Analysis of cerium oxide by arc atomic emission spectrometry

Materials based on rare earth elements (REE) are of great importance due to their unique chemical and physical properties, but the effectiveness of their use depends on the quality of raw materials. Therefore, further development of the methods of analytical control in relation to rare-earth materials is aimed at increasing the accuracy and sensitivity of the methods, as well as at expanding the nomenclature and concentration range of the determined elements. Cerium oxide is used in glasses, ceramics, catalysts, phosphors, composite and scintillation materials, as well as in medicine. The problem of developing a new arc spectral method is extremely urgent to match modern requirements for the accuracy and sensitivity of the impurity determination for monitoring the purity of cerium oxide. A technique for arc atomic emission analysis of cerium oxide which meets modern requirements for the accuracy and sensitivity of the impurity determination has been developed. The range of impurities to be determined is significantly expanded compared to the standardized technique of the 1970s. The goal of this work is to study and develop a modern method for arc optical emission spectral analysis of cerium oxide using the instrumental capabilities of the atomic emission complex «Grand Globula». To specify compromise conditions for the determination of 15 REE impurities and 19 elements more, analytical lines were selected and the dependence of their intensity on the operating mode of the generator, the shape and size of the electrodes, the interelectrode distance, the ratio of the masses of the analyzed sample and graphite powder, as well as on the presence of various carriers (Ga2O3, NaCl, NaF, KCl, S, GeO) was analyzed. Application of the considered methodological approach to the selection of conditions made it possible to develop a method for spectral analysis of cerium oxide without preliminary dissolution of the sample with an extended range of determinable impurities. When studying the curves of the impurity evaporation, an exposure time was chosen to be sufficient for their complete evaporation (100 – 120 sec). The study has shown the 0promising character and feasibility of the developed arc spectral techniques applicable to the analysis of REE-based materials as an alternative to the methods for analysis of solutions. The metrological characteristics of the proposed procedure for the analysis of cerium oxide were evaluated in comparison with the standardized technique.

Chiral Monolithic Silica-Based HPLC Columns for Enantiomeric Separation and Determination: Functionalization of Chiral Selector and Recognition of Selector-Selectand Interaction

This review draws attention to the use of chiral monolithic silica HPLC columns for the enantiomeric separation and determination of chiral compounds. Properties and advantages of monolithic silica HPLC columns are also highlighted in comparison to conventional particle-packed, fused-core, and sub-2-µm HPLC columns. Nano-LC capillary monolithic silica columns as well as polymeric-based and hybrid-based monolithic columns are also demonstrated to show good enantioresolution abilities. Methods for introducing the chiral selector into the monolithic silica column in the form of mobile phase additive, by encapsulation and surface coating, or by covalent functionalization are described. The application of molecular modeling methods to elucidate the selector–selectand interaction is discussed. An application for enantiomeric impurity determination is also considered.

Calibration of CFUL01 fission chambers in the standard neutron fields of the BR1 reactor at SCK CEN

Recent subcritical VENUS-F experiments showed that fission chambers with a threshold deposit like U-238 can essentially improve the on-line sub-criticality measurments with the beam interruption method, which is currently supposed to be the main method for the ADS MYRRHA. To suppress the uncertainty caused by fissions in the U-235 impurities, the fraction of U-235 in the U deposit should be accurately known. Three PHOTONIS CFUL01 type fission chambers with U-238 deposit were purchased for sub-critical experiments in the VENUS-F reactor. To verify the purity of their deposits, the effective U-235 masses were measured in the empty cavity of the BR1 reactor with a well-known thermal neutron spectrum. It turned out that the measured effective U-235 mass in two fission chambers is lower than the declared mass (as it should be), but this is not the case for the third fission chamber. Then, the effective U-238 mass in these FCs was measured in the well-known fast spectrum of the MARK-III convertor in the BR1 reactor. Finally, the isotopic composition was obtained and it was found that the purity of two CFUL01 FCs is in agreement with the values declared in the certificates but it is not the case for the third fission chamber. As the length of the deposit is bigger than the length of the MARK-III convertor, necessary corrections were calculated with MCNP. The developed procedure using the BR1 standard irradiation fields can be applied for calibration and impurity determination of large fission chambers.

Obtaining a Well-Aligned ZnO Nanotube Array Using the Hydrothermal Growth Method / Labi Sakārtotu Zno Nanocauruļu Kopu Iegūšana, Izmantojot Hidrotermālo Metodi

Optimal growing parameters have been found using the hydrothermal method to obtain well-aligned vertical ZnO nanorod and nanotube arrays. The influence of different growing factors (such as temperature, growing solution concentration, method of obtaining seed layer and condition) on nanotube morphology and size is described in the paper. Well-structured ZnO nanotubes have been obtained by using a selfselective etching method with lowering temperatures of growth during the hydrothermal process. It is shown that the optical properties of the nanostructure arrays obtained are sensitive to the medium in which they are placed, which is why they can be used as sensors for pure substance detection and in different solutions for impurity determination.