Under the Microscope Profile picture
Oct 6, 2022 6 tweets 9 min read Read on X
After yesterday's Nobel celebration we are back on track . I believe I promised something on #data #analysis
A thread 🧵on how we extract the data from our #robot beamtime @desynews @p021_desy and how we figure out the #arrangement of #atoms in our samples /@RPittkowski 1/6
We get these beautiful 2D images from where the #scattered #X-ray beam hits the detector plate. What you see below is the scattering recorded for LaB6 - not surprising that we use it as a standard for calibration when you look at the beautiful #rings 2/6
By radial integration we get a 1D diffraction pattern, which shows distinct Bragg peaks for each ring on the 2D image. I made a very boring #GIF where you can see how the #rings relate to #peaks in the pattern 3/6
Such a a beautiful #diffraction pattern we get for powder #crystalline samples. The #periodic lattice planes reflect the X-rays periodically which leads to interference. Maybe you remember #BraggsLaw 🤓 4/6 (image credit @kirsten_mj)
We can identify many #crystalline compounds based on their #diffraction #pattern which serves as a kind of #fingerprint and can be compared to #database structures. There exist many databases with hundreds of thousand structures - a good start to identify your structure 5/6
But what happens when we #go #nano ? By downsizing the crystal we lose most of the periodic lattice planes - so no more beautiful rings💍or Bragg peaks 🤔Not to worry, we can still get structural information - from #PDF (not the #fileformat 📰) - but that deserves its own🧵6/6

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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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