Precipitation Heat Treatment Research Articles

Conversion of cobalt from spent LIBs to Co3O4 electrode material for application in supercapacitors

ABSTRACT The cathode material of lithium-ion batteries (LIBs) is endowed with valuable metals, such as cobalt. The improper treatment of these batteries pollutes the environment and causes enormous resource waste. Therefore, the recovery of valuable metals from spent LIBs has attracted widespread attention. In this study, Co3O4 electrode materials were prepared by a simple homogeneous precipitation method and heat treatment using a leaching solution of spent LIBs-positive electrode material as the cobalt source. The crystal structure and morphology of the products were examined at different annealing temperatures, and their electrochemical performance was analyzed. The results show that low-temperature annealing contributes to grain refinement. The Co3O4 material prepared at 300°C annealing temperature has a rod-like structure with distinct pores and a specific surface area of 58.98 m2 g−1. Furthermore, electrochemical performance testing reveals that Co3O4 prepared at 300°C displays the best electrochemical performance as an electrode material, with a specific capacitance of 97.93 F g−1 and a cycle retention rate of 79.12% after 500 charge–discharge cycles. These findings demonstrate the feasibility of recycling valuable metal cobalt from spent LIBs cathode materials to produce Co3O4 materials for use as supercapacitor electrode materials, opening up new avenues for the recycling and utilisation of spent LIBs.

SnO2 nanoparticles: synthesis, characterization and photocatalytic activity

SnO2 nanoparticles have been synthesized using precipitation method and heat treatment. Firstly, SnCl4.5H2O was reacted with NaOH solution, and than the precipitate heat treated at 350 oC, 450 oC and 550 oC. The obtained materials were characterized by X-Ray diffraction (XRD) infrared spectra (IR) energy-dispersive X-ray spectroscopy (EDS) scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic degradation of rhodamine B (RhB) using SnO2 nanoparticles was investigated. The results show that the SnO2 nanoparticles exhibited a significantly enhanced photocatalytic activity. The photoactivity of SnO2 nanoparticles photocatalysts can be ascribed to the enhanced electron-hole separation.

Microstructure gradient formation in electron-beam melting powder-bed fusion of a gamma-prime Ni-based superalloy

Microstructure gradient is formed during the additive manufacturing of Ni-based superalloy Haynes® 282® via electron-beam melting powder-bed fusion (EB-PBF) process. The precipitation of secondary phases occurs owing to EB-PBF in-situ heat treatment as consequence of high temperature powder bed pre-heating and multiple melting and re-heating thermal cycles, which can be summarised as a carbide precipitation heat treatment at 1000–1025 °C/8 h, aging between 875 and 975 °C/30 h, followed by a slow cooling step. Relatively large precipitates formed inter- and intragranularly with M3B2 boride and gamma-prime (γ') have sizes of approximately 5 μm and 110 nm, respectively, at the bottom of the build. The size of the precipitates decreases along the build direction. In the top region, the precipitate sizes of boride and γ' are 1 μm and 50 nm, respectively. MC carbide with a size of <1 μm precipitated throughout the build. A good correlation is observed in terms of the γ' size to hardness with average values of 350 HV at the bottom and 400 HV at the top. The ultimate tensile strength (UTS), yield strength (YS), and elongation (EL.) values at the bottom and top regions are 1080 ± 40 MPa, 805 ± 25 MPa, and 20 ± 5%; and 1105 ± 20 MPa, 825 ± 15 MPa, and 25 ± 5%, respectively. Overall, EB-PBF Haynes® 282® exhibits higher UTS and YS but lower EL than those of the as-received wrought alloy (950 ± MPa, 650 ± 15 MPa, and 40 ± 5%, respectively).

Reassessment of the Matrix Composition of Co-Re-Cr-Based Alloys for Particle Strengthening in High-Temperature Applications and Investigation of Suitable MC-Carbides.

