As technology progress takes us closer to becoming more innovative. The nanotechnology is one of the most critical factors in it. Advanced sciences ranks nanotechnology as one of the driving forces with the potential to revolutionize material science of the current age.
For the synthesis of nanoparticles, the process of hydrothermal method is being increasingly favored globally, by industries and R&D labs alike.
Fundamentals of Hydrothermal Method
Hydrothermal synthesis process involves using any one of the several techniques to crystallize substances. It is done at high vapor pressure level and using high-temperature aqueous solution; hence it is termed as ‘Hydro’ + ‘Thermal’ = Hydrothermal method. The term has geological origins, and the natural process has been observed for more than 800 years now.
In simple terms, hydrothermal synthesis described as an artificial way to synthesize single-crystal (nanoparticles), depending on the solubility of aqueous solution under hot water and higher temperature levels. A strengthened container within the hydrothermal reactor, called ‘Autoclave,’ is filled with a solution. The process needs constant maintenance of temperature difference between the opposing ends of the crystallizing compartment.
The end with higher temperature is where the solvent dissolved, while the other end, which is comparatively cooler, is where the nanoparticle growth takes place.
How Hydrothermal Method for Nanoparticle Synthesis works?
Hydrothermal method for nanoparticle synthesis requires using special equipment, known as Hydrothermal Autoclave Reactor. It is a particular type of strengthened vessel which is designed to withstand high temperatures and higher pressure levels from within.
The autoclave consists of thick, steel-walled cylindrical vessels which have a hermetic sealing. This helps it to bear high levels of heat and pressure regularly and safely, for a long time.
Also, the material of the autoclave also needs to be resistant to solvents. The most important part of the hydrothermal autoclave is probably the ‘closure.’ Apart from this, the seals are the next important component of the autoclave.
As several hydrothermal processes require using solutions that have a corrosive effect on the interior material of the autoclave, special protective coatings are applied to prevent corrosion. These are usually designed to fit the interior of the autoclave seamlessly and can either cover the complete interior of the autoclave or part of it. These protective coatings typically made from gold, platinum, silver, carbon-free iron, titanium, glass or copper and Teflon. The specific type of protective layer will depend on the solution and the temperature used in the individual hydrothermal synthesis process.
Advantages of Hydrothermal Method for Nanoparticle Synthesis
These are some of the top benefits and advantages of using hydrothermal nanoparticle synthesis method, as compared to other ways, for crystallization and synthesis of nanomaterials:
Able to create crystalline phases which are not stable at higher temperatures safely.
- Grows materials which are known to have higher vapor pressure as their melting point gets closer.
- Creates larger-sized and high-quality crystals and nanoparticles, and at the same time, provide control over their content and composition.
We hope that this article was sufficient to give you a clearer idea of how the hydrothermal method for nanoparticle synthesis works in reality.