Method for inhibiting thermal dehydrogenation in yttrium hydride sintering process

Abstract

The invention provides a method for inhibiting thermal dehydrogenation in the yttrium hydride sintering process, yttrium hydride powder to be sintered is placed in a mold sintering area, the mold sintering area is a compressible sealing cavity, pressure is applied to the yttrium hydride powder through high-pressure compression of the sealing cavity, and in the heating sintering process, the sealing cavity forms a sealed high-hydrogen-pressure environment to inhibit dehydrogenation. In the sintering process, the surfaces of yttrium hydride powder particles are slightly decomposed, hydrogen forms high hydrogen pressure in a sealed sintering area, then subsequent decomposition is inhibited, a mold and a sample are cooled along with a furnace after sintering is completed, and released hydrogen can be absorbed into yttrium hydride again in the furnace cooling process. According to the method, thermal dehydrogenation in the yttrium hydride sintering process can be greatly reduced, and meanwhile the purposes of shortening the technological period and simplifying the technological process are achieved.

Description

Technical Field

[0001] The invention relates to the preparation of yttrium hydride, in particular to a method for inhibiting thermal dehydrogenation during the sintering process of preparing yttrium hydride. Background Art

[0002] Yttrium hydride has the advantages of high high-temperature hydrogen density, high thermal conductivity, and a single high-temperature phase structure. It is an ideal high-temperature neutron moderator material. The industry mainly uses powder metallurgy to prepare yttrium hydride. This method uses yttrium hydride powder as raw material and sinters it into yttrium hydride blocks through external means such as pressure and high temperature. The advantage of powder metallurgy is that the preparation process is simple and the size is controllable. However, the high-temperature thermal dehydrogenation characteristics of yttrium hydride pose a huge challenge to sintering densification. When the temperature reaches above 900°C, yttrium hydride begins to thermally dehydrogenate. In traditional powder metallurgy methods, due to process requirements, the sintering temperature of yttrium hydride is much higher than its thermal dehydrogenation temperature. Therefore, thermal dehydrogenation during the sintering process is difficult to avoid, resulting in a significant decrease in the hydrogen content in yttrium hydride. In 2023, the United States disclosed a technical route for preparing yttrium hydride by powder metallurgy. The yttrium hydride powder was pressed into shape at 150MPa and sintered at 1200℃. The thermal dehydrogenation was serious during the sintering process, so the sintered body needed to be hydrogenated again at about 700℃. The process cycle was long and complicated. How to avoid the thermal dehydrogenation of yttrium hydride during the sintering process has become a difficult problem that researchers in this field need to solve urgently. Summary of the invention

[0003] The invention aims to solve the problem of thermal dehydrogenation of yttrium hydride during sintering.

[0004] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0005] A method for inhibiting thermal dehydrogenation during the sintering process of yttrium hydride, wherein the yttrium hydride powder to be sintered is placed in a sintering area of ​​a mold, the sintering area of ​​the mold is a compressible sealed cavity, the yttrium hydride powder is pressurized by high-pressure compression of the sealed cavity, and during the temperature-raising sintering process, the sealed cavity forms a sealed high hydrogen pressure environment to inhibit dehydrogenation.

[0006] Furthermore, the compressible sealing cavity includes an inner liner ring, and gaskets are arranged on the upper and lower parts of the inner liner ring. The upper and lower gaskets are plastically deformed under the action of high pressure to form a sealed space between the inner liner ring, and the pressure is 800-1000MPa.

[0007] Furthermore, the temperature rising sintering method is any one of discharge plasma sintering and rapid hot pressing sintering, the heating rate is 100-200℃ / min, the sintering temperature is 800-1100℃, and the holding time is 5-20min; during the sintering process, a small amount of decomposition occurs on the surface of the yttrium hydride powder particles, and hydrogen forms a high hydrogen pressure in the sealed sintering area, thereby inhibiting subsequent decomposition. After sintering, the mold and sample can be cooled with the furnace. During the cooling process with the furnace, the released hydrogen can be reabsorbed into the yttrium hydride.

[0008] Furthermore, the mold is made of high-temperature resistant hard alloy; the inner liner ring and gasket are made of metal material, the outer diameter of the inner liner ring is in interference fit with the inner diameter of the mold, and the diameters of the upper and lower gaskets must be in interference fit with the outer diameter of the inner liner ring.

