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Sample records for glass temperature tg

  1. Fragility of chalcogenide glass in relation to characteristic temperature T0/Tg

    Shaker, A. M.; Shanker Rao, T.; Lilly Shanker Rao, T.; Venkataraman, K.

    2018-03-01

    The present study reports the mutual relationship between the fragility index m and the characteristic temperature T0/Tg. The fragility of the chalcogenide amorphous glass of Ge10Se50Te40 is calculated by utilizing glass transition temperature (Tg) measured by DSC (Differential Scanning Calorimetry) at different heating rates (β) in the range 5 to 20 K/min. Vogel-Fulcher-Tammann (VFT) equation is fitted to the data of Tg. In addition to the VFT method, three other methods are also used to evaluate m. The fragility index m of the Ge10Se50Te40 system showed the trend of decrease with increasing heating rate but remained stable around 22 for the heating rate 10 K/min. The value of m for the glass is near the lower limit (m ≈ 16) this indicates the alloy is a strong glass forming material in accordance of Angell’s interpretation of fragility. The calculated values of characteristic temperature T0/Tg is very close to 1 which also indicates that clearly the system is most fragile.

  2. High-temperature Brillouin scattering study of haplogranitic glasses and liquids: Effects of F, K, Na and Li on Tg and elastic properties

    Manghnani, M. H.; Hushur, A.; Williams, Q. C.; Dingwell, D. B.

    2010-12-01

    The density, compressibility and viscosity of silicate melts are important in understanding the thermodynamic and fluid dynamic properties of magmatic systems. Knowledge of the compressibility of silicate melts at 1 bar is an important component in the construction of accurate pressure-volume-temperature equations of state. In light of this, the velocity (nVp, Vp, Vs) and refractive index n of four anhydrous haplogranitic glasses and liquids with similar alkali abundances, but different cations, are measured at high temperature by Brillouin scattering spectroscopy through the glass transition temperature (Tg) in both platelet and back scattering geometry. The compositions of four haplogranites are 5 wt% of the components Li2O, Na2O, K2O and F each added to a base of haplogranitic (HPG8) composition. The glass transition temperature Tg of different haplogranite samples at the GHz frequency of the Brillouin probe are determined from the change in slope of the temperature-dependent longitudinal or transverse sound velocity. HPG8-Li5 has the lowest glass transition temperature (466°C), while HPG8-K5 has the highest glass transition temperature (575°C). Our Brillouin results, when compared with DSC measurements, show lower Tg values. This raises the possibility of a role of either heating rates or a frequency dependence of the glass transition in explaining the discrepancies in Tg values derived from the two methods. The sound velocity (nVp, Vp, Vs) shows markedly different temperature dependences (including differences in sign) below Tg depending on their different alkali contents. The unrelaxed elastic moduli of three haplogranitic glasses with added Li2O, Na2O and F components have been obtained as a function of temperature. The unrelaxed bulk modulus, shear modulus and Poisson’s ratio show strong compositional dependences at ambient temperature. On heating, The K initially decreases with increasing temperature up to ~ 135°C, then increases up to Tg, and then

  3. Effects of molecular weight on the glass transition temperature in Durolon polycarbonate; Os efeitos da massa molecular sobre a temperatura de transicao vitrea (Tg) para o policarbonato Durolon

    Miranda, Adelina; Sciani, Valdir [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1995-12-31

    The effect of variation of the dose rate on degradation mechanism of PC Durolon irradiated with gamma rays was determined trough out intrinsic viscosity and thermal analysis of DSC-type measurements. The results showed a linear relationship between the glass transition temperature and the viscosimetric average molecular weight. From the results it`s shown that with an increased of the dose rate it also increases the degradation of the material. (author). 12 refs., 3 figs.

  4. Fragile-to-fragile liquid transition at Tg and stable-glass phase nucleation rate maximum at the Kauzmann temperature TK

    Tournier, Robert F.

    2014-01-01

    An undercooled liquid is unstable. The driving force of the glass transition at T g is a change of the undercooled-liquid Gibbs free energy. The classical Gibbs free energy change for a crystal formation is completed including an enthalpy saving. The crystal growth critical nucleus is used as a probe to observe the Laplace pressure change Δp accompanying the enthalpy change −V m ×Δp at T g where V m is the molar volume. A stable glass–liquid transition model predicts the specific heat jump of fragile liquids at T≤T g , the Kauzmann temperature T K where the liquid entropy excess with regard to crystal goes to zero, the equilibrium enthalpy between T K and T g , the maximum nucleation rate at T K of superclusters containing magic atom numbers, and the equilibrium latent heats at T g and T K . Strong-to-fragile and strong-to-strong liquid transitions at T g are also described and all their thermodynamic parameters are determined from their specific heat jumps. The existence of fragile liquids quenched in the amorphous state, which do not undergo liquid–liquid transition during heating preceding their crystallization, is predicted. Long ageing times leading to the formation at T K of a stable glass composed of superclusters containing up to 147 atom, touching and interpenetrating, are evaluated from nucleation rates. A fragile-to-fragile liquid transition occurs at T g without stable-glass formation while a strong glass is stable after transition

  5. Investigation of low glass transition temperature on COTS PEMs reliability

    Sandor, M.; Agarwal, S.

    2002-01-01

    Many factors influence PEM component reliability.One of the factors that can affect PEM performance and reliability is the glass transition temperature (Tg) and the coefficient of thermal expansion (CTE) of the encapsulant or underfill. JPL/NASA is investigating how the Tg and CTE for PEMs affect device reliability under different temperature and aging conditions. Other issues with Tg are also being investigated. Some preliminary data will be presented on glass transition temperature test results conducted at JPL.

  6. Polymer brushes: a controllable system with adjustable glass transition temperature of fragile glass formers.

    Xie, Shi-Jie; Qian, Hu-Jun; Lu, Zhong-Yuan

    2014-01-28

    We present results of molecular dynamics simulations for coarse-grained polymer brushes in a wide temperature range to investigate the factors that affect the glass transition in these systems. We focus on the influences of free surface, polymer-substrate interaction strength, grafting density, and chain length not only on the change of glass transition temperature Tg, but also the fragility D of the glass former. It is found that the confinement can enhance the dependence of the Tg on the cooling rate as compared to the bulk melt. Our layer-resolved analysis demonstrates that it is possible to control the glass transition temperature Tg of polymer brushes by tuning the polymer-substrate interaction strength, the grafting density, and the chain length. Moreover, we find quantitative differences in the influence range of the substrate and the free surface on the density and dynamics. This stresses the importance of long range cooperative motion in glass formers near the glass transition temperature. Furthermore, the string-like cooperative motion analysis demonstrates that there exists a close relation among glass transition temperature Tg, fragility D, and string length ⟨S⟩. The polymer brushes that possess larger string length ⟨S⟩ tend to have relatively higher Tg and smaller D. Our results suggest that confining a fragile glass former through forming polymer brushes changes not only the glass transition temperature Tg, but also the very nature of relaxation process.

  7. Predicting the glass transition temperature of bioactive glasses from their molecular chemical composition.

    Hill, Robert G; Brauer, Delia S

    2011-10-01

    A recently published paper (M.D. O'Donnell, Acta Biomaterialia 7 (2011) 2264-2269) suggests that it is possible to correlate the glass transition temperature (T(g)) of bioactive glasses with their molar composition, based on iterative least-squares fitting of published T(g) data. However, we show that the glass structure is an important parameter in determining T(g). Phase separation, local structural effects and components (intermediate oxides) which can switch their structural role in the glass network need to be taken into consideration, as they are likely to influence the glass transition temperature of bioactive glasses. Although the model suggested by O'Donnell works reasonably well for glasses within the composition range presented, it is oversimplified and fails for glasses outside certain compositional boundaries. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  8. Exploration of a new method in determining the glass transition temperature of BMGs by electrical resistivity

    Guo, Jing; Zu, Fangqiu; Chen, Zhihao; Zheng, Shubin; Yuan, Yuan

    2005-07-01

    Based on a brief retrospect of the method in establishing Tg of the bulk metallic glasses (BMGs), some perplexities concerning this are pointed out. With the experimental results of Zr-Al-Ni-Cu-X (Nb,Ti) BMGs, a electrical resistivity method is proposed to determine the glass transition temperature of BMGs. With the method, we define two kinds of characteristic temperature related to the glass transition, Tg-dep and Tg-int, respectively. By comparing Tg-dep and Tg-int with Tg determined by the DSC method, we have found that, for the same alloy at the same heating rate, Tg-dep is very close to Tg-onset while Tg-int is approximate to Tg-mid. As a method to determine the glass transition temperature, the electrical resistivity method has proved to be more convenient and practical in comparison with the DSC method, especially when the DSC curve cannot show the glass transition character of BMGs. In addition, we would emphasize that when we refer to Tg, it is necessary to expatiate on the way of denoting the glass transition temperature, such as Tg-dep or Tg-int ( Tg-onset or Tg-mid), and on the heating rate, in order to avoid ambiguity.

  9. Long term aging of selenide glasses: evidence of sub-Tg endotherms and pre-Tg exotherms

    Chen, Ping; Boolchand, P.; Georgiev, D. G.

    2010-02-01

    Long term aging, extending from months to several years, is studied on several families of chalcogenide glasses including the Ge-Se, As-Se, and Ge-As-Se systems. Special attention is given to the As-Se binary, a system that displays a rich variety of aging behavior intimately tied to sample synthesis conditions and the ambient environment in which samples are aged. Calorimetric (modulated DSC) and Raman scattering experiments are undertaken. Our results show all samples display a sub-Tg endotherm typically 10-70 °C below Tg in glassy networks possessing a mean coordination number r in the 2.25 < r < 2.45 range. Two sets of AsxSe100-x samples aged for eight years were compared, set A consisted of slow cooled samples aged in the dark, and set B consisted of melt-quenched samples aged at laboratory environment. Samples of set B in the As concentration range, 35% < x < 60%, display a pre-Tg exotherm, but the feature is not observed in samples of set A. The aging behavior of set A presumably represents intrinsic aging in these glasses, while that of set B is extrinsic due to the presence of light. The reversibility window persists in both sets of samples, but is less well defined in set B. These findings contrast with a recent study by Golovchak et al (2008 Phys. Rev. B 78 014202), which finds the onset of the reversibility window moved up to the stoichiometric composition (x = 40%). Here we show that the up-shifted window is better understood as resulting due to demixing of As4Se4 and As4Se3 molecules from the backbone, i.e., nanoscale phase separation (NSPS). We attribute sub-Tg endotherms to compaction of the flexible part of the networks upon long term aging, while the pre-Tg exotherm is to NSPS. The narrowing and sharpening of the reversibility window upon aging is interpreted as the slow 'self-organizing' stress relaxation of the phases just outside the intermediate phase, which itself is stress free and displays little aging.

  10. Molecular structure of virgin and Tg cycled (Ag2Se)x (AsSe)1-x bulk glasses

    Wachtman, Jacob; Chen, Ping; Boochand, P.

    2009-03-01

    AsSe, the base glass (x = 0) in the titled ternary, is an interesting example of a chalcogenide that is partially de-mixed into As4Se4 molecules segregated from a connected AsSe network, with the latter determining glass network properties. Raman scattering reveals sharp modes of the Realgar molecules that are superimposed on broad modes coming from of the backbone. Upon Tg cycling virgin samples (as quenched melts), the concentration of de-mixed As4Se4 molecules decreases, suggesting that thermally induced polymerization occurs; molecules break up to form part of the connective tissue. Modulated DSC experiments reveal a broad exotherm near 140 ^oC in virgin samples, which becomes nearly extinct in Tg cycled samples. The exotherm may represent Realgar molecules nano-crystallizing as the temperature approaches Tg. Compositional trends in thermal parameters such as Tg(x), δCp(x), and the δHnr(x) as a function of Ag2Se content `x' of the glasses will be reported.

  11. Molecular Motion in Polymers: Mechanical Behavior of Polymers Near the Glass-Rubber Transition Temperature.

    Sperling, L. H.

    1982-01-01

    The temperature at which the onset of coordinated segmental motion begins is called the glass-rubber transition temperature (Tg). Natural rubber at room temperature is a good example of a material above its Tg. Describes an experiment examining the response of a typical polymer to temperature variations above and below Tg. (Author/JN)

  12. Investigation of low glass transition temperature on COTS PEM's reliability for space applications

    Sandor, M.; Agarwal, S.; Peters, D.; Cooper, M. S.

    2003-01-01

    Plastic Encapsulated Microelectronics (PEM) reliability is affected by many factors. Glass transition temperature (Tg) is one such factor. In this presentation issues relating to PEM reliability and the effect of low glass transition temperature epoxy mold compounds are presented.

  13. Depression of Glass Transition Temperatures of Polymer Networks by Diluents

    Brinke, Gerrit ten; Karasz, Frank E.; Ellis, Thomas S.

    1983-01-01

    A classical thermodynamic theory is used to derive expressions for the depression of the glass transition temperature Tg of a polymer network by a diluent. The enhanced sensitivity of Tg in cross-linked systems to small amounts of diluent is explained. Predictions of the theory are in satisfactory

  14. Sub-Tg enthalpy relaxation in an unstable oxide glass former: insights into the structural heterogeneity

    Yue, Yuanzheng; Zhang, Yanfei

    Structural heterogeneity plays a crucial role in determining functionality of glasses. In this work we have found that the sub-Tg enthalpy relaxation pattern in a hyperquenched glass is highly sensitive to structural heterogeneity. As a consequence, the former can be used as an effective approach...... to detect and quantify the structural heterogeneity in glass-forming liquids. However, the chemical nature of structural heterogeneity should be revealed by other means such as high resolution microscopic and spectroscopic methods. To study the impact of the structural heterogeneity on the sub-Tg relaxation...... chemical features and degrees of structural heterogeneity in glass-forming liquids. This finding contributes to the microscopic origin of both the primary and secondary relaxation in terms of structural heterogeneity. Finally the results provide insights into the relation between structural heterogeneity...

  15. Sub-Tg enthalpy relaxation in an extremely unstable oxide glass and its implication for structural heterogeneity

    Zhang, Yanfei; Hu, L.N.; Liu, S.J.

    2013-01-01

    We study the sub-Tg relaxation in an extremely unstable glass former, i.e., 65SiO2-35Al2O3, and its relation to structural heterogeneity (e.g., structurally ordered domains in glass matrix). This is done by hyperquenching (~106 K/s) the liquid, then annealing the hyperquenched glass below Tg...... and subsequently scanning the annealed hyperquenched glass in a differential scanning calorimeter. The results show that structural ordering can take place even below Tg. An endothermic pre-peak is observed when the hyperquenched sample is annealed at 0.75Tg for sufficiently long time, which is, however, much...... weaker compared to that of stable glass formers subjected to same annealing conditions. We also investigate the effect of the sub-Tg annealing on crystallization above Tg. The results imply that some structurally ordered domains exist already in the liquid state. The ordered domains lower the activation...

  16. Spatial glass transition temperature variations in polymer glass: application to a maltodextrin-water system.

    van Sleeuwen, Rutger M T; Zhang, Suying; Normand, Valéry

    2012-03-12

    A model was developed to predict spatial glass transition temperature (T(g)) distributions in glassy maltodextrin particles during transient moisture sorption. The simulation employed a numerical mass transfer model with a concentration dependent apparent diffusion coefficient (D(app)) measured using Dynamic Vapor Sorption. The mass average moisture content increase and the associated decrease in T(g) were successfully modeled over time. Large spatial T(g) variations were predicted in the particle, resulting in a temporary broadening of the T(g) region. Temperature modulated differential scanning calorimetry confirmed that the variation in T(g) in nonequilibrated samples was larger than in equilibrated samples. This experimental broadening was characterized by an almost doubling of the T(g) breadth compared to the start of the experiment. Upon reaching equilibrium, both the experimental and predicted T(g) breadth contracted back to their initial value.

  17. Citrate increases glass transition temperature of vitrified sucrose preparations

    Kets, E.P.W.; Lipelaar, P.J.; Hoekstra, F.A.; Vromans, H.

    2004-01-01

    The aim of this study was to investigate the effect of sodium citrate on the properties of dried amorphous sucrose glasses. Addition of sodium citrate to a sucrose solution followed by freeze-drying or convective drying resulted in a glass transition temperature (T-g) that was higher than the

  18. New Challenges for the Pressure Evolution of the Glass Temperature

    Sylwester J. Rzoska

    2017-11-01

    Full Text Available The ways of portrayal of the pressure evolution of the glass temperature (Tg beyond the dominated Simon–Glatzel-like pattern are discussed. This includes the possible common description of Tg(P dependences in systems described by dTg/dP > 0 and dTg/dP < 0. The latter can be associated with the maximum of Tg(P curve hidden in the negative pressures domain. The issue of volume and density changes along the vitrification curve is also discussed. Finally, the universal pattern of vitrification associated with the crossover from the low density (isotropic stretching to the high density (isotropic compression systems is proposed. Hypothetically, it may obey any glass former, from molecular liquids to colloids.

  19. Simultaneous Determination of Glass Transition Temperatures of Several Polymers.

    He, Jiang; Liu, Wei; Huang, Yao-Xiong

    2016-01-01

    A simple and easy optical method is proposed for the determination of glass transition temperature (Tg) of polymers. Tg was determined using the technique of microsphere imaging to monitor the variation of the refractive index of polymer microsphere as a function of temperature. It was demonstrated that the method can eliminate most thermal lag and has sensitivity about six fold higher than the conventional method in Tg determination. So the determined Tg is more accurate and varies less with cooling/heating rate than that obtained by conventional methods. The most attractive character of the method is that it can simultaneously determine the Tg of several polymers in a single experiment, so it can greatly save experimental time and heating energy. The method is not only applicable for polymer microspheres, but also for the materials with arbitrary shapes. Therefore, it is expected to be broadly applied to different fundamental researches and practical applications of polymers.

  20. Influence of entanglements on glass transition temperature of polystyrene

    Ougizawa, Toshiaki; Kinugasa, Yoshinori

    2013-03-01

    Chain entanglement is essential behavior of polymeric molecules and it seems to affect many physical properties such as not only viscosity of melt state but also glass transition temperature (Tg). But we have not attained the quantitative estimation because the entanglement density is considered as an intrinsic value of the polymer at melt state depending on the chemical structure. Freeze-drying method is known as one of the few ways to make different entanglement density sample from dilute solution. In this study, the influence of entanglements on Tg of polystyrene obtained by the freeze-dried method was estimated quantitatively. The freeze-dried samples showed Tg depression with decreasing the concentration of precursor solution due to the lower entanglement density and their depressed Tg would be saturated when the almost no intermolecular entanglement was formed. The molecular weight dependence of the maximum value of Tg depression was discussed.

  1. Predicting bioactive glass properties from the molecular chemical composition: glass transition temperature.

    O'Donnell, Matthew D

    2011-05-01

    The glass transition temperature (T(g)) of inorganic glasses is an important parameter than can be used to correlate with other glass properties, such as dissolution rate, which governs in vitro and in vivo bioactivity. Seven bioactive glass compositional series reported in the literature (77 in total) were analysed here with T(g) values obtained by a number of different methods: differential thermal analysis, differential scanning calorimetry and dilatometry. An iterative least-squares fitting method was used to correlate T(g) from thermal analysis of these compositions with the levels of individual oxide and fluoride components in the glasses. When all seven series were fitted a reasonable correlation was found between calculated and experimental values (R(2)=0.89). When the two compositional series that were designed in weight percentages (the remaining five were designed in molar percentage) were removed from the model an improved fit was achieved (R(2)=0.97). This study shows that T(g) for a wide range in compositions (e.g. SiO(2) content of 37.3-68.4 mol.%) can be predicted to reasonable accuracy enabling processing parameters to be predicted such as annealing, fibre-drawing and sintering temperatures. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Observation on Surface Change of Fragile Glass: Temperature - Time Dependence Studied by X-Ray Reflectivity

    Kikkawa, Hiroyuki; Kitahara, Amane; Takahashi, Isao

    2004-01-01

    The structural change of a fragile glass surface close to the glass transition temperature Tg is studied by using X-ray reflectivity. Measurements were performed on surfaces of maltitol, which is a typical polyalcohol fragile glass with Tg = 320K. Upon both heating and cooling, we find the following features which are also noticed in silicate glass surfaces: (i) On heating, the surface morphology indicates a variation at temperatures below Tg; (ii) A drastic increase in surface roughness occurs at a temperature about 333K on heating, which is 13K higher than Tg; (iii) During the cooling of the sample, formation of a low-density surface layer (3nm at 293K) is observed. Prior to the crystallization, nm - μm sized domains were grown at the surface, which might not be reported for other glasses

  3. Determination of the glass-transition temperature of proteins from a viscometric approach.

    Monkos, Karol

    2015-03-01

    All fully hydrated proteins undergo a distinct change in their dynamical properties at glass-transition temperature Tg. To determine indirectly this temperature for dry albumins, the viscosity measurements of aqueous solutions of human, equine, ovine, porcine and rabbit serum albumin have been conducted at a wide range of concentrations and at temperatures ranging from 278 K to 318 K. Viscosity-temperature dependence of the solutions is discussed on the basis of the three parameters equation resulting from Avramov's model. One of the parameter in the Avramov's equation is the glass-transition temperature. For all studied albumins, Tg of a solution monotonically increases with increasing concentration. The glass-transition temperature of a solution depends both on Tg for a dissolved dry protein Tg,p and water Tg,w. To obtain Tg,p for each studied albumin the modified Gordon-Taylor equation was applied. This equation describes the dependence of Tg of a solution on concentration, and Tg,p and a parameter depending on the strength of the protein-solvent interaction are the fitting parameters. Thus determined the glass-transition temperature for the studied dry albumins is in the range (215.4-245.5)K. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Effect of composition and temperature on the second harmonic generation in silver phosphate glasses

    Konidakis, I.; Psilodimitrakopoulos, S.; Kosma, K.; Lemonis, A.; Stratakis, E.

    2018-01-01

    We herein employ nonlinear laser imaging microscopy to explicitly study the dynamics of second harmonic generation (SHG) in silver iodide phosphate glasses. While glasses of this family have gained extensive scientific attention over the years due to their superior conducting properties, considerably less attention has been paid to their unique nonlinear optical characteristics. In the present study, firstly, it is demonstrated that SHG signal intensity is enhanced upon increasing silver content due to the random formation of silver microstructures within the glass network. Secondly, the SHG temperature dynamics were explored near the glass transition temperature (Tg) regime, where significant glass relaxation phenomena occur. It is found that heating towards the Tg improves the SHG efficiency, whereas above Tg, the capacity of glasses to generate second harmonic radiation is drastically suppressed. The novel findings of this work are considered important in terms of the potential employment of these glasses for the realization of advanced photonic applications like optical-switches and wavelength conversion devices.

  5. Glass Transition Temperature Measurement for Undercured Cyanate Ester Networks: Challenges, Tips, and Tricks (Briefing Charts)

    2014-01-29

    DISTRIBUTION A: Approved for public release; distribution is unlimited. Thermosetting Polymers Have a TG Envelope – Not Just a TG 4 • The glass transition...glass transition temperature of a thermosetting polymer can vary over a wide range of temperatures depending on how the polymer is processed • A... thermosetting polymer with only one kind of network formation and negligible side reactions, the conversion may be determined at every point in the scan. • By

  6. Experimental and computational prediction of glass transition temperature of drugs.

    Alzghoul, Ahmad; Alhalaweh, Amjad; Mahlin, Denny; Bergström, Christel A S

    2014-12-22

    Glass transition temperature (Tg) is an important inherent property of an amorphous solid material which is usually determined experimentally. In this study, the relation between Tg and melting temperature (Tm) was evaluated using a data set of 71 structurally diverse druglike compounds. Further, in silico models for prediction of Tg were developed based on calculated molecular descriptors and linear (multilinear regression, partial least-squares, principal component regression) and nonlinear (neural network, support vector regression) modeling techniques. The models based on Tm predicted Tg with an RMSE of 19.5 K for the test set. Among the five computational models developed herein the support vector regression gave the best result with RMSE of 18.7 K for the test set using only four chemical descriptors. Hence, two different models that predict Tg of drug-like molecules with high accuracy were developed. If Tm is available, a simple linear regression can be used to predict Tg. However, the results also suggest that support vector regression and calculated molecular descriptors can predict Tg with equal accuracy, already before compound synthesis.

  7. Deformation, Stress Relaxation, and Crystallization of Lithium Silicate Glass Fibers Below the Glass Transition Temperature

    Ray, Chandra S.; Brow, Richard K.; Kim, Cheol W.; Reis, Signo T.

    2004-01-01

    The deformation and crystallization of Li(sub 2)O (center dot) 2SiO2 and Li(sub 2)O (center dot) 1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range -50 to -150 C below the glass transition temperature (Tg). The glass fibers can be permanently deformed at temperatures about 100 C below T (sub)g, and they crystallize significantly at temperatures close to, but below T,, about 150 C lower than the onset temperature for crystallization for these glasses in the no-stress condition. The crystallization was found to occur only on the surface of the glass fibers with no detectable difference in the extent of crystallization in tensile and compressive stress regions. The relaxation mechanism for fiber deformation can be best described by a stretched exponential (Kohlrausch-Williams-Watt (KWW) approximation), rather than a single exponential model.The activation energy for stress relaxation, Es, for the glass fibers ranges between 175 and 195 kJ/mol, which is considerably smaller than the activation energy for viscous flow, E, (about 400 kJ/mol) near T, for these glasses at normal, stress-free condition. It is suspected that a viscosity relaxation mechanism could be responsible for permanent deformation and crystallization of the glass fibers below T,

  8. Determination of the glass transition temperature of cyclodextrin polymers.

    Tabary, Nicolas; Garcia-Fernandez, Maria Jose; Danède, Florence; Descamps, Marc; Martel, Bernard; Willart, Jean-François

    2016-09-05

    The aim of this work was to determine the main physical characteristics of β-cyclodextrin polymers, well known for improving complexation capacities and providing enhanced and sustained release of a large panel of drugs. Two polymers were investigated: a polymer of β-cyclodextrin (polyβ-CD) and a polymer of partially methylated (DS=0.57) β-cyclodextrin (polyMe-β-CD). The physical characterizations were performed by powder X-ray diffraction and differential scanning calorimetry. The results indicate that these polymers are amorphous and that their glass transition is located above the thermal degradation point of the materials preventing their direct observation and thus their full characterization. We could however estimate the virtual glass transition temperatures by mixing the polymers with different plasticizers (trehalose and mannitol) which decreases Tg sufficiently to make the glass transition observable. Extrapolation to zero plasticizer concentration then yield the following Tg values: Tg (polyMe-β-CD)=317°C±5°C and Tg (polyβ-CD)=418°C±6°C. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Determination of the glass transition temperature: methods correlation and structural heterogeneity

    Hutchinson, John M.

    2009-01-01

    The definition of the glass transition temperature, Tg, is recalled and its experimental determination by various techniques is reviewed. The diversity of values of Tg obtained by the different methods is discussed, with particular attention being paid to Differential Scanning Calorimetry (DSC) and to dynamic techniques such as Dynamic Mechanical Thermal Analysis (DMTA) and Temperature Modulated DSC (TMDSC). This last technique, TMDSC, in particular, is considered in respect of ways in which ...

  10. An isomerization-induced cage-breaking process in a molecular glass former below Tg

    Teboul, V.; Saiddine, M.; Accary, J.-B.; Nunzi, J.-M.

    2011-01-01

    A recent experimental [P. Karageorgiev, D. Neher, B. Schulz, B. Stiller, U. Pietsch, M. Giersig, L. Brehmer, Nature Mater. 4, 699 (2005)] study has found liquidlike diffusion below the glass-transition temperature in azobenzene-containing materials under irradiation. This result suggests that the isomerization-induced massive mass transport that leads to surface relief gratings formation in these materials, is induced by this huge increase of the matrix diffusion coefficient around the probe. In order to investigate the microscopic origin of the increase of the diffusion, we use molecular dynamics simulations of the photoisomerization of probe dispersed red 1 molecules dispersed inside a glassy molecular matrix. Results show that the increased diffusion is due to an isomerization-induced cage-breaking process. A process that explains the induced cooperative motions recently observed in these photoactive materials.

  11. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability.

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A S

    2015-11-10

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12h at temperatures 20°C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20°C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π-π interactions reduce the inherent physical stability of amorphous drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Local variation of fragility and glass transition temperature of ultra-thin supported polymer films.

    Hanakata, Paul Z; Douglas, Jack F; Starr, Francis W

    2012-12-28

    Despite extensive efforts, a definitive picture of the glass transition of ultra-thin polymer films has yet to emerge. The effect of film thickness h on the glass transition temperature T(g) has been widely examined, but this characterization does not account for the fragility of glass-formation, which quantifies how rapidly relaxation times vary with temperature T. Accordingly, we simulate supported polymer films of a bead-spring model and determine both T(g) and fragility, both as a function of h and film depth. We contrast changes in the relaxation dynamics with density ρ and demonstrate the limitations of the commonly invoked free-volume layer model. As opposed to bulk polymer materials, we find that the fragility and T(g) do not generally vary proportionately. Consequently, the determination of the fragility profile--both locally and for the film as a whole--is essential for the characterization of changes in film dynamics with confinement.

  13. Abnormal three-steplike sub-Tg enthalpy relaxation pattern in hyperquenched metallic glasses

    Hu, Lina; Yue, Yuanzheng

    Our recent work observed a quite different relaxation pattern, i.e., the abnormal three-steplike sub-Tg relaxation in CuZrAl GRs[1]. However, the generality and the origin of this remarkable thermodynamic anomaly remain enigmatic. By hyperquenching strategy, the present work investigated the depe......Our recent work observed a quite different relaxation pattern, i.e., the abnormal three-steplike sub-Tg relaxation in CuZrAl GRs[1]. However, the generality and the origin of this remarkable thermodynamic anomaly remain enigmatic. By hyperquenching strategy, the present work investigated...... in La55Al25Ni20 GRs. However, the correlation between Tf and the activation energy for initiating the energy releasing during thermal scanning is three-steplike for La55Al25Ni20, revealing the similar phenomenon with the abnormal ERP of Cu46Zr46Al8. These unexpected phenomena have been well explained...

  14. Evaluation of glass transition temperature and dynamic mechanical properties of autopolymerized hard direct denture reline resins.

    Takase, Kazuma; Watanabe, Ikuya; Kurogi, Tadafumi; Murata, Hiroshi

    2015-01-01

    This study assessed methods for evaluation of glass transition temperature (Tg) of autopolymerized hard direct denture reline resins using dynamic mechanical analysis and differential scanning calorimetry in addition to the dynamic mechanical properties. The Tg values of 3 different reline resins were determined using a dynamic viscoelastometer and differential scanning calorimeter, and rheological parameters were also determined. Although all materials exhibited higher storage modulus and loss modulus values, and a lower loss tangent at 37˚C with a higher frequency, the frequency dependence was not large. Tg values obtained by dynamic mechanical analysis were higher than those by differential scanning calorimetry and higher frequency led to higher Tg, while more stable Tg values were also obtained by that method. These results suggest that dynamic mechanical analysis is more advantageous for characterization of autopolymerized hard direct denture reline resins than differential scanning calorimetry.

  15. The peculiar behavior of the glass transition temperature of amorphous drug-polymer films coated on inert sugar spheres.

    Dereymaker, Aswin; Van Den Mooter, Guy

    2015-05-01

    Fluid bed coating has been proposed in the past as an alternative technology for manufacturing of drug-polymer amorphous solid dispersions, or so-called glass solutions. It has the advantage of being a one-step process, and thus omitting separate drying steps, addition of excipients, or manipulation of the dosage form. In search of an adequate sample preparation method for modulated differential scanning calorimetry analysis of beads coated with glass solutions, glass transition broadening and decrease of the glass transition temperature (Tg ) were observed with increasing particle size of crushed coated beads and crushed isolated films of indomethacin (INDO) and polyvinylpyrrolidone (PVP). Substituting INDO with naproxen gave comparable results. When ketoconazole was probed or the solvent in INDO-PVP films was switched to dichloromethane (DCM) or a methanol-DCM mixture, two distinct Tg regions were observed. Small particle sizes had a glass transition in the high Tg region, and large particle sizes had a glass transition in the low Tg region. This particle size-dependent glass transition was ascribed to different residual solvent amounts in the bulk and at the surface of the particles. A correlation was observed between the deviation of the Tg from that calculated from the Gordon-Taylor equation and the amount of residual solvent at the Tg of particles with different sizes. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  16. Polymer relaxations in thin films in the vicinity of a penetrant or a temperature induced glass transition

    Ogieglo, Wojciech; Wessling, Matthias; Benes, Nieck Edwin

    2014-01-01

    The transient properties of thin glassy polymer films in the vicinity of the glass transition are investigated. We compare the differences and similarities between sorption and temperature induced glass transitions, referred to as Pg and Tg, respectively. The experimental technique used is in situ

  17. CORRELATION OF THE GLASS TRANSITION TEMPERATURE OF PLASTICIZED PVC USING A LATTICE FLUID MODEL

    A model has been developed to describe the composition dependence of the glass transition temperature (Tg) of polyvinyl chloride (PVC) + plasticizer mixtures. The model is based on Sanchez-Lacombe equation of state and the Gibbs-Di Marzio criterion, which states that th...

  18. Temperature effects on waste glass performance

    Mazer, J.J.

    1991-02-01

    The temperature dependence of glass durability, particularly that of nuclear waste glasses, is assessed by reviewing past studies. The reaction mechanism for glass dissolution in water is complex and involves multiple simultaneous reaction proceeded, including molecular water diffusion, ion exchange, surface reaction, and precipitation. These processes can change in relative importance or dominance with time or changes in temperature. The temperature dependence of each reaction process has been shown to follow an Arrhenius relationship in studies where the reaction process has been isolated, but the overall temperature dependence for nuclear waste glass reaction mechanisms is less well understood, Nuclear waste glass studies have often neglected to identify and characterize the reaction mechanism because of difficulties in performing microanalyses; thus, it is unclear if such results can be extrapolated to other temperatures or reaction times. Recent developments in analytical capabilities suggest that investigations of nuclear waste glass reactions with water can lead to better understandings of their reaction mechanisms and their temperature dependences. Until a better understanding of glass reaction mechanisms is available, caution should be exercised in using temperature as an accelerating parameter. 76 refs., 1 tab

  19. Glass transition in thin supported polystyrene films probed by temperature-modulated ellipsometry in vacuum.

    Efremov, Mikhail Yu; Kiyanova, Anna V; Last, Julie; Soofi, Shauheen S; Thode, Christopher; Nealey, Paul F

    2012-08-01

    Glass transition in thin (1-200 nm thick) spin-cast polystyrene films on silicon surfaces is probed by ellipsometry in a controlled vacuum environment. A temperature-modulated modification of the method is used alongside a traditional linear temperature scan. A clear glass transition is detected in films with thicknesses as low as 1-2 nm. The glass transition temperature (T(g)) shows no substantial dependence on thickness for coatings greater than 20 nm. Thinner films demonstrate moderate T(g) depression achieving 18 K for thicknesses 4-7 nm. Less than 4 nm thick samples are excluded from the T(g) comparison due to significant thickness nonuniformity (surface roughness). The transition in 10-20 nm thick films demonstrates excessive broadening. For some samples, the broadened transition is clearly resolved into two separate transitions. The thickness dependence of the glass transition can be well described by a simple 2-layer model. It is also shown that T(g) depression in 5 nm thick films is not sensitive to a wide range of experimental factors including molecular weight characteristics of the polymer, specifications of solvent used for spin casting, substrate composition, and pretreatment of the substrate surface.

  20. Healing of interfaces of high and ultra-high-molecular- weight polystyrene below the bulk glass transition temperature

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    into contact to themselves below the glass transition temperature T-g of the bulk Tg-bulk, in a lap-shear joint geometry, at a constant healing temperature T-h for a healing time t(h) of 10 min to 24 h. The lap-shear strength sigma of the symmetric HMWPS-HMWPS and UHMWPS-URMWPS interfaces has been measured...

  1. Transport properties of glass-forming liquids suggest that dynamic crossover temperature is as important as the glass transition temperature.

    Mallamace, Francesco; Branca, Caterina; Corsaro, Carmelo; Leone, Nancy; Spooren, Jeroen; Chen, Sow-Hsin; Stanley, H Eugene

    2010-12-28

    It is becoming common practice to partition glass-forming liquids into two classes based on the dependence of the shear viscosity η on temperature T. In an Arrhenius plot, ln η vs 1/T, a strong liquid shows linear behavior whereas a fragile liquid exhibits an upward curvature [super-Arrhenius (SA) behavior], a situation customarily described by using the Vogel-Fulcher-Tammann law. Here we analyze existing data of the transport coefficients of 84 glass-forming liquids. We show the data are consistent, on decreasing temperature, with the onset of a well-defined dynamical crossover η(×), where η(×) has the same value, η(×) ≈ 10(3) Poise, for all 84 liquids. The crossover temperature, T(×), located well above the calorimetric glass transition temperature T(g), marks significant variations in the system thermodynamics, evidenced by the change of the SA-like T dependence above T(×) to Arrhenius behavior below T(×). We also show that below T(×) the familiar Stokes-Einstein relation D/T ∼ η(-1) breaks down and is replaced by a fractional form D/T ∼ η(-ζ), with ζ ≈ 0.85.

  2. Fragility Variation of Lithium Borate Glasses Studied by Temperature-Modulated DSC

    Matsuda, Yu; Fukawa, Yasuteru; Kawashima, Mitsuru; Kojima, Seiji

    2008-02-01

    The fragility of lithium borate glass system has been investigated by Temperature-Modulated Differential Scanning Calorimetry (TMDSC). The frequency and temperature dependences of dynamic specific heat have been observed in the vicinity of a glass transition temperature Tg. It is shown that the value of the fragility index m can be determined from the temperature dependence of the α-relaxation times observed by TMDSC, when the raw phase angle is properly corrected. The composition dependence of the fragility has been also discussed.

  3. Prediction of the Formulation Dependence of the Glass Transition Temperature for Amine-Epoxy Copolymers Using a Quantitative Structure-Property Relationship Based on the AM1 Method

    Morrill, Jason

    2004-01-01

    A designer Quantitative Structure-Property Relationsbip (QSPR) based upon molecular properties calculated using the AM1 semi-empirical quantum mechanical metbod was developed to predict the glass transition temperature (Tg...

  4. Relaxation dynamics of glass transition in PMMA + SWCNT composites by temperature-modulated DSC

    Pradhan, N. R.; Iannacchione, G. S.

    2010-03-01

    The experimental technique offered by temperature-modulated differential scanning calorimeter (TMDSC) used to investigate the thermal relaxation dynamics through the glass transition as a function of frequency was studied for pure PMMA and PMMA-single wall carbon nanotubes (SWCNTs) composites. A strong dependence of the temperature dependence peak in the imaginary part of complex heat capacity (Tmax) is found during the transition from the glass-like to the liquid-like region. The frequency dependence of Tmax of the imaginary part of heat capacity (Cp) is described by Arrhenius law. The activation energy obtained from the fitting shows increases while the characteristic relaxation time decreases with increasing mass fraction (phim) of SWCNTs. The dynamics of the composites during glass transition, at slow and high scan rates, are also the main focus of this experimental study. The change in enthalpy during heating and cooling is also reported as a function of scan rate and frequency of temperature modulation. The glass transition temperature (Tg) shows increases with increasing frequency of temperature modulation and phim of SWCNTs inside the polymer host. Experimental results show that Tg is higher at higher scan rates but as the frequency of temperature modulation increases, the Tg values of different scan rates coincide with each other and alter the scan rate dependence. From the imaginary part of heat capacity, it is obvious that Tmax is not the actual glass transition temperature of pure polymer but Tmax and Tg values can be superimposed when phim increases in the polymer host or when the sample undergoes a transition with a certain frequency of temperature modulation.

  5. Optical properties of alkaline earth borate glasses

    user

    The alkaline earth borate glasses containing heavy metal oxides show good solubility of rare-earth ions. Glasses containing PbO exhibit low glass transition temperature (Tg) and high ..... These oxygen ions carry a partial negative charge and.

  6. Molecular relaxation behavior and isothermal crystallization above glass transition temperature of amorphous hesperetin.

    Shete, Ganesh; Khomane, Kailas S; Bansal, Arvind Kumar

    2014-01-01

    The purpose of this paper was to investigate the relaxation behavior of amorphous hesperetin (HRN), using dielectric spectroscopy, and assessment of its crystallization kinetics above glass transition temperature (Tg ). Amorphous HRN exhibited both local (β-) and global (α-) relaxations. β-Relaxation was observed below Tg , whereas α-relaxation prominently emerged above Tg . β-Relaxation was found to be of Johari-Goldstein type and was correlated with α-process by coupling model. Secondly, isothermal crystallization experiments were performed at 363 K (Tg + 16.5 K), 373 K (Tg + 26.5 K), and 383 K (Tg + 36.5 K). The kinetics of crystallization, obtained from the normalized dielectric strength, was modeled using the Avrami model. Havriliak-Negami (HN) shape parameters, αHN and αHN .βHN , were analyzed during the course of crystallization to understand the dynamics of amorphous phase during the emergence of crystallites. HN shape parameters indicated that long range (α-like) were motions affected to a greater extent than short range (β-like) motions during isothermal crystallization studies at all temperature conditions. The variable behavior of α-like motions at different isothermal crystallization temperatures was attributed to evolving crystallites with time and increase in electrical conductivity with temperature. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

  7. Glass temperatures in free-standing canisters

    Hardy, B.J.; Hensel, S.J.

    1993-01-01

    The waste-forms produced by the Defense Waste Processing Facility (DWPF) are subject to the requirements of the Waste Acceptance Product Specifications (WAPS). The WAPS sets the maximum post cooldown temperature of the waste-form glass at 400 degrees C. This criterion must be satisfied for the ambient conditions and heat generation rates expected for the waste-forms. As part of the work described in task plan, WSRC-RP-93-1177, Rev. 0, a computer model was used to calculate the maximum glass temperatures in free standing wasteforms for a variety of ambient temperatures and heat generation rates

  8. Study on Modified Water Glass Used in High Temperature Protective Glass Coating for Ti-6Al-4V Titanium Alloy

    Shuang Yang

    2018-04-01

    Full Text Available Sodium silicate water glass was modified with sodium polyacrylate as the binder, the composite slurry used for high-temperature oxidation-resistant coating was prepared by mixing glass powder with good lubrication properties in the binder. The properties of the modified binder and high-temperature oxidation resistance of Ti-6Al-4V titanium alloy coated with composite glass coating were studied by XRD, SEM, EDS, TG-DSC and so on. Results showed that sodium polyacrylate modified water glass could obviously improve the suspension stability of the binder, the pyrolytic carbon in the binder at high temperature could increase the surface tension in the molten glass system, and the composite glass coating could be smooth and dense after heating. Pyrolytic carbon diffused and combined with oxygen in the coating under the heating process to protect the titanium alloy from oxidation. The thickness of the oxide layer was reduced 51% after applying the high-temperature oxidation-resistant coating. The coating also showed a nearly 30% reduction in friction coefficient due to the boundary lubricant regime. During cooling, the coating could be peeled off easily because of the mismatched CTE between the coating and substrate.

  9. Liquidus Temperature Data for DWPF Glass

    Piepel, G.F.; Vienna, J.D.; Crum, J.V.; Mika, M.; Hrma, P.

    1999-01-01

    This report provides new liquidus temperature (T L ) versus composition data that can be used to reduce uncertainty in T L calculation for DWPF glass. According to the test plan and test matrix design PNNL has measured T L for 53 glasses within and just outside of the current DWPF processing composition window. The T L database generated under this task will directly support developing and enhancing the current T L process-control model. Preliminary calculations have shown a high probability of increasing HLW loading in glass produced at the SRS and Hanford. This increase in waste loading will decrease the life-cycle tank cleanup costs by decreasing process time and the volume of waste glass produced

  10. 'Vanishing' structural effects of temperature in polymer glasses close to the glass-transition temperature

    Shantarovich, V.P.; Suzuki, T.; Ito, Y.; Yu, R.S.; Kondo, K.; Yampolskii, Yu. P.; Alentiev, A.Yu.

    2007-01-01

    Positron annihilation lifetime (PAL) measurements were used for observation of structural effects of temperature in polystyrene (PS), super-cross-linked polystyrene networks (CPS), and in polyimides (PI) below and in the vicinity of glass-transition temperature T g . 'Vanishing' of these structural effects in the repeating cycles of the temperature controlled PAL experiments due to the slow relaxation processes in different conditions and details of chemical structure is demonstrated. Obtained results illustrate complex, dependent on thermal history, inhomogeneous character of the glass structure. In fact, structure of some polymer glasses is changing continuously. Calculations of the number density of free volume holes in these conditions are discussed

  11. A molecular dynamics approach for predicting the glass transition temperature and plasticization effect in amorphous pharmaceuticals.

    Gupta, Jasmine; Nunes, Cletus; Jonnalagadda, Sriramakamal

    2013-11-04

    The objectives of this study were as follows: (i) To develop an in silico technique, based on molecular dynamics (MD) simulations, to predict glass transition temperatures (Tg) of amorphous pharmaceuticals. (ii) To computationally study the effect of plasticizer on Tg. (iii) To investigate the intermolecular interactions using radial distribution function (RDF). Amorphous sucrose and water were selected as the model compound and plasticizer, respectively. MD simulations were performed using COMPASS force field and isothermal-isobaric ensembles. The specific volumes of amorphous cells were computed in the temperature range of 440-265 K. The characteristic "kink" observed in volume-temperature curves, in conjunction with regression analysis, defined the Tg. The MD computed Tg values were 367 K, 352 K and 343 K for amorphous sucrose containing 0%, 3% and 5% w/w water, respectively. The MD technique thus effectively simulated the plasticization effect of water; and the corresponding Tg values were in reasonable agreement with theoretical models and literature reports. The RDF measurements revealed strong hydrogen bond interactions between sucrose hydroxyl oxygens and water oxygen. Steric effects led to weak interactions between sucrose acetal oxygens and water oxygen. MD is thus a powerful predictive tool for probing temperature and water effects on the stability of amorphous systems during drug development.

  12. Establishing Relationship between Process Parameters and Temperature during High Speed End Milling of Soda Lime Glass

    Nasima Bagum, Mst.; Konneh, Mohamed; Yeakub Ali, Mohammad

    2018-01-01

    In glass machining crack free surface is required in biomedical and optical industry. Ductile mode machining allows materials removal from brittle materials in a ductile manner rather than by brittle fracture. Although end milling is a versatile process, it has not been applied frequently for machining soda lime glass. Soda lime glass is a strain rate and temperature sensitive material; especially around glass transition temperature Tg, ductility increased and strength decreased. Hence, it is envisaged that the generated temperature by high-speed end milling (HSEM) could be brought close to the glass transition temperature, which promote ductile machining. In this research, the objective is to investigate the effect of high speed machining parameters on generated temperature. The cutting parameters were optimized to generate temperature around glass transition temperature of soda lime using response surface methodology (RSM). Result showed that the most influencing process parameter is feed rate followed by spindle speed and depth of cut to generate temperature. Confirmation test showed that combination of spindle speed 30,173 rpm, feed rate 13.2 mm/min and depth of cut 37.68 µm generate 635°C, hence ductile chip removal with machined surface Ra 0.358 µm was possible to achieve.

  13. Relaxation Dynamics of the Glass Transition in PMMA+SWCNT Composites by Temperature-Modulated DSC

    Pradhan, Nihar; Iannacchione, Germano

    2010-03-01

    Temperature Modulated Differential Scanning Calorimeter (TMDSC) used to investigate the thermal relaxation dynamics of PMMA-Single wall carbon nanotubes (SWCNTs) through the glass transition as a function of frequency. A strong dependence of the temperature dependence peak in imaginary part of complex heat capacity (Tmax) was found during the transition from glass like to liquid like region and can be described by Arhenius law. The activation energy shows increases while the charactersistic time decreases with increasing mass fraction (φm) of SWCNTs. Decreasing of enthalpy, while heating and slowly increasing while cooling at 2.0 K/min scan rate was observed and as frequency of temperature modulation increases. There is no relative change of enthalpy in heating and cooling observed at sufficiently slow scan rate. The glass transition temperature (Tg) shows increases as a function of frequency of temperature modulation, φm of SWCNTs and with increasing scan rate. From imaginary part of heat capacity, it obvious that Tmax is not the actual glass transition temperature of pure polymer but Tmax and Tg values can be superimpose when φm of SWCNT increases in polymer.

  14. CONDENSED MATTER: STRUCTURE, MECHANICAL, AND THERMAL PROPERTIES: Observation of β-Relaxation in Sub-Tg Isothermally Annealed Al-Based Metallic Glasses

    Yang, Hong-Wang; Tong, Wei-Ping; Zhao, Xiang; Zuo, Liang; Wang, Jian-Qiang

    2008-09-01

    Al85 Ni5 Y8 C02 and Al 85 Ni5 Y6 C02 Fe2 metallic glasses are fabricated by melt spinning. A kink or a small exothermic peak is observed for both the samples isothermally annealed at sub-glass transition temperatures. Temperature modulated differential scanning calorimetry (TMDSC) data disapprove amorphous phase separation. The activation energies derived from Kissinger plots of the exothermic process on DSC curve around glass transition temperature are consistent with those of β -relaxation of metallic glasses.

  15. Dielectric determination of the glass transition temperature (T sub g)

    Ries, Heidi R.

    1990-01-01

    The objective is to determine the glass transition temperature of a polymer using a dielectric dissipation technique. A peak in the dissipation factor versus temperature curve is expected near the glass transition temperature T sub g. It should be noted that the glass transition is gradual rather than abrupt, so that the glass transition temperature T sub g is not clearly identifiable. In this case, the glass transition temperature is defined to be the temperature at the intersection point of the tangent lines to the dissipation factor versus temperature curve above and below the transition region, as illustrated.

  16. Novel High Temperature and Radiation Resistant Infrared Glasses and Optical Fibers for Sensing in Advanced Small Modular Reactors

    Ballato, John [Clemson Univ., SC (United States)

    2018-01-22

    One binary and three series of ternary non-oxide pure sulfide glasses compositions were investigated with the goal of synthesizing new glasses that exhibit high glass transition (Tg) and crystallization (Tc) temperatures, infrared transparency, and reliable glass formability. The binary glass series consisted of Ges2 and La2S3 and the three glass series in the x(nBaS + mLa2S3) + (1-2x)GeS2 ternary system have BaS:La2S3 modifier ratios of 1:1, 1:2, and 2:1 with . With these glasses, new insights were realized as to how ionic glasses form and how glass modifiers affect both structure and glass formability. All synthesized compositions were characterized by Infrared (IR) and Raman spectroscopies and differential thermal analysis (DTA) to better understand the fundamental structure, optical, and thermal characteristics of the glasses. After a range of these glasses were synthesized, optimal compositions were formed into glass disks and subjected to gamma irradiation. Glass disks were characterized both before and after irradiation by microscope imaging, measuring the refractive index, density, and UV-VIS-IR transmission spectra. The final total dose the samples were subjected to was ~2.5 MGy. Ternary samples showed a less than 0.4% change in density and refractive index and minimal change in transmission window. The glasses also resisted cracking as seen in microscope images. Overall, many glass compositions were developed that possess operating temperatures above 500 °C, where conventional chalcogenide glasses such as As2S3 and have Tgs from ~200-300 °C, and these glasses have a greater than Tc – Tg values larger than 100 °C and this shows that these glasses have good thermal stability of Tg such that they can be fabricated into optical fibers and as such can be considered candidates for high temperature infrared fiber optics. Initial fiber fabrication efforts showed that selected glasses could be drawn but larger

  17. Sealed glass coating of high temperature ceramic superconductors

    Wu, Weite; Chu, Cha Y.; Goretta, Kenneth C.; Routbort, Jules L.

    1995-01-01

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor.

  18. Glass Transitions and Low-Frequency Dynamics of Room-Temperature Ionic Liquids

    Yamamuro, O.; Inamura, Y.; Hayashi, S.; Hamaguchi, H.

    2006-01-01

    We have measured the heat capacity and neutrion quasi- and inelastic scattering spectra of some salts of 1-butyl-3-methylimidazolium ion bmim+, which is a typical cation of room-temperature ionic liquids, and its derivatives. The heat capacity measurements revealed that the room-temperature ionic liquids have glass transitions as molecular liquids. The temperature dependence of configurational entropy demonstrated that the room-temperature ionic liquids are 'fragile liquids'. Both heat capacity and inelastic neutron scattering data revealed that the glassy phases exhibit large low-energy excitations usually called 'boson peak'. The quasielastic neutron scattering data showed that so-called 'fast process' appears around Tg as in molecular and polymer glasses. The temperature dependence of the self-diffusion coefficient derived from the neutron scattering data indicated that the orientation of bmim+ ions and/or butyl-groups of bmim+ ions is highly disordered and very flexible in an ionic liquid phase

  19. Electrochemical determination of the glass transition temperature of thin polyelectrolyte brushes at solid-liquid interfaces by impedance spectroscopy.

    Alonso-García, Teodoro; Rodríguez-Presa, María José; Gervasi, Claudio; Moya, Sergio; Azzaroni, Omar

    2013-07-16

    Devising strategies to assess the glass transition temperature (Tg) of polyelectrolyte assemblies at solid-electrolyte interfaces is very important to understand and rationalize the temperature-dependent behavior of polyelectrolyte films in a wide range of settings. Despite the evolving perception of the importance of measuring Tg under aqueous conditions in thin film configurations, its straightforward measurement poses a challenging situation that still remains elusive in polymer and materials science. Here, we describe a new method based on electrochemical impedance spectroscopy (EIS) to estimate the glass transition temperature of planar polyelectrolyte brushes at solid-liquid interfaces. To measure Tg, the charge transfer resistance (Rct) of a redox probe diffusing through the polyelectrolyte brush was measured, and the temperature corresponding to the discontinuous change in Rct was identified as Tg. Furthermore, we demonstrate that impedance measurements not only facilitate the estimation of Tg but also enable a reliable evaluation of the transport properties of the polymeric interface, i.e., determination of diffusion coefficients, close to the thermal transition. We consider that this approach bridges the gap between electrochemistry and the traditional tools used in polymer science and offers new opportunities to characterize the thermal behavior of complex polymeric interfaces and macromolecular assemblies.

  20. Effect of water content on the glass transition temperature of mixtures of sugars, polymers, and penetrating cryoprotectants in physiological buffer.

    Drake, Andrew C; Lee, Youngjoo; Burgess, Emma M; Karlsson, Jens O M; Eroglu, Ali; Higgins, Adam Z

    2018-01-01

    Long-term storage of viable mammalian cells is important for applications ranging from in vitro fertilization to cell therapy. Cryopreservation is currently the most common approach, but storage in liquid nitrogen is relatively costly and the requirement for low temperatures during shipping is inconvenient. Desiccation is an alternative strategy with the potential to enable viable cell preservation at more convenient storage temperatures without the need for liquid nitrogen. To achieve stability during storage in the dried state it is necessary to remove enough water that the remaining matrix forms a non-crystalline glassy solid. Thus, the glass transition temperature is a key parameter for design of cell desiccation procedures. In this study, we have investigated the effects of moisture content on the glass transition temperature (Tg) of mixtures of sugars (trehalose or raffinose), polymers (polyvinylpyrrolidone or Ficoll), penetrating cryoprotectants (ethylene glycol, propylene glycol, or dimethyl sulfoxide), and phosphate buffered saline (PBS) solutes. Aqueous solutions were dried to different moisture contents by equilibration with saturated salt solutions, or by baking at 95°C. The glass transition temperatures of the dehydrated samples were then measured by differential scanning calorimetry. As expected, Tg increased with decreasing moisture content. For example, in a desiccation medium containing 0.1 M trehalose in PBS, Tg ranged from about 360 K for a completely dry sample to about 220 K at a water mass fraction of 0.4. Addition of polymers to the solutions increased Tg, while addition of penetrating cryoprotectants decreased Tg. Our results provide insight into the relationship between relative humidity, moisture content and glass transition temperature for cell desiccation solutions containing sugars, polymers and penetrating cryoprotectants.

  1. Glass Transition Temperature- and Specific Volume- Composition Models for Tellurite Glasses

    Riley, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Vienna, John D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-09-01

    This report provides models for predicting composition-properties for tellurite glasses, namely specific gravity and glass transition temperature. Included are the partial specific coefficients for each model, the component validity ranges, and model fit parameters.

  2. Characterisation of moisture uptake effects on the glass transitional behaviour of an amorphous drug using modulated temperature DSC.

    Royall, P G; Craig, D Q; Doherty, C

    1999-12-01

    The purpose of this study was to investigate the depression of the glass transition temperature, T(g), of the protease inhibitor saquinavir in the first heating scan as a function of the quantity of sorbed water by the application of modulated temperature differential scanning calorimetry (MTDSC). Samples of amorphous saquinavir were pretreated under various humidity conditions and the quantity of sorbed water measured by thermogravimetric analysis. MTDSC runs were performed using hermetically and non-hermetically sealed pans in order to determine the glass transition temperature. MTDSC allowed the separation of the glass transition from the enthalpic relaxation, thereby allowing clear visualisation of T(g) for amorphous saquinavir in the first heating scan. The plasticizing effects of water were assessed, with the depression in T(g) related to the mole fraction of water sorbed via the Gordon-Taylor relationship. An expression has been derived which allows estimation of the water content which lowers the T(g) to the storage temperature, thereby considerably increasing the risk of recrystallisation. It is argued that this model may aid prediction of the optimal storage conditions for amorphous drugs.

  3. Effective temperature in relaxation of Coulomb glasses.

    Somoza, A M; Ortuño, M; Caravaca, M; Pollak, M

    2008-08-01

    We study relaxation in two-dimensional Coulomb glasses up to macroscopic times. We use a kinetic Monte Carlo algorithm especially designed to escape efficiently from deep valleys around metastable states. We find that, during the relaxation process, the site occupancy follows a Fermi-Dirac distribution with an effective temperature much higher than the real temperature T. Long electron-hole excitations are characterized by T(eff), while short ones are thermalized at T. We argue that the density of states at the Fermi level is proportional to T(eff) and is a good thermometer to measure it. T(eff) decreases extremely slowly, roughly as the inverse of the logarithm of time, and it should affect hopping conductance in many experimental circumstances.

  4. Glass transition temperature of polymer nano-composites with polymer and filler interactions

    Hagita, Katsumi; Takano, Hiroshi; Doi, Masao; Morita, Hiroshi

    2012-02-01

    We systematically studied versatile coarse-grained model (bead spring model) to describe filled polymer nano-composites for coarse-grained (Kremer-Grest model) molecular dynamics simulations. This model consists of long polymers, crosslink, and fillers. We used the hollow structure as the filler to describe rigid spherical fillers with small computing costs. Our filler model consists of surface particles of icosahedra fullerene structure C320 and a repulsive force from the center of the filler is applied to the surface particles in order to make a sphere and rigid. The filler's diameter is 12 times of beads of the polymers. As the first test of our model, we study temperature dependence of volumes of periodic boundary conditions under constant pressures through NPT constant Andersen algorithm. It is found that Glass transition temperature (Tg) decrease with increasing filler's volume fraction for the case of repulsive interaction between polymer and fillers and Tg weakly increase for attractive interaction.

  5. How carbon nanotubes affect the cure kinetics and glass transition temperature of their epoxy composites? – A review

    2009-09-01

    Full Text Available Motivated by the widespread and contradictory results regarding the glass transition temperature of carbon nanotube (CNT/epoxy composites, we reviewed and analyzed the literature results dealing with the effect of unmodified multiwall carbon nanotubes (MWNT on the cure behaviour of an epoxy resin (as a possible source of this discrepancy. The aim of this work was to clarify the effective role of unmodified multiwall carbon nanotubes on the cure kinetics and glass transition temperature (Tg of their epoxy composites. It was found that various authors reported an acceleration effect of CNT. The cure reaction was promoted in its early stage which may be due to the catalyst particles present in the CNT raw material. While SWNT may lead to a decrease of Tg due to their bundling tendency, results reported for MWNT suggested an increased or unchanged Tg of the composites. The present status of the literature does not allow to isolate the effect of MWNT on the Tg due to the lack of a study providing essential information such as CNT purity, glass transition temperature along with the corresponding cure degree.

  6. Short range structural models of the glass transition temperatures and densities of 0.5Na2S + 0.5[xGeS2 + (1 - x)PS5/2] mixed glass former glasses.

    Bischoff, Christian; Schuller, Katherine; Martin, Steve W

    2014-04-03

    The 0.5Na2S + 0.5[xGeS2 + (1 - x)PS5/2] mixed glass former (MGF) glass system exhibits a nonlinear and nonadditive negative change in the Na(+) ion conductivity as one glass former, PS5/2, is exchanged for the other, GeS2. This behavior, known as the mixed glass former effect (MGFE), is also manifest in a negative deviation from the linear interpolation of the glass transition temperatures (T(g)) of the binary end-member glasses, x = 0 and x = 1. Interestingly, the composition dependence of the densities of these ternary MGF glasses reveals a slightly positive MGFE deviation from a linear interpolation of the densities of the binary end-member glasses, x = 0 and x = 1. From our previous studies of the structures of these glasses using IR, Raman, and NMR spectroscopies, we find that a disproportionation reaction occurs between PS7/2(4-) and GeS3(2-) units into PS4(3-) and GeS5/2(1-) units. This disproportionation combined with the formation of Ge4S10(4-) anions from GeS5/2(1-) groups leads to the negative MGFE in T(g). A best-fit model of the T(g)s of these glasses was developed to quantify the amount of GeS5/2(1-) units that form Ge4S10(4-) molecular anions in the ternary glasses (∼ 5-10%). This refined structural model was used to develop a short-range structural model of the molar volumes, which shows that the slight densification of the ternary glasses is due to the improved packing efficiency of the germanium sulfide species.

  7. Glass transition temperature of hard chairside reline materials after post-polymerisation treatments.

    Urban, Vanessa M; Machado, Ana L; Alves, Marinês O; Maciel, Adeilton P; Vergani, Carlos E; Leite, Edson R

    2010-09-01

    This study evaluated the effect of post-polymerisation treatments on the glass transition temperature (T(g)) of five hard chairside reline materials (Duraliner II-D, Kooliner-K, New Truliner-N, Ufi Gel hard-U and Tokuso Rebase Fast-T). Specimens (10 x 10 x 1 mm) were made following the manufacturers' instructions and divided into three groups (n = 5). Control group specimens were left untreated. Specimens from the microwave group were irradiated with pre-determined power/time combinations, and specimens from the water-bath group were immersed in hot water at 55 degrees C for 10 min. Glass transition ( degrees C) was performed by differential scanning calorimetry. Data were analysed using anova, followed by post hoc Tukey's test (alpha = 0.05). Both post-polymerisation treatments promoted a significant (p glass transition of material Kooliner, with the effect being more pronounced for microwave irradiation.

