Why are low-energy ions relevant to the surface processing of electronic materials? The answer lies in the overriding trend of miniaturization in microelectronics. The achievement of these feats in ultrasmall architecture has required surface processing capabilities that allow layer addition and removal with incredible precision. The resulting benefits of greater capacity and speed at a plummeting cost per function are near legendary.

The ability of low-energy ions to enhance the precision of surface etching, cleaning, and deposition/growth processes (Figure 1) provides one basis for the interest in ion-assisted processes. Low-energy ions are used, for example, to enhance the sharpness of side walls in plasma etching and to improve step coverage by metal layers in sputter deposition. Emerging optoelectronic applications such as forming ridges for wave-guides and ultrasmooth vertical surfaces for lasers further extend piesent requirements, and low-energy ions again provide one tool to help in this area of ultraprecise materials control. Trends associated with the decreased feature size include the movement from wet chemical processing to dry processing, the continuing need for reductions in defect densities, and the drive toward reduced temperatures and times in process steps.

How do the above trends focus interest on studies of low-energy ion-assisted processes? In current applications, these trends are driving the need for increased atomic-level understanding of the ion-enhancement mechanisms, for example, in reactive ion etching to minimize defect production and enhance surface chemical reactions.

The U.S. Environmental Protection Agency (EPA) has determined that deep geologic disposal is appropriate for three types of radioactive waste generated in the United States: spent fuel, high-level waste, and transuranic waste. Spent fuel is nuclear fuel that has been discharged from a reactor after irradiation. High-level waste (HLW) is the highly radioactive material that remains after the reprocessing of spent fuel to recover uranium or plutonium. Transuranic (TRU) waste is any waste material contaminated with more than 100 nCi/g of elements having atomic numbers greater than 92 and half-lives longer than 20 years. Spent fuel and HLW can result from either commercial or governmental activities, although no commercially generated spent fuel has been reprocessed since 1972. TRU waste results primarily from the design and manufacture of nuclear weapons, not from nuclear power plants.

The physical characteristics of TRU waste differ substantially from those of spent fuel and HLW. This imposes different requirements on materials associated with containment and isolation, so TRU waste will be discussed separately from spent fuel and HLW Because all three are judged to be particularly dangerous to human beings and the environment, the EPA standard requires a demonstration of adequate 10,000-year performance of geologic repositories for these radioactive wastes. The U.S. Department of Energy (DOE) is responsible for implementing the standard by designing, siting, and building the repositories.

This article briefly describes TRU waste, HLW, and spent fuel and the two repositories currently planned by DOE. It con cludes by offering some observations on materials compatibility among waste, container materials, and host rock.

For most materials scientists, as for most people, John Donne's lines “and therefore never send to know for whom the bell tolls. It tolls for thee.” are simply inspired verse. Increasing recognition of the interplay between human economic activity and global environmental perturbations, however, are beginning to add a cold air of prescience to John's words: “Ask not for whom the CFCs are emitted. They are emitted for thee.”

The need for greater understanding, and new, more systematic approaches to these intertwined economic/environmental issues is becoming more apparent. What is perhaps not so clear is the critical role that materials scientists and engineers must play in this effort. An analysis of the symbiotic relationships among economic development, human population growth, and the uses and flows of materials throughout the economy clearly demonstrates this role.

The intuitive feeling held by many technologists—that they are part of the solution, not part of the problem—certainly appears to be correct. But it will require growth on our part, and a more systems-oriented and comprehensive view of our role, if this promise is to be fulfilled.

The total world production of water-soluble polymers is estimated to be greater than five million tons per year. Water-soluble polymers are most conveniently described according to their origin in three classes (see Structures 1-6):

∎ Natural polymers, including starch (1) and cellulose (2);

∎ chemically modified natural polymers, including, for example, hydroxyethyl starch (3) and cellulose acetate (4); and

∎ synthetic polymers, the most important of which are polyacrylamide (5) and polyvinyl alcohol (6), (commonly composed of both alcohol and acetate groups as shown). The widespread use of these materials is due to both their availability and the range of useful physical properties found in the various natural and chemically modified natural polymers.

Of the commercial water-soluble polymers, approximately 50–80% are based on natural polysaccharide materials. One of the primary reasons that these materials find such widespread use is the dramatic response of their properties to changes in their functionality and stereochemistry: chemical modification or the combination of polysaccharides with other polymeric materials has yielded materials whose applications range from explosives to food additives. Although efforts directed at controlling the properties of polysaccharides has resulted in a wide variety of useful materials, we felt control of the composition of carbohydrate-based polymers at the molecular level would provide materials with properties superior to those derived from natural and chemically modified polysaccharide materials.

Our approach for the preparation of new carbohydrate-based materials is to use the carbohydrate as a template for the introduction of desired functionality with complete regiochemical and stereochemical control by both chemical and enzymatic methods (Scheme I).

Friable natural products are often used in articles of personal adornment, and the perishable nature of these materials presents a unique challenge to museums. At the Smithsonian's National Museum of American History, a collection of gowns worn by the First Ladies of the United States is a popular display of historical and sentimental import. Opened to the public on February 1, 1914, fifteen gowns were displayed as part of a “Period Costumes“ exhibit in the U.S. National Museum (now known as the Arts and Industries Building). Within just a few years, the exhibit was recognized as “one of the most interesting and popular in the Museum.” A First Ladies' Hall was created in the mid-1950s to exhibit the gown collection in period room settings. This design theme continued when the Hall moved to the Museum of American History and Technology (now the National Museum of American History) in 1964. The First Ladies' Hall was closed for renovation in 1987, allowing the curatorial staff to reassess the collection's use and conservators to perform long overdue examinations and treatments. Reinstallation of the exhibit is scheduled for spring 1992.

The First Ladies' conservation project includes a history of each gown's use and exhibition as related to its physical condition and also includes stabilization treatments to meet the demands of future display. The current conservation project provided an unusual opportunity for extensive research into fabric deterioration of a popular and important collection. The goals of the research are twofold: first, to determine each object's state of preservation by studying the effectivenss of several analytical approaches with minimal destructive sampling and, second, to begin investigating the mechanisms involved in the degradation of silk, the material predominant in this collection.

An engineer or a research scientist developing a new process is not often encouraged to build quality systems into the product or manufacturing process. However, today's market places greater emphasis and focus on stability and reliability of manufactured products. Corning has developed “quality architecture” to help engineers and scientists define and build the system elements that allow quality to be built into a product, rather than rely on inspection. A researcher or engineer can then provide a first-generation prototype of the quality systems, in addition to the first-generation prototypes of equipment and processes.

What is Quality Architecture?

Quality architecture involves designing a system that controls the manufacturing process in a stable and consistent manner, and provides for continuous improvement. The architecture defines and ensures the appropriate interdependence between product specifications, materials used in and by the process, product and process measurements, statistical process control and information systems. This results in a consistent and reliable product—features valued in today's market.