Nb Oxide Research Articles

Analysis of surface roughness and oxidation of FeNi-based metal amorphous nanocomposite alloys

We report on a systematic investigation of newly developed (Fe 70 Ni 30 ) 80 Nb 4 B 14 Si 2 metal amorphous nanocomposites (MANCs) and the factors affecting their surface roughness, including oxide formation and phase evolution during the nanocrystallization process. Analysis of surface roughness using atomic force microscopy (AFM) revealed an average roughness of 9.33 nm after heat treatment compared with as-cast amorphous ribbons, which exhibited a roughness of 4.21 nm. A surface oxide layer thickness has been determined using X-ray photoelectron spectroscopy (XPS). For samples annealed at 400 °C for 1 h, 450 °C for 1 h, and 550 °C for 3 h in air, the average surface oxide layer thickness was determined to be 10.9, 11.7, and 54.4 nm, respectively. It was observed that oxygen is enriched at the outermost surface and decreases rapidly as the XPS sputtering depth increases. Fe-oxide appeared as a predominant metal oxide at the top surface, followed by the presence of Nb oxide. A boron content increase was observed at the interface between the top surface oxide layer and the bulk of the sample. A protective surface oxide layer on FeNi-MANCs, such as observed in this work, can provide sufficient electrical insulation to reduce interlaminate eddy current losses and lower overall losses in magnetic components. • Surface roughness and oxidation of FeNi-based metal amorphous nanocomposites. • Surface roughness in amorphous ribbon using atomic force microscopy (AFM). • Crystallization and activation energies in metal amorphous nanocomposite ribbons. • Phase fractions in metal amorphous nanocomposite ribbons. • Surface oxides partitioning in amorphous and nanocrystalline alloys.

Effect of Zr content on the physicochemical, electrochemical, and biological properties of Ti80Nb20-based alloys

The β-Ti alloys have become very attractive in the area of biomedical materials due to their corrosion resistance, biocompatibility, and low elastic modulus as compared with other materials. In this context, the Ti-Nb-Zr ternary system has gained more interest because Zr acts as secondary β-Ti stabilizing element when it is added together with β-stabilizing element such as Nb or Mo. According to the d-electron theory, the higher the Zr content, the lower elastic modulus values are obtained, which would allow to produce alloys with low elastic modulus, corrosion resistance, and shape memory. However, determining the ideal amount of Zr in a Ti-Nb-Zr alloy is still a matter of investigation. In this work, alloys with a nominal chemical composition of Ti80−x-Nb20-Zrx (x = 5, 10, 20, 30, and 40 at%) were produced by electric arc casting. The results show that the addition of Zr causes a decrease in both the elastic modulus and the hardness of the molten alloys, reaching values of 50.5 GPa for a sample with 40 at% Zr. The increase in the Zr content caused a microstructural difference between the phases, and the α” phase was detected for the Ti80Nb20, Ti75Nb20Zr5, and Ti60Nb20Zr20 alloys. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the environment influences the Ti-Nb-Zr surfaces, showing the growth of oxide layers, mainly Ti, Zr and, to a lesser extent, Nb oxides. All alloys with different Zr amounts showed wide passivation regions and no sign of pitting in the potential range that is characteristic of the human body. The Ti-Nb-Zr alloys showed good compatibility in cell growth tests, with the best results for the 20 at% Zr alloy, and a decrease in biocompatibility for higher Zr amounts due to reactions of Zr4+ with body fluids.

In Vitro and Electrochemical Characterization of Laser-Cladded Ti-Nb-Ta Alloy for Biomedical Applications

Titanium (Ti) and its alloys are predominant choices for use as biomaterials in human implants. Research has shown the adverse effects of using commercial Ti alloy Ti-6Al-4V in the human body, and this presents a need for viable alternatives. In this study, Ti alloy Ti-17Nb-6Ta was manufactured by laser cladding—a prominent additive manufacturing (AM) technology. Laser cladded specimens were evaluated for their in vitro and electrochemical behavior. A human osteosarcoma cell line (MG-63 cells) was used for in vitro investigations. Cell proliferation was good in the physiological medium, and cells were alive when in contact with the laser cladded alloy, even after two to three weeks, indicating good cell viability and compatibility with this alloy. Electrochemical characterization was carried out in Ringer’s solution, and noticeably lower corrosion current density and corrosion rate values were observed. The lower amounts of these parameters indicated the passivation behavior due to multi-layer Ti, Nb, and Ta alloy oxide films. These oxide films also enhanced osseointegration. Thus, the Ti-17Nb-6Ta alloy can be an ideal biocompatible alternative to Ti-6Al-4V.

