Overall application of inexpensive, non-vacuum chemical (CBD) and electrochemical deposition (ECD... more Overall application of inexpensive, non-vacuum chemical (CBD) and electrochemical deposition (ECD) techniques that can be scaled-up to industrial processes is targeted for processing the absorber-, buffer-, and window-layer of CISe/CIGSe TFSCs to overcome current process incompatibilities mainly resulting from the simultaneous use of moderate temperature non-vacuum (50-70oC) and high temperature (500-700oC) vacuum processes. Low cost ECD processing of ternary CuInSe2 and quaternary Cu(In,Ga)Se2 chalcopyrite semiconductor films with crystal quality similar to that of PVD grown films was achieved by as few as possible process steps skipping selenization at elevated temperatures. Chalcopyrite phase formation was confirmed already in as-deposited films. The film quality was further improved by subsequent annealing at 300oC, for 2h, in N2. ZnSe buffer- and ZnO window-layers were processed by CBD and ECD techniques, respectively. The properties of n-ZnO/i-ZnO bilayer were thoroughly inves...
ABSTRACT Coins and paper documents, such as books, are cultural heritage objects of great importa... more ABSTRACT Coins and paper documents, such as books, are cultural heritage objects of great importance, because of their special role in history and culture, both representing the political and social situation of each society in each epoch. Despite their differences in the methods of treatment for conservation purposes, laser tools are similar and we have chosen to treat them in parallel. Historical books and paper documents have a variety of surface alterations due to dirt encrustation or discoloration from the storage conditions and humidity. Biological deteriorations play an important role too. We currently proceed to the application of laser cleaning and diagnosis of biological stains (such as fungus) from cultural heritage books, identifying best practices and optimum laser parameters (i.e., energy dose). The method is applied to an historical book of the NTUA-Historic Library. The paper surface is cleaned using 355nm pulsed laser with fluence threshold of 0.102J/cm2 with 5Hz repetition rate and 160s exposure. The diagnostic technique available for the characterization of the paper surface is optical microscopy and SEM/EDX analyses. Ancient coins and metallic artworks develop patina or have encrustations from soil and other impurities. Lasers have been used in cleaning old coins and metallic artworks of cultural interest. A number of 18 coins from the 19th and 20th century are cleaned. In the current paper only a silver coin and a copper coin from the 20th century are presented. These coins are cleaned with a Q-Switched Nd:YAG laser with two different wavelengths 213nm and 1064nm. The cleaning performance of these two wavelengths is determined with optical microscopy and SEM/EDX analyses. Surface topography and composition are investigated. The chemical composition of the contamination seems to play an important role in metal deterioration during the cleaning process and therefore precise characterisation is very significant prior to and after cleaning.
The aim of this study was to evaluate the sealing ability and morphological microstructure of Bio... more The aim of this study was to evaluate the sealing ability and morphological microstructure of Biodentine in comparison to ProRoot mineral trioxide aggregate (MTA) after storage in an acidic environment. Biodentine and ProRoot MTA were prepared and packed into the canal lumen of dentin disks. Twenty specimens of each material were further randomly divided into two groups according to the storage media: group A: materials with saline as storage medium; group B: materials with citric acid buffered at pH 5.4 as storage medium. The sealing ability was evaluated at 1, 3, 6, and 24 h and 1 or 3 months, using a fluid transport model for quantitative analysis of endodontic microleakage. The morphological microstructures of the materials were also evaluated using scanning electron microscopy. During the first 24 h, MTA showed greater fluid transport values than Biodentine in both environments. At the 3-month measurement, when the materials were stored in saline, MTA showed greater ability to prevent fluid movement than Biodentine (p < 0.0001). However, when the materials were stored in an acidic environment, no statistical significant difference was found after 3 months. After storage in saline, both materials showed an uneven crystalline surface with similar hexagonal crystals. The microstructure of Biodentine changed after exposure to citric acid, showing a relatively smooth surface with more spheroidal crystals. The exposure to an acidic environment, within the limits of this study, seems to result in morphological changes of Biodentine in a different manner than MTA. MTA shows good ability to prevent fluid movement over time, in both environments. The ability of Biodentine to prevent fluid movement over time was enhanced in the acidic environment. The findings of the present study could imply that both materials are indicated for use in an acidic environment.
