Low-temperature Annealing Research Articles

Low-temperature β-relaxation promotes crystallization in oxide glasses

Primary (α) structural relaxation is known to influence the nucleation behavior in glasses and it has recently been proposed to account for the so-called classical nucleation theory “breakdown” in oxide glasses around the glass transition temperature. However, it is unclear whether secondary (β-) relaxation, predominant at lower temperatures, also plays a role in promoting crystallization. Here, we study the correlation between crystallization kinetics and β-relaxation of three types of oxide glasses with distinct chemical bonds by subjecting the glasses to low-temperature annealing. We find that the activation energy of crystallization (Ea) exhibits an exponential decay with increasing annealing duration for all studied glasses. Such a decrease in Ea is found to be associated with the structural rearrangements in the glasses, especially showing a negative correlation with the enhanced atomistic interplays around modifying cations. Our findings thus point to a universal linkage between β-relaxation and nucleation kinetics in oxide network glasses.

Effect of Annealing Temperature on Microstructure and Properties of Solid Solution Extruded Mg–2.0Zn–1.0Y–0.5Zr Alloys

In this investigation, the effects of different annealing temperatures (180, 200, 220, 240, 260, and 280 °C) on the microstructure evolution and properties of an extruded Mg–2.0Zn–1.0Y–0.5Zr (wt%) magnesium alloys were determined. Optical microscopy (OM), scanning electron microscopy (SEM), immersion corrosion, electrochemical corrosion experiments, and tensile testing were performed. Research has found that combining hot extrusion with subsequent low-temperature annealing significantly improves the strength, plasticity, and corrosion resistance of alloys due to grain refinement and a reduced dislocation density. The alloy was completely recrystallized at an annealing temperature of 240 °C for 4 h after solid solution extrusion, and the grains were fine and uniform, demonstrating the best comprehensive properties. Its corrosion rate, ultimate tensile strength, yield strength, and elongation were 0.454 ± 0.023 mm/y, 346.7 ± 8.9 MPa, 292.4 ± 6.9 MPa, and 19.0 ± 0.4%, respectively. The corrosion mechanism of the specimens under extruded and annealed conditions was analyzed. After annealing at 240 °C for 4 h, the dislocation and bimodal grain structure of the samples were almost eliminated, resulting in uniform and fine grains, which were conducive to the formation of a more uniform and denser oxide film, thus improving the corrosion resistance of the alloy.

Nanoparticle stressor-induced single-photon sources in monolayer WS2 emitting into a narrowband visible spectral range

A van der Waals heterostructure containing an atomically thin monolayer (ML) transition-metal dichalcogenide as a single-photon emitting layer is emerging as an intriguing solid-state quantum-photonic platform. Here, we report the utilization of spin-coating of silica nanoparticles for semi-deterministically creating the spectrally isolated, energetically stable, and narrow-linewidth single-photon emitters in ML-WS2. We also demonstrate that long-duration low-temperature annealing of the photonic heterostructure in the vacuum removes the energetically unstable emitters that are present due to fabrication-associated residue and lead to the emission of single-photons in a < 25 nm narrowband visible spectral range centered at ~620 nm. This work may pave the way toward realizing a hybrid-quantum-photonic platform containing a van der Waals heterostructure/device and an atomic-vapor system emitting/absorbing in the same visible spectral range.

Modificated microstructure and enhanced mechanical properties of Cu-Sn-P alloy with rare earth La addition

