Science Current Events | Science News | Brightsurf.com
 
Email a Friend Send to a friend
Printer Friendly Print Extra-large 'atoms' allow Penn physicists to solve the riddle of why things melt

Extra-large 'atoms' allow Penn physicists to solve the riddle of why things melt

July 01, 2005

PHILADELPHIA - Physicists at the University of Pennsylvania have experimentally discovered a fundamental principal about how solid materials melt. Their studies have shown explicitly that melting begins at defects within the crystalline structure of solid matter, beginning along the cracks, grain boundaries and dislocations that are present in the otherwise orderly array of atoms. Their findings, which will appear today in the journal Science, answer longstanding fundamental questions about melting and will likely influence research in physics, chemistry, materials science and engineering, as well as studies of biological importance.

"Melting is one of the most fundamental phenomena in physics and is one of the phase transitions most frequently seen in daily life," said Arjun Yodh, a professor in Penn's Department of Astronomy and Physics. "Yet major details about the mechanisms that drive the melting of an ice cube are missing. Superficially, the principle is straightforward. As a solid heats up, molecules within the ice acquire more energy and jiggle around more, driving the transition from a solid to a liquid. This is true in part, but reality is richer and more complex."




In the Science paper, the Penn physicists show direct evidence for a leading theory of melting, the notion that the start of melting - premelting - occurs at imperfections in the orderly structure of solid crystals. Premelting occurs in areas where the alignment of atoms is not perfect, especially at the boundaries within crystals where the patterns of atoms shift much like imperfections in the grain of a piece of wood.

One problem with proving theories of how things melt is size; one simply cannot see the atoms in a solid structure as it melts. Not only are the atoms very small, but the solid matter tends to obscure what goes on inside. To get around these problems, Yodh and his Penn colleagues made atoms bigger.

"We created translucent three-dimensional crystals from thermally-responsive colloidal spheres. The spheres are like small beads visible in an optical microscope," said Ahmed Alsayed, a doctoral student in the Department of Astronomy and Physics and lead author of the study. "The spheres swell or collapse significantly with small changes in temperature, and they exhibit other useful properties that allow them to behave like enormous versions of atoms for the purpose of our experiment."

As they raised the temperature of the colloidal particle crystal, the researchers could record changes within the crystal by following the motions of many individual spheres using a microscope and a video recorder.

"When we raised the temperature, we could track the vibrational movement of the spheres," Alsayed said. "Premelting was first revealed as an increased movement along the lines of defects in the crystal. These motions then spread into the more ordered parts of the crystal. We could see that the amount of premelting depended on the type of crystal defect and on the distance from the defect."

The researchers believe these observations will lead to a better understanding of the melting process and enable more quantitative predictions of just how a substance might melt.

"The existence of premelting inside solid materials implies that liquids exist within crystals before their melting temperature is reached," Yodh said. "Understanding this effect will provide insight for the design of strong materials that are more or less impervious to temperature changes and could also apply to our theories of how natural materials, such as water, evolve in our environment."

Other Penn researchers involved in this study are Mohammad Islam, Jian Zhang, and Peter Collings, who is also a professor of physics at Swarthmore College.

University of Pennsylvania



Related Solid Matter Current Events and Solid Matter News Articles
Secrets from within planets pave way for cleaner energy
Research that has provided a deeper understanding into the centre of planets could also provide the way forward in the world's quest for cleaner energy.

Pitt researchers create new form of matter
Physicists at the University of Pittsburgh have demonstrated a new form of matter that melds the characteristics of lasers with those of the world's best electrical conductors.

The optimal stuff
Most chaotic systems are hard to grasp. This is also true of the snarls of fibers found in filters, fabrics and insulation material that filtrate solutions, absorb noise or retain heat. Manufacturers typically approach product development by trial and error. What they expect to see as a result is more a question of experience than what they actually know about why and how their non-wovens function. Were more accurate information available, they could save costs by more precisely modifying material properties and production processes. Such analyses are now possible with "Geodict", a software program deve-loped by the Fraunhofer Institute for Industrial Mathematics ITWM. The program's

Laser scientists take step towards making fusion energy a reality
Scientists from the UK and Japan may have taken us one step further to the reality of fusion energy with a new answer to an old problem. Research by Dr Ryosuke Kodama and his colleagues at Osaka University, Japan and the UK team published in Nature on Thursday 23 August details a new technique for using lasers to start the fusion reaction. The British team comprises researchers from the CLRC Rutherford Appleton Laboratory (RAL) (Dr Peter Norreys) and Oxford University (Professor Steven Rose), Imperial College, London (Bucker Dangor, Dr Karl Krushelnick and Dr Matthew Zepf - who is now at Queens University, Belfast) and the University of York (Dr Roger Evans). "We have provided the first

