Controlled Heat Treatment Research Articles

Defect engineering on metal-organic frameworks for enhanced photocatalytic reduction of Cr(VI)

Cr(VI) stands as a profoundly toxic chemical and photocatalysis technology has shown promising potential in photocatalytic reduction of Cr(VI) to Cr(III), where the reduced Cr(III) is less toxic and can be further precipitated in a wide pH range. Metal-organic frameworks (MOFs), as emerging class of porous coordination polymers, is expected to be ideal platform for photocatalysis. In this study, defect engineering on MOFs was applied to promote photoreduction of Cr(VI). The obtained oxygen vacancy-containing MIL-125-NH2 samples showed modified electron structure, adjusted surface and porous properties, and enriched active sites. Among these oxygen vacancy-containing MIL-125-NH2 samples, the 300-M (MIL-125-NH2 heated at 300 °C for 2 h under N2 atmosphere) displayed the most remarkable performance in terms of photocatalytic Cr(VI) reduction. The pronounced efficacy of 300-M is evident from the achieved removal rate of Cr (VI), reaching an impressive 98 % in just 20 mins (19.6 mgCr(VI) g−1cata min−1), in stark contrast to MIL-125-NH2, which exhibited a modest removal rate of 53 %. Remarkably, the k-value for 300-M is 5.1 times that of MIL-125-NH2, further underscoring the superior efficiency of 300-M. The photoreduction mechanism of 300-M was further substantiated through a battery of advanced characterization techniques including transient photocurrent, electrochemical impedance spectroscopy, fluorescence spectroscopy, the Mott-Schottky analysis, and electron spin resonance. Those results disclosed that oxygen vacancies and mesopores introduced via controlled heat treatment play a pivotal role in facilitating the photoreduction of Cr(VI) within the MIL-125-NH2 structure. More advanced characterizations for the structures of photocatalysts and the photocatalytic mechanisms including charge transfer path need further studied. The systematic exploration of temperature-dependent effects on material properties opens avenues for future research in designing efficient and versatile MOF-based photocatalysts for environmental remediation applications.

The effect of carbon addition on the synthesis process and the physical/electrocatalytic properties of FeTiO3 nanopowder produced by solution combustion synthesis method

The FeTiO3 nanopowder is a vital engineering material known for its exceptional performance in energy generation, storage, electrochemical sensors, and catalysis. However, synthesizing FeTiO3 nanopowder with high crystallinity and phase purity typically requires specialized equipment and controlled heat treatment due to the instability of Fe2+ ions. Using the one-step solution combustion synthesis (SCS) method, FeTiO3 nanopowder withe high crystallinity were successfully produced utilizing basic equipment. Additionally, the influence of carbon additives on phase transitions, as well as the physical and physicochemical properties of the synthesized powder, was examined. XRD results indicate that increasing the amount of fuel, particularly glycine, creates a stable environment for the crystallization of FeTiO3 nanoparticles. Moreover, enhancing the carbon content in precursor solutions with urea enhances reduction conditions and boosts the stability of FeTiO3 in the final product. The presence of carbon additives in glycine-fuel samples leads to unfavorable outcomes by increasing the levels of TiO2 and Fe3O4 undesirable phases. Incorporating additive carbon into the urea-synthesized precursor solution resulted in a particle size increase exceeding 50 nm and raised the combustion temperature by a minimum of 230 °C. Furthermore, the presence of 15 wt% additive carbon in the sample synthesized with glycine improved the specific surface area of particles from 2.44 m2/g to 18.41 m2/g. Obtained results have shown that achieving high crystallinity of FeTiO3 nanopowder is feasible through a one-step solution combustion synthesis process. This can be accomplished by carefully choosing the synthesis conditions, such as the type and quantity of fuel, along with the carbon additive.

