JP5773869B2 - Manufacturing method of high purity molybdenum powder - Google Patents

Description

  The present invention relates to a high-purity molybdenum powder and a method for producing the same, and more particularly to a high-purity molybdenum powder having a purity of 99.99% or more (4N or more) and a method for producing the same.

  Conventionally, high-purity metal powder has been produced using various purification methods. However, when the metal particle material immediately after production is observed, it is not only composed of fine primary particles, but a large proportion of secondary particles in which metal particles adhere to each other and agglomerate to become coarse, and a single metal component Even with products made of, there were many defects that the characteristics differed depending on the product parts.

  High-purity molybdenum powder is often used as a raw material for sputtering targets by melting or sintering. As for the raw material powder used for the sputtering target for forming a wiring film such as a semiconductor microcircuit, the impurity management is stricter, and the purity is 99.99% (4N) to 99.999% (5N). ) High purity Mo powder must be used as a raw material.

  On the other hand, a sputtering target is required not only to have high purity but also to have a fine crystal grain size and a uniform crystal orientation. When a target having such a uniform structure is produced by a melting method, the raw material powder is once dissolved, so the presence of primary particles and secondary particles can be ignored to a certain extent. The influence of variation (non-uniformity) is small. However, in order to carry out the melting method, a large melting furnace is required, and there is a drawback that the initial investment of the facility is enormous.

  On the other hand, in order to carry out the sintering method, only a small-scale firing furnace is required, so there is an economic advantage because the initial investment of the production equipment can be less than that of the melting method. However, in order to make the target structure uniform, it is necessary to repeatedly perform a plurality of heat treatments, and there is a problem that the manufacturing cost is increased and the production efficiency is greatly reduced.

  The present inventor has investigated the factor that inhibits the homogenization of the metal structure (that is, the cause of nonuniformity), and has found that the ratio of the secondary particles of the raw material powder is greatly affected. The secondary particles are a plurality of primary particles, and in some cases, several tens of particles are adhered and aggregated to each other to form one coarse particle. If the proportion of secondary particles in the raw material powder is large, non-uniform structure will occur between the part where secondary particles are solidified and the part where primary particles are solidified when sintered, and the structure as a target is non-uniform. It was a big cause to bring.

  Such a problem of non-uniformity of the product structure occurs not only in the sputtering target but also in a molybdenum boat used as a firing jig or a crucible used as a firing container in a high temperature environment.

  As a conventional method for producing high-purity molybdenum powder, as disclosed in Japanese Patent Publication No. 6-10317 (Patent Document 1), a process of decomposing molybdenum raw material powder with aqueous hydrogen peroxide and the resulting aqueous solution In general, a production method comprising a step of treating a cation exchange resin with a cation exchange resin and a step of concentrating the treated aqueous solution and reducing it with hydrogen is generally used. According to such a manufacturing method, it is described that high purity molybdenum powder of 4N or more can be obtained.

  Conventionally, the highly purified molybdenum powder as described above has been obtained, but the obtained particles have a large proportion of coarse secondary particles, and when a sintered body is formed from the coarse secondary particles. However, there has been a problem that the sintered body structure is not uniform and the surface area required for powder application does not increase.

Japanese Patent Publication No. 6-10317

  As described above, the conventional high-purity molybdenum powder has a high purity and a small average particle diameter, but contains many secondary particles that are coarsened by adhering to the primary particles. For this reason, when the powder is used to make a product, there is a problem that the problem that the characteristics differ depending on the product part frequently occurs.

  The present invention has been made to solve the above-mentioned problems, and its object is to produce primary particles having a uniform and fine particle size in a high-purity molybdenum powder, particularly in a high-purity molybdenum powder of 4N (99.99%) or higher. An object of the present invention is to provide a high-purity molybdenum powder having a large ratio. Another object of the present invention is to provide a production method for efficiently obtaining such high-purity molybdenum powder by a simple processing step.

High-purity molybdenum powder according to the present invention has an average particle diameter of 0.5 to 100 [mu] m, the number ratio of the primary particles is 50% or more, further purity in high purity molybdenum powder which is 99.99% there are, Ru der those wherein the particle size of all the high-purity molybdenum powder is less than 2 times the average particle size. Also, the purity is preferably at least 99.999%. Further, the number ratio of primary particles is preferably 90% or more. Moreover, it is preferable that only one peak of the particle size distribution curve of the high-purity molybdenum powder exists.