Long‐Term Operation of Nb‐Coated Stainless Steel Bipolar Plates for Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolysis (PEMWE) is the most promising technology for green hydrogen production using renewable electricity, but it is expensive due to the Ti bipolar plates (BPPs). Herein, a PEMWE stack with coated stainless steel (ss) BPPs (Nb/Ti/ss‐BPP and Nb/ss‐BPP) is reported, which operates for about 14 000 h at 1.63 ± 0.12 A cm−2 and 65 °C. The average degradation rate is as low as 1.2% or 5.5 μV h−1. Scanning electrode microcopy reveals no signs of corrosion of the ss beneath the coatings. The interfacial contact resistance increases due to the formation of poorly conductive amorphous Nb oxides, as shown by atomic force microscopy and X‐Ray photoelectron spectroscopy, although it does not affect the cell performance. The results prove that Ti is not needed anymore as base material for manufacturing the BPPs, thus the cost of PEMWE can be significantly reduced.

Corrosion in Cr-Fe-Co-Ni-Nb hypoeutectic and hypereutectic high entropy alloys

In this paper, corrosion behavior and corresponding mechanism of CrFeCoNiNbx high entropy alloys (HEAs) with hypoeutectic (x = 0.38) and hypereutectic (x = 0.54) structures were systematically investigated. It is found that both HEAs have FCC + Lave dual-phase structure. Similar corrosion behavior could be observed on these HEAs during electrochemical polarization in 3.5 wt% NaCl solution at room temperature, and the hypereutectic HEA shows slightly higher corrosion resistance compared to the hypoeutectic one. Moreover, there are large proportions of Cr+Nb oxides with no significant difference in concentration in the passive films of these HEAs, which has close correlation with their high and similar corrosion resistance. This work provides a novel insight into better understanding of the corrosion mechanism in the Cr-Fe-Co-Ni-Nb HEAs, which is beneficial for their further applications.

Microstructural understanding of general and localized corrosion of Fe13Cr4Al2Mo1.2Nb alloy in high temperature aerated water and superheated steam

The corrosion behaviors of a Fe13Cr4Al2Mo1.2Nb alloy in 360 °C aerated water and 400 °C superheated steam were investigated. A similar dual-layered oxide scale was formed under both conditions. However, the inner oxide layer was much thicker in 400 °C steam than in 360 °C water, indicating the occurrence of steam-accelerated corrosion. Nodular corrosion was observed following exposure to 360 °C water, while localized corrosion and Ni segregation along the grain boundary occurred after 120-d exposure to 400 °C steam. The Fe2Nb phase experienced delayed oxidation with respect to matrix, which involved transformation from amorphous Nb oxides to crystalline Nb2O5.

Improved Performance of Li-Added Mo–Nb Oxide as the Anode for Li-Ion Batteries with N-Carbon Coating

Improved Performance of Li-Added Mo–Nb Oxide as the Anode for Li-Ion Batteries with N-Carbon Coating

Caustic potash assisted roasting of the Nigerian ferro-columbite concentrate and guanidine carbonate-induced precipitation: A novel technique for extraction of Nb–Ta mixed-oxides

The current study focuses on alkali-assisted roasting, dissolution, and recovery of mixed oxides of niobium (Nb) and tantalum (Ta) from a ferro-columbite concentrate collected from Jos Plateau in Nigeria. Alkali-assisted roasting and water-based leaching to extract Nb and Ta using guanidine carbonate salt were adopted for sustainable extraction. The concentrate was roasted with caustic potash (KOH) as flux at optimized conditions (250 °C, 100% mass flux-to-concentrate ratio, 1 h) and leached with water. This resulted in dissolution of 97-96% Nb, 80-96% Ta, 92-91% W and 64-65% Mn for −250 and + 250 μm size fractions respectively while leaving behind in the residue most of Sn (94-83%) and Fe (79-81%). The amount of Nb and Ta dissolved were selectively recovered with novel application of guanidine carbonate salt as precipitating agent. High extraction yield (∼100%) was achieved. The final recovery of approximately 96% Nb and 85% Ta contained in the +250 μm concentrate feed sample was obtained under optimum conditions of 50 mg/mL guanidine. The (Nb,Ta)-guanidine precipitate obtained was then calcined at 900 °C for 1 h and converted into mixed (Nb,Ta)2O5 (97%) and removed the guanidine. Based on material balance, it was found that approximately 734.5 kg of (Nb,Ta)-guanidine precipitate with purity higher than 84% could be obtained from one tonne of ferro-columbite feed concentrate. The current technique of alkali-assisted roasting, dissolution, and recovery of mixed oxides of Nb and Ta is a novel process and presents an environmentally benign, and it is an efficient technique to replace the traditional method which uses an environmentally harmful hydrofluoric acid to extract Nb and Ta.