Rare earths are often added to copper alloys as trace alloying elements to modify the structure and improve related properties. In this study, the Cu-7.8Sn-0.16 P and Cu-7.8Sn-0.16 P-0.15La alloy strips were fabricated through full-chain process of vacuum casting, cold rolling, intermediate annealing, cold rolling and low temperature annealing process. Then, the distinctive microstructure features and mechanical properties of Cu-7.8Sn-0.16 P and Cu-7.8Sn-0.16 P-0.15La alloys were comprehensively analyzed in special view of rare earth affected phase types and property evolution. The results indicate that the addition 0.15 wt% La has effectively refined the dendrite segregation and dispersed the microporosity. Specifically, La combines with P and form a stable and dispersed micron sized LaP2 intermetallic compound, which replaces the low melting point (α+δ+Cu3P) ternary phase in the La-free alloy. Furthermore, a new nanoscale La(Cu2P)2 precipitated phase is characterized in the Cu-7.8Sn-0.16 P-0.15La alloy during low-temperature annealing process. As well, the tensile strength of Cu-7.8Sn-0.16 P-0.15La strips display notable increase to 915 MPa from 834 MPa of Cu-7.8Sn-0.16 P after low-temperature annealing. Such increase in tensile strength is attributed to the formation of La-containing phase of varied sizes in the Cu-7.8Sn-0.16 P-0.15La alloy, where the nano scale La(Cu2P)2 precipitated phase makes the most significant contribution.

Comprehensive investigation of thermal induced reorganization of porous-germanium structures

Porous germanium (PGe) substrates have recently attracted significant attention for the development of lightweight and flexible solar cells and optoelectronic devices. A reliable approach for releasing epitaxial layers based on Germanium and reusing the substrate involves utilizing a bilayer structure of PGe. The growth of such detachable devices holds great potential for integration onto the Si platform. The used structure of PGe is made of a low-porosity layer serving as epitaxial seed on top of high-porosity one used as a weak separation layer. In this work, we investigate the impact of thermal annealing on the PGe morphology for deeper understanding of the mechanisms involved in the formation of the epitaxial seed layer and the voided weak layer underneath. Indeed, thermal-induced reconstruction has been investigated at various annealing temperatures and times for PGe layers with differing porosity levels, encompassing low, high, and gradual porosity profiles. Our findings reveal the formation of a modified substrate at low annealing temperatures, resulting in a suspended membrane on top of the fragile separation layer, rendering it suitable for detachment and subsequent substrate reuse.

Effect of post-annealing on magnetic anisotropy in La–Co co-substituted M-type strontium ferrite

We investigated the effect of post-annealing on the magnetic anisotropy in La–Co co-substituted magnetoplubite-type strontium ferrite, a matrix phase of commercial high-performance ferrite magnets. Post-annealing was found to be effective in controlling the distribution of substituted Co2+. The Co2+ distribution obtained by lower-temperature annealing shows higher magnetic anisotropy, suggesting that uniaxial magnetic anisotropy is enhanced only when Co2+ occupies the most stable occupied site, i.e., the 4f1 site in the tetrahedral coordination. Furthermore, the slower the cooling rate, the higher the anisotropy. The temperature-dependent Co2+ distribution predicted from the reported density functional theory calculations was compared with the actual anisotropy after annealing, yielding +2.3 meV/ion as the Co2+ anisotropy constant at the tetrahedrally coordinated site and −1.2 meV/ion as that at the octahedrally coordinated sites. Careful selection of heat treatment conditions leads to efficient use of cobalt, an element with supply risks.

Low temperature crystallization of atomic-layer-deposited SrTiO3 films with an extremely low equivalent oxide thickness of sub-0.4 nm

Despite SrTiO3(STO) possessing a high dielectric constant, its application as a capacitor dielectric in dynamic random-access memory(DRAM) capacitors faces challenges due to the high-temperature annealing for crystallization, its compositional inhomogeneity, and the high leakage currents of STO films. To address these issues, we employ atomic layer deposition(ALD) of STO films onto Pt substrates at elevated temperatures(340–380 °C). The use of low-reactivity Pt electrodes effectively mitigates the initial growth of excess Sr, ensuring enhanced compositional uniformity along the film growth direction. Coupled with ALD at high temperatures, this approach facilitates the crystallization of STO films in the as-grown state, further enhancing the crystallinity with increasing film thickness. Subsequent low-temperature post-deposition annealing (PDA) at 400 and 500 °C achieves full crystallization. This process results in a remarkable increase in the dielectric constant, reaching approximately 150. Furthermore, the absence of microcracks after PDA, attributed to the formation of adequately dense films, contributes to substantially improved dielectric properties. Consequently, these STO films exhibit an exceptionally low equivalent oxide thickness of 0.34 nm coupled with an ultralow leakage current of 3.7 × 10−8 A/cm2 at an operation voltage of 0.8 V, promising for advancing DRAM capacitors. This study presents a pathway for the sustainable scaling of DRAMs, addressing challenges in ALD-grown STO films.

