Nuran Ay

The use of waste ceramic tile in cement production

In ceramic tile production, because of various reasons, unsold fired products come out. These are waste tiles and only a little part of them are used. Remainings create environmental problems. If these waste tiles are used in cement production, this pollution decreases. In this study, usage of waste tile as pozzolan was studied. Waste tile was added into Portland cement in 25%, 30%, 35%, and 40% weight ratios. Pozzolanic properties of waste tile and setting time, volume stability, particle size, density, specific surface area, and strength of cement including waste tile were investigated. The test results indicated that the waste tiles show pozzolanic properties, and chemical and physical properties of the cement including tile conforms to cement standard up to the addition of 35% waste tile.

Effect of Nano Hexagonal Boron Nitride Lubricant Additives on the Friction and Wear Properties of AISI 4140 Steel

The aim of this study was to investigate the effects of nano hexagonal boron nitride(hBN) particles on the friction and wear properties of AISI 4140 steel material when the hBN particles are used as an oil additive. Nano hexagonal boron nitride powders, which were produced using a special process, were dispersed in engine oil (SAE10 W) to enhance lubrication. The amount of nano hexagonal boron nitride in the engine oil was varied from 0 to 10% by volume, and four different lubricant samples were prepared. Wear tests were conducted using ball-on-disc geometry. The worn surfaces of substrates were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The experiments showed that the nano hexagonal boron nitride particles that were used as an oil additive affected the friction and wear behavior. A 14.4% improvement in the friction coefficient and a 65% decrease in the wear rate were achieved through the use of the nano hBN as an oil additive.

Synthesis and Sintering of Cordierite at Low Temperature from Kaolin and Magnesium Hydroxide

Thermal reactions of ultrafine Mg(OH)2 mixtures of ultrafine particles and kaolin mixtures were investigated to obtain cordierite at low temperatures. Magnesium hydroxide was precipitated from magnesium chloride (MgCl2) solution. Kaolin with three different chemical composition (KI, KS and KK) was mixed with Mg(OH)2 to form cordierite at different temperatures (900-1200°C). Mole ratio of mixtures were MgO:Al2O3:2SiO2. To obtain dense cordierite, boron oxide in different quantities (in the form of magnesium borate 2MgO.B2O3) were added into mixtures of kaolin and Mg(OH)2. After sintering, it was observed that, by increasing the amount of B2O3 in the mixture, the density was not changed significantly. Introduction Rankin and Merwin found cordierite, Mg2Al3Si5AlO18, to be the only ternary phase in the MgO-Al2O3-SiO2 system [1]. Cordierite as a ceramic material has a wide range of uses and applications stemming from its important properties of low thermal expansion and dielectric constant coupled with high chemical and thermal stability. In addition, cordierite is expected to have great potential as a substrate material for integrated circuit boards [2] replacing alumina, which has a relatively lower dielectric constant in the high frequency region. There are no known large deposits of natural cordierite, and it probably is never available for introduction to ceramic bodies. A body having the theoretical composition of cordierite may consist of 39.6 % talc, 47.0 % clay and 13.4 % alumina. Bodies of this composition, however, have so short vitrification range that they cannot be fired in industrial kilns. Preparing dense cordierite glassceramics also has long been a problem because of this problem [3-5]. In this study, ultrafine particles of Mg(OH)2 were precipitated from aqueous solution of magnesium chloride. Cordierite ceramics were obtained by mixing Mg(OH)2 particles with different type of kaolin and firing between 900-1200°C. To obtain dense cordierite ceramic different amounts of B2O3 were added into mixtures. Experimental Procedure Sample preparation. Three types of kaolin, designated as KI, KS and KK, mined around Turkey were used as raw material to synthesise the cordierite ceramics. The particle size distribution and chemical composition of kaolins are given in Fig. 1 and Table 1, respectively. The classified kaolin consisted of tabular particles of kaolin with mean particle sizes of 1.5, 1.3 and 0.8 μm. As a source of MgO, ultrafine particles of magnesium hydroxide were prepared as in our previous work [6]. The kaolin and Mg(OH)2 were weighed according to the molar ratio of MgO:Al2O3:2SiO2 and were mixed using an agate mortar in ethanol media to prevent aggregation. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 925-928 doi:10.4028/www.scientific.net/KEM.264-268.925

Pressureless Sintering of Hexagonal Boron Nitride Powders

Pressureless sintering of hexagonal boron nitride (BN) with and without additives was performed using a powder which was previously nitrided at 900oC and then heat treated at 1400oC. Sintering additives were B2O3 (2, 4, 6 wt %) and Y2O3 (2, 4, 6 wt %) and sintering temperatures was 1900oC. Sintered samples were characterized by XRD, SEM, micro hardness, density and mercury porosimeter measurements. Maximum density values of samples were 1.56 g/cm3 without additives and 1.63 g/cm3 with additives. Hardness values of samples were found to improve with the presence of additives.

