Effects of chemical composition and mean coordination number on glass transitions in Ge–Sb–Se glasses

2017 ◽  
Vol 31 (36) ◽  
pp. 1750342 ◽  
Author(s):  
Wen-Hou Wei
Keyword(s):  
Glass Transition ◽  
Chemical Composition ◽  
Coordination Number ◽  
Structural Phase ◽  
Stoichiometric Composition ◽  
Glass Transitions ◽  
Fragility Index ◽  
Scanning Calorimetry ◽  
Transition Formula ◽  
The Mean

Glass transitions in the Ge–Sb–Se glasses were investigated by means of differential scanning calorimetry (DSC) under non-isothermal conditions. The glass transition temperature [Formula: see text], activation energy of glass transition [Formula: see text], and fragility index as functions of the mean coordination number (MCN) and atomic percent of Ge were examined. The maximum value of [Formula: see text] in each group of the glasses occurred at the chemically stoichiometric composition, suggesting a glass transition threshold. The [Formula: see text] and fragility index were calculated from the heating rate dependence of [Formula: see text]. Both [Formula: see text] and fragility index show the minima at MCN = 2.4 which can be attributed to the structural phase transition of a covalently glassy network at MCN = 2.4. The analysis of the experimental results suggests that both the chemical composition and MCN have significant effects on the glass transitions in Ge–Sb–Se glasses.

Differential Scanning Calorimetry (DSC) Analysis of Abaca Fibre (Musa Textile Nee) Reinforced High Impact Polystyrene (HIPS) Composites

2011 ◽  
Vol 295-297 ◽  
pp. 929-933 ◽  
Author(s):  
E.H. Agung ◽  
S.M. Sapuan ◽  
M.M.H. Megat Ahmad ◽  
H.M.D.K. Zaman ◽  
U. Mustofa
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Optimum Condition ◽  
Amorphous State ◽  
Heat Content ◽  
High Impact ◽  
Glass Transitions ◽  
Scanning Calorimetry ◽  
High Impact Polystyrene

Differential scanning calorimetry (DSC) was used to study the thermal behaviour of abaca fibre reinforced high impact polystyrene (HIPS) composites. Thermal analysis is based upon the detection of changes in the heat content (enthalpy) and the glass transition temperature (Tg) of optimum condition of abaca fibre reinforced HIPS composites. In this research, glass transitions temperature (Tg) of neat HIPS occurred below the Tg of optimum condition of composites as the temperature of an amorphous state. The endothermic peak of composites was in to range 430-435°C including neat HIPS and it observed that enthalpy of abaca fibre reinforced HIPS composites yielded below the neat HIPS 748.79 J/g.

Sorption Isotherm, Glass Transitions and State Diagram for Freeze-dried Plum Skin and Pulp

2006 ◽  
Vol 12 (3) ◽  
pp. 181-187 ◽  
Author(s):  
V. R. Nicoletti Telis ◽  
P. J. do Amaral Sobral ◽  
J. Telis-Romero
Keyword(s):  
Glass Transition ◽  
Moisture Content ◽  
Sorption Isotherm ◽  
State Diagram ◽  
Transition Curve ◽  
Glass Transitions ◽  
Water Addition ◽  
Scanning Calorimetry ◽  
Freeze Dried ◽  
The Matrix

Differential scanning calorimetry (DSC) was used to determine phase transitions of freeze-dried plums. Samples at low and intermediate moisture contents, were conditioned by adsorption at various water activities (0.11≤aw≤0.90) at 25°C, whereas in the high moisture content region (aw>0.90) samples were obtained by direct water addition, with the resulting sorption isotherm being well described by the Guggenheim-Anderson-deBoer (GAB) model. Freeze-dried samples of separated plum skin and pulp were also analysed. At aw≤0.75, two glass transitions were visible, with the glass transition temperature (Tg) decreasing with increasing aw due to the water plasticising effect. The first Tg was attributed to the matrix formed by sugars and water. The second one, less visible and less plasticised by water, was probably due to macromolecules of the fruit pulp. The Gordon-Taylor model represented satisfactorily the matrix glass transition curve for aw≤0.90. In the higher moisture content range Tg remained practically constant around Tg′ (−57.5°C). Analysis of the glass transition curve and the sorption isotherm indicated that stability at a temperature of 25°C, would be attained by freeze dried plum at a water activity of 0.04, corresponding to a moisture content of 12.9% (dry basis).

Glass Formation During Room Temperature, Isothermal Drying

2003 ◽  
Author(s):  
Alptekin Aksan ◽  
Mehmet Toner
Keyword(s):  
Glass Transition ◽  
Glassy State ◽  
Glass Transitions ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Glass Transition Kinetics ◽  
The Stability ◽  
Isothermal Drying ◽  
Kinetics Of

Isothermal drying and glass transition of solutions and films have drawn considerable attention from many industries. We here explore the feasibility of modifying the isothermal drying and vitrification kinetics of carbohydrate solutions in order to ensure the stability and quality of their ingredients. Modulated Differential Scanning Calorimetry experiments with isothermally dried trehalose and trehalose/dextran solutions were performed and the glass transition kinetics have been determined. Three distinct drying regimes were observed. With isothermal, isobaric drying at 0%RH, it was indeed possible to reach the glassy state for a trehalose and a trehalosedextran system. With the addition of high molecular weight sugars, the glass transitions of isothermally dried carbohydrate solutions can be accelerated as a function of dextran mass ratio in the sample.

