CN114799090A

CN114799090A - High-purity gallium casting forming method

Info

Publication number: CN114799090A
Application number: CN202210473584.9A
Authority: CN
Inventors: 黄杰杰; 何志达; 耿思宇
Original assignee: Guangdong Vital Micro Electronics Technology Co Ltd
Current assignee: Guangdong Vital Micro Electronics Technology Co Ltd
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2022-07-29

Abstract

The present disclosure provides a high purity gallium casting method, which includes: before casting, checking the temperature and humidity of a casting chamber, keeping the temperature and humidity within the specified temperature and humidity, setting the freezing temperature and humidity of a frost-free freezer, and setting the humidity in a glove box; placing the tank body containing the gallium liquid and the empty mold in a constant-temperature oven; pouring the gallium liquid in the tank body into a mould in a casting chamber; stacking the mold with the gallium liquid cast on a tray, scraping an oxide film by a scraper, placing the mold in a frost-free refrigerator, and so on, or placing the tray in the frost-free refrigerator, stacking the mold with the gallium liquid cast on the tray, scraping the oxide film by the scraper, and so on; covering the dust-free paper on the uppermost layer of the mould; freezing in a frost-free freezer; taking out the mold, and reversely buckling the mold on the dust-free paper for demoulding; putting the gallium ingot and the dust-free paper into a glove box; and (4) after the temperature of the gallium ingot is returned to the normal temperature, taking out the gallium ingot, weighing again and checking. The method does not need seed crystals, and the surface of the gallium ingot is free of oxidation discoloration, bright and mirror-like and has no dark spots.

Description

High-purity gallium casting forming method

Technical Field

The disclosure relates to the technical field of gallium, and more particularly relates to a high-purity gallium casting forming method.

Background

The high-purity gallium is gallium with the purity of more than or equal to 6N (99.9999 percent), is grey blue or silver white metal, is mainly used for preparing and manufacturing semiconductor gallium nitride, gallium arsenide, gallium phosphide and germanium semiconductor doping elements, and is used as a high-quality source material for MBE experiment epitaxy with the purity of more than 7N 5.

The melting point of gallium is only 29.8 ℃, liquid gallium is easily supercooled, i.e. cooled to 0 ℃ without solidification, and the higher the purity of gallium, the harder it is to solidify. In addition, gallium has the property of shrinking and swelling, i.e., gallium expands outward when solidified.

In view of the characteristics of supercooling and cold expansion of gallium, transportation and storage of high purity gallium are generally performed by solidifying gallium in HDPE bottles (< 95%) or by vacuum-pumping and storing in vacuum bags after casting into ingots.

Chinese patent document CN102873283A discloses a method for casting high purity gallium finished product, which comprises pouring gallium liquid into a mold, adding a certain amount of solid gallium into the gallium liquid, and cooling and solidifying in a refrigerator. This patent has the following drawbacks: 1. the material of the die is not limited, and gallium can stick to the die in the solidification process and is inconvenient to demould due to the cold expansion property of gallium; 2. the operation of smearing the gallium powder on the die is complex, the batch production is complex and time-consuming, and the risk of pollution is caused; 3. the humidity of the room or the refrigerator is not limited, for example, the humidity of the room or the refrigerator is high, the surface of the gallium ingot can absorb a large amount of moisture in the process of temperature return, and the gallium loses luster in humid air, so that the gallium ingot is oxidized and discolored.

Disclosure of Invention

In view of the problems in the background art, it is an object of the present disclosure to provide a high purity gallium cast molding method that addresses at least one of the deficiencies in the prior art.

Thus, in some embodiments, a high purity gallium cast molding method comprises the steps of: checking the temperature and humidity of a casting chamber before casting to be kept within the specified temperature and humidity, keeping the humidity of the casting chamber at less than 15%, setting the freezing temperature and humidity of a frostless refrigerator in the casting chamber, setting the humidity of the frostless refrigerator to be less than 20%, introducing protective gas into a glove box in the casting chamber, and setting the humidity to be less than 15%; placing the tank containing the gallium liquid and the empty mold in a constant-temperature oven in a casting room for constant-temperature heat preservation; taking the tank body and the hollow mold which are well insulated and contain the gallium liquid out of the constant-temperature oven in the casting chamber, and pouring the gallium liquid in the tank body into the mold; stacking the molds cast with the gallium liquid on a tray, scraping an oxide film on the surface of the gallium liquid cast in the molds by using a scraper, placing the tray and the stacked molds cast with the gallium liquid after the oxide film is removed in a frost-free freezer, repeating the steps and stacking a plurality of trays, or placing the tray in the frost-free freezer, stacking the molds cast with the gallium liquid on the tray, scraping the oxide film on the surface of the gallium liquid cast in the molds by using the scraper, repeating the steps and stacking the trays; covering the dust-free paper on the uppermost layer of the mould; step six, freezing the gallium liquid cast in the mold in a frostless freezer to solidify the gallium liquid and form a gallium ingot; step seven, after gallium liquid in the mold in the frostless freezer is solidified and formed into a gallium ingot, taking out the mold, and reversely buckling the mold on dust-free paper to enable the gallium ingot to be stripped; step eight, putting the gallium ingot demoulded on the dust-free paper and the dust-free paper into a glove box, and returning the gallium ingot to the temperature in the glove box; and step nine, after the temperature of the gallium ingot in the glove box returns to the normal temperature, taking out the gallium ingot and weighing again, and checking the appearance of the gallium ingot.

