Co-reporter:Qingchuan Wang, Bingchun Zhang, Yibin Ren, Ke Yang
Corrosion Science 2017 Volume 123(Volume 123) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.corsci.2017.04.006
•Detrimental effect of cold working was eliminated in 0.92 wt.% nitrogen HNS.•Nitrogen strongly enriched in the chromium oxide layer of passive film.•The nitrogen enrichment should be responsible for the exceptional behavior of HNS.The detrimental effect of cold working on pitting corrosion resistance was surprisingly found totally eliminated in high nitrogen stainless steels (HNS) with higher nitrogen content (0.92 wt.%) by electrochemical tests in chloride solution. Inclusions morphology and microstructure of cold-worked HNS were investigated. Then the passive film on HNS was analyzed by secondary ion mass spectroscopy (SIMS). For the first time nitrogen enrichment as a form of short range ordered [CrN] was observed in the chromium oxide layer of passive film on HNS. A possible reaction involving nitrogen enrichment is proposed to elucidate this exceptional behavior of corrosion resistance for HNS.Download high-res image (182KB)Download full-size image
Co-reporter:Xian-Bo Shi;Wei Yan;Mao-Cheng Yan;Wei Wang
Acta Metallurgica Sinica (English Letters) 2017 Volume 30( Issue 7) pp:601-613
Publication Date(Web):17 February 2017
DOI:10.1007/s40195-017-0545-z
In the present study, Cu-modified pipeline steels were fabricated to mitigate MIC by the antimicrobial ability of Cu element. The microstructure, mechanical properties and the antimircobial performance of the Cu-modified steel were systematically investigated. The Cu-modified steels showed good antimicrobial performance with remarkable strength enhancement by nanoscale Cu-rich precipitates and good impact toughness without changing the original base microstructures after the optimal aging treatment of 500 °C/1 h.
Co-reporter:Jing Zhao, Ling Ren, Bingchun Zhang, Zhiqiang Cao, Ke Yang
Journal of Materials Science & Technology 2017 Volume 33, Issue 12(Volume 33, Issue 12) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.jmst.2017.03.025
Cu-bearing stainless steel has been found to have obvious inhibition performance against encrustation in vitro. This study was aiming to further investigate the inhibitory effect of a Cu-bearing stainless steel (316L-Cu SS) on the infectious encrustation based on its antimicrobial activity. The encrustation in presence of bacteria, antibacterial performance, urease production and Ca and Mg precipitation were examined by scanning electron microscopy, antibacterial assay, enzyme-linked immunosorbent assay and inductively coupled plasma-mass spectrometry, respectively. It was found that 316L-Cu SS could inhibit the formation of bacterial biofilm due to the release of Cu2+ ions and then decrease the urease amount splitting by bacteria, which produced a neutral environment with pH around 7. However, more encrustations coupled with bacterial biofilms on the surface of comparison stainless steel (316L SS) with an alkaline environment were recorded. It can thus be seen that the 316L-Cu SS highlights prominent superiority against encrustation in the presence of microorganisms.
Co-reporter:Shanshan Chen, Lili Tan, Bingchun Zhang, Yonghui Xia, ... Ke Yang
Journal of Materials Science & Technology 2017 Volume 33, Issue 5(Volume 33, Issue 5) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.jmst.2016.09.011
When an orthopedics device is implanted into bone injury site, it will contact the soft tissue (skeletal muscle, fascia, ligament etc.) except for bone. Magnesium based biodegradable metals are becoming an important research object in orthopedics due to their bioactivity to promote bone healing. In this study, pure Mg rods with and without chemical conversion coating were implanted into the muscle tissue of rabbits. Implants and their surrounding tissues were taken out for weight loss measurement, cross-sectional scanning electron microscopy observation, elemental distribution analysis and histological examination. The results showed that the chemical conversion coating would increase the in vivo corrosion resistance of pure Mg and decrease the accumulation of calcium (Ca) and phosphorus (P) elements around the implants. For the bare magnesium implant, both Ca and P contents in the surrounding tissues increased at the initial stage of implantation and then decreased at 12 weeks implantation, while for the magnesium with chemical conversion coating, Ca and P contents in the surrounding tissues decreased with the implantation time, but were not significant. The histological results demonstrated that there was no calcification in the muscle tissue with implantation of magnesium for up to 12 weeks. The chemical conversion coating not only increased the in vivo corrosion resistance of pure Mg, but also avoided the depositions of Ca and P in the surrounding tissues, meaning that pure magnesium should be bio-safe when contacting with muscle tissues.
Co-reporter:Jun Li, Yibin Ren, Muhammad Ibrahim, Songbai Li, Ke Yang
Materials Letters 2017 Volume 202(Volume 202) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.matlet.2017.04.126
•Silicon brass with an exactly same susceptibility to human tissues is developed.•Silicon brass preforms acceptable mechanical properties and corrosion resistance.•Silicon brass shows nearly no magnetic susceptibility artifact.•Silicon brass is a promising material for high field MR-guided biopsy needles.This study was an attempt to see the possibility of a silicon brass for application in high field MR-guided biopsy application. The α + β phases silicon brass was found to have matched strength and toughness, and also showed acceptable corrosion resistance and Cu ion dissolution in short-term immersion test. It was found that silicon brass presented diamagnetic property with a low volume magnetic susceptibility, which is possible to reduce the magnetic susceptibility artifact (MSA). The artifact of silicon brass showed slightly larger than pure copper, but much less than pure titanium, located in both parallel and perpendicular to the direction of a 3-T magnetic field used in fast spin echo (FSE) scan sequence. In conclusion, the silicon brass is a promising material for application of high field MR-guided biopsy needles.Download high-res image (96KB)Download full-size image
Co-reporter:Junxiu Chen, Lili Tan, Ke Yang
Bioactive Materials 2017 Volume 2, Issue 1(Issue 1) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.bioactmat.2016.12.002
•The strength and corrosion resistance of ZK60 alloys are improved by T5 treatment due to the formation of small and uniformly distributed MgZn phases.•After T6 treatment, certain amount of MgZn2 phase is precipitated along the grain boundary which deteriorates the corrosion resistance.•The as-extruded ZK60 exhibits the worst corrosion resistance. The content of ZnZr phase is high in the second phase.ZK60 magnesium alloy possess good mechanical properties and is a potential biodegradable material. But its high degradation rate is not desirable. In this study the effect of heat treatment on the biodegradable property of ZK60 alloy was investigated. T5 treated, T6 treated, as-cast and as-extruded ZK60 alloys were studied. Microstructure characterization, electrochemical measurement and immersion test were carried out. The results showed that both the mechanical properties and degradation behavior were improved after T5 treatment due to the formation of small and uniformly distributed MgZn phases. The as-cast alloys also exhibited good corrosion resistance. However, the as-extruded and T6 treated samples were severely corroded due to the formation of large amounts of second phases accelerating the corrosion rate owing to the galvanic corrosion. The corrosion resistance of ZK60 alloy was as following: T5 treated > as-cast > T6 treated > as-extruded.Download high-res image (213KB)Download full-size image
Co-reporter:Yongming Shangguan, Peng Wan, Lili Tan, Xinmin Fan, Ling Qin, Ke Yang
Journal of Colloid and Interface Science 2016 Volume 481() pp:1-12
Publication Date(Web):1 November 2016
DOI:10.1016/j.jcis.2016.07.032
Magnesium-based metals are considered as promising biodegradable orthopedic implant materials due to their potentials of enhancing bone healing and reconstruction, and in vivo absorbable characteristic without second operation for removal. However, the rapid corrosion has limited their clinical applications. Ca-P coating by electrodeposition has been supposed to be effective to control the degradation rate and enhance the bioactivity. In this work, a brushite coating was fabricated on the Mg-Sr alloy by pulse electrodeposition (PED) to evaluate its efficacy for orthopedic application. Interestingly, an inner corrosion layer was observed between the PED coating and the alloy substrate. Meanwhile the results of in vitro immersion and electrochemical tests showed that the corrosion resistance of the coated alloy was undermined in comparison with the uncoated alloy. It was deduced that the existence of this corrosion layer was attributed to the worse corrosion performance of the alloy. The mechanism on formation of the inner corrosion layer and its influence on consequent degradation were analyzed. It can be concluded that the electrodeposition coating should be not suitable for those magnesium alloys with poor corrosion resistance such as the Mg-Sr alloy. More importantly, it should be noted that the process of coating formation combined with the nature of substrate alloy is important to evaluate the efficacy of coating for biodegradable Mg-based implants application.
Co-reporter:Li Nan, Guogang Ren, Donghui Wang, Ke Yang
Journal of Materials Science & Technology 2016 Volume 32(Issue 5) pp:445-451
Publication Date(Web):May 2016
DOI:10.1016/j.jmst.2016.01.002
Pathogen microorganisms exist in various environments such as dairy processing facilities. They are not easily eliminated, and significantly raise the risk of bacterial contamination. The inhibition ability of a novel type 304 Cu-bearing stainless steel (304CuSS) with nano-sized Cu-rich precipitates against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) added whole milk was investigated in this study. The results showed that after 24 h contact, the inhibition rates of the 304CuSS against S. aureus and P. aeruginosa added whole milk reached 99.2% ± 0.3% and 99.3% ± 0.2%, respectively, in contrast with the 304SS. In the plain whole milk, the inhibition rate of the 304CuSS also reached 66.9% ± 2.0% compared with the 304SS. The results demonstrated that the 304CuSS killed majority of the planktonic bacteria, and inhibited sessile bacteria adherence to the steel surface in the whole milk with and without bacteria addition, significantly reducing the bacterial growth rate. These research outcomes explicitly show an application potential of this novel antibacterial stainless steel in the dairy related food industry.
Co-reporter:Jian Liu, Wei Yan, Wei Sha, Wei Wang, Yiyin Shan, Ke Yang
Journal of Nuclear Materials 2016 Volume 473() pp:189-196
Publication Date(Web):May 2016
DOI:10.1016/j.jnucmat.2016.02.032
•The tensile behaviors of SIMP steel in LBE are investigated for the first time.•The SIMP is susceptible to LME at different strain rates and temperatures.•The total elongation is reduced greatly.•The ductility trough is wider under SSRT.•The tensile specimens rupture in brittle manner without obvious necking.In order to assess the susceptibility of candidate structural materials to liquid metal embrittlement, this work investigated the tensile behaviors of ferritic-martensitic steel in static lead bismuth eutectic (LBE). The tensile tests were carried out in static lead bismuth eutectic under different temperatures and strain rates. Pronounced liquid metal embrittlement phenomenon is observed between 200 °C and 450 °C. Total elongation is reduced greatly due to the liquid metal embrittlement in LBE environment. The range of ductility trough is larger under slow strain rate tensile (SSRT) test.
