High-purity quartz sand and method for producing the same

Abstract

The application discloses high-purity quartz sand and a preparation method thereof, relates to the technical field of inorganic materials, and discloses that the content of U elements in the high-purity quartz sand is less than 0.5 ppb, the content of Th elements is less than 1 ppb, and the total content of Al, B, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Ti and Zn elements in the high-purity quartz sand is less than 40 ppm; compared with the prior art, the high-purity quartz sand obtained by the application has lower contents of U and Th elements in addition to Al, B, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Ti and Zn elements, and the high-purity quartz sand is used to manufacture a chip, so that soft errors caused by radioactive elements in the operation process of the chip are reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of inorganic materials, in particular to high-purity quartz sand and a preparation method thereof. BACKGROUND

[0002] Quartz (SiO2) is an oxide of silicon with a framework structure, and is a general term for alpha-quartz (low-temperature quartz, trigonal system) and beta-quartz (high-temperature quartz, hexagonal system) and is widely distributed in nature. The transition temperature of alpha-quartz and beta-quartz is 573 DEG C, and when no specification is given, the so-called quartz usually refers to alpha-quartz.

[0003] High-purity quartz sand generally refers to quartz with a silicon dioxide content of greater than 99.9%. According to the purity of SiO2, high-purity quartz products can be divided into four grades, namely, high-end ω (SiO2) ≥ 99.998% (4N8), medium-high-end ω (SiO2) ≥ 99.995% (4N5), medium-end ω (SiO2) ≥ 99.99% (4N), and low-end ω (SiO2) ≥ 99.9% (3N) (see "Concept of High-Purity Quartz and Grade Division of Raw Materials", Mineral Protection and Utilization, October 2022, No. 5). However, natural quartz without processing cannot meet the quality requirements of high-purity quartz. That is, high-purity quartz is a quartz sand product with extremely high SiO2 purity, which is obtained by processing natural quartz ore as raw material through a relatively complex purification process. At the same time, high-purity quartz sand also has strict requirements on product particle size and mineral phase. Therefore, even if the non-crystalline silicon dioxide such as silicon powder has a very high purity, it is not high-purity quartz sand.

[0004] Impurity elements in natural quartz sand mainly include Al, K, Na, Li, Ca, Cu, B, Fe, Mn, Co, Ti, P, etc. Among these impurity elements, monovalent and divalent ions exist in the form of interstitial atoms at charge unbalanced defects in the quartz lattice, as compensation charges, and trivalent, tetravalent, and pentavalent ions (isomorphous impurities) mainly exist in the lattice. In order to remove the impurities in the quartz sand, various processes have been proposed by those skilled in the art. Zhang Haiqi et al. in the article "Research Progress of Impurity Characteristics in High-purity Quartz and Deep Chemical Purification Technology" (Mineral Protection and Utilization, August 2022, No. 4) records the existing quartz sand purification technology. At present, the main methods for purifying natural quartz sand include physical and chemical methods. Physical purification mainly includes color selection, scrubbing, gravity separation, magnetic separation, and flotation processes, but gas-liquid inclusions and isomorphous impurities in the lattice are the main sources of impurities, and these impurities are the key factors that restrict the preparation of high-purity quartz products. Physical purification cannot remove these impurities, and chemical deep purification is required. Chemical deep purification mainly includes acid (alkali, salt) treatment and heat treatment. Acid (alkali, salt) treatment mainly removes impurities in the form of inclusions on the surface of quartz sand particles or embedded in the particles, and heat treatment mainly uses high temperature to remove inclusions or isomorphous impurities in the lattice, such as high-temperature cracking and chlorination roasting. Compared with physical purification methods, chemical purification is complex and has high cost, but in the preparation of high-purity quartz, chemical treatment is the most effective and essential method.

[0005] However, the existing technology has the following problems:

[0006] 1) Quartzite needs to be subjected to acid washing, flotation, magnetic separation, gravity separation, high-temperature water quenching, chlorination roasting, and other steps before being processed into high-purity quartz sand. The process is long, the acid washing efficiency is low and complex, and foreign impurities such as iron, sodium, aluminum, and other metal elements are easily introduced during the impurity removal process.

[0007] 2) The concentration of hydrofluoric acid, hydrochloric acid, and nitric acid used in acid washing is high, and the amount used is large. A large amount of fluorine-containing and chlorine-containing wastewater is generated during acid washing, increasing the treatment cost.