This study reassesses the optimum matrix composition of Co-Re-Cr-based alloys for strengthening by MC-type carbides. It is found that the composition of Co-15Re-5Cr is ideally suited for this purpose as it allows the solution of the carbide-forming elements such as Ta, Ti, Hf, and C within a matrix consisting entirely of fcc-phase (typically at 1450 °C), having a high solubility for these elements, while precipitation heat treatment (typically at 900-1100 °C) occurs in a hcp-Co matrix, displaying a much lower solubility. In the case of the monocarbides TiC and HfC, this was investigated and achieved for the first time in Co-Re-based alloys. TaC and TiC emerged as suitable particles in Co-Re-Cr alloys for creep applications due to a large population of nano-sized particle precipitation, which is not the case for the mainly coarse HfC. Both Co-15Re-5Cr-xTa-xC and Co-15Re-5Cr-xTi-xC exhibit a formerly unknown maximum solubility close to x = 1.8 at.%. Therefore, further research on the particle-strengthening effect and the governing creep mechanisms of carbide-strengthened Co-Re-Cr alloys should focus on alloys with the following compositions: Co-15Re-5Cr-1.8Ta-1.8C and Co-15Re-5Cr-1.8Ti-1.8C.

Inhibiting cracking and improving strength for additive manufactured Al CoCrFeNi high entropy alloy via changing crystal structure from BCC-to-FCC

Hot cracking in laser powder bed fused (LPBF) AlxCoCrFeNi high entropy alloys (HEAs) plague the production of high strength parts. Here we show that the body-centered cubic (BCC) phase with very high hardness (∼670 HV) in LPBF printed AlxCoCrFeNi(x = 1, 0.7) HEAs causes cracking due to the plastic incompatibility between grain boundaries. To mitigate this, we propose a BCC to face-centered cubic (FCC) transformation strategy in the AlxCoCrFeNi HEAs to inhibit cracking and found that the Al0.5CoCrFeNi alloy (i.e., when x = 0.5) with a single FCC crystal structure possess low cracking sensitivity and well intergranular plastic compatibility, accompanied with decreased residual stress confirmed by using X-ray diffraction testing. The mechanical properties of the LPBF printed Al0.5CoCrFeNi HEA can be further enhanced by precipitation heat treatment. Scanning electron microscope/ transmission electron microscopy analysis show that nano-sized B2, L12 and σ phases precipitated from FCC Al0.5CoCrFeNi HEA when aged at 700 °C for 1 h. The ultimate tensile strength (UTS) increases from 899 MPa (as-print) to 1552 MPa (aged) with the elongation decreasing from 35.6 % (as-print) to 7.1 % (aged) due to the Orowan bypass mechanism of nano-precipitates. An increased aging temperature to 800–1000 ℃, decreases the UTS while increases the elongation, accompanied by the L12-to-B2 transformation and B2 phase coarsening. The deformation mechanism is mainly dominated by dislocations and stacking faults in the Al0.5CoCrFeNi HEA sample.

Effect of Homogenization and Precipitation Heat Treatments on Localized Corrosion of Al-Mn-Zr Alloy with Fe Impurity

This study aimed to enhance the corrosion resistance of an Al-Mn-Zr alloy containing Fe impurities by using heat-treatment processes. Three processes were implemented to distribute intermetallic particles uniformly, promote Al6(Mn, Fe) and Al3Zr particle formation, and eliminate Fe and Zr segregation. Increasing the amount of Al6(Mn, Fe) reduced the galvanic effect between the Al matrix and Al3Fe particles, leading to improved localized corrosion resistance. Al3Zr promoted smaller grain size by preventing recrystallization. Microstructure analysis confirmed the inhibitory effect on grain growth and the promotion of Al6(Mn, Fe) and Al3Zr particle formation. The effect of grain size on galvanic corrosion was evaluated through corrosion simulation. Furthermore, the improved localized corrosion resistance was evaluated through electrochemical and immersion tests. Consequently, the designed heat-treatment process significantly improved the localized corrosion resistance of the Al-Mn-Zr alloy with Fe impurities. These results demonstrate the effectiveness of the used heat-treatment processes in improving the corrosion resistance of the alloy.

