Material Types and Manufacturing Processes: Ceramics

We are, literally, surrounded by ceramics. While it is widely known that ceramic has artistic applications, i.e. pottery, and can be used for a variety of household items or utensils, i.e. plates, coffee mugs, and toilets, few recognize that the computers they use, the car they drive, and the television they watch—amongst thousands of other things used in daily life—rely on ceramic components.  This essay will argue that ceramics are one of the most versatile products available in manufacturing, usable in a wide variety of distinct applications. 

Material Sources

Ceramics were first made thousands of years ago, and some of the oldest artifacts discovered by archeologists include ceramic pottery, glass, and brick.  The term, “ceramics,” however is very broad and consists of a variety of nonmetallic and inorganic solid materials. As Woodford points out, it is in some ways easier to define ceramics in terms of what they are not—in other words, “ceramics are what we’re left with when we take away metals and organic materials (including wood, plastics, rubber, and anything that was once alive.”  Still, most ceramics, even the ones found in Asian art collections, are created from clay-based materials, often mixed with water and other materials, shaped, and fired at high temperatures. Six different types of clay, for instance, are commonly mined in the United States. The most commonly used types of clay, used for ceramics, include common clay (for bricks and cement), ball clay (used for dishes and tiles), and fire clay (used in refractory/high-temperature) bricks/cement).  Ceramics, however, are versatile precisely in the fact that the clays used as the base of a ceramic can be combined with a number of other materials granting the ceramic different kinds of utility. For example, polymer composites can be created by surrounding ceramic fibers with liquid plastic. One way to make a “tough” ceramic, reducing its susceptibility to brittleness, involves forming silicon carbide power into sheets, covering it with graphite, and pressing it together and sintering it without pressure.  

Material Extraction/Procurement/Refinement

For personal use, or for hobbyists, it is possible to extract clay suitable for pottery by hand. More specific and specialized applications, however, require specific attributes in the clay mined. Professional clay miners typically operate on large clay reserves, lay a grid across the property, and drill each section, testing the clay from samples. The samples are sent to laboratories to be tested and evaluated. If the deposit is satisfactory for mining, the dirt and topsoil are removed from the surface, and a drill rig is used to extract the clay in larger proportions.  Different grades of clay can be excavated in different ways without disrupting the future potential of germination in the soil, and depending upon the manufacturing process, will be combined with other materials and shaped in a verity of ways before they are fired. More specialized applications often involve molds and automated industrial refinement processes.  When high strength or other specific properties are necessary “the processing requirements are quite strict as compared with those for more fracture resistant materials.”  Due to the wide range of possible uses for ceramics, detailing the refining processes is impossible for these purposes. That said, the more specialized the use the more complicated and stricter the process typically becomes. Glass-ceramics, for instance, are normally produced in two general steps: “First, a glass is formed by a standard glass-manufacturing process. Second, the glass article is shaped, cooled and reheated above its glass transition temperature. The second step is sometimes repeated as a third step. In these heat treatments, the article partly crystallizes in the interior. In most cases, nucleating agents (e.g., noble metals, fluorides, ZrO2, TiO2, P2O5, Cr2O3 or Fe2O3) are added to the base glass composition to boost the nucleation process.” 

Tools/Processes to Decorate or Ornament Ceramics

Ceramics can be formed in a variety of ways, including the use of pottery wheels, or molds. Decorative pieces can be adorned by literally shaping the clay with patterns or in decorative flourishes prior to firing. They can also be painted and glazed. A wide range of tools, including cut-off wires, to potter’s needles, a variety of knives and scrapers, sponges, wood molding materials and brushes are used in common pottery.  

Finishing Processes

According to Woodford, “firing” is what most ceramics share in common, and the word “ceramic” is derived from Sanskrit meaning “to burn.”  While this is true, generally, the method of firing will vary depending upon the type of ceramic being produced. Bricks, for instance, are typically fired in a kiln and heated to temperatures exceeding 1000 degrees Celsius.  According to Woodford, “When you fire clay, the water evaporates and the aluminum, silicon, and oxygen atoms lock into a rigid structure made from aluminum silicate, bonded together by silicate glass—and that's why fired clay is so hard.” 

Process and Function

As technology has developed, allowing for more refined processes for “firing” ceramics, and higher or lower controlled temperatures, the processes involved in manufacturing ceramics has changed significantly. For example, low temperature co-fired ceramics, typically used in a variety of microelectronic devices, involves a “multi-layer, glass ceramic substrate which is co-fired with low resistance metal conductors, such as Ag or Cu, at low firing temperatures (less than 1000 C).”  In short, by combining ceramics with different materials and heating them in controlled, consistent, temperatures modern ceramics have developed a wide range of utilities, some of which will be illustrated below.  

Examples: Ceramic Applications

Ceramics have a variety of insulating properties, making them useful in electronics. Multilayer ceramic capacitors (right) in an electronic circuit “utilize the insulating properties of a ceramic material (called dielectric) placed between two or more metal layers to store electrical charges.”  

In recent decades, significant advancements in ceramic bonding techniques have increased the scope of use for ceramics in dental applications. Dental caps (right) are formed to the patient’s teeth, created “from a partially sintered block of zirconia oxide material…fired to the full sintering temperature and then fit the die”  

Lightweight “Stuffed Whipple Shields,” were designed by NASA engineers to protect spacecraft, satellites, and the international space station from both heat and debris when reentering earth’s atmosphere. These “shields” are made from 3M’s heat and flame-resistant Nextel fabric. The process involves creating ceramic fibers by “super-heating chemicals like silica until they are molten, and then spinning them into hair-like strands.”  

Conclusion

Ceramics have a wide range of uses, due both to the ability to form the material in endless ways and to cater the molecular structure of the product by combining different materials and heating it in different ways. Since ceramics also function as insulators, and recently some have been found to have magnetic properties,  it is likely that the use and application of ceramics will only expand further in the future.

Bibliography

Becher, Paul F. "Microstructural design of toughened ceramics." Journal of the American Ceramic Society 74, no. 2 (1991): 255-269.

Clegg, W. J., K. Kendall, N. McN Alford, T. W. Button, and J. D. Birchall. "A simple way to make tough ceramics." Nature 347, no. 6292 (1990): 455.

LHoist. “How we Mine Clay.” https://www.lhoist.com/us_en/how-we-mine-claymuRata,

“Low Temperature Co-Fired Ceramics (LTCC) Multi-layer Module Boards,” 2018. https://www.murata.com/~/media/webrenewal/support/library/catalog/products/substrate/ltcc/n20e.ashx

Plain, Charlie. “Superhero Ceramics!” NASA. July 16, 2004. https://www.nasa.gov/missions/science/spinoff9_nextel_f.html

Shenoy, Arvind, and Nina Shenoy. "Dental ceramics: An update." Journal of conservative dentistry: JCD 13, no. 4 (2010): 195.

The American Ceramic Society. “Ceramics and Glass in Electrical and Electronic Applications.” https://ceramics.org/about/what-are-engineered-ceramics-and-glass/ceramics-and-glass-in-electrical-and-electronic-applications

Woodford, Chris. “Ceramics.” ExplainThatStuff! June 7, 2018. https://www.explainthatstuff.com/ceramics.html

Zanotto, Edgar Dutra. "Bright future for glass-ceramics." American Ceramics Society Bulletin 89, no. 8 (2010): 19-27.