Pub Date : 2002-04-01DOI: 10.1080/13642810208224359
C. Bernard, S. Chaussedent, A. Monteil, M. Ferrari
Abstract We have performed molecular dynamics simulations of a TiO2–SiO2: Er3+ system for various compositions. Different distribution functions have been analysed to determine whether titanium ions are homogeneously distributed. A similar analysis has been carried out to characterize the erbium clustering ability. In particular, because of the simulation technique, the microscopic structure around erbium ions has been investigated. We discuss the role of both erbium and titanium concentrations in the structural properties of the simulated samples. For this purpose, the titanium distribution has been studied for [Ti]/[Si + Ti] concentrations ranging from 7.8 to 50% in undoped samples, and the erbium clustering trend has been characterized from three doped samples in which both erbium and titanium concentrations vary. A calculation of the crystal-field strength for the different kinds of erbium site has been interpreted in the light of the associated local structures.
{"title":"Molecular dynamics simulation of an erbium-activated titania–silica glass: Composition influence on the structural properties","authors":"C. Bernard, S. Chaussedent, A. Monteil, M. Ferrari","doi":"10.1080/13642810208224359","DOIUrl":"https://doi.org/10.1080/13642810208224359","url":null,"abstract":"Abstract We have performed molecular dynamics simulations of a TiO2–SiO2: Er3+ system for various compositions. Different distribution functions have been analysed to determine whether titanium ions are homogeneously distributed. A similar analysis has been carried out to characterize the erbium clustering ability. In particular, because of the simulation technique, the microscopic structure around erbium ions has been investigated. We discuss the role of both erbium and titanium concentrations in the structural properties of the simulated samples. For this purpose, the titanium distribution has been studied for [Ti]/[Si + Ti] concentrations ranging from 7.8 to 50% in undoped samples, and the erbium clustering trend has been characterized from three doped samples in which both erbium and titanium concentrations vary. A calculation of the crystal-field strength for the different kinds of erbium site has been interpreted in the light of the associated local structures.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80795623","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 : 2002-04-01DOI: 10.1080/13642810208224358
G. Baldacchini, S. Gagliardi, R. Montereali, A. Pace, R. B. Pode
Abstract Amorphous tris(8-hydroxyquinoline) aluminium (Alq3) thin films were deposited on fused silica substrates by thermal evaporation. Optical absorption, emission and excitation spectra were measured at room temperature and, for the first time, at 80 K, on an Alq3 film in a spectral range extending from the near ultraviolet to the visible. Spectroscopic features were carefully investigated as a function of temperature.
{"title":"Optical spectroscopy of tris(8-hydroxyquinoline) aluminium thin films","authors":"G. Baldacchini, S. Gagliardi, R. Montereali, A. Pace, R. B. Pode","doi":"10.1080/13642810208224358","DOIUrl":"https://doi.org/10.1080/13642810208224358","url":null,"abstract":"Abstract Amorphous tris(8-hydroxyquinoline) aluminium (Alq3) thin films were deposited on fused silica substrates by thermal evaporation. Optical absorption, emission and excitation spectra were measured at room temperature and, for the first time, at 80 K, on an Alq3 film in a spectral range extending from the near ultraviolet to the visible. Spectroscopic features were carefully investigated as a function of temperature.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80996765","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 : 2002-03-29DOI: 10.1080/13642810208218367
S. Moehlecke, P. Ho, M. Maple
Abstract Superconducting characteristics such as the Meissner–Ochsenfeld state, screening supercurrents and hysteresis loops of type II superconductors were observed from the temperature and magnetic field dependences of the magnetic moment m(T,H) in graphite powders reacted with sulphur for temperatures below 9.0K. The temperature dependence of the lower critical field H cl (T) was determined and the zero-temperature penetration depth λ(0) was estimated (λ(0) = 2270 Å). The superconductivity was observed to be highly anisotropic and to coexist with a ferromagnetic state that has a Curie temperature well above room temperature. A continuous transition from the superconducting state to the ferromagnetic state could be achieved by simply increasing the applied magnetic field.
{"title":"Coexistence of superconductivity and ferromagnetism in the graphite–sulphur system","authors":"S. Moehlecke, P. Ho, M. Maple","doi":"10.1080/13642810208218367","DOIUrl":"https://doi.org/10.1080/13642810208218367","url":null,"abstract":"Abstract Superconducting characteristics such as the Meissner–Ochsenfeld state, screening supercurrents and hysteresis loops of type II superconductors were observed from the temperature and magnetic field dependences of the magnetic moment m(T,H) in graphite powders reacted with sulphur for temperatures below 9.0K. The temperature dependence of the lower critical field H cl (T) was determined and the zero-temperature penetration depth λ(0) was estimated (λ(0) = 2270 Å). The superconductivity was observed to be highly anisotropic and to coexist with a ferromagnetic state that has a Curie temperature well above room temperature. A continuous transition from the superconducting state to the ferromagnetic state could be achieved by simply increasing the applied magnetic field.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78174964","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: 10.1080/13642810208223140
C. Svanberg, R. Bergman
Abstract A general function for the susceptibility response of disordered systems was recently proposed. It is here shown to be suitable for describing the response of geometrically confined systems. We investigate its ability to describe experimental permittivity data from dielectric spectroscopy and compare its performance with other commonly used curve-fit functions. As a model system we choose to study a propylene carbonate-poly(methyl methacrylate) gel. The physical interpretations of the obtained curve-fit parameters are briefly discussed.
