Continuous Annealing Research Articles

Highly strained and heavily doped germanium thin films by non-equilibrium high-speed CW laser annealing for optoelectronic applications

The integration of light transmitters into electronic circuits is essential for the development of optical communication systems. A direct bandgap semiconductor with excellent electrical properties is preferable for a cost-effective and high-performance device. Germanium is considered a promising candidate for CMOS-compatible optoelectronics, even though the light emission is inefficient due to its indirect bandgap property. It has been reported that applying tensile strain modifies the energy band structure thus making quasi-direct bandgap emission possible. In addition, n-type doping has been expected to improve this emission. We have realized high tensile strain in polycrystalline germanium grown on a quartz substrate by employing continuous wave laser annealing (CWLA). In this study, we investigated the implementation of a similar annealing technique with antimony doped samples to combine both tensile strain and n-type doping in a Ge-on-insulator (GeOI) structure. We investigated various samples with different interfaces to achieve large-grained polycrystalline films on insulator. Characterizations of the CWLA processed samples revealed the successful introduction of both tensile strain and n-type doping in GeOI. The properties were confirmed by the enhancement of direct Γ-LH emission that observed even for room-temperature optical measurements. These results provide an important insight that will assist the feasible and large-scale development of germanium-based optoelectronic devices.

Comparison of the Methodologies for Studying Ferrite Recrystallization Kinetics in Continuous Annealing

Comparison of the Methodologies for Studying Ferrite Recrystallization Kinetics in Continuous Annealing

Time-Dependent Evolution of Volume Fraction and Stability of Retained Austenite in a Hot-Rolled and Intercritically Annealed Al-Alloyed Medium-Mn Steel

The development of superior mechanical properties in medium-Mn requires the optimization of microstructural parameters such as retained austenite (RA) stability, volume fraction, and morphology. The present work explores the possibility of using a continuous annealing approach instead of conventional batch annealing to perform an intercritical annealing (IA) treatment in a hot-rolled strip of an Al-alloyed 5Mn steel. Dilatometric studies were performed at a temperature of 680 ºC with soaking times ranging from 1 to 300 min to follow the microstructural changes as a function of time. The microstructures thus obtained were thoroughly characterized by means of X-ray diffraction, SEM and TEM, TEM-EDS microanalysis and EBSD phase and orientation maps. It was observed that with increasing soaking times, the volume fraction of retained austenite gradually increases, albeit at the cost of its stability. The comparison of martensite start temperatures (Ms) based on the chemical composition of austenite at 680 ºC with that experimentally obtained at higher process temperature revealed the effect of the grain size on the reduction of RA stability for longer process times. Accordingly, mechanical tests results showed that the yield stress, tensile strength and hardness decrease with an increase in the IA soaking time.

Strain Rate Dependence and Recrystallization Modeling for TC18 Alloy during Post-Deformation Annealing.

In this paper, the dependence of dynamic recrystallization (DRX) and post-dynamic recrystallization (PDRX) of TC18 alloy on strain rate within the range of 0.001 s-1~1 s-1 was investigated through isothermal compression and subsequent annealing in the single-phase region. Electron backscatter diffraction (EBSD) characterization was employed to quantify microstructure evolution and to reveal the recrystallization mechanism. At the thermo-deformation stage, the DRX fraction does not exceed 10% at different strain rates, due to the high stacking fault energy of the β phase. During the subsequent annealing process, the total recrystallization fraction increases from 10.5% to 79.6% with the strain rate increasing from 0.001 s-1 to 1 s-1. The variations in the geometrically necessary dislocation (GND) density before and after annealing exhibit a significant discrepancy with the increasing strain rate, indicating that the GND density is a key factor affecting the PDRX rate. The PDRX mechanisms, namely meta-dynamic recrystallization (MDRX), continuous static recrystallization (CSRX) and discontinuous static recrystallization (DSRX), were also revealed during the annealing process. A new kinetic model coupling DRX and PDRX was proposed to further describe the correlation between recrystallization and the strain rate during continuous deformation and annealing. This new model facilitates the prediction of recrystallization fraction during isothermal deformation and annealing of titanium alloys.

