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| Ceralink, Inc. |
Our published abstracts and full papers are available:
Microwave Assist Technology for Product Improvement and Energy Efficiency
Holly S. Shulman, PhD., Morgana Fall, Shawn Allan, Ceralink Inc.
Presented at the 4th Korea/Japan International Symposium on Material Science and Resources Recycling, March 8, 2007
(pdf full paper) | (pdf presentation)Abstract
A technology (MAT) was developed to overcome the difficulties encountered in microwave heating of ceramic materials. Many ceramics do not couple (suscept) well in a microwave field at room temperature, however, at elevated temperatures, they often heat extremely well. Microwave Assist Technology (MAT) refers to the combination of microwaves with radiant heat from electric elements or gas. This engineering solution provides the initial heating necessary to elevate the temperature of the ceramics to a regime where they can couple directly in the microwave field. The radiant heat also compensates for heat loss from the ceramic, to provide uniform heating, and avoid the "inverse temperature profile". This allows the ceramic to be heated more rapidly than if only radiant heat is used. Energy savings and fine grain microstructures are positive results of the fast uniform heating conditions. An example is given from a calcination study of nano-grained barium titanate for multilayer capacitors. It was found that 130-170 nm grains of the correct tetragonal phase were obtained using MAT. Without the assistance of microwaves, the average grains grew to 550 NM to obtain equivalent tetragonality.Microwave Science, Processing and Applications
Dr. Holly S. Shulman, Morgana Fall, Shawn Allan, Ceralink Inc.
Presentation for KICET and KITECH, South Korea, March 2007
(pdf presentation)Breaking Barriers to the Commercialization of High Temperature Microwave Processing
Holly S. Shulman, Ceralink Inc.
Presented at Microwellen-Thermoprozesstechnik, November 2002
(pdf full paper) | (pdf presentation)Abstract
The barriers to the practical use of microwaves are identified, microwave furnace companies are identified and compared, and the recent developments using microwaves for high temperature processes are discussed. The effectiveness of using microwaves to promote heating for drying, calcination, binder removal, glass melting, and sintering of ceramics and powdered metals has been demonstrated in laboratories throughout the world. Microwave drying of materials has become an industrial reality, however, high temperature processing (1000-2200 C) is just beginning to find it's way into commercial products. The obstacles to the wide spread industrial up-take of this technology include, 1) the lack of commercial microwave furnaces, and 2) the lack of materials process know how. As practical recipes can be developed with less expense, and more furnace companies rise to the challenge, there will be a significant shift towards the production of advanced materials using high temperature microwave processes.Microwave Assist Technology for Product Improvement and Energy Efficiency Holly S. Shulman, PhD., Morgana Fall, Shawn Allan, Ceralink Inc. Presented at the 4th Korea/Japan International Symposium on Material Science and Resources Recycling (pdf full paper) (pdf full presentation) ...these are attached Abstract A technology (MAT) was developed to overcome the difficulties encountered in microwave heating of ceramic materials. Many ceramics do not couple (suscept) well in a microwave field at room temperature, however, at elevated temperatures, they often heat extremely well. Microwave Assist Technology (MAT) refers to the combination of microwaves with radiant heat from electric elements or gas. This engineering solution provides the initial heating necessary to elevate the temperature of the ceramics to a regime where they can couple directly in the microwave field. The radiant heat also compensates for heat loss from the ceramic, to provide uniform heating, and avoid the "inverse temperature profile". This allows the ceramic to be heated more rapidly than if only radiant heat is used. Energy savings and fine grain microstructures are positive results of the fast uniform heating conditions. An example is given from a calcination study of nano-grained barium titanate for multilayer capacitors. It was found that 130-170 nm grains of the correct tetragonal phase were obtained using MAT. Without the assistance of microwaves, the average grains grew to 550 nm to obtain equivalent tetragonality.
Fast Manufacture of Silicon Nitride for Aeorospace, Defense, and Automotive Industries
Holly S. Shulman, Ceralink Inc., Alair Emory, Javalin 3D.
Presented at the 27th Annual Cocoa Beach Conference and Exposition on Advanced Ceramics and Composites, Cocoa Beach, Florida, January 2003
(pdf full paper) | (pdf full presentation)Abstract
Prototyping combined with microwave sintering can provide a fast manufacturing route, from virtual to finished part in less than one day. This combination can also be used for rapid qualification of materials and design development. Silicon nitride compositions were fabricated by rapid prototype using a layering method. The challenge was to develop a thermal package and microwave sintering parameters for achieving high density test specimens with an inexpensive 1.3 kilowatt microwave. This work is part of a larger project to qualify a material for an aerospace application. Preliminary results are presented on the microwave densification of rapid prototype silicon nitride.Precision Microgear Fabrication and Sintering with Microwaves
Shawn Allan, Ceralink Inc., Carlos Chang, New York State College of Ceramics at Alfred University, Holly Shulman, Ceralink Inc., Alfredo Morales, Sandia National Laboratories.
