Critical issues of double-metal layer coating on FBG for applications at high temperatures

Use of fiber Bragg gratings (FBGs) to monitor high temperature (HT) applications is of great interest to the research community. Standard commercial FBGs can operate up to 600 ∘ C. For applications beyond that value, specific processing of the FBGs must be adopted to allow the grating not to deteriorate. The most common technique used to process FBGs for HT applications is the regeneration procedure (RP), which typically extends their use up to 1000 ∘ C. RP involves a long-term annealing of the FBGs, to be done at a temperature ranging from 550 to 950 ∘ C. As at that temperature, the original coating of the FBGs would burn out, they shall stay uncoated, and their brittleness is a serious concern to deal with. Depositing a metal coating on the FBGs prior to process them for RP offers an effective solution to provide them with the necessary mechanical strengthening. In this paper, a procedure to provide the FBG with a bimetallic coating made by copper and nickel electrodeposition (ED) is proposed, discussing issues related to the coating morphology, adherence to the fiber, and effects on the grating spectral response. To define the processing parameters of the proposed procedure, production tests were performed on dummy samples which were used for destructive SEM-EDS analysis. As a critical step, the proposed procedure was shown to necessitate a heat treatment after the nickel ED, to remove the absorbed hydrogen. The spectral response of the FBG samples was monitored along the various steps of the proposed procedure and, as a final proof test for adherence stability of the bimetallic coating, along a heating/cooling cycle from room temperature to 1010 ∘ C. The results suggest that, given the emergence of Kirkendall voids at the copper-nickel interface, occurring at the highest temperatures (700-1010 ∘ C), the bimetallic layer could be employed as FBG coating up to 700 ∘ C

Gold and Silver joining technologies in the Moche Tombs “Señor de Sipán” and “Señora de Cao jewelery

About 200 gold and silver funerary ornaments from the Moche tombs “Señor de Sipán” and “Señora de Cao” were analyzed to determine their metallurgic characteristics. Of particular interest was the question about the gold-silver joining process. To this aim, following methods were employed, all based on the use of X-rays: - energy dispersive X-ray fluorescence; - transmission of monoenergetic fluorescent X-rays; - radiography. At least three joining methods were possibly identified: - of gluing gold and silver sheets; - of brazing using a proper solder; - of using a mercury amalgam

Gilding for Matter Decoration and Sublimation. A Brief History of the Artisanal Technical Know-how

IJCS it is an open access journal. All content is freely available without charge to any user or his/her institutionInternational audienceThe process used to decorate art objects with thinner and thinner gold coatings varied during centuries. Foil or leaf metal gilding technology was complemented around the beginning of the Christian era by mercury gilding. Simultaneously was developed in some geographic areas the surface depletion process for gilded copper/silver alloys. This paper is motivated by the recent publication by the authors of a didactic opus devoted to the description and the discussion of the technical history of the various gilding procedures, based on the study by modern investigation techniques of a number of gilded museum objects. Through examples from laboratory studies on museum objects, the main evolution steps of gold application are described. A recent mechanical modelling work about gold leaf forming by beating is reported. The different coating processes are discussed, depending on the substrate nature and surface treatment before gilding. It includes high temperature firing for mercury gilding, or powder gilding, e.g. on Middle-Age Syria glass. The paper ends with a listing of the research perspectives open for the presently poorly developed study of the adhesion mechanisms between gold leaf and its substrate. It discusses the important issue of gold-metal interdiffusion during metal gilding processes involving a high temperature step

Symbols of protection : the significance of animal-ornamented shields in early Anglo-Saxon England

The significance of shields with animal ornament on the boss and/or board in early Anglo-Saxon society is sought in the coincidence of artefactual, stylistic and iconographic symbolism. Twenty shields buried in the 6th to earliest 7th century, together with seventeen further mounts which were probably originally designed for shields, form the basis of a systematic typological review; decoration in Salin's Style I is emphasised. Analysis of dating, distribution and use in burial establishes cultural and social contexts. The meaning of the ornamental repertoire is sought through iconographic analogies, notably with Scandinavian bracteates and their putative association with a cult of Óðinn/Woden. It is proposed that the animal ornament invested the shields with a specific apotropaic quality, which emphasised, and amplified, the protective role of select adult males, and hence their authority over kin, community and even kingdo

