DIAMOND AND RELATED MATERIALS
·
2021
·
IF 3.315
Xiaoyu Zhang,Juan Yi,Yanan Yin,Yiheng Song,Chuanxi Xiong
In recent years, with the increasing demands of portable and high-speed electronic devices, highly integrated equipment attracts people's attention more and more. However, it is a great challenge to guarantee the long-term stability of electronic products at high temperatures. Hexagon boron nitride (h-BN), which owned excellent thermal conductivity and insulation properties , was preferred for electronics. For better compatibility of inorganic fillers and silicone rubber, a biological modification by coating polydopamine (DA) on h-BN was adopted. Herein, the composites based on h-BN@PDA and silicone rubber were fabricated. Compared with h-BN/silicone rubber composites , the thermal conductivity of h-BN@PDA/silicone rubber composites increased and volume resistance of materials had been decreasing. When the amount of h-BN@PDA fillers was 30 wt%, the thermal conductivity of h-BN@PDA/silicone rubber composite increased to 0.95 W m −1 K −1 . The volume resistivity of 30 wt% h-BN@PDA/silicone rubber composite reached 2.5 × 10 11 Ω·cm, which was the lowest one among others, which still exceeded requirements of electronic materials.
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高影响因子
APPLIED ORGANOMETALLIC CHEMISTRY
·
2020
·Vol. 34
·期 11
·e5925
·
IF 3.14
Jie Yao,Yan Wang,Suleiman Sabo Bello,Guangwen Xu,Lei Shi
As it is well known, Brønsted acid sites in 8-MR of H-MOR (mordenite) are selective for dimethyl ether (DME) carbonylation to methyl acetate, whereas those in 12-MR are more prone to methanol to olefin reaction. Interestingly, we observed that the Brønsted acid sites in 12-MR of H-MOR are highly active for dimethoxymethane (DMM) carbonylation to methyl methoxyacetate (MMAc), whereas those in 8-MR led to the formation of DME. A series of modified H-MOR catalysts with accurate regulation of Brønsted acid sites in 12-MR or 8-MR were successfully synthesized by selective Na + exchange or pyridine (Py) adsorption. Fourier-transform infrared (FT-IR) spectra, NH 3 -temperature-programmed desorption, Py-FT-IR, and inductively coupled plasma analyses suggested that Na + first occupied Brønsted acid sites in 8-MR and then replaced those in 12-MR. All Na + -exchanged catalysts exhibited significant acceleration on MMAc selectivity, and the ratio of Brønsted acid amount in 12-MR/total had a positive correlation with MMAc selectivity. The MMAc selectivity (78%) of H-MOR-0.15Na was nearly 2.5 times more than that of untreated H-MOR (31%). However, H-MOR-Py showed almost no carbonylation activity (<1% MMAc) and a highest DME selectivity (98%), indicating that Brønsted acid sites in 12-MR were the only active sites for DMM carbonylation, whereas those in 8-MR tended to accelerate DMM disproportionation to DME.
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高影响因子
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
·
2020
·Vol. 2020
·期 25
·3889-3895
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IF 2.889
Xinpeng Jiang,Zongchen Zhao,Zhifeng Shen,Keda Chen,Liyun Fang,Chuanming Yu
Graphical A metal-free aerobic oxidative C–H sulfenylation of aryl-fused cyclic amines with various thiols was developed with excellent functional compatibility. While flavin I catalyzed the C–H sulfenylation of indolines to afford 3-sulfenylindoles, flavin II enabled transformations resulting in substitution at the position para to the N atom on the aryl ring to obtain 6-sulfenylquinolines. We report an aerobic oxidative C–H sulfenylation of aryl-fused cyclic amines with various thiols catalyzed by flavin/I 2 for the first time. While flavin I catalyzed the C–H sulfenylation of indolines to afford 3-sulfenylindoles, flavin II enabled transformations resulted in substitution at the position para to the N atom on the aryl ring to obtain 6-sulfenylquinolines. The advantages of this metal-free oxidative C–S coupling approach utilizing ambient oxygen as the terminal oxidant were that it was conducted under mild conditions with good atom-efficiency and excellent functional compatibility.