Co-reporter:Yang Li, Xuqiang Liu, Lili Tan, Ling Ren, Peng Wan, Yongqiang Hao, Xinhua Qu, Ke Yang, Kerong Dai
Journal of Materials Science & Technology 2016 Volume 32(Issue 9) pp:865-873
Publication Date(Web):September 2016
DOI:10.1016/j.jmst.2016.07.013
Implant-associated infection remains a difficult medical problem in orthopedic surgery. Therefore, the development of multifunctional bone implants for treating infection and regenerating lost bone tissue, which may be a result of infection, is important. In the present study, we report the fabrication of enoxacin-loaded poly (lactic-co-glycolic acid) (PLGA) coating on porous magnesium scaffold (Enox-PLGA-Mg) which combine the favorable properties of magnesium, the antibacterial property and the effect of inhibition of osteoclastic bone resorption of enoxacin. The drug loaded PLGA coating of Mg scaffold enables higher drug loading efficiency (52%–56%) than non-coating enoxacin loaded Mg scaffold (Enox-Mg) (4%–5%). Enox-PLGA-Mg exhibits sustained drug release for more than 14 days, and this controlled release of enoxacin significantly inhibits bacterial adhesion and prevented biofilm formation by Staphylococcus epidermidis (ATCC35984) and Staphylococcus aureus (ATCC25923). Biocompatibility tests with Balb/c mouse embryo fibroblasts (Balb/c 3T3 cells) indicate that PLGA-Mg has better biocompatibility than Mg. Finally, we also demonstrate that Enox-PLGA-Mg extract potently inhibited osteoclast formation in vitro. Therefore, Enox-PLGA-Mg has the potential to be used as a multifunctional controlled drug delivery system bone scaffolds to prevent and/or treat orthopedic peri-implant infections.
Co-reporter:Shujing Jin, Ling Ren, Ke Yang
Journal of Materials Science & Technology 2016 Volume 32(Issue 9) pp:835-839
Publication Date(Web):September 2016
DOI:10.1016/j.jmst.2016.06.022
Although being an essential trace element required for human body health, Cu has long been seriously considered toxic when its amount exceeds certain limitation, which significantly limited the wide application of Cu in biomaterials. However, more and more bio-functions and benefits of Cu were found and confirmed, attracting the attention from biomaterials researchers in recent years. People have tried to immobilize Cu into biomaterials by various ways, in order to develop novel bio-functional Cu containing biomaterials with better bio-adaptions, and several different bio-functions of them have been demonstrated. This paper makes a review of the development of novel bio-functional Cu containing biomaterials, and focuses on their unique roles in enhancing bio-adaption of biomedical materials, including antibacterial performance, stimulating angiogenesis, promoting osteogenesis and inhibition of in-stent restenosis, aiming at proposing a prospective development direction for biomedical materials with better bio-adaptions.
Co-reporter:Junjie Han, Peng Wan, Yu Sun, Zongyuan Liu, Xinmin Fan, Lili Tan, Ke Yang
Journal of Materials Science & Technology 2016 Volume 32(Issue 3) pp:233-244
Publication Date(Web):March 2016
DOI:10.1016/j.jmst.2015.11.012
Considering the compatibility between degradation and bioactivity of magnesium-based implants for bone repair, micro-arc oxidation is used to modify the magnesium alloy surface in aqueous electrolytes, allowing strontium, calcium, and phosphorus to be incorporated into the coating. The thickness, composition, morphology and phase of this Sr–Ca–P containing coating are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffraction. The in vitro and in vivo degradation of the coating is evaluated by immersion test, electrochemical test and implantation test. Moreover, the cytocompatibility is tested with osteoblast cell according to ISO 10993. The results show that Sr, Ca and P elements are incorporated into the oxide coating, and a refined structure with tiny discharging micro-pores is observed on the surface of the coating. The Sr–Ca–P coating possesses a better corrosion resistance in vitro and retards the degradation in vivo. Such coating is expected to have significant medical applications on orthopedic implants and bone repair materials.
Co-reporter:Peng Wan, Lili Tan, Ke Yang
Journal of Materials Science & Technology 2016 Volume 32(Issue 9) pp:827-834
Publication Date(Web):September 2016
DOI:10.1016/j.jmst.2016.05.003
Magnesium (Mg) and its alloys as a novel kind of biodegradable material have attracted much fundamental research and valuable exploration to develop its clinical application. Mg alloys degrade too fast at the early stage after implantation, thus commonly leading to some problems such as osteolysis, early fast mechanical loss, hydric bubble aggregation, gap formation between the implants and the tissue. Surface modification is one of the effective methods to control the degradation property of Mg alloys to adapt to the need of organism. Some coatings with bioactive elements have been developed, especially for the micro-arc oxidation coating, which has high adhesion strength and can be added with Ca, P, and Sr elements. Chemical deposition coating including bio-mimetic deposition coating, electro-deposition coating and chemical conversion coating can provide good anticorrosion property as well as better bioactivity with higher Ca and P content in the coating. From the biodegradation study, it can be seen that surface coating protected the Mg alloys at the early stage providing the Mg alloy substrate with lower degradation rate. The biocompatibility study showed that the surface modification could provide the cell and tissue stable and weak alkaline surface micro-environment adapting to the cell adhesion and tissue growth. The surface modification also decreased the mechanical loss at the early stage adapting to the load-bearing requirement at this stage. From the interface strength between Mg alloys implants and the surrounding tissue study, it can be seen that the surface modification improved the bio-adhesion of Mg alloys with the surrounding tissue, which is believed to be contributed to the tissue adaptability of the surface modification. Therefore, the surface modification adapts the biodegradable magnesium alloys to the need of biodegradation, biocompatibility and mechanical loss property. For the different clinical application, different surface modification methods can be provided to adapt to the clinical requirements for the Mg alloy implants.
Co-reporter:Yanjin Lu, Chaoqian Zhao, Ling Ren, Sai Guo, Yiliang Gan, Chunguang Yang, Songquan Wu, Junjie Lin, Tingting Huang, Ke Yang, Jinxin Lin
Materials Science and Engineering: C 2016 Volume 63() pp:37-45
Publication Date(Web):1 June 2016
DOI:10.1016/j.msec.2016.02.057
•The bonding strength of metal-porcelain was slightly decreased with Cu addition;•Cu not only led to promote the diffusion of O and W element but also inhibited the diffusivity of Co in the outward direction;•The changed oxidation behavior resulted in lowering the bonding strength;In this work, a novel Cu-bearing CoCrW alloy fabricated by selective laser melting for dental application has been studied. For its successful application, the bonding strength of metal-porcelain is essential to be systematically investigated. Therefore, the aim of this study was to evaluate the metal-porcelain bonding strength of CoCrWCu alloy by three-point bending test, meanwhile the Ni-free CoCrW alloy was used as control. The oxygen content was investigated by an elemental analyzer; X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemical composition of CoCrW based alloy after preoxidation treatment; the fracture mode was investigated by X-ray energy spectrum analysis (EDS) and scanning electron microscope (SEM). Result from the oxygen content analysis showed that the content of oxygen dramatically increased after the Cu addition. And the XPS suggested that Co-oxidation, Cr2O3, CrO2, WO3, Cu2O and CuO existed on the preoxidated surface of the CoCrWCu alloy; the three-point bending test showed that the bonding strength of the CoCrWCu alloy was 43.32 MPa, which was lower than that of the CoCrW group of 47.65 MPa. However, the average metal-porcelain bonding strength is significantly higher than the minimum value in the ISO 9693 standard. Results from the SEM images and EDS indicated that the fracture mode of CoCrWCu-porcelain was mixed between cohesive and adhesive. Based on the results obtained in this study, it can be indicated that the Cu-bearing CoCrW alloy fabricated by the selective laser melting is a promising candidate for use in dental application.
Co-reporter:Jing Zhao, Zhiqiang Cao, Ling Ren, Shanshan Chen, Bingchun Zhang, Rui Liu, Ke Yang
Materials Science and Engineering: C 2016 Volume 68() pp:221-228
Publication Date(Web):1 November 2016
DOI:10.1016/j.msec.2016.04.103
•316LCu-SS exhibited strong antibacterial performance against E.coli in the urine.•316LCu-SS had less crystals deposition on its surface compared to NiTi.•316LCu-SS showed no toxicity and promoted migration of epithelial cells.•316LCu-SS is prospective to be a new candidate material to relieve UTIs.Ureteral stents have been used to relieve ureterostenosis. Complications such as infection and encrustation occur in the long time of stent implantation, which is a clinical problem needs to be resolved. Indwelling ureteral stents have shown to develop microbial biofilm that may lead to recurrent infection and encrustation. This study was aiming to reduce those complications by using a novel material, Cu-bearing antibacterial stainless steel. The antibacterial performance, encrustation property, and biocompatibility were examined by SEM, image analysis, MTT and would healing. The in vitro immersion test showed that 316LCu-bearing stainless steel (316LCu-SS) not only inhibited proliferation of bacteria and formation of biofilm, but also had less encrustation deposition. Its antibacterial effectiveness against Escherichia coli reached to 92.7% in the artificial urine for 24 h and 90.3% in the human urine for 6 h. The encrustation surface coverage percentage was 30.2% by 12 weeks, which was nearly one half of NiTi alloy. The in vitro tests showed that 316LCu-SS had no toxicity, and promoted the migration of urethral epithelial cells.
Co-reporter:Qingchuan Wang;Bingchun Zhang
Metallurgical and Materials Transactions A 2016 Volume 47( Issue 7) pp:3284-3288
Publication Date(Web):2016 July
DOI:10.1007/s11661-016-3532-5
A series of high nitrogen steels were studied by using thermodynamic calculations to investigate the effect of manganese on the stability of austenite. Surprisingly, it was found that the austenite stabilizing ability of manganese was strongly weakened by chromium, but it was strengthened by molybdenum. In addition, with an increase of manganese content, the ferrite stabilizing ability of chromium significantly increased, but that of molybdenum decreased. Therefore, strong interactions exist between manganese and the other alloying elements, which should be the main reason for the difference among different constituent diagrams.
