Optimum Annealing Conditions Research Articles

Superconducting critical current density enhanced to 285 A cm−2 for Sr2VFeAsO3−δ tapes fabricated by ex situ powder-in-tube process

Superconducting critical current density (Jc) at 4.2 K for superconducting Sr2VFeAsO3−δ tape fabricated by powder−in−tube process was enhanced up to 285 A cm−2. Cross−sectional SEM images for superconducting Sr2VFeAsO3−δ wire/tapes indicated that void fraction fvoid was reduced from 12.8% for the round wire to ∼2.5% for the tapes. The decrease in fvoid suppresses the so−called “weak−links” and therefore enhances the Jc. In order to enhance Jc, the annealing condition should be optimized. The optimal annealing condition enforces the link between grains and avoids the loss of oxygen atoms in the superconducting core.

Integrated manufacture of polymer and conductive tracks for real-world applications

The present study demonstrates for the first time a unique UK-designed and built Additive Manufacturing (AM) hybrid system that combines polymer based structural deposition with digital deposition of electrically conductive elements. This innovative manufacturing system is based on a multi-planar build approach to improve on many of the limitations associated with AM, such as poor surface finish, low geometric tolerance and poor robustness. Specifically, the approach involves a multi-planar Material Extrusion (ME) process in which separated build stations with up to 5 axes of motion replace traditional horizontally-sliced layer modelling. The construction of multi-material architectures also involved using multiple print systems in order to combine both ME and digital deposition of conductive material. To demonstrate multi-material 3D Printing (3DP) we used three thermoplastics to print specimens, on top of which a unique Ag nano-particulate ink was printed using a non-contact jetting process, during which drop characteristics such as shape, velocity, and volume were assessed using a bespoke drop watching system. Electrical analysis of printed conductive tracks on polymer surfaces was performed during mechanical testing (static tensile and flexural testing and dynamic fatigue testing) to assess robustness of the printed circuits. Both serpentine and straight line patterns were used in the testing of Ag particle loaded ink and they showed very similar resistance changes during mechanical exposure. Monitored resistance and stress changed as a function of strain exhibiting hysteresis with more prominent residual strain during stretching and compression cycles and 3-point bending flexural tests of PA and CoPA substrates. Bare and encapsulated tracks exhibited low electrical resistivity (1–3*10−6 Ω*m), and its change was more rapid on ABS and minor on PA and CoPA when increasing tensile and flexural strain up to 1.2% and 0.8%, respectively. Resistance of Ag tracks on ABS also increased rapidly during fatigue testing and the tracks easily fractured during repeated stretching-compression cycles at 1% and 1.2% strain. No resistance changes of Ag tracks printed on PA and CoPA were observed at lower strain amplitudes whereas at higher strain amplitudes these changes were the lowest for conductive tracks on CoPA. Thermal analyses were conducted to determine the printed material’s glass transition temperature (Tg), stability and degradation behavior to find the optimum annealing conditions post printing. The novel AM printer has the ability to fabricate fully functional objects in one build, including integrated printed circuitry and embedded electronics. It enables product designers and manufactures to produce functional saleable electronic products. This new technology also gives the opportunity for designers to improve existing products, as well as create new products with the added advantages of geometrically unconstrained 3DP.

Investigation of Optimum Mg Doping Content and Annealing Parameters of Cu2MgxZn1-xSnS4 Thin Films for Solar Cells.

Cu2MgxZn1−xSnS4 (0 ≤ x ≤0.6) thin films were prepared by a simple, low-temperature (300 °C) and low-cost sol–gel spin coating method followed by post-annealing at optimum conditions. We optimized the annealing conditions and investigated the effect of Mg content on the crystalline quality, electrical and optical performances of the Cu2MgxZn1−xSnS4 thin films. It was found that the Cu2MgxZn1−xSnS4 film annealed at 580 °C for 60 min contained large grain, less grain boundaries and high carrier concentration. Pure phase kesterite Cu2MgxZn1−xSnS4 (0 ≤ x ≤ 0.6) thin films were obtained by using optimal annealing conditions; notably, the smaller Zn2+ ions in the Cu2ZnSnS4 lattice were replaced by larger Mg2+ ions. With an increase in x from 0 to 0.6, the band gap energy of the films decreased from 1.43 to 1.29 eV. When the ratio of Mg/Mg + Zn is 0.2 (x = 0.2), the grain size of Cu2MgxZn1−xSnS4 reaches a maximum value of 1.5 μm and the surface morphology is smooth and dense. Simultaneously, the electrical performance of Cu2MgxZn1−xSnS4 thin film is optimized at x = 0.2, the carrier concentration reaches a maximum value of 3.29 × 1018 cm−3.