Microstructure evolution in A356 alloy subjected to controlled heat treatment regimes processes

Aluminium–silicon alloys are highly regarded for their lightweight and unique mechanical properties, making them crucial for various industrial applications. Achieving optimal mechanical behavior in Al-Si-based alloys necessitates meticulous control over their microstructure. The research investigated the impacts of heat treatment regimes on the microstructure of A356 hypoeutectic alloys by light optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectroscope (EDS). The alloy, produced via stir-casting, underwent homogenization at 540 °C/5 h, one-step (200 °C for 0.5–8 h (T1)) and two-step (T2 (200 °C/0.5 h/180 °C/0.5–8 h)), and T2L (200 °C/0.5 h/160 °C/0.5–8 h)) aging processes. The findings revealed significant microstructural changes due to heat treatment. Homogenization reduced the average grain size of eutectic silicon by 20.5%. The T1 treatment increased the grain size and changed the grain morphology with prolonged aging, negatively impacting the mechanical properties. The T2 and T2L treatments resulted in finer, more uniform grain structures. The T2L treatment produced the finest eutectic silicon and the most uniform grain distribution, indicating the superior potential for mechanical performance. Overall, this study underscores the importance of tailored heat treatment regimes to optimize the microstructure and enhance the structural sensitive properties of Al-Si alloys, benefiting automotive and aerospace industries.

Selective Synthesis of 3D Aligned VO2 and V2O5 Carbon Nanotube Hybrid Materials by Chemical Vapor Deposition.

3D carbon nanotube hybrid materials containing VO2 and V2O5 evenly distributed onto vertically aligned carbon nanotubes (VACNTs) is reported. Adjustable loading of particles in controllable sizes onto the VACNTs was developed via a stepwise chemical vapour deposition (CVD) approach. Solid VO(acac)2 is chosen as vanadium source. CO2 acts as reactive gas for the pre-functionalisation of the VACNTs. The process temperature was identified as key parameter to control the deposited vanadium oxide phase. A temperature of 550°C results in monoclinic VO2, while 600 °C results in the deposition of V2O5 onto the VACNT support. The morphology and the amount of deposited material was found to be dependent on the reactor dimensions and the degree of functionalization of the carbon support. An increase of the D/G ratio of the VACNT from 0.75 to 1.08 caused by a CO2 treatment step within the process led to an increase of the particle coverage from a scarce coverage without prior CO2 treatment to a dense coverage of the VACNT support after 15 min of CO2 exposure time. Size and crystallinity of the as deposited particles can be further adjusted by a controlled heat treatment after VO(acac)2 precursor deposition.

Achieving superior high-temperature strength in an additively manufactured high-entropy alloy by controlled heat treatment

High-entropy alloys (HEAs) usually exhibit high strengths at ambient and low temperatures but rapidly degraded tensile properties with increased temperature. In this study, a high-strength HEA, (CoCrNi)94(TiAl)6, is selected and subjected to laser powder bed fusion (L-PBF) and ageing treatment. The microstructural evolution and mechanical property development of the material over a wide range of temperatures are thoroughly investigated. It is found that the as-printed microstructure is dominated by numerous ultrafine cellular structures (∼1 μm) with cell boundaries decorated by Al2O3 nanoparticles, leading to high 0.2% yield strength (YS = 725∼750 MPa) and excellent elongation (>28%) at room temperature. The cellular structures remain up to 700 °C but disappear at or above 800 °C. Ageing at or above 600 °C leads to significant γ′ precipitation with the particle size increasing constantly with increased temperature. The samples containing both cellular structures and coarsened γ′ precipitates (aged at 700 °C) exhibit the highest YS (∼1227 MPa) and ultimate tensile strength (UTS∼1539 MPa) at room temperature and display unprecedented YS at high temperatures, i.e., 949 MPa at 600 °C and 728 MPa at 700 °C, respectively. The exceptional tensile strengths are mainly due to the γ′ precipitates and cell boundaries decorated by Al2O3 nanoparticles which may have acted as strong barriers for dislocation motion. At room temperature, the sample deforms mainly by dislocation slip and formation of stacking faults while at elevated temperatures, deformation becomes increasingly planar as characterized by the formation of increased number of stacking faults and the activation of twinning.