[0008] 3) For isomorphous impurities with low content, such as radioactive U and Th elements, the above acid washing removal effect is not good. SUMMARY

[0009] The technical problem to be solved by the present application is to provide a high-purity quartz sand and a preparation method thereof. The impurity element content of the high-purity quartz sand is low, and the preparation method is simple, easy to operate, and low in production cost.

[0010] The technical problem to be solved by the present application is solved by the following technical solution:

[0011] One of the purposes of the present application is to provide a high-purity quartz sand, the content of U element in the high-purity quartz sand is less than 0.5 ppb, and the content of Th element is less than 1 ppb.

[0012] The total content of Al, B, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Ti, Zn elements in the high-purity quartz sand is less than 40 ppm.

[0013] The second purpose of the present application is to provide a preparation method of high-purity quartz sand, comprising the following steps:

[0014] (1) weighing boric acid and silicon dioxide, and mixing uniformly;

[0015] (2) putting the mixture obtained in step (1) into a clean container, high-temperature calcining to melt the silicon dioxide, and then cooling to make the silicon dioxide precipitate from the boric acid;

[0016] (3) taking out the material obtained in step (2) after cooling, grinding and dispersing, and washing the boric acid in the material with pure water until EC < 10 us / cm, drying to obtain high-purity quartz sand.

[0017] The third purpose of the present application is to provide a high-purity quartz sand obtained by the preparation method.

[0018] The beneficial effects of the present application are:

[0019] 1、The high-purity quartz sand obtained by the present application has lower contents of U and Th elements in addition to Al, B, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Ti, Zn and other elements, and is beneficial to reduce soft errors caused by radioactive elements in the operation process of the chip.

[0020] 2、The present application uses silicon dioxide and boric acid (white powder weak acid, melting point 169℃) as raw materials, and removes impurity elements by precipitating silicon dioxide from boric acid after melting, to obtain high-purity quartz sand with high purity. Compared with the prior art (acid washing, flotation, magnetic separation, gravity separation, high-temperature water quenching, chlorination roasting and other steps), the preparation process provided by the present application is simple and easy to operate, avoids the risk of introducing exogenous impurities due to too long process route, and the waste liquid is only boric acid aqueous solution, which is easy to recover.

[0021] 3、From the impurity removal efficiency, compared with the prior art, the present application can remove multiple impurity elements at the same time by using a process, which is more efficient. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The XRD pattern of the sample obtained in Example 5. DETAILED DESCRIPTION

[0023] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific embodiments.

[0024] The present application provides a high-purity quartz sand, wherein the content of U element is less than 0.5 ppb and the content of Th element is less than 1 ppb.

[0025] Preferably, the content of U element in the high-purity quartz sand is less than 0.1 ppb and the content of Th element is less than 0.1 ppb.

[0026] The total content of Al, B, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Ti and Zn elements in the high-purity quartz sand is less than 40 ppm.

[0027] The present application also provides a preparation method of high-purity quartz sand, comprising the following steps:

[0028] (1) weighing boric acid and silicon dioxide and mixing them uniformly;

[0029] (2) putting the mixture obtained in step (1) into a clean container, high-temperature calcining to melt the silicon dioxide, and then cooling to make the silicon dioxide precipitate from the boric acid;

[0030] (3) taking out the material obtained in step (2) after cooling, grinding and dispersing, and washing the boric acid in the material with pure water until EC < 10 us / cm, drying to obtain high-purity quartz sand.

[0031] Preferably, the silicon dioxide in step (1) is at least one of amorphous silicon dioxide and crystalline silicon dioxide.

[0032] Preferably, the purity of the silicon dioxide in step (1) is greater than 99%.

[0033] Further preferably, the silicon dioxide in step (1) is silicon dioxide with a purity greater than 99.99%.

[0034] Preferably, the purity of the boric acid in step (1) is greater than 99%.

[0035] Preferably, the mass ratio of the silicon dioxide to the boric acid in step (1) is (15-35) : (65-85).

[0036] Preferably, the high-temperature calcining in step (2) is heat preservation at 1000℃ or above for 2-10 h.

[0037] Preferably, the cooling in step (2) is heat preservation at 400-700℃ for 2-10 h.

