JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2021
·Vol. 105
·期 1
·461-468
·
IF 3.784
Baoyu Deng,Yiming Ma,Tianxiang Chen,Huajing Wang,Jinfeng Lin,Cong Lin,Xiao Wu,Chunlin Zhao,Tengfei Lin,Min Gao,Xinghua Zheng,Changqing Fang
Dense (K, Na)NbO 3 ceramics are successfully fabricated via the cold sintering process at 350°C under a uniaxial pressure of 400 MPa for 4 h. Equimolar KOH and NaOH solutions were utilized as a transient alkaline flux. The microstructure and dielectric properties were studied in detail. Scanning electron microscope and the relative densities reveal dense structures of the ceramics. After post-annealing at 800°C for 1 h, the ceramics show good electrical performance. The relative dielectric permittivity is 829 (at 10 kHz) at room temperature, and the piezoelectric constant ( d 33 ) reaches up to 148 pC/N. The cold sintering technique with equimolar KOH and NaOH solutions as a transient alkaline flux endow KNN ceramics with excellent dielectric and piezoelectric properties, showing a potential way to fabricating other KNN-based ceramics at low temperature.
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JOURNAL OF ALLOYS AND COMPOUNDS
·
2021
·
IF 5.316
Nan Xin,Yifei Li,Guihua Tang,Longyun Shen
High-efficient and environment-friendly thermoelectric materials have attracted much attention. The single crystal tin selenide (SnSe) has a record high thermoelectric figure of merit ( ZT ) of 2.6 at ~800 K. Polycrystalline SnSe has better mechanical-strength but inferior ZT values than the single crystal, attribute to the paradoxically higher thermal conductivity ( κ ). In this work, we synthesized K x Sn 1−x Se (x = 0, 0.01, 0.02, 0.03 and 0.04) by doping K 2 CO 3 . A large number of point defects and dislocations generated with CO 2 volatilization, which possibly reduces κ . Based on this process, the K x Sn 1−x Se powders were followed by the hydrogen reduction with 4% H 2 − 96% Ar atmosphere to reduce tin oxide and potassium oxide which have high κ . These strategies lead to an ultra-low κ 0.32 Wm −1 K −1 in K 0.03 Sn 0.97 Se at 798 K. The effects of K doping on electronic transport performance of SnSe were studied by density functional theory calculation and experimental measurement. Doing K can narrow the band gap, increase hole concentration and enhance the electrical conductivity ( σ ) of SnSe. At 298 K, the σ of K x Sn 1−x Se increased by more than 2.5 times compared with the pristine SnSe. In high temperature region (623 K< T < 823 K), the σ is mainly affected by thermal excitation. High doping level of K (x = 0.03 and 0.04) suppresses the thermal excitation and limits the maximum of ZT . As the result, A high ZT of 1.06 is obtained at 798 K from K 0.01 Sn 0.99 Se perpendicular to the pressing direction, which is 103.8% larger than that of pristine SnSe. In addition, the hot-pressing polycrystalline K x Sn 1−x Se remains obvious lamellar morphology and show anisotropy. The σ and κ of K x Sn 1−x Se samples perpendicular to the pressure direction are much higher than those of the samples parallel to the pressure direction. This anisotropy decreases with the increasing K content.
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MICROPOROUS AND MESOPOROUS MATERIALS
·
2021
·
IF 5.455
Ying Shi,Qiuming Zhou,Zhangfeng Qin,Zhiwei Wu,Weiyong Jiao,Mei Dong,Weibin Fan,Jianguo Wang
The aromatization of alkanes is an important process for improving the quality of Fischer-Tropsch synthesis (FTS) gasoline and producing high-valued aromatics from naphtha ; however, currently available catalysts in this regard are often deficient due to the low aromatics yield and short lifetime. In this work, a series of hierarchically structured Beta (Beta-HS) zeolites with high crystallinity and meso-porosity were synthesized by steam treatment with various organosilanes as pore-forming reagent and ethanol as solvent. The nano-sized Beta-HS zeolites were further modified with K through ion-exchange and with Pt through incipient wetness impregnation; the resultant Pt/K-Beta-HS catalysts were then used in the aromatization of n -heptane. The results indicate that the abundant mesopores present in Beta-HS are conducive to the diffusion of reactants and products, whilst the modification with K is able to passivate the strong Brønsted acid sites and the loading of Pt metal can promote the dehydrogenation of alkanes and cycloalkanes, which can effectively suppress the cracking and carbonaceous deposition reactions and enhance the dehydrogenation aromatization activity. As a result, the Pt/K-Beta-HS catalysts exhibit excellent performance in the aromatization of n -heptane, with a much longer lifetime (205 h), higher selectivity to aromatics (80%) and larger turnover number of aromatic products (Pt-based TON, 240 × 10 3 ) than conventional Beta zeolites. These results prove that the steam treatment with organosilanes as pore-forming reagent is a facile and cost-effective strategy to synthesize the hierarchically structured Beta zeolites and after loading K and Pt, the Pt/K-Beta-HS zeolites can be an efficient catalyst for the conversion of n -heptane to aromatics.
