Chemical compositions of solid particles present in the Greenland NEEM ice core over the last 110,000 years

This study reports the chemical composition of particles present along Greenland’s North Greenland Eemian Ice Drilling (NEEM) ice core, back to 110,000 years before present. Insoluble and soluble particles larger than 0.45 μm were extracted from the ice core by ice sublimation, and their chemical composition was analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy and micro-Raman spectroscopy. We show that the dominant insoluble components are silicates, whereas NaCl, Na₂SO₄, CaSO ₄, and CaCO₃ represent major soluble salts. For the first time, particles of CaMg(CO₃)₂ and Ca(NO₃)₂ 4H₂O are identified in a Greenland ice core. The chemical speciation of salts varies with past climatic conditions. Whereas the fraction of Na salts (NaCl + Na₂SO₄) exceeds that of Ca salts (CaSO₄+ CaCO₃) during the Holocene (0.6–11.7 kyr B.P.), the two fractions are similar during the Bølling-Allerød period (12.9–14.6 kyr B.P.). During cold climate such as over the Younger Dryas (12.0–12.6 kyr B.P.) and the Last Glacial Maximum (15.0–26.9 kyr B.P.), the fraction of Ca salts exceeds that of Na salts, showing that the most abundant ion generally controls the salt budget in each period. High-resolution analyses reveal changing particle compositions: those in Holocene ice show seasonal changes, and those in LGM ice show a difference between cloudy bands and clear layers, which again can be largely explained by the availability of ionic components in the atmospheric aerosol body of air masses reaching Greenland.

Experimental and numerical study of cw green laser crystallization of a-Si:H thin films

Crystallization and grain growth technique of thin film silicon are among the most promising methods for improving efficiency and lowering cost of solar cells. A major advantage of laser crystallization and annealing over conventional heating methods is its ability to limit rapid heating and cooling to thin surface layers. Laser energy is used to heat the amorphous silicon thin film, melting it and changing the microstructure to polycrystalline silicon (poly-Si) as it cools. Depending on the laser density, the vaporization temperature can be reached at the center of the irradiated area. In these cases ablation effects are expected and the annealing process becomes ineffective. The heating process in the a-Si thin film is governed by the general heat transfer equation. The two dimensional non-linear heat transfer equation with a moving heat source is solve numerically using the finite element method (FEM), particularly COMSOL Multiphysics. The numerical model help to establish the density and the process speed range needed to assure the melting and crystallization without damage or ablation of the silicon surface. The samples of a-Si obtained by physical vapour deposition were irradiated with a cw-green laser source (Millennia Prime from Newport-Spectra) that delivers up to 15 W of average power. The morphology of the irradiated area was characterized by confocal laser scanning microscopy (Leica DCM3D) and Scanning Electron Microscopy (SEM Hitachi 3000N). The structural properties were studied by micro-Raman spectroscopy (Renishaw, inVia Raman microscope).

