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Why Does Diamond Not Turn Into Graphite?

Why Does Diamond Not Turn Into Graphite?

People think that diamonds last forever – but is that really the case? Unfortunately, the answer is not simple. 

Considering the fact that diamonds and graphite are both crystalline forms of pure carbon, many would assume that, in time, every diamond will degrade to graphite. Yet, we do not see that happen. 

So, the question is: Why does diamond not turn into graphite? Prepare yourself for some easy-to-understand, fun science!

Diamond Vs. Graphite

As we have already mentioned, both diamond and graphite are pure carbon crystalline forms. So, what is the difference?

The carbon atoms are differently arranged and bonded – that makes all the difference, believe it or not! What does the structure of each look like, you ask? 

  • In diamonds, one carbon atom is bonded to four adjacent carbon atoms. Together they form a close-connected 3D grid.
  • In graphite, one carbon atom connects with three neighboring carbon atoms in a plane. These planes connect to each other loosely, as well. 

Since the graphite is a lower-energy configuration, diamonds should degrade to graphite in typical conditions. It often happens in nature that atoms rearrange internally to a lower energy state. No chemical reaction with some external material is needed to induce this process. 

So, how come diamonds do not turn to graphite all the time?

That’s due to the substantial kinetic energy barrier that carbon atoms should overcome to reach the lower energy state. Therefore, even though graphite is a more stable form of crystalline carbon, diamond is in a metastable state and will not change its structure without inputted energy.  

It is simple chemistry:  If you want to form new chemical bonds, you have to break the original bonds – and you cannot do that without inputting energy.

Imagine you are at the bottom of a small hole in the ground. Next to your hole, there’s an even deeper hole – but you’re separated from it by a thick wall. 

Can you fall into a bigger hole? 

No, the barrier prevents you from doing that. However, if you receive an energy boost strong enough to help you jump over the wall, you can get into the deeper hole. 

The small hole in this story stands for the energy state of a diamond. The deeper hole represents the energy state of graphite. How can you add the energy needed to change diamond into graphite? 

You can either heat the diamond or try bombarding it with ions. Once the atoms receive the needed energy input, they will breach the energy barrier. In this way, the diamond will turn to graphite. 

Does this happen under normal conditions? Will diamond ever change to graphite in your everyday life?

No, it does not – and it will not. 

The kinetic energy of atoms in normal conditions is too small to overcome the energy barrier we’ve talked about earlier. In translation: It would take millions – if not billions – of years for a diamond to turn into graphite. The process is so slow that we can safely say that it is virtually non-existent. 

Therefore, wearing your diamond jewelry at standard temperatures and away from high ion sources guarantees that it will not change – at least not in any foreseeable future. 

All this makes the well-known saying “diamonds are forever” very believable. In terms of our human time scale, they really are. 

What should you do to change a diamond into graphite, then? As we have already suggested, you have two options:

  • Exposing the diamond to higher temperatures 
  • Putting the diamond under intense ion bombardment

No matter which method you opt for, the outcome will be the same – you will speed up the degradation of diamond to graphite. The question is, why is all this important to know? 

After all, you are not likely to ever want to turn your valuable diamond into more-less worthless graphite. Well, that is precisely it! You need to know this in order to prevent it from happening. 

There are important practical implications of everything you have learned today – especially for diamonds used for purposes other than jewelry.

For instance, being the hardest material on Earth, diamonds are often used for cutting purposes. They are instrumental in forming cutting edges and grinding grit. 

By applying the rules we have learned today, people can avoid very high temperatures when cutting or grinding, thus preventing diamonds from degrading to graphite and flaking off.  

How come diamonds do not degrade to graphite deep in the Earth where temperatures can be high, as well?

The pressure deep in the Earth is much higher than it is at the surface. As we have learned, diamond is the more stable configuration of pure carbon than graphite. 

Hence, even under high underground pressure, diamonds form spontaneously and do not turn to graphite.

And what happens if you try to burn diamonds at high temperatures?

Considering the fact that diamonds are made out of carbon, they will burn just like coal, especially if there’s enough oxygen. So, if you burn diamonds at high temperatures, they will not turn into graphite but combust and form carbon dioxide instead. 

In conclusion, if you want to degrade diamond into graphite, you have to heat it up in the absence of oxygen. Does this work the other way around? Let’s discover that together.

Learn More: What Is The Difference Between Diamonds And Graphite?

Can You Turn Graphite Into Synthetic Diamonds?

In short – yes, you can! Both pressure and heat work in both ways. As a result, you can utilize them to convert graphite into non-natural diamonds. 

There is no need to talk about why this is important. We all already know how big the synthetic diamond market is worldwide. Even though graphite and diamond are made out of the same chemical element, carbon, their properties are very different. 

The planar sheet arrangement of carbon atoms makes graphite very soft. Such properties make graphite an ideal material for pencil lead.

