Distinct nonequilibrium plasma chemistry of C2 affecting the synthesis of nanodiamond thin films from C2H2 (1%)/H2/Ar-rich plasmas

6 pages, 5 figures, 6 tables.We show that the concentrations of the species C2 (X 1Σg+), C2 (a 3Πu), and C2H exhibit a significant increase when the argon content grows up to 95% in medium pressure (0.75 Torr) radio frequency (rf) (13.56 MHz) produced C2H2 (1%)/H2/Ar plasmas of interest for the synthesis of nanodiamond thin films within plasma enhanced chemical vapor deposition devices. In contrast, the concentrations of CH3 and C2H2 remain practically constant. The latter results have been obtained with an improved quasianalytic space–time-averaged kinetic model that, in addition, has allowed us to identify and quantify the relative importance of the different underlying mechanisms driving the nonequilibrium plasma chemistry of C2. The results presented here are in agreement with recent experimental results from rf CH4/H2/Ar-rich plasmas and suggest that the growth of nanodiamond thin films from hydrocarbon/Ar-rich plasmas is very sensitive to the contribution of C2 and C2H species from the plasma.This work was partially funded by CICYT (Spain) under a Ramón y Cajal project and under Project No. TIC2002- 03235. One of the authors (F.J.G.V.) acknowledges a Ramón y Cajal contract from the Spanish Ministry of Science and Technology (MCYT). One of the authors (J.M.A.) acknowledges partial support from CICYT (Spain) under Project No. MAT 2002-04085-C02-02.Peer reviewe

Design model for reinforcement corrosion

The performance-based durability design of reinforced concrete structures for corrosion of reinforcement is currently limited to the initiation period. That includes modelling the transport processes of chlorides and carbon dioxide into the concrete structure. Up to now, the subsequent time period after depassivation of the reinforcement, in which corrosion propagates, could not be modelled in a comparable manner. The task of the research project presented here, which was part of German Research Unit 537, was to develop a design model that enables a reinforced concrete structure to be designed against reinforcement corrosion for its entire service life. Therefore, a physically well-defined damage model for corrosion propagation was chosen as a basis. All system parameters in the damage model were investigated on the basis of numerical and laboratory studies carried out in the subprojects of the research unit. Statistical analysis allowed the simplification of the complex damage model into a user-friendly design model. This paper presents the working steps, the basic results of the analysis and the user-friendly full-probabilistic design model for reinforcement corrosion