| 摘要 |
<PICT:0977907/C1/1> Fused silica articles, particularly the inner surfaces of metal vapour electric discharge lamps, are coated over at least part of the surface with an adherent film of boron nitride. The heated article is contacted with vapour of trichloroborazole. As shown, a discharge envelope 1 of fused silica, with electrodes 2 already sealed in the ends, is provided with a pumping stem 13 and stems 14 open to atmosphere, the whole enclosed in a furnace 15, which is heated to maintain the inner surface of the envelope 1 at between 1200 DEG and 1300 DEG C. The stem 13 is connected to a closed vessel 16 with an inlet tube 17, through which substantially pure argon is pumped, and a tube 18 with a stopper 19 through which trichloroborazole crystals 30 are dropped when the vessel 16 is at the required temperature of about 120 DEG C. The vessel 16 is surrounded by molten Wood's metal 21, heated by a gas flame 22, to maintain the temperature and the connecting tube to stem 13 may also be heated. Instead of using a stream of argon, the envelope may be connected to a vacuum pump to draw the similarly produced trichloroborazole vapour through the envelope, the internal temperature of the envelope being maintained between 1000 DEG and 1050 DEG C. and the vessel being maintained at about 60 DEG C. Reference has been directed by the Comptroller to Specification 908,860. |
