scholarly journals Use of Temperature Controlled Stage Confocal Raman Microscopy to Study Phase Transition of Lead Dioxide (Plattnerite)

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 468
Author(s):  
Ilaria Costantini ◽  
Pier Paolo Lottici ◽  
Kepa Castro ◽  
Juan Manuel Madariaga
Keyword(s):  
Phase Transition ◽  
Laser Power ◽  
Lead Dioxide ◽  
Degradation Process ◽  
Excitation Power ◽  
Study Phase ◽  
Secondary Products ◽  
Temperature Ramps ◽  
Red Lead ◽  
Temperature Controlled

The present work concerns the study of the phase transition of plattnerite [β-PbO2 lead (IV) oxide]-based samples when they are analysed by Raman spectroscopy. The laser-induced degradation process was carried out either on historical painting samples, where plattnerite was present as a degradation product of lead-based pigments, or commercial plattnerite samples as powder and pellets. The Raman spectra of plattnerite taken at low excitation power, to avoid phase transformations, are reported up to low wavenumbers, and they were characterized by the features at 159, 380, 515 and 653 cm−1 and a shoulder at 540 cm−1. The degradation of plattnerite was induced by increasing the laser power on the sample, and the formation of its secondary products red lead (Pb3O4), litharge (α-PbO) and massicot (β-PbO), when varying the laser power, is discussed. The analyses were performed in a controlled condition by coupling the Raman spectrometer to a temperature-controlled stage (Linkam THMS600- Renishaw), which allows for varying the sample temperature (from room temperature up to 600 °C) and keeping it constant inside the stage during the analysis. In this way, commercial plattnerite samples were heated by increasing the cell temperature to verify the temperature range at which the phase transitions of lead dioxide occur. In addition, thanks to the construction of temperature ramps, all the degradation pathways were shown, and other lead compounds were identified, generated by the laser power contribution. A different behaviour was found between pigments from historical painting samples and commercial samples under the effect of the laser. This information could be useful in order to recognize their nature when they are found in cultural heritage materials.

scholarly journals Construction of Spectral Discoloration Model for Red Lead Pigment by Aging Test and Simulating Degradation Experiment

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Jinxing Liang ◽  
Xiaoxia Wan ◽  
Chan Li ◽  
Junfeng Li ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Lead Dioxide ◽  
Degradation Process ◽  
Experimental Result ◽  
X Ray Diffraction ◽  
X Ray ◽  
Test Conditions ◽  
Aging Test ◽  
Digital Restoration ◽  
Red Lead

The construction of spectral discoloration model, based on aging test and simulating degradation experiment, was proposed to detect the aging degree of red lead pigment in ancient murals and to reproduce the spectral data supporting digital restoration of the ancient murals. The degradation process of red lead pigment under the aging test conditions was revealed by X-ray diffraction, scanning electron microscopy, and spectrophotometer. The simulating degradation experiment was carried out by proportionally mixing red lead and lead dioxide with referring to the results of aging test. The experimental result indicated that the pure red lead was gradually turned into black lead dioxide, and the amount of tiny particles of the aging sample increased faced with aging process. Both the chroma and lightness of red lead pigment decreased with discoloration, and its hue essentially remains unchanged. In addition, the spectral reflectance curves of the aging samples almost started rising at about 550 nm with the inflection moving slightly from about 570 nm to 550 nm. The spectral reflectance of samples in long- and in short-wavelength regions was fitted well with the logarithmic and linear function. The spectral discoloration model was established, and the real aging red lead pigment in Dunhuang murals was measured and verified the effectiveness of the model.

scholarly journals Structural elastic and thermal properties of SrxCd1−x O mixed compounds — a theoretical approach

2014 ◽  
Vol 32 (3) ◽  
pp. 350-357
Author(s):  
Purvee Bhardwaj
Keyword(s):  
Phase Transition ◽  
Vibrational Energy ◽  
Zero Point ◽  
Study Phase ◽  
Energy Effect ◽  
Phase Transition Pressure ◽  
Vegard’S Law ◽  
Extended Interaction ◽  
Experimental Values ◽  
Good Agreement

