Annealing Temperatures In Excess Research Articles

Purifying VO2 phase synthesized by sol-gel method via annealing process

Vanadium dioxide (VO2) film has significant interesting phase transition properties called metal-semiconductor transition (MST) which occurs at 68 °C. This transition behavior makes it suitable for various applications, including thermochromic materials for smart windows, sensors, and electronics devices. In this study, we aimed to focus on the purification of VO2 through the sol-gel synthesis method from vanadium alkoxide (VO(OC3H7)3. To analyze the effects of annealing temperature (500 °C-600 °C) on the resulting structural, morphology, and electrical properties, x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), temperature dependent resistance, and infrared (IR) thermal image were considered. The resistance as a function of the temperature shows an abrupt change confirming the phase transition. However, XRD shows an impurity of other vanadium oxides such as V6O13. In addition, the sample annealed at 600 °C shows a non-uniform surface filled with island clusters, while the sample annealed at 500 °C has a smooth and uniform surface. Raman spectra further supports the formation of VO2 (M) clusters mixed with V6O13 in smooth area, resulting in a decrease in electrical properties, significant reduced resistance change at the excessive annealing temperature.

Impact of nitrogen annealing on the electrical properties of HgCdTe epitaxial films

The nitrogen annealing of HgCdTe materials grown by molecular beam epitaxy (MBE) was carried out to manipulate their electrical properties. The results show that the annealing temperature, annealing time and cooling process all have significant influences on the electrical properties of HgCdTe materials. Excessive annealing temperature or long annealing time can make voids emerge on the surface of the CdTe passivation layer. Carrier concentration and mobility vary exponentially with annealing time and they reach an equilibrium value determined by annealing temperature over a long annealing duration. Moreover, time constants are given and a longer time is needed for mobility to reach an equilibrium value than carrier concentration. The relationship between equilibrium carrier concentration and annealing temperature is given and the activation energy under nitrogen annealing is calculated as 0.63 eV. For a long cooling duration, Hg vacancies are annihilated by Hg atoms diffusion, which makes carrier concentration lower and mobility higher. In addition, some outlier data were found in this experiment and explained by the combination between Te antisites and Hg vacancies.

The Influence of Annealing on the Microstructural and Textural Evolution of Cold-Rolled Er Metal.

The microstructural and textural evolution of 60% cold-rolling-deformation Er metal (purity ≥ 99.7%) during annealing were investigated by electron-backscattered diffraction (EBSD) and X-ray diffraction (XRD). The research results showed that the texture of the (0001) plane orientation was strengthened, but there was no apparent enhancement of the (011¯0) and (1¯21¯0) plane orientations with increasing the annealing temperature. The recrystallization frequency and grain sizes gradually stabilized after the annealing duration of more than 1 h at 740 °C; the annealing duration and the recrystallization frequency were fitted to the equation: y=1 - exp (-0.3269x0.2506). HAGBs were predominant, and the distribution of grain sizes was the most uniform after annealing at 740 °C × 1 h, which was the optimal annealing process of the Er metal with 60% cold-rolling deformation. However, the recrystallization was transferred to the substructure due to grain boundary migration and twining under an excessive annealing temperature and duration.

A pressure-assisted annealing method for high quality CsPbBr3 film deposited by sequential thermal evaporation.

All-inorganic CsPbBr3 perovskite solar cells have triggered incredible interest owing to their superior stability, especially under high temperature conditions. Different from the organic–inorganic hybrid perovskites, inorganic CsPbBr3 perovskite always need a high annealing temperature for the formation of a cubic phase. Generally, the higher temperature (over 300 °C) and longer annealing time will promote the growth of CsPbBr3, resulting in larger grain sizes and lower trap density in the crystals. However, CsPbBr3 perovskite can also be damaged by excessive annealing temperature (∼350 °C) and time, since PbBr2 only has a melting temperature close to 357 °C. To address this issue, herein, we developed a novel pressure-assisted annealing method to prevent the sublimation of PbBr2 at high temperature. The CsPbBr3 films were firstly deposited by sequential thermal evaporation, and then annealed at 335 °C in an alloy pressure vessel. By controlling the pressure of the vessel, we obtained CsPbBr3 films with various morphologies. At normal atmospheric pressure, the as-prepared CsPbBr3 film exhibited small grain sizes and was full of pinholes. With the increase of annealing pressure, the grain sizes of the film showed a significant increasing trend, and the pinholes gradually vanished. When the pressure value came to 10 MPa, compact and uniform CsPbBr3 films with large grain sizes were obtained. Based on these films, CsPbBr3 perovskite solar cells with FTO/compact-TiO2/CsPbBr3/carbon architecture achieved a champion power conversion efficiency of 7.22%.