  8. Oxidation and diffusion process in the ferrous iron-bearing glass fibres near glass temperature

    Yue, Yuanzheng; Korsgaard, Martin; Kirkegaard, Lise

    2004-01-01

    The Fe2+ oxidation and the network modifier diffusion in the Fe2+-bearing glass fibers are studied using differential scanning calorimetry (DSC), thermogravimetry (TG), and secondary neutral mass spectrometry (SNMS). The results show two couplings: 1) between the Fe2+ oxidation and the network...... of the Fe2+-bearing fibers with an average diameter of 3.5 m by knowing the heat-treatment conditions and vice versa....

  9. Investigation of thermodynamic properties of magnesium chloride amines by HPDSC and TG. For application in a high-lift high-temperature chemical heat pump

    Bevers, E.R.T.; Oonk, H.A.J.; Haije, W.G.; Ekeren, P.J. van

    2007-01-01

    The formation as well as the decomposition of magnesium chloride ammonia complexes was studied by high-pressure differential scanning calorimetry (HPDSC) and thermogravimetric analysis (TG). HPDSC runs were performed under constant ammonia pressure conditions to determine the transition temperatures

  10. Relationship between thermal expansion coefficient and glass transition temperature in metallic glasses

    Kato, H.; Chen, H.-S.; Inoue, A.

    2008-01-01

    The thermal expansion coefficients of 13 metallic glasses were measured using a thermo-mechanical analyser. A unique correlation was found between the linear thermal expansion coefficient and the glass transition temperature-their product is nearly constant ∼8.24 x 10 -3 . If one assumes the Debye expression for thermal activation, the total linear thermal expansion up to glass transition temperature (T g ) is reduced to 6 x 10 -3 , nearly 25% of that at the fusion of pure metals

  11. Using Combined Computational Techniques to Predict the Glass Transition Temperatures of Aromatic Polybenzoxazines

    Mhlanga, Phumzile; Wan Hassan, Wan Aminah; Hamerton, Ian; Howlin, Brendan J.

    2013-01-01

    The Molecular Operating Environment software (MOE) is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc.) are obtained and quantitative structure property relationships (QSPR) models are formulated. Three QSPR models (formulated using up to 5 descriptors) are first used to make predictions for the initiator data set (n = 9) and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.63–1.86 K of the entire dataset). The water accessible surface area is found to be the most important descriptor in the prediction of Tg. Molecular modelling simulations of the benzoxazine polymer (minus initiator) carried out at the same time using the Materials Studio software suite provide an independent prediction of Tg. Predicted Tg values from molecular modelling fall in the middle of the range of the experimentally determined Tg values, indicating that the structure of the network is influenced by the nature of the initiator used. Hence both techniques can provide predictions of glass transition temperatures and provide complementary data for polymer design. PMID:23326419

  12. Using combined computational techniques to predict the glass transition temperatures of aromatic polybenzoxazines.

    Phumzile Mhlanga

    Full Text Available The Molecular Operating Environment software (MOE is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc. are obtained and quantitative structure property relationships (QSPR models are formulated. Three QSPR models (formulated using up to 5 descriptors are first used to make predictions for the initiator data set (n = 9 and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.63-1.86 K of the entire dataset. The water accessible surface area is found to be the most important descriptor in the prediction of T(g. Molecular modelling simulations of the benzoxazine polymer (minus initiator carried out at the same time using the Materials Studio software suite provide an independent prediction of T(g. Predicted T(g values from molecular modelling fall in the middle of the range of the experimentally determined T(g values, indicating that the structure of the network is influenced by the nature of the initiator used. Hence both techniques can provide predictions of glass transition temperatures and provide complementary data for polymer design.

  13. Isotope effect in glass-transition temperature and ionic conductivity of lithium-borate glasses

    Nagasaki, Takanori; Morishima, Ryuta; Matsui, Tsuneo

    2002-01-01

    The glass-transition temperature and the electrical conductivity of lithium borate (0.33Li 2 O-0.67B 2 O 3 ) glasses with various isotopic compositions were determined by differential thermal analysis and by impedance spectroscopy, respectively. The obtained glass-transition temperature as well as the vibrational frequency of B-O network structure was independent of lithium isotopic composition. This result indicates that lithium ions, which exist as network modifier, only weakly interact with B-O network structure. In addition, the glass-transition temperature increased with 10 B content although the reason has not been understood. The electrical conductivity, on the other hand, increased with 6 Li content. The ratio of the conductivity of 6 Li glass to that of 7 Li glass was found to be 2, being larger than the value (7/6) 1/2 calculated with the simple classical diffusion theory. This strong mass dependence could be explained by the dynamic structure model, which assumes local structural relaxation even far below the glass-transition temperature. Besides, the conductivity appeared to increase with the glass-transition temperature. Possible correlations between the glass-transition temperature and the electrical conductivity were discussed. (author)

  14. Age-related changes in core body temperature and activity in triple-transgenic Alzheimer’s disease (3xTgAD mice

    Elysse M. Knight

    2013-01-01

    Alzheimer’s disease (AD is characterised, not only by cognitive deficits and neuropathological changes, but also by several non-cognitive behavioural symptoms that can lead to a poorer quality of life. Circadian disturbances in core body temperature and physical activity are reported in AD patients, although the cause and consequences of these changes are unknown. We therefore characterised circadian patterns of body temperature and activity in male triple transgenic AD mice (3xTgAD and non-transgenic (Non-Tg control mice by remote radiotelemetry. At 4 months of age, daily temperature rhythms were phase advanced and by 6 months of age an increase in mean core body temperature and amplitude of temperature rhythms were observed in 3xTgAD mice. No differences in daily activity rhythms were seen in 4- to 9-month-old 3xTgAD mice, but by 10 months of age an increase in mean daily activity and the amplitude of activity profiles for 3xTgAD mice were detected. At all ages (4–10 months, 3xTgAD mice exhibited greater food intake compared with Non-Tg mice. The changes in temperature did not appear to be solely due to increased food intake and were not cyclooxygenase dependent because the temperature rise was not abolished by chronic ibuprofen treatment. No β-amyloid (Aβ plaques or neurofibrillary tangles were noted in the hypothalamus of 3xTgAD mice, a key area involved in temperature regulation, although these pathological features were observed in the hippocampus and amygdala of 3xTgAD mice from 10 months of age. These data demonstrate age-dependent changes in core body temperature and activity in 3xTgAD mice that are present before significant AD-related neuropathology and are analogous to those observed in AD patients. The 3xTgAD mouse might therefore be an appropriate model for studying the underlying mechanisms involved in non-cognitive behavioural changes in AD.

  15. Age-related changes in core body temperature and activity in triple-transgenic Alzheimer’s disease (3xTgAD) mice

    Knight, Elysse M.; Brown, Timothy M.; Gümüsgöz, Sarah; Smith, Jennifer C. M.; Waters, Elizabeth J.; Allan, Stuart M.; Lawrence, Catherine B.

    2013-01-01

    SUMMARY Alzheimer’s disease (AD) is characterised, not only by cognitive deficits and neuropathological changes, but also by several non-cognitive behavioural symptoms that can lead to a poorer quality of life. Circadian disturbances in core body temperature and physical activity are reported in AD patients, although the cause and consequences of these changes are unknown. We therefore characterised circadian patterns of body temperature and activity in male triple transgenic AD mice (3xTgAD) and non-transgenic (Non-Tg) control mice by remote radiotelemetry. At 4 months of age, daily temperature rhythms were phase advanced and by 6 months of age an increase in mean core body temperature and amplitude of temperature rhythms were observed in 3xTgAD mice. No differences in daily activity rhythms were seen in 4- to 9-month-old 3xTgAD mice, but by 10 months of age an increase in mean daily activity and the amplitude of activity profiles for 3xTgAD mice were detected. At all ages (4–10 months), 3xTgAD mice exhibited greater food intake compared with Non-Tg mice. The changes in temperature did not appear to be solely due to increased food intake and were not cyclooxygenase dependent because the temperature rise was not abolished by chronic ibuprofen treatment. No β-amyloid (Aβ) plaques or neurofibrillary tangles were noted in the hypothalamus of 3xTgAD mice, a key area involved in temperature regulation, although these pathological features were observed in the hippocampus and amygdala of 3xTgAD mice from 10 months of age. These data demonstrate age-dependent changes in core body temperature and activity in 3xTgAD mice that are present before significant AD-related neuropathology and are analogous to those observed in AD patients. The 3xTgAD mouse might therefore be an appropriate model for studying the underlying mechanisms involved in non-cognitive behavioural changes in AD. PMID:22864021

  16. Age-related changes in core body temperature and activity in triple-transgenic Alzheimer's disease (3xTgAD) mice.

    Knight, Elysse M; Brown, Timothy M; Gümüsgöz, Sarah; Smith, Jennifer C M; Waters, Elizabeth J; Allan, Stuart M; Lawrence, Catherine B

    2013-01-01

    Alzheimer's disease (AD) is characterised, not only by cognitive deficits and neuropathological changes, but also by several non-cognitive behavioural symptoms that can lead to a poorer quality of life. Circadian disturbances in core body temperature and physical activity are reported in AD patients, although the cause and consequences of these changes are unknown. We therefore characterised circadian patterns of body temperature and activity in male triple transgenic AD mice (3xTgAD) and non-transgenic (Non-Tg) control mice by remote radiotelemetry. At 4 months of age, daily temperature rhythms were phase advanced and by 6 months of age an increase in mean core body temperature and amplitude of temperature rhythms were observed in 3xTgAD mice. No differences in daily activity rhythms were seen in 4- to 9-month-old 3xTgAD mice, but by 10 months of age an increase in mean daily activity and the amplitude of activity profiles for 3xTgAD mice were detected. At all ages (4-10 months), 3xTgAD mice exhibited greater food intake compared with Non-Tg mice. The changes in temperature did not appear to be solely due to increased food intake and were not cyclooxygenase dependent because the temperature rise was not abolished by chronic ibuprofen treatment. No β-amyloid (Aβ) plaques or neurofibrillary tangles were noted in the hypothalamus of 3xTgAD mice, a key area involved in temperature regulation, although these pathological features were observed in the hippocampus and amygdala of 3xTgAD mice from 10 months of age. These data demonstrate age-dependent changes in core body temperature and activity in 3xTgAD mice that are present before significant AD-related neuropathology and are analogous to those observed in AD patients. The 3xTgAD mouse might therefore be an appropriate model for studying the underlying mechanisms involved in non-cognitive behavioural changes in AD.

  17. Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    Films of high-molecular-weight amorphous polystyrene (PS, M-w = 225 kg/mol, M-w/M-n = 3, T-g-bulk = 97degreesC, where T-g-bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M-w = 87 kg/mol, M-w/M-n = 2, Tg-bulk = 109degreesC) were brought into contact...

  18. Effect of borojo (Borojoa patinoi Cuatrecasas) three-phase composition and gum arabic on the glass transition temperature.

    Rodríguez-Bernal, Jenny M; Tello, Edisson; Flores-Andrade, Enrique; Perea-Flores, Maria de Jesús; Vallejo-Cardona, Alba A; Gutiérrez-López, Gustavo F; Quintanilla-Carvajal, Maria X

    2016-02-01

    The search for natural, novel, high-quality, stable food ingredients is an ongoing practice in the food industry. Pulp of borojo (Borojoa patinoi Cuatrecasas), which is a fruit of the Colombian Pacific region, can be separated into three phases: liquid (LP), medium (MP) and solid (SP) phases. The objective of this work was to evaluate the effect of the three-phase composition and gum arabic on their glass transitions temperatures (T(g)). The best mixture, LP-MP, MP-SP and LP-SP and gum arabic (GA) was identified by response surface methodology. When adding GA to SP borojo phase in a 1:1 proportion, the resulting T(g) of the mixture was 132.27 °C whereas Tg for GA and SP-phase were 154.89 °C and 79.86 °C respectively, which supported this combination as attractive from a processing perspective and supports an industrial advantage of using borojo as food ingredient. Phases were characterized by high-performance liquid chromatography, Fourier transform infrared spectroscopy, confocal laser scanning microscopy and mass spectrometry. Low molecular weight compounds such as fructose for MP lowered T(g) whereas the presence of lignin increased T(g) of the mixtures as with the SP. The addition of GA significantly increased T(g) of borojo phases so leading to propose them as novel food processing materials. © 2015 Society of Chemical Industry.

  19. Determination of the Glass-Transition Temperature of GRPS and CFRPS Using a Torsion Pendulum in Regimes of Freely Damped Vibrations and Quasi-Stastic Torsion of Specimens

    Startsev, V. O.; Lebedev, M. P.; Molokov, M. V.

    2018-03-01

    A method to measure the glass-transition temperature of polymers and polymeric matrices of composite materials with the help of an inverse torsion pendulum over a wide range of temperatures is considered combining the method of free torsional vibrations and a quasi-static torsion of specimens. The glass-transition temperature Tg of a KMKS-1-80. T10 fiberglass, on increasing the frequency of freely damped torsional vibrations from 0.7 to 9.6 Hz, was found to increase from 132 to 140°C. The value of Tg of these specimens, determined by measuring the work of their torsion through a small fixed angle was 128.6°C ± 0.8°C. It is shown that the use of a torsion pendulum allows one to determine the glass-transition temperature of polymeric or polymer matrices of PCMs in dynamic and quasi-static deformation regimes of specimens.

  20. Mobility of supercooled liquid toluene, ethylbenzene, and benzene near their glass transition temperatures investigated using inert gas permeation.

    May, R Alan; Smith, R Scott; Kay, Bruce D

    2013-11-21

    We investigate the mobility of supercooled liquid toluene, ethylbenzene, and benzene near their respective glass transition temperatures (Tg). The permeation rate of Ar, Kr, and Xe through the supercooled liquid created when initially amorphous overlayers are heated above their glass transition temperature is used to determine the diffusivity. Amorphous benzene crystallizes at temperatures well below its Tg, and as a result, the inert gas underlayer remains trapped until the onset of benzene desorption. In contrast, for toluene and ethylbenzene the onset of inert gas permeation is observed at temperatues near Tg. The inert gas desorption peak temperature as a function of the heating rate and overlayer thickness is used to quantify the diffusivity of supercooled liquid toluene and ethylbenzene from 115 to 135 K. In this temperature range, diffusivities are found to vary across 5 orders of magnitude (∼10(-14) to 10(-9) cm(2)/s). The diffusivity data are compared to viscosity measurements and reveal a breakdown in the Stokes-Einstein relationship at low temperatures. However, the data are well fit by the fractional Stokes-Einstein equation with an exponent of 0.66. Efforts to determine the diffusivity of a mixture of benzene and ethylbenzene are detailed, and the effect of mixing these materials on benzene crystallization is explored using infrared spectroscopy.

  1. Evaluation of a Novel Temperature Sensing Probe for Monitoring and Controlling Glass Temperature in a Joule-Heated Glass Melter

    Watkins, A. D.; Musick, C. A.; Cannon, C.; Carlson, N. M.; Mullenix, P.D.; Tillotson, R. D.

    1999-01-01

    A self-verifying temperature sensor that employs advanced contact thermocouple probe technology was tested in a laboratory-scale, joule-heated, refractory-lined glass melter used for radioactive waste vitrification. The novel temperature probe monitors melt temperature at any given level of the melt chamber. The data acquisition system provides the real-time temperature for molten glass. Test results indicate that the self-verifying sensor is more accurate and reliable than classic platinum/rhodium thermocouple and sheath assemblies. The results of this test are reported as well as enhancements being made to the temperature probe. To obtain more reliable temperature measurements of the molten glass for improving production efficiency and ensuring consistent glass properties, optical sensing was reviewed for application in a high temperature environment

  2. Time-temperature-transformation kinetics in SRL waste glass

    Jantzen, C.M.; Bickford, D.F.; Karraker, D.G.

    1983-01-01

    Time-temperature-transformation (TTT) curves have been determined for SRL 165 waste glass. Extent and sequence of crystallization were determined by XRD and SEM. The incipient crystallization product, spinel, can be determined at one volume percent by magnetic susceptibility. The type and percentage of crystallization is correlated with waste glass durability. 20 references, 5 figures, 1 table

  3. An investigation into the effects of residual water on the glass transition temperature of polylactide microspheres using modulated temperature DSC.

    Passerini, N; Craig, D Q

    2001-05-18

    The objective of the study was to ascertain residual water levels in polylactide and polylactide-co-glycolide microspheres prepared using the solvent evaporation technique and to investigate the effects of that water on the glass transitional behaviour of the microspheres. Microspheres were prepared from polylactic acid (PLA) and polylactide-co-glycolide (PLGA) 50:50 and 75:25 using a standard solvent evaporation technique. The glass transition was measured as a function of drying conditions using modulated temperature DSC. The microspheres were found to contain very low levels of dichloromethane, while residual water levels of up to circa 3% w/w were noted after freeze or oven drying, these levels being higher for microspheres containing higher glycolic acid levels. The residual water was found to lower the T(g) following the Gordon-Taylor relationship. The data indicate that the microparticles may retain significant water levels following standard preparation and drying protocols and that this drying may markedly lower the T(g) of the spheres.

  4. A universal reduced glass transition temperature for liquids

    Fedors, R. F.

    1979-01-01

    Data on the dependence of the glass transition temperature on the molecular structure for low-molecular-weight liquids are analyzed in order to determine whether Boyer's reduced glass transition temperature (1952) is a universal constant as proposed. It is shown that the Boyer ratio varies widely depending on the chemical nature of the molecule. It is pointed out that a characteristic temperature ratio, defined by the ratio of the sum of the melting temperature and the boiling temperature to the sum of the glass transition temperature and the boiling temperature, is a universal constant independent of the molecular structure of the liquid. The average value of the ratio obtained from data for 65 liquids is 1.15.

  5. Temperature-induced structural changes in fluorozirconate glasses and liquids

    Sen, S.; Youngman, R.E.

    2002-01-01

    The atomic structure and its temperature dependence in fluorozirconate glasses and supercooled liquids have been studied with high-resolution and high-temperature 19 F and 23 Na nuclear-magnetic-resonance (NMR) spectroscopy. The 19 F NMR spectra in these glasses show the presence of multiple F environments. Temperature dependence of the 19 F magic-angle-spinning NMR spectra indicates a progressive change in the average F coordination environment in the glass structure, besides motional narrowing due to substantial mobility of F - ions. The observed change in the average 19 F NMR chemical shift is consistent with progressive breaking of the Zr-F-Zr linkages in the glass structure with increasing temperature. The onset of such a change in F speciation is observed at temperatures well below T g . This result is evidence of changes in the average equilibrium structure in an inorganic glass-forming liquid at T g , albeit on a local scale. The 23 Na NMR spectra indicate that the cations in these glasses become significantly mobile only at temperatures T≥T g , which allows for the onset of global structural relaxation and viscous flow

  6. High-Temperature Thermal Diffusivity Measurements of Silicate Glasses

    Pertermann, M.; Hofmeister, A. M.; Whittington, A. G.; Spera, F. J.; Zayac, J.

    2005-12-01

    Transport of heat in geologically relevant materials is of great interest because of its key role in heat transport, magmatism and volcanic activity on Earth. To better understand the thermal properties of magmatic materials at high temperatures, we measured the thermal diffusivity of four synthetic end-member silicate glasses with the following compositions: albite (NaAlSi3O8), orthoclase (KAlSi3O8), anorthite (CaAl2Si2O8), and diopside (CaMgSi2O6). Thermal diffusivity measurements were conducted with the laser-flash technique and data were acquired from room temperature to a maximum temperature near 1100°C, depending on the glass transition temperature. The presence of sub-mm sized bubbles in one of the orthoclase samples had no discernable effect on measured diffusivities. At room temperature, the three feldspar-type glasses have thermal diffusivity (D) values of 0.58-0.61 mm2/s, whereas the diopside glass has 0.52 mm2/s. With increasing temperature, D decreases by 5-10% (relative) for all samples and becomes virtually constant at intermediate temperatures. At higher temperatures, the anorthite and diopside glasses exhibit significant drops in thermal diffusivity over a 50-100°C interval, correlating with previously published heat capacity changes near the glass transition for these compositions. For anorthite, D (in mm2/s) decreases from 0.48 at 750-860°C to 0.36 at 975-1075°C; for diopside, D changes from 0.42 at 630-750°C to 0.30 at 850-910°C, corresponding to relative drops of 24 and 29%, respectively. Albite and orthoclase glasses do not exhibit this change and also lack significant changes in heat capacity near the glass transition. Instead, D is constant at 400-800°C for albite, and for orthoclase values go through a minimum at 500-600°C before increasing slightly towards 1100°C but it never exceeds the room temperature D. Our data on thermal diffusivity correlate closely with other thermophysical properties. Thus, at least in case of simple

  7. Oxide glass to high temperature ceramic superconductors - a novel route

    Chaudhuri, B.K.; Som, K.K.

    1992-01-01

    Recently it has been discovered that many of transition metal oxide (TMO) glasses like Bi-Sr-Ca-Cu-O, Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O etc. can be directly converted to the corresponding high temperature superconducting phases by properly annealing the respective glasses. In this review recent developements in this field are summarised. The structural, electrical, dielectrical, magnetic, optical, and other properties of these new type of (TMO) glass systems have been elucidated comparing them with the corresponding results of already known (TMO) glasses which do not become superconductors on annealing above their glass transition temperatures (T g ). The electrical properties of this novel glass system have been analysed with reference to the various existing theoretical models based on polaron hopping conduction mechanism. The electrical, magnetic, and other properties of the respective superconductors obtained from their corresponding glass phases by annealing above (T g ) and the possibility of drawing wires, ribbons etc. from these glass matrices and then converting them to their high T c superconducting phases have also been discussed. (author). 107 refs., 32 figs., 5 tabs

  8. Low temperature sintering of fluorapatite glass-ceramics

    Denry, Isabelle; Holloway, Julie A.

    2014-01-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disc-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. PMID:24252652

  9. Low temperature sintering of fluorapatite glass-ceramics.

    Denry, Isabelle; Holloway, Julie A

    2014-02-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Polymorphic crystallization of metal-metalloid-glasses above the glass transition temperature

    Koster, U.; Schunemann, U.; Stephenson, G.B.; Brauer, S.; Sutton, M.

    1992-01-01

    Crystallization of metal-metalloid glasses is known to proceed by nucleation and growth processes. Using crystallization statistics in partially crystallized glasses, at temperatures below the glass transition temperature, time-dependent heterogeneous nucleation has been found to occur at a number of quenched-in nucleation sites. Close to the glass transition temperature crystallization proceeds so rapidly that partially crystallized microstructures could not be obtained. Initial results form fully crystallized glasses exhibit evidence for a transient homogeneous nucleation process at higher temperatures. These conclusions are derived post mortem. At there may be some change of the microstructure after crystallization is finished or during he subsequent quenching, it is desirable to directly obtain information during the early stages of crystallization. Recently reported work by Sutton et al. showed that structural changes can be observed in situ during crystallization by time-resolved x-ray diffraction on time scales as short as milliseconds. The aim o the paper is to present the authors study of the crystallization behavior at temperatures near the glass transition by in-situ x-ray diffraction studies and by microstructural analysis after rapid heating experiments. The results are compared to those derived from a computer model of the crystallization process

  11. Glass precursor approach to high-temperature superconductors

    Bansal, Narottam P.

    1992-01-01

    The available studies on the synthesis of high T sub c superconductors (HTS) via the glass precursor approach were reviewed. Melts of the Bi-Sr-Ca-Cu-O system as well as those doped with oxides of some other elements (Pb, Al, V, Te, Nb, etc.) could be quenched into glasses which, on further heat treatments under appropriate conditions, crystallized into the superconducting phase(s). The nature of the HTS phase(s) formed depends on the annealing temperature, time, atmosphere, and the cooling rate and also on the glass composition. Long term annealing was needed to obtain a large fraction of the 110 K phase. The high T sub c phase did not crystallize out directly from the glass matrix, but was preceded by the precipitation of other phases. The 110 K HTS was produced at high temperatures by reaction between the phases formed at lower temperatures resulting in multiphase material. The presence of a glass former such as B2O3 was necessary for the Y-Ba-Cu-O melt to form a glass on fast cooling. A discontinuous YBa2Cu3O(7-delta) HTS phase crystallized out on heat treatment of this glass. Attempts to prepare Tl-Ba-Ca-Cu-O system in the glassy state were not successful.

  12. Lifetime Prediction of Nano-Silica based Glass Fibre/Epoxy composite by Time Temperature Superposition Principle

    Anand, Abhijeet; Banerjee, Poulami; Prusty, Rajesh Kumar; Ray, Bankin Chandra

    2018-03-01

    The incorporation of nano fillers in Fibre reinforced polymer (FRP) composites has been a source of experimentation for researchers. Addition of nano fillers has been found to improve mechanical, thermal as well as electrical properties of Glass fibre reinforced polymer (GFRP) composites. The in-plane mechanical properties of GFRP composite are mainly controlled by fibers and therefore exhibit good values. However, composite exhibits poor through-thickness properties, in which the matrix and interface are the dominant factors. Therefore, it is conducive to modify the matrix through dispersion of nano fillers. Creep is defined as the plastic deformation experienced by a material for a temperature at constant stress over a prolonged period of time. Determination of Master Curve using time-temperature superposition principle is conducive for predicting the lifetime of materials involved in naval and structural applications. This is because such materials remain in service for a prolonged time period before failure which is difficult to be kept marked. However, the failure analysis can be extrapolated from its behaviour in a shorter time at an elevated temperature as is done in master creep analysis. The present research work dealt with time-temperature analysis of 0.1% SiO2-based GFRP composites fabricated through hand-layup method. Composition of 0.1% for SiO2nano fillers with respect to the weight of the fibers was observed to provide optimized flexural properties. Time and temperature dependence of flexural properties of GFRP composites with and without nano SiO2 was determined by conducting 3-point bend flexural creep tests over a range of temperature. Stepwise isothermal creep tests from room temperature (30°C) to the glass transition temperature Tg (120°C) were performed with an alternative creep/relaxation period of 1 hour at each temperature. A constant stress of 40MPa was applied during the creep tests. The time-temperature superposition principle was

  13. Glasses

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  14. Task plan: Temperatures in DWPF Glass Waste Storage Building

    Hardy, B.J.

    1993-01-01

    The Bechtel National, Inc. Detailed Design Instructions for Structural Design (DDI-02) requires that concrete components of the GWSB not exceed 150 degrees F for structural elements and 200 degrees F locally over a 24 hour period. In addition, the Waste Acceptance Product Specifications (WAPS) sets the maximum post cooldown temperature of the glass waste-form at 400 degrees C. Various scenarios can be postulated which result in elevated glass and concrete temperatures in the GWSB. Therefore, it is important to determine the concrete and glass temperatures during both normal and off-normal conditions. This document details specific tasks required to develop a technically defensible and verifiable methodology for determining maximum temperatures for the waste-forms and the GWSB concrete structures. All models used in this analysis will satisfy Quality Assurance requirements and be defensible to review and oversight committees

  15. Molecular Orientation in Two Component Vapor-Deposited Glasses: Effect of Substrate Temperature and Molecular Shape

    Powell, Charles; Jiang, Jing; Walters, Diane; Ediger, Mark

    Vapor-deposited glasses are widely investigated for use in organic electronics including the emitting layers of OLED devices. These materials, while macroscopically homogenous, have anisotropic packing and molecular orientation. By controlling this orientation, outcoupling efficiency can be increased by aligning the transition dipole moment of the light-emitting molecules parallel to the substrate. Light-emitting molecules are typically dispersed in a host matrix, as such, it is imperative to understand molecular orientation in two-component systems. In this study we examine two-component vapor-deposited films and the orientations of the constituent molecules using spectroscopic ellipsometry, UV-vis and IR spectroscopy. The role of temperature, composition and molecular shape as it effects molecular orientation is examined for mixtures of DSA-Ph in Alq3 and in TPD. Deposition temperature relative to the glass transition temperature of the two-component mixture is the primary controlling factor for molecular orientation. In mixtures of DSA-Ph in Alq3, the linear DSA-Ph has a horizontal orientation at low temperatures and slight vertical orientation maximized at 0.96Tg,mixture, analogous to one-component films.

  16. Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

    Wong DeRieux, Wing-Sy; Li, Ying; Lin, Peng; Laskin, Julia; Laskin, Alexander; Bertram, Allan K.; Nizkorodov, Sergey A.; Shiraiwa, Manabu

    2018-05-01

    Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg). We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol-1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ˜ 1100 g mol-1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg/T) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ˜ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon-Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ), and the Gordon-Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2-5 orders

  17. Fluorinated epoxy resins with high glass transition temperatures

    Griffith, James R.

    1991-01-01

    Easily processed liquid resins of low dielectric constants and high glass transition temperatures are useful for the manufacture of certain composite electronic boards. That combination of properties is difficult to acquire when dielectric constants are below 2.5, glass transition temperatures are above 200 C and processability is of conventional practicality. A recently issued patent (US 4,981,941 of 1 Jan. 1991) teaches practical materials and is the culmination of 23 years of research and effort and 15 patents owned by the Navy in the field of fluorinated resins of several classes. In addition to high fluorine content, practical utility was emphasized.

  18. Standard test method for determining liquidus temperature of immobilized waste glasses and simulated waste glasses

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 These practices cover procedures for determining the liquidus temperature (TL) of nuclear waste, mixed nuclear waste, simulated nuclear waste, or hazardous waste glass in the temperature range from 600°C to 1600°C. This method differs from Practice C829 in that it employs additional methods to determine TL. TL is useful in waste glass plant operation, glass formulation, and melter design to determine the minimum temperature that must be maintained in a waste glass melt to make sure that crystallization does not occur or is below a particular constraint, for example, 1 volume % crystallinity or T1%. As of now, many institutions studying waste and simulated waste vitrification are not in agreement regarding this constraint (1). 1.2 Three methods are included, differing in (1) the type of equipment available to the analyst (that is, type of furnace and characterization equipment), (2) the quantity of glass available to the analyst, (3) the precision and accuracy desired for the measurement, and (4) candi...

  19. TIME-TEMPERATURE-TRANSFORMATION DIAGRAMS FOR THE SLUDGE BATCH 3 - FRIT 418 GLASS SYSTEM

    Billings, A.; Edwards, Tommy

    2009-01-01

    As a part of the Waste Acceptance Product Specifications (WAPS) for Vitrified High-Level Waste Forms defined by the Department of Energy - Office of Environmental Management, the phase stability must be determined for each of the projected high-level waste (HLW) types at the Savannah River Site (SRS). Specifically, WAPS 1.4.1 requires the glass transition temperature (Tg) to be defined and time-temperature-transformation (TTT) diagrams to be developed. The Tg of a glass is an indicator of the approximate temperature where the supercooled liquid converts to a solid on cooling or conversely, where the solid begins to behave as a viscoelastic solid on heating. A TTT diagram identifies the crystalline phases that can form as a function of time and temperature for a given waste type or more specifically, the borosilicate glass waste form. In order to assess durability, the Product Consistency Test (PCT) was used and the durability results compared to the Environmental Assessment (EA) glass. The measurement of glass transition temperature and the development of TTT diagrams have already been performed for the seven Defense Waste Processing Facility (DWPF) projected compositions as defined in the Waste Form Compliance Plan (WCP). These measurements were performed before DWPF start-up and the results were incorporated in Volume 7 of the Waste Form Qualification Report (WQR). Additional information exists for other projected compositions, but overall these compositions did not consider some of the processing scenarios now envisioned for DWPF to accelerate throughput. Changes in DWPF processing strategy have required this WAPS specification to be revisited to ensure that the resulting phases have been bounded. Frit 418 was primarily used to process HLW Sludge Batch 3 (SB3) at 38% waste loading (WL) through the DWPF. The Savannah River National Laboratory (SRNL) fabricated a cache of glass from reagent grade oxides to simulate the SB3-Frit 418 system at a 38 wt % WL for glass

  20. Breaking Through the Glass Ceiling: Recent Experimental Approaches to Probe the Properties of Supercooled Liquids near the Glass Transition.

    Smith, R Scott; Kay, Bruce D

    2012-03-15

    Experimental measurements of the properties of supercooled liquids at temperatures near their glass transition temperatures, Tg, are requisite for understanding the behavior of glasses and amorphous solids. Unfortunately, many supercooled molecular liquids rapidly crystallize at temperatures far above their Tg, making such measurements difficult to nearly impossible. In this Perspective, we discuss some recent alternative approaches to obtain experimental data in the temperature regime near Tg. These new approaches may yield the additional experimental data necessary to test current theoretical models of the dynamical slowdown that occurs in supercooled liquids approaching the glass transition.

  1. Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

    Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

    2015-01-01

    Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...... at elastic stage. The concentrated stress in crystals at elastic stage provided adequate energy for the direct gamma-alpha phase transition under T-g. The force to promote the gamma-phase into a phase directly is insufficient at the yield stage and a transient phase as a compromise was formed. The transient...... phase was confirmed by DSC measurements and assisted the gamma-alpha phase transition indirectly. The gamma-phase slips into incomplete fragments at yield point, and the parts along tensile direction are responsible for the formation of transient phase. The gamma-fragments after yield is oriented...

  2. Predict the glass transition temperature and plasticization of β-cyclodextrin/water binary system by molecular dynamics simulation.

    Zhou, Guohui; Zhao, Tianhai; Wan, Jie; Liu, Chengmei; Liu, Wei; Wang, Risi

    2015-01-12

    The glass transition temperature, diffusion behavior and plasticization of β-cyclodextrin (β-CD), and three amorphous β-CD/water mixtures (3%, 5% and 10% [w/w] water, respectively) were investigated by molecular dynamics simulation, which were performed using Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field and isothermal-isobaric ensembles. The specific volumes of four amorphous cells were obtained as a function of temperature. The glass transition temperatures (T(g)) were estimated to be 334.25 K, 325.12 K, 317.32 K, and 305.41 K for amorphous β-CD containing 0%, 3%, 5% and 10% w/w water, respectively, which compares well with the values observed in published literature. The radial distribution function was computed to elucidate the intermolecular interactions between amorphous β-CD and water, which acts as a plasticizer. These results indicate that the hydrogen bond interactions of oxygen in hydroxyl ions was higher than oxygen in acetal groups in β-CD amorphous mixtures with that in water, due to less accessibility of ring oxygens to the surrounding water molecules. The mobility of water molecules was investigated over various temperature ranges, including the rubbery and glassy phases of the β-CD/water mixtures, by calculating the diffusion coefficients and the fractional free volume. In β-CD amorphous models, the higher mobility of water molecules was observed at temperatures above Tg, and almost no change was observed at temperatures below T(g). Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Confinement and the Glass Transition Temperature in Supported Polymer Films: Molecular Weight, Repeat Unit Modification, and Cooperativity Length Scale Investigations

    Mundra, Manish K.

    2005-03-01

    It is well known that the glass transition temperatures, Tgs, of supported polystyrene (PS) films decrease dramatically with decreasing film thickness below 60-80 nm. However, a detailed understanding of the cause of this effect is lacking. We have investigated the impact of several parameters, including polymer molecular weight (MW), repeat unit structure, and the length scale of cooperatively rearranging regions in bulk. There is no significant effect of PS MW on the Tg-confinement effect over a range of 5,000 to 3,000,000 g/mol. In contrast, the strength of the Tg reduction and the onset of the confinement effect increase dramatically upon changing the polymer from PS to poly(4-tert-butylstyrene) (PTBS), with PTBS exhibiting a Tg reduction relative to bulk at a thickness of 300-400 nm. PTBS also shows a Tg reduction relative to bulk of 47 K in a 21-nm-thick film, more than twice that observed in a PS film of identical thickness. Characterization of the length scale of cooperatively rearranging regions has been done by differential scanning calorimetry but reveals at best a limited correlation with the confinement effect.

  4. Phase transitions and glass transition in a hyperquenched silica–alumina glass

    Zhang, Y.F.; Zhao, D.H.; Yue, Yuanzheng

    2017-01-01

    We investigate phase transitions, glass transition, and dynamic behavior in the hyperquenched 69SiO2–31Al2O3 (mol%) glass (SA glass). Upon reheating, the SA glass exhibits a series of thermal responses. Subsequent to the sub-Tg enthalpy release, the glass undergoes a large jump in isobaric heat...... capacity (ΔCp) during glass transition, implying the fragile nature of the SA glass. The mullite starts to form before the end of glass transition, indicating that the SA glass is extremely unstable against crystallization. After the mullite formation, the remaining glass phase exhibits an increased Tg...... and a suppressed ΔCp. The formation of cristobalite at 1553 K indicates the dominance of silica in the remaining glass matrix. The cristobalite gradually re-melts as the isothermal heat-treatment temperature is raised from 1823 to 1853 K, which is well below the melting point of cristobalite, while the amount...

  5. Origin of broad NIR photoluminescence in bismuthate glass and Bi-doped glasses at room temperature

    Peng, Mingying; Zollfrank, Cordt; Wondraczek, Lothar [Lehrstuhl fuer Glas und Keramik, WW3, Friedrich Alexander Universitaet Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen (Germany)], E-mail: mingying.peng@ww.uni-erlangen.de, E-mail: lothar.wondraczek@ww.uni-erlangen.de

    2009-07-15

    Bi-doped glasses with broadband photoluminescence in the near-infrared (NIR) spectral range are presently receiving significant consideration for potential applications in telecommunications, widely tunable fiber lasers and spectral converters. However, the origin of NIR emission remains disputed. Here, we report on NIR absorption and emission properties of bismuthate glass and their dependence on the melting temperature. Results clarify that NIR emission occurs from the same centers as it does in Bi-doped glasses. The dependence of absorption and NIR emission of bismuthate glasses on the melting temperature is interpreted as thermal dissociation of Bi{sub 2}O{sub 3} into elementary Bi. Darkening of bismuthate glass melted at 1300 deg. C is due to the agglomeration of Bi atoms. The presence of Bi nanoparticles is confirmed by transmission electron microscopy, high-resolution energy dispersive x-ray spectroscopy and element distribution mapping. By adding antimony oxide as an oxidation agent to the glass, NIR emission centers can be eliminated and Bi{sup 3+} is formed. By comparing with atomic spectral data, absorption bands at {approx}320 , {approx}500 , 700 , 800 and 1000 nm observed in Bi-doped glasses are assigned to Bi{sup 0} transitions {sup 4}S{sub 3/2}{yields}{sup 2}P{sub 3/2}, {sup 4}S{sub 3/2}{yields}{sup 2}P{sub 1/2}, {sup 4}S{sub 3/2}{yields}{sup 2}D{sub 5/2}, {sup 4}S{sub 3/2}{yields}{sup 2}D{sub 3/2}(2) and {sup 4}S{sub 3/2}{yields}{sup 2}D{sub 3/2}(1), respectively, and broadband NIR emission is assigned to the transition {sup 2}D{sub 3/2}(1){yields}{sup 4}S{sub 3/2}.

  6. Note on the glass transition temperature of poly(vinylphenol)

    Kratochvíl, Jaroslav; Šturcová, Adriana; Sikora, Antonín; Dybal, Jiří

    2009-01-01

    Roč. 45, č. 6 (2009), s. 1851-1856 ISSN 0014-3057 Institutional research plan: CEZ:AV0Z40500505 Keywords : Poly(4-vinylphenol) * glass transition temperature * differential scanning calorimetry Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.310, year: 2009

  7. Temperature dependence of fluctuation time scales in spin glasses

    Kenning, Gregory G.; Bowen, J.; Sibani, Paolo

    2010-01-01

    Using a series of fast cooling protocols we have probed aging effects in the spin glass state as a function of temperature. Analyzing the logarithmic decay found at very long time scales within a simple phenomenological barrier model, leads to the extraction of the fluctuation time scale of the s...

  8. A simple method for tuning the glass transition process in inorganic phosphate glasses

    Fulchiron, Ren?; Belyamani, Imane; Otaigbe, Joshua U.; Bounor-Legar?, V?ronique

    2015-01-01

    The physical modification of glass transition temperature (Tg ) and properties of materials via blending is a common practice in industry and academia and has a large economic advantage. In this context, simple production of hitherto unattainable new inorganic glass blends from already existing glass compositions via blending raises much hope with the potential to provide new glasses with new and improved properties, that cannot be achieved with classical glass synthesis, for a plethora of ap...

  9. Thermodynamic Properties, Sorption Isotherms and Glass Transition Temperature of Cape Gooseberry (Physalis peruviana L.

    Jessica López

    2014-01-01

    Full Text Available Adsorption and desorption isotherms of fresh and dried Cape gooseberry (Physalis peruviana L. were determined at three temperatures (20, 40 and 60 °C using a gravimetric technique. The data obtained were fitted to several models including Guggenheim-Anderson- De Boer (GAB, Brunauer-Emmett-Teller (BET, Henderson, Caurie, Smith, Oswin, Halsey and Iglesias-Chirife. A non-linear least square regression analysis was used to evaluate the models. The Iglesias-Chirife model fitted best the experimental data. Isosteric heat of sorption was also determined from the equilibrium sorption data using the Clausius-Clapeyron equation and was found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy-controlled sorption process. Glass transition temperature (Tg of Cape gooseberry was also determined by differential scanning calorimetry and modelled as a function of moisture content with the Gordon-Taylor, the Roos and the Khalloufi models, which proved to be excellent tools for predicting glass transition of Cape gooseberry.

  10. Predictions of glass transition temperature for hydrogen bonding biomaterials.

    van der Sman, R G M

    2013-12-19

    We show that the glass transition of a multitude of mixtures containing hydrogen bonding materials correlates strongly with the effective number of hydroxyl groups per molecule, which are available for intermolecular hydrogen bonding. This correlation is in compliance with the topological constraint theory, wherein the intermolecular hydrogen bonds constrain the mobility of the hydrogen bonded network. The finding that the glass transition relates to hydrogen bonding rather than free volume agrees with our recent finding that there is little difference in free volume among carbohydrates and polysaccharides. For binary and ternary mixtures of sugars, polyols, or biopolymers with water, our correlation states that the glass transition temperature is linear with the inverse of the number of effective hydroxyl groups per molecule. Only for dry biopolymer/sugar or sugar/polyol mixtures do we find deviations due to nonideal mixing, imposed by microheterogeneity.

  11. Low sintering temperature glass waste forms for sequestering radioactive iodine

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  12. The effective complex permittivity stability in filled polymer nanocomposites studied above the glass transition temperature

    Elhaouzi F.

    2018-01-01

    Full Text Available The temperature effecton the dielectric response of nanocomposite at low frequencies range is reported. The investigated samples are formed by a semi-crystalline ethylene-co-butyl acrylate (EBA polymer filled with three concentrations of the dispersed conducting carbon black (CB nanoparticles. The temperature dependence of the complex permittivity has been analyzedabove the glass transition temperature of the neat polymer matrix Tg=-75°C. For all CB concentrations, the dielectric spectra follow a same trend in frequency range 100-106Hz. More interestingly, the stability of the effective complex permittivity ɛ=ɛ' -iɛ'' with the temperature range of 10-70°C is explored. While the imaginary part of the complex permittivity ɛ'' exhibits a slight decreasewith temperature, the real part ɛ' shows a significant reduction especially for high loading samples. The observed dielectric response may be related to the breakup of the three-dimensional structurenetwork formed by the aggregation of CB particles causing change at the interfaceEBA-CB.This interface is estimated bythe volume fraction of constrained polymer chain according to loss tangent data of dynamic mechanical analysis.

  13. Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

    W.-S. W. DeRieux

    2018-05-01

    Full Text Available Secondary organic aerosol (SOA accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH, and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg. We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds with molar mass less than 450 g mol−1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol−1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg∕T as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7 as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon–Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ, and the Gordon–Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS, resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI and atmospheric pressure photoionization (APPI. Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and

  14. Low-temperature bonded glass-membrane microfluidic device for in vitro organ-on-a-chip cell culture models

    Pocock, Kyall J.; Gao, Xiaofang; Wang, Chenxi; Priest, Craig; Prestidge, Clive A.; Mawatari, Kazuma; Kitamori, Takehiko; Thierry, Benjamin

    2015-12-01

    The integration of microfluidics with living biological systems has paved the way to the exciting concept of "organson- a-chip", which aims at the development of advanced in vitro models that replicate the key features of human organs. Glass based devices have long been utilised in the field of microfluidics but the integration of alternative functional elements within multi-layered glass microdevices, such as polymeric membranes, remains a challenge. To this end, we have extended a previously reported approach for the low-temperature bonding of glass devices that enables the integration of a functional polycarbonate porous membrane. The process was initially developed and optimised on specialty low-temperature bonding equipment (μTAS2001, Bondtech, Japan) and subsequently adapted to more widely accessible hot embosser units (EVG520HE Hot Embosser, EVG, Austria). The key aspect of this method is the use of low temperatures compatible with polymeric membranes. Compared to borosilicate glass bonding (650 °C) and quartz/fused silica bonding (1050 °C) processes, this method maintains the integrity and functionality of the membrane (Tg 150 °C for polycarbonate). Leak tests performed showed no damage or loss of integrity of the membrane for up to 150 hours, indicating sufficient bond strength for long term cell culture. A feasibility study confirmed the growth of dense and functional monolayers of Caco-2 cells within 5 days.

  15. Low-temperature bonding process for the fabrication of hybrid glass-membrane organ-on-a-chip devices

    Pocock, Kyall J.; Gao, Xiaofang; Wang, Chenxi; Priest, Craig; Prestidge, Clive A.; Mawatari, Kazuma; Kitamori, Takehiko; Thierry, Benjamin

    2016-10-01

    The integration of microfluidics with living biological systems has paved the way to the exciting concept of "organs-on-a-chip," which aims at the development of advanced in vitro models that replicate the key features of human organs. Glass-based devices have long been utilized in the field of microfluidics but the integration of alternative functional elements within multilayered glass microdevices, such as polymeric membranes, remains a challenge. To this end, we have extended a previously reported approach for the low-temperature bonding of glass devices that enables the integration of a functional polycarbonate porous membrane. The process was initially developed and optimized on specialty low-temperature bonding equipment (μTAS2001, Bondtech, Japan) and subsequently adapted to more widely accessible hot embosser units (EVG520HE Hot Embosser, EVG, Austria). The key aspect of this method is the use of low temperatures compatible with polymeric membranes. Compared to borosilicate glass bonding (650°C) and quartz/fused silica bonding (1050°C) processes, this method maintains the integrity and functionality of the membrane (Tg 150°C for polycarbonate). Leak tests performed showed no damage or loss of integrity of the membrane for up to 150 h, indicating sufficient bond strength for long-term cell culture. A feasibility study confirmed the growth of dense and functional monolayers of Caco-2 cells within 5 days.

  16. Investigations into the stabilization of drugs by sugar glasses : III. The influence of various high-pH buffers

    Eriksson, Jonas H C; Hinrichs, Wouter L J; de Jong, Gerhardus J; Somsen, Govert W; Frijlink, Henderik W

    PURPOSE: To study the effect of the high-pH buffers ammediol, borax, CHES, TRIS, and Tricine on the glass transition temperature of the freeze concentrated fraction (Tg') of trehalose/buffer and inulin/buffer solutions at pH 6.0 and pH 9.8. Also, the glass transition temperature (Tg) of sugar

  17. Influence of the sintering temperature in the microstructure of foam glass obtained from waste glass

    Pokorny, A.; Vicenzi, J.; Bergmann, C.P.

    2012-01-01

    In this work, foam glasses were produced from grounded soda-lime glass and a synthetic carbonate, used as a foaming agent, with a similar composition to a dolomite lime, added with different oxides (SiO 2 , Al 2 O 3 , Fe 2 O 3 , MnO 2 , Na 2 O, K 2 O, TiO 2 and P 2 O 5 ). The objective was to evaluate the influence of sintering temperature on the properties and microstructure of the obtained material. In addition, the effect of addition of the oxides in the expansion of the ceramic bodies was evaluated. The ceramic bodies were formulated with 3 weight percent of synthetic carbonate, uniaxially pressed and fired within the temperature range from 700 deg C to 950 deg C, with a heating rate of 150K/h. The technological characterization of the ceramic bodies involved the determination of the volumetric expansion and their microstructures have been characterized by optical microscopy and scanning electron microscopy. The experimental results have shown foam glass can be obtained from grounded soda-lime glass, using synthetic carbonate, with the introduction of the different oxides, as foaming agent. (author)

  18. Does Brillouin light scattering probe the primary glass transition process at temperatures well above glass transition?

    Voudouris, P; Gomopoulos, N; Le Grand, A; Hadjichristidis, N; Floudas, G; Ediger, M D; Fytas, G

    2010-02-21

    The primary alpha-relaxation time (tau(alpha)) for molecular and polymeric glass formers probed by dielectric spectroscopy and two light scattering techniques (depolarized light scattering and photon correlation spectroscopy) relates to the decay of the torsional autocorrelation function computed by molecular dynamics simulation. It is well known that Brillouin light scattering spectroscopy (BLS) operating in gigahertz frequencies probes a fast (10-100 ps) relaxation of the longitudinal modulus M*. The characteristic relaxation time, irrespective of the fitting procedure, is faster than the alpha-relaxation which obeys the non-Arrhenius Vogel-Fulcher-Tammann equation. Albeit, this has been noticed, it remains a puzzling finding in glass forming systems. The available knowledge is based only on temperature dependent BLS experiments performed, however, at a single wave vector (frequency). Using a new BLS spectrometer, we studied the phonon dispersion at gigahertz frequencies in molecular [o-terphenyl (OTP)] and polymeric [polyisoprene (PI) and polypropylene (PP)] glass formers. We found that the hypersonic dispersion does relate to the glass transition dynamics but the disparity between the BLS-relaxation times and tau(alpha) is system dependent. In PI and PP, the former is more than one order of magnitude faster than tau(alpha), whereas the two relaxation times become comparable in the case of OTP. The difference between the two relaxation times appears to relate to the "breadth" of the relaxation time distribution function. In OTP the alpha-relaxation process assumes a virtually single exponential decay at high temperatures well above the glass transition temperature, in clear contrast with the case of the amorphous bulk polymers.

  19. Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

    Eloi, J-C; Okuda, M; Jones, S E Ward; Schwarzacher, W

    2013-06-18

    For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  20. Structure, glass transition temperature and spectroscopic properties of 10Li2O-xP2O5-(89-x)TeO2-1CuO (5≤x≤25 mol%) glass system.

    Upender, G; Babu, J Chinna; Mouli, V Chandra

    2012-04-01

    X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), infrared (IR), Raman, electron paramagnetic resonance (EPR) and optical absorption studies on 10Li2O-xP2O5-(89-x)TeO2-1CuO glasses (where x=5, 10, 15, 20 and 25 mol%) have been carried out. The amorphous nature of the glasses was confirmed using XRD and FESEM measurements. The glass transition temperature (Tg) of glass samples have been estimated from DSC traces and found that the Tg increases with increasing P2O5 content. Both the IR and Raman studies have been showed that the present glass system consists of [TeO3], [TeO4], [PO3] and [PO4] units. The spin-Hamiltonian parameters such as g∥, g⊥, and A∥ have been determined from EPR spectra and it was found that the Cu2+ ion is present in tetragonal distorted octahedral site with [Formula: see text] as the ground state. Bonding parameters and bonding symmetry of Cu2+ ions have been calculated by correlating EPR and optical data and were found to be composition dependent. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. A novel approach for analyzing glass-transition temperature vs. composition patterns: application to pharmaceutical compound+polymer systems.

    Kalogeras, Ioannis M

    2011-04-18

    In medicine, polymer-based materials are commonly used as excipients of poorly water-soluble drugs. The success of the encapsulation, as well as the physicochemical stability of the products, is often reflected on their glass transition temperature (T(g)) vs. composition (w) dependencies. The shape of the T(g)(w) patterns is critically influenced by polymer's molecular mass, drug molecule's shape and molecular volume, the type and degree of shielding of hydrogen-bonding capable functional groups, as well as aspects of the preparation process. By altering mixture's T(g) the amorphous solid form of the active ingredient may be retained at ambient or body temperatures, with concomitant improvements in handling, solubility, dissolution rate and oral bioavailability. Given the importance of the problem, the glass transitions observed in pharmaceutical mixtures have been extensively analyzed, aiming to appraise the state of mixing and intermolecular interactions. Here, accumulated experimental information on related systems is re-evaluated and comparably discussed under the light of a more effective and system-inclusive T(g)(w) equation. The present analysis indicates that free volume modifications and conformational changes of the macromolecular chains dominate, over enthalpic effects of mixing, in determining thermal characteristics and crystallization inhibition/retardation. Moreover, hydrogen-bonding and ion-dipole heterocontacts--although favorable of a higher degree of mixing--appear less significant compared to the steric hindrances and the antiplasticization proffered by the higher viscosity component. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Deducting the temperature dependence of the structural relaxation time in equilibrium far below the nominal Tg by aging the decoupled conductivity relaxation to equilibrium.

    Wojnarowska, Z; Ngai, K L; Paluch, M

    2014-05-07

    Using broadband dielectric spectroscopy we investigate the changes in the conductivity relaxation times τσ observed during the physical aging of the protic ionic conductor carvedilol dihydrogen phosphate (CP). Due to the large decoupling of ion diffusion from host molecule reorientation, the ion conductivity relaxation time τσ(Tage,tage) can be directly measured at temperatures Tage below Tg for exceedingly long aging times tage till τσ(Tage,tage) has reached the equilibrium value τσ(eq)(Tage). The dependence of τσ(Tage,tage) on tage is well described by the stretched exponential function, τσ(Tage, tage) = Aexp[-((tage)/(τage(Tage)))(β)] + τσ(eq)(Tage), where β is a constant and τage(Tage) can be taken as the structural α-relaxation time of the equilibrium liquid at T = Tage. The value of τσ(eq)(Tage) obtained after 63 days long annealing of CP, deviates from the Vogel-Fulcher-Tammann-Hesse (VFTHσ) dependence of τσ(T) determined from data taken above Tg and extrapolated down to Tage. Concurrently, τage(Tage) also deviates from the Vogel-Fulcher-Tammann-Hesse (VFTHα) dependence. The results help to answer the longstanding question of whether the VFTH dependence of τσ(T) as well as the structural α-relaxation time τα(T) holds or not in the equilibrium liquid state far below Tg.

  3. Measurement of the volatility and glass transition temperatures of glasses produced during the DWPF startup test program

    Marra, J.C.; Harbour, J.R.

    1995-01-01

    The Defense Waste Processing Facility (DWPF) will immobilize high-level radioactive waste currently stored in underground tanks at the Savannah River Site by incorporating the waste into a glass matrix. The molten waste glass will be poured into stainless steel canisters which will be welded shut to produce the final waste form. One specification requires that any volatiles produced as a result of accidentally heating the waste glass to the glass transition temperature be identified. Glass samples from five melter campaigns, run as part of the DWPF Startup Test Program, were analyzed to determine glass transition temperatures and to examine the volatilization (by weight loss). Glass transition temperatures (T g ) for the glasses, determined by differential scanning calorimetry (DSC), ranged between 445 C and 474 C. Thermogravimetric analysis (TGA) scans showed that no overall weight loss occurred in any of the glass samples when heated to 500 C. Therefore, no volatility will occur in the final glass product when heated up to 500 C

  4. Raman scattering boson peak and differential scanning calorimetry studies of the glass transition in tellurium-zinc oxide glasses.

    Stavrou, E; Tsiantos, C; Tsopouridou, R D; Kripotou, S; Kontos, A G; Raptis, C; Capoen, B; Bouazaoui, M; Turrell, S; Khatir, S

    2010-05-19

    Raman scattering and differential scanning calorimetry (DSC) measurements have been carried out on four mixed tellurium-zinc oxide (TeO(2))(1 - x)(ZnO)(x) (x = 0.1, 0.2, 0.3, 0.4) glasses under variable temperature, with particular attention being given to the respective glass transition region. From the DSC measurements, the glass transition temperature T(g) has been determined for each glass, showing a monotonous decrease of T(g) with increasing ZnO content. The Raman study is focused on the low-frequency band of the glasses, the so-called boson peak (BP), whose frequency undergoes an abrupt decrease at a temperature T(d) very close to the respective T(g) values obtained by DSC. These results show that the BP is highly sensitive to dynamical effects over the glass transition and provides a means for an equally reliable (to DSC) determination of T(g) in tellurite glasses and other network glasses. The discontinuous temperature dependence of the BP frequency at the glass transition, along with the absence of such a behaviour by the high-frequency Raman bands (due to local atomic vibrations), indicates that marked changes of the medium range order (MRO) occur at T(g) and confirms the correlation between the BP and the MRO of glasses.

  5. Processing of high-temperature simulated waste glass in a continuous ceramic melter

    Barnes, S.M.; Brouns, R.A.; Hanson, M.S.

    1980-01-01

    Recent operations have demonstrated that high-melting-point glasses and glass-ceramics can be successfully processed in joule-heated, ceramic-lined melters with minor modifications to the existing technology. Over 500 kg of simulated waste glasses have been processed at temperatures up to 1410 0 C. The processability of the two high-temperature waste forms tested is similar to existing borosilicate waste glasses. High-temperature waste glass formulations produced in the bench-scale melter exhibit quality comparing favorably to standard waste glass formulations

  6. Temperature Effects on Aluminoborosilicate Glass and Melt Structure

    Wu, J.; Stebbins, J. F.

    2008-12-01

    Quantitative determination of the atomic-scale structure of multi-component oxide melts, and the effects of temperature on them, is a complex problem. Ca- and Na- aluminoborosilicates are especially interesting, not only because of their major role in widespread technical applications (flat-panel computer displays, fiber composites, etc.), but because the coordination environments of two of their main network cations (Al3+ and B3+) change markedly with composition and temperature is ways that may in part be analogous to processes in silicate melts at high pressures in the Earth. Here we examine a series of such glasses with different cooling rates, chosen to evaluate the role modifier cation field strength (Ca2+ vs. Na+) and of non-bridging oxygen (NBO) content. To explore the effects of fictive temperature, fast quenched and annealed samples were compared. We have used B-11 and Al-27 MAS NMR to measure the different B and Al coordinations and calculated the contents of non-bridging oxygens (NBO). Lower cooling rates increase the fraction of [4]B species in all compositions. The conversion of [3]B to [4]B is also expected to convert NBO to bridging oxygens, which should affect thermodynamic properties such as configurational entropy and configurational heat capacity. For four compositions with widely varying compositions and initial NBO contents, analysis of the speciation changes with the same, simple reaction [3]B = [4]B + NBO yields similar enthalpy values of 25±7 kJ/mol. B-11 triple quantum MAS NMR allows as well the proportions of [3]B boroxol ring and non-ring sites to be determined, and reveals more [3]B boroxol ring structures present in annealed (lower temperature) glasses. In situ, high-temperature MAS NMR spectra have been collected on one of the Na-aluminoborosilicate and on a sodium borate glass at 14.1 T. The exchange of boron between the 3- and 4-coordinated sites is clearly observed well above the glass transition temperatures, confirming the

  7. The structure of phosphate and borosilicate glasses and their structural evolution at high temperatures as studied with solid state NMR spectroscopy: Phase separation, crystallisation and dynamic species exchange

    Wegner, S.; Van Wullen, L.; Tricot, G.; Tricot, G.

    2010-01-01

    In this contribution we present an in-depth study of the network structure of different phosphate based and borosilicate glasses and its evolution at high temperatures. Employing a range of advanced solid state NMR methodologies, complemented by the results of XPS, the structural motifs on short and intermediate length scales are identified. For the phosphate based glasses, at temperatures above the glass transition temperature Tg, structural relaxation processes and the devitrification of the glasses were monitored in situ employing MAS NMR spectroscopy and X-ray diffraction. Dynamic species exchange involving rapid P-O-P and P-O-Al bond breaking and reforming was observed employing in situ 27 Al and 31 P MAS NMR spectroscopy and could be linked to viscous flow. For the borosilicate glasses, an atomic scale investigation of the phase separation processes was possible in a combined effort of ex situ NMR studies on glass samples with different thermal histories and in situ NMR studies using high temperature MAS NMR spectroscopy including 11 B MAS, 29 Si MAS and in situ 29 Si{ 11 B} REAPDOR NMR spectroscopy. (authors)

  8. Development of DMBZ-15 High-Glass-Transition-Temperature Polyimides as PMR-15 Replacements Given R&D 100 Award

    Chuang, Kathy

    2004-01-01

    PMR-15, a high-temperature polyimide developed in the mid-1970s at the NASA Lewis Research Center,1 offers the combination of low cost, easy processing, and good high-temperature performance and stability. It has been recognized as the leading polymer matrix resin for carbon-fiber-reinforced composites used in aircraft engine components. The state-of-the-art PMR-15 polyimide composite has a glass-transition temperature (Tg) of 348 C (658 F). Since composite materials must be used at temperatures well below their glass-transition temperature, the long-term use temperatures of PMR-15 composites can be no higher than 288 C (550 F). In addition, PMR-15 is made from methylene dianiline (MDA), a known liver toxin. Concerns about the safety of workers exposed to MDA during the fabrication of PMR-15 components and about the environmental impact of PMR-15 waste disposal have led to the industry-wide implementation of special handling procedures to minimize the health risks associated with this material. These procedures have increased manufacturing and maintenance costs significantly and have limited the use of PMR-15 in commercial aircraft engine components.

  9. Thermal properties of superconducting bulk metallic glasses at ultralow temperatures

    Rothfuss, Daniel Simon

    2013-01-01

    This thesis describes the first investigation of thermal properties of superconducting bulk metallic glasses in the range between 6mK and 300K. Measuring the thermal conductivity provides the possibility to probe the fundamental interactions governing the heat flow in solids. At ultralow temperatures a novel contactless measuring technique was used, which is based on optical heating and paramagnetic temperature sensors that are read out by a SQUID magnetometer. Below the critical temperature T c the results can be described by resonant scattering of phonons by tunneling systems. Above T c the phonon contribution to the thermal conductivity can be described successfully within a model considering not only electrons and phonons but also localized modes as scattering centres. To expand the accessible temperature range for experiments an adiabatic nuclear demagnetization refrigerator was set up. For measuring the base temperature a novel noise thermometer was developed which enables continuous measuring of the temperature in this temperature range for the first time. Therefore the magnetic Johnson noise of a massive copper cylinder is simultaneously monitored by two SQUID magnetometers. A subsequent cross-correlation suppresses the amplifier noise by more than one order of magnitude. The thermometer was characterized between 42μK and 0.8K showing no deviation from the expected linear behaviour between the power spectral density of the thermal noise and the temperature.

  10. Self-bonding in an amorphous polymer below the glass transition

    Boiko, Yuri M.; Bach, Anders; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    was found to develop with (th)1/2 at Th = Tg-bulk - 33 °C (where Tg-bulk is the glass-transition temperature of the bulk sample), and log G was found to develop with 1/Th at Tg-bulk - 43 °C Th Tg-bulk - 23 °C. The smallest measured value of G = 1.4 J/m2 was at least one order of magnitude larger than...

  11. In Plane Loaded Glass Panes in Façades, Temperature Loads in Fixed Bonded Glass Panes

    Huveners, E.M.P.; Herwijnen, van F.; Soetens, F.; Hofmeyer, H.; Vitkala, J.

