Annealing Duration Research Articles

Dependence of mechanical properties of mitral valve annuloplasty rings on annealing modes

Objective : to investigate dependence of the mechanical properties of mitral annuloplasty rings on heat annealing modes. Materials and methods . The study evaluates the nature of change in stress–strain curves under uniaxial compression of experimental samples processed at varying annealing temperature, duration and pressure. Results . It was noted that higher exposure, temperature, and lower pressure led to increased structural rigidity and strength for small strains. Moreover, the extent of influence of annealing temperature and duration was comparable. A 40% (500–700 °C) change in temperature altered the mechanical properties of the ring – 20% increase in strength. A similar change in heat treatment time (4.5–6.5 min) resulted in a 27% increase in the force required for a 15% compression. Conclusion . The experimental dependences presented in the work allow recommending main parameters for heat treatment mode: temperature range 600–700 °C, 10.5 minutes exposure time, and 0.1–0.5 atm air pressure in the furnace chamber.

Structure and Properties of High‑Strength Ti Grade 4 Prepared by Severe Plastic Deformation and Subsequent Heat Treatment.

Severe plastic deformation represented by three passes in Conform SPD and subsequent rotary swaging was applied on Ti grade 4. This process caused extreme strengthening of material, accompanied by reduction of ductility. Mechanical properties of such material were then tuned by a suitable heat treatment. Measurements of in situ electrical resistance, in situ XRD and hardness indicated the appropriate temperature to be 450 °C for the heat treatment required to obtain desired mechanical properties. The optimal duration of annealing was stated to be 3 h. As was verified by neutron diffraction, SEM and TEM microstructure observation, the material underwent recrystallization during this heat treatment. That was documented by changes of the grain shape and evaluation of crystallite size, as well as of the reduction of internal stresses. In annealed state, the yield stress and ultimate tensile stress decreased form 1205 to 871 MPa and 1224 to 950 MPa, respectively, while the ductility increased from 7.8% to 25.1%. This study also shows that mechanical properties of Ti grade 4 processed by continual industrially applicable process (Conform SPD) are comparable with those obtained by ECAP.

Influence of silver nanoparticle on Raman and photoluminescence of heat treated Ag-Er codoped tungsten tellurite glasses

The glasses of composition TeO2-WO3-Li2O-Er2O3 with AgNO3 (TWLEOAG) were prepared by the high-temperature melting method. Surface Plasmon resonance (SPR) bands are observed in the range 520-535 nm and 640-650nm of without erbium-doped glass by absorption spectrum. The TEM measurement reveals the presence of spherical AgNPs in this glass. The DSC has also been analyzed for the stability of transition temperature Tg and on set crystallization T0 of this glass system. The Raman spectrum revealed that TWLEOAG glasses were mainly formed by the [TeO4], {TeO3}, [WO4] and [WO6] units and [TeO4] units convert to [TeO3] units with the addition of WO3 and Li2O content into tellurite glasses system. In particular TWLEOAG05 glass samples, heat-treated different time interval system reveal the enhancement in Raman peaks intensity with small shift in due to Ag nanoparticle. Also photoluminescence enhancement of red upconversion compare to green emission of TWLEOAG05 for different annealing duration has been observed under 808nm excitation. In this work optimum 0.5 mol% AgNP in TWEOAG glass would be useful for optical devices.

Breakthrough in the reduction of oxygen-annealing time for REBCO melt-textured bulks under an oxygen atmosphere containing water vapor

