A method for preparing silicon dioxide nano-spherical powder by electrofusion

Abstract

The present invention discloses a method for preparing nano-spherical silica powder by electrofusion, belonging to the field of inorganic non-metallic materials technology. High-quality quartz is used as the main raw material, and carbon materials and metallic silicon are used as auxiliary raw materials. These are ground into a mixed powder in a certain proportion. The mixed powder is then pelletized, dried, and sieved before being placed in an electric arc furnace. At high temperature, the metallic silicon (Si) reacts with the quartz (SiO2) to generate SiO gas. The quartz (SiO2) then reacts with carbon at higher temperatures to generate SiO gas. The SiO gas escapes from the electric arc furnace and interacts with oxygen in the air to form nano-spherical silica. The nano-spherical silica powder is then collected using a modular collection device and placed in a sealed plastic barrel. The silica powder prepared by this method is high in purity and good in dispersibility, and is a nano-level ultrafine spherical powder that meets the packaging material requirements of ultra-large-scale integrated circuits.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a method for preparing silicon dioxide nano-spherical powder by electric melting. Background Art

[0002] Silica powder, also known as silicon micropowder, is a key raw material for the electronic information industry. Silicon powder can be divided into two categories: crystalline and amorphous. It is non-toxic, odorless, and non-polluting, and is an inorganic, non-metallic material. However, it requires specialized processing to be made into spherical silica powder that meets the requirements of electronic packaging materials. With the rapid development of the electronic information industry, large-scale and ultra-large-scale integrated circuits are placing increasingly stringent demands on silicon powder. These powders must be ultrafine, high purity, and low in radioactive elements, with particular emphasis on spherical particle shape. The higher the density of integrated circuits, the higher the purity, finer the particles, and more spherical the silicon powder required in epoxy molding compounds. Spherical silicon powder is partially used in large-scale integrated circuits, while exclusively used in ultra-large-scale and ultra-large-scale integrated circuits with integration densities exceeding 8M.

[0003] There are two known production methods for spherical silicon powder:

[0004] 1. Chemical wet method: Silicon-containing compounds are reacted in a solution, and the growth rate is controlled uniformly through various means, so that the reaction products grow as evenly as possible in all directions, ultimately obtaining a spherical product. Spherical silicon micropowder produced by chemical methods can achieve 100% sphericity, spheroidization rate, and amorphism rate, and can also achieve very low radioactivity indicators. However, due to its low bulk density, when epoxy resin molding compounds are made entirely of this spherical powder, the density, strength, and linear expansion rate of the molding compound are affected. Therefore, in actual use, the maximum addition is limited to 40%.

[0005] Second, physical dry methods. According to the principles of solid thermodynamics, the liquid phase is likely to appear first at the sharp corners of high-temperature particles. The liquid phase has a high surface tension at the gas-liquid-solid three-phase interface, automatically smoothing the particles into spheres and completing the spheroidization process. Physical methods such as high-temperature plasma melting, high-temperature melt spraying, and gas combustion flame melting can produce silicon micropowders down to the micron level. However, due to severe surface energy agglomeration, the required purity, fineness, and particle uniformity are difficult to achieve, and the technology is currently not fully mature.

[0006] The preparation of spherical silicon micropowder abroad usually adopts the high-temperature melt spraying method of silicon dioxide, the controlled hydrolysis of tetraethyl orthosilicate and silicon tetrachloride in the liquid phase, etc., but due to the complexity of the process, these methods are still only in the laboratory stage in China and have great technical difficulties. This is one of the important reasons why my country has not been able to produce high-quality spherical silicon micropowder so far. Moreover, for a long time, major international companies such as the United States, Japan, and Germany have been monopolizing the technology, market and price of semiconductor polysilicon materials, and have been imposing a technological blockade on my country.

