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A categorization of corrosion morphologies of archaeological Sn bronzes was carried out on archaeological Iron Age objects. The objects come from a Celtic deposit located in central France (Tintignac, Corrèze) and are dated between 2nd and 3rd cent BC. Being samples of corroded metals taken from a single find spot, parameters connected to the features of the alloy and known to influence the corrosion morphologies were thoroughly considered. Global processes were highlighted, and corrosion mechanisms were characterized with a multi-analytical protocol (SEM-EDS, micro-Raman spectroscopy, image analyses) according to the detected morphology. Elaboration of the results was carried out with a multicomponent approach. Results show the presence of 5 different morphologies correlated to the alloys characteristics of the objects. Alloy composition, microstructure, degree of deformation and grain size were found to influence the corrosion products formed and the morphology of the attack. In particular, the ‘tentacle like corrosion’, associated to a microbial attack was the most susceptible to the effect of metallurgical features: their occurrence is connected to a higher presence of Fe and Pb in the alloy, a homogeneous deformation and a larger grain size.

An experimental investigation of the crystallographic, Raman and transport properties of the Ce1−x(Nd0.74Tm0.26)xO2−x/2 (0.1 ≤ x ≤ 0.6) doped ceria system was performed with the aim of setting out correlations between structural features and ionic conductivity of the material. The chosen composition ensures that the average size of the Nd3+ and Tm3+ doping ions coincides with the one of Sm3+; even so, the studied system presents larger cell parameters and a wider compositional extent of the CeO2-based solid solution than Sm-doped ceria. Moreover, the occurrence of two different activation energies to ionic conduction below and above ~750 K determines the existence of two distinct conduction regimes. The described experimental results agree with the formation below the threshold temperature of 1 V O . . 2 T m C e ' trimers, which promote the incorporation of Nd C e ' isolated defects into the CeO2-based solid solution. In the high temperature range the dissociation of trimers induces the appearance of a lower activation energy; the extrapolation of its value at infinite dilution provides a result in good accordance with the expected binding energy of 1 V O . . RE C e ' dimers, pointing at their stability even in the high temperature conduction regime.

Defect aggregates in doped ceria play a crucial role in blocking the movement of oxygen vacancies and hence in reducing ionic conductivity. Nevertheless, evaluation of their amount and the correlation between domain size and transport properties is still an open issue. Data derived from a high-pressure X-ray diffraction investigation performed on the Ce1–x(Nd0.74Tm0.26)xO2–x/2 system are employed to develop a novel approach aimed at evaluating the defect aggregate content; the results are critically discussed in comparison to the ones previously obtained from Sm- and Lu-doped ceria. Defect clusters are present even at the lowest considered x value, and their content increases with increasing x and decreasing rare earth ion (RE3+) size; their amount, distribution, and spatial correlation can be interpreted as a complex interplay between the defects’ binding energy, nucleation rate, and growth rate. The synoptic analysis of data derived from all of the considered systems also suggests that the detection limit of the defects by X-ray diffraction is correlated to the defect size rather than to their amount, and that the vacancies’ flow through the lattice is hindered by defects irrespective of their size and association degree., A novel approach to the treatment of high-pressure X-ray diffraction data is applied to several rare earth-doped ceria systems with the aim of providing an evaluation of the amount of defect aggregates and of the composition of the CeO2-based solid solution. By this method, it is possible to effectively correlate the structural properties and ionic conductivity of the studied material.

The structural, microstructural, Raman and ionic conductivity properties of (Gd,Sm)-doped ceria were studied and compared to the ones of similar ceria systems with the aim of deepening the comprehension of the correlations between defect chemistry and movement of oxygen vacancies in such materials, which are ideal candidates as electrolytes in solid oxide cells. The system was chosen as it combines the advantages of using the most effective doping ions for ceria, namely Sm

Artistic patination is a traditional colouring technique for metal sculpture, employed by artists in ancient and modern times for aesthetic purposes. Today, knowledge of the artistic value ...

A high temperature structural study (673–1073 K) was performed by means of synchrotron x-ray diffraction and μ-Raman spectroscopy on several compositions belonging to the Ce1−xSmxO2−x/2 system with the aim to investigate the crystallographic features of Sm-doped ceria electrolytes at the fuel cell operating temperatures; ionic conductivity of samples with x ranging between 0.1 and 0.4 was measured too in order to correlate the main structural features with transport properties. A slight shift toward lower x values of the fluorite-based/hybrid region boundary is observed with increasing temperature; moreover, the coefficient of thermal expansion reveals a strong slope change close to x = 0.3, which represents the crossover composition between the two atomic arrangements. The presence of C-structured RE2O3 nanodomains within the fluorite structure starting from x ~ 0.2 is revealed by μ-Raman spectroscopy and confirmed by the behaviour of total conductivity. The ordering effect exerted at each temperature by the Sm-vacancies aggregates on the fluorite structure within the hybrid region influences the behaviour of both the intensity and the full width at half maximum of the Raman signal typical of the CeO2 structure. The obtained results are discussed in comparison to the ones deriving from the Gd-doped ceria system.