Thermal post processing of FeSe1−xTex: formation of surface iron oxides and enhancement of Jc

We present the results from structural analysis of single crystalline FeSe1−xTex and magnetisation measurements of as-grown FeSe0.35Te0.65 samples and after they have been annealed in air. Raman spectroscopy revealed that air annealing leads to the formation of hematite (α-Fe2O3) and magnetite (Fe3O4) on the surface of FeSe1−xTex, with the bulk beneath being free of iron oxide. Furthermore, we observe an increase in the superconducting transition temperature, Tc, from 7 to 14 K, and in the critical current density, Jc, by one order of magnitude for all applied magnetic fields. A comparison of two FeSe0.35Te0.65 samples of different thickness indicates a possible size dependence for the optimal annealing conditions. Annealing for a second time (prolonged annealing) was found to induce a surface barrier, indicated by the transition from a symmetric to a highly asymmetric magnetic hysteresis loop.

Thermoelectric properties of plasma sprayed of calcium cobaltite (Ca2Co2O5)

The thermoelectric properties of calcium cobaltite deposits produced by the plasma spray process are investigated from room-temperature to 873 K. Synthesis of Ca3Co2O6 and Ca2Co2O5 powders were prepared by the solid-state reaction from CaO and CoOx starting powders. During their subsequent plasma spray Ca particles experience preferential evaporation within the plasma, resulting in a complex interplay among process conditions, stoichiometry, and resultant phases. The as-sprayed material predominantly contains amorphous and secondary phases. Upon annealing, the deposits show sensitivity to phase evolution and therefore thermoelectric properties. Through screening studies, optimal annealing conditions were identified which show a p-type Seebeck coefficient value of 180 μV K−1, electrical conductivity of 1.09 × 104 S m−1, thermal conductivity of 1.16 W m-1 K-1 at 873 K. The resultant figure of merit value reached 0.266 for this combination of processing and thermal treatment and is in line with data reported from other techniques for this system.

Optically stimulated luminescence of LiF:Mg,Cu,P with different dopant concentrations

A study of the optically stimulated luminescence (OSL) properties of LiF:Mg,Cu,P material has been performed with respect to the dopant concentrations in the following ranges: Mg (0.1–1.0 mol%), Cu (0.005–0.5 mol%), P (0.15–5.0 mol%). Over 40 differently doped LiF:Mg,Cu,P batches were successfully investigated for their OSL signal. Parameters describing the shape of the OSL decay curves after continuous (CW-OSL) and linear stimulation modes (LM-OSL), including the optimum annealing conditions have been evaluated. The results show that the OSL signal of the LiF:Mg,Cu,P is associated with the TL peak 1 and TL peak 2. Moreover, it was found that the OSL decay curve is composed of fast and slow components. The optimal concentration of the Mg, Cu, P activators for OSL were found to be in the following ranges: Mg (0.2–0.6 mol%), Cu (0.001–0.05 mol%), P (0.6–1.25 mol%). Another important finding was the fact that LiF:Mg,Cu,P requires different annealing conditions for OSL than for TL. The optimal annealing procedure for OSL was found to be: 240 °C/10 min followed by 190 °C/10 min. For this procedure the OSL sensitivity is increased by approximately 60% compared to the initial signal after standard annealing at 240 °C/10 min. LiF:Mg,Cu,P OSL signal shows high fading, reaching nearly 40% loss of the signal within 2 h storage time in the dark and at room temperature. The dose response of OSL signal was confirmed to be sublinear, similarly as in case of TL.

The properties of the earth abundant Cu2SnS3 thin film prepared by spray pyrolysis and rapid thermal annealing route

Ternary compound Cu2SnS3 (CTS) was fabricated by simple, low cost and high efficient spray pyrolysis and rapid thermal annealing route. The influences of annealing temperature and annealing duration on the properties of the prepared CTS thin film were investigated in detail. X-ray diffraction spectrometer, Scanning Electron Microscope, UV–Vis–IR spectrophotometer and I–V test system were employed for the analysis of the structural, morphological, optical and photoelectric properties of the prepared CTS thin film, respectively. The characterization results show that the CTS thin film prepared under the optimal annealing condition of 500 °C and 15 min presents as tetragonal structure with preferential (1,1,2), bandgap value of 1.44 eV, crystal grain size of around 80 nm and photoelectric conversion efficiency as high as 1.24%.

Low Temperature Solution-Processable 3D-Patterned Charge Recombination Layer for Organic Tandem Solar Cells.

