Tungsten Powder Application in Electrolytic Capacitor

A capacitor which made of tungsten powder has good leakage current (LC) performance

A tungsten powder which has tungsten silicide (such as W5Si3) on the surfaces of particles and has a silicon content of 0.05-7% by mass; a positive electrode body for capacitors; an electrolytic capacitor; a method for producing a tungsten powder; and a method for producing a positive electrode body for capacitors. The tungsten powder has an average primary particle diameter of 0.1-1 μm, and tungsten silicide is localized within 50 nm from the surface of each particle. The tungsten powder contains at least one of tungsten nitride, tungsten carbide and tungsten boride in a part of the surface of each particle. It is preferable for the tungsten powder that the content of phosphorus element is 1-500 ppm by mass, the oxygen content is 0.05-8% by mass, and the content of elements other than tungsten, silicon, nitrogen, carbon, boron, oxygen and phosphorus is 0.1% by mass or less. It is also preferable that the tungsten granulated powder has an average particle diameter of 50-200 μm and a specific surface area of 0.2-20 m2/g. According to the present invention, a tungsten capacitor which has good leakage current (LC) performance can be provided.The present invention relates to: a tungsten powder which has tungsten silicide (such as W5Si3) on the surfaces of particles and has a silicon content of 0.05-7% by mass; a positive electrode body for capacitors; an electrolytic capacitor; a method for producing a tungsten powder; and a method for producing a positive electrode body for capacitors. The tungsten powder has an average primary particle diameter of 0.1-1 μm, and tungsten silicide is localized within 50 nm from the surface of each particle. The tungsten powder contains at least one of tungsten nitride, tungsten carbide and tungsten boride in a part of the surface of each particle. It is preferable for the tungsten powder that the content of phosphorus element is 1-500 ppm by mass, the oxygen content is 0.05-8% by mass, and the content of elements other than tungsten, silicon, nitrogen, carbon, boron, oxygen and phosphorus is 0.1% by mass or less. It is also preferable that the tungsten granulated powder has an average particle diameter of 50-200 μm and a specific surface area of 0.2-20 m2/g. According to the present invention, a tungsten capacitor which has good leakage current (LC) performance can be provided.

The present invention is tungsten powder, the anode body of a capacitor using the same, and to an electrolytic capacitor using the anode.

Size of the shape of the electronic devices such as mobile phones and personal computers, high speed, with the weight reduction, the capacitors used in these electronic devices, lightly smaller, larger capacity, the lower the ESR is sought there.

As such a capacitor, an anode body of a capacitor made of a sintered body of valve metal powder such as that can be anodized tantalum was anodized to form a dielectric layer made of these metal oxides on the surface thereof is the electrolytic capacitor has been proposed.

Tungsten is used as the valve metal, electrolytic capacitors with sintered tungsten powder to the anode body, the volume of the anode body using a tantalum powder of the same particle size, compared to the electrolytic capacitor is obtained in the same formation voltage , it is possible to obtain a large capacitance, leakage current (LC) was not subjected to practical use as a large electrolytic capacitor. To improve this, tungsten and other alloys capacitor is considered that have been but the leakage current with the metal is not sufficient for those improved somewhat.

An object of the present invention, a tungsten powder can be solved the problem of leakage current (LC) in the electrolytic capacitor of the sintered body of tungsten powder and anode as a valve metal, anode body of a capacitor using the same, and an anode The present invention is to provide an electrolytic capacitor using the body as an electrode.

The present inventors have found that the silicon content can be solved the above problems by a sintered body of tungsten powder part was tungsten silicide on the surface so that the specific range is used as the anode body , and the present invention  has been completed .

According to the tungsten powder of the present invention, and conventional tungsten powder, as compared to the tungsten alloy powder in a volume equivalent or more, it is possible that the LC characteristics per volume producing a good electrolytic capacitor.

Tungsten powder used in the present invention (raw tungsten powder) is commercially available. Smaller tungsten powder particle size, for example, tungsten trioxide powder was triturated under a hydrogen atmosphere or a tungstic acid or tungsten halide by using a reducing agent such as hydrogen or sodium, selecting the reducing conditions appropriate It can be obtained by.

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Spherical Tungsten Powder Application in Cathode Substrate

Spherical tungsten powder has the advantages of regular shape, good uniformity and adequate liquidity, using spherical tungsten powder to prepare the cathode can meet the current needs of engineering applications, which will play a positive role in cathode studies.

Cathode as the electron emission source of vacuum device, its research direction and development have the large influence on the development level of vacuum devices even weapons systems.

Modern dispenser cathode nowadays is one of the key researches of cathode. The common structures are usually composed of three parts: the porous tungsten matrix, emitting material and heater assembly. Of which the porous tungsten matrix is the framework and launch materials’ support of the entire cathode. As can be seen from the hot cathode development course, the porous tungsten matrix is the results of hot cathode constant pursuit of high emission current density and high reliability. Properties of the porous tungsten matrix, especially the pore structure and the pore distribution will directly affect the emission size, low evaporation rate, emission uniformity and lifetime of the cathode. In the actual production, it requires that the cathode matrix have a uniform distribution of pores of 24-26%. The porous tungsten matrix processes include compression molding process and the sintering process, the development of process is dependent on the progress in powder metallurgy process level, as well as affected by the matrix powder properties. If the matrix porosity and pore distribution can be reasonable controlled by process control, there will be a positive role in the cathode research.

Spherical tungsten powder has the advantages of regular shape, good uniformity and adequate liquidity. These advantages are especially suitable for the automatic press with the automatic filling, and the porous tungsten matrix can be obtained with the suitable size of pore and uniform distribution, compared to conventional tungsten powder, it has quite a lot of advantages. During the process of spherical tungsten powder producing the cathode, relationship between the initial porosity and compaction pressure is in line with Heckel's Law. Cathode pulse emission test results show that in 1050 ℃, cathode substrate prepared by spherical tungsten powder can obtain inflection current density of 20.46A / cm2, which can fully meet the current needs of engineering applications.

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Lithium Tungsten Bronze Photocatalyst Preparation I

Environment pollution has caught great concern from many countries in the world, it has led to the drinking water source of people's lives and industrial water quality continue to decline, which leads to air pollution grow and results in the continuous destruction of the ecological environment,and poses a serious threat for human survival. In order to solve these problems, a variety of methods to control environmental pollution are carried out.

From the late 1970s, it is proposed the use of photocatalyst to decompose pesticides and malodorous substances and other organic matters in water and the atmosphere, as well as application examples like photocatalyst coated solid surfaces self-cleaning and so on. Currently, the photocatalyst is primarily titanium dioxide, which has been used to decompose pesticides and malodorous substances and other organic matter in water and the atmosphere, however the bandgap of titanium dioxide is 3.2eV, can only show activity in the ratio of 400nm shorter ultraviolet light and can only work indoors or where there is an ultraviolet lamp, hardly with visible light, which greatly limits the use of titanium dioxide photocatalyst.

In order to efficiently utilize the solar spectrum, finding the catalyst with light visible effect has aroused people's attention, so the application of oxide containing lithium tungsten bronze structure as visible effect photocatalyst is found.

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