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This study aims to provide a better understanding of the Raman spectra of cobalt-based pigments in works of art. Systematic analyses of 21 industrial blue cobalt-based pigments were carried out by using elemental energy dispersive spectroscopy and phase analyses by X-ray diffraction (XRD) and Raman microspectroscopy, which led to the identification of 17 spinel Co-based pigments. All the minerals contained in each pigment were characterised by all three techniques and subsequently attributed to diluents, extenders, mineralisers or unreacted reagents or to the main mineral phase, whether it was pure or contained doping or lattice modifier elements. In the particular case where doping elements were in low concentration in the host mineral lattice, their distinction by XRD from non-doped spinel was impossible. On the contrary, Raman microspectroscopy turned out to be a perfect tool for detecting the presence of the doping agents in the spinel lattice. The determination of the elemental and mineralogical composition of the industrial blue cobalt-based pigments commercially available for artists and studied in this survey represents a significant increase in the amount of analytical data available for this type of pigment as well as a valuable addition in the characterisation by Raman microspectroscopy of these compounds in situ, on works of art. Copyright © 2010 John Wiley & Sons, Ltd.

Raman microscopy (RM) is widely used in archaeometrical studies of pigments, geomaterials and biomaterials in the Cultural Heritage, but one domain has received relatively less attention: the colouring of stained glass. This feasibility study investigates the advantages and disadvantages of employing RM alone in this field by means of a study of modern commercial glasses, modern commercial pigments, and a few archaeological stained glasses, but especially by an experimental project whereby the authors created stained glass. The different kinds of possible unreacted or reacted material are rigorously established. The distinction between Na, K, Ca glasses was explored, as well as the red colouring of an industrial glass which was proved to be due to the presence of (Zn, Cd)S(x)Se(1-x). Yellow, green, blue and maroon pigments were studied before and after an initial firing and then after heating on glass. The quality of the Raman spectra varied enormously and was sometimes disappointing. Nevertheless RM successfully identified various coloured products such as bindheimite, crocoite, cobalt aluminate, haematite; relict reactants such as corundum, eskolaite and oxides of Co or Pb; and provided indications of other phases such as maghemite or Co-olivine. One conclusion is that the amount of chemical reaction between the pigments and the glass is small compared to the amount in between the pigments. Comments are made on the potential for dating archaeological glass from the known age of synthesis of the pigments, and of the dangers of this approach. Overall it has been shown that RM can be useful for studying stained glass, especially for remote in situ analytical operations with mobile RM, but one must expect some problems either with fluorescence or weak spectra.

The influence of niobium and/or palladium in MoV 0.4 O x on both solid state chemistry and catalytic properties in the oxidation of ethane to acetic acid and ethylene is examined. Catalysts without molybdenum (VNb 0.31 Pd 3e-4 O x ) are also studied for comparison. The structural properties of the precursors and of the catalysts obtained by calcination of precursors at 350 and 400 °C are studied by X-ray diffraction, and by laser Raman and X-ray photoelectron spectroscopies. These properties depend on the presence or absence of niobium, and to a lesser extent, of palladium. Nb-free precursors and catalysts are heterogeneous mixtures of crystalline oxides, among which hexagonal and orthorhombic MoO 3 . The presence of Pd favors the instability of both precursors and catalysts. The catalysts are poorly active (conversion S AA max = 61–73 mol%) and to CO x ( S C O x max = 30 − 72 mol % ). The Nb-containing precursors without or with Pd are more stable, and the catalysts are made up of nanocrystalline particles of V, Nb-doped Mo 5 O 14 and of V x Mo 1− x O 3− x /2 . They are active (conversion S tot = 90–96 mol%). The surface being enriched with vanadium in most cases, the discussion deals with the relative role of Nb and Pd and their possible location in the identified oxides. Because no M1 and/or M2 oxides could be identified, synergistic effects between nanocrystals of (VMoNb) 5 O 14 and V x Mo 1− x O 3−0.5 x are proposed to account for the high catalytic performance of the multicomponent MoVNb(Pd) oxides.

The theory for interaction coefficient of alloying additions on hydrogen activity in Al alloys has been generally discussed. In particular, the interaction coefficient of Cu addition on the hydrogen activity for the Al-Cu-H system has been evaluated based on hydrogen solubility values in pure aluminum and in Al-Cu alloy measured at different Cu concentrations by means of Sieverts’ apparatus. The Cu addition was found to reduce the hydrogen solubility, and its effect on hydrogen solubility was evaluated by the interaction coefficient γ H Cu , which is a function of Cu-addition concentration and melt temperature. The evaluated interaction coefficient was converted into an alloy correction factor CF(A) and a temperature correction factor CF(T), which are employed in industrial hydrogen measurement techniques such as TELEGAS and ALSCAN.

