Handbook of Advanced Ceramics and Composites

In recent times, the global science and technology is dominated by research in the nanotechnology domain, especially to explore novel materials with exotic properties, which are attributed to their nano-size regimes. Typically explored examples are metals (gold, silver, copper, etc.), organic and inorganic materials (metal oxides, polymers), carbon (graphene, CNTs, etc.), and so on, typically, in their pure and composites forms. The polymers are playing a vital role in this domain, to make the polymer-based nanocomposites, which are used for different applications in textiles, pharmaceutical, chemical, instrumentation, aerospace, aeronautical, and mechanical domains of engineering. However, one particular domain, which has sought the maximum attention of these nanomaterials, is the sensors. Sensors are an integral part of any instrumentation, mechanical assembly, automobile engineering, heavy engineering, and drug delivery vehicles or in national surveillance gadgets or in any electromagnetic application unit, such as antennas and communication electronics. A need for smart, miniaturized, extremely sensitive, selective, and accurate sensor is always on anvil.This chapter starts with a brief outline on the progress of science and technology, particularly in the domain of sensors, for low-field and low-frequency (electric and magnetic fields and ultra-low-frequency signals) detections and chemical-biological hazardous environment detections. Various approaches for sensing, used in the authors’ laboratory, would be elaborated, namely, the radio-frequency sensing approach, optical fiber approach, metamaterial approach, and conventional resistive approach. The relationships of the obtained properties would be associated with the physics and chemistry at nano-level and their energy dynamics for sensing a particular physical parameter. The chapter will be closely related to defense applications, such as chemical and biological warfare (CBW) diagnostics and hazardous environmental detections, and electromagnetic shielding applications, along with low-frequency detections for sonar technologyℕ.

Today is an era of low-power devices mainly dependent on battery source for energy which needs to be replaced when gets exhausted for its power or ends its life. Usually, devices are embedded in structure or employed at remote places; hence, obtaining them for their replacement can become a very expensive task or even may not be feasible in some of the cases. Batteries of such devices could be replaced by “PZT-based power harvesting unit” since they are excellent electromechanical energy converting devices. This necessitates formulating and processing the PZT composition so as to achieve properties suitable for power harvesting in order to generate optimum electrical output. Here, nanostructured Pb0.98La0.02(Ni1/3Sb2/3)0.05[(Zr0.52Ti0.48)0.995]0.95O3composition, suitable for power harvesting applications, was synthesized by columbite precursor method followed by mechanical activation (MA) from 5 h to 40 h of dry oxide powders using high- energy ball mill, thereby circumventing the calcination stage. Nanometer particle size and its morphology were confirmed by transmission electron microscopy (TEM). X-ray diffractometer (XRD) was used to probe for progressive perovskite phase formations and transformations during MA as well as reactive sintering. Effect of MA and reactive sintering (1170–1320 °C) on microstructure was analyzed using scanning electron microscopy (SEM). Electromechanical properties of samples were evaluated and systematically correlated with crystallographic and microstructural effects. Processing parameters were optimized to obtain superior piezoelectric properties for power harvesting applications. Compact microstructure, composition at morphotropic phase boundary, optimum tetragonality, and crystallinity obtained for the samples for 10 h mechanical activation and sintered at 1220 °C resulted in best possible piezoelectric charge coefficient, d33 (449 × 10−12 C/N); piezoelectric voltage coefficient, g33 (32 × 10−3m.V/N); and figure of merit for power harvesting, FoMPH (14,400 × 10−15 m-V.C/N2). Further, power harvesting module was developed, and electrical output in response to simulated random vibrations of aerospace vehicles was measured in frequency band of 20–2000 Hz which explored the suitability of this composition for power harvesting applications for aerospace vehicle.

In the past one-decade, nanostructured two-dimensional (2D) version of tungsten and molybdenum disulfides have found major attention after the emergence of graphene and its unique properties in 2004. It is now well established that the 2D-nanolayered MoS2 and WS2 can have a stable structure in the form of multilayered nanosheets (NS) or inorganic graphene (IG) if it has monolayer or few (less than ten) layers. Such 2D structured MoS2 and WS2 have shown spectacular properties primarily due to changes in the electronic structure caused by the lattice strain induced on such nanostructuring. The enormous prospect of these materials has triggered major efforts in the development of various top-down and bottom-up synthesis routes as well as post-synthesis processing for potential applications. In the present article, the evolution of these materials and various aspects of their properties and emerging strategic applications have been reviewed critically.

The choice of materials in strategic applications is a challenge due to very stringent requirements in size, weight, and power constraints. Most of these materials are specifically designed and developed to obtain unique properties and hence belong to special class of materials. “Aerogel” is one of such unique materials possessing extraordinary properties together. The ultralightweight and highly nanoporous nature give rise to excellent insulation for heat, sound, and electricity. It is possible to tailor-make them for desired chemical composition; physical forms such as monolith, powder, granules, sheets, etc.; surface chemistry to make them hydrophilic or hydrophobic; and so on. Aerogels can also serve as a host matrix for other materials to make lightweight and functional composites. Such flexibility in aerogel manufacturing can give customized solutions to many tactical requirements in the strategic field.To name a few applications, aerogel-based materials serve as thermal insulation in lightweight protective clothing and footwear for extreme temperatures, shelters for military personnel in the field, military and aerospace vehicles, protection for electronic equipment, tank engine, etc. It can serve as acoustic insulation along with the heat insulation. Aerogel composites can be specially made for stealth and sensor applications. The potential usage of this extraordinary material is limited by our imagination.This chapter introduces the aerogel material and describes its general methods of preparation, properties, and applications. Further, it illustrates the known and possible applications in defense and aerospace areas.

