How does different types of quartz behave when they are heated from 20 to 1500º C? The answer can make us able to produce materials with less waste.
Silicon has a range of applications in our everyday life. The smartphone you are holding in your hands contains it (and all other electronic devices which has a transistor in it), medical equipment contain it, aluminum alloys contain it and solar cells contain it. In other words, crucial in our life!
Quartz is a raw material used in the production of silicon. The mineral can be found almost everywhere, but in various forms. Quartz is for example a type of silicon dioxide that can be found on beaches. I am investigating how we can utilize the quartz to its maximum in silicon production.
The silicon production process is largely as follows:
- The quartz is added to a large furnace together with different carbon sources
- Energy is added to the process to increase the temperature
- Chemical reactions occur
- The result is liquid silicon
A silicon furnace in industry scale. The raw materials are added at the top, and will descend in the furnace. The diameter of the oven is about 10 meters. Courtesy of Elkem. Thorsteinn Hannesson. (2016). The Si Process – Drawings.
Same, same. But different
Even if the production of silicon sounds very easy (almost like baking a cake), it is very complex. One of the aspects that makes it complex is that what you put into your furnace will affect how it behaves and hence how well (how energy efficient) it produces the product that you want.
Since quartz is found all over the world, it has differences in its geological history, impurity content, and strain and stress through millions of years. This will affect how the quartz behaves in a silicon furnace at 2000 °C.
In my research I try to measure exactly this: How are different quartz types behaving at high temperatures, and why?
In total, only 10 % of the resources we extract from the earth’s crust end up in products we use. The rest is lost along the way as waste. This is not very sustainable, and we should be striving to use more of what we already have. One step along the way is to improve the knowledge on how quartz affects the production of silicon. I do that by shock heating the quartz to investigate what happens in the silicon furnace.
Shock heating the quartz
One of the properties I am measuring is how different quartz types withstand a temperature increase from room temperature to 1500° C. When quartz is subjected to such temperatures, it will crack and you will get a larger amount of smaller particles in your furnace. This will cause a more compact mass in the furnace, and affect how the furnace operates.
In total I will investigate three different quartz types, and five different properties. I will try to link the properties I measure to the fundamental properties of the quartz. Hopefully, I will be able to foresee how well a type of quartz will behave in a silicon furnace.
If we know this, we can do two things:
- Adapt the other furnace parameters to the quartz so that the production is as efficient as possible.
- Test new quartz deposits before we establish a quartz mine.
It this way, energy, emissions to the environment and interventions in nature can be reduced!
This research project is in collaboration with Elkem AS, and funded by the Research Council of Norway.