WHAT IS NANOTECHNOLOGY?

WHAT IS NANOTECHNOLOGY?

Dr. C P Dhanalakshmi,

Head Of the Department,

Chemistry,

Dhanalakshmi College of Engineering.

Nanotechnology is an extremely broad term, the definition of which varies from field to field. Most commonly, nanotechnology is defined as “…the understanding, control, and restructuring of matter on the order of nanometers (i.e., less than 100 nm) to create materials with fundamentally new properties and functions” There are two main types of approaches to nanotechnology: The “top-down” approach and the “bottom-up” approach. The “top-down” approach involves taking larger structures that are either reduced down in size until they reach the nano-scale, or are deconstructed into their composite parts. On the other hand, the “bottom-up” approach is where materials are constructed from the atomic or molecular components.

NANO TECHNOLOGY USED IN CIVIL ENGINEERING

Nano particles can also be used in coatings such as paints to give the coating “…self healing capabilities and corrosion protection under insulation. Since these coatings are hydrophobic and repel water from the metal pipe and can also protect metal from salt water attack.” The incorporation of nanotechnology in civil engineering and construction is immensely useful to the field. Nanotechnology can be used to increase the life of concrete, create fire-resistant materials such as steel, and give building materials qualities such as “self-healing” and “self-cleaning.” 

THE USE OF NANOTECHNOLOGY IN CONCRETE

One of the most common and beneficial uses of nanotechnology in terms of civil engineering, is the use of it in concrete. Concrete “is a nanostructured, multi-phase, composite material that ages over time. It is composed of an amorphous phase, nanometer to micrometer size crystals, and bound water,” It is used in almost all construction, from roads, to bridges, to buildings. Concrete can be modified in numerous ways; one of which is to add nanoparticles to it. Most research done with nanoparticles is done with nano-silica, nano-titanium oxide, and some studies involving nano-iron, nano-alumina and nanoclay. These “nanoparticles can act as nuclei for cement phases, further promoting cement hydration due to their high reactivity, as nanoreinforcement, and as filler, densifying the microstructure and the ITZ, thereby, leading to a reduced porosity,”. Each of the nanoparticles has a different on concrete. Nano-silica improves strength, resistance to water penetration, and helps control calcium leaching. Nano-titanium has been proven to assist in the “…self-cleaning of concrete and provides the additional benefit of helping to clean the environment,” Nano-iron has shown to give concrete self-sensing capabilities and improved it’s “…compressive and flexible strengths,” Other areas of research pertaining to nanotechnology in cement include hydrate hybridization, (which is the creation of “hybrid, organic, cementitious nanocomposites,”), as well as the use of nanoreinforments, (carbon nanotubes and nanofibers).

One example of how nanotechnology improved this vital construction material is when the engineers at the National Institute of Standards and Technology patented a method to increase the lifespan of concrete in 2009. In 2007, almost one quarter of all bridges in the country was defective or obsolete all together.  The reasoning for this was the Chloride and sulfate ions would infiltrate the concrete and cause internal structural damage, weakening the concrete and causing cracks. The engineers at the NIST wanted to “…change the viscosity of the solution in the concrete at the microscale to reduce the speed at which chlorides and sulfates enter the concrete,” in a project called “…viscosity enhancers reducing diffusion in concrete technology (VERDICT)” in order to attempt to double the lifespan of concrete.

NANOTECHNOLOGY IN STEEL

Steel is one of the most important building materials used today. One of the major problems of using steel however, is dealing with fatigue. “Fatigue is one of the significant issues that can lead to the structural failure of steel subject to cyclic loading,” Fatigue can occur at stresses that are lower than the yield stress of the steel and leads to a shortening of the steel’s life. The best way to reduce the fatigue is to add copper nanoparticles to the steel. The copper nanoparticles can help reduce the unevenness in the surface of the steel, which in turn reduces the amount of stress risers. Since the steel now has less stress risers, fatigue cracking is limited as well. “The new steel can also be developed with higher corrosion-resistance and weld ability,” Another steel-related issue that is resolved by nanotechnology is in the area of welding. Welding strength is an extremely important issue. The area affected by heat in a weld can be brittle and fail without warning at times. The addition of nanoparticles such as magnesium and calcium can help solve this issue by making “the heat affected zone grains finer in plate steel,” which leads to strong welds. Improved fire resistance can also be achieved through nanotechnology. This is frequently done through a coating however, where the coating is “produced by a spray-on-cementitious process,”

NANOTECHNOLOGY IN GLASS, WOOD, AND OTHER AREAS

Nanotechnology is used in many different materials, including wood and glass. Wood is made of nanotubes or nanofibrils, primarily “lignocellulosic (woody tissue) elements,” that are twice as strong as steel. Being able to use these nanofibrils would “...lead to a new paradigm in sustainable construction,” since the creation and use of the material would be a part of a renewable cycle. Using these lignocellulosic could open up the possibility of “self-sterilizing surfaces, internal self-repair and electronic lignocellulosic devices”

Glass also makes use of nanotechnology. Nano-Titanium dioxide is used to coat glass can give the glass a self-cleaning property. Titanium dioxide breaks down organic wastes and compounds, and because it also attracts water, the glass can attract rain water and use that to clean the dirt off of itself. Another use of nanotechnology in glass is to make it fire-protective. This can be done when a layer of silica nanoparticles is placed between glass panels. This layer turns into a fire-shield when heated.

Pavement is yet another area that can be improved by nanotechnology. Nanoscale materials can be added to current roads to improve features such as the hardness of the road, the durability, and water and skid resistance. With the application of ZnO₂, it is possible to make hydrophobic roads that cause quicker run-off and help prevent hydroplaning.

Nanotechnology can even be used in water treatment. Some of the uses of nanotechnology in water treatment include “...water purification separation and reactive media for water filtration,”. Nanotechnology also has the possibility to help improve water quality, availability, and “viability of water resources, such as through the use of advanced filtration materials that enable greater water reuse, recycling, and desalinization,”.

REFERENCES

[1] Sanchez, Florence, and Konstantin Sobolev. "Nanotechnology in concrete--a review." Construction and Building Materials Nov. 2010: 2060+. General OneFile. Web. 9 Oct. 2012.

[2]"List of Nanotechnology Applications." Wikipedia. Wikimedia Foundation, 30 Sept. 2012. Web. 09 Oct. 2012. <http://en.wikipedia.org/wiki/List_of_nanotechnology_applications>.

[3]"Nanotechnology Doubling the Service Life of Concrete." Nanotechnology Doubling the Service Life of Concrete. N.p., Jan. 2009. Web. 09 Oct. 2012. <http://www.azonano.com/news.aspx?newsID=9604>.