Method for preparing high-purity amorphous quartz sand by two-step heat treatment of white carbon black

Abstract

The application discloses a method for preparing high-purity amorphous quartz sand by heat treating white carbon black in a two-step method, and comprises the following steps: S1, soaking white carbon black powder in a mixed acid liquid of hydrofluoric acid and hydrochloric acid, taking out the solid, and cleaning and drying to obtain high-purity white carbon black powder; S2, pressing the high-purity white carbon black powder into a white carbon black block; S3, pre-heating the white carbon black block to remove residual moisture, hydroxyl groups and carbon-based impurities, and obtaining a sample after removing hydroxyl groups; S4, performing two-step heat treatment of high temperature and then low temperature on the sample after removing hydroxyl groups, and cooling to obtain a high-density quartz block; in the two-step heat treatment, the high temperature refers to heating to 1200 DEG C first, and the low temperature refers to heating to 1200 DEG C and then directly cooling to 1000-1100 DEG C without a heat preservation process for 2-10 h; and S5, crushing the high-density quartz block to obtain high-purity amorphous quartz sand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-purity quartz sand preparation, and particularly relates to a method for preparing high-purity amorphous quartz sand by two-step heat treatment of white carbon black. BACKGROUND

[0002] With the rapid development of the photovoltaic industry, semiconductor chips, intelligent computing and other fields, the demand for silicon wafers is increasing year by year, and the demand for high-purity quartz sand materials for producing silicon wafers is also increasing day by day. In particular, in the production process of photovoltaic and semiconductor silicon wafers, high-purity quartz sand is an indispensable key material, and its quality and supply stability have an important influence on the quality and yield of quartz crucibles, and is a serious bottleneck problem in the field of semiconductor manufacturing. It is necessary to vigorously develop high-purity quartz sand localization, and the whole process of quartz sand production does not rely on imports. At present, the source of high-purity quartz sand mainly has two forms, one is the purification of natural quartz ore, and the other is the synthesis of high-purity quartz sand by chemical method. Due to the small amount of high-purity quartz sand ore resources and the complex impurity content, the purification is difficult, which leads to a complex process of producing high-purity quartz sand from domestic ore, resulting in high requirements for equipment. Purification of imported ore from abroad will lead to high production cost of quartz sand, resulting in rising cost of the whole industry chain, which is not conducive to the localization of silicon wafers. The synthesis of quartz sand directly synthesizes high-purity quartz sand from chemical raw materials, ensures the continuous output of high quality, and is not limited by region, ore source and impurity removal process.

[0003] White carbon black powder is mainly composed of gas phase SiO2 nanoparticles, and its appearance is white fine flocculent powder, odorless, non-toxic and non-polluting, and its particle size is below 100 nm. The industrial synthesis of gas phase white carbon black is mainly composed of high-temperature reaction of by-products of industrial reagents such as SiCl4 or CH3SiCl3 for producing Si and gas composed of hydrogen and oxygen, to obtain high-purity gas phase SiO2 (purity > 99.8%) ultrafine powder. The synthesis process of white carbon black is simple, the raw material cost is relatively low, and it is a relatively inexpensive industrial SiO2 raw material. Using white carbon black as a raw material for synthesizing quartz sand can effectively reduce the production cost of synthetic quartz sand, provide long-term stable supply of raw materials, and is an ideal raw material for synthesizing quartz sand. White carbon black is treated by acid washing, cold pressing, heat treatment, crushing and screening processes, and the heat treatment process is the key step for densification of white carbon black, so it is necessary to explore the optimal densification heat treatment process parameters.

