Temperature Time Research Articles

Effect of Annealing Temperature and Time on the Magnetic Properties and Magnetic Anisotropy of a Temper-Rolled, Semi-processed Non-oriented Electrical Steel

The effect of final annealing temperature and time on the core loss, magnetic permeability, and magnetic anisotropy of a temper-rolled, semi-processed 0.5 wt.% Si non-oriented electrical steel was investigated. The magnetic properties of the steel sheets at 50–400 Hz and 0.5–1.50 T were measured by the Epstein frame method on strips cut along both the rolling (RD) and transverse directions (TD). Optimal magnetic properties were obtained when the annealing temperature was at 800–825°C, and the annealing time was 2–4 h. Relatively large magnetic anisotropy between the RD and TD was observed in samples after recrystallization (~ 10% in core loss and ~ 70% in relative permeability), while deformed and non-recrystallized samples showed small anisotropy in magnetic properties. Regardless of the processing state of the steel, i.e., temper-rolled, recovered, or recrystallized, the core loss followed quadratic polynomial functions with respect to both the frequency and magnetic flux density, while the relative magnetic permeability followed cubic polynomial functions with respect to both the frequency and magnetic flux density. The microstructure and texture of selected samples were characterized by electron backscatter diffraction, which revealed the correlations between the magnetic properties of the steel and the microstructure and texture.

Effects of the thermal treatments on the optical properties of SiO2 anti-reflective coatings on sapphire windows

The SiO2 films were deposited on sapphire substrates using radio frequency (RF) magnetron sputtering to enhance the mid-wave infrared (IR) transmittance. The effects of thermal treatments by annealing and in-situ heating on the SiO2 films were investigated. After annealing at 600 °C, the surface morphology, microstructure, chemical states, and optical constants were investigated. No obvious microcracks or delamination were observed on the film surfaces, indicating excellent adhesion to the sapphire substrates. With an increase in the annealing time, gradual oxidation of Si atoms within the SiO2 thin films occurred, resulting in the release of OH groups and evaporation of moisture. The refractive index exhibited slight changes, while the extinction coefficient showed a significant reduction, thus the transmittance was improved. According to the in-situ heating tests from the annealed samples, it revealed a slight increase in average transmittance with prolonged annealing time. Finally, we assessed the performance of the annealed samples by rapid heat shock to 600 °C at a very short time, which demonstrated outstanding optical performance and heat-resistant properties. The present work supports the feasibility of applying the SiO2 films under harsh high-temperature environments.

Microstructure and properties of AZ31 alloy by static recrystallisation at lower temperature

The microstructure evolution and mechanical properties of AZ31 Mg sheets that was processed by rolling and subsequent annealing at lower temperature were investigated. The results indicated that few-pass rolling with large deformation is a better strategy to prepare AZ31 Mg sheets with higher deformation restored energy and less rolling defects. After annealing, the static recrystallisation occurred and the recrystallisation degree increases with the annealing temperature and time. Finally, the best comprehensive mechanical properties were obtained by 3-pass rolling with large deformation and annealing at 200 °C for 150 s and the corresponding YS, UTS and TEF of the AZ31 sheet were 225 MPa, 305 MPa and 32%, respectively. The improvement in the microstructure and mechanical properties can be attributed to an optimised static recrystallisation at a relatively low temperatures and in a short time.

Decoupling Carrier-Phonon Scattering Boosts the Thermoelectric Performance of n-Type GeTe-Based Materials.

The coupled relationship between carrier and phonon scattering severely limits the thermoelectric performance of n-type GeTe materials. Here, we provide an efficient strategy to enlarge grains and induce vacancy clusters for decoupling carrier-phonon scattering through the annealing optimization of n-type GeTe-based materials. Specifically, boundary migration is used to enlarge grains by optimizing the annealing time, while vacancy clusters are induced through the aggregation of Ge vacancies during annealing. Such enlarged grains can weaken carrier scattering, while vacancy clusters can strengthen phonon scattering, leading to decoupled carrier-phonon scattering. As a result, a ratio between carrier mobility and lattice thermal conductivity of ∼492.8 cm3 V-1 s-1 W-1 K and a peak ZT of ∼0.4 at 473 K are achieved in Ge0.67Pb0.13Bi0.2Te. This work reveals the critical roles of enlarged grains and induced vacancy clusters in decoupling carrier-phonon scattering and demonstrates the viability of fabricating high-performance n-type GeTe materials via annealing optimization.

