Spherical high-purity quartz sand as well as preparation method and application thereof

Abstract

The invention provides spherical high-purity quartz sand as well as a preparation method and application thereof. The spherical high-purity quartz sand comprises a high-purity quartz sand inner core and barium salt coated on at least part of the surface of the inner core. The spherical high-purity quartz sand provided by the invention is of a core-shell structure, and the barium salt coated on the surface of the spherical high-purity quartz sand can avoid the risk of falling of the barium salt caused by non-uniform spraying of a barium carbonate coating on the surface of a quartz crucible, so that the service life of the quartz crucible can be prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of quartz crucibles, and particularly relates to a spherical high-purity quartz sand, a preparation method thereof, and an application thereof. Background Art

[0002] A quartz crucible is a container for holding molten silicon during the single-crystal silicon pulling process. Molten silicon is contained inside it, and it contacts with a crucible made of graphite or carbon material on the outside. During the process of pulling a single crystal by the Czochralski method, the one-time consumption of the quartz crucible and the time-consuming of disassembling and assembling the furnace account for a relatively high proportion in the cost. Under the traditional Czochralski method, the quartz crucible can only be used once, and only one silicon rod can be produced at a time; while in the continuous crystal pulling method, materials can be continuously added into the quartz crucible during the crystal pulling process, and new silicon rods can be continuously produced. Therefore, this poses requirements for the service life of the quartz crucible. The reason affecting the service life of the quartz crucible is that the quartz material on the inner wall of the crucible has a tendency to become silicon dioxide crystals after being used at high temperature for a long time, that is, the so-called crystallization phenomenon. After crystallization, exfoliated particles are formed and enter the melt, damaging the growth of single-crystal silicon.

[0003] At present, the industry generally uses barium carbonate to coat the surface of the prepared quartz crucible to solve the above problems. Although the barium carbonate coating can react with molten silicon to generate barium silicate with a high melting point, effectively blocking the penetration of molten silicon into the inner wall of the quartz crucible, affected by the coating uniformity of barium carbonate, there is a risk of barium salt shedding during the high-temperature material melting stage, affecting the service life of the quartz crucible. Summary of the Invention

[0004] The main object of the present invention is to provide a spherical high-purity quartz sand, which can avoid the risk of barium salt shedding, thereby improving the service life of the quartz crucible.

[0005] The present invention also provides a preparation method of the spherical high-purity quartz sand. This method can prepare the above-mentioned spherical high-purity quartz sand, and has a simple process and low cost.

[0006] The present invention also provides a quartz crucible. Since this quartz crucible includes the above-mentioned spherical high-purity quartz sand, therefore, this quartz crucible has a long service life.

[0007] In a first aspect, the present invention provides a spherical high-purity quartz sand, which includes a high-purity quartz sand core and barium salt coated on at least part of the surface of the core.

[0008] For the spherical high-purity quartz sand as described above, the particle size of the spherical high-purity quartz sand is 42μm - 83μm, and the spheroidization rate ≥ 99%.

[0009] For the spherical high-purity quartz sand as described above, the spherical high-purity quartz sand is prepared by a method including the following process:

[0010] The spherical high-purity quartz sand is obtained by successively performing hydrothermal treatment, preheating treatment, high-temperature spheroidization treatment, and cooling treatment on a mixed system including etched quartz sand and a barium-containing solution.

[0011] Second, the present invention provides a method for preparing the spherical high-purity quartz sand as described above, comprising the following steps:

[0012] 1) Etching the high-purity quartz sand with an alkali solution to obtain etched quartz sand;

[0013] 2) Performing hydrothermal treatment on a mixed system including the etched quartz sand and a barium-containing solution to obtain a first powder;

[0014] 3) Sequentially performing preheating treatment and high-temperature spheroidization treatment on the first powder to obtain a second powder;

[0015] 4) Performing cooling treatment on the second powder to obtain the spherical high-purity quartz sand.

[0016] In the preparation method as described above, the concentration of the alkali solution is 1 mol / L to 4 mol / L;

[0017] The mass ratio of the high-purity quartz sand to the alkali solution is (40 to 60):1.