Nano-crystalline iron-rich saponitic clay has been found to exist in Nakhla, most probably as in-... more Nano-crystalline iron-rich saponitic clay has been found to exist in Nakhla, most probably as in-filling of a hollow ovoid inside amorphous mesostasis of rhyolitic composition (Chatzitheodoridis et al., 2014). The hollow ovoid in Nakhla is interpreted to be the result of a shock event from a bolide impact that induced circulating hydrothermal fluids with sharp temperature gradients in the subsurface of Mars, which variably altered the parent rock. This seems to be more evident now, with the additional discovery of two phases of phyllosilicate minerals, one of which is an iron-rich chlorite, and the other is probably a mixed-layer phyllosilicate. These phyllosilicates are located in the same thin section of Nakhla, very close to where the ovoid was also found (Chatzitheodoridis et al., 2014). Chlorite is a very common hydrous, layered silicate mineral on Earth, very similar in nature to micas. It is found in low to middle grade metamorphic rocks, in sedimentary rocks during their dia...
Many aspects of the biotic or abiotic origin of iron-rich sedimentary rocks consisting mainly of ... more Many aspects of the biotic or abiotic origin of iron-rich sedimentary rocks consisting mainly of hematite, an important indicator for exobiology, remain unresolved. Here, we use combined optical microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry (SEM-EDS), Raman spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS), to image the spatial distribution, and determine the composition, of potential biogenic markers (microbial microfossils, trace elements, organic ion species) in hematite-microstromatolites and oncolite-like microstructures. These structures are identified in iron-rich material cementing a Quaternary fossil-beach conglomerate deposit in the Cape Vani area, NW Milos Island, Greece. The combined detection of morphological, chemical, and molecular organic-ion, biomarkers closely associated with possible hematite microfossils within microstromatolite laminae, strongly supports microbial mediation for their formation, and ind...
TOF-SIMS mass spectra are labour intensive to interpret because of the very large number of peaks... more TOF-SIMS mass spectra are labour intensive to interpret because of the very large number of peaks that are in the mass spectrum. In a previous work we concluded that it is possible to interpret TOF-SIMS mass spectra in detail, however, interpretation requires powerful proprietary software to handle the information (Chatzitheodoridis et al., 2005) and a perfect mass calibration (Antonopoulou-Athera et al., 2011). Only then fully automated interpretation can be performed, also resulting in detailed chemical patterns that can be useful for biosignature interpretation. Currently, biosignature interpretation is performed using a small number of characteristic peaks that are compared with pure, isolated biochemical phases, often assisted by statistical techniques, or by labelling specific molecules. Biochemical phases that have been investigated in the literature include proteins and their aminoacids (Quong et al., 2005), extracellular polymeric substances (de Brouwer et al., 2006), lipid...
Geometrical parameters of natural and crushed aggregates such as grain length, perimeter, area, e... more Geometrical parameters of natural and crushed aggregates such as grain length, perimeter, area, etc., underline the shape and flakiness indices definition. The latter indices have a measurable effect on the mechanical properties of aggregates–binder mixtures, e.g. concrete, mortar, bituminous mixtures. In this work, digital methods were developed with the mathematical software Matlab, by applying a statistical method called k-means clustering for the exact separation between background and aggregates to compute the aforementioned properties. The overall code can be ap-plied in real time by analysing quickly a large volume of data with accuracy and significant cost reduction. Currently, only the two dimensions of the grains could be measured. Future work will focus on full three-dimensional measurements by com-paring paired images taken from different angles but also aggregate segmentation in case of touching particles.
Coins and paper documents, such as books, are cultural heritage objects of great importance, beca... more Coins and paper documents, such as books, are cultural heritage objects of great importance, because of their special role in history and culture, both representing the political and social situation of each society in each epoch. Despite their differences in the methods of treatment for conservation purposes, laser tools are similar and we have chosen to treat them in parallel. Historical books and paper documents have a variety of surface alterations due to dirt encrustation or discoloration from the storage conditions and humidity. Biological deteriorations play an important role too. We currently proceed to the application of laser cleaning and diagnosis of biological stains (such as fungus) from cultural heritage books, identifying best practices and optimum laser parameters (i.e., energy dose). The method is applied to an historical book of the NTUA-Historic Library. The paper surface is cleaned using 355nm pulsed laser with fluence threshold of 0.102J/cm2 with 5Hz repetition ...
Overall application of inexpensive, non-vacuum chemical (CBD) and electrochemical deposition (ECD... more Overall application of inexpensive, non-vacuum chemical (CBD) and electrochemical deposition (ECD) techniques that can be scaled-up to industrial processes is targeted for processing the absorber-, buffer-, and window-layer of CISe/CIGSe TFSCs to overcome current process incompatibilities mainly resulting from the simultaneous use of moderate temperature non-vacuum (50-70oC) and high temperature (500-700oC) vacuum processes. Low cost ECD processing of ternary CuInSe2 and quaternary Cu(In,Ga)Se2 chalcopyrite semiconductor films with crystal quality similar to that of PVD grown films was achieved by as few as possible process steps skipping selenization at elevated temperatures. Chalcopyrite phase formation was confirmed already in as-deposited films. The film quality was further improved by subsequent annealing at 300oC, for 2h, in N2. ZnSe buffer- and ZnO window-layers were processed by CBD and ECD techniques, respectively. The properties of n-ZnO/i-ZnO bilayer were thoroughly inves...
