Dealloying of Cu-Mg-Ca alloys

The chemical dealloying of Cu-Mg-Ca alloys in free corrosion conditions was investigated for different alloy compositions and different leaching solutions. For some of the precursor alloys, a continuous, pure fcc copper with nanoporous structure can be obtained by dealloying in 0.04 M H2SO4 solution. Superficial nanoporous copper structures with extremely fine porous size were also obtained by dealloying in pure water and 0.1 M NaOH solutions. The dealloying of both amorphous and partially crystalline alloys was investigated obtaining bi-phase nanoporous/crystal composites with microstructures depending on the precursor alloy state. The fast dissolution of Mg and Ca makes the Cu-Mg-Ca system an ideal candidate for obtaining nanoporous copper structures with different properties as a function of different factors such as the alloy composition, the quenching process, and leaching conditions.Peer ReviewedPostprint (published version

Degradation of azo dyes by rapidly solidified metallic particles

Azo compounds are one of the most common families of dyes used in textile and leather treatments. An important step during the treatment of water polluted by these compounds, is the degradation of the compounds by decomposition of the -N=N- bonds, producing the de-colorization of the water. This de-colorization reaction can be activated by the presence of zero valent metallic particles. The metastable structures generated during rapid solidification tend to increase the chemical activity of the alloys. Recently, it has been discovered that the use of metallic particles in a metastable phase (amorphous or nanocrystalline) multiplies significantly the efficiency of the decolorization water-treatment step. Here we present the results obtained in the decolorization of water using alloys based on different metals (Fe, Mn, Ni and Al) produced by rapid solidification and posterior ball milling. For some Al-containing alloys the results show a fast reaction, even in neutral pH conditions. In this work, the efficiency of the different metastable alloys in the de-colorization process, the effects of the metastable structure and the processing conditions are presented and assessed.Peer ReviewedPostprint (published version

High efficiency decolorization of azo dye Reactive Black 5 by Ca-Al particles

This work studies the degradation of azo dye Reactive Black 5 by Ca-Al metallic particles prepared by melt-spinning and ball-milling. The morphology and the phase structure of the metallic powders were characterized and the decolorization efficiency of Reactive Black 5 solutions were assessed by monitoring the dye degradation by ultraviolet-visible absorption spectrophotometry. The decolorization process using the Ca-Al powders showed fast kinetics and high efficiency. 40 mg L-1 dye solution was successfully decolorized in 1 min using 0.1 g/100 mL of Ca65Al35 powder, suggesting it as an effective, low-cost means for degradation of azo-compounds.Peer ReviewedPostprint (author's final draft

Localised instanton in four dimensions

SIGLEAvailable from British Library Document Supply Centre- DSC:3630.84(DIAS-STP--86-10) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Thermal and structural study of nanocrystalline Fe(Co)NiZrB alloys prepared by mechanical alloying

Three nanocrystalline alloys, Fe75-xCox(Ni70 Zr30)15B10 (x = 0, 10, and 20), were synthesized from elemental powders in a planetary high-energy ball mill. Their microstructure, magnetic properties, and thermal stability were characterized by X-ray diffraction, transmission Mössbauer spectroscopy, transmission electron microscopy, scanning electron microscopy, induction coupled plasma, vibrating sample magnetometry, and differential scanning calorimetry. After 80 h ofmilling, the nanocrystallites size of alloys is in the range 6–10 ± 1 nm. The lattice parameter decreases when increasing (decreasing) milling time (Fe content). Furthermore, the thermal stability of the nanocrystalline phase increaseswhen increasingCo concentration. The activation energy of themain crystallization process, between 275 ± 8 and 311 ± 10 kJ mol-1, is associated with grain growth. Slight contamination from milling tools and milling atmosphere was detected. Minor differences were detected after Mössbauer analysis.Peer Reviewe

Thermal stability of ultrafine grains size of pure copper obtained by equal-channel angular pressing