Atomic-level investigation of structure and formation process of Y3Al5O12 with super-high content of Ce emitting anomalous orange-red emissions

Ce-doped yttrium aluminum garnet (YAG:Ce, Y3Al5O12:Ce) is the most commonly used yellow phosphor in white light-emitting diodes. Recently, we found that (Y1–xCex)3Al5O12:Ce with a super-high content of Ce (x = 0.11–0.21) can be prepared by a polymerized complex method and exhibits anomalous orange–red emission. To understand the nature of this anomalous behavior from the atomic level, we applied high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM-EDS), a state-of-the-art technique that enables analysis of the atomic-level elemental distributions of Al, Y, and Ce. STEM-EDS images on the atomic level were successfully obtained for YAG:Ce. It was found that Ce in Y site has spatially uneven for few nanometers. Ce–K edge extended X-ray absorption fine structure (EXAFS) analysis was also conducted, which revealed a high level of asymmetry around Ce. By combining the STEM-EDS and EXAFS results, a dynamic model for the red emission was proposed. STEM-EDS also revealed that CeO2 nanocrystals were firstly formed with low-temperature annealing and that the reaction of Y with the CeO2 nanocrystals subsequently yielded YAG:Ce, unlike in the conventional one-step high-temperature synthesis.

In-situ construction of bioactive nanostructures on Ti alloy surfaces through ultra-low concentration alkali treatment and low-temperature annealing

Osseointegration is crucial for the long-term stability of orthopedic implants. Nanosurfacing can impart osteoinductivity to the implant. However, the application potential of most available nanotechnologies in surface modification of implants is limited, and there is an urgent need to develop new effective nanosurfacing techniques with greater practicality. In this study, we for the first time, utilized an ultra-low concentration NaOH solution (0.55 mM) combined with low-temperature annealing to achieve solid-state dewetting (SSD) on Ti alloy surfaces, resulting in well-defined TiO2 nanoisland-like crystals. In vitro cell experiments demonstrated that the constructed nanostructures significantly affected the adhesion, proliferation, and osteogenic differentiation capability of MC3T3-E1 cells. The nanostructures formed at 550 °C exhibited the most pronounced enhancement of cell osteogenic differentiation capability. This method is simple, easy to operate, and scalable, holding significant application potential in the surface modification of Ti alloys.

Hydrogen embrittlement susceptibility of AISI 4140 alloy-steel under cathodic protection and in H2S and CO2 environment

The susceptibility to hydrogen embrittlement (HE) of AISI 4140 steel when subjected to environments such as those found in offshore oil and gas fields is investigated. Hydrogen charging was carried out for 15 days using two different hydrogen sources, cathodic protection (CP) and corrosion in a saline solution containing high concentrations of H2S and CO2 (SC-sour corrosion). The steel specimens were austenitized at 850 °C, oil-quenched at ambient temperature, followed by tempering for 18 min at 350, 450, and 600 °C. The effect of tempering temperatures on hydrogen embrittlement susceptibility was also investigated. Tensile strength testing, scanning electron microscopy (SEM), and fractography analysis were used to correlate the HE with microstructural and environmental conditions. The results revealed that both hydrogen charging conditions increased the steel hardness and decreased ductility, with this effect being more pronounced at lower tempering temperatures and SC-hydrogen charging. Fracture surfaces of the steel tempered at 600 °C with hydrogen charged exhibited predominantly ductile behavior with the presence of dimples, while at 350 and 450 °C surface fractures showed cleavage facets as a consequence of brittle behavior. In general, the AISI 4140 steel hydrogen embrittlement index (%EI) was higher for hydrogen charging induced by SC compared to CP.

