• Nekoreguojami


2024. 02. 22 -

K. Charniakova, who develops useful oxide coatings, to become a new PhD

Dr. Katsiaryna Charniakova. Photo: Dr. Renata Karpicz
Katsiaryna Kharniakova, a researcher in the Department of Electrochemical Material Science at FTMC, has been awarded a PhD in natural sciences. She defended her thesis on "Synthesis and Characterization of Functional Coatings and Nanoparticles" (academic supervisor: Dr. Arūnas Jagminas).
Congratulations to your colleague, and good luck in your research career!
Katsiaryna and colleagues are developing carbon-containing alumina (aluminum oxide). Why is carbon important here? It gives alumina its strength, rust resistance, and durability - and even helps produce coatings of desired colors. So, carbon helps alumina perform better and 'serve' a wide range of applications, from car manufacturing to electrical engineering. These composite materials are modern nanomaterials used as adsorbents, catalysts, catalyst supports, supercapacitors, and electrode materials for fuel cells. The usual carbon content in such materials is around 3%.
FTMC chemists say that one of the methods used to produce such carbon-containing alumina coatings is aluminum anodizing (a type of treatment of the aluminum surface that produces the desired coating on that surface).
"It is a fairly fast, inexpensive method of producing nanostructured alumina with controllable properties by electrochemical oxidation of aluminum and its alloys in solutions of various electrolytes. Recent studies have shown that creating an alumina coating with up to 5% carbon is possible. However, it requires high anodizing voltages ranging from 120 to 200 V. This can be problematic if you want to apply them in practice, not only in the laboratory.
So, we decided to modify this and introduce new electrolytes [a substance in a solution that promotes electrical conductivity - S. B.] to produce alumina coatings with the desired percentage of carbon, but at lower voltages," says Katsiaryna.
In the past, such tests were carried out with formic acid - 22 V, and a carbon percentage of 5% was sufficient - but the coatings produced were very thin. So, a researcher improved the electrolyte by adding ammonium heptamolybdate and sodium metavanadate, which promoted anodization and the formation of an alumina film and also reduced the pitting corrosion during aluminum anodizing in pure formic acid solution.
Anodizing in mixed electrolytes at 80 V produced the desired coatings with a carbon content of about 5%. However, one disadvantage was noted: the coating structure was very messy, and the surface was cracked.
Let's compare the usually ordered structure of nanoporous alumina (on the left) with the one seen by our chemist (on the right):
(Photos from Katsiaryna Charniakova's presentation)
The picture, of course, is not good. However, K. Charniakova found a solution: she added some oxalic acid to the electrolyte (which, if you are wondering, is 10,000 times stronger than acetic acid; oxalic acid and its salts are found in many plants, such as wood sorrel).
Adding a new component to the electrolyte significantly improved the surface and the "back side" of the film, making the structure of the derivative neat and, if we may say so, "beautiful"; the carbon content has not been reduced, and the required electrical voltage has remained the same.
Once this goal was achieved, a new idea was born. The main components of the film are alumina and carbon. The chemist decided to study the carbon part separately and, more specifically, as the alumina affected the properties of the carbonaceous component. So, Katsiaryna immersed the film in hydrochloric acid, hoping the alumina would dissolve and leave only the modified carbon in the solution. However, everything was dissolved... Or so it seemed at first glance, as the solution turned completely clear.
"I was completely disappointed. The first thought was: I've spoiled my samples that had to wait four weeks, and nothing! However, my colleague in the Department of Molecular Compound Physics, Dr. Renata Karpicz, said: 'Wait, we need to check.'
(Photo from Katsiaryna Charniakova's presentation)
When the solution was illuminated with a blue laser, we saw it was not a pure solution (with a constant composition) but colloidal. We realized that it was carbon nanoparticles remaining in the solution! We were very happy", she recalls one of the most joyful moments of her studies at FTMC.
These nanoparticles have been found to be useful - they are biocompatible and thus theoretically useful for medical experiments. These nanoparticles possess fluorescence (the phenomenon of absorption of electromagnetic radiation by a substance and the subsequent emission of a lower energy photon), which is useful in the laboratory for a wide range of studies.
FTMC information
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