Search NASA⌕ Search

SEARCH · Search NASA

Results for “STRESS CYCLE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

On the Mechanical Behavior of LP-DED C103 Thin-Wall Structures

Laser Powder Directed Energy Deposition (LP-DED) can produce thin-wall features on the order of 1 mm. These features are essential for large structures operating in extreme environments such as regeneratively cooled nozzles and heat exchangers, which often make use of refractory metals. In this work, the mechanical behavior of LP-DED C103 was investigated via quasi-static tensile testing and low cycle fatigue (LCF) testing. The effects of vacuum stress relief (SR) and hot isostatic pressing (HIP) heat treatments were investigated for specimens in the vertical and horizontal build orientations during tensile testing. The AB and SR properties were lower than literature values for wrought and laser powder bed fusion (L-PBF) bulk components but higher than electron beam powder bed fusion (EB-PBF). The application of a HIP cycle improved strength by 7% and ductility by 27% past the initial as-built condition. Fracture images reveal that interlayer stress concentration sites are responsible for fracture in specimens in the vertical orientation. Meanwhile, fracture in the horizontal specimens mainly propagates at a slanted angle typical of plane stress conditions. The LCF results show cycles to failure ranging from 100 cycles to 8000 cycles for max strain levels of 2% and 0.5%, respectively. Fractography on the fatigue specimens reveals an increasing propagation zone as max strain levels are increased. The impact of these findings and future work are discussed in detail.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nondissipative Martensitic Phase Transformation after Multimillion Superelastic Cycles

Superelastic alloys used for stents, biomedical implants, and solid-state cooling devices rely on their reversible stress-induced martensitic transformations. These applications require the alloy to sustain high deformability over millions of cycles without failure. Here, we report an alloy capable of enduring 10 × 10 7 tensile stress-induced phase transformations while still exhibiting over 2% recoverable elastic strains. After millions of cycles, the alloy is highly reversible with zero stress hysteresis. We show that the major martensite variant is reversible even after multimillions of cycles under tensile loadings with a highly coherent $(1\bar{1}0)_A$ interface. Finally, this discovery provides new insights into martensitic transformation, and may guide the development of superelastic alloys for multimillion cycling applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Grain reorientation and stress-state evolution during cyclic loading of an α -Ti alloy below the elastic limit

Here, high-energy synchrotron x-rays are used to track grain-averaged lattice reorientation and stress-state evolution in Ti–7Al as it is cyclically loaded to 90% of its macroscopic yield stress. This evolution provides clear indication of accumulating plastic strain even though the sample never exceeded the elastic limit. The largest changes in lattice orientation and stress state are observed following the first cycle then evolution continues at a lower rate with subsequent cycles. Variation of the axes about which lattice reorientation occurs is found to be highly dependent on the maximum resolved shear stress and corresponding activation of various families of slip systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Recent Advances in the Roles of HSFs and HSPs in Heat Stress Response in Woody Plants

A continuous increase in ambient temperature caused by global warming has been considered a worldwide threat. As sessile organisms, plants have evolved sophisticated heat shock response (HSR) to respond to elevated temperatures and other abiotic stresses, thereby minimizing damage and ensuring the protection of cellular homeostasis. In particular, for perennial trees, HSR is crucial for their long life cycle and development. HSR is a cell stress response that increases the number of chaperones including heat shock proteins (HSPs) to counter the negative effects on proteins caused by heat and other stresses. There are a large number of HSPs in plants, and their expression is directly regulated by a series of heat shock transcription factors (HSFs). Therefore, understanding the detailed molecular mechanisms of woody plants in response to extreme temperature is critical for exploring how woody species will be affected by climate changes. In this review article, we summarize the latest findings of the role of HSFs and HSPs in the HSR of woody species and discuss their regulatory networks and cross talk in HSR. In addition, strategies and programs for future research studies on the functions of HSFs and HSPs in the HSR of woody species are also proposed.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Evolution of the mechanical properties of a cobalt-based alloy under thermal shocks

