Increase Of Annealing Temperature Research Articles

The Annealing Temperature Effect Enhances the Structural and Optical Parameters of Bi2Te3 Thermally Evaporated Thin Films

Abstract The current work investigates the influence of the annealing temperature (373, 473K) on the structural and optical properties of Bi2Te3 thin films produced by the thermal evaporation technique. The crystal structure of samples is examined using an X-ray diffraction, indicating that Bi2Te3 thin films have a Rhombohedral structure with space group R-3m. The crystallite size (D) increased from 10.85 to 14.46 nm by increasing the annealing temperature. Additionally, increasing the annealing temperature reduces the micro-strain and the dislocation density from (3.33x10^(-3) to 2.5x10^(-3)) and (8.49x10^15 to 4.78x10^15 ) Lines⁄m^2 , respectively. These micro-strain and dislocation density reductions refer to the crystallinity enhancement of sample Bi2Te3 thin films. The transmittance and reflectance spectra were measured using an Fourier transform infrared spectrometer. All samples reveal direct and indirect transition types and both direct and indirect optical energy gap decreased with increased annealing temperature from (0.325 to 0.29 eV) and (0.24 to 0.274 eV), respectively. From transmittance and reflectance data, the refractive index is calculated. These results reveal the refractive index decreasing as temperature annealing increased from (2.45 – 1.79) at 3250 nm. Other optical parameters such as absorption index, dielectric constant, energy loss function, and optical conductivity were estimated.

THE EFFECT OF ANNEALING REGIME ON THE PRECIPITATION OF FeCoNiAl0.75Nb0.25 HIGH ENTROPY ALLOY

This paper investigates the effect of the annealing regime on the precipitation of FeCoNiAl0.75Nb0.25 high entropy alloy. The as-cast microstructure consists of coarse dendritic phases that are replaced by equiaxed morphology, and the distribution of the interdendritic phase becomes regularly better with increasing time and annealing temperature up to 825ºC. The precipitated process begins at 700ºC for 8 hours, shortening to 4 hours when the annealing temperature increases. The size of this phase is only a few μm. The fraction of the precipitated phase increases and the size of the dendritic phase is reduced as the annealing temperature is up to 825ºC, while this size rises in the 925ºC/16 hours regime. The microstructure is coarse, and the precipitated phase gradually disappears when the annealing is at 1000ºC. The HV3 hardness of the alloy increases with annealing time when the temperature is lower than 825ºC and reaches the highest value of ~ 614 kg/mm2 at 600ºC/ 24 hours; this value begins to decrease for the 925ºC/16 hours regime. Meanwhile, the hardness gradually decreases with increasing annealing time at 1000ºC. It can be expected due to the rapid coarsening of the dendritic phase, the decrease in the proportion of the precipitated phase in the alloy, and the appearance of plastic flow phenomena at grain boundaries.

Influence of Annealing and Aging Parameters on the Microstructure and Properties of 1200 MPa Grade Cold-Rolled Dual-Phase Steel

With the rapid development of the automotive industry, the requirements for bodywork materials are not only focused on high strength but also on improved forming properties. To develop a new generation of automotive steels with higher strength–plasticity matching, a high elongation 1200 MPa grade V-Nb microalloyed cold-rolled reinforced formable dual-phase steel was developed in this experiment through rational compositional design and precise process machining. The properties of the test steel are improved by varying the over-aging temperature as well as the annealing temperature to achieve a good strength–plasticity balance. The results show that as the aging temperature increases, the tensile strength and yield strength of the test steel decrease, while the elongation continues to increase. At an aging temperature of 310 °C, the steel exhibits not only high strength but also better ductility. As the annealing temperature increases, the tensile strength and yield strength of the test steel initially increase and then decrease, while the elongation continues to increase. When the heat treatment process involves an annealing temperature of 860 °C and an over-aging temperature of 310 °C, the test steel achieves the best strength–plasticity balance.