Drainage system still not fully developed
Drainage systems can be far better designed. This is one of the conclusions that Professor Fran'§ois Clemens comes to in his thesis, for which he received his PhD on Tuesday 13 March. “The models that are used for the development of drainage systems are not realistic,” says Clemens, “That means to many or to few measures are taken during the design. The consequences are that costs are too high or a small environmental disaster is created.” Drainage systems can be seen as one of the critical infrastructures in our society. Almost all Dutch households (97%) are connected to a sewerage purification plant. “The average investment is 80 billion Guilders, which is equ
More Solid Matter Current Events and Solid Matter News Articles
  The Solid Truth About States of Matter With Max Axiom, Super Scientist (Graphic Science)
by Agniesezka Biskup (Author), Cynthia Martin (Illustrator), Barbara Schulz (Illustrator)

Solid Truth about States of Matter with Max Axiom, Super Scientist is a Capstone Press publication.



Solid Matter

Solid Matter
Infinit Beats (Primary Contributor)



States of Matter: Solid, Liquid and Gas

States of Matter: Solid, Liquid and Gas

Show Me Science is an excellent in-class, library or home schooling tool for introducing the wonders of science. Comprised of 84 programs and grouped into coherent subject areas of 8-16 titles each, Show Me Science covers animal life, astronomy, biology, chemistry, health science, earth science, technology, environmental sciences and physics. Matter is anything that has mass or takes up space. Three of the recognized five states of Matter are solid, liquid and gas. (The other two are plasma and Bose-Einstein concentrates) As different forces are applied to matter, like heat, matter can change from one form to another: solid to liquid, liquid to gas, or solid to gas. Show Me Science: States of Matter: Solid, Liquid, and Gas describes what happens to matter at boiling, melting, freezing,...

  States of Matter: Solid, Liquid and Gas
Starring: Artist Not Provided



Trevor

Trevor
Starring: David Duchovny, Gillian Anderson
Also With: FOX (Producer)



Band Theory and Electronic Properties of Solids (Oxford Master Series in Condensed Matter Physics)

Band Theory and Electronic Properties of Solids (Oxford Master Series in Condensed Matter Physics)
by John Singleton (Author)

This latest text in the new Oxford Master Series in Physics provides a much need introduction to band theory and the electronic properties of materials. Written for students in physics and material science, the book takes a pedagogical approach to the subject through the extensive use of illustrations, examples and problem sets. The author draws on his extensive experience teaching band theory to provide the reader with a thorough understanding of the field. Considerable attention is paid to the vocabulary and quantum-mechanical training necessary to learn about the electronic, optical and structural properties of materials in science and technology. The text also offers several chapters on the newest experimental techniques used to study band structure. Concise yet rigorous, it fills a...

Tees For Change TODAY MATTERS Organic Cotton Long Sleeve Tee, Medium

Tees For Change TODAY MATTERS Organic Cotton Long Sleeve Tee, Medium
by Tees For Change

Made from 100% organic cotton, this scoop neck long sleeve tee is super soft, thinner and has the perfect fit. Longer length and sleeves make it great for layering.  Buy a tee, plant a tree!

Harcourt Science Activity Videos Matter and Energy Grade 1 Unit E

Harcourt Science Activity Videos Matter and Energy Grade 1 Unit E

Step in to a world of discovery with the Science Activity videos, designed to engage students in the hands-on investigations from Harcourt Science.

Soft Condensed Matter

Soft Condensed Matter
by Richard A.L. Jones (Author)

Probably one of the most fashionable areas in the physical sciences today, 'Soft Condensed Matter' provides an excellent introduction to the topic, and includes colloids, polymers, liquid crystals, and amphiphiles. It is suitable for advanced undergraduate and beginning graduate students of physics, chemistry, materials science and chemical engineering.

  Unitary Transformations in Solid State Physics (Modern Problems in Condensed Matter Science, Vol 15)
by Max Wagner (Author)

The main emphasis of this book is on the practical application of unitary transformations to problems in solid state physics. This is a method used by the author and his collaborators for years in the field of nonadiabatic electron-phonon phenomena where the Born-Oppenheimer approximation is no longer applicable. This book is intended as a tool for those who want to apply unitary transformations quickly and on a more elementary level and also for those who want to use this method for more involved problems. ``Unitary Transformations in Solid State Physics'' is divided into 6 chapters. The first three chapters are concerned with presenting quick applications of unitary transformations and chapter 4 presents a more systematic procedure. The last two chapters contain the major known examples...

© 2009 BrightSurf.com