Tag Archives: damage

The latest ‘golden’ age for electronics

I don’t know the dates for the last ‘golden’ age of electronics but I can certainly understand why these Japanese researchers are excited about their work. In any event, I think the ‘golden age’ is more of a play on words. From a June 25, 2019 news item on Nanowerk (Note: A link has been removed),

One way that heat damages electronic equipment is it makes components expand at different rates, resulting in forces that cause micro-cracking and distortion. Plastic components and circuit boards are particularly prone to damage due to changes in volume during heating and cooling cycles. But if a material could be incorporated into the components that compensates for the expansion, the stresses would be reduced and their lifetime increased.

Everybody knows one material that behaves like this: liquid water expands when it freezes and ice contracts when it melts. But liquid water and electronics don’t mix well – instead, what’s needed is a solid with “negative thermal expansion” (NTE).

Although such materials have been known since the 1960s, a number of challenges had to be overcome before the concept would be broadly useful and commercially viable. In terms of both materials and function, these efforts have only had limited success.

The experimental materials had been produced under specialized laboratory conditions using expensive equipment; and even then, the temperature and pressure ranges in which they would exhibit NTE were well outside normal everyday conditions.

Moreover, the amount they expanded and contracted depended on the direction, which induced internal stresses that changed their structure, meaning that the NTE property would not last longer than a few heating and cooling cycles.

A research team led by Koshi Takenaka of Nagoya University has succeeded in overcoming these materials-engineering challenges (APL Materials, “Valence fluctuations and giant isotropic negative thermal expansion in Sm1–xRxS (R = Y, La, Ce, Pr, Nd)”).

A June 22, 2019 Nagoya University press release (also on EurekAlert but published on June 25, 2019), which originated the news item, provides more technical detail,

Inspired by the series of work by Noriaki Sato, also of Nagoya University – whose discovery last year of superconductivity in quasicrystals was considered one of the top ten physics discoveries of the year by Physics World magazine – Professor Takenaka took the rare earth element samarium and its sulfide, samarium monosulfide (SmS), which is known to change phase from the “black phase” to the smaller-volume “golden phase”. The problem was to tune the range of temperatures at which the phase transition occurs. The team’s solution was to replace a small proportion of samarium atoms with another rare earth element, giving Sm1-xRxS, where “R” is any one of the rare earth elements cerium (Ce), neodymium (Nd), praseodymium (Pr) or yttrium (Y). The fraction x the team used was typically 0.2, except for yttrium. These materials showed “giant negative thermal expansion” of up to 8% at ordinary room pressure and a useful range of temperatures (around 150 degrees) including at room temperature and above … . Cerium is the star candidate here because it is relatively cheap.

The nature of the phase transition is such that the materials can be powdered into very small crystal sizes around a micron on a side without losing their negative expansion property. This broadens the industrial applications, particularly within electronics.

While the Nagoya University group’s engineering achievement is impressive, how the negative expansion works is fascinating from a fundamental physics viewpoint. During the black-golden transition, the crystal structure stays the same but the atoms get closer together: the unit cell size becomes smaller because (as is very likely but perhaps not yet 100% certain) the electron structure of the samarium atoms changes and makes them smaller – a process of intra-atomic charge transfer called a “valence transition” or “valence fluctuation” within the samarium atoms … . “My impression,” says Professor Takenaka, “is that the correlation between the lattice volume and the electron structure of samarium is experimentally verified for this class of sulfides.”

More specifically, in the black (lower temperature) phase, the electron configuration of the samarium atoms is (4f)6, meaning that in their outermost shell they have 6 electrons in the f orbitals (with s, p and d orbitals filled); while in the golden phase the electronic configuration is (4f)5(5d)1 -an electron has moved out of a 4f orbital into a 5d orbital. Although a “higher” shell is starting to be occupied, it turns out – through a quirk of the Pauli Exclusion Principle – that the second case gives a smaller atom size, leading to a smaller crystal size and negative expansion.

