Fabrication and plasma arc thermal shock resistance of HfB_2-based ultra high temperature ceramics

Two hafnium diboride based ceramic matrix composites containing 20% （volume fraction） SiC particle and with or without AIN as sintering additives were fabri,aated by hot-pressed sintering. The mechanical properties and microstructures of these two composites were tested and the thermal shock resistances were evaluated by plasma arc heater. The results indicate that the composite with A1N as sintering additive has a denser and finer microstructure than composite without sintering additive, and the mechanical properties, thermal shock resistance of the composite with A1N as sintering additive are also higher than those of the composite without A1N. Microstructure analysis on the cross-section of two composites after thermal shock tests indicates that a compact oxidation scale contains HfO2 and Al2O3 liquid phase is found on the surface of composite with A1N, which could fill the voids and cracks of surface and improve the thermal shock resistance of composite.

Design of the Vacuum Feedthrough for the EAST ICRF Antenna

Detailed design of the vacuum feedthrough for the ion cyclotron radio frequency （ICRF） antenna in EAST, along with an electro-analysis and thermal structural analysis, is pre- sented. The electric field, the voltage standing wave ratio （VSWR） and the stresses in the vacuum feedthrough are studied. A method using the rings of oxygen-free copper as the cushion and macro- beam plasma arc welding is applied in the assembly to protect the ceramic from being damaged during welding. The vacuum leak test on the prototype of vacuum feedthrough is introduced.

Improved Control Strategy for Carbonized Cable Preparation in Low-voltage Arc Fault Test

Outdated testing methods hinder the success rate of carbonized cable preparation in low-voltage arc fault tests,leading to incomplete tests and high failure rates.To address this issue,we finely categorized the preparation results of carbonized cable specimens by analyzing the experimental phenomena during the carbonization process and assessing the impact of high-voltage energization time on the outcomes,presenting a process control strategy aimed at optimizing the preparation results of carbonized cable specimens.This method utilizes three periodic moving algorithms(root-mean-square,average,and shoulder percentage)to classify the cable specimens into four preparation categories:open-circuit carbonization,under-carbonization,short-circuit carbonization,and successful carbonization.The high-voltage energization time during carbonization or secondary carbonization was adjusted to optimize the preparation of the carbonized cables by considering different discrimination outcomes.Finally,the proposed method was tested on a purpose-built carbonized cable experimental platform,which confirmed its effectiveness in differentiating the preparation outcomes of the carbonized cable specimens and improving the success rate of the carbonized cable preparation.The proposed method has significant potential for application in low-voltage arc fault test systems.