Thermal, stress, and traps effects in AlGaN/GaN HEMTs

GaN y AlN son materiales semiconductores piezoeléctricos del grupo III-V. La heterounión AlGaN/GaN presenta una elevada carga de polarización tanto piezoeléctrica como espontánea en la intercara, lo que genera en su cercanía un 2DEG de grandes concentración y movilidad. Este 2DEG produce una muy alta potencia de salida, que a su vez genera una elevada temperatura de red. Las tensiones de puerta y drenador provocan un stress piezoeléctrico inverso, que puede afectar a la carga de polarización piezoeléctrica y así influir la densidad 2DEG y las características de salida. Por tanto, la física del dispositivo es relevante para todos sus aspectos eléctricos, térmicos y mecánicos. En esta tesis se utiliza el software comercial COMSOL, basado en el método de elementos finitos (FEM), para simular el comportamiento integral electro-térmico, electro-mecánico y electro-térmico-mecánico de los HEMTs de GaN. Las partes de acoplamiento incluyen el modelo de deriva y difusión para el transporte electrónico, la conducción térmica y el efecto piezoeléctrico. Mediante simulaciones y algunas caracterizaciones experimentales de los dispositivos, hemos analizado los efectos térmicos, de deformación y de trampas. Se ha estudiado el impacto de la geometría del dispositivo en su auto-calentamiento mediante simulaciones electro-térmicas y algunas caracterizaciones eléctricas. Entre los resultados más sobresalientes, encontramos que para la misma potencia de salida la distancia entre los contactos de puerta y drenador influye en generación de calor en el canal, y así en su temperatura. El diamante posee une elevada conductividad térmica. Integrando el diamante en el dispositivo se puede dispersar el calor producido y así reducir el auto-calentamiento, al respecto de lo cual se han realizado diversas simulaciones electro-térmicas. Si la integración del diamante es en la parte superior del transistor, los factores determinantes para la capacidad disipadora son el espesor de la capa de diamante, su conductividad térmica y su distancia a la fuente de calor. Este procedimiento de disipación superior también puede reducir el impacto de la barrera térmica de intercara entre la capa adaptadora (buffer) y el substrato. La muy reducida conductividad eléctrica del diamante permite que pueda contactar directamente el metal de puerta (muy cercano a la fuente de calor), lo que resulta muy conveniente para reducir el auto-calentamiento del dispositivo con polarización pulsada. Por otra parte se simuló el dispositivo con diamante depositado en surcos atacados sobre el sustrato como caminos de disipación de calor (disipador posterior). Aquí aparece una competencia de factores que influyen en la capacidad de disipación, a saber, el surco atacado contribuye a aumentar la temperatura del dispositivo debido al pequeño tamaño del disipador, mientras que el diamante disminuiría esa temperatura gracias a su elevada conductividad térmica. Por tanto, se precisan capas de diamante relativamente gruesas para reducer ele efecto de auto-calentamiento. Se comparó la simulación de la deformación local en el borde de la puerta del lado cercano al drenador con estructuras de puerta estándar y con field plate, que podrían ser muy relevantes respecto a fallos mecánicos del dispositivo. Otras simulaciones se enfocaron al efecto de la deformación intrínseca de la capa de diamante en el comportamiento eléctrico del dispositivo. Se han comparado los resultados de las simulaciones de la deformación y las características eléctricas de salida con datos experimentales obtenidos por espectroscopía micro-Raman y medidas eléctricas, respectivamente. Los resultados muestran el stress intrínseco en la capa producido por la distribución no uniforme del 2DEG en el canal y la región de acceso. Además de aumentar la potencia de salida del dispositivo, la deformación intrínseca en la capa de diamante podría mejorar la fiabilidad del dispositivo modulando la deformación local en el borde de la puerta del lado del drenador. Finalmente, también se han simulado en este trabajo los efectos de trampas localizados en la superficie, el buffer y la barrera. Las medidas pulsadas muestran que tanto las puertas largas como las grandes separaciones entre los contactos de puerta y drenador aumentan el cociente entre la corriente pulsada frente a la corriente continua (lag ratio), es decir, disminuir el colapse de corriente (current collapse). Este efecto ha sido explicado mediante las simulaciones de los efectos de trampa de superficie. Por su parte, las referidas a trampas en el buffer se enfocaron en los efectos de atrapamiento dinámico, y su impacto en el auto-calentamiento del dispositivo. Se presenta también un modelo que describe el atrapamiento y liberación de trampas en la barrera: mientras que el atrapamiento se debe a un túnel directo del electrón desde el metal de puerta, el desatrapamiento consiste en la emisión del electrón en la banda de conducción