The primary particle size of fumed silica (fumed white carbon black) is between 7-80 nm,
with a specific surface area of 50-380 m ²/g, and the surface is rich in silicon hydroxyl groups.

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Its key optical characteristic is a refractive index of approximately 1.45~1.46,
 which is very close to the refractive index of most optical resins such as acrylic esters and siloxanes.

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Therefore, in a transparent system, it will not cause significant light scattering or haze, and the optical,
rheological, and durability properties of the coating can be precisely controlled without affecting transparency.

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It is mainly used in anti reflective (anti reflective) coatings, fiber optic coatings, LED packaging, and microlenses in optoelectronic coatings