1.)    Tougher and Harder Cutting Tools. a) Cutting tools made of nanomaterials, such as tungsten carbide, tatalum carbide, and titanium carbide, are much harder, much more wear-resistant, erosion-resistant, and last longer than their conventional (large grained) counterparts.

b)      For the miniaturization of microelectronics circuits, the industry needs micro drills (drill bits with diameter less than the thickness of an average human hair or 100 um) with enhanced edge retention and far better wear resistance. As nano-crystalline carbides are much stronger, harder, and wear-resistant, they are currently being used in these micro drills.

2) Automobile with Great Fuel Efficiency. a) As nanomaterials are stronger, harder, and much more wear-resistant and erosion-resistant, they are can be used in spark plugs.

a.) Also, automobiles waste significant amounts of energy by losing the thermal energy generated by the engine. Thus, the engine cylinders are envisioned to be coated with nanocrystalline ceramics, such as zirconia and alumina, which retain heat much more efficiently that result in complete and efficient combustion of the fuel.

3) Aerospace Components with Enhanced Performance Characteristics. a) The fatigue strength increases with a reduction in the grain size of the material. Nanomaterials provide such a significant reduction in the grain size over conventional materials that the fatigue life is increased by an average of 200-300%.

b)      In spacecrafts, elevated-temperature strength of the material is crucial because the components (such as rocket engines, thrusters, and vectoring nozzles) operate at much higher temperatures than aircrafts and higher speeds.

4) Ductile Ceramics. a) Ceramics are very hard, brittle, and hard to machine even at high temperatures. But, with a reduction in grain size, their properties change drastically.

b)      Nanocrystalline ceramics can be pressed and sintered into various shapes at significantly lower temperatures. For example, Zirconia is a hard, brittle ceramics, has even been rendered superplastic, i.e., it can deformed to great lengths (up to three times of its original length). However, these ceramics must possess nanocrystalline grains to be super-plastic.

c)      Ceramics based on silicon nitrid (Si₃N₄) and silicon carbide (SiC), have been used in automative applications as high-strength springs, ball bearings, and valve filters, and because they possess good formability and machinability combined with excellent physical, chemical, and mechanical properties.

d)     They are also used as components in high-temperature furnaces.

5) Better Insulation Materials. a) Aerogels are nanocrystalline porous and extermely lightweight materials and can withstand 100 times their weight. They are currently being used for insulation in offices, homes etc.

b)      They are also being used as materials for “smart” windows, which darken when the sun is too bright and they lighten themselves otherwise.

If you know more magnetic applications of nanomaterials, then please share with us.

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Electrical properties of nanomaterials:

1.)    High Energy Density Batteries. As we all know that conventional and rechargeable batteries are used in almost all applications that require electric power. The energy density or storage capacity of these batteries is quite low requiring frequent recharging. Nanocrystalline materials are good materials for separator plates in batteries because they can hold considerably more energy than conventional ones. Nickel-metal hydride batteries made of nanocrystalline nickel and metal hydrides are envisioned to require far less frequent recharging and to last much longer.

2.)    Large Electrochromic Display Devices. An electrochromic device consists of materials in which an optical absorption band can be introduced, or an existing band can be alerted by the passage of current through the materials, or by the application of an electric field. They are similar to liquid-crystal displays(LCDs) commonly used in calculators and watches and are primarily used in public billboards and ticker boards to convey information. The resolution, brightness, and contrast of these devices depend on the tungstic acid gel’s grain size. Therefore, nanomaterials, such as tungstic oxide gel, are being explored for this purpose.

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Magnetic Applications.

a) High Power Magnets. Nanotechnology has application in making of high power magnets. Magnets made of nanocrystalline yttrium-samarium-cobalt grains possess very unusual magnetic properties due to their extermely large surface area. The main applications for these high-power rare-earth magnets include quieter submarines, automobile alternators, land-based power generators, and motors for ships, ultra-sensitive analytical instruments, and magnetic resonance imaging (MRI) in medical diagnostics.

