# A Comprehensive Study of Ceramic Matrix Composites for Space Applications

Authors: S. Dhanasekar; Arul Thayammal Ganesan; Taneti Lilly Rani; Venkata Kamesh Vinjamuri; Medikondu Nageswara Rao; E. Shankar; Dharamvir; P. Suresh Kumar; Wondalem Misganaw Golie
Journal: Advances in Materials Science and Engineering
 (2022)

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## Abstract

Ceramic matrix composites (CMCs) have grown in popularity as a material for a range of high as well as protection components, increasing the need to better understand the impacts of multiple machining methods. It is primarily composed of ceramic fibers embedded in the matrix. Ceramic materials, especially carbon fibers and carbon were used to create the matrix and fibers. These ceramics include a huge variety of non-metallic inorganic materials that are regularly utilized under high temperatures. The aircraft industry became revolutionized by this unique combination of materials, which made parts better resistant under extreme conditions as well as lighter than the earlier technology. The development, properties, and production of ceramic matrix composites, as well as space applications, are discussed in this article. Ceramic materials have an interesting set of properties, including great strength and stiffness under extremely high temperatures, chemical inertness, low density, etc. In CMC, ceramics are used in the matrix as well as reinforcement. The matrix material keeps things running smoothly while the reinforcement delivers unique special properties. Ceramic matrix composites are developed for applications that required high thermal and mechanical characteristics, which include nuclear power plants, aircraft, chemical plants, space structures, and transportation services. Even though advanced aircraft relies on high-performance propulsion systems, improving the total impulses over the total mass ratio for rocket engines becomes essential for improving their performance that demands reduced engine structural weight as well as higher component heat resistance. The evolution of new ultra-high-temperature composites having high-temperature resistance as well as low density that a substitute super alloy and refractory metal material has become so essential and laid the foundation for high-performance engine design. The benefits of continuous fiber- reinforced CMC with high-temperature engine designs have long been recognized as a better measure of a country’s ability to design and produce spacecraft, modern aircraft, and weapons. Ceramic matrix composites materials are used in various aircraft type engines, aircraft brake disks, high-temperature gas turbines components, slide bearing components, hot gas duct, flame holders and components for burners are made by using oxide CMCs.


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## Body

## 1. Introduction

Composite material structures have attracted interest for various industrial applications based on their ability to improve their strength-to-weight proportion when analyzed with non-reinforced materials [1]. Digitalization will encompass the majority of engineering fields, with a bigger impact over wide-area communication networks involving fast data transmission [2–4]. A significant amount of research has been expended and recounted over various reviews in the field of machining composites [5–7]. Due to their unique form, CMCs have been considered challenging to machine processes. Due to the latest increase in demand for the long fiber-reinforced CMC, materials have been employed in high-temperature structural industries including nuclear power, automobiles, and aircraft [8, 9]. The engineered connections of fibers and the matrix have been devised to provide a regulated bridging technique for cracks in ceramic composites reinforced using long fibers, as a result, fracture toughness improves, and therefore viable mechanical properties are used in various structural applications like aero-engines and nuclear reactors [10]. To accomplish the objectives of efficiency, thrust-to-weight ratio, and fuel economy, new aviation engines need advanced materials. Ceramic matrix composite is a novel emerging technology for improving the hardness and durability of ceramics at extremely high-temperature applications, like engine hot area elements. By means of production of stiffer, harder, and smaller lighter materials able to withstand increased operating temperatures, CMC materials suggest the possibility of even greater advances in productivity and reduced weight. Composites also provide the ability to create novel materials having unique properties which are not found in traditional materials [11]. Sol-gel synthesized metal nanocomposite and hybrid ceramic substances, as well as quasi-crystalline materials with separated stages between 1–10 nm with variable design and structure, were studied. This idea for structured ceramic nanocomposites has been adopted as microstructural tailoring in structural ceramic composites using a nanocomposite method. This research was primarily supported by findings from the Si3N4/SiC as well as Al2O3/SiC systems [12]. These CMC composites have already been used to develop advanced airframe designs due to their high strength/weight as well as stiffness/weight characteristics. CMCs have been frequently utilized in complex parts of aero-engine vanes, and traditional machining is perhaps the most common method for reshaping the materials to meet the geometric and assembling needs. The developments of ceramic matrix composites are introduced in Section II of this article. The properties of ceramic matrix composites have been discussed in Section III. The manufacturing of ceramic matrix composites has been described in Section IV. The ceramic matrix composite, which is used in space applications are illustrated in Section 5. In the end, Section 6 concludes with remarks on the ceramic matrix composites.


