稀土铌钽矿中铌、钽、锆量的电感耦合等离子-原子发射光谱法测定

本文研究了用电感耦合等离子-原子发射光谱(ICP-AES)法测定稀土铌钽矿中的铌、钽、锆。实验考察了不同溶样方法及其对样品的溶解程度,确定了称样量及其熔融物提取的方法,选择了分析线波长,确定了仪器工作条件,考察了共存元素的干扰情况。对方法的准确度及精密度进行了考察。本法测定Nb、Ta和Zr的线性范围分别为0.50~5.00μg/mL、0.10~1.00μg/mL和5.00~50.00μg/mL,对于0.050%~0.20%Nb2O5、0.010%~0.20%Ta2O5、0.50%~5.00%ZrO2测定的相对标准偏差均小于7%。     

Determination of Nb, Ta, Zr and Hf in Micro-Phases at Low Concentrations by EPMA

 Depletion of high field strength elements (HFSE: Nb, Ta, Zr, Hf ) relative to other lithophile trace elements in arc magmas and variations of Nb/Ta and Zr/Hf ratios in mantle-derived rocks can be addressed through studies of minerals, which concentrate and fractionate these elements. The presence of rutile, a common accessory Ti-oxide phase in various mantle rocks, has often been invoked to explain the Nb and Ta depletion in arc lavas because it has the highest HFSE abundances among the known mantle minerals. In this study, we measure the concentrations of Nb, Ta, Zr and Hf (at > 200 ppm) in rutile of two metasomatized mantle lherzolites using a Cameca SX-100 electron microprobe and obtain Nb/Ta ratios with an accuracy of about ± 5%. Mass balance calculations indicate that ≤ 1−5% of Nb and Ta in the rocks reside in major minerals and that the balance is hosted by accessory Ti-oxides. The Nb/Ta ratios vary significantly in nearby rutile grains in both peridotites (17–33, average 23; 12–37, average 21). Therefore, individual rutile grains may not be representative of the total grain population. However, Nb/Ta ratios measured in the bulk rock lherzolites by solution ICP-MS (21 ± 0.3) are within the analytical error of the average Nb/Ta values calculated for 5–7 rutile grains in both samples. These results emphasise that a representative grain selection must be analysed in order to determine trace elements contents of bulk rocks from data on accessory phases.     

Preconcentration of Zr, Hf, Nb, Ta and W in seawater using solid-phase extraction on TSK-8-hydroxyquinoline resin and determination by inductively coupled plasma-mass spectrometry

Here, we present the first simultaneous preconcentration and determination of ultratrace (pmol kg⁻¹ level) Zr, Hf, Nb, Ta and W in seawater, both in the form of dissolved and acid-dissolvable species. 8-Hydroxyquinoline (8HQ) bonded covalently to a vinyl polymer resin, TSK-8HQ, was used in a chelating adsorbent column to concentrate the metals. The greatest advantage of this resin is its endurance to 5 M HF, since this is an effective eluent for all five metals. The analytes were successfully concentrated from 250 mL seawater with a 50-fold concentration factor through the column extraction and evaporation. The detection limit was 0.009-0.15 pmol kg⁻¹. The procedure blank determined using ultra pure water as a sample was 0.005-0.37 pmol kg⁻¹. The five metals were quantitatively recovered from seawater with good precision (2-4%). The effect of sample pH, sample flow rate, eluent composition and sample pretreatment were carefully studied. This method was applied to seawater.     

Group separation by solvent extraction from silicate rock matrix of Nb, Mo, Ta, and W at low levels for ICP-MS

Summary The extraction efficiency from silicate rock solutions in HF of Nb, Mo, Ta, and W as a function of fluoride activity in HCl solution, 3 mol/l, was investigated. At pF 3.5, N-benzoyl N-phenylhydroxylamine (BPHA) dissolved in CHCl₃ proved to be an ideal system for the separation of the four analyte elements from the rock matrix after HF dissolution. All major rock constituents except for titanium are left behind in the aqueous phase. Values for the distribution ratios are 500±100 for all four elements allowing cross calibration in ICP-MS between enriched isotopes of Mo and W added to the samples before dissolution (isotope dilution) and the neighbouring monoisotopic elements Nb and Ta. Previously such high distribution ratios have been reported for Mo only because Nb, Ta, and W are not normally available as reactive ions due to hydrolysis unless directly released from fluoride complexes by downwards adjustment of fluoride activity of the solution in the presence of BPHA. Analytical data from 20 geochemical reference standards document the practical value of the described analytical procedure. Using ICP-MS and BPHA-pentanol solutions standards, superior detection limits are demonstrated by Nb, Ta, and W values in the sub ppm range obtained for some ultrabasic rock standards for which reference values are not yet available. Using ICP-MS and BPHA-pentanol solutions, superior detection limits are demonstrated by concentration values in the sub ppm range obtained for some ultrabasic rock standards for which reference values are not yet available.     

