| 摘要 |
An inner tube through which the coating gas is supplied terminates short of the end of the outer tube which forms an annular channel around the inner tube for supply of the carrier gas, so that a chamber is formed between the ends of these channels and the connection of the outer tube to the bottom of the heated reaction container. A constriction is provided where the outer tube joins the reaction container with its aperture aligned with the common axis of the two gas supply tubes. The position of the end of the inner tube is adjustable to suit the particular gas feed rate. The inner tube never reaches the temperature at which the coating gas decomposes. The upper portion of the outer tube, particularly at the constriction, is at or above that temperature, but the flow of carrier gas along the hot surfaces prevents the deposit of a coating on these surfaces. A porous barrier in the annular channel assures a uniform velocity profile of the carrier gas, so that in the nozzle and even in the lowermost part of the reactor it will sheathe the stream of coating gas.
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