Annealing Duration Research Articles

Sonochemical Synthesis of Na0.7MnO2.05 and Na0.44MnO2 Insertion Materials for Na-Ion Batteries and Na-Ion Capacitors

Energy storage reign supreme in driving the modern lifestyle. Among various energy storage technologies, Lithium-ion batteries (LIBs) and Lithium-ion capacitors (LICs) have attracted much attention due to their high energy and power density respectively. The constraint in the lithium resource impels us to replace Li with other abundant elements. Sodium seems to be the most attractive element to replace lithium with comparable standard electrode potential (-2.71 V vs SHE) and practically unlimited resources making this technology cost effective. Cathode plays an important role in storage devices (batteries and supercapacitors). Various transition metal oxides and polyanionic compounds can be employed as efficient cathode materials, but oxides are favorable owing to their high energy density and ease of synthesis. Current work explores two manganese-based oxides as cathodes for Na-ion batteries (NIBs) and Na-ion Capacitors (NICs): (i) Na0.7MnO2.05 and (ii) Na0.44MnO2. Depending on the stoichiometry, sodium manganese oxides mainly have two kinds of structures: (i) layered structure (e.g. Na0.7MnO2.05) or (ii) tunnel structure (e.g. Na0.44MnO2), both having large number of vacancies accommodating constituent Na-ions. Na0.44MnO2 is particularly attractive as cathode in NIB because of its unique 3D crystal structure, which greatly facilitates Na+ mobility whereas Na0.7MnO2.05 is good candidate for cathode in NICs owing to its sloppy discharge profile. Here, ultrasonic sonochemical synthesis has been employed to obtain the target compounds, which restricts the final high-temperature annealing duration within 1-2 h. Herein, we will present (i) single crystalline Na0.7MnO2.05 nanoplates with preferential growth in (100) direction facilitating efficient Na+ (de)insertion leading to capacity over 140 mAh/g (average voltage = 2.4 V) and (ii) orthorhombic Na0.44MnO2 having a reversible capacity of 110 mAh/g (average voltage = 2.3 V). The salient features of sonochemical synthesis, structure, morphology and final electrochemical performance of NaxMnO2 oxides (both as NIB and NIC) will be presented combining experimental work as well as first-principle calculations.

Impact of Annealing on Deuterium Retention Behavior in Damaged W

The annealing effects on deuterium (D) retention for 0.1–1.0 dpa iron (Fe) ion damaged W were studied as a function of annealing duration. The D2 spectra for Fe damaged W with lower defect concentration showed that D trapped by vacancy clusters was clearly decreased as increasing annealing duration due to the recovery of vacancy clusters. On the other hand, at higher defect concentration, the desorption peak of D trapped by voids was shifted toward higher temperature side, which would be caused by aggregation of vacancies and vacancy clusters. It can be said that the recovery and aggregation behavior of defects are controlled by defect concentration. By disappearing of desorption of D trapped by vacancy clusters after annealing for longer duration, the desorption of D trapped by vacancies was increased, which could be explained by following two possibilities. One is that the retention of hydrogen isotope trapped by monovacancy was increased. The other is that number of vacancies during annihilation process of vacancy cluster were formed by annealing.

An X-ray photoelectron spectroscopy study on the annealing effects for Al/glass Interface during aluminum induced texturing process

The aluminum induced texturing method offers an effective light trapping scheme by random texture that is formed by U-shaped craters on the glass surface. The texture is mainly shaped by the reaction between Al and SiO2. However, the reaction mechanism is not totally understood. Besides, the influence of other components present in the glass such as Na2O, CaO, and MgO. is neglected. In this study, the evolution of Al films on soda-lime glass during annealing has been inspected by depth resolved X-ray photoelectron spectroscopy. The elemental distribution of Si, Al and O have been investigated for different annealing durations and compositional analysis has been conducted for Na, Ca and Mg in addition to Si, Al and O. According to results, a relevant evolution model for annealing process has been constructed.