Beneficiation of Nb and Ti carbides from pyrochlore ore via carbothermic reduction followed by magnetic separation

Beneficiation of niobium and titanium carbides from pyrochlore ore via carbothermic reduction followed by magnetic separation was investigated in this work. During carbothermic reduction, Nb, Ti and Fe oxides within the pyrochlore ore could be reduced into NbC, TiC and metallic iron, respectively. The carbides gather around and dissolve into the metallic iron grains, enabling the enrichment of niobium and titanium carbides by magnetic separation with the carrier of metallic iron. Under the optimal conditions: coke dosage of 6%, reducing temperature of 1400 °C and time of 120 min, a magnetic concentrate with 4.18% Nb, 4.60% Ti and 70.57% Fe can be obtained followed by wet magnetic separation. The corresponding recoveries of Nb, Ti and Fe were 70.5%, 59.8% and 92.6%, respectively.

A Unique Nanoflake‐Shape Bimetallic Ti–Nb Oxide of Superior Catalytic Effect for Hydrogen Storage of MgH2

MgH2 is one of the most promising solid hydrogen storage materials due to its high capacity, excellent reversibility, and low cost. However, its operation temperature needs to be greatly reduced to realize its practical applications, especially in the highly desired fuel cell fields. This work synthesizes a 2D nanoflake-shape bimetallic Ti-Nb oxide of TiNb2 O7 , which has high surface area and shows superior catalytic effect for the hydrogen storage of MgH2 . Incorporated with the TiNb2 O7 nanoflakes as low as 3 wt%, MgH2 shows a low onset dehydrogenation temperature of 178 °C, which is lowered by 100 °C compared with the pristine one. A dehydrogenation capacity as high as 7.0 wt% H2 is achieved upon heating to 300 °C. The capacity retention is as high as 96% after 30 cycles. The mechanism of the improved hydrogen storage properties is analyzed by density functional theory (DFT) calculation and the microstructural evolution during dehydrogenation and hydrogenation. This work provides an MgH2 system with high available capacity and low operation temperature by a unique structural design of the catalyst. The high surface area feature of the TiNb2 O7 nanoflakes and the synthesis method hopefully can develop the application of TiNb2 O7 .

Construction of heterojunctions CeO2 interfaced Nb, Sn, Ti, Mo and Zn metal oxide catalysts for photocatalytic oxidation of α-pinene inert C-H

• Heterojunctions CeO 2 -M (M = Zn, Ti, Sn, Mo, Nb) metal oxides catalysts are synthesized by sol–gel method. • CeO 2 -M catalysts show varying photoactivity for oxidation of α-pinene to aroma oxygenates. • CeO 2 -Mo shows the best photocatalytic performance for α-pinene conversion and selectivity to pinene oxide. • The contribution from interfaced redox, oxygen vacancies, and efficient separation of e - /h + are accountable for the enhanced photoactivity of CeO 2 -M catalysts than CeO 2 . • Pinene oxide is obtained with up to 64% selectivity at 66% α-pinene conversion within 5 h of reaction irradiation time. Construction of heterojunctions semiconductors provide an improvement in photo-optics for light absorption, photo carriers generation, and transfer for their efficient utilization in redox reactions. Herein, heterostructured CeO 2 catalysts containing Ti, Mo, Nb, Sn and Zn oxides nanostructures are synthesized and evaluated for their photoactivity in α-pinene selective oxidation using acetonitrile solvent at 25 °C reaction temperature. Both conversion and selectivity are affected by the nature of the hetero-interfaced metal oxide to CeO 2 . CeO 2 -Mo shows the best photocatalytic performance to achieve pinene oxide selectivity of 64% at 66% of pinene conversion after 5 h of light irradiation. The enhanced photoactivity of CeO 2 heterostructured catalysts compared to CeO 2 is ascribed to their red-shift light absorption edges to visible region because of the two metal oxides interactions and structure modifications, which improved the e - /h + charge carrier’s generation and separation for their efficient transfer due to suppressed recombination. Importantly, the combination of redox nature of interfaced CeO 2 heterostructured catalysts and oxygen vacancies shows to be pivotal for the photocatalytic activity enhancement in the selective oxidation of pinene inert C-H bond.

