Silver exchanged zeolite A (Ag–ZA) coatings have been proposed as effective materials in providing hydrophilic and antimicrobial surface properties for condensing heat exchangers onboard manned spacecraft. Ag–ZA coatings demonstrated super hydrophilic properties, retention of silver content, and high antimicrobial activity to Escherichia Coli after submersion in double de-ionized water over a one-year period. Ag–ZA coatings kill E. coli on contact with a small loss of Ag (∼0.4%) after each exposure to the bacterium. The coatings remain super hydrophilic even after 24 repeated E. coli exposures. The coatings have also shown effective resistance against bacteria Listeria innocua, Staphylococcus epidermidis and Pseudomonas putida, Fungus Aureobasidium pullulans, and marine yeast Rhodotorula mucilaginosa, and may provide an enhanced capacity to prevent outbreaks of several microbial species onboard manned spacecraft.

In this study, the impact of zeolite thin film coatings on bacterial deposition and "biofouling" of surfaces has been investigated in an aqueous environment. The synthesis of two types of zeolite coatings, ZSM-5 coated on aluminum alloy and zeolite A coated on stainless steel, and the characterization of the coated and bare metal surfaces are described. The extent of cell deposition onto the bare and zeolite-coated aluminum alloy and stainless steel surfaces is investigated in a parallel plate flow chamber system under a laminar flow conditions. The initial rates of bacterial transfer to the various surfaces are compared by utilizing a marine bacterium, Halomonas pacifica g, under a range of ionic strength conditions. H. pacifica g deposited onto bare metal surfaces to a greater extent as compared with cells deposited onto the zeolite coatings. The surface properties found to have the most notable effect on attachment are the electrokinetic and hydrophobicity properties of the metal and zeolite-coated surfaces. These results suggest that a combination of two chemical mechanisms-hydrophobic and electrostatic interactions-contribute to the antifouling nature of the zeolite surface. Additional observations on the relative role of the hydrodynamic and physical phenomena are also discussed.

Titanium alloy, Ti6Al4V, is widely used in dental and orthopedic implants. Despite its excellent biocompatibility, Ti6Al4V releases toxic Al and V ions into the surrounding tissue after implantation. In addition, the elastic modulus of Ti6Al4V ( approximately 110GPa) is significantly higher than that of bone (10-40GPa), leading to a modulus mismatch and consequently implant loosening and deosteointegration. Zeolite coatings are proposed to prevent the release of the toxic ions into human tissue and enhance osteointegration by matching the mechanical properties of bone. Zeolite MFI coatings are successfully synthesized on commercially pure titanium and Ti6Al4V for the first time. The coating shows excellent adhesion by incorporating titanium from the substrate within the zeolite framework. Higher corrosion resistance than the bare titanium alloy is observed in 0.856M NaCl solution at pHs of 7.0 and 1.0. Zeolite coatings eliminate the release of cytotoxic Al and V ions over a 7 day period. Pluripotent mouse embryonic stem cells show higher adhesion and cell proliferation on the three-dimensional zeolite microstructure surface compared with a two-dimensional glass surface, indicating that the zeolite coatings are highly biocompatible.

Titanium and its alloys, along with cobaltchromium alloys, have traditionally been used in orthopedic and dental implants due to their high corrosion resistance and high biocompatibility. Recently, biocompatibility of titanium alloy Ti6Al4V (~ 90% Ti, 6% Al, 4% V) has been questioned due to the release of harmful Al and V ions into the surrounding tissue. Specifically, vanadium ions have been shown to be cytotoxic, while aluminum ions can cause neurological disorders. Even a highly passive titanium surface (with a protective TiO2 layer) may allow release of ions into the surrounding tissue under corrosive and biologically active oral conditions. Release of metallic ions and particles diminishes the biocompatibility of titanium and its alloys over a long implant lifespan. Thus, there is an urgent need to enhance the biocompatibility of metallic alloys for long term implant use. We have been investigating the application of zeolite thin films on titanium and its alloys, and have demonstrated that high-silica-zeolite (HSZ) coating is a viable technology for corrosion protection of titanium and its alloys in aggressive pitting media. As-synthesized SDA-containing high-silicazeolite MFI coatings on Ti6Al4V (Figure 1) are nonporous and remarkably corrosion resistant in strong acid, base and pitting aggressive media (e.g., NaCl solution). We have also shown that the in-situ crystallization coating deposition process we use can coat surfaces of complex shapes and in confined spaces.

A hydrophilic and antimicrobial two-layer zeolite composite coating was formed on aluminum alloys. The base layer is a high-silica-zeolite (HSZ) MFI coating formed directly on the aluminum alloy by in situ crystallization. The top layer is a crystalline zeolite hybrid coating of low-silica-zeolite (LSZ) LTA (zeolite A, or ZA) crystals imbedded within a HSZ-MFI matrix and is formed by a seeded growth method. The two-layer composite coatings are demonstrated by using ASTM D 3359B-02 method to have excellent adhesion to the aluminum alloy substrates. The hybrid layer is hydrophilic with contact angles below 5° and when they are silver-ion exchanged the hybrid coating is highly antimicrobial.

