Polymer‐Derived Silicon Oxycarbide/Hafnia Ceramic Nanocomposites. Part II: Stability Toward Decomposition and Microstructure Evolution at T≫1000°C
This study presents first investigations on the high-temperature stability and microstructure evolution of SiOC/HfO2 ceramic nanocomposites. Polymer-derived SiOC/HfO2 ceramic nanocomposites have been prepared via chemical modification of a commercially available polysilsesquioxane by hafnium tetra (n-butoxide). The modified polysilsesquioxane-based materials were cross-linked and subsequently pyrolyzed at 1100°C in argon atmosphere to obtain SiOC/HfO2 ceramic nanocomposites. Annealing experiments at temperatures between 1300° and 1600°C were performed and the annealed materials were investigated with respect to chemical composition and microstructure. The ceramic nanocomposites presented here were found to exhibit a remarkably improved thermal stability up to 1600°C in comparison with hafnia-free silicon oxycarbide. Chemical analysis, X-ray diffraction, FTIR, and Raman spectroscopy as well as electron microscopy (SEM, TEM) studies revealed that the excellent thermal stability of the SiOC/HfO2 nanocomposites is a consequence of the in situ formation of hafnon (HfSiO4), which represents a concurrent reaction to the carbothermal decomposition of the SiOC matrix. Thus, by the annealing of SiOC/HfO2 materials at 1600°C, novel HfSiO4/SiC/C ceramic nanocomposites can be generated. The results presented emphasize the potential of these materials for application at high temperatures.
Congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is impaired by one or more specific mechanisms. Since the advent of next‐generation sequencing methods, the discovery of novel CMS targets and phenotypes ha ... more
Myasthenia gravis (MG) with antibodies to muscle‐specific kinase (MuSK) is characterized by fluctuating fatigable weakness. In MuSK MG, involvement of bulbar muscles, neck, and shoulder and respiratory weakness are more prominent than in acetylcholine receptor (AChR) MG. MuSK au ... more
Because of the failure of many promising therapeutics identified in preclinical evaluation, funding sources have established guidelines for increased rigor in animal evaluations. The myasthenia gravis (MG) community of scientists has developed guidelines for preclinical assessme ... more
Smart skin that can respond to external stimuli could have important applications in medicine and robotics. Using only items found in a typical household, researchers have created multi-sensor artificial skin that's capable of sensing pressure, temperature, humidity, proximity, pH, and air ... more
Mercury contamination in water and on land is of worldwide concern due to its toxic effects on ecosystems and human health. Mercury toxicity is of particular concern to reptiles because they are currently experiencing population declines. Also, reptiles are ideal indicators of mercury conta ... more
A team of pioneering South Korean scientists have succeeded in producing the polymers used for everyday plastics through bioengineering, rather than through the use of fossil fuel based chemicals. This groundbreaking research, which may now allow for the production of environmentally consci ... more