NANOTECHNOLOGY

• A basic definition of nanotechnology is the study manipulation manufacture of extremely minute machines or devices. These devices are so small to the point of manipulating the atoms themselves to form materials.

• Nanotechnology is an enabling technology that allows us to develop materials with improved or totally new properties

INTRODUCTION

Contd.,

• Nanotechnology is the use of very small particles of material. A nanometer is a billionth of a meter.

• Nanotechnology is not a new science and it is not a new technology. It is rather an extension of the sciences and technologies .

Advantages

• Nanotechnology will make most exiting products quite a bit more powerful and flexible.

• The nanotechnology promises a rapid improvement of technology at low cost and high convenience.

• Computers will compute faster, materials will become stronger and medicine will cure more diseases

Disadvantages

• The nanotechnology has potential of developing and fabricating dangerous weapons, drugs in large quantity.

• At this moment the main limitation is the high costs of nanotechnology. Also concerns with the environmental effects.

Introduction To Nano Materials

• Nano particle: It is defined as a particle with at least one dimension less than 200nm.

• Nano composite : It is produced by adding Nano particle to a bulk material in order to improve the bulk material’s properties.

Fig.Nanotube on a small cement grain

Carbon Nano Tubes(CNT) • They are cylindrical with nanometer diameter.• They have 5 times the Young’s modulus and 8 times

(theoretically 100 times) the strength of steel.

Contd.,

Contd.,

Titanium oxide(TiO2)• Titanium dioxide is a widely used white

pigment.

• When incorporated into outdoor building materials can substantially reduce concentrations of airborne pollutants.

• Additionally, as TiO2 is exposed to UV light, it becomes increasingly hydrophilic ,thus it can be used for selfcleaning windows.

Nanotechnology In Construction

• Concrete is stronger, more durable and more easily placed.

• • Steel is made tougher .• • Glass is self-cleaning.• • Paints are made more insulating and

water repelling.

Nanotechnology in concrete• As we know, Concrete is a mixture of

cement, sand(fine aggregate), coarse aggregate and water.

• As concrete is most usable material in construction industry it’s been require to improve its quality.

• Concrete is, after all, a macro-material strongly influenced by its nano-properties.

Fig.Engineered Cementitious Composites (ECC) used to repair a bridge deck

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Nano-silica in concrete• Particle packing in concrete can be

improved by using nano-silica which leads to a densifying of the micro and nanostructure resulting in improved mechanical properties.

• • Related to improved particle packing as

a result, the compressive strength of the refined material is also 3 to 6 times Increased then the ordinary portland cement.

Fig.ECC suppresses cracking and becomes flexible

Nano-cement in concrete• Average size of Portland cement particle

is about 50 microns.

• Nano-cement is having particle size about 5 microns so it is used in thinner final products and for faster setting time.

• Hydration tests indicated that the Nano-cement had a more rapid hydration rate than Portland cement.

Contd.,

TiO2 in concrete• It can be used as an excellent reflective

coating.

• As when rain water is attracted to the surface and forms sheets which then collect the pollutants and dirt particles ,TiO2 then washes them off.

• The resulting concrete, already used in projects around the world, has a white color that retains its whiteness very effectively.

Contd.,

Fig.A building coated with TiO2

CNTs in concrete• The addition of small amounts (1% wt)

of CNT’s can improve the mechanical properties of samples consisting of the main Portland cement phase and water.

• Oxidized multi-walled Nano tubes (MWNT’s) show the best improvements both in compressive strength (+ 25 N/mm2) and flexural strength (+ 8 N/mm2) compared to the samples without the reinforcement.

Contd.,

Nanotechnology and steel

• Fatigue is a significant issue that can lead to the structural failure of steel subject to cyclic loading, such as in bridges or towers.

• Stress risers are responsible for initiating cracks from which fatigue failure results and research has shown that the addition of copper Nanoparticle reduces the surface unevenness of steel which then limits the number of stress risers and hence fatigue cracking.

• Two products in international market Sandvik Nanoflex

MMFX2 steel produced by Sandvik Materials

Technology(Sweden),having desirable qualities of a high Young’s Modulus and high strength and resistant to corrosion is due to the presence of very hard nanometer-sized particles.

• MMFX steel also launched by MMFX steel corporation (America) has the mechanical properties of conventional steel.

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• As the use of the stainless steel in the construction is limited for the sake of economy.

• The MMFX Steel is an alternative to conventional stainless steel, but at a lower cost.

• High rise structures require high strength joints and this in turn leads to the need for high strength bolts.

• Vanadium and Molybdenum Nanoparticle has shown that they improve the delayed fracture and hence improving the steel micro-structure.

• To block light& heat coming through windows, self cleaning glass using TiO2 is used in Nanoparticle form to coat glazing since it has sterilizing and anti-fouling properties.

• Fire-protective glass is another application of nanotechnology.

• This is achieved by using a clear intumescent layer sandwiched between glass panels (an inter-layer) formed of fumed silica (SiO2) Nanoparticle which turns into a rigid and opaque fire shield when heated.

Nanotechnology and glass

Contd.,

• As an active solution, thermo chromic technologies are being studied which react to temperature and provide insulation to give protection from heating while maintaining adequate lighting.

• A third strategy, that produces a similar outcome by a different process, involves photo chromic technologies which react to changes in light intensity.

• Nanotechnology is being applied to paints and insulating properties, produced by the addition of nano-sized cells, pores and particles, giving very limited paths for thermal conduction, are currently available.

• This type of paint is used, for corrosion protection under insulation since it is hydrophobic and repels water from the metal pipe and can also protect metal from salt water attack.

Nanotechnology and paints

• These can also be used for Elimination of toxic gases.

• The absorption of carbon monoxide is done by using cuprous salt and adsorption of hydrocarbons is done by using a complex nanomaterial. i.e., Carbon Monolithic Aero gels.

Contd.,

• These have found increasing application in civil structures .

• Due to super-elastics properties, the elastic deformation of SMAs is followed by a large increase of strain under an almost constant stress. After unloading, only elastic strain recovers and the residual stain can be removed through heating.

Shape memory alloys(SMAs)

Fig(a) Tendon buckles during loading

Fig(b)Tendon recovers after heating

Case Studies

Fig(a) Concrete cracks upon loading

Fig(b) Crack is closed up after heating

Fig. 7mm thick concrete wall

• The barely visible blue-green area at the top of this X-ray shows that very few chloride ions (in green) penetrate into the concrete. Infiltrating chloride and sulphate ions cause internal structural damage over time that leads to cracks and weakens the concrete.

• This can be removed rather than change the size and density of the pores in concrete, it would be better to change the viscosity of the solution in the concrete at the microscale to reduce the speed at which chlorides and sulphates enter the concrete.

• www.ieee.org• www.nanowerk.com/news/newsid=905• http://hello-engineers.blogspot.com/• www.futuretechnologies.com• Nanotechnology: A gentle introduction to

the next big idea by Mark A Ratner, Daniel Ratner technology-2002.

• http://www.slideshare.net

Refrences

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