GB427757A - Incandescence bodies and methods of making the same for use as filaments of incandescent electric lamps and for other purposes - Google Patents

Abstract

427,757. Electric incandescent lamp filaments. SAKAKURA, Y., 62, Mukoyama Machi, Shibuya Ku, Tokio. Nov. 16, 1933, No. 31997. Convention date, May 19. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 6, 1934.] [Class 39 (ii)] In making bodies adapted to be heated to incandescence, such as rods, ribbons, or wires to be used as electric incandescent lamp filaments, a shaped body such as a slug formed from a powder of refractory metal, for example tungsten, is first caused to absorb substances which are capable of becoming materials for obstructing grain growth, or for augmenting thermionic activity, or modifying the physical properties of the metals by rendering them easier for mechanical treatment through alloying with one another, and then the surfaces of the shaped bodies are washed or steeped in water to remove the absorbed substances at or near the surface. The slug is subsequently sintered and subjected to mechanical treatment in known manner. In an example a slug of pressed tungsten powder is sprayed with a fairly concentrated solution of thorium nitrate, or the solution is applied by wrapping the slug in a soaked cloth, or with a brush, after which the thorium nitrate is removed from the surface layers by washing or " soaking out in distilled water. By repeating the soaking, washing, and drying processes a condition can be attained wherein there is little or no thorium nitrate at or near the surface of the slug and more -towards the core, or there may be little or none at or near the surface and core with a rich intermediate zone. The doped slug is dried in air at a temperature of about 200‹ C., and then baked in an electric furnace at 800 to 1200‹ C., in hydrogen. Other materials that may be used for obstructing grain growth are tantalum pentoxide, beryllium oxide, erbium oxide, indium sesquioxide, strontium oxide, magnesium oxide &c. Thus the pressed slug may be caused to absorb liquid beryllium nitrate, or may be heated in contact with powdered beryllium nitrate. After absorbing one kind of liquid the slug may be caused to absorb another kind, the absorbed liquids being subsequently diluted by washing.