Ceramics

Exploring Materials Engineering



Ceramics

Ceramic materials are inorganic, nonmetallic materials. Most ceramics are compounds between metallic and nonmetallic elements for which the interatomic bonds are either totally ionic or predominantly ionic but having some covalent character. The term ceramic comes from the Greek word keramikos, which means burnt stuff, indicating that desirable properties of these materials are normally achieved through a high-temperature heat treatment process called firing.
Taken from Materials Science and Engineering: An Introduction, William D. Callister, Jr., John Wiley & Sons, Inc., New York.

Ceramic materials are important in today's society. Consider the ceramic engine and what advantages it offers in terms of fuel economy, efficiency, weight savings and performance. Below are three gif's showing a montage of a prototype ceramic engine and some of the internal automotive components made from ceramics. The reference source URL is Kyocera Corporation of Japan





For more information about ceramic materials for gas-turbine engines, read the feature article in the Mechanical Engineering Magazine, "Ceramics for Turbine Engines", September '97. For another look at a prototypic ceramic engine, visit the YouTube Video about the Isuzu 295 bhp Turbo 1600cc ceramic engine.

What about fabricating a ceramic turbine in the millimeter range for some very, very small engine of the future? The future is not that far off! To the left you see a radial inflow turbine wheel manufactured from silicon using deep reactive ion etching. This turbine wheel made at MIT measures just 4 millimeters in diameter. It is part of a new technology for producing micro-electromechanical systems, termed MEMS. The entire device, complete with an integrated electric generator, is expected to weigh in at just 1 gram. According to the MIT researchers, a prototype silicon microturbine produced using semiconductor-type microfabrication methods may be operating by the turn of the century. If that initial effort meets success, the researchers plan to use similar lithographic techniques to construct another radial inflow turbine engine from silicon carbide, a refractory ceramic material. For more about the MIT research, view the following video clip or search the Mechanical Engineering Online magazine. For more information about micro-machining, visit the following web pages at Sandia Laboratories.

Quartz envelopes make light bulbs and other lamps possible. Some of the lamp applications are shown in the GE product montage. Quartz tubing is fabricated from beach sand, and the sand is produced into a quartz ingot. A rather large ingot used to produce furnace quartzware, is also shown. GE produces quartz products in great quantity. The reference source URL is General Electric [Momentive] Quartz Products



You may think that copper is a good conductor of electricity. It is pretty good, really. But do you realize that a ceramic can be a better conductor of electricity than copper!? This is true of the recently discovered, high-temperature superconducting ceramic materials. At100 degrees Kelvin and below, these materials offer no resistance to conduction of electrons. In addition, these materials reject magnetic flux lines (the Meissner effect) so that a magnet can be suspended in the space above the superconductor. This is shown below. In Japan, a high-speed, levitated train is being developed based on the principle illustrated in the photo. In the United States, research at Purdue University (the reference URL for the Meissner effect image) is focused on superconductivity and other ceramic material's performance. For further illustration of superconductivity and magnetic levitation, visit this YouTube site.

The representation of inorganic crystals, silicate and aluminate aggregates, and other elements and compounds, is often made with coordination polyhedra. Each vertex of the polyhedra corresponds to a ligand position. In the image below, the crystal structure of a high-temperature superconductor material is represented. Visit the web pages of Professor Woodward at Ohio State to get a better idea of the coordination polyhedra description of crystals.

Some of you may be interested in knowing more about crystal structure and of the role crystallography plays in the field of materials engineering. Please visit the Structure web pages in this series.

Graphites are refractory, lightweight and corrosion resistant materials. These properties are critical for many applications, such as dies for continuous casting, rocket nozzles, and heat exchangers for the chemical industry. However, the relatively poor resistance of graphites to wear and oxidation limits their use. The addition of titanium carbide (TiC) coatings, which possess excellent resistance to wear, oxidation and corrosion, as well as having other desirable properties, greatly extends the use of graphites. Here we see TiC coated parts from Solar Atmospheres, Inc.


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Please send any comments to Patrick P. Pizzo, Professor of Materials Engineering
Created by Dr. Pizzo on August 1, 1997.
Last Revision, December 02, 2011