Sodium dodecyl benzene sulfonate-assisted synthesis through a hydrothermal reaction

The effects of the anionic surfactant on the morphology, size and crystallization of NiSe precipitated from NiCl₂·6H₂O and SeCl₄ in presence of hydrazine (N₂H₄·H₂O) as reductant were investigated. The products have been successfully synthesized in presence of sodium dodecyl benzene sulfonate (SDBS) as surfactant via an improved hydrothermal route. A variety of synthesis parameters, such as reaction time and temperature, capping agent and amount of reducing agent have a significant effect on the particle size, phase purity and morphology of the obtained products. The sample size became bigger with decreasing reaction temperature and increasing reaction time. In the presence of 2 ml hydrazine, the samples were found to be the mixture of Ni₃Se₂ and NiSe. With increasing the reaction time and amount of hydrazine a pure phase of hexagonal NiSe was obtained. X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) images indicate phase, particle size and morphology of the products. Chemical composition and purity of the products were characterized by X-ray energy dispersive spectroscopy (EDS). Photoluminescence (PL) was used to study the optical properties of NiSe samples.     

The electrochemical behavior of a Ti50Ni47Fe3 shape memory alloy

The corrosion performance of Ti₅₀Ni₄₇Fe₃ alloy in 0.9% NaCl physiological, artificial saliva and Hank's solutions with different pH values at 37 °C was investigated by means of open circuit potential (OCP) measurement and linear polarization (LP) measurement techniques, respectively. The OCP stabilized at − 0.2925, − 0.3111 and − 0.3454 mV/SCE in sequence for 0.9% NaCl, artificial saliva and Hank's solutions, respectively. LP results demonstrated that the Ti₅₀Ni₄₇Fe₃ alloy has a low passive current and a wide passive range. The surface roughness and in-depth distribution of the passive films after immersion in corrosion media was characterized by using Atomic Force Measurement (AFM) and X-ray electron spectroscopy (XPS). AFM results shows that the electrochemical measurements have little influence on the surface roughness of the Ti₅₀Ni₄₇Fe₃ alloy, and the XPS analysis results revealed that the outer passive film consisting mainly of a layer of TiO₂ which is deemed to be important for all biomaterials.     

Thermal synthesis of nanocrystalline fcc Fe–Ni alloy by gaseous reduction of coprecipitated NiFe2O4 from secondary resources

Abstract

Nanocrystalline fcc Fe–Ni alloy has been fabricated by gaseous reduction of coprecipitated NiFe₂O₄ from fly ash. Pure crystalline nickel ferrite is obtained by thermal treatment of coprecipitated hydrated sulphate mixture of iron and nickel produced from treatment of fly ash. The produced powders of NiFe₂O₄ were isothermally reduced in pure hydrogen at 800–1100°C to synthesise fcc Fe–Ni alloy. The reduction behaviour of nanosized NiFe₂O₄ was investigated. The formed phases after reduction processes were identified by X-ray phase analysis. The microstructures of partially and completely reduced samples were examined by a scanning electron microscope and an optical microscope. The kinetics data obtained from reduction process were used to elucidate the reduction mechanism under isothermal condition. It was found that nanocrystalline fcc Fe–Ni alloy (Fe_0·64Ni_0·36) can be obtained from NiFe₂O₄ powders. The reduction rate increased with increasing reduction temperature in both the initial and final reduction stages. At the initial stages of reduction, the reaction rate was controlled by gaseous diffusion mechanism while the combination of gaseous diffusion and chemical reaction mechanism controlled the final stages. Grain growth and coalescence of the formed Fe_0·64Ni_0·36 grains took place by increasing the reduction temperature.     

Electrochemical passivation behaviour of nanocrystalline Fe80Si20 coating in borate buffer solution

Passivation behaviour of nanocrystalline coating (Fe₈₀Si₂₀) obtained by in situ mechanical alloying route is studied and compared with that of the commercial pure iron and cast Fe₈₀Si₂₀ in sodium borate buffer solution at two different pH values (7·7 and 8·4). The coating reveals single passivation at a pH of 7·7 and double stage passivity at a pH of 8·4. The first passive layer is due to the dissolution mechanism and second passivity is related to stable passivation. The cast sample shows single stage passivity in the solution of pH 8·4. The difference in the passivation behaviour for the cast alloy (Fe₈₀Si₂₀) and the coating is related to the presence of highly iron-enriched localized regions, formed during the processing stage of coating.     