[0004] The traditional one-step calcination process (heating-keeping- cooling) is accompanied by rapid grain growth during the heating process, leading to grain coarsening. Due to the uneven heating of particles at different positions, the inconsistent grain growth rate causes uneven particle growth during the heat treatment process, especially in the later stage of calcination, it is difficult to obtain quartz sand particles with high density and uniform organization. The two-step heat treatment process separates the grain boundary diffusion and grain boundary migration processes by controlling different heat treatment temperature ranges, i.e. separating the sintering densification and grain growth stages. Currently, there are two heating methods for the two-step heat treatment process. The first method is to obtain a dense material by low-temperature long-time heat preservation and then to improve the bonding force and control the microstructure by high-temperature short-time sintering. The second method is to provide a higher activation energy required for sintering by high-temperature short-time sintering, and then to inhibit grain growth and achieve densification by low-temperature long-time sintering. The present application simultaneously uses these two heat treatment methods to treat white carbon black powder, and compares and analyzes the effects of the two heat treatment methods on the sintering densification behavior. SUMMARY

[0005] The present application solves the problems of the existing industrial-grade white carbon black purification, dehydroxylation, densification and other processes for preparing high-purity amorphous quartz sand, and proposes the following technical solutions:

[0006] [1] A method for preparing high-purity amorphous quartz sand by two-step heat treatment of white carbon black, comprising the steps of:

[0007] S1, soaking white carbon black powder in a mixed acid solution of hydrofluoric acid and hydrochloric acid, then taking out the solid and washing and drying to obtain high-purity white carbon black powder;

[0008] S2, pressing (specifically, cold pressing, etc.) the high-purity white carbon black powder into a white carbon black block;

[0009] S3, pre-heating the white carbon black block to remove residual water, hydroxyl groups and carbon-based impurities, and obtaining a dehydroxylated sample;

[0010] S4, performing two-step heat treatment of high temperature followed by low temperature on the dehydroxylated sample, and cooling to obtain a high-density quartz block; in the two-step heat treatment, the high temperature refers to heating to 1200 ℃ first, and the low temperature refers to heating to 1200 ℃ without holding and then directly cooling to 1000-1100 ℃ for 2-10 h;

[0011] S5, crushing the high-density quartz block to obtain high-purity amorphous quartz sand.

[0012] In step S1, the molar ratio of hydrofluoric acid to hydrochloric acid in the mixed acid solution can be 1:1-5, such as 1:1, 1:2, 1:3, 1:4, 1:5, etc.

[0013] In step S1, the mass ratio of the white carbon black powder to the mixed acid solution can be 1:1-3, for example, 1:1, 1:2, 1:3, etc.

[0014] In step S1, the soaking time can be 6-48 h, further 10-20 h.

[0015] In step S1, the washing can specifically include repeatedly washing several times with deionized water and ethanol and suction filtration.

[0016] In step S1, the drying can be vacuum drying, further, the vacuum drying temperature can be 115-120 ℃, and the vacuum drying time can be 24-72 h.

[0017] In step S2, the pressing pressure can be 100-400 MPa.

[0018] In step S3, the white carbon black block can be preheated at a temperature increasing rate of 5-10 ℃ / min, the preheating temperature can be 400-600 ℃, and the holding time can be 2-10 h.

[0019] In step S4, the temperature increasing and decreasing rates can be independently 2-10 ℃ / min, for example, 2 ℃ / min, 3 ℃ / min, 5 ℃ / min, 10 ℃ / min, etc.

[0020] In step S4, the sample after the removal of hydroxyl groups can be subjected to two-step heat treatment of high temperature followed by low temperature in a negative pressure inert environment at a pressure of-0.1 MPa or less. The inert environment refers to an atmosphere environment that does not participate in the reaction, for example, nitrogen and / or rare gas (such as argon, etc.) atmosphere environment. The negative pressure can be achieved by inert gas washing and vacuumization. The inert gas refers to a gas that does not participate in the reaction, for example, nitrogen and / or rare gas (such as argon, etc.).

[0021] In step S5, the particle size of the high-purity amorphous quartz sand can be 50-250 μm, further can be classified into every 50 μm screening interval.

[0022] In step S5, the true density of the high-purity amorphous quartz sand can be 2.23-2.27 g / cm 3 .