In some embodiments, in step one, the temperature of the casting chamber is maintained at 20-28 ℃.

In some embodiments, in step one, the freezing temperature of the frostless freezer is set to be-20 to-30 ℃.

In some embodiments, in step one, a desiccant is disposed within the frost-free freezer.

In some embodiments, in step one, the humidity inside the glove box is < 15%.

In some embodiments, in the second step, the constant temperature of the constant temperature oven is 40-50 ℃ and the holding time is 4-6 h.

In some embodiments, in step three, the quality of the mold casting gallium liquid is determined by the electronic level.

In some embodiments, in step four, the tray stacks up to three layers in a frost free freezer.

In some embodiments, in step six, the time for freezing in the frost-free freezer is 3-5 hours.

In some embodiments, in step six, opening and closing of the door of the frost-free freezer, shaking of the frost-free freezer, or other operations that affect the smooth operation of the frost-free freezer are prohibited during freezing.

In some embodiments, the high purity gallium cast molding method further comprises: step ten, vacuumizing and packaging the gallium ingot.

The beneficial effects of this disclosure are as follows: in the high-purity gallium casting and forming method, the mould is used for casting the gallium liquid, and the gallium liquid is solidified and formed into the gallium ingot without adopting the seed crystal in the prior art, so that the operation of the seed crystal is avoided, and the risk of pollution to the formed gallium ingot caused by the introduced seed crystal and the impurities introduced from the mould by the seed crystal friction mould is avoided; the surface of the prepared gallium ingot can be free from oxidation and discoloration by keeping the humidity of the casting chamber at less than 15%, setting the humidity of the frost-free freezer at less than 20% and setting the humidity in the glove box at less than 15%, and the surface of the prepared gallium ingot is bright and is mirror-surface and free from dark spots by scraping off an oxide film on the surface of the gallium liquid cast in the mold by a scraper.

Drawings

Fig. 1 is a schematic view of a high purity gallium cast molding system according to the present disclosure.

Fig. 2 is a top view of a mold of the high purity gallium cast molding system of fig. 1.

Fig. 3 is a cross-sectional view of the mold of fig. 2 taken along line a-a.

Fig. 4 is a cross-sectional view of the mold of fig. 2 taken along line B-B.

Fig. 5 is a top view of a tray of the high purity gallium cast molding system of fig. 1.

Fig. 6 is a cross-sectional view of the tray of fig. 2 taken along line C-C.

Fig. 7 is a cross-sectional view of the tray of fig. 2 taken along line D-D.

Wherein the reference numerals are as follows:

100 high-purity gallium casting molding system 3 constant-temperature oven

200 gallium liquid 4 casting chamber

1 can body 5 tray

2 mould 6 scraper

21 front inner surface 7 frost-free refrigerator

22 rear inner surface 8 dust-free paper

23 left inner surface 9 glove box

24 right inner surface 10 dehumidifier

25 bottom inner surface 11 desiccant

Alpha-angle 12 electronic balance

Detailed Description

The accompanying drawings illustrate embodiments of the present disclosure and it is to be understood that the disclosed embodiments are merely examples of the disclosure, which can be embodied in various forms, and therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

[ high purity gallium casting molding System ]

Referring to fig. 1, the high purity gallium cast molding system 100 includes a tank 1, a mold 2, a constant temperature oven 3, a casting chamber 4, a tray 5, a scraper 6, a frost-free freezer 7, dust-free paper 8, and a glove box 9.

The tank body 1 is used for containing gallium liquid 200. The material of the tank 1 can be any suitable material, for example, the tank 1 is a PP (polypropylene) barrel.

The mould 2 is used for casting gallium liquid, and the gallium liquid is solidified into a gallium ingot without adopting seed crystals. That is, the mould 2 does not need to set solid gallium of the same grade as the seed crystal as in the background art when casting the gallium liquid, which not only avoids the operation of the seed crystal, but also avoids the risk that the introduced seed crystal itself and the seed crystal friction mould introduce impurities from the mould to cause pollution to the formed gallium ingot. In addition, the temperature control requirement of the cast mold is very strict because the solid state of the seed crystal is maintained as the solidification starting point, and the temperature control requirement of the cast mold 2 is reduced because the seed crystal is not needed in the high-purity gallium casting molding system 100 of the present disclosure.

