Mohamad Johari Abu

Effect of Excess Silicon on the Formation of Ti3SiC2 Using Free Ti/Si/C Powders Synthesized via Arc Melting

The aim of this study is to investigate the effect of excess silicon on the formation of from free Ti/Si/C powders synthesized via arc melting. The reactant mixture was prepared according to the off-stoichiometric ratio of 3Ti : ()Si : 2C, where (excess Si) varied from 0 to 0.5. Samples were analyzed using X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), and energy-dispersive spectroscopy (EDS). The relative density and porosity of products were calculated using the Archimedes method. Through optimization of the arcing schedules (time) and excess Si amounts, 86.9 wt% of with a relative density of 86% was obtained. For all products, was identified as the main phase, while TiC, , and were identified as secondary phases. grains were in the form of elongated platelets; they were nucleated and grew on the surface of equiaxed TiC grains. The microporosity present in the TiC-equiaxed grains affected the density and porosity of the products.

Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

(1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss w...

Synthesize CCTO Using Different Mixing Media

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.

Effect of Calcination Temperature on the Breakdown Strength and Energy Density of CaCu 3 Ti 4 O 12 Ceramic

The effect of calcination temperature on the breakdown strength and energy density of CaCu3Ti4O12 (CCTO) ceramics was studied. CCTO ceramics were prepared via solid state reaction method. The raw materials of CCTO were wet mixed for 24 hours and then dried overnight in oven. CCTO mixtures were calcined at three different temperature which is at 900°C, 930°C and 950°C for 12 hours. The calcined powders were compacted at 250 MPa and then were sintered at 1040°C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase and secondary phases of CuO and CaTiO3 for C900 calcined powders but single phase of CCTO was obtained by C930 and C950 calcined powders. Single phase of CCTO also were seen for all sintered samples. Observation on Scanning Electron Microscopy (SEM) micrographs showed large grain size was seen in C900 sintered sample and finer grain size was observed for C930 and C950 sintered samples. C900 sintered sample obtained highest dielectric constant (8617), highest breakdown strength (7.92 kV/cm), highest energy density (2.392 J/cm3).

Dielectric Properties of CaCu3Ti4O12/Al2O3 Composites

In this work, (1-x)CaCu3Ti4O12/xAl2O3 (x = 0, 0.01, 0.03, 0.05 and 0.1) composite samples were prepared by the conventional solid-state reaction method. The dielectric properties of the samples were investigated at frequency range of 20 – 106 Hz. X-ray diffractogram results show that the samples with Al2O3 sintered at 1040 °C/10 h are mixed phase and consist of CaCu3Ti4O12, CuAl2O4, TiO2 and Al2O3. The average grain size of the samples increased greatly for x = 0.01, then abruptly depressed for x ≥ 0.03. Al2O3-added (x = 0.01) has been shown to increase the dielectric permittivity (ε’) up to ~5000 over frequency range of 102 – 105 Hz, while retaining the dielectric loss (tan δ ~ 0.15) at 1 kHz. With further increase of Al2O3 content, the ε’ and tan δ values of the samples are decreased monotonically in all frequency ranges. The improvement of dielectric properties in the composite sample was attributed to the enhanced grain boundary resistance.

Heterogeneous Combustion of Ti/Si/C Powders with Estimated Ti3SiC2 Routes Morphologies

In this study, about 62.2 wt% Ti3SiC2 was synthesized via tungsten inert gas (TIG) welding method, as potential in advanced material applications. This arced sample was characterized using XRD and FESEM analysis to observe the phase presence, and its morphology. Ti3SiC2 phase favours to form at 5 s and produces elongated platelets (Ti3SiC2) grain, micro-porous equiaxed (TiC) grain and melt regions (Ti-Si), when observed at the dense surfaces. Meanwhile, fine dendrite, quasi-spherical, and pyramidal grains were observed at the pore sites. The laminate dendrite of Ti3SiC2 was estimated to form at the origin of TiC faced pyramidal crystal, which nucleated toward TiC pyramidal crystal surface at the specific angle.