Electrophoretic deposition of hydroxyapatite-hexagonal boron nitride composite coatings on Ti substrate

In this study, commercial pure titanium samples were coated with nano hydroxyapatite-nano hexagonal boron nitride (nano HA-nano hBN) composite by electrophoretic deposition (EPD). The effect of process parameters (applied voltage, deposition time and solid concentration) on the coating morphology, thickness and the adhesion behavior were studied systematically and crack free nano hBN-nano HA composite coating production was achieved for developing bioactive coatings on titanium substrates for orthopedic applications. For the examination of structural and morphological characteristics of the coating surfaces, various complementary analysis methods were performed. For the structural characterization, XRD and Raman Spectroscopy were used while, Scanning Electron Microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and Transmission Electron Microscopy (TEM) techniques were carried out for revealing the morphological characterization. The results showed that nano HA-nano hBN were successfully deposited on Ti surface with uniform, crack-free coating by EPD. The amounts of hBN in suspension are considered to have no effect on coating thickness. By adding hBN into HA, the morphology of HA did not change and hBN has no significant effect on porous structure. These nanostructured surfaces are expected to be suitable for proliferation of cells and have high potential for bioactive materials.

Study of the boron levels in serum after implantation of different ratios nano-hexagonal boron nitride-hydroxy apatite in rat femurs.

Boron and its derivatives are effective in bone recovery and osteointegration. However, increasing the boron levels in body liquids may cause toxicity. The aim of our study is to investigate serum boron levels using ICP-MS after implantation of different ratios of nano-hBN-HA composites in rat femurs. All rats were (n=126) divided into five experimental groups (n=24) and one healthy group (6 rats); healthy (Group1), femoral defect + %100 HA (Group2), femoral defect + %2.5 hBN + %97.5 HA (Group3), femoral defect + %5 hBN + %95 HA (Group4), femoral defect + %10 hBN + %90 HA (Group5), femoral defect + %100 hBN (Group6). The femoral defect was created in the distal femur (3mm drill-bit). Each implant group was divided into four different groups (n=24) also 6 rats sacrificed for each groups in one week intervals during four weeks. In our results; at 1, 2, 3, and 4 weeks after implantation near bone tissue, serum levels of boron were evaluated using ICP-MS. We demonstrated that neither short-term nor long-term implantation of hBN-HA composite resulted in statistically increased serum boron levels in experimental groups compared to healthy group. In conclusion, this study investigated the implant material produced form hBN-HA for the first time. Our data suggest that hBN is a new promising target for biomaterial and implant bioengineers.

Wear Characteristics of Traditional Manganese Phosphate and Composite hBN Coatings

In this study, the tribological properties of traditional manganese phosphate coatings and composite hBN coatings composed of nano-hexagonal boron nitride (hBN) in layered manganese phosphate crystals on AISI 1040 steel were investigated. Wear tests were carried out under controlled temperature and humidity using ball-on-disc tribometers for samples that were either submerged in oil or retaining oil on their surfaces at a sliding speed of 2.5 cm/s with loads of 1, 3, 5, and 10 N and sliding distances of 40, 80, 100, and 120 m. The surface profiles before and after the tests were used to characterize the wear. The surfaces of the coated samples were examined using scanning electron microscopy (SEM). The coefficients of friction and wear rates of the coated samples were also measured. The average wear rates of the composite hBN-coated samples were significantly lower than those of the traditional manganese phosphate–coated samples for each of the loading conditions for the oil submersion and retained oil tests. The coefficient of friction (COF) values for the traditional manganese phosphate–coated samples did not change significantly with increasing load. The COF values for the composite hBN coated–samples decreased with increasing load in the oil submersion test.

