Era of Nanotechnology

Nanotechnology is a revolutionary step in the field of construction which deals with the synthesis, characterization, utilization and analysis of materials at the nano scale. These can be utilized to improve the mechanical properties, and furthermore, to examine the microstructure of concrete.

Pawandeep Kaur, Post Graduate Student, Punjab Agricultural University, Ludhiana, and
Dr. Jaspal Singh, Chief Engineer, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana

There has been an exceptional change in the realm of industrialization. The quantity of industries is expanding step by step which has emotional impact on nature. Because of the expansion in number of industries, the degree of carbon dioxide outflows is expanding at a pinnacle rate. Carbon dioxide has become a significant method of reasoning for the yielding of greenhouse impact which is mainly due to the cement production as depicted by the green technology research. The expenses of cement are likewise expanding day by day. The manufacturing of concrete needs colossal vitality, therefore, release same measure of carbon dioxide which is exceptionally perilous for the human well being. Because of this vulnerability, it has gotten compulsory to alleviate the creation of cement by replacing it with alternative materials, for instance, fly ash, bottom ash, ground granulated blast furnace slag, rice husk ash, corn cob ash etc which has the similar properties as that of cement. As it is well known fact that Ordinary cement and concrete composites offer much flexibility and cost effectiveness in their utilization but they are exposed to physical and chemical attacks which affects their performance; therefore, these requires costly repair and maintenance works. Under different loads and situations, ordinary concrete is not much advantageous for effective service life. Therefore, it is pertinent to produce the modified concrete with outstanding properties so that minimum amount of cement is highly desired with the intention that economical and sustainable construction may be achieved along with the reduction in CO₂ emissions in the atmosphere.


The journey of nanotechnology begins from the talk of well known Nobel Laureate Richard Feyman in 1959 at the California Institute of Technology. Nano technology brought a great revolution in the construction world during the past few decades. Nanotechnology is commonly considered to deal with particles in the size range less than 100 nm and with the nano materials manufactured using nano particles. It is a revolutionary step in the field of construction which deals with the synthesis, characterization, utilization and analysis of materials at the nano scale. These can be utilized to improve the mechanical properties and furthermore, to examine the microstructure of concrete. Nano materials have the incredible potential to act as filler which lessens the likelihood of permeability. There are various sorts of nano materials, for example, Nano-silica (NS), colloidal Nano Silica (CNS), Nano-Al₂O₃, Nano-TiO₂, Nano-ZnO, Nano-Fe₂O₃, Carbon Nano tubes (CNT), Nano Fly ash (NFA), Nano concrete, Nano silica fume (NSF) which will brings about the decrease of carbon dioxide discharges.

Commonly used Nano materials and their properties:

Nano-silica (nano-SiO₂): Nano Silica particle can be produced by the different methods such as: Sol-gel method, Electric-Arc-method, biological methodology, precipitation methodology.

Applications of silica nano particles:

1. These are used as an additive for the manufacture of rubber and plastics.
2. It is acting as strengthening filler for concrete and other construction composites.
3. It also acts as a stable, non-toxic platform for biomedical applications such as drug delivery.

Nano-alumina (nano-Al₂O₃): Nano size alumina particles are in the spherical form and have high specific surface area. Methods for obtaining alumina in nano form:

1. By grinding the particles of alumina powder to a nanometer level (for instance, 10-50 nm).
2. By the decomposition of Al(OH)₃ to aluminium oxide in the rapid achievement of the temperature of decomposition 175 °C and use for it the pressure of 5 bars within thirty minutes. When the decomposition temperature is achieved, aluminium oxide particles in nano size can be obtained.

Nano titania (nano-TiO₂): These are the particles of titanium oxide having diameters less than 100 nm. Ultra fine titanium oxide has the capability to block the ultra violet radiations thereby these acting as sunscreens. These are considered as safer than the other substances for UV protection. Ultrafine TiO₂ is used in housing and construction as an additive to paints, plastics, cements, windows, tiles.

Carbon nano tubes (CNTs): Carbon nanotubes (CNTs) are cylindrical molecules which are rolled-into the sheets of single-layer carbon atoms (graphene). These can be categorized into types such as single-walled carbon nano tubes (SWCNT) having diameter of less than 1 nanometer (nm) and multi-walled carbon nano tubes (MWCNT) having several concentrically interlinked nanotubes with diameters more than 100 nm. CNTs have outstanding thermal, electrical and mechanical properties substantially relying on their dimensions. The diameters for multi walled carbon nano tubes and single walled carbon nano tubes are in the range of 1.4–100 and 0.4–3 nm, respectively.


CNTs are produced by the three different methods such as:

• Arc Discharge
• Laser ablation of graphite
• Chemical vapor deposition (CVD)

Graphite is combusted electrically or by means of laser in the first two methods and CNTs developing in the gaseous phase are separated.

