Lucalox Alumina: The Ceramic That Revolutionized Outdoor Lighting
- PDF / 9,490,063 Bytes
- 9 Pages / 576 x 777.6 pts Page_size
- 77 Downloads / 146 Views
required a considerable amount of enlightened empirical work, but it raised many questions the answers to which contributed to an understanding of the competitive processes that occur during sintering. This article** will emphasize the research that led to the new ceramic, the circumstances under which it was performed, and the new understanding that it produced. Doping with MgO plays an important role in permitting the development of the necessary microstructure in the ceramic, and the mechanism by which it operates is still being argued. Toward the end of the article, I briefly discuss this problem. This is primarily a personal narrative because I was closely involved with nearly all the steps. The development of the lamp itself followed the ceramic development by several years and was done independently at the Large Lamp Division of GE. I shall discuss that work only briefly. Early Work By the mid-1950s, the great effort to make metallurgy scientific, which started at the end of World War II, was in full swing. Its goals were more to understand and quantitatively explain wellknown properties of metals than to develop improved alloys. Solid-state diffusion, the origins of microstructure by the nucleation and growth of new phases, crystal growth, grain growth and sintering, and the role of microstructure and dislocations in controlling properties such as flow resistance, work hardening, and fracture were among the phenomena studied. Ceramics then, to the purist, were materials made from clay mixed with other
* Lucalox is a trademark of the General Electric Company.
I
** Part of this paper draws upon the manuscript for a seminar on the new lamp and new ceramic given to the Massachusetss Institute of Technology Metallurgy Department in December 1967.
MRS BULLETIN/JUNE 1996
Links of Science & Technology describes the origin, science, technology, and unique accomplishments of advances in materials science that have had significant practical value.
minerals and then fired to consolidate them. The final product consisted of crystalline phases bonded by a silicate glass. A few new single-phase, nonmetallic, polycrystalline inorganic materials such as barium titanate ferroelectrics, ferrimagnetic ferrites, and uranium dioxide nuclear fuel had been developed during or after World War II. Some older materials such as "recrystallized" alumina were sometimes called ceramics, particularly in the United States, but the usage was rare except there. However, this class of materials was becoming technologically important. I had been active in metals research for most of the previous decade. In 1954 1 was asked by Herbert Hollomon, manager of the Metallurgy Department of the GE Research Laboratory, to form a group to study ceramics. The goals were to understand the origin of properties and to learn to control them by using the ideas and techniques then being used in metals research as well as any other appropriate methods. A group of people with a variety of backgrounds in metallurgy, crystallography, chemistry, and of course
Data Loading...
