We just got back from a group lunch/farewell to @ashok_menon12. I will use this opportunity to talk a little bit about what Ashok has done during his PhD. Ashok has worked with what is known as Li and Mn-rich layered oxides.
The Li and Mn rich oxide materials are interesting as they have the potential to store a lot more energy compared to regular battery cathodes. Image
The reason is due to the excess lithium which sits in the transition metal layer. The presence of Li in this layer creates local Li-O-Li bonding environments allowing of anionic redox due to unhybridised O orbitals. Below I show the regular LiCoO2 (yellow) and Li2MnO3 (purple). ImageImage
However, this excess lithium has other structural consequences. Namely, the formation of a hexagonal arrangement of cations in the transition metal layer. ImageImage
However, how these layers in the structure arrange can shift. Leading to a kind of disorder known as stacking faults. In the clip I represent Li and Mn environments as hexagons. The shifts show how two adjacent layers can be placed relative to each other.
The question that Ashok aimed to answer was how the synthesis route impacted the degree of faulting and properties in the relatively simple compound Li2MnO3. pubs.acs.org/doi/10.1021/ac…
It turns out that the synthesis route did have a significant impact with a solid state "shake and bake" route producing a mix of faulted and unfaulted structures and the solgel route forming a more homogeneous structure.
We didn't know it at the time...but this would be significant foreshadowing for what would become the theme of his whole PhD thesis. More on that soon

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More from @RealSci_Nano

Aug 15, 2023
Today we’ll refresh our knowledge of some of the battery terms. Let’s start from the beginning: we call a battery a device that converts chemical into electric energy using redox reactions. To narrow it down, let’s focus on batteries which use Li (Li-ion batteries).
image:iStock Image
It is a secondary (rechargeable) battery which uses reversible reactions with Li-ion to store energy.
fig: https://t.co/P4WUqJLAp4ul.org
Image
Redox (oxidation-reduction) reactions involve transfer of electrons between two substances. As a result of gaining or losing electron, oxidation state of the substances changes.
Read 13 tweets
Nov 6, 2022
I still don't know what kind of job I want to do after I finish my PhD.

But at least I found the answer to what kind of job I do not want:

I don't want a bullshit job!

(and they are way more common than we want to admit, even among "blue-collar" jobs.

en.wikipedia.org/wiki/Bullshit_…
BS job="a form of paid employment that is so completely pointless, unnecessary, or pernicious that even the employee cannot justify its existence even though, as part of the conditions of employment, the employee feels obliged to pretend that this is not the case."
I promised that I would talk about career opportunities after the PhD and other @AltAcChats using a university-organized event that I attended this week.

Well, I was recommended not to, sorry!

However, this book (50% read atm) is helping me clarify that.
Read 5 tweets
Nov 6, 2022
Imagine that you design the perfect cake. Due to the combination of different layers of ingredients, it will have awesome unrealistic properties. A #meta cake!

But: will the structure withstand the temperatures needed during baking?

Thread on my paper 👇
onlinelibrary.wiley.com/doi/10.1002/ad… https://www.epicurious.com/expert-advice/how-to-fix-a-broken
Instead of a cake, we designed a near-perfect absorber.

Less than 0.1% of the light hitting it can escape it!

How is that possible? By disorder!

Turns out that having the layers of ingredients intermix a bit makes an even better cake!

1st lesson: it's not always worth it to find a fabrication technique that avoids intermixing.

Those techniques are way slower and don't necessarily improve their properties.

A step towards scalable, large-area #metamaterials.

Read 14 tweets
Nov 6, 2022
If you have been folowing the account his week, you might have guessed that I have a thing for definitions and debates over definitions.

What is a metal?



What is a metamaterial?



And now: what is a cake?

That is the discussion that delayed our lab's (@LNM_eth) baking competitions.

Do cakes need to be sweet?

Are all cakes flour based?

Are all cakes layered?

Are all cakes round?

(and much more)
Maybe the reason for this discussion is that we discussed it in Switzerland, a country known for its polyglotism:

Turns out that @Wikipedia defines it differently in different languages!

In French, for example, salty cakes pass the filter:

fr.wikipedia.org/wiki/G%C3%A2te…
Read 6 tweets
Nov 4, 2022
On Wednesday I tried to define a #metamaterial.

Now it's time to define #metals, which should be way easier, right?

Spoiler: even in a #metallurgy group @LNM_eth, not everyone agrees!

First a list of "high-school science" definitions that don't really help us. The

"Metals are reflective": Yes but not all reflective things are metals. Not definition friendly. Image
"Metals are ductile and malleable, easy to work with": Not necessarily. Good luck working with Tungsten, which is definitely metal.

This article tells a bit about how hard making the Tungsten filaments that we used on lights was!

americanscientist.org/article/tungst…
Read 16 tweets
Oct 6, 2022
Finally, the thread (you didn't know) you have been waiting for 🥳 "How can we use X-ray scattering to learn about the way the atoms sit in a #small #nanoparticle?" - lets use the Pair Distribution Function #PDF ! It's all about the neighbors 1/6 /@RPittkowski
To get information from small #nanoparticles, where periodic lattice planes are rare, we measure the X-ray scattering to very large scattering angles. This is called #Xray #totalscattering. So we need to come veeeery close with the detector to our sample.😱😬 2/6
Again, we integrate our scattering image (check up older tweets), but we are not done yet. More data treatment is necessary. We use a #Fouriertransform and transform from reciprocal (Q) space to #real #space - and there we have it, our PDF 😍3/6
Read 6 tweets

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