Characterization of metal oxide-doped lutetium orthoferrite powders from the pigmentary point of view

This thesis deals with the preparation and characterization of inorganic pigments based on perovskite structure of metal oxide-doped LuFeO₃. Powder samples were prepared by the conventional ceramic method, i.e., solid-state reaction. Heating temperature was chosen according to results of TG/DTA. Prepared pigments were incorporated into an organic binder system, and their color properties were evaluated by measuring the reflectance in the visible region of light. The most interesting color properties were obtained by preparation of sample Lu_0.98Ca_0.02FeO_3?δ with mineralizer LiF at the temperature 900 °C. Mean size of its particles is 4 μm. X-ray diffraction analysis confirmed a single-phase orthorhombic structure with lattice parameters a = 0.521310 nm, b = 0.55535 nm, and c = 0.75626 nm. Thermal stability of the sample is limited by the temperature of 1,150 °C. Further, the effectiveness of other metal oxide (CoO-, ZnO-, Bi₂O₃-, and Sb₂O₃)-doped Lu_0.98Ca_0.02FeO_3?δ system was evaluated with respect to their phase composition, thermal stability, particle size distribution, and color properties. The conclusions of the research showed that a sample containing antimony oxide is the mixture with the best pigmentary-application properties. The powder has a clear orange color, high thermal stability up to 1,340 °C, and mean particle size 4 μm.     

Comparison of Three Accelerated Oxidation Tests Applied to Red Wines with Different Chemical Composition

Background: Three accelerated oxidation tests were proposed to simulate red wine oxidation thus providing information useful to correctly manage moderate oxygen exposure of wine during aging in regard to phenolic composition and wine color. Since the results of the tests have never been compared on wines with different initial composition, the aim of this study was to find a suitable method to simulate oxidation of any still red wine. Methods: Aglianico, Barbera, Gaglioppo, Magliocco, and Nerello wines were treated with (1) three cycles of air saturation, (2) the addition of hydrogen peroxide, and (3) the addition of acetaldehyde. Changes in chromatic characteristics and phenolic composition were determined by spectrophotometric and HPLC methods. Results: Important differences in the behavior of the different wines were detected: the highest formation of polymeric pigments was observed in Barbera and Aglianico wines. In contrast, Gaglioppo and Magliocco wines showed a lower variability before and after the oxidation probably due to the lower anthocyanin/tannin ratio. Among the accelerated oxidation tests applied, no significant differences in color parameters and phenolic composition were detected in samples treated with the addition of H₂O₂ and the air saturation method. Conclusion: The study demonstrated that H₂O₂ addition is a successful tool to predict the evolution of different phenolic compounds during the air saturation treatment of wines.     

Synthesis and characterization of environmentally benign calcium-doped Pr2Mo2O9 pigments: Applications in coloring of plastics

A new class of environmentally benign rare earth pigments of general formula Pr_2−xCa_xMo₂O_9−δ (x ranges from 0 to 1.0) displaying colors ranging from green to yellow were synthesized by traditional solid-state route, as alternatives to lead, cadmium and chromium colorants. The products were characterized by X-ray powder diffraction, UV-vis spectroscopy and CIE-L*a*b* 1976 color scales. The coloring mechanism is based on the strong absorptions of the pigments in the blue and red regions due to electronic transitions between 4f²→4f¹5d¹ states of Pr³⁺. The designed pigments consist of non-toxic elements and further found to be thermally and chemically stable. The yellow-green pigments were found to be interesting alternatives to existing toxic pigments for coloration of plastics.     