[0018] In the preparation method as described above, the concentration of the barium-containing solution is 0.1 mol / L to 0.3 mol / L;

[0019] The mass ratio of the barium-containing solution to the etched quartz sand is 1:(80 to 120).

[0020] In the preparation method as described above, the temperature of the etching treatment is 120°C to 150°C, and the time is 0.5 h to 24 h;

[0021] And / or, the temperature of the hydrothermal treatment is 135°C to 175°C, and the time is ≥72 h.

[0022] In the preparation method as described above, the temperature of the preheating treatment is 500°C to 550°C;

[0023] And / or, the temperature of the high-temperature spheroidization treatment is 1700°C to 1800°C.

[0024] In the preparation method as described above, before the etching treatment, screening treatment is further included on the high-purity quartz sand to obtain screened high-purity quartz sand;

[0025] The particle size of the screened high-purity quartz sand is 50 mesh to 200 mesh;

[0026] And / or, after the etching treatment, washing and drying treatment are further included on the etched quartz sand;

[0027] The temperature of the drying treatment is 120°C to 170°C, and the time is ≥2 h.

[0028] In a third aspect, the present invention provides a quartz crucible, which includes the spherical high-purity quartz sand as described above or the spherical high-purity quartz sand prepared by the preparation method as described above.

[0029] The spherical high-purity quartz sand provided by the present invention has a core-shell structure, and the barium salt coated on its surface can avoid the risk of barium salt shedding caused by uneven spraying of the barium carbonate coating on the surface of the quartz crucible, thereby improving the service life of the quartz crucible. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention or related technologies. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a schematic structural diagram of a spherical high-purity quartz sand provided by the present invention;

[0032] Figure 2 It is a schematic structural diagram of a spheroidizing furnace provided by the present invention. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0034] In a first aspect, the present invention provides a spherical high-purity quartz sand, which includes a high-purity quartz sand core and a barium salt coated on at least part of the surface of the core.

[0035] The spherical high-purity quartz sand in the present invention has a core-shell structure, such as Figure 1As shown, it includes a high-purity quartz sand core and a barium salt coated on at least part of the surface of the core, where the barium salt can be selected from at least one of barium hydroxide, barium nitrate, and barium acetate. This spherical high-purity quartz sand, as a raw material for the inner layer of a quartz crucible, can be evenly attached to the inner surface of the quartz crucible, and an arc method is used to prepare a vacuum transparent layer on the inner surface of the crucible. The barium salt coated on the surface of the spherical high-purity quartz sand can react with the molten silicon in the quartz crucible to generate barium silicate with a high melting point, avoiding direct contact between the inner wall of the quartz crucible and the molten silicon, and also preventing the risk of barium salt shedding caused by uneven spraying of the barium carbonate coating on the surface of the quartz crucible during the high-temperature material melting stage, thereby improving the service life of the quartz crucible.

[0036] In some embodiments of the present invention, the particle size of the spherical high-purity quartz sand is 42μm to 83μm. For example, it can be 42μm, 50μm, 60μm, 70μm, 80μm, 83μm, or any range composed of any two of them. The spheroidization rate ≥ 99%. For example, it can be 99.1%, 99.3%, 99.5%, 99.7%, 99.9%, or any range composed of any two of them.

[0037] In the present invention, the particle size of the spherical high-purity quartz sand is within an appropriate range, and the spheroidization rate is relatively high, with good fluidity, which can increase the bulk density of the spherical high-purity quartz sand. When melting into the inner layer of the quartz crucible, it can effectively improve the strength of the quartz crucible, avoid cracking of the crucible body, and reduce the problem of crucible crystallization caused by heat deformation of the quartz crucible and damage to the original inner wall coating.

[0038] In some embodiments of the present invention, the spherical high-purity quartz sand is prepared by a method including the following process:

[0039] The mixed system including etched quartz sand and a barium-containing solution is subjected to hydrothermal treatment, preheating treatment, high-temperature spheroidization treatment, and cooling treatment in sequence to obtain the spherical high-purity quartz sand.

