Synthesis of nickel-iron spinel by non-conventional methods

Nickel-iron black ceramic pigments of (Fe_0.8Mg_0.2)(Fe_0.2Ni_0.8Cr)O₄ and (Fe_0.8Mg_0.1Zn_0.1)(Fe_0.2Ni_0.8Cr)O₄ compositions have been prepared by non conventional methods such as coprecipitation, microemulsion and polymeric gel routes (alkoxides hydrolysis-condensation), and compared with ceramic samples prepared by the solid state reaction from oxide precursors. The mineralising effect of a 2NaCl:NaF flux agent has been also analysed. Both non conventional methods and mineraliser presence increase the reactivity of the samples. The highest reactivity and the best black colour are obtained in the polymeric gel sample prepared from alkoxides; coprecipitated and microemulsion fired pigments are partially solubilised by glazes due to the small particle size exhibited, leading to brown colours.     

Whole-cell optical biosensor for mercury — operational conditions in saline water

The present study demonstrates the influences of chlorides, fluorides and bromides of potassium and sodium on the growth and Hg²⁺-induced bioluminescence of bioreporter Escherichia coli ARL1. In a Luria-Bertani medium (LB), cell growth was inhibited by concentrations of sodium and potassium fluorides above 0.2 mol L^?1. The addition of NaCl increased cell tolerance to the toxic effects of fluorides and bromides. Lag periods of 10 h and more were observed for cultivations in LB without NaCl and with halides (NaCl, KCl, NaBr, KBr, NaF and KF) at concentrations lower than 0.06 mol L^?1. In a phosphate buffer (PB), the bioluminescence of E. coli ARL1, induced with HgCl₂, was increased by the addition of NaCl, KCl, NaBr, KBr, NaF and KF (concentration of 0–0.25 mol L^?1). In a saline phosphate buffer (PBS), the maxima of induced bioluminescence declined to 50 %, in the case of NaF (0.12 mol L^?1), and to zero for KF. An addition of tryptone to the induction medium increased induced light emission ten-fold. Concentrated artificial sea water (ASW) (70–100 % ASW) inhibited bioluminescence induction. The new detection assay with E. coli ARL1 made possible the detection of 0.57 µL^?1 of HgCl₂ in double-diluted artificial sea water (25 % ASW).     

Preparation of Cr-Doped YAlO_3 Red Ceramic Pigment and the Coloration Mechanism

The red ceramic pigment is widely used in industrial production, but the pigments with pure color and bright red performance are rare. Therefore, it is important to study and develop new red ceramic pigment with perfect color performance. This paper reports the preparation of Cr-doped YAlO_3 red ceramic pigment rendering by sol-gel method with high temperature resistance, good color and proposed color mechanism. The prepared samples were characterized by XRD, SEM, EDS and UV-vis, and the effects of Cr on the crystal structure, color rendering properties and color mechanism were discussed. The results showed that the optimum concentration of coloring agent(Cr) in Cr:YAlO_3 red ceramic pigment was 3 at.%. The main color mechanism was also discussed. Compared with the solid phase sintering and precipitation methods for the synthesis of red ceramic pigment, the sol-gel method possessed obvious advantages, such as perfect mixing of the raw materials, uniform dispersion of doping ions and the pure color.     

Iron oxide pigmenting powders produced by thermal treatment of iron solid wastes from steel mill pickling lines

Phase changes of iron containing solid wastes from steel mill pickling lines after thermal treatments were investigated aiming the determination of the appropriate conditions for its transformation to be useful for industrial raw materials. Above 275°C, the thermally treated wastes contain a mixture of α-Fe₂O₃ (hematite) and γ-Fe₂O₃ (maghemite) in different proportions, depending on the maximum heating temperature of the thermal treatment. Increasing the maximum temperature the maghemite participation is decreased through its transformation to hematite. Above 850°C hematite is the main constituent, suggesting that thermal treatment of the wastes in this temperature will give a product that could be used as red iron pigment.     

Effect of NaOH and NaCl on the disodiumn-decane phosphonate micellar aggregation number

The diffusion coefficient of disodiumn-decane phosphonate micelles was studied by polarography at 25°C in NaCl and in NaOH solutions, and the size and aggregation number of the micelles was computed as a function of Na⁺ concentration. All other conditions being equal, the addition of NaCl produces micelles with an aggregation number one order of magnitude larger than the NaOH addition. This is due to the increase of the effective charge per micellized head group produced by the reaction of OH- with the hydrolized head groups which are mainly present as-PO₃H- in the micellar Stern layer.     

