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TAPPI Spring Technical Conference and Exhibit

作者： Dimetry, Basant G. Bousfield, Douglas W. Paper Surface Science Program Department of Chemical Engineering University of Maine Orono ME 04469-5737 United States

ISBN: (纸本)1930657064

Polymers are added to paper coatings to modify rheology and for water retention. Recent papers have reported conflicting results with regard to the relationship between coating rheology and the final coating structure. The final coating structure is important because it determines the physical, optical, and printing properties. This work focuses on expanding the database related to the influence of various polymers on rheology and the final coating structure. Coatings with different polymers were characterized in terms of steady shear and viscoelastic properties. These coatings were applied onto paper and plastic film with a laboratory rod coater. The final coating structure after drying was characterized in terms of void fraction, water absorption rate, gloss, and light scattering coefficient. A relationship between the elasticity of the suspensions and the final coating structure was found for the associative thickeners. However, the concentration and molecular weights of cellulosic thickeners did change the wet state rheology, but not the final coating structure. For all coatings, a correlation is found between shear viscosity and gloss. These results confirm past work and show that certain types of polymers must be able to preserve the wet state structure during the drying event, but other types do not.

关键词： Paper coating

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Activity generation on single wire tables

Activity generation on single wire tables

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TAPPI Spring Technical Conference and Exhibit

作者： Bousfield, Douglas W. Wildfong, Vaughn Porter, Joseph Foils, Johnson Johnson, Asten Paper Surface Science Program Department of Chemical Engineering University of Maine Orono ME 04469-5737 United States

ISBN: (纸本)1930657064

For a number of years, papermakers have known that it is important to generate good "activity" on the table in order to produce a good quality product with good formation. However, little has been done on a fundamental level to understand this phenomenon. In this paper, a model is proposed to predict the activity level based on the local curvature of the wire. The results depend on the stock layer thickness, fluid properties, and the local curvature of the wire. When the conditions are sufficient for instabilities to grow, columns of fluid are predicted to erupt from the surface. The size of these columns are related to the size of the drops that would be formed if these columns. Predictions are compared to actual mill results. The time for the drops to form and their size are predicted by the model.

关键词： Papermaking

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Surface tension driven leveling of spray droplets

Surface tension driven leveling of spray droplets

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Proceedings of the 2003 TAPPI 8th Advanced Coating Fundamentals Symposium

作者： Bousfield, Douglas W. Toivakka, Martti Paper Surface Science Program Department of Chemical Engineering University of Maine Orono ME 04469 United States Laboratory of Paper Chemistry Åbo Akademi University FIN-20500 Turku Finland

ISBN: (纸本)1930657048

Spray coating has the potential to be a major non-contact coating method. However, to obtain good coverage and uniformity of the coating layer on paper, sufficient leveling of droplets must take place. Though there has been some work on the leveling of scratches in coating layers due to blades [1,2], little has been done to understand the leveling of droplets on paper. A model of surface tension driven leveling is developed that can start with the shape after the droplet impact event, and follow the leveling of the fluid layer as a function of time. The model accounts for surface tension of fluid, viscosity, and base paper absorption characteristics, such as void fraction, pore size and contact angle. The competing processes of leveling and absorption determine the final surface uniformity. The key parameters during leveling are droplet size and fluid viscosity. Other parameters such as coating solids content and filter cake flow resistance can also result in incomplete leveling and lead to poor quality coating layers. The basic predictions of the model are supported by the general trends reported on spray coating.

关键词： Paper coating

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Theoretical and experimental study of barium zinc-cadmium tantalate-based microwave dielectrics

Theoretical and experimental study of barium zinc-cadmium ta...

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Materials, Integration and Packaging Issues for High - Frequency Devices

作者： Liu, Shaojun Van Schilfgaarde, Mark Sun, Jian Badd, Louisa Smith, David Petrovixc, Novak S. Taylor, R. Newman, N. Chemical Engineering Department United States Sci./Eng. of Materials Program United States Center for Solid State Science Arizona State University Tempe AZ 85287-6006 United States Electrical Engineering Department Queens Land University Paddington 4064 Australia

Single-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic was not formed from solid-state diffusion alone. The resulting Ba(Cd0.327Zn0.006Ta2/3)O3 material sintered at 1550°C exhibits a dielectric constant of ∼33 and loss tangent of -5 at 2 GHz. In our more recent work, we have used boron as a sintering aid to facilitate sintering at temperatures as low as 1300°C, enhance the structural quality and improve the microwave properties of Ba(Cd1/3Ta2/3)O3 dielectrics. TEM results indicate that the liquid sintering mechanism is an important factor for boron concentrations exceeding 0.5wt%, while a point defect mechanism plays the dominant role at lower boron concentrations. The presence of superstructure peaks and splitting of the (220) and (214) peaks in X-ray diffraction spectra are direct evidence for the distortion from cubic symmetry as a result of Cd and Ta ordering on the B-site. Ab-initio electronic structure calculations within the local density functional approximation have been used to give insight into the unusual properties of this class of materials. In both Ba(Zn 1/3Ta2/3)O3 and Ba(Cd/3Ta 2/3)O3, the conduction band maximum and valence band minimum are composed of mostly weakly itinerant Ta 5d-and Zn-3d/Cd-4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and possibly inherently lower intrinsic microwave loss than comparable ionic materials.