Effect of heat treatment on microstructure and mechanical anisotropy of direct energy deposited Ti-6.0Al-2.5Nb-2.2Zr-1.2Mo alloy

Ti-6.0Al-2.5Nb-2.2Zr-1.2Mo alloy (Ti-6321) exhibits excellent corrosion resistance and impact toughness, which can be used as a deep-sea pressure-resistant hull. However, the alloy tends to have high strength but low plasticity, poor impact toughness, and anisotropic mechanical properties by fabricating by direct energy deposition (DED) technology. In order to improve the impact toughness of DEDed Ti-6321 alloy while reducing its anisotropy of mechanical properties, this study manipulates the microstructure and mechanical properties of the alloy through heat treatment. The research finds that with the increase of the single-stage annealing temperature within the (α+β) two-phase region, the width of the α phase increases, the Ultimate Tensile Strength (UTS) remains essentially unchanged, the Yield Strength (YS) decreases, and the impact absorption energy significantly improves. For double annealing heat treatment at two-phase region, temperature increase at the first-stage annealing enlarges the width and decreases the aspect ratio of the primary α phase. Leading to the decrease of the UTS & YS and increase of the impact absorption energy, with a conversely tendency at 1000 °C. The increase in the second-stage annealing temperature raises the size and volume fraction of the secondary α phase, causing the alloy's UTS and YS to initially rise then fall, with a slight increase in impact absorption energy. The anisotropy in the mechanical properties of DEDed Ti-6321 alloy mainly addressed from the different distribution of α phase orientations at different loading directions, and can be eliminated through sufficient β single-phase zone annealing.

The effect of annealing on the microstructure and wear performance of laser-clad high-entropy alloy composite coatings for monorail crane braking systems

Laser cladding was utilized to fabricate WC ceramic particle-reinforced CoCrFeMnNi high-entropy alloy (HEA) composite coatings, with an investigation into the influence of annealing heat treatment on the microstructure and wear behavior of the composite coatings. The HEA composite coatings with a WC particle content of 30 wt% primarily consist of a face-centered cubic (FCC) solid solution phase, various M6C carbides with blocky, fishbone, and dendritic morphologies, and incompletely melted WC ceramic particles. The microstructure of the composite coatings remains stable up to a temperature of 570°C. After annealing at 600°C, the microstructure transforms into a typical dendritic morphology with rod-like carbides precipitating from the solid solution and discontinuously distributed in the interdendritic regions. Due to the annealing softening effect, the microhardness of the coating decreases from 488.1 HV0.3 to 443.1 HV0.3. Following annealing at a high temperature of 800°C, recrystallization leads to a refined equiaxed grain microstructure, with precipitated carbides continuously distributed along the grain boundaries, forming a network. The combined effects of precipitation hardening and fine grain strengthening result in an increase in the microhardness of the coating to 568.6 HV0.3 after annealing at 800°C. As the annealing temperature increases, the wear rate of the WC particle-reinforced CoCrFeMnNi HEA composite coatings also increase. The wear mechanism for the unannealed coating is oxidative wear, and the reduction in hardness leads to adhesive phenomena in the coating after annealing at 600°C. The network of carbides reduces the ductility of the HEA and also the toughness of the oxide film, resulting in the highest wear rate for the coating annealed at 800°C, reaching 38.636×10−6 mm3/(N·m). This study provides valuable insights for the fabrication of advanced wear-resistant coatings.

The effect of differing Y concentrations on the evolution of the structure and mechanical properties of FeCrAl alloy