Microwave materials are fundamental building blocks for defense and aerospace applications, which have been used as dielectric resonators, radomes, multilayer packages, electromagnetic shield, and so on. These materials and devices made of them should survive in harsh environmental conditions, and hence the availability of suitable materials is limited. Microwave materials are used for signal propagation as well as shielding unwanted signals in military and aerospace applications depending on their properties. The essential material characteristics required for signal propagation applications are very low relative permittivity, low dielectric loss, low-temperature variation of relative permittivity/resonant frequency, and low coefficient of thermal expansion. The materials used for these applications are in the form of substrates, foams, inks, bulk resonators, high-temperature co-fired ceramics (HTCC), low-temperature co-fired ceramics (LTCC), printed circuit boards (PCBs), etc. The materials should absorb or reflect microwaves for electromagnetic interference (EMI) shielding applications. The present chapter gives an overview of microwave material requirements, properties, and their applications in antennas, filters, and oscillators in the military and aerospace sector.

Lead lanthanum zirconium titanate (PLZT) ceramics belong to the family of materials known as smart materials, which can be used as sensors and actuators; however, the high dielectric, ferroelectric (Pr), and piezoelectric (d33 and g33) properties decide the end applications. The d33 is related to charge generation or electric field-induced strain in the materials. On the other hand, g33 and kp are related to the voltage generation and conversion of mechanical stress to the electric charge, respectively. High values of d33, g33, and kp are good for energy harvesting applications; however, the high-strain materials are more useful for actuators. The remanent polarization (Pr) and coercive field (Ec) are taken into cognizance for memory and energy density applications. High dielectric constant materials can be used for charge storage applications. (Pb0.92La0.08)(Zr0.60Ti0.40)O3 (PLZT 8/60/40) ceramics are known to show all of the above electrical properties. Further improvement of these properties is possible by modified processing approaches. In this study, it was found that a combination of mechanical activation (high-energy milling or HEM) with a cold isostatic process (CIP) not only reduces the processing temperatures and time but also circumvents the need to add any excess PbO in the starting materials. At the same time, the high density of ceramics was not compromised. No binder was added in this process, thereby avoiding the contamination risk involved and also the possibility of reduced density. Apart from the above two processes, yet another process that was used to improve the electrical properties output was a scientific study of the electrical poling process. The optimized poling results in the significant enhancement of electrical properties, which successfully increased piezoelectric properties multiple times. The PLZT 8/60/40 ceramics were effectively poled at fields less than the coercive field (<0.5Ec), which could be very advantageous especially in the case of ceramics having poor resistivity. Such PLZT ceramics are used for different types of defense applications.

Today, the development of ceramic radome materials for hyper velocity (> Mach 5) missiles is a top research priority for several countries for the purposes of both surveillance and combat. The ceramic materials with low and stable dielectric properties against frequency and temperature variation among others are especially important. The radome property requirement for missiles launched from surface-to-air, air-to-surface, and air-to-air differs considerably. Moisture absorbing materials despite having desired dielectric and thermal properties are not suitable for radome applications as the dielectric constant of water is significantly high (80.4). So far no single material has been identified to meet all the requirements of a high-speed radome application. The advantages and disadvantages associated with various ceramic radome materials have been presented and discussed in this chapter together with the information about the radome design with respect to the wall thickness vs. radar frequency (RF) signals, bore-sight error, and the importance as well as generation principle of ogive shaped radome. Among various materials investigated so far, the slip-cast fused silica (SCFS) has been identified to be superior for hypervelocity radome applications. Furthermore, SCFS radomes can be fabricated with near-net shape using aqueous colloidal suspensions. However, SCFS radomes suffer from poor mechanical strength and from low rain and abrasion resistance properties apart from having considerably high internal porosity (up to 18%). Various methods employed so far to improve the properties of SCFS radomes required for hyper-velocity applications have been reviewed in this chapter while citing all the important references. Among the various fused-silica composites, the Nitroxyceram (SiO2-BN-Si3N4 composite) exhibits the best combination of properties required for radome applications, and it can be consolidated and densified by following conventional powder processing techniques prevalent at industry.

Ceramics due to their good mechanical, thermal, and chemical properties are one of the sought-after engineering materials. These materials cater to wide range of applications, such as household pottery, advanced ceramics and other components for strategic sector. Owing to their unique properties such as high structural stability, resistance to corrosion, compatibility with other printing materials, and high strength, ceramics are considered as a promising material for additive manufacturing for development of various parts; components related to medical and dental implants; aircraft components; architectural, aesthetic, or decorative purposes; mechanical and metallurgical applications; etc. This chapter attempts to review the current state-of-the-art and latest trends in the field of additive manufacturing of ceramics through patents, with a special focus on ceramic materials for aerospace and strategic applications. Recent advancements and progress in the field of additive manufacturing of ceramics and methods thereof from a patent viewpoint have been presented in terms of patent landscapes, themes, and trends generated using important parameters such as patenting timelines, priority applications, key players, etc. From the patent landscaping and review, it is noted that additive manufacturing of ceramics has progressed remarkably in Asia when compared to other regions of the world. Three-dimensional printing of ceramic materials has been widely accepted by the healthcare sector especially dentistry and orthopedics, and 3D printing is also making its mark in aerospace industry. Innovations in ceramic-based composite materials suitable for additive manufacturing are on the rise owing to their adaptability, suitability, and mechanical properties for high-end applications.

Survivability of the combat system depends on three key parameters such as mobility, protection, and firepower. Armour materials are used to provide protection to the combat systems against various threats with a minimal weight penalty. Low Dense ceramics and polymer composite materials are explored by various researchers to design lightweight armours for personnel and vehicular armour applications. Ceramics such as high purity alumina, silicon carbide, and boron carbide are used in combination with some composite laminates. Advanced fiber-reinforced laminates such as glass, aramid, and high-modulus polyethylene are used as stand-alone as well as a backing to ceramic armours both in add-on and structural composite armour applications. The present chapter describes the various types of ceramic and composite laminates used to design lightweight armours, and their processing methods. It has also covered ballistic test standards, penetration mechanisms, and the way forward for future armour materials.

