Influence of calcination conditions on phase formation and particle size of indium niobate powders synthesized by the solid-state reaction

A wolframite-type phase of indium niobate, InNbO₄, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The formation of the InNbO₄ phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. Single-phase InNbO₄ powders have been obtained successfully for calcination condition of 900 °C for 4 h or 950 °C for 2 h with heating/cooling rates of 30 °C/min. Higher temperatures and longer dwell times clearly favoured particle growth and the formation of large and hard agglomerates.     

Synthesis, formation and characterization of lead indium niobate–lead titanate powders

In this study, powders of lead indium niobate–lead titanate (1???x)Pb(In_1/2Nb_1/2)O₃–(x)PbTiO₃ (PINT) binary system near the morphotropic phase boundary (MPB) composition with x?=?38 mol% PbTiO₃ are synthesized with the conventional mixed oxide and the wolframite methods via a rapid vibro-milling technique for the first time. The preparation method and calcination temperature have been found to show pronounced effects on the phase formation behavior of the PINT powders. The stabilized perovskite phase form of PINT can be synthesized by the wolframite method, while precursor phases are still found in powders prepared by the conventional method. Finally, this study shows that the rapid vibro-milling mixing technique is effective in preparing the phase pure perovskite of PINT powders.     

Effect of Li addition on phase formation behavior and electrical properties of (K0.5Na0.5)NbO3 lead free ceramics

In this work, Li-modified KNN ceramic compositions ((K_0.5Na_0.5)_1−xLi_x)NbO₃ with x = 0.03, 0.04, 0.05, 0.06, 0.65 and 0.07 were prepared by a conventional solid-state mixed-oxide method. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been found that a morphotropic phase boundary (MPB) between orthorhombic phase and tetragonal phases should exist between compositions with Li contents of 6-6.5%. The Curie temperature (T_c) of the ceramics shifted to higher temperature with increasing Li content. The room temperature dielectric constant was also seen to be higher than the pure KNN ceramics. In addition, the ferroelectric properties were found to enhance at near MPB compositions. This study clearly showed that the addition of Li could improve the dielectric and ferroelectric properties in (K_0.5Na_0.5)NbO₃ ceramics.     

Thermal expansion measurements in the relaxor ferroelectric PIN-PT system

Thermal expansion was measured for the ceramic compositions (1 − x)Pb(In_0.5Nb_0.5)O₃-(x)PbTiO₃ (x = 0.0, 0.1, 0.2 and 0.3) prepared via the wolframite method. The deviation from the straight line below Burns temperature for all the compositions was due to the dynamic polarization fluctuations. Burns temperature was determined and found to increase with increasing PT concentration. The local polarization was calculated from the thermal expansion data. The calculated local polarization and the measured reversible spontaneous polarization were compared and the relaxor behavior of the PIN-PT compositions was analyzed.     

The potential for decentralized reclamation and reuse of household greywater in peri‐urban areas of Bangkok

A survey was conducted of 400 households in the peri‐urban area of Bangkok to investigate typical household water consumption, daily water use activities, public perception towards wastewater reuse and detergent consumption. Four categories of greywater, including cooking, dish washing, bathing and laundry washing wastewater, their properties and potential application for reuse were examined. Average water consumption was estimated to be 208 L/person/day. The wastewater was already reused in 42% of households, and that laundry wastewater was widely used for plant watering and floor washing. More than 80% of households accepted the use of treated greywater, while 50% of households did not accept the use of treated blackwater. Biochemical oxygen demand (BOD), chemical oxygen demand (COD) and suspended solid (SS) were high in cooking, dish washing and laundry, and lower in bathing wastewater, while anionic surfactant were high in laundry and dish washing wastewater. The finding results clearly demonstrate the possibility of greywater reclamation and reuse in the area.     

Dielectric Properties and Relaxor Behavior of PIN Based System

Several compositions in the two PIN based systems (1-x)Pb(In_0.5Nb_0.5)O₃-(x)PbTiO₃ and (0.8-x)Pb(In_0.5Nb_0.5)O₃-(x)PbTiO_3-0.2BaTiO₃ (x = 0.0, 0.1, 0.2 and 0.3) were synthesized via the wolframite method. Dielectric properties were measured in the frequency range between 100 Hz and 100 kHz and were analyzed for understanding relaxor behavior in the system. The temperature dependence of the dielectric properties was analyzed by studying the deviation from the Curie-Weiss law while the frequency dependence of the dielectric properties was analyzed by the Vogel-Fulcher relation. The results showed that the addition of BT increased the dielectric constant and decreased the shift of the maximum dielectric constant temperature (T_m) of (1-x)PIN-(x)PT compositions. Finally, the analysis also confirmed that, when added to PIN, PT decreased and BT increased the relaxor behavior of the PIN-based ceramics.     

