Abstract: An in-liquid plasma electrode according to the present invention is an in-liquid plasma electrode for generating plasma in a liquid and has an electrically conductive member having an electric discharge end surface in contact with the liquid, and an electrically insulating member covering an outer periphery of the conductive member at least except the electric discharge end surface. Preferably, d and x satisfy ?2d?x?2d, where d is a length of a minor axis of the cross section when a conductive end portion of the electrically conductive member having the electric discharge end surface has an approximately circular cross section, or d is a length of a short side of the cross section when the conductive end portion has an approximately rectangular cross section, and x is a distance from a reference plane to a plane containing the electric discharge end surface when the reference plane is an end surface of the electrically insulating member that is approximately parallel with the electric discharge end surface.

Abstract: An in-liquid plasma electrode 1 according to the present invention is an in-liquid plasma electrode for generating plasma in a liquid L and has a conductive member 11 having an electric discharge end surface 111 in contact with the liquid L, and an insulating member 16 covering an outer periphery of the conductive member 11 at least except the electric discharge end surface 111. Preferably, d and x satisfy ?2d?x?2d, where d is a length of a minor axis of the cross section when a conductive end portion 110 of the conductive member 11 having the electric discharge end surface 11 has a roughly circular cross section, or d is a length of a short side of the cross section when the conductive end portion 110 has a roughly rectangular cross section, and x is a distance from a reference plane 161 to a plane containing the electric discharge end surface 111 when the reference plane 161 is an end surface 161 of the insulating member 16 in roughly parallel with the electric discharge end surface 111.

Abstract: This invention provides a powder material, which is capable of obtaining a heating value flat is greater than that of MgFe2O4, and the manufacturing method thereof. The powder material is expressed by the general formula Mg1-xAxFe2O4 (where A in the formula is at least one element selected from the group of Ca, Sr and Ba, and the range of x in the formula is 0.05?x?0.95). It is preferred that the range of x in the general formula be 0.2?x?0.8. Also, it is preferred that the size of crystallites on the (440) surface be 80 to 200 ?.