Dynamic operation optimization based on improved dynamic multi-objective dragonfly algorithm in continuous annealing process

The continuous annealing production process is the strip iron heat treatment process. Considering the numerous disturbance parameters and frequent environmental changes in the production process, dynamic multi-objective optimization is studied. (1)To anticipate whether the environment will change, this paper proposed dynamic detection based on Long-Short Term Memory (LSTM) prediction mechanism. A single-step prediction method is adopted to predict the strip hardness at the next moment which is compared with the value at the previous moment. (2)To track the dynamic Pareto frontier, the Information Fusion (IF) strategy in Dynamic Multi-Objective Dragonfly Algorithm (DMODA) is proposed. The population is updated by integrating the environmental offset with the evolution information. Computational experiments show the proposed strategy is effective when dealing with dynamic problems and it has been well applied in the continuous annealing process. The strip steel quality and production capacity can remain stable during the dynamic production process.

The Effect of Partitioning Temperature on Residual Austenite and Mechanical Properties of Q&P High Strength Steel during the Continuous Annealing Process

Q&P steel has the advantages of high strength and high elongation, but the key to the production of Q&P steel is the control of heat treatment temperatures, such as the annealing temperature and the partitioning temperature. In this work, SEM, TEM, EBSD, and other methods are used to study the effects of different partitioning temperatures on the microstructure and properties of 2.0 Mn low-carbon Q&P steel during the continuous annealing process. The results show that the grain size and quantity of the residual austenite (RA) increase significantly with the increase in the partitioning temperature, and the strength of the machine can reach 27.2 GPa% at the partitioning temperature of 370 °C. Meanwhile, the retention mechanism of the residual austenite at the partitioning stage is also clarified.

Surface defect passivation by 1,8-Naphthyridine for efficient and stable Formamidinium-based 2D/3D perovskite solar cells

• 1,8-Naphthyridine (1,8-ND) as a modifier is implanted at the interface of PVK/HTL. • 1,8-ND reconstructs perovskite to fabricate efficient α-FAPbI 3 phase and 2D/3D PSCs. • 1,8-ND coordinate with Pb 2+ to passivate defects and construct quasi-2D perovskite. • 1,8-ND modified 2D/3D PSC achieved a champion PCE of 23.8% with excellent stability. The ionic properties of components determine that perovskite films will generate numerous charged surface defect under continuous high-temperature annealing, resulting in suboptimal performance and poor stability of perovskite solar cells (PSCs). Based on the principle of Lewis acid-base coordination, 1,8-naphthyridine (1,8-ND) with electron-rich structure was used to form complexes with Pb 2+ ions, and high-quality 2D/3D perovskite films with effective defect passivation were prepared by surface modification. Benefiting from suppressed nonradiative recombination, extended carrier lifetime, modified charge transport, improved hydrophobic properties and the optimized phase stability of α-FAPbI 3 , 1,8-ND modified 2D/3D PSCs with negligible hysteresis and satisfactory stability achieved a champion power conversion efficiency of 23.8% whose open circuit voltage was significantly improved from 1.09 V to 1.15 V, providing a resultful strategy to passivate surface defect while constructing 2D/3D perovskite.

Influence of stress-induced anisotropy on domain structure and magnetic properties of Fe-based nanocrystalline alloy under continuous tension annealing

The correlation among microstructures, magnetic properties and domain patterns for the FINEMET nanocrystalline ribbons treated in a home-made continuous tension annealing equipment under different tensile stresses (σ) were investigated in detail. Results show that the effective permeability (μe) of the nanocrystalline ribbons can be expediently adjusted from 412.83 to 1659.96 by manipulating the magnitude of stress-induced anisotropy constant (Ku), wherein the Ku and σ are in a linear relationship. Owing to the increasing domain wall energy induced by the increase of σ for the nanostructured ribbons, the attenuation of μe with the elevating applied field and frequency can be effectively suppressed, the average domain width between the strip-like domain patterns gradually decreases, and the domination of magnetization process alters from domain-wall displacement to homogeneous rotation. These results will provide a referable idea for current transformers to meet the requirements of higher precision and lower energy consumption.

