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Ceramic Based Biomaterials
Published in Yaser Dahman, Biomaterials Science and Technology, 2019
Zirconia can also be combined with alumina to create a bioceramic that exhibits higher hydrothermal stability and superior wear resistance. Zirconia-toughened alumina (ZTA) is composed of 80% tetragonal zirconia polycrystal and 20% alumina ceramics. This component is made of an alumina rich composition with evenly disperses zirconia in the alumina matrix. ZTA has superior tribological and mechanical properties compared to zirconia and alumina (Kurtz et al., 2014). ZTA has been used for implants for load-bearing applications such as total hip replacements. Since ZTA materials have higher fracture toughness, it is possible to create thinner liners and larger femoral heads, which allows for a greater range of motion in the joint. In a study by Lombardi et al. (2010) the performance of 65 ZTA femoral head implants was monitored for 6.1 years. They recorded the ZTA implants to have 95% survivorship with no cases of osteolysis recorded. The implants also had no squeaking noise reported, which is a common problem for metal implants (Lombardi et al., 2010). This study helps to demonstrate the advantageous properties found in ZTA composites and how they can be used as an alternative to alumina or metals to treat load-bearing complications such as a total hip replacement.
Toughening of Ceramics
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
As discussed earlier in this chapter, fine (submicron) particles of ZrO2 can be added to other materials and result in the transformation toughening of these materials. Some examples are listed in Table 20.6. Especially good results have been achieved with Al2O3 as the matrix. Strength greater than 1000 MPa and toughness greater than 10 MPa·m1/2 have been reported for Al2O3 containing only 16 vol% ZrO2. In addition, the resistance to thermal shock damage and to slow crack growth are increased for zirconia-toughened alumina (ZTA). Rice43 reported that Al2O3 with 14 vol% ZrO2 had a critical ΔT for thermal shock damage of about 700–900°C, compared to 300°C for Al2O3. Furthermore, the strength dropped from 700 to about 500 MPa for the Al2O3–14% ZrO2 compared to a drop from 320 MPa to less than 150 MPa for Al2O3 without ZrO2 addition.
Bioceramic Nanoparticles for Tissue Engineering
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
The initial applications of both of these ceramics in total joint replacement was found to be associated with certain limitations (Thamaraiselvi and Rajeswari 2003, Roualdes et al. 2010). High fracture rates were found in the case of alumina, whereas zirconia was found to be unstable and get transformed catastrophically into the monoclinic phase, depending on its manufacturing conditions and hydrothermal effects in vivo (Kurtz et al. 2014). To address these clinical problems, the development of mixed oxides ceramic materials known as “composite” materials represents a major new advancement of clinically available orthopaedic biomaterials. Ceramic composites act synergistically to give properties, better than those provided by either component alone and also, enjoy the superiority due to similarity with bone minerals (Thamaraiselvi and Rajeswari 2003). Two types of composites known as zirconia-toughened alumina (ZTA), in which alumina matrix is embedded with zirconia particles, and alumina-toughened zirconia (ATZ) where zirconia matrix is dispersed with particles of alumina, exhibiting superior strength and toughness, can be fabricated from mixtures of alumina and zirconia (Affatato et al. 2006). The concerns related to hydrothermal firmness still persist in the case of ATZ (Affatato et al. 2006). The properties such as high strength, toughness, hardness, wear resistance, and low susceptibility of stress-assisted degradation of alumina make ZTA increasingly important as a structural material for orthopaedic applications (Kurtz et al. 2014) (Affatato et al. 2006). All these properties of the ZTA reduce the risk of dislocation and impingement and enhance the stability of implants. However, the magnitude of all these mechanical as well as biological properties is completely dependent on the different processing routes proposed for ZTA composites. Affatato et al. (Affatato et al. 2006) reported the development of high-density ZTA nanocomposites with superior properties such as very homogenous microstructure, high crack resistance, increased fracture toughness, and hydrothermal stability. Further, they observed no significant differences between the wear behaviours and osteoblast growth onto nanocomposite samples of ZTA in comparison with commercial alumina and experimental alumina specimens. In another study by Roualdes et al. (Roualdes et al. 2010), the in vitro and in vivo biocompatibility of a ceramic composite composed of alumina-zirconia, processed by a standard powder-mixing technique, was investigated. The results showed that in vitro, the ZTA composite resulted in no deleterious effects on cell growth and its phenotypical features, and extra-cellular matrix production by fibroblasts and osteoblast cultured upon sintered ceramic discs and in the presence of submicron-sized alumina or zirconia particles at various dose concentrations. A very normal and non-specific response of the synovial membrane leading to the formation of granulomatous tissue, but no major pain or inflammation was observed at local or systemic site in Sprague Dawley rats after intra-articular injection of ZTA particulates.