## 2. Development of Ceramic Matrix Composites

To overcome the issues and demanding requirements for materials application in the 21st decade in various vital industries ranging between architecture, transportation, and energy, there will be an upcoming need to create unique stringer and more rigid structural materials. Depending on the materials used to form the matrix, composites are categorized into ceramic matrix composites, metal matrix composites (MMC), and polymer matrix composite (PMC) [13]. Due to its excellent physical, mechanical, as well as thermal properties, each of these composites plays an essential part in the present technology. These polymer composite materials have a natural polymer grid that allows the series on smaller consistent filaments. The polymer matrix composites were created to transfer loads among the filaments as well as matrix materials [14]. MMCs are naturally adaptable and also provide superior flexibility, toughness, strength, and dimensional stability, particularly for aviation components seem to be the most prominent usage [15]. Ceramic matrix composites are emerged as potential choices because of their excellent mechanical and physical properties. CMCs were heterogeneous materials with their second phase embedded throughout the ceramic matrix. CMCs have features, including hardness, self-healing, and functioning because of the nature of a reinforcement material [16].Ceramic matrix composites were created to address monolithic ceramics inherent fragility as well as loss of mechanical durability, despite their high strength and hardness [17]. Developing probabilistic, non-destructive analysis methodologies depending on the failure of micromechanics, trying to devise processing methods to remove critical defects, as well as continuing to develop hardened ceramics with damage tolerance are three approaches that ensure the ceramics reliability. Continuous or long and discontinuous or short-fibers composites are used to reinforce ceramic matrix composites. The discontinuous or short-fiber composites consist of non-oxide alumina as well as oxide alumina materials using traditional ceramic processes. zirconium oxides (ZrO2), silicon carbide (SiC), titanium boride (TiB2), aluminum nitride (AlN) are used to reinforce the ceramic matrix. Silicon carbide fibers have been utilized extensively to reinforce the bulk of CMCs due to their high elastic modulus and strength. The addition of whiskers with the short-fiber-ceramic matrix composite improves its hardness and crack resistance. The continuous or long fibers have higher durability that maintains a load even when the ceramic matrix cracks and reduces the fracture development. The short fibers and whiskers are used to improve crack resistance. The continuous monofilament fibers in the dispersed phase are manufactured using chemical vapor deposition (CVD) with silicon carbide in the substrate which is composed of tungsten as well as carbon fibers, delivering the most effective strengthening. Monofilament fibers offer a better interface connection, which makes the matrix materials more durable [18].Ceramic matrix composites are composite materials that have ceramics in matrix and reinforcement. The matrix material binds everything together while the reinforcement delivers its unique characteristics. Figure1 shows the various types of composite matrixes and materials used in each composite. CMCs were created for applications that required high mechanical and thermal performance which include aircraft, nuclear power plants, land transportation, chemical plants, and space structures. In ceramic matrix composites, reinforcing materials, such as alumina, alumina-silica, carbon, and silicon carbide are used. Refractory fibers include nanofibers, long fibers, short fibers, particles, and whiskers. These fibers have a polycrystalline structure similar to traditional ceramics. CMCs are less susceptible to these crack defects in the materials, but once a fracture starts to grow, failure can be devastating [19]. The matrix materials with ultra-high-temperature, non-oxide ceramics are added for special applications. Advanced ceramics have been widely used in the production of ceramic matrix composites to overcome a major disadvantage in traditional ceramics, which is their brittleness. The commonly used non-oxide CMCs are carbon/silicon carbide (C/SiC), carbon/carbon (C/C), as well as silicon carbide (SiC). These names are usually derived from the structure of the fiber and matrix material types. For nearly 50 years, researchers have been working on ceramic materials for use in the hot portion of the gas turbine engines. Ceramic gas turbine components have been designed, produced, and evaluated with rigs and engines including aviation, industrial, automotive as well as utility power applications. Ceramic matrix composites will be used as the preferred material in both present and prospective engine parts due to their substantially higher fracture toughness [20].Figure 1
Types of composites materials.


