Papers by Keyword: NiTi Alloy

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Authors: Hui Min Zhou, Qing Fen Li, Li Li, Yu Feng Zheng
Abstract: Dental diamond bur is now a regular rotary tool, with its head made of diamond particles embedded into nickel coating, and its shank made of stainless steel. There are strong demands from the dentist on prolongation of usage life and avoiding of breakage. To solve this problem, on the one hand, since diamond is hard to be wetted under the condition of normal temperature and pressure due to the high interfacial energy between diamond and general metals and alloys. Diamond particles coated with titanium layer was used for the preparation of composite electroplating with the intention of improving the interfacial adhesion between diamond and metal matrix; on the other hand, superelastic biomedical NiTi alloy was used as the substrate to improve the flexibility and prevent the breakage. In this study, the optimal preparation parameters of Ni/surface-modified diamond electroplating were determined by orthogonal test, and the bonding conditions between the diamond particles and the NiTi alloy substrate were studied by scanning electron microscope. Further performance comparison of Ni/modified and Ni/un-modified diamond composite electroplating was conducted on a pin-on-disc wear machine under the dry sliding condition, and the material removal volume was used as the evaluating criterion of wear resistance. The results showed that the binding strength between diamond particles and NiTi alloy substrate could be enhanced, as well as the wear resistance, which may give direction on the future design of dental bur.
Authors: Harald Fischer, B. Vogel, A. Grünhagen, K.P. Brhel, M. Kaiser
Authors: Beata Cwalina, Weronika Dec, Wojciech Simka, Joanna Michalska, Marzena Jaworska-Kik
Abstract: Bacteria of Desulfovibrio genus belong to group of widespread sulphate-reducing bacteria (SRB). D. desulfuricans is considered one among many bacterial species involved in microbiologically influenced corrosion (MIC) of metals, mainly of stainless steels and other alloys. SRB can produce gaseous hydrogen sulphide. This gas is released into the environment leading to formation of metal sulphides that significantly influence electrochemical processes and ultimately enhance the corrosion of materials. Biofilms formed by these bacteria are especially harmful for highly alloyed steels and many alloys. The aim of this work was to compare the character of growth and biofilm formation by three strains of D. desulfuricans (standard soil strain DSM and two wild intestinal strains: DV/A and DV/B) on the surface of NiTi alloy.
Authors: Aldo Roberto Boccaccini, E.J. Minay, D. Krause
Abstract: 45S5 Bioglass® coatings have been produced on superelastic nickel-titanium wires using electrophoretic deposition (EPD). Aqueous suspensions of Bioglass® particles (< 5 &m mean particle size) were used. EPD led to the formation of thick and uniform coatings covering the wires very homogeneously, without the development of any microcracks during the drying stage. Best results were achieved with suspensions containing 20 wt% Bioglass®, an applied voltage of 5 V, and a deposition time of 5 min. Samples sintered for 1 hour at temperatures > 800 °C exhibited diffusion of nickel and titanium into the Bioglass® coating. Scanning electron microscopy (SEM) was used to analyse the microstructure of the Bioglass® coatings in terms of level of uniformity, densification, and to discover the possible presence of microcracks, as well as to gain information about the thickness of the coating produced on the different substrates. The results demonstrate that the EPD technique is a very convenient method to produce uniform Bioglass® coatings on wires for biomedical applications.
Authors: Wendy C. Crone, Alief N. Yahya, John H. Perepezko
Authors: Rutchadakorn Isarapatanapong, Surachai Dechkunakorn, Niwat Anuwongnukroh, Nattiree Chiranavanit, Julathep Kajorchaiyakul, Anak Khantachawana
Abstract: Objective: The study aimed to clarify the compositions of 14 brands of superelastic NiTi orthodontic wires. Materials and Methods: The compositions were analysed through scanning electron microscopy and energy-dispersive X-ray microanalysis. The wires were tested in differential scanning calorimetry to find the transitional temperature range. Results: The compositions were nickel (50.085%-51.605%), titanium (46.675%-48.140%), copper (0.995%-1.155%), aluminum (0.220%-1.325%), chromium (0%-0.275%) and iron (0%-0.030%). None contained cobalt. G&H, Ormco, AMDG, IMD, Smart, TruFlex, Force 1, NIC, Sentalloy, Ortho Supply and Flexwire were almost or completely austenitic in the oral environment, whereas Highland, Grikin and Unitex were a mixture of austenitic and martensitic phase. The wires showed austenitic finish temperatures ranging from 17°C to 59°C. Conclusions: The results show that NiTi orthodontic arch wires have differences in composition and phase transformation. This information is valuable to evaluate differences in NiTi orthodontic wires for clinical use.
Authors: G. Rondelli, M. Francesca Brunella, Luigi de Nardo, Alberto Cigada
Authors: B. Coluzzi, A. Biscarini, Giovanni Mazzolai, Fabio M. Mazzolai, Ausonio Tuissi, Elena Villa
Abstract: The internal friction (IF) and the Young’s modulus (E) of NiTi based alloys have been investigated at 1 Hz and 1 kHz frequencies after various sequences of thermo-mechanical treatments and hydrogen-doping given to the materials. Differential scanning calorimetry (DSC) has also been used as a complementary investigation tool. Apart from the transient effects, only occurring at 1 Hz frequencies, the data indicate a substantial insensitivity of damping to frequency. The results show that the H-Snoek and the H-twin boundary relaxations get their maximum height for H contents nH (nH=H/Me) equal to about 0.025 and 0.008, respectively. At kHz frequencies the IF peaks associated with these relaxations occur at around room temperature in the Ni49Ti51 and Ni30Ti50Cu20 alloys. Thus, these appear to be the most promising materials for applications aimed at the reduction of vibrations.
Authors: Pavel Novák, Pavel Salvetr, Andrea Školáková, Miroslav Karlík, Jaromír Kopeček
Abstract: NiTi alloy is usually prepared by casting and forming. As an innovative process, reactive sintering powder metallurgy is tested worldwide, aiming to prepare pure NiTi alloy easily from nickel and titanium powders. This process enables to prepare both porous and low-porosity alloy, depnding on the process conditions. However, the formation of NiTi phase in this process is always accompanied by the Ti2Ni phase, which is hard, brittle, less corrosion resistant and does not have the shape memory. In this work, various alloying elements (Al, Si, Mg, Fe, Nb, V) were added to Ni-Ti alloy in order to lower the amount of Ti2Ni phase or at least to minimize its undesirable effect on the alloy properties. The reactive sintering behaviour, phase composition and mechanical properties of Ni-Ti-X alloys were described.
Authors: Beata Cwalina, Weronika Dec, Wojciech Simka, Adrian Mościcki, Marzena Jaworska-Kik, Edyta Kaczmarek
Abstract: NiTi alloys are used for both medical and veterinary purposes, and also for production of surgical instruments. Sulphate-reducing bacteria (SRB) colonize various anaerobic environments, including human oral cavity. Desulfovibrio desulfuricans is the SRB species responsible for corrosion of many metals including highly alloyed steels as well as titanium and its alloys. The aim of this work was to compare growth of D. desulfuricans biofilms on NiTi alloy submerged in artificial saliva or in inflammatory saliva. The results of investigations showed differences between D. desulfuricans biofilms formed on NiTi alloy in the presence of artificial saliva and inflammatory saliva. The growth medium influenced biofilm structure; inflammatory saliva promotes its formation. The biofilms grown on samples immersed in inflammatory saliva were much thicker as compared with samples emerged in artificial saliva. After 28 days of incubation in inflammatory saliva, plentiful mature biofilm was present on alloy surface.
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