Phase equilibria,thermal analysis,and reactivity of tin tungsten bronzes and related phases

Crystal chemistry and phase relations of the bronze forming region of the SnWO system have been investigated. Above 780°C the tin bronzes Sn_xWO₃ are shown to be thermally unstable and an equilibrium diagram is established at 700°C which shows that the composition limits of the tetragonal phase are 0.21 ? x ? 0.29. Below x = 0.21 a series of single and two phase regions containing orthorhombic bronzes exists for which the composition limits have been established. In the range 0.29 ? x ? 0.76 the system comprises the tetragonal bronze, Sn₂W₃O₈ and SnWO₄, while above 0.76 there is no bronze, only Sn₂W₃O₈, SnWO₄ and free Sn. The phase Sn₂W₃O₈ has been isolated and shown to have a hexagonal unit cell, a = 7.696 Å, c = 18.654 Å. The evidence of differential thermal analysis and X-ray studies suggests that this hexagonal phase arises from the decomposition of the tungsten bronze phase and is itself decomposed to cubic SnWO₄ above 700°C. Small thermal effects observed in the DTA scans of tin-containing tetragonal bronzes are interpreted in terms of an order-disorder phenomenon arising from asymmetric tunnel occupancy by Sn²⁺ ions caused by the presence of the lone pair of electrons. Hydrogen reduction of Sn_xWO₃ has been shown to result in complete removal of oxygen, producing Sn + α-W in the range 600–850°C. Some activation energy data are given for the reduction process.     

A novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry based on sample mixing with a non-enriched standard

In this work, a novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 μg/L of the target elements for isotopic analysis. δ⁶⁵Cu, δ⁵⁶Fe, and δ⁵⁷Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 μL of whole blood). The δ⁶⁵Cu values obtained using mixtures containing 40 % (200 μg/L) of Cu from the blood samples and 60 % (300 μg/L) of Cu from the in-house standard were in good agreement with the δ⁶⁵Cu value obtained using the conventional approach (bias ≤0.15?‰).     

Performance evaluation of k 0-instrumental neutron activation analysis and flame atomic absorption spectrophotometry in the characterization of various types of alloys

Certified alloys of Ni–Cu based, Fe based and Cu–Sn based were analysed by semi-absolute, standardless k ₀-instrumental neutron activation analysis (k ₀-INAA) and flame atomic absorption spectrophotometry (FAAS) aiming at evaluating their comparative performances. In k ₀-INAA measurements, the irradiations were performed at miniaturized neutron source reactor having thermal neutron flux of about 1 × 10¹² cm^?2 s^?1. The experimentally optimized parameters for INAA suggested a maximum of three irradiations for the quantification of 21 elements within 5 days. The same experiments also produced quantitative results of 13 elements not reported in the certificates of the reference materials. AAS was, however, unable to determine any of those elements. Accuracy of the two techniques was assessed by comparing their average root mean squared errors. The data analysis concluded that k ₀-INAA had better sensitivity and accuracy than FAAS.     

Corrosion evolution of UNS C90300 bronze in simulated acid rain of Hong Kong

Corrosion evolutions of UNS C90300 bronzes with and without artificial patina were investigated in the simulated acid rain of Hong Kong. The corrosion products mainly composed of cuprite were formed on the surface exhibiting slight protection for the bronze substrate. The ratios of Sn and Zn in the corrosion products are lower than in the alloy. The artificial patina effectively enhances the corrosion resistance of bronze substrate, even after 30 days of immersion. For both bare and patinated bronzes the Sn- and Zn-based species are absent in the outer layers of corrosion products, and Cu₂O species in the outer layer can partially transform into Cu (II) ionic state due to the abundant supply of dissolved oxygen.     

Chromatographic Zinc Isotope Separation by Chelating Exchange Resin

Zinc isotope separations were studied by displacement chromatography using the chelating properties of malate, citrate and lactate exchange resin and EDTA as ligands. After each chromatographic operation, the heavier zinc isotopes were found to preferentially fractionated into the carboxylate complex solution phase. The separation coefficients (ε) for zinc isotope separation had the largest value and were obtained for the isotopic pairs ⁶⁸Zn/⁶⁴Zn (7.16 × 10^?4) and ⁶⁶Zn/⁶⁴Zn (3.08 × 10^?4), respectively, at 298 ± 1 K. The separation coefficient per unit mass differences (ε/ΔM) for the isotopic pair of ⁶⁸Zn/⁶⁴Zn was found to range around 1.55 × 10^?4.     