[0040] When preparing the spherical high-purity quartz sand in the present invention, the high-purity quartz sand can be first etched with an alkali solution to obtain etched quartz sand, and then the mixed system obtained by mixing the etched quartz sand and the barium-containing solution is subjected to hydrothermal treatment to adsorb the barium salt at the etched part of the etched quartz sand, and then preheating treatment, high-temperature spheroidization treatment, and cooling treatment are carried out to obtain the spherical high-purity quartz sand.

[0041] The preparation method in the present invention can prepare spherical high-purity quartz sand, and this spherical high-purity quartz sand, as a raw material for the inner layer of a quartz crucible, can improve the service life of the quartz crucible.

[0042] In the second aspect, the present invention provides a preparation method of the spherical high-purity quartz sand as described above, including the following steps:

[0043] 1) Etch high-purity quartz sand with an alkaline solution to obtain etched quartz sand;

[0044] 2) Hydrothermally treat a mixed system including the etched quartz sand and a barium-containing solution to obtain a first powder;

[0045] 3) Preheat and then perform high-temperature spheroidization treatment on the first powder in sequence to obtain a second powder;

[0046] 4) Cool the second powder to obtain the spherical high-purity quartz sand.

[0047] In the present invention, through etching treatment, hydrothermal treatment, preheating treatment, high-temperature spheroidization treatment, and cooling treatment of high-purity quartz sand, the spherical high-purity quartz sand of the first aspect of the present invention can be obtained.

[0048] Specifically, in step 1), using an alkaline solution to etch the pore channels of high-purity quartz sand is beneficial for subsequent infiltration of barium salts into the etched areas of high-purity quartz sand, so as to finally form spherical high-purity quartz sand with a barium salt coating on the surface. The present invention does not limit the specific type of the alkaline solution, as long as it can etch high-purity quartz sand, for example, at least one of strong alkalis such as sodium hydroxide and potassium hydroxide can be selected.

[0049] In step 2), the etched quartz sand and the barium-containing solution can be mixed and then added to a hydrothermal reaction kettle for hydrothermal reaction, and after filtration and drying, a first powder is obtained. The present invention does not limit the specific type of the solute in the barium-containing solution, as long as it can provide barium salts and enable the barium salts to be adsorbed on the etched areas of high-purity quartz sand, for example, at least one of barium hydroxide, barium nitrate, and barium acetate can be used.

[0050] In step 3), the above-mentioned first powder can be sprayed into a spheroidization furnace (such as Figure 2As shown in the figure, the spheroidizing furnace at least includes three parts: a preheating chamber, a hot spheroidizing chamber, and a cooling section from top to bottom. First, the first powder is sent to the preheating chamber for preheating treatment. In the preheating chamber, barium salt in the first powder can react with silicon dioxide to form barium silicate and adhere to the etched part of high-purity quartz sand. The role of preheating can, on the one hand, remove the adsorbed water and hydroxyl groups on the surface of high-purity quartz sand, and on the other hand, prevent high-purity quartz sand from directly generating a thermal shock reaction at overheated temperatures, so that high-purity quartz sand will not cause internal stress or deformation due to rapid temperature changes. After the high-purity quartz sand is preheated, it enters the hot spheroidizing chamber of the spheroidizing furnace for high-temperature spheroidizing treatment. At this stage, the high-purity quartz sand and barium silicate on its surface will be quickly melted simultaneously and form spheres under the action of surface tension, and barium silicate will wrap around the outer layer of the spheroidized high-purity quartz sand. Specifically, the air, oxygen combustion-supporting channels, and natural gas channels in the preheating chamber and the hot spheroidizing chamber can be opened first, and the volume flow ratio of natural gas and oxygen in the preheating chamber and the hot spheroidizing chamber can be adjusted. At the same time, the electromagnetic igniters set at the nozzles below the preheating chamber and the hot spheroidizing chamber are ignited and burned. After the above operations are completed, the first powder is sprayed into the preheating chamber for preheating under the action of positive pressure. By controlling the space ratio of the hot spheroidizing chamber and the preheating chamber, it is ensured that the sprayed first powder has enough time for preheating and high-temperature spheroidizing treatment.

