Low-cost and eco-friendly Cu2S has attracted wide research interest in recent years. Here, we synthesized Cu2−xS via a facile solvothermal method. The thermoelectric performance of the as-sintered ...Cu2−xS can be easily tuned via kinetic-condition control due to subsequently changed phase contents. Based on detailed characterization, it is found that reducing the NaOH amount can preferentially boost the formation of tetragonal Cu1.96S and monoclinic Cu1.94S phases instead of monoclinic Cu2S phase. This phase content change can promote the formation of Cu vacancies in the high-temperature cubic Cu2−xS after the phase transition at ∼700 K. The enhanced Cu vacancy levels can effectively enhance both the power factor (S2σ) and figure of merit (zT) due to simultaneously optimized hole concentration (nH) and reduced phase transition temperature. A peak zT of ∼1.1 is achieved in the Cu2−xS synthesized with 2 ml NaOH with an average composition of Cu1.95S. An average zT of as high as ∼0.76 (T = 573–833 K) is obtained due to both optimized nH leading to enhanced S2σ and reduced phase transition temperature (at ∼700 K).
In this work, a LaB
-alloying strategy is reported to effectively boost the figure-of-merit (ZT) of Ge
Bi
Te-based alloys up to ≈2.2 at 723 K, attributed to a synergy of La-dopant induced band ...structuring and structural manipulation. Density-function-theory calculations reveal that La dopant enlarges the bandgap and converges the energy offset between the sub-valence bands in cubic-structured GeTe, leading to a significantly increased effective mass, which gives rise to a high Seebeck coefficient of ≈263 µV K
and in turn a superior power factor of ≈43 µW cm
K
at 723 K. Besides, comprehensive electron microscopy characterizations reveal that the multi-scale phonon scattering centers, including a high density of planar defects, Boron nanoparticles in tandem with enhanced boundaries, dispersive Ge nanoprecipitates in the matrix, and massive point defects, contribute to a low lattice thermal conductivity of ≈0.67 W m
K
at 723 K. Furthermore, a high microhardness of ≈194 H
is witnessed in the as-designed Ge
Bi
Te(LaB
)
alloy, derived from the multi-defect-induced strengthening. This work provides a strategy for developing high-performance and mechanical robust middle-temperature thermoelectric materials for practical thermoelectric applications.
Enantioselective radical
-heterobicyclization of
-allylsulfamoyl azides have been developed via metalloradical catalysis (MRC). The Co(II)-based catalytic system can homolytically activate the ...organic azides with varied electronic and steric properties for asymmetric radical
-heterobicyclization under mild conditions without the need of oxidants, allowing for stereoselective construction of chiral 3.1.0-bicyclic sulfamoyl aziridines in excellent yields with high diastereoselectivities and enantioselectivities. The key to achieving the enantioselective radical process relies on catalyst development through ligand design. We demonstrate that the use of new-generation
-symmetric chiral bridged amidoporphyrin ligand HuPhyrin with judicious variation of the alkyl bridge length can dictate both reactivity and selectivity of Co(II)-based MRC. We present both experimental and computational studies that shed light on the working details of the unprecedented mode of asymmetric induction consisting of enantioface-selective radical addition and stereospecific radical substitution. We showcase the synthetic applications of the resulting enantioenriched bicyclic aziridines through a number of stereospecific transformations.
