Volume 36(2) - Summer 2020

Rigaku has been supplying the compact desktop 3D micro CT “CT Lab HX”, a wide field of view and highresolution CT imaging system, since 2018.

CT Lab HX is suitable for computed tomography (CT) imaging of electronic devices, castings, pharmaceutical devices, industrial parts, resins, minerals, etc., and is widely used for fundamental research and quality control.

However, to perform CT scans, it used to be necessary to replace samples manually. In the field of product inspection and performance testing, where imaging of many samples is needed, a function that enables automatic sequential CT scans was desired.

Also, the filters to control X-ray energy had to be manually exchanged. There were requirements for a mechanism that facilitates CT scanning through seamless management of automatic filter exchange and calibration. The Automatic Sample Changer and the Automatic Filter Changer were developed to meet these demands.

Copper is the most popular target material for an X-ray generator in general X-ray diffraction measurements, but sometimes other materials are chosen depending on the composition and shape of the sample and the measurement purpose. Rigaku’s automated multipurpose X-ray diffractometer, SmartLab, can utilize X-ray source materials such as cobalt, chromium, molybdenum, silver, etc. in addition to copper, depending on the sample and the measurement purpose.  The 9 kW–60 kV type SmartLab is an advanced model of the high-brightness X-ray diffractometer equipped with the PhotonMax rotating anode X-ray generator.

X-ray fluorescence (XRF) spectrometry is one instrumental analysis method used to determine the composition of solid and liquid samples. Compared to other methods, it can achieve high-precision analysis. XRF is widely used for quality control in manufacturing. It is an effective method for trouble analysis during production and research and development of materials and products.

Rigaku’s ZSX Primus series of sequential wavelength dispersive X-ray fluorescence spectrometers includes tube-above high-end ZSX Primus IV, basic ZSX Primus III+ , and high-end tube-below ZSX Primus. The different instruments in this series are optimal for coping with a variety of analysis purposes. There are noteworthy advantages to both tube-above and tube-below optics.

The ZSX Primus IVi, a successor to the tube-below ZSX Primus, is newly developed based on the latest technology cultivated in the ZSX Primus IV.

X-ray fluorescence (XRF) analysis has a wide range of applications because it allows quick and non-destructive qualitative and quantitative analysis of contained elements with simple sample preprocessing and has excellent measurement reproducibility. It is used in the industrial fields of steel, non-ferrous metals, mining, petroleum, ceramics, cement, and for R & D and quality control of electronic materials such as multilayer capacitors and piezoelectric elements.

In the environmental analysis field, XRF analysis is mainly used for hazardous element analysis, and is applied to screening analysis of restricted substances according to the RoHS directive and contaminated soil. XRF analysis is environmentally friendly because it does not produce waste liquid unlike ICP and ICP-MS analysis, both official methods for water analysis. Therefore, the application of XRF analysis to water quality management of industrial wastewater, agricultural water, springs, rivers, lakes is expected to increase.
 

Until the late 2000s, only scintillation counters (SC) were used as the detectors for general-purpose powder X-ray diffractometers. Thereafter, the core technologies that combine to create an X-ray diffractometer evolved dramatically. A one-dimensional (1D) detector—and subsequently a two-dimensional (2D) detector—came on the market, followed by new optical devices such as multilayer mirrors, in which layering technologies of super-thin film were applied. Analysis software functionality also improved remarkably. For instance, in addition to calculating crystallite size and lattice constants, programs implemented new algorithms and parameters, such as the application of whole pattern fitting, the Fundamental Parameter (FP) method, consideration of anisotropy and distribution in crystallite size.

The 1D and 2D measurement conditions described below are somewhat different from those with an SC.  The factors to which we should pay attention have changed when thinking about the optimal conditions to obtain high-quality data. Even in references in which only measurements using the focusing method and a zero-dimensional detector were described, useful hints to obtain high-quality data were rarely discussed. For this reason, in the series of articles making up this basic powder XRD course, we will explain the fundamentals of X-ray diffraction and expertise, sprinkled with the latest applications.

In this overview article, the principles and instruments used in the powder X-ray diffraction method, and what experiments can evaluate, are explained.
 

For more than 50 years, X-ray topography (XRT) has been an indispensable industrial and research tool for crystal growth of functional materials, since crystalline defects, such as dislocations, stacking faults, etc., can be detected with this technique non-destructively. Industrial demand for almost dislocation-free Si has greatly contributed to this technique, providing important insights for the improvement of crystal quality.  These days, various functional bulk single crystals other than Si have been grown and industrial application of these crystals have been explored. X-ray topography is also employed to investigate growth conditions and correlations between physical properties and crystalline qualities of these crystals.