Microwave Hydrothermal Preparation of VO2

As a thermal phase transition material, VO2 is famous for its phase transition performance. When the temperature is lower than the phase transition temperature, VO2 behaves as a semiconductor with high infrared transmittance. When the temperature exceeds the phase transition temperature, VO2 exhibits a metallic state and has a high refractive index for infrared. Regulation of phase transition temperature is key to the application of VO2. In this article, microwave hydrothermal is used to prepare VO2. H+ concentration, microwave power, annealing temperature, and annealing time are used as variable conditions to find the best preparation conditions. The preparation of samples is studied by X‐ray diffractometer, scanning electron microscope, and differential scanning calorimeter. After comparative research, the optimum preparation process of vanadium dioxide by microwave hydrothermal method is found. In addition, by varying the acidic conditions and microwave power during the preparation process, the phase transition temperature of VO2 can be regulated.

Enhancing the upconversion of Er3+ incorporated BaTiO3 by introducing oxygen vacancies.

Lanthanide-incorporated crystals display the phenomenon of upconversion (UC), wherein near-infrared (NIR) light is converted into ultraviolet-visible (UV-Vis) emission with a narrow bandwidth. This unique photophysical property renders lanthanide UC materials highly promising for diverse applications. However, the limited quantum efficiency (∼3%) hinders the broader utilization of UC materials. Consequently, numerous studies have focused on overcoming this low efficiency. Notably, it has been observed that manipulation of the site symmetry in UC materials significantly enhances their UC efficiency. In this study, we investigate the UC enhancement of Er3+ incorporated BaTiO3 (E-BT) crystals through the introduction of oxygen vacancies (OV). The OV were created using a post-heat treatment method, and the annealing time was varied to control the quantity of OV. An optimal annealing time of 6 hours was determined for efficient OV generation, beyond which the OV content decreased. Remarkably, E-BT crystals with OV exhibited up to three-fold greater UC compared to those without OV. This outcome suggests that OV induce symmetry changes in the E-BT crystal structure. Furthermore, the degree of UC enhancement in E-BT was found to be proportional to the amount of OV present.

Microstructure and soft magnetic properties of nanocrystalline Fe–Si–B–Cu–Nb soft magnetic alloy by laser annealing

The impact of laser annealing on the nanocrystalline Fe–Si–B–Cu–Nb soft magnetic alloy has been investigated. The experimental results showed that the microstructure of nanocrystals produced by laser annealing is comparable to that of furnace annealing. However, the annealing time plays a crucial role in determining the grain size and crystalline fraction evolution, thereby affecting both the coercivity and saturation magnetization. Nonetheless, the volume crystalline fraction of the laser annealed samples is lower than that of the furnace annealed ones due to the ultrahigh heating and cooling rate, which hinders the growth of nanocrystals and crystallization region. In addition, laser annealed samples demonstrate no distinct crystallization at high scanning speeds, even with noticeable changes in soft magnetic properties. Furthermore, the correlation between coercivity and grain size is examined, revealing a progressive decline in coercivity with a decrease in grain size. It is also found that the rule Hc ∝ D6 is also valid in laser annealing for relatively larger grains, whereas the rule becomes Hc ∝ D3 for smaller grains.

On the role of selective nucleation and growth to recrystallization texture development in a Mg–Gd–Zn alloy

One of the main material properties altered by rare earth additions in magnesium alloys is texture, which can be specifically adjusted to enhance ductility and formability. The current study aims at illuminating the texture selection process in a Mg–0.073at%Gd–0.165at%Zn alloy by investigating recrystallization nucleation and early nucleus growth during static recrystallization. An as-cast sample of the investigated alloy was deformed in uniaxial compression at 200 °C till 40% strain and was then cut into two halves for subsequent microstructure characterization via ex situ and quasi in situ EBSD investigations. In order to gain insights into the evolution of texture during recrystallization, the contributions from dynamic and static recrystallization were initially separated and the origin of the non-basal orientation of recrystallization nuclei was traced back to several potential nucleation sites within the deformed matrix. Considering the significant role of double-twin band recrystallization in determining the recrystallization texture, this type of recrystallization nucleation was further investigated via quasi-in situ EBSD on a deformed sample, annealed at 400 °C for different annealing times. With progressive annealing, a noticeable trend was observed, in which the basal nuclei gradually diminished and eventually vanished from the annealed microstructure. In contrast, the off-basal nuclei exhibited continuous growth, ultimately becoming the dominant contributors to the recrystallization texture. The study therefore emphasizes the importance of particular nucleation sites that generate favorably oriented off-basal nuclei, which over the course of recrystallization outcompete the neighboring basal-oriented nuclei in terms of growth and thereby dominate the recrystallization texture.

