Organic matrix compounds

Sohd rocket propellants represent a very special case of a particulate composite ia which inorganic propellant particles, about 75% by volume, are bound ia an organic matrix such as polyurethane. An essential requirement is that the composite be uniform to promote a steady burning reaction (1). Further examples of particulate composites are those with metal matrices and iaclude cermets, which consist of ceramic particles ia a metal matrix, and dispersion hardened alloys, ia which the particles may be metal oxides or intermetallic compounds with smaller diameters and lower volume fractions than those ia cermets (1). The general nature of particulate reinforcement is such that the resulting composite material is macroscopicaHy isotropic. 

The organic inclusion compound 2,4,6-tris-(4-bromophenoxy)-l,3,5-triazine was used to create an ordered arrangement of endohedral fullerenes in a crystalline host matrix <06CPL327>. 

The matrix compound is typically mixed together in an aqueous/ organic solution with the analyte, such that the relative concentration of matrix to analyte is on the order of 5000 or 10,000 to 1. The solution is applied to a surface that will be irradiated by the laser beam and the solvent is allowed to evaporate, leaving a solid, crystalline deposit of matrix and analyte. Many of the original applications described instruments in which the surface containing the dried matrix/ analyte sample was introduced into the vacuum housing of a mass spectrometer source housing for irradiation. However, recently it has been demonstrated that MALDI can be successfully carried out at atmospheric pressure (outside the vacuum chamber of the mass spectrometer), much in the same way as the ESI, APCI and APPI techniques. 

In a sediment system, the hydrolysis rate constant of an organic contaminant is affected by its retention and release with the sohd phase. Wolfe (1989) proposed the hydrolysis mechanism shown in Fig. 13.4, where P is the organic compound, S is the sediment, P S is the compound in the sorbed phase, k and k" are the sorption and desorption rate constants, respectively, and k and k are the hydrolysis rate constants. In this proposed model, sorption of the compound to the sediment organic carbon is by a hydrophobic mechanism, described by a partition coefficient. The organic matrix can be a reactive or nonreactive sink, as a function of the hydrolytic process. Laboratory studies of kinetics (e.g., Macalady and Wolfe 1983, 1985 Burkhard and Guth 1981), using different organic compounds, show that hydrolysis is retarded in the sohd-associated phase, while alkaline and neutral hydrolysis is unaffected and acid hydrolysis is accelerated. 

Some silicon dioxide ceramics are made by the sol-gel process. In this process, an organic silicon compound is dissolved in water and polymerized into a network structure. As the gel forms, many cross-links are formed. These cross-links form a rigid, strong matrix that is free of... 

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