Electrochemical characteristics of amorphous MgTixNi （x = 0,0.1, and 0.2） hydrogen storage alloys

MgTi _x Ni (x = 0, 0.1, and 0.2) alloys were successfully prepared by mechanical alloying (MA), and the influence of milling time on the electrochemical characteristics of the electrodes was discussed. MgTi _x Ni alloys after 90 h milling displayed the best electrochemical performance. The X-ray diffraction patterns showed that the alloy ball-milled for 90 h was amorphous with a widened diffraction peak. The charge-discharge tests indicated that these alloys had good electrochemical activation properties, and the MgTi_0.2Ni alloy electrode exhibited the best cycle performance. The initial discharge capacity of the MgTi_0.2Ni alloy reached up to 401.1 mAh·g⁻¹, and the retention rate of capacity was 31.0% after 30 cycles, much higher than that of MgNi (17.3%). The Tafel polarization curves revealed that Ti addition could enhance the anticorrosion performance of these alloys in alkali solution, which was responsible for the ameliorated cyclic stability of these alloy electrodes.     

Corrosion and Carburization Behaviour of Ni-<Emphasis Type="Italic">x</Emphasis>Cr Binary Alloys in a High-Temperature Supercritical-Carbon Dioxide Environment

Pure Ni and Ni-xCr (x = 7, 14, 22 and 27 wt%) binary alloys were exposed to supercritical-carbon dioxide environment at 600 °C and 20 MPa for 200 h. For pure Ni, a thick NiO layer was formed on the surface. Meanwhile, for Ni-7Cr alloy, an inner oxide layer consisted of rather irregular chromia and NiO was formed below the outer NiO layer. When Cr content was greater than 14%, a continuous chromia layer was formed, resulting in much lower weight gain and oxide thickness. However, amorphous carbon layers had developed along the oxide–matrix interface when chromia was formed. The presence of the carbon layer was explained in view of the high C activity corresponding to the low equilibrium oxygen potential of chromia.     

Adsorption of Ni(II), Cu(II), and Zn(II) ions by natural alumosilicate modified with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-<Emphasis Type="Italic">bis</Emphasis>(3-triethoxysilylpropyl)thiocarbamide

Immobilization of N,N'-bis(3-triethoxysilylpropyl)thiocarbamide on the surface of natural alumosilicates from Eastern Transbaikal has been carried out. Adsorption isotherms of Ni(II), Cu(II), and Zn(II) ions on modified adsorbents have been plotted. The experimental data have been treated using the Langmuir, Freundlich, BET, and Dubinin–Radushkevich models. The constants of these equations have been determined. It has been shown that adsorption on alumosilicates modified with N,N'-bis(3-triethoxysilylpropyl)thiocarbamide is described in the best way by the Freundlich and Langmuir adsorption models. The Dubinin–Radushkevich model has been employed for the calculation of free energy of adsorption. For all the specimens under study, the free energy of adsorption indicates the presence of an ion-exchange mechanism, while the adsorption of heavy-metal ions has a chemical nature.     

Effect of chloride ions on electrochemical properties of anodized <Emphasis Type="Italic">AV</Emphasis> and <Emphasis Type="Italic">D</Emphasis>16 aluminum alloys in aqueous and glycerin-containing aqueous sodium sulfate solutions

The effect of chloride ions (0.01 N NaCl) on the electrochemical properties of anodized (in chromic anhydride or sulfuric acid) AV and D16 aluminum alloys in aqueous sulfate (0.5% Na₂SO₄) and glycerin-containing aqueous sulfate (0.5% Na₂SO₄, 33% glycerin) solutions is studied. Depending on the conditions of anodizing and the composition of the alloy and environment, currents on the anodized alloys in the passive range are shown to be smaller by one to four orders of magnitude compared to those on nonanodized alloys. Anodizing increases the resistance of alloys against pitting corrosion. Alloys anodized in sulfuric acid and then treated in dichromate are not susceptible to pitting corrosion. Alloys anodized in chromic anhydride are less resistant against pitting.     

Synthesis and protection effect of fullerenol-<Emphasis Type="Italic">d</Emphasis>. II. Modification of water-soluble priming enamel with fullerenol-<Emphasis Type="Italic">d</Emphasis>

A significant increase in scuffing resistance and improving of the adhesion properties toward steel for anticorrosive acrylate priming enamel for ferrous materials VAK VD-AK-012PK modified with fullerenol-d synthesized by direct oxidizing fullerene C₆₀ is demonstrated.     

