Ceramics Processing Research Laboratory
Prior Research @ CPRL
Binder Removal:
Binder removal from ceramic injection molded components (3M)
Binder removal from lead-based ceramic components (TDK)
Drying:
Tape Casting:
Processing science for tape casting (Hitachi Ltd.)
Ion-Beam Assisted Deposition:
Planarization of epitaxial oxide films by ion-beam assisted deposition
Growth of biaxial aligned films (CSE/ARPA)
Ion-beam assisted deposition of zirconia thermal barrier coatings (Sumitomo Metals)
Ceramic Metallization:
Aluminum nitride metallization processes (Carborundum Microelectronics, TRP)
Solidification of HTSC Oxides:
Intergrowth in high temperature superconductors (TEPCO)
3D Printing of Structural Materials:
Structural ceramics by 3DP (ARPA)
Functionally-graded materials by 3DP (ARPA)
Slip casting tools by 3DP (ONR/ARPA)
Tooling by 3DP (TRP)
3D Printing of Therapeutic Medical Devices:
Medical devices by 3DP (Therics)
Pulsatile Contraceptive Implant Feasibility Assessment (Therics)
Binder removal from ceramic injection molded components (3M)
PI: Prof. Michael J. Cima
Precision injection molded components must not distort during post processing. Binder removal from these articles is often accompanied by significant shrinkage and distortion as the binder begins to flow and volatilize during the thermolysis cycle. Our studies involve precision in situ measurements during debinding of small components. The distribution of binder within partially debound parts and in porous setter materials is also examined. These studies are part of an comprehensive binder removal research program that is on going at the Ceramics Processing Research Laboratory.
Binder removal from lead-based ceramic components (TDK)
PI: Prof. Michael J. Cima
Laminated ceramic-metal composites are often cofired to produce many types of electronic components, such as multilayer capacitors and ceramic packages. Binder removal for low temperature metal-ceramic cofire systems is difficult because the ceramic must be made to sinter at temperatures where the organic material has not been completely removed. We have shown that reactions between the organic material and ceramic surface promote the formation of char which contaminates the final product and changes its electronic properties. We are currently, studying the surface reactivity of lead-based dielectrics for multilayer chip capacitors. Results show that lead-rich surfaces cause increased carbon contamination.
PI: Prof. Michael J. Cima
Coatings on granular material are required for many applications. We are performing the first study of manufacturing-scale coating technology for roofing granules. Pigment-sodium silicate slurries are poured on to heated grains of rock substrate in a rotary calciner. The kinetics of spreading of the rock surface and drying must be carefully controlled so that the rock substrate is adequately coated. Excess coating is, however, not an option because of its cost. Our studies follow three main objectives; optical properties of the coatings, identification of the controlling physical/chemical processes during coating, and leach resistance of the coating after firing. Diffuse reflectance optical measurements are being used to assess the minimum thickness for the coating and study the relationship between processing and optical performance. The production process has been separated into three steps for study: wetting and spreading of the slurry, viscosity increase/ gelation, and drying of the gelled slurry. Analytical models for the penetration of the slurry into the rock bed have been shown to be consistent with experimental observations and related the rhelogical properties of the slurry to penetration into the rock bed. The drying stresses of the gel will be measured with an optical interference technique. Fracture toughness values can be calculated from this data and measurements of film critical cracking thickness', giving information on the mechanical properties of the gelled film during drying.
Processing science for tape casting (Hitachi Ltd.)
PI: Prof. Michael J. Cima
Contemporary electronic packaging requires precise dimensional control. Dimensional specifications for today's packages often exceed what can be reliably delivered by conventional powder processing technology. The origin of such minute changes in shrinkage must be understood to develop a reliable manufacturing procedure. Most ceramic packaging is produced so that the final ceramic structure is near full density. Thus, variation in shrinkage is largely caused by variation in the component green density. Similarly, camber can be caused by variation in packing density through the thickness of the green sheet. This project systematically studies factors which account for distortion in laminated ceramic bodies. The study focuses on three elements of processing that can effect component density or composition gradient; slurry stability and homogeneity, casting and drying, and lamination. Methods have been developed to measure tape camber during heating and binder removal. Other experimental methods are being developed to measure local packing density as a function of position through the thickness of the tape.
Planarization of epitaxial oxide films by ion-beam assisted deposition (ONR/ARPA)
PI: Prof. Michael J. Cima
Planarization technology is crucial for successful development of HTSC and optoelectronic applications. Patterned features need to be planarized by intermediate layers of dielectric film. These dielectric layers, however, must often be made epitaxial. Thus, conventional planarization methods can not be used. Our proposed solution is to use ion beam assisted deposition (IBAD) to planarize patterned surfaces with an oriented dielectric buffer layer. IBAD is a technique that has been used successfully to grow dielectric films with improved properties and more recently, biaxially aligned films on amorphous substrates. Results show that IBAD can be used to epitaxially planarize a surface with mechanisms that are related to those that are active in rf bias sputtering. This process has important implications for the manufacture of many new HTSC devices. Our findings show that consideration of etching and bulk deposition only is insufficient for accurately predicting the rate of planarization. Redeposition was found to be a significant secondary effect.
