Trace characterisation of lithium niobate by neutron activation analysis

Summary Coprecipitation behaviour of As, Au, Co, Cr, Cu, Eu, Fe, Ir, La, Lu, Mn, Mo, Nb, Ni, Pd, Pt, Sb, Sc, Ta, W, Zn and Zr during precipitation of hydrous oxide of niobium from lithium niobate was investigated. The matrix was dissolved in HF-HNO₃, evaporated to dryness and niobium was precipitated from HNO₃-H₂O₂ medium. The recovery studies were made using radiotracers. A radiochemical separation scheme based on group precipitation has been developed for the determination of Au, Co, Cr, Cu, Fe, Mn, Ni, Pd, Pt, Zn, Zr and rare earth elements. The method was applied to the analysis of lithium niobate. This analysis has provided fruitful information for improving the quality of the crystal.     

The photocatalytic properties of amorphous TiO2 composite films deposited by magnetron sputtering

The preparation of amorphous TiO₂ film coupled with various metal-oxide semiconductors and their photocatalytic activities evaluated by photo-degradation of methylene blue and rhodamine B aqueous solution are briefly reviewed. The proposed photoreaction mechanism of the amorphous composite semiconductor and the differences between amorphous TiO₂-based films and crystalline TiO₂ photocatalytic materials in terms of preparation and usage are addressed. The inactive intrinsic amorphous TiO₂ film coupled with various metal oxides were found to gain high photocatalytic activity. These dopants induce forming new energy levels in the band gap of TiO₂ to enhance the charge separation of the photoinduced electrons and holes and extend the light absorption of TiO₂-based photocatalytic films into the visible region. In addition, two different effects of coupling metal oxides have been proved: the introduction of oxides of W, Cr, V, Ag, and Mo can significantly increase the photo-reactivity of amorphous TiO₂ film, while the combination of oxides of Zr, Sn, Sb, Cu, Ta, Fe, and Ni cannot affect the inactivity of pure amorphous TiO₂ film.     

Emission of secondary ions from 3d, 4d, and 5d transition metals under chloro-trifluoro-methane CClF3 as reactant gas

Surface interactions of CClF₃ with polycrystalline samples of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Rh, Pd, Ag, Ta, W, Re, Ir, and Pt were investigated by means of moderate dynamic SIMS. As observed with other reactant gases these transition metals in most cases appear to be discernible into “dissociative” and (partial) “molecular” adsorbents. Small signals of oxidic secondary ions which are detectable for residual gas conditions vanished under the action of CClF₃. However, due to strong polarization by either of the halogens, the emission of Me²⁺ ions is enhanced for Ti, V, and Nb.     

Co-doping a metal (Cr,Mn, Fe,Co, Ni,Cu, and Zn) on Mn/ZSM-5 catalyst and its effect on the catalytic reduction of nitrogen oxides with ammonia

Selective catalytic reduction (SCR) of NO_x by NH₃ over a series of Mn–M/Z catalysts (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, and Z = the ZSM-5 Zeolite) synthesized by wet impregnation method was investigated. Mn–Fe/Z, Mn–Co/Z, and Mn–Cu/Z catalysts exhibited approximately 100 % NO_x conversion over a wide temperature range (200–360 °C) in a defined atmospheric condition, which was noticeably greater than that of Mn–Cr/Z (340–360 °C). Furthermore, the effect of addition of second metal oxide species to the initial Mn/Z catalyst on the structure of catalysts was studied by several characterization techniques. BET measurements revealed high surface area and pore volume of the Mn–Cu/Z catalyst. In addition, the XRD and UV–Vis DR results showed that addition of co-doped metal oxide species improved the dispersion of metal ions and inhibited crystallization of metal oxides. UV–Vis studies also were in good accordance with DTA/TG results confirming the formation of cobalt oxide and copper oxide clusters in Mn–Co/Z and Mn–Cu/Z catalysts, respectively. The FTIR spectra of pyridine adsorption, in addition, suggested the Mn–Cu/Z catalyst contained the most Lewis acid sites leading to more NO_x adsorption capacity.     