Since REBCO melt-textured bulks are produced in an extremely carrier underdoped state after melt-growth, oxygen-annealing is required for a few hundred hours to control the oxygen composition throughout the bulks due to their slow oxygen-diffusivity. In this study, we discovered that the oxygen-annealing time can be largely reduced with the introduction of water vapor to the oxygen-annealing process for Ag-added YBCO melt-textured bulks without any degradation of the superconducting properties. It was revealed that highly dense stacking faults were induced to the matrix during this wet oxygen-annealing, which are considered to act as fast diffusion paths of oxygen. The estimated chemical diffusion coefficients of oxygen at 400 °C for the bulk annealed under wet O2 was ∼4.3 × 10−11 m2s−1, which is almost twice as high as that annealed under standard dry O2 atmosphere. High Jc without a decrease in Tc was confirmed for the sample annealed under wet O2, when the wet O2 annealing was performed for a moderate time. In addition, a combined oxygen-annealing process, where wet O2 was supplied for the first 24 h followed by a dry O2 process for the remaining period, was found to be more effective to achieve both enhanced oxygen-diffusion and maintain high field trapping properties. These improvements are probably because moderate amounts of defects were introduced to the bulk as a function of the duration of the wet O2 annealing. The introduction of water vapor to the oxygen-annealing process will become a versatile technique to reduce the total processing time of REBCO melt-textured bulks.

Моделирование кривых дифракционного отражения рентгеновских лучей от протонообменных слоев монокристалла ниобата лития

In this work, within the framework of the dynamic theory of the X-ray scattering, a model is constructed that describes the diffraction reflection curves obtained from the proton-exchange layers of a lithium niobate monocrystal subjected to the post-exchange annealing. Planar proton-exchange waveguides based on the X-cut of the lithium niobate monocrystal are obtained experimentally. It was shown that the proton implantation leads to the formation of the new crystalline phases with a larger lattice parameter. The structure changes (by the method of the diffraction structural analysis) and the optical properties (by the method of the mode spectroscopy) of the obtained waveguides are investigated in the various temperature regimes. The microstrain of the crystal lattice caused by еру proton implantation was estimated by the analysis of X-ray diffraction line broadening. It is shown the thickness of the waveguide layer and the number of new crystalline phases depend not only on the temperature regime of the proton exchange, but also on the duration of post-exchange annealing. The simulation of the experimentally obtained curves of the diffraction reflection is carried out within the framework of the described model. As a result of the modeling, the depth of the waveguide layer was determined, which is consistent with the data obtained by the method of the mode spectroscopy. The models of the assumed profiles of the crystal lattice deformation caused by proton implantation are presented. The average values of the lattice microstrain and the phase composition of proton-exchange lithium niobate layers are determined.

Phototransferred thermoluminescence of annealed synthetic quartz: Analysis of illumination-time profiles, kinetics and competition effects

Phototransferred thermoluminescence (PTTL) induced from annealed synthetic quartz using 470 nm blue light is reported. The quartz was annealed at 900 °C for 10, 30 and 60 min prior to use. A glow curve of conventional TL measured at 1 °C s−1 following irradiation to 200 Gy for the sample annealed for 10 min shows six peaks at 90, 122, 176, 210, 240 and 340 °C. The sample annealed for 30 min has peaks at 80, 110, 136, 196, 240 and 330 °C. Similarly, the sample annealed for 60 min also has six peaks at 80, 120, 134, 188, 235 and 340 °C. For ease of reference, these are labelled I-VI respectively. Peaks observed under PTTL are referred to as A1 onwards. Of the six peaks, only the first three are reproduced under phototransfer for the sample annealed for 60 min. When the duration of annealing is reduced to 10 min, PTTL is induced only at peaks A1 and A3. Interestingly, for the intermediate duration of annealing of 30 min, the only peak that appears under phototransfer is the first one, A1. For quartz annealed for 10 min, the PTTL appears as long as the preheating temperature does not exceed 560 °C. On the other hand, in the quartz annealed for 30 and 60 min, PTTL only appears for preheating to and below 450 °C. This shows that the occupancy of deep electron traps at temperatures beyond 450 or 560 °C is low in the said samples. The activation energy for peaks A1 and A3 was found to be about 0.68 eV. The PTTL peaks were studied for thermal quenching and peaks A1 and A3 were determined to be subject to this effect. The activation energy for thermal quenching was determined as 0.62±0.04 eV in analysis using peak A1. In all cases, the PTTL intensity goes through a peak as a function of illumination time. The experimental dependence of PTTL intensity on illumination time is modelled using sets of coupled linear differential equations based on systems of donors and acceptors whose number is determined by preheating temperature. Competition effects involved in the PTTL have been discussed.

