Open Access
Article
15 September 2025Heat Resistance of Centrifugally Cast Tubes Made of 32%Cr-43%Ni Refractory Alloy and Its Welded Joints at Temperatures up to 1150 °C
The results of microstructura l analysis, short-term and long-term strength tests of modified sparingly alloyed refractory alloy of 32%Cr-43%Ni and its welded joints are presented. A quantitative analysis of the dispersed phases in the initial state and after long-term strength tests has been carried out. It is shown that the network of carbide-intermetallic precipitates persists after long-term strength tests at a temperature of 1150 °C. This ensures the ability of the developed alloy and its welded joints to withstand high-temperature creep for a long time. It has been established that after long-term strength tests at a temperature of 1150 °C, niobium carbide particles present in the base metal and weld metal are almost completely transformed into an intermetallic phase based on Cr-Ni-Si-Nb-N. The penetration of atmospheric nitrogen into the metal stimulates this process.
Open Access
Review
29 September 2025Review of Gallium Nitride Devices and Integrated Circuits at High Temperatures
In various industrial applications, including aviation, electric vehicles, and drilling, the demand for semiconductor devices and associated circuits with high thermal stability is progressively increasing. Wide-bandgap semiconductor Gallium Nitride (GaN) devices exhibit the advantages of fast switching capability, low on-resistance, and the ability to operate at high temperatures. These advantages have made them potential candidates for integrated circuits in high-temperature environments in recent years. Lateral GaN devices promote monolithic integration, which consequently increases power density and reduces cost of cooling systems. Hence, it is worthwhile to investigate the performance of GaN devices in high-temperature environments. This review aims to present a thorough review of high-temperature characteristics of GaN devices and integrated circuits. The performance of GaN devices at high temperatures, such as threshold voltage，saturation current and on-resistance, has been reviewed in response to different structures. The underlying degradation mechanisms related to the intrinsic properties of structures and fabrication technology are discussed at high temperatures. The thermal performance of GaN small signal integrated circuits and power converters was presented. This paper systematically examines the advantages and challenges of GaN devices and integrated circuits at high temperature environments.
Open Access
Article
17 October 2025Enhancing Ablation Resistance of C/C-HfC-SiC Composites by In-Situ Growth of HfC Nanowires
C/C-HfC-SiC composites are promising ablation-resistant ultra-high temperature thermal protection materials. To further enhance their performance in extreme thermal environments, the introduction of HfC nanowires (HfCNWs) into the composite has been identified as an effective strategy. The quantity and morphology of the introduced HfCNWs significantly influence the ablation resistance of the composites. In this study, by controlling the concentration of Ni salt during the hydrothermal synthesis process, the loading amount of Ni catalysts on the surface of carbon fibers was regulated, thereby achieving control over the quantity and structure of HfCNWs in the C/C-HfC-SiC composites. It was found that a low Ni loading facilitates the growth of sparse and slender HfCNWs. As the Ni loading increases, the number of HfCNWs rises, gradually evolving into a high-density, multi-oriented network structure. However, excessive Ni tends to induce short, thick, and clustered growth of the nanowires. Based on this, three types of HfCNWs-modified C/C-HfC-SiC composites were prepared using the polymer impregnation and pyrolysis (PIP) process. The quantity and diameter of the HfCNWs significantly affect the ablation resistance of the composites. Among them, the composite prepared with a 4.38 wt% Ni loading exhibited excellent ablation resistance, with mass and linear ablation rates of 0.47 mg·s−1·cm−2 and 5.50 μm·s−1, respectively. The performance improvement is attributed to the formation of a continuous HfO2 skeletal structure after the oxidation of an appropriate amount of HfCNWs. This continuous HfO2 skeleton significantly enhances the ability of the oxide layer to resist high-speed gas flow erosion and oxygen penetration. This study can provide support for the design of HfCNWs-reinforced C/C-HfC-SiC composites and promote their engineering application in the field of aerospace thermal protection.