Growth of biaxial aligned films (CSE/ARPA)
PI: Prof. Michael J. Cima
This study reports the deposition of biaxially aligned YSZ on pyrex glass substrates by ion beam assisted electron beam (e-beam) evaporation. Production of high quality biaxially aligned films on non lattice-matched substrates would be a significant technical achievement. Such films could be used to further deposit other materials which require single crystal-like substrates. Low energy ion bombardment (<1keV) during deposition is known to produce restricted fiber texture, or biaxial alignment in other systems. The development of a textured microstructure is thought to be the result of the higher sputtering yields of all orientations other than the channeling direction. Thus, careful balance of the deposition rate and ion-beam induced sputtering can yield net deposition of only those crystallites oriented in the low sputtering yield direction. Our studies with yttria stabilized zirconia (YSZ) films deposited using ion assisted, electron beam deposition (IAD) on pyrex glass substrates, however, suggest that the mechanism is governed by competitive growth of columnar grains.
Ion-beam assisted deposition of zirconia thermal barrier coatings (Sumitomo Metals)
PI: Prof. Michael J. Cima
Ion-beam assisted deposition of zirconia is being used to produce thermal barrier coatings for advanced gas turbine engines. The gas turbine engines found in modern commercial aircraft are typically composed of Ni-based superalloys that have melting points of ~1300C. The combustion gas temperatures though can exceed 1370C during typical application. Thus, advanced turbine engines require complex cooling processes and thin thermal barrier coatings. These ceramic coatings are 100 microns thick and in combination with an underlying intermetallic bond and oxidative resistant coating, have proved to be most effective thermal barrier and oxidation resistive coatings. Plasma sprayed coatings are being replaced with e-beam evaporated films because of their better adhesion and spalling resistance. Columnar structures produced by e-beam deposition accommodate the thermal expansion mismatch between the substrate and the film. Our research focuses on the role by which low energy ion beams modify the film orientation and density.
Aluminum nitride metallization processes (Carborundum Microelectronics, TRP)
PI: Prof. Michael J. Cima
Metallization of ceramics is extremely important in the electronics industry for active devices as well as ceramic dielectrics. This project focuses on metallization of aluminum nitride ceramics for electronic packaging applications. Aluminum nitride is becoming increasingly important in the electronics and mobile communications industry because of its high thermal conductivity. Electroless gold plating is performed as one of the last metallization steps in high volume production of ceramic packages. Electroless gold baths have been developed that work very effectively for aluminum oxide-based packages. Aluminum nitride, however, corrodes rapidly in the high pH conditions of these baths. The high pH is necessary to stabilize the reducing agent against hydrolysis. No current commercial supplier produces gold baths which are nonreactive toward AlN and have high enough stability to be suitable for commercial production. Our research involves methods to stabilize the surface of AlN toward this type of corrosion reaction and to develop advanced methods by which to perform gold metallization.
Intergrowth in high temperature superconductors (TEPCO)
PI: Prof. Michael J. Cima
Our research of YBa2Cu3O7-d (123) has shown that intergrowth of the YBa2Cu4O8 (124) phase during low-temperature annealing produces flux pinning centers and dramatically increases the Jc of the superconducting materials. Production of such pinning centers during high-temperature solidification is currently being investigated. Laser Heated Floating Zone (LHFZ) growth is being used to directionally solidify single crystal 123 filaments. Sample composition as well as solidification parameters such as growth rate, maximum zone temperature, and oxygen partial pressure are being systematically varied. Optical microscopy, Scanning Electron Microscopy (SEM), x-ray diffraction, and SQUID magnetometry are being used to correlate microstructure and superconducting properties with variations in processing parameters. Seeded growth of bulk single crystals is also being investigated.
Structural ceramics by 3DP (ARPA)
PI: Prof. Michael J. Cima, Prof. Emanuel Sachs
This program is developing the MIT 3DP process for rapid prototyping of components directly from a CAD representation of the desired object. Two of the inventors are MIT faculty, Prof. E. Sachs and Prof. M. Cima. The process is being used to create ceramic tooling for metal casting, metal tooling for injection molding plastic parts, and for the preparation of ceramic preforms for metal matrix composites. Research for the development of 3D Printing is funded by several sources. Seed funds were provided by the LFM program. The MIT team was also awarded one of the first strategic manufacturing initiative grants from the NSF. Most recently, a consortium of companies has been formed to further the development of 3D printing. The consortium has six corporate sponsors and is actively pursuing talks with other companies. A new program sponsored by ARPA has allowed us to design 3DP machines to produce fine ceramic components. We have demonstrated the preparation of complex-shaped alumina components that are greater than 98% dense. These components also have excellent mechanical properties (flexural strength >360Mpa) and can be made into complex shapes without the need for tooling.