    2005-01-01

    The author discusses the use of glass panes as transparent stability elements in vertical façade structures subjected to in-plane loads including temperature loads. In the present façade architecture, glass is normally used non-structural. The only mechanical requirement is to resist transversal

  12. Effect of In-situ Cure on Measurement of Glass Transition Temperatures in High-temperature Thermosetting Polymers

    2015-01-01

    TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING POLYMERS 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...illustrated the difficulties inherent in measurement of the glass transition temperature of this high-temperature thermosetting polymer via dynamic...copyright protection in the United States. EFFECT OF IN-SITU CURE ON MEASUREMENT OF GLASS TRANSITION TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING

  13. Glass Transitions in a Monatomic Liquid with Two Glassy States

    Gordon, Andrew; Giovambattista, Nicolas

    2014-04-01

    We perform out-of-equilibrium molecular dynamics simulations of a monatomic liquid that exhibits liquid and glass polymorphism, with two distinct glasses, low- (LDA) and high-density (HDA) amorphous solids. By performing isobaric heating simulations of LDA and HDA at different pressures, we determine (a) the glass transition temperature of LDA and HDA, TgLDA(P) and TgHDA(P), as well as (b) the corresponding glass-glass transformation temperatures, TLDA-HDA(P) and THDA-LDA(P). It is found that TgLDA(P) is anomalous; i.e., it decreases with increasing pressure, while TgHDA(P) increases with increasing pressure. Interestingly, the TgLDA(P) and TLDA-HDA(P) loci, as well as the TgHDA(P) and THDA-LDA(P) loci, constitute smooth single lines in the P -T plane, suggesting that heating-induced glass-glass and glass transitions are related. We discuss the present results in the context of water experiments and simulations.

  14. Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition Time of Polydextrose.

    Buehler, Martin G; Kindle, Michael L; Carter, Brady P

    2015-06-01

    Dielectric relaxation spectroscopy was used to characterize the glass transition time, tg , of polydextrose, where the glass transition temperature, Tg , and water activity, aw (relative humidity), were held constant during polydextrose relaxation. The tg was determined from a shift in the peak frequency of the imaginary capacitance spectrum with time. It was found that when the peak frequency reaches 30 mHz, polydextrose undergoes glass transition. Glass transition time, tg , is the time for polydextrose to undergo glass transition at a specific Tg and aw . Results lead to a modified state diagram, where Tg is depressed with increasing aw . This curve forms a boundary: (a) below the boundary, polydextrose does not undergo glass transition and (b) above the boundary, polydextrose rapidly undergoes glass transition. As the boundary curve is specified by a tg value, it can assist in the selection of storage conditions. An important point on the boundary curve is at aw = 0, where Tg0 = 115 °C. The methodology can also be used to calculate the stress-relaxation viscosity of polydextrose as a function of Tg and aw , which is important when characterizing the flow properties of polydextrose initially in powder form. © 2015 Institute of Food Technologists®

  15. Effects of dynamic heterogeneity and density scaling of molecular dynamics on the relationship among thermodynamic coefficients at the glass transition

    Koperwas, K.; Grzybowski, A.; Grzybowska, K.; Wojnarowska, Z.; Paluch, M.

    2015-01-01

    In this paper, we define and experimentally verify thermodynamic characteristics of the liquid-glass transition, taking into account a kinetic origin of the process. Using the density scaling law and the four-point measure of the dynamic heterogeneity of molecular dynamics of glass forming liquids, we investigate contributions of enthalpy, temperature, and density fluctuations to spatially heterogeneous molecular dynamics at the liquid-glass transition, finding an equation for the pressure coefficient of the glass transition temperature, dTg/dp. This equation combined with our previous formula for dTg/dp, derived solely from the density scaling criterion, implies a relationship among thermodynamic coefficients at Tg. Since this relationship and both the equations for dTg/dp are very well validated using experimental data at Tg, they are promising alternatives to the classical Prigogine-Defay ratio and both the Ehrenfest equations in case of the liquid-glass transition

  16. Effects of dynamic heterogeneity and density scaling of molecular dynamics on the relationship among thermodynamic coefficients at the glass transition

    Koperwas, K., E-mail: kkoperwas@us.edu.pl; Grzybowski, A.; Grzybowska, K.; Wojnarowska, Z.; Paluch, M. [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1A, 41-500 Chorzow (Poland)

    2015-07-14

    In this paper, we define and experimentally verify thermodynamic characteristics of the liquid-glass transition, taking into account a kinetic origin of the process. Using the density scaling law and the four-point measure of the dynamic heterogeneity of molecular dynamics of glass forming liquids, we investigate contributions of enthalpy, temperature, and density fluctuations to spatially heterogeneous molecular dynamics at the liquid-glass transition, finding an equation for the pressure coefficient of the glass transition temperature, dTg/dp. This equation combined with our previous formula for dTg/dp, derived solely from the density scaling criterion, implies a relationship among thermodynamic coefficients at Tg. Since this relationship and both the equations for dTg/dp are very well validated using experimental data at Tg, they are promising alternatives to the classical Prigogine-Defay ratio and both the Ehrenfest equations in case of the liquid-glass transition.

  17. Temperature measurement of flat glass edge during grinding and effect of wheel and workpiece speeds

    Moussa, Tala; Garnier, Bertrand; Peerhossaini, Hassan

    2017-01-01

    Flat glass temperature at the vicinity of the grinding wheel during grinding can become very high and reach that of the glass transition (typically around 550–600 °C). In such cases, the mechanical strength of glass is greatly affected and the grinding process cannot be carried out properly. Hence, thermal phenomena must be managed by adjusting the machining parameters to avoid overheating. For this purpose, it is very important to be able to measure the glass temperature, especially at the grinding interface. However, measuring the interfacial glass temperature is difficult and none of the existing methods for metal grinding is adequate for glass grinding. This work shows a novel temperature method that uses constantan and copper strips on both sides of the glass plates; thermoelectric contact being provided by the metallic binder of diamond particles in the grinding wheel. This new technique allows the measurement of the glass edge temperature during the wheel displacement around the glass plate. The experimental results show an average glass edge temperature between 300 and 600 °C depending on the value of the machining parameters such as work speed, wheel speed, depth of cut and water coolant flow rate. As this new thermal instrumentation is rather intrusive, glass temperature biases were analysed using a 3D heat transfer model with a moving source. Model computations performed using finite elements show that the temperature biases are less than 70 °C, which is smaller than the standard deviation of the glass edge temperatures measured during grinding. (paper)

  18. Reorientational dynamics in molecular liquids as revealed by dynamic light scattering: from boiling point to glass transition temperature.

    Schmidtke, B; Petzold, N; Kahlau, R; Rössler, E A

    2013-08-28

    We determine the reorientational correlation time τ of a series of molecular liquids by performing depolarized light scattering experiments (double monochromator, Fabry-Perot interferometry, and photon correlation spectroscopy). Correlation times in the range 10(-12) s-100 s are compiled, i.e., the full temperature interval between the boiling point and the glass transition temperature T(g) is covered. We focus on low-T(g) liquids for which the high-temperature limit τ ≅ 10(-12) s is easily accessed by standard spectroscopic equipment (up to 440 K). Regarding the temperature dependence three interpolation formulae of τ(T) with three parameters each are tested: (i) Vogel-Fulcher-Tammann equation, (ii) the approach recently discussed by Mauro et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 19780 (2009)], and (iii) our approach decomposing the activation energy E(T) in a constant high temperature value E∞ and a "cooperative part" E(coop)(T) depending exponentially on temperature [Schmidtke et al., Phys. Rev. E 86, 041507 (2012)]. On the basis of the present data, approaches (i) and (ii) are insufficient as they do not provide the correct crossover to the high-temperature Arrhenius law clearly identified in the experimental data while approach (iii) reproduces the salient features of τ(T). It allows to discuss the temperature dependence of the liquid's dynamics in terms of a E(coop)(T)/E∞ vs. T/E∞ plot and suggests that E∞ controls the energy scale of the glass transition phenomenon.

  19. Environmental effects on fatigue of alkaline earth aluminosilicate glass with varying fictive temperature

    Striepe, Simon; Deubener, Joachim; Smedskjær, Morten Mattrup

    2013-01-01

    The influence of relative humidity on microhardness, stress intensity, crack resistance, and sub-critical crack growth of an alkaline earth aluminosilicate glass has been studied by Vickers indentation. Quenched and annealed glasses with a wide range of fictive temperatures (ΔTf ≈ 130 K) are comp......The influence of relative humidity on microhardness, stress intensity, crack resistance, and sub-critical crack growth of an alkaline earth aluminosilicate glass has been studied by Vickers indentation. Quenched and annealed glasses with a wide range of fictive temperatures (ΔTf ≈ 130 K....... The glasses with lower fictive temperature exhibit a larger change in the micromechanical properties when comparing wet and dry conditions. Finally, it is found that sub-critical crack growth is larger in the low fictive temperature glasses, indicating a diminished resistance against fatigue and stress...

  20. Unified approach for determining the enthalpic fictive temperature of glasses with arbitrary thermal history

    Guo, Xiaoju; Potuzak, M.; Mauro, J. C.

    2011-01-01

    We propose a unified routine to determine the enthalpic fictive temperature of a glass with arbitrary thermal history under isobaric conditions. The technique is validated both experimentally and numerically using a novel approach for modeling of glass relaxation behavior. The technique is applic......We propose a unified routine to determine the enthalpic fictive temperature of a glass with arbitrary thermal history under isobaric conditions. The technique is validated both experimentally and numerically using a novel approach for modeling of glass relaxation behavior. The technique...... is applicable to glasses of any thermal history, as proved through a series of numerical simulations where the enthalpic fictive temperature is precisely known within the model. Also, we demonstrate that the enthalpic fictive temperature of a glass can be determined at any calorimetric scan rate in excellent...

  1. Alternating copolymerization of propylene oxide with biorenewable terpene-based cyclic anhydrides: a sustainable route to aliphatic polyesters with high glass transition temperatures.

    Van Zee, Nathan J; Coates, Geoffrey W

    2015-02-23

    The alternating copolymerization of propylene oxide with terpene-based cyclic anhydrides catalyzed by chromium, cobalt, and aluminum salen complexes is reported. The use of the Diels-Alder adduct of α-terpinene and maleic anhydride as the cyclic anhydride comonomer results in amorphous polyesters that exhibit glass transition temperatures (Tg ) of up to 109 °C. The polymerization conditions and choice of catalyst have a dramatic impact on the molecular weight distribution, the relative stereochemistry of the diester units along the polymer chain, and ultimately the Tg of the resulting polymer. The aluminum salen complex exhibits exceptional selectivity for copolymerization without transesterification or epimerization side reactions. The resulting polyesters are highly alternating and have high molecular weights and narrow polydispersities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. PENGARUH SORPSI AIR DAN SUHU TRANSISI GELAS TERHADAP LAJU PENCOKLATAN NON-ENZIMATIS PADA PANGAN MODEL [The Effect of Water Sorption and Glass Transition Temperature on Non-Enzymatic Browning Reaction of Food Models

    Dede R Adawiyah1

    2005-12-01

    Full Text Available This research was aimer/ to study the extend of non enzymatic browning reaction in food models containing the mixture of tapioca starch, casein, sucrose and oh at different moisture contents (2.55%, 5.26%, 7.54%, 15.20%. 15.93% and 23.99% and storage temperatures (30, 55 and 700C. The non-enzymatic browning reaction was detected from brown color intensity measured by spechtrophotometer and colorimetric methods. The non-enzymatic browning reaction or food model follow pseudo-zero order reaction, suggesting that browning reaction occurred at moisture content above monolayer zone. T-Tg (T storage - Tg prediction and reaction rate constant (k plots showed that browning reaction occurred at temperature around glass transition and increased significantly at 150 above Tg of casein. Tapioca starch in the food model was under glassy condition. The mobility of substrate increased and diffused at amorphous matrix.

  3. Temperature-stress phase diagram of strain glass Ti48.5Ni51.5

    Wang, Y.; Ren, X.; Otsuka, K.; Saxena, A.

    2008-01-01

    The temperature and stress dependence of the properties of a recently discovered strain glass Ti 48.5 Ni 51.5 , which is a glass of frozen local lattice strains, was investigated systematically. It was found that the ideal freezing temperature (T 0 ) of the strain glass decreases with increasing stress. When the stress exceeds a critical value σ c (T), the pseudo-B2 strain glass transforms into B19' martensite. However, the stress-strain behavior associated with such a stress-induced transition showed a crossover at a crossover temperature T CR , which is ∼20 K below T 0 . Above T CR , the sample showed superelastic behavior; however, below T CR , the sample demonstrated plastic behavior. More interestingly, the σ c vs. temperature relation for unfrozen strain glass obeys the Clausius-Clapyeron relationship, whereas that for frozen strain glass disobeys this universal thermodynamic law. A phenomenological explanation is provided for all the phenomena observed, and it is shown that all the anomalous effects come from the broken ergodicity of the glass system and a temperature-dependent relative stability of the martensitic phase. Based on experimental observations, a temperature-stress phase diagram is constructed for this strain glass, which may serve as a guide map for understanding and predicting the properties of strain glass

  4. Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers

    Bouhadja, M.; Jakse, N.; Pasturel, A.

    2014-01-01

    Molecular dynamics simulations are used to study the structural and dynamic properties of calcium aluminosilicate, (CaO-Al 2 O 3 ) 1−x (SiO 2 ) x , glass formers along three joins, namely, R = 1, 1.57, and 3, in which the silica content x can vary from 0 to 1. For all compositions, we determined the glass-transition temperature, the abundances of the non-bridging oxygen, triclusters, and AlO 5 structural units, as well as the fragility from the temperature evolution of the α-relaxation times. We clearly evidence the role played by the non-bridging oxygen linked either to Al atoms or Si atoms in the evolution of the glass-transition temperature as well as of the fragility as a function of silica content along the three joins

  5. Density crosslink study of gamma irradiated LDPE predicted by gel-fraction, swelling and glass transition temperature characterization

    Cardoso, Elisabeth C.L.; Scagliusi, Sandra R.; Moraes, Guilherme F.; Ono, Lilian S.; Parra, D.F.; Lugao, Ademar B.

    2011-01-01

    Experimental results showed that the crosslink density of polymeric stocks may be predicted from values of gel content based on the reactive portion of the stocks, that is, exclusive of plasticizers and fillers. Where entanglements may be neglected, the crosslink density is directly proportional to functions of the gel and sol contents. In order to predict the behavior of carbon-chain polymers exposed to ionizing radiation, an empirical rule can be used. According to this rule, polymers containing a hydrogen atom at each carbon atom predominantly undergo crosslinking. During irradiation, chain scission occurs simultaneously and competitively with crosslinking, the end result being determined by the ratio of the yields of the two reactions. The ratio of crosslinking to scission depends basically on factors including total irradiation dose, dose rate and the presence of oxygen. The glass transition temperature (Tg), temperature below which the polymer segments do not have sufficient energy to move past one another, marks the onset of segmental mobility for a polymer. Properties such as melt index, melt strength, crystallinity, glass transition, gel fraction, swelling ratio and elasticity modulus were assessed in LDPE (2.6 g.10 min -1 melt index) gamma irradiated within a 10, 15, 20 and 30 kGy and results obtained were further discussed prior conclusion. (author)

  6. Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

    Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

    2015-01-01

    Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers.

  7. Formulation and Characterization of Waste Glasses with Varying Processing Temperature

    Kim, Dong-Sang; Schweiger, M. J.; Rodriguez, Carmen P.; Lepry, William C.; Lang, Jesse B.; Crum, Jarrod V.; Vienna, John D.; Johnson, Fabienne; Marra, James C.; Peeler, David K.

    2011-10-17

    This report documents the preliminary results of glass formulation and characterization accomplished within the finished scope of the EM-31 technology development tasks for WP-4 and WP-5, including WP-4.1.2: Glass Formulation for Next Generation Melter, WP-5.1.2.3: Systematic Glass Studies, and WP-5.1.2.4: Glass Formulation for Specific Wastes. This report also presents the suggested studies for eventual restart of these tasks. The initial glass formulation efforts for the cold crucible induction melter (CCIM), operating at {approx}1200 C, with selected HLW (AZ-101) and LAW (AN-105) successfully developed glasses with significant increase of waste loading compared to that is likely to be achieved based on expected reference WTP formulations. Three glasses formulated for AZ-101HLW and one glass for AN-105 LAW were selected for the initial CCIM demonstration melter tests. Melter tests were not performed within the finished scope of the WP-4.1.2 task. Glass formulations for CCIM were expanded to cover additional HLWs that have high potential to successfully demonstrate the unique advantages of the CCIM technologies based on projected composition of Hanford wastes. However, only the preliminary scoping tests were completed with selected wastes within the finished scope. Advanced glass formulations for the reference WTP melter, operating at {approx}1200 C, were initiated with selected specific wastes to determine the estimated maximum waste loading. The incomplete results from these initial formulation efforts are summarized. For systematic glass studies, a test matrix of 32 high-aluminum glasses was completed based on a new method developed in this study.

  8. Formulation and Characterization of Waste Glasses with Varying Processing Temperature

    Kim, Dong-Sang; Schweiger, M.J.; Rodriguez, Carmen P.; Lepry, William C.; Lang, Jesse B.; Crum, Jarrod V.; Vienna, John D.; Johnson, Fabienne; Marra, James C.; Peeler, David K.

    2011-01-01

    This report documents the preliminary results of glass formulation and characterization accomplished within the finished scope of the EM-31 technology development tasks for WP-4 and WP-5, including WP-4.1.2: Glass Formulation for Next Generation Melter, WP-5.1.2.3: Systematic Glass Studies, and WP-5.1.2.4: Glass Formulation for Specific Wastes. This report also presents the suggested studies for eventual restart of these tasks. The initial glass formulation efforts for the cold crucible induction melter (CCIM), operating at ∼1200 C, with selected HLW (AZ-101) and LAW (AN-105) successfully developed glasses with significant increase of waste loading compared to that is likely to be achieved based on expected reference WTP formulations. Three glasses formulated for AZ-101HLW and one glass for AN-105 LAW were selected for the initial CCIM demonstration melter tests. Melter tests were not performed within the finished scope of the WP-4.1.2 task. Glass formulations for CCIM were expanded to cover additional HLWs that have high potential to successfully demonstrate the unique advantages of the CCIM technologies based on projected composition of Hanford wastes. However, only the preliminary scoping tests were completed with selected wastes within the finished scope. Advanced glass formulations for the reference WTP melter, operating at ∼1200 C, were initiated with selected specific wastes to determine the estimated maximum waste loading. The incomplete results from these initial formulation efforts are summarized. For systematic glass studies, a test matrix of 32 high-aluminum glasses was completed based on a new method developed in this study.

  9. Liquidus temperature and chemical durability of selected glasses to immobilize rare earth oxides waste

    Mohd Fadzil, Syazwani, E-mail: mfsyazwani86@postech.ac.kr [Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, 790784 Pohang, Gyeongbuk (Korea, Republic of); School of Applied Physics, Faculty of Science and Technology, The National University of Malaysia, 43650 Bandar Baru Bangi, Selangor (Malaysia); Hrma, Pavel [Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, 790784 Pohang, Gyeongbuk (Korea, Republic of); Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA (United States); Schweiger, Michael J.; Riley, Brian J. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA (United States)

    2015-10-15

    Pyroprocessing is are processing method for managing and reusing used nuclear fuel (UNF) by dissolving it in an electrorefiner with a molten alkali or alkaline earth chloride salt mixture while avoiding wet reprocessing. Pyroprocessing UNF with a LiCl–KCl eutectic salt releases the fission products from the fuel and generates a variety of metallic and salt-based species, including rare earth (RE) chlorides. If the RE-chlorides are converted to oxides, borosilicate glass is a prime candidate for their immobilization because of its durability and ability to dissolve almost any RE waste component into the glass matrix at high loadings. Crystallization that occurs in waste glasses as the waste loading increases may complicate glass processing and affect the product quality. This work compares three types of borosilicate glasses in terms of liquidus temperature (T{sub L}): the International Simple Glass designed by the International Working Group, sodium borosilicate glass developed by Korea Hydro and Nuclear Power, and the lanthanide aluminoborosilicate (LABS) glass established in the United States. The LABS glass allows the highest waste loadings (over 50 mass% RE{sub 2}O{sub 3}) while possessing an acceptable chemical durability. - Highlights: • We investigated crystallization in borosilicate glasses containing rare earth oxides. • New crystallinity and durability data are shown for glasses proposed in the literature. • Both liquidus temperature and chemical durability increased as the waste loading increased.

  10. Network structure and thermal stability study of high temperature seal glass

    Lu, K.; Mahapatra, M. K.

    2008-10-01

    High temperature seal glass has stringent requirement on glass thermal stability, which is dictated by glass network structures. In this study, a SrO-La2O3-Al2O3-B2O3-SiO2 based glass system was studied using nuclear magnetic resonance, Raman spectroscopy, and x-ray diffraction for solid oxide cell application purpose. Glass structural unit neighboring environment and local ordering were evaluated. Glass network connectivity as well as silicon and boron glass former coordination were calculated for different B2O3:SiO2 ratios. Thermal stability of the borosilicate glasses was studied after thermal treatment at 850 °C. The study shows that high B2O3 content induces BO4 and SiO4 structural unit ordering, increases glass localized inhomogeneity, decreases glass network connectivity, and causes devitrification. Glass modifiers interact with either silicon- or boron-containing structural units and form different devitrified phases at different B2O3:SiO2 ratios. B2O3-free glass shows the best thermal stability among the studied compositions, remaining stable after thermal treatment for 200 h at 850 °C.

  11. First principles process-product models for vitrification of nuclear waste: Relationship of glass composition to glass viscosity, resistivity, liquidus temperature, and durability

    Jantzen, C.M.

    1991-01-01

    Borosilicate glasses will be used in the USA and in Europe to immobilize radioactive high level liquid wastes (HLLW) for ultimate geologic disposal. Process and product quality models based on glass composition simplify the fabrication of the borosilicate glass while ensuring glass processability and quality. The process model for glass viscosity is based on a relationship between the glass composition and its structural polymerization. The relationship between glass viscosity and electrical resistivity is also shown to relate to glass polymerization. The process model for glass liquidus temperature calculates the solubility of the liquidus phases based on the free energies of formation of the precipitating species. The durability product quality model is based on the calculation of the thermodynamic hydration free energy from the glass composition

  12. Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition

    Mattern, N.; Hermann, H.; Roth, S.

    2003-01-01

    The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows...... the Debye theory up to the glass transition with a Debye temperature theta=296 K. Above the glass transition temperature T-g, the temperature dependence of S(q) is altered, pointing to a continuous development of structural changes in the liquid with temperature. The atomic pair correlation functions g......(r) indicate changes in short-range-order parameters of the first and the second neighborhood with temperature. The temperature dependence of structural parameters is different in glass and in supercooled liquid, with a continuous behavior through the glass transition. The nearest-neighbor distance decreases...

  13. Structural and thermal properties of vanadium tellurite glasses

    Kaur, Rajinder; Kaur, Ramandeep; Khanna, Atul; González, Fernando

    2018-04-01

    V2O5-TeO2 glasses containing 10 to 50 mol% V2O5 were prepared by melt quenching and characterized by X-ray diffraction (XRD), density, Differential Scanning Calorimetry (DSC) and Raman studies.XRD confirmed the amorphous nature of vanadium tellurite samples. The density of the glasses decreases and the molar volume increases on increasing the concentration of V2O5. The thermal properties, such as glass transition temperature Tg, crystallization temperature Tc, and the melting temperature Tm were measured. Tg decreases from a value of 288°C to 232°C. The changes in Tg were correlated with the number of bonds per unit volume, and the average stretching force constant. Raman spectra were used to elucidate the short-range structure of vanadium tellurite glasses.

  14. Communication: Glass transition and melting lines of an ionic liquid

    Lima, Thamires A.; Faria, Luiz F. O.; Paschoal, Vitor H.; Ribeiro, Mauro C. C.

    2018-05-01

    The phase diagram of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesufonyl)imide, [Pyrr1,4][NTf2], was explored by synchroton X-ray diffraction and Raman scattering measurements as a function of temperature and pressure. Glass transition Tg(p) and melting Tm(p) temperatures were obtained from atmospheric pressure up to ca. 2.0 GPa. We found that both the Tg(p) and Tm(p) curves follow essentially the same pressure dependence. The similarity of pressure coefficients, dTg/dp ≈ dTm/dp, is explained within the non-equilibrium thermodynamics approach for the glass transition by assuming that one of the Ehrenfest equations is appropriated for Tg(p), whereas Tm(p) follows the Clausius-Clapeyron equation valid for the first-order transitions. The results highlight that ionic liquids are excellent model systems to address fundamental questions related to the glass transition.

  15. Electrical conductivity and viscosity of borosilicate glasses and melts

    Ehrt, Doris; Keding, Ralf

    2009-01-01

    , 0 to 62·5 mol% B2O3, and 25 to 85 mol% SiO2. The glass samples were characterised by different methods. Refractive indices, density and thermal expansion were measured. Phase separation effects were investigated by electron microscopy. The electrical conductivity of glasses and melts were determined......Simple sodium borosilicate and silicate glasses were melted on a very large scale (35 l Pt crucible) to prepare model glasses of optical quality in order to investigate various properties depending on their structure. The composition of the glass samples varied in a wide range: 3 to 33·3 mol% Na2O...... by impedance measurements in a wide temperature range (250 to 1450°C). The activation energies were calculated by Arrhenius plots in various temperature regions: below the glass transition temperature, Tg, above the melting point, Tl, and between Tg and Tl. Viscosity measurements were carried out...

  16. Elevation of liquidus temperature in a gel-derived Na2O-SiO2 glass

    Weinberg, M. C.; Neilson, G. F.

    1983-01-01

    The liquidus temperatures of a 19 wt% soda-silica glass prepared by gel and conventional techniques were determined. X-ray diffraction measurements of the glasses which were heat-treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel-derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel-derived glass is elevated

  17. Proceedings of the national symposium on materials and processing: functional glass/glass-ceramics, advanced ceramics and high temperature materials

    Ghosh, A.; Sahu, A.K.; Viswanadham, C.S.; Ramanathan, S.; Hubli, R.C.; Kothiyal, G.P.

    2012-10-01

    With the development of materials science it is becoming increasingly important to process some novel materials in the area of glass, advanced ceramics and high temperature metals/alloys, which play an important role in the realization of many new technologies. Such applications demand materials with tailored specifications. Glasses and glass-ceramics find exotic applications in areas like radioactive waste storage, optical communication, zero thermal expansion coefficient telescopic mirrors, human safety gadgets (radiation resistance windows, bullet proof apparels, heat resistance components etc), biomedical (implants, hyperthermia treatment, bone cement, bone grafting etc). Advanced ceramic materials have been beneficial in biomedical applications due to their strength, biocompatibility and wear resistance. Non-oxide ceramics such as carbides, borides, silicides, their composites, refractory metals and alloys are useful as structural and control rod components in high temperature fission/ fusion reactors. Over the years a number of novel processing techniques like selective laser melting, microwave heating, nano-ceramic processing etc have emerged. A detailed understanding of the various aspects of synthesis, processing and characterization of these materials provides the base for development of novel technologies for different applications. Keeping this in mind and realizing the need for taking stock of such developments a National Symposium on Materials and Processing -2012 (MAP-2012) was planned. The topics covered in the symposium are ceramics, glass/glass-ceramics and metals and materials. Papers relevant to INIS are indexed separately

  18. Thermal expansion at low temperatures of glass-ceramics and glasses

    White, G K [National Measurement Lab., Sydney (Australia)

    1976-08-01

    The linear thermal expansion coefficient, ..cap alpha.., has been measured from 2 to 32 K and from 55 to 90 K for a machineable glass-ceramic, an 'ultra-low expansion' titanium silicate glass (Corning ULE), and ceramic glasses (Cer-Vit and Zerodur), and for glassy carbon. ..cap alpha.. is negative for the ultra-low expansion materials below 100 K, as for pure vitreous silica. Comparative data are reported for ..cap alpha..-quartz , ..cap alpha..-cristobalite, common opal, and vitreous silica.

  19. Study of the glass formation of high temperature superconductors

    Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

    1992-01-01

    A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

  20. Origin of glass transition temperature behavior in polymer nanocomposites

    Kropka, Jamie; Ganesan, Venkat; Green, Peter

    2008-03-01

    Local composition variations inherent in multi-component materials, even when the material constituents are miscible, generally lead to heterogeneous behavior in the properties of mixtures relative to their single component counterparts. In contrast, experiments have suggested that some polymer nanocomposite materials exhibit changes in their bulk Tg without displaying excess heterogeneity in their dynamics, as measured mechanically, relative to the neat polymer. Incoherent neutron scattering measurements on materials that fit this description, C60-PMMA mixtures, suggest that modifications of the polymer melt dynamics are limited to the vicinity of the particles. A model by which the localized modifications of polymer dynamics can account for the apparent homogeneous change in Tg is proposed to explain the experimental findings. Computations based on percolation theory support the model.

  1. Low-temperature photoluminescence in chalcogenide glasses doped with rare-earth ions

    Kostka, Petr, E-mail: petr.kostka@irsm.cas.cz [Institute of Rock Structure and Mechanics AS CR, V Holešovičkách 41, 182 09 Praha 8 (Czech Republic); Zavadil, Jiří [Institute of Photonics and Electronics AS CR, Chaberská 57, 182 51 Praha 8, Kobylisy (Czech Republic); Iovu, Mihail S. [Institute of Applied Physics, Academy of Sciences of Moldova, Str. Academiei 5, MD-28 Chisinau, Republic of Moldova (Moldova, Republic of); Ivanova, Zoya G. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia (Bulgaria); Furniss, David; Seddon, Angela B. [Mid-Infrared Photonics Group, George Green Institute for Electromagnetics Research, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

    2015-11-05

    Sulfide and oxysulfide bulk glasses Ga-La-S-O, Ge-Ga-S and Ge-Ga-As-S doped, or co-doped, with various rare-earth (RE{sup 3+}) ions are investigated for their room temperature transmission and low-temperature photoluminescence. Photoluminescence spectra are collected by using external excitation into the Urbach tail of the fundamental absorption edge of the host-glass. The low-temperature photoluminescence spectra are dominated by the broad-band luminescence of the host glass, with superimposed relatively sharp emission bands due to radiative transitions within 4f shells of RE{sup 3+} ions. In addition, the dips in the host-glass luminescence due to 4f-4f up-transitions of RE{sup 3+} ions are observed in the Ge-Ga-S and Ge-Ga-As-S systems. These superimposed narrow effects provide a direct experimental evidence of energy transfer between the host glass and respective RE{sup 3+} dopants. - Highlights: • An evidence of energy transfer from host-glass to doped-in RE ions is presented. • Energy transfer is manifested by dips in host-glass broad-band luminescence. • This channel of energy transfer is documented on selected RE doped sulfide glasses. • Photoluminescence spectra are dominated by broad band host-glass luminescence. • Presence of RE ions is manifested by superimposed narrow 4f-4f transitions.

  2. An Overview of the Glass Transition Temperature of Synthetic Polymers.

    Beck, Keith R.; And Others

    1984-01-01

    Presents an overview of the glass-to-rubber transition, what it is, why it is important, and the major factors that influence it. Indicates that this information should be incorporated into chemistry curricula. (JN)

  3. Simulation of Temperature Field Distribution for Cutting the Temperated Glass by Ultraviolet Laser

    Yang, B. J.; He, Y. C.; Dai, F.; Lin, X. C.

    2017-03-01

    The finite element software ANSYS was adopted to simulate the temperature field distribution for laser cutting tempered glass, and the influence of different process parameters, including laser power, glass thickness and cutting speed, on temperature field distribution was studied in detail. The results show that the laser power has a greater influence on temperature field distribution than other paremeters, and when the laser power gets to 60W, the highest temperature reaches 749°C, which is higher than the glass softening temperature. It reflects the material near the laser spot is melted and the molten slag is removed by the high-energy water beam quickly. Finally, through the water guided laser cutting tempered glass experiment the FEM theoretical analysis was verified.

  4. High-temperature oxidation of tungsten covered by layer of glass-enamel melt

    Vasnetsova, V.B.; Shardakov, N.T.; Kudyakov, V.Ya.; Deryabin, V.A.

    1997-01-01

    Corrosion losses of tungsten covered by the layer of glass-enamel melt were determined at 800, 850, 900, 950 deg C. It is shown that the rate of high-temperature oxidation of tungsten decreases after application of glass-enamel melt on its surface. This is probably conditioned by reduction of area of metal interaction with oxidizing atmosphere

  5. Low-temperature photoluminescence in chalcogenide glasses doped with rare-earth ions

    Kostka, Petr; Zavadil, Jiří; Iovu, M.S.; Ivanova, Z. G.; Furniss, D.; Seddon, A.B.

    2015-01-01

    Roč. 648, NOV 5 (2015), s. 237-243 ISSN 0925-8388 R&D Projects: GA ČR GAP106/12/2384 Institutional support: RVO:67985891 ; RVO:67985882 Keywords : chalcogenide glasses * rare earth ions * low-temperature photoluminescence * optical transmission Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 3.014, year: 2015

  6. ARRHENIUS MODEL FOR HIGH-TEMPERATURE GLASS VISCOSITY WITH A CONSTANT PRE-EXPONENTIAL FACTOR

    Hrma, Pavel R.

    2008-01-01

    A simplified form of the Arrhenius equation, ln η = A + B(x)/T, where η is the viscosity, T the temperature, x the composition vector, and A and B the Arrhenius coefficients, was fitted to glass-viscosity data for the processing temperature range (the range at which the viscosity is within 1 to 103 Pa.s) while setting A = constant and treating B(x) as a linear function of mass fractions of major components. Fitting the Arrhenius equation to over 550 viscosity data of commercial glasses and approximately 1000 viscosity data of glasses for nuclear-waste glasses resulted in the A values of -11.35 and -11.48, respectively. The R2 value ranged from 0.92 to 0.99 for commercial glasses and was 0.98 for waste glasses. The Arrhenius models estimate viscosities for melts of commercial glasses containing 42 to 84 mass% SiO2 within the temperature range of 1100 to 1550 C and viscosity range of 5 to 400 Pa.s and for waste glasses containing 32 to 60 mass% SiO2 within the temperature range of 850 to 1450 C and viscosity range of 0.4 to 250 Pa.s

  7. A Simple Demonstration of the High-Temperature Electrical Conductivity of Glass

    Chiaverina, Chris

    2014-01-01

    We usually think of glass as a good electrical insulator; this, however, is not always the case. There are several ways to show that glass becomes conducting at high temperatures, but the following approach, devised by Brown University demonstration manager Gerald Zani, may be one of the simplest to perform.

  8. Effect of ion irradiation on tensile ductility, strength and fictive temperature in metallic glass nanowires

    Magagnosc, D.J.; Kumar, G.; Schroers, J.; Felfer, P.; Cairney, J.M.; Gianola, D.S.

    2014-01-01

    Ion irradiation of thermoplastically molded Pt 57.5 Cu 14.3 Ni 5.7 P 22.5 metallic glass nanowires is used to study the relationship between glass structure and tensile behavior across a wide range of structural states. Starting with the as-molded state of the glass, ion fluence and irradiated volume fraction are systematically varied to rejuvenate the glass, and the resulting plastic behavior of the metallic glass nanowires probed by in situ mechanical testing in a scanning electron microscope. Whereas the as-molded nanowires exhibit high strength, brittle-like fracture and negligible inelastic deformation, ion-irradiated nanowires show tensile ductility and quasi-homogeneous plastic deformation. Signatures of changes to the glass structure owing to ion irradiation as obtained from electron diffraction are subtle, despite relatively large yield strength reductions of hundreds of megapascals relative to the as-molded condition. To reconcile changes in mechanical behavior with glass properties, we adapt previous models equating the released strain energy during shear banding to a transit through the glass transition temperature by incorporating the excess enthalpy associated with distinct structural states. Our model suggests that ion irradiation increases the fictive temperature of our glass by tens of degrees – the equivalent of many orders of magnitude change in cooling rate. We further show our analytical description of yield strength to quantitatively describe literature results showing a correlation between severe plastic deformation and hardness in a single glass system. Our results highlight not only the capacity for room temperature ductile plastic flow in nanoscaled metallic glasses, but also processing strategies capable of glass rejuvenation outside of the realm of traditional thermal treatments

  9. Temperature-dependent magnetic properties of individual glass spherules, Apollo 11, 12, and 14 lunar samples.

    Thorpe, A. N.; Sullivan, S.; Alexander, C. C.; Senftle, F. E.; Dwornik, E. J.

    1972-01-01

    Magnetic susceptibility of 11 glass spherules from the Apollo 14 lunar fines have been measured from room temperature to 4 K. Data taken at room temperature, 77 K, and 4.2 K, show that the soft saturation magnetization was temperature independent. In the temperature range 300 to 77 K the temperature-dependent component of the magnetic susceptibility obeys the Curie law. Susceptibility measurements on these same specimens and in addition 14 similar spherules from the Apollo 11 and 12 mission show a Curie-Weiss relation at temperatures less than 77 K with a Weiss temperature of 3-7 degrees in contrast to 2-3 degrees found for tektites and synthetic glasses of tektite composition. A proposed model and a theoretical expression closely predict the variation of the susceptibility of the glass spherules with temperature.

  10. Experimental study on critical breaking stress of float glass under elevated temperature

    Wang, Yu; Wang, Qingsong; Shao, Guangzheng; Chen, Haodong; Sun, Jinhua; He, Linghui; Liew, K.M.

    2014-01-01

    Highlights: • Critical breaking stresses of clear, ground and coated glass were measured. • Breaking stress and strain of smooth glass were measured from 25 °C to 400 °C. • At approximately 100 °C, critical stress reached the minimum value. • Surface treatment and ambient temperature have notable effects on glass breaking. - Abstract: Cracking and subsequent fallout of glass may significantly affect fire dynamics in compartments. Moreover, the breaking tensile stress of glass, a crucial parameter for breakage occurrence, is the least well known among mechanical properties. In this work, a series of experiments were conducted, through mechanical tensile tests, to directly measure the breaking stress of float glass using Material Testing System 810 apparatus. Clear, ground and coated glass samples with a thickness of 6 mm were measured under ambient conditions, with a room temperature of 25 °C. The breaking stress of smooth glass samples was also measured at 75 °C, 100 °C, 125 °C, 150 °C, 200 °C, 300 °C and 400 °C, respectively. The results show that surface treatment may decrease the critical tensile stress of glass panes. The average breaking stress also fluctuates considerably, from 26.60 to 35.72 MPa with the temperature variations investigated here. At approximately 100 °C, critical stress reached the minimum value at which glass breakage occurs more easily. In addition, the thermal expansion coefficient was established using a thermal dilatometer, to obtain the maximum temperature difference float glass can withstand. It is intended that these results will provide some practical guidelines for fire safety engineers

  11. Antireflectance coating on shielding window glasses using glacial acetic acid at ambient temperature

    Sathi Sasidharan, N.; Deshingkar, D.S.; Wattal, P.K.

    2006-01-01

    High density lead glasses having thickness of several centimeters and large dimensions are used as shielding windows in hot cells. To improve visibility, the reflection of light from its optically polished surfaces needs to be minimized to improve transmission as absorption of light in the thick glasses can not be avoided. Antireflectance coating of a material having low refractive index is required for this purpose. Selective leaching of lead at ambient temperature in glacial acetic acid develops a silica rich leached layer on glass surface. Since silica has low refractive index, the leached layer serves as antireflectance coating. Two optically polished discs of shielding window glasses were leached in glacial acetic acid at ambient temperature for 2, 5 and 10 days and their reflectance and transmittance spectra were taken to find effect of leaching. For transparent glass transmittance could be improved from 78.76% to 85.31% after 10 days leaching. Reflectance from the glass could be decreased from 12.48 to 11.67%. For coloured glass transmittance improved from 87.77% to 88.24% after 5 days leaching while reflectance decreased from 12.28% to 5.6% during same period. Based on data generated, 10 days leaching time is recommended for developing anti reflectance coating on transparent shielding window glass and 5 days for coloured shielding window glass. The procedure can be used for shielding windows of any dimensions by fabrication a PVC tank of slightly high dimensions and filling with acetic acid (author)

  12. Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting Polymers (Briefing Charts)

    2015-05-20

    TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING POLYMERS 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...temperature thermosetting polymer via dynamic mechanical analysis alone. These difficulties result from the residual cure of samples heated beyond their...98) Prescribed by ANSI Std. 239.18 Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting

  13. Heavy atom induced room temperature fluorescence quenching of PAH from a glucose glass

    Marlow, Matt, E-mail: matthew.marlow@nicholls.edu

    2017-06-15

    Sugar glasses are a relatively new matrix for solid-matrix luminescence. Molecular interactions within the sugar glass are not well understood. Fluorescence quenching was used to investigate molecular interactions within the sugar glass matrix. The room temperature fluorescence quenching of pyrene and naphthalene was observed from a glucose glass. The heavy atom salt NaI was the quencher. Two solvent compositions 50/50 and 60/40 MeOH/water, used for glass preparation, were examined for their effect on glass rigidity and molecular interactions. A complex static mechanism was observed for glasses prepared with 50/50 MeOH/water. This data was fit to the sphere of action model and associations constants determined. A Stern-Volmer static mechanism of quenching was observed for glasses prepared with 60/40 MeOH/water. This data fit the Stern-Volmer equation and association constants were determined. A larger association constant was observed for pyrene compared to naphthalene for both solvent systems used. Pyrene had a larger association constant with a sugar glass prepared with 60/40 MeOH/water compared to 50/50 MeOH/water implying a greater association between pyrene and iodide. The greater association is a reflection of a more rigid internal environment for the sugar glass prepared with 60/40 MeOH/water.

  14. Mobility of delocalized charge carriers in an ideal homopolar glass as a function of temperature

    Iskra, V.D.

    1986-01-01

    The relationship between temperature and the mobility of delocalized charge carriers for an intrinsic random field of a homopolar glass is investigated through application of a method of scattering amplitude calculation based on employing short-lived potential factorization

  15. Statistical approach to study of lithium magnesium metaborate glasses

    Nedyalkova Miroslava

    2017-03-01

    Full Text Available Alkali borate glasses and alkaline earth borate glasses are commonly used materials in the field of optoelectronics. Infrared (FTIR and Raman spectroscopy are valuable tools for structural investigation of borate glass networks. The compositional and structural variety of lithium magnesium metaborate glasses is usually determined by traditional instrumental methods. In this study a data set is classified by structural and physicochemical parameters (FTIR, Raman spectra, glass transition temperature-Tg. Characterisation of magnesium containing metaborate glasses by multivariate statistics (hierarchical cluster analysis to reveal potential relationships (similarity or dissimilarity between the type of glasses included in the data set using specific structural features available in the literature is conducted. The clustering of the glass objects indicates a good separation of different magnesium containing borate glass compositions. The grouping of variables concerning Tg and structural data for BO3 and BO4 linkage confirms that BO4/BO3 ratios strongly affect Tg. Additionally, patterns of similarity could be detected not only between the glass composition but also between the features (variables describing the glasses. The proposed approach can be further used as an expert tool for glass properties prediction or fingerprinting (identification of unknown compositions.

  16. The effect of temperature on guiding of slow highly charged ions through a mesoscopic glass capillary

    Bereczky, R J; Tökési, K; Kowarik, G; Ladinig, F; Schrempf, D; Aumayr, F

    2012-01-01

    We present first temperature dependent transmission measurements of slow highly charged ions through a single, straight Duran glass capillary with a high aspect ratio. By changing the temperature of the glass capillary the electrical conductivity of the Duran can be varied by several orders of magnitude. This held the promise to investigate the effect of conductivity on particle transport (build-up and removal of charge patches) through capillaries in more details.

  17. Polymeric nanoparticles - Influence of the glass transition temperature on drug release.

    Lappe, Svenja; Mulac, Dennis; Langer, Klaus

    2017-01-30

    The physico-chemical characterisation of nanoparticles is often lacking the determination of the glass transition temperature, a well-known parameter for the pure polymer carrier. In the present study the influence of water on the glass transition temperature of poly (DL-lactic-co-glycolic acid) nanoparticles was assessed. In addition, flurbiprofen and mTHPP as model drugs were incorporated in poly (DL-lactic-co-glycolic acid), poly (DL-lactic acid), and poly (L-lactic acid) nanoparticles. For flurbiprofen-loaded nanoparticles a decrease in the glass transition temperature was observed while mTHPP exerted no influence on this parameter. Based on this observation, the release behaviour of the drug-loaded nanoparticles was investigated at different temperatures. For all preparations an initial burst release was measured that could be attributed to the drug adsorbed to the large nanoparticle surface. At temperatures above the glass transition temperature an instant drug release of the nanoparticles was observed, while at lower temperatures less drug was released. It could be shown that the glass transition temperature of drug loaded nanoparticles in suspension more than the corresponding temperature of the pure polymer is the pivotal parameter when characterising a nanostructured drug delivery system. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Correlations of norbornenyl crosslinked polyimide resin structures with resin thermo-oxidative stability, resin glass transition temperature and composite initial mechanical properties

    Alston, William B.

    1988-01-01

    PMR (polymerization of monomeric reactants) methodology was used to prepare 70 different polyimide oligomeric resins and 30 different unidirectional graphite fiber/polyimide composites. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on resin thermo-oxidative stability and glass transition temperature (Tg) of the cured/postcured resins. A linear correlation of decreasing 316 C resin weight loss/surface area versus (1) decreasing aliphatic content, or (2) increasing benzylic/aliphatic content stoichiometry ratio over a wide range of resin compositions was observed. An almost linear correlation of Tg versus molecular distance between the crosslinks was also observed. An attempt was made to correlate Tg with initial composite mechanical properties (flexural strength and interlaminar shear strength). However, the scatter in mechanical strength data prevented obtaining a clear correlation. Instead, only a range of composite mechanical properties was obtained at 25, 288, and 316 C. Perhaps more importantly, what did become apparent during the correlation study was (1) the PMR methodology could be used to prepare composites from resins containing a wide variety of monomer modifications, (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins formulated exhibited satisfactory processing flow, and (3) that PMR resins exhibited predictable rates of 316 C weight loss/surface area based on their benzylic/aliphatic stoichiometery ratio.

  19. Measurement of glass transition temperature, residual heat of reaction and mixing ratio of epoxy resins using near infrared spectroscopy: a preliminary study

    Houmøller, Lars Plejdrup; Laursen, Peter Clemen

    2003-01-01

    As a measure of the degree of curing of epoxy resins, the glass transition temperature, Tg, and the residual heat of reaction, DeltaHr, are often used. In this study, near infrared spectroscopy and multivariate calibration (partial least squares regression (PLSR)) have been used to monitor the two...... variables, using differential scanning calorimetry (DSC) as the reference method. The epoxy under study was a commercial system consisting of the resin, trimethylolpropanetriglycidylether, and the hardener, 3-aminomethyl-3,5,5,-trimethylcyclohexylamine. Using samples cured under different conditions......, calibrations resulted in root mean square errors of cross-validation (RMSECV) of 18 J/g for DeltaHr (range for Hr: 6.1-231.3 J/g) and 7.2ºC for Tg (range for Tg: 41.5-98.8ºC). Also, a PLSR model for mixing ratio of hardener and resin was obtained, resulting in a RMSECV of 0.0040 (range for mixing ratio: 0.180-0.380)...

  20. Glass Transition Temperature of Saccharide Aqueous Solutions Estimated with the Free Volume/Percolation Model.

    Constantin, Julian Gelman; Schneider, Matthias; Corti, Horacio R

    2016-06-09

    The glass transition temperature of trehalose, sucrose, glucose, and fructose aqueous solutions has been predicted as a function of the water content by using the free volume/percolation model (FVPM). This model only requires the molar volume of water in the liquid and supercooled regimes, the molar volumes of the hypothetical pure liquid sugars at temperatures below their pure glass transition temperatures, and the molar volumes of the mixtures at the glass transition temperature. The model is simplified by assuming that the excess thermal expansion coefficient is negligible for saccharide-water mixtures, and this ideal FVPM becomes identical to the Gordon-Taylor model. It was found that the behavior of the water molar volume in trehalose-water mixtures at low temperatures can be obtained by assuming that the FVPM holds for this mixture. The temperature dependence of the water molar volume in the supercooled region of interest seems to be compatible with the recent hypothesis on the existence of two structure of liquid water, being the high density liquid water the state of water in the sugar solutions. The idealized FVPM describes the measured glass transition temperature of sucrose, glucose, and fructose aqueous solutions, with much better accuracy than both the Gordon-Taylor model based on an empirical kGT constant dependent on the saccharide glass transition temperature and the Couchman-Karasz model using experimental heat capacity changes of the components at the glass transition temperature. Thus, FVPM seems to be an excellent tool to predict the glass transition temperature of other aqueous saccharides and polyols solutions by resorting to volumetric information easily available.

  1. Property-Composition-Temperature Modeling of Waste Glass Melt Data Subject to a Randomization Restriction

    Piepel, Gregory F.; Heredia-Langner, Alejandro; Cooley, Scott K.

    2008-01-01

    Properties such as viscosity and electrical conductivity of glass melts are functions of melt temperature as well as glass composition. When measuring such a property for several glasses, the property is typically measured at several temperatures for one glass, then at several temperatures for the next glass, and so on. This data-collection process involves a restriction on randomization, which is referred to as split-plot experiment. The split-plot data structure must be accounted for in developing property-composition-temperature models and the corresponding uncertainty equations for model predictions. Instead of ordinary least squares (OLS) regression methods, generalized least squares (GLS) regression methods using restricted maximum likelihood (REML) estimation must be used. This article describes the methodology for developing property-composition-temperature models and corresponding prediction uncertainty equations using the GLS/REML regression approach. Viscosity data collected on 197 simulated nuclear waste glasses are used to illustrate the GLS/REML methods for developing a viscosity-composition-temperature model and corresponding equations for model prediction uncertainties. The correct results using GLS/REML regression are compared to the incorrect results obtained using OLS regression

  2. Foaming of CRT panel glass powder with Na2CO3

    Petersen, Rasmus Rosenlund; König, Jakob; Smedskjær, Morten Mattrup

    melt, while Na2O becomes incorporated into the glass structure. We have quantified the melt expansion through density measurements and the Na2O incorporation is indicated by the decrease of the glass transition temperature (Tg) of the final foam glass. The glass foaming quality depends on the foaming......Recycling of cathode ray tube (CRT) glass remains a challenging task. The CRT glass consists of four glass types fused together: Funnel-, neck-, frit- and panel glass. The three former glasses contain toxic lead oxide, and therefore have a low recycling potential. The latter on the other hand...... is lead-free, but since barium and strontium oxide are present, panel glass is incompatible with most common recycling methods. However, foam glass production is a promising approach for the recycling of panel glass waste, since the process parameters can be changed according to the glass waste...

  3. Pressure effect of glass transition temperature in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk metallic glass

    Jiang, Jianzhong; Roseker, W.; Sikorski, M.

    2004-01-01

    Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition was det...... range of 0-2.2 GPa. This method opens a possibility to study the pressure effect of glass transition process in glassy systems under high pressures (>1 GPa). (C) 2004 American Institute of Physics.......Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition...... was detected from the change of the slope of peak position as a function of temperature. It is found that the glass transition temperature increases with pressure by 4.4 K/GPa for the Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass, and the supercooled liquid range decreases with pressure by 2.9 K/GPa in a pressure...

  4. Size and pressure effects on glass transition temperature of poly (methyl methacrylate) thin films

    Lang, X.Y.; Zhang, G.H.; Lian, J.S.; Jiang, Q.

    2006-01-01

    A simple and unified model, without any adjustable parameter, is developed for size and pressure effects on glass transition temperatures of nanopolymers. The model is based on a model for size dependent glass transition temperature of nanopolymer glasses under ambient pressure, and a pressure-dependent function of the root of mean-square displacement of atom vibration. It is found that the size- and pressure-dependent glass transition temperatures of free-standing films or supported films having weak interaction with substrates decreases with decreasing of pressure and size. However, the glass transition temperature of supported films having strong interaction with substrates increases with the increase of pressure and the decrease of size. The predicted results correspond with available experimental evidences for atactic-Poly (methyl methacrylate) thin films under hydrostatic pressure or under the pressure induced by supercritical fluid CO 2 . In addition, the predicted glass transition temperature of isotactic-Poly (methyl methacrylate) thin films under ambient pressure is consistent with available experimental evidences

  5. Aging of Dielectric Properties below Tg

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    The dielectric loss at 1Hz in TPP is studied during a temperature step from one equilibrium state to another. In the applied cryostate the temperature can be equilibrated on a timescale of 1 second. The aging time dependence of the dielectric loss is studied below Tg applying temperature steps...

  6. Hydration of Rhyolitic Glasses: Comparison Between High- and Low-Temperature Processes

    Anovitz, L.; Fayek, M.; Cole, D. R.; Carter, T.

    2012-12-01

    While a great deal is known about the interaction between water and rhyolitic glasses and melts at temperatures above the glass transition, the nature of this interaction at lower temperatures is more obscure. Comparisons between high- and low-temperature diffusive studies suggest that several factors play an important role under lower-temperatures conditions that are not significant at higher temperatures. Surface concentrations, which equilibrate quickly at high temperature, change far more slowly as temperatures decrease, and may not equilibrate at room temperature for hundreds or thousands of years. Coupled with temperature-dependent diffusion coefficients this complicates calculation of diffusion profiles as a function of time. A key factor in this process appears to be the inability of "self-stress", caused by the in-diffusing species, to relax at lower temperatures, a result expected below the glass transition. Regions of the glass hydrated at low temperatures are strongly optically anisotropic, and preliminary calculations suggest that the magnitude of stress involved may be very high. On the microstuctural scale, extrapolations of high-temperature FTIR data to lower temperatures suggests there should be little or no hydroxyl present in glasses "hydrated" at low temperatures. Analyses of both block and powder samples suggest that this is generally true in the bulk of the hydrated glass, excluding hydroxyl groups that formed during the initial cooling of the melt. However, hydroxyl do groups appear to be present at the glass surface, where both SIMS and neutron reflectometry data suggest hydration levels may be higher than projected from the bulk of the glass. Isotopic exchange experiments also suggest that bonding is relatively weak, as hydration water exchanges readily with the enviroment. All of these observations lead to the conclusion that the observed stress is due to the presence of interstructural, rather than bonded, water. This likely explains the

  7. Temperature-dependent structural relaxation in As{sub 40}Se{sub 60} glass

    Golovchak, R., E-mail: roman_ya@yahoo.com [Lviv Sci. and Res. Institute of Materials of SRC ' Carat' , 202 Stryjska str., 79031 Lviv (Ukraine); Kozdras, A. [Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Academy of Management and Administration, 18 Niedzialkowski str., Opole, PL-45085 (Poland); Shpotyuk, O. [Jan Dlugosz University, 13/15, al. Armii Krajowej, 42201, Czestochowa (Poland); Gorecki, Cz. [Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Kovalskiy, A.; Jain, H. [Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States)

    2011-08-01

    The origin of structural relaxation in As{sub 40}Se{sub 60} glass at different annealing temperatures is studied by differential scanning calorimetry (DSC) and in situ extended X-ray absorption fine structure (EXAFS) methods. Strong physical aging effect, expressed through the increase of endothermic peak area in the vicinity of T{sub g}, is recorded by DSC technique at the annealing temperatures T{sub a}>90{sup o}C. EXAFS data show that the observed structural relaxation is not associated with significant changes in the short-range order of this glass. An explanation is proposed for this relaxation behavior assuming temperature-dependent constraints. -- Highlights: → In this study we report experimental evidence for temperature-dependent constraints theory. → Structural relaxation of As{sub 2}Se{sub 3} glass at higher annealing temperatures is studied by DSC technique. → Accompanied changes in the structure are monitored by in situ EXAFS measurements.

  8. Primary crystallization in Al-rich metallic glasses at unusually low temperatures

    Bokeloh, J.; Boucharat, N.; Roesner, H.; Wilde, G.

    2010-01-01

    The initial stage of the primary crystallization reaction and the glass transition of the marginal metallic glass Al 89 Y 6 Fe 5 were investigated by conventional differential scanning calorimetry (DSC) and modulated differential scanning calorimetry (MDSC), microcalorimetry, X-ray diffraction (XRD) and transmission electron microscopy. A sharp onset of the primary crystallization was found by microcalorimetry and XRD studies at temperatures which were 120 deg. C below the primary crystallization peak observed in conventional DSC. A systematic MDSC study of annealed samples revealed a wide spectrum of glass transition onsets, which show a strong dependence on the annealing conditions. In addition, the glass transition onsets can be linked to the initial stage of the primary crystallization. The spectrum of glass transition onsets observed is discussed with respect to the occurrence of phase separation preceding the nucleation and growth of dendritic aluminium nanocrystals.

  9. Glass transition temperatures of liquid prepolymers obtained by thermal penetrometry

    Potts, J. E., Jr.; Ashcraft, A. C.

    1973-01-01

    Thermal penetrometry is experimental technique for detecting temperature at which frozen prepolymer becomes soft enough to be pierced by weighted penetrometer needle; temperature at which this occurs is called penetration temperature. Apparatus used to obtain penetration temperatures can be set up largely from standard parts.

  10. On high temperature internal friction in metallic glasses

    Zolotukhin, I.V.; Kalinin, Yu.E.; Roshchupkin, A.M.

    1992-01-01

    High temperature background of internal friction in amorphous lanthanum-aluminium alloys was investigated. More rapid growth of internal friction was observed at temperature ∼ 453 K reaching maximal value at 495 K. Crystallization process was accompanied by decrease of internal friction. Increase of mechanical vibration frequency to 1000 Hz leads to rise of internal friction background in the range of room temperatures and to decrease at temperatures above 370 K. Bend was observed on temperature dependence of internal friction at 440 K

  11. Development of iodine waste forms using low-temperature sintering glass

    Krumhansl, James Lee; Nenoff, Tina Maria; Garino, Terry J.; Rademacher, David

    2010-01-01

    This presentation will describe our recent work on the use of low temperature-sintering glass powders mixed with either AgI or AgI-zeolite to produce a stable waste form. Radioactive iodine ( 129 I, half-life of 1.6 x 10 7 years) is generated in the nuclear fuel cycle and is of particular concern due to its extremely long half-life and its effects on human health. As part of the DOE/NE Advanced Fuel Cycle Initiative (AFCI), the separation of 129 I from spent fuel during fuel reprocessing is being studied. In the spent fuel reprocessing scheme under consideration, the iodine is released in gaseous form and collected using Ag-loaded zeolites, to form AgI. Although AgI has extremely low solubility in water, it has a relatively high vapor pressure at moderate temperatures (>550 C), thus limiting the thermal processing. Because of this, immobilization using borosilicate glass is not feasible. Therefore, a bismuth oxide-based glasses are being studied due to the low solubility of bismuth oxide in aqueous solution at pH > 7. These waste forms were processed at 500 C, where AgI volatility is low but the glass powder is able to first densify by viscous sintering and then crystallize. Since the glass is not melted, a more chemically stable glass can be used. The AgI-glass mixture was found to have high iodine leach resistance in these initial studies.

  12. Quantum-dot temperature profiles during laser irradiation for semiconductor-doped glasses

    Nagpal, Swati

    2002-01-01

    Temperature profiles around laser irradiated CdX (X=S, Se, and Te) quantum dots in borosilicate glasses were theoretically modeled. Initially the quantum dots heat up rapidly, followed by a gradual increase of temperature. Also it is found that larger dots reach higher temperatures for the same pulse characteristics. After the pulse is turned off, the dots initially cool rapidly, followed by a gradual decrease in temperature

  13. Quantum-dot temperature profiles during laser irradiation for semiconductor-doped glasses

    Nagpal, Swati

    2002-12-01

    Temperature profiles around laser irradiated CdX (X=S, Se, and Te) quantum dots in borosilicate glasses were theoretically modeled. Initially the quantum dots heat up rapidly, followed by a gradual increase of temperature. Also it is found that larger dots reach higher temperatures for the same pulse characteristics. After the pulse is turned off, the dots initially cool rapidly, followed by a gradual decrease in temperature.

  14. Low frequency elastic properties of glasses at low temperatures - implications on the tunneling model

    Raychaudhuri, A.K.; Hunklinger, S.

    1984-01-01

    We have measured the low frequency elastic properties of dielectric, normal conducting and superconducting metallic glasses at audio-frequencies (fapprox.=1 kHz) and temperatures down to 10 mK. Our results are discussed in the framework of the tunneling model of glasses. The major assumption of the tunneling model regarding the tunneling states with long relaxation time has been verified, but discrepancies to high frequency measurements have been found. In addition, our experiments on superconducting metallic glasses seem to indicate that the present treatment of the electron-tunneling state interaction is not sufficient. (orig.)

  15. DWPF glass transition temperatures: What they are and why they are important

    Marra, S.L.; Jantzen, C.M.; Ramsey, A.A.

    1991-01-01

    The Defense Waste Processing Facility (DWPF) at the Savannah River Site will immobilize high-level radioactive liquid waste in borosilicate glass. The glass will be poured into stainless steel canisters for eventual disposal in a geologic repository. The Department of Energy has defined a set of requirements for the DWPF canistered waste form which must be met in order to assure compatibility with, and acceptance by, the repository. These requirements are the Waste Acceptance Preliminary Specifications (WAPS). The WAPS require DWPF to report glass transition temperatures for the projected range of compositions. This information will be used by the repository to establish waste package design limits

  16. Low temperature uniform plastic deformation of metallic glasses during elastic iteration

    Fujita, Takeshi; Wang Zheng; Liu Yanhui; Sheng, Howard; Wang Weihua; Chen Mingwei

    2012-01-01

    Molecular dynamics simulations and dynamic mechanical analysis experiments were employed to investigate the mechanical behavior of metallic glasses subjected to iteration deformation in a nominally elastic region. It was found that cyclic deformation leads to the formation of irreversible shear transformation zones (STZs) and a permanent uniform strain. The initiation of STZs is directly correlated with the atomic heterogeneity of the metallic glass and the accumulated permanent strain has a linear relation with the number of STZs. This study reveals a new deformation mode and offers insights into the atomic mechanisms of STZ formation and low temperature uniform plastic deformation of metallic glasses.

  17. Transient thermal-mechanical behavior of cracked glass-cloth-reinforced epoxy laminates at low temperatures

    Shindo, Y.; Ueda, S.

