Aquadag

Aquadag graphite is an acronym for Aqua deflocculated acheson.

Aquadag is an aqueous suspension of colloidal graphite in gel-like fluids and was manufactured by Acheson Industries, a subsidiary of Imperial Chemical Industries (ICI ), Henkel today. Aspen are as ingredients agar, water, graphite powder and ammonia, which are mixed in a ball mill. It is used for example in vacuum technology, if electrically conductive, temperature-insensitive deposits are required with little tendency to secondary electron emission.

Use

Aquadag, in the manufacture of cathode ray tubes coated on the inside surface of a rear portion of the glass bulb in order to obtain electrically conductive layer which receive electron leakage and external electric fields to shield. During the annealing of the assembled tubes decompose the organic components and are sucked to the vacuum pump while leaving a clean, well-adhering and weakly conducting graphite layer on the glass bulb.

Often, particularly in television picture tubes, in addition applied to the rear outer side of the cathode ray tube, a second layer of Aquadag - while the inner layer is conductively connected to the high-voltage anode, the outer layer as the cathode is at ground level. Thus, the two layers can act as a high voltage-proof plate capacitor which smoothes the high voltage and thus compensates for irregularities in the high voltage output of the flyback transformer. An ordinary capacitor of the same capacitance and voltage resistance would be an oversized component, which would increase cost and size of the recipient's sensitive.

Also received early electron tubes in the area of the actual tube system an inside lining of Aquadag to prevent unwanted effects due to worn out of the flask secondary electrons. Aquadag also found in the production of magical eyes use. Applied between the anode and the light emission layer, facilitating the discharge of electrons and thus increases their luminosity.

Footnotes

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