Analysis of bioaccessible concentration of trace elements in plant based edible materials by INAA and ICPMS methods

The total metal concentration and bioaccessible concentration of Cr, Mn, Fe, Cu, Zn, Se in Momordica charantia, Asparagus racemosus, Terminalia arjuna and Syzyzium cumini were measured by instrumental neutron activation analysis and by inductively coupled plasma mass spectrometry analysis (ICP-MS). The bioaccessible concentrations were determined in the gastrointestinal digest obtained after treating dried powdered samples sequentially in gastric and intestinal fluid of porcine origin at physiological conditions. The bioaccessible concentration of Fe was in the range of 58–67 mg kg^?1, Mn was 10.2–14.6 mg kg^?1, Cu was 3.7–4.8 mg kg^?1 and Zn was 10.6–18.4 mg kg^?1, were within the safety limits set for vegetable food stuff set by Joint FAO/WHO. The bioaccessibility of Zn, an essential element, was high (40–50 %) in M. charantia and in S. cumini. In addition, the total metal contents and bioaccessible concentration of Ni, Se, Cd and Pb in these samples were measured by ICP-MS. The total Cd content in S. cumini (2.6 ± 0.2 mg kg^?1) and its bioaccessible concentration (0.6 mg kg^?1) were strikingly high as compared to the other samples. Though total Hg contents were determined by ICP-MS, but their bioaccessible concentrations were below the detection limit (0.036 mg kg^?1).     

A purification system for 64Cu produced by a biomedical cyclotron for antibody PET imaging

Ion exchange is a simple and efficient method for separating no-carrier-added ⁶⁴Cu from an irradiated Ni target. We developed a semi-automated two-round ⁶⁴Cu separation system equipped with a strong-base anion exchange resin column. We first verified the efficiency of the system using a non-radioactive substitute consisting of 25 mg of Ni and 127 ng of Cu, and confirmed that Cu was completely eluted at the second round of the separation step. After the bombardment, separation of ⁶⁴Cu from the Ni target was achieved with high radiochemical purity. ⁶⁴Cu produced and separated in this study had an extremely low level of Ni impurity. It could be used for labeling monoclonal antibodies for antibody positron emission tomography imaging and synthesizing radiopharmaceuticals.     

Nanosecond and femtosecond Laser Induced Breakdown Spectroscopic analysis of bronze alloys

In the present work we are studying the influence of pulse duration (nanosecond (ns) and femtosecond (fs)) at λ = 248 nm on the laser-induced plasma parameters and the quantitative analysis results for elements such as Sn, Zn and Pb, in different types of bronze alloys adopting LIBS in ambient atmosphere. Binary (Sn–Cu), ternary (Sn–Zn–Cu or Sn–Pb–Cu) and quaternary (Sn–Zn–Pb–Cu) reference alloys characterized by a chemical composition and metallurgical features similar to those used in Roman times, were employed in the study. Calibration curves, featuring linear regression coefficients over 98%, were obtained for tin, lead and zinc, the minor elements in the bronze alloys (using the internal standardization method) as well as for copper, the major element. The effects of laser pulse duration and energy on laser-induced plasma parameters, namely the excitation temperature and the electron density have been studied in our effort to optimize the analysis. Finally, LIBS analysis was carried on three real metal objects and the spectra obtained have been used to estimate the type and elemental composition of the alloys based on the calibration curves produced with the reference alloys. The results obtained are very useful in the future use of portable LIBS systems for in situ qualitative and quantitative elemental analysis of bronze artifacts in museums and archaeological sites.     

Synthesis,characterization and comparative DNA interaction studies of new copper(II) and nickel(II) complexes containing mesalamine drug using molecular modeling and multispectroscopic methods

Complexes of copper(II) and nickel(II) containing the drug mesalamine (5-ASA) have been synthesized and characterized by FT-IR, mass and UV–vis spectra, elemental analysis, and theoretical methods. The binding interactions between mesalamine and its Cu(II) and Ni(II) complexes with calf thymus DNA (ct-DNA) were investigated using absorption, fluorescence emission and circular dichroism (CD) spectroscopies, and viscosity measurements. Absorption spectra of 5-ASA, Cu(II) and Ni(II) complexes showed hypochromism. The calculated binding constants (K_b) obtained from UV–vis absorption studies were 1.27 × 10³, 1.6 × 10³, and 1.2 × 10⁴ M^?1 for 5-ASA, Cu(II) and Ni(II) complexes, respectively. The compounds induced detectable changes in the CD spectra of ct-DNA (B → A structural transition, B → C structural transition and stabilization of the right-handed B form, for mesalamine, Cu(II) and Ni(II) complexes, respectively). The competitive binding experiments with Hoechst 33258 indicated that 5-ASA and copper complex could interact as groove binders. Furthermore, Ni complex had no effect on the fluorescence intensity and peak position of MB-DNA system. Finally, the results obtained from experimental and molecular modeling showed that complexes bind to DNA via minor-groove binding.     