Thermal degradation analysis and optimization of controlled heat treatment for stacked high temperature superconducting tapes

Thermal degradation analysis and optimization of controlled heat treatment for stacked high temperature superconducting tapes

Thermal Transformation of Kaolinite Clays: Analyzing Dehydroxylation and Amorphization for Improved Pozzolanic Performance

This study explores the impact of heat treatment parameters on the dehydroxylation and amorphization processes of kaolinite-based materials, in particular natural kaolin clays. It develops a quantitative method for estimating the amorphous phase in heat-treated kaolinite, using differential thermal analysis/thermogravimetry (DTA/TGA), mass spectrometry, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Kaolin clays, subjected to controlled heat treatments between 600°C and 800°C, undergo significant structural transformations. The study identifies the degree of dehydroxylation (DTG) as a crucial measure of kaolinite performance after heat treatment, calculated as a function of sample weight loss. The transition from a crystalline to an amorphous phase strongly influences pozzolanic activity, characterized by its ability to react with portlandite (Ca(OH)₂) in water-rich environments.The materials used, including clay from the Benslimane region of Morocco, were finely ground and subjected to various thermal treatments. Thermal analyses revealed characteristic patterns of mass loss and phase transformation. XRD and FTIR analyses provided detailed information on structural changes, confirming the amorphization of kaolinite after dehydro.

Investigating Different Heat Treatment Methods to Enhance the Mechanical Properties of 9254 Steel

This study investigates the impact of varied heat treatment parameters on the mechanical and metallurgical characteristics of 9254 steel. Different cylindrical specimens underwent controlled heat treatments targeting three different phases. The interplay of time and temperature was systematically explored to understand their influence on bending strength, bending deflection, hardness, and microstructural evolution. The results revealed that a partially tempered martensitic structure exhibiting an exceptional ultimate strength of 4308 MPa. Achieving this involved a heat treatment, starting at 900°C for 30 minutes, followed by rapid cooling in an oil bath, quenching at 165°C for 5 minutes, annealing at 180°C for 60 minutes, and gradual air-cooling. This treatment regimen produced a specimen with a desirable combination of mechanical properties, showcasing its potential significance in advanced engineering applications.

Tribocorrosion Behavior of the ZK60Gd Alloy After Quench Control Heat Treatment

Tribocorrosion Behavior of the ZK60Gd Alloy After Quench Control Heat Treatment

Structural features and thermal expansion of zinc aluminosilicate quartz solid solutions

Zinc aluminosilicate (ZAS) glasses were synthesized along the peraluminous join (SiO2 contents between 95 and 50 mol%) by melt-quenching or sol-gel spray-drying and subjected to controlled heat treatments to obtain ZAS quartz solid solutions (Zn-Qz-ss). The precipitation of Zn-Qz-ss is non-stoichiometric with respect to their parent glass and the crystals undergo a compositional evolution during annealing, even in absence of secondary crystalline phases. Near-hexagonal high-quartz-like crystals with negative thermal expansion (down to −3 × 10−6 K−1) can be obtained in the range 50–80 mol% SiO2, while SiO2-richer crystals exhibit positive thermal expansion at room temperature (up to 29 × 10−6 K−1). Zn2+ ions occupy two distinct positions within the structural channels of quartz, with a strong preference for 4-fold coordination. In analogy to lithium aluminosilicate quartz solid solutions (Li-Qz-ss), the low-to-high phase transition exhibits a linear correlation to the composition of the crystals.

