查看更多>>摘要：A highly homogeneous single-phase La(FexSi1?x)13 was obtained by the heat-treatment of a parent alloy produced by the laser fusion of a powder mixture of Fe and La-Si compounds. Rapid homogenization was promoted owing to the formation of a characteristic microstructure during laser fusion even at a high Fe concentration (e.g., x = 0.91). The selective oxidation of La during laser fusion was prevented by the reduction of oxides on the surface of Fe particles. The maximum of the magnetic entropy change (ΔSM) for the specimen heat-treated at 1323 K for 24 h was ? 22 J/kg K under a magnetic field change of 1 T and the specimen heat-treated for a shorter duration of 2 h exhibited a ΔSM of ? 18 J/kg K. Thus, the production of the parent alloy by the laser fusion of the powder mixture significantly decreased the heat-treatment duration for the formation of a highly homogenized La(FexSi1?x)13 compound at a high Fe concentration. Consequently, the laser fusion process followed by post-annealing is possible to selectively form fine structures made of the 1:13 phase, and such a feature will lead a way to 3D precision modeling of the regenerator-bed with using the highly homogeneous La(FexSi1?x)13.
查看更多>>摘要：The conventional means for selectively capturing and subsequently degrading specific organic pollutants entails the development of an inorganic imprinted photocatalytic material with visible light response, high activity, and high stability. Hence, the inorganic imprinted oxygen vacancy CdO0.5S0.5 (II-OV-CdO0.5S0.5) was prepared by S2- ion exchange assisted inorganic imprinting technology. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and thermogravimetry analysis (TGA) were used to comprehensively prove that S element only permeated the surface of the material, and there were imprinted cavities and a few oxygen defects caused by inorganic imprinting. Photoelectrochemistry experiments and DFT theoretical calculation showed that the electrons gathered near the oxygen defects around the imprinted cavities (specific reaction sites), and the reactive center formed was more favorable to the specific adsorption of tetracycline (TC). Since TC was confined to the specific reaction sites enriched in electrons, the apparent rate constant of II-OV-CdO0.5S0.5 (0.0220 min?1) was 2.18 times that of CdO0.5S0.5 (0.0101 min?1) after TC photodegradation for 60 min under visible light. More importantly, although the space size of ciprofloxacin (CIP) was smaller than that of TC, because the imprinted cavities not only had a size effect, but also possessed the specific adsorption sites, there was no significant enhancement in the degradation of CIP. Therefore, II-OV-CdO0.5S0.5 demonstrated excellent orientation photocatalytic ability for the target (TC), under the premise of improving the photodegradation of the target, II-OV-CdO0.5S0.5 effectively inhibited the photodegradation of other reference pollutants. This work provides an exemplary method for the design of functionalized photocatalytic materials and the orientation removal of specific pollutants.
查看更多>>摘要：Herein, we report the synthesis of ZnIn2S4 nanoparticles on bulk WC by a facile hydrothermal process to construct novel and highly efficient noble metal-free Schottky junction heterojunction photocatalysts. Morphology characterization revealed that the ZnIn2S4 nanoparticles were deposited on the surface of the WC. Meanwhile, the combination of the ZnIn2S4 and the metal-like WC formed the Schottky energy barrier, which greatly promoted the migration and separation of photo-generated carriers. Especially, the optimal ZnIn2S4/WC photocatalysts have a lower overpotential for hydrogen evolution (?0.35 V) than pristine ZnIn2S4 (?0.49 V). The hydrogen production ability of the optimal ZnIn2S4/WC photocatalyst (2400.3 μmol·h?1·g?1) was approximately 9.2 times higher than that of ZnIn2S4-1% Pt (260.1 μmol·h?1·g?1). Photocatalytic experiments demonstrated that metal-like WC plays an important role in replacing precious metal to increase the active site of ZnIn2S4. Moreover, a feasible Schottky junction reaction mechanism of intensive photocatalytic activity was discussed. This study proves that it is a very fascinating strategy to combine the advantages of ZnIn2S4 and metal-like to construct Schottky heterojunction for photocatalytic hydrogen production.
查看更多>>摘要：Polyaniline (PANI)-derived nitrogen-doped carbon nanofibres used as cathode electrodes in situ generate and activate H2O2 to form ?OH without metal catalysts. The degradation rates of ciprofloxacin hydrochloride (CIP) and methyl orange (MO) were 99.64% and 100%, respectively, and the mineralisation rates were 54.24% and 62.56% at the modified metal-free Fenton system for microbial fuel cells (MFC-Fenton) cathode. Micropores were introduced into the electrode to provide active sites such as pyridinic N and graphitic N, which improves the electron transfer rate and redox activity, as well as exhibiting excellent power generation capacity (783.48 ± 10.52 mV and 33.57 ± 0.14 W m? 3) in comparison with a single MFC process (543.14 ± 3.56 mV and 11.02 ± 1.03 W m? 3). The degradation intermediates and mechanisms of this process were studied in detail. This study provides a new understanding of MFC-Fenton systems for removing practical organic pollutants in wastewater.
