Key Engineering Materials Vols. 675-676

Abstract: Mixed-phase anatase/rutile titanium dioxide (TiO₂) composite powder is an important material due to the unique properties of photocatalytic activity that is higher than that of the only single anatase or rutile phase. In this study, the anatase/rutile mixed phase TiO₂ composite powders were prepared by ball milling of TiO₂ commercial grade powders. Effect of the anatase/rutile phase ratio and milling time on photocatalytic performance were investigated. The sample phase ratio is evaluated using X-ray diffraction (XRD) meanwhile the composite morphology is characterized using field emission scanning electron microscope (FE-SEM). The overall results revealed that the mixed-phase anatase/rutile provided significant enhancement in photocatalytic performance comparing to only anatase or rutile single phase. In addition, this ball-milling technique is considered as an effective process and cost-effectively on energy saving suitable for preparing anatase/rutile mixed-phase TiO₂ for photocatalytic application.

Abstract: Two different lime plasters with finely crushed brick are studied in this article. In the first plaster the pozzolan mixture was used as silica sand while in the second it was dosed as replacement of the lime substitute and silica sand (the substitution levels being 20% and 50%). Classic lime plaster was used as a reference material. Studied parameters were basic physical properties (measured by water vacuum saturation and by helium pycnometry), characterization of pore system (by mercury porosimetry) and transport of liquid water.

Abstract: The thermoelectric effects in oxide materials are developed to the Seebeck effect for thermal sensing. Thermal sensors are the thermal converters, in which an electrical, magnetic, mechanical, radiation, chemical signal are measured by converting it into heat and measuring the resulting temperature changes in the device. This proposes an analysis the electrical converters and radiation sensors by using single−junction of p−Ca₃Co₄O₉ and n−CaMnO₃ materials are presented into possible thermal sensing. Several thermal converters are measured the signal electrical resistivity, and Seebeck coefficient depended on temperature. Thermal radiation sensors are included the sensitivity, electricity, and specific detectivity. For application, thermoelectric oxide cell can be fabricated crowbar circuit for protection an overvoltage condition of a power supply which it yield 1.2 s turn off switch.

Abstract: Barium cerate (BaCeO₃) ceramics were synthesized via a solid-state reaction technique. Pure phase perovskite powders were obtained at a calcination temperature of 1200 °C. BaCeO₃ ceramics were fabricated from the calcined powder and their properties were investigated. XRD data of the ceramics was consistent with an orthorhombic symmetry. However, the pure phase perovskite of the BaCeO₃ ceramics was only observed for sintering temperatures less than 1500°C. The microstructural analysis indicated that grain sizes of the ceramics increased with increasing sintering temperature. The dielectric constant of the samples had a constant value over a very wide range of temperature. All ceramics showed very good dielectric performance where the ceramics sintered at 1450 °C showed the highest dielectric constant.

Abstract: Spherical rice husk zeolite NaY granules (RH-NaY_g) were prepared by cross-linking of alginate biopolymer and using bentonite as the binder to obtain a uniform shape. The composition of granulation mixture was rice husk zeolite NaY, bentonite clay and alginate in the ratio of 50:30:20, respectively. The RH-NaY_g were calcined at 600 °C to remove alginate and enhance the hardness of granules. Moreover, the RH-NaY_g were determined surface area by N₂ adsorption-desorption before utilization as the adsorbent for adsorption of Cu²⁺ at pH 5 for 90 min. The residual concentration of Cu²⁺ was reacted with NH₄OH to form the blue complex and measured at the wavelength of 606 nm by UV-vis Spectrophotometer. The average adsorption capacity of RH-NaY_g in 5000 ppm Cu²⁺ solution at pH 5 for 90 min was 242.27±0.12 mg/g. Spherical rice husk zeolite NaY granules (RH-NaY_g) were prepared by cross-linking of alginate biopolymer and using bentonite as a binder to obtain a uniform shape. The composition of granulation mixture was rice husk zeolite NaY, bentonite clay and alginate in the ratio of 50:30:20, respectively. The RH-NaY_g were calcined at 600 °C to remove alginate and enhance the hardness of granules. Moreover, the RH-NaY_g were determined surface area by N₂ adsorption-desorption before utilization as the adsorbent for adsorption of Cu²⁺ at pH 5 for 90 min. The residual concentration of Cu²⁺ was reacted with NH₄OH solution to form the blue complex and measured at the wavelength of 606 nm by UV-vis Spectrophotometer. The average adsorption capacity of RH-NaY_g in 5000 ppm Cu²⁺ solution at pH 5 for 90 min was 242.27±0.12 mg/g.

