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Synthesis and characterization of nickel free titanium–hydroxyapatite composite coating over Nitinol surface through in-situ laser cladding and alloying
摘要： In this study, a high power fibre laser was used to synthesize titanium hydroxyapatite composite coating over biomedical-grade Nitinol surface through laser in-situ formation, cladding and alloying processes. The laser fluence is varied in the range of 2 kJ/cm2 to 8 kJ/cm2 in view of establishing a relationship between various in-situ phase-formation characteristics along with the rate of diffusion of the base material in the cladding zone with molten pool temperature. The alloying with base Nitinol material and subsequent diffusion of titanium to the in-situ formed calcium phosphate cladding layer are observed in the samples treated with laser fluence of 4 kJ/cm2 or above. Double layer configuration of the solidified molten pool is mostly found in all the cladding samples. At the fluence of 6 kJ/cm2 or above, the top layer primarily comprises segregated titanium-hydroxyapatite phase along with diffusion of titanium from the base material. Whereas, the bottom part of the molten pool is dominated with titanium-rich nickel–titanium intermetallic reinforced with nano particles. The steady-state variations of calcium and elemental presence of titanium through the cladding cross-section along with no nickel or oxide presence are confirmed through EDS line scans. The spherical and lamellar structures of formation of titanium-hydroxyapatite on the top surface also help to improve the overall corrosion resistance properties as compared to the bare surface. The modulus of elasticity is controlled by the variation of the top layer and intermediate layer composition and thickness, which varies with laser fluence. It falls in the range of 6–30 GPa which is similar to natural bone. Thus this nickel-free alloying and cladding layer of titanium-hydroxyapatite can serve as one of the potential candidates for use as a coating over the load bearing Nitinol implants to arrest the nickel release phenomena.
关键词： Titanium–calcium coating,Biocompatible functional coating,Hydroxyapatite,Nitinol surface modification,Laser cladding and alloying
更新于2025-09-23 15:22:29
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POST WELD HEAT TREATMENT OF NiTinol SHAPE MEMORY ALLOY USING LASER POWER SOURCE
摘要： In this work, attempt is made to carry out post weld heat treatment (PWHT) on NiTinol samples using laser power source. Initially, 1 mm thick NiTinol sheets were welded in butt joint position using Ytterbium: Yttrium aluminum garnet (Yb: YAG) laser power source. Laser welding was carried out in continuous mode, and the quality of the weld was assessed with respect to phase transformation temperatures, microhardness, tensile strength, and corrosion resistance. To improve the quality of the welded samples, PWHT was done by passing a laser beam over the welded samples. It was found that PWHT had a significant effect on the phase transformation temperatures, microhardness, tensile strength and corrosion behavior of the welded NiTinol joints.
关键词： laser heat treatment,NiTinol,laser welding,mechanical properties,corrosion behavior
更新于2025-09-19 17:13:59
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In-Situ Plasma Monitoring during the Pulsed Laser Deposition of Ni60Ti40 Thin Films
摘要： The properties of pulsed laser deposited of Ni60Ti40 shape memory thin films generated in various deposition conditions were investigated. In-situ plasma monitoring was implemented by means of space- and time-resolved optical emission spectroscopy, and ICCD fast camera imaging. Structural and chemical analyses were performed on the thin films using SEM, AFM, EDS, and XRD equipment. The deposition parameters influence on the chemical composition of the thin films was investigated. The peeled layer presented on DSC a solid-state transformation in a different transformation domain compared to the target properties. A fractal model was used to describe the dynamics of laser produced plasma through various non-differentiable functionalities. Through hydrodynamic type regimes, space-time homographic transformations were correlated with the global dynamics of the ablation plasmas. Spatial simultaneity of homographic transformation through a special SL(2R) invariance implies the description of plasma dynamics through Riccati type equations, establishing correlations with the optical emission spectroscopy measurements.