Effect of Annealing on the Microstructure, Texture, and Properties of Cold-Rolled Ti50Ni47Fe3 Shape Memory Alloy Sheets

A systematic study was conducted on the impact of annealing treatments on the microstructure and properties of cold-rolled Ti50Ni47Fe3 alloys using optical microscopy, scanning electron microscopy, electron backscattered diffraction, and an electronic universal testing machine. It was found that, during low-temperature annealing (400 °C and 500 °C), the annealing time had no significant effect on the microstructure or properties of the Ti50Ni47Fe3 alloy. Only elongation (δ) increased with the increase in the annealing time, and the grain orientation of the Ti50Ni47Fe3 alloy was &lt;111&gt;//RD (rolling direction). When annealing at medium–high temperature (600 °C), as the annealing time increased, recrystallization and grain growth processes occurred, resulting in a continuous decrease in strength and an increase in δ. Meanwhile, it was found that the grain orientation of the cold-rolled Ti50Ni47Fe3 alloy changed from &lt;111&gt;//RD during the recovery and recrystallization processes to &lt;101&gt;//RD after the grain growth process. The orientation distribution function cross-section φ2 = 45° results indicate that the texture was mainly distributed along the γ orientation line (φ1 = 0~90°, Φ = 54.7°, φ2 = 45°). When annealed at 400 °C and 500 °C, the texture of the Ti50Ni47Fe3 alloys was (111)[uvw]. When the annealing treatment was 600 °C for 120 min, a (110)[uvw] texture occurred. Additionally, ductile fracture occurred in all specimens, and the crack origin was located on one side of the fracture surface, with obvious “Y”-shaped propagation. This article studied annealing treatments of cold-rolled Ti50Ni47Fe3 alloys, providing corresponding theoretical guidance for subsequent production applications.

Strengthening Al0.1CoCrFeNi high-entropy alloy via multiaxial cryogenic forging and low temperature annealing

Face-centered cubic (FCC) high-entropy alloys (HEAs) exhibit excellent fracture toughness and fatigue properties at both ambient and cryogenic temperatures. However, the relatively low strength of FCC HEAs at room temperature limits their widespread application. Herein, we present a novel approach to tailoring the microstructure of the Al0.1CoCrFeNi HEA and improving its room temperature tensile strength through multiaxial cryogenic forging (MACF) and low temperature annealing (LTA). After the treatments, the tensile strength increases from 687 MPa for the as-prepared fine-grained HEA to 1487 MPa for the MACF specimens annealed at 673 K for 48 h. Our analysis indicates that the strengthening mechanisms are twofold: the tensile strength increased by about 455 MPa after the MACF treatment, which is due to the synergistic effect of dislocations and nanotwins; after LTA, the tensile strength abnormally increased by about 345 MPa, which can be attributed to stacking faults, hexagonal close-packed, and 9R structures formed by thermal relaxation of nanotwin boundaries.

Effect of annealing temperature on carbide precipitation, microstructure and mechanical properties of Fe-Mn-C- (Cr, Mo, W, Ni, Nb, Ti, V) multi-alloying TWIP steel

The effect of annealing temperature on the microstructure, carbide precipitation and mechanical properties of a cold-rolled multi-alloying TWIP steel were investigated by means of Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) analysis, tensile and impact tests. As the temperature increases from 400 °C to 800 °C, the amount of carbides climbed to the peak at 700 °C and then decreased, having a strong opposite relationship with the impact energy, which was minimum 26 J at 700 °C. The main distribution of carbides underwent a transition from intragranular, intragranular + intergranular to intergranular, and the composition of carbides changed from (Nb, Ti and W) to (Cr, Mo and W). Compared with the cold-rolled sample, Fe21W2C6 precipitated out at low annealing temperature of 400 °C, when the tensile and yield strengths and elongation were all simultaneously improved due to the precipitation recovery annealing. And the 600 °C annealing sample exhibited identical yield and tensile strengths. Subsequently, the yield strengths decreased but the tensile strengths and elongation increased at 650 °C and 700 °C attributed to the interaction of carbide precipitation and recrystallization. The recrystallization started at 650 °C and finished at 750 °C. And Fe3Mo3C was identified at 750 °C.