Emission of secondary ions from 3d, 4d, and 5d transition metals under chloro-trifluoro-methane CClF3 as reactant gas

Surface interactions of CClF₃ with polycrystalline samples of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Rh, Pd, Ag, Ta, W, Re, Ir, and Pt were investigated by means of moderate dynamic SIMS. As observed with other reactant gases these transition metals in most cases appear to be discernible into “dissociative” and (partial) “molecular” adsorbents. Small signals of oxidic secondary ions which are detectable for residual gas conditions vanished under the action of CClF₃. However, due to strong polarization by either of the halogens, the emission of Me²⁺ ions is enhanced for Ti, V, and Nb. Received: 6 August 1997 / Revised: 22 December 1997 / Accepted: 29 December 1997     

Verfahren zur Spurenanalyse aus metallischen Proben

Zusammenfassung Ein neues lösungsspektrographisches Zerstäubungsverfahren wird beschrieben, bei dem die Lösung so zerstäubt wird, daß sie die Graphitelektroden nicht berührt. Mit diesem Verfahren könnten 10^–3 bis 10^–5 % Al, B, Cr, Cu, Mg, Mn, Mo, Ni, Si, Sn, Ti, V und Zr in Eisen und Stahl bestimmt werden.Zur Bestimmung von Verunreinigungen oder Einschlüssen in Stahl wird ein spektrographisches Verfahren mit Preßlingselektroden empfohlen, das nur 0,1–1 mg Rückstand benötigt. Oxide von Al, B, Ca, Co, Cu, Cr, Fe, Mg, Mn, Mo, Nb, Ni, Pb, Si, Sn, Sr, Ti, V, Zn und Zr konnten bis herab zu etwa 10^–7 g erfaßt werden.

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Methods for the determination of trace elements from metallic samples

The principles of a new spectrographical atomizing-method of solution are described. The solution has to be atomized into a gap without contacting the surface of the graphite electrodes. In this way the exact determination of 10^–3 to 10^–5 % of Al, B, Cr, Cu, Mg, Mn, Mo, Ni, Si, Sn, Ti, V and Zr in iron and steel is possible.The microanalytical determination of impurities or inclusions in steel has been achieved by a spectrographical method with briquette electrodes. The necessary amount of isolation residue is only 0.1–1 mg. The oxides of Al, B, Ca, Co, Cu, Cr, Fe, Mg, Mn, Mo, Nb, Ni, Pb, Si, Sn, Sr, Ti, V, Zn and Zr can be accurately determined by this procedure. The limit of determination is about 10^–7 g.

     

Uran-haltige Komplexboride

Ternary complex borides of formulaMM′B₄ have been prepared within the systems U-{V, Cr, Mo, W, Mn, Re, Fe, Co}-B. The phases U(Mo, W, Re)B₄ are isotypic with ThMoB₄-type structure; U(V, Cr, Mn, Fe, Co)B₄ crystallize with YCrB₄-type structure.     

Choline Chloride Assisted Synthesis of N and Metal Codoped TiO2 and their Photocatalytic Activity under Visible Light

A few nanocrystalline N,metal codoped TiO₂ (metal = Cr, Mn, Fe, Co, Ni, Cu and Zn) have been synthesized by a simple sol–gel method using choline chloride which is biodegradable, low cost, nontoxic ionic salt both as a structure directing agent and source of nitrogen. The prepared samples were well characterized by XRD, HRTEM, FTIR, DRS, EDX, XPS and BET techniques. The photocatalytic activity of all synthesized N, metal codoped TiO₂ has been carried out for the degradation of Reactive Black 5 dye under visible light irradiation and among them, N, Fe codoped TiO₂ was found to be the best for the degradation of Reactive Black 5 dye. The effect of incorporated metals on the photocatalytic activity of the various modified TiO₂ has been discussed in detail based on the mechanism involved in the degradation of dye and their physico‐chemical properties which includes surface area, particle size, defect sites, phase, band gap and electron–hole recombination effect.     

The application of discontinuous,countercurrent, liquid-liquid extraction to the study of the distribution of metal ions between hydrochloric acid and methyl isobutyl ketone

Summary The extraction of the elements Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, As, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, La, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb and Bi from hydrochloric acid into methyl isobutyl ketone has been studied as a function of hydrochloric acid concentration. The results are presented in graphical form. The data were obtained by studying the distribution patterns of the elements after equilibration on a Craig countercurrent liquid-liquid extraction apparatus.