Co-reporter:Tong Xi, M. Babar Shahzad, Dake Xu, Jinlong Zhao, Chunguang Yang, Min Qi, Ke Yang
Materials Science and Engineering: A 2016 Volume 675() pp:243-252
Publication Date(Web):15 October 2016
DOI:10.1016/j.msea.2016.08.058
The effect of precipitation hardening on mechanical properties and coarsening behavior of Cu-rich precipitates in a Cu-bearing 316L austenite stainless steel after aging at 700 °C for different time were systematically investigated. The variations of morphology and composition of Cu-rich precipitates as a function of aging time were respectively characterized by electrical resistivity, atom probe tomography (APT) and transmission electron microscopy (TEM). It was found that both hardness and mechanical strength increased to peak value within short aging time, and remained nearly unchanged with prolonged aging time. The TEM observation confirmed a coherent interface between Cu-rich precipitates and austenite matrix, while high number densities of spheroidal Cu-rich precipitates were observed in all aged samples. APT analyses confirmed virtually 100% Cu core composition of Cu-rich precipitates, whereas the average radius was slightly increased from 1.38±0.46 nm to 2.39±0.81 nm with increasing the aging time. The relatively slow growth and coarsening behavior of Cu-rich precipitates was largely attributed to the slower diffusion kinetics of Cu, low interfacial energy and high strain energy of Cu-rich precipitates in the austenite matrix, and was well predicted by the Lifshitz-Slyozov-Wagner theory. The slow increase in average radius of Cu-rich precipitates was consistent with the modest change in hardness and yield strength with extended aging. In addition, the precipitation strengthening effects of Cu-rich precipitates were quantitatively evaluated and analyzed. These cumulative results and analyses could provide a solid foundation for much wider applications of Cu-bearing stainless steels.
Co-reporter:Yongming Shangguan, Lina Sun, Peng Wan, Lili Tan, Chengyue Wang, Xinmin Fan, Ling Qin, Ke Yang
Materials Science and Engineering: C 2016 Volume 69() pp:95-107
Publication Date(Web):1 December 2016
DOI:10.1016/j.msec.2016.06.073
•The MAO, PED and Sr-P coating were fabricated on Mg-Sr alloy to evaluate the degradation.•The MAO coating showed the greatest degradation performance among these three coatings.•The PED coating exhibited worse corrosion resistance even than Mg-Sr substrate.•The value of cell proliferation and ALP activity were ranked in the following order: MAO > Sr-P > PED.To solve the problem of rapid degradation for magnesium-based implants, surface modification especially coating method is widely studied and showed the great potential for clinical application. However, as concerned to the further application and medical translation for biodegradable magnesium alloys, there are still lack of data and comparisons among different coatings on their degradation and biological properties. This work studied three commonly used coatings on Mg-Sr alloy, including micro-arc oxidation coating, electrodeposition coating and chemical conversion coating, and compared these coatings for requirements of favorable degradation and biological performances, how each of these coating systems has performed. Finally the mechanism for the discrepancy between these coatings is proposed. The results indicate that the micro-arc oxidation coating on Mg-Sr alloy exhibited the best corrosion resistance and cell response among these coatings, and is proved to be more suitable for the orthopedic application.
Co-reporter:Weidan Wang, Junjie Han, Xuan Yang, Mei Li, Peng Wan, Lili Tan, Yu Zhang, Ke Yang
Materials Science and Engineering: B 2016 Volume 214() pp:26-36
Publication Date(Web):December 2016
DOI:10.1016/j.mseb.2016.08.005
•A non-toxic Mg-based alloy system with nutrient elements Si, Sr, Ca is proposed.•Properties improved due to morphology of coarse Mg2Si change into small polygon.•Fewer, finer and homogenized Mg2Si particles are obtained after anneal-treated.•Cytocompatibility results indicate a potential application in orthopedic.Magnesium has been widely studied as a biodegradable material, where its mechanical property and biocompatibility make it preferred candidate for orthopedic implant. Proper alloying can further improve the properties of Mg. First and foremost, to guarantee the biosafety for biomedical application, the alloying element should be toxic free. To address this point, nutrient elements including Si, Sr and Ca were selected due to their biological functions in human body, especially in bone regeneration and repair. In this study, 0.5–1.0 wt% Sr and Ca were used to refine and modify the morphology of coarse Mg2Si in Mg-1.38wt% Si to obtain an uniform microstructure. Microstructure, mechanical and degradation properties of as-cast and homogenizing-annealed quaternary Mg-1.38Si-xSr-yCa (x, y = 0.5–1 wt%) alloys were investigated by optical microscopy, scanning electronic microscopy, X-ray diffraction, tensile and electrochemical measurement. Addition of Sr and Ca element cause a morphological change in Mg2Si particles from coarse Chinese script shape to small polygonal type. The presences of intermetallic phases, such as Mg2Si, CaMgSi and Mg17Sr2, were confirmed in quaternary alloys, of which content was applied to interpret the results for the quaternary system. Compared with the as-cast state, fewer, finer and homogenized microstructure were observed after an anneal heat treatment under 500 °C. The mechanical properties were improved with increase of Ca and Sr additions, which was related to the evolution of the microstructure and second phases, however, also causing an increase of corrosion rate due to the galvanic-corrosion at the same time. The cytocompatibility results revealed that the Mg-Si-Sr-Ca alloys promote the proliferation of preosteoblasts and exhibit cytotoxicity of Grade 0–1, indicating their acceptable biosafety and potential for the orthopedic applications.
Co-reporter:Junjie Han, Peng Wan, Ye Ge, Xinmin Fan, Lili Tan, Jianjun Li, Ke Yang
Materials Science and Engineering: C 2016 Volume 58() pp:799-811
Publication Date(Web):1 January 2016
DOI:10.1016/j.msec.2015.09.057
•Three different statuses of Mg–Sr alloys are used to compare the efficacy for bone graft application.•The rapid degradation is due to intergranular distribution of Mg17Sr2 and galvanic corrosion.•The as-cast alloy with MAO coating exhibited tailored degradation and good biocompatibility.•The in vivo compatible degradation with bone healing is observed for the as-cast alloy with coating.Bone defects are very challenging in orthopedic practice. There are many practical and clinical shortcomings in the repair of the defect by using autografts, allografts or xenografts, which continue to motivate the search for better alternatives. The ideal bone grafts should provide mechanical support, fill osseous voids and enhance the bone healing. Biodegradable magnesium–strontium (Mg–Sr) alloys demonstrate good biocompatibility and osteoconductive properties, which are promising biomaterials for bone substitutes. The aim of this study was to evaluate and pair the degradation of Mg–Sr alloys for grafting with their clinical demands. The microstructure and performance of Mg–Sr alloys, in vitro degradation and biological properties including in vitro cytocompatibility and in vivo implantation were investigated. The results showed that the as-cast Mg–Sr alloy exhibited a rapid degradation rate compared with the as-extruded alloy due to the intergranular distribution of the second phase and micro-galvanic corrosion. However, the initial degradation could be tailored by the coating protection, which was proved to be cytocompatible and also suitable for bone repair observed by in vivo implantation. The integrated fracture calluses were formed and bridged the fracture gap without gas bubble accumulation, meanwhile the substitutes simultaneously degraded. In conclusion, the as-cast Mg–Sr alloy with coating is potential to be used for bone substitute alternative.
Co-reporter:Ling Ren, Kaveh Memarzadeh, Shuyuan Zhang, Ziqing Sun, Chunguang Yang, Guogang Ren, Robert P. Allaker, Ke Yang
Materials Science and Engineering: C 2016 Volume 67() pp:461-467
Publication Date(Web):1 October 2016
DOI:10.1016/j.msec.2016.05.069
•Novel CoCrCu alloys were fabricated by using selective laser melting (SLM).•SLM CoCrCu alloys showed satisfied antimicrobial and antibiofilm activities.•SLM CoCrCu alloys have no cytotoxic effect on normal cells.•Other properties of SLM CoCrCu alloys were similar to SLM CoCr alloys.•SLM CoCrCu alloys have the potential to be used as coping metals.ObjectiveThe aim of this study was to fabricate a novel coping metal CoCrCu alloy using a selective laser melting (SLM) technique with antimicrobial and antibiofilm activities and to investigate its microstructure, mechanical properties, corrosion resistance and biocompatibility.MethodsNovel CoCrCu alloy was fabricated using SLM from a mixture of commercial CoCr based alloy and elemental Cu powders. SLM CoCr without Cu served as control. Antibacterial activity was analyzed using standard antimicrobial tests, and antibiofilm properties were investigated using confocal laser scanning microscope. Cu distribution and microstructure were determined using scanning electron microscope, optical microscopy and X-ray diffraction. Corrosion resistance was evaluated by potential dynamic polarization and biocompatibility measured using an MTT assay.ResultsSLM CoCrCu alloys were found to be bactericidal and able to inhibit biofilm formation. Other factors such as microstructure, mechanical properties, corrosion resistance and biocompatibility were similar to those of SLM CoCr alloys.SignificanceThe addition of appropriate amounts of Cu not only maintains normal beneficial properties of CoCr based alloys, but also provides SLM CoCrCu alloys with excellent antibacterial and antibiofilm capabilities. This material has the potential to be used as a coping metal for dental applications.
Co-reporter:Chen Liu;Peng He;Peng Wan;Mei Li;Kehong Wang;Lili Tan;Yu Zhang
Journal of Biomedical Materials Research Part A 2015 Volume 103( Issue 7) pp:2405-2415
Publication Date(Web):
DOI:10.1002/jbm.a.35374
Abstract
Mg alloys are gaining interest for applications as biodegradable medical implant, including Mg–Al–Zn series alloys with good combination of mechanical properties and reasonable corrosion resistance. However, whether the existence of second phase particles in the alloys exerts influence on the biocompatibility is still not clear. A deeper understanding of how the particles regulate specific biological responses is becoming a crucial requirement for their subsequent biomedical application. In this work, the in vitro biocompatibility of Mg17Al12 as a common second phase in biodegradable Mg–Al–Zn alloys was investigated via hemolysis, cytotoxicity, cell proliferation, and cell adhesion tests. Moreover, osteogenic differentiation was evaluated by the extracellular matrix mineralization assay. The Mg17Al12 particles were also prepared to simulate the real situation of second phase in the in vivo environment in order to estimate the cellular response in macrophages to the Mg17Al12 particles. The experimental results indicated that no hemolysis was found and an excellent cytocompatibility was also proved for the Mg17Al12 second phase when co-cultured with L929 cells, MC3T3-E1 cells and BMSCs. Macrophage phagocytosis co-culture test revealed that Mg17Al12 particles exerted no harmful effect on RAW264.7 macrophages and could be phagocytized by the RAW264.7 cells. Furthermore, the possible inflammatory reaction and metabolic way for Mg17Al12 phase were also discussed in detail. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103: 2405–2415, 2015.