Problems of Pad Welding Structural Steels with Martensitic Filler Metal

Abstract There is a problem in obtaining a suitable impact strength of the padding weld after cladding with a martensitic filler metal. Too low annealing temperature below 580°C and the excessive annealing temperature above 650°C do not provide adequate impact strength of the padding weld. A heat treatment technology for mixed joints has been developed based on the results of the microscopic observations, X-ray diffraction measurements and transmission electron microscope examination. The problem was identified and a special technology of heat treatment for the dissimilar joint was elaborated. This technology provides a high impact resistance of the padding weld and an appropriate properties of the base material.

Transgranular region preference of crack propagation along Bi-2212 crystal structure due to Au nanoparticle diffusion and modeling of new systems

This study delves into the changes of mechanical performances and mechanical characteristics of Bi-2212 inorganic materials exposed to the Au nanoparticles diffusion with respect to annealing temperature in the range from 923 K (650 °C) to 1123 K (850 °C) by means of Vickers hardness measurements at different applied indentation test loads (0.245 N ≤ F ≤ 2.940 N) and theoretical approaches. It is found that the mechanical performances belonging to the Bi-2212 superconductors improve considerably with the enhancement of the diffusion annealing temperature of 1073 K (800 °C) as a consequence of the reduced disorders in orientation of adjacent layers, lattice strains, local structural distortions, defects and grain boundary couplings. Existence of Au inclusions in the system, accordingly, makes the critical stress values augment for the diversion of crack-initiating flaws, crack and dislocation propagation. In other word, the optimum annealing temperature of 1073 K (800 °C) leads to develop the mechanical durability, fracture toughness and flexural strength towards the static compression loads as a consequence of the stabilization of durable tetragonal phase. Nevertheless, the excess annealing temperature causing the further Au impurities inserted in the Bi-2212 crystal structure serves as the stress raisers and crack initiation sites. Thus the induced cracks, voids and dislocations reach immediately to the critical propagation speed and the propagation of induced cracks, voids and dislocations is difficult to control. At the same time, the experimental findings enable us to determine the variation of mechanical characteristic properties as regards elastic modulus, yield strength, fracture toughness, elastic stiffness coefficient and brittleness index parameters. Based on the results of elastic modulus and yield strength parameters, the optimum Au foreign additives in the Bi-2212 crystal lattice degrade the limited number of operable slip systems. This is attributed to the fact that the crack propagation more proceeds throughout the transgranular regions. Conversely, the excess annealing temperature results in the increment of intergranular fracture. As for the theoretical examinations, all the materials prepared shows typical indentation size effect (ISE) feature as a result of reversible (elastic) and irreversible (plastic) deformations simultaneously. Moreover, Hays–Kendall (HK) theoretical approach is observed to be the best model for determination of the real mechanical characteristics for the pure and Au surface-layered Bi-2212 superconducting materials.

Structural and optical properties of nano-crystalline ZnO thin films synthesized by sol–gel method

Nano-crystalline ZnO thin films on glass substrates have been prepared by sol–gel method at annealing temperatures of 300–550 °C. Zinc acetate, anhydrous ethanol, and mono-ethanolamine were used as raw materials. The thermal behaviors curves of the dried gel were examined and found that evaporation of solvent and the decomposition of the organics have completed before 250 °C. The effect of thermal annealing on structural and optical properties was investigated. X-ray diffraction patterns showed the gradual increase in orientation of (0 0 2) along c-axis. The transmittance spectra revealed the high transmission (T > 80% above annealing 400 °C) in visible region. The optical band gap (E g) of the samples is in the range from 3.24 to 3.28 eV. The photoluminescence spectra in ultraviolet were studied and found the continuous increased intensity of peaks at 387 and 393 nm respectively from intrinsic emission and near the band edge emission. Surface micrographs was observed by the atomic force microscopy and found the larger grain size and the compacter morphology before 500 °C. However, the excessive annealing temperature at 550 °C deteriorated the structural and optical properties of the samples. The transmittance is still enhanced as rising annealing temperature up to 500 °C which is more attributed to the decrease in grain boundaries and defect concentration. The poor transmission of films annealed at low temperatures is attributed to unsatisfactory crystalline quality. The stable and high transparency (>80%) in the visible region is presented above 400 °C. The UV–Vis transmittance spectra of ZnO thin films at different annealing temperature.

