We synthesized a series of poly (glycerol, sebacate and lactic acid) (PGSL) with 1:1:0, 1:1:0.25, 1:1:0.5, 1:1:1mole ratio of glycerol, sebacate and lactic acid, in order to elucidate the relation of microstructure to thedegradation rate and mechanical properties. The microstructure of the polymer with lactic acid in the ratio of0.25 displayed phase separation structure. The crystallization temperature (Tc) and absolute crystallizationenthalpy (ΔHc) of PGSL tended to decrease with the increasing ratio of lactic acid. Degradation rate of PGSLwith lactic acid in the ratio of 0.25 was fastest in vitro and 35% mass loss occurred after 60 day degradation. Inthe range of 0, 0.5 and 1, the degradation rate decreased slightly with the lactic acid increasing and 18% massloss occurred after 60 day degradation when lactic acid was doped in the ratio of 1.0. All PGSL polymersinhibited platelet adhesion, prolonged whole blood clotting time, activated partial thromboplastin time andprothrombin time. In conclusion, doping lactic acid can modulate the microstructure of poly (glycerol,sebacate) (PGS), thereby control the degradation rate and mechanical property of PGS.

Zr-ZrC-ZrC/DLC gradient nano-composite films have been prepared on the NiTisubstrates by the technique of plasma immersion ion implantation and deposition (PIIID) combiningwith plasma-enhanced chemical vapor deposition (PECVD). The influence of C2H2 flow rate rangingfrom 30 sccm to 50 sccm on the chemical structure, microstructure, mechanical properties andcorrosion resistance of resulting thin films are investigated by Raman spectrum, XPS, XRD, frictioncoefficient test, nano-indentation, electrochemical corrosion test and atomic absorption spectrometry.XPS and XRD results indicate that on the outmost layer, the Zr ions are mixed with the DLC film andform ZrC phase, the binding energy of C 1s and the composition concentration of ZrC depend heavilyon the C2H2 flow rate. With the increase of C2H2 flow rate, the content of ZrC and the ratio of carbonsp3/sp2 decreases. The nano-indentation and friction experiments indicate that the gradient compositefilm at 30 sccm has a higher hardness and lower friction coefficient compared with that of the bareTiNi alloy. The microscratch curve tests indicate that Zr-ZrC-ZrC/DLC gradient composite filmshave an excellent bonding property with the substrate. Based on the electrochemical measurementand ion releasing tests, we have found that the Zr-ZrC-ZrC/DLC gradient composite films exhibitbetter corrosion resistance property and higher depression ability for the Ni ion releasing from theNiTi substrate in the Hank's solution at 37℃.

Dental diamond bur is now a regular rotary tool, with its head made of diamond particlesembedded into nickel coating, and its shank made of stainless steel. There are strong demands fromthe dentist on prolongation of usage life and avoiding of breakage. To solve this problem, on the onehand, since diamond is hard to be wetted under the condition of normal temperature and pressure dueto the high interfacial energy between diamond and general metals and alloys. Diamond particlescoated with titanium layer was used for the preparation of composite electroplating with the intentionof improving the interfacial adhesion between diamond and metal matrix; on the other hand,superelastic biomedical NiTi alloy was used as the substrate to improve the flexibility and prevent thebreakage. In this study, the optimal preparation parameters of Ni/surface-modified diamondelectroplating were determined by orthogonal test, and the bonding conditions between the diamondparticles and the NiTi alloy substrate were studied by scanning electron microscope. Furtherperformance comparison of Ni/modified and Ni/un-modified diamond composite electroplating wasconducted on a pin-on-disc wear machine under the dry sliding condition, and the material removalvolume was used as the evaluating criterion of wear resistance. The results showed that the bindingstrength between diamond particles and NiTi alloy substrate could be enhanced, as well as the wearresistance, which may give direction on the future design of dental bur.