Effect of Electron Beam Annealing Duration on the Properties of Zno Thin Films

The effect of electron beam (EB) annealing duration on the properties of pure ZnO thin films was studied. Pure ZnO precursor films prepared by sol-gel spin coating method were directly annealed by EB for different duration from 20 s to 480 s. The structural, optical and electrical properties were investigated. XRD patterns show (002) preferential growth for all the ZnO films. SEM results reveal that the average grain size changes from ∼10 nm to ∼70 nm with the increase of annealing duration and AFM results show the surface RMS roughness is less than 3 nm. The optical transmittance spectra present the absorption edge of the films is at about 380 nm and the average transmittance is more than 85% in visible region. It’s exciting to find that the ZnO film annealed for only 120 s exhibits resistivity 2×10−2 Ωcm and carrier concentration as high as 5.5×1019 cm−3, which shows an advantage of EB annealing in the preparation of ZnO transparent conductive films.

Lithium-conducting Solid Electrolytes Synthesized by the Sol-Gel Method in the System Li7La3Zr2O12-Li5La3Nb2O12

Solid electrolytes Li7−xLa3Zr2−xNbxO12 (x = 0.0–2.0) were synthesized by the sol-gel method, with Nb2O5 used as one of the starting compounds. The suggested synthesis procedure made it possible to lower the annealing temperature and shorten the annealing duration as compared with the solid-phase synthesis method, from 1200°C during 36 h to 1150°C during 1 h. The influence exerted by the doping of the Li7La3Zr2O12 compound in the Zr sublattice with niobium (Nb5+) on its crystal structure, morphology, and electrical conductivity. It was found that the compounds obtained with x > 0.1 are single-phase and have the Ia−3d cubic structure. The scanning electron microscopy was used to examine the morphology and the grain size of the resulting solid electrolytes. The average grain size of the ceramic samples was found to be 1–4 µm. The resistivity of the solid electrolytes Li7−xLa3Zr2−xNbxO12 (x = 0.0–2.0) was measured by the method of electrochemical impedance. It was found that Li6.75La3Zr1.75Nb0.25O12 has the highest total lithium-ion conductivity at 25°C: 4.0 × 10−5 S cm−1. It was shown that the sol-gel method is promising and can be used to obtain solid electrolytes based on Li7La3Zr2O12 doped with Nb5+ ions.

Formation of Oxide Layers on the Surface of Copper and its Alloys Modified by a High-Power Ion Beam

The change in the phase and elemental composition of the surface layers of copper and its alloys, brasses LS59-1, L63, and bronze BrAZh9-4, preliminarily irradiated with a high-power ion beam, after oxidation in air at 400°C is studied. It is shown that depletion of the brass surface by zinc under irradiation with a high-power ion beam does not lead to a noticeable increase in the oxidation of brass during thermal annealing in air due to the diffusion of Zn from the volume to the surface. The annealing of high-power ion-beam-irradiated copper under similar conditions does not change the composition of oxidation products, and the phase ratio is determined by the duration of annealing. For BrAZh9-4 bronze irradiated by a high-power ion beam, enrichment of the surface with copper leads to the intensification of oxidative processes. Possible mechanisms for the observed changes in copper and its alloys are considered.

