Artifacts from manganese reduction in rock samples prepared by focused ion beam (FIB) slicing for X-ray microspectroscopic analysis

Abstract. Manganese (Mn)-rich natural rock coatings, so-called rock varnishes, are discussed controversially regarding their genesis. Biogenic and abiogenic mechanisms, as well as a combination of both, have been proposed to be responsible for the Mn oxidation and deposition process. We conducted scanning transmission X-ray microscopy - near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) measurements to examine the abundance and spatial distribution of the different oxidation states of Mn within these nano- to micrometer thick crusts. Such microanalytical measurements of thin and hard rock crusts require sample preparation with minimal contamination risk. Focused ion beam (FIB) slicing, a well-established technique in geosciences, was used in this study to obtain 100–200 nm thin slices of the samples for X-ray transmission spectroscopy. However, even though this preparation is suitable to investigate element distributions and structures in rock samples, we observed that, using standard parameters, modifications of the Mn oxidation states occur in the surfaces of the FIB slices. Based on our results, the preparation technique likely causes the reduction of Mn4+ to Mn2+/3+. We draw attention to this issue, since FIB slicing, SEM imaging, and other preparation and visualization techniques operating in the keV range are well-established in geosciences, but researchers are often unaware of the potential for reduction of Mn and possibly other elements in the samples’ surface layers

Solid lubricants

The state of knowledge of solid lubricants is reviewed. The results of research on solid lubricants from the 1940's to the present are presented from a historical perspective. Emphasis is placed largely, but not exclusively, on work performed at NASA Lewis Research Center with a natural focus on aerospace applications. However, because of the generic nature of the research, the information presented in this review is applicable to most areas where solid lubricant technology is useful

Transparent varnishes on copper alloys dating from the 19th century: characterization and identification strategies

International audienceMany varnished copper-based artefacts dating from the 19th century can be found in museum collections. Although conservators deal on a daily basis with these surface finishes, few studies on this topic have been conducted during the last few decades on European objects. A more thorough understanding of these historical coatings would be helpful to establish accurate diagnoses and to contextualise the results with respect to the historical written sources. This paper presents the first results of the LacCa (Lacquered Copper Alloys) project currently being undertaken by an international multidisciplinary team. LacCa aims to develop a methodology that conservators can apply to identify and preserve these coatings. To this end, both historical objects and ancient varnish recipes have been studied. In a first step, the identification and characterisation protocol was validated using mock-ups, the results of which are presented in this paper

Ounce of Prevention: Care and Conservation of Works of Art

Exhibition, Apr. 21-June 24, 1979https://digitalcommons.bowdoin.edu/art-museum-miscellaneous-publications/1009/thumbnail.jp

Effect of gamma radiation on selected organic protective coatings

The purpose of this investigation was to prepare pigmented and non-pigmented organic protective coatings and to irradiate them with gamma rays. The coatings received a constant radiation dose of eight million rads. Seven tests were performed on the various coatings. The data from the tests were tabulated so that a direct comparison could be made as to the effect of the radiation on the coatings. The data from the tests also enabled comparisons to be made to determine if the various pigments had imparted any specific properties that would be desirable in coatings being exposed to radiations --Introduction, page 2

Heavy metals and aluminium intake from stored canned tomato, sardines and tuna in Algeria

This study assessed heavy metals intake and their impacts on healthcare in Algeria. Peculiar attention was given to heavy metals found in largely consumed canned foods in Algeria such as double concentrated tomato, tuna crumbs and sardines. Chemical analyses of the metal and aluminium containers (foil, tray) were performed by X-Ray Fluorescence (XRF) and EDS spectrometry (Energy Dispersive Spectrometry). The determination of the trace metal content in canned food (element metal trace EMT) was achieved by Atomic Absorption Spectrometry (AAS). The approach proposed in this study aimed to highlight the interaction of the product and packaging material, and thus to identify and quantify heavy metals traces that were able to undergo specific or overall migration to food. The morphology of the contact surface food / packaging was observed by Scanning Electron Microscope (SEM) and showed a slight degradation of the base metal (Black Iron).  There was an obvious increase in EMTs during tuna, sardines and tomatoes storage and artificial aging. A special interest was given to cooking modes using aluminium foil and trays.  ‎‎The respective dosages of aluminium, in baked food (fresh tuna) were obtained. Specific Aluminium migration was noticed and was strong for the flame cooking mode

The protection of duralumin from corrosion

Different types of coatings to protect duralumin from corrosion are discussed. Plating, etching, brushing, coloring, painting and varnishing are all investigated

Breaking down banners: analytical approaches to determining the materials of painted banners

Background: This paper investigates a range of analytical techniques to yield information about the materials and processes used in making painted banners. A textile conservator, technical art historian and paintings conservator, and materials scientist have joined forces to develop a greater understanding of the potential of analytical findings in the identification of materials. Results: Visual examination using low level magnification and microscopy proved to be a crucial starting point and for identification of areas for further analysis. High magnification microscopy of cross sections was invaluable to gather information regarding the build-up of the layers, their interaction and condition. Scanning electron microscopy (SEM) of ion-milled samples showed that different areas of the banner had been prepared in different ways. SEM-EDX (scanning electron microscopy energy-dispersive X-ray spectroscopy) confirmed the presence of the main elements of pigments. Raman enabled identification of specific pigments. Raman also provided confirmation of specific materials (such as the paint filler). Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) enabled the identification of oil and resin, confirmation of pigments and fibres. Thin layers made sampling and identification challenging. Presence of materials such as silk and lead white dominated some analysis making interpretation of other materials more difficult. Conclusions: Sample preparation had a significant bearing on the effectiveness of the analysis. Ion-milling provided high quality surface on the cross section samples that enabled material interfaces to be clearly seen. The challenges of finding effective wavelengths for analysis of samples using Raman were clearly evident in this study. Microscopy showed fibres blends, easily missed using FTIR, whereas FTIR was particularly effective in the identification of man-made fibres. While portable instrumentation may be useful, for in-depth understanding of the heterogeneous layered materials sample taking still remains crucial. Commercial makers used many typical grounds and pigments but these were used sparingly, in thin layers, in order to produce a flexible object and also perhaps to reduce costs. The textile was however of high quality, in this case silk. Unexpectedly, the preparation layers do not appear to be consistent across the banner; the reasons for this need further investigation

The Care and Cleaning of Furniture and Furnishings

Exact date of bulletin unknown.PDF pages: 1