Volume 40(2) - Summer 2024

A 3D real-space structural model for fuel cell catalysis systems, consisting of Pt and Gd-doped CeO₂ nanoparticles, was constructed to match simulated small angle X-ray scattering (SAXS) intensity and observed SAXS intensity using the reverse Monte–Carlo (RMC) method. The observed SAXS patterns were well reproduced by those of the simulations. The SAXS–RMC simulation results indicated that the number of nanometer-sized Pt particles is much smaller than the introduced amount. This suggests that most Pt particles are not uniformly distributed throughout the catalysts. Additionally, the coordination number of Pt particles, calculated from the structural model, tends to decrease as the amount of Pt loaded increases, which is consistent with the transmission electron microscopy (TEM) images. 3D pore size distributions using the obtained structure models were compared with the Barrett–Joyner–Halenda (BJH) analysis results for nitrogen gas adsorption data, and the lower quartiles and medians of the pore diameters were reasonably consistent. The presented SAXS-RMC modeling can evaluate both local arrangement of the constituent primary particles and aggregated mesoscale structure.

It is known that pharmaceutical raw materials can undergo phase transitions to other crystal polymorphs due to temperature and humidity, and that differences in crystal structures affect the bioavailability and safety of pharmaceutical products. Acetaminophen, which has been used worldwide for more than 100 years for a variety of treatments, has been reported to have multiple stable and metastable crystal polymorphs however, the details of its crystallization control, evaluation methods, thermal behavior, and some crystal structure information are not known very well. In this article, a combination of several different evaluation methods using Rigaku technologies was applied to the analysis of crystal structures and physical properties of acetaminophen crystal polymorphs. As a result, the thermal behavior and crystal structure of acetaminophen were clarified by the combination of these analyses, and the details are described herein.

In the seventh lecture of the Powder X-ray Diffraction Basic Course, we will describe lattice constants. Lattice constants are a set of fundamental parameters used in various analyses by the X-ray diffraction method. There are three methods for lattice constant calculation; 1. a simple method using the Miller indices of one observed diffraction peak and the d value converted from the peak position using Bragg’s law; 2. the least-squares method using multiple diffraction peaks and the Miller indices of each peak; 3. the WPPF (Whole Powder Pattern Fitting) method using a wide range of diffraction patterns. Analysis methods 2 and 3 allow angle calibration using an angle standard reference material. There are external and internal standard methods, each with their own advantages and disadvantages. The WPPF method also allows angle calibration using a peak shift model function without measurement of angle standards. In-situ measurements are also possible using a temperature control attachment, where the temperature of the sample can be changed and the diffraction pattern is acquired in situ. High-temperature measurements of LSMO (lanthanum strontium manganese oxide), a solid oxide fuel cell, revealed that the behavior of the lattice expansion was different for the a- and c-axes.

In wavelength dispersive X-ray fluorescence (WDXRF) analysis, liquid and some powder samples are usually measured under helium atmosphere while other samples are measured under vacuum atmosphere. As of 2024, the global shortage of helium gas has resulted in high prices and long delivery times, making analysis using helium gas difficult. Originally, the benchtop WDXRF analyzer Supermini200 measured samples while the sample chamber and optical chamber were either in vacuum or helium atmosphere. Rigaku has developed a new feature for the Supermini200 to measure all forms of samples, including solids, powders, and liquids, without helium gas. This paper describes the details of air/vacuum atmosphere measurement with the Supermini200 and introduces actual analysis examples.

The nano3DX from Rigaku is a laboratory-based X-ray microscope that enables nondestructive observation of three-dimensional structures of a sample by CT reconstruction from X-ray projection images. As an example of biological applications of laboratory-based X-ray microscopy, the X-ray CT observation of kidney microstructure has been performed. By observing mouse kidney sections stained with heavy-element reagents and resin-embedded in sheet form, a three-dimensional rendering of nephrons, the functional units of the kidney, has been obtained successfully at micron-level spatial resolution. Furthermore, a detailed statistical analysis of CT images from five independent nephrons showed that heavy-element-stained proximal and distal tubules can be distinguished by brightness values. Future developments in laboratory-based X-ray microscopy are expected to include applications in medicine and structural biology.

While TG-MS and TG-FTIR are effective for analyzing evolved gases, these techniques involve complex setups. They require the integration of STA with MS or FTIR instruments via transfer lines, which can pose challenges regarding the installation environment and associated costs. Additionally, they may not identify complex gases evolved during the pyrolysis of polymers and biomaterials due to their limited separation capabilities, unlike chromatography. We have proposed the TG-Solid Phase Microextraction (SPME) method to address these limitations. This simplified method enhances evolved gas analysis and is now available as the TG-SPME attachment for Rigaku’s STA.

TG-DTA-MS requires an interface for gas transport in order to accurately introduce the gas generated from the sample section of the TG-DTA analyzer into the MS instrument.

Two typical interfaces are capillary and skimmer types. In the conventional capillary type, the two instruments are connected by a 1 to 2 m long narrow tube (capillary), and the capillary is heated at a constant temperature. This method requires uniform heating at the connection points between the capillary and both instruments, but the long route and complicated connections cause cold points, which lead to accumulation of high-boiling point gases. The skimmer type, on the other hand, incorporates a differential evacuation unit based on the jet separator principle inside the electric furnace of the thermal analyzer. This method enables the gas generated from the sample section at atmospheric pressure to be introduced into the MS chamber in a vacuum atmosphere over a short distance of approximately 160 mm. However, the connection on the MS side is difficult to heat due to its configuration so, although the path is short, there are cold points just as in the capillary method.

In this new interface for Thermo Mass Photo, Rigaku succeeded in developing a capillary interface without cold points, enabling the detection of high