Publications

Effects of microstructural changes induced by prestraining on hydrogen transport and hydrogen embrittlement (HE) of austenitic stainless steels were studied by hydrogen precharging and tensile testing. Prestrains higher than 20% at 20 °C significantly enhance the HE of 304L steel as they induce severe α′ martensite transformation accelerating hydrogen transport and hydrogen entry during subsequent hydrogen exposure. In contrast 304L steel prestrained at 50 and 80 °C and 316L steel prestrained at 20 °C exhibit less HE due to less α′ after prestraining. The increase of dislocations after prestraining has a negligible influence on apparent hydrogen diffusivity compared with pre-existing α′. The deformation twins in heavily prestrained 304L steel can modify HE mechanism by assisting intergranular (IG) fracture. Regardless of temperature and prestrain level HE and apparent diffusivity ( Dapp ) increase monotonously with α′ volume fraction ( f_α′ ). D_app can be described as log D_app=log(D_α′s_α′/s_γ)+log[f_α′/(1−f_α′)] for 10%<f_α′<90% with Dα′ is diffusivity in α′ s_α′ and s_γ are solubility in α′ and austenite respectively. The two equations can also be applied to these more typical duplex materials containing both BCC and FCC phases.

The paper presents a sustainable electric powertrain for a transit city bus featuring an electrochemical battery-free power unit consisting of a hydrogen fuel cell stack and a kinetic energy storage system based on high-speed flywheels. A rare-earth free high-efficiency motor technology is adopted to pursue a more sustainable vehicle architecture by limiting the use of critical raw materials. A suitable dynamic energetic model of the full vehicle powertrain has been developed to investigate the feasibility of the traction system and the related energy management control strategy. The model includes losses characterisation as a function of the load of the main components of the powertrain by using experimental tests and literature data. The performance of the proposed solution is evaluated by simulating a vehicle mission on an urban path in real traffic conditions. Considerations about the effectiveness of the traction system are discussed.

Niobium microalloying is the backbone of modern low-carbon high strength low alloy (HSLA) steel metallurgy providing a favorable combination of strength and toughness by pronounced microstructural refinement. Molybdenum alloying is established in medium-carbon quenching and tempering of steel by delivering high hardenability and good tempering resistance. Recent developments of ultra-high strength steel grades such as fully martensitic steel can be optimized by using beneficial metallurgical effects of niobium and molybdenum. The paper details the metallurgical principles of both elements in such steel and the achievable improvement of properties. Particularly the underlying mechanisms of improving toughness and reducing the sensitivity towards hydrogen embrittlement by a suitable combination of molybdenum and niobium alloying will be discussed.

Metastable austenitic stainless steels (ASSs) have excellent ductility but low strength so that their usage as load-bearing components is significantly limited. Rolling is an effective method of increasing strength whereas the effect of rolling temperature on microstructural evolution the hydrogen embrittlement (HE) sensitivity and fracture mechanisms is still unclear. In present study the effect of cold/warm rolling on detailed microstructural characteristics of 304 ASS was quantitatively investigated and the corresponding HE sensitivity was evaluated via slow strain rate test. The results suggest that cold-rolling led to high strength but poor plasticity and deteriorated HE sensitivity while warm-rolled samples provided combination of high strength and ductility and also superior HE resistance. Compared with 18% α′-martensite in cold -rolled steel warm-rolled specimens consisted of complete austenite less twins and lower dislocation density，moreover the favorable {112} ND and {110} ND textures replaced the harmful {001} ND texture. Based on in-situ EBSD observation during SSRT the HE sensitivity was governed by the combined effect of pre-deformation microstructures and the dynamic microstructural evolution. Advanced method of time-of-flight secondary ion mass spectrometry was used to observe the distribution of hydrogen and the hydrogen content of specimens was determined by the gas chromatograph thermal desorption analysis method. An exceedingly small amount of hydrogen entered the warm-rolled samples while a large amount of hydrogen was trapped at grain boundaries of cold-rolled sample leading to complete intergranular fracture. Therefore warm rolling is an effective pathway for obtaining high combination of strength and ductility together with excellent HE sensitivity.

The report documents current knowledge of the social issues surrounding hydrogen projects. It reviews leading practice stakeholder engagement and communication strategies and findings from focus groups and research activities across Australia.

The full report can be found at this link.

This paper deals with the concept of micro-fracture map (MFM) and its role in structural integrity evaluations in materials science and engineering on the basis of previous research by the author on notch-induced fracture and hydrogen embrittlement of progressively cold drawn pearlitic steels and 316L austenitic stainless steel. With regard to this some examples are provided of assembly of MFMs in particular situations.

We have studied hydrogen gas production using photocatalysis from C2-C5 carbon chain polyols cyclic alcohols and mono and di-saccharides using palladium nanoparticles supported on a TiO2 catalyst. For many of the polyols the hydrogen evolution rate is found to be dictated by the number of hydroxyl groups and available a-hydrogens in the structure. However the rule only applies to polyols and cyclic alcohols while the sugar activity is limited by the bulky structure of those molecules. There was also evidence of ring opening in photocatalytic reforming of cyclic alcohols that involved dehydrogenation and decarbonylation of a CC bond.

