Key Engineering Materials Vol. 811

Abstract: Study on pyrrole electropolymerization is the preliminary step in synthesizing polypyrrole membranes, which can be used for various purposes in biosensor. In this work, electropolymerization process and electrochemical analysis of polypyrrole as an electroactive polymer have been studied by cyclic voltammetry. Pyrrole was electropolymerized to form polypyrrole in an aqueous potassium chloride solution at different pHs using phosphate buffer. The results showed that a potential range of 0-1200 mV is suitable for polypyrrole electropolymerization using the Ag|AgCl electrode as the reference. The formation of polypyrrole is stable at a scan rate of 100 mV/s. In addition, the optimized pyrrole electropolymerization was obtained using 0.1 M pyrrole and phosphate buffer at pH of 2-6. Taken together, this study can be used as a reference for the synthesis of other conducting polymers.

Abstract: This study indicated the deterioration of the steel pipe and beam structure in west coast Sumatra made of ASTM A252, and also pipeline along Riau land-Jambi - Batam Island. It was found that severest corrosion occurs at the rate up to 1.6 mm/year (63 mpy) on the steel cross beam-800 on west coast Sumatra. Whereas the corrosion rates on ASTM A234 and API 5L steel structures along the pipeline across Riau - Jambi - Batam occur from the high-to-severe up to 0.43 mm/year (17 mpy) mainly on pipe elbow 16” diameter. Due to this corrosion attack, the steel infrastructure requires whole protection including sacrificial thickness, surface coating, and cathodic protection. The corrosion attack data may be used to provide the required effort and its priority to protect the steel pile and pipe infrastructures on Sumatra Island.

Abstract: Fuel cell is one of the future alternative energy sources. Commercial fuel cell membrane currently used is Nafion which has several disadvantages including low stability at high temperature, and low conductivity at low humidity. Therefore, it is necessary to study an alternative membrane for PEMFC. The purpose of this research is to synthesis an alternative fuel cell membrane from sulfonated PVDF doped with nanocomposites of natural zeolite of Cipatujah, West Java, Indonesia and TiO₂ nanoparticles. The synthesis of zeolite-TiO₂ nanocomposites was performed by sol-gel method using TEOT and zeolite of Cipatujah. The nanocomposites were added to PVDF in DMSO solvent prior to ultrasonification for 1, 2 and 3 hours. The membrane was casted and sulfonated with concentrated sulfuric acid for 4, 6 and 8 hours. The membrane was characterized with FTIR, SEM-EDX, and four-point probe spectroscope. The FTIR analysis shows the existence of sulfone in the polymer. The SEM-EDX results show that the SiO₂ from the zeolite and TiO₂ have been successfully inserted to the membrane. The conductivity analysis shows that the best membrane conductivity, 0.00389 S/cm was achieved for 6 hours sulfonation and 3 hours ultrasonication.

Abstract: 4-Sebacoylbis (1-phenyl-3-methyl-5-pyrazolone) (H₂SbBP) ligand has been successfully synthesized, characterized and used as ionophores in Nd (III) selective electrode, using polytetrafluoroethylene (PTFE) membranous as a support. Prior to use the PTFE membrane soaked ionophores 1.5% w/v in chloroform for 24 hours. The performance of electrode studied by seeing the influence of pH and concentration of KNO₃ as a buffer solution ionic strength. Variations in pH of the solution was set at pH ranges between 1 to 10 using a solution of HCl and NaOH, while KNO₃ concentration varied between 10^-4 to 10^-1 M. Nd³⁺ concentration range is between 10^-6 up to 10^-2 M. The best electrode performance was obtained at pH 5 and 10^-2 M KNO₃ concentration with a sensitivity of (18.5 ± 0.2) mV/decade and its response time less than 25 seconds.

Abstract: This research is aimed to study the effect of sintering temperature on crystalline structure and surface morphology of NdFeO₃ oxide alloy materials. NdFeO₃ was synthesized by solid state reaction method with mixing of 99.9% Nd₂O₃ and 99.9% Fe₂O₃ as precursors. Three samples with different process were made in this experiment. The 1^st (#1) and 2^nd (#2) samples were sintered for 84 hours at 950°C and 600°C. Calcination procces was carried out at 950°C for 50 hours. The 3^rd (#3) sample was sintered for 84 hours at 600°C without calcination process. The samples were characterized by using SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction). Based on the SEM characterization result, it was obtained that the sintering temperature influence on surface morphology of NdFeO₃ grain size. The XRD analyze was obtained FWHM (Full Width at Half Maximum) value of sample #1, #2 and #3 are 0.11°, 0.10°, and 0.31°, respectively. The value of FWHM was associated with the peak at 2Θ of 32.53° for all sample, it is indicated of hkl (121). Further calculation based on crystallography data was carried out by rietveld method with rietica software and the best quality will be applied as a gas sensor materials.

Abstract: Fibers are materials with advantageous properties such as lightweight material properties, has small pore size, and has high surface area, porosity,and permeability. An easy and simple method to prepare fibers is electrospinning. Using this method poly(methyl methacrylate) (PMMA) fibers were prepared. Several parameters include polymer concentration, solution flow rate, the distance of the nozzle tip to the collector, and the applied voltage were investigated to control the morphology, structure, and diameter of PMMA fibers. The Optimal electrospinning conditions for PMMA fibers production were a PMMA concentration is 8% (w/v), a power supply voltage is 20 kV, a distance of the tip of the nozzle to the ground collector is 15 cm, and a flow rate is 0.004 mL/min. The diameter distribution and morphology of the fibers were determined and characterized by Optical Microscopy and Scanning Electron Microscope (SEM), which showed that the produced fiber had an average diameter of 1.4925 µm, the contact angle of fiber PMMA is 125.307^o and the spreading time of fibers PMMA is about 360 minutes

Abstract: Thixoforming process is one method to improve the mechanical properties, especially in the manufacture of magnesium alloy components. This method is an alternative to lightweight structures and simultaneously efficient use of raw materials, fuel efficiency and environmental friendliness. The aim of this study is investigates the effect of ZnO nanoparticles addition on grain refinement of Mg-Al-Zn alloy by thixoforming. In these experiments, ZnO nanoparticles added from 0.1, 0.2, 0.3, 0.4 and 0.5 wt. % to Mg-Al-Zn alloy and thixoforming temperature set-up at 530°C. The results showed that the increasing of weight % ZnO nanoparticles cause decreasing grain size average of Mg-Al-Zn alloy both as-cast and thixoforming. On 0.5 wt. % ZnO addition was obtained grain refinement 39.87 μm (decreased 29.29%) and hardness 73.80 HB (increased 53.94%) compared to as-cast.

Abstract: The flexibility in replacing the organic part of the organic-inorganic hybrid material has become an interesting material parameter to tune the functionality of their inorganic part. Based on the optical absorption in the UV-VIS region, we are able to observe the d-d transition of the Mn²⁺ in (C₆H₅CH₂CH₂NH₃)₂-MnCl₄, and (NH₂CH₂CH₂NH₂)₂-MnCl₄ hybrid compounds. The results of this the experiment clearly indicate that there are six transitions related to the d-d transition of the Mn²⁺ from the high spin state, ⁶S, to the excited states of ⁴G, ⁴D and ⁴P. The transition energies are fitted to the Tanabe-Sugano diagram. The different in organic part change its Racah parameters and crystal field energy. This shows that the organic part could modify the bond strength between the Mn and the Cl as well as the electronic interaction.