Fuzzy c-means and simulated annealing for planar location-routing problem

Location-routing problem (LRP) contains two Np-hard problems as, facility location (FL) and vehicle routing problem (VRP), in the same content. Since both problems directly affect the cost of distributions of the products and supply chain, the decision of location and routing is important for the success of companies. Therefore, many attempts are made to solve LRP problem in the literature. Researchers proposed exact and heuristic methods for LRP. However, exact methods cannot provide solutions for considerably large instances. In this paper, a new heuristic method is proposed for continuous or planar LRP. The proposed method contains fuzzy c-means for continuous location problem and simulated annealing algorithm for vehicle routing problem, respectively. The proposed method is applied to both capacitated and uncapacitated LRP instances that are widely used in the literature. Results of the proposed method are compared with successful researches that are made on this problem in terms of the total cost.

Development of Low-Alloyed Low-Carbon Multiphase Steels under Conditions Similar to Those Used in Continuous Annealing and Galvanizing Lines

In the present work, a Cr+Mo+Si low-alloyed low-carbon steel was fabricated at laboratory scale and processed to produce multiphase advanced high-strength steels (AHSS), under thermal cycles similar to those used in a continuous annealing and galvanizing process. Cold-rolled steel samples with a microstructure constituted of pearlite, bainite, and martensite in a matrix ferrite, were subjected to an intercritical annealing (817.5 °C, 15 s) and further isothermal bainitic treatment (IBT) to investigate the effects of time (30 s, 60 s, and 120 s) and temperature (425 °C, 450 °C, and 475 °C) on the resulting microstructure and mechanical properties. Results of an in situ phase transformation analysis show that annealing in the two-phase region leads to a microstructure of ferrite + austenite; the latter transforms, on cooling to IBT, to pro-eutectoid ferrite and bainite, and the austenite-to-bainite transformation advanced during IBT holding. On final cooling to room temperature, austenite transforms to martensite, but a small amount is also retained in the microstructure. Samples with the lowest temperature and largest IBT time resulted in the highest ultimate tensile strength/ductility ratio (1230.6 MPa-16.0%), which allows to classify the steel within the third generation of AHSS. The results were related to the presence of retained austenite with appropriate stability against mechanically induced martensitic transformation.

Ultrafine Carbide-Free Bainite in High-Carbon Steel After Continuous Annealing with Different Cooling Rates

Ultrafine Carbide-Free Bainite in High-Carbon Steel After Continuous Annealing with Different Cooling Rates

Diffusionless α′ to γ transformation and its effect on hot ductility in a high-nickel steel

The role of diffusionless α′ to γ transformation on the microstructure evolution and hot ductility of high-nickel steel is investigated. In-situ Auger electron spectroscopy fracture test reveals the correlation of ductility loss and sulfur segregation at the grain boundary. The α′ to γ transformation start temperature is measured by heating the initial α′-martensite at various rates. The transformation temperature remains constant when the heating rate is higher than 15 °C/s. Despite the α′ to γ phase transformation, the diffusionlessly transformed specimen shows a similar γ grain size with the initial prior γ grain size. The γ grain size decreases dramatically after the continuous annealing of the transformed specimen. The temperature-dependent recrystallization behavior and corresponding hot-ductility are evaluated. The improved hot ductility is achieved by active recrystallization at 900–1100 °C. Due to the late recrystallization behavior, the improvement of hot ductility is limited after annealing at 800 °C. The origin of hot ductility loss and enhancement depending on the thermal cycles is discussed by sulfur segregation at the grain boundary and recrystallization behavior after diffusionless transformation.

