Thermogravimetric And Differential Thermal Analysis Research Articles

Dicyclopentadiene Hydroformylation to Value-Added Fine Chemicals over Magnetically Separable Fe3O4-Supported Co-Rh Bimetallic Catalysts: Effects of Cobalt Loading

Six Co-Rh/Fe3O4 catalysts with different cobalt loadings were prepared by the co-precipitation of RhCl3, Co(NO3)2, and Fe(NO3)3 using Na2CO3 as the precipitant. These catalysts were tested for dicyclopentadiene (DCPD) hydroformylation to monoformyltricyclodecenes (MFTD) and diformyltricyclodecanes (DFTD). The results showed that the MFTD formation rate increased with increasing cobalt loading, whereas the DFTD formation rate initially increased and then decreased when the cobalt loading was greater than twice that of Rh. The DFTD selectivity was only 21.3% when monometallic Rh/Fe3O4 was used as the catalyst. In contrast, the selectivity was 90.6% at a similar DCPD conversion when the bimetallic 4Co-2Rh/Fe3O4 catalyst was employed. These catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and thermogravimetric and differential thermal analyses (TG-DTA). The results obtained by these complimentary characterization techniques indicated that adding cobalt to the Rh/Fe3O4 catalyst enhanced the Rh reducibility and dispersion; the Rh reducibility was easily altered, and increasing the cobalt loading improved the Rh dispersion. It was concluded that the enhanced catalytic performance with increasing cobalt loading might be due to the formation of a more reactive Rh species with a different Rh–phosphine interaction strength on the catalyst surface.

Manganese oxide-based catalysts for toluene oxidation

Four different catalysts based on manganese oxide were prepared: a perovskite (LaMnO3), via sol-gel method; Mn2O3, rapid method and an Octahedral Molecular Sieve (OMS-2) by two different preparation methods, via solid state (OMSs) and hydrothermal method (OMSh). The physicochemical properties of these catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption at −196°C, thermogravimetric and differential thermal analysis (TGA/DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and temperature-programmed reduction with hydrogen (H2-TPR). Their catalytic performances were evaluated in the catalytic oxidation of toluene. Three consecutive catalytic cycles were performed for each catalyst in order to reach steady state performances. In order to assess the stability of the catalysts under reaction conditions, the catalytic performances were studied upon long term experiments running for 24h at 25% of toluene conversion. For comparison purposes, the catalytic activity of the present manganese oxide catalysts was compared with that of typical industrial catalysts such as a commercial Pd/Al2O3 catalyst containing 0.78% Pd. The crystalline features detected in the XRD patterns, are well-consistent with the formation of the desired structures. Based on their specific surface area and their low-temperature reducibility, the catalysts were ranked as follows: OMSs>Mn2O3>OMSh>LaMnO3. This trend was in good agreement with the performances observed in the catalytic removal of toluene. A kinetic model was proposed and a good agreement was obtained upon fitting with the experimental data.

In situ preparation and optical properties of metal-8-hydroxyquinoline decoration of layered silicate: Self-assembly in the magadiite interface by solid-solid reaction

We succeeded in the self-assembly of 8-hydroxyquinoline (8Hq)-Li (I), Al (III) and Cu (II) complexes into the interlayer surfaces of layered silicate magadiite (Na2Si14O29·nH2O) and investigated the luminescence of organic metal-chelates in the confined spaces. The measurements, including X-ray diffraction (XRD), Fourier-transform infrared spectra (FT-IR), thermo-gravimetric analysis and differential thermal analysis (TG/DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), ultraviolet–visible spectroscopy (UV–Vis) and Photoluminescence spectra (PL), confirmed that the metal-organic chelates species were immobilized onto the silicate sheets via ion-dipole interaction and free diffusion. The encapsulation was obtained by a flexible solid-solid reaction, and the present reaction and products have a potential of application to industrial uses. A speculative mechanism is proposed for reaction by the combination of solid-solid and solid-gas intercalation. Furthermore, it was found that the complexes in the interlayer space showed a special fluorescence property than in the crystal state and the confined space of phyllosilicate shows an influence on properties of complexes. Here, a possibility of synthesizing metal-organic complexes that encapsulated in phyllosilicate is given.

