Performance and application of mullite fiber whisker porous reinforcement reinforced silica airgel composite material prepared by liquid phase method
A technology of silica aerogel and mullite fiber, which is applied in the application, heat exchange materials, ceramic products, etc., can solve the problems of long preparation cycle, complex preparation method and high cost, so as to reduce preparation cost and improve mechanics The effect of improving performance and strength
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Embodiment 1
[0047] This example introduces the preparation of several mullite fiber whisker reinforcements (in the form of NH 4 The mixed solution of F and ammonia water is the dipping solution).
[0048] Step 1: Alkaline silica sol and Al(NO 3 ) 3 ·H 2 O is the solute, deionized water is the solvent, and 0.17mol / L SiO is prepared 2 Dilute sol and 0.5mol / L Al(NO 3 ) 3 Mix the solution, stir evenly, pour it into a beaker filled with mullite fiber felt and vacuum impregnate for 40min to ensure sufficient vacuum impregnation. Then air-dried at 60°C for 7 hours to obtain a completely dried fiber mat.
[0049] Step 2: Prepare 100ml of NH with a concentration of 2mol / L respectively 4 F solution and 0.5mol / L ammonia solution, after stirring evenly, pour into the beaker containing the completely dried fiber felt obtained in step 1 and vacuum impregnate for 40min to ensure sufficient vacuum impregnation. Then air-dried at 60°C for 12 hours to obtain a fully dried fiber mat.
[0050] Step ...
Embodiment 2
[0054] This example is aimed at analyzing the properties of the reinforcements prepared in Comparative Example 1 and Example 1.
[0055] 1. Effect of ammonia concentration on mullite whisker reinforcement
[0056] SEM pictures of No. 1-4 mullite fiber whisker reinforcement figure 1 Shown, where (a), (b), (c), (d) are the partial enlargements of (1), (2), (3), (4) respectively.
[0057] When the concentration of ammonia water is 0mol / L, that is, the impregnation solution only contains NH 4 In case F (reinforcement No. 1), mullite whiskers with a length of 1 μm and a diameter of less than 100 nm grow on the mullite fiber. There is no overlap between the whiskers, a large number of pores in the fiber mat are not filled, and the whiskers are long. The diameter ratio is about 5; when the concentration of ammonia water in the impregnation solution is 0.5mol / L (No. The aspect ratio in the -200nm range is 20-30, filling some pores between fibers, and some mullite whiskers that are ...
Embodiment 3
[0077] In this example, mullite fiber whiskers No. 2-7 prepared in Example 1 are used to reinforce and prepare multi-scale composite materials.
[0078] Step 1: Use tetraethyl orthosilicate (TEOS) as silicon source, N,N-dimethylformamide (DMF) as chemical drying control agent, ethanol (EtOH) as solvent, water as solvent and hydrolysis reactant, hydrochloric acid As a catalyst for the hydrolysis reaction, mix N,N-dimethylformamide, ethyl orthosilicate, ethanol, and water in a molar ratio of 0.75:1:8:6, and then add catalyst hydrochloric acid to promote the hydrolysis reaction. Hydrochloric acid and orthosilicate The molar ratio of ethyl silicate is 1*10 -4 :1. Stir for 4 hours under sealed conditions to hydrolyze tetraethyl orthosilicate; obtain silica sol;
[0079] Step 2: Add 0.6ml of 25wt.% ammonia water that has been diluted ten times to the silica sol obtained in step 1, stir while adding, and pour the mullite fiber whisker with number 2 after stirring for 1min Vacuum i...
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