Grzegorz Dercz

Bioactivity of coatings formed on Ti-13Nb-13Zr alloy using plasma electrolytic oxidation.

In this work, we investigated the bioactivity of anodic oxide coatings on Ti-13Nb-13Zr alloy by plasma electrolytic oxidation (PEO) in solutions containing Ca and P. The bioactive properties of the films were determined by immersion in simulated body fluid (SBF), and their biocompatibility was examined using adult human bone marrow derived mesenchymal stem cells (hBMSCs). The oxide layers were characterised based on their surface morphology (SEM, AFM, profilometry) as well as on their chemical and phase compositions (EDX, XRF, XRD, XPS). We report that anodic oxidation of Ti-13Nb-13Zr led to the development of relatively thick anodic oxide films that were enriched in Ca and P in the form of phosphate compounds. Furthermore, the treatment generated rough surfaces with a significant amount of open pores. The surfaces were essentially amorphous, with small amounts of crystalline phases (anatase and rutile) being observed, depending on the PEO process parameters. SBF soaking led to the precipitation of small crystals after one week of experiment. During culturing of hBMSCs on the bioactive Ti-13Nb-13Zr surfaces the differentiation of human mesenchymal stem cells toward osteoblasts was promoted, which indicated a potential of the modified materials to improve implant osseointegration.

Surface characterisation of Ti–15Mo alloy modified by a PEO process in various suspensions

This paper reports on the surface modification of a Ti-15Mo alloy by plasma electrolytic oxidation (PEO). This process was carried out in solutions of 0.1M Ca(H2PO2)2 with various concentrations of tricalcium phosphate (Ca3(PO4)2), wollastonite (CaSiO3), or silica (SiO2) using voltages of up to 350V. The surface microstructure (SEM, cross-section of coating), roughness and chemical composition (energy-dispersive X-ray spectroscopy, thin layer X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy) of the porous oxide layers were investigated. The concentration of powder added to the solution changed the chemical composition and morphology of PEO coatings on the Ti-15Mo alloy surface. Calcium and phosphorous compounds were detected in the coatings formed on the substrate by the PEO process at 300V.

Modification of niobium surfaces using plasma electrolytic oxidation in silicate solutions

Herein, a study of the plasma electrolytic oxidation (PEO) of niobium in an anodising bath composed of potassium silicate (K2SiO3) and potassium hydroxide (KOH) is reported. The effects of the K2SiO3 concentration in the bath and the process voltage on the characteristics of the obtained oxide layers were assessed. Compact, barrier-type oxide layers were obtained when the process voltage did not exceed the breakdown potential of the oxide layer. When this threshold was breached, the morphology of the oxide layer changed markedly, which is typical of PEO. A significant amount of silicon, in the form of amorphous silica, was incorporated into the oxide coatings under these conditions compared with the amount obtained with conventional anodising. This surface modification technique led to an improvement in the corrosion resistance of niobium in Ringer’s solution, regardless of the imposed process conditions.

Formation of bioactive coatings on Ti–13Nb–13Zr alloy for hard tissue implants

In an attempt to increase the bioactivity of a vanadium-free titanium alloy, Ti–13Nb–13Zr, the plasma electrolytic oxidation (PEO) process for surface modification was utilised. Select samples were subjected to further treatment, either thermal or alkali. The morphology, chemical composition, and phase composition of the treated Ti–13Nb–13Zr alloy were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It was observed that during the anodic process under sparking discharge conditions, the simultaneous incorporation of calcium and phosphorus in the forming oxide layer occurs. The resulting layers were porous and exhibited the typical morphology for layers formed during the PEO process. After the alkali treatment of samples oxidised at 150 V, a gel-like titanate layer was formed. The bioactivity investigations in simulated body fluid (SBF) solution indicated that after anodising at 150 V and following alkali treatment the Ti–13Nb–13Zr alloy exhibits osteoinductive properties. The approach presented here may be applied for fabricating Ti–13Nb–13Zr-based implants for hard tissue regeneration.