Graphite intercalated polyaniline composite with superior anticorrosive and hydrophobic properties, as protective coating material on steel surfaces

Solid polymer composite systems are widely being used for potential technological applications in secondary energy sources and electrochromic devices. In this study, we synthesized and characterized a composite material composed of polyaniline (PANI) and natural needle platy (NPG) vein graphite. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis, thermogravimetric and differential thermal analysis (TGA/DTA), transmission electron microscopy (TEM) were used to study the structural and electrochemical properties of the prepared PANI/NPG graphite composite. XPS, FTIR, and micro-Raman analysis confirmed the existence of relevant functional groups and bonding in the prepared PANI/NPG composite material. The composite shows a very low corrosion rate, approximately 29μm per year, and high hydrophobicity on steel surfaces, which helps to prevent the corrosion due to O2 penetration towards the metal surface. It indicates that the composite can be used as a high potential surface coating material to anticorrosion. The specific capacitance of PANI/NPG composite is 833.3Fg−1, which is higher than that of PANI. This synergistic electrical performance result proves the prepared PANI/NPG graphite composite as a suitable protective coating material for steel surfaces.

Optical and dielectric characterization of gadolinium aluminate ceramic nanoparticles synthesized by combustion technique

Single phase nanocrystalline Gadolinium aluminate (GdAlO3) has been synthesized from Gadolinium oxide and Aluminium nitrate by auto-ignition citrate complex combustion process. The thermal decomposition of precursor and successive phase formation has been investigated using X-ray diffraction analysis (XRD), Thermo-Gravimetric Analysis and Differential Thermal Analysis (TGA/DTA) and Fourier Transform Infrared (FT-IR) spectroscopy analysis. X-ray diffraction analysis (XRD) revealed the formation of GdAlO3 with orthorhombic perovskite structure in the Pbnm space group. Transmission Electron Microscopy (TEM) has been employed for the particle-size analysis. The nanoparticle size is in the range of 30–50 nm. Surface morphology of the sintered pellet was obtained from High Resolution Scanning Electron Microscopy (HR-SEM). The absorption spectrum of the GdAlO3 nanoparticles shows characteristic cut edge which was attributed to direct allowed transitions through optical band gap of 3.15 eV. The dielectric measurements as a function of temperature have been carried out on the sample in the frequency range 1 Hz-1 MHz. Values of dielectric constant ε’ and loss tangent tanδ were found to be temperature and frequency dependent. The dielectric constant and loss tangent at 100 KHz were ∼8.62 and ∼0.02 respectively.

Synthesis and characterization of rare-earth elements substituted Ni-Zn ferrites

ABSTRACTThe spinel Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites with RE˭Ce and Y are fabricated by the polyacrylamide gel method. The effect of rare earth ions substitution for iron ions on the structure, morphology, electromagnetic and microwave-absorbing properties of Ni-Zn ferrites are investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric and differential thermal analysis (TG-DTA) and HP8510B network analyzer, respectively. The results indicate that Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites form a pure cubic spinel structure, and Ce3+ and Y3+ substitute into the crystal lattice. Both the real ϵ′ and imaginary ϵ″ parts values of complex permittivity for Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites are higher than those for Ni-Zn ferrites in X-band (8.2-12.4 GHz) frequency range. When RE ions substitute for iron ions, the real μ′ and imaginary μ″ parts values of complex permeability for Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites decrease and increase, respectively. The microwave-absorbing properties are better for RE-substituted Ni-Zn ferrites than Ni-Zn ferrites. For Ni0.7Zn0.3Ce0.04Fe1.96O4 ferrites, the minimum loss is −12.5 dB at 18 GHz for an absorber thickness of 2 mm.

