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Facilitating effect of heavy metals on di(2-ethylhexyl) phthalate adsorption in soil: New evidence from adsorption experiment data and quantum chemical simulation
No full textIn terms of researching and treating farmland pollution, interactions between organic and inorganic pollutants are very important aspects. Herein, the effects of heavy metals on di(2-ethylhexyl) phthalate (DEHP) adsorption in soil were investigated. The presence of Cd2+/Cu2+ increased the adsorption capacity of DEHP (>23%) in a nonlinear manner. Fourier transform infrared spectroscopy revealed that the stretching vibration of soil functional groups changed under different pollution combinations, while quantum chemical simulation, including an independent gradient model and localized orbital locator, proved that outer-orbital complexes could be formed by electrostatic interaction between Cd2+/Cu2+ and DEHP. The electron transfer process was analyzed by charge decomposition analyses, and these, combined with bond critical point analyses, revealed that metal ions reduced DEHP stability. The binding energy and binding free energy of different combinations were calculated and analyzed, using the key soil organic matter (SOM) information obtained through pyrolysis gas chromatography mass spectrometry. This effectively explained the adsorption behavior, and showed that SOM polar functional groups played an important role in the effect of heavy metals on DEHP adsorption. The study described here has provided a new basis for understanding the multiple interactions, acaimulation, and transformation of pollutants in the soil. (C) 2021 Elsevier B.V. All rights reserved
A deep insight into polybenzoxazole formation in the heterocycle-containing polybenzoxazine: An enlightening thought for smarter precursor design
No full textWhen artificially introducing an ortho-amide group into benzoxazine monomer, the conversion of polybenzoxazine (PBZ) into polybenzoxazole (PBO) could happen at higher temperature. However, the mechanism investigation for this reaction is far from enough, which is very significant for the PBO fabrication from PBZ. In this work, we designed three kinds of benzoxazines (PIC-abz, 4-MEP-abz and 6-MEP-abz) containing both pyridyl and amide group with similar structures. The existence of intramolecular N-HMIDLINE HORIZONTAL ELLIPSISN H-bonding involved with amide group and the N atom in pyridine ring, as well as the N-HMIDLINE HORIZONTAL ELLIPSISO H-bonding between the amide N-H and the O atom in oxazine ring, were confirmed by 1H-1H nuclear overhauled effect spectroscopy (NOESY) and concentration dependent 1H NMR spectra. In addition, the respective strength of these H-bonding in different precursors was calculated by non-covalent interaction (NCI) simulation. Results showed that besides the performance of resulted PBZ, the conversion temperature of PBZ into PBO was significantly influenced by the N-HMIDLINE HORIZONTAL ELLIPSISN hydrogen bonding involved with pyridyl and amide groups. Based on which, the mechanism of PBO formation was proposed and systematically investigated. The outcome of this work will help us to obtain PBO in a more efficient and reasonable manner starting from PBZ
On the dependence of interfacial resistance on contact materials between cathode and interconnect in solid oxide fuel cells
No full textThe dependence of interfacial contact resistance (ICR) on contact materials between cathode and interconnect is systematically studied under both isothermal oxidation and thermal cycling conditions. Three kinds of cathode current-collecting layer (CCCL) are used, (La,Sr) (Co,Fe)O-3 (LSCF), LSCF+10% Ag, and Ag, and tested in a SUS430/CCCL/SUS430 sandwich structure to simulate the actual operation of the solid oxide fuel cells (SOFCs). Experimental results show that the ICR of LSCF+10% Ag exhibits the smallest value, in comparison with the specimens with LSCF and Ag paste, as well as the sample without a CCCL. For LSCF+10% Ag contact, the ICR increases from 0.0069 m Omega cm(2) to 3.74 m Omega cm(2) under an isothermal condition for 150 h, then increases from 3.74 m Omega cm(2) to 10.79 m Omega cm(2) after 15 thermal cycles. This work provides information for the understanding of possible mechanisms of performance degradation of SOFCs. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
High ionic conductivity and dendrite-resistant NASICON solid electrolyte for all-solid-state sodium batteries