Coherency loss marking the onset of degradation in high temperature creep of superalloys: Phase-field simulation coupled to strain gradient crystal plasticity

A dislocation density based crystal plasticity — phase-field model is applied to investigate directional coarsening during creep in CMSX-4 Ni-based superalloys in the high temperature and low stress regime. Coherency between the ordered γ′ precipitates and the disordered γ channels prevents the generation of geometrically necessary dislocations, since the precipitate can be considered undeformable in the low stress regime. After coherency loss between the γ matrix phase and the γ′ precipitates the constraint against generation of geometrically necessary dislocations is relaxed, causing rotation of the crystal lattice under uniaxial load, known as “Schmid rotation”. As a consequence, the creep rate in the matrix increases, whereby degradation can be measured by the number density of geometrically necessary dislocations. The state of coherency loss is associated with the minimum creep rate in a creep experiment under constant load. The presented simulations start from a coherent γ′ precipitates distribution with random size and position generated during a precipitation heat treatment process. Simulations of N-type and P-type rafting under tensile and compressive load respectively are presented. The effect of coherency loss, coalescence of precipitates and lattice rotation due to generation of geometrically necessary dislocations is discussed in correlation with experimental findings.

Advancements in the Additive Manufacturing of Magnesium and Aluminum Alloys through Laser-Based Approach.

Complex structures can now be manufactured easily utilizing AM technologies to meet the pre-requisite objectives such as reduced part numbers, greater functionality, and lightweight, among others. Polymers, metals, and ceramics are the few materials that can be used in AM technology, but metallic materials (Magnesium and Aluminum) are attracting more attention from the research and industrial point of view. Understanding the role processing parameters of laser-based additive manufacturing is critical to maximize the usage of material in forming the product geometry. LPBF (Laser powder-based fusion) method is regarded as a potent and effective additive manufacturing technique for creating intricate 3D forms/parts with high levels of precision and reproducibility together with acceptable metallurgical characteristics. While dealing with LBPF, some degree of porosity is acceptable because it is unavoidable; hot ripping and cracking must be avoided, though. The necessary manufacturing of pre-alloyed powder and ductility remains to be the primary concern while dealing with a laser-based additive manufacturing approach. The presence of the Al-Si eutectic phase in AlSi10Mg and AlSi12 alloy attributing to excellent castability and low shrinkage, attaining the most attention in the laser-based approach. Related studies with these alloys along with precipitation hardening and heat treatment processing were discussed. The Pure Mg, Mg-Al alloy, Mg-RE alloy, and Mg-Zn alloy along with the mechanical characteristics, electrochemical durability, and biocompatibility of Mg-based material have been elaborated in the work-study. The review article also summarizes the processing parameters of the additive manufacturing powder-based approach relating to different Mg-based alloys. For future aspects, the optimization of processing parameters, composition of the alloy, and quality of powder material used will significantly improve the ductility of additively manufactured Mg alloy by the LPBF approach. Other than that, the recycling of Mg-alloy powder hasn't been investigated yet. Meanwhile, the post-processing approach, including a homogeneous coating on the porous scaffolds, will mark the suitability in terms of future advancements in Mg and Al-based alloys.

Laser cladding of aluminum alloys with concurrent cryogenic quenching for improved microstructure and hardness

In this study, a method to deposit quench-sensitive age-hardening aluminum alloy clads is presented, which produces a hardness similar to the T6 temper without the requirement of solution heat treatment. A high-powered diode laser is scanned across the workpiece surface and material feedstock is delivered and melted via off-axis powder injection. The cladding process is immediately followed by quenching with liquid nitrogen, which improves the cooling rate of the quench-sensitive material and increases the hardness response to subsequent precipitation heat treatment. The method was demonstrated on the laser cladding of aluminum alloy 6061 powder on 6061-T6511 extruded bar substrates of 12.7 mm thickness. Single-track single-layer clads were deposited at a laser power of 3746 W, scan speed of 5 mm/s, and powder feed rate of 18 g/min. The in-situ liquid nitrogen quenching improved the clad hardness by 15.7% from 73.1 HV to 84.6 HV and the heat-affected zone hardness by 19.3% from 87.1 HV to 103.9 HV. Extending the process to multi-track multi-layer cladding further increased the clad hardness to 89.3 HV, close to the T6 temper hardness of 90 HV. Transmission electron microscopy revealed the increased precipitate density in the liquid nitrogen quenched clads were responsible for the higher hardness.