A modified method for the determination of uranium in Nb/Ta minerals by LED fluorimetry

A modified LED fluorimetry determination of uranium in Nb/Ta minerals has been developed. The mineral is brought into solution by fusion with mixed phosphate flux (NaH₂PO₄, H₂O and Na₂HPO₄). Iron quenches uranium fluorescence when it is present above the ratio of (iron to uranium) 100. Uranium is separated in ethyl acetate by solvent extraction and then stripped back into pyrophosphate buffer (pH ~ 7) prior to its LED fluorimetry determination. This modified method has been applied for the determination of uranium in synthetic mixtures and Nb/Ta minerals including Certified Reference Materials (X1807) with high degree of accuracy and precision.

     

Determination of V(V), Nb(V) and Ta(V) as their 2-(5-nitro-2-pyridylazo)-5-diethylaminophenol complexes by reversed-phase high performance liquid chromatography

A method for the reversed-phase liquid chromatographic separation and determination of V(V), Nb(V) and Ta(V) as 2-(5-nitro-2-pyridylazo)-5 diethylaminophenol (5-NO₂-PADAP) complexes is reported. The metal complexes were eluted in 9 min with a mobile phase of methanol-water (54 : 46, v/v) containing 10 mmol L^–1 acetate buffer (pH 3.0) on an ODS column. The detection limits for V, Nb and Ta were 0.09, 0.13 and 1.41 ng mL^–1, respectively, with S/N=3. The analysis of a reference sample of a mineral is discussed. The results corresponded to the certified values, and recoveries of 98.3–101.4% have been obtained.     

Determination of Fe, Ni and V in asphaltene by ICP OES after extraction into aqueous solutions using sonication or vortex agitation

A simple procedure for the extraction of Fe, Ni and V from asphaltene into acid solutions prior to the ICP OES determination is proposed. Either sonication or vortex agitation was used to disperse the organic sample into concentrated nitric acid, achieving efficient analyte extraction into the aqueous acid solution. Both procedures were compared and the advantage of the ultrasound-assisted procedure was evaluated. In both cases, pre-heating of sample–acid mixtures was necessary to enable quantitative extractions. Optimized conditions for the ultrasonic bath were established: 1 L of water at room-temperature, 20 min of sonication and tubes (maximum of eight) in vertical position. By using the vortex, 50 min of vigorous mechanical agitation was needed for each one of the tubes containing samples. The acid solution obtained after extraction was directly aspirated into the ICP in order to perform quantification by optical emission. Calibration was made with aqueous analyte standards containing Sc as internal standard. The procedures were tested using certified fuel oil (SRM NIST 1634c) and the method was applied for the determination of Fe, V and Ni in one asphaltene sample obtained by the fractionation of the SRM NIST 1634c. Recoveries above 90% were achieved and limits of quantification in the asphaltene sample were 1.5, 15 and 1.0 μg g^− 1 estimated for Fe, Ni and V, respectively.     

双显色双波长分光光度法研究——铌和钽的高灵敏同时测定

本文选择SAF和5Br-PADAP两个显色体系构成显色体系对,建立双显色双波长分光光度法。可不经分离,同时高灵敏地测定铌和钽,应用在合金钢分析中获得满意的结果。     

Determination of Ta impurities in Nb samples by X-rays in neutron activation analysis

Ta impurities in Nb samples have been determined by X-rays in 14 MeV neutron activation analysis. For X-ray detection, (HP) Ge detector with Be-window is used. The sensitivity of the determination has been found to be about 30 g (in Nb).This work was supported by the National Foundation for Research (Contract No. 259).     

