[en] The bulk magnetic compound Sm₂(Fe_0.5Co_0.5)₁₇ was nitrided by two different processes: gaseous nitrogenation and fluidized bed nitrogenation. The nitrogen distribution was investigated by scanning electron microscopy, X-ray diffraction and chemical analysis. The cross-sectional nitrogen distribution differed according to the nitrogenation process: (1) nitrogen mainly diffuses along microcracks present in the samples with the gaseous nitrogenation, while it forms a nitrided layer parallel to the surface with the fluidized bed process, (2) the nitriding kinetics is controlled by diffusion (parabolic rate law) for the fluidized bed nitrogenation, whereas it is accelerated in the gaseous process. (orig.)

[en] In order to understand plasma processes and to obtain technological control in thin film deposition, the study of surface-plasma interactions is essential. Apart from the type and flux of the impinging ions/neutral atoms on the surface, the ion energy distribution (IED) is an important parameter in understanding surface modification due to the plasma. In this paper, results of ion energy analysis of the Thermionic Vacuum Arc (TVA) plasma ignited in carbon vapours are presented. An in-house, computer-controlled retarding field analyzer was used for determining experimentally ion energy distributions of the carbon ions arriving at the substrate. The correlation of the carbon IED with the applied arc voltage in the TVA plasma was put in evidence for the first time.

[en] Full text of publication follows: In this paper, a systematic study for the correlation of electrical parameters of the Tungsten plasma with ion energy distributions and deposition rate is presented. Tungsten films were deposited on stainless steel substrates for different plasma conditions. Thermal shock assessment was undertaken for all the films deposited under these conditions. Adherence tests were also performed for all samples. The deposition method used in this study was Thermionic Vacuum Arc (TVA) ignited in Tungsten vapors. The TVA deposition method briefly consists in obtaining a plasma in the vapors of the material to be evaporated. The vapors are obtained by heating the material with thermo electrons generated by an externally heated filament. The plasma is localized above the anode. The ions created in this plasma are accelerated towards the chamber walls (and subsequently towards the substrate) due to the potential difference between the plasma and the grounded walls. The energy of ions is directly proportional to this potential difference. This is an important feature of the method, as ion energy can be relatively easily controlled by external parameters. In plasma deposition, plasma diagnostic techniques are essential for understanding the process parameters. Ion energy and deposition rate are key parameters for technological control. An in-house, computer-controlled RFA analyzer was used for determination of ion energy distributions in these plasmas. The retarding field analyzer (RFA) is an electrical probe capable of providing ion energy distributions in plasmas. It was found that the ion energy increases with the power introduced into the system and it also decreases with decreasing filament current. The deposition rate was also measured for different values of plasma parameters using a computer-assisted Cressington gauge. A relative measurement of film adherence using a computer-assisted pull-off test equipment was also used. A clear picture of the optimal TVA plasma conditions for the highest adherence and also for the highest thermal shock is presented. (authors)

[en] Full text of publication follows: The JET main wall will be made of solid Be tiles. In order to assess the erosion rate of the thick Be wall tiles due to the plasma, an interlayer of Ni was used under a beryllium coating of a few microns. The 'marker' tiles will be placed in the areas of interest such as Outer Poloidal Limiters (OPL) and Inner Wall Guard Limiters (IWGL). The 'marker' is a Be tile with a stripe of an easily detected heavy metal (Ni) deposited on it as a thin interlayer, and with a few microns layer of the bulk-like Be on top of that. If the outer layer is eroded at the same rate as the bulk, then the erosion rate can be determined by measuring the distance of the interlayer from the final surface, for an eroded layer of a thickness that of the outer. An overview of the principles of manufacturing processes using plasma ignited in pure metal vapors by Thermionic Vacuum Arc (TVA) method [1] and the properties of the prepared coatings will be presented. The optimization of the manufacturing process (layer thickness, structure and purity) has been carried out on various substrates: glass, silicon, metals. The plasma diagnostic (the ion energy and electron temperature) during deposition and the results of the optimization process and analysis (SEM, TEM, XRD, Auger, RBS, AFM) of the coatings will be presented. Reference: [1] C. P. Lungu, I. Mustata, V. Zaroschi, A. M. Lungu, A. Anghel, P. Chiru, M. Rubel, P. Coad G. F. Matthews and JETEFDA contributors, Beryllium Coatings on Metals: Development of Process and Characterizations of Layers, Phys. Scr. T128 (2007) 157-161. (authors)

[en] Highlights: • Generated high dielectric constant polymer by blending two lower dielectric constant dipolar polymers. • Introduction of excess free volume using nanostructure engineering. • Highest dielectric constant with significantly low loss among dipolar polymers has been achieved. It is a great challenge in dielectric polymers to achieve a high dielectric constant while maintaining low dielectric loss and high operating temperatures. Here we report that by blending two glassy state dipolar polymers i.e., poly(arylene ether urea) (PEEU, K=4.7) and an aromatic polythiourea (ArPTU, K=4.4) to form a nanomixture, the resulting blend exhibits a very high dielectric constant, K=7.5, while maintaining low dielectric loss (<1%). The experimental and computer simulation results demonstrate that blending these dissimilar dipolar polymers causes a slight increase in the interchain spacing of the blend in its glassy state, thus reducing the barriers for reorientation of dipoles in the polymer chains along the applied electric field and generating a much higher dielectric response than the neat polymers.