Polymer derived ceramics (PDCs) are ceramic materials formed by the pyrolysis of preceramic polymers, usually under inert atmosphere. The compositions of PDCs most commonly include

silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal s ...

(SiC), silicon oxycarbide (SiO_xC_y),

silicon nitride Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...

(Si₃N₄), silicon carbonitride (Si_3+xN₄C_x+y) and

silicon oxynitride Silicon oxynitride is a ceramic material with the chemical formula SiOxNy. While in amorphous forms its composition can continuously vary between SiO2 ( silica) and Si3N4 ( silicon nitride), the only known intermediate crystalline phase is Si2N2O. ...

(SiO_xN_y). The composition, phase distribution and structure of PDCs depend on the polymer precursor compounds used and the pyrolysis conditions applied. The key advantage of this type of ceramic material is the versatility afforded by the use of polymeric precursors in terms of processing and shaping. Polymer derived ceramics can be additively manufactured (3D printed) my means of

stereolithography Stereolithography (SLA or SL; also known as vat photopolymerisation, optical fabrication, photo-solidification, or resin printing) is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a lay ...

that uses photopolymerization of

preceramic polymers The term preceramic polymer refers to one of various polymeric compounds, which through pyrolysis under appropriate conditions (generally in the absence of oxygen) are converted to ceramic compounds, having high thermal and chemical stability. Ce ...

. Such processing of PDCs is used in applications requiring thermally and chemically stable materials in complex shapes that are challenging to achieve through more conventional ceramic processing routes, such as powder

sintering Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing ...

and

slip casting Slip casting, or slipcasting, is a ceramic forming technique for pottery and other ceramics, especially for shapes not easily made on a wheel. In this method, a liquid clay body slip (usually mixed in a blunger) is poured into plaster mou ...

. PDCs are also valuable for synthesis of porous and mesoporous materials and thin films.

Chemistry

PDCs are mainly fabricated through the pyrolysis of preceramic polymers. C8ta09054h-f2_hi-res

In the families of preceramic polymers, polysiloxanes are the most famous preceramic polymers. The backbones comprise carbon and oxygen atoms. Poly(organo)siloxanes are polysiloxanes with organic groups in the backbones, e.g., polyborosiloxanes, poly(carbosiloxanes). Another important category of preceramic polymers are polycarbosilanes and poly(organo)carbosilanes, containing alternating carbon and silicone atoms in the backbones. Similarly, polymers made up of Si-N bonds are classified as

polysilazane Polysilazanes are polymers in which silicon and nitrogen atoms alternate to form the basic backbone. Since each silicon atom is bound to two separate nitrogen atoms and each nitrogen atom to two silicon atoms, both chains and rings of the formula ...

, poly(organosilazanes) and poly(organosilylcarbodiimides). Different polymer compositions influence processing temperatures, microstructure transitions, ceramic yields and stabilities. The conversion of preceramic polymers to PDCs can be divided into four phases, shaping, cross-linking, pyrolysis, crystallization. Typically, PDC processing is completed at 1100 °C-1300 °C. To form a crystalline PDC, some materials require higher temperature to crystalize, usually over 1700 °C.

Properties

PDCs are characteristic with many properties, including: *

Mechanical properties A materials property is an intensive property of a material, i.e., a physical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another ...

: high

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

, modulus and strength. * Stability in extreme environments: good

thermostability In materials science and molecular biology, thermostability is the ability of a substance to resist irreversible change in its chemical or physical structure, often by resisting decomposition or polymerization, at a high relative temperatu ...

, high oxidation and corrosion resistance. *

Adhesion Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can ...

properties: high adhesive attraction and low

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) t ...

. *

Durability Durability is the ability of a physical product to remain functional, without requiring excessive maintenance or repair, when faced with the challenges of normal operation over its design lifetime. There are several measures of durability in us ...

: wear resistance, anti-

fouling Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surf ...

and anti-biofilm formation properties. * Low

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

and

biocompatibility Biocompatibility is related to the behavior of biomaterials in various contexts. The term refers to the ability of a material to perform with an appropriate host response in a specific situation. The ambiguity of the term reflects the ongoing de ...

. The combination of PDCs and other materials with different properties can develop combining properties for PDC-based composite materials. PDC-based composite materials can extend functions and usages of PDCs to a wide range of areas, for example, in biological, medical, electrical, magnetic, engineering and optical applications.

Uses

Coatings

Compared with other coating methods, the thermal treatment (e.g.

thermal spraying Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame). Thermal sprayi ...

) of PDC processing is simple and low-cost. PDC coatings are good components in

electronic devices The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

and gas separation membranes. Due to the intrinsic stability of PDC materials, PDC coatings are also commonly used in environmental barrier coatings (EBCs).

3D printing

Specific

3D printing 3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer co ...

techniques such as direct ink writing (DIW), stereolithography (SLA) and digital light processing (DLP) can control the structure of preceramic polymers from nanoscale to macroscale. 3D printing of PDCs can facilitate the fabrication and integration of advanced ceramic materials.

Biomedical engineering

Biocompatible PDCs and PDC-based composites can be applied in various biological systems. They are usually used to produce interface or surface with multi-functionality and complex shapes for biomedical applications, such as tissue regeneration, implant design, drug delivery, and wound dressing.

Electronics

Hybrid PDC materials are feasible and tunable for substrate manufacturing in

lithium ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also see ...

sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...

actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...

s, high temperature electrical devices, etc. Common processing strategies of PDC composites for electronic applications include chemical modification, blending with metal or metal oxides, and incorporating with functional fillers.

References

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