| It has been paid attention to do research in the coatings to be used for fusion first wall in the world. The problem of chemical erosion for low Z coatings as facing materials has not been effectively solved up to now, even though a lot of work has been done and there has been made a great achievement in this field. Study of SiC coatings as low Z material was focused on the neutron irradiation resistance and measurements of permeability of H, D, T etc, the systematic study of mechanism in resistant H^ irradiation has rarely been reported yet. More attentions are paid to high Z materials because of their high melting point and low sputter rate, but such materials remain the problems of brittleness to which is harmful for their application. Research in W and Mo is focused on their erosion rate due to plasma etching and mechanical properties of W alloys in the developed countries while it seems that these work has not been done in our country.C-SiC coatings as low Z materials were selected to especially study the mechanism of H+ irradiation resistance, and W and Mo coatings as high Z materials were selected to study their ductility and tT irradiation resistance in our work.The main fields of our research work in C-SiC coatings as low Z materials are listed as below:1. Study in the preparation technologies of coatings: C-SiC coatings with lifferent SiC content on stainless steel substrate prepared by the techniquesof ion beam mixing and electron beam melting;2. Study in the structures of coatings: micro-morphology of C-SiC coatings analyzed by SEM and phases checked with XRD, TEM and Raman analyses:3. Study in hydrogen resistance and its mechanism: hydrogen resistance for C-SiC coatings measured by SIMS and its mechanism analyzed by XPS and IR.The main fields of our research work of W coatings as high Z materials are listed as below:1. Study in preparation technique of W coatings: prepared by ion beam mixing:2. Study in micro-structure of W coatings: micro-morphology of W coatings analyzed by SEM and phases checked with XRD, Raman and XPS analyses:3. Study in ductility and H irradiation resistance: ductility checked with Charpy instrumented impact tests and H irradiation resistance analyzed by SIMS.The main Conclusions with innovation significance are as follows: 1. Stud}' in mechanism of H irradiation resistance for C-SiC coatings has been firstly proceeded with IR and XPS analyses according to the effect of hydrogen on the chemical bonding states of the elements in the coatings.. Evidences of the configurations related to Hydrogen such as Si-CH2, Si-CH3, Si-H, C-H, C-H2, and C-H3 characterized by IR and XPS are firstlv discovered to connect to H irradiation resistance.3. It is found that N* ion implantation can improve the property of H irradiation resistance of C-SiC coatings which has not been done by other people yet.4. Based on the result in the improvement of H irradiation resistance of C-SiC coatings due to nitrogen ion implantation, the suggestion on its mechanism has been firstly made that N replaces C in SiC and active C from SiC moves to the surface as a new source, which reacts with H to form hydrocarbon bonds like C-H. Again, N reacts with H to form N-H bond by N* ion implantation, which increases the bonding with H. Obviously, such a double function for inhibit hydrogen permeation is due to N ion implantation.5. W coatings were prepared on stainless steel by ion beam mixing technique, which has not been carried out by other people.6. Charpy instrumented impact tests were first used for W coating specimens to check their ductility. It has been found that the ductile-brittle transition temperature for W coated specimens is in the range from about -66 癈 to about -87 癈, the SEM morphology on cross-section of the fracture of W coated specimens made at higher than -70癈 shows dimple ductile fracture. The results indicate that W coated specimens have a better ductility.
|
PDF Full Text Request