Silicon-based powder and method for producing the same

Abstract

The present invention relates to a silicon-based powder and a method for manufacturing the same. The method comprises a hydrolysis step, a condensation step and a drying step of a silicon precursor having an alkoxy group. By using a specific weight ratio of water to the silicon precursor having an alkoxy group and a silicon precursor having a secondary amino group and an alkyl group, the method can perform the condensation step without using an organic solvent and modify the silicon-based colloid to improve the process safety and the hydrophobicity of the silicon-based powder, and reduce its thermal conductivity and pseudo-specific gravity.

Description

Technical Field

[0001] The present invention relates to a silicon-based powder and a method for manufacturing the same, and in particular to a method for manufacturing the silicon-based powder without using an organic solvent, and the silicon-based powder thus manufactured. Background Art

[0002] Silicon-based powder is a material with a porous mesh structure. The mesh structure has high porosity, high surface area and small pore size, and the pores of the mesh structure are filled with gas (e.g., air), so its pseudo-specific gravity is low and its thermal conductivity is low, and it is used as an insulation material. The traditional method for manufacturing silicon-based powder includes a hydrolysis step, a condensation step and a drying step. In the condensation step, a silicon precursor and an alkali catalyst undergo a condensation reaction in an organic solvent. The organic solvent can dissolve the silicon precursor in (or disperse it in) the reaction system, and in the subsequent drying step, a solvent replacement is performed to remove the water in the pores, wherein the surface tension of the organic solvent is lower than that of water, so that the water with high surface tension is prevented from destroying the structure of the silicon-based powder during drying. However, when an organic solvent is used to replace water, a large amount of organic gas will be generated in the drying step, so it is necessary to use a condensation method to recover the organic solvent, which increases the risk, complexity and cost of the process.

[0003] Secondly, the conventional manufacturing method uses an additional alkali catalyst to catalyze the condensation reaction, but this causes a violent condensation reaction and reduces the density of the silicon-based powder structure, thereby increasing its apparent specific gravity and thermal conductivity.

[0004] In addition, the hydrophobicity of the silicon-based powder is insufficient and cannot be used in hydrophobic insulation materials. Therefore, the conventional method for manufacturing silicon-based powders requires an additional long-term surface modification step after the condensation step to modify the hydrophobic functional groups on the surface of the silicon-based colloid, thereby improving the hydrophobicity of the silicon-based powders.

[0005] In view of this, there is an urgent need to develop a silicon-based powder and a method for manufacturing the same, so as to improve the above-mentioned shortcomings of the existing silicon-based powder and the method for manufacturing the same. Summary of the invention

[0006] Accordingly, one aspect of the present invention provides a method for manufacturing silicon-based powders. The method selects a specific silicon precursor having a secondary amino group and an alkyl group and controls a specific weight ratio of water to a silicon precursor having an alkoxy group, so as to perform a condensation step without using an organic solvent, thereby improving the safety and hydrophobicity of the process and reducing its thermal conductivity and pseudo-specific gravity.

[0007] Another aspect of the present invention provides a silicon-based powder, which is prepared by the aforementioned method for preparing silicon-based powder. The silicon-based powder has high hydrophobicity, low thermal conductivity and low specific gravity.

[0008] According to one aspect of the present invention, a method for manufacturing a silicon-based powder is provided. This manufacturing method excludes the use of an organic solvent. In this manufacturing method, a first silicon precursor, an emulsifier and water are subjected to a hydrolysis step to obtain a hydrolyzed solution. Then, a second silicon precursor aqueous solution is prepared, wherein the second silicon precursor aqueous solution comprises a second silicon precursor and dilution water. Next, a condensation step is performed on the hydrolyzed solution and the second silicon precursor aqueous solution to obtain a silicon-based colloid. Then, a drying step is performed on the silicon-based colloid to obtain a silicon-based powder.

[0009] According to one embodiment of the present invention, the first silicon precursor includes a non-silane compound and / or a silane compound. The non-silane compound includes an alkali metal silicate and / or an ammonium silicate. The silane compound includes a methylsiloxane compound, and the methylsiloxane compound is selected from one or more compounds of the group consisting of methyltrimethoxysilane (MTMS), methyltriethoxysilane, dimethyldimethoxysilane and dimethyldiethoxysilane.