Even for Si wafers that are originally dislocationfree, there is a possibility that strains and/or defects will be introduced during steps in device fabrication processes; thus, there arises a need for non-destructive characterization without changing the device structure fabricated on the Si wafers. X-ray topography is, therefore, used not only for characterization of slices of ingots or bare wafers, but also for the inspection of processed wafers.

In this article, important features and functions equipped in Rigaku’s latest X-ray topograph apparatus, XRTmicron™ are reviewed briefly and application data from this apparatus related to modern functional crystals will be introduced.

String cheese, which has a texture similar to that of jerky, the taste of fresh cheese, and strands that can be split apart, is a type of immature natural cheese. Natural cheese is generally prepared by adding lactic acid bacteria and rennet to milk, followed by adding salt to the coagulated milk protein to solidify it. String cheese is made from natural mozzarella cheese. After soaking the mozzarella cheese in hot water at 80°C, it can be stretched into a bar shape at room temperature and folded in half. This folding process is repeated to prepare the fibrous string cheese.

There is limited information about the history of string cheese. Some documents indicate that it was prepared in homes in Europe for a long time as a way of preserving fresh cheese, and/or it spread mainly as a menu item in pubs along the US coast. As a Japanese product, string cheese was developed by the Cheese Research Laboratory in Kobuchizawa in Yamanashi Prefecture in Japan, and string cheeses of various flavors are now on sale. According to an article by the Food Industry newspaper on July 27, 2019, annual domestic consumption of cheese is 350,000 tons, of which household consumption is 140,000 tons, and total cheese consumption is increasing every year. String cheese ranks high for its unique texture and strands, and its popularity has rapidly increased. However, there is a problem with insufficient milk supply due to an increase in the consumption of dairy products. For example, six pieces of string cheese, 1.5 cm in diameter and 10 cm in length each, require about 200 g of mozzarella cheese, which is prepared from 2 L of milk, corresponding to one-tenth of the daily production of a cow. The BBC News has criticized European laboratories for research into the efficacy of piercing a cow’s body to inject feed directly into its stomach to increase milk yield. Research and development on substitutes for string cheese are urgently needed.

Substitutional foods reproduce the texture, such as chewiness and softness, and the taste of original food. However, studying relevant parameters that reflect the characteristics of the original food is not simple because the texture and the taste of food generally depend on subjective factors such as individual differences in sense of taste and smell, changes in taste related to age, and amount of chewing and smelling. On the other hand, there are some objective factors that can be approached scientifically, such as internal structure, degree of crystallinity, crystal phase, and melting and crystallization process. X-ray measurement is one of the critical tools used to study these parameters. X-rays penetrate the material, are absorbed, and interact with the atoms and molecules that constitute the material to cause a diffraction phenomenon. Using the characteristics of X-rays, the internal structure at the micrometer (1 μm＝10⁻⁶ mm) to nanometer (1 nm＝10⁻⁹ mm) or Angstrom (1 Å＝10⁻¹⁰ mm) level can be visualized without destroying the material. The components of the material can be identified and quantified from the X-ray diffraction data. In addition to X-ray analyses, thermal analysis is also a powerful tool to study texture and taste. It allows the investigation of phase transition, melting, and crystallization temperature of materials, and so on.

In this study, we observed the internal structure of string cheese at the micrometer level and the periodic structure at the molecular level using X-ray analyses. The key features that were strongly related to the characteristics of texture and taste of string cheese are studied and the question of why string cheese splits is discussed in conjunction with an examination of the results of thermal analysis.

Thermogravimetry (TG) is regarded as one of the most powerful techniques to investigate the fundamental characteristics of inorganic compounds. For a certain compound, information on the temperature-vs-mass relationship leads to a deep understanding of thermal behaviors as well as interactions with the surrounding atmosphere. Nevertheless, the interpretation would not be straightforward only with TG, when multiple gas species are involved in the thermal behaviors. Then, TG combined with a gas analyzer will effectively work.  The combination of thermobalance and quadrupole mass spectrometer (Q-MS), the so-called “TG-MS,” is commercially available, but this technique has the following drawbacks relating to Q-MS: (i) poor quantitative accuracy in the gas amounts, (ii) the complexity caused by fragmentations of gas molecules in the ionization process, (iii) strict limitations of the measuring atmosphere due to the necessity of differential evacuation. For detailed studies on inorganic materials, an alternative analytical method that is capable of quantitative gas analyses under various atmospheres is highly desirable to compensate for the drawbacks of TG-MS.

The authors have recently designed and developed a novel system, “TG-GC,” which employs gas chromatography (GC) as a gas analyzer instead of Q-MS. As mentioned, TG-GC has several advantages, making this system a complementary tool to conventional TG-MS. In this article, we will show a basic concept and the capability of TG-GC. Then, some case studies with the use of TG-GC will be reviewed.