[0007] Japan leads the world in nano-scale ultrafine quartz powder spheroidization technology. They have already invested in large-scale production and applied it to aerospace, ultra-large-screen electronic imaging, and large-scale integrated circuits. They are also the world's leading exporter of spherical silica powder. my country's main competitors in the nano-spherical silica powder market include Denka, Micron, and Tatsumori, all of which control 70% of the global market. Japan's Admatechs dominates the market for spherical silica powders below 1μm. In recent years, a few domestic companies, such as Huafei Electronics and Lianrui New Materials, have broken through foreign technological barriers and gradually mastered the gas combustion flame fusion method for producing high-purity, small-particle (above 5μm) spherical silica powders. The technology for producing spherical silica powders below 2μm using natural high-quality silica ores, such as quartz, has only recently developed in my country, leaving a significant gap compared to other countries. In particular, spheroidization technology for silica powders below 500nm is virtually nonexistent, typically synthesized using chemical methods, making mass production difficult.

[0008] In order to meet the requirements of ultra-large-scale integrated circuits for packaging materials, combined with the current domestic production technology level and product quality, according to international development trends, we should increase the technical development of spherical silicon powder and guide it towards high purity, ultrafineness, high dispersion, high uniformity and high sphericity. Summary of the Invention

[0009] To solve the above technical problems, the present invention addresses the requirements of large-scale and ultra-large-scale integrated circuits for silica micropowder, which require it to be not only ultrafine but also highly pure, and in particular, to be spherical in shape. The present invention provides a method for preparing nano-spherical silica powder, wherein the particle size of the nano-spherical powder is less than 100 nm, and the product obtained is of high purity, thus filling the gap in the spheroidization technology for silicon micropowder with a particle size of less than 500 nm.

[0010] The technical solution adopted in the present invention is:

[0011] A method for preparing silicon dioxide nano-spherical powder by electrofusion, comprising the following steps:

[0012] Step 1, co-grinding: Take 100 parts by weight of high-quality quartz powder, 15-22 parts by weight of carbon material, and 0.5-10 parts by weight of metallic silicon powder, grind them together in a grinder to less than 100 mesh, and obtain a co-grinded mixture;

[0013] Step 2: Disc granulation: put the co-ground mixture into the disc granulator, spray glue while rolling the disc to granulate into small balls of 2-12mm;

[0014] Step 3, drying the balls: Place the balls granulated in step 2 into a drying oven at 110°C for 24 hours;

[0015] Step 4: Screening the balls: Place the balls dried in step 3 into a vibrating screen to remove balls smaller than 2 mm and fine powder;

[0016] Step 5: Electric melting and gasification: The 2-12 mm dried pellets obtained after screening in step 4 are placed in an electric arc furnace and heated. A high-temperature chemical reaction generates SiO2 gas, which escapes from the electric arc furnace and interacts with oxygen in the air to form nano-spherical silicon dioxide.

[0017] Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic bucket.

[0018] Furthermore, the high-quality quartz powder in step 1 has a SiO2 content greater than 99.5%, a particle size less than 80 mesh, and is pickled to remove iron, so that the iron oxide content of the high-quality quartz powder is less than 0.01%.

[0019] Furthermore, the carbon material in step 1 has a fixed carbon C content greater than 99.5%, a particle size less than 80 mesh, and is pickled to remove iron, so that the iron oxide content of the carbon material is less than 0.01%.

[0020] Preferably, the carbon material is any one or more of petroleum coke, graphite, charcoal, bamboo charcoal, waste electrodes, and coke.

[0021] Furthermore, the metallic silicon powder in step 1 has a Si content greater than 99.5% and a particle size less than 80 mesh.

[0022] Preferably, the glue sprayed during the disc granulation in step 2 is silica sol, or any one of organic material glues selected from polyvinyl alcohol, polyethylene glycol, and yellow dextrin.

[0023] Furthermore, in step five, the electric arc furnace uses dense high-power electrodes, the electrode volume density is greater than 1.80 g / cm3, the operating voltage is 100-380 V, and the operating current is 4-15 KA.