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FUEL
·
2020
·
IF 5.578
Hongliang Li,Hua Han,Yue Wang,Xianshu Dong,Hongli Yang,Minqiang Fan,Yang Hu,Zeyu Feng
In coal beneficiation, the clean coal would be easily contaminated with the super fine montmorillonite particles coating on it. This interaction between coal (hydrophobic) and montmorillonite (hydrophilic) surfaces is the interactions between the asymmetric systems. Previous studies detected the force between the montmorillonite and graphite or between the montmorillonite mounted tip and coal substrate to represent the interactions between 001 surface and coal. However, there is still lack of experimental direct measurement on the interaction between montmorillonite 001 surface and coal macerals. In this study, proposes methods for determinine the interactions between coal macerals and 001 surface of Na-, K- and Ca- montmorillonite directly by using an atomic force microscope (AFM). The results indicate that the 001 surface of Na- and Ca- montmorillonite served as the chaotropic and kosmotropic surface when it is adjacent to coal surfaces, with an attractive force and repulsive force occurring between them, respectively. The 001 surface of K-montmorillonite served as the chaotropic surface and kosmotropic surface while it is close to liptinite and inertinite, respectively. This chaotropic or kosmotropic property of the surface is determined by the coordination number of the cations and wettability of the hydrophobic surface simultaneously.
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JOURNAL OF POLYMER RESEARCH
·
2020
·Vol. 27
·期 11
·1-8
·
IF 2.426
Wang Qi,Pu Zejun,Zheng Xiaoyi,Tian Yuhan,Li Xinyue,Zhong Jiachun
Polyarylene ether nitrile (PEN) random copolymers were prepared from 6AF, BHPF, and 2, 6-dichlorobenzonitrile according to the nucleophilic aromatic substitution polymerization. The chemical structure of PEN random copolymers was characterized by the FT-IR and 1 H-NMR spectrum, respectively. The thermal properties of the PEN random copolymers were investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The resulting PEN copolymers have excellent thermal stability with high glass transition temperature ( T g ) ranging from 187℃ to 271℃ and the 5% weight loss temperature ( T 5% ) of PEN copolymers greater than 490℃ in nitrogen atmospheres. Meanwhile, the PEN films have excellent mechanical property, the tensile strength ranges from 55 to 95 MPa. Moreover, the dielectric properties of the PEN random copolymers were investigated by dielectric tests. The dielectric constants ( k ) and loss tangent (tan δ) of PEN (PEN-6-AF/BHPF100) film is only 2.3 and 0.03 at 1 kHz, respectively. More importantly, the dielectric properties were found to be relatively stable until the T g , which can be attributed to the existence of BHPF units in the molecular backbone.
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FUEL
·
2020
·
IF 5.578
Long Ma,Shuzhen Chen,Changlei Qin,Susu Chen,Weiyang Yuan,Xu Zhou,Jingyu Ran
Li 4 SiO 4 is a well-acknowledged CO 2 sorbent in the sorption-enhanced reforming system for low-cost H 2 production with a high purity. However, the inevitable presence of H 2 S in the biomass-derived syngas etc. could possibly affect the in-situ CO 2 adsorption significantly, which is important but has never been reported. In this work, the adsorption of CO 2 using Li 4 SiO 4 was investigated under varying H 2 S concentrations and reaction temperatures, and a series of characterization techniques were utilized to understand the effect of H 2 S and its action mechanism. The results show that the presence of H 2 S causes a rapid loss-in-capacity of Li 4 SiO 4 in capturing CO 2 during the cyclic reactions, and a higher concentration greatly exacerbates the problem. Moreover, the negative impact of H 2 S is found to have a strong relationship to the reaction temperature. It is proposed that at 325~475 °C, Li 4 SiO 4 and H 2 S react to form bits of Li 2 S and some kinds of sulfates, and at 625~775 °C, a large amount of dense KLiSO 4 is generated covering the surface of the sorbent. In contrast, at a high temperature above 925 °C, sintering of Li 4 SiO 4 plays a critical role, leading to a significant change on its microstructure.
