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Fabrication of Al/Al_2Cu in situ nanocomposite via friction stir processing

Transactions of Nonferrous metals Society of China 2017年第4期27卷 779-788页

作者： m.AZIZIEH D.IRANPARAST m.a.g.dezfuli Z.BALAK H.S.KIm Department of materials Science and Engineering College of Engineering Ahvaz Branch Islamic Azad University Department of materials Science and Engineering Pohang University of Science and Technology (POSTECH)

The aim of present work is fabrication of Al/Al2Cu in situ nanocomposite by friction stir processing(FSP)as well asinvestigation of FPS parameters such as rotational speed,travel speed,number of FSP passes,and pin profile on the microstructure,chemical reaction,and microhardness of Al based *** Al2Cu particles were formed rapidly due to mechanicallyactivated effect of FSP as well as high heat generation due to Al?Cu exothermic *** microstructure of the nanocompositesconsisted of a finer grained aluminium matrix(~15μm),unreacted Cu nanoparticles(~40nm),and reinforcement nanoparticles *** morphology of Al2Cu is attributed to the local melting during *** diameter has a higher effect on themicrostructure and hardness *** hardness measurements exhibited enhancement by57%compared with the base metal.

关键词： friction stir processing composite materials hardness microstructure surface properties

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Influence of HEPES buffer on the local pH and formation of surface layer during in vitro degradation tests of magnesium in DmEm

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Progress in Natural Science:materials International 2014年第5期24卷 531-538页

作者： S.Naddaf dezfuli Zhigang Huan J.m.C.mol m.A.Leeflang Jiang Chang Jie Zhou Department of Biomechanical Engineering Delft University of Technology Biomaterials and Tissue Engineering Research Center Shanghai Institute of Ceramics Chinese Academy of Sciences Department of materials Science and Engineering Delft University of Technology

The human body is a buffered environment where p H is effectively maintained. HEPES is a biological buffer often used to mimic the buffering activity of the body in in vitro studies on the degradation behavior of magnesium. However, the influence of HEPES on the degradation behavior of magnesium in the DmEm pseudo-physiological solution has not yet been determined. The research aimed at elucidating the degradation mechanisms of magnesium in DmEm with and without HEPES. The morphologies and compositions of surface layers formed during in vitro degradation tests for 15–3600 s were characterized. The effect of HEPES on the electrochemical behavior and corrosion tendency was determined by performing electrochemical tests. HEPES indeed retained the local p H, leading to intense intergranular/interparticle corrosion of magnesium made from powder and an increased degradation rate. This was attributed to an interconnected network of cracks formed at the original powder particle boundaries and grain boundaries in the surface layer, which provided pathways for the corrosive medium to interact continuously with the internal surfaces and promoted further dissolution. Surface analysis revealed significantly reduced amounts of precipitated calcium phosphates due to the buffering activity of HEPES so that magnesium became less well protected in the buffered environment.

关键词： magnesium Intergranular corrosion HEPES DmEm Local pH

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Pediatric Supracondylar Humerus Fractures: Are medial Pins Indicated?

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Open Journal of Orthopedics 2014年第5期4卷 123-129页

作者： Bobby dezfuli Christopher Larkins John T. Ruth Lisa m. Truchan Department of Orthopaedic Surgery University of Arizona Medical Center Tucson AZ USA Department of Orthopaedic Surgery University of Texas Health Science Center San Antonio TX USA

Background: Pediatric supracondylar humerus fractures are the most common elbow fractures in children. Operative management includes closed reduction and placement of 2 to 3 laterally based pins. Occasionally, a medial pin is used to create a crossed fixation pattern, despite risk of nearly 10% iatrogenic ulnar nerve injury. The objective of this study was to assess the trends and outcomes in the operative management of pediatric supracondylar humerus fractures at a level one academic trauma center. materials & methods: A retrospective review was performed on all children sustaining a gartland type II or III supracondylar humerus fractures treated by closed or open reduction and percutaneous pinning in 2006-2008 and 2009-2011 at a level one academic trauma center by two of the authors (JTR, LmT). Pin placement patterns were evaluated and compared based on year performed. Outcomes measured were rates of ulnar nerve symptoms, non-union, re-operation, and varus malalignment. Data analysis was performed using a Fisher exact test on STATA software. Results: A total of 49 patients met inclusion criteria. Of 22 patients treated in 2006-2008, 5 (23%) were type II and 17 (77%) were type III. From 2009-2011, 16 (59%) were type II and 11 (41%) were type III. Comparison of pinning pattern in type II fractures between 2006-2008 and 2009-2011 did not indicate statistical significance (p = 0.429). Comparison of pinning pattern in type III fractures during the same time period did show that there was a statistically significant decrease (p = 0.010) in the number of cross pin fixations. There were no ulnar nerve injuries, non-unions, re-operations, or varus malalignment in any patient on final follow-up. Conclusion: This study shows that there has been a significant decrease in cross pin fixation for pediatric type III supracondylar humerus fractures with equivalent clinical outcomes at a Level I trauma center. Furthermore, performing lateral pinning for type III fractures has elimi

关键词： Supracondylar Humerus Fracture Pin Fixation Ulnar Nerve Injury Biomechanical Stability

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