Details on Cenospheres

What are they?

The word cenosphere is derived from two Greek words, κενός (kenos: hollow, empty) and σφαίρα (sphaera: sphere), literally meaning “hollow sphere

A cenosphere is a lightweight, inert, hollow sphere made largely of silica and alumina and filled with air or inert gas, typically produced as a byproduct of coal combustion at thermal power plants. The color of cenospheres varies from gray to almost white and their density is about 0.4–0.8 g/cm3 (0.014–0.029 lb/cu in), which gives them a great buoyancy ( they float on water /lightweight)


Chemical Properties of Cenospheres
SiO2 55-65%
Al2O3 20-35%
Fe2O3 8% Maximum
Loss on Ignition on 800C 2% Maximum
Colour Light Grey
Specific Gravity 0.65-0.85 g/cc Max
Sinkers 8% Maximum
Moisture 0.3% Maximum
Packaging Factor 60-65%
Mohs Scale Hardness of Shell 5
Thermal Conductivity 0.11 Wm-1K-1
Typical Crush Strength 1500-3000 PSI
Particle Size Distribution
% Passing through 500 Micron 99-100%
% Passing through 300 Micron 85-100%
% Passing through 150 Micron 30-80%

*Product can be custom manufactured as per the required specifications. (Particle Size, Sinkers and others).

Average Composition of the above noted Is based on fuel type they originate from ( coal, asphalt, nat gas, etc) henceforth forming the fly ash. Also they may be grey or white again dependent on fuel type as is composition with respect to silica, alumina, or iron. Additionally the “manufactured will differ from the above noted

composition as well and even the fly ash origin are commonly coated with various substances to suit the industrial purpose e.g. resin as an abrasive for blasting or with silver for use as a conductive media. Here We primarily discuss those of fly ash origin specifically coal ash.

Electron Microscope Cenosphere
Electron Micrograph
Naked Eye Cenosphere
Naked Eye
Where do they come from?/ How produced
The process of burning coal ( or other carbonaceous fuel) in thermal power plants produces fly ash containing ceramic particles made largely of alumina and silica. They are produced at temperatures of 1,500 to 1,750 °C (2,730 to 3,180 °F) through complicated chemical and physical transformation. Their chemical composition and structure varies considerably depending on the composition of coal that generated them.

The ceramic particles in fly ash have three types of structures. The first type of particles are solid and are called precipitator. The second type of particles are hollow and are called cenospheres. The third type of particles are called plerospheres, which are hollow particles of large diameter filled with smaller size precipitator and cenospheres.

“Floatation” the process of literally floating cenospheres on water is a common method of separating the Cenospheres from the other two components found in fly ash.

Note cenospheres are also manufactured when the composition of the desired sphere is different than the “native” found as a byproduct of combustion primarily at

power plants and formed of different heavy fuels vs light fuels. Manufacturing is obviously an expensive process. The type of fuel determines size and composition when formed naturally as a combustion byproduct.


Because of their low density, small size, spherical shape, mechanical strength, high melting temperature, chemical inertia, insulating properties and low porosity, microspheres [also known as cenospheres] find a wide range of applications in industry. In particular, [they are ideal] for reinforcing materials or imparting properties of resistance to corrosion, or thermal and sound insulation to coatings or paints. They can be described as multifunctional fillers and integrate well in resins and binders such as thermoplastics and thermosetting.”

Development acoustic improvement, acrylic, cements, coatings, sponsor board, divider boards, concretes, cosmopolitan marble, epoxy, explosives, Exterior Insulation Finishing Systems (EIFS), fiberglass, covers, light weight total, engineered wood, spackle, rug sponsorship, geothermal bonds, solid fiber board, joint compound, wood fillers.

Pozzolanic response – Bonding in the middle of cenospheres and concrete. This keeps on happening over years and makes longer-term holding and solidifying. The run of the mill proportion is somewhere around 15% and 20% cenospheres to bond.

Cenospheres additionally have high heat reflectivity that can be utilized as a part of coatings for parkways, carports, underground pipes, that require heat/thermal stability protection prerequisites. Their properties make them ideal for undersea link protection and waterproofing applications. Amusement flotation, playing balls, surf sheets, golf gear, marine mixes, KAYAKS.

Marine- Putties, maritime concretes, submerged floatation gadgets, marine specialty, surf loads up.

