Małgorzata Karolus

Preparation of Fe-Based Bulk Amorphous and Nanocrystalline Alloys by Mould Suction Casting Technique

In this paper we present self-designed mould suction casting apparatus allowing preparation of bulk samples in a form of rods (1.5 mm in diameter and about 3 cm in length). Making use of the apparatus the following compositions of Fe80Nb6B14, Fe76.2Nb5.7B13.8Gd4.8, Fe69.9Nb5.2B12.2Gd13, Fe76.2Nb5.7B13.8Y4.8, Fe69.9Nb5.2B12.2Y13, Fe61.5Nb4.6B10.8Y23.1 alloys were prepared. Phase and microstructure identification were curried out by making use of X-ray diffraction measurements. The obtained results show that the constructed apparatus fulfill all conditions required for such technique. Gadolinium as an alloying addition causes full amorphization in the case of the Fe76.2Nb5.7B13.8Gd4.8 alloy. In the other cases the structure was found to be nanocrystalline which is discussed in the paper.

Studies on Electrodeposited Ni-Mo Nanocrystalline Alloy

The studies on structure of electrodeposited Ni-Mo nanocrystalline lloys are the subject of this paper. The contents of molybdenum in alloys was growing with the change of current density and they were in a range from 3.5 to 23 [at.%]. X-ray diff raction was performed using a Philips Diffractometer PW1130 with cooper radiation ( λ = 1.5418 Å) and graphite monochromator on the diffracted beam. The structure analysis was prepared b y Rietveld Refinement using DBWS 1988 RR version program. The received accuracy parameters: Rp and Rwp were in a ran ge from 2.3 to 8.3 % and goodness of fit was in a range from 1.17 to 2.9 %. Based on the Rietveld refinement results, the change of lattice parameters – a (from 3.50 to 3.58 Å), the crysta lline ize – D (from 3 to 22 nm), and the lattice strain – a a ∆ (from 3.4 to 16.5 x 10 ) were also studied.

Cini-Sawatzky's Model in Studies of Electrodeposited Ni-Mo Alloys with Polymers

Electronic structures of electrodeposited Ni-Mo layers with polyethylene, polytiophene and polypyrrole were studied by Auger electron spectroscopy using the Cini-Sawatzkys model. Comparison of the theoretical and experimental lines was carried out using the asymmetry parameter of the spectral lines. It is pointed out that the changes of the spectral main lines Ni and Mo are connected with the ways of polymerization. It has been also shown that the application of the Cini-Sawaztky model to the experimental spectral lines can be used to explain the distortion appearing in the materials. Model parameters, i.e., intra-atomic correlation and bandwidth were determined.

Structural Studies of the Relaxed Amorphous Phase in the Fe81B14Nb5 Alloy

Amorphous alloys based on iron, obtained by melt spinning technique, are modern and very promising soft magnetic materials. The thermal annealing at temperatures closed to the crystallization temperature can cause an increase of magnetic permeability more than 10 times i.e. the so called enhancement of soft magnetic properties effect (ESMP). It is usually explained by formation of iron nanocrystallites in amorphous surroundings or by formation of the relaxed amorphous phase. Such a microstructure leads to averaging out of magnetic anisotropy and cause the ESMP.

The Structure Studies on Si-N Thin Layers

In structure studies performed using the Grazing Incident X-ray Diffraction Geometry (GIXD) for different incident angles it was indicated that the Si-N layers are non-homogenous and their structure depends on the penetration depth. The layers close to substrate (α = 2, 1°) show the presence of the Si3N4, SiO2, SiO2, SiC phases and an amorphous Si-N phase as well. The layers near the surface (α = 0.5; 0.25; 0.15°) are poorer in Si-N phases. There are only observed the presence of the Si3N4 and SiO2 phases. The obtained results confirm the non-homogenity of layers.

