Conference Agenda

Nano-porous oxides on Al, as well as on other important metals and its alloys such as Ti or Zr, continuously receive an interest from many branches of nanotechnology, batteries and supercapacitors industry, and in corrosion science. The ultimate goal is to form a tailored highly ordered nano-porous oxide film on a large scale by electrochemical methods, much cheaper than photolithography. Thus, understanding interdependencies and mastering the parameters leading to formation of highly order porosity is a key to achieve it. A number of articles have been published that have provided new insights into the mechanism of formation of porous anodic oxide films on aluminum [i.e. 1,2]. In plain view, an idealized film consists of close-packed hexagonal cells of anodic alumina, with each cell containing a pore at its center. A thin, non-porous, barrier layer is located at the base of the film, where a high electric field is present that results in ionic transport in the alumina, thus enabling formation of the film. The film is formed due to inward migration of oxygen and outward migration of Al under the electric field above the critical value allowing the transport and, most likely, plasticization and flow of the alumina under the mechanical stress.

The exact mechanism of the alumina formation during the anodizing process is not fully understood yet, with very little work done on the movements of oxygen or hydrogen, which is also present in the film. Our study utilized tracer ¹⁸O to scrutinize the porosity formation process and surface analysis methods sensitive to oxygen isotopes. A comparison was made between plasma profiling time-of-flight mass spectrometry (PP-TOFMS), nuclear reaction analysis (NRA) Narrow Resonance Depth Profilling (NRDP) and (Time of Flight Secondary Ion Mass Spectrometry) ToF-SIMS of ¹⁸O tracer in alumina. The findings from ToF-SIMS and PP-TOFMS reveal a partitioning of the tracer between the surface regions and buried layers of the films, in agreement with the NRDP. It demonstrated a level of complementarity of Tof-SIMS PP-TOFMS and potentially becoming a faster method for ¹⁸O depth profiling than NRDP.

[1] Baron-Wiechec A., Burke M.G., Hashimoto T., Liu H., Skeldon P., Thompson G.E., Ganem J.-J., Vickridge I.C.,Tracer study of pore initiation in anodic alumina formed in phosphoric acid, Electrochimica Acta 2013, 113, 302–312,

[2] Baron-Wiechec A., Skeldon P., Ganem J.-J., Vickridge I.C., Thompson G.E., Porous anodic alumina growth in borax electrolyte, Journal of Electrochemical Society 2012, 159, C583-C589

By observing ancient statues with optical microscopy or XRF, traces of coloured pigments can be revealed, mostly in areas best protected from the weathering (gaps, dimples) [1]. Organic materials associated to these colours can be binders for pigments, or coatings applied to the painted statues to protect them from the environment. A particular coating technique, called “ganosis” is described both in Greek and Latin sources (such as Plutarch, Pliny the Elder or Vitruvius writings). A saponified emulsion of beeswax is prepared by boiling it in sea water in presence of a sodium carbonate, natrium, (hydrated Na₂CO₃). It is then mixed with oil and applied on the statue surface, before being heated and polished with beeswax. This specific finishing application process could have had a ritual importance and there is little solid material evidence of such wax use on ancient marble statues.

A colossal Roman marble head from the 2^nd-3^rd century presenting polychromy remains was excavated in 1927 in the Roman theatre of Dougga (Tunisia) and its size suggests it was standing outside. Two cross-sections taken from the face to investigate the superficial layers were analysed using Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). On millimetric flat surfaces, TOF-SIMS can provide high spatial resolution ion images (down to 400 µm) of both organic and inorganic compounds, combined with high mass resolution [2]. The imaging abilities of the technique proved suitable to study samples from historical or archaeological objects, such as Renaissance paintings, which are often multi-layered heterogeneous organic-inorganic materials, having interacted in uncontrolled environments for centuries [3]. Combining TOF-SIMS data with a deep knowledge of the historical context, sources, recipes, and materials, as well as their behaviour over time, can inform about the ingredients used when the object was fabricated.

