GB1418532A - Anodes for x-ray tubes - Google Patents

Abstract

1418532 X-ray tubes; electrode materials and processing SIEMENS AG 10 Jan 1973 [17 Jan 1972] 1415/73 Heading HID An anode (e.g. rotary type) for an X-ray tube comprises a disc with a zone for electron bombardment and, distinct from that zone, a layer of black material which has been produced by heating a mixture containing titanium dioxide and at least one other refractory oxide. The other refractory oxides may be Al 2 O 3 , CaO, MgO, and ZrO 2 . For example, heating 50% of TiO 2 and 50% Al 2 O 3 produces a black substance with a high coefficient of heat radiation. Additionally the product does not react with common anode materials, e.g. Mo, W, Ta and Nb, below the m.p. of the layer, and adheres to purified and roughened surfaces of same Roughening may be by sandblasting and purification by scouring, ultrasonics, pickling or heat tratment. Additions to the TiO 2 increase stability for TiO 2 content > 20%. A 68 : 32 mixture of CaO with TiO 2 has m.p. > 2100‹ C. The black layer may be provided by plasma spraying and then heated in vacuo at # 1000‹ C. for 10 mins, the range 500 to 800‹ C. being passed through at < 5‹ C./min. Alternatively, the mixture may be applied, then heated, e.g. an oxide mix applied to the anode by a bonding agent, and heated for at least or about 30 mins. for at least or a about 1600‹ C. Thickness may be a few Á to about 100 Á depending on grain size. In the Figure, anode support disc 10 is of 5% W with 95% Mo, impurities apart. Inclined bombardment zones 12, 13, separately or similtaneously emissive, are on 1À5 mm. layer 14 of W alloy with 10% Rh. Zones 12 and 13 may be downwardly inclined at 10 and 15 degrees respectively. Layer 15 on the lower, peripheral, and inner upper face, is the product of a reaction between 56% Al 2 O 3 -44% TiO 2 . The layer may also be only on the lower face.