Reaction of calcium and phosphate ions with titanium,zirconium, niobium,and tantalum

To understand the bone formation ability of constituent metal elements of new titanium alloys, titanium, zirconium, niobium, and tantalum, these metals were immersed in various electrolytes containing calcium and/or phosphate ions and characterized using X‐ray photoelectron spectroscopy. In addition, cathodic polarization of the metals in the electrolytes was performed to evaluate the stability of the surface oxide films on the metals in the electrolyte. The calcium phosphate layer formed on Ti in electrolytes containing calcium and phosphate ions is relatively protective against mass transfer throughout the layer. However, the zirconium phosphate layer formed on Zr is much more protective and stable than that on Ti. Therefore, calcium ions were not incorporated. Nb and Ta formed calcium phosphate, but the amount was smaller than that in Ti, because phosphates formed on Nb and Ta are somewhat protective and the incorporation of the calcium ion is inhibited. Titanium played the most important role in forming calcium phosphate, while zirconium inhibited the formation of calcium phosphate on titanium alloys. The control of bone formation is feasible by the design of titanium alloys. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of niobium promoter on iron-based catalyst for Fischer-Tropsch reaction

Niobium-promoted Fe/CNTs catalysts were prepared using a wet impregnation method.Samples were characterized by nitrogen adsorption,H2-TPR,TPD,XRD and TEM.The Fischer-Tropsch Synthesis(FTS) was carried out in a fixed-bed microreactor at 220 ℃,1 atm and H2/CO=2 for 5 h.Addition of niobium into Fe/CNTs increased the dispersion,decreased the average size of iron oxide nanoparticles and the catalyst reducibility.Niobium-promoted Fe catalyst resulted in appreciable increase in the selectivity of C5+ hydrocarbons and suppressed methane formation.These effects were more pronounced for the 0.04%Nb/Fe/CNTs catalyst,compared to those observed from other niobium compositions.The 0.04%Nb/Fe/CNTs catalyst enhanced the C5+ hydrocarbons selectivity by a factor of 67.5% and reduced the methane selectivity by a factor of 59.2%.     

Multi-element trace analysis of tungsten

Investigations carried out in order to determine traces of 25 elements in tungsten in the lower g/g range are reported on. Atomic absorption spectrometry and plasma atomic emission spectrometry as well as solution photometry and activation analysis were the main techniques used.     

Bis(pyrene)metal complexes of vanadium,niobium and titanium: isolable homoleptic pyrene complexes of transition metals

Reduction of VCl₃(THF)₃ (THF is tetrahydrofuran) and NbCl₄(THF)₂ by alkali metal pyrene radical anion salts in THF affords the paramagnetic sandwich complexes bis[(1,2,3,3a,10a,10b‐η)‐pyrene]vanadium(0), [V(C₁₆H₁₀)₂], and bis[(1,2,3,3a,10a,10b‐η)‐pyrene]niobium(0), [Nb(C₁₆H₁₀)₂]. Treatment of tris(naphthalene)titanate(2−) with pyrene provides the isoelectronic titanium species, isolated as an (18‐crown‐6)potassium salt, namely catena‐poly[[(18‐crown‐6)potassium]‐μ‐[(1,2‐η:1,2,3,3a,10a,10b‐η)‐pyrene]‐titanate(−I)‐μ‐[(1,2,3,3a,10a,10b‐η:6,7‐η)‐pyrene]], {[K(C₁₂H₂₄O₆)][Ti(C₁₆H₁₀)₂]}_n. The first two compounds have very similar packing, with neighboring molecules arranged orthogonally to one another, such that aromatic donor–acceptor interactions are likely responsible for the specific arrangement. The asymmetric unit contains a half‐occupancy metal center η⁶‐coordinated to one pyrene ligand, with the full M(pyrene)₂ molecule generated by a crystallographic inversion center. In the titanium compound, the cations and anions are in alternating contact throughout the crystal structure, in one‐dimensional chains along the [101] direction. As in the other two compounds, the asymmetric unit contains a half‐occupancy Ti atom η⁶‐coordinated to one pyrene ligand. Additionally, the asymmetric unit contains one half of an (18‐crown‐6)potassium cation, located on a crystallographic inversion center coincident with the K atom. The full formula units are generated by those inversion centers. In all three structures, the pyrene ligands are eclipsed and sandwich the metals in one of two inversion‐related sites. These species are of interest as the first isolable homoleptic pyrene transition metal complexes to be described in the scientific literature.     

Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60?s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 10³–10⁴ fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0?pg?mL^?1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1?µg?L^?1 levels.     

低价钛引起的硝基化合物与羧酸衍生物的反应

在低价钛(TiCl~4-Zn)试剂作用下, 酰氯或硝基化合物发生分子间交叉还原偶联生成酰胺, 提供了合成酰胺的一种简便方法.     

Ion-exchange separation of vanadium, zirconium, titanium, molybdenum, tungsten and niobium

Schemes for the separation of two or more of the elements vanadium, zirconium and/or titanium, molybdenum and tungsten from each other and from relatively large amounts of niobium have been developed, a strongly basic anion-exchange resin being used. Interference from niobium is avoided by using hydrofluoric acid to elute vanadium, zirconium, titanium and molybdenum. The application of coupled columns to improve the efficiency of separation of multicomponent mixtures is demonstrated. The use of an "interval" equation defining the volume interval between successively eluted solutes is proposed for calculating the column length required for a particular separation. This equation is especially useful for determining the extent to which a column must be lengthened when overlapping occurs because of high column loading.     

Titanium dioxide nanoparticles heavily doped with niobium: A light-induced electron paramagnetic resonance study

Light-induced electron paramagnetic resonance (EPR) spectra of titanium dioxide nanoparticles heavily doped with niobium(v) are studied. At low temperatures, the EPR signal caused by interband illumination is associated with paramagnetic Ti³⁺ sites in anatase, which, as the temperature rises above 210 K, are discharged to the non-paramagnetic Ti⁴⁺ state due to the escape of trapped photoelectrons and their recombination with holes. The temperature dependence of the integral EPR signal has a non-Curie character, especially in the temperature range where the discharge of Ti³⁺ centers is already significant.     

Study of kinetics of reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw materials with sulphuric acid has been studied in a non-isothermal-non-adiabatic type calorimeter. The influence of different starting conditions, temperature and ilmenite particle-size distribution on the thermo-kinetics of the reaction was investigated. A kinetic model is presented for this heterogeneous system for a specified ilmenite particle-size distribution and starting temperature. On the basis of this model and experimentally determined parameters it it possible to analyse by simulation the autothermic reaction of digestion of different titanium ores with sulphuric acid.     

电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚铌钽锂矿石中的铌、钽、锂

经过三种样品前处理实验对比,选择采取氢氟酸-高氯酸-王水溶样,酒石酸-王水浸取,电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚地区铌钽矿石中铌、钽、锂元素。对元素的分析谱线、酒石酸浓度等工作条件进行了优化,选择各元素的最佳分析谱线,并进行加标回收实验,探讨了各元素的加标回收率。选取Nb 269.7 nm、Ta 240.0 nm、Li 670.78 nm作为仪器分析谱线,计算得到的方法检出限分别为:Nb 0.5μg/g、Ta 1.5μg/g、Li 15.0μg/g。对比各种溶样方法,选取一种最简洁方便的样品前处理途径,经国家一级标准物质GBW07153、GBW07155和GBW07185验证,测定值的相对误差为-2.82%~1.77%,方法精密度(RSD,n=6)为0.11%~1.2%,测定尼日利亚地区铌钽锂矿石中的铌、钽、锂元素,结果无显著性差异,方法能够满足尼日利亚铌钽矿石中相关组分的准确测定。     

Solid-state reaction of niobium with diamond carbon at high pressure and high temperature to form superconducting composite

1. Download : Download high-res image (116KB)
2. Download : Download full-size image

     

Spectrophotometric determination of molybdenum and tungsten in niobium with dithiol

A new procedure for the determination of molybdenum and tungsten in niobium has been developed. The method involves the formation of the intensely colored complex of molybdenum with toluene-3,4-dithiol in an aqueous medium and its extraction into carbon tetrachloride followed by the reduction of tungsten and the formation and extraction of its complex. The recommended reagent is stable for at least 90 days. Both the molybdenum and the tungsten dithiol complexes are formed quantitatively within 5 min. Interlaboratory evaluation of the method reveals within-laboratory and between-laboratory relative standard deviations of about 1.5% and 2.9% respectively.     

