Change in corrosion behavior of amorphous FePC alloys by alloying with various metallic elements

Comprehensive work to examine the effect of metallic alloying elements M on the corrosion behavior of amorphous FeM13 P7 C alloys was performed. All alloying elements except manganese are effective in increasing the corrosion resistance of amorphous alloys in various acidic and neutral solutions, regardless of anionic species, pH and oxidizability. The addition of elements more active than iron to amorphous FePC alloy decrease the corrosion rate in an active region during immersion tests, depending upon the passivation capabilities of the alloying elements themselves. When elements nobler than iron are added, the nobler is the alloying element, the higher is the corrosion resistance of amorphous FeM13 P7 C alloys.     

The study of transformation kinetics of the amorphous PdSi alloys

The kinetics of transformation behavior of roller-quenched amorphous Pd₈₃Si₁₇ and Pd₈₀Si₂₀ alloys after linear and isothermal heating is reported. The transformation was examined with electron microscopy, electron diffraction and electrical resistivity measurement. The crystallization of amorphous alloys with 17 at% Si begins with metastable ordered fcc solid solution. The ordered fcc solution is transformed to a ordered metastable phase with, probably, orthorhombic structure. The crystallization of amorphous alloys with 20 at% Si begins by formation of spherulites with lamellar structure. Using electron diffraction we found that spherulites consist of two phases - orthorhombic Pd₃Si silicide and Pd-rich silicide. From resistivity measurements, activation energies of 28.5 kcal/mol for Pd₈₃Si₁₇ and 80 kcal/mol for Pd₈₀Si₂₀, respectively, were calculated.     

Studies of amorphous GeSeTe alloys (I): Preparation and calorimetric observations

We have used differential scanning calorimetry (DSC) to examine the thermally induced transformations of bulk and thin-film amorphous alloys within a large portion of the GeSeTe system. Most chalcogen-rich compositions showed a discontinuous increase of heat capacity when heated through the glass transition temperature T_G. The Ge-rich compositions, which could only be prepared as sputtered amorphous films, were invariably characterized by an irreversible exothermic crystallization process on heating, beginning at the crystallization temperature T_X. Values of T_g and T_X have been tabulated for all alloys investigated and the compositional dependence of T_g has been examined in the light of recent models for viscous flow in glass-forming chalcogenide systems. In addition, a region of liquid immiscibility has been observed in the vicinity of Ge₂₀Se₄₀Te₄₀ in which a GeSe₂-rich liquid phase segregates from a tellurium-rich liquid phase. The existence and limits of this immiscibility region have been rationalized on the basis of ionic perturbations to the covalent bonding. The segregation of a GeSe₂-rich liquid increases the concentration of GeSe bonds which are the strongest and most ionic of the six angle-bond types which can occur in this system.     

Effect of germanium on the microstructure and the magnetic properties of Fe–B–Si amorphous alloys

In this work, we present a systematic study on the crystallization kinetics and the magnetic properties of melt-spun Fe₈₀B₁₀Si_10 ? xGe_x (x = 0.0 ? 10.0) amorphous alloys. The activation energy for crystallization, determined by differential scanning calorimetry, displayed a strong dependence on the Ge content, reflecting a deleterious effect on the alloys' thermal stability and their glass forming ability with increasing Ge concentration. On the other hand, the alloys exhibited excellent soft magnetic properties, i.e., high saturation magnetization values (around 1.60 T), alongside Curie temperatures of up to 600 K. Complementary, for increasing Ge substitution, the ferromagnetic resonance spectra showed a microstructural evolution comprising at least two different magnetic phases corresponding to a majority amorphous matrix and to Fe(Si, Ge) nanocrystallites for x ≥ 7.5.     

Dependences of the crystallization behavior of Al–Ni–La amorphous alloys on La and Ni contents

Crystallization behaviors of Al–Ni–La amorphous alloys with a fixed Ni (La) content of 6 at.% were investigated by X-ray diffraction and differential scanning calorimeter when the La (Ni) content changes from 3 to 9 at.%. The results show that the thermal stability of the amorphous alloys monotonically increases with increasing the La (Ni) content. Glass transition only exists in the alloys with the La (Ni) content higher than 6 at.%. La plays a more significant role than Ni in promoting the glass-forming ability, improving the thermal stability, stabilizing the supercooled liquid region, depressing the precipitation of fcc-Al in the first crystallization process and increasing the apparent activation energy of the first reaction.     

