Abstract: A minute metal powder is obtained by a method which comprises melting a metal, imparting ultrasonic vibration to the resulting melt, introducing an inert or reducing gas into the ultrasonically vibrated melt thereby producing minute bubbles therein, allowing cavitation to occur as soon as the bubbles reach the surface of the melt and consequently convert the melt into minute droplets, exposing or not exposing the minute droplets to oxygen, nitrogen, or propane, and solidifying the minute droplets by cooling. An apparatus for working the method described above comprises a metal melting tank, metal feeding means, gas feeding means, an ultrasonic vibration generator, means for detecting and retaining the surface of melt, and means for converting melt into minute droplets and solidifying the minute droplets by cooling.

Abstract: A material comprising an organic compound capable of inducing its own photo-isomerization, a photosensitizer, and a side-reaction inhibitor exhibits an ability to convert solar energy into another form of energy and store it in such form.