Materials Science Forum Vol. 840

Abstract: La_0.8Sr_0.2MO_3+δ, (M=Mn, Fe, Cr, Co) ceramics were prepared by using solid state reaction method. All raw materials were mixed and ground using mortar. Homogenized powders were calcined at 900°C for three hour followed by grounding and uniaxial pressed at 100MPa. Compacted pellets were further pressed using cold isostatic pressing machine at 2600kg/m.s and sintered at 1300°C with heating rate 5°C/min for 4 hour. Crystal structure and phase transformation of sintered samples were obtained using X-ray diffraction. Density and porosity are measured by using Archimedes principle. The morphology of sintered samples is observed using scanning electron microscopy, while elemental analysis using the EDX.

Abstract: The effect of glass addition on the properties of CaCu₃Ti₄O₁₂ (CCTO) ceramics was studied. CCTO ceramics with BaO-SrO-Nb₂O₅-B₂O₃-SiO₂ (BSNBS) glass additive were prepared using solid state reaction method. The raw materials of CCTO and BSNBS were wet mixed separately for 24 hours, dried overnight and subsequently the BSNBS powders was melted at 1450°C for 2 hours while CCTO powders was calcined at 900°C for 12 hours. BSNBS glass then was grinded to form a fine powders. Different weight percentages of BSNBS powder were added into CCTO and the powders were wet mixed at 24 hours. The mixtures were dried, compacted at 250 MPa and then sintered at 1050°C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase for all sintered samples while secondary phase of CuO phase was identified for sintered BSNBS 1.0 sample. Observation on Scanning Electron Microscopy (SEM) micrographs showed abnormal grain growth was seen in CCTO sample and grain size of the samples become finer with increasing the concentration glass addition. CCTO sample obtained the highest dielectric constant (8670) while the lowest dielectric loss (0.38) was recorded by BSNBS 0.10 sample, measured at 1 MHz.

Abstract: Despite the impressive development in understanding transformation toughening, tailoring the toughness of zirconia toughened alumina (ZTA) ceramics remained a major challenge. In our research, a simple route based on the powders mixing process of ZTA powders with varying CeO₂ additions (0 - 10 wt.%) is developed to investigate this issue. The experimental results clearly reveal that the fracture toughness of ZTA ceramics can be tailored by mixing of ZTA starting powders.

Abstract: Sr - doped NiO ceramic was prepared using solid state method. The calcination temperature used at 950 oC for 4 hours and the sintering temperatures was varied from 1100 to 1300 oC for 3 hours. The results depict the microstructures increasing in grains size (1-8 μm) by increase of sintering temperatures. The density and porosity testing support the result of microstructures analysis. The larger grains size induced the increase in density and lower in porosity. The dielectric properties is observed in a wide frequency range of (1 - 1 000 MHz). The increase of dielectric constant is associated with the decrease of dielectric loss. The optimum sintering temperature was obtained at 1200 oC depict the grain size range (1 - 2 μm) with highest dielectric constant (1.61 x 103) and lowest dielectric loss (1.15) at 1MHz.

Abstract: PZT ceramic is synthesis by using sol gel method.Introducing a dopant to the pure PZT can help to enhance the properties of the piezoelectric ceramic. The effects of sintering temperature on phase formation, densification of the ceramics have been investigated using XRD, SEM and Archimedes method. The bulk density and porosity of PZT decreased as the sintering temperature increased.

Abstract: This paper aims at studying the porous cordierite ceramics prepared by using the non-stochiometric cordierite composition formulation (2.8MgO.1.5Al₂O₃.5SiO₂) by PU sponge impregnated method. The ceramic suspension were prepared with non-stoichiometric formulation of cordierite and sintered at 1250 °C, 1275 °C, 1285 °C, 1300 °C and 1325 °C. The phase transformation of non-stochiometric formulation cordierite was investigated by XRD. This paper also aims to compare the effect of linear shrinkage, porosity and density of 20 wt.% PEG treated PU sponge with untreated PU sponge respectively corresponding to different pore content (100 ppi, 80 ppi, 60 ppi, and 40 ppi). The pore structure was analyzed by SEM.