mediante túnel asistido por fonones. El modelo también simula la corriente de puerta, debida a la emisión electrónica dependiente de la temperatura y el campo eléctrico. Además, también se ilustra la corriente de drenador dependiente de la temperatura y el campo eléctrico. ABSTRACT GaN and AlN are group III-V piezoelectric semiconductor materials. The AlGaN/GaN heterojunction presents large piezoelectric and spontaneous polarization charge at the interface, leading to high 2DEG density close to the interface. A high power output would be obtained due to the high 2DEG density and mobility, which leads to elevated lattice temperature. The gate and drain biases induce converse piezoelectric stress that can influence the piezoelectric polarization charge and further influence the 2DEG density and output characteristics. Therefore, the device physics is relevant to all the electrical, thermal, and mechanical aspects. In this dissertation, by using the commercial finite-element-method (FEM) software COMSOL, we achieved the GaN HEMTs simulation with electro-thermal, electro-mechanical, and electro-thermo-mechanical full coupling. The coupling parts include the drift-diffusion model for the electron transport, the thermal conduction, and the piezoelectric effect. By simulations and some experimental characterizations, we have studied the device thermal, stress, and traps effects described in the following. The device geometry impact on the self-heating was studied by electro-thermal simulations and electrical characterizations. Among the obtained interesting results, we found that, for same power output, the distance between the gate and drain contact can influence distribution of the heat generation in the channel and thus influence the channel temperature. Diamond possesses high thermal conductivity. Integrated diamond with the device can spread the generated heat and thus potentially reduce the device self-heating effect. Electro-thermal simulations on this topic were performed. For the diamond integration on top of the device (top-side heat spreading), the determinant factors for the heat spreading ability are the diamond thickness, its thermal conductivity, and its distance to the heat source. The top-side heat spreading can also reduce the impact of thermal boundary resistance between the buffer and the substrate on the device thermal behavior. The very low electrical conductivity of diamond allows that it can directly contact the gate metal (which is very close to the heat source), being quite convenient to reduce the self-heating for the device under pulsed bias. Also, the diamond coated in vias etched in the substrate as heat spreading path (back-side heat spreading) was simulated. A competing mechanism influences the heat spreading ability, i.e., the etched vias would increase the device temperature due to the reduced heat sink while the coated diamond would decrease the device temperature due to its higher thermal conductivity. Therefore, relative thick coated diamond is needed in order to reduce the self-heating effect. The simulated local stress at the gate edge of the drain side for the device with standard and field plate gate structure were compared, which would be relevant to the device mechanical failure. Other stress simulations focused on the intrinsic stress in the diamond capping layer impact on the device electrical behaviors. The simulated stress and electrical output characteristics were compared to experimental data obtained by micro-Raman spectroscopy and electrical characterization, respectively. Results showed that the intrinsic stress in the capping layer caused the non-uniform distribution of 2DEG in the channel and the access region. Besides the enhancement of the device power output, intrinsic stress in the capping layer can potentially improve the device reliability by modulating the local stress at the gate edge of the drain side. Finally, the surface, buffer, and barrier traps effects were simulated in this work. Pulsed measurements showed that long gates and distances between gate and drain contact can increase the gate lag ratio (decrease the current collapse). This was explained by simulations on the surface traps effect. The simulations on buffer traps effects focused on illustrating the dynamic trapping/detrapping in the buffer and the self-heating impact on the device transient drain current. A model was presented to describe the trapping and detrapping in the barrier. The trapping was the electron direct tunneling from the gate metal while the detrapping was the electron emission into the conduction band described by phonon-assisted tunneling. The reverse gate current was simulated based on this model, whose mechanism can be attributed to the temperature and electric field dependent electron emission in the barrier. Furthermore, the mechanism of the device bias via the self-heating and electric field impact on the electron emission and the transient drain current were also illustrated.