No full textThe low ionic conductivity and poor dendrites suppression capability of Na3Zr2Si2PO12 solid electrolyte limit the practical application of all-solid-state sodium batteries. Herein, the optimized Na3.4Mg0.1Zr1.9Si2.2P0.8O12 electrolyte is obtained by simultaneously substituting the Zr4+ with Mg2+ and P5+ with Si4+ through solid-state reaction. The Na3.4Mg0.1Zr1.9Si2.2P0.8O12 electrolyte has superior room temperature ionic conductivity of 3.6 x 10(-3) S cm(-1), which is 17 times higher than that of pristine Na3Zr2Si2PO12. No short circuit of the Na/Na3.4Mg0.1Zr1.9Si2.2P0.8O12/Na symmetric battery is observed up to 2.0 mA cm(-2), and the symmetric battery displays stable sodium plating/stripping cycles for over 2000 h at 0.1 mA cm(-2) and 300 h at 1.0 mA cm(-2). The resultant Na3.4Mg0.1Zr1.9Si2.2P0.8O12 electrolyte is further employed in two all-solid-state sodium batteries. The Na3V2(PO4)(3)/Na3.4Mg0.1Zr1.9Si2.2P0.8O12/Na all-solid-state sodium battery maintains a discharge capacity of 93.3 mAh g(-1) at 0.1C after 50 cycles, and the FeS2/Na3.4Mg0.1Zr1.9Si2.2P0.8O12/Na all-solid-state sodium battery delivers a discharge capacity of 173.1 mAh g(-1) at 0.1C after 20 cycles, which are significantly enhanced compared with those based on pristine Na3Zr2Si2PO12. This strategy provides an efficient method to prepare optimized NASICON solid electrolytes with high ionic conductivity and excellent dendrites suppression capability and promotes the practical application of all-solid-state sodium batteries. (C) 2021 Elsevier Ltd. All rights reserved
Spatial Characteristics of the Tourism Flows in China: A Study Based on the Baidu Index
No full textThe characteristics of information flow, as represented by the Baidu index, reflect the pattern of tourism flows between different cities. This paper is based on the Baidu index and applies the seasonal concentration index and social network analysis (SNA) methods to study the spatial structure characteristics of tourism flows in China. The results reveal that: (1) both the search volume of the Baidu index in different cities and the online attention to different scenic areas exhibit obvious spatial heterogeneity and seasonal differences; (2) regions with strong tourism flow connections mainly occur in the areas between metropolises or among the inner cities of urban agglomerations, which are largely distributed on the southeast side of the Heihe-Tengchong Line; (3) the development of the whole tourism flow network in China is low, with an unbalanced development between tourism supply and demand, indicating that tourism resources are concentrated in a few cities and that most of the information interaction among cities occurs in core areas, while a weak interaction is observed in peripheral areas; (4) cities like Beijing and Wuhan attain obvious advantages in regard to their tourism resources, whereas other cities, including Beijing, Shanghai, Shenzhen and Guangzhou, exhibit a high demand for tourism. Moreover, tourism information flow networks are concentrated in several cities with an important role in the Chinese urban system, such as Beijing, Wuhan, and Chengdu, because they contain abundant tourism resources, well-developed transportation systems and advanced economic and societal development levels. (5) Cities such as Beijing, Lhasa, Wuhan, and Zhengzhou possess numerous advantages due to structural holes, and they thus occur at an advantageous position in the tourism flow network
Cyanogel and its derived-materials: properties, preparation methods, and electrochemical applications
No full textCyanogel, a novel inorganic polymeric hydrogel, is constituted by chlorometallates and transition-metal cyanometallates, which is thought as fascinating and promising precursor to produce highly alloyed materials with stereochemical structures. In this review, the properties, synthesis methods, and electrochemical applications of the cyanogel and its derivates are systematically discussed. With intrinsic properties such as 3D interconnected backbones, uniform distributions of metals at atomic level, and porous structures, the cyanogel-derived materials exhibit superior activities and stabilities. During the synthesis process, the skeleton of cyanogel serves as soft template for generating metal structures without any surfactant. Due to the versatility and tunability of cyanogels, their derivatives not only provide foreseeable opportunities for preparation of highly efficient nanomaterials in electrocatalytic reactions, but also broaden their practical applications in energy-related devices such as fuel cells, water splitting electrolyzers, metal-air batteries, energy storage batteries, and supercapacitors. Through this review, we aim to provide valuable guidelines for constructing highly effective materials in practice. (C) 2021 Elsevier Ltd. All rights reserved
Effects of post-sinter annealing on microstructure and magnetic properties of Nd-Fe-B sintered magnets with Nd-Ga intergranular addition*