In one example, the mold 2 is a teflon mold. Due to the cold expansion property of gallium, the polytetrafluoroethylene mold can ensure that the gallium liquid does not stick to the mold 2 in the solidification process and is convenient for demoulding after the gallium liquid is solidified and formed into a gallium ingot.

In one example, the surface roughness Ra of the inner surface of the mold 2 is < 0.4. If the surface roughness of the inner surface of the mold 2 is higher than 0.4, the gallium liquid is solidified and molded into a gallium ingot, and then the mold is difficult to be removed.

Referring to fig. 2 to 4, in one example, the front inner surface 21, the rear inner surface 22, the left inner surface 23 and the right inner surface 24 of the mold 2 for molding a gallium ingot each have an angle α of 94 ° to 98 ° with the bottom inner surface 25. If the included angle alpha is smaller than 94 degrees, the gallium ingot is difficult to demould; if the included angle is higher than 98 degrees, the gallium liquid is easy to segregate when being solidified and formed into a gallium ingot, and the cavity volume of the die 2 is reduced or the gallium liquid becomes flat under the same volume, so that the whole outer contour is increased, and the space use is influenced.

And the constant-temperature oven 3 is used for placing the tank body 1 containing the gallium liquid and the mould 2 in the constant-temperature oven for constant-temperature heat preservation before the mould 2 casts the gallium liquid. As shown, the constant temperature oven 3 may be arranged in layers, the tank 1 is placed at the bottom of the constant temperature oven 3, and the mold 2 is placed on a partition at the upper part of the constant temperature oven 3. The tank body 1 containing the gallium liquid and the mold 2 are placed in the constant-temperature oven 3 for constant-temperature heat preservation, so that the gallium liquid and the mold 2 can have the same temperature, the gallium liquid is cast in the mold 2 without temperature difference with the mold 2 when the casting chamber 4 is used for casting, the multiple molds 2 are solidified from the same initial temperature when being frozen and solidified in the frost-free freezer 7 to form gallium ingots, and the quality consistency of the gallium ingots formed by the multiple molds 2 in the same batch taken out of the frost-free freezer 7 is improved.

In one example, the constant temperature oven 3 has a constant temperature of 40-50 ℃ and a holding time of 4-6 h. The constant temperature should not be too high or too low. Because the temperature of the casting chamber 4 is lower than the constant temperature of the constant temperature oven 3, if the constant temperature of the constant temperature oven 3 is too low (i.e. lower than 40 ℃), the gallium liquid in the tank body 1 is solidified before being cast when the gallium liquid in the tank body 1 is cast into the plurality of molds 2 in the casting chamber 4 due to insufficient total heat storage amount of the gallium liquid. If the constant temperature of the constant temperature oven 3 is too high (namely higher than 50 ℃), the gallium liquid in the tank body 1 is easy to oxidize, thereby influencing the quality and the yield of the final gallium ingot.

The casting chamber 4 is used for providing a working space, and the mould 2, the constant-temperature oven 3, the tray 5, the scraper 6, the frost-free freezer 7, the dust-free paper 8 and the glove box 9 are all arranged in the casting chamber 4. During operation, in the casting chamber 4, the tank body 1 which is well insulated and is filled with the gallium liquid and the hollow mould 2 are placed in the casting chamber 4, and the gallium liquid in the tank body 1 is poured into the mould 2.

In one example, the temperature of the casting chamber 4 is maintained between 20-28 ℃, and the humidity of the casting chamber 4 is maintained at < 15%. The upper temperature limit (i.e. 28 ℃) of the casting chamber 4 is controlled to be slightly lower than the melting point of gallium, but the lower temperature limit (i.e. 20 ℃) and the humidity of the casting chamber 4 are preferably controlled to prevent a large amount of water drops from being condensed on the gallium ingot when the mold 2 with the solidified gallium ingot is taken out from the frost-free refrigerator 7 and the gallium ingot is stripped from the mold 2, so that the situation that the surface of the gallium ingot absorbs a large amount of moisture to cause that the gallium ingot cannot be rapidly dried when the temperature in the glove box 9 is returned, and watermark is formed on the surface of the gallium ingot, the surface of the gallium ingot is oxidized to be discolored and the surface of the gallium ingot loses luster after the temperature is returned is avoided.