We propose a novel method to pattern the charge recombination layer (CRL) with a low-temperature solution-processable ZnO layer (under 150 °C) for organic solar cell applications. Due to the optimal drying process and thermal annealing condition, ZnO sol-gel particles formed a three-Dimensional (3D) structure without using a high temperature or ramping method. The generated 3D nano-ripple pattern showed a height of around 120 nm, and a valley-to-valley distance of about 500 nm. Based on this newly developed ZnO nano-ripple patterning technique, it was possible to pattern the CRL without damaging the underneath layers in tandem structure. The use of nano-ripple patterned ZnO as the part of CRL, led to the concomitant improvement of the power conversion efficiency (PCE) of about 30%, compared with non-patterned CRL device.

Effects of rapid thermal annealing on the electrical and structural properties of Mo/SiC schottky contacts

In this work, the effects of rapid thermal annealing on the electrical and structural properties of Mo/SiC Schottky contacts which fabricated by FTS system were investigated. As-fabricated Mo/SiC Schottky contacts were thermally treated in Ar atmosphere at the temperature of 500–700 °C, for 120s. By the rapid thermal annealing process, the SBHs of diodes were decreased while other parameters including series resistance and ideality factor were not changed significantly. However significant degradation in reverse blocking performance was occurred with the annealing temperature of 700 °C. This was in tendency of proportional to the thickness of interfacial layers between Mo and SiC. Optimal annealing condition for Mo/SiC Schottky contacts was found to be at 600 °C for 120 sec.

UV‐Induced Ferroelectric Phase Transformation in PVDF Thin Films

AbstractThin films of polyvinylidene fluoride (PVDF) enable access to efficient hybrid devices that operate at low voltages. However, the preparation of thin films from solution typically yields nonferroelectric crystalline phases that require additional processing steps to transform the nonferroelectric phases to the more desirable ferroelectric polymorphs. Here, a rapid photonic annealing technique is reported that induces an α‐ to β‐phase transformation in PVDF thin films, opening up the opportunity to process the material via high‐throughput processing conditions such as roll‐to‐roll processing. This photonic annealing process uses a microsecond‐scale light pulse to transform the spin‐coated films into the desired ferroelectric PVDF phase. The structural evolution in these films is investigated under brief pulses of light, and it is shown that under optimal photonic annealing conditions, robust devices with a remnant polarization (P r) up to 5.4 µC cm−2 and a coercive field (E c) around 120 MV m−1 can be achieved.

XRD, AFM, DRS and Photosensitivity of CZTSe Thin Films Prepared by Vacuum Evaporation Method

This article reports the preparation and study the influence of annealing temperature on Cu2ZnSnSe4 (CZTSe) thin films by thermal evaporation method. The structural, morphology and optical properties of the CZTSe thin films were studied by using X-ray diffraction (XRD), atomic force microscope (AFM), diffuse reflection spectroscopy (DRS) and photoluminescence (PL) techniques respectively. The diffraction analysis indicates that the annealed films showed improved crystallite size with annealing temperature. The CZTSe film annealed at 300 °C shows better optical absorption and good photosensing behavior among the films. It could be attributed to the number of bigger size particles are rich in 300 °C annealed films as well as lower band gap energy 1.45 eV. The thin film annealed at 300 °C shows good photosensitivity. From the experimental studies the optimum annealing condition for obtaining pure CZTSe thin films was found to be 300 °C.

Enhancement of recrystallization texture in non-equiatomic Fe-Ni-Co-Al-based high entropy alloys by combination of annealing and Cr addition

Formation of strong <001> recrystallization texture in new non-equiatomic Fe-Ni-Co-Al-based high entropy alloys has been investigated. Optimal annealing temperature and time to obtain strong <001> texture is subsequently determined through microstructure and recrystallization texture study of cold-rolled NCACB (34.95Fe-27.5Ni-17.5Co-11.5Al-8.5Cr-0.05B at.%) at 1200 °C and 1300 °C for different annealing times. It has also been found that the recrystallization texture is influenced by grain growth and the relative grain size (d/t, d-grain size, t-sheet thickness). Furthermore, contribution of chemical composition to <001> texture has been examined in two additional cold-rolled non-equiatomic high entropy alloys, NCAB (Fe-27.5Ni-17.5Co-11.5Al-0.05B at.%) and NCATB (Fe-27.5Ni-17.5Co-11.5Al-2.5Ta-0.05B at.%), under the same optimal annealing condition used for NCACB. Comparison of texture intensity of NCAB, NCATB, and NCACB demonstrates that Cr is very effective in the formation of strong <001> recrystallization texture of Fe-Ni-Co-Al-based alloys. Based on low-angle boundary statistics, it is hypothesized that decrease in stacking fault energy is responsible for the enhanced recrystallization texture in NCACB. Additionally, it is demonstrated employing a Zener-type model for the pinning of grain boundaries by second-phase particles, that precipitated NiAl particles facilitate the abnormal grain growth in NCACB. The tensile tests results show that strong recrystallization texture and bamboo-like structure improve the ductility of NCACB.

