Wyniki 1-10 spośród 10 dla zapytania: authorDesc:"Jarosław Jakubowicz"

Experimental and computational results of porous silicon formation

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The properties of porous silicon prepared at different illumination and electrochemical conditions were studied. Here, the illumination was applied from the backside of the wafer (side not immersed in the electrolyte), from the topside (side immersed in the electrolyte), and for the highly doped silicon, etching proceeds without illumination. The electrolyte contains HF in the range of 2-50 w[...]

High and low voltage anodic etching of microand nanocrystalline Ti-based biomaterials

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Titanium based materials are commonly used as biomaterials due to their excellent biocompatibility and mechanical properties. In respect to biomedical applications, usually we are interesting in pure Ti, Ti-6Al-4V and other alloys as well as Ti-ceramic biocomposites [1÷8]. To improve biocompatibility, osseointegration or corrosion resistance, the implant surface improvement is required, which provide sufficiently high roughness. The rough surface of the implant for hard tissue applications can be prepared mainly by mechanical [9] or electrochemical [10, 11] methods. In the electrochemical process, the material is an anode immersed in the electrolyte, so the process is called anodic oxidation. The anodic etching can be made at broad potential range, which results in different oxide type. The etching usually proceeds in H3PO4 or CH3COOH electrolytes with small HF or NH4F content. These small additions, usually in the range of 0.1÷2%, result in increasing current density followed to enhanced surface dissolution. Additionally, the etching rate can be substantially improved by decreasing grain size. For nanostructure materials, the large volume fraction of the grain boundaries states an easy way for the electrolyte penetration. Atoms, which lie on the grain boundaries are firstly removed and additionally small nanograins are easily released from the alloy, resulting in pores formation. That material has lower density than microcrystalline counterpart and the etched surface is comparable in morphology to the metallic foams. Due to large pores, this material is attractive for strong fixation with bones. experimental data In this work, the electrochemical etching was applied to the surface modification of the microcrystalline Ti, as well as micro- and nanocrystalline Ti-6Al-4V alloys. The microcrystalline materials were bought in Godfellow and, nanocrystalline one was prepared by 48 h mechanical alloying in SPEX 8000 [...]

Cathodic deposition of silver particles on anodized titanium DOI:10.15199/28.2017.3.2

  1. INTRODUCTION The present state of knowledge related to implantology, material engineering, biomechanics and physiology allows developing biomaterials meeting our basic expectations. Implants whose working time is expected in excess of 20 years must be continually adapted. The slow rate of degradation of the metal in the human body is unavoidable (infiltration of metal ions into the body) [1÷3]. The implant is affected differently than the bone on the surrounding tissue. Troublesome is also the question of optimizing the osseointegration process. This phenomenon is still not fully understood. Therefore, it is difficult to predict the effect of modifications of the implant surface on the osseointegration process [4, 5]. The anodized layer exhibits the best properties of the modified surface layer on titanium [6]. Anodizing can change the surface properties, such as chemical composition, thickness, microstructure, and surface morphology. It is possible to produce oxides of approx. 1 μm of thickness over the complex shape of the implant. Such possibilities place anodic oxidation before other methods of surface treatment of titanium. In the field of surface treatment of titanium for biomedical purposes, we know what factors affect the effective process of osseointegration [7]. We can evaluate the impact of mechanical action of the implant on the surrounding tissue and then modify its shape in order to minimize the transmitted forces. The acquired clinical hands-on experience of osseointegration allows the use of better materials [8]. The present state of knowledge has contributed to a significant shortening of postoperative healing. Anodic oxidation of titanium and its alloys in the electrolyte containing H3PO4 is well known [9]. Currently no comprehensive research exists on the anodic oxidation of titanium in the electrolyte containing H3PO4 with the addition of HF [10]. The obtained surface oxide didn’t have a sati[...]