The internal friction and elastic modulus of amorphous Pd–Si and Fe–P–C alloys

The internal friction and the shear modulus of the amorphous Pd₈₀–Si₂₀–, Fe₈₀–P₁₃–C₇ and Fe₅₀–Ni₃₃–P₁₂–C₅ alloys have been measured at about 0.5 Hz over a temperature range from room temperature to about 550°C. The internal friction rises steeply with temperature and shows maxima around the crystallization temperature. The activation energy for the steeply rising internal friction has been estimated by the two different procedures; from the shift of the curve by the frequency change and from the slope of the In Q^?1 versus 1/T plot. The two values are very different, which indicates the existence of a wide distribution of activation energies. Crystallization of the amorphous alloys resulted in an increase of about 30% in the shear modulus.     

Formation and mechanical behavior of (Fe0.5Ni0.5)80−xMoxB20 (x = 0–8) amorphous alloys

Glass forming ability, thermal stability and mechanical behavior of (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ (x = 0, 2, 4, 6, 8) amorphous alloys were studied by XRD, TEM, SEM, DSC, tensile test, microhardness test and tearing test. The effects of Mo addition on glass formation, strength and ductility of (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ amorphous alloys were discussed. The substitution of Mo for Fe and Ni simultaneously causes improvement in glass forming ability and thermal stability, and changes the crystallization process. The tensile fracture strength of amorphous alloy depends on both hardness and ductility; the alloy with high hardness and good ductility simultaneously also has a high tensile fracture strength. The (Fe_0.5Ni_0.5)₇₈Mo₂B₂₀ amorphous alloy exhibits good glass forming ability and the highest tensile fracture strength among (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ alloys. Micro-plastic deformation occurred in ductile and brittle amorphous alloys that both show viscous flow characteristics. The mechanical behavior of (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ amorphous alloys is related to the average outer shell electron concentration of metal atoms.     

The effect of Ag addition on the glass-forming ability of Mg–Cu–Y metallic glass alloys

The effect of Ag substitution for Cu on the glass forming ability was studied in Mg₆₅Cu_25−xAg_xY₁₀ (x=0,5,10,15,20,25) alloys by using thermal analysis and X-ray diffractometry (XRD). With increasing x from 0–25, the glass transition temperature, T_g, of melt spun Mg₆₅Cu_25−x Ag_xY₁₀ alloys increases slightly from 426 to 436 K, and the crystallization temperature, T_x, decreases from 494 to 459 K, resulting in a decrease in the supercooled liquid region. However, a partial substitution of Cu by Ag in Mg₆₅Cu₂₅Y₁₀ promotes the glass formation. The maximum diameter for amorphous phase formation by injection casting increases from 4 mm in Mg₆₅Cu₂₅Y₁₀ to 6 mm in Mg₆₅Cu₁₅Ag₁₀Y₁₀ alloy. Both amorphous Mg₆₅Cu₁₅Ag₁₀Y₁₀ alloys prepared by melt spinning and injection casting showed similar crystallization process during continuous heating in differential scanning calorimetry (DSC). The relationship between the critical diameter for the formation of an amorphous phase in injection casting and the parameters reflecting glass-forming ability was examined.     

The effects of annealing and rate of deposition on the electrical,optical and structural properties of amorphous GeSi alloy films

The electrical, optical and structural properties of rf-sputtered amorphous GeSi alloy films have been investigated as functions of the rate of deposition between 90 and 360 Å min^?1, and various annealing conditions. The stabilization evidenced in the electrical conductivity, optical absorption and density of these films deposited at higher rates and/or annealing temperatures may be explained in terms of the reduction of imperfections in the as-deposited films.     

The effects of electrode materials on the switching behaviour of the amorphous semiconductors Si12Ge10As30Te48

The switching behaviour of the amorphous chalcogenide alloy Si₁₂Ge₁₀As₃₀Te₄₈ has been systematically investigated using silver, indium, aluminum, and graphite for electrodes. The experimental results show that the stability in both the threshold voltage for the onset of switching action, and the holding current required to maintain the conducting state, depends strongly on electrode materials. The switching mechanisms related to the electrical and thermal properties of various electrode materials are discussed, and experimental evidence of the deteriorating effect of some electrode materials is given.     

