R&D OVERVIEW: Advancing Ceramic and Glass Technology

August 1, 2006
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Research under way at some of today's premier universities and laboratories promises to create new opportunities for ceramic and glass manufacturing

From nanomaterials and nanotubes to ceramic membranes and transparent ceramics, today's universities and research laboratories are pioneering exciting advances in ceramic and glass technology. Following are some highlights of technologies that are on the verge of commercialization.

Experiments have shown that Grancrete is stronger than concrete, is fire resistant and can withstand both tropical and sub-freezing temperatures.

Ceramic Building Material for Low-Cost Housing

Scientists at Argonne National Laboratory (ANL) and Casa Grande LLC are developing a promising new technology that may lead to affordable housing for the world's poorest people. Grancrete, a tough new ceramic material that is almost twice as strong as concrete, may be the key to providing high-quality, low-cost housing throughout developing nations.

Pioneered by Arun Wagh in ANL's Energy Technology Division, Grancrete is made from an environmentally friendly mix of readily available chemicals. When sprayed onto a rudimentary frame, the ceramic material dries to form a lightweight but durable surface. Experiments have shown that Grancrete is stronger than concrete, is fire resistant and can withstand both tropical and sub-freezing temperatures, making it ideal for a broad range of geographic locations. It insulates so well that it keeps dwellings in arid regions cool and those in frigid regions warm. Argonne and Casa Grande have extensively field-tested Grancrete for structural properties, post-application behavior and production costs. Their next step will be to test it for both earthquake and hurricane resistance, after which they will make the product available worldwide.

For more information, visit http://www.anl.gov or http://www.grancrete.net .

Ceramic Membranes for Steam Recovery

Research activities at the Colorado Center for Advanced Ceramics within the Colorado School of Mines (CSM) are expanding significantly to support technologies that require high-temperature membranes for gas separation and solid oxide fuel cells (SOFCs). One example is the barium cerate (BaCeO3) and barium zirconate (BaZrO3) ceramics that are being developed to serve as selective steam permeable membranes.

Any process that uses hydrocarbons has high-temperature exhaust gases. Membranes placed selectively in the exhaust streams can be used to recover steam and heat so that both can be used to reform the incoming fuel, thereby increasing fuel efficiency. "These membranes can boost the thermal efficiency of hydrocarbons by at least 10%," said Grover Coors, Ph.D., of CoorsTek Inc., Golden, Colo., which works closely with CSM in membrane and SOFC activities. In principle, this technology works for any energy generation device that uses hydrocarbons as fuel. Research is focused on understanding the process of diffusion of H2O through these ceramics.

For more information, contact Ivar Reimanis, Ph.D., director of the Colorado Center for Advanced Ceramics, at (303) 273-3549 or reimanis@mines.edu .

Graduate student Eric Sunden (left), Assistant Professor of Mechanical Engineering Samuel Graham (center) and Assistant Professor of Mechanical Engineering William King examine a microelectromechanical device made from carbon nanotubes. Information from a systematic study of nanostructure growth will facilitate development of such devices in the future.

New Technique for Carbon Nanotube Analysis

Researchers at the Georgia Institute of Technology have developed a new technique that could provide detailed information about the growth of carbon nanotubes and other nanometer-scale structures as they are being produced. The technique offers a way for researchers to rapidly and systematically map how changes in growth conditions affect the fabrication of nanometer-scale structures.

Instead of a large furnace that is normally used to grow nanotubes as part of the chemical vapor deposition process, the Georgia Institute of Technology researchers grew bundles of nanotubes on a micro-heater built into an atomic force microscope (AFM) tip. The tiny device provided highly localized heating for only the locations where researchers wanted to grow the nanostructures.

Because the resonance frequency of the cantilever changed as the nanotubes grew, the researchers were able to use it to accurately measure the mass of the structures they produced. The next step in the research will be to combine the growth and measurement processes to permit in situ study of mass change during nanostructure growth.

Using arrays of cantilevers operating at different temperatures would allow researchers to accelerate the process for mapping the kinetics of nanostructure growth. Because the cantilevers can be heated and cooled more rapidly than a traditional furnace, batches of nanostructures can be produced in just 10 minutes, compared to two hours or more for traditional processing. By demonstrating that carbon nanotubes can be grown on an AFM cantilever, the technique also provides a new way to integrate nanometer-scale structures with microdevices.