Batch annealing enhances the yield strength of a high quenching temperature Q&P steel through accelerated bainitic transformation

Hot-dip galvanized quenching and partitioning (Q&P) steels exhibit excellent corrosion resistance and strength-ductility synergies. However, production using conventional continuous galvanizing lines (CGLs) is challenging because these lines cannot meet the required quenching and reheating capacity. The presence of ferrite and absence of sufficient primary martensite led to a substantial decrease in the yield strength of the material. To solve this problem, we propose a simple batch annealing (BA) treatment prior to continuous annealing and galvanization. The BA treatment resulted in spheroidization of cementite in the coiled samples and enrichment of Mn. During the intercritical annealing process, the higher Mn content in the cementite of the BA sample retards cementite dissolution. The retained cementite particles served as nucleation sites and significantly promoted bainite formation during quenching and partitioning. Consequently, the yield strength increased by approximately 90%, from 438 MPa to 821 MPa. The total elongation of the BA samples was not affected due to the simultaneous stabilization of the retained austenite. The effect of batch annealing time was also investigated, and the balance between Mn enrichment in cementite and the number density of spheroidized cementite before Q&P treatment was revealed.

Calculation Model, Influencing Factors, and Dynamic Characteristics of Strip Temperature in a Radiant Tube Furnace during Continuous Annealing Process

Strip temperature control is central to the continuous annealing process, and a strip temperature calculation model is necessary to realize accurate and stable strip temperature control. This paper focuses on the radiant tube furnace (RTF), which is the most important and most difficult to control in the continuous annealing process. A calculation model of strip temperature distribution is established using the heat balance method, which is suitable for online control. The model is verified to be accurate and reliable based on the measured data. On this basis, the influencing factors of strip temperature distribution in RTFs are further analyzed. The results show that strip thickness, line speed, and the radiant tube temperature of each column have significant influence on strip temperature distribution, while strip width has little influence. Furthermore, the dynamic characteristics of strip temperature under different working conditions are also investigated. The results reflect that strip temperature at the RTF exit has different response times, and amplitudes to the change of line speed, strip thickness, and radiant tube temperature. After changing the process parameters, the re-stabilization process of strip temperature shows a significant time lag.

Crystallization Of Tensile Strained n-Type Ge By Continuous Wave Laser Annealing

In recent years, germanium (Ge) has attracted a lot of attention for the development of next generation devices due to its higher carrier mobilities compared with silicon (Si) and its compatibility for complementary metal-oxide-semiconductor (CMOS) applications. It is widely known that Ge is an indirect-band semiconductor like Si. However, by introducing tensile strain, the 136 meV difference between direct and indirect gaps can be reduced. Furthermore, in the case of 0.2-0.3% tensile strained Ge, n-type doping in the order of 1019 cm-3 were expected to be resulted in quasi direct-band light emission around 1550 nm wavelength. [1] The realization of this tensile strained n-Ge is promising for the integration of light sources on next generation Ge-based devices. Here, we focused on n-type Ge deposition using molecular beam epitaxy (MBE) method and have succeeded in realizing highly Sb-doped epitaxial n-Ge films by modulating the deposition temperatures. [2] Moreover, we have recently reported the crystallization of amorphous Ge by high-speed continuous wave laser annealing (CWLA), which more importantly also resulted in the introduction of 0.55-0.62% tensile strain. [3] In this study, we applied the similar annealing technique for crystallization of Sb-doped Ge toward the realization of tensile strained n-type Ge films.Sb-doped poly-crystalline Ge films with high Sb concentration (approximately 1019 cm-3) and thickness of about 100 nm were deposited on quartz substrate by molecular beam deposition at 450ºC substrate temperature. Then, 300 nm of SiO2 capping layer was deposited by sputtering in room temperature, such that the sample structure become that shown in Fig.1(a). The samples then annealed in the CWLA system equipped with Nd:YVO4 solid state laser with wavelength of 532 nm as the light source, which scan laser light at the speed (vscan) of 800 m/min. Also, the laser is focused to 20 μm diameter and shifted at 5 μm to scan the samples. Here, the laser power (Elaser) was changed from 300 to 1000 mW. After laser annealing, the capping layer were removed then the samples were characterized by micro-Raman spectroscopy.The annealed sample surface shows brighter contrast compared to the as-deposited samples, as shown in Fig.1(b) and (c), which indicate the structural change of Ge layer. Raman spectra measured at surface of annealed Ge layers are summarized in Fig.2. Here, Ge-Ge peak around 300.2 cm-1 confirmed on the samples, indicating the crystallization of the Ge layers. This peak is not shifted in low Elaser but largely shifted in high Elaser at up to -2.4 cm-1 for undoped and -3.6 cm-1 for the Sb-doped Ge films. This difference could be explained by the liquid phase recrystallization after Ge layer melted in high Elaser (≥600 mW). During recrystallization process, tensile strain is accumulated upon cooling as the tensile strain amount (0.43-0.63%) is agree with the thermal expansion value of Ge between solidification temperature and room temperature (-0.60%). This mechanism is similar to the crystallization of amorphous Ge films on quartz substrates in our previous work. [3] These results show the successful crystallization of tensile strained n-Ge layer by the CWLA method. This finding will be useful for the growth of Ge-based films and a promising step toward the development of CMOS-integrated optoelectronics. Further investigation of the annealing conditions and its relations with the properties of Sb-doped Ge films will be discussed in the main presentation. References Liu, J., Kimerling, L. C. & Michel, J. Semicond. Sci. Technol. 27, (2012).Saputro, R.H., Matsumura, R. & Fukata, N. Cryst. Growth & Des. 21, 6523–6528 (2021).Matsumura, R. & Fukata, N. ECS J. Solid State Sci. Technol. 9, 063002 (2020). Figure 1

