Ceramic

An inorganic, nonmetallic solid prepared by the action of heat

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This article is about the material properties of ceramics. For other uses, see Ceramic (disambiguation)

Short timeline of ceramic in different styles

A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature.[1][2] Common examples are earthenware, porcelain, and brick.

The earliest ceramics made by humans were fired clay bricks used for building house walls and other structures. Other pottery objects such as pots, vessels, vases and figurines were made from clay, either by itself or mixed with other materials like silica, hardened by sintering in fire. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates.[3] Ceramics now include domestic, industrial, and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as semiconductors.

The word ceramic comes from the Ancient Greek word κεραμικός (keramikós), meaning "of or for pottery"[4] (from κέραμος (kéramos) 'potter's clay, tile, pottery').[5] The earliest known mention of the root ceram- is the Mycenaean Greek ke-ra-me-we, workers of ceramic, written in Linear B syllabic script.[6] The word ceramic can be used as an adjective to describe a material, product, or process, or it may be used as a noun, either singular or, more commonly, as the plural noun ceramics.[7]

Materials

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Silicon nitride rocket thruster. Left: Mounted in test stand. Right: Being tested with H2/O2 propellants.

Ceramic material is an inorganic, metallic oxide, nitride, or carbide material. Some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in shearing and tension. They withstand the chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F).

A low magnification SEM micrograph of an advanced ceramic material. The properties of ceramics make fracturing an important inspection method.

The crystallinity of ceramic materials varies widely. Most often, fired ceramics are either vitrified or semi-vitrified, as is the case with earthenware, stoneware, and porcelain. Varying crystallinity and electron composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators (researched in ceramic engineering). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity), the breadth of the subject is vast, and identifiable attributes (hardness, toughness, electrical conductivity) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high moduli of elasticity, chemical resistance, and low ductility are the norm,[8] with known exceptions to each of these rules (piezoelectric ceramics, low glass transition temperature ceramics, superconductive ceramics).

Composites such as fiberglass and carbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family.[9]

Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories: either making the ceramic in the desired shape by reaction in situ or "forming" powders into the desired shape and then sintering to form a solid body. Ceramic forming techniques include shaping by hand (sometimes including a rotation process called "throwing"), slip casting, tape casting (used for making very thin ceramic capacitors), injection molding, dry pressing, and other variations.

Many ceramics experts do not consider materials with an amorphous (noncrystalline) character (i.e., glass) to be ceramics, even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to those of ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known as glass-ceramic.[10]

Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recent materials include aluminium oxide, more commonly known as alumina. Modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance and are therefore used in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medical, electrical, electronics, and armor industries.

History

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Earliest known ceramics are the Gravettian figurines that date to 29,000&#;25,000 BC.

Human beings appear to have been making their own ceramics for at least 26,000 years, subjecting clay and silica to intense heat to fuse and form ceramic materials. The earliest found so far were in southern central Europe and were sculpted figures, not dishes.[11] The earliest known pottery was made by mixing animal products with clay and firing it at up to 800 °C (1,500 °F). While pottery fragments have been found up to 19,000 years old, it was not until about 10,000 years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery: the Corded Ware culture. These early Indo-European peoples decorated their pottery by wrapping it with rope while it was still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface.

Corded-Ware culture pottery from  BC

The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming (throwing) technique, like the pottery wheel. Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of glazing techniques, which involved coating pottery with silicon, bone ash, or other materials that could melt and reform into a glassy surface, making a vessel less pervious to water.

Archaeology

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Ceramic artifacts have an important role in archaeology for understanding the culture, technology, and behavior of peoples of the past. They are among the most common artifacts to be found at an archaeological site, generally in the form of small fragments of broken pottery called sherds. The processing of collected sherds can be consistent with two main types of analysis: technical and traditional.