An atomic charge study of highly ionic diatomic molecular systems

Four atomic charge formalisms are compared using highly ionic diatomic molecules, such as LiF, NaF, KF, LiCl, NaCl, KCl, BF, AlF, GaF, BeO, and MgO. All calculations were done at the QCISD/6‐311G(2df) level. The only formalism consistent with the characteristics of all these systems is Quantum theory of atoms in molecules (QTAIM). Absolute Mulliken charge values are small. ChelpG charges are not reliable for systems in which the atoms are largely anisotropic. Generalized atomic polar tensor values are contaminated with charge fluxes and atomic dipole fluxes and fail when these contributions are important and do not cancel each other. Finally, the charge–charge flux–dipole flux model was applied to dipole moment derivatives with QTAIM. This analysis shows that charge flux and atomic dipole flux contributions during bond stretching are almost null, except for oxides. There are also evidences that the lone electron pair at Group 13 elements in fluorides becomes less localized as the bond is stretched. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm^–3 (TOA); HF concentration in the feed solution, 0.01 mol·dm^–3 and concentration of NaOH used as stripping agent 2.5 mol·dm^–3. The maximum flux and permeability determined under optimum conditions are 3.06·10^–5 mol·m^–2·s^–1 and 8.44·10^–11 mol· ·m²·s^–1 at 25±2°C and 4.21·10^–5 mol·m^–2·s^–1 and 11.55·10^–11 mol·m²·s^–1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10^–11 mol·m²·s^–1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.     

Extraction of Pd(II) ions using tri-n-octylamine xylene base supported liquid membranes

Membranes, based on tri-n-octylamine (TOA) xylene liquid, supported in hydrophobic microporous films have been used to study the transport of Pd(II) ions, after extraction into the membrane. Various parameters, such as the effect of hydrochloric acid concentration in the feed solution, TOA concentration in the membrane phase, effect of stripping agent like nitric acid concentration, and temperature on the flux of Pd(II) ions across the liquid membranes have been investigated. The optimum conditions of transport for these metal ions determined are, TOA concentration, 1.25 mol·dm^–3, HCl concentration in the feed solution, 5 mol·dm^–3, and concentration of nitric acid used as a stripping, agent 5 mol·dm^–3. The maximum values of the flux and permeability determined under the optimum condition are 23·10^–6 mol·m^–2·s^–1 and 2.40·10³ m²·s^–1 at 25°C. The results obtained have been used to elucidate the mechanism of palladium transport.     

Vibrational spectroscopy applied to the study of archeological ceramic artifacts from Guarani culture in Brazil

An archeological artifact can be seen as a chronological element, which helps to determine the age of certain society and to understand the thinking, values and the way of life of this society. Thus, the classification of archeological artifacts is one of the approaches used to study the cultural system of antique societies trying to reconstruct their history. The “Centro de Museologia, Antropologia e Arqueologia (CEMAARQ)” of the “Unesp Univ Estadual Paulista” in Presidente Prudente, Sao Paulo state, Brazil, develops projects within this context (identification and preservation). This is the case of the archeological site named “Lagoa São Paulo-02” discovered in 1993 at the margins of the Parana river in the region of Presidente Epitácio city, São Paulo state, Brazil. This site has ceramic fragments of different shapes and sizes that have a strong influence of traces of the Guarani culture, which is one of the Brazilian native populations. These samples were basically characterized via micro-Raman scattering and Fourier transform infrared absorption (FTIR) spectroscopies. The main objective was to identify the pigments used in the manufacture of the ceramic artifacts and to analyze the composition of the ceramic body to understand how the artifacts were made. Three pigments were found: red, black and white. For the red pigment were identified characteristic bands of hematite, an iron oxide found in the red rocks of the river banks that were eroded by water. The black pigment, probably, is due to the use of vegetal charcoal, which is found in nature as the product of burning organic material such as wood. For the white pigment, the FTIR spectra suggested the use of kaolin, either in the ceramic body or in the proper white pigment, due to the presence of the characteristic bands of the kaolinite. Complementary, the additives applied as anti-plastics were identified as charcoal and quartz, being the latter found in the rocks present in the archeological site.     

Cathodic stripping voltammetry of technetium in the tetraphenylarsonium chloride/chloroform extract at a hanging mercury drop electrode

Technetium(VII) was separated from interfering substances by extraction with 0.01M tetraphenylarsonium chloride in chloroform. To avoid back-extraction, enrichment at the hanging mercury drop electrode (HMDE) has been carried out directly in the organic phase after addition of 0.01M NaOH as an electrolyte and ethanol as a homogenized agent. By application of a deposition voltage of –1.6 V, as well as DPCSV, a distinct current signal at –0.26 V (vs. Ag/AgCl) was obtained. The detection limit was found to be 3·10^–8 M Tc.     

