Hydrophilic and Antimicrobial Zeolite Coatings for Gravity‐Independent Water Separation

Abstract

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.

Antibacterial activity of silver-carried sodium zirconium phosphate prepared by ion-exchange reaction

“…Compared to organic antibacterial agents, inorganic antibacterial agents possessed so many outstanding properties, such as longlasting effects, broad-spectrum antibiosis and better heat resistance, that they can be used in the manufacture of antibacterial materials and products. 1) Silver ion is known to possess higher antibacterial activity and less toxicity comparing to other metal ions, 2)-5) thus several kinds of silver-carried antibacterial agents using different inorganic carriers, such as zeolite, 6) phosphate, 7), 8) titanium dioxide, 9) activated carbon, 10) montmorillonite, 11) water-soluble glass 12) and mesoporous silica 13) have been investigated now. Silver-carried zirconium phosphate (AgZrP) was recently emerging as various commercial products due to its best color stability among silvercarried antibacterial agents, and the study was especially focused on the preparation and the properties for practical applications.…”

Comparison of microbiological parameters in experimental and conventional recirculation aquaculture systems

“…Aerobic bacteria were present on root surface, suggesting root oxygen release [13]. The zeolite very effectively removes a large number of cells of sanitary bacteria in water over a short amount of time [5,14]. Salmonella spp.…”

“…The macrophytes in pond systems performed very well in the removal of coliforms and enterobacteria [4]. Furthermore the zeolite is extremely effective at killing a large number of cells of sanitary bacteria in water over a short amount of time [5]. The water of a RAS includes the presence of large populations consisting of bacteria.…”

Permeability Study of Austenitic Stainless Steel Surfaces Produced by Selective Laser Melting

“…Other methods have been employed to control the wetting properties of surfaces for preparing (a) hydrophilic surfaces via hydrophilic coatings [21,22], plasma treatments [23,24], or chemical treatments [25] and (b) hydrophobic surfaces via hydrophobic coatings [27,[30][31][32][33]. However, these methods are generally expensive, complicated, and time consuming.…”

“…The ability to control the wetting properties of metal alloys is extremely beneficial, in many areas for scientific and industrial applications. Wetting controllability includes the enhancement of heat transfer [22][23][24], improvement of surface coatings [25], and self-cleaning and anti-icing surface fabrications [26,27]. An alternative way to control wettability is the use of conical microstructures formed by the irradiation of surfaces with femtosecond laser pulses, in order to modify their properties for conducting contact angle evaluations [28,29].…”