Mossbauer studies of structure relaxations near nanocrystallization region in amorphous Fe90Zr7B3 alloy

Transmission Mössbauer spectra and high-resolution electron microscopy investigations for amorphous Fe90Zr7B3 alloy in the as-quenched state and after annealing in vacuum at temperatures 673, 723 and 743 K have been performed. In the as-quenched state the microstructure reveals the presence of medium range order BCC- or FCC-like structure regions 1−3 nm in size which grow during annealing at 673 K being the nuclei of grains of α-Fe phase. After annealing at 723 K for 1 h, the grains 16 nm in diameter and with the average distance of 110 nm between them are embedded in the paramagnetic amorphous matrix. This distance is large enough to prevent magnetic interaction between the grains, and superparamagnetic behavior is observed. After longer annealing at 723 K and at 743 K, the Mössbauer spectra show a crystalline component of the α-Fe phase with the inhomogeneous amorphous matrix consisting of paraand ferromagnetic phases. The hyperfine induction of the crystalline phase slightly increases with time and annealing temperature which is ascribed to the faster diffusion of atoms

Analysis of the nanocrystalline phase formation process in amorphous Fe-X-Si-B alloys

The process of nanocrystalline phase formation, affecting magnetic properties, in amorphous Fe78Si8 Bι4, Fe76 ΑI2 Si8 Β14 , Fe76 Cr2 Si8 B14 and Fe76 Mo2 Si8 B14 alloys has been studied in the paper. Investigations have been carried out using the electrical resistivity method, magnetic methods, transmission electron microscopy and X-ray diffraction. A nanocrystalline phase in the amorphous matrix has been obtained by isochronous or isothermal vacuum annealing. Phase composition of samples has been determined directly after manufacturing and after crystallization annealing on the basis of X-ray diffraction and electron diffraction. Transmission electron microscopy was used to determine phase morphology, dimensions of formed nanocrystalline phase and transition phase. Alloying elements have been found to affect changes of magnetic properties in amorphous and nanocrystalline states. For Fe76Mo2 Si8 Β14 alloys a significant increase in crystallization temperature, making difficult nanocrystalline phase growth and increase in thermal stability of magnetic permeability have been observed

Martensitic transformation in NiTi alloy covered by protective multi-layers

Commercial NiTi shape memory alloy was covered with multi-layers. First, titanium nitride and titanium oxide was deposited on polished surface of the NiTi alloy. Layers were deposited in one process - a glow discharge technique. Second, on the top of the TiN/TiO2 layer the hydroxyapatite (HAp) was deposited using electrophoresis. The HAp layer was sintered at temperature from 5000C up to 9000C for 5 minutes. Influence of the thermal treatments, realized during processing stages, on a course of the martensitic transformation was studied using differential scanning calorymetry (DSC)

Influence of structural changes of Co78Si9B13 metallic glass on magnetic properties

The primary crystallization of Co78Si9B13 metallic glass starts at 648 K and as a consequence of this the ε-Co(Si) phase with needle morphology is created. The second stage of crystallization (at 773 K) is the eutectic and as a result of this α-Co(Si) and boron phases: (Co,Si)3B, (Co,Si)2B are formed. The crystallites of these phases have layer morphology. These characteristic morphologies in the first and second stages lead to the increase in coercivity

Structure of TiN/hydroxyapatite multilayers deposited on surface of NiTi shape memory alloy

In order to improve a corrosion resistance and biocompatibility of NiTi shape memory alloys, the surface of the NiTi alloy was covered by protective layers. The paper presents results of the layers composed of titanium nitride and hydroxyapatite (HAp). The TiN layers were deposited using the glow discharge technique and then the bioactive hydroxyapatite layer was formed from simulated body fluids solution. The results of the structure studies and microscopic observations confirmed that on the surface of the NiTi alloy a thin titanium nitride layer 35-50 nm thick (depending on the glow discharge technique parameters) was obtained. The structure of the deposited layers was studied by means of the X-ray diffraction technique. Also, mechanical parameters of obtained layers were characterized using nanoindentation. On the top of the titanium nitride, a layer consisted of hydroxyapatite and NaCl was formed. Applied parameters of deposition process did not lead to decomposition of the NiTi parent phase (B2) to the equilibrium ones

Ordering of [alpha]-FeCo phase in the nanocrystalline Fe83-xCoxNb3B13Cu1 (x = 6, 25 or 41.5) alloys

