Hydroxyapatite (HAp) is one of the constituent minerals of bone and teeth, that has been widely used for synthesizing bone graft. Due to the limitation on properties of the hydroxyapatite, it is doping with Magnesium (HAp-Mg). The addition of Chitosan (Chi) was expected to improve the antibacterial properties of HAp-Mg. The present research aims to study the influence of Chitosan with 0, 5, 15, and 25 wt% addition on biocompatibility properties of Chi/HAp-Mg composite. HAp-Mg was synthesized using the sol-gel method; meanwhile, Chi/HAp-Mg composite was manufactured by mixing Chitosan in acetic acid, and HAp-Mg was added into the mixture. The synthesized samples were characterized using XRD and SEM. In vitro antibacterial activities of the Chi/HAp-Mg composite were evaluated against Escherichia coli bacteria. Biocompatibility analysis from antibacterial activity showed that composite with the optimal composition on the addition of 15 wt% Chitosan has the best ability in inhibiting the growth of E. coli bacteria. Abstrak Studi Antibakteri Komposit Kitosan/Hidroksiapatit Terdoping Magnesium sebagai Material untuk Aplikasi Cangkok Tulang. Hydroxyapatite (HAp) adalah salah satu mineral penyusun tulang dan gigi yang telah banyak digunakan untuk sintesis cangkok tulang. Karena keterbatasan pada sifat hidroksiapatit diperlukan doping dengan Magnesium (HAp-Mg). Penambahan Chitosan (Chi) diharapkan dapat meningkatkan sifat antibakteri dari HAp-Mg. Penelitian ini bertujuan untuk mempelajari pengaruh Chitosan dengan penambahan 0, 5, 15, dan 25 wt.% pada sifat biokompatibilitas komposit Chi/HAp-Mg. HAp-Mg disintesis menggunakan metode sol-gel; Sementara itu, komposit Chi/HAp-Mg diproduksi dengan mencampurkan Chitosan dalam asam asetat kemudian HAp-Mg ditambahkan ke dalam campuran. Sampel yang disintesis dikarakterisasi menggunakan XRD dan SEM. Aktivitas antibakteri in vitro dari komposit Chi/HAp-Mg diuji terhadap bakteri Escherichia coli. Analisis biokompatibilitas dari aktivitas antibakteri menunjukkan bahwa komposit dengan komposisi optimal pada penambahan 15 wt.% Chitosan memiliki kemampuan terbaik dalam menghambat pertumbuhan bakteri E. coli.
In this work, Myrmecodia pendans, or sarang semut, was successfully extracted as a potential organic inhibitor. Various concentrations of Myrmecodia pendans extract in 1 M H 2 SO 4 solution were applied in the range of 100-500 mg/L for corrosion inhibition. Gas chromatography-mass spectroscopy (GC-MS) showed that the Myrmecodia pendans extracts contained a high-benzenediol compound with rich oxygen atom content, which played an important role in the inhibition process. The 300 mg/L Myrmecodia pendans extract had the highest effect, decreasing the rate of corrosion from 177.73 mpy to 47.4 mpy. This was attributed to the chemical compounds present in the Myrmecodia pendans extract on the surface of mild steel, which prohibited the corrosion rate.
Weld overlay is one of veneering method that do by welding on the base metal, so there is wear resistant, additional layer and corrosion resistant. Vibration load that work continue on engine block causing worn out on the components that be in the engine block, one of which occurs on both sides of the main cap that directly intersect to the engine block, however it needed an appropriate repair method that is weld overlay method that giving additional layer and wear resistant. This research is using filler ERNi-CI dan ERNiFe-CI on weld overlay method GTAW with current variation on main cap that made from nodular cast iron. Trials that did is conducted metallography and hardeness. The observation result of metallography show that micro structure in HAZ area and base metal contain more ferrite on the lower current. The more heat input however the more it decreasing hardeness value on weld metal and fusion line. This is caused by the more heat input, however cooling that happens become slow. The hardeness value of welding filler ERNiFe-CI is more high than the hardeness value of welding filler ERNi-CI effect of influence the numbers of nickel composition on the filler.
The purpose of this study was to analyze the effect of CO2 on the composition of the Ar-CO2 shielding gas in DSS 31803 duplex welding using GMAW on carbon deposition, ferrite fraction, microstructure, weld and HAZ mechanical properties. This study uses A (100% Ar), M1 (95% Ar + 5% CO2), M2 (90% Ar + 10% CO2), M3 (85% Ar + 15% CO2), M4 (80% Ar + 20 % CO2), M5 (75% Ar + 25% CO2) and C (100% CO2). From the results of the study, the microstructure of the weld metal in each specimen contained grain boundary austenite (GBA), Widmanstätten austenite (WA), intragranular austenite (IGA), and partial transformed austenite (PTA). Scanning electron microscopy (SEM) identifies the occurrence of chrome carbide precipitation (Cr23C6) HAZ region in specimens M5 and specimen C. The equilibrium phase of ferrite and austenite in weld metal areas is fulfilled in specimens A (34.8), M1 (38.9), M2 (36.4), M3 (38.4) and M5 (45.9). The highest average hardness value of vikers in weld metal area is found in M5 specimen which is 255 HV. While the lowest value in specimen C is 238 HV.The highest Vickers average hardness value in the heat affected zone (HAZ) is in specimen A which is 271 HV and the lowest hardness is in specimen C which is 245 HV. High tensile strength values are found in specimen M5 with value 800 MPA. While the value of low tensile strength in M4 specimens which is 652 MPA.
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