Pub Date : 2002-03-01DOI: 10.1080/13642810208223131
R. Le Parc, B. Champagnon, L. David, A. Faivre, C. Levelut, P. Guenot, J. Hazemann, C. Rochas, J. Simon
Abstract Low-OH-content silica samples having fictive temperatures in the interval 1000–1500°C, have been studied by small-angle X-ray scattering using synchrotron radiations both at room temperature and from 20 to 1500deg;C. The limit for zero-angle X-ray scattering intensity is analysed in term of density fluctuations. We demonstrate that density fluctuations are strongly related to structural relaxation; both depend on thermal history (i.e. the fictive temperature) of the sample, in the temperature range below Tg.
{"title":"Temperature dependence of the density fluctuations of silica by small-angle X-ray scattering","authors":"R. Le Parc, B. Champagnon, L. David, A. Faivre, C. Levelut, P. Guenot, J. Hazemann, C. Rochas, J. Simon","doi":"10.1080/13642810208223131","DOIUrl":"https://doi.org/10.1080/13642810208223131","url":null,"abstract":"Abstract Low-OH-content silica samples having fictive temperatures in the interval 1000–1500°C, have been studied by small-angle X-ray scattering using synchrotron radiations both at room temperature and from 20 to 1500deg;C. The limit for zero-angle X-ray scattering intensity is analysed in term of density fluctuations. We demonstrate that density fluctuations are strongly related to structural relaxation; both depend on thermal history (i.e. the fictive temperature) of the sample, in the temperature range below Tg.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73078774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223151
L. de Francesco, M. Cutroni, A. Mandanici
Abstract The dielectric spectroscopy technique has been used over a broad-band range of frequencies to compare the dynamic response of some supercooled liquids down to the glass transition temperature Tg . Glycerol, 1,2-propanediol and 2,3-butanediol have been chosen because they differ in both their chain lengths, that is the number of carbon atoms, and their hydroxyl groups OH. The frequency and temperature dependences of the real and imaginary parts of the dielectric permittivity seem to be correlated to the structure of the molecules.
{"title":"Broad-band dielectric spectroscopy of some alcohols down to the glass transition temperature Tg","authors":"L. de Francesco, M. Cutroni, A. Mandanici","doi":"10.1080/13642810208223151","DOIUrl":"https://doi.org/10.1080/13642810208223151","url":null,"abstract":"Abstract The dielectric spectroscopy technique has been used over a broad-band range of frequencies to compare the dynamic response of some supercooled liquids down to the glass transition temperature Tg . Glycerol, 1,2-propanediol and 2,3-butanediol have been chosen because they differ in both their chain lengths, that is the number of carbon atoms, and their hydroxyl groups OH. The frequency and temperature dependences of the real and imaginary parts of the dielectric permittivity seem to be correlated to the structure of the molecules.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83369033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223149
S. Grandi, P. Mustarelli, A. Magistris
Abstract Silica glasses doped with GeO2 in the range 10−3-10mol % have been prepared by means of a new sol-gel recipe. Medium-density aerogels, shaped as discs or cylinders, have been obtained in an autoclave using ethanol as the supercritical fluid. The densification treatment has been performed under a controlled atmosphere, originating in samples in the centimetre range. Fewer than 5 % of the aerogels were fractured and, overall, the chosen route is particularly convenient in terms of simplicity and time saving. The Ge content was checked by means of inductively coupled plasma mass spectroscopy and neutron activation analysis techniques. The glass structures have been characterized by means of 29Si magic angle spinning nuclear magnetic resonance, density, thermal gravimetric and differential thermal analyses.
