A composite is a new material created by combining two or more different materials to give the new material improved characteristics and properties.
Composite materials draw a great deal of attention from several industries, providing distinctive effects for diverse applications. From medical devices to aerospace, composite materials offer the possibility to enhance the nature of many devices, components, and coatings.
A strong, controlled, flexible, and customizable production process is required to make ground-breaking ceramic composite materials. Innovnano’s Emulsion Detonation Synthesis (EDS) is one such process. This proprietary manufacturing process provides a unique path, both for the mass production of nanostructured ceramic powders, such as yttria-stabilized zirconia, as well as for the design and development of novel materials, such as optimized composites.
The EDS Process
The EDS process is primarily used by Innovnano to manufacture large amounts of nanostructured ceramic powders. A water-in-oil emulsion is detonated under high temperature and pressure conditions to produce a shock wave that triggers chemical reactions, either behind or inside the reaction zone.
Additionally, adjusting the precursors and the experimental conditions used in the EDS reaction also allows the formation of new and better composite materials.
Figure 1. Schematic representation of the Emulsion Detonation Synthesis (EDS) method for the production of nanostructured ceramic powders and improved composite materials
The initial step in the basic EDS process is to consistently disperse a broad range of high purity soluble powder precursors into the emulsion matrix, which comprises of two phases - an external oil phase (combustible) and an internal aqueous phase (oxidizer).
Then, powder precursors in a water-in-oil emulsion endure detonation under high temperatures (approximately 1400 °C) and high pressures (more than 10 GPa) to produce a plasma with an even distribution of reaction products. The detonation products are then quenched very quickly, resulting in a nanostructured ceramic dry powder.
Each process feature is responsible for imparting advantageous properties to the ceramic powder end product. When high temperatures are used, dense spherical particles are formed, and when high pressures are used smaller primary particle sizes are formed. This guarantees a desired crystalline phase. The rapid quenching of the particles also supports both smaller crystallite sizes and a high surface area.
Innovation with EDS
Innovnano uses EDS to develop a collection of nanostructured ceramic powders that offer improved properties for the latest, high-tech applications with challenging requirements. These ceramic powders are used to create coatings and components that are harder and more durable, and include additional flexural strength and better resistance properties to thermal shock.
Also, Innovnano uses EDS as a design tool for better composite materials. In these applications, the emulsion composition is a very significant factor of the process, as it describes the type of material manufactured.
Many material possibilities can be tested based on the precursors used. This is the reason behind the versatility, and advantages of, the EDS process, making it possible to advance new material innovation. Thanks to the major flexibility in precursor preference, powders can be designed to include properties that are improved for specific applications.
EDS process control is also a significant factor, and the reaction’s kinetics, temperature, and pressure can all be modified to explore potential new materials.
In terms of composite materials, a variety of “designer” materials can be achieved:
- Single/multiple solid solution compounds created from micro and nanoparticles
- Micro and/or nanoparticles coated with a layer of nanoparticles
- Mixture of different phase compounds in the same particle
- Micro and nanoparticles coated with carbon
Producing Composite Materials
Using base particles coated with nanoparticles as an example, these composite materials are in huge demand in applications in the biomedicine, chemistry, ceramic, electronics, and energy fields. The aim is to impart these composite materials with the ceramic base particle properties, as well as the exceptional effects introduced by the nanoparticle layer coating the surface.
In this manner, new characteristics and properties are assigned to the end ceramic composite material, because of the two precursor materials and the technique used to create the composite.
The traditional techniques available for developing ceramic particle coatings, and therefore this type of inter-granular ceramic composite material, are generally divided into numerous categories:
- Dry coating methods
- Wet chemistry processes
- Gaseous phase deposition
However, these methods are subject to difficulties and limitations. Often, it is difficult to coat each individual ceramic particle; something that becomes more laborious as the base particle size reduces. Additionally, these techniques make it difficult to produce uniform coatings formed from single nanoparticles, and there are also frequent issues in producing coatings with a reliable adhesion to the base particle.