The traditional analysis involves sorting ceramic artifacts, sherds, and larger fragments into specific types based on style, composition, manufacturing, and morphology. By creating these typologies, it is possible to distinguish between different cultural styles, the purpose of the ceramic, and the technological state of the people, among other conclusions. Besides, by looking at stylistic changes in ceramics over time, it is possible to separate (seriate) the ceramics into distinct diagnostic groups (assemblages). A comparison of ceramic artifacts with known dated assemblages allows for a chronological assignment of these pieces.[12]

The technical approach to ceramic analysis involves a finer examination of the composition of ceramic artifacts and sherds to determine the source of the material and, through this, the possible manufacturing site. Key criteria are the composition of the clay and the temper used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage and is used to aid the subsequent drying process. Types of temper include shell pieces, granite fragments, and ground sherd pieces called 'grog'. Temper is usually identified by microscopic examination of the tempered material. Clay identification is determined by a process of refiring the ceramic and assigning a color to it using Munsell Soil Color notation. By estimating both the clay and temper compositions and locating a region where both are known to occur, an assignment of the material source can be made. Based on the source assignment of the artifact, further investigations can be made into the site of manufacture.

Properties

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The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition. Solid-state chemistry reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by the Hall-Petch equation, hardness, toughness, dielectric constant, and the optical properties exhibited by transparent materials.

Ceramography is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from nanometers to tens of micrometers (µm). This is typically somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye.

The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of materials science and engineering include the following:

Mechanical properties

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Cutting disks made of silicon carbide

Mechanical properties are important in structural and building materials as well as textile fabrics. In modern materials science, fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the physics of stress and strain, in particular the theories of elasticity and plasticity, to the microscopic crystallographic defects found in real materials in order to predict the macroscopic mechanical failure of bodies. Fractography is widely used with fracture mechanics to understand the causes of failures and also verify the theoretical failure predictions with real-life failures.

Ceramic materials are usually ionic or covalent bonded materials. A material held together by either type of bond will tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the more ductile failure modes of metals.

These materials do show plastic deformation. However, because of the rigid structure of crystalline material, there are very few available slip systems for dislocations to move, and so they deform very slowly.

To overcome the brittle behavior, ceramic material development has introduced the class of ceramic matrix composite materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic disc brakes are an example of using a ceramic matrix composite material manufactured with a specific process.

Scientists are working on developing ceramic materials that can withstand significant deformation without breaking. A first such material that can deform in room temperature was found in .[13]

Ice-templating for enhanced mechanical properties

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If a ceramic is subjected to substantial mechanical loading, it can undergo a process called ice-templating, which allows some control of the microstructure of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically, the strength is increased when this technique is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for solid oxide fuel cells and water filtration devices.[14]

To process a sample through ice templating, an aqueous colloidal suspension is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid,[clarification needed] for example Yttria-stabilized zirconia (YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces ice crystals to grow in compliance with the unidirectional cooling, and these ice crystals force the dissolved YSZ particles to the solidification front[clarification needed] of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then heated and at the same the pressure is reduced enough to force the ice crystals to sublime and the YSZ pockets begin to anneal together to form macroscopically aligned ceramic microstructures. The sample is then further sintered to complete the evaporation of the residual water and the final consolidation of the ceramic microstructure.[citation needed]

During ice-templating, a few variables can be controlled to influence the pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials.[15]

Electrical properties

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Semiconductors

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Some ceramics are semiconductors. Most of these are transition metal oxides that are II-VI semiconductors, such as zinc oxide. While there are prospects of mass-producing blue LEDs from zinc oxide, ceramicists are most interested in the electrical properties that show grain boundary effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain threshold voltage. Once the voltage across the device reaches the threshold, there is a breakdown of the electrical structure[clarification needed] in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several megohms down to a few hundred ohms. The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for surge-protection applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in electrical substations, where they are employed to protect the infrastructure from lightning strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as gas sensors. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced.

Superconductivity

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The Meissner effect demonstrated by levitating a magnet above a cuprate superconductor, which is cooled by liquid nitrogen

Under some conditions, such as extremely low temperatures, some ceramics exhibit high-temperature superconductivity (in superconductivity, "high temperature" means above 30 K). The reason for this is not understood, but there are two major families of superconducting ceramics.

