Preparation method of silicon-iron composite aerogel
A composite aerogel and acidic silica sol technology, applied in chemical instruments and methods, colloidal chemistry, colloidal chemistry and other directions, can solve the problems of complex drying residue composition, difficult recovery, long time, etc., and achieve environmental friendliness and technological process. Simple, effect of reducing the use of additives
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Embodiment 1
[0028] Measure 100 grams of acidic silica sol (pH value is 2.2) containing 20% (mass content) silicon dioxide, add 100 grams of 8% (mass content) ferric nitrate aqueous solution, add dropwise 5% (mass content) under rapid stirring ammoniacal water to a pH value of 7.2, gel after standing at 70°C for 2 hours, first soak in 1000 ml of 70°C water for 1 hour, then replace twice with 95% (volume content) ethanol at 70°C, each time Amount of 1000 milliliters, followed by modification with 1000 milliliters of hexamethyldisilazane solution of 20% hexamethyldisilazane by mass fraction for 2 hours, drying under normal pressure and reclaiming hexamethyldisiloxane to obtain SiO 2 -Fe 2 o 3 brown translucent airgel blocks.
[0029] Take the above SiO 2 -Fe 2 o 3 The airgel block is placed in a tube furnace, and hydrogen gas is introduced, and at the same time, the temperature is gradually raised to 500°C and maintained for 2 hours to obtain brown SiO 2 -Fe composite airgel.
Embodiment 2-4
[0037] The preparation method is the same as that in Example 1, except that the dosage of the gel catalyst and ferric nitrate is adjusted, and their influence on the performance of the airgel is detected.
[0038] Table 2:
[0039]
[0040] Analysis: as shown in Table 2:
[0041] 1, the present invention is gel catalyst with sodium hydroxide (or sodium carbonate, sodium bicarbonate, ammoniacal liquor) aqueous solution, with iron salt itself as gel accelerator; Can reduce the use of gel accelerator like this, simultaneously, from prepared Airgel performance analysis, compared with the performance of existing prepared aerogels, it has been improved in some aspects.
[0042] 2. By controlling the content of the gel catalyst and ferric nitrate, better composite airgel performance can be obtained, as shown in Table 2: the lower the content of ferric nitrate, the lower the iron content of the prepared aerogel and the weaker ferromagnetism , directly affect the performance and a...
Embodiment 5
[0044] The preparation method is the same as in Example 1, the difference is that: the hexamethyldisiloxane recovered in Example 1 is used, and the recovered solvent is directly used as a modifying agent to continue to be used in the preparation of airgel.
[0045] table 3:
[0046]
[0047] Analysis: as shown in table 3, the present invention adopts the hexamethyldisiloxane solution (HMDZ / MM) of hexamethyldisilazane as a modifier, and hexamethyldisilazane is modified to generate hexamethyldisilazane Methyldisiloxane, without separation, can be recycled and reused directly. It has been proved by experiments that the above-mentioned solvents still have a good modification effect after recycling 5-10 times, which greatly saves costs and reduces the amount of organic waste. emissions, has a very good environmental protection effect.
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