No full textWe investigate the effects of post-sinter annealing on the microstructure and magnetic properties in B-lean Nd-Fe-B sintered magnets with different quantities of Nd-Ga intergranular additions. The magnet with fewer Nd-Ga additions can enhance 0.2 T in coercivity, with its remanences nearly unchanged after annealing. With the further increase of the Nd-Ga addition, the annealing process leads coercivity to increase 0.4 T, accompanied by a slight decrease of remanence. With the Nd-Ga addition further increasing and after annealing, however, the increase of coercivity is basically constant and the change of remanence is reduced. Microstructure observation indicates that the matrix grains are covered by continuous thin grain boundary phase in the magnets with an appropriate Nd-Ga concentration after the annealing process. However, the exceeding Nd-Ga addition brings out notable segregation of grain boundary phase, and prior formation of part RE 6Fe13Ga phase in the sintered magnet. This prior formation results in a weaker change of remanence after the annealing process. Therefore, the diverse changes of magnetic properties with different Nd-Ga concentrations are based on the respective evolution of grain boundary after the annealing process
Facile Synthesis of Unimodal Polymethacrylates with Narrow Dispersity via NIR LED Light-Controlled Bromine-Iodine Transformation Reversible-Deactivation Radical Polymerization
No full textA facile and clean strategy for synthesizing unimodal polymethacrylates with narrow dispersity (D < 1.10) is successfully developed by a near-infrared (NIR) light-emitting diode (LED) light (lambda(max) = 740 nm)-controlled in situ bromine-iodine transformation reversible-deactivation radical polymerization system without the use of NIR dyes and expensive catalysts. In this system, alkyl iodide ethyl alpha-iodophenylacetate (EIPA) initiator is generated in situ by the nucleophilic substitution reaction between an alkyl bromide compound ethyl alpha-bromophenylacetate and sodium iodide (NaI). At the same time, excessive NaI is also acted as a highly active catalyst by forming halogen bonds with terminal iodine of the polymer chains in this system to make it capable of precisely synthesizing polymethacrylates with narrow dispersities (D = 1.03-1.10). In addition, the strong penetration ability of NIR LED light is illustrated by the successful polymerization even through 11 pieces of A4 paper
Temperature-Triggered Structural Dynamics of Non-Coordinating Guest Moieties in a Fluorescent Actinide Polyrotaxane Framework
No full textWe present here the synthesis of a novel fluorescent actinide polyrotaxane compound URCP1 through the utilization of an end-cutting pseudorotaxane precursor with only the cucurbit[6]uril (CB[6]) macrocyclic components acting as linking struts. The non-coordinating guest motif in the obtained polyrotaxane, with increased freedom and structural flexibility, can display intriguing temperature-triggered conformational variations inside the cavity of CB[6], which was clearly evidenced by crystallographic snapshots at different temperatures. Notably, this observation of temperature-triggered structural dynamics in URCP1 represents the first report of actinide polyrotaxane with such feature in solid-state. Moreover, URCP1 has a high photoluminescence quantum yield (PLQY) of 49.8 %, comparable to other luminescent uranyl compounds, and can work as a fluorescent probe to selectively detect Fe3+ over other eight competing cations in aqueous solution, with the limit of detection being as low as 4.4x10(-3) ppm
Three-Dimensional-Printable Thermo/Photo-Cross-Linked Methacrylated Chitosan-Gelatin Hydrogel Composites for Tissue Engineering
No full textBiomimetic constructs imitating the functions, structures, and compositions of normal tissues are of great importance for tissue repair and regeneration. Three-dimensional (3D) printing is an innovative method to construct intricate biomimetic 3D tissue engineering scaffolds with spatiotemporal deposition of materials to control the intrinsic architectural organization and functional performance of the scaffold. However, due to the lack of bioinks with suitable printability, high structural integrity, and biological compatibility, producing constructs that mimic the anisotropic 3D extracellular environments remains a challenge. Here, we present a printable hydrogel ink based on methylacrylate-modified chitosan (ChMA) and gelatin (GelMA) embedding nanohydroxyapatite (nano-Hap). This polymer composite is first physically cross-linked by thermal gelation for postprinting structural stability, followed by covalent photo-cross-linking of ChMA and GelMA to form a long-term stable structure. The rheological behavior of the hydrogels and the mechanical strengths of the printed constructs are tuned by adjusting the content of GelMA, which in turn enhances the shape retention after printing and enables the precise deposition of multilayered 3D scaffolds. Moreover, the formulated biomaterial inks exhibit biological characteristics that effectively support the spreading and proliferation of stem cells seeded on the scaffolds after 7 days of in vitro culture. Adding Hap has minor influences on the mechanical rigidity and cytocompatibility of the hydrogels compared with the group free of Hap. Together, the printable biomaterial inks with shear thinning and good structural integrity, along with biological cues, are promising for tissue engineering application