Key Engineering Materials Vol. 840

Abstract: Hydroxyapatite (HAp) made of capiz shell has been successfully coated onto stainless steel 316L substrate using electrophoretic deposition (EPD) method. In this study, three variations were applied, they were the voltages of 25 V and 50 V, the withdrawal speeds of 0.1 mm/s, 0.5 mm/s, and 1 mm/s, and the sintering temperatures of 750, 850, and 950 °C. These variations were applied to determine the differences in morphology and crystal structure of the layers so that the most suitable result was obtained as a candidate for the bone implant. Characterization was done by Scanning Electron Microscope and X-Ray Diffractometer. The EPD process and the application of sintering temperature eliminated the phase of B type apatite carbonate which made the purity of the HAp layer higher. The SEM results show that the layer was more homogeneous and free of cracking at a voltage of 50 V and the withdrawal speed of 0.1 mm/s. The layer density was higher as the voltage and sintering temperature increased. Higher sintering temperature also made the layer more homogeneous, but at 950 °C, stainless steel 316L substrate underwent a phase transformation which caused the decreasing of the purity of the HAp layer. The best results were obtained by applying a50 V voltage, a withdrawal speed of 0.1 mm/s, and a sintering temperature of 850 °C.

Abstract: The proportion of MTA powder and water is a common factor impacted on the properties of the material in clinical application. The purpose of this research was to determine the compressive strength and porosity of Mineral Trioxide Aggregate (MTA) mixed with varying water-to-powder (WP) ratios. ROOTDENT MTA was investigated. One gram of cement was mixed with 0.28, 0.33 or 0.40 grams of distilled water and was submerged either for 1, 7, or 28 days in the water. The chemical composition of un-hydrated MTA was characterized by X-ray fluorescence. Samples were carried out for compression and porosity test. ROOTDENT MTA was composed primarily of calcium, oxygen, and zirconium. Minor quantities of sodium, aluminum, and silicon were presented in the cement and lack of bismuth was found. The highest mean compressive strength value was MTA with 0.33 WP ratio submerged in the water for 28 days. The percentage of porosity increased as the WP ratio increased. The percentage of porosity submerged in the water for 7 and 28 days showed no significant differences while the lowest porosity was MTA with 1 day in the water.

Abstract: Preparation of mucoadhesive patch film containing Virgin Coconut Oil (VCO) has been made as a medium to inhibit the growth of Streptococcus mutans. This research was conducted to make patch film which meets the standard physical characteristic of patch mucoadhesive film. The physical characteristic is weight uniformity, thickness, folding endurance resistance, swelling index and pH of the patch solution. The presence of fatty acids which trapped in patch was analyzed with Gas Chromatography Mass Spectrometry (GC-MS). The result showed that the patch film has uniformity value of weights ranging from 0.04 to 0.17 g. The thickness of patch was 0.53 to 0.61 mm and have folding endurance resistance more than 300 times. Swelling index for each patch increase in the 5^th minutes and decrease in the 10^th minutes. The surface pH of the patch almost close to pH 7. GC-MS chromatogram showed that lauric acid (C8), meristic acid (C14), palmitic acid (C16) and linoleic acid (C18) were trapped in the patch. The patch film containing VCO can inhibit the growth of Streptococcus mutans with inhibition zone of 157.30 ±1.088 mm².

Abstract: Synthesis and stability of silver nanoparticles (AgNPs) using tyrosine as a reducing and capping agent have been done. Synthesis of AgNPs was performed by mixing silver nitrate (AgNO₃) solution as a precursor with tyrosine amino acid and heating it in a boiling water bath until characterized by the appearance of color change from colorless to yellow. Variations in pH, concentration, and reaction time affecting the formation of AgNPs were studied using UV-Vis spectrophotometry in the wavelength range of 300-700 nm as the main device. The synthesis was successfully conducted at pH 11 for 45 min with the optimum tyrosine concentration was 3 mM for 0.5 mM AgNO₃. The optimum mole ratio AgNO₃ 0.5 mM to tyrosine 3 mM was 1:6. TEM and PSA characterizations showed that the particle was a round shape and 29.5 nm is average size, respectively.

Abstract: Tissue engineering has shown a remarkable result in medical applications. Further exploration, these multidisciplinary fields are also given a possibility as an alternative medication for intervertebral disc (IVD) degeneration. Focusing on the annulus fibrous repair, to improve the mechanical properties of biomaterials, a composite made of chitosan and polycaprolactone (PCL) was developed in this present study. Due to its tuneable properties, the electrospinning-based method was used in the experiment to create the chitosan/PCL composite. Varies concentration of PCL (11, 12, and 13 wt%) and a different ratio of precursors chitosan to PCL (1:1; 1:3; 1:5) were used to optimize the composition of natural and synthetic polymer in the composite nanofibers. The obtained nanofibers were then characterized using Scanning Electron Microscopy (SEM) to observe the morphology, swelling test, Fourier Transform Infrared (FTIR) spectroscopy, and Differential Scanning Calorimetry (DSC). The results show that the increasing concentration and composition of PCL could form the more homogeneous and larger diameter of nanofiber with fewer beads compare to the lower composition of PCL nanofiber. Meanwhile, the swelling percentage decreases by increasing the amount of PCL. FTIR results also show that all samples of composite nanofibers contain both chitosan and PCL.

