Nanocomposite
A nanocomposite is as a multiphase nanosolid material or structures having nano-scale repeat distances between the different phases that make up the material. It includes porous media, colloids, gels and copolymers, but is more usually taken to mean the solid combination of a bulk matrix and nano-dimensional phases differing in properties due to dissimilarities in structure and chemistry. These nanomaterials have various functional expressions due to the quantum size effect.
Nanocomposite synthesis
Various synthesis strategies have been developed such as co precipitation,flame hydrolysis, impregnation, and chemical vapour deposition, sol-gel and non-hydrolytic sol-gel routes for the synthesis of nanocomposites. Current technologies available for the manufacture of functional nanopowders are dispersion, mixing (normal, ordered or precision), coating, fusion, reactions (solid-solid surface), Mechano Chemical Bonding (MCB), shape control, agglomeration, nanogrinding and drying from nanoslurries. Once nano sized materials are produced either in liquid or gas phase, elements of classical powder technologies are applied to further process them. These processes can involve drying, blending or agglomeration of the particulates.
Mechano Chemical Bonding
This technique can modify the shape of dry particles and bond them together using mechanical energy alone without any binders. It is reported to be an environmentally friendly process. It overcomes powder mixing problems caused by the segregation and agglomeration of particles and allows each component in the composite powder to express its inherent designed function. MCB Technology is a unique dry particle processing technique that enables the use of nanoparticles to create multi-functional nanocomposites contributing to the development of advanced devices for energy storage applications.
Merits of MCB treatment
By applying the MCB treatment, powders can achieve particle coating, precision mixing, sphericalization, and surface modification in one processing step. The MCB process can practically produce any type of composite powders without the constraint of chemical compositions. Depending on the particle size and mass ratio of guest and core particles, core-shell type of composite particles or core particles with embedded guest particles can be fabricated.
Principle
The basic Principle is based on Hosokawa Mechanical Treatment. The unit contains a press head, rotating casing, inside of which powder is supplied. Due to centrifugal force and rotation of casing, powders can achieve particle coating, precision mixing, sphericalization and surface modification in one processing step. The MCB technique takes the advantages of passing dry powder mixtures with preferred particle size ratios through a narrow gap, so that smaller guest particles are bonded onto the surface of larger core particles under the influences of various types of mechanical forces. By this principle solid-solid composite materials can be produce in a dry process without the use of a binder by only applying mechanical force. It is also a multi-functional processing method for precision mixing, particle surface modification and shape enhancement.
MCB treatment for Lithium-ion batteries
To cite an example of the application of MCB technique, the development of new generation materials for rechargeable batteries for the energy storage applications can be considered. However, in addition to the chemistry of electrode materials, the energy density, power density, rate capability and cycle life of rechargeable batteries can be improved by controlling the size, morphology, and surface properties of the particulate materials used in the electrodes. Mechano Chemical Bonding is a unique technology that can effectively improve the performance of Lithium-ion rechargeable batteries. It treats powders to increase electrode densities and to reduce the required amount of organic solvent and carbon black used in the battery manufacturing. Lithium-ion rechargeable batteries made by MCB treated powders can exhibit high capacity, long cycle life, and low internal ohmic resistance at high discharge rate.