Supercool! Model unscrambles complex crystallization puzzle

August 30, 2004

To the wonderment---and the befuddlement---of scientists, the patterns that form as plastics, metals and many other materials crystallize can vary incredibly, ranging from sea-urchin-like spheres to elaborate tree-like branches.

Now, Hungarian and National Institute of Standards and Technology scientists report in the September issue of Nature Materials* that they have developed a way to predict the polycrystalline microstructures that will form as complex liquid mixtures cool and solidify. Ultimately, the team's new simulation tool could help manufacturers of everything from plastic bags to airplane wings to design new products with improved strength, durability and other properties.

Images generated with the team's mathematical model match up almost feature for feature with the seemingly random crystal patterns formed in experiments as temperatures or other processing variables are modified. The model accurately predicts how both impurities (or additives) and process differences affect the sizes, shapes and orientations of crystals that form during the so-called supercooling process.

Whether initiated by "dirt" or by processing conditions, the resulting patterns can be strikingly similar. This "duality in the growth process," notes NIST's James Warren, may help explain why polycrystalline growth patterns are so prevalent in polymers and other materials derived from complex mixtures.

Findings based on the model indicate that instabilities along the boundary between liquid and solid areas during solidification effectively clash with the otherwise orderly process of crystallization. Tiny crystals-in-the-making move and position themselves along the growth front, assuming an orientation peculiar to the energy conditions at their location. Varying local conditions produce crystals in seemingly disordered arrays, accounting for the rich diversity of microstructural patterns.
Laszlo Granasy, of Hungary's Research Institute for Solid State Physics and Optics, led the research effort. *L. Gránásy, T. Pusztai, T. Börzsönyi, J.A. Warren, and J.F. Douglas. A general mechanism of polycrystalline growth. 2004. Nature Materials advance on-line publication, Aug. 8, 2004.

National Institute of Standards and Technology (NIST)

Related Crystals Articles from Brightsurf:

A new method to measure optical absorption in semiconductor crystals
Tohoku University researchers have revealed more details about omnidirectional photoluminescence (ODPL) spectroscopy - a method for probing semiconducting crystals with light to detect defects and impurities.

Fat crystals trigger chronic inflammation
A congenital disorder of the fat metabolism can apparently cause chronic hyperreaction of the immune system.

First ever observation of 'time crystals' interacting
For the first time ever, scientists have witnessed the interaction of a new phase of matter known as 'time crystals'.

'Blinking" crystals may convert CO2 into fuels
Imagine tiny crystals that ''blink'' like fireflies and can convert carbon dioxide, a key cause of climate change, into fuels.

Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.

Rubies on sapphire: Recipe for making crystals in flux
The effect of the holding temperature and solubility curve of rubies was elucidated, for Al2O3:Cr in MoO3 from 1050 to 1200.

Transparency discovered in crystals with ultrahigh piezoelectricity
Use of an AC rather than a DC electric field can improve the piezoelectric response of a crystal.

New photonic liquid crystals could lead to next-generation displays
A new technique to change the structure of liquid crystals could lead to the development of fast-responding liquid crystals suitable for next generation displays -- 3D, augmented and virtual reality -- and advanced photonic applications such as mirrorless lasers, bio-sensors and fast/slow light generation, according to an international team of researchers from Penn State, the Air Force Research Laboratory and the National Sun Yat-sen University, Taiwan.

The secret behind crystals that shrink when heated
Scientists at Brookhaven Lab have new experimental evidence and a predictive theory that solves a long-standing materials science mystery: why certain crystalline materials shrink when heated.

Engineered protein crystals make cells magnetic
If scientists could give living cells magnetic properties, they could perhaps manipulate cellular activities with external magnetic fields.

Read More: Crystals News and Crystals Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to