Preparation method of gallium nitride

Abstract

The invention provides a preparation method of gallium nitride. The preparation method comprises the following steps: S1, carrying out vacuum melting treatment on a mixture of gallium-containing wastes and carbon to obtain gallium; and S2, nitriding the gallium obtained in the step S1 to obtain gallium nitride. According to the method, the adopted gallium extraction raw material is unique and is the gallium-containing waste containing trace gallium, and by adding carbon as a reducing agent, low-melting-point substances of the gallium-containing waste can be reduced and removed in the subsequent first vacuum melting process. And then, in the subsequent second vacuum melting process, oxide of iron in the gallium-containing waste and gallium in an oxidation state are further reduced under the action of carbon, the gallium is changed into gallium steam, the gallium steam is separated from residual solid substances, and the gallium with the purity of 6-8 N is obtained. And finally, directly producing gallium nitride from the obtained high-purity gallium. Therefore, the method is short in production flow and good in impurity removal effect.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical production, and specifically relates to a method for preparing gallium nitride. Background Art

[0002] As an important strategic resource, a series of compounds prepared with gallium metal as the matrix, such as semiconductor materials, electronic optical materials, new functional materials, special alloys and organic metal compounds, are important basic supporting materials in the fields of modern electronic computers, communications, aerospace, new energy, medicine and health, and military industry. At present, about 90% of the world's primary gallium is recovered from the production process of alumina, with a mature industrial chain. At the same time, gallium is also enriched in the process of zinc smelting and coal ash, but the gallium enriched in the above two raw materials has not been industrialized due to the long extraction process and high cost.

[0003] Gallium nitride (GaN), as one of the third-generation nitride semiconductors, is a direct bandgap semiconductor with a bandgap width of 3.4 eV. It has excellent properties such as high electron mobility, high breakdown voltage, and high thermal conductivity, and is widely used in the field of semiconductor technology. At present, the raw material for preparing gallium nitride is generally high-purity gallium. For example, CN116590792A uses seed growth to prepare gallium nitride. Its raw material needs to use gallium with higher purity for reaction, and the residence time in the high temperature section is longer, and the pressure required for the reaction is slightly negative to slightly positive. CN112680604A uses sodium as a co-solvent to first obtain metallic gallium, and then crystallizes to generate gallium nitride. There are also documents showing that gallium nitride can be prepared using high-purity gallium oxide as a raw material, but the economic cost is higher than that of gallium metal as a raw material.

[0004] It can be seen that in the traditional process of preparing gallium nitride, high-purity gallium is required as raw material. However, obtaining high-purity gallium first requires extracting crude gallium, which then undergoes deep processing, and the process is relatively complicated. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing gallium nitride, which has a short production process and good impurity removal effect.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing gallium nitride, comprising the following steps:

[0008] S1: vacuum smelting a mixture of gallium-containing waste and carbon to obtain gallium;

[0009] S2: performing nitridation treatment on the gallium obtained in step S1 to obtain gallium nitride;

[0010] Wherein, the vacuum melting process includes a first vacuum melting process and a second vacuum melting process in sequence;

[0011] The temperature of the first vacuum melting treatment is 600-1000 o C, time is 0.5~2 h;

[0012] The temperature of the second vacuum melting treatment is 1000~1300 o C, time is 0.5~2 h.

[0013] Preferably, the composition of the gallium-containing waste is: 89~95 wt% iron oxide, 0~2 wt% SiO2, 1~5wt% ZnO, and a total amount of less than 10 wt% of any one or more of Na2O, MgO, CaCO3, Al2O3, TiO2, V2O5, Cr2O3, MnO, PbO, CuO or NiO.

[0014] Preferably, the gallium content in the gallium-containing waste is 100-500 g / t.

[0015] Preferably, the carbon is selected from coke and / or graphite.

[0016] Preferably, the carbon content in the mixture is 3-10 wt%.

[0017] Preferably, the carbon content in the mixture is 6-10 wt%.

[0018] Preferably, the vacuum degree of the vacuum melting process is 1-150 Pa.

[0019] Preferably, the purity of the gallium is 6~8N.

[0020] Preferably, the nitridation treatment is performed using nitrogen and / or ammonia.

