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We report about the sharp change of spectral, intensity for nonelastic scattering of light at frequencies close enough to the exciting line frequency. 相似文献
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The angular dependence of light scattering from the homogeneous ternary system polystyrene + polyisobutylene + toluene was measured at a fixed (critical) concentration as a function of temperature. On approaching the critical temperature the scattering becomes very large and strongly angle-dependent. The experiments show that the interaction range rG is of the same order of magnitude as the molecular radius of gyration of the polymer, but cannot be set equal to it as in the case of a binary system of one polymer in a single solvent. The temperature dependence of the various interaction parameters does not depend on the molecular weights of the polymers. 相似文献
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Wolfram Hrtl 《Current Opinion in Colloid & Interface Science》2001,6(5-6):479-483
Colloidal suspensions are important model systems for the study of phase transitions. The glass transition, especially, can be followed more directly with colloidal systems and compared to theoretical predictions. At high volume fractions of the colloidal particles the density fluctuations are partially frozen in. This can be identified by the typical plateau values in the time correlation function. If one compares the experimental results with the mode coupling theory, a very good agreement can be obtained. Currently, some new experimental results concerning the dynamical heterogeneity in colloidal systems are under discussion and will certainly initiate new theoretical developments. 相似文献
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Bioactive glasses prepared in SiO2–CaO–Na2O and P2O5 system are used as biomaterials in orthopaedic and maxillofacial surgery. Zn presents high physiological interest. It enhances physiological effects of implanted biomaterials. In this work, the thermal characteristics (T g, T c and T f) of pure bioactive glass elaborated with different amounts of CaO, Na2O in pure glass and with different amounts of introduced Zn in glass (ranging from 0.1 to 10 in mass%), were studied. The excess entropy was calculated for different compounds. Glasses were prepared by the melting process. The thermal behaviour of obtained bioactive glasses was determined using differential thermal analysis. Therefore, the glass transition (T g), the crystallization (T c) and the melting temperatures (T f) were revealed. Moreover, according to Dietzel formula, the thermal stability (TS) of the studied bioactive glasses has been calculated. The first results concerning the impact of different oxides, revealed a decrease of the TS, T g, T c and T f when the SiO2/CaO increases and revealed an increase of these thermal characteristics when the SiO2/Na2O and CaO/Na2O ratios increase. Introducing Zn into the bioactive glasses induces a decrease of T f and an increase of TS. Contrary to crystals, prepared glasses have entropy different to zero at T = 0 K and vary versus T f. The excess entropy of pure glasses and Zn-doped glasses were calculated. The significant variations were registered. 相似文献
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Glass-forming liquids have been extensively studied in recent decades, but there is still no theory that fully describes these systems, and the diversity of treatments is in itself a barrier to understanding. Here we introduce a new simple model that (possessing both liquid-crystal and glass transition) unifies different approaches, producing most of the phenomena associated with real glasses, without loss of the simplicity that theorists require. Within the model we calculate energy relaxation, nonexponential slowing phenomena, the Kauzmann temperature, and other classical signatures. Moreover, the model reproduces a subdiffusive exponent observed in experiments of dense systems. The simplicity of the model allows us to identify the microscopic origin of glassification, leaving open the possibility for theorists to make further progress. 相似文献
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DTA investigations of glasses in the system Al2(SO4)3-H2O/55–65 mass% Al2(SO4)3 revealed effects at the glass transformation (T
g), crystallization and melting temperature. During storage at ambient temperature,T
g increased, probably due to an annealing process; the increase was the least at the stability maximum for the glasses, at 61–63% Al2(SO4)3.
Zusammenfassung Gläser des Systems Al2(SO4)3-H2O mit 55–65 Masse-% Al2(SO4)3 zeigen bei der DTA Effekte bei den Temperaturen von Glasumwandlung (T g), Kristallisation und Schmelzen. Aufbewahren bei Raumtemperatur führt zum Ansteigen vonT g, wahrscheinlich in Folge eines Temperprozesses; dieser Anstieg ist am geringsten bei der Zusammensetzung mit 61–63% Al2(SO4)3, d. h. am Stabilitätsmaximum der Gläser.
- 55–65 . % , g, . g, (61–63 .% ).相似文献
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Silico-phosphate glasses of Ca3/2PO4-SiO2 and NaCaPO4-SiO2 systems have been the topic of our studies. Microscopic and EDX investigations which have been carried out have shown that
liquation occurs only in the case of glasses belonging to the NaCaPO4-SiO2 system. Additionally, it has been found that there are significant differences in the chemical compositions of the matrix
and the inclusions. Based on the spectroscopic investigations it has been shown that the glasses of both series are characterized
by complex domain composition and the structure of domains is close to that of the corresponding crystalline phase. Interpretation
of the DTA results has been based on the knowledge of the texture and the structure of the materials studied. It has been
found that liquation of the glasses is a multi-step process in which the matrix and the inclusions crystallize separately.