High rate growth of nanocrystalline diamond films using high microwave power and pure nitrogen/methane/hydrogen plasma

In this work, we investigate the impact of minute amounts of pure nitrogen addition into conventional methane/hydrogen mixtures on the growth characteristics of nanocrystalline diamond (NCD) films by microwave plasma assisted chemical vapour deposition (MPCVD), under high power conditions. The NCD films were produced from a gas mixture of 4% CH4/H2 with two different concentrations of N2 additive and microwave power ranging from 3.0 kW to 4.0 kW, while keeping all the other operating parameters constant. The morphology, grain size, microstructure and texture of the resulting NCD films were characterized by using scanning electron microscope (SEM), micro-Raman spectroscopy and X-ray diffraction (XRD) techniques. N2 addition was found to be the main parameter responsible for the formation and for the key change in the growth characteristics of NCD films under the employed conditions. Growth rates ranging from 5.4 μm/h up to 9.6 μm/h were achieved for the NCD films, much higher than those usually reported in the literature. The enhancing factor of nitrogen addition on NCD growth rate was obtained by comparing with the growth rate of large-grained microcrystalline diamond films grown without nitrogen and discussed by comparing with that of single crystal diamond through theoretical work in the literature. This achievement on NCD growth rate makes the technology interesting for industrial applications where fast coating of large substrates is highly desirable.

Effect of methane concentration in hydrogen plasma on hydrogen impurity incorporation in thick large-grained polycrystalline diamond films

We investigate the impact of methane concentration in hydrogen plasma on the growth of large-grained polycrystalline diamond (PCD) films and its hydrogen impurity incorporation. The diamond samples were produced using high CH4 concentration in H2 plasma and high power up to 4350 W and high pressure (either 105 or 110 Torr) in a microwave plasma chemical vapor deposition (MPCVD) system. The thickness of the free-standing diamond films varies from 165 µm to 430 µm. Scanning electron microscopy (SEM), micro-Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the morphology, crystalline and optical quality of the diamond samples, and bonded hydrogen impurity in the diamond films, respectively. Under the conditions employed here, when methane concentration in the gas phase increases from 3.75% to 7.5%, the growth rate of the PCD films rises from around 3.0 µm/h up to 8.5 µm/h, and the optical active bonded hydrogen impurity content also increases more than one times, especially the two CVD diamond specific H related infrared absorption peaks at 2818 and 2828 cm−1 rise strongly; while the crystalline and optical quality of the MCD films decreases significantly, namely structural defects and non-diamond carbon phase content also increases a lot with increasing of methane concentration. Based on the results, the relationship between methane concentration and diamond growth rate and hydrogen impurity incorporation including the form of bonded infrared active hydrogen impurity in CVD diamonds was analyzed and discussed. The effect of substrate temperature on diamond growth was also briefly discussed. The experimental findings indicate that bonded hydrogen impurity in CVD diamond films mainly comes from methane rather than hydrogen in the gas source, and thus can provide experimental evidence for the theoretical study of the standard methyl species dominated growth mechanism of CVD diamonds grown with methane/hydrogen mixtures.

A new regime for high rate growth of nanocrystalline diamond films using high power and CH4/H2/N2/O2 plasma

In this work, we report high growth rate of nanocrystalline diamond (NCD) films on silicon wafers of 2 inches in diameter using a new growth regime, which employs high power and CH4/H2/N2/O2 plasma using a 5 kW MPCVD system. This is distinct from the commonly used hydrogen-poor Ar/CH4 chemistries for NCD growth. Upon rising microwave power from 2000 W to 3200 W, the growth rate of the NCD films increases from 0.3 to 3.4 μm/h, namely one order of magnitude enhancement on the growth rate was achieved at high microwave power. The morphology, grain size, microstructure, orientation or texture, and crystalline quality of the NCD samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, and micro-Raman spectroscopy. The combined effect of nitrogen addition, microwave power, and temperature on NCD growth is discussed from the point view of gas phase chemistry and surface reactions. © 2011 Elsevier B.V. All rights reserved.