Co-reporter:Mingjun Li, Li Nan, Dake Xu, Guogang Ren, Ke Yang
Journal of Materials Science & Technology 2015 Volume 31(Issue 3) pp:243-251
Publication Date(Web):March 2015
DOI:10.1016/j.jmst.2014.11.016
Tap water is one of the most commonly used water resources in our daily life. However, the increasing water contamination and the health risk caused by pathogenic bacteria, such as Staphylococcus aureus and Escherichia coli have attracted more attention. The mutualism of different pathogenic bacteria may diminish antibacterial effect of antibacterial agents. It was found that materials used for making pipe and tap played one of the most important roles in promoting bacterial growth. This paper is to report the performance of an innovative type 304 Cu-bearing stainless steel (304CuSS) against microbes in tap water. The investigation methodologies involved were means of heterotrophic plate count, contact angle measurements, scanning electron microscopy for observing the cell and subtract surface morphology, atomic absorption spectrometry for copper ions release study, and confocal laser scanning microscopy used for examining live/dead bacteria on normal 304 stainless steel and 304CuSS. It was found that the surface free energy varied after being immersed in tap water with polar component and Cu ions release. The results showed 304CuSS could effectively kill most of the planktonic bacteria (max 95.9% antibacterial rate), and consequently inhibit bacterial biofilms formation on the surface, contributing to the reduction of pathogenic risk to the surrounding environments.
Co-reporter:Zheng Ma, Ling Ren, Rui Liu, Ke Yang, Yu Zhang, Zhenhua Liao, Weiqiang Liu, Min Qi, R.D.K. Misra
Journal of Materials Science & Technology 2015 Volume 31(Issue 7) pp:723-732
Publication Date(Web):July 2015
DOI:10.1016/j.jmst.2015.04.002
A copper-bearing Ti–6Al–4V–5Cu alloy was processed and subjected to different heat treatments to explore the relationship among microstructure, antibacterial performance, and cytocompatibility. Characterization of microstructure revealed that the solution treated alloy consisted of α phase, α′ phase and β phase, while besides these phases, the aged alloy also contained the precipitations of intermetallic Ti2Cu compound. The solution treated alloy showed better antibacterial performance with increasing the solution temperature. The Cu ions released from Ti–6Al–4V–5Cu alloy could effectively inhibit the formation of bacterial biofilm on the surface of alloy, and do not induce any cytotoxicity. The optimal heat treatment for Ti–6Al–4V–5Cu alloy was solution treated at 930 °C, at which it could exhibit both promising antibacterial performance and no cytotoxicity.
Co-reporter:Quanqiang Shi, Jian Liu, He Luan, Zhenguo Yang, Wei Wang, Wei Yan, Yiyin Shan, Ke Yang
Journal of Nuclear Materials 2015 Volume 457() pp:135-141
Publication Date(Web):February 2015
DOI:10.1016/j.jnucmat.2014.11.018
Co-reporter:Qingchuan Wang;Yibin Ren;Chunfa Yao
Metallurgical and Materials Transactions A 2015 Volume 46( Issue 12) pp:5537-5545
Publication Date(Web):2015 December
DOI:10.1007/s11661-015-3160-5
A series of high-nitrogen stainless steels (HNS) containing δ-ferrite, which often retained in HNS, were studied to establish the relationship between composition and microstructure. Both ferrite and nitrogen depletions were found in the center regions of cast ingots, and the depletion of nitrogen in that area was found to be the main reason for the existence of δ-ferrite. Because of the existence of heterogeneity, the variation of microstructure with nitrogen content was detected. Hence, the critical contents of nitrogen (CCN) for the fully austenitic HNS were obtained. Then the effects of elements such as N, Cr, Mn, and Mo on austenite stability were investigated via thermodynamic calculations. The CCN of HNS alloys were also obtained by calculations. Comparing the CCN obtained from experiment and calculation, it was found that the forged microstructure of the HNS was close to the thermodynamic equilibrium. To elucidate the above relationship, by regression analysis using calculated thermodynamic data, nitrogen equivalent and a new constitution diagram were proposed. The constitution diagram accurately distinguishes the austenitic single-phase region and the austenite + ferrite dual-phase region. The nitrogen equivalent and the new constitution diagram can be used for alloying design and microstructural prediction in HNS. According to the nitrogen equivalent, the ferrite stabilizing ability of Mo is weaker than Cr, and with Mn content increases, Mn behaves as a weak austenite stabilizer first and then as a ferrite stabilizer.
Co-reporter:Jian Liu;Quanqiang Shi;He Luan;Wei Yan;Wei Sha;Wei Wang
Oxidation of Metals 2015 Volume 84( Issue 3-4) pp:383-395
Publication Date(Web):2015 October
DOI:10.1007/s11085-015-9560-5
In order to investigate the compatibility of candidate structural materials with liquid metals, two kinds of ferritic/martensitic steels were chosen to contact with lead–bismuth eutectic in sealed quartz–glass tubes. The corrosion exposures were for 500 and 3000 h. Results showed that the oxidation layer and carbide dissolution layer on the two steels grew with contact time under oxygen unsaturated condition. Short-term corrosion behavior of a newly developed steel showed better lead–bismuth eutectic corrosion resistance than T91 at 873 K.
Co-reporter:Quanqiang Shi;Jian Liu;Wei Wang;Wei Yan;Yiyin Shan
Oxidation of Metals 2015 Volume 83( Issue 5-6) pp:521-532
Publication Date(Web):2015 June
DOI:10.1007/s11085-015-9532-9
The oxidation behavior of two ferrite/martensite (F/M) steels, including a novel 9–12 % Cr modified F/M steel named SIMP steel and a commercial T91 steel, were studied in air at 700 °C for up to 1,000 h. The oxides formed on the two steels were characterized and analyzed by XRD, XPS, SEM and EPMA. The results showed that the oxide formed on SIMP steel was single-layer including flake-like Cr2O3 with Mn1.5Cr1.5O4 spinel particles, while the oxide on T91 steel exhibited a double layers structure consisting of an outer hematite Fe2O3 layer and an inner Fe–Cr spinel layer. The reason why the SIMP steel showed better high temperature oxidation resistance than T91 steel was analyzed to be due to the higher Cr and Si contents that could form compact and continuous oxide layer on the steel. Based on all the results, a kinetic model describing nucleation, growth and degradation of the oxide scale formed on surfaces of the two steels was proposed.
Co-reporter:Wanli Zhong, Wei Wang, Xu Yang, Wensheng Li, Wei Yan, Wei Sha, Wei Wang, Yiyin Shan, Ke Yang
Materials Science and Engineering: A 2015 Volume 639() pp:252-258
Publication Date(Web):15 July 2015
DOI:10.1016/j.msea.2015.05.012
Laves phase has been widely accepted to cause the impact brittleness of 9–12Cr martensitic heat-resistant steels after long time aging at elevated temperatures. However, in the present research, the impact toughness of the already brittle P92 steel aged at 600 °C for 2035 h could be restored to the original level by reheating at 700 °C for 1 h, with Laves phase barely changed. This interesting result strongly indicated that the presence of Laves phase might not be the real reason for the impact brittleness.
Co-reporter:Wenfeng Zhang, Qingyong Su, Wei Yan, Wei Wang, R. Devesh K. Misra, Yiyin Shan, Ke Yang
Materials Science and Engineering: A 2015 Volume 639() pp:173-180
Publication Date(Web):15 July 2015
DOI:10.1016/j.msea.2015.04.101
The stress relaxation curves for three different hot deformation processes in the temperature range of 750–1000 °C were studied to develop an understanding of the precipitation behavior in a nitride-strengthened martensitic heat resistant steel. The first sharp jump in the stress relaxation plots was assumed to be indicative of the commencement of precipitation in this paper, according to the abrupt change in ∂σ/∂t∂σ/∂t curve and the microstructure observation of the samples. The precipitation revealed by the stress jumps in the stress relaxation plots was further studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and energy dispersive X-ray analysis (EDAX). The results confirmed that, under the deformation situation of “Group C”, almost all the Nb atoms would precipitate as Nb(C,N) particles at its optimum precipitation temperature of 940 °C; Nearly all the C+N atoms would be consumed in forming M23C6 particle at its nose precipitation temperature of 800 °C; only 60% V atoms would deposit as V(C,N) particles at its fastest nucleation temperature of 750 °C.
Co-reporter:Junlei Li, Lili Tan, Peng Wan, Xiaoming Yu, Ke Yang
Materials Science and Engineering: C 2015 Volume 49() pp:422-429
Publication Date(Web):1 April 2015
DOI:10.1016/j.msec.2015.01.029
•The extruded NZ20 alloy appeared fine-grained and globular.•A lot of fine granular particles were observable in the E1 sample.•Both E1 and E2 presented excellent plasticity.•Compared with E2, E1 exhibited a relatively lower corrosion rate.Mg–2Nd–0.2Zn (NZ20) alloy was prepared for the application as biodegradable implant material in this study. The effects of the extrusion process on microstructure, mechanical and corrosion properties of the alloy were investigated. The as-cast alloy was composed of α-Mg matrix and Mg12Nd eutectic compound. The solution treatment could lead to the Mg12Nd phase dissolution and the grain coarsening. The alloy (E1) preheated at 380 °C for 1 h and extruded at 390 °C presents fine grains with amounts of tiny Mg12Nd particles uniformly dispersed throughout the boundaries and the interior of the grains. The alloy (E2) preheated at 480 °C for 1 h and extruded at 500 °C exhibits relatively larger grains with few nano-scale Mg12Nd phase particles dispersed. The alloy of E1, compared with E2, showed relatively lower corrosion rate, higher yield strength and slightly lower elongation.