CVD process
CVD method produce large amount of CNTs under controllable conditions and also these produces at a very low cost. In this process, a metal catalyst can be combined with the carbon-containing reaction gases (such as hydrogen or carbon monoxide) to form carbon nanotubes on the catalyst inside a high-temperature furnace.

Applications of Nano Technology in various fields:

1. Nano Technology in Construction:
   Nanotechnology has been used in various disciplines of civil engineering including better design and construction processes. Nanotechnology is helpful for the development of different structural materials with their different properties, lighter weight and stronger composites, self-disinfecting surfaces. A lot of analysis has been done on the concrete at the nano level to be aware of its structure.
   • Nano Silica: Silica fumes in micro form are added to the concrete for the purpose of filling the voids, decrease alkalinity and also increasing the resistance against chemical attack. Thus it is well established that silica fumes increase the strength of concrete and produce a denser and more homogeneous matrix. It was believed that the nano silica particles will be more effective than the micro silica fumes. Nano silica can be added to the concrete due to many reasons such as:
     • Increasing the density
     • Reducing porosity leading to a decreased water penetration.
     • Improving the bond between cement matrix and aggregates
     • Results into enhancing the mechanical properties of concrete.
   • Nano Alumina: It performs similarly as nano silica performs as it leads to a more compacted microstructure of cementitious composites by decreasing the porosity and enhances the compressive strength. It is worth noting that nano-alumina was proved to improve concrete performance at both elevated and low temperatures.
   
   • Nano Titania: Nano titanium dioxide is another material which has gained popularity for its usage in concrete. These nano particles accelerate the rate of hydration and increase the degree of hydration. Further, the incorporation of nano-titania (nano-TiO₂) may lead to enhancement in the strengths in addition to the improvement in resistance against chloride penetration. The impact of nano-titania addition on the performance of cementitious composites at an elevated temperature turned out to be comparable to composites incorporating nano-alumina.
   • Carbon nano tubes (CNTs): The addition of CNTs in cementitious composites is a challenging task due to the difficulty of obtaining uniform dispersion of CNTs in the cement matrix. If the CNTs are not properly dispersed in the cement matrix, then these results into the poor microstructure which greatly affects the mechanical properties. The compressive and flexural strength of composites containing CNTs greatly enhances up to 50 and 87%, respectively. It also improves both the fracture energy and flexural toughness. CNTs increase the crack bridging capacity of cementitious composites acting as networks between the crack and the pores. CNTs act as the nano filler of voids and thus reduce porosity. The incorporation of CNTs in the cement composites decreases the drying shrinkage. It is worth noting that the influence of CNTs on the microstructure, porosity and thereby mechanical properties of cementitious composites is highly dependent on the quality of their dispersion within cement matrix as well as on the type of surfactant to be used. The benefits of CNTs in concrete are as follows:
     • Durability
     • Crack Prevention
     • Helps in the enhancement of mechanical and thermal properties
   Presently, the utilization of nano materials in construction is reduced, due to the following reasons:
   • The lack of information regarding the suitable nano materials
   • The lack of detailed information regarding the nano products content
   • Cost of nano materials are extremely high
   • The risks of health associated with nano materials
2. Nano Technology in medicine: The medical application of nanotechnology is nano medicine where it ranges from the medical applications of nano materials and biological devices to nano electronic biosensors and even possible future applications of molecular nanotechnology such as biological machines. Presently, the problem arises due to the toxicity and environmental impact of nano scale materials used for the nano medicine.
3. Nano Technology in electronics and IT: Nano technology made a great revolution in computing and electronics leading to faster, smaller and more portable systems which can manage and store larger amount of information. These includes:
   • Transistors: These are the switches which enable all the modern computing, its size can be reduced with the help of nano technology. As nano technology helps in achieving the smaller, better and faster transistors which only means that the entire computers memory can be stored into a single tiny chip.
   • Ultra-high definition displays and televisions are now being sold that use quantum dots to produce more vibrant colors while being more energy efficient.
   • Using magnetic random access memory (MRAM), computers will be able to “boot” almost instantly. MRAM is enabled by nanometer-scale magnetic tunnel junctions and can save data quickly and effectively during a system shutdown or enable resume-play features.
   • Nano particle copper suspensions have been developed as a safer, cheaper and more reliable alternative to lead-based solder and other hazardous materials commonly used to fuse electronics in the assembly process.
4. Energy Applications of nano technology: Nanotechnology also plays a vital role in traditional energy sources and is greatly enhancing alternative energy approaches to meet the increasing demand of energy in the world. Numerous researchers are investigating approaches to develop perfect, reasonable and sustainable power sources alongside intend to reduce energy utilization and lessen toxicity burdens on the environment:
   • Nanotechnology is improving the productivity of fuel production from crude oil materials through better catalysis. It is additionally empowering reduced fuel utilization in vehicles and power plants through higher-proficiency combustion and decreased friction.
   • Nanotechnology is additionally being applied to oil and gas extraction through, for instance, the utilization of nanotechnology-empowered gas lift valves in offshore activities or the utilization of nano particles to identify microscopic down-well oil pipeline fractures.
   • Scientists are exploring carbon nano tube “scrubbers” and films to isolate carbon dioxide from power plant exhaust.
   • Scientists are creating wires containing carbon nanotubes that will have a lot of lower resistance than the high-strain wires as of now utilized in the electric grid, therefore reducing transmission power loss.
   • Nanotechnology can be joined into solar based panels to change over daylight to power all the more proficiently, encouraging cheap solar power in the future. Nano structured solar cells could be less expensive to fabricate and simpler to introduce, since they can utilize print-like assembling forms and can be made in adaptable rolls as opposed to discrete boards. More current research recommends that future solar converters may even be “paintable.”
   • Nanotechnology is as of now being utilized to create numerous new sorts of batteries that are faster charging, progressively productive, lighter weight, have a higher power density and hold electrical charge longer.
   • An epoxy containing carbon nanotubes is being utilized to make windmill cutting edges that are longer, more grounded and lighter-weight than different sharp edges to build the measure of power that windmills can create.
   • In the area of energy harvesting, researchers are developing thin-film solar electric panels that can be fitted onto computer cases and flexible piezoelectric nano wires woven into clothing to generate usable energy on the go from light, friction and/or body heat to power mobile electronic devices. Similarly, various nano science-based options are being pursued to convert waste heat in computers, automobiles, homes, power plants, etc., to usable electrical power.
   • Energy efficiency and energy saving products are increasing in number and types of application. In addition to those noted above, nanotechnology is enabling more efficient lighting systems; lighter and stronger materials for the transportation sector; lower energy consumption in advanced electronics and light-responsive smart coatings for glass.