[0021] Preferably, the temperature of the nitriding treatment is 500-800°C.

[0022] Preferably, the purity of the gallium nitride is 6-8 N.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a short process for preparing gallium nitride by vacuum melting of low gallium-containing waste. The method has simple steps. Gallium nitride can be obtained by vacuum melting and nitriding a mixture of gallium-containing waste and carbon in sequence. Among them, the gallium extraction raw material used in the present invention is unique. It is gallium-containing waste with a trace amount of gallium. By adding carbon as a reducing agent, the gallium-containing waste can reduce and remove low-melting point substances in the subsequent first vacuum melting process. Then, in the subsequent second vacuum melting process, the iron oxides and oxidized gallium in the gallium-containing waste are further reduced under the action of carbon, and at the same time, at 1000~1300 o C, gallium turns into gallium vapor and is separated from the remaining solid matter to obtain gallium with a purity of 6-8 N. Finally, the obtained high-purity gallium is used to directly produce gallium nitride. It can be seen that this method does not require the intermediate products of crude gallium and high-purity gallium, and directly produces gallium nitride, with a short production process and good impurity removal effect.

[0025] In addition, after the second stage of vacuum melting treatment is completed, the liquid metallic iron produced can be used as the anode plate for electrolytic refined iron after solidification. Therefore, this method not only has a short production process and the obtained gallium nitride has high purity, but also can produce economically valuable by-products. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. 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.

[0027] The present invention provides a method for preparing gallium nitride, which comprises the following steps:

[0028] S1: vacuum smelting a mixture of gallium-containing waste and carbon to obtain gallium;

[0029] S2: Perform nitridation treatment on the gallium obtained in step S1 to obtain gallium nitride.

[0030] In the present invention, the gallium-containing waste is vanadium-extracting converter sludge, and its components are: 89~95 wt% iron oxide, 0~2 wt% SiO2, 1~5 wt% ZnO, and a total amount of less than 10 wt% of any one or more of Na2O, MgO, CaCO3, Al2O3, TiO2, V2O5, Cr2O3, MnO, PbO, CuO or NiO; preferably 90~93 wt% iron oxide, 0.5~1.5 wt% SiO2, 2~4 wt% ZnO, and a total amount of less than 8 wt% of any one or more of Na2O, MgO, CaCO3, Al2O3, TiO2, V2O5, Cr2O3, MnO, PbO, CuO or NiO. In the present invention, the gallium content in the gallium-containing waste is a trace amount, specifically 100-500 g / t, preferably 200-500 g / t, and more preferably 300-500 g / t.

[0031] The present invention utilizes vanadium-extracting converter sludge as a raw material for extracting gallium, which not only realizes waste recycling and saves economic costs, but also provides a new idea for extracting high-purity gallium.

[0032] In the present invention, the carbon is used as a reducing agent. After being mixed with gallium-containing waste, in the subsequent vacuum smelting process, the oxidized metal and gallium can be reduced in a specific temperature range and the purpose of impurity removal can be achieved. In the present invention, the carbon is selected from coke and / or graphite. In order to ensure that the carbon can achieve an excellent reduction effect and the principle of making the best use of everything, the present invention screens the carbon content in the mixture of carbon and gallium-containing waste to 3~10 wt%, preferably 6~10 wt%, and more preferably 7~8 wt%.

[0033] In the present invention, after the gallium-containing waste and carbon are mixed, the mixture is preferably subjected to vacuum melting treatment. The vacuum melting equipment used in the vacuum melting includes but is not limited to any one of a vacuum induction melting furnace, a vacuum arc melting furnace or a vacuum electron beam melting furnace. In this process, the mixture is reduced with a carbonaceous reducing agent at high temperature, and the vacuum degree is controlled at 1~150 Pa, preferably 5~120 Pa, and more preferably 10~80 Pa. The vacuum environment can reduce the gasification temperature of gallium and other volatile elements, and dissociate the gallium element dissolved in the iron oxide.

[0034] In some embodiments of the present invention, the vacuum melting process sequentially includes a first vacuum melting process and a second vacuum melting process.