    1997-01-01

    We consider the transient thermal-mechanical response of cracked G-10CR glass-cloth-reinforced epoxy laminates with temperature-dependent properties. The glass-cloth-reinforced epoxy laminates are suddenly cooled on the surfaces. A generalized plane strain finite element model is used to study the influence of warp angle and crack formation on the thermal shock behavior of two-layer woven laminates at low temperatures. Numerical calculations are carried out, and the transient temperature distribution and the thermal-mechanical stresses are shown graphically

  18. Ultrasound-induced crystallization around the glass transition temperature for Pd40Ni40P20 metallic glass

    Ichitsubo, Tetsu; Matsubara, Eiichiro; Kai, Satoshi; Hirao, Masahiko

    2004-01-01

    We have found that crystallization of a Pd 40 Ni 40 P 20 bulk metallic glass is accelerated in the vicinity of the glass transition temperature T g when it is subjected to sub/low-MHz frequency ultrasonic vibration. Resonance frequencies and internal frictions have been measured with the electromagnetic acoustic resonance (EMAR) technique. In the initial heating process of an as-cast glassy sample, the resonance frequencies jump up just above T g under ultrasonic excitation, which is attributed to nano-crystallization that is confirmed by the X-ray diffraction profile. However, such a notable change is not observed without ultrasonic vibration. The irregular Λ-shaped internal-friction peaks are also observed prior to the abrupt crystallization. This rapid crystallization is considered to be caused by a stochastic resonance, in which the jump frequency of atoms matches the frequency of the interatomic-potential change by the ultrasonic vibration

  19. Thermodynamic consequences of the kinetic nature of the glass transition

    Koperwas, Kajetan; Grzybowski, Andrzej; Tripathy, Satya N.; Masiewicz, Elzbieta; Paluch, Marian

    2015-01-01

    In this paper, we consider the glass transition as a kinetic process and establish one universal equation for the pressure coefficient of the glass transition temperature, dTg/dp, which is a thermodynamic characteristic of this process. Our findings challenge the common previous expectations concerning key characteristics of the transformation from the liquid to the glassy state, because it suggests that without employing an additional condition, met in the glass transition, derivation of the two independent equations for dTg/dp is not possible. Hence, the relation among the thermodynamic coefficients, which could be equivalent to the well-known Prigogine-Defay ratio for the process under consideration, cannot be obtained. Besides, by comparing the predictions of our universal equation for dTg/dp and Ehrenfest equations, we find the aforementioned supplementary restriction, which must be met to use the Prigogine-Defay ratio for the glass transition. PMID:26657017

  20. Glass transition temperature of PMMA/modified alumina nanocomposite: Molecular dynamic study

    Mohammadi, Maryam; Davoodi, Jamal; Javanbakht, Mahdi; Rezaei, Hamidreza

    2017-01-01

    In this study, the effect of alumina and modified alumina nanoparticles in a PMMA/alumina nanocomposite was investigated. To attain this goal, the glass transition behavior of poly methyl methacrylate (PMMA), PMMA/alumina and PMMA/hydroxylated alumina nanocomposites were investigated by molecular dynamic simulations (MD). All the MD simulations were performed using the Materials Studio 6.0 software package of Accelrys. To obtain the glass transition temperature, the variation of density vs. t...

  1. Pressure effect on crystallization temperature in Zr70Pd30 metallic glass

    Jiang, Jianzhong; Jeppesen, S; Saida, J.

    2004-01-01

    The pressure effect on amorphous-to-quasicrystalline-to-intermetallic phase transformations in a Zr70Pd30 metallic glass has been investigated by in situ x-ray diffraction measurements using synchrotron radiation. It is found that the glass crystallizes in two steps: (1) amorphous...... temperature for the formation of quasicrystals has been further discussed with the nucleation theory. ©2004 American Institute of Physics....

  2. Mathematical modeling of photoinitiated coating degradation: Effects of coating glass transition temperature and light stabilizers

    Kiil, Søren; G.de With, R.A.T.M.Van Benthem

    2013-01-01

    A mathematical model, describing coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature, was extended to simulate the behavior of a coating with a low glass transition temperature. The effects of adding light stabilizers (a UV...

  3. Structure-to-glass transition temperature relationships in high temperature stable condensation polyimides

    Alston, W. B.; Gratz, R. F.

    1985-01-01

    The presence of a hexafluoroisopropylidene (6F) connecting group in aryl dianhydrides used to prepare aromatic condensation polyimides provides high glass transition temperature (T sub g) polyimides with excellent thermo-oxidative stability. The purpose of this study was to determine if a trifluorophenyl-ethylidene (3F) connecting group would have a similar effect on the T sub g of aromatic condensation polyimides. A new dianhydride containing the 3F connecting group was synthesized. This dianhydride and an aromatic diamine also containing the 3F connecting group were used together and in various combinations with known diamines or known dianhydrides, respectively, to prepare new 3F containing condensation polyimides. Known polyimides, including some with the 6F connecting linkage, were also prepared for comparison purposes. The new 3F containing polymers and the comparison polymers were prepared by condensation polymerization via the traditional amic-acid polymerization method in N,N-dimethylacetamide solvent. The solutions were characterized by determining their inherent viscosities and then were thermally converted into polyimide films under nitrogen atmosphere at 300 to 500 C, usually 350 C. The T sub g's of the films and resin discs were then determined by thermomechanical analysis and were correlated as a function of the final processing temperatures of the films and resin discs. The results showed that similarities existed in the T sub g's depending on the nature of the connecting linkage in the monomers used to prepare the condensation polyimides.

  4. Multilevel Tunnelling Systems and Fractal Clustering in the Low-Temperature Mixed Alkali-Silicate Glasses

    2013-01-01

    The thermal and dielectric anomalies of window-type glasses at low temperatures (T glasses in recent times, magnetic effects in the organic glasses, and also some older data from mixed (SiO2)1−x(K2O)x and (SiO2)1−x(Na2O)x glasses indicate the need for a suitable extension of the 2LS-STM. We show that—not only for the magnetic effects, but also for the mixed glasses in the absence of a field—the right extension of the 2LS-STM is provided by the (anomalous) multilevel tunnelling systems (ATS) proposed by one of us for multicomponent amorphous solids. Though a secondary type of TS, different from the standard 2LS, was invoked long ago already, we clarify their physical origin and mathematical description and show that their contribution considerably improves the agreement with the experimental data. In spite of dealing with low-temperature properties, our work impinges on the structure and statistical physics of glasses at all temperatures. PMID:23861652

  5. Multilevel Tunnelling Systems and Fractal Clustering in the Low-Temperature Mixed Alkali-Silicate Glasses

    Giancarlo Jug

    2013-01-01

    Full Text Available The thermal and dielectric anomalies of window-type glasses at low temperatures (T<1 K are rather successfully explained by the two-level systems (2LS standard tunneling model (STM. However, the magnetic effects discovered in the multisilicate glasses in recent times, magnetic effects in the organic glasses, and also some older data from mixed (SiO21−x(K2Ox and (SiO21−x(Na2Ox glasses indicate the need for a suitable extension of the 2LS-STM. We show that—not only for the magnetic effects, but also for the mixed glasses in the absence of a field—the right extension of the 2LS-STM is provided by the (anomalous multilevel tunnelling systems (ATS proposed by one of us for multicomponent amorphous solids. Though a secondary type of TS, different from the standard 2LS, was invoked long ago already, we clarify their physical origin and mathematical description and show that their contribution considerably improves the agreement with the experimental data. In spite of dealing with low-temperature properties, our work impinges on the structure and statistical physics of glasses at all temperatures.

  6. High temperature oxidation and crystallization behavior of phosphate glass compositions

    Russo, Diego; Rodriguez, Diego; Grumbaum, N.; Gonzalez Oliver, Carlos

    2003-01-01

    We analyzed the thermal transformation of three iron phosphate glasses having the following nominal compositions: M4 [70% P 2 O 5 , 30% Fe 2 O 3 ], M5 [85% M4, 15% UO 2 ] y M7 [69.7% P 2 O 5 , 28.6% Fe 2 O 3 , 1,7% Al 2 O 3 ]. Thermogravimetric analysis, DTA (differential thermal analysis) and SAXS (Small Angle X-ray Scattering) were performed.It was observed that it is easily possible to produce glasses in these systems having very low crystallinity.We could determine the final stable crystalline phases [Fe 4 (P 2 O 7 ) 3 , Fe(PO 3 ) 3 and Fe 3 (P 2 O 7 ) 2 ].The presence of uranium ions affects not only the redox effects but also the crystallization of the system.SAXS data obtained during the heating in vacuum up to ∼600degC, gave some variation of scattering intensities vs. scattering vector suggesting the development of an extra phase or some kind inhomogeneities that seems to disappear on heating

  7. The pseudo‐brookite spin‐glass system studied by means of muon spin relaxation

    Brabers, V.A.M.; Boekema, C.; Lichti, R.L.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.; MacLaughlin, D.E.

    1987-01-01

    Zero-field muon spin relaxation (µSR) experiments have been performed on the spin glass Fe1.75Ti1.25O5. Above the spin-glass temperature of 44 K a distinct exponential µSR rate (¿) is observed, while below Tg a square-root exponential decay occurs, indicating fast spin fluctuations. Near 8 K, a

  8. High-temperature mechanical relaxation in glass-like B2O3

    Lomovskoj, V.A.

    1987-01-01

    The study of high-temperature mechanical relaxation in glass-like B 2 O 3 was carried out at the temperatures from 470 to 620 K using the method of internal friction at freely damped tortional vibrations (frequency range is 0.05 - 10 Hz) and forced torsional vibrations (frequency range is 0.1 -0.00001 Hz). Possible mechanisms of high-temperature mechanical relaxation are considered. It is shown that several possible mechanisms of high-temperature mechanical relaxation in glass-like B 2 O 3 can be singled out. Switching of B-O bridge bond between two boroxol cycles of boroxol grouping for oxygen vacancy in spatial structure of glass-like B 2 O 3 , formed as a result of thermal breaking of one out of three B-O bonds, according to diffusion theory of glass viscosity. The slip of one layer boroxol groupings as to another one in the presence of only tricoordinated boron atoms in the structure of glass-like B 2 O 3

  9. Preparation and Dynamic Mechanical Properties at Elevated Temperatures of a Tungsten/Glass Composite

    Gao, Chong; Wang, Yingchun; Ma, Xueya; Liu, Keyi; Wang, Yubing; Li, Shukui; Cheng, Xingwang

    2018-03-01

    Experiments were conducted to prepare a borosilicate glass matrix composite containing 50 vol.% tungsten and examine its dynamic compressive behavior at elevated temperatures in the range of 450-775 °C. The results show that the homogenous microstructure of the tungsten/glass composite with relative density of 97% can be obtained by hot-pressing sintering at 800 °C for 1 h under pressure of 30 MPa. Dynamic compressive testing was carried out by a separate Hopkinson pressure bar system with a synchronous device. The results show that the peak stress decreases and the composite transforms from brittle to ductile in nature with testing temperature increasing from 450 to 750 °C. The brittle-ductile transition temperature is about 500 °C. Over 775 °C, the composite loses load-bearing capacity totally because of the excessive softening of the glass phase. In addition, the deformation and failure mechanism were analyzed.

  10. Characterization of frequency-dependent glass transition temperature by Vogel-Fulcher relationship

    Bai Yu; Jin Li

    2008-01-01

    The complex mechanical modulus of polymer and polymer based composite materials showed a frequency-dependent behaviour during glass transition relaxation, which was historically modelled by the Arrhenius equation. However, this might not be true in a broad frequency domain based on the experience from the frequency dependence of the complex dielectric permittivity, which resulted from the same glass transition relaxation as for the complex mechanical modulus. Considering a good correspondence between dielectric and mechanical relaxation during glass transition, the Vogel-Fulcher relationship, previously proposed for the frequency dependence of dielectric permittivity, is introduced for that of the mechanical modulus; and the corresponding static glass transition temperature (T f ) was first determined for polymer and polymer based composite materials. (fast track communication)

  11. LIQUIDUS TEMPERATURE AND ONE PERCENT CRYSTAL CONTENT MODELS FOR INITIAL HANFORD HLW GLASSES

    Vienna, John D.; Edwards, Tommy B.; Crum, Jarrod V.; Kim, Dong-Sang; Peeler, David K.

    2005-01-01

    Preliminary models for liquidus temperature (TL) and temperature at 1 vol% crystal (T01) applicable to WTP HLW glasses in the spinel primary phase field were developed. A series of literature model forms were evaluated using consistent sets of data form model fitting and validation. For TL, the ion potential and linear mixture models performed best, while for T01 the linear mixture model out performed all other model forms. TL models were able to predict with smaller uncertainty. However, the lower T01 values (even with higher prediction uncertainties) were found to allow for a much broader processing envelope for WTP HLW glasses

  12. Dynamics and thermodynamics of polymer glasses.

    Cangialosi, D

    2014-04-16

    The fate of matter when decreasing the temperature at constant pressure is that of passing from gas to liquid and, subsequently, from liquid to crystal. However, a class of materials can exist in an amorphous phase below the melting temperature. On cooling such materials, a glass is formed; that is, a material with the rigidity of a solid but exhibiting no long-range order. The study of the thermodynamics and dynamics of glass-forming systems is the subject of continuous research. Within the wide variety of glass formers, an important sub-class is represented by glass forming polymers. The presence of chain connectivity and, in some cases, conformational disorder are unfavourable factors from the point of view of crystallization. Furthermore, many of them, such as amorphous thermoplastics, thermosets and rubbers, are widely employed in many applications. In this review, the peculiarities of the thermodynamics and dynamics of glass-forming polymers are discussed, with particular emphasis on those topics currently the subject of debate. In particular, the following aspects will be reviewed in the present work: (i) the connection between the pronounced slowing down of glassy dynamics on cooling towards the glass transition temperature (Tg) and the thermodynamics; and, (ii) the fate of the dynamics and thermodynamics below Tg. Both aspects are reviewed in light of the possible presence of a singularity at a finite temperature with diverging relaxation time and zero configurational entropy. In this context, the specificity of glass-forming polymers is emphasized.

  13. Temperature dependent charge transport studies across thermodynamic glass transition in P3HT:PCBM bulk heterojunction: insight from J-V and impedance spectroscopy

    Sarkar, Atri; Rahaman, Abdulla Bin; Banerjee, Debamalya

    2018-03-01

    Temperature dependent charge transport properties of P3HT:PCBM bulk heterojunction are analysed by dc and ac measurements under dark conditions across a wide temperature range of 110-473 K, which includes the thermodynamic glass transition temperature (Tg ˜320 K) of the system. A change from Ohmic conduction to space charge limited current conduction at higher (⩾1.2 V) applied bias voltages above  ⩾200 K is observed from J-V characteristics. From capacitance-voltage (C-V) measurement at room temperature, the occurrence of a peak near the built-in voltage is observed below the dielectric relaxation frequency, originating from the competition between drift and diffusion driven motions of charges. Carrier concentration (N) is calculated from C-V measurements taken at different temperatures. Room temperature mobility values at various applied bias voltages are in accordance with that obtained from transient charge extraction by linearly increasing voltage measurement. Sample impedance is measured over five decades of frequency across temperature range by using lock-in detection. This data is used to extract temperature dependence of carrier mobility (μ), and dc conductivity (σ_dc ) which is low frequency extrapolation of ac conductivity. An activation energy of  ˜126 meV for the carrier hopping process at the metal-semiconductor interface is estimated from temperature dependence of σ_dc . Above T g, μ levels off to a constant value, whereas σ_dc starts to decrease after a transition knee at T g that can be seen as a combined effect of changes in μ and N. All these observed changes across T g can be correlated to enhanced polymer motion above the glass transition.

  14. Traction and lubricant film temperature as related to the glass transition temperature and solidification. [using infrared spectroscopy on EHD contacts

    Lauer, J. L.; Peterkin, M. E.

    1978-01-01

    Does a traction fluid have to be a glass or solid under operating conditions. Infrared spectra on dynamic EHD contacts of several types of fluid were used to determine the surface and oil-film temperatures. Polarized spectral runs were made to study molecular alignment. Static glass transition pressures at appropriate temperatures were between 0.1 and 2.0 GPa, with the traction fluid showing the highest. In the EHD contact region, the traction fluid showed both the highest film temperatures as well as the greatest degree of molecular alignment. A plot of the difference between the film and surface temperatures vs shear rate resulted in a master plot valid for all the fluids. From this work, the authors propose a model of 'fluid' traction, where friction between parallel rough molecules provides the traction.

  15. Densification of MgSiO3 glass with pressure and temperature

    Yamada, A; Gaudio, Sarah; Lesher, Charles

    2010-01-01

    The density and structure of MgSiO3 glass (v-En) recovered from a series of annealing experiments up to 1000°C at 2.0, 5.5 and 8.5 GPa have been investigated using Archimedes' method and Raman spectroscopy, respectively. The densities of recovered glasses are found to be a complex function...... of pressure and temperature. At room temperature, compression up to 8.5 GPa, followed by decompression, yields a glass with a density within 0.6 % of the 1-atm value. Likewise, the 1-atm density is fully recovered in glass heated up to ~500°C at 2.0 GPa at higher pressures. A sharp increase in recovered...... density is observed between 500°C and 800°C at 2.0 GPa, 200°C and 500°C at 5.5 GPa and from room-T and 300°C at 8.5 GPa. At higher annealing temperatures the changes in density are more modest. This break in slope occurs for a glass density of 2.89 g/cm3 at 2.0 GPa and 2.95 g/cm3 at 5.5 and 8.5 GPa. Above...

  16. Low temperature spin-glass-like phases in magnetic nano-granular composites

    Zhang, Bei

    2012-09-01

    It is a common understanding that the dipole-dipole interaction among the magnetic nanoparticles may result in a low-temperature spin-glass phase, which has been evidenced by observation of aging effect and memory effect. However, several studies on the nano-particles systems showed that some of the observed spin-glass-like phenomena could be due to the existence of spin-glasslike shells surrounding the ferrimagnetic cores. Therefore, it is very important to understand that how the dipole-dipole interaction induce the spin-glass phase. In order to address this issue, we have fabricated Co-SiO 2 and Fe-SiO 2 nano-granular thin films and measured the memory effect for them. Spin-glass-like phase has been observed at low temperatures. We found that, after annealing, the size of the clusters increased significantly. Based on a simple model, the dipole-dipole interaction between the clusters must be increased accordingly for the annealed samples. Interestingly, the memory effect is greatly weakened in the annealed films, which strongly suggested that the dipole-dipole interaction may not be the major factor for the formation of the low-temperature spin-glass-like phase. Copyright © 2012 American Scientific Publishers All rights reserved.

  17. Determination of heat conductivity and thermal diffusivity of waste glass melter feed: Extension to high temperatures

    Rice, Jarrett A.; Pokorny, Richard; Schweiger, Michael J.; Hrma, Pavel R.

    2014-01-01

    The heat conductivity (λ) and the thermal diffusivity (a) of reacting glass batch, or melter feed, control the heat flux into and within the cold cap, a layer of reacting material floating on the pool of molten glass in an all-electric continuous waste glass melter. After previously estimating λ of melter feed at temperatures up to 680 deg C, we focus in this work on the λ(T) function at T > 680 deg C, at which the feed material becomes foamy. We used a customized experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples, which monitored the evolution of the temperature field while the crucible with feed was heated at a constant rate from room temperature up to 1100°C. Approximating measured temperature profiles by polynomial functions, we used the heat transfer equation to estimate the λ(T) approximation function, which we subsequently optimized using the finite-volume method combined with least-squares analysis. The heat conductivity increased as the temperature increased until the feed began to expand into foam, at which point the conductivity dropped. It began to increase again as the foam turned into a bubble-free glass melt. We discuss the implications of this behavior for the mathematical modeling of the cold cap

  18. Time-temperature-transformation diagram of Zr-based Zr-Al-Cu-Ni metallic glasses

    Goh, T.T.; Li, Y.; Ng, S.C.

    1996-01-01

    The critical cooling rates R c for glass formation in four Zr-based Zr-Al-Cu-Ni alloys were determined using techniques developed by Uhlmann based on theories of homogeneous nucleation, crystal growth and transformation kinetics. It involves the construction of a time-temperature-transformation curve which requires the knowledge of the viscosity-temperature curve of the alloys. Two types of viscosity-temperature expressions, namely Andrade expression and Doolittle expression, were used to model the viscosity of the Zr-based alloys and the choice of the viscosity-temperature expression which gives the best estimate of the calculated time-temperature-transformation curve is discussed. (author)

  19. Effect of the glass transition temperature on alpha-amylase activity in a starch matrix.

    Chaudhary, Vinita; Panyoyai, Naksit; Small, Darryl M; Shanks, Robert A; Kasapis, Stefan

    2017-02-10

    This study optimises a protocol for the estimation of α-amylase activity in a condensed starch matrix in the vicinity of the glass transition region. Enzymatic activity on the vitrified starch system was compared with that of a reference substrate, maltodextrin. The activity was assayed as the rate of release of reducing sugar using a dinitrosalicylic acid procedure. The condensed carbohydrate matrices served the dual purpose of acting as a substrate as well as producing a pronounced effect on the ability to enzymatic hydrolysis. Activation energies were estimated throughout the glass transition region of condensed carbohydrate preparations based on the concept of the spectroscopic shift factor. Results were used to demonstrate a considerable moderation by the mechanical glass transition temperature, beyond the expected linear effect of the temperature dependence, on the reaction rate of starch hydrolysis by α-amylase in comparison with the low-molecular weight chain of maltodextrin. Copyright © 2016. Published by Elsevier Ltd.

  20. Free volume model: High-temperature deformation of a Zr-based bulk metallic glass

    Bletry, M.; Guyot, P.; Blandin, J.J.; Soubeyroux, J.L.

    2006-01-01

    The homogeneous deformation of a zirconium-based bulk metallic glass is investigated in the glass transition region. Compression tests at different temperatures and strain rates have been conducted. The mechanical behavior is analyzed in the framework of the free volume model, taking into account the dependence of the flow defect concentration on deformation. The activation volume is evaluated and allows one to gather the viscosity data (for the different strain rates and temperatures) on a unique master curve. It is also shown that, due to the relation between flow defect concentration and free volume, it is not possible to deduce the equilibrium flow defect concentration directly from mechanical measurements. However, if this parameter is arbitrarily chosen, mechanical measurements give access to the other parameters of the model, these parameters for the alloy under investigation being of the same order of magnitude as those for other metallic glasses

  1. A simple method for tuning the glass transition process in inorganic phosphate glasses

    Fulchiron, René; Belyamani, Imane; Otaigbe, Joshua U.; Bounor-Legaré, Véronique

    2015-02-01

    The physical modification of glass transition temperature (Tg) and properties of materials via blending is a common practice in industry and academia and has a large economic advantage. In this context, simple production of hitherto unattainable new inorganic glass blends from already existing glass compositions via blending raises much hope with the potential to provide new glasses with new and improved properties, that cannot be achieved with classical glass synthesis, for a plethora of applications such as computers screens, glass-to-metal seals, and storage materials for nuclear wastes. Here, we demonstrate that blends of the specific glass compositions studied are miscible in all proportions, an unreported phenomenon in hard condensed matter like glass. Interestingly, excellent agreement was found between the obtained data and calculated Tgs from theoretical equations (Supplementary information) for predicting the composition dependence of Tg for miscible blends with weak but significant specific interactions between the blend components. That this blending method is at present not applied to inorganic glasses reflects the fact that water and chemically resistant phosphate glasses with relatively low Tgs have become available only recently.

  2. Unique sodium phosphosilicate glasses designed through extended topological constraint theory.

    Zeng, Huidan; Jiang, Qi; Liu, Zhao; Li, Xiang; Ren, Jing; Chen, Guorong; Liu, Fude; Peng, Shou

    2014-05-15

    Sodium phosphosilicate glasses exhibit unique properties with mixed network formers, and have various potential applications. However, proper understanding on the network structures and property-oriented methodology based on compositional changes are lacking. In this study, we have developed an extended topological constraint theory and applied it successfully to analyze the composition dependence of glass transition temperature (Tg) and hardness of sodium phosphosilicate glasses. It was found that the hardness and Tg of glasses do not always increase with the content of SiO2, and there exist maximum hardness and Tg at a certain content of SiO2. In particular, a unique glass (20Na2O-17SiO2-63P2O5) exhibits a low glass transition temperature (589 K) but still has relatively high hardness (4.42 GPa) mainly due to the high fraction of highly coordinated network former Si((6)). Because of its convenient forming and manufacturing, such kind of phosphosilicate glasses has a lot of valuable applications in optical fibers, optical amplifiers, biomaterials, and fuel cells. Also, such methodology can be applied to other types of phosphosilicate glasses with similar structures.

  3. Compressive fatigue tests on a unidirectional glass/polyester composite at cryogenic temperatures

    Stone, E.L.; El-Marazki, L.O.; Young, W.C.

    1979-01-01

    The fatigue testing of a unidirectional glass-reinforced polyester composite at cryogenic temperatures to simulate the cyclic compressive loads of the magnet support struts in a superconductive magnetic energy storage unit is reported. Right circular cylindrical specimens were tested at 77, 4.2 K and room temperature at different stress levels using a 1-Hz haversine waveform imposed upon a constant baseload in a load-controlled closed-loop electrohydraulic test machine. Two failure modes, uniform mushrooming near one end and a 45 deg fracture line through the middle of the specimen, are observed, with no systematic difference in fatigue life between the modes. Fatigue lives obtained at 77 and 4.2 K are found to be similar, with fatigue failure at 100,000 cycles occurring at stress levels of 70 and 75% of the ultimate compressive strengths of specimens at room temperature and 77 K, respectively. The room temperature fatigue lives of the glass/polyester specimens are found to be intermediate between those reported for glass/epoxy composites with different glass contents costing over twice as much

  4. On the nature of low temperature internal friction peaks in metallic glasses

    Khonik, VA; Spivak, LV

    Low temperature (30 glass Ni60Nb40 subjected to preliminary inhomogeneous deformation by cold rolling, homogeneous tensile deformation or electrolytic charging with hydrogen is investigated. Cold rolling or hydrogenation result in appearance of similar

  5. Relationship between energy landscape and low-temperature dynamics of ±J spin glasses

    Kobe, S.; Krawczyk, J.

    2004-01-01

    Clusters and valleys in the exact low-energy landscape of finite Edwards-Anderson ±J spin glasses are related to the distribution of spin domains and free spins in the ground states. The time evolution of the spin correlation function reflects a walk through the landscape at a given temperature and shows typical glassy behaviour

  6. Interactions in a blend of two polymers greatly differing in glass transition temperature

    Kratochvíl, Jaroslav; Šturcová, Adriana; Sikora, Antonín; Dybal, Jiří

    2011-01-01

    Roč. 49, č. 14 (2011), s. 1031-1040 ISSN 0887-6266 Institutional research plan: CEZ:AV0Z40500505 Keywords : differential scanning calorimetry (DSC) * fouriertransform infrared spectroscopy (FT-IR) * glass transition temperature Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.531, year: 2011

  7. Effect of elevated temperature on the tensile strength of Napier/glass-epoxy hybrid reinforced composites

    Ridzuan, M. J. M.; Majid, M. S. Abdul; Afendi, M.; Firdaus, A. Z. Ahmad; Azduwin, K.

    2017-11-01

    The effects of elevated temperature on the tensile strength of Napier/glass-epoxy hybrid reinforced composites and its morphology of fractured surfaces are discussed. Napier/glass-epoxy hybrid reinforced composites were fabricated by using vacuum infusion method by arranging Napier fibres in between sheets of woven glass fibres. Napier and glass fibres were laminated with estimated volume ratios were 24 and 6 vol. %, respectively. The epoxy resin was used as matrix estimated to 70 vol. %. Specimens were tested to failure under tension at a cross-head speed of 1 mm/min using Universal Testing Machine (Instron) with a load cell 100 kN at four different temperatures of RT, 40°C, 60°C and 80°C. The morphology of fractured surface of hybrid composites was investigated by field emission scanning electron microscopy. The result shows reduction in tensile strength at elevated temperatures. The increase in the temperature activates the process of diffusion, and generates critical stresses which cause the damage at first-ply or at the centre of the hybrid plate, as a result lower the tensile strength. The observation of FESEM images indicates that the fracture mode is of evolution of localized damage, from fibre/matrix debonding, matric cracking, delamination and fibre breakage.

  8. Note: surface acoustic wave resonators for detecting of small changes of temperature: a thermometric "magnifying glass".

    Kryshtal, R G; Medved, A V

    2014-02-01

    Application of surface acoustic wave resonators with a phase format of an output signal as the thermometric "magnifying glass" is suggested. Possibilities of monitoring and measuring of small changes of temperature from 0.001 K to 0.3 K of objects having thermal contact with the resonator's substrate are shown experimentally.

  9. Material properties and glass transition temperatures of different thermoplastic starches after extrusion processing

    Janssen, Léon P.B.M.; Karman, Andre P.; Graaf, Robbert A. de

    Four different starch sources, namely waxy maize, wheat, potato and pea starch were extruded with the plasticizer glycerol, the latter in concentrations of 15, 20 and 25% (w/w). The glass transition temperatures of the resulting thermoplastic products were measured by Dynamic Mechanical Thermal

  10. Corrosion of glass-bonded sodalite as a function of pH and temperature

    Morss, L. R.; Stanley, M.; Tatko, C.; Ebert, W. L.

    1999-01-01

    This paper reports the results of corrosion tests with monoliths of sodalite, binder glass, and glass-bonded sodalite, a ceramic waste form (CWF) that is being developed to immobilize radioactive electrorefiner salt used to condition spent sodium-bonded nuclear fuel. These tests were performed with dilute pH-buffered solutions in the pH range of 5-10 at temperatures of 70 and 90 C. The pH dependence of the forward dissolution rates of the CWF and its components have been determined. The pH dependence of the dissolution rates of sodalite, binder glass, and glass-bonded sodalite are similar to the pH dependence of dissolution rate of borosilicate nuclear waste glasses, with a negative pH dependence in the acidic region and a positive pH dependence in the basic region. Our results on the forward dissolution rates and their temperature and pH dependence will be used as components of a waste form degradation model to predict the long-term behavior of the CWF in a nuclear waste repository

  11. Low temperature isotope effects of hydrogen diffusion in metallic glasses

    Hofmann, A.; Kronmueller, H.

    1989-01-01

    Snoek-like relaxation peaks of Hydrogen and Deuterium in amorphous Fe 80 B 20 , Fe 40 Ni 40 P 14 B 6 and Fe 91 Zr 9 are detected. At low H, D concentrations the peaks are near 200 K and show small isotope effects of the average activation energies (anti Q H ≅ 0.6 eV, anti Q D - anti Q H ≤ 10 meV). For higher H, D-contents the peaks shift to lower temperatures around to 120 K and show distinct isotope effects in the activation energies (anti Q H ≅ 0.3 eV, anti Q D - anti Q H ≅ 30 meV) and in the amplitude of the low temperature tails of the relaxation peaks. This points to isotope mass dependent deviations from the Arrhenius law due to nonthermal tunneling processes. (orig.)

  12. Composite properties for S-2 glass in a room-temperature-curable epoxy matrix

    Clements, L. L.; Moore, R. L.

    1979-01-01

    The authors have measured thermal and mechanical properties of several composites of S-2 glass fiber in a room-temperature-curable epoxy matrix. The filament-wound composites ranged from 50 to 70 vol% fiber. The composites had generally good to excellent mechanical properties, particularly in view of the moderate cost of the material. However, the composites showed rapid increases in transverse thermal expansion above 50 C, and this property must be carefully considered if any use above that temperature is contemplated.

  13. On the nature of low temperature anomalies of metallic glass inelastic properties

    Spivak, L.V.; Khonik, V.A.

    1997-01-01

    Low-temperature (30 60 Nb 40 metallic glass (MG) exposed to the preliminary cold deformation via rolling, to high-temperature homogeneous deformation or to electrolytic hydrogen absorption were investigated. Conclusion is made that the published low-temperature peaks of the internal friction in quick-hardened cold-deformed or hydrogen absorbed MGs are of the common dislocation-like nature. Effect of 2 MeV electron irradiation on the temperature dependence of the internal friction and on the elasticity module of hydrogenated specimens was investigated, as well [ru

  14. Measurement of mechanical properties of metallic glass at elevated temperature using sonic resonance method

    Kaluvan, Suresh; Zhang, Haifeng; Mridha, Sanghita; Mukherjee, Sundeep

    2017-04-01

    Bulk metallic glasses are fully amorphous multi-component alloys with homogeneous and isotropic structure down to the atomic scale. Some attractive attributes of bulk metallic glasses include high strength and hardness as well as excellent corrosion and wear resistance. However, there are few reports and limited understanding of their mechanical properties at elevated temperatures. We used a nondestructive sonic resonance method to measure the Young's modulus and Shear modulus of a bulk metallic glass, Zr41.2Ti13.8Cu12.5Ni10Be22.5, at elevated temperatures. The measurement system was designed using a laser displacement sensor to detect the sonic vibration produced by a speaker on the specimen in high-temperature furnace. The OMICRON Bode-100 Vector Network Analyzer was used to sweep the frequency and its output was connected to the speaker which vibrated the material in its flexural mode and torsional modes. A Polytec OFV-505 laser vibrometer sensor was used to capture the vibration of the material at various frequencies. The flexural and torsional mode frequency shift due to the temperature variation was used to determine the Young's modulus and Shear modulus. The temperature range of measurement was from 50°C to 350°C. The Young's modulus was found to reduce from 100GPa to 94GPa for the 300°C temperature span. Similarly, the Shear modulus decreased from 38.5GPa at 50°C to 36GPa at 350°C.

  15. Free volume from positron lifetime and pressure-volume-temperature experiments in relation to structural relaxation of van der Waals molecular glass-forming liquids.

    Dlubek, G; Shaikh, M Q; Rätzke, K; Paluch, M; Faupel, F

    2010-06-16

    Positron annihilation lifetime spectroscopy (PALS) is employed to characterize the temperature dependence of the free volume in two van der Waals liquids: 1, 1'-bis(p-methoxyphenyl)cyclohexane (BMPC) and 1, 1'-di(4-methoxy-5-methylphenyl)cyclohexane (BMMPC). From the PALS spectra analysed with the routine LifeTime9.0, the size (volume) distribution of local free volumes (subnanometer size holes), its mean, [v(h)], and mean dispersion, σ(h), were calculated. A comparison with the macroscopic volume from pressure-volume-temperature (PV T) experiments delivered the hole density and the specific hole free volume and a complete characterization of the free volume microstructure in that sense. These data are used in correlation with structural (α) relaxation data from broad-band dielectric spectroscopy (BDS) in terms of the Cohen-Grest and Cohen-Turnbull free volume models. An extension of the latter model allows us to quantify deviations between experiments and theory and an attempt to systematize these in terms of T(g) or of the fragility. The experimental data for several fragile and less fragile glass formers are involved in the final discussion. It was concluded that, for large differences in the fragility of different glass formers, the positron lifetime mirrors clearly the different character of these materials. For small differences in the fragility, additional properties like the character of bonds and chemical structure of the material may affect size, distribution and thermal behaviour of the free volume.

  16. Deformation and structure evolution of glassy poly(lactic acid) below the glass transition temperature

    Zhou, Chengbo; Li, Hongfei; Zhang, Yao

    2015-01-01

    , the onset of the mesocrystal formation is delayed to a higher strain value, whereas corresponding to the same critical orientation degree of amorphous chains (f(am) approximate to 0.45). The DSC results indicated that the post-T-g endothermic peak corresponding to the melting of mesocrystal appears...... and shifts to a higher temperature with increasing stretching temperature, followed by the down-shifts (to a lower temperature) of the exothermic peak of cold crystallization of PLA. The appearance of a small exothermic peak just before the melting peak related to the transition of the alpha' to alpha...... crystal implies the formation of an alpha' crystal during cold crystallization in the drawn PLA samples. The structure evolution of glassy PLA stretched below T-g was discussed in details....

  17. Thyroglobulin (Tg) Testing Revisited: Tg Assays, TgAb Assays, and Correlation of Results With Clinical Outcomes.

    Netzel, Brian C; Grebe, Stefan K G; Carranza Leon, B Gisella; Castro, M Regina; Clark, Penelope M; Hoofnagle, Andrew N; Spencer, Carole A; Turcu, Adina F; Algeciras-Schimnich, Alicia

    2015-08-01

    Measurement of thyroglobulin (Tg) by mass spectrometry (Tg-MS) is emerging as a tool for accurate Tg quantification in patients with anti-Tg autoantibodies (TgAbs). The objective of the study was to perform analytical and clinical evaluations of two Tg-MS assays in comparison with immunometric Tg assays (Tg-IAs) and Tg RIAs (Tg-RIAs) in a cohort of thyroid cancer patients. A total of 589 samples from 495 patients, 243 TgAb-/252 TgAb+, were tested by Beckman, Roche, Siemens-Immulite, and Thermo-Brahms Tg and TgAb assays, two Tg-RIAs, and two Tg-MS assays. The frequency of TgAb+ was 58%, 41%, 27%, and 39% for Roche, Beckman, Siemens-Immulite, and Thermo-Brahms, respectively. In TgAb- samples, clinical sensitivities and specificities of 100% and 74%-100%, respectively, were observed across all assays. In TgAb+ samples, all Tg-IAs demonstrated assay-dependent Tg underestimation, ranging from 41% to 86%. In TgAb+ samples, the use of a common cutoff (0.5 ng/mL) for the Tg-MS, three Tg-IAs, and the USC-RIA improved the sensitivity for the Tg-MSs and Tg-RIAs when compared with the Tg-IAs. In up to 20% of TgAb+ cases, Tg-IAs failed to detect Tg that was detectable by Tg-MS. In Tg-RIAs false-high biases were observed in TgAb+ samples containing low Tg concentrations. Tg-IAs remain the method of choice for Tg quantitation in TgAb- patients. In TgAb+ patients with undetectable Tg by immunometric assay, the Tg-MS will detect Tg in up to 20% additional cases. The Tg-RIA will detect Tg in approximately 35% cases, but a significant proportion of these will be clinical false-positive results. The undetectable Tg-MS seen in approximately 40% of TgAb+ cases in patients with disease need further evaluation.

  18. Glass transition temperature of dried lens tissue pretreated with trehalose, maltose, or cyclic tetrasaccharide.

    Kawata, Tetsuhiro; Matsuo, Toshihiko; Uchida, Tetsuya

    2014-01-01

    Glass transition temperature is a main indicator for amorphous polymers and biological macromolecules as materials, and would be a key for understanding the role of trehalose in protecting proteins and cells against desiccation. In this study, we measured the glass transition temperature by differential scanning calorimetry of dried lens tissues as a model of a whole biological tissue to know the effect of pretreatment by trehalose and other sugars. Isolated porcine lenses were incubated with saline, 100 or 1000 mM concentration of trehalose, maltose, or cyclic tetrasaccharide dissolved in saline at room temperature for 150 minutes. The solutions were removed and all samples were dried at room temperature in a desiccator until no weight change. The dried tissues were ground into powder and placed in a measuring pan for differential scanning calorimetry. The glass transition temperature of the dried lens tissues, as a mean and standard deviation, was 63.0 ± 6.4°C (n = 3) with saline pretreatment; 53.0 ± 0.8°C and 56.3 ± 2.7°C (n = 3), respectively, with 100 and 1000 mM trehalose pretreatment; 56.0 ± 1.6°C and 55.8 ± 1.1°C (n = 3), respectively, with 100 and 1000 mM maltose pretreatment; 60.0 ± 8.8°C and 59.2 ± 6.3°C (n = 3), respectively, with 100 and 1000 mM cyclic tetrasaccharide pretreatment. The glass transition temperature appeared lower, although not significantly, with trehalose and maltose pretreatments than with saline and cyclic tetrasaccharide pretreatments (P > 0.05, Kruskal-Wallis test). The glass transition temperature of the dried lens tissues with trehalose pretreatment appeared more noticeable on the thermogram, compared with other pretreatments. The glass transition temperature was measured for the first time in the dried lens tissues as an example of a whole biological tissue and might provide a basis for tissue preservation in the dried condition.

  19. Practical Considerations for Determination of Glass Transition Temperature of a Maximally Freeze Concentrated Solution.

    Pansare, Swapnil K; Patel, Sajal Manubhai

    2016-08-01

    Glass transition temperature is a unique thermal characteristic of amorphous systems and is associated with changes in physical properties such as heat capacity, viscosity, electrical resistance, and molecular mobility. Glass transition temperature for amorphous solids is referred as (T g), whereas for maximally freeze concentrated solution, the notation is (T g'). This article is focused on the factors affecting determination of T g' for application to lyophilization process design and frozen storage stability. Also, this review provides a perspective on use of various types of solutes in protein formulation and their effect on T g'. Although various analytical techniques are used for determination of T g' based on the changes in physical properties associated with glass transition, the differential scanning calorimetry (DSC) is the most commonly used technique. In this article, an overview of DSC technique is provided along with brief discussion on the alternate analytical techniques for T g' determination. Additionally, challenges associated with T g' determination, using DSC for protein formulations, are discussed. The purpose of this review is to provide a practical industry perspective on determination of T g' for protein formulations as it relates to design and development of lyophilization process and/or for frozen storage; however, a comprehensive review of glass transition temperature (T g, T g'), in general, is outside the scope of this work.

  20. Fabrication of high activity glasses in the cells VULCAIN and PIVER. Leaching at three temperatures of some of these glasses in the VULCAIN cell

    Jacquet-Francillon, N.; Laude, F.; Magnier, A.; Vernaz, E.

    1982-01-01

    The methods for manufacturing and leaching four blocks of glass and one of vitreous ceramic made as from actual solutions of fission products in the Vulcain cell are described. The four blocks of glass and the vitreous ceramic are in lumps weighing from 1.6 to 1.9 kg. The volatilities measured during the making of these blocks of glass by a pot (intermittent) method and expressed as a percentage of the total activity trapped in the condenser vary from 30.7 to 9.4 for ruthenium. In the case of cesium, strontium and cerium, the volatilization rates are between 0.01 and 0.5%. The behaviour under leaching of the vitreous ceramic is less good than its mother glass. The increase in leaching rates with temperature differs from one glass to the next and according to the components

  1. Development of models and software for liquidus temperatures of glasses of HWVP products. Final report

    Hrma, P.R.; Vienna, J.D.; Pelton, A.D.

    1996-03-01

    In an earlier report [92 Pel] was described the development of software and thermodynamic databases for the calculation of liquidus temperatures of glasses of HWVP products containing the components SiO 2 -B 2 O 3 -Na 2 O-Li 2 O-CaO-MgO-Fe 2 O 3 -Al 2 O 3 -ZrO 2 -open-quotes othersclose quotes. The software package developed at that time consisted of the EQUILIB program of the F*A*C*T computer system with special input/output routines. Since then, Battelle has purchased the entire F*A*C*T computer system, and this fully replaces the earlier package. Furthermore, with the entire F*A*C*T system, additional calculations can be performed such as calculations at fixed O 2 , SO 2 etc. pressures, or graphing of output. Furthermore, the public F*A*C*T database of over 5000 gaseous species and condensed phases is now accessible. The private databases for the glass and crystalline phases were developed for Battelle by optimization of thermodynamic and phase diagram data. That is, all available data for 2- and 3-component sub-systems of the 9-component oxide system were collected, and parameters of model equations for the thermodynamic properties were found which best reproduce all the data. For representing the thermodynamic properties of the glass as a function of composition and temperature, the modified quasichemical model was used. This model was described in the earlier report [92 Pel] along with all the optimizations. With the model, it was possible to predict the thermodynamic properties of the 9-component glass, and thereby to calculate liquidus temperatures. Liquidus temperatures measured by Battelle for 123 CVS glass compositions were used to test the model and to refine the model by the addition of further parameters

  2. Determination of Material Properties Near the Glass Transition Temperature for an Isogrid Boom

    Blandino, Joseph R.; Woods-Vedeler, Jessica A. (Technical Monitor)

    2002-01-01

    Experiments were performed and results obtained to determine the temperature dependence of the modulus of elasticity for a thermoplastic isogrid tube. The isogrid tube was subjected to axial tensile loads of 0-100 lbf and strain was measured at room and elevated temperatures of 100, 120, 140, 160, 180, 190, and 200 F. These were based on tube manufacturer specifying an incorrect glass transition temperature of 210 F. Two protocols were used. For the first protocol the tube was brought to temperature and a tensile test performed. The tube was allowed to cool between tests. For the second protocol the tube was ramped to the desired test temperature and held. A tensile test was performed and the tube temperature ramped to the next test temperature. The second protocol spanned the entire test range. The strain rate was constant at 0.008 in/min. Room temperature tests resulted in the determination of an average modulus of 2.34 x 106 Psi. The modulus decreased above 100 F. At 140 F the modulus had decreased by 7.26%. The two test protocols showed good agreement below 160 F. At this point the glass transition temperature had been exceeded. The two protocols were not repeated because the tube failed.

  3. Density-temperature scaling of the fragility in a model glass-former

    Schrøder, Thomas; Sengupta, Shiladitya; Sastry, Srikanth

    2013-01-01

    . Such a scaling, referred to as density-temperature (DT) scaling, is exact for liquids with inverse power law (IPL) interactions but has also been found to be approximately valid in many non-IPL liquids. We have analyzed the consequences of DT scaling on the density dependence of the fragility in a model glass......Dynamical quantities e.g. diffusivity and relaxation time for some glass-formers may depend on density and temperature through a specific combination, rather than independently, allowing the representation of data over ranges of density and temperature as a function of a single scaling variable......-former. We find the density dependence of kinetic fragility to be weak, and show that it can be understood in terms of DT scaling and deviations of DT scaling at low densities. We also show that the Adam-Gibbs relation exhibits DT scaling and the scaling exponent computed from the density dependence...

  4. On the nature of low temperature internal friction peaks in metallic glasses

    Khonik, V.A. [State Pedagogical Univ., Voronezh (Russian Federation); Spivak, L.V. [State Univ., Perm (Russian Federation)

    1996-01-01

    Low temperature (30 < T < 300 K) internal friction in a metallic glass Ni{sub 60}Nb{sub 40} subjected to preliminary inhomogeneous deformation by cold rolling, homogeneous tensile deformation or electrolytic charging with hydrogen is investigated. Cold rolling or hydrogenation result in appearance of similar internal friction peaks and hysteresis damping. Homogeneous deformation has no influence on low temperature internal friction. The phenomenon of microplastic deformation during hydrogenation of weakly stressed samples is revealed. It is argued that microplastic deformation of metallic glasses during hydrogenation without external stress takes place too. Plastic flow both on cold rolling and hydrogenation occurs via formation and motion of dislocation-like defects which are the reason of the observed anelastic anomalies. It is concluded that low temperature internal friction peaks described in the literature for as-cast, cold deformed and hydrogenated samples have common dislocation-like origin.

  5. Effects of high-temperature gas dealkalization on surface mechanical properties of float glass

    Senturk, Ufuk

    The surface topography, and the near-surface structure and mechanical property changes on float glass, that was treated in atmospheres containing SOsb2, HCl, and 1,1 difluoroethane (DFE) gases, at temperatures in the glass transition region, were studied. Structure was investigated using surface sensitive infrared spectroscopy techniques (attenuated total reflectance (ATR) and diffuse reflectance (DRIFT)) and the topography was evaluated using atomic force microscopy (AFM). The results obtained from the two FTIR methods were in agreement with each other. Mechanical property characteristics of the surface were determined by measuring microhardness using a recording microindentation set-up. A simple analysis performed on the three hardness calculation methods-LVH, LVHsb2, and Lsb2VH-indicated that LVH and LVHsb2 are less effected by measurement errors and are better suited for the calculation of hardness. Contact damage characteristics of the treated glass was also studied by monitoring the crack initiation behavior during indentation, using acoustic emission. The results of the studies, aiming for the understanding of the structure, topography, and hardness property changes indicate that the treatment parameters-temperature, time, and treatment atmosphere conditions-are significant factors influencing these properties. The analysis of these results suggest a relation to exist between the three properties. This relation is used in understanding the surface mechanical properties of the treated float glasses. The difference in the thermal expansion coefficients between the dealkalized surface and bulk, the nature of surface structure changes, structural relaxation, surface water content, and glass transformation temperature are identified as the major factors having an influence on the properties. A model connecting these features is suggested. A difference in the structure, hardness, and topography on the air and tin sides of float glass is also shown to exist. The

  6. Introduction to the crystallization phenomenon in nuclear glass

    Jacquet Francillon, N.

    1997-01-01

    Crystallization is a subject for concern because of its potentially detrimental effects on the technological feasibility of high-temperature melting, and on the chemical durability of the material at intermediate and low temperatures during interim storage or after disposal. The tendency of glass to crystallize depends to a large extent on the composition of the frit and/or of the waste to be solidified. It depends too of the thermal history of the glass generally, the knowledge is mainly upon determination of the time-temperature-transition (TTT) curves, crystal identification and quantification techniques, and their effects on the durability of the glass matrix. French experience is presented. Only a few authors addressed the long-term development of crystalline phases, notably at temperatures below the vitreous transition temperature Tg. Some recommendations for glass crystallization studies are made but glass crystallization after disposal is acceptable provided some conditions are met. (author)

  7. Temperature Dependence of Arn+ Cluster Backscattering from Polymer Surfaces: a New Method to Determine the Surface Glass Transition Temperature.

    Poleunis, Claude; Cristaudo, Vanina; Delcorte, Arnaud

    2018-01-01

    In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to study the intensity variations of the backscattered Ar n + clusters as a function of temperature for several amorphous polymer surfaces (polyolefins, polystyrene, and polymethyl methacrylate). For all these investigated polymers, our results show a transition of the ratio Ar 2 + /(Ar 2 + + Ar 3 + ) when the temperature is scanned from -120 °C to +125 °C (the exact limits depend on the studied polymer). This transition generally spans over a few tens of degrees and the temperature of the inflection point of each curve is always lower than the bulk glass transition temperature (T g ) reported for the considered polymer. Due to the surface sensitivity of the cluster backscattering process (several nanometers), the presented analysis could provide a new method to specifically evaluate a surface transition temperature of polymers, with the same lateral resolution as the gas cluster beam. Graphical abstract ᅟ.

  8. Low temperature high density plasma nitriding of stainless steel molds for stamping of oxide glasses

    Aizawa Tatsuhiko

    2016-01-01

    Full Text Available Various kinds of stainless steels have been widely utilized as a die for mold- and direct-stamping processes of optical oxide glasses. Since they suffered from high temperature transients and thermal cycles in practice, they must be surface-treated by dry and wet coatings, or, by plasma nitriding. Martensitic stainless steel mold was first wet plated by the nickel phosphate (NiP, which was unstable at the high temperature stamping condition; and, was easy to crystalize or to fracture by itself. This issue of nuisance significantly lowered the productivity in fabrication of optical oxide-glass elements. In the present paper, the stainless steel mold was surface-treated by the low-temperature plasma nitriding. The nitrided layer by this surface modification had higher nitrogen solute content than 4 mass%; the maximum solid-solubility of nitrogen is usually 0.1 mass% in the equilibrium phase diagram. Owing to this solid-solution with high nitrogen concentration, the nitrided layer had high hardness over 1400 HV within its thickness of 50 μm without any formation of nitrides after plasma nitriding at 693 K for 14.4 ks. This plasma-nitrided mold was utilized for mold-stamping of two colored oxide glass plates at 833 K; these plates were successfully deformed and joined into a single glass plate by this stamping without adhesion or galling of oxide glasses onto the nitrided mold surface.

  9. Correlation between in vitro Elastomeric Force Degradation and Glass Transition Temperature determined by Dynamic Mechanical Analysis

    Manu Krishnan

    2012-01-01

    Conclusion: Tg can be considered as a dependable parameter in envisaging the force properties of an elastomeric chain. Clinically, it suggested that a polymer with higher Tg can give higher or optimum levels of force for tooth movement.

  10. The descent into glass formation in polymer fluids.

    Freed, Karl F

    2011-03-15

    Glassy materials have been fundamental to technology since the dawn of civilization and remain so to this day: novel glassy systems are currently being developed for applications in energy storage, electronics, food, drugs, and more. Glass-forming fluids exhibit a universal set of transitions beginning at temperatures often in excess of twice the glass transition temperature T(g) and extending down to T(g), below which relaxation becomes so slow that systems no longer equilibrate on experimental time scales. Despite the technological importance of glasses, no prior theory explains this universal behavior nor describes the huge variations in the properties of glass-forming fluids that result from differences in molecular structure. Not surprisingly, the glass transition is currently regarded by many as the deepest unsolved problem in solid state theory. In this Account, we describe our recently developed theory of glass formation in polymer fluids. Our theory explains the origin of four universal characteristic temperatures of glass formation and their dependence on monomer-monomer van der Waals energies, conformational energies, and pressure and, perhaps most importantly, on molecular details, such as monomer structure, molecular weight, size of side groups, and so forth. The theory also provides a molecular explanation for fragility, a parameter that quantifies the rate of change with temperature of the viscosity and other dynamic mechanical properties at T(g). The fragility reflects the fluid's thermal sensitivity and determines the manner in which glass-formers can be processed, such as by extrusion, casting, or inkjet spotting. Specifically, the theory describes the change in thermodynamic properties and fragility of polymer glasses with variations in the monomer structure, the rigidity of the backbone and side groups, the cohesive energy, and so forth. The dependence of the structural relaxation time at lower temperatures emerges from the theory as the Vogel

  11. High-temperature expansion and knock-out properties of moulding sands with water glass

    Major-Gabryś K.

    2007-01-01

    Full Text Available The article focuses on the topic of improving the knock-out properties of moulding sand with water glass and ester hardener. It is settled that the cause of worse knock-out properties of moulding sand can be brought by their thermal expansion in increased temperatures. There is a presentation of the influence of different additives, containing Al2O3, on moulding sands’ expansion in increased temperatures. Within the frames of research, there was an elaboration of the influence of authors own additive- Glassex, on the expansion phenomenon of moulding sands with water glass and ester hardener. It is concluded, that the new additive stops the expansion of moulding sands and as well it improves their knock-out properties.

  12. Effects of molecular weight on the glass transition temperature in Durolon polycarbonate

    Miranda, Adelina; Sciani, Valdir

    1995-01-01

    The effect of variation of the dose rate on degradation mechanism of PC Durolon irradiated with gamma rays was determined trough out intrinsic viscosity and thermal analysis of DSC-type measurements. The results showed a linear relationship between the glass transition temperature and the viscosimetric average molecular weight. From the results it's shown that with an increased of the dose rate it also increases the degradation of the material. (author). 12 refs., 3 figs

  13. Temperature profiles for laser-induced heating of nanocrystals embedded in glass matrices

    Bhatnagar, Promod K.; Nagpal, Swati

    2001-05-01

    Quantum confined nanostructures are very important because of their application towards optoelectronic devices. Commercial colored glass filters, which have large semiconductor particles, are being used to manufacture nanocrystals by suitable heat treatments. The progress in this area has been hampered by high size dispersion of these dots in the glass matrix which leads to reduction in higher order susceptibility thereby reducing non-linearity. In the present paper attempt has been made to theoretically model the temperature profiles of a laser irradiated CdS doped Borosilicate sample. Laser being used has a beam diameter of 1.5 mm and energy for 10 nsec pulse is 10 mJ. Two different particle radii of 5 nm and 10 nm have been considered. It is found that larger particles reach higher temperatures for the same pulse characteristics. This is because smaller particles have larger surface to volume ratio and hence dissipates out heat faster to the surrounding. Hence bigger particles will reach dissolution temperature faster than smaller particle and particle beyond a certain size should dissolve in the glass matrix when a sample is heat treated by laser. This could lead to a reduction in size dispersion of the nanocrystals. Also photodarkening effect found in semiconductor doped glasses is a big handicap for practical application of these materials in fast optical switching and non-linear optical devices. Photodarkening effect has been established to be a photochemical effect and it is important to study the temperature profiles around a particle since it will effect the impurity migration.

  14. DWPF glass transition temperatures - What they are and why they are important

    Marra, S.L.; Applewhite-Ramsey, A.L.; Jantzen, C.M.

    1991-01-01

    The Department of Energy has defined a set of requirements for the DWPF canistered waste form which must be met in order to assure compatibility with, and acceptance by, the first geologic repository. These requirements are the Waste Acceptance Preliminary Specifications (WAPS). The WAPS require DWPF to report glass transition temperatures for the projected range of compositions. This information will be used by the repository to establish waste package design limits

  15. Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

    Chen, Chang-hong; Feng, Ke-qin; Zhou, Yu; Zhou, Hong-ling

    2017-08-01

    Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature (900-1060°C) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060°C. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength (16.64 MPa) among the investigated samples and a relatively low bulk density (0.83 g/cm3), were attained in the case of the foamed glass-ceramics sintered at 1000°C.

  16. Effect of sintering temperature on physical, structural and optical properties of wollastonite based glass-ceramic derived from waste soda lime silica glasses

    Karima Amer Almasri

    Full Text Available The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3 based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM, Fourier transforms infrared reflection spectroscopy (FTIR, and X-ray diffraction (XRD. The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature. Keywords: Soda lime silica glass, Wollastonite, Sintering, Structural properties, Optical properties

  17. Asymptotic solutions of glass temperature profiles during steady optical fibre drawing

    Taroni, M.

    2013-03-12

    In this paper we derive realistic simplified models for the high-speed drawing of glass optical fibres via the downdraw method that capture the fluid dynamics and heat transport in the fibre via conduction, convection and radiative heating. We exploit the small aspect ratio of the fibre and the relative orders of magnitude of the dimensionless parameters that characterize the heat transfer to reduce the problem to one- or two-dimensional systems via asymptotic analysis. The resulting equations may be readily solved numerically and in many cases admit exact analytic solutions. The systematic asymptotic breakdown presented is used to elucidate the relative importance of furnace temperature profile, convection, surface radiation and conduction in each portion of the furnace and the role of each in controlling the glass temperature. The models derived predict many of the qualitative features observed in real industrial processes, such as the glass temperature profile within the furnace and the sharp transition in fibre thickness. The models thus offer a desirable route to quick scenario testing, providing valuable practical information about the dependencies of the solution on the parameters and the dominant heat-transport mechanism. © 2013 Springer Science+Business Media Dordrecht.

  18. Experimental evidence for excess entropy discontinuities in glass-forming solutions.

    Lienhard, Daniel M; Zobrist, Bernhard; Zuend, Andreas; Krieger, Ulrich K; Peter, Thomas

    2012-02-21

    Glass transition temperatures T(g) are investigated in aqueous binary and multi-component solutions consisting of citric acid, calcium nitrate (Ca(NO(3))(2)), malonic acid, raffinose, and ammonium bisulfate (NH(4)HSO(4)) using a differential scanning calorimeter. Based on measured glass transition temperatures of binary aqueous mixtures and fitted binary coefficients, the T(g) of multi-component systems can be predicted using mixing rules. However, the experimentally observed T(g) in multi-component solutions show considerable deviations from two theoretical approaches considered. The deviations from these predictions are explained in terms of the molar excess mixing entropy difference between the supercooled liquid and glassy state at T(g). The multi-component mixtures involve contributions to these excess mixing entropies that the mixing rules do not take into account. © 2012 American Institute of Physics

  19. Yersinia enterocolitica-Specific Infection by Bacteriophages TG1 and ϕR1-RT Is Dependent on Temperature-Regulated Expression of the Phage Host Receptor OmpF.

    Leon-Velarde, Carlos G; Happonen, Lotta; Pajunen, Maria; Leskinen, Katarzyna; Kropinski, Andrew M; Mattinen, Laura; Rajtor, Monika; Zur, Joanna; Smith, Darren; Chen, Shu; Nawaz, Ayesha; Johnson, Roger P; Odumeru, Joseph A; Griffiths, Mansel W; Skurnik, Mikael

    2016-09-01

    Bacteriophages present huge potential both as a resource for developing novel tools for bacterial diagnostics and for use in phage therapy. This potential is also valid for bacteriophages specific for Yersinia enterocolitica To increase our knowledge of Y. enterocolitica-specific phages, we characterized two novel yersiniophages. The genomes of the bacteriophages vB_YenM_TG1 (TG1) and vB_YenM_ϕR1-RT (ϕR1-RT), isolated from pig manure in Canada and from sewage in Finland, consist of linear double-stranded DNA of 162,101 and 168,809 bp, respectively. Their genomes comprise 262 putative coding sequences and 4 tRNA genes and share 91% overall nucleotide identity. Based on phylogenetic analyses of their whole-genome sequences and large terminase subunit protein sequences, a genus named Tg1virus within the family Myoviridae is proposed, with TG1 and ϕR1-RT (R1RT in the ICTV database) as member species. These bacteriophages exhibit a host range restricted to Y. enterocolitica and display lytic activity against the epidemiologically significant serotypes O:3, O:5,27, and O:9 at and below 25°C. Adsorption analyses of lipopolysaccharide (LPS) and OmpF mutants demonstrate that these phages use both the LPS inner core heptosyl residues and the outer membrane protein OmpF as phage receptors. Based on RNA sequencing and quantitative proteomics, we also demonstrate that temperature-dependent infection is due to strong repression of OmpF at 37°C. In addition, ϕR1-RT was shown to be able to enter into a pseudolysogenic state. Together, this work provides further insight into phage-host cell interactions by highlighting the importance of understanding underlying factors which may affect the abundance of phage host receptors on the cell surface. Only a small number of bacteriophages infecting Y. enterocolitica, the predominant causative agent of yersiniosis, have been previously described. Here, two newly isolated Y. enterocolitica phages were studied in detail, with the aim of

  20. On the Frequency Correction in Temperature-Modulated Differential Scanning Calorimetry of Glass Transition

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    2012-01-01

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Simulations of TMDSC signals were performed for Corning EAGLE XG® glass over a wide range of modulation frequencies. Our results reveal that the frequency...... correction commonly used in the interpretation of TMDSC signals leads to a master nonreversing heat flow curve independent of modulation frequency, provided that sufficiently high frequencies are employed in the TMDSC measurement. A master reversing heat flow curve can also be generated through the frequency...

  1. Effect of γ-radiation on glass transition temperature of Poly(Bisphenol A carbonate) (PC)

    Kalkar, A.K.; Kundagol, S.

    1988-01-01

    Thin films of pure Poly(Bisphenol A carbonate) (PC) were γ-irradiated at room temperature from Co 60 source for varied doses, for the systematic study of γ-radiation on glass transition temperature (Tsub(g)) of PC. It was found that Tsub(g) of PC decreases with increasing doses. Irradiation of γ-rays on PC results in evolution of CO, CO 2 and H 2 from carbonate linkage and methyl group and which results in lowering of average mol.wt. of bul k polymer. Hence, overall increase in free volume increases chain mobility and thus reduces the Tsub(g). (author)

  2. Effect of SiO2 addition and gamma irradiation on the lithium borate glasses

    Raut, A. P.; Deshpande, V. K.

    2018-01-01

    The physical properties like density, glass transition temperature (Tg), and ionic conductivity of lithium borate (LB) glasses with SiO2 addition were measured before and after gamma irradiation. Remarkable changes in properties have been obtained in the physical properties of LB glasses with SiO2 addition and after gamma irradiation. The increase in density and glass transition temperature of LB glasses with SiO2 addition has been explained with the help of increase in density of cross linking due to SiO4 tetrahedra formation. The increase in ionic conductivity with SiO2 addition was explained with the help of ‘mixed glass former effect’. The increase in density and Tg of LB glasses with SiO2 addition after gamma irradiation has been attributed to fragmentation of bigger ring structure into smaller rings, which increases the density of cross linking and hence compaction. The exposure of gamma irradiation has lead to decrease in ionic conductivity of LB glasses with SiO2 addition. The atomic displacement caused by gamma irradiation resulted in filling of interstices and decrease in trapping sites. This explains the obtained decrease in ionic conductivity after gamma irradiation of glasses. The obtained results of effect of SiO2 addition and gamma irradiation on the density, Tg and ionic conductivity has been supported by FTIR results.

