Preparation of Zn(Cd)O:Ga–SiO2 composite scintillating materials

Composite material consisting of highly luminescent Zn(Cd)O:Ga powder embedded in the silica matrix was prepared. It was found out that ZnO:Ga with less developed crystals (i.e. annealed at lower temperatures) is more prone to interact with the SiO₂ matrix and form zinc silicates, which in turn resulted in the decrease in the excitonic emission. Pre-annealing of the powders at temperatures above 600 °C prevented the interaction with the SiO₂ matrix. ZnO:Ga with well-developed crystals at such a high temperatures was not affected by the matrix and retained its properties, i.e. high radioluminescence intensity and ultrafast sub nanosecond photoluminescence decay. Introducing Cd into the ZnO lattice caused observable red shift in the excitonic luminescence, without negatively affecting the total intensity or the decay.     

Synthesis,Crystal Structure and Properties of Novel Composite Complex: [La(Nmp)4(H2o)4][HsiMo12O40]·2nmp·H2o

A new composite complex of [La(NMP)₄(H₂O)₄][HSiMo₁₂O₄₀]·2NMP·H₂O (NMP = N-methyl-2- pyrrolidone) was synthesized and characterized by IR, UV, ESR, TG-DTA and single crystal structural analysis. The water and organic ligands (NMP) coordinate directly with La(III) to form a dodecahedral complex and the SiMo₁₂O^4? ₄₀ anion is the counter ion. IR and X-ray analysis show that there is strong interaction between the polyoxometalate and organic donors. The complex is strongly photosensitive under irradiation with sunlight, resulting in a charge-transfer complex by oxidation of the N-methyl-2-pyrrolidone and reduction of the polyoxometalate. Low temperature ESR spectra indicate thermal electron delocalization among the Mo atoms in the title compound.     

硅橡胶包覆十八烷/聚(St-MMA)储能微胶囊复合材料制备及热性能

以十八烷/聚(苯乙烯-甲基丙烯酸甲酯)(P(St-MMA))微胶囊为相变材料,硅橡胶作为载体,制备了十八烷/P(St-MMA)/硅橡胶复合材料。研究了微胶囊的加入方式及加入量,硅橡胶包覆方法。通过红外光谱(IR)和扫描电镜(SEM)研究复合材料的结构和形貌。通过力学性能测试如拉伸强度、扯断伸长率,确定最佳的加工方法。通过热重分析法(TG)、差示扫描量热法(DSC)和储热性能对复合材料的热性能进行研究。结果表明,十八烷制成微胶囊加入到硅橡胶中,且微胶囊加入量是2份时,十八烷/P(St-MMA)微胶囊/硅橡胶的热稳定性热稳定性及力学性能较好。室温硅橡胶包覆微胶囊掺混固化法制备的复合材料的力学性能优于直接共混后热固化法和混炼涂抹后热固化法。十八烷/P(MMA-St)/硅橡胶复合材料的焓值为67.6J/g,储能效果好。     

Homogenization of parabolic problem with nonlinear transmission condition

In this paper, we investigate the periodic homogenization of nonlinear parabolic equation arising from heat exchange in composite material problems. This problem, defined in periodical domain, is nonlinear at the interface. This nonlinearity models the heat radiation on the interface, which constitutes the transmission boundary conditions, between the two components of the material. The main challenge is, first, to show the well-posedness of the microscopic problem using the topological degree of Leray–Schauder tools. Then, we apply the two scale convergence to identify the equivalent macroscopic model using homogenization techniques. Finally, in order to confirm the efficiency of the homogenization process, we present some numerical results obtained via finite element approximation.     

Influence of thermal and UV treatment on the polypropylene/graphite composite

Electrically conductive polypropylene/graphite (PP/graphite) composites were prepared via blending granulated PP with maleic anhydride grafted PP and natural graphite. Electrical conductivity of prepared samples containing either 65, 70, or 75 wt% of graphite was measured and the most conductive sample containing 75 wt% of graphite was exposed to UV irradiation for 1 and 24 h or thermally treated at 170 °C for 1 h. The influence of thermal and UV exposure on the structural and electrical changes in such treated samples was studied. Local current measurements on the surface were made using scanning spreading resistance microscopy and morphology of the surface was studied by atomic force microscopy. X-ray diffraction analysis, infrared and Raman spectroscopy were also used for the structural characterization. Properties of treated and untreated samples are compared and differences are discussed.     

GO/PVA nanocomposites with significantly enhanced mechanical properties through metalion coordination

In this study, a simple and efficient way is demonstrated to create strong interfacial interaction between graphene oxide(GO) filler and poly(vinyl alcohol)(PVA) matrix through metal ion coordination. The coordination bonding provides efficient load transfer during the tensile process, and enhances the mechanical properties of the nanocomposites significantly. After being coordinated with Cu(Ⅱ) ions, GO/PVA composites show much higher Young's moduli and yield stresses than pure PVA and noncoordinated GO/PVA. UV–vis and FTIR spectra are performed to confirm the successful coordination between GO and PVA. Ethylene diamine tetraacetic acid disodium salt(EDTA-2 Na) is used to confirm the important role of coordination in enhancing the composites. This research provides a new approach to manufacture polymer-matrix nanocomposites with significantly improved mechanical performances.     

Preparation and photochromic properties of pyrazolones/polyvinyl alcohol composite films

Novel photochromic composite films have been successfully fabricated by dispersing pyrazolone derivative:1,3-Diphenyl-4-(3-chlorobenzal)-5-hydroxypyrazole 4-phenylsemicarbazone (1a) into hydrosol of polyvinyl alcohol (PVA). The microstructure, photochromic behaviors and thermal bleaching properties were investigated by Raman spectroscopy, X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and ultraviolet-visible absorption spectroscopy (UV-vis). The results showed that 1a was not only blended but also well dispersed in the PVA polymer films with a suitable content of chromophore. Upon UV light irradiation, the composite films gradually changed from colorless to yellow and recovered fully to the initial state upon thermal bleaching. The time constants of photochromic reactions were almost the same as those of 1a observed in their crystalline state, indicating that the photochromic phenomenon is barely disturbed by the polymer matrix.     

On the free vibration response of rectangular plates,partially supported on elastic foundation

Rectangular plates on distributed elastic foundations are widely employed in footings and raft foundations of variety of structures. In particular, mounted columns and single footings may partially occupy the rectangular plate of any kind.     

Composite Likelihood Inference in a Discrete Latent Variable Model for Two-Way “Clustering-by-Segmentation” Problems

We consider a discrete latent variable model for two-way data arrays, which allows one to simultaneously produce clusters along one of the data dimensions (e.g., exchangeable observational units or features) and contiguous groups, or segments, along the other (e.g., consecutively ordered times or locations). The model relies on a hidden Markov structure but, given its complexity, cannot be estimated by full maximum likelihood. Therefore, we introduce a composite likelihood methodology based on considering different subsets of the data. The proposed approach is illustrated by simulation, and with an application to genomic data.     

Structural, optical and electromagnetic properties of aluminum-clay nanocomposites

Aluminum pillared and exchanged bentonite particles were synthesized by the ion exchange method. The characteristics of the particles were investigated by Fourier-transform infrared spectra (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDS), reflectance spectrophotometer (RS) and electromagnetic transition instrument (ETI). FTIR spectra showed a successful incorporation of Al complexes into the clay interlayer. The TGA result demonstrated an improvement in thermal stability of the Al-pillared clay compared with the untreated particles. SEM and EDX results showed the presence of aluminum aggregates on the surface of clay. It was also found that Al ions affect electromagnetic properties of the clay particles.