[0024] Specifically, in the high-temperature chemical reaction that occurs when the electric arc furnace is powered on and heated in step 5, metallic silicon (Si) reacts with quartz at a temperature greater than 1400°C to generate SiO gas, activating the quartz lattice. When the temperature is further raised to 1765°C, SiO2 in the activated quartz begins to chemically react with carbon, accelerating the generation of SiO gas. The SiO gas escapes from the electric arc furnace and, during the escape process, encounters oxygen in the air to generate nano-spherical silicon dioxide.

[0025] Specifically, the combined collection equipment in step six is ​​a device formed by two series-connected ceramic multi-cyclone dust collectors connected to a pulse bag dust collector. Spherical powder larger than 3 microns is first removed by the two series-connected ceramic multi-cyclone dust collectors, and then finer nano-scale spherical powder is collected by the pulse bag dust collector and placed in a sealed plastic barrel.

[0026] Beneficial effects of the present invention:

[0027] 1. The present invention uses high-quality quartz with an SiO2 content greater than 99.5% as a main raw material, a carbon material with a fixed carbon content greater than 99.5%, and metallic silicon (Si) with an Si content greater than 99.5% as auxiliary raw materials. The high-quality quartz, the carbon material, and the metallic silicon are ground together in a certain proportion into a mixed powder. The mixed powder is pelletized, dried, and sieved, and then placed in an electric arc furnace. The metallic silicon (Si) reacts with the quartz (SiO2) at high temperature to generate SiO2 gas. The quartz (SiO2) and the carbon react with each other at high temperature to generate SiO2 gas. The two streams of SiO2 gas escape from the electric arc furnace and, during the escape process, interact with oxygen in the air to generate nano-spherical silicon dioxide. The nano-spherical silicon dioxide powder is collected using a specific combination of collection equipment and placed in a sealed plastic barrel. The silicon dioxide micropowder prepared by this method has high purity, good dispersibility, and is a nano-level ultrafine spherical powder that can meet the packaging material requirements of ultra-large-scale integrated circuits.

[0028] 2. The preparation method of the present invention can meet the requirements of ultra-large-scale and extra-large-scale integrated circuits for packaging materials, and innovates the two production methods of original spherical silicon micropowder (chemical wet method and physical dry method). The silicon dioxide nano-spherical powder prepared by the present invention achieves ultrafineness, high dispersibility, high uniformity and high sphericity, so that it can fully meet the requirements of large-scale and ultra-large-scale integrated circuits for silicon micropowder.

[0029] 3. The present invention adopts the process steps of disc granulation and ball making, and then drying and screening the balls. Firstly, it can prevent dust from flying when the material enters the furnace, affecting the purity of the collected gas and powder. Secondly, it can improve the air permeability of the material in the furnace, preventing the material from generating too much gas during the electric melting gasification process, which cannot be removed in time and causes the furnace to blow out, thereby affecting the purity of the collected gas and powder.

[0030] 4. The present invention adds metallic silicon powder as an auxiliary raw material. When the temperature is greater than 1400°C, metallic silicon Si reacts with quartz SiO2 to chemically generate SiO gas. The starting temperature for the high-temperature chemical reaction between quartz SiO2 and C to generate SiO gas is 1765°C. The high-temperature chemical reaction between metallic silicon Si and quartz SiO2 takes precedence over the high-temperature chemical reaction between quartz SiO2 and C. Firstly, the purity of the SiO gas generated by the high-temperature chemical reaction between quartz SiO2 and C can be supplemented to ensure that the silicon oxide content of the finally obtained silica nano-spherical powder is greater than 99.9%. Secondly, the quartz lattice can be activated, which is conducive to accelerating the high-temperature chemical reaction between quartz SiO2 and C.

[0031] 5. The present invention adopts a combined collection equipment, that is, a collection equipment composed of two series-connected ceramic multi-cyclone dust collectors connected to a pulse bag dust collector. The gas generated in the electric arc furnace is first passed through the two series-connected ceramic multi-cyclone dust collectors to remove spherical powder larger than 3 microns, and then the finer nano-scale spherical powder is collected by the pulse bag dust collector and placed in a sealed plastic barrel. The use of such a combination of collection equipment can prevent the silicon dioxide nano-spherical powder from being secondary contaminated during the collection process.