The influence of Nb addition on the passivity of CoCrNiNb multi-principal element alloys

The effect of Nb addition on the passivation behavior of CoCrNiNbx (x = 0 ∼ 0.5) multi-principal element alloy (MPEA) were investigated with surface characterization and electrochemical techniques. With the addition of Nb, the Nb-riched HCP dendrite phase gradually precipitates from the original FCC phase. The corrosion resistance of CoCrNiNbx MPEAs increases firstly and then starts to decrease, reaching an optimal value at x = 0.2. XPS depth profiles and ToF-SIMS characterization of the surface passive films demonstrate that the film structure is transformed from a single layer to the bilayer which consists of a Cr-enriched outer layer and an Nb-enriched inner layer. Analysis of the pitting and passivation behavior of the CoCrNiNbx MPEAs suggests that a moderate content of Nb thickens the passive film, promotes the production of Nb oxides and Cr2O3, and thus stabilizes the passive film and finally reduces pitting sensitivity.

Study of cluster ions produced from ToF-SIMS analysis of a U-6%Nb target

Cluster ions have been previously observed during time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of metals and metal oxides. Here, we have used ToF-SIMS to investigate cluster ions formed from the hydrocarbon-containing overlayer, the mixed U and Nb surface oxide, and underlying metal of a U-6 %Nb (U6Nb) target. In the overlayer, we observe UxOy+ oxides and U-species likely containing hydrocarbons. In the surface oxide, we observe UO2+, U2O2+, U3O5+, and U4O6+ as the most intense ions for each family of oxide ions containing x U atoms. Nb oxides for NbO1-2- were only observed in negative polarity. In contrast to the oxide, analysis of the underlying U6Nb alloy resulted in repeating units of Un+, Un(Nb)+, and Un(Nb2) + ions for n = 3–11 as the highest intensity ions for each family of ions containing n U atoms. Nbn+ clusters were not observed. Un+, Un(Nb)+, and Un(Nb2)+ clusters containing C- and O-species were observed and were likely produced from soluble C or O species or precipitates known to be present in U6Nb.Cleaning of the surface oxide with varying ion current density of 25 keV 69Ga+ to perturb local chemistry did not influence ion distributions and suggests that observed high intensity ions are stable lattice fragments ejected from the surface oxide. Cleaning of the underlying alloy with varying ion current density increased the content of Un+, Un(Nb)+, or Un(Nb2)+ clusters in comparison to the C and O-containing species. These results suggest a different mechanism of cluster ion formation than what was observed in the metal oxide. Preferential sputtering of U from the surface or low local Nb content may also contribute to the enrichment of U in observed clusters. We conclude that cluster ions may be of great value in studying local chemistry, contaminants, and impurities in oxides and alloys.

Investigative properties of CeO2 doped with niobium: A combined characterization and DFT studies

Abstract Catalytic capacity of ceria mainly stems from a facile switch in the Ce oxidation states from +4 to +4 − x. While various experimental and computational studies pinpoint the reduction chemistry of Ce atom through the creation of oxygen vacancies, the analogous process when ceria surface is decorated with cations remains poorly understood. Where such results are available, a synergy between experimental and first principle calculation is scarce. Niobium materials are evolving and their use in catalysis is being widely investigated due to their high surface acidity and thermal and chemical stability. This study aims to report structural and electronic properties of various configurations of mixed Ce–Nb oxides and elaborates on factors that underpin potential catalytic improvements. Evaluations of the samples through X-ray diffraction (XRD), Fourier transform infrared (FTIR), N2-adsorption–desorption, scanning electron microscope (SEM), energy dispersive spectroscope (EDS), and thermogravimetric (TGA) analyses are examined and discussed. First principles density functional theory (DFT) calculations provide structural features of the Ce–Nb solutions at low concentration of Nb via computing atomic charge distribution. Contraction in the lattice parameter after Nb doping was confirmed with both XRD and DFT results. SEM analysis reveals particle growth at the loading of 50 wt%. FTIR results established the Ce–Nb–O bond at 1,100 cm−1 and the TGA analysis confirms the thermal stability of Nb-doped ceria. Tetrahedral O atoms demonstrate an increase in electronegativity and this in turn facilitates catalytic propensity of the material because the O atoms will exhibit higher affinity for adsorbed reactants. Cerium oxide (CeO2) after Nb doping displays a noticeable band gap narrowing, confirming the possible improvement in the catalytic behavior. The 4d states of the Niobium pentoxide (Nb2O5) is found to fill up the 4f states of CeO2 around the Fermi energy level promoting electrons excitation in the CeO2. Reported electronic, structural, and thermal characteristics herein indicate promising catalytic applications of niobium-promoted ceria.

