Glass microspheres are
microscopicMicroscopic or Micro is a term used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...
spheres of
glassIn general Glass refers to a solid, brittle, transparent material, commonly used for windows, bottles, or eyewear. Examples of glassy materials include, but are not limited to, soda-lime glass, borosilicate glass, acrylic glass, sugar glass, Muscovy-glass, or aluminium oxynitride. The term glass...
manufactured for wide a variety of uses in
researchResearch can be defined to be search for knowledge or any systematic investigation to establish facts. The primary purpose for applied research is discovering, interpreting, and the development of methods and systems for the advancement of human knowledge on a wide variety of scientific matters of...
,
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, consumer goods and various industries. Glass microspheres are usually between 1 to 1000 micrometers in diameter. The term is also used for glass spheres between 100 nanometers to 5 millimeters in diameter. Hollow glass microspheres, sometimes termed
microballoons, have diameters ranging from 10 to 300
micrometerA micrometre or micron is one millionth of a metre,or equivalently one thousandth of a millimetre....
s.
Glass microspheres are
microscopicMicroscopic or Micro is a term used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...
spheres of
glassIn general Glass refers to a solid, brittle, transparent material, commonly used for windows, bottles, or eyewear. Examples of glassy materials include, but are not limited to, soda-lime glass, borosilicate glass, acrylic glass, sugar glass, Muscovy-glass, or aluminium oxynitride. The term glass...
manufactured for wide a variety of uses in
researchResearch can be defined to be search for knowledge or any systematic investigation to establish facts. The primary purpose for applied research is discovering, interpreting, and the development of methods and systems for the advancement of human knowledge on a wide variety of scientific matters of...
,
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, consumer goods and various industries. Glass microspheres are usually between 1 to 1000 micrometers in diameter. The term is also used for glass spheres between 100 nanometers to 5 millimeters in diameter. Hollow glass microspheres, sometimes termed
microballoons, have diameters ranging from 10 to 300
micrometerA micrometre or micron is one millionth of a metre,or equivalently one thousandth of a millimetre....
s.
Hollow spheres are used as a lightweight
fillerAggregate is the component of a composite material used to resist compressive stress. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes...
in
composite materialComposite materials are engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure.- History :The most primitive composite materials were straw...
s such as
syntactic foamSyntactic foams are composite materials synthesized by filling a metal, polymer or ceramic matrix with hollow particles called microballoons. The presence of hollow particles results in lower density, higher strength, a lower coefficient of thermal expansion, and, in some cases, radar or sonar...
and light weight concrete . Microballoons give syntactic foam its light weight, low
thermal conductivityIn physics, thermal conductivity, , is the property of a material that indicates its ability to conduct heat. It appears primarily in Fourier's Law for heat conduction.-Measurement:...
, and a resistance to
compressive stressCompressive stress is the stress that, when applied, acts towards the center of that material. When a material is subjected to compressive stress, then this material is under compression. Usually, compressive stress applied to bars, columns, etc. leads to shortening.Loading a structural element or...
that far exceeds that of other foams. These properties are exploited in the hulls of
submersible***Also see Submersible drilling rig for offshore drillingA submersible is a commerical or non-military midget submarine with limited service range and is typically transported to its area of operation by a surface vessel or large submarine....
s and deep-sea oil drilling equipment, where other types of foam would implode. Hollow spheres of other materials create syntactic foams with different properties, for example ceramic balloons can make a light syntactic
aluminiumAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
foam.
Hollow spheres also have uses ranging from storage and slow release of pharmaceuticals and
radioactive tracerA radioactive tracer, also called a radioactive label, is a substance containing a radioisotope. Tracers can be used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or a tissue...
s to research in controlled
storageHydrogen storage describes the methods for storing H
2 for subsequent use. The methods span many approaches, including high pressures and cryogenics, but usually focus on chemical compounds that reversibly release H
2 upon heating. Hydrogen storage is a topical goal in the...
and release of
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
. Microspheres are also used in composites to fill polymer resins for specific characteristics such as weight, sandability and sealing surfaces. When making surfboards for example, shapers seal the EPS foam blanks with epoxy and microballoons to create an impermeable and easily sanded surface upon which fiberglass laminates are applied.
Glass microspheres can be made by heating tiny droplets of dissolved
water glassSodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and...
in a process known as
ultrasonicUltrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, it is approximately 20 kilohertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound...
spray
pyrolysisPyrolysis is the chemical decomposition of condensed organic substances by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition"....
, and properties can be improved somewhat by using an acid treatment to remove some of the
sodiumSodium is a metallic element with a symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals within "group 1"...
.
Dispensing microspheres
Dispensing microballons is one of the most difficult applications. When adding microspheres as a filler via standard mixing and dispensing machines, a breakage rate of up to 80% can occur, depending upon factors such as pump choice, material viscosity, material agitation, and temperature. Customized dispensers for microballon-filled materials reduce the microballon breakage (shrinkage rate) to a minimal amount. A
Progressive cavity pumpA progressive cavity pump is also known as a progressing cavity pump, eccentric screw pump or even just cavity pump and, as is common in engineering generally, these pumps can often be referred to by using a genericized trademark...
is the pump of choice for dispensing materials with microspheres; reducing microsphere breakage as much as 80%.
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