ONLINE EXTRA: Cold-Formed Ceramics

December 1, 2008
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A new process has been developed for the production of ceramic composites that utilizes a cold liquid aluminum phosphate matrix precursor.



Most products made in the ceramic industry are fired in a kiln, with the related expenses in energy and time. A new process has been developed for the production of composites that utilizes a cold liquid aluminum phosphate matrix precursor. The new process eliminates the firing requirement without negatively affecting the quality of the finished product.

Background

Since patent number 2,075,101 by Henry Dreyfus of London (March 30, 1937), the use of aluminum phosphate has been known as a catalyst for carbon-related chemical reactions. It enables the hydrogenation of carbon, which provides a liquification process for turning different forms of carbon into oil. Many attempts have been made since 1937 to achieve results that cost less to produce and maintain.

It is desirable to have as little crystallization as possible in ceramic materials, because it can cause flaws that lead to reduced strength. The more amorphous a ceramic material is, the stronger it is in use. When greenware that contains many crystals is fired, the material melts in place, reducing the number of crystals and making the material more glass-like.

The amorphous property of the ceramic material (defined by the lack of crystallization or a low level of crystallinity) can be determined through nuclear magnetic resonance (NMR) spectroscopy or other suitable techniques. A compound that contains less than 60% (and preferably less than 50%) crystalline formations is considered to be amorphous.

Between the initial 1937 patent and today, aluminum phosphate has been employed in many different and useful ways, including in high-temperature parts, coatings, catalysts, photoluminescent powders, and inorganic matrixes. In most instances, the ceramic product needs to be heated to high temperatures for some time to achieve a higher level of the amorphous property.

Back when the cost of energy was low, and the greenhouse we live in was not so warm, the amount of CO2 that went into the atmosphere wasn’t really considered an issue. Today, however, the cost of producing a ceramic part increases as the cost of energy increases. Though regulated, natural gas prices have continued to increase. Propane costs about $5 a gallon, and electricity is also more expensive to buy and produce. Those in the industry know how much fuel/energy it takes to fire a load.

New Process

Liquid aluminum phosphate (LAP), or meta-aluminum phosphate (MAP), mixes easily with powdered metals and their oxides, phosphates, carbides, nitrides, sulfates, and other compounds and materials to create composites through a process that uses no extra external heating. Instead, the liquid mixture goes to a solid phase in a matter of minutes at room temperature after mixing is complete.

Aluminum hydroxide, phosphoric acid and hydrochloric acid are mixed to create a liquid ceramic resin. The mixture of the acids and base are heated at a boiling point until clear in appearance to form the reaction that creates the liquid aluminum phosphate resin. Any water comes directly from the acid and base portions of the precursor materials, and no organics are used. The liquid material can then be easily combined with other materials to create cold-formed ceramic composite materials.

Applications and Benefits

The new process could be used in a host of applications. One potential application is the formation of ceramic composite tubes. With suitable plumbing connections, these tubes could be used in a high-temperature, high-pressure setting such as the conversion of any organic compound (from coal and plastics to plants and manure) into sweet-light crude oil and carbonated mineral water. The material could also be used to create very hard ceramic composite cutting tools for the manufacturing industry, or coffee mugs that won’t chip or break.

Ceramic composites made into electronic parts could improve the performance and quality of multilayer electronics. Planned fiberoptic data and address paths can be formed and embedded in sheets of ceramic composite material made with very thin fabric-type materials by pushing the ceramic resin through the surface of the woven fiberoptic fabric to form the sheet. In addition, materials like Kevlar®, fiberglass, nylon, polypropylene or other fibrous types formed into sheets that can be precut can also be used.

Electrodes, circuit traces and the like could be silk-screened in place in such a way that the thickness of the parts is less than the sheet of the next layer. The patterns can be molded and then metallized or formed in situ. Cold-formed piezo-ceramic glass, inductors, capacitors, diodes and resistors embedded in ceramic material are also possibilities for the future.

The new cold-forming process can be considered green because it nearly eliminates the need for post firing. It saves time, money and energy; reduces CO2 emissions; and will help increase manufacturers’ profit margins.

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