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Gina Allyn, Roy D Bloebaum, Richard T Epperson, Mattias B Nielsen, Kevin A Dodd, Dustin L Williams
The skin/implant interface of osseointegrated (OI) implants is susceptible to infection, causing excess pain, increased morbidity, and possibly implant removal. Novel distal femoral OI implants with binary nitride coatings have been developed with little physiological modeling to collect microbiological evidence of resistance to bacterial attachment. This in vitro study evaluated a Ti-6Al-4V alloy coated with TiNbN and treated with low plasticity burnishing (LPB) to assess attachment and biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA) under physiologically-modeling conditions compared to standard Ti-6Al-4V alloy materials with a polished ("Color Buff") or non-polished finish ("Satin Finish")...
October 20, 2018: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
Xing-Jian Hu, Wen-Cong-Hui Wu, Nian-Guo Dong, Jia-Wei Shi, Jun-Wei Liu, Si Chen, Chen Deng, Feng Shi
A tissue engineering model of heart valve calcification induced in a bioreactor was established to evaluate the calcification induced by abnormal mechanical stimulation and explore the underlying molecular mechanisms. Polyethylene glycol (PEG)-modified decellularized porcine aortic leaflets seeded with human valve interstitial cells (huVICs) were mounted on a Ti-Ni alloy frame to fabricate two-leaflet and threeleaflet tissue engineered valves. The two-leaflet model valves were exposed to abnormal pulsatile flow stimulation with null (group A), low (1000 mL/min, group B), medium (2000 mL/min, group C), and high velocity (3000 mL/min, group D) for 14 days...
October 2018: Current medical science
Yilong Lei, Yanqiu Sun, Yi Zhang, Hongyang Zhang, Haihua Zhang, Zhengong Meng, Wai-Yeung Wong, Jiannian Yao, Hongbing Fu
Integrating together two dissimilar π-conjugated molecules into controlled complex topological configurations remains a largely unsolved problem owing to the diversity of organic species and their respective different assembly features. Here, we find that two structurally similar organic semiconductors, 9,10-bis(phenylethynyl)anthracene (BA) and 5,12-bis(phenylethynyl)naphthacene (BN), co-assemble into two-component helices by control of the growth kinetics as well as the molar ratio of BA/BN. The helical superstructures made of planar and twisted bis(phenylethynyl) derivatives can be regarded as (BA)x (BN)1-x alloys, which are formed due to compatible structural relationship between BA and BN...
October 19, 2018: Nature Communications
Diker Nurettin, Bayram Burak
The objective of this study was to conduct a computer assessment of the biomechanical stability of locking fixation plates of different thicknesses, made of titanium alloy and carbon-fiber- reinforced polyetheretherkotone (CFR-PEEK) in Class III atrophic mandibular fractures. Class III atrophic mandibular models were constructed using three-dimensional finite element models. After simulation of fracture on the left side, plates with different thicknesses (1.0, 1.5, 2.0, and 2.5 mm) were adapted to the models and three locking screws on each side of the fracture were used for fixation...
September 27, 2018: Journal of Cranio-maxillo-facial Surgery
Wenke Wang, Qing Miao, Xuemin Chen, Yang Yu, Wencong Zhang, Wenzhen Chen, Erde Wang
In this work, the influence of various rolling temperatures and thickness reductions on the dynamic recrystallization (DRX) behavior of AZ31 magnesium alloy sheets was investigated. Meanwhile, the texture variation controlled by DRX behavior was analyzed. Results suggested that, with the help of DRX behavior, reasonable matching of rolling temperature and thickness reduction could effectively refine the grain size and improve the microstructure homogeneity. Using the grain refinement and microstructure homogeneity as the reference, the critical rolling process parameters were 400 °C-30%, 300 °C-30%, and 250 °C-40% in the present work...
October 18, 2018: Materials
Henry Proudhon, Nicolas Guéninchault, Samuel Forest, Wolfgang Ludwig
In this paper, we present a comprehensive 4D study of the early stage of plastic deformation in a polycrystalline binary AlLi alloy. The entire microstructure is mapped with X-ray diffraction contrast tomography, and a set of bulk grains is further studied via X-ray topotomography during mechanical loading. The observed contrast is analyzed with respect to the slip system activation, and the evolution of the orientation spread is measured as a function of applied strain. The experimental observations are augmented by the mechanical response predicted by crystal plasticity finite element simulations to analyze the onset of plasticity in detail...
October 18, 2018: Materials
Dezhou Guo, Shuangxi Song, Ruichun Luo, William A Goddard, Mingwei Chen, Kolan Madhav Reddy, Qi An
The recent observation of the reverse Hall-Petch relation in nanocrystalline ceramics offers a possible pathway to achieve enhanced ductility for traditional brittle ceramics via the nanosize effect, just as nanocrystalline metals and alloys. However, the underlying deformation mechanisms of nanocrystalline ceramics have not been well established. Here we combine reactive molecular dynamics (RMD) simulations and experimental transmission electron microscopy to determine the atomic level deformation mechanisms of nanocrystalline boron carbide (B_{4}C)...