In this work, winery industry wastes were valorised through the extraction of high added value compounds (polyphenols), followed by thermal conversion of the exhausted solid residues. For this purpose, three different temperatures (623, 723 and 823 K) were tested. The increase of the heat treatment temperature resulted in a significant increment in gas production containing methane and other hydrocarbons. Lipophilic liquid product quantity in grape marc was limited both before and after the polyphenol extraction. The recovery of phenolic compounds before the thermal treatment notably decreases the chemical oxygen demand level of the resulting hydrophilic liquid fraction. The pyrolysis residue represents from 30 to 55% of the initial mass but corresponds to a relevant decrease of its volume, and can be considered a good source of graphitic carbon with higher calorific value with respect to the initial grape waste and applicable for energy production.

Tellurides are in years considered among the best intermetallic compounds for thermoelectric applications in the low-intermediate- temperature range. The corrosion behaviour of pure Pb, Sb and Bi tellurides is investigated in this work through a spectroscopic approach. The samples are synthesized using a muffle furnace and then placed in 0.1 M NaCl aerated solution at room temperature for 48 days. All samples are characterized, prior to and after immersion, in terms of crystal structure, morphology and phases composition (SEM-EDXS, XRD). A study of the ionic release, using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) analysis, is also carried out. Furthermore, a microRaman spectroscopy study is performed on surface corrosion products. The preliminary results reveal that PbTe and Bi 2 Te 3 show the best corrosion resistances in the considered environment.

Titanium dioxide (TiO2) thin films were prepared by means of electrochemical anodisation or anodic spark deposition (ASD) from thin and flat metallic titanium (Ti) films pre-deposited on high quality quartz substrates by electron beam evaporation. AFM analysis indicates the formation of uniform mesoporous layers and a definite increase about 50% of the film thickness upon anodisation and about 90% upon annealing. Anodised mesoporous TiO2films have been characterized by Raman spectroscopy, which indicates the presence of well-defined peaks related to anatase structure. Phase transformation from anatase to rutile was observed after annealing at temperatures up to 900°C for 3h.

Filled skutterudites are currently studied as thermoelectric materials to be used in the automotive and nautical field; the study of their resistance to a saline environment is therefore mandatory. To this purpose, the corrosion behavior of several compositions belonging to the Smy(FexNi1−x)4Sb12 skutterudites system was investigated by immersing samples in differently concentrated (0.1 and 0.5 M) NaCl solutions. The effect of the treatment was analyzed both by SEM–EDS on the sample surface and at fixed times by ICP-AES on the solution. The formation of an oxide layer was observed on the surface of all the samples: the film results uniformly grown on specimens treated in NaCl at the lower concentration, while it is cracked and not spread over the whole surface in the other samples. Relying on the oxide layer thickness, the oxidation resistance results to increase with increasing the Fe content; correspondingly, the Sb concentration in the more diluted solution decreases at each time considered with increasing the Fe amount, pointing at a strict correlation between the cationic release and the oxide formation, and suggesting a possible mechanism for the growth of the protective film.

Sm-Doped ceria is one of the most promising materials to be used as electrolyte in solid oxide fuel cells due to its remarkable ionic conductivity values in the intermediate temperature range. Transport properties and local structural features of Ce1-xSmxO2-x/2 (0.1 ≤ x ≤ 0.7) were studied by an impedance/μ-Raman spectroscopy coupled approach up to 1073 K. Results suggest that C-based nanosized defect clusters are responsible for the drop in ionic conductivity observed even at x = 0.2, i.e. at a Sm content lower than necessary to allow C domains to reach the percolation threshold through crystallites. Moreover, within the fluorite-type compositional region, with increasing the Sm content, defect clusters undergo a rearrangement resulting in the enlargement of C-based domains rather than in the increase of their number; at higher x, on the contrary, both the size and amount of C domains increase in parallel.

