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Topic: Glass transition

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	Glass transition temperature - Wikipedia, the free encyclopedia
		This means that glass transition is not merely a kinetic effect, i.e.
		In contrast to the melting points of crystalline materials the glass transition temperature is therefore somewhat dependent on the time-scale of the imposed change.
		is cooling-rate (or frequency) dependent as the glass is formed, the glass transition is not considered a true thermodynamic phase transition by many in the field.
	en.wikipedia.org /wiki/Glass_transition (1276 words)

	Encyclopedia :: encyclopedia : Glass (Site not responding. Last check: 2007-10-31)
		The transparency is due to an absence of electronic transition states in the range of visible light, and to the fact that such glass is homogeneous on all length scales greater than about a wavelength of visible light (inhomogeneities cause light to be scattered, breaking up any coherent image transmission).
		Glass is produced in standard metric thicknesses of 2, 3, 4, 5, 6, 8, 10, 12, 15, 19 and 22 mm.
		Glass is very durable, but an evacuated glazing unit cannot be effective forever, even in ideal conditions, since it is inevitable that eventually enough gas molecules from the air will permeate through the glass and into the void that its insulative properties are destroyed.
	www.hallencyclopedia.com /Glass (4513 words)

	GLASS TRANSITION
		The glass transition can be detected as the temperature where the storage modulus starts to fall rapidly with increasing temperature from the very high value in the glassy state.
		The glass transition temperature is dependent on the water content of the food material, similarly to the influence of plasticisers on synthetic polymers.
		The glass transition temperature denoted by Tg' is the glass transition temperature of the unfrozen portion of a maximally freeze concentrated unfrozen matrix.
	www.rpi.edu /dept/chem-eng/Biotech-Environ/Porto/CRISTINA/TG.HTM (1383 words)

	Is glass liquid or solid?
		It is sometimes said that glass in very old churches is thicker at the bottom than at the top because glass is a liquid, and so over several centuries it has flowed towards the bottom.
		Glass can be made from pure silica, but fused silica has a high glass transition point at around 1200° C which makes it difficult to mould into panes or bottles.
		Glass such as Pyrex (used for test-tubes and ovenware) is usually based on boro-silicates or alumino-silicates, which withstand heating better and typically have a higher glass transition temperature.
	math.ucr.edu /home/baez/physics/General/Glass/glass.html (2574 words)

	Is glass liquid or solid?
		It is sometimes said that glass in very old churches is thicker at the bottom than at the top because glass is a liquid and over several centuries it has flowed towards the bottom.
		Glass such as Pyrex used for test-tubes, ovenware etc. is usually based on boro-silicates or alumino-silicates which withstand heating better and typically have a higher glass transition temperature.
		There is no clear answer to the question "Is glass solid or liquid?." In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid or simply that glass is another state of matter which is neither liquid or solid.
	www.amsky.com /atm/miscellaneous/glass/glass.html (2624 words)

	MDC Vacuum Products Corp.- Glass Components- Introduction
		Five glass seal geometries are offered, these include flange to glass with open end, flange to flange with glass transition, flange to glass with sealed end, flange to glass with open end and flexible bellows transition and glass to glass with flexible bellows transition.
		The flange to glass with open end versions are designed for installation to a flanged system on one end and to either a quick disconnect elastomer sealed compression fitting or for fusing directly to a glass tube, apparatus or system.
		Flange to glass adapters with a sealed glass end can be mounted to a flanged system and provide a bell jar like glass enclosure that is ideally suited for experiments requiring the transparency of glass.
	www.mdcvacuum.com /searchs/doc/GlassComponents-Intro.htm (397 words)

	University of Cincinnati News: Researchers Create Glass Within a Glass
		Boolchand says the unusual glass forming properties of silver iodide relate to the mobility of silver ions and the ability of silver iodide to serve as a solid electrolyte.
		The University of Cincinnati researchers also saw the unusual glass transition in silver selenide, and they are now extending their work on both the experimental and theoretical fronts.
		Their calculations can predict where the glass transition will occur, and they are now testing new combinations of solid electrolytes and base glasses, including glasses which normally are insulators rather than semiconductors.
	www.uc.edu /news/agglass.htm (476 words)

