Authors:Shi Xu, Sheng Li, Yun Wei, Li Zhang and Fei Xu
Titanium dioxide (TiO2), polythiophene and polythiophene/TiO2 were prepared by sol–gel and solid-state reaction methods. Water-free iron(III) chloride (FeCl3) was used as an oxidant. The phase composition, morphology and the spectral properties of the products were characterized by XRD, TEM, UV–Vis and FT-IR techniques. The photocatalytic activity of the products was evaluated by the degradation of methyl orange under sunlight irradiation. TEM results showed that the polythiophene/TiO2 composite particles were well dispersed, rod-like shaped with 20 × 80 nm dimensions. UV–Vis analysis indicated that the absorption edge of polythiophene/TiO2 was 605 nm. Compared with the unmodified TiO2 and bare polythiophene, polythiophene/TiO2 exhibited largely enhanced activity for the photocatalytic degradation of methyl orange under sunlight irradiation. A degradation efficiency of methyl orange of 85.6% could be obtained within 120 min. The sensitization mechanism of polythiophene for the TiO2 photocatalyst is discussed briefly.
A simple and rapid method, using online ultraperformance liquid chromatography with photodiode array detection and electrospray ionization mass spectrometry (UPLC-PDA-eλ-ESI-MS/MS), was developed for the in-depth analysis of 50 batches Radix et Rhizoma Rhei. The analysis was performed on a UPLC BEH C18 column using a gradient elution system. Baseline separation could be achieved in less than 7.5 min. At the same time, on the basis of the 50 batches of samples collected from representative cultivated regions, a novel chromatographic fingerprint was devised by UPLC-PDA, in which 27 common peaks were detected and identified by the developed UPLC-MS/MS method step by step according to fragmentation mechanisms, MS/MS data, standards, and relevant literature. Many active components gave prominent [M - H]− ions in the ESI mass spectra. These components include anthraquinones, sennosides, stilbenes, glucose gallates, naphthalenes, and catechins. Furthermore, based on the information of these Radix et Rhizoma Rhei components, and further combined with discriminant analysis, a novel discriminant analysis equation (DAE) was established for the quality control of Radix et Rhizoma Rhei for the first time.
Authors:Guohua Jiang, Shi Shan, Lan Jiang and Xuesong Xu
Developing the probability function to describe rank-size Zipfian phenomena, i.e., a form like P(R = r) c/ra (a>0) with a rank type random variable R, has been an important problem in scientometrics and informetrics. In this article a new rank-size distribution of Zipf"s law is presented and applied to an actual distribution of scientific productivities in Chinese universities.
Authors:C. Tian, Z. Shi, H. Zhang, J. Xu, J. Shi and H. Guo
The thermal degradation of cotton cellulose treated with chemical mixtures containing P and N was studied by thermal analysis,
infrared spectroscopy, Char yield and limiting-oxygen-index (LOI). Our experiments demonstrated the following facts. The temperatures
and activation energies of pyrolysis were lower for cotton cellulose treated with flame retardants than those for untreated
samples and the values of Char yield and LOI were greater for treated cotton than those for untreated one.
Authors:Qiwu Shi, Wanxia Huang, Yubo Zhang, Yang Zhang, Yuanjie Xu and Gang Guo
Polyester powder coating modified with 2 mass% of rutile nano-sized titanium dioxide (nano-TiO2) was prepared by melt-blend extrusion method. The nano-TiO2 dispersion state in the powder coating matrix was analyzed by field emission scanning electron microscopy (FE-SEM), which presented a well dispersion of modified nano-TiO2 in the polyester powder coating. The effect of nano-TiO2 on the curing of polyester powder coating was investigated by differential scanning calorimeter (DSC). Kissinger and Crane methods were used to study the activation energy (E) and reaction order (n) of the coating. The results indicated that 2 mass% of nano-TiO2 additive played a prompting role in the curing of polyester powder coatings, due to the hydroxyl functional groups existed on the surface of nano-TiO2. Furthermore, real-time Fourier transform infrared (FT-IR) spectroscopy with a heating cell was also employed to record the curing actions, of which results were consistent with the DSC experiments.
Authors:Jun Zhang, Shuangjun Chen, Jun Su, Xuming Shi, Jing Jin, Xiaolin Wang and Zhongzi Xu
Non-isothermal crystallization kinetics and subsequent melting behavior for three kinds of ethylene-acrylic acid copolymer
(EAA) are investigated via differential scanning calorimetry (DSC). From the Jeziorny method, the crystallization rate of
the primary stage is significantly influenced by the competitive mobility of chains. While the crystallization rate in the
secondary stage decreases in order of acrylic acid (AA) content in copolymers. Mo’s method can also provide a good fitting.