Ferroelectricity and supersets

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Piezoelectricity, a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to measure time in watches and other electronics. Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating a signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again.

The piezoelectric effect is generally stronger in materials that also exhibit pyroelectricity, and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in motion sensors, where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal.

In turn, pyroelectricity is seen most strongly in materials that also display the ferroelectric effect, in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in ferroelectric capacitors, elements of ferroelectric RAM.

The most common such materials are lead zirconate titanate and barium titanate. Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency loudspeakers, transducers for sonar, and actuators for atomic force and scanning tunneling microscopes.

Positive thermal coefficient

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Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of heavy metal titanates. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until joule heating brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles.

At the transition temperature, the material's dielectric response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of the material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures. Titanates with critical temperatures far below room temperature have become synonymous with "ceramic" in the context of ceramic capacitors for just this reason.

Optical properties

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Optically transparent materials focus on the response of a material to incoming light waves of a range of wavelengths. Frequency selective optical filters can be utilized to alter or enhance the brightness and contrast of a digital image. Guided lightwave transmission via frequency selective waveguides involves the emerging field of fiber optics and the ability of certain glassy compositions as a transmission medium for a range of frequencies simultaneously (multi-mode optical fiber) with little or no interference between competing wavelengths or frequencies. This resonant mode of energy and data transmission via electromagnetic (light) wave propagation, though low powered, is virtually lossless. Optical waveguides are used as components in Integrated optical circuits (e.g. light-emitting diodes, LEDs) or as the transmission medium in local and long haul optical communication systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal infrared (IR) portion of the electromagnetic spectrum. This heat-seeking ability is responsible for such diverse optical phenomena as night-vision and IR luminescence.

Thus, there is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light (electromagnetic waves) in the visible (0.4 &#; 0.7 micrometers) and mid-infrared (1 &#; 5 micrometers) regions of the spectrum. These materials are needed for applications requiring transparent armor, including next-generation high-speed missiles and pods, as well as protection against improvised explosive devices (IED).

In the s, scientists at General Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especially aluminium oxide (alumina), could be made translucent. These translucent materials were transparent enough to be used for containing the electrical plasma generated in high-pressure sodium street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones for heat-seeking missiles, windows for fighter aircraft, and scintillation counters for computed tomography scanners. Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including:

Products

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By usage

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For convenience, ceramic products are usually divided into four main types; these are shown below with some examples:[17]

Ceramics made with clay

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Frequently, the raw materials of modern ceramics do not include clays.[19] Those that do have been classified as:

1. Earthenware, fired at lower temperatures than other types
2. Stoneware, vitreous or semi-vitreous
3. Porcelain, which contains a high content of kaolin
4. Bone china

Classification

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Ceramics can also be classified into three distinct material categories:

Each one of these classes can be developed into unique material properties.

Applications

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Kitchen knife with a ceramic blade Technical ceramic used as a durable top material on a diving watch bezel insert

See also

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Goto Zmdy Ceramics to know more.

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• Ceramic chemistry &#; Science and technology of creating objects from inorganic, non-metallic materials

  Pages displaying short descriptions of redirect targets

• Ceramic engineering &#; Science and technology of creating objects from inorganic, non-metallic materials
• Ceramic nanoparticle
• Ceramic matrix composite &#; Composite material consisting of ceramic fibers in a ceramic matrix
• Ceramic art &#; Decorative objects made from clay and other raw materials by the process of pottery
• Pottery fracture &#; Result of thermal treatment on ceramic

References

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Further reading

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• Guy, John (). Guy, John (ed.). Oriental trade ceramics in South-East Asia, ninth to sixteenth centuries: with a catalogue of Chinese, Vietnamese and Thai wares in Australian collections (illustrated, revised ed.). Oxford University Press. ISBN 978-0-19--0.