Interaction between phase transformation and static recrystallization during annealing of rolled TC18 titanium alloy

TC18 titanium alloy was subjected to hot rolling at 840 °C, followed by annealing experiments at 830, 860, and 890 °C for different time lengths. The effects of annealing temperature and time on phase transformation and static recrystallization (SRX) behavior, as well as the interaction between phase transformation and SRX, were studied. The results showed that at the low annealing temperature of 830 °C, the microstructure underwent β → α phase transformation and α grain growth with the increase of annealing time, and the SRX of β phase proceeded through subgrain nucleation mechanism induced by α particles. At the middle annealing temperature (860 °C), the α → β phase transformation occurred before the SRX of β phase, and the SRX of β phase was dominated by the grain boundary (GB) bulge mechanism. Meanwhile, the reduction of α phase content accelerated the SRX rate and grain growth. As the annealing temperature (890 °C) exceeded the β transus temperature, the α phase completely transformed to the β phase, and the SRX of the β phase proceeded with a very fast grain growth rate. In addition, the interaction between phase transformation and SRX affected the distribution of α particles. The large-sized α particles (830 °C) were located at the triple GB junction and hindered the SRX β grain growth, while smaller α particles (860 °C) were bypassed by β GB and dispersed within the SRX β grains.

Utilization of Modified Touchdown qPCR to Enhance Sensitivity and Specificity for Genes with Restricted Expression and Low Optimum Temperature Primers

Abstract Background: Quantitative polymerase chain reaction (qPCR) is one of the most used methods to analyze gene expression. However, if the annealing temperature in the qPCR cycle is lower than 55°C, nonspecific amplification may occur. On the other hand, some sets of primers can only function optimally at the annealing temperature below 55°C. Thus, a protocol allowing both specific amplification and large yield in low annealing temperature is needed. Methods: qPCR on the target ribosomal protein L13a (rpl13a) and natriuretic peptide A (nppa) from samples of zebrafish embryos and larvae was performed in triplicates using three different protocols: routine qPCR, gradient qPCR, and modified touchdown qPCR. The cycle of quantification (Cq) value and melt peak data were compared between the routine or gradient qPCR and the modified touchdown qPCR. Results: For rpl13a that was adequately and specifically amplified by both routine and touchdown qPCR, modified touchdown qPCR decreased the average Cq by 3.68–4.66 (P &lt; 0.05). For nppa, a gene with restricted expression that could only be amplified substantially but nonspecifically at the annealing temperature of 50°C, modified touchdown qPCR increased the amplification specificity by forming only one melt peak during melt curve analysis and yielding a substantial amount of amplicon with the Cq of 22.48–22.51. Conclusions: The modified touchdown qPCR with low final annealing temperature was able to produce specific amplification with better yield and detection sensitivity. This method is especially useful for primer sets with low optimum annealing temperature.

Effect of Low-temperature Annealing on Mechanical Properties of Warm-rolled High Silicon Steel Produced by Twin-roll Strip Casting

Effect of Low-temperature Annealing on Mechanical Properties of Warm-rolled High Silicon Steel Produced by Twin-roll Strip Casting

Fabrication of a Three-Dimensional Microfluidic System from Poly(methyl methacrylate) (PMMA) Using an Intermiscibility Vacuum Bonding Technique.

In this study, the fabrication of microfluidic chips through the bonding of poly (methyl methacrylate) (PMMA) boards featuring designed patterns to create a three-dimensional sandwich structure with embedded microchannels was explored. A key focus was optimization of the interface quality of bonded PMMA pairs by adjusting the solvent, such as such as acetone, alcohol, and their mixture. Annealing was conducted below 50 °C to leverage the advantages of low-temperature bonding. Because of the differences in the chemical reactivity of PMMA toward acetone, alcohol, and their combinations, the resulting defect densities at the bonding interfaces differed significantly under low-temperature annealing conditions. To achieve the optimal sealing integrity, bonding pressures of 30 N, 40 N, and 50 N were evaluated. The interface was analyzed through microstructural examination via optical microscopy and stress measurements were determined using digital photoelasticity, while the bonding strength was assessed through tensile testing.