	Glass Transition
		Above the glass transition temperature there is an increase to the slope of the specific volume vs. temperature function.
		The phenomenon called "the glass transition" is somewhat of a misnomer since the term 'transition' implies an equilibrium phenomenon that is invariant to the speed of the heating or cooling.
		The crosslinking reaction of a thermoset polymer resin raises the glass transition temperature.
	web.umr.edu /~wlf/Bulk/glasstrans.html (610 words)

	DoITPoMS TLP - The Glass Transition in Polymers
		For many polymers the transition between the solid and liquid states is rather diffuse and difficult to pinpoint.
		The second stage of the phase transition is the growth of the nucleated seeds.
		It is possible to calculate a value for the glass transition temperature by measuring the elastic modulus of the polymer as a function of the temperature, for example by using a torsion pendulum.
	www.doitpoms.ac.uk /tlplib/glass-transition/printall.php (3317 words)

	Non-oxide & heavy-metal oxide glass fibers - IR Fiber Review
		A distinctive difference between these glasses and the other IR fiber glasses is that they do not transmit well in the visible region and their refractive indices are quite high.
		In general, chalcogenide glass fibers have proven to be an excellent candidate for evanescent wave fiber sensors and for IR fiber image bundles.
		Chalcogenide glass is made by combining highly purified (>6 nines purity) raw elements in an ampoule which is heated in a rocking furnace for about 10 hours.
	irfibers.rutgers.edu /ir_rev_glass.html (1717 words)

	glass transition (Site not responding. Last check: 2007-10-31)
		The glass transition is common in quite different and important classes of materials (for example, polymers, oxides, chalcogenides, metals, and molecular solids), and continues to attract much attention from a fundamental and a practical point of view.
		Experimental results for the apparent activation energy that is measured when approaching the glass transition from below, using both TSDC and dielectric permittivity, record a very high activation energy (enthalpy) at temperatures slightly below the glass transition (a transition in polymers).
		Near the glass transition the change of configurational energy with temperature is very large and causes the observation of an anomalously high apparent activation energy.
	www.elp.uji.es /juan_home/research/glass_transition.htm (341 words)

	Translational hydration water dynamics drives the protein glass transition Biophysical Journal - Find Articles
		Experimental and computer simulation studies have revealed the presence of a glasslike transition in the internal dynamics of hydrated proteins at ~200 K involving an increase of the amplitude of anharmonic dynamics.
		The results show that the protein transition is driven by a dynamical transition in the hydration water that induces increased fluctuations primarily in side chains in the external regions of the protein.
		The water transition involves activation of translational diffusion and occurs even in simulations where the protein atoms are held fixed.
	www.findarticles.com /p/articles/mi_qa3938/is_200309/ai_n9288188 (769 words)

	Condensed Matter Research at Brandeis - Glasses (Site not responding. Last check: 2007-10-31)
		The nature of this transition is one of the outstanding puzzles in condensed matter physics.
		The notion of an entropy vanishing transition underlying the glass transition was proposed a few decades ago by Adam and Gibbs.
		It is tempting to speculate that such structures are forced into supercooled liquids by the frustrations inherent in the system and that the glass transition owes its origin to an underlying instability towards the disappearance of these structures.
	matter.cc.brandeis.edu /research/glasses/transition (298 words)

	Glass Transition
		Upon further cooling, the rotational motions slow down and eventually freeze in what is called an orientational glass transition.
		Because the molecules lie on a lattice, this glass transition should be much easier to model theoretically that the more complicated structural glass transition seen in supercooled liquids.
		We have studied the cyclo-octanol and ethanol, the latter being unique in that it is quite simple to prepare it either as a supercooled liquid or as a rotator phase crystal.
	www.pa.msu.edu /cmp/birge-group/pages/researchd.htm (337 words)

