Abstract: In this study, magnetorheological elastomers (MREs) were synthesized using silicone rubber (SR) as the matrix element interspersed with 70 weight percent of corroded carbonyl iron particles (CIPs). The CIPs were corroded in dilute hydrochloric acid (HCl) for 4 hours. The rheological properties related to MR effect were experimentally examined in the absence and presence of magnetic field at various current using a rheometer. The experimental results depicted the MR effect of the MRE with corroded CIPs decreased one-half, 27% as compared to the non-corroded samples, 58%. The correlation between the purity of CIPs and storage modulus of MR elastomer is examined in this study.
Abstract: This paper aims to investigate the damping properties of plate-like carbonyl iron particle (CIP) magnetorheological elastomer (MRE). The damping properties of MRE is mainly dependent on the strength of magnetic field. Anisotropic MRE was fabricated under various magnetic fields strength (70, 210, 345, and 482 mT) and its damping property prior to frequency-dependent was measured using a rheometer. Firstly, the plate-like CIP was first synthesized from spherical CIP using a ball-milling method. The microstructure of plate-like CIP was observed using low vacuum scanning electron microscope. Subsequently, two types of MREs which are isotropic and anisotropic were fabricated using 70 weight percent (wt.%) of plate-like CIP. The experimental results showed that the anisotropic MRE has lower damping factor than isotropic MRE. Meanwhile, the damping factor increases with the increase of frequency.
Abstract: This study introduces a sucrose acetate isobutyrate (SAIB) as an additive of magnetorheological elastomers (MREs) to be added in silicone rubber matrix and carbonyl iron particles (CIPs) as their filler. The CIPs were fixed at 60 wt% and two types of MREs sample were fabricated which are isotropic and anisotropic. Rheological properties related to shear storage modulus were measured using a rheometer (MCR 302, Anton Paar). The experimental results demonstrated that the magnetorheological (MR) effect of anisotropic MREs-based Silicone/SAIB was 126 % as compared to isotropic MREs-based Silicone/SAIB, 64%. The fabricated MREs samples were frequency and strain dependent. The relative MR effect for both samples showed decreasing trend with the increment of strain amplitude and excitation frequency.
Abstract: In this study, anisotropic magnetorheological elastomers (MREs) mold design with capability of aligning the filler in several angles (0 ̊, 45 ̊, and 90 ̊) were developed. The mold was equipped with electromagnet coil to generate the magnetic flux. The distribution of magnetic flux density in the mold and inside the chamber was investigated by using finite element magnetic analysis. Magnetic flux density of 0.3 T was considered best value to form good particle alignment in the matrix. Moreover, the mold design was fabricated using same material as in the simulation. The magnetic flux density was taken at casing wall and measured by gauss-meter. The data was compared with simulation results. The differences between experimental and simulation is in the range of 6-40 mT. Since the difference is insignificant, it can be said that the data is valid. Finally, the model can be used for further magnetic flux density prediction inside the chamber. In the simulation, it was found that the current needed to generate at least 0.3 T inside the chamber for 0 ̊, 45 ̊, and 90 ̊ are 0.2A, 0.1A, and 3A, respectively.
Abstract: We report on the green synthesis of silver nanoparticles utilizing the P.purpureum leaf extract. Controlling the surface plasmon absorption of silver nanoparticles was achieved by regulating the amount of extract concentration and the molarity of silver nitrate solution. The surface plasmon absorption peak is found at around 430nm. The surface plasmon absorption peak have shifted to lower wavelength as the amount of extract is increased, while plasmon absorption peak shifts on a higher wavelength as the concentration of silver nitrate is increased before it stabilized at 430nm. This can be explained in terms of the available nucleation sites promoted by the plant extract as well as the available silver ions present in silver nitrate solution.
