A recent development in oxide glass technology from the University of Tokyo could lead to commercialization in as little as five years of an advanced material that is flexible, stronger, and lighter than current glasses while being virtually unbreakable. Like conventional oxide glass, the material is transparent and colorless and has a high refractive index.

Researchers at the university's Institute of Industrial Science say the glass would be suitable for a variety of applications, from automotive windshields and building windows to smartphone screens and thin-film transistor displays.

In a paper published in Scientific Reports in November, lead authors Atsunobu Masuno and Gustavo A. Rosales-Sosa credit the high elastic modulus and hardness values of the oxide glass to its primary components: alumina (Al2O3) and tantalum pentoxide (Ta2O5). These materials, in particular the alumina, have high dissociation energies (chemical bond strength) as well as high atomic packing density.

The material composition appears to be 54% alumina and 46% tantalum pentoxide based on the research paper's chemical description of the material as 54AL2O3-46Ta2O5.

The modulus and hardness values of the material are among the highest ever measured for oxide glass, the researchers note; Young's modulus is 158.4 GPa and Vickers hardness is 9.1 GPa.

No one on the research team could be reached for comment, and the paper does not cite specific end-use benefits of the material. However, a virtually unbreakable, flexible glass would at least offer such design advantages as thinwalling, lightweighting, and downsizing. It might also allow economical material substitution -- for example, a crack-resistant screen for a smartphone, tablet, or other electronic device. The glass could also challenge the small but growing market for polycarbonate automotive windows and windshields.

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The material could, as well, replace conventional safety glass in some applications, eliminating the need for the polyvinyl butyral sandwich structure and yielding a one-piece part.

Market penetration will of course depend on product cost and manufacturability. The technology described in the paper includes sample fabrication in an aerodynamic levitation furnace, in which crushed pellets of raw material levitate in an oxygen gas flow and are melted by two CO₂ lasers at 2,000C (3,632F). Turning off the lasers cools the melt at 300C/sec, producing vitrified samples 2 mm in diameter.

Aerodynamic levitation, and the containerless glass processing it allows, is necessary because the alumina loading gives the material a high melt point and causes premature crystallization if it comes in contact with a conventional bulk glass container. The paper suggests that the addition of chemicals known as network formers might overcome the need for containerless processing and thus simplify fabrication.

Pat Toensmeier has more than 30 years of experience writing for business-to-business publications. His main areas of coverage have been defense, design, manufacturing, technology and chemicals, especially plastics and composites. He has reported extensively on developments in these areas from the U.S. and Europe, and covered industry events as well in Brazil and Asia. Toensmeier has held various positions at major publishers such as the McGraw-Hill Companies and Hearst Corporation. A graduate of the University of Missouri, he is a contributing editor for several print and online publications. Toensmeier is based in suburban New Haven, Conn.

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