Standards and Technology, Gaithersburg, - PDF document

Standards and Technology, Gaithersburg, Ceramic Society-Handwerker et In 1955, Coble joined General Electric Research Laboratories. those days the notion major industries should support research on fundamental problems at “campuslike” laboratories had been Cyril Stanley Institute for the Metals at Chicago, put together GE’s ceramics group, including Coble, E. Carter, Charles, M. Mitoff, and H. Rhodes; Dave Kingery collaborated this group as a consultant GE. Dave assembled the metallurgy counterpart, containing J. W. E. W. Kasper, and R. A. Oriani; F. C. Frank served as a consultant These two groups worked closely other GE materials scientists, including T. Aust, C. Fisher, J. Gilman, J. Swalin, and The interaction between ceramists and metallurgists brought forth a whole concepts and research tools ceramic microstructures, even including the ceramists looked their materials. Before World War ceramic microstructures had more in common geologic specimens than the fine-grained materials as polycrystalline ceramics. Ceramics were typically multiphase, large-grained, usually porous, refractory materials, examined using petrographic sections for the thickness the section smaller than the grain size the ceramic. Through his interactions Clarence Zener in Chicago, Burke found the features being discovered in metal microstructures were observable in ceramics using metallo- graphic polished sections instead thin sections. With this better view grain boundaries and other microstructural features, high-temperature kinetics processes that controlled microstructure evolution became a reasonable goal for the ceramics group. According to a report written year Coble joined the company, the specific charter Burke’s Ceramics Studies section answers to the question, ‘How does the the composition, crystal structure, and various conditions, and are the relations between this structure and the mechanical, magnetic, electrical, and optical behav- systematic approach metals group) base their studies has led over the metals, but is something the study Metals and Ceramics Report, 1955, p. 9.) approach and the interaction among ceramists and metallurgists to a host scientific and technological discoveries. active member Ceramics Research Department, Coble flourished in this stimulating scientific atmosphere and to the idea of additives to change the degree grain boundaries. The notion Zener pinning grain boundaries had gained greater credibility when manganese sulfide particles were found to be the critical element ling the grain size in the important alloy used for transformers. Likewise for ceramics, the discovery (by Coble and Burke) that pores ceramics could pin grain boundaries or could grain boundaries and entrapped the grains, depending on the processing chemistry, was important in understanding sintering. Since pores dropped from boundaries virtually stopped shrinking, down grain-boundary motion that pores could keep attached became important working strategy. came one the most important discoveries ceramists and GE: Coble’s invention in 1957 adding small magnesia to alumina to allow it to sinter to theoretical density without pores becoming entrapped within grains and out the concomitant abnormal grain growth. Suddenly the impossible was possible: alumina fully, all pores remained attached to grain boundaries during sintering, and the grain size remained small and uniform. This process to make dense alumina, made possible the production high-pressure sodium-vapor lamps highway illumination. this inven- tion, Coble awarded the National Institute Ceramic Engineers’ Professional Achievement Award in Coble’s technological achievement inspired the ceramics community expect better microstructures materials and trig- gered considerable innovative scientific research on the mechanisms sintering and grain growth over the following dopant additions being effective in concert with the emergence hot pressing