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

Plasma modification of carbon coating produced by RF CVD on oxidized NiTi shape memory alloy under glow-discharge conditions

Our previous work has shown that for cardiac applications, combining low-temperature plasma oxidation with an amorphous carbon coating (a-C:N:H type) constitutes a prospective solution. In this study, a short-term modification by low-temperature oxygen plasma is proposed as an example and a method for shaping the topography and surface energy of the outer amorphous carbon coating, produced via the Radio-Frequency Chemical Vapour Deposition (RFCVD) method on NiTi alloy oxidized under glow-discharge conditions. This treatment alters the chemical composition of the outer zone of the surface layer. A slight increase is also noted in the surface roughness at the nanoscale. The contact angles were shown to increase by about 20% for water and 30% for diiodomethane, while the surface free energy decreased by ca. 11%. The obtained results indicate that even short-term contact with low-temperature plasma can shape the surface properties of the carbon coating, an outcome which shows potential in terms of its use in medical applications

Wear and Corrosion Characteristics of the Layers Type (Mn-P) Formed on Aluminium Alloys

score: 0collation: 149-15

Corrosion resistance of NiTi shape memory alloy after nitriding and oxynitriding processes under glow discharge conditions for medical applications

abstractEN: NiTi alloy is being increasingly used in medicine due to its unique properties, i.e. shape memory and superelasticity. As a self-passivating material it is characterized by relatively high biocompatibility, however its use for long-term medical implants is questionable due to the nickel content of ≥ 50%. Therefore, the investigations on the surface modification of NiTi alloy are carried out to improve its corrosion resistance and thus reduce the metalosis effect, i.e. the migration of the alloy constituents, especially nickel, into the surrounding tissue. In this paper, the surface topography and corrosion resistance of NiTi alloy (50,8%Ni) both before and after low temperature nitriding and oxynitriding processes under glow discharge conditions, are presented.The study of surface topography showed a slight increase in roughness parameters after nitriding process and a significant increase in these parameters after the oxynitriding process. A similar trend was observed in the study of corrosion resistance. Both processes increase the corrosion resistance of NiTi alloy, as shown by both the impedance spectroscopy results, the values of corrosion potential (-65 mV for the alloy in the initial state, - 45 mV for the alloy with the nitride layer, + 18 mV for the alloy with the oxynitrided layer) and the values corrosion current (respectively 0.047 μA/cm2, 0.043 μA/cm2, 0.015 μA/cm2). These comparative studies present an improvement of corrosion resistance of NiTi after the processes under glow discharge. The best results were obtained for the oxynitrided layer.score: 8collation: 92-9

The Use of Trimethylaluminum for Producing Surface Layers by the PACVD Method

score: 0collation: 3887-389

Magnetic Force Microscopic Description of the Structure of Glow Discharge Nitrided Layers Produced on Ni27Ti2AlMoNb Steel

score: 0collation: 851-85

Processing by Hydrostatic Extrusion of Titanium Coated with Aluminides

score: 0collation: 63-6

Structure and Properties of the High Temperature Nitrided/Oxided Surface of Ni-Ti Alloy

score: 0collation: 53-5