Advanced Materials Research Vol. 858

Abstract: Cordierite (2MgO.2Al₂O₃.5SiO₂) is widely used in high temperature applications due to its high melting temperature and high resistance to thermal, chemical and corrosion shock. The use of various structure of cordierite especially porous structure became more popular where its properties can be tailored by controlling the open and closed porosity, cell size distribution and cell morphology. In this study, porous cordierite was synthesized using sol-gel method followed by replication of polymeric sponge method using three different types of polymeric sponge (Type A, B and C). Immersed sponge were then sintered at 1300°C to determine better sponge types to produce porous cordierite. Sponge was characterized using FTIR and porous sample produced were characterized using Scanning Electron Microscope (SEM) and density and porosity testing.

Abstract: In this work, PLLA microspheres were prepared via emulsion solvent evaporation technique. Several synthesis parameters were studied to evaluate their effect on the size of PLLA microspheres. PLLA pallets before emulsion and PLLA microspheres surface chemistry after emulsion were determined using Fourier Transform Infra-red (FTIR). Results showed that PLLA pallets and microspheres FTIR obtained an identical spectrum. Microspheres size and surface morphology were determined using Scanning Electron Microscopy (SEM). In conclusion, the parameters that significantly affect the size of PLLA microspheres were PLLA concentration, DCM to water volume ratio, PVA concentration and stirring speed. PVA molecular weight variation showed no significant change in microspheres size.

Abstract: This paper describes a novel fabrication technique to grow gold nanoparticles (AuNPs) by using the sacrificial templated growth hydrothermal reaction approach. The effect of zinc nitrate Zn (NO₃)₂ concentration in the hydrothermal reaction on the formation of AuNPs was studied by varying the concentration from 0.01 M, 0.05 M, 0.1 M and 0.2 M. The increase of Zn (NO₃)₂ concentration lead to formation of smaller size and lower area density of AuNPs. XRD analysis proved the formation of AuNPs by using this approach. From scanning electron microscope images, the sample with 0.1M of Zn (NO₃)₂ concentration showed better AuNPs distribution. In order to investigate the memory properties of AuNPs embedded in organic insulator, polymethylsilsesquioxane (PMSSQ) was spin coated as insulator layer between the AuNPs. I-V and C-V characteristics showed hysteresis properties that indicated charge storage capability of AuNPs embedded organic insulator. AuNPs grown on 300°C annealed ZnO template in 0.1M of Zn (NO₃)₂ hydrothermal bath produced the best memory properties whereby 54 of electron charges has been stored per AuNPs in C-V measurement.

Abstract: Natural Aloe vera paste has been reported as an alternative organic dielectric material. In this study, natural Aloe vera paste incorporated with silicon dioxide (SiO₂) nanoparticles (NPs) has been investigated. The natural Aloe vera paste with different weight loading (0.5 to 3.8 wt%) of SiO₂ NPs was screen printed on aluminum (Al) layer supported by a soda lime glass substrate and dried at room temperature. The solidified sample with 1.5 wt% of SiO₂ NPs showed the lowest leakage current density. Next, the solidified samples were additional dried in an oven at 40°C for 30 minutes to study its effect against room temperature. The additional drying process facilitated cross-linking on natural Aloe vera layer and consequently enhanced the dielectric properties of the natural Aloe vera with 1.5 wt% of SiO₂ NPs, whereby leakage current and dielectric constant were decreased and increased, respectively.

Abstract: Thermoplastic elastomer (TPE) nanocomposites based on 70:30 of linear low density polyethylene (LLDPE) and silicone rubber (SR) filled with nanosilica (SiO₂) and nanoboron nitride (BN) was prepared. The effect of different types of nanofiller and sequence of blending on dielectric breakdown strength, dielectric properties and morphological properties of the blend was evaluated. The results showed that the presence of nanofiller improved the dielectric strength of LLDPE/SR. BN filled system had better dielectric strength as compared to SiO₂ filled system. The addition of nanofillers also increased dielectric constant and dielectric loss of the blends. The sequence of blending significantly affected the properties of the material. The indirect blending (sample prepared master batch of SR/nanofiller) showed higher dielectric strength compared to the sample prepared through direct blending. The result was explained through SEM observation which showed the presence of fewer interfaces in the indirect blending sample, thus resulting in less weak points. This would have resulted in higher dielectric strength compared to direct blending sample which had various interfaces. The sample prepared through direct blending also showed remarkably higher dielectric contant and loss which is not suitable for insulator.

