100 Nano-Stories: Solid Structures (Part 2)!
Episode #93: Crystalline & Amorphous Solid Properties!
Preface! ✨
It’s your favorite material science & nanotechnology enthusiast! Today, we will cover the geometry and properties of solid structures, along with the concept of pH gelation time for a silica aerogel (sol-gel chemistry)!
Here is an article to prepare you for today’s topic:
TL;DR → Solid Structures! 🔑
- The classification of these materials is based on the atomic structure of how the atoms are arranged in the material, which allows for certain materials to behave in certain ways.
- Amorphous Solids → Not flexible and lack in (geometric) shape.
- Crystalline Solids → Not flexible but have a geometric shape.
- Crystalline solids have higher melting and boiling points than amorphous solids.
- The distance in Amorphous solids’ atoms varies throughout the material, which means that the melting and boiling point is within a certain range, but not an exact number.
- Rapid cooling techniques allow us to skip the time-temperature changes in the cooling points of certain chemicals/molecules to get amorphous solids.
Authors Note:
This was an overview of the previous article. If you are left confused or want to know why the mechanisms work behind solid structures, I highly recommend reading the article above for detailed information! 🙏🏽
TL;DR complete! Let’s jump into today’s topic! 😄
Crystalline & Amorphous Solids + pH Values Explained! 💡
Stress/Cuts! 🔑
No, I don’t mean the word “stress” like the sensation you feel when taking your AP Calc AB Exam. 😅
I mean the stress response from a crystalline and/or amorphous material. In a crystalline material, the atoms are arranged in a geometric shape, which means the atoms are arranged in an orderly manner.
Because of this, crystalline solids will break easily if the stress/place that you’re trying to break the crystalline solid is between adjacent molecules. Or in simpler terms, if you were to cut a crystalline material, it would cut cleanly and be split (split/cut can be also called “cleavage” in a certain direction) in a perfectly straight line.
In an amorphous solid, the bonds between the atoms vary, and there is a chance if you were to try and cut/split an amorphous solid, you would eventually run into the molecules, which leaves you with irregular/non-straight cuts on the material (because the molecules that were on the plane/direction you wanted to cut the material through are resisting the break).
Isotropic & Anisotropic! 🔑
Isotropic means that if you were to draw a line or point in a direction along the material, the values/results of a certain property in the material are the same (in any direction).
Anisotropic means that if you were to draw a line or point in a direction along the material, the values/results of a certain property in the material are different (in any direction).
Isotropic is only found in amorphous solids (liquids and gases too), while anisotropic is only found in crystalline solids.
The reason why isotropic is found in amorphous solids is that the atoms are arranged randomly, so all the various atoms/molecules with their unique properties are arranged unevenly. Therefore, if you were to travel in two random directions, you would eventually meet the same molecules, and the properties are the same in those two directions.
For example, it doesn't matter which direction you hit the glass, it will shatter 100% of the time because glass is an amorphous solid, so the atoms are arranged randomly.
The reason why anisotropic is found in crystalline solids only is that the atoms are arranged evenly, so for a certain direction, you will get a certain result (depending on the property you measure of the crystalline solid/material).
For example, if I wanted to measure the value of stress on a certain crystalline material, it will cut/break depending on the direction I want to hit/cut the material.
If you notice Line 1, I will have to get through 5 molecular structures/crystals to complete the cut.
But if you notice Line 2, I will have to get through 2 molecular structures/crystals to complete the cut.
This means that Line 2 is the easier direction to break the crystalline solid. Line 1 will be much harder to break the crystalline solid in that direction.
Closing Thoughts! 💭
This completes the overall introduction to the fundamental characteristics of amorphous and crystalline solids!
Summary:
- Crystalline Solids cut cleanly through materials (cleavage), while amorphous solids cut irregularly. The reason why is that crystalline solids have their atoms arranged evenly, while the arrangement of atoms in an amorphous material varies.
- Isotropic is only found in amorphous solids (liquids and gases too), while anisotropic is only found in crystalline solids. The reason why is because of the arrangement of the atoms.
- In an amorphous material, the irregular arrangement of the atoms allows for the properties of the atoms to be spread throughout the material, allowing for the value of a certain property in the material to be the same in whatever direction.
- In a crystalline material, the geometrical arrangement of the atoms only allows the properties of the material to be in certain directions. The properties aren’t scattered (like amorphous materials). Therefore, the value of a property of a material varies depending on the direction you want to go (throughout the material).
See you tomorrow for the final Sol-Gel Chemistry Lessons via pH Value/Concentration in Silica Aerogels! ✌🏽😢
Vocabulary! 📓
Amorphous Solids → Not flexible and lack in (geometric) shape.
Crystalline Solids → Not flexible but have a geometric shape.
Process Energy → The amount of energy placed/added on the material to cool the liquid to solid.
Isotropic → The values/results of a certain property in the material are the same (in any direction).
Anisotropic → The values/results of a certain property in the material are different (in any direction).
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© 2021 by Carlos Manuel Jarquin Sanchez. All Rights Reserved.