唐代彩绘陶俑中无机颜料的化学组成

采用X射线粉末衍射（XRD）、X射线荧光光谱（XRF）和扫描电子显微镜-能谱（SEM-EDS）等测试技术对西安西曹M16唐墓出土的2尊唐代彩绘陶俑颜料进行了化学组成分析。结果表明,陶俑中含有丰富的无机颜料,其中红色颜料的显色成分为铅丹（Pb₃O₄）;白色颜料的显色成分为铅白（PbCO₃）和石灰石（CaCO₃）;粉色颜料的主要显色成分为铅丹和铅白的混合物;青色颜料为铜绿（Cu₂（OH）₂CO₃）和青石（Cu₃（OH）₂（CO₃）₂）混合物。     

Transient thermal response of phase change material embedded with graphene nanoplatelets in an energy storage unit

This research was focused on the preparation of mixed metal oxide pigments doped with terbium ions with the general formula of Sn_0.752Co_0.08P_0.16Tb_0.008O₂. These pigments were synthesised by solid-state reactions at high calcination temperatures. The temperature range was chosen from 1350 to 1500 °C. The goal was to develop conditions for the synthesis of this type of pigments and to determine the influence of terbium ions on the colour properties of these compounds. All prepared pigments were applied into the organic matrix and into the ceramic glaze. Thermal behaviours of the reaction mixtures were investigated using differential thermal and thermogravimetric analysis. Synthesised Sn_0.752Co_0.08P_0.16Tb_0.008O₂ pigments were compared with concurrently prepared pigment Sn_0.760Co_0.08P_0.16O₂ depending on the calcination temperature with respect to the colour properties in CIE L*a*b* colour space, furthermore from the point of particle size distribution and phase composition. All compounds provided blue–violet hues that are stable in ceramic glazes.     

食品中柠檬黄铝色淀和日落黄铝色淀的毛细管区带电泳分析

发展了一种新的采用毛细管区带电泳分析柠檬黄铝色淀和日落黄铝色淀的方法。通过前处理步骤成功实现了铝色淀中铝基质与色素的分离。利用石英毛细管柱（48.50 cm（有效长度40.00 cm）×50 μm）,分别针对柠檬黄铝色淀和日落黄铝色淀进行了电泳条件的优化,并得到最优分离结果。所建立的定量分析方法的检出限对于柠檬黄铝色淀和日落黄铝色淀分别达0.26 mg/L和0.27 mg/L,线性范围分别为0.53~1.3×10²mg/L和0.54~1.4×10²mg/L,两种被分析物的测定重复性（RSD,n=6）分别为4.3%和5.7%,日间重复性（RSD,n=6）分别为5.6%和6.0%。经过更深入研究后,该方法可以发展为食品中相应色淀的检测方法。     

Anatase–rutile transformation at the synthesis of rutile pigments (Ti,Cr,Nb)O2 and their color properties

Synthesis of rutile pigments is based on solid state reaction and on Hedvall effect, i.e., phase transformation from anatase to rutile. Therefore, it is important to know the thermal behavior of these compounds (the temperature of this change). The goal was to prepare rutile pigments of type Ti_1?3xCr_xNb_2xO_2+x/2 by conventional solid state method from titanium dioxide TiO₂ (AV-01, anatase), to determine an influence of composition (x = 0, 0.05, 0.10, 0.20, 0.30, 0.50) and calcination temperature (850; 900; 950; 1,000; 1,050; 1,100; 1,150 °C) on color properties of these compounds and to analyze other starting compounds of titanium (hydrated anatase paste TiO₂·nH₂O, titanyl sulfate dihydrate TiOSO₄·2H₂O (VKR 611), hydrated sodium titanium oxide paste Na₂Ti₄O₉·nH₂O) and their reaction mixtures for x = 0.05 by simultaneous TG–DTA analysis. According to the highest chroma C of color, the optimal conditions for synthesis of these pigments are concentration x = 0.05 and calcination temperature 1,050 °C and higher. It was observed that initial temperature 760–830 °C is needful for a formation of rutile structure. This temperature is the lowest for hydrated Na₂Ti₄O₉ paste (760 °C) and similar for other starting compounds of titanium.     

