Topic
Glass transition
About: Glass transition is a research topic. Over the lifetime, 40774 publications have been published within this topic receiving 1002766 citations. The topic is also known as: glass–liquid transition.
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TL;DR: In this paper, the authors derived a relation between the diffusion constant D in a liquid of hard spheres and the free volume vf, which is based on the concept that statistical redistribution of free volume occasionally opens up voids large enough for diffusive displacement.
Abstract: We have derived, by using simple considerations, a relation between the diffusion constant D in a liquid of hard spheres and the ``free volume'' vf. This derivation is based on the concept that statistical redistribution of the free volume occasionally opens up voids large enough for diffusive displacement. The relation is D=A exp[−γv*/vf], where v* is the minimum required volume of the void and A and γ are constants. This equation is of the same form as Doolittle's [J. Appl. Phys. 22, 1471 (1951)] empirical relation between the fluidity φ of simple hydrocarbons and their free volume. It has been shown [Williams, Landel, and Ferry, J. Am. Chem. Soc. 77, 3701 (1955)] that the Doolittle equation also can be adapted to describe the abrupt decrease in molecular kinetic constants with decreasing temperature that accompanies the glass transition in certain liquids. Our result predicts that even the simplest liquids would go through this glass transition if sufficiently undercooled and crystallization did not oc...
3,365 citations
TL;DR: In this article, the properties of a new family of metallic alloys which exhibit excellent glass forming ability are reported, where the critical cooling rate to retain the glassy phase is of the order of 10 K/s or less.
Abstract: We report on the properties of one example of a new family of metallic alloys which exhibit excellent glass forming ability. The critical cooling rate to retain the glassy phase is of the order of 10 K/s or less. Large samples in the form of rods ranging up to 14 mm in diameter have been prepared by casting in silica containers. The undercooled liquid alloy has been studied over a wide range of temperatures between the glass transition temperature and the thermodynamic melting point of the equilibrium crystalline alloy using scanning calorimetry. Crystallization of the material has been studied. Some characteristic properties of the new material are presented. The origins of exceptional glass forming ability of these new alloys are discussed.
2,305 citations
01 Jan 2007
TL;DR: Theoretical models and simulations of polymers have been used to study the molecular dynamics of different molecular architectures and properties of polymeric networks and gels as discussed by the authors, including the properties of different types of networks.
Abstract: Preface to the Second Edition. -Preface to the First Edition. -STRUCTURE. -Chain Structures. -Names, Acronyms, Classes, and Structures of Some Important Polymers. -THEORY. -The Rotational Isomeric State Model. -Computational Parameters. -Theoretical Models and Simulations of Polymer Chains. -Scaling, Exponents, and Fractal Dimensions. -THERMODYNAMIC PROPERTIES. -Densities, Coefficients of Thermal Expansion, and Compressibilities of Amorphous Polymers. -Thermodynamic Properties of Proteins. -Heat Capacities of Polymers. -Thermal Conductivity. -Thermodynamic Quantities Governing Melting. -The Glass Temperature. -Sub-Tg Transitions. -Polymer-Solvent Interaction Parameter c. -Theta Temperatures. -Solubility Parameters. -Mark-Houwink-Staudinger-Sakurada Constants. -Polymers and Supercritical Fluids. -Thermodynamics of Polymer Blends. -SPECTROSCOPY. -NMR Spectroscopy of Polymers. -Broadband Dielectric Spectroscopy to Study the Molecular Dynamics of Polymers Having Different Molecular Architectures. -Group Frequency Assignments for Major Infrared Bands Observed in Common Synthetic Polymers. -Small Angle Neutron and X-Ray Scattering. -MECHANICAL PROPERTIES. -Mechanical Properties. -Chain Dimensions and Entanglement Spacings. -Temperature Dependences of the Viscoelastic Response of Polymer Systems. -Adhesives. -Some Mechanical Properties of Typical Polymer-Based Composites. -Polymer Networks and Gels. -Force Spectroscopy of Polymers: Beyond