关键词： thin films,in situ plasma monitoring,nitinol,pulsed laser deposition,fractal modelling,SL(2R) invariance,homographic transformations,Riccati equation
更新于2025-09-19 17:13:59
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Biocompatibility of micro/nanostructures nitinol surface via nanosecond laser circularly scanning
摘要： We present three novel scanning patterns on nitinol by nanosecond laser for controllable fabricating biocompatible micro/nanostructures. The surface morphology and formation mechanism of micro/nanostructures were respectively observed and analyzed. The production of surface oxide film provides a biocompatible cell living environment. Also, micro/nanostructures greatly promote cell adherence and growth. It is worth noting that ns laser circularly scanning can effortlessly produce various micro/nanostructures and endue biologically inert nitinol implants with enhanced osseointegration and bioactivity.
关键词： Microstructure,Nitinol,Laser processing,Surfaces,Biocompatibility
更新于2025-09-11 14:15:04
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Scalable laser powder bed fusion processing of nitinol shape memory alloy
摘要： The authors report on pulsed laser powder bed fusion fabrication of nitinol (NiTi) shape memory materials. The authors ?rst performed single-track laser parameter sweeps to assess melt pool stability and determine energy parameters and hatch spacing for larger builds. The authors then assessed the melt pool chemistry as a function of laser energy density and build plate composition. Brittle intermetallics were found to form at the part/build plate interface for both N200 and Ti-6-4 substrates. The intermetallic formation was reduced by building on a 50Ni–50Ti substrate, but delamination still occurred due to thermal stresses upon cooling. The authors were able to overcome delamination on all substrates and fabricate macroscopic parts by building a lattice support structure, which is both compliant and controls heat transfer into the build plate. This approach will enable scalable fabrication of complex NiTi parts.
关键词： additive manufacturing,shape memory alloy,nitinol,scalable fabrication,laser powder bed fusion
更新于2025-09-11 14:15:04
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A comparative study of surface characterization and corrosion performance properties of laser surface modified biomedical grade nitinol
摘要： Laser melting and quick solidification of shape memory alloy surfaces promise to explore the multifunctional capabilities required for enhanced biocompatibility of different implantable medical devices. Before subsequent bio-trial, understanding of the effect of cooling rate vis-à-vis laser fluence on surface characteristics and corrosion protection performance is essential before designing a tailor-made biocompatible surface for various implantable devices. The current study systematically investigates the effect of laser fluence on physical, mechanical and chemical surface characteristics along with corrosion protection performance of the modified surface as compared to bare Nitinol surface. Various phases were prominent on the top surface, namely nickel and titanium-rich phase along with different nickel-titanium intermetallics and nano-structure of titanium oxide, based on varying melting pool recirculation time and cooling rate with laser fluence energy. At low laser fluence up to 4 J/mm2, no significant melting pool were formed and only transformation to the martensitic phase of Nitinol took place on the top surface, which seemed to be highly too much corrosion-prone under simulated body fluid. At moderate laser fluence of 6–8 J/mm2, mostly titanium-rich phases are prominent on the surfaces on account of optimum recirculation of melting pool and subsequent surfacing out of comparably light phase of titanium. Titanium-rich phases on top surface exhibit superior corrosion resistance as compared to all other samples including bare nitinol. However, titanium oxide nano-particles-reinforced martensitic structure is formed under high laser fluence due to over recirculation of molten pool. The modulus of elasticity also varied from 10 to 110 GPa based on top surface formation under different fluence levels, and thus this process can act as a tailor-made controllable pre-treatment process over the traditional coating processes.
关键词： Corrosion protection performance,Laser melting and re-solidification,Surface characteristics,Nitinol surface modification
更新于2025-09-11 14:15:04
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Pr?zisionspulskapsulotomie; Precision pulse capsulotomy;
摘要： The manual capsulorhexis created by Neuhann is still the standard procedure for opening the anterior capsule for cataract surgery. A limitation is the inaccuracy in the size and placement of the opening due to manual execution. In addition to the femtosecond laser a possible improvement in the standardization of capsulorhexis is provided by the Zepto procedure (precision pulse capsulotomy, PPC). In this case a 5.25 mm rhexis is created in a standardized fashion with a flexible suction adapter in which a nitinol ring is located. Whether the strength of PPC is comparable or better than that of the manual technique and how it behaves in terms of capsule shrinkage has not yet been finally clarified.
关键词： Standardization,Rhexis,Capsule shrinkage,Nitinol,Cataract surgery
更新于2025-09-10 09:29:36