The method for producing high-purity molybdenum powder according to the present invention comprises a step of preparing a first molybdenum powder by hydrogen reduction of an ammonium molybdate powder and a step of reacting the first molybdenum powder with hydrogen peroxide to produce molybdenum. A step of preparing a first aqueous solution containing a compound, a step of preparing a second aqueous solution containing a molybdenum compound by contacting the first aqueous solution with a cation exchange resin, and an oxidation by drying the second aqueous solution A step of preparing molybdenum powder, a step of placing the molybdenum oxide powder in a vessel whose inner wall is covered with molybdenum and heat-treating it at a temperature of 400 to 600 ° C., a step of pulverizing the obtained molybdenum oxide powder, and an inner wall of molybdenum The above crushed molybdenum oxide powder is put into a container covered with, and the temperature is 950 to 1100 ° C. A step of original, by having a, purity Ri der 99.99% and a particle size of all the high-purity molybdenum powder is less than twice the average particle size, the ratio of the number of primary particles 50 % Molybdenum powder is obtained.

  In the method for producing high-purity molybdenum powder, as a step of preparing the molybdenum oxide powder by drying the second aqueous solution containing the molybdenum compound, after the second aqueous solution is charged into the resin container, the temperature is 50 ° C. or more and 100 ° C. It is preferable to use a step of drying at a temperature of 0 ° C. or lower.

  Furthermore, in the manufacturing method, as the step of preparing the molybdenum oxide powder by drying the second aqueous solution containing the molybdenum compound, the second aqueous solution is sprayed onto a rotating plate to form fine droplets, and a liquid containing the molybdenum compound It is preferable to use a step of drying with a spray dryer in the middle of dropping the droplets from the rotating plate.

  Moreover, in the said manufacturing method, it is preferable that the container which covered the said inner wall with molybdenum is a container which covered the inner wall with the molybdenum whose purity is 99.99% or more.

  Furthermore, in the above manufacturing method, the container whose inner wall is covered with molybdenum is configured by placing a lid member made of molybdenum having a purity of 99.99% or more on a molybdenum boat having a purity of 99.99% or more as an interior material. It is preferable that

  Moreover, in the said manufacturing method, it is preferable that the high purity molybdenum powder whose purity is 99.999% or more is obtained. Furthermore, it is preferable that the ratio of the primary particles in the obtained high purity molybdenum powder is 50% or more. Moreover, it is preferable that the average particle diameter of the high purity molybdenum powder obtained is 0.5-100 micrometers.

  According to the high-purity molybdenum powder according to the present invention, it is possible to provide a high-purity molybdenum powder having a large proportion of primary particles even though the average particle size is 0.5 to 100 μm and a fine powder. Moreover, according to the method for producing high-purity molybdenum powder according to the present invention, high-purity molybdenum powder having a fine particle size can be efficiently produced with a high production yield using a simple production facility.

It is sectional drawing which shows an example of the apparatus which implements the drying process implemented with this invention method. It is sectional drawing which shows another example of the apparatus which implements the drying process implemented with this invention method.

The high-purity molybdenum powder of the present invention is characterized in that the average particle diameter is in the range of 0.5 to 100 μm, the number ratio of primary particles is 50 % or more, and the purity is 99.99% or more. To do.

  When the average particle size is too small, such as less than 0.5 μm, or when the average particle size is too large so as to exceed 100 μm, it is difficult to produce the high-purity molybdenum powder described later. This average particle diameter is preferably in the range of 1 to 30 μm. The average particle size of the high-purity molybdenum powder is measured with a particle size distribution meter.