Medicinal Applications.

a) Researchers are developing customized nanoparticales the size of molecules that can deliver drugs directly to diseased cells in our body. When it’s perfected, this method should greatly reduce the damage treatment such as chemotherapy does to a patient’s healthy cells.

b.)    Nanomedicine refers to future developments in medicine that will be based on the ability to build nanorobots. In the future these nanorobots could actually be programmed to repair specific diseased cells, functioning in a similar way to antibodies in our natural healing processes.

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1) The physical and chemical properties of magnetic nanoparticles mainly depend upon the chemical structure and method of synthesis. For example, nano scale particles of magnetite show superparamagnetism at a transition temperature, which is smaller than the transition temperature of bulk material.

2.) Nanocomposite magnets consisting of uniform mixture of magnetically hard and soft phases have been extensively investigated in recent years due to their useful hard magnetic properties.

3.) High energy products and relatively high coercivities can be developed in these nanocomposite magnets. These magnets are high value of remanence and low cost.

4.) Magnetic studies in nanostructured materials have focused on the interaction between electron charges and magnetic spins and these studies have led to discoveries of new and unique phenomena that are neither observable in traditional bulk materials, nor explainable using classical theories. For examples: Giant Magnetoresistance (GMR) in multilayers and metallic granular solids, spin valves, spin injection etc.

5.) Magnetostrictive materials are of great scientific importance to us. Magnetostriction is the process in which magnetic material deformed due to presence of magnetic field.

6.) Magnetorestrictive nano scale films can allow such functions, which cannot be done using existing integrated circuits. For example these constitute driving elements of micro robots, pumps, motors etc. These can also be used for magnetic control of elastic properties or dependence of stress or strain on magnetic permeability to develop various electronic devices like a resonator with magnetically adjustable frequency and stress controlled inductance.

These are the magnetic properties of nanomaterials, if you know others, then you can share with us.

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1.) The preponderance of surface is a major reason for the change in behaviour of materials at the nanoscale. As up to half of all the atoms in nanoparticles are surface atoms, properties such as electrical transport are no longer determined by solid-state bulk phenomenon.

2.) The atoms in nanomaterials have a higher average energy than atoms in longer structures, because of the larger proportion of surface atoms. For example, catalytic materials have a greater chemical activity per atom of exposed surface as the catalyst is reduced in size at the nanoscale.

3.) Defects and impurities may be attracted to surfaces and interfaces, and interactions between particles at those small dimensions can depend on the structure and nature of chemical bonding at the surface.

4.) Molecular monolayers may be used to change or control surface properties and to mediate the interaction between nanoparticles.

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1.) Bulk level steel is highly stronger than carbon (graphite) but at nanoscale cylinders of carbon are 100 times stronger than steel and very flexible.

2.) Melting point goes on decreasing with decrease in size. Let us discus the reason:

The melting point as a layman definition is the temperature at which a material melts. According to the microscopic definition of a substance, it is defined as the temperature at which molecules in it posses just enough energy to overcome intermolecular forces that hold them in a fixed position in a solid. Atoms on the surface of a substance require less energy to move because these are in contact with lesser number of atoms of substance. While atoms inside the bulk of sample are surrounded by large number of atoms and require more energy to move. Therefore at macroscale level if size of sample is changed then percentage change in the number of atoms in size at macroscopic level. However at nanoscale level if size of object is changed then percentage change in number of atoms on the surface is very large.

Due to this melting point starts depending on the size of object and melting point goes on decreasing with decrease in size.

Note: If you know more mechanical properties of nanomaterials then please share with us.

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1. Conductivity of a bulk or large material does not depend upon dimensions like diameter or area of cross section and twist in the conducting wire etc. However it is found that in case of carbon nanotubes conductivity changes with change in area of cross section.

2.) It is also observed that conductivity also changes when some shear force (in simple terms twist) is given to nanotube.

3.) Conductivity of a multiwalled carbon nanotube is different than that of single nanotube of same dimensions.

