At present, the determination of tantalum pentoxide and niobium pentoxide in tantalum-iron and niobium-iron concentrate usually adopts gravimetric method, while the determination of titanium dioxide adopts diantipyrylmethane spectrophotometry or inductively coupled plasma atomic emission spectrometry (ICP-AES). However, these determination methods have long operation procedures, and the sample cannot be determined simultaneously in once sample preparation, which hardly meet the requirements of detection efficiency. In this study, the determination method of tantalum pentoxide, niobium pentoxide and titanium dioxide in tantalum-iron and niobium-iron concentrates by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) with fusion sample preparation was established. The working parameters of the instrument were optimized by experiments, and the melting temperature and time were studied. It was found that the optimal melting temperature and time were 1 100 ℃ and 10 min, respectively. The fluidity of melt flow good, the test piece was uniform without non-melt. In addition, the effects of internal standard correction and direct determination on the linear correlation coefficient of the calibration curve were compared. The results showed that the linear correlation coefficient of the calibration curve of tantalum pentoxide was significantly improved after correction with hafnium dioxide. There was no significant difference in the linear correlation coefficient of the calibration curve using internal standard and direct determination for niobium pentoxide and titanium dioxide. The contents of tantalum pentoxide, niobium pentoxide and titanium dioxide in three tantalum-iron and niobium-iron concentrate samples were determined according to the experimental method. The relative standard deviations (RSD, n=9) of determination results were less than 3%. The components of tantalum-iron and niobium-iron concentrate samples were determined by this method and the chemical wet method, and there was no significant difference in the results.

The chemical composition of refined slag in iron and steel metallurgical enterprises is generally determined by X-ray fluorescence spectrometry (XRF). Although there are national standard methods for reference, the analysis speed cannot meet the production requirements in front of the smelting furnace. In this study, the sample was prepared by pressed powder pellet method. The grinding time was 40 s, the pressure was 40 MPa, and the holding time was 40 s. Eight self-made refined slag samples were selected as calibration samples to establish the calibration curve. The method for determination of eight major components in refined slag, including silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, phosphorus pentoxide, manganese oxide, titanium dioxide, and iron, was established by XRF with pressed powder pellet sample preparation. The linear correlation coefficients of calibration curves of components were all greater than 0.98. The contents of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, phosphorus pentoxide, manganese oxide, titanium dioxide, and iron in the refined slag sample were determined according to the experimental method. The relative standard deviations (RSD, n=11) of determination results were all less than 0.06%. Three refined slag samples were determined according to the experimental method, and the measured results were consistent with those obtained by the chemical wet methods (where, the content of silicon dioxide was determined by perchloric acid dehydration gravimetry-silicon molybdenum blue spectrophotometry; the contents of aluminum oxide and calcium oxide were determined by EDTA titration; the contents of magnesium oxide, phosphorus pentoxide, manganese oxide, titanium dioxide, and iron were analyzed by inductively coupled plasma atomic emission spectrometry).

It is of great significance to determine chromium (Ⅵ) accurately in site soil for the management and remediation of contaminated site. Alkali solution extraction-flame atomic absorption spectrometry is one of the main analysis methods for determination of chromium (Ⅵ) in site soil. The certified reference materials and actual samples of site soil were used as research object, and the effects of heating method, stirring speed, liquid-solid ratio and reducing remediation reagent on the determination of chromium (Ⅵ) were investigated. The results showed that the extraction of chromium (Ⅵ) in site soil was more complete when the water bath heating was used, and the stability of determination results were better than that of electrical heating. The stirring rate could significantly affect the determination results of chromium (Ⅵ), and the continuous and steady medium speed stirring showed best effect. Under normal conditions, the liquid-solid ratio of 10∶1 could satisfy the effective extraction of chromium (Ⅵ) in conventional soil samples. However, for the site soil samples with chromium (Ⅵ) content exceeding the upper limit of linear range of calibration curve, the optimal liquid-solid ratio should be obtained by reducing sample mass to ensure the accuracy and reliability of determination results. The reducing remediation reagent had negative interference with the standard addition tests of chromium (Ⅵ). Hydrogen peroxide was added before extraction followed by ultrasonic reaction at room temperature for 5 min. It could change the reducing properties of sample matrix, and meanwhile, keep the chemical form stability of chromium (Ⅵ) in soil sample. The spiked recoveries of chromium (Ⅵ) increased to 75.0%-97.5%. Therefore, the interference of reducing remediation reagent with the spiked recovery test of chromium (Ⅵ) could be effectively eliminated.