ABSTRACT Coins and paper documents, such as books, are cultural heritage objects of great importa... more ABSTRACT Coins and paper documents, such as books, are cultural heritage objects of great importance, because of their special role in history and culture, both representing the political and social situation of each society in each epoch. Despite their differences in the methods of treatment for conservation purposes, laser tools are similar and we have chosen to treat them in parallel. Historical books and paper documents have a variety of surface alterations due to dirt encrustation or discoloration from the storage conditions and humidity. Biological deteriorations play an important role too. We currently proceed to the application of laser cleaning and diagnosis of biological stains (such as fungus) from cultural heritage books, identifying best practices and optimum laser parameters (i.e., energy dose). The method is applied to an historical book of the NTUA-Historic Library. The paper surface is cleaned using 355nm pulsed laser with fluence threshold of 0.102J/cm2 with 5Hz repetition rate and 160s exposure. The diagnostic technique available for the characterization of the paper surface is optical microscopy and SEM/EDX analyses. Ancient coins and metallic artworks develop patina or have encrustations from soil and other impurities. Lasers have been used in cleaning old coins and metallic artworks of cultural interest. A number of 18 coins from the 19th and 20th century are cleaned. In the current paper only a silver coin and a copper coin from the 20th century are presented. These coins are cleaned with a Q-Switched Nd:YAG laser with two different wavelengths 213nm and 1064nm. The cleaning performance of these two wavelengths is determined with optical microscopy and SEM/EDX analyses. Surface topography and composition are investigated. The chemical composition of the contamination seems to play an important role in metal deterioration during the cleaning process and therefore precise characterisation is very significant prior to and after cleaning.
The aim of this study was to evaluate the sealing ability and morphological microstructure of Bio... more The aim of this study was to evaluate the sealing ability and morphological microstructure of Biodentine in comparison to ProRoot mineral trioxide aggregate (MTA) after storage in an acidic environment. Biodentine and ProRoot MTA were prepared and packed into the canal lumen of dentin disks. Twenty specimens of each material were further randomly divided into two groups according to the storage media: group A: materials with saline as storage medium; group B: materials with citric acid buffered at pH 5.4 as storage medium. The sealing ability was evaluated at 1, 3, 6, and 24 h and 1 or 3 months, using a fluid transport model for quantitative analysis of endodontic microleakage. The morphological microstructures of the materials were also evaluated using scanning electron microscopy. During the first 24 h, MTA showed greater fluid transport values than Biodentine in both environments. At the 3-month measurement, when the materials were stored in saline, MTA showed greater ability to prevent fluid movement than Biodentine (p < 0.0001). However, when the materials were stored in an acidic environment, no statistical significant difference was found after 3 months. After storage in saline, both materials showed an uneven crystalline surface with similar hexagonal crystals. The microstructure of Biodentine changed after exposure to citric acid, showing a relatively smooth surface with more spheroidal crystals. The exposure to an acidic environment, within the limits of this study, seems to result in morphological changes of Biodentine in a different manner than MTA. MTA shows good ability to prevent fluid movement over time, in both environments. The ability of Biodentine to prevent fluid movement over time was enhanced in the acidic environment. The findings of the present study could imply that both materials are indicated for use in an acidic environment.
Nano-crystalline iron-rich saponitic clay has been found to exist in Nakhla, most probably as in-... more Nano-crystalline iron-rich saponitic clay has been found to exist in Nakhla, most probably as in-filling of a hollow ovoid inside amorphous mesostasis of rhyolitic composition (Chatzitheodoridis et al., 2014). The hollow ovoid in Nakhla is interpreted to be the result of a shock event from a bolide impact that induced circulating hydrothermal fluids with sharp temperature gradients in the subsurface of Mars, which variably altered the parent rock. This seems to be more evident now, with the additional discovery of two phases of phyllosilicate minerals, one of which is an iron-rich chlorite, and the other is probably a mixed-layer phyllosilicate. These phyllosilicates are located in the same thin section of Nakhla, very close to where the ovoid was also found (Chatzitheodoridis et al., 2014). Chlorite is a very common hydrous, layered silicate mineral on Earth, very similar in nature to micas. It is found in low to middle grade metamorphic rocks, in sedimentary rocks during their dia...
