Aaron Berko

Synthesis of ordered mesoporous NiO with crystalline walls and a bimodal pore size distribution

A mesoporous solid with crystalline walls and an ordered pore structure exhibiting a bimodal pore size distribution (3.3 and 11 nm diameter pores) has been synthesized. Previous attempts to synthesize solids with large ordered mesopores by hard templating focused on the preparation of templates with thick walls (the thick walls become the pores in the target materials), something that has proved difficult to achieve. Here the large pores (11 nm) do not depend on the synthesis of a template with thick walls but instead on controlling the microporous bridging between the two sets of mesopores in the KIT-6 template. Such control determines the relative proportion of the two pore sizes. The wall thickness of the 3D cubic NiO mesopore has also been varied. Preliminary magnetic characterization indicates the freezing of uncompensated moments or blocking of superparamagnetism.

XAS studies of the effectiveness of iron chelating treatments of Mary Rose timbers

The oxidation of sulfur in marine archaeological timbers under museum storage conditions is a recently identified problem, particularly for major artefacts such as historic ships excavated from the seabed. Recent work on the Vasa has stressed the role of iron in catalysing the oxidative degradation of the wood cellulose and the polyethylene glycols used to restore mechanical integrity to the timbers. In developing new treatment protocols for the long term preservation of Henry VIII of Englands flagship, the Mary Rose, we are investigating the potential of chelating agents to neutralise and remove the iron products from the ships timbers. We have explored the use of aqueous solutions of chelating agents of calcium phytate, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) and ammonium citrate to extract the iron compounds. All of these solutions exhibit some level of iron removal; however the key is to find the most effective concentration at pH of around 7 of the reagent solution, to minimise the treatment time and find the most cost-effective treatment for the whole of the Mary Rose hull. Fe K-edge XAFS data from samples of Mary Rose timbers, before and after treatment by the chelating agents mentioned has been collected. The data collected provide valuable insights into the effectiveness of the treatment solutions.

Application of Microfocus X-Ray Beams from Synchrotrons in Heritage Conservation

Synchrotron-based techniques are becoming increasingly important in heritage science and the aim of this article is to describe how recently developed microfocus methods can probe the elemental composition, speciation and structure at the micron level in samples from structures. Firstly an outline is given of the major techniques that are used, namely x-ray fluorescence, diffraction and absorption spectroscopy, and the information that they can provide. This is followed by a description of the experimental set-up and procedures. The application of the methods is exemplified by case studies of the degradation of three types of historic structural materials; marble, glass and ship timbers. The results of the studies and their role in developing conservation strategies are described.

An Investigation of the Sulfur–Iron Chemistry in Timbers of the Sixteenth Century Warship, the Mary Rose, by Synchrotron Micro-X-Ray Spectroscopy

The problem of sulfur oxidation in archaeological marine timbers and the risk this poses to historically important wood built ships was first discovered in 2000 by conservators of the Vasa in Stockholm. They identified outbreaks of sulfur salts on the ship in their care, which were prevalent under raised humidity levels in the display environment and had the potential to produce sulfuric acid, with obviously damaging consequences to the timber. The original source of sulfur is due to concentration of sulfur dissolved in sea water during the time of the vessel’s burial in the marine environment and the occurrence of these sulfur salts is enhanced by the presence of iron corrosion products within the timber (Sandstrom et al. 2002, 2005). The issue of sulfur contamination and subsequent oxidation has come to be known simply as “the sulfur problem”.

Ionic transport and structure in doped plastically crystalline solids

Abstract There is considerable interest in plastic crystalline electrolytes which have good room temperature ionic conductivities and potential technological applications as membranes for devices such as batteries. Conductivity and X-ray absorption spectroscopy measurements have been used to study succinonitrile (1, 2-dicyanoethane) doped with copper(I) and (II) triflate (trifluoromethanesulfonate) and TFSI (bis(trifluoromethane)sulfonimide). The conductivities at room temperature are reasonably good, particularly for Cu(I)TFSI doped at 1 mol %, where the conductivity is ∼1 × 103 S cm-1, which is consistent with previous work on this system. The Cu K-edge EXAFS in 1 mol % doped copper salts show that in all cases, whether Cu(I) or Cu(II), the ion is predominantly in a well-defined and ordered local environment. A tentative model of the conduction process is described that will account for this local structural information; however, the process is clearly complex even in these apparently simple systems.

A Combined Conductivity and XAS Study of Plastically Crystalline Electrolytes

We report a study of the conductivity of LiBr and copper salt doped succinonitrile along with X-ray absorption measurements for the bromide and copper ions. The work shows that the ions are in well-ordered sites for most of the plastic phase and relatively high conductivity is due to a small fraction of the ions which are mobile.