[0023] In step S5, the SiO2 purity in the high-purity amorphous quartz sand is greater than 4N8.

[0024] [2] The high-purity amorphous quartz sand prepared by the method of [1].

[0025] [3] Use of the high-purity amorphous quartz sand according to [2] in the manufacture of a quartz crucible. Furthermore, the quartz crucible can be used to prepare single crystal silicon.

[0026] The method of the present invention first involves pickling silica using a mixture of hydrofluoric acid and hydrochloric acid to remove metallic impurities from the particles. Subsequently, the pickled precipitate is washed and dried multiple times to obtain high-purity silica powder. The high-purity silica powder is then pressed to form a block, increasing the sintering neck formation energy between the particles. A two-step, staged calcination heat treatment process is employed, densifying the silica using a high-temperature followed by a low-temperature heating process, ultimately yielding a high-density quartz block in the amorphous SiO2 state. Finally, a crushing step is performed to produce high-purity amorphous quartz sand.

[0027] The preparation technology proposed in this paper efficiently utilizes silica, an industrial byproduct. By implementing acid purification and high-temperature calcination densification techniques, the purity of silica is significantly improved. While maintaining the amorphous SiO2 state, the density is maximized, achieving the performance indicators of photovoltaic-grade quartz sand, reducing environmental pollution and minimizing silicon resource waste. The resulting high-purity amorphous quartz sand is suitable for making quartz crucibles.

[0028] The technology of the present invention is characterized by its simple operation, high cost-effectiveness, and ease of large-scale production. Furthermore, the technology of the present invention solves the problem of recycling white carbon black, a byproduct of silane production in existing technologies, improves the utilization rate of silicon resources, and can produce high-purity quartz sand with high economic value. This has important application value in industries such as semiconductors, optoelectronics, and photovoltaics.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention uses staged heat treatment of silica powder to produce highly dense, high-purity amorphous quartz sand. This primarily increases the particle size and density of amorphous nano-sized SiO2 particles, meeting the application standards for industrial-grade quartz sand. Compared to the traditional one-step sintering process, the two-step sintering process exhibits significant advantages in particle densification. It not only enhances the formation of sintering necks between particles, promoting particle growth, but also improves the efficiency of removing pores within the particles, thereby increasing the internal density of the sand grains. Furthermore, compared to traditional high-temperature sintering methods, the two-step sintering method can achieve high density at lower temperatures, thereby saving energy and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The X-ray diffraction (XRD) patterns of silica after heat treatment at different temperatures;

[0032] Figure 2 Metallographic photos of silica after heat treatment at different temperatures;

[0033] Figure 3 XRD pattern and metallographic photo after heat treatment of Example 1;

[0034] Figure 4 XRD pattern and metallographic photo after heat treatment of Example 2;

[0035] Figure 5 XRD pattern and metallographic photo after heat treatment of Example 3;

[0036] Figure 6 XRD pattern and metallographic photo after heat treatment of Example 4;

[0037] Figure 7 XRD pattern and metallographic photo after heat treatment of Example 5;

[0038] Figure 8 Comparison chart of true density of each example after two-step heat treatment, original white carbon black and commercial amorphous quartz sand. DETAILED DESCRIPTION

[0039] The application will be further described below in conjunction with the drawings and specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application.

[0040] Example 1:

[0041] Step 1: 20 g of white carbon black powder was weighed by an electronic balance into 20 mL of mixed acid solution of hydrochloric acid and hydrofluoric acid with a mole ratio of 1:1, and the particles were slowly stirred to mix with the acid solution uniformly. After acid immersion for 20 h, the upper layer of acid solution was removed, and the lower layer of white suspension was filtered by a sand core funnel, and then repeatedly washed by deionized water and ethanol to obtain a white powder, which was vacuum dried at 120 ℃ for 48 h to obtain a white high-purity SiO2 powder (high-purity white carbon black powder);

[0042] Step 2: The dried white powder was moved into a tablet columnar mold with a diameter of 20 mm, and was pressed into a cylindrical high-purity SiO2 block under a pressure of 400 MPa;

[0043] Step 3: The high-purity SiO2 block was moved into a corundum crucible and placed in a tube furnace, and was set to a temperature rising rate of 10 ℃ / min to rise to 600 ℃ for 2 h, and then cooled to room temperature, so as to remove the residual moisture and most of the hydroxyl groups and carbon-based impurities in the block.