Co-reporter:Li Nan, Dake Xu, Tingyue Gu, Xiu Song, Ke Yang
Materials Science and Engineering: C 2015 Volume 48() pp:228-234
Publication Date(Web):1 March 2015
DOI:10.1016/j.msec.2014.12.004
•304L-Cu SS showed strong adherence resistance performance against Escherichia coli.•304L-Cu SS reduced the maximum MIC pit depth and weight loss compared with 304L SS.•Pitting corrosion occurrence was reduced on 304L-Cu SS surface compared with 304L SS.Cu-bearing antibacterial stainless steels have been gaining popularity in recent years due to their strong antibacterial performances. However, only a few studies were reported for their actual performances against microbiologically influenced corrosion (MIC). In this study, electrochemical methods and surface analytical techniques were applied to study the MIC resistance characteristics of a 304L-Cu stainless steel (SS) against Escherichia coli in comparison with 304L SS as control. Corrosion tests for specimens after a 21-day exposure to a Luria–Bertani (LB) culture medium with E. coli demonstrated that the 304L-Cu SS considerably reduced the maximum MIC pit depth and the specific weight loss compared with 304L SS (8.3 μm and 0.2 mg/cm2 vs. 13.4 μm and 0.6 mg/cm2). Potentiodynamic polarization tests showed that the corrosion current density of the 304L-Cu SS was as much as 4 times lower than that of the 304L SS, indicating that the 304L-Cu SS is a better choice for applications in MIC-prone environments.
Co-reporter:Ling Ren;Hoi Man Wong;Chun Hoi Yan;Kelvin W.K. Yeung
Journal of Biomedical Materials Research Part B: Applied Biomaterials 2015 Volume 103( Issue 7) pp:1433-1444
Publication Date(Web):
DOI:10.1002/jbm.b.33318
Abstract
A newly developed copper-bearing stainless steel (Cu-SS) by directly immobilizing proper amount of Cu into a medical stainless steel (317L SS) during the metallurgical process could enable continuous release of trace amount of Cu2+ ions, which play the key role to offer the multi-biofunctions of the stainless steel, including the osteogenic ability in the present study. The results of in vitro experiments clearly demonstrated that Cu2+ ions from Cu-SS could promote the osteogenic differentiation by stimulating the Alkaline phosphatase enzyme activity and the osteogenic gene expressions (Col1a1, Opn, and Runx2), and enhancing the adhesion and proliferation of osteoblasts cultured on its surface. The in vivo test further proved that more new bone tissue formed around the Cu-SS implant with more stable bone-to-implant contact in comparison with the 317L SS. In addition, Cu-SS showed satisfied biocompatibility according to the results of in vitro cytotoxicity and in vivo histocompatibility, and its daily released amount of Cu2+ ions in physiological saline solution was at trace level of ppb order (1.4 ppb/cm2), which is rather safe to human health. Apart from these results, it was also found that Cu-SS could inhibit the happening of inflammation with lower TNF-α expression in the bone tissue post implantation compared with 317L SS. In addition to good biocompatibility, the overall findings demonstrated that the Cu-SS possessed obvious ability of promoting osteogenesis, indicating a unique application advantage in orthopedics. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1433–1444, 2015.
Co-reporter:Xian-Bo Shi;Wei Yan;Wei Wang;Lian-Yu Zhao
Acta Metallurgica Sinica (English Letters) 2015 Volume 28( Issue 7) pp:799-808
Publication Date(Web):2015 July
DOI:10.1007/s40195-015-0257-1
In this study, hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSC) behaviors of high-strength pipeline steels in four different strength grades (X70, X80, X90 and X100) with the microstructure of acicular ferrite were estimated. The results showed that both of X70 and X80 steels exhibited better HIC resistance, and their susceptibility to HIC increased with the strength grade. HIC parameters, including cracking length ratio, cracking thickness ratio (CTR) and cracking sensitivity ratio, were all increased, and among these, the CTR increased most, with the increase in the strength grade. HIC was found to initiate and grow along the hard boundaries such as large size martensite/austenite (M/A) islands and bainitic ferrite. In addition, the density of hydrogen-induced blister on the steel surface was increased with the decrease in pH value for the same-grade pipeline steels. SSC susceptibilities of X80, X90 and X90-C were revealed to subsequently decrease, which was related to the large size M/A islands.
Co-reporter:Lili Tan, Qiang Wang, Xiao Lin, Peng Wan, Guangdao Zhang, Qiang Zhang, Ke Yang
Acta Biomaterialia 2014 Volume 10(Issue 5) pp:2333-2340
Publication Date(Web):May 2014
DOI:10.1016/j.actbio.2013.12.020
Abstract
In this study the loss of mechanical properties and the interface strength of coated AZ31B magnesium alloy (a magnesium–aluminum alloy) screws with surrounding host tissues were investigated and compared with non-coated AZ31B, degradable polymer and biostable titanium alloy screws in a rabbit animal model after 1, 4, 12 and 21 weeks of implantation. The interface strength was evaluated in terms of the extraction torque required to back out the screws. The loss of mechanical properties over time was indicated by one-point bending load loss of the screws after these were extracted at different times. AZ31B samples with a silicon-containing coating had a decreased degradation rate and improved biological properties. The extraction torque of Ti6Al4V, poly-l-lactide (PLLA) and coated AZ31B increased significantly from 1 week to 4 weeks post-implantation, indicating a rapid osteosynthesis process over 3 weeks. The extraction torque of coated AZ31B increased with implantation time, and was higher than that of PLLA after 4 weeks of implantation, equalling that of Ti6Al4V at 12 weeks and was higher at 21 weeks. The bending loads of non-coated AZ31B and PLLA screws degraded sharply after implantation, and that of coated AZ31B degraded more slowly. The biodegradation mechanism, the coating to control the degradation rate and the bioactivity of magnesium alloys influencing the mechanical properties loss over time and bone–implant interface strength are discussed in this study and it is concluded that a suitable degradation rate will result in an improvement in the mechanical performance of magnesium alloys, making them more suitable for clinical application.
Co-reporter:Xiao Lin, Xiaoming Yang, Lili Tan, Mei Li, Xin Wang, Yu Zhang, Ke Yang, Zhuangqi Hu, Jianhong Qiu
Applied Surface Science 2014 Volume 288() pp:718-726
Publication Date(Web):1 January 2014
DOI:10.1016/j.apsusc.2013.10.113
Highlights
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Strontium element was incorporated into the phosphate MAO coatings.
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The degradation of MAO coating was accompanied with the CaP deposition.
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A degradation model of the phosphate MAO coating was proposed.
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The biocompatibility/bioactivity was enhanced by the incorporation of strontium.
Co-reporter:Ling Ren, Zheng Ma, Mei Li, Yu Zhang, Weiqiang Liu, Zhenhua Liao, Ke Yang
Journal of Materials Science & Technology 2014 Volume 30(Issue 7) pp:699-705
Publication Date(Web):July 2014
DOI:10.1016/j.jmst.2013.12.014
Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti–6Al–4V–xCu (x = 1, 3, 5 wt%), were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element. The metallography, X-ray diffraction, antibacterial ability, corrosion resistance and cytotoxicity of Ti–6Al–4V–xCu alloys were preliminarily studied with comparison to the commercial medical Ti–6Al–4V alloy. The Ti–6Al–4V–xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility, and the antibacterial role was enhanced with increasing Cu content, which has significant potential for clinical applications as surgical implant materials.
Co-reporter:Mei Li, Ling Ren, LiHua Li, Peng He, GuoBo Lan, Yu Zhang, Ke Yang
Journal of Materials Science & Technology 2014 Volume 30(Issue 9) pp:888-893
Publication Date(Web):September 2014
DOI:10.1016/j.jmst.2014.04.010
Biocompatible and biodegradable magnesium (Mg) based metals have attracted great interest for use in orthopedic implants and devices. Based on our previous study that Mg with and without micro-arc oxidation (MAO) coating showed obvious cytotoxic effect on tumor cells due to the increase of pH value during the degradation of Mg, this study further evaluated the cytotoxic effect of Mg and MAO coated Mg on osteosarcoma (MG-63) cells by analyzing the cell adhesion, morphology and number through observation of scanning electron microscope, as well as live/dead staining, lactate dehydrogenase (LDH) activity and 4, 6-diamidino-2-phenylindole (DAPI) assay. The results indicated that, compared to titanium, Mg could strongly inhibit the cell adherence, morphology and number of MG-63 on the surface of the naked Mg, whereas the MAO coated Mg showed relative weak cytotoxic effect on MG-63 cells, expecting that magnesium based metals with suitable coating can be designed to be applied as tumor prosthesis in the clinical practice.
Co-reporter:Junlei Li, Feng Zheng, Xun Qiu, Peng Wan, Lili Tan, Ke Yang
Materials Science and Engineering: C 2014 Volume 42() pp:705-714
Publication Date(Web):1 September 2014
DOI:10.1016/j.msec.2014.05.078
•A 3D FEA model of MAS model was proposed.•The strain can be decreased by adding a peak-to-valley unit to the stent.•The mechanical behavior of the stent can be optimized by the gradual strut.•The annealing technology helps to decrease the residual stress of the stent.•Experiments were carried out for a preliminary validation of the simulation.Stents made of biodegradable magnesium alloys are expected to provide a temporary opening into a narrowed arterial vessel until it remodels and will progressively disappear thereafter. Inferior mechanical properties and fast corrosion of the magnesium alloys are the two crucial factors that impede the clinical application of the magnesium alloy stents (MAS). In the present study, gradual strut width, addition of the peak-to-valley unit and introduction of the annealing technology were designed and investigated by finite element analysis in order to improve the performance of the MAS. Two experiments were carried out for a preliminary validation of the simulation.
Co-reporter:Chen Liu, Huazhe Yang, Peng Wan, Kehong Wang, Lili Tan, Ke Yang
Materials Science and Engineering: C 2014 Volume 35() pp:1-7
Publication Date(Web):1 February 2014
DOI:10.1016/j.msec.2013.10.020
•Degradation of Mg17Al12 was investigated via experiment and calculations.•Normal and inflammatory response environment were simulated with different pH.•Degradation mechanism of Mg17Al12 second phase and magnesium matrix was discussed.The in vitro biodegradation behavior of Mg17Al12 as a second phase in Mg–Al–Zn alloys was investigated via electrochemical measurement and immersion test. The Hank's solutions with neutral and acidic pH values were adopted as electrolytes to simulate the in vivo environment during normal and inflammatory response process. Furthermore, the local orbital density functional theory approach was employed to study the thermodynamical stability of Mg17Al12 phase. All the results proved the occurrence of pitting corrosion process with crackings for Mg17Al12 phase in Hank's solution, but with a much lower degradation rate compared with both AZ31 alloy and pure magnesium. Furthermore, a preliminary explanation on the biodegradation behaviors of Mg17Al12 phase was proposed.