Improvement of AlSiO/GaN interface by a novel post deposition annealing using ultra high pressure

In this study, a novel post-deposition annealing (PDA) technique employing ultra-high pressure was demonstrated for the first time. A 40 nm thick AlSiO gate insulator was deposited using atomic layer deposition (ALD) on n-type gallium nitride (GaN) epitaxial layers grown on free-standing GaN substrates. These PDA techniques were performed at 600 °C in a nitrogen ambient under 400 MPa, with normal pressure conditions used as the references. The annealing duration varied within the range of 10, 30, 60, and 120 min. For normal pressure annealing, the flat-band voltage of capacitance-voltage curves exhibited a shift towards the positive bias direction as the annealing time increased. Conversely, for the 400 MPa annealing, the flat-band voltage approached the ideal curve as the annealing time extended. For 400 MPa and 120 min, low interface state density of ∼5 × 1011 cm−2 eV−1 or less at E c −0.20 eV was obtained. These results suggest that post-deposition annealing under ultra-high pressure could be a viable method for improving the interfacial characteristics of AlSiO/GaN.

Effect of rapid tempering at high temperature on microstructure, mechanical properties and stability of retained austenite of medium carbon ultrafine bainitic steel

Rapid tempering at high temperature is beneficial to release residual stress. However, the evolution of microstructure and mechanical properties of ultrafine bainitic steel after rapid tempering at high temperature is still unclear. In this research, the effect of rapid tempering at high temperature on microstructure, mechanical properties and mechanical stability of retained austenite (RA) of a medium-carbon ultrafine bainitic steel were studied in detail. Results show that after a rapid tempering at 550 °C, the volume fraction of RA decreased gradually, and the carbon atoms in bainitic ferrite (BF) gradually diffused out of the lattice and finally formed carbides, and the BF plate gradually coarsened. When the tempering time is only 2 min, the carbon clusters formed, strengthening the matrix and stabilizing the RA, which result in the highest yield strength, and the highest impact toughness of the steel. With the extension of tempering time, nano-carbides precipitated and gradually grew up, and the dislocation density in steel decreased, resulting in a gradual decrease in the yield strength of the steel and the mechanical stability of RA. However, the deformation ability and strain hardening ability of the BF matrix gradually increase, so that the tensile strength of the steel gradually increases. The decomposition of RA and the formation of brittle martensite making the impact toughness of the steel gradually decrease. This study can provide theoretical support for the development of rapid tempering process of ultrafine bainitic steel.

Using ohmic heating to shorten the tempering time for frozen fish

SummaryThawing is necessary to restore the freshness of fish before cooking because fish is often frozen to retain its freshness. Frequently, fish is partially thawed (or ‘tempered’) as it is easier to handle in this form than fully thawed fish. However, the conventional tempering techniques – immersion in water and still air tempering – take a long time and alter the fish's characteristics. Hence, the aim of this study was to use the heat generated inside the frozen fish, or ohmic heating, to alter the tempering process. Compared with conventional tempering operations, in this study, three voltage levels (20, 30 and 40 V/cm) were used for ohmic tempering. The fish quality and yield findings revealed that 30‐V/cm ohmic heating was more appropriate, even though ohmic heating at 40 V/cm provided the shortest tempering time. The main operating expense for ohmic tempering was the power cost of USD 58.5/100 kg, whereas the major operating expense for water immersion was the cost of water supply and wastewater treatment, which was around USD 108/100 kg. By using ohmic heating instead of still air and water immersion to temper the frozen fish, not only was less time required while retaining the freshness of the fish but the cost of tempering was also reduced.

