JPS5877506A - Reduction of metal oxide to metal powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention utilizes a liquid metal reducing agent to reduce gold 8.
The present invention relates to a method for reducing 11 compounds to metal powder. This invention particularly relates to the reduction of oxides of reactive metals such as nathane, hafnium and zirconium.

The difficulty of reducing oxides of metals such as titanium, zirconium, thorium, uranium, vanadium, etc. is explained in U.S. Patent No. 1. J-73, Og No. 3, No. 1, 7θ
lI,, 2j7, no.i, gi 7/? No., 2nd, +
lIt, o No. 44, No. 2,337,048', No. 653. g6wa and 2nd, 7θ7. A79 θ) was reduced by the use of a liquid metal reducing agent. Although other reducing agents may be used, liquid hydroxide is particularly preferred because its free energy of oxide formation is very negative.

However, the use of liquid calcium as a reducing agent has been limited to temperatures above the SOC, which is the melting point of pure calcium. The actual reduction temperature taught by prior researchers is about 90[theta]C to /3 soc. These high reduction temperatures, together with localized high temperatures due to the heat released by the reduction reaction itself, tended to result in powder agglomerates forming. These powder agglomerates are harmful because they also trap and contain calcium oxide, calcium, and other impurities that are difficult to remove by the leaching techniques used to clean the metal powders.

Accordingly, the present invention creates a reaction mixture of a metal oxide and a liquid metal reducing agent in an amount in excess of the stoichiometric amount required to completely reduce the metal oxide, and A method for reducing a metal oxide to a substantially non-oxidized metal powder, comprising reacting the metal oxide with a liquid metal reducing agent in a step where the metal oxide is otherwise reduced to a substantially non-oxidized metal powder. It is in.

During the reduction reaction, it has been found convenient to reduce the number and size of the metal powder agglomerates formed by stirring or stirring the reaction mixture of metal oxide and reducing agent.

It is desirable to reduce the metal oxide at a temperature of about too much C or less. The liquid metal reducing agent used herein is selected from the group consisting of lithium, lithium-sodium, lithium-magnesium and lithium-calcium, calcium, magnesium and sodium. Preferably, the reaction mixture is stirred during the reduction reaction itself.

Excess liquid metal remaining after reducing the metal oxide with an excess amount of liquid metal reducing agent is distilled off. Preferably, the liquid metal reducing agent is lithium.

In a particularly advantageous embodiment of the invention, a mixture of titanium oxide and liquid lithium is produced in excess of the stoichiometric amount required to completely reduce the titanium oxide. The reduction reaction is carried out in an inert atmosphere at a temperature of about 330C, AOOC such that the titanium oxide is substantially reduced to the non-oxidized metal. Excess lithium is then removed from the reaction mixture by vacuum distillation, leaving behind titanium powder and lithium oxide powder. The reaction mixture during the reduction step and distillation process is agitated to limit agglomeration of the powder particles. After distillation, lithium oxide and any remaining metallic lithium are leached from the titanium powder, and the resulting titanium powder is (k, purified,
dry.

The basic particle size of the obtained metal powder is approximately 0.7 microfron ~
approximately 0.5 microns, which is suitable for the production of powder metal parts.
Can be used as a material for bamboo getter.

