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11.
The absorption and fluorescence spectroscopic responses of three pyridinium hemicyanine dyes to anions F−, Cl−, Br−, I−, H2PO4−, HSO4− and OAc− were investigated. At lower concentrations of OAc− (less than 1 equiv.), both the absorption and the fluorescence intensities of 1 – 3 were more effectively changed than F− at identical concentrations. At higher concentrations of OAc− (more than 1 equiv.), the interaction was opposite for each compound. 1H NMR results indicated the interaction between 1 , 2 or 3 and F− proceeded through hydrogen bonding. The results showed that these dyes are promising to develop dual fluorescence and chromogenic chemosensors toward F− and OAc− according to the subtle difference in the affinity of F− and OAc−. 相似文献
12.
The thermal decomposition behavior of double‐base rocket propellant SQ‐2 was studied by a Calvet microcalorimeter at four different heating rates. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The critical temperature of thermal explosion (Tb), the self acceleration decomposition temperature (TSADT), the adiabatic decomposition temperature rise (ΔTad), the time‐to‐explosion of adiabatic system (t), critical temperature of hot‐spot initiation (Tcr), critical thermal explosion ambient temperature (Tacr), safety degree (SD) and thermal explosive probability (PTE) were presented to evaluate the thermal hazard of SQ‐2. 相似文献
13.
通过示差扫描量热仪(DSC)和广角X射线衍射仪(WAXD)研究了聚左旋乳酸(PLLA)的光学纯度(91.6%、93.3%、94.0%、97.0%、98.4%)对聚乳酸结晶和熔融行为的影响。 在非等温结晶过程中,随着光学纯度的提高,聚乳酸的结晶峰值温度、熔点、熔融焓均提高。 在等温结晶过程中,PLLA的半结晶时间(t1/2)随着光学纯度的增加而减少,在结晶温度100~110 ℃区间内半结晶时间均达到最小值;含有不同光学纯度PLLA的Avrami指数n≈3,表明光学纯度的变化不能改变聚乳酸以三维球晶生长的异相成核机理。 随着光学纯度的增加,聚乳酸δ-晶型转变为α-晶型的临界温度升高。 聚乳酸的结晶和熔融行为对光学纯度具有依赖性。 相似文献
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15.
Peng Sun Zihan Xia Zhongfang Li Ziwei Fan Fengqi He Qiang Liu Xiaoyan Yin 《Materials Today Chemistry》2022
A high-temperature proton exchange membrane with high proton conductivity over a wide humidity range still remains a challenge. PBI dendrimer containing triazine rings (TPBI) was synthesized to approach this aim considering its high content of hygroscopic terminal groups and of larger free volume. A novel proton conductor previously synthesized (zirconium 3-sulfopropyl phosphonate, ZrSP) was doped due to its good proton conductivity over a wide humidity range. TPBI was post-crosslinked with a tetrafunctional epoxy resin (N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane, TGDDM) to enhance the mechanical stability at low cross-linking degrees, which allowed high doping levels of ZrSP, and thus, high conductivity. The prepared membranes (TPBI-TGDDM/ZrSP) showed good thermal stability, high proton conductivity over wide humidity range, and good dimensional stability. At suitable degrees of branching, TPBI-TGDDM/ZrSP exhibited superior mechanical property, oxidative stability, methanol barrier property, and membrane selectivity than its linear analog (mPBI-TGDDM/ZrSP). As ZrSP instead of PA was applied as the proton conductor, TPBI-TGDDM/ZrSP showed good durability of proton conductivity, especially in comparison with TPBI-TGDDM/PA, which highly retarded decline in conductivity caused by PA leaking. The proton conductivity at 180 °C of TPBI(20)-TGDDM(10)/ZrSP(50) achieved 142, 84.2 and 23.6 mS cm?1 at 100%, 50%, and 0 RH, respectively. 相似文献
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A new rhodamine-based derivative bearing a naphthyridine group (compound 1) was synthesized as a colorimetric and fluorescent “off-on” chemosensor for Cu2+ in aqueous solutions. The sensing behaviors of 1 toward various metal ions in neutral aqueous solutions were investigated by absorption and fluorescence spectroscopies. Compound 1 is found to exhibit a significant increase in absorbance at 561 nm and an amplified fluorescence at 590 nm toward Cu2+ in a selective, sensitive and rapid manner. The quantification of Cu2+ by 1 using an absorption spectroscopy method was satisfactory in the linear working range 0.9–10 μM, with a detection limit of 5.4?×?10?8?M for Cu2+ and good tolerance of other metal ions. Upon addition of Cu2+, the spirolactam ring (colorless and nonfluorescent) of 1 was opened to ring-opened amide (red color and fluorescent) and a 1:1 stoichiochemetry for the 1-Cu2+ complex was formed with an association constant of 1.57?×?104?M?1. 相似文献
18.
