Sneaking up on the glassy transition of water

ScienceDaily (Sep. 27, 2011) — Researchers claim to have settled a long-standing debate over the exact temperature at which water transforms into an exotic glass-like substance believed to be present in comets and other icy objects in the outer solar system, as well as in the coldest regions of Earth's atmosphere.

Rapid cooling of ordinary water or compression of ordinary ice: either of these can transform normal H2O into an exotic substance that resembles glass in its transparency, brittleness, hardness, and luster. Unlike everyday ice, which has a highly organized crystalline structure, this glass-like material's molecules are arranged in a random, disorganized way. Scientists have studied glassy water for decades, but the exact temperature at which water acquires glass-like properties has been the subject of heated debate for years, due to the difficulty of manipulating pure glassy water in laboratories.

Now, in a paper published in the AIP's Journal of Chemical Physics, physicists from the University of Pisa and the Consiglio Nazionale delle Ricerche at the Institute for Chemical-Physical Processes (CNR-IPCF) in Pisa, Italy, claim to have put an end to the controversy. Unlike previous attempts in which scientists tried to measure the transition temperature directly, the CNR team "snuck up" on the answer by inferring the temperature from a thorough study of the dynamics of water. They examined water's behavior in bulk and at the nano-scale, at high temperatures and low, combining their own experimental results with 15 decades' worth of research by colleagues.

They also measured the glass transition temperature and the molecular behavior of water that had been doped with other materials, and used this information to set lower and upper boundaries on the transition temperature for pure water. Taken together, their evidence points to a magic number of approximately 136 Kelvin (-137 Celsius). The authors say their work supports traditional views of this phenomenon and refutes recent claims that the transition is above 160 Kelvin (-113 Celsius). The research could find uses in technology associated with food science and the cryopreservation of biological materials, as well as in the study of water in comets and on the surface of planets.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

S. Capaccioli, K. L. Ngai. Resolving the controversy on the glass transition temperature of water? The Journal of Chemical Physics, 2011; 135 (10): 104504 DOI: 10.1063/1.3633242

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Sneaking up on the glassy transition of water

ScienceDaily (Sep. 27, 2011) — Researchers claim to have settled a long-standing debate over the exact temperature at which water transforms into an exotic glass-like substance believed to be present in comets and other icy objects in the outer solar system, as well as in the coldest regions of Earth's atmosphere.

Rapid cooling of ordinary water or compression of ordinary ice: either of these can transform normal H2O into an exotic substance that resembles glass in its transparency, brittleness, hardness, and luster. Unlike everyday ice, which has a highly organized crystalline structure, this glass-like material's molecules are arranged in a random, disorganized way. Scientists have studied glassy water for decades, but the exact temperature at which water acquires glass-like properties has been the subject of heated debate for years, due to the difficulty of manipulating pure glassy water in laboratories.

Now, in a paper published in the AIP's Journal of Chemical Physics, physicists from the University of Pisa and the Consiglio Nazionale delle Ricerche at the Institute for Chemical-Physical Processes (CNR-IPCF) in Pisa, Italy, claim to have put an end to the controversy. Unlike previous attempts in which scientists tried to measure the transition temperature directly, the CNR team "snuck up" on the answer by inferring the temperature from a thorough study of the dynamics of water. They examined water's behavior in bulk and at the nano-scale, at high temperatures and low, combining their own experimental results with 15 decades' worth of research by colleagues.

They also measured the glass transition temperature and the molecular behavior of water that had been doped with other materials, and used this information to set lower and upper boundaries on the transition temperature for pure water. Taken together, their evidence points to a magic number of approximately 136 Kelvin (-137 Celsius). The authors say their work supports traditional views of this phenomenon and refutes recent claims that the transition is above 160 Kelvin (-113 Celsius). The research could find uses in technology associated with food science and the cryopreservation of biological materials, as well as in the study of water in comets and on the surface of planets.

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and Google +1:

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

S. Capaccioli, K. L. Ngai. Resolving the controversy on the glass transition temperature of water? The Journal of Chemical Physics, 2011; 135 (10): 104504 DOI: 10.1063/1.3633242

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Matter shows abrupt escape from flatness: Lead made to undergo a rapid transition from 'pancake' to hemisphere

ScienceDaily (Sep. 28, 2011) — At first glance, it seems as if billions of lead atoms have mysteriously disappeared. When exposed to heat, a layer of lead coated onto a nickel surface becomes almost invisible from one moment to the next. In reality, the slightest disturbance causes these atoms to suddenly switch from a broad “flat pancake” shape to a compact hemisphere.

This remarkable phenomenon was first revealed by researchers at the University of Twente’s MESA+ Institute for Nanotechnology, who have since published their results in Physical Review Letters.

A lead coating on a nickel surface has unusual electronic properties which cause it to form flat "pancakes," consisting of billions of atoms arranged in a crystalline structure. These "pancakes" of solid lead are quantum mechanically stabilized and just a couple of dozen atoms thick. When exposed to gradual heating, nothing much changes at first. At about 520 Kelvin (247 degrees Celsius), however, the lead coating suddenly seems to disappear completely. Within the space of a few milliseconds, the lead "slivers" transform into hemispheres with a radius (or "height") of a few micrometers. Interestingly, this all takes place at a temperature below the melting point of lead. The hemispheres, too, consist of solid lead. So no mass has been lost, the material has simply taken on a different spatial configuration.