[0035] Wherein, the temperature of the first vacuum melting treatment is 600~1000 o C, preferably 700~900 oC; the residence time is 0.5~2 h, preferably 1~1.5 h; in this process, due to the relatively low temperature, low melting point substances (such as Pb, Zn, etc.) will be reduced and volatilized through the flue of the vacuum melting equipment, achieving preliminary impurity removal, and sodium volatilizes out of the flue in the form of oxides. It should be noted that the residence time depends on the temperature of the first vacuum melting. The higher the temperature, the shorter the required residence time; conversely, the lower the temperature, the longer the required residence time.

[0036] The temperature of the second vacuum melting treatment is 1000~1300 o C, preferably 1100~1200 o C; this temperature range is the vacuum melting volatilization temperature of gallium, gallium can be volatilized, and thus separated from other substances, until all gallium is volatilized and the heating is stopped, the generally required residence time is 0.5~2 h, preferably 1~1.5 h. Similarly, the residence time depends on the temperature of the second vacuum melting, the higher the temperature, the shorter the required residence time; conversely, the lower the temperature, the longer the required residence time. The temperature of the second vacuum melting treatment is 1000~1300 o C range, it can be ensured that only metal gallium can be converted into gaseous form in the component system, and the purity of metal gallium can reach 6 N~8 N. At the same time, the liquid metal iron in the furnace body can be poured into the sand mold, and can be used as an anode plate for electrolytic refined iron after solidification. It can be seen that the method of the present invention can not only obtain high-purity gallium, but also obtain by-products with economic value.

[0037] According to the present invention, after obtaining high-purity gallium, it is subjected to nitridation treatment to obtain gallium nitride.

[0038] In some embodiments of the present invention, it is preferred to introduce high-purity gaseous gallium into an atmospheric pressure furnace, the temperature of which is 500 to 800 o C, preferably 550~700 o C, and use one or more of preheated nitrogen, ammonia or nitrogen-containing gases to nitride the high-purity gallium vapor. The process time is 0.5~1 h, preferably 0.6~0.8 h. Generally, the higher the temperature, the shorter the nitridation time; conversely, the lower the temperature, the longer the nitridation time.

[0039] In the present invention, the pressure in the atmospheric pressure furnace is normal pressure, which is generally 1 standard atmospheric pressure, namely 0.1013 MPa.

[0040] After the above nitridation treatment, the obtained gallium nitride is in liquid state and can flow out through a flue with a dry and inert atmosphere, preferably argon protection. At this time, the purity of the gallium nitride is 6-8 N.

[0041] It should be noted that if ammonia is used for nitriding, the by-products such as hydrogen will be discharged in gaseous form along with the excess argon protective gas flue and can be recycled.

[0042] In order to further illustrate the present invention, the following examples are used to provide a detailed description. The vanadium-extracting converter sludge used in the following examples of the present invention is provided by Panzhihua Iron and Steel Group Co., Ltd.

[0043] Example 1

[0044] The raw materials of the gallium nitride preparation method involved in this embodiment include vanadium extraction converter sludge, whose main components are 95wt% iron oxide, 2wt% SiO2, 1.25wt% ZnO, and the rest are 0.02wt%Na2O, 0.2wt%MgO, 0.04wtCaCO3, 0.1wt%Al2O3, 0.2wt% TiO2, 0.5wt%V2O5, 0.2wt%Cr2O3, 0.2wt%MnO, 0.1wt%PbO, 0.04wt%CuO, and the remainder is NiO. The gallium content in the raw material is 500 g / t.

[0045] The specific preparation method is as follows:

[0046] (1) Mixing gallium-containing waste with coke to obtain a mixed material, wherein the carbon content accounts for 10wt% of the mass of the mixed material;

[0047] (2) The mixed material obtained in step (1) is reduced by using a vacuum induction melting furnace, and the vacuum degree is controlled at 1 Pa; the process includes a first melting stage and a second melting stage:

[0048] 2.1 In the first stage of smelting, when the temperature reaches 1000 o C, stay for 0.5 h until the low melting point substances such as lead and zinc are completely reduced and evaporated through the flue;

[0049] 2.2 As the temperature continues to rise, in the second stage of smelting, the temperature is 1300 o C, stay for 0.5 hours until all gallium is volatilized. At this time, gallium is in gaseous form and the purity of gallium can reach 8 N. At the same time, the liquid metal iron in the furnace is poured into the sand mold and can be used as an anode plate for electrolytic refined iron after solidification.