  3. Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

    Varghese, Jobin; Vahera, Timo; Ohsato, Hitoshi; Iwata, Makoto; Jantunen, Heli

    2017-10-01

    In this paper, a novel low-temperature sintering substrate for low temperature co-fired ceramic applications based on indialite/cordierite glass ceramics with Bi2O3 as a sintering aid showing low permittivity (εr) and ultralow dielectric loss (tan δ) is described. The fine powder of indialite was prepared by the crystallization of cordierite glass at 1000 °C/1 h. The optimized sintering temperature was 900 °C with 10 wt % Bi2O3 addition. The relative density achieved was 97%, and εr and tan δ were 6.10 and 0.0001 at 1 MHz, respectively. The composition also showed a moderately low temperature coefficient of relative permittivity of 118 ppm/°C at 1 MHz. The obtained linear coefficient of thermal expansion was 3.5 ppm/°C in the measured temperature range of 100 to 600 °C. The decreasing trend in dielectric loss, the low relative permittivity at 1 MHz, and the low thermal expansion of the newly developed composition make it an ideal choice for radio frequency applications.

  4. Thyroglobulin (Tg) recovery testing with quantitative Tg antibody measurement for determining interference in serum Tg assays in differentiated thyroid carcinoma

    Persoon, ACM; Links, TP; Wilde, J; Sluiter, WJ; Wolffenbuttel, BHR; van den Ouweland, JMW

    Background: Thyroglobulin (Tg) measurements are complicated by interference from Tg autoantibodies (TgAbs) or heterophilic antibodies (HAMAs). We used a new automated immunochemiluminometric assay (ICMA) with Tg recovery (TgR) on the Nichols Advantage (R) platform to reassess the clinical utility of

  5. Effect of thermal history on mechanical properties of polyetheretherketone below the glass transition temperature

    Cebe, Peggy; Chung, Shirley Y.; Hong, Su-Don

    1987-01-01

    The effect of thermal history on the tensile properties of polyetheretherketone neat resin films was investigated at different test temperatures (125, 25, and -100) using four samples: fast-quenched amorphous (Q); quenched, then crystallized at 180 C (C180); slowly cooled (for about 16 h) from the melt (SC); and air-cooled (2-3 h) from the melt (AC). It was found that thermal history significantly affects the tensile properties of the material below the glass transition. Fast quenched amorphous films were most tough, could be drawn to greatest strain before rupture, and undergo densification during necking; at the test temperature of -100 C, these films had the best ultimate mechanical properties. At higher temperatures, the semicrystalline films AC and C180 had properties that compared favorably with the Q films. The SC films exhibited poor mechanical properties at all test temperatures.

  6. Glass transition in thaumatin crystals revealed through temperature-dependent radiation-sensitivity measurements

    Warkentin, Matthew, E-mail: maw64@cornell.edu; Thorne, Robert E. [Physics Department, Cornell University, Ithaca, New York (United States)

    2010-10-01

    Radiation damage to protein crystals exhibits two regimes of temperature-activated behavior between T = 300 and 100 K, with a crossover at the protein glass transition near 200 K. These results have implications for mechanistic studies of proteins and for structure determination when cooling to T = 100 K creates excessive disorder. The temperature-dependence of radiation damage to thaumatin crystals between T = 300 and 100 K is reported. The amount of damage for a given dose decreases sharply as the temperature decreases from 300 to 220 K and then decreases more gradually on further cooling below the protein-solvent glass transition. Two regimes of temperature-activated behavior were observed. At temperatures above ∼200 K the activation energy of 18.0 kJ mol{sup −1} indicates that radiation damage is dominated by diffusive motions in the protein and solvent. At temperatures below ∼200 K the activation energy is only 1.00 kJ mol{sup −1}, which is of the order of the thermal energy. Similar activation energies describe the temperature-dependence of radiation damage to a variety of solvent-free small-molecule organic crystals over the temperature range T = 300–80 K. It is suggested that radiation damage in this regime is vibrationally assisted and that the freezing-out of amino-acid scale vibrations contributes to the very weak temperature-dependence of radiation damage below ∼80 K. Analysis using the radiation-damage model of Blake and Phillips [Blake & Phillips (1962 ▶), Biological Effects of Ionizing Radiation at the Molecular Level, pp. 183–191] indicates that large-scale conformational and molecular motions are frozen out below T = 200 K but become increasingly prevalent and make an increasing contribution to damage at higher temperatures. Possible alternative mechanisms for radiation damage involving the formation of hydrogen-gas bubbles are discussed and discounted. These results have implications for mechanistic studies of proteins and for

  7. Degradation of glass-fiber reinforced plastics by low temperature irradiation

    Nishijima, S.; Nishiura, T.; Ueno, S.; Tsukazaki, Y.; Okada, T.; Okada, T.M.; Miyata, K.; Kodaka, H.

    1998-01-01

    Low-temperature irradiation effects of glass-fiber reinforced plastics (GFRP) have been investigated in terms of mechanical properties such as interlaminar shear strength and creep, in order to obtain the selection standard of insulating materials of superconducting magnets used for fusion reactor. It was revealed that the degradation of interlaminar shear strength was strongly dependent of characteristics of matrix and/or glass/epoxy interface. Especially, the research has been carried out towards the creep behaviour of epoxy which is the matrix of GFRP, by both experimental and simulation method. It was suggested that the synergistic effects was observed in creep test. From the molecular dynamics simulation it was found that the cage effects was the one of the main reason of the stress effects of creep behavior under irradiation. (author)

  8. Effectiveness of high temperature innovative geometry fixed ceramic matrix regenerators used in glass furnaces

    Wołkowycki Grzegorz

    2016-03-01

    Full Text Available The paper presents the effectiveness of waste heat recovery regenerators equipped with innovative ceramic matrix forming an integral part of a real glass furnace. The paper full description of the regenerators’ matrix structure with its dimensions, thermo-physical properties and operating parameters is included experimentally determined was the effectiveness of the regenerators has been descrbed using the obtained experimental data such as the operating temperature, gas flows as well as the gases generated during the liquid glass manufacturing process. The effectiveness values refer not only to the heating cycle when the regenerator matrix is heated by combustion gases but also to the cooling cycle in which the matrix is cooled as a result of changes in the direction of the flowing gas. On the basis of the determined effectiveness values for both cycles and measurement uncertainties it was possible, to calculate the weighted average efficiency for each of the regenerators.

  9. Candidate Low-Temperature Glass Waste Forms for Technetium-99 Recovered from Hanford Effluent Management Facility Evaporator Concentrate

    Ding, Mei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tang, Ming [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rim, Jung Ho [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chamberlin, Rebecca M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-07-24

    Alternative treatment and disposition options may exist for technetium-99 (99Tc) in secondary liquid waste from the Hanford Direct-Feed Low-Activity Waste (DFLAW) process. One approach includes development of an alternate glass waste form that is suitable for on-site disposition of technetium, including salts and other species recovered by ion exchange or precipitation from the EMF evaporator concentrate. By recovering the Tc content from the stream, and not recycling the treated concentrate, the DFLAW process can potentially be operated in a more efficient manner that lowers the cost to the Department of Energy. This report provides a survey of candidate glass formulations and glass-making processes that can potentially incorporate technetium at temperatures <700 °C to avoid volatilization. Three candidate technetium feed streams are considered: (1) dilute sodium pertechnetate loaded on a non-elutable ion exchange resin; (2) dilute sodium-bearing aqueous eluent from ion exchange recovery of pertechnetate, or (3) technetium(IV) oxide precipitate containing Sn and Cr solids in an aqueous slurry. From the technical literature, promising candidate glasses are identified based on their processing temperatures and chemical durability data. The suitability and technical risk of three low-temperature glass processing routes (vitrification, encapsulation by sintering into a glass composite material, and sol-gel chemical condensation) for the three waste streams was assessed, based on available low-temperature glass data. For a subset of candidate glasses, their long-term thermodynamic behavior with exposure to water and oxygen was modeled using Geochemist’s Workbench, with and without addition of reducing stannous ion. For further evaluation and development, encapsulation of precipitated TcO2/Sn/Cr in a glass composite material based on lead-free sealing glasses is recommended as a high priority. Vitrification of pertechnetate in aqueous anion exchange eluent solution

  10. Impact of cationic diffusion on properties of iron-bearing glass fibres

    Smedskjaer, Morten M.; Yue, Yuanzheng; Deubener, Joachim

    2010-01-01

    A silica-rich surface layer of Fe3+-containing aluminosilicate glass fibres is created by means of an inward diffusion process of divalent network modifying cations. The latter is caused by the reduction of Fe3+ to Fe2+ when the fibres undergo a heat treatment at temperatures around the glass...... transition temperature (Tg) in a reducing H2/N2 atmosphere. The thickness of the surface layer can be adjusted by varying the temperature or the duration of the heat treatment. The reduction process has a significant impact on the glass transition and crystallization behaviour, high temperature stability...

  11. Avaliação da temperatura de transição vítrea de compósitos poliméricos reparados de uso aeronáutico Evaluation of glass transition temperature of the repaired polymeric composites of aeronautical use

    Jane M. F. de Paiva

    2006-03-01

    Full Text Available Este trabalho mostra a avaliação da temperatura de transição vítrea (Tg, por DMTA, de três famílias de compósitos poliméricos reparados, tendo como laminados base tecidos de fibras de carbono/resina epóxi modificada com elastômero (F584, vidro/resina epóxi (F161 e aramida/resina epóxi (F161. Os compósitos foram laminados manualmente por processo convencional e curados em autoclave de indústria aeronáutica. Posteriormente, danos foram simulados sendo, em seguida, reparados adotando-se a técnica de sobreposição de camadas de pré-impregnados de resina epóxi (F155, com adição de filme adesivo de epóxi (FM 73. As curvas DMTA mostram os efeitos da combinação de diferentes sistemas de resinas na Tg e, conseqüentemente, na temperatura de serviço do componente reparado. O material de reparo utilizado, baseado em pré-impregnados com resina epóxi F155 e filme adesivo de epóxi, provocou a redução da Tg dos compósitos reparados. Para os laminados base com tecido de fibras de carbono e vidro foram verificadas reduções de aproximadamente 30 °C na Tg. Este efeito foi mais pronunciado (redução de aproximadamente 40 °C quando o laminado reparado de aramida foi submetido a condicionamento higrotérmico a temperatura e umidade elevadas. Esta redução na Tg dos laminados reparados é atribuída à migração do adesivo para o pré-impregnado de resina epóxi F155 utilizado no reparo, durante o processo de cura, e à plasticização do sistema polimérico pela água, durante o condicionamento higrotérmico. A redução da Tg leva a uma conseqüente redução da temperatura de serviço do compósito polimérico reparado.This work shows the evaluation of the glass transition temperature (Tg by DMTA of three different families of repaired polymeric composites, manufactured with carbon fiber fabric/epoxy F584, glass fabric/epoxy F161 and aramide fabric/epoxy F161, respectively. The composites were laminated by conventional hand

  12. Lap shear strength of selected adhesives (epoxy, varnish, B-stage glass cloth) in liquid nitrogen and at room temperature

    Froelich, K.J.; Fitzpatrick, C.M.

    1976-12-01

    The adhesives included several epoxy resins, a varnish, and a B-stage glass cloth (a partially cured resin in a fiberglass cloth matrix). Several parameters critical to bond strength were varied: adhesive and adherend differences, surface preparation, coupling agents, glass cloth, epoxy thickness, fillers, and bonding pressure and temperature. The highest lap shear strengths were obtained with the B-shear glass cloth at both liquid nitrogen and room temperatures with values of approximately 20 MPa (3000 psi) and approximately 25.5 MPa (3700 psi) respectively

  13. Studies on thermal decomposition of phenol binder using TG/DTG/DTA and FTIR-DRIFTS techniques in temperature range 20-500 °C

    *Artur Bobrowski

    2018-03-01

    Full Text Available This paper presents results of thermoanalytical and structural research on phenolic binder used in foundry for the preparation of moulding sand. The binder has been prepared based on resole type phenolic resin with the addition of ester hardener. The aim of the study was to determine the structural changes taking place in the phenolic binder under the influence of temperature. Results show that in the investigated range of temperatures,phenolic binder exhibits three exothermic thermal effects accompanying the decomposition process. The test results using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS technique show that the addition of a hardener stabilizes the binder structure within methylene bridges. The reduction in the reaction rate observed in the DTA curve at about 330 癈 can be associated with the formation of gaseous products by decomposition of the binder or, as suggested by the literature data, the formation of triple bonds and CN-HCN groups.

  14. Electrochromic Glasses.

    1980-07-31

    this glass and that dipole-dipole correlations contribute to the "ferroelectric-like" character of this amorphous system. The TeO2 -W03 glasses can only...shows the dielectric constant and Fig. I(b) glass from pure TeO2 ot pure WO. In addition, glass the tan 8 of the WO glass as a function of temperature... glasses containing WO, in various glass forming nitworks of LifO-B1O0, Na:O-BzO,, and TeO2 were prepared from reagent grade oxides at 800 C - 9SO C in

  15. High-Tg TOPAS microstructured polymer optical fiber for fiber Bragg grating strain sensing at 110 degrees

    Markos, Christos; Stefani, Alessio; Nielsen, Kristian

    2013-01-01

    We present the fabrication and characterization of fiber Bragg gratings (FBGs) in an endlessly single-mode microstructured polymer optical fiber (mPOF) made of humidity-insensitive high-Tg TOPAS cyclic olefin copolymer. The mPOF is the first made from grade 5013 TOPAS with a glass transition...... temperature of Tg = 135°C and we experimentally demonstrate high strain operation (2.5%) of the FBG at 98°C and stable operation up to a record high temperature of 110°C. The Bragg wavelengths of the FBGs are around 860 nm, where the propagation loss is 5.1dB/m, close to the fiber loss minimum of 3.67d...

  16. Study of boro-tellurite glasses doped with neodymium oxide

    Sanjay, Kishore, N.; Sheoran, M. S.; Devi, S.

    2018-05-01

    Borotellurite glasses doped with Nd2O3 [xB2O3(95-x)TeO25Nd2O3] have been prepared by the standard melt-quenching technique. Amorphous nature of the present system was estimated by XRD patterns. The thermal parameters like glass transition temperature (Tg), crystallization (Tc) and melting (Tm) temperatures have been estimated from differential scanning calorimetry (DSC) traces. Density and molar volume have been determined. It was found that Tg is increased due to increasing number of Te-O bonds were replaced by a number of stronger B-O bonds whereas density was decreased with an increase in B2O3 content is due to the higher degree of cross-bonding between the Boron and non-bridging oxygen ions resulting in a strengthening of glass network.

  17. Nano-phase separation and structural ordering in silica-rich mixed network former glasses.

    Liu, Hao; Youngman, Randall E; Kapoor, Saurabh; Jensen, Lars R; Smedskjaer, Morten M; Yue, Yuanzheng

    2018-06-13

    We investigate the structure, phase separation, glass transition, and crystallization in a mixed network former glass series, i.e., B2O3-Al2O3-SiO2-P2O5 glasses with varying SiO2/B2O3 molar ratio. All the studied glasses exhibit two separate glassy phases: droplet phase (G1) with the size of 50-100 nm and matrix phase (G2), corresponding to a lower calorimetric glass transition temperature (Tg1) and a higher one (Tg2), respectively. Both Tg values decrease linearly with the substitution of B2O3 for SiO2, but the magnitude of the decrease is larger for Tg1. Based on nuclear magnetic resonance and Raman spectroscopy results, we infer that the G1 phase is rich in boroxol rings, while the G2 phase mainly involves the B-O-Si network. Both phases contain BPO4- and AlPO4-like units. Ordered domains occur in G2 upon isothermal and dynamic heating, driven by the structural heterogeneity in the as-prepared glasses. The structural ordering lowers the activation energy of crystal growth, thus promoting partial crystallization of G2. These findings are useful for understanding glass formation and phase separation in mixed network former oxide systems, and for tailoring their properties.

  18. Tensile testing and damage analysis of woven glass-cloth/epoxy laminates at low temperature

    Kumagai, S.; Shindo, Y.; Horiguchi, K.

    2002-01-01

    In order to evaluate the tensile properties of SL-ES30 glass-cloth/epoxy laminates for superconducting magnets in fusion energy systems, tensile tests were examined both experimentally and analytically. The tensile tests were conducted in accordance with JIS K 7054 at room temperature and liquid nitrogen temperature (77 K). The general specimen geometry was a rectangular dog-bone shape with constant gage length, but with each specimen size having a different specimen width. The experimental finding provides the data for analytical modeling. The model utilizes two damage variables which are determined from experimental data. A finite element method coupled with damage was adopted for the extensional analysis. The effects of temperature, specimen geometry and gripping method on the tensile properties are examined

  19. On the nature of low temperature internal friction peaks in metallic glasses

    Khonik, V.A.; Spivak, L.V.

    1996-01-01

    Low temperature (30 60 Nb 40 subjected to preliminary inhomogeneous deformation by cold rolling, homogeneous tensile deformation or electrolytic charging with hydrogen is investigated. Cold rolling or hydrogenation result in appearance of similar internal friction peaks and hysteresis damping. Homogeneous deformation has no influence on low temperature internal friction. The phenomenon of microplastic deformation during hydrogenation of weakly stressed samples is revealed. It is argued that microplastic deformation of metallic glasses during hydrogenation without external stress takes place too. Plastic flow both on cold rolling and hydrogenation occurs via formation and motion of dislocation-like defects which are the reason of the observed anelastic anomalies. It is concluded that low temperature internal friction peaks described in the literature for as-cast, cold deformed and hydrogenated samples have common dislocation-like origin

  20. High temperature glass thermal control structure and coating. [for application to spacecraft reusable heat shielding

    Stewart, D. A.; Goldstein, H. E.; Leiser, D. B. (Inventor)

    1983-01-01

    A high temperature stable and solar radiation stable thermal control coating is described which is useful either as such, applied directly to a member to be protected, or applied as a coating on a re-usable surface insulation (RSI). It has a base coat layer and an overlay glass layer. The base coat layer has a high emittance, and the overlay layer is formed from discrete, but sintered together glass particles to give the overlay layer a high scattering coefficient. The resulting two-layer space and thermal control coating has an absorptivity-to-emissivity ratio of less than or equal to 0.4 at room temperature, with an emittance of 0.8 at 1200 F. It is capable of exposure to either solar radiation or temperatures as high as 2000 F without significant degradation. When used as a coating on a silica substrate to give an RSI structure, the coatings of this invention show significantly less reduction in emittance after long term convective heating and less residual strain than prior art coatings for RSI structures.

  1. Discontinuous and heterogeneous glass transition behavior of carbohydrate polymer-plasticizer systems.

    Kawai, Kiyoshi; Hagura, Yoshio

    2012-07-01

    In order to understand the glass transition properties of carbohydrate polymer-plasticizer systems, glass transition temperatures of dextrin-glucose and dextrin-maltose systems were investigated systematically using differential scanning calorimetry. The onset (Tg(on)) and offset (Tg(off)) of the glass transition decreased with increasing plasticizer (glucose or maltose) content, and showed an abrupt depression at certain plasticizer content. The abrupt depression of Tg(off) occurred at higher plasticizer content than that of Tg(on). The glass transition was much broader for intermediate plasticizer content. From the enthalpy relaxation behavior of samples aged at various temperatures, it was found that two different glass transitions occurred contentiously in the broad glass transition. These results suggested that carbohydrate polymer-plasticizer systems can be classified into three regions: the entrapment of the plasticizer by the polymer, the formations of the polymer-plasticizer and plasticizer-rich domains, and the embedment of polymer into the plasticizer. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Ti-based bulk metallic glass with high cold workability at room temperature

    Park, J.M.; Park, J.S.; Kim, J.H.; Lee, M.H.; Kim, D.H.; Kim, W.T.

    2005-01-01

    The cold workability of Ti-based bulk metallic glasses (BMGs) have been investigated. Ti 45 Zr 16 Be 20 Cu 10 Ni 9 BMG with a large compressive plastic strain of 4.7% shows a high cold workability, i.e. total reduction ratio of 50% by cold rolling at room temperature. The multiple shear bands formed during rolling are effective in enhancing the plasticity. The cold rolled Ti 45 Zr 16 Be 20 Cu 10 Ni 9 BMG (reduction ratio: 30%) exhibits a large plastic strain of ∝14%. (orig.)

  3. The role of the dynamic crossover temperature and the arrest in glass-forming fluids.

    Mallamace, F; Corsaro, C; Stanley, H E; Chen, S-H

    2011-09-01

    We discuss the role of the dynamic glass-forming fragile-to-strong crossover (FSC) in supercooled liquids. In the FSC, significant dynamic changes such as the decoupling (the violation of the Stokes-Einstein relation) of homologous transport parameters, e.g., the density relaxation time τ and the viscosity η, occur at a characteristic temperature T(c). We study the FSC using a scaling law approach. In particular, we use both forms of the mode-coupling theory (MCT): the original (ideal) and the extended form, which explicitly describes energy hopping processes. We demonstrate that T(c) plays the most important physical role in understanding dynamic arrest processes.

  4. Thermodynamic evidence for cluster ordering in Cu46Zr42Al7Y5 ribbons during glass transition

    Zheng, H.J.; Lv, Y.M.; Sun, Q.J.

    2016-01-01

    This work investigated the response of Cu46Zr42Al7Y5 glass ribbons to both dynamic and static heating using differential scanning calorimeter (DSC). The DSC curve manifests three exothermic responses to dynamic heating, among which the first and the third one are the signatures of the normal sub......-Tg (Tg, glass transition temperature) relaxation and the crystallization process, respectively. The second one is attributed to a partial overlap between the endothermic response to the glass transition and the exothermic response to the formation of ordered clusters. The cluster ordering, which begins...... at the final stage of glass transition, has been verified by the differences in the activation energy of the sub-Tg relaxation, the cluster ordering and primary crystallization for both the as-spun and annealed ribbons. The cluster ordering could be driven by the large difference between the Zr–Y mixing...

  5. Unraveling the interplay between hydrogen bonding and rotational energy barrier to fine-tune the properties of triazine molecular glasses.

    Laventure, Audrey; De Grandpré, Guillaume; Soldera, Armand; Lebel, Olivier; Pellerin, Christian

    2016-01-21

    Mexylaminotriazine derivatives form molecular glasses with outstanding glass-forming ability (GFA), high resistance to crystallization (glass kinetic stability, GS), and a glass transition temperature (Tg) above room temperature that can be conveniently modulated by selection of the headgroup and ancillary groups. A common feature of all these compounds is their secondary amino linkers, suggesting that they play a critical role in their GFA and GS for reasons that remain unclear because they can simultaneously form hydrogen (H) bonds and lead to a high interconversion energy barrier between different rotamers. To investigate independently and better control the influence of H bonding capability and rotational energy barrier on Tg, GFA and GS, a library of twelve analogous molecules was synthesized with different combinations of NH, NMe and O linkers. Differential scanning calorimetry (DSC) revealed that these compounds form, with a single exception, kinetically stable glasses with Tg values spanning a very broad range from -25 to 94 °C. While variable temperature infrared spectroscopy combined to chemometrics reveals that, on average, around 60% of the NH groups are still H-bonded as high as 40 °C above Tg, critical cooling rates obtained by DSC clearly show that molecules without H-bond donating linkers also present an outstanding GFA, meaning that H bonding plays a dominant role in controlling Tg but is not required to prevent crystallization. It is a high interconversion energy barrier, provoking a distribution of rotamers, that most efficiently promotes both GFA and resistance to crystallization. These new insights pave the way to more efficient glass engineering by extending the possible range of accessible Tg, allowing in particular the preparation of homologous glass-formers with high GS at ambient temperature in either the viscous or vitreous state.

  6. Physical, thermal and structural properties of Calcium Borotellurite glass system

    Paz, E.C. [CCSST – UFMA, Imperatriz, MA (Brazil); IFMA, Açailândia, MA (Brazil); Dias, J.D.M. [CCSST – UFMA, Imperatriz, MA (Brazil); Melo, G.H.A. [CCSST – UFMA, Imperatriz, MA (Brazil); IFMA, Imperatriz, MA (Brazil); Lodi, T.A. [CCSST – UFMA, Imperatriz, MA (Brazil); Carvalho, J.O. [CCSST – UFMA, Imperatriz, MA (Brazil); IFTO, Araguaína, TO (Brazil); Façanha Filho, P.F.; Barboza, M.J.; Pedrochi, F. [CCSST – UFMA, Imperatriz, MA (Brazil); Steimacher, A., E-mail: steimacher@hotmail.com [CCSST – UFMA, Imperatriz, MA (Brazil)

    2016-08-01

    In this work the glass forming ability in Calcium Borotellurite (CBTx) glass system was studied. Six glass samples were prepared by melt-quenching technique and the obtained samples are transparent, lightly yellowish, with no visible crystallites. The structural studies were carried out by using XRD, FTIR, Raman Spectra, density measurements, and the thermal analysis by using DTA and specific heat. The results are discussed in terms of tellurium oxide content and their changes in structural and thermal properties of glass samples. The addition of TeO{sub 2} increased the density and thermal stability values and decreased glass transition temperature (Tg). Raman and FTIR spectroscopies indicated that the network structure of CBTx glasses is formed by BO{sub 3}, BO{sub 4}, TeO{sub 3}, TeO{sub 3+1} and TeO{sub 4} units. CBTx system showed good glass formation ability and good thermal stability, which make CBTx glasses suitable for manufacturing process and a candidate for rare-earth doping for several optical applications. - Highlights: • Glass forming ability on Calcium Borotellurite system was studied. • The glass structure was investigated by XRD, Raman and FTIR. • The glass network structure of the CBTx glasses is formed by BO{sub 3}, BO{sub 4}, TeO{sub 3}, TeO{sub 3+1} and TeO{sub 4} units. • The density and thermal stability of the CBTx glass decreases with TeO{sub 2} while the Cp and the Tg decreases. • The obtained CBTx glasses are suitable for manufacturing process and rare-earth doping for several optical applications.

  7. Cooling and cracking of technical HLW glass products

    Kienzler, B.

    1989-01-01

    The author discusses various cooling procedures applied to canisters filled with inactive simulated HLW glass and the measured temperature distributions compared with numerically computed data. Stress computations of the cooling process were carried out with a finite element method. Only those volume elements having temperatures below the transformation temperature Tg were assumed to contribute thermoelastically to the developing stresses. Model calculations were extended to include real HLW glass canisters with inherent thermal power. The development of stress as a function of variations of heat flow conditions and of the radioactive decay was studied

  8. Structural and topological aspects of borophosphate glasses and their relation to physical properties

    Hermansen, Christian; Youngman, R.E.; Wang, J.

    2015-01-01

    We establish a topological model of alkali borophosphate and calcium borophosphate glasses that describes both the effect of the network formers and network modifiers on physical properties. We show that the glass transition temperature (Tg), Vickers hardness (HV), liquid fragility (m) and isobaric....... The origin of the effect of the type of network modifying oxide on Tg, HV, m and ΔCp of calcium borophosphate glasses is revealed in terms of the modifying ion sub-network. The same topological principles quantitatively explain the significant differences in physical properties between the alkali...... and the calcium borophosphate glasses. This work has implications for quantifying structure-property relations in complex glass forming systems containing several types of network forming and modifying oxides....

  9. Low-Cost, High Glass-Transition Temperature, Thermosetting Polyimide Developed

    Chuang, Kathy C.

    1999-01-01

    PMR-15 polyimide, developed in the mid-1970's at the NASA Lewis Research Center, is recognized as a state-of-the-art high-temperature resin for composite applications in the temperature range of 500 to 550 F (260 to 288 C). PMR-15 offers easy processing and good property retention at a reasonable cost. For these reasons, it is widely used in both military and commercial aircraft engine components. Traditionally, polyimide composites have been designed for long-term use at 500 to 600 F over thousands of hours. However, new applications in reusable launch vehicles (RLV's) require lightweight materials that can perform for short times (tens of hours) at temperatures between 800 and 1000 F (425 and 538 C). Current efforts at Lewis are focused on raising the use temperature of polyimide composites by increasing the glass-transition temperature of the matrix resins. Achieving this dramatic increase in the upper use temperature without sacrificing polymer and composite processability is a major technical challenge.

  10. Treatments of intrinsic viscosity and glass transition temperature data of poly(2,6-dimethylphenylmethacrylate)

    Hamidi, Nasrollah; Massoudi, Ruhullah

    2003-01-01

    A useful relationship, ln(T g )=ln(T g,∞ )-m[η] -ν , between intrinsic viscosity and glass transition temperature for a series of homologous polymers was obtained by combining the Mark-Houwink-Kuhn-Sakurada (MHKS) relation for intrinsic viscosity and molecular mass, and the Fox-Flory equation for glass transition temperature and number-average molecular mass. This relationship was applied to poly(2,6-dimethylphenylmethacrylate) (PDMPh) in a variety of solvents (ideal to good) such as toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems. The parameter α estimated by this procedure in toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems are 0.50 6 , 0.51 1 , 0.56 7 , and 0.67 3 , respectively which are in agreement with those of Mark-Houwink-Kuhn-Sakurada values by less than 5% differences. The T g,∞ quantity estimated from this equation also is within the standard deviation of that obtained from the Fox-Flory method. The m quantity is increasing as the thermodynamic quality of the solvent improves, therefore, m may be considered as an indicator of coil conformations in a given solvent

  11. Comparison study of ITO thin films deposited by sputtering at room temperature onto polymer and glass substrates

    Guillen, C.; Herrero, J.

    2005-01-01

    Indium tin oxide (ITO) thin films have been grown simultaneously onto glass and polymer substrates at room temperature by sputtering from ceramic target. The structure, morphology and electro-optical characteristics of the ITO/glass and ITO/polymer samples have been analyzed by X-ray diffraction, atomic force microscopy, four-point electrical measurements and spectrophotometry. In the selected experimental conditions, the polycrystalline ITO coating shows higher average grain size and higher conductivity, with similar visible transmittance, onto the polymer than onto the glass substrate

  12. Applicability test of glass lining material for high-temperature acidic solutions of sulfuric acid in thermochemical water-splitting IS process

    Iwatsuki, Jin; Tanaka, Nobuyuki; Terada, Atsuhiko; Onuki, Kaoru; Watanabe, Yutaka

    2010-01-01

    A key issue for realizing the thermochemical IS process for hydrogen production is the selection of materials for working with high-temperature acidic solutions of sulfuric acid and hydriodic acid. Glass lining material is a promising candidate, which is composed of steel having good strength and glass having good corrosion resistance. Since the applicability of glass lining material depends strongly on the service condition, corrosion tests using glass used in glass lining material and heat cycle tests using glass lining piping were carried out to examine the possibility of using the glass lining material with high-temperature acidic solutions of sulfuric acid. It was confirmed that the glass lining materials exhibited sufficient corrosion resistance and heat resistance in high-temperature sulfuric acid of the IS process. (author)

  13. Remote and direct plasma regions for low-temperature growth of carbon nanotubes on glass substrates for display applications

    Tabatabaei, M K; Ghafouri fard, H; Koohsorkhi, J; Khatami, S; Mohajerzadeh, S

    2011-01-01

    A novel method for growing carbon nanotubes (CNTs) on glass substrates is introduced in this study. A two-stage plasma was used to achieve low-temperature and vertically aligned CNTs. Ni deposited on indium tin oxide/glass substrate was used as the catalyst and hydrogen and acetylene were used as gas feeds. In this investigation a new technique was developed to grow vertically aligned CNTs at temperatures below 400 deg. C while CNT growth by plasma-enhanced chemical vapour deposition required high temperatures. Low-temperature growth of vertically aligned CNTs was suitable for the fabrication of micro-lens and self-oriented displays on glass substrates. Also, we have reported a new configuration for CNT-based display by means of controlling the refractive index of liquid crystal around the CNT by applying a proper voltage to the top and bottom array.

  14. Fabrication of Metallic Glass Powder for Brazing Paste for High-Temperature Thermoelectric Modules

    Seo, Seung-Ho; Kim, Suk Jun; Lee, Soonil; Seo, Won-Seon; Kim, Il-Ho; Choi, Soon-Mok

    2018-06-01

    Metallic glass (MG) offers the advantage of outstanding oxidation resistance, since it has disordered atomic-scale structure without grain boundaries. We fabricated Al-based MG ribbons (Al84.5Y10Ni5.5) by a melt spinning process. We evaluated the adhesion strength of interfaces between the Al-based MG and a Ni-coated Cu electrode formed under various conditions at high temperature. In addition, we attempted to optimize the process conditions for pulverizing MG ribbons to high-energy ball milling and planetary milling. We confirmed that the electrical resistivity of the Al-based MG ribbon was substantially reduced after annealing at high temperature (over 300°C) due to crystallization.

  15. Observation of the anisotropic spin-glass transition and transverse spin ordering in pseudo-brookite through muon spin relaxation

    Boekema, C.; Brabers, V.A.M.; Lichti, R.L.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.; MacLaughlin, D.E.; Dodds, S.A.

    1986-01-01

    Zero-field longitudinal muon-spin-relaxation (µSR) experiments have been performed on single crystals of pseudo-brookite (Fe2-xTil+x O 5; x=0.25), an anisotropic spin-glass system. The spinglass temperature (Tg) is determined to be 44.0±0.5K. Above Tg, a distinct exponential muon-spin-relaxation

  16. Colloidal glasses

    First page Back Continue Last page Overview Graphics. Colloidal glasses. Glassy state is attained when system fails to reach equilibrium due to crowding of constituent particles. In molecular glasses, glassy state is reached by rapidly lowering the temperature. In colloidal glasses, glassy state is reached by increasing the ...

  17. Computer Modeling Of High-Level Waste Glass Temperatures Within DWPF Canisters During Pouring And Cool Down

    Amoroso, J.

    2011-01-01

    This report describes the results of a computer simulation study to predict the temperature of the glass at any location inside a DWPF canister during pouring and subsequent cooling. These simulations are an integral part of a larger research focus aimed at developing methods to predict, evaluate, and ultimately suppress nepheline formation in HLW glasses. That larger research focus is centered on holistically understanding nepheline formation in HLW glass by exploring the fundamental thermal and chemical driving forces for nepheline crystallization with respect to realistic processing conditions. Through experimental work, the goal is to integrate nepheline crystallization potential in HLW glass with processing capability to ultimately optimize waste loading and throughput while maintaining an acceptable product with respect to durability. The results of this study indicated severe temperature gradients and prolonged temperature dwell times exist throughout different locations in the canister and that the time and temperatures that HLW glass is subjected to during processing is a function of pour rate. The simulations indicate that crystallization driving forces are not uniform throughout the glass volume in a DWPF (or DWPF-like) canister and illustrate the importance of considering overall kinetics (chemical and thermal driving forces) of nepheline formation when developing methods to predict and suppress its formation in HLW glasses. The intended path forward is to use the simulation data both as a driver for future experimental work and, as an investigative tool for evaluating the impact of experimental results. Simulation data will be used to develop laboratory experiments to more acutely evaluate nepheline formation in HLW glass by incorporating the simulated temperatures throughout the canister into the laboratory experiments. Concurrently, laboratory experiments will be performed to identify nepheline crystallization potential in HLW glass as a function of

  18. Effect of temperature on surface error and laser damage threshold for self-healing BK7 glass.

    Wang, Chu; Wang, Hongxiang; Shen, Lu; Hou, Jing; Xu, Qiao; Wang, Jian; Chen, Xianhua; Liu, Zhichao

    2018-03-20

    Cracks caused during the lapping and polishing process can decrease the laser-induced damage threshold (LIDT) of the BK7 glass optical elements, which would shorten the lifetime and limit the output power of the high-energy laser system. When BK7 glass is heated under appropriate conditions, the surface cracks can exhibit a self-healing phenomenon. In this paper, based on thermodynamics and viscous fluid mechanics theory, the mechanisms of crack self-healing are explained. The heat-healing experiment was carried out, and the effect of water was analyzed. The multi-spatial-frequency analysis was used to investigate the effect of temperature on surface error for self-healing BK7 glass, and the lapped BK7 glass specimens before and after heat healing were detected by an interferometer and atomic force microscopy. The low-spatial-frequency error was analyzed by peak to valley and root mean square, the mid-spatial-frequency error was analyzed by power spectral density, and the high-spatial-frequency error was analyzed by surface roughness. The results showed that the optimal heating temperature for BK7 was 450°C, and when the heating temperature was higher than the glass transition temperature (555°C), the surface quality decreased a lot. The laser damage test was performed, and the specimen heated at 450°C showed an improvement in LIDT.

  19. Characterization of dynamics in complex lyophilized formulations: I. Comparison of relaxation times measured by isothermal calorimetry with data estimated from the width of the glass transition temperature region.

    Chieng, Norman; Mizuno, Masayasu; Pikal, Michael

    2013-10-01

    The purposes of this study are to characterize the relaxation dynamics in complex freeze dried formulations and to investigate the quantitative relationship between the structural relaxation time as measured by thermal activity monitor (TAM) and that estimated from the width of the glass transition temperature (ΔT(g)). The latter method has advantages over TAM because it is simple and quick. As part of this objective, we evaluate the accuracy in estimating relaxation time data at higher temperatures (50 °C and 60 °C) from TAM data at lower temperature (40 °C) and glass transition region width (ΔT(g)) data obtained by differential scanning calorimetry. Formulations studied here were hydroxyethyl starch (HES)-disaccharide, HES-polyol, and HES-disaccharide-polyol at various ratios. We also re-examine, using TAM derived relaxation times, the correlation between protein stability (human growth hormone, hGH) and relaxation times explored in a previous report, which employed relaxation time data obtained from ΔT(g). Results show that most of the freeze dried formulations exist in single amorphous phase, and structural relaxation times were successfully measured for these systems. We find a reasonably good correlation between TAM measured relaxation times and corresponding data obtained from estimates based on ΔT(g), but the agreement is only qualitative. The comparison plot showed that TAM data are directly proportional to the 1/3 power of ΔT(g) data, after correcting for an offset. Nevertheless, the correlation between hGH stability and relaxation time remained qualitatively the same as found with using ΔT(g) derived relaxation data, and it was found that the modest extrapolation of TAM data to higher temperatures using ΔT(g) method and TAM data at 40 °C resulted in quantitative agreement with TAM measurements made at 50 °C and 60 °C, provided the TAM experiment temperature, is well below the Tg of the sample. Copyright © 2013 Elsevier B.V. All rights

  20. Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

    Carla Castiglia Gonzaga

    2008-09-01

    Full Text Available The objective of this work was to evaluate biaxial-flexural-strength (σf, Vickers hardness (HV, fracture toughness (K Ic, Young's modulus (E, Poisson's ratio (ν and porosity (P of two commercial glass-ceramics, Empress (E1 and Empress 2 (E2, as a function of the hot-pressing temperature. Ten disks were hot-pressed at 1065, 1070, 1075 and 1080 °C for E1; and at 910, 915, 920 and 925 °C for E2. The porosity was measured by an image analyzer software and s f was determined using the piston-on-three-balls method. K Ic and HV were determined by an indentation method. Elastic constants were determined by the pulse-echo method. For E1 samples treated at different temperatures, there were no statistical differences among the values of all evaluated properties. For E2 samples treated at different temperatures, there were no statistical differences among the values of σf, E, and ν, however HV and K Ic were significantly higher for 910 and 915 °C, respectively. Regarding P, the mean value obtained for E2 for 925 °C was significantly higher compared to other temperatures.

  1. Studying the Adhesion Force and Glass Transition of Thin Polystyrene Films by Atomic Force Microscopy

    Kang, Hua; Qian, Xiaoqin; Guan, Li

    2018-01-01

    microscopy (AFM)-based forcedistance curve to study the relaxation dynamics and the film thickness dependence of glass transition temperature (T-g) for normal thin polystyrene (PS) films supported on silicon substrate. The adhesion force (F-ad) between AFM tip and normal thin PS film surfaces...

  2. [Glass transition of Chinese medicine extract powder and its application].

    Luo, Xiao-Jian; Liu, Hui; Liang, Hong-Bo; Xiong, Lei; Rao, Xiao-Yong; Xie, Yin; He, Yan

    2017-01-01

    Glass transition theory is an important theory in polymer science, which is used to characterize the physical properties. It refers to the transition of amorphous polymer from the glassy state to the rubber state due to heating or the transition from rubber state to glassy state due to cooling. In this paper, the glassy state and glass transition of food and the similar relationship between the composition of Chinese medicine extract powder and food ingredients were described; the determination method for glass transition temperature (Tg) of Chinese medicine extract powder was established and its main influencing factors were analyzed. Meanwhile, the problems in drying process, granulation process and Chinese medicine extract powder and solid preparation storage were analyzed and investigated based on Tg, and then the control strategy was put forward to provide guidance for the research and production of Chinese medicine solid preparation. Copyright© by the Chinese Pharmaceutical Association.

  3. Evaluation of Foaming Behavior of Glass Melts by High-Temperature Microscopy

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    2016-01-01

    Optical monitoring techniques can record in situ the size of glass samples during a dynamic heating process. This allowed us to study sintering and expansion rate of panel glass from cathode ray tube using MnO2 as foaming agent. We show the maximum expansion rate of glass melt foaming (in situ va...... such as type and concentration of foaming agent, glass composition and particle size to obtain foam glass with high porosity and closed pores. Using this approach we show that the foaming of bottle glass is preferentially conducted at a SiC concentration of 1‒4 wt%....

  4. Effect of Feed Melting, Temperature History and Minor Component Addition on Spinel Crystallization in High-Level Waste Glass

    Izak, Pavel; Hrma, Pavel R.; Arey, Bruce W.; Plaisted, Trevor J.

    2001-01-01

    This study was undertaken to help design mathematical models for high-level waste (HLW) glass melter that simulate spinel behavior in molten glass. Spinel, (Fe,Ni,Mn) (Fe,Cr)2O4, is the primary solid phase that precipitates from HLW glasses containing Fe and Ni in sufficient concentrations. Spinel crystallization affects the anticipated cost and risk of HLW vitrification. To study melting reactions, we used simulated HLW feed, prepared with co-precipitated Fe, Ni, Cr, and Mn hydroxides. Feed samples were heated up at a temperature-increase rate (4C/min) close to that which the feed experiences in the HLW glass melter. The decomposition, melting, and dissolution of feed components (such as nitrates, carbonates, and silica) and the formation of intermediate crystalline phases (spinel, sodalite (Na8(AlSiO4)6(NO2)2), and Zr-containing minerals) were characterized using evolved gas analysis, volume-expansion measurement, optical microscope, scanning electron microscope, thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. Nitrates and quartz, the major feed components, converted to a glass-forming melt by 880C. A chromium-free spinel formed in the nitrate melt starting from 520C and Sodalite, a transient product of corundum dissolution, appeared above 600C and eventually dissolved in glass. To investigate the effects of temperature history and minor components (Ru,Ag, and Cu) on the dissolution and growth of spinel crystals, samples were heated up to temperatures above liquidus temperature (TL), then subjected to different temperature histories, and analyzed. The results show that spinel mass fraction, crystals composition, and crystal size depend on the chemical and physical makeup of the feed and temperature history

  5. Fuel retention properties of thin-wall glass target in low temperature

    Gao Dangzhong; Huang Yong; Tang Yongjian; Wen Shuhuai

    2001-01-01

    In room temperature the fuel gas storage half-life of the thin-wall (wall-thickness less than 1μm) glass microsphere is only a few days, it is difficult to be used for ICF. To efficiently prolong the half-life of such type targets, and meet the need of ICF experiments, the special device for storing the targets was developed. All the targets are immerged in liquid-nitrogen (LN 2 ), after being sealed in vacuum. During this period the change of Si 1.74 keV X-ray counts were measured a few times with the low energy X-ray multi-channel analyzer. The results of experiment indicate that, in the environment of -196 degree C, the fuel storage half-life of target has been successfully extended to 100-300 d from 3-10 d. However, the surface roughness of target was not obviously changed

  6. Photoluminescence at room temperature of liquid-phase crystallized silicon on glass

    Michael Vetter

    2016-12-01

    Full Text Available The room temperature photoluminescence (PL spectrum due band-to-band recombination in an only 8 μm thick liquid-phase crystallized silicon on glass solar cell absorber is measured over 3 orders of magnitude with a thin 400 μm thick optical fiber directly coupled to the spectrometer. High PL signal is achieved by the possibility to capture the PL spectrum very near to the silicon surface. The spectra measured within microcrystals of the absorber present the same features as spectra of crystalline silicon wafers without showing defect luminescence indicating the high electronic material quality of the liquid-phase multi-crystalline layer after hydrogen plasma treatment.

  7. High-temperature laser annealing for thin film polycrystalline silicon solar cell on glass substrate

    Chowdhury, A.; Schneider, J.; Dore, J.; Mermet, F.; Slaoui, A.

    2012-06-01

    Thin film polycrystalline silicon films grown on glass substrate were irradiated with an infrared continuous wave laser for defects annealing and/or dopants activation. The samples were uniformly scanned using an attachment with the laser system. Substrate temperature, scan speed and laser power were varied to find suitable laser annealing conditions. The Raman spectroscopy and Suns- V oc analysis were carried out to qualify the films quality after laser annealing. A maximum enhancement of the open circuit voltage V oc of about 100 mV is obtained after laser annealing of as-grown polysilicon structures. A strong correlation was found between the full width half maximum of the Si crystalline peak and V oc. It is interpreted as due to defects annealing as well as to dopants activation in the absorbing silicon layer. The maximum V oc reached is 485 mV after laser treatment and plasma hydrogenation, thanks to defects passivation.

  8. Experimental evidence for a Mott-Wigner glass phase of magnetite above the Verwey temperature

    Boekema, C.; Lichti, R.L.; Chan, K.C.B.; Brabers, V.A.M.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.

    1986-01-01

    New muon-spin-relaxation (μSR) results on magnetite are reported and discussed in light of earlier Moessbauer, neutron, and μSR results. Modification of the μSR anomaly (observed at 247 K in zero field), when an external magnetic field is applied, provides evidence that the anomaly results from cross relaxation between the muon Larmor precession and the electron-correlation process in the B sublattice. The combined results strongly indicate that phonon-assisted electron hopping is the principal conduction mechanism above the Verwey transition temperature (T/sub V/). Together with theoretical evidence, these data support Mott's suggestion that above T/sub V/ magnetite is in the Wigner-glass state

  9. Reaction of soda-lime-silica glass melt with water vapour at melting temperatures

    Vernerová, Miroslava; Kloužek, Jaroslav; Němec, Lubomír

    2015-01-01

    Roč. 416, MAY 15 (2015), s. 21-30 ISSN 0022-3093 R&D Projects: GA TA ČR TA01010844 Institutional support: RVO:67985891 Keywords : glass melt * sulfate * water vapour * bubble nucleation * melt foaming * glass melting Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.825, year: 2015

  10. Casting of organic glass by radiation-induced polymerization of glass-forming monomers at low temperature. II. Optical strain of remaining stress type

    Okubo, H.; Yoshii, F.; Kaetsu, I.; Honda, S.

    1978-01-01

    Previously it was found that casting could be carried out efficiently without strain formation by radiation-induced polymerization of glass-forming monomers. Two types of strain were observed in casting: thermal stream type, which was studied previously, and remained stress type. In this report, the effect of various factors on the formation of remaining stress-type strain in radiation-induced casting polymerization was studied. It was found that the molecular weight of prepolymer did not affect strain formation, while prepolymer concentration and viscosity of the system had a serious influence on strain formation. It could be deduced that this type of strain formed as a result of remaining inner stress due to poor relaxation of the shrinking stress. It was realized that less volume shrinkage of glass-forming monomers accompanying casting polymerization reduced the strain formation of this type in radiation-induced casting polymerization at low temperatures

  11. Characterization of Fibre-Direction Dependent Damping of Glass-Fibre Composites at Low Temperatures and Low Frequencies

    Kliem, Mathias; Høgsberg, Jan Becker; Dannemann, Martin

    2016-01-01

    This paper deals with the characterization of the fibre-direction dependent damping capability of glass fibre reinforced plastics (GFRP) to be used in electrical power transmission pylons. A fibre-direction dependent damping analysis of unidirectional (UD) GFRP samples was carried out using...... a Dynamic Mechanical Analysis (DMA) for five different fibre orientations (0˚ | 30˚ | 45˚ | 60˚ and 90˚) and two different matrix systems (epoxy and a vinyl ester resin). Based on the dynamic characteristics the damping performance of the various composite materials was studied at three temperatures (-10˚C......, 0˚C and 10˚C) and three vibration frequencies (1 Hz, 10 Hz and 30 Hz). It was observed that the loss factor of Glass Fibre Reinforced Vinyl-Ester (GF-VE) was in general slightly higher compared to the Glass Fibre Reinforced Epoxy (GF-EP). The loss factor increased slightly with temperature, while...

  12. Study of the alteration of the Vatnajokull volcanic glasses (Iceland). Mechanisms and situation at low temperature

    Le Gal, X.

    1999-01-01

    Volcanic glasses have been considered for several years to be good analogues of nuclear glasses. The main objective of this study is to look at the long term behaviour of natural glasses subjected to meteoric alteration. Basaltic hyalo-clasts, essentially from Hengill, Husafell and Vatnajokull, in Iceland, were studied. These glasses, ranging from 0.09 to 4 My in age, and altered by meteoric water, are surrounded by alteration layers. In the youngest samples ( 18 O measurements indicate, major modification of the initial glass structure during gel formation. Chemical budgets show that elements are not completely retained by alteration products in such geological environments. (author)

  13. Effects of Sb2O3 on the Mechanical Properties of the Borosilicate Foam Glasses Sintered at Low Temperature

    Chenxi Zhai

    2014-01-01

    Full Text Available The physical properties and microstructure of a new kind of borosilicate foam glasses with different Sb2O3 doping content are comprehensively investigated. The experimental results show that appropriate addition of Sb2O3 has positive impact on the bulk porosity and compressive strength of the foam glass. It is more suitable in this work to introduce 0.9 wt.% Sb2O3 into the Na2O-K2O-B2O3-Al2O3-SiO2 basic foam glass component and sinter at 775°C. And the obtained foam glasses present much more uniform microstructure, large pore size, and smooth cell walls, which bring them with better performance including a lower bulk density, low water absorption, and an appreciable compressive strength. The microstructure analysis indicates that, with the increase of the content of Sb2O3 additives, the cell size tends to increase at first and then decreases. Larger amounts of Sb2O3 do not change the crystalline phase of foam glass but increase its vitrification. It is meaningful to prepare the foam glass at a relatively low temperature for reducing the heat energy consumption.

  14. Corrosion of inconel in high-temperature borosilicate glass melts containing simulant nuclear waste

    Mao, Xianhe; Yuan, Xiaoning; Brigden, Clive T.; Tao, Jun; Hyatt, Neil C.; Miekina, Michal

    2017-10-01

    The corrosion behaviors of Inconel 601 in the borosilicate glass (MW glass) containing 25 wt.% of simulant Magnox waste, and in ZnO, Mn2O3 and Fe2O3 modified Mg/Ca borosilicate glasses (MZMF and CZMF glasses) containing 15 wt.% of simulant POCO waste, were evaluated by dimensional changes, the formation of internal defects and changes in alloy composition near corrosion surfaces. In all three kinds of glass melts, Cr at the inconel surface forms a protective Cr2O3 scale between the metal surface and the glass, and alumina precipitates penetrate from the metal surface or formed in-situ. The corrosion depths of inconel 601 in MW waste glass melt are greater than those in the other two glass melts. In MW glass, the Cr2O3 layer between inconel and glass is fragmented because of the reaction between MgO and Cr2O3, which forms the crystal phase MgCr2O4. In MZMF and CZMF waste glasses the layers are continuous and a thin (Zn, Fe, Ni, B)-containing layer forms on the surface of the chromium oxide layer and prevents Cr2O3 from reacting with MgO or other constituents. MgCr2O4 was observed in the XRD analysis of the bulk MW waste glass after the corrosion test, and ZrSiO4 in the MZMF waste glass, and ZrSiO4 and CaMoO4 in the CZMF waste glass.

  15. Efficient room temperature cw Yb:glass laser pumped by a 946nm Nd:YAG laser

    Koch, R.; Clarkson, W.A.; Hanna, D.C.; Jiang, S.; Myers, M.J.; Rhonehouse, D.; Hamlin, S.J.; Griebner, U.; Schönnagel, H.

    1997-01-01

    By pumping with a cw diode-pumped Nd:YAG laser operating at 946nm laser operation of a new Yb-doped phosphate glass with 440mW cw output power and a slope efficiency of 48% with respect to the absorbed pump power was achieved at room temperature

  16. 4-(ALPHA, ALPHA-DIMETHYLBENZYL)PHENYL METHACRYLATE .3. SYNTHESIS, TACTICITY AND GLASS-TRANSITION TEMPERATURES OF ITS POLYMERS

    VANEKENSTEIN, GORA; TAN, YY

    Depending on the kind of initiator, anionic Polymerization of 4-(alpha,alpha-dimethylbenzyl)phenyl methacrylate in toluene at -78-degrees-C led either to highly isotactic or predominantly syndiotactic polymers as determined by C-13 NMR spectro copy. The glass transition temperature difference

  17. Structure-to-property relationships in addition cured polymers. II - Resin Tg and composite initial mechanical properties of norbornenyl cured polyimide resins

    Alston, William B.

    1986-01-01

    PRM (polymerization of monomeric reactants) methodology was used to prepare thirty different polyimide oligomeric resins. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on glass transition temperature (Tg) of the cured/postcured resins. An almost linear correlation of Tg versus molecular distance between the crosslinks was observed. An attempt was made to correlate Tg with initial mechanical properties (flexural strength and interlaminar shear strength) of unidirectional graphite fiber composites prepared with these resins. However, the scatter in mechanical strength data prevented obtaining as clear a correlation as was observed for the structural modification/crosslink distance versus Tg. Instead, only a range of composite mechanical properties was obtained at the test temperatures studied (room temperature, 288 and 316 C). Perhaps more importantly, what did become apparent during the attempted correlation study was: (1) that PMR methodology could be used to prepare composites from resins that contain a wide variety of monomer modifications, and (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins selected were melt processable.

  18. High Tg and fast curing epoxy-based anisotropic conductive paste for electronic packaging

    Keeratitham, Waralee; Somwangthanaroj, Anongnat

    2016-03-01

    Herein, our main objective is to prepare the fast curing epoxy system with high glass transition temperature (Tg) by incorporating the multifunctional epoxy resin into the mixture of diglycidyl ether of bisphenol A (DGEBA) as a major epoxy component and aromatic diamine as a hardener. Furthermore, the curing behavior as well as thermal and thermomechanical properties were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA). It was found that Tg obtained from tan δ of DGEBA/aromatic diamine system increased from 100 °C to 205 °C with the presence of 30 percentage by weight of multifunctional epoxy resin. Additionally, the isothermal DSC results showed that the multifunctional epoxy resin can accelerate the curing reaction of DGEBA/aromatic diamine system. Namely, a high degree of curing (˜90%) was achieved after a few minutes of curing at low temperature of 130 °C, owing to a large number of epoxy ring of multifunctional epoxy resin towards the active hydrogen atoms of aromatic diamine.

  19. Physicochemical properties of new As2Se3–Ag4SSe–CdTe glasses

    Aljihmani, Lilia; Vassilev, Venceslav; Hristova-Vasileva, Temenuga; Fidancevska, Emilija

    2009-01-01

    Chalcogenide glasses from the As 2 Se 3 –Ag 4 SSe–CdTe system were synthesized. The basic physicochemical parameters such as density (d), microhardness (HV) and the temperatures glass transition Tg were measured. Compactness (C) and some thermomechanical characteristics such as volume (Vh) and formation energy (Eh) of micro-voids in the glassy network, as well as the module of elasticity (E) were calculated. A correlation between the composition and properties of the As 2 Se 3 –Ag 4 SSe–CdTe glasses was established and comprehensively discussed. Keywords: chalcogenide glasses, density, microhardness, compactness, elasticity modulus, thermomechanical characteristics

  20. Operating Range for High Temperature Borosilicate Waste Glasses: (Simulated Hanford Enveloped)

    Mohammad, J.; Ramsey, W. G.; Toghiani, R. K.

    2003-01-01

    The following results are a part of an independent thesis study conducted at Diagnostic Instrumentation and Analysis Laboratory-Mississippi State University. A series of small-scale borosilicate glass melts from high-level waste simulant were produced with waste loadings ranging from 20% to 55% (by mass). Crushed glass was allowed to react in an aqueous environment under static conditions for 7 days. The data obtained from the chemical analysis of the leachate solutions were used to test the durability of the resulting glasses. Studies were performed to determine the qualitative effects of increasing the B2O3 content on the overall waste glass leaching behavior. Structural changes in a glass arising due to B2O3 were detected indirectly by its chemical durability, which is a strong function of composition and structure. Modeling was performed to predict glass durability quantitatively in an aqueous environment as a direct function of oxide composition

  1. Aluminosilicate melts and glasses at 1 to 3 GPa: Temperature and pressure effects on recovered structural and density changes

    Bista, S; Stebbins, Jonathan; Hankins, William B.; Sisson, Thomas W.

    2015-01-01

    In the pressure range in the Earth’s mantle where many basaltic magmas are generated (1 to 3 GPa) (Stolper et al. 1981), increases in the coordination numbers of the network-forming cations in aluminosilicate melts have generally been considered to be minor, although effects on silicon and particularly on aluminum coordination in non-bridging oxygen-rich glasses from the higher, 5 to 12 GPa range, are now well known. Most high-precision measurements of network cation coordination in such samples have been made by spectroscopy (notably 27Al and 29Si NMR) on glasses quenched from high-temperature, high-pressure melts synthesized in solid-media apparatuses and decompressed to room temperature and 1 bar pressure. There are several effects that could lead to the underestimation of the extent of actual structural (and density) changes in high-pressure/temperature melts from such data. For non-bridging oxygen-rich sodium and calcium aluminosilicate compositions in the 1 to 3 GPa range, we show here that glasses annealed near to their glass transition temperatures systematically record higher recovered increases in aluminum coordination and in density than samples quenched from high-temperature melts. In the piston-cylinder apparatus used, rates of cooling through the glass transition are measured as very similar for both higher and lower initial temperatures, indicating that fictive temperature effects are not the likely explanation of these differences. Instead, transient decreases in melt pressure during thermal quenching, which may be especially large for high initial run temperatures, of as much as 0.5 to 1 GPa, may be responsible. As a result, the equilibrium proportion of high-coordinated Al in this pressure range may be 50 to 90% greater than previously estimated, reaching mean coordination numbers (e.g., 4.5) that are probably high enough to significantly affect melt properties. New data on jadeite (NaAlSi2O6) glass confirm that aluminum coordination increase

  2. Investigation of Er doped zinc borate glasses by low-temperature photoluminescence

    Kostka, Petr; Kabalci, I.; Tay, T.; Gladkov, Petar; Zavadil, Jiří

    2017-01-01

    Roč. 192, DEC 2017 (2017), s. 1104-1109 ISSN 0022-2313 Institutional support: RVO:67985891 ; RVO:67985882 Keywords : borate glasses * rare-earth ions * stark levels * photoluminiscence Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; JH - Ceramics, Fire-Resistant Materials and Glass (URE-Y) OBOR OECD: Ceramics; Ceramics (URE-Y) Impact factor: 2.686, year: 2016

  3. Low-temperature deposition of ZnO thin films on PET and glass substrates by DC-sputtering technique

    Banerjee, A.N.; Ghosh, C.K.; Chattopadhyay, K.K.; Minoura, Hideki; Sarkar, Ajay K.; Akiba, Atsuya; Kamiya, Atsushi; Endo, Tamio

    2006-01-01

    The structural, optical and electrical properties of ZnO thin films (260 - 490 nm thick) deposited by direct-current sputtering technique, at a relatively low-substrate temperature (363 K), onto polyethylene terephthalate and glass substrates have been investigated. X-ray diffraction patterns confirm the proper phase formation of the material. Optical transmittance data show high transparency (80% to more than 98%) of the films in the visible portion of solar radiation. Slight variation in the transparency of the films is observed with a variation in the deposition time. Electrical characterizations show the room-temperature conductivity of the films deposited onto polyethylene terephthalate substrates for 4 and 5 h around 0.05 and 0.25 S cm -1 , respectively. On the other hand, for the films deposited on glass substrates, these values are 8.5 and 9.6 S cm -1 for similar variation in the deposition time. Room-temperature conductivity of the ZnO films deposited on glass substrates is at least two orders of magnitude higher than that of ZnO films deposited onto polyethylene terephthalate substrates under identical conditions. Hall-measurements show the maximum carrier concentration of the films on PET and glass substrate around 2.8 x 10 16 and 3.1 x 10 2 cm -3 , respectively. This report will provide newer applications of ZnO thin films in flexible display technology

  4. Optical temperature sensor based on the Nd{sup 3+} infrared thermalized emissions in a fluorotellurite glass

    Lalla, E.A. [Departamento de Física, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); León-Luis, S.F., E-mail: sleonlui@ull.es [Departamento de Física, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); Malta Consolider Team, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); Monteseguro, V. [Departamento de Física, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); Malta Consolider Team, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); Pérez-Rodríguez, C. [Departamento de Física, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); Cáceres, J.M. [Departamento de Ingeniería Industrial, Universidad de la Laguna, San Cristóbal de la Laguna, 38200 Santa Cruz de Tenerife (Spain); and others

    2015-10-15

    The temperature dependence of the infrared luminescence of a fluorotellurite glass doped with 0.01 and 2.5 mol% of Nd{sup 3+} ions was studied in order to use it as a high temperature sensing probe. For this purpose, the emission intensities of the ({sup 4}S{sub 3/2}, {sup 4}F{sub 7/2}), ({sup 2}H{sub 9/2}, {sup 4}F{sub 5/2}),{sup 4}F{sub 3/2}→{sup 4}I{sub 9/2} transitions were measured in a wide range of temperatures from 300 upto 650 K. The changes in the emission profiles were calibrated by means of the fluorescence intensity ratio technique. The calibrations showed a strong dependence on the Nd{sup 3+} ions concentration, having the low-doped concentrated sample the best response to changes of temperature. The maximum value obtained for the thermal sensibility is 17×10{sup −4} K{sup −1} at 640 K, being one of the highest values found in the literature for Nd{sup 3+} optical temperature sensors. Finally, the experimental calibrations were compared with the theoretical temperature luminescence response calculated from the Judd–Ofelt theory. - Highlights: • Nd{sup 3+}-doped fluorotellurite glasses were prepared. • The intensities of the ({sup 4}S{sub 3/2},{sup 4}F{sub 7/2}),({sup 2}H{sub 9/2},{sup 4}F{sub 5/2}), {sup 4}F{sub 3/2}→{sup 4}I{sub 9/2} transitions. • The highest thermal sensitivity has been obtained for the glass with the lowest concentration of Nd{sup 3+} ions. • The Nd{sup 3+}-doped fluorotellurite glass fits the requirement for a good temperature sensor.