A high-performance TiO2 nanotube supercapacitor by tuning heating rate during H2 thermal annealing

TiO2 nanotube is a promising material for supercapacitor electrodes. Thermal annealing has been proved as an effective way enhancing the performance of TiO2 nanotube supercapacitors. However, heating rate, as an important parameter in the thermal annealing, has been overlooked as a factor that can influence the electrochemical performance of TiO2 nanotube supercapacitors. In this paper, we demonstrate that the electrochemical performance of TiO2 nanotube supercapacitors fabricated by anodization process can be significantly improved by tuning heating rate during hydrogen thermal annealing. At the optimal condition, the areal capacitance of TiO2 nanotube supercapacitors increased from 27.36 to 52.40 mF cm−2 with a scan rate of 100 mV s−1, while maintaining a high capacitance retention of 65.9% when the scan rate increased from 10 to 1000 mV s−1. Moreover, outstanding long-term cycling stability with only 4.8% capacitance reduction after 5000 charge–discharge cycles is observed. It is found that the electronic carrier densities, surface hydroxyl group density, as well as crystallite size in TiO2 are maximized at the optimal annealing condition, all of which are accounted for the enhancement of the electrochemical performance.

Composition and Structure of a Nanofilm Multilayer System of the SiO2/Si/CoSi2/Si(111) Type Obtained via Ion Implantation

A SiO2/Si/CoSi2/Si(111) heterostructure is synthesized via successive Co+- and O 2 + -ion implantation into silicon followed by annealing. The optimal implantation and annealing conditions needed to obtain such a structure are determined. It is demonstrated that CoSi2 and SiО2 layers formed in the surface region are single- and polycrystalline, respectively.

Thermal stability of nanocomposite Mo2BC hard coatings deposited by magnetron sputtering

The investigation of hard coatings under thermal load is crucial in order to obtain information on the thermal stability and possible changes of microstructure and mechanical properties. In addition, advanced heating studies may also provide feedback for the grain growth mechanism occurring during annealing and thus, help to predict optimum post-growth annealing conditions for producing high-performance hard coatings. Here, we investigate the thermal response of Mo2BC, deposited by bipolar pulsed direct current magnetron sputtering in an industrial chamber on a silicon substrate at a substrate temperature of 380 °C. Ex-situ and in-situ X-ray diffraction and transmission electron microscopy studies are performed at elevated temperatures to track changes in the structure. Whereas the as-deposited nanocomposite coating exhibits small spherical nanocrystals (1.2 nm in diameter) embedded in an amorphous matrix, a fully crystalline structure, mainly consisting of elongated and interconnected crystals with lengths of up to 1 μm, is obtained at elevated annealing temperatures. Hardness and Young's modulus increase by ~8% and ~47%, respectively, compared to the as-deposited coating. Delamination from the silicon substrate only occurs at temperatures above 840 °C. Thus, our detailed study of the micro- and nanostructure evolution upon thermal annealing suggests that heat treatments below 840 °C are a suitable method to improve the crystallinity and mechanical properties of nanocomposite Mo2BC coatings.

Pseudo-texture memory in AISI 321 austenitic stainless steel

In this study, a 45 µm-sized AISI 321 austenitic stainless steel was cryo-rolled at -196 °C to 50 % thickness reduction to completely transform the γ-austenite phase to α'-martensite. The cryo-rolled sample was subsequently annealed in the temperature range of 923 - 1073 K for 30-28800s (0.5 - 480 mins) to reverse the α'-martensite back to γ-austenite and develop ultrafine grain (UFG) structure at an optimum annealing condition. Average austenite grain sizes of 0.22 and 0.31 µm were obtained at an optimum annealing conditions of 923 K for less than 480 minutes and 1023 K for 10 minutes, respectively. High resolution EBSD and XRD texture results shows that ζ-fibre ({110}<uvw>) is the major texture component of austenite grains in the UFG structure and it is stronger in specimen annealed at 923 K than those of higher temperatures (973, 1023 and 1073 K) used in this study. The strong intensity of ζ-fibre in UFG is attributed to pseudo-texture memory in AISI 321 i.e. the ability of the steel to memorize the crystallographic orientation of the deformed austenite, rather than the conventional as-received austenite phase that is random.

