Using XRD to Investigate Mesoporous MCM-41 Material

Mesoporous materials are a class of materials with pore sizes ranging from 2 to 50 nm. These are formed by a matrix typically created with amorphous silica, alumina, or transition metal oxides. These types of materials have found application as catalysts or catalyst supports, but the most widely used material is mesoporous carbon.

Mesoporous carbon has found wide application in energy storage devices, and, contrasting zeolites, the pores are larger in mesoporous carbon and both the pore size and their distribution can be adjusted easily.

ARL EQUINOX 3000 X-ray diffractometer.

Figure 1. ARL EQUINOX 3000 X-ray diffractometer.

MCM-41 and MCM-48 are two of the most widely used mesoporous materials made from silica. The pores range from 2 to 6.5 nm and MCM-41 has found use in catalyst applications for chemical reactions, and as an adsorbent for the treatment of wastewater. Recent studies have hypothesized that these materials could even be used in drug delivery as a system support material.

Using XRD to Investigate Mesoporous MCM-41 Material

Utilizing X-ray diffraction (XRD) makes the direct measurement of pore size and structural arrangement possible. It is necessary to measure at very low (<1° 2θ) diffraction angles, which is possible with the Thermo Scientific™ ARL™ EQUINOX 3000. This instrument is able to measure the low angles needed for this type of investigation, and does not require any preparations; low-angle measurements can be carried out easily in the standard setup (Figure 1).

About the ARL EQUINOX 3000

The ARL EQUINOX 3000 is an entry-level full-scale laboratory instrument. It uses a 3 kW generator, which powers a long, fine focus, X-ray tube that is connected to both focal or parabolic mirror optics, or a Ge (111) monochromator, which offers Kα radiation with the highest flux or brilliant Kα1 radiation, which is perfect for the highest resolution.

The ARL EQUINOX 3000 is highly flexible and offers a wide range of accessories to facilitate use in quality control and quality assurance and in-situ studies. The unique curved position sensitive detector (CPS), used to measure all diffraction peaks in real-time and simultaneously, has been specially designed for the asymmetric setup seen in the ARL EQUINOX instrument series. Because of this, it is easy to obtain both reflection and transmission measurements without needing to realign the instrument.

Case Study

X-ray diffraction measurements were run with an ARL EQUINOX 3000 XRD, that has been equipped with a Cu tube and a Ge (111) monochromator. Using a powdered sample, a 10-minute measurement in reflection was carried out with an incidence angle of 0.5°, and data was evaluated using MDI JADE 2010 and ICDD pdf4+ database.

Diffraction pattern on MCM-41 from 0.74° - 10° 2? (reference positions for MCM-41 as green tick marks).

Figure 2. Diffraction pattern on MCM-41 from 0.74° - 10° 2θ (reference positions for MCM-41 as green tick marks).

Results

In using a low incidence angle of 0.5°, it was deemed possible to measure intensities beginning at 0.74 ° 2θ (Figure 2). The resulting measurement clearly illustrates a diffraction pattern that is in direct accordance with MCM-41’s structure (Figure 2, green tick marks). An excellent signal to noise ratio was also clearly evident. It was also concluded that even shorter measurement times would still produce valuable data.

Summary

By using the ARL EQUINOX 3000 XRD in conjunction with MDI JADE 2010 software suite and the ICDD pdf4+ database, users can enjoy a suitable tool to analyze mesoporous materials, even at very low diffraction angles of 0.74° 2θ. Users are able to clearly identify the structure, such as that seen with MCM-41, even with short measurement times.

These types of analyses do not require a specific setup or any special preparations, making the ARL EQUINOX 3000 a tool particularly suitable for quality control and quality assurance that is not only accessible, flexible, and user-friendly, but will also satisfy the advanced analytical demands seen in academic institutions.

Acknowledgments

Produced from materials originally authored by Dr Simon Welzmiller and Ju Weicai from Thermo Fisher Scientific.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers.

For more information on this source, please visit Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers.

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