4D printing and annealing of PETG composites reinforced with short carbon fibers

In this study, for the first time, post-heat treatment was applied to improve the stress recovery of short carbon fiber reinforced PETG (SCFRPETG). PETG and SCFRPETG composite were printed under optimal conditions, and constrained and free shape memory cycles were applied under compression and three-point bending loadings to assess shape and stress recovery. The results of the free shape memory test for both vertical and horizontal patterns showed that PETG composite also has a higher shape memory effect (SME) compared to PETG. The SME was significantly improved by performing heat treatment. The stress recovery values for pure PETG, reinforced PETG before and after annealing are 2.48 MPa, 3.04 MPa and 3.18 MPa, respectively. It showed that the addition of 1.5% carbon fiber increases the stress recovery by 22%. The increasing trend reaches 28% by performing post-heat treatment. Additionally, altering the printing pattern affects the programming and stress recovery values. For the SCFRPETG composite samples before and after annealing, changing the printing pattern from horizontal to vertical, resulted in a 16% and 7% increase in recovery stress, respectively. SEM results confirm that the annealing process removes the layered structure, micro-holes caused by shrinkage and 4D printing mechanism. Using the controlled heat treatment method can be a practical solution to solve the problem of adhesion and reduce the anisotropy of FDM 3D printed layers.

Optimized growth of LiZnBO3 monoclinic phase in lithium zinc borate glass ceramics for electrode material

Glass-ceramics (GCs) of glass composition 20ZnO.30Li2O.50B2O3 were prepared via controlled heat treatment at hold times of 2h, 4h, 6h and 8h at crystallization peak temperature (846K). The effect of the hold time of heat treatment on the physical, structural, optical, and electrochemical properties was studied. XRD study revealed the formation of a pure LiZnBO3 crystalline phase. FTIR study revealed the transformation of BO4 units to BO3 units with an increase in the time of heat treatment. Optical band gap energy has been estimated from Diffuse Reflectance spectroscopy and, its values range from 3.26eV–3.36eV. Electrochemical properties were studied using Cyclic Voltammetry and compared with parent glass composition. The GC 20ZnO.30Li2O.50B2O3 heat treated for 8h exhibits the highest value of specific capacitance (∼48 mAh/gV) and energy density (∼18 J/g) indicating that it can be used as an electrode material in Li-ion batteries.

Elucidating the effects of −OH content on phase transition and Li-ion transport of anti-perovskite solid electrolytes

Anti-perovskite materials such as Li2(OH)Cl have garnered considerable interest as solid electrolytes due to their numerous advantages. However, the low ionic conductivity of the orthorhombic Li2(OH)Cl near room temperature presents a significant challenge for the application. In this study, we intricately modulate the −OH content in Li2(OH)Cl through a controlled heat treatment process. This method effectively increases the cubic phase content and lowers the phase transition temperature, thereby enhancing the ionic conductivity at 30 °C by more than an order of magnitude. Theoretical calculations illustrate that the removal of −OH content significantly reduces the barrier for phase transition, leading to substantial alterations in the Li-ion transport pathway and migration barrier. Furthermore, LiHClO-600 demonstrates exceptional resistance to lithium reduction and is compatible with lithium metal and LiFePO4, rendering it a viable solid electrolyte for batteries. Both experimental findings and theoretical calculations cohesively highlight the pivotal role of −OH content in driving phase transition and facilitating Li-ion transport in anti-perovskite solid electrolytes, paving the way for their potential utilization in all-solid-state batteries.

Tailoring of nanocrystals Bi2WO6 glass ceramics decorated with Sm3+ and Eu3+ ions for improving photocatalytic activity

