Materials Science Forum Vols. 561-565

Abstract: N-carboxyethyl chitosan (ACS) was formed by a Micheal reaction. Through the analysis of IR and 1H-NMR spectra, the Micheal reaction was carried out between - NH2 of chitosan and - C = C - of acrylic acid. ACS hydrogel (ACSG) was prepared by cross-linking with glutaraldehyde. ACSG show pH-sensitive swelling behavior, and the smallest swelling rate (SR) of ACSG is in pH5.0 buffer solution.With dosage of glutaraldehyde increasing, the SR of ACSG decreased. With grafting degree (GD) increasing, the SR of ACSG increased first and decreased afterward. Using bovine serum albumin (BSA) as a model medicine, the releasing behaviors of ACSG were investigated in vitro. In simulated gastric and intestinal fluid, the ACSG loading BSA (GD=20.45%) has better releasing behaviors.

Abstract: Understanding of interaction reactions between materials and tissue in the body is necessary for the success of implant devices. Impedance and polarisation properties at the interface on 316L stainless steel and pure Ti under cell culture environment of fibroblast L929 or with collagen coating were examined. Limitation of mass diffusion at the interface by cell bodies and extracellular matrix is probably a corrosion factor of the presence of cells, which causes the decrease of protectiveness of passive film on 316L steel. Surface composition of 316L steel and Ti formed with L929 was compared with that formed in human body. Similar elements were detected on the surface formed in both the environments. The precipitated sulphur on the surface formed under cell culture and in the human body appears to be originated from proteins that might be produced by cells.

Abstract: In this paper, single crystal of CuAlNiBe shape memory alloy (SMA) was prepared in a high temperature gradient directional solidification furnace with a selective growing crystallizer. And its performance characters were systematically studied. The results show that the mechanical and shape memory properties of the single crystal of CuAlNiBe SMA alloy has much better than that of the polycrystalline material. This may be explained that the stress concentration at grain boundary caused by the difference of bilateral strains is the dominant reason of deterioration of fatigue properties; therefore single crystal alloy possesses the excellent properties duo to its elimination of grain boundary.

Abstract: A new therapeutic trial based on the self-healing potential of cells to naturally induce tissue regeneration, has been recently noted. To realize this regenerative medical therapy, it is highly required to efficiently combine cells with their local environment which basically allows cells to survive and biologically function in vivo through the essential interaction. Tissue engineering is a biomedical technology or methodology to create the local environment which promotes the proliferation and differentiation of cells to induce tissue regeneration. There are some cases where tissue regeneration can be induced only by supplying a cell scaffold of biomaterials. Drug delivery system (DDS) with biomaterials enhanced the in vivo biological activities of un-stable growth factor and gene for cell-induced tissue regeneration. The controlled release technology enabled growth factors to achieve the regeneration of various tissues experimentally and clinically. The DDS technology also augmented the biological functions of plasmid DNA and small interference RNA. The cells genetically engineered by the DDS gene system showed an enhanced therapeutic efficacy in cell-based tissue regeneration (cell-gene hybrid therapy). By making use of DDS technology, it is possible to suppress the deterioration and proceeding of chronic fibrotic diseases based on the self-healing potential inherently equipped in the living body. This paper emphasizes significance of biomaterials in tissue engineering for regenerative medical therapy.

Abstract: The effect of oxygen content on aging behavior and invar characteristics of Ti-29Nb-13Ta-4.6Zr (TNTZ) were investigated. The age hardening of TNTZ aged at 573 K and 723 K is enhanced with the oxygen content. The ω phase precipitates and grows from early stage of aging in TNTZ regardless of the oxygen content when aged at 573 K. The lath-like shape α phase precipitated in TNTZ aged at 723 K increases in size with the oxygen content. The elastic modulus increases with the oxygen content and aging. The ω phase increase the elastic modulus to a greater extent than the increase due to the α phase. The tensile strength increases with the oxygen content and aging, while the elongation decreases. TNTZ with oxygen content of 0.1 mass% exhibits invar-like characteristics through severe cold working. A higher oxygen content suppresses the invar-like characteristics of TNTZ.

Abstract: To create a new material with good biocompatibility and high mechanical strength for artificial organs, titanium (Ti) and segmented polyurethane (SPU) were bonded through 3-(trimethoxysilyl) propyl methacrylate (γ-MPS), and specify causes governing the bonding strength of Ti/γ-MPS/SPU interface. The number of cross-links of SPU and the concentration of active hydroxyl groups on the surface oxide film of Ti were controlled by UV-irradaiton and hydrogen peroxide immersion. The number of cross-links of SPU was measured by differential scanning calorimetry (DSC) and the concentration of the active hydroxyl groups was also determined using a zinc-complex substitution technique. Consequently, Ti/γ-MPS/SPU shear bonding stress was increased with the increase of the number of cross-links of SPU. In addition, the increase of cross-links in SPU also improved the Ti/γ-MPS/SPU shear bonding stress.

Abstract: Effects of rotation speed on the microstructure and transformation behavior were investigated for Ti-48at%Ni melt-spun ribbons. The Ti-48at%Ni shape memory alloy ribbons were fabricated by the melt-spinning method with various rotation speeds ranging from 2500rpm to 7500rpm. The melt-spun ribbons were completely crystallized to TiNi B2 phase during solidification at lower rotation speeds less than 4000rpm. Amorphous and B2 phase coexisted in the melt-spun ribbons fabricated at higher rotation speeds of 5000rpm and 7500rpm. The martensitic transformation behavior was investigated both in the as-spun and heat-treated ribbons. The transformation temperature increased with decreasing cooling rate and increasing heat-treatment temperature.

Abstract: An experimental study of stress induced martansite transformation by electrical strain gauges is present. The studies were performance on polycrystalline Cu-Al-Be Shape Memory Alloys. Beams and a bar in cantilever flexion hold to punctual load were instrumented with electrical strain gauges in several points where the state of stress is: a) simple tension, b) simple shear and b) tension-shear. Employing the trasforational load values in each plot was calculated critical principal stresses. Employing the results obtained, 1 2 σ −σ plots were constructed and a comparison with the yield Von-Mises criteria, Patoor model and Buchheit model for the critical stress were do.

Abstract: The corrosion behavior of Zr-Ti and Zr-Hf alloys with various concentrations in properly deaerated Hanks’ solution were investigated by electrochemical techniques. The effects of the thermal treatment with the purpose of homogenization of chemical composition on the pitting potentials of the Zr-Ti alloys were also examined. The results indicated that sufficient addition of Ti to Zr improved its corrosion resistance, especially in terms of the pitting potential and the passive current density. On the other hand, addition of Hf totally lowered the corrosion resistance of the alloy. The thermal treatment improved the pitting corrosion property of Zr-Ti alloys, and Zr alloys with over 5mol% Ti showed much higher pitting potentials than that of pure Zr. The treatment also improved the reproducibility of the measurement and narrowed the data scattering. This phenomenon was discussed with the model of rapidly-cooled metallographic structure.

Abstract: The heat treatment effect of a cast shape memory alloy (SMA) from self-propagating high temperature synthesis (SHS) ingot was investigated. The composition of SHS ingot was Ti-50.8at%Ni. DSC and Tensile test specimens were cast by lost-wax process from SHS ingot. The heat treatment conditions were 400°C-60min., 500°C-60min. and 600°C-60min. for DSC and 400°C-60min. and 500°C-60min. for tensile test. Transformation temperatures were measured by differential scanning calorimetry (DSC). Mechanical properties were measured by a tensile test at several temperatures. The effects of heat treatment temperatures were same as a general TiNi wire material.