Structural characterization of mesoporous organosilica films for ultralow-k dielectrics

\u3cp\u3eA method to control the hydrophobicity and dielectric constant of mesoporous silica films for ultralow-k-applications is described. Several surfactants have been used as sacrificial materials in (organo)silicate matrixes, prepared from tetraethoxysilane and methyltrimethoxysilane. To elucidate the relation between the composition of the films and their structure, the synthesis, chemical composition, mechanical properties, pore structure, crystallinity, and dielectric constant of the films were investigated. The high extent to which organic groups can be incorporated in these thin films opens the possibility to obtain a fully hydrophobic surface. Further, a combination of tetraethoxysilane and methyltrimethoxysilane leads to dense matrixes. The film properties were optimized for low-A- applications by varying the processing conditions. Films containing 50-60% methyltrimethoxysilane in tetraethoxysilane and cetyl trimethylammonium bromide as a surfactant appear most attractive as a low-A- material. These films are hydrophobic, have a dense matrix, and exhibit the smallest pore sizes (∼3 nm), which may facilitate integration issues.\u3c/p\u3

Ship particulate pollutants: Characterization in terms of environmental implication

International audienceA major aspect of monitoring the atmosphere is the quantification of man-made pollution and their interactions with the environment. Key physico-chemical characteristics of diesel exhaust particulates of sea-going ship emissions are presented with respect to morphology, microstructure, and chemical composition. Heavy fuel oil (HFO)-derived particles exhibit extremely complex chemistry. They demonstrate three distinct morphological structures with different chemical composition, namely soot, char and mineral/ash. The composition analysis investigates the content of environmentally-dangerous pollutants: metals, inorganic/mineral species, and soluble, volatile organic and ionic compounds. It is found that hazardous constituents from HFO combustion, such as transitional and alkali earth metals (V, Ni, Ca, Fe) and their soluble or insoluble chemical forms (sulfides, sulfates, oxides, carbides), are released together with particles into the atmosphere. The water soluble fraction, more than 27 wt%, is dominated by sulfates and calcium cations. They cause the high hygroscopicity of ship exhaust particles and their possible ability to act as cloud nuclei in humid marine environment