Elemental Analysis Of Samples Research Articles

Chemical Compatibility Investigation of Thin‐Film Oxygen Transport Membranes on Metallic Substrates

Thin‐film La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF58428) exhibits high oxygen permeability due to its high ionic and electronic conductivity. In order to increase the oxygen flux, a thin‐film membrane on a structural substrate is beneficial. Different Ni‐based alloys were studied as potential substrate materials. The chemical compositions and thermal expansion coefficients of Ni‐based alloys were measured in this study. LSCF58428 layers were screen printed on Ni‐based alloys and cofired at a high temperature in air. Microstructural and elemental analyses of samples were conducted using a scanning electron microscope and energy‐dispersive X‐ray spectroscope. X‐ray diffraction was used to investigate the phase compositions. The Ni‐based alloy, MCrAlY (with M=Ni, Co), with a high Al content showed better chemical compatibility with perovskite material at high temperatures than other Ni‐based alloys. A reaction occurred between Sr in the perovskite and the alumina‐based surface layer on MCrAlY. However, the reaction zone was found to be stable in mid‐term annealing at 800°C in air. Hence, it is expected that this reaction will not prevent application as an oxygen transport membrane. Three different cofiring atmospheres were investigated. Air was found to be the only possible cofiring atmosphere.

Applications of the Cracow X-Ray Microprobe in Tomography

A nuclear microprobe at the IFJ PAN in Cracow has found numerous applications in different fields of research, mostly in biophysics, medical sciences, geology, and material research. In order to extend the research possibilities, a new X-ray microprobe was constructed. This new microprobe consists of three experimental lines dedicated to: (i) X-ray irradiation of biological specimens, (ii) elemental analysis of samples by micro X-ray fluorescence or total reflection X-ray fluorescence methods and (iii) computer microtomography. In this paper the computer microtomography line was described. The line consists of an open type Hamamatsu L9191 X-ray tube with microfocusing to about 2 μm, a high resolution X-ray sensitive CCD camera, and a precise goniometer composed of six piezoelectric motors. Depending on the required X-ray energy, the Hamamatsu tube is used with Ti, Mo, Ag, or W targets. A small focus size and short focus-to-object distance enable to obtain images of samples with a magnification of more than 1000× and resolution of the order of 2 μm. The computer microtomography measurements are carried out using home developed codes combined with commercial software. Details of the microprobe construction and preliminary results of the computer microtomography experiments are presented.

The influence of char surface oxidation on thermal annealing and loss of combustion reactivity

Thermal annealing associated with heat treatment of coal chars affects gasification reactivity and levels of unburned carbon in residual ash from coal-fired furnaces. The present study addresses the effect of char surface oxidation, occurring upon exposure to oxygen, on the course of thermal annealing, and related loss of combustion reactivity. This goal is pursued by comparing the extent of thermal annealing suffered by coal char upon heat treatment in a nitrogen atmosphere with that of chars that underwent oxidation prior to or during heat treatment. Oxidation of char was accomplished by supplying single or multiple pulses of air during the heat treatment, which were sufficient to oxidize the char surface but small enough to limit carbon gasification to less than 5%. The extent of thermal annealing was characterized both in terms of the loss of combustion reactivity and of the development of structural anisotropy of char samples, investigated by HRTEM. Results of the present study confirm that heat treatment reduces oxyreactivity of char samples, the effect being more pronounced at temperatures exceeding 1200 °C. Oxidation of samples mitigates the effects of heat treatment, as demonstrated by the smaller loss of gasification reactivity and by the more limited development of structural anisotropy of oxidized samples. Correspondingly, elemental analysis of samples indicates the formation of stable surface oxides upon oxidation, that are subsequently desorbed upon heat treatment. At temperatures exceeding 1200 °C, the effect of oxidation vanishes. Results are analysed and discussed in the light of the possible hindrance of thermal annealing due to the formation of stable surface oxides and of the parallel modifications occurring to the ash constituents.

Luminescence dating of fine-grain Holocene sediments from a coastal setting

Abstract A detailed study of a core of Holocene age from a site (Adventurers’ Land, F21) in the Fenlands, UK, based on the measurement of infra-red-stimulated luminescence (IRSL) with silt-sized fractions of water-laid deposits has yielded a sequence of 24 luminescence ages. An additive dose procedure was applied to evaluate the palaeodose, and the annual dose was assessed on the basis of radioactivity and elemental analyses of samples taken from the core. The proportions by weight of the mineral fraction of water and organic material within the sediments ranged from c. 20 to 170% for the former and between c. 10 and 25% for the latter. Overall, the sequence of IRSL age evaluations is consistent with the calibrated radiocarbon ages obtained for three intercalated organic horizons within the core. Although the luminescence ages for F21A do not possess a resolution that would enable rates of sedimentation between the organic sediments to be determined with confidence, the general trend of the luminescence ages with depth suggests a chronological resolution of the order of 1 ka or better.

Application of the fundamental parameter method to the in vivo x-ray fluorescence analysis of Pt

The application of the fundamental parameter method (FPM) to the in vivo x-ray fluorescence (XRF) analysis of Pt has been investigated. The FPM is conventionally used to carry out elemental analysis of samples in vitro without the need to use standard samples of accurately known composition for system calibration. The present work has involved the use of the FPM to calculate the concentration of Pt solutions in phantoms, with concentrations ranging from 25-1000 ppm. The phantoms simulate the measurement of Pt-based chemotherapy drugs in head and neck tumours. The radiation sources were a 150 kV tungsten-anode x-ray tube and the isotope Tc. The minimum detection limit measured for Pt was in the range 8-30 ppm (depending on radiation source and geometry), using a narrow (5 mm) diameter beam. Dose rates in the phantom were . Average differences between nominal and calculated values of Pt concentration were <8% using the phantoms in air to simulate measurement of Pt in superficial body sites. If the phantoms were placed in a water bath, to simulate measurement at greater depths of overlying tissue, higher systematic differences (15-20%) were observed. This effect is probably due to multiple scattering processes in the surrounding medium.

Elemental analysis of samples using 14 MeV neutrons and charged particles

Thorough descriptions on the methods of elemental analyses of samples using 14 MeV neutron activation and charged particle induced X-ray fluorescence are presented. Applications of these methods are demonstrated by means of Chinese medicinal samples which are in powder form. The results of analyses show good agreement between the data resulting from these two different methods. Typical results of the analyses are presented and comparisons on the various aspects of these two methods are made.