[0044] Step 4: High-purity nitrogen was first introduced into the corundum tube, and then the gas in the tube was pumped out by a mechanical pump, so that the pressure in the tube was maintained at -0.1 MPa. The above operation was repeated three times to clean the air in the corundum tube completely, and finally the pressure in the tube was maintained at negative pressure -0.1 MPa.

[0045] Step 5: The SiO2 block obtained in step 3 is densified by two-step calcination, first heated to 1000℃ at a heating rate of 10 ℃ / min, then heated to 1200℃ at a heating rate of 5 ℃ / min, then directly cooled to 1000℃ at a cooling rate of 5 ℃ / min without holding, and then cooled to 300℃ at a cooling rate of 5 ℃ / min, and then cooled to room temperature, to obtain a high-density SiO2 block.

[0046] Step 6: The high-density SiO2 block is crushed, ground, and sieved to obtain quartz sand particles with particle sizes ranging from 50 to 100 μm, 100 to 150 μm, 150 to 200 μm, and 200 to 250 μm, and the SiO2 purity is greater than 4N8.

[0047] Example 2:

[0048] The difference from Example 1 is only in step 5: The SiO2 block obtained in step 3 is densified by two-step calcination, first heated to 1000℃ at a heating rate of 10 ℃ / min, then heated to 1200℃ at a heating rate of 5 ℃ / min, then directly cooled to 1100℃ at a cooling rate of 5 ℃ / min without holding, and then cooled to 300℃ at a cooling rate of 5 ℃ / min, and then cooled to room temperature, to obtain a high-density SiO2 block. The rest is the same. The SiO2 purity of the obtained quartz sand particles is greater than 4N8.

[0049] Example 3:

[0050] The difference from Example 1 is only in step 5: The SiO2 block obtained in step 3 is densified by two-step calcination, first heated to 1000℃ at a heating rate of 10 ℃ / min, then heated to 1400℃ at a heating rate of 5 ℃ / min, then directly cooled to 1200℃ at a cooling rate of 5 ℃ / min without holding, and then cooled to 300℃ at a cooling rate of 5 ℃ / min, and then cooled to room temperature, to obtain a high-density SiO2 block. The rest is the same. The SiO2 purity of the obtained quartz sand particles is greater than 4N8.

[0051] Example 4:

[0052] The difference from Example 1 is only in step 5: the SiO2 block obtained in step 3 is subjected to densification heat treatment by two-step calcination, first heated to 800 ℃ at a heating rate of 10 ℃ / min, and then heated to 1000 ℃ at a heating rate of 5 ℃ / min for 10 h, after the reaction is completed, cooled to room temperature after being reduced to 300 ℃ at a cooling rate of 5 ℃ / min, to obtain a high-density SiO2 block. The rest is the same. The SiO2 purity of the obtained quartz sand particles is greater than 4N8.

[0053] Example 5:

[0054] The difference from Example 1 is only in step 5: the SiO2 block obtained in step 3 is subjected to densification heat treatment by two-step calcination, first heated to 800 ℃ at a heating rate of 10 ℃ / min, and then heated to 1100 ℃ at a heating rate of 5 ℃ / min for 10 h, after the reaction is completed, cooled to room temperature after being reduced to 300 ℃ at a cooling rate of 5 ℃ / min, to obtain a high-density SiO2 block. The rest is the same. The SiO2 purity of the obtained quartz sand particles is greater than 4N8.

[0055] Comparative Example:

[0056] Step 1: same as step 1 of Example 1.

