Dear Ng Kei,

This is quite logical that you cannot see any big change in your XRD pattern. The peak intensity would be decreased only if your measurement procedure is exactely the same and sample area for example can have an effect. But indeed it´s not so important the direct influence of the amount of crystalline phase vs. amorphous on the peak intensity, because this is not the way to determine the amorphous content. Indeed, you only need to measure XRD data with an exactely weighed amount of (known) perfectely cristalline reference (Al2O3 corindon or Si are offen used but many other works, the importance is to have peaks where your sample does not, better for data treament). You can use 20 wt% of reference and 80 of your total sample, but this is to adjust in function of the way your sample diffracts (symmetry,...). Then you measure your XRD data and carry out a Rietveld refinement (Fullprof, GSAS, Jana, MAUD are current programs, Topas if you are rich ;-)), from which you can extract precise amount of each crystalline phases. The refinement will probably give you higher amount of your reference; that´s normal as you have an amorphous phase and by deduction you can easily calculate the weight fraction of amorphous (considering this is only the polymer) phase. The assumption is that the mineral phase is purely crystalline, what can not be the case perfectly if some part of your ceramic can be also amorphous... The total amount of amorphous will be found. TGA can be complementary, at least once.

Good luck!

Gilles

Actually, I did that test. However, for the XRD results, the peak are the same. when I match them. I heard Rietveld method able to determine it, however, the theory is so hard to understand.

I think you should go for some analysis like DTA or TGA to determine the amount of polymer.

Dear Ng Kei,

This is quite logical that you cannot see any big change in your XRD pattern. The peak intensity would be decreased only if your measurement procedure is exactely the same and sample area for example can have an effect. But indeed it´s not so important the direct influence of the amount of crystalline phase vs. amorphous on the peak intensity, because this is not the way to determine the amorphous content. Indeed, you only need to measure XRD data with an exactely weighed amount of (known) perfectely cristalline reference (Al2O3 corindon or Si are offen used but many other works, the importance is to have peaks where your sample does not, better for data treament). You can use 20 wt% of reference and 80 of your total sample, but this is to adjust in function of the way your sample diffracts (symmetry,...). Then you measure your XRD data and carry out a Rietveld refinement (Fullprof, GSAS, Jana, MAUD are current programs, Topas if you are rich ;-)), from which you can extract precise amount of each crystalline phases. The refinement will probably give you higher amount of your reference; that´s normal as you have an amorphous phase and by deduction you can easily calculate the weight fraction of amorphous (considering this is only the polymer) phase. The assumption is that the mineral phase is purely crystalline, what can not be the case perfectly if some part of your ceramic can be also amorphous... The total amount of amorphous will be found. TGA can be complementary, at least once.

Good luck!

Gilles

As Asif Hussain said, to get the amount of amorphous polymer, DSC (or DTA) could give more information than XRD experiment on polymers.

TGA give informations about the amount of Polymer and ceramic, DSC give informations about the amount of amorphous phase and about crystalline phase of the polymer.

Using DSC, you can determine melting enthalpy of crystalline phase.

You need to have the theoretical value of total melting enthalpy to compare your experimental data. Knowing the amount of crystalline phase, you

can determine the amount of amorphous phase by complementary.

Be careful :

- Collected datas by DSC consider the amount of ceramic and imply a shift of the curve. (DSC equipements have possibility to normalize heat flow to the total mass of sample). Make calculation considering the amount of polymer in the material

- If polymer has a cold crystallisation.

Dear all, as Ng´s question concerned XRD and how determine the amorphous content in a material, I only focused on that but of course, many other techniques could be used; the only thing is that perhaps he doesn´t have access to TGA or DSC. I nevertheless agree that XRD is perhaps not the easiest way to determine the amount o polymer in your composite and if we want to be really pragmatic, a simple heat treatment at high temperature in air (if the ceramic is known in composition and doesn´t vary during treatment) with weighing before and after would be sufficient.

Best

Hi everybody, I am glad to have the response from you all. However, TGA machine in my uni is under repair right now. Actually i did the TGA testing to find out the mass difference when I increase the concentration of PEG with HAP powder. but I am unable to do DSC since my tg for PEG is -60 deg C. The machine in my uni unable to support it since it starts with -30 deg C only and the person in charge of the machine is not helpful.

I supposed to expect lower XRD peak with increasing amount of PEG and smaller powder crystalline size. That's the reason why I stick with XRD, no matter how many times I redo with the powder, the peak is still the same.

How are you determining those peak's areas? Have you considered the existence of a underlying amorphous contribution to the diffraction pattern, this one containing the information that you are looking for?

Regards.

Hi fellow researchers, I snap shot my XRD results for the view of all. The peak looks the same. It will have some difference especially when i compare the intensity of ONE peak. My SV asked me to draw a line underneath each XRD plot. But I still unable to understand that.