But this is only part of the fundamental picture. In the black phase, samarium sulfide and its doped offshoots are insulators – they do not conduct electricity; while in the golden phase they turn into conductors (i.e. metals). This is suggesting that during the black-golden phase transition the band structure of the whole crystal is influencing the valance transition within the samarium atoms. Although nobody has done the theoretical calculations for the doped samarium sulfides made by Professor Takenaka’s group, a previous theoretical study has indicated that when electrons leave the samarium atoms’ f orbital, they leave behind a positively charged “hole” which itself interacts repulsively with holes in the crystal’s conduction band, affecting their exchange interaction. This becomes a cooperative effect that then drives the valence transition in the samarium atoms. The exact mechanism, though, is not well understood.

Nevertheless, the Nagoya University-led group’s achievement is one of engineering, not pure physics. “What is important for many engineers is the ability to use the material to reduce device failure due to thermal expansion,” explains Professor Takenaka. “In short, in a certain temperature range – the temperature range in which the intended device operates, typically an interval of dozens of degrees or more – the volume needs to gradually decrease with a rise in temperature and increase as the temperature falls. Of course, I also know that volume expansion on cooling during a phase transition [like water freezing] is a common case for many materials. However, if the volume changes in a very narrow temperature range, there is no engineering value. The present achievement is the result of material engineering, not pure physics.”

Perhaps it even heralds a new “golden” age for electronics.

I worked in a company for a data communications company that produced hardware and network management software. From a hardware perspective, heat was an enemy which distorted your circuit boards and cost you significant money not only for replacements but also when you included fans to keep the equipment cool (or as cool as possible).

Enough with the reminiscences, here’s a link to and a citation for the paper,

Valence fluctuations and giant isotropic negative thermal expansion in Sm1–xRxS (R = Y, La, Ce, Pr, Nd) by D. Asai, Y. Mizuno, H. Hasegawa, Y. Yokoyama, Y. Okamoto, N. Katayama, H. S. Suzuki, Y. Imanaka, and K. Takenaka. Applied Physics Letters > Volume 114, Issue 14 > 10.1063/1.5090546 or Appl. Phys. Lett. 114, 141902 (2019); https://doi.org/10.1063/1.5090546. Published Online: 12 April 2019

This paper is behind a paywall.

Seeing ghosts: recovering images from dageurreotypes with help from the Canadian Light Source (synchrotron)

A daguerreotype plate with the photograph hidden by the tarnish (left) yet visible when imaged with synchrotron X-rays (right). Courtesy of Madalena Kozachuk.

Amazing, yes? Especially when you consider how devastating the inadvertent destruction of important daguerreotypes in an exhibition of US Civil War photography must have been to the curators and owners of the images. The ‘destruction’ occurred in 2005 and inspired research into the cause of the destruction, which was first covered here in a January 10, 2013 posting and followed up in a November 17, 2015 posting about an exhibit showcasing the results of the research.

A daguerreotype plate with the photograph hidden by the tarnish (left) yet visible when imaged with synchrotron X-rays (right). Courtesy of Madalena Kozachuk.

This latest research into daguerreotypes was performed at the Canadian Light Source (CLS; Saskatoon, Saskatchewan, Canada). Unlike my previous postings, this research was an attempt to retrieve the original image rather than research the reasons for its ‘destruction’. From a June 22, 2018 CLS news release (also on EurekAlert) by Lana Haight and Jeffrey Renaud (Note: Links have been removed),

Art curators will be able to recover images on daguerreotypes, the earliest form of photography that used silver plates, after scientists learned how to use light to see through degradation that has occurred over time.

Research published today [June 22, 2018] in Scientific Reports includes two images from the National Gallery of Canada’s photography research unit that show photographs that were taken, perhaps as early as 1850, but were no longer visible because of tarnish and other damage. The retrieved images, one of a woman and the other of a man, were beyond recognition.

“It’s somewhat haunting because they are anonymous and yet it is striking at the same time,” said Madalena Kozachuk, a PhD student in the Department of Chemistry at Western University [formerly University of Western Ontario] and lead author of the scientific paper.

“The image is totally unexpected because you don’t see it on the plate at all. It’s hidden behind time. But then we see it and we can see such fine details: the eyes, the folds of the clothing, the detailed embroidered patterns of the table cloth.”

The identities of the woman and the man are not known. It’s possible that the plates were produced in the United States, but they could be from Europe.