Difference between the Jeziorny method and Mo’s method analysis is because of a higher effect of non-crystallizable chain
ends. The effective activation energy is also determined via Kissinger’s method.
Authors:Jun Zhang, Shuangjun Chen, Jing Jin, Xuming Shi, Xiaolin Wang and Zhongzi Xu
Non-isothermal crystallization kinetics of the ethylene–acrylic acid copolymer (EAA) in diluents during thermally induced
phase separation (TIPS) process was investigated via differential scanning calorimetry (DSC). Dioctyl phthalate (DOP), diphenyl
ester (DPE), and peanut oil were used as diluents. Kinetic models, such as Jeziorny theory, Ozawa theory, and Mo’s approach,
were utilized for description. The effective activation energy of EAA component in mixture was calculated by Friedman’s method.
In the results, the Jeziorny theory and Mo’s approach could obtain good linear fitting relationship with the primary crystallization
behavior of EAA, but the Ozawa theory failed to get a suitable result. The homogeneous nucleation of EAA proceeded at the
end of liquid–liquid phase separation, while the non-isothermal crystallization developed within a solid–liquid phase separation
environment. In the mixtures, the molecular weight, polar groups, and conformation of the diluent molecules would affect the
nucleation of EAA, and its growth rate. Comparing with the non-isothermal crystallization of neat EAA, EAA in diluents obtained
a higher Avrami index n, and comparatively lower crystallization rate. Peanut oil facilitated the homogeneous nucleation of EAA, leading to a higher
melting peak temperature of EAA in the subsequent melting endotherms. The largest EAA’s Avrami index obtained in peanut oil
also indicated a higher crystal growth dimensional geometry. The crystallization rate and crystallinity of EAA during the
non-isothermal process decreased in the sequence: EAA/DPE > EAA/DOP > EAA/peanut oil.
Authors:B. Tong, Z. Tan, X. Lv, L. Sun, F. Xu, Q. Shi and Y. Li
The molar heat capacities Cp,m of 2,2-dimethyl-1,3-propanediol were measured in the temperature range from 78 to 410 K by means of a small sample automated
adiabatic calorimeter. A solid-solid and a solid-liquid phase transitions were found at T-314.304 and 402.402 K, respectively, from the experimental Cp-T curve. The molar enthalpies and entropies of these transitions were determined to be 14.78 kJ mol−1, 47.01 J K−1 mol− for the solid-solid transition and 7.518 kJ mol−1, 18.68 J K−1 mol−1 for the solid-liquid transition, respectively. 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 310 K, Cp,m/(J K−1 mol−1)=117.72+58.8022x+3.0964x2+6.87363x3−13.922x4+9.8889x5+16.195x6; x=[(T/K)−195]/115. In the temperature range of 325 to 395 K, Cp,m/(J K−1 mol−1)=290.74+22.767x−0.6247x2−0.8716x3−4.0159x4−0.2878x5+1.7244x6; x=[(T/K)−360]/35. The thermodynamic functions HT−H298.15 and ST−S298.15, were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The thermostability
of the compound was further tested by DSC and TG measurements. The results were in agreement with those obtained by adiabatic
Authors:Ruiqin Zhao, Yuhai Tang, Saili Wei, Xiaoqian Xu, Xiaoyu Shi and Guangbin Zhang
Asymmetric electro-epoxidation of olefins had been achieved with sodium hypochlorite (NaClO) as an oxidant, which was generated by electrolysis in two-phase systems of aqueous sodium chloride (NaCl) and ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4)). The electrolysis conditions by different current densities (0.8, 0.9, 1.0, 1.1 and 1.3 mA/cm2) and pH values (8, 9, 10, 11, 12 and 13) were optimized and 1.1 mA/cm2 and pH 11 were selected. The proposed reaction mechanism is also discussed. The performance of new catalytic systems in four kinds of reaction media in the presence or absence of ammonium acetate (NH4OAc) as a cocatalyst was investigated systematically. Compared to the chemical epoxidation systems, the enantiomeric excess (ee) values and yields for the epoxidation of styrene, α-methylstyrene and indene were acceptable in the electrocatalytic epoxidation systems.