In this chapter, configurations of ceramic-composite armour for resisting ballistic impact shall be introduced. Mechanics of impact shall be explained. Penetration, perforation, and various energy-absorbing mechanisms shall be enlisted. Relative contributions of multiple parameters to penetration resistance such as material properties and geometric configurations shall be discussed. A range of materials can be used for armour. Effect of the choice of material on aspects such as armour weight and thickness shall be included. Key issues of concern while designing ceramic-composite armour such as relative thicknesses of constituents, shape of ceramic tiles, and their sizes shall be discussed. A few probable approaches for improving energy absorption during impact and post-impact residual strength such as use of layered ceramics, embedding nanofillers, and improving toughness of the composite matrix shall be presented. Aspects of multi-hit resistance in ceramic-composite armour and key challenges encountered by armour designers to achieve multi-hit capability shall be discussed. In closure, shortcomings in currently used ceramic-composite armour design and envisioned future trends for improving its performance shall be highlighted.

Ceramic materials that are transparent to visible light with excellent mechanical properties are emerging as suitable candidate materials for ballistic armor applications. Various advanced materials such as single crystal sapphire, spinel, and aluminum oxynitride have been developed to withstand the penetration of the projectile during impact. The armors produced from these materials exhibit outstanding ballistic performance compared to the conventional soda-lime glass and glass-ceramics due to their remarkable hardness in combination with other superior mechanical properties. This chapter presents an overview of various transparent ceramic materials that have been explored hitherto for the armor applications along with various processing fundamentals required to produce these materials. This chapter also reviews the fabrication and comparative evaluation of conventional and advanced transparent armor materials for ballistic applications.

“Glass-ceramics” are glasses with controlled crystallization having certain extraordinary properties and therefore unique applications. Since their accidental discovery in the early 1950s of the last century, extensive research and development have been carried out leading to commercialization of several products for both consumer and strategic sectors. Glass structure being thermodynamically metastable is prone to get converted to a stable crystallized structure through a diffusion-controlled nucleation a growth mechanism. Crystallization is normally facilitated by adding a nucleating agent, the refractory oxides which do not normally dissolve in the glassy matrix. Microstructurally, glass-ceramic materials invariably contain some residual glassy phase together with one or more crystalline phases.Glass-ceramics possess a wide range of unusual properties; they are much tougher than conventional glasses with a wide range of thermal expansion coefficient and unlike crystalline ceramics do not contain any porosity. It is easier to seal them with metallic counter parts and therefore used extensively in different kind of seals.Glass-ceramic materials become transparent to visible light if the dispersed crystallites are much smaller than the wavelength of visible light or the difference between the refractive index of the crystallites and that of glassy matrix is very small. There are several aluminosilicate-based glass-ceramic systems in which these conditions are satisfied and therefore can be referred as “transparent glass-ceramics.” The crystal phases are solid solutions of β-quartz, β-spodumene, spinel, mullite, cordierite, etc. One of the most widely used transparent glass-ceramic products is known as Zerodur® made by Schott AG, Germany. It possesses extremely low coefficient of thermal expansion, which is very close to zero or slightly negative in certain temperature ranges. Its transparency is quite good in the range 400–2,300 nm. “Zerodur” is extensively used for lightweight mirror blanks used in large astronomical telescopes and satellites. Their size ranges from a few centimeters to more than 8 m. The most recent application of transparent glass-ceramics is, however, in the area of lighting systems based on white LEDs for which the glass-ceramics are used as the dispersion medium for the phosphors replacing commonly used organic silicone.Certain varieties of glass-ceramics particularly containing mica crystals are fairly soft, giving rise to their machinable property. Different manufacturers market them with their trade names. The most common is the MACOR® developed and marketed by Corning Glass Works and is used extensively in different technologies; DICOR® on the other hand is primarily used to make dental crown. MACOR® contains around 55% fluorophlogopite mica (KMg3AlSi3O10F2) and 45% borosilicate glass. Complex shapes can be machined with precision dimensional tolerance, thermally stable up to a temperature of 1000 °C. They possess very good electrical as well as thermally insulating property. Combined with zero porosity, they are excellent materials for fabrication of vacuum feedthroughs. In addition, there are several other applications in electronics, aerospace, defense, and nuclear technologies. They also find extensive use in microwave tube industry.

Transparent magnesium aluminate (MgAl2O4) spinel is a material of special interest due to its superb optical properties coupled with excellent mechanical properties. MgAl2O4 exhibit cubic crystal structure if processed under optimum conditions, effect of thickness on transparency can be minimized allowing fabrication of complex geometries for harsh environment. Further, broadband transparency from 0.4 μm to 6.0 μm is an added advantage in most of the applications. Transparent windows for armor and high Mach number missile domes are a few of the emerging applications in the strategic sector. Spinel is also used as the high-energy laser windows, as high-temperature furnace monitoring windows, and also as a part for nuclear fusion reactor power core insulations. In view of the significant scientific and technological importance, spinel is regarded as one of the futuristic transparent polycrystalline ceramics. Though spinel offers flexibility in processing through powder metallurgy route, the mechanical and optical properties are a strong function of starting powder properties and also dictated by the processing route and parameters. This chapter presents an overview on transparent spinel processing along with the comparative evaluation of various processing techniques.

Zinc sulfideZinc sulphide ceramics (ZnS) is a well-known wide gap semiconductor ceramic that finds application in infrared (IR) optics, electroluminescent devices, flat panel displays, and photocatalysis. This chapter presents an overview of ZnS ceramic as a candidate material for focusing on IR optics. Monolithic ZnS fabrication by various processes such as chemical vapor deposition (CVD) and hot isostatic pressing (HIP) of high purity ZnS powders and also post-CVD thermal treatments under pressure and pressure-less conditions to enhance the transmission of desired wavelength ranges are attempted. Physico-chemical, thermal, mechanical, and optical properties of CVD, post-thermal CVD-processed, and powder-processed ZnS specimens are reported. The results were correlated with the type of process employed in addition to process parameters. The thermodynamic feasibility of the CVD reaction based on zinc and hydrogen sulfide was evaluated and deposition conditions along with flow parameters are elucidated. Physico-chemical and optical properties indicated the superiority of CVD processing in achieving optical quality ZnS. Single-step consolidation of ZnS powder under HIP conditions resulted in relatively low density along with the presence of minor quantities of hexagonal wurtzite phase, leading to relatively low transmission values. Unlike post-CVD thermal treatment under pressure-less conditions, the HIP eliminates not only zinc hydride but also the healing of residual micro-porosity, extending transmission to the mid-wave infrared and visible ranges. Microstructure of ZnS is significantly influenced by process conditions, which in turn dictate the mechanical properties.

