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Oxidation behaviour of ferritic stainless steel grade Crofer 22 APU at 700 °C in flowing Ar−75%CO{sub 2}−12%H{sub 2}O
The oxidation of Ferritic Stainless Steel (FSS) grade Crofer 22 APU has been investigated. FSS alloys were exposed to isothermal conditions in a horizontal tube furnace at a 700 °C in flowing Ar−75%CO{sub 2}−12%H{sub 2}O at a pressure of approximately 1 atm. The results showed that the growth of non protective Fe{sub 2}O{sub 3} and spinel was observed after 50 h exposure in the presence of 12% H{sub 2}O. The weight was increased significantly with time of exposure. The formation of different oxides is presented on the interface of the specimen such as MnCr{sub 2}O{sub 4}, Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} were revealed by X-ray diffraction and supported by EDAX analysis. FSS did not form a protective Cr{sub 2}O{sub 3} layer due to water vapour accelerates the kinetics oxidation. Data of microstructure observation is presented and discussed in this paper in term of water vapour effects.
Solid Acid Fuel Cell Stack for APU Applications
Solid acid fuel cell technology affords the opportunity to operate at the 200-300 degree centigrade regime that would allow for more fuel flexibility, compared to polymer electrode membrane fuel cell, while avoiding the relatively more expensive and complex system components required by solid oxide fuel cell. This project addresses many factors such as MEA size scalability, fuel robustness, stability, etc., that are essential for successful commercialization of the technology.
Sandia previews initial mini-application ports to AMD's next generation Trinity APU and Tahiti Southern Island GPU Technologies.
Abstract not provided.
Unleashing the Power of Physically Unified CPU-GPU Memory in AMD MI300A APU in HPC Applications
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Low Cost, Compact Plasma Fuel Reformer for APU's
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Multiple Decay Mechanisms and 2D-UV Spectroscopic Fingerprints of Singlet Excited Solvated Adenine-Uracil Monophosphate
The decay channels of singlet excited adenine uracil monophosphate (ApU) in water are studied with CASPT2//CASSCF:MM potential energy calculations and simulation of the 2D-UV spectroscopic fingerprints with the aim of elucidating the role of the different electronic states of the stacked conformer in the excited state dynamics. The adenine 1 L a state can decay without a barrier to a conical intersection with the ground state. In contrast, the adenine 1 L b and uracil S(U) states have minima that are separated from the intersections by sizeable barriers. Depending on the backbone conformation, the CT state can undergo inter-base hydrogen transfer and decay to the ground state through a conical intersection, or it can yield a long-lived minimum stabilized by a hydrogen bond between the two ribose rings. This suggests that the 1 L b , S(U) and CT states of the stacked conformer may all contribute to the experimental lifetimes of 18 and 240 ps. We have also simulated the time evolution of the 2D-UV spectra and provide the specific fingerprint of each species in a recommended probe window between 25 000 and 38 000 cm -1 in which decongested, clearly distinguishable spectra can be obtained. This is expected to allow the mechanistic scenarios to be discerned in the near future with the help of the corresponding experiments. Our results reveal the complexity of the photophysics of the relatively small ApU system, and the potential of 2D-UV spectroscopy to disentangle the photophysics of multichromophoric systems.
Experimental review of the performances of protective coatings for interconnects in solid oxide fuel cells
Ferritic stainless-steel interconnects are used in solid oxide fuel cells; however, coatings are required to improve their performance. Although several types of coatings have been proposed, they have been scarcely investigated under similar conditions. This study compares the characteristics of uncoated Crofer 22 APU and eight different coatings on Crofer 22 APU for up to 3,000 hours at 800°C. The coatings were deposited at various research laboratories around the world, and the experiments were performed at Chalmers University of Technology, Sweden. Cross-sections of the samples were analysed using scanning electron microscopy and energy-dispersive x-ray spectroscopy. The (Co,Mn)-based coated steels showed more than 50-fold lower chromium evaporation and at least 3 times thinner Cr 2 O 3 scale thickness compared to uncoated steel. The coated steel samples showed lower area-specific resistance (ASR) values than the uncoated steel after 3,000 hours of exposure, irrespective of the coating thickness, composition and deposition method.
Effects of thermal aging and ionizing radiation on sPVC and aromatic polyether urethane used to store nuclear materials
In this work, we tested the degradation of two polymeric materials under conditions routinely encountered in nuclear applications. Polymers in the form of plastic bags are commonly used along with metal containers to store and transport nuclear materials. The role of the bag, also known as bag-out bag, is to prevent contamination in case the metal containers are breached. Polymeric materials of interest are sPVC and aromatic polyether urethane (APU-ether), which in this study were exposed to alpha, gamma and thermal conditions. These conditions were specifically chosen to simulate the harsh environments normally encountered in the storage of nuclear materials. The physical, chemical and mechanical properties of these materials were investigated by a series of characterization methods before and after exposures. Our results highlight the superior stability of APU-ether under thermal aging and ionizing radiation and provide new insights into the durability of polymeric materials used in nuclear applications. In conclusion, these findings will serve as the foundation for a rational selection of new bag-out bag materials to be considered in the nuclear industry.