Influence of post-weld heat treatment (PWHT) on the structure and properties of welded joints of chromium–nickel stainless steel with soft martensite

This paper reviews the results of investigations on how post-weld heat treatment (PWHT) influences the hardness and microstructures of welded joints in stainless steel X3Cr-NiMo 13-4. It is known that welding leads to high segregation of components in the solidification process, which has an influence on phase transitions in PWHT. The investigated steel has a very narrow PWHT range, about 600–620°C, which provides optimum levels of hardness and toughness. Excessive annealing temperature leads to decreased toughness, which in turn causes exceeding of the Ac1 temperature in the segregation range, which then leads to increased ‘fresh’ martensite content.

AN INTENSITY TESTING MODEL AND EXAMINATION OF GOLD–SILICON WAFER BONDING

A bonding intensity testing method, called Press-arm model, has been successfully designed and verified by Ansys finite element analysis. The gold–silicon bonding strength [σ2] = 238 MPa has been measured by the Press-arm model. We can probably determine the [σ2] value and compare the bonding strengths by the Press-arm length l. The model can also be used in other type of bonding. The bond region is sufficiently stronger than the silicon substrate. A substrate- Si/Cr/Au/poly - Si/Au and a silicon substrate is bonded at 380–450°C. It occurs as soon as the dissolving of the SiO 2 layer by silicidation of the Cr barrier layer. To avoid gold contamination to the silicon die, an excess annealing temperature (about 20°C higher than Au – Si eutectic horizontal) is used. The bonding surface with brick pattern is in favor of Au – Si bonding.

Structure and magnetic properties of melt-spun PrFe10Mo2Nx compounds

The structure and magnetic properties of PrFe10Mo2Nx compounds prepared by melt spinning have been investigated. A single-phase structure of ThMn12-like has been obtained in ribbons quenched at velocities vs below 40 m/s. The desired ThMn12 structure is considerably more stable for Pr(Fe, Mo)12 compounds than for Nd(Fe, Mo)12 compounds. Only at higher speeds than 50 m/s the PrFe10Mo2 ribbons quench into TbCu7-like compound of which Curie temperature is about 580 K. Annealing temperatures in excess of 1023 K are required to form ThMn12 crystal structure for the ribbons melt spun at 50 m/s. Upon nitrogenation at 723 K, the Curie temperatures increase to 663 and 580 K for TbCu7- and ThMn12-like nitrides, respectively. A coercivity of 3.3 kOe with a magnetization up to 118 emu/g at a field of 20 kOe has been obtained in the present ribbons.

Electron Spin Resonance and Thermoluminescence Dosimetry of Clear Fused Quartz: Its Possible Use for Personal, High Dose and High Temperature Dosimetry

The thermoluminescence (TL) properties and electron spin resonance (ESR) response of clear fused quartz (CFQ) have been studied. Small cylindrical samples of CFQ were exposed to a range of doses from a 60 Co source and then subjected to TL readout or ESR measurement. It was found that the minimum detectable dose (i.e. the dose which corresponds to twice the standard deviation of the background signal) is about 40 μGy for TL and about I Gy for ESR (three scans being accumulated at room temperature). The TL response of the samples exhibits good linearity at doses of up to 250 Gy, above which the signal rapidly saturates. The ESR response is linear up to a dose of about 200 Gy and sub-linear up to the largest evaluated dose of 3 X 10 4 Gy. Annealing studies have shown that the TL signal is reduced by more than two orders of magnitude following heating at 300°C for 20 min. At this temperature the ESR signal is reduced by only about 30% and remains measurable following annealing temperatures in excess of about 600°C. These results for CFQ suggest that TL can be used for personal dosimetry and ESR for high dose and high temperature dosimetry.