If you can weigh precisely a piece of your composite, then you can measure the volume by placing it in a pycnometre, a kind of volumetric flask used to determine densities of liquids with high prcision, it has a perfectly defined volume

you fill the pycnometzer with puer water you the have the mass and the volume of water in the pycnometer, now you put your sample in the pycnometre and fill it with water

its mass is mass water + mass sample , as you know the mass of your sample, you can deduce the mass of water and by difference with the first experiment the volume of your sample.

You can use water or another solvent

Hello Jon, Can you deposit your nanocomposite on any substrate. If it is possible to deposit on any substrate then (1) Weigh the substrate, (2) deposit your nanocomposite on it using a mask of specific area and then again reweigh, (3) subtract these two masses then you will get the mass of your film. (4) measure the thickness of your film by any thickness measurement method for example profilometer. This way you can calculate density, without cutting the films.

You can see some different methods also like X-ray and

see this paper also

http://www.ncbi.nlm.nih.gov/pubmed/17411199

Thank you for your response! They look like good methods! Thank you very much for your help! :)

We had the shop make up a square piece of steel that is 10 cm x 10 cm. It has a little handle on one side of it. We hold that against the coating (which is on a polymer substrate, and that is placed on a cutting board). Then we cut out the film with a razor blade. Then we weigh the film plus coating. Then dissolve off the coating, then weigh the film. This gives the coating weight. At 75 microns, you would be weighing a hundred mgs or more of weight this way, and that is easy to resolve on a scale. Then, by knowing the thickness, and the 100 cm^2 area, you get the density.

A problem you may be having is water weight. This can be several percent of your film weight, and can create uncertainty in the measurement. You may need to dry the film out in a vac oven first. You can do that, then put the sample on the scale, and watch the weight increase as it picks up water from the air. I've done this measurement in a nitrogen dry box, or even a glove bag, to eliminate the water problem.

If you can weigh precisely a piece of your composite, then you can measure the volume by placing it in a pycnometre, a kind of volumetric flask used to determine densities of liquids with high prcision, it has a perfectly defined volume

you fill the pycnometzer with puer water you the have the mass and the volume of water in the pycnometer, now you put your sample in the pycnometre and fill it with water

its mass is mass water + mass sample , as you know the mass of your sample, you can deduce the mass of water and by difference with the first experiment the volume of your sample.

You can use water or another solvent

The method proposed by Jean Pinson (with pycnometer) is the most accurate among the other proposed so far, and it is relatively easy (our students are using this during standard laboratory exercises). The most accurate method is with use of calibrated density gradient columns, in which piece of polymer is submerged - I guess however that you have no access to such columns.

Thank to all of you for your help in this subject! :) very nice from your part.

Regarding to the exposed methods i found them very interesting. i have a small question regarding to the X-Ray method, and is that one of my nanofillers is the nanoclays (montmorionite) .

The nanoclays are "sheets" of 300x700x3 nm and they are "hydrated sodium calcium aluminium magnesium silicate hydroxide " (extracted from wikipedia).

The X-Ray diffraction is used to see the dispersion of these sheet, i mean, the sheet have the size i have already said (300x700x3) but they are strongly attached each other and thank to X-Ray diffraction we can know the basal space between sheets.

I´m just saying this because really I dont know if this fact can have any interference in this method.

A technique utilizing the reflection of x‐rays to determine material density at flat surfaces is described (in the paper which i linked in the end). The effects of sample misalignment limit the accuracy of x‐ray reflectivity as typically practiced. These effects may be properly accounted for by measuring the critical angle for reflection at many different x‐ray wavelengths simultaneously from which an extrapolation of the position of the critical angle at infinite wavelength may be made. This extrapolation has the effect of correcting for sample misalignment.

1), http://dx.doi.org/10.1063/1.115007 (for thin films single‐crystal silicon surfaces)

2), Rev Sci Instrum. 2007 Mar;78(3):034104 (for small organic molecules).

Hi,

For measuring the density of the thin film with precision, you may go for XRR(x-ray reflectivity studies) or ellipsometry. But for both of these things you need to take care of the roughness of the film and the film-substrate interface. For XRR the roughness should be in the order of nm and for ellipsometry it can be in the order of Angstorms.But for ellipsometry your material should be transparent to visible range of light.

If you have a multilayer kind of structure you can straight away go for XRR. But you need to be extremely careful about the roughness at the surface and at each interface, otherwise the data will not be good.

I have measured hyaluronic acid films with a density tool kit that can be incorporated to the balance. It is based on the Arquimedes theory so you only need to know the weight of your samples and then measure it in immersion in a liquid of known density that does not interfere or degrade your sample. In my case, I used n-octane. With these data and applying a balance of forces you can obtain the density of your polymer.

Hi,

You can also try this: after depositing the film on a substrate, do an RBS measurement together with an XRR for thickness extraction. by comparing the two result you can get the density from the RBS simulation.

Hello, I have been using the ARchimedes method using a density kit attached to the balance to measure the density of circular chitosan based films. I used ethanol or water as non-solvent. I have observed more reproducible results by directly measuring the weight of dry films and calculating the accurating volume after measuring the thicknes with a digital micrometer. If you doubt that water or any other solvent can have interference with your material, I'd wonder if you could try to swell your polymer films in them and measure the density again and substract values.