The effects of cold rolling and building orientation on sensitization of laser powder bed fused 316L stainless steel

The effects of cold rolling, building orientation and sensitization annealing time on the microstructures and corrosion resistance of laser powder bed fused 316L stainless steel were studied. Normal direction face showed higher sensitization level than build direction face. The cold rolling significantly suppressed sensitization of laser powder bed fused samples. Longer sensitization time had little influence on sensitization degree of cold rolled laser powder bed fused samples. Refined grains and high-density dislocations promoted diffusion of Cr and Mo elements into depletion region and effectually inhibited the sensitization.

Rapid Manufacturing of Thin Films for Perovskite Solar Cells

The perovskite solar technology has shown impressive improvements in just over a decade with efficiencies rivalling traditional devices. However, much of this work is done using spin coating and long annealing times. In this work we demonstrate the deposition of several thin films (NiO, perovskite and SnO2) using a blade coating technique and annealed using an intense pulsed light technique. These processes allow for the complete deposition and post-process to be completed in just seconds, yielding quality devices at high manufacturing speeds. The talk will discuss the formulation of the individual inks, deposition and annealing. Results from I-V, UV-Vis, XRD and SEM will establish the working principals of the rapid manufacturing technique.

Interaction and evolution of phases at the coating/substrate interface in galvannealed 3rd Gen AHSS with high Si content

Optimization of the galvannealing for cutting-edge 3rd generation AHSS requires detailed structural and chemical characterization. Alloying elements such as Si dramatically modify the steel surface, forming an oxide layer during pre-annealing, which suppresses the desired interfacial interaction. Progress is impossible without understanding the phases' interplay at the steel-coating interface. We investigated this area in high-Si (1.49 wt%) galvanized AHSS at different annealing times via TEM and revealed that while hot-dip galvanizing at 460 °C the surface oxide prevents the desired Fe-Al reaction and liquid Zn penetrating gaps in the oxide membrane forms a δ phase layer underneath. Located between the steel substrate and the oxide layer, the δ phase can grow during subsequent annealing due to incoming liquid Zn, while Fe diffusion into the coating is suppressed. The oxide film remains stable even after long-term annealing (120 s at 480 °C) separating the coating from the reaction zone. The growing δ layer interacting with the steel substrate consumes dissolved Si. Reaching a certain threshold concentration, supersaturated δ decomposes forming a δ matrix with Fe-Si-Al-based nanoprecipitates. Using EDX data, phase configuration was refined via Thermo-Calc by the Fe–Zn–Si–Al system simulation suggesting that nanoprecipitates are based on Al- and Si-rich type of α-Fe.

Tailoring structure and nanoscale surface topography in Mg–N doped CuCrO[formula omitted] thin films via post deposition annealing for optothermoelectric application

In this study, we explored how varying the annealing temperature and the duration of post-annealing affect the structural, optical, and thermoelectric characteristics of thin films doped with Mg–N in CuCrO2. As the annealing time increased, we observed that all the annealed films exhibited enhanced conductivity at room temperature. Additionally, both the power factor and Seebeck coefficient also exhibited increases. The quantitative assessment of the nanometric dimensional surface roughness and the surface nano-texture of the deposited film was done by atomic force microscopy analysis. The spiky peaks and positive roughness skewness (Rsk) value made the two-hour annealed film suitable for energy harvesting. Wide band gap and high transmission of more than 60% were found by UV–Vis spectroscopic analysis and Fermi energy of 7 meV is calculated and determined the possibility of the film from being used in ohmic contact with delafossite to prevent Schottky barriers and track the work function of the material.