• Riedel, Ralf; Chen, I-Wei, eds. (). Ceramics Science and Technology. doi:10./. ISBN 978-3-527--1.

Ceramics is a non-metallic and inorganic material, and after passing forming and sintering steps, due to its unique mechanical and physical properties, they are used in a variety of industries, such as construction, medicine, and automobile manufacturing.

Ceramics are a wide classification of non-metallic and inorganic materials constructed from a combination of artificial or natural compounds and have different properties like high-temperature endurance, high stiffness, and high chemical resistance. The ceramic production process includes selecting and preparing consumable raw materials, forming ceramic sections, and finally, cooking the pieces. 

From eating utensils and cooking equipment to cutting tools and electronic equipment, ceramics has many applications in our daily lives. Due to their unique characteristics, these materials have multiple uses, and their usage has increased as material development and production progress. Throughout this paper, we aim to become familiar with this material from A to Z.

Ceramics are a wide classification of non-metallic and inorganic materials constructed from a combination of artificial or natural compounds. They are usually formed by shaping a compound of clay soil, mineral, and other additives and then cooking them at a high temperature to produce a stiff and high-endurance substance.

Ceramics can be found in a wide variety of productions, from building tile and decorative clay utensils to electronic and Aerospace tools with advanced technology. They are valuable because of their durability, stiffness, and resistance against heat, corrosion, and abrasion.

In addition to clay-based traditional ceramics, modern technologies made it possible to develop ceramics made of carbides, nitrides, and oxides. These advanced ceramics are more durable than traditional ones and are useful in applications such as cutting tools, engine components, biomedical implants, and bulletproof vests. 

Depending on their properties and specific requirements, ceramic materials can provide advantages over steel in certain applications. A ceramic material, for example, has greater stiffness and durability than steel, which makes it ideal as a material for applications requiring resistance to abrasion and heavy abrasion. Ceramic materials can tolerate higher temperatures compared to steel without melting or destruction. Due to this feature, they are highly suitable for use in environments with high temperatures, such as jet engines. Aside from this, some of these ceramic materials are environmentally friendly, so they can be used safely without causing undesirable reactions in contact with the body.

What is ceramic made of?

Ceramics can be provided from minerals like clay, oxides, carbides, and nitrides. The compound of ceramic depends on the intended use and desired properties of the ultimate production. Traditional ceramics like clay and porcelain are usually made from a complex of clay, feldspar, and quartz, along with other additives like kaolin, bullet, and bone ash.

This mixture is formed in the desired shape and cooked at a high temperature to create a stiff and enduring material.

On the other hand, advanced ceramics can be made of a wide variety of materials. For example, silicon carbide and alumina are usually used for creating cutting tools and abrasives, while zirconia is used in dental crowns and artificial joints. Usually, ceramics are made of a combination of materials, like carbide cement, which is composed of tungsten carbide grains and joined with steel adhesives. In general, ceramics are made of minerals and processed by using high temperatures to create a stiff and enduring material with specific properties.

Ceramic production steps

Below is a general summary of the ceramic manufacturing process:

1. Selection and preparation of raw consumable materials
2. Forming ceramic pieces
3. Thermal operation of ceramics
4. Complementary and ultimate operation (if needed)

Following a thorough evaluation of the raw materials, they are ground into a suitable grade. It is essential to avoid the entrance of impurities during the preparation process. The final step of this part is mixing powder materials in wet, dry, and semi-dry states and in the presence of adhesive or its absence. The next step is shaping ceramic sections aiming to achieve a sound piece. In the final step, thermal and sintering operations are carried out. 

Note that in the first step, which is selecting raw materials, parameters such as purity, the particle size of raw materials, existing fuzzy transformations in materials, and other parameters should be considered.