查看更多>>摘要：The surface with micro-convex prepared by laser ablation is beneficial to improving the functional properties of metallic glasses (MGs). However, accompanied by the formation of micro-convex, surface hardness of the ablated area generally decreases due to the softening effect caused by laser thermal shock. Previous studies have shown that the mechanical properties of laser-ablated MG surface are significantly different when using different gas atmospheres. In this study, a comparative investigation was performed to analyze the influence of gas atmosphere (i.e. argon, nitrogen, and air) on the formation of micro-convex as well as its surface characteristics and mechanical properties. Experimental results showed that the atmosphere type did not affect the formation of micro-convex, but significantly affected the surface morphology and element composition of the laser-ablated area. The element analysis and Raman spectral measurements indicated that laser ablation in nitrogen or air atmosphere resulted in local nitridation or oxidation. The results of nanoindentation tests demonstrated that laser ablation in nitrogen or air atmosphere also resulted in surface hardness inhomogeneity, i.e., softening and hardening effects coexist in the ablated area, which could be attributed to the combined influence of laser thermal shock, the introduction of secondary phase as well as laser ablation induced loose structure.
查看更多>>摘要：To optimize the structure and composition of the metal oxide semiconductor is one of effective approaches to improve its gas-sensing performance. In this paper, Zn2SnO4 solid octahedrons were first synthesized by a hydrothermal method, then converted to hollow structures with a shape preserved through a simple and practical acid etching process. Ultimately, the hierarchical ZnSnO3/Zn2SnO4 hollow composite with porous structure was designed and prepared by in situ growth of ZnSnO3 nanosheets on the surface of Zn2SnO4 hollow octahedrons in the seed mediated wet-chemical way. It was found that through the structure evolution from solid octahedron to hollow structure, the sensitivity of gas sensor toward triethylamine (TEA) was visibly improved. Significantly, superior TEA-sensing properties, such as lower optimal working temperature, higher sensitivity, wider linear response range, more rapid response/recovery speed and more excellent selectivity were further achieved by decorating Zn2SnO4 hollow octahedrons with ZnSnO3 nanosheets. It was remarkable that the sensor based on hierarchical ZnSnO3/Zn2SnO4 porous hollow octahedrons displayed long-term stability to TEA and anti-humidity property, suggesting its potential practical applications in detection of highly toxic TEA. The improved sensing mechanism on the strength of structure and composition evolution for the gas sensor was discussed in detail.
查看更多>>摘要：In the present study, we investigated the dynamic precipitation (DP) of Mg17Al12 phase accompanying dynamic recrystallization (DRX) during the deformation of an Mg-Al-Zn-RE alloy. Hot compressions at various strains, strain rates and temperatures were followed by microstructural characterization via scanning electron microscope (SEM) and energy-dispersive X-ray spectroscope (EDS). The precipitation during heating and holding was avoided by proper treatment to guarantee initial microstructures without Mg17Al12 phase. During hot compression, the DP of Mg17Al12 particles with blocky shape accompanies the DRX process and mainly occurs on the DRXed grain boundaries. The volume fraction, number density and average size of Mg17Al12 precipitates depend on both temperature and strain rate, while the influence of temperature is more prominent for volume fraction. Phenomenological models bridging the number density and average size of precipitates with deformation conditions (temperature and strain rate) were established and validated. The pinning effect of DP on the grain growth makes DRXed grain size deviate from the values predicted by the classical function of the Zener-Hollomon parameter. Influenced by the sensitiveness of the pinning effect, temperature makes more sense in trimming DRXed grain size than strain rate. Vickers hardness tests were also conducted after hot compression. The influence of DP on microhardness lies in its effect on grain refinement.
