The addition of a high content niobium (Nb) in IN718 alloy leads to the precipitation of a large number of niobium-containing phases. The morphology, area fraction, quantity and shape of these niobium-containing phases are main factors affecting the properties of IN718 alloy. Therefore, the quantitative characterization of niobium-containing phases is of great significance for the study of the structure-activity relationship of the alloy. In this paper, the images of niobium-containing phases in the large field of view of IN718 alloy were efficiently acquired using high-throughput field emission scanning electron microscope based on its characteristics such as high imaging flux, fast automatic scanning speed and strong data processing ability. The image segmentation, recognition and statistical analysis module of niobium-containing phases were established by MIPAR image processing software, realizing the high efficiency extraction and quantitative statistical distribution characterization of niobium-containing phases in large size range of alloys. 1 225 backscattered electron (BSE) images were collected for each sample. These images were rapidly processed in batch using the established image processing module of niobium-containing phases. The information such as morphology and area fraction of niobium-containing phases in different regions of the cross section of IN718 alloy forged bar was obtained. It was found that the niobium phases in the core mostly had the shape of needles and long strips, and the area fraction was relatively high. However, there were more short-rod and round granular precipitated phases at the edge of the forgings. These data would provide guidance for the improvement of forging process and performance.

Q690D steel has excellent properties in strength and toughness. The inclusion in the steel is an important factor affecting the strength and toughness. The modification of inclusions is an important measure to improve the product performance. In order to investigate the modification effect of magnesium on inclusions in Q690D steel for construction machinery, the distribution pattern and size of inclusions in the steel before and after magnesium treatment were compared and analyzed using metallurgical microscopy, scanning electron microscopy, inclusion three-dimensional etcher and FactSage thermodynamic software. The results showed that the inclusions in Q690D steel after calcium treatment were mainly composed of CaO-Al₂O₃, and some of them were wrapped by CaS. The inclusions in magnesium treated steel were mainly composed of MgO·Al₂O₃ or MgO, and some of them were wrapped by MgS. Magnesium could make Al₂O₃ finer and more uniformly distributed, and the average equivalent diameter of inclusions was reduced. The number density and area fraction of inclusions in the magnesium treated rolling stock were 65 mm² and 0.031%, respectively, which were lower than those after treatment by calcium, i.e., 96 mm² and 0.050%, respectively. Magnesium treatment showed better effect to purity the molten steel and improve the size and distribution of inclusions.

A method for analysing and characterizing the three-dimensional morphology and three-dimensional structural characteristic parameters of inclusions in steel was developed based on X-ray microscopy. Three different types of steels were selected to analyse the three-dimensional structural characteristic parameters and three-dimensional spatial distribution of inclusions, including the volume fraction, equivalent diameter, shape factor, diameter and volume distribution, sphericity and orientation. The results showed that the X-ray microscope could accurately characterize the inclusions with size of 1-500 μm in steel. It could also distinguish the high-density phase, non-metallic inclusions and micro-porosity based on the difference of contrast or grey. When the deformation of stainless steel reached 50%, the three-dimensional morphology of plastic inclusions evolved from spherical to flat, and the shape factor decreased from 0.67 to 0.57, and the spatial orientation angle (Phi) increased from 63.48° to 77.40°. For the steel treated with Te, the element of Te was wrapped outside the MnS to form a composite inclusion, which improved the corrosion resistance of the steel. According to the three-dimensional structural characteristic parameters of MnS inclusions, the three-dimensional grain boundaries of sulphur-containing steel were divided, and the relationship between the precipitation process of grain boundary inclusions and solidification selective crystallization was explained. A new method for characterizing the three-dimensional morphology and structural of inclusions in steels was established instead of synchrotron radiation, which was to promote the research of controlling the inclusions modification evolution of characterizing inclusions using X-ray microscopy. The proposed method provided more accurate and reliable analytical and testing approaches for the control of inclusions.

As an advanced means of micro and nano processing, the focused ion beam technology has a wide application prospect in the steel industry. In this paper, 82A cord steel billets and 55SiCr spring steel billets were selected as the test materials. A series of slicing and three-dimensional (3D) reconstruction of the composite inclusions were performed using the focused ion beam(FIB). It was found that there were some factors having adverse effects on the results in the 3D reconstruction process, such as method calibration and phase contrast differences. The results showed that the problems of distortion of reconstructed morphology and large deviation of size determination could be solved by introducing the offset calculation formula. Moreover, the reconstruction possibility of phases with insignificant differences in phase contrasts was realized by introducing energy dispersive spectroscopy mapping analysis in the series slicing process, which effectively solved the difficulties encountered in the current 3D reconstruction process and made the reconstruction results better support the project of research and development.