[0010] According to another embodiment of the present invention, based on 100 parts by weight of the first silicon precursor, the weight of the emulsifier is 0.1 parts by weight to 1 part by weight.

[0011] According to another embodiment of the present invention, the pH value of the hydrolysis step is controlled at 2.5 to 4.0.

[0012] According to another embodiment of the present invention, the second silicon precursor comprises one or more compounds having a structure as shown in the following formula (I):

[0013]

[0014] In formula (I), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is an alkylene group having 1 to 4 carbon atoms, and b1 and b2 are independently 0 or 1; when b1 and b2 are both 0, a1 and a2 are both 3; when b1 and b2 are both 1, a1 and a2 are both 1.

[0015] According to another embodiment of the present invention, the second silicon precursor is one or more compounds selected from the group consisting of tetraalkyldisilazane and hexaalkyldisilazane.

[0016] According to another embodiment of the present invention, the weight ratio of the first silicon precursor to the second silicon precursor is 1:0.005 to 1:0.05.

[0017] According to another embodiment of the present invention, the weight ratio of the dilution water to the first silicon precursor is greater than 11.

[0018] According to another embodiment of the present invention, the initial pH value of the condensation step is greater than 7 and less than 8.

[0019] According to another embodiment of the present invention, the pressure of the drying step is 0.5 atm to 1.5 atm, and the drying temperature of the drying step is 80° C. to 150° C.

[0020] Another aspect of the present invention provides a silicon-based powder. The silicon-based powder is prepared by the aforementioned method for preparing silicon-based powder, wherein the thermal conductivity of the silicon-based powder is less than 0.035 W / m·K, and the apparent specific gravity of the silicon-based powder is less than 0.05 g / cm 3 .

[0021] According to an embodiment of the present invention, the contact angle of the silicon-based powder is greater than 140°.

[0022] The silicon-based powder and the manufacturing method thereof of the present invention are applied, wherein a specific silicon precursor having a secondary amino group and an alkyl group is used, and a specific weight ratio of water to a silicon precursor having an alkoxy group is adjusted. This manufacturing method can perform a condensation step without using an organic solvent, and modify the silicon-based colloid to improve the safety of the process, the hydrophobicity of the prepared silicon-based powder, and reduce its thermal conductivity and pseudo-specific gravity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a more complete understanding of the embodiments of the present invention and its advantages, please refer to the following description in conjunction with the accompanying drawings. It must be emphasized that the various features are not depicted to scale and are for illustration purposes only.

[0024] The contents of the relevant drawings are described as follows:

[0025] Figure 1 A flow chart of a method for manufacturing silicon-based powder according to an embodiment of the present invention is shown.

[0026] FIG. 2A to FIG. 2C Electron microscope photographs of silicon-based powders according to Examples 1 to 3 of the present invention are shown.

[0027] Figures 2D to 2F Electron microscope photographs of silicon-based powders according to Comparative Examples 1 to 3 of the present invention are shown. DETAILED DESCRIPTION

[0028] The manufacture and use of the embodiments of the present invention are discussed in detail below. However, it is to be understood that the embodiments provide many applicable inventive concepts that can be implemented in a variety of specific contexts. The specific embodiments discussed are for illustration only and are not intended to limit the scope of the present invention.

[0029] The method for manufacturing silicon-based powder of the present invention hydrolyzes the monomer of silicon-based powder (i.e., the first silicon precursor described later) and acid (i.e., the acid catalyst described later) to produce a first silanol compound, and then further mixes the obtained hydrolysis solution with a second silicon precursor aqueous solution. Among them, the acid catalyst can hydrolyze the second silicon precursor to produce ammonia water and a second silanol compound. The generated ammonia water can promote the condensation reaction of the first silanol compound. Since the hydrolysis rate of the second silicon precursor is slow, the ammonia water can be generated slowly and continuously, and the generated ammonia water is diluted by a large amount of dilution water, so the pH value of the reaction system (i.e., the mixture of the hydrolysis solution and the second silicon precursor aqueous solution) also increases slowly. This gradually increasing pH value makes the condensation reaction proceed slowly, so the polysiloxane condensed from the first silanol compound can form small and uniform particles, and a three-dimensional network structure of silicon-based colloid is formed through the aggregation (or stacking) of the particles. The three-dimensional network structure has good compactness and high porosity, and can maintain the integrity of the structure during the drying step, thereby reducing the pseudo-specific gravity and thermal conductivity of the prepared silicon-based powder.