Reducing the γ'-Particle Size in CMSX-4 for Membrane Development.

Colloidal emulsions for lipophilic drugs can be fabricated using premix membrane emulsification. The state of the art is the application of membranes made from, for example, polycarbonate or polyester, which, however, are prone to fouling and cause waste, due to the low number of cycles. With the use of metallic membranes made from the nickel based single crystalline superalloy CMSX-4, these key disadvantages are eliminated. However, instead, the pore size and the resulting droplet size distribution need to be adjusted and improved. This can be realized by tailoring the size of the γ′-particles, which is controllable by the time and temperature used during precipitation heat treatment and the quenching method after homogenization heat treatment. Therefore, we utilized different heat treatment protocols, varying the cooling rate (water quenching and air cooling) after homogenization heat treatment and the holding time and temperature during precipitation heat treatment. Then, we investigated the γ/γ′-microstructure, including the γ′-morphology and γ′-particle size. We show that water quenching has a significant impact on the γ/γ′-microstructure and often leads to irregular-shaped and poorly aligned γ′-particles after precipitation heat treatment. In comparison, air cooling, followed by a subsequent precipitation heat treatment, results in well-aligned and cubic shaped γ′-particles and is, therefore, favorable for membrane fabrication. A reduction in precipitation temperature leads to morphology changes to the γ′-particles. A reduction of the holding time during precipitation heat treatment diminishes the γ′-particle growth, resulting in smaller γ′-particles. Additionally, a suitable heat treatment protocol for membrane fabrication was identified with a γ′-edge length of 224 ± 52 nm and well-aligned, cubic shaped γ′-particles.

Effects of Precipitation Hardening Variables on Al–Zn–Mg-Sn Alloy as Sacrificial Anode in Seawater: Experimental and Statistical Analysis

This research investigated the effects of tin composition and heat treatment variables on the Al-Zn-Mg alloy as sacrificial anode in seawater using gravimetric technique and statistical analysis. Tin was alloyed with Al-Zn-Mg in varied proportions (0%, 0.01%, 0.05% and 0.1%) to determine the optimum anode efficiency in the marine environment. Precipitation heat treatment was performed by first subjecting the samples to solution treatment at 5380C for 2 hours and later subjected to varying hardening temperatures and times. The samples were hardened for 4, 8 and 12 hours at each of the hardening temperatures of 1300, 1600 and 1900 centigrade. The anode efficiency increases as the tin concentration increases. The experimental result of this study showed that the Al-Zn-Mg alloy with 0.1% tin gives the optimum anode efficiency. It was revealed that the Al-Zn-Mg alloy without tin composition exhibited high output current capacity when hardened at 1900C for 4 hours. Predictive model developed in this work was in consonance with experimental observation except the following; at hardening temperature of 1600C, the model recommended 12 hours as against 4 hours of laboratory experiment and at hardening temperature of 1300C it advocated 8 hours as against 12 hours.Keywords - aluminum alloy, corrosion, precipitation hardening, regression and correlation analysis, and sacrificial anode

The Influence of Heat Treatment on Low Cycle Fatigue Properties of Selectively Laser Melted 316L Steel.

The paper is a project continuation of the examination of the additive-manufactured 316L steel obtained using different process parameters and subjected to different types of heat treatment. This work contains a significant part of the research results connected with material analysis after low-cycle fatigue testing, including fatigue calculations for plastic metals based on the Morrow equation and fractures analysis. The main aim of this research was to point out the main differences in material fracture directly after the process and analyze how heat treatment affects material behavior during low-cycle fatigue testing. The mentioned tests were run under conditions of constant total strain amplitudes equal to 0.30%, 0.35%, 0.40%, 0.45%, and 0.50%. The conducted research showed different material behaviors after heat treatment (more similar to conventionally made material) and a negative influence of precipitation heat treatment of more porous additive manufactured materials during low-cycle fatigue testing.