On the flip side, the carbon atoms in diamonds are strongly connected in all directions, which makes diamonds extremely hard. Yet, the extensive industrial application of diamonds is not based solely on their strength; they have exceptional electrical, optical, and chemical properties, too.

Scientists have devised several methods to induce the transition between these two different carbon forms. They can now successfully transform one into another – but it is not an easy job by any means.

In order for the conversion to take place, scientists have to expose graphite to temperatures well above 1700K, or pressure exceeding 12 GigaPascals. 

You now understand why diamonds are so expensive and rare, don’t you? If you want to make synthetic diamonds by applying pressure, you need to utilize approximately 150,000 times the atmospheric pressure at the Earth’s surface. 

When using heat, you have to secure the absence of oxygen and extreme temperatures. The most commonly applied method for making cultured diamonds is called chemical vapor distillation. The process is not too complicated. 

In essence, microwaves are used to create a semiliquid mixture of graphite plasma which is expeditiously cooled to form a crystal structure.

Recent studies show that treating graphite with high-power ultrasound is a valid method to create lab diamonds, too. However, this technique has no commercial application yet.

A new study suggests yet another alternative way – the hydrogenation of graphene. If it proves successful, scientists could use it to synthesize ultrathin diamond-like films without applying any pressure.

Can You Make A Synthetic Diamond At Home?

As you can see, it is possible to make cultured diamonds in the lab by utilizing a pretty straightforward process. The scientists use microwaves, so why shouldn’t you try it, too?

Of course, you cannot create the ideal lab conditions – but that does not mean you can’t have some fun experimenting. With a few ordinary household items, you can turn graphite into a diamond. 

You will not make a fortune on it, nor a beautiful piece of jewelry, but you can make something to remind you of your success.

So, let’s start gathering the necessary supplies and try to make a diamond at home!  What will you need to turn graphite into a diamond at your home?

  • A microwave oven (make sure you clean it well, supposedly that secures better results)
  • Two coffee mugs
  • Two toothpicks
  • Three pieces of graphite pencil lead (3 mm)
  • A couple of drops of extra virgin olive oil
  • Five inches of 100% cotton thread

Here’s the step by step procedure:

  1. Start by preparing the olive oil. You will need only a few drops, but without it, the process would not work at all. The thin layer of oil serves to concentrate the heat to the particular area of the graphite and make it more reactive to microwaves. It also helps remove the binder and the graphite.
  2. Lay the cotton thread on top of the olive oil. Allow it to absorb some oil, and then lift it and tie a loose knot. 
  3. Slip a piece of graphite through the knot in the oily thread. Put the graphite on a plate but use two toothpicks to suspend it above the plate.
  4. Tighten the knot around the graphite and let it sit for about half an hour for the oil to soak into it. 
  5. Remove the thread by carefully clipping it off of the graphite. Try to avoid sliding the thread up and down since it is crucial for the oil to stay concentrated in one spot.
  6. Turn one mug upside down and place the remaining two graphites (non-oiled) on it. They should be parallel to each other.
  7. Position the oiled graphite over the other two pieces.
  8. Put the second coffee mug over the “construction.”
  9. Carefully transfer the mugs into the microwave and set it to maximum power and maximum cooking time. Most microwaves can work for about 100 minutes; that should be enough for success! Do not be alarmed if you see some sparks – it is the oil reacting with the binder from the pencil lead. 
  10. When the microwave stops, let the mugs cool off completely and then take them out. Be careful! The temperature your microwave has generated exceeds 1,200 degrees, and you can get seriously injured if you are reckless.
  11. Lift the top coffee mug. The oiled graphite will be broken, while the other two pieces will look the same as before. Pay special attention to the oiled section of the broken graphite. If your experiment was a success, you should find a small diamond there – a little bit bigger than a grain of sand.

We hope congratulations are in order! The quality of your homemade diamond is poor – but it should still fluoresce like a “real” thing. Enjoy the fruits of your labor!

See Also: Can Diamonds Withstand A Nuke?

Conclusion

Diamonds are forever! Under normal conditions, they will eventually turn to graphite. Yet, the process is so slow that it is virtually non-existent. 

Why is that so? 

At standard temperature and pressure, graphite’s energy structure is more stable than that of a diamond. Due to this, a pretty large energy wall has to be breached for the carbon atoms to rearrange from the diamond lattice to the graphite lattice.

If you raise the temperature high enough and remove the oxygen from the equation, the carbon atoms will get the energy boost they need to cross the barrier. 

Consequently, the material will spontaneously transform from a less stable form to a more stable one.

The theory works in both directions. 

Therefore, you can use high temperature and pressure to turn graphite into diamonds too. Scientists already apply different methods to create diamonds for industrial use. 

The good news is – you can do it at home, too! You won’t get rich, but the fun is guaranteed!

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