Microstructure and mechanical properties in Ni45·4Mn39·5In13·1Gd2 alloy with high transformation temperature

Abstract

A Heusler Ni_45·4Mn_39·5In_13·1Gd₂ alloy with high transformation temperature has been obtained by substituting 2 at-%Gd for Mn in a ternary Ni_45·4Mn_41·5In_13·1 ferromagnetic shape memory alloy. It is shown that the microstructure of Ni_45·4Mn_39·5In_13·1Gd₂ alloy consists of a matrix and a Gd rich phase. The Ni_45·4Mn_39·5In_13·1Gd₂ alloy exhibits a martensitic transformation start temperature of 726 K, and the transformation hysteresis is A_f?M_s?=?148°C. At room temperature, non-modulated martensite of tetragonal L1₀ structure is observed in Ni_45·4Mn_39·5In_13·1Gd₂ alloy. In addition, it is revealed that the addition of Gd significantly enhances the compressive strength and improves the ductility of Ni_45·4Mn_39·5In_13·1Gd₂ alloy.     

Reaction between Si3N4 and Fe-Ni alloy

In relation to the joining of silicon nitride ceramics to metal, the reaction between Si₃N₄ and Fe-Ni alloy was investigated under a nitrogen or an argon atmosphere at temperatures from 1123 to 1573 K. Reaction rates were determined by thermogravimetry and reaction products were examined by X-ray diffraction. Fe-Ni-Si solid solution, Ni₃Si, Ni₅Si₂, NiSi₂, Fe₃Si, Fe₅Si₃ and FeSi were produced. The initial rate obeyed a linear rate law. The rate at the late stage of reaction was described by a parabolic rate law or Fick's second law. The reaction mechanism and the rate-determining step were proposed.     

Structure and magnetic properties of mechanically synthesized nanocrystalline Co52Fe26Ni22 alloy

Mechanical alloying method was used to prepare nanocrystalline Co₅₂Fe₂₆Ni₂₂ alloy. X-ray diffraction was applied for determination of the structure of the alloy. During milling Co-based solid solution with f.c.c. lattice was formed. After 80 h of synthesis the lattice parameter was equal to 0.3575 nm while the average grain sizes and the mean level of internal strains were about 24 nm and 0.72%, respectively. Mössbauer spectroscopy was adopted to characterize the local atomic order of the Co₅₂Fe₂₆Ni₂₂ alloy. In the nearest neighbourhood of ⁵⁷Fe isotopes there are at least six Co atoms, three Ni atoms and three Fe atoms giving the hyperfine magnetic field equal to 32.45(1) T. Magnetization measurements allowed to determine the effective magnetic moment of the Co₅₂Fe₂₆Ni₂₂ alloy to be equal to 1.63 μ_B per formula unit. Curie temperature of the obtained alloy is equal to 1000 K.     

Microstructure and martensitic transformation and mechanical properties of cast Ni rich NiTiCo shape memory alloys

Abstract

The influence of Co additions on the microstructure, second phase precipitates, phase transformation and mechanical properties of cast Ni_51?xTi₄₉Co_x (x?=?0, 0·5, 1·5 and 4 at-%) shape memory alloys was investigated. At the expense of Ni, Co added to NiTi alloy significantly increases the martensitic transformation temperature. The matrix phase in the microstructure of Ni₅₁Ti₄₉Co₀ alloy is the austenite phase (B2) in addition to martensite phase (B19′) and precipitates of NiTi intermetallic compounds. However, the parent phase in the other three alloys, Ni_50·5Ti₄₉Co_0·5, Ni_49·5Ti₄₉Co_1·5 and Ni₄₇Ti₄₉Co₄, is martensite. Ti₂Ni phase was found in the microstructures of the all investigated alloys; however, Ni₃Ti₂ phase precipitated only in the NiTi alloy with 0 at-%Co. The volume fraction of Ti₂Ni phase decreased by the additions of 0·5 and 1·5 at-%Co, while it is slightly increased with 4 at-%Co. The hardness value of NiTi alloy is affected by Co additions.     