Optimization and Validation of Dual Element Ultrasound Transducers for Improved Pulse-Echo Measurements of Material Nonlinearity

In nonlinearity parameter ( $\beta $ ) measurements of solids, the pulse-echo method is more desirable than the through-transmission method. Dual element transducers consisting of an outer ring transmitter and an inner disk receiver have been found to be an efficient alternative to single element transducers because such configuration provides an improved second harmonic generation and dependence on the total correction in the pulse-echo mode. For accurate and reliable measurements of $\beta $ for relatively thin samples, further improvement is needed by optimizing the transmitter and receiver size of dual element transducers for a given sample thickness and frequency. The optimized transducer should provide the largest possible second harmonic reception and a total correction value close to one. In this paper, optimization of the dual element transducer is performed for 1 cm thick Al specimen at 5 MHz fundamental frequency, and the results are presented for the received second harmonic amplitude and the total correction. The optimized dual element transducer is fabricated and experimentally characterized to be applied to determine the absolute $\beta $ of Al specimens whose microstructure changes due to precipitation heat treatment. The experimental results validate the transducer optimized for pulse-echo $\beta $ measurements on 1 cm specimens, and provide a quantitative correlation between the $\beta $ and the microstructural change.

Comparison of Different Heat Treatment Processes of Selective Laser Melted 316L Steel Based on Analysis of Mechanical Properties.

In this study, we analyzed the mechanical properties of selectively laser melted (SLM) steel obtained via different modifications during and after the manufacturing process. The aim was to determine the effects of precipitation heat treatment on the mechanical properties of elements additively manufactured using three different process parameters. Some samples were additionally obtained using hot isostatic pressing (HIP), while some were treated using two different types of heat treatment and a combination of those two processes. From each manufactured sample, a part of the material was taken for structural analysis including residual stress analysis and microstructural investigations. In the second part of the research, the mechanical properties were studied to define the scleronomic hardness of the samples. Finally, tensile tests were conducted using a digital image correlation (DIC) test and fracture analysis. The treated samples were found to be significantly elongated, thus indicating the advantages of using precipitation heat treatment. Additionally, precipitation heat treatment was found to increase the porosity of samples, which was the opposite compared to HIP-treated samples.

SYNTHESIS AND CHARACTERIZATION OF MoS2 –GRAPENE OXIDE ON Ni-Co-MnO2 NANOFIBER LIKE BINARY COMPOSITE FOR NICKEL FOAM BASED FLEXIBLE ELECTRODE FABRICATION

Nickel/cobalt co-doped porous manganese oxide(MnOx) is fabricated by feasible nonionic surfactant route followed by precipitation heat treatment method. The as prepared metal ion modified manganese oxide further impregnated via reducing graphene oxide and MoS2 nanoparticles by ultra-sonication assisted deposition method. The as prepared binary nanocomposite is characterized by XRD and HR-TEM for crystalline phase formation analysis and structure morphology determination. Binder free flexible electrode fabrication on nickel foam using MoS2/graphene modified Ni-Co-MnO2 have also been studied and it shows higher super capacitor performance like 1190 F/g in aqueous acidic conditions.

Crack Growth Behavior of Additively Manufactured 316L Steel-Influence of Build Orientation and Heat Treatment.

The effects of build orientation and heat treatment on the crack growth behavior of 316L stainless steel (SS) fabricated via a selective laser melting additive manufacturing process were investigated. Available research results on additively manufactured metallic parts still require a substantial expansion. The most important issue connected with the metal properties after additive manufacturing are the high anisotropy properties, especially from the fatigue point of view. The study examined the crack growth behavior of additively manufactured 316L in comparison to a conventionally made reference material. Both groups of samples were obtained using precipitation heat treatment. Different build orientations in the additively manufactured samples and rolling direction in the reference samples were taken into account as well. Precipitation heat treatment of additively manufactured parts allowed one to achieve microstructure and tensile properties to similar to those of conventionally made pieces. The heat treatment positively affected the fatigue properties. Additionally, precipitation heat treatment of additively manufactured elements significantly affected the reduction of fatigue cracking velocity and changed the fatigue cracking mechanism.

