Issue No. 2, August

Abstract

The aim of this study is to determine the properties of metarhyolites from Ilgin-Konya (Turkey) area and to decide whether or not metarhyolites are suitable as a flux agent for porcelain stoneware tile production. For this aim, the chemical and mineralogical properties of metarhyolite were determined by chemical analyses, XRD and SEM studies. Starting from the reference mix composition, different amounts 4, 8, 12 and 16 wt.% of potassium feldspar were replaced with the same amounts of metarhyolite. All the samples were fired under industrial conditions at 1200 °C for 49 min. The physical and mechanical properties of the fired porcelain stoneware bodies such as water absorption, linear shrinkage, bulk density and fired flexural strength were measured. Fired bodies were subjected to colour measurements and X-ray diffraction (XRD). The results indicate the possible use of metarhyolite as an effective fluxing agent in porcelain tile bodies.

Abstract

The effects of nepheline tailing and ZnO on the physical, mechanical, microstructure and dielectric properties were investigated. Specimens fired at 1125 °C from batches containing 40 mass % nepheline tailing (product nepheline syenite beneficiation process) and 2 mass % ZnO showed a maximum MOR of 44.81 MPa. The main phases recorded were quartz, cristobalite, albite, hematite and gahnite. The dielectric constant (ε’) and dielectric loss (ε”) of ceramic bodies based on nepheline syenite tailing and clay as well as with 2 and 5% Zn were determined at temperatures between (25 to 275 °C) and over a wide range of frequency between 100 Hz and 1MHz. It was found that both ε’ and ε” showed increase with rise in temperature and fall in frequency. On the other hand, both ε’ and ε” showed a decrease on the addition of zinc oxide, attributed to the presence of gahnite (ZnAl₂O₄), which significantly enhanced their dielectric properties.

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

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

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

Propulsion (launcher, satellites and missiles) and gas generator applications (i.e. rescue systems) need the catalytic decomposition of energetic compounds. The energetic liquids, called monopropellants, are decomposed on catalytic beds, which must present very good thermal and mechanical properties to resist frequent thermal shocks and high flow rates. Compared to conventional aluminabased supports developed about 40 years ago (extrudates, pellets, spheres), honeycomb monolithic reactors represent very attractive alternatives to overcome the current and future challenges. An overview is given and different case studies are discussed: hydrazine, energetic ionic liquids, hydrogen peroxide

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.

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.