[0038] Preferably, the temperature of the pure water in step (3) is above 80℃. Using hot water to clean the material is more beneficial to the dissolution of boric acid and reduces the amount of water used.

[0039] The present application also provides high-purity quartz sand obtained by the above preparation method.

[0040] The following raw materials are used in the embodiments of the present application:

[0041] The D50 of the silicon powder A is 1.4 μm. 50 The particle size is 1 μm, the specific surface area is 13 m 2 / g, and the crystal is amorphous.

[0042] The D50 of the silicon powder B is 1.4 μm. 50 The particle size is 1.4 μm, the specific surface area is 11 m 2 / g, and the crystal is amorphous.

[0043] The purity of the boric acid is 99%.

[0044] Example 1

[0045] 15 g of the silicon powder A and 85 g of boric acid are weighed, mixed uniformly, and then loaded into a 500 mL platinum crucible, and the crucible is placed in a muffle furnace. The muffle furnace is first heated to 1200℃ for 2 h, and then the muffle furnace is cooled to 500℃ for 2 h. The muffle furnace is naturally cooled to room temperature, the material is taken out, ground to a particle size of 100-150 μm, and then washed with 80℃ pure water until the EC is less than 10 us / cm, and then dried to obtain a sample.

[0046] Example 2

[0047] 25 g of the silicon powder A and 75 g of boric acid are weighed, mixed uniformly, and then loaded into a 500 mL platinum crucible, and the crucible is placed in a muffle furnace. The muffle furnace is first heated to 1200℃ for 2 h, and then the muffle furnace is cooled to 500℃ for 2 h. The muffle furnace is naturally cooled to room temperature, the material is taken out, ground to a particle size of 100-150 μm, and then washed with 80℃ hot pure water until the EC is less than 10 us / cm, and then dried to obtain a sample.

[0048] Example 3

[0049] 35 g of the silicon powder A and 65 g of boric acid are weighed, mixed uniformly, and then loaded into a 500 mL platinum crucible, and the crucible is placed in a muffle furnace. The muffle furnace is first heated to 1200℃ for 2 h, and then the muffle furnace is cooled to 500℃ for 2 h. The muffle furnace is naturally cooled to room temperature, the material is taken out, ground to a particle size of 100-150 μm, and then washed with 80℃ hot pure water until the EC is less than 10 us / cm, and then dried to obtain a sample.

[0050] Example 4

[0051] Take 25 g of silicon powder A and 75 g of boric acid, mix them evenly, and then put them into a 500 mL platinum crucible, and place the crucible in a muffle furnace. First, raise the temperature of the muffle furnace to 1050°C and keep it for 10 h, and then lower the temperature of the muffle furnace to 700°C and keep it for 8 h. Let the muffle furnace cool down naturally to room temperature, take out the material, grind it to a particle size of 100-150 μm, and wash it with 90°C hot pure water until the EC is less than 10 us / cm, and then dry it to obtain the sample.

[0052] Example 5

[0053] Take 25 g of silicon powder B and 75 g of boric acid, mix them evenly, and then put them into a 500 mL platinum crucible, and place the crucible in a muffle furnace. First, raise the temperature of the muffle furnace to 1200°C and keep it for 2 h, and then lower the temperature of the muffle furnace to 500°C and keep it for 2 h. Let the muffle furnace cool down naturally to room temperature, take out the material, grind it to a particle size of 100-150 μm, and wash it with 80°C hot pure water until the EC is less than 10 us / cm, and then dry it to obtain the sample.

[0054] Example 6

[0055] Take 40 g of silicon powder A and 60 g of boric acid, mix them evenly, and then put them into a 500 mL platinum crucible, and place the crucible in a muffle furnace. First, raise the temperature of the muffle furnace to 1200°C and keep it for 2 h, and then lower the temperature of the muffle furnace to 500°C and keep it for 2 h. Let the muffle furnace cool down naturally to room temperature, take out the material, grind it to a particle size of 100-150 μm, and wash it with 80°C hot pure water until the EC is less than 10 us / cm, and then dry it to obtain the sample.

[0056] Example 7

[0057] Take 35 g of silicon powder A and 65 g of boric acid, mix them evenly, and then put them into a 500 mL platinum crucible, and place the crucible in a muffle furnace. Raise the temperature of the muffle furnace to 180°C (melting of boric acid) and keep it for 2 h, and then let the muffle furnace cool down naturally to room temperature, take out the material, grind it to a particle size of 100-150 μm, and wash it with 80°C hot pure water until the EC is less than 10 us / cm, and then dry it to obtain the sample.