Abstract: Surface mechanical attrition treatment (SMAT) has been recognized as a potential surface treatment for improving the strength and the wear resistance of magnesium (Mg) and its alloy. However, this treatment potentially increases the degradation rate of these particular materials. Therefore, additional treatments might be needed to overcome such limitation of the SMAT. In this research, the influence of polishing on the degradation of the SMAT-processed AZ31B Mg alloy was investigated. Weight losses measurement and pH monitoring were carried out to determine degradation behavior of the Mg alloy during an immersion test in 3.5 wt.% NaCl solution. The results showed that the degradability of the Mg alloy decreased with the application of polishing to remove the rough surface layer and the Fe contaminant on the material surface generated by the SMAT. Based on all the findings in this work, it can be concluded that the SMAT is indeed a promising technique for lowering the degradability of AZ31B Mg alloy, but such an advantage was masked by the increased roughness and contamination of the alloy surface with this treatment.

Abstract: Chemosensor of imidazole derivative (4-(4,5-diphenyl-1H-imidazol-2-yl)-2-methoxy-6-nitrophenol) (IMD-1) has been synthesized and tested for amines sensor. IMD-1 was synthesized from the reaction of 5-nitrovanillin, 1,2-diphenylethane-1,2-dione (benzil), and ammonium acetate using reflux method. IMD-1 showed fast respond and color change from light orange to orange in naked eye compared with the imidazole derivative without nitro group (IMD-0). The IMD-1 could detect butylamine quantitatively with detection limit of 1.03 x 10^-4 M.

Abstract: Simple and low-cost homemade Rotating Analyzer Ellipsometer (RAE) configuration has been developed. Ellipsometer measures the changes of the reflected light polarization of the sample, yielding to the ratio of amplitude (ψ) and phase difference (Δ) between p- and s-polarization. Based on the ψ and Δ values, the dielectric constant of the sample can be extracted. However, the available manufacturer-made ellipsometer is quite expensive and is not a good choice for the student to learn the optical concept since the complexity of its structure could hide the simple optical concept during the measurement. In this work, we have built RAE that constituted of relatively simple components and low-cost as well as simple configuration. Here, we also show the principle of measurement and the ellipsometry data analysis using the optical model related to the system under study Drude-Lorentz model. The calibration of our SE has been done by measuring standard materials in the energy range of 1.5 to 3.3 eV and it was compared to the reference measurement using standard ellipsometer. The result is surprisingly accurate within the error of 5%. This research can be used for studying the several important optical concepts as well as for investigating nanostructured materials.

Abstract: Using a CO₂ laser photoacoustic spectroscopy with intracavity setup and multicomponent method we have done measurement on the ammonia, ehtylene and acetone gas concentrations in the breath of liver disease patients and in the healthy volunteers. The results of multicomponent analysis show that the average concentration of ammonia gas obtained from the breath of liver disease patients and healthy volunteers are (3.27 ± 0.75) and (1.34 ± 0.24) ppm, respectively. The highest and the lowest ammonia gas concentration of liver disease patients are 4.77 and 1.99 ppm. While, the highest and the lowest ammonia gas concentration of healthy volunteers are 1.89 and 1.08 ppm. For the ethylene and acetone concentrations, we found no significant difference between the average concentrations in the liver disease patients and in the healthy volunteers.

Abstract: The development of portable instrumentation for heavy metals analysis was increased rapidly. However, the quality of data from portable methods has so far been questioned when compared to conventional instrumentation. In this research, a comparative study of conventional and portable instrumentations for Cr(VI) analysis on liquid waste water of Chemistry Laboratory at Universitas Gadjah Mada (UGM) was conducted. This research started with validation and statistical evaluation of instrumentation methods which are UV-Visible spectrophotometer, portable spectrophotometer (PiCOEXPLORER) and Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). The validation methods consist of determination of linearity, sensitivity, limit of detection and limit of quantification. The results showed that the validation methods of ICP-AES were better than PiCOEXPLORER and UV-Vis spectrophotometer. Based on t-test, it was obtained that the result of Cr(VI) analyses with the comparison of UV-Vis and PiCOEXPLORER, ICP-AES and PiCOEXPLORER, and UV-Vis and ICP-AES; there were no significant difference (t_count< t_table). The ANOVA test (F test) results showed that the F_count value is less than F_table so that the results of Cr(VI) analysis in the standard solution and liquid waste samples measured by three instrumentations. Thus, it was concluded that portable instrumentations was good and gives the same quality as conventional instrumentations (UV-Vis and ICP AES).