Development of cost effective method for production of 64Cu from natNi

A ^natNi foil was used for the production of ⁶⁴Cu via ⁶⁴Ni(p,n)⁶⁴Cu nuclear reaction when the necessary investment for target material (350 mg) is 50 times less using the ^natNi instead of ⁶⁴Ni. The produced 32.2 ± 1.8 MBq of “no carrier added” ⁶⁴Cu is sufficient for 10 mice trials on small animal PET. The radionuclide contamination was <13 ± 12 kBq for ⁵⁵Co and 4 ± 2 kBq for ⁵⁷Ni comparing to minimum detectable activity and only 52 ± 2 kBq of ⁶¹Cu was in ⁶⁴Cu due to the modified ion exchange separation. The concentration of Fe(III) was maintained under 1.7 ppm by precipitation and filtering of Fe(OH)₃ due to the chemical purity was required.     

Synthesis and characterisation of Ni(II), Cu(II), and Zn(II) complexes with an acyclic Mannich base functionalised with thioglycolate moiety

New complexes ML(CNS)·nH₂O [M = Ni, n = 0.5; M = Cu, n = 4.5; M = Zn, n = 0.5, HL: 6-mercapto-(1,4,8,11-tetraazaundecanyl)-6-carboxylic acid)] have been synthesised, chemical analysed, and characterised by different spectroscopic techniques (IR, UV–Vis–NIR, ¹H NMR, EPR, ESI–MS), and magnetic measurements. Based on the IR spectra a dinuclear structure with the 1,3-CSN coordination was proposed for Ni(II) and Cu(II) complexes. The dinuclear structure of Cu(II) complex is also consistent with both magnetic behaviour and EPR spectrum. According to TG, DTG and DTA curves the thermal transformations are complex processes, including dehydration, Mannich base oxidative degradation and thiocyanate decomposition. The final product of decomposition is the most stable metallic oxide, as XRD data indicates. The new complexes were also screened for their microbicidal and antibiofilm properties.     

Isolation and quantification of Fe and Ni in reactor effluents using extraction chromatography and liquid scintillation analysis

A novel extraction chromatographic resin based on diisobutyl ketone has been developed for the isolation of ⁵⁵Fe. This material has been used in conjunction with a dimethylglyoxime-based resin for the sequential separation of ⁵⁵Fe and ⁶³Ni and isolation of these radionuclides from associated contaminants. The preparation and characterisation of these resins is described along with an assessment of their performance for the isolation of ⁵⁵Fe and ⁶³Ni from a mixture of nuclear activation products. In addition, a refined approach for the measurement of these nuclides by liquid scintillation counting is discussed. The findings of these studies have been combined to develop a robust procedure for the analysis of ⁵⁵Fe and ⁶³Ni in reactor effluents which is now the preferred method for a number of UK analytical laboratories.     

Development of a simple and fast ultrasound-assisted extraction method for trace element determination in tobacco samples using ICP-MS

The current study describes a simple and fast method for the determination of Ba, Cd, Co, Cr, Cu, Mn, Ni and Pb in tobacco samples. Commercial cigarettes obtained from local market stores were analysed by inductively coupled plasma mass spectrometry (ICP-MS) after ultrasound-assisted extraction in acidic medium, and the results were compared to those obtained following microwave-assisted digestion of the samples. The sonication time was evaluated from 0 to 60 min, and a 30 min extraction time was selected. The concentration of HNO₃ was also optimised at 0.7 mol L^?1. In order to verify the accuracy of the proposed method, a certified reference material was submitted to the same extraction protocol adopted for the samples, and good agreement with the certified values was obtained at a 95% confidence level, except for Co. The extraction of Pb was also semi-quantitative. A total of four tobacco samples were analysed, with concentrations ranging from 0.4 for Cr to 214.6 µg g^?1 for Mn. The proposed method was demonstrated to be fast, sensitive, precise and accurate for the determination of Ba, Cd, Cr, Cu, Mn an Ni and for the semi-quantitative analysis of Co and Pb in tobacco samples.     

