Manufacturing, high heat flux testing and post mortem analyses of a W-PIM mock-up

In the framework of the European material development programme for fusion power plants beyond the international thermonuclear experimental reactor (ITER), tungsten (W) is an attractive candidate as plasma facing material for future fusion reactors. The selection of tungsten is owing to its physical properties such as the high melting point of 3420 °C, the high strength and thermal conductivity, the low thermal expansion and low erosion rate. Disadvantages are the low ductility and fracture toughness at room temperature, low oxidation resistance, and the manufacturing by mechanical machining such as milling and turning, because it is extremely cost and time intensive. Powder Injection Molding (PIM) as near-net-shape technology allows the mass production of complex parts, the direct joining of different materials and the development and manufacturing of composite and prototype materials presenting an interesting alternative process route to conventional manufacturing technologies. With its high precision, the PIM process offers the advantage of reduced costs compared to conventional machining. Isotropic materials, good thermal shock resistance, and high shape complexity are typical properties of PIM tungsten. This contribution describes the fabrication of tungsten monoblocks, in particular for applications in divertor components, via PIM. The assembly to a component (mock-up) was done by Hot Radial Pressing (HRP). Furthermore, this component was characterized by High Heat Flux (HHF) tests at GLADIS and at JUDITH 2, and achieved 1300 cycles @ 20 MW/m². Post mortem analyses were performed quantifying and qualifying the occurring damage by metallographic and microscopical means. The crystallographic texture was analysed by EBSD measurements. No change in microstructure during testing was observed

Future directions and trends of the carbon fibre market

Carbon fibre production and its postprocessing is a sub-sector of the chemical industry. With the beginning of carbon fibre production in 1971, the market for those fibres is rather young. Commercial production of carbon fibres began in Japan and was initiated by companies like Toray, Toho Rayon (nowadays: Toho Tenax) and Mitsubishi. These companies still are among the biggest producers in the world. During the mid-1980s, US and European companies (e.g. Zoltek, Cytec and Hexcel) also have begun the production of carbon fibres, and there is also one important established producer (Formosa Plastics) from Taiwan. Although the latest developments show that more and more enterprises from related branches, most notably from polyacrylonitrile fibre production, and other regions are aiming at entering the carbon fibre market. Today polyacrylonitrile based carbon fibre production is dominated by 8 large companies. These 8 companies have more than 88 % of the worldwide production capacity of carbon fibres. Seen from a historical perspective, the main development direction of carbon fibres was maximizing of strength and Young's modulus and not mainly on the properties, which are needed for a proper CFRP layout. Furthermore, the required fibre properties are even unidentified in some cases

Optimization of process parameters during carbonization for improved carbon fibre strength

Based on their extraordinary properties, carbon fibres nowadays play a significant role in modern industries. In the last years carbon fibres are increasingly used for lightweight constructions in the energy or the transportation industry. However, a bigger market penetration of carbon fibres is still hindered by high prices (similar to 22 $/kg) [3]. One crucial step in carbon fibre production is the process of carbonization of stabilized fibres. However, the cause effect relationships of carbonization are nowadays not fully understood. Therefore, the main goal of this research work is the quantification of the cause-effect relationships of process parameters like temperature and residence time on carbon fibre strength

High strength and low weight hollow carbon fibres

Carbon fibres have strengths of 2.5 to 5 GPa in the fibre direction and an elastic modulus of 200 to 500 GPa. Carbon fibres have equal mechanical properties as steel but 20% of the weight. But the material is more expensive than steel. Therefore, they are only used in industry sectors where the benefits legitimate the high costs. The use of hollow rather than solid fibres allows an even lower weight of the components. At the same time, similar mechanical properties are achieved by the circular cross section. Carbon fibres are obtained from polyacrylonitrile fibers (PAN). These can be produced as hollow fibres. As a first step stabilization and carbonization of hollow PAN precursors is investigated to produce hollow carbon fibres