Chip-DSC 100 – Xerogel nanoparticles
Alumina nanoparticles – humidity – melting – nanofluids
A gel is defined as a semi-solid sample, often containing liquid and solid components and is defined as a dilute cross-linked system that does not show a flow when in steady-state, however is mostly liquid. The linking in the liquid part gives the macroscopic “solid” character. Gels exist in different types and shapes, frequently used in pharmaceuticals or as an adhesive. A special version of gels are so called xerogels, as the swelling agents are usually removed. Examples for a xerogel would be dried silica gel or gelatin. Gels can be easily characterized by DSC, as it is frequently done in quality control.
The curve shows a linear DSC run of Alumina Nano Particles in Gel Matrix, heated with linear heating rate of 10K/min in nitrogen atmosphere. The signal shows two significant effects during the run that are worth closer consideration:
There is a loss of water in the range up to 120°C, leading to a shift in baseline due to the Cp change that is caused by the mass change of the sample. As a consequence of this effect, a dry gel matrix containing the nanoparticles is remaining – the so called xerogel.
At around 200°C, there is a phase transition of the nanoparticles from ordered to amorphous Alumina structure that can be seen as a small sharp peak. These two effects are reproducible and characterize the nanoparticle gel quite well.