Double Layer Glaze Applications for the Vitrifies Glazes and Surface Properties

Sanitaryware glazes are of the raw type and have zirconium silicate as an opacifier. Glaze compounds affect glaze properties such as mechanical strength, surface properties etc. In this study, glazes were prepared in order to observe the effect of zircon presence in glaze and further alumina content. Melting behavior of glazes was determined by using hot stage microscope. Samples were prepared as once-fire and twice-fire with two layers. Surface smoothness, gloss, color and scratchiness of samples fired at approximately 1210 o C were investigated. Introduction Paralleling the improvements on the world ceramic industry, sanitarywares are becoming more open to new improvements and technologies as well. The majority of these studies have been aimed to expand the usage area and to enhance product’s overall properties. Additionally, to be able to produce environmental and user friendly products, many studies have been done. Another main expectation from sanitaryware is having smooth surfaces and as a result of this to achieve easy clean surfaces and products [1-4]. In this study, the achievement of smooth surface texture and easy-clean surfaces were aimed for the sanitarywares using two layers of glazing Experimental Studies In this study, regular zircon containing, zircon free and alumina added glazes were prepared and melting behavior of these glazes was investigated by Leica hot stage microscope. Samples were glazed and fired at 1210 o C under the 4 o C/min firing condition by using Protherm brand lab kiln. In Table 1, information about applied glazes can be seen. In Table 2, Seger formula of zircon free and zircon containing glazes were stated. To evaluate the surface texture and to take pictures of cross section of the fired samples, Olympus BX60M brand optic microscope was used. The microstructure of the samples was examined by using CamScan brand scanning electron microscope and the chemical analyses of crystals and bubbles in to the glazed body were made by EDX. Surface characteristics such as gloss and color were analyzed by using Minolta glossmeter and Minolta spectrophotometer. As a result, considering the final product’s surface smoothness and judging the easy-clean behavior, scratching test was done with HB type pencil. Results and Discussions In Figure 1, commercial glazes cross-section scanning electron microscopy (SEM) picture can be seen. Considering chemical analyses (EDX) obtained from the bubbles in the glaze structure, it was concluded that zircon crystals were moving to surface by bubbles and due to that, surface was becoming uneven (Figure 2). Chemical analysis of this mentioned area is given in Table 3. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 1673-1676 doi:10.4028/www.scientific.net/KEM.264-268.1673

The Effect of Ferrochromium Fly Ash as a Pigment on Wall Tile Glaze

Fly ash is a waste of ferrochromium production which contains high amount of Cr2O3 and Fe2O3. In this study, fly ash was incorporate into pigment recipe for the purpose of coloring due to its high Cr2O3 and Fe2O3 content. Pigments were produced by using Cr2O3, Fe2O3, CoO and fly ash, added to glaze composition at different ratios (wt. 1-5 %). Glazes were applied on ceramic tiles and fired at 1145 °C/ 30 min. Glazed tiles were analyzed by using Autoclave, Harcourt and color measurement tests. Increasing of fly ash content in glaze, the color of glaze changed from brown to grey. The results of Autoclave and Harcourt tests of glazed tiles meet the requirement. This data shows that the fly ash could be used as color additives in glaze.

Effects of hexagonal boron nitride nanoparticles on antimicrobial and antibiofilm activities, cell viability

The objective of this work was to investigate the antimicrobial and antibiofilm activities of hBN nanoparticles against Streptococcus mutans 3.3, Staphylococcus pasteuri M3, Candida sp. M25 and S. mutans ATTC 25175. Minimum Inhibitory Concentration (MIC) of hBN nanoparticles were determined against Streptococcus mutans 3.3, Staphylococcus pasteuri M3, Candida sp. M25 growth. In addition, we aimed to evaluate the cytotoxic effects of hBN nanoparticles on human normal skin fibroblast (CCD-1094Sk, ATCC® CRL 2120 ™) and Madin Darby Canine Kidney (MDCK) cells by using various toxicological endpoints. Cell viability was assessed by MTT, SRB and PicoGreen assays. After experimental analyses, it was revealed that hBN nanoparticles show better MIC results. The MIC values were higher for Streptococcus mutans ATTC 25175 and Staphylococcus pasteuri M3 and lower against Streptococcus mutans 3.3, Candida sp. M25. Surprisingly, hBN nanoparticles showed a high antibiofilm activity on preformed biofilm, which inhibited biofilm growth of S. mutans 3.3, S. mutans ATTC 25175 and Candida sp.M25. These results show that hBN nanoparticles may be an option to control oral biofilms. In cell viability tests, the cells were exposed to 0.025-0.4 mg/mL concentrations of hBN nano particle suspension. The exposure time to the hBN nanoparticle suspensions were 24 h and 48 h. The results indicate that there is no cytotoxic effect on CRL 2120 and MDCK cells at the concentration range of 0.025-0.1 mg/mL. However, on both first and second day, hBN caused mild cytotoxicity on CRL-2120 cells at high hBN concentration (0.2-0.4 mg/mL). Considering all the results of this study, in appropriate concentration (0.1 mg/mL) hBN nanoparticles can be considered a potential safe oral care product.