Luminescence, energy transfer, and up-conversion mechanisms of Yb3+ and Tb3+ co-doped LaNbO4

Novel green-emitting Yb3+ and Tb3+ co-doped LaNbO4 particles were prepared through a facile sol-gel and combustion method. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric and differential thermal analysis (TG-DTA), up-conversion luminescence (UCL) with different powers and varied concentrations, and luminescent lifetimes were employed to test the prepared samples. The XRD data exhibit that a sample with high crystallinity can be acquired at 1000 °C. FE-SEM images show homogeneous and spherical grains after Yb3+ and Tb3+ are co-doped in the LaNbO4 samples. TG-DTA reveals that the LaNbO4 synthetic process is accompanied by a temperature increase. In our work, we utilize a 980 nm laser to excite Yb3+ ions to achieve the 2F7/2 → 2F5/2 transition, and the LaNbO4:Yb3+, Tb3+ sample exhibits intense green emission. Luminescent spectra at different powers demonstrated the two-photon absorption process; meanwhile, the corresponding energy transfer mechanism from Yb3+ to Tb3+ and the emission of Tb3+ under 980 nm laser excitation was described via an energy level diagram. Moreover, concentration-dependent up-conversion luminescent properties were systematically explored, and it was confirmed that LaNbO4:0.15Yb3+,0.02Tb3+ exhibits the strongest luminescent properties. In particular, as the content of Yb3+ ions increases, the 5D4 → 7F6 transition quickly becomes stronger, resulting in the emitted color shifting from green to blue. Therefore, the emitted color can be tuned by adjusting the content of Yb3+ ions. The excellent up-conversion emission properties of the obtained samples allow for their potential application in the fields of 3D display technologies and solid-state lasers.

Application of Ultrasonic Assisted-Dispersive Solid Phase Extraction Based on Ion-Imprinted Polymer Nanoparticles for Preconcentration and Trace Determination of Lead Ions in Food and Water Samples

In this paper, we describe ultrasonic assisted-dispersive solid phase extraction based on ion-imprinted polymer (UA-DSPE-IIP) nanoparticles for the selective extraction of lead ions. Ultrasound is a good and robust method to facilitate the extraction of the target ions in the sorption step and elution of the target ions in the desorption step. The ion-imprinted polymer nanoparticles used in the UA-DSPE-IIP were prepared by precipitation polymerization technique. The ion-imprinted polymer nanoparticles was synthesized using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as the cross-linker, 2,2′- azobisisobutyronitrile as the initiator, 1,3,4-thiadiazole-2,5-dithiol as the ligand, methanol/dimethyl sulfoxide as the solvent, and lead as the template ion, through precipitation polymerization technique. The IIP nanoparticles were characterized by Fourier transformed infra-red spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TGA/DTA), and scanning electron microscopy (SEM). Box-Behnken design (BBD) was used for optimization of sorption and desorption steps in UA-DSPE-IIP. In the sorption step: pH of solution, IIP amount (mg), sonication time (min) for sorption and in the desorption step: concentration of eluent (mol L−1), volume of eluent (mL), and sonication time (s) for desorption was investigated and optimized by the Box-Behnken design. The optimum conditions for the method were pH of solution: 7.5, sonication time for sorption 7.5 min, IIP amount 24 mg, type and concentration of eluent HCl 1.4 mol L−1, volume of eluent 2.1 mL, and sonication time for desorption 135 s. Under the optimized conditions, the limit of detection and relative standard deviation for the detection of lead ions by UA-DSPE-IIP was found to be 0.7 μg L−1 and <4%, respectively.

Synthesis of the semi-organic nonlinear optical crystal l-glutamic acid zinc chloride and investigation of its growth and physiochemical properties

The aim of this study is to synthesize and investigate the growth and physiochemical properties of the nonlinear optical semi-organic crystal l-glutamic acid zinc chloride (LGAZC). An optically transparent and defect-free crystal was grown with the slow evaporation solution growth technique under optimized conditions. The induction periods were measured at various supersaturations, and the interfacial energies were evaluated. Single crystal X-ray diffraction reveals that the crystal has an orthorhombic structure with space group P212121, and the calculated lattice parameters are a=5.20Å, b=6.99Å, c=17.58Å, α=β=γ=90° and volume=623.411 Å3. Spectroscopic properties were investigated by recording the Fourier transform infrared and optical transmission spectra. The thermal decomposition of the grown crystal was investigated by Thermo Gravimetric and Differential Thermal Analysis (TG/DTA). The LGAZC crystal exhibits second harmonic generation (SHG) efficiency 1.5 times that of inorganic KDP crystal. The presence of the metal ion (Zn+) in a grown crystal was identified by EDAX spectrum analysis. The photoconductivity study demonstrates that LGAZC crystal has a positive photo conducting nature. The dielectric response of the LGAZC crystal was investigated and reported.

