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Advanced Materials
Pages 35-62

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From page 37...
... Early artisans and builders discovered secrets to transforming substances into functional materials often by happenstance, and modern-day experimentalists established trends through systematic study and categorization. Until recently, most material discoveries have resulted from exhaustive searches by trial and error.
From page 38...
... Physical understanding of atomistic and molecular processes at this level can be used to construct atomistic-based continuum equations to study processes at the mesoscopic level of a few microns using finite difference and finite element solution methods. Finally, all of this knowledge can be coarse "rained into constitutive laws and other continuum equations that, combined with finite element simulation techniques, can be used to model the bulk structural, electronic, thermal, and relax ational properties of materials.
From page 39...
... rithmic limitations make the simulation of long-time processes such as phase separation in bulk polymeric materials with atomistic methods extremely time consuming. Three examples of using simulation to elucidate trends and guide experiments in pattern formation in polymer blends are as follows: · Phase separation of ultrathin polymer-blend films on patterned substrates.
From page 40...
... with a modulated boundary interaction on the substrate surface. The boundary interaction was designed such that the magnitude of the chemical potential favoring a particular component alternated on the substrate surface with some chosen periodicity.
From page 41...
... · Pattern formation in liquid crystal display materials. Materials used in liquid crystal displays, like those in laptop computers, are typically composed of droplets of liquid crystal dispersed in a polymer matrix (so-called polymerdispersed liquid crystals)
From page 42...
... 42 A B ADVANCED MATERIAES FIGURE 3 (a) Intermediate stage of dPS/PB-blend film phase separating on a patterned substrate.
From page 43...
... Composition waves radiate outward from the filler particle and join with the "normal" spinodal decomposition pattern in the bulk. Eventually, only a thin wetting layer remains.
From page 44...
... >I'd; (USE: FIGURE 5 (a) Computer simulation using the Cahn-Hilliard method of a polymer-blend phase separating in the presence of many filler particles.
From page 45...
... (c) Computer simulation of a polymer-dispersed liquid crystal undergoing phase separation following a thermal quench from a mixed, isotropic phase to a de-mixed, nematic liquid crystal-rich phase coexisting with an isotropic polymer-rich phase.
From page 46...
... 1995. Computer simulations of spinodal decomposition in polymer blends.
From page 47...
... Since the ability to shrink feature size is critically dependent on the technologies involved in delineation of the circuit pattern, advances in high-resolution imaging materials could be considered one of the key enablers that have contributed to the unprecedented growth in microelectronics technologies (Thompson et al., 1994~. The lithographic technology for printing integrated circuits consists of three main elements: the exposure tool, the mask technology, and the resist technology.
From page 48...
... light source because of their opacity and low throughput owing to insufficient photospeeds because of low quantum yields and low-energy density at the wafer plane of the deep-UV exposure tools. The materials community met the challenge by delivering the first revolutionary change in resist materials chemistry by adopting chemically amplified resist schemes, in which one photoproduct catalyzes several hundred
From page 49...
... The invention and innovation of materials that use partially protected polyvinyl phenol or its copolymers in combination with PAGs that generate weaker photoacids and addition of bases to resist formulation have allowed the use of chemically amplified resists for optical projection printing at and below the conventional Rayleigh diffraction limit, contributing to the extension of optical lithography. The chemically amplified principles have also been applied to all other resist systems for photospeed, resolution, and process latitude enhancements.
From page 50...
... While resists based on these materials showed some promise, etch stability and incompatibility with conventional aqueous-base developers are issues that are still unresolved. Bell Labs has pioneered cyclo-olefin-maleic anhydride alternating copolymers with acrylates as an attractive alternative to methacrylate-based matrix resins and other alternate "all alicyclic backbone" polymers (Houlihan et al., 1997~.
From page 51...
... iodonium cyclamate PDB FIGURE 2 193-nm resist components. Alternating copolymers of norbornene with maleic anhydride with acrylic acid and t-butyl acrylate "impurities," monomeric and oligomeric dissolution inhibitors, photoacid generators (PAG)
From page 52...
... Base additives generally have been added to chemically amplified resist formulations to "buffer" the resist from the fluctuations in airborne adventitious amine (e.g., ammonia, N-methyl pyrrolidone) concentrations in clean room environments.
From page 53...
... Such a perspective is grossly inaccurate, and thus it is gratifying and appropriate to see steel included in the Advanced Materials session of the National Academy of Engineering's Symposium on Frontiers of Engineering. This paper will provide an introduction to the importance of technology in the steel industry, an overview of current developments related to automotive applications of sheet steels, and specific highlights of recent accomplishments in the area of "bake-hardening" sheet steels.
From page 54...
... It is not possible to review these opportunities in depth here. Readers are referred to the Steel Industry Technology Roadmap published in March 1998, which was prepared by the domestic steel industry (member companies of the American Iron and Steel Institute and the Steel Manufacturers Association)
From page 55...
... Steels compete vigorously with other materials in many of these applications, but steel has generally remained the material of choice due to its favorable combination of property characteristics and economics. Automotive sheet steels will be used here to provide an example of some current development areas in steel technology, and a specific product development area also will be highlighted.
From page 56...
... , etc. Enhanced liquid steel processing (e.g., refining, casting)
From page 57...
... One consequence of the trend toward reduced thickness of sheet steels for weight reduction is increased sensitivity to denting of the outer panels, from shopping carts, doors opening/closing, hail, flying stones, etc. New steel grades with improved dent resistance have been developed for such applications, including "bake-hardenable" products, which are becoming extensively used and derive a portion of their strength from metallurgical changes that are designed to occur in the elevated temperature paint curing cycle during poststamping assembly of the vehicle.
From page 58...
... It is appropriate to consider one particular metallurgical development in more depth to appreciate some of the excitement, interest, and opportunity that remains in the field of ferrous physical metallurgy. Ferrous physical metallurgy remains at the heart of steel product development, and we will consider specifically here the development of bake-hardenable sheet steels for dent-resistant auto body applications produced via a hot-dip coating process.
From page 59...
... Identification of an alloying approach associated with "intermediate" carbide stability was considered to be promising, which eventually led to the selection of vanadium as a key component for subsequent laboratory investigation. Vanadium is not a common alloy addition in formable sheet steels.
From page 60...
... REFERENCES American Iron and Steel Institute, Steel Manufacturers Association, and Department of Energy.
From page 61...
... 1998. Development of vanadium-alloyed, bake-hardenable sheet steels for hot-dip coated applications.


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