Experimental Tests of a Theoretically Predicted Noncausal Correlation between Dynamics and Thermodynamics in Glass-forming Polymer Melts

2021 ◽  
Author(s):  
Baicheng Mei ◽  
Yuxing Zhou ◽  
Kenneth S. Schweizer
Keyword(s):  
Polymer Melts ◽  
Experimental Tests ◽  
Glass Forming

scholarly journals Influence of Branching on the Configurational and Dynamical Properties of Entangled Polymer Melts

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1045 ◽  
Author(s):  
Alexandros Chremos ◽  
Jack F. Douglas
Keyword(s):  
Correlation Function ◽  
Molecular Mass ◽  
Polymer Melts ◽  
Pair Correlation ◽  
Polymer Melt ◽  
Coarse Grained ◽  
Density Correlation ◽  
Glass Forming ◽  
Entangled Polymer ◽  
Simulation Results

We probe the influence of branching on the configurational, packing, and density correlation function properties of polymer melts of linear and star polymers, with emphasis on molecular masses larger than the entanglement molecular mass of linear chains. In particular, we calculate the conformational properties of these polymers, such as the hydrodynamic radius R h , packing length p, pair correlation function g ( r ) , and polymer center of mass self-diffusion coefficient, D, with the use of coarse-grained molecular dynamics simulations. Our simulation results reproduce the phenomenology of simulated linear and branched polymers, and we attempt to understand our observations based on a combination of hydrodynamic and thermodynamic modeling. We introduce a model of “entanglement” phenomenon in high molecular mass polymers that assumes polymers can viewed in a coarse-grained sense as “soft” particles and, correspondingly, we model the emergence of heterogeneous dynamics in polymeric glass-forming liquids to occur in a fashion similar to glass-forming liquids in which the molecules have soft repulsive interactions. Based on this novel perspective of polymer melt dynamics, we propose a functional form for D that can describe our simulation results for both star and linear polymers, covering both the unentangled to entangled polymer melt regimes.

Understanding Activation Volume in Glass-Forming Polymer Melts via Generalized Entropy Theory

2020 ◽  
Vol 53 (17) ◽  
pp. 7239-7252 ◽  
Author(s):  
Wen-Sheng Xu ◽  
Jack F. Douglas ◽  
Wenjie Xia ◽  
Xiaolei Xu
Keyword(s):  
Activation Volume ◽  
Polymer Melts ◽  
Entropy Theory ◽  
Generalized Entropy ◽  
Glass Forming

Numerical Model of Thermal Field Developed in Fe67Cr4Mo4Ga4P12B5C4 Bulk Amorphous Alloy Processing

2016 ◽  
Vol 254 ◽  
pp. 249-254
Author(s):  
Bogdan Radu ◽  
Dragoş Buzdugan ◽  
Cosmin Codrean ◽  
Viorel Aurel Şerban ◽  
George Vișan
Keyword(s):  
Amorphous Alloy ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Thermal Field ◽  
Good Control ◽  
Experimental Tests ◽  
Glass Forming Ability ◽  
Bulk Amorphous Alloy ◽  
Bulk Amorphous Alloys ◽  
Glass Forming

Metallic amorphous materials were developed during 80’s as new materials, with very interesting industrial properties (heat conductivity, magnetic properties, fusion temperature, corrosion resistance, etc.). Technology to obtain these materials, based on very rapid cooling of a melted alloy with glass forming ability, has limitations for the dimensions of the products that can be obtained with amorphous structure (thickness has to be very thin), which can be overpassed by development of bulk amorphous alloys with high glass forming ability and good control of the cooling speed. Numerical modeling of thermal field during ultra-high cooling, developed in researches presented in this paper, allows researchers to estimate the results of applying in reality certain cooling conditions. This model will help developers of bulk amorphous alloys in checking if are ensured conditions to obtain an amorphous alloy with fewer experimental tests, less time and low expenses.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

The effect of an aluminum heat-sink layer on the laser-induced amorphization of SiOx/TeGeSn/SiOx phase-change recording films

1989 ◽  
Vol 47 ◽  
pp. 574-575
Author(s):  
Matthew R. Libera ◽  
Martin Chen
Keyword(s):  
Thin Film ◽  
Phase Change ◽  
Heat Sink ◽  
Multilayer Film ◽  
Glassy Phase ◽  
Film Structure ◽  
Glass Forming ◽  
Active Storage ◽  
Dielectric Layers ◽  
Amorphous States

Phase-change erasable optical storage is based on the ability to switch a micron-sized region of a thin film between the crystalline and amorphous states using a diffraction-limited laser as a heat source. A bit of information can be represented as an amorphous spot on a crystalline background, and the two states can be optically identified by their different reflectivities. In a typical multilayer thin-film structure the active (storage) layer is sandwiched between one or more dielectric layers. The dielectric layers provide physical containment and act as a heat sink. A viable phase-change medium must be able to quench to the glassy phase after melting, and this requires proper tailoring of the thermal properties of the multilayer film. The present research studies one particular multilayer structure and shows the effect of an additional aluminum layer on the glass-forming ability.

Crystallization in Al 88 RE 8 Ni 4 glass-forming alloys

2002 ◽  
Vol 82 (12) ◽  
pp. 2483-2497 ◽  
Author(s):  
T. K. Croat ◽  
A. K. Gangopadhyay ◽  
K. F. K Elton
Keyword(s):  
Glass Forming
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