I was trying to find activation energy of thermal decomposition using Horowitz and Metzger model. in this model Ea is calculated from slope of ln(ln(1/1-alpha) v/s T-Tmax .
alpha = (W0-Wf)/(Wt-Wf)
where, w0 is the initial weight of the sample, ‘wf’ is the final weight of the sample and ‘Wt'is the weight of the sample at temperature t.
According to this equation 'alpha' is always greater than 1. therefore (1-alpha) will be negative. (Please find the excel sheet for calculation).
Since natural logarithm is not defined for negative values, how can we plot ln(ln(1/1-alpha) v/s T-Tmax . ?
I have gone through many publications that reports this method. But I have the above question uncleared and its not working with my data. Is this model a wrong one?
Can anyone please help me out to solve this model?
you have done wrong calculation for alpha.you have to take w0 as initial degradation value ,wt as weight loss at particular temperature ,wf - final weight loss .ie., wo-wt/ wo-wf.you will get positive 1/1-alpha value .for that calculate ln.
Thenmozhi Karthikeyan Thank you ma'am for your valuable input.
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