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Gong S.,York University | Zhu Z.H.,York University | Li J.,York University | Li J.,Hubei Institute of Aerospace Chemotechnology | Meguid S.A.,King's College
Journal of Applied Physics | Year: 2014

This paper investigated the effect of carbon nanotube (CNT) agglomeration on the electrical conductivity of CNT-polymer composites by experimental characterization and theoretical modeling. The present experimental results show that the acid treatment of CNTs has significantly alleviated the CNT agglomeration in CNT-polymer composites and improved the electrical conductivity of the composites compared with CNT-polymer composites made from the same pristine CNTs. The improvement by the acid treatment is further studied by a multiscale CNT percolation network model that considers the CNT agglomeration based on experimental observation. Numerical results are in good agreement with the experimental data. The smaller the size of CNT agglomerates is in the experiments, the closer the measured electrical conductivity of CNT-polymer composites is to its theoretical limit. The current study verifies that (i) the CNT agglomeration is the main cause that leads to a lower electrical conductivity of CNT-polymer composites than their theoretical limit, and (ii) the current multiscale percolation network model can quantitatively predict the electrical conductivity of CNT-polymer composites with CNT agglomeration. The comprehensiveness of the developed modeling approach enables an evaluation of results in conjunction with experimental data in future works. © 2014 AIP Publishing LLC.

Tang G.,Huazhong University of Science and Technology | Tang G.,HuBei Institute of Aerospace Chemotechnology | Tian S.,Huazhong University of Science and Technology | Tian S.,Wuhan University of Technology | And 8 more authors.
Journal of Physical Chemistry C | Year: 2014

ZnO micro/nanocrystals with different percentages of the exposed (0001) facets were synthesized by a facile chemical bath deposition method. Various characterizations were carried out to understand the relationship between particle shape, exposed (0001) facets, and catalytic activity of ZnO nanocrystals for the thermal decomposition of ammonium perchlorate (AP). An enhancement in the catalytic activity was observed for the ZnO micro/nanocrystals with a higher percentage of the exposed (0001) facets, in which the activation energy Ea of AP decomposition was lowered from 154.0 ± 13.9 kJ/mol to 90.8 ± 11.4 kJ/mol, 83.7 ± 15.1 kJ/mol, and 63.3 ± 3.7 kJ/mol for ZnO micro/nanocrystals with ca. 18.6%, 20.3%, and 39.3% of the exposed (0001) facets. Theoretically evidenced by density functional theory calculations, such highly exposed (0001) facets can be favorable for the adsorption and diffusion of perchloric acid, and also facilitate the formation of active oxygen which can lead to the oxidation reaction of ammonia more completely in the catalytic decomposition of AP. © 2014 American Chemical Society.

Tang G.,Huazhong University of Science and Technology | Tang G.,Hubei Institute of Aerospace Chemotechnology | Wen Y.,Huazhong University of Science and Technology | Pang A.,Hubei Institute of Aerospace Chemotechnology | And 7 more authors.
CrystEngComm | Year: 2014

Distinct from the common well faceted ZnO nanorods (R-ZnO), ZnO nanotetrapods (T-ZnO) exhibited a remarkable catalytic activity for the thermal decomposition of ammonium perchlorate (AP): the activation energy at high temperature decomposition (HTD) was significantly decreased to 111.9 kJ mol -1, much lower than 162.5 kJ mol-1 for pure AP and 156.9 kJ mol-1 for AP with R-ZnO. This was attributed to more abundant atomic steps on the surface of T-ZnO than that of R-ZnO, as evidenced by HRTEM and density function theory (DFT) calculations. It was shown that the initiation step of perchloric acid (PA) decomposition happened much faster on stepped T-ZnO edges, resulting in the formation of active oxygen atoms from HClO 4. The formed oxygen atoms would subsequently react with NH 3 to produce HNO, N2O and NO species, thus leading to an obvious decrease in the activation energy of AP decomposition. The proposed catalytic mechanism was further corroborated by the TG-IR spectroscopy results. Our work can provide atomic insights into the catalytic decomposition of AP on ZnO nanostructures. © 2014 The Royal Society of Chemistry.