X-ray diffraction determination of root-mean-square displacements of atoms in <Emphasis Type="Italic">B</Emphasis>2 and <Emphasis Type="Italic">R</Emphasis> phases of titanium nickelide

Intensities of 15 fundamental and 11 superlattice reflections of the B2 phase have been measured in a titanium nickelide single crystal using X-ray Mo Kα radiation. Structure factors for these reflections and root-mean-square displacements of nickel and titanium atoms from the crystal-lattice sites have been calculated. The mean squared displacements of nickel atoms are equal to 〈u ²〉_Ni=0.087 ± 0.006 Ų; those of titanium atoms, 〈u ²〉_Ti = 0.039 ± 0.003 Ų. The temperature dependence of root-mean-square displacements in the B2 phase and in the temperature range of the B2 → R transformation has been determined. Root-mean-square atomic displacements in the R phase have been calculated. The Debye temperature has been determined and the root-mean-square atomic displacements in the B2 phase have been separated into static and dynamic ones.     

Biocompatibility of a modified metallic surface of pure Ti and Ti-6Al-4V alloy with the connective tissue of mouse

The surface of implantable biomaterials is in direct contact with the host tissue and plays a critical role in determining biocompatibility. In order to improve the integration of implants, some attempts have been made to coat the surface of the biomaterial with calcium phosphate. In this investigation pure Ti, Ti-6A1-4V alloy and alkali treated specimens were used as implanted materials in the abdominal wall of mice. The implants were kept there for 3 months and then their biocompatibility was evaluated by optical microscope. Surface structural changes of specimens due to the alkali treatment and soaking in Hank’s solution were analyzed by XRD, SEM and XPS. Alkali treated specimens formed a dense and uniform bone-like apatite layer on the specimen surface when they were soaked in Hank’s solution. The average thickness of the fibrous capsule formed around the implant was much thinner for the alkali-treated specimens than the others. The number of macrophages was much less for the alkali-treated specimens than the others. The results of this evaluation indicate that alkali treated pure Ti and the Ti-6A1-4V alloy have better biocompatibility compared to the other metals tested.     

Hard and Corrosion-Resistant Ni-<Emphasis Type="Italic">x</Emphasis>Al-<Emphasis Type="Italic">y</Emphasis>Ti Nanocomposite Coatings for CNT/Al Composites

The ternary Ni-xAl-yTi (x, y in wt.%) nanocomposite protective coatings were electroplated on carbon nanotubes (CNT)/Al composite by the co-deposition of Al and Ti particles at several current densities. The dependences of microstructure, microhardness, residual stress, and corrosion resistance of the ternary nanocomposite coating on current density were investigated. The results showed that the embedded Al and Ti particles caused the crystallite refinement and the decrease of [200] fiber texture of nanocrystalline Ni matrix when current density decreased. The microstructure evolution endowed the ternary nanocomposite coating with high microhardness and corrosion resistance. The surface residual stress of the ternary nanocomposite coating increased with decreasing current density.     

Simulation of hydrogen diffusion in TiH<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> structures

Quantum-mechanical calculations of the energies of the formation of Frenkel pairs and barriers for hydrogen migration via different mechanisms in the titanium hydride δ-TiH _x and in the α phase of titanium have been carried out. Using the potential of interaction developed for the molecular-dynamic simulation, diffusion coefficients of hydrogen in fcc and hcp lattices of TiH _x were calculated depending on the temperature. The opportunity to approximate the coefficients of hydrogen self-diffusion has been analyzed in terms of the model of non-interacting point defects. For δ-TiH _x , the range of concentrations and temperatures was separated where the self-diffusion of hydrogen becomes liquid-like (ceases be dependent on the hydrogen concentration), upon the transition into which there takes place a sharp increase in the isochoric heat capacity. The effect of defects in the Ti sublattice on the coefficient of self-diffusion of H has been investigated.     

Interfacial microstructure and properties of diamond/Cu-<Emphasis Type="Italic">x</Emphasis>Cr composites for electronic packaging applications

Diamond/Cu-xCr composites were fabricated by pressure infiltration process.The thermal conductivities of diamond/Cu-xCr(x = 0.1,0.5,0.8) composites were above 650 W/mK,higher than that of diamond/Cu composites.The tensile strengths ranged from 186 to 225 MPa,and the bonding strengths ranged from 400 to 525 MPa.Influences of Cr element on the thermo-physical properties and interface structures were analyzed.The intermediate layer was confirmed as Cr3C2 and the amount of Cr3C2 increased with the increase of Cr concentration in Cu-xCr alloys.When the Cr concentration was up to 0.5 wt.%,the content of the Cr3C2 layer was constant.As the thickness of the Cr3C2 layer became larger,the composites showed a lower thermal conductivity but higher mechanical properties.The coefficients of thermal expansion(CTE) of diamond/Cu-xCr(x = 0.1,0.5,0.8) composites were in good agreement with the predictions of the Kerner’ model.     