The photochromic effect of bismuth vanadate pigments. Part I: Synthesis, characterization and lightfastness of pigment coatings

We report on investigations of the photochromic effect of BiVO₄ pigments. Emphasis is placed on an approach widely used in industrial color testing. By means of colorimetry ΔE_ab^*-values, which measure the perceived color difference, can be calculated from reflectance spectra of non-illuminated and illuminated pigment coatings. Pigments were prepared by either wet-chemical precipitation or solid-state reactions. Depending on the choice of starting compounds, lightfastness was found to vary significantly. Small amounts of impurity phases do not seem to affect photochromism. In contrast, impurities like Fe and Pb cause intense photochromism. The role of Fe is suggested by trace analyses, which (in case of pigments synthesized by precipitation reactions) reveal a correlation between concentration and ΔE_ab^*. Indications are found that other effects like pigment-lacquer interactions might also be of importance. Difference reflectance spectra turn out to vary in shape depending on the type and concentration of impurities or dopants. For BiVO₄ at least three different mechanisms of photochromism can be assumed.     

On the synthesis of glass and glass-crystalline black-blue facing on thin ceramic

By x-ray phase analysis the optimal temperature is established for the spinel formation in the oxide system Co₂O₃-Fe₂O₃ at the producing ceramic black-blue pigment and the phases playing the role of basic chromophores. The synthesized pigments provide the glass facing with black-blue color and strong flashing (up to 86%) and with semi-dull fine crystalline facture based on the developed unfritted glaze characterized by strong and stable color in a wide range of roasting temperature.     

Development of High NIR-Reflective Red Li2MnO3 Pigments

In this work, the development of a novel class of eco-friendly red pigments based on doped Li₂MnO₃ is reported. These new compounds offer red color values of a* > 34, which are recognizably higher than the red value provided by the commonly used red pigment iron oxide Bayferrox 4130. However, the real outstanding attribute of these novel substances is their strikingly high NIR-reflectance that gives promise for a new class of materials for the practical utilization as cool pigments in building components and ceramics. We have synthesized the inorganic pigments by conventional solid-state reactions at 900 °C and subsequently carried out the structural characterizations by X-ray powder diffraction (XRPD) and Rietveld analysis. We recorded the diffuse reflectance spectra of the obtained powders and determined the color properties by means of CIE L*a*b* coordinates. Finally, we measured the NIR reflectance and calculated the NIR solar reflection of these compounds affording values above 85 % in the range from 700 to 2500 nm.     

A noninvasive complementary study of an Egyptian polychrome cartonnage pigments using SEM,EPMA, and Raman spectroscopy

Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) were used to study pigments on an Egyptian cartonnage from the Ptolemaic period (305–30 bc ). The surface morphology of each color region was examined using backscattering (BS) and secondary electron imaging. SEM X-ray energy dispersive spectrometry and EPMA wavelength dispersive spectroscopy provided semiquantitative chemical analysis of each pigment. Raman spectroscopy was used to identify the minerals associated with the pigments. This technique confirmed the presence of cinnabar (α-HgS) in the red part of the fragments. A mixture of orpiment (As₂S₃) and bonazziite (β-As₄S₄) and/or alacránite (As₈S₉) was detected in the yellow regions of the fragments. The orange pigment was confirmed to be a mixture of orpiment, uzonite (χ-As₄S₅), and pararealgar (As₄S₄). Egyptian blue (CaCuSi₄O₁₀) and Egyptian green ((Cu,Ca)SiO₃) pigments were detected from blue/green dark-colored regions of the fragments.     