Mathematical model for the growth of phases in binary multiphase systems upon isothermic annealing

A phenomenological mathematical model of the formation and growth of phases in a binary multiphase system with allowance for factors influencing the process of diffusion in a binary system is presented. It is shown that phases can grow for a certain time at different ratios between diffusion parameters according to a parabolic law that depends on the duration of isothermic annealing. They then slow their growth after successor phases appear at their interface with one component and can completely disappear from a diffusion layer or begin to grow again, but only at a rate slower than during their initial formation. The dependence of the thickness of each phase layer in a multiphase diffusion zone on the duration of isothermic annealing and the ratio between the diffusion parameters in neighboring phases is obtained. It is established that a certain ratio between the phase growth and rates of dissolution with allowance for the coefficients of diffusion in each phase and the periods of incubation can result in the complete disappearance of one phase as early as the onset of the growth of phase nuclei and be interpreted as a process of reaction diffusion.

Rapid Thermal Annealing for Solution Synthesis of Transparent Conducting Aluminum Zinc Oxide Thin Films

Transparent conducting oxide films with optimized dopant molar ratio have been prepared with limited pre- and postdeposition annealing duration of 10 min. Multiple aluminum zinc oxide (AZO) layers were spin-coated on ordinary glass substrates. The predeposition consolidation temperature and dopant molar ratio were optimized for electrical conductivity and optical transparency. Next, a group of films were deposited on Corning glass substrates from precursor solutions with the optimized dopant ratio, followed by postdeposition rapid thermal annealing (RTA) at different temperatures and in controlled environments. The lowest resistivity of 10.1 × 10−3 Ω cm was obtained for films receiving RTA at 600°C for 10 min each in vacuum then in N2-5%H2 environment, while resistivity of 20.3 × 10−3 Ω cm was obtained for films subjected to RTA directly in N2-5%H2. Optical measurements revealed average total transmittance of about 85% in the visible region. A direct allowed transition bandgap was determined based on the absorption edge with a value slightly above 3.0 eV, within the typical range for semiconductors. RTA resulted in desorption of oxygen with enhanced carrier concentration and crystallinity, which increased the carrier mobility with decreased bulk resistivity while maintaining the required optical transparency.

Evolution of implanted Fe ions in SiO2/Si wafer into uniformly sized catalyst particles for carbon nanotube forest growth

We report the synthesis of carbon nanotube (CNT) forests with a narrow diameter distribution based on Fe ion implantation method. By annealing the Fe-implanted SiO2/Si wafer in an Ar atmosphere at 800 °C for 15 min, the Fe particles on the surface of SiO2 layer are successfully formed by the diffusion of Fe atoms from the SiO2 layer. Interestingly, the size distribution of Fe catalyst particles for Fe-implanted SiO2/Si wafers does not change with the prolonged annealing durations of up to 12 h. Using secondary ion mass spectroscopy and transmission electron microscopy (TEM), we confirmed that the implanted Fe atoms diffuse out of the SiO2 layer and form Fe particles on both the SiO2 surface and the interface between SiO2 and Si. The cross-sectional TEM images indicate that the Fe catalyst particles are anchored in the SiO2 layer, which limits the particles' mobility and results in an invariant catalyst size distribution for prolonged annealing durations. Therefore, we anticipate that implantation can be an efficient alternative catalyst preparation method for CNT forest growth which can solve various growth issues that are inherently caused by conventional physical vapor deposition method.