  5. Water’s second glass transition

    Amann-Winkel, Katrin; Gainaru, Catalin; Handle, Philip H.; Seidl, Markus; Nelson, Helge; Böhmer, Roland

    2013-01-01

    The glassy states of water are of common interest as the majority of H2O in space is in the glassy state and especially because a proper description of this phenomenon is considered to be the key to our understanding why liquid water shows exceptional properties, different from all other liquids. The occurrence of water’s calorimetric glass transition of low-density amorphous ice at 136 K has been discussed controversially for many years because its calorimetric signature is very feeble. Here, we report that high-density amorphous ice at ambient pressure shows a distinct calorimetric glass transitions at 116 K and present evidence that this second glass transition involves liquid-like translational mobility of water molecules. This “double Tg scenario” is related to the coexistence of two liquid phases. The calorimetric signature of the second glass transition is much less feeble, with a heat capacity increase at Tg,2 about five times as large as at Tg,1. By using broadband-dielectric spectroscopy we resolve loss peaks yielding relaxation times near 100 s at 126 K for low-density amorphous ice and at 110 K for high-density amorphous ice as signatures of these two distinct glass transitions. Temperature-dependent dielectric data and heating-rate–dependent calorimetric data allow us to construct the relaxation map for the two distinct phases of water and to extract fragility indices m = 14 for the low-density and m = 20–25 for the high-density liquid. Thus, low-density liquid is classified as the strongest of all liquids known (“superstrong”), and also high-density liquid is classified as a strong liquid. PMID:24101518

  6. Discovery of room-temperature spin-glass behaviors in two-dimensional oriented attached single crystals

    Ma, Ji; Chen, Kezheng, E-mail: kchen@qust.edu.cn

    2016-05-15

    In this study, room-temperature spin-glass behaviors were observed in flake-like oriented attached hematite (α-Fe{sub 2}O{sub 3}) and iron phosphate hydroxide hydrate (Fe{sub 5}(PO{sub 4}){sub 4}(OH){sub 3}·2H{sub 2}O) single crystals. Remarkably, their coercivity (H{sub C}) values were found to be almost invariable at various given temperatures from 5 to 300 K. The spin topographic map in these flakes was assumed as superparamagnetic (SPM) “islands” isolated by spin glass (SG)-like “bridges”. A spin-glass model was then proposed to demonstrate the spin frustration within these “bridges”, which were formed by the staggered atomic planes in the uneven surfaces belonging to different attached nanoparticles. Under the spatial limitation and coupling shield of these “bridges”, the SPM “islands” were found to be collectively frozen to form a superspin glass (SSG) state below 80 K in weak applied magnetic fields; whereas, when strong magnetic fields were applied, the magnetic coupling of these “islands” would become superferromagnetic (SFM) through tunneling superexchange, so that, these SFM spins could antiferromagnetically couple with the SG-like “bridges” to yield pronounced exchange bias (EB) effect. - Highlights: • Room-temperature spin-glass state was found in 2D oriented attached single crystals. • Coercivity values were found to be almost invariable at different temperatures. • The spin topographic map was assumed as SPM “islands” isolated by SG-like “bridges”.

  7. Quantitative determination of the specific heat and the glass transition of moist samples by temperature modulated differential scanning calorimetry.

    Schubnell, M; Schawe, J E

    2001-04-17

    In differential scanning calorimetry (DSC), remnant moisture loss in samples often overlaps and distorts other thermal events, e.g. glass transitions. To separate such overlapping processes, temperature modulated DSC (TMDSC) has been widely used. In this contribution we discuss the quantitative determination of the heat capacity of a moist sample from TMDSC measurements. The sample was a spray-dried pharmaceutical compound run in different pans (hermetically-sealed pan, pierced lid pan [50 microm] and open pan). The apparent heat capacity was corrected for the remaining amount of moisture. Using this procedure we could clearly identify the glass transition of the dry and the moist sample. We found that a moisture content of about 6.2% shifts the glass transition by about 50 degrees C.

  8. Slow dynamics and glass transition in simulated free-standing polymer films: a possible relation between global and local glass transition temperatures

    Peter, S; Meyer, H; Baschnagel, J; Seemann, R

    2007-01-01

    We employ molecular dynamics simulations to explore the influence that the surface of a free-standing polymer film exerts on its structural relaxation when the film is cooled toward the glass transition. Our simulations are concerned with the features of a coarse-grained bead-spring model in a temperature regime above the critical temperature T c of mode-coupling theory. We find that the film dynamics is spatially heterogeneous. Monomers at the free surface relax much faster than they would in the bulk at the same temperature T. The fast relaxation of the surface layer continuously turns into bulk-like relaxation with increasing distance y from the surface. This crossover remains smooth for all T, but its range grows on cooling. We show that it is possible to associate a gradient in critical temperatures T c (y) with the gradient in the relaxation dynamics. This finding is in qualitative agreement with experimental results on supported polystyrene (PS) films (Ellison and Torkelson 2003 Nat. Mater. 2 695). Furthermore we show that the y dependence of T c (y) can be expressed in terms of the depression of T c (h)-the global T c for a film of thickness h-if we assume that T c (h) is the arithmetic mean of T c (y) and parameterize the depression of T c (h) by T c (h) = T c /(1+h 0 /h), a formula suggested by Herminghaus et al (2001 Eur. Phys. J. E 5 531) for the reduction of the glass transition temperature in supported PS films. We demonstrate the validity of this formula by comparing our simulation results to results from other simulations and experiments

  9. Surface chemistry, microstructure and friction properties of some ferrous-base metallic glasses at temperatures to 750 C

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analysis, transmission electron microscopy, diffraction studies, and sliding friction experiments were conducted with ferrous-base metallic glasses in sliding contact with aluminum oxide at temperatures from room to 750 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on the friction properties, surface chemistry, and microstructure of metallic glasses. The relative concentrations of the various constituents at the surface of the sputtered specimens were very different from the normal bulk compositions. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and silicon oxide at 350 C and boron nitride above 500 C. The coefficient of friction increased with increasing temperature to 350 C. Above 500 C the coefficient of friction decreased rapidly. The segregation of contaminants may be responsible for the friction behavior.

  10. The effect of nanocrystallization and free volume on the room temperature plasticity of Zr-based bulk metallic glasses

    Mondal, K.; Ohkubo, T.; Toyama, T.; Nagai, Y.; Hasegawa, M.; Hono, K.

    2008-01-01

    To understand the mechanism of the room temperature plasticity of bulk metallic glasses (BMGs), microstructure observations, density measurements and positron annihilation studies were carried out for Zr-based BMGs cast at various temperatures and post-annealed under different conditions. We found that higher casting temperatures cause partial crystallization, which enhance the plasticity as long as the volume fraction of the crystalline phase is low. However, a similar nanocrystalline microstructure produced by post-annealing often leads to a large loss of plasticity, while certain conditions enhance the plasticity. Based on density measurements and positron annihilation lifetime spectroscopy, we conclude that the relative contribution of free volume and nanocrystallization is important for acquiring plasticity in metallic glasses

  11. Glass and crystallization like transitions at low temperature in Zr-Cu based glasses by internal friction measurements

    Aboki A.T.

    2011-05-01

    Full Text Available Low temperature β internal friction peak evolution upon thermal cycles shows two peculiar peaks similar to high temperature internal friction peak. The modulus softening associated to these peaks suggest a phase transformation phenomenon and the relaxation time τo in order of 10-23–10-35s, close to that observed in grains boundary sliding are due to interface motions in the amorphous structure under combined thermal and mechanical energies.

  12. Simulation of an Aspheric Glass Lens Forming Behavior in Progressive GMP Process

    Chang, Sung Ho; Lee, Young Min; Kang, Jeong Jin; Hong, Seok Kwan; Shin, Gwang Ho; Heo, Young Moo; Jung, Tae Sung

    2007-01-01

    Recently, GMP(Glass Molding Press) process is mainly used to produce aspheric glass lenses. Because glass lens is heated at high temperature above Tg (Transformation Temperature) for forming the glass, the quality of aspheric glass lens is deteriorated by residual stresses which are generated in a aspheric glass lens after forming. In this study, as a fundamental study to develop the mold for progressive GMP process, we conducted a aspheric glass lens forming simulation. Prior to a aspheric glass lens forming simulation, compression and thermal conductivity tests were carried out to obtain mechanical and thermal properties of K-PBK40 which is newly developed material for precision molding, and flow characteristics of K-PBK40 were obtained at high temperature. Then, using the flow characteristics obtained, compression simulation was carried out and compared with the experimental result for the purpose of verifying the obtained flow characteristics. Finally, a glass lens press simulation in progressive GMP process was carried out and we could forecast the shape of deformed glass lenses and residual stresses contribution in the structure of deformed glass lenses after forming

  13. Dynamic and thermodynamic characteristics associated with the glass transition of amorphous trehalose-water mixtures.

    Weng, Lindong; Elliott, Gloria D

    2014-06-21

    The glass transition temperature Tg of biopreservative formulations is important for predicting the long-term storage of biological specimens. As a complementary tool to thermal analysis techniques, which are the mainstay for determining Tg, molecular dynamics simulations have been successfully applied to predict the Tg of several protectants and their mixtures with water. These molecular analyses, however, rarely focused on the glass transition behavior of aqueous trehalose solutions, a subject that has attracted wide scientific attention via experimental approaches. Important behavior, such as hydrogen-bonding dynamics and self-aggregation has yet to be explored in detail, particularly below, or in the vicinity of, Tg. Using molecular dynamics simulations of several dynamic and thermodynamic properties, this study reproduced the supplemented phase diagram of trehalose-water mixtures (i.e., Tg as a function of the solution composition) based on experimental data. The structure and dynamics of the hydrogen-bonding network in the trehalose-water systems were also analyzed. The hydrogen-bonding lifetime was determined to be an order of magnitude higher in the glassy state than in the liquid state, while the constitution of the hydrogen-bonding network exhibited no noticeable change through the glass transition. It was also found that trehalose molecules preferred to form small, scattered clusters above Tg, but self-aggregation was substantially increased below Tg. The average cluster size in the glassy state was observed to be dependent on the trehalose concentration. Our findings provided insights into the glass transition characteristics of aqueous trehalose solutions as they relate to biopreservation.

  14. A model for phosphate glass topology considering the modifying ion sub-network

    Hermansen, Christian; Mauro, J.C.; Yue, Yuanzheng

    2014-01-01

    In the present paper we establish a temperature dependent constraint model of alkali phosphate glasses considering the structural and topological role of the modifying ion sub-network constituted by alkali ions and their non-bonding oxygen coordination spheres. The model is consistent with availa......In the present paper we establish a temperature dependent constraint model of alkali phosphate glasses considering the structural and topological role of the modifying ion sub-network constituted by alkali ions and their non-bonding oxygen coordination spheres. The model is consistent...... with available structural data by NMR and molecular dynamics simulation and dynamic data such glass transition temperature (Tg) and liquid fragility (m). Alkali phosphate glasses are exemplary systems for developing constraint model since the modifying cation network plays an important role besides the primary...... phosphate network. The proposed topological model predicts the changing trend of the Tg and m with increasing alkali oxide content for alkali phosphate glasses, including an anomalous minimum at around 20 mol% alkali oxide content. We find that the minimum in Tg and m is caused by increased connectivity...

  15. The glass transition, crystallization and melting in Au-Pb-Sb alloys

    Lee, M. C.; Allen, J. L.; Fecht, H. J.; Perepezko, J. H.; Ohsaka, K.

    1988-01-01

    The glass transition, crystallization and melting of Au(55)Pb(22.5)Sb(22.5) alloys have been studied by differential scanning calorimetry DSC. Crystallization on heating above the glass transition temperature Tg (45 C) begins at 64 C. Further crystallization events are observed at 172 C and 205 C. These events were found to correspond to the formation of the intermetallic compounds AuSb2, Au2Pb, and possibly AuPb2, respectively. Isothermal DSC scans of the glassy alloy above Tg were used to monitor the kinetics of crystallization. The solidification behavior and heat capacity in the glass-forming composition range were determined with droplet samples. An undercooling level of 0.3T(L) below the liquidus temperature T(L) was achieved, resulting in crystallization of different stable and metastable phases. The heat capacity C(P) of the undercooled liquid was measured over an undercooling range of 145 C.

  16. Ultrasonic and Thermal Properties of Borate and Phosphate Glasses Containing Bismuth and Lead

    Aziz, Sidek Hj. Abd.; Ahmad, Hamezan; Wahab, Zaidan A.; Sulaiman, Zainal Abidin; Talib, Zainal Abidin; Shaari, A. Halim; Senin, H. B.

    2007-01-01

    Systematic series of (B2O3,P2O5)-Bi2O3-PbO glasses have been successfully prepared by using the rapid quenching technique in which each oxide content changes for every series on the basis of its weight percentage. Their amorphous natures were confirmed earlier by the x-ray diffraction technique. The experimental results show that the density of both glasses, determined by using the Archimedes principle, increases with the glass modifier content. This is due to the replacement of Bi2O3 and PbO in the borate and phosphate glassy networks. The molar volume for borate glass increases with the addition of bismuth and lead oxides, but a reverse trend occurs for the phosphate glass. The longitudinal and shear ultrasound velocities, determined by the MBS 8000 system, of both lead bismuth borate and phosphate glasses show a decreasing trend as more PbO and Bi2O3 are added to the glass system. The increase in PbO/Bi2O3 content was probably related to the progressive increase in the concentration of non-bridging oxygen (NBOs). Thermal studies of the glass, using the Labsys DTA-Setaram machine, show that the value of the glass transition temperature (Tg) is closely related to the chemical bond in the system. In lead bismuth borate glasses, the addition of more Pb2+ and Bi3+ results in a more dominant ionic bond character in the system and hence decreases Tg of the sample. However, in lead bismuth phosphate glasses, the addition of Pb2+ and Bi3+ not only failed to weaken the covalent character in P-O-P bonds, but strengthened it further, leading to an increment in the values of Tg

  17. Comparison of mechanical properties and structural changes of continous basalt and glass fibres at elevated temperatures

    Černý, Martin; Glogar, Petr; Goliáš, V.; Hruška, J.; Jakeš, P.; Sucharda, Zbyněk; Vávrová, I.

    2007-01-01

    Roč. 51, č. 2 (2007), s. 82-88 ISSN 0862-5468 R&D Projects: GA ČR GA106/05/0817 Institutional research plan: CEZ:AV0Z30460519 Keywords : basalt fibre * glass fibre * tensile properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.488, year: 2007

  18. From boiling point to glass transition temperature: transport coefficients in molecular liquids follow three-parameter scaling.

    Schmidtke, B; Petzold, N; Kahlau, R; Hofmann, M; Rössler, E A

    2012-10-01

    The phenomenon of the glass transition is an unresolved problem in condensed matter physics. Its prominent feature, the super-Arrhenius temperature dependence of the transport coefficients, remains a challenge to be described over the full temperature range. For a series of molecular glass formers, we combined τ(T) collected from dielectric spectroscopy and dynamic light scattering covering a range 10(-12) s < τ(T) < 10(2) s. Describing the dynamics in terms of an activation energy E(T), we distinguish a high-temperature regime characterized by an Arrhenius law with a constant activation energy E(∞) and a low-temperature regime for which E(coop)(T) ≡ E(T)-E(∞) increases exponentially while cooling. A scaling is introduced, specifically E(coop)(T)/E(∞) [proportionality] exp[-λ(T/T(A)-1)], where λ is a fragility parameter and T(A) a reference temperature proportional to E(∞). In order to describe τ(T) still the attempt time τ(∞) has to be specified. Thus, a single interaction parameter E(∞) describing the high-temperature regime together with λ controls the temperature dependence of low-temperature cooperative dynamics.

  19. Characterization of structural relaxation in inorganic glasses using length dilatometry

    Koontz, Erick

    The processes that govern how a glass relaxes towards its thermodynamic quasi-equilibrium state are major factors in understanding glass behavior near the glass transition region, as characterized by the glass transition temperature (Tg). Intrinsic glass properties such as specific volume, enthalpy, entropy, density, etc. are used to map the behavior of the glass network below in and near the transition region. The question of whether a true thermodynamic second order phase transition takes place in the glass transition region is another pending question. Linking viscosity behavior to entropy, or viewing the glass configuration as an energy landscape are just a couple of the most prevalent methods used for attempting to understand the glass transition. The structural relaxation behavior of inorganic glasses is important for more than scientific reasons, many commercial glass processing operations including glass melting and certain forms of optical fabrication include significant time spent in the glass transition region. For this reason knowledge of structural relaxation processes can, at a minimum, provide information for annealing duration of melt-quenched glasses. The development of a predictive model for annealing time prescription has the potential to save glass manufacturers significant time and money as well as increasing volume throughput. In optical hot forming processes such as precision glass molding, molded optical components can significantly change in shape upon cooling through the glass transition. This change in shape is not scientifically predictable as of yet though manufacturers typically use empirical rules developed in house. The classification of glass behavior in the glass transition region would allow molds to be accurately designed and save money for the producers. The work discussed in this dissertation is comprised of the development of a dilatometric measurement and characterization method of structural relaxation. The measurement and

  20. On the size and temperature dependence of the energy gap in cadmium-selenide quantum dots embedded in fluorophosphate glasses

    Lipatova, Zh. O., E-mail: zluka-yo@mail.ru; Kolobkova, E. V.; Babkina, A. N.; Nikonorov, N. V. [ITMO University (Russian Federation)

    2017-03-15

    The temperature and size dependences of the energy gap in CdSe quantum dots with diameters of 2.4, 4.0, and 5.2 nm embedded in fluorophosphate glasses are investigated. It is shown that the temperature coefficient of the band gap dE{sub g}/dT in the quantum dots differs from the bulk value and depends strictly on the dot size. It is found that, furthermore, the energy of each transition in these quantum dots is characterized by an individual temperature coefficient dE/dT.

  1. On the temperature dependence of the Adam-Gibbs equation around the crossover region in the glass transition

    Duque, Michel; Andraca, Adriana; Goldstein, Patricia; del Castillo, Luis Felipe

    2018-04-01

    The Adam-Gibbs equation has been used for more than five decades, and still a question remains unanswered on the temperature dependence of the chemical potential it includes. Nowadays, it is a well-known fact that in fragile glass formers, actually the behavior of the system depends on the temperature region it is being studied. Transport coefficients change due to the appearance of heterogeneity in the liquid as it is supercooled. Using the different forms for the logarithmic shift factor and the form of the configurational entropy, we evaluate this temperature dependence and present a discussion on our results.

  2. Final Report - Crystal Settling, Redox, and High Temperature Properties of ORP HLW and LAW Glasses, VSL-09R1510-1, Rev. 0, dated 6/18/09

    Kruger, Albert A.; Wang, C.; Gan, H.; Pegg, I. L.; Chaudhuri, M.; Kot, W.; Feng, Z.; Viragh, C.; McKeown, D. A.; Joseph, I.; Muller, I. S.; Cecil, R.; Zhao, W.

    2013-11-13

    The radioactive tank waste treatment programs at the U. S. Department of Energy (DOE) have featured joule heated ceramic melter technology for the vitrification of high level waste (HLW). The Hanford Tank Waste Treatment and Immobilization Plant (WTP) employs this same basic technology not only for the vitrification of HLW streams but also for the vitrification of Low Activity Waste (LAW) streams. Because of the much greater throughput rates required of the WTP as compared to the vitrification facilities at the West Valley Demonstration Project (WVDP) or the Defense Waste Processing Facility (DWPF), the WTP employs advanced joule heated melters with forced mixing of the glass pool (bubblers) to improve heat and mass transport and increase melting rates. However, for both HLW and LAW treatment, the ability to increase waste loadings offers the potential to significantly reduce the amount of glass that must be produced and disposed and, therefore, the overall project costs. This report presents the results from a study to investigate several glass property issues related to WTP HLW and LAW vitrification: crystal formation and settling in selected HLW glasses; redox behavior of vanadium and chromium in selected LAW glasses; and key high temperature thermal properties of representative HLW and LAW glasses. The work was conducted according to Test Plans that were prepared for the HLW and LAW scope, respectively. One part of this work thus addresses some of the possible detrimental effects due to considerably higher crystal content in waste glass melts and, in particular, the impact of high crystal contents on the flow property of the glass melt and the settling rate of representative crystalline phases in an environment similar to that of an idling glass melter. Characterization of vanadium redox shifts in representative WTP LAW glasses is the second focal point of this work. The third part of this work focused on key high temperature thermal properties of

  3. Linear thermal expansion coefficient (at temperatures from 130 to 800 K) of borosilicate glasses applicable for coupling with silicon in microelectronics

    Sinev, Leonid S.; Petrov, Ivan D.

    2017-01-01

    Processing results of measurements of linear thermal expansion coefficients and linear thermal expansion of two brands of borosilicate glasses --- LK5 and Borofloat 33 --- are presented. The linear thermal expansion of glass samples have been determined in the temperature range 130 to 800 K (minus 143 to 526 $\\deg$C) using thermomechanical analyzer TMA7100. Relative imprecision of indirectly measured linear thermal expansion coefficients and linear thermal expansion of both glass brands is le...

  4. Oxidation behaviour of Zr-based bulk metallic glasses

    Wang, Bin

    2011-01-01

    The Zr-based bulk metallic glasses, developed since the late 1980's, have very interesting mechanical properties, which can be considered for many applications including working under oxidizing atmosphere conditions at high temperatures. It is therefore interesting to study their oxidation resistance and to characterize the oxide scale formed on alloys surface. The fundamental objective of this thesis is to enhance the understanding of the role of various thermodynamic and chemistry parameters on the oxidation behaviour of the Zr-based bulk metallic glasses at high temperature under dry air, to determine the residual stresses in the oxide layer, in comparison with their crystalline alloys with the same chemical composition after an annealing treatment. The oxidation kinetics of these glasses and the crystalline structure of oxide scale ZrO 2 depend on the temperature and the oxidation duration: for short periods of oxidation or at a temperature below Tg, the kinetics follows a parabolic law, whereas, if the sample is oxidized at T ≥ Tg, the kinetics can be divided into two parts. The crystalline counterparts are oxidized by a parabolic rule whatever the temperature; for long oxidation duration at a temperature close to Tg, the kinetics becomes more complex because of the crystallisation of the glasses during the oxidation tests. Also the crystalline structure of the oxide layers depends on the oxidation temperature: the oxide layer consists only in tetragonal Zirconia at T ≤ Tg, while monoclinic Zirconia was formed at higher temperature. The mechanism of the formation of the oxide scale is due to both the interior diffusion of Oxygen ions and the external diffusion of Zirconium ions. However the diffusion of Zirconium ions slows gradually during the crystallisation process of the glass matrix. When the crystallisation is completed, the formation of Zirconia is controlled by only the internal diffusion of oxygen ions. The corresponding residual stresses

  5. Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water

    Giovambattista, Nicolas; Loerting, Thomas; Lukanov, Boris R.; Starr, Francis W.

    2012-01-01

    Water has multiple glassy states, often called amorphous ices. Low-density (LDA) and high-density (HDA) amorphous ice are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. Direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we explore the implications of a LLPT on the pressure dependence of Tg(P) for LDA and HDA by performing computer simulations of two water models – one with a LLPT, and one without. In the absence of a LLPT, Tg(P) for all glasses nearly coincide. When there is a LLPT, different glasses exhibit dramatically different Tg(P) which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario including a LLPT. PMID:22550566

  6. Feasibility Study of Using High-Temperature Raman Spectroscopy for On-Line Monitoring and Product Control of the Glass Vitrification Process

    Windisch, C.F. Jr.; Piepel, G.F.; Li, H.; Elliott, M.L.; Su, Y.

    1999-01-01

    A pulse-gating Raman spectroscopy setup was developed in this project. The setup was capable of performing in-situ high-temperature Raman measurements for glasses at temperatures as high as 1412 C. In the literature, high-temperature Raman measurements have only been performed on thin films of glass to minimize black-body radiation effects. The pulse-gating Raman setup allows making high-temperature measurements for bulk melts while effectively minimizing black-body radiation effects. A good correlation was found between certain Raman characteristic parameters and glass melt temperature for sodium silicate glasses measured in this project. Comparisons were made between the high-temperature Raman data from this study and literature data. The results suggest that an optimization of the pulse-gating Raman setup is necessary to further improve data quality (i.e., to obtain data with a higher signal-to-noise ratio). An W confocal Raman microspectrometer with continuous wave laser excitation using a 325 nm excitation line was evaluated selectively using a transparent silicate glass ad a deep-colored high-level waste glass in a bulk quantity. The data were successfully collected at temperatures as high as approximately 1500 C. The results demonstrated that the UV excitation line can be used for high-temperature Raman measurements of molten glasses without black-body radiation interference from the melt for both transparent and deep-color glasses. Further studies are needed to select the best laser system that can be used to develop high-temperature Raman glass databases

  7. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  8. Crystallization In Multicomponent Glasses

    Kruger, A.A.; Hrma, P.R.

    2009-01-01

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  9. Pressure dependence of glass transition in As2Te3 glass.

    Ramesh, K

    2014-07-24

    Amorphous solids prepared from their melt state exhibit glass transition phenomenon upon heating. Viscosity, specific heat, and thermal expansion coefficient of the amorphous solids show rapid changes at the glass transition temperature (Tg). Generally, application of high pressure increases the Tg and this increase (a positive dT(g)/dP) has been understood adequately with free volume and entropy models which are purely thermodynamic in origin. In this study, the electrical resistivity of semiconducting As(2)Te(3) glass at high pressures as a function of temperature has been measured in a Bridgman anvil apparatus. Electrical resistivity showed a pronounced change at Tg. The Tg estimated from the slope change in the resistivity-temperature plot shows a decreasing trend (negative dT(g)/dP). The dT(g)/dP was found to be -2.36 °C/kbar for a linear fit and -2.99 °C/kbar for a polynomial fit in the pressure range 1 bar to 9 kbar. Chalcogenide glasses like Se, As(2)Se(3), and As(30)Se(30)Te(40) show a positive dT(g)/dP which is very well understood in terms of the thermodynamic models. The negative dT(g)/dP (which is generally uncommon in liquids) observed for As(2)Te(3) glass is against the predictions of the thermodynamic models. The Adam-Gibbs model of viscosity suggests a direct relationship between the isothermal pressure derivative of viscosity and the relaxational expansion coefficient. When the sign of the thermal expansion coefficient is negative, dT(g)/dP = Δk/Δα will be less than zero, which can result in a negative dT(g)/dP. In general, chalcogenides rich in tellurium show a negative thermal expansion coefficient (NTE) in the supercooled and stable liquid states. Hence, the negative dT(g)/dP observed in this study can be understood on the basis of the Adams-Gibbs model. An electronic model proposed by deNeufville and Rockstad finds a linear relation between Tg and the optical band gap (Eg) for covalent semiconducting glasses when they are grouped

  10. Room temperature growth of biaxially aligned yttria-stabilized zirconia films on glass substrates by pulsed-laser deposition

    Li Peng; Mazumder, J

    2003-01-01

    Room temperature deposition of biaxially textured yttria-stabilized zirconia (YSZ) films on amorphous glass substrates was successfully achieved by conventional pulsed-laser deposition. The influence of the surrounding gases, their pressure and the deposition time on the structure of the films was studied. A columnar growth process was revealed based on the experimental results. The grown biaxial texture appears as a kind of substrate independence, which makes it possible to fabricate in-plane aligned YSZ films on various substrates.

  11. Asymptotic solutions of glass temperature profiles during steady optical fibre drawing

    Taroni, M.; Breward, C. J. W.; Cummings, L. J.; Griffiths, I. M.

    2013-01-01

    In this paper we derive realistic simplified models for the high-speed drawing of glass optical fibres via the downdraw method that capture the fluid dynamics and heat transport in the fibre via conduction, convection and radiative heating. We

  12. Monitoring gaseous CO2 and ethanol above champagne glasses: flute versus coupe, and the role of temperature.

    Gérard Liger-Belair

    Full Text Available In champagne tasting, gaseous CO(2 and volatile organic compounds progressively invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. Simultaneous quantification of gaseous CO(2 and ethanol was monitored through micro-gas chromatography (μGC, all along the first 15 minutes following pouring, depending on whether a volume of 100 mL of champagne was served into a flute or into a coupe. The concentration of gaseous CO(2 was found to be significantly higher above the flute than above the coupe. Moreover, a recently developed gaseous CO(2 visualization technique based on infrared imaging was performed, thus confirming this tendency. The influence of champagne temperature was also tested. As could have been expected, lowering the temperature of champagne was found to decrease ethanol vapor concentrations in the headspace of a glass. Nevertheless, and quite surprisingly, this temperature decrease had no impact on the level of gaseous CO(2 found above the glass. Those results were discussed on the basis of a multiparameter model which describes fluxes of gaseous CO(2 escaping the liquid phase into the form of bubbles.

  13. Monitoring gaseous CO2 and ethanol above champagne glasses: flute versus coupe, and the role of temperature.

    Liger-Belair, Gérard; Bourget, Marielle; Pron, Hervé; Polidori, Guillaume; Cilindre, Clara

    2012-01-01

    In champagne tasting, gaseous CO(2) and volatile organic compounds progressively invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. Simultaneous quantification of gaseous CO(2) and ethanol was monitored through micro-gas chromatography (μGC), all along the first 15 minutes following pouring, depending on whether a volume of 100 mL of champagne was served into a flute or into a coupe. The concentration of gaseous CO(2) was found to be significantly higher above the flute than above the coupe. Moreover, a recently developed gaseous CO(2) visualization technique based on infrared imaging was performed, thus confirming this tendency. The influence of champagne temperature was also tested. As could have been expected, lowering the temperature of champagne was found to decrease ethanol vapor concentrations in the headspace of a glass. Nevertheless, and quite surprisingly, this temperature decrease had no impact on the level of gaseous CO(2) found above the glass. Those results were discussed on the basis of a multiparameter model which describes fluxes of gaseous CO(2) escaping the liquid phase into the form of bubbles.

  14. Liquid -to-glass transition in bulk glass-forming Cu55-xZr45Agx alloys using molecular dynamic simulations

    Celtek M.

    2011-05-01

    Full Text Available We report results from molecular dynamics (MD studies concerning the microscopic structure of the ternary, bulk metallic glass-forming Cu55-x Zr45Agx (x=0,10,20 alloys using tight-binding potentials. Understanding of the nature of Glass Forming Ability (GFA of studied alloys, GFA parameters, glass transition temperature (T-g, melting temperature (T-m, reduced glass transition temperature (T-g/T-m, the supercooled liquid region and other parameters were simulated and compared with experiments. The computed pair distribution functions reproduce well experimental x-ray data of Inoue and co-workers. Structure analysis of the Cu-Zr-Ag alloy based on MD simulation will be also presented

  15. Thermal stress modification in regenerated fiber Bragg grating via manipulation of glass transition temperature based on CO₂-laser annealing.

    Lai, Man-Hong; Lim, Kok-Sing; Gunawardena, Dinusha S; Yang, Hang-Zhou; Chong, Wu-Yi; Ahmad, Harith

    2015-03-01

    In this work, we have demonstrated thermal stress relaxation in regenerated fiber Bragg gratings (RFBGs) by using direct CO₂-laser annealing technique. After the isothermal annealing and slow cooling process, the Bragg wavelength of the RFBG has been red-shifted. This modification is reversible by re-annealing and rapid cooling. It is repeatable with different cooling process in the subsequent annealing treatments. This phenomenon can be attributed to the thermal stress modification in the fiber core by means of manipulation of glass transition temperature with different cooling rates. This finding in this investigation is important for accurate temperature measurement of RFBG in dynamic environment.

  16. Crystallization in lead tungsten fluorophosphate glasses

    Nardi, R.P.R.D.; Braz, C.E.; Cassanjes, F.C.; Poirier, G.

    2014-01-01

    The glass forming ability was investigated in the ternary system NaPO 3 -WO 3 -PbF 2 with a constant NaPO 3 /WO 3 ratio of 3/2 and increasing amounts of PbF 2 . It has been found that glass samples can be obtained from PbF 2 contents from 0 mole% to 60 mole%. The most lead fluoride concentrated samples (50% and 60%) were chosen for a crystallization study in order to investigate the possibility of obtaining glass-ceramics containing crystalline lead fluoride. DSC measurements allowed to determine the characteristic temperatures such as Tg, Tx, Tp and Tf. These glass samples were heat-treated near the crystallization peaks observed by thermal analysis. X-ray diffraction results of these heat-treated glasses pointed out that the dominant phase which precipitates from the glass sample containing 50% of PbF 2 is the lead fluorophosphates phase Pb 5 F(PO 4 ) 3 whereas the sample containing 60% of PbF 2 exhibits a preferential crystallization of cubic lead fluoride β-PbF 2 . (author)

  17. Crystallization in lead tungsten fluorophosphate glasses

    Nardi, R.P.R.D.; Braz, C.E.; Cassanjes, F.C.; Poirier, G., E-mail: gael.poirier@unifal-mg.edu.br [Universidade Federal de Alfenas (UNIFAL), Pocos de Caldas, MG (Brazil). Instituto de Ciencia e Tecnologia

    2014-07-01

    The glass forming ability was investigated in the ternary system NaPO{sub 3}-WO{sub 3}-PbF{sub 2} with a constant NaPO{sub 3}/WO{sub 3} ratio of 3/2 and increasing amounts of PbF{sub 2}. It has been found that glass samples can be obtained from PbF{sub 2} contents from 0 mole% to 60 mole%. The most lead fluoride concentrated samples (50% and 60%) were chosen for a crystallization study in order to investigate the possibility of obtaining glass-ceramics containing crystalline lead fluoride. DSC measurements allowed to determine the characteristic temperatures such as Tg, Tx, Tp and Tf. These glass samples were heat-treated near the crystallization peaks observed by thermal analysis. X-ray diffraction results of these heat-treated glasses pointed out that the dominant phase which precipitates from the glass sample containing 50% of PbF{sub 2} is the lead fluorophosphates phase Pb{sub 5}F(PO{sub 4}){sub 3} whereas the sample containing 60% of PbF{sub 2} exhibits a preferential crystallization of cubic lead fluoride β-PbF{sub 2}. (author)

  18. Preparation of hollow hydroxyapatite microspheres by the conversion of borate glass at near room temperature

    Yao, Aihua; Ai, Fanrong; Liu, Xin; Wang, Deping; Huang, Wenhai; Xu, Wei

    2010-01-01

    Hollow hydroxyapatite microspheres, consisting of a hollow core and a porous shell, were prepared by converting Li 2 O-CaO-B 2 O 3 glass microspheres in dilute phosphate solution at 37 o C. The results confirmed that Li 2 O-CaO-B 2 O 3 glass was transformed to hydroxyapatite without changing the external shape and dimension of the original glass object. Scanning electron microscopy images showed the shell wall of the microsphere was built from hydroxyapatite particles, and these particles spontaneously align with one another to form a porous sphere with an interior cavity. Increase in phosphate concentration resulted in an increase in the reaction rate, which in turn had an effect on shell wall structure of the hollow hydroxyapatite microsphere. For the Li 2 O-CaO-B 2 O 3 glass microspheres reacted in low-concentration K 2 HPO 4 solution, lower reaction rate and a multilayered microstructure were observed. On the other hand, the glass microspheres reacted in higher phosphate solution converted more rapidly and produced a single hydroxyapatite layer. Furthermore, the mechanism of forming hydroxyapatite hollow microsphere was described.

  19. Determining the dissolution rates of actinide glasses: A time and temperature Product Consistency Test study

    Daniel, W.E.; Best, D.R.

    1995-01-01

    Vitrification has been identified as one potential option for the e materials such as Americium (Am), Curium (Cm), Neptunium (Np), and Plutonium (Pu). A process is being developed at the Savannah River Site to safely vitrify all of the highly radioactive Am/Cm material and a portion of the fissile (Pu) actinide materials stored on site. Vitrification of the Am/Cm will allow the material to be transported and easily stored at the Oak Ridge National Laboratory. The Am/Cm glass has been specifically designed to be (1) highly durable in aqueous environments and (2) selectively attacked by nitric acid to allow recovery of the valuable Am and Cm isotopes. A similar glass composition will allow for safe storage of surplus plutonium. This paper will address the composition, relative durability, and dissolution rate characteristics of the actinide glass, Loeffler Target, that will be used in the Americium/Curium Vitrification Project at Westinghouse Savannah River Company near Aiken, South Carolina. The first part discusses the tests performed on the Loeffler Target Glass concerning instantaneous dissolution rates. The second part presents information concerning pseudo-activation energy for the one week glass dissolution process

  20. B2O3/SiO2 substitution effect on structure and properties of Na2O-CaO-SrO-P2O5-SiO2 bioactive glasses from molecular dynamics simulations.

    Ren, Mengguo; Lu, Xiaonan; Deng, Lu; Kuo, Po-Hsuen; Du, Jincheng

    2018-05-23

    The effect of B2O3/SiO2 substitution in SrO-containing 55S4.3 bioactive glasses on glass structure and properties, such as ionic diffusion and glass transition temperature, was investigated by combining experiments and molecular dynamics simulations with newly developed potentials. Both short-range (such as bond length and bond angle) and medium-range (such as polyhedral connection and ring size distribution) structures were determined as a function of glass composition. The simulation results were used to explain the experimental results for glass properties such as glass transition temperature and bioactivity. The fraction of bridging oxygen increased linearly with increasing B2O3 content, resulting in an increase in overall glass network connectivity. Ion diffusion behavior was found to be sensitive to changes in glass composition and the trend of the change with the level of substitution is also temperature dependent. The differential scanning calorimetry (DSC) results show a decrease in glass transition temperature (Tg) with increasing B2O3 content. This is explained by the increase in ion diffusion coefficient and decrease in ion diffusion energy barrier in glass melts, as suggested by high-temperature range (above Tg) ion diffusion calculations as B2O3/SiO2 substitution increases. In the low-temperature range (below Tg), the Ea for modifier ions increased with B2O3/SiO2 substitution, which can be explained by the increase in glass network connectivity. Vibrational density of states (VDOS) were calculated and show spectral feature changes as a result of the substitution. The change in bioactivity with B2O3/SiO2 substitution is discussed with the change in pH value and release of boric acid into the solution.

  1. Glass transition and the rigid amorphous phase in semicrystalline blends of bacterial polyhydroxybutyrate PHB with low molecular mass atactic R,S-PHB-diol

    Hoehne, G.W.H.

    2004-01-01

    The glass transition and the crystallinity of blends of isotactic bacterial PHB and low molecular mass atactic R, S-PHB-diols was investigated by means of differential scanning calorimetry (DSC), temperature-modulated DSC and dielectric spectroscopy. It was found that (i) Tg of crystallized blends

  2. Influence of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers: does otolith growth cease at low temperatures?

    Fukuda, N; Kuroki, M; Shinoda, A; Yamada, Y; Okamura, A; Aoyama, J; Tsukamoto, K

    2009-06-01

    The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30 degrees C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25 degrees C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20-30 degrees C or after 20 days at 15 degrees C, but no feeding occurred at 5 and 10 degrees C. No otolith growth occurred at 5 and 10 degrees C except in two individuals with minimal increment deposition at 10 degrees C. Otolith growth was proportional to water temperature within 15-25 degrees C and not different between 25 and 30 degrees C. At 15, 25 and 30 degrees C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0.00-0.01 day(-1) at 5 and 10 degrees C, 0.43-0.48 day(-1) at 15 degrees C and 0.94-1.07 day(-1) at 20-30 degrees C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.

  3. Temperature-dependent evolution of RbBSi2O6 glass into crystalline Rb-boroleucite according to X-ray diffraction data

    Levin, Aleksandr A.; Filatov, Stanislav K.; Krzhizhanovskaya, Maria G.; Paufler, Peter; Bubnova, Rimma S.; Russian Academy of Sciences, St. Petersburg; Meyer, Dirk C.; Technische Univ. Bergakademie Freiberg

    2013-01-01

    The temperature-dependent evolution of the glass into a crystalline phase is studied for a rubidium borosilicate glass of composition 16.7 Rb 2 O . 16.7 B 2 O 3 . 66.6 SiO 2 employing X-ray diffraction (XRD) data. A glass sample was prepared by melt quenching from 1500 within 0.5 hour. The glass sample was step-wise annealed at 13 distinct temperatures from 300 C up to 900 C for 1 h at every annealing step. To investigate changes in the glass structure, angle-dispersive XRD was applied by using an energy-resolving semiconductor detector. The radial distribution functions (RDFs) were calculated at every stage. For polycrystalline states the crystal structure of the samples with different thermal history was refined using the Rietveld method. Comparing correlation distances estimated from RDFs of glass and polycrystalline samples and mean interatomic distances calculated for polycrystalline samples by using atomic coordinates after Rietveld refinement, it is concluded that the borosilicate glass under study is converted into the crystalline state in the temperature range of 625-750 C (i.e. in the temperature range close to the glass transition range 620-695 C as determined by differential scanning calorimetry by using of heating rate of 20 K/min) at an average heating rate of about 0.35 K/min. When the heating rate is increased up to 10 or 20 K/min, the crystallisation temperature shifts sharply up to 831-900 C and 878-951 C, respectively. XRD data give evidence that distinctive traces of cubic RbBSi 2 O 6 appear from glass at about 625 C and a two-phase range exists up to 750 C. After annealing at higher temperatures (800-900 C) the crystal structure practically does not change any more. (orig.)

  4. Enhanced luminescence from silver nanoparticles integrated Er{sup 3+}-doped boro-tellurite glasses: Impact of annealing temperature

    Said Mahraz, Zahra Ashur; Sahar, M.R., E-mail: mrahim057@gmail.com; Ghoshal, S.K.

    2015-11-15

    Considerable enhancement of rare earth ions luminescence intensity stimulated via metal nanoparticles (NPs) inclusion inside inorganic glass matrix opened a new avenue to achieving efficient lasing glass media. Tuning the localised surface plasmon resonance (LSPR) band of noble metal NPs through their precise size manipulation is demonstrated to be the key for such accomplishment. We report the influences of annealing (heat treatment) temperature (AT) on the down-conversion luminescence features of erbium (Er{sup 3+}) doped zinc-boro-tellurite (ZBT) glasses containing silver NPs. The AT dependent (between 390 and 450 °C) variations in refractive index and density are ascribed to the generation of non-bridging oxygen (NBO) ions. X-ray diffraction pattern confirmed the amorphous nature of the melt-quenched synthesized glass samples. TEM micrograph revealed the nucleation of Ag NPs inside the glass matrix having average diameter between 8.4 (un-annealed sample) to 11.8 nm (annealed). The UV–Vis spectra exhibited seven absorption bands corresponding to {sup 4}f–{sup 4}f transitions of Er{sup 3+} ions. Annealed samples displayed a red shift of SPR bands positioned at 550 and 580 nm. Judd–Ofelt theory is used to evaluate the intensity parameters for radiative transitions within 4f{sup n} configuration of Er{sup 3+} ion. Annealing up to 410 °C is found to stimulate the plasmonic effect through the enlargement of NPs. Consequently, the PL intensity is enhanced by a factor of 3.23 ({sup 2}H{sub 11/2} → {sup 4}I{sub 15/2}), 4.10 ({sup 4}S{sub 3/2} → {sup 4}I{sub 15/2}), and 3.79 ({sup 4}F{sub 9/2} → {sup 4}I{sub 15/2}). This achieved excellent down-conversion luminescence efficiency of proposed glasses shows their potential implementation in photonic devices and solid state lasers. - Highlights: • The changes in the physical properties are ascribed to the generation of NBO. • TEM images confirmed the presence of Ag NPs in the glass matrix. • The achieved

  5. INTERACTION OF SILVER MOLECULAR CLUSTERS, INTRODUCED BY LOW-TEMPERATURE ION EXCHANGE METHOD, WITH NANOPARTICLES OF CdS IN FLUORINE PHOSPHATE GLASSES

    N. D. Grazhdanov

    2015-09-01

    Full Text Available Glasses with metallic and semi-conductive nano-particles appear to be perspective non-linear and luminescent materials of photonics. It was shown in theory that composite optical materials containing semi-conductive CdS-core with Ag shell (or vice versa are optimal for enhancement of non-linear Kerr effect. Interaction of such an ensemble of particles leads to the forming of Ag island structures on the CdS particle, and formation of acanthite Ag2S on the two phases border (CdS-Ag is minimal. In glasses synthesis of CdS quantum dots occurred due to thermal treatment close to glass transition temperature; introduction of silver was realized by low-temperature ion exchange (LIE. The main object of this work is investigation of Ag+ -LIE effect on the growth of CdS nano-particles. Two glasses were explored in this work: without CdS (glass 1 and with CdS (glass 2, processed by LIE at the temperature of 320°С for 10, 20 and 30 minutes and subsequent heat treatment at temperatures of 410°С and 420°С. In case of glass 1, intensive luminescence appears as a result of LIE, and subsequent heat treatment results in surface resonance at λ=410 nm. In case of glass 2, absorbance spectra change appears that is specific for formation of acanthite and weak luminescence shifting to long-wavelength region (from 550 to 700 nm as a result of applying LIE and heat treatment. It indicates the growth of CdS quantum dots. Experiment has shown that quantum efficiency increases to 70% for glass 2 containing CdS quantum dots without LIE, while glass that contains silver shows steep decrease of quantum efficiency to 0%. That decrease is caused by formation of acanthite Ag2S on the surface of CdS quantum dot.

  6. Mechanical response of novel SiOC glasses to high temperature exposition

    Halasová, Martina; Chlup, Zdeněk; Strachota, Adam; Černý, Martin; Dlouhý, Ivo

    2012-01-01

    Roč. 32, č. 16 (2012), s. 4489-4495 ISSN 0955-2219 R&D Projects: GA ČR GA106/09/1101 Institutional research plan: CEZ:AV0Z30460519; CEZ:AV0Z40500505 Institutional support: RVO:68081723 ; RVO:61389013 Keywords : Glass * Hardness * Mechanical properties Subject RIV: JL - Materials Fatigue, Friction Mechanics; CD - Macromolecular Chemistry (UMCH-V); JH - Ceramic s, Fire-Resistant Materials and Glass (USMH-B) Impact factor: 2.360, year: 2012

  7. Modeling glass transition and aging processes in nanocomposites and polymer thin films

    Pryamitsyn, Victor; Ganesan, Venkat

    2010-03-01

    We use a lattice kinetic model of glass transition to study the role of confinement and the presence of nano-inclusions. We have studied freely suspended films of glass-formers and its nanocomposites with ``plastifying'' and ``hardening'' nanoparticles. Using our model we determine the thickness and nanoparticle load dependencies of the Kauzmann temperature T0 and the fragility parameter. We found the glass transition temperature increases with the thickness of the film and the volume fraction of ``hardening'' nanoparticles , while Tg decreases with increase in the loading of ``plastifying'' nanoparticles. We found that the isothermal free volume relaxation rate of the nanocomposite thin film, usually referred as an aging, correlates with the glass transition temperature shift. We also studied the relations between our lattice model and Curro's, Kovacs and Struik's phenomenological models of free volume reduction to deduce physical insights into the mechanisms governing aging processes in thin films and nanocomposites.

  8. Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

    Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

    2016-01-13

    Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

  9. 1998 Annual Study Report. Standardization of methods for evaluating properties of new glass at high temperature; 1998 nendo seika hokokusho. New glass koon bussei no hyoka hoho no hyojunka

    NONE

    1999-03-01

    High-temperature properties of glass melts, e.g., density, volume expansion coefficient, surface tension, viscosity, specific heat, thermal and electrical conductivity, redox equilibrium and gas solubility, are basic factors that must be considered in high quality glass melting technology and computer simulation of the glass tank furnace. The structure of the glass melts is also important for understanding these properties. This R and D program is aimed at proposing the international standards for the methods of measuring these high-temperature properties of the melts. The 1988 efforts are directed to the measuring technologies for density, volume expansion coefficient, surface tension, viscosity, specific heat, thermal and electrical conductivity, redox equilibrium, gas solubility and melt structures of soda-lime-silica glass melts. The R and D for measuring methods for high-temperature melts through international cooperation and establishment of the international standards for these methods are proposed in the joint CGR/HVG/TNO/GPF conference, which provides the arena for information exchange by glass manufacturers. (NEDO)

  10. Influence of low-temperature annealing on magnetic properties of (Nd0.625Ni0.375)85Al15 metallic glass

    Xu Feng; Wang Zhiming; Chen Guang; Jiang Jianzhong; Du Youwei

    2008-01-01

    After a review of the selection process of (Nd 0.625 Ni 0.375 ) 85 Al 15 as a metallic glass with a relatively high glass-forming ability, we investigate the influences of its phase transitions by duplicating the heating process of the isochronal thermal analysis with low-temperature annealings. The structure, thermal stability and magnetic properties are characterized. And the influences on magnetic properties are particularly discussed with emphasis. Both the annealing processes, to the glass-transition temperature and to the onset temperature of crystallization, bring about a higher coercivity of the sample and a higher freezing temperature of the spin-glass-state. For the sample annealed to the onset temperature of crystallization, the influence is quite obvious and is ascribed to the formation of ferrimagnetic Nd 7 Ni 3 phase, as detected by XRD. For the sample annealed to the glass-transition temperature, the indistinct influence is further identified with the analysis of the frequency dependence of the spin-glass-state, and it is mainly attributed to the change of the short-range order in the amorphous matrix

  11. Effect of sugar addition on glass transition temperatures of cassava starch with low to intermediate moisture contents.

    Figueroa, Yetzury; Guevara, Marvilan; Pérez, Adriana; Cova, Aura; Sandoval, Aleida J; Müller, Alejandro J

    2016-08-01

    This work studies how sucrose (S) addition modifies the thermal properties of cassava starch (CS). Neat CS and CS-S blends with 4, 6 and 8% sugar contents (CS-S-4%, CS-S-6% and CS-S-8%) were prepared and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), in a wide range of moisture levels (2-20%). In equilibrated samples with moisture contents lower than 10%, twoendothermic steps were observed during first DSC heating scans and two corresponding relaxation maxima in tan δ were detected by DMTA. The first transition, detected at around 45-55°C by both DSC and DMTA, is frequently found in starchy foods, while the second observed at higher temperatures is associated to the glass transition temperature of the blends. At higher moisture contents, only one thermal transition was observed. Samples analyzed immediately after cooling from the melt (i.e., after erasing their thermal history), exhibited a single glass transition temperature, regardless of their moisture content. Addition of sugar promotes water plasticization of CS only at high moisture contents. In the low moisture content range, anti-plasticization was observed for both neat and sugar-added CS samples. Addition of sugar decreases the moisture content needed to achieve the maximum value of the glass transition temperature before plasticization starts. The results of this work may be valuable for the study of texture establishment in low moisture content extruded food products. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Mean-field solution of the Potts glass near the transition temperature to the ordered phase

    Janiš, Václav; Klíč, Antonín

    2011-01-01

    Roč. 84, č. 6 (2011), "064446-1"-"064446-10" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520 Keywords : Potts glass * hierarchic solutions with replicated spins * continuous replica-symmetry breaking Subject RIV: BE - Theoretical Physics Impact factor: 3.691, year: 2011

  13. Greenhouse Effect: Temperature of a Metal Sphere Surrounded by a Glass Shell and Heated by Sunlight

    Nguyen, Phuc H.; Matzner, Richard A.

    2012-01-01

    We study the greenhouse effect on a model satellite consisting of a tungsten sphere surrounded by a thin spherical, concentric glass shell, with a small gap between the sphere and the shell. The system sits in vacuum and is heated by sunlight incident along the "z"-axis. This development is a generalization of the simple treatment of the…

  14. Optical bistability in Er-Yb codoped phosphate glass microspheres at room temperature

    Warda, Jonathan M.; O'Shea, Danny G.; Shortt, Brian J.; Chormaic, Sile Nic

    2007-01-01

    We experimentally demonstrate optical bistability in Er(3+)-Yb(3+) phosphate glass microspheres at 295 K. Bistability is associated with both Er(3+) fluorescence and lasing behavior, and chromatic switching. The chromatic switching results from an intrinsic mechanism exploiting the thermal coupling

  15. Room temperature deposition of perpendicular magnetic anisotropic Co{sub 3}Pt thin films on glass substrate

    Chen, Yu-Shen; Dai, Hong-Yu; Hsu, Yi-Wei [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China); Ou, Sin-Liang, E-mail: slo@mail.dyu.edu.tw [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Chen, Shi-Wei [National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300, Taiwan (China); Lu, Hsi-Chuan; Wang, Sea-Fue [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Sun, An-Cheng, E-mail: acsun@saturn.yzu.edu.tw [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China)

    2017-03-01

    Co{sub 3}Pt alloy thin films were deposited on the glass substrate at room temperature (RT) and 300 °C, which showed high perpendicular magnetic anisotropy (PMA) and isotropy magnetic behaviors, respectively. Co{sub 3}Pt HCP (0002) planes grew along the substrate plane for the films deposited at RT. The easy axis [0001] was consequently vertical to the substrate surface and obtained the predominant PMA. Large magnetic domains and sharp boundary also supported high PMA in RT-deposited samples. On the other hand, the PMA was significantly decreased with increasing the deposition temperature from RT to 300 °C. Hard HCP(0002) and soft A1(111) co-existed in the film and the magnetic exchanged coupling between these two phases induced isotropy magnetic behavior. In addition, the various thicknesses (t) of the RT-deposited Co{sub 3}Pt films were deposited with different base pressures prior to sputtering. The Kerr rotation loops showed high PMA and out-of-plane squareness (S{sub ⊥}) of ~0.9 were found in low base pressure chamber. Within high base pressure chamber, Co{sub 3}Pt films just show magnetic isotropy behaviors. This study provides a fabrication method for the preparation of high PMA HCP-type Co{sub 3}Pt films on the glass substrate without any underlayer at RT. The results could be the base for future development of RT-deposited magnetic alloy thin film with high PMA. - Highlights: • Fabricated high perpendicular magnetic anisotropy Co{sub 3}Pt thin film on glass substrate. • Prepared HCP Co{sub 3}Pt thin film at room temperature. • The key to enhance the PMA of the Co{sub 3}Pt films. • Thinner film is good to fabricate PMA Co{sub 3}Pt thin films.

  16. Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

    Abel, Brett M.; Morgan, James M.; Mauro, John C.

    2013-01-01

    . In the composition range of interest for industrial glasses, Tliq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO2, SiO2+Al2O3, and SrO contents, respectively. By comparison...... with the phase diagrams for CaO-Al2O3-SiO2 and MgO-Al2O3-SiO2 systems, we have found that for the highest [RO]/[Al2O3] ratios, Tliq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging...... to the SrO-Al2O3-SiO2 family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature....

  17. The role of shape memory alloy on impact response of glass/epoxy laminates under low temperature

    Kang, K. W.; Kim, H. J.

    2007-01-01

    The paper aims to evaluate the impact response of glass/epoxy laminates with embedded shape memory alloy (SMA) subject to low velocity impact at various temperatures. For the goal, the impact tests were performed by using an instrumented impact-testing machine at three temperatures: 293K, 263K and 233K for the baseline (laminates without SMA wires) and SMA laminates (laminates with embedded SMA wires). And the resultant damages were inspected through the scanning acoustic microscope (SAM). Also, based on the impact force history and the damage configuration, the impact resistance parameters were employed to evaluate damage resistance of laminates with embedded SMA wires. As a result, it was observed that the damage resistance of glass/epoxy laminates is influenced by embedded SMA wires and embedding SMA wires into laminates does not compromise the structure any differently to laminates without wires. In fact, it has been shown that under lower temperature, the SMA laminates have a little superior damage resistance compared with the baseline laminates

  18. Influence of ejection temperature on structure and glass transition behavior for Zr-based rapidly quenched disordered alloys

    Wang, X.H.; Inoue, A.; Kong, F.L.; Zhu, S.L.; Stoica, M.; Kaban, I.; Chang, C.T.; Shalaan, E.; Al-Marzouki, F.; Eckert, J.

    2016-01-01

    We examined the influence of ejection liquid temperature (T el ) on the structure, thermal stability and crystallization of Zr−Al−Ni−Cu ribbons prepared by the melt-spinning technique. The increase in T el was found to cause the formation of an oxide phase on the ribbon surface, more loose atomic configurations, the absence of glass transition (GT) and supercooled liquid (SL) region, and the rise of crystallization temperature. The changes in the GT and SL region occur reversibly by controlling the T el . Neither the change in alloy composition except oxygen nor the difference in crystallized phases is seen. Their hardness increases significantly by the disappearance of GT and SL region. The reversible changes in the appearance and disappearance of GT and SL region was found for different Zr-based glassy ribbons, being independent of alloy compositions. The disappearance is presumably due to the change in atomic configurations from high-coordinated to less-coordinated atomic packing in the melt-spun ribbons by freezing high-temperature liquid. The observed phenomenon of the reversible changes provides a novel opportunity for deep understanding of mutual correlations among liquid structure, GT, stability of SL and bulk glass-forming ability for metallic alloys.

  19. EFFECTS OF TRITIUM GAS EXPOSURE ON THE GLASS TRANSITION TEMPERATURE OF EPDM ELASTOMER AND ON THE CONDUCTIVITY OF POLYANILINE

    Clark, E; Marie Kane, M

    2008-12-12

    Four formulations of EPDM (ethylene-propylene diene monomer) elastomer were exposed to tritium gas initially at one atmosphere and ambient temperature for between three and four months in closed containers. Material properties that were characterized include density, volume, mass, appearance, flexibility, and dynamic mechanical properties. The glass transition temperature was determined by analysis of the dynamic mechanical property data per ASTM standards. EPDM samples released significant amounts of gas when exposed to tritium, and the glass transition temperature increased by about 3 C. during the exposure. Effects of ultraviolet and gamma irradiation on the surface electrical conductivity of two types of polyaniline films are also documented as complementary results to planned tritium exposures. Future work will determine the effects of tritium gas exposure on the electrical conductivity of polyaniline films, to demonstrate whether such films can be used as a sensor to detect tritium. Surface conductivity was significantly reduced by irradiation with both gamma rays and ultraviolet light. The results of the gamma and UV experiments will be correlated with the tritium exposure results.

  20. The structural properties of Zr-based bulk metallic glasses subjected to high pressure torsion at different temperatures

    Boltynjuk, E. V., E-mail: boltynjuk@gmail.com; Ubyivovk, E. V.; Kshumanev, A. M. [Saint Petersburg State University, 28 Universitetskiy pr., Saint Petersburg, 198504 (Russian Federation); Gunderov, D. V.; Lukianov, A. V. [Ufa State Aviation Technical University, K. Marks 12, Ufa, 450000 (Russian Federation); Bednarz, A. [Faculty of Mechanical Engineering and Aeronautics, Department of Aircraft and Aircraft Engines, Rzeszow University of Technology, Al. Powstancow Warszawy 8, 35-959 Rzeszow (Poland); Valiev, R. Z. [Saint Petersburg State University, 28 Universitetskiy pr., Saint Petersburg, 198504 (Russian Federation); Ufa State Aviation Technical University, K. Marks 12, Ufa, 450000 (Russian Federation)

    2016-06-17

    The structural properties of a Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} bulk metallic glasses were investigated. Cylindrical rods of the Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} BMG were subjected to high pressure torsion at temperatures of 20°C and 150°C. X-ray diffraction, transmission electron microscopy were used to determine peculiarities of the modified structure. Analysis of fracture surfaces, nanohardness measurements were conducted to investigate the influence of structural changes on mechanical behavior of processed samples.

  1. The structural properties of Zr-based bulk metallic glasses subjected to high pressure torsion at different temperatures

    Boltynjuk, E. V.; Ubyivovk, E. V.; Kshumanev, A. M.; Gunderov, D. V.; Lukianov, A. V.; Bednarz, A.; Valiev, R. Z.

    2016-01-01

    The structural properties of a Zr_6_2Cu_2_2Al_1_0Fe_5Dy_1 bulk metallic glasses were investigated. Cylindrical rods of the Zr_6_2Cu_2_2Al_1_0Fe_5Dy_1 BMG were subjected to high pressure torsion at temperatures of 20°C and 150°C. X-ray diffraction, transmission electron microscopy were used to determine peculiarities of the modified structure. Analysis of fracture surfaces, nanohardness measurements were conducted to investigate the influence of structural changes on mechanical behavior of processed samples.

  2. Local structural mechanism for frozen-in dynamics in metallic glasses

    Liu, X. J.; Wang, S. D.; Wang, H.; Wu, Y.; Liu, C. T.; Li, M.; Lu, Z. P.

    2018-04-01

    The nature of the glass transition is a fundamental and long-standing intriguing issue in the condensed-matter physics and materials science community. In particular, the structural response by which a liquid is arrested dynamically to form a glass or amorphous solid upon approaching its freezing temperature [the glass transition temperature (Tg)] remains unclear. Various structural scenarios in terms of the percolation theory have been proposed recently to understand such a phenomenon; however, there is still no consensus on what the general percolation entity is and how the entity responds to the sudden slowdown dynamics during the glass transition. In this paper, we demonstrate that one-dimensional local linear ordering (LLO) is a universal structural motif associated with the glass transition for various metallic glasses. The quantitative evolution of LLO with temperature indicates that a percolating LLO network forms to serve as the backbone of the rigid glass solid when the temperature approaches the freezing point, resulting in the frozen-in dynamics accompanying the glass transition. The percolation transition occurs by pinning different LLO networks together, which only needs the introduction of a small number of "joint" atoms between them, and therefore the energy expenditure is very low.

  3. Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water

    Giovambattista, Nicolas

    2013-03-01

    Most liquids can form a single glass or amorphous state when cooled sufficiently fast (in order to prevent crystallization). However, there are a few substances that are relevant to scientific and technological applications which can exist in at least two different amorphous states, a property known as polyamorphism. Examples include silicon, silica, and in particular, water. In the case of water, experiments show the existence of a low-density (LDA) and high-density (HDA) amorphous ice that are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation evolves into a first-order liquid-liquid phase transition (LLPT) at temperatures above the glass transition temperature Tg. However, obtaining direct experimental evidence of the LLPT has been challenging since the LLPT occurs at conditions where water rapidly crystallizes. In this talk, I will (i) discuss the general phenomenology of polyamorphism in water and its implications, and (ii) explore the effects of a LLPT on the pressure dependence of Tg(P) for LDA and HDA. Our study is based on computer simulations of two water models - one with a LLPT (ST2 model), and one without (SPC/E model). In the absence of a LLPT, Tg(P) for all glasses nearly coincide. Instead, when there is a LLPT, different glasses exhibit dramatically different Tg(P) loci which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario that includes a LLPT (ST2 model) and hence, our results support the view that a LLPT may exist for the case of water.

  4. Pressure-controlled nucleation and growth in Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass close to and beyond glass transition temperature

    Pan Mingxiang; Yao Yushu; Zhao Deqian; Zhuang Yanxin; Wang Weihua

    2002-01-01

    By high-pressure annealing close to and beyond glass transition temperature, the behavior of nucleation and growth of crystals in Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass (BMG) is investigated. The experimental results indicate that exerting a high pressure during annealing can markedly decrease the nucleation temperature of the BMG. The growth rate of crystals first increases and then decreases with increase of annealing pressure. The effect of pressure on nucleation and growth of crystals is phenomenologically explained

  5. Transient regimes during high-temperature deformation of a bulk metallic glass: A free volume approach

    Bletry, M.; Guyot, P.; Brechet, Y.; Blandin, J.J.; Soubeyroux, J.L.