The fcc/bcc phase transition in Fe<Subscript>x</Subscript>Ni<Subscript>100−x</Subscript> nanoparticles resolved by first-order reversal curves

One-pot polyol processing was successfully used for the preparation of Fe_xNi_100?x nanoparticles. By increasing Ni concentration in Fe_xNi_100?x alloy, the phase transition from bcc to fcc crystalline structure was clearly indicated by the XRD data as well as the measured hysteresis loops. FORC diagrams demonstrated that the prepared samples consist of single-domain magnetic particles with a uniform particle size. By changing the molar ratio of the precursors, different compositions of FeNi alloy were obtained. The influence of the temperature, solvent, surfactant, and amount of NaOH was also studied on the particle size, structure, and magnetic properties of the products.     

Statistical thermodynamic approach to carbon solubility in face centred cubic Fe1-yNiy alloy lattice

Carbon solubility in a face centred cubic (fcc) Fe_1-yNi_y alloy lattice was analysed on the basis of statistical thermodynamics assuming negligible C—C interaction in the fcc Fe_1-yNi_y lattice. The minimum carbon solubility was observed for values of y of ~ 0·6–0·7 and appeared to be ascribable to the minimum number of available interstitial sites for occupation by carbon atoms in the fcc Fe_1-yNi_y lattice around this composition. Accordingly, the extent of stabilisation for carbon atoms in the fcc Fe_1-yNi_y was estimated to be a minimum around this composition. The observed variation for the carbon solubility and the extent of stabilisation of the carbon atoms in the fcc Fe_1-yNi_y lattice with respect to the composition y appeared to be related to the stability of the ferromagnetic phase.

MST/3251     

Synthesis,microstructure and oxidation of Co-MgAl2O4 and Ni-MgAl2O4 nanocomposite powders

MgAl₂O₄-CoAl₂O₄ and MgAl₂O₄-NiAl₂O₄ solid solutions are synthesized by combustion in urea of the appropriate metal nitrates. The selective reduction in hydrogen of these oxides gives rise to a dispersion of nanometric Co or Ni particles in the spinel matrix. The reduction of the Co²⁺ and Ni²⁺ ions is complete at 900 and 1000 °C respectively. Owing to the homogeneity of the starting oxide solid solution, the size distribution of the metal particles is narrow and their average size is about 10 nm. During a thermal treatment in air, the nanometric metal particles located in the open porosity of the matrix are totally oxidized at temperatures lower than 700 °C, whereas those dispersed inside the matrix grains are stable up to 900 °C. These latter particles account for more than half of the total metal content.     

Effect of heat treatment on structure and magnetic properties of FeCoNi/CNTs nanocomposites

Fe₄₆Co₃₅Ni₁₉/CNTs nanocomposites have been prepared by an easy two-step route including adsorption and heat treatment processes. We investigated the effect of heat treatment conditions on structure, morphology, nanoparticle sizes and magnetic properties of the Fe₄₆Co₃₅Ni₁₉ alloy nanoparticles attached on the carbon nanotubes by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-disperse X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM). When the reducing temperature changes from 300–450°C, a transition of the crystalline structure from bcc phase to fcc-bcc dual phase and an increase in particle size of Fe₄₆Co₃₅Ni₁₉ nanoparticles together with a local maximum at 350°C are observed. Meanwhile, the saturation magnetization (M _s) for Fe₄₆Co₃₅Ni₁₉ nanoparticles increases with the increase of reducing temperature and the coercivity (H _c) decreases rapidly with a local minimum at 350°C. When the reducing time (tr) changes from 2–5 h, bcc phase is predominant in the Fe₄₆Co₃₅Ni₁₉ alloy particles. Both the particle size and M _s have a maximum at tr = 3 h, and the H _c reaches a maximum at tr = 4 h.     