[0032] 6. The silicon dioxide nano-spherical powder prepared by the present invention has high purity and silicon dioxide content is greater than 99.9%. The particle size thereof is less than 100 nm as observed by electron microscope. Figure 2 The electron microscope photo fills the gap in the spheroidization technology of silicon micropowder less than 500nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a process flow chart for preparing silicon dioxide nano-spherical powder according to the present invention;

[0034] Figure 2 This is an electron microscope photograph of the silicon dioxide nano-spherical powder prepared by the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only preferred specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

[0036] The present invention provides a method for preparing silicon dioxide nano-spherical powder by electrofusion, such as Figure 1 As shown, it includes the following steps:

[0037] Step 1: Grind together:

[0038] Take 100 parts by weight of high-quality quartz powder, 15-22 parts by weight of carbon material, and 0.5-10 parts by weight of metallic silicon powder, and grind them together to a size of less than or equal to 100 mesh in a mill with a polyurethane lining on the inner wall and silicon nitride as a grinding medium to obtain a co-ground mixture.

[0039] The SiO2 content of the high-quality quartz powder in step 1 is ≥99.5%, the particle size is less than 80 mesh, and the quartz powder is pickled to remove iron, so that the iron oxide content of the quartz powder is less than 0.01%.

[0040] The carbon material in step 1 has a fixed carbon C content greater than 99.5%, a particle size less than 80 meshes, and is pickled to remove iron, so that the iron oxide content of the carbon material is less than 0.01%.

[0041] The carbon material is one or more of petroleum coke, graphite, charcoal, bamboo charcoal, waste electrodes, and coke.

[0042] The Si content of the metallic silicon powder in the step 1 is greater than 99.5%, and the particle size thereof is less than 80 mesh.

[0043] Step 2: Disc granulation:

[0044] The co-ground mixture is put into the disc granulator, and the disc is rolled while spraying glue to granulate into small balls of 2-12 mm.

[0045] The glue sprayed during the disc granulation in step 2 is silica sol or any one of polyvinyl alcohol, polyethylene glycol, and yellow dextrin.

[0046] Step 3: Bake the balls:

[0047] The pellets granulated in step 2 were placed in a drying oven at 110° C. for 24 hours.

[0048] Step 4: Sieve the balls:

[0049] Place the dried pellets in step 3 into a vibrating sieve to remove pellets smaller than 2 mm and fine powder.

[0050] Steps 2 to 4, including disc granulation, ball drying and ball screening, are designed to prevent dust from flying during the material feeding process, which would affect the purity of the collected gas and powder. Secondly, they are designed to improve the air permeability of the material in the furnace and prevent excessive gas generated during the electric melting and gasification process, which would cause the furnace to blow out due to insufficient removal, thus affecting the purity of the collected gas and powder.

[0051] Step 5: Electric melting and gasification:

[0052] The 2-12 mm pellets sieved in step 4 are placed in an electric arc furnace and heated by electricity. Metal silicon Si reacts with quartz SiO2 at high temperature to generate SiO gas. Quartz SiO2 and C undergo a high-temperature chemical reaction to generate SiO gas. The SiO gas escapes from the electric arc furnace and meets oxygen in the air during the escape process to generate nano-spherical silicon dioxide.

[0053] The electric arc furnace in step 5 is one of a three-phase electric arc furnace, a DC electric arc furnace, a plasma arc furnace or a high-frequency induction furnace, and the electric arc furnace uses a dense high-power electrode with a volume density greater than 1.80 g / cm 3 , the working voltage is 100-380V, and the working current is 4-15KA.

[0054] The electric arc furnace uses dense high-power electrodes to avoid electrode decarburization and powdering during the electric melting process, which affects the purity of the final silica nano-spherical powder.