    2007-01-01

    The homogeneous deformation of a zirconium-based bulk metallic glass is investigated in the glass transition range. Compression and stress-relaxation tests have been conducted. The stress-strain curves are modeled in the framework of the free volume theory, including transient phenomena (overshoot and undershoot). This approach allows several physical parameters (activation volume, flow defect creation and relaxation coefficient) to be determined from a mechanical experiment. This model is able to rationalize the dependency of stress overshoot on relaxation time. It is shown that, due to the relationship between flow defect concentration and free volume model, it is impossible to determine the equilibrium flow defect concentration. However, the relative variation of flow defect is always the same, and all the model parameters depend on the equilibrium flow defect concentration. The methodology presented in this paper should, in the future, allow the consistency of the free volume model to be assessed

  6. Freeform Fabrication of Magnetophotonic Crystals with Diamond Lattices of Oxide and Metallic Glasses for Terahertz Wave Control by Micro Patterning Stereolithography and Low Temperature Sintering

    Maasa Nakano

    2013-04-01

    Full Text Available Micrometer order magnetophotonic crystals with periodic arranged metallic glass and oxide glass composite materials were fabricated by stereolithographic method to reflect electromagnetic waves in terahertz frequency ranges through Bragg diffraction. In the fabrication process, the photo sensitive acrylic resin paste mixed with micrometer sized metallic glass of Fe72B14.4Si9.6Nb4 and oxide glass of B2O3·Bi2O3 particles was spread on a metal substrate, and cross sectional images of ultra violet ray were exposed. Through the layer by layer stacking, micro lattice structures with a diamond type periodic arrangement were successfully formed. The composite structures could be obtained through the dewaxing and sintering process with the lower temperature under the transition point of metallic glass. Transmission spectra of the terahertz waves through the magnetophotonic crystals were measured by using a terahertz time domain spectroscopy.

  7. Crystallization kinetics, optical and dielectric properties of Li2OṡCdOṡBi2O3ṡSiO2 glasses

    Rani, Saroj; Sanghi, Sujata; Ahlawat, Neetu; Agarwal, Ashish

    2015-10-01

    Crystallization kinetics, optical absorption and electrical behavior of lithium cadmium silicate glasses with different amount of bismuth oxide were investigated using non-isothermal crystallization approach, UV-VIS-NIR spectroscopy and impedance spectroscopy, respectively. These glasses were synthesized by normal melt quenching technique. Variation in physical properties, viz. density, molar volume with Bi2O3:SiO2 ratio were related to the structural changes occurring in the glasses. The glass transition temperature (Tg), crystalline peak temperature (Tp) and melting temperature (Tm) of these glasses were determined using differential scanning calorimeter at various heating rates. The dependence of Tg and Tp on heating rate has been used for the determination of the activation energy of glass transition and crystallization. Thermal stability parameters have revealed high stability of the glass prepared with 40 mol% of Bi2O3 content. The crystallization kinetics for the glasses was studied by using the Kissinger and modified Ozawa equations. Appearance of a sharp cut-off and a wide and reasonable transmission in VIS-NIR region makes these glasses suitable for IR transmission window. The cut-off wavelength, optical band gap and Urbach's energy have been analyzed and discussed in terms of changes in the glass structure. By analyzing the impedance spectra, the ac and dc conductivities, activation energy for dc conduction (Edc) and for relaxation (EM″) were calculated. The results obtained from dc conductivity confirm the network forming role of Cd2+ ion in the glasses. The scaling of the conductivity spectra has been used to interpret the temperature dependence of the relaxation dynamics. The observed conductivity spectra follows power law with exponent 's' which decreases with temperature and satisfies the correlated barrier hopping (CBH) model. The perfect overlying of normalized plots of electrical modulus on a single 'master curve' depicts temperature as well as

  8. High temperature mechanical behaviour of glass-ceramics in the YSiAlON and ErSiAlON systems

    Bondanini, A.; Massouras, G.; Besson, J.L. [ENSCI, Limoges (France). SPCTS

    2002-07-01

    The high temperature mechanical behaviour of oxynitride glass-ceramics in the YSiAlON and ErSiAlON systems was studied in the 950-1150 C temperature range under compressive stresses ranging from 20 to 100 MPa. The parent glass had a composition of 35 Y(or Er)-45 Si-20 Al-83 O-17 N in equivalent percent. Starting from these glasses, glass-ceramics were prepared using a two stage heat treatment: nucleation at the optimum nucleation temperature followed by crystal growth at 1050, 1150 or 1250 C. The two parent glasses had similar viscosities, with that of the Er-glass being slightly less than that of the Y-glass. After the devitrification treatment at 1050 C, B-phase (M{sub 2}SiAlO{sub 5}N) was the only crystalline phase formed in both systems. The creep behaviour was similar for the yttrium and the erbium materials. It was characterised by a long transient stage, due to the viscoelastic response of the residual glass, with recovered strain after unloading decreasing as loading time increased. The creep resistance was compared to that of the parent glasses in terms of apparent viscosity. The crystallisation of 75% of the glass resulted in an increase in viscosity such that a temperature some 100 C higher showed the same viscosity value. After heat treatment at 1150 C, the phase assemblage in the yttrium material changed with the formation of wollastonite and partial conversion of B-phase into Iw-phase. The apparent viscosity was 2 orders of magnitude higher than that of the samples heat treated at 1050 C and no strain recovery was observed upon unloading. In contrast, the erbium materials retained the same microstructure as after the heat treatment at 1050{sup b}C and there was no difference in the creep behaviour of the samples heat treated at 1050 or 1150 C. After a crystallisation treatment at 1250 C of the yttrium parent glass, the glass-ceramic consisted of yttrium aluminium garnet, N-apatite and {beta}-Y{sub 2}Si{sub 2}O{sub 7} and showed excellent creep

  9. The Effect of Temperature and Nanoclay on the Low Velocity and Ballistic Behavior of Woven Glass-Fiber Reinforced Composites

    Patrin, Lauren

    The objective of this research was to study the effect of nanoclay and temperature on the behavior of woven glass-fabric reinforced epoxy composite under low velocity and ballistic impacts. The materials used in manufacturing the composite were S2 (6181) glass-fibers, epoxy resin (EPON 828), hardener (Epikure 3230), nanoclay and Heloxy 61 modifier. The nanoclay addition was 0%, 1%, 3% and 5% by weight, with respect to the resin. All specimens were manufactured at the City College facilities using vacuum infusion. Tensile tests were conducted to characterize the material and obtain the Young's modulus, ultimate stress, failure strain, Poisson's ratio, shear modulus and shear strength and their variation with nanoclay percentage and temperature. The tests were conducted at room temperature (21°C/70°F), -54°C (-65°F), -20°C (-4°F), 49°C (120°F) and 71°C (160°F). Next composite specimens with 0%, 1%, 3% and 5% nanoclay by weight, with respect to the resin, were subjected to low velocity impact at the previously specified temperatures to determine dynamic force, displacement and energy correlations. The extent of damage was studied using the ultrasound technique. Then ballistic tests were conducted on the nanoclay infused specimens at room temperature to obtain the ballistic limit (V50) and the damage behavior of the composite. The dynamic finite element analysis (FEA) software LS-DYNA was used to model and simulate the results of low velocity impact tests. Good agreement was obtained between experimental and numerical (FEA) results. Analytical analyses were undertaken to compare the results from the tensile experiments. The finite element analysis (FEA) allowed for further analytical comparison of the results. The FEA platform used was LS-DYNA due to its proficient dynamic and damage capabilities in composite materials. The FEA was used to model and simulate the low velocity impacts and compare the results to experiments.

  10. An evaluation of the use of modulated temperature DSC as a means of assessing the relaxation behaviour of amorphous lactose.

    Craig, D Q; Barsnes, M; Royall, P G; Kett, V L

    2000-06-01

    To evaluate the use of Modulated Temperature DSC (MTDSC) as a means of assessing the relaxation behaviour of amorphous lactose via measurement of the heat capacity, glass transition (Tg) and relaxation endotherm. Samples of amorphous lactose were prepared by freeze drying. MTDSC was conducted using a TA Instruments 2920 MDSC using a heating rate of 2 degrees C/minute, a modulation amplitude of +/-0.3 degrees C and a period of 60 seconds. Samples were cycled by heating to 140 degrees C and cooling to a range of annealing temperatures between 80 degrees C and 100 degrees C, followed by reheating through the Tg region. Systems were then recooled to allow for correction of the Tg shift effect. MTDSC enabled separation of the glass transition from the relaxation endotherm, thereby facilitating calculation of the relaxation time as a function of temperature. The relative merits of using MTDSC for the assessment of relaxation processes are discussed. In addition, the use of the fictive temperature rather than the experimentally derived Tg is outlined. MTDSC allows assessment of the glass transition temperature, the magnitude of the relaxation endotherm and the value of the heat capacity, thus facilitating calculation of relaxation times. Limitations identified with the approach include the slow scanning speed, the need for careful choice of experimental parameters and the Tg shift effect.

  11. Electrical switching in Sb doped Al23Te77 glasses

    Pumlianmunga; Ramesh, K.

    2017-08-01

    Bulk glasses (Al23Te77)Sbx (0≤ x≤10) prepared by melt quenching method show a change in switching type from threshold to memory for x≥5. An increase in threshold current (Ith) and a concomitant decrease in threshold voltage (Vth) and resisitivity(ρ) have been observed with the increase of Sb content. Raman spectra of the switched region in memory switching compositions show a red shift with respect to the as prepared glasses whereas in threshold switching compositions no such shift is observed. The magic angle spinning nuclear magnetic resonance (MAS NMR) of 27Al atom shows three different environments for Al ([4]Al, [5]Al and [6]Al). The samples annealed at their respective crystallization temperatures show rapid increase in [4]Al sites by annihilating [5]Al sites. The melts of threshold switching glasses (x≤2.5) quenched in water at room temperature (27 °C) show amorphous structure whereas, the melt of memory switching glasses (x>2.5) solidify into crystalline structure. The higher coordination of Al increases the cross-linking and rigidity. The addition of Sb increases the glass transition(Tg) and decreases the crystallization temperature(Tc). The decrease in the interval between the Tg and Tc eases the transition between the amorphous and crystalline states and improves the memory properties. The temperature rise at the time of switching can be as high as its melting temperature and the material in between the electrodes may melt to form a filament. The filament may consists of temporary (high resistive amorphous) and permanent (high conducting crystalline) units. The ratio between the temporary and the permanent units may decide the switching type. The filament is dominated by the permanent units in memory switching compositions and by the temporary units in threshold switching compositions. The present study suggests that both the threshold and memory switching can be understood by the thermal model and filament formation.

  12. On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

    Muniz, R. F., E-mail: robsonfmuniz@yahoo.com.br [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Ligny, D. de [Department of Materials Science, Glass and Ceramics, University of Erlangen Nürnberg, Martensstr. 5, 91058 Erlangen (Germany); Le Floch, S.; Martinet, C.; Guyot, Y. [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Rohling, J. H.; Medina, A. N.; Sandrini, M.; Baesso, M. L. [Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Andrade, L. H. C.; Lima, S. M. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul, C.P. 351, Dourados, MS (Brazil)

    2016-06-28

    From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca{sub 3}Mg(SiO{sub 4}){sub 2}] and diopside [CaMgSi{sub 2}O{sub 6}]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f{sup 6}5d{sup 1} → 4f{sup 7} transition of Eu{sup 2+} was studied in both host systems. Additionally, the {sup 5}D{sub 0} → {sup 7}F{sub J} transition of Eu{sup 3+} was used as an environment probe in the pristine glass and the glass-ceramic.

  13. Relationship of Cure Temperature to Mechanical, Physical, and Dielectric Performance of PDMS Glass Composite for Electric Motor Insulation

    Miller, Sandi G.; Becker, Kathleen; Williams, Tiffany S.; Scheiman, Daniel A.; McCorkle, Linda S.; Heimann, Paula J.; Ring, Andrew; Woodworth, Andrew

    2017-01-01

    Achieving NASAs aggressive fuel burn and emission reduction for N-plus-3 aircraft will require hybrid electric propulsion system in which electric motors driven by either power generated from turbine or energy storage system will power the fan for propulsion. Motors designed for hybrid electric aircraft are expected to operate at medium to high voltages over long durations in a high altitude service environment. Such conditions have driven research toward the development of wire insulation with improved mechanical strength, thermal stability and increased breakdown voltage. The silicone class of materials has been considered for electric wire insulation due to its inherent thermal stability, dielectric strength and mechanical integrity. This paper evaluates the dependence of these properties on the cure conditions of a polydimethyl-siloxane (PDMS) elastomer; where both cure temperature and base-to-catalyst ratio were varied. The PDMS elastomer was evaluated as a bulk material and an impregnation matrix within a lightweight glass veil support. The E-glass support was selected for mechanical stiffness and dielectric strength. This work has shown a correlation between cure conditions and material physical properties. Tensile strength increased with cure temperature whereas breakdown voltage tended to be independent of process variations. The results will be used to direct material formulation based on specific insulation requirements.

  14. Effect of temperature and pressure on non-linear conduction in GeTeSe chalcogenide glass

    El-Mansy, M.K.

    1998-01-01

    The I-V characteristic curves were studied in the temperature range 301-359 K and pressure range up to 7.15 x 10 9 Pa which illustrate a non-linear behaviour below (high-resistance region) and beyond (negative-resistance region) a breakdown point characterising Ge 27 Te 62 Se 11 chalcogenide glasses. The general behaviour is shifted towards lower voltage and higher current when the ambient temperature and/or the applied pressure were increased. The non-linear behaviour in the pre breakdown region is discussed according to the Poole-Frenkel field emission of electrons from deep traps located at a depth equal to 0.372eV. The analysis of the effect of field on the non-linear conduction in Ge 27 Te 62 Se 11 chalcogenide glass suggests a modification of the energy difference between filled and empty sites, where the effect of pressure suggests a reduction of the energy gap width. The analysis based on simple thermal effects in the region closer to the breakdown point implies the electrothermal process initiating the negative resistance region. The results of post breakdown region (negative-resistance region) imply the electron hopping between filled and empty localised states at Fermi level. The density of localised states is estimated which lies in the range 5.7 x 10 16 -1.84 x 10 18 cm -3 /eV

  15. In situ electron beam irradiated rapid growth of bismuth nanoparticles in bismuth-based glass dielectrics at room temperature

    Singh, Shiv Prakash; Karmakar, Basudeb

    2011-01-01

    In this study, in situ control growth of bismuth nanoparticles (Bi 0 NPs) was demonstrated in bismuth-based glass dielectrics under an electron beam (EB) irradiation at room temperature. The effects of EB irradiation were investigated in situ using transmission electron microscopy (TEM), selected-area electron diffraction and high-resolution transmission electron microscopy. The EB irradiation for 2–8 min enhanced the construction of bismuth nanoparticles with a rhombohedral structure and diameter of 4–9 nm. The average particle size was found to increase with the irradiation time. Bismuth metal has a melting point of 271 °C and this low melting temperature makes easy the progress of energy induced structural changes during in situ TEM observations. This is a very useful technique in nano-patterning for integrated optics and other applications.

  16. Observation of room temperature ferromagnetism in ZnTe:Cr films grown onto glass substrate by thermal evaporation method

    Soundararajan, D; Mangalaraj, D; Nataraj, D [Thin Film Laboratory, Department of Physics, Bharathiar University, Coimbatore -641 046 (India); Dorosinskii, L [National Institute of Metrology (TUBITAK -UME), P.K. 54, 41470, Gebze -Kocaeli (Turkey); Santoyo-Salazar, J, E-mail: dorosins@ume.tubitak.gov.t [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, Mexico D.F. 04510 (Mexico)

    2009-03-01

    ZnTe and ZnTe:Cr films were prepared onto glass substrates using thermal evaporation method. Structural properties of the prepared samples were analyzed using X-ray diffractometer, and the presence of ZnCrTe phase was identified along with poor crystallinity. Composition analysis was done using XPS and the Cr content in the film was found to be 0.05 atomic percent. Transmittance spectra were recorded using UV-Vis spectrophotometer. The valence state of Cr in ZnTe:Cr film is determined to be +2 using electron spin resonance (ESR) spectroscopy. Magnetic moment data as a function of magnetic field were recorded using Superconducting Quantum Interference Device (SQUID) magnetometer at temperatures 5, 77 and 300 K. The results showed minority ferromagnetic behavior even at room temperature. Magnetic domains were observed using Magnetic Force Microscopy and the average value of domain size is 3.7 nm.

  17. Effect of composition and temperature on viscosity and electrical conductivity of borosilicate glasses for Hanford nuclear waste immobilization

    Hrma, P.; Piepel, G.F.; Smith, D.E.; Redgate, P.E.; Schweiger, M.J.

    1993-04-01

    Viscosity and electrical conductivity of 79 simulated borosilicate glasses in the expected range of compositions to be produced in the Hanford Waste Vitrification Plant were measured within the temperature span from 950 to 1250 degree C. The nine major oxide components were SiO 2 , B 2 O 3 , Li 2 O, Na 2 O, CaO, MgO, Fe 2 O 3 , Al 2 O 3 , and ZrO 2 . The test compositions were generated statistically. The data were fitted by Fulcher and Arrhenius equations with temperature coefficients being multilinear functions of the mass fractions of the oxide components. Mixture models were also developed for the natural logarithm of viscosity and that of electrical conductivity at 1150 degree C. Least squares regression was used to obtain component coefficients for all the models

  18. Temperature dependence of charge-transfer fluorescence from extended and U-shaped donor-bridge-acceptor systems in glass-forming solvents.

    Goes, M.; de Groot, M.; Koeberg, M.; Verhoeven, J.W.; Lokan, N.R.; Shephard, M.J.; Paddon-Row, M.N.

    2001-01-01

    Abstract: The behavior is reported of three fluorescent D-bridge-A systems that display a fascinating temperature dependence in glass forming solvents over the temperature range between 77 and 293 K. In two of these systems, a rigid, saturated alkane bridge maintains an extended conformation, and as

  19. Reactive Uptake of Sulfur Dioxide and Ozone on Volcanic Glass and Ash at Ambient Temperature

    Maters, Elena C.; Delmelle, Pierre; Rossi, Michel J.; Ayris, Paul M.

    2017-09-01

    The atmospheric impacts of volcanic ash from explosive eruptions are rarely considered alongside those of volcanogenic gases/aerosols. While airborne particles provide solid surfaces for chemical reactions with trace gases in the atmosphere, the reactivity of airborne ash has seldom been investigated. Here we determine the total uptake capacity (NiM) and initial uptake coefficient (γM) for sulfur dioxide (SO2) and ozone (O3) on a compositional array of volcanic ash and glass powders at 25°C in a Knudsen flow reactor. The measured ranges of NiSO2 and γSO2 (1011-1013 molecules cm-2 and 10-3-10-2) and NiO3 and γO3 (1012-1013 molecules cm-2 and 10-3-10-2) are comparable to values reported for mineral dust. Differences in ash and glass reactivity toward SO2 and O3 may relate to varying abundances of, respectively, basic and reducing sites on these materials. The typically lower SO2 and O3 uptake on ash compared to glass likely results from prior exposure of ash surfaces to acidic and oxidizing conditions within the volcanic eruption plume/cloud. While sequential uptake experiments overall suggest that these gases do not compete for reactive surface sites, SO2 uptake forming adsorbed S(IV) species may enhance the capacity for subsequent O3 uptake via redox reaction forming adsorbed S(VI) species. Our findings imply that ash emissions may represent a hitherto neglected sink for atmospheric SO2 and O3.

  20. Rare earth ion controlled crystallization of mica glass-ceramics

    Garai, Mrinmoy; Karmakar, Basudeb

    2016-01-01

    In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO_2, Nd_2O_3, Sm_2O_3 and Gd_2O_3 doped K_2O−MgO−B_2O_3−Al_2O_3−SiO_2−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm"−"3) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T_g) and crystallization temperature (T_c). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg_3(AlSi_3O_1_0)F_2 by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10"−"6/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque fluorophlogopite mica glass-ceramics by single-step heat treatment. • Nanocrystalline glass

  1. Greenhouse effect: temperature of a metal sphere surrounded by a glass shell and heated by sunlight

    Nguyen, Phuc H; Matzner, Richard A

    2012-01-01

    We study the greenhouse effect on a model satellite consisting of a tungsten sphere surrounded by a thin spherical, concentric glass shell, with a small gap between the sphere and the shell. The system sits in vacuum and is heated by sunlight incident along the z-axis. This development is a generalization of the simple treatment of the greenhouse effect given by Kittel and Kroemer (1980 Thermal Physics (San Francisco: Freeman)) and can serve as a very simple model demonstrating the much more complex Earth greenhouse effect. Solution of the model problem provides an excellent pedagogical tool at the Junior/Senior undergraduate level.

  2. Enhancement of room-temperature plasticity in a bulk metallic glass by finely dispersed porosity

    Wada, Takeshi; Inoue, Akihisa; Greer, Alan Lindsay

    2005-01-01

    Melts of Pd 42.5 Cu 30 Ni 7.5 P 20 (at. %) held under pressurized hydrogen are cast into bulk metallic glass (BMG) rods with fine (20-30 μm diameter) pores uniformly dispersed. The low overall porosities ( -3 , compared to 16 MJ m -3 for the pore-free BMG. The pores force the proliferation of shear bands below the overall failure stress, a process of interest for toughening BMGs, materials for which shear localization in deformation restricts structural applications

  3. Vanishing Hall conductance in the phase-glass Bose metal at zero temperature

    May-Mann, Julian; Phillips, Philip W.

    2018-01-01

    Motivated in part by numerical simulations [H. G. Katzgraber and A. P. Young, Phys. Rev. B 66, 224507 (2002), 10.1103/PhysRevB.66.224507; J. M. Kosterlitz and N. Akino, Phys. Rev. Lett. 81, 4672 (1998), 10.1103/PhysRevLett.81.4672; Phys. Rev. Lett. 81, 4672 (1998), 10.1103/PhysRevLett.81.4672] that reveal that the energy to create a defect in a gauge or phase glass scales as Lθ with θ power law as does the longitudinal conductance. This prediction can be verified experimentally by applying a ground plane to the 2D samples.

  4. Characterization of the hidden glass transition of amorphous cyclomaltoheptaose.

    Tabary, Nicolas; Mahieu, Aurélien; Willart, Jean-François; Dudognon, Emeline; Danède, Florence; Descamps, Marc; Bacquet, Maryse; Martel, Bernard

    2011-10-18

    An amorphous solid of cyclomaltoheptaose (β-cyclodextrin, β-CD) was formed by milling its crystalline form using a high-energy planetary mill at room temperature. The glass transition of this amorphous solid was found to occur above the thermal degradation point of the material preventing its direct observation and thus its full characterization. The corresponding glass transition temperature (T(g)) and the ΔC(p) at T(g) have, however, been estimated by extrapolation of T(g) and ΔC(p) of closely related amorphous compounds. These compounds include methylated β-CD with different degrees of substitution and molecular alloys obtained by co-milling β-CD and methylated β-CD (DS 1.8) at different ratios. The physical characterization of the amorphous states have been performed by powder X-ray diffraction and differential scanning calorimetry, while the chemical integrity of β-CD upon milling was checked by NMR spectroscopy and mass spectrometry. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Calorimetric evidence for two distinct molecular packing arrangements in stable glasses of indomethacin.

    Kearns, Kenneth L; Swallen, Stephen F; Ediger, M D; Sun, Ye; Yu, Lian

    2009-02-12

    Indomethacin glasses of varying stabilities were prepared by physical vapor deposition onto substrates at 265 K. Enthalpy relaxation and the mobility onset temperature were assessed with differential scanning calorimetry (DSC). Quasi-isothermal temperature-modulated DSC was used to measure the reversing heat capacity during annealing above the glass transition temperature Tg. At deposition rates near 8 A/s, scanning DSC shows two enthalpy relaxation peaks and quasi-isothermal DSC shows a two-step change in the reversing heat capacity. We attribute these features to two distinct local packing structures in the vapor-deposited glass, and this interpretation is supported by the strong correlation between the two calorimetric signatures of the glass to liquid transformation. At lower deposition rates, a larger fraction of the sample is prepared in the more stable local packing. The transformation of the vapor-deposited glasses into the supercooled liquid above Tg is exceedingly slow, as much as 4500 times slower than the structural relaxation time of the liquid.

  6. High temperature spin-glass-like transition in La0.67Sr0.33MnO3 nanofibers near the Curie point.

    Lu, Ruie; Yang, Sen; Li, Yitong; Chen, Kaiyun; Jiang, Yun; Fu, Bi; Zhang, Yin; Zhou, Chao; Xu, Minwei; Zhou, Xuan

    2017-06-28

    The glassy transition of superparamagnetic (SPM) (r glass-like (SGL) behavior near the Curie point (T C ), i.e., T 0 = 330 K, in La 0.67 Sr 0.33 MnO 3 (LSMO) nanofibers (NFs) composed of nanoparticles beyond the SPM size (r ≫ r 0 ), resulting in a significant increase of the glass transition temperature. This SGL transition near the T C of bulk LSMO can be explained to be the scenario of locally ordered clusters embedded in a disordered host, in which the assembly of nanoparticles has a magnetic core-shell model driven by surface spin glass. The presence of a surface spin glass of nanoparticles was proved by the Almeida-Thouless line δT f ∝ H 2/3 , exchange bias, and reduced saturation magnetization of the NF system. Composite dynamics were found - that is, both the SPM and the super-spin-glass (SSG) behavior are found in such an NF system. The bifurcation of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization vs. temperature curves at the ZFC peak, and the flatness of FC magnetization involve SSG, while the frequency-dependent ac susceptibility anomaly follows the Vogel-Fulcher law that implies weak dipole interactions of the SPM model. This finding can help us to find a way to search for high temperature spin glass materials.

  7. The Effects of Oxygen Partial Pressure on Liquidus Temperature of a High-Level Waste Glass with Spinel as the Primary Phase

    Izak, Pavel; Hrma, Pavel R.; Wilson, Benjamin K.; Vienna, John D.

    2000-01-01

    The redox state of iron affects spinal crystallization in vitrified high-level waste (HLW) glass. Simulated HLW glass with spinel as the primary crystalline phase field was heat treated at constant temperatures within the interval from 850 C to 1300 C under varying atmospheres with oxygen partial pressure, Po2, ranging from 1x10-16 kPa (pure CO) to 101 kPa (pure O2). Liquidus temperature (TL) of glass increased with decreasing Po2 up to Po2 > 3 x 10-9 kPa. At Po2 < 3 x 10-9 kPa, Ni-Fe alloy precipitated from the glass, and TL decreased. Samples were analyzed with optical microscope and scanning electron microscope. The mass fraction of spinel in glass was determined using quantitative X-ray diffraction. Spinel composition was investigated with energy disperse spectroscopy. Ferrous-ferric equilibrium at TL was calculated in a HLW glass as a function of temperature and Po2, based on the previous studies by Schreiber. TL/FeO over the interval 0.0063 < gFeO < 0.051 (1x10-2 kPa < Po2 < 3x10-9 kPa) was estimated from calculated ferrous-ferric equilibrium at TL as 1835 C

  8. Temperature dependence of luminescence from silica glasses under in-reactor and 60Co gamma-ray irradiation

    Takahara, Shogo; Yoshida, Tomoko; Tanabe, Tetuo; , Tatuya, Ii; Hirano, Masahiro; Okada, Moritami

    2004-06-01

    In order to investigate the temperature effects on the dynamic radiation damaging process, we have carried out in situ measurements of in-reactor luminescence (IRL) and gamma-ray induced luminescence (GIL) of a silica glass at temperatures ranging from 70 K to 370 K. Both luminescence spectra were found to consist of two broad emission centers at 3.1 eV and 4.1 eV with an additional temperature independent emission around 2.5 eV. The 2.5 eV emission different from the other two showed long tail to the lower energy side and was attributed to the Cherenkov radiation. The 3.1 eV band was attributed to a B 2 β oxygen deficient center on the basis of our photoluminescence measurement. The intensity of the 3.1 eV IRL increased with increasing temperature up to ca. 200 K and saturated above 200 K, which is clearly different from the reported temperature dependence of 3.1 eV photoluminescence, suggesting the existence of some different relaxation mechanism of excited electron under ionizing radiations.

  9. Relationship between low-temperature boson heat capacity peak and high-temperature shear modulus relaxation in a metallic glass

    Vasiliev, A. N.; Voloshok, T. N.; Granato, A. V.; Joncich, D. M.; Mitrofanov, Yu. P.; Khonik, V. A.

    2009-01-01

    Low-temperature (2 K≤T≤350 K) heat capacity and room-temperature shear modulus measurements (ν=1.4 MHz) have been performed on bulk Pd 41.25 Cu 41.25 P 17.5 in the initial glassy, relaxed glassy, and crystallized states. It has been found that the height of the low-temperature Boson heat capacity peak strongly correlates with the changes in the shear modulus upon high-temperature annealing. It is this behavior that was earlier predicted by the interstitialcy theory, according to which dumbbell interstitialcy defects are responsible for a number of thermodynamic and kinetic properties of crystalline, (supercooled) liquid, and solid glassy states.

  10. Glass transition behavior of octyl β-D-glucoside and octyl β-D-thioglucoside/water binary mixtures.

    Ogawa, Shigesaburo; Asakura, Kouichi; Osanai, Shuichi

    2010-11-22

    The lyotropic behavior and glass-forming properties of octyl β-D-glucoside (C8Glu) and octyl β-D-thioglucoside (C8SGlu)/water binary mixtures were evaluated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The results clearly indicate that the mixture forms a glass in the supercooling state of liquid crystalline phases such as cubic, lamellar, and smectic. The glass transition temperature (T(g)) of the mixture was strongly dependent on solute concentration, with a higher concentration correlating with a higher T(g). The experimental T(g) was consistent with the predicted value calculated using the Couchman-Karasz equation in both the C8Glu and C8SGlu/water mixtures. The change of heat capacity at T(g) showed the two bending points under variation of concentrations. And the highest temperature of phase transition from lamellar to isotropic solution was observed at around 50% molar concentration. It was expected that non-percolated state of water existed in extremely higher concentration ranges. Copyright © 2010 Elsevier Ltd. All rights reserved.

  11. Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica.

    Leenakul, Wilaiwan; Tunkasiri, Tawee; Tongsiri, Natee; Pengpat, Kamonpan; Ruangsuriya, Jetsada

    2016-04-01

    45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts--the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300 °C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050 °C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650 °C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050 °C, with a high density of 2.27 g/cm(3), 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7 days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Optical and spectroscopic study of erbium doped calcium borotellurite glasses

    Gomes, J. F.; Lima, A. M. O.; Sandrini, M.; Medina, A. N.; Steimacher, A.; Pedrochi, F.; Barboza, M. J.

    2017-04-01

    In this study, 10CaF2 - (29.9-0.4x)CaO - (60-0.6x)B2O3 - xTeO2 - 0,1Er2O3 (x = 10, 16, 22, 30 and 50 mol %) glasses were synthesized, and their optical and spectroscopic properties were investigated. X-ray diffraction, density, glass transition temperature (Tg), crystallization temperature (Tx), refraction index, luminescence, radiative lifetime and optical absorption measurements were carried out. Molar volume (Vm), thermal stability (Tx-Tg), electronic polarizability (αm), optical bang gap energy (Eg) and Judd-Ofelt (JO) parameters Ωt (2,4,6) were also calculated. The results are discussed in terms of tellurium oxide content. The increase of TeO2 in the glasses composition increases density, refractive index and electronic polarizability. The optical band gap energy decreases varying from 3.37 to 2.71 eV for the glasses with 10 and 50 mol% of TeO2, respectively. The optical absorption coefficient spectra show characteristic bands of Er3+ ions. Furthermore, these spectra in NIR region show a decrease of hydroxyl groups as a function of TeO2 addition. Luminescence intensity and radiative lifetimes at 1530 nm show an increasing with the TeO2 content. The JO parameters of Er:CaBTeX glasses follow the trend Ω2 > Ω4 > Ω6 and the quality factor values (Ω4/Ω6) were between 1.37 and 3.07. By comparing the measured lifetime with the calculated radiative decay time, quantum efficiency was calculated. The luminescence emission intensity at 1530 nm decreases with the increase of temperature. The lifetime values show a slight trend to decrease with the temperature increase, from 300 to 420 K, for all the samples.

  13. TOPEM, a new temperature modulated DSC technique - Application to the glass transition of polymers

    Fraga Rivas, Iria; Montserrat Ribas, Salvador; Hutchinson, John M.

    2007-01-01

    TOPEM is a new temperature modulated DSC technique, introduced by Mettler-Toledo in late 2005, in which stochastic temperature modulations are superimposed on the underlying rate of a conventional DSC scan. These modulations consist of temperature pulses, of fixed magnitude and alternating sign, with random durations within limits specified by the user. The resulting heat flow signal is analysed by a parameter estimation method which yields a so-called ‘quasi-static’ specific heat capac...

  14. Predicting glass-to-glass and liquid-to-liquid phase transitions in supercooled water using classical nucleation theory

    Tournier, Robert F.

    2018-01-01

    Glass-to-glass and liquid-to-liquid phase transitions are observed in bulk and confined water, with or without applied pressure. They result from the competition of two liquid phases separated by an enthalpy difference depending on temperature. The classical nucleation equation of these phases is completed by this quantity existing at all temperatures, a pressure contribution, and an enthalpy excess. This equation leads to two homogeneous nucleation temperatures in each liquid phase; the first one (Tn- below Tm) being the formation temperature of an "ordered" liquid phase and the second one corresponding to the overheating temperature (Tn+ above Tm). Thermodynamic properties, double glass transition temperatures, sharp enthalpy and volume changes are predicted in agreement with experimental results. The first-order transition line at TLL = 0.833 × Tm between fragile and strong liquids joins two critical points. Glass phase above Tg becomes "ordered" liquid phase disappearing at TLL at low pressure and at Tn+ = 1.302 × Tm at high pressure.

  15. Fibre Tip Sensors for Localised Temperature Sensing Based on Rare Earth-Doped Glass Coatings

    Erik P. Schartner

    2014-11-01

    Full Text Available We report the development of a point temperature sensor, based on monitoring upconversion emission from erbium:ytterbium-doped tellurite coatings on the tips of optical fibres. The dip coating technique allows multiple sensors to be fabricated simultaneously, while confining the temperature-sensitive region to a localised region on the end-face of the fibre. The strong response of the rare earth ions to changing temperature allows a resolution of 0.1–0.3 °C to be recorded over the biologically relevant range of temperatures from 23–39 °C.

  16. Pressure and Temperature Studies of Glass Properties Related to Vibrational Spectra.

    1974-12-01

    Press, New York, 61 (1972). (61 G.K. White, Cryogenics 4, 2, (1964). (71 A. Dietzel and H.A. Sheybany, Verres et Refractaires 2, 63 (1948); Ceramic...Go 0 0 0 0 C64 44 CL a 1-4 k %% 4. OD 4 v. .0 0 0 04 6 r4 vI 1. 4 .- 4v- - 0) 60 en %D %. . I 4 0 n Nt 40 4 0ý Wa Lo 4A Le Nn LO %a 4o 4 0. ൴ ;1I c...M.I1. MANGHNANI TA• LE I. comn•i~sltIIm of Na2O-810O glasnse. TABLE U. Sodium silicate glasses. Observed infrared absorp-tions at ambient pressure (cMa

  17. Synthesis of styrene/isoprene/butadiene integrated rubber with wide glass transition temperature by reactive extrusion

    Huang, Tianhua; Zheng, Anna; Zhan, Pengfei; Shi, Han; Li, Xiang; Guan, Yong; Wei, Dafu

    2018-05-01

    In this work, styrene/isoprene/butadiene integrated rubber (SIBR) was synthesized with n-butyllithium as the initiator and tetrahydrofuran as structure modifier in a co-rotating intermeshing twin-screw extruder. The content of diene in these terpolymers reached a surprising 70 wt% by feeding the monomers in two different sites of the twin-screw extruder. 1H-NMR, GPC and TEM results showed that the molecular structures of terpolymers changed with the variation of feeding site. Dynamic mechanical analysis of the vulcanized SIBR showed that the terpolymer had a wide glass transition region, which assured an excellent combination of high antiskid properties and low rolling resistance. Different from traditional solution polymerization, the present work provides a green approach to prepare the SIBR via bulk polymerization without solvent.

  18. Relationships between individual behaviour and morphometry under different experimental conditions of temperature and feeding in glass eels (Anguilla anguilla

    A. Bardonnet

    2008-01-01

    Full Text Available After Anguilla anguilla larvae reach the European coast, metamorphosing glass eels exhibit an estuarine migration phase and can potentially colonize the continental area. Associated behaviours to upstream movement in estuary and river basin differ strongly: passive tidal transport in estuary, active swimming beyond the upstream tidal limit. Moreover, the migratory behaviour may shift towards a density-dependent dispersal beyond this limit. A positive relationship has previously been established between glass eels’ body condition and migratory behaviour in estuary and also higher in the river basin. An experiment was settled to test for the density-dependent versus migratory behaviour under controlled conditions. The relationships between some behaviours (swimming, grouping, feeding, and aggressiveness and body condition was investigated at the individual level. Two controlled factors were crossed, leading to four combinations of high and low levels of food and temperature. The high level of food led to a lesser loss in body condition. Swimming activity was positively related to initial body condition and loss in body condition, but these two variables were not related to aggressiveness. We conclude that the density-dependent dispersal hypothesis was not reinforced by these present results.

  19. Relationships between individual behaviour and morphometry under different experimental conditions of temperature and feeding in glass eels (Anguilla anguilla

    Bardonnet A.

    2009-02-01

    Full Text Available After Anguilla anguilla larvae reach the European coast, metamorphosing glass eels exhibit an estuarine migration phase and can potentially colonize the continental area. Associated behaviours to upstream movement in estuary and river basin differ strongly: passive tidal transport in estuary, active swimming beyond the upstream tidal limit. Moreover, the migratory behaviour may shift towards a density-dependent dispersal beyond this limit. A positive relationship has previously been established between glass eels’ body condition and migratory behaviour in estuary and also higher in the river basin. An experiment was settled to test for the density-dependent versus migratory behaviour under controlled conditions. The relationships between some behaviours (swimming, grouping, feeding, and aggressiveness and body condition was investigated at the individual level. Two controlled factors were crossed, leading to four combinations of high and low levels of food and temperature. The high level of food led to a lesser loss in body condition. Swimming activity was positively related to initial body condition and loss in body condition, but these two variables were not related to aggressiveness. We conclude that the density-dependent dispersal hypothesis was not reinforced by these present results.

  20. Comparative study by TG and DSC Of membranes polyamide66/bentonite clay nanocomposite; Estudo comparativo por TG e DSC de membranas de nanocompositos poliamida66/argila bentonitica

    Medeiros, K.M. de; Kojuch, L R; Araujo, E M; Lira, H.L., E-mail: keilamm@ig.com.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais; Lima, F [Universidade Estadual da Paraiba (UEPB), Campina Grande, PB (Brazil). Dept. de Quimica

    2010-07-01

    In this study, it was obtained membranes of nanocomposites polyamide66 with 3 and 5% bentonite clay consists of silicates in layers from the interior of Paraiba. The clay was treated with a quaternary ammonium salt in order to make it organophilic. The membranes were prepared by phase inversion technique from the nanocomposites in solution. The clays were characterized by X-ray diffraction (XRD) and thermogravimetry (TG). Also the membranes were characterized by differential scanning calorimetry (DSC) and TG. The XRD and TG confirmed the presence of salt in the clay and thermal stability of the treated clay. For DSC, it was observed that there was no change in melting temperature of the membranes of nanocomposites compared to membrane pure polyamide66. By TG, it was found that the decomposition of the membranes of polyamide66 with treated clay were higher compared with the untreated clay. (author)

  1. Relaxations in spin glasses: Similarities and differences from ordinary glasses

    Ngai, K.L.; Rajagopal, A.K.; Huang, C.Y.

    1984-01-01

    Relaxation phenomena have become a major concern in the physics of spin glasses. There are certain resemblances of these relaxation properties to those of ordinary glasses. In this work, we compare the relaxation properties of spin glasses near the freezing temperature with those of glasses near the glass transition temperature. There are similarities between the two types of glasses. Moreover, the relaxation properties of many glasses and spin glasses are in conformity with two coupled ''universality'' relations predicted by a recent model of relaxations in condensed matter

  2. Thermal and optical properties of Tm3+ doped tellurite glasses.

    Ozen, G; Demirata, B; Oveçoğlu, M L; Genç, A

    2001-02-01

    Ultraviolet, visible (UV/VIS) and differential thermal analysis (DTA) measurements were carried out in order to investigate the optical and thermal properties of various 0.5 mol.% Tm2O3 containing (1 - x)TeO2 + xLiCl glasses in molar ratio. The samples were prepared by fusing the mixture of their respective reagent grade powders in a platinum cricuble at 750 degrees C for 30 min. DTA curves taken in the 23-600 degrees C temperature range with a heating rate of 10 degrees C/min reveal a change in the value of the glass transition temperature, Tg, while melting was not observed for the glasses containing LiCl content less than 50 mol.%. These glasses were found to be moisture-resistant. However, the glasses with LiCl content higher than 50 mol.%, in which a melting peak was observed at Tc = 401 degrees C, were moisture-sensitive. Absorption measurements in the UV/VIS region of the glasses without Tm2O3 content show that the Urbach cutoff occurs at about 320 nm and, is relatively independent of the LiCl content. Six absorption bands were observed in the Tm2O3 doped glasses corresponding to the absorption of the 1G4, 3F2, 3F3 and 3F4, 3H5 and 3H4 levels from the 3H6 ground level of Tm3+ ions. The spectra also show that the integrated absorption cross-section of each band depends on the glass composition. Judd-Ofelt theory was used to determine the Judd-Ofelt parameters as well as the radiative transition probabilities for the metastable levels of Tm3+ ions in (0.3)LiCl + (0.7) TeO2: 0.01 Tm2O3 glass which is moisture-resistant.

  3. Optical properties of nanocrystalline potassium lithium niobate in the glass system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5).

    Ahamad, M Niyaz; Varma, K B R

    2009-08-01

    Optically clear glasses of various compositions in the system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5) (2 glasses comprising potassium lithium niobate (K3Li2Nb5O15) microcrystallites on the surface and nanocrystallites within the glass were obtained by controlled heat-treatment of the as-quenched glasses just above the glass transition temperature (T(g)). The optical transmission spectra of these glasses and glass-crystal composites of various compositions were recorded in the 200-2500 nm wavelength range. Various optical parameters such as optical band gap, Urbach energy, refractive index were determined. Second order optical non-linearity was established in the heat-treated samples by employing the Maker-Fringe method.

  4. Influence of sintering temperature on microstructures and energy-storage properties of barium strontium titanate glass-ceramics prepared by sol-gel process

    Zhu, Jia; Zhang, Yong; Song, Xiaozhen; Zhang, Qian; Yang, Dongliang; Chen, Yongzhou [Beijing Key Laboratory of Fine Ceramics, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084 (China)

    2015-12-15

    The sol-gel processing, microstructures, dielectric properties and energy-storage properties of barium strontium titanate glass-ceramics over the sintering temperature range of 1000-1150 C were studied. Through the X-ray diffraction result, it is revealed that the crystallinity increases as the sintering temperature increased from 1000 to 1080 C and has reached a steady-state regime above 1100 C. Scanning electron microscopy images showed that with the increase of sintering temperature, the crystal size increased. Dielectric measurements revealed that the increase in the sintering temperature resulted in a significant increase in the dielectric constant, a strong sharpness of the temperature-dependent dielectric response and a pronounced decrease of the temperature of the dielectric maximum. The correlation between charge spreading behavior and activation energies of crystal and glass was discussed by the employment of the impedance spectroscopy studies. As a result of polarization-electric field hysteresis loops, both the charged and discharged densities increased with increasing sintering temperature. And the maximum value of energy storage efficiency was found to occur at 1130 C. Finally, the dependence of released energy and power densities calculated from the discharged current-time (I-t) curves on the sintering temperature was studied. The relationship between the energy storage properties and microstructure was correlated. Polarization-electric field hysteresis loops for the BST glass-ceramics sintered at different temperatures. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Influence of annealing temperature on the nanostructure TiO2-SnO2 prepared by electron gun method on the glass substrate and the aluminum/glass

    N Beigmohammadi

    2013-09-01

    Full Text Available  TiO2-SnO2 thin films were coated on glass and Al / glass substrates by electron gun method. In coating process, the vacuum was 1.5×10-5 torr. Then, films were annealed at 450, 500 and 550 ˚ C. The crystallographic structure and film morphology were investigated by means of XRD and SEM. The electrical (I-V and optical properties were studied by the two point props system and UV/Vis/NIR spectrophotometer. The results showed the films under 550 ˚ C were crystalline. The thickness and grain size were 350 and 50 nm respectively. The electrical conductivity in the sample with Al / glass substrate under 550 ˚ C was better than the other samples. When temperature increased, the energy gap decreased from 4.05 to 4.03 eV for direct cases.

  6. Annealing effect reversal by water sorption-desorption and heating above the glass transition temperature-comparison of properties.

    Saxena, A; Jean, Y C; Suryanarayanan, R

    2013-08-05

    Our objective is to compare the physical properties of materials obtained from two different methods of annealing reversal, that is, water sorption-desorption (WSD) and heating above glass transition temperature (HAT). Trehalose was annealed by storing at 100 °C for 120 h. The annealing effect was reversed either by WSD or HAT, and the resulting materials were characterized by differential scanning calorimetry (DSC), water sorption studies, and positron annihilation spectroscopy (PAS). While the products obtained by the two methods of annealing reversal appeared to be identical by conventional characterization methods, they exhibited pronounced differences in their water sorption behavior. Positron annihilation spectroscopy (PAS), by measuring the fractional free volume changes in the processed samples, provided a mechanistic explanation for the differences in the observed behavior.

  7. Advanced temperature measurement system for the US glass industry melt tanks and delivery system. Phase 1 [final] report

    NONE

    1997-04-01

    Improved temperature measurement in the melting and delivery systems of the glass making process will aid in energy conservation. The ``Needs Analysis`` survey found the greatest problem was the inability to identify in situ decalibration (drift). Phase I objectives are: a more rugged reliable sensor; high quality inner protective sheath; improved data transmission hardened to the melt tank environs; a system that reduces or eliminates drift; and an improved outer protection sheath. Results show that 4 of the 5 problem areas have been resolved; with the help of the Univ. of Missouri-Rolla`s materials group, the fifth may be solvable. The major identified problem, the inability to identify in-situ drift has been solved.

  8. Alloying effect on the room temperature creep characteristics of a Ti-Zr-Be bulk metallic glass

    Gong, Pan; Wang, Sibo; Li, Fangwei; Wang, Xinyun

    2018-02-01

    The effect of alloying elements (e.g. Fe, Al, and Ni) on the room temperature creep behavior of a lightweight Ti41Zr25Be34 bulk metallic glass (BMG) was investigated via nanoindentation tests. The generalized Kelvin model was adopted to describe the creep curves. The strain rate sensitivity m has been derived as a measure of the creep resistance. The compliance spectrum and retardation spectrum were also derived. The results show that the creep resistance of Ti41Zr25Be34 alloy can be obviously improved with the addition of alloying elements, and the most effective element is found to be Al. The mechanism for enhancing the creep resistance was discussed in terms of the scale variation of the shear transformation zone induced by alloying.

  9. A new VME timing module: TG8

    Beetham, C.G.; Daems, G.; Lewis, J.; Puccio, B.

    1992-01-01

    The two accelerator divisions of CERN, namely PS and SL, are defining a new common control system based on PC, VME and Workstations. This has provided an opportunity to review both central timing systems and to come up with common solutions. The result was, amongst others, the design of a unique timing module, called TG8. The TG8 is a multipurpose VME module, which receives messages distributed over a timing network. These messages include timing information, clock plus calendar and telegrams instructing the CERN accelerators on the characteristics of the next beam to be produced. The TG8 compares incoming messages with up to 256 programmed actions. An action consists of two parts, a trigger which matches an incoming message and what to do when the match occurs. The latter part may optionally create an output pulse on one of the eight output channels and/or a bus interrupt, both with programmable delay and telegram conditioning. (author)

  10. Transglutaminase (TG) involvement in early embryogenesis

    Maccioni, R.B.; Arechaga, J.

    1986-01-01

    Transglutaminase (TG) has been examined in different stages of preimplantation mouse embryogenesis. The specific activity of this enzyme in the soluble cellular fraction increases 2-fold from 2-cell embryos to 8-cell morulae and 4-fold from 2-cell embryos to blastocyst. The same developmental profile was seen when either N,N-dimethylcasein or endogenous substrates were used in the TG assay. Using high-speed supernatants from different stage embryos as a source of enzyme and [ 3 H]putrescine as acyl acceptor, the major acyl donor components were tubulin and a high molecular weight (HMW) cross-linkage product, as assessed by electrophoresis and immunoblotting. When either assembled or monomeric cytoskeleton proteins were compared as subtrates, microtubules were the best acyl donors. These studies indicate that TG activity is modulated during the changing demands of blastomeres for microtubule cytoskeleton in early embryogenesis

  11. In vitro solubility and bioactivity of Sr and Mg co-doped calcium phosphate glass-ceramics derived from different heat-treatment temperatures

    Cai Shu; Li Jianxin; Xu Guohua; Li, Xudong; Ye Xiaojian; Jiang Wei

    2011-01-01

    Highlights: ► Porous glass ceramics were prepared by controlled heat treatment process. ► A fast release of Mg ions has a great influence on the Ca/P ratio of the deposits. ► The chemical stability of the deposited apatite directly affects cell behavior. ► The glass ceramics heat-treated at 760 °C and 780 °C show less glass. ► The degradation rates are both compatible with cell growth and differentiation. - Abstract: CaO–P 2 O 5 –Na 2 O–SrO–MgO glass–ceramic system was prepared by controlled heat treatment process. Solubility and bioactivity of glass-ceramics were measured and evaluated in simulated body fluid (SBF) and cell culture medium respectively. The dissolution behavior of these glass-ceramics strongly depends on the amount and microstructure of the crystals precipitated by sintering treatment. Concerning the bioactivity, the onset of the apatite formation on the glass–ceramic system was directly dependent on the amount of bioactive glass amount which can be controlled using different temperatures of heat treatment. After immersing glass–ceramic in SBF, Mg ion as one of system composition can be released from residual glass and provides a high impact on the Ca/P ratio and chemical stability of the deposited apatite layer that directly affects cell attachment and proliferation in in vitro cell culture system. The glass ceramics heat-treated at 760 °C and 780 °C show less glass amount, and their degradation rates are both compatible with cell growth and differentiation.

  12. Immobilization of Uranium Silicide in Sintered Iron-Phosphate Glass

    Mateos, Patricia; Russo, Diego; Rodriguez, Diego; Heredia, A; Sanfilippo, M.; Sterba, Mario

    2003-01-01

    This work is a continuation of a previous one performed in vitrification of uranium silicide in borosilicate and iron-silicate glasses, by sintering.We present the results obtained with an iron-phosphate glass developed at our laboratory and we compare this results with those obtained with the above mentioned glasses. The main objective was to develop a method as simple as possible, so as to get a monolithic glass block with the appropriate properties to be disposed in a deep geological repository.The thermal transformation of the uranium silicide was characterized by DTA/TG analysis and X-ray diffraction.We determined the evolution of the crystalline phases and the change in weight.Calcined uranium silicide was mixed with natural U 3 O 8 , the amount of U 3 O 8 was calculated to simulate an isotopic dilution of 4%.This material was mixed with powdered iron-phosphate glass (in wt.%: 64,9 P 2 O 5 ; 22,7 Fe 2 O 3 ; 8,1 Al 2 O 3 ; 4,3 Na 2 O) in different proportions (in wt%): 7%, 10% y 15%.The powders were pressed and sintered at temperatures between 585 y 670 °C. Samples of the sintered pellet were prepared for the lixiviation tests (MCC-1P: monolithic samples; deionised water; 90° C; 7, 14 and 28 days).The samples showed a quite good durability (0,6 g.m -2 .day -1 ), similar to borosilicate glasses.The microstructure of the glass samples showed that the uranium particles are much better integrated to the glass matrix in the iron-phosphate glasses than in the borosilicate or iron-silicate glasses.We can conclude that the sintered product obtained could be a good alternative for the immobilization of nuclear wastes with high content of uranium, as the ones arising from the conditioning of research reactors spent fuels

  13. A low temperature co-fired ceramic power inductor manufactured using a glass-free ternary composite material system

    Li, Yuanxun; Xie, Yunsong; Xie, Ru; Chen, Daming; Han, Likun; Su, Hua

    2018-03-01

    A glass-free ternary composite material system (CMS) manufactured employing the low temperature ( 890 ° C ) co-fired ceramic (LTCC) technique is reported. This ternary CMS consists of silver, NiCuZn ferrite, and Zn2SiO4 ceramic. The reported device fabricated from this ternary CMS is a power inductor with a nominal inductance of 1.0 μH. Three major highlights were achieved from the device and the material study. First, unlike most other LTCC methods, no glass is required to be added in either of the dielectric materials in order to co-fire the NiCuZn ferrite, Zn2SiO4 ceramic, and silver. Second, a successfully co-fired silver, NiCuZn, and Zn2SiO4 device can be achieved by optimizing the thermal shrinkage properties of both NiCuZn and Zn2SiO4, so that they have a very similar temperature shrinkage profile. We have also found that strong non-magnetic elemental diffusion occurs during the densification process, which further enhances the success rate of manufacturing co-fired devices. Last but not least, elemental mapping suggests that strong magnetic elemental diffusion between NiCuZn and Zn2SiO4 has been suppressed during the co-firing process. The investigation of electrical performance illustrates that while the ordinary binary CMS based power inductor can deal with 400 mA DC, the ternary CMS based power inductor is able to handle higher DC currents, 700 mA and 620 mA DC, according to both simulation and experiment demonstrations, respectively.

  14. Low temperature magnetic behaviour of glass-covered magnetic microwires with gradient nanocrystalline microstructure

    Serrano, I. G.; Hernando, A.; Marín, P. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, P.O. Box 155 las Rozas, Madrid 28230 (Spain)

    2014-01-21

    Slow nanocrystallization driving dynamics can be affected by the combination of two factors: sample residual stresses and sample geometry. This effect is evidenced at the initial stages of nanocrystallization of amorphous CoFeSiBCuNb magnetic microwires. Transmission electron microscopy observations indicate how crystallization at temperatures between 730 and 780 K results in a graded microstructure where the crystallization at the surface skin of the microwire, which remains almost amorphous, differs from that of the middle, where elongated grains are observed, and inner regions. However, samples annealed at higher temperatures present a homogeneous microstructure. The effect of gradient microstructure on magnetic properties has been also analyzed and a loss of bistable magnetic behaviour at low temperatures, from that obtained in the amorphous and fully nanocrystallized sample, has been observed and ascribed to changes in sign of magnetostriction for measuring temperatures below 100 K.

  15. Is uranium dioxide a glass at high temperature: the reason for its irradiation resistance?

    Desgranges, Lionel

    2008-01-01

    Electronic intrinsic carriers are shown to have some influence on UO 2 high temperature properties. The physical nature of these carriers, called polarons, is discussed and it is proposed that they could correspond to quasi-broken bonds, in a similar way to intrinsic electronic defects in SiO 2 . It is shown that this hypothesis provides an explanation, at least qualitative, for UO 2 specific behavior at high temperature and under irradiation. (author)

  16. Kinetics of CO(2) fluxes outgassing from champagne glasses in tasting conditions: the role of temperature.

    Liger-Belair, Gérard; Villaume, Sandra; Cilindre, Clara; Jeandet, Philippe

    2009-03-11

    Measurements of CO(2) fluxes outgassing from a flute poured with a standard Champagne wine initially holding about 11 g L(-1) of dissolved CO(2) were presented, in tasting conditions, all along the first 10 min following the pouring process. Experiments were performed at three sets of temperature, namely, 4 degrees C, 12 degrees C, and 20 degrees C, respectively. It was demonstrated that the lower the champagne temperature, the lower CO(2) volume fluxes outgassing from the flute. Therefore, the lower the champagne temperature, the lower its progressive loss of dissolved CO(2) concentration with time, which constitutes the first analytical proof that low champagne temperatures prolong the drink's chill and helps retains its effervescence. A correlation was also proposed between CO(2) volume fluxes outgassing from the flute poured with champagne and its continuously decreasing dissolved CO(2) concentration. Finally, the contribution of effervescence to the global kinetics of CO(2) release was discussed and modeled by the use of results developed over recent years. The temperature dependence of the champagne viscosity was found to play a major role in the kinetics of CO(2) outgassing from a flute. On the basis of this bubbling model, the theoretical influence of champagne temperature on CO(2) volume fluxes outgassing from a flute was discussed and found to be in quite good accordance with our experimental results.

  17. A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses

    Wang, Shi-Qing; Cheng, Shiwang; Lin, Panpan; Li, Xiaoxiao

    2014-09-01

    This work formulates, at a molecular level, a phenomenological theoretical description of the brittle-ductile transition (BDT) in tensile extension, exhibited by all polymeric glasses of high molecular weight (MW). The starting point is our perception of a polymer glass (under large deformation) as a structural hybrid, consisting of a primary structure due to the van der Waals bonding and a chain network whose junctions are made of pairs of hairpins and function like chemical crosslinks due to the intermolecular uncrossability. During extension, load-bearing strands (LBSs) emerge between the junctions in the affinely strained chain network. Above the BDT, i.e., at "warmer" temperatures where the glass is less vitreous, the influence of the chain network reaches out everywhere by activating all segments populated transversely between LBSs, starting from those adjacent to LBSs. It is the chain network that drives the primary structure to undergo yielding and plastic flow. Below the BDT, the glassy state is too vitreous to yield before the chain network suffers a structural breakdown. Thus, brittle failure becomes inevitable. For any given polymer glass of high MW, there is one temperature TBD or a very narrow range of temperature where the yielding of the glass barely takes place as the chain network also reaches the point of a structural failure. This is the point of the BDT. A theoretical analysis of the available experimental data reveals that (a) chain pullout occurs at the BDT when the chain tension builds up to reach a critical value fcp during tensile extension; (b) the limiting value of fcp, extrapolated to far below the glass transition temperature Tg, is of a universal magnitude around 0.2-0.3 nN, for all eight polymers examined in this work; (c) pressurization, which is known [K. Matsushige, S. V. Radcliffe, and E. Baer, J. Appl. Polym. Sci. 20, 1853 (1976)] to make brittle polystyrene (PS) and poly(methyl methacrylate) (PMMA) ductile at room temperature

  18. Temperature dependence of the ultraviolet luminescence of Pr3+-doped 20Al(PO3)3-80LiF glass scintillator

    Tsuboi, Mizuki; Takeda, Kohei; Nakazato, Tomoharu

    2017-01-01

    The development of scintillator materials for scattered neutrons is essential in studying laser fusion experiments. We have previously investigated and proposed Pr 3+ -doped 20Al(PO 3 ) 3 -80LiF (APLF + Pr) glasses as scintillators for neutron detection. The APLF + Pr glass emissions are then investigated with synchrotron radiation excitation and varying sample temperature. APLF + Pr glasses exhibit luminescence emission located at 200 to 300 nm and 400 nm attributed to the 4f5d → 4f 2 and 4f 2 → 4f 2 ( 1 S 0 → 3 P j + 1 I 6 ) transitions, respectively. In addition, the 200 to 300-nm emission is not substantially affected by temperature, while the 400-nm emission intensities increase with decreasing sample temperature. This temperature dependence is attributed to cross relaxation whose effect can be controlled by the Pr-doping concentration. Our results suggest that doping concentration of APLF + Pr must be optimized and that APLF + Pr glasses must operate a low temperatures for better neutron detection. (author)

  19. Enthalpy and high temperature relaxation kinetics of stable vapor-deposited glasses of toluene

    Bhattacharya, Deepanjan; Sadtchenko, Vlad

    2014-01-01

    Stable non-crystalline toluene films of micrometer and nanometer thicknesses were grown by vapor deposition at distinct rates and probed by fast scanning calorimetry. Fast scanning calorimetry is shown to be extremely sensitive to the structure of the vapor-deposited phase and was used to characterize simultaneously its kinetic stability and its thermodynamic properties. According to our analysis, transformation of vapor-deposited samples of toluene during heating with rates in excess 10 5 K s −1 follows the zero-order kinetics. The transformation rate correlates strongly with the initial enthalpy of the sample, which increases with the deposition rate according to sub-linear law. Analysis of the transformation kinetics of vapor-deposited toluene films of various thicknesses reveal a sudden increase in the transformation rate for films thinner than 250 nm. The change in kinetics seems to correlate with the surface roughness scale of the substrate. The implications of these findings for the formation mechanism and structure of vapor-deposited stable glasses are discussed

  20. An application for impedance spectroscopy in the characterisation of the glass transition during the lyophilization cycle: the example of a 10% w/v maltodextrin solution.

    Smith, Geoff; Arshad, Muhammad Sohail; Polygalov, Eugene; Ermolina, Irina

    2013-11-01

    Impedance spectroscopy has been used for the measurement of the glass transition of a 10 % maltodextrin solution contained within a glass vial, with externally attached electrodes. Features of the pseudo-relaxation process, associated with the composite impedance of the glass vial-solution assembly, were characterised by the peak amplitude, C(peak)(″), and peak frequency, f(peak), of the capacitance spectra and the equivalent circuit elements that model the impedance spectra (i.e. the solution resistance and solution capacitance) and monitored every 3 min during re-heating of the solution. The time derivatives of all four parameters studied provided a glass transition in close agreement with DSC measurements (-17 °C) and at a precision of ± 0.5 °C. The temperature dependencies of the solution resistance and peak frequency were then characterised with the Arrhenius and Vogel-Fulcher-Tammann fit functions, at temperatures below and above Tg, respectively. The energy of activation (below Tg) was estimated at ~20 kJ mol(-1), and the fragility index (If) of the glass forming liquid (above Tg) was estimated at 0.9. The significance of the fragility index to the development, optimisation and control of the freeze-drying cycle is highlighted. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Temperature dependence of poly(lactic acid) mechanical properties

    Zhou, Chengbo; Guo, Huilong; Li, Jingqing

    2016-01-01

    The mechanical properties of polymers are not only determined by their structures, but also related to the temperature field in which they are located. The yield behaviors, Young's modulus and structures of injection-molded poly(lactic acid) (PLA) samples after annealing at different temperatures....... The crystallinity increases with increasing annealing temperature and a' form crystal is formed when the annealing temperature is higher than 100 oC. The stretched samples with low crystallinity show the first yield at draw temperatures below the glass transition temperature (Tg) and the second yield above Tg....... For the samples annealed between 80 and 120 oC, a peculiar double yield appears when stretched within 50–60 oC and only the first or the second yield can be found at the lower and higher draw temperatures. The yield strain and yield stress together with Young's modulus were obtained and discussed in terms...

