RESUMO
The powder bed selective laser process (sintering/melting) has revolutionised many industries, including aerospace and biomedicine. However, PBSLP of ceramic remains a formidable challenge. Here, we present a unique slurry-based approach for fabricating high-strength ceramic components instead of traditional PBSLP. A special PBSLP platform capable of 1000 °C pre-heating was designed for this purpose. In this paper, PBSLP of Al2O3 was accomplished at different SiC loads up to 20 wt%. Several specimens on different laser powers (120 W to 225 W) were printed. When the SiC content was 10 wt% or more, the chemical interaction made it difficult to process. Severe melt pool disturbances led to poor sintering and melting. The structural analysis revealed that the micro-structure was significantly affected by the weight fraction of SiC. Interestingly, when the content was less than 2 wt%, it showed significant improvement in the microstructure during PBSLP and no effects of LPS or chemical interaction. Particularly, a crack pinning effect could be clearly seen at 0.5 wt%.
RESUMO
Aortic coarctation (AC) is a significant cause of secondary hypertension and is diagnosed in childhood in the vast majority of patients. Mild or moderate coarctation may exist undetected into adult life, when it usually presents due to its sequelae. The authors present the case of a 20-year-old woman, previously extensively investigated for severe hypertension, who was admitted following sever, sudden-onset headache. CT scanning of the head showed the presence of subarachnoid blood (SAH), with subsequent CT angiography revealing two intracerebral aneurysms as the source. On attempting to catheterise the femoral artery her pulses were noted to be weak and during passage of the catheter she was found to have significant AC. The aneurysms were duly treated with detachable coils and the clinical course with regard to the SAH was unremarkably safe for high-pressure headache.
