G. Kaya

Influences of Eu2+ and Dy3+ Contents on the Properties of Long Afterglow Strontium Aluminate Phosphors

The detailed preparation process of Eu2+ and Dy3+ ion co-doped phosphor powders in Sr4Al14O25:Eu2+/Dy3+ phosphor system with bluish-green long afterglow produced by solid state reaction method under reducing atmosphere is here reported. X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis were made to assign the effects of Eu and Dy ions on the luminescent properties of the synthesized phosphors, which were determined by measuring the photoluminescence spectra. The maximum emission intensity of these phosphors under excitation was investigated. As a result, the relevant values were obtained from the phosphorescent pigment with 0.21% and 0.05% molar percent of Eu2+ and Dy3+.

Effects of Firing Temperature and Time on the Luminescency of Phosphors in Strontium Aluminate System Co-Doped by Eu2O3 and Dy2O3 and Prepared by Solid State Reaction Processing

In the current study long afterglow phosphors in strontium aluminate system doped with Eu2+ and Dy3+ were synthesized at different firing temperatures for various time. Photoluminescency and crystallisation during sintering under reducing atmosphere were examined as functions of sintering time and temparature. XRD was employed to characterize the crystal phases of phosphors. Scanning electron microscopy (SEM) investigations were carried out to understand surface morphology and to confirm the XRD results. The optical properties of the phosphors were investigated by a phosphorescence spectrophotometer. The changes in emission and excitation spectrum were discussed accounting firing time and temperature.

Utilisation of Concentrator Wastes of Etibor Kirka Borax Company in the Recipe of an Opaque Frit Used for Wall Tile Glazes as an Acid Boric Replacement

Turkey holds ~63 % of total boron deposition shares of the world with 803 million tons. Eti Holding, being the most important producer, possesses 31 % of total world production on the B2O3 basis. Like every other industrial companies, depending upon the production rate, Eti Holding also struggles with the waste materials progressively occupying very large landfills day by day. This is an unpleasant occurrence from the environmental points of view. Therefore, to recycle these wastes several studies are still being carried out. In order to widen their possible utilisation fields concentrator wastes of Etibor Kirka Borax Company, which is one of the several branches in Eti Holding, were added into the recipe of a standard opaque frit suitable for wall tile glazes replacing acid boric content. The glazes prepared with this newly produced frits were applied onto green wall tiles and single fired. Final products were tested for determining the maturation attitude of their glazes, thermal shock and stain resistances, durability to several chemicals and colour parameters. All the results showed that these wastes could replace acid boric content of the starting frit batches in appropriate proportions and therefore be evaluated.

Effects of the Red Mud Based Pigment Addition on the Physical and Micro-Structural Properties of Porcelain Tiles

In the production of conventional porcelain tiles colouring agents, being either in the form of pure oxides or pigments, are commonly and widely used at considerably high amounts to increase the attraction impact of final products. This, of course, raises the manufacturing costs. Having stated that, producing pigments at a reasonable cost really becomes an important concept for such a type of product. When producing aluminium metals through Bayer process Seydisehir aluminium factory of Turkey disposes huge amounts of red mud, which consists of high iron oxide and was thought to be valuable in terms of cheap pigment production. In the present study, pigments with the shades of black, brown and dark green colours were produced from the mixtures of red mud, CoO, Cr2O3 and MnO by following standard pigment preparation routes. Then, they were added into a porcelain tile composition separately. All the samples produced undergone through certain standard tests. The effect of red mud based pigments on the micro-structure of porcelain tiles was also searched.