The temperature control of the casting chamber 4 may be performed by any suitable means, such as temperature control means for heating and cooling, heat insulation means for insulating the walls of the casting chamber 4, heat insulation means for sealing the doors for the operator to enter and exit, temperature monitoring means for temperature sensing, and the like. The casting chamber 4 is preferably sized to allow an operator to easily operate the casting chamber and to allow the operator to place and operate the relevant equipment (e.g., a thermostatic oven 3, an electronic level 12, a tray 5, a scraper 6, a frost-free freezer 7, a glove box 9, a dehumidifier 10, etc.).

The humidity control of the casting chamber 4 may be performed by any suitable means, for example, referring to fig. 1, a dehumidifier 10 is provided in the casting chamber 4, and the dehumidifier 10 is used for dehumidifying the casting chamber 4 to control the humidity in the casting chamber 4 to meet the required requirement (for example, the humidity of the casting chamber 4 is less than 15% as described above).

The scraper 6 is used for scraping off an oxide film on the surface of the gallium liquid cast in the mold 2, so that the surface of the gallium ingot is a mirror surface (i.e. no dark spot) after the gallium liquid cast in the mold 2 is solidified and formed into the gallium ingot in the frost-free freezer 7. The scraper 6 may be made of any suitable material, for example, the scraper 6 is a polypropylene spatula. The operation of the scraper 6 can be carried out immediately after the casting of the gallium liquid in the mould 2 or after the placement of the tray 5 in the frost-free freezer 7.

The tray 5 is used for stacking the molds 2 cast with the gallium liquid and for placing in a frost-free freezer 7.

Any suitable material may be used for the tray 5, for example, the tray 5 is a polypropylene tray.

Referring to fig. 1 in conjunction with fig. 5 to 7, the size of each tray 5 is determined according to the number of the stacking molds 2, and each tray 5 can be stacked by a single row of molds 2 or stacked by a plurality of rows of molds 2.

The number of trays 5 is prepared depending on the production scale. The number of layers the trays 5 are stacked in the frost-free freezer 7 is determined by the freezing capacity and space of the frost-free freezer 7 and the time-efficient cost required for freezing into gallium ingots. In one example, referring to FIG. 1, tray 5 stacks up to three layers in a frost free freezer 7.

In one example, a plurality of trays 5 may be stacked such that a first empty tray 5 is placed in a frost-free freezer 7, followed by a mold 2 cast with gallium liquid, and when the tray 5 is fully stacked with the mold 2 cast with gallium liquid, a second empty tray 5 is stacked on the first tray, and so on. In an alternative embodiment, each tray 5 can be stacked with the molds 2 cast with gallium liquid before being placed in the frost-free freezer 7, and stacked with the mold 2 cast with gallium liquid after the tray 5 is stacked with the molds 2 cast with gallium liquid in the frost-free freezer 7. No matter which mode is adopted, the stacking operation process of the tray 5 and the tray 5 is stacked on the die 2, the action is kept stable, the vibration is avoided, and then the gallium liquid is prevented from shaking, and the surface qualification rate of the gallium ingots is influenced.

In the stacked plurality of trays 5, the uppermost surface of the mold 2 between two adjacent trays 5 above and below is spaced apart from the tray 5 above the mold 2 by a predetermined space (i.e., a space, see fig. 1), so that on the one hand, the lower surface of the tray 5 above the mold 2 is prevented from contacting the gallium liquid in the mold 2, and on the other hand, the space between the mold 2 and the tray 5 above the mold 2 forms a cold air flow passage, thereby increasing the cooling solidification rate.

The frost-free refrigerator 7 is used for placing the tray 5 and freezing the gallium liquid in the mold 2 which is stacked on the tray 5 and is cast with the gallium liquid, so that the gallium liquid in the mold 2 is solidified and formed into a gallium ingot.

The frost-free freezer 7 itself can be set with freezing temperature and humidity. In one example, the freezing temperature of the frostless freezer 7 is set to-20 to-30 ℃ and the humidity is less than 20%. If the temperature of the frost-free refrigerator 7 is frozen to be lower than minus 30 ℃, the solidification speed of the gallium liquid is too high, so that the surface of the formed gallium ingot is uneven; if the freezing temperature of the frost-free refrigerator 7 is higher than minus 20 ℃, the gallium liquid is slowly solidified, which is not beneficial to improving the production efficiency. If the humidity of the frost-free refrigerator 7 exceeds 20%, the mold 2 with the solidified gallium ingot is taken out from the frost-free refrigerator 7, and the surface of the gallium ingot carries with the moisture in the frost-free refrigerator 7, so that the mold cannot be dried quickly when the temperature in the glove box 9 is returned, and the watermark, the oxidation discoloration and the tarnishing of the surface of the gallium ingot are caused after the temperature is returned.