The use of amorphous, SiO2-TiO2 nanolayered coatings has been proposed recently for the mirrors of 3rd-generation interferometric detectors of gravitational waves, to be operated at low temperature. Coatings with a high number of low-high index sub-units pairs with nanoscale thickness were found to preserve the amorphous structure for high annealing temperatures, a key factor to improve the mechanical quality of the mirrors. The optimization of mirror designs based on such coatings requires a detailed knowledge of the optical properties of sub-units at the nm-thick scale. To this aim we have performed a Spectroscopic Ellipsometry (SE) study of amorphous SiO2-TiO2 nanolayered films deposited on Si wafers by Ion Beam Sputtering (IBS). We have analyzed films that are composed of 5 and 19 nanolayers (NL5 and NL19 samples) and have total optical thickness nominally equivalent to a quarter of wavelength at 1064 nm. A set of reference optical properties for the constituent materials was obtained by the analysis of thicker SiO2 and TiO2 homogeneous films (∼ 120 nm) deposited by the same IBS facility. By flanking SE with ancillary techniques, such as TEM and AFM, we built optical models that allowed us to retrieve the broad-band (250–1700 nm) optical properties of the nanolayers in the NL5 and NL19 composite films. In the models which provided the best agreement between simulation and data, the thickness of each sub-unit was fitted within rather narrow bounds determined by the analysis of TEM measurements on witness samples. Regarding the NL5 sample, with thickness of 19.9 nm and 27.1 nm for SiO2 and TiO2 sub-units, respectively, the optical properties presented limited variations with respect to the thin film counterparts. For the NL19 sample, which is composed of ultrathin sub-units (4.4 nm and 8.4 nm for SiO2 and TiO2, respectively) we observed a significant decrease of the IR refraction index for both types of sub-units; this points to a lesser mass density with respect to the thin film reference. The results are discussed in the light of the existing literature on nanofilms of amorphous oxides.

To better understand corrosion behaviour of lead (Pb)-based alloys exposed to volatile organic compounds – specifically acetic and formic acid – a preliminary research has been carried out on laboratory-made samples replicating such alloys. Replicas have been manufactured by simulating specific types of Pb-based alloys, with antimony (Sb) and tin (Sn) as alloying elements, in order to characterise corrosion products and evaluate the influence of each alloying element. Replicas were cast in a refractory mould and later placed in size-specific desiccators and exposed to concentrated acetic and formic acid vapours for 15 days. Each specimen was also subjected to gravimetric measurements and periodically monitored in order to understand the corrosion behaviour. Micro Raman Spectroscopy (μRS) and Scanning Electron Microscopy together with energy Dispersive X-Ray Spectroscopy were used for the characterisation of Pb-based replicas. Results showed the presence of typical corrosion products – more or less hydrated forms of Pb and Sn acetates and formates – and also a sudden increase in the volume and brittleness of some Sb-rich specimens as well as the presence of seldom-detected metallic Sb peaks with μRS. In this perspective, the influence of Sb as an alloying element on the corrosion of Pb-based artefacts may generate serious problems when such objects have to be restored and particular attention should be given to conservation/stabilisation procedures. Copyright © 2014 John Wiley & Sons, Ltd.

Archaeological artefacts made from iron and steel are often of critical importance for archaeometallurgical studies, which aim to understand the process of manufacturing, as the nearly complete alloy mineralization does not allow for any type of metallographic interpretation. In this study, three Iron Age sword blades dated from the second century BC (LaTene B2/D1) found in the archaeological site of Tintignac (Commune de Naves, Correze, France), were investigated. A multianalytical approach was employed to acquire a complete range of data from the partially or totally corroded objects. Analyses were carried out with the use of light optical microscopy, micro Raman spectroscopy, and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy (EDXS). Remnants of metallographic features—ghost microstructure—in the corrosion layers of the blades were observed, allowing for a partial reconstruction of the manufacturing process.

The catalytic conversion of ethyl acetate (EA) has been investigated over faujasite zeolites NaX, USY and HY. Characterization using pyridine adsorption shows that Lewis acid sites only exist on NaX while both Bronsted and Lewis acid sites are evident on both HY and USY. Catalytic experiments were performed in gas phase from 473 K to 973 K at atmospheric pressure with 2.16 h−1 WHSV in nitrogen. Cracking of EA to ethene and acetic acid is the predominant primary reaction in all cases. As a successive step, ketonization and decomposition of acetic acid occur. Over protonic zeolites Bronsted acidity catalyzes further oligomerization of ethene and cyclization of the further products, that finally produce coke precursors. The low-alumina protonic zeolite USY shows the highest conversion at low temperature, reaching total conversion at 673 K. Protonic zeolites cover by coke and slowly deactivate progressively. Fresh NaX is the least active but its catalytic activity is more stable, significant deactivation starting only after 5 h on stream.