Ming Zhang Fengqi Zhao Yanjing Yang Hui Li Jiankan Zhang Wenzhe Ma Hongxu Gao Na Li 《物理化学学报》2020,36(6):1904027-0
Energy components used in solid rocket propellants are beneficial for improving the energy performance, and their thermal decomposition characteristics significantly affect the combustion properties of the propellants. As a kind of energetic material with both high energy and low sensitivity (impact and friction), 5, 5'-bistetrazole-1, 1'-diolate (TKX-50) can effectively improve the energy and safety characteristics of solid propellants. Burning catalyst is another important component of solid propellants, which can significantly improve the burning rate of the propellant and reduce the pressure exponent. Among various burning catalysts, nanoscale transition metal oxides can promote the thermal decomposition of the energetic component, thus enhancing the combustion properties of the solid propellant. However, the catalytic effects of nanoscale transition metal oxides with different morphologies on the thermal decomposition of TKX-50 have rarely been studied. Based on the excellent catalytic activity of Fe2O3 for TKX-50 thermal decomposition, nano-Fe2O3 particles with spherical and tubular microstructures were used for TKX-50 thermal decomposition. The Fe2O3 nanoparticles were successfully fabricated via the solvothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. The XRD, FT-IR, and XPS results confirmed the successful fabrication of spherical and tubular Fe2O3 samples. The SEM and TEM images showed that the spherical Fe2O3 samples are composed of agglomerated Fe2O3 nanoparticles with an average particle size of 110 nm. In addition, the average diameter and length of hollow tubular Fe2O3 nanoparticles are 120 nm and 200 nm, respectively. The catalytic activities of spherical and tubular Fe2O3 for TKX-50 decomposition were studied by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) methods. The DSC and TG-DTG curves showed that both tubular and spherical Fe2O3 could effectively promote TKX-50 thermal decomposition. The first thermal decomposition peak temperature (TFDP) of TKX-50 was reduced by 36.5 K and 26.3 K in the presence of tubular and spherical Fe2O3, respectively, at 10 K·min−1. The activation energy (Ea) of TKX-50, determined by the iso-conversional method, was significantly reduced in the presence of both tubular and spherical Fe2O3. The results indicated that the microstructure of the catalyst has a significant effect on its catalytic performance for TKX-50 thermal decomposition, and that tubular Fe2O3 with hollow microstructure possesses better catalytic activity than spherical Fe2O3. The excellent catalytic activity of tubular Fe2O3 can be attributed to the hollow microstructure, which has more active sites for TKX-50 thermal decomposition. 相似文献
19.
(C6H(14)N2)[NH4(ClO4)3] is a newly developed porous hybrid inorganic-organic framework material with easy access and excellent detonation performances,however,its thermal properties is still unclear and severely hampered further applications.In this study,thermal behaviors and non-isothermal decomposition reaction kinetics of(C6H(14)N2)[NH4(ClO4)3] were investigated systematically by the combination of differential scanning calorimetry(DSC) and simultaneous thermal analysis methods.In-situ FTIR spectroscopy technology was applied for investigation of the structure changes of(C6H(14)N2) NH4(ClO4)3]and some selected referents for better understanding of interactions between different components during the heating process.Experiment results indicated that the novel molecular perovskite structure renders(C6H(14)N2)[NH4(ClO4)3] better thermal stability than most of currently used energetic materials.Underhigh temperature s,the stability of the cage skeleton constructed by NH4^+and ClO4^-ions determined the decomposition process rather than organic moiety confined in the skeleton.The simple synthetic method,good detonation performances and excellent thermal properties make(C6H(14)N2)[NH4(ClO4)3] an ideal candidate for the preparation of advanced explosives and propellants. 相似文献
20.
Jiang HL Liu B Lan YQ Kuratani K Akita T Shioyama H Zong F Xu Q 《Journal of the American Chemical Society》2011,133(31):11854-11857
In this work, with a zeolite-type metal-organic framework as both a precursor and a template and furfuryl alcohol as a second precursor, nanoporous carbon material has been prepared with an unexpectedly high surface area (3405 m(2)/g, BET method) and considerable hydrogen storage capacity (2.77 wt % at 77 K and 1 atm) as well as good electrochemical properties as an electrode material for electric double layer capacitors. The pore structure and surface area of the resultant carbon materials can be tuned simply by changing the calcination temperature. 相似文献