Abstract: An element recovery method and an element recovery apparatus are provided by which an element containing a high-purity rare earth element can be recovered at low cost. The element recovery method includes the steps of: preparing molten salt containing a rare earth element; and controlling electric potentials in a pair of electrode members at prescribed values while keeping the pair of electrode members in contact with the molten salt, thereby depositing the rare earth element existing in the molten salt on one of the pair of electrode members. In this way, as compared with the conventional wet separation method, an element such as a rare earth element that is to be recovered can be directly recovered from the molten salt in which the element is dissolved, so that the steps of the recovery method can be simplified and reduced in cost.

Abstract: A method of producing a spherical boron nitride fine particle includes reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.

Abstract: A boron nitride fine particle has low major diameter/thickness (aspect) ratio, high purity and high crystallinity, and also has an average particle diameter of 0.05 to 2.0 ?m, a graphitization index of 3 or less, and a total oxygen content of 0.20% by mass or less, with an average value of a major diameter/thickness ratio of scaly particles being 6.0 or less. A method of producing a boron nitride fine particle includes introducing ammonia and an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 5 in a reaction vessel in an inert gas atmosphere for heating at 800 to 1,350° C. within 30 seconds thereby obtaining a boron nitride precursor, and then heating the boron nitride precursor at 1,650 to 2,200° C. for at least 0.5 hour in an inert gas atmosphere.

Abstract: A spherical boron nitride fine particle suited for use as a highly thermoconductive filler or the like has an average particle diameter of 0.01 to 1.0 ?m, an orientation index of 1 to 15, a boron nitride purity of 98.0% by mass or greater, and an average circularity of 0.80 or greater. A method of producing a spherical boron nitride fine particle includes reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.

Abstract: A boron nitride fine particle has low major diameter/thickness (aspect) ratio, high purity and high crystallinity, and also has an average particle diameter of 0.05 to 2.0 ?m, a graphitization index of 3 or less, and a total oxygen content of 0.20% by mass or less, with an average value of a major diameter/thickness ratio of scaly particles being 6.0 or less. A method of producing a boron nitride fine particle includes introducing ammonia and an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 5 in a reaction vessel in an inert gas atmosphere for heating at 800 to 1,350° C. within 30 seconds thereby obtaining a boron nitride precursor, and then heating the boron nitride precursor at 1,650 to 2,200° C. for at least 0.5 hour in an inert gas atmosphere.

Abstract: A spherical boron nitride fine particle suited for use as a highly thermoconductive filler or the like has an average particle diameter of 0.01 to 1.0 ?m, an orientation index of 1 to 15, a boron nitride purity of 98.0% by mass or greater, and an average circularity of 0.80 or greater. A method of producing a spherical boron nitride fine particle includes reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.

Abstract: An element recovery method and an element recovery apparatus are provided by which an element containing a high-purity rare earth element can be recovered at low cost. The element recovery method includes the steps of: preparing molten salt containing a rare earth element; and controlling electric potentials in a pair of electrode members at prescribed values while keeping the pair of electrode members in contact with the molten salt, thereby depositing the rare earth element existing in the molten salt on one of the pair of electrode members. In this way, as compared with the conventional wet separation method, an element such as a rare earth element that is to be recovered can be directly recovered from the molten salt in which the element is dissolved, so that the steps of the recovery method can be simplified and reduced in cost.