Reuse of glass waste in the manufacture of ceramic tableware glazes

Today, various studies are carried out to spread the understanding of sustainability. The sustainability of production processes gains importance in corporate areas. In this study, the use of glass waste instead of frit used in glaze compositions in the ceramic industry was evaluated. The chemical and physical properties of glass wastes on samples were examined. The glaze formulations were prepared using 3%, 5%, and 8% by weight of glass waste instead of frit. Glass wastes were added to glaze compositions and 12 different glaze formulation studies were carried out. Transparent, Opaque, and Matte test glazes were prepared with glass waste added glaze formulations, and these glazes were applied to ceramic bodies. SEM (scanning electron microscope) analysis of standard glaze and glass waste added glazes was performed to determine the microstructural and morphological characterizations. Also, surface whiteness, brightness, L*a*b values, glaze flows, harcort test results, and final water absorption values were compared. As a result of the studies, it has been determined that it is appropriate to use 3% glass waste by weight instead of the frit in the production of ceramic tableware.     

Macroporous poly(N-isopropylacrylamide) networks

Summary Effects of the gel preparation temperature T _prep and the initial monomer concentration c on the swelling and the porosity properties of poly(N-isopropylacrylamide) (PNIPA) networks are described. PNIPA networks were prepared by free-radical crosslinking copolymerization of N-isopropylacrylamide and N,N'-methylene(bis)acrylamide (BAAm) in aqueous solutions. The crosslinker (BAAm) concentration in the initial monomer mixture was kept constant at 30 wt %. It was shown that macroporous PNIPA networks with a stable porous structure can be prepared at T _prep = 22.5°C and at an initial monomer concentration c > 5 w/v %. The PNIPA networks contain pores of about 0.1 μm in radius, corresponding to the interstices between the microspheres. The experimental data also show collapse of the porous structure in PNIPA networks formed at higher temperatures. Received: 30 January 2002 / Revised version: 16 May 2002 / Accepted: 1 June 2002     

Optimizing the structural and photocatalytic performance of Ag-decorated ZnO/Zn(OH)2 nanoparticles for RhB degradation

In this study, as-prepared and Ag-decorated ZnO/Zn(OH)₂ composite nanoparticles (NPs) were obtained using the sol–gel technique. First, the effect of aging on the structural, optical, and morphological features was examined. Ag NPs can interact with the electronic structure of ZnO/Zn(OH)₂ NPs, resulting in changes in their energy levels. It was found that the composite NPs obtained after 6 h solution aging increased in full width at half maximum and good crystallinity of the structures from the X-ray diffraction (XRD) measurements. The Raman spectrum supports the experimental data obtained from XRD and Fourier transform infrared, a material containing a mixture of ZnO and Zn(OH)₂. From the morphological study, Ag NPs were successfully decorated on the ZnO/Zn(OH)₂ surface, and composite NPs did not change the morphological appearance of the structure. Second, the photocatalytic performance of the samples was investigated. In the experimental setting, ultra-violet A light was employed as the irradiation source, whereas rhodamine B (RhB) was used as the dyestuff. The photo-degradation of the RhB dyestuff on composite NPs was observed to be 98.5% and 92.5% for 6 and 2 h aged samples, respectively. On Ag NPs, the catalytic performance of the sample was increased up to 95% after 180 min.     

The Effect of Different Polishing Sequences on the Adhesion of Streptococcus mutans to Feldspathic Porcelain

The aim of this research was to determine whether extra-oral surface treatments on feldspathic porcelain surfaces influence initial adhesion of Streptococcus mutans. Ninety-six porcelain specimen discs were fabricated and divided into six equal groups according to surface treatment: fine-grit diamond polishing (Group 1); self-glazing (Group 2); overglazing (Group 3); overglazing followed by a finishing procedure and then overglazing (Group 4); Pearl Surface polishing (Group 5); and Diamond Twist SCL^TM polishing (Group 6). Surface roughness and hydrophobicity were assessed. An S. mutans suspension was incubated on each specimen group and evaluated. A one-way analysis of variance, post-hoc Tukey honestly significantly different test, Friedman test, and t-test were used for statistical analysis. Group 1 showed the highest surface roughness (p < 0.001) and bacterial adhesion (p < 0.05). Groups 5 and 6 specimen surfaces presented significantly higher contact angles (p < 0.05). Group 1 had the highest S. mutans adhesion, followed by Groups 3, 5, 6, 2, and 4 (p < 0.05). Reglazing after grinding may therefore decrease bacterial adhesion beneficially.     