Anticorrosive Influence of <Emphasis Type="Italic">Acetobacter aceti</Emphasis> Biofilms on Carbon Steel

Microbiologically influenced corrosion (MIC) of carbon steel infrastructure is an emerging environmental and cost issue for the ethanol fuel industry, yet its examination lacks rigorous quantification of microbiological parameters that could reveal effective intervention strategies. To quantitatively characterize the effect of cell concentration on MIC of carbon steel, numbers of bacteria exposed to test coupons were systematically controlled to span four orders of magnitude throughout a seven-day test. The bacterium studied, Acetobacter aceti, has been found in ethanol fuel environments and can convert ethanol to the corrosive species acetic acid. A. aceti biofilms formed during the test were qualitatively evaluated with fluorescence microscopy, and steel surfaces were characterized by scanning electron microscopy. During exposure, biofilms developed more quickly, and test reactor pH decreased at a faster rate, when cell exposure was higher. Resulting corrosion rates, however, were inversely proportional to cell exposure, indicating that A. aceti biofilms are able to protect carbon steel surfaces from corrosion. This is a novel demonstration of corrosion inhibition by an acid-producing bacterium that occurs naturally in corrosive environments. Mitigation techniques for MIC that harness the power of microbial communities have the potential to be scalable, inexpensive, and green solutions to industrial problems.     

Effect of <Emphasis Type="Italic">r</Emphasis>-value and texture on plastic deformation and necking behavior in interstitial-free steel sheets

Three initial tensile specimens having different textures and, in consequence, different r-values were cut from a sheet of an interstitial-free steel. Using these specimens, the effect of r-value and texture on plastic deformation and the necking behavior were studied by tackling the strain state and texture during tensile tests. A reduced decrease in work hardening rate of tensile specimens with higher r-values led to a slower onset of diffuse necking which offers an increased uniform elongation. A slower reduction in thickness of specimens with a higher r-value provided a favorable resistance against onset of failure by localized necking.     

Adsorption of <Emphasis Type="Italic">n</Emphasis>-pentane on a microporous carbon adsorbent with a narrow pore size distribution

A model of thermochemical synthesis of a microporous carbon adsorbent of silicon carbide is developed. Isotherms of absolute adsorption of n-pentane on an AUK microporous carbon adsorbent of SiC with a narrow pore size distribution are measured in the pressure range of 1 Pa to 50 kPa and in the temperature interval of 243–393 K. The parameters of adsorption equilibrium of the adsorption isostere calculated in the same range are adequately approximated by straight lines. The differential molar isosteric heat of adsorption of n-pentane on the AUK adsorbent decreases of 58-46 kJ/mol in the whole region of micropore filling; this fact counts in favor of energetic heterogeneity in the micropores, which presumably appears in the process of thermochemical synthesis of the microporous carbon adsorbent of silicon carbide.     

Structure,Magnetic and Magnetocaloric Properties of Nonstoichiometric TbCo<Subscript>2</Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Compounds

TbCo₂Mn_x (x ≤ 1) alloys were synthesized and their crystal structure, heat capacity, magnetic and magnetocaloric properties were studied. Single-phase compounds with the MgCu₂-type structure were formed at х < 0.4. In alloys with х > 0.4, additional phases with the PuNi₃- and Th₆Mn₂₃-type structures form. It was shown that there is a substantial increase in the Curie temperature and magnetic moment of 3d?metal sublattice of the nonstoichiometric compounds when compared to those of the TbCo₂ binary compound. The magnetocaloric effect of single- and multiphase alloys were estimated based on magnetic and heat capacity measurements.     

Effect of nanostructured surface of radiation-oxidized aluminum on radiolytic processes in <Emphasis Type="Italic">n</Emphasis>-hexane

The effect of a nanostructured surface of radiation-oxidized aluminum on radiolytic processes in n-hexane was investigated. It was ascertained that the decreased thickness of oxide films on Al surface by approximately two orders of magnitude (from 600 to 8 nm) led to an increase in the rate of molecular hydrogen formation by a factor of ∼7 (from 1.1 to 7.6 × 10¹⁵ molecule g⁻¹ s−1); meanwhile, the radiation chemical yield of H₂ changed from 4.3 to 8.2 molecules/100 eV. The results obtained were interpreted in terms of the difference in the degree of imperfection of the surfaces of radiation-generated Al plates and enhancement of radiation-generated centers, which was evidenced by AFM images and RTL measurements.     

Interfacial Interactions Between W<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>N Substrates and a Gold-Tin Alloy

Au-Sn is an excellent material with superior attributes and is the solder of choice, with no obvious alternatives, in many microelectronic applications. Recently, this alloy has been chosen as a potential candidate for bonding in wafer level hermetic packaging at high temperature using WN as diffusion barrier. In this application, good wetting of WN by the liquid Au-Sn alloy is a key factor for the bonding process. To this end, wetting of W _x N (covered or not by a gold layer) by Au-Sn20 alloy was studied at 380 °C under high vacuum. Excellent wetting was observed when W _x N was protected from oxidation by a thin Au layer. The spreading process was found to be followed by a complete dissolution of a protection layer and slight receding of the triple line. Some preliminary bonding tests using Au-Sn alloy were also performed.     