High temperature (800 °C) oxidation of AISI 441 stainless steel with Mn–Co contact layers for SOFC stacks

Characteristics of stainless steel grade AISI 441 deposited with Mn, Co and 10 wt% La0·6Sr0·4CoO3-δ (LSC) powder mixtures as cathode contact materials in solid oxide fuel cell (SOFC) stacks are studied. Microstructures of both uncoated and coated steel are examined after ageing at 800 °C for 10,000 h in air. It is found that the free surfaces of both uncoated and Mn–Co coated (Mn/Co ratio = 1:2 and 2:1) steel coupons suffer severe oxide scale spallation. In contrast, on the contact surfaces of uncoated coupons Mn–Cr–Fe spinels develop; and Mn–Co spinels grow on Mn–Co and Mn–Co-LSC coated (Mn/Co ratio = 1:1) coupons. Precipitates of Ti, Si and Nb oxides segregate at the steel/scale interface, weakening scale adherence. Area specific resistance (ASR) of steel/powder/La0·6Sr0·4Co0·2Fe0·8O3-δ (LSCF) assemblies is measured at 800 °C for 5043 h in air. The Mn–Co-LSC mixtures (Mn/Co ratio = 1:1 and 1:2) display close ASR values of 21–24 mΩ cm2, less than the value of 71 mΩ cm2 from the Mn–Co mixture (Mn/Co ratio = 2:1). This is attributed to the lower intrinsic resistivity of the derived Mn–Co oxides as well as good contact with steel and the LSCF wafer.

Influence of the Characteristics of Multilayer Interference Antireflection Coatings Based on Nb, Si, and Al Oxides on the Laser-Induced Damage Threshold of ZnGeP2 Single Crystal

In this work, the effect of the defect structure and the parameters of antireflection interference coatings based on alternating layers of Nb2O5/Al2O3 and Nb2O5/SiO2 layers on the laser-induced damage threshold of ZGP crystals under the action of Ho:YAG laser radiation at a wavelength of 2.097 μm was determined. Coating deposition was carried out using the ion-beam sputtering method. The laser-induced damage threshold of the sample with a coating based on alternating layers Nb2O5 and SiO2 was W0d = 1.8 J/cm2. The laser-induced damage threshold of the coated sample based on alternating layers of Nb2O5 and Al2O3 was W0d = 2.35 J/cm2. It has been found that the presence of silicon conglomerates in an interference antireflection coating leads to a decrease in the laser-induced damage threshold of a nonlinear crystal due to local mechanical stresses and the scattering of incident laser radiation.

Ten Thousand-Cycle Ultrafast Energy Storage of Wadsley-Roth Phase Fe-Nb Oxides with a Desolvation Promoting Interfacial Layer.

Developing advanced electrode materials with enhanced charge-transfer kinetics is the key to realizing fast energy storage technologies. Commonly used modification strategies, such as nanoengineering and carbon coating, are mainly focused on electron transfer and bulk Li+ diffusion. Nonetheless, the desolvation behavior, which is considered as the rate-limiting process for charge-storage, is rarely studied. Herein, we designed a nitridation layer on the surface of Wadsley-Roth phase FeNb11O29 (FNO-x@N) to act as a desolvation promoter. Theoretical calculations demonstrate that the adsorption and desolvation of solvated Li+ is efficiently improved at FNO-x@N/electrolyte interphase, leading to the reduced desolvation energy barrier. Moreover, the nitridation layer can also help to prevent solvent cointercalation during Li+ insertion, leading to advantageous shrinkage of block area and reduced volume change of lattice cell during cycling. Consequently, FNO-x@N exhibits a high-rate capacity of 129.7 mAh g-1 with negligible capacity decay for 10 000 cycles.