  The purity of the molybdenum powder is 99.99% or higher, preferably 99.999% or higher. Purity is calculated by uranium (U), thorium (Th), sodium (Na), K (potassium), iron (Fe), Cr (chromium), Ni (nickel), magnesium (Mg), calcium (Ca). The content of copper (Cu), manganese (Mn), zinc (Zn), tungsten (W), and aluminum (Al) was determined by mass%, and the total value was subtracted from 100% to determine the purity of molybdenum. And

  In the present invention, the uranium (U) content in the molybdenum powder can be 0.1 ppb or less, and the thorium (Th) content can be 0.1 ppb or less. Further, the sodium (Na) content is 0.5 ppm or less, the K (potassium) content is 0.5 ppm or less, the iron (Fe) content is 0.5 ppm or less, the Cr (chromium) content is 0.5 ppm or less, Ni (nickel) content 0.5 ppm or less, magnesium (Mg) content 0.5 ppm or less, calcium (Ca) content 0.5 ppm or less, copper (Cu) content 0.5 ppm or less, manganese ( Mn) content may be reduced to 0.5 ppm or less, zinc (Zn) content to 0.5 ppm or less, tungsten (W) content to 0.5 ppm or less, and aluminum (Al) content to 0.5 ppm or less. it can.

  Furthermore, the sodium (Na) content is 0.05 ppm or less, the K (potassium) content is 0.05 ppm or less, the iron (Fe) content is 0.05 ppm or less, and the Cr (chromium) content is 0.05 ppm or less. Ni (nickel) content 0.05 ppm or less, magnesium (Mg) content 0.05 ppm or less, calcium (Ca) content 0.05 ppm or less, copper (Cu) content 0.05 ppm or less, manganese The (Mn) content is 0.05 ppm or less, the zinc (Zn) content is 0.05 ppm or less, the tungsten (W) content is 0.05 ppm or less, and the aluminum (Al) content is as low as 0.05 ppm or less. be able to.

  In the high-purity molybdenum powder according to the present invention, the molybdenum purity is 99.99% or higher (4N), further 99.999% (5N) or higher, and the average particle size is 0.5 to 100 μm. While maintaining the diameter, the ratio of the primary particles can be 50% or more, further 90% or more.

  Here, the primary particles mean particles in a state where fine particles are individually separated without agglomeration. The primary particles are aggregated by adhering to each other to form secondary particles. The primary particle ratio measurement method counts the number of primary particles and the number of secondary particles in a field of view of 200 particles. And the ratio of a primary particle is computed with the following formula.

[Number of primary particles / (number of primary particles + number of secondary particles)] × 100% = ratio of primary particles

In the present invention, the proportion of primary particles is as high as 50% or more, and there are few secondary particles adhered and agglomerated. Therefore, this high-purity molybdenum powder is used as a raw material to sinter such as sputtering targets and sintered parts. When a knot is produced, a product having a uniform tissue state can be obtained.

  Further, since the ratio of primary particles is high in the high-purity molybdenum powder, all the molybdenum powder particles can be made to be twice the average particle diameter or less. That is, when the particle size distribution of the powder is created, there can be provided particles having a uniform particle size with little variation in particle size, in which there are no particles having a particle size of twice or more the average particle size.

  Furthermore, since the proportion of coarse secondary particles is small, there is only one particle size distribution peak when the particle size distribution is measured, so there is no occurrence of multiple maximal or minimal particle groups, and the particle size is uniform. High purity molybdenum powder is obtained. In addition, it is possible to provide a powder having a sharp particle size distribution in which the half width of the peak of the particle size distribution is 50% or less of the peak value.

  The high-purity molybdenum powder according to the present invention is applied to various fields such as sputtering targets, plate members used in sintering furnaces (boats, etc.), sintered parts such as cold cathode tube electrodes, molybdenum foils, various powdered catalysts, etc. Can do.

  Since the high-purity molybdenum powder of the present invention has a large proportion of primary particles, it is possible to eliminate unevenness of the structure when a sintered body is formed. Moreover, since the purity is high, it is possible to effectively prevent impurities from being mixed into other products used at the same time.

  Next, the manufacturing method of the high purity molybdenum powder based on this invention is demonstrated. The production method of the high-purity molybdenum powder of the present invention is not particularly limited, but the following method is adopted as a production method for obtaining it efficiently.

  The method for producing high-purity molybdenum powder of the present invention comprises preparing a first molybdenum powder by hydrogen reduction of ammonium molybdate powder, and reacting the first molybdenum powder with hydrogen peroxide to produce a molybdenum compound. A step of preparing a first aqueous solution containing, a step of preparing a second aqueous solution containing a molybdenum compound by bringing the first aqueous solution into contact with a cation exchange resin, and a molybdenum oxide powder by drying the second aqueous solution. A process in which the molybdenum oxide powder is put into a vessel whose inner wall is covered with molybdenum, the heat treatment is performed at a temperature of 400 to 600 ° C., the obtained molybdenum oxide powder is pulverized, and the inner wall is covered with molybdenum. Put the pulverized molybdenum oxide powder in a dry container and reduce it at a temperature of 950 to 1100 ° C. By providing the step, the one in which the subject matter that the purity obtained molybdenum powder 99.99% or more.

