Investigation Of Magnesium Doped Calcium Copper Titanate (Cacu3ti4o12) On Ca And Cu Site Prepared By Solid State Reaction Method

In this research, the effect of magnesium (Mg) dopant on dielectric properties of CaCu3Ti4O12 (CCTO) was investigated. Undoped CCTO and Mg-doped CCTO on Ca and Cu site (Ca1-xMgxCu3Ti4O12 and CaCu3-xMgxTi4O12 have been prepared by solid state reaction method. Starting materials of CaCO3, CuO, TiO2 and MgO were wet milled for 1 hour by using three wetting agents which are acetone, deionized water and ethanol. XRD analysis on calcined powders shows the formation of CaCu3Ti4O12 (CCTO) phase with present of minor secondary phases (CuO and TiO2). Mixing process in deionized water gave better mixing and produces higher intensity of CCTO phase after calcined at 900°C for 12 hours. Compacted pellet was sintered at 1020°C, 1030°C and 1040°C for 10 hours. The sintering profile of 1030°C/10 hours was identified as an optimum parameter in the formation of single phase of CCTO with fine grain growth, high density and low porosity. MgO composition had been verified from 1 until 10 mole percent for Ca and Cu site of CCTO structure. SEM images show that the grain size becomes larger with increasing the concentration of dopant. Density and porosity of sintered samples were improved by dopant

Effect of Calcination Temperature on Dielectric Properties of CaCu3Ti4O12 Ceramics

AbstractThe effect of calcination temperature on the properties of CaCu3Ti4O12 (CCTO) ceramics was studied. CCTO ceramics were prepared using solid state reaction method. The raw materials of CCTO were wet mixed for 24 hours and was dried overnight. CCTO powders were then calcined at three different temperature which is at 900̊C, 930̊C and 985̊C for 12 hours. The calcined powders were compacted at 250 MPa and then were sintered at 1040̊C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase and secondary phases of CuO for C900 calcined powder but single phase of CCTO was obtained by C930 and C985 calcined powders. Single phase of CCTO also were seen for all sintered samples. Observation on Scanning Electron Microscopy (SEM) micrographs showed abnormal grain growth or large grain size was seen in C900 sample and finer grain size was observed for C930 and C985 sintered samples. C900 sintered sample obtained the highest dielectric constant (10,462) and the lowest dielectric loss (0.061) measured at 1 MHz

Risk factors associated with development of dengue haemorrhagic fever or dengue shock syndrome in adults in Hospital Tengku Ampuan Afzan Kuantan

A retrospective study was conducted to investigate 183 serologically-confirmed cases of dengue fever (DF) admitted from October 2004 to March 2005 in a large hospital in Pahang. Clinical and laboratory features, progress and outcome of these patients were analysed in order to identify risk factors associated with development of dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS). Individually, we found that older patients, secondary dengue infection, high baseline haematocrit levels, low platelet levels and prolonged activated partial thromboplastin time (APTT) ratio were significant associations with bleeding tendencies. Of these risk factors, haematocrit and APTT ratio were two independent significant risk factors on multivariate analysis. Older patients with primary infection and younger patients with secondary infection had significant bleeding tendencies. We also verified the validity of the haematocrit levels suggested as cut-off levels for plasma leakage for the Malaysian population by Malaysian Clinical Practice Guidelines for Dengue Infection in Adults (2003)

Effective dielectric loss (tan δ) reduction of CaCu3Ti4O12 (CCTO) via various addition of glasses

