The 2011 Laureates / Advanced Technology Category / Materials Science and Engineering

"Outstanding Contribution to Alloy Materials Engineering by the Establishment of Spinodal Decomposition Theory"
Dr. John W. Cahn developed the theory of spinodal decomposition in alloy materials by incorporating the strain energy term into the free energy of the alloy system. It has made it possible to predict the optimal microstructures of alloy materials and to maximize their functions. The theory has led to the establishment of a design guideline for the development of alloy materials and contributed to the progress of both materials science and materials industry.

Contribution to Alloy Materials Engineering by the Establishment of Spinodal Decomposition Theory

Spinodal decomposition and Dr. Cahn’s contributions to materials engineering

When cooled rapidly, a homogeneous mixture of two components exhibits a phenomenon called phase separation. More specifically, depending on their proportions and cooling rate, the two components will sometimes separate to form a heterogeneous mixture that has a special structure, in which small regions of the two different components intertwine. This phenomenon is known as spinodal decomposition. Dr. Cahn formulated the structure of this phase separation process and developed a theory to explain it.

Structural materials are commonly chosen for their dynamic characteristics (mostly strength), while functional materials are often chosen for their electrical or optical characteristics. Most of these are alloy materials containing two or more elements, and their development requires the selection of optimal constituents and the determination of the material’s microstructure. The process of material development through spinodal decomposition is not an exception to this, and researchers had no other option but to repeat a trial and error process, hoping that they would obtain a product with the desired material properties. Dr. Cahn changed all this by developing alloy materials design guides, which used knowledge of spinodal decomposition to predict which microstructures would be created when a mixture separated into two phases under a given set of conditions. His work helped to substantially shorten development time, thus making significant contributions to the development of superior new materials. Dr. Cahn’s research findings have serves as the foundation for the phase-field method, which is now a widely used technique that incorporates more recent theories and makes use of computer simulations.

Example of materials developed by utilizing spinodal decomposition

*Heat-resistant glass
Heat-resistant glass with a maximum working temperature of 1,200°C is created by taking advantage of spinodal decomposition, and is used for mercury lamps, laboratory apparatus, and spacecraft windows.

*Partially stabilized zirconia ceramic
Resistant to bending stress and external force, this ceramic has found a wide range of applications in various industrial components. A familiar application is rust-free and wear-resistant kitchen knives.

*ABS (acrylonitrile butadiene styrene) resin
With high strength and thermal shock resistance, this lustrous and visually attractive resin is frequently chosen for automobile interiors, and is widely used for the exterior of such commonly used appliances as refrigerators, air-conditioners, and microwave ovens.

Brief history of spinodal decomposition research

The existence of the phenomenon now known as spinodal decomposition was recognized on an empirical basis in the 19th century, but scientists lacked any theoretical understanding of it, not knowing why it occurred or how it could be controlled. The term itself was coined by Dr. Johannes Diderik van der Waals, a Dutch physicist who received the Nobel Prize for Physics in 1910. In 1956, Dr. Mats Hillert of Sweden was first to provide a theoretical explanation of spinodal decomposition, but his theory was not directly applicable to the actual process of materials synthesis. Together with Dr. John E. Hilliard, Dr. Cahn expanded the model three-dimensionally and then completed it by incorporating an elastic strain energy term, which is an important factor, and the two proposed the completed model in 1961. This made it possible to apply spinodal decomposition to the actual development of synthetic materials, which was a significant contribution to the advancement of materials science and the primary materials industry.

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