Influência das espécies ativas na absorção de intersticiais durante a carbonitretação a plasma do TI

Physical-chemical properties of Ti are sensible to the presence of interstitial elements. In the case of thermochemical treatments plasma assisted, the influence of different active species is not still understood. In order to contribute for such knowledge, this work purposes a study of the role played by the active species atmosphere into the Ar N2 CH4 carbonitriding plasma. It was carried out a plasma diagnostic by OES (Optical Emission Spectroscopy) in the z Ar y N2 x CH4 plasma mixture, in which z, y and x indexes represent gas flow variable from 0 to 4 sccm (cm3/min). The diagnostic presents abrupt variations of emission intensities associated to the species in determined conditions. Therefore, they were selected in order to carry out the chemical treatment and then to investigate their influences. Commercial pure Ti disks were submitted to plasma carbonitriding process using pre-established conditions from the OES measurements while some parameters such as pressure and temperature were maintained constant. The concentration profiles of interstitial elements (C and N atoms) were determined by Resonant Nuclear Reaction Analysis (NRA) resulting in a depth profile plots. The reactions used were 15N(ρ,αγ)12C and 12C(α,α)12C. GIXRD (Grazing Incidence X-Ray Diffraction) analysis was used in order to identify the presence of phases on the surface. Micro-Raman spectroscopy was used in order to qualitatively study the carbon into the TiCxN1 structure. It has been verified which the density species effectively influences more the diffusion of particles into the Ti lattice and characteristics of the layer formed than the gas concentration. High intensity of N2 + (391,4 nm) and CH (387,1 nm) species promotes more diffusion of C and N. It was observed that Hα (656,3 nm) species acts like a catalyzer allowing a deeper diffusion of nitrogen and carbon into the titanium lattice.

Variedades e estilos na obra atribuída a Frei Carlos: novas perspetivas

Este trabalho de investigação centra-se no contributo dos exames de superfície e nas análises micro-analíticas no estudo de vinte e uma pinturas atribuídas à oficina de Frei Carlos, um dos grandes Mestres Luso-Flamengos ativos em território Nacional durante a primeira metade do século XVI. A "Pintura Luso-Flamenga" é uma expressão comummente usada na história da pintura Portuguesa do primeiro terço do século XVI e no seu sentido mais básico designa o trabalho de mestres flamengos que se instalaram em Portugal durante o reinado de D. Manuel I (1495- 1521) contribuindo decisivamente para o processo de renovação da pintura Portuguesa na época. O estudo integrado combina a pesquisa histórica em fontes documentais com exames de superfície e de caracterização material das obras de arte. O estudo material das pinturas foi realizado através de microscopia ótica, microscopia de infravermelhos com transformada de Fourier, espectroscopia de micro-Raman, microscopia eletrónica de varrimento acoplada com espectrometria de energia dispersiva de raios X, micro- difração de raios-X, cromatografia líquida de alta eficiência e pirólise acoplada à cromatografia gasosa /espectrometria de massa. Esta investigação envolveu técnicas complementares de análise de superfície e de ponto no estudo técnico e material das preparações, imprimitura, desenho subjacente, camadas pictóricas e sucessões estratigráficas, dando a conhecer os materiais utilizados na execução técnica das pinturas e evidenciando especificidades técnicas da produção artística. Este estudo pretende inclusivamente evidenciar alguns detalhes técnicos do artista que possivelmente estão relacionados com a herança das práticas Flamengas. O conhecimento de algumas particularidades da técnica deste Mestre também permitiu estabelecer comparações com duas pinturas que haviam sido atribuídas, com algumas reservas, a esta oficina de pintura Luso-Flamenga. Mais recentemente, como resultado de um estudo colaborativo, foi realizada uma ampla campanha de reflectografia infravermelhos, introduzindo novos dados acerca da execução técnica do desenho subjacente, o que contribuiu para diferenciar, nestas duas pinturas, outra "mão", atribuída então a um seguidor de Frei Carlos. Esta investigação introduz um novo e profundo conhecimento sobre a Oficina de Frei Carlos, permitindo estabelecer comparações com a obra do seu seguidor e com uma pintura também atribuída a esta oficina e que incorpora o Museu da National Gallery (NG5594), evidenciando os materiais utilizados na técnica de produção artística e especificidades técnicas aliadas aos processos criativos/ construtivos que permitem estabelecer os pontos de contacto e de diferenciação entre estas obras; Varieties and styles in the works attributed to Frei Carlos - new perspectives Abstract: This investigation is focused on the contributions of surface exams and micro-analytical research in the study of twenty one paintings attributed to Frei Carlos workshop, one of the most important Portuguese-Flemish painters active in our country during the first half of sixteen Century. "Portuguese-Flemish Painting" is a common expression used in the history of Portuguese painting of the first third of the sixteenth century and in its most basic meaning designates the work of Flemish masters who settled in Portugal during the reign of King Manuel I (1495-1521) contributing decisively to the process of renewal of Portuguese painting at the time. The integrated approach combines historical research on documental sources with surface examination and material characterization of the paintings by using state-of-art analytical techniques. Microanalysis was carried out by optical microscopy, micro-Fourier-transform infrared-spectroscopy, micro-Raman spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry, micro-X-ray diffraction analysis, high performance liquid chromatography and Pyrolysis gas chromatography mass spectrometry. This complementary surface and analytical research was involved in the technical and material characterization of grounds, underdrawings, primings, paint layers and its multi-layered build-up, providing access to the painter´s materials used in the technical execution of the paintings and details of the technique of artistic production. This study also intends to expose some usual details of the artist’s technique which are possibly related to the Master´s Flemish influence. The knowledge of some particularities of the Master´s technique also allowed a new comparison with two paintings that had been attributed with some reserves to this Portuguese-Flemish workshop. More recently, as a result of a collaborative study, an extensive infrared reflectography campaign was made, giving new data concerning underdrawings technical execution and contributing to differentiate, in these two paintings, another “hand”, attributed to a follower of Frei Carlos. Complementary analytical research also added a new and deep insight into Frei Carlos workshop, his follower and a panel that still attributed to Frei Carlos workshop that integrates the National Gallery´s Museum (NG5594), evidencing the materials used in technical production, their models and sources of artistic inspiration, techniques and pictorial construction procedures that could specifically relate or distinguish between them.

