RESUMO
In this study, the morphology of an immiscible polymer blend system at various regions of interests was analyzed using different microanalytical methods with varying surface sensitivities. As a model immiscible polymer blend, a HDPE/PP (80/20â¯wt%) polymer film was used. The blend film was subjected to polarized light microscopy (PLM), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and time of flight secondary ion mass spectrometry (ToF-SIMS). The obtained results were compared regarding the sensitivities, informational values and overall applicability of the analytical methods. It was evaluated which methods can be applied for a fast analysis of the morphology (surface and bulk) of the immiscible polymer blend with low preparation efforts, which is especially important for the analysis of new materials, for example materials manufactured via recycling. It was demonstrated that PLM, as well as SEM on wet-etched material, provide sufficient information to evaluate the bulk morphology. Additionally, the presented study shows the advantage of applying ToF-SIMS imaging for the characterization of the surface of immiscible polymer blend. As expected, the domain distribution of HDPE and PP varied between the bulk and the surface of the films. The proposed procedures can be taken as a guideline for other investigations concerning the morphology of heterogeneous polyolefin systems.
RESUMO
Innovative materials for phosphor converted white light-emitting diodes are in high demand owing to the huge potential of the light-emitting diode technology to reduce energy consumption worldwide. As the primary blue diode is already highly optimized, the conversion phosphors are of crucial importance for any further improvements. We report on the discovery of the high performance red phosphor Sr[Li2Al2O2N2]:Eu2+ meeting all requirements for a phosphor's optical properties. It combines the optimal spectral position for a red phosphor, as defined in the 2016 Research & Development-plan of the United States government, with an exceptionally small spectral full width at half maximum and excellent thermal stability. A white mid-power phosphor-converted light-emitting diode prototype utilising Sr[Li2Al2O2N2]:Eu2+ shows an increase of 16% in luminous efficacy compared to currently available commercial high colour-rendering phosphor-converted light-emitting diodes, while retaining excellent high colour rendition. This phosphor enables a big leap in energy efficiency of white emitting phosphor-converted light-emitting-diodes.
