WATER.
Monday, November 16, 2009
ELIMINATING BAR REINFORCEMENT
WATER.
Sunday, November 15, 2009
CNT PROPERTIES
CHEMICAL -- SP2 bonding structure, stronger than that of SP3 bonding in diamonds. Are considered anisotropic
ELECTRICAL -- In theory, metallic nanotubes can carry an electrical current density of 4 × 109 A/cm2 which is more than 1,000 times greater than metals such as copper. It has also recently been reported that SWNTs can route electrical signals at high speeds (up to 10 GHz) when used as interconnects on semi-conducting devices.
Source: azonano.com
MECHANICAL -- Since CNTs have a low density for a solid of 1.3 to 1.4 g•cm−3, its specific strength of up to 48,000 kN•m•kg−1 is the best of known materials, compared to high-carbon steel's 154 kN•m•kg−1.
THERMAL –- It is predicted that CNTs will be able to transmit up to 6000 W•m−1•K−1 at room temperature; compare this to copper, a metal well-known for its good thermal conductivity, which transmits 385 W•m−1•K−1. The temperature stability of CNTs is estimated to be up to 2800 °C in vacuum and about 750 °C in air.
OPTICAL -- Graphene, a single layer of carbon atoms in sheet form (imagine a CNT unrolled) is transparent but exhibits the most extreme properties of any known material.
U.N.O. Source: Wikipedia (various, please see associated bibliography)
ELECTRICAL -- In theory, metallic nanotubes can carry an electrical current density of 4 × 109 A/cm2 which is more than 1,000 times greater than metals such as copper. It has also recently been reported that SWNTs can route electrical signals at high speeds (up to 10 GHz) when used as interconnects on semi-conducting devices.
Source: azonano.com
MECHANICAL -- Since CNTs have a low density for a solid of 1.3 to 1.4 g•cm−3, its specific strength of up to 48,000 kN•m•kg−1 is the best of known materials, compared to high-carbon steel's 154 kN•m•kg−1.
THERMAL –- It is predicted that CNTs will be able to transmit up to 6000 W•m−1•K−1 at room temperature; compare this to copper, a metal well-known for its good thermal conductivity, which transmits 385 W•m−1•K−1. The temperature stability of CNTs is estimated to be up to 2800 °C in vacuum and about 750 °C in air.
OPTICAL -- Graphene, a single layer of carbon atoms in sheet form (imagine a CNT unrolled) is transparent but exhibits the most extreme properties of any known material.
U.N.O. Source: Wikipedia (various, please see associated bibliography)
PRODUCTION OF CNTs
CNTs are made by the following major processes:
ARC-DISCHARGE -- 2 rods of graphite (anode+cathode) are electrified, the carbon gas produces the nanotubes. This process produces more pure (usually multi-walled) tubes with very few defects, but it doesn’t produce very many tubes. Many other ‘shapes’ of tubes are also produced which are hard to separate.
CHEMICAL VAPOR DEPOSITION (CVD) –– start with carbon-based gas and ‘grow’ tubes from metal catalysts. The solution is heated to anywhere from 300 - 1150 degrees Celsius. Can produce long tubes, but with impurities and vague structure. Can easily alter diameter of tube by altering the catalyst, as well as the length of the tube by altering the period which heat is applied. This process easily allows for the introduction of other ‘additives’ like boron or nitrogen.
LASER ABLATION –- Process uses a laser to vaporize the carbon from graphite rods. Single-wall tubes are produced.
ELECTROLYSIS – Process similar to CVD, but the graphite is immersed in molten ionic salts. Only multi-walled (10-15) tubes are produced which are inevitably bundled (generally a weak organization).
Single Wall CNTs are produced at 50 grams per hour through a process developed by Idaho Space Materials, which is currently the highest production rate. For a list of USA CNT suppliers follow the link to the right.
ARC-DISCHARGE -- 2 rods of graphite (anode+cathode) are electrified, the carbon gas produces the nanotubes. This process produces more pure (usually multi-walled) tubes with very few defects, but it doesn’t produce very many tubes. Many other ‘shapes’ of tubes are also produced which are hard to separate.
CHEMICAL VAPOR DEPOSITION (CVD) –– start with carbon-based gas and ‘grow’ tubes from metal catalysts. The solution is heated to anywhere from 300 - 1150 degrees Celsius. Can produce long tubes, but with impurities and vague structure. Can easily alter diameter of tube by altering the catalyst, as well as the length of the tube by altering the period which heat is applied. This process easily allows for the introduction of other ‘additives’ like boron or nitrogen.