Performance Impact and Trade-Offs for Tuning Key Architectural Parameters on CPU+GPU Systems
In this work, we performed an initial design space exploration of an accelerated processing unit (APU)—a hybrid CPU+GPU architecture that integrates both compute units (CUs) and memory into a unified system. This integration aims to reduce data movement, enhance memory locality, and improve energy efficiency by enabling the CPU and GPU to share memory directly. This effort focused on the interplay of key design components—cache line size, the number of CUs, and main memory technology—and the trade-offs of each configuration were analyzed. This paper highlights the various configurations’ impact on memory accesses, data reuse, and power utilization. The results provide valuable insights that can be leveraged to optimize APU architectures for high-performance and energy-efficient computing and thus create a balanced architecture. This optimization can be achieved by adopting dynamic cache management, runtime CU scaling, and advanced memory integration, highlighting the potential of APUs to address critical challenges in compute, data movement, and memory power consumption.
LANL PVC bag-out-bag replacement [Slides]
The US material at 8 months aging, at room temperature and exposed to gamma at 80 degrees C has been completed. The FTIR data does not show any discernible difference between the US APU-ether material and the British material. There are some differences and the curves of the FTIR, but the behavior shows that the US material is behaving comparable to the British material. The British Blue sample exposed to gamma at 70 degrees C did have an observable change in the contact angle. This was the only notable change between the two different types of polymer the TGA on both the US and the British had no observable difference. Mechanical testing samples (dog-bones) are being prepared for tensile, shear, and puncture testing. This data will be provided in later meetings. Mass spec testing is needed to measure the headspace gases that are being seen during the aging study to better health characterize the radiolytic degradation of the APU ether samples, this is also ongoing.
Electrical Generation for More-Electric Aircraft Using Solid Oxide Fuel Cells
This report examines the potential for Solid-Oxide Fuel Cells (SOFC) to provide electrical generation on-board commercial aircraft. Unlike a turbine-based auxiliary power unit (APU) a solid oxide fuel cell power unit (SOFCPU) would be more efficient than using the main engine generators to generate electricity and would operate continuously during flight. The focus of this study is on more-electric aircraft which minimize bleed air extraction from the engines and instead use electrical power obtained from generators driven by the main engines to satisfy all major loads. The increased electrical generation increases the potential fuel savings obtainable through more efficient electrical generation using a SOFCPU. However, the weight added to the aircraft by the SOFCPU impacts the main engine fuel consumption which reduces the potential fuel savings. To investigate these relationships the Boeing 787-8 was used as a case study.
Optimal management of electric hotel loads in mild hybrid heavy duty truck
Here, the problem of engine idling for heavy-duty trucks has been under study for decades with Auxiliary Power Units (APUs) and Truck Stop Electrification (TSE) as the most compelling solutions. With the electrification of trucks approaching feasibility in terms of cost-effective technology, hybridization offers another “degree of freedom” to tackle the problem. Here, this work aims at exploiting a battery pack of a 48 V mild-hybrid heavy-duty truck to store sufficient onboard energy for powering the auxiliary loads during the hoteling. This problem is not trivial, as the battery packs typically cannot recover the entire energy required through regeneration alone; hence an optimal energy management strategy needs to be employed to charge the battery through the engine during drive operation. This strategy optimizes powertrain performances among the four modes: (i) Engine of Coasting (EOC), (ii) Regeneration by braking, (iii) Regeneration by engine, and (iv) engine idling. This paper presents the development of a Dynamic Programming (DP) framework that employs a multi-objective cost function to minimize the fuel consumption and maximize the regeneration using the above-mentioned four modes. A typical heavy-duty truck drive cycle is used to represent the drive phase, with mandatory hoteling stops as per regulations. A comprehensive powertrain model is developed using validated components’ model. The DP employs two state variables: battery State-of-Charge (SOC) and engine mode, and three control inputs: (i) the engine ON–OFF state, (ii) clutch engagement state, and (iii) power request at the Electric Machine (EM) for calculating optimal SOC trajectory. The framework also tackles rapid engine ON–OFF scenarios to avoid the challenges associated with DP and the compromises in fuel cost with those approaches. Finally, the effectiveness of the proposed framework is tested for potential fuel savings on two different battery packs by performing the full cycle simulations. The results show 6.47% of fuel consumption reduction as compared to traditional APU-based heavy-duty truck.
