共查询到10条相似文献,搜索用时 310 毫秒
1.
Xiaoyi Xu Tongjun Liu Shaohui Liu Kai Zhang Zhen Shen Yuxin Li Xiabin Jing 《Journal of materials science. Materials in medicine》2009,20(5):1167-1173
The current study investigates the feasibility of using a biodegradable polymeric stent in common bile duct (CBD) repair and
reconstruction. Here, poly(l-lactide-co-glycolide) (PLGA, molar ratio LA/GA = 80/20) was processed into a circular tube- and dumbbell-shaped specimens to determine
the in vitro degradation behavior in bile. The morphology, weight loss, and molecular weight changes were then investigated
in conjunction with evaluations of the mechanical properties of the specimen. Circular tube-shaped PLGA stents with X-ray
opacity were subsequently used in common bile duct exploration (CBDE) and primary suturing in canine models. Next, X-ray images
of CBD stents in vivo were compared and levels of serum liver enzymes and a histological analysis were conducted after stent
transplantation. The results showed that the PLGA stents exhibited the required biomedical properties and spontaneously disappeared
from CBDs in 4–5 weeks. The degradation period and function match the requirements in repair and reconstruction of CBDs to
support the duct, guide bile drainage, and reduce T-tube-related complications. 相似文献
2.
F. Rosalbino S. De Negri A. Saccone E. Angelini S. Delfino 《Journal of materials science. Materials in medicine》2010,21(4):1091-1098
The successful applications of magnesium-based alloys as biodegradable orthopedic implants are mainly inhibited due to their high degradation rates in physiological environment. This study examines the bio-corrosion behaviour of Mg–2Zn–0.2X (X = Ca, Mn, Si) alloys in Ringer’s physiological solution that simulates bodily fluids, and compares it with that of AZ91 magnesium alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy results showed a better corrosion behaviour of AZ91 alloy with respect to Mg–2Zn–0.2Ca and Mg–2Zn–0.2Si alloys. On the contrary, enhanced corrosion resistance was observed for Mg–2Zn–0.2Mn alloy compared to the AZ91 one: Mg–2Zn–0.2Mn alloy exhibited a four-fold increase in the polarization resistance than AZ91 alloy after 168 h exposure to the Ringer’s physiological solution. The improved corrosion behaviour of the Mg–2Zn–0.2Mn alloy with respect to the AZ91 one can be ascribed to enhanced protective properties of the Mg(OH)2 surface layer. The present study suggests the Mg–2Zn–0.2Mn alloy as a promising candidate for its applications in degradable orthopedic implants, and is worthwhile to further investigate the in vivo corrosion behaviour as well as assessed the mechanical properties of this alloy. 相似文献
3.
F. C. Liu M. J. Tan J. Liao Z. Y. Ma Q. Meng K. Nakata 《Journal of Materials Science》2013,48(24):8539-8546
A Mg–Li–Al–Zn alloy was friction stir processed (FSP) under water, and the microstructures and superplastic behavior in the FSP alloy were investigated. The FSP Mg–Li–Al–Zn alloy consisted of a mixed microstructure with fine, equiaxed, and recrystallized α (hcp) and β (bcc) grains surrounded by high-angle grain boundaries, and the average grain size of the α and β grains was ~1.6 and ~6.8 μm, respectively. The fine α grains played a critical role in providing thermal stability for the β grains. The FSP Mg–Li–Al–Zn alloy exhibited low-temperature superplasticity with a ductility of 330 % at 100 °C and high strain rate superplasticity with ductility of ≥400 % at 225–300 °C. Microstructural examination and superplastic data analysis revealed that the dominant deformation mechanism for the FSPed Mg–Li–Al–Zn alloy is grain boundary sliding, which is controlled by the grain boundary diffusion in the β phase. 相似文献
4.
In this research, binary Mg–Zn (up to 3 wt% Zn) and ternary Mg–Zn–Gd (up to 3 wt% Gd, 3 wt% Zn) alloys were prepared by induction melting in an argon atmosphere. The structures of these alloys were characterized using light and scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and X-ray fluorescence. In addition, Brinell hardness measurements were taken to supplement these studies. Corrosion behavior was evaluated by immersion tests and potentiodynamic measurements in a physiological solution (9 g/l NaCl). Depending on the composition, structures of the as-cast alloys contained α-Mg dendrites, MgZn, Mg5Gd and Mg3Gd2Zn3 phases. Compared to pure Mg, zinc improved the corrosion resistance of binary Mg–Zn. Gadolinium also improved the corrosion resistance in the case of Mg–1Zn–3Gd alloy. The highest corrosion rate was observed for Mg–3Zn–3Gd alloy. Our results improve the understanding of the relationships between the structure and corrosion behavior of our studied alloy systems. 相似文献
5.
