Preparation method of high-purity rhenium strip

Abstract

The invention belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of a high-purity rhenium strip. The high-purity rhenium strip is prepared by generally taking an ammonium perrhenate crude product as a raw material, and carrying out purification, hydrogen reduction and isostatic pressing to obtain a green body; and sintering the green body to obtain the high-purity rhenium strip. According to the preparation method, an ion exchange method is usually adopted during purification of an ammonium perrhenate crude product, and the problems of high loss of metal rhenium and low content of final rhenium strips exist. The invention discloses a preparation method of a high-purity rhenium strip, which comprises the following steps: firstly, dissolving an ammonium perrhenate crude product into deionized water, and adding an organic solvent to separate out a colloidal substance; then, colloidal substances are separated through centrifugal sedimentation, sedimentation liquid is subjected to evaporative crystallization, and a refined ammonium perrhenate product is obtained; then, the ammonium perrhenate refined product is subjected to hydrogen reduction, and high-purity rhenium powder is obtained; and finally, the high-purity rhenium powder is subjected to cold isostatic pressing and sintering, and the high-purity rhenium strip is obtained. The preparation method has the advantages of low metal rhenium loss and high metal rhenium strip content.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to a method for preparing a high-purity rhenium bar. Background Art

[0002] Metal rhenium (Re), atomic number: 75, density: 21.04 g / cm 3 , melting point: 3186℃, boiling point: 5596℃. Metallic rhenium is one of the rarest metals on the earth's surface, with an average estimated content of one part per billion. It is a by-product of the refining process of molybdenum and copper. Rhenium bars are long strips with a gray-silver surface and a metallic luster. They are mainly used in high-temperature alloy parts in the fields of aerospace and aviation equipment manufacturing, as well as other high-temperature resistant fields. They are also used in some special structural parts or coating targets. The preparation of high-purity rhenium bars usually uses crude ammonium perrhenate as raw material, and obtains high-purity metallic rhenium powder through purification, reduction and other processes. The high-purity metallic rhenium powder is isostatically pressed to obtain a green body, and the green body is sintered to obtain a high-purity rhenium bar. However, this preparation method generally has the problems of large metal rhenium loss and low metal rhenium bar content in the purification process of crude ammonium perrhenate.

[0003] In 2022, "CN 114619037A" disclosed a method for preparing a sintered rhenium plate. The application uses crude ammonium perrhenate as raw material, and obtains high-purity ammonium rhenate through ammonia dissolution, impurity removal, and crystallization. The high-purity ammonium rhenate is subjected to secondary hydrogen reduction, multi-step hydrogen sintering, and surface pickling to obtain a high-purity sintered rhenium plate. This preparation method has the problems of low impurity removal efficiency and large amount of evaporated crystallization water.

[0004] In 2022, "CN 114349058A" disclosed a method for preparing high-purity ammonium rhenate. The preparation method firstly performs ion exchange treatment on an ammonium rhenate aqueous solution containing ammonium rhenate to obtain a rhenic acid aqueous solution; then, the rhenic acid aqueous solution is evaporated and concentrated to obtain a high-concentration rhenic acid solution; finally, ammonia water or ammonia gas is added to the high-concentration rhenic acid solution to form a high-purity ammonium rhenate solution, and high-purity ammonium rhenate is obtained by evaporation and crystallization. This preparation method has the problems of low impurity removal efficiency and large amount of evaporated crystallization water.

[0005] In summary, the existing methods for preparing high-purity rhenium powder and high-purity rhenium bars generally use crude ammonium perrhenate as raw material. First, the impurity ions are removed by ion exchange to obtain fine ammonium perrhenate; then, rhenium powder is obtained by hydrogen reduction; finally, high-purity rhenium bars are prepared by isostatic pressing and sintering. The use of ion exchange to purify ammonium perrhenate generally has the problems of low impurity removal efficiency and large amount of evaporated crystal water. Summary of the invention

[0006] In view of the above technical problems, the present invention aims to provide a method for preparing high-purity rhenium bars, which specifically comprises the following steps:

[0007] (1) The crude ammonium perrhenate is subjected to a multi-step purification process to obtain the fine ammonium perrhenate;

[0008] (2) The refined ammonium perrhenate is reduced to obtain high-purity rhenium powder;

[0009] (3) High-purity rhenium powder is cold isostatically pressed to obtain a green body;

[0010] (4) The green body is sintered in a hydrogen atmosphere to obtain high-purity rhenium bars.