a viable technique the expectation that a fine-grained, dense microstructure should be attainable virtually any ceramic or refractory material. Such reflected in the fab- nitride, initially hot-pressing in England, and then silicon carbide, sintering; the latter covered in 1975 Svante Prochazka, a former Coble student, then at GE. plus that others, including Coble and former MIT students W. H. Rhodes and R. E. Mistler, reinforced the slowly emerging concept that, for density should pressureless sintering the use the proper dopant and sintering atmosphere and good submicrometer powder. Similar advances followed for electrical and functional ceramics. addition, the mechanisms leading to the changes in alumina the addition magnesia have been long studied and debated. In the book, Coble for his 60th in 1988, Martin Harmer cited over papers in which the authors to unravel the mystery magnesia does expedite the sintering alumina. These revealed interesting phenomena, but also seemed largely con- Coble’s early intuition boundary migration solute drag was the predominant factor in producing high-den- sity alumina. 1960, Coble rejoined at MIT, this time as assistant professor the metallurgy department. a vision establishing the foundations physical ceramics and processing science. successful collaboration between Coble and Kingery continued funding from the Energy and its predecessor agencies (AEC and ERDA) years. The academic group grew to a peak seven faculty members, plus staff, students, and stimulating visitors. Coble became an associate professor 1962, received tenure in 1966, was named a full professor in 1969, and was granted emeritus status he retired 1988. During his 28 years on the MIT faculty, Coble was the thesis advisor for 24 masters degree students, 43 students, and coadvised published over 114 papers. MIT, Coble established his reputation deriving proper theoretical descriptions mass transport during sintering and creep and for understanding relationships among various processes. In terms both ceramic science and engineering, achievements were contributions to the understanding microstructural changes during sintering. Equally important to advancement of ceramic science Coble’s commitment, along Kingery, to doing all the measurements necessary for critical and quantitative tests of theory. seminal papers on the modeling of intermediate- and final-stage sintering, hot-press- ing, and creep grain-boundary diffusion are classic works which helped define the field. These, especially the creep paper, his cited, were also crucial understanding the high-temperature behavior metals. Coble received the Ross Coffin Purdy Award from the American Ceramic Society in 1970 paper on the relationship between sintering and pressing. This clearly showed the similarity in the diffusional transport that occurs between pores and grain boundaries response to external and capillary forces. His theoretical and experimental on the critical steps the sintering process is summarized classic paper, “Current Paradigms Ceramic Powder Processing.” Coble’s contribution to ceramic science goes beyond the simple aspects solid-state sintering. recognized early the impor- liquid-phase sintering, enhanced sintering the eutectic, chemical reactions during sintering, and diffusion-induced grain-boundary migration. He also addressed the effects particle-size distributions on differential densification and internal stress generation. He a pioneer in promoting composition control in ceramics basic science research. For example, effects compositional changes the structure and composition grain boundaries in alumina were identified by P. A. Morris and Coble. Fluorescence measurements of internal stress alumina were Blendell and Coble and were recently developed Clarke and co-workers into precise technique measuring the stress in individual grains. Finally, Coble illustrated his breadth and his propensity conceiving clever experiments in the study electrical conductivity