查看更多>>摘要：? 2022 Elsevier B.V.Depending on their chemical composition, Yb compounds often exhibit different valence states. Here we investigate the valence state of YbFe4Al8 using X-ray photoelectron spectroscopy (XPS) and first-principles calculations. The XPS valence band of YbFe4Al8 consists of two contributions coming from divalent (Yb2+) and trivalent (Yb3+) configurations. The determined value of the valence at room temperature is 2.81. Divalent and trivalent contributions are also observed for core-level Yb 4d XPS spectra. We study several collinear antiferromagnetic models of YbFe4Al8 from the first-principles and for comparison we also consider LuFe4Al8 with a fully filled 4f shell. We predict that only Fe sublattices of YbFe4Al8 carry significant magnetic moments and that the most stable magnetic configuration is AFM-C with antiparallel columns of magnetic moments. We also present a Mulliken electronic population analysis describing charge transfer both within and between atoms. In addition, we also study the effect of intra-atomic Coulomb U repulsion term applied for 4f orbitals on Yb valence and Fe magnetic moments.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, we fabricated a novel surface plasmon resonance (SPR) photocatalyst Au(T)-TiO2(MS) by anchoring Au thorns on TiO2 hierarchical microspheres (MS). It was found that the flower-like TiO2 microspheres with a size of ~800 nm consist of many lamellar petals and the Au thorns with length of dozens of nanometers were anchored on TiO2(MS). By analyzing the DRS, PL spectra, transient photocurrents and electrochemical impedance spectra, it was disclosed that Au thorns not only respond to visible and NIR light but also effectively promote the separation of photogenerated charge carriers in TiO2(MS). The photocatalytic inactivation of E. coli K12 indicated that Au(T)-TiO2(MS) displayed excellent bactericidal activity and stability under red and NIR light irradiation. Due to the special structure of Au(T)-TiO2(MS), it can produce reactive species outside and within bacteria, both of which work together responsible for the inactivation of E. coli K12. The EPR spin-trap measurements with DMPO and reactive species trapping experiments revealed that all of h+, ?OH and ?O2? are produced over Au(T)-TiO2(MS), while ?O2? and h+ are the main reactive species for bacterium inactivation.
查看更多>>摘要：? 2022Due to the difficulty in controlling the post-selenization/sulfurization process accurately, single-graded structure with a lower bandgap on the surface is easy to form in the Cu2ZnSn(S, Se)4 absorber. This will lower the built-in potential and lead to the formation of undesirable “cliff” type band alignment in the device, and hence a drastic Voc-deficit and lower efficiency are expected. Herein, an effective and versatile method to improve the Voc and efficiency of Cu2ZnSn(S, Se)4 solar cells through bandgap engineering was presented in this work. A sharp surface bandgap gradient with larger surface bandgap was constructed simply by sputtering a nanoscale Cu2ZnSnS4 layer on the surface of Cu2ZnSn(S, Se)4 absorber. Under the coactions of surface sharp bandgap gradient and the single bandgap gradient existed in the Cu2ZnSn(S, Se)4 absorber naturally, a quasi-U-shaped bandgap gradient was constructed inside the absorber. Benefited from the enlarged surface bandgap, favorable U-shaped bandgap gradient and appropriate band alignment at the absorber/buffer interface, a best efficiency of 9.9% with a Voc of 450 mV, a Jsc of 35.26 mA/cm2 and a fill factor (FF) of 62.73% was achieved.
