Issue No. 3

Abstract

In this study the use of the kaolinite, which contains very low levels of pyrophyllite, as a ceramic tiles material was studied. Chemical, mineralogical analysis and thermal behaviours of the clay were determined. After analysing the chemical, mineralogical content and thermal behaviour of the clay, the shaping properties were determined according to Atterberg and Pfefferkorn plasticity tests. The samples that had been shaped with vacuum extrusion were fired at between 600 °C to 1200 °C with 100 °C internals. Mineralogical, physical-mechanical properties and microstructure of fired samples were determined. As a result, it was seen that the grain size of the clay and its plasticity values are suitable for ceramic tile and formation of secondary mullite as well as lamellar shaped pore structure at low temperatures (1100 °C) has positive effect on mechanical properties. It was determined that ceramic tile can be produced at 1000 °C for Group AIIb and at 1100 °C for Group AIIa according to Turkish Standard (TS EN ISO 14411). The colour and aesthetic appearance of the fired products correspond the market demands with smooth surface.

Abstract

Frost resistance of roofing tiles is of both practical and scientific interest, especially since the frost action mechanisms are still not well understood. Textural characteristics and low temperature dilatometrical behavior (from -40 to +40 °C) of clay roofing tiles are correlated with the type of frost damage identified by the standard procedure, EN 539-2, method C, giving the insight into the dominant frost action mechanism (mechanism of closed container, hydraulic pressure, and the ice lens mechanism). The samples of clay roofing tiles from the same batch were fired in laboratory conditions at different temperatures (920, 970, 995, 1015, 1055 and 1085 °C) and in the industrial plant (1100 °C). Based on the mentioned correlations, the change of the dominant frost action mechanism is explained by porous structure differentiation with the temperature, from a closed container at lower to micro ice lens formation at higher temperatures, with the hydraulic pressure mechanism contributing considerably in all the temperatures. The obtained correlations are of specific importance in taking fast and right corrective measures in a defined production line in order to improve the frost resistance characteristics of the final product.

Abstract

Aim of this study was to investigate the relations between chemical composition and firing behaviour of porcelain stoneware formulations. The effects of magnesia and/or calcia incorporation in varying amounts into a standard stoneware formulations through combined use of calcite and magnesite on firing behaviour was studied by means of a non-contact optical dilatometer. It was shown that suitable combination of magnesite/calcite noticeably lowered peak firing temperature without narrowing the firing range. Peak firing temperatures of these bodies were also at commercially acceptable levels. Further formulations prepared with calcite, kaolin and a local clay high in iron oxide content were also shown to give acceptable chromatic co-ordinates. It was also possible to develop bodies with high whiteness values without employing zircon.

Abstract

The effects of six additives, i.e. sodium tripolyphosphate (TPP), sodium hexametaphosphate (SHMP), Rheobuild, Darvan, Glenium and Castament, on rheological behavior of microsilica containing ultra low cement Al₂O₃-SiC vibration castables, were investigated. The behavior of the various deflocculants in these castables was evaluated in terms of flowability, workability and physical properties. It was concluded that Glenium, a deflocculant based on polycarboxylate ethers, was the most appropriate deflocculant for the ultra low cement castables of the Al₂O₃-SiC system. Glenium 110 IR gave simultaneous good flowability and workability at an optimum content of 0.12 wt%.

Abstract

In the pseudo ternary MgO-Si₃N₄-Al₂O₃ system at 1800 °C the occurrence of liquid phase is limited to areas near the MgO-Si₃N₄ line, close to Si₃N₄. The area near the MgO-Al₂O₃ line is interesting from the point of view of refractory materials. The results of investigations into the properties and microstructure of magnesia-spinel materials with oxynitride and nitride matrix obtained by sintering are presented. The materials with a matrix composed of AlN polytypoids were characterized by very high refractoriness under load (RUL) in reducing conditions (T_0.6>1700 °C) and relatively high RUL in air (min T_0.5>1620 °C). The TG curves showed that the oxidation course was similar to and depended on the composition and mixture of samples. A very good correlation was found between the calculated values of Rst coefficient and resistance to thermal shocks sustained by the cylinders subjected to sudden heating up to 950 °C and cooling.

Abstract

Nanotechnology is defined as the use of materials with at least one dimension less than 100 nm. Although nanotechnology has revolutionized many fields to date, it use in medical applications remains at its infancy. This manuscript describes recent promising studies made towards increasing tissue regeneration through the use of nano compared to conventional materials.

Abstract

Cost effective ceramic manufacturing with green and dense machining perspectives has been described. An advanced CNC green machining based complex shape forming technology developed at Saint-Gobain is described which has been shown to be robust and capable of rapid prototyping. Utilizing a systems approach involving green blank properties, type of cutting tools and machining parameters the procedure has been optimized. Integral Bladed Rotors (IBR) for microturbine applications have been fabricated with dimensional controls within 0.15% and successfully spin tested at 143330 rpm without failure. Following this approach, a cost effective machining and prototype fabrication procedure is under development for IBR and Vane rings for various civilian and military applications.