Julie Juliewatty Mohamed

Effect of Side and Tip Gaps of a Piezoelectric Fan on Microelectronic Cooling

A combination of experimental and numerical analyses is conducted to investigate the coupled effect of side gap (Gs) and tip gap (δ) on the performance of a piezoelectric fan in microelectronic cooling. Two parallel adjustable walls are set at the fan sides to facilitate the variation of Gs. The piezoelectric fan is oriented vertically to the heat source (chip). A 3-D simulation using FLUENT 6.3.2 is performed to assess the transient flow and the resulting heat transfer from the chip. The coupled effect of Gs and δ on the fan tip deflection is detected by a laser displacement sensor (KEYENCE LK-G152). Both Gs and δ had noticeable effects on the flow behavior and Re. The effect of δ is more significant on the heat-transfer coefficient than that of Gs. The flow profiles and the temperature contours are found to be consistent with each other, and the predictions are in good agreement with the experimental results. The piezoelectric fan enhances the heat-transfer coefficient 1.95 to 2.7 times, corresponding to the best and worst cases, respectively.

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.

The Effect of MgO Dopant on the Dielectric Properties of CaCu3Ti4O12 Ceramics

The properties of undoped and Mg-doped CaCu3Ti4O12 (CCTO) ceramics have been studied. The samples were calcined at 900°C for 12 hours, and sintered at 1030°C for 10 hours. X-ray diffraction analysis on calcined samples shown the formation of CCTO phase with trace of secondary phases meanwhile completed formation of CCTO single phase obtained for sintered pellets. The peak positions of Mg-doped CCTO were slightly left-shifted from the undoped CCTO, attributed to the lattice expansion. Scanning electron microscopy analysis showed that the grains size becomes larger with the increment of dopant amount. Enhanced dielectric constant was observed in the Ca1-xMgxCu3Ti4O12 ceramics with x = 0.05 for the frequency range from 1 MHz to 1 GHz. The dielectric loss seem to be at lowest value when Ca1-xMgxCu3Ti4O12 ceramics with x = 0.10 at the same frequency range. The results indicate that Mg ions have effectively changed the properties of CCTO.

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.

Synthesis of Ti3SiC2 via Modified-SHS System through Arc Melting

Inter-metallic compound of Ti3SiC2 was produced via modified-SHS (self-propagating high temperature synthesis). Elemental powders of titanium, silicon and graphite were weighed according to their stoichiometric ratios (3:1:2) respectively. These powders were ball milled for 1 hour, then compacted into cylindrical shape. Synthesis of Ti3SiC2 was carried out by using arc melting method. The effect of different arc melting time of 10, 30 and 60 seconds was studied. Phase formation and microstructure were analyzed by using XRD and SEM. The formation of Ti3SiC2 was confirmed by XRD, and the SEM micrograph shows that the grain is in needle shape. XRD result also shows that the impurities are present in all the samples. TiC appeared to be the common and dominant impurity in all samples, with relatively low intensities in Ti5Si3 and TiSi2 phases. Some raw materials phase was still existed in sample arc melted for 10 and 30 seconds. Hence, it can be deduced that the raw materials had not yet fully taking part in the formation of Ti3SiC2.

Influence of Soda Lime Glass Addition on the Dielectric Properties of CCTO Ceramics

The dielectric properties of CCTO ceramics with soda-lime glass addition was investigated. The addition of soda lime glass was varied from 0 - 0.05 wt.% by solid-state reaction. Both XRD patterns of CCTO and CCTO-glass sintered samples showed the formation of CCTO phase with minor peaks of CuO phase, respectively. The phase area analysis of CCTO and CCTOglass proved that the CCTO phase was found to be decreased while the grain boundaries area of CuO + glass was then increased after the addition of soda-lime glass. The dielectric properties of corresponding samples indicated that both er and tan δ were reduced with glass addition. Thus, it shows that the soda lime glass addition has a significant effect on dielectric properties of CCTO ceramics.

Fabrication of Calcium Doped PlSZT Ceramics using High Planetary Mill Method

Ca-doped modified lead Lanthanum Strontium Zirconium Titanate (PLSZT) ceramic, was synthesized with different concentrations of dopant in order to enhance the properties of PZT. Calcium carbonate, CaCO3 have been used as a source of Ca dopant in the preparation of PCLSZT using high planetary ball mill, palletized and sintered at 1200 oC for 3 hours. The uses of high planetary milling benefit in shorten the time for powder preparation where the calcination was not required. The concentration of CaCO3 was varied from 0.01, 0.03, 0.05 and 0.10 mol% and their effects on phase formation, surface morphology, density and porosity have been studied using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD results showed that all Ca-doped PLSZT samples present a tetragonal phase. Whereas SEM results showed that the grain size of the samples was increased with increasing calcium concentration. In addition, the density was observed to be decreased with increasing amount of Ca concentrations.

Effect of Poling Parameter on Piezoelectric and Dielectric Properties of La and Sr Doped PZT

La and Sr co-doped, modified lead zirconium titanate (PZT) ceramics, with composition Pb0.93La0.02Sr0.05 (Zr0.52Ti0.48) O3 was synthesized by dry-mixed planetary mill. The incorporation of La3+ and Sr2+ in the PZT lattice enhanced the tetragonality and suppressed grain growth thereby promoted piezoelectric and dielectric properties of the ceramics. The objective of this research is to determine the optimum poling parameters on La and Sr co-doped PZT (PLSZT) for better electrical properties. The optimum poling parameters (temperature, electric field and time) have been investigated via design of experiment (DOE) concept for the effective results. The results showed that when using the poling temperature at 140 °C with 4 kV/mm of electric field, the d33 and ɛr values were found to be highest at 327 pC/N and 1620, respectively. It revealed that poling temperature and applied electric field plays a dominant role in influencing electrical performance of PLSZT which may be suitable for possible device applications.

Effect of Sintering Heating Rate on CaCu 3 Ti 4 O 12 Formation

CaCu3Ti4O12 (CCTO) is an electroceramic material with complex cubic perovskite-like oxide. It possessed a giant dielectric constant of about 105 over a wide temperature range (100-600 K). In this work, CCTO was synthesized through solid state method. The effect of different heating rate during sintering process was studied. The raw materials - CaCO3, CuO and TiO2 were wet ball milled for 24 hours and calcined at 900 °C for 10 hours. Then the calcined powder was pressed into pellet shape at 300 MPa. Sintering was done at 1040 °C for 12 hours with different heating rates: 3, 5 and 10 °C/min. The phase formation and surface morphology was investigated by X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM), respectively. The density was measured by Archimedes Principle. XRD pattern proves the CCTO single phase formation for the calcined powder and sintered pellet. The SEM images show the different grain size for different heating rate. The density of the pellet was found to be reduced when faster sintering heating rate was used.