Rh & Rg: which is best?

Characterization of TiO2 within the paint and pigment industry is a critical component of paint development. X-ray diffraction and DLS are important techniques as they identify the material and various features like particle size, shape, and size distribution. The physical properties of the final product depend on these features. Thus the webinar focused on highlighting the usage of XRD and DLS techniques within this domain.

Our specialists shared tips that manufacturers can engage to fully optimize the use of their pigments for high-performance products.

For those that could not attend the live event, a recording of the event can be found here.

At the live event we have had some good questions so we thought we would put this little blog together as a type of FAQ as many of you may also have similar questions. 

Can we identify the surface treatment of TiO2 pigments with XRD?

If the surface capping entities are crystalline then they can be observed in X-ray diffraction (XRD) pattern. Moreover capping changes the size, size distribution and shape of particles which can be observed in Small Angle X-ray Scattering (SAXS) experiments which can now be done on a multipurpose Empyrean diffractometer.

Why the peaks in XRD become broader with decrease in particle size?

A diffraction peak originates from volume which is exposed to X-rays. The broadness of a diffraction peak is governed by two properties: size and strain of crystallites within this diffraction volume. When crystal grow to smaller sizes and the effect of defects in producing strained crystals is pronounced which results in producing broad peak in a diffraction pattern. But broadness is only partly due to strain. Size effects originates since distribution of coherently scattering domain (which produces diffraction intensity) increases with smaller sizes. For amorphous material it is almost truly randomly oriented, hence the peak is broadest.

TiO2 is UV light active ……How could we use in paints and it may damage the paints?

The UV active TiO2 produces radicals which break down the adjoining chemicals especially polymers. This leads to weathering of paint.

For agglomeration tendencies of pigments in actual paint products, how can we use DLS and XRD to assess this?

One can study agglomeration by taking successive SAXS scans which will show change in shape, size and size distribution of particles within the sample.

How can we distinguish nanoparticles and amorphous using SAXS

SAXS is sensitive to “particle” size, shape and size distribution only, it is not sensitive to crystalline nature of material. XRD on other hand is sensitive to crystalline nature, hence one must perform XRD scan of sample to distinguish between crystalline nanoparticles and amorphous particles.

How about the hematite based pigment. what is the advantage and disadvantage comparing with TiO2?

Hematite pigment is a non-white colored pigment that can be identified and quantified using XRD. With Cu K-alpha radiation, it produces fluorescence. This makes an higher background within an XRD scan and thus make it difficult for phase quantification. Usage of multi-core optics in combination with 1Der detector solves the problem of fluorescence and hence makes it possible to identify and quantify hematite in extremely low quantities.

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