To further control the humidity within the frost-free ice bin 7, in one example, referring to fig. 1, a desiccant 11 is provided within the frost-free ice bin 7. The drying agent 11 is used for dehumidifying and drying the interior of the frost-free refrigerator 7 so as to control the humidity of the interior of the frost-free refrigerator 7. The desiccant 11 may be placed in any form, for example in a bag. The material of the desiccant 11 may be selected from any suitable material.

The frost-free freezer 7 closes the freezer door of the frost-free freezer 7 after all trays 5 are required to be placed therein. In the freezing process of the frost-free freezer 7, the opening and closing of the freezer door of the frost-free freezer 7 are strictly forbidden, the frost-free freezer 7 is shaken or other operations affecting the stability of the frost-free freezer 7 are strictly forbidden, so that the gallium liquid in the mold 2 is prevented from shaking due to the influence on the stability of the frost-free freezer 7, and the surface qualification rate of the formed gallium ingot is prevented from being influenced.

The freezing time of the frost-free freezer 7 is based on that the gallium liquid in each mould 2 in the frost-free freezer 7 is solidified and formed into gallium ingots. In one example, the time for freezing in the frost-free freezer 7 is 3-5 h.

The dust-free paper 8 is used for covering the mould 2 on the uppermost layer after the mould 2 cast with gallium liquid is stacked on the tray 5 and placed in the frost-free freezer 7, and the mould 2 on the uppermost layer cannot be shielded by the tray 5 above like the mould 2 on the layer below the mould 2 on the uppermost layer, so that the mould 2 on the uppermost layer is covered by the dust-free paper 8 to prevent water drops possibly generated in the frost-free freezer 7 from dropping on the mould 2 on the uppermost layer and avoid affecting the surface quality of gallium ingots; and the dust-free paper 8 is used for reversely buckling the gallium liquid in the mould 2 in the frost-free refrigerator 7 to form a gallium ingot and then demoulding the gallium ingot (namely, taking the gallium ingot out of the frost-free refrigerator 7 and reversely buckling the gallium ingot in the casting chamber 4). The number of dust-free paper 8 may be the same as the number of molds 2 in the frost-free freezer 7 or less than the number of molds 2 in the frost-free freezer 7 (i.e. one dust-free paper 8 may hold a plurality of gallium ingots).

The glove box 9 is used for heating the gallium ingot stripped on the dust-free paper 8 to normal temperature.

In order to avoid the influence of moisture and impurities contained in the air in the glove box, a protective gas is introduced into the glove box 9. The shielding gas may be nitrogen or argon. The protective gas is used for cleaning and replacing air in the glove box 9 before operation, and forms flowing heat exchange air flow in the process of reheating the gallium ingot so as to rapidly reheat the gallium ingot to normal temperature. The higher the purity of nitrogen or argon, the better, avoiding the introduction of impurities.

In operation, the humidity inside the glove box 9 is < 15%. The humidity of the glove box 9 may be set by itself (a commercially available glove box has this function). By setting the humidity of the glove box 9, it is avoided that moisture in the glove box 9 is absorbed by the surface of the gallium ingot after the gallium ingot stripped on the dust-free paper 8 is placed in the glove box 9 (air is introduced due to the airtightness of the glove box 9 itself, or moisture possibly contained in the shielding gas or air is remained at a part of the glove box 9 which cannot be cleaned despite the cleaning of the shielding gas), so that the gallium ingot cannot be dried quickly when being cooled back in the glove box 9, and watermarks are formed on the surface of the gallium ingot, the surface of the gallium ingot is oxidized and discolored, and the surface of the gallium ingot loses gloss after being cooled back. Of course, like the frost-free refrigerator 7, a desiccant (bag) may be provided in the glove box 9 to assist the humidity control.

In addition, in the process of temperature return, the dust-free paper 8 can also adsorb moisture in the glove box 9, so that moisture in air is removed in an auxiliary manner before the protective gas is introduced and before replacement is completed, and it is noted that the moisture absorbed by the dust-free paper 8 can be carried out by the flowing protective gas in the process of temperature return.

As shown in fig. 1, the high purity gallium casting system 100 further includes an electronic balance 12, the electronic balance 12 is disposed in the casting chamber 4, and the electronic balance 12 is used for determining the mass of the casting gallium liquid of each mold 2. Specifically, in the casting chamber 4, the tank body 1 and the mold 2 containing the gallium liquid after the constant temperature heat preservation in the constant temperature oven 3 is finished are taken out from the constant temperature oven 3, the mold 2 subjected to the constant temperature heat preservation treatment is placed on the electronic balance 12, and then the gallium liquid in the tank body 1 containing the gallium liquid after the constant temperature heat preservation is poured into the mold 2 on the electronic balance 12, so that the quantitative gallium liquid is poured into the mold 2.

In an embodiment, the high purity gallium casting system 100 further comprises a vacuum packaging mechanism (not shown) for vacuum packaging the gallium ingot after the glove box 9 is cooled.

