Low-cost yttrium-doped silicon composite aerogel and simple preparation method thereof

Abstract

The invention discloses a low-cost yttrium-doped silicon composite aerogel and a preparation method thereof, and relates to the field of thermal insulation materials, and the preparation method comprises the following steps: 1) introducing acid gas into a silicon source solution of an inorganic silicon source, and continuously stirring; (2) stamping the yttrium source solution by using compressed gas, pressing the yttrium source solution into the mixture obtained in the step (1), and quickly releasing the pressure after stirring to obtain yttrium-doped silicon composite wet gel; and 3) collecting the yttrium-doped silicon composite wet gel obtained in the step 2), and performing aging, washing and supercritical drying to obtain the yttrium-doped silicon composite aerogel. The raw materials adopted by the invention are cheap inorganic silicon source and inorganic yttrium source, and the addition amount of yttrium is low, so that the preparation cost of the yttrium-doped silicon composite aerogel is effectively reduced. Compared with traditional epoxyalkane gels, the method has the advantages that the gelation process is mastered by controlling the pressure of carbon dioxide, the speed is higher, and the method is more environmentally friendly. The preparation process is simple and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the field of thermal insulation materials, and in particular to a low-cost yttrium-doped silicon composite aerogel and a simple preparation method thereof. Background Art

[0002] With the vigorous development of society and the rapid progress of science and technology, the performance requirements of thermal insulation materials in various fields are constantly increasing, and there is an urgent need to develop thermal insulation materials with excellent high temperature resistance. Aerogel is widely regarded as the material with the best thermal insulation performance at present due to its extremely low density, high specific surface area and high porosity.

[0003] Silica aerogel is the most studied and mature type of aerogel in the aerogel field, and it is also the only aerogel that has achieved industrial mass production. There are currently a series of products based on silica aerogel on the market, but pure silica aerogel has poor temperature resistance. When the temperature is higher than 650°C, the aerogel particles will quickly sinter, causing the microporous structure to collapse, thereby losing its thermal insulation properties, which greatly limits its application in high-temperature fields.

[0004] Rare earth silicates have excellent heat resistance and phase stability. Incorporating rare earth elements during the preparation process is currently an effective way to improve the temperature resistance and thermal insulation properties of silica aerogels. Yttrium, as a rare earth element, is a commonly used doping element. The Chinese invention patent with publication number CN116692881A discloses a method for preparing hydrophobic rare earth-based silica aerogels. Phenyl-alkoxysilane and tetraalkoxysilane are used as silicon sources, and yttrium and other rare earth element salt solutions are used as dopants to prepare hydrophobic rare earth-doped silica gels. However, the silicon sources used in this process are all organic silicon, and phenyl-alkoxysilane accounts for a large proportion, which is costly and limits its industrial production.

[0005] The Chinese invention patent with publication number CN109534351A discloses a yttrium silicate aerogel nanocomposite material and a preparation method thereof, which uses tetraethyl orthosilicate as a silicon source and yttrium containing a ligand as a yttrium source, assisted by a gelling agent, to obtain a composite aerogel through a gelation reaction and supercritical drying, and then the aerogel is subjected to high-temperature heat treatment to obtain a yttrium silicate aerogel nanocomposite material. The obtained material has good thermal insulation properties, but the process is complex and requires high-temperature segmented heat treatment. The heat treatment temperature is high (up to 1200°C), and the gelling agent in the raw materials used is a controlled toxic alkylene oxide and the amount used is large (6-8 times the molar amount of the yttrium source), which is not conducive to its industrial promotion.

[0006] As can be seen from the above, the current preparation of yttrium-doped silicon composite aerogel generally has the problems of using organic silicon as raw material, using a large amount of yttrium salt and using a controlled gelling agent, which greatly limits the industrial development of yttrium-doped silicon aerogel. Summary of the invention

[0007] The purpose of the present invention is to solve the above problems in the prior art and to provide a high temperature resistant yttrium-doped silicon composite aerogel and a preparation method thereof which has a simple process and whose raw materials are all cheap and readily available inorganic materials.

[0008] In order to achieve the above object, the present invention adopts the following technical scheme:

[0009] A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof, comprising the following steps:

[0010] 1) introducing an acidic gas into a silicon source solution of an inorganic silicon source and continuously stirring;

[0011] 2) using compressed gas to press the yttrium source solution into the mixture of step 1), and then quickly releasing the pressure after stirring to obtain a yttrium-doped silicon composite wet gel;

[0012] 3) Collecting the yttrium-doped silicon composite wet gel obtained in step 2), and obtaining the yttrium-doped silicon composite aerogel through aging, washing and supercritical drying.

[0013] The inorganic silicon source is one or more of silica sol, orthosilicic acid, metasilicic acid, sodium silicate and water glass.

[0014] The yttrium source is one or more of yttrium chloride, yttrium sulfate and yttrium nitrate.

[0015] In step 1), the molar concentration of silicon in the silicon source solution is 0.1 to 1 mol / L.

[0016] In step 2), the molar concentration of yttrium in the yttrium source solution is 0.015 to 0.6 mol / L.

[0017] In the present invention, the molar ratio of yttrium in the yttrium source to silicon in the silicon source is 0.01 to 0.1:1.

[0018] The supercritical drying is carbon dioxide supercritical drying, and the pressure is 12-15 MPa.

[0019] A low-cost yttrium-doped silicon composite aerogel is prepared by the above preparation method.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] 1. The raw materials used in the present invention are all cheap inorganic silicon sources and inorganic yttrium sources, and the amount of yttrium added is low, which effectively reduces the preparation cost of yttrium-doped silicon composite aerogel.

