100 Nano-Stories: Haze In Transparent Aerogels (Concept)!

Episode #55: Mechanism of Aerogels!

Carlos Manuel Jarquín Sánchez
4 min readMar 29, 2021

Preface! ✨

It’s your favorite material science & nanotechnology enthusiast! Finally, we can begin our dive into Transparent Aerogels! If you don’t know what I am talking about, I highly recommend you check out my original idea behind Transparent Aerogels!

Don’t worry, the article on my idea in transparent aerogels is only a 4-minute read!

The first thing I want to cover in the research behind Transparent Aerogels is what does the word “transparency” means!

Transparent means that all the light will pass through a material, and it won’t be reflected, absorbed, or scatter in a material!

In a transparent aerogel, all the light that passes through the material will pass through without being scattered, absorbed, or reflect. Anyone who looks at a transparent aerogel will be able to clearly see through the material!

Transparent Aerogel!

So What Is Haze? 🤔

Now that we have an understanding of the meaning behind a transparent aerogel, we can move on to what is haze in aerogel and why must we remove it!

Haze in aerogel is defined as a lack of transparency, or that the aerogel looks somewhat cloudy rather than clear.

If you need a visual understanding of what haze is, perhaps this photo of a silica aerogel can help you:

There is Haze in The Silica Aerogel!

But why is there haze in a silica aerogel if it is about 98–99.8 % air by volume, Carlos?

The reason why the silica aerogel will have a haze to it is that it does not allow all the light to go through the material. Some of the light will go through the aerogel, which is known as a direct transmittance. Other times, the light will be scattered (similar to Rayleigh Scattering) across the network of nano-sized particles so much that it will exit the aerogel from the other side at a specific angle. This is known as diffuse transmittance.

However, some of the light will get diverted or absorbed when it encounters some of the nano-sized particles & the air in the aerogel. This is what is known as absorption or scattering (similar to Rayleigh Scattering). Other times, the light will exit the same way as it entered the aerogel. When this happens, this is known as diffuse reflectance.

So if this is the case, Carlos, how do we remove the haze in a transparent aerogel?

The answer is behind the particle sizes in the aerogel! Having a smaller particle size can reduce the haze of an aerogel depending on its thickness!

The reason why we should make the particles smaller is that they will have less of a chance to scatter wavelengths of light such as blue or violet. Silica aerogel looks blue (most of the time) because the particles and air molecules have the same size as the wavelength of blue light, and those particles will reflect/scatter the blue light around like crazy!

More explanation on Rayleigh Scattering in an article below! 😄

The other reason why we should decrease the haze in an aerogel is that it can allow us to forget about the thickness of the aerogel! The haze no longer depends on the thickness of the aerogel. So we could decrease the aerogel thickness to close to an inch/three centimeters thick and increase the surface area.

Closing Thoughts! 💭

Perfect! We have now covered up the concept of transparent aerogels and how we can remove the haze in the aerogel!

See you tomorrow on the mathematics of haze and how to use it to our advantage for transparency in aerogels! ✌🏽

Vocabulary! 📓

Rayleigh Scattering → Light rays are being redirected in different directions on passing through particles/atoms/molecules that are comparable to the wavelength of the light.

Surface Area → A measure of the total area that the surface of a 3-dimensional object covers/occupies.

Haze → In aerogel, haze is defined as a lack of transparency, or that the aerogel looks somewhat cloudy rather than clear.

Transparency → All the light will pass through a material, and it won’t be reflected, absorbed, or scatter in a material.

Direct Transmittance → Light passes through the aerogel without scattering.

Diffuse Transmittance → Light passes through the aerogel and is scattered throughout the network of pores. The light will leave the aerogel at an angle rather than straight through the aerogel.

Diffuse Reflectance → Light enters through the aerogel and is reflected the way it entered through the aerogel due to scattering between the nano-sized particles.

Density → Mass per unit volume of a material/substance. (m / v)

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