PubMed | Beijing Institute of Technology, Harbin Institute of Technology and Hubei Institute of Aerospace Chemotechnology
Type: | Journal: Scientific reports | Year: 2016

Lithium-sulfur (Li-S) batteries are a promising candidate of next generation energy storage systems owing to its high theoretical capacity and energy density. However, to date, its commercial application was hindered by the inherent problems of sulfur cathode. Additionally, with the rapid decline of non-renewable resources and active appeal of green chemistry, the intensive research of new electrode materials was conducted worldwide. We have obtained a sheet-like carbon material (shaddock peel carbon sheets SPCS) from organic waste shaddock peel, which can be used as the conductive carbon matrix for sulfur-based cathodes. Furthermore, the raw materials are low-cost, truly green and recyclable. As a result, the sulfur cathode made with SPCS (SPCS-S), can deliver a high reversible capacity of 722.5mAh g(-1) at 0.2C after 100 cycles with capacity recuperability of ~90%, demonstrating that the SPCS-S hybrid is of great potential as the cathode for rechargeable Li-S batteries. The high electrochemical performance of SPCS-S hybrid could be attributed to the sheet-like carbon network with large surface area and high conductivity of the SPCS, in which the carbon sheets enable the uniform distribution of sulfur, better ability to trap the soluble polysulfides and accommodate volume expansion/shrinkage of sulfur during repeated charge/discharge cycles.

Gu J.,University of Western Ontario | Gu J.,Hubei Institute of Aerospace Chemotechnology | Hu M.J.,University of Western Ontario | Guo Q.Q.,University of Western Ontario | And 3 more authors.
RSC Advances | Year: 2014

A facile and high-yielding hydrothermal method for synthesizing graphene quantum dots (GQDs) from glucose is presented. The GQDs, with fluorescence quantum yield (FL QY) of 44.3%, demonstrate strong green photoluminescence (PL) and excitation-independent PL emission characteristics. This journal is © the Partner Organisations 2014.

Gu J.,Hubei Institute of Aerospace Chemotechnology | Gu J.,University of Western Ontario | Zhang X.,Hubei Institute of Aerospace Chemotechnology | Pang A.,Hubei Institute of Aerospace Chemotechnology | Yang J.,University of Western Ontario
Nanotechnology | Year: 2016

A one-step hydrothermal method for synthesizing nitrogen-doped graphene quantum dots (N-GQDs) from organic carbon sources is presented in this paper. The high-quality N-GQDs can be obtained via tuning the degree of dehydration/carbonization of citric acid and doping of nitrogen atoms into the graphene lattice. The micromorphology, chemical structure, composition and photoluminescence (PL) characteristics of the N-GQDs were characterized systematically. The size of the obtained N-GQDs is about 5-10 nm with typical topographic heights of 0.8-2.5 nm. There is intense blue emission and excitation-independent PL behavior when the N-GQDs are in aqueous solution. The most remarkable innovation is that the fluorescence quantum yield (FL QY) of our N-GQDs is up to 75.2%, which is much higher than that of most reported GQDs (less than 25%). Thus, it is initially believed that synthesis parameters, hydrothermal process and nitrogen doping may greatly influence the surface state and bandgap of the GQDs, which are important in determining the PL characteristics of the N-GQDs. © 2016 IOP Publishing Ltd.