In the method for producing the high-purity molybdenum powder, first, the first molybdenum powder is prepared by hydrogen reduction of the ammonium molybdate powder. Examples of the ammonium molybdate powder include ammonium dimolybdate ((NH ₄ ) ₂ Mo ₂ O ₇ .nH ₂ O) powder, and the average particle size is preferably in the range of 50 to 300 μm. When the average particle size is less than 50 μm or the average particle size exceeds 300 μm, the average particle size of the finally obtained powder is unlikely to be in the range of 0.5 to 100 μm. Also, in terms of price, ammonium molybdate powder having an average particle diameter of 50 to 300 μm is easily available on the market.

  The hydrogen reduction operation is preferably carried out at a temperature of 530 to 600 ° C. for 2 to 4 hours in a hydrogen reducing atmosphere at a hydrogen stream velocity of 1 liter / minute or more and 10 liter / minute or less. By this reduction step, the first molybdenum powder is obtained. The molybdenum powder at this stage has low purity and a coarse particle size.

  Then, next, the first molybdenum powder is reacted with hydrogen peroxide to prepare the first aqueous solution containing the molybdenum compound, and the process is performed. By this reaction with the hydrogen peroxide solution, a reaction based on the following reaction formula proceeds.

2Mo + 7H ₂ O ₂ → 2HMoO ₄ + 6H ₂ O
A first aqueous solution containing a molybdenum compound is prepared by the above reaction. The reaction with the hydrogen peroxide solution is preferably carried out at a temperature of 80 ° C. or lower. That is, it should be noted that if this reaction temperature exceeds 80 ° C., the hydrogen peroxide solution may explode.

Next, the first aqueous solution is brought into contact with the cation exchange resin so that impurities are adsorbed on the cation exchange resin as cations, while the second aqueous solution containing the complexed Mo component is prepared. To do. Since the first aqueous solution containing the molybdenum compound has impurity metal as a cation, contact with the cation exchange resin removes the cation impurity and separates the molybdate anion such as MoO ^4- anion. To do. The material of the cation exchange resin is not particularly limited, but for example, Diaion SK, Amber, etc. can be suitably used as trade names.

  A cation exchange resin having an average particle diameter of about 50 to 100 μm is used and packed in a cylindrical column. Impurity cations are separated and removed through a first aqueous solution containing a molybdenum compound in a column filled with a cation exchange resin.

  The step of bringing the cation exchange resin into contact with the first aqueous solution containing the molybdenum compound is performed by filling a cation exchange resin having an average particle diameter of 50 to 100 μm in a column having a diameter of 30 to 50 mm × length of 350 mm or more. Are arranged in the vertical direction and the first aqueous solution containing the molybdenum compound is allowed to pass through. When the purity of the final product is 99.99% or more and less than 99.999%, a length of about 350 to 450 mm is sufficient for the column. In order to achieve a purity of 99.999% or higher, the column length is preferably 450 mm or higher.

  The upper limit of the column length is not particularly limited, but is preferably 800 mm or less in consideration of workability of the processing operation. Further, it is preferable to use a resin column such as polypropylene in order to prevent metal impurities from being mixed into the liquid to be treated from the column.

By passing through the step of bringing the cation exchange resin into contact with the first aqueous solution, a second aqueous solution containing molybdate anion (MoO ⁴⁻ ) can be obtained.

Next, a step of preparing the molybdenum oxide powder by drying the second aqueous solution is performed. In this step, molybdenum oxide powder (MoO ₃ ) can be obtained by drying the second aqueous solution in an atmosphere at a temperature of 300 ° C. or lower.

  As the drying step, for example, a method such as the following first drying step or second drying step can be employed.

  That is, as a 1st drying process, after putting 2nd aqueous solution in a polyethylene container, it is a process made to dry over 6 to 8 hours at the temperature of 50 to 100 degreeC. FIG. 1 shows an example of the first drying step.

