Annealing Rate Research Articles

Direct Hydrogen Production Promoted by Laser-Induced Water Plasma.

Hydrogen, as a clean energy carrier, plays an important role in addressing the current energy and environmental crisis. However, conventional hydrogen production technologies require extreme reaction conditions, such as high temperature, high pressure, and catalysts. Herein, we study the microscopic mechanism of laser-induced water plasma and subsequent H2 production with real-time time-dependent density functional theory simulations and ab initio molecular dynamics simulations. The results demonstrate that intense laser excites liquid water to generate nonequilibrium plasma in a warm-dense state, which constitutes a superior reaction environment. Subsequent annealing leads to the recombination of energetic reactive particles to generate H2, O2, and H2O2 molecules. Annealing rate and laser wavelength are shown to modulate the product ratio, and the energy conversion efficiency can reach ∼9.2% with an annealing rate of 1.0 K/fs. This work reveals the nonequilibrium atomistic mechanisms of hydrogen production from laser-induced water plasma and shows far-reaching implications for the design of optically controllable hydrogen technology.

Influence of Graphene on Sheet Resistivity and Urbach Enery of Nano TiO<sub>2</sub> for DSSC Electrode

Importance of renewable energy cannot be over emphasized. Titanium IV oxide (TiO<sub>2</sub>) is the most suitable semiconductor for dye sensitized solar cell (DSSC) due to its chemical stability, non toxicity and excellent optoelectronic properties. In this research TiO<sub>2</sub> is coated on graphene to enhance its charge transport aiming to reduce recombination which is a main set back in DSSCs. undestanding graphene- TiO<sub>2 </sub>contact is therefore essential for DSSC application. TiO<sub>2</sub> thin films were deposited on single layer graphene (SLG) as well as on flourine tin oxide (FTO) using doctor blading technique. The films were annealed at rates of 2°C /min and 1°C/min up to a temperature of 450°C followed by sintering at this temperature for 30 minutes. Four point probe SRM-232 was used to measure sheet resistance of the samples. The film thickness were obtained from transmittance using pointwise unconstrained minimization approximation (PUMA). UV –VIS spectrophotometer was employed to measure transmittance. Resistivity of TiO<sub>2</sub> on both FTO and Graphene were of order 10<sup>-4</sup> Ωcm. However, TiO<sub>2</sub> annealed on graphene matrix exhibited a slightly lower resistivity 5.6 x10<sup>-4</sup> Ωcm as compared to 6.0x10<sup>-4 </sup>Ωcm on FTO. Optical transmittance on visible region was lower for TiO<sub>2</sub> on FTO than on SLG, 71.48% and 80.11% respectively. Urbach energy (Eu) for weak absorption region decreased with annealing rate. Urbach energies for 1°C/min TiO<sub>2 </sub>on FTO and SLG were 361 meV and 261meV respectively. This was used to account for decrease of disoders of films due to annealing. A striking relation between sheet resistivity and urbach was reported suggesting SLG as a suitable candidate for photoanode of a DSSC.

Grain growth kinetics, phase evolution during annealing and strain rate sensitivity of TRIP-assisted, dual-phase, non-equiatomic high entropy alloy

Transformation-induced plasticity-assisted dual-phase high-entropy alloys (TRIP-DP-HEAs) belong to a recently developed class of HEAs. TRIP-DP-HEAs have been reported to exhibit superior strength-ductility combination at room temperature as well as at high temperatures. Small amounts of carbon additions to TRIP-DP-HEAs are known to further improve the strength as a result of interstitial solid solution and nanoprecipitate strengthening effects. Current investigation compares the grain growth kinetics in a metastable, dual-phase (FCC and HCP), Fe49.5Mn30Co10Cr10C0.5, carbon-containing high entropy alloy (C-DP-HEA) with that in the corresponding carbon-free variant, Fe50Mn30Co10Cr10 HEA (DP-HEA). The alloys after being subjected to cold rolling, were annealed at 900 °C, 1000 °C and 1100 °C for 3, 30, 60 and 120 min, followed by water quenching. Slower grain growth kinetics was observed in C-DP-HEA due to Zener pinning by carbide particles. The activation energy for grain growth in C-DP-HEA was determined to be 339.71 kJ/mol, which is larger than that of DP-HEA (282.68 kJ/mol). The microstructures of the C-DP-HEA samples, after annealing at 900 °C for different durations of times and quenching, were investigated. The HCP phase fraction in the microstructure initially decreased with increase in annealing time/grain size and later increased with further increase in annealing time/grain size. This is explained based on the counteracting effect of grain boundary density and back stresses acting in samples having increased grain size. Strain rate sensitivity (SRS) parameter, ‘m’, was evaluated for both C-DP-HEA and DP-HEA. The strain rate jump tests were conducted at two quasi-static strain rates, 1 × 10−3 s−1 and 5 × 10−3 s−1, and at room temperature as well as at higher temperatures, 900 °C, 1000 °C and 1100 °C. The ‘m’ value was found to depend on the grain size, test temperature, and the presence of carbon in the alloy.