Chemical stability of KNbO3, NaNbO3, and K0.5Na0.5NbO3 in aqueous medium

In recent years, potassium sodium niobate (K_0.5Na_0.5NbO₃, KNN) has become popular and promising among perovskite lead‐free piezoceramic systems. In this study, the chemical stability of KNN powders in aqueous medium was investigated as a function of pH, time, and powder surface area. To better understand the dissolution behavior of the complex KNN stoichiometry, subconstituents such as potassium niobate (KNbO₃, KN) and sodium niobate (NaNbO₃, NN) were investigated separately first. Results showed that all of the cations in the structure underwent dissolution in different values. Indicating that KNN undergoes incongruent dissolution in aqueous medium, the dissolution of A site cations was higher at lower pH while the dissolution of B site cations increased at higher initial pH. The order of released cation concentrations (C_A1 = K > C_{A2 = Na} > C_B = Nb) fits with inverse relationship of cation field strength (FS) order, B = Nb⁵⁺_FS > A₂ = Na⁺_FS>A₁ = K⁺_FS, at pH 4, 7 and 10 for NN, KN, and KNN. Calculated diffuse layer thickness from the ICP data confirmed to outer amorphous layer in TEM image. Also, the ratio of normalized cation concentration versus surface area of powders showed that incongruent dissolution kinetic was driven by the diffusion step.     

In Vitro Cytotoxicity of D18 and Y6 as Potential Organic Photovoltaic Materials for Retinal Prostheses

Millions of people worldwide are diagnosed with retinal dystrophies such as retinitis pigmentosa and age-related macular degeneration. A retinal prosthesis using organic photovoltaic (OPV) semiconductors is a promising therapeutic device to restore vision to patients at the late onset of the disease. However, an appropriate cytotoxicity approach has to be employed on the OPV materials before using them as retinal implants. In this study, we followed ISO standards to assess the cytotoxicity of D18, Y6, PFN-Br and PDIN individually, and as mixtures of D18/Y6, D18/Y6/PFN-Br and D18/Y6/PDIN. These materials were proven for their high performance as organic solar cells. Human RPE cells were put in direct and indirect contact with these materials to analyze their cytotoxicity by the MTT assay, apoptosis by flow cytometry, and measurements of cell morphology and proliferation by immunofluorescence. We also assessed electrophysiological recordings on mouse retinal explants via microelectrode arrays (MEAs) coated with D18/Y6. In contrast to PFN-Br and PDIN, all in vitro experiments show no cytotoxicity of D18 and Y6 alone or as a D18/Y6 mixture. We conclude that D18/Y6 is safe to be subsequently investigated as a retinal prosthesis.     

Optimization of electro-blown polysulfone nanofiber mats for air filtration applications

Durable, robust, and hydrophobic air filtration media was produced via electro-blow spinning (EBS) technique using polysulfone (PSU) due to its superior properties. To our knowledge, this is the first optimization study of PSU nanofiber production via EBS technique for air filtration applications. Concentration, air pressure, and voltage were determined as independent variables for the optimization based on “smaller is the better” approach of Taguchi Design of Experiment. The optimized values which supplied the smallest average fiber diameter (AFD) possible were obtained as 13 wt% PSU, 3 bar, and 7.5 kV. The AFD of the sample obtained from the confirmation experiment was calculated as 105 ± 34 nm. Surface morphologies, porosity values, and wettability behaviors of the samples were investigated by using scanning electron microscopy, gravimetric method, and water contact angle measurements, respectively. PSU nanofiber mats exhibited superhydrophobic behavior (water contact angle values up to 159.8°) which is important for various separation processes. Samples prepared at different deposition times (15, 30, 45, and 60 min) were investigated in terms of particle capture efficiency and pressure drop. The 0.3 μm particle filtration efficiency was found to be 98.09% at an expense of 202 Pa pressure drop which would be suitable for various respiratory and HVAC filter applications.     