[0057] Step 2: move the high-purity SiO2 powder into a corundum crucible and place it in a tube furnace, set the temperature to 600 ℃ at a heating rate of 10 ℃ / min, and then cool to room temperature after being kept for 2 h, to remove the residual water and most of the hydroxyl groups and carbon-based impurities in the block.

[0058] Step 3: the SiO2 powder obtained in step 2 is subjected to densification heat treatment by two-step calcination, 5 g of sample is taken as a group, and 4 groups of samples are taken.

[0059] The first group of samples is heated to 1000 ℃ at a heating rate of 10 ℃ / min, and then heated to 1100 ℃ at a heating rate of 5 ℃ / min for 2 h, after the reaction is completed, cooled to room temperature after being reduced to 300 ℃ at a cooling rate of 5 ℃ / min, to obtain a white powder sample.

[0060] The second group of samples is heated to 1000 ℃ at a heating rate of 10 ℃ / min, and then heated to 1200 ℃ at a heating rate of 5 ℃ / min for 2 h, after the reaction is completed, cooled to room temperature after being reduced to 300 ℃ at a cooling rate of 5 ℃ / min, to obtain a white powder sample.

[0061] The sample of the 3rd group was heated to 1000 °C at a heating rate of 10 °C / min, then heated to 1300 °C at a heating rate of 5 °C / min and kept for 2 h, after the reaction was completed, it was cooled to 300 °C at a cooling rate of 5 °C / min and then cooled to room temperature, to obtain a white powder sample.

[0062] The sample of the 4th group was heated to 1000 °C at a heating rate of 10 °C / min, then heated to 1400 °C at a heating rate of 5 °C / min and kept for 2 h, after the reaction was completed, it was cooled to 300 °C at a cooling rate of 5 °C / min and then cooled to room temperature, to obtain a white powder sample.

[0063] Characterization analysis:

[0064] The original white carbon black without pressure was subjected to high-temperature calcination by one-step heat treatment process. The sample after heat treatment was subjected to XRD phase characterization, and the results are shown in Figure 1 When the white carbon black powder was heated to 1100 °C and 1200 °C, the XRD diffraction peak was located at 22° position, showing a standard amorphous peak shape, which was consistent with the standard amorphous SiO2(JCPDS 29-0085) card, proving that the white carbon black powder was still amorphous structure when heated to 1200 °C. When the heat treatment temperature was increased to 1300 °C, the XRD results showed that the crystal structure of the white carbon black was phase transition, and the diffraction peak position was consistent with the standard cristobalite (JCPDS 39-1425) card. Further increasing the heat treatment temperature to 1400 °C, the XRD test results still showed cristobalite phase. Figure 2 The optical photos of the four groups of samples are shown in Figure 2 (a) and Figure 2 (b) are the optical photos of the white carbon black powder after heat treatment at 1100 °C and 1200 °C, and the results show that before phase transition, the particle size is uneven, highly agglomerated and loose. Figure 2 (c) and Figure 2 (d) are the optical photos of the white carbon black powder after heat treatment at 1300 °C and 1400 °C, and the test results show that after phase transition temperature treatment, the white carbon black particles are agglomerated into blocks, the particle size is 200-600 μm, the distribution is uneven, there is obvious grain boundary and the structure is loose. High heat treatment temperature leads to the phase transition of white carbon black powder from amorphous phase to cristobalite phase, and micro-pores are formed in the phase transition process, resulting in loose structure of the particles after phase transition, reducing the density of quartz sand. At the same time, the existence of cristobalite phase in the sand particles will affect the performance of the pulled silicon ingot in the application of high-purity quartz crucible, mainly due to the fact that the existence of cristobalite phase in the crucible will lead to the epitaxial growth of silicon according to the cristobalite lattice, forming polycrystalline silicon and affecting the preparation of single crystal silicon. Therefore, it is necessary to avoid the phase transition to cristobalite during heat treatment, and the heat treatment temperature should be limited below 1200 °C.