Presented at the 27th Annual Cocoa Beach Conference and Exposition on Advanced Ceramics and Composites, Cocoa Beach, Florida, January 2003
(pdf full paper) | (pdf presentation)Abstract
Great strides are being made in the U.S. in the design and fabrication of Microsystems. Micro-electro-mechanical-systems (MEMS) require high precision microcomponents. A novel technique for fabricating precision ceramic microgears and other devices is under investigation at Sandia National Laboratories. This involves making a precision mold and epoxy-casting with ceramic powders. Alumina and zirconia toughened alumina microgears were fabricated and microwave sintered. The gears were held flat between zirconia discs and microwave sintered to temperatures between 1300 and 1550 degrees C in less than 1 hour. Microstructure and the uniformity of shrinkage were observed by SEM and compared to conventionally fired gears.A Comparison of Energy Consumption for Microwave Heating of Alumina, Zirconia, and Mixtures
Morgana Fall, Ceralink Inc., Holly S. Shulman, Ceralink Inc.
Presented at the 105th Annual Meeting and Exposition of the American Ceramic Society
Nashville, Tennessee, April 2003
(pdf presentation)Microwave Heating Ceramics
Holly S. Shulman, Ceralink Inc.
Presented at the Alfred University Undergraduate Seminar at Alfred University, December 2002
(pdf presentation)Optimization of Stress-Induced Transformation in Zirconia-Toughened Alumina
Holly S. Shulman, Ceralink Inc., William J. Walker, New York State College of Ceramics at Alfred University.
Presented at the 25th Annual International Conference on Advanced Ceramics & Composites
Cocoa Beach, Florida, January 2001
(pdf presentation)Precision Epoxy-Cast Ceramics by Conventional and Microwave Processing
Shawn Allan, Ceralink Inc., Holly S. Shulman, Ceralink Inc., Carlos Chang, Alan Meier, NYS College of Ceramics at Alfred University, Alfredo Morales, Sandia National Laboratories.
Presented at the 105th Annual Meeting and Exposition of the American Ceramic Society
Nashville, Tennessee, April 2003
(pdf presentation)
Microwaves in High-Temperature Processes
Holly S. Shulman, Ceralink Inc., Alfred NY; Industrial Heating Magazine, March 2003
(pdf full paper)Abstract
The use of microwaves is making inroads into many high-temperature processes, such as firing ceramics, heat treating and melting. Because of the wide variety of microwave technologies to choose from, it can be helpful to use an independent microwave testing facility to ensure that you get the best value from microwave heating.
Mapping Applicator Uniformity: Microwave Sintering of Alumina and Zirconia
H.S. Shulman, Ceralink Inc., Alfred NY; H. Giesche, Alfred University, Alfred, NY; Ozan Ugurlu, Graduate Student, Alfred University, Alfred, NY.
Presented at the 3rd World Congress on Microwave & Radio Frequency Applications in Sydney Australia Sept 2002
(pdf full paper Part 1) | (pdf full paper Part 2)Abstract
Alumina and zirconia samples are sintered to > 99% theoretical density in less than 1 hour total cycle time. The study investigates the effects of input power and cycle time on heating rates, microstructure, density and mechanical properties (hardness and MOR). Properties are compared to conventional sintering conditions, which resulted in similar densities. In addition the effects of various sintering conditions, e.g. location of sample within the microwave chamber (hot spots), number of samples within a given insulation box, number, shape and position of various SiC susceptors, and aging effects of the insulation as well as susceptors, are investigated. Additionally, samples from a rapid prototyping process (gelation casting) are investigated.
A Comparison of Microwave Furnaces for Sintering Ceramics
H.S. Shulman, Ceralink Inc., W. J. Walker, Jr., New York State College of Ceramics at Alfred University.
Presented at the 3rd World Congress on Microwave & Radio Frequency Applications in Sydney Australia Sept 2002
(pdf full slide show)Abstract
A market is developing for microwave furnaces, now that it is clear microwave heating is an effective method for sintering ceramics. Companies with manufacturing experience in furnaces and/or microwave equipment are developing research and industrial microwave furnaces to meet the demand. As the availability and affordability of microwave furnaces improves, this in turn stimulates the commercialization of microwave sintering, especially for advanced ceramics. It is important to understand the different features available in microwave furnaces and to make comparisons, so that the appropriate system can be used in materials research, product development, and production.Early microwave materials research was performed using systems built "in house" and/or designed with little consideration for manufacturing expense. It is difficult to compare the features of these systems, or to determine the feasibility of scaling up microwave processes from the literature. Recently, microwave system designs have improved, becoming more user friendly and cost effective. In this work, the different approaches to microwave furnace design are discussed, the important operating parameters are described, and direct comparisons are made by sintering known ceramic "standards" in the different microwave furnaces. Where possible, commercially available microwave furnaces were used.