Limitations of Nanotechnology

• Perhaps the greatest detriment that the world is confronting a direct result of nanotechnology is the lack of employment in the fields of conventional farming, fabricating and industrial sector and that is due to the huge advancement of the nanotechnology. Nanotech gadgets and machines have taken place of people to work quicker and proficiently, which has reduced the significance of man power in the field of practical work.
• Another huge threat, which is brought into the world with the coming of nanotechnology, is the easy availability of nuclear weapons. Nanotechnology has made these weapons more powerful and more destructive. Unauthorized, criminal bodies can reach nuclear weapons easily, and its formulation could be stolen. Unapproved, criminal bodies can reach atomic weapons effectively and its plan could be stolen.
• Nanotechnology has increased the chance of the health issues. Because of minute size of nano particles, it increases the danger of inhalation that can seriously harm lungs and could likewise prompt deadly medical problems. It enhances the risk of harming the lungs if nano particles are breathed in for 60 seconds.
• At present nanotechnology is on the most expensive technologies and its cost is increasing day by day. The main reason for not being cost efficient is the molecular structure and processing of the product. It is difficult for the manufacturers to randomly produce dynamic products using nanotechnology. Huge pricing of nanotech machines makes it unaffordable currently.
• There are some ethical issues which include the poisoning of mass material which has been processed at a nano scale. It may leave negative impacts on the health and industry. Mass poisoning could happen only if the coatings on the products that nanotechnology has to produce include poisonous micro particles that can penetrate into the brain when it comes in contact with humans.
• While nanotechnology can help to produce a wide range of goods and improved products, however the particles that are made are so tiny to such an extent that they may cause inevitable medical issues in the bodies of purchasers.
• Nanotechnology has raised the standard of living but at the same time, it also enhanced the risk pollution in water and air. The pollution caused by nanotechnology is known as Nano Pollution. Such kind of pollution is very dangerous for living organisms under water & on earth.

Conclusions
Due to the potential benefits of nano particles, nano materials and nano technologies have gained considerable scientific interest in various fields. Nanotechnology makes the structure lighter and more efficient than the other materials. Although construction materials may constitute only a small part of this overall effort, it could pay enormous rewards in the areas of technological breakthroughs and economic benefits. Although today the total market share of nano products for construction is small and deemed to be applied in niche markets, this share is expected to grow in the near future. Nano particles play a significant role as a basis for the design, development and production of materials in the construction industry. Nano materials assist in enhancing the properties of concrete.

Until today, concrete has primarily been seen as a structural material but nanotechnology can help to make it as multipurpose “smart” functional material. They can improve the overall performance of concrete since they have high surface area to volume ratio providing the potential for tremendous chemical reactivity. Due to the negative impact of nano technology, its use may be reduced. The people working with the nanotechnology or nano materials have to be more careful as these helps in creating health issues and these also put a greater effort in creating pollution called as nano pollution.