These factors significantly affect the quality of the final production. For example, impurities in many ordinary ceramics can be explained by their glassy phase formation and ability to help cook, although it has some limitations. However, as there are specific properties and behaviors required in engineering ceramics, impurities can cause severe changes in intended properties. Therefore, it is essential to reduce impurities in raw materials compounds as much as possible. Accordingly, raw materials preparation is of high importance. This preparation includes three overall and separate steps:

1. Grinding raw materials using a grinder or mill
2. Grading crushed materials (using different methods with a sieve) or suction with the air
3. Mixing graded materials to form a homogenous compound before crystallizing

After providing raw materials in the form of powder or granules, the next step of the ceramics manufacturing process is shaping. The most common methods to shape ceramics are:

• slip casting
• plastic formation (clay)/extrusion
• powder press (uniaxial and biaxial dry and semi-dry hot press, cold and warm isostatic press)
• melting and casting
• injection molding
• tape casting
• formation and covering thick and thin layers (CVD) and similar methods

The section complexity, raw material type, used equipment, investment amount in this field, required and intended quality, accessibility of facilities, the final price of the raw materials, and final production are crucial parameters in this step of shaping ceramic pieces using different methods, production type and considering problems. After shaping ceramic pieces and drying the system if moisture is present, sintering and cooking ceramics are the next step. The sintering aims to reduce porosity percentage, heal particles, and increase density and durability. If we heat steel or compressed ceramic powders to a temperature roughly equivalent to half of their melting point and more, they form a stick together, and an inter-particle bond is formed. This phenomenon, which has important impacts such as dimension changes, fuzzy changes, and releasing internal stresses of the section, is called sintering

What are the properties of ceramic?

Ceramics have various properties that can be classified into some general groups. In the following, we mention some of these properties. 

Mechanical properties of ceramics

As the name suggests, mechanical properties are related to properties that are accompanied by stress (force). Tensile and compressive strength, stiffness, and fracture resistance are among the criteria for evaluating the mechanical properties of these materials. A main challenge of using ceramics is their brittle nature and low tensile resistance, which limits some of their applications. However, significant electrical, thermal, and optical properties of ceramics make them appropriate for various uses in industries like aerospace, medicine, and energy. 

Compressive strength of ceramic

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The durability of a material is its ability to tolerate stress without deformation or fracture. The compressive strength of ceramics is high, and ceramics can tolerate load under pressure without deformation. It makes them suitable for applications requiring high endurance, like cutting tools and engine parts.

Ceramic durability is affected by factors such as microscopic structure, compound, and construction process. For instance, ceramics with a fine microscopic structure and high impurity has higher endurance compared to ceramics with a coarse microscopic structure. 

Fracture resistance of ceramic

Fracture resistance is the ability of a material to resist breaking the crack. Ceramics are breakable in general, which means they easily break under stress. However, some ceramics show a high fracture resistance due to the plastic deformation ability before fracture. This feature is crucial for applications involving hit or shock loads, such as bumper or cutting equipment. 

Ceramic stiffness

Stiffness is the resistance of a material against compression and surface scratch. Ceramics are known for their high stiffness, which makes them suitable for applications requiring resistance against abrasion and scratch, such as abrasion and cutting tools. 

Physical properties of ceramics

Physical properties of a substance are properties observable or measurable without change in the chemical compounds of the material. Ceramics are a various group of materials with a wide variety of physical properties. In the following, we note some of the most crucial physical properties of ceramics:

• Density and porosity

Ceramics have a high density, meaning they are rather heavy. Ceramics can have different levels of porosity that can affect their strength and durability and create various applications for them. 

• Thermal conductivity

Thermal conductivity is the ability of heat transfer in a material. Contrary to steel materials, ceramics are weak and conducive to heat, making them useful in applications with high temperatures that require insulation. 

• Thermal expansion coefficient

Ceramics have a relatively low thermal expansion coefficient, meaning that they expand or contract less than other materials by changing temperature. 

• Transparency and light transition

Some ceramics are transparent and trespass the light, while other ones are opaque. 

Chemical properties of ceramics

Ceramics are highly required in hard environments and environments with high temperatures and electronic pieces due to their chemical properties. In this section, we investigate the measurement criteria of chemical properties of ceramics, including chemical endurance, resistance against chemical corrosion, and stability in high temperatures. 

