Method for the preparation of a double-coated body of boron nitride
US5882730A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 7, 1995 |
| Grant date | Mar 16, 1999 |
| Priority date | — |
| Expiry date | Jul 7, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01C7/021
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
An improvement is proposed in the preparation of, for example, a ceramic heater consisting of a substrate plate of boron nitride, a patterned layer of pyrolytic graphite (PG) on the substrate to serve as an electric resistance element and an overcoating layer of pyrolytic boron nitride (PBN) in a process comprising the steps of depositing PG on the substrate surface, pattern-wise removing the PG layer by mechanical working to form grooves and depositing PBN all over. According to the inventive improvement, which can be obtained by forming the grooves in such a fashion that the angle between the direction of a normal line to the facet surface formed by the mechanical working and the growing direction of the substrate of boron nitride is in the range from 0.degree. to 45.degree. so that the internal stress caused in the overcoating layer, which is due to the anisotropy in the thermal expansion of boron nitride, is decreased to prevent the overcoating layer from occurrence of cracks and falling during service.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.