[0051] In step 4), under the action of negative pressure in the furnace, the high-purity quartz sand wrapped with barium salt after melting and spheroidizing enters the cooling section for cooling treatment. The main role of the cooling treatment is to stabilize the particle morphology of the spheroidized high-purity quartz sand and prevent it from undergoing irregular deformation and internal stress concentration during the cooling process, thereby ensuring the stability of its mechanical strength and physical and chemical properties. Finally, spherical high-purity quartz sand powder is collected through a cyclone separator and a bag filter.

[0052] The preparation method in the present invention can prepare the spherical high-purity quartz sand of the first aspect of the present invention. As the inner layer raw material of the quartz crucible, it can prevent the uneven spraying of the barium carbonate coating on the surface of the quartz crucible and the risk of barium salt shedding during the high-temperature melting stage, thereby improving the service life of the quartz crucible.

[0053] In some embodiments of the present invention, the concentration of the alkali solution is 1 mol / L to 4 mol / L. For example, it can be 1 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, or the range composed of any two of them;

[0054] The mass ratio of the high-purity quartz sand to the alkali solution is (40 to 60):1. For example, it can be 40:1, 45:1, 50:1, 55:1, 60:1, or the range composed of any two of them.

[0055] In the present invention, the concentration of the alkali solution and the mass ratio of high-purity quartz sand to the alkali solution are within a suitable range, such that the alkali solution can provide sufficient hydroxide ions to react with the silicon atoms on the surface of the quartz sand, and will not cause an overly fast etching rate due to too high a concentration, which is difficult to control. A suitable etching rate helps to achieve a relatively uniform etching depth, can also ensure that the etching process is relatively stable, reduce the occurrence of surface roughness and non-uniformity, and improve the etching quality.

[0056] In some embodiments of the present invention, the concentration of the barium-containing solution is 0.1 mol / L to 0.3 mol / L. For example, it can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, or a range composed of any two of them;

[0057] The mass ratio of the barium-containing solution to the etched quartz sand is 1:(80 - 120). For example, it can be 1:80, 1:90, 1:100, 1:110, 1:120, or a range composed of any two of them.

[0058] In the present invention, the concentration of the barium-containing solution and the mass ratio of the barium-containing solution to the etched quartz sand are within a suitable range, such that the barium-containing solution can provide sufficient barium salts to infiltrate the surface of the high-purity quartz sand, and can improve the uniformity of the infiltration of the barium salts, which is beneficial to the formation of spherical high-purity quartz sand with a barium salt coating on the surface. As the inner layer raw material of the quartz crucible, it can improve the service life of the quartz crucible.

[0059] In some embodiments of the present invention, the temperature of the etching treatment is 120°C to 150°C. For example, it can be 120°C, 125°C, 130°C, 140°C, 150°C, or a range composed of any two of them. The time is 0.5 h to 24 h. For example, it can be 0.5 h, 1 h, 3 h, 5 h, 10 h, 15 h, 20 h, 24 h, or a range composed of any two of them.

[0060] And / or, the temperature of the hydrothermal treatment is 135°C to 175°C. For example, it can be 135°C, 140°C, 145°C, 150°C, 160°C, 170°C, 175°C, or a range composed of any two of them. The time ≥ 72 h. For example, it can be 72 h, 80 h, 85 h, 90 h, 95 h, or a range composed of any two of them.

[0061] In the present invention, the temperature of the etching treatment is 120°C to 150°C and the time is 0.5 h to 24 h, such that the rate of the etching reaction is relatively suitable and can proceed uniformly, and can also make the etching depth relatively suitable, which is beneficial to the subsequent infiltration of barium salts into the etched part of the high-purity quartz sand.

[0062] The hydrothermal treatment temperature of the present invention is 135°C to 175°C, and the time is ≥72 h. When the temperature and time of the hydrothermal treatment are within an appropriate range, the barium salt can fully and evenly infiltrate and etch the etched part of the quartz sand, and the rate of the hydrothermal reaction is relatively stable, which is beneficial to improving the purity of the product.

[0063] In some embodiments of the present invention, the preheating treatment temperature is 500°C to 550°C. For example, it can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, or the range composed of any two of them.

