Handbook of Advanced Ceramics and Composites

Table of Contents

1. Frontmatter

2. Ceramic Materials for Defense Applications

   1. Frontmatter

   2. 1. Manifestations of Nanomaterials in Development of Advanced Sensors for Defense Applications

      Rohini Kitture, Sangeeta Kale

      Abstract

      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.

   3. 2. Nanocrystalline PNS-PZT-Based Energy Harvester for Strategic Applications

      H. H. Kumar, C. M. Lonkar, Balasubramanian Kandasubramanian

      Abstract

      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 Pb_0.98La_0.02(Ni_1/3Sb_2/3)_0.05[(Zr_0.52Ti_0.48)_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, FoM_PH (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.

   4. 3. 2D-Nanolayered Tungsten and Molybdenum Disulfides: Structure, Properties, Synthesis, and Processing for Strategic Applications

      Harish Kumar Adigilli, A. K. Pandey, Joydip Joardar

      Abstract

      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.

   5. 4. Nanoporous Aerogels for Defense and Aerospace Applications

      Neha Hebalkar, Keerthi Sanghamitra Kollipara, Yamini Ananthan, Murali Krishna Sudha

      Abstract

      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.

   6. 5. Microwave Materials for Defense and Aerospace Applications

      J. Varghese, N. Joseph, H. Jantunen, S. K. Behera, H. T. Kim, M. T. Sebastian

      Abstract

      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.

   7. 6. Development of PLZT Electroceramics with Ultrahigh Piezoelectric Properties by a Novel Material Engineering Approach

      A. R. James, Ajeet Kumar

      Abstract

      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 (P_r), 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 k_p are related to the voltage generation and conversion of mechanical stress to the electric charge, respectively. High values of d₃₃, g₃₃, and k_p are good for energy harvesting applications; however, the high-strain materials are more useful for actuators. The remanent polarization (P_r) and coercive field (E_c) are taken into cognizance for memory and energy density applications. High dielectric constant materials can be used for charge storage applications. (Pb_0.92La_0.08)(Zr_0.60Ti_0.40)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 (<0.5E_c), 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.

   8. 7. Slip-Cast Fused Silica Radomes for Hypervelocity Vehicles: Advantages, Challenges, and Fabrication Techniques

      Ibram Ganesh, Yashwant Ramchandra Mahajan

      Abstract

      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.

   9. 8. Patent Trends in Additive Manufacturing of Ceramic Materials

      Priya Anish Mathews, Swati Koonisetty, Sanjay Bhardwaj, Papiya Biswas, Roy Johnson, G. Padmanabham

      Abstract

      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.

3. Ceramic Materials for Ballistic Armor Applications

   1. Frontmatter

   2. 9. Ceramic Composite Armour for Ballistic Protection

      P. Rama Subba Reddy, S. Geasin Savio, Vemuri Madhu

      Abstract

      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.

   3. 10. Multilayered Ceramic-Composites for Armour Applications

      Kiran Akella

      Abstract

      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.

   4. 11. Transparent Ceramics for Ballistic Armor Applications

      Rajendran Senthil Kumar, Papiya Biswas, Roy Johnson, Yashwant Ramchandra Mahajan

      Abstract

      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.

4. Transparent and Optical Ceramics for Defense and Aerospace

   1. Frontmatter

   2. 12. Transparent and Machinable Glass-Ceramics

      Himadri Sekhar Maiti

      Abstract

      “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.

   3. 13. Processing of infrared Transparent Magnesium Aluminate Spinel: An Overview

      Papiya Biswas, Roy Johnson, Yashwant Ramchandra Mahajan, G. Padmanabham

      Abstract

      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.

   4. 14. Zinc Sulfide Ceramics for Infrared Optics

      Roy Johnson, Papiya Biswas, Pandu Ramavath, Yashwant Ramchandra Mahajan

      Abstract

      Zinc sulfide (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.

   5. 15. Advances in Nano-finishing of Optical Glasses and Glass Ceramics

      Mahender Kumar Gupta, I. Abdul Rasheed, M. Buchi Suresh

      Abstract

      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.

   6. 16. Electric Field/Current-Assisted Sintering of Optical Ceramics

      Hidehiro Yoshida

      Abstract

      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.