The silica sol is a colloidal solution of silica fine particles dispersed in water, also known as silica sol, or silica hydrosol.
As an important inorganic polymer material, with no curing agent, good durability, improve wettability, strong adsorption, good insulation and other performance, widely used in the chemical, precision casting, textiles, paper, paints, food, electronics, mineral processing and other fields.
According to metal powder supplier, silicon powder dissolved to prepare silica sol, not only lower costs, with high product purity, also with good stability, is a rise new process for the preparation of sol in recent years. Added the silica fume, deionized water to the flask, and heated to a certain temperature, activated the silicon powder, then added sodium hydroxide, heated and control the reaction temperature, the reaction to a certain period of time, cooling and standing overnight, and then vacuum pumping was filtered off, obtain the sol, non-complete reaction silicon powder can be recycled.
Elemental silicon dissolution method using alkali as a catalyst, through the reaction of the silica fume and water, first generated hydrated silicic acid monomer, and then the monomer polymerization was continued into a binary body, trimers, and even polybasic body, finally form of the sol. The sol performance can through its viscosity, Baume degrees (density) and pH values to express. There are many factors affecting the synthesis of silica sol, reaction temperature, reaction time, silica fume and sodium hydroxide dosage will affect the sol preparation.
Temperature has a certain degree influence on the preparation of silica sol, the control of deionized water was used 200mL, silica fume used 25g, sodium hydroxide used 0.16g, the reaction time is 8h, the experiment found, when the temperature lower than 900, the reaction is relatively stable, while the temperature exceeds 900, the reaction is violent, difficult to control. at 65 to 900, sol viscosity and Baume degree gradually increasing, the pH value gradually decreasing, at 900, sol viscosity and Baume degree reaches a maximum, and then gradually decreased, so the preferred temperature of sol preparation is selected 900.
Experimental control of deionized water was used in an amount of 200 ml, silica fume used 25g, sodium hydroxide used 0.16g, the reaction temperature was 900. With the reaction time increasing, the viscosity and Baume degree of the silica sol also gradually increased, and the pH value is gradually reduced. When the reaction temperature is 8h, the viscosity and Baume degree of the silica sol is stabilized, when the reaction time continued to increase, the viscosity and Baume degree of the silica sol, and the pH value did not change a lot, therefore the sol preparation’s better reaction time is 8h.
Experimental control of deionized water was used in an amount of 200ml, and the sodium hydroxide used 0.16g, the reaction temperature was 900°C, the reaction time is 8h, studied the influence of the silicon powder amount on sol preparation, the experimental results indicate that the silicon powder amount have a certain impact on sol viscosity and Baume degrees, and pH, as the silicon powder amount increases, the sol’s viscosity is increasing, but when the silicon powder used in an amount of 25g, the Baume degrees reaches a maximum, thereafter gradually reducing, it is visible that the preferably silicon powder used in an amount of 25g in preparing sol.
Experimental control of deionized water was used in an amount of 200ml, silica fume used 25g, the reaction temperature was 900°C, reaction time is 8h, the experimental results show that the amount of catalyst on the silica sol performance has an important influence. If the catalyst amount is too small, it will not achieve the role of the catalyst, also it is not easy to make the reaction generating silica sol; while the amount of the catalyst is too high, the electrostatic repulsion between the colloidal particles reduced, the colloid will merge due to collide, on the contrary, will hinder the formation of the silica sol. So that the sol preparation’s preferred amount of catalyst is 0.16g.
The experimental results show that the preferred process conditions of sol preparation is: added 25g of silicon powder and 0.16g of sodium hydroxide in 200ml of deionized water, to react 8h at a temperature of 900.
Source:http://www.mhcmp.com
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