Single Chain Mechanics. -REINFORCING PHASES. -Carbon Black. -Properties of Polymers Reinforced with Silica. -Physical Properties of Polymer/Clay Nanocomposites. -Polyhedral Oligomeric Silsesquioxane (POSS). -Carbon Nanotube Polymer Composites: Recent Developments in Mechanical Properties. -Reinforcement Theories. -CRYSTALLINITY AND MORPHOLOGY. -Densities of Amorphous and Crystalline Polymers. -Unit Cell Information on Some Important Polymers. -Crystallization Kinetics of Polymers. -Block Copolymer Melts. -Polymer Liquid Crystals and Their Blends. -The Emergence of a New Macromolecular Architecture: 'The Dendritic State'. -Polyrotaxanes. -Foldamers: Nanoscale Shape Control at the Interface Between Small Molecules and High Polymers. -Recent Advances in Supramolecular Polymers. -ELECTRO-OPTICAL AND MAGNETIC PROPERTIES. -Conducting Polymers: Electrical Conductivity. -Conjugated Polymer Electroluminescence. -Magnetic, Piezoelectric, Pyroelectric, and Ferroelectric Properties of Synthetic and Biological Polymers. -Nonlinear Optical Properties of Polymers. -Refractive Index, Stress-Optical Coefficient, and Optical Configuration Parameter of Polymers. -RESPONSES TO RADIATION, HEAT, AND CHEMICAL AGENTS. -Ultraviolet Radiation and Polymers. -The Effects of Electron Beam and g-Irradiation on Polymeric Materials. -Flammability. -Thermal-Oxidative Stability and Degradation of Polymers. -Synthetic Biodegradable Polymers for Medical Applications. -Biodegradability of Polymers. -Properties of Photoresist Polymers. -Pyrolyzability of Preceramic Polymers. -OTHER PROPERTIES. -Surface and Interfacial Properties. -Acoustic Properties. -Permeability of Polymers to Gases and Vapors. -MISCELLANEOUS. -Definitions. -Units and Conversion Factors. -Subject Index
2,230 citations
TL;DR: In this paper, the authors designed epoxy networks that can rearrange their topology by exchange reactions without depolymerization, and showed that they are insoluble and processable.
Abstract: Permanently cross-linked materials have outstanding mechanical properties and solvent resistance, but they cannot be processed and reshaped once synthesized Non–cross-linked polymers and those with reversible cross-links are processable, but they are soluble We designed epoxy networks that can rearrange their topology by exchange reactions without depolymerization and showed that they are insoluble and processable Unlike organic compounds and polymers whose viscosity varies abruptly near the glass transition, these networks show Arrhenius-like gradual viscosity variations like those of vitreous silica Like silica, the materials can be wrought and welded to make complex objects by local heating without the use of molds The concept of a glass made by reversible topology freezing in epoxy networks can be readily scaled up for applications and generalized to other chemistries
1,901 citations
TL;DR: The glass-forming tendency of a given material is determined principally by a set of factors which can be specified to some extent in the laboratory, namely, the cooling rate, - T, the liquid volume, v], and the seed density, ps and depending upon the materials constants: the reduced crystal-liquid interfacial tension, α the fraction, f, of acceptor sites in the crystal surface, and the reduced glass temperature, Trg.
Abstract: Summary Generally substances are more stable in a crystalline than in a glassy state. Therefore, to form a glass, crystallization must be bypassed. Under certain conditions, the melts of many substances can be cooled to the glass state. Whether or not the melt of a given material forms a glass is determined principally by a set of factors which can be specified to some extent in the laboratory, namely, the cooling rate, - T, the liquid volume, v], and the seed density, ps and upon a set of materials constants: the reduced crystal–liquid interfacial tension, α the fraction, f, of acceptor sites in the crystal surface, and the reduced glass temperature, Trg . The glass-forming tendency will be greater the larger are - T and Trg and the smaller are v]. ps, and f. The number and variety of substances which have been prepared in a glassy or ‘amorphous solid’ form have been greatly increased with techniques in which the material is condensed from solution on to a surface held well below its glass temperature. T...
1,896 citations