Optical glass and glass ceramic components with angstrom-level surface roughness and nanometer-level dimensional accuracy are in potential demand for sophisticated optical fabrication. In recent years, aspherical and free-form surfaces are gaining prominence for high performance applications. Moreover, the new optical materials and fabrication process which exhibit superior mechanical properties are being developed to meet the stringent requirements and harsh environment. Fabrication of complex-shaped high optical finish components becomes a significant challenge as conventional finishing techniques are unable to machine aspherical or free-form surfaces precisely. This situation demands few highly advanced and precise finishing processes which ensure stress-free surfaces. Mostly, the optical components are fabricated by shaping or pre-finishing methods followed by final finishing processes. Final finishing processes include more deterministic and flexible polishing techniques that can achieve desired surface finish, figure accuracy and surface integrity to make it suitable for shorter wavelength applications. In this chapter, basic principle, mechanism of various material removal processes, and precision polishing techniques such as magnetorheological fluid-based finishing were discussed and are compared with the convention polishing techniques.

This chapter aims to provide an updated and comprehensive description of the development of electric field/current-assisted sintering (ECAS) technique for the production of dense, structural/functional ceramics, particularly transparent polycrystalline ceramics. ECAS is gaining interest in recent decades due to the accelerated consolidation compared to conventional, pressureless sintering and pressure-assisted sintering (such as hot-pressing). In particular, spark plasma sintering (SPS) or pulsed electric current-assisted sintering (PECS), in which pulsed direct current is applied to directly heat up material under compressive stress, has been extensively studied as an extremely powerful tool. This process is capable of producing nanoceramics and transparent ceramics in a relatively short sintering time and low sintering temperature, being promoted for practical use. The short sintering time and low sintering temperature are in fact desirable for attaining high transparency and excellent mechanical properties for polycrystalline materials.ECAS process is still drastically improving with new findings and technologies being actively reported. For instance, flash sintering, where densification occurs almost immediately (typically <5 s) under strong electric field, has been developed in recent decade and has been attracting extensive attention as an innovative sintering technique. In this chapter, the earlier experimental works on SPS methods and characteristic properties of the produced transparent materials are summarized, and recent attempts for elucidation of the underlying mechanisms responsible for the SPS are briefly introduced.

The progress of the development of SiC fiber-reinforced SiC (SiC/SiC) composites focusing on applying the composites to nuclear fusion systems is overviewed. The physical and mechanical properties of SiC/SiC composites prepared with chemical vapor infiltration (CVI), polymer impregnation and pyrolysis (PIP), reaction sintering (RS), and liquid-phase sintering (LPS) are presented. Among various SiC/SiC composites, LPS SiC/SiC composite formed by, so-called nano-powder infiltration and transient eutectoid (NITE) process, with a density close to that of monolithic SiC shows the highest thermal conductivity and mechanical properties. CVI and NITE SiC/SiC composites demonstrate excellent neutron irradiation resistance on thermal conductivity, swelling, flexural strength, and creep properties at up to temperature 1000 °C. The composites also offer low induced activity, favorable chemical compatibility with liquid candidate coolant of Pb-Li and solid breeder materials, and preferable joining characteristics.

Fast-neutron reactors constitute clean energy systems that could provide sustainable nuclear energy for several centuries through efficient utilization of the uranium as well as thorium resources. Ceramic fuels are the current choice for fast reactors. Oxides of uranium and plutonium have been irradiated to levels of burn-up (a measure of energy production per unit mass of fuel) as high as 200,000 MWd/t, and internationally, there has been substantial experience on the fuel cycle of oxides, from fabrication to reprocessing. The irradiation behavior of oxide fuels has been studied extensively and has been well understood. Carbides and nitrides and metallic alloys of uranium and plutonium have been much less studied with respect to power production. However, they possess several advantages such as high thermal conductivity, high metal atom density, and a higher breeding potential, which make them the potential choices for the future fast reactors. At the same time, each fuel form has its challenges and technical issues to be dealt with.This chapter presents an overview on the advanced ceramic fuels and particularly carbide and nitride fuels for FBRs. Advantages, challenges, and issues of each type of fuel are dealt with relevant details. Basic properties of advanced fuels including the phase diagrams and their behavior under irradiation are highlighted. Further, their irradiation behavior in general and swelling and fission gas release in particular in the context of fuel element design have been brought out. On the fuel cycle aspects, details of different fabrication routes, challenges in each of them, and reprocessing technologies are brought out. Also, a brief section on the international experience is included.

Boron is one of the few elements to possess nuclear properties, which warrant its consideration as neutron absorber material due to its high neutron absorption cross section of 3838 barns (for thermal neutrons, 0.025 ev) for 10B isotope. Boron-based ceramics are used as a control/shutoff rod, neutron shielding for the nuclear reactor as well as spent fuel storage bays, neutron sensors for measuring the neutron flux in a nuclear reactor, and space applications. Refractory and rare earth metal borides possess superior thermophysical properties, which enables to use for high-temperature structural/functional applications. These borides are potential for high-temperature nuclear reactors of Generation IV as neutron absorbers, second-generation solar (receiver materials of concentrated solar power), and space applications such as rocket and hypersonic vehicle components, nozzles, leading edges, and engine components [81, 97, 109, 115]. Refractory metal borides are suitable for space application due to attractive combination of properties such as high melting point (>3000 °C), thermal conductivity, low thermal expansion coefficient, retention of strength at high temperatures, good thermal shock, oxidation, and erosion resistance [61, 81, 105, 118]. Various boron-based ceramics such as B4C, TiB2, ZrB2, HfB2, NbB2, CrB2, LaB6, CeB6, NdB6, SmB6, YbB6, PrB6, GdB4, and EuB6 and its composites were synthesized and consolidated by various methods which are cited in the literature. This chapter reviews the work carried out on synthesis, consolidation, properties, and applications of important transition/refractory/rare earth metal borides.

