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Abstract  

Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO2 composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression method. The results show that the kinetic models for the decomposition process of PANI/ZrO2 composite and PANI are all D3, and the corresponding function is ƒ(α)=1.5(1−α)2/3[1−(1-α)1/3]−1. The correlated kinetic parameters are E a=112.7±9.2 kJ mol−1, lnA=13.9 and E a=81.8±5.6 kJ mol−1, lnA=8.8 for PANI/ZrO2 composite and PANI, respectively.

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Abstract  

Nano-ZnO flakes were synthesized by calcination of the precursor of Zn(OH)2 obtained via the reactive ion exchange method between an ion exchange resin and ZnSO4 solution at room temperature. Scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscope, UV-Vis diffuse reflection spectrum and Na2EDTA titration were used to characterize the structure features and chemical compositions of the as-prepared ZnO. The results show that the as-prepared ZnO flakes have uniform structure and high purity. Heat capacities in the temperature range of 83 to 396 K were measured. The measured heat capacities values were compared with those of coarse crystal powders and the difference between this two heat capacity curves was analyzed.

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Abstract  

A novel AB2-type monomer diethyl 5-(4-hydroxyethoxyphenylazo)isophthalate for preparing hyperbranched azo polymers (HBPAZO) was synthesized. The monomer obtained was characterized by IR spectra, UV–Vis spectra, 1H NMR spectrum and C NMR spectrum. The TG-DTG/DTA curves show that the decomposition of the monomer proceeds in four steps. During the second-step decomposition, the mass loss occurs between 480.5 K and 579.0 K and the phenomena of condensing to HBPAZO for the melted monomer was found. So it is inferred that this temperature range is the best for polycondensation of the melted monomer, which is very important for synthesizing of HBPAZO.

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Thermodynamic investigation of several natural polyols (II)

Heat capacities and thermodynamic properties of sorbitol

Journal of Thermal Analysis and Calorimetry
Authors: B. Tong, Z. Tan, Q. Shi, Y. Li, and S. Wang

Abstract  

The low-temperature heat capacity C p,m of sorbitol was precisely measured in the temperature range from 80 to 390 K by means of a small sample automated adiabatic calorimeter. A solid-liquid phase transition was found at T=369.157 K from the experimental C p-T curve. The dependence of heat capacity on the temperature was fitted to the following polynomial equations with least square method. In the temperature range of 80 to 355 K, C p,m/J K−1 mol−1=170.17+157.75x+128.03x 2-146.44x 3-335.66x 4+177.71x 5+306.15x 6, x= [(T/K)−217.5]/137.5. In the temperature range of 375 to 390 K, C p,m/J K−1 mol−1=518.13+3.2819x, x=[(T/K)-382.5]/7.5. The molar enthalpy and entropy of this transition were determined to be 30.35±0.15 kJ mol−1 and 82.22±0.41 J K−1 mol−1 respectively. The thermodynamic functions [H T-H 298.15] and [S T-S 298.15], were derived from the heat capacity data in the temperature range of 80 to 390 K with an interval of 5 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement with those obtained from heat capacity measurements.

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Abstract  

Conducting polyaniline/Cobaltosic oxide (PANI/Co3O4) composites were synthesized for the first time, by in situ deposition technique in the presence of hydrochloric acid (HCl) as a dopant by adding the fine grade powder (an average particle size of approximately 80 nm) of Co3O4 into the polymerization reaction mixture of aniline. The composites obtained were characterized by infrared spectra (IR) and X-ray diffraction (XRD). The composition and the thermal stability of the composites were investigated by TG-DTG. The results suggest that the thermal stability of the composites is higher than that of the pure PANI. The improvement in the thermal stability for the composites is attributed to the interaction between PANI and nano-Co3O4.

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Abstract  

The principle for the electro-generative simultaneous leaching (EGSL) is applied to simultaneous leaching of pyrite-MnO2 in this paper. A galvanic system for the bio-electro-generative simultaneous leaching (BEGSL) has been set up. The equation of electric quantity vs. time is used to study the effect of produced sulfur on electro-generative efficiency and quantity. It has been shown that the resistance decreased in the presence of Acidithiobacillus thiooxidans (A. thiooxidans) with the increase of electro-generative efficiency. The effects of temperature and grain size on rate of ferrous extraction from pyrite under the conditions of presence and absence of A. thiooxidans were studied, respectively. The changes in the extraction rate of Fe2+ as particle size in presence of A. thiooxidans were more evident than that in the absence, which indicated that the extraction in bio-electro-generative leaching was affected by particle size remarkably. Around the optimum culture temperature for A. thiooxidans, the bigger change in the conversion rate of Fe2+ was depending on temperature. The transferred charge in BEGSL including part of S0 to sulfate group in the presence of (A. thiooxidans) which is called as biologic electric quantity, and the ratio of biologic electric quantity reached to 58.10% in 72 h among the all-transferred charge.

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Abstract  

Positron annihilation lifetime measurements of PMMA, PEMA, PiPMA, PnPMA and PnBMA were performed in the temperature range between 15 and 300 K, where , and relaxational transitions occur for these polyalkylmethacrylates. The variations of free volume size and content calculated from the longest lifetime component against temperature are correlated to the results obtained by dielectric, viscoelastic and dynamic mechanical relaxation data of the polymers. The variations of free volume sizes and contents, apparent free volume fraction and size distribution of the polyalkylmethacrylates are well correlated with the rotational transitions of side chains. The location of free volumes, in which positronium annihilates can be estimated near the vicinity of alkyl groups bound to oxygen atom of side ester chains.

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Abstract  

AP/HTPB based composite propellants with additives such as ammonium oxalate (AO), mixture of ammonium oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG and FTIR experiments. The results show that the burning rates of these propellants are decreased significantly. TG-DTG experiments indicate that decomposition temperatures of AP with these additives are increased. Furthermore, the activation energy of the decomposition reaction of AP is also increased in the presence of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition of AP. The burning rates of these propellants are decreased. The burning rate temperature sensitivity of AP/HTPB based propellants is reduced significantly by the addition of AO or AO/SC. But the effect of AO is less than that of AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the same time, to reduce pressure exponent. The reduced heat release at the burning surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity. Synergetic action is probably produced between AO and SC within AP/HTPB based propellants in the pressure range tested. This synergetic effect causes the heat release to reduce and the burning surface temperature to increase. Moreover, it makes the net exothermal reaction of condensed phase become little dependent on T 0. Thus, the burning rate temperature sensitivity is reduced.

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Abstract  

The concentration of radon in an underground research facility (URF) was measured by setting up 12 sampling points in the URF and with 3 different measurement methods. All the methods were calibrated in the radon laboratory of the No. 6 Institute of Nuclear Industry. The accumulation of radon in the URF was observed before a ventilation system was applied. The reduction of radon concentration in the URF by 1-hour ventilation was also observed. Experimental result indicates that the concentration of radon in the URF increased from 15 to 50 Bq·m−3 in 5 days without ventilation, and decreased to less than 10 Bq·m−3 with 1-hour ventilation. Applying the average working time of 4 hours per day of the workers in the URF, the additional effective dose is 0.75 msv·y−1 when 1 hour ventilation is applied before entering the URF and 13 mSv·y−1 without ventilation. These figures strongly suggest that for the health of the workers, ventilation in such underground research facilities is needed.

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