For more information, contact Bill King at (404) 385-4224 or william.king@me.ga-tech.edu , or Samuel Graham at (404) 894-2264 or sam.graham@me.gatech.edu .

Figure 1. The CVD process involves the absorption, accumulation and decomposition of gaseous reactants on solid surfaces under high temperature or energy conditions.

Low-Temperature CVD Process for Ceramic Coatings

The Nanocrystalline Materials and Thin Film Systems research division at Leibniz Institute for New Materials in Saarbrücken, Germany, is applying thermal and plasma-enhanced chemical vapor deposition (CVD/PECVD) techniques to functionalize surfaces and deposit protective coatings. The CVD process involves the absorption, accumulation and decomposition of gaseous reactants on solid surfaces under high temperature or energy conditions (see Figure 1). The organization's "molecules to materials" concept allows molecular precursors to be designed and produced in large quantities, and these precursors can be used as source materials in the CVD process. During the synthesis of the precursor, researchers are able to a priori tune the essential properties and compositional features of the desired coating material at the molecular scale. This approach predefines the process of material formation at the atomic level and offers precise control over morphology, microstructure and phase structure.

Plasma-induced decomposition of the molecular building blocks enables the development of coatings at reduced process temperatures (<100°C), which opens new opportunities for temperature-sensitive substrates such as polymers. This method also drastically shortens the deposition cycles by eliminating the need for substrate heating (>400°C) and cooling, which are essential in conventional thermal CVD procedures. Furthermore, the application of the PECVD process combined with the synthesis of new molecular starting materials allows the development of new functional thin film products and faster adaptation to industrial needs.

For more information, contact Professor Sanjay Mathur, Ph.D., at (49) 681-9300274 or Sanjay.Mathur@inm-gmbh.de , or visit http://www.inm-gmbh.de .

Nanomaterials for Enhanced Building Products

The Traditional and Innovative Ceramic Materials group of the Institute of Science and Technology for Ceramics (ISTEC-CNR) in Faenza, Italy, is working to advance the use of nanotechnology in the building materials field to enhance chemical-biological, electrical-magnetic and optical-aesthetic properties. The group's research is focused on developing new materials (such as glass-ceramics and pigments with electrical and magnetic properties) and on applying different coating techniques (such as ink-jet, laser printing and physical vapor deposition). To ensure reliable results, the group characterizes both the surface and bulk properties of nanomaterials using different analytical techniques, and then optimizes parameters to allow the resulting industrial nanomaterials to be used as inks on ceramic surfaces. Preliminary results have confirmed the commercial viability of nanomaterials in building material applications. Future efforts will be focused on synthesizing nanomaterials and applying them as multifunctional products in the green chemistry field.

For more information, contact Michele Dondi, Ph.D., at (39) 0546-699728 or dondi@istec.cnr.it , or Mariarosa Raimondo, Ph.D., at (39) 0546-699718 or mrosa@istec.cnr.it .

10 x 10 x 2 cm ceramic Nd:YAG.

Transparent Ceramics for High-Powered Lasers

A Lawrence Livermore National Laboratory research team led by Thomas Soules acquired ceramic neodymium-doped yttrium-aluminum-garnet (Nd:YAG) technology from Konoshima Ltd. in Japan to determine whether the ceramics could meet the optical requirements needed for Livermore's Solid-State Heat Capacity Laser (SSHCL). The team has found that amplifier slabs made from transparent ceramics offer several advantages over those produced from crystals. Perhaps most important is the knowledge that the slabs can be obtained regularly, on time, and without unexpected additional costs. Ceramic materials are also more easily fabricated into large sizes for greater power, and ceramics can be made in any size and shape, limited only by the size of the sintering furnace. The time required to produce the slabs from start to finish is much shorter than the time needed to grow crystal boules-days instead of weeks. In addition, multiple samples can be fired in one furnace at the same time. The researchers have also been looking at and testing possible applications of these materials for use in other Livermore lasers. Potential applications include scalable components and advanced drivers for laser-driven fusion power plants.