	Glass Transition
		The temperature at which the transition in the amorphous regions between the glassy and rubbery state occurs is called the glass transition temperature.
		The glass transition temperature of the gum is somewhere between 0
		because the glass phase is not at equilibrium.
	www.lasalle.edu /academ/chem/ms/polymersRus/Resources/GlassTrans.htm (530 words)

	What are Colloidal Glasses?
		What's weird is that structurally, glasses are the same as liquids -- if you just look at a microscopic snapshot of the position of the atoms, you can't tell the difference (whereas it's really obvious that a crystal is something different from a liquid).
		A simple definition of a glass is a liquid with a viscosity that is 10,000,000,000,000 times larger than the viscosity of water.
		It has also been found that the glass transition is related to the suspension of insect life in a desert during a drought.
	www.deas.harvard.edu /projects/weitzlab/research/glasses.html (1477 words)

	Glass Transition
		The glass transition is a transition which happens to amorphous polymers; that is, polymers whose chains are not arranged in ordered crystals, but are just strewn around in any old fashion, even though they are in the solid state.
		To be sure, by the time we get down to the glass transition temperature, it is already too cold for the polymer molecules, tangled up in each other as they are, to move any distance in one direction.
		The only change we see at the glass transition temperature is an increase in the slope, which means, of course, that we have an increase in heat capacity.
	www.pslc.ws /macrog/tg.htm (2859 words)

	PHYSICAL PARAMETERS OF COOLING IN CRYONICS
		Glasses have lower thermal conductivity than crystalline materials, which makes the problem serious for fully vitrified cryonics patients than for partially frozen cryonics patients, despite the lower thermal expansion of glasses.
		The critical difference lies in the fact that metals and even non-biological glasses cohere by means of stronger (usually covalent) bonds than are found in the glasses formed by biologically vitrifying cryoprotectants.
		Metalworkers have long known that internal stresses in metals that have been subjected to nonuniformly cooling or to the plastic deformation of "cold working" (rolling, stamping, pressing, etc.) can be relieved of that stress by a temporary rewarming until uniform temperature is obtained -- a process known as annealing.
	www.benbest.com /cryonics/cooling.html (5625 words)

	Glass (disambiguation) - Wikipedia, the free encyclopedia
		Glass (EP), a 2003 EP by The Sea and Cake
		Glassing, verb, violent attack with glass used as a weapon
		This is a disambiguation page: a list of articles associated with the same title.
	en.wikipedia.org /wiki/Glass_(disambiguation) (109 words)

	Nonequilibrium Phase and Glass Transition Behavior of [beta]-Lactoglobulin, The Biophysical Journal - Find Articles
		For small applied stresses, the material has the solidlike characteristics of a glass with the particles forming jammed structures that are stress bearing.
		As shortranged attractive interactions between particles are introduced (9), the attraction first "melts" the glass and then leads to the formation of a qualitatively different glassy state.
		Earlier research (13) examined the colloidal glass transition behavior of a globular protein (bovine serum albumin) where there was a net repulsion between the protein globules.
	www.findarticles.com /p/articles/mi_qa3938/is_200508/ai_n14899372 (850 words)

	Probing Surface Dynamics near the Glass Transition by Correlation Spectroscopy with Coherent X-rays - ESRF (Site not responding. Last check: 2007-10-31)
		The right-hand scattering image from the glass appears "speckled" due to the static surface and the coherent X-ray beam employed.
		Whether that is a signature of a "surface glass transition", a Q-dependant viscosity, or related to other phenomena is currently under investigation.
		Ongoing studies also include the influence of thermal history and ageing of the glass surface as well as non-ergodicity effects.
	www.esrf.fr /NewsAndEvents/Spotlight/spotlight14glasstransition (500 words)

	Glass Transition Temperature — Tg (Site not responding. Last check: 2007-10-31)
		Glass Transition Temperature — Tg Glass Transition Temperature — Tg
		Amorphous (noncrystalline) polymeric solids are either glasses or rubbers.
		The glass transition temperature (Tg) separates glassy from rubbery behavior.
	www-ee.technion.ac.il /people/nir/Glass_Transition_Temperature.htm (281 words)