Co-reporter:Wen Feng Zhang, Wei Sha, Wei Yan, Wei Wang, Yi Yin Shan, Ke Yang
Materials Science and Engineering: A 2014 Volume 604() pp:207-214
Publication Date(Web):16 May 2014
DOI:10.1016/j.msea.2014.02.050
Hot compression tests were carried out on 9Cr–Nb–V heat resistant steels in the temperature range of 600–1200 °C and the strain rate range of 10−2–100 s−1 to study their deformation characteristics. The full recrystallization temperature and the carbon-free bainite phase transformation temperature were determined by the slope-change points in the curve of mean flow stress versus the inverse of temperature. The parameters of the constitutive equation for the experimental steels were calculated, including the stress exponent and the activation energy. The lower carbon content in steel would increase the fraction of precipitates by increasing the volume of dynamic strain-induced (DSIT) ferrite during deformation. The ln(εc) versus ln(Z) and the ln(σc) versus ln(Z) plots for both steels have similar trends. The efficiency of power dissipation maps with instability maps merged together show excellent workability from the strain of 0.05 to 0.6. The microstructure of the experimental steels was fully recrystallized upon deformation at low Z value owing to the dynamic recrystallization (DRX), and exhibited a necklace structure under the condition of 1050 °C/0.1 s−1 due to the suppression of the secondary flow of DRX. However, there were barely any DRX grains but elongated pancake grains under the condition of 1000 °C/1 s−1 because of the suppression of the metadynamic recrystallization (MDRX).
Co-reporter:Wen-Feng Zhang, Xiao-Li Li, Wei Sha, Wei Yan, Wei Wang, Yi-Yin Shan, Ke Yang
Materials Science and Engineering: A 2014 590() pp: 199-208
Publication Date(Web):
DOI:10.1016/j.msea.2013.10.020
Co-reporter:Xue Hu, Lixin Huang, Wei Yan, Wei Wang, Wei Sha, Yiyin Shan, Ke Yang
Materials Science and Engineering: A 2014 Volume 607() pp:356-359
Publication Date(Web):23 June 2014
DOI:10.1016/j.msea.2014.04.005
In the process of room-temperature low cycle fatigue, the China Low Activation Martensitic steel exhibits at the beginning cyclic hardening and then continuous cyclic softening. The grain size decreased and the martensitic lath transformed to cells/subgrains after the tests. The subgrains increase in size with increasing strain amplitude.
Co-reporter:Xue Hu, Lixin Huang, Wei Yan, Wei Wang, Wei Sha, Yiyin Shan, Ke Yang
Materials Science and Engineering: A 2014 613() pp: 404-413
Publication Date(Web):
DOI:10.1016/j.msea.2014.06.069
Co-reporter:Lixin Huang, Xue Hu, Wei Yan, Wei Sha, Furen Xiao, Yiyin Shan, Ke Yang
Materials & Design 2014 63() pp: 333-335
Publication Date(Web):
DOI:10.1016/j.matdes.2014.06.028
Co-reporter:Lin Zhu, Peng Wan, Jiaohong Duan, Lili Tan, Ke Yang
Progress in Natural Science: Materials International 2014 Volume 24(Issue 5) pp:441-445
Publication Date(Web):October 2014
DOI:10.1016/j.pnsc.2014.09.003
Organisms invading root canal systems result in serious pulpal and periapical disease. To eliminate microorganisms and restrain secondary infections, dental materials with antibacterial properties are urgently needed in endodontics. Magnesium is considered as a promising biodegradable and biocompatible implant material. However, there are barely researches about its application in endodontic therapy. This work investigated the in vitro efficacy of magnesium powder against Enterococcus faecalis and Candida albicans compared with a common disinfectant, calcium hydroxide. With Calcium hydroxide served as a comparison it demonstrated the qualified antibacterial and anti-fungus properties of Mg as root canal disinfectant due to its high alkalinity of degradation, and the antimicrobial efficacy enhanced with the decreasing powder size.
Co-reporter:Yanjin Lu, Peng Wan, Bingchun Zhang, Lili Tan, Ke Yang, Jinxin Lin
Materials Science and Engineering: C 2014 Volume 43() pp:264-271
Publication Date(Web):1 October 2014
DOI:10.1016/j.msec.2014.06.039
•Double-layer Ca–P coating was successfully fabricated on AZ31 alloy by chemical deposition.•Effect of processing temperatures on coating formation and performance was studied.•The coating obtained at 70 °C showed better corrosion resistance by electrochemical and immersion tests.•The formation mechanism of dual-layer coating influenced by deposition temperature was proposed.In this study, the effect of varied processing temperatures on the corrosion resistance and formation of dual-layer calcium phosphate coating on AZ31 was investigated. The microstructure, phase and morphology were characterized by a scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometer (XRD), respectively. The in vitro degradation behavior of coated AZ31 samples were evaluated by electrochemical and immersion tests in simulated body fluid. The results showed that the varied processing temperatures responded to different microstructure, phase and morphology; and a dual-layer coating was formed during the deposition process at 70 °C. Meanwhile the higher processing temperature induced a faster coating formation rate and greater surface coverage. The in vitro degradation tests in simulated body fluid indicated that the corrosion rates of AZ31 alloy were effectively decreased with increasing processing temperature, which was attributed to the denser protective coating. The formation mechanism of dual-layer coating influenced by deposition temperature was proposed.
Co-reporter:Xiao Lin, Lili Tan, Qiang Zhang, Ke Yang, Zhuangqi Hu, Jianhong Qiu, Yong Cai
Acta Biomaterialia 2013 Volume 9(Issue 10) pp:8631-8642
Publication Date(Web):November 2013
DOI:10.1016/j.actbio.2012.12.016
Abstract
Magnesium has attracted much attention as a class of biodegradable metallic biomaterials. In this study, a silicate electrolyte-based micro-arc oxidation (MAO) treatment was adopted to prepare forsterite-containing MAO coatings on a ZK60 magnesium alloy in order to decrease the degradation rate and increase the biological property of the alloy. Four anodization voltages were chosen to prepare the MAO coatings. The cell experiment showed a cytotoxicity of grade 0 for the MAO-coated alloy to L929 cells and the hemolytic ratio was dramatically decreased for the MAO-coated alloy compared with the bare one. The corrosion resistance and the degradation behavior of the MAO-coated ZK60 alloy were studied using drop tests, electrochemical measurements and immersion tests. The results indicate that the MAO coating could effectively decrease the initial degradation rate of the alloy. The corrosion resistance of MAO coating was increased with the elevation of the preparation voltage. A degradation model for ZK60 alloy with a forsterite-containing MAO coating was proposed. Based on the model, the MAO-coated alloy experiences destruction and restoration simultaneously, and the coating fails in a peeling-off mode.
Co-reporter:Lili Tan, Xiaoming Yu, Peng Wan, Ke Yang
Journal of Materials Science & Technology 2013 Volume 29(Issue 6) pp:503-513
Publication Date(Web):June 2013
DOI:10.1016/j.jmst.2013.03.002
With attractive research and development of biomaterials, more and more opportunities have been brought to the treatments of human tissue repairs. The implant is usually no need to exist in the body accompanied with the recovery or regeneration of the tissue lesions, and the long-term effect of exotic substance to human body should be reduced as lower as possible. For this purpose, biodegradable materials, including polymers, magnesium alloys and ceramics, have attracted much attention for medical applications due to their biodegradable characters in body environment. This paper in turn introduces these three different types of widely studied biodegradable materials as well as their advantages as implants in applications for bone repairs. Relevant history and research progresses are summarized.
Co-reporter:Ling Ren, Ke Yang
Journal of Materials Science & Technology 2013 Volume 29(Issue 11) pp:1005-1010
Publication Date(Web):November 2013
DOI:10.1016/j.jmst.2013.09.008
A new concept for development of metallic biomaterials is proposed in this article, i.e., a certain bio-function can be realized for a metal implant through continuous release of a designed bio-functional metal element from surface of the metal implant in the body environment. This creative idea has been verified to be possible by several different in vitro and in vivo experimental evidences on the Cu-bearing stainless steels and magnesium based metals. It was indicated that a trace amount of Cu release from the Cu-bearing steels could have obvious bio-functions of reduction of the in-stent restenosis (ISR), anti-bacterial infection, inhibiting the inflammatory cells and even promoting the early osteogenesis. Furthermore, the degradation of magnesium based metals in bones could promote the new bone formation, enhance the bone mineral density for the osteoporosis modeled animal, and even have strong anti-bacterial ability and strong cytotoxicity to bone tumor cells due to the enhancement of pH. Special bio-function with satisfied load-bearing capacity for metallic biomaterials will bring higher application values for the implant made of this novel material. This is an attractive direction for research and development with many challenges, but the final success will be much beneficial to the majority of patients.
Co-reporter:Xiao Lin, Lili Tan, Qiang Wang, Guangdao Zhang, Bingchun Zhang, Ke Yang
Materials Science and Engineering: C 2013 Volume 33(Issue 7) pp:3881-3888
Publication Date(Web):October 2013
DOI:10.1016/j.msec.2013.05.023
•Both the bare and MAO-coated ZK60 alloy degraded completely within 12 weeks.•The initial degradation rate of ZK60 alloy was decreased by the MAO coating.•The initial surrounding tissue response was enhanced by the MAO coating.•Undesired degradation acceleration of the MAO-coated sample was found.•Gas cavities around the implants disappeared at 12 weeks of implantation.Magnesium alloys were studied extensively as a class of biodegradable metallic materials for medical applications. In the present study, ZK60 magnesium alloy was considered as a candidate and the micro-arc oxidation (MAO) treatment was adopted in order to reduce the degradation rate of the alloy. The in vivo degradation behaviors and biological compatibilities of ZK60 alloys with and without MAO treatment were studied with a transcortical model in rabbits. The implant and the surrounding bone tissues were characterized by CT, SEM and histological methods at 2, 4 and 12 weeks after the implantation. The results demonstrated that both the bare and MAO-coated ZK60 alloys completely degraded within 12 weeks in this animal model. The MAO coating decreased the degradation rate of ZK60 alloy and enhanced the response of the surrounding tissues within the first 2 weeks. After then, an acceleration of the degradation of the MAO-coated ZK60 alloy was observed. It was found that the alloy could be degraded before the complete degradation of the MAO coating, leading to the local peeling off of the coating. An in vivo degradation mechanism of the MAO-coated ZK60 alloy was proposed based on the experimental results. The severe localized degradation caused by the peeling off of the MAO coating was the main reason for the acceleration of the degradation of the MAO-coated ZK60 alloy.
