| 摘要 |
1,131,064. Thermistors. VICTORY ENG. CORP. 30 Nov., 1965 [10 Feb., 1965], No. 50824/65. Heading H1K. Metal oxide thermistors are made by forming a dispersion of particles of metal oxide or metal oxide forming materials, having three distinct size-range fractions the largest of which has an average particle diameter not exceeding 1À5 microns, in a solution of a binder vehicle comprising a polymer having an hydroxyl content. The dispersion is deposited on a flat surface, levelled with a doctor blade and dried, and is then fired to sinter the oxide. The coherent flake so formed may then be cleaned by ultrasonic means, and may have electrodes applied to opposite faces, e.g. by vacuum evaporation of aluminium, gold, silver, platinum or other metals or alloys. In the preferred embodiment the metal oxide particles comprise a ground mixture of manganese oxide, nickel oxide and cobalt oxide, the three size fractions having average diameters of not more than 1À5 microns, 1À0 microns and 0À5 microns respectively and being present in equal amounts by weight. The binder vehicle preferably consists of volatile and non- volatile components. The non-volatile component comprises a polyvinyl butyral resin having a chain length of not more than 500 Š, an hydroxyl content of the order of 20% by weight and an acetate content of the order of 2À5% by weight, and a polyvinyl alcohol polymer also having a chain length not exceeding 500 Š. The volatile component preferably comprises a mixture of methyl alcohol, amyl acetate and toluol. After formation and levelling of the dispersion on an optical flat a suitably shaped blank may be cut and dried with absorbent paper. The blank is then covered by a refractory powder and fired. Alternatively the blank may be laid on a substrate of ceramic, metal or silicon, and cemented thereto by application of a solvent prior to firing. |