Functionally-graded materials by 3DP (ARPA)
PI: Prof. Michael J. Cima, Prof. Emanuel Sachs
3DP involves deposition of second phase matter onto the base material. Dispensing second phase through the nozzle causes localized compositional variation in the final 3DP part. The second phase can be added as dispersions, dissolved matter in liquid vehicle, or molten matter. One can build components with spatially controlled composition (SCC) by precisely monitored deposition of second phase. Possible benefits of this unprecedented control in green body formation are innumerable. Designers will not only be able to fabricate any macroscopic shape of choice, but can control the microstructure and composition within the object. A single component with several regions of different properties suited for different tasks can be designed with CAD and manufactured by 3DP. Manufacturers can benefit from these "Function Integration" (FI) components by lowered parts count, inventory, cost and weight. Functionally Gradient Materials (FGM) are examples of FI components that can be fabricated by 3DP. For example, gradual blending of materials with different coefficient of thermal expansion (CTE) is possible with 3DP. Ceramic coating of metal parts for high temperature applications can be carried out with 3DP. Wear resistant species can be selectively deposited near the wear-prone surfaces. Internal residual stresses can be modified with second phases to strengthen or toughen materials. Incorporation of multiple jet printheads is increasing the complexity of possible microstructures by introducing third and fourth phases. Production rate can be also increased by using multiple jet printing. The scale-up potential of 3DP guarantees a smooth transition between prototyping and production of advanced ceramic components.
Slip casting tools by 3DP (ONR/ARPA)
PI: Prof. Michael J. Cima
Slip cast molds for pressure slip casting and full thickness castings are difficult to design because uniform casting rates lead to defects within the casting. This study exploits the 3DP process for the fabrication of molds where the local casting rate varies from point to point of the surface of the mold. The internal structure of the mold is varied so as to increase the local resistance to fluid flow. Two methods of local control are being investigated. Complex structures of large open pores may be built beneath the surface of the mold so as to increase the fluid resistance. Alternatively, the local composition can be varied by printing glass precursors or a dispersion of glass particles. The glass fills the local porosity and increases the resistance to fluid flow. This project is being performed in cooperation with Soligen Inc., Northridge, California.
PI: Prof. Emanuel Sachs, Prof. Samuel Allen, Prof. Michael J. Cima
This TRP Program is focused on the fabrication of injection mold tooling through the use the 3DP process. The Consortium members involved in this program include the following eight organizations: 3M, Advanced Healthcare Systems (a Johnson & Johnson Co.), AMP, Extrude Hone, Hasbro, MIT, Soligen and United Technologies. Tooling fits in two areas: tools for existing DoD infrastructure and tools for new systems under development. The cost to maintain readiness of our armed services is consuming an ever increasing share of the military budget. Replacement parts impose logistical constraints as well as inventory costs. Our program seeks to address these issues by providing technology for rapid tooling of plastic parts. Tools can be prepared in a fraction of the time needed for conventional tools. Thus, manufacturing can be rapidly started at those locations where it makes both economic and logistical sense. No inventories of tools will be required if our project is successful. The goals of this program are: 1). Fabricate tooling for prototypes within 1 day, and 2). Fabricate tooling for part production in 5 days.
Medical devices by 3DP (Therics)
PI: Prof. Michael J. Cima, Prof. Linda Cima, Prof. Emanuel Sachs
This project represents a revolutionary new concept for drug delivery
and biomaterials development; computer-aided design and construction
of implant materials with functional microstructures. The program
explores construction of medical devices by
Pulsatile Contraceptive Implant Feasibility
Assessment (Therics)
PI: Prof. Michael J. Cima, Prof. Linda Cima
This program is a highly focused study to demonstrate the 3DP
process for manufacture of a specific drug delivery device. Drugs
used for birth control or hormone replacement therapy are used
for extended periods of time, making both compliance and ease
of use limitations during therapy. Oral birth control preparations
are taken in a cyclical fashion, and provide a constant dose of
drugs on dosing days. Drugs administered by periodic injection
or implantation are dependent on relatively constant release of
a single therapeutic agent, which does not mimic either normal
physiology or highly effective oral therapies. Current oral agents
are inconvenient, requiring daily dosing, and may not be the most
effective therapy due to swings in blood levels of the therapeutic
agent(s). The proposed solution is the development of implantable,
extended drug release systems providing the lowest appropriate
dose for the longest time; and, allowing for multidrug, cyclical
dosing for birth control or hormone replacement therapy. An implantable
system would use 3DP fabrication technology to achieve extended
(3 months to 1-2 years) sustained prescriptive drug release. These
systems would be simple to use, and increase therapeutic efficacy
while decreasing adverse events.