Improvement of Li-ion batteries energy storage by graphene additive

In this work, the layered compound of LiCo0.525Ni0.475O2, (LCNO) was prepared by self-propagating combustion reaction for the cathode of lithium-ion battery. We used self-propagating combustion reaction to prepare the compound of LiCo0.525Ni0.475O2, (LCNO) as a cathode material of lithium-ion battery, then we added Graphene (G) to LCNO as additive to obtain LCNO/G (LCNOG). Graphene weight is (4 %) of the total weight of LCNO, in a typical preparation, 10 g of LCNO, 0.4 g from G and 200 ml of ethanol were stirred together at room temperature to reach full dryness. We used thermo-gravimetric analysis (TGA) to determine the optimum range of annealing temperatures of LCNO and LCNOG. The value found were (650, 750 and 850) ∘C for 12 h in air. Changes in the structural and morphological properties were also studied.The structural properties of LCNO and LCNOG powder were studied by means of X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectrometry (EDS), Atomic Force Microscopy (AFM) and a Vibrating Sample Magnetometer (VSM). XRD analysis shows that all the powders are crystallized in the Space group R-3m, crystal system is trigonal (hexagonal axes) and present a random orientation and surface morphology of the LCNOG powder consists of Nano-crystalline grains with uniform coverage of the substrate surface with randomly oriented. XRD analysis showed that all the powders are crystallized in the Space group R-3m, crystal system is trigonal (hexagonal axes) and present a random orientation. Surface morphology of the LCNOG powder consists of Nano-crystalline grains with uniform coverage of the substrate surface with random orientation. Hysteresis behavior analysis proved that the powder possessed soft magnetic properties. Thermo-gravimetric analysis showed that the best annealing temperature and duration that leads to particles in the range several nm of the targeted composition are 750 °C for 12 h.

Recrystallization Kinetics of Niobium with Submicrocrystalline Structure

Abstract—Transmission and scanning electron microscopy have been used to study the kinetics of recrystallization at 400 and 700°C of niobium in which a submicrocrystalline structure was created as a result of high-pressure torsion. It has been shown that the recrystallization at 700°C occurs in accordance with the kinetics of normal grain growth. A decrease in the rate constant with an increase in the duration of annealing to more than 1 h is due to textural changes, rather than the completion of primary recrystallization. Upon the low-temperature recrystallization (400°C), a stable fine-grained structure is formed, which remains almost unchanged with increasing duration of annealing.

Decreasing yield ratio of 70 GPa·% grade hot-rolled medium Mn steel by weakening multi-strengthening effects

The yield ratio of investigated steel decreased significantly from 0.93 to 0.59 by prolonging intercritical annealing duration to weak multi-strengthening effects. The contribution of each effect was qualified by theoretical calculation. The grain refinement strengthening and dislocation strengthening dominate the yield strength, while the reduction of precipitation strengthening and martensite strengthening mainly leads to the decrease of yield strength.

Facile Universal Mass Production Strategy to Sub-3 nm Monodisperse Nanocrystals of Transition-Metal Oxides and Their Excellent Cyclability for Li-Ion Storage.

Nanoparticles, especially ultrasmall ones in sub-3 nm realms, are fundamental to high activity, high efficiency, and high utilization (3-H) important for many fields. Meanwhile, controlling the crystallinity, surfaces/interfaces, and pores, especially dimension-tunable aspect in them, is also of great significance in synthetic chemistry and nanoengineering. However, controlling crystallization down to a scale of sub-3 nm in mass production, even of subnucleus scale, is rare and still challenging. Here, using Mn, Co, and Zn elements as examples, homogeneous subnuclei smaller than 1 nm and size-tunable sub-3 nm monodisperse nanocrystals have been realized in laminated transition-metal oxides bulk foams (TMOBFs) of gram scale by a two-step fast evaporation-solidification (FE-S) and annealing strategy. Realization of the challenging size controllability in ultrasmall nanocrystals benefits from the FE-S-related burst nucleation process and in situ inhibition of crystal growth, while formation of the nanosheet skeletons is impelled by multiscale bubbling effect. Relying on annealing temperature and durations, the involved TMOBFs also exhibit controllable inorganic crystallization, organic surface/interfaces, and abundant micro/mesopores. In an illustration of the proof-of-concept application, TMOBFs with sub-3 nm nanocrystals substantiate universally ultrasteady cycling performance and approximate 100% utilization efficiency as anodes materials for lithium-ion batteries as expected.