• Chemical stability

A crucial feature of ceramics is their stability. In hard environments where chemical and acid contact is avoided, ceramics are ideal since they are resistant to chemical reactions with other materials. This feature is due to strong covalent bonds between ceramic atoms. Covalent bonds form a stable and durable formation against chemical attacks. As ceramics are chemically stable, they are useful materials for storing and transporting corrosive substances in planets of chemical production. Ceramics are also used in creating reactors and chemical pipes, which provide a long-term and durable solution for problems related to chemical corrosion. 

Resistance to chemical corrosion

In addition to chemical stability, ceramics are also highly resistant to chemical corrosion. The reason for this feature is that ceramics are formed from metallic or non-metallic elements with oxygen, nitrogen, or carbon. The bonds between these elements are stable and resistant to chemical attacks, which makes ceramics usable in corrosive chemical environments. 

Stability in high temperatures

Ceramics can tolerate high temperatures without experiencing significant changes in their structure or chemical properties. It is because of the high melting point of ceramics, which means they can maintain their stability and structure in high temperatures. 

Electric properties of ceramics

In this section, we focus on the electric properties of ceramics, including electrical conductivity, electrical insulation, and Piezoelectric properties. Ceramics involve a wide domain of electric properties. Some of them do not allow passing electric flow even in powerful fields, and some are conductors. Ceramics can be categorized into conductors, semi-conductors, or dielectrics. 

Semiconductor ceramics has a medium electric conductivity. This ceramics' interesting property is the adjustability of electric conductivity. With the help of changing chemical compounds and production methods, engineers can produce their intended semiconductor ceramic and use it in different applications, such as electronic devices, solar cells, and thermoelectric generators. Semiconductor ceramics exhibit flow following energy adsorption due to changes in their electronic structure.

Insulation ceramics have low electrical conductivity and are used in applications demanding electric insulation, such as electric insulators and capacitors. Ceramic materials with high electric resistance are called dielectric. Although these materials are not conductive, they undergo some changes in their electric charge balance when placed in a dielectric field and acquire new properties. Dielectric constants serve as a measure of the amount of electric energy a substance can store. It is an important feature in applications like capacitors and sensors. 

Piezoelectric ceramics are a type of dielectric ceramics. Piezoelectricity is the property of some ceramics that enables them to transform mechanical energy into electric energy and vice versa. These properties are used in various applications such as sensors, operators, and transducers. 

Types of ceramics

Types of ceramic in terms of material

Ceramics are divided into two categories: Standard (traditional) and engineering ceramics. Standard ceramics, known as traditional ceramics, include ceramics like chinaware, all sorts of tiles, such as tiles for the floor and walls, ceramic sanitary tools, and other ceramic products installed using  ceramic adhesive. Consumable raw materials for this type of ceramic are usually clay, silica feldspar, and other materials. As a result of the abundance and cheapness of their raw materials, standard ceramics are common in Iran, and, also, as a result of the high value-added of their products, this industry has experienced significant growth and is still developing.

Processed mineral raw materials and common construction techniques are used to produce standard ceramics. There are several divisions for each group of standard ceramics; for example, one can mention provided divisions about chain wares which are sometimes based on their application and sometimes based on the properties of soft and rigid chain wares. Generally, ceramics of this type are made with clay, feldspar, and silica, but other materials can also be utilized if necessary. Engineering ceramics are used to respond to specific requirements such as higher thermal strength, better mechanical properties, particular electric properties, and chemical resistance.

These ceramics are:

1- Pure oxide ceramics: Oxides like Alumina (Aluminum oxide), zirconia (Zirconium oxide), Thoria (thorium oxide), beryllia (beryllium oxide), and magnesia (magnesium oxide) are mostly used.

2. Non-oxide ceramics: These ceramics have all kinds of nitride (aluminum nitride, silicon nitride, and boron nitride, which are refractory and have high durability in high temperatures), carbide (such as silicon carbide and boron carbide), and boride.