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高影响因子
Materials Chemistry Frontiers
·
2020
·Vol. 4
·期 4
·1158-1163
·
IF 6.788
Zewen Zhuang,Yu Wang,Zheng Chen,Dingsheng Wang,Chen Chen,Qing Peng,Yadong Li
Densely populated metal atomic site catalysts play a key role in practical catalysis applications. Herein, we report an amorphous nanobox with high-density atomic platinum species which are uniformly dispersed into the ZIF-8 skeleton through cation exchange. During the dispersing process, the ZIF-8 core was gradually etched into the hollow structure though the Kirkendall effect, and a great amount substitutions of Pt with Zn breaks the initial long-range ordered ZIF-8 topology into a distorted skeleton which leads to the significantly unsaturated coordination of atomic Pt species. The high-density atomic Pt nanoboxes exhibit excellent performance in direct C–H bond borylation of arenes which are usually catalyzed by homogeneous complexes. Such high-density atomic site heterogeneous catalysts could serve as a bridge to convert from homogeneous to heterogeneous catalysis.
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高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Cuishuang Jiang,Mingyi Zhang,Guojun Dong,Tong Wei,Jing Feng,Yueming Ren,Tianzhu Luan
It is highly desirable but challenging to control nitrate contamination using photocatalytic reduction technology over non-mental catalysts. Herein, hexagonal boron nitride (h-BN), a typical non-metal catalyst, was employed to photocatalytic denitration in water with formic acid (FA) as a hole scavenger. Compared with a mental catalyst TiO 2 and a non-mental catalyst g-C 3 N 4 , h-BN obtained a more effective reduction performance with nitrate conversion of 97.16% and N 2 selectivity of 95.42%. After three cyclic use, it still presented excellent reduction activity and structure stability. In the h-BN system, the initial pH had a significant effect on the nitrate reduction performance because it determined the surface charge property of the catalyst or the dispersibility in water, and the presence of anions slightly decreased the nitrate conversion process since the competitive adsorption of NO 3 – or NO 2 – . Photocatalytic denitration over h-BN was well according with the Extended-Langmuir-Hinshelwood model. By comparing the average stoichiometric ratio of consumed FA and removed NO 3 – (i.e. experiment value) with the theoretical value, it was determined that there were additional electrons involved in the reduction reaction in addition to CO 2 •- radicals, which was also supported by the quenching experiments. Moreover, CO 2 •- radicals were mainly responsible for the conversion of NO 2 – to N 2 . Exposed B atoms on the h-BN edges behaved as the adsorption sites of nitrogen oxide anions. This study provides a proof-of-concept demonstration of non-mental photocatalyst h-BN for more effective management of nitrate contamination.
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Journal of Advanced Ceramics
·
2021
·Vol. 10
·期 6
·1317-1325
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IF 6.707
Liu Zetan,Zhao Shiqiang,Yang Tian,Zhou Ji
It is possible to improve the machinability of aluminum nitride-hexagonal boron nitride (AlN-h-BN) ceramics while maintaining high strength and high thermal conductivity. The composite ceramics with 0–30 wt% BN as secondary phase were prepared by hot pressed sintering, using yttrium oxide (Y 2 O 3 ) as sintering aid. The phase composition, density, microstructure, mechanical properties, thermal conductivity, and dielectric properties were investigated. The sintering additives were favorable to purify the grain boundaries and improve densification, reacting with oxide impurities on the surface of raw material powder particles. The optimum BN content improved the flexural strength and fracture toughness of composite ceramics with 475 MPa and 4.86 MPa·m 1/2 , respectively. With increasing the amount of BN, the thermal conductivity and hardness of composites gradually decreased, but the minimum value of thermal conductivity was still 85.6 W·m −1 ·K −1 . The relative dielectric constant and dielectric loss tangent of the samples ranged from 6.8 to 8.3 and from 2.4 × 10 −3 to 6.4 × 10 −3 , respectively, in 22–26 GHz.
