Issue No. 2

Abstract

The surfaces polishing of porcelain stoneware tiles induces both aesthetical improvements and deteriorations of their performances. To reduce this problem, the possibility to treat the polished surface of three different commercial porcelain stoneware tiles, with a waterproofing material, FILA MP/90, was evaluated. The stain resistance results were correlated to the morphological surface characteristics of the products, in the conditions: as fired, polished and treated with FILA MP/90, directly or after washing. The research showed as the surfaces, washed with an acid detergent and subsequently treated with FILA MP/90, presented great stain resistance, comparable to the corresponding as fired surfaces.

Abstract

An experimental and a theoretical study of the heat and mass transfer mechanism, and of the mechanical behaviour which occur during convective drying of clay material are reported. The model is valid only for biphasic media and it describes the critical first stage of the drying process where the material is exposed to shrinkage which may lead to large deformations and cracks. Some essential physico-chemical properties of three variety of clay are determined by experimental investigations. To check the validity of the mathematical model, drying experiments were carried out at different conditions of temperature, air velocity and relative humidity. Representative drying curves as well as moisture and temperature profiles are presented and discussed. Comparison between predicted and experimental results provides satisfactory agreement for this model. Displacement and stress fields using the elastic behaviour of the material are also presented and commented.

Abstract

The gelcasting technique in shaping sanitary ceramics is very complex and difficult to control. The use of a modified artificial neural network (ANN) was proposed to model the nonlinear relationship between gelcasting parameters and dry strength and dry shrinkage of the green body. The improved model for processing dataset and selecting its topology was developed using the Levenberg-Marquardt training algorithm and trained with comprehensive dataset of ceramic sanitaryware collected from experimental data. A basic repository on the domain knowledge of gelcasting process for ceramic sanitaryware is established via sufficient data mining by the network. With the help of the repository stored in the trained network, the influence of monomer content, cross-linker content, initiator content and catalyzer content on the dry strength and dry shrinkage can be analyzed and predicted. The results show that the ANN system is effective and successful in analyzing the influence of organic additives contents for gelcasting processes in shaping ceramic sanitaryware.

Abstract

Rice husk can be an interesting source of raw material for obtaining silica, due to its composition, availability and cost. The extraction process of silica from rice husk can be divided in two parts. First some components of rice husk are removed by acid leaching, using HCl, H₂SO₄, or a mixture of them, followed by calcination for burning out carbon compounds. The residue obtained after calcination is composed of about 95% amorphous silica. In this work, silica was produced from rice husk following the steps previously described, using leaching solutions of 10% HCl, 10% H₂SO₄ and a mixture of 10% HCl and 10% H₂SO₄ Calcination of leached materials was carried out at 600 or 700 °C for 3 h. The silica powder obtained presented a mean particle size of 18 μm, around 98% amorphous SiO2 with a specific surface area of about 300 m2/g.

Abstract

Nowadays finding a remedy to environmental pollution is a crucial topic. Photocatalysis is one of the most promising natural processes, because it can easily decompose pollutants. The present work is a review about the use of TiO₂ as photocatalyst. At first, photocatalysis process is described; later on, the anatase preparation and modification methods, required to delay the phase transformation temperature are discussed. Finally, the possibility to use rutile as photocatalyst is reported.

Abstract

The reduction of pollution from the stack gases of spray driers is without any doubt an important aim to be pursued from the Italian floor and wall tile industry, mainly into the Disctrict of Sassuolo, where the big concentration of factories affects and broadens the environmental impact in term of high energy consumption, therefore high carbon dioxide emission, and water consumption, thus lowering water-bearing strata and impoverishing water resources. A technique able to get a partial recovery of waste heat from the stack gases of a spray drier, thus allowing a partial condensation of the water steam contained in the stack gases themselves is described. The plant, installed at the Emilceramica factory in Fiorano (Modena, Italy), has been running from 2003 with the following result: 545 TOE heat per year, equivalent to 660,000 Sm3 natural gas, recovered for warming the working environment in the winter season. From the environmental point of view, the plant allows to get a 1,250 ton per year reduction in carbon dioxide emission and a 14,000 m³ per year reduction in water consumption.

Abstract

Ceramic materials were obtained from mixtures of aluminium sludge and slate powder (with different Al₂O₃:SiO₂ molar proportions), which were dried, shaped by uniaxial pressing and sintered at temperatures in the range of 950 to 1300 oC, in order both to detoxify the sludge by fixing the metals in a leach-resistant ceramic matrix and to yield a new material from the reactions of the above compounds at high temperature. The most promising material was obtained from the 2:1 mixture sintered at 1300 oC, which was also found to be inert after leaching tests. The average Vickers hardness HV3 (683), bend strength (126 MPa), Young’s modulus (161GPa) and fracture toughness (3,35 MPa.m^1/2) were significantly higher than those found for the as sintered slate powders, which was attributed to the increased fraction of a-alumina and reduced content of glassy phase in the microstructure due to the sludge addition. Weibull modulus (m= 9) had a value typical for technical ceramics.

Abstract

Due to the classification of crystalline silica as a human carcinogen, health regulations necessitate the determination of a-quartz in respirable dust and bulk materials in the industrial environment. A variety of analytical methods, including X-ray diffraction and infrared spectroscopy (IR), have been used to determine crystallinity degree of quartz in bulk materials. In addition to determination of crystalline silica in respirable dust, Murata and Norman (1976) proposed a semiquantitative XRD method for measuring quartz crystallinity in bulk materials as well as minerals. The determination of full-width-at-half-maximum (FWHM) for quartz diffraction line in sample such as clay, coal and cement containing quartz as accessory mineral can be used to evaluate Murata’s crystallinity index for the quartz. The measurement of FWHM for quartz in bulk materials will accelerate practically the determination of crystallinity of quartz.