The Role of Various Powders during the Hydration Process of Cement-Based Materials

The role of various powders including glass powder (GP), limestone powder (LP), and steel slag powder (SSP) during the hydration process of cement-based materials was investigated by using X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), and strength tests. GP has adverse impact on early strength, but the pozzolanic reaction at later stage enhances the strength development greatly. LP can significantly improve early strength. SSP has a good contribution to the early and later strength of the paste when its content is less than 15%. GP has little effect on the kind of hydration products but relatively large effects on the quantity. Calcium hydroxide (CH) content of GP paste decreases over curing age gradually, which is different from pure cement paste because its pozzolanic activity consumes more CH than that generated from the cement hydration. SSP and LP mainly play a role of filling effect at early stage. Nucleating effect of LP also promotes the early hydration of cement. The hydration of LP occurs at later stage and forms the calcium carboaluminate hydrates. The hydration of SSP is relatively slow, which generates CH at later stage and is effective in the strength development.

Preparation of nanoscaled yttrium oxide by citrate precipitation method

The nano-Y2O3 was prepared from YCl3 by the citrate precipitation method. The precursor powders were prepared by 0.1 mol/L YCl3 solution and 0.1 mol/L hydrochloric acid in the presence of 1% surfactant PEG2000, which was dried via an ethanol azeotropic distillation method. The effects of reaction temperature, precursor concentration, hydrochloric acid concentration, surfactant, and calcination temperature on the mean sizes of nano-Y2O3 were studied. It was found that the highest yield of precursor was about 70% at the pH value of 5.0, and the yield decreased rapidly at the pH value below 4 or over 6. The reaction temperature revealed no effect on the size of precursor. The optimized precursor concentration and hydrochloric acid concentration were both 0.1 mol/L. Several typical analytic techniques such as particle size analyzer, X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TG-DTA) and scanning electron microscopy (SEM) were used to determine the characteristics of the prepared nano powders. Homogeneous torispherical nano-Y2O3 with the smallest size (20 nm) could be obtained by calcining the precursor powders at 800 °C for an hour.

Synthesis and Dielectric Properties of Nanocrystalline Strontium Bismuth Niobate.

Herein, we report the synthesis, characterization and dielectric properties of nanocrystalline ferroelectric ceramic of strontium bismuth niobate (SrBi₂Nb₂O₉; SBN). The material was prepared by simple sol–gel combustion route using strontium nitrate, bismuth nitrate pentahydrate and niobium oxide in presence of sucrose. During synthesis, the sucrose played dual role, i.e., as the gelling agent and combustion fuel. The prepared material was characterized in detail using several techniques such as differential thermal analysis and thermogravimetric (DTA-TG), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscope (SEM). These techniques were utilized to describe the thermal stability, crystal structure, crystallite size and morphologies of the prepared material. Further, the dielectric properties of the prepared SBN sample were investigated at various frequencies and temperatures.

Synthesis and Characterization of a [Li&amp;lt;sub&amp;gt;0+x&amp;lt;/sub&amp;gt;Mg&amp;lt;sub&amp;gt;2-2x&amp;lt;/sub&amp;gt;Al&amp;lt;sub&amp;gt;1+x&amp;lt;/sub&amp;gt;(OH)&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt;][Cl&amp;amp;middot;mH&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O] Solid Solution with X = 0 - 1 at Different Temperatures