Influence of Ta,Y substitutions on the thermal stability,microhardness and magnetic properties of melt spun Fe–B–Si amorphous alloys

In the present research work, thermal stability, magnetic properties and microhardness of Fe₇₂B_19.2Si_4.8M₄ (M = Ta or Y) amorphous ribbons obtained by chill block melt-spinning technique are reported. The crystallization temperatures resulted as high as 1129 K (for M = Ta) and of 1167 K (for M = Y), which indicate a considerable thermal stability for both alloys. On the other hand, the saturation polarization (μ₀M_s) together with the Curie temperature (T_c) also showed excellent combination of values, with 0.95 ± 0.12 T and 586 ± 8 K, respectively (for the Ta-containing alloy) and of 1.55 ± 0.18 T and 698 ± 6 K, respectively (for the Y-containing alloy). Additionally, the Vickers microhardness exhibited values over 1100 kg/mm² for both alloys.     

The effect of degree of amorphousness on electronic transport behaviors in the Ni–Nb–Zr–H glassy alloys with subnanometer-sized clusters

Material and electronic properties of Ni–Nb–Zr–H glassy alloys were investigated as a function of the rotating wheel speed in the amorphous ribbon-preparation method. Increase in density and amorphous colony size indicates that the degree of amorphousness increases with increase in the rotating speed. Supercooling, which reached by rotating wheel speed of 10,000 rpm (104.7-m/s), of the molten alloy produces a ballistic conductor with electrical conductivity of about 0.1 nΩ cm (× 10^? 9 Ω cm, 0.01% of silver (1.62 μΩ cm)) for (Ni_0.36Nb_0.24Zr_0.40)_94.6 H_5.4 glassy alloy and a room-temperature discrete Coulomb oscillation for (Ni_0.36Nb_0.24Zr_0.40)_91.6H_8.4 glassy alloy. The increase in degree of amorphousness by supercooling induces uniformity of cluster morphology.     

Corrosion behavior of Fe-based ferromagnetic (Fe,Ni)–B–Si–Nb bulk glassy alloys in aqueous electrolytes

Fe-based ferromagnetic [(Fe_1?xNi_x)_0.75B_0.2Si_0.05]₉₆Nb₄ (x = 0, 0.2 and 0.4) bulk glassy alloys (BGAs) with a diameter of 2 mm were prepared by copper mold casting. The corrosion behavior of glassy alloy rods obtained was investigated in 0.5 M NaCl, 0.5 M NaOH and 0.5 M H₂SO₄ aqueous electrolytes, respectively, using weight loss and electrochemical polarization measurements. It was found that the corrosion rates significantly decrease with an increase in Ni content in all examined solutions. The Ni-containing BGAs are spontaneously passivated with wide passive regions and low passive current densities in NaCl and NaOH solutions, but exhibit the active–passive–transpassive behavior in H₂SO₄ solution. The partial substitution of Ni for Fe results in a considerable improvement on the corrosion resistance of [(Fe_1?xNi_x)_0.75B_0.2Si_0.05]₉₆Nb₄ BGAs, because of the structural and chemical homogeneousness of the amorphous phase and the effect of Ni on promoting the formation of a passive film. Besides their high glass-forming ability (GFA), excellent soft-magnetic properties and good mechanical performance, which have been reported before, these FeNi-based BGAs also feature rather high corrosion resistance.     

Crystallization behavior of Ce70−xAl10Cu20Cox (x = 0, 1, 3, 5 at.%) amorphous alloys

The effect of Co addition (substituting for Ce) on crystallization behavior of Ce₇₀Al₁₀Cu₂₀ amorphous alloys has been investigated using X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The Co addition has an obvious effect on topological short-range ordering of Ce–Al–Cu–(Co) amorphous alloys. Moreover, the Co addition can slightly improve the thermal stability of Ce–Al–Cu based amorphous alloys. The 1 and 3 at.% Co additions do not obviously change the crystallization behavior of the Ce–Al–Cu–(Co) amorphous alloys, and the final crystallization products are FCC–CeAlCu(Co)O. However, the 5 at.% Co addition can alter the crystallization behavior of the Ce₇₀Al₁₀Cu₂₀ amorphous alloys. Proper content of Co can effectively suppress the formation of oxide phases during annealing of the Ce–Al–Cu–(Co) amorphous alloys.     