Dielectric and Ferroelectric Properties of Complex Perovskite Ceramics Under Compressive Stress

Dielectric and ferroelectric properties of complex perovskite PZT-PZN ceramic system were investigated under the influence of the compressive stress. The results showed that the dielectric properties, i.e. dielectric constant ( εr ) and dielectric loss ( tan δ), and the ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis loops, the saturation polarization ( P(sat) ), and the remnant polarization (Pr) changed significantly with increasing compressive stress. These changes depended strongly on the ceramic compositions. The experimental results on the dielectric properties could be explained by both intrinsic and extrinsic domain-related mechanisms involving domain wall motions, as well as the de-aging phenomenon. The stress-induced domain wall motion suppression and non-180° ferroelectric domain switching processes were responsible for the changes observed in the ferroelectric parameters. In addition,a significant decrease in those parameters after a cycle of stress was observed and attributed to the stress induced decrease in switchable part of spontaneous polarization. This study clearly show that the applied stress had significant influence on the electrical properties of complex perovskite ceramics.     

Brominated phenol–formaldehyde resin as an adhesive for plywood

A brominated phenol–formaldehyde resin was investigated as a plywood adhesive to study the effect of bromine on the physical and flammability properties of this resin. The results of these studies showed that brominated phenol–formaldehyde resin of 10% bromine content by weight of the phenol–formaldehyde resin was suitable to be used as a plywood adhesive. The optimal compressing temperature and compressing time were 110°C and 30 min, respectively. The prepared plywood obtained from the optimal condition gave a high shear strength, good flame retardancy, and good resistance to both hot and cold water. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1918–1924, 2003     

Dielectric and ferroelectric properties of lead indium niobate ceramic prepared by wolframite method

The dielectric and ferroelectric properties of lead indium niobate (Pb(In_1/2Nb_1/2)O₃, PIN) ceramic prepared by an oxide-mixing method via wolframite route were investigated. The 98.5% perovskite fine-grained PIN ceramics with average grain sizes of 1–2 μm were obtained by sintering at 1050 °C for 2 h. The dielectric properties of the PIN were of relaxor ferroelectric behavior with temperature of dielectric maximum (T_m) 53 °C and dielectric constant (_r) 4300 (at 1 kHz). The P–E hysteresis loop measurements at various temperatures showed that the ferroelectric properties of the PIN ceramic changed gradually from the paraelectric behavior at temperature above T_m to slim-loop type relaxor behavior at temperature below T_m. Moreover, the P–E loop became more open at temperatures much lower than T_m. At −25 °C, the maximum polarization is found to be 8 μm/cm² at a field of 30 kV/cm, with P_r value of 2.5 μm/cm² and E_c of +7.5 kV/cm.     

Properties of zeolite Y in various forms and utilization as catalysts or supports for cerium oxide in ethanol oxidation

Zeolite Y in sodium form (NaY) was synthesized using silica source from rice husk, transformed to ammonium form (NH₄Y), and calcined to convert to proton form (HY). The direct conversion of NH₄Y to HY resulted in loss of the zeolite crystallinity and lower surface area. Thus, the NH₄Y was further used in the preparation of cerium (Ce) catalysts. The NH₄Y was also treated with a basic solution in an attempt to generate mesopores but only site defects were likely formed. The supported Ce catalysts with good Ce dispersion were prepared by wetness impregnation of Ce precursor solution on NaY, NH₄Y, and base-treated NH₄Y. Upon calcination, the generated catalysts were notated as Ce/NaY, Ce/HY, and Ce/YB. In catalytic testing on ethanol oxidation at varying temperature in a continuous laboratory-scale fixed-bed reactor, all the zeolites gave low ethanol conversion at 100–300 °C. The catalytic activity significantly improved with the presence of Ce. The Ce/YB showed the higher ethanol conversion and CO₂ yield than Ce/NaY and Ce/HY probably because of the presence of more local site defects on the zeolite.