Materials Science Forum Vol. 802

Abstract: The high coercivity region of the Nd-Fe-B and Sm-Co phase diagrams is discussed. Slow cooling heat treatments may eliminate lattice defects, which are responsible for nucleation of reverse magnetization. The concept of diffusion length can be used for the design of heat treatments. Analytical formulas for calculation of the diffusion length as function of the cooling rate of the heat treatment are presented.

Abstract: The study of nanoparticles involves a new field of research in various areas of technology, whose production and use have been recognized as multiple benefits to the society. However, the uncontrolled emission to the environment of nanoparticles is growing exponentially over the last decade. Thus, knowledge of the influence of nanoparticles and how they can modify the ecosystem is extremely importantand demand specific studies. Therefore, it is of fundamental importance to increase the knowledge of the interactions and transport of nanoparticles in soil, in particular this research will study the T_iO₂ nanoparticles (TiNPs). Aiming to improve such knowledge, this paper addressed tests on columns with soil collected in the landfill Volta Redonda located in the state of Rio de Janeiro, Brazil. Aliquots of TiO2-nanoparticle suspensions in soil were collected periodically after their preparation, and analyzed the aggregate of particles distribution and Ti concentration. Experimental results suggest that the higher stability of T_iO₂ suspensions resulted in a higher mobility of T_iO₂ through soil layers with lower retention rate.

Abstract: This paper presents the experimental and numerical results for soil contamination profiles by leachate with and without the presences of a geomembrane. Soil samples of the Rio das Ostras Landfill were assessed and examined. The batch tests were carried out with local virgin soil and with leachate. Molecular diffusion tests with and without the presences of a geomembrane were compared with the virgin soil of the sanitary landfill of Rio das Ostras (Brazil) and its leachate. The studies focused on the chloride and sodium ions. The model MPHMTP (Multi Phase Heat and Mass Transfer Program) was used in the computer simulations to estimate the diffusion coefficients through the compacted soil and geomembrane over a layer of compacted soil to forecast ion migration and predict the performance of the system in long term operation. The geomembrane used was a 2 mm of the high density polyethylene (HDPE). The results showed that the presence of the geomembrane strongly reduced the ion concentrations in the soil during the experiments carried out.

Abstract: Volatile organic compounds (VOCs) are an important category of air pollutants and adsorption has been widely recognized as an effective means of controlling emissions to the atmosphere. The current study used theoretical model to analyze the rate of xylene adsorption from inert gaseous stream on the granular activated carbon in a fixed bed column under varying operating conditions. The model considers the inner diffusion of VOC into the activated carbon particles. Experimental results of another author study were used to validate the present model and the methodology proposed to determine the xylene concentrations at the outlet of the column and corresponding inner particles.

Abstract: The martensitic stainless steel X45CrSi93 is widely used in the automotive industry. One way to improve its properties is the deposition of high adhesiveness DLC films, which are well known for their excellent properties such as high hardness, low friction coefficient, chemical inertness, biocompatibility and excellent wear resistance. In this work, the adhesion between substrate and film was studied, by growing silicon interfaces with different deposition parameters. The technique used for growing these films was PECVD pulsed-DC. In order to obtain information of the silicon interface formation, ionic sub-implantation simulations were performed, by the software SRIM/TRIM. Raman spectroscopy was used to verify the atomic structure of the films. Scratch tribological test was performed to study adhesion. It was observed that the mechanical and tribological properties were greatly improved with the deposition of DLC films on the silicon interface. A correlation between the residual stress and adhesion of DLC films was found.