Tag: degradation

Is it light or humidity? Scientists identify the culprits of emerald green degradation in masterpieces

Is it light or humidity? Scientists identify the culprits of emerald green degradation in masterpieces

An international team of researchers have found what triggers degradation in one of the most popular pigments used by renowned 19th and 20th century painters. Using a multi-method approach, including advanced synchrotron radiation techniques, they’ve unveiled how light and humidity affect the masterpieces over time, and have proposed a strategy for its mitigation and monitoring. The results are out now in Science Advances.
During the 19th century, the Second Industrial Revolution sparked major advances in chemistry, giving rise to synthetic pigments that transformed art. Among them was emerald green, a vivid copper arsenite pigment admired for its brilliance and intensity.


Emerald green was used by well-known late 19th and early 20th century painters, such as Paul Cézanne, Claude Monet, Vincent van Gogh, Edvard Munch, and Robert Delaunay. Some of these painters, including Van Gogh, quickly realised that the paint would change over time, losing its original brilliant colour, cracking and triggering surface deformations. It was discovered later that it was also highly toxic.


Light and humidity


Researchers believe emerald green degrades because its chemical composition is highly unstable under light, humidity, and certain atmospheric gases. These conditions can cause the pigment to react and release arsenic compounds, alter its colour, or form dark copper oxides.
Now a research team led by the Institute of Chemical Sciences and Technologies “Giulio Natta” (SCITEC) of CNR and the Department of Chemistry, Biology and Biotechnology of the University of Perugia, in collaboration with the ESRF, the European Synchrotron, and the University of Antwerp, has investigated what triggers the degradation of emerald green. The study1 aims to improve strategies for preserving the masterpieces containing this pigment and to develop new methods to monitor their conservation state. “It was already known that emerald green decays over time, but we wanted to understand exactly the role of light and humidity in this degradation”, explains Letizia Monico, senior researcher at the SCITEC-CNR, corresponding and first author of the publication, together with Sara Carboni Marri, a former PhD student from the same research group.

Read more on the ESRF website

Image:  Photograph of The Intrigue (1890, Royal Museum of Fine Arts Antwerp, KMSKA) by James Ensor

Credit: Royal Museum of Fine Arts Antwerp, KMSKA

Manufacturing defects in silicon-based Li-ion batteries trigger degradation

Manufacturing defects in silicon-based Li-ion batteries trigger degradation

Li-ion batteries are widely used in mobile devices, transportation and energy storage, but they have limitations, including durability and degradation over time. When and why defects and failure appear in commercial batteries is still mostly unknown.

Now scientists from the ESRF, the ILL and the CEA-IRIG, Materials Center Leoben Forschung GmbH and battery manufacturer VARTA Innovation GmbH have used non-destructive X-ray and neutron imaging at the ESRF and ILL, respectively, to determine one of the origins and causes of the degrading mechanism in silicon-based Li-ion batteries.

X-rays and neutrons analysis

The samples were industrially graded batteries that are currently being tested for future commercialisation and that include large amount of silicon. The difference with current batteries lies in the anode, which is often made of state-of-the-art graphite in commercial batteries. In the new batteries, the anode consists of a slurry mix of silicon and graphite composite. “This new anode configuration, with silicon in it, enables manufacturers to introduce a bigger quantity of lithium in the same space, increasing the capacity of the battery”, explains Jakub Drnec, corresponding author of the publication and scientist in charge of ID31.

In order to characterise the new materials and determine their behaviour, the team first used the ILL’s instrument NEXT, as neutrons are an optimal tool to observe the distribution of lithium in the battery. At NeXT, 3D high resolution neutron tomography is coupled with X-ray tomography to image the entire cell. Subsequently they analysed the samples on beamlines BM05 and ID31 at the ESRF in operando conditions, i.e. while they were charged and discharged. In particular, they tracked Li dynamics and the morphology of the composite and how it changed over time using the technique of small angle X-ray scattering (SAXS). They also used X-ray diffraction (XRD) to study the cathode charging and absorption X-ray tomography to investigate the voids created that can lead to mechanical failure.

 “This is a unique multi-modal study where we have combined neutron and X-ray tomography data from the same battery together and got a full picture of what is happening”, explains Drnec. “It shows how vast and comprehensive our research is when we use both X-rays and neutrons”, he adds.

Silicon agglomerations

The results show that the way the slurry of materials is mixed during wet electrode processing is uneven, with large silicon chunks not being mixed with graphite, and this triggers a break of chemistry around the anode. That part of the battery then becomes inactive and the defects can cause mechanical failure in the cell. “What is surprising is that after the first charge of the battery we already observe this phenomenon”, says Drnec.

Read more on ESRF website

Image: Multimodal correlative data and 3D rendering of the cell. Top part: X-ray CT data. Middle part: neutron CT data. Bottom part: Combined NXCT data in false color. A 2D SWAXS CT slice is also shown in the measured position. Right: Integrated graphite intensity. Left: Integrated SAXS intensity. The insert highlights the various components and internal cell damage as observed with NXCT.

Credit: Lübke E. et al, Energy and Environmental Science, 14 May 2024.

Molecular motion in tire rubber

Molecular motion in tire rubber

Scientists have observed the molecular motion of rubber components typically used in automobile tires—polybutadiene and carbon black—with the world’s fastest time resolution. The study reveals a clear interaction between the two components on the atomic scale, paving the way towards improved diagnostics of tire rubber degradation and the development of materials with enhanced durability.

Tire rubber is a composite material that typically includes synthetic rubber, such as polybutadiene, and added nanoparticles, such as carbon black, to improve its physical properties. During driving, strong forces act on the tire, causing its components to move against each another, which can lead to wear and degradation of the material. To evaluate tire performance, it is therefore important to understand not only the static structure of the complex particle network formed by the polymer and the nanoparticles, but also their interaction and respective movements, as these dynamics directly influence material properties such as wear resistance. Because some of these molecular movements happen extremely quickly, time-resolved measurements at atomic resolution on the fastest possible time scale are critical for developing and validating dynamic models of such materials.  

An international research team led by scientists from the University of Tokyo, Ibaraki University, and European XFEL has now observed the molecular motion within samples of polybutadiene and carbon black, which occurs naturally as a result of the material structure, with a time resolution of 890 nanoseconds (billionths of a second)—the fastest resolution obtained in such studies so far—at the European XFEL’s SPB/SFX instrument. 

Read more on XFEL website