Synthesis,structural, spectroscopic,biological and catalytic activity of Co(II), Ni(II) and Cu(II) complexes of benzilic hydrazide (BH)

Co(II), Ni(II) and Cu(II) chloro complexes of benzilic hydrazide (BH) have been synthesized. Also, reaction of the ligand (BH) with several copper(II) salts, including NO₃ ^?, AcO^?, and SO₄ ^? afforded metal complexes of the general formula [CuLX(H₂O) _n ]·nH₂O, where X is the anion and n = 0, 1 or 2. The newly synthesized complexes were characterized by elemental analysis, mass spectra, molar conductance, UV–vis, IR spectra, magnetic moment, and thermal analysis (TG/DTG). The physico-chemical studies support that the ligand acts as monobasic bidentate towards metal ion through the carbonyl and hydroxyl oxygen atoms. The spectral data revealed that the geometrical structure of the complexes is square planar for Cu (II) complexes and tetrahedral for Co(II) and Ni(II) complexes. Structural parameters of the ligand and its complexes have been calculated. The ligand and its metal complexes are screened for their antimicrobial activity. The catalytic activities of the metal chelates have been studied towards the oxidative decolorization of AB25, IC and AB92 dyes using H₂O₂. The catalytic activity is strongly dependent on the type of the metal ion and the anion of Cu(II) complexes.     

The formation of a series of barium tungsten bronzes

The phases occurring in samples of gross composition Ba_xWO₃ (0.01 < x < 0.33) heated at temperatures between 1073 and 1373°K have been determined using X-ray diffraction and electron microscopy. At all temperatures a tetragonal tungsten bronze phase with a narrow homogeneity range of x = 0.20?0.21 was observed to form. In addition, at temperatures up to 1273°K, a series of orthorhombic intergrowth bronzes forms within a restricted composition range around x = 0.04. The latter phases are unstable at higher temperatures and were not found in preparations made at 1323°K. Similarly a new type of bronze phase forms at x = 0.14?0.16 at temperatures up to 1323°K, but not at 1373°K. The structure of this phase is unknown. Aspects of the crystal chemistry of the barium bronzes and the relationships to other bronze phases are discussed.     

Synthesis,characterization, crystal structure,electrochemical properties and electrocatalytic activity of an unexpected nickel(II) Schiff base complex derived from bis(acetylacetonato)nickel(II), acetone and ethylenediamine

The synthesis, crystal structure and electrochemical properties of a Ni(II) Schiff base complex, [Ni(L)]PF₆ (where L is 2,4,9,11,11-pentamethyl-2,3,4 triaza-1-one-4-amine) are reported herein. The complex has been characterized by its electrochemical behavior, X-ray crystallographic structural analysis, physio-chemical methods and spectroscopic techniques. Electrospray mass spectroscopic analysis gives a dominant ion peak with m/z = 296 which corresponds to the {[Ni(L)]PF₆–HPF₆}⁺ fragment. Cyclic voltammograms for [Ni(L)]PF₆, obtained in DMF (0.1 M Bu₄NPF₆) at a glassy carbon electrode with a scan rate of 100 mV s^?1, exhibit reversible ([Ni^II(L)]⁺/[Ni^I(L)]) reduction and chemically irreversible ([Ni^II(L)]⁺/[Ni^III(L)]²⁺→ electroactive product) oxidation processes at ?2.05 and 0.62 V, respectively. The diffusion coefficient, calculated using the Randles–Sevcik relationship, is 9.7 × 10^?6 cm² s^?1. Electrochemical studies reveal that the Ni^I reduced form of the complex is capable of catalyzing CO₂ reduction at a potential that is thermodynamically more favorable than for the reduced [Ni(N,N′-ethylenebis(acetylacetoneiminato)]complex. Spectroelectrochemical analyses following bulk electrolysis of [Ni(L)]PF₆ under CO₂ revealed the formation of oxalate and bicarbonate.     

Rapid separation of nickel for 59Ni and 63Ni activity measurement in radioactive waste samples

A separation procedure of Ni has been described for the quantification of ⁵⁹Ni and ⁶³Ni in radioactive wastes discharged from nuclear power plants and various research activities related to the nuclear fuel cycle. For a rapid separation of the Ni-nuclides in sixteen sample solutions in 0.2 M NH₄-oxalate, a separation system composed of a peristaltic pump with sixteen channels and the same number of Ni–Resin columns was constructed. After sorption of the Ni-nuclides by sequentially passing 100 mL of the sample solution in 0.2 M NH₄-oxalate, 130 mL of 0.1 M NH₄-oxalate solution and 10 mL of deionized water as a wash into the columns, these were purely recovered by passing 10 mL of 9 M HCl into the Ni–Resin columns stacked in series on the anion exchange resin columns. The separation of the Ni-nuclides in sixteen sample solutions can be achieved within 7 h. The chemical yield of the proposed procedure is 92.3 ± 0.8 % (n = 5) and the gravimetric recovery in the preparation stage of the Ni-nuclide sources is also acceptable, 88.5 ± 1.3 % (n = 5).     