{"title":"Sol–gel preparation of GeO2-doped SiO2 glasses","authors":"S. Grandi, P. Mustarelli, A. Magistris","doi":"10.1080/13642810208223149","DOIUrl":"https://doi.org/10.1080/13642810208223149","url":null,"abstract":"Abstract Silica glasses doped with GeO2 in the range 10−3-10mol % have been prepared by means of a new sol-gel recipe. Medium-density aerogels, shaped as discs or cylinders, have been obtained in an autoclave using ethanol as the supercritical fluid. The densification treatment has been performed under a controlled atmosphere, originating in samples in the centimetre range. Fewer than 5 % of the aerogels were fractured and, overall, the chosen route is particularly convenient in terms of simplicity and time saving. The Ge content was checked by means of inductively coupled plasma mass spectroscopy and neutron activation analysis techniques. The glass structures have been characterized by means of 29Si magic angle spinning nuclear magnetic resonance, density, thermal gravimetric and differential thermal analyses.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76795143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223135
V. Privalko, B. Gorodilov, N. A. Rekhteta, E. Privalko, A. Bartolotta, G. Carini, G. D’Angelo, G. Tripodo
Abstract The specific heats of miscible blends of amorphous poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF) have been measured between 2.0 and 65 K. The behaviour of the specific heat of pure PMMA is consistent with the universal feature expected for a solid in which the topological disorder introduces an excess of low-energy vibrational modes; the peak in C p/T 3, compared with that revealed in semicrystalline PVDF, is enhanced. The PMMA-PVDF binary blends are wholly amorphous and show heat capacities which below 15 K are not dependent on the compositions and equal to that measured in PMMA. These striking observations have been interpreted in terms of a simple linear overlap of the contributions to the specific heat from wholly amorphous PMMA and PVDF, weighted by their proportions.
{"title":"Low-temperature specific heat capacities of the miscible blends of poly(methyl methacrylate) and poly(vinylidene fluoride)","authors":"V. Privalko, B. Gorodilov, N. A. Rekhteta, E. Privalko, A. Bartolotta, G. Carini, G. D’Angelo, G. Tripodo","doi":"10.1080/13642810208223135","DOIUrl":"https://doi.org/10.1080/13642810208223135","url":null,"abstract":"Abstract The specific heats of miscible blends of amorphous poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF) have been measured between 2.0 and 65 K. The behaviour of the specific heat of pure PMMA is consistent with the universal feature expected for a solid in which the topological disorder introduces an excess of low-energy vibrational modes; the peak in C p/T 3, compared with that revealed in semicrystalline PVDF, is enhanced. The PMMA-PVDF binary blends are wholly amorphous and show heat capacities which below 15 K are not dependent on the compositions and equal to that measured in PMMA. These striking observations have been interpreted in terms of a simple linear overlap of the contributions to the specific heat from wholly amorphous PMMA and PVDF, weighted by their proportions.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88127650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223137
T. Toccoli, A. Boschetti, S. Iannotta, P. Scardi, G. Barbarella, G. Sotgiu
Abstract Supersonic molecular beam epitaxy can be fruitfully used to grow films of organic materials, controlling their degree of ordering and their morphologies. This is due to the fine control on the initial state of the compounds in the beam. Very sharp and ‘tuneable’ energy distributions in the beam can be achieved so that the growth is not governed by processes at thermodynamic equilibrium but by the kinetics. This allows us, in some cases, to ‘force’ the growth in the desired directions instead of leaving this only to the interplay between the weak interaction forces and to the equilibrium thermodynamics to drive the growth. Comparing the optical response, morphology and structure of films grown under different degrees of supersonicity of the beam we show that one can control the growth in details. The grain size and density of defects can be drastically changed by appropriately tuning the beam's parameters. X-ray diffraction and pole figure analysis of the films are reported and discussed.
{"title":"Growth by supersonic molecular-beam epitaxy of oligothiophene films with controlled properties","authors":"T. Toccoli, A. Boschetti, S. Iannotta, P. Scardi, G. Barbarella, G. Sotgiu","doi":"10.1080/13642810208223137","DOIUrl":"https://doi.org/10.1080/13642810208223137","url":null,"abstract":"Abstract Supersonic molecular beam epitaxy can be fruitfully used to grow films of organic materials, controlling their degree of ordering and their morphologies. This is due to the fine control on the initial state of the compounds in the beam. Very sharp and ‘tuneable’ energy distributions in the beam can be achieved so that the growth is not governed by processes at thermodynamic equilibrium but by the kinetics. This allows us, in some cases, to ‘force’ the growth in the desired directions instead of leaving this only to the interplay between the weak interaction forces and to the equilibrium thermodynamics to drive the growth. Comparing the optical response, morphology and structure of films grown under different degrees of supersonicity of the beam we show that one can control the growth in details. The grain size and density of defects can be drastically changed by appropriately tuning the beam's parameters. X-ray diffraction and pole figure analysis of the films are reported and discussed.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85176703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223134
E. Cazzanelli, S. Capoleoni, L. Papalino
Abstract In several amorphous or nanocrystalline systems, the local heating associated with a focused laser beam of visible light induces a transformation towards ‘bulk crystal’ order. The various steps of this transformation can be monitored through the change in their Raman spectra, collected by a confocal microscope. In fact, these different steps of the evolution of the Raman spectra, reflecting different crystallization degrees, can be observed also as spatial variations by performing a Raman mapping on film samples that appear homogeneous under optical investigation. These variations, on the scale of micrometres, could reveal, in principle, the topography of the crystallinity of the film or the space variation of a ‘crystallization compliance’. These laser-induced transformations have been studied in transparent oxide films, having thickness of the order of a micrometre, obtained by different deposition techniques; here two examples are presented, concerning tungsten trioxide films made via sputtering techniques and mixed titanium oxide-vanadium oxide films deposited by a sol-gel method.