Nanosecond Laser Irradiation for Interface Bonding Characterization

Hydrophilic direct bonding is nowadays widely used in microelectronics for SOI substrate fabrication and 3D integration. Trapped water at the bonding interface plays a key role in the adhesion and adherence mechanisms [1]. Previous studies also reported that water could penetrate the bonding interface. This may modify the radial inhomogeneity of water [2]. However, this reported technique requires specific Silicon-to-Silicon bonding, lacks precision and needs additional characterizations (XRR, FTIR) to quantify the amount of trapped water at the bonding interface. In this work, we present an original methodology that can both accurately characterize and quantify water imbibition.Pulsed nanosecond laser annealing enables to reach extremely high temperatures, above the silicon melting point (1414°C), for very short durations (from a few tens of ns to a few hundred ns). These annealing conditions result in silicon surface melt. The beginning of melting is heterogeneous and leads to a particular surface topology with the formation of molten islands during laser annealing [3]. Recrystallization of these molten islands results in a localized increase of roughness (see fig. 1a). This roughness can exceed the direct bonding critical roughness. Non-bonded areas, i.e. bonding defects, can then be intentionally and precisely placed at the direct bonding interface.In a first step, bonding defects were thus formed along a wafer diameter with a 2 mm pitch. Then, using high-resolution acoustic microscopy, the bonding defects radii evolution was measured over time after direct bonding and without annealing (see fig. 1b). A progressive growth of defect radii was evidenced when getting closer and closer to the wafer edge. An additional water amount coming from the clean room atmosphere resulted in silicon oxidation at room temperature and di-hydrogen generation. Di-hydrogen was then trapped by bonding defects. In other words, bonding defects acted as humidity sensors. We could then record the penetration length and plot it as a function of the square root of time (fig. 1c). The penetration rate is the equivalent of a diffusion coefficient that could be calculated for both Silicon-to-Silicon and Silicon-to-Oxide bonding. We noted a very good agreement with Tedjini’s results for Silicon-to-Silicon bonding [2]. Meanwhile the calculated diffusion coefficient for Silicon-to-Oxide bonding was surprisingly about twice higher.Second, a bonding defect network with the same 2 mm pitch in both X and Y direction was created. After direct bonding, various duration 500°C temperature anneals were performed. The defects radii evolution was once again measured. As it increased over time, we could write the Griffith equilibrium between elastic (due to defect pressure) and surface (γ) energies. Describing defects as circular blisters, the amount of di-hydrogen trapped molecules could then be calculated. Plotting this number of H2 molecules, N, as a function of the annealing time (fig. 1d), we observe that a plateau was reached, meaning that all the di-hydrogen produced in the network was collected in the bonding defects. The water amount responsible for this di-hydrogen generation could then be evaluated and compared to data from other measurements. REFERENCES [1] F. Fournel, C. Martin-Cocher, D. Radisson, V. Larrey, E. Beche, C. Morales, P. A. Delean, F. Rieutord, and H. Moriceau, “Water Stress Corrosion in Bonded Structures”, ECS Journal of Solid State Science and Technology, 4 (5) P124-P130 (2015)[2] Tedjini M, Fournel F, Moriceau H, Larrey V, Landru D, Kononchuk O, et al. Interface water diffusion in silicon direct bonding. Appl Phys Lett. 12 sept 2016;109(11):111603.[3] L. Dagault, S. Kerdilès, P. Acosta Alba, J.-M. Hartmann, J.-P. Barnes, P. Gergaud, E. Scheid, and F. Cristiano, Investigation of Recrystallization and Stress Relaxation in Nanosecond Laser Annealed Si1−xGex/Si Epilayers, Appl. Surf. Sci. 527, 146752 (2020). Figure 1

Preparation and characterization of SbSeI thin films

Metal chalcohalides are promising candidates for next-generation technologies that include energy conversion, information storage, and quantum computing. Among them, antimony selenoiodide (SbSeI) has received rising interest for different optoelectronic devices, including photovoltaics, due to its bandgap energy, strong optical absorption, stability, and earth abundant, low-cost, and low toxicity constituents. In this work, SbSeI thin films were prepared through a two-step process. At first, antimony selenide (Sb2Se3) thin films were deposited at 300 °C (Sb2Se3-300) and at room temperature (Sb2Se3-RT) onto molybdenum covered soda-lime glass substrates by a magnetron sputtering method. The formation of SbSeI thin films was performed by isothermally annealing the as-deposited Sb2Se3 thin films in sealed quartz ampoules in the atmosphere of antimony iodide (SbI3) with the presence of 100 Torr of argon pressure. The influence of the annealing temperature and time during the iodization of different types of substrates on the morphology and composition of SbSeI thin films was investigated. The well-oriented and dense single-phase SbSeI thin films with stoichiometric composition and single-crystal micro-columnar structures were achieved by annealing Sb2Se3-RT in SbI3 atmosphere at 250 °C for 5 min under 100 Torr of Ar pressure. The room temperature photoluminescence (RT-PL) of SbSeI exhibited a broad asymmetric PL band with a maximum at 1.67 eV. The low-temperature (T = 8 K) PL study of SbSeI showed a broad and asymmetric PL band at 1.4 eV, being quite distant from the bandgap. This PL band at 1.4 eV with obtained small thermal quenching activation energy of 12.7 meV is proposed to originate from the deep donor-deep acceptor pair (DD-DA) recombination.