AbstractIn the present paper, the structural and mechanical properties of alkaline earth oxides mixed compound SrxCd1−x O (0 ≤ x ≤ 1) under high pressure have been reported. An extended interaction potential (EIP) model, including the zero point vibrational energy effect, has been developed for this study. Phase transition pressures are associated with a sudden collapse in volume. Phase transition pressure and associated volume collapses [ΔV (Pt)/V(0)] calculated from this approach are in good agreement with the experimental values for the parent compounds (x = 0 and x = 1). The results for the mixed crystal counterparts are also in fair agreement with experimental data generated from the application of Vegard’s law to the data for the parent compounds.

scholarly journals Unique Phase Transition of Exogenous Fusion Elastin-like Polypeptides in the Solution Containing Polyethylene Glycol

2019 ◽  
Vol 20 (14) ◽  
pp. 3560
Author(s):  
Zhongqi Ge ◽  
Ziyang Xiong ◽  
Dandan Zhang ◽  
Xialan Li ◽  
Guangya Zhang
Keyword(s):  
Phase Transition ◽  
Polyethylene Glycol ◽  
Transition Temperature ◽  
Fluorescence Spectroscopy ◽  
Fusion Protein ◽  
Molecular Mechanism ◽  
Phase Transition Temperature ◽  
Temperature Controlled

Elastin-Like polypeptides (ELPs), as well-known temperature-controlled bio-macromolecules, are widely used. However, little is known about the interactions between ELPs and macromolecules, which is an important yet neglected problem. Here, the phase transition characteristics of an ELPs-SpyCatcher fusion protein (E-C) in the presence of polyethylene glycol (PEG) in single salts (Na2CO3, Na2SO4, NaCl) solutions were investigated using a UV spectrophotometer, DLC, and fluorescence spectroscopy, and we got some interesting results. The phases transition of E-C occurred at a concentration lower than 0.5 mol/L Na2CO3/PEG2000, while in single Na2CO3 (<0.5 mol/L), the phase transition of E-C did not occur. In the Na2CO3/PEG solution, we observed a unique two-step phase transition of E-C when the Na2CO3 concentration was 0.5 mol/L and PEG2000 concentration was less than 0.15 g/mL, respectively. In the Na2CO3/PEG2000 solution, the phase-transition temperature of E-C decreased with the increase of PEG concentration, but increased in the Na2SO4/PEG2000 solution, while it remained unchanged in the NaCl/PEG2000 solution. However, the phase-transition temperature of the linear ELPs40 decreased under the same salts/PEG2000 solutions. We also addressed the possible molecular mechanism of the interesting results. In contrast to the current well-understood salts-ELPs interactions, this work provides some new insights into the interaction between the PEG-salts-ELPs in solution.

Influence of Cholesterol on the Phase Transition of Lipid Bilayers: A Temperature-Controlled Force Spectroscopy Study

Langmuir ◽  
2012 ◽  
Vol 28 (35) ◽  
pp. 12851-12860 ◽  
Author(s):  
Lorena Redondo-Morata ◽  
Marina I. Giannotti ◽  
Fausto Sanz
Keyword(s):  
Phase Transition ◽  
Lipid Bilayers ◽  
Force Spectroscopy ◽  
Spectroscopy Study ◽  
Temperature Controlled

X-ray microdiffraction study of the half-V-shaped switching liquid crystal

2004 ◽  
Vol 19 (1) ◽  
pp. 53-55 ◽  
Author(s):  
Kazuhiro Takada ◽  
Takashi Noma ◽  
Takeshi Togano ◽  
Taihei Mukaide ◽  
Atsuo Iida
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Formation Process ◽  
Ferroelectric Liquid Crystal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transient Layer ◽  
Smectic C ◽  
Layer Structures ◽  
Temperature Controlled

Local layer structures and their formation process in a half-V-shaped switching ferroelectric liquid crystal (HV-FLC) were investigated by means of synchrotron X-ray microdiffraction. The HV-FLC is a FLC that has a cholesteric–chiral smectic C (Ch–SmC*) phase transition sequences. X-ray microdiffraction measurements revealed that the SmC* phase in the HV-FLC was composed of asymmetric chevron and inclined-bookshelf structures. In addition, temperature-controlled X-ray diffraction measurements showed that the transient layer structures appeared during the Ch to SmC* phase transition.