Abstract: In the research, the properties of barium titanate - bismuth sodium titanate [(1-x)BaTiO₃-(x)Bi_0.5Na_0.5TiO₃: (1-x)BT-(x)BNT] ceramics prepared by conventional mixed oxide method with various molecular weight of BNT or x between 0.0 and 0.3 were investigated. The optimum condition for calcined powders of x = 0.0 was found at 900 °C for 2 h, and x = 0.1 - 0.3 were found at 850 °C for 2h. The calcined powders were pressed and sintered at 1000 – 1200 °C for 2h. The phase structure was examined by x-ray diffraction (XRD). The microstructure was examined by scanning electron microscopy (SEM). Density of sintered samples was measured by Archimedes method with distilled water as the fluid medium. It was found that, all various x of (1-x)BT-(x)BNT ceramics XRD patterns display the tetragonality increased with increasing sintering temperature. All the peaks shift to higher angles when increasing x value indicating the decrease of lattice parameter “a” and increase of lattice parameter “c”. The average grains size of (1-x)BT-(x)BNT ceramics was increased with increasing sintering temperature. The highest density was 5.53 g/cm³ and was obtained from the sample sintered at 1200 °C.

Abstract: Today, Use of the natural reducer in the green synthesis of metallic nanoparticles has gained more attention due to the development of eco-friendly technologies in materials science that emphasised in environment-friendly chemicals, solvents and renewable materials. In the present work, bread crust, Browning product of thermally processed bread, extracts have been determined for reducing property by using DPPH and hydroxyl radical scavenging assay. The results showed that bread crust extracts have promising reducing property for the green synthesis of metallic nanoparticles.

Abstract: Silicon-silicon carbide (Si-SiC) composite powders were synthesized by in-situ self- propagating high-temperature synthesis using rice husk ash (RHA)/carbon/Mg as precursors in argon atmosphere. The as-SHS powders were leached by two leaching steps. The microstructure and chemical composition of the obtained Si-SiC composite powders were examined using scanning electron microscope (SEM) and x-ray diffractometer (XRD), respectively.

Abstract: Structure–property relationship has been performed in the lanthanum-modified lead–zirconate–titanate (PLZT) with a lanthanum content 8 and Zr/Ti ratio 40/60. The X-ray diffraction analysis, scanning electron microscopy, and sintering behavior have evidently demonstrated that it is possible to tailor the structural properties of PLZT 8/40/60. Structure of PLZT 8/40/60 had pure perovskite with tetragonal without secondary phase. Tetragonality (c/a) was observed in the range of 1.01093-1.02095. SEM micrographs were shown a development of mean grain size to clarify the development of grain after sintering processing. The result shows that increasing of sintering temperature resulted in mean grain size increasing from 1.70 to 3.08 μm. Ferroelectricity of PLZT ceramics were normal ferroelectric and dielectric constant increased with the increasing sintering temperature.

Abstract: In the present study batch biosorption studies were carried out for the adsorption of Cu (II) from aqueous solution with Amusium Pleuronectes shell. Variables of the batch experiments include initial concentration of Cu (II), solution pH, contact time, were investigated. The experimental results explored that the maximum pH for efficient sorption of Cu (II) was 9. The optimum conditions of sorption were found to be contact time of 200 min, initial Cu concentration 250 mg/L. Another that, the X-Ray Driffraction (XRD) was used to confirmed the binding site between the bio sorbent and the Cu (II) ions. From XRD pattern the result suggests that the mechanism of bio sorption is rather chemisorption than physical adsorption.