%0 Journal Article
%A Raumann, Leonard
%A Coenen, Jan Willem
%A Riesch, Johann
%A Mao, Yiran
%A Schwalenberg, Daniel
%A Gietl, Hanns
%A Linsmeier, Christian
%A Guillon, Olivier
%T Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser Wf/W Composites
%J Metals
%V 11
%N 7
%@ 2075-4701
%C Basel
%I MDPI
%M FZJ-2021-03231
%P 1089 -
%D 2021
%X Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall and armor material for future fusion devices. However, its intrinsic brittleness and its embrittlement during operation bears the risk of a sudden and catastrophic component failure. As a countermeasure, tungsten fiber-reinforced tungsten (Wf/W) composites exhibiting extrinsic toughening are being developed. A possible Wf/W production route is chemical vapor deposition (CVD) by reducing WF6 with H2 on heated W fabrics. The challenge here is that the growing CVD-W can seal gaseous domains leading to strength reducing pores. In previous work, CVD models for Wf/W synthesis were developed with COMSOL Multiphysics and validated experimentally. In the present article, these models were applied to conduct a parameter study to optimize the coating uniformity, the relative density, the WF6 demand, and the process time. A low temperature and a low total pressure increase the process time, but in return lead to very uniform W layers at the micro and macro scales and thus to an optimized relative density of the Wf/W composite. High H2 and low WF6 gas flow rates lead to a slightly shorter process time and an improved coating uniformity as long as WF6 is not depleted, which can be avoided by applying the presented reactor model.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000676817800001
%R 10.3390/met11071089
%U https://juser.fz-juelich.de/record/894452