Tian Liu

Chromium (Cr) poisoning from metallic interconnects (ICs) is widely regarded as a critical degradation pathway in solid oxide cells (SOCs). This study systematically investigates the operational-mode-dependent Cr migration-comparing fuel cell mode (solid oxide fuel cells, SOFCs) vs. electrolysis mode (solid oxide electrolysis cells, SOECs)-from button cells to a scaled-up, large-area configuration. In button cell tests (~1,500 h), SOFC mode showed severe degradation, with an area-specific resistance (ASR) increase of ~180%, driven by deep inward Cr diffusion, Sr-Cr co-segregation, and precipitation of resistive secondary phases extending down to the barrier layer interface. Under both SOEC modes (50% and 90% steam), Cr-induced degradation was negligible, with ASR degradation rates of uncoated IC cells closely matching those of reference cells at each steam content (within ~1% and ~6%, respectively). Further, a scaled-up cell with an uncoated interconnect operated stably under SOEC mode for ~1,000 h, and post-mortem analysis along the flow path confirmed that Cr penetration into the electrode bulk remained predominantly suppressed across the entire active area, with only modest spatial variation toward the outlet. This asymmetry is proposed to arise from a coupled physical and electrochemical mechanism: the continuous outward O₂ flux generated during oxygen evolution reaction (OER) acts as a convective barrier against incoming Cr species, while anodic operation concurrently suppresses electrochemical Cr deposition at active boundaries. These findings broaden material selection tolerances and relax coating requirements for electrolysis-dominated stack configurations.

This study investigates the long-term durability of solid oxide electrolysis cells (SOECs) with a focus on how commercially sourced nickel oxide (NiO) precursors affect the stability of Ni–YSZ hydrogen functional electrodes. Cells fabricated using different commercial NiO powders were operated for 1500 h under both potentiostatic and galvanostatic conditions. Initial electrochemical performance and long-term durability were both found to vary with the NiO precursors and the operating mode. Electrochemical impedance spectroscopy coupled with distribution of relaxation time analysis showed that degradation evolves through coupled contributions from charge-transfer-related polarization and interfacial integrity. Post-mortem microstructural characterization revealed dark intragranular features in all cells; however, their prevalence varied among cells derived from nickel oxides obtained from different commercial sources. Under potentiostatic operation, degradation was dominated by Ni coarsening/agglomeration with limited interfacial damage, whereas galvanostatic operation more clearly exposed interfacial vulnerability, evidenced by delamination at the hydrogen functional electrode/YSZ interface. Elemental mapping showed localized Si- and Mg-rich oxides near active regions without evidence of continuous insulating-layer growth within the investigated timeframe under both operation modes. The findings indicate that tailoring the chemical and microstructural characteristics of NiO precursors provides a viable route to enhance long-term SOEC durability.

With the rapid development of affordable energy, hydrogen can serve as an ideal long‐term energy storage medium and a commodity chemical/fuel precursor for energy conversion. Solid oxide electrolysis cells produce hydrogen from water with a high electrical efficiency in an environmentally friendly manner. However, the long‐term durability of solid oxide electrolysis cells is yet to be fully understood, especially in terms of decoding the fundamentals behind the degradation mechanisms. In this work, testing of solid oxide electrolysis cells was conducted at voltages well above the thermoneutral voltage of ~1.3 V to expose potential degradation mechanisms that could occur when solid oxide electrolysis cell is tested in a galvanostatic mode with voltage increasing over time. While standard electrochemical techniques did not reveal obvious degradation beyond the initial break‐in period, high‐resolution analyses uncovered intergranular and transgranular voids and cracks in the yttria‐stabilized zirconia electrolyte that were not observed during normal operation at 1.3 V. A comprehensive study of representative state‐of‐the‐art and thin‐film electrolyte and barrier layers was performed to establish a correlation between high voltages and structural changes in yttria‐stabilized zirconia. Void formation in yttria‐stabilized zirconia was attributed to strain‐vacancy interactions at high voltages, whereas the barrier/electrolyte interdiffusion layer and Ni precipitation in yttria‐stabilized zirconia were ruled out as triggers of void formation. This study provides insight into the operational boundaries of real‐time solid oxide electrolysis cells service, indicating that operating at voltages well above the thermoneutral voltage should be avoided.

In a blockchain system based on the HashGraph consensus algorithm, picking a target server for block propagation is a key step. The traditional HashGraph blockchain system uses a completely random approach to pick the target server, which has the advantage of ensuring the security of the system and reducing the impact of attacks and single server failures received by the system. However, the random selection of target servers may lead to a situation where low performance servers are under high load but high performance servers are under load. In order to make each server process the block data with maximum performance, this paper proposes a balanced up-linking strategy, which calculates the server's reputation by evaluating the status of four dimensions, such as remaining performance, security, response time, and trustworthiness of the server, and then constructs a geometric probability model by Markov model and Monte Carlo method, so that the block is randomly propagated to each server with a specific probability according to the server status. In the process of running the blockchain system with this strategy, the probability of propagation to each server is dynamically adjusted according to the changing server status, so that the frequency distribution of all servers in the cluster receiving blocks obeys the target probability distribution. We evaluate the performance of our approach through extensive simulations and experiments, and the results demonstrate the feasibility and effectiveness of the proposed approach.

An extensive experimental and computational investigation of the fatigue behavior of friction stir welding (FSW) of aluminum–lithium alloy (AA2099) is presented. In this study, friction stir butt welds were created by joining AA2099 using two different welding parameter sets. After FSW, microstructure characterization was carried out using microhardness testing, scanning electron microscopy, and transmission electron microscopy techniques. In particular, the metastable strengthening precipitates T₁ (Al₂CuLi) and δ’(Al₃Li) seen in the base metal were observed to coarsen and dissolve due to the FSW process. In order to evaluate the static and fatigue behavior of the FSW of the AA2099, monotonic tensile and fully-reversed strain-controlled fatigue testing were performed. Mechanical testing of the FSW specimens found a decrease in the ultimate tensile strength and fatigue life compared to the base metal. While the process parameters had an effect on the monotonic properties, no significant difference was observed in the number of cycles to failure between the FSW parameters explored in this study. Furthermore, post-mortem fractography analysis of the FSW specimens displayed crack deflection, transgranular fracture, and delamination failure features commonly observed in other parent Al–Li alloys. Lastly, a microstructurally-sensitive fatigue model was used to elucidate the influence of the FSW process on fatigue life based on variations in grain size, microhardness, and particle size in the AA2099 FSW.