Many aspects of the biotic or abiotic origin of iron-rich sedimentary rocks consisting mainly of ... more Many aspects of the biotic or abiotic origin of iron-rich sedimentary rocks consisting mainly of hematite, an important indicator for exobiology, remain unresolved. Here, we use combined optical microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry (SEM-EDS), Raman spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS), to image the spatial distribution, and determine the composition, of potential biogenic markers (microbial microfossils, trace elements, organic ion species) in hematite-microstromatolites and oncolite-like microstructures. These structures are identified in iron-rich material cementing a Quaternary fossil-beach conglomerate deposit in the Cape Vani area, NW Milos Island, Greece. The combined detection of morphological, chemical, and molecular organic-ion, biomarkers closely associated with possible hematite microfossils within microstromatolite laminae, strongly supports microbial mediation for their formation, and ind...
TOF-SIMS mass spectra are labour intensive to interpret because of the very large number of peaks... more TOF-SIMS mass spectra are labour intensive to interpret because of the very large number of peaks that are in the mass spectrum. In a previous work we concluded that it is possible to interpret TOF-SIMS mass spectra in detail, however, interpretation requires powerful proprietary software to handle the information (Chatzitheodoridis et al., 2005) and a perfect mass calibration (Antonopoulou-Athera et al., 2011). Only then fully automated interpretation can be performed, also resulting in detailed chemical patterns that can be useful for biosignature interpretation. Currently, biosignature interpretation is performed using a small number of characteristic peaks that are compared with pure, isolated biochemical phases, often assisted by statistical techniques, or by labelling specific molecules. Biochemical phases that have been investigated in the literature include proteins and their aminoacids (Quong et al., 2005), extracellular polymeric substances (de Brouwer et al., 2006), lipid...
Geometrical parameters of natural and crushed aggregates such as grain length, perimeter, area, e... more Geometrical parameters of natural and crushed aggregates such as grain length, perimeter, area, etc., underline the shape and flakiness indices definition. The latter indices have a measurable effect on the mechanical properties of aggregates–binder mixtures, e.g. concrete, mortar, bituminous mixtures. In this work, digital methods were developed with the mathematical software Matlab, by applying a statistical method called k-means clustering for the exact separation between background and aggregates to compute the aforementioned properties. The overall code can be ap-plied in real time by analysing quickly a large volume of data with accuracy and significant cost reduction. Currently, only the two dimensions of the grains could be measured. Future work will focus on full three-dimensional measurements by com-paring paired images taken from different angles but also aggregate segmentation in case of touching particles.
Coins and paper documents, such as books, are cultural heritage objects of great importance, beca... more Coins and paper documents, such as books, are cultural heritage objects of great importance, because of their special role in history and culture, both representing the political and social situation of each society in each epoch. Despite their differences in the methods of treatment for conservation purposes, laser tools are similar and we have chosen to treat them in parallel. Historical books and paper documents have a variety of surface alterations due to dirt encrustation or discoloration from the storage conditions and humidity. Biological deteriorations play an important role too. We currently proceed to the application of laser cleaning and diagnosis of biological stains (such as fungus) from cultural heritage books, identifying best practices and optimum laser parameters (i.e., energy dose). The method is applied to an historical book of the NTUA-Historic Library. The paper surface is cleaned using 355nm pulsed laser with fluence threshold of 0.102J/cm2 with 5Hz repetition ...
The Rhodope Massif in northern Greece is a newly established ultrahigh-pressure metamorphic (UHPM... more The Rhodope Massif in northern Greece is a newly established ultrahigh-pressure metamorphic (UHPM) province in the world (Mposkos and Kostopoulos, 2001). Microscopic observations on zircons separated from a garnet gneiss revealed a simple zoned structure consisting of a somewhat rounded detrital core and a metamorphic overgrowth rim. Numerous mineral and fluid inclusions were found in the metamorphic rim especially near the interface of the two domains. We carried out a detailed laser µ-Raman spectroscopic study of the inclusions and their zircon host in both domains. Quartz and monazite were identified in the detrital core whereas diamond, albite, phengite, hematite, rutile and CO 2 gas were identified in the rim. Interestingly, albite occurs always in pockets with phengite and diamond whereas the latter two phases can occur independently. We interpret these pockets as precipitates from a melt phase at high pressures. The microdiamonds were probably formed by dissociation of CO2 ; the thus liberated oxygen was combined with iron available from the fluid / melt phase to precipitate hematite. Importantly, there is clear-cut distinction in the Raman spectra of detrital and rim zircon, with the latter being additionally characterised by a broad band at ~1332 cm-1. What is more significant is that by approaching the included diamonds the above band in zircon increases dramatically in intensity. This can either be assigned to carbon occupying interstitial sites in zircon and in all probability reflects a luminescence band or to enhanced carbon solubility in zircon (Shcheka et al., 2006), with the diamonds reflecting sites locally supersaturated in carbon. We favour the former explanation since similar bands, often associated with CO2 peaks, were also observed in inclusions in garnet for which C solubility is negligible.
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Papers by Elias Chatzitheodoridis