A cobalt-base alloy manufactured by hot isostatic pressing sintering (HIP) was investigated in the present work. A series of quenching thermal-shock experiments were carried out to study the effects of thermal-cycle shocks on this new cobalt-based alloy. Scanning Electron Microscope (SEM) and Energy Dispersion Spectrum (EDS) were employed to observe the evolution of microstructures under thermal-shock cycles. Results show that some floccus Co 3 W 3 C precipitated around the WC particles after several thermal-shock cycles. These precipitates and the carbide particles correspond to the locations with the high-stress concentration. The mechanical properties evolution under thermal-shock cycles was analyzed by Nanoindentation tests. The nanohardness presents no noticeable change with thermal-shock cycles. However, the reduced modulus demonstrates a decreasing trend with the thermal-shock cycles. The variation of the mechanical properties has an unestimated relationship with the residual stress and densities of dislocations caused by thermal shocks. Furthermore, the present work pointed out that the precipitates around the carbides are the places where the thermal fatigue crack initiated. How to deal with the precipitates will be the optimized way for this material.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Metabolic profiling of epidermal and mesophyll tissues under water-deficit stress in Opuntia ficus-indica reveals stress-adaptive metabolic responses

Cactus pear (Opuntia ficus-indica) is a high productivity species within the Cactaceae grown in many semiarid parts of the world for food, fodder, forage, and biofuels. O. ficus-indica utilises obligate crassulacean acid metabolism (CAM), an adaptation that greatly improves water-use efficiency (WUE) and reduces crop water usage. To better understand CAM-related metabolites and water-deficit stress responses of O. ficus-indica, comparative metabolic profiling was performed on mesophyll and epidermal tissues collected from well-watered and water-deficit stressed cladodes at 50% relative water content (RWC). Tissues were collected over a 24-h period to identify metabolite levels throughout the diel cycle and analysed using a combination of acidic/basic ultra-high-performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) and gas chromatography/mass spectrometry (GC/MS) platforms. A total of 382 metabolites, including 210 (55%) named and 172 (45%) unnamed compounds, were characterised across both tissues. Most tricarboxylic acid (TCA) cycle and glycolysis intermediates were depleted in plants undergoing water-deficit stress indicative of CAM idling or post-idling, while the raffinose family oligosaccharides (RFO) accumulated in both mesophyll and epidermal tissues as osmoprotectants. Levels of reduced glutathione and other metabolites of the ascorbate cycle as well as oxylipins, stress hormones such as traumatic acid, and nucleotide degradation products were increased under water-deficit stress conditions. Notably, tryptophan accumulation, an atypical response, was significantly (24-fold) higher during all time points in water-deficit stressed mesophyll tissue compared with well-watered controls. Many of the metabolite increases were indicative of a highly oxidising environment under water-deficit stress. A total of 34 unnamed metabolites also accumulated in response to water-deficit stress indicating that such compounds might play important roles in water-deficit stress tolerance.

Plant Sciences↗
DOE OSTI2023

Influence of the Ozone Dose Time during Atomic Layer Deposition on the Ferroelectric and Pyroelectric Properties of 45 nm-Thick ZrO 2 Films