{"title":"New general susceptibility response function: Comparison with dielectric relaxation data of a glass former in confinement","authors":"C. Svanberg, R. Bergman","doi":"10.1080/13642810208223140","DOIUrl":"https://doi.org/10.1080/13642810208223140","url":null,"abstract":"Abstract A general function for the susceptibility response of disordered systems was recently proposed. It is here shown to be suitable for describing the response of geometrically confined systems. We investigate its ability to describe experimental permittivity data from dielectric spectroscopy and compare its performance with other commonly used curve-fit functions. As a model system we choose to study a propylene carbonate-poly(methyl methacrylate) gel. The physical interpretations of the obtained curve-fit parameters are briefly 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":"84117697","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: 10.1080/13642810208223126
L. Andreozzi, M. Bagnoli, M. Faetti, M. Giordano, D. Palazzuoli
Abstract Dynamic processes effective on the nanometre length scale are of interest in supercooled fluids and polymers owing to their influence on structural and dynamic properties of these materials. In particular, nanometre and nanosecond scales mark the crossover from liquid to solid properties when approaching the glass transition. A possible explanation of the complex dynamic response of these systems for these length and time regions is provided in terms of heterogeneity. Heterogeneity in supercooled materials manifests itself by the presence of different domains, which relax towards equilibrium with different rates. Therefore, experimental techniques, which are sensitive to slow and fast molecules and able to follow their dynamics, are of paramount importance in this field of research. The present work is devoted to investigate heterogeneity in a polymer. We focused our attention on a side-chain liquid-crystal polymer (SCLCP). In this study a nanometre-scale molecular probe is dissolved in the SCLCP and its rotational dynamics are studied by linear and nonlinear electron spin resonance (ESR) spectroscopies, which are sensitive to the long and short time scales respectively of the rotational relaxation. In particular, linear ESR spectroscopy evidenced the presence of heterogeneity while on the short time scale detected by nonlinear ESR the correlation decay turns out to be homogeneous.
{"title":"Decoupling from structural relaxation of short- and longtime dynamics of a paramagnetic tracer dissolved in a liquid-crystal polymer","authors":"L. Andreozzi, M. Bagnoli, M. Faetti, M. Giordano, D. Palazzuoli","doi":"10.1080/13642810208223126","DOIUrl":"https://doi.org/10.1080/13642810208223126","url":null,"abstract":"Abstract Dynamic processes effective on the nanometre length scale are of interest in supercooled fluids and polymers owing to their influence on structural and dynamic properties of these materials. In particular, nanometre and nanosecond scales mark the crossover from liquid to solid properties when approaching the glass transition. A possible explanation of the complex dynamic response of these systems for these length and time regions is provided in terms of heterogeneity. Heterogeneity in supercooled materials manifests itself by the presence of different domains, which relax towards equilibrium with different rates. Therefore, experimental techniques, which are sensitive to slow and fast molecules and able to follow their dynamics, are of paramount importance in this field of research. The present work is devoted to investigate heterogeneity in a polymer. We focused our attention on a side-chain liquid-crystal polymer (SCLCP). In this study a nanometre-scale molecular probe is dissolved in the SCLCP and its rotational dynamics are studied by linear and nonlinear electron spin resonance (ESR) spectroscopies, which are sensitive to the long and short time scales respectively of the rotational relaxation. In particular, linear ESR spectroscopy evidenced the presence of heterogeneity while on the short time scale detected by nonlinear ESR the correlation decay turns out to be homogeneous.","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":"88044985","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: 10.1080/13642810208223130
V. Crupi, D. Majolino, P. Migliardo, V. Venuti
Abstract In this paper we report the results of a study of low-frequency vibrational dynamics and electron-vibration coupling in water in the bulk and confined state, at different hydration percentages. The simultaneous use of both Raman spectroscopy and time-of-flight inelastic neutron scattering allowed us to determine the respective vibrational densities of states (VDOSs), g R eff(ω) and g N(ω). Both the VDOSs show clear evidence of surface-induced vibrational modes, due to the local order distortion with respect to the bulk state.