关键词： Barium compounds

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Particle motion modeling for particle size distributions in blade geometries

Particle motion modeling for particle size distributions in ...

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Proceedings of the 2003 TAPPI 8th Advanced Coating Fundamentals Symposium

作者： Lyons, Anthony Iyer, Rajan Bousfield, Douglas W. IMERYS 618 Kaolin Rd. Sandersville GA 31082 United States Paper Surface Science Program Department of Chemical Engineering University of Maine Orono ME 04469-5737 United States

ISBN: (纸本)1930657048

For several years it has been seen that narrow particle size distributions tend to need to be run at lower solids than broad particle size distributions. In addition, some pigments tend to be associated with build up on blades during coating, while others can be linked to rapid blade wear. Little detailed understanding of the mechanisms behind these issues has been reported in the literature. An improved Stokesian Dynamics technique is used to describe the motion of several thousand particles in the entrance region of a blade. The new technique uses some storage and time saving methods, allowing for an increase in number of particles to be run in the simulation on a personal computer. Any particle size distribution can be input into the model, but the method is limited to spherical particles. This method represents an improvement over past work. Boundary roughness can be included by using boundary particles in fixed locations. In all cases, an accumulation of fine particles is seen in the stagnation region and along boundaries. This agrees with the work of Toivakka and Eklund (1996) for flow in a pipe. If a significant number of these small particles are latex, the forces on these particles could cause a buildup of solid material on the back side of the blade. There is also an accumulation of fine particles along the surface of the blade. This result may point to the coating layer being either latex or colloidal fraction rich at the exit of the blade. The average blade forces are different between different particle size distributions, but these differences are not large.

关键词： Pigments

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Lateral Epitaxial Overgrowth of InAs on (100) GaAs Substrates

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MRS Online Proceedings Library 2003年第1期744卷 1-6页

作者： Suryanarayanan, Ganesan Khandekar, Anish A. Hawkins, Brian E. Kuech, Thomas F. Babcock, Susan E. Materials Science Program University of Wisconsin - Madison Madison USA Department of Chemical Engineering University of Wisconsin - Madison Madison USA Department of Materials Science and Engineering University of Wisconsin - Madison Madison USA

The microstructure of epitaxial InAs thin films grown by MOCVD on mask-patterned “LEO” (lateral epitaxial overgrowth) GaAs and on unpatterned GaAs substrates was studied using double-crystal x-ray diffraction, scanning electron microscopy and cross-sectional transmission electron microscopy. This paper describes the improvement in crystal quality (factor of 20 reduction in x-ray rocking curve width), the order of magnitude reduction in dislocation density, and the rearrangement of the remaining extended defects that were observed in the LEO material when compared to the film grown on the unpatterned wafer.

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Ordered structures in Ba(Cd1/3Ta2/3)O3 microwave ceramics: A transmission electron microscopy study

Ordered structures in Ba(Cd1/3Ta2/3)O3 microwave ceramics: A...

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Materials, Integration and Packaging Issues for High - Frequency Devices

作者： Sun, J. Liu, S.J. Newman, N. Smith, David J. Center for Solid State Science Arizona State University Tempe AZ 85287 United States Department of Chemical Engineering Materials and Engineering Program Arizona State University Tempe AZ 85287 United States Department of Physics Arizona State University Tempe AZ 85287 United States Sch. of Mat. Science and Engineering Shanghai Jiao-Tong University Shanghai 20003 China

Ordered structures of Ba(Cd1/3Ta1/2)O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-ordered structure of 1:2 with hexagonal symmetry for Ba(Cd1/3Ta1/2)O3 with boron additive. No significant changes in ordered structures were observed after long-period annealing. The 1:2 ordered domain structures (average domain size ∼ 18 nm) and high-density domain boundaries induced by ordering were observed for Ba(Cd1/3Ta1/2)O3 without boron additive sintered at relatively high temperature. The sintering process has a profound influence on the microstructure of Ba(Cd1/3Ta2/3)O 3 ceramics.