October 5, 2018: Physical Review Letters
Xiao-Xiang Yu, Ahmet Gulec, Quentin Sherman, Katie Lutton Cwalina, John R Scully, John H Perepezko, Peter W Voorhees, Laurence D Marks
We report experimental results on the composition and crystallography of oxides formed on NiCrMo alloys during both high-temperature oxidation and aqueous corrosion experiments. Detailed characterization using transmission electron microscopy and diffraction, aberration-corrected chemical analysis, and atom probe tomography shows unexpected combinations of composition and crystallography, far outside thermodynamic solubility limits. The results are explained using a theory for nonequilibrium solute capture that combines thermodynamic, kinetic, and density functional theory analyses...
October 5, 2018: Physical Review Letters
Dor Amram, Christopher A Schuh
Grains in crystalline materials usually grow with increased thermal exposure. Classical phenomena such as recrystallization may lead to a purely temporary decrease in the grain size, while recent advances in alloy design can yield thermally stable nanocrystalline materials in which grain growth stagnates. But grains never shrink, since there is a lack of interface-generating mechanisms at high temperatures, which are required to decrease the grain size if such was the system's thermodynamic tendency. Here we sidestep this paradigm by designing a nanocrystalline alloy having an allotropic phase transformation-an interface-generating mechanism-such that only the high-temperature phase is stabilized against grain growth...
October 5, 2018: Physical Review Letters
Yi Feng, Zhe Li, Hui Liu, Cunku Dong, Jiaqi Wang, Sergei A Kulinich, Xi-Wen Du
Laser ablation in liquid was used to prepare homogenous copper-zinc alloy catalysts that exhibited excellent selectivity for C2H4 in CO2 electro-reduction, with Faradaic efficiency values as high as 33.3% at a potential of -1.1 V (vs. RHE). The high proximity of Cu and Zn atoms on the catalyst's surface was found to facilitate both the stabilization of the CO* intermediate and its transfer from Zn atoms to their Cu neighbors, where further dimerization and protonation occurs to give rise to a large amount of ethylene product...
October 19, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Pedro Filipe Alhais Lopes, Hugo Paisana, Anibal T de Almeida, Carmel Majidi, Mahmoud Tavakoli
We introduce a soft ultrathin and stretchable electronic skin with surface mounted components that can be transferred and wrapped around any 3D surface or self-adhere to human skin. The ~5 µm thick circuit is fabricated by printing the pattern over a temporary tattoo paper using a desktop laser printer, which is then coated with a silver ink and eutectic gallium-indium (EGaIn) liquid metal (LM) alloy. The resulting Ag-In-Ga traces are highly conductive and maintain low electrical resistivity as the circuit is stretched to conform to non-developable 3D surfaces...
October 19, 2018: ACS Applied Materials & Interfaces
Bao Lin, Max Döbeli, Stephen Mudie, Adrian Hawley, Peter Hodgson, Lingxue Kong, Ralph Spolenak, Ludovic F Dumée
The development of non-noble nano-porous metal materials is hindered by surface oxidation reactions and from the difficulty to generate long range order pore arrays. Dealloying is a promising route to generate such materials by selective chemical etching of metal alloy materials. This process can generate nano-metal materials with superior plasmonic, catalytic and adsorptive surface properties. Here, the impact of properties of the etching solution on the dealloying process to generate nano-pores across thin film alloys was investigated by in-situ SAXS dealloying experiments...
October 18, 2018: Scientific Reports
Luigi Manfredi, Alfred Cuschieri
Shape memory alloys (SMAs) are smart materials used in robotics because of its light weight and high force-to-weight ratio. The low energy efficiency, up to 5%, has limited their use for large actuators. However, they have shown advantages in the design of mini-robots because of the limited volume required for the actuation system. The present study reports the design and construction of a mini compliant joint (MCJ) with a 2 degrees of freedom (DOFs) intersecting axis. The MCJ prototype has a 20 mm external diameter surrounding a cavity of 8 mm, weighs 2 g, is 20 mm high and can perform an angle rotation of 30 ∘ in less than 260 ms...
October 17, 2018: Materials
Shuo Wang, Yuhong Zhao, Huijun Guo, Feifei Lan, Hua Hou
In this paper, the mechanical properties and minimum thermal conductivity of ZnZr, Zn₂Zr, Zn₂Zr₃, and MgZn₂ are calculated from first principles. The results show that the considered Zn-Zr intermetallic compounds are effective strengthening phases compared to MgZn₂ based on the calculated elastic constants and polycrystalline bulk modulus B , shear modulus G , and Young's modulus E . Meanwhile, the strong Zn-Zr ionic bondings in ZnZr, Zn₂Zr, and Zn₂Zr₃ alloys lead to the characteristics of a higher modulus but lower ductility than the MgZn₂ alloy...