The types of microwave systems investigated included, 1) several sizes of multimode 2.45 GHz, 2) hybrid microwave + electric, 3) hybrid microwave with 2 frequencies, and 4) millimeterwave. It was found that microwave firing parameters were readily transferred between different microwave systems, if similar refractory packages were used. Equivalent properties and microstructures can be achieved using different microwave systems, however, temperature measurements may not be comparable. Energy savings will vary between systems and depend on the insulation, load size, and type of ceramic. There is now an excellent selection of microwave furnaces available for research and production. It is anticipated that for material scientists, the research focus will shift from fabricating furnaces, to developing useful processes. Ceralink Inc. is currently developing microwave processes for many types of advanced ceramics and exploring the feasibility and challenges of scaling up.
Sintering Uniformity and Reproducibility with 2.45 GHz Microwaves in an Industrial Sized Chamber
H.S. Shulman, Ceralink Inc.; M.L. Fall, Ceralink Inc.; Dr. W. J. Walker, Jr. New York State College of Ceramics at Alfred University; Dr. T.A. Treado, Communications and Power Industries - Beverly Microwave Division; S.J. Evans, M. Marks & M.L. Tracy, Communications and Power Industries - Beverly Microwave Division.
(pdf full paper) | (pdf presentation)Abstract
The scale-up of microwave processes for production requires the systematic study of 1) the uniformity of microwave sintered materials and 2) the reproducibility of material properties for given processing parameters. In this study, a microwave power versus time recipe for sintering zirconia ceramics to full density was successfully transferred from a 1.1 kW modified kitchen microwave to a large 3 kW chamber (35" d x 54" l). The effects of increasing the load and refractory box volume, as well as the box position were investigated. The uniformity and reproducibility of the density, hardness, and microstructure were explored.
Sintering Wear Parts with Microwave Heating
M.L. Fall, Alfred University, H.S. Shulman, Ceralink Inc., L. Wolfe, EPL Ceramics W. J. Walker, Jr., New York State College of Ceramics at Alfred University
Presented at the 104th Annual Meeting and Exposition of the American Ceramic Society, St. Louis, MO, April 28th to May 1st, 2002
(pdf full paper)Abstract
Zirconia and alumina samples were sintered to over 99.5% of theoretical density using a 1.1 KWatt microwave in less than 45 minutes, or 1.5 hours "cold to cold". The density and vickers hardness were comparable to dense conventionally sintered specimens fired in 12 to 16 hours. The impact of container volume and susceptor position were investigated on the heating rate and uniformity. The relationship between the applied power, the heating rate, temperature and properties of the specimens will be discussed. In addition, scale up experiments for microwave sintering of zirconia were performed.
A Novel Approach to Understanding Microwave Heating of Zirconia
Malte Moeller, Linn High Therm, Holly S. Shulman, Ceralink, Inc., Herbert Giesche, New York State College of Ceramics at Alfred University.
Presented at the 104th Annual Meeting and Exposition of the American Ceramic Society, St. Louis, MO, April 28th to May 1st, 2002
(pdf full paper)Abstract
Savings in processing time (up to 90%) and energy (20-80%) are expected in microwave sintering of ceramics, as this technology breaks through into industrial firing processes. Linn High Therm had developed a high temperature hybrid microwave system in anticipation of industries needs. Typically, silicon carbide susceptors are used to initiate heating from room temperature, where many ceramics have low dielectric losses. The loss increases with temperature, and at some "kick in" transition temperature, the ceramic load heats preferentially over the susceptors. In this work the effect of dopant type and crystal structure of zirconia on the "kick in" temperature was observed using silicon carbide susceptors.
Fractographic Study of Zirconia Toughened Alumina
Holly S. Shulman, Ceralink, Inc, James Varner, Ward Votava, NYS College of Ceramics,
Alan Clarke, Industrial Research, Ltd. New Zealand
Ceramic Transactions, Volume 122, Fractography of Glasses and Ceramics IV, The American Ceramic Society, Westerville, 2001, 145-156.Proceedings of the Fourth Alfred Conference on the Fractography of Glasses and Ceramics held July 9th-12th, 2000 at Alfred University, Alfred, NY.
