Search

To meet the demands for high-temperature performance and lightweight materials in aerospace engineering, the Au-Ni solder is often utilized for joining dissimilar materials, such as Ti3Al-based alloys and Ni-based high-temperature alloys. However, the interaction between Ti and Ni can lead to the formation of brittle phases, like Ti2Ni, TiNi, and TiNi3, which diminish the mechanical properties of the joint and increase the risk of crack formation during the welding process. Cu doping has been shown to enhance the mechanical properties and high-temperature stability of the Au-Ni brazed joint's central area. Due to the difficulty in accurately controlling the solid solution content of Cu in the Au-Ni alloy, along with the high cost of Au, traditional experimental trial-and-error methods are insufficient for the development of Au-based solders. In this study, first principles calculations based on density functional theory were employed to analyze the effect of Cu content on the stability of the Au-2.0Ni-xCu (x = 0, 0.25, 0.5, 0.75, 1.0, 1.25 wt%) alloy phase structure. The thermal properties of the alloy were determined using Gibbs software fitting. The results indicate that the Au-2.0Ni-0.25Cu alloy exhibits the highest plastic toughness (B/G = 5.601, ν = 0.416, Cauchy pressure = 73.676 GPa) and a hardness of 1.17 GPa, which is 80% higher than that of Au-2.0Ni. This alloy balances excellent strength and plastic toughness, meeting the mechanical performance requirements of brazed joints. The constant pressure specific heat capacity (Cp) of the Au-2.0Ni-xCu alloy is higher than that of Au-2.0Ni and increases with Cu content. At 1000 K, the Cp of the Au-2.0Ni-0.25Cu alloy is 35.606 J·mol−1·K−1, which is 5.88% higher than that of Au-2.0Ni. The higher Cp contributes to enhanced high-temperature stability. Moreover, the linear expansion coefficient (CTE) of the Au-2.0Ni-0.25Cu alloy at 1000 K is 8.76 × 10−5·K−1, only 0.68% higher than Au-2.0Ni. The lower CTE helps to reduce the risk of solder damage caused by thermal stress. Therefore, the Au-2.0Ni-0.25Cu alloy is more suitable for brazing applications in high-temperature environments due to its excellent mechanical properties and thermal stability. This study provides a theoretical basis for the performance optimization and engineering application of the Au-2.0Ni-xCu alloy as a gold-based solder. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting, a sustainable method for hydrogen production, faces the challenge of slow oxygen evolution reaction (OER) kinetics. Iridium oxide (IrO2) is widely regarded as the most effective catalyst for OER due to its excellent properties. Compared to nanoparticles, IrO2 thin films exhibit significant advantages in OER, including a uniform and stable catalytic interface and excellent mechanical strength. This paper reviews recent advancements in one-step deposition techniques for the preparation of IrO2 thin films and their application in OER. Additionally, it analyzes the advantages and disadvantages of various methods and the latest research achievements, and briefly outlines the future trends and applications. [ABSTRACT FROM AUTHOR]

In this study, a HfO2 coating was developed on an Ir matrix using a customized open-tube airflow, cold-wall chemical vapor deposition instrument. The preparation process and structure of the as-prepared coating were investigated to gain insights into its characteristics. The HfO2 coating effectively prevents direct contact between Ir and O, leading to a reduction in the oxidation rate of Ir. Furthermore, defects such as micropores and cracks generated during sealed oxidation erosion contribute to Ir's decelerated oxidation failure. The as-prepared HfO2 coating exhibits low thermal conductivity and a high heat radiation rate, reducing the coating's surface temperature. These characteristics significantly enhance adversity tolerance and increase the working temperature of the coating. Moreover, the as-prepared HfO2 coating can serve as a diffusion barrier, blocking both the direct contact of O with the Ir coating and the diffusion of other elements to the Ir coating. As a result, the rates of diffusion of other elements to the Ir coating are reduced. [ABSTRACT FROM AUTHOR]

The lattice parameters, bulk modulus, shear modulus, Young's modulus and other mechanical constants of Ir-xRh (x=0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 17, 20, 22, 25, 27, 30) alloys were calculated by using the first-principles analysis method based on density functional theory. The calculation model is established by the virtual crystal potential function approximation method. The effect of Rh doping on the mechanical properties of Ir-Rh alloy was also analyzed from the electronic point of view by calculating the enthalpy change value, electron density of state and energy band structure. The results show that the strength and hardness of the material can be improved by doping a small amount of Rh in Ir. The peak point at Ir-5Rh decreases slightly and then continues to rise, reaching the maximum at Ir-10Rh, and the value is basically the same as that of Ir-5Rh. With the increase of Rh content, the absolute value of enthalpy changed gradually increased from 0.186 eV to 0.634 eV, and the thermodynamic stability of Ir-Rh alloy was improved. In addition, the density of states and band structure of Ir-Rh alloy show that the bond energy increases with the increase of Rh content, and the brittleness of Ir-Rh alloy increases gradually. [ABSTRACT FROM AUTHOR]

Genes significantly altered at both the DNA hydroxymethylation and transcription expression levels were identified as epigenetic biomarkers of cold and heat syndromes of RA and the correlation was preliminarily analyzed. Cold indicates patients with rheumatoid arthritis (RA) cold syndrome. In conclusion, our study confirmed that unique epigenetic biomarker genes of cold and heat syndromes of RA exist, and these genes, together with the encoded proteins, constitute the "disease-syndrome-biomarker" epigenetic regulatory network. [Extracted from the article]

ABSTRACT A 4 x 4 factorial experiment was conducted to determine the effects of salinity (0.2 ‰, 11 ‰, 21 ‰, and 31 ‰) and temperature (20°C, 24°C, 28°C, and [...]

ABSTRACT The culture of Litopenaeus vannamei in low-salinity waters is now popular in many regions of the world, A 6 x 3 factorial experiment was conducted to determine the effects [...]