The influence of different Y concentrations on the evolution of the structural and mechanical properties of FeCrAl alloys is investigated in this work. The ingot casting process was used to produce alloys with Y mass fractions of 0%, 0.03%, and 0.25%, respectively. They were then annealed for 15 min at 850°C, 950°C, and 1050°C before being quenched by water to room temperature. Microstructure and mechanical properties were analyzed using OM, EPMA, EBSD, and tensile tests. The addition of 0.03% Y to FeCrAl alloy and annealing at 850°C resulted in the greatest overall performance of the alloy. This had a tensile strength of 635.62 MPa, yield strength of 465.48 MPa, and elongation of 27.04%. With an increase in Y concentration or annealing temperature, the tensile, yield, and elongation properties decrease. This phenomenon can be attributed to the incorporation of Y, which creates a fine Y-rich second phase in the alloy. These phases act as heterogeneous nuclei, pinning the grains during solidification, effectively reducing grain growth and refining the grains. Grain refinement and an increase in the number of grain boundaries hinder dislocation movement, thereby enhancing the alloy's tensile and yield strength. Simultaneously, this prevents the disappearance of α-fiber textures and the creation of γ-fiber textures during recrystallization and reduces the strength of the γ-fiber textures in the alloy microstructure. However, as the annealing temperature increases, microstructure grain growth and the number of grain boundaries decrease. Moreover, higher Y concentrations result in the formation of large, striated Fe-Y phases, which impair the forming properties of the alloy and consequently reduce its tensile properties. Therefore, future research should focus on effectively avoiding the formation of coarse second phases in the microstructure of FeCrAl alloy to enhance its overall performance.

Effect of intermediate annealing temperature and cold rolling deformation on the texture of yttrium bearing oriented silicon steel

The cold rolling and intermediate annealing process, along with the incorporation of rare earth elements, play an important role in the microstructure, texture, and inhibitors of oriented silicon steel. Currently, there is limited research on the impact of rare earth yttrium on texture evolution during the cold rolling and intermediate annealing processes. Therefore, the effects of different cold rolling deformations and intermediate annealing temperatures on the microstructure and texture of Y bearing oriented silicon steel have been studied. The experimental results demonstrate that the average grain size of the intermediate annealed plate progressively decreases with increasing the cold rolling deformation. This is because the high cold rolling deformation brings more additional dislocations and distortions, consequently enhancing the driving force for recrystallization. Observing the microstructure with various cold rolling deformation, the results show that the annealed plate with a 72 % reduction rate exhibited the highest Goss texture percentage of 4.83 %. This is because the cold-rolled sheet with a reduction rate of 72 % exhibits an abundance of Goss oriented substructures. These substructures quickly dominate the {111}<112> deformed matrix during the initial recrystallization, and promote grains nucleation and growth. As the annealing temperature increases, the driving force for the growth of recrystallized grains also increases, leading to a gradual increase in grain size. The plate annealed at 940 °C exhibits the highest percentage (4.83 %) of Goss texture. The addition of rare earth Y can lead to an increase in grain size in the intermediate annealed plate and facilitate the formation of {411}<148> texture. This is advantageous for the abnormal growth of Goss texture. The results demonstrate that a cold rolling deformation rate of 72 % and an intermediate annealing temperature of 940 °C are good for promoting abnormal growth of Goss orientation. The study results on precipitation kinetics suggests that the grain boundary nucleation of AlN and dislocation nucleation of MnS are the most effective way of nucleation. The precipitates in oriented silicon steel without Y are Al2O3 and MnS, while those in the samples with Y are AlN, YS, and YOxSy. The addition of rare earth Y leads to a reduction in both the density and size of precipitates. Moreover, With the increase of annealing temperature, the size of precipitates decreases and the amount of precipitates increases. Additionally, the addition of Y makes the steel more clean, meanwhile, the pinning effect of inclusions on grain boundaries is weakened. Therefore, the grain size of the steel with Y is larger.

Achieving a superior combination of strength and ductility by adjusting heterogeneous structure in a Fe–Mn–Al–Mo–C lightweight steel

