AZoM speaks to Joseph Ferrara, VP X-Ray Research Laboratory at Rigaku, about their new nano3DX x-ray microscope to find out what it is, what it does and who it will be of use to.
Rigaku have a long history of involvement in x-ray technology. Can you give us a quick run down on this involvement?
Rigaku has been producing X-ray instrumentation since its inception in 1951. Rigaku introduced its first rotating anode in 1954 and has been continuously improving the technology since. From diffusion pumps to TMPs, oil seals to ferrofluidic seals, and micro focus rotating anodes that can change wavelengths at the push of a button. Rigaku has developed numerous support technologies including optics, detectors and software. The X-ray Research Laboratory also develops novel methods for data interpretation.
At the ACMM23/ICONN2014 Rigaku launched a new product, the nano3DX, which is an x-ray microscope. Can you explain what an x-ray microscope is?
An x-ray microscope is a tool for looking at the internal structure of materials that are too opaque or too thick to view with a visible microscope. As the name suggests the light in an x-ray microscope comes from an x-ray source rather than a visible light source. With x-rays we can probe samples and generate a complete 3D view of the object without damaging the specimen. It is completely analogous to the CT you get in the hospital but the 3D pixel (voxel) resolution can be as low as 0.27 μm.
What is the largest sample that the nano3DX can examine and what technology allows you to do this?
The largest sample we can measure in one scan is 14.4 mm x 10 mm at a 4 μm pixel size. The image is 3300 pixels by 2500 pixels. The nano3DX can measure relatively large samples at high resolutions thanks to the high power rotating anode x-ray source and high-resolution CCD imaging system. The rotating anode allows very fast rates of data acquisition, as well as providing the ability to switch anode materials to optimise data acquisition.
What is the benefit of being able to switch anode materials?
The benefit is that the user can tailor the wavelength to maximize contrast or enhance transmission. For example, a thin biological or organic film would be best observed with chromium radiation. Small organic samples such as an API in a pharmaceutical tablet would show superb results with copper radiation . Carbon fibre reinforced polymers also benefit from copper radiation. Molybdenum radiation is useful for bone, silicates and aluminium composites.
What resolution and contrast can you achieve with the Nano3DX and how does this compare to other similar instruments?
This is a complex question. At its best resolution the Nano3DX operates with a voxel size of 0.27µm and a special resolution in the 0.6µm - 0.8µm range. This is as good as any other equipment in this class of instrument. Most instruments can only achieve these resolutions on a very small sample. The nano3DX however uses microscope optics and can achieve this on larger samples and with a much larger field of view.
In regards to contrast, the nano3DX has various anode options and a 1.2KW source. This means that x-ray absorption on traditionally difficult materials is far superior. For low density samples at high resolution the nano3DX absorption contrast capability has no equal. It also achieves these scans with impressive speed.
Are there limitations as to what materials can be investigated?
Yes, of course. The maximum energy of the anode is 60 kV so samples of tens of millimetres or that are very dense are not possible.
The system is suited to a wide range of materials and samples including those with low absorption contrast like carbon fibre reinforced plastic composites.
Most of us have heard of CT as a medical analytical technique, is the nano3DX in any way similar to those medical systems?
As I mentioned before the basic concept is the same, except we rotate the sample in the x-ray beam. In the CT data acquisition, a series of images at different rotation angles are collected. A reconstruction algorithm is used to create a tomogram from these images. We can then take this tomogram and process it with various software packages to gain significant insight into the internal structure of the specimen. We used Drishti to create the videos like the carbon fibre reinforced polymer shown above.
What sort of information can a user get from an x-ray microscope?
We can see changes in the material composition and density. For example, the coating on tablet, defects in materials, or voids or cracks in carbon fibre reinforced polymers. We can analyse the distribution of particle sizes or the orientation of fibres and provide quantitative information to the user. Porosity and pore connectivity is also another hot topic.
The nano3DX generates a 3-dimensional computer model. Can the user easily manipulate these to view structures from different angles and view deep within structures?
Yes, we provide software tools for doing the basic manipulations. Ajay Limaye at ANU has written a package called Drishti which is an excellent tool for creating breathtaking animations of the data from the CT experiment. This is freeware and extremely powerful.
What are some applications of x-ray microscopy and can you briefly outline how this technique will benefit them?
One application is the study of film coating thickness on pharmaceutical product packaging. The film coating on a tablet determines the speed of uptake so the physical properties of the coating can be correlated to the bioavailability. Furthermore, the same particle can be tested for bioavailability after the CT experiment, since x-ray microscopy is a non-destructive technique.
Mice provide models for many diseases. One such disease is osteoporosis. The nano3DX has been used to perform the first whole bone analysis of a mouse fibula in a study of this disease.
Carbon fibre reinforced polymers are becoming mainstream materials for many industrial products. Just look at the Boeing 787. As part of the validation process it is important understand the internal structure to ensure their performance at 10,000 metres.
Is it likely that you will build larger versions of the nano3DX in the future to cater for larger samples such that it may be used as a more widespread form of NDT?
It is likely as Rigaku sees a lot of growth potential in the market for evaluating materials through tomography.
About Joseph D. Ferrara Ph.D.
Joseph Ferrara is presently Chief Science Officer of Rigaku Americas Corp., Vice President, X-ray Research Laboratory, Rigaku Corp, and a member of the board of directors for Rigaku Innovative Technologies. Dr. Ferrara directs or participates in the development of X-ray systems and software for direct space and reciprocal space imaging.
Dr. Ferrara received his B.S. in Chemistry from Case Institute of Technology in 1983 and his Ph.D. in Chemistry from Case Western Reserve University in 1988 under the tutelage of Wiley J. Youngs. Dr. Ferrara joined Molecular Structure Corporation in 1988, which became part of the Rigaku Group in 1996 and became Rigaku Americas Corporation in 2005.
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