[0055] Step five is a key step in the preparation method. The principle is that the metallic silicon powder added in step one reacts with quartz SiO2 at high temperature to generate SiO gas in step five. Firstly, it is to supplement the purity of SiO gas generated by the high-temperature chemical reaction of quartz SiO2 and C to ensure that the silicon oxide content of the finally obtained silica nano-spherical powder is greater than 99.9%; secondly, it is to activate the quartz lattice, which is conducive to accelerating the high-temperature chemical reaction of quartz SiO2 and C; when the temperature is greater than 1400°C, metallic silicon Si reacts with quartz SiO2 to chemically generate SiO gas, and the starting temperature of the high-temperature chemical reaction of quartz SiO2 and C to generate SiO gas is 1765°C. The high-temperature chemical reaction of metallic silicon Si with quartz SiO2 takes precedence over the high-temperature chemical reaction of quartz SiO2 with C.

[0056] Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic bucket.

[0057] Furthermore, the silicon dioxide nano-spherical powder is collected in step six by using a combined collection equipment, that is, a collection equipment composed of two series-connected ceramic multi-cyclone dust collectors connected to a pulse bag dust collector. The gas generated in the electric arc furnace first passes through the two series-connected ceramic multi-cyclone dust collectors to remove spherical powder larger than 3 microns, and then the finer nano-scale spherical powder is collected by the pulse bag dust collector and placed in a sealed plastic barrel.

[0058] The ceramic multi-cyclone dust collector in step six is ​​a new generation of high-efficiency, low-resistance dust removal equipment developed in recent years. It has the advantages of corrosion resistance, wear resistance, high temperature resistance, no clogging, long service life, simple operation and management, no cost, and no secondary pollution. It is suitable for the collection of high-purity gases and powders. When the dust-laden gas enters the dust collector, it passes through the ceramic guide and rotates at high speed inside multiple groups of cyclones. Under the action of centrifugal force, the dust and gas are separated, and the dust falls into the dust collection box and is discharged through the ash discharge valve. The purified gas forms an ascending vortex and enters the pulse bag dust collector through the exhaust pipe. This combination of collection equipment is used to prevent the silica nano-spherical powder from being secondary contaminated during the collection process.

[0059] The above is the method for preparing the silicon dioxide nano-spherical powder by electrofusion. Figure 1 As shown in FIG, after the preparation process of co-grinding - disc granulation - ball drying - ball screening - electric melting gasification - collection, the obtained silicon dioxide nano-spherical powder has high purity and a silicon oxide content of more than 99.9%; Figure 2 As shown, the particle size is less than 100 nm as observed by electron microscopy, filling the gap in the spheroidization technology of silicon micropowder less than 500 nm; the silicon dioxide nano-spherical powder prepared by the present invention achieves ultrafineness, high dispersibility, high uniformity and high sphericity, and can meet the requirements of ultra-large-scale integrated circuits for packaging materials.

[0060] Example 1

[0061] A method for preparing silicon dioxide nano-spherical powder by electrofusion, comprising the following steps:

[0062] Step 1: co-grinding: 100 parts by weight of high-quality quartz powder, 22 parts by weight of petroleum coke with a fixed carbon C content greater than 99.5%, and 0.5 parts by weight of metallic silicon powder are ground together in a mill with a polyurethane lining and silicon nitride as a grinding medium to a size of 100 mesh or less to obtain a co-ground mixture;

[0063] Step 2: Disc granulation: put the co-ground mixture into the disc granulator, spray silica sol glue while rolling the disc to granulate into small balls of 2-12mm;

[0064] Step 3: Dry the pellets. Place the pellets granulated in step 2 into a drying oven and dry them at 110°C for 24 hours.

[0065] Step 4: Sieve the balls. Put the balls dried in step 3 into a vibrating sieve to remove balls smaller than 2mm and fine powder.

[0066] Step 5: Electric melting and gasification: The 2-12mm pellets sieved in step 4 are placed in a high-frequency induction furnace and heated. Metallic silicon (Si) reacts with quartz (SiO2) at high temperature to generate SiO gas. The temperature is continuously raised, and the quartz (SiO2) reacts with carbon to generate SiO gas through a high-temperature chemical reaction. The SiO gas escapes from the electric arc furnace and, during the escape process, encounters oxygen in the air to generate nano-spherical silicon dioxide.