Preparation by hydrolysis of aerosols and properties of Cr, Mn and Co doped alumina spherical particles

 A method for the preparation of chromium-doped (pink), manganese-doped (brown) and cobalt-doped (blue) alumina pigments consisting of spherical particles of broad size distribution (<5 μm) is reported. The procedure, based on the room-temperature hydrolysis of aerosols generated from a mixture of aluminum sec-butoxide and a solution of the corresponding metal nitrates in sec-butanol, yields amor-phous solids. The temperature of calcination and the composition of the so produced powders were varied to investigate their effects on the color properties of the pigments, which were also characterized in terms of their composition, crystalline structure and electrokinetic behavior. Received: 15 April 1997 Accepted: 25 June 1997     

Gold Gilding and Pigment Identification on a Post-Byzantine Icon from Kastoria,Northern Greece

The investigation of gilded gold, black and red pigments from the Byzantine icon of Panagia from the church of Agioi Anargyroi Gymnasiou in Kastoria, northern Greece is the aim of this study. Small fragments, having a gold leaf finish, were detached from the icon and were analyzed by Environmental Scanning Electron Microscopy coupled to Energy Dispersive System (ESEM-EDS) and Raman microscopy. The chemical (EDS) composition of the gilding material revealed a high gold content alloy (Au 81.34 wt%) with trace amounts of silver (Ag 1.66 wt%), copper (Cu 0.62 wt%) and iron (Fe 0.58 wt%). The Raman spectrum of the gold leaf showed characteristic bands at 236, 369, and 468 cm^?1. The red pigment on the surface comprises of Hg, S, and minor amounts of Pb and is attributed to the minerals cinnabar (HgS) and minium (Pb₃O₄). The black pigment has high carbon content, attributed to organic material (black carbon). The micro-Raman spectroscopy provided a more detailed determination of the composition of the red and black pigments. In particular, the vivid red color was attributed to cinnabar (bands at 253 and 342 cm^?1). Particles of black carbon (bands at 1345 and 1577 cm^?1) and oxalates (band at 861 cm^?1) were determined on the black pigments. Dark regions on the pigmented surface were assigned to a mixture of cinnabar [bands at 253 and 342 cm^?1] and minium [bands at 120, 142, 288, and 545 cm^?1]. The latter lead oxides might have been used either as a dryer or a burnish agent for the gold leaf. The micro-structural and chemical analysis of several distinct strata of the icon, as observed under ESEM, revealed a red-colored stratum beneath the gold leaf, with an iron aluminosilicate composition. This is the so-called bole (red clay) commonly used as sub-strata for gilding art objects. Multiple layers of white ground material, composed of gesso (gypsum) underlie the bole strata. Moreover, one thin organic binder (animal glue) was is observed within the gesso ground of the icon.     

Preparation and characterization of Cr2O3 system optically variable pigment

An optically variable pigment was produced by wet chemical method, where TiO₂-coated mica with interference colors acted as the substrate materials. The structure of the pigment was characterized by X-ray diffraction (XRD), and its optically variable effect was investigated by X-Rite MA86 II five angles spectrophotometer. The impact of different interference substrate materials for improving the color travel effect was studied, and the influence of white and black background on the hue and the color travel effect were studied. Results showed that optically variable pigments can be prepared by coating Cr₂O₃ on the surface of the pretreated TiO₂-coated mica. The color travel effect was sensitive to the change of substrate materials, and different backgrounds can influence the hue and the color travel effect of the pigment. __________ Translated from Chemistry, 2006, (11): 831–835 [译自: 化学通报]     

Classification of Chili Powders by High Performance Liquid Chromatography‐Diode Array Detection

Abstract

The color pigments of six chili powders of different origins (China, Bali, Pakistan, Malaysia, India, and Thailand) were separated and quantified by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) using a narrow‐bore octadecylsilica column (Purospher, 125×3 mm I.D., Merck, Darmstadt, Germany), gradient elution, and diode array detector (DAD). The similarities and dissimilarities among the pigment composition of chili powders have been elucidated by principal component analysis (PCA). The RP‐HPLC separated 71–111 pigment fractions depending on the detection wavelength and on the origin of chili powder. The pigment composition of chili powders from Malayia and China showed marked similarities while the composition of pigments of other chili powders was different. It was concluded that RP‐HPLC–DAD can be successfully employed for the separation and quantitative determination of pigments of chili powders of various origins and may help the classification of chili powders and facilitate the authenticity test of such food products.     