For the first time in glass ceramics, pure Bi2WO6 nanocrystals were synthesized. This was achieved by preparing glass samples have a specific composition of SiO2-B2O3-NaF-WO3-SeO2-Na2O-Bi2O3 with 0.05 mol.% (Sm3+ or/and Eu3+) via melt-quenching technique. Then through a differential scanning calorimetry (DSC) study, the controlled heat treatment process for the glass samples was determined at 500°C/2hrs to obtain their glass-ceramic counterparts. Doping by Sm3+ or/and Eu3+ decreased the glass transition temperature (Tg) from 467, 426, 350 to 344° C and the crystallization temperature from 535, 508, 481 to 433° C for the samples in the order of W, WSm, WEu, and WSE, respectively. Vibrational modes associated with SiO4, BO4 and BO3 units were confirmed by FTIR measurements. RE-doped glass showed characteristic visible - NIR absorption peaks due to the respective rare earth ions. Orthorhombic Bi2WO6 nanocrystals were obtained in glass ceramic samples, except WSE sample exhibited crystallization of Bi2WO6 as a major phase beside traces of Bi2O3, as shown by X-rays. Bi2WO6 crystallized in 2D sheet-like nanocrystals measuring less than 10 nm in size based on SEM and TEM studies. XPS analysis confirmed the triple valence of Eu3+ and Sm3+ ions into Bi2WO6. Photoluminescence measurements revealed distinct emission peaks from Sm and Eu ions in both glass and glass-ceramic samples, ranging from red to white light. Using UV–vis DRS, the optical band gap energy (Eopt) was estimated for glass-ceramic samples, showing values within the semiconductor range (∼2.8 eV). Photocatalytic activity was evaluated by degradation of methylene blue (MB) under UV and natural sunlight. All studied glass ceramics showed high photocatalytic efficiency. Remarkably, doping with Eu3+ significantly enhanced photocatalytic activity, exceeding 85% after 1 hour under UV or sunlight irradiation, followed by Sm3+ doping, and then doping with both Eu3++ Sm3+. Based on the obtained results, the studied samples are potentially useful as visible light photocatalysts, semiconductors, and photoluminescent glass ceramics.

Indium Doped Gan Porous Micro‐Rods Enhanced CO2 Reduction Driving By Solar Light

AbstractPhotocatalytic CO2 reduction plays an important role in solar energy storage and carbon balance. GaN as an III‐V semiconductor material has received extensive attention in the field of photocatalysis. In this study, the porous indium‐doped GaN (In/GaN) micro‐rods are synthesized successfully by a facile hydrothermal method and subsequent controlled atmosphere heat treatment. Photocatalytic CO2 reduction performance of In/GaN is higher than that of pure GaN due to the In doping improves the light absorption efficiency. The primary products are CO and CH4. Among the samples, 3%‐In/GaN exhibits the highest catalytic activity as well as stability and reusability. The yield rates of CO and CH4 can be reached 50.2 and 14.6 µmol · g−1 · h−1, respectively. Furthermore, density functional theory (DFT) calculations reveal that the bandgap is narrowed and the adsorption energy of CO2 molecules is improved by In doping. Moreover, the N‐vacancy detected by electron paramagnetic resonance (EPR) increases with the In doping, resulting in an increase in the number of unpaired electrons, which is conducive to carrier transport. This work provides a new study In/GaN prepared by simple method for the light‐driven photocatalytic conversion of CO2 to high‐value‐added products.

Annealing approach to form a nanotube from graphdiyne ribbon: A theoretical prediction

A precisely controllable heat treatment process is critical for nanofabrication. We developed a two-step method to fabricate a graphdiyne nanotube (GNT) through heat treatment in an argon environment. Initially, we...

Effect of Controlled Heat Treatment and Aluminum Additions on the Strengthening of Cu–Ni-Based Alloys

In this investigation, Cu–Ni alloys with different aluminum additions were synthetized under a vacuum atmosphere to reduce the material density. Annealed alloys in a He atmosphere with low aluminum concentration exhibited a coarse dendritic structure, while samples with high aluminum concentration exhibited a refined dendritic structure. Structural defects analyses have shown relatively low vacancy concentrations. Hardness evaluations indicated an increment by approximately 5 times i.e., 370 HVN, more than that for the alloyed samples compared with the as-cast and unalloyed samples. Compression tests have shown a noticeable strengthening improvement (360 MPa), mainly in samples heat treated with 10 at.% Al, while samples with 5 at.% Al showed an acceptable resistance (270 MPa) as well. In general, the sample with 10 at.% Al presented the best performance to be considered as potential structural material.