For the past three years, Kozachuk and an interdisciplinary team of scientists have been exploring how to use synchrotron technology to learn more about chemical changes that damage daguerreotypes.

Invented in 1839, daguerreotype images were created using a highly polished silver-coated copper plate that was sensitive to light when exposed to an iodine vapour. Subjects had to pose without moving for two to three minutes for the image to imprint on the plate, which was then developed as a photograph using a mercury vapour that was heated.

Kozachuk conducts much of her research at the Canadian Light Source and previously published results in scientific journals in 2017 and earlier this year. In those articles, the team members identified the chemical composition of the tarnish and how it changed from one point to another on a daguerreotype.

“We compared degradation that looked like corrosion versus a cloudiness from the residue from products used during the rinsing of the photographs versus degradation from the cover glass. When you look at these degraded photographs, you don’t see one type of degradation,” said Ian Coulthard, a senior scientist at the CLS and one of Kozachuk’s supervisors. He is also a co- author on the research papers.

This preliminary research at the CLS led to today’s [June 22, 2018] paper and the images Kozachuk collected at the Cornell High Energy Synchrotron Source where she was able to analyze the daguerreotypes in their entirety.

Kozachuk used rapid-scanning micro-X-ray fluorescence imaging to analyze the plates, which are about 7.5 cm wide, and identified where mercury was distributed on the plates. With an X-ray beam as small as 10 by 10 microns (a human scalp hair averages 75 microns across) and at an energy most sensitive to mercury absorption, the scan of each daguerreotype took about eight hours.

“Mercury is the major element that contributes to the imagery captured in these photographs. Even though the surface is tarnished, those image particles remain intact. By looking at the mercury, we can retrieve the image in great detail,” said Tsun-Kong (T.K.) Sham, Canada Research Chair in Materials and Synchrotron Radiation at Western University. He also is a co-author of the research and one of Kozachuk’s supervisors.

This is one of the many examples of successful research collaboration between Western University and CLS scientists.

Kozachuk’s research, which is ongoing, will contribute to improving how daguerreotype images are recovered when cleaning is possible and will provide a way to see what’s below the tarnish when cleaning is not possible. She will be back at the CLS this fall to continue her work.

The prospect of improved conservation methods intrigues John P. McElhone, recently retired as the chief of the Conservation and Technical Research branch at the Canadian Photography Institute of the National Gallery of Canada. He provided the daguerreotypes from the institute’s research collection.

“There are a lot of interesting questions that at this stage of our knowledge can only be answered by a sophisticated scientific approach,” said McElhone, another of the co-authors of today’s paper.

“A conservator’s first step is to have a full and complete understanding of what the material isand how it is assembled on a microscopic and even nanoscale level. We want to find out how the chemicals are arranged on the surface and that understanding gives us access to theories about how degradation happens and how that degradation can possibly or possibly not be reversed.”

As the first commercialized photographic process, the daguerreotype is thought to be the first “true” visual representation of history. Unlike painters who could use “poetic licence” in their work, the daguerreotype reflected precisely what was photographed.

Thousands and perhaps millions of daguerreotypes were created over 20 years in the 19th century before the process was replaced. The Canadian Photography Institute collection numbers more than 2,700, not including the daguerreotypes in the institute’s research collection.

By improving the process of restoring these centuries-old images, the scientists are contributing to the historical record. What was thought to be lost that showed the life and times of people from the 19th century can now be found. [emphases mine]

That last sentence seems to be borrowing from a line in the song, Amazing Grace, “I once was lost, but now am found,” from the song’s Wikipedia entry.

Here’s a link to and a citation for the paper,

Recovery of Degraded-Beyond-Recognition 19th Century Daguerreotypes with Rapid High Dynamic Range Elemental X-ray Fluorescence Imaging of Mercury L Emission by Madalena S. Kozachuk, Tsun-Kong Sham, Ronald R. Martin, Andrew J. Nelson, Ian Coulthard, & John P. McElhone. Scientific Reports volume 8, Article number: 9565 (2018) DOI:10.1038/s41598-018-27714 Published online June 22, 2018

This paper is open access. By the way, the research into the ‘destruction’ of the daguerreotypes in the 2005 exhibition? It’s cited in this paper.