Over a decade ago, ferroelectricity was discovered in doped HfO 2 thin films. The HfO 2 -based thin films have attracted much attention due to their remarkable scalability and CMOS compatibility. Other than the HfO 2 -based thin films, the undoped ZrO 2 thin films are understudied despite their commonly reported antiferroelectric behavior. However, being of the same fluorite structure as HfO 2 -based thin films, the undoped ZrO 2 also displayed considerable ferroelectricity as demonstrated in recent studies. Here, 45 nm-thick polycrystalline undoped ZrO 2 films are synthesized using atomic layer deposition with different ozone dose times. The ZrO 2 films are crystallized after atomic layer deposition at 350 °C without anneals. In general, the longer ozone dose time causes a lower in-plane tensile stress and oxygen vacancy content, which help facilitate an irreversible non-polar tetragonal to polar orthorhombic phase transition with electric-field cycling. However, the lower in-plane tensile stress and oxygen vacancy content also stabilize the monoclinic phase so that a long ozone dose time (>17.5 s) reduces the ferroelectric behavior. After wake-up cycles, the ZrO 2 thin film with an ozone dose time of 17.5 s exhibits a remanent polarization of 6 μC·cm –2 and a pyroelectric coefficient of -35 μC·K –1 ·m –2 . Moreover, the wake-up behavior is consistent between the ferroelectric and pyroelectric response. As essential factors in optimizing the growth of fluorite-structure thin films for ferroelectric applications, the in-plane tensile stress and oxygen vacancy content significantly influence the ferroelectric and pyroelectric properties. Additionally, the low thermal budget for processing ferroelectric ZrO 2 thin films is valuable for semiconductor back-end-of-line processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Elastocaloric effect in vanadium (IV) oxide

Elastocaloric cooling utilizes the latent heat associated with stress-induced reversible phase transformations to achieve cooling. Currently, the key barrier to this technology is its prohibitive cost due to the high elastocaloric material cost and the large stress required to drive the cooling cycle. Vanadium (IV) oxide (VO 2 ) is a good candidate, and it is relatively cheap. Our calorimetry study shows it exhibits a reversible phase transformation with a large latent heat of 31.5 J/g, as well as excellent functional stability. Its transformation temperature and latent heat are tunable via heat treatment. We demonstrated that VO 2 powders can be cyclically compressed in a steel tube using a steel plunger to drive the elastocaloric effect. The application of relatively low stress of 300 MPa is sufficient to result in a reversible temperature change of 0.5 °C on the powder compact. Further improvement of reversible temperature change to 1.6 °C under 300MPa is achieved by adding conductive copper powders. Future efforts should focus on improving material properties such as heat capacity and thermal conductivity for candidate ceramic oxides to maximize elastocaloric effects.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Facile Synthesis of Micrometer-sized Hierarchical Porous Si@C Anodes for High-Performance Lithium-Ion Batteries

Extensive studies have been conducted to determine if replacing graphite anodes with silicon is feasible since silicon possesses a high capacity and is an abundant resource; however, Si anodes suffer significant volume changes during cycling, which pulverizes its structure and subsequently causes rapid capacity fading. We used SiO2 nanoparticles (nSiO2) and low-cost coal-derived humic acid as a feedstock to synthesize high performance Si-C anodes for Li-ion Batteries through spray drying, calcination, and magnesiothermic reductions. Our Si-C anodes features micrometer-sized porous Si coated with a graphitized carbon shell (mpSi@C). The hierarchical graphitized carbon shell and porous silicon structure relieve the mechanical stress of the Si phase upon cycling, which stabilizes the structure. This mpSi@C composite design allows for a high initial discharge capacity of 2199.9 mAh g-1 at 0.1 A g-1 and a cycling performance of 68% capacity retention after 100 cycles at 1.0 A g-1. The multipoint contact between the Si anode and C structure allows for a remarkable performance rate of 566.3 mAh g-1 at 5.0 A g-1.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Drought-induced decoupling between carbon uptake and tree growth impacts forest carbon turnover time

The ability of forests to withstand, and recover from, acute drought stress is a critical uncertainty regarding the impacts of climate change on the terrestrial carbon (C) cycle, but it is unclear how drought responses scale from individual trees to whole forests. Here, we assembled a dataset of tree-ring chronologies co-located within the footprint of eddy covariance towers across North America and Europe, with the aim of quantifying the sensitivity of tree radial growth versus gross primary productivity (GPP) during and following drought. We found that drought induced a large decoupling across C cycle processes, whereby GPP was relatively resistant to water stress despite large reductions in tree-ring widths. This decoupling also occurred in the year following drought (i.e., a ‘drought legacy effect’), and was similar in magnitude in response to both summer and winter droughts. By modeling whole-forest C turnover time, we show that a radial growth-GPP decoupling has important ramifications for the forest C cycle, especially if the C not used to support radial growth is instead allocated towards pools with short residence times. Furthermore, our results demonstrate that quantifications of drought impacts that rely solely on C uptake are missing this fundamental pathway through which drought alters the forest C cycle and the resulting feedbacks to the climate system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Correlation-based network analysis combined with machine learning techniques highlight the role of the GABA shunt in Brachypodium sylvaticum freezing tolerance