The effect of composition and temperature on the amount and type of nanoferrite particles inserted in Fe2O3–ZnO–MgO–SiO2 glass–ceramics

Glass–ceramics with the composition 2Fe₂O₃.1ZnO.1MgO.96SiO₂ [4ZnMgFe] and 2Fe₂O₃.2ZnO.3MgO.93SiO₂ [7ZnMgFe] (mol%) were prepared using the sol–gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron diffraction (ED) and Mössbauer spectroscopy (MS) were used to investigate the glass–ceramics structure. The samples contain ferrite nanoparticles embedded in a glass matrix. However, zinc ferrite nanoparticles seems to be the preferential crystalline phase formed. The amount of ferrite particles depends on treatment temperature and sample composition. The Mössbauer spectroscopy measurements show that ferrite nanoparticles can exhibit a ferrimagnetic behaviour combined with superparamagnetism.     

The effect of ionic and metallic silver on the crystalline phases developed in CaO–Al2O3–TiO2–P2O5 glasses

Development of crystallization in the CaO–Al₂O₃–TiO₂–P₂O₅ system glasses was investigated in the presence of ionic and metallic silver. Differential thermal analysis, X-ray diffractometry, ultra violet–visible spectrophotometry, atomic force microscopy and scanning electron microscopy were used to evaluate the resulted glasses and glass-ceramics. It was found that silver ions facilitated crystallization by decreasing the viscosity of the glasses. However, metallic silver, which was formed through heat treatment in hydrogen atmosphere, improved heterogeneous crystallization of the reduced glasses in the subsequent heat treatment. The preformed metallic silver led to effective crystallization of calcium titanium phosphate (CaTi₄(PO₄)₆), calcium metaphosphate (Ca(PO₃)₂) and calcium pyrophosphate (Ca₂P₂O₇) phases at significantly decreased temperatures. The two latter phases were partially dissolved out by leaching in acidic solution and left out a porous structure of calcium titanium phosphate glass-ceramic.     

In situ immobilization on the silica gel surface and adsorption capacity of poly[4-methacroyloxy-(4′-carboxy-2′-nitro)-azobenzene] on toxic metals ions

Abstract

A new organo-mineral composite material has been synthesized by in situ immobilization of poly[(4-methacroyloxy-(4′-carboxy-2′-nitro)azobenzene on the silicagel surface. As a result of thermogravimetric analysis and DSC-MS analysis it has been found that the composition of synthesized composite includes 10,1?wt. % of polymer. It has been found that the synthesized composite exhibits the sorption ability in terms of microquantities of Cu (II), Cd (II), Pb (II) and Fe (III) ions in a neutral aqueous medium. The maximum degree of sorption of ions Cu (II), Pb (II) and Fe (III) is achieved during the first minutes of contact, and for Cd (II) ions the equilibrium is established within a day. The sorption capacity of silica gel as a result of modification by this polymer increases with respect to Cu (II) ions more than 14 times, with respect to Pb (II) ions - 5 times.     

The effect of zirconia content on properties of Al2O3–ZrO2 (Y2O3) composite nanopowders synthesized by aqueous sol–gel method

Al₂O₃–ZrO₂ (Y₂O₃) nanopowders containing 5, 10 and 15 wt% ZrO₂ were synthesized by aqueous sol–gel method using aluminum sec-butoxide and zirconium butoxide as precursors. BET analysis shows that, increasing the zirconia content results in a decrease in surface area, 152, 125 and 121 m²/g, and an increase in pore size, 5.63, 9.79 and 11.05 nm for 5, 10 and 15 wt% ZrO₂, respectively. Furthermore, a shift toward higher temperatures is observed for transition of transitional aluminas to stable α-alumina phase through increasing the zirconia content. SEM micrograph of calcined nanopowders revealed nanosize spherical particles in the range of 15–75 nm.