## 3. Properties of Ceramic Matrix Composites

Advanced ceramics have a unique number of properties, including high tensile strength under high temperatures, superior corrosion, high hardness, erosion resistance, low density, strong elastic modulus, and reduced coefficients of friction, making them reasonable alternatives for a variety of structural applications as compared with pure metals [21]. Cutting tools, heat exchangers, wear components and coatings are just a few of the current applications of advanced ceramics. But, to use ceramics in new areas like engines and turbines, their reliability and brittleness must be improved. Ceramic matrix composites have the benefit of higher toughness, catastrophic failure resistance, good strength, low weight, low thermal expansion, and capacity which sustains high temperatures for oxidation resistance. Ceramic materials were more resistant to high temperatures as well as harsh environments than metals as well as other traditional engineering materials. Ceramics constitute inorganic non-metallic materials made up of non-metallic and metallic elements bound together by ionic and/or covalent bonds. Thermal shock resistance and toughness are limited in traditional ceramics. The usage of fiber reinforcement in ceramic matrix composites overcomes these problems.Ceramic matrix composites have a number of common features which include (i) high tolerance to thermal shock and creep, (ii) resistance to high temperatures, (iii) excellent corrosion and wear resistance, (iv) intolerance to corrosive chemicals, (v) reinforcement improves fracture toughness, and (vi) at high temperatures, the strength of the material remains high [22]. Long fiber composites and dispersion composites and are the two types of ceramic composites most commonly used. Carbon–carbon fiber composites were extensively researched and are used in a variety of applications, including wing, front fuelage as well as brake components, particularly within the aircraft sectors. Furthermore, the C/C composites are oxidation-sensitive, and numerous coatings, impregnants, as well as inhibitors were tried to prevent carbon gasification. Ceramic fiber-ceramic matrix composites are likely to be appropriate materials in structural applications owing to reduced brittleness. SiC fibers can oxidize when exposed to high temperatures. Platelet composites, particle composites, and silicon carbide whiskers (Sic-w) are all examples of dispersion composites. Mechanical property improvements have been made to a large extent by means of ceramic matrix dispersion. In ceramic matrix composites, mullite-ZrO2, hafnia (Hf02) and zirconia (Zr02) were employed as particles. Due to their durability, hardness, as well as creep resistance, silicon carbide whiskers improve mechanical characteristics significantly. Apart from applications in which thermal shock resistance is required, SiC whisker reinforcement has been found to lower deformation rates under high-temperature creep, allowing these materials to satisfy the criteria of several challenging applications [23]. Platelets were likely to provide an option for whisker reinforcement. Platelets typically range in size between 10 and 50 microns, and the coarser platelets will function as significant defects.The fundamental process underlying mechanical properties of CMCs has an embedded fibers bridge and it performs whenever the matrix would move along with fibers, emphasizing that the fibers, as well as the matrix, would have a weak bond. As with traditional ceramics, a strong bond would necessitate a high extension capability in the fiber across the crack, causing a brittle failure. The thermal and electrical properties of CMCs are determined by the composition of their constituents, which include pores, fibers, and matrices. Oxide CMCs have good electrical insulators, however, due to their high permeability, whose thermal insulation remains significantly superior to the oxide ceramics. Excluding the oxidation in temperatures exceeding 1000°C, there is a scarcity of corrosion data on CMCs. The components, mainly matrix, and fiber determine these characteristics. Generally, ceramic materials are corrosion resistant. Corrosion tests require a wide range of manufacturing procedures using mixtures, various sintering additives, porosities as well as glass phases. CMCs are substances that have a significant amount of chemical and a structural distinct component which is less than 5%, are scattered inside a continuous matrix and have unique ultimate properties. Its damage tolerance but also excellent mechanical qualities across a wide temperature range could also be emphasized [24]. The matrix in CMCs is typically a technical ceramic made by rather sophisticated methods using large raw materials having nano or microscale particle sizes. Ceramics have a low density, refractoriness, chemical resistance, and great hardness, and they generate hybrid chemical connections among covalent as well as ionic forms. Despite significant progress in these characteristics during the last two decades, monolithic ceramic materials have remained limited by their low tensile strength, mechanical shock, and thermal stress resistance [25].