Thermal analysis of Cu-14.82 wt% Al-0.4 wt% Be shape memory alloy

The phase transitions proceeding during melting of selected Sn–Ag–Cu alloys were determined by means of the DSC technique. Twelve compositions were studied along two cross-sections with silver to copper molar ratios X(Ag)/X(Cu) = 1 and 7/3 and tin concentration from 0.4 to 0.9 mol fraction. The transition temperatures were calculated using Pandat software package and thermodynamic parameters from the SOLDERS database. The experimental results were compared with both available literature data and calculation results, and a good agreement was observed. Deconvolution of DSC complex curves was performed using PeakFit v.4.12 software package. Eutectic mixture mass fractions involved in the eutectic transformation were determined. The obtained results were compared with the data calculated using thermodynamic parameters and good agreement was achieved in the case of alloys of higher content of Sn. The discrepancy was found in the case of alloys with lower Sn content where initial structure of the samples subjected to DCS analysis was partly a result of the occurrence of peritectic transformation.     

Synthesis, spectral and thermal studies of N,N − -pyridine-2,6-diyl bis[N −-phenyl(thiourea)] and its metal complexes

Four new metal complexes with the general formula, [ML·mH₂O]nH₂O (where, M = Cu(I), Co(II), Ni(II) or Zn(II); L = N,N ^?-pyridine–2,6-diyl bis[N ^?-phenyl (thiourea)] (PDPT); m = 1 or 3 and n = 0.5 or 4.0), have been synthesized and characterized by elemental analyses, spectral analyses (IR, UV–Vis., ¹H-NMR and MS), thermal analyses (TGA), conductivity and magnetic measurements. The results showed that the ligand (PDPT) acts in a mononegative tridentate manner towards Cu(I) ion coordinating via the two thiol sulfurs and pyridyl nitrogen groups with displacement of only one hydrogen atom from the thiol group, while the ligand behaves in a binegative tridentate manner towards the Co(II), Ni(II) and Zn(II) ions with displacement of two hydrogen atoms from the two thiol groups. The value of magnetic measurements showed a diamagnetic character of the copper complex indicating the reduction of Cu(II) to Cu(I). Semi-empirical calculations of the ligand and its metal complexes have been used to study the molecular geometry using ZINDO/1, PM3 and AM1. Also, the harmonic vibration spectra of the ligand and its metal complexes have been investigated with the purpose to assist the experimental assignment of metal complexes. The results of the optical absorption studies reveal that the optical transition is direct with band gaps energy (E_g) values 2.62, 1.98 and 1.85 eV for Cu, Co and Ni complexes, respectively, indicating that these complexes can behave as semi-conductors.     

Concentration and pollution assessment of hazardous metal elements in sediments of the Xiangjiang River, China

The concentrations of 21 metals in surface sediments collected from 16 stations in lower reach of Xiangjiang River (Zhuzhou–Xiangtan–Changsha section) were determined by using high-resolution inductively coupled plasma mass spectroscopy and their pollution levels were assessed by applying enrichment factor (EF), the geo-accumulation index (I _geo) and pollution index (PI). The results show the total concentrations in μg g^?1 are as follows: 1.80–14.88 for Sc, 16.66–144.29 for V, 13.27–87.99 for Cr, 159.50–2413.74 for Mn, 2.21–23.14 for Co, 4.71–42.45 for Ni, 5.31–188.89 for Cu, 38.41–1250.47 for Zn; 5.1–22.15 for Ga, 91.8–161.57 for Rb, 20.4–62.51 for Sr, 0.2–2.45 for Mo, 0.9–81.79 for Cd, 3.8–30.3 for Sn, 5.9–18.33 for Cs, 208.10–464.74 for Ba, 1.6–22.05 for W, 18.90–198.01 for Pb, 0.3–8.54 for Bi, 2.6–18.27 for Th, 0.6–13.62 for U. The mean concentrations in sediments divided by the UCC value decrease in the order of Cd > Bi > W > Zn > Pb > Cs > Sn > Mn > Cu > 1.5 times > Cr > U = Ni > V > Co > Rb > 1.0 time > Th > Ga > Sc > Mo > Ba > Sr. The calculated EF and I _geo of metals implied the lower reach of Xiangjiang River had widespread been polluted by Cd, Bi, W, Cs, Pb, Zn, Sn, and locally been polluted by Cu and Mn, and not been polluted by other 12 metals. The PI values indicated almost all stations had been polluted by metals in this river.