Study on the dimensional, configurational and optical evolution of palladium nanostructures on c-plane sapphire by the control of annealing temperature and duration

Metallic nanostructures can find various applications such as in optoelectronic devices, nanostructure synthesis and catalytic applications and their applicability vary depending on their size, density and configuration dependent properties. In this paper, the dimensional and configurational evolution of self-assembled palladium (Pd) nanostructures is systematically studied on c-plane sapphire with the control of annealing temperature (AT) and annealing duration with the initial Pd layers of various thicknesses. Depending on the AT, two distinct growth regimes are observed based on the concurrent effect of surface diffusion, surface energy minimization and Pd sublimation: i.e. (i) agglomeration of Pd nano-clusters from voids (500<AT≤650°C) and (ii) round nanoparticle (NP) fabrication (650°C<AT≤900°C). At 950°C, due to the sublimation of Pd atoms, substantial decrease in the NP dimension is witnessed and results in the ring patterns around the NPs. Additional investigation is performed at 950°C to reveal the annealing duration effect on the NP evolution. Due to the dual effect of the Oswald ripening and atom sublimation, initially the dimension of NPs is grown and then gradually decays along with the duration, resulting in an inverted ‘V’ pattern evolution in diameter and height. Moreover, the evolution of optical properties such as absorption band and average reflectance are studied with the corresponding reflectance spectra as a function of wavelength over UV, visible and NIR region. The Raman spectra analysis depicts the variation of lattice vibration peak intensity and position based on the surface morphology of the Pd nanostructures.

Annealing effect on residual stress of Sn-3.0Ag-0.5Cu solder measured by nanoindentation and constitutive experiments

In this study, residual stress in Sn-3.0Ag-0.5Cu lead-free solder after annealing at varying temperature and duration was investigated by nanoindentation and uniaxial tensile experiments. Based on the unloading response of load-penetration depth, the contact stiffness was theoretically calculated and found to be decreased with increasing annealing duration especially at the annealing temperature of 210°C. Additionally, the effect of residual stress on constitutive behaviour at strain rates of 1×10−3s−1, 5×10−4s−1 and 1×10−4s−1 was consistently observed. By correlating residual stress and elastic indentation recovery, it was confirmed that greater contact stiffness is induced by greater compressive residual stress. Therefore, the optimal annealing condition of SAC305 solder is 210°C for 12h, which is believed to minimize the residual stress and stabilize the mechanical property of annealed solder.

Microstructure and mechanical properties of friction welded steel-aluminum hybrid components after T6 heat treatment

In the present study, friction welded rods made of AW6082 aluminum alloy and 20MnCr5 steel were subjected to different T6 heat treatments of solution annealing and aging. The bond strength of the joints was determined using tensile tests and the intermetallic compound (IMC) layer thickness along the bond zone was measured by scanning electron microscopy (SEM) analyses. It is shown that bond strength strongly depended on the annealing temperature and duration. For an annealing temperature of 500°C, a process window could be established that led to an increase in bond strength compared to the as-weld condition. The IMC-layer thickness was found to be distributed inhomogeneously along the bond zone and the mean IMC-layer thickness showed parabolic growth behavior. With increasing mean IMC-layer thickness, the bond strength decreased linearly. The fracture surfaces of tensile test specimens were analyzed by SEM and are discussed with respect to the corresponding bonding strengths and failure mechanisms. It is shown that the IMC-layer / steel interface seems to play an important role for bond strength.

Alloyed Si/Al-based ohmic contacts to AlGaN/GaN nitride heterostructures

For the first time in Russia, the Si/Al/Ti/Au alloyed contact composition is investigated for the formation of ohmic contacts to AlGaN/GaN heterostructures using thermal annealing. The obtained results are compared with those for conventional Ti/Al/Ni/Au ohmic contacts. Use of the composition under investigation makes it possible to decrease the annealing temperature to 675–700°C, which results in improvement in the morphology of alloyed ohmic contacts in comparison with conventional contacts. The value of the contact resistance using the Si/Al-based composition to the AlGaN/GaN heterostructure is obtained in relation to the temperature and annealing duration. It is shown that no qualitative change in the resistance occurs at an annealing duration of several minutes in the temperature range of 700–750°C. In the temperature range of 675–700°C, there is an asymptotic decrease in the contact resistance with increasing annealing duration. The smallest value of the contact resistance amounts to 0.41 Ω mm.