Effect of Molecular Weight on Glass Transition by Differential Scanning Calorimetry

1974 ◽  
Vol 52 (18) ◽  
pp. 3170-3175 ◽  
Author(s):  
Louis-Philippe Blanchard ◽  
Jean Hesse ◽  
Shadi Lal Malhotra
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Glass Transition ◽  
Heating Rate ◽  
Low Molecular Weight ◽  
Glass Transitions ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Polystyrene Sample

The influence of molecular weight (900 to 1.8 × 106) on the glass transition temperature of low polydispersity polystyrene (anionically prepared) has been studied by differential scanning calorimetry at heating rates of 5 to 80 °C min−1. Over the range of molecular_weight studied, and at an extrapolated heating rate of 1 °C min−1,[Formula: see text] A thermally prepared polystyrene sample ([Formula: see text]and Pd = 3.2) showed a Tge value of 93 °C, some 10° below the value predicted by the above equation. Low molecular weight species in the highly polydisperse sample are believed to be responsible for the discrepancy. The changes in heat capacity brought about by the glass transitions are accompanied in all cases on heating by an endothermic peak and this regardless of the heating rate (even extrapolated to 1 °C min−1) or the molecular weight of the sample, suggesting that the glass transition phenomenon encountered with polystyrene is a process involving a positive heat effect.

scholarly journals Sustainable Plastics from Biomass: Blends of Polyesters Based on 2,5-Furandicarboxylic Acid

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 225 ◽  
Author(s):  
Niki Poulopoulou ◽  
Dimitra Smyrnioti ◽  
George N. Nikolaidis ◽  
Ilektra Tsitsimaka ◽  
Evi Christodoulou ◽  
...  
Keyword(s):  
Glass Transition ◽  
Polarized Light ◽  
Glass Transitions ◽  
Scanning Calorimetry ◽  
Immiscible Blends ◽  
Melt Polycondensation ◽  
Miscible Blends ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
Poly Propylene

Intending to expand the thermo-physical properties of bio-based polymers, furan-based thermoplastic polyesters were synthesized following the melt polycondensation method. The resulting polymers, namely, poly(ethylene 2,5-furandicarboxylate) (PEF), poly(propylene 2,5-furandicarboxylate) (PPF), poly(butylene 2,5-furandicarboxylate) (PBF) and poly(1,4-cyclohexanedimethylene 2,5-furandicarboxylate) (PCHDMF) are used in blends together with various polymers of industrial importance, including poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalate) (PEN), poly(L-lactic acid) (PLA) and polycarbonate (PC). The blends are studied concerning their miscibility, crystallization and solid-state characteristics by using wide-angle X-ray diffractometry (WAXD), differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEF blends show in general dual glass transitions in the DSC heating traces for the melt quenched samples. Only PPF–PEF blends show a single glass transition and a single melt phase in PLM. PPF forms immiscible blends except with PEF and PBF. PBF forms miscible blends with PCHDMF and PPF, whereas all other blends show dual glass transitions in DSC and phase separation in PLM. PCHDMF–PEF and PEN–PEF blends show two glass transition temperatures, but they shift to intermediate temperature values depending on the composition, indicating some partial miscibility of the polymer pairs.

STUDY OF GLASS TRANSITION KINETICS FOR Co66Si12B16Fe4Mo2 METALLIC GLASS

2013 ◽  
Vol 22 ◽  
pp. 321-326 ◽  
Author(s):  
ASHMI T. PATEL ◽  
ARUN PRATAP
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Glass Forming Ability ◽  
Fragility Index ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Glass Transition Kinetics ◽  
Glass Forming ◽  
The Given ◽  
Kinetics Of

Metallic glasses have received considerable attention in comparison to normal metallic materials due to their superior physical, mechanical, electrical and magnetic properties. Understanding the glass transition kinetics of metallic alloys is of great importance in order to know its thermal stability. In the present paper, kinetics of glass transition of metallic glass Co66Si12B16Fe4Mo2 is studied using thermal analysis technique, i.e. differential scanning calorimetry (DSC), by non-isothermal heating of the sample at four different heating rates. The activation energy (E) of the glass transition region is determined by two most frequently used methods, namely, Moynihan’s method and Kissinger’s equation. The fragility index, m is also calculated using Tg, which is a measure of glass forming ability of the given system. The results show that the fragility index ‘m’ of the given system falls below 16. This clearly indicates that the given system is strong liquid with excellent glass forming ability (GFA).

Stoichiometric composition of thin-film surface structures and its influence on the functional characteristics as regards gyroscopic devices

2020 ◽  
pp. 78-90
Author(s):  
M. A. Tit ◽  
S. N. Belyaev
Keyword(s):  
Thin Film ◽  
Titanium Nitride ◽  
Niobium Carbide ◽  
Structural Phase ◽  
Stoichiometric Composition ◽  
Film Surface ◽  
Surface Structures ◽  
Functional Surface ◽  
Base Surface ◽  
Thin Film Surface

This article considers the research results of the effect of stoichiometry on the properties of titanium nitride thin-film coatings of the float and electrostatic gyroscopes. It presents the results of tests of such mechanical and optical characteristics of titanium nitride thin-film structures as microhardness, resistance to wear and friction, and image contrast determined by the reflection coefficients of a titanium nitride base surface and a raster pattern formed by local laser oxidation. When making a rotor of a cryogenic gyroscope, the prospects of use and technological methods for the formation of functional surface structures of niobium carbide and nitride are considered. It is shown that during the formation of coatings of the required composition, the most important is the thermodynamic estimation of possible interactions. These interactions allow us to accomplish the structural-phase modification of the material, which is determined by the complex of possible topochemical reactions leading to the formation of compounds, including non-stoichiometric composition.

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