Multi-step crystallization of the glasses belonging to the NaCaPO4-SiO2 system has been confirmed by the high temperature XRD investigations. 相似文献
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K. Nitsch A. Cihlář D. Klimm M. Nikl M. Rodová 《Journal of Thermal Analysis and Calorimetry》2005,80(3):735-738
Summary The present paper deals with preparation, thermal properties and radioluminescence of Ce-doped Na-Gd phosphate glasses. Thanks to their high radioluminescence intensity, three times greater than that of BGO, these glasses are promising materials for the detection of neutrons, - and X-rays. The glasses with a Gd concentration up to 89 mol% were prepared by a rapid quenching technique in air. Their thermal properties were determined using DSC and temperatures of glass transition were measured in addition using TMA. Temperatures of glass transition, crystallization and melting depend on Gd concentration and they follow the liquidus line in a phase diagram of binary system in which two eutectics and a congruently melting compound exist. High glass-forming ability of this glass system was found evidenced. The glasses containing at least 30 mol% Gd were moisture resistant. 相似文献
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S. A. Polishchuk L. N. Ignatieva Yu. V. Marchenko V. M. Buznik 《Journal of Structural Chemistry》2016,57(5):901-909
The example of bismuth-containing glasses based on InF3 and ZrF4 is used to consider the effect of bismuth on glass formation, properties, and structure and the appearance of broadband luminescence at low wavelengths in the IR spectra of fluorozirconate glasses. 相似文献
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Yoshino H 《The Journal of chemical physics》2012,136(21):214108
We present a first principle scheme to compute the rigidity, i.e., the shear-modulus of structural glasses at finite temperatures using the cloned liquid theory, which combines the replica theory and the liquid theory. With the aid of the replica method which enables disentanglement of thermal fluctuations in liquids into intra-state and inter-state fluctuations, we extract the rigidity of metastable amorphous solid states in the supercooled liquid and glass phases. The result can be understood intuitively without replicas. As a test case, we apply the scheme to the supercooled and glassy state of a binary mixture of soft-spheres. The result compares well with the shear-modulus obtained by a previous molecular dynamic simulation. The rigidity of metastable states is significantly reduced with respect to the instantaneous rigidity, namely, the Born term, due to non-affine responses caused by displacements of particles inside cages at all temperatures down to T = 0. It becomes nearly independent of temperature below the Kauzmann temperature T(K). At higher temperatures in the supercooled liquid state, the non-affine correction to the rigidity becomes stronger suggesting melting of the metastable solid state. Inter-state part of the static response implies jerky, intermittent stress-strain curves with static analogue of yielding at mesoscopic scales. 相似文献
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Rada S Dehelean A Culea M Culea E 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(2):320-324
FTIR, UV-VIS and EPR spectra of manganese doped lead-tellurate glasses with composition xMnO·(100-x)[4TeO2·PbO2] where x=0, 1, 5, 10, 20, 30, 40mol% have been studied. The FTIR spectra show the formation of the Mn-O-Pb and Mn-O-Te bridging bonds by increasing of MnO concentration. The UV-VIS spectra show the Mn(+3) species exhibit pronounced absorption, which masks the Mn(+2) spin-forbidden absorption bands when Mn(+2) ions are in high concentrations in these glasses. The EPR spectra exhibit resonance signals characteristic of Mn(+2) ions. The resonance signal located at g≈2 is due to Mn(+2) ions in an environment close to octahedral symmetry, whereas the resonance at g≈4.3 and 3.3 are attributed to the rhombic surroundings of the Mn(+2) ions. The increase in the MnO content gives rise to absorption at g≈2.4 and the paramagnetic ions are involved in dinuclear manganese centers. 相似文献
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Crystallization of iron phosphate glasses 总被引:1,自引:0,他引:1
Differential thermal analysis (DTA), thermogravimetric analysis (TG), X-ray diffraction and Mössbauer spectroscopy were employed in the investigation of crystalline products of FeOx-P2O5 glasses generated by various heat treatments. In glasses with a high value of =Fe2+/(Fe2+ + Fe3+), absorption of oxygen occurs in a broad temperature range identified by TG. Depending on the value of , two exotherms appear in the DTA curves, the low-temperature one corresponding to crystallization of the Fe3(PO4)2 type regions, and the high-temperature one being related to various phases with dominating FePO4. Each exotherm has its own transformation region, identical in absolute value. The Mössbauer spectra of glasses which underwent thermal treatment at higher temperatures exhibit some indication of phases of the types Fe3(PO4)2 · xH2O and FePO4 · xH2O.
The authors thank Mrs. Simonyiová for assistance in the experimental part of these investigations, and Dr. Horváth and Dr. Vondrovic for performing the X-ray and TG analyses. 相似文献
Zusammenfassung Differentialthermoanalyse (DTA), thermogravimetrische Analyse (TG), Röntgendiffraktion und Mössbauerspektroskopie wurden bei der Untersuchung (von kristalliner Produkte) durch verschiedene thermische Behandlungen hergestellten FeOx-P2O5 Gläsern eingesetzt. In den Glasarten mit einem hohen Wert von =Fe2+/(Fe2+ + Fe3+) erfolgt die Sauerstoffabsorption in einem durch TG [nachgewiesenen breiten Temperaturbereich. In Abhängigkeit von dem -Wert erscheinen zwei Exothermen in den DTA-Kurven, von denen der bei niedriger Temperatur die Kristallisation des Fe3(PO4)2 entspricht, und jener bei höheren Temperaturen in verschiedenen Phasen dem FePO4. Jede Exotherme hat ihr eigenes Umwandlungsgebiet, das in absolutem Wert identisch ist. Die Mössbauer-Spektren der Gläser welche einer Wärmebehandlung bei höheren Temperaturen unterzogen worden sind, weisen einige Indikationsphasen der Typen Fe3(PO4)2 · xH2O und FePO4 · xH2O auf.
, , FeOx-P2O5, . , =Fe2+/(Fe2++Fe3+) . , - : Fe3(PO4)2, – FePO4. , . , , Fe3(PO4)2 · 2 FePO4 · 2.
The authors thank Mrs. Simonyiová for assistance in the experimental part of these investigations, and Dr. Horváth and Dr. Vondrovic for performing the X-ray and TG analyses. 相似文献
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Connie B. Roth 《Journal of Polymer Science.Polymer Physics》2010,48(24):2558-2560