Advanced Materials Research Vols. 197-198

Abstract: Lithium iron phosphate (LiFePO₄) cathode materials containing different low concentration ion dopants (Mg²⁺, Al³⁺, Zr⁴⁺, and Nb⁵⁺) were prepared by a solid-state reaction method in an inert atmosphere. The effects of the doping ions on the properties of as-synthesized cathode materials were investigated. XRD results indicate that the ion dopants do not affect the structure of the materials. The galvanostatically charge and discharge tests show that ion dopants can considerably improve the electrochemical performance of the materials, especially large current discharge behaviors. LiFePO4 samples doped with Nb⁵⁺ have an initiate capacity of 146.8 mAh•g^-1 at 0.1C. Further cycle performance measurements reveal the sample doped with Nb⁵⁺ shows the best cycleability. The results also verify that LiFePO₄ doped with ions of suited radius and higher valence shows better electrochemical characters.

Abstract: LiFePO₄/C nano-particles were synthesized by microwave assisted carbothermal reduction method, using LiOH•H₂O,FePO₄•2H₂O and sucrose as raw materials. LiFePO₄/C samples with different particle sizes were prepared by heating at different temperatures in an industrial microwave oven. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, laser particle sizer analysis and electrochemical performance test. The results showed that the average size of samples is about 100 to 300 nm. The first discharge capacity decreased with the increase of temperature. The LiFePO₄/C particles prepared at temperature of 700°С for 15 min exhibited the best capacity of 156.9mAh/g at 0.2C rate, and had just ~6% capacity loss after 50th cycles.

Abstract: Pt-counter electrodes were manufactured by dip coating, spin coating and sputtering methods for dye-sensitized solar cells (DSSCs). Their properties were analyzed with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), energy disperse spectroscopy (EDS). We also fabricated the TiO₂ nanotubes of 1.04 μm length as photoanode. The analytic results show that spin coating method has higher Pt content deposited on FTO glass, better performance of charge-transfer, more positive potential of tri-iodide reduction and higher efficiency of DSSCs.

Abstract: Poly(lactic acid) and Poly(butylenes succinate) grafting glycidyl methacrylate (PLA-g-GMA and PBS-g-GMA) and PLA/PLA-g-GMA/PBS and PLA/PBS-g-GMA/PBS blends were prepared by melt mixed method. The morphological structures of the blends were characterized by SEM and ESEM. The effects of graft polymer on the mechanical, dynamic mechanical and the rheological properties of the blends were studied.

Abstract: The characteristics of host-guest complexes between cucurbit[n]uril (CB [n]) and phenylalanine were investigated by UV-visible absorption spectroscopy in acetate buffer solution at room temperature. It was found that the UV-visible absorption increased steadily with constantly dropping the high concentration of cucurbit[6]uril (CB [6]) and cucurbit[8]uril (CB [8]) in the phenylalanine solution which indicates that there are some interaction betweenCB [n] and phenylalanine.Then CB [6] and phenylalanine at molar ratio of 1:1 to weigh while CB [8] and phenylalanine at molar ratio of 1:2, respectively, are both demonstrated by 1H NMR spectra. 1H NMR spectrum of complexes was obtained, indicating an enthalpic driving force for host-guest complexes. The possible interaction mechanism and inclusion mode were also discussed. This work may extend the application range of CB [n] in supramolecular and pharmaceutical analysis.

Abstract: The layered Y-doped SnO₂/C anode materials were prepared by a co-precipitation method. The physical properties of the Y-doped SnO₂/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that the Y-doped SnO₂/C has the same layered structure as the undoped SnO₂/C. The SEM images exhibited that the particle size of Y-doped SnO₂/C is smaller than that of the undoped SnO₂/C and the smallest particle size is only about 1µm. The Y-doped SnO₂/C samples were investigated on the Lithium extraction/insertion performances by charge/discharge, cyclic voltammograms (CV), and electrochemical impedance spectra (EIS). The results showed that the optimal doping content of Y was that x=0.07 and 2% content of carbon nanotubes samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility and electronic conductivity were enhanced, and the charge transfer resistance was decreased through Y-doping.

Abstract: In this study, composite films were prepared with Konjac glucomannan (KGM) and Starch, In the process of preparation, add Lactic acid as modifier, deal with Ammonia as crosslinker. Pretreatment with microwave, and used solvent (water) casting method to prepare the KGM/starch composite films, and used orthogonal matrix L25 (5,6) to analyze the influencing factors. The results showed that: the tensile strength of films is 7.96~25.68Mpa, and the fracture elongation rate is 1.25~5.00%. It can reach the tensile strength requirements of films for food packaging materials (polyethylene films) and the optimal level is A₂B₄C₃D₃. By XRD analysis, KGM/starch composite films showed amorphous. Preliminary degradation experiments shows that the decomposition period of KGM/starch composite films is 2 weeks in the soil suspension. Therefore, KGM/starch composite films are potential biodegradable film materials.

Abstract: The effect of intumescent flame retardant (IFR) contained microencapsulated red phosphorus on the flame retardance of E-44 epoxy resin (EP) was studied. The test results indicated that good flame retardancy can be realized when epoxy resin treated with 30% IFR. Thermogravimetric analysis showed that the charring amount at high temperature of EP can increase substantially when IFR was incorporated. In order to further explain this phenomenon, Dolye integration method of thermal degradation dynamics was employed to study the thermal degradation process of EP treated with IFR based on the microencapsulated red phosphrous according to the thermal gravimetry analysis results.The activation energy and reactor order of different thermal degradation stages were obtained. The results of thermal degradation dynamics implied the intumescent flame retardants can improve the flame retardance of the epoxy resin through decrease the degradation speed and increase the activation energy of the second thermal degradation stage.

Abstract: Polyurethane/modified kaolin foam composites were prepared via in situ polymerization with calcined kaolin as well as intercalated kaolin by one-step procedure. The lattice structures of the kaolin were characterized by XRD. The calcined kaolin under 600°C became amorphous structure and were well dispersed in the polyurethane (PU) matrix. The interlayer spacing of intercalated kaolin with potassium acetate shifted from 0.715nm to 1.407nm and were occurred clusters in the PU matrix. FTIR showed that the two kaolin had tiny effect on the structure of the PU and the hydrogen bonding played less role on mechanical performance. The mechanical properties induced by the addition of both of modified kaolin were analyzed. The mechanical properties of the foams with calcined kaolin were better than that with intercalated kaolin. The distribution of modified kaolin were analyzed by TEM. The dispersed particles of calcined kaolin were smaller than that of intercalated kaolin and the dispersion of kaolin played more role on mechanical performance.

Abstract: Polymers have more complicated properties since they display both elastic and viscous type responses at different strain rates. As the application of polymers increase, a thorough understanding of the mechanical behavior of these materials becomes vital in order to perform innovative and economical designs of various components. The main objective of this paper is to develop an effective method with the use of Laplace integral transform to describe the creep and relaxation properties of viscoelastic polymers. This general approach is on the basis of the integral constitutive functions for viscoelastic polymers, avoiding the use of differential stress-strain relations. Using this method, the time domain stress-stain relation can be easily obtained. As its application, the creep and relaxation properties of the materials are exhibited in the numerical examples.