Improving the oscillating wear response of cold sprayed Ti-6Al-4V coatings through a heat treatment

Cold spray (CS) coating technique is being studied as a potential solution for repairing aircraft Ti-6Al-4V components. This work is focused on the restoration of damaged components due to wear induced by vibrations. It is known that Ti-6Al-4V CS deposition shows difficulties to obtain non-porous coatings due to the high strength of this material, that is detrimental for wear resistance. In this sense, performing a post-heat treatment leads to lower porosity CS Ti-6Al-4V coatings and improves their mechanical properties, and thus, a better tribological behaviour is also expected. Therefore, the objective of this study was to determine the effect of a post-heat treatment on the wear resistance of Ti-6Al-4V coatings deposited by the CS technique. Ti-6Al-4V CS coatings were used, which have been sprayed with nitrogen as process gas at a temperature of 1100 °C and a pressure of 50 bar. The coatings were subjected to a solution heat treatment followed by a precipitation heat treatment. Oscillating and unidirectional sliding wear experiments were conducted on the coatings at room temperature and at 450 °C. A pin on disc configuration was used with a bearing steel counterbody. The results were compared to those obtained on the substrate (which represents the material to be repaired) and on the as-sprayed coating, which were derived from a previous work. The heat treated coating presented improved wear behaviour as compared to the substrate as well as to the as-sprayed coating, particularly during the high temperature tests. Wear at high temperature was dominated by material transference from the counterbody to the Ti-6Al-4V coating.

Preparation and Characterization of Hydroxyapatite by the precipitation method and heat treatment

Hydroxyapatite is a synthetic substance in the form of microspheres composed of calcium and phosphate, present in human bones and tooth enamel. The objective of the work was to synthesize hydroxyapatite, from the solution of calcium nitrate and diamonic phosphate by the method of precipitation and heat treatment, obtaining the hydroxyapatite in powder form. To study its structural evolution, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy were used. The results show that the hydroxyapatite nanocrystalline can be successfully produced by the precipitation technique from raw materials.

Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure

Compositionally complex polycrystalline γ/γ′ CoNi-base superalloys, such as CoWAlloy2 (Co41-Ni32-Cr12-Al9-W5-Ti0.3-Ta0.2-Si0.4-Hf0.1-C-B-Zr) are interesting candidates for new high-temperature materials. To maximize their high-temperature strength, the γ/γ′ microstructure has to be optimized by adjusting the multi-step heat treatments. Various microstructures after different heat treatments were analyzed by scanning and transmission electron microscopy and especially in-situ small-angle neutron scattering during heat treatment experiments. The corresponding mechanical properties were determined by compression tests and hardness measurements. From this, an optimum γ′ precipitate size was determined that is adjusted mainly in the first precipitation heat treatment step. This is discussed on the basis of the theory of shearing of γ′ precipitates by weak and strong pair-couplings of dislocations. A second age hardening step leads to a further increase in the γ′ volume fraction above 70% and the formation of tertiary γ′ precipitates in the γ channels, resulting in an increased hardness and yield strength. A comparison between two different three-step heat treatments revealed an increase in strength of 75 MPa for the optimized heat treatment.

Development of thermo-mechanical processing to form high density of uniformly distributed nanosized carbides in austenitic stainless steels

Model alloys and thermomechanical processing (TMP) were developed to form a high density of uniformly distributed nanosized (<10 nm) carbides in an austenitic stainless steel matrix. The composition of the model alloys was determined to control the formation of precipitates during the TMP. The TMP consisted of homogenization at 1200 °C for 1 h, multiple hot-rolling passes above and below the non-recrystallization temperature (TNR), and precipitation heat treatment at 800 °C for 2 h. By proper division of the rolling passes above and below TNR, a microstructure with a homogeneous grain size and a well-developed dislocation structure was obtained. Then, subsequent precipitation heat treatment produced a microstructure containing a high density (~1.1 × 1022/m3) of uniformly distributed and coherent NbC precipitates in the austenitic matrix. The evolution of the nanosized NbC during the precipitation heat treatment was coupled with the dislocation characteristics, such as the density and distribution, which were controlled by the hot-rolling conditions.