Advanced ceramics is referred to as precision ceramics, technical ceramics, engineering ceramics or industrial ceramics, fine ceramics etc. These terms cover many different and in part highly-specialized ceramic materials with unique mechanical, electrical, thermal and biochemical properties and property combinations. Advanced ceramics are frequently viewed as a direct replacement material for expensive alloys such as tool steels, stellite and tungsten carbides. Ceramic materials exhibit hardness, excellent heat and corrosion resistance, and electrical insulation properties. Typical examples include china, firebricks, cements and glass.
Precision ceramic offer a wide range of advanced technical ceramic materials to ensure that the right material for many different fields of application. Advanced ceramics can relate a wide variety of forms including sheets, tubes, square bars, rods and finished custom components. On the other hand, technical applications must satisfy extremely high demands in terms of the advanced ceramic properties. The property spectrum ranges from wear and heat resistance, temperature and corrosion resistance all the way to biocompatibility and food compatibility.
In addition to these properties, advanced ceramics have many advanced mechanical, electrical, electronic, magnetic, optical, chemical and biochemical characteristics. Today, advanced ceramics have many roles in fields such as semiconductors, automobiles, telecommunications, industrial machinery and healthcare.
Furthermore, Advanced Ceramic materials include the area of materials having their own characteristics e.g., magnetic, electrical, dielectric, pyro-electric, piezoelectric, conductivity, semi-conductivity, superconductivity and other areas. A large group is represented by so-called electro-ceramics and also materials for electrical engineering. Another group is represented by the magnetic properties of the ceramics. The electrical and magnetic properties of ceramics varies considerably due to the 6 difference in composition and the crystal structure. Many ceramics have a high insulation quality and are used for cable insulation, while some of them have excellent high temperature superconductivity.
Advanced ceramic can usually extend to the following categories based on materials and applications, such as Aluminum Oxide, Zirconium Oxide, Silicon Nitride, and porous ceramic. Each of the materials has its properties that can be applied to different applications according to the requirements of the needs.
Advanced ceramics are also frequently being used to replace metals, polymers, and refractory materials in a wide variety of applications due to their notable high temperature capability, hardness, and electrical properties. By altering the chemical formulation or manufacturing processes, their properties can be tailored to meet a large range of demanding conditions. When used correctly, ceramics have the ability to increase product lifespan, increase efficiency, reduce overall maintenance costs, and improve product performance.
Ceramics, defined by the broad definition of “inorganic solids”, are one of the main classes of materials, along with metals, polymers, and composites. There are several different types of ceramics, with advanced ceramics being the group with the highest performing mechanical, electrical, and/or thermal properties. Their high performance is due in part to their extremely high purities which are most commonly metal compounds combined with oxides, carbides, or nitrides. Ceramics have the ability to increase product lifespan, increase efficiency, reduce overall maintenance costs, and improve performance.
These specific characteristics can be further developed, optimized and matched for use in technical applications. It is also possible to combine different properties. Materials like these can be used to design advanced components that perform the required tasks with optimum precision and can be light years ahead of competing materials such as metal or plastic in the respective field of application. Components made from ceramic materials are increasingly the only solution available for technical challenges that cannot be overcome with conventional materials.
The Differences Between Traditional Ceramics and Advanced ceramics
The physical differences between ceramics and advanced ceramics mainly arise from their raw materials and manufacturing processes. Ceramics are manufactured by mixing, shaping and firing natural minerals including pottery stones, feldspar and clay. In contrast, advanced ceramics are manufactured using highly purified natural raw materials, artificial raw materials synthesized through chemical processes and other non-naturally occurring compounds. Through a series of precisely controlled, complex processes such as forming, machining, firing and grinding, these compounded raw materials turn into high-value-added products with excellent dimensional accuracy and functional characteristics.
One of the most common properties of engineered ceramics is extreme hardness (& stiffness) – some are more than 4 times harder than stainless steel. This high hardness directly translates into excellent wear resistance, meaning that many technical ceramics have the ability to keep their precise, high-tolerance finish much longer than any other material.
Extreme Compressive Strength
Advanced ceramics have very high strength, however, this is only when compressed. For example, many technical ceramics can withstand extremely high loads ranging from 1000 to 4000 MPa. Titanium on the other hand, which is regarded as a very strong metal, only has 1000 MPa of compressive strength.