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ADVANCED MATERIALS
·
2020
·Vol. 33
·期 3
·2006118
·
IF 27.398
Zhengping Ding,Chen Yang,Jian Zou,Shulin Chen,Ke Qu,Xiumei Ma,Jingmin Zhang,Jing Lu,Weifeng Wei,Peng Gao,Liping Wang
Fluorographites (CF x ) are ultrahigh-energy-density cathode materials for alkaline-metal primary batteries. However, they are generally not rechargeable. To elucidate the reaction mechanism of CF x cathodes, in situ transmission electron microscopy characterizations and ab initio calculations are employed. It is found that it is a two-phase mechanism upon K/Na/Li ion insertion; crystalline KF (crystalline NaF nanoparticles and amorphous LiF) is generated uniformly within the amorphous carbon matrix, retaining an unchanged volume during the discharge process. The diffusivity for K/Na/Li ion migration within the CF x is ≈2.2–2.5 × 10 –12 , 3.4–5.3 × 10 –12 , and 1.8–2.5 × 10 –11 cm 2 s –1 , respectively, which is comparable to the diffusivity of K/Na/Li ions in liquid-state cells. Encouraged by the in situ transmission electron microscopy (TEM) results, a new rechargeable all-solid-state Li/CF x battery is further designed that shows a part of the reversible specific discharge capacity at the 2nd cycle. These findings demonstrate that a solid-state electrolyte provides a different reaction process compared with a conventional liquid electrolyte, and enables CF x to be partly rechargeable in solid-state Li batteries.
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PubMed
高影响因子
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
·
2020
·Vol. 217
·期 8
·1900806
·
IF 1.759
Jingbo Li,Yu Liu,Fang Xu,Junping Hu,Nan Chen,Guoping Du,Changshuang Jiang
As a 2D material, Ti 3 C 2 (MXene) has been recently used as electrodes for electrochemical capacitors. Herein, a two-step procedure is used to obtain a highly opened layer structure for Ti 3 C 2 , which differs from the methods used in the literature for synthesizing exfoliated MXene. First, the mild NH 4 HF 2 etching agent is used to prepare the regular Ti 3 C 2 MXene. Second, KOH is added into the obtained solution for K + to intercalate the MXene. The K + intercalation is found to greatly increase the (002) crystal planar spacing of the Ti 3 C 2 from 10.8 to 12.4 Å. More importantly, this K + -intercalated MXene exhibits a highly opened layer structure, whereas the regular MXene only has a partially opened layer structure. Consequently, the former is expected to allow much more active sites exposed to liquid electrolyte, and also facilitates remarkably higher ion and electron transport efficiency. To investigate their electrochemical capacitance properties, the regular and K + -intercalated Ti 3 C 2 MXenes are used to fabricate binder-free electrodes on nickel foams by an electrophoretic deposition method. The K + -intercalated MXene-based electrode is found to have twice higher specific capacitance than the regular MXene. Furthermore, the K + -intercalated Ti 3 C 2 MXene-based electrode exhibits an excellent cyclic stability.
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CARBOHYDRATE POLYMERS
·
2019
·
IF 6.044
Maruthupandy Muthuchamy,Rajivgandhi Govindan,Kadaikunnan Shine,Veeramani Thangasamy,Naiyf S. Alharbi,Muneeswaran Thillaichidambaram,Jamal M. Khaled,Jun-Li Wen,Khalid F. Alanzi
In this study graphene/chitosan nanoparticles (GR/CS NCs) were developed. The homogenous combination of GR and CS was confirmed by FTIR spectroscopy. The combination of CS with GR sheets reduced the XRD intensity of the GR peak in GR/CS NCs, while TEM images revealed the immobile CS coating of GR sheets. Further, the anti-biofilm activity of GR/CS NCs was tested. The tests showed that the formation of biofilm by Pseudomonas aeruginosa and Klebsiella pneumoniae was inhibited at 40□g/mL GR/CS NCs up to 94 and 92 %, respectively. The intracellular and cell surface damage of the bacteria was observed by CLSM and SEM. Also, GR/CS NCs produced a toxic effect of 90 % on Artemia franciscana at 70□g/mL upon 24 h incubation. The recorded properties of the synthesized GR/CS NCs qualify them as potential agents against multi-drug resistant bacteria.