A set of nine samples with nominal composition Ce 0.5 RE 0.5 O 1.75 (RE ≡ Dy-Lu, Sm, Gd and Y) has been used to develop a novel method based on Raman spectroscopy, useful to evaluate the RE coordination number within the fluorite-type structure (F) of the CeO 2 -based solid solution. The RE coordination number is a crucial indicator of defects aggregation in doped ceria, and thus of the drop in ionic conductivity observed even well below the compositional limit of the F structure. The method has been tested on several Ce 1 − x RE x O 2 − x /2 compositions (RE ≡ Sm, Gd and Lu, 0.1 ≤ x ≤ 0.4); the obtained results are compared to literature data deriving from EXAFS spectroscopy, and advantages and criticisms of the method are thoroughly discussed. Samples were prepared by a coprecipitation method, their cationic composition was checked by SEM-EDS and their structural features were analyzed by room temperature synchrotron powder x-ray diffraction.

The N-doped TiO2 has been synthesized by sol–gel method, using titanium isopropoxide, isopropanol and an aqueous solution of ammonia with ratio 2:1:10. The concentrations used for the NH3 aqueous solution were 3, 7, 10 and 15 %. The samples have been analysed by X-ray diffraction, electron microscopy (SEM and TEM) thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), micro-Raman spectroscopy and diffuse reflectivity. TEM, SEM, DSC and TGA showed that the morphology is influenced by the presence of N3− ions but not by the concentration of the solution. Instead reflectance gave us a relation between values of the energy gap and the concentration of N3− ions: the gap between valence and conduction band lowers as the concentration of NH3 in the starting solution increases. From these results we can say that the properties of the material have been tuned by doping with nitrogen ions because the particles absorb more light in the visible range, and this is important for photovoltaic and photocatalytic applications.

Two different synthetic routes to synthesize the magnetic superconductor RuSr2Gd1.4Ce0.6Cu2O10-? (Ru-1222) have been reported as an alternative method to the solid state reaction starting from the oxides of Ru, Gd, Ce, Cu and SrCO3. The 1222-phase has been namely prepared by mixing and reacting proper amounts of: (a) the 1212-phase (RuSr2GdCu2O8) with the mixed oxide Ce0.6Gd0.4O1.8; (b) the 1212-phase with the separate oxides Gd2O3 and CeO2. The possibility to obtain a pure Ru-1222 phase has been discussed and the effect of the different synthetic paths on the purity, structural and physical properties of the compound has been presented.

The phase stability of the system Gd2O3-Nd2O3 up to 1350°C was studied. Mixed oxides were synthesized by coprecipitation of mixed oxalates. Depending on the thermal treatment, three possible structures of the oxides, namely the A (hexagonal, P63/mmm), B (monoclinic, C2/m) and C (cubic, Ia3) forms, were obtained. Below 1300°C the system Gd2O3-Nd2O3 shows three monophasic (A, B and C phase) and three biphasic regions (A+B, B+C and A+C phase). Below 550°C the C phase is stable over the whole composition range. A validation procedure for the existence of the C phase in pure Nd2O3 was also set up.

Several (Gd1-xNdx)(2)[C2O4](3)center dot nH(2)O samples (0

A structural study of the filled skutterudite Smy(FexNi1-x)4Sb12 was performed by means of X-ray powder diffraction and μ-Raman spectroscopy with the aim to unveil the correlations between structural and electronic properties of this material and to favor the improvement of its thermoelectric performance. Samples were prepared by direct reaction of the elements at 1223 K, followed by quenching and subsequent sintering at 873 K; microstructure and composition of the obtained products were determined by SEM-EDS. The position of the boundary separating regions that obey hole- and electron-based conduction mechanisms was found by X-ray diffraction at x ≈ 0.63 and y ≈ 0.30, confirmed by measurements of room-temperature Seebeck coefficient, and discussed on the basis of crystallographic data. The presence of a discontinuity is observed in several structural and spectroscopic parameters at the p/n crossover; it is interpreted as associated with the change in the conduction mechanism. The role of the rare earth filling fraction in driving the structural response of the material is investigated too. The advantage of using X-ray diffraction and μ-Raman spectroscopy as aids in the study of electronic properties of this material is highlighted, as well as the complementarity of the two techniques.

The scientific investigation on metal artwork is meant to expand the knowledge regarding the technical skills developed by artists in sculpture manufacturing. Moreover, all the gathered data support the speculation about the motivations behind the choices of certain material or a specific casting and/or finishing method (e.g., aesthetic, economic or technical reasons, or both) and give fundamental information for planning adequate restoration interventions. The subject of this study is the Virtues sculptural group made at the end of the XVI century by Giambologna to decorate the Grimaldi Chapel in the church of San Francesco di Castelletto (Genoa, Italy). Six life-size statues depicting Charity, Justice, Hope, Fortitude, Faith, and Temperance (i.e., the artwork discussed in this article); seven bas-reliefs; and six winged representations of putti are what remains of the original monumental project. Different micro-invasive analytical techniques (scanning electron microscopy and energy dispersive x-ray spectroscopy, SEM–EDS; micro-Raman Spectroscopy, μRS; gas chromatography–mass spectrometry, GC–MS) were applied to determine the chemical nature and the state of conservation of the “artistic” and natural patinas visible on the Virtues surfaces. Some patination tests were performed taking into account the collected analytical data and the indications provided by the scientific literature and the historical documents. The combination of the results obtained through the scientific investigations and the experimental work allowed for supposing the materials and the patination technique selected by the artist to adorn the sculptures and providing indications for the correct conservation of the six sculptures.

