Modeling of thermal studies on melt quenched Ge18Bi4Se78 chalcogenide

2021 ◽  
Author(s):  
Ahmed M. Abdel Hakeem ◽  
M. M. Abd El-Raheem ◽  
Mostafa Mohamed Wakkad ◽  
Hany Mohamed ◽  
Hazem Mahmoud Ali ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crystallization Process ◽  
Thermal Studies ◽  
Experimental Results ◽  
Avrami Exponent ◽  
Topological Constraints ◽  
Isothermal Conditions ◽  
Dta Curves

Abstract The crystallization characteristics for Ge18Bi4Se78 glass are studied in this work by means of DTA under the non-isothermal conditions. One stage endothermic glass transition and one exothermic crystallization are observed in the DTA curves. The results of topological constraints for Ge18Bi4Se78 glass show that the calculated value of glass transition temperature (Tg) is very close to that of the experimental results. The as-prepared as well as the annealed samples are examined using XRD, EDX, SEM techniques. Avrami exponent reveals the complicated stage of growth. Many models are used to estimate the activation energies for glass transition (Eg) and crystallization (Ec). The crystallization process found to be described by the Sestak- Berggren SB(M,N) model.

Nanocomposite Epoxy Resin for SiC Module

2011 ◽  
Vol 2011 (HITEN) ◽  
pp. 000196-000200 ◽  
Author(s):  
Kenji Okamoto ◽  
Yuji Takematsu ◽  
Miyako Hitomi ◽  
Yoshinari Ikeda ◽  
Yoshikazu Takahashi
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Epoxy Resin ◽  
Molecular Motion ◽  
Experimental Results ◽  
Power Module ◽  
Operation Temperature ◽  
Thermal Stability Of

There is a demand to improve the thermal stability of epoxy molding resins used in the power module of SiC power chips operating at temperatures of 200°C or more. This paper describes a technique for increasing the thermal stability of the resin by decreasing molecular motion through the addition of nanofiller. The experimental results showed that the glass transition temperature (Tg) of the epoxy resin increased by approximately 30°C when the silica nanofiller was added. The epoxy resin added nanofiller was investigated in order to achieve the operation temperature 200°C of power module.

Design of low dielectric constant polybenzoxazine nanocomposite using mesoporous mullite

2016 ◽  
Vol 29 (2) ◽  
pp. 141-150 ◽  
Author(s):  
K Ilango ◽  
P Prabunathan ◽  
E Satheeshkumar ◽  
P Manohar
Keyword(s):  
Thermal Stability ◽  
Dielectric Constant ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Thermal Studies ◽  
Microscopic Analysis ◽  
Low Dielectric Constant ◽  
Low Dielectric ◽  
Porous Morphology

In this present work, porous mullites (PM0–5) were synthesized through a template-assisted method using various weight percentages of pluronic (P-123). PM5 obtained using 10 wt% of P-123 was found to show maximum porosity (3.8 Å) and low dielectric constant value (2.4). PM5 was functionalized using glycidyl-terminated silane and denoted as FPM and various weight percentages of FPM were reinforced with polybenzoxazine (PBZ) matrix in order to develop FPM/PBZ nanocomposites. The thermal studies indicate that 1.5 wt% of FPM/PBZ nanocomposite showed improved thermal stability with 34% char yield at 800°C and 162°C as glass transition temperature. It also exhibits low dielectric constant (2.6) than that of the neat PBZ matrix and other FPM/PBZ nanocomposites. The microscopic analysis confirms the homogenous dispersion of FPM into the PBZ polymer that has a porous morphology. The results suggest that the as-synthesized mesoporous mullite with low dielectric constant ( k), synthesized via template-assisted method can be used as a reinforcement to decrease the dielectric constant of polymeric material, which is of industrial significance.

Study on the Composites Epoxy Resin/Nano-TiO2/Polyester

2013 ◽  
Vol 787 ◽  
pp. 408-412
Author(s):  
Jiao Yan Ai ◽  
Quan Chen ◽  
Xiao Bo Wang
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Epoxy Resin ◽  
Diethylene Glycol ◽  
Epoxy Resins ◽  
Experimental Results ◽  
Hydroxybenzoic Acid ◽  
Suitable Amount

Two kinds of polyester bis (p-hydroxybenzoic acid) butanediolatepolyester (BDPET) and bis (p-hydroxybenzoic acid) diethylene glycol (DGPET) were synthesized through melting transesterification reaction.Then the epoxy resins were modified with BDPET or DGPET,and nanoTiO2. The composites were characterized by DSC and SEM. The experimental results showed that the polyester can act as an effective toughening modifier for the epoxy resin. The mechanical properties of the composites were greatly improved and reached to the maxium at 4wt.%PET. The PET/EP system modified by adding suitable amount of nanoTiO2have better performance.The glass transition temperature (Tg) of PET/EP and nanoTiO2/PET/EP system improved about 20°Cand 27.8°C,respectively.