[0064] And / or, the high-temperature spheroidization treatment temperature is 1700°C to 1800°C. For example, it can be 1700°C, 1720°C, 1740°C, 1760°C, 1780°C, 1800°C, or the range composed of any two of them.

[0065] In the present invention, when the preheating treatment temperature and the high-temperature spheroidization treatment temperature are within an appropriate range, the adsorbed water and hydroxyl groups on the surface of the high-purity quartz sand can be further removed, the thermal stress generated due to the sharp temperature change can be reduced, and the high-purity quartz sand can be prevented from cracking; in addition, it is also beneficial to form spherical high-purity quartz sand with a target particle size and a high spheroidization rate, improve the fluidity and bulk density of the quartz sand, and thus improve the strength of the quartz crucible.

[0066] In some embodiments of the present invention, before the etching treatment, the high-purity quartz sand is also subjected to a screening treatment to obtain screened high-purity quartz sand;

[0067] The particle size of the screened high-purity quartz sand is 50 mesh to 200 mesh. For example, it can be 50 mesh, 80 mesh, 100 mesh, 150 mesh, 200 mesh, or the range composed of any two of them;

[0068] And / or, after the etching treatment, it also includes: washing and drying the etched quartz sand;

[0069] The drying treatment temperature is 120°C to 170°C. For example, it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or the range composed of any two of them. The time is ≥2 h. For example, it can be 2 h, 3 h, 4 h, 5 h, 6 h, 10 h, 20 h, 30 h, or the range composed of any two of them.

[0070] Before the etching treatment of the present invention, high-purity quartz sand with a particle size of 50 mesh to 200 mesh, preferably 60 mesh to 180 mesh, is first screened out through a sieve, which is beneficial to improving the uniformity of etching. The high-purity quartz sand with an appropriate particle size can provide an appropriate specific surface area, enabling the alkali solution to effectively contact the surface of the quartz sand and undergo an etching reaction, which is beneficial to preparing spherical high-purity quartz sand with a target particle size.

[0071] After the etching treatment, the etched quartz sand can be washed three times in the steps of deionized water - absolute ethanol - deionized water, filtered by suction and placed in a vacuum drying oven, and dried at 120 °C for 2 h or more. The excessive alkali solution can be washed away, and the moisture and impurities in the etched quartz sand can be removed, thereby improving the purity of the product.

[0072] In a third aspect, the present invention provides a quartz crucible, which comprises the spherical high-purity quartz sand as described above or the spherical high-purity quartz sand prepared by the preparation method as described above.

[0073] The spherical high-purity quartz sand in the present invention has better fluidity and larger bulk density compared with angular large-particle quartz sand. Therefore, when melting into the inner layer of the quartz crucible, the strength and heat resistance of the quartz crucible can be effectively improved, and the phenomenon of cracking of the crucible body can be avoided. At the same time, the spherical high-purity quartz sand with a dense surface coating containing barium salt is used as the induced crystallization layer, which adheres more firmly to the surface of the quartz crucible than surface barium coating. Each substance in the coating can act as a bonding phase at high temperature, fill the voids between quartz crystals, improve the density of the quartz crucible, inhibit grain growth, and further avoid cracking of the quartz crucible body.

[0074] Hereinafter, the technical solutions of the present invention will be further described in conjunction with specific embodiments.

[0075] Example 1

[0076] The preparation method of the spherical high-purity quartz sand in this example includes the following steps:

[0077] 1) Mix 10 kg of high-purity quartz sand powder with a particle size of 80 mesh to 150 mesh and 200 g of 1 mol / L NaOH solution, perform etching treatment at 130 °C for 0.5 h, and wash the etched high-purity quartz sand powder three times in the steps of deionized water - absolute ethanol - deionized water, filter by suction and place it in a vacuum drying phase, and dry it at 120 °C for 2 h to obtain etched quartz sand;

[0078] 2) Add the 0.3 mol / L Ba(OH) 2 solution and the etched quartz sand into a hydrothermal reaction kettle for hydrothermal reaction. Among them, the mass ratio of the Ba(OH) 2 solution to the etched quartz sand is 1:100. Seal the reaction kettle, raise the temperature in the kettle to 175 °C and react for 72 h. After the reaction is completed, filter and dry to obtain the first powder;