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高影响因子
Asian Journal of Organic Chemistry
·
2018
·Vol. 7
·期 8
·1626-1634
·
IF 2.496
Wen-Jing Pan,Zhong-Xia Wang
Graphical Cut my bonds into pieces : The C−H benzylation of oxazoles and benzoxazoles with benzyl trimethylammonium triflates was performed under mild conditions via Pd-catalyzed C−H/C−N cleavage. The method exhibits a wide scope of substrates and good compatibility of functional groups. The C−H benzylation of oxazoles and benzoxazoles with benzylic ammonium triflates was performed in reasonable to good yields via Pd-catalyzed C−H/C−N cleavage. The method exhibits a wide scope of azoles and benzylic ammonium triflates. A range of functional groups including F, CF 3 , COOEt, C(O)NMe 2 , OMe, OPh, pyridyl and thienyl groups can be tolerated.
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DYES AND PIGMENTS
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2015
·
IF 3.966
Bin Shan,Xing Tong,Wei Xiong,Wenzhu Qiu,Bingtao Tang,Rongwen Lu,Wei Ma,Yi Luo,Shufen Zhang
A new kind of reactive dyes containing both monoazo and anthraquinone chromophores was obtained by using 1,4-bis((4-aminophenyl)amino)anthrancene- 9,10-dione as diazo component and 1-amino-8-naphthol-3,6-disulfonicacid (H-acid) derivatives as coupling components. The dyes were characterized by UV–Vis, IR, MS, 1 H NMR and 13 C NMR. The results showed that the maximum absorption wavelengths of the dyes were all about 590 nm, which indicated that they were a kind of blue dyes. 1 H NMR and 13 C NMR results revealed that there were two kinds of tautomerisms in dye structure and a new conjugated system formed between the anthraquinone ring and the phenyl azo linkage. Density functional theory (DFT) calculations also proved the formation of the new larger conjugated system from which the blue colour was generated. The fixations of the dyes on cotton were over 88% and the light fastness reached 5 grade.
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JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2016
·Vol. 99
·期 8
·2615-2624
·
IF 2.787
Zhaoju Yu,Pei Zhang,Yao Feng,Shuang Li,Yaxing Pei
We present a template-free synthesis of Fe 3 O 4 /SiOC(H) nanocomposites with in situ formed Fe 3 O 4 nanoparticles with a size of about 50 nm embedded in a nanoporous SiOC(H) matrix obtained via a polymer-derived ceramic route. Firstly, a single-source precursor (SSP) was synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with Fe-acetylacetonate [Fe(acac) 3 ] at 140°C. The SSP was heat-treated at 170°C to generate Fe 3 O 4 nanocrystals in the cross-linked polymeric matrix. Subsequently, the SSP was pyrolyzed at 600°C–700°C in argon atmosphere to yield porous Fe 3 O 4 /SiOC(H) nanocomposites with the high BET surface area up to 390 m 2 /g, a high micropore surface area of 301 m 2 /g, and a high micropore volume of 0.142 cm 3 /g. The Fe-free SiOC(H) ceramic matrix derived from original AHPCS is nonporous. The in situ formation of Fe 3 O 4 nanoparticles embedded homogeneously within a nanoporous SiOC(H) matrix shows significantly enhanced catalytic degradation of xylene orange in aqueous solution with H 2 O 2 as oxidant as compared with pure commercial Fe 3 O 4 nanoparticles.