Ultrafine grain of pure copper 99.98% was produced by severe plastic deformation using the equalchannel angular pressing (ECAP) method. Copper samples were ECAPed from 1 to 8 passes following route BC; fine grain sizes of 250 nm were developed after eight passes. Important enhancement in the mechanical strength properties was obtained. Subsequent heat treatments (HT) were carried out to evaluate the thermal stability of the grains of the ECAPed samples. Microstructure and mechanical properties were evaluated to determine the recovery and recrystallization temperatures. Differential scanning calorimetry (DSC) tests were conducted to all samples in order to determinate these temperatures. The activation energy of the recrystallization process was also determined by the DSC technique and good correlation was obtained with the microstructure and mechanical properties. An important decrease in the mechanical properties and an increasing heterogeneous grain size distribution were observed when heat treatments were performed.Peer Reviewe

Dealloying of Cu-Mg-Ca alloys

The chemical dealloying of Cu-Mg-Ca alloys in free corrosion conditions was investigated for different alloy compositions and different leaching solutions. For some of the precursor alloys, a continuous, pure fcc copper with nanoporous structure can be obtained by dealloying in 0.04 M H2SO4 solution. Superficial nanoporous copper structures with extremely fine porous size were also obtained by dealloying in pure water and 0.1 M NaOH solutions. The dealloying of both amorphous and partially crystalline alloys was investigated obtaining bi-phase nanoporous/crystal composites with microstructures depending on the precursor alloy state. The fast dissolution of Mg and Ca makes the Cu-Mg-Ca system an ideal candidate for obtaining nanoporous copper structures with different properties as a function of different factors such as the alloy composition, the quenching process, and leaching conditions.Peer Reviewe

Influence of a magnetic field applied during the quenching process on the spin density and nanoscale structure of an amorphous Fe-B ribbon

The application of a magnetic field to the melt in the transverse direction of the wheel rotation during the solidification process induces magnetic anisotropy in amorphous magnetic ribbons. This procedure is here applied to a FeB amorphous alloy in order to check their influence on local electronic and nanoscale structure by comparing two samples (as quenched without field and field quenched). The existence of magnetic domains was showed via the Bitter technique. Mössbauer spectra analysis confirms an increase in the spin density (from 28 to 48%) in the applied field direction for the field quenched ribbon. Positron lifetime spectra analysis determines that at room temperature there is no influence on the nanoscale structure, but the annealing at 300 °C provokes the beginning of the nanocrystallization process in the field quenched sample while the samples as quenched without field remain fully amorphous.Peer ReviewedPostprint (published version

High efficiency decolorization of azo dye Reactive Black 5 by Ca-Al particles

This work studies the degradation of azo dye Reactive Black 5 by Ca-Al metallic particles prepared by melt-spinning and ball-milling. The morphology and the phase structure of the metallic powders were characterized and the decolorization efficiency of Reactive Black 5 solutions were assessed by monitoring the dye degradation by ultraviolet-visible absorption spectrophotometry. The decolorization process using the Ca-Al powders showed fast kinetics and high efficiency. 40 mg L-1 dye solution was successfully decolorized in 1 min using 0.1 g/100 mL of Ca65Al35 powder, suggesting it as an effective, low-cost means for degradation of azo-compounds.Peer Reviewe

Thermal and structural study of nanocrystalline Fe(Co)NiZrB alloys prepared by mechanical alloying

Three nanocrystalline alloys, Fe75-xCox(Ni70 Zr30)15B10 (x = 0, 10, and 20), were synthesized from elemental powders in a planetary high-energy ball mill. Their microstructure, magnetic properties, and thermal stability were characterized by X-ray diffraction, transmission Mössbauer spectroscopy, transmission electron microscopy, scanning electron microscopy, induction coupled plasma, vibrating sample magnetometry, and differential scanning calorimetry. After 80 h ofmilling, the nanocrystallites size of alloys is in the range 6–10 ± 1 nm. The lattice parameter decreases when increasing (decreasing) milling time (Fe content). Furthermore, the thermal stability of the nanocrystalline phase increaseswhen increasingCo concentration. The activation energy of themain crystallization process, between 275 ± 8 and 311 ± 10 kJ mol-1, is associated with grain growth. Slight contamination from milling tools and milling atmosphere was detected. Minor differences were detected after Mössbauer analysis.Peer Reviewe