The microstructure and ordering of α-FeCo phase of the nanocrystalline Fe83−xCoxNb3B13Cu1 (x = 6, 25 or 41.5) alloys were investigated. We have stated that α-FeCo phase is atomically ordered in the Fe83−xCoxNb3B13Cu1 (x = 25 or 41.5) samples crystallized by the heat treatment in a furnace. However, after flash annealing (by current or laser) that phase is disordered. Moreover, we have found that Co concentration in the crystalline α-FeCo phase strongly depends on Co content in the as-quenched ribbons. The annealing conditions influence also the grain diameter of the crystalline phase. In the nanocrystalline alloys obtained by a flash annealing of the amorphous ribbons finer grains are present

TEM investigations of laser texturized polycrystalline silicon solar cell

Purpose: The presented in this paper research results concern investigation of phase transformation of the surface structure of polycrystalline silicon solar cell. The surface of boron doped polycrystalline silicon wafers were texturised by means of diode-pumped pulsed neodymium-doped yttrium aluminium garnet laser crystal (Nd:YAG). Investigations were carried out on transmission electron microscope (TEM) to observe the changes that occurred after laser treatment of the surface layer. Changes in microstructure of the surface layer of solar cells under the influence of the laser beam are presented using the analysis phase and dislocations present in the microstructure. Observations were carried out on prepared thin foils. Moreover, diffraction patterns from selected regions of textured wafers were solved to qualify phase transformations under influence of laser beam. Design/methodology/approach: Investigations were carried out on the Transmission Electron Microscope JEM 3010 supplied by JEOL with 300 kV accelerating voltage equipped with an electronic camera configured with a computer. The microstructure was obtained in the bright field image as well dark field working in a magnification range of 10000x to ca. 100000x. Phases identification was performed by means of selected area diffraction (SAD) method, where for diffraction pattern calculations the computer software “Eldyf” was used, kindly supplied by the Institute of Materials Science, University of Silesia. Findings: The research included analyze of the influence of laser treatment conditions on geometry, roughness and size of laser made surface texture of silicon wafer applied for solar cells. Research limitations/implications: Paper contributes to research on silicon surface processing using laser beam. Practical implications: Conducted investigations may be applied in optimisation process of solar cell surface processing. Originality/value: The range of possible applications increases for example as materials for solar cells placed on building constructions, elements in electronics and construction parts in automobile industry

Nanocrystallization studies of rapidly quenched Fe85.4-xCoxZr6.8-yNbyB6.8Cu1 (x=0 or 42.7, y=0 or 1) alloys

The microstructure of amorphous and nanocrystalline Fe42.7Co42.7Zr6.8−xNbxB6.8Cu1 (x = 0 or 1) alloys was investigated. We have stated that the nanocrystalline samples consist of the crystalline α-FeCo grains about 8 nm in diameter embedded in an amorphous matrix which is rich in cobalt. From Mössbauer spectroscopy studies we have found that the crystalline α-FeCo phase in the nanocrystalline samples obtained by the conventional annealing is atomically ordered. Moreover, the order degree depends on the annealing time. As for the samples partially crystallized during rapid quenching, the crystalline α-FeCo phase is atomically disordered

The effect of deformation on the change of hydrogen diffusion in C-Mn-Si-P trip 800 steel

Hydrogen diffusion characteristics were studied in C-Mn-Si-P TRIP 800 steel. The steel was tested in as-received state and in states after 5 and 10% tensile deformation. The steel microstructure consisted predominantly of ferrite, bainite and retained austenite. The tensile deformation resulted in a decrease of the retained austenite content. Hydrogen diffusion characteristics were studied by means of electrochemical permeation method for two current densities in build-up transients. Hydrogen diffusion coefficients of the studied TRIP steel varied from 1, 610-7 cm2・s-1 for the as-received state to 1, 310-6 cm2・s-1 for the state after 5% tensile deformation. The hydrogen diffusion coefficients increased markedly during the second build-up transient reflecting thus the fact that hydrogen trapping was less pronounced

The effect of deformation on the change of hydrogen diffusion in C-Mn-Si-P Trip 800 steel

Hydrogen diffusion characteristics were studied in C - Mn - Si - P TRIP 800 steel. The steel was tested in as-received state and in states after 5 and 10 % tensile deformation. The steel microstructure consisted predominantly of ferrite, bainite and retained austenite. The tensile deformation resulted in a decrease of the retained austenite content. Hydrogen diffusion characteristics were studied by means of electrochemical permeation method for two current densities in build-up transients. Hydrogen diffusion coefficients of the studied TRIP steel varied from 1,610-7 cm2 ·s-1 for the as-received state to 1,310-6 cm2 ·s-1 for the state after 5 % tensile deformation. The hydrogen diffusion coefficients increased markedly during the second build-up transient reflecting thus the fact that hydrogen trapping was less pronounced.Web of Science55336436