Key Engineering Materials Vol. 851

Abstract: Subsequent processing through machining for biocompatible Zr-based BMG previously developed is needed in order to enlarge the material application, especially for medical devices. In this study the performance of CuCr tool on EDM process was investigated to cut biocompatible Zr-based BMG having low machinability nature. The experiment utilized volume loss technique to measure the TWR and consecutive SEM observation to reveal the tool wear mechanism of selected tool samples. The tool wear behavior was strongly characterized by the combination of discharge current and pulse-on time, where the larger TWR obtained by higher current and shorter pulse-on time. By SEM analysis, the irregular-shaped surface morphology with the presence of debris was observed on the tool wear region resulted by high discharge energy process. Additionally, the larger crater size, microvoids and numerous debris particles were also appeared on BMG workpiece surface machined using higher discharge energy.

Abstract: Properties of Bacterial Cellulose was depended on the fermentation conditions to produce BC as well as the processing steps for modifying the Bacterial Cellulose microstructure. This study reports on the comparison effect of drying method on Bacterial Cellulose films structure produced from Pineapple Peel Extract. The drying method was done in the oven and freeze-drying. Pellicle as results of fermentation by bacteria was dried in the oven. High-pressure homogenization was applied before the freeze-drying method. BC film structure was observed using scanning electron microscopy and evaluated using X-ray diffraction. The results show that the peak of diffractogram shows crystalline peaks in a relatively similar position, which are at about 14° and 22°. High-pressure homogenizer process before freeze-drying results the structure with higher crystalline compare than oven drying. The index of crystalline and degree of crystalline of BC film in the freeze-drying method were higher than those in the oven with a value of 83% and 86% compared than 81% and 84%, respectively. Drying methods to pellicle in the oven and freeze-drying results in the degree of crystalline of 79% and 71%, respectively. The morphology of the freeze-drying methods contains a more porous structure.

Abstract: Bacterial cellulose (BC) has applied as a versatile biomaterial in a wide variety of applications, such as biomedical devices, acoustics, electronics, and paper products. The controlling of the procedure could significantly improve the chemical and structure properties of the BC foams. This study aims to compare the features of BC foam that synthesized from BC disintegrated by a high-speed blender (HSB) and high-pressure homogenizer (HPH). The methods are the synthesis of BC using pineapple skin extract, disintegration process using both HSB and HPH following by freeze-drying process and characterization using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and FTIR. The results show that freeze-drying to the pellicle did not produce a foam structure of BC. SEM morphology indicates that the disintegration process using HPH produces a better porous BC foam compared than HBS process. XRD analysis shows three peaks associated with the structure of BC, which are at 14.47°, 16.85°, and 22.69°. The crystalline structure of BC foam produced from HPH process has higher than BC foam produced from HBS process. FTIR analysis shows that there is a new peak find out in BC foam after the disintegration process.

Abstract: Bacterial cellulose is natural polymers materials produced by Acetobacter xylinum with attractive physical properties because they are ordinary and uniform in structure. An alternative of cellulose from renewable source with more effective results to produce bacterial cellulose fibers. For this reason, the purpose of this paper is to show the effect of alkalization process on the bacterial cellulose film structure. The methods were the synthesis of bacterial cellulose using the extracts of pineapple waste. The pellicle product was treated using in the concentration of 0%, 1%, 5% and 10% then bacterial fiber films obtained from drying process of treated pellicle. Furthermore, the XRD and FTIR of bacterial cellulose were observed. The results of the structure of bacterial cellulose film was changed after a process in a high concentration of NaOH.

Abstract: This study aims to describe the results of characterization of physical properties and design comparation of knee implant. the characterization of the material was intended to determine the morphology using SEM, crystal structure using XRD, and chemical composition using XRF. In both designs, the simulation was carried out to get the total deformation value. Simulation is carried out by loading humans walking, jumping, and downstairs in 0-1.1 seconds. While the comparation was focused on comparizing the total deformation value from the human activity of walking, jumping, and downstairs to determine the optimum design. The finding of this study were SEM showed that many parallel strokes on Ti6Al4V, then XRD test showed that the crystallinity peak was at position 40.5189˚ which were indicated by the crystal orientation index [200] reaching 29.35 counts (cts), and Full Width Half Maximum (FWHM) at an angle of 0.288˚ which had an atomic distance along the length of 2.2246 (Å ) with a relative intensity of 100%. And the XRF test showed the highest chemical content of Ti6Al4V was Ti, amounting to 85.12%. This was indicated by the total maximal deformation of the first design 0.23030 micormeter while the second design was 2.109600 micrometer, so the first design was more recommended for implant use. While comparation of total deformation showed that the first design had the lowest maximum average deformation value. The results showed that the first implant design was the optimum design.