[0058] Example 8

[0059] Take 100 g of silicon powder B and put it into a 500 mL platinum crucible, and place the crucible in a muffle furnace. First, raise the temperature of the muffle furnace to 1200°C and keep it for 2 h, and then lower the temperature of the muffle furnace to 500°C and keep it for 2 h. Let the muffle furnace cool down naturally to room temperature, take out the material, grind it to a particle size of 100-150 μm, and wash it with 80°C hot pure water until the EC is less than 10 us / cm, and then dry it to obtain the sample.

[0060] Example 9

[0061] 40 g of silicon powder A and 60 g of boric acid were weighed and mixed uniformly, and then loaded into a 500 mL platinum crucible, and the crucible was placed in a muffle furnace. The muffle furnace was first heated to 1600°C for 2 h, and then the muffle furnace was cooled to 600°C for 2 h. The muffle furnace was naturally cooled to room temperature, and the material was taken out, ground to a particle size of 100-150 μm, and washed with 80°C hot pure water until the EC was less than 10 us / cm, and then dried to obtain the sample.

[0062] The raw materials and the samples prepared in the above examples were tested for impurity content by ICP-OES method, and the results are shown in Tables 1-1 and 1-2:

[0063] Table 1-1 Test results of impurity content of raw materials and samples prepared (unit ppm)

[0064]

[0065] Table 1-2 Test results of impurity content of raw materials and samples prepared (unit ppm)

[0066]

[0067] Note: The detection limit of ICP is 1 ppb; the reference sample is ITOA-6 high purity quartz sand of Umicore.

[0068] The raw materials and the samples prepared in the above examples were tested for radioactive element content by ICP-MS method, and the results are shown in Table 2:

[0069] Table 2 Test results of radioactive element content of raw materials and samples prepared (unit ppt)

[0070]

[0071] Note: The detection limit of ICP-MS is 1 ppt; the reference sample is ITOA-6 high purity quartz sand of Umicore.

[0072] Comparing Examples 1, 2, 3, 6, 9, it can be seen that when the proportion of boric acid is reduced, the impurity element content is not effectively reduced under the condition of calcination temperature 1200°C; the impurity element content is significantly reduced by increasing the calcination temperature to 1600°C. The possible reason is that when the content of boric acid is low, the silicon powder A is not effectively melted, and after increasing the temperature, the silicon powder A is melted and crystallized during the subsequent cooling process, and the impurity elements are removed.

[0073] Comparing Examples 3 and 7, it can be seen that by only increasing the temperature to melt the boric acid, the silicon powder A is not melted, and the impurity element content cannot be effectively reduced.

[0074] Comparing Examples 5 and 8, it can be seen that directly calcining the raw material silicon micropowder B at high temperature without adding boric acid cannot effectively reduce the content of impurity elements.

[0075] Depend on Figure 1 It can be seen that after boric acid and silicon micro powder B are melted at high temperature, α-type silicon dioxide crystals precipitate after cooling.

[0076] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing high purity quartz sand, characterized by, The method comprises the following steps: (1) weighing boracic acid and silica, and mixing them uniformly; (2) putting the mixture obtained in step (1) into a clean container, and high-temperature calcining to make the silica melt, and then cooling to make the silica precipitate from the boracic acid; (3) taking out the material obtained in step (2) after cooling, grinding and dispersing, and washing the boracic acid in the material with pure water until the EC is less than 10 us / cm, and drying to obtain high-purity quartz sand; The mass ratio of the silica to the boracic acid in step (1) is (15-35):(65-85). The high-temperature calcining in step (2) is keeping the temperature above 1000℃ for 2-10 hours. The cooling in step (2) is cooling to 400-700℃ for 2-10 hours.

2. The production method according to claim 1, characterized by: The silica in step (1) is at least one of amorphous silica and crystalline silica.

3. The production method according to claim 1, wherein: The purity of the silica in step (1) is greater than 99%.

4. The production method according to claim 3, characterized by: The purity of the silica in step (1) is greater than 99.99%.

5. The production method according to claim 1, wherein: The purity of the boracic acid in step (1) is greater than 99%.

6. The production method according to claim 1, wherein: The temperature of the pure water in step (3) is above 80℃.

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