Diesel engines are known to emit high number concentrations of nanoparticles (diameter < 50 nm), but the physical and chemical mechanisms by which they form are not understood. Information on chemical composition is lacking because the small size, low mass concentration, and potential for contamination of samples obtained by standard techniques make nanoparticles difficult to analyze. A nano-differential mobility analyzer was used to size-select nanoparticles (mass median diameter approximately 25-60 nm) from diesel engine exhaust for subsequent chemical analysis by thermal desorption particle beam mass spectrometry. Mass spectra were used to identify and quantify nanoparticle components, and compound molecular weights and vapor pressures were estimated from calibrated desorption temperatures. Branched alkanes and alkyl-substituted cycloalkanes from unburned fuel and/or lubricating oil appear to contribute most of the diesel nanoparticle mass. The volatility of the organic fraction of the aerosol increases as the engine load decreases and as particle size increases. Sulfuric acid was also detected at estimated concentrations of a few percent of the total nanoparticle mass. The results are consistent with a mechanism of nanoparticle formation involving nucleation of sulfuric acid and water, followed by particle growth by condensation of organic species.

The chemical composition of secondary organic aerosol formed in an environmental chamber from ozonolysis of 1-tetradecene in humid and dry air was determined using a thermal desorption particle beam mass spectrometer (TDPBMS). The major products are R-hydroxytridecyl hydroperoxide and bis(R-hydroxytridecyl) peroxide in humid air and symmetric C26 and asymmetric C14 secondary ozonides in dry air. The hydroperoxide is formed by reaction of stabilized Criegee biradicals with water vapor, and the peroxide (a peroxyhemiacetal) is formed by subsequent reaction of the hydroperoxide with tridecanal. The secondary ozonides are formed by reactions of stabilized Criegee biradicals with tridecanal and formaldehyde. Tridecanoic acid was also observed in both experiments. These compounds have very low vapor pressures and are stable on the 3-h time scale of the environmental chamber experiments. When collected aerosol was analyzed by gas chromatography, the hydroperoxides, peroxides, and secondary ozonides thermally decomposed to more volatile compounds, including tridecanal, tridecanoic acid, and a few unidentified products.

Over the last 15 years there has been considerable and increasing interest in the synthesis of zeolite films for separation-membrane and membrane-reactor applications. [1] Preparation of zeolite films on nonporous substrates for chemical sensor applications has also been reported.[2] These efforts were mostly motivated by the desire to take advantage of zeolites inherent molecular-sieve characteristics. But recently, other interesting applications, which do not rely on the molecular-sieve effect, have been demonstrated, [3] such as corrosion-resistant coatings, [4] films with low dielectric constants, [5] hydrophilic and antimicrobial coatings, [6] and heat pumps. [7] These new applications promise to offer even more exciting opportunities.High-silica zeolite (HSZ) MFI coatings for aluminum alloys, stainless steels, and carbon steels show excellent corrosion resistance, strong adhesion to the substrates, and extraordinary thermal and mechanical properties.[4] All these properties, plus the fact that zeolites are nontoxic, suggest that zeolite coatings have the potential to become an environmentally friendly alternative for the most commonly used, toxic, carcinogenic, and strictly regulated chromate conversion coating. However, zeolite coatings are normally synthesized on the substrates in water (hydrothermal synthesis) or other traditional organic solvents (solvothermal synthesis) in sealed reactors. The current hydrothermal deposition process for HSZ-MFI coatings is considered inconvenient by the surface-finishing industry, because it involves the autogenous pressure (about 9 atm at 175 8C for HSZ-MFI coating synthesis), while the chromate conversion coating can be deposited at ambient pressure.Recently, a new ionothermal method was introduced to the synthesis of zeolite powders under ambient pressure in open vessels, [8][9][10] in which ionic liquids were used instead of water or organic solvents. An ionic liquid is a substance that consists only of ions and has a melting temperature below 100 8C. Ionic liquids have been recognized as environmentally benign solvents and "designer solvents", because they have negligible vapor pressure, high chemical and thermal stability, high ionic conductivity, wide electrochemical potential windows, can act as catalysts, are nonflammable, and have tunable physicochemical properties by suitable choice of cations and anions. [11,12] These remarkable properties enable ionic liquids to be widely used in organic, inorganic, polymer, and biocatalytic synthesis. [12] AEL powder is the first example of a zeolite successfully synthesized ionothermally.[8] It was prepared under ambient pressure in a convection oven in 68 h at 150 8C using 1-methyl-3-ethylimidazolium bromide ([emim]Br) as both solvent and template. This method is also successful with microwave heating, in which case only one hour was needed for the crystallization owing to the rapid microwave absorption of ionic liquids.[9]Herein, we present the first ionothermal synthesis of zeolite films by in situ crystallization o...

Corrosion resistant high-silica-zeolite ͑HSZ͒ MFI coatings have been synthesized by in situ crystallization using a single solution formulation on a series of aluminum alloys with rather different chemical compositions including AA-2024-T3, AA-5052-H32, AA-6061-T4, and AA-7075-T6. The coatings are continuous, compact, and of uniform thickness ͑ϳ10 m͒. The coatings are demonstrated by using ASTM D 3359B-02 method to have excellent adhesion to all metal substrates tested. The cross-sectional composition analysis shows a gradual and continuous change of Si/Al ratio from pure aluminum at the substrate surface to almost infinity at the free coating surface, and this is suggested to be the origin of excellent of adhesion observed. In addition, a simple detergent solution pretreatment is shown to be adequate for the reproducible formation of high quality coatings.

Condensing heat exchangers onboard manned spacecraft require hydrophilic fin surfaces to facilitate wetting and wicking of condensate to achieve gravity‐independent water separation in the zero‐ or micro‐gravity environment of space. In order to prevent the proliferation of microbes, the coating must also be biocidal. Here we show for the first time that zeolite A and ZSM‐5 coatings deposited via in‐situ crystallization on stainless steel and aluminum alloys have excellent hydrophilicity, biocidal properties, and adhesion. Water contact angles below 5° were obtained on most substrates tested. When silver‐ion exchange is carried out on the zeolite A coating, it becomes highly antibacterial. This biocidal capability of zeolite A is regenerative by repeated ion exchange. All coatings exhibit the highest rating of 5B as determined by adhesion test ASTM D‐3359‐02 (American Society for Testing and Materials). These properties, in addition to zeolite coating's low‐temperature crystallization process and demonstrated corrosion resistance, make zeolite coatings advantageous over the current sol–gel coatings and well suited for use in condensing heat exchangers onboard manned spacecraft.