This article discusses a new concept in history learning with a thematic history approach, namely environmental history. This concept is needed forlearning in schools in order to achieve several SDGs indicators, to welcome Society 5.0, and to meet the needs of learning innovation in the Merdeka Curriculum. This study uses qualitative research methods with data collection techniques through in-depth interviews, documentation, literature, and questionnaires. Data analysis was carried out by: (1) data reduction; (2) data presentation; and (3) data verification. The results of this study consist of theoretical basis for the implementation of thematic history learning in schools; the concept of Ecohistory and its relevance to the achievement of the SDGs to meet Society 5.0; and its implementation at school. Keywords: learner-centered instruction, teacher-centered instruction, English proficiency, student teachers

The plasma-facing components (PFCs) of future fusion reactors will have intricate structures and require multiple materials because no one material can simultaneously satisfy all the requirements of the component. The dissimilar material joints in PFCs must withstand extreme thermal and stress gradients under neutron irradiation. The Fusion Research Oriented to Neutron Irradiation and Tritium Behavior at Material Interfaces (FRONTIER) U.S.-Japan collaboration seeks to explore and explain the behavior of internal solid interfaces in PFCs under neutron irradiation. The first step of the collaboration was to identify the leading PFCs that should be studied further and prepare them for the next step, which will include neutron irradiation. Different strategies for material development are being pursued worldwide to produce robust PFCs. Here, an overview is presented of some of the most promising materials in the areas of copper alloys, tungsten-copper composites, tungsten-steel composites, additively manufactured tungsten, particle-reinforced tungsten, and tungsten and SiC fiber composites. Each material's fabrication and benefits are described, and some discussion of remaining questions is given.

Micro-tensile testing has been used to study the response of pure tungsten and two tungsten alloys to helium ion irradiation. Commercially supplied plates of W, W-5Ta and W-5Re were irradiated using 6 MeV helium ions at room temperature. The ion energy was attenuated with an energy spreading device such that a uniform level of damage at 0.6 dpa (and 11,000 appm He) was deposited at the 3–9 µm depth. Focused ion beam milling was used to fabricate dog-bone shaped, micro-tensile samples 5 × 5 µm in cross-sectional area and 17 µm in length from the unirradiated and irradiated samples. All micro-tensile samples were tested at a quasi-static strain rate and the stress–strain curves were analysed to determine the mechanical properties. A close correlation was found between micro-tensile results and the bulk mechanical properties reported in the literature. Comparison between the unirradiated micro-tensile properties of W-5Re and W-5Ta with W showed that, as expected, W-5Re was softer than W whilst W-5Ta had only minor differences in micro-tensile properties compared with W. The micro-tensile results of the irradiated W, W-5Ta and W-5Re showed an increase in strength and an almost complete loss of ductility compared to the unirradiated samples. In comparing micro-tensile results to nanoindentation measurements, it was found that micro-tensile offers comparable level of precision in measurement of irradiation hardening amongst W, W-5Ta and W-5Re. The implications of the results with respect to the future performance of tungsten-based materials in the divertors in fusion reactors are discussed in detail.

Atom probe tomography was used to characterise two low-Cu (< 0.04 at. %) model steels after exposure to long-term thermal ageing. Mn-Ni-Si-rich features were observed to form after as little as 20,731 h (similar to 2.4 years) of ageing. The composition of these features were compared to those predicted by thermodynamic models and the similarities and differences are discussed. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A cobalt-free tungsten carbide cermet (WC-FeNi) has been subjected to oxyacetylene flame tests to simulate extreme operating conditions such as a worst-case fusion reactor accident. In such an accident, air-ingress to the reactor may impinge on components operating at surface temperatures in excess of 1000 degrees C, leading to tungsten oxide formation and its subsequent hazardous volatilisation. Here, the most challenging accident stage has been simulated, where the initial air-ingress could lead to extremely rapid air-flow rates. These conditions were simulated using an oxidising oxyacetylene flame. The separation between flame nozzle and sample was varied to permit peak surface temperatures of similar to 950-1400 degrees C. When the peak temperature was below 1300 degrees C, the cermet gained mass due to the dominance of oxide scale formation. Above 1300 degrees C, the samples transitioned into a mass loss regime. The mass loss regime was dominated by liquid-phase ablation of the scale rather than its volatili-sation, which was confirmed by performing a systematic thermogravimetric kinetic analysis. The result was unexpected as in other candidate shielding materials, e.g. metallic tungsten, volatilisation is considered the primary dispersion mechanism. The unusual behaviour of the cermet scale is explained by its relatively low melting point and by the lower volatility of its FeWO4 scale compared to tungsten's WO3 scale. The substantially lower volatility of the WC cermet scale compared to metallic W scales indicates it may have a superior accident tolerance.