  In FIG. 1, reference numeral 1 is a second aqueous solution, 2 is a resin container, 3 is a stirring rod, 4 is a heating container, and 5 is a heating medium.

  By using a polyethylene container, a polytetrafluoroethylene container or the like as the resin container 2, it is possible to prevent metal impurities from being mixed into the second aqueous solution 1. Of the resins constituting the resin container 2, polyethylene is particularly excellent in terms of heat resistance, corrosion resistance, lightness, strength characteristics, and price. Hot water is preferably used as the heating medium 5. If necessary, the heating vessel 4 is warmed, and the second aqueous solution is heated and concentrated while indirectly heating the resin vessel.

  Further, during the heating operation, it is preferable to advance the drying while stirring the second aqueous solution with the stirring rod 3.

  The drying step is continued until there is no water in the second aqueous solution. After the moisture is removed, the molybdenum oxide powder remains in the resin container 2 as a dry residue. In the first drying step, the obtained molybdenum oxide powder remains in the resin container 2, so the molybdenum oxide powder obtained at one time is affected by the size of the resin container 2. For this reason, this first drying step is effective when the amount of molybdenum oxide powder obtained in one batch (one batch treatment) is 1 kg or less. If the amount is 1 kg or less, a drying time of about 6 to 8 hours is preferable.

  On the other hand, the second drying step is a step of spraying the second aqueous solution onto the rotating plate and drying it with a spray dryer while the molybdenum compound is repelled and dropped by the rotating plate. FIG. 2 schematically shows a configuration example of a drying apparatus that performs the second drying step. In FIG. 2, reference numeral 1 denotes a second aqueous solution, 6 denotes an injection port for injecting the second aqueous solution 1, 7 denotes a rotating mechanism that rotates the rotating disk 8, 8 denotes a rotating plate that finely disperses the second aqueous solution 1, and 9 denotes A dry container, 10 is a spray dryer, 11 is a collection container, and 12 is a dried molybdenum oxide powder.

  When carrying out the second drying step, first, a disk-shaped rotating plate 8 is attached to the tip of the rotating mechanism 7, and the rotating plate 8 is rotated at a high speed. The rotation speed of the rotating plate 8 is preferably about 500 to 3000 rpm. When the second aqueous solution is continuously dripped onto the rotating rotating plate 8 from the injection port 6, the droplets of the second aqueous solution 1 are repelled by the rotating plate 8 and become finer droplets. Fly toward the inner wall. The droplets that are bounced and finely dispersed are dried by the high-temperature drying air current (warm air) ejected from the spray dryer 10 while falling in the drying container 9.

  The temperature of the hot air sprayed from the spray dryer 10 is preferably in the range of 50 to 100 ° C. The droplets that are introduced into the rotating plate 8 as droplets and repelled by the rotational force of the rotating plate 8 are further reduced. Since the liquid droplets finely dispersed by the rotating plate 8 are minute water droplets, even with a short period of time while falling in the drying container 9, the hot air blown from the spray dryer 10 It is possible to dry instantaneously in a short time.

  Then, the dried object to be processed becomes molybdenum oxide powder 12 and is deposited in the collection container 11. With this drying method, the drying process can be performed continuously, so that a large amount of molybdenum oxide powder 12 of 1 kg or more can be obtained per batch (one batch treatment). Further, if necessary, the drying capacity can be appropriately increased by increasing the longitudinal dimension of the drying container 9 or increasing the number of spray dryers 10 provided. Further, it is preferable that the inner wall of the drying container 9 is coated with a resin such as polytetrafluoroethylene so that the metal impurities can be effectively prevented from being mixed into the second aqueous solution 1 from the drying container 9. Moreover, you may increase the installation capacity | capacitance of the injection nozzle 6 which drops the 2nd aqueous solution 1, and may improve a drying capability.

  In the second drying step as described above, the labor and time required for transporting the aqueous solution can be greatly reduced as in the first drying step, so that workability is good and a clean working environment can be maintained. . In addition, since the drying operation is performed in a fine droplet state in the second drying step, there is little adhesion between the powders during the drying operation, and the aggregation of the finally obtained molybdenum oxide powders is effectively prevented. be able to.