[0030] The aforementioned second silanol compound has a silanol group and a plurality of alkyl groups, wherein the silanol group can react with the silanol groups on the surface of the silicon-based colloid, and these alkyl groups can enhance the hydrophobicity of the surface of the silicon-based colloid. After the surface of the silicon-based colloid becomes hydrophobic, it is beneficial to remove the water in the pores of the structure of the silicon-based colloid and retain the integrity of the structure (i.e., forming a three-dimensional network structure). Therefore, the method for manufacturing the silicon-based powder of the present invention does not need to add an organic solvent in the condensation step (the organic solvent helps to remove the water in the pores), thereby enhancing the process safety and reducing the pseudo specific gravity and thermal conductivity of the silicon-based powder.

[0031] See also Figure 1 , the method 100 for manufacturing a silicon-based powder first performs a hydrolysis step on a first silicon precursor, an emulsifier and water to obtain a hydrolysis solution, as shown in operation 110. In some embodiments, the first silicon precursor may include but is not limited to non-silane compounds and / or silane compounds. Specific examples of non-silane compounds may include but are not limited to alkali metal silicates and / or ammonium silicate salts, such as potassium silicate, sodium silicate, lithium silicate and ammonium silicate. When the aforementioned non-silane compound is used as the first silicon precursor, the non-silane compound can help the polysiloxane particles to aggregate (or stack) into a three-dimensional network structure of silicon-based colloids, thereby reducing the pseudo specific gravity and thermal conductivity of the prepared silicon-based powder.

[0032] In some specific examples, the silane compound may include but is not limited to a methylsiloxane compound. Preferably, the methylsiloxane compound is selected from one or more compounds of the group consisting of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane and dimethyldiethoxysilane. When the aforementioned silane compound is used as the first silicon precursor, the silanol compound produced by hydrolysis has three silanol groups and one lower alkyl group, so it is beneficial to manufacture a silicon-based colloid with a three-dimensional network structure and high porosity.

[0033] Specific examples of the emulsifier may include, but are not limited to, cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and cetyltrimethylammonium chloride (CTAC). In some embodiments, based on 100 parts by weight of the first silicon precursor, the weight of the emulsifier is 0.1 parts by weight to 1 part by weight. When the weight of the emulsifier is within the aforementioned range, sufficient emulsifier can emulsify the first silicon precursor to dissolve (or disperse) in water to form a first silicon precursor solution, thereby facilitating the subsequent hydrolysis step.

[0034] In the hydrolysis step, the silane compound of the first silicon precursor is hydrolyzed into silanol compounds and lower alcohols, and the non-silane compound is hydrolyzed into silicic acid and alkali metal ions or ammonium ions. The carbon number of the lower alcohol is determined by the structure of the silane compound of the first silicon precursor.

[0035] In some embodiments, the pH value of the hydrolysis step can be controlled within the range of 2.5 to 4.0, and preferably within the range of 3.5 to 3.8. The aforementioned control of the pH value can be achieved by adding an acid catalyst to the first silicon precursor solution. The acid catalyst may include, but is not limited to, an inorganic acid and a low-level organic acid. Specific examples of inorganic acids may include hydrochloric acid and phosphoric acid, and specific examples of low-level organic acids may include formic acid, acetic acid, and oxalic acid. When the pH value of the hydrolysis step is controlled within the range of 2.5 to 4.0, the hydrolysis reaction of the first silicon precursor is facilitated, and the condensation reaction of its hydrolysis product (i.e., the aforementioned first silanol compound) is avoided (this condensation reaction causes incomplete hydrolysis of the first silicon precursor), so as to facilitate the preparation of a silicon-based colloid having a three-dimensional network structure, thereby reducing the thermal conductivity and pseudo-specific gravity of the prepared silicon-based powder.