LASER ABLATION –- Process uses a laser to vaporize the carbon from graphite rods. Single-wall tubes are produced.
ELECTROLYSIS – Process similar to CVD, but the graphite is immersed in molten ionic salts. Only multi-walled (10-15) tubes are produced which are inevitably bundled (generally a weak organization).
Source: Women in Nano with nano2hybrids and Vega Science Trust
Single Wall CNTs are produced at 50 grams per hour through a process developed by Idaho Space Materials, which is currently the highest production rate. For a list of USA CNT suppliers follow the link to the right.
BRIEF HISTORY OF CNTs
Carbon Nanotubes (CNTs) were first observed in the 1950s by Roger Bacon, again observed by Morinobu Endo in the 1970s. Sumio Iijima of IBM is largely credited with observing and producing single and
multi-wall CNTs in 1991.
History compiled mostly from: http://www.nanogloss.com
A variety of nano-shapes can be produced:
HERRINGBONE (stacked cones)
FULLERENE (spherical)
ONIONS (concentric spheres)
PEAPODS (fullerenes inside a tube)
BUDS/WINGS (tubes with structural bulges)
GRAPHENE -- Imagine a carbon nanotube unrolled into a sheet, which is also considered transparent. One atom thick sheet of carbon atoms. Discovered in 2004.
As you now know, Steel is made up mostly of carbon atoms, usually with varying, but small, amounts of other elements which produce specific performance alloys. So, naturally we should look to carbon nanotechnology for keys to advancing this element of concrete.
See video regarding current and possible applications of CNTs
multi-wall CNTs in 1991.
History compiled mostly from: http://www.nanogloss.com
TUBE
SCROLL
HORN (cone)HERRINGBONE (stacked cones)
FULLERENE (spherical)
ONIONS (concentric spheres)
COILS
BAMBOO SHOOTSPEAPODS (fullerenes inside a tube)
BUDS/WINGS (tubes with structural bulges)
GRAPHENE -- Imagine a carbon nanotube unrolled into a sheet, which is also considered transparent. One atom thick sheet of carbon atoms. Discovered in 2004.
As you now know, Steel is made up mostly of carbon atoms, usually with varying, but small, amounts of other elements which produce specific performance alloys. So, naturally we should look to carbon nanotechnology for keys to advancing this element of concrete.
See video regarding current and possible applications of CNTs
BRIEF HISTORY OF CONCRETE
The Romans first used a form of concrete around 300 BC consisting of lime, broken stones and sand. With the discovery of Puzzolana, a kind of natural cement, near Mt. Vesuvius, the Romans were able to create a stronger bond than they attained with lime cement.
Then in 1824, Joseph Aspdin, from Leeds, England, patented a new type of cement made by treating, heating and cooling raw materials into clinker. These small rock-like shapes, made up mostly of calcium silicate, were then ground to a fine powder. This is first example of Portland Cement.
Manufacturing of Portland Cement in the U.S. did not begin until about 1872.
By now, you essentially have a material that is very strong in compression, but possesses no tensile strength. So, as both of these forces work dynamically on all structural components, an additional material would need to be used within concrete to accommodate these forces. Reinforced Concrete was first patented by a French gardener name F. Joseph Monier in 1857. The use of steel, which is extremely strong in resisting tensile forces, was necessary to make concrete as versatile as it is today. Steel is actually very strong in both tension and compression, but is extremely heavy and combustible. In my opinion, the combination of concrete and steel is one of history’s most important inventions.
From there, a handful of improvements were made regarding the technique of forming and reinforcing concrete. Prestressing, the act of stretching the steel reinforcement prior to the curing of concrete, was introduced by a French engineer named Freyssinet in the late 1920s. Of course we also have the technique of Post-stressing, which stretches steel tendons after the curing of concrete. The development of Prestressing and Post-stressing both meet the need for concrete to perform under extreme loading or span conditions.
Today, concrete is made up of five basic components, where their respective proportion by volume is indicated: Cement (11%), Water (16%), Air (6%), Fine Aggregate (26%), Coarse Aggregate (41%). Steel is not included in this list because it is not technically needed to make concrete, but is added to varying degrees and design per engineering standards to achieve desired strengths that are otherwise impossible. The chemical reaction between Cement and Water is what makes adhesion possible, and this ratio is a major determining factor for the strength of the concrete. So, I consider concrete to be extremely exciting because of the five (or six, if you count steel) components of concrete we’ve really only advanced two or three of them (more on this later). There are at least three other components that can be experimented with in order to yield cutting-edge development to increase the performance of concrete! My studies will address the advancement of reinforcement on a nano-scale with the use of Carbon Nanotube technology.