## 4. Production of Ceramic Matrix Composites

Due to their outstanding qualities, ceramic matrix composites employ as the finest material in diverse applications. As the first man-made substance, ceramics offer great strength and hardness, chemical stability, good thermal expansion, as well as good oxidation and corrosion resistance qualities [26]. CMCs have been the most suitable material for a variety of engineering purposes under severe and demanding environments, and they are widely employed in situations featuring thermal shocks and high temperatures. Due to their brittle performance, high hardness, heterogeneous structure made up of fibers, porosities, and matrix, as well as their orthotropic mechanical and thermal behavioral patterns, CMCs are challenging to manufacture. Ceramic fibers with a thickness of 3–20 micrometers are used to create ceramic matrix composites. A small diameter of the fiber which is normally made as yarns permits it to be flexible when more textile preparation is required. CMC form was created by continuous fibers that have been textile structured via braiding, weaving, knitting, cutting yarns, and making them as small fiber bundles. According to several researchers, ceramic matrix composites have been manufactured in a number of ways based on the need and use of the materials [27]. A lot of factors influence the processing method used to manufacture ceramic matrix composites, including the needed composite size and shape, working temperature, CMC application, reinforcement type, and so on.The most prevalent traditional ways for machining ceramics, as well as composites, are grinding and drilling. Traditional methods of machining ceramics and their composites are complex but also time-consuming. The three basic techniques for manufacturing CMCs are (i) liquid phase infiltration, (ii) polymer infiltration and pyrolysis (PIP), and (iii) hot press sintering approaches. Step one involves arranging and fixing the fibers, also known as rovings, employing methods identical to the fiber-reinforced plastic materials used, which include knotting, fabric lay-up, braiding as well as filament winding. This procedure produces fiber-preform, which is also known as a preform. The most popular technique is polymer infiltration and pyrolysis. The ceramic matrix in PIP has been created by infiltrating a fluid into the fiber reinforcement. The process of converting fluid toward ceramics, namely, (i) polymer infiltration and pyrolysis, (ii) reactive melt infiltration (RMI), (iii) liquid silicon infiltration (LSI), (iv) chemical vapor infiltration (CVI), and (v) ceramic slurry infiltration (CSI). The final machining process comprises grinding, milling, drilling, grinding as well as lapping, which needs diamond tools. CMCs will be processed with ultrasonic machining, water jet, and laser. Pyrolysis is the heat breakdown of carbon-containing organic material. This breakdown occurs under high temperatures in an inert environment and typically appears without oxygen. Pyrolysis is the process of decomposing a substance into the ceramic under nitrogen, argon as well as ammonia environment, depending upon the nature of the ceramic matrix utilized. Pyrolysis produces a variety of compounds, which are the most volatile. H2, CO, CO2, CH2 as well as H2O are examples of these products. A low-viscosity polymer has been infiltrated into fabric materials like tape and woven, which is formed by ceramic reinforcing material under the polymer infiltration and pyrolysis process method. Afterward, the infiltrated reinforcing material is heated in a sterile, oxygen-free environment.The polymer thermally breaks down into a ceramic when heated. A polymer-derived ceramic has been the resulting CMC. The above process is named the liquid polymer infiltration, or LPI. An infusing polymer in PIP is the preceramic polymers, popularly called polymer precursors. Pyrolysis can change preceramic polymers toward ceramics, which makes them unique. The spark plasma and hot pressing are capable of producing small geometrical shapes. Carbon and silicon are commonly found in these ceramics, although other components, including boron, nitrogen, aluminum, titanium as well as oxygen have also been present. Carbon or silicon carbide is the most common matrix material utilized in the PIP process. This process has a minimum of six steps: The first stage in the PIP process is Prepreg fabrication, in which the reinforcing ceramic fibers have been coated using resin. Either the resin is dried but rather partly hardened. Typically, a substance is added to the fibers that reduce the interfacial interaction between the matrix and fibers, with the aim of growing fiber pullout as well as crack strength. The fibers can be non-continuous, continuous as well as woven together to create a fabric. Lay-up relates to layering the prepreg substance in stage 2. Multiple layers are necessary and the characteristics of the final CMC are controlled by the order wherein layers with different orientations were placed. The prepreg lay-up becomes molded into the appropriate shape in the third stage, and this shape will resemble the final component. The pores inside the molded prepreg have been filled with low-viscosity preceramic polymer during the fourth stage of polymer infiltration. The polymer is driven into the pores by capillary forces, which can generally be achieved with normal pressure. To accomplish good pyrolytic decomposition, temperatures ranging from 1,472°F and 2,372°F will be needed in the fifth stage. The atmosphere is N2 or NH3 when nitride is used as matrix material is a nitride else Ar is utilized. Stages 4 and 5 have been repeated around 4 and 10 times in stage 6, based upon porosity for ceramic matrix following initial pyrolysis. Figure 2 illustrates the manufacturing methods for ceramic matrix composites.Figure 2
Manufacturing techniques for ceramic matrix composites.The PIP method is most commonly employed in carbon matrices and silicon carbide. Infiltration methods are often used to make reinforced ceramic matrix composites using continuous fiber, during which the ceramic matrix has been created using fluid infiltrating the fiber structure [28]. As a result, whether using nonconventional or conventional machining methods, additional processing is necessary. Chemical methods employed among many researchers for the production of ceramic and their composites create near-net-shape using a short processing period as well as low temperature, however, a composite produced through a reaction bonding process is much more porous, resulting in mechanical characteristics degradation. In the drying process of the sol-gel technique, the creation of cracks for the matrix phase has been a key issue. Low production and significant shrinkage volume occur in sol-gel as well as polymer processing, which necessitates many processes to accomplish densification.