Travelling waves in nonlinear diffusion-convection-reaction

The study of travelling waves or fronts has become an essential part of the mathematical analysis of nonlinear diffusion-convection-reaction processes. Whether or not a nonlinear second-order scalar reaction-convection-diffusion equation admits a travelling-wave solution can be determined by the study of a singular nonlinear integral equation. This article is devoted to demonstrating how this correspondence unifies and generalizes previous results on the occurrence of travelling-wave solutions of such partial differential equations. The detailed comparison with earlier results simultaneously provides a survey of the topic. It covers travelling-wave solutions of generalizations of the Fisher, Newell-Whitehead, Zeldovich, KPP and Nagumo equations, the Burgers and nonlinear Fokker-Planck equations, and extensions of the porous media equation. \u

New Leaf Gilding Alloys: Physico-Chemistry, Colour, Mechanical Behavior

International audienceIn the frame of a systematic investigation on leaf gilding history and processes, in a research program intending to propose gold leaf alloys specially devoted to restoration, new gold alloys containing low concentration additions of In or Pd were designed and leaves were elaborated in collaboration with the goldbeater Dauvet. The influence of those elements on the colour change induced by alloying was obtained by colorimetry. The microstructural and metallurgical properties of the alloys were studied by scanning electron microscopy (SEM). The foils and leaves were characterized at the different manufacturing steps by EBSD (Backscattered Electron Diffraction), in order to evaluate the effect of the fabrication process on the microstructure and crystallographic texture. Surface segregation of the alloying element, influencing surface colour, was sometimes evidenced and discussed. The mechanical properties of the foils or leaves were measured by micro-and nano-indentation. The obtained properties and behaviour of the new alloys were compared with those of the leaves currently used for leaf gilding. The results conducted the beating company to consider developing new gold leaves production range(s) devoted specially for restoration application. As a result of the present investigation, new manufacturing and gilding procedures have been proposed

Stereocomplex formation in ABA triblock copolymers of poly(lactide) (A) and poly(ethylene glycol) (B)

Two series of triblock copolymers of poly(ethylene glycol) (PEG, number-average molecular weight [bar M ]n = 6000) and poly(L-lactide) (PLLA) or poly(D-lactide) (PDLA) were prepared by ring-opening polymerization of lactide initiated by PEG end groups using stannous octoate as a catalyst, either in refluxing toluene or in the melt at 175°C. The weight percentage of PLA in the polymers varied between 15 and 75 wt.-%. Blends of polymers containing blocks of opposite chirality were prepared by co-precipitation from homogeneous solutions. The melting temperatures of the crystalline PEG and PLA phases strongly depended on the composition of the polymers. The melting temperature of the PLA phase in the blends was approximately 40°C higher than that of the single block copolymers. Stereocomplex formation between blocks of enantiomeric poly(lactides) in PEG/PLA block copolymers was established for the first time. Water uptake of polymeric films prepared by solution casting was solely determined by the PEG content of the film

Phase and compositional analysis of a Sèvres soft paste porcelain plate from 1781, with a review of early porcelain techniques

Optical microscopy, X-ray diffraction, X-ray fluorescence and scanning electron microscopy analyses were carried out on a typical Sèvres soft (frit) porcelain plate from 1781 in order to determine the chemical and mineralogical composition as well as the microstructure of its ceramic body, glaze, overglaze decoration and gilding. The body is rich in SiO₂ (73 mass%), CaO (16) and alkali oxide (8) and shows acicular wollastonite and tridymite crystals embedded in a glassy matrix consisting of SiO₂ (75), K₂O (12) and CaO (9). The 50–90 µm thick, transparent lead glaze (40.9 PbO) contains 47.6 SiO₂, 6.5 K₂O and 3.5 CaO and shows a 35–75 µm thick reaction zone (50 SiO₂, 30 PbO, 14 CaO) towards the body. The maximum thickness of the different paints is 50 µm, with 15 µm as mean thickness of the individual paint stroke. Two blue colours, for the dentil comb and the flower painting, are chemically distinct (colouring CoO in the dental rim 7, in the flower’s blue 2 mass%) and contain many As- and Pb- rich globules and dendrites. Pseudohexagonal shaped platelets of Pb–Sb–Sn triple oxide crystals, embedded in a colourless glassy matrix, generate the opacity and the colour of the yellow paints. Opaque olive green colours are created by the combination of such yellow crystals with a bluish, Cu and Co bearing glassy matrix. The opaque red overglaze enamel is a mechanical mix of yellow Pb–Sb oxide crystals with an iron- rich (16 Fe₂O₃) Pb–silica glass. Purple is very homogeneous and shows tiny drops of pure gold (max. diam. 0.5 µm) in a glassy matrix (47 PbO, 46 SiO₂, 5 K₂O). Violet is a mechanical blend of flower’s blue and purple. The pure (99.5 Au, 0.5 Fe₂O₃) gilt consists of several folded gold particles. The results of this study are only broadly consistent with the archival documented 18th century technologies. The compositional dissimilarities of the studied enamels suggest that each colour was independently fritted. Consequently, the original colour recipes written down by Hellot in 1753 must have been modified in the 30 years since then