A layer-by-layer deposition method is presented for the fabrication of compact c-oriented-MCM-22/silica films on aluminum alloys and porous (x-alumina discs. The film fabrication procedure combines deposition of platelike MCM-22 crystals on substrates by covalent attachment under reflux and/or by sonication-assisted covalent attachment (using the methods introduced by Yoon and co-workers and recently reviewed [Acc. Chem. Res. 2007, 40 (1), 29-40]) with evaporation-induced-self-assembly (EISA) of surfactant-templated silica. The composite c-oriented MCM-22/silica films exhibited corrosion resistance barrier properties comparable to commercial chromate conversion coatings. Moreover, they exhibited hydrogen ideal selectivities. (e.g., H-2/N-2 similar to 7) above those expected by Knudsen diffusion indicating molecular sieving potential.

Zeolithbeschichtungen bieten eine sichere und praktikable Alternative zu den üblicherweise genutzten, aber giftigen Chromatierverfahren für Aluminiumlegierungen und andere Metalle, erfordern aber normalerweise eine Hochdrucksynthese. In der Zuschrift auf S. 535 ff. präsentieren Y. S. Yan et al. das erste Ionothermalverfahren, durch das eine ausgerichtete Zeolithschicht auf einer Al-Legierung unter Normaldruck und Mikrowelleneinstrahlung synthetisiert werden kann. Diese Beschichtung ist bei Versiegelung mit Silan außergewöhnlich korrosionsbeständig.

Metal corrosion is a ubiquitous problem and generally costs an industrialized country several percent of its gross domestic product. The development of satisfactory protective finishes continues to be of great importance. Many of the protective finishes used today utilize chromium, which in its hexavalent state is a known human carcinogen. We have been investigating the application of zeolite films as chromium-free protective coatings on aluminum alloys and steels [1-4]. In this paper we summarize our most recent works that experimentally demonstrates that high-silica-zeolite (HSZ) coating on metal and metal alloys is a viable replacement technology for corrosion protection of metals.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Zeolites are microporous crystalline aluminosilicates with uniform and molecular sized pores. We have been investigating the application of zeolite films as chromium-free protective coatings on aluminum alloys. We have shown that as-synthesized organic template containing high-silica-zeolite (HSZ) MFI coatings on AA-2024-T3 are non-porous and have excellent corrosion resistance in strong acids, bases, and pitting aggressive media. We have also shown that the in-situ crystallization coating deposition process we used can coat surfaces of complex shapes and in confined spaces. Only one simple pretreatment and a single zeolite formulation are needed to synthesize MFI coatings on several different aluminum alloys. In this paper we show salt-fog accelerated weathering tests performed according to ASTM B117 on 7.5 um thick HSZ MFI coated 2024-T3 and their DC polarization profiles in 5 wt% NaCl aqueous solution. All HSZ MFI coated AA-2024-T3 panels were considered passing after more than 2000 hours continuous salt fog exposure.

Due to recent epidemiological studies that have found a correlation between atmospheric fine particle (diameter < 2.5 pm) mass concentrations and increased human morbidity and mortality, the chemistry of particles produced from diesel engines are of special concern. Diesel engines are known to emit high concentrations of nanoparticles (diameter < 50 nm), but due to their relatively small mass, chemical analysis is difficult. Here, a nano-differential mobility analyzer (Nano-DMA) was used to size select nanoparticles produced iiom diesel engine exhaust for subsequent chemical analysis by thermal desorption particle beam mass spectrometry (TDPBMS). A number of organic comp'ound classes and sulfuric acid have been identified and the approximate molecular weights and vapor pressures determined from calibrated desorption temperatures. The effect of particle size and engine operating conditions on the composition of diesel nanoparticles was also studied. diesel exhaust, nanoparticles, nucldation

The evaporation time and wetting limit temperature for a water droplet on the surface of a bare, Zeolite-A-coated, or ZSM-5-coated stainless steel substrate have been experimentally studied. Three stainless steel substrates are prepared with different finishes. The surface finishing of a substrate is shown to cause observable changes in the wettability of a bare or ZSM-5-coated surface. Contact angle measurements reveal that Zeolite-A coatings are the most hydrophilic and that bare stainless steel is the least hydrophilic. The evaporation time and wetting limit temperature of a water droplet placed on the surface of the bare and coated substrates are examined as surface temperature increases. The zeolite coatings decrease the evaporation time and increase the wetting limit temperature on the bare stainless steel substrate, with Zeolite-A coatings offering the best improvement. For the bare substrate and the substrates coated with the same zeolite, as hydrophilicity increases, the evaporation time decreases and wetting limit temperature increases.