[0022] 2. Compared with traditional epoxy alkylene gelling agents, the present invention controls the gelling process by controlling the acid gas pressure, which is faster and more environmentally friendly.

[0023] 3. The preparation process of the present invention is simple and suitable for large-scale industrial production. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] S1) 10 g of water glass is dissolved in 100 mL of ultrapure water under stirring to obtain a water glass solution, and then the solution is transferred to a reaction kettle and charged with sulfur dioxide.

[0027] S2) 0.24 g of yttrium chloride hexahydrate is dissolved in 3 mL of ultrapure water under stirring to obtain an yttrium chloride solution.

[0028] S3) The yttrium source solution is pressed into the reactor with compressed air, and the pressure is maintained and stirred for 30 minutes, and then the air is released to normal pressure.

[0029] S4) collecting the yttrium-doped silicon composite gel in the reaction kettle, aging it at 25° C. for 24 h, washing it three times with three times the volume of ultrapure water, and then washing it twice with two times the volume of anhydrous ethanol, followed by supercritical carbon dioxide drying at a drying pressure of 15 MPa, a temperature of 60° C., and a drying time of 2 h to obtain a yttrium-doped silicon composite aerogel.

[0030] The original specific surface area of ​​the yttrium-doped silicon composite aerogel prepared in Example 1 is 901 m 2 / g, pore volume is 5.9cm 3 / g; after heat treatment at 900℃ for 2h, the specific surface area is 291m 2 / g, pore volume is 1.9cm 3 / g.

[0031] Example 2

[0032] S1) dissolving 10 g of water glass in 100 mL of ultrapure water under stirring to obtain a water glass solution, then transferring the solution to a reaction kettle, filling it with NO2 gas, and maintaining the pressure.

[0033] S2) 0.45 g of yttrium chloride hexahydrate is dissolved in 3 mL of ultrapure water under stirring to obtain an yttrium chloride solution.

[0034] S3) The yttrium source solution is pressed into the reactor with compressed nitrogen, and the pressure is maintained and stirred for 30 minutes, and then the gas is released to normal pressure.

[0035] S4) collecting the yttrium-doped silicon composite gel in the reaction kettle, aging it at 25° C. for 24 h, washing it three times with three times the volume of ultrapure water, and then washing it twice with two times the volume of anhydrous ethanol, followed by supercritical carbon dioxide drying at a drying pressure of 15 MPa, a temperature of 60° C., and a drying time of 2 h to obtain a yttrium-doped silicon composite aerogel.

[0036] The original specific surface area of ​​the yttrium-doped silicon composite aerogel prepared in Example 2 is 713 m 2 / g, pore volume is 6.7cm 3 / g; after heat treatment at 900℃ for 2h, the specific surface area is 300m 2 / g, pore volume is 2.3cm 3 / g.

[0037] Example 3

[0038] S1) 14 g of sodium silicate nonahydrate was dissolved in 100 mL of ultrapure water under stirring, and the solution was then transferred to a reaction kettle and charged with SO3.

[0039] S2) 0.90 g of yttrium chloride hexahydrate is dissolved in 3 mL of ultrapure water under stirring to obtain an yttrium chloride solution.

[0040] S3) The yttrium source solution is pressed into the reactor with compressed carbon dioxide, and the pressure is maintained and stirred for 60 minutes, and then the gas is released to normal pressure.

[0041] S4) collecting the yttrium-doped silicon composite gel in the autoclave, aging it at 25° C. for 24 h, washing it three times with three times the volume of ultrapure water, and then washing it twice with two times the volume of anhydrous ethanol, followed by supercritical carbon dioxide drying at a drying pressure of 15 MPa, a temperature of 60° C., and a drying time of 2 h to obtain a yttrium-doped silicon composite aerogel.

[0042] The original specific surface area of ​​the yttrium-doped silicon composite aerogel prepared in Example 3 is 633 m 2 / g, pore volume is 2.5cm 3 / g; after heat treatment at 900℃ for 2h, the specific surface area is 327m 2 / g, pore volume is 1.1cm 3 / g.

Claims

1. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof, characterized in that: The following steps are involved: 1) introducing an acidic gas into a silicon source solution of an inorganic silicon source and continuously stirring; 2) using compressed gas to press the yttrium source solution into the mixture of step 1), and then quickly releasing the pressure after stirring to obtain a yttrium-doped silicon composite wet gel; 3) Collecting the yttrium-doped silicon composite wet gel obtained in step 2), and obtaining the yttrium-doped silicon composite aerogel through aging, washing and supercritical drying.

2. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof as claimed in claim 1, characterized in that: The inorganic silicon source is one or more of silica sol, orthosilicic acid, metasilicic acid, sodium silicate and water glass.

3. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof as claimed in claim 1, characterized in that: The yttrium source is one or more of yttrium chloride, yttrium sulfate and yttrium nitrate.

4. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof as claimed in claim 1, characterized in that: In step 1), the molar concentration of silicon in the silicon source solution is 0.1 to 1 mol / L.

5. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof as claimed in claim 1, characterized in that: In step 2), the molar concentration of yttrium in the yttrium source solution is 0.015 to 1 mol / L.

6. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof as claimed in claim 1, characterized in that: The molar ratio of yttrium in the yttrium source to silicon in the silicon source is 0.01 to 0.1:

1.

7. A low-cost yttrium-doped silicon composite aerogel and a preparation method thereof as claimed in claim 1, characterized in that: The supercritical drying is carbon dioxide supercritical drying, and the pressure is 12-15 MPa.

8. A low-cost yttrium-doped silicon composite aerogel, characterized by: Prepared by the preparation method according to any one of claims 1 to 9.