I have also determined the crystalline size for the powder mixture. Surprisingly, when content of amorphous increases, the crystalline size decreases. Still finding the reasoning.

This is the XRD plot that I am talking about, It has three plots together. But it doesn't have a very significant shift or difference

Dear Mr. Hoa, your supervisor was perhaps referring to drawing a baseline for better comparison of the spectra and to set a low limit against which to compare intensities.

Drawing baselines involves establishing a metric to find where the background signal of the equipment is and following that signal lengthwise. Some software packages do that process for you automatically, while others enables the user to perform that correction.

However, in your case, I am not sure wether the problem is baseline related. Perhaps the suggestions of planning calibration experiments with samples of known features may be more helpful.

Reagards.

If the absorbance of the polymer is low (much lower than the ceramic) it is almost impossible to see any difference because the radiated quantity of ceramic will hardly vary with the dilution. On other words, you are only measuring a fraction of the ceramics that you have in your sample, and when you dilute it you are measuring a larger fraction but nearly the same amount.

A possible way to enhance the difference would be to measure just a thin film of your sample (no more than 10-20 microns, perhaps 30 depending on the average absorbance of your sample). By this way the measure will be much more sensitive to ceramic/polymer ratio, because you will be measuring the whole amount of ceramic and thus the measure will be sensitive to dilution.

Perhaps, it's very hard to quantify it since the amount of polymer that I am using is low. and my sample is in a powder form. Now my SV asked me to find XRD pattern of PEG to make comparison. There are papers that reported higher PEG will reduce the intensity from 20-80wt.%.

Hi everybody,

Completely in agreement with Carlos, you have to be careful with the difference of X-ray absorbance of the polymer vs. ceramic, another problem to take into account but if the amount of polymer is low, perhaps this is not really an issue. Anyway, the solution of Carlos is the best but if you are in powder form, more difficult. I suggest to stick a thin layer of well dispersed powder on the sample holder (sieving the powder, for example at 20 o 50 microns, without loosing the composition of course, it means the pore size must be higher than both types of powder size) and vaseline grease, so you make the measurements nearly independant of problems of absorption.

Xrd

Some times small things create a big problem in your life. On the other hand satisfying your supervisor is not an easy job. It seems to be universal that supervisor not allow you to go ahead before you shake yourselves.

Hi fellow researchers. Hahaha. I am shaking my head all the way though. Well, this is just a small characterisation of my powder. And this is not even the main part of my research. I just wonder, how am I going to face the others.

It's logic as the comments up there stated that, the amount of polymer/ceramic is low. By the way, i don't understand why the vaseline grease is needed?

The PEG's XRD peak has a few sharp peaks. but it doesn't coincide with my XRD. Maybe as stated by @Gilles the ratio of polymer to ceramic is low.

Hi Ng,

Sorry for the loss of details. The grease is only to stick the powder in the case you have or want to use very low thickness of layer (be careful with statistic...) and avoid absoprtion problems as stated by Carlos. But, let me understand one thing, Ng, you can index all the peaks of your patterns with the ceramic part of your material or not? Because you are speaking about PEG´s XRD peaks... Sure your polymer is crystalline. It´s not often the case, even if I´ve found this article:

http://users.ox.ac.uk/~dplb0149/publication/pub108.pdf

Gilles

Index, means? match the ceramic with the JCPDS?

index means explain any XRD peak of the pattern using 1 or several phases without leaving one or having extra intense peak, so indeed "match the ceramic with the JCPDS" cards is the same thing.

Cheers

Gilles

Hi Gilles, Maybe I am not a full material student. So sometimes It's hard for me to understand the term. is it whether i can obtain the hkl, and the d spacing information?

The reason why at the beginning i suspect that PEG is amorphous, merely unable to detect. Now the PEG is found maybe is crystalline, then the problem is still there, un-detectable. But I will try with the grease thing if they allow

Rather than searching for a solution relying on acquired data, I feel the most appropriate approach is to prepare a series of reference samples with known compositions and use these to create a calibration curve to determine the amorphous content of unknown specimens. This should only take a couple of days work and may be of some use.

One more view i would like to share here. Instead searching for amorphous region in the crystalline phase, why don't you find some way to calculate the crystalline % in the ceramic sample and try to find how much the crystallinity got reduced after the polymer addition.

http://journals.iucr.org/j/issues/2014/03/00/he5635/he5635.pdf maybe this paper can help you. If you're interested in how to do it I can explain it better...

Dear Ng Kei,

XRD technique is not applicable for amorphous material. This is a limitation of XRD technique. This is the reason why peaks are not changing on increase in polymeric binders.

Dear, everybody. Thanks for the great and amazing suggestions. And there are lots more for me to learn.