Materials Science Forum Vol. 981

Abstract: Effect of complex magnetic oxide Co_0.5Ni_0.5Fe₂O₄ (CNFO) nanoparticles addition in (Bi_1.6Pb_0.4)Sr₂Ca₂Cu₃O₁₀ (Bi-2223) superconductor tapes was investigated. Ultrafine Bi-2223 powder precursor was prepared via co-precipitation method and was added with 0.01 – 0.05 wt.% Co_0.5Ni_0.5Fe₂O₄ nanoparticles during the final heating stage. The sample with 0.01 wt.% addition, Bi-2223(CNFO)_0.01 was found to have the highest critical current density, J_c. This sample were then chosen to be fabricated into Ag-sheathed superconductor tapes using the powder-in-tube (PIT) method. The tapes were sintered for 50 and 100 h at 845 °C. The phase, microstructure and J_c of the samples were determined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and four point probe, respectively. J_c of Ag-sheathed Bi-2223(CNFO)_0.01 tapes sintered for 100 h was 19830 A/cm² at 30 K and 3970 A/cm² at 77 K compared to tapes without addition which showed a much lower J_c (6370 A/cm² at 30 K). This study showed that CNFO nanoparticles could act as an effective flux pinning centers to enhance the critical current density in the Bi-2223 superconductor.

Abstract: The photosensitizer is an important part of Dye-Sensitized Solar Cells (DSSC). Photosensitizers function like photosynthesis by absorbing sunlight and turning it into energy. Photosensitizers also contribute to the efficiency of improving DSSC performance. This research is a continuation of previous research to find a candidate for natural and environmentally friendly photosensitizer (bio-energy) based local area in Indonesia. The photosensitizer used in this simulation is Tagetes erecta, Nyctanthes arbor-tritis, Brassica rapa Sub. Sp pekinensis, Delonix regia, Lawsonia inermis, Callistemon citrinus, and Daucus Carota. The purpose of this simulation is finding several candidates for bio-energy local area photosensitizer that produce high efficiency by displaying J-V curves and P-V curves. The highest efficiency was produced by photosensitizer Tagetes erecta at 1.5% [Voc 0.6385 Volt, 0.00383 A / cm2 Jsc, FF 0.605 and Pmax 0.00148 Watt], while the lowest efficiency was produced by photosensitizer Callistemon citrinus at 1.1% [Voc 0.6162 Volt, Jsc 0.0032 A / cm2, FF 0.557 and Pmax 0,0011 Watts]. These simulation results perform that one of reason give influence at DSSC performance is the absorption coefficient value in each bio-energy local area photosensitizer. The absorption coefficient also determines how much efficiency is produced and how much the photosensitizer's ability to absorb sunlight.

Abstract: Enhancing the optical performance of rare earth doped binary inorganic glasses is an ever-demanding quest. Samarium (Sm³⁺) doped zinc tellurite glasses containing Manganese (Mn) nanoparticles (NPs) with composition (59-x)TeO₂-20ZnCl₂-10ZnO-10Li₂O-1Sm₂O₃-(x)Mn₃O_4, where x = 0 to 0.06 mol% are prepared by melt quenching technique. The role played by Mn NPs in enhancing the optical behaviors are analyzed and discussed. The XRD patterns confirm the amorphous nature of the glass. The UV-Vis-NIR spectra reveal seven prominent absorption bands of Sm³⁺ ions. The photoluminescence spectra display four peaks corresponding to ⁴G_5/2→⁶H_5/2, ⁴G_5/2 →⁶H_7/2, ⁴G_5/2→⁶H_9/2 and ⁴G_5/2 →⁶H_11/2 transitions_. An enhancement in the luminescence intensity is observed up to 0.05 mol% concentration of NPs and the intensity quenches beyond it. The enhancement is attributed to local electric field effect of NPs in the proximity of Sm³⁺ ion. Our results on improved optical response via precise control of NPs contents may be useful for the development of solid state lasers and amplifiers.