Abstract: Ceramic foam are a class of high porosity materials that are used for various applications. In this study, foam ceramic porcelain powder was produced by using polymeric sponge replication method at different solid content ranging from 30 to 50 wt. %. Properties of ceramic foam was characterized for porosity and density. Ceramic foam then grafted with methyltriethoxysilane (MTMS) at different concentration ranging from 0 to 9.0% v/v to determine hydrophobic effect and oil absorption capacity. From the results, it was found that the density of ceramic foam increased while porosity was decreased with increasing solid contents. It is clearly seen that, MTMS grafting contribute to hydrophobic effect of ceramic foam which enable repelling of water. The amount of oil absorbed by ceramic was found increased by increasing concentration of MTMS for all solid contents. As conclusion, MTMS give significant effects on hyrdophobic ceramic foam and produce good absorption capacity. The lower solid content produced better oil absorption compared to higher solid content due to presence of higher porosity.

Abstract: ZTA based ceramic composite system is widely accepted as cutting tools for many of these harder and wear resistant workpiece materials. This is due to their beneficial mechanical properties i.e. high temperature strength, high hardness and ability to maintain its cutting edge shape at higher temperatures. Although a lot of works have focused on the effect of various sintering additives on the ZTA ceramic system, the effect of Magnesia (MgO) and Titania (TiO₂) on ZTA has not yet been studied. In this work, the physical properties of Zirconia Toughened Alumina (ZTA) ceramic composite with MgO and TiO₂ as additives was investigated. The composition of TiO₂ varied from 0 wt% to 3.5 wt% whereby other materials such as Al₂O₃, Yttria Stabilized Zirconia (YSZ) and MgO were kept at constant weight percentage. Sintered samples were then tested and analyzed by XRD, Vickers hardness and high precision densimeter to investigate phase content, hardness value and densification respectively. Results showed that the solubility limit of TiO₂ in ZTA-MgO ceramic composites is at 2.0 wt%. Further addition of TiO₂ resulted in the formation of secondary phase known as Zirconium titanium oxide (Zr_0.35TiO_0.65O₂) which deteriorate the properties exhibited by ZTA-MgO-TiO₂ ceramic composites.

Abstract: In recent years, there has been an increasing interest on high dielectric constant that have significant applications in electronic devices. Dielectric materials have many technological applications such as capacitors, resonators and filters. High dielectric ceramic capacitors based perovskite oxides are necessary for modern electronic devices and are found to be suitable for a wide range of applications. Subramanian et al. discovered the high dielectric constant of CaCu₃Ti₄O₁₂ (CCTO) ~ 10,000 at room temperature. CCTO has the cubic perovskite crystal structure and high dielectric constant of ~ 10⁴ up to 10⁵ at radio frequency and good temperature stability over a wide temperature range [1,2]. These properties were desired for various microelectronic applications. With the high dielectric constant, the material can store more charge and the values make CCTO an attractive material for ultra-high energy density capacitors. However, this properties can be accomplished if single phase of CCTO is formed. Many research have been done recently on the synthesis of the cubic perovskite CCTO and many techniques are working such as sol-gel route [3], combustion techniques [4], molten salt process [5] and etc., but this technique is difficult and complex process during sample preparation.

Abstract: Wood plastic composites (WPC) have been produced by compounding meranti wood flour (WF) with polypropylene (PP) copolymer using a twin-screw extruder. The meranti WF content was varied from 30 to 60 wt.%. The mechanical properties, i.e. tensile, flexural and impact of the composites were determined on injection-molded specimens. The tensile fractured surfaces were used to study the morphological properties of the composites. The result shows that the increment in WF content has given a significant improvement in modulus properties but at the expense of strength and toughness properties. A commercial maleic anhydride grafted polypropylene (MAPP) compatibilizer at 5 wt.% was incorporated into the PP40/WF60 formulation. The strength, stiffness and toughness properties were improved significantly in the presence of MAPP. The morphology of the composites was studied by scanning electron microscopy (SEM). The improvement of the fibre-matrix adhesion between the WF and PP matrix as revealed by SEM is believed to be one of the major reasons for the improved mechanical properties.