The Novel Combination of Strength and Ductility in 0.4C‐7Mn‐3.2Al Medium Manganese Steel by Intercritical Annealing

By altering the temperature and duration of intercritical annealing (IA), the mechanical stability of retained austenites (RAs) is intentionally regulated in newly designed cold‐rolled medium manganese steel of Fe‐0.4C‐7Mn‐3.2Al (in wt%). Consequently, a novel combination of ultimate tensile strength (UTS) and total elongation (TE) (e.g., 1118 MPa and 67%) is obtained in duplex steel, and the corresponding product of UTS and TE can reach 75 GPa%. Both twinning‐induced plasticity (TWIP) and transformation‐induced plasticity (TRIP) take effect step by step during deformation and are conducive to the outstanding properties.

Fast and Slow Stages of Lifetime Degradation by Boron–Oxygen Centers in Crystalline Silicon

A conflict between previous and recently published data on the two‐stage light‐induced degradation (LID) of carrier lifetime in boron‐doped oxygen‐containing crystalline silicon is addressed. The previous experiments showed the activation of two boron–oxygen recombination centers with strongly differing recombination properties for the fast and slow stages of LID, whereas more recent studies found only a single center for both stages. To resolve this controversy, the historic silicon samples of these previous examinations are re‐examined in this study after more than one decade. It is found that, in the historic samples, the fast stage can be either described by two different centers or a mixture of the two, depending on the duration of previous dark annealing. A possible solution is suggested based on the involvement of different activating impurities in the boron–oxygen defect. In dark‐annealed samples, the defect consisting of boron, oxygen, and the activation impurity is present in two latent configurations, which reconfigure during LID at a fast and a slow stage. In the examined historic silicon samples, which did not undergo a gettering pretreatment, a significant concentration of an additional boron–oxygen defect with a different kind of activating impurity attached exists. The historic and modern results are thus reconciled.

Experimental investigations in the intermetallic and microvoid formation in sub-200 °C Cu–Sn bonding

This paper reports the intermetallic growth and microvoid formation in the Cu–Sn layers, which were annealed at low temperatures (sub-200°C) for durations varying from 120 to 1440 min. A 10 µm thick tin was electrodeposited on copper samples. Both Cu6Sn5 and Cu3Sn IMCs were formed and had a non-uniform scalloped shaped profile but with different scallops sizes. Void growth was studied at three different locations, i.e., the Cu–Cu3Sn interface, within the Cu3Sn, and at the Cu3Sn–Cu6Sn5 interface. The void size in these locations increased with increasing annealing durations and temperatures due to the coalescence of nearby voids. The void fraction at the Cu–Cu3Sn and Cu3Sn–Cu6Sn5 interfaces was observed to decrease, whereas the void fraction within the Cu3Sn IMC increased with increasing annealing durations. The largest voids were seen at the Cu–Cu3Sn interface, while the highest void fraction was found within the Cu3Sn IMC. The overall void size and void fractions for all experimental conditions were always smaller than 3 µm2 and 1.44 µm−1, respectively. The obtained results can be used in the hermetic packaging of MEMS devices performed at sub-200 °C. Processing at these low temperatures result in reduced thermo-mechanical stress and also eliminate the molten tin squeezing-out from the bonding zone, which is a known issue in Cu–Sn solid–liquid inter-diffusion bonding performed at temperature > 232 °C.

