Metal Oxide Nanocomposites. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Прочая образовательная литература
Год издания: 0
isbn: 9781119364733
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Particulate Composites (e.g. concrete and wood particle boards): these are composed of particles (in flakes or powder form) distributed or embedded in a matrix body.

      2.4.1 Polymer Matrix Materials

      Polymers are the materials of choice for their easier fabrication, lightweight and tunable mechanical properties. Two types of polymers are available viz. thermosets and thermoplastics:

       2.4.1(a) Thermoplastics

       2.4.1(b) Thermosets

      2.4.2 Metal Matrix Materials

      Metal matrices materials are known for their high stiffness, toughness, strength and their ability to withstand elevated temperature in corrosive environment. Most of the metals and alloys can be used as matrices, however, they often require compatible reinforcement materials which are stable over a range of temperature and also non-reactive [11]. Light metals form the matrix for temperature application and the reinforcements, besides the aforementioned reasons are characterized by high module. The high strength in metallic matrix materials can be achieved by utilizing high modulus reinforcements. In such composites materials, the strength-to-weight ratios can be higher than most alloys. The physico-chemical properties of the matrix materials determine the service temperature of the composites and so the choice of reinforcements becomes more important in application demanding higher melting temperature [12].

      Ceramics are the solid materials which exhibit very strong ionic bonding with partial covalent bonding. Ceramic-based matrix materials exhibits good corrosion resistance, high melting points, high compressive strength and stability at elevated temperatures and therefore can be utilized in high temperatures applications (~1500 °C) [13]. The addition of reinforcements in ceramic overcomes the problems related with high modulus of elasticity and low tensile strain to obtain strength improvement. The addition of reinforcements in adequate amount causes the ceramics to effectively transfer the load to them which reduces the possibilities of ceramics rupture at high stress levels [6]. However, this does not mean that the addition of high-strength fiber will result in strengthening a weaker ceramic. In such a case, the reinforcement possessing high modulus of elasticity can solve the problem. Usually, if the thermal expansion coefficient of ceramics is higher than reinforcement materials, the resultant composite may not be possessing good strength. In such a case, the tendency of forming microcracks while cooling increases and these microcracks extends from fiber to fiber within the matrix [9].

      2.4.4 Carbon Matrices

      Carbon based materials are generally known for high temperature withstanding properties which remain unaffected up to 2300 °C. The carboncarbon composite can be synthesized using compaction of carbon or multiple impregnations of porous frames with liquid carboniser precursors and subsequent pyrolization or through chemical vapor deposition of pyrolytic carbon [14]. These composites can retain their temperature stability upto 2400 °C along with dimensional stability and thus make them the oblivious choice in space research, military and aeronautics. The components which are regularly exposed to higher temperature and responsible for demands of high standard performance generally utilize carbon-carbon composites [15].

      2.4.5 Glass Matrices