In collaboration with the University of California at Davis and Stanford University, the team is investigating other ceramic materials for lasers, including other oxides and fluorides. The team is also working to identify new commercial sources of ceramic Nd:YAG and determine their viability for Livermore lasers.

For more information, contact Thomas Soules at (925) 423-9260 or soules1@llnl.gov .

Ceramics and Glass for Advanced Applications

Researchers at Oregon State University (OSU) are pioneering a number of ceramic and glass advances. For example, researchers are processing and characterizing a new bulk metallic glass material that is a frozen metallic liquid with unique strength and elasticity properties. This material is currently being used in the manufacture of high-end golf clubs. Researchers are also conducting a study to better understand the mechanisms of damage initiation and crack propagation in composites for dental restoration applications. Other areas of research include the fracture and fatigue properties of a new class of ductile intermetallic compounds based on rare-earth elements alloyed with traditional metals, and the ductility and fracture toughness of molybdenum-silicon-boron based alloys targeted for high-temperature applications such as gas-turbine engines. Additionally, the Electroceramics Research Group at OSU is actively involved in research in many areas of electronic ceramics, including ceramic capacitors based on heterogeneous dielectrics, surface nanostructures in metal oxide systems, chemical sensors based on pn-heterocontacts, semiconducting and metallic metal oxides, and ferroelectric and piezoelectric materials.

For more information, contact William H. Warnes, Ph.D., at (541) 737-7016 or warnesw@engr.orst.edu , or visit http://me.oregonstate.edu/research/materials.html or http://www.chemistry.oregonstate.edu/materials/-index.html .

An electron micrograph of a coated 316 stainless steel coupon in cross-section shows the diffusion-reaction layers. Starting from the left side of the photo, which is the surface of the steel, the following layers are visible: 1) aluminum oxide outer layer (not visible at lower magnifications), 2) FeAl layer, 3) Fe3Al inner layer and 4) 316SS.

Ceramic-Based Coating for Steel and Superalloys

Researchers at Pacific Northwest National Laboratory (PNNL) have developed a new ceramic-based coating for steel and superalloys that prevents the corrosion, oxidation, carburization and sulfidation that commonly occur in gas, liquid, steam and other hostile environments. The coating bonds with the metal substrate and is "resilient, inexpensive and easy to apply," said PNNL scientist Chuck Henager. Because the coating is fabricated at significantly lower temperatures than typically required for ceramic coatings, the new process also can save energy and reduce harmful emissions, he said.

Researchers created the coating by mixing a liquid preceramic polymer with aluminum metal-flake powders to form a slurry that can be applied to a metal object by dipping, painting or air-spraying. A low-temperature curing process follows, using a commercial Ruthenium-based catalyst that enables polymer cross-linking and dries the slurry to a green state. The coated object is then heated in air, nitrogen or argon at 700 to 900¡C. Heat converts the green state layer into an aluminum diffusion/reaction layer that permeates the surface of the substrate and provides an aluminide surface coating.

According to PNNL Commercialization Manager Eric Lund, the diffusion reaction makes the coating so durable that it can't be chipped or scratched off. The reaction layer is much stronger than an external coating because it is an integral part of the metal. The coating is available for licensing and joint research opportunities through Battelle, which operates PNNL for the Department of Energy. For more information, contact Lund at (509) 375-3764 or eric.lund@pnl.gov .

A transmission electron microscope image of a single MoO3 nanowire.

Single Crystal Metal Oxide Nanowires

The Center for Nanomaterials and Sensor Development at the State University of New York (SUNY), led by Perena Gouma, Ph.D., has produced single crystal metal oxide (MoO3 and WO3) nanowires through electrospinning for use in opto-electronic applications, catalysis and chemical sensing. Single crystals are inherently stable structures, due to the absence of grain boundaries, and they typically grow along thermodynamically favorable directions. The high-aspect-ratio, one-dimensional nanostructures also offer high surface areas. Highly selective, sensitive and stable sensing probes have been developed using the electrospun nanowires. Targeted applications include breath analysis devices for disease diagnosis and metabolite monitoring (e.g., an isoprene probe that provides non-invasive monitoring of blood cholesterol). Arrays of such nanoprobes have also been used in a selective electronic nose configuration to detect the signature from cancerous cell lines.