Then in 1824, Joseph Aspdin, from Leeds, England, patented a new type of cement made by treating, heating and cooling raw materials into clinker. These small rock-like shapes, made up mostly of calcium silicate, were then ground to a fine powder. This is first example of Portland Cement.
Manufacturing of Portland Cement in the U.S. did not begin until about 1872.
By now, you essentially have a material that is very strong in compression, but possesses no tensile strength. So, as both of these forces work dynamically on all structural components, an additional material would need to be used within concrete to accommodate these forces. Reinforced Concrete was first patented by a French gardener name F. Joseph Monier in 1857. The use of steel, which is extremely strong in resisting tensile forces, was necessary to make concrete as versatile as it is today. Steel is actually very strong in both tension and compression, but is extremely heavy and combustible. In my opinion, the combination of concrete and steel is one of history’s most important inventions.
From there, a handful of improvements were made regarding the technique of forming and reinforcing concrete. Prestressing, the act of stretching the steel reinforcement prior to the curing of concrete, was introduced by a French engineer named Freyssinet in the late 1920s. Of course we also have the technique of Post-stressing, which stretches steel tendons after the curing of concrete. The development of Prestressing and Post-stressing both meet the need for concrete to perform under extreme loading or span conditions.
Today, concrete is made up of five basic components, where their respective proportion by volume is indicated: Cement (11%), Water (16%), Air (6%), Fine Aggregate (26%), Coarse Aggregate (41%). Steel is not included in this list because it is not technically needed to make concrete, but is added to varying degrees and design per engineering standards to achieve desired strengths that are otherwise impossible. The chemical reaction between Cement and Water is what makes adhesion possible, and this ratio is a major determining factor for the strength of the concrete. So, I consider concrete to be extremely exciting because of the five (or six, if you count steel) components of concrete we’ve really only advanced two or three of them (more on this later). There are at least three other components that can be experimented with in order to yield cutting-edge development to increase the performance of concrete! My studies will address the advancement of reinforcement on a nano-scale with the use of Carbon Nanotube technology.
Source: Simmons, H. Leslie. Construction – Principles, Materials and Methods. 7th Ed. John Wiley and Sons, Inc, New York, 2001.
PROPOSAL
Determine a concrete composition capable of eliminating traditional formwork and traditional bar reinforcement in order to rapidly and economically produce structural complex doubly-curved surfaces. It is proposed that Carbon Nanotube technology be employed in place of traditional reinforcement to ensure the feasibility of any degree curve. In relation to studies and the experience of Lafarge and VSL, whose steel fibre reinforced product is commonly known as Ductal, it is also proposed that no aggregate greater than 1cm (only fine, pure aggregate). Additionally, the concrete composition would need to utilize admixtures to ensure that the concrete is self-compacting. Should a particular section require multiple pours of successive and gradual strength, a water-reducing retarding admixture will ensure the cohesion of the separate 'lifts.' Where necessary, thermoformed fabric formwork should be used in conjunction with multiple lifts. As technology advances, this application should adapt to new and desired CNT shapes which exhibit ever-increasing strength and durability.
CHALLENGE
You will focus on engineered and scientific applications of smart materials and on their effects and actions on high performance building envelopes.
The analysis of design, engineering and manufacturing constraints related to emerging materials are to be related to case studies of innovative skin/cladding/surface solutions within an integrated building envelope/assembly of components and systems.
Accordingly to your interests, you will link academic research with the practical experience of fabrication’s methods and techniques, opening up a dialog with the industry and the latest technologies applied to smart materials.
Particularly, you will be involved with:
- 3D performance simulations, 3D modeling of your multi-layered building envelope;
- Physical mock-ups/prototypes in appropriate scale;
- Technical drawings with a clear understanding of the building components and building systems.
<<< Maria Perbellini, ARCH5334 - Construction IV
The analysis of design, engineering and manufacturing constraints related to emerging materials are to be related to case studies of innovative skin/cladding/surface solutions within an integrated building envelope/assembly of components and systems.
Accordingly to your interests, you will link academic research with the practical experience of fabrication’s methods and techniques, opening up a dialog with the industry and the latest technologies applied to smart materials.
Particularly, you will be involved with:
- 3D performance simulations, 3D modeling of your multi-layered building envelope;
- Physical mock-ups/prototypes in appropriate scale;
- Technical drawings with a clear understanding of the building components and building systems.
<<< Maria Perbellini, ARCH5334 - Construction IV
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