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PubMed
高影响因子
JOURNAL OF CHEMICAL AND ENGINEERING DATA
·
2019
·
IF 2.298
Chao Ye,Zhong-Zhong Wu,Shi-Hua Sang,Xiao-Yun Qi,Xing Liu
The solid–liquid phase equilibria of the ternary system KBr–LiBr–H2O at 273 and 308 K were determined by the isothermal dissolution equilibrium method. On the basis of the obtained experimental data, the stable phase diagrams of ternary system KBr–LiBr–H2O at 273 and 308 K were plotted, respectively. The results show that the ternary system is a simple cosaturated type at two different temperatures, and there is neither a solid solution nor a double salt in the system. Both of the phase diagrams include one invariant point, two univariant curves, and two crystalline regions (where the solids are LiBr·2H2O and KBr, respectively). The crystalline area of KBr is much larger than that of LiBr·2H2O, indicating that the solubility of KBr is much smaller than that of LiBr in the ternary system. The mass fraction of KBr in the equilibrium liquid phase is obviously reduced, which indicates that LiBr has a strong salting-out effect on KBr.
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高影响因子
ACS Applied Nano Materials
·
2026
·
IF 5.8
Chenglin Wang,Yibo Wang,Hanyang Li,Gaozhao Chen,He Liu,Wentao Hao,Fazl Ullah,Qiuyun Ouyang
Abstract To address intrinsic parity-forbidden transitions, strong electron-phonon coupling, and defect-assisted nonradiative recombination in Cs2NaInCl6 nanocrystals, K-doped Cs2NaInCl6:xK+ (x = 0−1) nanocrystal powders were synthesized via a hot-injection method. The powders were dispersed in methyl methacrylate to prepare organic glasses. The x = 0.2 sample exhibits the best performance. Nonlinear absorption was evaluated by open-aperture Z-scan measurements. Both undoped and K+-doped nanocrystals exhibit a transition from saturable absorption to reverse saturable absorption with increasing excitation energy. K+ doping significantly enhances the nonlinear absorption response. At 50 μJ, the nonlinear absorption coefficient of the K+-doped nanocrystals reaches 40 cm·GW−1, approximately 4.2 times that of the undoped nanocrystals (9.5 cm·GW−1). Meanwhile, the optical limiting threshold decreases from 4.69 to 3.53 J·cm−2. This enhancement is attributed to reduced nonradiative loss and prolonged excited-state lifetime induced by K+ incorporation, thereby facilitating carrier accumulation and strengthening excited-state absorption. In addition, the (Cs2NaInCl6:0.2K+)6/poly(methyl methacrylate) organic glass retains 97.14% of its initial nonlinear absorption response after five months. These results demonstrate that K+ doping is an effective strategy for regulating the nonlinear absorption performance of lead-free double perovskites and provide insights into the design of high-performance optical limiting and laser protection materials.
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APPLIED ENERGY
·
2023
·
IF 11.2
Juan Yi,Zhiwei Ye,Shixian Zhang,Yiheng Song,Zhilong Cao,Bin Liu,Chenjian Li,Shuang Liu,Shuai Nie,Chuanxi Xiong
Piezoelectric nanogenerators (PENGs) are mushrooming owing to demand of swift transformation of power supply from fossil fuel to green energy. Piezoelectric ceramics are enthusiastically chased because glorious PENGs demand for high piezoelectricity. Generally, brittleness of ceramics can be compensated by polymer, while the dielectric mismatch between low permittivity of polymer and high permittivity of ceramics plaguing researchers so long. Traditional contact poling is always interrupted by abrupt dielectric breakdown due to electric field concentration at interface between polymer and fillers. Here, we propose a strategy of using corona polarization instead of traditional contact polarization to insistently polarize large-area polymer composite films with high-k filler. The corona polarization technique can ignore the negative effect of local short circuit on polarization failure owing to prominent lateral insulation between deposited charges on surface of composites film, consequently obtaining well-performed piezoelectricity. Henceforth, polarization failure did not occur using corona even under poling voltage of 26 kV. The corona-poled PVDF/Y-ZnO PENG with only 15 wt% content of fillers generated output power density of ∼1064 μW/cm 3 . Our work will pilot the development of polymer composites with high-k filler and piezoelectric nanogenerators.
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危险品化学品经营许可证（带存储）