Structure of the inorganic compounds determines their electrical conductivity, dielectric, optical, magnetic properties, etc. These structure and properties together decide the suitability of employing these materials for a given technological application. If electrical conductivity of materials is exploited for application as sensor, the type of conductivity, viz., ionic, electron/hole, and ionic-cum-electronic, exhibited by them needs to be understood. Depending on the type of conduction, they are classified as solid electrolytes, semiconductors, and mixed conductors. Several solid electrolyte systems where conductivity due to cations such as H+, Li+, Na+, Ag+, etc. are known, while only a few systems for anions such as H-, O2-, and F- are known. The conducting ion present in the solid electrolyte dictates its application as sensor in a chosen process stream, although indirect methods can also be deployed to use a solid electrolyte whose ion of conduction is different from the species to be sensed. The magnitude of ionic conductivity, transport number of the conducting ions, and the stability of the solid electrolyte in the environment of the application need to be evaluated before its selection. Although several semiconducting elements and compounds (oxides, sulfides, nitrides, etc.) are known, the use of elemental semiconductors is generally restricted to electrical and electronic devices. On the other hand, oxide semiconductors find a large application as chemical sensors for process and environmental monitoring. The bandgap, intrinsic and extrinsic conductivity, stability of the compound in the operating environment, temperature, etc. are important parameters that decide their application as sensors. This chapter deals with the selection of solid electrolyte based on oxides, hydridehalides, aluminates, phosphates, and halides their application in various nuclear energy programs. The experience of using semiconducting oxides, niobates, molybdates, etc. for various process monitoring is discussed. A brief mention on the use of titanates for piezoelectric sensor application and molten electrolyte-based sensor systems is made.

The ever-increasing energy demand by the human civilization and rapid depletion of conventional fossil fuel has triggered the scientists and engineers to look for alternative source of energy. Fusion energy, where four hydrogen nuclei combine to produce one helium nucleus with subsequent release of enormous amount of energy, could very well meet the future energy demand. Radio-frequency (RF) power is used as one of the noninductive methods to maintain the fusion plasma current under steady-state condition. RF window, used in the transmission line, acts as a vacuum barrier and transmits the microwave (MW) power to the plasma and hence a very critical component in the transmission line. Microwave dielectric ceramics, with high-quality factor/low loss, high dielectric constant, good temperature stability, high dielectric strength, high thermal conductivity, high mechanical strength, and ability to braze to the base metal, are most preferred materials for RF window application. High-purity dense alumina ceramics is the most common material for such application as of now. But the lower dielectric constant of Al2O3 ceramic poses a serious problem in thermal management of the window sections, and hence an alternate material is preferred. Barium zinc tantalate Ba(Zn1/3Ta2/3)O3 (BZT) is a well-known microwave dielectric ceramics with excellent properties such as high dielectric constant (εr), low loss (tanδ), very low temperature coefficient of resonance frequency (τf), and high-quality factor in the microwave frequency range and hence could be a potential candidate for MW window application. But, the major drawback in processing BZT ceramics at high temperatures is the volatilization of low-melting Zn from the BZT composition rendering the final product containing lot of defects including the presence of other phases. This chapter deals with the processing of BZT ceramics with properties suitable for RF window application. The effect of processing conditions and sintering techniques on development of mechanically robust BZT ceramics with highest density (close to the theoretical density), high dielectric constant, low loss (high-quality factor, Q), very low and stable temperature coefficient of resonance frequency, and high thermal conductivity has been discussed in detail.

Carbon fiber-reinforced silicon carbide matrix composites (called C/SiC or C/C-SiC) represent a relatively new class of structural materials. These composites have emerged as one of the most promising materials for high-temperature applications in defense and aerospace sectors. They are fabricated via chemical vapor infiltration (CVI), polymer impregnation and pyrolysis (PIP), and liquid silicon infiltration (LSI) processing routes. Several new manufacturing processes have been developed during the last few years based on short fiber reinforcements and inexpensive precursor polymer, respectively. These composites possess high mass-specific properties, structural and dimensional stability at high temperature, low coefficient of thermal expansion, high thermal conductivity, and desirable oxidation resistance. These properties have gained increasing importance of the C/SiC composites and thus make them as most preferred materials for the aerospace, defense, and civil/industrial applications like thrust vectoring control vanes, nozzles, brake disks and pads, clutches, furnace charging devices, etc. This chapter presents the processing and characterization of the C/SiC composite fabricated by liquid infiltration routes, viz., PIP and LSI. Typical properties of the C/SiC composites like mechanical, thermal, and ablative are presented. Few established and potential application of these composites are discussed briefly.

Carbon fiber reinforced silicon carbide matrix composites (Cf/SiC & Cf/C-SiC) have been extensively studied as a new class of thermo-structural materials as an alternate candidate for Cf/C composites for increased oxidation resistance and for applications in the oxidizing environment for the past one to two decades. In recent years, many new processing techniques have been developed to process these composites. However, chemical vapor infiltration (CVI) and hybrid process [CVI+Molten silicon infiltration (MSI) and CVI+polymer impregnation and pyrolysis (CVI+PIP)] are more promising to develop the Cf/SiC composites with better properties. These composites possess superior properties such as high specific strength, specific modulus at high temperature, high-temperature chemical properties, and good tribological properties. Hence, they are being thoroughly studied for application in a hypersonic vehicle, some components in military engines and reusable space vehicle, brake disc for aircraft, jet vanes, emergency brakes in cranes, calibration plates, fuel tube in a nuclear fission reactor, furnace charges devices, etc. This chapter describes the general introduction about Cf/SiC and Cf/C-SiC composites, their various processing routes, properties, key results, and the prominent application areas.

