Masahiko Inagaki

Bond strength improvement of hydroxyapatite/titanium composite coating by partial nitriding during RF-thermal plasma spraying

Abstract The bond strength of plasma-sprayed HA/Ti composite coatings on Ti substrate was significantly improved by the partial nitriding of Ti deposits in the coatings during plasma spraying. HA/Ti composite coatings were deposited on titanium substrates by a radio-frequency thermal plasma spraying method with RF input powers of 12–27 kW. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the composition from Ti-rich to HA-rich towards the upper layer of the coating. When sprayed in plasma gas with 0.8% N2 added, the bond (tensile) strength of the obtained HA/Ti composite coatings sprayed at 12 kW was 41.4 MPa. On the contrary, the bond strength of coatings sprayed with pure Ar at 12 kW was 33.6 MPa regardless of the processing parameters which were almost the same except for plasma gas composition. When sprayed with 1.8% N2 added at 27 kW, the bond strength reached 65.3 MPa. XRD patterns of Ti coatings without HA showed that titanium nitrides formed in the titanium deposits sprayed with plasma gas containing N2. Scanning electron microscopic observation showed that these Ti deposits had an acicular texture.

Formation of highly oriented hydroxyapatite in hydroxyapatite/titanium composite coating by radio-frequency thermal plasma spraying

Highly oriented hydroxyapatite (HA) coatings with excellent adhesion were successfully obtained on titanium (Ti) and titanium alloy through a radio-frequency thermal plasma spraying method. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the composition from Ti-rich to HA-rich toward the upper layer of the formed coatings. The bond (tensile) strength of the HA/Ti composite coatings was ca. 40–50 MPa. XRD patterns showed that the topmost HA layer of the coatings had an apatite structure with (00l) preferred orientation. The degree of this orientation showed a tendency to increase with an increase in the substrate temperature during spraying.

Osteogenic activity of diphenyl ether-type cyclic diarylheptanoids derived from Acer nikoense

Osteogenic activity of six diarylheptanoids, acerogenin A (1), (R)-acerogenin B (2), aceroside I (3), aceroside B(1) (4), aceroside III (5) and (-)-centrolobol (6) and two phenolic compounds; (+)-rhododendrol (7) and (+)-cathechin (8), isolated from the stem bark of Acer nikoense (Nikko maple) was evaluated using alkaline phosphatase (ALP) activity as a marker for early osteoblast differentiation. We found that the diphenyl ether-type cyclic diarylheptanoids 1-5 promoted ALP activity in mouse preosteoblastic MC3T3-E1 cells without affecting cell proliferation, but linear-type diarylheptanoid 6 and phenolic compounds 7 and 8 did not. Diphenyl ether-type cyclic diarylheptanoids 1-4 also increased protein production of osteocalcin, a late stage maker for osteoblast differentiation, and induced osteoblastic mineralization. Structure-activity relationships of these compounds demonstrated that the stimulative efficacy of aglycones was higher than that of its glycosides. Taken together, diphenyl ether-type cyclic diarylheptanoids promote early- and late-stage osteoblastogenesis, which may open the possibility for the development of novel osteogenic agents.

Fabrication of micropatterned mesoporous silica film on a flexible polymer substrate through pattern transfer and subsequent photocalcination

A microfabrication method for mesoporous silica (MPS) film on a flexible polymer substrate is proposed. The method consists of three processes. First, by using a spatially defined microtemplate consisting of dual self-assembled monolayers (SAMs) with alternating trifluorocarbon (CF3) and amino (NH2) groups, a mesostructured silica/surfactant composite (MSSC) film was site-selectively deposited on the CF3-terminated SAM regions through hydrophobic and van der Waals interactions between the surfactant molecules and the hydrophobic SAM surface. Next, in order to transfer these prefabricated MSSC micropatterns to a poly(ethyleneterephthalate) (PET) substrate, the sample was pressed firmly against the PET surface for 60min at 90°C under a pressure of 4MPa. Due to the weak adhesion between the MSSC film and the CF3-terminated SAM surface, the deposited MSSC micropatterns readily peeled off the SAM surface and were transferred to the PET substrate while preserving both the morphology and the nanostructures of th...

Internal Friction near the Orthorhombic-to-Tetragonal Phase Transition in YBa2Cu3O7-x at 80–200 kHz

The internal friction and compliance of YBa 2 Cu 3 O 7-x are measured at temperatures from 300 to 1050K using a LiNbO 3 composite oscillator technique. An anelastic relaxation due to oxygen movement at 80-200 kHz is observed to be associated with the orthorhombic-to-tetragonal (O-T) phase transition in YBa 2 Cu 3 O 7-x at 850-900 K. By careful fitting for the measured internal friction against temperature, we provide data on the relaxation time and peak temperature in the highest frequency region for a linear Arrhenius plot that extends over 7 orders of magnitude.

