The properties of inorganic nanoparticles/polymer composites depend on the dispersivity of nanoparticles in a polymer matrix. The effect of surface modification on the dispersivity of ZnO nanoparticles in a polyurethane (PU) resin matrix was investigated. The nanocomposites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis, and X‐ray diffraction. The scanning electron micrographs show that ZnO nanoparticles (CDI–SA–APS–ZnO), which were modified by aminopropyltriethoxysilane (APS) and activated stearic acid (SA) by N,N′‐carbonyldiimidazole (CDI), can be homogeneously dispersed and had been encapsulated in the PU phase. The interfacial compatibility between ZnO nanoparticles and PU matrix was significantly improved by hydrophobically modifying ZnO nanoparticles with APS and SA. The tensile strength and elongation at break of PU/CDI–SA–APS–ZnO nanocomposites increased by 82 and 64% respectively, compared with the pure PU material. The thermal stability and ultraviolet‐shielding properties were also improved by incorporating ZnO nanoparticles into the PU matrix. POLYM. COMPOS., 35:237–244, 2014. © 2013 Society of Plastics Engineers

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The bubble behaviour has been studied in bubbling fluidized bed composed of the binary mixtures of titanium slag and carbon particles by analysis of pressure time series. The results show that the IOP analysis method can effectively filter out most of the compression wave components at low jetsam fraction and small light particles, but can't effectively remove the compression wave components at high jetsam fraction and large light particles in binary particle fluidized bed. IOP xy functions is significantly affected by the mixed state of binary particles, which means that bubble behavior depends on the segregation/mixing of binary particles in fluidized bed.Nomenclature COP xy coherent parts of power spectral density, Pa 2 /Hz d p particle diameter, m d pj heavy particle diameter, m d pl light particle diameter, m f frequency, Hz H bed height, m IOP xy incoherent parts of power spectral density, Pa 2 /Hz u g superficial gas velocity, m/s X J jetsam mass fraction X L flotsam mass fraction m density of binary mixtures xx , yy power spectral density, Pa 2 /Hz xy cross-power spectral density, IntroductionFluidized bed has been widely used in many industries because of its desirable characteristics such as high heat and mass transfer rates, temperature homogeneity, and rapid mixing of particulate materials. The component that tends to sink to the air distributor is referred to as "jetsam", while the component that tends to float on the fluidized bed surface is referred to as "flotsam" [1]. The gas bubble characteristics can be investigated with direct methods by measuring the local voidage in fluidized bed such as optical and capacitance, and indirect method by measuring pressure fluctuations. Measuring pressure fluctuations has received more attention due to its advantages such as relatively simple, non-intrusive, and inexpensive, and time-and frequency-domain analysis techniques have been widely used to analyze the pressure time signals [2][3][4]. Bi [5] and Sasic et al [3] reviewed the investigation of the fluid-dynamic behavior of gas-solid fluidized beds using pressure signals and the sources of pressure fluctuations, propagation features and the nature of pressure waves in fluidized beds. Falkowski and Brown [2] investigated the effect of bed parameters on the power spectra from the corresponding pressure fluctuations for developing pressure fluctuations as a diagnostic tool for fluidized-bed reactors and combustors.Origin of pressure wave is composed of two main sources, one is global compression wave (fast-travelling wave) that originates from bubble formation and bubble coalescence and can travel upwards and downwards through the bed from the point of their origin, the other is the local fluctuations caused by bubble passage and gas turbulence [6][7][8]. In order to obtain the information of bubble-passage from the pressure signals, the pressure fluctuations corresponding to compression waves need be removed. Van der Schaaf et al [9] proposed a decoupling method that splits the power spectral density (PSD) ...