Dedi Priadi

Tensile Characteristics of Coconut Fibers Reinforced Mortar Composites

Natural fibers such as coconut fibers are numerous in Indonesia. The tensile strength of coconut fibers produced in this country is among the highest of natural fibers ones. This paper is to determine the tensile strength of coconut fibers with or without special treatment (water washing dry) and assessment the ability of coconut fiber for reinforcement in mortar composites. Experimental observations on coconut fibers and mortars carried out. There were tensile tests and scanning electron microscopy (SEM) providing microstructural properties of coconut fibers. The results showed that the coconut fibers treatment increases tensile strength and provides higher failure strain values. It showed that coconut fibers largely improved tensile strength behavior of mortar composites. To a conclusion, the coconut fibers are able to be used as reinforcement for ductile mortar composites.

Synthesis of Amylopectin Macro-Initiator for Graft Copolymerization of Amylopectin-g-Poly(Methyl Methacrylate) by ATRP (Atom Transfer Radical Polymerization)

Graft copolymer of Amylopectin and PMMA was synthesized by atom transfer radical polymerization (ATRP) method. The hydroxyl groups of amylopectin partially substituted with tert-butyl a-bromoisobutyrate to form tert-butyl a-bromoisobutyrate (TBBiB ) groups. This compound is known as an efficient macro-initiator for ATRP process. This research, aimed to obtain a bio based polymer of Amylopectin, in which the amylopectin was used as macro-initiator in the ATRP of MMA. The experiment was carried out in the homogeneous system under temperature range of 40 – 70°C in DMSO solution using TEA as catalyst. The modified amylopectin-TBBiB then was grafted to methyl methacrylate trough ATRP. Product characterization indicates that the graft copolymer Amylopectin-g-PMMA is efficient and the obtained product owns well defined structures

Analysis of Coconut Carbon Fibers for Gas Diffusion Layer Material

The main compound of natural fibers is a hydrocarbon. The heating of hydrocarbon in inert gas produces charcoal or carbon. Carbon materials are widely used for several purposes depending on the physical and electric properties, for example for hydrogen storage, conductive or reinforced plastics, catalyst supports, batteries and fuel cells. The main raw material of Gas diffusion Layer (GDL) of the Proton Exchange Membrane Fuel Cell (PEMFC) is a carbon. The properties of GDL are porous and electron-conductive material, because of the function of GDL is to distribute the gas as fuel and electricity conductors. This study aims to analyze the carbon fibers made from coconut fibers for the application of GDL materials. The carbon fiber was made using pyrolysis process in the inert gas (nitrogen) at a certain temperature according to the analysis of Differential Thermal Analysis (DTA) 3000C, 4000C, 5000C, 6000C, and 9000C. The crystalstructure, carbon content, powder density and morphology of carbon fibers were observed using X-Ray Diffraction (XRD), fixed carbon according to ASTM D 1762-64, Archimedes method (BS 19202 Part 1A), and Scanning Electron Microscope (SEM), respectively. The results showed that the structure of carbon was amorphous, and content of 51% ̶ 71%, powder density of 0.42g/cm3 ̶ 0.71g/cm3. The morphology having many parallel hollows like a tube that are close to each other with diameters of 2m ̶ 10m, and in the wall of tube there are some porous with sizes around 1m. According to this analysis, the coconut carbon fiber enables to be applied as candidate for a basic material of GDL.

Study of the Electical Conductivity of Oil Palm Fiber Carbon

The physical properties of carbon from natural fibers are strongly influenced by the conditions of carbonization process. Temperature carbonization process of natural fibers affects the structure and electrical properties of carbon. This research studied the influence of carbonization process to the electrical conductivity and the microstructure of carbon from oil palm fibers. Oil palm fiber carbonization process has been carried out at the temperature of 500°C and 900°C for 1 hour in the atmosphere of inert gas (nitrogen) and at a temperature of 1300°C performed using a Spark Plasma Sintering (SPS). Structure of oil palm fiber carbon analyzed using XRD and SEM, electrical conductivity measurements carried out using LCR meter. XRD data analysis showed that the carbon structure is amorphous, and carbonization process up to 1300°C cause increase of the degree of crystallinity, that are 36.92%, 39.07% and 42.48% for 500°C, 900°C and 1300°C respectively. Increase of carbonization temperature also causes the electrical conductivity of carbon that are (3.3 x10-6) S/m – (4.8 x10-6) S/m for carbon 500°C, 1.29 S/m – 1.3 S/m for carbon 900°C, and (1.4 x10) S/m – (1.7 x10) S/m for carbon 1300°C.