In the high-purity gallium casting and forming system 100 of the present disclosure, the mold 2 is used for casting the gallium liquid, and the gallium liquid is solidified and formed into the gallium ingot without adopting the seed crystal in the prior art, which not only avoids the operation of the seed crystal, but also avoids the risk of pollution to the formed gallium ingot caused by the introduced seed crystal itself and the impurities introduced from the mold by the seed crystal friction mold; the oxide film on the surface of the gallium liquid cast in the die 2 is scraped by a scraper 6, so that the surface of the prepared gallium ingot is bright and is mirror-surface without dark spots.

[ method of casting and Molding high-purity gallium ]

The high-purity gallium casting and molding method adopts the high-purity gallium casting and molding system 100.

The high-purity gallium casting molding method comprises the following steps: the method comprises the following steps that firstly, the temperature and the humidity of a casting chamber 4 are checked to be kept within the specified temperature and humidity before casting, the humidity of the casting chamber 4 is kept to be less than 15%, the freezing temperature and the humidity of a frost-free refrigerator 7 in the casting chamber 4 are set, the humidity of the frost-free refrigerator 7 is set to be less than 20%, protective gas is introduced into a glove box 9 in the casting chamber 4, and the set humidity is less than 15%; placing the tank body 1 containing the gallium liquid 200 and the empty mould 2 in a constant-temperature oven 3 in a casting chamber 4 for constant-temperature heat preservation; taking the insulated tank body 1 containing the gallium liquid and the empty mold 2 out of the constant-temperature oven 3 in the casting chamber 4, and pouring the gallium liquid in the tank body 1 into the mold 2; step four, stacking the mold 2 cast with the gallium liquid on a tray 5, scraping an oxide film on the surface of the gallium liquid cast in the mold 2 by using a scraper 6, placing the tray 5 and the stacked mold 2 cast with the gallium liquid after the oxide film is removed in a frost-free freezer 7, repeating the steps and stacking a plurality of trays 5, or placing the tray 5 in the frost-free freezer 7, stacking the mold 2 cast with the gallium liquid on the tray 5, scraping the oxide film on the surface of the gallium liquid cast in the mold 2 by using the scraper 6, repeating the steps and stacking a plurality of trays 5; covering the dust-free paper 8 on the mould 2 at the uppermost layer; step six, freezing the gallium liquid cast in the mould 2 in a frostless freezer 7 so as to solidify the gallium liquid and form a gallium ingot; step seven, after gallium liquid in the mould 2 is solidified and formed into a gallium ingot in the frostless freezer 7, taking out the mould 2, and reversely buckling the mould 2 on the dust-free paper 8 to demould the gallium ingot; putting the gallium ingot which is subjected to the film removal on the dust-free paper 8 into a glove box 9, and returning the temperature of the gallium ingot in the glove box 9; and step nine, after the temperature of the gallium ingot in the glove box 9 is recovered to the normal temperature, taking out the gallium ingot and weighing again, and checking the appearance of the gallium ingot.

In one embodiment, in the first step, the temperature of the casting chamber 4 is maintained at 20-28 ℃.

In one embodiment, in the first step, the freezing temperature of the frostless freezer 7 is set to be-20 to-30 ℃.

In one embodiment, in step one, the frost-free freezer 7 is provided with a desiccant 11.

In one embodiment, the shielding gas is nitrogen or argon.

In one embodiment, in the second step, the constant temperature of the constant temperature oven 3 is 40-50 ℃ and the heat preservation time is 4-6 hours.

In one embodiment, in step three, the quality of the gallium liquid cast by the mold 2 is determined by the electronic level.

In one embodiment, in step four, the tray 5 is stacked in a frost free freezer 7 with up to three layers.

In one embodiment, in the sixth step, the time for freezing in the frost-free freezer 7 is 3-5 h.

In an embodiment, in the sixth step, in the freezing process, opening and closing of a refrigerator door of the frost-free refrigerator 7 is strictly prohibited, the frost-free refrigerator 7 is shaken or other operations affecting the stability of the frost-free refrigerator 7 are strictly prohibited, so that the vibration of the liquid level of the gallium liquid in the mold 2 is avoided, and the surface of the solidified gallium ingot is not flat and has protrusions which affect the surface flatness of the gallium ingot.

In one embodiment, the high purity gallium casting method further comprises: step ten, vacuumizing and packaging the gallium ingot.

Note that, with the high-purity gallium casting method, description of the same effects as those described in the aforementioned high-purity gallium casting system 100 is not repeated.