Conjugated oxazole‐based interfacial materials for efficient and stable inverted polymer solar cell with an efficiency of 16.52%

Organic solar cells (OSCs) using non-fullerene acceptors have delivered the highest efficiencies in the overall reported literatures. In order to improve the efficiency and stability of OSCs, great efforts are being made in designing and synthesizing new materials. Inverted OSCs were fabricated using three commercially available and inexpensive materials, 5-methylbenzoxazole (E1), 2-(4-biphenyl)-5-phenyloxazole (E2), and 4-bis(5-phenyl-2-oxazolyl)benzene (E3), as an interlayer between zinc oxide and the active layer. The new interlayer materials enhance the carrier injection/extraction properties and thus, the polymer solar cells (PSCs) exhibited an improved JSC and power conversion efficiency (PCE). PSCs showed an improved JSC of 27.18 from 24.88 mA/cm2 with the introduction of E3. The new interlayer, E3 in particular, forms well-aligned cascading energy levels between the PM6:Y6 active layer and zinc oxide layer. These cascading energy levels reduce the energy barrier for electron injection and collection at the interface. Thus, the PCE of devices reached a remarkable 16.52% using interlayer at the ZnO/active layer interface. The devices also exhibited improved device stability under continuous illumination, annealing, and high humidity.

Strip Hardness Prediction in Continuous Annealing Using Multiobjective Sparse Nonlinear Ensemble Learning With Evolutionary Feature Selection

In the iron and steel industry, the hardness of steel strips is one of the key performance indicators to evaluate strip quality and guide production for the continuous annealing production line (CAPL). However, the hardness cannot be measured online in the actual production process. Consequently, the precise prediction of the strip hardness based on practical data becomes one of the key tasks during production. In this article, a multiobjective sparse nonlinear ensemble learning with evolutionary feature selection (MOSNE-EFS) method is proposed, which is data-driven modeling of the soft sensor. The method mainly consists of two stages: 1) the construction of individual learners based on multiobjective feature selection learning (MOFSL) and 2) the selection and ensemble of individual learners based on sparse nonlinear ensemble learning via differential evolution (SNEL-DE). The final ensemble model obtained by SNEL-DE is used as the prediction model for strip hardness in CAPL. The proposed method is evaluated with industrial production data. Experimental results indicate that the two strategies, i.e., evolutionary feature selection and sparse nonlinear ensemble, are effective in improving the accuracy and robustness of the prediction model, and further comparison results demonstrate the superiority of the MOSNE-EFS model over the other existing methods. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Many quality metrics in the iron and steel industry cannot be online checked, which causes great difficulties in process monitoring, control, and operation optimization. The proposed multiobjective sparse nonlinear ensemble learning with evolutionary feature selection method can help practitioners to construct quality prediction models of many other similar production lines, such as hot rolling and cold rolling, and thus, better process monitoring, control, and optimization of product quality can be achieved.