The synthesis of a novel Li+ /Mg2+ /Al3+ containing layered double hydroxide (LDH) by using a hydrothermal synthesis route is represented in this work. The autoclaves were heated up to 100oC, 120oC, 140oC and 160oC for 10 h and 48 h with a water to solid ratio (W/S) of 15:1. The physicochemical properties of the synthesized LDHs were investigated by X-ray powder diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), thermo gravimetric and differential thermal analysis (TG-DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM). The formation of a solid solution phase depends strongly on the composition of the reactants and the synthesis temperature. Using an exact stoichiometric ratio of Li+/Mg2+/Al3+ resulted in the synthesis of amorphous phases without producing plenty of crystalline amounts of the expected solid solutions while using higher temperatures than 140oC resulted in a formation of AlO(OH). To avoid the formation of an Al containing amorphous phase or an AlO(OH) crystalline phase, the stoichiometric ratio of Li+ was changed. The results show solid solutions with the formula [Li0+xMg2-2xAl1+x(OH)6][Cl.mH2O] with X ≥ 0.9. The lattice parameters and chemical compositions for solid solutions with different compositions were determined and the pure solid solution with the highest amount of Mg (x = 0.9) is [Li0.9Mg0.2Al1.9(OH)6] [Cl.0.50H2O] with the lattice parameters a = 5.1004(4) Å, c = 15.3512(1) Å, V = 345.844(9) Å3. For X 2+ and a Li+ dominated solid solution, are coexistent.

Influence of the underground mining waste on the environmental tailings and wastewater characterization

In presented paper influence of the underground mining waste on the environmental was investigated. From that point tailings and wastewater characterization was performed on samples taken from lead and zinc mine Grot, Serbia. In order to obtain experiments necessary for characterization, representative samples were taken from three different parts of the tailings: outlet pipe of the flotation facility (JOF), hydro cyclone overflow (JHC) and crest of dam (JKB). Characterization of the tailing samples include: thermal (differential thermal analysis and thermo gravimetric analysis (DTA/TGA) and infrared analysis (FTIR), determination of the chemical composition and content of the heavy metals and qualitative roentgen analysis (XRPD). Also, wastewater samples have been taken from the tailings and concentrations of heavy metals in the taken samples were determined by using inductively coupled plasma mass spectrometry (ICPMS).

Iron (III) oxide fabrication from natural clay with reference to phase transformation γ- → α-Fe2O3

Amorphous iron (III) oxide was obtained from clay, using ammonium hydroxide as a precipitating agent. Influence of freeze drying under vacuum, as a drying method, on particle size, chemical composition, and crystallinity of obtained iron (III) oxide powder was investigated. After freeze drying, precipitate was annealed in air at 500?C and 900?C. X-ray diffraction, particle size analysis, scanning electron microscopy, energy dispersive spectrometry, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis were used to characterize obtained iron (III) oxide powder. All of three powders obtained by freeze drying and annealing, have low crystallinity and particles with irregular layered shape. Narrow particle size distribution was given by an average diameter value of around 50 ?m for all observed powders. Iron-bearing materials like ?-Fe2O3 and ?- Fe2O3 are obtained. Differential thermal analysis curve of obtained samples showed endothermic reaction at 620?C which could be ascribed to phase transition from cubic form ?- ? ?- Fe2O3. Thermal transformations of iron (III) oxide, obtained from clay as a natural source, is suitable to explore in the framework of materials chemistry, and opens the possibility to synthesize materials based on Fe2O3 with specific magnetic behavior.

Low temperature wet-chemical synthesis of spherical hydroxyapatite nanoparticles and their in situ cytotoxicity study

The present research work reports a low temperature (40oC) chemical precipitation technique for synthesizing hydroxyapatite (HAp) nanoparticles of spherical morphology through a simple reaction of calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate at pH 11. The crystallinity of the singlephase nanoparticles could be improved by calcinating at 600oC in air. Thermogravimetric and differential thermal analysis (TG-DTA) revealed the synthesized HAp is stable up to 1200oC. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies confirmed the formation of spherical nanoparticles with average size of 23.15+-2.56 nm and Ca/P ratio of 1.70. Brunauer-Emmett-Teller (BET) isotherm of the nanoparticles revealed their porous structure with average pore size of about 24.47 nm and average surface area of 78.4 m2g-1. Fourier transform infrared spectroscopy (FTIR) was used to confirm the formation of P-O, OH, C-O chemical bonds. Cytotoxicity and MTT assay on MG63 osteogenic cell lines revealed nontoxic bioactive nature of the synthesized HAp nanoparticles.