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Zusammenfassung Die Extraktion der Elemente Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, As, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, La, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb und Bi mit Methylisobutylketon aus salzsaurer Lösung als Funktion der Säurekonzentration wurde studiert. Die Ergebnisse wurden aus den Spitzen der Verteilungskurven nach Einstellung des Gleichgewichts in einem diskontinuierlichen Gegenstrom-flüssig-flüssig-Extraktionsapparat berechnet.

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Résumé On a étudié l'extraction des éléments Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, As, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, La, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb et Bi en solution chlorhydrique par la méthylisobutylcétone. On présente les résultats sous forme graphique. Les données ont été obtenues en étudiant les diagrammes de distribution des éléments après équilibrage sur un appareil Craig à extraction à contre-courant liquide-liquide.

     

Unmittelbare photometrische Bestimmung des Antimongehaltes von legierten St?hlen mit Jodid

Zusammenfassung Das photometrische Verfahren von Ploum [1,2] zur Antimonbestimmung mit Jodid in nichtlegierten Stählen wurde so modifiziert, daß einerseits die Arbeitszeit durch Vereinfachung der Methode herabgesetzt wird und es andererseits zur Untersuchung hochlegierter Stähle herangezogen werden kann. 20% Cr, 12% Ni, 3% Mo, 4% W, 2% Mn, 3% V, 1% Ti, 0,4% Si, 0,8% Nb, 0,04% Ta, 0,1% Co, 0,05% Al, 0,05% As, 0,014% Sn und 0,004% B haben keinen Einfluß. Cu > 0,2% stört. Es können Antimongehalte von 0,001–0,025% bestimmt werden.

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Direct photometric determination of antimony in alloy steels with iodide

The method of Ploum [1,2] for the direct determination of antimony in plain steels has been modified. It has been possible to reduce the working time in simplifying the method and to apply the procedure to the investigation of high-alloy steels. 20% Cr, 12% Ni, 3% Mo, 4% W, 2% Mn, 3% V, 1% Ti, 0.4% Si, 0.8% Nb, 0.04% Ta, 0.1% Co, 0.05% Al, 0.05% As, 0.014% Sn and 0.004% B have no effect. Cu >0.2% interferes. Sb contents from 0.001 to 0.025% can be determined.

     

过渡金属离子置换钛酸纳米管的制备和光催化活性

TiO2纳米粉体和纳米膜材料在光催化降解大气和水中的污染物等方面具有广泛的应用[1]。近年来,以TiO2为原料与浓N aO H反应合成的钛酸纳米管具有比其原料TiO2更大的表面积和孔体积,且对丙烯有光催化氧化降解活性而备受关注[2]。以往在对TiO2纳米粉体和纳米膜材料在光催化研究中,人们发现由于光激发产生的电子与空穴的复合,导致光量子效率很低。为克服这个缺点,人们使用过渡金属离子掺杂等多种手段对TiO2进行改性[3]。但钛酸纳米管相类似的研究还未见报道。对钛酸纳米管的结构和组成的研究表明[4],此纳米管状物的组成是N axH2-xTi3O7,…     

The site preference and doping effect on mechanical properties of Ni3Al-based γ′ phase in superalloys by combing first-principles calculations and thermodynamic model