Electronic Structure Research on Lattice Stability of V,Nb, and Ta by Density Functional Theory

The difference of energy and electronic structure of V, Nb, and Ta in different crystalline structures were investigated by different methods in density functional theory (DFT). Latticeconstants, total energies, and densities of states of these metals were calculated using the plane-wave pseudopotential method in DFT. Results were compared with those of projector augmented wave method, CALPHAD method, and experiments. Total energy and electronic structure analyses showed that valence electrons mostly transferred from s to p or d state, changing obviously with both the crystal structure and the elemental period number from V to Ta and leading to stronger cohesion, higher cohesive energy and more stable lattice of heavier metals.     

Tantalum,easy as Pi: understanding differences in metal–imido bonding towards improving Ta/Nb separations

The separation and purification of niobium and tantalum, which co-occur in natural sources, is difficult due to their similar physical and chemical properties. The current industrial method for separating Ta/Nb mixtures uses an energy-intensive process with caustic and toxic conditions. It is of interest to develop alternative, fundamental methodologies for the purification of these technologically important metals that improve upon their environmental impact. Herein, we introduce new Ta/Nb imido compounds: M(^tBuN)(TriNOx) (1-M) bound by the TriNOx³⁻ ligand and demonstrate a fundamental, proof-of-concept Ta/Nb separation based on differences in the imido reactivities. Despite the nearly identical structures of 1-M, density functional theory (DFT)-computed electronic structures of 1-M indicate enhanced basic character of the imido group in 1-Ta as compared to 1-Nb. Accordingly, the rate of CO₂ insertion into the M N_imido bond of 1-Ta to form a carbamate complex (2-Ta) was selective compared to the analogous, unobserved reaction with 1-Nb. Differences in solubility between the imido and carbamate complexes allowed for separation of the carbamate complex, and led to an efficient Ta/Nb separation (S_Ta/Nb = 404 ± 150) dependent on the kinetic differences in nucleophilicities between the imido moieties in 1-Ta and 1-Nb.

A selective separation of the critical metals tantalum and niobium was accomplished from π-bonding-based reactivity differences of imido complexes. New insights into Ta/Nb separations were gained through detailed kinetic and computational studies.     

溶胶-凝胶法制备高取向K(Ta,Nb)O3薄膜

K(Ta,Nb)O_3具有良好的电光特性、非线性光学特性和热释电特性.K(Ta,Nb)O_3薄膜在光电子集成电路中有着良好的应用前景.国外主要是进行K(Ta,Nb)O_3单晶和陶瓷的研究工作,近年来也有制备K(Ta,Nb)O_3薄膜的报导.我们采用溶胶-凝胶法制备KTa_(0.65)Nb_(0.35)O_3薄膜.制备过程如下:把Ta(OC_2H_5)_5,Nb(OC_2H_5)_5和K(OC_2H_5)溶于无水C_2H_5OH 中配成0.2     

Determination of zinc and copper in human hair by slurry sampling employing sequential multi-element flame atomic absorption spectrometry

The present work proposes a direct method based on slurry sampling for the determination of zinc and copper in human hair samples by multi-element sequential flame atomic absorption spectrometry. The slurries were prepared by cryogenic grinding and sonication of the samples. The optimization step was performed using univariate methodology and the factors studied were: nature and concentration of the acid solution, amount sample/slurry volume, sonication time, and particle size. The established experimental conditions are the use of a sample mass of 50 mg, 2 mol L^− 1 nitric acid solution, sonication time of 20 min and slurry volume of 10 mL. Adopting the optimized conditions, this method allows the determination of zinc and copper with detection limits of 88.3 and 53.3 ng g^− 1, respectively, and precision expressed as relative standard deviation (RSD) of 1.7% and 1.6% (both, n = 10) for contents of zinc and copper of 100.0 and 33.3 μg g^− 1, respectively. The accuracy was checked and confirmed by analysis of two certified reference materials of human hair. The procedure was applied for the determination of zinc and copper in two human hair samples. The zinc and copper contents varied from 100.0 to 175.6 and from 3.2 to 32.8 μg g^− 1, respectively. These samples were also analyzed after complete digestion in a closed system and determination by FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results.     