Ceramics, in general, are high temperature materials that have low density, low coefficient thermal expansion, excellent mechanical properties (strength, hardness), high thermo-oxidative stability, and excellent chemical resistance. Therefore, these have been extensively explored for high temperature structural applications. Among many ceramics, silicon carbide (SiC) is one of the most promising non-oxide ceramics for applications in extreme environmental conditions. It has excellent combination of thermomechanical, chemical, and oxidation resistance properties that qualifies it to be highly suited for aerospace, defense, and nuclear applications. Processing of complicated structures through conventional powder processing route is difficult which led to the development of precursor-based route for processing of complicated shapes of ceramics. Silicon-based polymeric precursors have been intensively researched as source of SiC ceramics. This chapter broadly covers the development of various polymeric materials as precursors for different ceramics. Various chemical synthetic methods have been included and a brief account of the processing of ceramics has been given. Main focus is on the organo-silicon precursor materials, particularly polysilanes and polycarbosilanes (PCSs), these are potential sources of SiC-based ceramics. Chapter ends with a brief outlook of precursors’ route for ceramics.

Ceramic matrix composites containing fiber reinforcements possess superior mechanical and tribological properties, as compared to their monolithic counterparts, that render them better suited for engineering applications demanding high strength, wear resistance, and resistance to thermal shock. Among the wide range of reinforcements used for toughening the otherwise intrinsically brittle bulk ceramic materials, carbon nanotubes (CNTs), owing to their excellent physical, mechanical, and thermal properties, are considered to be one of the most promising reinforcement types. The exceptional mechanical properties of CNTs offer excellent opportunities toward the development of considerably stronger and tougher ceramic nanocomposite systems for potential applications in aircraft and aerospace industries. However, there are many challenges with respect to the processing of CNT-reinforced bulk ceramic materials that limit their commercial applications to a considerable extent. Additionally, dispersion of the CNTs, optimization of the CNT volume fractions, development of suitable CNT/matrix interfaces, and distribution within the sintered polycrystalline ceramic microstructures are some of the aspects that need particular attention. Continuing research efforts have been directed toward addressing issues related to such aspects, in a bid to attain best possible combination of mechanical and tribological properties. With regard to microstructure development, achieving uniform distribution of well-dispersed CNTs within the sintered polycrystalline ceramic matrix (i.e., reinforcing the grain interiors and not just the grain boundaries with CNTs) has been found to be particularly difficult, until very recently. In these contexts, after discussing some of the basic aspects of carbon nanotubes and ceramic-CNT composites, the present chapter provides a comprehensive review of the overall status of research and development in CNT-reinforced ceramic matrix composites, with particular emphasis on a variety of processing techniques investigated to date in a bid to optimize the quality of CNT dispersion, character of the CNT-matrix interfaces, eventual densification of the composites, and also cost-effectiveness. The influences of CNT reinforcements on the properties of the some of the important ceramic systems for advanced structural applications are discussed, with an emphasis towards fracture behavior and the possible toughening mechanisms. This review also highlights the more recent research efforts that have been conducted to address the issues concerning inhomogeneous dispersion and distribution of CNTs within the ceramic matrix, thus aiming toward the realization of the full potential of CNTs as reinforcing fibers. Lastly, the various potential applications for ceramic-CNT composites as structural materials have been highlighted, with an outlook toward the scope for future developments and issues that need to be further addressed.

Inorganic and organometallic polymers capable of giving high ceramic residue (more than 50 wt%) on heat treatment in an inert atmosphere are called “preceramic polymers.” As they are polymeric in nature, processing techniques used for conventional polymer processing can be easily adopted. They can be applied as coating, cast into film and drawn into fiber and then converted into corresponding ceramic material. Amorphous materials that are thermally stable to very high temperatures with compositions not obtainable with common synthetic methods can be obtained from preceramic polymers. Kinetic stabilization of less stable phases, adaptability of various fabrication capabilities of polymer process engineering, formation of nanoceramics of desired composition, pressureless sintering, and machinability are the main advantages of obtaining ceramics from polymeric precursors.Polymer-derived ceramics find applications as oxidation resistant high temperature ceramic materials in the form of fiber, coatings and adhesives, and matrix of ceramic matrix composites for use by aerospace, nuclear, and defense establishments. In addition, they are also being investigated for end-use in biomedical devices, drug delivery systems, water remediation, energy storage devices, microelectronics, and nanosensors.The present chapter deals with synthesis, characterization, and ceramic conversion of silicon-based preceramic polymers, and ceramics from carbonaceous polymers, and their possible space applications. In view of the voluminous literature, equal emphasis could not be given to many of the developments in the area of preceramic polymers and the discussion is confined to relevant systems which have the scope for space applications.

Lead zirconate titanate (PZT)-based piezoelectric materials are well known for their superb piezoelectric properties, which makes them ideally suited for various applications ranging from household gas lighter to sensors and actuators in high-end aerospace applications such as vibration control of airplane wings, flutter control, structural health monitoring of airplane structures, vibration energy harvesting etc. Recently, R&D on lead-free piezoelectric materials are gaining attention due to toxic effect of lead-based PZTs. Lead-free materials of comparable piezoelectric properties to PZT have been developed; however, performance of these materials in multilayered device form is yet to be established. In recent years, research on renewable energy/clean energy is in great demand to control pollution level. Piezoelectric material-based energy harvesters are quite promising due to use of unused vibration energy. Power harvested from such systems in micro- to milliwatt level is very much suitable for charging mobile phone, functioning of TV remote, working of low-wattage sensors, etc. In this chapter, preparation of PZT- and BZT-based lead-free piezo materials; fabrication of multilayered devices (bimorphs, multilayered stacks, etc.) using tape casting technique; characterization of ferroelectric, piezoelectric, and dielectric properties; applications such as vibration control and energy harvesting especially aimed at aerospace sector have been described.

The rapid industrialization and increased space exploration activities necessitate the development of materials of low thermal conductivity capable of withstanding very high temperatures. These materials are called thermal protection materials. They are used either to protect the nearby persons from the heat flux of high-temperature heat treatments in industries or to protect the instruments and astronauts within the crew cabin of a space vehicle from the intense heat flux generated during its reentry into the atmosphere. The high-temperature ceramics such as alumina, silica, zirconia, mullite, SiC, silicon nitride, and silicon oxycarbide are capable of withstanding high temperatures. The materials of choice at extremely high temperatures (above 2000 °C) are either carbon or ultrahigh-temperature ceramics. They include borides and nitrides such as TiB2, ZrB2, HfB2, TiN, ZrN, etc. These materials in their dense state though withstand high temperatures they also exhibit relatively high thermal conductivity. In addition to the high-temperature capability, the thermal protection materials should be light in weight and have low thermal conductivity. The aspect of low density is of utmost importance in thermal protection materials used for space applications as an increase in weight increases the amount of fuel required for takeoff and subsequent reentry. The way to achieve lightweight and low thermal conductivity in ceramic materials is by making them porous. The porous ceramics with porosity greater than 70 vol% are called ceramic foams.