(pdf full paper)Abstract
Zirconia toughened alumina (ZTA) is a composite system which offers significant improvements in toughness over alumina, with superior hardness compared to zirconia. There are numerous applications that would benefit from the use of ZTA. Unfortunately, the commercially available materials often suffer from inadequate transformation toughening and processing flaws associated with spray drying. In this work, the feasibility of using a simple scalable process which avoids the spray drying step was explored. ZTA bars with optimized toughness from this process were broken in four-point-bend. Fracture surfaces for 40 vol.% zirconia ZTA were studied. Fracture analysis indicated that the strength was limited by cracks associated with slightly alumina rich agglomerates. The Weibull modulus was affected by the source of alumina powder, but the type of critical flaw was not affected.
Millimeter-Wave Sintering of 20 v% Zirconia Toughened Alumina
M.Samandi, H. Shulman, J. Young, and A. Clarke, Second World Congress on Microwave and Radio Frequency Processing, April 2-6, 2000, Orlando, FL, USA.
Optimization of Yttria Additions in Zirconia Toughened Alumina
H.S. Shulman, M.J. Ryan, N.I. Baxter, I.W.M. Brown, (Industrial Research Ltd, New Zealand), J. Aust. Ceramic Soc., 34[2] 127-131 (1998). Presented at AUSTCERAM 98 the18th Australasian ceramics conference Sept 28-30, 1998 at Monash University, Melbourne, Australia.Abstract
The stress-induced transformation of included zirconia from tetragonal phase to monoclinic phase offers an important contribution to toughening of ceramic composites. Stabilization of the tetragonal phase is affected by the zirconia content and its grain size, and by stabilizing agents such as yttria. The zirconia phases in zirconia toughened alumina (ZTA) with several levels of zirconia (5 to 40 vol%) and yttira additions (0 to 3.0 mol% of zirconia) were analyzed by quantitative X-Ray diffraction. The combined effect of zirconia and trria on hardness, toughness, and retention of the tetragonal phase was investigated. The amount of yttria required to stabilize the optimum mixture of tetragonal and monoclinic zirconia was determined for 5 vol% zirconia.
Niobium Doping and Dielectric Anomalies in Bismuth Titanate
H. S. Shulman, D. Damjanovic, N. Setter (Swiss Federal Institute of Technology (EPFL), Switzerland), J. Am. Ceram. Soc. 83 (3) p. 528-32 (2000).Abstract
A study of the complex permittivity in bismuth titanate was conducted to reveal the nature of an anomaly in the real part of the permittivity, which occurs below the Curie temperature. This anomaly is frequency dependent and is caused by a combination of two relaxation phenomena that appear in the imaginary part of the permittivity. One of the relaxations showed classic characteristics of an ion-jump process. Niobium doping suppressed this relaxation and eliminated the nonferroelectric anomaly in permittivity. Niobium is proposed to affect the ion-jump relaxation through a decrease in the concentration and possibly the mobility of oxygen vacancies.
Microstructure, Electrical Conductivity, and Piezoelectric Properties of Bismuth Titanate
H. S. Shulman, M. Testorf, D. Damjanovic, N. Setter, (Swiss Federal Institute of Technology (EPFL), Switzerland), Journal of the American Ceramic Society 79 (12) p. 3124-3129 (1996).
Additional PublicationsH.S. Shulman "Piezoelectric Bismuth Titanate Ceramics for High Temperature Applications" PhD Thesis (Thesis No 1646 1997) Ecole Polytechnique Federale de Lausanne, Switzerland)
H. S. Shulman (Brooks) M.S. Thesis "Sol-Gel Coating of Silicon Nitride Powder, Sialon Formation, and Selected Properties" 1992 University of Pittsburgh, Pittsburgh PA.
H. S. Shulman B. S. Thesis 1986 "Sol-Gel Coating of Barium Titanate for Positive Coefficient of Temperature Resistance", Alfred University, Alfred, NY.
H. S. Shulman, M. J. Ryan, A. L. Clarke, I. W. M. Brown, "Improvements in Zirconia Toughened Alumina", Proceedings of NZ-Korea Seminar on Engineering Materials, Waikato University, Hamilton Feb 1-2, 1999.
H. S. Shulman and D. Blumhardt, "New Zealand Copper Red", J. Australasian Ceramic Society. 34(2) (1998).
H. S. Shulman, D. Damjanovic (1993) "Microstructural Control of Bismuth Titanate Based Ceramics, Third Euro-Ceramics, P. Duran and J. F. Fernandez, ed., Vol. 2, p. 199-204 (1993).
P. K. Mehrotra, D. P. Ahuja, H. S. Shulman (Brooks) United States Patent No. 5,427,987, June 27, 1995, "Group IVB Boride Based Cutting Tools for Machining Group IVB Based Materials." Kennametal Inc, Latrobe Assignee: Pa.