A nuclear reactor pressure vessel (NRPV) wall is formed by two layer of different materials: an inner layer of stainless steel (cladding material) and an outer layer of low carbon steel (base material) which is highly susceptible to corrosion related phenomena. A reduction of the mechanical properties of both materials forming the wall would appear due to the action of the harsh environment causing hydrogen embrittlement (HE) related phenomena. As a result of the manufacturing process residual stresses and strains appear in the NRPV wall thereby influencing the main stage in HE: hydrogen diffusion. A common engineering practice for reducing such states is to apply a tempering heat treatment. In this paper a numerical analysis is carried out for revealing the influence of the heat treatment parameters (tempering temperature and tempering time) on the HE of a commonly used NRPV. To achieve this goal a numerical model of hydrogen diffusion assisted by stress and strain was used considering diverse residual stress-strain states after tempering. This way the obtained hydrogen accumulation during operation time of the NRPV provides insight into the better tempering conditions from the structural integrity point of view.

The UK Government signed legislation on 27th June 2019 committing the UK to a legally binding target of Net Zero emissions by 2050. Climate change is one of the most significant technical economic social and business challenges facing the world today.

The H21 NIC Phase 1 project delivered an optimally designed experimentation and testing programme supported by the HSE Science Division and DNV GL with the aim to collect quantifiable evidence to support that the UK distribution network of 2032 will be comparably as safe operating on 100% hydrogen as it currently is on

natural gas. This innovative project begins to fill critical safety evidence gaps surrounding the conversion of the UK gas network to 100% hydrogen. This will facilitate progression towards H21 Phase 2 Operational Safety Demonstrations and the H21 Phase 3 Live Trials to promote customer acceptability and ultimately aid progress towards a government policy decision on heat.

DNV GL and HSE Science Division were engaged to undertake the experimentation testing and QRA update programme of work. DNV GL and HSE Science Division also peer reviewed each other’s programme of work at various stages throughout the project undertaking a challenge and review of the experimental data and results to provide confidence in the conclusions.

A strategic set of tests was designed to cover the range of assets represented across the Great Britain gas distribution networks. The assets used in the testing were mostly recovered from the distribution network as part of the ongoing Iron Mains Risk Reduction Replacement Programme. Controlled testing against a well-defined master testing plan with both natural gas and 100% hydrogen was then undertaken to provide the quantitative evidence to forecast any change to background leakage levels in a 100% hydrogen network.

Key Findings from Phase 1a:

• Of the 215 assets tested 41 of them were found to leak 19 of them provided sufficient data to be able to compare hydrogen and methane leak rates.
• The tests showed that assets that were gas tight on methane were also gas tight on hydrogen. Assets that leaked on hydrogen also leaked
• on methane including repaired assets.
• The ratio of the hydrogen to methane volumetric leak rates varied between 1.1 and 2.2 which is largely consistent with the bounding values expected for laminar and turbulent (or inertial) flow which gave ratios of 1.2 and 2.8 respectively.
• None of the PE assets leaked; cast ductile and spun iron leaked to a similar degree (around 26-29% of all iron assets leaked) and the proportion of leaking steel assets was slightly less (14%).
• Four types of joint were responsible for most of the leaks on joints: screwed lead yarn bolted gland and hook bolts.
• All of the repairs that sealed methane leaks also were effective when tested with hydrogen.

The U.S. energy system is evolving as society and technologies change. Renewable electricity generation—especially from wind and solar—is growing rapidly and alternative energy sources are being developed and implemented across the residential commercial transportation and industrial sectors to take advantage of their cost security and health benefits. Systemic changes present numerous challenges to grid resiliency and energy affordability creating a need for synergistic solutions that satisfy multiple applications while yielding system-wide cost and emissions benefits. One such solution is an integrated hydrogen energy system (Figure ES-1). This is the focus of H₂@Scale—a U.S. Department of Energy (DOE) initiative led by the Office of Energy Efficiency and Renewable Energy’s Hydrogen and Fuel Technologies Office. H₂@Scale brings together stakeholders to advance affordable hydrogen production transport storage and utilization in multiple energy sectors. The H₂@Scale concept involves hydrogen as an energy intermediate. Hydrogen can be produced from various conventional and renewable energy sources including as a responsive load on the electric grid. Hydrogen has many current applications and many more potential applications such as energy for transportation—used directly in fuel cell electric vehicles (FCEVs) as a feedstock for synthetic fuels and to upgrade oil and biomass—feedstock for industry (e.g. for ammonia production metals refining and other end uses) heat for industry and buildings and electricity storage. Owing to its flexibility and fungibility a hydrogen intermediate could link energy sources that have surplus availability to markets that require energy or chemical feedstocks benefiting both. This document builds upon a growing body of analyses of hydrogen as an energy intermediate by reporting the results from our initial analysis of the potential impacts of the H₂@Scale vision by the mid-21st century for the 48 contiguous U.S. states. Previous estimates have been based on expert elicitation and focused on hydrogen demands. We build upon them first by estimating hydrogen’s serviceable consumption potential for possible hydrogen applications and the technical potential for producing hydrogen from various resources. We define the serviceable consumption potential as the quantity of hydrogen that would be consumed to serve the portion of the market that could be captured without considering economics (i.e. if the price of hydrogen were $0/kg over an extended period); thus it can be considered an upper bound for the size of the market. We define the technical potential as the resource potential constrained by real-world geography and system performance but not by economics. We then compare the cumulative serviceable consumption potential with the technical potential of a number of possible sources. Second we estimate economic potential: the quantity of hydrogen at an equilibrium price at which suppliers are willing to sell and consumers are willing to buy the same quantity of hydrogen. We believe this method provides a deeper understanding than was available in the previous analyses. We develop economic potentials for multiple scenarios across various market and technology-advancement assumptions.