Example Of Research Proposal On Functional Ceramics
Ceramic materials are the non-metallic and inorganic materials that are usually shaped into certain structures at room temperature. They typically acquire their characteristics during sintering process done at high temperatures. They are some called technical ceramics due to the technical application of the material. There are several groups for the ceramics based on the chemical composition. One of the primary groups of ceramics is the silicate ceramics. These are the ceramics that come from the natural raw materials with combination of the thermal, electrical, and mechanical properties of the technical ceramics. The base components of these ceramics include kaolin, clay, feldspar, and silicate carriers through the soap stones. Other necessary ingredients include Zirconia and alumina. Another type of ceramics is the oxide ceramics. These are the group that consists of around 90% of the single component metal oxides in single phase. These materials are mostly characterized by the glass-free or –low-glass phase. There are synthetic raw materials that have high level lead purity that endows strong structural properties during high temperatures of sintering. The other common group of ceramics is the non-oxide ceramics. These are the ceramics that are composed of aluminum, nitrogen, silicon, and carbon. These groups of ceramics have a high degree of covalent bonding giving strong and superior mechanical properties for the ceramics.
Ceramics are characterized by strong electrical insulation and conductivity, with strong voltage breakdown, having dielectric and piezoelectric properties. They are strong, rigid, and highly stable materials that resist wear and tear. They also have high thermal shock resistance, heat insulation and conductivity, and superior strength in high temperatures. They are also very resistant to corrosion and compatible with various uses particularly for food usage. The application of ceramics is wide and vase. They are almost use in various fields that include medical technology, electronics, high temperature requiring technology, kiln engineering, mechanical engineering, and many more (Think Ceramics, 2005).
There is diverse application for the functional ceramics. There is an increasing interest in the research and development for this area. In 2011, the functional ceramics is emphasized in the European Science Foundation Materials Science and Engineering Expert Committee. The discovery and the synthesis of the various academic bodies are complement with their work of other countries for the achievement of certain targeted applications. The US Department of Energy highlighted the issue with ceramics (EPSRC, 2015).
Cellular ceramics are combined with unique properties that include low density, low dielectric constant, low thermal conductivity, high permeability, high porosity, high wear resistance, and resistance to chemical corrosion. These ceramic materials have the advantage of high temperature and environment stability as compared with other materials such as metals and plastics. There are typical and new application for the ceramics that include radiant burners, molten metals filtration, catalyst supports, kiln furniture, electrodes, heat exchangers, and many more. The routes to these applications are highly are highly diverse where the processes are dependent on the nature and morphologies of the various raw materials. Every fabrication method is influenced by the level of cellular interconnectedness, the material’s relative density, and the strength of the parameters.
Foams out of ceramics are fabricated by various techniques. They can be processed through sacrificial foam template replication. This process was used for the production of the various macro-porous ceramic bodies. Primarily, it includes the impregnation of flexible polymeric sponge through the ceramic slurry, followed by centrifuging, drying, and elimination of the polymer template and sintering in high temperatures. The critical point in this process is the uniform ‘green’ production where there are sharp corners contained in the structure. This process is only possible for open-cell foams due to the limitations in the infiltration efficiency and the slip removal excess. Several developments for this technique have been employed nowadays. Most of these recent developments are directed to the foam strength increase via recoating or through the ceramic struts infiltration. It is also possible to have recoating of the reticulated ceramic foam right after the sintering process. Another way is for the immersion of the SiC reticulated foam in a precursor that is containing carbon with temperatures as low as 500-700 oC. It is then followed by pyrolysis with temperatures 1000oC followed by molten Si infiltration. The reaction of the Si with the carbon residues resulting to Si deposits art e tips of the voids of the struts. This process reduces the formation of fatigue cracks on the ceramics resulting to products that are highly permeable and maintaining a low thermal mass (Colombo, 2005).
Direct foaming is another process for ceramics. It involves the bubbles generation in the liquid slurry that contains the ceramic powders to create foams that needs to be set for gaining a porous morphology before the sintering process. There is a blowing agent involved where gas is developed in situ through chemical reactions. There is a nucleation of the gas bubbles inside the slurry due to the suspended particles presence. The bubbles have spherical shapes that later grows into polyhedral cells. Direct foaming allows the production of foams where the porosity grades are on one direction. The foam produced has superior versatility with regards to the final output shapes (Colombo, 2005).
Glass foams are other ceramic products that are produced by the combination of the solid foaming agents that includes sulphates, carbides, hydroxides, carbon, and glass powders. When these materials are subjected to heat, the glass turns into viscous liquid. The oxidation and decomposition of the foaming agents leads to bubble formations that are retained in the molten product. The glass are then cooled that made the cells collapse. Another process for ceramics is the decomposition or the burnt-out process of the fugitive pores. There are hollow cells that are produced with solid materials that occupy space and the volume disappears with high temperatures. Some of the substances involved are wax, starch, polymeric beads, carbon black, and sawdust. There is also the dual-phase approach in mixing the various substances for the interconnected porosity. The pore shapes and sizes are controlled through the sacrificial fillers and other graded structures obtained by the various layers of fillers with different dimensions (Colombo, 2005).