Another common property of technical ceramics is their low density, ranging from 2 to 6 g/cc. This is significantly lighter than stainless steel (8 g/cc) and titanium (4.5 g/cc) with only the much softer aluminum being similar in density. Due to their high hardness and low weight, technical ceramics are increasingly being used in a variety of industries in applications where no other material can match their performance & long life.
Excellent Wear Resistance
Many technical ceramics are able to withstand incredibly high temperatures while still retaining their mechanical & electrical properties. Where all metals and polymers will start to compromise their properties, technical ceramics will continue to function with consistent performance and reliability. This property makes ceramics appropriate for use in very high temperature applications like furnaces, jet engines, brake systems, and cutting tools.
Excellent Electrical Properties
Technical ceramics tend to be excellent electric insulators (high dielectric strength). They are especially useful in high-temperature applications where other materials’ mechanical & thermal properties tend to degrade. Some ceramics have low electrical loss & high dielectric permittivity; these are typically used in electronic applications like capacitors and resonators. Additionally, the ability to combine an insulator with a structural component has led to many product innovations.
Technical ceramics can function in situations where no metal (or nearly any other material) can maintain their properties. Some ceramics can operate in temperatures in excess of 1750°C, putting them in a class of their own as ultra-high-temperature materials. These ceramics have proven to be invaluable in high-temperature applications like engines, turbines, & bearings where they have increased the lifespan, performance, and efficiency.
Thermally Conductive or Insulative
Different types of technical ceramic materials have wildly varying thermal properties. There are some ceramics (Aluminum Nitride) that are highly thermally conductive and are commonly used as heat-sinks or exchangers in many electrical applications. Other ceramics are much less thermally conductive, making them suitable for a wide range of applications.
Chemically Inert & Corrosion Resistant
Technical Ceramics are very chemically stable and have low chemical solubility, making them highly resistant to corrosion. Metals and polymers cannot offer the same inertness or corrosion resistance, making ceramics a highly attractive option in many commercial and industrial applications, particularly when wear resistance is also needed.
Characteristics of advanced ceramics:
- ceramic materials are defined as non-metallic materials,
- the preparation of classic ceramics is based on natural raw materials with a different granulometry,
- Advanced ceramics puts an emphasis on the creation of structures (microstructure) of a so-called regulated particle-size (grain-size) composition,
- Advanced ceramics are made from synthetically produced materials with a predominant content of an inorganic, non-metallic phase (one phase can be glass),
- Advanced ceramics are prepared by special methods of forming
- a wide range of materials with irreplaceable properties,
- mainly made of synthetic materials,
- production with relatively low energy requirements,
- production is basically environmentally-friendly,
- usable in almost all industrial areas
Manufacture of Advanced ceramics:
The preparation of advanced ceramic materials usually begins with a finely divided powder that is mixed with an organic binder to help the powder consolidate, so that it can be molded into the desired shape. Before it is fired, the ceramic body is called “green.” The green body is first heated at a low temperature in order to decompose or oxidize the binder. It is then heated to a high temperature until it is “sintered,” or hardened, into a dense, strong ceramic. At this time, individual particles of the original powder fuse together as chemical bonds form between them. During sintering the ceramic may shrink by as much as 10 to 40 percent. Because shrinkage is not uniform, additional machining of the ceramic may be required in order to obtain a precise shape.
Sol-gel technology allows better mixing of the ceramic components at the molecular level, and hence yields more homogeneous ceramics, because the ions are mixed while in solution. In the sol-gel process, a solution of an organometallic compound is hydrolyzed to produce a “sol,” a colloidal suspension of a solid in a liquid. Typically the solution is a metal alkoxide such as tetramethoxysilane in an alcohol solvent. The sol forms when the individual formula units polymerize (link together to form chains and networks). The sol can then be spread into a thin film, precipitated into tiny uniform spheres called microspheres, or further processed to form a gel inside a mold that will yield a final ceramic object in the desired shape. The many crosslinks between the formula units result in a ceramic that is less brittle than typical ceramics.
Although the sol-gel process is very expensive, it has many advantages, including low temperature requirements; the ceramist’s ability to control porosity and to form films, spheres, and other structures that are difficult to form in molds; and the attainment of specialized ceramic compositions and high product purity.