查看更多>>摘要：With the development of the industry and the increase in the world population, there is also a growing concern about the effect that these factors cause on the environment. Among the pollutants from human activities are the synthetic dyes, which can have toxic and carcinogenic characteristics. Rhodamine B is a red dye used mainly in the textile and food industries. One of the main techniques studied to remove these pollutants from wastewater is the Advanced Oxidative Processes (AOPs) with emphasis on the Heterogeneous Photo-Fenton Process, which consists of the combination of an iron-based photocatalyst, an oxidizing agent and UV-Vis radiation. In the present study, zinc ferrite (ZnFe2O4) was synthesized and supported in different masses of chitin biochar (ZnFO1/B1, ZnFO1/B3, and ZnFO3/B1) and then characterized by FE-SEM, EDS, HR-TEM, FT-IR, XRD, UV-Vis Spectra and Zeta potential, which showed that the support of the ferrite on the biochar surface was properly done. The band gap energies of the prepared composites were narrower than the one of the ferrite alone, which increased their photocatalytic activities. The percentages of Rhodamine B removal were 20%, 85%, 100% and 70% for ZnFe2O4, ZnFO1/B3, ZnFO1/B1, and ZnFO3/B1 respectively, during 60 min of heterogeneous photo-Fenton tests carried under visible light. The ZnFO1/B1 composite was also proven to remain efficient during the recycling tests even after eight cycles of photo-Fenton reactions. The ZnFO1/B1 composite also was able to fully degrade solutions of the same dye at concentrations of 10 and 50 mg L?1 under solar light in 20 and 40 min, respectively. The ?OH radicals were determined to be the main reactive species involved in the dye degradation. The proposed composite in this work showed to be a promising material for treatment by photo-Fenton of wastewater contaminated by organic pollutants.
查看更多>>摘要：It is still challenging but essential to synthesize non-noble catalysts with rich and uncovered catalytic active sites towards oxygen reduction reaction (ORR). And the limited research of the ORR properties of FeNx atom clusters also hinders their practical implementations. Here, we report a two-dimensional (2D) non-precious ORR catalyst constructed by abundant and fully exposed FeNx atom clusters anchored on nitrogen-doped graphene nanosheets (Fe-N-C/NG), which derives from three-dimensional (3D) ZIF-8, 2D graphene oxide nanosheet, and ferrocene. The optimized Fe-N-C/NG delivers outstanding ORR activities (Eonset = 0.97 V, E1/2 = 0.84 V, Jd = 5.48 mA cm?2), excellent Tafel slope (57.7 mV dec?1), remarkable long-term durability, and strong methanol tolerance in an alkaline electrolyte. Its superior catalytic activity is possibly attributed to its unique conversion of nanoarchitecture and the synergistic effects: the change of morphology effectively utilizes the advantages of 2D graphene oxide and 3D ZIF-8, which guarantees sufficient and reachable active sites; the 2D porous nanoarchitecture of Fe-N-C/NG promotes the ion diffusion and mechanical stability; both the FeNx atom clusters and N-doped graphene nanosheets facilitate the catalytic activity. This work introduces an innovative strategy to rationally design the nanoarchitecture and facilely synthesize nonprecious ORR catalysts with sufficient and uncovered active sites for high efficiency and durability.
查看更多>>摘要：A series of Sm3+ doped and Li+/Na+/ K+ co-doped CaSr2(PO4)2 phosphors were prepared via solution combustion synthesis. The luminescence and thermometric studies of the phosphors were investigated to explore the phosphor for potential application in high power light emitting diodes and optical thermometry. The diffraction pattern showed that the structure of the phosphor is in accordance with the rhombohedral phase of CaSr2(PO4)2 having a space group R3c(161). Under near-ultraviolet (n-UV) excitation, the phosphors exhibited characteristic emission of the Sm3+ ions with the main orange-red peak at 600 nm. The host of the phosphor, according to the diffuse reflectance studies, was a broad bandgap material that successfully accommodated the dopants. Co-doping of alkali metal ions (Li+, Na+, K+) improved the fluorescence intensity significantly. The computed Commission Internationale de l′éclairage coordinates (0.59, 0.40) for the phosphors were found to be in the orange-red region of the spectrum with a high color purity of 97.3%. The temperature dependent photoluminescence studies demonstrated that the prepared phosphor had high thermal stability when working in the region of 303–473 K. The phosphor was also explored for thermometry, for this the temperature dependent spectra of the phosphor were measured up to 973 K. The fluorescence intensity ratios 4F3/2→6H5/2 (531 nm) to 4G5/2→6H5/2 (562 nm),4F3/2→6H5/2 (531 nm) to 4G5/2→6H7/2 (600 nm) and 4F3/2→6H5/2 (531 nm) to 4G5/2→6H9/2 (645 nm), were measured as a function of temperature in the range of 323→973 K. At 725 K, the greatest temperature sensitivity of 2.257 × 10?4 K?1 was attained for the4F3/2 → 6H5/2 to 4G5/2 → 6H5/2 ratio. The high thermal stability and good temperature sensitivity of the CaSr2(PO4)2:Sm3+, Li+ phosphors demonstrated that the material can be a potential candidate for n-UV-excited white light emitting diodes and optical thermometry applications.
NSTL
Elsevier