[0036] After operation 110, a second silicon precursor aqueous solution is prepared, as shown in operation 120. Since there is no order difference between operation 110 and operation 120, the two can be performed simultaneously or sequentially. The second silicon precursor aqueous solution includes a second silicon precursor and dilution water. In some embodiments, the second silicon precursor may include one or more compounds having a structure shown in formula (I):

[0037]

[0038] In formula (I), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is an alkylene group having 1 to 4 carbon atoms, and b1 and b2 are independently 0 or 1; when b1 and b2 are both 0, a1 and a2 are both 3; when b1 and b2 are both 1, a1 and a2 are both 1.

[0039] The second silicon precursor has a secondary amino group and a plurality of alkyl groups, so that the second silicon precursor can be slowly and continuously hydrolyzed into ammonia water and silanol compounds (i.e., the aforementioned second silanol compounds). Ammonia water can be used as an alkaline catalyst for the subsequent condensation reaction. During the condensation reaction, ammonia water is diluted by dilution water in large quantities to facilitate the gradual increase of the pH value of the reaction system, thereby facilitating the formation of a three-dimensional network structure of silicon-based colloids, thereby reducing the pseudo-specific gravity and thermal conductivity of the silicon-based powder produced.

[0040] The aforementioned silanol compounds can be used as modifiers for the surface of silicon-based colloids. A silanol group of the silanol compound can react with a silanol group on the surface of the silicon-based colloid to form a siloxy group. The multiple hydrophobic alkyl groups of the silanol compound can enhance the hydrophobicity of the surface of the silicon-based colloid, thereby facilitating the removal of moisture in the pores of the three-dimensional network structure of the silicon-based colloid, thereby maintaining the integrity of the silicon-based colloid structure, thereby reducing the pseudo-specific gravity and thermal conductivity of the silicon-based powder.

[0041] The existing method for manufacturing silicon-based powder directly adds a fixed amount of base catalyst (such as ammonia water) to promote the condensation reaction, so the pH value of the reaction system immediately increases, which easily leads to a violent condensation reaction, forming thicker dendrites or collapsed flakes, thereby increasing the pseudo-specific gravity and thermal conductivity of the silicon-based colloid. In addition, the hydrophobicity of the existing silicon-based colloid is mainly contributed by the first silicon precursor, but the first silicon precursor has only one hydrophobic alkyl group, so the hydrophobicity of the silicon-based colloid is poor.

[0042] In some embodiments, when b1 and b2 in formula (I) are both 0 and a1 and a2 are both 3, the number of hydrophobic alkyl groups is relatively large, which can further enhance the hydrophobicity of the silicon-based colloid. In other embodiments, when b1 and b2 are both 1 and a1 and a2 are both 1, the silicon-carbon double bond can provide a reaction site to facilitate the formation of a three-dimensional network structure of silicon-based powder.

[0043] In some preferred embodiments, the second silicon precursor is selected from one or more compounds of the group consisting of tetraalkyldisilazane and hexaalkyldisilazane. A specific example of hexaalkyldisilazane may include hexamethyldisilazane (HMDS). When the aforementioned second silicon precursor is used, since these second silicon precursors have more hydrophobic alkyl groups, the hydrophobicity of the prepared silicon-based powder is further improved, and its pseudo specific gravity and thermal conductivity are further reduced.

[0044] In some embodiments, the weight ratio of the first silicon precursor to the second silicon precursor is 1:0.005 to 1:0.05, preferably 1:0.01 to 1:0.03, and more preferably 1:0.015 to 1:0.02. When the weight ratio of the first silicon precursor to the second silicon precursor is within the aforementioned range, the silanol compound and ammonia water hydrolyzed from the second silicon precursor are sufficient to facilitate the formation of a three-dimensional network structure of silicon-based colloid and completely modify its surface, thereby improving the hydrophobicity of the prepared silicon-based powder and reducing its pseudo specific gravity and thermal conductivity.

[0045] The method 100 for manufacturing a silicon-based powder uses dilution water to prepare a second silicon precursor aqueous solution. In some embodiments, the weight ratio of the dilution water to the first silicon precursor may be greater than 11. Preferably, this weight ratio may be 15 to 35, and more preferably may be 20 to 30. When the weight ratio of the dilution water to the first silicon precursor is within the aforementioned range, in the condensation step, a sufficient amount of dilution water can dilute the first silicon precursor in large quantities to generate a porous three-dimensional network structure of silicon-based colloid, rather than a solid and compact bulk structure of silicon-based colloid. Incidentally, the method 100 for manufacturing a silicon-based powder of the present invention uses a second silicon precursor aqueous solution for the subsequent condensation step, and excludes the use of a gaseous second silicon precursor generated by heating the second silicon precursor. The reason is that heating may cause cracking or oxidation of the second silicon precursor.

