Epoxy/core-shell particle blends were prepared using a diglycidylether of bisphenol A epoxy and acrylics-type core-shell particles. The impact strength of the blends was tested, and the result showed that the epoxy was greatly toughened with optimum core-shell particle content. Meanwhile, the dielectric properties of both epoxy and its blends were investigated using a broadband dielectric analyzer. It was found that the dielectric constant of the epoxy blends with lower core-shell particle content were less than that of the epoxy in the investigated frequency range, while the dielectric loss was less than that of the neat epoxy over a low frequency range, even for the epoxy blends with the optimum core-shell particle content. The dielectric breakdown strength of the epoxy blends at room and cryogenic temperature were also investigated. To identify the primary relationship of the above properties and structure of the epoxy blends, the microstructure of the core-shell particle and the morphology of the samples were observed by transmission electron microscopy and scanning electron microscopy. It was considered that these epoxy/core-shell particle blends with improved toughness and desirable dielectric properties could have a potential application in the insulation of electronic packaging system.

The aesthetic defects of polymeric polarizers have a serious impact on the quality of thin film transistor liquid crystal display (TFT-LCD) panels. However, some of these slight and transparent defects can barely be imaged and characterized using conventional illumination. To inspect these special defects, a new and automated inspection method is proposed that employs structured-light illumination. A machine vision system that uses a LCD monitor to produce a binary stripe pattern was designed to enhance the imaging defects. Thus, subsequent image processing is straightforward and simple because of this enhancement. One hundred and fifty defect samples were successfully imaged and then processed and characterized by the Robust Principal Component Analysis (RPCA) algorithm. The total inspection accuracy was up to 99%. The experiments demonstrate that the width of the luminous stripe should be optimized at 2 to 3 times the size of the defect. The mechanism of the imaging enhancement is preliminarily discussed.

Spatially-resolved electroluminescence (EL) images in the triple-junction InGaP/InGaAs/Ge solar cell have been investigated to demonstrate the subcell coupling effect. Upon irradiating the infrared light with an energy below bandgap of the active layer in the top subcell, but above that in the middle subcell, the EL of the top subcell quenches. By analysis of EL intensity as a function of irradiation level, it is found that the coupled p-n junction structure and the photovoltaic effect are responsible for the observed EL quenching. With optical coupling and photoswitching effects in the multi-junction diode, a concept of infrared image sensors is proposed.

No abstract

Repeated impact has been introduced to evaluate different properties of hard coatings, such as impact wear resistance, bonding strength, fatigue, etc. The load and impact number relationships are similar to that of fatigue curves, and close to some real applications of coated parts. Cr-Cu-N coatings were performed on a hardened steel substrate and the repeated impact tests were conducted on the coating substrate system. At a low impact load, the intrinsic strength of the coating layer and the bonding strength between the coating and substrate are in competition. Coating layer cracking or delamination might occur and the strength plays an important role like that of high cycle fatigue. When the load is increased and towards the low cycle fatigue regime, toughness of the coating layer turns out to be predominant. The cohesive failure in high load regime preferentially depends on the toughness of the coating layer, and the failure cycles can be employed as a toughness criterion.