Surface Modification of SKD 61 by Electrical Discharge Coating (EDM/EDC) with Multilayer Cylindrical Electrode and Jatropha Curcas as Dielectric Fluid

Electrical Discharge Machining (EDM) is the most extensive non-conventional material removal processes used. In recent years, EDM researchers have been explore several sparking efficiency improvement methods including some unique experimental concepts that begin from the EDM traditional sparking phenomenon. This paper reports the use of layered cylindrical electrodes combined with jatropha curcas as dielectric fluid which is not widely used in the EDM process. The results are compared with the EDM process using kerosene dielectric fluid and single electrode (conventional). Dielectric fluid jatropha curcas is expected to substitute the commonly used dielectric fluid. Dielectric strength was tested by the impulse method. Furthermore, the EDM process is measured using surface roughness and microhardness of white layer values at various cutting conditions on the material SKD 61 as an indicator. The highest value of white layer hardness using jatropha curcas dielectric fluid is provided by three layers of electrodes, whereas the lowest is resulted of two layers of electrodes. Meanwhile, the use of kerosene dielectric fluid, the highest hardness value is achieved by two layers of electrodes, and the lowest is produced by three layers of electrodes. This study shows that jatropha curcas dielectric fluid is potential to be used in the EDM process since it produces a smoother surface and higher white layer hardness value.

Effect of Equal Channel Angular Pressing and Post Heating on Microstructure and Hardness of Cu-Zn 70/30

Severe plastic deformation (SPD) using various pass number of Equal Channel Angular Pressing (ECAP) experiment and followed heating at 400°C has been done for rod brass Cu-Zn 70/30 to investigate the operation on microstructure and hardness of the alloy. Optical microscopy and SEM are used to examine the microstructure change. Mechanical testing such as macro and micro hardness test is used in order to examine the change of mechanical properties. The grain structure of the alloy was refined from 34 μm to 2 μm after 4 passes ECAP and increased to 4 μm after post heating. The hardness of the alloy significantly increased from 78 Hv to 235 Hv after 4 passes and decreased to 135 Hv after post heating after ECAP. The microstructure and mechanical properties of the alloy was homogenous after 4 passes ECAP because the strain was found more homogenous.

Study of crystallization kinetics of peek thermoplastics using Nakamura equation

We have simulated the time evolution of relative crystallization of PEEK at various cooling rates (10, 15, 20 °C/min) and made comparison with the experiments. The simulation was conducted using Nakamura model which is a modified Avrami model. The model is a 1 cm radius of circle with the cooling plate which was placed in the upper part of the circle. The cooling plate temperature was varied in order to obtain particular cooling rates. The measurement point is located near upper boundary in order to minimize the heat transfer effect. The general trend of time evolution of crystallization was well captured although some discrepancies occured. These discrepancies may be attributed to the heat transfer effect and secondary crystallization.We have simulated the time evolution of relative crystallization of PEEK at various cooling rates (10, 15, 20 °C/min) and made comparison with the experiments. The simulation was conducted using Nakamura model which is a modified Avrami model. The model is a 1 cm radius of circle with the cooling plate which was placed in the upper part of the circle. The cooling plate temperature was varied in order to obtain particular cooling rates. The measurement point is located near upper boundary in order to minimize the heat transfer effect. The general trend of time evolution of crystallization was well captured although some discrepancies occured. These discrepancies may be attributed to the heat transfer effect and secondary crystallization.