Effects of Aydin Cine Region's Albite Flotation Wastes on the Properties of Floor Tile Bodies

Within the scope of determining new possible application fields of waste materials albite flotation wastes, being ore treatment outcome, of Aydin Cine region of Turkey, where very rich feldspar deposits are available, have been incorporated into stoneware, soft porcelain bodies and their glaze compositions in previously done studies confirming their usage in the relevant systems. Since the amount of these wastes increases during the albite ore treatment stage, recycling them at a possible highest rate is an effort of appreciation in many valuable ways. Therefore, they were added into floor tile body compositions replacing Na-feldspar at certain proportions in this study. Mechanical strength, water absorption, shrinkage-expansion tendencies and colour variation of the tiles single fired under industrial working conditions were determined. As a result, it was concluded that albite flotation wastes could replace feldspar content in floor tile bodies without leading undesired consequences. Introduction Feldspathic minerals have long been universally used in ceramic formulations for their fluxing power. Their preferred proportion are: earthenware < 25 %; sanitary ware 25-35 %; white ware 1530 %; floor and wall tiles 10-55 %; and electrical porcelain 30-50 %. In glazes and porcelain enamels the feldspar content will be 30-50 % by weight [1]. The ore treatment of feldspar is largely conducted by froth flotation method used to separate minerals, suspended in liquids, by attaching them to gas bubbles to provide selective levitation of the solid particles. It is the cheapest and most extensively preferred process for the separation of chemically similar minerals, and concentrating ores for economical smelting [2, 3]. Inorganic wastes discharged at the end of flotation contain considerable amounts of CaO-P2O5-TiO2-Al2O3 and SiO2, amongst which TiO2 and P2O5 act as nucleating agent and therefore, worth mentioning [4]. Ceramic floor and wall tiles are one of such value-added products where industrial wastes can be used as raw materials [5]. Therefore, positive outcomes of the related studies encourage new approaches in the way of utilisation of inorganic wastes [6-12]. Aydın-Cine region of Turkey possesses one of the larger albite (Na-feldspar) deposits with 100 million tons [13]. The present study was aimed at evaluating albite flotation wastes of this region in floor tile bodies as a replacement of Na-feldspar. Experimental Work Chemical analysis of raw materials and albite flotation waste (F.W.) used in the study are presented in Table 1. Fig. 1 shows X-ray diffraction (XRD) pattern of the waste. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 2429-2432 doi:10.4028/www.scientific.net/KEM.264-268.2429

Utilisation of a Natural Stone with Fluxing Ability in Floor Tile Body as a Na-Feldspar Replacement

In 1960’s the floor tile production of Turkey was started with a large use of K-feldspar as a fluxing agent. However, due to its limited deposits companies begun to employ Na-feldspar instead. At present, considerable level of Na-feldspar is in use. If there are long distances between mines and the factories then transportation costs play an increasing role on the overall production cost. In order to prevent such an occurrence attempts to seek alternative raw material sources have become very important. In this study, a natural stone with high fluxing capability, which is largely available in the regions quite close to the floor tile factories around Eskisehir, was added into floor tile bodies in certain proportion as a replacement of Na-feldspar. Standard tests were applied on the industrially produced floor tiles and results indicated that this stone could be evaluated in floor tile bodies as an alternative-fluxing agent. Introduction Ceramic tiles are one of the major functional and decorative units widely used in buildings. Tile is selected because it has a durable finish, is easily cleaned, and comes in many colours [1]. Ceramic tile production in the world increased from ~1960 million m in 1990 to more than 5000 million m in 2000, an increase of 155 %. The increase in world production was the natural response to an equivalent increase in consumption from 1850 million m in 1990 to ~4300 million m in 2000, an increase of 132 % [2]. Consequently, raw material requirements are also continuously rising. Feldspar content of floor tile bodies is relatively high [1]. This material based on the sodium, potassium and calcium alumina silicates firstly supplies permeability to the bodies into which it is added, facilitating the gas removal during drying and firing. Secondly, with its resulting glassy phase firing temperatures are lowered [3-5]. Since it completely dissolves during firing it wets the solid particles of other components. Surface tension pulls them together giving a densification of the body. As the temperature rises, the alkalis become more active and initially dissolve the clay particles, and then the free silica. Potassium feldspar has the advantage that it forms a melt of high viscosity decreasing only slightly with increased temperatures, resulting in good stability against distortion of the ceramic during firing [6]. Unlike albite and anorthite, orthoclase that has a wider sintering range is preferred from the viewpoint of obtaining high mechanical strength [7]. Ware containing Na-feldspar is generally weaker than that with K-feldspar [6]. In the current study, a natural stone having both Na2O and K2O contents was incorporated into a standard floor tile body with the aim of its economical and environmental evaluations. Experimental Procedures Chemical compositions of the natural stone and raw materials used are indicated in Table 1. Table 2 presents the results of hot stage microscopy studies belonging to the stone. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 1705-1708 doi:10.4028/www.scientific.net/KEM.264-268.1705