Structural Causes of Brittleness Changes in Aluminosilicate Glasses with Different Cooling Rates.

Numerous sources have already demonstrated that varying annealing rates can result in distinct toughness and brittleness in glass. To determine the underlying mechanisms driving this phenomenon, molecular dynamic (MD) simulations were employed to investigate the microstructure of aluminosilicate glasses under different cooling rates, and then uniaxial stretching was performed on them under controlled conditions. Results indicated that compared with short-range structure, cooling rate has a greater influence on the medium-range structure in glass, and it remarkably affects the volume of voids. Both factors play a crucial role in determining the brittleness of the glass. The former adjusts network connectivity to influence force transmission by manipulating the levels of bridging oxygen (BO) and non-bridging oxygen (NBO), and the latter accomplishes the objective of influencing brittleness by modifying the environmental conditions that affect the changes in BO and NBO content. The variation in the void environment results in differences in the strategies of the changes in BO and NBO content during glass stress. These findings stem from the excellent response of BO and NBO to the characteristic points of stress-strain curves during stretching. This paper holds importance in understanding the reasons behind the effect of cooling rates on glass brittleness and in enhancing our understanding of the ductile/brittle transition (DTB) in glass.

Study on the effect of annealing rate on the impact resistance of the H-ZLaF50 vehicle plate glass

The H-ZLaF50 glass has attracted much attention in the field of automotive glass applications due to its excellent mechanical properties. The effect of the annealing rate on the impact resistance of the H-ZLaF50 glass was studied. High-precision infrared stress meter was used to test the stress distribution of glass under different annealing rates and the influence of annealing rate on the stress distribution was found. Secondly, the impact resistance of the H-ZLaF50 glass samples was evaluated by the test method of electric falling ball impact resistance. The maximum impact energy of the H-ZLaF50 glass samples was 0.120 J. The results show that, compared with other annealing rates, the annealing rate of 1°C/min effectively improves the impact resistance of the H-ZLaF50 glass, which makes it more widely used in the automotive flat glass market.

Multiscale Process Modeling of Semicrystalline PEEK for Tailored Thermomechanical Properties.

Polyether ether ketone (PEEK) is a semicrystalline thermoplastic that is used in high-performance composites for a wide range of applications. Because the crystalline phase has a higher mass density than that of the amorphous phase, the evolution of the crystalline phase during high-temperature annealing processing steps results in the formation of residual stresses and laminate deformations, which can adversely affect the composite laminate performance. Multiscale process modeling, utilizing molecular dynamics, micromechanics, and phenomenological PEEK crystal kinetic laws, is used to predict the evolution of volumetric shrinkage, elastic properties, and thermal properties, as a function of crystalline phase evolution, and thus annealing time, in the 306-328 °C temperature range. The results indicate that lower annealing temperatures in this range result in a faster evolution of thermomechanical properties and shrinkage toward the pure crystalline values. Therefore, from the perspective of composite processing, it may be more advantageous to choose the higher annealing rates in this range to slow the volumetric shrinkage and allow PEEK stress relaxation mechanisms more time to relax internal residual stresses in PEEK composite laminates and structures.

Tensile stress regulated microstructures and ferroelectric properties of Hf0.5Zr0.5O2 films

The discovery of ferroelectricity in HfO2 based materials reactivated the research on ferroelectric memory. However, the complete mechanism underlying its ferroelectricity remains to be fully elucidated. In this study, we conducted a systematic study on the microstructures and ferroelectric properties of Hf0.5Zr0.5O2 (HZO) thin films with various annealing rates in the rapid thermal annealing. It was observed that the HZO thin films with higher annealing rates demonstrate smaller grain size, reduced surface roughness and a higher portion of orthorhombic phase. Moreover, these films exhibited enhanced polarization values and better fatigue cycles compared to those treated with lower annealing rates. The grazing incidence x-ray diffraction measurements revealed the existence of tension stress in the HZO thin films, which was weakened with decreasing annealing rate. Our findings revealed that this internal stress, along with the stress originating from the top/bottom electrode, plays a crucial role in modulating the microstructure and ferroelectric properties of the HZO thin films. By carefully controlling the annealing rate, we could effectively regulate the tension stress within HZO thin films, thus achieving precise control over their ferroelectric properties. This work established a valuable pathway for tailoring the performance of HZO thin films for various applications.

