| 摘要 |
PURPOSE:To permit to effect the film producing process of a heat collecting body without employing an equipment exclusive for the process by a method wherein a light transmitting vessel, accommodating the heat collecting body and a water containing substance, is heated under keeping the inside of the vessel in evacuated condition. CONSTITUTION:The heat collecting body 4 is accommodated in the light transmitting vessel 2 as it is an iron sheet itselt and the inside of the vessel 2 is evacuated to the pressure of 10<-2>mm Hg. Next, the vessel 2 is heated to the temperature of 350 deg.C or more under keeping the inside thereof in an evacuated condition. Subsequently, the inside of the vessel 2 is evacuated further under keeping the heating condition of the vessel 2. Water, released from the water containing substance, and the iron base sheet are reacted under the evacuation and heating of the vessel 2 in such a manner and a selective absorption film 4a, whose principal constituent is iron oxide (Fe3O4), is formed on the surface of the heat collecting body 4, therefore, the film may be produced by employing commonly the equipments utilized for successive heating and evacuating processes.
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