Materials Science Forum Vols. 486-487

Abstract: The Basel Convention (1989) and Rio Summit (1992) were two major instances to tackle with the main issues on Hazardous Waste. The first one is the mechanism to control the illegal traffic of hazardous waste, and to promote an Environmental Sound Management for the overall waste cycle. On the other hand, Rio Summit launched a renewed interest on regulatory environmental instruments for pollution prevention, control and mitigation of environmental damages generated by industrial activities. Among them, one of the major challenges is related to the hazardous waste management. In Latin America, as well as in the rest of the world, the theme has been considered mainly through the environmental regulations, pushing the enterprises to look for different solutions to face the high costs involved in the production processes. In this paper, a comparative assessment was made of the hazardous waste management in four Latin American oil-producing countries. The specific environmental regulations adopted are reviewed, to show the status of present environmental policies and legal measures to promote reuse, recycle, recovering and reduction of hazardous materials and wastes. Coincidential provisions are reported, as well as the differences in the legal approach, which is a clear signal of the efforts made in environmental regulations, trying to control and prevent the pollution generated by industries.

Abstract: Ferroelectric properties of Pb-free (Bi,La)4Ti3O12 (BLT) films were optimized on a newly developed MTP cell structure. BLT films were coated on Pt/IrOx/Ir bottom electrode using sol-gel solutions. The composition of the optimized BLT film was about Bi3.25La0.75Ti3.0O12, which was analyzed by ICP-MS method. The switchable polarization obtained in a 100nm-thick BLT film was about 20 uC/cm2 at the 3 V applied voltage, and the optimized BLT film showed little fatigue loss about 10% up to 1×1011 cycles. The imprint properties of the BLT film were also characterized at 25 °C and 90 °C operating temperature after 125 °C data storage. Regardless of operating temperature, switchable polarization of BLT had a sufficiently large margin for device operation up to 10 years.

Abstract: The interfacial reaction between eutectic Sn-3.5wt.%Ag solder and Ni substrate resulted in the formation of Ni3Sn4 intermetallic compound (IMC) layer. After formation of the Ni3Sn4 IMC, its grain coarsened and faceted continuously in a prolonged reflow reaction. The thickness of the IMC layer increased with reflow time. On the other hand, the brittleness of the joints increased with increasing reflow time, and the fracture occurred at the interface. The deterioration of the shear strength was found to be predominantly caused by the formation of the thick Ni3Sn4 IMC layer.

Abstract: A raw eggshell shows CaCO3 phase, and pure CaO can be obtained by calcination of the raw eggshell. And the morphology of the calcined eggshell is grape-type granular with uniform particles. By using the recycled eggshell, biocompatible and highly sinterable calcium phosphate bio-ceramics were successfully fabricated, such as hydroxyapatite (HAp) and b-tricalcium phosphate (b-TCP), and wollastonite (CaSiO3). The observed phases and microstructures on the powder synthesis process are dependent on the content of eggshell and calcination temperature. In this study, the crystalline development and the microstructure of synthesized powders and the densified specimens are examined by X-ray diffractometry and scanning electron microscopy.

Abstract: Nitride-related compounds containing AlN and AlON were synthesized from aluminum dross using a combustion reaction, irrespective of the content of Al in Al-dross. The formation of AlON is induced by the exothermic reaction between Al and nitrogen. On the occasion of using high-grade dross, unreacted Al was detected in the combustion products. This may be originated from Al in the dross because Al in dross exists in the dispersed oxide layer. Therefore, its reactivity with nitrogen is relatively lower, compared to Al powder mixed with the dross in the beginning. It is noted that, on the occasion of using low-grade dross, unreacted Al in the product can be controlled by means of adjusting particle size of dross, resulting in improvement of the permeation of nitrogen gas into the compact through the well established open pore channels.

Abstract: The hexavalent chromium used in chromium plating is so toxic that it is very hazardous to human body and even carcinogenic. Therefore, it is indispensable to develop an alternative deposition technique. To explore the feasibility of sputtering as an alternative technique for chromium plating, we investigated the dependences of the deposition rate, the phases, the hardness, the surface roughness and the corrosion-resistance of CrNx deposited on the high speed steel substrate by using a dual ion beam sputtering system on the rf-powers. The deposition rate of CrNx depends more strongly upon the rf-power for argon ion beam than that of the nitrogen ion beam. The hardness of the CrNx film can be maximized by optimizing the rf-power, so that the volume percent of the Cr2N phase in the film is highest. Amorphous films are obtained when the rf-power for nitrogen ion beam is much higher than that for argon ion beam. The CrNx film deposited by using the sputtering technique under the optimal condition provides corrosion-resistance comparable to that of the electroplated chromium.

Abstract: To improve the mechanical properties of concretes containing recycled aggregates, pozzolanic materials such as Silica Fume and Meta Kaolin were used to decrease the porosity of the recycled aggregates. These pozzolanic aterials were adhered on the surface of recycled aggregates and closed the open pores so that the water absorption was decreased 1~2% as the amount of adsorption was increased. Compressive strength of cement mortars and concretes using surface treated recycled aggregates reached above 95% of the strength of its natural counterparts. Investigation of the microstructures using the scanning lectron micrographs showed the formation of dense interface after the adsorption treatment of pozzolanics to recycled aggregates.

Abstract: The effect of RO components variation on some properties was studied in Pb free glass frit for PDP (Plasma Display Panel). One of the main components, BaO, was replaced progressively at fixed concentration of alkaline earth oxides. We studied the transparency, thermal expansion, softening point, and the high temperature microscopic behaviors of glass frits and TG(thermal gravimetry) of raw material. The compositional dependence of those properties was discussed from the view points of compositional diversity and production process of Pb free glass frit.

Abstract: It is well known that magnesium alloys have difficulties in room temperature formability because of their HCP structure. As a basic approach to enhance a cold formability, a new combination process including an extrusion followed by a cold equal channel angular pressing (ECAP) was attempted. ECAP die has an inner die corner angle of 135 degree, the fillet angle of 45 degree and thickness of 5mm. A finite element analysis with a three-dimensional thermo-coupled elasto-plastic model was also carried out to understand the change of stress and strain during ECAP. Experiments showed that the AZ31 alloy, which is extruded at a ratio of 20 and is heat-treated at 350°C, was successful in a cold ECAP. From the simulated results, it was found that the effective strain gradually decreased from the inner die side (0.533) to the outer die side. This was confirmed by the analytical analysis via von Mises criterion. Furthermore, it also matched well with the experiments, which showed a uniform shear deformation band. It was also interesting to note that compressive yield strength was drastically increased, which is caused by the occurrence of numerous twins spread across the materials during a cold ECAP.