Neutron shielding materials are a critical area of development for nuclear fusion technology. In the compact spherical tokamak, shielding efficiency improvements are particularly needed because of severe space constraints. The most spatially restricted component is the central column shield. It must protect the superconducting magnets from excessive radiation-induced degradation, but also from associated heating, so that energy consumption of the cryogenic systems is kept to an acceptable level. Recent simulations show that tungsten carbide and its composites form an attractive class of neutron-attenuating materials. In this paper, the key structure-property relationships of these materials are assessed, as they relate to generic materials challenges for plasma-facing materials. We first consider some fundamental materials properties of monolithic tungsten carbide including thermal transport, mechanical properties and plasma interaction. WC is found to have generally favourable properties compared to metallic tungsten shields. We then report progress on the development of a new candidate cermet material, WC-FeCr. Recent results on its accident safety, thermo-mechanical properties, and irradiation behaviour are presented. This review also highlights the need for further study, particularly in the areas of irradiation damage and hydrogen trapping. This article is part of a discussion meeting issue 'Fusion energy using tokamaks: can development be accelerated?'.

Tungsten carbide (WC) has been found to have higher resistance to plasma-induced thermal shock compared to rolled tungsten. The electron beam device JUDITH 1 was used to simulate likely thermal shock conditions induced by edge localised modes and plasma disruptions. Loading conditions of 100-1000 cycles, heat fluxes of 0.19-1.13 GW/m(2) and base temperatures of 400-1000 degrees C were employed on two candidate WC-based materials: a monolithic WC ceramic, and a WC-FeCr composite. Surprisingly, the monolith outperformed the composite under all conditions. This was unexpected, particularly at 400 degrees C, based on the calculated thermal shock resistance parameters. The result was explained by preferential melting of the metallic FeCr binder. Compared to available data collected under identical conditions on rolled tungsten plate, monolithic WC had lower surface roughness from thermal shock damage, particularly when tested at 400 degrees C. This shows promise for its use as a plasma facing material. Strategies for further improving performance are discussed. (C) 2019 Elsevier B.V. All rights reserved.

We demonstrate the outstanding dynamic strength of nano-quasicrystalline Al93Fe3Cr2Ti2 at.% alloy and composites. Unlike most crystalline Al alloys, this alloy exhibits substantial strain rate sensitivity and retains ductility at high strain rates. This opens new pathways for use in safety-critical materials requiring impact resistance.

Nano-quasicrystalline Al93Fe3Cr2Ti2 alloy has shown good specific tensile and compressive strength and thermal stability in previous studies, though with reduced ductility. In the present work, composites were produced with the addition of pure Al fibres to improve ductility. The first dynamic tensile and compressive tests ever performed on this alloy and composites showed outstanding flow stress reaching 1GPa. The tremendously high flow stress, coupled with the alloysu0027s strain hardening response opens new pathways for use as a candidate material for impact applications.

To understand the contribution of the long term thermal ageing to Reactor Pressure Vessel embrittlement a series of weld materials containing systematic variations of Ni has been thermally aged for times up to 100,000 h at 330 degrees C and 365 degrees C. Microstructural characterisation using Atom Probe Tomography was performed. Thermal ageing produced a high number density of nano-scale Cu-enriched clusters. Ni has a strong influence on Cu precipitation, enhancing the homogeneous nucleation of Cu clusters. The nanometre size Cu clusters have a Ni-Mn-Si rich interface which was found to be wider in steels with higher bulk Ni content. This interface reduces the interfacial energy of the Cu-enriched clusters through a combination of the minimising of unfavourable Fe Cu bonds and reduction in lattice strain. Matrix Cu levels after ageing for 90,000-100,000 h were found to be around 0.06-0.08 at%, close to the expected solubility limits for Cu in Fe.