In the high-purity gallium casting and forming method, the mould 2 is used for casting the gallium liquid, and the gallium liquid is solidified and formed into the gallium ingot without adopting the seed crystal in the prior art, so that the operation of the seed crystal is avoided, and the risk of pollution to the formed gallium ingot caused by the introduced seed crystal and the impurities introduced from the mould by the seed crystal friction mould is avoided; the surface of the prepared gallium ingot can be free from oxidation discoloration by keeping the humidity of the casting chamber 4 at < 15%, the humidity of the frost-free freezer 7 at < 20% and the humidity in the glove box 9 at < 15%, and the surface of the prepared gallium ingot is bright and mirror-like without dark spots by scraping off the oxide film on the surface of the gallium liquid cast in the mold 2 by the scraper 6.

[ test ]

Example 1

Step (a): before casting, checking whether various parameters are in a normal range, keeping the temperature of a casting chamber 4 at 20-28 ℃, keeping the humidity at less than 15%, setting the freezing temperature of a frost-free refrigerator 7 at-20 to-30 ℃, setting the humidity in the frost-free refrigerator 7 at less than 20%, arranging a drying agent 11 in the frost-free refrigerator 7, and introducing high-purity nitrogen or high-purity argon into a glove box 9, wherein the humidity is less than 15%;

step (b): placing the mold 2 and the gallium liquid 200 into a constant-temperature oven 3 in a casting chamber 4, and keeping the temperature for 4 hours, wherein the constant temperature of the constant-temperature oven 3 is 40 ℃;

step (c): placing a mould 2 on an electronic balance 12 in a casting chamber 4, slowly pouring heat-insulated gallium liquid into the mould 2, slowly placing the mould 2 on a PP tray 5 of a frostless freezer 7, scraping off a surface oxide film by using a PP scraper 6, stacking the moulds 2 on the tray 5 according to the method, stacking the trays 5 after filling the trays, stacking 3 layers, and covering the uppermost tray 5 with dust-free paper 8. In the whole operation process, the stable action is kept, the vibration is avoided, the refrigerator door of the frost-free refrigerator 7 is closed after all the refrigerator doors are placed, and the freezing time of the frost-free refrigerator 7 is set to be 5 hours;

step (d): in the freezing process, the opening and closing of the refrigerator door of the frost-free refrigerator 7, the shaking of the frost-free refrigerator 7 or other operations which affect the stability of the frost-free refrigerator 7 are strictly forbidden;

a step (e): after freezing, taking out the mold 2, reversely buckling the mold 2 on the dust-free paper 8 for demolding, and then putting the gallium ingot into the glove box 8 for temperature return;

step (f): and after the temperature of the gallium ingot in the glove box 9 is recovered to the normal temperature, taking out the gallium ingot to be weighed again, checking the appearance, and vacuumizing and packaging.

Example 2

The same procedure as in example 1 was repeated, except that the temperature in step (b) was maintained for 5 hours at a constant temperature of 45 ℃ and the freezing time in the frost-free freezer 7 in step (c) was 4 hours.

Example 3

The same procedure as in example 1 was repeated except that the temperature in step (b) was maintained for 6 hours and the constant temperature was 50 ℃.

Comparative example

Step (a): before casting, the casting chamber 4 is kept at the temperature of 20-28 ℃, the humidity of 40%, the freezing temperature of the frost-free refrigerator 7 is-20 to-30 ℃, the humidity of the frost-free refrigerator 7 is 45%, high-purity nitrogen or high-purity argon is introduced into the glove box 9 without a drying agent 11, and the humidity of 30%;

step (b): placing the die 2 and the gallium liquid 200 into a constant-temperature oven 3, and keeping the temperature for 4 hours, wherein the constant temperature is 40 ℃;

step (c): placing a mould 2 on an electronic balance, pouring heat-insulated gallium liquid into the mould 2, placing the mould 2 on a tray 5 made of PP (polypropylene) of a frost-free freezer 7, stacking the moulds 2 on the tray 5 according to the method in sequence, stacking one tray 5 after the tray is filled, stacking 3 layers, covering dust-free paper 8 on the uppermost layer, and setting the freezing time of the frost-free freezer 7 to be 5 hours;

step (d): opening a refrigerator door of the frost-free refrigerator 7 every 1 hour to observe the gallium liquid solidification condition;

a step (e): after freezing, taking out the mold 2, and reversely buckling the mold 2 on the dust-free paper 8 for demolding, and finding out a large amount of water drops rapidly condensed on the gallium ingot;

step (f): putting the gallium ingot into a glove box 9 for temperature return;

the results of the surface inspection of the comparative example and examples 1 to 3 are given in table 1.

In table 1, the surface flatness is measured by visually observing whether the surface of the gallium ingot has a protrusion or a wrinkle, and if the surface of the gallium ingot has the protrusion or the wrinkle, the surface flatness of the gallium ingot is unqualified; the surface brightness and the oxidative discoloration were visually observed.