[0065] Compared to traditional one-step heat treatment processes, the "low temperature first, high temperature" and "high temperature first, low temperature" heat treatment methods are more conducive to improving the sintering neck formation of nano-sized particles, promoting the migration of bubbles from the sand grains to the exterior, and increasing the density of the sand grains to meet the application requirements of commercial amorphous quartz sand. Purified silica powder was cold pressed at 400 MPa and then subjected to a two-step heat treatment. For the "low temperature first, high temperature" heating method, the low temperature stage is maintained at a low temperature to facilitate the migration of remaining hydroxyl groups to the exterior of the sand grains, while the high temperature stage promotes pore closure and completes densification. For the other "high temperature first, low temperature" heating method, the high temperature stage is conducive to activating the sintering neck properties between particles, accelerating the volume diffusion rate between particles and rapidly increasing the relative density of the bulk. When the temperature is reduced to a low temperature for maintenance, the sintering neck size exceeds the particle radius, and the pores between the particles gradually close, completing the particle densification.

[0066] The cold pressed silica blocks were heat treated at 1200 °C first and then at 1000 °C ( Figure 3 , Example 1), first high temperature 1200 ℃ and then low temperature 1100 ℃ heat treatment ( Figure 4 , Example 2), first high temperature 1400 ℃ and then low temperature 1200 ℃ heat treatment ( Figure 5 , Example 3), first heat treatment at low temperature 800 ℃ and then at high temperature 1000 ℃ ( Figure 6 , Example 4), first heat treatment at low temperature 800 ℃ and then at high temperature 1200 ℃ ( Figure 7 , Example 5). XRD phase analysis was performed on the samples of each embodiment, and the test results showed that the diffraction peaks of the samples measured in Example 1, Example 2, Example 4, and Example 5 were at around 22°, showing a standard amorphous peak morphology, which was consistent with the standard amorphous SiO2 (JCPDS 29-0085) card, proving that when the reaction temperature was around 1000°C, the test sample was still in an amorphous state. When the reaction temperature was 1200°C, the sample XRD results showed a mixed phase of amorphous and cristobalite, and its diffraction peaks were consistent with the standard amorphous SiO2 (JCPDS 29-0085) card and the standard cristobalite (JCPDS 39-1425) card. It was proved that the heat treatment method of first high temperature 1400°C and then low temperature 1200°C would induce phase transformation and could not meet the subsequent application requirements. In addition, metallographic structure analysis was performed on the samples of the five embodiments, and the results showed that the sample of Example 3 ( Figure 5 (b) After heat treatment at 1400 °C and then at 1200 °C, obvious grain boundaries appeared inside the block, proving that the treatment process caused phase transformation of the SiO2 block. Figure 3 (b) The test results of the sample showed that the block surface was smooth and the structure was uniform, with no obvious grain precipitation. Figure 4(b) The test sample results show that the bulk has obvious grain precipitation, and the grain size is 10-50 pm. Figure 6 (b) The test sample results show that the bulk has obvious grain precipitation, and the grain size is 10-50 pm. Figure 7 (b) The test sample results show that the bulk has obvious grain precipitation, and the grain size is 10-50 pm.