Effect of Zn addition on the precipitation kinetics and age-hardening response of Al–Mg–Si–Cu alloys was investigated by differential scanning calorimetry (DSC), hardness measurements, tensile tests and microstructural characterization. The results show that, compared with the Zn-free alloy, both the starting and peak temperatures in the DSC curve, and activation energy of β″ precipitation of Zn-added Al–Mg–Si–Cu alloy decrease significantly, corresponding to the greatly improved precipitation kinetics and age-hardening response, i.e., a hardness increment of 70HV after aging at 185 °C for 20 min. Moreover, the peak hardness and tensile properties can also be greatly enhanced after adding 3.0 wt% Zn even exhibiting a ductile fracture feature in the peak-aged state. No precipitates of the Al–Zn–Mg alloy system appear in the Zn-added Al–Mg–Si–Cu alloys after aging at 185 °C, and pre-β″, β″, and L precipitates are still the main precipitates in the two alloys after peak aging treatment. Finally, based on the microstructural evolution, a schematic diagram of precipitation in the Al–Mg–Si–Cu–Zn alloy is put forward, and the relationship between mechanical properties and microstructure is also established. 相似文献
6.
Jun Yan Yigang Chen Qingling Yuan Song Yu Wencai Qiu Chengguang Yang Zhigang Wang Jianfeng Gong Kaixing Ai Qi Zheng Jianan Li Shaoxiang Zhang Xiaonong Zhang 《Journal of materials science. Materials in medicine》2013,24(6):1515-1525
To evaluate the ability of Mg–6Zn to replace titanium nails in the reconstruction of the intestinal tract in general surgery, we compared the Mg–6Zn and titanium implants with respect to their effects on rat’s intestinal tract by biochemical, radiological, pathological and immunohistochemical methods. The results indicated that Mg–6Zn implants started to degrade at the third week and disintegrate at the fourth week. No bubbles appeared, which may be associated with intestinal absorption of the Mg–6Zn implants. Pathological analyses (containing liver, kidney and cecum tissues) and biochemical measurements, including serum magnesium, creatinine, blood urea nitrogen, glutamic–pyruvic–transaminase and glutamic–oxaloacetic–transaminase proved that degradation of Mg–6Zn did not harm the important organs, which is an improvement over titanium implants. Immunohistochemical results showed that Mg–6Zn could enhance the expression of transforming growth factor-β1. Mg–6Zn reduced the expression of tumor necrosis factor at different stages. In general, our study demonstrates that the Mg–6Zn alloy had good biocompatibility in vivo and performed better than titanium at promoting healing and reducing inflammation. It may be a promising candidate for stapler pins in intestinal reconstruction. 相似文献
7.
Shabnam Emami Kervee Parnian Pourshayan Farzaneh Nasrollahnezhad Saeed Khani Moghanaki Roland E. Logé 《Materials Science & Technology》2018,34(6):688-697
The non-isothermal aging behaviour of a newly developed Al–Zn–Mg–Cu alloy containing 17?wt-% Zn was investigated. Hardness and shear punch tests demonstrated that during non-isothermal aging, the mechanical properties of the alloy first increased and then decreased. The best properties were obtained in a sample which was non-isothermally aged upto 250°C with heating rate of 20°C?min?1, due to the presence of η′/η (MgZn2) phases. This was confirmed by differential scanning calorimetery. After homogenisation, residual eutectic phases remained at triple junctions or in a spherical form. During aging, these phases transformed into rodlike S (Al2CuMg)-phase at 400°C, with sizes ranging from 50 to 250?nm. The precipitation sequence in this high-Zn alloy was similar to that for conventional Al–Zn–Mg–Cu alloys. 相似文献
8.