The finite element (FE) method is used to characterize the thermal gradient, solidification rate, and molten pool sizes of Ti-6Al-4V plates in the process of selective laser melting (SLM). The ...results are verified by using the computational fluid dynamics (CFD) simulation. The proposed FE model contains a series of toolpath information that is directly converted from a G-code file, including hatch spacing, laser power, layer thickness, dwell time, and scanning speed generated by using Slic3r software from a CAD file. A proposed multi-layer, multi-track FE model is used to investigate the influence of the laser power, scanning speed, and scanning path on the microstructure in the Ti-6Al-4V plate built via SLM. The processing window is also determined based on the proposed FE model. The FE results indicate that, with a decrease in the laser power and an increase in the scanning speed, the morphology of the crystal grains, showing fully columnar crystals, gradually deviates from the fully equiaxed region. The formed grains are dependent on the laser power, scanning speed, and deposition position, but they are not sensitive to the scanning path, and with the deposition from the bottom layer to the top layer, the size of the formed grains is gradually increasing, which shows a good agreement with the experimental results.The finite element (FE) method is used to characterize the thermal gradient, solidification rate, and molten pool sizes of Ti-6Al-4V plates in the process of selective laser melting (SLM). The results are verified by using the computational fluid dynamics (CFD) simulation. The proposed FE model contains a series of toolpath information that is directly converted from a G-code file, including hatch spacing, laser power, layer thickness, dwell time, and scanning speed generated by using Slic3r software from a CAD file. A proposed multi-layer, multi-track FE model is used to investigate the influence of the laser power, scanning speed, and scanning path on the microstructure in the Ti-6Al-4V plate built via SLM. The processing window is also determined based on the proposed FE model. The FE results indicate that, with a decrease in the laser power and an increase in the scanning speed, the morphology of the crystal grains, showing fully columnar crystals, gradually deviates from the fully equiaxed region. The formed grains are dependent on the laser power, scanning speed, and deposition position, but they are not sensitive to the scanning path, and with the deposition from the bottom layer to the top layer, the size of the formed grains is gradually increasing, which shows a good agreement with the experimental results.
A theoretical demonstration is given of coherent thermal emission via the visible region by exciting magnetic polaritons in isolated metal-dielectric-metal multilayer nanoshells and the collective ...behavior in a trimer comprising multilayer nanoshells. The dipolar metallic core induces magnetic polaritons in the dielectric shell creating a large enhancement of the emissivity, whose mechanism is different from that of film-coupled metamaterials. The coupling effect of the magnetic polaritons and the electric/magnetic modes of symmetric nanoparticle trimers is discussed to understand the collective behavior in self-assembled nanoparticle clusters with potential solar energy utilizations. The concept of hybridization is employed to understand the collective magnetic polaritons of a multilayer nanoshell trimer. The fundamental understanding gained herein opens up new ways to explore, control, and tailor spectral absorptance, thus facilitating rational design of novel self-assembled nanoclusters for energy harvesting.
This paper demonstrates visible, infrared light absorption and hyperbolic metamaterial harvesting in a multilayer absorber made of tungsten and SiO
2
. High absorption peaks were obtained between ...0.4 µm and 3 µm for a uniform plane wave with normal incidence on the interface. The effective medium theory accurately predicted the absorption peak of the multilayer nanostructure. The magnetic and electric fields in the y = 0 plane are predicted at six different incident wavelengths (0.3 µm, 0.6 µm, 1 µm, 2 µm, 3 µm, and 4 µm) to describe the absorption mechanism. The efficient light harvesting can be explained by the slowlight mode and localized surface plasmon resonance. The dispersion relation of the effective medium can be described by a hyperbolic curve between 2 µm and 4 µm. Then, the current density distributions at 3 µm and 4 µm are given to explain the nature of the electric and magnetic resonances. Finally, the absorber characteristics are given for various geometric parameters. Absorbers with larger periodic unit cells had better absorption of the visible and infrared waveband. This artificial structure has great potential for many applications as thermal emitters and thermal absorbers.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
As a promising midtemperature thermoelectric material with both higher thermoelectric performance and mechanical property, Tellurium Antimony Germanium Silver (TAGS-
x
), written as (GeTe)
x
(AgSbTe
...2
)
1-
x
, especially (GeTe)
0.85
(AgSbTe
2
)
0.15
(TAGS-85), has attracted wide attention. Herein, we innovatively use Nd doping to synergistically decrease the carrier concentration to the optimal level leading to enhanced dimensionless figure of merit, zT. Our density-functional theory calculation results indicate that Nd-doping reduced carrier concentration should be attributed to the enlargement of band gap. The optimized carrier concentration results in an ultrahigh power factor of ~32
μ
W cm
-1
K
-2
at 727 K in Ge
0.74
Ag
0.13
Sb
0.11
Nd
0.02
Te. Simultaneously, the lattice thermal conductivity of Ge
0.74
Ag
0.13
Sb
0.11
Nd
0.02
Te retained as low as ~0.5 at 727 K. Ultimately, a record-high zT of 1.65 at 727 K is observed in the Ge
0.74
Ag
0.13
Sb
0.11
Nd
0.02
Te. This study indicates rare-earth Nd doping is effective in boosting the thermoelectric performance of TAGS-85 and approached a record-high level via synergistic effect.