Biodegradable hollow fibres for the controlled release of hormones

Poly(l-lactide), (PLLA), hollow fibres were prepared using a dry-wet phase inversion spinning process. The effect of several spinning parameters (i.e. bore medium flow rate, spinning dope extrusion rate, fibre take-up rate, and spinning height) on the hollow fibre dimensions is reported. The use of several spinning systems (i.e. different solvent/non-solvent pairs with or without additive) resulted in PLLA hollow fibres with varying asymmetric membrane structures, i.e. a porous matrix covered by an internal and external skin varying from very thick and dense to very thin and porous. Some of the differences in membrane structure were qualitatively explained on the basis of a model developed by Reuvers [52] for the formation of flat-sheet membranes by immersion precipitation. Release experiments were carried out using PLLA hollow fibres filled with a 25 wt.% dispersion of micronized 3H-levonorgestrel in castor oil, and a receiving fluid consisting of 40 wt.% aqueous ethanol. The hollow fibre levonorgestrel release rates were found to be dependent on the membrane structure of the hollow fibre wall. For the different hollow fibre samples, zero-order levonorgestrel release rates were found, in the range of 0.1–10 μg/cm/day. Possible release mechanisms are discussed. Preliminary in vivo (rabbit) release experiments showed that constant levonorgestrel blood plasma levels could be obtained for a period up to 210 days. It is concluded that the new biodegradable hollow fibre reservoir device shows very promising properties for possible application as a long-acting contraceptive delivery system

TWO RECIPES FROM PORTUGUESE TRADITION OF GILDING ON WOODEN SUPPORT BETWEEN LABORATORY REPRODUCTION AND ANALYTICAL INVESTIGATION

This paper has the main purpose to compile and highlight the first data obtained from experimental studies on docμmented reconstructions of gilded composites performed within a research project on gilding materials and techniques in Portugal (www.gilt-teller.pt) funded by FCT. Two water gilding recipes were appropriately chosen from the treatises written by the Portuguese Filipe Nunes (1615) and José Lopes Baptista de Almada (1749) as being representative for Baroque époque. Based on these recipes, the production of raw materials - “gesso grosso”, “gesso fino”, bole, animal glue (from lamb and goat skins) - was made as faithful as possible. Their application was then performed in laboratory following the indications given by these authors or by treatises of previous époques (e.g. the Bolognese treatise for thawing leather), on plane and curved wooden supports (pine and oak species) using three types of leaf: gold (Au/Ag/Cu) of 22 and 23.75 karat respectively and silver. After the completion of gilding, the samples’ surfaces were divided into areas and on each different finishing layers (wax, animal glue size) and decorations (punching, “esgrafitado”, “estofado”) were applied. An analytical campaign using optical microscopy (OM) and scanning electron microscopy (SEM) on surfaces and cross sections, X-ray diffraction (XRD), microcomputerized tomography (microCT) and colorimetry (CIEL*a*b*) was undertaken in order to characterize the gilded composites and to assess the faithfulness of the reproductions in the laboratory. Correlations between the information given by the recipes and the composition and stratigraphical patterns of the reconstructions can be established. Furthermore, the study aims to highlight the difficulties encountered in analyzing real samples and comparing the results with those from reproductions as the number and types of layered materials are not always reproducible. A critical approach is needed and criteria for faithful reproduction of ancient recipes are suggested