关键词： Barium compounds

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Growing the national innovation system: Reshaping professional graduate education to ensure a strong U.S. engineering workforce

Growing the national innovation system: Reshaping profession...

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2003 ASEE Annual Conference and Exposition: Staying in Tune with engineering Education

作者： Keating, Donald A. Stanford, Thomas G. Dunlap, Duane D. Depew, Dennis R. Tricamo, Stephen J. Sebastian, Donald H. Fenster, Saul K. Jakubowski, Gerald S. Mendelson, Mel I. Bennett, Ronald J. Snellenberger, Jay M. University of South Carolina Western Carolina University Purdue University New Jersey Institute of Technology Loyola Marymount University St Thomas University Rolls-Royce Corporation Department of Engineering University of St. Thomas School of Technology Purdue University Department of Engineering Technology Western Carolina University Department of Mechanical Engineering University of South Carolina Department of Chemical Engineering University of South Carolina Department of Industrial Engineering College of Science and Engineering Loyola Marymount University Department of Mechanical Engineering Eng. and Prod. Mgmt. Grad. Program Loyola Marymount University Rolls-Royce Corporation Indianapolis IN

This is the first paper in the special panel session on reshaping graduate education to better serve the needs of the practicing profession in industry to ensure a strong U.S. engineering workforce for competitiveness. The newly established National Collaborative Task Force of the Graduate Studies Division of ASEE is taking a key leadership role to enact major reform in graduate engineering education at the national level to spur U.S. technological innovation, unleash industrial creativity, and enhance competitiveness. This paper addresses the national urgency for reform in higher education to strengthen U.S. innovative capacity and outlines purposeful action that needs to be taken in transforming graduate education to better meet the needs of engineering practice for leadership of technology innovation. Further, it defines a road map for change to help guide the reshaping of professional graduate education as a "system for lifelong learning" that is specifically designed to support the continuous development of technology in industry and to grow the nation's engineering graduates as technology leaders in industry simultaneously.

关键词： engineering education

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Anistropy and breakup of extended droplets in immiscible blends

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Journal of Non-Newtonian Fluid Mechanics 2003年第1期113卷 29-48页

作者： Almusallam, Abdulwahab S. Larson, Ronald G. Solomon, Michael J. Department of Chemical Engineering College of Engineering University of Michigan Ann Arbor MI 48109-2136 United States Macromolecular Sci./Eng. Program University of Michigan Ann Arbor MI 48109 United States

A frame-invariant constitutive model is developed to describe the changes in droplet anisotropy and stress in a dilute blend of Newtonian droplets in a Newtonian matrix after imposition of a large step strain. The model, based on the Tomotika theory [Proc. R. Soc. London, Ser. A 150 (1935) 322], describes the evolution of components of the anisotropy tensor from values consistent with a cylindrical shape with undulations to values consistent with a series of fragmented spherical droplets. This model is compared to experimental measurements of droplet shape anisotropy for single droplets that were deformed to various degrees and then allowed to relax. Here, the droplet shape anisotropy is defined using the Doi-Ohta anisotropy tensor [J. Chem. Phys. 95 (1991) 1242], which is obtained by integrating over the droplet interfacial position as determined by microscopic image analysis. For moderately extended droplets, the anisotropy is affected by the ends of the droplet, and thus does not agree with breakup model predictions based on the Tomotika theory, which neglects contributions from the ends of the droplet. When droplet end-effects are subtracted, and only the effects of undulations in the droplet center remain, good agreement between theory and experiment is achieved. Data at various strains also superimpose on a single breakup line when end-effects are neglected. © 2003 Elsevier B.V. All rights reserved.

关键词： Newtonian flow

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Pressure, Temperature, and Thickness Dependence of CO2-Induced Devitrification of Polymer Films

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Physical Review Letters 2003年第17期91卷 175503-175503页

作者： Joseph Q. Pham Stephen M. Sirard Keith P. Johnston Peter F. Green Graduate Program in Materials Science and Engineering University of Texas at Austin Austin Texas 78712 USA Department of Chemical Engineering and Texas Materials Institute University of Texas at Austin Austin Texas 78712 USA

The glass transition temperature is known to increase with decreasing film thickness h for sufficiently thin poly(methyl methacrylate) films supported by silicon oxide substrates. We show that this system undergoes a CO2 pressure-induced devitrification transition, Pg, which is film thickness dependent, Pg(h)=ΔPg+Pgbulk. Pgbulk is the bulk glass transition and ΔPg can be positive or negative depending on T and P. The phenomenon of retrograde vitrification, wherein the polymer exhibits a rubbery-to-glassy-to-rubbery transition upon changing temperature isobarically, is also shown to occur in this system and it is film thickness dependent.

关键词： Polymethyl methacrylates

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