Notably, there are always limitations on the type of nanoparticle crystalline structures used for the coating, limiting the possibilities for new and novel products.
Using EDS for Composite Materials
EDS provides a reliable technique for the production of composite powders, without many of the difficulties or limitations associated with other coating processes. It creates composite powders that benefit from reduced sintering temperatures, and zirconia ceramic bodies with good particle distribution.
This translates into a final composite material with better magnetic, mechanical, and optical properties, which are attractive characteristics across several different industries.
EDS was successfully used for the production of enhanced composite materials at Innovnano, particularly with zirconia metal matrix composites (cermets).
These cermets include a robust bond coat of zirconia-base with either a metal or metal oxide nanoparticle coating, providing the benefits of both metals (for example, flexibility, toughness, and electrical conductivity) and ceramic materials (for example. wear resistance and high temperature performance).
Some more examples in development include colored zirconia ceramics based on a broad range of oxide pigments, ZTA and ATZ bioceramic composites, zirconia friction reduction composite, zirconia metal heterogeneous catalysts (nanostructured copper-zirconia) for catalyst reactions, and zirconia/NiO composites for solid oxide fuel cells.
Figure 2. A zirconia powder with a strong bond coat of different oxide or metal nanoparticles is used as a starting powder for obtaining intergranular ceramic composite materials.
Two variations on the basic EDS process can be used to uniformly coat ceramic base particles in a layer of nanoparticles, for use as starting powders to achieve intergranular ceramic composites. Sintering and additional processing of the composite powders created by the EDS process provide the final intergranular composite material for use in a variety of industries. Figure 3 shows an overview of the two process variants.
Figure 3. The two EDS process variants for the design and production of improved composite materials.
The first reaction is from the base ceramic particle precursors with extremely fast reaction kinetics, which means that they react inside the reaction zone. In contrast, the nanoparticle solid precursors react later, with slower reaction kinetics, and the decomposition reactions take place outside of the reaction zone.
This explains that these reactions take place after the formation of base particles, and as a result, the nanoparticles are deposited as a coating on the base particles. If the process variables are controlled, a host of nanoparticle coatings and base particles with different structures and dimensions can be produced.
The ceramic base particles are added as a pre-synthesized solid ceramic powder in the second variant of EDS, while the nanoparticle precursors are added as part of the water-in-oil emulsion. The precursors are decomposed into nanoparticles and deposited on the surface of the starting ceramic powder during detonation, creating the composite material.
Both EDS routes are very useful in the production of composite materials. Precursors of both components are used as starting materials in the first variant, which eliminates the need for pre-synthesis. Using a single process, both the ceramic powder and its coating are synthesized saving both time and cost. In the second variant, the base ceramic powder particle has to be pre-synthesized before adding it to the reaction.
As a result, temperature control is paramount to guaranteeing that the best possible environment is realized for the process to take place effectively. Additionally, the atmosphere composition and temperature must be properly controlled to ensure that no reaction occurs in the solid state between the nanoparticles and the base particle.
Both EDS routes are very useful in the manufacture of composite materials. The first variant, where precursors of both components are used as starting materials, eliminates the need for pre-synthesis. The ceramic powder as well as its coating is synthesized in a single process, saving both time and cost.
In the second variant, the base ceramic powder particle has to be pre-synthesized before it is added to the reaction. This makes it possible to use a more varied range of nanoparticle coatings and ceramic powders including nitrides, oxides, sulfides, carbides, and noble/inert metals, allowing the production of a greater range of innovative composite materials.
New materials should be able to match the constantly growing demands of our high-tech, fail-safe world. Production processes that enable the design and discovery of new materials with unique or improved properties are essential to take innovation to a new level.
EDS provides the opportunity to adapt protocols and regulate precursors to create new and attractive intergranular ceramic composite materials with precise features for individual applications.
This information has been sourced, reviewed and adapted from materials provided by Innovnano.
For more information on this source, please visit Innovnano.