[en] The thermodynamic metal ligand stability constants of rare earths, La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺ and Tb³⁺ with N-p-chlorophenyl-m-substituted benzohydroxamic acids in dioxan-water (60-70%) media at 25 deg C were determined by the potentiometric method. The effect of basicity of the ligand, central metal ion and the order of stability constants are discussed. The order of stability constants of rare earths with the hydroxamic acids is La< Pr< Nd< Sm< Eu< Gd>Tb. (author)

[en] The authors report on thin films produced by laser breakdown chemical vapor deposition from nickel and iron carbonyls and by implanting Ni foils with varying levels of characterized by transmission electron microscopy. Decomposition of Ni(CO)₄ produced polycrystalline films of fcc Ni and metastable ordered hexagonal Ni₃C. This metastable phase is identical to that produced by gas carburization, rapid solidification of Ni-C melts, and ion implantation of C into Ni at low concentration. Increasing the H₂ content in the gas mixture during laser deposition reduces the grain size of the films significantly with grain sizes smaller than 10 nanometers produced. Laser decomposition of Fe(CO)₅ produces films with islands of fcc gamma-Fe and finely dispersed metastable Fe₂O₃ and Fe₃O₄ were found in these samples. Implants of C into pure Ni foils at 77 degrees K and at a concentration of 35 at.% produced amorphous layers. Implants at the same dose at room temperature did not produce amorphous layers

[en] An adaptive controller has been designed for the water level of a Westinghouse type U-tube steam generator, and its operation has been demonstrated in the entire power range via computer simulations. The proposed design exhibits improved performance, at low operating powers, a,s compared to existing controller types. The continuous-time controller design is performed systematically via the Linear Quadratic Gaussian/Loop Transfer Recovery method, followed by gain adaptation allowing controller operation in the entire power range. Digital implementation of the controller is accomplished by a digital redesign which results in matching the digital and continuous-time system and controller states. It is only at this stage of the control system design process that issues such as microprocessor induced quantization effects are taken into account. The use of computer-aided-design software greatly expedites the design cycle, allowing the designer to maximize the controller stability robustness to uncertainties via numerous iterations. This inherent controller robustness can be exploited to tolerate incipient plant faults, such as deteriorating U-tube heat transfer properties, without significant loss of controller performance

[en] A sensitive and selective method for the micro-determination of Mo(VI) has been developed, involving selective extraction of the yellow Mo(VI) - N-phenylbenzohydroxamic acid -SCN- complex with a liquid ion exchanger, Aliquat 336, from a medium of 2-5 M hydrochloric acid. The molar absorptivity of the complex is 7.2x10⁴ l mol^-1 cm^-1 at 350 nm and the colour system obeys Beer's law in the range 0.34-10 p.p.m. of Mo(VI). The extracted metal can be quantitatively back-extracted with 0.3 M ammonia solution, thus rendering the method applicable for the concentration, determination and separation of Mo(VI) in samples containing very low levels of the metal. Molybdenum has been determined in standard steel samples and in a plant sample. (author)

[en] A method for the preconcentration and trace determination of thorium with crown hydroxamic acid (NHDTAHA) is described. The thorium is extracted from the chloroform solution of NHDTAHA at pH 4 which gives a colourless extract, λ_max = 365 nm; ε = 9.4 x 10^-3 1 x mol^-1 x cm^-1. The extract is directly inserted in the plasma for ICP-AES measurements of thorium. A linear calibration graph was obtained between 15-150 ng x ml^-1 of thorium. The proposed method has been applied for the determination of thorium in the presence of several diverse ions in monazite sand, rare earth sand and in sea water. (author)

[en] The influence of the temperature of tempering on the nature of the precipitate phase in dilute zirconium-tantalum alloys has been examined with the help of computed free enthalpy versus composition plots at various temperatures. The observed precipitation of the metastable β₁ phase at ageing temperatures lower than but not much below the monotectoid temperature has been rationalised in terms of these plots. (orig.)

[en] A new chromogenic calixarene with hydroxamic acid as chelating agent was synthesized by partial reduction of nitrocalixarene which was subsequently coupled with coumarin chloride. The reagent showed selective and quantitative extraction of Ti(IV) into chloroform at 6 M HCl and that of Zr(IV) at 0.5 M HCl. A facile liquid-liquid extraction method for the separation and spectrophotometric determination of Ti(IV) and Zr(IV) has been proposed. The validity of the method was checked by separating several synthetic mixtures. The method was successfully applied to the analysis of piezoelectric lead-zirconium-titanate (PZT) samples. The method shows remarkable simplicity and selectivity. The method can also be used for the determination of Ti(IV) and Zr(IV) in various environmental samples

[en] The final dismantlement of nuclear power stations could be made easier and less expensive by - making the suitable choice between otherwise comparable alternatives at the design stage; - introducing design changes mainly of a preparatory character for easing the processs of dismantlement. The paper discusses three examples of such choices or changes in the field of civil engineering of light water reactors

[en] Dielectric absorption of dibenzo-18-crown-6 (DB18C6) in solutions of 1,4-dioxane have been studied at 9.1 GHz frequency at three different temperatures 293.15, 303.15 and 313.15 K. A single frequency concentration variation method of Gopalkrishna was used to calculate relaxation time (τ_GK). Thermodynamical parameters, like free energy (ΔF), enthalpy (ΔH) and entropy (ΔS) of activation for the dielectric relaxation have been determined using dielectric data. Static permittivity, refractive index and density of liquid solutions are also measured at 293.15 K. Dipole moment of DB18C6 is determined using Gopalkrishna and Guggenheim’s method. (author)

[en] The preparation of W-type hexaferrite particles with the composition BaCa₂Fe₁₆O₂₇ by microemulsion and a stearic acid sol-gel method with and without surfactant has been investigated at various sintering temperatures. The structural and magnetic characteristics have been studied by X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and Fourier transform infrared (FTIR) techniques. The effect of sintering temperature on the properties of BaCa₂Fe₁₆O₂₇ hexaferrites has been studied. The value of saturation magnetization (M_s) depends on types of surfactant used. The sample prepared in the presence of polyoxyethylene (20) sorbitan monooleat (Tween 80) shows low saturation magnetization (M_s=15.10 emu/g), whereas the other sample prepared in the presence of a surfactant cetyltrimethylammonium bromide (CTAB) exhibits high saturation magnetization (M_s=24.60 emu/g) compared to the normal sample