APPLICATION OF NANOTECHNOLOGY-BASED THERMAL
INSULATION MATERIALS IN BUILDING CONSTRUCTION
The prefix “nano” is derived from the Greek “nanos”, meaning “dwarf”. A nano (symbol: n) is an SI prefix meaning one billionth. In the metric system this prefix denotes a factor of 10-9. Nanotechnology is science, engineering, and technology conducted on a nanoscale, which is about 1-100 nanometres. It is the study and application of extremely small things and can be used across other science fields, such as chemistry, biology, physics, materials science, and engineering. Its traditional sense means building things from the bottom up, with atomic precision.
Nanotechnology can also be used in architecture. The addition of nano-silica to cement-based materials can increase their durability and compressive strength. It can be used to increase the fluidity or water permeability of concrete. With the addition of nanotubes or nanofibers, the tensile and bending strength of concrete structures can be strengthened . Wood can be composed with nanotubes or nanofibers, and these products can be twice as strong as steel . Titanium dioxide (TiO2) is used in nanoparticle form to coat glazing because of its sterilizing and anti-fouling properties. Nanoparticle-based coatings can provide better adhesion, transparency, self-cleaning, corrosion and fire protection. We can also find some nanotechnology-based thermal insulation materials on the market:
• Expanded polystyrene products, including graphite powder additive
• Aerogel used for insulating transparent building structures.
• Nanoparticle-based vacuum insulation panels
• Nano-ceramic thermal insulation coatings.
Nanotechnology-based thermal insulation materials generally have a better thermal insulation quality than traditional materials. There are three ways of heat transport in traditional thermal insulation materials: thermal conduction (vibration of molecules inside cellular walls), heat flux (between air particles enclosed in cells) and thermal radiation (between opposing cellular walls). In nanotechnology-based thermal insulation materials, one or more ways of heat transport is hampered or blocked. This is why they can decrease the heat transfer coefficient of building structures.
Vacuum Insulation Panels
Vacuum insulation products were first used for insulating refrigerators and vehicles, but nowadays they are used in building construction to provide better insulation performance than conventional materials.In vacuum insulation panels two ways of heat transfer are hampered. The interfaces of silica crystals are very small, which causes difficulties in thermal conduction. Moreover, creating a vacuum (0.05 bar) practically eliminates convection, since this relies on the presence of gas molecules to be able to transfer heat energy by bulk movements. A small decrease in pressure has no effect on the thermal conductivity of a gas, because the reduction in energy carrying molecules is offset by a reduction in collisions between molecules. However, at a sufficiently low pressure, the distance between the collisions exceeds the size of the vessel; then the conductivity does reduce with pressure.
Aerogel Thermal Insulation
The application fields of aerogel insulations are limited because of the high cost of nanotechnology methods. It is useful for thermodynamic post-improvements of building constructions, which have become problematic due to a design or constructional error. It is also utilizable to remedy inherently problematic structural junctions of passive and low-energy houses. It can be applied indoors or outdoors to improve the thermal insulation capacity of monolithic concrete structures (lintels, pillars), window edges, roll covers, pipes, and containers. It is step-resistant and can usually be installed in a completely ordinary way without disrupting the structure. Stickable, plasterable and flexible, it is easy to fit to curved surfaces. The most important aerogel thermal insulation products used in building construction are:
• Aerogel thermal insulation blankets
• Self-adhesive insulating strips
• Nanoporous translucent glass
An aerogel thermal insulation blanket (e.g., Spaceloft®) is a flexible composite material, which is actually an aerogel embedded in a fiberglass spatial net. It is available in rolls, which enable rapid and wide-ranging applications. Compressible, plastic, and fire-resistant, it fits well anywhere without a loss of tensile strength and elasticity. Aerogel blankets are available in different widths, thicknesses (2-10 mm), and sizes. It can be optimally composed for different temperature ranges (from -200°C to +650°C).
Nanoceramic Thermal Insulation Coatings
Nano-ceramic thermal insulation coatings are flexible; non-toxic; mould-free; UV, fire and chemical resistant; washable; and friendly to the environment; they form a monolithic membrane that bridges hairline cracks. They can stick well to all types of surfaces such as concrete, ceramic, plaster, metal, glass, wood and plastic. These coatings are typically used for exterior and interior wall insulation, but they are also suitable for pipe insulation and protect against fire and corrosion. They can be easily transmitted to hard to-reach areas. Their most important advantage is that they can be applied in places where it is not possible to use thick thermal insulating panels (e.g., scheduled national monuments).
source : http://www.degruyter.com/view/j/sjce.2016.24.issue-1/sjce-2016-0003/sjce-2016-0003.xml?format=INT
The prefix “nano” is derived from the Greek “nanos”, meaning “dwarf”. A nano (symbol: n) is an SI prefix meaning one billionth. In the metric system this prefix denotes a factor of 10-9. Nanotechnology is science, engineering, and technology conducted on a nanoscale, which is about 1-100 nanometres. It is the study and application of extremely small things and can be used across other science fields, such as chemistry, biology, physics, materials science, and engineering. Its traditional sense means building things from the bottom up, with atomic precision.