3- Composite compound materials (ceramic-metallic): Both ceramic and metallic phases exist in these materials.

Introduction of Porcelain Ceramic

Porcelain ceramics are ceramics with water adsorption percentages lower than 0.5% from the kaolin soil compounds and are cooked at a temperature of around C. 

Compared to other standard ceramics, porcelain ceramics are highly compact, and the porosity in these ceramics is very small (roughly zero). Low porosity is the principal property of porcelain ceramics which causes desirable technical and chemical performance and high durability in this type of ceramic. In addition, porcelain ceramics are highly resistant to chemicals and detergents. High durability against corrosion and high fracture resistance, along with easy cleaning of porcelain ceramics, made them an ideal choice in industrial and congested spaces. 

View more: "What is porcelain ceramic; types and functions"

Types of ceramic in terms of application

Standard and traditional ceramics have various applications and are divided based on application:

• Cement productions (like hydraulic cement that are used in construction industries) 
• Whiteware (including crockeries, chain wares, and chain ware compounds)
• glazes
• Building clay productions (mostly made of bricks and tiles)
• refractory
• Glasses
• abrasive materials

In terms of function, engineering or industry ceramics can be divided into three groups functional engineering, structural engineering, and biological ceramics. Each classification has a specific performance, as stated in the following:

The first subset is known as functional engineering ceramics, which includes electroceramics, superconducting ceramics, semiconductor ceramics and electrical insulators, ceramic magnets, etc., and some productions of this subset are:

• Piezoelectric and pyroelectrics
• Insulators and ceramic dielectrics of insulators and capacitors
• Ceramic semiconductors
• Ceramic fuses
• Ceramic sensors
• Magnetic ceramics
• Optic ceramics
• electro-optic

Another subset of engineering ceramics is structural ceramics which includes engineering ceramics with better thermal and mechanical properties, such as ceramic oxide, non-oxide, and complex materials. In this set of ceramics, mechanical and thermomechanical properties are the most important ones. Some crucial structural engineering ceramics are:

•  Zirconia systems
•  Microfilters and membranes
• Catalysts and ceramic foams
•  Glass and glass-ceramics
•  Ceramic composites and cermet

The third subset is biological ceramics, which includes all types of biological ceramics and nanoceramics. Biological ceramics are drug-release systems, implants, and biodegradable ceramics.

Types of ceramic in terms of the fabrication method

Selecting a mechanism and technique to shape a ceramic piece depends on various parameters, including the following:

• Length to diameter ratio of the piece
• Size and complexity of the piece and mold design
• Raw materials type
• The possibility to form suspension or slurry
• Powder properties
• The porosity of the piece
• Accessibility of facilities
• The final price in association with internal, regional, and global competition

Generally, in standard ceramics, traditional methods like slurry casting and shaping clay are used. These methods are available in the country with inexpensive device costs. Because of the nature of methods, including the presence of water in the supply of raw materials and even in the provision of bodies, the final products have porosity. Furthermore, new techniques and machinery are used to improve properties in addition to the methods mentioned above.

Ceramic applications in various industries

Due to their unique properties, such as durability, resistance to temperature, and chemical stability, ceramics has many applications in our daily lives. We all use ceramic dishes like porcelain, clay, and stone utensils to cook and serve food. These utensils are used as tableware because of their significant resistance to heat, durability, attractiveness, beauty, and hygiene. Our house and workplace were furnished with ceramics, and the bathroom, kitchen, and other rooms were fitted with ceramic tiles. Porcelain ceramics are available in various colors and figures, which makes them a popular choice for house decoration.

Ceramic materials have been used in art and decoration for thousands of years. Ceramic statues, flowerpots, and statues are popular decorative tools used in our houses. The aesthetic appeal of ceramic materials like chain ware and clay makes them ideal for jewelry production. Among jewelry enthusiasts, ceramic marbles, earrings, and pendants are popular.