Objectives. The purpose of this studywas to investigate the corrosion behavior of Ti-Ag alloysin artificial saliva solutions.Methods. The corrosion behavior of experimental Ti-Ag alloys in artificial saliva was examinedby means of potentiodynamic polarization measurements. The surface passive filmformedwas analyzed by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD) methods.Results. The alloyswere found to develop surface passive films after immersion for 1.8×103s. In comparison with commercially pure Ti, the Ti-Ag alloys exhibited better corrosionresistance with lower anodic current densities, larger polarization resistances, and higheropen-circuit potentials. The passive film formed was predominantly composed of TiO2, asdetermined by XPS. When fluoride ions were added in the solution, the TiO2 passive filmwas destroyed and Na2TiF6 was formed.Significance. Addition of Agwas found to be effective in reducing the corrosion current densityand increasing the open circuit potential of titanium in artificial saliva environment. Additionof fluoride ions in the solution severely reduced the corrosion resistance of Ti-Ag alloys.

With CP Ti sample as control, the electrochemical measurements were used to investigate the corrosionresistance of low modulus Ti16Nb shape memory alloy in Hank's solution with pH value 7.4. The OCP curvesshow that the passive film on the Ti16Nb alloy surface is quite stable. The tafel plots and anodic polarizationcurves prove that the Ti16Nb alloy has excellent anti-corrosion properties in Hank's solution, which is evenbetter than that of CP Ti. The XPS analysis reveals that the composition of the oxide film on Ti16Nb alloy ismainly TiO2 and Nb2O5. The indirect cytotoxicity results prove that Ti16Nb alloy has an excellentbiocompatibility as CP Ti with high proliferation rate approaching that of the negative control group.

Ni50.8Ti49.2 alloy powders of different particle shapes and sizes have been prepared by ball milling. Thepowder milled for 1h has large flaky particles and are partially amorphous. The powder crystallizedthrough a single-stage exothermic transformation upon heating. Powders milled for longer durationsconsisted of partially amorphous Ni-Ti, [Fe,Ni] and Ni-Cr-Fe phases, indicating heavy contaminationfrom the milling vessel. Upon heating, the milled powders exhibited an endothermic event at ∼400℃. After annealing at 500℃, the milled powders were fully crystallized. The crystallized powders exhibitedmartensitic transformation with reduced heat effect. The critical temperatures of the transformationwerefound to decrease with increasing ball milling time.

The aim of this study was to investigate the effect of short-time DC heating on the phase transformation and superelasticity of a Ti-50.8at. %Ni alloy, which is extensively used as orthodontics arch wires. The alloy was pre-treated in three different conditions prior to the DC heating, including 15% cold-rolling (asreceived), 15% cold-rolling and 673K ageing (aged) and 15% cold-rolling and 973K annealing (annealed). DC heating was performed using a Shinwa Bender Soarer-II equipment. DSC, XRD and tensile tests were employed to study the alloy's phase transformation behaviour, phase constituents, and superelasticity, respectively. Itwas found that the aged sampleswere sensitive to the short-time DC heating treatment and the dissolution of Ti3Ni4 precipitates into TiNi matrix completed within 15 s. In contrast, the as-received and the annealed samples showed little response to the DC heating. Such findings are of direct relevance to applications of TiNi as orthodontic arch wires, which often involve rapid electrical heating for shape setting.

Mg-Zn-Ca bulk metallic glass with different compositions (Mg66Zn30Ca4 and Mg70Zn25Ca5) have been prepared for this study and their feasibility as biodegradable metallic materials have been evaluated by the microstructural, surface analysis, mechanical testing, corrosion and cytotoxicity tests. It was found that the Mg66Zn30Ca4 sample presents a more uniform corrosion morphology than as-rolled pure Mg and Mg70Zn25Ca5 samples, with much smaller micro-scale uniformly distributed pores beneath the corrosion product layer. The corrosion products were identified to be Mg(OH)2 and Zn(OH)2, and a uniform corrosion mechanism is proposed. Both indirect cytotoxicity and direct cell culture experiments were carried out using L929 and MG63 cell lines. The results show higher cell viabilities for Mg-Zn-Ca extracts than that for as-rolled pure Mg. In addition, L929 and MG63 cells were found to adhere and proliferate on the surface of Mg66Zn30Ca4 sample.