[0067] Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic barrel.

[0068] Example 2

[0069] A method for preparing silicon dioxide nano-spherical powder by electrofusion, comprising the following steps:

[0070] Step 1: co-grinding: 100 parts by weight of high-quality quartz powder, 20 parts by weight of charcoal powder, and 2 parts by weight of metallic silicon powder are ground together in a mill with a polyurethane lining and silicon nitride as a grinding medium to a size of 100 mesh or less to obtain a co-grinded mixture;

[0071] Step 2: Disc granulation: put the co-ground mixture into the disc granulator, spray polyvinyl alcohol glue while rolling the disc to granulate into small balls of 2-12mm;

[0072] Step 3: Ball drying: Place the 2-12 mm balls granulated in step 2 into a drying oven and dry at 110°C for 24 hours;

[0073] Step 4: Sieve the balls. Put the 2-12mm balls dried in step 3 into the vibrating sieve to remove the balls smaller than 2mm and fine powder.

[0074] Step 5: Electric melting and gasification: The 2-12mm pellets sieved in step 4 are placed in a DC arc furnace and heated. Metallic silicon (Si) reacts with quartz (SiO2) at high temperature to generate SiO gas. The temperature is continuously raised, and the quartz (SiO2) reacts with carbon to generate SiO gas through a high-temperature chemical reaction. The SiO gas escapes from the arc furnace and, during the escape process, encounters oxygen in the air to generate nano-spherical silicon dioxide.

[0075] Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic barrel.

[0076] Example 3

[0077] A method for preparing silicon dioxide nano-spherical powder by electrofusion, comprising the following steps:

[0078] Step 1: co-grinding: 100 parts by weight of high-quality quartz powder, 19 parts by weight of coke powder, and 4 parts by weight of metallic silicon powder are ground together in a mill with a polyurethane lining and silicon nitride as a grinding medium to a size of 100 mesh or less to obtain a co-ground mixture;

[0079] Step 2: Disc granulation: put the co-ground mixture into the disc granulator, spray polyethylene glycol glue while rolling the disc to granulate into small balls of 2-12mm;

[0080] Step 3: Ball drying: Place the 2-12 mm balls granulated in step 2 into a drying oven and dry at 110°C for 24 hours;

[0081] Step 4: Sieve the balls. Put the 2-12mm balls dried in step 3 into the vibrating sieve to remove the balls smaller than 2mm and fine powder.

[0082] Step 5: Electric melting and gasification: The 2-12mm pellets sieved in step 4 are placed in a three-phase electric arc furnace and heated. Metallic silicon (Si) reacts with quartz (SiO2) at high temperature to generate SiO gas. The temperature is continuously raised, and the quartz (SiO2) and carbon react with each other at high temperature to generate SiO gas. The SiO gas escapes from the electric arc furnace and, during the escape process, encounters oxygen in the air to generate nano-spherical silicon dioxide.

[0083] Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic barrel.

[0084] Example 4

[0085] A method for preparing silicon dioxide nano-spherical powder by electrofusion, comprising the following steps:

[0086] Step 1: co-grinding: 100 parts by weight of high-quality quartz powder, 15 parts by weight of waste electrode powder, and 10 parts by weight of metallic silicon powder are ground together in a mill with a polyurethane lining and silicon nitride as a grinding medium to a size of 100 mesh or less to obtain a co-grinded mixture;

[0087] Step 2: Disc granulation: put the co-ground mixture into the disc granulator, spray yellow dextrin glue while rolling the disc to granulate into small balls of 2-12mm;

[0088] Step 3: Ball drying: Place the 2-12 mm balls granulated in step 2 into a drying oven and dry at 110°C for 24 hours;

[0089] Step 4: Sieve the balls. Put the 2-12mm balls dried in step 3 into the vibrating sieve to remove the balls smaller than 2mm and fine powder.