and electronic structure alumina. Using an innovative tubular sample design, Kitazawa and Coble measured the electrical con- ductivity and transference numbers precisely than was then common; this revealed the conductivity to be electronic rather than ionic over wider range of conditions than expected. This discovery then motivated the subsequent development J. B. French, and Coble techniques to measure the optical reflectivity at unprecedentedly high temperatures from which much about the electronic structure and its temperature dependence has been deduced for wide-band-gap oxides. addition to Bob Coble’s public contributions to ceramic science, he inspired several generations students and colleagues dedication to ceramic science, enthusiasm research, ability to isolate the fundamental issues in many complex problems, and unas- suming attitude toward science. Coble’s research style was suited to the MIT academic environment. He enjoyed students and colleagues, both scientifically and socially. His favorite interactions were graduate students, he took great joy in challenging and inspiring students important, unanswered problems in being similarly challenged. problems for which the solutions were known held little interest him. Personal glory no importance to Coble. His philoso- was that nature presented puzzles, and, someone solved one problem before he could he was glad to know the solution he could to another, equally interesting problem. Above he was interested in knowing scientific truths, much more than in having personally been the discoverer these truths. While maintaining high standards for scholarship, he also believed that recreation and friendship were important parts his promotion to associate professor, external reviewer wrote, “In his undergraduate work at Bethany College received superior marks in the physics course offered, while keeping active social schedule.” This was in the laboratory out. Coble and his enriched the lives graduate students through innumerable Ver- skiing weekends and picnics at their home. Through the combined Coble, others on the MIT faculty, and the laboratory manager, Pat Kearney, the students received critical help needed their experiments as community from all differ- ent types interactions, from coffee breaks to monthly in-laboratory hot-dog roasts. Coble was the recipient many lectureships, prizes, and other external awards, but these means fully indicate the legacies he left to ceramic science and engineering. was made the National Academy and he received prestigious Humbolt Stiftung award in that permitted him Planck Institute in Stuttgart, Germany. His legacy, course, includes many people both academia and industry throughout the United States and several other countries, whose cre- ativity and standards for scholarship were, at least in part, inspired Coble as students or colleagues. Finally, his instincts for good problems and honest reporting are revealed in the ongoing research topics on which he instigated work. this edition shows the “Morris” grain boundary that was grown at float zone technique, under the inspiration Coble and the aid John Haggerty, and recently analyzed high-resolution TEM and modeled in unexpected detail by the group in Stutt- gart, under Ruhle, as reported in three different papers at the Schloss Ringberg meeting. That meeting also had presentations the same topics discussed above, course including one on the role magnesia in inhibiting abnormal grain growth, Finally, Coble’s papers, like his conversations, were not always easy understand: he assumed that the clearly see the dichotomy that he saw between was “understood” about process and him. Time and Coble to see others failed to see. spoke joyfully his students about “serendipity,” defined ster’s Dictionary as “the faculty finding valuable or agreeable things sought for.” Coble had this amazing gift. advised his students and colleagues to delve into some area that he had just learned about did not