{"title":"Space variation of the crystallization kinetics in pure and mixed oxide films: A micro-Raman determination","authors":"E. Cazzanelli, S. Capoleoni, L. Papalino","doi":"10.1080/13642810208223134","DOIUrl":"https://doi.org/10.1080/13642810208223134","url":null,"abstract":"Abstract In several amorphous or nanocrystalline systems, the local heating associated with a focused laser beam of visible light induces a transformation towards ‘bulk crystal’ order. The various steps of this transformation can be monitored through the change in their Raman spectra, collected by a confocal microscope. In fact, these different steps of the evolution of the Raman spectra, reflecting different crystallization degrees, can be observed also as spatial variations by performing a Raman mapping on film samples that appear homogeneous under optical investigation. These variations, on the scale of micrometres, could reveal, in principle, the topography of the crystallinity of the film or the space variation of a ‘crystallization compliance’. These laser-induced transformations have been studied in transparent oxide films, having thickness of the order of a micrometre, obtained by different deposition techniques; here two examples are presented, concerning tungsten trioxide films made via sputtering techniques and mixed titanium oxide-vanadium oxide films deposited by a sol-gel method.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78505921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223146
R. Rolli, M. Montagna, A. Chiasera, G. Righini, S. Pelli, A. Jha, V. Tikhomirov, S. Tikhomirova, A. Monteil, S. Chaussedent, M. Ferrari
Abstract A comparative study of the spectroscopic properties at 1.5 μm of erbiumdoped fluoride and tellurite glasses has been performed. Emission in the third telecommunications window has been observed upon excitation at 514.5 nm and the lifetime of the 4I13/2 level has been measured. Infrared-to-visible upconversion emission upon continuous-wave laser excitation at 976 nm has been detected in the different hosts. The upconversion results in green and red emissions, whose intensity has a quadratic dependence on the excitation power. Lifetime measurements have been performed in order to clarify the contributions of excited-state absorption and energy transfer to the upconversion process.
{"title":"A comparative study of the spectroscopic properties at 1.5 μm of erbium-activated fluoride and tellurite glasses","authors":"R. Rolli, M. Montagna, A. Chiasera, G. Righini, S. Pelli, A. Jha, V. Tikhomirov, S. Tikhomirova, A. Monteil, S. Chaussedent, M. Ferrari","doi":"10.1080/13642810208223146","DOIUrl":"https://doi.org/10.1080/13642810208223146","url":null,"abstract":"Abstract A comparative study of the spectroscopic properties at 1.5 μm of erbiumdoped fluoride and tellurite glasses has been performed. Emission in the third telecommunications window has been observed upon excitation at 514.5 nm and the lifetime of the 4I13/2 level has been measured. Infrared-to-visible upconversion emission upon continuous-wave laser excitation at 976 nm has been detected in the different hosts. The upconversion results in green and red emissions, whose intensity has a quadratic dependence on the excitation power. Lifetime measurements have been performed in order to clarify the contributions of excited-state absorption and energy transfer to the upconversion process.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78869336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223147
Carmela Mancuso, J. Capobianco, A. Speghini, Marco Bettinelli
Abstract A new sodium phosphotantalate glass of molar composition 4.4Na2B4O7-84.3NaPO3-10.8Ta2O5-0.5Eu2O3 was studied using laser-induced fluorescence line-narrowing techniques. From the site-selective luminescence spectra of Eu3+ at 77 K, the energies of the Stark components of the 7F1 and 7F2 multiplets were obtained and a crystal-field analysis was carried out assuming a C 2v site symmetry. The dependence of the crystal-field parameters B kq on the excitation energy is similar to that observed in other oxide glasses. The behaviour of the crystal-field ratios B 22/B 20 and B 44/B 40 agrees reasonably well with the values calculated using the geometric model proposed by Brecher and Riseberg and with previous observations made for different metaphosphate glasses. On the other hand, the crystal-field strength parameter 5 is distinctly lower than for these glasses.
