Properties of a CaCu3−xMn4+xO12 system synthesized via a solid-state reaction

Zainal Arifin Ahmad 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.6

Effect of rice husk ash and silica fume in ternary system on the properties of blended cement paste and concrete

Zainal Arifin Ahmad,Bun Kim Ngun,Hasmaliza Mohamad,Etsuo Sakai 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3

The effects of rice husk ash (RHA) and fume silica (SF) in both binary and ternary systems on the properties of cement pastes and the compressive strength of concretes were studied. The amount of cement replacement in both systems was 15%. The free calcium hydroxide (Ca(OH)2) content was analyzed using XRD and TG/DTA for the hardened cement pastes. The results showed that the amount of Ca(OH)2 decreased significantly the curing ages for all blended cement pastes. At 28 days, the amount of Ca(OH)2 in OPC is 17.31%, 8.18% in RHA and 6.43% in SF replacements, respectively. The ternary system similarly indicates a significant reduction of Ca(OH)2 content. The compressive strength of concretes was improved significantly by blending the aforementioned materials in both systems. In the ternary system, the concretes containing 7.5%SF and 7.5% RHA gave remarkable improvement in the compressive strength. For example after 90 days curing, the strength is 57.8 MPa whilst only 47.5 MPa for OPC. Therefore, the application of proper ratios of RHA and SF in a ternary system is able to increase the properties of the concrete.

Microstructure Evolution and Shear Strength Study of Sn–9Zn and Sn–8Zn–3Bi on Cu Substrate

Ramani Mayappan,Zainal Arifin Ahmad 한국전기전자재료학회 2024 Transactions on Electrical and Electronic Material Vol.25 No.1

In electronics assembly, solder joints not only serve as mechanical supporters-, but also as heat removers. Therefore, solder joint reliability is a major concern not only during production, but also during the life time of electronic products. It can be pointed out that reliability of solder joint determines the lifetime of electronics products. This issue becomes more important with the use of Pb-free soldering alloys. This study focuses on the reliability of Sn–9Zn and Sn–8Zn–3Bi lead-free solder joints with Cu substrates. This study deals with interface intermetallic morphology, solder joint strength and fracture surface analysis after isothermal aging at 50, 100, and 150°C for 100, 250, and 500 h. For all aging conditions, a flat Cu 5 Zn 8 intermetallic was formed, and as the aging conditions increased, Cu atoms diffused through the intermetallic to form isolated Cu5 Zn8 intermetallics in the bulk solder. Furthermore, Sn atoms from bulk the solder diffused through the intermetallic to form Cu6 Sn5 on the Cu side. The formation of a thick Cu5 Zn8 intermetallic and the diffusion of Sn and Zn atoms created a depletion zone near the solder/intermetallic boundary, which weakened the joint strength. As the intermetallic layer thickness increased, the joint strength decreased as the aging increased. The fracture path generally occurred at the bulk solder/intermetallic boundary under all aging conditions.

Effects of compaction pressure on lead zirconate titanate piezoelectric and dielectric properties prepared via high planetary mill

Nor Fatin Khairah Bahanurddin,Mohammad Hafizuddin Jumali,Julie Juliewatty Mohamed,Zainal Arifin Ahmad 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.2

Lead Zirconate Titanate (PZT) had previously been used as actuators and sensors in electronic application due to its remarkable piezoelectric properties. The main obstacle in the PZT syntheses through solid state sintering is the lost of substantial amount of PbO due to vaporation that accompanied high firing temperature. Elimination of the calcination step and alternative method of treatment could be of a great help. Thus, an investigation of the lead (Pb) Zirconate Titanate PZT properties (piezoelectric and dielectric) synthesized via solid-state reaction by varying compaction pressure (100-300 MPa) was conducted. Compaction pressure that was beneficial to the physical properties of PZT-based ceramic and also effectively improved the dielectric and piezoelectric properties of the PZT ceramics. Optimum average grain size was found to be a very important factor in determining the alignment of the d33 particle size value influence and the dielectric constant of PZT. Therefore, the optimum compaction pressure (200 MPa) played an important role in optimizing the sintering temperature. This also enhanced/improved the piezoelectric and dielectric properties of PZT.