The oxide scale samples of full hydrogen batch annealing steel coil of 40Cr13Mo and 40Cr13 produced by the same process were analyzed by scanning electron microscopy (SEM), X-ray energy dispersion spectrum (EDS) and X-ray diffraction (XRD). The results showed that the oxide scale of stainless steel 40Cr13Mo was dense with low peeling degree due to the addition of Mo. Only few small defects were observed inside. There was pressure stress in some parts and the strength was slightly higher than that of oxide scale. The bonding regions with matrix were colloidal, and there were “small wedge prominences” of 2FeO·SiO₂ (fayalite) with pinning depth of 0.81 μm. The oxide scale thickness was small but the range was large, and the bonding surface with matrix was uneven. The energy distribution trend of Cr was consistent with O in EDS surface scanning. The high-level regions accounted for above 90%, which were distributed in middle and lining of oxide scale. The middle-level regions of 10% were distributed in periphery of oxide scale, and there were no low-level regions. In the bonding regions with matrix, Si showed continuous middle-level stripes with width of 3 μm, and there were 3 μm high-level spots in stripes. The reduction process of oxide scale with hydrogen lagged behind seriously. The phases were mainly FeCr₂O₄ and FeO. Their contentsaccounted for 90.2% (mass fraction, the same above), and the contents of Fe, Cr and Cr_0.7Fe_0.3 were only 9.6%.

Rare metal ores are often associated with various dispersed metal elements such as zirconium, hafnium, uranium, thorium, thallium, gallium, tungsten and tin. However, there are few literatures on the related testing methods, and the existing rare metal ore reference materials also are in lack of certified values for associated elements such as zirconium, hafnium, gallium, thallium, uranium, and thorium. In this study, six types of rare metal ore reference materials were digested with nitric acid-hydrofluoric acid system with high pressure closed digestion. The residue was redissolved with aqua regia (1+1). The determination of zirconium, hafnium, gallium, thallium, uranium and thorium by inductively coupled plasma mass spectrometry (ICP-MS) was realized. The reference values of six associated elements in six rare metal ore reference materials were provided. The digestion effects of rare metal ore reference materials by three methods, namely open digestion with nitric acid-hydrofluoric acid-perchloric acid, open digestion with nitric acid-hydrochloric acid-hydrofluoric acid-perchloric acid, and closed digestion with nitric acid-hydrofluoric acid, were compared. The results showed that the sample could be completely digested by the high pressure closed digestion method. The rare metal ore reference materials were selected to investigate the redissolution effect by aqua regia (1+1). The results showed that the measurement values of zirconium and hafnium after redissolution with aqua regia (1+1) were consistent with those obtained by alkali fusion-ICP-MS and X-ray fluorescence spectrometry (XRF). It indicated that the hydrolysis problem of zirconium and hafnium could be solved using the oxidability of nitric acid and complexation effect of chlorine ion. The linear correlation coefficients of calibration curves of elements in this method were all higher than 0.999 9. The limit of detection and limit of quantification were 0.01-0.04 μg/g and 0.04-0.16 μg/g, respectively. The proposed method was applied for the determination of elements in certified reference materials GBW07103 (granite), GBW07832 (dispersed element ore), GBW07834 (dispersed element ore) and GBW04132 (sandstone uranium ore) with similar matrix and contents of testing elements. The relative standard deviations (RSD, n=8) of determination results were between 1.5% and 6.4%, which could meet the requirements in DZ/T 0130-2006 The specification of testing quality management for geological laboratories. The measurement results were basically consistent with the certified values of reference materials, and the relative errors (RE) were between -2.6% and 3.2%. The contents of zirconium, hafnium, gallium, thallium, uranium, and thorium in reference materials of rare metal ore (GBW07152-GBW07155, GBW07184 and GBW07185) were determined according to the experimental method, and the reference values of elements were provided. These data could be used as a reference for other studies and provided a foundation for further collaborative study and other work.

