Engineering topics

Cakmak, Ercan [ORNL] (ORCID:0000000172724815)

Publications and source records attributed to Cakmak, Ercan [ORNL] (ORCID:0000000172724815).

5 records

DOE OSTI2026

Impact of nitrogen on lithium-induced corrosion and cracking of RAFM steel

The emergence of private fusion enterprises, combined with advancements in U.S. and EU ITER-TBM as well as EU DEMO liquid breeder blanket concepts, has renewed focus on the materials challenges. This study examines the compatibility of reduced activation ferritic/martensitic (RAFM) steel in liquid Lithium (Li) containing various Nitrogen (N) concentrations, tested at 600 and 700 °C for 500 and 1000 h under static conditions. Microstructural characterization revealed the corrosion-induced dissolution and precipitation in Li containing 0.082 and 0.17 wt.% N at 600 °C, while limited dissolution and precipitation were observed in N-gettered Li using zirconium (Zr) and titanium (Ti) foils at 600 °C. Tensile testing at room temperature after Li exposure revealed a decrease in strength and ductility of the RAFM steel as a function of N content in Li. Severe embrittlement was observed after 500 h in Li containing 0.17 wt.% N at 600 °C and after 500 h in hot-gettered Li at 700 °C. Chromium (Cr) depletion from the steel matrix was observed, leading to the formation of M6C-type carbides on the surface identified by electron microscopy (SEM), X-ray diffraction (XRD), in agreement with thermodynamic calculations. These findings highlight the critical materials challenges posed by liquid Li breeder blanket concepts, emphasizing the need for improved strategies to address Li-induced dissolution, precipitation, and steel embrittlement due to N contamination of the coolant.

Romedenne, Marie [ORNL] (ORCID:0000000317936561)↗

DOE OSTI2026

Porous reaction-bonded silicon nitride: Size effects for pressureless nitriding of binder jet additively manufactured silicon

The direct nitridation of binder jet additively manufactured silicon to produce porous reaction-bonded silicon nitride was explored to determine the maximum thickness of the sample that could be converted to >99% silicon nitride. The maximum thickness that could be nitrided was investigated by nitriding cubes of increasing physical size on the millimeter scale. Highly porous samples with high conversion ( > 99%) to silicon nitride were achieved in cubes with 35 mm edge length. It was shown that the silicon nitride phase content changes with increasing sample size.

Aguirre, Trevor [ORNL] (ORCID:0000000281469630)↗

DOE OSTI2026

Iodine Capture with Copper-Electroplated Nickel Foams

This work explores the use of Ni0 foam scaffolds for Cu0 coatings for use as sorbents for iodine. The Cu0 electroplating was performed from aqueous copper(II) sulfate (CuSO4) solutions under different conditions to achieve a range of Cu0-layer thicknesses (4.89 ± 1.05 μm–57.32 ± 3.95 μm) with 900 A·m–2 current densities and coating times of 15–180 min. The thickest coatings resulted in Cu0-plated Ni0 foams with >89 mass % Cu0 in the final product. Iodine capture experiments showed very high Cu0 utilizations of 91.9–97.3 mass % at iodine loadings of 839–1774 mg·g–1 through the formation of CuI (marshite; space group F-43m). No evidence was found of iodine reactions taking place with the Ni0 scaffold, so it remained in iodine-loaded Cu-electroplated Ni foams as structural support to provide mechanical rigidity to the foams during the iodine loading process. Hot pressing of these materials can be used to create a CuI/Ni ceramic-metal composite waste form for disposal as demonstrated with spark plasma sintering.

Riley, Brian [Pacific Northwest National Laborator↗

DOE OSTI2026

Controlled lithium stripping enables a stable interface for long-cycling anode-free solid-state batteries

Anode-free solid-state batteries (AFSSBs) are a promising route toward achieving high energy density. In these cells, the anode contains no pre-stored lithium (Li). Instead, the entire Li inventory originates from the cathode and is freshly deposited onto a bare current collector during charging. However, achieving uniform and defect-free Li plating on this bare current collector remains a major challenge, often resulting in low Li plating/stripping efficiency and rapid capacity decay. Here, for the first time, operando neutron imaging is employed to visualize Li plating/stripping behavior in an anode-free full cell with LiNi0.82Mn0.07Co0.11O2 (NMC) as the cathode. Operando measurements reveal that complete stripping of Li leaves isolated Li residues on the current collector, which degrades the interfacial contact between the current collector and the solid-state electrolyte. To mitigate this interfacial issue and promote more uniform Li deposition, we implement a discharge-cutoff-voltage strategy that intentionally retains a thin residual Li layer after stripping. This preserved Li-containing interfacial reservoir not only improves interfacial contact but also serves as an in situ formed seed layer that enables more homogeneous subsequent Li plating. As a result, the optimized anode-free cell with limited stripping depth exhibits excellent long-term cycling stability, maintaining a discharge capacity of 112.1 mAh g−1 with a capacity retention of 80.6% and an average coulombic efficiency of approximately 99.9% after 500 cycles at 0.25 C. In contrast, the cell with a conventional discharge cutoff voltage of 2.8 V exhibits rapid capacity decay, retaining only 59.7 mAh g−1 after 50 cycles with a capacity retention of 40.7%. This work demonstrates that limiting deep stripping to preserve a thin Li-containing interfacial layer can effectively improve the cycling stability of sulfide-based AFSSBs.

Wang, Jiwei [Northeastern University, Boston]↗

DOE OSTI2025

Corrosion Resistance of an AlCeMg/Stainless-Steel Reactive Bond

A major issue for metal components in many industries is corrosion as it can substantially reduce their lifetime. This issue is especially problematic for materials used in heat exchanger applications. Al–Ce–Mg alloys, which exhibit corrosion resistance and can reactively bond with other metals, may be a viable solution to this problem. This investigation studied the corrosion behavior of Al–2Ce–6Mg (atomic percent)/stainless-steel (SS) reactive bond interfaces after full immersion in nitric, sulfuric, formic, and mixed acid for 267 h. This particular Al–Ce–Mg alloy was chosen due to its good castability. The results of scanning electron microscope characterization showed that reactive bond formations repeatedly occurred throughout the length of the casting in the as-cut samples and that these formations maintained a secure bonding between the alloy and the stainless-steel tubes. Transmission electron microscopy results showed that there was a clear compositional and microstructural transition across the reactive bond. The results of the immersion tests indicated that the nitric, sulfuric, and the mixed acid did not have an observably negative effect on the reactive bond structure. As for the sample exposed to formic acid only, noticable changes were seen in both the microstructural appearance and the elemental profile across the bond, suggesting that oxide formation occurred.

Brechtl, Jamieson [ORNL] (ORCID:0000000217394283)↗