  2. Specific heat of superconducting metallic glasses at low temperatures; Spezifische Waerme von supraleitenden metallischen Glaesern bei tiefen Temperaturen

    Reifenberger, Andreas

    2017-11-15

    In the framework of this thesis we performed, for the first time, an in-depth investigation of the thermodynamic properties of superconducting bulk metallic glasses (BMGs) by means of specific heat measurements in the temperature range between 25 mK and 300 K. To determine the specific heat we used a setup based on the well-established relaxation method. Furthermore we developed a novel micro-fabricated platform to measure superconducting, mg-sized samples down to T=5 mK. The platform temperature is measured by a metallic paramagnetic Ag:Er sensor that is inductively coupled to the input coil of a dc-SQUID by means of a micro-structured gradiometric meander coil. Thereby, we reached a temperature resolution of less than 30 nK/√(Hz) and a very low addenda heat capacity below 200 pJ/K at 50 mK. Connecting the obtained results with thermal conductivity data we were able to consistently model the various degrees of freedom in these BMGs and their interaction mechanisms: For temperatures T>2 K, we find pronounced low temperature anomalies in the phononic specific heat, which are attributed to localized harmonic vibration modes. In the superconducting state close to T{sub C}, where interactions of atomic tunneling systems with quasi-particles need to be taken into account, both measurements agree well with BCS-theory predictions. Far below T{sub C} we find good agreement between the data and the standard tunneling model predictions.

  3. Thermal behaviors of mechanically activated pyrites by thermogravimetry (TG)

    Hu Huiping; Chen Qiyuan; Yin Zhoulan; Zhang Pingmin

    2003-01-01

    The thermal decompositions of mechanically activated and non-activated pyrites were studied by thermogravimetry (TG) at the heating rate of 10 K min -1 in argon. Results indicate that the initial temperature of thermal decomposition (T di ) in TG curves for mechanically activated pyrites decreases gradually with increasing the grinding time. The specific granulometric surface area (S G ), the structural disorder of mechanically activated pyrites were analyzed by X-ray diffraction laser particle size analyzer, and X-ray powder diffraction analysis (XRD), respectively. The results show that the S G of mechanically activated pyrites remains almost constant after a certain grinding time, and lattice distortions (ε) rise but the crystallite sizes (D) decrease with increasing the grinding time. All these results imply that the decrease of T di in TG curves of mechanically activated pyrites is mainly caused by the increase of lattice distortions ε and the decrease of the crystallite sizes D of mechanically activated pyrite with increasing the grinding time. The differences in the reactivity between non-activated and mechanically activated pyrites were observed using characterization of the products obtained from 1 h treatment of non-activated and mechanically activated pyrites at 713 K under inert atmosphere and characterization of non-activated and mechanically activated pyrites exposed to ambient air for a certain period

  4. Short-range structure and thermal properties of lead tellurite glasses

    Hirdesh, Kaur, Amarjot; Khanna, Atul; Gonzàlez, Fernando

    2017-05-01

    PbO-TeO2 glasses having composition: xPbO-(100 - x)TeO2 (x = 10, 15 and 20 mol%) were prepared by melt quenching and characterized by X-ray diffraction, density measurements, differential scanning calorimetry and Raman spectroscopy. Glass density increases from 5.89 to 6.22 g cm-3 with increase in PbO concentration from 10 to 20 mol%, due to the replacement of TeO2 by heavier PbO. DSC studies found that glass transition temperature (Tg) decreases from a value of 295°C to 281°C. Raman studies found that glass short-range structure consists of TeO4 and TeO3 structural units and that PbO modifies the network by the structural transformation: TeO4 to TeO3.

  5. Short-range structure and thermal properties of barium tellurite glasses

    Kaur, Amarjot; Khanna, Atul; Gonzàlez, Fernando

    2017-05-01

    BaO-TeO2 glasses containing 10 to 20 BaO mol% were prepared and characterized by X-ray diffraction, density measurements, differential scanning calorimetry and Raman spectroscopy. Glass density decreases with increase in BaO concentration from 10 to 20 mol%, due to replacement of heavier TeO2 by lighter BaO, however glass transition temperature (Tg) increases significantly from a value of 318°C to 327°C due to increase in average single bond enthalpy of the tellurite network. Raman studies found that glass short-range structure consists of TeO4 and TeO3 structural units and BaO modifies the network by producing the structural transformation: TeO4→ TeO3.

  6. Influence of the sintering temperature in the microstructure of foam glass obtained from waste glass; Influencia da temperatura de queima na microestrutura de espumas vitreas obtidas a partir de residuos de vidro

    Pokorny, A.; Vicenzi, J.; Bergmann, C.P., E-mail: andrea_pokorny@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)

    2012-07-01

    In this work, foam glasses were produced from grounded soda-lime glass and a synthetic carbonate, used as a foaming agent, with a similar composition to a dolomite lime, added with different oxides (SiO{sub 2}, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}, MnO{sub 2}, Na{sub 2}O, K{sub 2}O, TiO{sub 2} and P{sub 2}O{sub 5}). The objective was to evaluate the influence of sintering temperature on the properties and microstructure of the obtained material. In addition, the effect of addition of the oxides in the expansion of the ceramic bodies was evaluated. The ceramic bodies were formulated with 3 weight percent of synthetic carbonate, uniaxially pressed and fired within the temperature range from 700 deg C to 950 deg C, with a heating rate of 150K/h. The technological characterization of the ceramic bodies involved the determination of the volumetric expansion and their microstructures have been characterized by optical microscopy and scanning electron microscopy. The experimental results have shown foam glass can be obtained from grounded soda-lime glass, using synthetic carbonate, with the introduction of the different oxides, as foaming agent. (author)

  7. Low temperature internal friction in La75Al20Si5 metallic glass

    Zolotukhin, I.V.; Kalinin, Yu.E.

    1991-01-01

    Results of investigation of temperature dependence of internal friction (IF) in amorphous alloy La 75 Al 20 Si 5 are presented. The amorphous state was atteined by quenching from liquid melt at a rate of 10 5 -10 6 K/s. Two IF maxima at Q -1 (T) dependence are observed at the temperatures of 185 and 230 K. Increase in the frequency of mechanical vibrations results in the shift of IF maxima to the side of high temperatures, which indicates their relaxation origin. The first peak of IF in the studied alloy La 75 Al 20 Si 5 is in all probability related to reorientation of chemical bonds La-La and La-Al. The maximum at T∼230 K is related to the switching of La-Si chemical bonds

  8. Temperature dependence of luminescence for different surface flaws in high purity silica glass

    Fournier, J.; Grua, P.; Neauport, J.; Fargin, E.; Jubera, V.; Talaga, D.; Del Guerzo, A.; Raffy, G.; Jouannigot, S.

    2013-01-01

    In situ temperature dependence of the Photoluminescence under 325 nm irradiation is used to investigate defect populations existing in different surface flaws in high purity fused silica. Five photoluminescence bands peaking at 1.9, 2.1, 2.3, 2.63 and 3.11 eV have been detected in the spectral area ranging from 1.6 up to 3.6 eV. The Gaussian deconvolution of spectra allows dividing the five luminescence bands in two categories. The former corresponds to bands showing a significant intensity enhancement while temperature decreases; the latter corresponds to bands remaining insensitive to the temperature evolution. Such a behavior brings new information on defects involved in laser damage mechanism at 351 nm in nanosecond regime. (authors)

  9. Mechanism for microstructural evolution induced by high temperature deformation in Zr-based bulk metallic glasses

    Cheng, Sirui; Wang, Chunju; Ma, Mingzhen; Shan, Debin; Guo, Bin

    2016-01-01

    In the Zr_4_1_._2Ti_1_3_._8Cu_1_2_._5Ni_1_0Be_2_2_._5 (Vit1) alloy undergoing high temperature deformation, its thermal properties and microstructure are quite different from those in the annealing alloy. In order to research the coupled effect of temperature and plastic strain on microstructural evolution of Zr-based amorphous, uniaxial compression test of Vit1 alloy with good amorphous nature has been performed, and then the structural state and thermal properties of Vit1 alloy after thermal deformation and isothermal annealing in the supercooled liquid region were investigated. It is revealed that the deformed specimens possess higher characteristic temperature and lower enthalpy change of microstructural relaxation. In addition, the smaller inter-atomic distance and higher order degree of atomic arrangement can be observed in those deformed Vit1 alloy. That can be deduced that thermal deformation is in favor of the microstructural evolution from a metastable amorphous state to stable crystallization state, because plastic strain promotes the annihilation of free volume and provide excess driving force of atomic diffusion. However, upon increasing the ambient temperature, the influence of plastic deformation on microstructure gradually decreased owing to the decreasing proportion of the plastic deformation-induced annihilation of free volume during the whole thermal deformation process. - Highlights: • The deformed specimens possess closer microstructure and higher characteristic temperatures. • The order degree of microstructures in deformed specimens is higher than that in annealed specimens. • Thermal deformation accelerates the microstructural evolution of Zr-based BMGs. • The influence of thermal deformation on microstructure decreases with the temperature increasing.

  10. Mechanism for microstructural evolution induced by high temperature deformation in Zr-based bulk metallic glasses

    Cheng, Sirui [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Chunju [Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150080 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Ma, Mingzhen [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Shan, Debin, E-mail: shandebin@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150080 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Guo, Bin [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2016-08-15

    In the Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} (Vit1) alloy undergoing high temperature deformation, its thermal properties and microstructure are quite different from those in the annealing alloy. In order to research the coupled effect of temperature and plastic strain on microstructural evolution of Zr-based amorphous, uniaxial compression test of Vit1 alloy with good amorphous nature has been performed, and then the structural state and thermal properties of Vit1 alloy after thermal deformation and isothermal annealing in the supercooled liquid region were investigated. It is revealed that the deformed specimens possess higher characteristic temperature and lower enthalpy change of microstructural relaxation. In addition, the smaller inter-atomic distance and higher order degree of atomic arrangement can be observed in those deformed Vit1 alloy. That can be deduced that thermal deformation is in favor of the microstructural evolution from a metastable amorphous state to stable crystallization state, because plastic strain promotes the annihilation of free volume and provide excess driving force of atomic diffusion. However, upon increasing the ambient temperature, the influence of plastic deformation on microstructure gradually decreased owing to the decreasing proportion of the plastic deformation-induced annihilation of free volume during the whole thermal deformation process. - Highlights: • The deformed specimens possess closer microstructure and higher characteristic temperatures. • The order degree of microstructures in deformed specimens is higher than that in annealed specimens. • Thermal deformation accelerates the microstructural evolution of Zr-based BMGs. • The influence of thermal deformation on microstructure decreases with the temperature increasing.

  11. Insights into glass transition and relaxation behavior using temperature-modulated differential scanning calorimetry

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Our simulations of TMDSC signals prove that the frequency correction of non-reversing heat flow can give a master curve within a certain range...... of frequencies. This frequency range is dependent not only on the measurement parameters such as linear heating/cooling rate and frequency and amplitude of the modulation, but also on the previous thermal history before the TMDSC measurement. The frequency correction for the reversing heat flow gives more...

  12. EPR reversible signature of self-trapped holes in fictive temperature-treated silica glass

    Lancry, Matthieu; Ollier, Nadège; Babu, B. H.; Herrero, Christian; Poumellec, Bertrand

    2018-03-01

    Post-mortem electron paramagnetic resonance spectroscopy experiments have been carried out between room temperature and 20 K to examine the radiation-induced defects in fictive temperature (Tf) treated Heraeus F300 silica (0.1 ppm OH, 1500 ppm Cl2). In particular, we focus our attention on Self-Trapped Hole (STH) centers detected in 1000 °C, 1100 °C, and 1200 °C Tf treated samples irradiated at room temperature by gamma rays at 6 kGy. By repeating annealing cycles between 77 and 300 K on the same samples, we observed that the EPR signal attributed to STH decreases as the temperature increases but in a reversible manner. We evidenced a deviation from the Curie law for T > 70 K and suggested an interpretation based on the decrease in the "strain-assisted TH" population by reversible excitation of the trapped hole to a delocalized state with an activation energy of 7.8 meV. This also means that the precursors of hole trapping sites (a local strain atomic configuration) remain stable until 300 K at least.

  13. Molecular dynamics simulations to calculate glass transition temperature and elastic constants of novel polyethers.

    Sarangapani, Radhakrishnan; Reddy, Sreekantha T; Sikder, Arun K

    2015-04-01

    Molecular dynamics simulations studies are carried out on hydroxyl terminated polyethers that are useful in energetic polymeric binder applications. Energetic polymers derived from oxetanes with heterocyclic side chains with different energetic substituents are designed and simulated under the ensembles of constant particle number, pressure, temperature (NPT) and constant particle number, volume, temperature (NVT). Specific volume of different amorphous polymeric models is predicted using NPT-MD simulations as a function of temperature. Plots of specific volume versus temperature exhibited a characteristic change in slope when amorphous systems change from glassy to rubbery state. Several material properties such as Young's, shear, and bulk modulus, Poisson's ratio, etc. are predicted from equilibrated structures and established the structure-property relations among designed polymers. Energetic performance parameters of these polymers are calculated and results reveal that the performance of the designed polymers is comparable to the benchmark energetic polymers like polyNIMMO, polyAMMO and polyBAMO. Overall, it is worthy remark that this molecular simulations study on novel energetic polyethers provides a good guidance on mastering the design principles and allows us to design novel polymers of tailored properties. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Effect of ZnO on the Thermal Properties of Tellurite Glass

    H. A. A. Sidek

    2013-01-01

    Full Text Available Systematic series of binary zinc tellurite glasses in the form (ZnOx(TeO2 (where x=0 to 0.4 with an interval of 0.05 mole fraction have been successfully prepared via conventional melt cast-quenching technique. Their density was determined by Archimedes method with acetone as buoyant liquid. The thermal expansion coefficient of each zinc tellurite glasses was measured using L75D1250 dilatometer, while their glass transition temperature (Tg was determined by the SETARAM Labsys DTA/6 differential thermogravimetric analysis at a heating rate of 20 K min−1. The acoustic Debye temperature and the softening temperature (Ts were estimated based on the longitudinal (VL and shear ultrasonic (Vs wave velocities propagated in each glass sample. For ultrasonic velocity measurement of the glass sample, MATEC MBS 8000 Ultrasonic Data Acquisition System was used. All measurements were taken at 10 MHz frequency and at room temperature. All the thermal properties of such binary tellurite glasses were measured as a function of ZnO composition. The composition dependence was discussed in terms of ZnO modifiers that were expected to change the thermal properties of tellurite glasses. Experimental results show their density, and the thermal expansion coefficient increases as more ZnO content is added to the tellurite glass network, while their glass transition, Debye temperature, and the softening temperature decrease due to a change in the coordination number (CN of the network forming atoms and the destruction of the network structure brought about by the formation of some nonbridging oxygen (NBO atoms.

  15. Glass transition temperatures of microphase separated semi-interpenetrating polymer networks of polystyrene-inter-poly(cross)-2-ethylhexyl-methacrylate

    de Graaf, L.A.; de Graaf, Leontine A.; Möller, Martin; Moller, M.

    1995-01-01

    The glass transition temperature of semi-interpenetrating polymer networks (semi-IPNs) of atactic polystyrene (PS) in crosslinked methacrylates was studied by systematic variation of the morphology, that is domain size, continuity and concentration in the domains. Semi-IPNs were prepared from

  16. Influence of mold temperature associated with glass fiber on the mechanical and thermal properties of a (PA6/GF/MMT) nanocomposite

    Damiani, Renato Adriano

    2017-01-01

    This work describes the second of a series of studies of the effects of injection molding conditions on the mechanical and thermal properties of Polyamide 6/Glass Fiber/Montmorillonite (PA6/GF/MMT) composites and was motivated by the lack of information about how the processing variables influence on the properties of three-phase composites containing fiber glass. By this time, the effects of the injection molding temperature associated with the fiber glass percentage on the mechanical and thermal properties of the composite are investigated. Some samples were processed, following a statistical experimental factorial planning, varying the mold temperature and the fiber glass percentage and maintaining 5 wt % of the MMT. The samples were submitted to tensile and flexural tests, XRD, SEM and DSC. The studies showed that an increase in the mold temperature and the fiber percentage improves the maximum tensile and flexural stresses. The increased mold temperature slows the cooling rate, which, over time, decreases the degree of crystallinity. However, there is an increase in the intercalation of the polymeric chains and the nanoclay lamellae, and the structure forms with fewer defects. (author)

  17. Influence of mold temperature associated with glass fiber on the mechanical and thermal properties of a (PA6/GF/MMT) nanocomposite

    Damiani, Renato Adriano, E-mail: eng.damiani@hotmail.com [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil). Programa de Pos-Graduacao em Ciencias e Engenharia de Materiais; Duarte, Glaucea Warmeling; Riella, Humberto Gracher, E-mail: gwduarte@gmail.com, E-mail: huberto.riella@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Programa de Pos-Graduacao em Engenharia Quimica; Silva, Luciano Luiz; Mello, Josiane Maria Muneron de; Fiori, Marcio Antonio; Batiston, Eduardo Roberto, E-mail: marciofiori@gmail.com, E-mail: lucianols@unochapeco.edu.br, E-mail: josimello@unochapeco.edu.br, E-mail: erbatiston@unochapeco.edu.br [Universidade Comunitaria da Regiao de Chapeco (UNOCHAPECO), Chapeco, SC (Brazil)

    2017-01-15

    This work describes the second of a series of studies of the effects of injection molding conditions on the mechanical and thermal properties of Polyamide 6/Glass Fiber/Montmorillonite (PA6/GF/MMT) composites and was motivated by the lack of information about how the processing variables influence on the properties of three-phase composites containing fiber glass. By this time, the effects of the injection molding temperature associated with the fiber glass percentage on the mechanical and thermal properties of the composite are investigated. Some samples were processed, following a statistical experimental factorial planning, varying the mold temperature and the fiber glass percentage and maintaining 5 wt % of the MMT. The samples were submitted to tensile and flexural tests, XRD, SEM and DSC. The studies showed that an increase in the mold temperature and the fiber percentage improves the maximum tensile and flexural stresses. The increased mold temperature slows the cooling rate, which, over time, decreases the degree of crystallinity. However, there is an increase in the intercalation of the polymeric chains and the nanoclay lamellae, and the structure forms with fewer defects. (author)

  18. Phase Separation and Crystallization in soda-lime borosilicate glass enriched in MoO{sub 3} studied by in situ Raman spectroscopy at high temperature

    Magnin, M.; Schuller, S.; Advocat, T. [CEA Valrho, DEN/DTCD/SCDV, Laboratoire d' Etude de Base sur les Verres, BP 17171, 30207 Bagnols-sur-Ceze Cedex (France); Caurant, D.; Majerus, O. [Laboratoire de Chimie de la Matiere Condensee de Paris- LCMCP - UMR-CNRS 7574, Ecole Nationale Superieure de Chimie de Paris - ENSCP, Paristech, 75231 Paris (France); Ligny, D. de [Laboratoire de Physico-Chimie des Materiaux Luminescents- LPCML - UMR-CNRS 5620, Universite Claude Bernard Lyon1, 69622 Villeurbanne (France)

    2008-07-01

    Phase separation and crystallisation processes may arise in molten glass when the MoO{sub 3} content exceeds its solubility limit. Molybdenum combined with other elements such as alkali and alkaline-earth may form crystalline molybdates, known as 'yellow phases' in nuclear glasses. In order to establish the sequence of phase separation and crystallization processes occurring during the cooling of the melt, a non-radioactive simplified glass composition was chosen in the SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-CaO system, with 2 mol.% MoO{sub 3}. Various cooling scenarios were tested: cooling by air blowing, quenching between two copper plates and cooling on metallic plate. The resulting glass specimens were then characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy in temperature. These observations made it possible to determine the sequence and the appearance temperature of phenomena upon cooling: first, a phase separation occurs, (small droplets dispersed in the molten glass) followed by molybdates crystallization inside the droplets. (authors)

  19. High-Tg Polynorbornene-Based Block and Random Copolymers for Butanol Pervaporation Membranes

    Register, Richard A.; Kim, Dong-Gyun; Takigawa, Tamami; Kashino, Tomomasa; Burtovyy, Oleksandr; Bell, Andrew

    Vinyl addition polymers of substituted norbornene (NB) monomers possess desirably high glass transition temperatures (Tg); however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. We have recently synthesized block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and n-butyl substituents (HFANB and BuNB) via living vinyl addition polymerization with Pd-based catalysts. Both series of polymers were cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes investigated for the isolation of n-butanol from dilute aqueous solution (model fermentation broth) via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as n-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance. While polyHFANB has much higher permeability and n-butanol selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the n-butanol pervaporation selectivity.

  20. Isotope effect in monolayer, localised, immobilised adsorption with special reference to neon adsorption on porous glass at cryogenic temperatures

    Srisaila, S.; Bajpai, M.B.

    1980-01-01

    Using statistical mechanics, a general formula for the separation factor of two isotopes between gas and adsorbate phases in a monolayer, localised, immobile adsorption on a heterogeneous surface, is derived. Special forms of this are discussed for which the familiar Bigeleisen form is one. Purer, Kalplan and Smith, in their work on neon isotopes separation by gas chromatography through porous glass column at cryogenic temperatures, have reported that the separation factor first increased and then decreased as the temperature was decreased, whereas monotonic increase was the normally expected behaviour. Moiseyev has attempted to explain the anomaly after assuming two types of adsorption sites. The present theory gives the conditions in which monotonic and nonmonotonic variations can occur and after making some assumptions, the experimental curve of Purer et al could be reproduced computationally using one form of the general expression. This theoretical treatment highlights the importance of both potential energy and force constant in isotope effect whereas it is only the potential energy that is much involved in most adsorption studies. (auth.)

  1. A program for the Calculation of the Correlated Colour Temperature. Application for Characterising Colour Changes in Glasses

    Garcia Rosillo, F.; Balenzategui, J. L.

    2000-01-01

    The purpose of this work is to present a program for the calculation of the Correlated Colour Temperature (CCT) of any source of radiation. The methodology of calculating the colour coordinates and the corresponding CCT value of any light source is briefly reviewed. Sample program codes, including one to obtain the colour candidatures of blackbody radiators at different temperatures, have been also Ust ed. This will allow to engineers and researchers to calculate and to obtain adequate solutions for their own illuminance problems. As an application example, the change in CCT values and colour coordinates of a reference spectrum when passing through semitransparent solar photovoltaic modules designed for building integration applications has been studied. This is used to evaluate the influence on the visual comfort of the building inner rooms. Several samples of different glass models used as covers in photovoltaic modules have been tested. Results show that all the samples tested do not modify substantially the initial characteristics of the sunlight, as otherwise expected. (Author) 5 refs

  2. High-Glass-Transition-Temperature Polyimides Developed for Reusable Launch Vehicle Applications

    Chuang, Kathy; Ardent, Cory P.

    2002-01-01

    Polyimide composites have been traditionally used for high-temperature applications in aircraft engines at temperatures up to 550 F (288 C) for thousands of hours. However, as NASA shifts its focus toward the development of advanced reusable launch vehicles, there is an urgent need for lightweight polymer composites that can sustain 600 to 800 F (315 to 427 C) for short excursions (hundreds of hours). To meet critical vehicle weight targets, it is essential that one use lightweight, high-temperature polymer matrix composites in propulsion components such as turbopump housings, ducts, engine supports, and struts. Composite materials in reusable launch vehicle components will heat quickly during launch and reentry. Conventional composites, consisting of layers of fabric or fiber-reinforced lamina, would either blister or encounter catastrophic delamination under high heating rates above 300 C. This blistering and delamination are the result of a sudden volume expansion within the composite due to the release of absorbed moisture and gases generated by the degradation of the polymer matrix. Researchers at the NASA Glenn Research Center and the Boeing Company (Long Beach, CA) recently demonstrated a successful approach for preventing this delamination--the use of three-dimensional stitched composites fabricated by resin infusion.

  3. Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

    Fred W. Calonego

    2010-09-01

    Full Text Available The Eucalyptus grandis logs temperatures were determined and correlated with the board's cracks during steaming. Thermocouples were inserted in the logs center, registering their temperatures during steaming at 90"C. The logs were sawed and the board's cracks measured. It was concluded that: (1 the logistic S-shaped curve explains the logs temperature variation; (2 the logs with diameter of 20 to As temperaturas em toras de Eucalyptus grandis, durante a vaporização, foram determinadas e correlacionadas com as rachaduras das tábuas. Nos centros das toras foram inseridos termopares e registradas suas temperaturas durante a vaporização à 90"C. As toras foram desdobradas e as rachaduras das tábuas mensuradas. Concluiu-se que: (1 o modelo estatístico sigmoidal logístico explica a variação da temperatura nas toras; (2 as toras com 20 a <25, 25 a <30 e 30 a <35 cm de diâmetro apresentaram, respectivamente, 84,2"C, 73,1"C e 45,8"C ao final da vaporização; e (3 as rachaduras foramsignificativamente menores nas toras que atingiram a temperatura de transição vítrea.

  4. AIR QUALITY IN THE CITY OF TG JIU

    Adina TĂTAR

    2014-05-01

    Full Text Available One of the most important problems of the modern age is the air pollution. Within this work I realized a description of Tgjiu City: geographic location, climate, hydrographical network, variations in temperature, terrain, sources of pollution. On the basis of registered values for the air quality indicator, sedimentable powders, and interpretation of results on the basis of the provisions of the standards in force, the comments were made in relation to particulate air pollution in the city area of sedimentableTg Jiu, identifying the polluters in the area, the proposed solutions for the reduction of pollution.

  5. Tb{sup 3+}/Eu{sup 3+}: YF{sub 3} nanophase embedded glass ceramics: Structural characterization, tunable luminescence and temperature sensing behavior

    Chen, Daqin, E-mail: dqchen@hdu.edu.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou, 310018 (China); Wang, Zhongyi; Zhou, Yang [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou, 310018 (China); Huang, Ping, E-mail: phuang@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on The Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Ji, Zhenguo, E-mail: jizg@hdu.edu.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou, 310018 (China)

    2015-10-15

    Tb{sup 3+}/Eu{sup 3+} co-doped transparent bulk glass ceramics containing orthorhombic β-YF{sub 3} nanocrystals were successfully synthesized by melt-quenching and subsequent heating. The partition of the active centers into the YF{sub 3} crystalline lattice was confirmed by elemental mapping in the scanning transmission electron microscope, emission spectra and decay curves. As a consequence, Tb{sup 3+} → Eu{sup 3+} energy transfer was demonstrated to be more efficient in the glass ceramic than in the precursor glass, which resulted in color tunable luminescence by simply modifying Eu{sup 3+} content and induced the linearly temperature-dependent fluorescence intensity ratio between the Tb{sup 3+}: {sup 5}D{sub 4} → {sup 7}F{sub 5} transition and the Eu{sup 3+}: {sup 5}D{sub 0} → {sup 7}F{sub 4} one in the Tb{sup 3+}/Eu{sup 3+} co-doped glass ceramic. It is expected that the investigated glass ceramic might be a promising candidate for solid-state lighting as well as optical temperature sensor. - Highlights: • Lanthanide doped glass ceramics containing YF{sub 3} nanocrystals were fabricated. • Tb{sup 3+} and Eu{sup 3+} dopants were confirmed to incorporate into YF{sub 3} lattice. • Tunable luminescence was realized via Tb{sup 3+} → Eu{sup 3+} energy transfer. • Linearly temperature-dependent fluorescence intensity ratio was detected.

  6. Formation of continuous nanocrystalline diamond layer on glass and silicon at low temperatures

    Kromka, Alexander; Rezek, Bohuslav; Remeš, Zdeněk; Michalka, M.; Ledinský, Martin; Zemek, Josef; Potměšil, Jiří; Vaněček, Milan

    2008-01-01

    Roč. 14, 7-8 (2008), s. 181-186 ISSN 0948-1907 R&D Projects: GA AV ČR KAN400100701; GA MŠk LC510; GA AV ČR KAN400100652; GA MŠk(CZ) 1M06002 Grant - others:Marie Curie RTN DRIVE(XE) MRTN-CT-2004-512224 Institutional research plan: CEZ:AV0Z10100521 Keywords : AFM * low temperature growth * nanocrystalline diamond * SEM * XPS Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.483, year: 2008

  7. Characterization of glass and glass ceramic nuclear waste forms

    Lutze, W.; Borchardt, J.; De, A.K.

    1979-01-01

    Characteristics of solidified nuclear waste forms, glass and glass ceramic compositions and the properties (composition, thermal stability, crystallization, phase behavior, chemical stability, mechanical stability, and radiation effects) of glasses and glass ceramics are discussed. The preparation of glass ceramics may be an optional step for proposed vitrification plants if tailored glasses are used. Glass ceramics exhibit some improved properties with respect to glasses. The overall leach resistance is similar to that of glasses. An increased leach resistance may become effective for single radionuclides being hosted in highly insoluble crystal phases mainly when higher melting temperatures are applicable in order to get more leach resistant residual glass phases. The development of glass ceramic is going on. The technological feasibility is still to be demonstrated. The potential gain of stability when using glass ceramics qualifies the material as an alternative nuclear waste form

  8. Acrylate oligomers in ultraviolet cured PSA's glass transition, molecular weight versus peel strength

    Miller, H.C.

    1999-01-01

    Typically those not skilled in the art relate Glass Transition Temperature to Pressure Sensitive Adhesives. You need a low Tg material to prepare good pressure sensitive adhesives. This report deals with a wide range acrylate terminated oligomers in a standard formulation. Molecular weight, chemical structure variations are examined versus the Glass Transition of the oligomers and final peel strength. Each formulated adhesive will require unique oligomer properties to reach one hundred newtons per 100 millimeters (5.71 pounds per square inch) peel strength. Excellent peel strengths may be obtained with oligomer molecular weight ranging from six thousand to one thousand molecular weight and glass transition temperatures ranging from minus seventy four degrees centigrade up to thirteen degrees centigrade

  9. Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

    Usuda, R.; Uchida, K.; Nozaki, S.

    2015-01-01

    Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiO x film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 10 11  cm −2 eV −1 by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H 2 O molecules and facilitate dissociation of the molecules into H and OH − . The OH − ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H 2 O molecules. The ionization results in the electron stimulated dissociation of H 2 O molecules and the decreased interface trap density

  10. Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

    Usuda, R.; Uchida, K.; Nozaki, S., E-mail: nozaki@ee.uec.ac.jp [Graduate School of Informatics and Engineering, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-1515 (Japan)

    2015-11-02

    Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiO{sub x} film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 10{sup 11 }cm{sup −2} eV{sup −1} by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H{sub 2}O molecules and facilitate dissociation of the molecules into H and OH{sup −}. The OH{sup −} ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H{sub 2}O molecules. The ionization results in the electron stimulated dissociation of H{sub 2}O molecules and the decreased interface trap density.

  11. Structural influence of mixed transition metal ions on lithium bismuth borate glasses

    Yadav, Arti; Dahiya, Manjeet S.; Hooda, A.; Chand, Prem; Khasa, S.

    2017-08-01

    Lithium bismuth borate glasses containing mixed transition metals having composition 7CoO·23Li2O·20Bi2O3·50B2O3 (CLBB), 7V2O5·23Li2O·20Bi2O3·50B2O3 (VLBB) and x(2CoO·V2O5)·(30 - x)Li2O·20Bi2O3·50B2O3 (x = 0.0 (LBB) and x = 2.0, 5.0, 7.0, 10.0 mol% (CVLBB1-4)) are synthesized via melt quench route. The synthesized compositions are investigated for their physical properties using density (D) and molar volume (Vm), thermal properties by analyzing DSC/TG thermo-graphs, structural properties using IR absorption spectra in the mid-IR range and optical properties using UV-Vis-NIR spectroscopy. The Electron Paramagnetic Resonance (EPR) spectra of vanadyl and cobalt ion have been analyzed to study compositional effects on spin-Hamiltonian parameters. The non linear variations in physical properties depict a strong structural influence of Co/V- oxides on the glassy matrix. The compositional variations in characteristic temperatures (glass transition temperature Tg, glass crystallization temperature Tp and glass melting temperature Tm) reveals that Tg for glass samples CLBB is relatively less than that of pure lithium bismuth borate (LBB) glass sample wherein Tg for sample VLBB is higher than that of LBB. The increase in Tg (as compared with LBB) with an enhanced substitution of mixed transition metal oxides (2CoO·V2O5) shows a progressive structure modification of bismuth borate matrix. These predictions are very well corroborated by corresponding compositional trends of Tp and Tm. FTIR studies reveal that Co2+& VO2+ ions lead to structural rearrangements through the conversion of three-coordinated boron into four coordinated boron and thereby reducing number of non-bridging oxygen atoms. Bismuth is found to exist in [BiO6] octahedral units only, whereas boroxol rings are not present in the glass network. The theoretical values of optical basicity (Λth) and corresponding oxide ion polarizability (αo2-) have also been calculated to investigate oxygen covalency of

  12. Characterisation of the glass transition of an amorphous drug using modulated DSC.

    Royall, P G; Craig, D Q; Doherty, C

    1998-07-01

    The use of modulated differential scanning calorimetry (MDSC) as a novel means of characterising the glass transition of amorphous drugs has been investigated, using the protease inhibitor saquinavir as a model compound. In particular, the effects of measuring variables (temperature cycling, scanning period, heating mode) have been examined. Saquinavir samples of known moisture content were examined using a TA Instruments 2920 MDSC at a heating rate of 2 degrees C/min and an amplitude of +/-0.159 degrees C with a period of 30 seconds. These conditions were used to examine the effects of cycling between - 50 degrees C and 150 degrees C. A range of periods between 20 and 50 seconds were then studied. Isothermal measurements were carried out between 85 degrees C and 120 degrees C using an amplitude of +/-0.159 degrees C with a period of 30 seconds. MDSC showed the glass transition of saquinavir (0.98 +/- 0.05%w/w moisture content) in isolation from the relaxation endotherm to give an apparent glass transition temperature of 107.0 degrees C +/- 0.4 degrees C. Subsequent temperature cycling gave reproducible glass transition temperatures of approximately 105 degrees C for both cooling and heating cycles. The enthalpic relaxation peak observed in the initial heating cycle had an additional contribution from a Tg "shift" effect brought about by the difference in response to the glass transition of the total and reversing heat flow signals. Isothermal studies yield a glass transition at 105.9 degrees C +/- 0.1 degrees C. MDSC has been shown to be capable of separating the glass transition of saquinavir from the relaxation endotherm, thereby facilitating measurement of this parameter without the need for temperature cycling. However, the Tg "shift" effect and the number of modulations through the transition should be taken into account to avoid drawing erroneous conclusions from the experimental data. MDSC has been shown to be an effective method of characterising the glass

  13. TG 220 MW hydraulic control system diagnostics

    Svabcik, A.

    1996-01-01

    The TG power output control system comprises a hydraulic and an electronic part. TG speed, power output or the main steam header pressure (HPK) depend on the steam flow at the turbine inlet. The steam admission into the turbine is controlled by four control valves and one by-pass valve in case of the HP part and by four capture flap valves in case of the LP part. The task of the SKODA K-220 MW turbine protection and control systems is to provide both the turbine speed and power output control to the setpoint value. Diagnostic measurements were aimed at getting an overview of both technical and functional states of all power output control elements. Principally, it can be stated that some deficiencies of a design nature originating from the manufacturer's factory were revealed and some other deficiencies related to hydraulic control elements functionality were identified more closely by the new method. 5 figs

  14. TG 220 MW hydraulic control system diagnostics

    Svabcik, A [Atomova Elektraren Bohunice, Jaslovske Bohunice (Slovakia)

    1997-12-31

    The TG power output control system comprises a hydraulic and an electronic part. TG speed, power output or the main steam header pressure (HPK) depend on the steam flow at the turbine inlet. The steam admission into the turbine is controlled by four control valves and one by-pass valve in case of the HP part and by four capture flap valves in case of the LP part. The task of the SKODA K-220 MW turbine protection and control systems is to provide both the turbine speed and power output control to the setpoint value. Diagnostic measurements were aimed at getting an overview of both technical and functional states of all power output control elements. Principally, it can be stated that some deficiencies of a design nature originating from the manufacturer`s factory were revealed and some other deficiencies related to hydraulic control elements functionality were identified more closely by the new method. 5 figs.

  15. TG-FTIR analysis of biomass pyrolysis

    Bassilakis, R.; Carangelo, R.M.; Wojtowicz, M.A. [Advanced Fuel Research Inc., Hartford, CT (United States)

    2001-10-09

    A great need exists for comprehensive biomass-pyrolysis models that could predict yields and evolution patterns of selected volatile products as a function of feedstock characteristics and process conditions. A thermogravimetric analyzer coupled with Fourier transform infrared analysis of evolving products (TG-FTIR) can provide useful input to such models in the form of kinetic information obtained under low heating rate conditions. In this work, robust TG-FTIR quantification routes were developed for infrared analysis of volatile products relevant to biomass pyrolysis. The analysis was applied to wheat straw, three types of tobacco (Burley, Oriental, and Bright) and three biomass model compounds (xylan, chlorogenic acid, and D-glucose). Product yields were compared with literature data, and species potentially quantifiable by FT-IR are reviewed. Product-evolution patterns are reported for all seven biomass samples. 41 refs., 7 figs., 2 tabs.

  16. Clinical electron beam dosimetry: transition from AAPM TG-25 to AAPM TG-70

    Mihailidis, Dimitris

    2017-01-01

    The absolute calibration of clinical electron beams is increasingly based on TG-51 protocol. In addition, recently published dosimetry data on electrons beams bring up the question of how would one need to modify the widely used TG-25 that originally was based on TG-21 calibration protocol? The answer to the question is given by the recently published TG-70. This new protocol operates as supplement and update to TG-25 on issues that need to be modified because of TG-51 approach to electron dosimetry and because of newer data on clinical electron beams. It describes in detail the procedure of converting measured depth-ionization curves with ion chambers into depth-dose curves, making use of recently published stopping-power ratios and other conversion factors. It also describes the use of water equivalent phantoms to perform relative electron dosimetry based on recently published conversions factors. The report discusses small and irregularly shaped electron field dosimetry using the concept of lateral buildup ratio (LBR) as an avenue to evaluate electronic equilibrium and compute dose per MU for those fields. Finally, it gives some common clinical examples where electron beam dosimetry are applied

  17. Kinetic Rate Law Parameter Measurements on a Borosilicate Waste Glass: Effect of Temperature, pH, and Solution Composition on Alkali Ion Exchange

    Pierce, Eric M.; McGrail, B PETER.; Icenhower, J P.; Rodriguez, Elsa A.; Steele, Jackie L.; Baum, Steven R.

    2004-01-01

    The reaction kinetics of glass is controlled by matrix dissolution and ion exchange (IEX). Dissolution of an alkali-rich simulated borosilicate waste glass was investigated using single-pass flow-through (SPFT) experiments. Experiments were conducted as a function of temperature, pH, and solution composition by varying the SiO 2 (aq) activity in the influent solution. Results showed that under dilute conditions matrix dissolution increased with increasing pH and temperature, and decreased with increasing SiO 2 (aq) activity. IEX rates decreased with increasing pH and temperature, and increased with increasing SiO 2 (aq) activity. Over the solution composition range interrogated in this study the dominant dissolution mechanism changed from matrix dissolution to IEX. These results suggest that ''secondary'' reactions may become dominant under certain environmental conditions and emphasize the need to incorporate these reactions into dissolution rate models

  18. Specific heat characteristics of Ce70Ga8.5Cu18.5Ni3 metallic glass at low temperatures

    Liu, Rentao; Zhong, Langxiang; Zhang, Bo

    2018-03-01

    Specific heat behaviors have been studied in Ce70Ga8.5Cu18.5Ni3 bulk metallic glass (BMG) from 2 K to 50 K. The low-temperature specific heat of the Ce-based metallic glass is a combined action of the Fermi liquids term, Debye oscillator term, and Einstein oscillator term as well as excess term. We also observed an intense boson peak around 15 K and attributed it to a harmonic localized Einstein mode influenced by the dense-packed atomic cluster structure. It is also demonstrated that Ce70Ga8.5Cu18.5Ni3 BMG belongs to the strongly correlated heavy-fermion system with a great electron specific heat coefficient and a high Wilson ratio. It exhibits a typical Fermi-Liquid feature when the temperature is above 10 K, while it exhibits a Non-Fermi-Liquid feature when the temperature is below 3.5 K.

  19. TG/FT-IR characterization of additives typically employed in EPDM formulations

    Natália Beck Sanches

    2015-06-01

    Full Text Available AbstractThermogravimetric analysis coupled to Fourier transform infrared spectroscopy (TG/FT-IR is a very popular technique for rubbers characterization. It involves analyses of the base polymer and additives. Ethylene–propylene–diene (EPDM rubbers are frequently investigated by TG/FT-IR; however, the focus has been the degradation temperature range of the polymer. In this study, unvulcanized and vulcanized EPDM rubber and its additives were investigated by TG/FT-IR, without solvent extraction, and in a wide temperature range. Initially, the additives were individually characterized. TG/FT-IR identified the characteristic groups of all the additives analyzed and distinguished them from each other. Afterwards, unvulcanized and vulcanized EPDM rubbers were investigated without prior extraction.TG/FT-IR detected absorptions due to the additives tetramethylthiuram monosulfide and 2-mercaptobenzothiazole. Both of these sulfur-containing additives were present in the EPDM formulation at concentrations of 0.7 phr (0.63 wt %. The TG/FT-IR technique had some limitations, because not all the additives in EPDM rubber were detected. Paraffin oil, stearic acid and 2,2,4-trimethyl-1,2-dihydroquinoline functional groups were not observed in either the unvulcanized or vulcanized EPDM. Nevertheless, in addition to the ability of this method to detect sulfur-containing groups, the lack of a pre-extraction reduces the time and effort required for additive analysis in rubbers.

  20. Temperature-controlled down-conversion luminescence behavior of Eu3+ -doped transparent MF2 (M = Ba, Ca, Sr) glass ceramics.

    Zhou, B; E, C Q; Bu, Y Y; Meng, L; Yan, X H; Wang, X F

    2017-03-01

    Eu 3 + -doped transparent glass ceramics containing MF 2 (M = Ba, Ca, Sr) nanocrystals were fabricated using a melt-quenching method, and the resulting structures were studied using X-ray diffraction. Levels 5 D 1 and 5 D 0 of Eu 3 + ions were verified as thermally coupled levels using the fluorescence intensity ratio method. The fluorescence intensity ratios, optical temperature sensitivity and thermal quenching ratios of the transparent glass ceramics were studied as a function of temperature. With an increase in temperature, the relative sensitivity (S R ) decreased sharply at first, then slowly increased, before finally decreasing. The minimum S R values of GCBaF 2 (GCB), GCCaF 2 (GCC) and GCSrF 2 (GCS) were 2.8 × 10 -4 , 0.8 × 10 -4 and 1.9 × 10 - 4  K -1 at 360, 269 and 319 K, respectively. Glass ceramics with an intense emission intensity can be used to convert the measured spectrum into temperature and may have an important role in temperature detectors. Copyright © 2016 John Wiley & Sons, Ltd.

  1. The low temperature specific heat of Lu-Cu-Y metallic glasses

    Mohammed, K.A.; Lanchester, P.C.

    1987-01-01

    The specific heat of a series of amorphous metallic alloys of the form Lu x Cu 0.37 Y 0.36 (x=0, 0.1, 0.3 and 0.4) has been measured between 2 and 50 K, primarily in order to be able to determine the non-magnetic contributions to the specific heat in magnetic Re-Cu-Y amorphous alloys. The data at low temperature fit the simple form C p =γT+βT 3 from which values of γ and θ D (0) have been determined. Consideration is given to the error that arises if Y is used rather than Lu or La in forming non-magnetic rare earth intermetallics for purposes of determining the non-magnetic contributions to the specific heat of magnetic samples. A simple procedure is described that allows a useful improvement in accuracy in estimating non-magnetic contributions below 20 K if Y is used. The method may also be useful if only a restricted range of compositions using Lu is possible. (orig.)

  2. Low temperature specific heat of Lu-Cu-Y metallic glasses

    Mohammed, K.A.; Lanchester, P.C.

    1987-02-01

    The specific heat of a series of amorphous metallic alloys of the form Lu/sub x/Cu/sub 0.37/Y/sub 0.36/ (x=0, 0.1, 0.3 and 0.4) has been measured between 2 and 50 K, primarily in order to be able to determine the non-magnetic contributions to the specific heat in magnetic Re-Cu-Y amorphous alloys. The data at low temperature fit the simple form C/sub p/=..gamma..T+..beta..T/sup 3/ from which values of ..gamma.. and theta/sub D/(0) have been determined. Consideration is given to the error that arises if Y is used rather than Lu or La in forming non-magnetic rare earth intermetallics for purposes of determining the non-magnetic contributions to the specific heat of magnetic samples. A simple procedure is described that allows a useful improvement in accuracy in estimating non-magnetic contributions below 20 K if Y is used. The method may also be useful if only a restricted range of compositions using Lu is possible.

  3. Fabrication of (PPC/NCC)/PVA composites with inner-outer double constrained structure and improved glass transition temperature.

    Cui, Shaoying; Li, Li; Wang, Qi

    2018-07-01

    Improving glass transition temperature (T g ) and mechanical property of the environment-friendly poly(propylene carbonate) via intermacromolecular complexation through hydrogen bonding is attractive and of great importance. A novel and effective strategy to prepare (polypropylene carbonate/nanocrystalline cellulose)/polyvinyl alcohol ((PPC/NCC)/PVA) composites with inner-outer double constrained structure was reported in this work. Outside the PPC phase, PVA, as a strong skeleton at microscale, could constrain the movement of PPC molecular chains by forming hydrogen bonding with PPC at the interface of PPC and PVA phases; inside the PPC phase, the rod-like NCC could restrain the flexible molecular chains of PPC at nanoscale by forming multi-hydrogen bonding with PPC. Under the synergistic effect of this novel inner-outer double constrained structure, T g , mechanical properties and thermal stability of (PPC/NCC)/PVA composite were significantly increased, e.g. T g of the composite researched the maximum value of 49.6 °C, respectively 15.6 °C, 5.7 °C and 4.2 °C higher than that of PPC, PPC/NCC and PPC/PVA composite. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Rapid Thermal Annealing and Hydrogen Passivation of Polycrystalline Silicon Thin-Film Solar Cells on Low-Temperature Glass

    Mason L. Terry

    2007-01-01

    Full Text Available The changes in open-circuit voltage (Voc, short-circuit current density (Jsc, and internal quantum efficiency (IQE of aLuminum induced crystallization, ion-assisted deposition (ALICIA polycrystalline silicon thin-film solar cells on low-temperature glass substrates due to rapid thermal anneal (RTA treatment and subsequent remote microwave hydrogen plasma passivation (hydrogenation are examined. Voc improvements from 130 mV to 430 mV, Jsc improvements from 1.2 mA/cm2 to 11.3 mA/cm2, and peak IQE improvements from 16% to > 70% are achieved. A 1-second RTA plateau at 1000°C followed by hydrogenation increases the Jsc by a factor of 5.5. Secondary ion mass spectroscopy measurements are used to determine the concentration profiles of dopants, impurities, and hydrogen. Computer modeling based on simulations of the measured IQE data reveals that the minority carrier lifetime in the absorber region increases by 3 orders of magnitude to about 1 nanosecond (corresponding to a diffusion length of at least 1 μm due to RTA and subsequent hydrogenation. The evaluation of the changes in the quantum efficiency and Voc due to RTA and hydrogenation with computer modeling significantly improves the understanding of the limiting factors to cell performance.

  5. Studies on fully transparent Al-Sn-Zn-O thin-film transistors fabricated on glass at low temperature

    Cong, Yingying; Han, Dedong; Wu, Jing; Zhao, Nannan; Chen, Zhuofa; Zhao, Feilong; Dong, Junchen; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2015-04-01

    High-performance fully transparent Al-Sn-Zn-O thin-film transistors (ATZO TFTs) with excellent electrical performance have been successfully fabricated by RF magnetron sputtering on glass at low temperatures. Two kinds of appropriate ATZO compositions are compared from several perspectives, including film material characteristics, device electrical performances, and fabrication process conditions. Finally, we achieve two excellent ATZO TFTs with competitive advantages. The ATZO TFT with larger amounts of dopants exhibits a superior field effect mobility μFE of 102.38 cm2 V-1 s-1, an ON/OFF current ratio (Ion/Ioff) of 1.18 × 107, and a threshold voltage VT of 1.35 V. The device with smaller amounts of dopants demonstrates better crystal quality and an excellent subthreshold swing SS of 155 mV/dec. Furthermore, it is less affected by oxygen partial pressure. The ATZO thin films display a high transmittance of over 80% in the visible light range.

  6. Fiscal 1999 technical achievement report. Development project on international standards for supporting new industry (Standardization of method for evaluating physical properties of new glass at high temperatures); 1999 nendo shinki sangyo shiengata kokusai hyojun kaihatsu jigyo seika hokokusho. New glass koon bussei no hyoka hoho no hyojunka

    NONE

    2000-03-01

    In the manufacture and processing of high quality glass to be used with electronic devices and displays, values representing its physical properties at high temperatures, such as viscosity, density, cubical expansion coefficient, and surface tension are necessary. Studies were conducted about techniques for evaluating physical values of such high temperature molten materials, and efforts were under way to develop the research results into international standards. Techniques for measuring physical values of high temperature molten soda ash based glass were improved for higher precision, and techniques for evaluating physical values of high temperature molten borosilicate glass were studied. Delegates were sent to International Commission on Glass (ICG) and technical committee TC18 for joining discussion, decision was made that researchers participate in robin tests on molten glass thermal conductivity, density, and cubical expansion coefficient, and pertinent activities were launched. (NEDO)

  7. On the dynamics of liquids in their viscous regime approaching the glass transition.

    Chen, Z; Angell, C A; Richert, R

    2012-07-01

    Recently, Mallamace et al. (Eur. Phys. J. E 34, 94 (2011)) proposed a crossover temperature, T(×), and claimed that the dynamics of many supercooled liquids follow an Arrhenius-type temperature dependence between T(×) and the glass transition temperature T(g). The opposite, namely super-Arrhenius behavior in this viscous regime, has been demonstrated repeatedly for molecular glass-former, for polymers, and for the majority of the exhaustively studied inorganic glasses of technological interest. Therefore, we subject the molecular systems of the Mallamace et al. study to a "residuals" analysis and include not only viscosity data but also the more precise data available from dielectric relaxation experiments over the same temperature range. Although many viscosity data sets are inconclusive due to their noise level, we find that Arrhenius behavior is not a general feature of viscosity in the T(g) to T(×) range. Moreover, the residuals of dielectric relaxation times with respect to an Arrhenius law clearly reveal systematic curvature consistent with super-Arrhenius behavior being an endemic feature of transport properties in this viscous regime. We also observe a common pattern of how dielectric relaxation times decouple slightly from viscosity.

  8. Local dynamics of glass-forming polystyrene thin films from atomistic simulation

    Zhou, Yuxing; Milner, Scott

    Despite a wide technological application ranging from protective coatings to organic solar cells, there still no consensus on the mechanism for the glass transition in polymer thin films a manifestation of the infamous glass problem under confinement. Many experimental and computational studies have observed a large deviation of nanoscale dynamical properties in thin films from the corresponding properties in bulk. In this work, we perform extensive united-atom simulations on atactic polystyrene free-standing thin films near the glass transition temperature and focus on the effect of free surface on the local dynamics. We study the segmental dynamics as a function of distance from the surface for different temperatures, from which relaxation time and thereby local Tg is obtained for each layer. We find the dynamics near free surface is not only enhanced but becomes less strongly temperature dependent as Tg is approached compared to the bulk. We find an increasing length scale associated with mobility propagation from the free surface as temperature decreases, but no correlation between local structure and enhanced relaxation rates near the surface, consistent with studies on bead-spring chains.

  9. Room Temperature Imprint Using Crack-Free Monolithic SiO2-PVA Nanocomposite for Fabricating Microhole Array on Silica Glass

    Shigeru Fujino

    2015-01-01

    Full Text Available This paper aims to fabricate microhole arrays onto a silica glass via a room temperature imprint and subsequent sintering by using a monolithic SiO2-poly(vinyl alcohol (PVA nanocomposite as the silica glass precursor. The SiO2-PVA suspension was prepared from fumed silica particles and PVA, followed by drying to obtain tailored SiO2-PVA nanocomposites. The dependence of particle size of the fumed silica particles on pore size of the nanocomposite was examined. Nanocomposites prepared from 7 nm silica particles possessed suitable mesopores, whereas the corresponding nanocomposites prepared from 30 nm silica particles hardly possessed mesopores. The pore size of the nanocomposites increased as a function of decreasing pH of the SiO2-PVA suspension. As a consequence, the crack-free monolithic SiO2-PVA nanocomposite was obtained using 7 nm silica particles via the suspension at pH 3. Micropatterns were imprinted on the monolithic SiO2-PVA nanocomposite at room temperature. The imprinted nanocomposite was sintered to a transparent silica glass at 1200°C in air. The fabricated sintered glass possessed the microhole array on their surface with aspect ratios identical to the mold.

  10. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

    A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO 4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  11. Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

    Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

    2018-05-01

    Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

  12. Thermal characteristics, Raman spectra, optical and structural properties of TiO2-Bi2O3-B2O3-TeO2 glasses

    Gupta, Nupur; Khanna, Atul; Gonzàlez, Fernando; Iordanova, Reni

    2017-05-01

    Tellurite and borotellurite glasses containing Bi2O3 and TiO2 were prepared and structure-property correlations were carried out by density measurements, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Raman and UV-visible spectroscopy. Titanium tellurite glasses require high melt-cooling rates and were fabricated by splat quenching. On adding B2O3, the glass forming ability (GFA) enhances, and glasses could be synthesized at lower quenching rates. The density of glasses shows a direct correlation with molecular mass of the constituents. UV-visible studies were used to determine the optical band gap and refractive index. Raman studies found that the co-ordination number of tellurium ions with oxygen (NTe-O) decreases with the increase in B2O3 as well as Bi2O3 content while, TiO2 produce only a small decrease in NTe-O, which explains the lower GFA of titanium tellurite glasses that do not contain Bi2O3 and B2O3. DSC studies show that the glass transition temperature (Tg) increases with B2O3 and TiO2 concentrations and that Tg correlates well with bond enthalpy of the metal oxides.

  13. Research and development on is process components for hydrogen production. (2) Corrosion resistance of glass lining in high temperature sulfuric acid

    Tanaka, Nobuyuki; Iwatsuki, Jin; Kubo, Shinji; Terada, Atsuhiko; Onuki, Kaoru

    2009-01-01

    Japan Atomic Energy Agency has been conducting a research and development on hydrogen production system using High Temperature Gas-Cooled Reactor. As a part of this effort, thermochemical water-splitting cycle featuring iodine- and sulfur-compounds (IS process) is under development considering its potential of large-scale economical hydrogen production. The IS process constitutes very severe environments on the materials of construction because of the corrosive nature of process chemicals, especially of the high temperature acidic solution of sulfuric acid and hydriodic acid dissolving iodine. Therefore, selection of the corrosion-resistant materials and development of the components has been studied as a crucial subject of the process development. This paper discusses corrosion resistance of commercially available glass-lining material in high temperature sulfuric acid. Corrosion resistance of a soda glass used for glass-lining was examined by immersion tests. The experiments were performed in 47-90wt% sulfuric acids at temperatures of up to 400degC and for the maximum immersion time of 100 hours using an autoclave designed for the concerned tests. In every condition tested, no indication of localized corrosion such as defect formation or pitting corrosion was observed. Also, the corrosion rates decreased with the progress of immersion, and were low enough (≅0.1 mm/year) after 60-90 hours of immersion probably due to formation of a silica rich surface. (author)

  14. Acoustic and thermal anomalies in a liquid-glass transition of racemic S(+)-R(-) ketoprofen

    Shibata, Tomohiko; Takayama, Haruki; Kim, Tae Hyun; Kojima, Seiji

    2014-01-01

    Acoustic and thermal properties of pharmaceutical racemic S(+)-R(-) ketoprofen were investigated in wide temperature range including glassy, supercooled liquid and liquid states by Brillouin scattering and temperature modulated DSC. Sound velocity and acoustic attenuation exhibited clear changes at 265 K indicating a liquid-glass transition and showed the typical structural relaxation above Tg. The high value of the fragility index m = 71 was determined by the dispersion of the complex heat capacity. New relaxation map was suggested in combination with previous study of dielectric measurement.

  15. Influence of the film thickness on the structure, optical and electrical properties of ITO coatings deposited by sputtering at room temperature on glass and plastic substrates

    Guillén, C; Herrero, J

    2008-01-01

    Transparent and conductive indium tin oxide (ITO) films with thickness between 0.2 and 0.7 µm were deposited by sputtering at room temperature on glass and polyethylene terephthalate (PET) substrates. All films were polycrystalline, with crystallite size increasing and lattice distortion decreasing when the film thickness was increased. Besides, transmission in the near-infrared region is found to be decreasing and carrier concentration increasing when the film thickness was increased. For the same thickness, the lattice distortion is slightly lower and the carrier concentration higher for the layers grown on PET substrates. A direct relationship between the lattice distortion and the free carrier concentration has been established, applying to the films grown on glass and plastic substrates. By adjusting ITO coating thickness, sheet resistance below 15 Ω sq −1 and average visible transmittance about 90% have been achieved by sputtering at room temperature

  16. Indium-tin oxide thin films deposited at room temperature on glass and PET substrates: Optical and electrical properties variation with the H2-Ar sputtering gas mixture

    Álvarez-Fraga, L.; Jiménez-Villacorta, F.; Sánchez-Marcos, J.; de Andrés, A.; Prieto, C.

    2015-07-01

    The optical and electrical properties of indium tin oxide (ITO) films deposited at room temperature on glass and polyethylene terephthalate (PET) substrates were investigated. A clear evolution of optical transparency and sheet resistance with the content of H2 in the gas mixture of H2 and Ar during magnetron sputtering deposition is observed. An optimized performance of the transparent conductive properties ITO films on PET was achieved for samples prepared using H2/(Ar + H2) ratio in the range of 0.3-0.6%. Moreover, flexible ITO-PET samples show a better transparent conductive figure of merit, ΦTC = T10/RS, than their glass counterparts. These results provide valuable insight into the room temperature fabrication and development of transparent conductive ITO-based flexible devices.

  17. Temporal Texture Profile and Identification of Glass Transition Temperature as an Instrumental Predictor of Stickiness in a Caramel System.

    Mayhew, Emily J; Schmidt, Shelly J; Schlich, Pascal; Lee, Soo-Yeun

    2017-09-01

    Stickiness is an important texture attribute in many food systems, but its meaning can vary by person, product, and throughout mastication. This variability and complexity makes it difficult to devise analytical tests that accurately and consistently predict sensory stickiness. Glass transition temperature (T g ) is a promising candidate for texture prediction. Our objective is to elucidate the temporal profile of stickiness in order to probe the relationship between T g and dynamic stickiness perception. Nine caramel samples with diverse texture and thermal profiles were produced for sensory testing and differential scanning calorimetry. Sixteen trained panelists generated stickiness-relevant terms to be used in a subsequent temporal dominance of sensation (TDS) test with the same panelists. Following the TDS study, these panelists also rated samples for overall tactile and oral stickiness. Stickiness ratings were then correlated to TDS dominance parameters across the full evaluation period and within the first, middle, and final thirds of the evaluation period. Samples with temporal texture profiles dominated by tacky, stringy, and enveloping attributes consistently received the highest stickiness scores, although the correlation strength varied by time period. T g was found to correlate well with trained panelist and consumer ratings of oral (R 2 trained = 0.85; R 2 consumer = 0.96) and tactile (R 2 trained = 0.78; R 2 consumer = 0.79) stickiness intensity, and stickiness intensity ratings decreased with T g of completely amorphous samples. Further, glassy samples followed a different texture trajectory (brittle-cohesive-toothpacking) than rubbery samples (deformable-tacky-enveloping). These results illuminate the dynamic perception of stickiness and support the potential of T g to predict both stickiness intensity and texture trajectory in caramel systems. © 2017 Institute of Food Technologists®.

  18. Protein Internal Dynamics Associated With Pre-System Glass Transition Temperature Endothermic Events: Investigation of Insulin and Human Growth Hormone by Solid State Hydrogen/Deuterium Exchange.

    Fang, Rui; Grobelny, Pawel J; Bogner, Robin H; Pikal, Michael J

    2016-11-01

    Lyophilized proteins are generally stored below their glass transition temperature (T g ) to maintain long-term stability. Some proteins in the (pure) solid state showed a distinct endotherm at a temperature well below the glass transition, designated as a pre-T g endotherm. The pre-T g endothermic event has been linked with a transition in protein internal mobility. The aim of this study was to investigate the internal dynamics of 2 proteins, insulin and human growth hormone (hGH), both of which exhibit the pre-T g endothermic event with onsets at 50°C-60°C. Solid state hydrogen/deuterium (H/D) exchange of both proteins was characterized by Fourier transform infrared spectroscopy over a temperature range from 30°C to 80°C. A distinct sigmoidal transition in the extent of H/D exchange had a midpoint of 56.1 ± 1.2°C for insulin and 61.7 ± 0.9°C for hGH, suggesting a transition to greater mobility in the protein molecules at these temperatures. The data support the hypothesis that the pre-T g event is related to a transition in internal protein mobility associated with the protein dynamical temperature. Exceeding the protein dynamical temperature is expected to activate protein internal motion and therefore may have stability consequences. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  19. Molecular dissipation phenomena of nanoscopic friction in the heterogeneous relaxation regime of a glass former.

    Sills, Scott; Gray, Tomoko; Overney, René M

    2005-10-01

    Nanoscale sliding friction involving a polystyrene melt near its glass transition temperature Tg (373 K) exhibited dissipation phenomena that provide insight into the underlying molecular relaxation processes. A dissipative length scale that shows significant parallelism with the size of cooperatively rearranging regions (CRRs) could be experimentally deduced from friction-velocity isotherms, combined with dielectric loss analysis. Upon cooling to approximately 10 K above Tg, the dissipation length Xd grew from a segmental scale of approximately 3 A to 2.1 nm, following a power-law relationship with the reduced temperature Xd approximately TR-phi. The resulting phi=1.89+/-0.08 is consistent with growth predictions for the length scale of CRRs in the heterogeneous regime of fragile glass formers. Deviations from the power-law behavior closer to Tg suggest that long-range processes, e.g., the normal mode or ultraslow Fischer modes, may couple with the alpha relaxation, leading to energy dissipation in domains of tens of nanometers.

  20. Dielectric relaxation of 2-ethyl-1-hexanol around the glass transition by thermally stimulated depolarization currents.

    Arrese-Igor, S; Alegría, A; Colmenero, J

    2015-06-07

    We explore new routes for characterizing the Debye-like and α relaxation in 2-ethyl-1-hexanol (2E1H) monoalcohol by using low frequency dielectric techniques including thermally stimulated depolarization current (TSDC) techniques and isothermal depolarization current methods. In this way, we have improved the resolution of the overlapped processes making it possible the analysis of the data in terms of a mode composition as expected for a chain-like response. Furthermore the explored ultralow frequencies enabled to study dynamics at relatively low temperatures close to the glass transition (Tg). Results show, on the one hand, that Debye-like and α relaxation timescales dramatically approach to each other upon decreasing temperature to Tg. On the other hand, the analysis of partial polarization TSDC data confirms the single exponential character of the Debye-like relaxation in 2E1H and rules out the presence of Rouse type modes in the scenario of a chain-like response. Finally, on crossing the glass transition, the Debye-like relaxation shows non-equilibrium effects which are further emphasized by aging treatment and would presumably emerge as a result of the arrest of the structural relaxation below Tg.