Results are reported on cemented tungsten carbide (cWC) and boride-containing composite materials for the task of shielding the centre column of a superconducting tokamak power plant. The shield is based on five concentric annular shells consisting of cWC and water layers of which the innermost cWC shield can be replaced with boride composites. Sample materials have been fabricated changing the parameters of porosity P, binder alloy fraction f(binder) and boron weight fraction f(boron). For the fabricated materials, and other hypothetical samples with chosen parameters, Monte Carlo studies arc made of: (i) the power deposition into the superconducting core, (ii) the fast neutron and gamma fluxes and (iii) the attenuation coefficients through the shield for the deposited power and neutron and gamma fluxes. It is shown that conventional Co-based cWC binder alloy can be replaced with a Fe-Cr alloy (92 wt.% Fe, 8 wt.% Cr), which has lower activation than cobalt with minor changes in shield performance. Boride-based composite materials have been prepared and shown to give a significant reduction in power deposition and flux, when placed close to the superconducting core. A typical shield of cemented tungsten carbide with 10 wt.% of Fe-8Cr binder and 0.1% porosity has a power reduction half-length of 0.06 in. It is shown that the power deposition increases by 4.3% for every 1% additional porosity, and 1.7% for every 1 wt.% additional binder. Power deposition decreased by 26% for an initial 1 wt.% boron addition, but further increases f(boron) showed only a marginal decrease. The dependences of power deposited in the core, the maximum neutron and gamma fluxes on the core surface, and the half attenuation distances through the shield have been fitted to within a fractional percentage error by analytic functions of the porosity, metallic binder alloy and boron weight fractions.

Atom Probe Tomography (APT) and Transmission Electron Microscopy (TEM) are combined for examining a case formation in Ti-6Al-4V, generated by air exposure at 800 degrees C. Below the oxide surface, the microstructure separates into a nanoscale mixture of the alpha-Ti and alpha(2) Ti3Al phases, of compositions Ti70-030 and Ti65-010-A120-V5 respectively. The alpha(2) phase exists either as bands or as nanoscale spherical precipitates. Nitrogen also penetrates the surface, but to a lesser extent, while vanadium partitions to alpha(2) or in distinctly separate phases. The results demonstrate that oxygen stimulates precipitation of alpha(2), helping to explain embrittlement produced in the O-enriched layer beneath the oxide. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A new candidate fusion engineering material, WC-FeCr, has been irradiated with He ions at 25 and 500 degrees C. Ions were injected at 6 keV to a dose of similar to 15 dpa and 50 at. % He, simulating direct helium injection from the plasma. The microstructural evolution was continuously characterised in situ using transmission electron microscopy. In the FeCr phase, a coarse array of 3-6 nm bubbles formed. In the WC, bubbles were less prominent and smaller (similar to 2 nm). Spherical-cap bubbles formed at hetero-phase interfaces of tertiary precipitates, indicating that enhanced processing routes to minimise precipitation could further improve irradiation tolerance. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd.

Tokamak Energy Ltd, UK, is developing spherical tokamaks using high temperature superconductor magnets as a possible route to fusion power using relatively small devices. We present an overview of the development programme including details of the enabling technologies, the key modelling methods and results, and the remaining challenges on the path to compact fusion.

A major concern for 17-4PH steels operating at elevated temperatures is embrittlement due to Fe-rich (alpha) and Cr-enriched (alpha') phase separation, along with precipitation of other detrimental phases. In this study the sequence of microstructural changes at the atomic scale in a 17-4PH steel is characterized by atom probe tomography (APT) at two different ageing temperatures, 480 degrees C and 590 degrees C. In the earliest stages of heat treatment at both temperatures, APT reveals that dislocations and matrix defects are highlighted by the segregation of NbN/CrN ionic species, providing heterogeneous nucleation sites for subsequent Cu-rich precipitates (CRPs) and Nb-rich precipitates, respectively. At the lower temperature, Cr-rich a'-phase also nucleates and ultimately a Mn, Ni, and Si-rich (MNS) phase was observed to form. The evolution in number density and fraction of CRPs and Cr-rich alpha'-phase, the latter of which was not observed at the higher temperature, has been quantified and their respective contributions to the overall precipitation hardening of the material has been estimated. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. This is an open access article under the CC BY license.