For more information, contact Gouma at (631) 632 4537 or pgouma@notes.cc.sunysb.edu .

Figure 1. An illustration comparing the structure of a conventional chromated coating system consisting of a pre-treatment/conversion coating, primer and topcoat to an environmentally friendly coating system consisting of a cerium oxide conversion coating and a UV-curable, zero-VOC self-priming top coat. (Note that the layer thicknesses are not drawn to scale.)

Corrosion Inhibitors for Military Coating Systems

Corrosion-related maintenance costs the U.S. military about $20 billion annually. The corrosion protection systems used for military aircraft typically consist of a chromated pre-treatment (conversion coating), an epoxy-polyamide primer containing chromate corrosion inhibitors, and a polyurethane topcoat. These systems are effective at preventing corrosion of the underlying metal. However, the coatings contain carcinogenic Cr(VI) compounds, and the coating processes require the use of volatile organic compounds (VOCs), hazardous air pollutants (HAPs) and chemicals on the toxic release inventory (TRI).

Figure 2. Photographs comparing aluminum alloy 2024-T6 panels (1.5 x 3 in.) with (a) an as-deposited cerium oxide conversion coating, (b) a cerium oxide conversion coating after two weeks of exposure to salt fog testing and (c) a bare aluminum panel after two weeks of exposure to salt fog testing.
Researchers at the University of Missouri-Rolla (UMR), in collaboration with Boeing and Light Curable Coatings, are developing environmentally friendly, chromate-free coating systems. The coating systems will combine rare-earth oxide-based conversion coatings (e.g., cerium oxide) developed at UMR with ultraviolet (UV) light-curable self-priming topcoats (see Figures 1 and 2). The coating systems employ environmentally friendly, rare-earth oxide-based corrosion inhibitors and will use coating processes that produce no VOCs, HAPs or waste streams containing chemicals on the TRI. This project builds on a successful collaboration between Boeing and UMR that resulted in the commercialization of epoxy-polyamide primers containing rare-earth oxide corrosion inhibitors. The U.S. Air Force is currently using a chromate-free primer containing corrosion inhibitors initially developed at UMR on F-15 aircraft. The new chromate-free, zero-VOC coating system is a candidate for carrier-based F/A 18 aircraft and other Navy fixed-wing and rotocraft, as well as Air Force fighters and transports.

For more information, contact Matthew J. O'Keefe at (573) 341-6764 or mjokeefe@umr.edu , or William G. Fahrenholtz at (573) 341-6343 or billf@umr.edu .

Micro-and nanospheres made from poly(meth-oxymethylsiloxane) and hydroxy-terminated linear poly(dimethylsiloxane).

Polymer-Derived Ceramics

In the Materials Science and Engineering Department at the University of Washington, Seattle, several liquid preceramic polymer systems have been developed for applications such as coatings, joining and pressureless room temperature casting. In one project, composite ceramic coatings made from polyhydrosiloxane are being investigated for a variety of metallic substrates. These coatings can be converted to amorphous or nanocrystalline microstructures at relatively low temperatures (600 to 800°C) and provide corrosion and erosion protection.

In a related project, ceramic micro- and nanospheres were made from poly(methoxymethylsiloxane) as a low-viscosity preceramic polymer and from hydroxy-terminated linear poly(dimethylsiloxane) as a source for in situ water generation. These preceramic polymers undergo fast crosslinking in the presence of water generated in situ. The spherical shape was generated by ultrasonicating the immiscible polymer and de-ionized water mixture in the presence of a catalyst [Bis (2-ethylhexanoate) tin]. The crosslinked samples were dried at 110°C for 12 hours and pyrolyzed at 1000°C in an Ar atmosphere.

For more information, contact Professor Rajendra K. Bordia at (206) 685-8158 or bordia@u.washington.edu , or visit http://depts.washington.edu/rkbgroup .

Editor's note: This article was compiled from information submitted by national laboratories and universities, and it is not intended to be a comprehensive overview of all ceramic and glass research that is currently in progress.

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