  Since the high-purity molybdenum powder is produced by reducing the molybdenum oxide powder having a large proportion of the primary particles, a high-purity powder having a large proportion of the primary particles is obtained for the finally obtained high-purity molybdenum powder. It is done. In particular, according to the production method of the present invention, it is possible to efficiently produce a fine and high-purity molybdenum powder having a uniform particle size such that the ratio of primary particles is 90% or more.

  Next, the obtained molybdenum oxide powder 12 is put into a container whose inner wall is covered with molybdenum, and is subjected to a heat treatment at a temperature of 400 to 600 ° C. If any moisture remains in the molybdenum oxide powder obtained by the drying step, the reduction step described later is affected. Therefore, complete dehydration is performed by sufficiently performing heat treatment in the temperature range of 400 to 600 ° C. .

  When the treatment temperature in the heat treatment step is less than 400 ° C., it is necessary to lengthen the heat treatment time. On the other hand, when the treatment temperature exceeds 600 ° C., the molybdenum oxide powder may grow or sublimate. A preferable heat treatment time is 2 hours or more.

The heat treatment is preferably performed in the atmosphere. Even when molybdenum oxide (MoO ₂ , Mo ₃ O ₈ , Mo ₉ O _26, etc.) having a different valence from the MoO ₃ powder coexists in the molybdenum oxide powder by performing heat treatment in the atmosphere The material species can be narrowed down to be composed of only MoO ₃ powder.

  Further, the heat treatment step may be performed in a hydrogen atmosphere. Performing heat treatment in a hydrogen atmosphere also has the effect of aligning the valence of molybdenum oxide. Thereby, the effect in the reduction | restoration process mentioned later can be exhibited uniformly.

  Next, a step of pulverizing the obtained molybdenum oxide powder is performed. Since the molybdenum oxide powder obtained in the heat treatment step has a coarse particle size and the reduction effect is not constant even if the reduction step is performed as it is, it is preferable to carry out the pulverization step in advance. The pulverization step is preferably performed using a pulverizer such as a ball mill. Further, by applying a resin coating such as polytetrafluoroethylene on the inner wall of the ball mill, it is possible to effectively prevent metal impurities from being mixed into the molybdenum oxide powder. It is also possible to adjust the average particle size of the finally obtained high-purity molybdenum powder by adjusting the pulverization degree.

  Next, the pulverized molybdenum oxide powder is put into a container whose inner wall is covered with molybdenum and heated to a temperature of 950 ° C. to 1100 ° C. for reduction. The container used for this reduction step is preferably a container whose inner wall is coated with molybdenum. Molybdenum covering the inner wall of the reducing vessel is preferably as high as possible. Specifically, it is preferable to use high-purity molybdenum of 99.99% or higher, more preferably 99.999% or higher. In addition, when using a molybdenum boat, the purity is 99.99% or more, and further 99.999% or more.

  Moreover, it is preferable to implement the said reduction | restoration process in the temperature range of 950-1100 degreeC. This reduction step is a step of reducing molybdenum oxide to convert it to metal molybdenum. When the reduction temperature is less than 950 ° C., the reduction reaction does not proceed sufficiently. On the other hand, when the reduction temperature exceeds 1100 ° C., molybdenum grows and it is difficult to make the target “the particle diameter of all high-purity molybdenum powders equal to or less than twice the average particle diameter”.

  Moreover, it is preferable to implement the said reduction | restoration process hold | maintaining molybdenum oxide for 3 hours or more at the reduction temperature mentioned above. When the holding time is less than 3 hours, there is a possibility that sufficient reduction reaction may not be performed when the amount of treatment in one batch is as large as 1 kg or more. Moreover, when the processing amount in 1 batch is less than 1 kg, the hydrogen air flow rate used as a reducing agent is preferably 1 liter / min or more.

  By the way, since unnecessary oxygen evaporates as water as the reduction reaction proceeds, when the reduction step is carried out in a sealed space, the evaporated water inhibits the reduction reaction. Therefore, it is important to consider the reduction reaction in a hydrogen stream environment so that the reduction reaction continues stably.

  By such a production process, a high-purity molybdenum powder having a purity of 99.99% or more, and further a purity of 99.999% or more can be obtained. In the molybdenum oxide powder stage, particles are prevented from agglomerating and the ratio of secondary particles is reduced, so the high-purity molybdenum powder obtained should have a primary particle ratio of 50% or more, more preferably 90% or more. Can do.