The solid waste resource regeneration is crucial for achieving the goals of "carbon peaking and carbon neutrality" and "zero-waste city construction", and it is also a key link in comprehensively promoting the achievement of a beautiful China. Zinc oxide concentrate (ZnO-C) is a mixture mainly containing ZnO obtained by pyrometallurgical volatilization and enrichment of Zn-containing solid waste. The impurities include metallic elements (such as iron, aluminum and calcium) and nonmetallic elements (such as fluorine, chlorine, silicon and sulfur). ZnO-C is powder-like with color of grey and black, and it is a typical waste resource utilization product. The quality of ZnO enrichment by pyrometallurgical method is different due to the difference of raw material components and technology level. In this study, the typical regeneration ZnO-C enriched material was focused on. The raw material components, enrichment process and technical parameters of pyrometallurgical enrichment were investigated. The production process and main physicochemical characteristics of ZnO-C were systematically discussed. Given that the composition of ZnO-C was crucial for subsequent processing and utilization, the content of ZnO phase as well as the composition and content of other phases in typical ZnO-C were also paid attention to. The accurately analysis and identification of ZnO-C was the key to port supervision of imported renewable resources and a prerequisite for achieving resource utilization.

Selenium (Se) is an amphoteric non-metallic element. As one of the essential trace elements for human body, the insufficient or excessive intake of Se will be harmful to human health. As the material basis for human survival, soil is the most fundamental source for people to obtain Se from the outside world. Therefore, it is of great practical significance to establish a highly sensitive and accurate method for the detection of Se in soil and stream sediments. Due to the characteristics of simple analysis operation, high sensitivity, fast analysis speed and low operating cost, the hydride generation-atomic fluorescence spectrometry (HG-AFS) is widely used for the determination of Se. However, the pretreatment method, light source and coexisting elements may interfere with the determination of Se, affecting the test results. In this paper, the sources and causes of the interference of Se in soil and stream sediments by atomic fluorescence spectrometry were focused on. The research and application progress of Se interference elimination were summarized and discussed. Moreover, the future development direction of hydride generation-atomic fluorescence spectrometry in the determination of Se in soil and stream sediments were prospected.

Platinum and palladium are precious metal elements with high price. The contents of platinum and palladium in crude selenium is an important indicator for trade settlement, so it is of great significance to accurately determine the contents of platinum and palladium in crude selenium. In this study, a method for the determination of platinum and palladium in crude selenium by inductively coupled plasma atomic emission spectrometry (ICP-AES) after selenium volatilization with perchloric acid was established. The samples were dissolved in aqua regia. The interference of selenium matrix was eliminated by perchloric acid smoke to volatilize the selenium. Pt 265.945 nm and Pd 360.955 nm were used as the analytical lines for the determination in the medium of 10% aqua regia. The results showed that 1.0 g of sample could be completely dissolved by adding 15 mL of aqua regia. Most of the selenium matrix could be removed by adding 10 mL of perchloric acid for volatilization at high temperature. A small amount of residual selenium matrix and other coexisting elements had no interference with the measurement. The weighing method was adopted during whole test to reduce the personal error and measurement instrument error caused by volume calculation method. The content of platinum and palladium in range of 0.02-15.0 μg/g was linear to the corresponding intensity. The correlation coefficients were 0.999 93 and 0.999 98, respectively. The limits of detection for platinum and palladium were 0.000 094% and 0.000 11%, and the limits of quantification were 0.000 31% and 0.000 33%, respectively. The experimental method was used to determine platinum and palladium in crude selenium, the relative standard deviations (RSD, n=7) were less than 5%. The measured results were consistent with those obtained by oxidizing roasting-lead fire assay-ICP-AES. The precision and trueness were superior to the conventional volume calculation method. The recoveries of platinum and palladium in crude selenium sample were 98%-105% and 99%-104%, respectively.

The accurate determination of iron in copper concentrate will affect the pricing and transaction of copper concentrate, the regulation of slag pattern in melting process, and the heat effect of smelting furnace. In this study, the sample was decomposed by hydrochloric acid, nitric acid, bromine, and sulfuric acid. Matrix copper in sample was converted into copper (Ⅱ), which was used as the reduction end-point indicator of iron (Ⅲ) as well as the catalyst of iron (Ⅲ) reduction. Iron (Ⅲ) was reduced to iron (Ⅱ) with potassium borohydride in sulfuric acid medium. Then the method for determination of iron content in copper concentrate by potassium dichromate titration was established using sodium diphenylamine sulfonate as the indicator. In experiments, 0.20 g of sample was dissolved with 0.1 g of ammonium bifluoride, 10 mL of hydrochloric acid, 5 mL of nitric acid, 0.5 mL of bromine, and 10 mL of sulfuric acid (1+1). After sulfuric acid smoke until the volume of solution was 1 mL, the acidity of potassium borohydride reduction process could be ensured. Copper (Ⅱ) in test solution had a catalytic effect on the reduction of iron (Ⅲ) by potassium borohydride, and it had no interference with the determination of iron. When the concentration of potassium borohydride was 20 g/L, iron (Ⅲ) could be effectively reduced to iron (Ⅱ), and meanwhile, it did not affect the determination of iron. The titration endpoint was clear when the amount of sulfuric acid and phosphoric acid mixture was 15 mL. The interference tests indicated that the interference of coexisting elements in sample with the determination of iron could be ignored. The copper concentrate reference materials and actual samples with different contents of copper were selected, and the content of iron was determined according to the experimental method. The relative standard deviations (RSD, n=7) of the determination results were between 0.20% and 0.55%. The national standard method GB/T 3884.15-2014 was used for method comparison,the t-test was conducted on the measurement results of the two methods, and the results showed that there was no significant difference between the two methods.The proposed method could be used for the rapid analysis and determination of iron content in copper concentrate in large quantities in smelting enterprises.

