摘要:
La présente a pour objet un carbure de bore caractérisé en ce qu'il répond à la formulation suivante B 4-X C avec 0 x 0,4, ledit carbure de bore ayant une structure cristallographique de type icosaédrique comprenant des liaisons chimiques C-C inter-icosaèdres formées entre deux atomes de carbone de distance égale à environ 0,18 +/- 0,02 nanomètres, à pression et température ambiantes. L'invention a aussi pour objet un procédé de fabrication du carbure de bore comprenant une opération de magnésiothermie à une température supérieure à 1000°C et sous pression au moins supérieure à 6 GPa.
摘要:
The invention relates to a method for producing a semiconductor ceramic material having a non-linear electrical resistance with a positive temperature coefficient, in which a precursor mass that comprises a donor-doped, ferroelectric material having a Perovskite structure and the general formula AxByO3 is sintered in a reduced atmosphere at temperatures of not more than 1200 °C. According to the invention, the sintered material has an average grain size in the sub-micrometer range. The sintered material is then reoxidized at its grain boundaries at temperatures of not more than 600 °C. The grain size of the precursor mass has an average primary grain size in the sub-micrometer range, preferably an average primary grain size of not more than 50 nm, more preferably of not more than 20 nm and even more preferably of not more than 10 nm. The semiconductor ceramic material produced by said method has also an average grain size in the sub-micrometer range, preferably in such a way that 80% of the grains are smaller than 800 nm, more preferably smaller than 300 nm and even more preferably smaller than 200 nm.
摘要:
Ceramic nanocomposite and methods for manufacturing thereof. One method comprising: receiving a fired green ceramic body comprising ceramic matrix; introducing to the fired green ceramic body submicron particles; and introducing at least one type of location-controlling dopant at an amount that is sufficient to cover the majority of the ceramic matrix grain boundaries, as well as the majority of the interfaces between the submicron particles and the ceramic matrix grains but less than an amount that would result in a concentration that exceeds the bulk solubility limit of the location-controlling dopant ions in the ceramic matrix, at the ceramic nanocomposite sintering temperature.
摘要:
La presente invención se refiere a un procedimiento de fabricación de cerámicas porosas y materiales multifásicos avanzados a partir de precursores vegetales, concretamente a partir de la infiltración de aleaciones metálicas en preformas de carbón obtenidas por pirólisis de precursores celulósicos. La invención incluye también un procedimiento de unión de estos materiales. La invención es aplicable fundamentalmente al ámbito de la obtención de materias primas utilizable en un amplio espectro de la industria, para la obtención de componentes para aplicaciones que se basen en sus propiedades de dureza, resistencia a la fricción, conductividad térmica, conductividad eléctrica, resistencia mecánica, alta superficie específica, porosidad, resistencia a la corrosión, resistencia al choque térmico, y baja densidad.