Abstract: Multi-functional materials are classified into those which have a photocatalytic layer 2 with a photocatalytic function directly disposed on the surface of a base 1 and those which have a photocatalytic layer 2 with a photocatalytic function disposed on the surface of a base 1 through a binder layer 6 interposed therebetween. Photocatalytic particles of the photocatalytic layer 2 are joined together by a surface energy or solid-state sintering. The photocatalytic layer 2 may have a structure in which fine particles fill interstices defined between photocatalytic particles or a structure in which no fine particles fill interstices defined between photocatalytic particles. A metal such as Ag, Pt, or the like may be fixed or not fixed to surfaces of the photocatalytic particles.

Abstract: A method of manufacturing a corona discharge device suitable for use as an ozonizer capable of producing a controlled small amount of ozone throughout a prolonged service life. A foreproduct of corona discharge device (50) is first prepared which is provided with first and second planar electrodes (54; 56) capacitively coupled with each other by a third floating electrode (64) which is coated by a protective layer (68) of chemically-resistive electrically-insulatingmaterial. A high frequency alternating voltage having a voltage level higher than an initial minimum flashover voltage level of the foreproduct is then applied until the protective layer is aged. Aging of the protective layer is effective in lowering the initial minimum flashover voltage of the final product thus obtained as well as in reducing any fluctuation of the initial minimum flashover voltage that would otherwise occur from product to product. Various other features are also disclosed.