the use of a cavity or plasmonic structure. This may benefit future integrated quantum photonic devices.
Agro-residues account for a large proportion of the wastes generated around the world. There is thus a need for a model to simulate the anaerobic digestion processes used in their treatment. We have ...developed model based on ADM1, to be applied to agro-wastes. We examined and tested the biodegradability of apple, pear, orange, rape, sunflower, pig manure and glycerol wastes to be used as the basis for feeding the model. Moreover, the fractions of particulate COD (
X
c) were calculated, and the disintegration constant was obtained from biodegradability profiles, considering disintegration to be the limiting process. The other kinetic and stoichiometric parameters were taken from the ADM1 model.
The model operating under mono-substrate and co-substrate conditions was then validated with batch tests. At the same time the model was validated on a continuous anaerobic reactor operating with pig manure at lab scale. In both cases the correlation between the model and the experimental results was satisfactory. We conclude that the anaerobic digestion model is a reliable tool for the design and operation of plants in which agro-wastes are treated.
We present a time-dependent density functional theory (TDDFT) study of the optical gaps of light-emitting nanomaterials, namely, pristine and heavily B- and P-codoped silicon crystalline ...nanoparticles. Twenty DFT exchange–correlation functionals sampled from the best currently available inventory such as hybrids and range-separated hybrids are benchmarked against ultra-accurate quantum Monte Carlo results on small model Si nanocrystals. Overall, the range-separated hybrids are found to perform best. The quality of the DFT gaps is correlated with the deviation from Koopmans’ theorem as a possible quality guide. In addition to providing a generic test of the ability of TDDFT to describe optical properties of silicon crystalline nanoparticles, the results also open up a route to benchmark-quality DFT studies of nanoparticle sizes approaching those studied experimentally.
Single-photon sources that provide non-classical light states on demand have a broad range of applications in quantum communication, quantum computing and metrology. Single-photon emission has been ...demonstrated using single atoms, ions, molecules, diamond colour centres and semiconductor quantum dots. Significant progress in highly efficient and entangled photons sources has recently been shown in semiconductor quantum dots; however, the requirement of cryogenic temperatures due to the necessity to confine carriers is a major obstacle. Here, we show the realization of a stable, room-temperature, electrically driven single-photon source based on a single neutral nitrogen-vacancy centre in a novel diamond diode structure. Remarkably, the generation of electroluminescence follows kinetics fundamentally different from that of photoluminescence with intra-bandgap excitation. This suggests electroluminescence is generated by electron-hole recombination at the defect. Our results prove that functional single defects can be integrated into electronic control structures, which is a crucial step towards elaborate quantum information devices.
Spin-lattice relaxation within the nitrogen-vacancy (NV) center's electronic ground-state spin triplet limits its coherence times, and thereby impacts its performance in quantum applications. We ...report measurements of the relaxation rates on the NV center's |m_{s}=0⟩↔|m_{s}=±1⟩ and |m_{s}=-1⟩↔|m_{s}=+1⟩ transitions as a function of temperature from 9 to 474 K in high-purity samples. We show that the temperature dependencies of the rates are reproduced by an ab initio theory of Raman scattering due to second-order spin-phonon interactions, and we discuss the applicability of the theory to other spin systems. Using a novel analytical model based on these results, we suggest that the high-temperature behavior of NV spin-lattice relaxation is dominated by interactions with two groups of quasilocalized phonons centered at 68.2(17) and 167(12) meV.
It is a fact that the rapid increase of biodiesel production over the last years has resulted in the generation of large and constant amounts of glycerine, which is causing an oversupply problem. ...Since glycerine is a biodegradable organic compound exempt of nitrogen, it can be applied as a co-substrate in the anaerobic digestion process of pig manure (PM). In order to analyze the feasibility of a mixture of pig manure and glycerine in anaerobic processes and to define the effect originated by the nitrogen limitation when large amounts of glycerine are added, several biodegradability batch tests were performed with different mixtures. These were named as: 100% PM, 80% PM, 60% PM, 40% PM and 20% PM, in pig manure wet weight-basis. Furthermore, a modified model based on anaerobic digestion model no.1 (ADM1) was used to simulate the methane production profiles for the mixtures tested. Specifically, both experimental and model results show the power of the co-digestion technology. In particular, the mixture of 80% PM produced the highest methane production with 215 mL CH4 g−1 COD, almost 125% more methane than when pig manure was mono-digested. In contrast, the one with 20% PM was clearly inhibited by the volatile fatty acid due to the low nitrogen concentration of the mixture. In addition, the specific methane production predicted by the model was in good agreement with the experimental results, although in some samples the shape of the profiles did not match perfectly. Moreover, the modified ADM1 appears to be a useful tool to predict the methane production and the limitations related to the lack/excess of nitrogen during the co-digestion process of pig manure and glycerine.
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