## 5. Applications for Ceramic Matrix Composites

The focus on high wireless communication has raised due to the impact of the growth of wideband wireless transmission networks [29, 30]. To achieve the performance objectives, modern aircraft propulsion systems involving hypersonic, subsonic, and supersonic flight operations generally need intensive materials. Beyond the large temperature range, advanced polymer, ceramic, as well as metal matrix composites, provides great promise in aviation engines and airplane spacecraft components. Ceramic composites are highly desirable toward aerospace applications due to its high-temperature utilization. CMCS was helpful for aircraft where mission success depends on lightweight as well as environmental durability. These materials have the ability to propel spacecraft more than 10 times faster using the same amount of fuel, considerably boosting travel distance and reducing vehicle size. While several lightweight ceramic materials are suitable for space applications, the silicon used in the ceramics like silicon nitride (Si3N4) as well as silicon carbide has the highest possibility of attaining the high-temperature structural parts. Their rigidity, thermal stability, high-temperature hardness, resistance toward thermal shock as well as thermal shock and oxidative conditions will contribute to these factors. Moreover, engine demonstration projects like the Advanced Gas Turbine project are evaluating structural capabilities for these materials through the monolithic structures. The Monolithic ceramics are used in the structural components for non-terrestrial engines, due to their low-cost structural behavior and predictability. Such materials are extremely sensitive to minor cracks and faults mostly in microstructure due to their poor toughness.


### 5.1. Sic-Sic and C-Sic Composites for Aeronautical Applications

In the aerospace industry, CMCs are used in a variety of real-world as well as futuristic scenarios. The majority are designed for high-temperature oxidation situations, like those found in aviation engines as well as re-entry spacecraft. Due to carbon oxidation sensitivity, ceramic matrices were created to substitute carbon to acquire substances suitable for long resistance at high thermal fluxes and also mechanical loads in oxidation conditions. These aircraft applications are best served by C–SiC, SiC–SiC composite materials. In-room temperature, the above materials have good toughness as well as a non-brittle characteristic which includes a failure strain of close to 0.5%. Several aero-engine components, thermal architectures, hot gas valve sections as well as Thermal protection systems (TPS) for the re-entry vehicles are made using ceramic-ceramic and carbon-ceramic materials. To manufacture reinforced SiC composites having outstanding high-temperature characteristics, sophisticated procedures such as chemical vapor infiltration has been needed currently. Furthermore, it is a time-consuming process and it will take more time to produce the components. In essential space applications, novel reinforced fiber composites such as SiC–SiC and C–SiC were currently restoring the older materials. They should find larger uses with additional innovations and improvements in further processing.


### 5.2. Ceramic Matrix Composite Brake Materials for Aircraft Applications

Aircraft brakes have become an important part of secure landings as well as takeoffs and they will function as frictional parts to create sufficient stopping force in various operational environmental circumstances, when the heat sinks, it will collect the aircraft’s kinetic energy and distribute force toward the tyres. The organic compounds which include non-asbestos organic brake materials and asbestos fiber-reinforced resin matrix composites have given way to powder metallurgy materials like copper as well as iron-based metallic and carbon/carbon composites brakes in the development of airplane brakes. The fast advancement in aviation engineering and innovation has resulted in aircraft that have significantly grown in size as well as weight. As a result, the tendency in brake material research has always focused on larger energy absorptions, and brake temperatures have been higher than traditional braking materials which are made up of organic and steel. To handle the high brake energy, the traditional brake weight has been raised in addition to improving the brake’s thermal capacity and lowering the temperature of the brakes. In order to further expand and reduce costs, China’s North-western Polytechnical University (NPU) has been working on short-fiber reinforcement SiC brake materials.As in the scientific community, C/SiC braking materials have grabbed the public’s curiosity. The C/SiC brake disk was first introduced in Porsche 911 GT2 in 2001 [31]. Elevator and crane emergency brakes have been made from brake materials of C/SiC. The aircraft brake made of C/SiC was used for limited batches in a variety of military aircraft. Pyrolysis technology (PIP), liquid silicon infiltration technology (LSI), and polymer infiltration are three common C/SiC brake techniques. The aircraft brake materials should have good frictional properties, mechanical characteristics, and thermal qualities and also have structural and frictional components and heat sinks. The Sandwich structure-based C/SiC braking materials were designed to improve phase distribution in the materials. The primary wear mechanisms used in 3D needled C/SiC brake materials are grain abrasion, fatigue wear, as well as adhesive wear which is created in chemical vapor infiltration (CVI) along with LSI. Each of these wears mechanisms occurred at the same time and collaborates with one another. Two exterior friction-reducing functional layers and an inner mechanical functioning layer have been made by Sandwich construction materials. Despite the fact that C/SiC brake materials were used in a variety of airplanes and high-end automobiles, the connection underlying properties and structure of C/SiC brakes remains unclear. The impact on the structure of C/SiC brake materials for mechanical characteristics, tri-biological properties, and thermal physical qualities requires more research.