The test of alkaline value can be used to evaluate the content of alkaline additives in engine oil, and it is one of important indicators for evaluating the performance of engine oil. In this study, the dissociation constants of 20 types of engine oils were introduced into the Henderson-Hasselbalch equation. By combining with the Nernst equation, the theoretical endpoint pH values of different engine oils were calculated. The statistical analysis was conducted using the robust statistical algorithm A in statistics, and it was found that the endpoint pH value applicable for all engine oils was -4.5. A method for determining the alkaline value of engine oil by pH potentiometric titration was established using the mixture of acetic acid and chlorobenzene as the solvent and using the mixture of perchloric acid and acetic acid as the titrant. The limit of detection of this method was 0.004 1 mg KOH/g. The standard substance of alkaline engine oil was diluted with base oil that contained no alkaline substances. After well mixing, the blank spiked samples with alkaline content of 2, 5, and 20 mg KOH/g were prepared and determined according to the experimental method. The relative standard deviations (RSD, n=6) of the measurement results were between 0.60% and 1.2%, and the recoveries of blank spiked samples were between 99% and 102%. Various engine oil Petroleum Product Alkalinity Determination Method (Perchlorate Potentiometric Titration Method) was used for method comparison. The results showed that the difference between the two methods was within the repeatability limit required by the industry standard SH/T 0251-1993. Four standard substances of engine oil with different alkaline levels were selected and determined according to the experimental method. The test results were within the range of standard deviation, and the RSDs (n=6) were between 0.37% and 0.81%. The proposed method was applied for the determination of five types of engine oil samples, and the RSDs (n=10) of measurement results were less than 1%.

The presence of oxygen and nitrogen impurities will seriously affect the performance of high purity copper. In this study, the sample surface was treated with lathe finishing followed by acid corrosion. Under the condition without flux, a method for the determination of trace oxygen and nitrogen in high purity copper by inert gas fusion-infrared absorption/thermal conductivity was established. The analytical power was 4 500 W. The effect of three surface treatment methods, including acid corrosion, lathe finishing, and lathe finishing followed by acid corrosion, on the determination of oxygen and nitrogen was investigated. The results showed that the influence of three surface treatment methods on the determination of nitrogen could be ignored. However, for the determination of oxygen, the determination results of lathe finishing followed by acid corrosion were much lower than those obtained by other two methods, indicating that the method of lathe finishing followed by acid corrosion could effectively remove the oxygen on sample surface. The certified reference materials of copper with low mass fraction as possible were selected to calibrate the analyzer for the determination of oxygen and nitrogen. The limits of quantification were 0.17 μg/g and 0.31μg/g for oxygen and nitrogen, respectively. The contents of oxygen and nitrogen in high purity copper sample were determined for seven times according to the experimental method. The results showed that the standard deviation (SD, n=7) of oxygen measurement values was 0.13-0.19 μg/g, and the SD (n=7) of nitrogen measurement values was 0.062-0.070 μg/g. The content of oxygen was also determined by glow discharge mass spectrometry (GD-MS) for method comparison. The measurement results of two methods were basically consistent. The high purity copper sample was selected and determined according to the experimental method. In addition, the certified reference material of copper was added for the spiked recovery test. The results showed that the recoveries of oxygen and nitrogen were between 80% and 120%.