查看更多>>摘要：? 2022 Elsevier B.V.Boron is being widely explored as a potential additive for high energy fuels because of its extraordinary gravimetric and volumetric energy content. However, its application is obstructed by the surface oxide layer which forms on the core boron particles, degrading its combustion and ignition performance. This oxide layer has a high vaporization temperature. To improve the combustion and ignition performance of boron, nickel nanoparticles were coated on the boron particle surface using a simple and unique spray drying technique. Numerous samples were prepared while varying the boron and nickel particles weight percent ratios. Surface morphological analyses showed that the nickel coated boron particles formed microspheres. These microspheres had a size distribution in the range of 2–15 μm and a mean diameter of 4.64 μm. The coating density of the crystalline nickel nanoparticles on the boron surface increased as the nickel percent used for the sample preparation was increased. X-ray diffraction (XRD) identifies the coating of nickel particles over the boron surface without any phase formation. Field emission scanning electron microscopy (FE-SEM), line scanning, elemental mapping and energy dispersive spectroscopy (EDS) studies provided an elemental analysis of the nickel coated boron particles that confirmed the surfaces of the boron particles were coated with nickel particles, and formed intimate contact between them. The oxidation performance of nickel, boron, and boron coated with nickel particles was studied by thermogravimetric analysis (TGA). The beginning of oxidation and the exothermic peaks of pure boron appeared earlier after the coating with nickel. Also, a decrease in weight gain was observed at 1000 °C in the boron coated with nickel. A shock tube experiment showed the nickel coated boron has a lower ignition delay time than the pure boron. The ignition delay times of the nickel coated boron samples, such as B:Ni= 40:1 and B:Ni= 10:1 samples decreased by 12% and 16%, respectively, compared to pure boron. Thus, spray drying prepared nickel coated boron particles demonstrated a substantial improvement in ignition performance versus uncoated boron.
查看更多>>摘要：? 2022 Elsevier B.V.We regret following corrigendum. This article has an error in the Fig. 2(a). The new Fig. 2(a) is shown below. The authors would like to apologize for any inconvenience caused. CRediT authorship contribution statement. Xiao Lan: Conceptualization, Investigation, Formal analysis, Writing – original draft. Haijuan Wang: Investigation, Formal analysis. Zhanhao Sun: Investigation, Writing – original draft. Xunyong Jiang: Conceptualization, Writing – review & editing, Supervision.
查看更多>>摘要：? 2022 Elsevier B.V.Lead halide perovskite solar cells (PSCs) have attracted intensive attention since their power conversion efficiency (PCE) increased sharply in recent years. Thereinto, triple cation perovskite (TCP) is a popular light absorption layer for PSCs due to its excellent thermal and humidity stability. However, a large amount of MA+ (≥15%) and Br- (≥15%) in TCP makes the bandgap widen drifting from the optimum value. There is some extent of a trade-off between PCE and stability for PSCs, and narrow-bandgap TCP is one of the best choices for light absorption material to achieve an optimum balance between PCE and stability. Herein, we prepared a narrow-bandgap (1.56 eV) high-quality TCP (Cs0.05FA0.86MA0.09Pb(I0.97Br0.03)3) film with an average grain size up to 1208 nm and corresponding PSC with high efficiency of 20.8%. Moreover, the intermediate process of the TCP film crystallization was carefully studied disclosing the critical α-Phase intermediate and corresponding roles of DMSO solvent and MACl additive through quasi-in-situ XRD in the film formation process, and the results may give critical clues to the fabrication of high-quality narrow-bandgap TCP based PSCs.