Microstructural characterization of titanium matrix composite coatings reinforced by in situ synthesized TiB ＋ TiC fabricated on Ti6AI4V by laser cladding

Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles between titanium and B₄C were successfully fabricated on Ti6Al4V by laser cladding. Phase constituents of the coatings were predicted by thermodynamic calculations in the Ti-B₄C-Al and Ti-B-C-Al systems, respectively, and were validated well by X-ray diffraction (XRD) analysis results. Microstructural and metallographic analyses were made by scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA). The results show that the coatings are mainly composed of α-Ti cellular dendrites and the eutecticum in which a large number of needle-shaped TiB and a few equiaxial TiC particles are embedded. C is enriched in α-Ti cellular dendrites and far exceeds the theoretical maximum dissolubility, owing to the extension of saturation during laser cladding. The coatings have a good metallurgical bond with the substrate due to the existence of the dilution zone, in which a great amount of lamella β-Ti grains consisting of a thin needle-shaped martensitic microstructure are present and grow parallel to the heat flux direction; a few TiB and TiC reinforcements are observed at the boundaries of initial β-Ti grains.     

Influence of the Size and Structural Factors on the Magnetism of Multilayer Films Based on 3<Emphasis Type="Italic">d</Emphasis> and 4<Emphasis Type="Italic">f</Emphasis> Metals

This work has presented some data on the layer structuring of films of 3d and 4f metals and their alloys, which have potential for practical use in magnetic sensors. The decrease in the thickness of magnetic layers with this structuring entails natural worsening of the crystallinity and leads to a degradation of magnetic ordering. However, the manifestation of these tendencies depends to a great extent on the conditions of preparation, the composition, and the sequence of the deposition of the contacting layers in the multilayer structures. The combination of these factors makes it possible to realize an optimum composition and optimum structural states of the films, which in a number of cases lead to the appearance of new combinations of functional properties.     

2D <Emphasis Type="Italic">M</Emphasis>-nanoaggregates in langmuir layers of calamite mesogen

It is shown that a representative of calamite mesogens, 4-(4′-nonyloxyphenylazo)cinnamic acid (NOPCA), forms floating monolayers on the surface of water at initial surface coverage c ≤ 22.8%; their structural elements are 2D face-on M-nanoaggregates. The main structure characteristics and properties of M-monolayers (the size of M-nanoaggregates formed in the layer, number of molecules in them, distance between the aggregates, water content in the aggregates and between them, compressibility, and pressure and surface concentration ranges of existence of the aggregates) are determined. It is shown that this compound manifests a specific behavior in Langmuir layers that is different from most of the compounds studied so far due to particularities of the molecular structure and formation of hydrogen bonds in layers on the surface of water. The formation of two types of floating NOPCA monolayers is observed and changes of their characteristics are studied in successive “compression-decompression” cycles.     

Evaluation of in vitro and in vivo tests for surface-modified titanium by H<Subscript>2</Subscript>SO<Subscript>4</Subscript> and H<Subscript>2</Subscript>O<Subscript>2</Subscript> treatment

Titanium is widely used as an implant material for artificial teeth. Furthermore, various studies have examined surface treatment with respect to the formation of a fine passive film on the surface of commercial titanium and its alloys and to improve the bioactivity with bone. However, there is insufficient data about the biocompatibility of implant materials in the body. The purpose of this study was to examine whether surface modification affects the precipitation of apatite on titanium metal. Specimens were chemically washed for 2 min in a 1∶1∶1.5 (vol.%) mixture of 48 %HF, 60%HNO₃ and distilled water. The specimens were then chemically treated with a solution containing 97%H₂SO₄ and 30%H₂O₂ at the ratio of 1∶1 (vol.%) at 40°C for 1h, and subsequently heat-treated at 400°C for 1h. All the specimens were immersed in HBSS with pH 7.4 at 36.5°C for 15d, and the surface was examined with TF-XRD, SEM, EDX and XPS. In addition, specimens of commercial pure Ti, with and without surface treatment, were implanted in the abdominal connective tissue of mice for 28 d. Conventional aluminum and stainless steel 316L were also implanted for comparison. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a solution of H₂SO₄ and H₂O₂. The average roughness was 2.175 μm after chemical surface treatment. The amorphous titania was subsequently transformed into anatase by heat treatment at 400°C for 1h. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was 47.1μm in the chemically treated Ti, and 52.2, 168.7 and 101.9μm, respectively, in the untreated commercial pure Ti, aluminum and stainless steel 316L.