Compton to Rayleigh scattering intensity ratios (IC/IR) have been measured using X‐rays with energy 17.44 keV for single‐component materials with atomic number Z from 4 (Be) to 31 (Ga) and binary compounds of stoichiometric composition. The measurements have been performed using two optical schemes: an energy‐dispersive X‐ray fluorescence scheme with a molybdenum secondary target and wavelength‐dispersive X‐ray fluorescence one. The processing of the spectra was carried out by fitting with Pearson VII functions. For single‐component and binary standards, the experimental dependence of the scattering intensity ratio on the atomic number was found to be the same. This confirms the additivity of the contribution of different atoms to the scattering. The dependence has a complex shape but is well described by the theoretical relationship for IC/IR with correction on the difference between Compton and Rayleigh radiation absorption coefficients. Two ranges of atomic number values are defined, in which the effective atomic number Zeff can be determined by the calibration method using this dependence: for Z from 4 to 7 with low error of ΔZeff =±0.15 and for Zeff from 10 to 18 with low error of ΔZeff =±0.69. A change in the shape of the Compton peak and an overestimated value of the of the Compton and Rayleigh peak intensity ratio when passing from a single‐component scatterer (Al or Si) to their oxides Al2O3 or SiO2, respectively, have been revealed.
A generalization of the Compton method for determining elements with a low atomic number Z from 1 (H) to 9 (F) by the ratio trueICIR of the intensities of incoherent (Compton) and coherent (Rayleigh) scattering is proposed. The generalization takes into account not only the dependence of this ratio on the effective atomic number of the scatterer material but also the momentum transfer variable x = sin0.5emθλ. The new method is based on the application of calibration function of trueICIR=g()Z,x obtained by measuring scattering spectra at two values of x1= 0.831 Å−1 and x2= 1.297 Å−1 with a WDXRF spectrometer. The elemental atomic numbers and their concentrations of binary compounds with unknown compositions are determined by the solution of a system of linear equations. Coefficients of the equations are calculated from the measured trueICIR ratios for the test sample and the regularization solution for the corresponding calibration. The experiments have been carried out for standard samples of single‐component, binary and triple stoichiometric compounds based on H, Li, Be, B, C, O and F. The identification of these elements was found to be possible in the absence of a relationship between the positions of scattering peaks and the composition of the sample, and a qualitative and quantitative analysis of the composition of the material was carried out as part of the solution of a single inverse problem.
The rapidity of determining trace precious metals in a low density filler is a rather important parameter of the measurement methods used in processing cer tain raw materials. X ray fluorescence (XRF) analysis is one of the better known methods for determining trace impurities and is valued as a relatively simple and nondestructive express method that does not require complicated sample preparation. The use of standard XRF analysis setups for determining trace precious metals is complicated by a strong scattered radiation background: the detection limit for trace impurities is 50-200 ppm, while it is necessary to determine the content of impurities as low as 1-10 ppm. Significant advances in determining trace quantities of precious metals were made with the use of polarized radiation designs where the detection limit C min ≈ 1 ppm [1,2]. However, these designs require complex collimation devices and intense primary radiation sources (~1 kW), and the spectrometers utilizing these designs are bulky and expensive [3]. It was shown in [4] that a high peak to background ratio in the spectra may be obtained even in a simple design with a secondary radiator if it is multilayered with an optimal combina tion of the absorber and radiator functions.The present study is aimed at reducing the gold detection limit in the X ray fluorescence analysis of an ion exchange resin to lower than 1 ppm through the use of portable X ray optics with a secondary radiator [4].The objects under study were reference samples of gold in an ion exchange resin with the gold content of 200, 50, 20, 10, and 0 ppm. The samples in the form of spheres with diameters on the order of 1 mm were arranged in a single layer on 3525 ULTRALENE (SPEX SamplePrep) ultrathin films.The measurements were conducted using a Sprut K (AO Ukrrentgen) energy dispersion spectrometer with an X 100 (Amptek) Si(Li) detector. The mea surement design is shown in Fig. 1. The BS 22 X ray tube with a through type silver target (1) irradiates the yttrium secondary radiator (3) through the 60 μm thick primary radiation filter made of silicon (2). The fluorescence radiation from the reradiator passes through the slit (4), reaches the sample surface (5), and excites the impurity atoms, the analytical lines of which are recorded by the detector (7). The scattering angle 2Θ ≈ 100°, and the aperture of this design is 8 × 10 -6 (X ray target-radiator, radiator-sample, and sample-detector). The X ray tube operating regime is as follows: U = 35 kV, I = 250 μA, and the exposure time is 600 s.Abstract-The use of portable X ray optics with a secondary radiator in the determination of trace gold in an ion exchange resin within the mass fraction range of 1-50 ppm is described. It is shown that the secondary radiator design with primary radiation filtering allows one to determine trace gold in an ion exchange resin when the mass fraction of gold is lower than 1 ppm.