Abstract: Gold nanoparticles were synthesized using brown seaweed (Sargassum crassifolium) extract and chloroauric acid solution. This is an easy, cheap and environment friendly synthesis method for the formation of gold nanoparticles. The gold nanoparticles with varying amount of seaweed extract was characterized using Ultraviolet-visible spectroscopy. Moreover, Transmission Electron Microscopy characterization was used to observe the shape and size of gold nanoparticles. Experimental results revealed that varying the amount of brown seaweed extract can control the optical absorption spectra of the produced gold nanoparticles. Greater amount of brown seaweed extract will exhibit peak in the lower wavelength while smaller amount of seaweed extract will exhibit peak in the higher wavelength. It is believed that the wavelength of free surface electrons resonance is related to the shift of absorption peak. TEM images revealed a more spherical and smaller particles as the amount of brown seaweed extract was increased. This simple green synthesis method of gold nanoparticles will give a cost effective route in the mass production of gold nanoparticles for biomedical applications.
Abstract: Absorption spectra of different composition of tellurite glasses were analyzed in order to estimate their lasing properties. Composition of the investigated tellurite glasses are: 55TeO2-(43-x)ZnO-2Bi2O3-xEr2O3 (x = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mol%). Glasses absorption spectra and density were measured at room temperature using UV-VIS-NIR Spectrophotometer and pycnometer, respectively; while their refractive index were measured by implying Brewster’s angle method. Lasing performance of glasses were then analyzed using Judd-Ofelt theory in order to obtain line strength (S), Judd-Ofelt parameters (Ωt, t = 1, 2, 3), and radiative life-times (τ). It is seen that incorporating Er3+ ions of up to 2.5 mol% resulted in decreasing the radiative lifetime of electrons sitting at 4I11/2. From Judd-Ofelt parameters analysis it can be concluded that these tellurite glasses tend to have the covalence nature of Er-O bond and thus represents the asymmetry around the Er3+ ions site.
Abstract: This study examined the chemical stability of malayaite pigments in ceramic glazes containing high amounts of zinc oxide (ZnO). The calcined pigments were embedded in a molten glaze which is basically corrosive glass. Within the glaze, ZnO has been known among potters to be undesirable as some pigments are not stable in glazes containing ZnO. The synthesized pigments’ particle size ranges from 4 to 18 μm without dominant preferential orientation. Their colors were in the red and yellow tones. Chemical stability between the pigments and glazes was tested using X-ray Diffraction (XRD). Slight changes were observed. Increasing amounts of ZnO resulted in an interfacial layer of approximately 50 μm between the crystalline pigment and surrounding amorphous glaze. The a color parameters gradually decreased while the b parameters switched to a negative value. The resulting glazes evolved from maroon to pale violet. The correlation between color and microstructural alterations was discussed.
Abstract: In this research, the influence of zinc oxide (ZnO) on the phase compositions and crystalline structure and microstructure of cement composite was studied. ZnO powder (0.5-1 wt% of cement) was used as an additive material. The Portland cement and ZnO powder were blended and mixed with water at the ratio constant (W/C) of 0.4. Then, the paste was cast into the molded for 24 hours. After these periods, the samples were dried at temperature 50°C for 24 hours. Those of samples were analyzed of crystalline structure and phase compositions by using X-ray diffraction technique (XRD). Microstructure analysis by using field emission scanning electron microscopy (SEM). It was found that the XRD spectra showed phases of calcium hydroxide (CH) and calcium silicate hydrated (CS), which were hydration products of cementitious material. Moreover, phase of zinc hydroxide (Zn(OH)2) is detected. Zn(OH)2 have affected on the retardation of hydration reaction (more than 48 h). Zn(OH)2 phase was formed on the surface of anhydrous tricalcium silicate (C3S) main compound in cement. The intensity of un-hydration products (C3S and C2S) increased with increasing content of ZnO nanoparticle in cement composites.
Abstract: Polylactic acid (PLA) is a bioplastic, which is produced from natural materials. It is well known that the PLA can be degraded in the environment which is alternatively rendered to replace the plastic from a petroleum base. In this paper, we study the physical properties of composite films prepared from PLA composited with zinc oxide nanoparticles (ZnO NPs) by using solvent casting technique. It was found that the ZnO NPs have affected to the morphological, water absorbency, mechanical and antibacterial properties of biocomposite films. In addition, we also found that the particles of ZnO NPs can disperse within the PLA matrices, which enhanced the stress and Young’s modulus of biocomposite films. Additionally, the result shown that the PLA/ZnO NPs films exhibit good antibacterial activity both in Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial strains.