Mieczysław Jurczyk

Nanocrystalline titanium-type metal hydride electrodes prepared by mechanical alloying

Abstract Mechanical alloying (MA) was employed to produce nanocrystalline TiFe 1− x Ni x alloys ( x =0, 0.25, 0.5, 0.75 and 1.0). XRD analysis showed that, after 25 h of milling, the starting mixture of the elements had decomposed into an amorphous phase. Following annealing in high purity argon at 750°C for 0.5 h, XRD confirmed the formation of the CsCl-type structures with crystallite sizes of about 50 nm. These materials were used as negative electrodes for a Ni–MH x battery. With increasing nickel content in TiFe 1− x Ni x , the material shows an increase in discharge capacity which passes through a maximum for x =0.75. In the nanocrystalline TiFe 0.25 Ni 0.75 powder, discharge capacities of up to 155 mA h g −1 (at 40 mA g −1 discharge current) were measured. The titanium-based hydrogen storage alloys are attractive for secondary batteries, because of inexpensive raw materials.

Nanocrystalline LaNi4.2Al0.8 prepared by mechanical alloying and annealing and its hydride formation

Abstract The formation of nanocrystalline LaNi 4.2 Al 0.8 material by mechanical alloying (MA) followed by annealing has been studied by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. The amorphous phase forms directly from the starting mixture of elements, without formation of other phases. Heating the MA powders at 750°C for 0.5 h in high purity argon resulted in the creation of hexagonal CaCu 5 -type structure. The surface chemical composition of the nanocrystalline LaNi 4.2 Al 0.8 alloy was studied by Auger electron spectroscopy and compared with that of a polycrystalline sample. Results showed that the surface segregation of lanthanum atoms in the MA nanocrystalline LaNi 4.2 Al 0.8 alloy is stronger than that of polycrystalline powders from arc-melted ingots. On the other hand, the level of oxygen impurities trapped in the mechanically alloyed powder during the processing is practically the same as in the arc-melted ingots. Small amounts of Fe impurities, which strongly segregate to the surface, could be responsible for the somewhat lower hydrogen storage capacity of the MA nanocrystalline LaNi 4.2 Al 0.8 alloy if compared with that of polycrystalline samples.

Structure and Electronic Properties of La(Ni,Al)5 Alloys

Nanocrystalline and polycrystalline La(Ni,Al) 5 alloys were prepared by mechanical alloying (MA) followed by annealing and arc melting method, respectively. The amorphous phase of MA samples forms directly from the starting mixture of the elements, without other phase formation. Heating the MA powders at 800 °C for 1 h resulted in the creation of hexagonal CaCu 5 -type nanocrystalline compound with mean crystallite size less than 80 nm. XPS studies showed that the shape of the valence band measured for the arc melted (polycrystalline) LaNi 5 is practically the same compared to that reported earlier for the single crystalline sample. The substitution of Ni in LaNi 5 by Al leads to significant modifications of the electronic structure of the polycrystalline sample. On the other hand, the XPS valence band of the MA nanocrystalline LaNi 4.2 Al 0.8 alloy is considerably broader compared to that measured for the polycrystalline sample. The strong modifications of the electronic structure of the nanocrystalline LaNi 4.2 Al 0.8 alloy could significantly influence on its hydrogenation properties.

Spin re-orientations in Nd(Fe,Co)10V2 system

Abstract The effect of cobalt substitution for iron on the spin re-orientation temperature in tetragonal NdFe 10− x Co x V 2 alloys ( x =0 3 and 5) has been investigated using X-ray, magneto-thermogravimetric and ac susceptibility techniques. At room temperature for x =0, NdFe 10 V 2 exhibits a uniaxial anisotropy, which is found to be strongly modified by cobalt substitution in Nd(Fe,Co) 10 V 2 alloys. In fact, alloys with x =3 and 5 were found to possess planar anisotropy at this temperature. The NdFe 10 V 2 and NdFe 5 Co 5 V 2 compounds were observed to exhibit spin re-orientations at 124 and ≈ 350 K, respectively. These appear to be cone to axial ( x =0) and plane to cone ( x =5) re-orientations with increasing temperature. The NdFe 7 Co 3 V 2 alloy undergoes two spin transitions: one at 210 K and the second at 518 K. The spin structure thus appears to be from a cone to planar, and planar to axial-type, respectively, with increasing temperatures. Thus, the substitution of cobalt in NdFe 10 V 2 causes the spin re-orientation to shift to higher temperatures.

Magnetic anisotropy in Dy(Fe,Co)10V2

We have studied random as well as field‐aligned powders of DyFe10−xCoxV2 alloys, (0≤x≤10), to investigate, by Co substitution for Fe, the effects on the saturation magnetization, anisotropy field, Curie and spin reorientation temperatures. In this system, which crystallizes with a ThMn12 structure, Co readily substitutes for iron in the whole composition range. X‐ray diffraction analyses on aligned powders indicate uniaxial anisotropy at 298 K. A phase diagram for the spin arrangements in Dy(Fe,Co)10V2 system is presented. A distinctive feature we observe is that with Co substitution the axial‐to‐cone spin reorientation is found to shift to higher temperatures, while at the same time the cone‐to‐plane spin reorientation is suppressed to lower temperatures. At 290 K, the anisotropy field, HA initially increases in Dy(Fe,Co)10V2, i.e., from HA = 25 kOe (x=0) to HA = 48 kOe (x=5) and for x≥ (R18)7.5 the anisotropy becomes conical. The above results obtained from x‐ray and magnetization measurements are consi...

