GLASS MICROSPHERE

Syntactic foam contains an orderly arrangement of hollow sphere fillers. They are usually glass microspheres approximately 100 microns (4 mils) in diameter, provide strong, impervious supports for otherwise weak, irregular voids. As a result, syntactic foam has attracted considerable attention both as a convenient and relatively lightweight buoyancy material and as a porous solid with excellent shock attenuating characteristics. The latter characteristic is achieved... 

Results of uniaxial strain static and gas gun compression tests on syntactic foam have been conducted. The foam was buoyant and composed of hollow glass microspheres (average diameter 100 microns) embedded in an epoxy plastic. Static testing consists of compressing a 0.25 cm x 2.5 cm dia. wafer between carefully aligned 2.5 cm dia. steel pistons. Lateral expansion of the wafer is... 

Figure 2. Irradiation of uranyl glass microspheres (A) and FITC-labeled microbeads (B) demonstrate photobleaching and stability of both materials.

The approach to standardization used by Haaijman (53) and others (66,67), in which the fluorophor is incorporated within or bound to the surface of a plastic sphere, is more versatile than the use of inorganic ion>doped spheres, since the standard can be tailored exactly to the specifications required by the analyte species. However, this approach increases the uncertainty of the measurement because the photobleaching characteristics of both the standard and the sample must be considered. The ideal approach is to employ both types of standards. The glass microspheres can be used to calibrate instruments and set instrument operating parameters on a day-to-day basis, and the fluorophor-doped polymer materials can be used to determine the concentration-instrument response function. 

Initially glass microspheres were used in the 1970s to overcome severe lost circulation problems in the Ural Mountains. The technology has been used in other sites [1189]. Hollow glass beads reduce the density of a drilling fluid and can be used for underbalanced drilling [1199-1201]. Field applications have been reported [73]. 

Foamed cement slurries have been used to provide a low density cement slurry to reduce permeability damage to highly sensitive formations through reduced fluid loss (29). Glass microspheres have also been used to substantially reduce cement slurry density (30, 31). Other additives which reduce cement slurry density to a lesser extent include bentonite, fly ash, silicates, perlite, gilsonite, diatomaceous earth, and oil emulsions (see citations in reference 29). 

Figure 7. Effect of solution pH on the release of 10 pm glass microspheres from a glass surface.

The polymer and glass microspheres employed in the pressure-sensitive release of chemicals range in size from 1 pm to 1 mm in diameter. (For comparison, a human hair is typically 80-100 pm in diameter.A scanning electron micrograph illustrating the morphology of the particles appears in color Fig. 14.2.1. ... 

Schmitt, M.L., J.E. Shelby and M.M. Hall, Preparation of hollow glass microspheres from sol-gel derived glass for application in hydrogen gas storage. /. Non-Crystalline Solids, 352, 626-631,2006. 

Rapid Thermal Decomposition of Solutions (RTDS) process, 6 850 Rapid thermal processing sintering ceramics processing, 5 663 Rare-earth alloys, 23 262 economic aspects of, 74 645 Rare earth aluminosilicate (REAS) glass microspheres, 72 612... 

Yttrium(Y), 14 644, 645 Yttrium aluminosilicate (YAS) glass microspheres, 12 612 Yttrium aluminum garnet (YAG), 19 411 color, 7 331... 

Since unsaturated polyester resins alone would have insufficient strength for structural application, reinforcements are used to enhance the physical strength of such resins. Typically, tensile strength, impact strength and stiffness are the physical properties of most interest. Reinforcements can be regular particulates, as in glass microspheres, irregular particulates, as in flakes, or fibers. 

Solid and hollow glass microspheres have been made for many years for a variety of applications. Fabrication techniques involving formation of microspheres were pioneered by Beck7 and later expanded by Howell8 and Marshall9. 

ENCAPSULATION OF PALLADIUM IN POROUS WALL HOLLOW GLASS MICROSPHERES... 

The experimental work involved two parts. The first part was to produce porous wall hollow glass microspheres. The second part was to fill the PWHGMs with palladium. 

Fabrication of Porous Wall Hollow Glass Microspheres (PWHGMs)... 

Figure 1. Flame former for producing hollow glass microspheres.

The HGMs produced were heat treated at 620 °C for 18 hours before they were leached in 4 molar HC1 solutions at 80 "C for 4 hours. Heat treatment produced phase separation which resulted in a silica-rich phase and a more soluble and interconnected, sodium borate phase. Leaching removed the soluble sodium borate phase of the glass and created porosity through the microsphere walls. The porous wall, hollow glass microspheres, sank to the bottom of the solution. These sinkers were collected, water washed and dried at 100 °C overnight. 

The porous wall hollow glass microspheres were filled with palladium by a soak-and-dry process followed by hydrogen reduction. Saturated solutions of palladium salt were prepared at room... 

The floaters collected in the flame forming step were hollow glass microspheres (HGMs). The size of the microspheres were in a range from about 5 to 150 microns with a true density of about 0.4 g/cc as measured using a helium pycnometer. The wall thicknesses were estimated to be between 1 to 5... 

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