	Glass transition temperature (Site not responding. Last check: 2007-10-31)
		In glasses (including amorphous metals and gels) Tg is related to the energy required break and re-form covalent bonds in a less than perfect (may be regarded as understatement) 3D lattice of covalent bonds.
		The Space Shuttle Challenger disaster was caused by a rubber that was below its glass transition temperature thus could not flex adequately to form proper seal around one of the two rocket boosters.
		Correlations of norbornenyl crosslinked polymide resin structures with resin thermo-oxidative stability, resin glass transition temperature and compos...
	www.freeglossary.com /Glass_transition_temperature (404 words)

	Translational Hydration Water Dynamics Drives the Protein Glass Transition -- Tournier et al. 85 (3): 1871 -- ...
		a characteristic of the glass transition (Angell, 1995
		Fitter, J. The temperature dependence of internal molecular motions in hydrated and dry alpha-amylase: the role of hydration water in the dynamical transition of proteins.
		Hydrated myoglobin's anharmonic fluctuations are not primarily due to dihedral transitions.
	www.biophysj.org /cgi/content/full/85/3/1871 (3013 words)

	Session ZC17 - Glass Transition and Glasses II.
		The simulated glass transition temperature (Tg) of the solution was computed to evaluate the quality of the model; the computed value of 241K was in fair agreement with the experimental value of 232 K. It was concluded that most of the water molecules are connected to more than one glucose molecule by hydrogen bonds.
		Using a new microscopic model of covalently-bonded glasses which incorporates the electronic states involved in the formation of bonds, we investigate the properties of the supercooled liquid state.
		The transition may be related to the onset of rigidity.
	flux.aps.org /meetings/YR99/CENT99/abs/S9550.html (1818 words)

	E401: Localization And The Glass Transition (Site not responding. Last check: 2007-10-31)
		Disorder-induced localized excitations (tunneling modes, soft harmonic vibrations) are believed to play a dominant role in the thermodynamics and transport properties of glasses at low temperature.
		We present evidence from computer simulations that the glass transition in two simple model systems is closely associated with a transition temperature, below which all unstable INM's become localized.
		This localization, analogous to the phenomenon of Anderson localization of electronic states in disordered solids, is a possible mechanism for the change in diffusion mechanism (from continuous flow to localized activated hopping) that is speculated to occur in fragile glass formers at a temperature above.
	www.hwi.buffalo.edu /ACA/ACA97/abstracts/text/E401.html (169 words)

	The Thermophysical Properties of Bulk Metallic Glass-Forming Liquids
		Crystallization kinetics is very complex, especially in the vicinity of the glass transition, due to the influence of phase separation and the decoupling of the diffusion constants of the different species.
		These bulk metallic glass (BMG) formers show high thermal stability of supercooled (undercooled) liquid with respect to crystallization, enabling the study of the thermophysical properties of metallic melts in the supercooled state and the exploration of their properties and possible applications.
		The fact that the glass transition temperature is a kinetic temperature makes the design and the interpretation of experiments that probe atomic motion difficult.
	www.tms.org /pubs/journals/JOM/0007/Busch-0007.html (3243 words)

	Glass Transition of Soy Globulins Using Differential Scanning Calorimetry and Mechanical Spectrometry (Site not responding. Last check: 2007-10-31)
		The glass transition of soy 7S and 11S globulin fractions, isolated from defatted soy flour by the method of Thanh and Shibasaki (J.
		Both proteins showed to be plasticizable by water, suggesting that their hydrophilic domains play an important role in determining their calorimetric and rheological properties.
		Due to the presence of a contaminating 7S fraction in the 11S fraction, and vice versa, the DSC and mechanical spectrometry scans from both fractions showed two different glass transitions which correspond to the 7S and 11S globulins, respectively.
	pubs.acs.org /cgi-bin/abstract.cgi/bipret/1997/13/i05/abs/bp9700519.html (241 words)

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