{"title":"Fluorescence line-narrowing spectroscopy of a sodium phosphotantalate glass doped with Eu3+","authors":"Carmela Mancuso, J. Capobianco, A. Speghini, Marco Bettinelli","doi":"10.1080/13642810208223147","DOIUrl":"https://doi.org/10.1080/13642810208223147","url":null,"abstract":"Abstract A new sodium phosphotantalate glass of molar composition 4.4Na2B4O7-84.3NaPO3-10.8Ta2O5-0.5Eu2O3 was studied using laser-induced fluorescence line-narrowing techniques. From the site-selective luminescence spectra of Eu3+ at 77 K, the energies of the Stark components of the 7F1 and 7F2 multiplets were obtained and a crystal-field analysis was carried out assuming a C 2v site symmetry. The dependence of the crystal-field parameters B kq on the excitation energy is similar to that observed in other oxide glasses. The behaviour of the crystal-field ratios B 22/B 20 and B 44/B 40 agrees reasonably well with the values calculated using the geometric model proposed by Brecher and Riseberg and with previous observations made for different metaphosphate glasses. On the other hand, the crystal-field strength parameter 5 is distinctly lower than for these glasses.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80626030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223148
P. Jund, W. Kob, R. Jullien
Abstract We study the dynamics of the Na atoms in amorphous Na2O-4SiO2 by means of molecular dynamics computer simulations. We find that at low temperatures the preferential pathways of these atoms form a well-connected network of pockets and channels that is quickly explored by each atom. We show that even for long times the volume occupied by these channels is relatively small and that they cannot be seen in individual snapshots of the Na atoms. By studying the distinct part of the van Hove correlation function we show that the lifetime for such a pocket shows an Arrhenius dependence on temperature. We also calculate the probability that an atom returns to a given site and show that such events are not very frequent.
{"title":"Transport properties of sodium in a silicate glass: A numerical study","authors":"P. Jund, W. Kob, R. Jullien","doi":"10.1080/13642810208223148","DOIUrl":"https://doi.org/10.1080/13642810208223148","url":null,"abstract":"Abstract We study the dynamics of the Na atoms in amorphous Na2O-4SiO2 by means of molecular dynamics computer simulations. We find that at low temperatures the preferential pathways of these atoms form a well-connected network of pockets and channels that is quickly explored by each atom. We show that even for long times the volume occupied by these channels is relatively small and that they cannot be seen in individual snapshots of the Na atoms. By studying the distinct part of the van Hove correlation function we show that the lifetime for such a pocket shows an Arrhenius dependence on temperature. We also calculate the probability that an atom returns to a given site and show that such events are not very frequent.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73453754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208218363
I. Fisher, X. P. Xie, I. Tudosa, C. Gao, C. Song, P. Canfield, A. Kracher, K. Dennis, D. Abanoz, M. Kramer
Abstract Systematic electrical transport data are presented for single quasicrystals in the Al–Pd–Re family across the accessible width of formation. The temperature dependence of the electrical conductivity can be accounted for in terms of weak localization and electron-electron interactions for all compositions studied, in contrast with previous studies of cast and annealed polygrain material. These results indicate that the conductivity mechanism in the Al–Pd–Re system is not dramatically different from that of other quasicrystal families.
{"title":"The electrical conductivity of single-grain Al–Pd–Re quasicrystals","authors":"I. Fisher, X. P. Xie, I. Tudosa, C. Gao, C. Song, P. Canfield, A. Kracher, K. Dennis, D. Abanoz, M. Kramer","doi":"10.1080/13642810208218363","DOIUrl":"https://doi.org/10.1080/13642810208218363","url":null,"abstract":"Abstract Systematic electrical transport data are presented for single quasicrystals in the Al–Pd–Re family across the accessible width of formation. The temperature dependence of the electrical conductivity can be accounted for in terms of weak localization and electron-electron interactions for all compositions studied, in contrast with previous studies of cast and annealed polygrain material. These results indicate that the conductivity mechanism in the Al–Pd–Re system is not dramatically different from that of other quasicrystal families.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74707979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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