### 5.3. Monolithic Ceramics for Ultra-High Temperature in Aerospace Applications

In the 21st century, advanced ceramics have been chosen as the primary choice for a variety of applications, which includes telecommunications, modern electronics, photonics, multifunctional, sensor, thermal engine, military, turbine, defense, and aviation applications. With the growing interest in reusable atmospheric re-entry vehicles and creating hypersonic aerospace vehicles, monolith ceramics materials have seen a considerable surge in popularity in recent years. Ceramics will concentrate on materials that are well-known and potentially relevant to ultra-high-temperature (UHT) applications, i.e., up to 1200°C. The objective of this research is to investigate the possible aerospace and defense applications, wherein UHT situations are common [32]. The majority of high-performance ceramics undergoing investigations are made of silicon carbide, silicon nitride, zirconia, and dispersion hardened alumina as well as ceramic matrix composites. Coatings made of Cr2O3 and zirconia is reported to be efficient in a variety of gas turbine as well as diesel applications. SiC, mullite fibers, and Al2O3 are being used as reinforcement for ceramic composites. TiB2 and ZrB2 are the most significant components in monolithic ceramics. These components are ideal for aerospace applications because of the unique combination of their characteristics.


#### 5.3.1. Titanium Boride Ceramics (Ti-B)

High stiffness, flexibility, chemical stability, thermal conductivity as well as high melting point are significant and useful features of Ti-B. Orthorhombic Ti3B4, hexagonal TiB2, and orthorhombic Ti-B are the three major compounds used in titanium boride ceramics. Ti-B composites are promising ceramic materials due to the strong Ti-B covalent bonding. In titanium metal matrix composites, Ti-B has been frequently employed for reinforcement.


#### 5.3.2. Zirconium Boride Ceramics (ZrB2)

ZrB2 is employed as a diffusion barrier for the semiconductors, the container of molten metal, as well as a burnable absorber for nuclear reactor cores, among other things. The thermal protective layer is commonly used in aircraft systems that involve hypersonic flight as well as atmospheric re-entry. There are three basic synthesis routes in ZrB2, namely (i) chemical routes, (ii) reduction procedures, and (iii) reactive processes. As a source, zirconia has been used, while in the reducing agent, carbon or boron was used.


### 5.4. Ceramic Matrix Composites Taking Flight at GE Aviation

General Electric (GE) has been working on CMC for the past 30 years, and the company has spent about $1.5 billion on technology during the last decade. The US Department of Energy, NASA, and Department of Defence actively contributed to the early innovation and expansion. GE Aviation had made considerable funds for the development of CMC products and methods, and also for manufacturing enhancements and supply chain management. As a result of this investment, CMC high-pressure turbine shrouds are now available for the LEAP engine [33]. Commercial LEAP engines for Boeing, Airbus as well as COMAC airplanes have already logged more than four million flight hours using CMC shrouds.The GE9X, the world’s largest aviation engine, includes five CMC components across the hot section of the engine. One outer liner, one combustor inner liner, HPT Stage 1 shrouds, HPT Stage 2 nozzles, and nozzles are five components for GE9X aviation. CMCs are being implemented into advanced military engine architectures which provide higher thrust and lower specific fuel consumption for future aircraft. GE developed the prepreg/melt infiltration (MI) method of producing SiC CMC turbine engine components with tiny, complex features and distinguishing characteristics. Within the next 10 years, GE anticipates a 10-fold increase in CMC component production. The capacity to manufacture the fiber to final CMC engine components for a broad range of modular components will be enabled by GE Aviation’s quick and flexible vertical distribution chain. Various polymer and metal matrix composites also used in other applications [34–38].


## 5.1. Sic-Sic and C-Sic Composites for Aeronautical Applications

In the aerospace industry, CMCs are used in a variety of real-world as well as futuristic scenarios. The majority are designed for high-temperature oxidation situations, like those found in aviation engines as well as re-entry spacecraft. Due to carbon oxidation sensitivity, ceramic matrices were created to substitute carbon to acquire substances suitable for long resistance at high thermal fluxes and also mechanical loads in oxidation conditions. These aircraft applications are best served by C–SiC, SiC–SiC composite materials. In-room temperature, the above materials have good toughness as well as a non-brittle characteristic which includes a failure strain of close to 0.5%. Several aero-engine components, thermal architectures, hot gas valve sections as well as Thermal protection systems (TPS) for the re-entry vehicles are made using ceramic-ceramic and carbon-ceramic materials. To manufacture reinforced SiC composites having outstanding high-temperature characteristics, sophisticated procedures such as chemical vapor infiltration has been needed currently. Furthermore, it is a time-consuming process and it will take more time to produce the components. In essential space applications, novel reinforced fiber composites such as SiC–SiC and C–SiC were currently restoring the older materials. They should find larger uses with additional innovations and improvements in further processing.


