RARE METALS
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2024
·
IF 9.6
Li Zhao-Yang,Zhao Wei-Jun,Sun Yu,Zhou Bing,Feng Yue-Zhan,Liu Chun-Tai
The pressing demand for ultrathin and flexible shields to counter electromagnetic interference (EMI) has sparked interest in Ti 3 C 2 T x MXene materials due to their exceptional electrical conductivity, tunable surface chemistry, and layered structure. However, pure Ti 3 C 2 T x MXene films often lack the mechanical properties required for practical engineering applications, and traditional reinforcement methods tend to reduce electrical conductivity. This work demonstrates an effective strategy to enhance the alignment and densely packed layered structure of Ti 3 C 2 T x MXene films by regulating the acidity and alkalinity of Ti 3 C 2 T x MXene aqueous solutions. This approach simultaneously improves mechanical strength and electromagnetic interference shielding effectiveness (EMI SE). Compared with original Ti 3 C 2 T x MXene films, MXene films modified with ammonia solution (NH 3 ·H 2 O) via OH − show a significant improvement in tensile strength (27.7 ± 1.9 MPa). Meanwhile, MXene films treated with hydrochloric acid (HCl) via H + reach an even higher tensile strength of 39 ± 1.5 MPa. Moreover, the EMI SE values of the treated MXene films increase significantly, each reaching 66.2 and 58.4 dB. The maximum improvements in EMI SE values for the acid- and alkali-treated samples are 17.9% and 4%, respectively. In conclusion, the simultaneous enhancement of mechanical strength and EMI shielding efficacy highlights the potential of acid- and alkali-treated Ti 3 C 2 T x MXene films for applications in ultrathin and flexible EMI shielding materials. Graphical abstract
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CEMENT AND CONCRETE RESEARCH
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2024
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IF 10.9
Binmeng Chen,Xu Fang,Yuyang Zhao,Zongjin Li
In recycling and reusing construction waste, carbonation of recycled concrete fine (RCF) has been successfully applied to produce value-added products, such as silica nanoparticles, via the breaking of calcium silicate hydrate (C-S-H) structure and condensation of silicate chains. However, the intricacies of carbonation of RCF with varying calcium to silicon (C/S) ratios and their implications on the size of generated silica nanoparticles remain unknown. In this work, we developed an optimized carbonation method at high water to solid ratio to fabricate silica nanoparticles from C-S-H with different C/S ratios. The particle size of silica nanoparticles was found to gradually decrease with the increased C/S ratio of C-S-H. Since as C/S ratio increased, silicate in Q 3 state shifted to Q 1 state and the silicate chain became shorter, shifting from long-range, disordered to short-range, ordered. As the disordered self-seeding growth of long silicate chains derived from C-S-H continued, the Si-O-Si network of silica nanoparticles became chaotic, leaving more unreacted Si-OH on its surface. On the contrary, the short silicate chains displayed higher possibility of condensation, making nanoparticles with a smaller diameter.
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JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
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2012
·Vol. 26
·期 1
·23-29
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IF 1.963
Chang-Di Chen,Wen-Bing Sheng,Guo-Jun Shi,Can-Cheng Guo
The regioselective hydroxylation of the aromatic C–H bond on a series of naphthalenes with different β-substituent R (R = H, Me, Et, i -Pr, OMe, COOH, Br, etc.) was studied, and the substituent effect on the regioselectivity was investigated. The electron-donating substituent afforded the aromatic C–H bond hydroxylation at the 1α position with more than 80% selectivity, while the electron-withdrawing substituent afforded the aromatic C–H bond hydroxylation at the 4α position with more than 60% selectivity of β-substituted naphthalene hydroxylated with metachloroperbenzoic acid catalyzed by tetrakis(pentafluorophenyl)porphyrin manganese(III) chloride. The research showed that the steric and electronic effects of the substituent appeared to play a significant role in determining the regioselectivity, and the electronic effect was of more importance than the steric effect of the substituent in the current situation. The studies may provide additional proofs for the stepwise mechanism of the aromatic C–H bond hydroxylation through a cationic intermediate. Copyright © 2012 John Wiley & Sons, Ltd.
