Williams Ebhota

By Williams S. Ebhota and Tien-Chien Jen

Mechanical, physical and chemical properties of a part depend on the size, morphology and dispersion of the constituents of the microstructure of the part’s material. Therefore, this chapter discusses the different processes of altering the microstructure of Al-Si–based alloys to desired functional properties. These processes, commonly called modification methods, were broadly categorised into three: chemical, thermal and mechanical methods. Chemical method, which involves the addition of some elements, in trace levels, to alloys to be modified, is the best modification option. The elements for modifying are called modifiers. The three commonly used modifiers (sodium, Na, strontium, Sr and antimony, Sb) are discussed. The chapter, however, notes that for optimal alloy’s mechanical attributes, thermal treatment is usually combined with both chemical and mechanical modification processes. The thermal method involves rapid cooling of alloy for modification, while the mechanical method depends on force to break up large α-Al dendrites and plate-like Si phases.

Part of the book: Aluminium Alloys

By Williams S. Ebhota and Tien-Chen Jen

This chapter discusses the concepts, casting techniques and applications of functionally graded materials metal matrix composites (FGMMCs). Considerations were given to bulk functionally graded aluminium matrix composites (FGAACs) production processes. Liquid-metal forging processes of FGAACs fabrication, such as infiltration process, squeeze casting, friction casting or compocasting, stir, and centrifugal casting were discussed. The chapter provides basic concepts of the processes and overview of their processing parameters, such as mould rotational speed; reinforcement particles size and volume; degassing method; melting and pouring temperatures; pressure; and stirrer. The study notes that functionally graded materials (FGMs) are commonly used in automotive, aircraft, aviation, chemical, medical, engineering, renewable energy, nuclear energy, and optics electronics industries.

Part of the book: Advanced Casting Technologies

By Williams S. Ebhota and Tien-Chien Jen

This study focuses on primary impurities, called intermetallics, in the microstructure of Al-Si-X alloys, their formation, effects and treatments to eliminate or ameliorate their deleterious effects. Intermetallic compounds are usually formed when alloying elements, such as Fe, Cu, Mn, Mg and Sr. are added to Al-Si based alloys. These elements are depicted by X in the alloys formation expression. The chapter noted that the most common intermetallics are iron (Fe) based, and several of these Fe-phases, including the most harmful Fe-phase, β-Al5SiFe, are listed and discussed. Fe-phase intermetallics are deleterious to the mechanical properties of Al-alloys; however, addition of <0.7% Fe helps prevent soldering in die casting mould. The effects of Fe-phase and other intermetallics formed by Cu, Mg and Mn were examined. Further, some techniques of eliminating or mitigating the negative influences of intermetallics were discussed.

Part of the book: Intermetallic Compounds

By Williams S. Ebhota and Tien-Chien Jen

The generation of energy to meet the increasing global demand should not compromise the environment and the future. Therefore, renewable energies have been identified as potential alternatives to fossil fuels that are associated with CO2 emissions. Subsequently, photovoltaic (PV) solar system is seen as the most versatile and the largest source of electricity for the future globally. Nanotechnology is a facilitating tool that offers a wide range of resources to resolve material challenges in different application areas. This studies X-rays, energy trilemma, potential nanotechnology-based materials for low-cost PV solar cell fabrication, and atomic layer deposition (ALD). In pursuance of improved performance, PV solar-cell technologies have revolutionized from first-generation PV solar cells to third-generation PV solar cells. The efficiency (19%) of second-generation PV cells is higher than the efficiency (15%) of first-generation cells. The second-generation PV cell technologies include a-Si, CdTe and Cu(In,Ga)Se2), Cu(In,Ga)Se2 (CIGS) cells. The third-generation PV cells are organic-inorganic hybrid assemblies, nanostructured semiconductors, and molecular assemblies. This nanocomposite-based technology aims at developing low-cost high efficiency PV solar cells. The nanotechnology manufacturing technique, ALD, is seen as the future technology of PV solar cell production.

Part of the book: Recent Developments in Photovoltaic Materials and Devices