Ceramic materials like zirconia and silicon carbide are used in cutting tools like knives and scissors because of their high stiffness and resistance to corrosion. In the following, we mention some of their new and more advanced applications.

Ceramic applications in medicine

Ceramic materials have a vast usage in medicine due to biocompatibility, significant mechanical properties, and resistance to corrosion and abrasion. Some applications of ceramics in medicine are:

1- dental implant: ceramic materials such as zirconia and alumina are used in dental implants because of biocompatibility, resistance to abrasion, and durability. They also can provide a more natural appearance than metallic implants. 

2- Joint replacement: Because of the resistance to corrosion and high biocompatibility, ceramic materials are used in joint replacement, such as hip and knee joints. Ceramic components can reduce inflammation and improve longevity compared to traditional metallic components. 

4- Graft substitutes: Ceramics like hydroxyapatite and tricalcium phosphate are used as graft replacements because of their similar components to natural bones. These materials can boost bone growth and gradually be adsorbed to the body. 

5- Surgery tools: Because of the resistance to corrosion and abrasion, ceramic materials are used in surgery tools. Also, they can be easily sterilized compared to traditional metallic tools. 

6- Diagnostic and imaging apparatuses: Due to significant electrical and thermal properties 

Ceramics are commonly used in diagnostic and imaging tools like X-ray tubes, ultrasound transducers, and dental imaging screens due to their electrical and thermal properties.

Ceramic application in the automobile industry

Because of significant mechanical properties like durability, rigidness, and resistance to corrosion, ceramic materials have a variety of applications in the automobile industry. Ceramic 

brake linings are increasingly used in vehicles with high efficiency because of their high resistance to temperature and corrosion. Brake linings can tolerate high temperatures without losing the function of their brake and, as a result, improve safety and reliability. 

Due to their durability, stiffness, and resistance to high corrosion, ceramic materials such as silicon nitride and alumina are used in parts of engines, including poppet valves, pistons, and turbochargers. Ceramic components of the engine can resist high temperatures, reduce corrosion and friction, and improve fuel efficiency. 

Ceramic bearings and bushings can be used in the automobile industry due to their high corrosion resistance, low friction, and high durability. Compared to metallic bearings, ceramic bearings can handle higher speeds and loads and provide superior performance and durability. Ceramics are used in exhaust systems to reduce greenhouse gas emissions and improvement of fuel efficiency. Ceramic materials can be used as a thermal shield, catalyst transducer, and diesel particle filter.

Ceramic application in the construction industry

Ceramic materials are typically used in the construction industry due to their significant mechanical properties and resistance to corrosion and abrasion. Some of the applications of ceramics in the construction industry are:

1-Floor finish: Due to durability, resistance to moisture, chemical, and corrosion, ceramic and tiles are usually used as floor finish materials in houses and commercial buildings and also as ceramic for the floor and facade of the building. 

2- Roof materials and bricks: Ceramic materials like brick and roof tiles are used widely in the construction industry because of their durability, thermal insulation properties, and resistance to water, air, and chemicals. 

3- Insulator materials: Ceramics are used as insulators in buildings to improve energy efficiency and reduce sound transmission. Ceramic insulator materials are usually used on walls, roofs, and floors. 

4- Facade and coating: Ceramic materials are used as facade and coating materials in buildings. Ceramic facades and coating materials can provide thermal and acoustic insulation properties. 

5- Cement and concrete additives: Ceramic materials such as fly ash and silica fume can be used as cement and concrete additives to improve strength, durability, and efficiency. Ceramic additives can reduce the environmental impacts of producing cement and concrete. 

Final words

We became familiar with ceramic materials in this paper. Ceramic materials play a significant role in our daily lives due to their unique properties, such as durability, heat resistance, and chemical stability. With the advancement of science, more advanced ceramics with better properties have become available to us. Porcelain ceramics are one of the results of ceramic science progression, which has a wide application in the floor and facade of the building. For more information about this production, please contact us.

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