Zn-assisted low-temperature reconstruction of NiCo heterogeneous catalysts for lithium-oxygen batteries

Developing catalysts with high catalytic activity and durability is an effective strategy for improving the electrochemical performance of lithium-oxygen batteries (LOBs). Metal atom doping and heterostructure construction have shown great potential in catalysis and are expected to be widely used in energy storage. In this study, a Zn-doped NiCo2O4/NiO heterostructured complex catalyst is designed and prepared as a cathode catalyst for LOBs. This metal-doped heterostructured complex catalyst, prepared at a lower annealing temperature, retains the most active sites. Additionally, the three-dimensional hollow structure of the catalyst not only facilitates mass transfer but also provides active sites through doping and heterostructure formation. The Zn-doped NiCo2O4/NiO catalyst exhibits excellent catalytic performance, resulting the generation of a silky Li2O2 discharge product film, and the higher adsorption energy for the intermediate product LiO2 also allows the discharge product to be tightly bound to the catalyst. The improved contact between the discharge products and the catalyst's active sites, along with the increased surface area, enhances charge transport and decomposition properties, leading to good reversibility of the LOB. Consequently, the LOB based on Zn-doped NiCo2O4/NiO heterostructure complex catalyst features high discharge capacity (12160 mAh/g at 200 mA g−1) and excellent durability (353 cycles, ∼1765 h). Furthermore, theoretical calculations show that the Zn-doped complex heterostructures have enhanced reaction kinetics of OER and ORR. This straightforward method of producing metal-doped heterostructured complex catalysts that induce uniform Li2O2 deposition valuable insights for enhancing the performance of LOBs.

A multi-scale microscopic study of phase transformations and concomitant α/β interface evolution in additively manufactured Ti-6Al-4V alloy

Ti-6Al-4V alloy produced by laser-based powder bed fusion (LPBF) technique consists of an α′-martensite phase which is usually brittle and hence required, microstructure optimization by heat treatment to improve ductility. In this study, detailed microstructure analysis in the as-built condition and its evolution after sub-transus annealing was investigated. On annealing, the α′-martensite decomposes into α- and β-phases with the evolution of the α/β interface. Considering that the composition and microstructure play a crucial role in deciding the mechanical properties and service performance, a multi-scale correlative microscopy approach involving Transmission Electron Microscopy (TEM), Transmission Kikuchi Diffraction (TKD), and Atom Probe Tomography (APT) was employed. In the as-built condition, predominant segregation of β-stabilizers at the defect site especially along grain boundaries was observed; and these act as potential nucleation sites for β-phase during subsequent annealing. Low temperature annealing (750ᵒC) transforms the V-rich regions into the β-phase in the form of nanoscale precipitates. However, as the annealing temperature increases above 800ᵒC, the β-phase adopts a rod-like morphology. Comparing α-stabilizers, it is realized that β-stabilizers have a twofold greater contribution to elemental partition. Further, the composition and width of the α/β interface significantly impacts the mechanical properties of the alloy. Annealing at 750 °C and 850 °C resulted in significant improvement in ductility by 57.5% and 62.7% respectively without much of a trade-off in strength (>1 GPa). The strength and ductility are seen to decline when annealing temperature is raised above 850 °C due to a rise in compositional fluctuation and broadening of the α/β interface.

High-Performance Organic Field-Effect Transistors of Liquid Crystalline Organic Semiconductor by Laser Mapping Annealing.

Organic semiconductors (OSCs), especially small molecule semiconductors, have received increasing attention due to their good designability and variability. Phase transitions and interfacial properties have a decisive influence on device performance. Here, 2-Dodecyl-7-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-12) devices are treated with low-power laser annealing, which is able to avoid the influence of the dewetting effect on the hole mobility of organic semiconductor materials. Ultraviolet ozone treatment and self-assembled monolayer treatment can improve the performance and stability of the device. Moreover, after low-temperature thermal annealing, the hole mobility of the device can even reach as high as 4.80 cm2 V-1 s-1, and we tested the optical response of the device to the ultraviolet wavelength and found that its maximum optical responsivity was 8.2 AW-1.