Optimum cleaning-in-place conditions for stainless steel microfiltration membrane fouled by terephthalic acid solids

Terephthalic acid (TPA) is a raw material of polyester fiber and polyethylene terephthalate. When TPA is produced by catalytic air oxidation of p-xylene in the presence of acetic acid solvent, most of produced TPA exists in the form of crystalline suspended solids. A microfiltration process may be used to recover TPA, but the microfilters are subjected to fouling and therefore cleaning-in-place (CIP) regimes need to be developed. In this research, the effects of variations to CIP conditions were investigated on the flux recovery accomplished in a TiO₂-sintered stainless steel microfiltration membrane (0.1 μm pore size) fouled with TPA. The extent of flux recovery was estimated as the ratio of the stabilized flux obtained during CIP to the water flux value achieved under corresponding operational conditions. Based upon batch solubility tests, sodium hydroxide (NaOH) was chosen as the major cleaning agent for the present experiment. The extent of flux recovery increased with increasing NaOH concentration over the range of 3–4% (w/v) NaOH, but decreased at NaOH concentrations above 4%. The flux recovery was favored at high cross-flow velocities, high temperatures and low transmembrane pressures. A high temperature run of cleaning did not produce any adverse effects up to 70 °C. The addition of surfactants (SDS and Tween 80) to the caustic cleaning agent led to a significant reduction in cleaning efficiency.     

Molecular complexes of copper(I): Easy access to CuF(PPh3)3 · 2ROH (R = Me or Et)

Treatment of a CuSO₄ · 5H₂O solution with NH₂OH · HCl and NaOH produces orange–yellow Cu₂O, which on being reacted with Ph₃P and aqueous HF (48%) in MeOH or EtOH yields CuF(PPh₃)₃ · 2ROH (R = Me or Et) in high yield. The volatile compounds have been characterised by spectroscopic techniques in addition to chemical analyses and solution electrical conductance measurements. Typically, CuF(PPh₃)₃ · 2MeOH appears to be stable up to 118 °C and loses 2 MeOH and 3 PPh₃ between 118 and 274 °C yielding volatile CuF at 274 °C.     

Characterization of colour pigments in pre-Columbian Chilean potteries by PIXE elemental analysis

Ancient ceremonial potteries belonging to pre-Columbian cultures in Chile, South America, are decorated with three different colours, red, white and black. Samples of these colours have been analyzed with induced X-ray fluorescence by a 6.6 MeV proton beam. The analyses show clearly distinct patterns for each pigment and also denote differences between the same colour in two cultures. Eight elements, from aluminium to copper were detected.Under partial support from the Departamento Técnico de Investigación de la Universidad de Chile, Grant 2438-8833.     

Determination of trace concentration of boron in ADU by the nuclear track technique

A method for the determination of boron concentration in extracted (NH₄)₂ U₂O₇·H₂O (ADU) has been used. One ml of the aqueous solution is irradiated with thermal neutrons from a 10 Ci Am/Be neutron source with a flux of 0.2·10⁵ n·cm^–2·s^–1 and thermal column in the IRT-5000 with a flux of about 10⁷ n·cm^–2·s^–1. The alpha-activity due to the reaction¹⁰B(n, )⁷Li is recorded by a CR-39 alpha track detector. After the exposure, the alpha tracks are made visible in an optical microscope at magnification of 800X by etching the detector in 6N NaOH, and the track density is determined using calibration curves of known concentrations of boron. The boron concentration of the extracted ADU was found to be 5 ppm.     

Shape,Size, and Phase‐Controlled Rare‐Earth Fluoride Nanocrystals with Optical Up‐Conversion Properties

High‐quality rare‐earth fluorides, α‐NaMF₄ (M=Dy, Ho, Er, Tm, Y, Yb, and Lu) nanocrystals and β‐NaMF₄ (M=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y, Yb, and Lu) nanoarrays, have been synthesized by using oleic acid as a stabilizing agent through a facile hydrothermal method at 130–230 °C. The phase, shape, and size of the products are varied by careful control of synthetic conditions, including hydrothermal temperature and time, and the amounts of reactants and solvents. Tuning the hydrothermal temperature, time, and the amount of NaOH can cause the transformation from the cubic α‐NaMF₄ to hexagonal phase β‐NaMF₄. Upon adjustment of the amount of NaOH, NaF, M³⁺, and ethanol, the morphologies for the β‐NaMF₄ nanoarrays can range from tube, rod, wire, and zigzagged rod, to flower‐patterned disk. Simultaneously, the size of the rare‐earth fluoride crystals is variable from 5 nm to several micrometers. A combination of “diffusion‐controlled growth” and the “organic–inorganic interface effect” is proposed to understand the formation of the nanocrystals. An ideal “1D growth” of rare‐earth fluorides is preferred at high temperatures and high ethanol contents, from which the tube‐ and rodlike nanoarrays with high aspect ratio are obtained. In contrast, the disklike β‐NaMF₄ nanoarrays with low aspect ratios are produced by decreasing the ethanol content or prolonging the reaction time, an effect probably caused by “1D/2D ripening”. Multicolor up‐conversion fluorescence is also successfully realized in the Yb³⁺/Er³⁺ (green, red) and Yb³⁺/Tm³⁺ (blue) co‐doped α‐NaYF₄ nanocrystals and β‐NaYF₄ nanoarrays by excitation in the NIR region (980 nm).     