Electrochemical synthesis of niobium methylate

The formation of niobium(V) methylate in methanol against the background of lithium chloride is studied. It is found that, in the anodic dissolution of niobium in the diaphragmless electrolyzer, formed niobium(V) methylate is partially reduced to the four-valent state at the cathode. In order to suppress the reduction of Nb(V), an electrolyzer was designed, which enabled one to separate the anolyte from the catholyte using the difference between their densities. Niobium methylate was not found in the anolyte; however, it forms as a result of mixing the anolyte with the catholyte after completion of electrolysis. The current efficiency of niobium methylate of 96–97% was achieved. Possible mechanism of the process is discussed.     

低价钛引起的羧酸衍生物与芳酮的还原偶联反应

本文报道了在低价钛试剂作用下羧酸衍生物与芳酮的还原偶联反应.     

差示法测量Cu30W70钨铜合金中钨的含量

研究了广泛用于军工、高压开关、电火花电极、电子封装的新型材料钨铜合金[1]中钨含量的定量分析,采用传统的湿化学差示分析方法。由于该材料的耐腐蚀性,试样溶解是关键,通过实验决定采用9 1盐硝酸和1 3硫磷酸混合酸低温加热溶解。加入草酸胺掩蔽铜的干扰。用硫氰酸胺显色。以Cu30W70为例用40%的钨为参比,配制一系列标准制作工作曲线。钨含量在5～10μg/ml内服从比耳定律。方法的精密度RSD=1.6%,回收率为97.2%～101.4%。适用范围为含钨45%以上的钨铜合金。     

Oxidation products of the niobium tungsten oxide Nb4W13O47: A high-resolution scanning transmission electron microscopy study

Nb₄W₁₃O₄₇, a member of the solid solution series Nb_8−nW_9+nO₄₇ (0?n?5), crystallizes in a threefold superstructure of the tetragonal tungsten bronze structure. While the oxidation of this reduced phase at T_OX=1200 °C leads to a separation into the thermodynamically stable phases, lower oxidation temperatures result in products that comprise new structural elements and ordering variants. The characterization of the oxidation products obtained at T_OX=1000 °C was performed by scanning transmission electron microscopy applying a high-angle annular dark field detector. At the selected imaging conditions (Z contrast), not only the metal positions are revealed by this technique but valuable additional information about the elemental distribution can be obtained simultaneously.     

Formation of carbene species in the reaction of lithium alkyls with molybdenum,tungsten, and cobalt chlorides

Ethyl derivatives of Mo and W and amyl derivatives of Mo undergo not only -cleavage with the formation of equimolar amounts of the corresponding alkane and alkene but also -cleavage accompanied by the generation of carbene species (methyl- and butylcarbenes) in these systems. The latter decomposition pathway is also proposed for ethyl and amyl cobalt derivatives.A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 117912 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 206–209, January, 1992.     

Formation of niobium boride from NB2O5 and boron with plasma arc

When a mixture of Nb₂O₅ and boron is heated to about 3000°C and subsequently annealed at about 2000°C in an argon plasma arc, NbB₂ is obtained. The products are found to be superconductors, theT _cof which is higher than 4 K. Some properties of the products, such as Vickers hardness and density, are comparable with those of NbB₂ prepared from niobium and boron. In the reaction forming NbB₂, a white powder is also obtained. The powder is identified as H₃BO₃ and is formed by the reaction between BO and water in the atmosphere. Therefore, the reaction of NbB₂ formation can be written as Nb₂O₅+9B=2NbB₂+5BO.     

活性钛与芳基丙酮的还原偶合反应

羰基化合物还原偶合是形成碳-碳键的一种重要方法。本文首次发现此类反应的产物不仅与反应物本身的结构和还原试剂体系有关，还与操作次序有很大关系，且在活性钛表面反应。     

Organophosphonate derivatives of titanium and niobium alkoxoanions

The organophosphonate-substituted alkoxides [Bu₄ⁿN]₂[{Ti(OMe)₃(O₃PPh)}₂] (1) and [Bu₄ⁿN]₂[{Nb(OMe)₃(O₃PPh)}₂(μ-O)] (2) have been prepared from [Bu₄ⁿN][PhPO₃H] and the metal alkoxides Ti(OMe)₄ or Nb(OMe)₅ respectively. In 1, the bridging phenylphosphonates occupy trans coordination sites, whereas in 2, a cis–bridging geometry is adopted.