[0090] Step 5: Electric melting and gasification: The 2-12mm pellets sieved in step 4 are placed in a plasma arc furnace and heated by electricity. Metallic silicon Si reacts with quartz SiO2 at high temperature to generate SiO gas. Quartz SiO2 and C react with carbon at high temperature to generate SiO gas. Two streams of SiO gas escape from the arc furnace. During the escape process, the SiO gas meets oxygen in the air to generate nano-spherical silicon dioxide.

[0091] Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic barrel.

[0092] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Claims

1. A method for preparing silicon dioxide nano-spherical powder by electrofusion, characterized in that: It includes the following steps: Step 1, co-grinding: Take 100 parts by weight of high-quality quartz powder, 15-22 parts by weight of carbon material, and 0.5-10 parts by weight of metallic silicon powder, grind them together in a grinder to less than 100 mesh, and obtain a co-grinded mixture; Step 2: Disc granulation: put the co-ground mixture into the disc granulator, spray glue while rolling the disc to granulate into small balls of 2-12mm; Step 3, drying the balls: Place the balls granulated in step 2 into a drying oven at 110°C for 24 hours; Step 4: Screening the balls: Place the balls dried in step 3 into a vibrating screen to remove balls smaller than 2 mm and fine powder; Step 5: Electric melting and gasification: The 2-12 mm dried pellets obtained after screening in step 4 are placed in an electric arc furnace and heated. A high-temperature chemical reaction generates SiO2 gas, which escapes from the electric arc furnace and interacts with oxygen in the air to form nano-spherical silicon dioxide. In step 5, the electric arc furnace uses dense high-power electrodes, and the volume density of the electrodes is greater than 1.80 g / cm 3 , the operating voltage is 100-380V, and the operating current is 4-15kA; the high-temperature chemical reaction that occurs when the electric arc furnace is powered on and heated in step 5 is that when the temperature is greater than 1400°C, the metallic silicon Si reacts with the SiO2 in the quartz to generate SiO gas, activating the quartz lattice. When the temperature is further increased to 1765°C, the SiO2 in the activated quartz begins to chemically react with C and accelerates the generation of SiO gas. The SiO gas escapes from the electric arc furnace and encounters oxygen in the air during the escape process to generate nano-spherical silicon dioxide; Step 6: Collection: Use a combined collection device to collect the silica nano-spherical powder and place it in a sealed plastic bucket.

2. The method for preparing a spherical silicon dioxide nanopowder by electric melting according to claim 1, characterized in that: The high-quality quartz powder in step 1 has a SiO2 content greater than 99.5%, a particle size less than 80 mesh, and is pickled to remove iron, so that the iron oxide content of the high-quality quartz powder is less than 0.01%.

3. The method for preparing silicon dioxide nano-spherical powder by fusion melting according to claim 1, characterized in that: The carbon material in step 1 has a fixed carbon C content greater than 99.5%, a particle size less than 80 mesh, and is pickled to remove iron, so that the iron oxide content of the carbon material is less than 0.01%.

4. The method for preparing silicon dioxide nano-spherical powder by fusion melting according to claim 3, characterized in that: The carbon material is any one or more of petroleum coke, graphite, charcoal, bamboo charcoal, waste electrodes and coke.

5. The method for preparing silicon dioxide nano-spherical powder by fusion melting according to claim 1, characterized in that: The metallic silicon powder in step 1 has a Si content greater than 99.5% and a particle size less than 80 mesh.

6. The method for preparing silicon dioxide nano-spherical powder by fusion melting according to claim 1, characterized in that: The glue sprayed during the disc granulation in step 2 is silica sol, or any one of organic material glues selected from polyvinyl alcohol, polyethylene glycol, and yellow dextrin.

7. The method for preparing silicon dioxide nano-spherical powder by fusion melting according to claim 1, characterized in that: The combined collection equipment in step six is ​​a device formed by two series-connected ceramic multi-cyclone dust collectors connected to a pulse bag dust collector. Spherical powder larger than 3 microns is first removed by the two series-connected ceramic multi-cyclone dust collectors, and then finer nano-scale spherical powder is collected by the pulse bag dust collector and placed in a sealed plastic barrel.

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