Caracterização material e microbiológica de espécimes fotográficos

Neste trabalho foram estudadas quatro espécies fotográficas, dois ambrótipos do séc. XIX e dois negativos de gelatina do séc. XX. Estas espécies são suscetiveis a degradações, físicas, químicas e microbiológicas. Técnicas de análise não destrutivas como, a fotografia, a microscopia ótica, a microscopia eletrónica de varrimento e espetroscopia de raios-X por dispersão em energias, a micro-espetroscopia de infravermelho em modo de reflexão total atenuada, a micro-espetroscopia de Raman e a micro-difração de raios-X foram utilizadas na caracterização material. A colonização microbiológica das amostras foi estudada através do isolamento e caracterização dos microrganismos contaminantes. Foram ainda realizados estudos de determinação de atividade celulolítica para os isolados fúngicos provenientes dos ambrótipos bem como ensaios de simulação, nos quais se utilizaram estes isolados para induzir contaminação em ambrótipos contemporâneos e assim avaliar o seu potencial biodeteriogénico. Foi ainda avaliado o potencial biodeteriogénico de isolados bacterianos em negativos de gelatina contemporâneos; Abstract: Material and microbiological characterization of photographic specimens This work presents a scientific study of four photographic specimens, two ambrotypes and two gelatin-silver negative plates from 19th and 20th century, respectively. These specimens are susceptible to physical, chemical and microbiological degradations. A non-destructive approach was used based on techniques such as technical photography, optical microscopy, scanning electron microscopy, infrared micro-spectroscopy, micro-Raman spectroscopy and X-rays micro-diffraction. Microbiological colonization of the samples was studied by isolation and characterization of the contaminating microorganisms. Studies to evaluate cellulolytic activity of fungal isolates from the ambrotypes were carried out and also simulation assays in which were used these isolated to induce contamination in contemporary ambrotypes were done to evaluate their biodeteriogenic potential. It was also studied the biodeteriogenic potential of the bacterial isolates from gelatin-silver negative plates which were subsequently inoculated in contemporary gelatin-silver negatives.