understand because he knew, them. His papers remain full important, still unrecognized connections and insights, and serve as a future generations who did not have the opportunity knowing the man himself. in the preparation this retrospective. The authors acknowledge the assistance Joe Burke. John Cahn, Toni Centorino, Merton Flemings, Dave Kingery, and and T. Vasilos, “Thermal Conductiv- Several Pure Ceram. Soc., Soc., 107-10 (1954). ’R. L. Coble and W. D. Kingery, “Effect of Porosity Am. Ceram. Soc., Soc., 35-37 (1955). ’R. L. Coble and W. D. Kingery, “Effect Physical Properties Sintered Alumina,” Am. Ceram. Soc., Soc., 11 377-85 (1956). 4R. L. Coble, “Initial Sintering Alumina and Am. Ceram. Ceram. 5542 (1958). ’R. L. Coble, “Effect Mechanical Properties Ceramic Materials”; pp 21 3-28 D. Kingery. Technology Press, and Wiley, New York, “Diffusion Sintering Solid State”; Edited by D. Kingery. Technology Press, MIT, and Burke, “Sintering in Crystalline Solids”; al. Elsevier, Amsterdam, “Sintering Crystalline Solids: Intermediate and Final Appl. Phys., Phys., 787-92 (1961). 9R. L. Coble, “Sintering Crystalline Solids: Experimental Test Test 793-99 (1961). “’R. L. Coble, “Sintering Alumina: Effect Am. Ceram. Ceram. 123-27 (1962). “M. C. Houle and “Ceramographic Techniques: Polycrystalline, Hard Materials,” Am. Ceram. Soc. Bull., Bull., 378-81 (1962). ‘’W. D. Kingery and R. “A Review the Effect Mechanical Behavior Polycrystalline Ceramics”; Crystalline Solids. National Bureau Standards Monograph National Bureau Standards, Gaithersburg, Reinforcement”; pp. Ice and D. Kingery. MIT Cambridge, MA, D. Kingery, and “Elastic and Time-Depen- dent Deformation Sheets”; pp. Edited by Press, Cambridge, D. Kingery and Sea Ice and Their Effects and Operations”; pp. Ice and D. Kingery. Paladin0 and Coble, “Effect Grain Boundaries Controlled Processes in Aluminum Am. Ceram. Soc., Soc., 133-36 (1963). “R. L. Coble, “Model Boundary Diffusion-Controlled Creep in Polycrys- talline Materials,” Appl. Phys., Phys., 1679-82 (1963). I8R. L. Coble and Y. H. Guerard, Polycrystalline Aluminum Ceram. Soc., Soc., 353-54 (1963). IqR. L. Coble and J. S. Ellis, “Hot-Pressing Alumina-Mechanisms rial Transport,” Am. Ceram. Ceram. 438-41 (1963). ’OR. L. Coble and Burke, “Sintering in Ceramics”; pp. Ceramic Science, Edited by Burke. Pergamon Press, Oxford, Coble, “Ceramic Metal Sintering: Mechanisms Material Trans- port and Density-Limiting Characteristics”; pp. Fundamental Phenom- Materials Sciences, Sintering and and H. Hausner. Plenum Deformation Behavior Refractory Compounds”; pp. Edited by F. Zackay. Wiley, New Ghoshtagore and Silicon Carbide,” Society-Handwerker et Famsworth and R. L. Coble, “Deformation Behavior of Dense Poly- Am. Ceram. 264-68 (1966). L. Coble, “Intermediate Stage Sintering: Modification and Correction of Lattice-Diffusion Model,” 26R. L. and E. A. Aitken, Processing and Sintering sile Ceramics”; pp. Non-Fissionable Ceramics Society and American Coble, “Mechanisms Densification During Hot Sintering and Related Phenomena. C. Kuczynski, Hooton, and Breach, New York, **R, L. and T. “Intermediate Stage Sintering”; Sintering and Related Phenomena. Edited by G. F. Gibbon. Roy and R. L. “Solubility of of 435-36 (1967). . ”3. K. Roy and R. Titania, and Magne- Aluminum Oxide,” Am. Ceram. Ceram. 14 (1968). ’IT. L. Francis and R. L. Coble, “Creep of Polycrystalline Silicon Carbide,” Carbide,” 115-16 (1968). ’,R. L. Coble, “Development of Microstructures in Systems”; pp. Ceramic Microstructures. Fulrath and A. Pask. E. Mistler L. Coble, “Microstructural Variation Due Due 237 (1968). ’‘R. E. Mistler and R. L. the Use of Log-Log Grain Growth Data,” Am. Cerum. [8] 472 Gupta and R. Coble, “Sintering of Zinc Densification and Grain Growth,” Am. Ceram. Ceram. 521-25 (1968). ’T. K. Gupta and R. L. Coble, “Sintering of Pore Growth During the Final Am. Ceram. Keig and R. L. Coble, Edge Dislocations Dislocations 525-28 (1968). tal Calcium Stage Sintiring: Atmosphere Effects,” Jones, R. L. Coble, Mogab, “Defect Diffusion Diffusion 331-34 (1969). 