The invention relates to a composition containing a catalyst suitable for producing ethylene and other C.sub.2+ hydrocarbons at high selectivity while improving both methane conversion and product yield. Particularly, the catalyst contains mixed metal oxides having at least one alkali earth metal and at least one rare earth metal along with an alkali metal promoter in the form of an alkali metal or in the form of an alkali metal tungstate. The invention further provides a method for preparing such a composition, using a calcination process to calcine the alkali metal promoters together with mixed metal oxides. Additionally, the invention further describes a process for producing C.sub.2+ hydrocarbons, using such a composition.

A method for manufacturing bacterially induced crystal particle includes culturing bacteria in a culture medium including a carbon source and a raw metal material including a transition metal, so that the bacteria induce a raw metal material to undergo a reduction-oxidation reaction; isolating a wet powder material from the culture medium; and drying the wet powder material to obtain a powder material. The powder material includes at least one bacterially induced crystal particle.

A method for manufacturing bacterially induced crystal particle includes culturing bacteria in a culture medium including a carbon source and a raw metal material including a transition metal, so that the bacteria induce a raw metal material to undergo a reduction-oxidation reaction; isolating a wet powder material from the culture medium; and drying the wet powder material to obtain a powder material. The powder material includes at least one bacterially induced crystal particle.

Disclosed are a core-shell structure type wave absorbing material and a preparation method therefor. The wave absorbing material has a core-shell structure with two-dimensional transition metal-chalcogen compound nanosheets as cores and hollow carbon spheres as shells. The preparation method includes: dissolving the hollow carbon spheres in a solvent, sequentially adding a transition metal source and a chalcogen source, taking a solvothermal reaction after dissolution through stirring, and then performing posttreatment to obtain the wave absorbing material. The present invention further discloses an application of the wave absorbing material in fields of military and civilian high-frequency electromagnetic compatibility and protection. The core-shell structure type wave absorbing material of the present invention has a density of 0.3 to 1.5 g/cm.sup.3, a maximum reflection loss value and an effective bandwidth of the material can be effectively improved in a frequency range of 2 to 40 GHz, and the core-shell structure type wave absorbing material is an electromagnetic compatibility and protection material capable of meeting requirements of civilian high-frequency electronic devices and military weapons and equipment such as airships and artillery shells.

Disclosed are a core-shell structure type wave absorbing material and a preparation method therefor. The wave absorbing material has a core-shell structure with two-dimensional transition metal-chalcogen compound nanosheets as cores and hollow carbon spheres as shells. The preparation method includes: dissolving the hollow carbon spheres in a solvent, sequentially adding a transition metal source and a chalcogen source, taking a solvothermal reaction after dissolution through stirring, and then performing posttreatment to obtain the wave absorbing material. The present invention further discloses an application of the wave absorbing material in fields of military and civilian high-frequency electromagnetic compatibility and protection. The core-shell structure type wave absorbing material of the present invention has a density of 0.3 to 1.5 g/cm.sup.3, a maximum reflection loss value and an effective bandwidth of the material can be effectively improved in a frequency range of 2 to 40 GHz, and the core-shell structure type wave absorbing material is an electromagnetic compatibility and protection material capable of meeting requirements of civilian high-frequency electronic devices and military weapons and equipment such as airships and artillery shells.

The present invention provides a method for the manufacture of transition metal oxide fine particles, the method comprising the steps of: heating a strong-alkaline aqueous solution while stirring same; adding to and dissolving in the heated strong-alkaline aqueous solution a transition metal oxide; adding a strong-acid aqueous solution to the strong alkaline aqueous solution in which the transition metal oxide is dissolved, while stirring same, thereby re-dissolving a solid generated at the interface between the strong-alkaline aqueous solution and the strong-acid aqueous solution; adjusting the pH of the mixed aqueous solution resulting from mixing the strong-alkaline aqueous solution and the strong acid aqueous solution, through adjustment of the adding rate and amount of the strong-acid aqueous solution, to precipitate transition metal oxide fine particles; and separating the transition metal oxide fine particles from the mixed aqueous solution and sequentially washing, drying, and thermally treating the separated transition metal oxide fine particles.

The invention relates to a composition containing a catalyst suitable for producing ethylene and other C.sub.2+ hydrocarbons at high selectivity while improving both methane conversion and product yield. Particularly, the catalyst contains mixed metal oxides having at least one alkali earth metal and at least one rare earth metal along with an alkali metal promoter in the form of an alkali metal or in the form of an alkali metal tungstate. The invention further provides a method for preparing such a composition, using a calcination process to calcine the alkali metal promoters together with mixed metal oxides. Additionally, the invention further describes a process for producing C.sub.2+ hydrocarbons, using such a composition.

A positive electrode active material for nonaqueous electrolyte secondary batteries and production method thereof that are able to improve the stability of positive electrode mixture material pastes used to produce nonaqueous electrolyte secondary batteries, as well as to improve the output characteristics and charge/discharge cycle characteristics of secondary batteries. A method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries includes mixing a fired powder formed of a lithium-metal composite oxide having a layered crystal structure, a first compound which is at least one selected from a group consisting of a lithium-free oxide, a hydrate of the oxide, and a lithium-free inorganic acid salt, and water and drying a mixture resulting from the mixing. The fired powder includes secondary particles formed by agglomeration of primary particles. The first compound reacts with lithium ions in the presence of water to form a second compound including lithium.

A positive electrode active material for nonaqueous electrolyte secondary batteries and production method thereof that are able to improve the stability of positive electrode mixture material pastes used to produce nonaqueous electrolyte secondary batteries, as well as to improve the output characteristics and charge/discharge cycle characteristics of secondary batteries. A method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries includes mixing a fired powder formed of a lithium-metal composite oxide having a layered crystal structure, a first compound which is at least one selected from a group consisting of a lithium-free oxide, a hydrate of the oxide, and a lithium-free inorganic acid salt, and water and drying a mixture resulting from the mixing. The fired powder includes secondary particles formed by agglomeration of primary particles. The first compound reacts with lithium ions in the presence of water to form a second compound including lithium.

The present invention discloses a method for decomposing medium-/low-grade scheelite, specifically comprising steps of: grinding medium-/low-grade scheelite, decomposing in an autoclave by using sodium phosphate and activated magnesium fluoride as leaching agents, and treating by solid-liquid separation to obtain crude sodium tungstate solution and residue. In this way, the medium-/low-grade scheelite is decomposed. Magnesium chloride is added in a sodium fluoride solution to prepare activated magnesium fluoride as a leaching agent. The present invention has the advantage that the high-efficiency decomposition of medium-/low-grade scheelite can be realized with low consumption of leaching agents, and the leaching cost can be greatly reduced in comparison to the existing decomposition processes using sodium hydroxide and sodium carbonate. This process is short in route, simple in operation, readily available and reliable in production equipment, and easy for industrialization.