Aviation Ceramic protection, convoluted way network, propeller sharpened pieces of steels. Lockheed Martin uses Cenospheres for stealth in the skin of the F-22 Raptor Fighter Jets. At the point when surface treated, the circles can viably forestall EMI (electromagnetic impedance) and Low Observable Technology (radar assimilation)

Most Common Uses-

➔ Oil field- Cementing, boring muds (diminish slurry thickness without expanded water content).

➔ Plastics- Polyethylene, polypropylene, nylon, PVC, exacerbating, film, urethane, potting mixes.

➔ Earthenware production Tiles, firebricks, coatings, obstinate, protecting materials, high temperature concrete.

➔ Car Soundproofing, under-coatings, brake cushions, sealants, body fillers and putties, composites, directing wheels.

Cenospheres in Petroleum Drilling

For proof of the unknown importance of cenospheres, you need look no further that the vital role they play in the petroleum industry. For while everyone knows of the importance of oil in the modern world, it is a little known fact that cenospheres have, as the French industry journal, Industrie & Technologies, states, “…been used for several years in the field of oil drilling to reduce the density of a petroleum cement paste without increasing the water

content.” This is Particularly important in lost circulation and zonal isolation when drilling and cementing casing. It becomes even more important when you consider the effect the cementing procedure has on completions, perforating and fracturing.

The following is a write up taken from Hart energy touting the effectiveness of cenospheres in cementing with an accompanying graphic representation and comparison of other aggregate materials available on the market.


Advantages of using lightweight oilwell cements with microspheres/ aka nanospheres , microballoons, bucky balls, etc.
Lightweight. Low-density. Makes it possible to reduce the proportion of cement mortar to 1.25-1.3 g/cm3 (for traditional lightweight gel-cement slurry 1,52-1,54 g/cm3), and as a consequence: reducing repression on the producing formation, reducing penetration of the filtrate into a productive formation zone, providing a predetermined height of the cement.

Cenospheres enhance flowability in this application. An increased workability of the cement allows for easier pumping especially in deep wells and more contact in the annulus casing and bore sides..

High Thermal stability. May be used in high temperature applications stable up to 1000 degrees and also makes its use suitable in type G portland ( high temperature cement).

Low shrinkage. Makes improving communication of the formation with the well casing pipes.

Easy mixing. Lightweight tamping can be prepared directly on the rig, mixing cenospheres with cement dry. This may be any standard mixer.

Economy. Reduce costs by eliminating the two-stage cementing technology and reduce the time of well construction.

The technology of using cenospheres for lightweight oilwell cements has long been known in the world, but until recently, its widespread use was limited due to the high prices of artificial cenospheres offered by European manufacturers. Offered by

us, aluminosilicate microspheres, are a byproduct formed during the combustion of coal, and the price is much lower than their artificial analogues.

Today many leading oil and gas companies have already switched to using lightweight oilwell cements with cenospheres. The Russian Federation has cemented more than 6 thousands wells in the past 14 years utilizing the cenosphere advantage.

Their experience shows that the use of this technology results in a two fold desireable effect: reducing capital costs while improving the quality of cementing.


Extension with hollow beads. Low Specific-gravity hollow ceramic beads (cenospheres) added to the slurry effectively displace water and cement components with tiny encapsulated air bubbles. They range in diameter from approximately 25 to 300+ microns. This method yields a homogeneous mix, and finished cement containing cenospheres have an increased strength-to-density ratio and lower permeability compared to water extended slurry.

It is also Noteworthy to mention that both the Haliburton and SLB Patents for this process are from the late 70’s and early 80 and are essentially identical. Both companies noted when the cenosphere content gets too high the compressive strength decreases but there are simple solutions to this such as the addition of fumed silica which actually restores and even boosts the compressive strengths at very low density..i.e. Very light concrete end products. Both articles are available as is much published research on the mechanical & thermal properties of concrete utilising the Cenospheres. Available on request. Also noteworthy is the comparison to the 3m product which are glass spheres with lower compressive strength and higher cost whic the Hart article mentions.

Cenospheres in Paints and Coatings

There are a great many uses for cenospheres in the paint and industrial coating industry, due to the additional qualities they provide. For example, cenospheres are often used in coatings to control infrared radiation, giving those coatings an advantage over ones that merely attempt to limit thermal conductivity.

Meanwhile, coating experts at Petra Buildcare Products, explain how cenospheres, “… improve the quality of the paint by improving the volume and density of the product. After application on the wall, the ceramic beads tend to shrink thereby creating a tightly packed film on the wall.”

Cenospheres in Syntactic Foams

Cenospheres are often used to make ‘syntactic foams’. These are specialized solids which use cenospheres as a filler to provide any number of advantages, from lower cost, to added strength, sound proofing, buoyancy and thermal protection.

