Papers by Keyword: Precipitation

Abstract: Applications of advanced heat resistant ferritic steels in boiler repairs require detailed information on the creep behaviour of welds made of various combinations of steels. The paper deals with the results of hardness and microstructure characterization of a dissimilar circumferential weld of 14MoV6-3 and P91 tubes after about 10 years of service exposure in a boiler operated at 580 °C and steam pressure of 10.3 MPa. The P91 tube (f38x4 mm) was welded to the 14MoV6-3 tube (f38x6.3 mm) using the GTAW (141) technology. Bőhler-FOX IN 9-IG (3Cr0.5Mo0.3V) wires were applied as a filler material. Microhardness evaluation after long-term service exposure revealed two carburized zones, values in these zones did not exceed 350 HV0.5. The slowdown of recrystallization in partially decarburized areas of the 14MoV6-3 and the WM suppressed the formation of soft ferritic bands along fusion lines. This phenomenon is related to the high thermodynamic stability of V(C,N) particles in vanadium-bearing low alloy heat resistant ferritic steels at temperatures below 600 °C.

Abstract: The exponential growth of electronic waste (e-waste), particularly from discarded SIM cards, has raised significant environmental concerns due to the presence of valuable metals such as copper (Cu). This study investigates the recovery of copper from SIM card waste through hydrometallurgical methods, focusing on the effects of pH and reaction time on the precipitation of Cu(OH)₂. The SIM card waste was leached using nitric acid, followed by copper precipitation through the addition of sodium hydroxide at various pH levels (11, 12, 13, and 14). The solid precipitates were analyzed using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) to determine their morphology and functional group composition. The results indicate that optimal conditions for copper precipitation were achieved at a pH of 11, yielding the highest purity and the lowest Cu concentration in the filtrate. SEM analysis revealed that Cu(OH)₂ particles formed distinct crystal structures that varied with pH, while FTIR confirmed the presence of Cu-OH functional groups, indicating successful copper recovery. This study highlights the potential of hydrometallurgical processes for environmentally friendly copper recovery from e-waste, providing insights into optimizing industrial-scale applications.

Abstract: To investigate the effect of the oxygen amount involved in mechanical alloying (MA) of Al and Y₂O₃ powders on the phase evolution of the alloy powders, two types of MA were performed: MA with low and high oxygen content in the MA atmosphere. Analyses of the lattice parameter and composition of the Al matrix by X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy, respectively, and the integrated intensity of Y₂O₃ indicated that in the low-oxygen MA, the driving force for Y₂O₃ precipitation was small and Y and O dissolved into the matrix, producing supersaturated solid solution powder, while in the high-oxygen MA, the driving force for Y₂O₃ precipitation was large, resulting in the formation of Y₂O₃-precipitated powder.

Abstract: The effects of silicon (Si) addition and continuous annealing (CA) parameters on the microstructure and mechanical properties of low carbon Nb-Ti steels were investigated. Steels with and without Si were subjected to CA simulations, varying annealing temperature, line speed (LS), and cold work (CW) levels. Low-temperature thermomechanical controlled processing (TMCP) during hot rolling produced a fine polygonal ferrite matrix with uniformly distributed, spherical cementite - finer and more homogeneously dispersed in the Si-containing steel. Surface oxides in the as-rolled Si steel consisted mainly of wüstite and magnetite, with no deleterious hematite or fayalite observed due to high temperature descaling. Recrystallization during CA began near 650°C and completed above 780°C but was delayed by Si addition, higher line speeds, and moderate cold work. The final ferrite grain size remained fine, averaging 4–5 μm, across a broad annealing temperature range, aided by effective grain boundary pinning from carbonitrides. In the 690–760°C annealing range, the Si-containing steel exhibited increased strength due to solid solution strengthening, carbonitride precipitation hardening and restricted recrystallisation. Despite this, elongation was preserved through the formation of fine, soft, ductile, uniformly dispersed spherical cementite (Fe₃C) in the Si steel. Higher levels of cold work reduced strength slightly after annealing above 780°C but improved elongation due to full recrystallisation and coarsening of NbTi (C,N) particles.

Abstract: According to Stokes, the time required for a particle to precipitate depends on several conditions such as sphericity and laminar flow, as well as key parameters like particle size, densities (particle and fluid) and fluid viscosity. Therefore, if any of these conditions or parameters are unknown or not met, it becomes impossible to estimate the precipitation time. Additionally, when the separation under 1-g (Earth gravity) takes days or months but an estimation is needed in just minutes, the separation time at 1-g can be approximated by relating it to conditions at other values of gravity (n-g). For example, in a centrifuge. However, this n-g value is not reached instantaneously but require to consider the acceleration, plateau, and deacceleration phases to obtain a reliable estimation. This task has been addressed before; however, the resulting models tend to be either complex for practical laboratory use, or fail to account for the relationship between distance travelled by a particle under 1-g and the distance travelled under centrifugal forces. Moreover, even during the plateau phase, centripetal acceleration is unsteady because the radial distance of the precipitating particle is constantly changing. Thus, the aim of this study is to simplify the methodology for estimating particle separation time at 1-g by using separation time obtained under the unsteady conditions of centrifugation, even when the properties of the particle and fluid are unknown, through a numerical approach.

