Nanocomposites
–
A Review
Balwinder Singh, S. Chauhan and Gaurav Verma
Dr. SSB University Institute of Chemical Engineering and Technology Panjab University Chandigarh, INDIA.
email:[email protected].
(Received on: September 19, 2015)
ABSTRACT
A nanocomposite is a matrix to which nanoparticles have been added to
improve a particular property of the material. The properties of nanocomposites have caused researchers and companies to consider using this material in several fields. The nanoparticles if added to the polymers matrix in the concentration of around. 5 to 2%, the properties of the composites like mechanical, physical, electrical, optical shows a dramatic change in their magnitude. The particle size and the concentration of the nano filler is the backbone this change. The particle size <100nm is considered the result oriented in these properties14. The characteristics of the particle nature are
also play a role in properties like electrical, magnetic and optical. Although for mechanical and physical properties the particle sizes are important.
Keywords: Nanocomposite, Nanoparticle, matrix , nanometer, nm.
INTRODUCTION
One of the desirable end-goals of materials science research is the development of multi-functional materials. These materials are defined as compositions that bring more than one property enhancement to a particular application, thus allowing the material to replace more than one other material in an engineered object, or to replace entire classes of materials which alone, are only capable of addressing one end-use need. The properties of the nano- composite materials depend not only on the properties of their individual parents but also on their morphology and interfacial characteristics. Fabrication process and controlling the nano particles dispersion the mechanical properties like strength, flexural strength, toughness and hardness, stiffness, elongation and thermal stability, adhesion resistance can be improved.
applications as compare to micro scale particles where loading is much higher to achieve the similar performance. The correct selection of the particle is essential to ensure the improvement in the desired properties, undesired nano-particles may lead to different properties.
NANO-PARTICLES
Nano particles are the particles with all the three dimensions is in the range of nano scale. Whereas nano materials have at least one dimension in in the nanoscale. These particles are also referred as ultrafine particles, may be obtained from natural sources like volcanoes, from forest fires and are by products of combustion processes15. The properties of these
materials depends not only their composition itself but more on the surface area. The surface in the nano particles is one of the factors that enhances the properties of the materials. Besides increasing general properties like mechanical properties, electrical properties, optical properties, these materials can be effectively used to protect the environment, can be used to design pharmaceuticals to target the specific organ to improve the therapeutic effectiveness.
Nano particles can also be added into cement, cloths and other materials to make them stronger and lighter. Manmade nano particles are produced and designed with specific properties, by laser ablation, high-pressure carbon mono oxide, chemical vapor condensation and arc discharge. These particles can be used in electronic, medicine, automobile, optical and electrical industry. On the basis of size the nano particles can be divided into three categories. First type of nanoparticles is spheres which are having all the three dimensions in the nanometer scale. Second type are generally cylindrical tubes which are having two dimensions in the nano meter scale where as one dimension in the micron meter scale. Third type of nano particles are having one dimension in the nano meter scale where as two dimensions in the micrometer scale these are called nano plates4.
DESCRIPTION AND APPLICATIONS
Nano-composites are the materials with one bulk phase and the others are dispersed in that bulk phase are small nano scale particles which are used to enhance the properties of the bulk phase. These nano scale particles are may be of one type or may be of different types are used to tailor made the properties of the bulk material/phase. The properties of the nanocomposites differ from the individual atoms and molecules or bulk matter. The controlling of the nanoparticles can control the properties of the materials like physical properties, mechanical properties3,16,18, chemical properties, biological properties, melting temperature,
Thermal stability2, magnetic properties, charge capacity, color, electronic and electrical
properties, optical properties, flame retardency1, corrosion prevention, superconducting
properties, Thermal properties, catalytic properties, refractive index, gas barrier properties10,
abrasion resistance and processing properties, surface activation for activation5, Mar and
abrasion resistance7,8, wear properties20 etc.
parts. Most of the nanocomposites are blends of organic / inorganic9 nano particles dispersed
in the bulk material. The nano particles are equally dispersed in the other phase and the interfacial properties of the nanoparticles and the bulk material will dictate the properties of the final nanocomposite. So the controlling of the nanoparticles is very critical to tailor made the properties of the nanocomposite. The controlling means the controlling of their particle sizes, loading, dispersion in the bulk phase, as well as the basic properties of the individual particles.