Controlling mechanical properties and energy absorption in AlSi10Mg lattice structures through solution and aging heat treatments

The use of Selective Laser Melting (SLM) has gained popularity due to its ability to produce complex-shaped parts, which includes lightweight lattice structures that are appealing to a variety of industries. AlSi10Mg alloy is a favored choice for SLM due to its excellent specific properties. The utilization of AlSi10Mg in lattice structures further reduces their mass while enhancing specific mechanical properties. However, the inherent brittle deformation behavior of as-built AlSi10Mg restricts the energy absorption potential of lattice structures. This study explores the control of mechanical properties and energy absorption in AlSi10Mg lattice structures and bulk tensile samples through solution and aging heat treatments, examining their impact on microstructural transformations. The results show that solution heat treatment decreases the mechanical properties of lattice structures and bulk tensile samples while improving their ductility and energy absorption. This change is attributed to the transformation of the alloy's fine cellular microstructure into coarser Si-precipitates. Subsequent aging treatments lead to increased mechanical properties in lattice structures solution heat treated at 500 and 550 °C, albeit with a slight reduction in energy absorption. Intriguingly, lattice structures heat treated at 460 °C exhibit unchanged mechanical properties and energy absorption, as confirmed by the t-test. Additionally, the absence of the Al5FeSi intermetallic phase suggests that aging did not occur following solution heat treatment at 460 °C. These findings offer valuable insights into manipulating the mechanical properties and energy absorption of AlSi10Mg lattice structures through controlled heat treatments. Such control can significantly enhance the performance and functionality of lattice structures in practical applications.

The direct experimental observation and solidification mechanism of heavy metals in blast furnace slag glass‐ceramics

AbstractGlass‐ceramics with high performance and high crystallinity was produced using rare earth blast furnace slag (REBFS) as the primary raw material, along with composite nucleating agents Fe2O3 and Cr2O3. The migration pattern, distribution characteristics, and solidification properties of heavy metals in glass‐ceramics were investigated by the controlled heat treatment. The findings indicated that the heat treatment temperature has a significant effect on the distribution and color of heavy metals in glass‐ceramic. In the crystallized glass‐ceramic, spinel acts as the crystal core for heavy metal solidification, Cr, Cu, and Mn can exist stably in the spinel by the solid solution. The glass‐ceramic was expected to be used as a decorative building material.

Laminar plasma quenching-tempering: A rapid surface heat treatment technique for controllable modification of the rail steel

Plasma selective quenching is promising in enhancing the rail's wear resistance by preparing martensitic hardened zones discretely embedded in the substrate on the surface layer. However, severe cracks and spalling occur in the hardened zone during the rail service, which may be related to its microstructure and hardness. To modify the microstructure and hardness of the hardened zone, a novel laminar plasma quenching-tempering (LPQT) technique that consists of performing laminar plasma quenching (LPQ) and laminar plasma tempering (LPT) successively was proposed to obtain the hardened zone with desired microstructure and hardness. LPQ is firstly performed on the rail surface to prepare martensitic hardened zones with high hardness. LPT is then performed on each hardened zone to modify its microstructure and hardness. The numerical simulation of LPT was established to determine the processing parameters of LPT for accurately controlling the tempering temperature of the hardened zone. The effects of the tempering temperature on the microstructure and hardness of the hardened zone were investigated. Results showed that with the increase of the tempering temperature from Ms temperature to austenitizing temperature, the hardness of the hardened zone was decreased from 800 HV to 450 HV as the acicular martensite in the hardened zone precipitated carbides and was transformed into the tempered martensite. Besides, the total processing time of LPQT for treating a hardened zone is normally <2 s. Application of LPQT in modification of the rail steel showed that it helped to eliminate the severe cracks and spalling in the LPQ treated hardened zone while its wear resistance was still improved compared with that of the untreated rail steel. Overall, LPQT is a rapid and controllable surface heat treatment technique for modifying the microstructure and hardness of the rail surface, which is promising to be used to balance the wear and RCF resistances based on the service condition of the rail.