The influence of CdSe and ZnSe nanoparticles on the optical properties of Sm3+ ions in lead borate glasses

The effect of glass composition and the presence of CdSe/ZnSe nanoparticles (NPs) on the optical absorption and fluorescence of Sm-doped lead borate glasses are studied. Three sets of glass samples xPbO:(99.5-x) B2O3:0.5Sm2O3, x = 29.5–69.5 mol%, xPbO:(96.5-x) B2O3:0.5Sm2O3: 3CdSe/ZnSe, x = 36.5, and 56.5 mol% are prepared. NPs are grown by annealing these glasses just below the glass transition temperature. Average size of both types of NPs increases with annealing time; however, CdSe NPs grew to a larger size range (2 to 20 nm) compared to ZnSe NPs (1 to 16 nm). We analyzed the hypersensitive transition, intensity parameters, radiative transition probability, stimulated emission cross section (σp), and the area ratio of the electric dipole/magnetic dipole transitions of Sm3+. The intensity parameters show a minimum at 11 h annealing for 36.5 mol% and a maximum for the same annealing duration in 56.5 mol% PbO containing CdSe NPs. The σp for 56.5 mol% of PbO with CdSe NPs is found to be a maximum when the average NP size is around 14 nm. ZnSe NPs containing glasses also show significant changes in σp when the average particle size is ~16 nm, for 36.5 mol% PbO. Our results suggest that the optical properties of Sm3+ in lead borate glasses are sensitive to its electronic environment which can be modified by varying the base glass composition and/or incorporating large NPs of CdSe/ZnSe. The large σp values that we observe for some of the glass compositions make them attractive materials for photonic devices and photovoltaic applications.

Modulating the extent of fast and slow boron-oxygen related degradation in Czochralski silicon by thermal annealing: Evidence of a single defect

The fast and slow boron-oxygen related degradation in p-type Czochralski silicon is often attributed to two separate defects due to the different time constants and the determination of different capture cross section ratios (k). However, a recent study using high lifetime samples demonstrated identical recombination properties for the fast and slow degradation and proposed an alternative hypothesis that these were in fact due to a single defect. The study presented in this article provides further experimental evidence to support the single defect hypothesis. Thermal annealing after light soaking is used to investigate the behaviour of subsequent boron-oxygen related degradation. Modifying the temperature and duration of dark annealing on pre-degraded samples is observed to alter the fraction of fast and slow degradation during subsequent illumination. Dark annealing at 173 °C for 60 s is shown to result in almost all degradation occurring during the fast time-scale, whereas annealing at 155 °C for 7 h causes all degradation to occur during the slow time-scale. This modulation occurs without changing the total extent of degradation or changing the capture cross-section ratio. The results are consistent with the fast decay being caused by defect formation from immediately available defect precursors after dark annealing, whereas the slow degradation is caused by the slow transformation of another species into the defect precursor species before the more rapid reaction of defect formation can proceed.

Radioluminescence of annealed synthetic quartz

The radioluminescence of synthetic quartz annealed at various temperatures up to 1000 °C is reported. The amplitude of the emission bands increases with annealing temperature. In addition, when samples are annealed at temperatures exceeding 700 °C, the intensity of the radioluminescence increases with duration of annealing. The corresponding emission spectra show seven emission bands at 2.04, 2.54, 2.77, 3.04, 3.40, 3.75 and 3.91 eV. The change in dominant emission band with annealing is consistent with annealing-induced variations in lifetimes determined previously from time-resolved optically stimulated luminescence spectra in the same samples.

