OPTIMIZATION OF MACHINING PARAMETERS ON THE SURFACE ROUGHNESS OF ALUMINUM IN CNC TURNING PROCESS USING TAGUCHI METHOD

In this research, Taguchi method is employed by focusing on spindle speed, feed rate, and depth of cut to optimize the CNC turning parameters for aluminum alloy 6063. The main goal of this study is to improve the surface roughness of the material. A L9 orthogonal array is used for experimentation, and the results are subsequently analyzed using ANOVA (Analysis of Variance). A spindle speed of 1300 rpm, a feed rate of 0.5 m/min, and a depth of cut of 1.5 mm are the optimal conditions to achieve the minimum average surface roughness (Ra). The main effect plot of the signal-to-noise (S/N) ratio provides significant evidence supporting the primary research goal. Furthermore, the ANOVA table reveals that spindle speed contributes 59.71%, feed rate contributes 29.80%, while depth of cut only contributes minimally at 0.72%. Based on the research findings, spindle speed and feed rate can be adjusted to control surface roughness. Both factors are highly significant in influencing the surface roughness of the material. The prediction equation from the linear regression analysis is Ra = 1.745 – 0.001024 spindle speed + 0.3000 feed rate – 0.0233 depth of cut. A coefficient of determination or R-squared value of 0.9115 indicates that the independent variables can explain 91.15% of the variation in the dependent variable. The experimental and predicted surface roughness (Ra) values have a predicted error percentage of 2.26%

Synthesis of Spinel-Hydroxyapatite Composite Utilizing Bovine Bone and Beverage Can

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage cans were cut and milled to obtain fine Al powder and then sieved to obtain three different particle mesh size fractions: +100#, −140# + 170#, and −170#, or Al particle size of >150, 90–150, and <90 µm, respectively. The SHC was synthesized using the self-propagating intermediate-temperature synthesis (SIS) method at 900 °C for 2 h with (HAp:Al:Mg) ratio of (87:10:3 wt.%) and various compaction pressure of 100, 171, and 200 MPa. It was found that the mechanical properties of the SHC are influenced by the Al particle size and the compaction pressure. Smaller particle size produces the tendency of increasing the hardness and reducing the porosity of the composite. Meanwhile, increasing compaction pressure produces a reduction of the SHC porosity. The increase in the hardness is also observed by increasing the compaction pressure except for the smallest Al particle size (<90 µm), where the hardness instead becomes smaller

Sustainable recovery of Fe(II) Oxalate from steel industry waste using leaching, hydrothermal, and photo-reduction routes

The iron and steel industries have continuously expanded in recent years. These manufacturing companies are one of the main contributors to the environmental problems due to their by-products such as slag and mill scale. These solid wastes from iron and steel industries consist of a high iron element. Hence, the recovery of iron from these steel wastes can reduce secondary pollution and can have an economic benefit. Fe(II) oxalate is a critical building block material for several applications such as lithium-ion batteries, photocatalysts, pigment, etc. This work proposes a green synthesis technology with near-zero waste for the preparation of Fe(II) oxalate from steel waste in Indonesia. The following steps of leaching, photochemical reduction, and hydrothermal methods were used to achieve the purpose. The leaching process of steel waste using oxalic acid was conducted to produce a yellow precipitate of Fe(II) oxalate and the greenish filtrate (Fe(III) oxalate aqueous solution) as a by-product. The optimum dose of steel waste in oxalic acid solution was found at 50 mg/mL. Subsequently, photochemical reduction and hydrothermal were utilized to produce another Fe(II) oxalate from the greenish filtrate with high purity of Fe(II) oxalate in the form of α-FeC2O4⋅2H2O and β-FeC2O4⋅2H2O. A rod-like microstructure of Fe(II) oxalate was found in various sizes, depending on the synthesis route. A major particle length in the range of 4–10 μm was found for the leaching and photoreduction routes, while a larger size with a length of 150–350 μm was found for the hydrothermal one. Our results indicate that different methods influenced α or β crystalline structure as well as the particle size of Fe(II) oxalate

Recent Progress in Colloidal Quantum Dot Thermoelectrics

Semiconducting colloidal quantum dots (CQDs) represent an emerging class of thermoelectric materials for use in a wide range of future applications. CQDs combine solution processability at low temperatures with the potential for upscalable manufacturing via printing techniques. Moreover, due to their low dimensionality, CQDs exhibit quantum confinement and a high density of grain boundaries, which can be independently exploited to tune the Seebeck coefficient and thermal conductivity, respectively. This unique combination of attractive attributes makes CQDs very promising for application in emerging thermoelectric generator (TEG) technologies operating near room temperature. Herein, recent progress in CQDs for application in emerging thin-film thermoelectrics is reviewed. First, the fundamental concepts of thermoelectricity in nanostructured materials are outlined, followed by an overview of the popular synthetic methods used to produce CQDs with controllable sizes and shapes. Recent strides in CQD-based thermoelectrics are then discussed with emphasis on their application in thin-film TEGs. Finally, the current challenges and future perspectives for further enhancing the performance of CQD-based thermoelectric materials for future applications are discussed

Co-pyrolysis of oil palm trunk and polypropylene: Pyrolysis oil composition and formation mechanism

Pyrolysis oil can be used as a precursor to synthesize value-added biochemicals. Co-pyrolysis of two or more feedstocks generally improves the selectivity and yield of the target compounds. In this work, oil palm trunk (OPT) was subjected to single-feed pyrolysis and co-pyrolysis with polypropylene (PP) from 500 to 700 °C. The highest pyrolysis oil yield of 26.33 wt.% was obtained from OPT at 700 °C, which mainly contributed by the lignin decomposition in OPT. Phenolics (51.77–57.78%) and oxygenates (36.31–46.99%) were the major compounds detected in the OPT-derived pyrolysis oil. The addition of PP enhanced the formation of hydrocarbons (5.19–10.22%) and decreased the contents of phenolics (34.01–41.85%) in the co-pyrolysis oil. In the case of co-pyrolysis, the intermolecular reactions between PP and OPT-derived radicals led to the formation of ketones and alcohols, which contributed to the increase of oxygenates content. The highest oil yield of 16.17 wt.% was obtained at 600 °C from co-pyrolysis, the oil of which contained mainly phenolic compounds, oxygenated compounds (i.e., ketones and furans), and hydrocarbons. These findings highlighted the potential of oil derived from the pyrolysis of OPT (single feed) and co-pyrolysis of OPT and PP (binary feed) for the production of value-added chemicals

Optical and Photodetection Properties of ZnO Nanoparticles Recovered from Zn Dross

In this study, we report the synthesis of ZnO nanoparticles from Zn dross via hydrometallurgical method by using acetic acid as a leaching agent. D205 dye molecules were then adsorbed onto Zn dross originated ZnO nanoparticle film. The optical absorption confirms the photosensitization of the synthesized ZnO nanoparticles with dye. The photoluminescence spectra reveal the excitonic- and defect-related emission of ZnO nanoparticles. Compared to ZnO nanoparticles only, the longer emission lifetime of ZnO nanoparticles with adsorbed dye indicates the transfer of photoexcited electrons from dye to the ZnO nanoparticles. Furthermore, photodetection characterization of ZnO film show the enhanced current density with the presence of dye under simulated solar illumination, while that measured at dark is similar in both films with and without dye. This result confirms the potentiality of Zn dross to be recycled into valuable ZnO nanoparticles particularly for the applications in the visible light region, especially for sensing