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Phosphatic porcelain (PP), commonly known as bone china, constitutes approximately 50 wt% bone ash, 25 wt% kaolin, and 25 wt% feldspar, and its primary characteristics are high translucency and a high impact resistance. However, the low plasticity of these ceramic raw materials makes its moulding difficult owing to the plastic deformation due to the throwing wheel. Plasticizers or plasticity-promoting additives, such as sodium bentonite and methyl hydroxyethyl cellulose, modify the rheological behavior to pseudoplastic with a yield stress. Ceramic raw materials with plasticizers were prepared and characterized using helium pycnometry density, X-ray fluorescence, X-ray diffraction, and particle size distribution. In addition, characterization analysis was performed in commercial porcelain P905 for comparison purposes. The squeeze flow technique (compression of a cylindrical sample between two parallel plates) was employed to assess and compare the rheological behavior of the PP compositions with and without additives with the behavior of the commercial material. Results show that the addition of 4 wt% bentonite in the PP introduced a plasticity similar to that of the commercial porcelain, easing the shaping process using a throwing wheel. Plasticity index (PI) from the Atterberg test is useful; however, it is not sufficiently detailed to predict conformation performance of the ceramic raw materials in the throwing wheel as per the rheological information provided by the squeeze flow test.
The aim of this study is to valorise clays from the Fez region in Morocco as aluminosilicate precursors for geopolymer synthesis. In addition to the clays, the use of calcite and dolomite as mineral additives was also investigated. At first, the Moroccan clays were thermally activated by calcining at 700 °C, and then, a potassium alkaline silicate solution was used for alkali activation. Samples were synthetized by combining clay, metakaolin and mineral additive in several ratios. Consolidated materials were successfully obtained, and geopolymerization reaction was monitored by in situ Fourier transform infrared spectroscopy (FTIR), which revealed several networks. The results demonstrated that composite geopolymers with a mechanical resistance range from 8 to 50 MPa could be obtained from Moroccan clays.
In 1975, the SiC fiber was made from polycarbosilane by Prof. Yajima, for the first time. We started to develop the industrial production of the SiC fiber and succeeded in development of manufacturing technology for the multi-filament continuous Si-C-O fiber (Nicalon) in 1978. Nicalon fiber has high tensile strength and modulus, and heat resistance at high temperature in air atmosphere. Nicalon fibers have been used for the reinforcements of composite materials such as Polymer Matrix Composite (PMC), Ceramic Matrix Composite (CMC). In recent years, it has been increasing demand for high performance CMC for high temperature applications. We have improved fiber properties by reducing oxygen content and excess carbon in chemical composition of the SiC fibers. In 1988, low-oxygen-content Si-C fibers (Hi-Nicalon) with 0.5wt% oxygen were prepared from polycarbosilane with electron beam irradiation curing and pyrolysis. The thermal stability of Hi-Nicalon fibers was significantly improved compared to Si-C-O fiber (Nicalon) with 12wt% oxygen. However, creep deformation occurred in the Hi-Nicalon fiber at high temperature, caused by SiC micro crystals and amorphous carbon. Then, stoichiometric and highly crystalline SiC fiber (Hi-Nicalon Type S) was prepared from EB irradiation cured fiber by pyrolysis in a hydrogen gas flow in 1994. Type S fibers had high tensile modulus, excellent thermal stability, and creep resistance at high temperature. Hi-Nicalon and Type S fibers appear to be the best candidates for the reinforcement of ceramic matrix composites. Hi-Nicalon and Type S fiber reinforced SiC composites are being developed as the components of gas turbines for aerospace and power generation.
Growing demands for energy in the modern world require increased efficiency in the use of resources to generate power. This paper identifies the opportunity for technology development in this space, and the requirements for a solution to this issue. Solid oxide fuel cells (SOFCs) at megawatt scale offer a potential solution at high (60+%) efficiency and benefit from a fuel flexibility not enjoyed by other types of fuel cell. This paper presents the Rolls-Royce Fuel Cell Systems Limited (RRFCS) technology to deliver a SOFC system at this scale and address the inherent challenges.
The present energy paradigms have to undergo significant changes for reaching the ultimate goal of a real sustainable energy future. Key point is the transition from a fossil fuel based chemical energy to a physical energy essentially based on electricity from renewable sources. Valuable technologies for an efficient exploitation of solar power, wind power, biomass conversion etc. are already available. So the transition will proceed more smoothly if all Society players will move in the same direction.
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