Crystallization kinetics evaluated by the modified formula and optical properties of CdO and ZnO in 0.5ZnO-0.5CdO thin films

Crystallization kinetics evaluated by the modified formula and optical properties of CdO and ZnO in 0.5ZnO-0.5CdO thin films have been investigated. The characterization used grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution TEM (HRTEM) and ultraviolet–visible (UV–Vis) spectrophotometry. When the thin films are annealed at temperatures from 573 K to 773 K for 10–60 min, the GIXRD results show that all the films are composed of CdO and ZnO as major and second phases, respectively. In addition, a trace phase of CdSiO3 appeared for thin films annealed at 723 K and 773 K for 45 and 60 min, respectively, while CdSiO3 also appeared when annealing at 773 K for 30 min. The crystallinity of CdO increases with annealing temperature and duration, whereas the crystallinity of ZnO increases only slightly with temperature and duration. The activation energies of ZnO and CdO crystallization in 0.5ZnO-0.5CdO thin films are 49.51 kJ/mol and 112.45 kJ/mol, respectively. The crystallization of CdO and ZnO can be described by a modified formula: ln(11−α′)=[30t×exp(−49.51×103RT)]0.24 and ln(11−α′)=[104820t×exp(−112.45×103RT)]0.27, for 573 K ≤ T ≤ 773 K and 10 min ≤ t ≤ 60 min, respectively. All films have an average optical transparency of nearly 80% in the wavelength range greater than 500 nm in the visible range, and the band gap energy of the thin films increases from 2.68 eV to 3.10 eV as the crystallinity of ZnO increases from 5.12% to 20.91% when the thin films are annealed for 60 min at 573 K–773 K and shows a blueshift effect.

Annealing to achieve lower resistivity in Ga-doped ZnO epitaxial films grown from low-temperature aqueous solution

Various annealing conditions were examined for enhancing the electrical conductivity of gallium-doped ZnO (ZnO:Ga) epitaxial films grown from a low-temperature aqueous solution. The resistivity of the films decreased with increasing annealing temperature, accompanying increases in both the carrier concentration and mobility. However, the improvement obtained from 0.5 h of annealing was limited because the films spalled when the temperature exceeded ∼300 °C. The temperature at which spalling of the films occurred depended on the annealing atmosphere, and it was lower in 5%H2–Ar than in air or vacuum. Thermal desorption spectroscopy showed that the cause of spalling was expulsion of H2O vapor from the interior of the film, indicating that water molecules or hydroxides were incorporated into the crystal during film growth. Analysis of the variations in electrical properties with increasing annealing duration revealed that the electrical properties were quickly improved upon heating before the film spalled. Thus, by limiting the annealing duration to ≤20 s, annealing could be performed at a temperature as high as 580 °C without spalling of the film, which yielded the lowest resistivity of 4.7 × 10−4 Ω cm. The annealed film exhibited transmittance as high as >75% in the visible spectrum.

Microwave Annealing as a Low Thermal Budget Technique for ZnO Thin-Film Transistors Fabricated Using Atomic Layer Deposition

Microwave annealing (MWA) and furnace annealing are compared for their low thermal budget capability to improve the characteristics of ZnO-based thin-film transistors (TFTs). Both the ZnO channel and the Al2O3 gate dielectric are fabricated using atomic layer deposition. Using Si-wafer-susceptor assisted MWA with a substantial reduction of both annealing temperature and duration, significant improvements of the characteristics of the ZnO TFTs can be attained. A multi-step MWA process is found to further improve the characteristics of the TFTs. For the same microwave power and total duration, the field-effect mobility of the multi-step MWA TFT is 42% greater than that of the one-step MWA TFT with a similar sub-threshold swing. The multi-step MWA process can serve the purpose at temperatures as low as 220 °C.

One DNA strand homo-polymerizes into defined nanostructures.

