I want to measure the heat capacity of my oxide thin film. Is it possible to measure it by DSC technique?
Dear colleague Shalu Pathak
Have a nice time and good day.
You can calculate calculate the next four distinct temperatures from DTA, DSC or TGA; glass transition, Tg the onset of crystallization, Tc Peak of crystallization, Tp and melting point Tm, please see the attached Figure. as depicted through the attached file. Also these parameters were used to study the thermal stability, so you need to know these four values to study the thermal stability and to calculate other constants. The following paragraph which supported by references may help you.
Glass transition temperature, Tg, can be defined as the temperature at which an amorphous system changes from the glassy to the rubbery state.
Or, The glass transition -point is the temperature (Tg) at a given moisture content where a transition from a glassy stable amorphous solid state to a rubbery amorphous solid state can begin to take place.
[K.A. Abbas ,Modern Applied Science , Vol. 4, No. 5; May 2010 ]
Tg also can be defined by the endothermic change in the DSC trace indicates a large change of viscosity, marking a transformation from amorphous solid phase to super cooled liquid state.
[ F.A. Al-Agel ,Journal of Alloys and Compounds 568 (2013) 92–97]
It depends on many parameters; softening, hardening, localized deformation, applied stress, temperature, the strain rate, viscosity, inhomogeneous deformation region, bond strength bond breakage, the mobility of the cations and anions, connectedness of the network, the average coordination number, the quality of connections, bond energies of heteropolar and homopolar bonds and heat capacity.
N. El-Kabany Vacuum 85 (2010) 5–9], [Binoy Kumar Maji, Hrudananda Jena, R.Asuvathraman Journal of Non-Crystalline Solids 434 (2016) 102–107].
The largest critical size for non-localized deformation at room temperature has the lowest glass transition temperature (Tg).
[Q.P. Cao, C. Wang, K.J. Bu, S.Y. Liu, X.D. Wang, D.X. Zhang and
J.Z. Jiang, Scripta Materialia 77 (2014) 64–67 ]
It has the next formula[[L. Wang, M.C. Liu, J.C. Huang, Y. Li, W.H. Wang, T.G. Nieh Intermetallics 26 (2012) 162-165 ]:
Tg = σyM/50ρ +T………………………..(1)
where σy is the yield strength, T is the ambient temperature, ρ is the
density, M is the molar mass, and Tg is the glass transition temperature.
==
The four distinct temperatures Of DTA or DSC are; glass transition, Tg the onset of crystallization, Tc Peak of crystallization, Tp and melting point Tm. [M. Dongol, M. Abou Zied, G.A. Gamal, A. El-Denglawey, Appl. Surf. Sci. 161(2000) 365-374., M. Dongol, M. Abou Zied, G.A. Gamal, A. El-Denglawey, Physica B 353 (2004) 169-175., J. A. Savage, J. Non-Cryst. Solids 11 (1972) 121-130].
Taking into account that the mentioned constants are rate processes so, the values may be affected by small differences [J. A. Savage, J. Non-Cryst. Solids 11 (1972) 121-130]. There are two stages of crystallizations; single and double stage [M. Messier, R. Roy, Mater. Res. Bull. 6 (1971) 535-536]. For single stage crystallization; alloys probably have many phases but they crystallize at identified temperatures while double stage crystallization; alloys consist of many phases, and the crystallization may occurs at more than one temperature. Tg, Tc, TP and Tm were used to generate the parameters of thermal stability. These parameters are the nucleation process retarding, ΔTcg, the reduced glass transition temperature, Trg, Hubry's criteria, Hc or glass forming ability, GFA and the resistance to devitrification after the formation of the glass, S. Trg is considered as a special case of Hc The constants ΔTcg, Trg, Hc and S can be calculated
from [A. Hruby Evaluation of glass-forming tendency by means of DTA.
Czechoslovak Journal of Physics B22 (1972) 1187–1188]:
[[[[[ please see equation No. 2 -attached]]]]]
It is noticed that the common term of ΔTcg, Trg, Hc and S is Tg and for Hc and S is ΔTcg. The higher values of these parameters mean the higher thermal stability of these glasses.
I wish this is useful and help you.
Yours
A. El-Denglawey
i
Is you thin film deposited on something or stand alone - for stand alone see previous methods.
For deposited best to look for electrical properties that varies with temperature.
Dear Prof. A. Eldenglawey
Thank you very much for detailed explanation.
Heat capacity and specific heat, and their variation with temperature can be determined by both methods, DTA and DSC, but generally the preferred method is DSC, which in this case provides greater accuracy. The variation of the heat capacity with temperature different is produced in a crystalline solid characterized by a melting temperature Tt and a non- crystalline solid characterized by the glass transition temperature Tg. The heat capacity can be determined by the dimensional relationships, dividing the flow of heat from the heating rate of the sample: (δQ/τ)/(δT/τ)=δQ/δT=Cp . It can be written with the help of the heat flow, physical quantity which is obtained directly from the DSC curve. Specific heat capacity is calculated using the formula : (1/m).(δQ/τ)/(δT/τ)=Cp, the (δQ/dτ) is the heat flux given by the DSC curve, m is the sample mass and (dT/dτ) = β is the hea ting rate of the sample.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films