Search

Successful upscaling of tungsten fiber‐reinforced tungsten composites (Wf/W) on industrial level could represent an important milestone for future nuclear fusion reactors. The primary objective of these materials is to enhance the durability and operational lifespans of critical components. Developing mature manufacturing approaches remains a challenge, highlighting the need for innovative solutions. This study evaluates the feasibility of merging chemical vapor deposition (CVD) with spark plasma sintering (SPS) for producing such composites. This analysis indicates that combining CVD‐W sealed tungsten fabrics with SPS requires additional manufacturing steps or the utilization of tungsten powders for effective sintering. The process is currently only suitable for simple textile structures utilizing single filaments, mitigating one of the main advantages of CVD. Configurations such as radially braided yarns are currently less compatible to the high stress levels during SPS. A key outcome of this work is the introduction of a thin secondary CVD‐W interface into the composite design, substantially improving the stability of the yttria‐interface and effectively shielding the W‐fibers from potential matrix interactions. This innovation reduces issues such as carbon embrittlement and allows the potential integration of tungsten fibers into different matrix materials such as ceramics, broadening the potential application range of tungsten fiber‐reinforcements. [ABSTRACT FROM AUTHOR]

For the future fusion reactor, tungsten is the main candidate material as the plasma-facing material. However, considering the high thermal stress during operation, the intrinsic brittleness of tungsten is one of the issues. To overcome the brittleness, tungsten fiber reinforces tungsten composites (Wf/W) developed using extrinsic toughening mechanisms. The powder metallurgy process and chemical vapor deposition process are the two production routes for preparing Wf/W. For the powder metallurgy route, due to technical limitations, previous studies focused on short random distributed fiber-reinforced composites. However, for short random fiber composites, the strength and reinforcement effect are considerably limited compared to aligned continuous fiber composites. In this work, aligned long tungsten fiber reinforced tungsten composites have been first time realized based on powder metallurgy processes, by alternately placing tungsten weaves and tungsten powder layers. The produced Wf/W shows significantly improved mechanical properties compared to pure W and conventional short fiber Wf/W. [ABSTRACT FROM AUTHOR]

For future fusion reactors, tungsten (W) is currently the main candidate for the application as plasma‐facing material due to its several advanced properties. To overcome the brittleness of W, randomly distributed short W fiber‐reinforced W (Wf/W) composites have been developed using field‐assisted sintering technology (FAST). Herein, Wf/W materials with different fiber volume fraction (20–60%) are manufactured by FAST process to study the fiber volume fraction influence on the composite properties. Wf/W with ductile fibers and brittle fibers is produced using different tool setups during the production. Three‐point bending tests on prenotched samples, 4‐point bending tests, and tensile tests have been performed to determine the fracture behavior and flexural/tensile strength of the material. Wf/W materials with 30–40% fiber volume fraction exhibit a promising pseudoductile behavior, similar to fiber‐reinforced ceramic composites. However, Wf/W with 20% and >50% fiber volume fraction shows only a limited extrinsic toughening effect. In terms of flexural strength, with increasing fiber volume fraction, the tensile/flexural strength does not show a clear increasing tendency, or even lightly decreases. [ABSTRACT FROM AUTHOR]

• We investigated the ductile to brittle transition temperature (DBTT) of tungsten fiber-reinforced tungsten. • The DBTT of the used tungsten fiber is very low (∼−50 °C) while it is relatively high (∼1000 °C) for the tungsten matrix. • Increasing fiber volume fracture would lead to a measurable Charpy impact energy already at room temperature. Tungsten features a unique combination of properties that makes it a favorable plasma-facing material in fusion reactors. The main drawbacks of tungsten are its brittleness at room temperature and the potential embrittlement during operation. Tungsten fiber–reinforced composites have the potential to overcome these limitations. Charpy impact tests ranging from −150 °C to 1000 °C have been performed. To identify the ductile-to-brittle transition temperature and understand the behavior at high temperature a detailed microscopic investigation was used to identify the transition temperature of fiber and matrix, which was between −100 °C to −50 °C and 1000 °C, respectively. [ABSTRACT FROM AUTHOR]

During an accident with loss-of-coolant and air ingress in DEMO, the temperature of tungsten first wall cladding may exceed 1000 °C and remain for months leading to tungsten oxidation. The radioactive tungsten oxide can be mobilized to the environment at rates of 10–150 kg per hour. Smart tungsten-based alloys are under development to address this issue. Alloys are aimed to function as pure tungsten during regular plasma operation of DEMO. During an accident, alloying elements will create a protective layer, suppressing release of W oxide. Bulk smart alloys were developed by using mechanical alloying and field-assisted sintering technology. The mechanical alloying process was optimized leading to an increased powder production by at least 40 %. Smart alloys and tungsten were tested under a variety of DEMO-relevant plasma conditions. Both materials demonstrated similar sputtering resistance to deuterium plasma. Under accident conditions, alloys feature a 40-fold reduction of W release compared to that of pure tungsten. [ABSTRACT FROM AUTHOR]