A combination of high strength and good ductility was achieved by adjusting heterogeneous structure through varying annealing temperatures ranging from 750 to 900 °C after cold rolling in a Fe–Mn–Al–Mo–C lightweight steel. The microstructure consists of heterogeneous recrystallized, unrecrystallized grains containing nanoscale Mo2C precipitates, and intergranular Mo-enriched carbides. As annealing temperature increases, the fraction of recrystallization, and the average Schmid factor increase, while the average grain sizes and the volume fraction of Mo2C decrease. Annealing at 825 °C forms a desirable heterogeneous structure characterized by a normal bimodal grain distribution and diffuse precipitation of intragranular Mo2C particles. Tensile test results indicated that higher annealing temperatures decrease strength but enhance ductility. However, the yield strength of the 825 °C annealed sample only slightly decreases compared to the 800 °C annealed sample owing to the synergistic contributions of various strengthening mechanisms, including grain boundary, solid solution, precipitation, and heterogeneous deformation-induced strengthening. Furthermore, its ductility significantly improves, approaching that of the 850 °C annealed sample, facilitated by sustained heterogeneous deformation-induced strengthening effects and significant refinement in grain structure. The high strain hardening rate of the C825 sample is attributed to dynamic slip band refinement and local stress adjustments during later deformation stages. The heterogeneous grain structure induces a strong HDI strengthening effect due to uneven deformation, which also contributes to the high strain hardening rate. These findings highlight the potential of Fe–26Mn–8Al-1.2C–3Mo lightweight steel for applications requiring a balance of strength and ductility.

Influence of annealing on the interfacial structure, recrystallization behaviour, and texture evolution of hot extruded Mg/Al laminated composites

The hot extrusion process is ideal for Mg/Al laminated materials; however, there is limited research on annealing for hot extruded Mg/Al laminated composites. In this study, Mg/Al composite tubes were prepared using the direct extrusion-shear deformation (DESD) process. The morphology of the Mg/Al interface at different annealing temperatures was investigated using scanning electron microscopy (SEM). As the annealing temperature increases, the bonding layer thickens, and the number of intermetallic compounds (IMCs) increases. Most of the IMCs tend to grow in a columnar manner perpendicular to the interface bonding layer. The β-Al3Mg2 layer is notably thicker than the γ-Al12Mg17 layer, attributable to the lower diffusion activation energy of β-Al3Mg2. The microstructure and texture evolution of the interfacial region were analyzed using backscattered electron diffraction (EBSD). The results show that the local average misorientation (LAM) within the Al layer is higher than that within the Mg layer, suggesting that the Al layer undergoes more significant plastic deformation and accumulates more strain energy than the Mg layer. The static recrystallization (SRX) fraction of the Mg layer is higher than that of the Al layer. However, The SRX proportion of Mg decreases with increasing annealing temperature due to secondary recrystallization. The annealing temperature significantly affects the grain orientation. As the annealing temperature increases, the deformation texture (S, Brass) of the Al layer gradually transitions to the recrystallization texture (Cube) and finally forms {123}<102> texture.

Investigation of the impact of non-magnetic Si element addition and heat treatment on the electromagnetic wave absorption properties of medium entropy FeCoNiSi alloy particles

