A fast solidification process makes material crackle
by Staff Writers
Espoo, Finland (SPX) Feb 08, 2016
What does it sound like when liquids solidify very fast? Researchers from the Centre of Excellence in Computational Nanoscience at Aalto University and their colleagues at Brown University and the University of California, Irvine, have developed a theory that answers this question by combining for the first time the understanding of vibrations in solid material and the solidification of liquid at a microscopic level.
The results were published in the renowned scientific publication Physical Review Letters in January.
'Earlier theories have focused on slow solidification. It is effectively diffusion in which the movement of atoms is slow and random. When solidification is fast, the atoms do not move only randomly, but the reaction is as if they had been compressed together.
'What our model can predict is the sound wave that is formed when the compression relaxes,' describes doctoral candidate Vili Heinonen.
Liquids usually solidify so slowly that no sound is created. When the process is fast, as it is when supercool water freezes, large defects are formed in the lattice structure of the material.
According to Vili Heinonen, the wave formed when the defects relax resembles a kind of crackling. Effectively, the human ear cannot hear the sound, as supercool liquids that occur in nature are small droplets.
In addition to the crackling, the model also reveals a lot more.
'It helps us understand and predict the defects that are formed in materials - especially in metals - when they solidify. Also, materials often have different interfaces that are not always compatible.
'By understanding these defects we can also understand better why metals produced in certain temperatures have certain properties - and whether we can do something about it,' Heinonen explains.
The researchers proved the functionality of the model by analysing vibrations theoretically and computationally. In the computational test, the model was compared with predictions given by earlier theories, and it was demonstrated that the properties of the new theory are vitally important when we want to understand how, for example, the microscopic structure of metals changes in high temperatures.
In addition to enabling control over the process of metal production, understanding these matters could in future enable a cheap method to produce intelligent nanostructures.
Science Paper: Consistent Hydrodynamics for Phase Field Crystals
Space Technology News - Applications and Research
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.|