Utilizationof dta for two-step synthesisof Cu–Mn–Cr spinel

The novel two-step synthesis method decreasing the calcining temperature necessary for formation of spinel lattice and as well for reaching of bright and clear hue of the pigments prepared were investigated. This work aims to utilization of DTA for synthesis monitoring. Influence of raw materials and temperature of calcination on color properties were observed. The characterization of the samples was performed by X-ray diffraction and colorimetry in the CIE L*a*b* system. It was proved that the black spinel pigment Cu_2.3Mn_2.8Cr_4.9O_x can be prepared at finally temperature 700°C as one-phase system with high quality black hue.     

ISOMER COMPOSITION and SPECTRA OF THE DARK and LIGHT ADAPTED FORMS OF ARTIFICIAL BACTERIORHODOPSINS*

Abstract– The isomer composition and spectral properties of 15 artificial bacteriorhodopsin (bR) pigments, based on a series of retinal analogs with polyene residue modified below C₉ are determined for both dark-adapted (DA) and light-adapted (LA) forms. Similarly to native bR, in all cases only two isomers, C₁₃=C₁₄cis (13-cis) and M-trans, are observed. However, the artificial DA pigments have a lower 13-d.s content than native DA bR (? 66%) while the corresponding LA pigments have a much higher 13-cis content (11-69%) than native LA bR (<2%). Thus, in variance with the native pigment, in all of the artificial systems light also induced the reversed all-trans13-cis process. The data are accounted for in terms of specific steric interactions between the polyene and the protein binding site which allow a (C₁₅-anti)(C_ls-syn) isomerization during the photocycle of the artificial pigments, but not in the case of native bR. This accounts for the high proton pumping efficiency of the natural pigment. The nature of a highly red shifted light-adapted form of two of the artificial pigments is investigated and discussed. It is also shown that, in variance with native bR, several artificial pigments exhibit identical absorption spectra for their 13-cis and all-trans isomers. It is concluded that the spectral data for the above species of artificial pigments do not lead to a clear molecular model for the origin of the spectral shift between 13-cis and all-trans bR.     

In situ investigations of vault paintings in the Antwerp cathedral

X-ray fluorescence spectroscopy (XRF) and Raman spectroscopy have been used to examine 15th century mediaeval and 16th century renaissance vault paintings in the Our Lady's Cathedral (Antwerp, Belgium) in view of their restoration. The use of mobile instruments made it possible to work totally non-destructively. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the pigments. For the 15th century vault painting the pigments lead–tin yellow (Pb₂SnO₄), lead white (2PbCO₃·Pb(OH)₂), vermilion (HgS), massicot (PbO) and azurite (2CuCO₃·Cu(OH)₂) could be identified. The pigments used for the 16th century vault painting could be identified as red lead (Pb₃O₄), hematite (Fe₂O₃), lead white (2PbCO₃·Pb(OH)₂) and azurite (2CuCO₃·Cu(OH)₂). For both paintings the presence of the strong Raman scatterer calcite (CaCO₃) resulted in a difficult identification of the pigments by Raman spectroscopy. The presence of gypsum (CaSO₄·2H₂O) on the mediaeval vault painting probably indicates that degradation took place.     

Oscillatory diffuse X-ray scattering from lead chalcogenides

New inorganic compounds having the general formula (Bi₂O₃)_1−x (Lu₂O₃) _x (x ranges from 0.1 to 0.5) displaying orange colours have been synthesized by traditional solid-state route, as viable alternatives to lead, cadmium and chromium based yellow toxic inorganic pigments. The host lattice of these pigments is Bi₂O₃ that is doped by Lu³⁺ ions. The goal was to develop conditions for the synthesis of these compounds and to determine the influence of calcination temperature and lutetium content on their colouring effects. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. The pigments were also evaluated from the standpoint of their structure and particle sizes.