As seen from Table 1, in the comparative example, the gallium liquid level is vibrated due to frequent opening and closing of the refrigerator door of the frost-free refrigerator 7, and the surface is not flat and has bulges after solidification; 2) humidity control of the casting chamber 4, the frost-free freezer 7 and the glove box 9 is not enough, a large amount of water drops are condensed on the surface of the gallium ingot during demoulding, rapid drying cannot be realized, and the surface has the conditions of watermarks and discoloration after temperature returning; the oxide film is not scraped, and dark spots are formed on the surface after solidification.

The above detailed description describes exemplary embodiments, but is not intended to limit the combinations explicitly disclosed herein. Thus, unless otherwise specified, various features disclosed herein can be combined together to form a number of additional combinations that are not shown for the sake of brevity.

Claims

1. The casting molding method of the high-purity gallium is characterized by comprising the following steps:

the method comprises the following steps that firstly, the temperature and the humidity of a casting chamber (4) are checked to be kept within the specified temperature and humidity before casting, the humidity of the casting chamber (4) is kept to be less than 15%, the freezing temperature and the humidity of a frost-free refrigerator (7) in the casting chamber (4) are set, the humidity of the frost-free refrigerator (7) is set to be less than 20%, protective gas is introduced into a glove box (9) in the casting chamber (4), and the set humidity is less than 15%;

placing the tank body (1) containing the gallium liquid (200) and the empty mold (2) in a constant-temperature oven (3) in a casting chamber (4) for constant-temperature heat preservation;

taking the tank body (1) containing the gallium liquid and the hollow mold (2) which are well insulated from the constant-temperature oven (3) in the casting chamber (4), and pouring the gallium liquid in the tank body (1) into the mold (2);

fourthly, stacking the mold (2) cast with the gallium liquid on a tray (5), scraping an oxidation film on the surface of the gallium liquid cast in the mold (2) by using a scraper (6), stacking the tray (5) and the mold (2) cast with the gallium liquid after the oxidation film is removed in a frost-free freezer (7), repeating the steps and stacking a plurality of trays (5), or placing the tray (5) in the frost-free freezer (7), stacking the mold (2) cast with the gallium liquid on the tray (5), scraping an oxidation film on the surface of the gallium liquid cast in the mold (2) by using the scraper (6), repeating the steps and stacking the plurality of trays (5);

covering the dust-free paper (8) on the mould (2) at the uppermost layer;

sixthly, freezing the gallium liquid cast in the mold (2) in a frost-free freezer (7) to solidify the gallium liquid and form a gallium ingot;

seventhly, after gallium liquid in the mold (2) in the frostless freezer (7) is solidified and formed into a gallium ingot, taking out the mold (2), and reversely buckling the mold (2) on dust-free paper (8) to enable the gallium ingot to be stripped;

step eight, putting the gallium ingot demoulded on the dust-free paper (8) and the dust-free paper (8) into a glove box (9), and returning the gallium ingot to the temperature in the glove box (9);

and step nine, after the temperature of the gallium ingot in the glove box (9) is returned to the normal temperature, taking out the gallium ingot and weighing again, and checking the appearance of the gallium ingot.

2. The method for casting and molding high purity gallium according to claim 1,

in the first step, the temperature of the casting chamber (4) is kept between 20 and 28 ℃.

3. The method for casting and molding high purity gallium according to claim 1,

in the first step, the freezing temperature of the frostless freezer (7) is set to be-20 to-30 ℃.

4. The method for casting and molding high purity gallium according to claim 1,

in the first step, a drying agent (11) is arranged in the frost-free freezer (7).

5. The method for casting and molding high purity gallium according to claim 1,

in step one, the humidity inside the glove box (9) is < 15%.

6. The method for casting and molding high purity gallium according to claim 1,

in the second step, the constant temperature of the constant temperature oven (3) is 40-50 ℃, and the heat preservation time is 4-6 hours.

7. The method for casting and molding high purity gallium according to claim 1,

in the third step, the quality of the gallium liquid cast by the mould (2) is determined by the electronic level.

8. The method for casting and molding high purity gallium according to claim 1,

in step four, the tray (5) is stacked in a frost-free freezer (7) with at most three layers.

9. The method for casting and molding high purity gallium according to claim 1,

in the sixth step, the time for freezing in the frost-free freezer (7) is 3-5 h.

10. The method for casting and molding high purity gallium according to claim 1,

in the sixth step, in the freezing process, the opening and closing of the refrigerator door of the frost-free refrigerator (7), the shaking of the frost-free refrigerator (7) or other operations influencing the stability of the frost-free refrigerator (7) are strictly forbidden.

11. The high-purity gallium cast molding method according to claim 1, further comprising:

step ten, vacuumizing and packaging the gallium ingot.