12 results on '"I. Tsilika"'
Search Results
2. Crystallization process of thermally treated vitrified EAFD waste
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Th. Kehagias, I. Eleftheriadis, I. Tsilika, Eleni Pavlidou, Ph. Komninou, and Th. Karakostas
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Materials science ,Diopside ,Mineralogy ,engineering.material ,Fick's laws of diffusion ,Wollastonite ,law.invention ,Annealing (glass) ,Metal ,Optical microscope ,Chemical engineering ,law ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,engineering ,Crystallization ,Electric arc furnace - Abstract
Electric arc furnace dust (EAFD) powder was mixed and vitrified with 55% SiO 2 , 10% Na 2 CO 3 and 35% CaCO 3 raw materials. The resulting glass was thermally treated at the same temperature at different annealing times. The process towards crystallization of the glass–ceramics produced, as a function of annealing time, was examined by means of optical microscopy, electron microscopy techniques and X-ray diffraction. While at small crystallization times wollastonite was the only crystalline phase separated from the amorphous matrix, as the time of crystallization increased crystals of diopside emanating from wollastonite were also observed. The emergence of diopside crystals was attributed to the tendency of the metallic elements of EAFD, incorporated in the wollastonite structure, to move towards the neighbouring glass matrix causing local maxima of concentration in the vicinity of wollastonite crystals. This diffusive motion of the metallic elements of EAFD, such as Fe, Zn, was found to follow the 2nd Fick law and plays a crucial role in the stability region of the crystallized structures of the system.
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- 2010
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3. EAFD-loaded vitreous and glass–ceramic materials
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Th.A. Ioannidis, S. Kokkou, P. Kavouras, I. Tsilika, Th. Karakostas, Konstantinos Chrissafis, Th. Kehagias, and Anastasios I. Zouboulis
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Glass-ceramic ,Materials science ,Scanning electron microscope ,Mineralogy ,engineering.material ,Wollastonite ,law.invention ,Devitrification ,Chemical engineering ,law ,Transmission electron microscopy ,Differential thermal analysis ,Materials Chemistry ,Ceramics and Composites ,engineering ,Vitrification ,Crystallization - Abstract
SiO2, Na2O and CaO were mixed and co-melted with electric arc furnace dust waste. The resulting vitreous materials, produced by quenching at ambient atmosphere, were transformed into glass–ceramics by two-stage heat treatment, under thermal conditions that were determined by differential thermal analysis. X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry and transmission electron microscopy were employed to investigate the physical properties of all products. It was found that whilst wollastonite (CaSiO3) separates from the parent matrix as the dominant crystalline phase in all glass–ceramic products, the crystallization mode depends on the batch composition. Leaching tests evidenced that vitreous products were chemically durable. Devitrification did not significantly affect leach resistance so glass–ceramic materials retain the leach resistance that was achieved by vitrification.
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- 2007
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4. Structural characterization of Na2O–CaO–SiO2 glass ceramics reinforced with electric arc furnace dust
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I. Tsilika and Ph. Komninou
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Materials science ,Scanning electron microscope ,Sodium oxide ,Metallurgy ,Mineralogy ,Microstructure ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Transmission electron microscopy ,visual_art ,X-ray crystallography ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Ceramic ,Crystallization ,Electric arc furnace - Abstract
The microstructure of three different compositions of electric arc furnace dust (EAFD) from steel scrap recycling facilities mixed with cheap raw materials (SiO 2 , Na 2 O, CaO), treated under the same conditions were examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Wollastonite-type crystals were identified as the major crystalline phases. The initial composition of the mixtures was found to influence the type of crystals formed. The distribution of the elements in the glass matrix and the crystals in the as-casted and crystallized samples as well as the role of EAFD in the crystallization process were studied in an attempt to understand the mechanism of wollastonite-type crystals formation.
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- 2007
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5. High-pressure-induced metastable phase in tetragonal 2D polymeric C60
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S. Assimopoulos, Bertil Sundqvist, I. Tsilika, K. P. Meletov, G. A. Kourouklis, S. Ves, Thomas Wågberg, and J. Arvanitidis
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chemistry.chemical_classification ,Condensed matter physics ,Chemistry ,Analytical chemistry ,General Physics and Astronomy ,Polymer ,symbols.namesake ,Tetragonal crystal system ,Structural stability ,Phase (matter) ,Metastability ,High pressure ,symbols ,Physical and Theoretical Chemistry ,Raman scattering - Abstract
The structural stability of the tetragonal two-dimensional (2D) polymeric phase of C60 has been studied under pressure up to 24 GPa and room temperature by means of in situ Raman scattering. An irr ...