Cellulose acetate, developed about 100 years ago as a versatile, semisynthetic plastic material, is used in a variety of applications and is perhaps best known as the basis of photographic film stock. Objects made wholly or partly from cellulose acetate are an important part of modern and contemporary cultural heritage, particularly in museum collections. Given the potential instability of the material, however, it is imperative to understand the aging mechanisms and deterioration pathways of cellulose ester plastics to mitigate decomposition and formulate guidelines for storage, exhibition, and conservation. One important aspect of this process is the ability to fully characterize the plastic, because variations in composition affect its aging properties and ultimate stability. In this Account, we assess the potential of a range of analytical techniques for plastics made from cellulose acetate, cellulose propionate, and cellulose butyrate. Comprehensive characterization of cellulose ester plastics is best achieved by applying several complementary analytical techniques. Fourier-transform IR (FTIR) and Raman spectroscopy provide rapid means for basic characterization of plastic objects, which can be useful for quick, noninvasive screening of museum collections with portable instruments. Pyrolysis GC/MS is capable of differentiating the main types of cellulose ester polymers but also permits a richly detailed compositional analysis of additives. Thermal analysis techniques provide a wealth of compositional information and thermal behavior. Thermogravimetry (TG) allows for quantitative analysis of thermally stable volatile additives, and weight-difference curves offer a novel means for assessing oxidative stability. The mechanical response to temperature, such as the glass transition, can be measured with dynamic mechanical analysis (DMA), but results from other thermal analysis techniques such as TG, differential scanning calorimetry (DSC), and dynamic load thermomechanical analysis (DLTMA) are often required to more accurately interpret the results. The analytical results from this study form the basis for in-depth studies of works of art fabricated from cellulose acetate. These objects, which are particularly at risk when stored in tightly sealed containers (as is often the case with photographic film), warrant particular attention for conservation given their susceptibility toward sudden onset of deterioration.

The identification of organic colorants in works of art (such as dyes on textiles or organic pigments) by Raman spectroscopy is generally limited by the presence of a strong fluorescence background. In this paper, the effectiveness of minimizing fluorescence in the analysis of Cape Jasmine (Gardenia augusta L.) by dispersive Raman spectroscopy at three different excitation wavelengths (633, 785 and 1064 nm) and by surface-enhanced Raman spectroscopy (SERS) with and without acid hydrolysis is evaluated and compared. It is shown that these vibrational techniques offer an alternative analytical approach, when, as is particularly the case of Cape Jasmine, sample preparation procedures that are routinely applied for natural organic dyes and pigments cause alterations that lead to low sensitivity in the more classical high-performance liquid chromatography-photodiode array (HPLC-PDA) analytical protocols. Samples of the yellow dye G. augusta L. in the following forms were analyzed: dyed on alum mordanted wool, dyed on nonmordanted and alum mordanted silk, pigment precipitated on hydrated aluminum oxide, extract mixed with a protein binder and painted on glass, and as a water-based glaze applied on a mock-up of a typical Chinese wall-painting. Raman bands at 1537, 1209 and 1165 cm−1 are identified as discriminating markers for the carotenoid colorant components crocetin and crocin. Copyright © 2009 John Wiley & Sons, Ltd.

Several approaches have been investigated to prepare fluorite-type compositions within the (1-x) CeO{sub 2}-xYO{sub 1.5} system. The optical properties of the resulting modified-ceria materials have been characterized in order to evaluate their potential abilities as inorganic UV absorbers. Diffuse reflectance analyses reveal a strong optical absorption between 390 and 400 nm for all substituted compositions and the spectral selectivities are estimated suitable for the targeted application. Additionally, time resolved microwave conductivity (TRMC) and phenol photodegradation analyses do not indicate any photocalatytic activity for these compositions. Aqueous colloidal suspensions of the Ce{sub 0.7}Y{sub 0.3}O{sub 1.85} UV absorber have been carried out. - Graphical abstract: Comparison between diffuse reflectance spectra of ceria (x=0) and yttrium modified ceria (x=0.3)

Three commercial TiO2 compounds (Degussa P25, Sachtleben UV100, and Millenium PC50) and their platinized forms have been studied by the time-resolved microwave conductivity (TRMC) method to follow their charge-carrier dynamics and to relate it to the photocatalytic activity for phenol degradation in TiO2 aqueous suspensions. The degradation reaction has been studied in detail, following the time evolution of the concentration of phenol and its intermediates by liquid chromatography. The results show that platinization has a distinct influence on the commercial compounds, decreasing globally the activity of P25 and increasing the activity of PC50 and UV100. An influence of charge-carrier lifetimes on the photoactivity of pure and platinized TiO2 samples has been evidenced.