scholarly journals Used of Chemically Modified Titanium Dioxide Particles to Mediate the Non-isothermal Cold Crystallization of Poly(latic acid)

2020 ◽  
Vol 64 (2) ◽  
Author(s):  
J. A. Gonzalez-Calderon ◽  
Guadalupe Mendoza ◽  
M. G. Peña-Juárez ◽  
Elias Perez
Keyword(s):  
Titanium Dioxide ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Chemical Modification ◽  
Dicarboxylic Acid ◽  
Crystallization Process ◽  
Polymer Chains ◽  
Cold Crystallization ◽  
Crystal Formation

In this work, the effect of the chemical modification of titanium dioxide particles on the non-isothermal crystallization process of polylactic acid (PLA) was studied. Cold crystallization in some polymers occurs above the glass transition temperature (Tg) when the polymer chains gain sufficient mobility to organize themselves into the ordered structure (i.e. the crystal structure) by folding the chains. Cold crystallization in general is caused by the ordering of the molecular chains in the crystalline PLA due to the increased mobility during heating. Through an analysis of the cool crystallization process in DSC at different cooling rates, it was observed that the behavior of PLA and its composites made with titanium dioxide, neat and functionalized with dicarboxylic acids, can be described through the models used for crystallization of the polymer carrying out during cooling, such as Mo’s and Jeziorny’s model. In addition, it was determined that the chemical modification of TiO2 performed with silane increases the crystallization rate in the last step of the process; while the chemical modification with dicarboxylic acid has an accelerated effect on the crystal formation process attributed to the affinity between the aliphatic part of this group and the polymer chains. Also, it was shown that the inclusion of the silanized particles has no effect on the energy requirement compared to the pure PLA process; however, the addition of particles with the dicarboxylic acid decreases the energy value required to complete the crystalline state due to affinity at the surface to immobilize the polymer chains. Finally, it is emphasized that the activation energy required to perform the crystallization of PLA and its composites has positive values, which is an indicator that the crystallization was performed while heating, after reaching and passing the glass transition temperature and before melting.

Thermosetting Polyimides with Improved Impact Toughness and Excellent Thermal and Thermo-Oxidative Stability

2001 ◽  
Vol 13 (4) ◽  
pp. 287-299 ◽  
Author(s):  
T J Xiao ◽  
S Q Gao ◽  
A J Hu ◽  
X C Wang ◽  
S Y Yang
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Impact Toughness ◽  
Impact Strength ◽  
Oxidative Stability ◽  
Experimental Results ◽  
High Glass Transition Temperature ◽  
Polyimide Matrix ◽  
Thermosetting Polyimides

Thermoset polyimides were prepared by thermally curing B-staged endcapped polyimide resins that were obtained by thermally baking PMR polyimide matrix resins. The polyimide matrix resins were prepared by incorporating flexible ether-bridged aromatic segments [–Ar–O–Ar–] into PMR polyimide backbone to improve their processability and impact toughness. Experimental results indicated that the B-staged polyimide resins possessed adjustable and easily controllable thermal processability which ensure that thermoset polyimides are produced with improved impact strength and high glass transition temperature compared with PMR-15. Thermal and thermo-oxidative stability as well as hygrothermal resistance of the thermoset polyimides were also systemically investigated.

Glass transition temperature and topological constraints of sodium borophosphate glass-forming liquids

2013 ◽  
Vol 139 (12) ◽  
pp. 124502 ◽  
Author(s):  
Qi Jiang ◽  
Huidan Zeng ◽  
Zhao Liu ◽  
Jing Ren ◽  
Guorong Chen ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Topological Constraints ◽  
Glass Forming ◽  
Borophosphate Glass

scholarly journals A topologically driven glass in ring polymers

2016 ◽  
Vol 113 (19) ◽  
pp. 5195-5200 ◽  
Author(s):  
Davide Michieletto ◽  
Matthew S. Turner
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Dynamic Properties ◽  
Polymer Physics ◽  
Concentrated Solutions ◽  
Polymeric Systems ◽  
Topological Constraints ◽  
Ring Polymers

The static and dynamic properties of ring polymers in concentrated solutions remains one of the last deep unsolved questions in polymer physics. At the same time, the nature of the glass transition in polymeric systems is also not well understood. In this work, we study a novel glass transition in systems made of circular polymers by exploiting the topological constraints that are conjectured to populate concentrated solutions of rings. We show that such rings strongly interpenetrate through one another, generating an extensive network of topological interactions that dramatically affects their dynamics. We show that a kinetically arrested state can be induced by randomly pinning a small fraction of the rings. This occurs well above the classical glass transition temperature at which microscopic mobility is lost. Our work both demonstrates the existence of long-lived inter-ring penetrations and realizes a novel, topologically induced, glass transition.

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