Highly Oriented Hydroxyapatite Coating Using rf Plasma Spraying

Highly oriented hydroxyapatite (HA) coatings were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. XRD patterns showed that the HA coating layer had an structure with (00l) preferred crystal orientation. TEM observation showed that 200-800 nm-width prismatic crystals were formed in HA splats and the longitudinal axis of such prismatic crystals oriented vertical to the coatings surface. TEM images also indicate that the interface between prismatic crystals became compacted. SAD pattern show that the longitudinal axis of prismatic crystals corresponds to the <001> axis of HA.

Improvement of bond strength of plasma-sprayed hydroxyapatite/titanium composite coatings on titanium: Partial nitriding of titanium deposits by rf thermal plasma

The bond strength of plasma-sprayed HA/Ti composite coatings on Ti substrate was significantly improved by the partial nitriding of Ti deposits in the coatings during plasma spraying. HA/Ti composite coatings were deposited on titanium substrates by a rf thermal plasma-spraying method with rf input powers of 12–27 kW. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the coating composition from Ti rich to HA rich toward the upper layer. When sprayed in plasma gas with 0.8% N2 added, the bond (tensile) strength of the obtained HA/Ti composite coatings sprayed at 12 kW was 41.4 MPa. On the contrary, the bond strength of coatings sprayed with pure Ar at 12 kW was 33.6 MPa despite the other processing parameters being almost the same. When sprayed with 1.8% N2 added at 27 kW, the bond strength reached 65.3 MPa. X-ray diffraction patterns of Ti coatings without HA showed that titanium nitrides were formed in the titanium deposits sprayed with ...

In situ formation of bioactive titanium coating using reactive plasma spraying

In vitro nucleation of apatite was studied on surface-modified Ti coatings prepared by reactive plasma spraying (RPS). The in situ surface modification of Ti particles was conducted by making use of plasma-enhanced reactions between the Ti particles and the reactive gaseous species in the plasma flame during RPS. Surface-modified Ti coatings were deposited on Ti substrates by rf-RPS using a thermal plasma of Ar gas containing 1%–6% N2 and/or 1%–6% O2. As a means of surface modification, Ti powders impregnated with 0.05–0.2mol% Ca were also sprayed. Compositional changes in the coatings’ surface after soaking in simulated body fluid (SBF) were evaluated by Fourier transform infrared spectroscopy and thin-film x-ray diffraction analyses (TF-XRD). The Ti coatings prepared with Ar-O2 and Ar-N2-O2 plasma formed bone-like apatite after three days of soaking in SBF. On the other hand, no compositional change was observed in the surface of the Ti coatings sprayed with Ar-N2 plasma, even after seven days of soakin...

Preparation of Novel Bioactive Titanium Coatings on Titanium Substrate by Reactive Plasma Spraying

A simple treatment method using radio-frequency reactive plasma spraying (rf-RPS) was studied to induce bioactivity of titanium (Ti) coatings. Ti coatings were deposited on Ti substrates by an rf-RPS method using a thermal plasma of Ar gas containing 1-6% N2 and/or O2 at a input power of 16 kW. Composition change of coatings surface during soaked in a simulate d body fluid (SBF) was examined by micro Fourier transform infrared spectroscopy and thin fi lm X-ray diffraction. Ti coatings prepared with Ar-O 2 and Ar-N2-O2 plasma formed apatite after 3 days of soaking in 40 ml SBF. This indicates that such coatings have the ability to form a biologicall y a tive bone-like apatite layer on the surface. In the XRD patterns for both Ti coatings, minut e peaks ascribable to TiO 2 (anatase and rutile phase) were commonly observed. On the other hand, compos iti n change of coatings surface cannot be observed for Ti coating sprayed with ArN2 plasma after 7 days of soaking in SBF.

Synthesis and Formation Process of LaxY1-xBa2Cu3Oy Powder by Aqueous Chelate-Mix Technique.

LaxY1-xBa2Cu3Oy powders were synthesized by the aqueous chelate-mix technique using ethylenediamine-tetraacetic acid (EDTA), nitrilo-tri-acetic acid (NTA) and imino-di-acetic acid (IDA) as chelating agents. The intermediate products obtained in each formation process were investigated by thermogravimetry, X-ray diffraction technique and infrared spectroscopy. It was found that the formation of the 123 phase from precursor-gel proceeds in the following four steps; (1) decomposition of ammonium acetate and Cu-EDTA and formation of metal-copper at 120-220°C, (2) decomposition of carboxyl group of chelate at 340-410°C, (3) combustion of the residual organics and formation of BaCO3 and other oxides at 410-480°C, and (4) decomposition BaCO3 and formation of 123 phase around 800°C.