Addition of nanoplatelets such as the montmorillonite clays I think should be reflected in the bulk density of the film you measure.

you have two options : normal one follow the ASTM or ISO standards employing densimeters.

Rule of mixtures, if you know the % of each component you can apply the formula and it match really well.

after you can compare both results to check the goodness of the aproximation for this case.

regards

I have a similar problem measuring 600 nm thick porous films. You, at least, have a more accurate mass measurement. I find a lot of error in the film coverage area but have reduced it using a digital camera. I take a picture with a ruler and the sample, then use ImageJ software to calibrate the distance and perfectly measure the surface area of the sample.

You can use X-Ray reflectometry (XRR). XRR, is a surface-sensitive analytical technique used in chemistry, physics, and materials science to characterize surfaces, thin films and multilayers. It is related to the complementary techniques of neutron reflectometry and ellipsometry.

"The basic idea behind the technique is to reflect a beam of x-rays from a flat surface and to then measure the intensity of x-rays reflected in the specular direction (reflected angle equal to incident angle). If the interface is not perfectly sharp and smooth then the reflected intensity will deviate from that predicted by the law of Fresnel reflectivity. The deviations can then be analyzed to obtain the density profile of the interface normal to the surface."

You can go for X-Ray Reflectivity measurements for the density measurements. It gives good accuracy in density measurements.

I would also recommend an X-ray reflectivity scan. Just be careful:

1) align accurately the sample. If you use a very thin beam (20 um wide or so) the alignment can be improved and you avoid systematic effects.

2) in order to fit the reflectivity scan, have you in hand a reliable table of the optical constants of your material? If you have not, you can compare the cutoff angle with the one of a bulky material sample. The cutoff angles are proportional to the square root of the density values, hence via a simple proportion the density can be inferrered.

3) beware of the surface roughness. It can completerly destroy the X-ray reflectivity.

Hope this helps. Bye!

I suggest X ray reflectivity will serve best for the thin fims

I have the same opinion with some colleagues who have posted above: the best method is X-ray reflectivity, as alternative can be Archimedes method if you have a kit of density attached to a balance with high sensibility.

Hi. The way I usually proceed is to measure the thickness by AFM (only works if you manage to get a sharp step between the film and substrate) or XRR and then do RBS. You can simulate the RBS results using a program called RUMP and you will be able to get a surface atomic density fort your film (at/cm2) which if you divide by the thickness gives you the density for that film.

I hope it helps.

Hi! I would like to strongly thank everybody for your support in this difficult task. I have received a lot of info and this is going to be really useful to make a decision. Thank you very much for your help!

Dear Jon! What if you look at the "quartz balance" method and try to deposit your films to the same size quartz resonators? Maybe you will need thinner films for the method to work...

Hi Jon. I believe all those nice tools as AFM, RBS and XRR are not applicable to your 75 microns thick films. Quartz balance - this is a tool for thin films too, I do not think you can adopt it either.

If you can get a good contrast between the surface of the film and of the substrate - use a profilometer to get the thickness. Otherwise, you can try a well calibrated microscope. I think you should look at some absorption techniques in order to figure out the amount of material. The refractive index is also a function of the density, although you might be susceptible to gradients.

I am curious if you find a useful technique...

Hi. I don't really know how it will work for PLD but I use sputtering and what I do is I make a mark in the substrate before the deposition with a CD marker and then deposit on top. Then after the deposition, if you drop the film in acetone, given that the film is not really stuck to the substrate on that region it will lift where you made the mark leaving a very nicely marked step that you can easily measure using AFM. What you have to be careful is that sometimes in the zone of the lift you have a elevation on the edge of the film, so you should make a scan a little bit wider to make sure you are not overestimating the thickness.

I believe the only problem with this is if you use high temperatures for the deposition, because it can lead to contamination of the films. But if you do a calibration of your deposition system using "dummy" samples just for thickness check it shouldn't be a problem.

Good luck =)

XRR is indeed a very good technique to measure density as well as thickness of films, however the thickness of the film must not be so high... 75 micron is too thick a film to be analysed by this method for sure... Ellipsometry is also limited upto 1-2 micron thick films that too one with good transparency. I am sure these two methods will definitely not work in ur case... you may try the rest suggestve techniques though. good luck

Simple weight method will give an approximate idea of the density of your film.

You must know the thickness of your film accurately.

K. Sreenivas

Dear Jon

Unfortunately I faced your question now BUT for any one else that has your problem, I put  my answer here:

Gas (Nitrogen or Helium) Pycnometer is suitable for measuring the density of the films and composites.

Wish you success

Perhaps you can use indirect method of measurement. You can stretch the film over small circular ring till it reaches some chosen level of tension and then excite the membrane to first mode. Frequency of vibration can then be measured using a high speed camera or any other device capable of recording rapid oscillations. The frequency is dependent on areal density of membrane and tension per unit length of the stretched membrane and you know one of it thus enabling you to calculate the other.

Now I don't know if you can make films of dimensions which will enable you to stretch it over some circular ring or not, but if you can this seems simpler than many other methods written above which involve very specialised equipment for measurement. Again I don't know if this will be useful to you or not.