PubMed | Nanjing University of Science and Technology and Hubei Institute of Aerospace Chemotechnology
Type: Journal Article | Journal: Journal of molecular modeling | Year: 2016

Anisotropic mechanical response and chemical reaction process of cyclotrimethylene trinitramine (RDX) along crystal orientations were studied with molecular dynamics simulations using ReaxFF potential under repeated stress wave loading. In the simulations, shocks were propagated along the [010], [001], [210], [100], [111], and [102] orientations of crystal RDX at initial particle velocity Up in the range of 14km/s. For shocks at Up2km/s, local stacking fault and molecular conformational change can only cause marginal temperature and pressure increase without molecular decomposition. As shocks increase to Up2.5km/s, rupture of N-NO2 bond accompanied by partial HONO elimination dominates the main chemical reactions at the initial stage. The ordering of the follow-up consumption of NO2 and ring-breaking rate is directly consistent with that of increasing rate in temperature and pressure. The (210) and (100) planes are more sensitive to shocks in temperature and pressure profiles than the (111) plane, which agrees well with experimental observations and theoretical results in the literature. Therefore, the repeated dynamic loading model in conjunction with MD simulation using ReaxFF potential for crystal RDX indicates that these methods can be applied to study the mechanical response and chemical reaction process of polymer bonded explosives that are commonly subjected to compressive and tensile stress waves observed in practice.

Wang X.,Shenzhen University | Hu W.,Hubei Institute of Aerospace Chemotechnology | Gui D.,Shenzhen University | Chi X.,Hubei Institute of Aerospace Chemotechnology | And 5 more authors.
Bulletin of the Chemical Society of Japan | Year: 2013

The proton transfer effects on the urethane formation between 2,4-diisocyanatotoluene (2,4-TDI) and methanol was investigated by using density functional theory (DFT) calculations at the B3LYP/6-311G(d,p) level. The calculations show that the direct addition of methanol to 2,4-TDI follows a concerted path with an energy barrier of 31.71 kcal mol-1 and an activation free energy of 39.32 kcal mol-1. With the methanol, diphenylamine, and methyl N-methylcarbamate molecule serving as a proton transporter or a reactive catalyst, the energy barriers were significantly reduced to 12.28, 17.93, and 20.13 kcal mol-1 respectively, and the free energies of activation were lowered to 25.22, 32.54, and 36.86 kcal mol-1 correspondingly. The results indicate that the labile hydrogen-containing compounds play a key role in accelerating the reaction rate and the proton transfer. In the case of one extra methanol molecule serving as a proton transporter, the energy barrier was estimated to be 12.28 kcal mol -1, which is in good agreement with the experimental activation energy between 8.6 and 12.0 kcal mol-1. The urethane formation between 2,4-TDI and methanol is more likely a third-order reaction with respect to the initial reactants. © 2013 The Chemical Society of Japan.

PubMed | Hubei Institute of Aerospace Chemotechnology and Huazhong University of Science and Technology
Type: | Journal: Scientific reports | Year: 2016

Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5-2.3eV for GO, which is an insulator, to 3.9-1.24eV for GNM-5h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO() is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique.

Lu S.,Hubei Institute of Aerospace Chemotechnology
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2015

Strain invariant failure theory (SIFT) is a new type of strength theory for composites based on physical failure mode, which is applied to the failure analysis of composite structures widely. In order to improve the accuracy of theoretical analysis, SIFT was extended to be used to analyze the static loading compressive progressive failure mechanism and strength for carbon fiber reinforced polymer (CFRP) composite laminate open-hole structures firstly. The implementation methods of developed SIFT include two parts of material strength characterization and structure strength prediction. The structure strength prediction based on the ABAQUS platform and was realized by using the user defined material subroutine (UMAT) wrote by Fortran scripts. Then, the predicted values of SIFT as well as the predicted results of classical composites strength theories such as Tsai-Wu and Hashin theories were compared with the testing results, and the results showed that the accuracy of SIFT prediction was the best. Meanwhile, based on SIFT, the failure mechanisms evolution from initial failure to final failure of AS4/3501-6 laminate open-hole structures under static loading compression were analyzed in details. Finally, the static loading compressive failure mechanisms of AS4/3501-6 laminate open-hole structures predicted by SIFT were compared with testing results. The results show that the progressive failure mechanisms predicted by SIFT agree well with the testing results. The obtained conclusions provide new thoughts for the strength prediction of CFRP structures. © 2015, BUAA Culture Media Group Ltd.. All right reserved.

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