[0079] 3) Preheat the first powder. Control the flame temperature in the preheating chamber at 550 °C and the flame length at 1 / 2 of the length inside the reaction furnace cavity, and then perform high-temperature spheroidization treatment. The flame temperature in the thermal spheroidization chamber is 1700 °C and the flame length is 2 / 3 of the length inside the reaction furnace cavity to obtain the second powder;

[0080] 4) After the second powder is cooled, spherical high-purity quartz sand is collected.

[0081] The particle size range of the spherical high-purity quartz sand prepared in this example is between 43 μm and 80 μm, and the spheroidization rate is greater than 99%.

[0082] The spheroidization rate for a single measurement is calculated according to the following formula:

[0083] γ a = (q - q a ) / q × 100

[0084] In the formula:

[0085] γ a - Spheroidization rate for a single measurement, %;

[0086] q - Total number of particles in a single image, pieces;

[0087] q a - Total number of non-spherical particles in a single image, pieces.

[0088] The measurement result of the spheroidization rate is the arithmetic mean of 5 γ a , and particles with incomplete image edges are not measured.

[0089] Example 2

[0090] The preparation method of the spherical high-purity quartz sand in Example 2 is basically the same as that in Example 1, except that the concentration of the NaOH solution in step 1) is 2 mol / L.

[0091] Example 3

[0092] The preparation method of the spherical high-purity quartz sand in Example 3 is basically the same as that in Example 1, except that the concentration of the NaOH solution in step 1) is 3 mol / L.

[0093] Example 4

[0094] The preparation method of the spherical high-purity quartz sand in Example 4 is basically the same as that in Example 1, except that the concentration of the NaOH solution in step 1) is 4 mol / L.

[0095] Example 5

[0096] The preparation method of the spherical high-purity quartz sand in Example 5 is basically the same as that in Example 3, except that the etching treatment time in step 1) is 1 h.

[0097] Example 6

[0098] The preparation method of the spherical high-purity quartz sand in Example 6 is basically the same as that in Example 3, except that the etching treatment time in step 1) is 3 h.

[0099] Example 7

[0100] The preparation method of the spherical high-purity quartz sand in Example 7 is basically the same as that in Example 3, except that the etching treatment time in step 1) is 5 h.

[0101] Example 8

[0102] The preparation method of the spherical high-purity quartz sand in Example 8 is basically the same as that in Example 3, except that the etching treatment time in step 1) is 12 h.

[0103] Example 9

[0104] The preparation method of the spherical high-purity quartz sand in Example 9 is basically the same as that in Example 3, except that the etching treatment time in step 1) is 18 h.

[0105] Example 10

[0106] The preparation method of the spherical high-purity quartz sand in Example 10 is basically the same as that in Example 7, except that the concentration of the Ba(OH) 2 solution in step 2) is 0.1 mol / L.

[0107] Example 11

[0108] The preparation method of the spherical high-purity quartz sand in Example 11 is basically the same as that in Example 7, except that the concentration of the Ba(OH) 2 solution in step 2) is 0.2 mol / L.

[0109] Example 12

[0110] The preparation method of the spherical high-purity quartz sand in Example 12 is basically the same as that in Example 1, except that the alkali solution selected in step 1) is a 3 mol / L KOH solution.

[0111] Example 13

[0112] The preparation method of the spherical high-purity quartz sand in Example 13 is basically the same as that in Example 1, except that the barium-containing solution selected in step 2) is a 0.3 mol / L Ba(NO 3 ) 2 solution.

[0113] Example 14

[0114] The preparation method of the spherical high-purity quartz sand in Example 14 is basically the same as that in Example 1, except that in step 2), the barium-containing solution is 0.3 mol / L Ba(CH 3 COO) 2 solution.

[0115] Example 15

[0116] The preparation method of the spherical high-purity quartz sand in Example 15 is basically the same as that in Example 1, except that in step 2), the concentration of the Ba(OH) 2 solution is 0.1 mol / L.