Convergence rates for ansatz‐free data‐driven inference in physically constrained problems

AbstractWe study a Data‐Driven approach to inference in physical systems in a measure‐theoretic framework. The systems under consideration are characterized by two measures defined over the phase space: (i) A physical likelihood measure expressing the likelihood that a state of the system be admissible, in the sense of satisfying all governing physical laws; (ii) A material likelihood measure expressing the likelihood that a local state of the material be observed in the laboratory. We assume deterministic loading, which means that the first measure is supported on a linear subspace. We additionally assume that the second measure is only known approximately through a sequence of empirical (discrete) measures. We develop a method for the quantitative analysis of convergence based on the flat metric and obtain error bounds both for annealing and the discretization or sampling procedure, leading to the determination of appropriate quantitative annealing rates. Finally, we provide an example illustrating the application of the theory to transportation networks.

Magnetic, DC Electrical, and Impedance Properties of Zn Doped Yttrium Iron Garnet Nanoparticles

Y3Fe5-xZnxO12 with x = 0; 0.02; 0.04; 0.06; 0.08; 0.1 (YIG) particle materials were fabricated by sol-gel method combined with heat treatment at 900 °C and 1,000 °C with different annealing times (2 h and 5 h) and heating rates (5 °C/min and 2 °C/min). X-ray diffraction patterns show that the obtained samples are single crystalline phases at the condition of an annealing temperature of 900 °C for 5 h and a heating rate of 2 degrees/min. FESEM images of the samples show particle sizes from the submicron to the micrometer. The magnetization of the samples decreases as the doping concentration increases. I-V characteristics and complex impedance spectra at room temperature of samples were measured. The results show that the resistivity value of the doped samples decreases in the range of 5-6 orders in magnitude compared with that of the pure YIG sample. The contribution of the grain boundaries to the impedance was analyzed. The conducting process is explained due to the tunneling of charge carriers across the grain boundary.

Enhancing performance in organic solid structures and heat transfer with single annealing process and variable rates

Molecular dynamics has been widely adopted in a variety of fields, especially for organics. Annealing is an extensively used model-optimization method that can be found in many studies. However, how to achieve the best-annealed model within limited calculation time has not been studied. Therefore, using n-octadecane as an example, we investigated the effect of annealing on the structure and properties within the same calculation time. Two different types of annealing were performed. One was multiple cycles with uniform annealing rates, the other was a single cycle with variable annealing rates. The degree of order in the molecule and the system was characterized by the radius of gyration and X-Ray diffraction, and the mechanism was explained through density variation. The effect of annealing on the properties was investigated by simulating thermal conductivity and the reasons were analyzed using vibration power spectra. The results showed that at the same calculation time, a single annealing cycle with a reduced annealing rate of the solid phase can achieve a better structure. If the annealing rate is higher than the initial cooling rate, the system structure will be damaged. The well-annealed system exhibited serious overheating and slight supercooling, and had a high thermal conductivity. Annealing can affect the intensity of the characteristic peak, but it does not change its frequency. The value of thermal conductivity is positively correlated with the total intensity of characteristic peaks. Our study aims to guide future simulations involving annealing processes to significantly improve the accuracy of solid-state models and prevent structural damage caused by improper annealing operations.

Postannealing Temperature Effects on the Etching Behavior and Field Emission Properties of Cu‐Implanted Diamond

To investigate the postannealing temperature effects on the surface etching behavior and electron field emission (EFE) properties of the Cu‐implanted microcrystalline diamond (MCD) films, they are subjected to furnace annealing in a temperature range of 600–900 °C under N2 atmosphere at a rapid annealing rate. The etching behavior happens when the samples are annealed at 700 °C and above. The EFE performances enhance first and then decrease with the increasing annealing temperature. The optimum EFE property with a low turn‐on field of 6.42 V μm−1 is obtained after the Cu‐implanted MCD film is annealed at 700 °C. The enhancement in EFE properties originates from the presence of nanographitic phase and the formation of electron‐rich Cu nanoparticles, which encourage a higher efficient electron transport. In contrast, the structural studies reveal that when the samples annealed at 800 °C and above, Cu nanoparticles evaporate from the diamond surface and the sp2‐bonded carbon decomposes. Consequently, etch pits appear on the surface of the MCD sample. Moreover, it demonstrates that graphitization is the dominant mechanism of the diamond surface etching behavior and the enhancing of EFE properties.