40S. Prochazka and R. L. Coble, “Surface Diffusion in the Alumina: I, Model Considerations,” Considerations,” 1-18 (1970). 4’S. Prochazka and R. L. Coble, “Surface Diffusion in the Initial Sintering Sintering 1-14 (1970). 42S. Prochazka and R. Coble, “Surface Diffusion in the Initial Sintering Sintering 15-33 (1970). 41R. N. Katz and “Dislocation Etch Pits and Evidence Temperature Microplasticity SrF, Single Crystals,” Appl. Phys., Phys., 1871-73 (1970). 44R. L. Coble, “Diffusion Models for Hot Pressing with Energy and Pressure Effects as Driving Forces,” in Polycrystalline and Initiation of Brittle Fracture,” E. Mistler Coble, “Rate-Determining in Diffusion-Con- in Alumina,” Am. Ceram. Ceram. 6M1 (1971). 47R. L. Coble Flemings, “Removal of Pores from Castings 48R. L. Parikh, “Fracture in Ceramics”; pp. Liebowitz. Academic Press, 49C. F. Yen and R. L. “Spheroidizdtion of Tubular Voids in Oxide Crystals at High Temperatures,” Temperatures,” 101 507-509 (1972). 9. C. Samanta and R. L. Grain Size and Density ing Intermediate-Stage Sintering of Ag,” Am. Ceram. Ceram. 583 (1972). ”R. L. Coble, “Effects Particle-Size Distribution 461-66 (1973). Coble, “Progress Theory”; pp. Sintering and Related Phenomena. Kuczynski. Plenum Press, New York, R. L. Coble, “Growth Uranium Dioxide Single Crystals Crystals 26146 (1974). ’OR. E. Mistler and Coble, “Grain-Boundary Diffusion and Metals and Appl. Phys., Phys., 1507-509 (1974). ”J. M. Neve and R. L. Coble, “Initial Am. Ceram. SOC., Kitazawa and Coble, “Electrical Conduction in Single-Crystal and Polycrystalline A120, at High Temperatures,” Am. Cerum. s7K. Kitazawa and R. L. Coble, “Chemical Diffusion in Polycrystalline Determined from Electrical Conductivity Am. Cerum. Kitazawa and R. L. Coble, “Use Stabilized ZrO, ZrO, 36M3 (1974). “R. L. Sintering” (in Teoriya Tekhnologiya Spekaniya, Mezhdunarodnom Kollokviume Katz and R. L. Coble, “Effect Dislocation Velocity “Dynamic Dislocation Behavior in Oxide Single Appl. Phys., N. Singh and R. “Dynamic Dislocation in Iron-Doped Magnesium Oxide Crystals,” Crystals,” 99695 (1974). 63R. N. Singh and R. “Dynamic Dislocation in Iron-Doped Oxide Crystals Containing Dislocation Dipoles,” Appl. Phys., Phys., 5129-35 (1974). MR. M. Cannon and R. L. Coble, “Review Ceramic Materials. Bradt and Tressler. Plenum Press, New and R. L. Coble, “Grain Boundaries Grain Boundary Hot-Forged Alkali Halides”; pp. Bradt and R. Press, New York, P. Hirth, R. L. L. 19-22 (1976). 67R. L. Coble, “The Status of Understanding Diffusion-Controlled Sintering, Hot Pressing, and Creep”; pp. Vannerberg. Plenum M. Cannon, Bowen, and R. Coble, “Space-Charge to Grain-Boundary Diffusion,” Am. Ceram. Ceram. 126 27 (1977). “1. E. Blendell, Arising from Thermal Expansion Anisotropy During Edited by R. M. Fulrath A. Pask. Westview Press, C. Johnson and R. Coble, “A Test of the Second-Phase and Impurity- Segregation Models for MgO-Enhanced Densification of Sintered Alumina,” Am. Ceram. and R. M. Cannon, “Current Paradigms in Materials Science Research, Vol. Edited by Plenum Press, Blendell and Numerical Simulation of Applicabil- in Final-Stage Sintering,” Powder Metall. Metall. 65-68 (1978). ”R. L. Coble, “Hot Consolidation Rapidly Solidified Powders: Sintering, Hot Pressing (HP), Isostatic Pressing (HIP) the Super- Super- 128-30 (1978). 74C. F. Yen and R. L. Coble, “Defect Centers in Crystal Aluminum Oxide,” M. Cannon, and R. L. Solid-state Sintering Models. A Critical Analysis and Assessment”; Science Research, Vol. New York, M. Dynys, Coble, W. Coblenz, and R. M. During Initial-Stage Sintering of Materials Science Research, Vol. G. C. Plenum Press, Cannon, “The Role Grain Size Distributions in Diffusional Diffusional 1285-90 (1981). ”N. J. Dudney, R. L. Coble, and H. L. Tuller, “Galvanic Cell Measurements with Stabilized and Platinum Probes,” Am. Ceram. Ceram. 621- 24 (1981). 