Silane-based Coatings Research Articles

Improved oxidation resistance of SmCo magnetic alloy powders by silanization

The thermal stability of Sm2Co17 powders coated with four different silanes was studied between 25°C and 500°C and isothermally at 400°C. Thermogravimetry data indicated that the silane-based coatings provided improved oxidation resistance. The microstructural analysis of uncoated powders oxidized for 10h at 400°C revealed the formation of a featureless ca. 10μm thick shell, surrounding the unreacted core. The development of this shell was attributed to the inward diffusion of oxygen, decomposition of intermetallic phases and redistribution of alloying elements. The EDS elemental maps revealed that the shell was rich in O, Fe and Co, and depleted in Sm, Zr and Cu. In the presence of the silane-based coatings the thickness of the shell was reduced by more than 80% (to less than 2μm) and the redistribution of alloying elements was insignificant. Based on the thermogravimetric analysis at or above ca. 400°C and the microstructural analysis it was possible to assess the relative effectivity of the different silanes in preventing the oxidation of the SmCo powder. Methyltrimethoxysilane (MTMS), which also formed the thinnest coating, was the best silane. (3-Glycidyloxypropyl)trimethoxysilane, forming a thicker coating, was less effective than MTMS, but superior to the two amine-functionalized silanes ((3-aminopropyl)triethoxysilane and (3-aminopropyl)trimethoxysilane).

Stabilization of lithium metal anodes using silane-based coatings

For energy storage systems that use a charged cathode, the source of lithium is typically lithium metal. For several high energy systems under study, notably those that utilize elemental sulfur or oxygen (air) as the cathode, their very high capacity makes lithium metal anodes essential. In this study we evaluated the cycling performance of a series of silane-based coatings formed on a cleaned lithium metal surface before exposure to electrolyte. These substituted silane (R 3Si-) based coatings are formed from the self-terminating reaction of the R 3Si-Cl with lithium surface hydroxyl groups. The cycling performance of a trimethyl silyl coated surface and a triisopropyl silyl coated surface were compared to an uncoated sample and the results explained by a combination of surface coverage density and the ability of the coating to inhibit free solvent attack of the metal electrode surface.

Surface Characteristics and Water Absorption of Sol-Gel Coated Impregnated Paper Pressed onto Plywood

Two silane-based hybrid coatings were developed to modify the surface energy of phenolic resin impregnated paper. The coated paper samples were further pressed onto surfaces of plywood. The surface properties and water repellence of coated paper were investigated by AFM, XPS and water contact angle measurements. The water absorption of plywood with pressed paper was studied by water uptake tests. It was found that the sol-gel coatings had slightly improved the water repellence of the impregnated paper. The water absorption of plywood was also slightly decreased.

Silane-based coatings on polypropylene, deposited by atmospheric pressure glow discharge plasmas

The aim of this paper is to show the possibility to synthesize silicon-based deposits on a polypropylene substrate, using a glow dielectric barrier discharge at atmospheric pressure, and to correlate the gas phase behavior with the properties of the thin film deposits. The discharge is generated in a mixture of nitrous oxide and silane, diluted in nitrogen. The influence of the [N2O]/[SiH4] ratio on the layer characteristics is mainly studied. Deposits are analyzed by XPS, SSIMS, AFM and wetting angle measurements. The discharges are also characterized by their optical emission spectra. Measurements are made as a function of the distance from the gas inlet, and they allow one to correlate these spectra with the film thickness and its chemical composition. Finally, chemical kinetics of the reactive gas decomposition reactions are proposed.