The reaction of steam with ethanol, ethanol + phenol, ethanol + phenol + tetrahydrothiophene, methanol + phenol, methanol + naphthalene and methanol + phenol + naphthalene mixtures in the vapour phase has been studied over catalysts based on Ni/Al2O3. The main conclusion is that Ni-alumina based steam reforming catalysts are effective for steam reforming of phenol and naphthalene even mixed each other and with light alcohols at T > 973 K in the absence of sulphur. However, at lower temperatures and when deactivated by sulphur they may become active catalysts in converting these molecules in a number of polyalkylphenols which represent low-volatility secondary and tertiary tars.

A room temperature structural study has been performed through the whole compositional range of the (Ce1-xLux)O2-x/2 system by synchrotron X-ray diffraction and ?-Raman spectroscopy. Samples were synthesized by thermal treatment in air at 1373 K of coprecipitated mixed oxalates. A CeO2-based solid solution with a fluorite-type structure (F) was found to be stable up to x = 0.4, while at higher Lu content a (F + C) biphasic region was observed, with C being the cubic atomic arrangement typical of sesquioxides of the heaviest rare earths. A comparative approach including also results deriving from other (Ce1-xREx)O2-x/2 systems (RE ? Gd and Sm) allowed us to conclude that the compositional extent of the F solid solution is a complex function of RE3+ size and RE compressibility. On this basis, the dependence of ionic conductivity on the RE identity was interpreted as related both to the Ce4+/RE3+ size closeness and to RE compressibility. Ce4+/RE3+ dimensional issues were also revealed to rule the appearance of the hybrid structure observed in the two aforementioned systems, consisting of the intimate intergrowth of C microdomains within the F-based host lattice. Moreover, a more extended definition of F-based solid solution, including also the hybrid structure, is formulated; the latter is meant as a modification of the former, occurring when mainly RE-vacancy aggregates are incorporated into the host lattice in spite of isolated RE ions. By ?-Raman spectroscopy it was possible to demonstrate that the mechanism of oxygen vacancy formation is common to all the systems studied, provided that the structure of the F-based solid solution, also including the hybrid structure, is retained.

The tensile properties and fracture surfaces of N-methylmorpholine-N-oxide (NMMO) regenerated silk fibroin fibers produced with a range of draw ratios has been characterized and related to their microstructure with data obtained from Raman spectroscopy and birefringence measurements. The spinning process allows control of two different draw ratios, coagulation, and postspinning, and it has been found that the microstructure and the properties of the fibers can be modified by the proper combination of both draw ratios. NMMO regenerated silk fibroin fibers subjected to postspinning drawing yield tensile properties comparable to other regenerated fibers and strain at breaking comparable to natural Bombyx mori silk fibers. Tensile strength; however, is still significantly lower than that of natural fibers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2568–2579, 2007

The aim of the present work is to study the thermal decomposition of the mixed oxalates (Ce1-xGdx)(2)(C2O4)(3)center dot nH(2)O. The mechanisms of decomposition of Ce and Gd oxalate are different, and mixed oxalates behave in-an intermediate way. Their dehydration stages are more similar to those of Gd oxalate, as not all the molecules of water are equivalent like the cerium oxalate. The decomposition leads to (Ce1-xGdx)O2-x/2. For x close to 0 or to 1 two solid solutions exist, while for the central composition, the presence of a biphasic region can not be excluded.

A thermal study was performed on the RuSr2GdCu2O8 (Ru-1212) magnetic superconductor phase to investigate the effect of the annealing treatments in flowing O2 on the stability limit of the phase and on its structural, magnetic and transport properties. DTA-TG measurements were utilized to determine the decomposition process and the dependence of the decomposition temperature on the annealing atmosphere. The decomposition of the Ru-1212 phase was found sensitive to the oxygen partial pressure and increases with PO2 and the annealing time. The annealing treatments exert a depressing effect on the strength of the magnetic interaction, an enhancement on the superconductive properties and the vanishing of the magnetostriction. A decomposition reaction of Ru-1212 phase was proposed and discussed.