Revealing the secrets of PCR

The polymerase chain reaction (PCR) method and its quantitative variant (qPCR) were a landmark discovery for detection and quantification of small amounts of unambiguous deoxyribonucleic acids (DNA) due to its enormous sensitivity and specificity. The current methods for qPCR protocol optimization provide no information of the PCR propagation during the cycles as only single data point is extracted at the end of each thermal cycles, limiting a thorough understanding of reaction details. In this study, we utilized the continuous fluorescence monitoring method to observe progress of the reaction in real time with over 100 data points per each cycle, thus gaining a profound insight into the PCR itself. This provided information about the real-time PCR status, dominating reactions and their completion/incompletion during each cycle as well as their reaction kinetics. We then adjusted the duration of either annealing or elongation steps to ensure their completion within each cycle, resulting in the protocol optimization with complete amplification, enhancing PCR efficiency and taking < 20 min to obtain maximum product amount. The proposed method was verified using DNA with lengths of 177 base pairs (bp), 250 bp, and 400 bp. It can also be adopted for helping with qPCR troubleshooting as well as protocol optimizing just by reprogramming commercial real-time PCR cyclers.

Sub-nm-Scale Depth Profiling of Nitrogen in NO- and N&lt;sub&gt;2&lt;/sub&gt;-Annealed SiO&lt;sub&gt;2&lt;/sub&gt;/4H-SiC(0001) Structures

We demonstrated an x-ray photoelectron spectroscopy (XPS)-based technique to reveal the detailed nitrogen profile in nitrided SiO2/4H-SiC structures with sub-nanometer-scale-resolution. In this work, nitric oxide (NO)- and pure nitrogen (N2)-annealed SiO2/4H-SiC(0001) structures were characterized. The measured results of NO-annealed samples with various annealing duration indicate that preferential nitridation just at the SiO2/SiC interfaces (~0.3 nm) proceeds in the initial stage of NO annealing and a longer duration leads to the distribution of nitrogen in the bulk SiO2 within few nanometers of the interface. The high-temperature N2 annealing was found to induce not only SiO2/SiC interface nitridation similarly to NO annealing but also SiO2 surface nitridation.

Simultaneously probabilistic and deterministic approach (SPADA) for the materials design: methodology and experimental validation

This manuscript presents a relatively simple simultaneously probabilistic and deterministic approach (SPADA) for the experiment organization. To exemplify the efficacy and flexibility of the method, we optimized the conditions for the synthesis of the Al2O3–SiC–AlN composite. Optimal synthesis parameters were predicted by evaluation of the impact of five variables (four related to mixture composition and one to annealing duration) on four different levels each. Compressive strength of the resulting composites was monitored as an output parameter for the material characterization. Such optimizations are arduous when done by full-factor experimental design (625 experiments necessary), whereas using SPADA design we accomplished the task by doing only 16 experiments. Maximum compressive strength of the composite was increased by 320% as compared to the starting experiment and by 45% as compared to the highest result produced by direct search; additionally, suggestions for the further improvements were outlined on the basis of calculated correlations.

The effect of hardening by annealing in ultrafine-grained Al–0.4Zr alloy: influence of Zr microadditives

ABSTRACTInfluence of annealing on the microstructure and mechanical properties has been studied for Al–Zr (0.4 wt.%) alloy with the ultrafine-grained (UFG) structure formed by high-pressure torsion (HPT) at room temperature. A drastic hardening effect by short-term annealing in the temperature range of 90–280°С was observed for the HPT-processed Al–Zr alloy. The effect of hardening by annealing for the HPT-processed Al–Zr alloy is compared with that for the HPT-processed commercial purity (CP) Al. It was shown that addition of 0.4 wt.% Zr in Al does not cause a significant impact on the magnitude of hardening by annealing up to 150°С, however it leads to a shift of its maximum to higher annealing temperatures and expansion of the thermal stability range of strength up to 280°С. The kinetics of hardening by annealing for CP Al and Al–Zr alloys in the UFG state has been studied for the first time. It was shown that in both materials the strength first increases linearly with the duration of annealing and then reaches saturation. The temperature dependence of the rate of hardening by annealing was analysed through an Arrhenius law, and apparent activation energy was extracted for both systems. The addition of Zr results in the reduction of the activation energy of annealing-induced hardening by ∼2 times. Possible physical mechanisms controlling the kinetics of hardening by annealing are discussed for the ultrafine-grained CP Al and Al–Zr alloy.