Perennial grasses will account for approximately 16 billion gallons of renewable fuels by the year 2022, contributing significantly to carbon and nitrogen sequestration. However, perennial grasses productivity can be limited by severe freezing conditions in some geographical areas, although these risks could decrease with the advance of climate warming, the possibility of unpredictable early cold events cannot be discarded. We conducted a study on the model perennial grass Brachypodium sylvaticum to investigate the molecular mechanisms that contribute to cold and freezing adaption. The study was performed on two different B. sylvaticum accessions, Ain1 and Osl1, typical to warm and cold climates, respectively. Both accessions were grown under controlled conditions with subsequent cold acclimation followed by freezing stress. For each treatment a set of morphological parameters, transcription, metabolite, and lipid profiles were measured. State-of-the-art algorithms were employed to analyze cross-component relationships. Phenotypic analysis revealed higher adaption of Osl1 to freezing stress. Our analysis highlighted the differential regulation of the TCA cycle and the GABA shunt between Ain1 and Osl1. Osl1 adapted to freezing stress by repressing the GABA shunt activity, avoiding the detrimental reduction in fatty acid biosynthesis and the concomitant detrimental effects on membrane integrity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Sweet Sorghum Genotypes Tolerant and Sensitive to Nitrogen Stress Select Distinct Root Endosphere and Rhizosphere Bacterial Communities

The belowground microbiomes have many beneficial functions that assist plant growth, including nutrient cycling, acquisition and transport, as well as alleviation of stresses caused by nutrient limitations such as nitrogen (N). Here we analyzed the root endosphere, rhizosphere and soil bacterial communities of seven sweet sorghum genotypes differing in sensitivity to N-stress. Sorghum genotypes were grown in fields with no (low-N) or sufficient (high-N) N. The dry shoot weight ratio (low-N/high-N) was used to determine N-stress sensitivity. Our hypothesis was that genotypes tolerant and sensitive to N-stress select distinct bacterial communities. The endosphere and rhizosphere bacterial community structure were significantly different between the N-stress sensitive and tolerant genotypes in the high-N field, but not in the low-N field. However, significant changes in the relative abundance of specific bacterial taxa were observed in both fields. Streptomyces, a bacterial genus known to alleviate plant abiotic stresses, was enriched in the endosphere and rhizosphere of the tolerant genotypes in the low-N field. Our study indicates that sweet sorghum genotypes tolerant to N-stress select taxa that can potentially mitigate the N-stress, suggesting that the interactions between N-stress tolerant lines and the root-associated microbiome might be vital for coping with N-stress.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Modeling of Stress Distribution in Molten Salt Thermal Energy Storage Tanks for In-Service Central Receiver Power Plants

Failures in molten nitrate salts thermal energy storage tanks (TES) have been occurring in several concentrating solar power (CSP) plants around the world after a few months or years of operation. These failures are mainly related to a combination of high stress, corrosion, large deformation, and thermal cycling. Most of these failures are a consequence of the infancy of this technology; technical standards for design, fabrication, implementation, and operation of molten salt tanks operating at temperatures up to 565 degrees Celsius do not exist and most of current in-service tanks have been designed using the recommendations from the American Petroleum Institute (API) 650 and the American Society of Mechanical Engineers ASME section II standards, which are applicable for TES tanks operating at lower temperatures. We have developed a 3-dimensional model of a representative molten salt hot tank design that uses typical CSP plant operation conditions and allows determining the temperature and stress distribution in the tank. The model also considers the initial floor residual stresses and distortion after its welding fabrication. We have identified critical thermal gradients in the tank floor and shell and locations in the tank where the stresses are high and could become susceptible points for failure.