[0117] Example 16

[0118] The preparation method of the spherical high-purity quartz sand in Example 16 is basically the same as that in Example 1, except that in step 2), the temperature of the hydrothermal treatment is 135 °C.

[0119] Example 17

[0120] The preparation method of the spherical high-purity quartz sand in Example 17 is basically the same as that in Example 1, except that in step 3), the temperature of the preheating treatment is 500 °C.

[0121] Example 18

[0122] The preparation method of the spherical high-purity quartz sand in Example 18 is basically the same as that in Example 1, except that in step 3), the temperature of the high-temperature spheroidization treatment is 1800 °C.

[0123] Comparative Example 1

[0124] Comparative Example 1 is high-purity quartz sand without barium salt coating on the surface.

[0125] Test Example

[0126] Bulk density: The bulk density is measured as the true bulk density. A certain mass of the spherical high-purity quartz sand of Examples 1-18 and the high-purity quartz sand of Comparative Example 1 are added to a dry and clean graduated cylinder, and the graduated cylinder is repeatedly shaken until the volume is minimized. The mass of the sample contained in the unit volume is calculated as the measured true bulk density.

[0127] Melting point and high-temperature life: The spherical high-purity quartz sand of Examples 1-18 and the high-purity quartz sand of Comparative Example 1 are taken as the inner layer raw materials of the quartz crucible. Samples are taken from the made quartz crucible to test the melting point and the high-temperature life of the quartz crucible. The high-temperature life refers to the time when the inner layer of the quartz crucible is completely devitrified (crystallized) in an argon atmosphere at 1500 °C.

[0128] Table 1

[0129]

[0130] As can be seen from Table 1, compared with the comparative example, the spherical high-purity quartz sand provided by the present invention has a core-shell structure, and the barium salt coated on its surface can avoid the risk of barium salt shedding caused by uneven spraying of the barium carbonate coating on the surface of the quartz crucible, thereby improving the service life of the quartz crucible.

[0131] From the comparison between Examples 1-18 and Comparative Example 1, it can be seen that when the concentration of the alkali solution is 3 mol / L, the concentration of barium hydroxide is 0.3 mol / L, and the etching treatment time is 5 h, the bulk density of the prepared spherical high-purity quartz sand is the largest, so that the melting point of the prepared quartz crucible is the highest and the high-temperature life is the longest.

[0132] It can be seen from Examples 2-4 that as the alkali concentration increases, the surface polarity of quartz sand is further weakened, the frictional force between particles becomes smaller, and the quartz sand sprayed into the hot spheroidization chamber can form uniformly spheroidized quartz powder. When using the powder to prepare a quartz crucible, since the packing density between the powders becomes more compact and the packing density of the powder increases, the density of the quartz glass increases. Through the comparative analysis of Examples 5-9, as the etching treatment time increases, the number of etching pits on the surface of high-purity quartz sand gradually increases, and the density of the barium salt solution covering the surface of high-purity quartz sand gradually increases. The high-temperature life of the prepared quartz crucible is relatively long, generally reaching more than 400 h. However, if the etching treatment time is too long, large and deep etching pits will appear on the high-purity quartz sand. After subsequent high-temperature spheroidization treatment, continuous destructive cracks will appear on the surface of the high-purity quartz sand, and the integrity of the spherical particles will decrease, affecting the overall high-temperature resistance effect of the quartz crucible. Through the comparative analysis of Examples 7, 10-11, it can be seen that different barium salt concentrations will also affect the life of the quartz crucible. When the barium salt concentration is increased from 0.1 mol / L to 0.3 mol / L, the melting point of the glass phase rises. At high temperatures, the strength and hardness of the quartz crucible can be maintained, and the high-temperature life of the quartz crucible increases to 430 h. For excessive barium salts, due to the limitation of the size and depth of the etching pits on the barium salt adhesion amount, the melting point and high-temperature life of the quartz crucible made of spherical high-purity quartz sand increase to a certain extent, but the increase is not very obvious. Through the comparison of Examples 11-12, it can be seen that when using KOH solution or NaOH solution for etching treatment, the high-temperature resistance life and melting point of the quartz crucible are similar. Therefore, KOH solution can also be used as the alkali solution for etching treatment. Through the comparison of Examples 1, 13, and 14, it can be seen that by using different barium salt solution types for hydrothermal treatment, the melting point and high-temperature life of the quartz crucible can be improved. Therefore, barium hydroxide, barium nitrate, and barium acetate can all be used as the solutes of the barium salt solution for hydrothermal treatment with etched quartz sand. Through the comparison of Examples 1, 10, 15, and 16, it can be seen that the length of the etching treatment time has a greater impact on the life of the prepared crucible than the concentration of the barium-containing solution. When the temperature of the hydrothermal treatment is relatively low, the degree of barium salt adhesion to the quartz sand is lower, and the high-temperature resistance and melting point of the prepared quartz sand crucible will decrease. Through the comparison of Examples 1 and 17, it can be seen that when the preheating treatment temperature is relatively low, the particle size range of the prepared spherical high-purity quartz sand is relatively large, the bulk density decreases, and the melting point and life of the prepared quartz crucible decrease because when the preheating treatment temperature decreases, the adsorbed water and hydroxyl groups on the surface of the spherical high-purity quartz sand may not be removed sufficiently, resulting in more pores inside the quartz crucible. During use, these pores will reduce the structural strength of the quartz crucible, making it more likely to be damaged under high temperature and external force, reducing the service life of the quartz crucible.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spherical high-purity quartz sand, characterized in that: The invention comprises a high-purity quartz sand inner core and a barium salt coated on at least a part of the surface of the inner core.

