Jeremiasz Krzysztof Koper

Corrosion resistance of porous titanium surface prepared at moderate and high potentials in H3PO4/HF electrolytes

In this work a corrosion resistance study of porous layers formed on Ti in anodic oxidation process was shown. The anodic oxidation process was realized from moderate 30 V to high 240 V potentials. As the electrolytes, a mixtures of 2M H3PO4 and 0.2–2 wt % HF were applied. The corrosion resistance of the layers was investigated with respect to possible hard tissue implant applications, which means that surface, which provide porosity for osseointegration should possess high corrosion resistance, too. We have applied XRD and SEM techniques for surface characterization. The corrosion resistance was investigated in Ringer’s electrolyte using potentiodynamic method. For corrosion parameters determination, polarization curves were analyzed. Linking the structure, morphology and corrosion resistance gives conditions, which could be optimal for the implant surfaces. The structure, morphology and corrosion resistance of the anodized layers are strongly correlated with the processing conditions. We found that for possible hard tissue implant applications best morphology and corrosion resistance show Ti oxidized at 210 V in 2M H3PO4 + 0.2 wt % HF electrolyte.

Microstructure and Electrochemical Properties of Refractory Nanocrystalline Tantalum-based Alloys

The nanocrystalline refractory tantalum alloys were made using mechanical alloying. The tantalum alloys were modified by niobium, molybdenum and tungsten in the concentration of 5, 10, 20 and 40 wt.%. The nanocrystalline powders were consolidated (hot-pressed) using the pulse plasma sintering mode. The hot pressing at the temperature of 1300 o C results in an increase of the grain size, in comparison to mechanically alloyed powders. However, the lowest grain size (significantly below 100 nm) was achieved for Ta-W alloys (approximately 40-60nm). The grain size was confirmed by XRD, TEM and AFM. The most uniform microstructure is also exhibited by the Ta-W alloys. The corrosion resistance was measured using the potentiodynamic mode in a chloride solution. The nanocrystalline Ta-Mo and Ta-W alloys achieved the same level of corrosion resistance as microcrystalline pure tantalum and 3 orders of magnitude better than pure nanocrystalline tantalum. Among all the prepared nanocrystalline tantalum alloys, the most promising properties exhibit those having 10% of the tungsten addition.

Design, Manufacture, and Application of Chamber for the Magnetohydrodynamic Deposition Made of PP

Magnetohydrodynamic deposition can allow deposition of layers or particles that are difficult or impossible to obtain by other methods. This is related to the presence of additional forces during electrochemical processes. Due to the complexity of the method, it is necessary to properly design and manufacture the chamber with all parameters in mind. The paper presents the design process and the chamber manufacture. It is included a detailed description of the method of 3D printing using PP filament. A test was performed in the chamber, confirm the significant effect of magnetic field on the iron corrosion processes. The silver particles deposited on the surface of the titanium at different magnetic field parameters showed different morphology. Occurrence of the magnetic field has a significant effect on the current density during of silver deposition process.

Molecular analysis of biocompatibility of anodized titanium with deposited silver nanodendrites

Titanium (>99.6% purity) and its anodically oxidized modifications, with and without deposited silver nanodendrites regarding its biocompatibility were evaluated. In human gingival fibroblasts and osteoblast cell lines grown on tested samples, the level of expression of genes encoding αV (ITGAV) and β1 (ITGB1) integrin subunits also genes encoding focal adhesion (FAK) and extracellular-signal regulated (ERK) kinases was assessed. For this purpose, the qualitative and quantitative PCR technique was used. The expression of studied genes was dependent on the origin of cell lines and the type of evaluated material. The high expression of PBGD and ITGAV genes in fibroblasts grown on the surface of anodically modified titanium with deposited silver nanodendrites indicates potentially high biocompatibility of these samples for soft tissue cells. The high expression of the ITGB1 and ERK1 genes and the enhanced expression of the FAK gene in osteoblasts cells grown on the tested material was also observed. Summarizing, the nanocrystalline Ti modified with silver deposits showed higher biocompatibility in comparison with the conventional pure Ti samples.