7YN. J. Dudney, R. L. Tuller, “Electrical Conductivity of Pure and Yttria-Doped Uranium Am. Ceram. Ceram. 627-31 (1981). ‘“J. B. Blum, R. L. Coble, and P. A. Keamey, “High-Temperature Vacuum Ultraviolet Reflectometer,” Reflectometer,” 1855-56 (1981). “J. B. Blum, H. L. Tuller, and R. “Temperature Dependence Iron Acceptor Level in Aluminum Am. Ceram. [8] 379-82 Coble, “Defect Diffusion in Single Crystals and Polycrystals of Am. Ceram. Soc., Soc., 33W2 (1982). 83J. E. Blendell and R. L. Coble, “Measurement of Stress Due to Thermal in Alumina,” Am. Ceram. Ceram. 174-78 (1982); (1982); 274 (1982). A. Handwerker, R. L. Coble, aration and Characterization of High-Purity Powder Compacts”; pp. Powder Processing. Edited by K. W. Lay. TMS-AIME, Warrendale, PA, Evans, and R. L. “Microstructure Development During FinaVIntermediate Pore/Grain Boundary Separation,” Separation,” 1269-79 (1982). “R. L. Coble, “Reactive Sintering”; pp. Elsevier, Amsterdam, The Cui and Coble, “Effect Technological Parameters Sintering of Alumina Ceramics” (in Chin.), Chin.), 3744 (1982). “K. M. Friederich and R. L. Coble, “Influence Chemical Inter- SIC during Conversion of Silicon Fibers to Am. Cerum. Cerum. ()”C. A. Handwerker, R. L. Blendell, “Diffusion-Induced Grain Boundary Migration and Discontinuous Precipitation Experiments in Advances in Ceramics, Vol. Yan and Heuer. American Ceramic Society, Bowen, “Grain-Boundary Segregation in Advances in and A. H. Heuer. American R. L. and R. Brook, “Applicability Law to the Sintering pp. 63-80 in Sintering G. C. Sargent. Plenum New York, 1984. ”R. H. Jenssen, and R. L. L. 51-53 (1983/1984). ”R. H. Coble, “High-Temperature Isr. Phys. Phys. 26143 (1983/ 1984). 94J. E. Blendell, H. K. Bowen, and R. L. Coble, “High-Purity Alumina trolled Precipitation from Aluminum Sulphate Cannon, and L. Cable, “Final Stage Sintering in Advances Edited by Kingery. American Ceramic Soci- ety, Columbus, Brook, C. tering and Grain Growth in Alumina and Magnesia”; pp. Advances in Kingery. American Ceramic Society, Columbus, P. A. D. R. and R. Howard, “Characterization of Low-Alpha-Particle-Emitting Ceramics”; in Proceedings 34th Electronic Components Conference. IEEE/EIA, NJ, 1984. French and L. Coble, “Temperature Dependence cal Spectra and Band pp. 126-29 in Basic Optical Materials, National Bureau Standards Special Publication Bureau of Standards, Gaithersburg, MD, Gabbe, and Howard, “Processing Low-Alpha-Particle-Emitting Ceramics,” Muter. Res. 40,89-95 (1985). IMP. A. “C0,-Laser Crystal Growth and Trace Analysis of 6th Inter- Maferials. Herausgegeben Akademie der Wissenschaften der Zentralinstitut fuer Festkoperphysik Oberlungwitz, DDR, 1985. R. L. N. Tebbe, and “Clean-Room and C0,-Laser Processing Proc., 60,79-86 (1986). and R. L. Coble, Boundary Structures Grown from Melt,” Muter. Muter. 797-802 (1984). ““R. H. French, R. L. Kasowski, and Theoretical Studies the Electronic Structure Structure (1988). IMF. N. Tebbe, P. A. Morris, R. Aluminum Hydroxide from Triethylaluniinum,” Triethylaluniinum,” C-204-c-206 (1988). ‘“C. A. A. Morris, and Coble, “Effects Grain Growth Growth 13&36 (1989). IMC. A. Handwerker, J. E. Blendell, and R. L. Sintering. Edited York, 1989. H. French, and Coble, “Effect of Residual Electronic Structure and Magnesia,” Magnesia,” 990- 94 (1989). (“D. B. Cannon, and R. Diffusion and Stoichiometric and Hyperstoichiometric Uranium Diox- ide,” Acta Metall., 2103-23 (1989). Dynys, R. Reference Line Technique for Obtaining Dihedral Angles from Surface Thermal Thermal 1365-70 (1990). M. Cannon, and R. L. Magnesia and and 1371-77 (1990). “‘H. Song and R. L. “Origin and Growth Kinetics of Platelike Grains in Liquid-Phase-Sintered Alumina,” Alumina,” 2077-85 (1990). ”*H. Song and R. L. Coble, “Morphology Platelike Abnormal Coble, “Band Structure Calculations Magnesium Oxide,”J. Oxide,”J. 3195-99 (1990). Il4C. A. Handwerker, Cannon, “Dihedral Angles in Magnesia and Alumina: Distributions from Internal Pores”: unpub- lished work. 20, 1962. “Transparent Alumina and Method