The advantages of the reflective optics over the refractive one for optical imaging in the spaceborne telescopes have been demonstrated over the years. The performance of such optical systems is continually increasing through the use of lightweight and larger mirrors. The use of several materials including ultra-low expansion (ULE) glass, Zerodur glass-ceramics, monolithic aluminum, optical grade beryllium, etc. as the mirrors for space optics is known for decades. Nowadays, silicon carbide (SiC)-based space mirrors have become the most attractive choice because of their excellent mechanical and thermal figure of merits. The superior mechanical and thermal properties of SiC allow in accommodating the complex designs and higher lightweighting over the conventional materials. In addition, a very high surface figure precision (< λ/20) and very low surface roughness (~ 0.1 nm) can be achieved in SiC. This chapter discusses the superiority of SiC as mirrors over the existing materials for application in space optics. Subsequently, the detailed processing of SiC-based lightweight mirror blanks involving the production of sintered SiC (S-SiC) substrates followed by cladding with a fully dense SiC coating by chemical vapor deposition (CVD) technique is discussed.

There is a strong push in recent years for development of high-performance materials to be used in the hot-end components of aero-engines at temperatures beyond the operating range for nickel-based superalloys. The interest in silicides and silicide-matrix composites arises from their high melting points, ability of strength retention, along with impressive oxidation resistance at elevated temperatures, which are considered as desirable. Among the silicides, the molybdenum-, titanium-, and niobium-based multiphase alloys and composites have been found to be the most promising. Whereas MoSi2 has the best high-temperature oxidation resistance among the silicides, its ambient temperature fracture toughness as well as high-temperature strength retention are poor, and then, there are serious difficulties in near-net shaping of components. Therefore, starting from MoSi2 based composites with ceramic reinforcements, a significant attention has been paid during the last two decades to the development of multiphase Mo-Si-B based ternary alloys with bcc-Moss, Mo3Si, and Mo5SiB2. While crack-arrest and plastic deformation of the ductile bcc-Moss contributes to toughening, the presence of Mo3Si and Mo5SiB2 assists in retention of high-temperature strength, as well as formation of a borosilicate scale to protect against oxidation. In the multicomponent Nb-Si-X alloys, the presence of ductile Nbss is responsible for toughness enhancement, whereas the intermetallic silicides or Laves phases contribute to strength retention. This chapter will provide an overview of the crystal structures and phase equilibria in Mo-Si, Ti-Si, and Nb-Si based systems, processing methodologies, evolution of microstructure, mechanical properties, oxidation behavior, and potential applications.

In recent years, there is a very strong interest for the development of zirconium and hafnium diboride-based ultrahigh-temperature composites (UHTCs) for use in nose cones and leading edges of hypersonic vehicles, which are subjected to high temperatures and ablative environment during reentry into the earth atmosphere. An overview of the literature on high-temperature environmental degradation behavior of zirconium and hafnium diboride-based UHTCs has been presented, with emphasis on their resistance to oxidation under non-isothermal, isothermal, and cyclic conditions, as well as under ablative conditions during reentry at ~2000 °C. It has been observed that using SiC and Si-bearing reinforcements such as Si3N4 and MoSi2 aids in the formation of a borosilicate scale on the surfaces, which is capable of protecting partially or fully against further damage under extreme environments, depending on the temperature. Formation of oxidation products at grain boundaries and interfaces during creep contributes to damage by grain boundary sliding and intergranular cracking. Both nature of oxidation products and mechanisms of their formation leading to degradation are found to vary significantly with the temperature regimes of exposure. On subjecting to ablative exposure at temperatures close to 2000 °C, active oxidation of SiC along with vaporization of B2O3 influences the kinetics and mechanisms of degradation. Formation of ZrO2-rich oxide scale at such temperatures is believed to play the role of an in situ formed thermal barrier coating, which protects the composite underneath from damage. The effects of reinforcements and their volume fractions on oxidation and ablative behavior have been discussed.

Hybrid supercapacitor-battery is one of the most attractive material candidates for high energy as well as high power density rechargeable lithium (Li) as well as sodium ion (Na) batteries. Mostly two types of hybrids are being actively studied for electric vehicles and storage of renewable energies. Internal serial hybrid is an asymmetric electrochemical capacitor with one electric double-layer capacitor and another battery-type electrode. On the other hand, in internal parallel hybrids, supercapacitor and battery materials are mixed together to form bi-material-type electrode. A brief literature review provides the state of the art of various asymmetric electrochemical capacitors reported in recent times. Subsequently we have described the role of current densities and electrode potential window in designing the internal serial hybrid electrodes. Mass ratio between the two electrodes grossly influences the electrochemical performance of internal serial hybrids. Theoretical basis of the calculation of voltage, specific capacitance, energy, and power densities of internal serial hybrid has been described in detail. The theoretically estimated parameters match quite well with the experimentally obtained values for activated carbon (AC)//lithium nickel manganese oxide (LNMO) asymmetric electrochemical capacitor made in our laboratory. As compared to serial hybrid, limited reports are available on internal parallel hybrid for Li- and/or Na-ion batteries. A brief literature review on this type of hybrids is made to illustrate the outstanding research issues of this type of hybrids. We have reported excellent electrochemical performance of sodium vanadium phosphate (Na3V2(PO4)3)-activated carbon (AC) bi-material electrodes for lithium-ion rechargeable batteries.

