A target assembly, composed of several collinear molybdenum (Mo)‐based and tungsten (W)‐based cylindrical blocks, will reside in the core of the new beam dump facility (BDF) being designed at the European Laboratory for Particle Physics (CERN). The target blocks will be protected from the cooling water erosion‐corrosion by a tantalum (Ta)‐based cladding.
In order to obtain intimate and reliable bonding between the several cylinders composing each target block and with the cladding, hot isostatic pressing (HIP) assisted diffusion bonding technique was explored. Several down‐scaled target block prototypes were conceived to investigate the bondings. Starting from the previously gained experience in Ta cladding on W from neutron spallation targets, here, we present results on Ta cladding on TZM (Mo alloy), Ta2.5W (Ta alloy) cladding on TZM and W, and on TZM to TZM and W to W self‐bondings. The resulting interfaces were systematically characterized with electron microscopy, tensile testing, and thermal conductivity measurements.
Successful diffusion bonding was achieved for all the studied material combinations, resulting in homogeneous and defect‐free interfaces, strong interfacial bondings, and limited interfacial thermal contact resistance. The HIP parameters and diffusion interfacial aids were of great importance to optimize the interface and bulk material properties.
Graphite provides a good opportunity for the development of new metal matrix composites (MMCs) due to its interesting properties, including thermal conductivity, high internal damping, and low density. According to the particular application, metal–graphite composites with their tailored properties can be used in the areas of thermal management of electronic devices. Metal–graphite composites show anisotropic properties due to the orientation of the graphite flakes during consolidation. Powder metallurgical technologies can be used to manufacture composites with graphite contents up to 90 vol. %. Besides copper, other matrices were investigated like tungsten, aluminium, and iron. The thermophysical properties (thermal conductivity, thermal expansion) as well as damping properties were characterized as a function of the composition. Interesting metal–graphite composites combining tungsten and 70 vol. % graphite flakes show a thermal conductivity in two directions of 400 W/mK in combination with a physical coefficient of thermal expansion of 3·5 ppm/K and a high damping
Determining the thermal conductivity is crucial whenever heat transfer issues are considered which play a major role in many technological applications. However, various materials are sensitive to oxygen or moisture and, therefore, cannot be examined with commonly used equipment under ambient conditions. Here, we present a novel approach which combines the inert requirements of ambient-sensitive specimens with the flash method in which the apparatus, a Netzsch LFA 447 NanoFlash®, is placed under ambient conditions. A new measuring cell with flash-transparent windows was constructed which resembles a gas-tight specimen chamber. This device can be easily adapted to other apparatuses based on the flash method. The thermal conductivities of reference materials in inert and ambient conditions were examined in a temperature range from 25 to 275 °C. In general an excellent agreement was found. Further, the usability of this special sample cell is demonstrated for the investiga tion of the thermal conductivities of two complex hydride systems which are important for solid-state hydrogen storage applications
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