The synthesis and physical characterization of single phase polycrystalline samples with composition RuSr 2 GdCu 2 O 8 has been performed. We report on the electrical and magnetic measurements carried out in order to investigate and relate the properties of this compound subjected to different annealing routes. We show that while intrinsic properties as T c and structural properties as lattice parameters remain unchanged, the physical properties are strongly affected by the final annealing in flowing Oxygen. Coexistence of superconductivity and ferromagnetism is observed in all specimens studied, while Meissner effect visibility is induced by the annealing process.

Spectroscopic and catalytic properties of “pure” and “ultrapure” γ-Al 2 O 3 samples, both from Sasol, are compared. The “pure” sample has additional absorption in the UV region, much stronger luminescence in the Raman scattering experiments, slightly different skeletal surface OH groups IR spectra, and more evident features of weakly adsorbed pyridine. These effects are attributed to small amounts of Fe 3 + , Ti 4 + , surface silanol groups and Na + ions. The “ultrapure” sample is more selective for the production of ethylene from ethanol at total conversion, while in the presence of oxygen is less active in oxidizing ethanol to other oxygenates and to CO x .

Ten zirconia powders have been characterized by XRD, FT-IR/FT-FIR and Raman skeletal spectroscopies and DR-UV electronic spectroscopy. The vibrational features of a yttria-stabilized cubic zirconia and of tetragonal, monoclinic and tetragonal + monoclinic pure zirconia mixtures have been discussed. Assignments for the vibrational features of cubic and tetragonal samples are proposed. The origin of very broad vibrational peaks in tetragonal zirconia is briefly addressed. The vibrational spectra provide evidence for the presence of trigonal oxide ions in the monoclinic phase only. The UV spectra show that monoclinic zirconia (where the coordination of zirconium is sevenfold) absorbs at lower energy than the cubic and tetragonal phases (where the coordination of zirconium is eightfold). However, it absorbs at higher energy than the perovskite SrZrO3 where Zr adopts octahedral coordination. The origin of the shifts of the corresponding absorption edges is discussed.

The flux method is the most popular technique to obtain high quality and large side single crystals of YBa 2 Cu 3 O x (YBCO) and REBa 2 Cu 3 O x (REBCO). It is known that, for the YBCO, the interval of temperature for growing single crystals is between about 1010°C and 930°C, whereas, for the REBCO phases, the maximal temperature changes as function of rare earth. In this work, we studied the effect of different thermal programs on the side the YBCO crystals. The initial temperature and the cooling rate were changed. We studied the influence of a different initial ratio between Nd and Ba and between Sm and Ba on the equilibrium composition in NdBCO and SmBCO crystals.

The high thermoelectric performance of the β-phase Zn 4 Sb 3 has drawn much attention for its application in the intermediate temperature range. In this work we explore the corrosion behaviour properties of pure Zn 4 Sb 3 compound and after partial substitution of Zn with Al and Ag. In particular, Zn 4 Sb 3 , (Zn 1x Al x ) 4 Sb 3 and (Zn 1x Ag x ) 4 Sb 3 ( x = 0.01) compounds were synthesized using a muffle furnace and characterized in terms of crystal structure, morphology and phases composition (SEM-EDXS, XRD). All samples were placed in 0.1 M NaCl aerated solution at room temperature for 48 days. A study of the amount of cations released in solution was carried out using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) analysis. Analytical data reveal a higher value of zinc amount for doped samples. The microRaman spectroscopy analysis carried out on surface corrosion products revealed the presence of anhydrous and hydrate zinc hydroxy chlorides. No worsening on corrosion behaviour of Zn 4 Sb 3 intermetallic compounds was observed after Al or Ag doping.

Introduction Anodisation of pure titanium has been carried out in sulphuric and in phosphoric acid solutions at potentials ranging from 50 to 150V. The SEM and AFM morphological analysis indicates that, within this potential range, oxidation in sulphuric acid solution produces better developed mesoporous oxide layers. XPS analysis of the Ti2p core level region and Raman spectroscopy measurements show that oxide layers grown in sulphuric acid are characterised by a better defined oxidation state of titanium and by a higher content in anatase crystalline phase. XPS measurements indicate that oxidation in phosphoric acid solution produces oxide layers with two components of stoichiometric oxide and with the presence of phosphate inclusions which can be interesting in view of biomedical applications. Titanium and its alloys are largely employed for the development of orthopaedic and dental implants because of their good mechanical strength and low density. Thanks to its thin native oxide layer which prevents ion release, titanium offers good resistance to corrosion in body fluids and good biocompatibility. These properties can be further improved by surface treatments able to grow thicker oxide layers with controlled morphological and physico-chemical properties. Several methods have been used to this purpose, from thermal treatment [1-3], to acid solution immersion [4], peroxide immersion [5], anodic-plasma chemical treatment [6], plasma immersion ion implantation [7] and anodisation [8,9]. Volume 1 | Issue 1