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- 2001
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6. High-Pressure Effects in Hydrofullerene C60H36 Studied by Raman Spectroscopy
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G. A. Kourouklis, K. P. Meletov, S. Ves, S. Assimopoulos, V.I. Kulakov, Salavat S. Khasanov, I. Tsilika, and I. O. Bashkin
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Phase transition ,Carbon atom ,Hydrogen ,Chemistry ,Phonon ,Hydrostatic pressure ,chemistry.chemical_element ,Pressure dependence ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Crystallography ,High pressure ,symbols ,Raman spectroscopy - Abstract
The effect of hydrostatic pressure on the Raman spectrum of hydrofullerene C 60 H 36 , at room temperature has been investigated up to 12 GPa. The samples were synthesized by means of high-pressure hydrogenation. The pressure dependence of the phonon frequencies exhibits two reversible changes one at ∼0.6 GPa and another one at ∼6 GPa. The first may be probably related to a phase transition from the initial orientationally disordered bcc structure to an orientationally ordered one. The second one, at ∼6 GPa, is probably driven by pressure-induced bonding of hydrogen to a carbon atom of a neighboring hydrofullerene cage.
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- 2001
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7. Isotopic and isomeric effects in high-pressure hydrogenated fullerenes studied by Raman spectroscopy
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V.I. Kulakov, S. Assimopoulos, I. O. Bashkin, G. A. Kourouklis, K. P. Meletov, I. Tsilika, and Salavat S. Khasanov
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Fullerene ,Hydrogen ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Mass ratio ,Molecular dynamics ,symbols.namesake ,chemistry ,Deuterium ,Isotopic shift ,Homogeneity (physics) ,symbols ,Physical and Theoretical Chemistry ,Raman spectroscopy - Abstract
Raman spectra of hydro- and deuterofullerenes, C60H36 and C60D36, prepared under hydrogen or deuterium pressure of 3.0 GPa at diAerent conditions of temperature and hydrogenation time, have been measured at room temperature and normal pressure. Spatially resolved micro-Raman study shows that the homogeneity and optical properties of the samples depend primarily on the synthesis temperature. The Raman spectrum of hydrofullerene contains a large number of prominent peaks originating from the various isomers. The comparison of the experimental data with results of molecular dynamics calculations shows that various isomers are present in the samples, with the most abundant of them being the ones with symmetries S6, T and D3d. The Raman spectrum of the deuterofullerene is similar in structure to that of the hydrofullerene, however, significant diAerences occur in the frequency positions of the C‐H and C‐D stretching and bending modes which are expected from the isotopic eAect. In particular, the isotopic shift ratio for the stretching mode, XH=XD 1:32, is smaller than the expected one from the mass ratio for pure C‐H and C‐D stretching modes. ” 2001 Elsevier Science B.V. All rights reserved.
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- 2001
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8. Caregivers' anxiety and self-efficacy in palliative care
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Mystakidou, K. Parpa, E. Panagiotou, I. Tsilika, E. Galanos, A. Gouliamos, A.
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MYSTAKIDOU K., PARPA E., PANAGIOTOU I., TSILIKA E., GALANOS A. & GOULIAMOS A. (2012) European Journal of Cancer Care22, 188-195 Caregivers' anxiety and self-efficacy in palliative care This study examined the relationship between caregivers' anxiety supporting a patient with advanced cancer and self-efficacy and their socio-demographic characteristics, and then whether these variables could influence their self-efficacy. One hundred and seven caregivers of advanced cancer patients participated in the study and completed the Greek versions of the State-Trait Anxiety Inventory (STAI) and the General Perceived Self-efficacy Scale (GSE). Significant comparisons were found between State anxiety and female gender (P= 0.009), cohabitation (P= 0.002) and relationship with the patient (P= 0.004); statistically significant associations were found between State, Trait anxiety and self-efficacy scores of caregivers (P < 0.0005 respectively). A multiple regression model (enter method) showed women (P= 0.005), spouses (P= 0.01) and self-efficacy (P= 0.02) as the significant predictors of State anxiety. Furthermore, self-efficacy seemed to be the strongest contributor of trait anxiety (P < 0.0005). Female caregivers and spouses of advanced cancer patients experience more state anxiety levels than men and other caregivers respectively. In addition, caregivers with low self-efficacy are more likely to have elevated anxiety scores than self-efficacious caregivers. These findings can help healthcare professionals focus on some problems common to caregivers of cancer patients and plan appropriate interventions. Copyright © 2013 Blackwell Publishing Ltd 22 2 March 2013 10.1111/ecc.12012 Original Articles Original Article © 2012 Blackwell Publishing Ltd.
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- 2013
9. Exsolution phenomena in glass-ceramic systems
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Th. Karakostas, G. P. Dimitrakopulos, Th. Kehagias, Ph. Komninou, and I. Tsilika
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Materials science ,Diopside ,Energy-dispersive X-ray spectroscopy ,Pyroxene ,engineering.material ,Wollastonite ,Augite ,Transmission electron microscopy ,Chemical physics ,Phase (matter) ,visual_art ,Pigeonite ,engineering ,visual_art.visual_art_medium - Abstract
Exsolution is a known mechanism of phase transformation in pyroxenes. In particular, the transformation of the pyroxenes augite to pigeonite and vice-versa has been a subject of extent and thorough study since 1941 [1]. The transformation process involves the formation of nuclei, which gradually grow in lamellae during cooling. The precise orientation of the lamellae in relation to the parent structure is determined by the minimum interfacial energy. Transmission electron microscopy studies in these systems reveal submicroscopic textures such as periodic exsolution and micro-twinning [2]. In the present study, the phase transformation of wollastonite to diopside via the mechanism of exsolution is reported, by means of conventional and high-resolution transmission electron microscopy (TEM-HRTEM) and X-ray energy dispersive spectroscopy (EDS) microanalysis. This is a pyroxenoid to pyroxene transformation that takes place via cation substitution, i.e. a diffusion controlled process. The exact mechanism of the pyroxenoid-pyroxene transformation, which is caused by changes in pressure, temperature and cation size, has not been elucidated so far [3].