October 17, 2018: Materials
Yuehua Liu, Hui Wu, Lingwei Ma, Sumeng Zou, Yunhan Ling, Zhengjun Zhang
Silver (Ag) nanostructures have been intensively studied as one of the most promising surface-enhanced Raman scattering (SERS) substrates; however, their practical applications have been limited by the chemical instability with regard to oxidation, sulfuration and etching of Ag. Therefore, designing and fabricating highly active Ag nanostructures with high SERS stability has been recognized as an important research area. Herein, Ag-Ti alloy nanorods (Ag-Ti alloy NRs) are designed and fabricated by the oblique angle deposition (OAD) method to protect Ag...
October 18, 2018: Nanoscale
Jingfeng Guo, Tieshan Cao, Congqian Cheng, Xianming Meng, Jie Zhao
The magnetism and microstructure of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes after 5 years of service were investigated in this paper. The saturation magnetization of the Cr25Ni35Nb alloy tube in the thickness direction is more than 20 emu/g, and the tube becomes ferromagnetic. The inner and outer walls of Cr35Ni45Nb alloy tubes also become ferromagnetic. But the saturation magnetization of the Cr35Ni45Nb alloy tubes approaches to zero in the center zone. The primary carbides M7C3 and NbC are changed into M23C6 and G phase at the outer region of the furnace tube...
October 2018: Microscopy and Microanalysis
Zhiqiang Fu, Lin Jiang, Jenna L Wardini, Benjamin E MacDonald, Haiming Wen, Wei Xiong, Dalong Zhang, Yizhang Zhou, Timothy J Rupert, Weiping Chen, Enrique J Lavernia
High-entropy alloys (HEAs) are a class of metallic materials that have revolutionized alloy design. They are known for their high compressive strengths, often greater than 1 GPa; however, the tensile strengths of most reported HEAs are limited. Here, we report a strategy for the design and fabrication of HEAs that can achieve ultrahigh tensile strengths. The proposed strategy involves the introduction of a high density of hierarchical intragranular nanoprecipitates. To establish the validity of this strategy, we designed and fabricated a bulk Fe25 Co25 Ni25 Al10 Ti15 HEA to consist of a principal face-centered cubic (fcc) phase containing hierarchical intragranular nanoprecipitates...
October 2018: Science Advances
M Caccia, M Tabandeh-Khorshid, G Itskos, A R Strayer, A S Caldwell, S Pidaparti, S Singnisai, A D Rohskopf, A M Schroeder, D Jarrahbashi, T Kang, S Sahoo, N R Kadasala, A Marquez-Rossy, M H Anderson, E Lara-Curzio, D Ranjan, A Henry, K H Sandhage
The efficiency of generating electricity from heat using concentrated solar power plants (which use mirrors or lenses to concentrate sunlight in order to drive heat engines, usually involving turbines) may be appreciably increased by operating with higher turbine inlet temperatures, but this would require improved heat exchanger materials. By operating turbines with inlet temperatures above 1,023 kelvin using closed-cycle high-pressure supercritical carbon dioxide (sCO2 ) recompression cycles, instead of using conventional (such as subcritical steam Rankine) cycles with inlet temperatures below 823 kelvin1-3 , the relative heat-to-electricity conversion efficiency may be increased by more than 20 per cent...
October 2018: Nature
Kurt Mills, Gui Wang, David StJohn, Matthew Dargusch
This study evaluated the effect of UltraSonic Treatment (UST) on a range of Al⁻Mg alloys. Previous research was carried out on single magnesium compositions. However, the amount and type of the alloy addition are known to affect the grain size even under UST, and the aim of this study was to determine whether or not alloy composition plays a similar role in the case of Al⁻Mg alloys. By testing binary Al⁻Mg alloys cast under regular casting conditions and under the presence of an ultrasonic field, it was found that while the addition of Mg solute is important, the amount of solute has little effect when UST is applied...
October 16, 2018: Materials
Kousik Bhunia, Moumita Chandra, Debabrata Pradhan
This review focuses on the recent progress in shape-controlled synthesis and exposed facets-dependent catalytic properties of widely used nanostructured noble metals (Pd, Pt, and Au), bimetallic alloys involving one noble metal, and oxides of first row d-block elements such as titanium oxide (TiO₂), vanadium oxide (V₂O5 ), chromium oxide (Cr₂O₃), manganese oxide (MnO₂), iron oxide (Fe₂O₃), cobalt oxide (Co₃O₄), nickel oxide (NiO), copper oxide (Cu₂O), and zinc oxide (ZnO). The major emphasis is given on the role of shape-controlling agents and experimental parameters to control the exposed facets of the nanocrystals...
January 1, 2019: Journal of Nanoscience and Nanotechnology
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