Papers by Keyword: Cu

Abstract: CO₂ conversion to methanol via thermocatalytic hydrogenation is one of the viable alternatives to address climate change problem while producing a valuable industrial product. However, this comes with a challenge, i.e., predicting the performance of catalytic systems. In this work, we present a data-driven study to predict the performance of Cu-based catalyst based on a compiled dataset consisting of 15 features obtained from experiment data. Furthermore, we implement feature selection techniques such as univariate, RFE, and XGBoost to investigate how the performance of the prediction model changes with varied number of features. The results show that features selected by RFE method yields the best performance with 7 number of features, capable of even outperforms the baseline model in terms of accuracy and feasibilty. This suggests that feature selection technique is relevant in terms of constructing a machine learning model for predicting methanol production via CO₂ thermocatalytic hydrogenation.

Abstract: The degradation behavior of adhesion between cycloaliphatic epoxy resin and copper under high temperature and high humidity conditions was investigated. The Cu/resin joints were aged at 175°C and at 85°C in 85% R. H. The degradation behavior of the joint interface was analyzed by tensile tests and Fourier infrared transform spectroscopy (FT-IR). As a result, it was confirmed that the adhesion strength was retained after aging at 175°C for 1000 h, while it decreased with an increase in the aging time by aging at 85°C in 85% R. H. Furthermore, the interfacial fracture mode increased with aging at 175°C. In contrast, cohesive fracture was the main fracture mode and hardly changed by aging at 85°C in 85% R. H. The FT-IR analysis results showed that the peak intensity of the carbonyl group increases and that of the methylene group decreases by aging at 175°C. The result indicates that the resin was oxidized. Moreover, the peak intensities of carboxy and hydroxyl groups increased and that of ester groups decreased by aging at 85°C in 85% R. H. The results suggest that ester groups may be hydrolyzed due to aging and thus the adhesion is degraded.

Abstract: The influence of polyamide-6 (PA6), polyamide-12 (PA12), and their compositions was analyzed to determine the rheological behavior of the feedstock with 43% solid loading. The feedstock with Cu/PA composite constituents were extruded into filaments. The sphericity of particles, particle distribution, and voids was identified using Scanning Electron Microscopy (SEM). The capillary rheometer method was utilized to examine how shear rate and temperature impact the results. The viscosity and shear rate of the material was assessed at different temperatures and shear rates using an L/D ratio of 20 mm and a diameter of 11 mm capillary rheometer. The test results indicated that the polyamide composition influenced the feedstock's rheological properties. The viscosity of the feedstock decreased with an increase in the polyamide composition. Feedstock Cu/PA6 with a composition of 14wt%-Cu has the higher rheological properties among the variation of other composition both for PA-6 and PA-12. Viscosity and Flow energy activation Cu/PA-12 higher than Cu/PA-6.

Abstract: This article reports on the degradation behavior of adhesion strength of the resin/copper interface under aging in high temperature and high humidity environment. The adhesion strength of a Cu joint with resin was investigated by a tensile test. The fracture surface was analyzed by Fourier transform infrared spectroscopy to investigate the degradation mechanism. As a result, it was found that the degradation of the adhesion strength is mainly caused by water absorption and subsequent volume expansion of the resin, and embrittlement of hydrogen bonding in the joint interface. Evaluation of deterioration life of the joint revealed that the relationships between the deterioration life and the temperature and humidity are confirmed above the glass transition temperature.

Abstract: Competitive reactions and formation mechanism of microstructures in Mg/Cu super-laminate composites (SLCs) during initial hydrogenation were studied. During initial hydrogenation of Mg/Cu SLCs, hydrogenation of Mg and alloying of Mg with Cu followed by hydrogenation of Mg₂Cu are competitive. It is found that microstructures of Mg/Cu SLCs during initial hydrogenation have changed drastically depending on the order of hydrogenation of Mg and Mg₂Cu. The microstructures of Mg/Cu SLCs after initial hydrogenation can be categorized in 3 types.