Abstract: Metal oxide semiconductor gas sensors have been widely utilized in a variety of different roles and industries. They are relatively inexpensive, robust, lightweight, long lasting and benefit from high material and quick response time compared to other sensing technologies. However, there are major challenges need to overcame by developers in order to construct a semiconductor metal oxide gas sensor that is efficient, and durable and most importantly can work at lower temperature. Therefore, in this research, TiO₂ dopants was introduced into conventional high purity ZnO gas sensor whereby the samples were prepared in pellet form using powder metallurgy route. The improvement in the mechanical properties as well as the electrical properties of the samples was wished to be observed through this research. The density measurement showed that the adding of TiO₂ was efficient to promote the densification of ZnO sample in which 9 wt% TiO₂ doped ZnO sample showed the highest density. The XRD results showed that the diffraction pattern was basically attributed to the wurtzite structure of ZnO. This was proven by the plane (1 0 1) had the highest intensity in all the samples except 6 wt% TiO₂ and 9 wt% TiO₂ doped ZnO sample. SEM showed that the grain size of ZnO decreased with the addition of TiO₂. This was caused by the formation of the new phase which was Zn₂TiO₄. The smaller the grain size, the higher the specific surface area and oxygen adsorption quantity, and therefore the higher the gas sensitivity is. UV-Vis showed that the wavelength of all samples was located around 380 nm. Therefore, the calculated exitonic energy was around 3.20 eV which was nearly matched with the theoretical band gap of ZnO (3.37 eV). The measurement of the resistivity using four point probe showed that the electrical resistivity of the samples decrease up to addition of 9 wt% TiO₂. This was attributed to increased carrier concentration. Vickers hardness test showed that the doping of TiO₂ had increased the hardness of the sample whereby the 9 wt% TiO₂ doped ZnO sample showed the highest value of hardness. The addition of TiO₂ into high purity ZnO has influenced the mechanical and electrical properties of ZnO. From observing the microstructural and density measurement to the measurement of the surface resistivity as well as the determination of the Vickers hardness value, it was found that 9 wt% TiO₂ doped ZnO was predicted as a candidate for substituting a conventional high purity ZnO as the gas sensor.

Abstract: Electronics and energy storage industry demand production of high-quality graphene which currently still a challenge. Chemical vapor deposition (CVD) has shown promises for high-quality graphene production. However, it involves control of many parameters from different aspects such as thermal fluid, mass transport, and chemical reaction. Thermal fluid aspect plays a significant role in CVD production of graphene but yet to be explored extensively. For a tubular hot-wall CVD with the heating reactor, issue of flow instability that will prolong the existence of vortices and spiral flow until the substrate required attention. Therefore current study aims to find the optimum substrate position inside the furnace. For that purpose the gas flow streamline will be observed, and minimum axial distance of the substrate will be determined. The tubular CVD is modeled using ANSYS Fluent^®. The current model will not consider the chemical reaction involves and only single gas is used. This should be enough to seek the influence of thermal fluid aspects involves in CVD. The CVD tube will be divided into 3 sections where the middle part (furnace) was heated up to 1273K and the other two sections were kept at 300K. Gas was supplied to the tube and the distance from the furnace inlet to the point where the flow is fully developed is measured. Streamlines for the flow is also observed. The streamline shows that there is an induced secondary flow starting at the inlet which lasted until a certain axial distance. For flow with 50 sccm of flowrate needs an axial distance of 5 cm while flow with 250 sccm of flowrate needs 7 cm in order to become a smooth flow. Our results show that the placement of the substrate in the tubular hot-wall CVD required attention in CVD design. For flow with higher flowrate, it requires longer distance for the flow to become smooth and laminar and vice versa.

Abstract: One of the considerations for renewable energy that can be accepted by society is energy based on nature (green future) and environmentally friendly (local wisdom). Dye-sensitized solar cells give to the world, easily and simple implemented technology for future renewable energy. This research was conducted by simulating the performance of DSSC using dye based on green future and local wisdom. Dye is one of the most important components influencing solar cell performance because dye determines the photoresponse of the DSSC. Several dyes that used in this research included Vasica nees, W. fruticose L, U. dioical L, R. arborium, Myrica nagi, Curcuma angustifiola dan Berberies aristate. The reason for this choice of dye included it is easily found in Indonesia, does not cause environmental pollution, and is thought to have good prospects to be applied to DSSC. The best performance results produced by DSSC are using dye W.fruticose L with an efficiency of 1.6%, and the lowest performance are using dye R. arborium with an efficiency of 1 %.