Based on chemical liquid phase reduction and high temperature annealing, the effects of non-magnetic Si element addition and heat treatment regime on the microstructure, magnetic properties, and electromagnetic wave absorption properties of medium entropy alloy particles FeCoNiSi were studied. The results show that the prepared Fe1Co0.8Ni1Six alloy particles have a spherical structure, and with the increase of Si content, the particle size continuously decreases, with the average particle size decreasing from 150 to 200 nm to 20-50 nm. After high temperature annealing, the alloy particles undergo some agglomeration and growth. The as-prepared Fe1Co0.8Ni1Six alloy particles exhibit an amorphous state, and crystallization occurs during high temperature annealing, but the increase in Si element content has a certain inhibitory effect on the crystallization of the alloy particles. With the increase of Si element content and annealing temperature, the specific saturation magnetization intensity of the material shows a decreasing trend, while the residual magnetism and coercivity show an increasing trend. With the increase of Si element content, the real and imaginary parts of the permeability change alternately in different frequency ranges. The magnetic loss mechanism for the three alloy particles was eddy current loss in the frequency ranges of 10-14GHz and 16.5-18GHz. With the increase of Si element content, the magnetic loss shows an increasing trend, and the impedance matching shows a decreasing trend. The Fe1Co0.8Ni1Si0.5 alloy particle sample has the maximum reflection loss |RLmax| of 28.2 dB at thickness of 2.3 mm, and the Fe1Co0.8Ni1Si0.7 alloy particle sample has an effective absorption bandwidth of 1.7GHz at thickness of 1.9 mm. Eddy current loss was the main magnetic loss mechanism for Fe1Co0.8Ni1Si0.6 alloy particles under 400 °C and 600 °C annealing conditions, and for Fe1Co0.8Ni1Si0.7 alloy particles under 600 °C annealing conditions. With the increase of annealing temperature, the fluctuation of dielectric loss with frequency decreases in the low frequency range, and increases in the high frequency range, while annealing reduces the fluctuation of magnetic loss with frequency. Under 400 °C annealing conditions, the attenuation constant of the three alloy particles was lower than that of the unannealed alloy particles, and under 600 °C annealing conditions, the attenuation constant of Fe1Co0.8Ni1Si0.5 alloy particles in the frequency range of 6-15GHz was higher than that of unannealed and 400 °C annealed alloy particles, and that of Fe1Co0.8Ni1Si0.6 alloy particles in the frequency range of 7-14GHz was higher than that of unannealed and 400 °C annealed alloy particles. High temperature annealing was not able to effectively improve the impedance matching performance of Fe1Co0.8Ni1Six alloy particles. The maximum reflection loss |RLmax| of Fe1Co0.8Ni1Si0.6 alloy particles under 600 °C annealing conditions was 37.8 dB.

Effect of annealing temperature on interfacial microstructure and tensile fracture behavior of titanium-steel clad plate

To ensure that the rolled composite plate has excellent processing properties. Annealing is an effective means of modulating organization and mechanical properties. In this study, annealing treatments at different temperatures were applied to the rolled titanium-steel clad plate. The evolution of the interfacial organization was observed using scanning electron microscopy. The strain distribution of the composite plate in the tensile process was investigated using a tensile experiment combined with the DIC method. The results indicate the presence of compounds such as TiC, Fe2Ti, and FeTi after hot rolling. As the annealing temperature increases, the thickness of the interlayer diffusion of elements between the two plates increases. The geometric dislocation generated between the grains after hot rolling is significantly improved after annealing treatment, and the geometric dislocation density decreases with the increase in annealing temperature. In the titanium layer, the titanium grains, after annealing at 550 °C and 600 °C, are in the recovery stage, and the amount of recrystallization does not change significantly. However, after annealing at 650 °C, the titanium grains are completely recrystallized, the grains are equiaxed, and the grain-to-grain anisotropy is eliminated. The sample annealed at 550 °C fractures almost simultaneously in the tensile test in the titanium layer and steel layer, with an elongation of 32.3% and a tensile strength of 477.1 MPa, showing the best comprehensive performance. Based on DIC strain curve analysis, The strain curve after annealing at 550 °C is smoother, the necking is relatively consistent, and it reaches a point of relatively consistent local strain instability.

Annealing temperature induced micro-structural, opto-electronic, electrical and fluorescence properties of the sol–gel synthesized CdO nanoparticles through the analytical study of vacancy-type defects