An automated procedure has been developed for the reconstruction of field ion microscopy (FIM) data that maintains its atomistic nature. FIM characterizes individual atoms on the specimen’s surface, evolving subject to field evaporation, in a series of two-dimensional (2D) images. Its unique spatial resolution enables direct imaging of crystal defects as small as single vacancies. To fully exploit FIM’s potential, automated analysis tools are required. The reconstruction algorithm developed here relies on minimal assumptions and is sensitive to atomic coordinates of all imaged atoms. It tracks the atoms across a sequence of images, allocating each to its respective crystallographic plane. The result is a highly accurate 3D lattice-resolved reconstruction. The procedure is applied to over 2000 tungsten atoms, including ion-implanted planes. The approach is further adapted to analyze carbides in a steel matrix, demonstrating its applicability to a range of materials. A vast amount of information is collected during the experiment that can underpin advanced analyses such as automated detection of “out of sequence” events, subangstrom surface displacements and defects effects on neighboring atoms. These analyses have the potential to reveal new insights into the field evaporation process and contribute to improving accuracy and scope of 3D FIM and atom probe characterization.

Rapidly solidified nano-quasicrystalline Al93Fe3Cr2Ti2 at% alloy has previously shown outstanding tensile and compressive strength and microstructural stability up to elevated temperatures. Despite this, no study had previously assessed the effect of plastic deformation at elevated temperature to simulate thermal-mechanical forging processes for the production of engineering components. The present work analysed bars consisting of a nano-quasicrystalline Al93Fe3Cr2Ti2 at% alloy matrix, with the addition of 10 and 20vol% pure Al ductilising fibres, produced through gas atomisation and warm extrusion. The microstructure was made primarily of nanometre-sized icosahedral particles in an α-Al matrix. Compression tests were performed across a range of temperatures and strain rates. The measured yield strength at 350°C was over 3x that of “high strength” 7075 T6 Al alloy, showing outstanding thermal stability and mechanical performance. However, the microstructure was shown by XRD to undergo a phase transformation which resulted in the decomposition of the icosahedral phase around ~500°C into more stable intermetallic phases. Serrated flow associated with dynamic strain ageing was observed and a semi-quantitative analysis matching elemental diffusion speeds with dislocation speed at specific strain rates was performed, which tentatively identified Ti as the solute species responsible within the selected range of temperatures and strain rates.

Numerical studies have been made to improve the performance of the central column of a superconducting spherical tokamak fusion pilot plant. The assumed neutron shield includes concentric layers of tungsten carbide and water. The relative thickness of the water layers was varied and a minimum power deposition was found at about 17% of water. It was found advantageous to have an approximately 1.7 times thicker water layer next to the core and a similarly thinner layer next to the plasma. The use of tungsten boride instead of tungsten carbide was shown to make an improvement especially if placed close to the central superconducting core, the inner layer alone reducing the power deposition by 29%. Engineering features such as a central steel tie-bar, an insulating thermal vacuum gap, a wall gap next to the plasma and knowledge of the vertical energy distribution are essential to a successful design and their effects on the power deposition are shown in an appendix. The results have been fitted to model distributions and incorporated into the Tokamak Energy System Code, which can then give predictions of the power deposition as a function of other parameters such as the plasma major radius and the maximum magnetic field permitted on the superconductors.

An automated procedure has been developed for the 3D reconstruction of field ion microscopy (FIM) data that maintains the atomistic nature of the technique. FIM characterises individual atoms on the surface of a specimen, that is evolving subject to the process of field evaporation, in a series of 2D time-ordered images. It’s unique spatial resolution enables the direct imaging of crystal defects, as small as single vacancies. In order to exploit the full potential of FIM, automated analysis tools are required. The reconstruction algorithm developed in this work relies on minimal assumptions and is sensitive to the atomic coordinates of all imaged atoms. It tracks the atoms across a sequence of FIM images and allocates each one to its respective crystallographic plane. The result is a highly accurate 3D lattice-resolved reconstruction. The procedure is applied here to over 2000 tungsten atoms, including several ionimplanted planes of the sample. The approach is also adapted for the analysis of carbides in a bearing steel matrix, to demonstrate its potential applicability to the study of a broader range of materials. A vast amount of additional information is collected during the experiment. This information can underpin advanced analyses such as automated detection of ‘out of sequence’ events, sub-angstrom displacements of atoms and defects effects on neighbouring atoms. These analyses have the potential to reveal new insights into the field evaporation process and contribute to improving accuracy and scope of 3DFIM and atom probe characterisation.