Silicon carbide deoxidizer is a kind of high-performance complex deoxidizer. The determination of titanium content can trace the elemental introduction and loss in smelting process, thus more effectively improving the properties of steel. The composition of silicon carbide deoxidizer is complicated. In this study, the sample was treated by melting at high temperature. Sodium carbonate and sodium peroxide were used as mixed flux. The nickel crucible containing sample and mixed flux was heated in high-temperature furnace at 400 ℃. Then the temperature was increased to 900 ℃ and kept for 30 min to melt the sample. After complete fusion, the sample was leached with hot water and acidified with hydrochloric acid. After dilution to the mark, the solution was filtered. Ti 334.941 nm was selected as the analytical line for titanium. The calibration curve was plotted by matrix matching method. The content of titanium in filtrate was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Consequently, the determination of titanium in silicon carbide deoxidizer was established. The linear correlation coefficient of calibration curve for titanium was above 0.999 9. The limit of detection was 0.000 5% (mass fraction). The content of titanium in silicon carbide deoxidizer sample was determined according to the experimental method, and the relative standard deviation (RSD, n=7) of measurement results was 2.0%. The spiked recoveries were between 98% and 102%. The contents of titanium in seven silicon carbide deoxidizer samples were determined according to the experimental method and spectrophotometry in national standard GB/T 16555-2017. The results were consistent.

The accurate determination of iron content in lanthanum cerium carbonate is of great significance for quality control and subsequent application of its products. The content of iron in lanthanum cerium carbonate is commonly measured by spectrophotometry. However, when the iron content was low (below 0.3%), the color change was not obvious in the determination. Moreover, the coloring process is very easily affected by other impurity ions. In this study, the sample was dissolved with hydrochloric acid, and its acidity in solution was controlled at 2%. Fe 259.939 nm was selected as the analytical line for iron. The calibration curve was prepared by standard addition method to eliminate the influence of factors such as lanthanum cerium carbonate matrix on the determination results. The content of iron in lanthanum cerium carbonate was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The linear correlation coefficient of calibration curve was 0.999 9. The limit of detection of the method was 0.001%. The content of iron in lanthanum cerium carbonate was determined according to the experimental method. The relative standard deviations (RSD, n=11) of the measurement results were between 1.3% and 3.3%, and the spiked recoveries were between 98% and 103%.

The content of CaF₂ in cassiterite and lead zinc sulfide co/associated fluorite is in range of 1%-50% (mass fraction, the same below). However, the current industry standard method is applicable for fluorite samples with CaF₂ content higher than 3%. There is an empirical correction coefficient of 0.30% in industry standard methods, so the accuracy of CaF₂ determination results below 10% is not high. In this study, acetic acid (1+9) was used to separate and remove calcium containing impurities such as CaCO₃ and CaSO₄ that are easily soluble in acetic acid. Then the content of F^- which was slightly soluble in the filtrate was determined by ion selective electrode method. The residue was extracted using AlCl₃, and In was selected as the internal standard element. The content of Ca in the extraction solution was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results of two methods were converted into CaF₂ and then added together to obtain the CaF₂ content in fluorite. Therefore, a method for the determination of calcium fluoride in cassiterite and lead zinc sulfide co/associated fluorite by ion selective electrode combined with ICP-AES was established. The effects of AlCl₃ solution mass concentration, AlCl₃ solution extraction time, and the selection of Ca and its internal standard element spectral lines on the determination of Ca were investigated. The limit of detection of CaF₂ in the method was 0.010%, and the limit of quantification was 0.040%. The contents of CaF₂ in actual samples of cassiterite, lead zinc sulfide, and fluorite certified reference material were determined according to the experimental method. The relative deviations (RSD, n=6) of the measurement results were between 0.22% and 0.90%, and the relative errors (RE) were between 0.08% and 0.63%. The method solved the problem of empirical correction coefficient in the CaF₂ determination process. The internal standard method was employed in ICP-AES to eliminate the impact of instrument drift caused by environmental temperature fluctuations and changes in electronic component performance on the analysis results. The measurement range of the proposed method was effectively improved, and it could be used for the determination of CaF₂ in cassiterite and lead zinc sulfide co/associated fluorite.

A special zinc sulfate solution has appeared in the raw material procurement market for wet zinc smelting. Such zinc sulfate solution contains high contents of manganese and aluminum, which will cause interference with the determination of zinc content, seriously affecting the determination results. In this study, the zinc sulfate solution containing high content of manganese and aluminum were treated for precipitation separation of manganese in solution. Then, excessive EDTA was added to complex zinc and aluminum in acetate-sodium acetate buffer solution. The excess EDTA was titrated with zinc standard solution to obtain the total amount of EDTA that was used to complex zinc and aluminum. The Al-EDTA complex was then decomposed with ammonium fluoride, and the released EDTA was titrated with zinc standard solution. The content of zinc in zinc sulfate solution could be indirectly measured by subtracting the amount of Al-EDTA complex released EDTA from the total amount of EDTA. The contents of zinc in three high-manganese and high-aluminum zinc sulfate solution samples were determined according to the experimental method. The relative standard deviations (RSD,n=11) of measurement results were between 0.27% and 0.29%, which was less than the 0.30% required in general titration operations. The recoveries were between 95% and 101%.