MFC 5.0: An exascale many-physics flow solver
Many problems of interest in engineering, medicine, and the fundamental sciences rely on high-fidelity flow simulation, making performant computational fluid dynamics solvers a mainstay of the open-source software community. Previous work MFC 3.0 was made a published, documented, and open-source solver via Bryngelson et al. Comp. Phys. Comm. (2021) with numerous physical features, numerical methods, and scalable infrastructure. MFC 5.0 is a significant update to MFC 3.0, featuring a broad set of well-established and novel physical models and numerical methods, as well as the introduction of GPU and APU (or superchip) acceleration. Here, we exhibit state-of-the-art performance and ideal scaling on the first two exascale supercomputers, OLCF Frontier and LLNL El Capitan. Combined with MFC’s single-accelerator performance, MFC achieves exascale computation in practice, and achieved the largest-to-date public CFD simulation at 200 trillion grid points as a 2025 ACM Gordon Bell Prize finalist. New physical features include the immersed boundary method, N-fluid phase change, Euler–Euler and Euler–Lagrange sub-grid bubble models, fluid-structure interaction, hypo- and hyper-elastic materials, chemically reacting flow, two-material surface tension, magnetohydrodynamics (MHD), and more. Numerical techniques now represent the current state-of-the-art, including general relaxation characteristic boundary conditions, WENO variants, Strang splitting for stiff sub-grid flow features, and low Mach number treatments. Weak scaling to tens of thousands of GPUs on OLCF Summit and Frontier and LLNL El Capitan achieves efficiencies within 5% of ideal to over 90% of their respective system sizes. Strong scaling results for a 16-times increase in device count show parallel efficiencies over 90% on OLCF Frontier. MFC’s software stack has undergone further improvements, including continuous integration, which ensures code resilience and correctness through over 300 regression tests; metaprogramming, which reduces code length while maintaining performance portability; and code generation for computing chemical reactions
Ferritic stainless steel interconnects for protonic ceramic electrochemical cell stacks: Oxidation behavior and protective coatings
Protonic ceramic fuel or electrolysis cells (PCFC/PCEC) have shown promising performance at intermediate temperatures. However, these technologies have not yet been demonstrated in a stack, hence the oxidation behavior of the metallic interconnect under relevant operating environments is unknown. In this work, ferritic stainless steels 430 SS, 441 SS, and Crofer 22 APU were investigated for their use as interconnect materials in the PCFC/PCEC stack. Specifically, the bare metal sheets were exposed to a humidified air environment in the temperature range from 450 °C to 650 °C, to simulate their application in a PCFC cathode or PCEC anode. Breakaway oxidation with rapid weight gain and Fe outward diffusion/oxidation was observed on all the selected stainless steel materials. A protective coating is deemed necessary to prevent the metallic interconnect from oxidizing. To mitigate the observed breakaway oxidation, state-of-the-art protective coatings, Y 2 O 3 , Ce 0.02 Mn 1.49 Co 1.49 O 4 , CuMn 1.8 O 4 and Ce/Co, were applied to the stainless steel sheets and their oxidation resistance was investigated. Dual atmosphere testing further validated the effectiveness of the protective coatings in realistic PCFC/PCEC environments, with a hydrogen gradient across the interconnect. Several combinations of metal and coating material were found to be viable for use as the interconnect for PCFC/PCEC stacks.
Performance of stainless steel interconnects with (Mn,Co) 3 O 4 -Based coating for solid oxide electrolysis
Mixed transition-metal oxide coatings are commonly applied to stainless steel interconnects for solid oxide cell stacks. Such coatings reduce oxidation and Cr evaporation rates, leading to improved degradation rate and stack lifetime. Here, the ChromLok™ MCO-based composition (Mn,Co) 3 O 4 is applied to Crofer 22 APU stainless steel and evaluated specifically for application in solid oxide electrolyzer stacks operating around 800 °C and utilizing oxygen-ion-conducting solid oxide cells. The MCO coating is found to decrease the stainless steel oxidation rate by about one order of magnitude, and decrease the Cr evaporation rate by fourfold. Furthermore, the coating also dramatically lowers the rate of area-specific resistance increase for stainless steel coupons oxidized for 500 h with constant current applied, from 33 mΩ*cm 2 kh -1 for an uncoated coupon to less than 4 mΩ*cm2 kh -1 for coated coupons. The coating is demonstrated on full-scale interconnects for single-cells, where the coating dramatically reduces degradation rate, and for a stack, which displays stable operation for 700 h.
Dynamic oxidation of (Mn,Co) 3 O 4 -Coated interconnects for solid oxide electrolysis cells
Solid oxide electrolysis cell stacks are expected to experience dynamic conditions when using renewable electricity derived from wind or solar power. To address this scenario, (Mn,Co) 3 O 4 (MCO)-coated Crofer 22 APU interconnect coupons are subjected to thermal cycling, and intermittent current density, with gas compositions relevant to high-temperature electrolysis (elevated steam:hydrogen ratio and oxygen content). Defects are also intentionally introduced in the MCO coating, to assess whether the difference in oxidation properties of the adjacent coated and uncoated (defective) surfaces causes sufficient stress to damage the protective oxide scale. Specimens with defects are subjected to oxidation for 1000 h at 800 °C, or thermal cycling. Before thermal cycling, some specimens are pre-oxidized to create a thick oxide scale to mimic the scale thickness expected after ~30 kh operation. In all cases, the coating and oxide scale remain well adhered with no cracking observed. Area-specific resistance (ASR) is monitored in both single-atmosphere and dual-atmosphere conditions, and the ASR is stable and is not impacted by dynamic cycling of the current density. Finally, this work provides confidence that the MCO coated interconnect will function as needed in dynamic operation conditions, even with coating defects.