Materials Science Forum Vols. 610-613

Abstract: In the present study, three types of tetracalcium phosphate (TTCP) were prepared by solid-solid reaction or co-precipitation method and by different cooling modes. The effect of TTCP on the performance of calcium phosphate cement (CPC) was investigated. The result showed that the characteristic of TTCP varied with preparation method and played an important role in CPC performance. A solid-solid reacted TTCP yielded smaller particle size and resulted in bad workability and mechanical strength of CPC. The fast cooling of sintering TTCP by liquid nitrogen could avoid the decomposition of TTCP and make pure TTCP. TTCP prepared by wet-precipitation could improve performance of CPC and was promising to optimization of CPC.

Abstract: Nano-hydroxyapatite/collagen composite was processed at room temperature, 180°C, 200°C and 220°C under atmosphere for 10 min respectively. The morphology of the samples was characterized by scanning electron microscopy (SEM). The structure and components of the samples were investigated by energy dispersive spectrograph (EDS), X-ray powder diffractometer (XRD) and Fourier transform infrared (FTIR). The results of SEM and EDS for nHAC changed greatly at 200°C and 220°C in comparison with room temperature. The morphology and structure of nHAC at 180°C were similar to those at room temperature. It was demonstrated that nHAC possessed thermal stability in morphology and structure.

Abstract: Nano-HAP (10-20nm) were obtained from East China University of Science and Technology. The osteoblasts were primary cultured from rat calvaria and then treated with five different concentrations(20，40，60，80，100µg/ml) of nano-HAP, the osteoblasts without nano-HAP was used as control group. Inhibition ratio, apoptotic rate were evaluated by MTT assay and flow cytometry (FCM), respectively. The specific surface area of nano-HAP was detected by BET. All date were expressed as mean ± standard deviation.Statistical analysis was performed by t test using software SPSS11.0 for Windows. The results indicated that the nano-HAP could inhibit the growth of osteoblasts in a dose-dependent manner. When the concentrations of nano-HAP were 20, 40, 60, 80, 100µg/ml, the inhibition ratio were 2.8%, 22.2%, 26.9%, 38% and 47.7%, and the apoptotic rate were 4.63%, 6.75%, 9.47%, 11.49%, 17.22%, respectively, which were obviously higher than that of control group. The nano-HAP significantly induced apoptosis in osteoblasts. There were the same tendency that the apoptotic and inhibition ratio of osteoblasts were rising with the increasing of the concentration of the nano-HAP. The specific surface area of nano-HAP was 148.140m2/g.

Abstract: Hydroxyapatite (HAP) coatings have been successfully electrodeposited on the titanium substrate by using Na2EDTA as chelate in electrolytes. The samples obtained were characterized by XRD and SEM. The XRD result indicated that the HAP crystals were preferentially oriented along c-axis. The SEM showed that the HAP crystals were rod like precipitates with a well-defined hexagonal cross section. The size of HAP crystals was well controlled by the addition of Na2EDTA and electrochemical parameters such as deposition times, pH value. It was discussed that the formation of Ca–EDTA complexes effectively restrained the growth of the HAP crystals.

Abstract: Scanning electron microscope (SEM) observation was performed and showed that shank bone is a kind of bioceramic composite consisting of laminated hydroxyapatite and organic materials. The hydroxyapatite layers are parallel with the surface of the bone and consist of numerous thin and long hydroxyapatite sheet fibers. The hydroxyapatite sheet fibers in different hydroxyapatite make a little angle with each other and compose a kind of screwy microstructure. The maximum pullout force of the screwy microstructure was investigated and compared with that of parallel microstructure. It shows that the maximum pullout force of the screwy microstructure is markedly larger than that of the parallel microstructure, which was experimentally validated.

Abstract: Collagen has been widely used in biomedical field, such as scaffolds for tissue engineering. However, the rapidly biodegradation and weak mechanical strength of collagen limited its application. In this study, an insoluble collagen extracted from cattle hide was designed as scaffold to act as a three-dimensional substrate for tissue engineering. The received insoluble collagen sponge was analyzed by scanning electron microscopy, infrared spectroscopy, mechanical testing and thermogravimetric-differential thermal analysis. In addition, the degradation was performed in vitro using collagenase. The results showed that the insoluble collagen had the same triple helical domain as acid-soluble collagen, while the compression strength was greatly improved and the degradation rate was reduced. The insoluble collagen sponge with good stability should be promising in tissue engineering scaffold applications.

Abstract: Recently Ni-free Ti-based shape memory alloys have been actively studied for biomedical applications in order to replace Ti-Ni alloys which bear the possibility of Ni-hypersensitivity. In this paper, The Ti-(40-65) Ta (wt. %) alloys have been studied with regard to their microstructure, mechanical and shape memory properties, as well as the effect of heat treatment on their shape memory behaviors. The results show that Ti-40wt. %Ta exhibits single orthorhombic structure (''), Ti-55wt. %Ta mainly '' and a little BCC structure (β), and Ti-65wt. % Ta mainly β and a little '' at room temperature. The tensile strengths of Ti-Ta alloys are all over 550 MPa, and the elongations over 17%. The Young’s modulus of Ti-Ta alloys ranges from 66 to 75 GPa, which are closer to the modulus of human bone as compared with that of Ti-6Al-4V alloy. The maximal shape memory strain of 3.32% was obtained in Ti-55wt. %Ta alloy quenched at 1273 K followed by aging at 723 K for 10min. The obtained results will be beneficial for developing Ti-Ta alloys for biomedical applications.

Abstract: Papers reported that the pH value was rising slowly with the prolonging of soaking time when bioglass was studied into simulated body fluids, and it influenced the formation of apatite layer on the surface of bioglass obviously. An Intelligent Multi-parameter in vitro Simulated Evaluation （IMSE system） was used to study the bio-mineralization properties of 58S bioglass. The deposition of apatite formation on the surface of bioglass (BG) from dynamic r-SBF was studied systemically with IMSE system, which could control and stable such parameters as temperature, fluid rate, ion concentrations and pH value etc. precisely. Results showed that the rate of apatite formation was slowed down when pH value was stabled at about 7.35.

Abstract: In the present study, an Intelligent Multi-parameter Simulated Evaluation in vitro （IMSE system） was used to study the deposition properties of apatite formation on the surface of biphasic calcium phosphate porous ceramic (BCP) from static and dynamic r-SBF. Results showed that apatite formed on the surface of BCP from static and dynamic r-SBF differed between each other. In static r-SBF, ions were transferred by diffusion, which could not compensate the consuming of calcium ions, and mist apatite layer was formed on the surface of samples. But in the dynamic r-SBF, simulated fluid was adjusted precisely and flowed forcedly, the concentrations of ions were homogeneous; with the compensation of ions, calcium and phosphate were supersaturated, and the free energy of apatite formation was negative, bone-like apatite sheets were formed on the surface of samples.

Abstract: . It is very difficult to polish the surface of magnesium materials because of its explosion and fragility properties. Magnetic Abrasive Polishing (MAP) process is one of the nontraditional machining technologies newly developed. In the MAP process, a cutting tool that consists of ferrous particles and nonferrous abrasives under oil lubricant is flexible. Because of this flexibility, the tool can remove a very small amount of material from a workpiece and better surface can be produced after polishing the workpiece. In this study, the MAP of a magnesium material was performed. In the experimental verification, design of experimental method was performed to evaluate parameters’effect of the MAP on polishing results of the magnesium material. As a result, it was seen that the MAP was very useful for finishing the magnesium material.