No abstract

Opportunities for the synthesis of ultrafine spherical particles with uniformly distributed components and phases are of special importance when materials for photonic application are considered. In this study, the nanophase, spherical, luminescent polycrystalline Gd 2 O 3 :Eu and YAG:Ce particles were synthesized from aerosols of the corresponding nitrate solutions ultrasonically generated with frequencies of 1.7 MHz and 800 kHz, respectively. Detailed phase and structural analysis, compositional homogeneity, and particle morphology were determined in accordance to X-ray diffraction ͑XRD͒, scanning electron microscopy ͑SEM͒, and energy dispersive X-ray spectroscopy ͑EDS͒. Quantitative SEM/EDS analysis indicated high material purity and compositional homogeneity. The phase development and structural changes imply nanocrystalline inner structure ͑crystallites below 60 nm after thermal treating͒, which influences luminescence behavior. Luminescence measurements indicate that both the radioluminescence and thermoluminescence emission spectra of the Gd 2 O 3 :Eu are totally dominated by the line emission characteristic of the Eu, fully substituted onto host lattice sites. By contrast, the cerium dopants in YAG display only very weak Ce luminescence after annealing, but there are broad emission bands characteristic of host lattice defect sites. The spectra are clearly altered by heat treatments and the thermoluminescence indicates a range of independent defect emission sites.

Recently, polymer composites reinforced with low fractions of thermomiotic nanoceramics have triggered a lot of research. The efforts have been focused on achieving considerable reduction of the coefficient of thermal expansion (CTE) of polymeric materials without deterioration of other physical properties. In this context, polyethylene (PE) composites reinforced with different loads of Al 2 Mo 3 O 12 nanofillers (0.5-4 mass %) were fabricated by micro-compounding. To enhance the interfacial interaction between the two components, chemical functionalization of Al 2 Mo 3 O 12 was performed with vinyltrimethoxysilane (VTMS) prior to micro-compounding. Infrared spectroscopy and thermogravimetry demonstrated the successful grafting of VTMS on the Al 2 Mo 3 O 12 surface. The composites showed strongly decreased CTEs, up to 46 % reduction for loadings of 4 mass % compared with neat PE, suggesting intimate filler-matrix interactions. The variation of CTEs of the composites in terms of the filler fraction was successfully described by Turner's model allowing calculation of the bulk modulus of monoclinic Al 2 Mo 3 O 12 (13.6 ± 2.6 GPa), in agreement with the value obtained by an ultrasonic method. The thermal stability of the composites was improved, although the addition of functionalized fillers decreased the degree of crystallinity of the PE to a small extent. The Young's modulus and yield strength of the composites increased from 6.6 to 19.1 % and 4.0-6.0 %, respectively, supporting the existence of strong filler-matrix interactions, contributing to an efficient load transfer. Finite element analysis of thermal stresses Electronic supplementary material The online version of this article (

No abstract