Guoqiang Li Jinghuai Zhang Ruizhi Wu Yan Feng Shujuan Liu Xiaojun Wang Yufeng Jiao Qiang Yang Jian Meng 《材料科学技术学报》2018,34(7):1076-1084
A new cast Mg–2 Gd–2 Nd–2 Y–1 Ho–1 Er–0.5 Zn–0.4 Zr(wt%) alloy was prepared by direct-chill semicontinuous casting technology. The microstructure, mechanical properties and thermal conductivity of the alloy in as-cast, solid-solution treated and especially peak-aged conditions were investigated. The as-cast alloy mainly consists of β-Mg matrix,(Mg, Zn)_3 RE phase and basal plane stacking faults. After proper solid-solution treatment, the microstructure becomes almost Mg-based single phase solid solution except just very few RE-riched particles. The as-cast and solid-solution treated alloys exhibit moderate tensile properties and thermal conductivity. It is noteworthy that the Mg alloy with 8 wt% multiple RE exhibits remarkable age-hardening response( HV = 35.7), which demonstrates that the multiple RE(RE = Gd, Nd, Y, Ho, Er) alloying instead of single Gd can effectively improve the age-hardening response.The peak-aged alloy has a relatively good combination of high strength/hardness(UTS(ultimate tensile strength) 300 MPa; TYS(tensile yield strength) 210 MPa; 115.3 HV), proper ductility(ε≈ 6%) and moderate thermal conductivity(52.5 W/(m K)). The relative mechanisms mainly involving aging precipitation of β¢ and β' phases were discussed. The results provide a basis for development of high performance cast Mg alloys. 相似文献
9.
Zhanhui Wang Jun Yan Jianan LiQi Zheng Zhigang WangXiaonong Zhang Shaoxiang Zhang 《Materials Science and Engineering: B》2012,177(4):388-393
In this study, intestinal epithelial cells (IEC)-6 were cultured in different concentration extracts of Mg-6Zn alloys for different time periods. To achieve a total of three concentrations (100%, 60% and 20% concentration), the extracts were serially diluted with Dulbecco's modified Eagle medium High Glucose to observe a dose-response relationship. We studied the indirect effects of Mg-6Zn alloys on IEC-6 cells apoptosis. The apoptosis of IEC-6 cells was measured using flow cytometry. And the apoptosis of IEC-6 cells was evaluated by investigating the expression of caspase-1and Bcl-2 using real-time polymerase chain reaction (PCR) and Western blotting tests. It was found that the levels of apoptosis in IEC-6 cells cultured in 100% Mg-6Zn alloy extracts were significantly higher than those in 60% and 20% extracts; the 100% extract can down-regulate expression of Bcl-2 after culture. The in vitro results indicated that the conspicuous alkaline environment and excessive Mg concentration, even Zn concentration caused by rapid corrosion of Mg-6Zn alloys promote IEC-6 cells apoptosis, although further experiments will be necessary to formally prove our conclusions. Therefore, the adjustment of the degradation rate is needed for using Mg-Zn alloy as a surgical suture material. 相似文献
10.
Li Li Yongchang Liu Huixia Gao Zhiming Gao 《Journal of Materials Science: Materials in Electronics》2013,24(1):336-344
Eutectic Zn–4Al–3Mg alloy is one of the potential candidates as high-temperature lead-free solders. The phase formation sequence of eutectic Zn–4Al–3Mg alloy under different solidification conditions were investigated in this work. The results show that the microstructure is strongly affected by the difference of solidification conditions. The microstructure of the furnace-cooled eutectic Zn–4Al–3Mg alloy with a lamellar eutectic structure is composed of (α-Al + η-Zn)eutectoid, Mg2Zn11 and η-Zn three phases, while the metastable MgZn2 phase acts as primary phase during the rapid solidification of the air-cooled and water-cooled alloy specimens, and it evolves into the Mg2Zn11 phase later through a peritectic reaction ( $ {\text{MgZn}}_{ 2} + {\text{L}} \to {\text{Mg}}_{ 2} {\text{Zn}}_{ 1 1} $ ). Actually, the final solidified microstructure exhibited a feature of the primary MgZn2 phase surrounded by the Mg2Zn11 phase due to the incompleteness of the peritectic transformation. Compared with the air-cooled eutectic Zn–4Al–3Mg alloy specimen, the water-cooled eutectic Zn–4Al–3Mg alloy microstructure displayed a dendritic structure resulting from more rapid cooling rate. Furthermore, the difference between the microhardness in the eutectic Zn–4Al–3Mg alloy under various solidification conditions was mainly attributed to the high-hardness phases concluding Mg2Zn11 and MgZn2. 相似文献