Use of Tuncbilek Thermal Power Plant's Fly Ash in Stoneware Glazes as a Colouring Agent

With the increased energy needs thermal power plants enlarge their production rates. In spite of high productivity in energy supplies, the concentration of fly ash filtered in the chimneys of these plants raises subsequently. Such a problem is also faced in Tuncbilek thermal power plant of Turkey. Due to the colouring capability of the relevant ashes, it was considered that their use in coloured transparent and opaque stoneware glazes could be possible. As well as examining their colouring effect in the glazes, thermal shock and stain resistance of the newly produced glazes were tested throughout the current study. The results suggest that fly ashes can be evaluated in the stoneware glazes for colouring purposes without changing any production parameter.

Evaluation of a Natural Stone with Fluxing Capability in Stoneware Glazes

New glaze systems have been continuously developed in order to supply certain advantages to ceramic bodies such as resistance against external thermal and mechanical forces and an aesthetic appearance as well as hygiene. Besides modifying ceramic systems already present, efforts on finding new applicable raw materials and their evaluation are of scientific and industrial importance. The current study was conducted to determine whether the natural stone, the chemical composition of which is 61.55 SiO2, 16.08 Al2O3, 6.18 Na2O, 2.80 K2O, 2.92 CaO, 1.64 MgO, 3.68 SrO, 2.33 ZrO2, 2.82 Fe2O3 (in wt %), can be evaluated in some of colourless and coloured stoneware glazes instead of K-feldspar because of its outstanding fluxing behaviour. At the end of the study ease of its use in the relevant glazes was confirmed.

Chemical Durability Behaviour of Bulk Glasses in the Er-SiAlON System: Surface Characterisation by SEM

Er-SiAlON glasses were produced by melting appropriate powder mixtures under nitrogen at 1715 °C using a cation ratio composition of Er:Si:Al = 3.45:3:2 and with varying nitrogen contents (N= 5 to 22 equivalent %). Chemical durability tests were performed by immersing the specimens into 1M NaOH solution at 75 °C. The results were evaluated based on the weight changes of the specimens that were recorded at regular intervals of one week. In this work, the effect of nitrogen content in the glass structure on chemical durability is discussed. Surface features (cavities etc.) on each of the chemical durability tested samples were observed and analysed by a scanning electron microscopy (SEM). Initial results present that ErSiAlON glasses can be good candidates for applications involving high basicity environments.

Use of Concentrator Wastes of Etibor Kirka Borax Company in Soft Porcelain Opaque Glazes as an Alternative Fluxing Agent

Both manufacturers and customers in ceramic sector like all industrial branches always demand high quality products with less cost. With the increase in consumption levels of final products the considerable decreases in deposits of readily used raw materials take place all around the world. Therefore, economical and conscious usage of these deposits is crucial. Consequently, numerous numbers of searches for finding alternative raw materials and recycling wastes as a possible replacement have been conducted. In the present study concentrator wastes of Etibor Kirka Borax Company of Turkey with the chemical composition of 27.69 SiO2, 4.58 Al2O3, 7.52 Na2O, 2.77 K2O, 8.95 CaO, 12.45 MgO, 14.28 B2O3, 0.04 ZnO, 0.07 TiO2, 0.96 Fe2O3, 0.04 Li2O, 0.02 PbO, 20.63 loss on ignition (in wt %) were incorporated into a soft porcelain opaque glaze recipe as a replacement of K-feldspar. Such a modification in starting glaze batches led to the improvement in opacity without deteriorating maturation and final properties. Therefore, it was concluded that these wastes could easily be added into the relevant glaze system.