4.) The carbon nanotubes can act as conductor or semiconductor in behaviour but we all know that large carbon (graphite) is good conductor of electricity.

These are the important electrical properties of nanomaterials with their examples.

Note: If you know more electrical properties of nanomaterials then please share with us.

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Optical Properties.

1) The properties like colour and transparency are considered as optical properties. These properties are observed to change at nanoscale level. For example bulk gold appear yellow in colour while in nanosize gold appear red in colour.

2.) Bulk silicon appears grey in colour while nanosized silicon appears red in colour. 3.) Zinc oxide, which at bulk scale blocks ultraviolet light and scatters visible light and gives white appearance. While nanoscale zinc oxide is very small in particle size compared with wavelength of visible light and it does not scatters it. Thus it appears transparent.

Reason for change in optical properties in nanoscale

1.) The main reason for change in optical properties at nanoscale level is that nanoparticles are so small that electrons in them are not as much free to move as in case of bulk material. Due to  this restricted movement of electrons, nanoparticles react differently with light as compared to bulk material.

If you know more properties of nanomaterials, then please share with us.

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The sol-gel technique for synthesis of nanomaterials  is a wet- chemical technique. It is also known as chemical solution deposition. Such techniques are used for the fabrication of materials starting from a chemical solution (sol, short for solution) which acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Precursors in the form of acetates or carbonates or nitrates are taken and then dissolved in deionized water. This starting material is used to produce a colloidal suspension known as gel. After that a gelling agent for example, polyvinyl alcohol is added and this will produce a gel.

A this fil coating is made on a substrate for example, Ni or Ti sheets, glass. It depends upon the requirement. The pH, temperature and viscosity should be under control. At last the film is annealed at suitable temperature and then characterized.

Common precursors are metal alkoxides and metal chlorides, which undergo hydrolysis and olycondensation reactions to from either a network “elastic solid” or a colloidal suspension or dispersion– a system composed of discrete often amorphous submicrometer particles dispersed to various degrees in a host fluid. In the case of the colliod, the volume fraction of particles (or particle density) may be so low that a significant amount of fluid may need to be removed initially for the gel like properties to be recognized.

sol-gel synthesis Merits:

• Produce materials at ultra-low temperatures (around 150-600 ^oF vis –a- vis 2500-6500 ^OF for conventional techniques),
• Synthesise Large quantities relatively cheaply,
• Co-synthesize  two or more materials simultaneously,
• Coat one or more materials onto materials (metals or ceramic particulates, and three-dimensional objects),
• Produce extermely homogenous alloys and composites,
• Synthesize ultra- high purity (99.9999%) materials,
• control the microstructure of the final products, and precisely control the physical, mechanical, and chemical properties of the final products.

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Steps in ball milling method;

1. As the name suggests, the ball milling method consists of balls and a mill chamber. Therefore over all a ball mill contains a stainless steel container and many small iron, hardened steel, silicon carbide, or tungsten carbide balls are made to rotate inside a mill (drum).

2. The powder of a material is taken inside the steel container. This powder will be made into nanosize using the ball milling technique. A magnet is placed outside the container to provide the pulling force to the material and this magnetic force increases the milling energy when milling container or chamber rotates the metal balls.

3. The ball to material mass ratio is normally maintained at 2 ratio1.

3. These silicon carbide balls provide very large amount of energy to the material powder and the powder then get crushed. This process of ball milling is done approximately 100 to 150 hrs to get uniform fine powder.

4. Ball milling is a mechanical process and thus all the structural and chemical changes are produced by mechanical energy.

I have seen an interesting image at for ball milling method at wikipedia. You can see the image here.

Advantages of ball milling process:

1. Nanopowders of 2 to 20 nm in size can be produced. The size of nanopowder also depends upon the speed of the rotation of the balls.

2. It is an inexpensive and easy process.

Disadvantages;

1. As the process is not so sophisticated, therefore the shape of the nanomaterial is irregular.

2. There may be contaminants inserted from ball and milling additives.

3. This method produces crystal defects.

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