In-situ investigation of solid phase evolution during lyophilization of mannitol-based antibody formulations using an XRPD climate chamber

Crystalline mannitol is commonly used as bulking agent in antibody formulations to provide structure to the lyophilized cake and prevent collapse. Depending on the lyophilization process conditions mannitol can either crystallize as α-, β-, δ-mannitol, mannitol-hemihydrate, or transition to its amorphous state. While crystalline mannitol helps to create a firmer cake structure this is not true for amorphous mannitol. The hemihydrate is also an undesired physical form as it may reduce the drug product stability by releasing bound water molecules into the cake. Our aim was to simulate lyophilization processes in an X-ray powder diffraction (XRPD) climate chamber. In the climate chamber, the process can be carried out fast with low sample quantities to determine optimal process conditions. Insights on the emergence of desired anhydrous mannitol forms helps to adjust the process parameters in larger scale freeze-dryers. In our study we have identified the critical process steps for our formulations and then varied relevant process parameters, which were the annealing temperature, annealing time and temperature ramp rate of the freeze-drying process. Furthermore, the effect of the presence of antibodies on excipient crystallization was investigated by performing the studies on placebo solutions versus two respective antibody formulations. A comparison of the products obtained in a freeze-dryer and the simulated process in the climate chamber showed good accordance demonstrating the method as suitable tool to identify ideal process conditions on a laboratory scale.

Annealing Rate as a Crucial Parameter Controlling the Photoelectrochemical Properties of AuCu Mosaic Core–Shell Nanoparticles

Thermal processing is an essential step during the synthesis of various metal nanostructures and for tailoring their morphology, optical, and electrochemical properties. Herein, a profound impact of the annealing rate and time on photoactivity of gold–copper nanostructures by changes in the position and alignment of energy levels and surface states is reported. AuCu nanoparticles (NPs) are fabricated by sputtering of thin metal layers on the Ti nanopatterned foil followed by slow (0.67 °C s−1) or fast (30 °C s−1) treatment in the rapid thermal annealing furnace and then utilized as photoanodes. Photocurrent in the visible range of the slow‐heated AuCu materials is 77 times higher, whereas for the fast heated 24 times higher than for pure Ti platform. On the other hand, the fast‐heated material exhibits higher photon‐to‐current efficiency, longer recombination rate which reaches 10s, and higher carrier transport rate of 150 μs. Based on the simulated projected local density of states analysis and the characteristics of intensity‐modulated spectra, this phenomenon is attributed to the presence of deeper midgap states in the electronic band structure for the fast‐heated samples. Furthermore, photocurrent is enhanced by the presence of Au inside NPs, which increases tunneling across copper oxides junction.

Intrinsic properties of anodic TiO2 nanotube layers: In-situ XRD annealing of TiO2 nanotube layers

In this work, in-situ annealing of TiO2 nanotube (TNT) layers in an XRD chamber was carried out to investigate the crystallization process of the TNT layers in details. TNT layers of different thicknesses, i.e. 1, 5 and 20 μm, and of different morphology, i.e. double wall vs. single wall, were annealed in the temperature range from room temperature to 500 °C with two distinctly different annealing rates. Additionally, three different annealing atmospheres were explored, namely air as an oxidative, N2 as an inert, and 5%H2/95%N2 as a reductive atmosphere. XRD patterns were measured every 15 °C of the heating ramp and the crystallite sizes of anatase phase were calculated from the anatase peak using Scherer equation at each data point. The differences in crystallization behavior for the different TNT layers as well as the effect of the annealing atmosphere for 5 μm thick TNT layers are described and discussed.

Initial ice growth control mechanism for CMC-Na in model systems

In this study, CMC-Na solutions with different DS and concentrations were frozen at −20 °C and −40 °C. At the macroscopic level, the nucleation temperature and nucleation start time were analysed by freezing curves, and the morphology, size, and quantity of ice crystals after recrystallization were captured dynamically at the microlevel. The results show that CMC-Na can effectively accelerate the nucleation process, shorten the phase transition time, and evenly promote the formation of numerous distributed small ice crystals, and there is no significant difference in the effect of CMC-Na at different freezing temperatures. At the microlevel, a high concentration of CMC-Na can inhibit the recrystallization process more effectively, probably because it is readily attached to the surface of ice crystals, and the reduction in surface tension increases the free energy, which prevents the growth of ice crystals. When CMC-Na is added to the ice cream system, it can reduce the nucleation temperature, increase the degree of supercooling, and promote the internal generation of abundant ice crystals. At the same annealing rate, CMC-Na can effectively inhibit the occurrence of recrystallization, which is consistent with the conclusion of the solution system.

The effect of repeat length on Marcal1-dependent single-strand annealing in Drosophila.