Phase Transition of C5H5 NHSbBr4 Having a Hypervalent Bond: A 2H NMR and X-Ray Diffraction Study [Phase Transition of C5H5NHSbBr4]

1996 ◽  
Vol 51 (5-6) ◽  
pp. 739-744
Author(s):  
K. Yamada ◽  
T. Ohtani ◽  
S. Shirakawa ◽  
H. Ohki ◽  
T. Okuda ◽  
...  
Keyword(s):  
Phase Transition ◽  
Nearest Neighbor ◽  
Study Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Deuterated Analog ◽  
Librational Motion ◽  
Diffraction Patterns

Abstract The second order phase transition at 253 K of pyridinium tetrabromoantimonate(III), C5H5NHSbBr4 , has been characterized by means of X-ray diffraction and 2H NMR. As was suggested from the 81Br NQR spectra, the Rietveld refinements of the X-ray diffraction patterns at 297 K and 116 K confirm the structural change of the anion from SbBr-4 to SbBr3 • Br-. The line shape analysis of the 2H NMR using the deuterated analog revealed that the librational amplitude of the pyridinium ring about the axis normal to the plane increased with temperature and its rms amplitude reaching ca. 25° at Tc . The librational motion may induce the phase transition breaking the hydrogen bonds of the type N-H … Br. However, nearest-neighbor 2π/6 jump or reorientation such as seen in benzene were not observed even at 350 K.

Thermodynamics of a 3 — D charged rotating hairy black hole

Open Physics ◽  
2014 ◽  
Vol 12 (9) ◽  
Author(s):  
Jalil Naji ◽  
Saba Heydari ◽  
Ali Amjadi
Keyword(s):  
Phase Transition ◽  
Black Hole ◽  
Free Energy ◽  
Total Energy ◽  
Specific Heat ◽  
Three Dimensions ◽  
Study Phase ◽  
First Law Of Thermodynamics ◽  
The Stability ◽  
Hairy Black Hole

AbstractIn this paper, we consider a charged rotating black hole in three dimensions with a scalar charge, and discuss thermodynamics quantities. We find effects of the black hole parameters on the temperature, entropy, free energy, total energy and specific heat. We also investigate the stability of the black hole and study phase transition. We consider the first law of thermodynamics and find that satisfied.

scholarly journals Degradation of Emerald Green: Scientific Studies on Multi-polychrome Vairocana Statue in Dazu Rock Carvings, Chongqing, China

2020 ◽  
Author(s):  
Zhimin Li ◽  
Lele Wang ◽  
Huili Chen ◽  
Qinglin Ma
Keyword(s):  
Cross Sections ◽  
Degradation Products ◽  
Gold Foil ◽  
Paint Layer ◽  
Precipitation Reaction ◽  
Secondary Products ◽  
Ultramarine Blue ◽  
Heritage Science ◽  
Red Lead ◽  
World Cultural Heritage

Abstract The spontaneous degradation of pigments in painting may occur depending on environment, especially the surrounding condition of high humidity and soluble salts. Even some of these are well studied, more investigations are still in need for heritage science. Paint cross sections from Vairocana Statue in Dazu Rock Carvings, one of World Cultural Heritage, Chongqing, China are studied by optical microscopy (OM), Raman spectroscopy (Raman) and mapping, and scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDS). Ultramarine blue, emerald green, synthetic atacamite, vermilion, red lead, gold foil, orpiment, cerussite, gypsum and barite are identified as pigments. Moreover, lavendulan (NaCaCu 5 (AsO 4 ) 4 Cl·5H 2 O) and mimetite (Pb 5 (AsO 4 ) 3 Cl) are degradation products of emerald green (Cu(C 2 H 3 O 2 ) 2 ·3Cu(AsO 2 ) 2 ) and cerussite (PbCO 3 ) originally used as green pigment with mixture. These secondary products is formed via multistep progresses as degradation of emerald green and cerussite, oxidation of arsenite ((AsO 2 ) - ), migration of arsenate ((AsO 4 ) 3- ) and precipitation reaction of these ions with other necessary ions from environmental conditions. Based on the pigment and paint layer stratigraphy analysis, the paintings of the statue have been executed at least four times and the most recent may be after 1850s. The formation of lavendulan give rise to a highlight for identification of green copper-arsenic containing pigments and characterization of degradation in complex conditions.

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