Improvements in and connected with processes using electrical glow discharges

摘要

805,165. Discharge apparatus. BERGHAUS, B. Dec. 9, 1954 [Dec. 9, 1953; Nov. 6, 1954], No. 38546/57. Dividedoutof 805,163. Drawings to Specification. Class 39(1). A method of carrying out technical processes (e.g. metallurgical or chemical) by means of an electrical glow discharge in a receptacle with at least two insulating leading-in connections, between which there is a voltage of at least about 100 volts, and connections for the outlet, and supply of gas, is characterized in that in the immediate proximity of at least the surfaces participating in the process a state of gas discharge is produced and maintained in which the electronic current emitted by the surfaces is everywhere more than compensated by the ionic current to the said surfaces, the ionic current density being adjusted to at least 0À1 mA/cm2, so that said over-compensation is ensured also at any localized overheated parts of the surfaces and so that a cathode drop is maintained, and a transition into an unstable region of the discharge characteristic and the contraction of the discharge to a burning spot are avoided. Curves are given showing a typical current/voltage characteristic of a glow discharge compared with a characteristic obtainable by the method according to the invention. Further curves show plots of thermal emission against temperature as obtained from the Richardson formula for various chemically pure metals and metal compounds, together with plots which can be used for estimating the maximum possible emission current in the case of workpieces which are not chemically pure, thus giving a value for the discharge current necessary, which value is attained mainly by increasing the gas pressure in the receptacle. In one example a molybdenum pipe is heated by a glow discharge to a temperatue of about 2000‹C. in an atmosphere of hydrogen at a pressure of 9 mm. of mercury. Further results, some obtained using a mixture of nitrogen and hydrogen are tabulated and curves are given showing the inter-relationship between current, voltage and gas pressure, the permissible working limits being indicated.