  Moreover, since the ratio of primary particles is high in the high-purity molybdenum powder, the obtained high-purity molybdenum powder has a fine average particle diameter of 0.5 to 100 μm without performing a sieving operation. It becomes powder. In addition, when the particle size distribution is measured, there is no powder having a particle size that is twice or more the average particle size of the total molybdenum powder. Also, in the particle size distribution curve, it is possible to obtain Mo powder having a uniform particle size such that only one peak at a predetermined fine particle size exists.

[Example]
Next, embodiments of the high-purity molybdenum powder and the method for producing the same according to the present invention will be described more specifically with reference to the following examples and comparative examples.

(Examples 1-5 and Comparative Example 1)
First, ammonium dimolybdate (average particle size 100 μm) powder was prepared as a raw material common to each example and comparative example. Next, ammonium dimolybdate powder as the raw material was reduced in a hydrogen stream at a flow rate of 5 liters / minute for 3 hours at a temperature of 580 ° C. to prepare a first molybdenum powder.

  Next, a first aqueous solution containing a molybdenum compound was prepared by reacting the obtained first molybdenum powder with a hydrogen peroxide solution while adjusting the temperature so as not to exceed 60 ° C.

  On the other hand, a cation exchange resin powder having an average particle size of 70 μm was packed in a column 40 mm in diameter × 500 mm in length. Next, a second aqueous solution containing a molybdenum compound from which the cation was removed was prepared by passing the first aqueous solution through a column packed with a cation exchange resin.

  Next, the drying process of the said 2nd aqueous solution was implemented by each method shown in Table 1. That is, in Examples 1 and 2, as shown in FIG. 1, the second aqueous solution was heated by the stirring rod 3 while the resin container 2 charged with the second aqueous solution 1 was heated with warm water as a heating medium in the heating container 4. 1 was processed by the 1st drying process dried with stirring.

  On the other hand, in Examples 3 to 5, as shown in FIG. 2, the second aqueous solution 1 is dropped and dispersed on the rotating plate 8, and the dispersed fine droplets are warm air jetted from the spray dryer 10. By the second drying step, which is air-flow dried.

  Each molybdenum oxide powder was obtained by this drying process. For comparison, Comparative Example 1 was obtained by changing the temperature conditions of the drying process.

In the drying process, the specifications of the drying container used (materials, presence / absence of interior), 1 amount of the second aqueous solution (1 batch amount: Kg) charged into the drying container per batch, and the drying conditions are shown in Table 1 below. Show.

Next, each molybdenum oxide powder obtained in the drying step is put into an interior container whose inner wall is coated with molybdenum having a purity of 99.999% or more and heat-treated at a temperature of 550 ° C. to completely remove moisture. Drying was performed. Next, the dried molybdenum oxide powder was pulverized with a pot mill using a rod made of high-purity Mo material as a pulverized ball in a pot whose inner wall was covered with molybdenum. The average particle diameter of each molybdenum oxide powder before and after pulverization is as shown in Table 2 below.

  As is clear from the results shown in Tables 1 and 2, it was found that for each example, a difference appears in the average particle diameter at the stage of the molybdenum oxide powder due to a difference in conditions in the drying process.

Next, the pulverized molybdenum oxide powder was reduced in a hydrogen stream atmosphere under the conditions shown in Table 3. That is, for Examples 1 to 5, each of the reduction containers internally made of high-purity Mo material is used, while in Comparative Example 1, the interior material is not used and a reduction container made of stainless steel (SUS304) is used. The reduction temperature, reduction time, and hydrogen flow rate were as shown in Table 3.

Each high-purity molybdenum powder obtained by the above reduction treatment was measured for average particle size, primary particle ratio, particle size distribution, and purity characteristics without carrying out sieving. The average particle size and particle size distribution were measured with a particle size distribution meter. The ratio of primary particles was determined by taking an enlarged photograph at a magnification such that about 200 grains of each powder can be observed in the observation field, counting the number of primary particles, and the number of secondary particles.
[Number of primary particles / (number of primary particles + number of secondary particles)] × 100 (%)
Calculated based on As for purity, uranium (U), thorium (Th), sodium (Na), potassium (K), iron (Fe), chromium (Cr), nickel (Ni), magnesium (Mg), calcium (Ca) Copper (Cu), Manganese (Mn), Zinc (Zn), Tungsten (W) and Aluminum (Al) were each mass%, and the total value was subtracted from 100% to obtain the purity of molybdenum.

