Computed tomography (CT) is a non-destructive technique for visualizing internal features within solid objects. It enables the examination of the structure of an object and provides information such as size, shape and location of any internal feature or defect.
Economists say that we are going through a ‘third industrial revolution’, which is fuelled by additive manufacturing. This can be defined as the process of joining materials from 3D computer models. Methods such as computed tomography will be important for either analyzing the results of such a printing process or use the data from a CT scan to print a new part, for example as a replacement. Since the introduction of the Empyrean and the PIXcel3D detector, Malvern Panalytical has been the first and only company to market a diffractometer capable of performing computed tomography analysis too. With the addition of the new GaliPIX3D detector, which makes optimal use of hard radiation, Malvern Panalytical makes a further step into CT by extending the range of samples that can be measured.
Computed tomography experiments were performed on a Malvern Panalytical Empyrean diffractometer equipped with an X-ray source with a molybdenum anode, a CT stage and the new GaliPIX3D detector. This detector has an efficiency of ~100% for Mo and Ag radiation, thanks to the CdTe sensor used to detect the X-ray photons. For this data sheet we have studied two samples of highly porous concrete, with different pore sizes. The sample size is 8 x 13 x 50 mm3.
Figure 1. Example of a sample (battery cell) mounted on the CT stage in front of the GaliPIX3D detector
Porous concrete is a special type of concrete with high porosity. It is used in applications that allow water from precipitation and other sources to pass directly through, reducing runoff and allowing groundwater recharge. It is traditionally used in parking areas, residential streets, pedestrian walkways and greenhouses. The amount of porosity as well as the type, size, connectivity and three-dimensional distribution of pores are some the most important features of cement and ceramic materials. They determine the materials’ properties (e.g. surface area, permeability, heat transport or strength), their field of application and also their quality and have to be observed and adjusted throughout the development and manufacturing process. In this example, two samples were measured using Mo radiation; one with large pores and one with small pores. By using the software VG Studio MAX 2.2.6 with the Porosity/ Inclusion module it is possible to obtain a value for the porosity of the concrete slab, as well as the pore size distribution, shown in Figure 3. The porosity for both samples is reported in Table 1.
Table 1. Porosity values for the two types of porous concrete
Figure 2. Porous concrete. Top row with small pores, bottom row with large pores. a) picture of the concrete slab, b) 3D view using Isosurface render, c) cross section of the sample showing in more detail the pores (blue) and the concrete framework related to the selected area where the pores are determined in.
Figure 3. Pore size distribution plots. The sample with large pores shows a larger distribution of sizes compared to the one with small pores.
As an example of CT data, we show the comparison between two aereate concrete samples, obtaining the porosity for each sample. This demonstrates the possibilities of performing CT on a multipurpose diffractometer. The new GaliPIX3D detector is the ideal partner for CT with different X-ray radiation, from Cu to Ag due to its excellent efficiency with hard radiation.