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Glasses

The beauty of vitroceramics

Images reflect the production of one of the world's leading research centers on vitreous materials

Vlad Fokin / Lamav/UfscarTiny, needle-shaped wollastonite crystalsVlad Fokin / Lamav/Ufscar

The evolution of electronic microscopes, which are increasingly being used, has resulted in countless benefits for human beings, especially in the field of health care. However, electronic microscopes have also fueled knowledge on metal and ceramic materials. In addition, they have unveiled the often spectacular forms of tiny samples placed under their lens and mapped by means of electron beams. These beautiful images can be colored artificially on a computer screen and thus lead to a better understanding of the samples’ structure and composition, especially of new materials developed by science researchers.

In line with this reasoning, which combines knowledge and beauty, professor Edgar Dutra Zanotto, coordinator of the Vitreous Materials Laboratory (LaMaV) of the Materials Engineering Department (DEMa) of the Federal University of São Carlos (UFSCar), has compiled the book Cristais em vidro – Ciência e arte. The book was launched to celebrate the 35th anniversary of the LaMaV. As a result, many of the 50 thousand scientific and artistic photo micrographs generated during these years are now available to readers outside the academic community.

The focus of the research studies conducted at the laboratory headed by Zanotto concentrates on the development of new types of glass, on the study of the chemical and physical properties of glass, and on in-depth research of the kinetics and crystallization mechanisms of vitreous materials, essential for the development of vitroceramics. This material, first synthesized 59 years ago, has a combination of special properties, such as strength and toughness, transparency, very low thermal expansion coefficient, chemical durability, and low or zero porosity. This is why the material has been used in a wide array of applications, ranging from kitchen utensils, especially stovetops on electrical stoves, to high-tech products, such as huge mirrors for telescopes, computer hard disk substrates, and artificial teeth.

Vitroceramics is the result of the control of crystallization, a phenomenon that occurs when glass, mixed with a nucleation agent – an additive such as titanium oxide, or phosphorus, silver or copper oxide – is submitted to high temperatures ranging from 500 to 1,100 degrees Celsius. These were the main agents that have been used ever since the LaMaV lab went into operation. In the book, Zanotto mentions that lab studies on kinetics and glass crystallization mechanisms began in 1977, while he was working on his master’s thesis, and continued during his doctorate studies. “In January 1977, I had just concluded my materials engineering course at UFSCar (…) and came across a book on vitroceramics written by Peter McMillan. I was immediately attracted to the subject. It occurred to me that this new kind of material could be the topic of major research work in the field of materials sciences and engineering, and I followed my intuition,” says Zanotto.

Thirty-five years later, LaMaV has acquired international prestige, thanks to the publication of approximately 200 scientific articles in specialized journals. It is considered as one of the seven leading centers for research on vitroceramics, and is on the same level of excellence as similar labs at Japan’s Nagaoka University, at the University of Missouri in the United States, at Jena, in Germany, and at the private research institutes run by Nippon Electric Glass, in Japan, by Corning Glass, in the United States, and by Schott Glass, in Germany. “Our studies have contributed significantly towards a better understanding of the processes that control nucleation and crystal growth in countless glass materials. In the field of science, we have described kinetic processes and have tested theoretical models. In the field of technology, we have created and improved several vitroceramics, some of which have reached the commercial stage,” says Zanotto.

Vlad Fokin and Dani Cassar Superficial nucleation of a lithium metasilicate crystal in the shape of a star fruitVlad Fokin and Dani Cassar

“The most significant fact is that some of the leading glass manufacturers that manufacture vitroceramics have resorted to several of our articles to base the development of their products,” the researcher reports in the book. In addition to being the head of LaMaV, Zanotto is the chairman of the Nucleation, Crystallization and Vitroceramics Committee of the International Commission on Glass, the world’s leading glass research organization. Last November, Zanotto was elected as member of the Academy of Sciences for the Developing World (TWAS).

A description of the activities conducted at LaMaV shows that in the course of its existence, the lab has accounted for the education of a number of researchers with masters, doctorate, and post-doctorate degrees, and to the development of a number of vitreous materials. More specifically, these materials are glass —ceramics that imitate expensive stones, such as marble and granite; bioglass, used to manufacture artificial bones and teeth; vitroceramics derived from blast furnace slag, a major industrial waste; and bioactive materials, such as biosilicate, for dental treatment. Biosilicate has already been patented and licensed for use by a Brazilian company called Vitrovita (see Pesquisa FAPESP nº 158).

“Some of our innovations involved partnerships. An example is the bioglass used for teeth and bones, developed in partnership with the University of Florida. This material is already being marketed by American Biomaterials,” says Zanotto. LaMaV partners with a network of 30 institutions, 20 of which are international and 10 are Brazilian. LaMaV has already filed 12 patents, the latest ones in 2010 and 2011, for glass-ceramic to be used in the production of stove cooktops. Two companies have already manifested their interest in manufacturing these stovetops in Brazil. The other material is a bioactive glass- ceramic scaffold. This is a bioactive material that resembles a sponge. It can be used as support for bone cell growth,” explains LaMaV´s coordinator.

The research studies developed by Zanotto, together with professors Ana Cândida Rodrigues, Oscar Peitl and their group, have received funding from various funding agencies, such as FAPESP, the National Council for Scientific and Technological Development (CNPq) and the Agency for the Promotion of Post-Graduate Studies (Capes). The researcher has coordinated two major projects funded by the Foundation, namely, “Current problems related to glass crystallization,” which has already been concluded; and “Kinetic processes in glass and vitroceramics,” which is still ongoing. The projects were conducted at the 800 square-meter laboratory in São Carlos.

The Projects
1. Current problems related to glass crystallization (nº 1999/00871-2); Modality Thematic Project; Coordinator Edgar Dutra Zanotto – UFSCar; Investment R$ 468,674.44 and US$ 190,408.30 (FAPESP)
2. Kinetic processes in glass and vitroceramics (nº 2007/08179-9); Modality Thematic Project; Coordinator Edgar Dutra Zanotto – UFSCar; Investment R$ 343,670.74 and US$ 573,410.28 (FAPESP)

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