Reaction between LiF and MF5 (M = Ta, Nb) in a fluorine atmosphere

LiMF₆ (M = Ta, Nb) was prepared by the reaction between LiF and MF₅ (M = Ta, Nb) in F₂ gas. Pure LiMF₆ (M = Ta, Nb) salts were obtained by using the reaction at temperatures higher than 473 K under 80 kPa (F₂) for 24 h. The x values in LiMF_x (M = Ta, Nb) were confirmed as 5.7-6.0 by XRD-Rietveld analysis. Results showed that LiMF₆ (M = Ta, Nb) has a trigonal structure (, Z = 3). The respective lattice parameters of LiTaF₆ and LiNbF₆ are a₀ = 0.533 nm, c₀ = 1.362 and a₀ = 0.532 nm, c₀ = 1.360. The equivalent conductivities of both LiMF₆ (M = Ta, Nb) in propylene carbonate (PC) are equal at 15.2 Ω⁻¹ cm² mol⁻¹ at 0.01 mol dm⁻³. The electrochemical potential window of TaF₆⁻ is 7.0 V, which is 0.4 and 0.2 V wider, respectively, than those of BF₄⁻ and PF₆⁻.     

Simultaneous Kinetic‐Spectrophotometric Determination of Nb(V) and Ta(V) Using H‐Point Standard Addition Method

A simple, rapid, precise and accurate kinetic method for simultaneous spectrophotometric determination of Nb(V) and Ta(V) is described. This method is based on the difference between the rate of the reaction of Nb(V) and Ta(V) with 4‐(2‐pyridylazo)resorcinol (PAR) in the presence of tartaric acid. H‐point standard addition method (HPSAM) was used to resolve the mixtures. The results showed that Nb(V) and Ta(V) can be determined simultaneously in the ranges of 0.10–5.0 and 0.50–12.0 μg mL^?;1, respectively. The proposed method was successfully applied to the simultaneous determination of Nb(V) and Ta(V) in several alloy samples.     

Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry

The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO₂ as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm^–2. Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from ±6% to ±11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from ±9% to ±14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.     

Phase composition and phase transformation in Bi(Sb,Nb,Ta)O4 system

In this work Bi(Sb_xNb_yTa_z)O₄ (x + y + z = 1) samples are prepared using mixed-oxide method. A pseudo-ternary phase diagram of Bi(Sb,Nb,Ta)O₄ system is given below the melting point. It is composed of a monoclinic phase region, an orthorhombic phase region and a monoclinic–orthorhombic co-existing phase region. In the orthorhombic phase region, the transformation from orthorhombic to triclinic phase is found to be sensitive to the composition and sintering temperature. Both the transformation from monoclinic to orthorhombic structure and the transformation from orthorhombic to triclinic structure have been studied by the cell parameters.     

Hydrolysis of Nb(V) and Ta(V) in aqueous KCl at 25°C. Part II: Construction of a thermodynamic model for Ta(V)

In this work the hydrolysis of Ta(V) in 3.0M KCl has been studied by measuring the H₃O⁺ ion concentration with a glass electrode. The experimental work consisted of automatically controlled potentiometric titrations. The results were treated using graphical and numerical methods and, as a result, the hydrolysis process can be considered as a homonuclear protolysis. Finally, the results obtained were compared with other data found in the literature and a hydrolysis model for Ta(V) was built by means of the modified Bromley theory.     

Darstellung und Kristallstruktur von Niob-Tantal-Nitridphasen (Nb,Ta)N∼1

Preparation and Crystal Structures of Niobium-Tantalum-Nitride Phases (Nb, Ta)N_～1 Ta? Nb alloys with graduated composition are nitrided with NH₃ at 1100–1450°C. The mononitrides formed are investigated by X-ray diffraction. Their nitrogen content is evaluated by chemical analysis. Seven Ta? Nb nitride phases are observed. Depending on the temperature, the phases appear in a strictly defined sequence along the variation of the Ta:Nb relation. Corresponding to this sequence, the density (formula volume) of this nitride phases varies.     

Fe x Ti1−2x M x O2 (M=Nb,Ta) rutile solid solutions from gels

In this study, Fe _x Ti_1–2x M _x O₂ (M=Nb, Ta) rutile solid solutions have been synthesized from gels made from Fe(III) acetylacetonate, NbCl₅, TaCl₅, Ta(V) ethoxide, TiCl₄ and Ti(IV) isopropoxide. The results obtained are compared with those obtained by the ceramic method. The solid solutions synthesized from gels were obtained at lower temperatures than these synthesized by the ceramic method.