[0046] After operation 120, the hydrolysis solution and the second silicon precursor aqueous solution are subjected to a condensation step to obtain a silicon-based colloid, as shown in operation 130. As previously mentioned, the ammonia water generated by the hydrolysis of the second silicon precursor of the second silicon precursor aqueous solution can promote the condensation of the first silanol compound into polysiloxane particles to form a silicon-based colloid with a three-dimensional network structure having fine dendrites, and the generated silanol compound (also referred to as the second silanol compound) can further modify the surface of the silicon-based colloid to enhance the hydrophobicity of the silicon-based colloid surface, so that the contact angle of the prepared silicon-based powder is greater than 140°. Therefore, the manufacturing method 100 of the present invention can simultaneously perform a modification reaction in the condensation step to simplify the process.

[0047] As mentioned above, the condensation reaction of the first silanol compound and the hydrolysis reaction of its condensation product (i.e., the aforementioned polysiloxane) can be affected by the pH value of the reaction system. In some embodiments, the initial pH value of the condensation step can be controlled within a range of greater than 7 and less than 8, that is, when the hydrolysis solution is initially mixed with the second silicon precursor aqueous solution, and as the second silicon precursor participates in the reaction, the pH value of the system will slowly increase, which is superior to the existing method of using ammonia water, which directly causes the pH value of the reaction system to rise rapidly, resulting in a violent condensation reaction, thereby forming a silicon-based colloid with a three-dimensional network structure of coarse dendrites or collapsed sheets rather than fine dendrites.

[0048] After operation 130, the silicon-based colloid is subjected to a drying step to obtain silicon-based powder, as shown in operation 140. The drying step is used to remove the solvent used before the drying step, which includes the water in the pores of the three-dimensional network structure of the silicon-based colloid, to obtain a dry silicon-based powder. Since the surface of the silicon-based colloid has high hydrophobicity, it is conducive to drying the solvent and water. Accordingly, the manufacturing method 100 of the present invention can simplify the conditions of the drying step.

[0049] In some embodiments, the pressure of the drying step may be 0.5 atm to 1.5 atm, and the drying temperature may be 80° C. to 150° C. When the pressure and / or drying temperature are within the aforementioned ranges, the water in the pores of the silicon-based colloidal structure can be removed while retaining its integrity, thereby reducing the pseudo specific gravity and thermal conductivity of the silicon-based powder. In some specific examples, an oven, fluidized bed, spray, or microwave drying equipment may be used for the drying step.

[0050] Another aspect of the present invention provides a silicon-based powder, which is prepared by the aforementioned method for preparing silicon-based powder. The thermal conductivity of the silicon-based powder is less than 0.035 W / mK, and the apparent specific gravity of the silicon-based powder is less than 0.05 g / cm 3 Therefore, the prepared silicon-based powder can be applied to hydrophobic thermal insulation materials. Specific application examples of hydrophobic thermal insulation materials may include but are not limited to waterproof thermal insulation blankets, hydrophobic fire blankets and fire extinguishing blankets. Preferably, the thermal conductivity coefficient may be 0.01W / mK to 0.035W / mK, and the specific gravity may be less than 0.045g / cm 3 .

[0051] In some embodiments, the contact angle of the silicon-based powder is greater than 140°, preferably 140° to 150°. When the pseudo specific gravity of the silicon-based powder is within the aforementioned range, the silicon-based powder is more suitable for use in thermal insulation materials, in particular, for making thermal insulation fabrics, thermal insulation blankets, thermal insulation clothing, and other fabrics.

[0052] The following embodiments are used to illustrate the application of the present invention, but they are not used to limit the present invention. Any technical skills in the art can make various changes and modifications without departing from the spirit and scope of the present invention.