摘要本文报道了不同水化百分比下体积态和密闭态水中低频振动动力学和电子振动耦合的研究结果。同时使用拉曼光谱和飞行时间非弹性中子散射使我们能够确定各自的状态振动密度(VDOSs)， g R eff(ω)和g N(ω)。由于相对于体态的局部阶畸变，两种VDOSs都表现出明显的表面诱导振动模式。
{"title":"Low-frequency dynamics in confined water: A comparative analysis by Raman and inelastic neutron scattering","authors":"V. Crupi, D. Majolino, P. Migliardo, V. Venuti","doi":"10.1080/13642810208223130","DOIUrl":"https://doi.org/10.1080/13642810208223130","url":null,"abstract":"Abstract In this paper we report the results of a study of low-frequency vibrational dynamics and electron-vibration coupling in water in the bulk and confined state, at different hydration percentages. The simultaneous use of both Raman spectroscopy and time-of-flight inelastic neutron scattering allowed us to determine the respective vibrational densities of states (VDOSs), g R eff(ω) and g N(ω). Both the VDOSs show clear evidence of surface-induced vibrational modes, due to the local order distortion with respect to the bulk state.","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":"75589018","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: 10.1080/13642810110084560
S. Grandi, P. Mustarelli, A. Magistris
{"title":"Sol-gel preparation of GeO 2 -doped SiO 2 glasses","authors":"S. Grandi, P. Mustarelli, A. Magistris","doi":"10.1080/13642810110084560","DOIUrl":"https://doi.org/10.1080/13642810110084560","url":null,"abstract":"","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":"85432002","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: 10.1080/13642810208223143
M. Ricci, P. Bartolini, R. Torre
Abstract We measured the dynamics of the fragile glass former m-toluidine in its supercooled phase by the time-resolved optical Kerr effect. Using an experimental time filtering of the internal molecular vibrations a better insight into the fast relaxation processes has been achieved. We analysed the dynamic features of these fast processes and compared them with the mode-coupling theory predictions.
{"title":"Fast dynamics of a fragile glass former by time-resolved spectroscopy","authors":"M. Ricci, P. Bartolini, R. Torre","doi":"10.1080/13642810208223143","DOIUrl":"https://doi.org/10.1080/13642810208223143","url":null,"abstract":"Abstract We measured the dynamics of the fragile glass former m-toluidine in its supercooled phase by the time-resolved optical Kerr effect. Using an experimental time filtering of the internal molecular vibrations a better insight into the fast relaxation processes has been achieved. We analysed the dynamic features of these fast processes and compared them with the mode-coupling theory predictions.","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":"82855233","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: 10.1080/13642810208223127
L. Andreozz, M. Faetti, M. Giordano, D. Palazzuoli
Abstract The physical ageing of a side-chain liquid-crystal polymer is investigated by means of differential scanning calorimetry, which allows one to follow the enthalpy relaxation of the glass. Measurements are performed for different thermal treatments and compared with the predictions of two phenomenological models where the nonlinearity of the ageing process is accounted for by multiparameter expressions. The experimental results can be described with the model based on the Narayanaswamy expression for nonlinearity, although it seems that the model based on the Hodge expression fits experimental data more satisfactorily. In particular, a single set of parameters is determined which describes different experiments. However, the value of the enthalpy loss as a function of the ageing time is greatly overestimated by both models.
{"title":"A calorimetric study of structural relaxation in the glassy state of a liquid-crystal polymer","authors":"L. Andreozz, M. Faetti, M. Giordano, D. Palazzuoli","doi":"10.1080/13642810208223127","DOIUrl":"https://doi.org/10.1080/13642810208223127","url":null,"abstract":"Abstract The physical ageing of a side-chain liquid-crystal polymer is investigated by means of differential scanning calorimetry, which allows one to follow the enthalpy relaxation of the glass. Measurements are performed for different thermal treatments and compared with the predictions of two phenomenological models where the nonlinearity of the ageing process is accounted for by multiparameter expressions. The experimental results can be described with the model based on the Narayanaswamy expression for nonlinearity, although it seems that the model based on the Hodge expression fits experimental data more satisfactorily. In particular, a single set of parameters is determined which describes different experiments. However, the value of the enthalpy loss as a function of the ageing time is greatly overestimated by both models.","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":"87443781","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: 10.1080/13642810208223144
D. Prevosto, P. Bartolini, Renato Torre, S. Capaccioli, Marilena Ricci, A. Taschin, Dario Pisignano, M. Lucchesi
Abstract We present a comparative analysis of dielectric spectroscopy and optical Kerr effect measurements of relaxation processes in glass-forming phenyl glycidyl ether. In particular we focus our attention on the structural α-relaxation process and the most important finding is the existence of a constant scaling factor between the characteristic times obtained by the two experiments in the high-temperature region.
{"title":"Structural relaxation process in glass-forming liquids: A comparison between the optical Kerr effect and dielectric spectroscopy","authors":"D. Prevosto, P. Bartolini, Renato Torre, S. Capaccioli, Marilena Ricci, A. Taschin, Dario Pisignano, M. Lucchesi","doi":"10.1080/13642810208223144","DOIUrl":"https://doi.org/10.1080/13642810208223144","url":null,"abstract":"Abstract We present a comparative analysis of dielectric spectroscopy and optical Kerr effect measurements of relaxation processes in glass-forming phenyl glycidyl ether. In particular we focus our attention on the structural α-relaxation process and the most important finding is the existence of a constant scaling factor between the characteristic times obtained by the two experiments in the high-temperature region.","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":"76158993","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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