concentrating solar power↗
DOE OSTI2025

Understanding the Role of Borohydride Doping in Electrochemical Stability of Argyrodite Li 6 PS 5 Cl Solid‐State Electrolyte

This work elucidates the mechanism by which lithium borohydride (LiBH 4 ) doping into argyrodite-type Li 6 PS 5 Cl (LBH-LPSCl) solid-state electrolyte (SSE) enhances electrochemical stability. State-of-the-art electrochemical performance is achieved with 5 wt% borohydride. Symmetric cells achieve critical current density (CCD) of 7.3 mA cm −2 , versus 2.6 mA cm −2 for baseline-LPSCl. All solid-state batteries (ASSBs) employing lithium metal and NMC811 cathode are stable over 400 cycles at 0.5C, with capacity retention of 83%. An anode-free ASSB (AF-ASSB) is stable over 600 cycles, with capacity loss of 0.04% per cycle. 5LBH-LPSCl allows for enhanced low temperature operation, down to −14 °C. Yet the difference in electrolytes’ bulk microstructures and hardnesses are minimal, while ionic conductivity is incrementally improved (≈50%). Theoretical modeling indicates limited effect of substitution on thermodynamic stability of PS 4 3- units, which decompose when contacting Li. Instead, enhanced electrochemical stability is site-specific kinetic effect: In situ electrodeposition experiments using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveal tri-layer SEI based predominately on Li 3 P/LiBH 4 /Li 2 S that blocks electrons while facilitating ion transport. This SEI manifests reduced interface resistance and accelerated nucleation and growth of metallic Li. With baseline-LPSCl the SEI based on Li 3 P/Li 2 S is substantially thicker, generating localized stresses that promote interfacial cracking while cycling.

argyrodite↗
DOE OSTI2022

Thermally Grown Oxide Stress in PS-PVD and EB-PVD Thermal Barrier Coatings Observed at Various Lifetimes Via Synchrotron X-ray Diffraction

The current standard application method for thermal barrier coatings (TBCs) on turbine blades for jet engines is electron-beam physical vapor deposition (EB-PVD) due to its high strain tolerance and low thermal conductivity. An emerging deposition method, plasma-spray physical vapor deposition (PS-PVD), presents an opportunity for a tailorable microstructure, and non-line-of-sight deposition that is faster and less expensive. To compare the lifetime behavior of both PS-PVD and EB-PVD coatings, samples subjected to 300 and 600 thermal cycles were measured during a 1 h thermal cycle to determine the strains, which were converted to stress, in the thermally grown oxide (TGO) layer of the TBCs using synchrotron X-ray diffraction (XRD). Room temperature XRD measurements indicated among samples that PS-PVD coatings experienced greater variation in in-plane room temperature strain in the TGO after cycling than the EB-PVD coatings. In-situ XRD measurements indicated similar high-temperature strain and no spallation after 600 thermal cycles for both coatings. Further, microscopy imaging after cycling showed greater rumpling in PS-PVD coatings that led to different failure modes between the two coatings’ TGO layers. The tailorability of PS-PVD coatings allows for adjustments in the processing parameters to improve their overall performance after aging and bridge the differences between the two deposition methods.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Design Basis Document / Owner’s Technical Specification for Nitrate Salt Systems in CSP Projects (Final Technical Report)

