| 摘要 |
A crucible used for optical or X-ray spectral analysis of useable sample bodies by oxidative melting of the sample material in lithium borate flux comprises a ceramic material with an open porosity. At least part of the crucible that comes into contact with the sample material, flux or melt is coated with an air permeable protective layer essentially comprising boron nitride particles. The preparation of these crucibles is also claimed, comprising the formation of a crucible body from a ceramic casting material that contains a high proportion of chamotte, then drying and firing the cast at ca. 1100-1200 deg.C, and then coating part of the porous crucible with a boron nitride slurry using spraying, slurry casting, doping or other application techniques, before finally drying the coated crucible. Preferably the boron nitride slurry comprises 50-80 % volatile organic liquid, 10-30 % boron nitride particles, 1-10 % combustible organic binder, 1-10 % high temperature inorganic binder and an even smaller amount of anti-foaming agent and pH regulator. The slurry coating is pre-dried and then wetted with an aqueous silica sol before the final drying step. |