  Moreover, in the comparative example 1, the reduction | restoration process was processed on the conditions shown in Table 3, and the same measurement as each Example was implemented.

The measurement results are shown in Table 4 below.

  As is clear from the results shown in Table 4 above, the high-purity molybdenum powder according to each example has a primary particle ratio of 50% or more. In particular, in the high-purity molybdenum powders of Examples 3 to 5 using the second drying step, the proportion of primary particles was as good as 90% or more. Further, even if no special sieving treatment was carried out, there was only one particle size distribution peak, and particles having a particle size exceeding twice the average particle size were not confirmed.

  On the other hand, when the conditions of the drying process were not desirable as in Comparative Example 1, the ratio of primary particles was less than 50%. Moreover, in the comparative example 1, since the reduction | restoration container equipped with the high purity molybdenum material by the last reduction | restoration process is not used, the impurity from a stainless steel container mixes in the powder side, and purity also fell.

  As described above, according to the high-purity molybdenum powder according to the present invention, a high-purity molybdenum powder having a large primary particle ratio of 50% or more despite having a fine particle diameter of 0.5 to 100 μm. Can be provided. Moreover, according to the method for producing high-purity molybdenum powder according to the present invention, high-purity molybdenum powder having a fine particle size can be efficiently produced with a high production yield using a simple production facility.

DESCRIPTION OF SYMBOLS 1 ... 2nd aqueous solution, 2 ... Resin container, 3 ... Stirring rod, 4 ... Heating container, 5 ... Heating medium, 6 ... Injection port, 7 ... Rotating mechanism, 8 ... Rotating plate, 9 ... Drying container, 10 ... Spray Dryer, 11 ... recovery container, 12 ... molybdenum oxide powder.

Claims (7)

Preparing a first molybdenum powder by hydrogen reduction of ammonium molybdate powder;
Preparing a first aqueous solution containing a molybdenum compound by reacting the first molybdenum powder with hydrogen peroxide;
Preparing a second aqueous solution containing a molybdenum compound by contacting the first aqueous solution with a cation exchange resin;
Preparing a molybdenum oxide powder by drying the second aqueous solution;
Putting the molybdenum oxide powder into a container whose inner wall is covered with molybdenum and heat-treating it at a temperature of 400 to 600 ° C .;
Crushing the obtained molybdenum oxide powder;
And a step of introducing the pulverized molybdenum oxide powder into a container whose inner wall is covered with molybdenum and reducing it at a temperature of 950 to 1100 ° C., whereby the purity is 99.99% or more, and all high purity A method for producing a high-purity molybdenum powder, characterized in that the molybdenum powder has a particle size of not more than twice the average particle size and a primary particle number ratio of 50% or more. The step of preparing the molybdenum oxide powder by drying the second aqueous solution containing the molybdenum compound includes using the step of drying at a temperature of 50 ° C. to 100 ° C. after the second aqueous solution is charged into the resin container. The method for producing a high-purity molybdenum powder according to claim 1 . As the step of preparing the molybdenum oxide powder by drying the second aqueous solution containing the molybdenum compound, the second aqueous solution is sprayed onto the rotating plate to form fine droplets, and the droplets containing the molybdenum compound are repelled from the rotating plate. in the course of dropping have him, the method of producing a high-purity molybdenum powder according to claim 1, characterized in that a step of drying with a spray dryer. Vessel the inner wall is covered with molybdenum, high purity according to any one of claims 1 to 3 purity characterized in that it is a container covering the inner wall of molybdenum is 99.99% Method for producing molybdenum powder. The container whose inner wall is covered with molybdenum is configured by placing a lid member made of molybdenum having a purity of 99.99% or more on a molybdenum boat having a purity of 99.99% or more on an interior material. process for producing a high-purity molybdenum powder according to any one of claims 1 to 4,. Process for producing a high-purity molybdenum powder according to any one of claims 1 to 5, characterized in that high-purity molybdenum powder purity is at least 99.999% is obtained. Process for producing a high-purity molybdenum powder according to any one of claims 1 to 6 average particle diameter of the high-purity molybdenum powder obtained is characterized in that it is a 0.5 to 100 [mu] m.

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