Binary MgeCa alloys with various Ca contents were fabricated under different working conditions. X-ray diffraction (XRD) analysis and optical microscopy observations showed that MgexCa (x ¼ 1e3 wt%) alloys were composed of two phases, a(Mg) and Mg2Ca. The results of tensile tests and in vitro corrosion tests indicated that the mechanical properties could be adjusted by controlling the Ca content and processing treatment. The yield strength (YS), ultimate tensile strength (UTS) and elongation decreased with increasing Ca content. The UTS and elongation of as-cast Mge1Ca alloy (71.38±3.01 MPa and 1.87±0.14%) were largely improved after hot rolling (166.7±3.01 MPa ±and 3±0.78%) and hot extrusion (239.63±7.21 MPa and 10.63±0.64%). The in vitro corrosion test in simulated body fluid (SBF) indicated that the microstructure and working history of MgexCa alloys strongly affected their corrosion behaviors. An increasing content of Mg2Ca phase led to a higher corrosion rate whereas hot rolling and hot extrusion could reduce it. The cytotoxicity evaluation using L-929 cells revealed that Mge1Ca alloy did not induce toxicity to cells, and the viability of cells for Mge1Ca alloy extraction medium was better than that of control. Moreover, Mge1Ca alloy pins, with commercial pure Ti pins as control, were implanted into the left and right rabbit femoral shafts, respectively, and observed for 1, 2 and 3 months. High activity of osteoblast and osteocytes were observed around the Mge1Ca alloy pins as shown by hematoxylin and eosin stained tissue sections. Radiographic examination revealed that the Mge1Ca alloy pins gradually degraded in vivo within 90 days and the newly formed bone was clearly seen at month 3. Both the in vitro and in vivo corrosion suggested that a mixture of Mg(OH)2 and hydroxyapatite formed on the surface of Mge1Ca alloy with the extension of immersion/implantation time. In addition, no significant difference (p>0.05) of serum magnesium was detected at different degradation stages. All these results revealed that Mge1Ca alloy had the acceptable biocompatibility as a new kind of biodegradable implant material. Based on the above results, a solid alloy/liquid solution interface model was also proposed to interpret the biocorrosion process and the associated hydroxyapatite mineralization.

As bioabsorbable materials, magnesium alloys are expected to be totally degraded in the body and their biocorrosion products not deleterious to the surrounding tissues. It's critical that the alloying elements are carefully selected in consideration of their cytotoxicity and hemocompatibility. In the present study, nine alloying elements Al, Ag, In, Mn, Si, Sn, Y, Zn and Zr were added into magnesium individually to fabricate binary Mg-1X (wt.%) alloys. Pure magnesium was used as control. Their mechanical properties, corrosion properties and in vitro biocompatibilities (cytotoxicity and hemocompatibility) were evaluated by SEM, XRD, tensile test, immersion test, electrochemical corrosion test, cell culture and platelet adhesion test. The results showed that the addition of alloying elements could influence the strength and corrosion resistance of Mg. The cytotoxicity tests indicated that Mg-1Al, Mg-1Sn and Mg-1Zn alloy extracts showed no significant reduced cell viability to fibroblasts (L-929 and NIH3T3) and osteoblasts (MC3T3-E1); Mg-1Al and Mg-1Zn alloy extracts indicated no negative effect on viabilities of blood vessel related cells, ECV304 and VSMC. It was found that hemolysis and the amount of adhered platelets decreased after alloying for all Mg-1X alloys as compared to the pure magnesium control. The relationship between the corrosion products and the in vitro biocompatibility had been discussed and the suitable alloying elements for the biomedical applications associated with bone and blood vessel had been proposed.