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MOLECULES
·
2017
·Vol. 22
·期 7
·1068
·
IF 2.861
Yalu Dong,Panpan Peng,Baoping Hu,Hui Su,Shenghua Li,Siping Pang
High-energy metal–organic frameworks (MOFs) based on nitrogen-rich ligands are an emerging class of explosives, and density is one of the positive factors that can influence the performance of energetic materials. Thus, it is important to design and synthesize high-density energetic MOFs. In the present work, hydrothermal reactions of Cu(II) with the rigid polynitro heterocyclic ligands 5,5′-dinitro-2H,2′H-3,3′-bi-1,2,4-triazole (DNBT) and 5,5′-dinitro-3,3′-bis-1,2,4-triazole-1-diol (DNBTO) gave two high-density MOFs: [Cu(DNBT)(ATRZ)3]n(1) and [Cu(DNBTO)(ATRZ)2(H2O)2]n(2), where ATRZ represents 4,4′-azo-1,2,4-triazole. The structures were characterized by infrared spectroscopy, elemental analysis, ultraviolet-visible (UV) absorption spectroscopy and single-crystal X-ray diffraction. Their thermal stabilities were also determined by thermogravimetric/differential scanning calorimetry analysis (TG/DSC). The results revealed that complex1has a two-dimensional porous framework that possesses the most stable chair conformations (like cyclohexane), whereas complex2has a one-dimensional polymeric structure. Compared with previously reported MOFs based on copper ions, the complexes have higher density (ρ = 1.93 g cm−3for complex1and ρ = 1.96 g cm−3for complex2) and high thermal stability (decomposition temperatures of 323 °C for complex1and 333.3 °C for complex2), especially because of the introduction of an N–O bond in complex2. We anticipate that these two complexes would be potential high-energy density materials.Keywords:energetic materials;metal organic frameworks;densities;polynitro heterocyclic ligands
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JOURNAL OF ALLOYS AND COMPOUNDS
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2017
·
IF 3.133
Chuanling Sun,Dajiang Mei,Jingli Xu,Yuandong Wu
Two new mixed bismuth (III) tellurite nitrate/sulfate, H[Bi 3 O(Te 3 O 9 )](NO 3 ) 2 and [Bi 2 (TeO 3 ) 2 ](SO 4 ) were synthesized under hydrothermal conditions. H[Bi 3 O(Te 3 O 9 )](NO 3 ) 2 crystallizes in the hexagonal space group P 6 ¯ 2 m (No. 189) with lattice parameters a = 9.8465(4), b = 9.8465(4), c = 4.1917(4) Å, V = 351.95(4) Å 3 , Z = 1, while [Bi 2 (TeO 3 ) 2 ](SO 4 ) crystallizes in the monoclinic space group C 2/ c (No. 15) with lattice parameters a = 15.7657(13), b = 7.4285(5), c = 8.0959(6) Å, β = 112.693(2) ° , V = 874.75(11) Å 3 , Z = 4. The structure of H[Bi 3 O(Te 3 O 9 )](NO 3 ) 2 features one-dimensional cationic 1 ∞ [Bi 3 O(Te 3 O 9 )] + chains along c axis, which are composed of [BiO 7 ] and [TeO 4 ] polyhedra by sharing corners and edges, whereas [Bi 2 (TeO 3 ) 2 ](SO 4 ) possesses a new three-dimensional framework consisting of two-dimensional zigzag layers of 2 ∞ [Bi 2 (TeO 3 ) 2 ] 2+ that are linked by SO 4 2- anions. Title compounds were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, Raman spectra, infrared spectra and solid state UV-vis-NIR diffuse reflectance spectroscopy .