Исследовано влияние температуры на предел прочности (σ uts ) и удлинение до разрушения (δ) при растяжении образ-цов никелида титана (50.2 ат.% Ni) с исходной крупнозернистой структурой и структурами после abc-прессования при 873К (сплав 1, истинная деформация е = 2.2) и после прессования с понижением температуры в последователь-ности 873К→673К (сплав 2, е = 4.2). Размер зёрен в образцах сплава 1 (2-40 мкм) меньше, чем в исходных образцах (20-70 мкм). Образцы сплава 2 имели субмикрокристаллическую структуру (зёрна/субзёрна 100-700 нм). Показано, что при охлаждении и нагреве в исходных образцах реализуется мартенситные превращения (МП) В2←→В19ʹ (фазы с кубической и моноклинной структурами, соответственно), а в сплавах 1 и 2 МП протекают в последовательности В2→R→В19ʹ→В2 (R -мартенситная фаза с ромбоэдрической структурой). Завершение МП В19ʹ→В2 в этих образцах происходит при температурах 340-355 К. Растяжение образцов проводили при 293К, 343К и 473К (или 523К), то есть в мартенситной фазе В19ʹ, предпереходной области температур и в В2 фазе. Зависимости «напряжение-деформа-ция», полученные при этих температурах, для всех образцов качественно подобны. В процессе растяжения при 293К и 343К наблюдается площадка псевдотекучести, связанная с переориентацией кристаллитов фазы В19ʹ или форми-рованием деформационной мартенситной фазы В19ʹ. Генерации мартенситной фазы В19ʹ в процессе растяжения при 473К (или 523К) не наблюдается. Показано, что σuts повышается после abc-прессования. Максимум σuts наблюдается в процессе растяжения сплавов 1 и 2 при 293К и 343К (в мартенситной фазе В19ʹ). Наиболее пластичными являются образцы сплава 1 (δ около 80% при 293-343 К). При повышении температуры деформирования до 473К (или 523К) σ uts и δ существенно понижаются (в ~ 2 раза). Ключевые слова: тёплая деформация, никелид титана, механические свойстваThe effect of warm deformation by abc-pressing method on mechanical properties of titanium nickelide The effect of temperature on the ultimate tensile strength (σ uts ) and fracture elongation (δ) under tension of titanium nickelide (50.2 at.% Ni) with initial coarse-grained structure and structures after abc-pressing at 873K (alloy 1, true deformation е = 2.2) and after "step-by-step" pressing at 873K→673K (alloy 2, е = 4.2) are studied. The grain dimensions in the samples of alloy 1 (2-40 μm) are smaller than ones in initial samples (20-70 μm). The structure of alloy 2 is submicrocrystalline (grain/ subgrain dimensions are 100-700 nm). It was found that the martensitic transformations (MT) B2←→B19ʹ had been observed under cooling and heating of initial samples. The sequences of В2→R→В19ʹ→В2 MT were observed in alloys 1 and 2 (R -the rhombohedral martensitic phase). The finish of B19ʹ→B2 MT take place in the temperature range 340-355 K. The tension tests were carried out at temperatures 293K, 343K and 473K (or 523 K), i.e. in the B19ʹ phase, pretransition temperature range and B2 phase, accordingly. The "stress-strain" dependences obtained at these temperatures are quantitavely the same for all
An alternative method is proposed for the determination of the inorganic constituent mass fraction (ash) in solid fuel by the ratio of Compton and Rayleigh X-ray scattering peaks I/I subject to the iron fluorescence intensity. An original X-ray optical scheme with a Ti/Mo (or Sc/Cu) double-layer secondary radiator allows registration of the combined fluorescence-and-scattering spectrum at the specified scattering angle. An algorithm for linear calibration of the Compton-to-Rayleigh I/I ratio is proposed which uses standard samples with two certified characteristics: mass fractions of ash (A) and iron oxide (W ). Ash mass fractions have been determined for coals of different deposits in the wide range of A from 9.4% to 52.7% mass and W from 0.3% to 4.95% mass. Due to the high penetrability of the probing radiation with energy E > 17 keV, the sample preparation procedure is rather simplified in comparison with the traditional method of A determination by the sum of fluorescence intensities of all constituent elements.
The application of the arrangement with a secondary target for the X ray fluorescent analysis of microimpurities in water solutions without sample destructions and preliminary sample preparations is con sidered. The limiting contrast values of fluorescence spectra are estimated, the limits of detecting impurities by the arrangement are theoretically calculated and experimentally measured (C min is smaller than 0.5 ppm). The range of chemical elements, which are efficiently excited by the secondary target, is determined by the C min criterion.
Comparative studies of niobium carbide and niobium carbonitride coatings deposited on AISI 430 stainless steel have been presented. The NbC and NbCN coatings have been deposited by vacuum-arc evaporation in Bulat-type device by using the pulsed biasing mode with repetition frequency 50 kHz, allowing decreasing the micro-arcs formation. An additional magnetic coil for plasma flow focusing was used, allowing one to enhance deposition rate up to 35 µm/h. The phase composition of the obtained coatings was analyzed via X-ray diffraction. The surface morphology was monitored by scanning electron microscopy; whereas, chemical composition was examined by using energy dispersive X-ray analysis. X-ray fluorescent analysis was used to evaluate the thickness of the coatings. The reflectance R(λ) of the obtained coatings in the wavelength 300-625 nm at normal incidence was measured. The XRD data from NbC coating revealed the existence of the niobium carbide phase with a NaCl-type lattice with fine-crystalline grains ranging from 14 to 16 nm. For the NbCN coating, the two-phase state with c-NbC and hexagonal NbN 0.95 phases was monitored. The average grain size for c-NbC phase comprised 16-17 nm; whereas, for NbN 0.95 the average grain size was only 1-2 nm, confirming formation of a nanocrystalline structure. Surface nanomechanical behavior under nanoindentation of NbC and NbCN was studied. It was revealed that nanohardness for a NbC coating was varied from 30 to 43 GPa; whereas, for NbCN the data spread comprised 30-48 GPa. It was established that the surface of the grown coatings was very smooth with an extremely low amount of macroparticles.
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