Studies on functional ceramics mostly focus on material properties and modification of components to suit specific application requirements. For functional ceramic based on lead zirconate titanate solid solutions (Pb[ZrxTi1x]O3, PZT), the Zr/Ti-ratio may be varied. In this case, optimum value of the composition is located at the morphotropic phase boundary (MPB). Other means of component modification is indicated by the addition of several transition-metal or rare-earth elements in smaller amounts. This method allows the control of the defect structure, which is normally achieved by aliovalent doping, rendering ‘soft’or‘hard’ piezoelectric materials (Eichel, 2009).
Alternatively, studies are being made to find ways in developing lead-free alternatives on lead zirconate titanate (PZT) solid solutions due to environmental concerns (Eichel, 2009). As for the case of bismuth-based layered ceramics, Bismuth Titanate (BIT) component is commonly studied due to its ferroelectric properties and lead-free nature. BIT is a high temperature ferroelectric ceramic (Tc = 650degC). It is generally used for optical memory, high-temperature piezoelectric and electro-optic devices. Current studies on BIT ceramics focus on the decrease of the anisotropic electrical conductivity. Doping with donor dopants indicate significant decrease in electrical conductivity. Excellent results have been obtained by using the transition metals from group V and VI such as Nb 5+, V5+ and W6+, 9-12 (Jardiel et.al, 2008).
The various fabrication methods for ceramics, the possibilities of the extension of other ranging features of the cellular material produced are very wide. There are applications that can explore on the wash coat additions over a specific surface area, improve catalytic applications, higher development for affinity of slap type micro-inclusions affinity in the molten metals, and higher efficiency in the filtering methods. There are also the applications of the zeolites that grow on the surface. Other multifunctional cellular ceramics are also fabricated through additional of raw materials that further enhance the electrical conductivity, magnetic properties, refractoriness, degree of permeability, and reduced weight. These advances in the fabrication techniques that offer the best methods for ceramic production open wide possibilities. The manufacture of the cellular materials includes the consideration of the basic properties of the raw materials, how they are built for specific applications, and the choice of special applications. The improved manufacturing techniques consider the overall economics of the process and the various applications (Colombo, 2005).
In an advanced method in the processing of ceramics, the miniaturized ceramic components are being investigated nowadays for the scaling with microns and nano-scaled oxide substances and powders. This process of ceramic shaping method is a novel method in the field of ceramics that allow the structural surfaces through the micro-contact printing. It also includes molding of the photo-resistant structure surfaces, embossing, and the micro-molding in capillaries (MIMIC). For these techniques to be fully established there are gas sensors used that are not seen by the naked eye with approximately 4 to 10 sq micrometers. The micro-sensor designs are very small where the photonic band gaps are significant. Also, these micro-sensors can be integrated with silicon semiconductors that are state of the art devices that include micro-hotplates from the micromachining of the standard silicon. It also paves way for the direct use of the colloidal dispersion used in the generation of functional ceramic microstructures.
The technology of the micromolding in capillaries (MIMIC), the substance involve include polydimethylsiloxane elastomers where there are micro-channels that serve as molds. These molds are then filled spontaneously through ceramic suspensions due to capillary forces. The micro-thick film structures that result from this method reach to several micrometers in height, with varying thickness of the film. There are also film-lines that are produced with around 1 to 2 micrometers width.
The ceramic powder micro-patterns are obtained through the printed micro-contact surfaces selective wetting through the use of organic templates. The aqueous colloidal dispersions follow the hydrophobic micropatterns. It also repel with the hydrophobic environment with a simple dip process of coating. The selective wetting and printing provides resolution feature of about 5 micrometers. Furthermore, another method that can be used is the micro-fabrication approach done through the photoresist casting. The produced ceramic microstructures results to surface cross sectionals from 5 to 10 square microns. These outputs are possible produced through the conventional photolithography (Heule et al, 2015). The ceramics and the ceramic composites are advancing in terms of the methods and technology. These products are indispensable in the many applications. The new methods are finding the best ways that operate safely, efficiently, and with the minimum cost.
Colombo, p.(2005). Conventional an Novel Processing Methods for cellular ceramics. The Royal
EPSRC. (2015). Functional Ceramics and Inorganics. Engineering and Physical Sciences
Heule, M., Schonholzer, U., Vuillemien, S., and Gauckler, L. (2015). Functional Ceramic Micro
Components for Microsystems Technology. Nonmetallic Inorganic Materials. ETHZ
Jardiel, Teresa, et al. "Control of Functional Microstructure in WO3‐Doped Bi4Ti3O12
Ceramics." Journal of the American Ceramic Society 91.4 (2008): 1083-1087.
Think Ceramics. (2005). Ceramics. Technical Ceramics Information Center. Accessed through http://www.keramverband.de/keramik/englisch/kontakt.htm
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