José de Escovar at the Chapel of the Souls: Technical and Material Study of a 1603 Panel Painting

This article reports the preliminary results of a technical and material study carried out on a 17th century panel painting located at the Chapel of the Souls in the main church of Vila Nova da Baronia (30 km away from Evora city, in southern Portugal). This painting is attributed to Jose the Escovar, a painter that worked for Evora Archiepiscopate between 1583 and 1622. Jose the Escovar is known by his mural paintings all across the Alentejo region. This is the first time that a panel painting made by this artist was studied. Analytical methods used included in situ technical photography (visible (Vis), raking light (RAK), infrared (IR), and ultraviolet (UV)), optical microscopy of cross sections, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), micro Raman spectroscopy, and micro Fourier transform infrared spectroscopy (m-FT-IR). The goal was to ascertain the techniques and colored materials used by Escovar on this painting so that the data can be used in future comparisons with others works attributed to this painter based on stylistic aspects.

Uncover the mantle: rediscovering Gregório Lopes palette and technique with a study on the painting “Mater Misericordiae”

Grego´rio Lopes (c. 1490–1550) was one of the most prominent painters of the renaissance and Mannerism in Portugal. The painting “Mater Misericordiae” made for the Sesimbra Holy House of Mercy, circa 1535–1538, is one of the most significant works of the artist, and his only painting on this theme, being also one of the most significant Portuguese paintings of sixteenth century. The recent restoration provided the possibility to study materially the painting for the first time, with a multianalytical methodology incorporating portable energy-dispersive X-ray fluorescence spectroscopy, scanning electron microscopy–energy-dispersive spectroscopy, micro-X-ray diffraction, micro-Raman spectroscopy and high-performance liquid chromatography coupled to diode array and mass spectrometry detectors. The analytical study was complemented by infrared reflectography, allowing the study of the underdrawing technique and also by dendrochronology to confirm the date of the wooden panels (1535–1538). The results of this study were compared with previous ones on the painter’s workshop, and significant differences and similitudes were found in the materials and techniques used

New insight on the underdrawing of 16th Flemish-Portuguese easel paintings by combined surface analysis and microanalytical techniques

This paper focusses on the study of the underdrawings of 16th century easel paintings attributed to the workshop of the Portuguese-Flemish Master Frei Carlos. This investigation encompasses multidisciplinary research that relates the results of surface exams (infrared reflectography, standard light photography and infrared photography) with analytical investigations. The surface analysis of Frei Carlos’ underdrawings by infrared reflectography has shown heterogeneous work, revealing two different situations: (1) an abundant and expressive underdrawing, revealing a Flemish influence and (2) a simple and outlined underdrawing. This preliminary research raised an important question related to this Portuguese-Flemish workshop and to the analytical approach: Is the underdrawing's heterogeneity, as observed in the reflectograms, related to different artists or is this rather an effect that is produced due to the use of different materials in the underdrawing's execution? Consequently, if different materials were used, how can we have access to the hidden underdrawings? In order to understand the reasons for this dissemblance, chemical analysis of micro-samples collected in underdrawing areas and representing both situations were carried out by optical microscopy, micro Fourier transform infrared spectroscopy (μ-FTIR), scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX) and micro-Raman spectroscopy (μ-Raman). Taking into account the different possibilities and practical and theoretical limitations of surface and punctual examinations in the study of easel painting underdrawings, the methodology of research was adjusted, sometimes resulting in a re-analysis of experimental results. This research shows the importance of combining multispectral surface exams and chemical analysis in the understanding of the artistic creative processes of 16th century easel paintings.

Scanning electron microscopy with energy dispersive spectroscopy and Raman and infrared spectroscopic study of tilleyite Ca5Si2O7(CO3)2-Y

The mineral tilleyite-Y, a carbonate-silicate of calcium, has been studied by scanning electron microscopy with chemical analysis using energy dispersive spectroscopy (EDX) and Raman and infrared spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the tilleyite structure. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water in different molecular environments in the structure of tilleyite. Vibrational spectroscopy offers new information on the mineral tilleyite.