Key Engineering Materials Vols. 342-343

Abstract: Mechanical properties and elastic modulus were examined in order to clarify the influence on microstructures in Ti-26Nb-xSi, where x= 0.5, 1 in atomic percent, prepared by arc melting, cold rolling and recrystallization heat treatment. On the basis of microstructural observations and phase analyses, it is evidently revealed that the microstructure of as-quenched sample appeared to mixture appearance consisting of mostly bcc-structured β phase and small amount of orthorhombic-structured α″ phase. Elongated structure parallel to the rolling direction was observed in cold rolled samples, and equiaxed structure with the average grain size of about 20μm was developed for the sample after recrystallization heat treatment. Randomly distributed feature of pole figure was characterized without showing a specific texture component in asquenched sample. Rotated cube, α-fiber and γ-fiber texture components were detected in cold-rolled sample. After recrystallization heat treatment the intensity of α-fiber texture component was markedly decreased, while the rotated cube component becomes sharpened and γ-fiber component remains relatively unchanged. From both elastic modulus and strength point of view recrystallization treatment would be desirable to meet the required mechanical properties of the present alloys for biomedical applications.

Abstract: The sliding wear of four different compositions of novel low temperature degradation-free zirconia/alumina (LTD-free Z/A) composites were characterized in a ceramicceramic point contact pair. The wear tests were performed by a pin-on-disk type wear tester in a linear reciprocal sliding motion with a point contact in both dry and bovine serum lubricated conditions at room temperature. For the dry sliding wear tests, AZ-2 (20 vol% (Y,Nb,Ce)-TZP/ 80 vol% Al2O3) showed the best wear resistance among four kinds of LTD-free Z/A composites. For the bovine serum lubricated sliding wear tests, wear was too little to be measured for all kinds of Z/A composites. These novel LTD-free Z/A composites having excellent wear resistance demonstrated a potential as the alternative materials for the ceramic- ceramic contact pairs of femoral head and acetabular liner in total hip replacement.

Abstract: This study was carried out to investigate the effect of acid-alkali treatment and alkaliheat treatment on the push-out strength and tissue response of the porous titanium in vivo. Porous titanium with different treatment was implanted in dog bony site for 2 months and 5 months and the push-out strength was tested. At 2 months, the mean push-out strengths of the acid-alkali treated and alkali-heat treated porous titanium were 11.3 and 15 MPa, respectively. At 5 months, the values reached 29.8 and 35 MPa, respectively. Histological observation showed a close contact between implants and bone, and more bone tissue filled inside the pores of porous titanium increasing with implantation time. The results indicated higher bonding strength between bone and porous titanium in alkali-heat treated samples. Therefore, alkali-heat treatment can provide porous titanium implants with better fixation as a bone substitute for clinical use under load-bearing conditions.

Abstract: Nano-titania ceramics is a potential biomaterial for orthopaedic application. In our previous studies, a bioactive nano-titania ceramics was prepared by using alkali-heat treatment. In this paper, hydroxyapatite was used as a grain growth inhibitor additive to get nano-titania ceramics with different grain size, and the effect of grain size on the bioactivity was studied in vitro.

Abstract: In this study, a current density contour map of TiNi shape memory alloy in sodium sulfate solutions was constructed by potentiodynamic polarization technique. The current density contour map of TiNi alloy, constructed in a 0.5 M sodium sulfate solution over the pH range 1 to 13 at 37oC, showed only hydrogen evolution region, passive region, and oxygen evolution region. The localized corrosion region did not exist and the susceptibility of localized corrosion was not exhibited. We also investigated the effects of chloride ions on the pitting corrosion of TiNi alloy in sodium sulfate solutions. Pitting corrosion occurred with addition of 0.2 M NaCl in a sulfate solution. And it was observed that pitting potential got lower as the concentration of chloride ion went up. However, repassivation potential was not affected by the addition of chloride ion up to 0.5 M. It is concluded that a TiNi shape memory alloy exists as a passive state and a good corrosion resistance in sulfate solutions over the pH range 1 to 13, and the sulfate ion performs a role of inhibiting localized corrosion in chloride environment.

Abstract: In order to investigate the corrosion behavior of TiNi shape memory alloy, especially electrochemical behavior of pitting and crevice corrosion in a human body, current density contour(CDC) map of TiNi alloy was constructed by potentiodynamic polarization technique in simulated physiological sodium chloride solutions of pH ranging from 1 to 13 at 37oC. Morphology of pits and corrosion products in sodium chloride solutions of various pH were analyzed by SEM and EDX, and susceptibility and mechanism of localized corrosion were also discussed.

Abstract: The interactions between biological cells and nanometer-scale structured surfaces are very important issues in nanobiotechnology. Most current methods of fabricating such surfaces are costly and are not suitable for the production of a nanometer-scale structured surface that will be used merely as a disposable tool in cell biological studies. We developed and optimized an embossing method of polymers with nanoporous AAOs which is easy, cheap and fast in fabricating nanometer-scale structures on the surface of polymers. We think this method can be applied not only in cellular nanobiotechnogy but also in other areas of nanotechnogy.

Abstract: Gait analysis is essential to identify accurate cause and knee condition from patients who display abnormal walking. Traditional linear tools can, however, mask the true structure of motor variability, since biomechanical data from a few strides during the gait have limitation to understanding the system. Therefore, it is necessary to propose a more precise dynamic method. The chaos analysis, a nonlinear technique, focuses on understanding how variations in the gait pattern change over time. Healthy eight subjects walked on a treadmill for 100 seconds at 60 Hz. Three dimensional walking kinematic data were obtained using two cameras and KWON3D motion analyzer. The largest Lyapunov exponent from the measured knee angular displacement time series was calculated to quantify local stability. This study quantified the variability present in time series generated from gait parameter via chaos analysis. Gait pattern is found to be chaotic. The proposed Lyapunov exponent can be used in rehabilitation and diagnosis of recoverable patients.

Abstract: This work focused on the effect of Co content on the corrosion resistance of high pitting resistance equivalent (PRE), super ferritic, Ni-free stainless steels in simulated biosolutions. The effect of Co in Ni-free alloys was evaluated by cytotoxicity test. Anodic polarization test and AC impedance measurement were performed to evaluate the effect of Co on corrosion resistance of the alloys. The cytotoxicity test result for 4 experimental alloys shows non-cytotoxic but mild cytotoxic for 316L stainless steel due to relatively poor corrosion resistance. However, the effect of Co on the passivity was positive in bio-solution but it was negative in acidic chloride solution.

Abstract: The titanium oxide layer with nano–micro hybrid structure on the titanium substrate was formed by grit-blasting and anodic oxidation treatment. A micro rough surface can be formed by grit-blasting and nanotube arrays can be formed by anodic oxidation or NaOH treatment after anodic oxidation. We investigated the surface characterization on titanium and the response of the osteoblast like cell (MG-63) to the surfaces made by different treatments. Surface structure (morphology), wettability characterized by SEM, contact angle. The attachment and proliferation behavior of MG-63 cells on the titanium surface by different surface treatments were characterized by SEM observation and MTT assay.The attachment and proliferation of osteoblast cells is accelerated by the topography of the nano structure like a nanotube, the nano surface acts as an attachment point for the filopodia of growing cells. Nano structure increases surface area and nano-micro structure significantly increases surface area. Such nano–micro hybrid structure on the titanium substrate can be useful for a well-adhered bioactive surface layer on Ti implant used metals for orthopedic and dental implants.