Abstract: This article explained the tolerance analysis method in the micro-manufacture area on the keychain cranioplasty plate product dimensions. This research aimed to compare the simulations of keychain cranioplasty plate product dimensions using the ISO 286 tolerance standard. The manufacturing process to produce the keychain cranioplasty plate used the blanking process. The dimensions analysis aimed to observe the effect of punching speed and tool punch material on the product’s quality. The ISO 286 tolerance on blanking product used IT Grade of 10 for the punching process. The keychain cranioplasty plate dimensions from the blanking process simulation had an excellent quality if the sizes were close to the actual product’s dimensions. The keychain cranioplasty plate product had to have a high precision level between 10–100 μm so that the medical field could use it.

Abstract: This research aimed to analyze the results of a hip joint implant made from Mg alloy using experimental and simulation methods with Finite Element Analysis (FEA). The experimental method’s target was to observe the microstructure, crystallite size, and magnesium alloy chemical composition. The simulation method was designed to analyze the total deformation, maximum principal stress, and maximum shear stress with time and load variations. This research used SEM, XRD, and XRF instruments to obtain the above data whereas FEA simulation used the ANSYS software. The simulation was conducted through walking, jumping, and walking down the stairs activities for 0–4.5 seconds. The SEM results showed that Mg alloy powder had an irregular shape or non-uniform particles with cracks or porous. The XRD results indicated that the crystallite size was 0.516 x 10^-4 nm. Then, the XRF results presented that Mg alloy powder had 11% Mg, 61.17% Ca, and 5.73% Zn. FEA results showed that the hip joint implant had a total deformation of 0.38 nm in walking activity, 0.82 nm in jumping activity, and 0.90 nm in walking down the stairs activity. The maximum shear strains were125.98 MPa in walking, 264 MPa in jumping, and 291 MPa in walking down the stairs. The maximum principal stress in walking activity was 192.76 MPa, in jumping was 397.48 MPa, and in walking down the stairs was 438.85 MPa.

Abstract: Nanofiber through electrospinning process has been developed as a promising material for wound dressing due to its large porosity and high surface area. This characteristic of nanofiber provides an adequate gas permeability surrounding the wound which prevents the healing failure. The best wound dressing not only maintain a wound to have a good gas permeability but also to have an active agent giving an antibacterial and antiinflammation property. This research aims to combine a synthetic polymer and active agent, polyvinylpyrrolidone (PVP) and Bassela rubra linn leaf extract (BRLE), become nanofibrous material. The electrospinning process was conducted in two steps. The first step is to obtain the best voltage of PVP electrospinning by using the voltage of 10, 12, 15, 17 kV. The other step is combining PVP to 2%, 5%, 8% of BRLE. The first step shows the best operation condition is using 12 kV. Hence, it is used to obtain nanofiber with different BRLE percentage. Based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the result indicates that increase the BRLE composition will rise the antioxidant activity because of the smaller diameter size.

Abstract: Mechanical failure of zeolite-high density polyethylene (HDPE) material applied to skull bone implants is a material fracture that cannot be controlled. An important step to minimize failure due to fracture is to understand the fracture characteristics indicated by the propagation path pattern. This study aimed to investigate the fracture propagation pathways of zeolite-HDPE composites in quasi-static conditions. UV-irradiated Double-edge cracked zeolite-HDPE composite was tested in mode I (a stress perpendicular to the plane of the crack) in a universal testing machine (UTM) with a crosshead speed of 2 mm/min at a constant room temperature of approximately 25°C. The stress and elongation were registered by the UTM. During loading, the evolution of cracks in the ligament length region was recorded with the camera so that the crack propagation pathway until the total fracture occurs can be clearly observed. The results show that the crack propagation pathway patterns were not all straight and parallel to the ligament length. They are also found in a deviant state of the ligament length line by forming an angle α. created between the ligament length line and the fracture propagation deviation direction. This deviation occurs after the crack propagates straight away from the initial-cracks.

Abstract: Pyrolytic characteristics and kinetics of cassava stalks as a renewable energy source were delved via a thermogravimetric (TG) analyzer. About 10 mg powder of the sample was heated up in the TG cavity under inert conditions with 50 ml.min^-1 nitrogen flow rate and operated at 20 °C min^-1 of heating program. The pyrolysis process of cassava stalks was taken place into three main stages, in which the peak reaction occurred at the second stage with 70% of the mass was degraded. The differential method of Arrhenius kinetic evaluation resulted in the values of reaction order (n) that was 0.99, activation energy that was 89.46 kJ/mol and logarithmic frequency factor (log A) was 7.7 min^-1.