Fabrication of punch and die of micro-blanking tool

The difficulties of tool fabrication in micro level provide an enormous challenge due to the dimension limitation. Reducing the difficulty and tool cost fabrication should always be considered by determining the simplicity of tool geometry, precision tolerance, and an appropriate material selection. This paper study about the manufacturing of micro-blanking punch-die. The mechanical material removal method was chosen to fabricate punch-die since this is a single piece production and intended for small-scale production of micro parts. The manufacturing process consists of punch-die design and fabrication, tool assembly, and clearance measurement. The stress analysis is also conducted to ensure the strength of the punch-die. A micro-blanking experiment was held to observe the tool performance. The result showed that micro-blanking tool can be manufactured successfully and used well to conduct the micro-blanking experiment.

PENGEMBANGAN METODE EVALUASI KEKUATAN PROFIL BAJA PERSEGI MENGGUNAKAN PEMANFAATAN GABUNGAN TEORI MEKANISME PLASTIS DAN ELASTIS = DEVELOPMENT OF STRENGTH EVALUATION METHOD OF A SQUARE HOLLOW STEEL SECTION USING THE APPLIACATION OF COMBINED THEORIES OF PLASTIC MECHANISMS AND ELASTIC APPROACH

Metode analisis disain yang dikembangkan didalam penelitian ini tidak menggunakan faktor keamanan sehingga dapat digunakan untuk mendisain struktur baja yang mampu mendukung beban kerja dengan berat yang seringan mungkin sehingga diperoleh struktur yang efektif dan efisien dari segi teknis dan ekonomi. Dalam penelitian ini, suatu metode cut-off strength digunakan sebagai dasar untuk memprediksi kekuatan profil baja ringan berpenampang persegi (SHS) akibat interaksi beban tekan memusat dan momen lentur. Metode cut-off strength diilustrasikan dalam bentuk dua kurva beban-defleksi plastis dan elastis, dimana nilai beban diperpotongan kedua kurva tersebut diasumsikan sebagai kekuatan teoritis profil baja SHS terhadap interaksi tekan memusat dan momen lentur. Kurva plastis dibentuk berdasarkan persamaan beban-defleksi yang dikembangkan melalui analisis kesetimbangan energi model mekanisme kerusakan plastis profil baja SHS. Sementara itu, kurva elastis dibentuk berdasarkan persamaan beban-defleksi yang dikembangkan melalui analisis non-linear elastic profil baja SHS dengan mempertimbangkan efek local buckling pada penampang profil yang tertekan. Metode analisis ini diimplementasikan dengan menggunakan perangkat lunak (software) komputer. Untuk mengukur ketelitian model analisis disain yang dikembangkan dalam penelitian ini, hasil prediksi kekuatan profil baja SHS diverifikasi menggunakan data kekuatan aktual yang dihasilkan melalui pengujian sejumlah profil baja SHS akibat interaksi beban tekan memusat dan momen lentur sampai rusak. Hasil verifikasi menunjukkan bahwa rasio data prediksi analitis dan eksperimental masih tersebar dalam batas-batas toleransi yang umum digunakan yaitu ± 20 %.

Interaction of Purple Sweet Potato Extract with Ascorbic Acid in FeCl3 Solution

Utilization of ascorbic acid as corrosion inhibitor has several weaknesses. These weaknesses are easy to oxidize in solution form and reduction of its antioxidant properties due to heat, light, oxidizing agent, dissolve oxygen, and heavy metals. Purple sweet potato extract is an alternative green corrosion inhibitor with major contains of anthocyanin compound. Anthocyanin will withstand enzymatic reaction and oxidation process of ascorbic acid. Addition of purple sweet potato extract in ascorbic acid will enhance inhibition efficiency of steel compare to the used of ascorbic acid alone. Interaction of purple sweet potato extract with 0.01M ascorbic acid in 0.1M FeCl3 environment was analyzed using FTIR spectroscopy. The result shows that interaction of purple sweet potato extract with ascorbic acid in 0.1M FeCl3 build ability to form iron chelate.