[0050] (3) 8 N high purity gallium gas is introduced into a normal pressure furnace at a temperature of 800 o C, using nitrogen preheated to 750°C to nitride the high-purity gallium vapor, the process time is 0.5 h;

[0051] (4) The gallium vapor nitrided in step (3) is gallium nitride. At this time, the gallium nitride is in liquid form and can be discharged through a dry flue protected by argon to obtain gallium nitride with a purity of 8 N. The by-product hydrogen gas is discharged through the flue with excess argon gas and can be recycled.

[0052] Example 2

[0053] The raw material of the gallium nitride preparation method involved in this embodiment is vanadium extraction converter sludge, the main components of which are 89 wt% iron oxide, 5 wt% ZnO, and the rest are 0.2 wt% Na2O, 1.2 wt% MgO, 0.5wt CaCO3, 0.3 wt% Al2O3, 0.5 wt% TiO2, 0.6 wt% V2O5, 0.6 wt% Cr2O3, 0.5 wt% MnO, 0.2 wt% PbO, 0.2 wt% CuO, and the remainder is NiO. The gallium content in the raw material is 100 g / t.

[0054] The specific preparation method is as follows:

[0055] (1) Gallium-containing waste is mixed with a mixture of coke and graphite to obtain a mixed material, wherein the carbon content accounts for 3 wt% of the mass of the mixed material;

[0056] (2) Reducing the mixed material obtained in step (1) using a vacuum arc melting furnace, with the vacuum degree controlled at 150 Pa; the process includes a first stage melting and a second stage melting:

[0057] 2.1 In the first smelting process, when the temperature reaches 600 o C, stay for 2 h until the low melting point substances are reduced and evaporated through the flue;

[0058] 2.2 As the temperature continues to rise, in the second melting process, the temperature is 1000 o C, stay for 2 hours until all the gallium is volatilized. At this time, the gallium is in gaseous form and the purity of gallium can reach 6 N. At the same time, the liquid metal iron in the furnace is poured into the sand mold and can be used as an anode plate for electrolytic refined iron after solidification;

[0059] (3) High-purity gaseous gallium is introduced into a normal pressure furnace at a temperature of 500 o C, using ammonia gas at a preheated temperature of 450°C to nitride the high-purity gallium vapor, the process time is 1 h;

[0060] (4) The gallium vapor nitrided in step (3) is gallium nitride. At this time, the gallium nitride is in liquid form and can flow out through a dry flue protected by argon. At this time, the purity of the gallium nitride is 6 N. The by-product hydrogen gas is discharged through the flue with the excess argon gas and can be recycled.

[0061] Comparative Example 1

[0062] The raw material for the gallium nitride preparation method involved in this comparative example is vanadium extraction converter sludge, whose main components are 95 wt% iron oxide, 2 wt% SiO2, 1.25 wt% ZnO, and the rest are 0.02 wt% Na2O, 0.2 wt% MgO, 0.04 wtCaCO3, 0.1 wt% Al2O3, 0.2 wt% TiO2, 0.5 wt% V2O5, 0.2 wt% Cr2O3, 0.2 wt% MnO, 0.1 wt% PbO, 0.04 wt% CuO, and the remainder is NiO. The gallium content in the raw material is 500 g / t.

[0063] The specific preparation method is as follows:

[0064] (1) Gallium-containing waste is mixed with coke to obtain a mixed material, wherein the carbon content accounts for 10 wt% of the mass of the mixed material;

[0065] (2) The mixed material obtained in step (1) is reduced by using a vacuum induction melting furnace, and the vacuum degree is controlled at 1 Pa; the process includes a first melting stage and a second melting stage:

[0066] 2.1 In the first stage of smelting, when the temperature reaches 1000 o C, stay for 0.5 h until the low melting point substances such as lead and zinc are completely reduced and evaporated through the flue;

[0067] 2.2 As the temperature continues to rise, in the second stage of smelting, the temperature is 1400 o C, and stay for 0.5 h until all the gallium is volatilized. Due to the high temperature, part of the iron is reduced during the smelting process and forms a gallium-iron alloy with the gallium.