Lithium-ion battery is a promising energy storage solution for effective use of renewable energy sources due to higher volumetric and gravimetric energy density. The advancement of lithium-ion battery technology in terms of energy, power density, cost, safety, operating temperature, and charging/discharging cycle life depends on performance of electrode materials: cathode, anode, and electrolyte. While graphite or hard carbon is mainly used as anode, three types of cathode chemistry, (i) lithium transition metal layered oxide, (ii) derivatives of spinel LiMn2O4, and (iii) phospho-olivine, are used in the commercial lithium-ion batteries. Modifications such as composition, protective coating, doping, and morphological tailoring had continuously led into the enhanced performance of the active materials and are further expected to improve. Continuous efforts in development of new class of materials such as conversion and alloying electrode materials are being carried out in order to improve energy and power density of lithium-ion batteries. In this chapter we will be discussing the recent development of traditional cathode and anode materials like graphite, hard carbon, lithium transition metal layered oxide, and derivatives of spinel LiMn2O4, LiFePO4, and new class of active materials.

Functional materials such as electro-optic or opto-electric ceramics are of fundamental as well as of technological interest in the context to energy application. Since, natural resources those include sunlight, wind, water, are available in abundance on our planet earth, ever-growing human energy requirements necessitates and demands a way to make their use for generation of renewable energy. Ceramics are excellent candidates in view of their exciting optical, mechanical, thermal, electrical, and corrosion-resistant properties. Photocatalytic material systems have fascinating ability to split water molecules under the presence of photon and electrical energy, by virtue of their suitable band energetics with respect to water redox levels. The water splitting phenomenon is important wrt hydrogen energy technology which demands energy production via renewable energy sources. Photo−/electrocatalysts which are capable of efficiently splitting water molecule with a sustainable performance are highly desirable. The physicochemical study of materials to identify best suited photocatalyst has been a topic of prime interest. The present chapter discusses nano-configured photocatalysts reported till date and compares their performance and scope with respect to their commercialization for hydrogen-producing technologies.

Plasma spraying with liquid feedstock offers an exciting opportunity to obtain coatings with characteristics that are vastly different from those produced using conventional spray-grade powders. The two extensively investigated variants of this technique are suspension plasma spraying (SPS), which utilizes a suspension of fine powders in an appropriate medium, and solution precursor plasma spraying (SPPS), which involves use of a suitable solution precursor that can form the desired particles in situ. The advent of axial injection plasma spray systems in recent times has also eliminated concerns regarding low deposition rates/efficiencies associated with liquid feedstock. The 10–100 μm size particles that constitute conventional spray powders lead to individual splats that are more than an order of magnitude larger compared to those resulting from the fine (approximately 100 nm–2 μm in size) particles already present in suspensions in SPS or formed in situ in SPPS. The distinct characteristics of the resulting coatings are directly attributable to the above very dissimilar splats (“building blocks” for coatings) responsible for their formation. This chapter discusses the salient features associated with SPS and SPPS processing, highlights their versatility for depositing a vast range of ceramic coatings with diverse functional attributes, and discusses their utility, particularly for high-temperature applications through some illustrative examples. A further extension of liquid feedstock plasma processing to enable use of hybrid powder-liquid combinations for plasma spraying is also discussed. This presents a novel approach to explore new material combinations, create various function-dependent coating architectures with multi-scale features, and enable convenient realization of layered, composite, and graded coatings as demonstrated through specific examples.

Sol-gel technique is a wet chemical synthesis procedure involving the hydrolysis of either a fully hydrolyzable metal/silicon alkoxide or an organically modified silane followed by condensation and polymerization reactions. Through this method, ceramics, glasses, and hybrid nanocomposite materials of high purity and homogeneity can be produced than when obtained through conventional processes that involve high-temperature treatment conditions. Sol-gel-derived hybrid nanocomposite coatings combine the interesting properties such as flexibility, hardness, etc. drawn from an organic polymer and an inorganic glass and hence are of great interest for aerospace, energy, and defense applications, due to their distinct advantages. Varied functionalities like corrosion protection, antireflection, scratch resistance, antibacterial, water/oil repellant, erosion resistant, and antistatic are possible to be obtained using this technique. Sol-gel nanocomposite films on appropriate substrates are also capable of being used as sensors for detecting chemical/biological warfare agents as well as for sensing ionizing radiation in the environment. Despite many advantages of this technique, there are still certain challenges that need to be circumvented in order to fully harness the potential of the coatings derived from this process. This chapter mainly focuses on the potential applications of sol-gel nanocomposite coatings for aerospace, energy, and strategic sectors, where challenges in using them for applications and future perspectives on how they can be mitigated are discussed.

Thermal barrier coatings (TBCs) are being used for the past few decades for providing thermal insulation to metallic components of hot parts of gas turbine engines. The low thermal conductivity ceramic coatings contribute toward maintaining a large temperature difference between the hot gases in the gas turbine and the superalloy components. High engine efficiency as well as prolonged component lifetime can be achieved by integrating TBCs with gas turbine components at the design stage itself. While yttria-stabilized zirconia emerged as the work-horse TBC material, a few other advanced compositions are also being used by some of the engine manufacturers. Prominent among these are zirconia-based compositions with rare-earth oxide additions, either with tetragonal or pyrochlore structure. A lot of research activity has focused on durability issues relevant to the TBC technology, for enhancing reliability as well as performance. Phase transformations, oxidation-induced residual stress, changes in fracture toughness, and thermochemical attack by contaminants ingested by the engine are some of the important degradation mechanisms governing durability.

This chapter deals with a variety of ceramic and cermet composite coatings capable of protecting the industrial components including strategic and aerospace sectors from various damage mechanisms such as wear, corrosion, oxidation, thermal, fatigue, and combinations thereof. To enable such coating deposition, a spectrum of processing techniques such as plasma spray, high-velocity oxy-fuel spray, detonation spray, micro-arc oxidation, and laser cladding techniques were utilized and considered for detailed discussion. Under each of the aforementioned techniques, the processing fundamentals, influence of process variables, typical microstructures, properties, and performance of the resulting coatings were briefly presented. However, only the coatings that are functionally relevant in the working temperature up to 800 °C were considered in this chapter. A special emphasis has been placed to provide the understanding of structure-property-performance aspects of different coatings such that the information can be correlated with the typical industrial requirements. Further, both the demonstrated and potential applications specifically pertaining to strategic and aerospace sectors were exemplified.