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Machining of DTC Materials (Ceramics and Composites) by Traditional and Non-Traditional Methods
Published in Helmi Youssef, Hassan El-Hofy, Non-Traditional and Advanced Machining Technologies, 2020
The earliest ceramics, called traditional, were pottery objects made from clay and then glazed and fired to create a colored surface. These were generally used as domestic and art products. In the 20th century, advanced ceramic materials were developed, which found far wider applications in engineering than traditional porcelain and pottery. Table 6.8 shows some classifications and properties of advanced ceramics and metallic materials. The advanced ceramics are classified as structural ceramics (i.e. engineering ceramics) and functional ceramics. Functional ceramics are generally employed as a part of electronic components due to their inherent physical features, such as electric, magnetic, dielectric, ferroelectric, optical, or other properties, which play an active role in the electronic industry. Engineering ceramics are applied as structural components in most engineering industries. Compared with other engineering materials (e.g. metals or polymers), engineering ceramics offer numerous enhancements in performance, durability, reliability, chemical stability, hardness, mechanical strength at elevated temperatures, wear resistance, and thermal resistance.
Nanoscale Ceramics
Published in Debasish Sarkar, Nanostructured Ceramics, 2018
Most of the ceramics have electrical and thermal insulation, high temperature resistance, and corrosion resistant behavior. In comparison to metals, these materials have lower electrical and thermal conductivity, higher stiffness, good resistance to corrosive environments, and lower fracture toughness, but exceptional thermal conductivity is also noticed, for example, some nonoxide ceramics such as SiC [19]. Polymers are generally organic compounds. This group of material has very large molecular structures, consisting of unit structures known as monomers. Usually, these are light weighed, low density materials, and not stable at high temperatures. From a day-to-day activities point of view, polymers are mostly used materials due to their easy moldability, in turn, can be formed into complex shapes. Their strength, stiffness, and melting temperatures are generally much lower than those of metals and ceramics. Their lightweight, low cost, and ease of forming make them the preferred material for many engineering applications.
Solid Dielectrics
Published in N. H. Malik, A. A. Al-Arainy, M. I. Qureshi, Electrical Insulation in Power Systems, 2018
N. H. Malik, A. A. Al-Arainy, M. I. Qureshi
Whereas the dominant loss portion in polymers is due to orientational polarization, the dielectric loss in glasses and ceramics is mainly electronic and ionic in nature. Electrical grade glasses consist, to a large extent, of SiO2, B2O3 or phosphoric anhydride (P2O5) structures. These are sufficiently open to permit ionic diffusion and migration. The conduction losses in this case mainly result from sodium (alkali) impurity ions. Ceramics are composed of various materials that are formed permanently into durable, hard dielectrics by either firing or sintering processes. Various clays are also used as fillers. These are the source of ionizable impurities that give rise to significant losses. The main charge carriers responsible for generating dielectric losses may be either electrons or ions, or both types of species may contribute. However, because of the complex structure of ceramic materials, it has not always been possible to delineate clearly which charge carrier process may be responsible for the observed dielectric loss [15].
Facile fabrication of monodispersed α- and γ-Al2O3 microspheres through controlled calcination of alumina precursors synthesized by homogeneous precipitation
Published in Journal of Dispersion Science and Technology, 2023
Zia Ullah Khan, Khalida Akhtar
Ceramics are non-metallic compound of inorganic nature that provides the basis for the manufacture of so many tools of technological and industrial importance.[1] Among various ceramics, alumina is one of the most essential ceramics with extraordinary properties, such as high-temperature stability, remarkable hardness, high melting point, corrosion resistance, large band gap energy, and high chemical inactivity.[2] Owing to its exceptional properties, it has numerous applications, both as functional and structural materials including adsorbent, abrasive, catalyst support or heterogeneous catalyst, wear-resistant coatings, electrical component, cutting tools, medical devices, microelectronics, and various other industrial applications.[3]
3D printing of complex-shaped polymer-derived ceramics with enhanced structural retention
Published in Materials and Manufacturing Processes, 2022
Jian Liu, Shufeng Xiong, Hui Mei, Zhangwei Chen
3D printing, as an advanced manufacturing technology based on the accumulation of layers, has attracted widespread attention in recent years.[1–4] Compared with traditional manufacturing processes, it can be used to realize rapid prototyping, highly customizable designs, and near net-shape and mold-free manufacturing. Additionally, nearly any complex structures can be manufactured, as the forming cycle is shorter and the cost can be further reduced. In recent years, researchers have explored the feasibility of various materials for 3D printing, and a large number of reports have demonstrated important progress. Ceramics have attracted the attention of researchers because of their excellent properties, such as high temperature resistance, wear resistance, and corrosion resistance. However, because of the high hardness and brittleness of ceramics, traditional machining methods have issues such as tool wear and interference. Hence, the processing of ceramic parts is challenging and the forming and manufacturing of complex ceramic structures are difficult to achieve. As a revolutionary manufacturing technology, the application of 3D printing to ceramic manufacturing paves a new way to address the above issues.[3,5]
Study on preparation and tribological properties of as-sprayed 8YSZ/Graphite coating
Published in Surface Engineering, 2020
Wen Deng, Xiaoqin Zhao, Yulong An, Jianmin Chen, Huidi Zhou
The wear-out will cause premature failure of components, and the failure of mechanical components in key parts can result in disastrous consequences. Therefore, the problems of lubrication and wear resistance under extreme conditions have become a bottleneck affecting the reliability and lifetime of mechanical systems [1,2]. Ceramics possess high hardness, wonderful chemical and thermal stability, excellent wear and high-temperature resistance, which are extensively applied in engine parts, space mechanisms, high-speed cutting tools and other industrial fields [3–5]. Ceramics become one of the optimal options for wear-resistant components. However, the plasticity of ceramics is limited, and the ductility is much lower than that of metal. The intrinsic brittleness of ceramics is the main factor leading to severe abrasive wear [6,7]. To overcome this bottleneck, the lubricating phase must be introduced into the ceramic coatings to improve their tribological properties.