The fundamental aspects of site preference of alloying elements on sublattice of the strengthen γ′ phase with L1₂ structure have not been well understood, which hinders the optimized design of advanced Ni-based high-temperature alloys. In this contribution, the temperature- and composition-dependent site occupying preferences of the binary, ternary, and quaternary of Ni₃Al-based γ′ phase alloyed with M_i where M_i represents the additional transitional metals Co, Cr, Cu, Fe, Mn, Mo, Re, Ta, Ti, V, or W atoms (arranged in alphabetical order) chosen frequently, were studied using a two-sublattice thermodynamic model (Ni, Al, M_i)_1a(Ni, Al, M_i)_3c. The site occupying fractions (SOFs) were calculated based on a thermodynamic database established in this work, where the thermodynamic data of the end-members involved were obtained using first-principles calculations and phonon spectrum calculations. The calculated SOFs results show that there is an obvious site preference for stoichiometry binary Ni₃Al, and its site configuration changes from (Al)_1a(Ni)_3c at room temperature to (Al_0.9984Ni_0.0015)_1a (Al₀Ni_0.9994)_3c at 1273 K. For the γ′ phase with the composition 78Ni-26Al-4M_i (atom ratio and x_Ni/x_Al = 3:1), Mo atoms always preferred to occupy the 1a sublattice (Al site), Co, Mn, and Ti atoms always prefer the 3c sublattice (Ni site) in the whole temperature range, while the site preference of Cr, Cu, Fe, Re, Ta, V, or W atom is affected by temperature. For example, when the heat treatment temperature is lower than 700 K, Cr, Cu, Fe, Ta, V, and W atoms occupy the 1a and 3c sublattice randomly, and Re atoms prefer to 3c sublattice, while when the heat treatment temperature is higher than 1273 K, Cr, Cu, and W atoms prefer 3c sublattice, Fe and Ta atoms prefer to 1a sublattice, while all Re atoms occupy the 3c sublattice exclusively, and all V atoms occupy the 1a sublattice exclusively, respectively. Likewise, the site preference of the quaternary system with selective compositions 78Ni-26Al-2 M₁-2 M₂ was also predicted. Based on calculated SOFs results, the mechanical and thermodynamic properties were studied at the ground state. It has been revealed that Cr, Re, and V doping can improve the microhardness of Ni₃Al alloys; in particular, the effect of Cr is extraordinary; and all elements, except Mn, Mo, and Ti, would enhance the bulk modulus of Ni₃Al-based γ′ phase, in which Mn have the greatest influence on reducing the bulk and shear modulus, respectively. Furthermore, all the B/G ratios of the computed Ni₃Al-based γ′ phase are >1.75, showing inherent ductility. Only Cr doping significantly enhances the Debye temperature of the Ni₃Al-based γ′ phase.     

Systematic study of the solvent extraction of metal oxinates

The extraction of 32 metals (Be, Mg, Ca, Sr, Ba, Sc, La, Ti, Zr, Th, V, Nb, Cr, Mo, W, U, Mn, Fe, Co, Ni, Pd, Cu, Ag, Zn, Cd, Hg, Al, Ga, In, Tl, Pb and Bi) with oxine solution has been studied. The effects of pH, oxine concentration and water-soluble complexing agents (oxalic acid, tartaric acid, hydrocyanic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid and 1,2-diaminocyclohexanetetraacetic acid) have been investigated. From these results the extraction constants and stability constants ot the metal complexes with the various complexing agents investigated have been calculated.     

Determination of tungsten with iron(III) after reduction with mercury in thiocyanate medium

Tungsten(V) is formed by shaking for 2 min sodium tungstate solution in 0.4 M potassium thiocyanate-4M hydrochloric acid medium, with mercury. It is titrated with standard iron(III) solution. The thiocyanate present stabilizes W(V) to aerial oxidation and also acts as indicator. The W(V) can also be titrated potentiometrically in 7M hydrochloric acid, a tungsten wire electrode being used. Fe, Ni, Cr, Zr, Bi, Sb, Ce, Al, Pb, Ca and U do not interfere. Cu, V and As can be tolerated up to 5 mg. Co, Mo, Re, Nb and Mn interfere, but not in the potentiometric determination. The method is direct, simple, rapid, accurate and reproducible.     

Persulfate Oxidation and Diphenylcarbazide Photometric Determination of Chromium in Super Alloys

The quantitative analysis of Cr in super alloys with the presence of a wide variety of elements, Al, B, C, Co, Cu, Hf, Fe, Mn, Mo, Ni, Nb, P, Si, S, Ti, Ta, W, Zr; and trace amounts (a few ppm) of Pb, Se, Bi, Tl and Te has been studied. Persulfate oxidation and diphenylcarbazide photometric method were studied with the purpose of developing a relatively fast and reliable measurement for Cr by wet chemical analysis. The results indicate that the latter is supperior to the former in practical view. In the photometric method, solid sample (0.1g alloys) when treated with HClO₄ and H₂SO₄ took ca. 72 hrs. for complete dissolution. When treated with HCl followed by HNO₃, 0.1 g alloys were completely dissolved within 1&1/2; hours. The best experimental conditions for diphenylcarbazide photometric determination of Cr was thus established. Photometric determination of Cr complexes was made at 540 nm.     