Influence of barium titanate nanofiller on PEO/PVdF-HFP blend-based polymer electrolyte membrane for Li-battery applications

Organic-inorganic hybrid membranes based on poly(ethylene oxide) (PEO) 6.25 wt%/poly(vinylidene fluoride hexa fluoro propylene) [P(VdF-HFP)] 18.75 wt% were prepared by using various concentration of nanosized barium titanate (BaTiO3) filler. Structural characterizations were made by X-ray diffraction and Fourier transform infrared spectroscopy, which indicate the inclusion of BaTiO3 in to the polymer matrix. Addition of filler creates an effective route of polymer-filler interface and promotes the ionic conductivity of the membranes. From the ionic conductivity results, 6 wt% of BaTiO3-incorporated composite polymer electrolyte (CPE) showed the highest ionic conductivity (6 × 10−3 Scm−1 at room temperature). It is found that the filler content above 6 wt% rendered the membranes less conducting. Morphological images reveal that the ceramic filler was embedded over the membrane. Thermogravimetric and differential thermal analysis (TG-DTA) of the CPE sample with 6 wt% of the BaTiO3 shows high thermal stability. Electrochemical performance of the composite polymer electrolyte was studied in LiFePO4/CPE/Li coin cell. Charge-discharge cycle has been performed for the film exhibiting higher conductivity. These properties of the nanocomposite electrolyte are suitable for Li-batteries.

Strength and microstructure of mortar containing glass powder and/or glass aggregate

The compressive strength of mortar containing glass powder (GP) and/or glass aggregate (GA) was tested, and its microstructure was also studied by thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy dispersive spectroscopic analysis (EDX), and X-ray diffraction (XRD) techniques. The incorporation of GA would decrease the compressive strength of the mortar in the absence of GP. Incorporating both GA and GP could change the hydration environment, promote pozzolanic reaction of GP and improve the compressive strength. GP does not lead to but can effectively control ASR (Alkali Silica Reaction). GP and GA do not transform the type of hydrates, but have a great influence on the amounts of hydration products, and generate more calcium silicate hydrate (C-S-H gel) with lower Ca/Si ratio. GP and GA with good gradation will make the microstructure denser.

Enhanced optical, thermal and piezoelectric behavior in dye doped potassium acid phthalate (KAP) single crystal

Dye inclusion crystals have attracted researchers in the context of crystal growth for applications in solid state lasers. Pure and 0.1mol% amaranth doped KAP single crystals, were grown from aqueous solutions by slow evaporation technique at room temperature. The grown crystals are up to the dimension of 12×10×3mm3. Attempt is made to improve the growth rate, optical, piezoelectric and photoconductive properties of pure KAP single crystal with addition of amaranth dye as a dopant. Various characterization studies were made for both pure and dye doped KAP. Thermal stability of the crystals is tested from thermogravimetric and differential thermal analysis (TG/DTA). There is only one endothermic peak indicating decomposition point. Higher optical transparency for dye doped KAP crystal was identified from the UV–vis spectrum. Etching studies showed an improvement in the optical quality of the KAP crystal after doping with amaranth dye. The positive photoconductive nature is observed from both pure and amaranth doped KAP.

Natural or Artificial? Multi-Analytical Study of a Scagliola from Estoi Palace Simulating Imperial Red Porphyry.

In this paper the characterization of a gypsum plaster sample from the end of the 19th century simulating imperial red porphyry using a multi-analytical approach is presented and discussed. The results of X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TGA-DTA), physical and mechanical properties are summarized. In order to have further insight into the microstructure, polarized light microscopy (PLM), scanning electron microscopy coupled with energy dispersive X-ray spectrometer (SEM-EDS), and micro Raman spectroscopy analyzes were also made. They helped to clarify the main issues raised by the other complementary analytical techniques and allowed the establishment of interrelations between the different properties, providing important information about the materials, the skills, and the technological development involved in the art of imitating noble stones with gypsum pastes. This study also contributes to our knowledge concerning the preservation of these types of elements that are important in the context of European decorative arts and rarely reported in the literature.