The number of commercial coal, gas, and nuclear projects built over the past 100 years number in the thousands. As such, there is a large database, available to a wide range of commercial engineering contractors, on proven designs. In essence, unsuccessful designs have, through generations of iterations, been identified and then deleted from further consideration. In contrast, the number of commercial parabolic trough projects using nitrate salt for the thermal storage media is perhaps 60. Further, the number of commercial central receiver projects using nitrate salt as the working fluid is on the order of 20, including estimates for China. Given the relative immaturity of salt technology, and commercial pressures to successfully bid new solar projects into a mature electricity market, solar projects often promise more than has been delivered. The Design Basis Document / Owner’s Technical Specification is a first step in the iteration process. The report describes the successful features of commercial projects, outlines a range equipment and system failures in projects that didn’t operate as intended, and provides a draft set of design changes intended to correct the known problems. The product of the study is 3 volumes of technical material; one volume is on parabolic trough technologies; a second is on central receiver technologies, and the third is on potential design changes to parabolic trough and central receiver projects. The 3 volumes, which total some 590 pages, can be found at https://www.solardynllc.com/csp-plant-technologies. One of the principal topics in the report is the use of functional or prescriptive specifications. Functional specifications describe what the equipment needs to do, consistent with the minimum legal requirements of the local jurisdictions. The details of how this is to be accomplished is developed by the engineering contractor. Prescriptive specifications, which are developed by the Owner, prescribe to the engineering contractor how the functional requirements are to be met. This arrangement ensures that the favorable experience from a previous project is repeated. One example is the design code for the hot salt tank in central receiver projects. The closest design basis is API Standard 650 Welded Steel Tanks for Oil Storage. However, the maximum design temperature in API 650 is 260 °C. As such, solar projects have typically adopted a hybrid Code approach, in which allowable material stresses are taken from ASME Section II Materials. Further, since the tanks experience daily changes in temperature and in (static) pressure, and since portions of the tank can operate at stresses beyond the elastic range, the low cycle fatigue life of the tank is conducted using the rules of Section VIII Division 2. However, in a recent study by NREL, the principal damage mechanism was identified as creep rather than fatigue. Further, design stresses permitted under Section VIII Division 2, corresponding to a fatigue life of 30 years, result in projected creep lifetimes of only 2 to 5 years. An alternate design approach, prescribed by the Owner, would be based on Code sections intended for high temperature service in the creep regime. A candidate is Section III Division 5. Granted, this is a nuclear code section, and it’s use would not likely be mandated by local jurisdictions. However, the effects of creep have been deemed to be of sufficient importance that one nuclear project developer, and one central receiver project developer, have stipulated in the tank design specification that the equipment be designed to the requirements of Section III Division 5.

14 SOLAR ENERGY↗
DOE OSTI2021

New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer

This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc link. Such flyback operation with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for DC-DC, multiport AC-DC, and AC-AC conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Lastly, a case study of a three-phase AC-AC S4T over a power range from 1 kVA to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation.

14 SOLAR ENERGY↗
DOE OSTI2025

Creating Favorable Pt/Co Interfaces via a Two‐Step Approach for Constructing Highly Durable PtCo Intermetallic Fuel Cell Catalysts

Structurally ordered PtCo intermetallics are one of the most promising oxygen-reduction catalysts in proton exchange membrane fuel cells (PEMFCs) due to their intrinsically improved catalytic activity and stability relative to PtCo solid-solution alloys. However, increasing the heating temperature to achieve a desirable high degree of ordering results in severe particle agglomeration and low mass activity and stability. Herein, a two-step synthesis approach is developed to create an L1 2 -Pt 3 Co intermetallic structure with an increased ordering degree and well-dispersed ultrafine particles. The first step of the synthesis yields ultrafine Pt nanoparticles that are well-dispersed on the ZIF-8-derived carbon support. The second adsorption step enables us to fine-tune the Pt and Co interfaces, assisted by optimal amino acids, to establish a favorable Co-rich environment around fine Pt nanoparticles, facilitating Co diffusion into the Pt crystalline under mild thermal conditions (<800 °C). In conclusion, this two-step ordered L1 2 -Pt 3 Co catalyst is systematically evaluated using membrane electrode assemblies under heavy-duty vehicle (HDV) conditions and demonstrated exceptional performance and durability, retaining 1.35 A cm -2 only a 7% loss in current density at 0.7 V after an extensive accelerated stress test of 150,000 voltage cycles.

30 DIRECT ENERGY CONVERSION↗