Ceramic coatings of the Al2O3/SiO2 composition by the sol-gel method on carbon fibers were obtained in order to prevent oxidation and destruction of the fiber at temperatures above 450°C. Various combinations and ratios of aluminum and silicon oxides were used. The results of scanning electron microscopy and X-ray diffraction showed a change in the topographic properties of carbon fiber during the deposition of coatings thereon. Thermal analysis showed that oxidative stability improved significantly due to coverage, increased to 1100°C.
The national standards on measuring the breakdown voltage of liquid dielectrics are considered, in particular, the measurement procedure and the measuring cell main parameters. The breakdown voltage of PDMS-1000, PDMS-12500 and PDMS-30000 liquids produced by various manufacturers was measured, and the main problems faced in carrying out measurements were identified. It is shown, using the example of polydimethylsiloxane liquid dielectrics, that after breakdown of viscous liquids, a channel is produced in them, which consists of gas bubbles held by the surface tension force, due to which the channel may in many cases persist for a long time. Theoretical calculations confirmed by an experiment were performed, based on which the velocity of air bubbles in polydimethylsiloxane liquids can be estimated. A conclusion has been drawn about the necessity to increase the time intervals between individual measurements, as well as the time interval before the start of measurements after pouring the test liquid into the measurement cell. It is shown that visual control of the interelectrode region and a special method of mixing the liquid are also necessary. It can be stated based on the accomplished study that the existing standards for breakdown voltage measurements in viscous liquids need to be refined.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.