Proper repair of DNA double-strand breaks is essential to the maintenance of genomic stability and avoidance of genetic disease. Organisms have many ways of repairing double-strand breaks, including the use of homologous sequences through homology-directed repair. While homology-directed repair is often error free, in single-strand annealing homologous repeats flanking a double-strand break are annealed to one another, leading to the deletion of one repeat and the intervening sequences. Studies in yeast have shown a relationship between the length of the repeat and single-strand annealing efficacy. We sought to determine the effects of homology length on single-strand annealing in Drosophila, as Drosophila uses a different annealing enzyme (Marcal1) than yeast. Using an in vivo single-strand annealing assay, we show that 50 base pairs are insufficient to promote single-strand annealing and that 500-2,000 base pairs are required for maximum efficiency. Loss of Marcal1 generally followed the same homology length trend as wild-type flies, with single-strand annealing frequencies reduced to about a third of wild-type frequencies regardless of homology length. Interestingly, we find a difference in single-strand annealing rates between 500-base pair homologies that align to the annealing target either nearer or further from the double-strand break, a phenomenon that may be explained by Marcal1 dynamics. This study gives insights into Marcal1 function and provides important information to guide the design of genome engineering strategies that use single-strand annealing to integrate linear DNA constructs into a chromosomal double-strand break.

Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

Study on Filling Capacity of Optical Glass in a Novel Rapid Hot Embossing Process

This paper aims to present a novel rapid hot embossing approach and to study filling capacity of optical glass in the hot embossing process. Firstly, a novel rapid hot embossing device is developed, which consists of a rapid heating module and a precision loading module. Particularly, the rapid heating module allows a maximum temperature of 800 °C and a heating rate of 300 °C/min, with decent temperature control accuracy and uniform temperature distribution. In hot embossing process, by incompletely filling the microhole of silicon carbide mold, a microlens would be formed on the surface of glass disc, and the filling capacity of glass is quantified by the maximum height of the microlens. The tailor-made hot embossing device was exploited to conduct a series of experiments for evaluating effects of process parameters on the filling capacity of N-BK7 glass. Experimental results indicate that the filling capacity of glass could be enhanced by increasing the embossing force, the embossing temperature, the soaking time but decreasing the annealing rate. Furthermore, compared to soaking time and annealing rate, embossing force and embossing temperature have more significant influence on the filling capacity of N-BK7 glass. Therefore, the novel rapid hot embossing is a practical and promising technology for fabricating microstructures on glass materials with high softening points.

Effects of Bias and Temperature on Interface-Trap Annealing in MOS and Linear Bipolar Devices

This article reviews the effects of applied bias and temperature on Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface-trap buildup and annealing rates. Electrical and spectroscopic methods are described to estimate interface-trap densities at oxidized Si surfaces, in MOS capacitors and transistors, and in linear bipolar devices. Illustrative results provide insights into the kinetics and energetics of interface-trap annealing. Interface traps in MOS and linear bipolar devices anneal much more easily at 0 V bias than at positive or negative applied bias. Hydrogen transport and reactions play critical roles in interface-trap buildup and annealing processes. The complex interplay between H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> diffusion and H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> drift is illustrated via coupled experimental and theoretical studies. Interface-trap annealing imposes significant constraints on hardness-assurance techniques. Current MOS standard tests that incorporate accelerated aging at elevated temperature at worst case, static, positive bias enable successful assessment of MOS devices in low-dose-rate environments. However, it is not similarly possible to use elevated-temperature irradiation and/or annealing at worst case, 0 V bias to predict low-dose-rate response for linear bipolar devices and ICs. Temperature-switching during irradiation appears to be a promising approach to address this issue.

Sol-Gel Synthesis of Multifunctional Bismuth Ferrite Nanostructures: Effect of Heating Conditions on their Photocatalytic Activity

Bismuth ferrite (BiFeO3) is a multifunctional perovskite material well-known for its lead-free chemistry, multiferroic properties at room temperature, photovoltaic properties, and photocatalytic activity. BiFeO3 nanostructures were synthesized using sol-gel method by varying annealing temperature and annealing rate. The formation of phase-pure BiFeO3 was confirmed using X-ray diffraction and Raman spectroscopy.Using scanning electron microscopy, the size of BiFeO3nanostructures was evaluated to be around 100-500 nm depending on the annealing parameters. The bandgap of the synthesized nanostructures was estimated to be 2.18-2.26 eV, with UV diffuse reflectance spectroscopy. The photocatalytic activity was assessed by the degradation of malachite green dye under visible light irradiation and their correlation with heating parameters is discussed in detail.