Two-step coating

With very smooth, high quality y-alumina supporting layers on a a-alumina support ultra-thin (100 nm) silica membranes with a pore diameter of 0.45-0.5 nm could be obtained. High quedity membranes with low defect levels are obtained in a two-step coating process. The thermal stability of these systems is limited to about 500°C and relatively low water partial pressures. Reseeirch to improve this is necessary. 

A combination of the previous two synthetic methods was used for the coating of magnetite and boehmite particles by PhUipse et al. [72]. The surface properties of these materials made it necessary to device such a two-step coating procedure. 

TABLE 3 Stability as Measured by Amount of Iron Leached Out in Acid (pH 2.5) and Saturation Magnetization of Silica-Coated y-Fe203 Dense Liquid, Sol-Gel, and Two-step Coating Processes at 11% Si02... 

Chanhan and Darbre [80] developed a single-step coating procedure for SCOT column preparation. This procedure gives reproducibility and it is less time-consuming than another well known two-step coating procedure (see, e.g. [81, 82]). 

H. Zhou, H. Wang, H. Niu, A. Gestos and T. Lin. Robust, self-heahng superomniphobic fabrics prepared by two-step coating of fluoro-containing polymer, fluoroalkyl silane, and modified silica nanoparticles. Adv. Funct. Mater., 23.1664-1670(2013). 

Most electroless silver appHcations are for silvering glass or metallizing record masters. Mirror production is the principal usage for electroless silver. The glass support is cleaned, catalyzed using a two-step catalyst, and coated on one side with an opaque silver film (46). Silver-plated nylon cloth is used as a bacteriostatic wound dressing. A tiny current appHed to the cloth causes slow silver dissolution. The silver acts as a bactericide (47). 

The model for a filled system is different. The filler is, as before, represented by a cube with side a. The cube is coated with a polymer film of thickness d it is assumed that d is independent of the filler concentration. The filler modulus is much higher than that of the d-thick coat. A third layer of thickness c overlies the previous one and simulates the polymeric matrix. The characteristics of the layers d and c are prescribed as before, and the calculation is carried out in two steps at first, the characteristics of the filler (a) - interphase (d) system are calculated then this system is treated as an integral whole and, again, as part of the two component system (filler + interphase) — matrix. From geometric... 

Fabrication of composite colloidal spheres involves two steps submicron particles are fabricated from a material preferentially responsive to one class of chemicals followed by a step in which the submicron spheres are coated with a shell that is preferentially responsive to another class of chemicals. A colloidal crystal array is subsequently self-assembled into a 3D ordered film. 

When painting wood, the most important step is to thoroughly sand the wood to a smooth finish. All burrs and rough spots must be removed, and the surface should be silky smooth to the touch. After cleaning the wood, one should give it two coats of primer. This neutral colored paint soaks into the grain and seals it. Once dried, the wood is ready for two more coats of the final color. 

In the one-step process, the reactants are mixed in the proportions desired in the final composite. In the two-step process, the polymer-coated clay prepared in the first step is compounded with additional EE. The two-step process yields composites with better mechanical properties than the one-step process. 

The coatings were cured in two steps first, a room temperature exposure for at least five hours to allow any solvent present to evaporate and/or the resin to gel and, second, an elevated temperature cure. The vinyl ester, polyester and epoxies were baked at 60°C for 4-16 hours. The coating thickness after curing was measured with a micrometer, subtracting the substrate thickness. The thickness of the coatings ranged from 6 to 12 mils (150-300 urn) and is shown for each type in Table I. 

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