Abstract: The escalating interest of researchers to use industrial waste materials in the manufacture of ceramic products is growing. This work is aimed at studying the properties of granite waste (GW) upon incorporation in ceramic bodies. Initially, the GW was characterized in terms of chemical and mineralogical compositions. Then, the GW was added (in the range 40-60 wt.%) to a ball clay. Firing was carried out at 1100°C to1200°C and then the properties of the fired specimens were determined. The results showed that specimens with GW 50 wt.% fired at 1150°C exhibited the best properties, i.e. minimum water absorption of <0.36%, the best bulk density (2.48 g/cm³) and strength (21.34 MPa). This showed that GW can act as a fluxing agent and reduces the firing temperature of the ceramic body with additional advantages in terms of cost and reuse of waste materials.

Abstract: Continuous porous hydroxyapatite (HA) scaffold has been considered to be used in bone tissue engineering. However, the low fracture property of HA scaffold has been a problem to be solved. In the present study, polycaprolactone (PCL) was introduced as a secondary phase into the porous structure of HA scaffold to improve the low fracture property. HA scaffolds were firstly fabricated using the template method. The HA scaffolds were then coated with PCL by changing the solution concentration from 1 to 5 wt%. Compression tests and SEM were done to examine the mechanical properties and the morphology of the two-phase composite scaffolds. It was found that the compression strength and modulus increased with increasing PCL concentration. It is also noted that PCL coating can greatly improve the brittleness of pure HA scaffolds. XRD test was also done to study the phase stability of HA and the two-phase scaffolds. There was no chemical reaction between PCL and HA observed by the XRD results. On the overall, these results indicated that PCL coating can effectively improve the low fracture property of pure HA scaffold and the two-phase scaffold could be a potential candidate for bone regeneration.

Abstract: The object of this study is to develop an easy and simple technique to fabricate iron-free hydroxyapatite (HA) powder from CaCO₃ using precipitation method. Previously, we successful to fabricate HA from Ca(OH)₂ and H₃PO₄, however, the calcining HA at 1000°C expose the green color with [Fe] is around 177ppm. In order to improve the quality of synthetic HA, CaCO₃ was used to fabricate Fe-free Ca(OH)₂ or Synthetic Ca(OH)₂ The resultant study indicates that CaCO₃ precursor helps to improve the quality of synthetic HA powder.

Abstract: In this study the effect of cerium addition on the microstructure of hypereutectic Al-15Si alloy was investigated. Experiments have been conducted on Al15Si alloys with Ce content in the alloy varied from 0 to 2.51 wt.%. The alloys were produced by casting in a permanent mould. Optical microscopy, X-Ray Diffraction (XRD) and Vickers microhardness were used in this investigation. The results showed that the addition of 0 to 2.5 wt.% of cerium led to the formation of precipitation of rod-like Al₃Ce phase in the Al-matrix. The microhardness of the alloys increases with the increase in cerium content as a result of the Al₃Ce precipitation.

Abstract: In this study, the effects of alloying elements Fe (0.2 wt.%), Sb (0.5 wt.%) and Ce (0.5 wt.%) on the Sn-3.0Ag-0.5Cu lead-free solder system were investigated. The solder alloy was reflowed on electroless Cu/NiP-coated substrates and their behavior such as microstructure, wetting angle and intermetallic compound (IMC) formation were analyzed. The results showed that the presence of Fe, Ce and Sb reduced the grain size of β-Sn as compared to solder without addition of alloying element. The addition of Fe and Ce was the most significantly refined the microstructure of Sn-3.0Ag-0.5Cu solder alloys. Sn3.0Ag0.5Cu0.2Fe0.5Ce solder was revealed better spreading behavior on Cu/NiP coated substrates which have the lowest IMC thickness of 0.558 μm.