Addition of various glasses has successfully reduced tan δ of CCTO‐based ceramics. Less amounts (0‐1.0 wt%) of glasses (BaO‐SrO‐Nb2O5‐B2O3‐SiO2 [BSNBS] and SrO‐B2O3‐SiO2 [SBS], respectively) were added into pure CCTO and sintered at 1040°C for 10 hours. The phase formation and microstructure of each sample were characterized using X‐ray diffraction and scanning electron microscopy, respectively. The dielectric behavior of the samples was measured at 1 MHz. The addition of BSNBS and SBS glasses (≤0.5 wt%) successfully reduced tan δ of CCTO from 0.5 until 0.4 and 0.39, respectively, and simultaneously increased εr. Smaller tan δ and ɛr were further obtained when the added glasses were more than 0.5 wt%. These behaviors were due to segregation of glasses together with precipitation of CuO which decreased the grain size, and caused the presence of pores at grain boundaries. Therefore, small amount of various additions of glasses could modify the CCTO dielectric properties

Characterization of microstructures evolution on electrical responses of CaCu3Ti4O12 ceramics

CaCu3Ti4O12 (CCTO) ceramics was prepared by solid state method. The raw materials of CaCO3, CuO, and TiO2 were ball milled for 1 h. The mixed powders were calcined at 900 oC for 12 h. The phase formations of calcined powders were analyzed by using X-ray Diffraction (XRD). The calcined powders were pressed into pellet shape at 300 MPa and then were sintered at 1020, 1030 and 1040 oC for 10 h, respectively. The sintered samples were subjected to XRD, Scanning Electron Microscopy (SEM) and Impedance Analyzer for phase formation, microstructural and dielectric measurement analysis respectively. XRD analysis shows the presence of CCTO and secondary phases for the calcined powders. The samples sintered at 1020 and 1040 oC show the formation of CCTO phase with trace of secondary phases while complete formation of CCTO single phase was obtained for the sample sintered at 1030 oC. SEM analysis shows the phenomena of abnormal grain growth for the samples sintered at 1020 and 1040 oC while fine grain was observed for the sample sintered at 1030 oC. Sample sintered at 1040 oC was the densest sample while the sample sintered at 1020 oC had the highest percent of porosity. The highest dielectric constant (-3748) was achieved for samples sintered at 1040 oC while the lowest dielectric loss (-0.025) was obtained for the samples sintered at 1020 oC. These results indicate that sintering temperatures 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 oC for 12 h before sintered at 1040 oC for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 oC 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 while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude

Microstrip patch antenna: A review and the current state of the art

The mobile technology is fast-developing nowadays owing to its large impact on social life. Accordingly, there is a need to study the progress of the antenna systems as they are considered as core devices for wireless technology. The modern antenna designs allow a single element to be employed in many systems. The microstrip patch antennas are essentially considered in the advancement of the latest communication mechanisms in contrast to the conventional type because they offer the advantage of being low profile along with simple or inexpensive manufacturing procedures. In the recent four decades, extensive research has been carried out on the antenna systems. Consequently, this review paper provides a comprehensive account of the former and subsequent research achievements of the microstrip patch antennas. The various types of systems considered for comparison include millimeter-wave, broad banding, dual/multi-band or reconfigurable structure, size-reduction, compact, low profile, impedance bandwidth, high gain or linear and circular polarization applications. © 2019, Institute of Advanced Scientific Research, Inc.. All rights reserved

A Novel Negative Meander Line Design of Microstrip Antenna for 28 GHz mmWave Wireless Communications

The increasing applications for nomadic computing have experienced enormous development over the preceding decade. This has eventually caused the lack of bandwidth. Therefore, to accomplish the need of consumers, compact antennas shall be designed for mmWave wireless communications. Consequently, this paper presents a novel negative meander line based microstrip antenna system being composed of inductors (L) and capacitors (C). A detailed impedance analysis of the configuration is reported. The effects of changing the radiating element’s width and length on the resonant frequency have been studied. The finalized arrangement involved 243 sq. mm area and functioned at 28 GHz with a bandwidth of 2.16 GHz. At resonant frequency, the system exhibited gain and efficiency values of 8.40 dBi and 83.51%, respectively. Furthermore, the proposed design demonstrated better bandwidth and gain capabilities in comparison with the conventional microstrip patch antenna and meander line antenna