Hydrothermal synthesis and magnetic properties of CoxFe1−x/CoyLazFe3−y−zO4 composites

A series of iron–cobalt alloy and cobalt–ferrite composites doped with La³⁺ (Co_xFe_1−x/Co_yLa_zFe_3−y−zO₄) in which the Fe–Co alloy has either a bcc or a fcc structure and the oxide is a spinel phase, have been synthesized by using the disproportionation of Fe (OH)₂ and the reduction of Co (II) by Fe⁰ in a concentrated and hot KOH solution. when x ≤ 0.1, the structures of the Fe_xCo_1−x alloy and cobalt–ferrite are fcc structure; and when x ≥ 0.25, the structures of the Fe_xCo_1−x alloy is bcc structure. The fcc structure of alloy is favored for [KOH] close to 9 N, Co(II)/Fe(II) ratios between 0.5 and 0.9 and short reaction time of synthesis. And the bcc structure of the alloy is favored for [KOH] close to 1 N, Co(II)/Fe(II) ratios between 0.1 and 0.5 and long reaction time of synthesis. A low [KOH] favors nucleation leading to octahedral of 1 μm. And [KOH] of 9–12 N favors particle growth. The metal occurs in square particles of 100–150 nm included within the spinel. Powder X-ray diffraction (XRD), thermal gravity analysis (TGA) and different thermal analysis (DTA), scanning electron microscope (SEM), transmission electron micrograph (TEM) and vibrating sample magnetometer (VSM) were employed characterize the crystallite sizes, structure, morphology and magnetic properties of the composites. And the effect of the Co(II)/Fe (II) ratio (0 ≤ Co/Fe ≤ 1), concentration of KOH, reaction time and substitution Fe³⁺ ions by La³⁺ ions on structure, magnetic properties of the composites were investigated.     

Ionic mobility and conduction in the 50PbF2 · 30BiF3 · 20NaF solid solution studied by NMR and impedance spectroscopy

Ionic mobility and electrical transport in the 50PbF₂ · 30BiF₃ · 20NaF fluorite solid solution have been studied by ¹⁹F and ²³Na NMR and impedance spectroscopy. Analysis of the NMR spectra allowed us to assess the temperature effect on the nature of ion motion in the fluorine and sodium sublattices, to identify the types of ionic mobility, and determine the corresponding temperature ranges. The results demonstrate that, at temperatures above 390 K, the dominant type of ion motion in 50PbF₂ · 30BiF₃ · 20NaF is the diffusion of fluoride and sodium ions. The ionic conductivity of the solid solution reaches 4.4 × 10^?4 S/cm at 535 K, suggesting that the 50PbF₂ · 30BiF₃ · 20NaF solid solution can be used as a key component for engineering new functional materials.     

Effect of annealing on the characteristics of Au layers grown on the high-temperature deposited Ni50Fe50 layers

80 nm-thick Ni₅₀Fe₅₀ layers were sputter-deposited on glass substrates at 400 °C and then Au layers were sputter-deposited on the Ni₅₀Fe₅₀ layers. The Au/Ni₅₀Fe₅₀ bilayer films were annealed in a vacuum of 5×10⁻⁴ Pa from 250 to 450 °C for 30 min or 90 min. The characteristics of the Au layers were studied by Auger electron spectroscopy, field emission scanning electron microscopy, X-ray diffraction and a four-point probe technique. When the annealing temperature reaches 450 °C, Fe and Ni atoms diffuse markedly into the Au layer and the Fe content is more than the Ni content. When the annealing temperature is lower than 450 °C, the grain size of the Au layers does not change markedly with annealing temperature. However, as the annealing temperature reaches 450 °C, the annealing promotes the grain growth of the Au layer. As the annealing temperature exceeds 300 °C, the resistivity of the bilayer films increases with increasing annealing temperature. The diffusion of Fe and Ni atoms into the Au layer results in an increase in the resistivity of the annealed bilayer film. Large numbers of Fe and Ni atoms diffusing into the Au layer of the annealed Au/Ni₅₀Fe₅₀ bilayer film lead to a significant decrease in the lattice constant of the Au layer.     

Synthesis of magnetic crosslinked starch-graft-poly(acrylamide)-co-sodium xanthate and its application in removing heavy metal ions

ABSTRACT

This paper describes the synthesis and characterisation of a magnetic crosslinked starch-graft-poly(acrylamide)-co-sodium xanthate (M-CSAX) nanocomposite based on magnetic starch (MCS), acrylamide (AM) and sodium xanthate that underwent heavy metal ions removal in response to an external magnetic field. The material was prepared using magnetic particle Fe₃O₄ nanoflakes (NFs) together with vinylated starch and poly(acrylamide)-co-sodium xanthate via an ultrasound-assisted radical crosslinking/polymerisation reaction. MCS was synthesised by a direct compounding method using Fe₃O₄ NFs as nuclear and vinylated starch as shell. The obtained M-CSAX has a saturation magnetisation value of 19.21 emu·g^?1. Flocculation experiment results showed that the composites have functions of removing both turbidity and heavy metal ions from aqueous solution, and can adsorb 78.3% of Pb²⁺ and 63% of Cu²⁺ from the corresponding salt solutions. The findings of the present work highlight the potential for using M-CSAX as an effective and recyclable adsorbent for wastewater treatment.     