Nanostructured Titanium-10 wt% 45S5 Bioglass-Ag Composite Foams for Medical Applications

The article presents an investigation on the effectiveness of nanostructured titanium-10 wt% 45S5 Bioglass-1 wt% Ag composite foams as a novel class of antibacterial materials for medical applications. The Ti-based composite foams were prepared by the combination of mechanical alloying and a “space-holder” sintering process. In the first step, the Ti-10 wt% 45S5 Bioglass-1 wt% Ag powder synthesized by mechanical alloying and annealing mixed with 1.0 mm diameter of saccharose crystals was finally compacted in the form of pellets. In the next step, the saccharose crystals were dissolved in water, leaving open spaces surrounded by metallic-bioceramic scaffold. The sintering of the scaffold leads to foam formation. It was found that 1:1 Ti-10 wt% 45S5 Bioglass-1 wt% Ag/sugar ratio leads to porosities of about 70% with pore diameter of about 0.3–1.1 mm. The microstructure, corrosion resistance in Ringer’s solution of the produced foams were investigated. The value of the compression strength for the Ti-10 wt% 45S5 Bioglass-1 wt% Ag foam with 70% porosity was 1.5 MPa and the Young’s modulus was 34 MPa. Silver modified Ti-10 wt% 45S5 Bioglass composites possess excellent antibacterial activities against Staphylococcus aureus. Porous Ti-10 wt% 45S5 Bioglass-1 wt% foam could be a possible candidate for medical implants applications.

Mechanical and corrosion properties of titanium ― hydroxyapatite nanocomposites

In the present work Ti-HA (3, 10, 20, 50 vol%) nanocomposites were produced by the combination of mechanical alloying and powder metallurgical process. The experimental results show, that Ti-HA nanocomposites have better mechanical and corrosion properties in comparison with microcrystalline titanium. For example: Vickers microhardness of Ti-10 vol% HA nanocomposite is 1500 HV0.2 (pure Ti metal – 250 HV0.2) and corrosion resistance in Ringer solution is Ic = 1.19 • 10-7 A/cm2, Ec = -0.41 V for Ti-10 vol% HA and Ic = 1.31 • 10-5 A/cm2, Ec = -0.36 V for Ti. In conclusion, titanium – ceramics nanocomposite are suitable for hard tissue replacement from the point of view of both mechanical and corrosion properties.

Nanoscale size effect in in situ titanium based composites with cell viability and cytocompatibility studies

Novel in situ Metal Matrix Nanocomposite (MMNC) materials based on titanium and boron, revealed their new properties in the nanoscale range. In situ nanocomposites, obtained through mechanical alloying and traditional powder metallurgy compaction and sintering, show obvious differences to their microstructural analogue. A unique microstructure connected with good mechanical properties reliant on the processing conditions favour the nanoscale range of results of the Ti-TiB in situ MMNC example. The data summarised in this work, support and extend the knowledge boundaries of the nanoscale size effect that influence not only the mechanical properties but also the studies on the cell viability and cytocompatibility. Prepared in the same bulk, in situ MMNC, based on titanium and boron, could be considered as a possible candidate for dental implants and other medical applications. The observed relations and research conclusions are transferable to the in situ MMNC material group. Aside from all the discussed relations, the increasing share of these composites in the ever-growing material markets, heavily depends on the attractiveness and a possible wider application of these composites as well as their operational simplicity presented in this work.

Electronic Structure of Mg_2Ni_{1-x}Cu_{x}

Nanocrystalline Mg2Ni doped alloys are good materials for hydrogen storage. In this work we present the influence of the chemical disorder on the electronic structure of Mg2Ni1−xCux alloys for 0 < x < 0.2. The electronic structure was calculated by ab initio full potential scalar relativistic local-orbital method in the coherent potential approximation. We observe the change of the density of states near the Fermi energy.

Antibacterial activity of nanostructured Ti–45S5 bioglass–Ag composite against Streptococcus mutans and Staphylococcus aureus

Mechanical alloying and annealing at 1150 °C for 2 h under an argon atmosphere were used to prepare Ti–45S5 bioglass nanocomposites. Ti–45S5 bioglass material was chemically modified by silver. The antibacterial activity of Ti–10% 45S5 bioglass nanocomposite containing silver against Streptococcus mutans and Staphylococcus aureus was studied. Nanocomposites were characterized by X-ray diffraction, scanning electron microscopy equipped with an electron energy dispersive spectrometer and transmission electron microscopy to evaluate phase composition, crystal structure and grain size. In vitro bacterial adhesion study indicated a significantly reduced number of Streptococcus mutans and Staphylococcus aureus on the bulk nanostructured Ti–45S5 bioglass–Ag plate surface in comparison to that on microcrystalline Ti plate surface. Nanostructured Ti-based biomaterials can be considered to be the future generation of dental implants.