Clarifying relationship between Glass Forming Ability and Atomic Arrangement (Press Release)
- Release Date
- 23 Aug, 2011
- BL04B2 (High Energy X-ray Diffraction)
Japan Synchrotron Radiation Research Institute (JASRI)
JASRI organized an international joint research team with Tempere University of Technology, Yamagata University, Japan Atomic Energy Agency, Materials Development Inc., Aberystwyth University, and Argonne National Laboratory to examine the relationship between glass forming ability and atomic arrangement, for the first time in the world, by measurement using high-brilliance and high-energy synchrotron X-rays at SPring-8 and by computer simulation. The results of this study will provide important knowledge for solving the unresolved problems underlying how glass is formed. Glass is indispensable to our daily lives because most glass is transparent, hard, resistant to chemicals and has a smooth surface. The atomic structure of glass is not regular as in crystals; therefore, it is difficult to understand its structure. A typical glass synthesis method is to produce a melt*1 from a solid substance at a high temperature and then cool the melt. When the cooling rate is too low, the melt is crystallized and the resulting product does not have the properties of glass. Enstatite*2 and forsterite*3 are known as principal minerals constituting the Earth. Their melts and the structures and properties of their glasses have been investigated by many researchers. Although both enstatite and forsterite include silica (SiO2), which is required to form glass, silica-rich enstatite forms glass more easily than forsterite. A high-temperature melt of forsterite is easily crystallized simply by rapid cooling and is transformed into a glass by containerless processing.*4 In this study, the difference in the ring distribution of the atomic arrangement of enstatite and forsterite glasses with different silica contents was discovered for the first time, and the relationship between the ring distribution and glass forming ability was determined. The achievement of this study will provide important data relating the glass structure, which has been examined since early days, to the theory of glass formation, and a new direction for the design of practical glass materials and their application, such as high-refractive-index lenses for cellphone cameras. This achievement was realized by a collaborative research group led by Shinji Kohara (Senior Scientist) of JASRI and was published online in Proceedings of the National Academy of Sciences of the United States of America (PNAS) on 23 August 2011. Publication: |
<<Glossary>>
*1 Melt
A melt is essentially the same as a liquid. A molten solid at a high temperature is called a melt.
*2 Enstatite
Enstatite is a mineral (silicate mineral) and a Mg-rich orthopyroxene. Its chemical formula is MgSiO3; the pyroxene in which Mg is replaced with Fe2+ is called ferrosilite. Enstatite and ferrosilite (Fs) form a solid solution series. Enstatite is also a rock-forming mineral and a constituent of igneous rock and metamorphic rock.
*3 Forsterite
Olivine is a silicate mineral of Mg and Fe and is a solid solution series of MgSiO4 and Fe2SiO4. Mg2SiO4 is the chemical formula of forsterite.
*4 Containerless processing
In containerless processing, a material is heated by a laser to obtain a melt, onto which an inactive gas (such as argon or nitrogen gas) is target-blown, then the material is maintained in zero gravity without using a container. This method is used to transform a material with a high melting point*5 to a melt (liquid) because a high temperature exceeding 2,000oC is easily realized. Also, there is no risk of the container material dissolving into the melt. In addition, a liquid state is maintained at temperatures lower than the melting point (i.e., supercooled liquid state) because there are no boundaries between the melt and the container (crystal). The absence of a boundary prevents the crystallization of the liquid. As a result, even glasses with low glass formability can be synthesized (refer to Fig. 1).
*5 Melting point
The melting point is the temperature at which a solid melts and changes to a liquid.
<<Figures>>
Samples are made to float in a gas target-blown from a conical nozzle and are then heated to melt by a CO2 laser. The photograph shows a floating oxide melt (glass bead melt) at 2,000oC.
The lower the silica (SiO2) content, the narrower the ring distribution, making it more difficult to form a glass.
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For more information, please contact: Dr. Kentaro Suzuya (Japan Atomic Energy Agency) |
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