## 5.2. Ceramic Matrix Composite Brake Materials for Aircraft Applications

Aircraft brakes have become an important part of secure landings as well as takeoffs and they will function as frictional parts to create sufficient stopping force in various operational environmental circumstances, when the heat sinks, it will collect the aircraft’s kinetic energy and distribute force toward the tyres. The organic compounds which include non-asbestos organic brake materials and asbestos fiber-reinforced resin matrix composites have given way to powder metallurgy materials like copper as well as iron-based metallic and carbon/carbon composites brakes in the development of airplane brakes. The fast advancement in aviation engineering and innovation has resulted in aircraft that have significantly grown in size as well as weight. As a result, the tendency in brake material research has always focused on larger energy absorptions, and brake temperatures have been higher than traditional braking materials which are made up of organic and steel. To handle the high brake energy, the traditional brake weight has been raised in addition to improving the brake’s thermal capacity and lowering the temperature of the brakes. In order to further expand and reduce costs, China’s North-western Polytechnical University (NPU) has been working on short-fiber reinforcement SiC brake materials.As in the scientific community, C/SiC braking materials have grabbed the public’s curiosity. The C/SiC brake disk was first introduced in Porsche 911 GT2 in 2001 [31]. Elevator and crane emergency brakes have been made from brake materials of C/SiC. The aircraft brake made of C/SiC was used for limited batches in a variety of military aircraft. Pyrolysis technology (PIP), liquid silicon infiltration technology (LSI), and polymer infiltration are three common C/SiC brake techniques. The aircraft brake materials should have good frictional properties, mechanical characteristics, and thermal qualities and also have structural and frictional components and heat sinks. The Sandwich structure-based C/SiC braking materials were designed to improve phase distribution in the materials. The primary wear mechanisms used in 3D needled C/SiC brake materials are grain abrasion, fatigue wear, as well as adhesive wear which is created in chemical vapor infiltration (CVI) along with LSI. Each of these wears mechanisms occurred at the same time and collaborates with one another. Two exterior friction-reducing functional layers and an inner mechanical functioning layer have been made by Sandwich construction materials. Despite the fact that C/SiC brake materials were used in a variety of airplanes and high-end automobiles, the connection underlying properties and structure of C/SiC brakes remains unclear. The impact on the structure of C/SiC brake materials for mechanical characteristics, tri-biological properties, and thermal physical qualities requires more research.


## 5.3. Monolithic Ceramics for Ultra-High Temperature in Aerospace Applications

In the 21st century, advanced ceramics have been chosen as the primary choice for a variety of applications, which includes telecommunications, modern electronics, photonics, multifunctional, sensor, thermal engine, military, turbine, defense, and aviation applications. With the growing interest in reusable atmospheric re-entry vehicles and creating hypersonic aerospace vehicles, monolith ceramics materials have seen a considerable surge in popularity in recent years. Ceramics will concentrate on materials that are well-known and potentially relevant to ultra-high-temperature (UHT) applications, i.e., up to 1200°C. The objective of this research is to investigate the possible aerospace and defense applications, wherein UHT situations are common [32]. The majority of high-performance ceramics undergoing investigations are made of silicon carbide, silicon nitride, zirconia, and dispersion hardened alumina as well as ceramic matrix composites. Coatings made of Cr2O3 and zirconia is reported to be efficient in a variety of gas turbine as well as diesel applications. SiC, mullite fibers, and Al2O3 are being used as reinforcement for ceramic composites. TiB2 and ZrB2 are the most significant components in monolithic ceramics. These components are ideal for aerospace applications because of the unique combination of their characteristics.


### 5.3.1. Titanium Boride Ceramics (Ti-B)

High stiffness, flexibility, chemical stability, thermal conductivity as well as high melting point are significant and useful features of Ti-B. Orthorhombic Ti3B4, hexagonal TiB2, and orthorhombic Ti-B are the three major compounds used in titanium boride ceramics. Ti-B composites are promising ceramic materials due to the strong Ti-B covalent bonding. In titanium metal matrix composites, Ti-B has been frequently employed for reinforcement.


### 5.3.2. Zirconium Boride Ceramics (ZrB2)

ZrB2 is employed as a diffusion barrier for the semiconductors, the container of molten metal, as well as a burnable absorber for nuclear reactor cores, among other things. The thermal protective layer is commonly used in aircraft systems that involve hypersonic flight as well as atmospheric re-entry. There are three basic synthesis routes in ZrB2, namely (i) chemical routes, (ii) reduction procedures, and (iii) reactive processes. As a source, zirconia has been used, while in the reducing agent, carbon or boron was used.