Abstract: When solar energy irradiates conductive metal surfaces, it is primarily converted into heat due to the generation of eddy currents on the metal surface. However, combining metals with inorganic ceramic long-persistent phosphors enables the storage and reuse of solar energy. In this study, a chemical precipitation method was employed to coat nickel precursors onto SrAl₂O₄:Eu²⁺,Dy³⁺ (SAO) ceramic phosphors, which emit a broad green spectrum at 520 nm under 440 nm excitation. A uniform nickel shell was successfully deposited on the surface of the phosphor particles, with only a slight decrease in photoluminescence intensity. The formation of a complete shell layer was confirmed through EDS elemental mapping analysis. Advanced oxidation heat treatment effectively produced a NiO shell and enhanced the structural integrity of SrAl₂O₄. Subsequent reduction heat treatment converted the NiO into a metallic nickel shell. This metallic layer improved the wettability and interfacial bonding between SAO and nickel backbone, providing increased resistance to mechanical stress. Due to the larger surface area of the foamed nickel structure, the resulting porous phosphor composite demonstrated superior luminescent performance compared to traditional phosphor-metal castings. This innovative phosphor-metal composite shows great potential for novel lighting applications in the metal and lighting industry.

Abstract: Pre-precipitate (cluster) strengthening is an integral aspect in the design of novel aluminum alloys. To investigate the impact of clusters on the strength of different aluminum alloys, Monte Carlo methods and the modified embedded atom method potential function were employed to simulate dilute aluminum-rich solid solutions, and these ten elements (silicon, magnesium, manganese, titanium, zirconium, chromium, iron, lithium, copper and nickel) were added as solute elements. The yield strength was evaluated and then the relationships among cluster size, cluster number, yield strength, and alloy compositions were analyzed. Finally, in the binary aluminum alloys the introduction of zirconium produces the largest yield strength among these ten elements, on the opposite side, the yield strength of Fe added alloy is the lowest. In most ternary aluminum alloys, after Mg, Zr and Li were added, the yield strength was increased compared to the results of the binary alloy, and the yield strength of Al-Li-Zr alloys is the largest in all ternary alloys. For multi-component aluminum alloy, the increase in type and number of elements resulted in fewer clusters, larger cluster size, and higher yield strength.

Abstract: Iron oxide was produced from lathe waste using green tea leaf extracts. Green tea leaves contain catechins, has been produced as a possible reducing, precipitating, stabilizing, and capping agent. Another advantage of applying green tea leaves to synthesize iron oxide is reducing toxicity. Various temperatures of synthesis utilizing the precipitation method proved successful in the formation of hematite. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscope (SEM) were used to characterize the synthesis product. According to the XRD results, the magnetite transition phase was obtained after precipitation, while hematite formed after calcination. The crystallite sizes were 50.5 nm, 45.4 nm, and 39 nm, respectively. According to FTIR identification, the iron oxide was generated before and after calcination in the presence of a specific Fe-O group at the wavenumbers 553 cm^-1 and 451 cm^-1. The SEM results revealed that the particle size ranges from 4.61 nm – 20.74 nm, and the shape was not uniform, and aggregation.

Abstract: Hydroxyapatite Carbonate (CHA) is a material that is found to have a composition more similar to bone, with a higher bioactivity than Hydroxyapatite (HA). CHA was synthesized using precipitation and hydrothermal methods using (NH₄)₂HPO₄ as a phosphate source, NH₄HCO₃ as a carbonate source, and Pokea shells as a calcium source. In this study, the Pokea shells were crushed, calcined, and characterized based on physicochemical tests. CaO from Pokea shell contains 74.33% calcium. CHA was successfully produced by precipitation method at room temperature and hydrothermal at 120 C for 8 h. Sample characterization was carried out using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Scanning Electron Microscope Energy Dispersive X-Ray Spectroscopy (SEM-EDX). Based on XRD data, there are differences in the crystal size of CHA produced via precipitation and hydrothermal methods, where the crystal sizes of Precipitation CHA-1 and Hydrothermal CHA-2 are 6.388 nm and 25.969 nm. The FTIR results of both CHA show the functional groups typical of CHA, namely OH-, CO, CaO, PO₄^3-, and CO₃^2-. From the Ca/P EDX data results, Precipitation CHA-1 and Hydrothermal CHA-2 do not differ much, namely 1.71 and 1.69, and this value indicates that CHA has been formed.

Abstract: The increasing demand for electric vehicles affects the high demand for nickel-based batteries, including Nickel Manganese Cobalt (NMC) batteries. Generally, NMC is processed from high-quality ore (sulfide ore) to produce nickel (II) sulfate hexahydrate or NiSO₄.6H₂O. But sulfide ore face scarcity due to a long history of mining and exploitation. Thus, laterite-type nickel ore can be an alternative to nickel resources. This study aims to produce mixed sulfate precipitates from a ferronickel leaching solution that can be utilized further to produce NiSO₄.6H₂O. Also, this research will study the pH effect of the precipitation process on the product's elemental composition, recovery, and compounds formed. The precipitation process was conducted using 5% MgO (weight basis) with a pH range of 2.5 to 6.5 with one increment. The mixed sulfate precipitates were characterized using AAS, EDX, and XRD. When using a pH of 3.5, a nickel concentration of 1473.00 ppm, nickel recovery of 23.02%, and Nickel grade of 3.18% could be obtained. As a result, the phase of NiSO₄.6H₂O was formed. Also, the other phases were formed after precipitation, such as CoSO₄, FeSO₄, and MgSO₄.