AIM:To study the clinical efficacy of traditional Chinese medicine(TCM)intervention"tonifying the kidney to promote liver regeneration and repair by affecting stem cells and their ...microenvironment"("TTK")for treating liver failure due to chronic hepatitis B.METHODS:We designed the study as a randomized controlled clinical trial.Registration number of Chinese Clinical Trial Registry is Chi CTR-TRC-12002961.A total of 144 patients with liver failure due to infection with chronic hepatitis B virus were enrolled in this randomized controlled clinical study.Participants were randomly assigned to the following three groups:(1)a modern medicine control group(MMC group,36patients);(2)a"tonifying qi and detoxification"("TQD")group(72 patients);and(3)a"tonifying the kidney to promote liver regeneration and repair by affecting stem cells and their microenvironment"("TTK")group(36patients).Patients in the MMC group received general internal medicine treatment;patients in the"TQD"group were given a TCM formula"tonifying qi and detoxification"and general internal medicine treatment;patients in the"TTK"group were given a TCM formula of"TTK"and general internal medicine treatment.All participants were treated for 8 wk and then followed at 48 wk following their final treatment.The primaryefficacy end point was the patient fatality rate in each group.Measurements of various virological and biochemical indicators served as secondary endpoints.The one-way analysis of variance and the t-test were used to compare patient outcomes in the different treatment groups.RESULTS:At the 48-wk post-treatment time point,the patient fatality rates in the MMC,"TQD",and"TTK"groups were 51.61%,35.38%,and 16.67%,respectively,and the differences between groups were statistically significant(P<0.05).However,there were no significant differences in the levels of hepatitis B virus DNA or prothrombin activity among the three groups(P>0.05).Patients in the"TTK"group had significantly higher levels of serum total bilirubin compared to MMC subjects(339.40μmol/L±270.09μmol/L vs 176.13μmol/L±185.70μmol/L,P=0.014).Serum albumin levels were significantly increased in both the"TQD"group and"TTK"group as compared with the MMC group(31.30 g/L±4.77g/L,30.72 g/L±2.89 g/L vs 28.57 g/L±4.56 g/L,P<0.05).There were no significant differences in levels of alanine transaminase among the three groups(P>0.05).Safety data showed that there was one case of stomachache in the"TQD"group and one case of gastrointestinal side effect in the"TTK"group.CONCLUSION:Treatment with"TTK"improved the survival rates of patients with liver failure due to chronic hepatitis B.Additionally,liver tissue was regenerated and liver function was restored.
The extremely demanding fabrication precision has been a main block for real application of nanoscale metamaterial. To overcome this, a graphene-based tunable filter has been theoretically ...demonstrated to exhibit generally high filtering efficiency for the filter with mismatched geometry parameters. Rigorous coupled-wave analysis has been employed to investigate the transmission spectrum and electromagnetic field distributions for TM wave. The selectivity is understood as the excitations of surface plasmon polariton (SPP), magnetic polaritons (MP) and Fabry-Perot-like (FP) resonance. The dispersion relationship of SPP and inductor and capacitor of MP are utilized to quantitatively predict the resonance wavelengths. Moreover, the propagating electron wave on the conducting surface is employed to investigate the tuning effects. The fundamental understanding gained herein facilitates the rational design of novel graphene-based metamaterials.
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