2. The spherical high-purity quartz sand according to claim 1, characterized in that: The particle size of the spherical high-purity quartz sand is 42 μm to 83 μm, and the spheroidization rate is ≥ 99%.

3. The spherical high-purity quartz sand according to claim 1 or 2, characterized in that: The spherical high-purity quartz sand is prepared by a method comprising the following steps: The mixed system including the etched quartz sand and the barium-containing solution is subjected to hydrothermal treatment, preheating treatment, high-temperature spheroidization treatment and cooling treatment in sequence to obtain the spherical high-purity quartz sand.

4. A method for preparing spherical high-purity quartz sand according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Etching high-purity quartz sand with an alkaline solution to obtain etched quartz sand; 2) hydrothermally treating the mixed system including the etched quartz sand and the barium-containing solution to obtain a first powder; 3) performing preheating treatment and high-temperature spheroidization treatment on the first powder in sequence to obtain a second powder; 4) Cooling the second powder to obtain the spherical high-purity quartz sand.

5. The preparation method according to claim 4, characterized in that: The concentration of the alkaline solution is 1 mol / L to 4 mol / L; The mass ratio of the high-purity quartz sand to the alkaline solution is (40-60):

1.

6. The preparation method according to claim 4 or 5, characterized in that: The concentration of the barium-containing solution is 0.1 mol / L to 0.3 mol / L; The mass ratio of the barium-containing solution to the etched quartz sand is 1:(80-120).

7. The preparation method according to any one of claims 4 to 6, characterized in that: The etching process is performed at a temperature of 120°C to 150°C and for a time of 0.5h to 24h; And / or, the temperature of the hydrothermal treatment is 135° C. to 175° C., and the time is ≥ 72 h.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The temperature of the preheating treatment is 500°C to 550°C; And / or, the temperature of the high temperature spheroidization treatment is 1700°C~1800°C.

9. The preparation method according to any one of claims 4 to 8, characterized in that: Before the etching process, the high-purity quartz sand is screened to obtain screened high-purity quartz sand; The particle size of the screened high-purity quartz sand is 50 mesh to 200 mesh; And / or, after the etching process, the etching process further includes: washing and drying the etched quartz sand; The drying process is carried out at a temperature of 120° C. to 170° C. and for a time of ≥ 2 h.

10. A quartz crucible, characterized in that: The invention comprises the spherical high-purity quartz sand described in any one of claims 1 to 3 or the spherical high-purity quartz sand prepared by the preparation method described in any one of claims 4 to 9.

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