Abstract: Wood as a porous structure has weak durability and unsatisfactory mechanical properties which limits its utilization. For this reason, the study presents a two-step method to prepare a new modified wood material—Wood Polymer Composite. Maleic anhydride(Man) firstly penetrates into the porous structure of wood, followed by a reaction with wood cell walls. Then, Styrene(St) with some Man and a few amount of initiator, AIBN, permeate through the whole wood and react with the above modified wood. The structural characterization of wood polymer composite with SEM and FTIR indicates that Man reacts successfully with the hydroxyl group of wood cell wall by its anhydride group, and further reacts fully with styrene as a free radical copolymerization form by its double bond; and thus the polymer fills in wood cell lumina as a solid form, which combines the wood cell walls without any evident crack. The testing results of properties show that the mechanical properties of wood polymer composite increase by about 50%-250% over those of unmodified wood, and its durability improve 1.9-4.89 times than untreated wood.
Abstract: A new thermosensitive hydrogel had been prepared that could be transformed into gel at 37 °C from chitosan and a mixture of α- and β-glycerophosphate (αβ-GP). The appearance of hydrogel was compact and corrugated. There was little granule in the appearance of gel loaded with adriamycin and the granules might be crystals of the added model drug. In vitro cytotoxicity of the hydrogel was tested by the MTT method using mouse embryonic fibroblasts (MEF). MEF cultured with leachates of CS-αβ-GP were investigated and the relative growth rate (RGR) was calculated and the cytotoxicity was graded by generally accepted standard. The study of in vitro degradation of CS-αβ-GP hydrogels included hydrolysis and degradation by lysozyme. The CS-αβ-GP thermosensitive hydrogel was degradable in vitro and the degradation rate was faster in lysozyme solution than that in the medium of PBS. So the CS-αβ-GP system had good cell biocompatibility and biodegradability which provided possibilities and foundations for the further research.
Abstract: Ga2xIn2(1-x)O3 thin films with different gallium content x [x = Ga/(Ga+In) atomic ratio] have been prepared on -Al2O3 (0001) substrates at 650°C by metalorganic chemical vapor deposition (MOCVD). Structural, electrical and optical properties of these films have been investigated in detail. The XRD analysis revealed that, as the gallium content increased, the crystalline quality of the films decreased. The highest Hall mobility of the films was 41.32 cm2v−1s−1. The absolute average transmittance of the Ga2xIn2(1-x)O3 thin films in the visible range exceeded 91%. The band gap could be tuned from 3.59 to 4.87 eV as gallium content increased.
Abstract: SnO2 thin films have been deposited on 6H-SiC(0001) substrates by metalorganic chemical vapor deposition (MOCVD) system. The structural and optical properties of SnO2 films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectrophotometry. The XRD analysis revealed that the prepared samples were SnO2 epitaxial films of rutile structure with a clear relationship of SnO2(100)// 6H-SiC(0001). The average transmittance for the deposited SnO2 samples in the visible range was about 60%.
Abstract: A series of conductive composites polyaniline(PANI)-cellulose were heterogeneously synthesized by chemical oxidative polymerization of aniline with native cellulose pretreated by ultrasonic. The morphology and chemical structure of the composites were examined by SEM and FTIR. TGA was used to study their thermal properties. The electrical conductivity was measured at room temperature by the standard four-probe method. For the sake of illuminating the influence of ultrasonic pretreatment on the structure and properties of PANI-cellulose composites, the SEM microphotographs, FTIR spectrum and TG curve of the PANI-cellulose composites prepared with native cellulose without any treatment were also shown in this paper to serve as reference. The PANI content and electrical conductivity of these two composites were also compared. It was found that cellulose surface was severely eroded by ultrasonic wave, and PANI homogeneously dispersed on this eroded cellulose surface in the form of particles. In reverse, the PANI particles loaded on the surface of untreated cellulose with evident aggregation. The homogeneous dispersion of PANI particles would be favor for the improvement of the electrical conductivity of the composites. From the FTIR spectra, it was verified that there was no difference between these two composites. It indicated that ultrasonic force did not lead to the variation of the chemical structure of cellulose. TG curves revealed that the thermal stability of PANI-cellulose composites was obviously enhanced than pure cellulose due to the protection of PANI particles deposited on its surface. Nevertheless, ultrasonic has a negative effect on the thermal stability of the composites, which resulted in the long cellulose molecular chains change into shorter ones, so the decomposition of composite occurred at lower temperature. It was because that ultrasonic pretreatment contributed to the homogeneous dispersion of PANI and more PANI particle depositing on the cellulose surface. Therefore, the PANI-cellulose composites with ultrasonic pretreated cellulose have more PANI content and higher electrical conductivity than the composites with untreated cellulose. Moreover, the difference of these two factors between the two composites became more and more marked with increasing of the amount of aniline. When aniline used was up to 0.5 g, the PANI content in the former was 48.2% more than the latter. This work provided a facile method for the synthesis of PANI-cellulose conductive composites with excellent conductivity.
