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Research Interests
Shape-controlled fabrication of Ag nanostructures on oxide templates on nitinol by electrodeposition
Control of the electrolyte by collagen concentration caused a change in Ag shape and aggregation. Preferred growth along Ag (111) by orientated attachment of the Ag led to the formation of Ag dendrites in the AgC2H3O2 solution. Spherical Ag nanostructures, which were well dispersed on the templates, were obtained by electrodeposition in an AgC2H3O2-collagen solution on templates. Increasing the concentration of collagen caused aggregated Ag to form coarse spherical structures with a non-uniform distribution.
Synergistic effects of collagen and silver on the deposition characteristics, antibacterial ability, and cytocompatibility of a collagen/silver coating on titanium
Implant-associated infections may be prevented by coating silver on a titanium implant; however, the excessive release of Ag+ can induce cytotoxicity. This study fabricated a silver/collagen coating on titanium surface to improve the antibacterial ability without compromising cytocompatibility. The silver/collagen coating can effectively prevent adhesion and proliferation of Escherichia coli. Based on MTT assay tests, the amounts for the silver/collagen coated surfaces after 72 h of MG63 osteoblast cell adhesion were greater than those obtained from the silver coated surfaces.
Anti-fracture performance of micro-arc oxidization films on TiNiSi shape memory alloy after elongation, bending and shape recovery
The adhesion of a coating on a shape memory alloy (SMA) as an implant is very crucial. This study investigated parameters for micro-arc oxidation (MAO) applied to TiNiSi SMA from the viewpoint of coating adhesion. Four kinds of adhesion tests were utilized to evaluate the adhesion of a coating: pull out, scratch, tension-recovery, and bending-recovery tests. The adhesive strength of the MAO films formed by 80 V, 120 V, and 150 V were 33.8±6.4, 42.6±4.8, and 78.9±4.2 MPa, respectively. The critical load of the MAO films was increased with the anodic voltage: its values for the oxide films formed at 80 V, 120 V, and 150 V were 71.2+2.3, 90.9+2.8, and 112.7+2.4 mN, respectively, and they were measured by scratch tests. However, the use of a low anodic voltage or short duration is beneficial to MAO film adhesion when plastic deformation is imposed to the substrate. Specimens anodized at 80 V remained unbroken, but the films were detached at 120 V and 150 V after their elongation by tensile force and subsequent recovery by heating.
Microstructure and mechanical properties of Ti nitride/Ni metal-based composites fabricated by reactive sintering
A Ti nitride/Ni metal-based composite was fabricated by the carbothermal reduction reaction during the sintering process. During sintering, Ti particles were transformed to Ti nitride as TiN0.3 at 850 °C, and then gradually transformed to TiN0.3 and TiN at 950 °C accompanied by TiO2 formation. The Ti oxide layer surrounding the outer surface of the Ti nitride particles is regarded as a buffer layer which can improve the adhesion of the Ti nitride particles and the Ni matrix.
Improvement in hydroxyapatite attachment on Ti by gas-assisted electrical discharge coating
Electrical discharge coating (EDC) has been applied to prepare a bioactive hydroxyapatite (HA) layer on Ti alloys as implant applications. This study aimed to enhance HA incorporation in the coating by absorbing HA on gas using gas-assisted perforated electrodes. Using gas-assisted perforated electrodes at an appropriate gas flow rate (0.02 L/min) enhanced the HA amount in the coating. After hydrothermal treatment, the needle and prism HA crystals precipitated on the coating surface, exhibiting hydrophilic property.
The feasibility of eco-friendly electrical discharge machining for surface modification of Ti: A comparison study in surface properties, bioactivity, and cytocompatibility
This study provided an eco-friendly manufacturing method for Ti implants by electrical discharge machining (EDM). The feasibility of this EDM was evaluated by tested the bioactivity and cytocompatibility of the EDM-treated Ti and the commercially micro-arc oxidation (MAO)-treated Ti was used as a control group. The two surface modification processes were compared. Furthermore, in vitro bioactivity and cellular biocompatibility of the MAO- and EDM-treated Ti films were tested. The MAO-formed films were fractured, but the EDM-formed films maintained their original structure under tensile stress, tested according to the ASTM C633 standard. The bioactivity of the EDM-treated surface was higher than that of the MAO-treated and untreated Ti surface. After 24 h cell incubation, the EDM-treated surface exhibited a significantly higher number of cells than untreated Ti and the MAO-treated surface.
Surface modification of Ti-based alloys by gas, liquid, and powder mixed EDM
Various EDM processes were developed for surface treatment of Ti-based alloys. The EDM process includes dry-EDM, liquid-EDM, and powder-mixed EDM. The surface characteristics (morphology, roughness, composition, hardness, and wettability) were investigated.
Surface modification and machining of TiNi/TiNb-based alloys by electrical discharge machining
Effects of the composition of the TiNi/TiNb-based alloys and electrical discharge machining (EDM) parameters on the properties of the materials were investigated. The addition of Mo to TiNi or of Nb to Ti clearly reduced the material removal rate (MRR), electrode wear rate, surface roughness, and recast layer thickness, which was attributed to the increased melting temperature and thermal conductivity of the materials. The surface roughness of the EDMed alloys obeyed the empirical equation Ra = β(Ip × τp)α.
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