The Influence of Magnetohydrodynamic Power on the Deposition of Silver Dendrites on the Titanium the Surface of Titanium after Anodic Oxidation

The publication presents the influence of an external magnetic field of 1.2T on the process of silver deposition. The external magnetic field interacted perpendicularly to the sample surface during the deposition process. The surface of the titanium sample was pre-modified by anodic oxidation. Such a surface modification causes the deposited silver to take the form of dendrites. As a result of the influence of the magnetic field, the silver dendrites were shortened and the size of their crystallites was reduced. Changes have also been reported at the nucleation stage during the deposition process. The negative magnetic field accelerated the process, causing the deposited silver particles to become thinner. The positive magnetic field slowed down the process, causing the deposited silver particles to become thicker. By modifying the magnetic field, the morphology of the deposited silver particles can be changed.

Cathodic deposition of silver particles on anodized titanium

The paper presents the process of high voltage anodic oxidation of titanium in the electrolyte containing 2 M H3PO4 + 1% HF. The anodization of titanium was performed at various potentials in the range of 30÷210 V and the time of 30 minutes. As a result, a developed surface titanium oxide on titanium was obtained. Then, on the surfaces of the oxides, silver particles were deposited by cathodic method using the electrolyte containing 0.01 M HNO3 + 0.01 M AgNO3. During the deposition of silver particles, a potential of –1 V was applied for 60 s with respect to the open circuit potential. In order to properly characterize the surface, research techniques were used such as XRD, EDS, SEM as well as corrosion testing. The XRD and EDS examinations have shown the presence of the silver particles on the surface of the titanium oxide. The SEM observations were used to assess the shape and surface morphology of the titanium oxide after anodizing and evaluate the amount of silver particles. The silver particles deposited on the anodized titanium surface exhibited a dendritic shape. On the basis of their arrangement and having monitored the deposition process, it can be assumed that they grow directly from the pores on the oxide surface. This is particularly evident in the most developed oxide surface obtained after oxidation of titanium at 210 V. This research allowed determining the suitability of combined anodic and cathodic treatment of titanium in various electrolytes for medical applications — implants. The resulting morphology of the titanium oxide was evaluated, taking into account the features necessary for the proper osseointegration process (structure, high corrosion resistance and surface morphology). Silver deposited on the anodic oxidized titanium surface causes the oxide layer to exhibit additional bactericidal properties, which is extremely advantageous in medical applications. Excess silver has a negative impact on the surrounding tissue in medical applications. For this reason, the dendritic shape of the obtained particles (high surface area) and their relatively small amount generates a potential in medicine applications.

Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

Effect of the High Voltage Anodic Oxidation on the Titanium Corrosion Resistance

The paper describes anodic oxidation of titanium surface in a potential range from 30 to 240 V in a 2M H3PO4 electrolyte with the addition of 0÷2 % HF. The aim of the treatment was to form titanium oxide with a developed, rough morphology, useful for biomedical application. The morphology of the anodically oxidized samples was examined using SEM and AFM. The phase structure of the oxides was determined by XRD. One of the main parameters determining the suitability of that material for biomedical application is the corrosion resistance in an environment comparable to human body (Ringer’s solution). It has been observed that corrosion resistance of the anodized surfaces increases with the increase of the anodizing voltage for the samples oxidized in an electrolyte containing 0 % and 0.2 % HF. In electrolytes with the addition of 1 % and 2 % HF an inverse relationship was observed. The corrosion resistance of all tested surfaces was sufficiently high for the application as a biomaterial. The most promising anodizing treatment, providing best surface morphology and corrosion resistance was performed at 210 V in a 2M H3PO4 + 1 % HF electrolyte.