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ORGANIC & BIOMOLECULAR CHEMISTRY
·
2014
·Vol. 12
·期 18
·2969-2978
·
IF 3.487
Jiajun Zhang,Pinhua Li,Lei Wang
A novel KOAc-promoted α-position C–H activation and alkynylation of ethers with alkynyl bromides to 2-alkynyl ethers has been developed under transition-metal-free and simple reaction conditions. In addition, this methodology can also be extended to the vinylation of ethers with vinyl bromides in excellent regio- and stereo-selectivity. A wide range of direct C(sp)–C(sp3) and C(sp2)–C(sp3) bonds has been formed through this protocol, which offers a new and alternative route.
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CHEMICAL ENGINEERING JOURNAL
·
2015
·
IF 4.321
Lei Yue,Guangqian Li,Guijin He,Yongsheng Guo,Li Xu,Wenjun Fang
The precise investigations on modeling properties and performance of practical fuels are usually complicated because of the multi-component nature. On the basis of hydrogen to carbon ratio (H/C), as a simple and overall characterization parameter for hydrocarbon fuels, this work provides a comprehensive insight into the study of kerosene-based hydrocarbon fuels (H/C = 1.6–2.3). The fundamental properties and supercritical cracking performance of hydrocarbon fuels are influenced intrinsically by their H/C values and molecular weights ( M ) due to the compositional and structural effects. Thus, a new combined parameter, (H/C)/ M a , is proposed to model the performance of hydrocarbon fuels. It is found that the hydrocarbon fuel with a higher H/C has a higher net heating value, and that with a higher (H/C)/ M 0.1 has a lower density. The viscosity decreases with the increase of (H/C)/ M 0.5 . The flash point shows a decreasing trend against the increase of (H/C)/ M 2 . The densities, viscosities and net heating values of 23 hydrocarbon fuels are calculated by means of the regression equations with the H/C and M data, and they are in agreement with the corresponding experimental values with the relative errors less than 2.5%, 10% and 1.5%, respectively. As investigated in an electrically heated tube reactor, the hydrocarbon fuel with a higher H/C performs thermal cracking more easily, absorb more heat and form fewer cokes. As a result, the cracking performance of hydrocarbon fuels can be predicted reasonably to a certain extent on the basis of H/C values.
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ORGANIC & BIOMOLECULAR CHEMISTRY
·
2014
·Vol. 12
·期 21
·3493-3498
·
IF 3.487
Yaping Zhao,Lu Sun,Tieqiang Zeng,Jiayi Wang,Yanqing Peng,Gonghua Song
Copper-catalyzed direct olefination of benzaldehydes into 1,3-diarylpropenes by a novel domino Knoevenagel-decarboxylation-Csp3-H activation sequence is reported. This method provides a concise and effective route toward the synthesis of unsymmetrical 1,3-diarylpropene derivatives.
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CERAMICS INTERNATIONAL
·
2016
·
IF 2.758
Fengrui Zhai,Shuang Li,Jialin Sun,Zhongzhou Yi
h -BN-SiC ceramic composites with different SiC contents were fabricated by spark plasma sintering . The results indicate that the addition of hard SiC particles has a remarkable effect on the densification, microstructure, mechanical properties and thermal shock resistance of the composites. Compared with pure h -BN ceramic, the relative density and mechanical properties of h -BN-SiC ceramic composites were improved obviously. The optimal properties of h -BN-SiC ceramic composites were obtained at SiC content of 25%, and the relative density, flexural strength and fracture toughness reached 97.8%, 289.2 MPa and 3.45 MPa m 1/2 , respectively. Moreover, the relationship of fracture toughness and fracture mode was discussed. The thermal shock test results showed that the h -BN-SiC ceramic composite with the SiC content of 25% exhibited excellent thermal shock resistance, presenting critical temperature difference up to 900 °C. The high temperature oxidation of h -BN and SiC on material surface led to the formation of borosilicate glass phase, which could heal the surface microcracks and then improve the thermal shock resistance.