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- 2008
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10. Glass-ceramic materials from electric arc furnace dust
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Th. Karakostas, Th. Kehagias, G. Kaimakamis, S. Kokkou, D. Papadopoulos, Konstantinos Chrissafis, I. Tsilika, and P. Kavouras
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Ceramics ,Hazardous Waste ,Environmental Engineering ,Materials science ,Hot Temperature ,Health, Toxicology and Mutagenesis ,Mineralogy ,Industrial Waste ,Indentation hardness ,law.invention ,law ,Differential thermal analysis ,Environmental Chemistry ,Ceramic ,Hardness Tests ,Composite material ,Thermal analysis ,Waste Management and Disposal ,Electric arc furnace ,Glass-ceramic ,Dust ,Pollution ,Refuse Disposal ,Devitrification ,Steel ,visual_art ,Knoop hardness test ,visual_art.visual_art_medium - Abstract
Electric arc furnace dust (EAFD) was vitrified with SiO2, Na2CO3 and CaCO3 powders in an electric furnace at ambient atmosphere. Vitreous products were transformed into glass-ceramic materials by two-stage heat treatment, at temperatures determined by differential thermal analysis. Both vitreous and glass-ceramic materials were chemically stable. Wollastonite (CaSiO3) was separated from the parent matrix as the dominant crystalline phase, verified by X-ray diffraction analysis and energy dispersive spectrometry. Transmission electron microscopy revealed that wollastonite crystallizes mainly in its monoclinic form. Knoop microhardness was measured with the static indentation test method in all initial vitreous products and the microhardness values were in the region of 5.0–5.5 GPa. Devitrification resulted in glass-ceramic materials with microhardness values strongly dependent on the morphology and orientation of the separated crystal phase.
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- 2006
11. Optical Properties of Hydrofullerene C60H36 Underpressure
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Dimitrios Christofilos, S. Assimopoulos, S. Ves, G. A. Kourouklis, I. O. Bashkin, I. Tsilika, and K. P. Meletov
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Tetragonal crystal system ,symbols.namesake ,Phase transition ,Materials science ,Photoluminescence ,Fullerene ,Hydrostatic pressure ,symbols ,Luminescence ,Raman spectroscopy ,Molecular physics ,Raman scattering - Abstract
We report the hydrostatic pressure dependence, up to 13 GPa, of the Raman scattering and the Photoluminescence (PL) emission in hydrofiillerene C60H36 at room temperature, as well as the PL emission at selective temperatures down to 10 K. The Raman spectrum, compared to that of C60, contains additional lines due to the lowering of molecular symmetry from the presence of H. The photoluminescence studies show that the PL band consists of four peaks all of them exhibiting a blue pressure induced energy shift at rates of 2.3, 2.0, 0.3 and 5.1 meV/GPa, respectively. The pressure coefficients of the Raman frequencies show changes at~0.6 GPa and ~ 6 GPa, while the emission PL band show a change from blue to red at ~6 GPa. The first discontinuity may be related to a structural phase transition from the initial orientationally disordered cubic structure to an orientationally ordered tetragonal one and the second one, at ~6 GPa, to a pressure-induced hydrogen bonding to a carbon atom of a neighbouring hydrofullerene cage. Finally, our PL measurements do not imply any temperature induced phase transition of C60H36 down to 10 K.
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- 2001
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12. High pressure effects on the Raman spectrum of CsC60 polymer
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Kosmas Prassides, I. Tsilika, G. Kanellis, Konstantinos Papagelis, S. Ves, G. A. Kourouklis, J. Arvanitidis, and Katsumi Tanigaki
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Diffraction ,chemistry.chemical_classification ,Materials science ,Phonon ,macromolecular substances ,Polymer ,Pressure dependence ,Condensed Matter Physics ,Molecular physics ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Nuclear magnetic resonance ,stomatognathic system ,chemistry ,High pressure ,symbols ,sense organs ,Electrical and Electronic Engineering ,Raman spectroscopy ,Constant (mathematics) - Abstract
The effect of high pressure (up to 11 GPa) on the phonon modes of o -CsC 60 polymer has been studied by means of Raman spectroscopy. The pressure dependence of all the observed phonon frequencies exhibits reversible changes in the pressure region 4.3±0.5 GPa. The width of the H g (8) mode increases almost linearly with increasing pressure up to ∼4.3 GPa, above which it seems to remain constant. All the above changes may be related to the metal–insulator transition observed below 50 K for the material under investigation and/or with the structural changes, induced by pressure and observed also by X-ray diffraction measurements.
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