Thermophysical Properties of Zirconia Toughened Alumina Ceramics with Boron Nitride Nanotubes Addition
Published in Heat Transfer Engineering, 2020
Chi Heon Kim, Eun Byul Go, Hyo Tae Kim
Alumina is a typical ceramic package substrate material [4] due to its excellent physical properties such as high thermal, corrosion and wear resistance, as well as a good electrical insulation. To improve its mechanical strength further, zirconia (ZrO2) or yttria-stabilized zirconia (YSZ) has been added to alumina as a toughening agent [5], so called zirconia-toughened alumina (ZTA) ceramics. There is abundance of mechanical properties information on ZTA ceramics since they are mostly used in the structural ceramics and electronic packaging industry. The thermal conductivities of selected compositions such as 15 vol% zirconia containing alumina (15ZTA) or 25 vol% zirconia containing alumina (25ZTA) are known by the manufacturer’s technical data sheet, but it is hardly found the comprehensive information on the thermal conductivity of ZTA ceramic composite system.
Development and machinability evaluation of MgO doped Y-ZTA ceramic inserts for high-speed machining of steel
Published in Machining Science and Technology, 2018
Bipin Kumar Singh, Himadri Roy, Biswanath Mondal, Shibendu Sekhar Roy, Nilrudra Mandal
In recent manufacturing areas, new technologies are constantly replacing the conventional systems due to high demand and low cost of production. The area of machining science and technology also demands advent of newer materials at the forefront of research, which would lead to increase in productivity. The major factor on which selection of tool depends upon is the type of material to be machined and the type of operation. The additional factors that affect the selections of tools are machine capacity, i.e., tool horsepower, availability of inserts, speed range, rigidity of the machine, tooling budget limitations, productivity demands, machine tool burden rate, etc. Ceramic cutting tools have shown great potential in the manufacturing sector as they fit in all the above-mentioned criteria quite well. Among the various available ceramic tools, Al2O3-based ceramics are widely used in aerospace, manufacturing and automobile industries due to its excellent stability, oxidation resistance, low density, low thermal coefficient, high strength at elevated temperature and less wear (Miles and Feltham, 1971; Wang and Stevens, 1989; Kumar et al., 2007). However, low toughness and high brittleness restrict the use of alumina ceramics in structural applications. But, a class of Al2O3 ceramics, i.e., zirconia-toughened alumina (ZTA) shows considerable improvement in strength and toughness over standard alpha alumina. In this ceramics, alumina provides high strength and hardness, whereas tetragonal zirconia favors a toughening effect. In 1970, Garvie et al. (1975) demonstrated a peculiar characteristic of zirconia i.e. transformation toughening which enables it to use in various applications due to enhancement in mechanical properties. Thereafter, many researchers worked in this field to increase the toughness of ceramics. Few other researchers (Xu et al., 1996; Kelly and Denry, 2008) observed that the crystal structure of pure zirconia changes from monoclinic (at room temperature) to tetragonal (around 1,700°C) to cubic (at around 2,370°C). It is notable that during the transformation of tetragonal (t) to monoclinic (m) in cooling, there is an expansion in the volume (approximately 4.5%) (Nevarez-Rascon et al., 2009), sufficient to prevent catastrophic failure (Ramzan et al., 2011).