Thermally-induced drift of A-site cations at solid–solid interface in physically paired lead halide perovskites

The promise of hybrid organic–inorganic halide perovskite solar cells rests on their exceptional power conversion efficiency routinely exceeding 25% in laboratory scale devices. While the migration of halide ions in perovskite thin films has been extensively investigated, the understanding of cation diffusion remains elusive. In this study, a thermal migration of A‑site cations at the solid–solid interface, formed by two physically paired MAPbI3 and FAPbI3 perovskite thin films casted on FTO, is demonstrated through continuous annealing at comparably low temperature (100 °C). Diffusion of methylammonium (CH3NH3+, MA+) cations into the low‑symmetry yellow δ‑FAPbI3 phase triggers a transition from the yellow (δ) to black (α) phase evident in the distinctive color change and verified by shifts in absorption bands and X‑ray diffraction patterns. Intermixing of the A‑site cations MA+ and FA+ (CH(NH2)2+) occurred for both systems, α‑MAPbI3/δ‑FAPbI3 and α‑MAPbI3/α‑FAPbI3. The structural and compositional changes in both cases support a thermally activated ion drift unambiguously demonstrated through changes in the absorption and X-ray photoelectron spectra. Moreover, the physical contact annealing (PCA) leads to healing of defects and pinholes in α‑MAPbI3 thin films, which was correlated to longer recombination lifetimes in mixed MAxFA1−xPbI3 thin films obtained after PCA and probed by ultrafast transient absorption spectroscopy.

A committee machine with intelligent experts (CMIE) for estimation of fast and slow shear wave velocities utilizing petrophysical logs

Petrophysical properties determination of a reservoir such as shear wave velocity plays a crucial role in exploration and production management. The purpose of this study is to develop a robust committee machine model for estimating fast and slow shear wave velocities from petrophysical logs. To this end, appropriate inputs were determined and different algorithms including artificial neural network, fuzzy logic and neuro-fuzzy were applied. Afterward, the obtained outputs were merged by utilizing optimization methods consisting of Ant Colony Optimization for Continuous Domain, Genetic and Simulated Annealing approaches. The construction of the committee machine was done using a case study including 2000 data samples from the Sarvak Formation in one of the southwestern Iran oilfields. The utilized dataset was divided into training and testing data which contain 1600 and 400 samples, respectively. Mean Squared Error was presented as a determinative factor for evaluating system performance. To obtain the best system performance with the lowest Mean Squared Error, the parameters setting of each algorithm were coded in different ranges. A total 52416, 76896 and 29400 cases were run to optimize the parameter settings of genetic algorithms, simulated annealing and continues ant colony optimization models, respectively. A weight factor is assigned to each method indicating their contribution in the final estimation. The desirable weights' combination is acquired using optimization methods. Among the individual systems, fuzzy logic and artificial neural network obtained the best performance for estimating fast and slow shear wave velocities, respectively. Also, the results of committee machine algorithms indicate a well optimization on individual systems and have superior performance over them. The most efficient optimization algorithms in the structure of committee machines for fast shear wave velocity are Genetic and Simulated Annealing and for slow shear wave velocity is Genetic Algorithm, in terms of Mean Squared Error criteria.

Crystallization Of Tensile Strained n-Type Ge By Continuous Wave Laser Annealing

Germanium has attracted a lot of attention for the development of next generation electronic devices. Moreover, the small difference of band gap at Γ-point and L-point gives interesting properties for optical applications as well. Introducing tensile strain to a Ge film was known to reduce those band gap difference, although it is very challenging to transform Ge into direct-band semiconductor. In this research, we investigated the growth of tensile strained n-type Ge films by continuous wave laser annealing, which is promising approach to realize quasi direct-band recombination.