Transmission, Distribution & Storage

This report is commissioned by the Henry Royce Institute for advanced materials as part of its role around convening and supporting the UK advanced materials community to help promote and develop new research activity. The overriding objective is to bring together the advanced materials community to discuss analyse and assimilate opportunities for emerging materials research for economic and societal benefit. Such research is ultimately linked to both national and global drivers namely Transition to Zero Carbon Sustainable Manufacture Digital & Communications Circular Economy as well as Health & Wellbeing.

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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.

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.

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.

Twinning-induced plasticity (TWIP) steels have higher strength and ductility than conventional steels. Deformation mechanisms producing twins that prevent gliding and stacking of dislocations cause a higher ductility than that of steel grades with the same strength. TWIP steels are considered to be within the new generation of advanced high-strength steels (AHSS). However some aspects such as the corrosion resistance and performance in service of TWIP steel materials need more research. Application of TWIP steels in the automotive industry requires a proper investigation of corrosion behavior and corrosion mechanisms which would indicate the optimum degree of protection and the possible decrease in costs. In general Fe−Mn-based TWIP steel alloys can passivate in oxidizing acid neutral and basic solutions however they cannot passivate in reducing acid or active chloride solutions. TWIP steels have become as a potential material of interest for automotive applications due to their effectiveness impact resistance and negligible harm to the environment. The mechanical and corrosion performance of TWIP steels is subjected to the manufacturing and processing steps like forging and casting elemental composition and thermo-mechanical treatment. Corrosion of TWIP steels caused by both intrinsic and extrinsic factors has posed a serious problem for their use. Passivity breakdown caused by pitting and galvanic corrosion due to phase segregation are widely described and their critical mechanisms examined. Numerous studies have been performed to study corrosion behaviour and passivation of TWIP steel. Despite the large number of articles on corrosion few comprehensive reports have been published on this topic. The current trend for development of corrosion resistance TWIP steel is thoroughly studied and represented showing the key mechanisms and factors influencing corrosion processes and its consequences on TWIP steel. In addition suggestions for future works and gaps in the literature are considered.

A systematic study of different ratios of CO CO₂ N₂ gas components on the hydrogen storage properties of the Na₃AlH₆ complex hydride with 4 mol% TiCl3 8 mol% aluminum and 8 mol% activated carbon is presented in this paper. The different concentrations of CO and CO₂in H₂ and CO CO₂ N₂ in H₂ mixture were investigated. Both CO and CO₂gas react with the complex hydride forming Al oxy-compounds NaOH and Na₂CO₃ that consequently cause serious decline in hydrogen storage capacity. These reactions lead to irreversible damage of complex hydride under the current experimental condition. Thus after 10 cycles with 0.1 vol % CO + 99.9 vol %H₂ and 1 vol % CO + 99 vol %H₂ the dehydrogenation storage capacity of the composite material decreased by 17.2% and 57.3% respectively. In the case of investigation of 10 cycles with 1 vol % CO₂ + 99 vol % H₂ gas mixture the capacity degradation was 53.5%. After 2 cycles with 10 vol % CO +90 vol % H₂  full degradation was observed whereas after 6 cycles with 10 vol % CO₂+ 90 vol % H₂ degradation of 86.8% was measured. While testing with the gas mixture of 1.5 vol % CO + 10 vol % CO₂+ 27 vol % H₂ + 61.5 vol % N2 the degradation of 94% after 6 cycles was shown. According to these results it must be concluded that complex aluminum hydrides cannot be used for the absorption of hydrogen from syngas mixtures without thorough purification.

Interest in hydrogen fuel is growing for automotive applications; however safe dense solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material protected from oxygen and moisture by the rGO layers exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H₂ per litre in the total composite). As rGO is atomically thin this approach minimizes inactive mass in the composite while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.

The EU has set a goal of achieving climate neutrality by 2050 and decided to raise its 2030 climate target to 55%. For this the EU needs to transform its energy system. It is of paramount importance that it will become more efficient affordable and interconnected. Hydrogen can play a pivotal role in the EU’s decarbonisation efforts and be at the centre of the energy system integration supporting transport of renewable energy over very long distances and facilitating renewables storage from one season to another.<br/><br/>ENTSOG GIE and Hydrogen Europe have joined forces on a factsheet that answers a number of fundamental questions about gaseous and liquid hydrogen transport and storage titled “How to transport and store hydrogen? Facts and figures”. This factsheet provides an objective and informative analysis on key concepts terminology and facts and figures from different public sources.<br/><br/>The factsheet illustrates the EU’s potential to enable a global hydrogen economy and to become a global technology leader due to its extensive gas infrastructure that can be used to transport blends of hydrogen or be converted to transport pure hydrogen.

This study focuses on structural imperfections caused by hydrogen impurities in AlN thin films obtained using atomic layer deposition method (ALD). Currently there is a severe lack of studies regarding the presence of hydrogen in the bulk of AlN films. Fourier-transform infrared spectroscopy (FTIR) is one of the few methods that allow detection bonds of light elements in particular - hydrogen. Hydrogen is known to be a frequent contaminant in AlN films grown by ALD method it may form different bonds with nitrogen e.g. amino (–NH2) or imide (–NH) groups which impair the quality of the resulting film. Which is why it is important to investigate the phenomenon of hydrogen as well as to search for the suitable methods to eliminate or at least reduce its quantity. In this work several samples have been prepared using different precursors substrates and deposition parameters and characterized using FTIR and additional techniques such as AFM XPS and EDS to provide a comparative and comprehensive analysis of topography morphology and chemical composition of AlN thin films.

The rapid development of hydrogen energy requires the use of natural gas infrastructure for hydrogen transportation. It is very important to study hydrogen-added natural gas transportation technology which is a key way to rapidly develop coal-based gas and renewable energy. This study aims to study the influence of X80 pipeline steel's fatigue performance in hydrogen environment and perform fatigue tests on notched round rod specimens under different hydrogen concentration. The experimental results show that hydrogen seriously affects the fatigue life of pipeline steel. After reaching a certain hydrogen concentration as the hydrogen concentration continues to increase the fatigue life decreases gradually. Combined with SEM analysis of fracture morphology the decrease in the size and density of the dimples reduces the displacement amplitude while the increase in the planar area increases the displacement during fatigue fracture due to accelerated crack propagation. From this study we can know the influence of hydrogen concentration on the fracture morphology of pipeline steel which provides an understanding of the effect of hydrogen on fatigue fracture morphology and a broader safety analysis.