Experts at Engineered Syntactic Systems describe syntactic foam as follows;

“The ‘syntactic’ portion refers to the ordered structure provided by the hollow spheres. The ‘foam’ term relates to the cellular nature of the material. Thanks to its unique properties of

high strength at low density, syntactic foam has become widely used in subsea buoyancy applications. Syntactic materials are resistant to the combined effect of hydrostatic pressure and long-term exposure which make them ideal for oceaneering projects such as cable and hardball floats and instrumentation support. They also provide strength and structural integrity at a significantly lower weight per volume than most traditional materials which make them an attractive choice in many defence and civil engineering applications.”

cenopshere application

Pictured are some of the wide variety of syntactic foams available.

Cenospheres in Plastics and Polymers

Cenospheres also have a use in the manufacture of plastics and polymers, as their re-formable shape or strength helps to avoid shrinkage in thermoplastics and thermosetting plastics.

They are also being used in modern composites in the automobile industry. For example, the 2016 Chevrolet Corvette contains a “sheet molding compound in which glass microspheres

replace calcium carbonate filler and shave 20 pounds [9kg] off the sports car’s Stingray Coupe model weight.” The Vice President of the manufacturer, Continental Structural

Plastics Inc., Probir Guha, explains the reason for the inclusion of cenospheres in the composite, in saying that, “the typical SMC formula for this type of vehicle application comprises 20% by volume of glass fiber reinforcement, 35% resin and 45% filler, usually calcium carbonate,” adding that, “This new SMC [sheet moulding compound] is cost competitive with aluminium.”

Cenospheres in Concrete

For years, cenospheres have been a useful additive to concrete, providing additional strength, and or sound insulation, whilst also lowering density. Jeff Girard, President at The

Concrete Countertop Institute, explains these advantages, saying, “In theory, cenospheres can replace some of the normal-weight sand used in concrete. Cenospheres have a density that is less than water (averaging 0.7 vs. Water’s 1.0); quartz sand particles typically have a density of about 2.65. This means that 1 pound of cenospheres takes up the same absolute volume as about 3.8 lbs. of sand.”

Industrie & Technologies, also outlines the use of cenospheres as a means of lowering noise pollution, stating that, “[Cenospheres are used] in building materials to lighten concrete, while maintaining a compressive strength of 30 MPa at a density of 1.6 T / m3, improving their tightness and reducing their sound transmission. For example, the St. Petersburg

Scientific and Technical Center of Applied Nanotechnologies (STCAN) is involved in building bridges with such concretes in Russia, [for a quieter road surface]. Cenospheres are also used to improve the thermal and sound insulation qualities of plasters, mortars and plasters, used for walls, floors and ceilings. An addition of 40% volume cenospheres halves the noise transmission coefficient.”

Cenospheres in Pharmaceuticals

Cenospheres have been used in the pharmaceutical industry for many years, as the small balls can act as a near-perfect transport device when coated with drugs. Additionally, as the French industry journal, Industrie & Technologies, notes, “Cenospheres covered with silver oxide may, for example, be integrated into dressings in order to accelerate wound healing.”

Cenospheres in Advanced Industries

A great deal of research is being conducted to discover new uses for this versatile

by-product. For example, new catalysts for the methane oxidation process are being developed using magnetic cenospheres.

Cenospheres are also being used in the development of metal matrix composites (MMC), a variety of materials that attempts to combine the high energy absorption, impact resistance, and low density of the spheres with the qualities of other substances. Others, such as Paul

Biju-Duval of the Georgia Institute of Technology based in Atlanta, have worked hard in the development of cementless building materials. His work continues, adding to a cenosphere mix, items such as bamboo and metallic tubing as a means to finding alternative, cheaper, stronger, and more environmentally-friendly construction methods.

Meanwhile, the Institute of Chemistry and Chemical Technology of the Russian Academy of

Sciences in Krasnoyarsk, is studying ways that cenospheres could be used in catalytic transformations. While BAE systems is attempting to use cenospheres in paint as a means to support invisibility in the infrared spectrum, thus enabling military craft to have ‘invisibility cloaks’.

With such a wide range of uses, and an even wider range of potential uses, it is no wonder why interest in cenospheres is growing. As long as product developers are looking for lightweight fillers, improved drug delivery systems, improved coatings, cement substitutes,

and composite additives, then there will be a need for cenospheres. Plus with increased research into new uses for these versatile spheres, then only time will tell where the future of cenospheres lies.