[0011] When high-purity rhenium bars are prepared using crude ammonium perrhenate as a raw material, fine ammonium perrhenate can be obtained by purifying the crude ammonium perrhenate, and the fine ammonium perrhenate is reduced, sintered, and other processes to prepare high-purity rhenium bars. Crude ammonium perrhenate can also be roasted to obtain rhenium oxide, and the rhenium oxide is purified to obtain high-purity rhenium oxide, and the high-purity rhenium oxide is reduced, sintered, and other processes to prepare high-purity rhenium bars. The inventors found that the method of purifying crude ammonium perrhenate to obtain fine ammonium perrhenate has the advantages of high purification efficiency and high purification rate over the method of purifying rhenium oxide to obtain high-purity rhenium oxide. Based on this, the present invention first purifies the crude ammonium perrhenate in multiple steps to obtain fine ammonium perrhenate; then, the fine ammonium perrhenate is prepared according to a conventional method to obtain a high-purity rhenium bar. The multi-step purification process of the present invention can effectively remove other metal impurities in crude ammonium perrhenate, and has the advantages of high separation efficiency and high purification rate.

[0012] The above is the basic technical solution of the present invention. On the basis of the basic technical solution, in order to facilitate those skilled in the art to understand and implement the technical solution of the present invention, the present invention also has the following additional technical features:

[0013] In a preferred technical solution, the content of the crude ammonium perrhenate in step (1) is ≥ 99.0wt%. The higher the content of the crude ammonium perrhenate, the less the loss of ammonium perrhenate during the purification process; the lower the content of the crude ammonium perrhenate, the more the loss of ammonium perrhenate during the purification process. When the content of ammonium perrhenate is less than 99wt%, the content of ammonium perrhenate can be first increased to more than 99wt% by methods such as ion exchange, and then the method described in the present invention is used to purify the ammonium perrhenate. When this strategy is used, the total loss of ammonium perrhenate is minimized.

[0014] In a preferred technical solution, the multi-step purification process in step (1) includes the following steps:

[0015] s1. Add crude ammonium perrhenate into deionized water and dissolve by heating to obtain a solution;

[0016] s2, adding an organic solvent to the dissolved solution to obtain a suspension;

[0017] s3, the suspension is centrifuged to obtain a sediment;

[0018] s4. The sedimentation liquid is evaporated and crystallized to obtain fine ammonium perrhenate.

[0019] In the multi-step purification process of the present invention: first, crude ammonium perrhenate is added to deionized water to obtain a dissolving solution. By controlling the amount and temperature of deionized water, other impurity ions in the crude ammonium perrhenate will also dissolve in the deionized water to form a transparent dissolving solution; then, an organic solvent is added to the dissolving solution. With the addition of the organic solvent, the impurity ions and a small amount of ammonium perrhenate in the dissolving solution will precipitate colloidal insoluble matter to obtain a suspension; then, the suspension is subjected to centrifugal sedimentation to separate the colloidal insoluble matter from the suspension to obtain a clarified precipitate. At this time, the impurity ions are mainly enriched in the residue formed by centrifugal sedimentation, and the impurity ion concentration in the precipitate is reduced to the minimum; finally, the precipitate is evaporated and crystallized to obtain a fine ammonium perrhenate.

[0020] In a further preferred technical solution, the mass ratio of the deionized water to the crude ammonium perrhenate in step s1 is 6-15:1. The amount of deionized water used in step s1 is closely related to the size of the subsequent centrifugal separation factor and the amount of evaporated crystallization water. It is generally better to use deionized water 6-15 times the mass of the crude ammonium perrhenate to dissolve the crude ammonium perrhenate. If this ratio is too small, the centrifuge speed needs to be increased during centrifugal sedimentation to increase the centrifugal separation factor; if this ratio is too large, the centrifuge speed can be reduced during centrifugal sedimentation to reduce the centrifugal separation factor, but the amount of water during evaporation and crystallization is large, and the energy consumption is high.

[0021] In a further preferred technical solution, the temperature of the heating dissolution process in step s1 is 60-90° C. Compared with room temperature, when the dissolution temperature is 60-90° C., the solubility and dissolution rate of the crude ammonium perrhenate in deionized water can be increased.

[0022] In a further preferred technical solution, the mass ratio of the organic solvent in step s2 to the deionized water in step s1 is 0.02-0.10:1; the organic solvent is selected from at least one of methanol, ethanol, propanol, and isopropanol. Adding methanol, ethanol, propanol, and isopropanol to the transparent solution reduces the solubility of ammonium perrhenate in water, and precipitates a small amount of colloidal suspensions. These colloidal suspensions have a large specific surface area and can adsorb other impurity ions dissolved in deionized water. A small amount of impurity ions have a low solubility in a mixed solvent of deionized water and alcohol solvents, and crystals will precipitate with the addition of alcohol solvents. Ultimately, the impurity ions are enriched on the surface of the precipitated trace ammonium perrhenate colloid.