Abstract: This study was conducted to investigate the efficiency of Minimum Quantity Lubrication (MQL) technique by using Modified Jatropha Oil (MJO) bio-based lubricant with the presence of 10% Ammonium Ionic Liquid (MJO+AIL10%) and 1% Phosphonium Ionic Liquid (MJO+PIL1%) additives respectively at various temperature of 200 °C, 300 °C and 400 °C heat treatment to determine the ability to exhibit corrosion and wear throughout the process. Fourier-Transform Infrared Spectroscopy (FTIR) analysis revealed prominent peaks of functional groups in these bio-lubricants; esters (C-O) and (C=O), alkanes (C-H), hydroxide (O-H), and nitrile groups deposited on the cutting tool surface. Initially, nitrile group is detected on cutting tool surface without lubricants at 2200 to 2300 absorption band reduced to lower intensity and most likely concealed by MJO+AIL10% compared to MJO+PIL1% where the nitrile group remains reflected in FTIR spectrum. In this work, it is proved that MJO+AIL10% has higher viscosity as compared to MJO+PIL1%. in the context of functional groups and supported the previous study on MJO+AIL10% as corrosion inhibitor.

Abstract: Hierarchical ZSM-5 was successfully synthesized by hydrothermal crystallization of kaolin clay. A statistical experimental design Taguchi method with analysis of variance (ANOVA) with an L₉ Orthogonal array (OA) was used to optimize the formation of high mesoporosity in hierarchical ZSM-5. Samples from kaolin mixtures crystallized at 80-175°C for 12, 24 and 48 h, respectively using hydrothermal followed by addition of mesoporogen cetyltrimethylammonium bromide (CTABr) surfactant. The presence of pentasil zeolite groups and large mesopores surface area and pore volume has observed on the samples by FTIR and N₂ adsorption-desorption technique.The optimum synthesis conditions studied by Taguchi analysis based on S/N ratio for temperature and time of hydrothermal. The optimum condition was 127.5°C and 48 h giving the highest mesoporosity. Data analysis of interaction plot for S/N ratio showed there was interaction between temperature and time in the crystallization of hierarchical ZSM-5. Hydrothermal temperature was the most influencing factors for the formation of hierarchical ZSM-5 with a percent contribution of 83%.

Abstract: Interest in the nanotechnology invention has been increased among the researcher and industries which lead to many investigations and studies to develop a product with better performance. In this research, hydroxypropyl methylcellulose (HPMC) and poly (vinyl) alcohol (PVA) nanofiber with the ratio 1:1 and the concentration of 5 wt% and 7 wt%, respectively, were successfully fabricated by using electrospinning technique. The HPMC/ PVA was then blended with the different concentration of cellulose nanocrystal (CNC) at 2 wt%, 4 wt%, 6 wt% and 8 wt%. The SEM results of HPMC/PVA/CNC nanofibers shown random orientation fibers with average diameters of 62.28 nm - 252.80 nm. The TGA results showed three major weight loss that prove the decomposotion of HPMC/PVA/CNC was occured with three maximum temperature peaks around 69 °C, 290 °C and 392 °C. As for DSC, the peak intensity of the T_g in the electrospun nanofiber are decreasing as the concentration of CNCs increased might be due to the interfering of the CNC with the crystallization of the polymer causing mobility of the amorphous regions to be higher. Therefore, the study on the thermal properties of HPMC/PVA incorporated with CNCs nanofibers could be a reference for various potential applications.

Abstract: In this study, a renewable phenolic component was synthesized using empty fruit bunch fibers via microwave-assisted liquefaction known as Liquefied Empty Fruit Bunch (L_EFB). L_EFB can be used as phenolic derivative to replace petroleum-based phenol as it contains aromatic group in lignin that can be used as starting materials to synthesis polybenzoxazine resins. A Lignin-based benzoxazine (L-PBz) has been synthesized using a solventless approach from the reaction of L_EFB, furfurylamine as the amine component and paraformaldehyde via Mannich condensation reaction. Two different ratios of L_EFB:furfurylamine:paraformaldehyde which are 1:1:1 and 1:1:2 were investigated. The thermal properties and polymerization behavior of the L-PBz were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. In addition, cured-polybenzoxazine composites were also prepared by hot-pressing the uncured L-PBz at 250 °C for 4 hours, and the mechanical properties of the composites were assessed through Izod impact strength test. TGA analysis showed that, L-PBz with ratio of 1:1:1 exhibit a high char yield compared to 1:1:2 which is 47% vs 43%, respectively, after being heated until 900 °C. However, L-PBz with ratio of 1:1:2 showed good polymerization behavior compared to 1:1:1 which indicated by the curing temperature 215 °C vs 238 °C. L-PBz composites, which added with cellulose nanocrystal (CNC) fillers have better strength compared with the absence of fillers. As a conclusion, the aromatic structure of lignin in empty fruit bunch fibers has presented a promising alternative to replace petroleum-based phenol in polybenzoxazine synthesis.