Thermal decomposition of bivalent transition metal malonates in various atmospheres

The thermal decomposition of the malonates of bivalent transition metals (Mn, Fe, Co, Ni, Cu and Zn) was investigated by mainly TG-DTA, X-ray diffraction analysis and evolved gas analysis in atmospheres of N₂, CO₂ and O₂ and in the air. It was shown that CO₂ has an inhibiting effect on the decomposition whereas O₂ and air have the accelerating effects on the basis of N₂. The decomposition of the salts investigated can be classified into three groups from solid decomposition products: Mn and Zn malonates gave the metal oxides including 1–1.5 moles of elementary carbon, while Cu and Ni malonates gave the metals with 1–1.5 moles of the carbon. Fe and Co malonates in the last group gave once the metal oxides with 1-0.5 moles of the carbon and the oxides produced were subsequently reduced to the metals by the carbon. A possible reaction mechanism for the malonates was discussed and compared with those of the corresponding oxalates and succinates.     

Interferences in the determination of aluminium by means of atomic absorption spectrophotometry

Summary The following substances have been investigated with regard to their interfering effect in the determination of aluminium by atomic absorption spectrophotometry: HCl, H₂SO₄, HNO₃, H₃PO₄, alkali and alkaline earth metals, Cu, Fe, Zn, Ni, Mn, Co, Mo, Ti, Cr, V, Si. Ternary systems with La have been examined also. Si exerts a strong depressive effect, whereas other elements in certain concentration ranges exhibit positive effects.

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Störungen bei der atomabsorptionsspektralphotometrischen Bestimmung von Aluminium

Zusammenfassung Folgende Substanzen wurden hinsichtlich einer möglichen Beeinflussung der Aluminiumbestimmung untersucht: HCl, H₂SO₄, HNO₃, H₃PO₄, Alkalimetalle, Erdalkalimetalle, Cu, Fe, Zn, Ni, Mn, Co, Mo, Ti, Cr, V, Si. Ternäre Systeme mit La wurden ebenfalls geprüft. Si übt eine stark depressive Wirkung aus, während andere Elemente in bestimmten Konzentrationsbereichen positiv wirken.

Lecture given on the 2nd Czechoslovak Conference on Flame Speotroscopy, Zvíkov, June 5–8, 1973.     

The determination of minor elements in steel by proton-induced prompt gamma-ray spectrometry

Pure elemental targets of Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo and W were irradiated with protons from 3.5 to 6.0 MeV, interference-free sensitivities were calculated for analysis by prompt gamma-ray spectrometry and sensitivity curves were plotted to show the variation of sensitivity with bombarding energy. Appropriate bombarding energies were selected for analysis and the extent of possible inter-element interferences and background effects were determined. Standard reference steels were used to evaluate this method for the determination of the minor elements Si, V, Cr, Mn and Co.     

过渡金属氧化物催化剂上NH3 分解Claus反应机理研究

运用浸渍法制备了七种过渡金属氧化物催化剂.对于NH3 分解反应均可获得很高的NH3转化率;对于NH3分解Claus反应则可以获得较高的SO2转化率和单质硫选择性.通过比较发现Co3O4-TiO2和Fe2O3-TiO2催化剂的低温活性比较高.经过XRD表征发现,在NH3分解Claus反应中,催化剂的活性相可能是过渡金属硫化物.结合活性评价和XRD表征结果提出了NH3分解Claus反应的机理.     

Reductive precipitation as a separation method for the determination of trace elements in tellurium oxide and bismuth oxide by flame and electrothermal AAS

Matrix separation by reductive precipitation with hydrazine allows the ET-AAS and flame-AAS determination of Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb and V in high-purity TeO₂ and Bi₂O₃.