Role of nanoscale surface defects on Sn adsorption and diffusion behavior on oxidized Nb(100)

Nanoscale structural defects such as grain boundaries, atomic dislocations, and surface roughness inhibit the stoichiometrically homogeneous growth of Nb3Sn on Nb. This is a critical technological bottleneck for the implementation of next-generation Nb3Sn superconducting radio frequency cavities, as thin film inhomogeneities are known to degrade superconducting properties that are essential for reaching optimal cavity performance. To determine the influence of structural defects on Nb3Sn film growth, low and moderate surface defect densities were intentionally induced onto a (3 × 1)-O Nb(100) substrate, which serves as a model system to study atomic-scale Sn adsorption and diffusion. Scanning tunneling microscopy shows that, while initial Sn adsorption behavior at room temperature differs between the low and moderate defect density Nb(100) surfaces, the overall diffusion pathways at elevated temperatures are guided by the underlying oxide structure with variations resulting from increased nanoscale surface defects. The (3 × 1)-O Nb(100) surface with a moderate defect density also demonstrates enhanced Sn thermal stability, with the Sn desorption threshold occurring between 850 and 900 °C, approximately 50 °C higher than desorption from both the low defect density and pristine thin oxide surfaces. This suggests that structural surface defects may stabilize adsorbed Sn species on oxidized Nb at the elevated temperatures utilized in Nb3Sn alloy growth procedures. Auger electron spectroscopy shows no significant difference in surface composition following Sn deposition at varying coverages on the pristine and defect-induced (3 × 1)-O Nb(100) surfaces. This indicates that the surface and near-surface composition are not influenced by the presence of nanoscale surface defects despite slight attenuations in Sn diffusion pathways on defected substrates. These results provide the first in situ visualization of Sn adsorption and diffusion behavior on oxidized Nb at the nanoscale, revealing the significance of the underlying Nb oxide surface structure and defect density on Nb3Sn film growth and, ultimately, cavity performance.

Effect of annealing temperature on magnetic properties and corrosion resistance of Fe75.8Si12B8Nb2.6Cu0.6P1 alloy

Fe-based nanocrystalline alloys obtained through isothermal annealing of their amorphous counterparts have emerged as an indispensable soft magnetic material. The development of Fe-based nanocrystalline alloys with excellent soft magnetic properties and good corrosion resistance is highly desirable. In this study, the magnetic properties and corrosion resistance of Fe75.8Si12B8Nb2.6Cu0.6P1 alloys are investigated a function of the annealing temperature. Upon crystallization, the permeability (μ) and coercivity (Hc) of the alloy gradually improve with an increase in the annealing temperature owing to the formation of homogeneous and fine α-Fe(Si) grains. However, excessively high temperatures promote the precipitation of Fe2B and Fe23B6 phases, significantly deteriorating the soft magnetic properties. The alloy annealed at 843 K exhibits excellent magnetic softness with a high saturation magnetization of 1.41 T, a good μ of 2.7 × 104 at 1 kHz and a low Hc of 0.8 A/m. On the other hand, the corrosion resistance of the alloy is sensitive to the annealing temperature, and the higher the annealing temperature, the better the corrosion resistance will be. The improved corrosion resistance is due to the increase in the crystalline volume fraction resulting in the formation of an insoluble protective layer rich in Si and Nb oxides. This study further reveals the relationship between the annealing temperature and alloy properties and can facilitate the development of soft magnetic nanocrystalline alloys with good corrosion resistance.

Determination Of Silver In Geological Samples Using Aerosol Dilution ICP-MS After Water-Bath Extraction With Inverse Aqua Regia

A valid method for trace silver (Ag) detection in geological samples was developed in this study using aerosol dilution inductively coupled plasma-mass spectrometry after extraction with inverse aqua regia. This was proposed primarily to reduce the interference from Nb and Zr during mass spectrometric measurements. Almost 93% of Nb and Zr was removed after the extraction. By mixing an appropriate amount of Ar with the sample aerosol using an aerosol dilution system prior to plasma, the residual Nb oxides and Zr oxides or hydroxides could be successfully removed. The relative yields of the interfering oxides and hydroxides were as low as 0.087% (NbO/Nb) and 0.013% (ZrOH/Zr), which were 3–5 times lower than those in the traditional mode without the addition of Ar. Moreover, the signal-to-noise ratio of Ag was five times higher than that in the traditional mode. The proposed method was applied to the determination of Ag in 68 standard reference materials (SRMs) of soil, sediment, and rock. The results for 47 of these geological SRMs were in good agreement with the reference values. The Ag levels in three SRMs (GSP-2 Granodiorite, STM-2, and SGR-1b) are being reported for the first time herein. For these SRMs, 10 separate aliquots of the sample were digested and analyzed over a period of three months, and analysis revealed that the determined values were reasonable. Thus, the proposed method shows significant potential for the accurate determination of trace Ag in various geological samples.