Texture Evolution of a 2.8 wt% Si Non-Oriented Electrical Steel during Hot Band Annealing

To optimize the magnetic properties of non-oriented electrical steels, it is necessary to carefully control all the stages of thermomechanical processing during the production of the steel sheets, since the microstructure and crystallographic texture at an early step will usually affect those at the subsequent steps. Many studies have shown that hot band annealing may have a positive effect on the texture of the final sheet, but it is not clear what are the optimal annealing conditions to obtain the desired final textures. In this study, the evolution of microtexture and microstructure of a 2.8 wt% Si non-oriented electrical steel during hot band annealing is studied by using electron backscatter diffraction (EBSD) techniques. A region of the hot-rolled sample was marked by micro-indents so that the same area could be examined at various annealing times (under the same temperature) to investigate the evolution of the microstructure and microtexture during recrystallization. In this way, the mechanisms of texture evolution was elucidated, and optimal annealing conditions can be determined.

CHARACTERISTICS OF THERMOLUMINESCENCE LiF:Mg,Cu,Ag NANOPHOSPHOR.

A nanophosphor of LiF:Mg,Cu,Ag was prepared by planetary ball milling for the first time in the laboratory. The size and shape of the nanophosphor were confirmed by XRD and SEM, which showed that it was cubic in shape and ~53 nm in size. The thermoluminescence (TL) characteristics of this nanophosphor were then investigated. It was found that the optimum annealing condition was 250°C for 10 min. The TL sensitivity of the prepared nanopowder was less than that of its micropowder counterpart and the TL glow curve structure exhibited several peaks. The LiF:Mg,Cu,Ag nanophosphor exhibited a linear response over a range of doses from 1 Gy to ~10 kGy. From this study, it appears that LiF:Mg,Cu,Ag nanophosphor is a good candidate for dosimetry because of its linearity over a range of doses, low tendency to fade, good repeatability and simple glow curve structure.

TbYxOy Electrolyte-Insulator-Semiconductor Glucose Biosensor

We report a glucose biosensor based on glucose oxidase (GOD) immobilized on TbYxOy sensing film deposited on the Si substrate through reactive cosputtering in this study. The structural properties of TbYxOy sensing films annealed at different temperatures (600, 700, 800, and 900 °C) were carried out using X-ray photoelectron spectroscopy and atomic force microscopy to obtain the optimal annealing condition. The TbYxOy electrolyte-insulator-semiconductor (EIS) sensor annealed at 900°C exhibited a higher sensitivity of 59.79 mV/pH, a lower drift rate of 0.26 mV/h, and a smaller hysteresis voltage of 1 mV in comparison with the other annealing temperatures. We attribute this behavior to the formation of a honeycomb-like structure and the reduction of lattice defects to improve the TbYxOy stoichiometry. Moreover, we compared two surface modification techniques with 3-aminopropyltriethoxysilane (APTES) and APTES+glutaraldehyde (GA) to immobilize the TbYxOy film surface and thus the enzymatic GOD was covalently bounded to the functionalized surface of a TbYxOy EIS sensor. The TbYxOy glucose biosensor prepared with APTES+GA has a high sensitivity (19.85 mV/mM) in solutions containing glucose at concentrations in the range 2–8 mM. This TbYxOy EIS biosensor is very promising sensing membrane materials for general clinical examination of blood glucose.

Microstructures and mechanical properties of duplex low carbon steel

The microstructures behavior of duplex cold-rolled low carbon steel for automotive applications has been investigated. Intercritical annealing treatment is commonly used to develop a duplex low carbon steel containing ferrite and martensite. To get a duplex phase ferrite and martensite, the specimens were heated at inter-critical annealing temperature of 775°C - 825°C, for heating time up to 20 minutes, followed by water-quenched. The hardness of specimens was studied. The optical microscopy was used to analyze the microstructures. The optimal annealing conditions (martensite volume fraction approaching 20%) at 775°C with a heating time of 10 minutes was achieved. The highest hardness value was obtained in cold-rolled specimens of 41% in size reduction for intercritical annealing temperature of 825°C. In this condition, the hardness value was 373 HVN. The correlation between intercritical annealing temperature and time can be expressed in the transformation kinetics as fγ/fe = 1-exp(-Ktn) wherein K and n are grain growth rate constant and Avrami’s exponent, respectively. From experiment, the value of K = 0.15 and n = 0.461. Using the relationship between temperatures and heating time, activation energy (Q) can be calculated that is 267 kJ/mol.