In the research of inclusions control, how to accurately characterize and analyze the inclusions in steel is the key link. Focused ion beam (FIB)-scanning electron microscopy (SEM) can realize the internal structure analysis and three-dimensional reconstruction of inclusions in steel as well as the sample preparation for transmission electron microscopy (TEM), so it has become an important detection method for the study of inclusions in alloy steel. In this paper, the working principle of FIB-SEM and its application in internal structure analysis, three-dimensional reconstruction of inclusions and TME sample preparation were discussed. By examining the structure, composition and distribution of inclusions in low alloy steel, high strength steel, bis steel and bearing steel, the formation process and reason of various inclusions such as magnesium aluminum spinel and sulfide complex inclusions, nitride and manganese sulfide complex inclusions, calcium aluminate and titanium nitride complex inclusions were analyzed. Through the three-dimensional reconstruction of inclusions in bearing steel, the size, three-dimensional morphology and spatial distribution of (Ti,V)N solid solution inclusions in steel were obtained. Moreover, the sample preparation for TEM was conducted. This paper provided method reference and theoretical reference for solving the problem of tracing the inclusions in alloy steel.

The accurate determination of alloying elements and impurities in titanium alloy is important for the performance study and quality control of alloy products. In experiments, the samples were prepared by turning or milling. After correcting the interference of coexisting elements, the analytical lines of each element were selected, i.e., Al 396.110 nm and Al 394.403 nm, Cr 425.433 nm and Cr 313.210 nm, Cu 324.710 nm and Cu 510.514 nm, Fe 259.940 nm, Mn 257.660 nm and Mn 293.310 nm, Mo 386.411mm and Mo 281.610 nm, Ni 231.604 nm, Si 288.158 nm, Sn 147.510 nm and Sn 317.505 nm, V 437.924 nm and V 290.810 nm, Zr 357.247 nm. A series of standard samples of titanium alloy for spectral analysis were used to draw the calibration curves, which were then fitted and optimized. A method for the determination of 11 alloying elements and impurities including aluminum, chromium, copper, iron, manganese, molybdenum, nickel, silicon, tin, vanadium and zirconium by spark discharge atomic emission spectrometry was established. The determination coefficients of the calibration curves were all greater than 0.999. The limits of detection were between 0.000 03% and 0.002 94%. The contents of eleven elements in the standard samples of titanium alloy were determined according to the experimental method, the relative standard deviations (RSD, n=11) of determination results were between 0.31% and 4.9%. The absolute value of relative errors (RE) between the determination results and standard values of elements were not more than 8.1%. Three grades of titanium alloy samples were analyzed and compared. The samples were determined according to the experimental method, and the found results were basically consistent with those obtained by YS/T 1262-2018.

The accurate determination of potassium content in tungsten-rhenium alloys is of great significance for studying the high-temperature properties of materials and the room temperature plasticity after recrystallization. In this study, the sample was dissolved with nitric acid and hydrofluoric acid. The cesium chloride solution was added as an ionizing agent to suppress the ionization of potassium and eliminate ionization interference. A method for the determination of potassium with mass fraction of 0.000 5%-0.010% in tungsten-rhenium alloy by flame atomic absorption spectrometry (FAAS) was established. The interference test showed that tungsten or rhenium matrices had a significant impact on the measurement. Therefore, the matrix matching method was used to draw calibration curves to overcome the matrix effect of tungsten or rhenium. The influence of other elements in the sample, except for the matrix tungsten and rhenium, on the determination could be ignored. The experimental results showed that the correlation coefficients of calibration curves for sample WRe5 and WRe25 were 0.999 8 and 0.999 6, respectively, and the characteristic concentrations of potassium were both 0.007 6 μg/mL. The precision tests were conducted using four tungsten-rhenium alloy samples with different potassium content levels according to the experimental methods, and the relative standard deviations (RSD, n=9) of the measurement results ranged from 1.7% to 3.1%. The contents of potassium in WRe5 and WRe25 tungsten-rhenium alloy samples were determined according to the experimental method. Different amounts of 1 μg/mL potassium standard solution were added for the spiked recovery tests, with recovery rates ranging from 98% to 104%. The inductively coupled plasma mass spectrometry (ICP-MS) was used for method comparison and validation. The t-test analysis showed that there was no significant difference between the ICP-MS and the experimental method.