What is the Difference Between Sol-Gel and Hydrothermal Method

The key difference between sol-gel and hydrothermal method is that the Sol-gel method cannot produce nanomaterials that are not stable at high temperatures, whereas the hydrothermal method can generate nanomaterials that are not stable at high temperatures.

The Sol-gel method and hydrothermal method are very important industrial techniques useful in generating nanomaterials.

CONTENTS

1. Overview and Key Difference
2. What is Sol-Gel Method 
3. What is Hydrothermal Method 
4. Sol-Gel vs Hydrothermal Method in Tabular Form
5. Summary – Sol-Gel vs Hydrothermal Method 

What is Sol-Gel Method?

The sol-gel method is a process that involves the synthesis of various nanostructures and metal oxide nanoparticles. The molecular precursor in this method is dissolved in water or alcohol to be converted into gel via heating and stirring through hydrolysis/alcoholysis.

The most important advantage of using the sol-gel method in producing nanomaterials is that it can be carried out at room temperature, and it allows producing a large number of novel and functional materials with potential applications in different areas. It is very beneficial compared to other methods. This is a wet chemical method, also known as chemical solution deposition. It involves several steps, including hydrolysis, polycondensation, gelation, aging, drying, densification, and crystallization.

There can be some disadvantages of the sol-gel method as well, including the comparatively high cost of raw materials, large volume shrinkage and cracking that occurs during the drying step, unable to produce nanomaterials that are unstable at high temperatures, etc.

What is Hydrothermal Method?

The hydrothermal method is a solution reaction-based approach in nanotechnology that is used to produce nanomaterials. It is a chemical reaction involving water in a sealed pressure vessel. It is, in fact, a type of reaction that occurs at both high temperature and pressure. This method uses an aqueous solution as the reaction system that is included in a special closed reaction vessel, which creates a high-temperature, high pressure reaction environment via heating the reaction system and pressurizing it.

In this method, the chemical purity of the powder material is very high because it starts with high-purity precursors. It has a crystallization step in which growing crystals tend to reject impurities that occur in the growth environment. This means we are expected to remove the impurities such as ions coming from metal salts or PH adjusting from the system along with the crystallization solution.

What is the Difference Between Sol-Gel and Hydrothermal Method?

Production of nanomaterials is a complicated process with many different approaches. The sol-gel method and hydrothermal method are two such approaches. The key difference between sol-gel and hydrothermal method is that the sol-gel method cannot produce nanomaterials that are not stable at high temperatures, whereas the hydrothermal method can generate nanomaterials that are not stable at high temperatures. In the sol-gel method, the molecular precursor is dissolved in water or alcohol and converted into a gel by heating and stirring via hydrolysis, whereas the hydrothermal method involves a chemical reaction in water in a sealed pressure vessel that occurs at a high temperature and pressure.

The following table summarizes the difference between sol-gel and hydrothermal method.

Summary – Sol-Gel vs Hydrothermal Method

The sol-gel method is a process that involves the synthesis of various nanostructures and metal oxide nanoparticles while the hydrothermal method is a solution reaction-based approach used in nanotechnology to produce nanomaterials. The key difference between sol-gel and hydrothermal method is that sol-gel method cannot produce nanomaterials that are not stable at high temperatures, whereas the hydrothermal method can generate nanomaterials that are not stable at high temperatures.

Reference:

“Hydrothermal Synthesis.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Sol Gel Process” By C. Su, B.-Y. Hong, C.-M. Tseng – Science Direct (CC BY-SA 4.0) via Commons Wikimedia
2. “Quartz synthase” By Didier Descouens – Own work (CC BY-SA 4.0) via Commons Wikimedia