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Foods
·
2024
·Vol. 13
·期 17
·2652
·
IF 4.7
Na Li,Xiao Wu,Qin Yin,Zeng Dong,Lele Zheng,Yihui Qian,Yulu Sun,Ziping Chen,Kefeng Zhai
The extraction of total flavonoids fromHylotelephium spectabile(Boreau) H. Ohba (H. spectabile) leaves was studied through the use of a double enzyme-assisted ultrasonic method, and the extraction process was optimized using the Box–Behnken design. Eight different macroporous resins were screened for purification in single-factorial experiments, and the flavonoid compounds in the extract ofH. spectabileleaves were identified using HPLC-MS. Through the evaluation of the total reducing capacity and capacity for reducing 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH), hydroxyl radicals (·OH), and 2,2’-biazobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), the in vitro antioxidant activities of the crude extracts of the total flavonoids and purified total flavonoids ofH. spectabileleaves were investigated. The results showed that the most efficient conditions for flavonoid extraction were an ultrasonic extraction time of 60 min, an ethanol concentration of 35%, a liquid-to-material ratio of 20:1 mL/g, and an amount of enzyme (cellulose/pectinase = 1:1) of 1.5%, formingH. spectabilepowder. Under these conditions, the total flavonoid extraction rate in theH. spectabileleaf extract was 4.22%. AB-8 resin showed superior performance in terms of purification, and the optimal adsorption and desorption times were 1.5 h and 3 h, respectively. The recommended parameters for purification included a liquid volume of 5.5 BV, a flow rate of 1.2 BV/min, a pH of 5, and a concentration of 0.8 mg/mL. The observed order for reducing capacity was ascorbic acid (VC) > rutin > purified total flavonoids > crude extract of total flavonoids. The purified total flavonoid extract fromH. spectabileshowed a good scavenging ability against DPPH, ·OH, and ABTS·+, suggesting strong antioxidant activity. Therefore, this study can serve as technical support and reference data for the further development and utilization ofH. spectabileresources.
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PubMed
高影响因子
SOLAR ENERGY MATERIALS AND SOLAR CELLS
·
2024
·
IF 6.3
Ziqiang Cheng,Gang Xu,Yong Liu,Gaorong Han
Benefitting from large-sized ion tunnels and stable crystalline structures, hexagonal WO 3 (h-WO 3 ) is a promising electrochromic (EC) material. However, long reaction times and highly controlled reaction conditions for preparation hinder the practical application. Here, a novel method with a simple process and moderate condition, named topotactic layer-to-tunnel crystallization (TLTC), to prepare h-WO 3 films is reported. The hexagonal tunnel structure is transformed from a layered structure by annealing, assisted by the structure director. The ACTEM with atomic resolution reveals the position of the structure director in the crystal lattice, which is left in the hexagonal tunnel. The mechanism of TLTC has been studied by the characterization of samples at different formation stages, and the key is the structure director, which maintains the hexagonal tunnel by steric effect. The prepared h-WO 3 film exhibits significant optical modulation (65.8 % at 633 nm and 72.8 % at 1200 nm) and outstanding cyclic stability (98.1 % of initial optical modulation remained over 600 cycles). The TLTC method is based on the structure transition to construct large tunnels in lattice, providing a new technical route to prepare h-WO 3 and showing great potential for EC materials manufacturing.
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ACS Nano
·
2025
·
IF 16
Shengxi Li,Yanxin Shang,Xuening Ren,Anqi Zhao,Nan Chen,Li Li,Feng Wu,Renjie Chen
Aqueous lithium-ion batteries (ALIBs) have attracted increasing attention for their inherent safety and environmental benefits. However, the narrow electrochemical stability window of water (1.23 V) imposed by hydrogen evolution reaction (HER) and high melting point (0 °C) critically limits the energy density and low-temperature operation. In this work, we report an electrolyte design principle that water activity can be suppressed by strengthening the O–H bonds between water molecules and regulating the pH. A strong polar solvent N,N-dimethylformamide (DMF) interacts with H2O through intermolecular hydrogen bonds, thereby reinforcing the covalent O–H bonds of water. Meanwhile, KOH renders the electrolyte alkaline, inhibiting water dissociation kinetics and consequently raising the HER overpotential. The designed LD1.7W0.6–KOH electrolyte exhibits a freezing point below −82 °C and expanded electrochemical stability window of 4.3 V. The 2.5 V aqueous LiMn2O4/Li4Ti5O12 full cell delivers 2000 cycles at a rate of 6 C with a Coulombic efficiency of 99% at 30 °C and over 1950 cycles at 0 °C. This work offers atomic-level insights into alkaline HER while providing guidance for advancing low-temperature aqueous batteries by tuning the electrolyte structures.
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PubMed
高影响因子
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