Transport of titanium(IV) ions across di-2-ethylhexylphosphoric acid-CCl4 supported liquid membranes

Transport study for Ti(IV) ions using di-2-ethylhexylphosphoric acid (D2EHPA) (carrier)-CCl₄ (diluent) liquid supported membrane in microporous polypropylene hydrophobic film has been performed. The parameters studied are effects of carrier, H₂SO₄, stripping agent (NH₄F) concentrations and temperature variation on flux and permeability coefficients of the metal ion. The optimum concentrations of transport found are 2.04 mol·dm^–3 D2EHPA, 1.0 mol·dm^–3 H₂SO₄ in the feed and 1 mol·dm^–3 NH₄F as stripping agent. The maximum flux and permeability coefficient determined are 1.32·10^–5 mol·m^–2·s^–1 and 8.02·10^–12 mol·m^–2·s^–1, respectively. The transport of this metal ion is increased with increase in temperature. The mechanism of transport appears to be based on coupled counter ion transport phenomenon.     

Mechanochemical reactions of fluorides with hemin

Hemin has two potential sites to react with fluorides, the peripheral acid groups and the central Fe^III cation. The mechanochemical reactions of hemin with fluorides (LiF, NaF, KF, CsF, NH₄F and AgF) were monitored using X-ray diffraction (XRD), and IR and Mössbauer spectroscopies. LiF and NaF were found inert when milled with hemin, however KF, CsF, NH₄F and AgF react at both hemin sites. At the iron site Cl⁻ is replaced by F⁻ with formation of KCl, CsCl, NH₄Cl, and AgCl, as detected by XRD, while with the peripheral acid groups, fluorides collect the acidic protons to form KHF₂, CsHF₂, NH₄HF and AgHF₂. The reactions of hemin with the reactive fluorides take place first at the iron site and then at the propionic acid groups.     

Spectroscopic Characterization of the Architectural Painting from the Cizhong Catholic Church of Yunnan Province,China

The Cizhong Catholic Church, which incorporates local Chinese architectural styles and artistic motifs, witnessed the transmission of Catholicism in Yunnan Province in the late Qing Dynasty. The pigments of the paintings from the church were identified by micro-Raman Spectroscopy, micro X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The analyses indicated that chromogenic substances of the white pigment was calcite, that of the black pigment was carbon black, that of the red pigment was hematite, that of the blue pigment was artificial ultramarine, and that of the green pigment was emerald green. The study also revealed that artificial ultramarine and emerald green were probably imported or brought by French missionaries from Europe. In addition, emerald green was identified to have partially degraded into cornwallite.     

Effect of the nature of solid metal fluorides on the alkylation kinetics of CH-acids in the presence of onium salts

The selective C-alkylation of ethyl 2-methylacetoacetate by prenyl chloride in the presence of solid metal fluorides proceeds at room temperature with yields of from 2.5 to 87.5% depending on the nature of the deprotonating agent. The alkylation rate increases in going from LiF to CsF. A linear correlation was found between the activation free energy for the alkylation reaction and the crystal lattice energy of the solid metal fluorides. Ion exchange was not observed between tetrabutylammonium chloride and solid KF, CsF, and CaF₂ in acetonitrile. The extent of the exchange with KF·2H₂O over 10 h did not exceed 6%. Deprotonation of ethyl 2-methylacetoacetate by the action of the solid metal fluorides was not observed. Loss of the CH-acid is found in the presence of an onium salt, which varies upon, changing the nature of the deprotonating agent: LiF-NaF=KF (30%), RbF (54%), CsF (90%), CaF₂ (35%).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2690–2696, December, 1989.     

Thermal analysis of the Ce<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Tb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> pigments

Compounds based on CeO₂ were synthesized as high-temperature environment-friendly inorganic pigments with interesting hues. The pigments have been synthesized by using the solid state reaction in the temperature range from 1,300 to 1,600 °C. The host lattice of these pigments is CeO₂ that is doped by terbium ions. The incorporation of doped ions provides interesting orange colours after application into ceramic glaze. The goal was to develop conditions for the synthesis of these compounds and to determine the influence of calcination temperature on their colouring effects. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. The pigments were also evaluated from the standpoint of their structure and particle sizes.