[0023] In a further preferred technical solution, the turbidity of the suspension in step s2 is n, and 100NTU≦n≦300NUT. The inventors compared the amount of alcohol solvent added and the relationship between the turbidity value of the suspension and the mass of the lost metal rhenium, and determined that the best comprehensive effect is to add an amount of alcohol solvent to control the turbidity of the suspension between 100NUT-300NUT. If the turbidity of the suspension is too low, the removal of impurities is incomplete; if the turbidity of the suspension is too high, the loss of metal rhenium increases.

[0024] In a further preferred technical solution, the centrifugal separation factor of the centrifugal sedimentation process in step s3 is controlled to be 3000-8000. Under the premise of adopting the above technical solution, the centrifugal separation factor of the centrifugal sedimentation process is controlled to be 3000-8000, and the centrifugal sedimentation time does not exceed 10 minutes to achieve better results. A fine ammonium perrhenate with a content of more than 99.99% can be obtained. The residue of the centrifugal sedimentation can be enriched and the ammonium perrhenate therein can be recovered by ion exchange and the like.

[0025] The method for preparing high-purity rhenium bars of the present invention is to purify crude ammonium perrhenate into fine ammonium perrhenate, and then prepare the high-purity rhenium bars through reduction, cold isostatic pressing, sintering and other processes. The preparation method has the advantages of simple process, high preparation efficiency and high purification rate. DETAILED DESCRIPTION

[0026] The present invention is described in detail below by way of examples, but the present invention is not limited to these examples.

[0027] Example 1

[0028] (1) Preparation of dissolving solution:

[0029] Add 98.500g of crude ammonium perrhenate (content: 99.031wt%) and 850g of 75℃ deionized water to a 2000ml beaker. Add a magnetic stirring rotor to the beaker and place the beaker on a magnetic stirrer with electric heating function. Adjust the heating voltage to control the temperature in the beaker at 75℃ and stir and dissolve for 10 minutes. After dissolution, a solution is obtained.

[0030] (2) Preparation of suspension:

[0031] The temperature of the solution was controlled, and 43 g of ethanol was slowly added to the beaker with a rubber-tipped dropper. A white colloidal suspension was precipitated from the solution in the beaker to obtain a suspension. The turbidity of the suspension was 164 NTU.

[0032] (3) The suspension was transferred in batches to a centrifugal sedimentator for centrifugal sedimentation (centrifuge diameter: 0.25 m), the sedimentator speed was controlled to be 4500 r / min, the centrifugal separation factor was about 5600, and the centrifugal sedimentation was carried out for 10 minutes. The sediment in the test tube was concentrated and ammonium perrhenate was recovered by ion exchange method.

[0033] (4) Transfer the sediment to a 2000 ml three-necked flask equipped with a magnetic stirring rotor, a thermometer, and a recovery condenser, control the vacuum degree to -0.085 MPa, the temperature to 80°C, and evaporate the water under reduced pressure. Evaporate the water to dryness to obtain the fine ammonium perrhenate.

[0034] (5) Reduction: The ammonium perrhenate product was transferred to a quartz boat, and the quartz boat was placed in a tube furnace. The temperature in the tube furnace was controlled to be 850°C, and hydrogen was introduced for reduction. After 5 hours of hydrogen reduction, 63.123 g of high-purity rhenium powder was obtained, with a content of 99.9972 wt%, and a rhenium recovery rate of 93.22%.

[0035] (6) Cold isostatic pressing: transfer the high-purity rhenium powder into the rubber sleeve, introduce argon gas to replace the air in it, transfer the rubber sleeve into the isostatic press and control the pressure to 300 MPa. Press for 5 hours to obtain the green body.

[0036] (8) Sintering: The green body is sintered in a hydrogen atmosphere to obtain a 5 mm*5 mm*120 mm high-purity rhenium bar. The content of the high-purity rhenium bar is detected to be 99.9951 wt%.

[0037] Example 2

[0038] The preparation process and process parameters of Example 2 are basically the same as those of Example 1, except that the amount of deionized water used in preparing the dissolving solution is increased to 1480 g, the amount of ethanol used is increased to 75 g, and the turbidity of the prepared suspension is 102 NTU. The obtained high-purity rhenium powder is 63.945 g, the content is 99.9924 wt%, and the rhenium recovery rate is 94.42%. The content of the high-purity rhenium strip is detected to be 99.9903 wt%.