Chemically prepared amorphous Fe-Ni-B alloy particles

Amorphous Fe-Ni-B alloy particles have been prepared by chemical reduction of Fe²⁺ and Ni²⁺ in aqueous solution by NaBH₄. It was found that within a limited range of NaBH₄ concentrations and pH values of the metal salt solution the particles are amorphous. Outside this range the precipitates are partly crystalline. The magnetic hyperfine fields of the amorphous particles, estimated from⁵⁷Fe Mössbauer spectroscopy, are similar to those of amorphous ribbons with the same compositions.     

Nanocrystal Model for Liquid Metals and Amorphous Metals

A nanocrystal model for liquid metals and amorphous metals has been developed. With the nanocrystal model, the broadening peak profiles (BPPs) of Cu, Al, Al₆₅Cu₂₀Fe₁₅ alloy, Cu₇₀Ni₃₀ alloy and Fe₅₀Si₅₀ alloy were gained by broadening the X-ray diffraction (XRD) peaks of a crystal lattice. By comparing the BPPs with the XRD intensity curves measured on the liquid metals, it is found that the BPPs are closely in agreement with the XRD intensity curves, respectively, except the Fe₅₀Si₅₀ alloy. Therefore, the nanocrystal model can be used to determine if the atomic cluster structure of the liquid metal is similar to the structure of its crystal lattice.     

Studies on fluoride adsorption of iron-impregnated granular ceramics from aqueous solution

This study evaluated the effectiveness of iron-impregnated granular ceramics in removing fluoride from aqueous solution. Kanuma mud, zeolite, starch and FeSO₄·7H₂O/Fe₂O₃ mixed to prepare granular ceramic at room temperature by granulation procedure with the mass ratio of 4:3:2:1. Both the adsorbents were characterized by SEM, EDS and BET surface area. The various experimental parameters investigated for fluoride adsorption from aqueous solution were: contact time, initial pH, initial fluoride concentration and temperature. The GC (FeSO₄·7H₂O) is more effective for fluoride removal than GC (Fe₂O₃) in adsorption capacity. The optimum pH for fluoride removal on GC (FeSO₄·7H₂O) and GC (Fe₂O₃) was 7.0 and 4.0, respectively. The experimental data fitted reasonably well to both Langmuir and Freundlich isotherm models for these two adsorbents. The two adsorption process followed pseudo-second-order kinetics with intra-particle diffusion as the rate determining step. The calculated thermodynamic parameters showed that both of the adsorption processes were thermodynamically favorable, spontaneous and endothermic in nature.     

Iron-substituted AB5-type MH electrode

The present investigation is aimed to study MmNi₅-type (Mm = Mischmetal) hydrogen storage alloys with composition, Mm_0·8La_0·2Ni_3·7Al_0·38Co_0·3Mn_0·6?x Mo_0·02Fe _x (x = 0, 0·1, 0·2 and 0·3). The alloys are synthesized by radio-frequency induction melting. To study their electrochemical properties via measurements of discharge capacity, activation process, rate capability and cyclic stability, electrodes are fabricated using as-synthesized and annealed version of the alloys. The maximum discharge capacity is recorded as 288 mAhg^?1 for the iron concentration, x = 0·1, as compared to 270 mAhg^?1 for the alloy electrode without iron. Similarly, 99% cyclic stability is observed in annealed alloy electrode (x = 0·1) as compared to 78% in the alloy electrode without iron. Hence, small amount of iron-substitution (x = 0·1) in the alloy is found to improve the electrochemical properties. This improvement is thought to be due to less pulverization of the alloy in electrochemically-cycled alloy, as confirmed through structural and microstructural characterizations carried out by X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically-cycled electrodes.