The effect of calcium carbonate particle size on the formations β-tricalcium phospate

Shah Rizal Kasim,Yeong Meng How,Hazman Seli,Hazizan Md Akil,Zainal Arifin Ahmad 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.5

β-tricalcium phosphate (β-TCP) powder was synthesized using various calcium carbonate (CaCO3) particles sizes (40 nm- 780 μm) with phosphoric acid (H3PO4) at room temperature (25℃). CaCO3 was first dissolved in deionized water at room temperature followed by the addition of H3PO4. The mixture was stirred until reaching a stable pH between 5.5-6.5 for 1 hour. The time taken to reach pH 5.5 increased from 12.5 minutes to 1140 minutes as the CaCO3 particle size increased from 40 nm to 780 μm. The slurry was filtered, dried in oven at a temperature of 80℃ for 24 hours then crushed with an agate mortar and calcined at a temperature of 850℃ to form the β-TCP phase. XRD quantitative analysis showed that the amount of the â-TCP synthesized from CaCO3 as the starting material decreased from 81.9% to 20.3% as the CaCO3 particle size increased from 40 nm to 780 μm. FESEM analysis showed that the morphology of CaCO3 as the starting material was not maintained after it was synthesized to β-TCP powder. β-tricalcium phosphate (β-TCP) powder was synthesized using various calcium carbonate (CaCO3) particles sizes (40 nm- 780 μm) with phosphoric acid (H3PO4) at room temperature (25℃). CaCO3 was first dissolved in deionized water at room temperature followed by the addition of H3PO4. The mixture was stirred until reaching a stable pH between 5.5-6.5 for 1 hour. The time taken to reach pH 5.5 increased from 12.5 minutes to 1140 minutes as the CaCO3 particle size increased from 40 nm to 780 μm. The slurry was filtered, dried in oven at a temperature of 80℃ for 24 hours then crushed with an agate mortar and calcined at a temperature of 850℃ to form the β-TCP phase. XRD quantitative analysis showed that the amount of the â-TCP synthesized from CaCO3 as the starting material decreased from 81.9% to 20.3% as the CaCO3 particle size increased from 40 nm to 780 μm. FESEM analysis showed that the morphology of CaCO3 as the starting material was not maintained after it was synthesized to β-TCP powder.

Role of mixing mediums in the synthesis of single phase CaCu3Ti4O12 (CCTO)

Rosyaini Afindi Zaman,Wan Fahmin Faiz Wan Ali,Mohamad Johari Abu,Julie Juliewatty Mohamed,Mohd. Fadzil Ain,Zainal Arifin Ahmad 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.6

The role of mixing mediums on synthesizing high purity CCTO as a function of calcination temperature was systematicallyinvestigated via solid state reaction (SSR) route. The efficacy of the mediums (ethanol, deionised water, distilled water, and drymix) was primarily determined by X-ray diffraction (XRD) technique and FESEM, respectively. It is found that, a single phaseCCTO was successfully synthesized in all mediums, with the deionised water showed the lowest reaction temperature (950 oC)to fully crystallize the powder mixtures compared to other mediums. No significant changes were seen in the grain shape sinceonly a bimodal structure with grain size ranging from 0.5 μm to 2.57 μm was observed. The effect of media was also seen intheir dielectric properties of the calcined powders. Dry mixing (DM) had the highest dielectric permittivity (εr = 118) whereasothers are only between 59-99. Therefore, this observation proved that mixing medium could influence the formationtemperature and dielectric properties of CCTO.

A Low-Profile Quasi-Loop Magneto-Electric Dipole Antenna Featuring a Wide Bandwidth and Circular Polarization for 5G mmWave Device-to-Device Communication

Kamal Shahanawaz,Ain Mohd Fadzil Bin,Ullah Ubaid,Mohammed Abdullahi S. B.,Hussin Roslina,Omar Mohamad Faiz Bin Mohamed,Najmi Fathul,Ahmad Zainal Arifin,Rahman Mohd Fariz Ab,Mahmud Mohd Nazri,Othman Mo 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.4

The deployment of the millimeter (mmWave) frequency spectrum by fifth-generation (5G) device-to-device (D2D) wireless networks is anticipated to meet the growing demands for increased capacity. The antenna is regarded of as an important determinant that guarantees the maximum performance of wireless communication. This paper presents a low-profile magneto-electric (ME) dipole antenna for 5G mmWave D2D communication. A single-element quasi-loop radiator was designed to excite horizontal polarization, and a coaxial probe was used to produce vertical polarization. Subsequently, the structure of the radiator was transformed into a two-element quasi-loop an- tenna to achieve an omnidirectional radiation pattern with relatively enhanced gain. A coaxially fed T-junction microstrip element was implemented to equally distribute the signal between the two quasi-loop radiators and attain proper impedance matching. Furthermore, a pair of shorting pins was introduced into the two-element design to maintain the circularly polarized (CP) radiation. The finest values of the axial ratio and |S11| were derived by rigorously optimizing all the geometry parameters. Both single-element and two-element quasi- loop antennas were fabricated and characterized experimentally on the air substrate. The advantage of avoiding a physical substrate is to realize a wide bandwidth, circumvent dielectric losses, and ascertain the maximum gain. The measured and simulated results agree thor- oughly with each other. Stable in-band CP radiation were accomplished, thus confirming an appropriate field vector combination from the coaxial probe and the radiator. The finalized antenna engaged an area of ~7.6λ for operation at 23.9–30.0 GHz with an axial ratio <3 dB, radiation efficiency ~80%, and gain >5 dBic.