Odporność korozyjna prasowanych na gorąco nanokrystalicznych stopów tantalu DOI:10.15199/40.2017.11.2

  1. Wstęp Tantal jest metalem o bardzo dobrych właściwościach fizyko-chemicznych. Do jego głównych zalet zalicza się odporność na działanie mocnych kwasów. Posiada również wysoką temperaturę topnienia - 3017°C. Dzięki tym właściwościom zastosowanie znalazł w wielu gałęziach przemysłu. Tantal może być również stosowany jako biomateriał, dla przykładu w elementach sztucznych stawów biodrowych. Bardzo często porównywany jest do tytanu. Można wzbogacać go o dodatki stopowe takie jak niob, wolfram, węgiel, azot, molibden w celu polepszenia jego właściwości. Jedną z głównych wad tego materiału jest jego wysoka cena [2]. Materiały o nanostrukturze są obecnie coraz częściej stosowane w przemyśle i medycynie. Mogą one występować w postaci czystych metali lub ich stopów [5]. Różnią się one również właściwościami mechanicznymi, biologicznymi, fizykochemicznymi. Materiały o strukturze nanokrystalicznej można wytwarzać między innymi poprzez zastosowanie dużych odkształceń plastycznych (metody wyciskania lub skręcania). Jednak obecnie bardzo częstym sposobem wytworzenia takich materiałów jest wysoko-energetyczne mielenie kulowe (ang. High-Energy Ball Milling, HEBM) lub proces mechanicznej syntezy (ang. Mechanical Alloying, MA). Do syntezy wykorzystuje się reaktory, w których znajdują się proszki wraz z kulami mielącymi instalowane w specjalistycznych młynkach [3-6, 8]. Ważną cechą każdego materiału jest odporność korozyjna. Jest ona istotna jeżeli materiał pracuje w środowisku agresywnym. W takim przypadku powierzchnia jest narażona na działanie czynników niszczących. O ile korozja równomierna jest możliwa[...]

Preparation and corrosion properties of Ti-45S5 Bioglass nanocomposites with electrochemically modified surface

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Commercially pure titanium and titanium alloys have become predominant in dentistry [1]. The high degree of biocompatibility of Ti and its alloys is connected with the passive oxide film formed on the metallic surface, consisting mainly of amorphous titanium dioxide (TiO2) [2]. However, low hardness and poor tribological properties of these alloys may become critical factor when wear phenomena are involved. On the other hand, bioactive glasses are materials, which can adhere to bone and tissues through the formation of calcium phosphate (hydroxyapatite - HA) at the interface of the material. This layer is chemically and structurally equivalent to the mineral phase in bone and is responsible for interfacial bonding. Due to low fracture toughness, glass cannot serve as a bulk implant material. The connection of good mechanical properties of titanium with excellent biocompatibility of bioactive glasses seems to be a promising candidate way to expend the biomedical applications [3, 4]. Surface properties of titanium implants are known as key factors for successful osseointegration [5]. Till now, various surface modification methods have been applied to dental implants in attempts to improve their clinical performance [6, 7]. Surface treatment of the implant material can result in surface roughening, attractive for tissue growth and fixing of implant for hard tissue applications [8, 9]. The promising route in surface roughening is an electrochemical etching [10, 11]. The treatment in H3PO4 electrolytes results in pits formation, acting as anchors for the tissue. The etching procedure can be applied for pure Ti as well as its alloys. In the nanocomposites, due to the large volume of the grains boundaries, the electrochemical etching proceeds fast and is suitable for the sufficient surface roughening [12]. During the etching an anodic oxide layer is formed resulting in good corrosion resistance. The additional [...]

Effect of manufacturing technology of ball-and-socket joint made of Co28Cr6Mo alloy on its tribological properties DOI:10.15199/28.2017.1.5

