Materials Science Forum Vols. 610-613

Abstract: Zr-ZrC-ZrC/DLC gradient nano-composite films have been prepared on the NiTi substrates by the technique of plasma immersion ion implantation and deposition (PIIID) combining with plasma-enhanced chemical vapor deposition (PECVD). The influence of C2H2 flow rate ranging from 30 sccm to 50 sccm on the chemical structure, microstructure, mechanical properties and corrosion resistance of resulting thin films are investigated by Raman spectrum, XPS, XRD, friction coefficient 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 and form ZrC phase, the binding energy of C 1s and the composition concentration of ZrC depend heavily on the C2H2 flow rate. With the increase of C2H2 flow rate, the content of ZrC and the ratio of carbon sp3/sp2 decreases. The nano-indentation and friction experiments indicate that the gradient composite film at 30 sccm has a higher hardness and lower friction coefficient compared with that of the bare TiNi alloy. The microscratch curve tests indicate that Zr-ZrC-ZrC/DLC gradient composite films have an excellent bonding property with the substrate. Based on the electrochemical measurement and ion releasing tests, we have found that the Zr-ZrC-ZrC/DLC gradient composite films exhibit better corrosion resistance property and higher depression ability for the Ni ion releasing from the NiTi substrate in the Hank’s solution at 37°C.

Abstract: Melt blending of PLA and biodegradable PE-b-A has been performed in an effort to toughen the PLA. With the PE-b-A contents increasing, the elongation at break of composites increased and the brittle break became ductile break. When the PE-b-A content is 10%, the tensile strength of composite is similar with neat PLA, and the elongation increased significantly. The composites showed wonderful shape-memory effect. The composites occurred to deformation upon tensile load, and recovered to original shape quickly with temperature increasing. PE-b-A acts as stress concentrator in system with the stress release locally and energy-dissipation process. These will prevent PLA matrix from breaking under high deformation and make the PLA molecular orientation. Consequently, releasing the stress by heating up the material will reform the shape back to the original shape.

Abstract: Binary NiTi shape memory alloy cast ingots with large scale size are produced by using vacuum induction melting (VIM) in lime crucible, the oxygen and carbon contents are less than 500ppm. Usually, oxygen was introduced into the melts by the dissolution of lime during melting, resulting in higher content of oxygen over 500ppm. VAR + VIM ingot metallurgy is prone to produce materials with a good chemical homogeneity. However, it is difficult for one single melting of NiTi by VIM in the lime crucible. So in the present paper, the segregation of chemical composition and the consistency of transformation temperature in NiTi alloys in as-casted condition along the cross-section area on edge and center, in homogeneization-treated condition, and in as-forged condition along the longitudinal-section area on head and tail, are measured and analyzed by differential scanning calorimetry (DSC), OM, SEM, and XRD, to indicate the chemical homogeneity in microscopic and macroscopic scale.

Abstract: In the present study an innovative tissue engineering scaffold was developed which can be used on wound dressing with a controllable drug-releasing capability. By coaxial electrospinning a coaxial nanofibrous mats were obtained which was made from Poly(L-lactid-co-ε-caprolactone) (PLLACL) and Tetracycline Hydrochloride (TCH), with P(LLA-CL) as the shell and TCH as the core. The TCH release behavior of the coaxial nanofibrous mats was measured by ultraviolet-visible (UV-vis) spectroscopy in vitro environment of 37°C for a maximum 180 hours. To compare with the method of mix electrospinning, TCH without any other material could encapsulated in P(LLA-CL) nanofibers very well and released for a long time.

Abstract: The hydroxyapatite (HA) was synthesized by wet mechanochemical method；the effects of surfactant, such as triethanolamine, polyethylene glycol (200000), sodium hexametaphosphate, polyvinylpyrrolidone (K30), on the particle size distribution of as-prepared HA powder were studied. Results were characterized by means of X-ray diffraction (XRD), Scanning electron microscopy (SEM), Laser Scattering Particle Size Distribution Analyzer. The results show that the addition of surfactants eliminated the agglomeration of the powder and the uniform, fine particles (D10=0.1149μm, D50=0.12551μm, D90=0.1481μm) were obtained with the Triethanolamine (6 wt %) and Sodium hexametaphosphate (4 wt %) respectively. Our work demonstrates applicability of the mechanosynthesis for reproducible and low-cost synthesis of uniform, fine HCA powder in large batch-sizes.