[0067] In order to characterize the density of the sample, the density of the sample, the white carbon black powder and the commercial amorphous quartz sand were tested, and the test results are shown in Table 1. Figure 8 The results show that the true density of the white carbon black powder without heat treatment is 2.1302 g / cm 3 , which is lower than the theoretical true density of amorphous SiO2 2.2 g / cm 3 . The true density of the sample obtained by two-step heat treatment is 2.2658 g / cm 3 , which has reached the theoretical density of amorphous SiO2. The test result is much higher than that of the untreated white carbon black powder sample, and is higher than the true density of the commercial amorphous quartz sand, indicating that the heat treatment process can effectively exclude the hydroxyl group inside the SiO2 bulk and promote the closure of the pores to achieve the densification requirement. With the increase of the reaction temperature, the density test result of Example 2 is 2.3083 g / cm 3 , which is close to the theoretical density of cristobalite (2.32 g / cm 3 ), indicating that the crystal structure has been partially converted to cristobalite. The true density test results of Example 4 and Example 5 are both 2.29 g / cm 3 , which proves that there is a small part of the particles inside them have been converted to cristobalite, which will reduce the application quality of the subsequent quartz crucible. The above results show that the heat treatment process of "high temperature first and then low temperature" can effectively improve the sintering neck performance between particles, accelerate the volume diffusion rate between particles, and quickly improve the relative density of the bulk. In the low-temperature holding stage, the sintering neck size exceeds the particle radius, and the pores between the particles will gradually close to complete the densification heat treatment. The heat treatment time of "high temperature first and then low temperature" is significantly shorter than that of "low temperature first and then high temperature". The "high temperature first" process has no holding time, which not only reduces the excessive consumption of energy, but also effectively inhibits the phase transition of SiO2 bulk to cristobalite, and reaches the application standard of commercial amorphous quartz sand, which is especially suitable for making quartz crucible for single crystal silicon preparation.

[0068] In addition, it should be understood that, after reading the above description of the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application.

Claims

1. A method for preparing high purity amorphous quartz sand from heat-treated white carbon black by a two-step process, characterized in that, The method comprises the steps of: S1, soaking white carbon black powder in a mixed acid solution of hydrofluoric acid and hydrochloric acid, taking out the solid and cleaning and drying to obtain high-purity white carbon black powder; S2, pressing the high-purity white carbon black powder into a white carbon black block; S3, pre-heating the white carbon black block to remove residual water, hydroxyl groups and carbon-based impurities, to obtain a sample after removal of hydroxyl groups; S4, performing two-step heat treatment of high temperature and then low temperature on the sample after removal of hydroxyl groups, and cooling to obtain a high-density quartz block; in the two-step heat treatment, the high temperature refers to heating to 1200℃ first, and the low temperature refers to heating to 1200℃ without holding and directly cooling to 1000-1100℃ for holding for 2-10h; S5, crushing the high-density quartz block to obtain high-purity amorphous quartz sand.

2. The method of claim 1, wherein, In step S1: In the mixed acid solution, the molar ratio of hydrofluoric acid to hydrochloric acid is 1:1-5; The mass ratio of the white carbon black powder to the mixed acid solution is 1:1-3; The soaking time is 6-48h; The cleaning specifically comprises repeatedly cleaning several times with deionized water and ethanol and then suction filtration; The drying is vacuum drying, the vacuum drying temperature is 115-120℃, and the vacuum drying time is 24-72h.

3. The method of claim 1, wherein, In step S2, the pressing pressure is 100-400MPa.

4. The method of claim 1, wherein, In step S3, the white carbon black block is pre-heated at a temperature increasing rate of 5-10℃ / min, the pre-heating temperature is 400-600℃, and the holding time is 2-10h.

5. The method of claim 1, wherein, In step S4, the temperature increasing and decreasing rates are independently 2-10℃ / min.

6. The method according to claim 1 or 5, characterized in that, In step S4, the sample after removal of hydroxyl groups is subjected to two-step heat treatment of high temperature and then low temperature in a negative pressure inert environment at a pressure of-0.1MPa or less.

7. The method of claim 1, wherein, In step S5: The particle size of the high-purity amorphous quartz sand is 50-250μm, and the sand is further classified into classification intervals with an interval of 50μm; The high-purity amorphous quartz sand has a true density of 2.23-2.27 g / cm 3 ; The SiO2 purity in the high-purity amorphous quartz sand is greater than 4N8.

8. The high-purity amorphous quartz sand prepared by the method according to any one of claims 1-7.

9. The high-purity amorphous quartz sand according to claim 8 is used for manufacturing a quartz crucible.

10. Use according to claim 9, characterized in that, The quartz crucible is used for preparing single crystal silicon.

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