  The article presents the results of friction and wear testing of ball-and-socket joints, made of ASTM F75 alloy powder, applying the technologies of selective laser melting and spark plasma sintering. The reference material constituted joints produced by machining from a ASTM F1537 LC rod. The tribological tests were carried out using the movement simulator of a spinal motion segment of our own design, in the environment of distilled water. The test results consisted of a comparison of the friction resistance values occurring in the friction couple and comparison of the wear indicators of the upper and lower components, which simulate the tribological system of an intervertebral disc endoprosthesis in the spinal lumbar segment. Analysis of the wear mechanism of the bearing surfaces was performed on the basis of microscopic observations and measurements of friction surface roughness. Regardless of the manufacturing technology, the coefficient of friction varied in the range of 0.25 to 0.30, wherein a median value for all the tested material combinations was in the range of 0.27 to 0.29. The lowest resistance to tribological wear was demonstrated by the joints produced employing spark plasma sintering technology. The wear of the joints produced with this technology was about 20% higher in comparison to those joints formed by selective laser melting, and about 30% higher compared to the joints produced in a conventional manner from ASTM F1537 LC alloy. Observations performed using scanning electron microscopy showed that regardless of the production technology, the dominant type of wear was abrasive-adhesive wear. Unlike the joints produced in a conventional manner, the bearing surfaces of the components produced by means of selective laser melting and spark plasma sintering technologies, there is evidence of fatigue damage. The results call into question the possibility of using alternative technologies in the manufacturing process of endoprosthe[...]

Wpływ technologii wytwarzania wyrobów ze stopu Co28Cr6Mo na ich właściwości fizyczne, mechaniczne i odporność korozyjną DOI:10.15199/28.2015.1.1

  Komponenty metalowe endoprotez stawów człowieka często są wykonywane ze stopów na osnowie kobaltu. Stopy te swoją popularność zawdzięczają dużej wytrzymałości doraźnej i zmęczeniowej, satysfakcjonującej odporności korozyjnej w środowisku płynów ustrojowych oraz, co najważniejsze, względnie największej odporności na zużycie tribologiczne w porównaniu z innymi biomateriałami metalowymi. Coraz większe wymagania stawiane biomateriałom skłaniają do ciągłego opracowywania nowych materiałów lub modyfikacji już istniejących. Podjęto więc badania mające na celu określenie wpływu wybranych innowacyjnych technologii wytwarzania na właściwości fizyczne, mechaniczne oraz odporność korozyjną stopu Co28Cr6Mo. Próbki do badań wytworzono z zastosowaniem technologii selektywnego przetapiania laserowego oraz iskrowego spiekania plazmowego. Jako materiał odniesienia zastosowano próbki referencyjne, które wytworzono ze stopu po procesie kucia ASTM F1537 LC. Niezależnie od zastosowanej technologii w mikrostrukturze stopu dochodziło do przemiany fazowej [...]

Effect of manufacturing technology on tribological properties of Co28Cr6Mo alloy DOI:10.15199/28.2016.5.7

  The physical, chemical, mechanical properties of alloys used in endoprosthesis components in the osteoarticular system or dental implants depend not only on the chemical composition, but also on the applied production technology. The article presents the results of friction and wear testing of samples produced by selective laser melting and spark plasma sintering of the ASTM F75 alloy powder (Co28Cr6Mo alloy). As reference material, an ASTM F1537 LC rod was used from which samples were prepared by machining. The friction and wear tests were conducted by means of a tribological tester with a block-ring tribosystem. The tests were performed without lubricating fluid at ambient temperature. The test results constituted a comparison of the frictional resistance in contact with bearing steel 100Cr6 as well as a comparison of the wear values depending on the given friction pair load as a function of sliding distance. Analysis of the wear mechanism of the test materials was based on microscopic observation of the friction surfaces, chemical composition analysis of the surfaces using energy dispersive X-ray spectroscopy as well as roughness measurements. For the friction pair involving the reference sample, the friction coefficient was characterized by a constant value of about 0.40 regardless of the load or travelled sliding distance. In the case of the samples greater frictional resistance was found. The friction coefficient for the friction pairs involving samples produced using the technology of selective laser melting and spark plasma sintering varied in the range 0.50 to 0.62 and from 0.70 to 0.74. Based on the obtained results of weight loss, it was calculated that the reference material sample was characterized by the smallest wear coefficient, while the largest was demonstrated by samples produced by spark plasma sintering. Microscopic observations showed that regardless of the employed technology to produce the samples, the dominant type of w[...]

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