## 5.3.1. Titanium Boride Ceramics (Ti-B)

High stiffness, flexibility, chemical stability, thermal conductivity as well as high melting point are significant and useful features of Ti-B. Orthorhombic Ti3B4, hexagonal TiB2, and orthorhombic Ti-B are the three major compounds used in titanium boride ceramics. Ti-B composites are promising ceramic materials due to the strong Ti-B covalent bonding. In titanium metal matrix composites, Ti-B has been frequently employed for reinforcement.


## 5.3.2. Zirconium Boride Ceramics (ZrB2)

ZrB2 is employed as a diffusion barrier for the semiconductors, the container of molten metal, as well as a burnable absorber for nuclear reactor cores, among other things. The thermal protective layer is commonly used in aircraft systems that involve hypersonic flight as well as atmospheric re-entry. There are three basic synthesis routes in ZrB2, namely (i) chemical routes, (ii) reduction procedures, and (iii) reactive processes. As a source, zirconia has been used, while in the reducing agent, carbon or boron was used.


## 5.4. Ceramic Matrix Composites Taking Flight at GE Aviation

General Electric (GE) has been working on CMC for the past 30 years, and the company has spent about $1.5 billion on technology during the last decade. The US Department of Energy, NASA, and Department of Defence actively contributed to the early innovation and expansion. GE Aviation had made considerable funds for the development of CMC products and methods, and also for manufacturing enhancements and supply chain management. As a result of this investment, CMC high-pressure turbine shrouds are now available for the LEAP engine [33]. Commercial LEAP engines for Boeing, Airbus as well as COMAC airplanes have already logged more than four million flight hours using CMC shrouds.The GE9X, the world’s largest aviation engine, includes five CMC components across the hot section of the engine. One outer liner, one combustor inner liner, HPT Stage 1 shrouds, HPT Stage 2 nozzles, and nozzles are five components for GE9X aviation. CMCs are being implemented into advanced military engine architectures which provide higher thrust and lower specific fuel consumption for future aircraft. GE developed the prepreg/melt infiltration (MI) method of producing SiC CMC turbine engine components with tiny, complex features and distinguishing characteristics. Within the next 10 years, GE anticipates a 10-fold increase in CMC component production. The capacity to manufacture the fiber to final CMC engine components for a broad range of modular components will be enabled by GE Aviation’s quick and flexible vertical distribution chain. Various polymer and metal matrix composites also used in other applications [34–38].


## 6. Conclusion

This article discusses the development, manufacture, and characteristics of ceramic matrix composites, as well as potential space applications. Ceramic matrix composite preparation and its properties using existing reinforcements is a developing technology that finds new important applications. A variety of aircraft type engines, aircraft brake disks, high-temperature gas turbine components, and sliding bearing components are made by ceramic matrix composite materials. Ceramic matrices have greater melting points, hardeners, lower coefficients of thermal expansion, and superior chemical inertness as compared with polymer and metal matrices. Ceramic matrices are available in a wide variety of shapes and sizes. CMCs include oxides, such as MgO, Al2O3, Mullite, Spinel, and ZrO2 as well as non-oxides, such as Si3N4, SiC, TiB2, TiC, and B4C. Due to their excellent mechanical and physical characteristics, CMCs are a fast emerging and evolving technology sector in aeronautical applications. To manufacture reinforced SiC composites under high-temperature characteristics, complicated procedures such as chemical vapor infiltration have been needed. In demanding aerospace applications, novel reinforced fiber composites which include C-SiC and SiC-SiC was currently taken over the previous composites. The C/SiC brakes have better frictional characteristics, including a lower wear rate, higher static friction coefficient, higher braking efficiency, and less sensitivity to wet circumstances. C/SiC brake materials are novel, cost-effective brake materials that are used in airplanes, high-speed trains, heavy trucks, elevator and crane emergency brakes, and other applications. The usage of monolithic, as well as composite ceramic materials had gradually increased in India due to the development of aircraft, space systems, and missiles over the last two to three decades. Nevertheless, due to a shortage of high-quality powder production facilities in India and there is a significant gap in the technological development and manufacturing of these materials. HPT nozzles, combustor liners, and shrouds are the component used in the GE9x engine due to GE progressive extension of CMC production. GE aviation uses big data concepts to connect data points and use the CMC facilities for the production process. Ceramic matrix composites with ultra-high temperatures were the CMCs newer branch that is employed for hypersonic vehicle components and rockets.



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