Nanotechnology can also be used in architecture. The addition of nano-silica to cement-based materials can increase their durability and compressive strength. It can be used to increase the fluidity or water permeability of concrete. With the addition of nanotubes or nanofibers, the tensile and bending strength of concrete structures can be strengthened . Wood can be composed with nanotubes or nanofibers, and these products can be twice as strong as steel . Titanium dioxide (TiO2) is used in nanoparticle form to coat glazing because of its sterilizing and anti-fouling properties. Nanoparticle-based coatings can provide better adhesion, transparency, self-cleaning, corrosion and fire protection. We can also find some nanotechnology-based thermal insulation materials on the market:
• Expanded polystyrene products, including graphite powder additive
• Aerogel used for insulating transparent building structures.
• Nanoparticle-based vacuum insulation panels
• Nano-ceramic thermal insulation coatings.
Nanotechnology-based thermal insulation materials generally have a better thermal insulation quality than traditional materials. There are three ways of heat transport in traditional thermal insulation materials: thermal conduction (vibration of molecules inside cellular walls), heat flux (between air particles enclosed in cells) and thermal radiation (between opposing cellular walls). In nanotechnology-based thermal insulation materials, one or more ways of heat transport is hampered or blocked. This is why they can decrease the heat transfer coefficient of building structures.
Vacuum Insulation Panels
Vacuum insulation products were first used for insulating refrigerators and vehicles, but nowadays they are used in building construction to provide better insulation performance than conventional materials.In vacuum insulation panels two ways of heat transfer are hampered. The interfaces of silica crystals are very small, which causes difficulties in thermal conduction. Moreover, creating a vacuum (0.05 bar) practically eliminates convection, since this relies on the presence of gas molecules to be able to transfer heat energy by bulk movements. A small decrease in pressure has no effect on the thermal conductivity of a gas, because the reduction in energy carrying molecules is offset by a reduction in collisions between molecules. However, at a sufficiently low pressure, the distance between the collisions exceeds the size of the vessel; then the conductivity does reduce with pressure.
Aerogel Thermal Insulation
The application fields of aerogel insulations are limited because of the high cost of nanotechnology methods. It is useful for thermodynamic post-improvements of building constructions, which have become problematic due to a design or constructional error. It is also utilizable to remedy inherently problematic structural junctions of passive and low-energy houses. It can be applied indoors or outdoors to improve the thermal insulation capacity of monolithic concrete structures (lintels, pillars), window edges, roll covers, pipes, and containers. It is step-resistant and can usually be installed in a completely ordinary way without disrupting the structure. Stickable, plasterable and flexible, it is easy to fit to curved surfaces. The most important aerogel thermal insulation products used in building construction are:
• Aerogel thermal insulation blankets
• Self-adhesive insulating strips
• Nanoporous translucent glass
An aerogel thermal insulation blanket (e.g., Spaceloft®) is a flexible composite material, which is actually an aerogel embedded in a fiberglass spatial net. It is available in rolls, which enable rapid and wide-ranging applications. Compressible, plastic, and fire-resistant, it fits well anywhere without a loss of tensile strength and elasticity. Aerogel blankets are available in different widths, thicknesses (2-10 mm), and sizes. It can be optimally composed for different temperature ranges (from -200°C to +650°C).
Nanoceramic Thermal Insulation Coatings
Nano-ceramic thermal insulation coatings are flexible; non-toxic; mould-free; UV, fire and chemical resistant; washable; and friendly to the environment; they form a monolithic membrane that bridges hairline cracks. They can stick well to all types of surfaces such as concrete, ceramic, plaster, metal, glass, wood and plastic. These coatings are typically used for exterior and interior wall insulation, but they are also suitable for pipe insulation and protect against fire and corrosion. They can be easily transmitted to hard to-reach areas. Their most important advantage is that they can be applied in places where it is not possible to use thick thermal insulating panels (e.g., scheduled national monuments).
source : http://www.degruyter.com/view/j/sjce.2016.24.issue-1/sjce-2016-0003/sjce-2016-0003.xml?format=INT
Civil Scholar is a Blog by Aravind Samala on Construction, Environment, Technology, Trends and Innovation.