Cadmium oxide (CdO) nanoparticles (NPs) have been synthesized through the simple sol–gel route using cadmium nitrate tetrahydrate and aqueous ammonium hydroxide as precursors. Synthesised products were annealed at different temperatures in the range of 250 °C–500 °C. The annealed samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Selected area electron diffraction (SAED), Field emission scanning electron microscopy (FESEM), UV–visible absorption (UV–Vis), room temperature Fluorescence (FL) measurements, Positron annihilation lifetime spectroscopic measurements (PALS) and resistivity measurements. Through the utilization of XRD method, it was shown that the particle size varies from 15 nm to 35 nm and unit cell volume exhibit an increase, while the lattice strain decreases as the annealing temperature is raised. The interplanar distance reduces as temperature increases, and the presence of defects can explain the minimal fluctuation in lattice characteristics. There is an inverse relationship between lattice strain and dislocation density of the pristine CdO NPs. The Williamson-Hall (W-H) analysis demonstrated a decrease in compressive lattice strain as particle sizes increased. The TEM and FESEM techniques were used to analyze the nearlyspherical morphological characteristics of CdO NPs, and thesize-related XRD results were further supported by the histogram plots from TEM. UV–Vis spectroscopy revealed that the band gap energy drops from 4.02 eV to 3.33 eV as the particle size increases, which may be attributed to the quantum confinement effect and the presence of defect states in the energy band gap. The distinct emission peaks of CdO NPs are detected in the fluorescence spectra at the wavelengths 488 nm, 529 nm and 584 nm. These findings indicate a modest correlation between the emission bands and the energy band gap. The strength of the emission peaks has been amplified as the annealing temperature increases, indicating a higher concentration of oxygen vacancies with increase in annealing temperatures. PALS shows the concentration of vacancy-clusters are reduced with the increase in temperature, which justifies the decrease in resistivity (from ∼ 1 × 102 to 2 × 10−2 Ω cm) with rise in annealing temperature as measured by the standard four-probe method. These characteristics of the NPs can be utilized in various optoelectronic and energy storage applications.

Effect and mechanism of hydrogen annealing temperature on the HER performance of RuO2-based catalysts in acid media

Annealing as an experimental means is often used to treat various electrocatalysts for improving their hydrogen evolution reaction (HER) performance. Herein, in order to investigate the effect of hydrogen annealing temperature on the HER performance of RuO2-based electrocatalysts, commercial RuO2, self-synthesized RuO2, and self-synthesized RuO2/MoO3 composite are annealed at 150, 300, 500, and 700 °C in a hydrogen atmosphere, respectively. It's found that RuO2 is gradually deduced at 150 °C, ultimately, completely reduced to Ru under 300 °C. Meanwhile, the content of RuO2 at the samples surface is gradually decreases as the annealing temperature increase to 700 °C. However, for all samples, the 500 °C annealed sample shows the best HER performance in acid solutions, including the lowest over potential, the smallest Tafel slope, and the largest double-layer capacitance. We inferred that the optimal HER performance of the 500 °C annealed samples maybe attributed to their appropriate Ru/RuO2 ratio. Density functional theory (DFT) calculations reveal that significant electron transfer across the Ru/RuO2 interface, thereby optimizing the adsorption free energy of H on Ru and RuO2, ultimately resulting in Ru/RuO2 catalyst exhibiting better HER activity than bare Ru and RuO2. The study provides guidance on the preparation of RuO2-based electrocatalysts for achieving efficient hydrogen evolution.

Atomic-Resolution Interfacial Reaction Mechanism between Bi2Te3-Based Alloys and Ni Electrodes.

Interdiffusion and solid-solid phase reaction at the interface between thermoelectric (TE) materials and the electrode critically influence interfacial transport properties and the overall energy conversion efficiency during service. Here, the microstructural evolution and diffusion mechanisms at the interfaces between the most widely used Bi2Te3-based TE materials, n-type Bi2Te2.7Se0.3 (BTS) and p-type Bi0.5Sb1.5Te3 (BST), and Ni electrodes were investigated at atomic resolution using spherical aberration-corrected scanning transmission electron microscopy (STEM). The BTS(0001)/Ni and BST(0001)/Ni interfaces were constructed by depositing Ni nanoparticles on mechanically exfoliated BTS and BST bulk materials and subsequent annealing. The interfacial reaction is initially dominated by Ni diffusion into the TE matrix to form NiAs-type NiM intermetallics, while Ni trans-quintuple-layer diffusion only occurs in Sb-rich BST. The Bi-rich BTS is more influenced by the Ni-Te preferential reaction, resulting in NiM abnormal grain growth and the formation of tilted and rotated interfaces. Bi diffusion into the BTS matrix forms a Bi double layer at the interface or Bi2[Bi2(Te,Se)3] as the annealing temperature increases, while Bi diffusion into the Ni thin film greatly accelerates the interfacial reaction rate, as elucidated by in situ heating STEM. The results provide essential structural details to understand and prevent the degradation of TE device performance.