Abstract: A new correction instrument of pectus excavatum is introduced which is designed for a minimally invasive technique (Nuss procedure). The instrument was made of pure titanium plates, and finished by machining, surface treatment and so on. The instrument was made up of correcting bar and fixing bar. The mechanical properties of the instrument was measured with electron universal material testing machine, the safety and validity was verified by clinical doctors after being implanted into the patient. Results showed that the mechanical properties of the instrument keep constantly after implantation for two years. It is lighter than the like product, and can lighten the patent’s and the doctor’s operation bearing. It had been applied in national hospitals, and results showed that it was of better biocompatibility, and few complications were found. Clinical treatment effects were satisfactory.

Abstract: Crosslinked UPM/PHBV/PVP fibers were successfully prepared using electrospinning process. The active pharmaceutical ingredient tetracycline hydrochloride (TH) was loaded onto the electrospun fibers through after-treatment method. Scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) and in vitro dissolution tests were carried out to characterize the medicated electrospun fibers. The SEM and FTIR results clearly showed the difference between the UPM / PHBV and UPM/ PHBV/ PVPelectrospun fibers. The pharmaceutical tests results indicated that the fibers had good drug-loaded capability and sustained-release properties. The as-prepared fibers might find possible applications as wound dressings or transdermal drug delivery systems.

Abstract: The interconnected porous scaffolds are crucial to support the attachment, differentiation, proliferation of cells so to construct 3-dimensional (3-D) tissues. Up to now, there are several approaches to prepare porous scaffolds. In our experiments, we designed a novel porous bioceramic scaffold, called the hydroxyapatite (HA) spherule scaffold, by accumulating HA spherules in an HA porous tube to establish an interconnected porous structure which can be reconstructed exactly. The porous HA tube was manufactured by polymer sponge template while HA spherules were prepared by sol-gel process. In the animal experiment, the HA spherule scaffolds were implanted at 2 different non-osseous sites such as muscle and abdominal cavity in dogs. The new bone growth was investigated after six months. The preliminary results demonstrated that the proliferation of osteocytes on the scaffolds in muscle was obviously better than in abdominal cavity, and about ten times more blood vessels (BVs) were appeared in the former site than those in the latter site. This study presents an alternative way to reveal the relationship between the porous structure of scaffolds and ectopia bone growth because the interconnection and porosity can be controlled easily by the size and porosity of HA spherules.

Abstract: Dental diamond bur is now a regular rotary tool, with its head made of diamond particles embedded into nickel coating, and its shank made of stainless steel. There are strong demands from the dentist on prolongation of usage life and avoiding of breakage. To solve this problem, on the one hand, since diamond is hard to be wetted under the condition of normal temperature and pressure due to the high interfacial energy between diamond and general metals and alloys. Diamond particles coated with titanium layer was used for the preparation of composite electroplating with the intention of 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 the breakage. In this study, the optimal preparation parameters of Ni/surface-modified diamond electroplating were determined by orthogonal test, and the bonding conditions between the diamond particles and the NiTi alloy substrate were studied by scanning electron microscope. Further performance comparison of Ni/modified and Ni/un-modified diamond composite electroplating was conducted on a pin-on-disc wear machine under the dry sliding condition, and the material removal volume was used as the evaluating criterion of wear resistance. The results showed that the binding strength between diamond particles and NiTi alloy substrate could be enhanced, as well as the wear resistance, which may give direction on the future design of dental bur.

Abstract: Large osseous defects are difficult to treat because of deficient blood supply on the defected area. To get sufficient blood supply, we designed to establish the adenovirus simultaneously encoding both VEGF and Ang-1 (pAd-VIA) to accelerate the formation of new vessels in the process of bone defect repair. The construction of the adenovirus was performed according to the method reported by Tong-Chuan HE with a tiny modification. Three kinds of adenoviruses were acquired. They are adenovirus pAd-VIA simultaneously encoding VEGF and Ang-1, adenovirus pAd-VEGF encoding VEGF, and adenovirus pAd-Ang-1 encoding Ang-1. The adenovirus prepared in this study could successfully transfer VEGF and Ang-1 into mesenchymal stem cells(MSCs) with high efficiency. Two-gene modified artificial bone was established by use of these adenovirus. In the end, the two-gene modified artificial bone was proved to have good biocompatibility and biological function. Study reports presented here will pave the way for further exploration of vascularization in the process of large osseous defects repair.