Co-reporter:Xiaoming Yang, Mei Li, Xiao Lin, Lili Tan, Guobo Lan, Lihua Li, Qingshui Yin, Hong Xia, Yu Zhang, Ke Yang
Surface and Coatings Technology 2013 Volume 233() pp:65-73
Publication Date(Web):25 October 2013
DOI:10.1016/j.surfcoat.2013.01.052
There is a great attraction to apply magnesium alloy as an orthopedic implant material due to its biodegradable feature and suitable mechanical properties. In order to further improve the biocompatibility of magnesium alloy, a Mg2SiO4-containing micro-arc oxidation (MAO) coating was generated on ZK60 magnesium alloy, in this study. The surface characterization by SEM, XRD and EDS showed that a rough and porous reaction layer with major composition of O, Mg and Si was formed on the surface of ZK60 alloy. The result of polarization test showed that the MAO coating significantly enhanced the corrosion resistance of biodegradable ZK60 alloy. In vitro biocompatibility/bioactivity evaluation of the MAO-coated alloy compared with the naked alloy was performed using murine bone marrow stem cells (BMSCs). The results revealed that the extract of MAO-coated alloy had no obvious cytotoxicity during the 5 days culturing, and the surface of MAO coating exhibited a better cell adhesion and affinity. Alkaline phosphatase (ALP) activity assay demonstrated that the ALP level of the BMSCs in the extract of MAO-coated alloy was much higher than that of the naked alloy, indicating that the release of Mg and Si ions from the coating was beneficial for the differentiation of BMSCs. Result of blood hemolysis test showed that the MAO coating group had a drastically decreased hemolytic ratio (1.04%) compared with the naked alloy group (28.78%) (p < 0.01), meaning a great improvement of hemocompatibility. In conclusion, the results of this study suggested that the Mg2SiO4-containing MAO coating is an effective way to improve the biocompatibility/bioactivity of magnesium alloys.Highlights► A rough and porous micro-arc oxidation (MAO) coating was generated on ZK60 alloy. ► The MAO-coated ZK60 alloy exhibited a great improvement of biocompatibility. ► The MAO-coated ZK60 alloy showed an enhancement of bioactivity.
Co-reporter:Jinhao Zeng;Ling Ren;Yajiang Yuan
Journal of Materials Science: Materials in Medicine 2013 Volume 24( Issue 10) pp:2405-2416
Publication Date(Web):2013 October
DOI:10.1007/s10856-013-4982-6
Pure magnesium (Mg) granules were implanted into the tibial medullary cavity of osteomyelitis modeled animals after debridement, and the animals without implant were taken as the control group. The antibacterial and osteogenic effects on bone tissue during Mg degradation were evaluated through detecting Mg ions, counting bacteria culture in peripheral blood, histology and iconography. The results showed that there was no significant difference for the concentration of serum Mg between the preoperative and postoperative animals within 5 weeks, maintaining in the normal range, and the number of bacteria in bone tissue of the Mg implant group was significantly lower than that of the control group. Mg implantation showed good biocompatibility no harmful to the liver, spleen, kidney and other organs in the modeled animals. In addition, the formation rate of new bone tissues around the implanted Mg was faster, indicating that the degradation of Mg could also promote the osteogenic process with good biocompatibility.
Co-reporter:Jingyao Wu;Xi Lu;Lili Tan;Bingchun Zhang
Journal of Biomedical Materials Research Part B: Applied Biomaterials 2013 Volume 101( Issue 7) pp:1222-1232
Publication Date(Web):
DOI:10.1002/jbm.b.32934
For biodegradable iron coronary stents, the major problem is the low degradation rate in body environment. In this study, a new strategy was proposed to increase the degradation rate of iron in vitro. The hydrion evolution was intended to be introduced into the degradation system to increase the degradation rate. To realize this strategy, polylactic-co-glycolic acid (PLGA) was coated onto the surface of pure iron. The degradation process and mechanism of pure iron coated with PLGA were investigated. The results showed that iron coated with PLGA exhibited higher degradation rate in the static immersion test all along. With the degradation of PLGA, the oligomers of PLGA could release abundant H+ which could dissolve the ferrous oxide to make the electrolyte and oxygen to reach the surface of iron again and simultaneity trigger the hydrion evolution at the middle stage of the degradation. The study also revealed that the solution ions failed to permeate the PLGA coating and the deposition of calcium and phosphorus in the degradation layer was inhibited which further enhanced the degradation. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1222–1232, 2013.
Co-reporter:Yanjin Lu, Lili Tan, Hongliang Xiang, Bingchun Zhang, Ke Yang, Yangde Li
Journal of Materials Science & Technology 2012 Volume 28(Issue 7) pp:636-641
Publication Date(Web):July 2012
DOI:10.1016/S1005-0302(12)60109-1
Co-reporter:Li Nan, Jinglong Cheng, Ke Yang
Journal of Materials Science & Technology 2012 Volume 28(Issue 11) pp:1067-1070
Publication Date(Web):November 2012
DOI:10.1016/S1005-0302(12)60174-1
Co-reporter:Yu Zhang, Ling Ren, Mei Li, Xiao Lin, Huafu Zhao, Ke Yang
Journal of Materials Science & Technology 2012 Volume 28(Issue 9) pp:769-772
Publication Date(Web):September 2012
DOI:10.1016/S1005-0302(12)60128-5
Co-reporter:Y.X. Chen, W. Yan, W. Wang, Y.Y. Shan, K. Yang
Materials Science and Engineering: A 2012 Volume 534() pp:649-653
Publication Date(Web):1 February 2012
DOI:10.1016/j.msea.2011.12.022
This study addresses the overestimation of the time–temperature-parameter (TTP) method on the allowable creep strength of 9–12% Cr heat resistant steels. Creep data of 9% Cr heat resistant steels are divided into several data sets according to the creep controlling mechanism. Constitutive equations of the minimum creep rate ε˙m depending on applied stress σ and temperature T have been constructed, and the modeling results are found to be well in agreement with the experimental data. The influence of the second phase particles in the power-law-breakdown (PLB) region on 9% Cr heat resistant steels is well reflected by introducing a parameter, σ0, into the equation. Furthermore, the construction of constitutive equations of ε˙m from the PLB region to the power-law (PL) region for 9% Cr heat resistant steels has been shown to be feasible.Highlights► Constitutive equations of the minimum creep rate have been constructed. ► Creep data are divided according to the creep controlling mechanism. ► The influence of the second phase particles is emphasized. ► The influence of the second phase particles is well reflected. ► Constitutive equations from the PLB region to the PL region should be feasible.
Co-reporter:Ling Ren, Ke Yang, Lei Guo, Hong-wei Chai
Materials Science and Engineering: C 2012 Volume 32(Issue 5) pp:1204-1209
Publication Date(Web):1 July 2012
DOI:10.1016/j.msec.2012.03.009
In this study the copper (Cu)-bearing stainless steel was developed to reduce the incidence of implant-associated infections in clinical areas. A 317L austenitic stainless steel containing 4.5% Cu (317L-Cu SS) was designed and fabricated, and its anti-infective function was preliminarily studied both in vitro and in vivo by means of antibacterial test, confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM) observations, and animal implantation. The results indicated that the 317L-Cu SS possessed strong antibacterial rates against both Escherichia coli and Staphylococcus aureus, and showed anti-infective ability by inhibiting the formation of bacterial bio-film on surface of the steel due to the release of Cu ions from the steel surface. The microbiological and histological evaluations from animal implantation further proved that the 317L-Cu SS could obviously reduce the happening of bacterial infection, and is potential to be used as a new class of surgical implant material with anti-infective function.Highlights► 317L stainless steel containing 4.5% Cu (317L-Cu SS) showed strong antibacterial role. ► 317L-Cu SS could inhibit the formation of bacterial bio-film on its surface. ► 317L-Cu SS showed anti-infective role in vivo.
Co-reporter:Ke Yang;YiBin Ren;Peng Wan
Science China Technological Sciences 2012 Volume 55( Issue 2) pp:329-340
Publication Date(Web):2012 February
DOI:10.1007/s11431-011-4679-3
Currently commercialized coronary stents are mainly made of the medical 316L stainless steel and cobalt-based alloy (L605) due to their good combination of properties, especially excellent mechanical properties. However, the presence of high quantity of nickel and/or cobalt elements, the agents known to trigger the toxic and allergic responses, in these materials has caused many clinic concerns. The potential adverse effect of nickel ions release has prompted the development of high nitrogen nickelfree austenitic stainless steels for medical application. Nitrogen in steel is not only to replace the nickel but also improve the properties of steel. In this paper, the harmfulness and release of nickel from metallic stents, and the advantages in mechanical properties and hemocompatibility of high nitrogen nickel-free stainless steels for coronary stents are reviewed. Apart from the highlight of nickel-free, the superiority of high strength and better hemocompatibility of high nitrogen nickel-free stainless steels can guarantee to manufacture thinner strut coronary stents with remarkable anticoagulation ability. High nitrogen nickelfree stainless steels as a promising coronary stents material will attract more and more clinical doctors and stents makers to bring them into clinical application.
Co-reporter:Ling Ren;Lu Xu;Jingwen Feng;Yang Zhang
Journal of Materials Science: Materials in Medicine 2012 Volume 23( Issue 5) pp:1235-1245
Publication Date(Web):2012 May
DOI:10.1007/s10856-012-4584-8
A novel 316L type Cu-bearing stainless steel was developed in present work, aiming at reducing the occurrence of the in-stent restenosis after implantations of coronary stents, through trace amount of Cu release from surface of the steel in body fluid. It was found that there was a trace amount of Cu released from the Cu-bearing steel in a simulated body fluid, with no cytotoxicity. All the in vitro experimental results proved that this Cu-bearing steel could not only inhibit the proliferation of vascular smooth muscle cells, reducing the formation of thrombosis, which are the main reasons for happening of the in-stent restenosis, but also promote the proliferation of vascular endothelial cells needed for the revascularization, showing that this novel steel is prospective to be a new material for manufacturing coronary stents with function of reducing the in-stent restenosis.