Metal-organic decomposed lanthanum cerium oxide thin films: A study of chemical and surface properties

Lanthanum cerium oxide thin films have been deposited on n-type (100) silicon wafers using the spin coating technique. The post-deposition annealing was performed over spin-coated films. The compositional studies were conducted by performing Fourier transform infrared spectroscopy, Energy dispersive X-ray spectroscopy, and X-ray diffraction. Ellipsometry was used to determine the thickness and atomic force microscopy was performed to understand the surface morphology of the deposited thin films. The effect of rapid thermal annealing at different temperatures over the structural and chemical properties of the LaCeO2 thin films was observed. The FTIR spectra show the formation of silicates at the interface of the oxide and semiconductor, while XRD results show that the films become crystalline with increased annealing temperature. The refractive index was observed to be reduced with an increase in the annealing temperature and a minor reduction in the physical thickness as per the sample standard deviation of 0.2981[Formula: see text]nm.

The role of annealing in optimizing the electrical, linear, and nonlinear optical properties ZIf-8@TiO2 films for possible use in photonic and optoelectronic devices

Here, we fabricate zeolitic imidazolate framework-8 (ZIF-8)–doped 5 wt% nanosized TiO2 (ZIf-8@TiO2) thin films using a vapor coating unit. The effects of annealing up to 473 K on the physical characteristics of fabricated ZIf-8@TiO2 thin films were studied. XRD, FTIR, and UV–vis spectroscopy were utilized to investigate the structural properties of the as-deposited and annealed samples. An increase of approximately 18% was observed in the electrical conductivity. As the annealing temperature increased, the light transmission decreased. This could be due to the growth or aggregation of TiO2 particles during annealing. Raising the annealing temperature by 100 K enhanced the refractive index (n) and energy gap (Eg) by approximately 33% and 8%, respectively. The decrease in ε 1 and ε 2 in response to the annealing temperature increase was due to the evaporation of MOF organic linkers. The nonlinear optical results indicated a dependence on the annealing temperatures that improved charge carrier mobility and coherent light–matter interactions. Our thesis findings can improve the overall performance and efficiency of optoelectronic devices.

Superior mechanical properties of additively manufactured FV520B matrix composites by microstructure tailoring

The additively manufactured martensitic stainless steel (SS) parts often manifest the strength-ductility trade-off dilemma, which severely limits their practicality. In this study, the TiC-reinforced FV520B metal matrix composites (MMCs) were deposited via laser powder bed fusion (LPBF), and the as-built MMCs exhibited a superior strength-ductility synergy (ultimate tensile strength of 1,389±29 MPa, and fracture elongation of 30.1±0.6 %) when compared to their matrix alloy. This strength-ductility synergy can be attributed to a high-density of well-dispersed TiC nanoparticles, in-situ grain boundary engineering induced by TiC particles, fully austenite structure, and progressive transformation-induced plasticity effect. Furthermore, the microstructure, and mechanical properties of the MMCs annealed at 400–700 °C were compared. As the annealing temperature increases, the matrix progressively transforms from a fully austenite structure to a fully martensite structure, enabling substantial enhancements in tensile strength and work hardening capabilities. Notably, a high number density of the Cu-rich precipitates (CRPs) can be observed in the high-temperature annealed specimen, which can yield considerable strengthening through the Orowan looping mechanism. This work paves a pathway to fabricate structural materials with unique microstructures and excellent mechanical properties for practical engineering applications.

