Nanotechnology - Civil Engineering (CE) PDF Download

Nanotechnology
 What is Nanoscience?
Nanoscience is study of material behavior at nanoscale.

What is nanoscale? 
Dimension which is of the order of 1nm to 100nm is called nanoscale. Any material whose dimension is less than 100nm can be considered as nano material. 1nm = 10⁻⁹m 8.3

What is nanotechnology?
The term nanotechnology was coined by Norio Taniguchi in 1947. Nanotechnology is the manipulation of matter at nanoscale to create novel structure, devices and systems. Ex:
Structure:- Carbon nano tubes, graphene, bucky ball.
Devices:- nanodiodes, capacitors,..etc..
Systems:- NEMS-nano electro mechanical systems.

What do we look forward in nanotechnology?
In nano technology we look forward to
1. Explore more about the nature of the matter.
2. Develop new theories.
3. Find new questions and answers in many areas.
4. Develop new technologies to make human life more comfortable.

What is the basic principle of nanotechnology?
The properties of a material depends on the arrangement of atoms and molecules. Arrangement of atoms and molecules in nanoscale materials differ from that of bulk arrangement of same material. Hence when arrangement changes material behavior changes.

Number of physical phenomenon became noticeably different as the size of the system decreases. This is the basic principle of nanotechnology. Ex:- Nano gold and Bulk gold exhibit different properties.

Bulk Gold 
1. It is yellow in colour.
2. It has the property of luster.
3. It is inert.
4. It is a good conductor.

Nano Gold
1. Depending on scale, they turn red, blue, yellow and other colours.
2. It looses lusture property.
3. It is a good catalyst.
4. It is a semiconductor.

Mention different types of nanomaterials. Give an example for each.
There are three types. Namely,
1. One dimensional nanomaterials. Ex:- Graphene.
2. Two dimensional nanomaterials. Ex:- nanofibres, wires, CNT.
3. Three dimensional nanomaterials. Ex:- Fullernes, quantum dots, quantum drivers.

Explain different types of preparation of nanomaterials?
Basically there are two methods of preparation of nanomaterials, namely
1. Bottom-up approach.
2. Top-down approach.

Synthesis of nanoparticles can also be classified into physical and chemical methods.

Physical Methods Ball milling method:-
This method is basically used to prepare nanoparticles of metals and alloys in the form of powder. Ball mills are equipped with grinding media composed of hardened steel balls. Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. The balls rotate with high speed inside a drum and then fall on the solid with the gravity force and crush the solid into nano crystallites.

The significant advantage of this method is that it can be readily implemented commercially. Ball milling can be used to make carbon nanotubes. It is commonly used to prepare metal oxides nano crystals like Cerium Oxide(CeO2) and Zinc oxide(ZnO).

Vapour deposition Method:-
There are two types namely physical vapour deposition method and chemical vapour deposition method.In physical vapour deposition method material is directly deposited on a surface. In chemical method, it involves a chemical reaction followed by the deposition.

In physical method, material kept in crucible is heated so that it gets evaporated. It is blown towards a substrate with the help of a inert gas to avoid formation of large particles. Atoms / molecules blown by inert gas are allowed to condense on a substrate. The particles grow while traveling from crucible to substrate. Hence the particle size can be controlled by changing the distance between crucible and substrate and also the vapour pressure. Particles deposited on substrate is removed using scrapers.

In CVD method vapour condensed on substrate undergo chemical reaction to form a nano film.

Sol-Gel method:- 
This method is also known as thermal decomposition. This process involves the formation of colloidal suspension or solution(sol) and gelation of the sol to form nano powders is a continuous liquid phase(gel). The solution is kept at suitable temperature. Gelling agents are added under controlled viscosity and PH value.

The particles in sol are polymerized through the removal of the stabilizing components and produces a gel. The final heat treatment (evaporation of liquid) pyrolyze the remaining organic and inorganic components and form a nano particles coating on a substrate.

Molecular manufacturing
Molecular manufacturing is a future technology based on Feynman’s vision of factories using nanomachines to build complex products, including additional nanomachines. It promises to bring great improvements in the cost and performances of manufacture goods,while making possible a range of products impossible today.

Every manufacturing method is a method for arranging atoms. Most methods arrange atoms crudely; even the finest commercial microchips are irregular at the atomic scale. Many of today’s nanotechnologies face the same limit.

The basic idea is simple:
Where chemists mix molecules in solution, allowing them to wander and bump together at random, nanomachines will instead position molecules, placing them in specific locations in a carefully chosen sequence. Letting molecules bump at random leads to unwanted reactions - a problem that brows worse as products get larger. By holding and positioning molecules, nanomachine will control how molecules react, building up complex structures with atomically precise control.