Quasi-deterministic localization of Er emitters in thin film TiO2 through submicron-scale crystalline phase control

With their shielded 4f orbitals, rare-earth ions (REIs) offer optical and electron spin transitions with good coherence properties even when embedded in a host crystal matrix, highlighting their utility as promising quantum emitters and memories for quantum information processing. Among REIs, trivalent erbium (Er3+) uniquely has an optical transition in the telecom C-band, ideal for transmission over optical fibers, making it well suited for applications in quantum communication. The deployment of Er3+ emitters into a thin film TiO2 platform has been a promising step toward scalable integration; however, like many solid-state systems, the deterministic spatial placement of quantum emitters remains an open challenge. We investigate laser annealing as a means to locally tune the optical resonance of Er3+ emitters in TiO2 thin films on Si. Using both nanoscale x-ray diffraction measurements and cryogenic photoluminescence spectroscopy, we show that tightly focused below-gap laser annealing can induce anatase to rutile phase transitions in a nearly diffraction-limited area of the films and improve local crystallinity through grain growth. As a percentage of Er:TiO2 is converted to rutile, the Er3+ optical transition blueshifts by 13 nm. We explore the effects of changing laser annealing time and show that the amount of optically active Er:rutile increases linearly with laser power. We additionally demonstrate local phase conversion on microfabricated Si structures, which holds significance for quantum photonics.

Microstructure and Texture of Pure Copper under Large Compression Deformation and Different Annealing Times

In this study, the plastic deformation of pure copper under room-temperature compression and different annealing times was examined, and the microstructure and texture evolution were studied via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and microhardness tests. The results showed that when the deformation degree was 93.75%, the microhardness increased from 76 HV (Vickers hardness) before deformation to 110 HV. After annealing, the hardness decreased with increasing annealing time, and the pure copper grain size could be refined from 150 μm to 6.15 μm. An increase in annealing time did not continue to promote recrystallization, while the effect on grain refinement was weakened. The geometrically necessary dislocation (GND) density decreased from 6.0 × 1014/m2 to 4.83 × 1014/m2 after annealing, which implies that static recrystallization occurs at the cost of dislocation consumption during the annealing process. The compression deformation of pure copper produced a strong deformation weave (<001> orientation), and a portion of the deformation weave within the material was transformed into a recrystallization weave (<111> orientation) after the annealing process.

Effects of annealing treatment on microstructure and mechanical properties of laser melting-deposited VCoNi medium-entropy alloy

Additive manufacturing (AM) is a promising approach to producing high- or medium-entropy alloys (HEAs or MEAs) with excellent properties. However, some undesirable microstructural defects and unstable precipitated phases were formed owing to the repeated heating and cooling steps and the rapid solidification nature of the AM process. Annealing treatment after AM fabrication is often beneficial for adjusting the comprehensive mechanical properties and stabilizing the microstructures. In this study, a VCoNi MEA single wall sample was fabricated successfully via laser melting deposition (LMD), and the effects of post-annealing treatments on the microstructures and mechanical properties were explored. The grain size and σ-phase particle size increase and the σ-phase particles undergo fragmentation, spheroidization, and coarsening during annealing. As the annealing time increases, the tensile strain increases, but the tensile strength decreases. An excellent combination of strength and ductility can be obtained after annealing for 1.5 h (The yield strength, ultimate tensile strength, and tensile strain are 741.2 MPa, 1287.8 MPa, and 30.5 %, respectively). HDI hardening is the most important strengthening mechanism in this work. The decrease in tensile stress after the annealing treatment is mainly attributed to the decrease of heterogeneity of microstructure, and the increase in tensile strain after the annealing treatment is mainly attributed to the decrease of the pores and the spheroidization of the rod-like σ-phase particles. This work provides practical insight into adjusting the microstructure and comprehensive mechanical properties of HEAs and MEAs for AM.