A novel method for measuring dynamic contact angles of fibers with spindle-knots

The determination of the dynamic contact angle is of significant interest for the characterization of the wettability of technical fibers and textiles in diverse fields of science and technology. There exist traditional methods for dynamic contact angle measurements of flat surfaces and of fibers with a uniform cross-sectional shape along the fiber. So far, however, no method has been reported which is suitable for structured fibers, particularly for spindle-knotted structured fibers of varying cross-sections. This article describes a new method for measuring the dynamic contact angle for polydimethylsiloxane (PDMS) spindle-knotted structured fibers. The method is an outcome of integrating the results obtained from experiments (applying force tensiometry) and a proposed theoretical model describing such fibers. The reliability and conformity of the results are shown by comparing the measured dynamic contacts angle of PDMS as spindle-knot and as a flat surface. This method may pave the road for better wettability analysis of various structured fibers. It also allows to measure the local receding and advancing contact angles for macroscopic/microscopic structured fibers (especially when they are not accessible as flat surfaces) against the various test liquids.     

Can we restore the colour of long-term discoloured resin composites by noninvasive methods?

The aim of this study is to investigate the effect of toothbrushing and paste repolishing on the colour restitution of long-term coffee discoloured prefabricated and direct resin composites. One prefabricated (Componeer-Coltène) and three direct resin composites (Brilliant Ever Glow-Coltène, Essentia-GC, Harmonize-Kerr) were tested. Componeer samples were prepared with and without polishing while the other groups were all polished. After baseline colour-measurement, the specimens were immersed in coffee for 3-month and colour-measurement was repeated, then a simulation of 1-year of toothbrushing (Toothbrush Simulation ZM-3.4-SD Mechatronics) with Pro-Expert Professional Protection-Ipana, 3D White Luxe Perfection-Ipana, and White Ruscello-GC toothpaste was performed. Colour-changes (ΔE) after toothbrushing and repolishing with polishing paste (Enamelize, Cosmodent) were calculated. The discolouration occurred after prolonged exposure to a coffee solution was above the clinically acceptable level of ΔE = 2 in all groups, except Componeer polished group. The lowest discoloured group was Componeer polished (ΔE = 1.66 ± 0.32) while the highest was Essentia group (ΔE = 4.30 ± 0.48). The samples toothbrushed with White Ruscello exhibited the greatest colour restitution (ΔE = 2.06 ± 0.75) (P < .05). After paste repolishing, slight colour restitution was observed among all the groups, but the differences between them remained the same as after the toothbrushing procedure. Prolonged exposure to coffee solution affects the colour of the resin composites and noninvasive methods can provide colour restitution below the critical value for visual perception (ΔE = 3.3). Noninvasive procedures such as toothbrushing with a whitening toothpaste or repolishing with a polishing paste may ensure the colour restitution of direct resin composite restorations until a clinically acceptable level.     

Restriction fragment length polymorphism analysis of highly virulent strains of infectious bursal disease viruses from Holland, Turkey, and Taiwan

Ascorbyl free radical (AFR), can be considered as an atoxic and endogenous indicator of oxidative stress. The purpose of our experiments was to investigate the influence of the severity and length of ischemia on the extent of AFR release during myocardial ischemia and reperfusion. For that purpose, isolated perfused rat hearts were submitted to a global ischemia, either total (residual flow 0%) or low flow (residual flow 5%), of 20 or 60 min length. Coronary effluents were collected at different times of experimentation and analyzed with Electron Spin Resonance (ESR) spectroscopy. AFR ESR doublet (g = 2.0054, aH = 0.188 MT) was not detected in coronary effluents collected during control perfusion periods. Nevertheless, during low-flow ischemia, a weak AFR release was noted. Moreover, a sudden and massive AFR liberation was observed at the time of reperfusion: this AFR release was weaker after low-flow ischemia than after total ischemia and was enhanced when the duration of ischemia increased from 20 min to 60 min. The large liberation of AFR noticed during global total ischemia was associated with a greater depression in myocardial contractile function and a lower recovery in coronary flow. In conclusion, our study demonstrates that AFR production at the time of reperfusion depends on the duration and strength of the ischemia, and is related to free radical injury. According to previously described ascorbate/AFR properties, we can conclude that AFR liberation in coronary effluents could represent a marker of oxidative stress during ischemia and/or reperfusion of hearts. This AFR release could be considered a sign of the severity of the ischemic episode, and could be related to the functional impairment during reperfusion.