[0053] Preparation of silicon-based powder

[0054] Example 1

[0055] The silicon-based powder of Example 1 was subjected to a hydrolysis step, a preparation step, a condensation step, and a drying step according to the contents listed in Table 1 below to obtain the silicon-based powder of Example 1, and was evaluated by the evaluation test described below. The emulsifier used in the hydrolysis step was 0.5 parts by weight of hexadecyltrimethylammonium bromide, the amount of the acid catalyst used was 6 parts by weight, and the solvent was 114 parts by weight of water. The pH value of the hydrolysis step was controlled at 3.5 to 3.8. In addition, the conditions of the drying step were a pressure of 0.5 atm to 1.5 atm and a drying temperature of 80° C. to 150° C.

[0056] Examples 2 to 4 and Comparative Examples 1 to 4

[0057] Examples 2 to 4 and Comparative Examples 1 to 4 were prepared using the same method as Example 1. The difference is that Examples 2 to 4 and Comparative Examples 3 to 4 changed the type of acid catalyst, the weight ratio of dilution water to the first silicon precursor, and the weight ratio of the first silicon precursor to the second silicon precursor. Comparative Examples 1 and 2 did not use the second silicon precursor but used a base catalyst, and Comparative Example 2 further changed the type of solvent in the preparation step. The specific conditions and evaluation results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Tables 1 and 2, respectively. Figures 2A to 2F shown.

[0058] Evaluation method

[0059] 1. Test of thermal conductivity

[0060] The thermal conductivity test is based on the ISO 22007-2 standard method. The thermal conductivity of silicon-based powder is measured by a thermal conductivity analyzer under the conditions of 10mW power and 20 seconds or 80 seconds detection time. The thermal conductivity is evaluated by the thermal conductivity. When the thermal conductivity is less than 0.036W / m K, the silicon-based powder has good thermal insulation.

[0061] 2. Contact angle test

[0062] The contact angle test is conducted according to the ASTM C813 standard method using a static contact angle measuring instrument, wherein the silicon-based powder is spread flat on the surface of a double-sided tape, the unpasted powder is removed, and a uniform single layer of powder is adhered to the surface. The other side of the double-sided tape is then pasted on an observation platform, and water drops are dropped on the powder layer. The contact angle of the water drop is then measured, and the hydrophobicity of the silicon-based powder is evaluated by the contact angle. When the contact angle is greater than 140°, the silicon-based powder has good hydrophobicity.

[0063] 3. Test of false specific gravity

[0064] The test of apparent specific gravity is based on the ISO 60 standard method, which evaluates the characteristics of silicon-based powder materials during filling and storage by testing the density of silicon-based powder in a natural filling state under gravity. This apparent specific gravity is also called loose packing density or sparse packing density.

[0065] 4. Test of powder form

[0066] Powder Morphology Test The morphology of the silicon-based powder was observed using a scanning electron microscope to evaluate its structure.

[0067] Table 1

[0068]

[0069] Please refer to Table 1. Figure 2A and 2D Compared with Comparative Example 1, Example 1 uses hexamethyldisilazane, and the released ammonia and trimethylsilanol can be beneficial to the preparation of a three-dimensional network structure of silicon-based powder, thereby reducing its pseudo specific gravity and thermal conductivity.

[0070] Next, please refer to Table 1. Figure 2A and 2E Compared with Comparative Example 2, Example 1 uses water to prepare the second silicon precursor aqueous solution. The prepared silicon-based powder has a smaller thermal conductivity coefficient, and the powder morphology is a three-dimensional network structure. Therefore, using water to prepare the second silicon precursor aqueous solution can be beneficial to the generation of a three-dimensional network structure of silicon-based powder, thereby reducing its thermal conductivity coefficient.

[0071] Furthermore, please refer to Table 1. Figure 2B , 2C and 2F. Compared with Comparative Example 3, the weight ratio of the first silicon precursor to the second silicon precursor used in Examples 2 and 3 falls within an appropriate range (1:0.005 to 1:0.05). The silicon-based powders prepared in these two examples have smaller thermal conductivity coefficients and pseudo-specific gravity, and the powder morphology is a three-dimensional network structure. Therefore, the weight ratio of the two silicon precursors within the aforementioned range can be beneficial to the generation of a three-dimensional network structure of silicon-based powders, thereby reducing its thermal conductivity coefficient and pseudo-specific gravity.

