What are Porous Ceramics and how are they different from regular ceramics?
Ceramics are solids made of non-metallic materials such as zirconia and alumina which are shaped and hardened by firing in a furnace oven at elevated temperatures. They are known for their outstanding chemical stability as well as high heat resistance, corrosion resistance, and electrical insulation properties. Porous ceramics have all the benefits of regular ceramics plus additional desirable features due to their unique structure. These unique features can be exploited to create vacuum chucks to mount electronic parts, chemical filters, and heat and radiation shields.
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The Structure of Porous Ceramics
Ceramics are made by shaping a mixture of non-metallic powders such as zirconia and alumina and hardening them at elevated temperatures in a furnace oven. This method creates exceptionally fine and complex shapes while maintaining high heat and corrosion resistance. They also have exceptionally good electric insulation properties and never corrode or rust. Ceramics can be as hard as diamonds but unlike diamonds, they can be shaped into any desired shape before the firing process. Industrial parts such as cutting and polishing tools and bearings, electronics parts such as ceramic insulators and IC, as well as medical devices such as dentures are some applications of this versatile material.
As the name suggests, porous ceramics are ceramics that have a large number of minute holes (pores) in their structure. They have the same strength, rigidity, heat resistance, and chemical stability as regular ceramics but are much lighter because they have substantial number of pores that are filled with air. Since the pores are filled with air, the heat capacity and thermal conductivity are also exceedingly small.
Most ceramics are made up of a collection of randomly sized and oriented open and closed pores. In contrast, the pores of porous ceramic are open pores that are straight and oriented unidirectionally. Pore size, configuration, and porosity (the number of pores in each area) can be controlled to suit a wide range of functional needs.
For example, if the pores are open pores and their size and shape are consistent, gasses and liquids can flow through them at a stable rate. The ability of the ceramic to absorb water can be optimized by adjusting the pore sizes and increasing porosity. This can be used to partially suction or float small components. Due to the extremely high heat tolerances of the ceramic, a ceramic that has trapped a large volume of liquid can be dried and treated at elevated temperatures repeatedly.
Features and Applications of Porous Ceramics
These characteristics allow ceramics to be used in a wide range of applications. Due to their rigidity and high structural stability, and because air can flow through the pores, porous ceramics are used to make vacuum packing for electronics equipment to hold electronic components and semiconductor wafers in place during processing. Ceramics for vacuum packing can be made very flat and smooth through special polishing techniques and are indispensable for holding components firmly in place during precision processing. In addition, instead of suction, air can be blown out of the porous ceramic to slightly levitate components off the surface so they can be transported easily.
In addition, due to their high strength and low weight, ceramics can be used to make equipment and buildings lighter. Because they are tolerant to high heat, ceramics can be used in and around equipment and processes that reach elevated temperatures. Ceramics can also repeatedly absorb water and be dried out. They can be used as humidity control tiles in construction projects.
Due to its low heat capacity and low thermal conductivity, even if one side of a ceramic is heated to elevated temperatures, the other side will still stay cool, and any accumulated heat will dissipate quickly. These characteristics make ceramics ideal for use in heat insulators, dissipators, and jigs and vessels for elevated temperature processes. In addition, the numerous pores are good for absorbing sounds. Porous ceramics can be used to dampen noises from objects that produce significant impact and vibration sounds. As mentioned earlier, pore sizes can be controlled, and very minute pores with diameters of a few dozen microns can be created. Such a large number of pores results in a large surface area. The tiny pores can be used for separation, selection, or adsorption of substances. Filtration of exhaust gas, air purification, and drinking water purification are some applications that take advantage of this feature of porous ceramics.
Production of High-Quality Porous Ceramics
Porous ceramics are made by hardening ceramic powers at elevated temperatures just below their melting point to prevent densification. They can also be created by adding pore forming substances to the mixture and removing them at a later step. The powder mixture, firing conditions, and other factors must be precisely controlled to produce high-quality ceramics. Such fine control of the process allows for pore sizes, and range of sizes to be controlled. Pore shape and structure of the ceramic can also be controlled. To create ceramics with pore sizes of just one micron to several dozen microns with pores arranged in a unidirectional pattern while maintaining high porosity, the dispersion of particles and shrinkage of the ceramic in the baking process must be controlled at extremely elevated levels. Ceramics made in this way demonstrate both high porosity and high rigidity (able to support 10,000 times its own weight). They can even be made lighter than conventional resin sponges while maintaining high strength and porosity. Furthermore, it is possible to create a densified layer on the outer surface of the porous ceramic which allows even highly porous ceramics to be grasped easily, making them easier to handle.
Due to their superior performance characteristics, porous ceramics are used in industrial and construction applications, and increased application for environmental protection is expected soon.
Orbray’s Porous Ceramics
The pores of Orbray’s Porous Ceramics can be created in any size and oriented in any desired direction. Contrary to most other porous ceramics on the market, the pores in our ceramics are connected to the outer surface, creating an open cell structure that contributes to high stiffness and rigidity.
Pore sizes can be controlled from several microns to approximately ten microns, depending upon the customer’s needs. Other difficult ceramics can also be created and produced using our various expertise and experiences.
Please feel free to contact us directly.
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