The nano fillers / particles are Aluminium oxide (Al2O3), MgO2 Magnesium oxide,
Silica oxide (SiO2), Titanium oxide (TiO2), clays, organoclays, ceramics, bentonite etc. The
selection of the nanoparticles as well as the bulk phase is the challenging job in controlling the properties of the nanocomposites. Processing technique of the nanocomposite, dispersion, distribution of the nanoparticles in the bulk phase, amount of the nano fillers in the bulk phase plays important role in the improvement of the properties of the nanocomposite. These particles are added in a very small amount as compare to the bulk phase and because of this weight loss as compare to traditional materials with same properties is achieved which help this nano composite to act in many other light weight applications6,11.
As we have achieved higher surface area in these nano composites so we have a great opportunity to get the improved mechanical properties, gas barrier properties, thermal properties, flame retardency, physical properties. Metal nanocomposites can be used for high abrasion resistance properties. If the wrong set of bulk phase as well as nano particles are chosen, nano composite formed may not be having adequate properties or nano particles have not dispersed well in the bulk phase, poor mixing of the particles may lead to a failure product which might be having inferior properties than the parent constituents. And the final requirement of properties will dictate the all parameters controlling.
The nanoparticles improve the properties in more than one areas, nanocomposites prepared for higher temperature applications may also gives some savings in weight loss and can be used in engine as well as auto parts. And give the nanocomposites with increase in flexural / tensile modulus while keeping high the impact performance also. Nano composite used in flame retardant applications can improve the strength for packaging applications and while meeting the fire safety ratings it will improve strength and wear resistance, chemical resistance, mechanical strength, Thermal resistance. And more the composites will give the cheaper alternatives to the traditional ones.
Nano composites have the lesser diffusivity for gases, oxygen as well for water as they are making surface interaction with the bulk phase and clay fillers create a more zig-zag path, and thus find a huge use in food packaging industry. Due to this when nano sized anti microbial agents such as metal ions metal oxides etc., are used they also give the property the antimicrobial to bulk phase and find a use in antimicrobial/food packaging industry13,17,19.
Reinforcing properties of silicates will make the material tougher along with improving the properties of solvent resistance, reducing permeability, increased flame retarding properties.
the surface into inter phase of different properties. Due to which the required properties are reached at very low concentration of the nano particles and the geometrical shape of the nano particle influence to determine the properties of the nanocomposite.
The nano composites can be formed from polymer and its interaction with the layered fillers is as shown in the diagram below. Phase separated micro composites are when there is no polymer in the inter layer of the filler platelets. Where as in the intercalated nano composites the polymer is in between the layers but they are at equal distance or spacing from each other. Whereas in the exfoliated composites there is no fixed spacing in the layered platelets and polymer is widely distributed in the space between the layers15. There other different ways of
producing nanocomposites from polymers and fillers like in situ polymerization, melt compounding etc.
The values of the critical particle sizes for different properties are labeled different although the properties of the particle nature also influence the final property. The catalytic property the values of the particle size may be of the range 2-5nm, 100 nm for mechanical properties and super paramagnetism, 50nm for refractive index change, 20nm for making magnetic material soft are generally used to get the properties change12.
DISADVANTAGE
Besides the great effects on the properties of the nano composites their effects on human body and environment are not well studied yet. Nano particles can enter into the body through inhalation or ingestion and can cause many defects like inflammation in the lungs like asbestos do. Some times nano particles reduce14 the properties instead of improving them and
properties like brittleness and opacity are observed in nano composites. So there is a need to better understand the behavior of nano particles for effective use of them.
CONCLUSIONS
Nano composite is vey vast and versatile field of research. This technique can give us the materials with multi area enhancement of the material properties and can lead to multifunctional materials. Along with this we may add two or more type of nano particles to improve the various different types of properties of the composites. Even particle size of the nano dispersed phase will change the specific property to manifolds. This technique is creating a revolution in the material technology.
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