We report a strategy for programmed DNA self-assembly that is favorable in terms of both thermodynamics and kinetics. In a previous study, it has been demonstrated that DNA self-assembly is primarily driven by thermodynamics and the assembly kinetics is not considered. To reach such stable states at equilibria, prolonged annealing duration is needed. In addition, there are cases where the desired structures could not compete with alternative structures. For example, a single-stranded DNA with a palindromic sequence quickly folds into a one-stranded hairpin instead of forming a two-stranded DNA duplex. Given that most of the DNA tiles are multi-stranded complexes, the kinetic trap represents a challenge to DNA self-assembly. To overcome this problem, we have developed a one-stranded motif that can intramolecularly and quickly fold from a single DNA strand and can be programmed to assemble into a range of nanostructures, including a one-dimensional (1D) ladder, a 1D chain, a two-dimensional (2D) array, and a three-dimensional (3D) triangular prism. All structures have been characterized by polyacrylamide gel electrophoresis (PAGE) and atomic force microscopy (AFM) imaging.

Effects of intercritical annealing process on microstructures and tensile properties of cold-rolled 7Mn steel

Influences of intercritical annealing temperature and duration on the microstructures and tensile properties of a newly designed medium Mn steel, Fe-7wt% Mn-0.3wt%C-2wt% Al, have been studied and discussed in this paper. Two types of cold-rolled ferritic microstructures, i.e. cell-like and lath-like, could transform to granular and lamellar austenite grains respectively during the subsequent intercritical annealing (IA). Both the IA temperature and duration strongly affect the fraction of retained austenite that have transformed during tensile deformation and the resultant tensile properties. In comparison with a Al-free 7Mn steel, it is found that the addition of Al has led to the reduced fraction but enhanced stability of RA grains; thus, they may transform gradually during deformation, which can make the maximum contribution to the sustainable work hardening. The developed steel exhibits the product of strength and plasticity up to 66GPa·%, which is much better than the Al-free 7Mn steel and almost one of the best tensile properties among the existing medium-Mn steels but with relatively lean alloying.

The Effect of Ar Ambient Pressure and Annealing Duration on the Microstructure, Superconducting Properties and Activation Energies of MgB2 Superconductors

MgB2 samples are produced by ex situ reaction method under vacuum, and various (0, 10, 20 Bar) Ar pressure for 0.5 and 1 h. The effect of ambient pressure and annealing duration on the microstructure and electrical properties of bulk samples are investigated. XRD, SEM, and magnetoresistance measurements are made. The a and c lattice parameters and the grain size values are the highest for the samples produced under vacuum and their values decrease with increasing Ar pressure. Moreover, these values increase when the annealing duration increases from 0.5 to 1 h. The increasing pressure reduces the bond lengths between the atoms thus the grain sizes decrease. Smaller grain size promotes the connection between grains which results in an increase of the critical current density (Jc). SEM micrographs reveal that the produced samples have granular structure which is a characteristic feature of MgB2. The decrease of grain sizes and thus enhancement in grain connectivity with increasing pressure is also confirmed by SEM images. Magneto resistivity measurements show that Tc values of the samples produced under vacuum are the highest. Tc values decrease with increasing ambient pressure and applied magnetic field. The activation energies (U0) of the samples are calculated using Arrhenius plots due to thermally activated flux flow theory. Existence and increase of Ar pressure causes increase of activation energies. The samples produced with 0.5-h annealing have higher activation energies than the ones produced with 1-h annealing.

The Fabrication of MgB&lt;sub&gt;2&lt;/sub&gt; Film and Nano-Bridge by EB and FIB

100nm thin Mg/B precursor films were prepared on SiC substrates in ZZSX-500 vacuum coating machine. They were annealed by electron-beam(EB) which only took fractions of a second. In this paper the best annealing duration to fabricate the superconducting MgB2 thin films was investigated. Under the optimized annealing condition(accelerating voltage 15kV, electron beam current 5mA, annealing duration 0.7s), the superconducting MgB2 thin film with critical temperature Tconset~35.3 K and transition width ∆Tc~1K was fabricated. Besides that, a nano-bridge (about 100×200nm2) was etched on the superconducting MgB2 thin film by Focused Ion Beam (FIB). It’s a relative simple and efficient method. The nano-bridge exhibited the effect of Josephson junction with RSJ characteristics. At the same time a little loss of superconducting property was detected.