Abstract: Stress-strain responses and microstructure of multi-phase CoCrCuMnNi and CoCrMnFeCu alloys in which Fe or Ni was replaced by Cu from Cantor alloy were studied. The deformation mechanisms of CoCrCuMnNi and CoCrMnFeCu were observed to be influenced by the presence of brittle sigma phase and the separated Cu-rich and the matrix phase. CoCrCuMnNi exhibited the relatively lower strength and excellent deformability, while CrMnFeCoCu alloy exhibited higher strength and lower ductility. The higher strength and the lower ductility of CoCrCuMnNi is associated with the presence more frequent and coarser sigma phase than those in CoCrCuMnNi.

Abstract: In bioleaching processes using autotrophic bacteria, CO₂ is the carbon source for the growth of the microorganisms and its availability is dependent on gas mass transfer. The objective of this study was to investigate the demand in CO₂ in complex copper concentrate bioleaching operations and to optimize CO₂ supply. Batch tests in 2L-stirred reactors at 10%_w/v solid load were performed to study the need for CO₂-supplementation and to determine the adequate CO₂ partial pressure in the gas inlet. The results show that Fe oxidation (and thus microbial activity) is delayed when air is injected without CO₂-supplementation. CO₂-supplementation improves leaching kinetics since Cu dissolution rate increases from 84 mg/L/h with air solely to 120 mg/L/h when CO₂ is added to air. The study proposes also a methodology to determine G/L transfer components and to asses CO₂ limitations in the system. It shows that the microorganisms are not only sensitive to the transfer rate of CO₂ from the gas to the liquid phase, but also to the availability of CO₂ in solution.

Abstract: The mechanical properties of sintered nanostructured Pb_1-xCu_xTe (0 ≤ x ≤ 0.2) alloy systems were investigated using nanoindentation technique. The powder precursors of the designed systems were prepared by ball milling technique and sintered by hot isostatic pressing. Cu acts as a dopant in these alloy systems, and an increase in its concentration, up to x = 0.1, leads to a more dense and refined nanostructure along with enhancements in both hardness and Young’s modulus. The Cu addition caused an apparent embrittlement in the materials, and spalling of the materials was recognized when x exceeded 0.15. These results imply that design parameters of complex mechanical environments under thermal shocks and vibrations cannot be determined only in terms of hardness and Young’s modulus of thermoelectric systems like Pb_1-xCu_xTe alloys.

Abstract: AlMgSi alloys (6XXX series) provide a good strength due to the precipitation of β” and β (Mg₂Si) phases. They have also very good formability which is required for different forming process after appropriate heat treatments.This work was carried out to investigate the effect of the addition of copper and the excess of Si on the response of natural and artificial aging of two Al-Mg-Si alloys. The aging parameters on precipitation sequence of two Al-Mg-Si alloys with and without excess Si were studied by DSC, MET and Vickers hardness measurement. The combined effect of Cu, Fe and excess of Si was found to accelerate the precipitation of the hardening phases. The additions of copper to the AlMgSi refine the average of the grain size and have a greater hardening effect compared to the excess silicon addition.

Abstract: This paper presents the novel microstructure design, called Harmonic Structure, which gives structural metallic materials outstanding mechanical properties through an innovative powder metallurgy process. Homogeneous and ultra-fine grain (UFG) structure enables the materials high strength. However, such a “Homo-“ and “UFG” microstructure does not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in the early stage of the deformation. As opposed to such a “Homo-and UFG“ microstructure, “Harmonic Structure” has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the harmonic structure is heterogeneous on micro-but homogeneous on macro-scales. In the present work, the harmonic structure design has been applied to pure metals and alloys via a powder metallurgy route consisting of controlled severe plastic deformation of the corresponding powders by mechanical milling or high pressure gas milling, and subsequent consolidation by SPS. At a macro-scale, the harmonic structure materials exhibited superior combination of strength and ductility as compared to their homogeneous microstructure counterparts. This behavior was essentially related to the ability of the harmonic structure to promote the uniform distribution of strain during plastic deformation, leading to improved mechanical properties by avoiding or delaying localized plastic instability.