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SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
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2017
·
IF 2.536
Huihui Li,Cailing Yang,Xinyue Zhu,Haixia Zhang
A simple ratiometric fluorescent sensor for fructose was presented. It consisted of 10-hydroxybenzo[ h ]quinoline (HBQ) which showed emission at 572 nm and 3-pyridylboronic acid (PDBA) whose complex with HBQ gave emission at 500 nm. The reaction of fructose with PDBA inhibited the complexation of HBQ with PDBA, resulting in the change of dual-emission intensity ratio. The sensor well quantified fructose in the range of 0.015–2.5 mM with detection limit of 0.005 mM. Besides, this sensor exhibited excellent selectivity and was successfully applied to fructose detection in food. This work provides a simple ratiometric sensing platform for sensitive and selective detection of fructose.
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FUEL
·
2024
·
IF 6.7
Jun Zhang,Shuyue Liu,Shiyu Lu,Chunyuan Wang,Pingjuan Liang,Huan Yi,Mengjie Li,Laizheng Luo,Rong Wang,Guangming Jiang
Improving the utilization of hydrogen radicals (H*) is of great significance for effective Pd-mediated electrocatalytic hydrodechlorination (EHDC) in detoxifying chlorinated organic pollutants (COPs). However, the limited H* utilization by single Pd arises from its inadequate performance in adsorbing/activating COPs and inferior mass transfer of low-concentration COPs. In this study, an urchin-like yolk/shell TiO 2 spheres with mesoporous structure are developed for supporting Pd nanoparticles (Pd/U-TiO 2 ), which exhibits superior EHDC activity and selectivity for 2,4-DCP reduction. Notably, the prepared Pd/U-TiO 2 catalyst achieves a mass activity of 4.2 min −1 g Pd -1 and a specific activity of 1.94 min −1 mol Pd -1 when detoxifying 50 mg/L of 2,4-DCP at −0.85 V, surpassing the most reported catalysts. Furthermore, the Pd/U-TiO 2 catalyst consistently demonstrates higher H* utilization efficiency compared to single Pd, regardless of the 2,4-DCP concentration or reaction mode (batch or continuous-flow). This enhanced H* utilization efficiency is attributed to two key factors: the urchin-like and yolk/shell structure of U-TiO 2 enhances the mass diffusion of 2,4-DCP, and the strong interactions between Pd and U-TiO 2 generate electron-rich Pd species that enhance the adsorption and activation of COPs. Overall, this work highlights the synergistic effects of strong metal-support interactions and mass diffusion in enhancing atomic H* utilization. This study lays a significant experimental and theoretical foundation for designing efficient electrocatalysts for the detoxification of chlorinated organic pollutants and various other halogenated organic pollutants.
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CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Zhefei Zhao,Xuyao Yao,Ruopeng Yu,Xingyu Luo,Minhao Chen,Xiangxiang Zhang,Yinghua Xu,Youqun Chu,Xinbiao Mao,Huajun Zheng
Electrocatalytic hydrodechlorination (EHDC) stands out as an economical and prospective technology for eliminating chlorinated organic pollutants. Single-atom catalyst engineering and metal-support interaction (MSI) offer the promising strategies for developing electrocatalysts with high atom utilization and reactivity. Herein, atomically dispersed palladium (Pd) anchored on the iron (Fe)-introduced nickel phosphide (NiFeP) support is reported. The prepared NiFeP-Pd electrode exhibits outstanding electrocatalytic activity in 4-CP removal efficiency (98.8 %) with an ultra-low dosage of Pd (0.0497 mg cm −2 ) and the highest reported MA value (446.01 min −1 g −1 ), surpassing Ni 2 P-Pd by 6.34 times. Experimental results combined with theoretical calculations suggest that the superior performance of NiFeP-Pd stems from the modulated support by Fe introduction, which not only enhances the generation of adsorbed atomic hydrogen species (H*), but also reduces the energy barrier of C-H formation on Pd sites by regulating the MSI. In addition, single-Pd-atom construction on NiFeP with good conductivity and large specific surface area makes the contributions as well.
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