Abstract Extremely small, three-dimensional articles, such as fusion targets having glass shells (20 to 500 microns in diameter) are coated with alternate layers of colloidal materials. This is accomplished by depositing particles of opposite charge from colloidal suspensions (sols). Articles to be coated are suspended within a drop held in the open end of a closed capillary tube, and colloidal particles are deposited by dipping the capillary into the sols. Alternate monolayers of the particles adhere to the surface of the article. Multilayer coatings are built up by repeated alternate deposition of the monolayers from the sols. Between each deposition, the layers are rinsed with water and the water removed by dipping the capillary tube into a bath of water and then into a bath containing a water displacing agent such as ethanol or dimethyl sulfoxide.
A three-dimensional glass microballoon of maximum dimensions from about 20 to 500 microns coated on all surfaces thereof and of material having an inherent surface charge of one polarity, a multitude of alternate monolayers of particles of material of positive and negative opposite charge adhered to said surfaces onto each other, the first of said monolayers being particles of polarity opposite to said one polarity.
Claim 2
Dependent Claim
65 words
A three-dimensional glass microballoon of maximum dimensions from about 20 to 500 microns coated on all surfaces thereof and of material having an inherent surface charge of one polarity, a multitude of alternate monolayers of particles of material of positive and negative opposite charge adhered to said surfaces onto each other, the first of said monolayers being particles of polarity opposite to said one polarity.
Claim 3
Dependent Claim
15 words
The invention as set forth in claim 1 wherein said article is a closed shell.
Claim 4
Dependent Claim
26 words
The invention as set forth in claim 2 wherein alternate ones of said monolayers are of different inorganic material with an organic material between said particles.
Claim 5
Dependent Claim
56 words
The invention as set forth in claim 3 wherein said inorganic materials of said positively charged particles are selected from Al 2 O 3 and Cr 2 O 3 , and said material of said negatively charged particles is SiO 2 , said organic material is selected from the group consisting of acrylates, styrenics, and butadienes.
Claim 6
Dependent Claim
44 words
The invention as set forth in claim 2 wherein said positively charged particles are metal oxide particles of maximum dimensions from 50 to 150 Angstroms and said negatively charged particles are organic polymer latex particles of maximum dimension from about 0.05 to 5 microns.