Crystallite Size Determination of MgO Nanopowder from X-Ray Diffraction Patterns Registered in GIXD Technique

The problem of the crystallite size determination for nanomaterials from X-ray diffraction data obtained in asymmetrical GIXD geometry was analyzed. The studies were performed on nanocrystalline MgO powder prepared by sol-gel synthesis. The nanopowder was preliminary characterized from X-ray diffraction pattern registered in classical Bragg-Brentano geometry and electron microscope observation. The estimated crystallite size, calculated form Williamson-Hall method, equals to 5 nm whereas the lattice distortion is negligible (0.1%). The X-ray diffraction patterns were registered in 30-135º 2θ range using tunnel GIXD technique for the incident α angle: 0.25; 0.5; 1; 2.5 and 5 degrees, respectively. Additional broadening of diffraction lines originated from applied geometry was observed. The calculated crystallite size deviate significantly in comparison to results obtained from classical Bragg-Brentano data. Corrections for additional line broadening were determined, which should be applied for accurate crystallite size calculation in studies of thin nanocrystalline layers using GIXD technique.

Lattice and Peak Profile Parameters in GIXD Technique

Grazing incident X-ray diffraction technique was applied to determine the influence of incident beam angle (α angle) on structural parameters as well as peak profile. X-ray diffraction patterns were registered in asymmetrical geometry, in which a parallel beam was formed by Soller and divergence slits. Lowering of the α angle results in accuracy decrease of lattice parameters as well as in significant broadening of a half-width of X-ray diffraction line.

Structural, Magnetic and Crystallization Study of Fe-Based Bulk Metallic Glasses

The work presents the structural, thermal and magnetic properties analysis of Fe72B20Si4Nb4 bulk metallic glasses in as-cast state and crystallization study of bulk amorphous alloy after annealing process. The studies were performed on bulk metallic glasses in of rods form with diameter of 1,5 and 2 mm. The structure analysis of the samples in as-cast state and phase analysis of studied alloy after annealing process was carried out by the X-ray diffraction (XRD) methods. Mössbauer spectroscopy (MS) was also used to investigate the local structure for studied bulk metallic glasses. Thermal properties associated with glass transition, onset and peak crystallization temperatures was examined by differential scanning calorimetry (DSC). The soft magnetic properties examination of tested material contained initial magnetic permeability and disaccommodation of magnetic permeability.

Outstanding Catalytic Activity of Ultra-Pure Platinum Nanoparticles

Small (4 nm) nanoparticles with a narrow size distribution, exceptional surface purity, and increased surface order, which exhibits itself as an increased presence of basal crystallographic planes, can be obtained without the use of any surfactant. These nanoparticles can be used in many applications in an as-received state and are threefold more active towards a model catalytic reaction (oxidation of ethylene glycol). Furthermore, the superior properties of this material are interesting not only due to the increase in their intrinsic catalytic activity, but also due to the exceptional surface purity itself. The nanoparticles can be used directly (i.e., as-received, without any cleaning steps) in biomedical applications (i.e., as more efficient drug carriers due to an increased number of adsorption sites) and in energy-harvesting/data-storage devices.

Structure of Fe-Based Metallic Glass after Crystallization Process

The work presents a crystallization process of Fe-based amorphous alloy by characterization of the influence of annealing temperature on structural changes and magnetic properties of Fe72B20Si4Nb4 metallic glass. The studies were performed on the samples in the form of ribbons and rods. Crystallization behaviour of the studied alloy was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods. The studies of soft magnetic properties of tested material involved magnetic permeability, saturation induction, coercive field and magnetic after-effects measurements.

Effect of Heat Treatment on Structure and Phase Transformation of Rare Earth (Gd) Zirconate

In the present work, zirconium gadolinium oxide (Gd2Zr2O7) ceramics were prepared by annealing in different conditions and with APS (air plasma sprayed) techniques for thermal barrier coating (TBC) application. Thermal properties, phase transformation, crystal structure and cross-sectional morphologies of these materials were investigated. The thermal behaviour of the material was investigated from room temperature to 1500°C using the differential thermal analysis (DTA). The X-ray diffraction methods were used for the qualitative phase analysis. The structure of the studied samples has been characterized by employing powerful Rietveld’s whole X-ray profile fitting technique using the DBWS 9807a program. The SEM and EDS techniques were used to in the ceramic samples morphology analysis and for their chemical composition, respectively. The research showed that further stages of annealing result in the phase transformation of the parent substances and the main phase Gd2Zr2O7. It was found out that complete phase transformation into Gd2Zr2O7 phase takes place only for the air plasma sprayed sample. The analysis of the morphology of the initial powder revealed the spherical shape of the powder particles, which have a porous internal structure.