Lithium is the preferred liquid gold reducing agent because lithium has a low melting point of about 3,301 ns, which makes it possible to use it for the reduction of transition metal oxides. . All transferable metals except zirconium, haunium, thorium, lanthanum, uranium, scandium and ythtrium can be produced by this liquid metal reduction method using lithium. A lithium-magnesium solution containing about 50% magnesium can be used in place of pure lithium. A solution containing lithium at about Sθ and magnesium at So is about 270C~3! ; It has a highest melting point of O'Q. The above-mentioned exceptions are based on the unfavorable thermodynamics of these reduction reactions. Lithium is also advantageous in that it can be easily distilled under reduced pressure at 60OC. The oxides already mentioned,
Alternatively, in the case of more stable oxides such as zirconium, hafnium, thorium, lanthanum, uranium, lithium and calcium liquids can be used. The liquid metal reducing agent solution of lithium and calcium can contain up to about 75% calcium by weight and have a melting point of about -300 at maximum calcium content. These low melting points allow EJ eggs to perform liquid reduction of transition metal oxides at temperatures much lower than those traditionally used in prior art liquid calcium reduction operations. Any temperature between 6θOC and the melting point of the liquid reducing agent can be used. Although pure magnesium with a melting point of 65θC or pure calcium with a melting point of
Less preferable than using calcium solution. The higher temperatures required when using magnesium or calcium reduction operations result in more agglomerates of metal powder particles being produced. However, this can be alleviated to some extent by stirring the mixture during the reduction operation so as to keep the titanium metal particles produced in suspension in solution. However, the use of these pure refractory metals is clearly less preferred. Reduction of metal oxides by liquid metal reducing agents is accomplished thermodynamically by using an amount of transition agent in excess of the stoichiometric amount required for the reduction reaction. Although small amounts of reducing agent, such as 200% of the stoichiometric amount, can be used with this invention, they not only drive the reaction to completion;
The presence of a stoichiometric amount of at least /θOθ liquid reducing agent necessary to increase the fluidity of the reaction mixture and to facilitate agitation of the mixture and limit contact between suspended metal particles. preferable. It is important that the chemical reactions between the oxide to be reduced and the liquid metal reducing agent are controlled in a sealed manner and that they are as pure as possible. This places particular limits on nitrogen, since it is not removed by the liquid metal reducing agent, and in fact is often absorbed by the metal being produced. Additionally, the use of metal chlorides must be avoided. The reason for this is that metal chlorides impure metal powders and are harmful when using metal powders for powder metallurgy. As previously mentioned, the reaction mixture containing the metal oxide and liquid metal reducing agent must be agitated during the reduction operation to reduce the formation of metal powder agglomerates.

This stirring or agitation can be in the form of mechanical means. That is, the stirring means may be installed within the reaction vessel to actually stir the reaction mixture, or may be a vibration mechanism that vibrates the chamber housing the reaction vessel. The stirring means may take the form of a magnetic pump that pumps the reaction mixture through the reaction mixture vessel, or it may be in the form of a Magnenac e-stirrer that stirs the reaction mixture without contacting the reaction mixture with the stirrer. . Historically, baffles or other barriers have been placed in each vessel containing the reaction mixture to assist in breaking up the metal powder agglomerates by impacting them with the baffle barrier. A paddle may be provided.

This invention will be explained below with reference to Examples.

Example 50 g of high purity tw IJ Naum ingot was charged into a stainless steel container. This lithium typically contains nitrogen;
If it has a purity of 0 ppm or less, it is acceptable. Approximately yog of pigment grade sodium oxide was added to the rustless copper container. The amount of lithium at the above-mentioned charging ratio was approximately 7 g θθ≠, which was less than the stoichiometric amount required to reduce titanium dioxide to sodium chloride. A stainless steel container containing a mixture of these substances is then heated until the concentration is /gO'l:
When J:f was exceeded, the lithium ingot melted and the mixture was stirred for 1 hour, forming a suspension of titanium dioxide particles in liquid lithium in the mixture. About 3! ; Signs of the beginning of the reaction were observed for the first time in OC. The reaction mixture was heated to
It was heated to ooC and kept at that temperature for several minutes to complete the reduction of titanium dioxide. This reduction reaction proceeds according to the following formula: Tie, +da Li→Ti +, 2 LiO.

This reduction was carried out in an airtight box (glovθbox) that maintained an argon atmosphere at a pressure slightly higher than atmospheric pressure. The mixture now contains lithium metal, titanium metal and lithium oxide, and the mixture is transferred to a vacuum distillation apparatus and mixed.
A was heated to about 600C under 10' vacuum. This mixture was stirred during the distillation. This distillation operation is used to distill off substantially all of the metallic lithium from the metallic titanium and lithium oxide, and the metallic lithium is passed over a cold tentacle spread within the distillation chamber. The metallic titanium powder and the lithium oxide powder remain in the non-magnetic steel vaporizer. The mixture of titanium metal powder and lithium oxide powder is then washed with an aqueous medium to dissolve the lithium oxide particles and any lithium metal that may remain in the mixture. Although many solvents containing acids can be used, such as pentachloride-containing solvents, such as hydrochloric acid, should be avoided to prevent contamination of the metallic titanium powder. After the leaching process as described above, the metallic titanium powder is washed in deionized water and then dried.

