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Topic: Differential Scanning Calorimetry  (Read 2841 times)

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Offline rjb

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Differential Scanning Calorimetry
« on: March 31, 2011, 06:33:24 AM »
Hello,

I've been reading up on Hyper-DSC which is basically a more rapid and sensitive method of standard DSC thermal analysis. The process involves using a huge ramp rate ~300-400 C/min to heat the sample and this apparently leads to much improved sensitivity allowing it to be used in the analysis of a single man-made fibre, which within a forensic context is a huge improvement over standard DSC instrumentation... What I don't understand is the fact that "a fundamental property of the DSC measurement
is that the sensitivity is directly related to the temperature ramp rate" which seems counter intuitive to me and not one of my colleagues (physical chemists amongst them) can explain why this is the case...

Any thoughts...

Kind Regards

R

Offline enahs

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Re: Differential Scanning Calorimetry
« Reply #1 on: April 01, 2011, 02:36:48 PM »
Simplified down:

heat / time = q/t = heat flow
 
temperature increase / time =  :delta: t / t = heating rate


heat flow / heating rate = (q/t) / ( :delta: t / t) = q /  :delta: t

Well, q /  :delta: t = Cp = heat capacity of whatever you are looking at.

Well, the heat capacity is a constant for whatever you are looking at (ok, it is not, it changes with temperature and pressure, but whatever, like I said, simplification).

Well, if your  :delta: t is big, then you q has to be "big" as well in order to make it equal Cp. If you can make your  :delta: t smaller, you need less heat to satisfy the equation; ultimately meaning you can use a smaller sample.

Offline Frank_SO4

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Re: Differential Scanning Calorimetry
« Reply #2 on: January 28, 2021, 02:15:03 PM »
Well said, but I would like to add that these huge ramps will also translate into significant temperature ranges at the beginning of you analysis, and whenever the heating/cooling ramp changes in slope, that won't be in steady state, which may make the analysis from much more complex to impossible, depending on the specifics. So, keep an eye for that ;)

Offline wildfyr

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Re: Differential Scanning Calorimetry
« Reply #3 on: January 31, 2021, 09:41:53 AM »
Call or email the company. A rep looking to make a sale will be happy to explain, or bring in a technical person who can.

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