Hexagonal as well as tetragonal rare earth oxycarbonates can act as hosts for optically active ions; hence, the knowledge of the structural modifications occurring when foreign hosts are inserted into the parent compound is of fundamental importance for the design of new phosphors. In this article, a phase stability study of the pseudobinary system Gd2O2CO3–Nd2O2CO3 at P = 1 atm. CO2 between 420 and 850 °C is presented, to study the amplitude of the existence fields of the different structures typical of rare earth oxycarbonates. The samples were prepared by thermal decomposition of the corresponding oxalates in CO2 atmosphere. According to composition and temperature, all the three structural forms reported for oxycarbonates (hexagonal, tetragonal, and monoclinic) have been observed. Above a certain temperature, that depends on composition and increases with Nd amount, all the samples decompose into the corresponding Gd–Nd-mixed oxides and crystallize into one of the three possible structural forms typical of rare earth sesquioxides. Structural refinements performed on the hexagonal oxycarbonates demonstrate that the insertion of Nd3+ in Gd2O2CO3 results in a linear increase of the lattice parameters (Vegard’s law) and in a reorganization of the distances between and in the CO 3 2− groups and the (Nd/Gd2O2)2+ layers.

The substitution of Sb with As in the NiSbS intermetallic compound was studied in the framework of evaluating a possible increase of the thermoelectric properties. Different NiSb1−xAsxS samples were synthesized with increasing amounts of As (0

Ni/alumina catalytic materials (with 0, 5, 16, 39, 125 and ∞ % wtNi/Wsupport, using a 5% silica-containing alumina with 170 m2/g surface area) have been characterized by XRD, IR, MicroRaman, UV–vis–NIR techniques. Three types of nickel oxide species have been identified: i) isolated Ni2+ species dispersed and strongly interacting with the support surface, predominant when the NiO coverage is well below that of the ‘theoretical monolayer’. (ii) Ni oxide-like particles having a vibrational environment similar to that of NiO nanoparticles, but with different Raman and UV spectra, predominant near or well above the ‘theoretical monolayer’. (iii) normal NiO particles at even higher Ni oxide contents, characterized by (2 M) magnonic and several phononic peaks in the Raman spectrum and normal position for the optical gap (absorption edge at ca. 300 nm). IR spectra of adsorbed CO recorded after reduction in hydrogen suggest that species i) predominantly gives rise to isolated Nio atoms, producing Nio polycarbonyls, while species ii) gives rise by reduction to Ni metal particles, over which unusually CO adsorbs producing only terminal species, without any formation of bridging CO species. This may be due to an unusual structure or morphology of these particles. The catalysts have been tested in the steam reforming of ethanol–phenol mixture as well as of pure ethanol. XRD, UV–vis–NIR and Raman studies show that the spent catalysts are largely reduced to metal with the appearance of hexagonal nickel, although unreduced or easily oxidixable centers are also detected.

In order to contribute to the improvement of restoration and conservation sciences of metallic artefacts belonging to Cultural Heritage, a wide research has been started on the study of artificial (artistic) and natural (corrosion or alteration) patinas of copper-based alloys. Micro-Raman spectroscopy (μRS) coupled with scanning electron microscopy (SEM) equipped with energy Dispersive X-Ray Spectroscopy (EDXS) were applied for the characterization of a number of patinas made on metallic substrate reproducing the typical copper-based alloys used for statuary. A non alloyed copper sheet has been also used to simulate the architectural cover typically used after a specific cold spray coating. To reach these goals, a number of patinas were experimentally produced in our laboratory using the torch technique and reactive solutions based on water as a solvent containing, respectively, copper nitrate, iron nitrate and potassium sulfide (‘liver of sulfur’). The only exception is a sample reproducing the architectural cover of a recent building nearly completely covered with copper sheets coated with copper salts. All the produced patinas were aged in a salt spray chamber and then studied with μRS, SEM and EDXS in order to understand their evolution between the two known terms and therefore the reactions involved in all patinas. μRS allowed us to detect as main constituents of the ‘artistic’ patinas, before and after ageing: copper oxides (Cuprite and Tenorite), copper nitrates (Rouaite and Gerhardtite), copper chlorides (Botallackite, Atacamite and Paratacamite), a copper sulfate (Posnjakite), iron oxides (Magnetite and Hematite) and an iron hydroxide (Limonite). Copyright © 2012 John Wiley & Sons, Ltd.