Structure Studies of Electrodeposited Ni-Mo Alloys with Polymers after Annealing

Electrolytical layers of Ni-Mo alloys with polypyrrole, polytiofene and polyethylene were deposited on steel substrate (St3S, 4 cm2). After structural analyses of as quenched samples performed by X-ray diffraction it was noticed that the solid solution of Mo in Ni is observed. After annealing in an argon atmosphere the solid solution of Mo in Ni is becomeing more stable and crystalites are growing to the size of 200 – 300 Å. After annealing in an air atmosphere X-ray diffraction patterns show presence of phases: NiO, MoO, NiCO3, Mo2N. The unit cell parameters of solid solution after annealing are smaller than parameters of as quenched samples what means that the solid solution has been decomposing.

Preparation and Structural Examinations of Gd+Ni Nanocomposites

In the paper Gd+Ni nanoparticles were obtained using chemical reaction of Gd nanopowder in the bath based on C4H6O4Ni (pH=7) at temperature 323 K. TEM examinations show Gd+Ni nanoparticles (about 200 nm) covered by GdF3 intermediate layer and Ni-P final layer Magnetization vs. temperature (5-320 K) show the Curie point of Gd at 290 K and at low temperature a paramagnetic component related to GdF3. The obtained Gd+Ni nanopowder of 200 nm in diameter can be used in future application without fear of oxidation.

The Study of Zink-Nickel Composite Coatings after Annealing

The Zinc composite coatings containing Ni powder were obtained by the electrodeposition and electroless methods. Electrodeposited Zn+Ni coatings were plated with the current density jk = 150 mA/cm2 from the zinc chloride bath containing the suspension of nickel powder. Electroless (Zn-Ni)+Ni coatings were obtained by chemical reduction of Ni2+ and Zn2+ ions from the sulphate bath containing sodium hypophosphite as a reducing agent and mechanically dispersed Ni powder suspension. The thickness of (Zn-Ni)+Ni layer was ~8 m. In order to enhance the Zn content the obtained coatings were covered with the electrolytic Zn layers of different thickness (5 m, 8 m and 14 m) – (Zn-Ni)+Ni/Zn. The thermal treatment of the obtained composites was carried out at a temperature of 320oC, during 2h in argon atmosphere. The electrodeposited coatings show the presence of Zn, Ni(Zn) and ZnO phases. The electroless coatings show the presence of Zn, Ni(Zn) and ZnO phases. The additional electrodeposition of Zn leads to the creation of dilayer coatings (Zn-Ni)+Ni/Zn. The annealing of such obtained coatings leads to the creation of Ni2Zn11 intermetalic phase. The average Ni(Zn) and Ni crystallite size before annealing is in a range of 200 Å and after annealing the size is increasing to values of 600-800 Å.

The X-Ray Studies on Amorphous Fe78Nb2B20 Alloy

In this paper there are presented results of structure analyses of the Fe78Nb2B20 amorphous alloy after annealing. Basing on the initial analyses the “hypothetical” model structure was chosen as the combination of different kind of the Fe structure deformations: change of unit cell parameters (change of unit cell shape) and change of line broadening (change of crystallite size). The crystallite size (in meaning of the size of the ordered regions) for the amorphous state is in a range of 7 – 37 Å and for the crystalline state is about of 1100 Å. The comparison of the values of the unit cell parameters shows that the value of the basic – hypothetical unit cell in an amorphous state is bigger of 0.2 Å than in a crystalline state. After crystallisation there are detected Fe and Fe3B phases.

The influence of Cr, Mo and Mn on structural changes and magnetic properties of Co75,5Fe4,5Si6B14 amorphous alloy

The annealing of amorphous alloys, that is needed in order to improve their properties, is connected with various changes of structure and properties. The understanding of such changes is interesting both from fundamental and applied views. On that reason the influence of Mo and Cr admixtures on the main structure parameters and physical and chemical properties has been studied. For investigation of amorphous alloys the X-ray-diffraction, differential scanning calorimetry, magnetic susceptibility and High-resolution microscopy methods were used. Experimental data allowed us to estimate the changes in crystallization kinetics and to calculate the activation energies. These results were analyzed conjointly with data on X-ray diffraction and magnetic measurements.