查看更多>>摘要：? 2022 The Author(s)We report the first nanoscale investigation of FeCoNi(AlMn)x high-entropy alloys (HEAs) processed by laser metal deposition. The structural evolution of the alloy upon chemical composition variation (0.2 ≤ x ≤ 1.5) was investigated by combining imaging and spectroscopies in (scanning) transmission electron microscopy (S)TEM with density functional theory (DFT). A gradual change from a face-centered cubic (FCC) towards an ordered full-Heusler (L21) phase by increasing the Al and Mn contents was observed. Direct imaging and atomic-scale calculations revealed a nanoscale interplay between B2 and L21 ordered structures for x = 1.5, wherein the latter, Al and Mn occupy two different Wyckoff sites. By decreasing x, the FCC phase dominates exhibiting intense phase separation tendency, ordering phenomena, and nano-precipitation. Although not chemically discriminated, plasmon-peak splitting in low-loss electron energy loss spectra revealed the presence of two valence electron densities within the FCC phase. Lorentz TEM showed that the ordered nano-precipitates and nano-sized grains with a structure based on a tripled FCC unit cell are pinning-sites for magnetic domain walls and dislocations. All alloy compositions exhibited soft-magnetic behavior with coercivity (Hc) values< 1000 A/m. The FeCoNi(AlMn)1.5 alloy with L21/B2 nanostructure showed the highest magnetization (Ms) with relatively low Hc, attributed to the large magnetic moment of Mn and the synergistic effect of Mn-Al according to DFT, whilst ordering does not impose a negative effect. Phase separation trends within the FCC phase seem to decrease the Ms however, the overall impact on the magnetic behavior is not intense, opening up for new avenues for tuning FeCoNiAlMn properties through chemically-designed phase decomposition regimes.
查看更多>>摘要：? 2022 Elsevier B.V.Giant magnetoresistance (GMR) effect exhibits high potential applications in ultrahigh density magnetic recording, magnetic sensors and electronic devices. Many methods were developed to improve the GMR, such as changing the diameters or content ratio of Co to Cu etc. In this work, we have successfully grown a new Co/Cu multilayered magnetic nanowires arrays (MNAs) with gradient diameter (GDMNAs). Very interestingly, we demonstrate much enhanced GMR in the GDMNAs. Moreover, it shows higher thermal stability simultaneously. This is a novel strategy to improve GMR. Generally, the diameter (d) and edge-to-edge separation (s) of MNAs play a significant role in determining the magnetic properties. If d<s, exchange interaction dominants. If d>s, dipolar interaction dominates. When we design a new GDMNAs with d<s at one end and d>s at the other, much better multilayered structures are observed on the larger end. Surprisingly, the magnetic anisotropy is found to be dominated by the portion of MNAs with d<s. Combining both properties in GDMNAs, we achieve the highest GMR value of 27% in reported Co/Cu MNAs. This design strategy not only reveals new interesting physics, which remains to be understood, but also useful to other applications based on MNAs.
查看更多>>摘要：? 2022 Elsevier B.V.A new, microwave-assisted technique has been developed for the synthesis of microporous vanado-molybdate catalysts with an M1-type orthorhombic structure. This method allows various cations such as Sb, Bi and - for the first time - Pb, to be introduced into the hexagonal channels of the structure, without using any expensive structure directing agent. The influence of the aforementioned elements with lone pairs of electrons on the framework structure has been studied, and the crystalline structure of the Pb-containing phase was refined using the Rietveld method and powder diffraction data. The structure determination data are in good agreement with those obtained by different analytical or spectroscopic techniques. The catalytic properties of the catalysts have been determined for the oxidative dehydrogenation of ethane, and for the oxidation of propane into acrylic acid.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, silicon carbide was prepared by microwave sintering method with graphene as carbon source and ethyl orthosilicate as the silicon source. First, SiO2 particles were in situ covered on the surface of graphene by sol-gel method, and then one-dimensional silicon carbide nanowires were obtained by carbothermal reduction reaction. The macro morphology of SiC nanowires with different sintering temperatures was observed, and the samples were characterized and analyzed by XRD, FTIR, and SEM. From the XRD results, we can see there were sharp diffraction peaks of SiC sintering at1500 °C, indicating that β-SiC was generated at 1500 °C via microwave sintering. It can be shown that one-dimensional SiC nanowires were interwoven into the two-dimensional SiC nanonetworks due to using graphene sheets as the templates. The results showed that SiC nanowires could be successfully prepared by microwave sintering using graphene/SiO2 as precursors; the optimal sintering temperature is 1500 °C, and the keeping time is 40 min. Therefore, using microwave sintering to synthesize SiC is a more appropriate way to reduce manufacturing energy consumption, save cost and improve production efficiency.
NSTL
Elsevier