Examples of the manufactured titanium metal powder are shown in FIGS. 7 and 1. These figures are scanning electron micrographs of titanium powder.

As can be seen from the figure, the metallic titanium powder is in the form of aggregates, and as can be seen in Figure 2, which shows the powder at a higher magnification than in Figure 1, the basic particle size is about 0.1 micron to about θ,
3-micron. The aggregates r1 observed in Figure 1 are made from these 0) elementary particles.

The hydroxide Rinauno produced by leaching is treated with co, +at□ to produce lithium chloride according to the formula below. The lithium chloride is then treated with vinegar to recover lithium and chlorine: , 2 Lion -4-co, →Li0O3-1-H,
O(/ILi, CO, -1-0f2-), 211i0
ffi (-Co, -1-30, (,2) electrolytic 2T, 1G1-yo:lr, j10z,
(,r) Net reaction: ,2'I,10H→koLt +H20+2o.

Through the above-mentioned operations, metallic lithium is recovered, recycled, and further used for the reduction of metal ingots.

[Brief explanation of drawings]

FIG. 1 is a scanning electron micrograph of metallic titanium powder, and FIG. 2 is a scanning electron micrograph similar to that of FIG. 1 at a higher magnification.

Claims (1)

[Claims] l A reaction mixture of a metal oxide and a liquid metal reducing agent in excess of the chemical composition necessary to completely reduce the metal oxide is prepared, and trace amounts of impurities are removed. The process is characterized in that the metal oxide is reacted with a liquid metal reducing agent once the metal oxide is reduced to a substantially non-oxidized metal powder except for acid accumulation, A method of reducing the top to non-oxidized metal powder. 2. The method of claim 7, wherein the metal oxide is reacted with the liquid metal reducing agent at a temperature of about 6θOc or less. 3. A method according to claim 1 or claim 2, wherein excess liquid metal reducing agent is distilled off from the substantially reduced metal. x 1 metal promoter is calcicum, magnesium,
fg consisting of lithium, sodium extract and their mutual
Claims 1 or 2 selected from liquids!
or the method described in Section 3. 42. The method of claim 41, wherein the liquid metal reducing agent is selected from lithium-magnesium baths, lithium-sodium baths, and lithium-calcium solutions. B The liquid metal reducing agent is a lithium-calcium solution,
The method according to any one of claims 1yA to S4, wherein the metal oxide proboscis is an oxide of a transition metal. 2. The method according to claim 6, jKi, wherein the metal oxide is an oxide of a transition metal of group Ⅰ of the periodic table. ? The metal oxide is a titanium oxide, and the liquid metal reducing agent is lithium.
The method according to any of the i+ terms. ? 1111. The method according to any of claims 1 to 8, wherein the reaction mixture is stirred throughout the reaction chamber. /θ A method according to any one of claims 1 to 9, in which the metal powder is separated from the reaction mixture and cleaned. // A reaction mixture of titanium oxide and an excess amount of liquid lithium from the essential stoichiometric gutter is prepared, and the titanium oxide and liquid lithium are mixed in an inert atmosphere at a temperature of about 3 t OC - θ OC. The reaction is carried out in a trench where the titanium is substantially reduced to a non-oxidized metal, and the excess liquid lithium is distilled under reduced pressure from the substantially reduced titanium, and the reaction and vaporization trade T4! ,! The method of claim 1r consists of stirring the reaction mixture, leaching the linium oxide and any remaining metallic lithium from the titanium, and washing the obtained metallic titanium powder in water and drying it. 2. The method according to claim 1, wherein metallic lithium separated from the distillation step and the leaching step is recycled and reused.