[0039] Example 3

[0040] The preparation process and process parameters of Example 3 are basically the same as those of Example 1, except that the amount of deionized water used in preparing the dissolving solution is reduced to 590 g, the amount of ethanol used is reduced to 30 g, and the turbidity of the prepared suspension is 298 NTU. The high-purity rhenium powder is 62.874 g, the content is 99.9982 wt%, and the rhenium recovery rate is 92.85%. The content of the high-purity rhenium strip is detected to be 99.9942 wt%.

[0041] Example 4

[0042] The preparation process and process parameters of Example 4 are basically the same as those of Example 1, except that the amount of ethanol is increased to 85 g when preparing the suspension, and the turbidity of the prepared suspension is 303 NTU. The high-purity rhenium powder is 61.458 g, the content is 99.9991 wt%, and the rhenium recovery rate is 90.76%. The content of the high-purity rhenium strip is 99.9963 wt%.

[0043] Example 5

[0044] The preparation process and process parameters of Example 5 are basically the same as those of Example 1, except that the amount of ethanol is reduced to 17 g when preparing the suspension, and the turbidity of the prepared suspension is 104 NTU. The high-purity rhenium powder is 64.012 g, the content is 99.9921 wt%, and the rhenium recovery rate is 94.52%. The content of the high-purity rhenium strip is 99.9908 wt%.

[0045] Example 6

[0046] The preparation process and process parameters of Example 6 are basically the same as those of Example 1, except that the centrifuge speed is reduced to 3300 r / min during centrifugal sedimentation, and the centrifugal separation factor is about 3000. Finally, 64.153 g of high-purity rhenium powder is obtained, with a content of 99.9913 wt%, and a rhenium recovery rate of 94.73%. The content of the high-purity rhenium strip is detected to be 99.9903 wt%.

[0047] Example 7

[0048] The preparation process and process parameters of Example 7 are basically the same as those of Example 1, except that: during centrifugal sedimentation, the centrifuge speed is increased to 5350 r / min, and the centrifugal separation factor is about 8000. The high-purity rhenium powder is obtained: 63.547 g, the content is: 99.9986 wt%, and the rhenium recovery rate is: 93.84%. The content of the high-purity rhenium strip is detected to be: 99.9953 wt%.

[0049] Comparative Example 1

[0050] The preparation method and process parameters of Comparative Example 1 are basically the same as those of Example 1, except that the amount of deionized water is reduced to 460 g when preparing the suspension, and ethanol is not added. The turbidity of the prepared suspension is 24 NTU. The obtained high-purity rhenium powder is 65.425 g, with a content of 99.1240 wt%, and a rhenium recovery rate of 95.77%. The content of the high-purity rhenium strip is 99.1211 wt%.

[0051] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-purity rhenium bars, characterized in that: The specific steps include: (1) The crude ammonium perrhenate is subjected to a multi-step purification process to obtain the fine ammonium perrhenate; (2) The refined ammonium perrhenate is reduced to obtain high-purity rhenium powder; (3) High-purity rhenium powder is cold isostatically pressed to obtain a green body; (4) The green body is sintered in a hydrogen atmosphere to obtain high-purity rhenium bars.

2. The preparation method according to claim 1, characterized in that: The content of the crude ammonium perrhenate in step (1) is ≥ 99.0wt%.

3. The preparation method according to claim 1, characterized in that: The multi-step purification process of step (1) includes the following steps: s1. Add crude ammonium perrhenate into deionized water and dissolve by heating to obtain a solution; s2, adding an organic solvent to the dissolved solution to obtain a suspension; s3, the suspension is centrifuged to obtain a sediment; s4. The sedimentation liquid is evaporated and crystallized to obtain fine ammonium perrhenate.

4. The preparation method according to claim 3, characterized in that: In step s1, the mass ratio of the deionized water to the crude ammonium perrhenate is 6-15:

1.

5. The preparation method according to claim 3, characterized in that: The temperature of the heating and dissolving process in step s1 is 60-90°C.

6. The preparation method according to claim 3, characterized in that: The mass ratio of the organic solvent in step s2 to the deionized water in step s1 is 0.02-0.10:1; the organic solvent is selected from at least one of methanol, ethanol, propanol and isopropanol.

7. The preparation method according to claim 3, characterized in that: The turbidity of the suspension in step s2 is n, and 100NTU≦n≦300NUT.

8. The preparation method according to claim 3, characterized in that: The centrifugal separation factor of the centrifugal sedimentation process in step s3 is controlled to be 3000-8000.