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The catalytic activity for the production of biodiesel with three morphologically different nanocrystalline MgO materials prepared using simple, green and reproducible methods was investigated. The nanocrystalline samples studied were MgO(111) nanosheets (MgO (I)), conventionally prepared MgO (MgO (II)) and aerogel prepared MgO (MgO (III)). The methods to produce the catalysts included: (a) 4-methoxy-benzyl alcohol templated sol-gel process followed by supercritical drying and calcination in air at 773 K (MgO (I)), (b) from a commercial MgO that was boiled in water, followed by drying at 393 K, and dehydration under vacuum at 773 K (MgO (II)), and (c) via hydrolysis of Mg(OCH 3 ) 2 in a methanol-toluene mixture, followed by supercritical solvent removal with the formation of a Mg(OH) 2 aerogel that was dehydrated under vacuum at 773 K (MgO (III)). These catalysts were characterized by TEM, DRIFT, and DR-UV-Vis and tested in the transesterification of sunflower and rapeseed vegetable oils at low temperatures, under different experimental conditions: autoclave, microwave and ultrasound. Working with these materials under microwave conditions provided higher conversions and selectivities to methylesters compared to autoclave or ultrasound conditions. Under ultrasound, a leaching of the magnesium has been evidenced as a direct consequence of a saponification reaction. These systems also allow working with much lower ratios of methanol to vegetable oil than reported in the literature for other heterogeneous systems. The activation temperature providing the most active catalysts was found to vary depending on the exposed facet: for MgO(111) structures (i.e. MgO (I)) this was 773 K, while for MgO (110) and (100) (i.e. MgO (II) and MgO (III)) this was 583 K.

A model semi-metallic brake lining was subjected to full scale automotive brake dynamometer tests. The structural properties and surface topography of brake linings were analyzed at different stages of wear testing and correlated to frictional performance. Characteristics of released wear particles were also addressed. A combination of abrasive and adhesive wear with oxidative processes dominated the friction process. Formation of a friction layer adhering to the friction surfaces of pads and discs is the major feature responsible for friction performance. Characteristics of the friction layer depend mostly on surface temperature, normal pressure, and sliding speed. It is a newly formed sintered composite matter consisting of a mixture of wear particulates. Wear rates and friction levels depend on chemistry, structure and hardness of the friction layer covering the surface of a pad or a disc; however, there is no simple Archard-type relationship between wear and measured hardness.Wear debris generated during the dynamometer tests was collected from containers placed under the brake inside dynamometer chamber. The collected debris was compared with ball-milled particles from identical brake lining. It is necessary to combine several analytical methods to characterize wear particles properly. The presence of copper and iron oxides as well as carbonaceous components is typical for all collected debris samples. Chemistry of wear debris resembles chemistry of the friction layer. Composition, mutagenic potency and pulmonary toxicity of wear debris and ball-milled particles were also analyzed. Mutagenic potency of initial friction composite and wear particles was evaluated by two in vitro bacterial microbioassays (SOS Chromotest, Ames test). Obtained results show potency of wear particles for interacting with DNA after metabolic activation, which indicates the presence of indirect mutagens. The pulmonary toxicity test on rats revealed an acute response of the lung tissue to the ball-milled particles. Further research is necessary to address the role of brake wear particles and potential impact of sub-chronic exposure to wear debris.