The organic and inorganic compounds were characterized in the pigmented layers and in the two superficial layers above it in the cross-sections. Both contain beeswax, and the ions detected in the deepest of both superficial layers could be associated to beeswax modified with natrium [4]. This result relied on the comparison with reference spectra of beeswax, sodium carbonate and saponified waxes. TOF-SIMS imaging of the stratigraphy in polychromy remains showed a multi-layered application of different waxes matching well with the recipes of “ganosis” from ancient sources. This shows that TOF-SIMS imaging has a good potential in exploring superficial structures found on ancient surfaces of cultural importance.

References

[1] E. Neri, et al. Archaeol Anthropol Sci, 14 (2022), 118.

[2] Q. P. Vanbellingen, et al. Rapid Commun. Mass Spectrom. 29 (2015), 1187–1195.

[3] C. Bouvier, et al. J Mass Spectrom. 57(1) (2022), e4803.

[4] E. Neri, C. Bouvier, et al. J. Cult. Herit. 51 (2021), 29-36.

The wreck of the Mary Rose, the flagship of Henry VIII's fleet, was recovered from the Solent in 1982. In order to preserve this artefact from further deterioration, various methods were employed such as seawater, soft water and polyethylene glycol (PEG) sprays (with three different molecular weights of PEG) as well as antibacterial coatings. Such treatments were used in order to retain the mechanical integrity of the wreck as well as preserving the recovered wood from further damage. However it is unclear as to which depth the PEG has reached within the planks of the hull of the ship, as well as what damage the polymer itself has undergone in the years since the treatment was stopped.

Investigations were conducted using cores extracted from the hull of the Mary Rose. Cylindrical samples (ca. 6 mm in diameter) were sectionned into pieces of approximately 4mm thickness and analysed using ToF-SIMS (Surrey) and by OrbiSIMS (Nottingham). Straighforward inspection of the data as well as semiquantitative approaches together with chemometrics (simsMVA) methods were used for interpretation and analysis of the spectra.

Initial analysis indicated that the PEG had reached a depth of around 14mm but the subsequent OrbiSIMS data also show that the PEG of Mw = 2000 has reached a depth of 20mm, having already undergone degradation within the ten years since the treatment was completed. Indeed, chain scission is observed, in some cases, with a loss of two repeat units and spectra consistent with those obtained from an oxidative degradation mechanism.

Another aspect of the chemistry of the cores was also examined by ToF-SIMS, relating the presence of inorganic ions indicative of salt and/or wash water, with penetration of the water into the wood of the Mary Rose, as well as damage of the wood itself.

It is anticipated that this work will lead to a better understanding of the conservation process and an improved development of the preservation routines to ensure the Mary Rose and other artefacts of similar significance survive for future generations.

Hot particles are microscopic particles deriving from nuclear fuel that have contaminated the environment in accident scenarios such as Chornobyl and Fukushima. The sensitivity and spatial resolution of secondary ionization mass spectrometry (SIMS), makes it well suited to characterizing microscopic fragments of nuclear material [1]. However, isobaric interferences deriving from these complex materials pose significant barriers to their assessment in nuclear forensics and radioecology. Untreated environmental samples yield mass spectra particularly crowded due to many organic compounds on top of isobars in the actinides: ²³⁸U:²³⁸Pu and ²⁴¹Pu:²⁴¹Am, as well as in the fission products: ¹³⁵Cs:¹³⁵Ba and ¹³⁷Cs:¹³⁷Ba [2]. This problem is circumvented by applying resonance ionisation, i.e. selective laser ionization to target single elements and suppress the isobaric interferences typically found in mass spectrometry.

In this work [3], two specialized instruments, combining SIMS and RIMS, were used to analyse single hot particles from Chornobyl: SIRIUS at the IRS in Hannover, Germany, and LION at LLNL in Livermore, USA. Results from multiple particles are presented with interpretations of isotope ratios in U, Pu, Cs, Rb, Sr and Ba.

[1] Fallon, C.M., et al., 2020. ACS Omega 5 (296–303), 1.

[2] Morooka, K., et al., 2021. Sci Total Environ 773, 6.

[3] van Eerten, D.E., et al., 2023. J Haz Mat 452, 131338.