High-temperature-resistant silica-alumina composite aerogel and preparation method thereof

Abstract

The application relates to a high-temperature-resistant silicon-aluminum composite aerogel and a preparation method thereof, and relates to the field of heat-insulating materials. The preparation method comprises the following steps: adding a silicon source, a skeleton toughening agent, a radiation shielding agent and a valence electric adjuster into deionized water, adjusting the pH of the mixed solution, and obtaining a silicon source solution; adding an aluminum source and a template agent into water, stirring, and obtaining an aluminum source solution; conveying the silicon source solution and the aluminum source solution to two opposite spray ports of a double-cone container under the action of compressed nitrogen, and realizing micro-interface compounding of the silicon source solution and the aluminum source solution under the action of atomization; placing and aging the silicon-aluminum composite sol, obtaining a silicon-aluminum composite wet gel; preheating and continuously conveying the silicon-aluminum composite wet gel to a drying chamber for supercritical drying or directly freeze-drying without preheating, and preparing the silicon-aluminum composite aerogel. The raw materials used in the application are inorganic aluminum sources and inorganic silicon sources, and strong acid is not needed for controlling the gel reaction, the preparation process is simple, the raw materials are cheap and easy to obtain, the operation is safe, and the application is suitable for large-scale industrial production.

Claims

1. A method for preparing a high-temperature resistant silicon-aluminum composite aerogel, characterized in that, Includes the following steps: S1: Silicon source solution preparation: Add silicon source, skeleton toughening agent, radiation shielding agent, and valence modifier to deionized water to obtain a mixed solution. Stir and adjust the pH of the mixed solution to alkaline to obtain silicon source solution A. S2: Preparation of aluminum source solution: Add aluminum source and template agent to deionized water, stir, and obtain aluminum source solution B; S3: Silicon-aluminum composite sol micro-interface composite: Silicon source solution A and aluminum source solution B are respectively transported to two opposite nozzles of a double-cone container under the action of compressed nitrogen. The silicon source solution and aluminum source solution are atomized and collided, and composited through a micro-interface to obtain silicon-aluminum composite sol C. S4: Gel aging: Add gelling agent to silica-alumina composite sol C, let stand and age to obtain silica-alumina composite wet gel; S5: After removing impurities from the silicon-aluminum composite wet gel, it is preheated at a temperature of 120-250℃ and a conveying pressure of 0.5-10MPa and continuously conveyed to a high-temperature, high-pressure drying chamber for supercritical drying or freeze-drying without preheating to obtain silicon-aluminum composite aerogel.

2. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, The silicon source mentioned in S1 is one or more of sodium silicate, potassium silicate, orthosilicic acid, and silica sol; The skeleton toughening agent is one or more of the following: single-walled carbon nanotubes, nano-ceramic fibers, calcium silicate nanofibers, nano-aramid 1313 fibers, α-silica nanopowder, β-silica nanopowder, and diisocyanate. The radiation shielding agent is one or more of the following: rutile titanium dioxide nanopowder, magnesium oxide nanopowder, silica, carbon black powder, mica powder, yttrium oxide, nano-silicon carbide fiber, silicon carbide whiskers, vanadium pentoxide, iron oxide powder, and boron carbide powder. The valence modifier is one or more of polyferric sulfate, polyaluminum chloride, triethanolamine salt, and sodium tripolyphosphate.

3. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, The pH of the silicon source solution described in S1 is 8–14, and the molar concentration of the silicon source is 0.1–10 mol / L. The mass ratio of the skeleton toughening agent to the silicon source is 0.002 to 0.0055:1; The mass ratio of radiation shielding agent to silicon source is 0.0015 to 0.003:1; The molar solubility of the electrostatic agent is 0.001–0.03 mol / L.

4. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, The aluminum source in S2 is one or more of aluminum chloride, aluminum nitrate, aluminum sulfate, sodium aluminate, potassium aluminate, and polyaluminum chloride; the molar concentration of the aluminum source is 0.15 to 10 mol / L.

5. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, The template agent mentioned in S2 is one or more of polyethylene glycol, hexamethylenediamine, hexadecyltrimethylammonium bromide, and sodium salicylate, and the molar concentration of the template agent is 0.03 to 1 mol / L.

6. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, The molar ratio of aluminum to silicon in the silicon-aluminum composite sol C described in S3 is 3 to 25:1; the atomization flow rate ratio of the silicon source solution to the aluminum source solution is 3 to 25:

1.

7. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, The gelling agent described in S4 is glacial acetic acid and anhydrous ethanol. The mass ratio of glacial acetic acid to composite sol C is 0.002 to 0.025:1, and the mass ratio of ethanol to composite sol C is 0.05 to 0.15:

1. The static aging temperature of the silica-alumina composite sol C is 10 to 90°C, and the static aging time is 0.5 to 48 hours.

8. The method for preparing a high-temperature resistant silicon-aluminum composite aerogel according to claim 1, characterized in that, In step S5, the temperature of the drying chamber is 150–300℃ and the pressure is 2–10 MPa.

9. The high-temperature resistant silicon-aluminum composite aerogel prepared by the method according to any one of claims 1-8.

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