Effect of annealing temperature on the evolution of microstructure, texture, and mechanical properties of hot-rolled 12Cr-ODS steel

To achieve high thermal efficiency, today's nuclear reactor structures are exposed to higher temperatures and pressures, which requires the use of high-strength steels with specific properties, such as ODS steels. There is a need to clarify the evolution of the microstructure and properties of steels at elevated temperatures. This study systematically investigates the evolution of microstructure, texture, and mechanical property variations of 12Cr-ODS steels after hot-rolling and subsequent annealing at 1000 °C and 1200 °C. The investigation utilizes optical microscopy, electron backscatter diffraction technique, and mechanical property measurements. The microstructure of hot-rolled samples shows a layered alternating distribution, which is distinguished by a notable presence of the α-fiber texture. Following annealing at 1000 °C, the martensite grains are smaller with a reduced hardness, while maintaining a strong α-fiber texture. After annealing at 1200 °C, there is a rapid increase in the growth of martensite grains, a significant rise in hardness, a reduction in the α-fiber texture characteristics, and an improvement in the γ-fiber texture characteristics. Moreover, the maximum intensity of the α-fiber texture diminishes as the annealing temperature increases. The mechanical properties of the samples deteriorated after annealing at 1200 °C, which can be attributed to the coarse martensite grains and the texture components containing the {001} cleavage plane dominating the occurrence of brittle cleavage fracture. The 0.1Y sample after annealing at 1000 °C exhibits an excellent combination of strength (1458 MPa) and ductility (20.3%), which is owing to the unique heterogeneous grain structure and the evolution of favorable texture.

Synthesis, negative thermal expansion and optical performances of In0.5Sc1.5Mo3O12 thin films via sol-gel spin coating

Orthorhombic In0.5Sc1.5Mo3O12 thin films have been synthesized using the sol-gel spin coating. Influences of post-annealing temperatures on crystal structure, morphology, negative thermal expansion (NTE) and optical performances of the thin films were studied using XRD, SEM, XPS, high-temperature XRD and UV–Vis–NIR spectrophotometer. XRD and SEM results show that as-prepared thin film is in an amorphous state with a smooth and dense surface. Orthorhombic In0.5Sc1.5Mo3O12 thin films were obtained after post-annealing in 550–750 °C. The higher the annealing temperature in 550–750 °C, the better the crystallinity of orthorhombic In0.5Sc1.5Mo3O12 thin films. In addition, the grain size of the In0.5Sc1.5Mo3O12 thin film also grows as the annealing temperature increases. The resulting orthorhombic In0.5Sc1.5Mo3O12 thin films exhibit anisotropic NTE. Its volumetric coefficient of thermal expansion (CTE) is −3.44 × 10−6 °C−1, while the CTEs in a-, b- and c-axis directions are −4.70 × 10−6 °C−1, 5.37 × 10−6 °C−1, and -4.10 × 10−6 °C−1 in 25–700 °C, respectively. In addition, the transmittance of orthorhombic In0.5Sc1.5Mo3O12 thin films post-annealed at 750 °C is around 87.75 %–95.03 %.

Effect of high temperature annealing on microstructure and mechanical properties of Morlion735 alumina fiber

Continuous alumina fiber-reinforced alumina (Al2O3/Al2O3) composite is a very promising candidate for thermal structural materials in aerospace vehicles and other applications. Alumina fibers used in Al2O3/Al2O3 composites play a crucial role in enhancing their mechanical properties and thermostability. In this article, the effect of annealing on the tensile strength and microstructure of Morlion735 alumina fiber was investigated. The results showed that the phase transformation occurs at 1147 °C, resulting in a mullite phase with an orthogonal lattice structure. As the annealing temperature increases, the crystal domain size of the mullite gradually increases. Both the phase transformation and the increasing crystal domain size lead to more lattice defects, which significantly affect the tensile strength and tensile modulus of alumina fibers. A 0.67 GPa reduction in tensile strength (from 1.14 GPa to 0.47 GPa) was observed when the annealing temperature increased from 1200 °C to 1400 °C. Weibull statistical analysis revealed that as the annealing temperature increased, the tensile strength dispersion of Morlion735 fiber also increased. This can be attributed to the volume-dependent flaw distributions. These results provide an in-depth understanding of the tensile strength evolution mechanism under high temperatures.