The structure of ethyl 5-methyl- 10-(2,4,6-trimethylphenyl)-8-oxa-1,2,9-triazabicyclo[5.3.0]deca-3,5,9-triene-2-carboxylate (I) has been determined. The 1,2-diazepine ring has a twisted-sofa form and the 1,2,4-oxadiazole ring has an envelope conformation, with the bridgehead C7 atom out of the plane of the ring. The terminal methyl group of the side chain is disordered, being split over two different positions

(Pb0.8La0.2)(Mg0.4Nb0.6)O3 relaxor ceramics have been prepared by columbite method by using (i) MgO and (ii) (MgCO3)4·Mg(OH)2·4H2O precursors (denoted as PLMN1 and PLMN2 respectively). The dielectric data show relaxor behaviour in the frequency range of 10 Hz to 1 MHz, with dielectric constant values in the range of 310–350 for PLMN1 and 240–260 for PLMN2 and a permittivity maxima at the temperature Tm = 179 K and Tm = 174 K, respectively (for f = 1 MHz). The Raman spectra proved the stability of the nanopolar order far above Tm, as observed in many Pb-based relaxors. This is demonstrated by the existence of some modes (at ∼300, 500 and 780 cm−1) up to around 773 K. Anomalies of some Raman modes (integrated intensity and FWHM) have been found in the range of Tm, proving the phase transition from pseudo-cubic relaxor to cubic paraelectric state, where the stability of the vibration modes is affected by the fluctuations associated to the phase transitions.

A stability study of perovskitic LaREO3 oxides (RE = Dy, Ho, Er, Tm, Yb, Lu) as a function of temperature was undertaken. A correlation between the Goldschmidt t value and the perovskitic stability field amplitude was found: the latter widens as t increases. Magnetic measurements, performed on all the perovskitic samples, showed that t is also related to the exchange interactions. LaREO3 oxides were synthesized by thermal decomposition of the corresponding coprecipitated oxalates at temperatures ranging between 600 and 1800 °C. Simultaneous differential thermal and thermogravimetric analyses showed that all the La–RE mixed oxalates decompose similarly. All the oxides, except LaDyO3, crystallize in the perovskitic form in a temperature range that depends on the ionic size difference between La and the smaller rare earth; above and below the perovskitic stability field, the B or C form, typical of rare earth sesquioxides, is present. Rietveld refinements, carried out on all the LaREO3 samples synthesized at 1200 °C, showed the occurrence of an orthorhombic distorted perovskitic structure belonging to the Pnma space group.

Phase relation studies in the Gd 2 O 3 –Nd 2 O 3 system have been performed on (Gd 1− x Nd x ) 2 O 3 samples (0⩽ x ⩽1) with the purpose of performing a systematic study of the composition effects on their structural and magnetic properties. All the samples were synthesized by calcination of the related oxalates at 1200 °C in order to ensure the complete decomposition of the oxalates. Five phase regions, namely an A-type hexagonal, a B-type monoclinic, a C-type cubic solid solution and two biphasic mixtures of the former three phase fields were detected in this system. The magnetic susceptibility measurements showed the presence of antiferromagnetic interactions in all samples. The Curie–Weiss temperature shows a nonlinear dependence on concentration. Deduced effective magnetic moments are close to the free ion values.

The problems of the preparation of High Temperature Superconductors by sintering and melting are examined. Results of the thermal properties of the total substitution of Yttrium by a rare earth element are reported. The process of fabrication of HTSC after high temperature decomposition is indicated. The results of first characterisation are also reported.

Raman spectra of cubic Sc 2 O 3 , Y 2 O 3 and C-type rare earth oxides are presented. Cubic Nd 2 O 3 is prepared by thermal decomposition of its hydroxide. The decomposition mechanism happens in two steps. At the end of this process cubic Nd 2 O 3 form. All Raman spectra are characterised by the presence of a very strong band in the range 320–420 cm −1 , depending on the lattice parameter of each oxide. Frequency of this line decreases increasing the cell constant, meaning that the structure becomes less rigid. A simply approach is used in order to give a consistent evaluation of the force constant of each oxide. The position of the low wave number bands depends mainly on the cationic mass, meaning that these bands are not due to stretching vibrations, but rather to bending vibrations.

A system formed by a bar of Y2BaCuO5 (Y211) phase supported on two YBa2Cu3Ox (Y123) pellets was processed by thermal treatment at high temperature. The first effect was a change in chemical composition inside the bar, yielding new phases: mostly Y123 and BaCuO2. Their concentrations were higher near the bar ends. A second, very interesting result was the growth of two kinds of acicular crystals underneath the whole bar: green, transparent Y211 needles and needles with a green core of Y211, covered by a Y123 layer. Micro Raman and SEM analyses clearly identified the two different phases. XRD inspection has confirmed that Y211 crystals are high-quality single crystals. The preferential growth direction for Y211 needles is along the crystallographic b axis. A possible explanation, based on the VLS mechanism, for their growth is suggested.