Low energy electron microscope

The technique used by the researchers to observe this process is known as Low Energy Electron Microscopy (LEEM). There are only a few such microscopes in existence, but two have recently been installed in the Netherlands. They are designed to bombard surfaces with low energy electrons. This makes them especially well suited to making accurate observations of surface phenomena and events in thin films.

Beyond the scope of our current knowledge

The abrupt transformation from flat to spherical can be explained in terms of the most energetically favourable shape. From this viewpoint, hemispheres make much more effective use of surfaces, whereas pancakes are not very stable. There has recently been a massive expansion in our understanding of atomic processes right down to the level of single atoms, facilitated by experimental techniques such as Scanning Tunnelling Microscopy (STM), together with newly developed theories. Even so, we cannot account for the sheer speed at which this transition takes place.

Group process

However, this recently discovered super-fast transition from two to three dimensions is based on a delicate interplay between several atoms, a kind of group process. In their published article, these researchers from Twente express the view that a more detailed explanation of the very rapid transition from flat to spherical will only be possible when we have a better fundamental theoretical understanding of meso-level phenomena. LEEM can be used to make direct observations of new phenomena at the meso-scale, thereby generating data crucial to our knowledge of this field. The importance of these results is that they will give us a more profound understanding of the stability of nanostructures.

This study was carried out by Prof. Harold Zandvliet's Physics of Interfaces and Nanomaterials group. Funding was provided by the FOM Institute. The group is part of the University of Twente's MESA+ Institute for Nanotechnology. The LEEM equipment used in this study was purchased with funds provided by the Dutch Technology Foundation (STW).

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Twente.

Journal Reference:

Tjeerd Bollmann, Raoul van Gastel, Harold Zandvliet, Bene Poelsema. Anomalous Decay of Electronically Stabilized Lead Mesas on Ni(111). Physical Review Letters, 2011; 107 (13) DOI: 10.1103/PhysRevLett.107.136103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Matter shows abrupt escape from flatness: Lead made to undergo a rapid transition from 'pancake' to hemisphere

ScienceDaily (Sep. 28, 2011) — At first glance, it seems as if billions of lead atoms have mysteriously disappeared. When exposed to heat, a layer of lead coated onto a nickel surface becomes almost invisible from one moment to the next. In reality, the slightest disturbance causes these atoms to suddenly switch from a broad “flat pancake” shape to a compact hemisphere.

This remarkable phenomenon was first revealed by researchers at the University of Twente’s MESA+ Institute for Nanotechnology, who have since published their results in Physical Review Letters.

A lead coating on a nickel surface has unusual electronic properties which cause it to form flat "pancakes," consisting of billions of atoms arranged in a crystalline structure. These "pancakes" of solid lead are quantum mechanically stabilized and just a couple of dozen atoms thick. When exposed to gradual heating, nothing much changes at first. At about 520 Kelvin (247 degrees Celsius), however, the lead coating suddenly seems to disappear completely. Within the space of a few milliseconds, the lead "slivers" transform into hemispheres with a radius (or "height") of a few micrometers. Interestingly, this all takes place at a temperature below the melting point of lead. The hemispheres, too, consist of solid lead. So no mass has been lost, the material has simply taken on a different spatial configuration.

Low energy electron microscope

The technique used by the researchers to observe this process is known as Low Energy Electron Microscopy (LEEM). There are only a few such microscopes in existence, but two have recently been installed in the Netherlands. They are designed to bombard surfaces with low energy electrons. This makes them especially well suited to making accurate observations of surface phenomena and events in thin films.

Beyond the scope of our current knowledge

The abrupt transformation from flat to spherical can be explained in terms of the most energetically favourable shape. From this viewpoint, hemispheres make much more effective use of surfaces, whereas pancakes are not very stable. There has recently been a massive expansion in our understanding of atomic processes right down to the level of single atoms, facilitated by experimental techniques such as Scanning Tunnelling Microscopy (STM), together with newly developed theories. Even so, we cannot account for the sheer speed at which this transition takes place.

Group process

However, this recently discovered super-fast transition from two to three dimensions is based on a delicate interplay between several atoms, a kind of group process. In their published article, these researchers from Twente express the view that a more detailed explanation of the very rapid transition from flat to spherical will only be possible when we have a better fundamental theoretical understanding of meso-level phenomena. LEEM can be used to make direct observations of new phenomena at the meso-scale, thereby generating data crucial to our knowledge of this field. The importance of these results is that they will give us a more profound understanding of the stability of nanostructures.

This study was carried out by Prof. Harold Zandvliet's Physics of Interfaces and Nanomaterials group. Funding was provided by the FOM Institute. The group is part of the University of Twente's MESA+ Institute for Nanotechnology. The LEEM equipment used in this study was purchased with funds provided by the Dutch Technology Foundation (STW).

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Twente.

Journal Reference:

Tjeerd Bollmann, Raoul van Gastel, Harold Zandvliet, Bene Poelsema. Anomalous Decay of Electronically Stabilized Lead Mesas on Ni(111). Physical Review Letters, 2011; 107 (13) DOI: 10.1103/PhysRevLett.107.136103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here