[0009] The present invention has the following beneficial effects:

[0010] At present, the sintering idea of ​​suppressing the thermal decomposition of single-phase materials is mainly to reduce the sintering temperature to below the thermal decomposition temperature through powder activation treatment, high-pressure sintering and other methods, but it is difficult for yttrium hydride to achieve densification sintering through this method. The present invention realizes the sintering densification of yttrium hydride above its decomposition temperature for the first time, and suppresses its thermal dehydrogenation through local high hydrogen pressure. Through the implementation of the present invention, the thermal dehydrogenation of yttrium hydride during the sintering process can be greatly reduced, while achieving the purpose of shortening the process cycle and simplifying the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the preparation process of yttrium hydride. DETAILED DESCRIPTION

[0012] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] Example 1

[0014] Before sintering: select yttrium hydride powder with a purity of more than 99%, an average particle size of 5μm, and an H / Y ratio of 1.85. The mold is a carbide mold with an inner diameter of 10mm, the inner liner ring is a metal Mo ring with a thickness of 0.5mm and an outer diameter of 10mm, and the upper and lower gaskets are metal Mo gaskets with a thickness of 0.5mm and a diameter of 9mm. Among them, the outer diameter of the Mo ring is an interference fit with the inner diameter of the mold, and the diameter of the Mo gasket is an interference fit with the outer diameter of the inner liner ring. Figure 1 Assemble as shown and apply a pressure of 800MPa to the mold ram.

[0015] Sintering process: The mold was transferred into a spark plasma sintering furnace and heated to 1100°C at a heating rate of 200°C / min and kept at this temperature for 5 minutes. A pressure of 300MPa was applied during the sintering process, and 0.04MPa Ar gas was used for atmosphere protection.

[0016] After sintering: Cooling in the furnace, the mold is taken out of the sintering furnace, and the metal Mo liner is peeled off from the sample to obtain a yttrium hydride block with a diameter of about 9.5 mm.

[0017] The yttrium hydride bulk obtained by this method has a density of 99% and an H / Y ratio of 1.83.

[0018] Example 2

[0019] Before sintering: Choose yttrium hydride powder with a purity of more than 99%, an average particle size of 1μm, and an H / Y ratio of 1.74. The mold is a carbide mold with an inner diameter of 15mm, the inner liner ring is a metal Cu ring with a thickness of 1mm and an outer diameter of 15mm, and the upper and lower gaskets are metal Cu gaskets with a thickness of 1mm and a diameter of 13mm. The outer diameter of the Cu ring is an interference fit with the inner diameter of the mold, and the diameter of the Cu gasket is an interference fit with the outer diameter of the inner liner ring. Figure 1 Assemble as shown and apply a pressure of 1000MPa to the mold ram.

[0020] Sintering process: The mold is transferred into a spark plasma sintering furnace and heated to 900°C at a heating rate of 100°C / min and kept at this temperature for 20 minutes. A pressure of 400MPa is applied during the sintering process, and 0.04MPa Ar gas is used for atmosphere protection.

[0021] After sintering: Cooling in the furnace, the mold is removed from the sintering furnace, and the metal Cu liner is peeled off from the sample to obtain a yttrium hydride block with a diameter of about 14 mm.

[0022] The yttrium hydride bulk obtained by this method has a density of 98% and an H / Y ratio of 1.73.

[0023] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0024] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for inhibiting thermal dehydrogenation during the sintering process of yttrium hydride, characterized in that: The yttrium hydride powder to be sintered is placed in the sintering area of ​​the mold. The sintering area of ​​the mold is a compressible sealed cavity. The yttrium hydride powder is pressurized by high-pressure compression of the sealed cavity. During the temperature-raising sintering process, the sealed cavity forms a sealed high hydrogen pressure environment to inhibit dehydrogenation.

2. A method for inhibiting thermal dehydrogenation during sintering of yttrium hydride according to claim 1, characterized in that: The compressible sealing cavity comprises an inner liner ring, and gaskets are arranged on the upper and lower parts of the inner liner ring; the upper and lower gaskets are deformed under the action of high pressure to form a sealing space between the inner liner ring.

3. A method for inhibiting thermal dehydrogenation during sintering of yttrium hydride according to claim 1, characterized in that: The pressure is 800-1000 MPa.

4. A method for inhibiting thermal dehydrogenation during sintering of yttrium hydride according to claim 1, characterized in that: The temperature-raising sintering method is any one of spark plasma sintering and rapid hot pressing sintering.

5. A method for inhibiting thermal dehydrogenation during sintering of yttrium hydride according to claim 1 or 4, characterized in that: The heating rate is 100-200°C / min, the sintering temperature is 800-1100°C, and the heat preservation time is 5-20min.

6. A method for inhibiting thermal dehydrogenation during sintering of yttrium hydride according to claim 1, characterized in that: The mold is made of high temperature resistant hard alloy.

7. A method for inhibiting thermal dehydrogenation during sintering of yttrium hydride according to claim 2, characterized in that: The inner liner ring and the gasket are made of metal material.

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