Co-reporter:Ling Ren, Li Nan, Ke Yang
Materials & Design (1980-2015) 2011 Volume 32(Issue 4) pp:2374-2379
Publication Date(Web):April 2011
DOI:10.1016/j.matdes.2010.11.030
Copper (Cu) precipitation behavior in a type 304 Cu-bearing austenitic antibacterial stainless steel was studied by analyses of variations in micro-hardness, electrical resistivity, electrochemical impedance and lattice constant of the steel, complemented with transmission electron microscopy (TEM) observation, showing more or less changes on these properties of the steel with different aging time. It was found that both micro-hardness and electrical resistivity measurements were relatively sensitive and accurate to reflect the Cu precipitation behavior in the experimental steel, indicating the beginning and finishing points of the precipitation, which are more simple and effective to be used for development of the new type of antibacterial stainless steels.
Co-reporter:Ling Ren, Jinming Zhu, Li Nan, Ke Yang
Materials & Design 2011 Volume 32(Issue 7) pp:3980-3985
Publication Date(Web):August 2011
DOI:10.1016/j.matdes.2011.03.068
The Cu precipitation in a high Cu austenitic antibacterial stainless steel (3.8–5.0% Cu) was studied by using differential scanning calorimetry (DSC) analysis. The results indicated that DSC analysis could be used to detect the Cu precipitation in the experimental steel with different Cu additions. Two stages of precipitation were identified in the steel by DSC analysis, clustering of Cu-rich phases and dissolution/coarsening of the precipitates formed at the first stage. DSC analyses also showed that with increase of the Cu content in the steel, the start temperature of Cu precipitation was decreased and the peak area of Cu precipitation was enlarged. The activation energy for Cu precipitation in the steel was determined to be 181 kJ/mol, indicating that the process should be mainly related to the diffusion of Cu atoms in the steel.Highlights► Cu precipitation in the Cu-bearing stainless steel could be detected by DSC analysis. ► Two stages of Cu precipitation in the steel were identified by DSC analysis. ►The activation energy of Cu precipitation in steel was determined to be 181 kJ/mol.
Co-reporter:Ling Ren, Xiao Lin, Lili Tan, Ke Yang
Materials Letters 2011 Volume 65(23–24) pp:3509-3511
Publication Date(Web):December 2011
DOI:10.1016/j.matlet.2011.07.109
Antibacterial behaviors of magnesium (Mg) based metal, pure Mg and AZ31 alloy, with and without surface coatings were studied. The results indicated that both pure Mg and AZ31 alloy had strong antibacterial effect against Escherichia coli and Staphylococcus aureus with rapid increases of pH values of the bacterial suspensions. Pure Mg with porous silicon-contained (Si) coating by micro-arc oxidation still maintained its antibacterial ability while with a mild increase of the pH value. However, pure Mg and AZ31 alloy with fluorine-contained (F) and Si coatings by chemical conversion, respectively, lost their antibacterial abilities with nearly no change of the pH values, owing to the much dense coatings on surfaces.Highlights► Mg based metals, pure Mg and its alloys possess antibacterial functions. ► Antibacterial functions of Mg based metals are related to the increase of pH. ► Surface coating on Mg based metals can affect their antibacterial abilities. ► Loose and porous coating on Mg could maintain its antibacterial ability. ► Dense coating on Mg and its alloy could lose its antibacterial ability.
Co-reporter:Qiang Wang, Lili Tan, Wenli Xu, Bingchun Zhang, Ke Yang
Materials Science and Engineering: B 2011 Volume 176(Issue 20) pp:1718-1726
Publication Date(Web):15 December 2011
DOI:10.1016/j.mseb.2011.06.005
Surface modification can be an effective way to control the biodegradation behavior of magnesium alloys and even improve their biological properties. Much attention has been paid to the initial protection ability and biological properties of magnesium alloys coating. In this work, the dynamic behaviors of a Ca–P coated AZ31B magnesium alloy during the degradations in vitro and in vivo, including hemolysis, mechanical loading capability and implantation in animals, were investigated. The hemolytic rates of the alloy with and without coating were all declined to be lower than 5% after more than 20 days immersion in PBS, though an increase happened to the alloy at the early immersion of 3–7 days. Reduction of the mechanical loading capacity was gradually evolved for the coated alloy and the peak load retention of 85% was still maintained after 120 days degradation. The in vivo implantation indicated that the Ca–P coated AZ31B alloy showed a more suitable time dependent degradation behavior which was favorable for growth of the new tissue and the healing dynamics of bones, making it a promising choice for medical application.
Co-reporter:Li Nan, Ke Yang
Journal of Materials Science & Technology 2010 Volume 26(Issue 10) pp:941-944
Publication Date(Web):2010
DOI:10.1016/S1005-0302(10)60152-1
Co-reporter:Wei Wang;Wei Yan;Yiyin Shan
Journal of Materials Engineering and Performance 2010 Volume 19( Issue 8) pp:1214-1219
Publication Date(Web):2010 November
DOI:10.1007/s11665-010-9603-7
The temperature dependence of tensile behaviors of two nitrogen-alloyed austenitic stainless steels, an annealed 316LN steel and a high-nitrogen austenitic stainless steel (Fe-Cr-Mn-0.66% N), was investigated by tensile test at different temperatures from 293 K down to 77 K. It was found that strength of the two steels increased with decrease of temperature. With a decrease in temperature, the uniform elongation increased for the 316LN steel, whereas it increased followed by a decrease for the high-nitrogen steel. A three-stage hardening behavior occurred in the 316LN steel, but not in the high-nitrogen steel, with decrease of temperature. The strain-induced martensite transformation in the 316LN steel could retard void nucleation and increase the strain-hardening rate, resulting in much higher tensile stress and higher uniform elongation of 316LN steel. It was analyzed that stacking fault energy of the high-nitrogen steel decreased with decrease of temperature, which promoted the twinning and planar slipping in the steel, and resulted in brittle fracture at cryogenic temperatures.
Co-reporter:Wei Wang, Wei Yan, Qiqiang Duan, Yiyin Shan, Zhefeng Zhang, Ke Yang
Materials Science and Engineering: A 2010 527(13–14) pp: 3057-3063
Publication Date(Web):
DOI:10.1016/j.msea.2010.02.002
Co-reporter:Wei Wang, Songtao Wang, Ke Yang, Yiyin Shan
Materials & Design (1980-2015) 2009 Volume 30(Issue 5) pp:1822-1824
Publication Date(Web):May 2009
DOI:10.1016/j.matdes.2008.08.009
Temperature dependence of tensile behavior of a high nitrogen Fe–Cr–Mn–Mo stainless steel with nitrogen content of 0.66% was investigated. It was found that strength of the steel increased with decrease of temperature, and the deformation microstructure of the steel which determines the strain-hardening behavior was strongly dependent on temperature. It was analyzed that stacking fault energy (SFE) of the steel decreased with decrease of temperature, which promoted the twinning and planar slipping in the steel, and thus made brittle fracture to occur at cryogenic temperature.
Co-reporter:F. Geng;L. L. Tan;X. X. Jin;J. Y. Yang
Journal of Materials Science: Materials in Medicine 2009 Volume 20( Issue 5) pp:1149-1157
Publication Date(Web):2009 May
DOI:10.1007/s10856-008-3669-x
Biodegradable and bioactive β-tricalcium phosphate (β-TCP) coatings were prepared on magnesium (Mg) in order to improve its biocompatibility by a chemical method. The tensile bonding strength of β-TCP coating and Mg substrate was measured by the standard adhesion test (ISO 13779-4). And the cytocompatibility of β-TCP coated Mg was studied by using human osteoblast-like MG63 cells. It was found that the MG63 cells could grow well on the surface of β-TCP coated Mg and the cell viability on β-TCP coated Mg was above 80% during the cocultivation of MG63 cells and β-TCP coated Mg for 10 days, indicating no cytotoxicity. It was concluded that the β-TCP coated Mg had good cytocompatibility. The degradation of Mg substrate with β-TCP coating in vitro was studied in detail by XRD, EDX, SEM, and ICP. The results showed that a bone-like apatite continually formed on the surface of the sample with the degradation of both Mg substrate and β-TCP coating in Hank’s solution (a simulated body fluid). The biodegradation mechanism was preliminarily analyzed in the paper.
Co-reporter:Yang Li, Lina Liu, Peng Wan, Zanjing Zhai, Zhenyang Mao, Zhengxiao Ouyang, Degang Yu, Qi Sun, Lili Tan, Ling Ren, Zhenan Zhu, Yongqiang Hao, Xinhua Qu, Ke Yang, Kerong Dai
Biomaterials (November 2016) Volume 106() pp:250-263
Publication Date(Web):November 2016
DOI:10.1016/j.biomaterials.2016.08.031
Co-reporter:Yang Li, Lina Liu, Peng Wan, Zanjing Zhai, Zhenyang Mao, Zhengxiao Ouyang, Degang Yu, Qi Sun, Lili Tan, Ling Ren, Zhenan Zhu, Yongqiang Hao, Xinhua Qu, Ke Yang, Kerong Dai
Biomaterials (November 2016) Volume 106() pp:250-263
Publication Date(Web):November 2016
DOI:10.1016/j.biomaterials.2016.08.031
Treatment of chronic osteomyelitis (bone infection) remains a clinical challenge; in particular, it requires an implantable material with improved antibacterial activity. Here, we prepared biodegradable magnesium (Mg)-copper (Cu) alloys with different Cu contents (0.05, 0.1, and 0.25 wt%) and assessed their potential for treating methicillin-resistant Staphylococcus aureus-induced osteomyelitis. We evaluated the microstructures, mechanical properties, corrosion behavior, and ion release of the alloys in vitro, and their biocompatibility and antibacterial activity in vitro and in vivo. The antibacterial activity of the Mg-Cu alloys in vitro was demonstrated by microbiological counting assays, bacterial viability assays, biofilm formation observations, and the expression of biofilm, virulence, and antibiotic-resistance associated genes. The antibacterial activity of Mg-Cu alloys in vivo was confirmed by imaging examination, microbiological cultures, and histopathology. The biocompatibility of Mg-Cu alloys was confirmed by cell proliferation, vitality, and morphology assays in vitro and Cu2+ or Mg2+ ion assays, blood biochemical tests, and histological evaluation in vivo. The alloy containing 0.25 wt% Cu exhibited the highest antibacterial activity among the tested alloys, with favorable biocompatibility. Collectively, our results indicate the potential utility of Mg-Cu alloy implants with 0.25 wt% Cu in treating orthopedic infections.
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