Abstract: A new nanocomposite consisting of polyaniline (PANI), montmorillonite (MMT) and La3+ was developed via in-situ polymerization of aniline in the presence of MMT and La3+ through emulsion polymerization, and also a novel network structure consisting of nanowires had been shaped. The morphology and the chemical structure of the product were studied by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The thermal property was exmined by mean of gravimetric analysis (TGA). The results indicated that PANI/MMT/ La3+ namocomposite has formed nanowires with diameter about 5 nm. The novel network structure consisting of nanowires has been shaped and overlapped towards certain direction. The formation of this network structure reveals that PANI molecules have been successfully inserted into the interlayer of MMT. Meanwhile, this conductivity network is believed to lead to the great improvement of the electrical conductivity for the nanocomposites. The FT-IR spectra reveal that PANI is obtained via in situ polymerization of the aniline monomer and there is a strong interaction between PANI and MMT. From XRD analysis, it can be also seen that the PANI molecules had been successfully intercalated into the galleries of the MMT. Moreover, the arrangement of PANI is more ordered in PANI/MMT/La3+ nanocomposite than that of pure PANI. From TGA curves, it is apparent that the introduction of MMT and rare-earth ions (La3+) exhibited a beneficial effect on the thermal stability of pure PANI. This markedly enhanced thermal stability of the nanocomposites can be ascribed to the MMT nanolayers acting as barriers for the degradation of PANI in the interlayer spacings and the inorganic nanoparticles trammeled the movement of the PANI molecule chains. They make the thermal decomposition of the nanocomposites at a disadvantage. As a consequence, the needed energy of the thermal decomposition increased, the thermal stability of nanocomposite increased. The paper offers a novel PANI/MMT/La3+ nanowire composites.
Abstract: A novel structure of nan0Composite consisting of conducting Polyaniline (PANI), graphite nanosheets (NanoGs) and Eu3+ was synthesized through emulsion polymerization. NanoGs were prepared via powdering the expanded graphite with the aid of sonication in aqueous ethanol solution. Then NanoGs and rare earth ions (Eu3+) were directly organised with sonication, using p-toluene-sulfonic acid (P-TSA) as an emulsifier and dopant, (NH4)2S2O8 as inducing reagent and the polymerization of aniline monomer simultaneously. The product was characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), Fouier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA). From the thermogravmetric analysis, the introduction of NanoGs and rare-earth ions (Eu3+) exhibited a beneficial effect on the thermal stability of pure PANI.
Abstract: Cubic assembly composed of platinum nanoparticles has been prepared by a simple reaction between H2PtCl6•6H2O, NaOH and NaBH4 in the presence of deionized gelatin. Gelatin played a decisive role as an inhibitor of the direct reaction of NaBH4 with H2PtCl6•6H2O and coagulation of the growing platinum in producing the cubic assembly composed. In the absence of gelatin, we can only obtain irregular large platinum particles. With decreasing the temperature, the viscosity of the solution increased. The diffusions of BH4- ions and PtCl62− ions are slower. The assembly composed of platinum nanoparticles was synthesized at 10 oC. The products were characterized by X-ray powder diffraction, scanning electron microscope, X-ray photoelectron spectra and UV-visible absorption spectroscopy. The scanning electron microscope images show the as prepared platinum with cubes and the average dimensions is about 0.35-0.45 μm. The UV-visible absorption spectrum of the as prepared platinum particles dispersed in ethanol solution shows one absorption peaks at 215nm. The size of the subunits of the polycrystalline platinum particles was calculated to be about 4 nm according to half width of the diffraction peaks using Debye–Scherer equation.
Abstract: The study of nanoparticle-modified asphalt is an intense popular interest and also a heading issue of transportation materials. To make the most of excellent properties of nanoparticle-modified asphalt, the mutual adaptability between the additive and asphalt as well as the dispersive stability in nanoparticles-modified asphalt system must considered at the first. In this paper, the basic principle of nanoparticles-modified asphalt is introduced. The mutual adaptability between the additive and asphalt as well as the dispersive stability in nanoparticles-modified asphalt system is studied. In addition, emulsified nanoparticles-modified asphalt and other issues are presented briefly.
Abstract: The notched strength of AS-4/PEEK (APC-2) composite laminates with a central hole at elevated temperature was systematically studied by both analytical and empirical methods. First, the APC-2 cross-ply [0/90]4s panels were fabricated and cut into samples. Each sample was drilled a hole in the center with five kinds of diameters, such as d=0(unnotched), 1, 2, 3, and 4mm. Then, the samples were subjected to quasi-static tensile tests at elevated temperatures, including 25°C (RT), 75, 100, 125, 150 and 175°C, to measure their mechanical properties. The average values of received notched strength were affected significantly by stress concentration and high temperature. In analysis the prediction of residual strength by point stress criterion (PSC) was adopted first and found unsatisfactory due to at least 15% errors with experimental data. Then, the modified PSC was used with the varied characteristic length dependent on nature of material and specimen geometry. The predicted notched strengths by the modified PSC model were in very good agreement with experimental data. The predictive results were not only precisely validated, but extended to the application at elevated temperature.