[0072] In addition, please refer to Table 1. Compared with Comparative Example 4, the weight ratio of water to the first silicon precursor used in Example 4 is greater than 11, and the prepared silicon-based powder has a smaller thermal conductivity coefficient and apparent specific gravity, and the powder morphology is a three-dimensional network structure with finer dendrites. Therefore, sufficient dilution water can be beneficial to the generation of silicon-based powder with a three-dimensional network structure with finer dendrites, thereby reducing its thermal conductivity coefficient and apparent specific gravity.

[0073] In summary, the silicon-based powder and the manufacturing method thereof of the present invention are applied, wherein a silicon precursor having a secondary amino group and an alkyl group is used, and a specific weight ratio of water to a silicon precursor having an alkoxy group is adjusted. Therefore, the manufacturing method can perform the condensation step without using an organic solvent, and modify the silicon-based colloid to improve the safety of the process and the hydrophobicity of the prepared silicon-based powder, and reduce its thermal conductivity and pseudo-specific gravity.

[0074] Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Those skilled in the art to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the following claims.

[0075]

Explanation of symbols

[0076] 100: Method

[0077] 110,120,130,140: Operation.

Claims

1. A method for producing a silicon-based powder, characterized in that: Include: A first silicon precursor, an emulsifier, an acid catalyst and water are subjected to a hydrolysis step to obtain a hydrolysis solution, wherein the first silicon precursor comprises a non-silane compound and a silane compound, the non-silane compound is composed of potassium silicate, sodium silicate, lithium silicate and ammonium silicate, the first silicon precursor is subjected to the hydrolysis step to produce a first silanol compound, and the pH value of the hydrolysis step is controlled to be 2.5 to 4.0; A second silicon precursor aqueous solution is prepared, wherein the second silicon precursor aqueous solution comprises a second silicon precursor and dilution water, and the second silicon precursor comprises one or more compounds having a structure as shown in the following formula (I): In formula (I), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is an alkylene group having 1 to 4 carbon atoms, and b1 and b2 are independently 0 or 1; when b1 and b2 are both 0, a1 and a2 are both 3; when b1 and b2 are both 1, a1 and a2 are both 1; Performing a condensation step on the hydrolysis solution and the second silicon precursor aqueous solution to obtain a silicon-based colloid, wherein the second silicon precursor is hydrolyzed by the acid catalyst into ammonia water and a second silanol compound, and the ammonia water is configured to cause the first silanol compound to undergo the condensation step; as well as The silicon-based colloid is dried to obtain the silicon-based powder. The method for producing the silicon-based powder excludes the use of organic solvents.

2. The method for producing silicon-based powder according to claim 1, characterized in that: The silane compound includes a methylsiloxane compound, and the methylsiloxane compound is one or more compounds selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane and dimethyldiethoxysilane.

3. The method for producing silicon-based powder according to claim 1, characterized in that: Based on 100 parts by weight of the first silicon precursor, the weight of the emulsifier is 0.1 parts by weight to 1 part by weight.

4. The method for producing silicon-based powder according to claim 1, characterized in that: The second silicon precursor is one or more compounds selected from the group consisting of tetraalkyldisilazane and hexaalkyldisilazane.

5. The method for producing silicon-based powder according to claim 1, characterized in that: The weight ratio of the first silicon precursor to the second silicon precursor is 1:0.005 to 1:0.

05.

6. The method for producing silicon-based powder according to claim 1, characterized in that: The weight ratio of the dilution water to the first silicon precursor is greater than 11.

7. The method for producing silicon-based powder according to claim 1, characterized in that: The initial pH value of the condensation step is greater than 7 and less than 8.

8. The method for producing silicon-based powder according to claim 1, characterized in that: The pressure of the drying step is 0.5 atm to 1.5 atm, and the drying temperature of the drying step is 80° C. to 150° C.

9. A silicon-based powder, characterized in that: The method for producing a silicon-based powder according to any one of claims 1 to 8 is used, wherein the thermal conductivity of the silicon-based powder is less than 0.035 W / m·K, and the apparent specific gravity of the silicon-based powder is less than 0.05 g / cm 3 .

10. The silicon-based powder according to claim 9, characterized in that: The contact angle of the silicon-based powder is greater than 140°.

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