[0068] At this time, the gallium content of the gallium-iron alloy is 90 wt% (obtained by quantitative test by chemical titration after digestion (or dissolution)), which fails to reach the gallium content in the gallium nitride nitridation process.

[0069] Comparative Example 2

[0070] The raw material for the gallium nitride preparation method involved in this comparative example is vanadium extraction converter sludge, the main components of which are 89 wt% iron oxide, 5 wt% ZnO, and the rest are 0.2 wt% Na2O, 1.2wt% MgO, 0.5wt% CaCO3, 0.3 wt% Al2O3, 0.5wt% TiO2, 0.6 wt% V2O5, 0.6 wt% Cr2O3, 0.5 wt% MnO, 0.2wt% PbO, 0.2wt% CuO, and the remainder is NiO. The gallium content in the raw material is 100 g / t.

[0071] The specific preparation method is as follows:

[0072] (1) Mixing gallium-containing waste with a mixture of coke and graphite to obtain a mixed material, wherein the carbon content is 3 wt% of the mass of the mixed material;

[0073] (2) Reducing the mixed material obtained in step (1) using a vacuum arc melting furnace, with the vacuum degree controlled at 150 Pa; the process includes a first stage melting and a second stage melting:

[0074] 2.1 In the first smelting process, when the temperature reaches 500 o C, stay for 2 h until the low melting point substances are reduced and evaporated through the flue;

[0075] 2.2 As the temperature continues to rise, in the second melting process, the temperature is 1000 o C for 2 hours until all gallium is volatilized. At this time, gallium is in gaseous form and the purity of gallium can reach 3 N. At the same time, the liquid metallic iron in the furnace is poured into the sand mold and can be used as an anode plate for electrolytic refined iron after solidification;

[0076] (3) High-purity gaseous gallium is introduced into a normal pressure furnace at a temperature of 500 o C, using the preheated temperature of 500 o C ammonia gas nitridates high-purity gallium vapor, and the process takes 1 h;

[0077] (4) The gallium vapor nitrided in step (3) is gallium nitride. At this time, the gallium nitride is in liquid form and can flow out through a dry flue protected by argon. At this time, the purity of gallium nitride is 3 N

[0078] It can be seen that since the temperature in step 2.1 did not reach the temperature for removing all volatiles, a small amount of lead and zinc elements were mixed in, and the purity of gallium nitride could not be reached to be directly used.

[0079] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing gallium nitride, characterized in that: The following steps are involved: S1: vacuum smelting a mixture of gallium-containing waste and carbon to obtain gallium; S2: performing nitridation treatment on the gallium obtained in step S1 to obtain gallium nitride; Wherein, the vacuum melting process includes a first vacuum melting process and a second vacuum melting process in sequence; The temperature of the first vacuum melting treatment is 600-1000 o C, time is 0.5~2 h; The temperature of the second vacuum melting treatment is 1000~1300 o C, time is 0.5~2 h.

2. The preparation method according to claim 1, characterized in that: The composition of the gallium-containing waste is: 89~95 wt% iron oxide, 0~2 wt% SiO2, 1~5 wt% ZnO, and a total amount of less than 10 wt% of any one or more of Na2O, MgO, CaCO3, Al2O3, TiO2, V2O5, Cr2O3, MnO, PbO, CuO or NiO.

3. The preparation method according to claim 1 or 2, characterized in that: The gallium content in the gallium-containing waste is 100-500 g / t.

4. The preparation method according to any one of claims 1 to 3, characterized in that The carbon is selected from coke and / or graphite; The carbon content in the mixture is 3-10 wt %.

5. The preparation method according to claim 4, characterized in that: The carbon content in the mixture is 6-10 wt%.

6. The preparation method according to any one of claims 1 to 5, characterized in that The vacuum degree of the vacuum melting process is 1-150 Pa.

7. The preparation method according to any one of claims 1 to 6, characterized in that The purity of the gallium is 6~8N.

8. The preparation method according to any one of claims 1 to 7, characterized in that The nitriding treatment is performed using nitrogen and / or ammonia.

9. The preparation method according to any one of claims 1 to 8, characterized in that The temperature of the nitriding treatment is 500-800°C.

10. The preparation method according to any one of claims 1 to 9, characterized in that The purity of the gallium nitride is 6~8N.