Structural shift elucidated with large-scale atomic simulations
Iron-nickel alloys' structure changes as they heat up and cool down
2015-07-06
(Press-News.org) Iron-nickel alloys are ubiquitous: they are found at the earth's core and in meteorites. What is fascinating about such alloys is that their inner structure can change with rapid temperature swings. Heated up above 730 °C (1,340 °F), these alloys enter what is referred to as an austenitic phase. Alternatively, they can be turned into very hard alloys, referred to as a martensitic phase, by subjecting them to extremely rapid cooling. Now a team of scientists from Germany has, for the first time, created a large-scale simulation involving 275,000 atoms representing iron-nickel alloys in proportions found in nature. They show that transitions from one alloy structure to the other occurs in both an orderly and a disorderly way, depending on whether it is heated up or cooled down, respectively. These findings have been published in EPJB by Emilia Sak-Saracino and Herbert Urbassek from the Research Center OPTIMAS at the University of Kaiserslautern, in Germany.
Sak-Saracino showed that using a simulation model makes it possible to uncover morphological changes in iron-nickel crystals occurring as the temperature radically changes. They show that large-scale alloys behave differently than found by previous studies, which focused on samples of the order of thousands of atoms.
Here, the authors show that as the single crystal sample heats up, the alloy's structure changes as a result of the homogeneous nucleation of several grains of poly-crystalline structure, towards an austenitic phase. Conversely, quick cooling of an alloy made of a single crystal type forming a hard alloy proceeds via the heterogeneous nucleation into a martensitic-style structure. This transformation, they show, requires a larger temperature window for completion than the reverse.
The team also focused on the effect on the alloy structure of the incorporation of nickel into the iron crystal. They show that it lowers the transition temperature necessary to reach the austenitic structure, in agreement with the experimental findings.
INFORMATION:
Reference:
E. Sak-Saracino and H. M. Urbassek (2015), Temperature-induced phase transformation of Fe1-xNix alloys: molecular-dynamics approach, Eur. Phys. J. B, DOI: 10.1140/epjb/e2015-60117-x
For more information visit: http://www.epj.org
The full-text article is available to journalists on request.
ELSE PRESS RELEASES FROM THIS DATE:
2015-07-06
Researchers at the University of Adelaide have discovered a new method for culturing stem cells which sees the highly therapeutic cells grow faster and stronger.
The research, which was published in the prestigious international journal, Stem Cells, is expected to eventually lead to new treatments for transplant patients.
Kisha Sivanathan, a PhD student in the University of Adelaide's School of Medicine and the Renal Transplant Unit at the Royal Adelaide Hospital, says this is an exciting breakthrough in stem cell research.
"Adult mesenchymal stem cells, which ...
2015-07-06
A study of 311 patients by The University of Manchester has found that it may be possible to predict early which rheumatoid arthritis (RA) patients will fail to respond to the biologic drugs given to treat them. These findings could help better manage patients' symptoms.
RA is a chronic disease which affects up to 1.5% of the population. It is a significant health burden for patients, who can experience pain, reduced mobility and premature death unless they receive effective treatment.
Biologics are a relatively new form of treatment for RA. Given by injection, ...
2015-07-06
Pursuant to the Act on the Reform of the Market for Medicinal Products (AMNOG), the German Institute for Quality and Efficiency in Health Care (IQWiG) reassessed fingolimod (trade name: Gilenya), a drug for the treatment of adults with highly active relapsing remitting multiple sclerosis (RRMS). The Federal Joint Committee (G-BA) had limited its decision on the first assessment from 2012 to three years because it considered the certainty of the data as insufficient. This obliged the drug manufacturer to submit a second dossier.
It did not submit any new studies, but reanalysed ...
2015-07-06
Scientists believe that a simple two-hour emotional awareness course aimed at making young offenders less aggressive could hold the key to significantly reducing the seriousness of their future crimes.
In the first ever study of its kind, psychologists from Cardiff University recorded a 44% drop in the severity of crimes committed by persistent reoffenders, six months following the completion of a course designed to improve their ability to recognise other people's emotions. The findings are published today in PLOS ONE journal.
Much has been published previously to ...
2015-07-06
ITHACA, N.Y. - To protect consumers from foodborne illness, produce farmers should wait 24 hours after a rain or irrigating their fields to harvest crops, according to new research published in the journal Applied and Environmental Microbiology.
Rain or irrigation creates soil conditions that are more hospitable to Listeria monocytogenes, which when ingested may cause the human illness Listeriosis. Waiting to harvest crops reduces the risk of exposure to the pathogen, which could land on fresh produce.
Cornell scientists, along with other agricultural researchers from ...
2015-07-06
Astronomers have found evidence for a large population of hidden supermassive black holes in the Universe.
Using NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) satellite observatory, the team of international scientists detected the high-energy x-rays from five supermassive black holes previously clouded from direct view by dust and gas.
The research, led by astronomers at Durham University, UK, supports the theory that potentially millions more supermassive black holes exist in the Universe, but are hidden from view.
The findings are being presented at the ...
2015-07-06
For cell division to be successful, pairs of chromosomes have to line up just right before being swept into their new cells, like the opening of a theater curtain. They accomplish this feat in part thanks to structures called centrioles that provide an anchor for the curtain's ropes. Researchers at Johns Hopkins recently learned that most cells will not divide without centrioles, and they found out why: A protein called p53, already known to prevent cell division for other reasons, also monitors centriole numbers to prevent potentially disastrous cell divisions.
Details ...
2015-07-06
Richland, Wash. -- Despite decades of industrial use, the exact chemical transformations occurring within zeolites, a common material used in the conversion of oil to gasoline, remain poorly understood. Now scientists have found a way to locate--with atomic precision--spots within the material where chemical reactions take place, and how these spots shut down.
Called active sites, the spots help rip apart and rearrange molecules as they pass through nanometer-sized channels, like an assembly line in a factory. A process called steaming causes these active sites to cluster, ...
2015-07-06
Anti-inflammatory drug is one thousandth of the cost of the current drug which works in the same way
Discovery may open up cost effective treatment options not just for the NHS but also cancer patients across the world
Scientists at the University of Sheffield have discovered that a common drug given to arthritis sufferers could also help to treat patients with blood cancers.
Myeloproliferative neoplasms (MPN) are diagnosed in around 3,300 UK patients every year and cause an overproduction of blood cells creating a significant impact on quality-of-life, with symptoms ...
2015-07-06
ANN ARBOR, Mich. -- Over the same time period that multiple outbreaks of measles and whooping cough made headlines around the country, parents' views on vaccines became more favorable, according to a new nationally-representative poll.
The University of Michigan C.S. Mott Children's Hospital National Poll on Children's Health asked parents in May how their views on vaccinations changed between 2014 and 2015 - during which two dozen measles outbreaks were reported in the U.S., including a multi-state outbreak traced to Disneyland.
One-third of parents who participated ...
LAST 30 PRESS RELEASES:
[Press-News.org] Structural shift elucidated with large-scale atomic simulations
Iron-nickel alloys' structure changes as they heat up and cool down
