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A detailed mechanism of degradation behaviour of biodegradable as-ECAPed Zn-0.8Mg-0.2Sr with emphasis on localized corrosion attack

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Bioactive Materials 2023年第9期27卷 447-460页

作者： Jan Pinc Andrea Skolakova vojtech hybasek Sarka Msallamova Petr Vertat Petr Ashcheulov Martin Vondracek Jan Duchon Ingrid McCarroll Matej Hývl Swarnendu Banerjee Jan Drahokoupil Jirí Kubasek Dalibor vojtech Jaroslav Capek Institute of Physics of the Czech Academy of Sciences Na Slovance 1999/2Prague 818221Czech Republic University of Chemistry and Technology Faculty of Chemical TechnologyDepartment of Metals and Corrosion EngineeringTechnicka 516628Praha 6-DejviceCzech Republic Max-Planck-Institut Für Eisenforschung Max-Planck-Straße 140237DüsseldorfGermany

In this study, advanced techniques such as atom probe tomography, atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy were used to determine the corrosion mechanism of the as-ECAPed Zn-0.8Mg-0.2Sr alloy. The influence of microstructural and surface features on the corrosion mechanism was investigated. Despite its significance, the surface composition before exposure is often neglected by the scientific community. The analyses revealed the formation of thin ZnO, MgO, and MgCO3 layers on the surface of the material before exposure. These layers participated in the formation of corrosion products, leading to the predominant occurrence of hydrozincite. In addition, the layers possessed different resistance to the environment, resulting in localized corrosion attacks. The segregation of Mg on the Zn grain boundaries with lower potential compared with the Zn-matrix was revealed by atom probe tomography and atomic force microscopy. The degradation process was initiated by the activity of micro-galvanic cells, specifically Zn - Mg2Zn11/SrZn13. This process led to the activity of the crevice corrosion mechanism and subsequent attack to a depth of 250 μm. The corrosion rate of the alloy determined by the weight loss method was 0.36 mm⋅a􀀀 1. Based on this detailed study, the degradation mechanism of the Zn-0.8Mg-0.2Sr alloy is proposed.

关键词： Biodegradable metals Zinc-based alloy Characterization Mechanism ECAP

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3D numerical parametric study of the influence of open-pit mining sequence on existing tunnels

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International Journal of Mining Science and Technology 2017年第3期27卷 459-466页

作者： Beyabanaki Amir Reza Gall vojtech McMillen Jacobs Associates San Francisco CA 94105 USA Gall Zeidler Consultants Ashburn VA 20147 USA

The development of open-pit mines can adversely affect and even damage existing access tunnels. To ensure the safety and serviceability of them, it is essential to know potential adverse effects of the mining sequence on existing tunnels such as displacements of the lining and additional loads on the lining. In this paper, three-dimensional numerical parametric study is performed to explore this complex interaction. This study investigates the effects of different parameters that may affect the tunnel response. These parameters are： excavation sequence method, horizontal/vertical stress ratio, slope angle, and tunnel diameter. This study shows that the mining sequence affects the stability of the tunnels. The open-pit mining activities lead to both higher axial forces in rock bolts and normal forces and bending moments in the lining. The results of the analysis also demonstrate that the mining sequence causes tunnel heave and significant tensile forces in the lining. Based on the study in this paper a better understanding of the interaction between oDen-oit minin~ seouence and tunnels will he ohtained

关键词： Three-dimensionalNumerical parametric studyExisting tunnelOpen-pit mining sequenceModeling

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Optimizing laser coupling,matter heating,and particle acceleration from solids using multiplexed ultraintense lasers

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Matter and Radiation at Extremes 2024年第4期9卷 16-28页

作者： Weipeng Yao Motoaki Nakatsutsumi Sébastien Buffechoux Patrizio Antici Marco Borghesi Andrea Ciardi Sophia N.Chen Emmanuel d’Humières Laurent Gremillet Robert Heathcote vojtech Horny Paul McKenna Mark N.Quinn Lorenzo Romagnani Ryan Royle Gianluca Sarri Yasuhiko Sentoku Hans-Peter Schlenvoigt Toma Toncian Olivier Tresca Laura Vassura Oswald Willi Julien Fuchs LULI-CNRS CEASorbonne UniversitéEcole PolytechniqueInstitut Polytechnique de ParisF-91128 Palaiseau CedexFrance Sorbonne Université Observatoire de ParisUniversité PSLCNRSLERMAF-75005 ParisFrance INRS-EMT 1650 BoulLionel-BouletVarennesQuebec J3X 1S2Canada Center for Plasma Physics School of Mathematics and PhysicsQueen’s University BelfastBelfast BT71NNUnited Kingdom “Horia Hulubei”National Institute for Physics and Nuclear Engineering 30 Reactorului StreetRO-077125 Bucharest-MagureleRomania University of Bordeaux Centre Lasers Intenses et ApplicationsCNRSCEAUMR 5107F-33405 TalenceFrance CEA DAMDIFF-91297 ArpajonFrance Université Paris-Saclay CEALMCE91680 Bruyères-le-ChatelFrance Central Laser Facility STFC Rutherford Appleton LaboratoryDidcotUnited Kingdom SUPA Department of PhysicsUniversity of StrathclydeGlasgow G40NGUnited Kingdom Department of Physics University of NevadaRenoNevada 89557USA Institute of Laser Engineering Osaka University2-6 YamadaokaSuitaOsaka 565-0871Japan Institut fur Laser und Plasmaphysik Heinrich Heine Universitat DusseldorfDusseldorfGermany

Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology ***,we investigate how to optimize their coupling with solid ***,we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation of hot electrons at the target front and ion acceleration at the target *** underlying mechanisms are analyzed through multidimensional particle-in-cell simulations,revealing that the self-induced magnetic fields driven by the two laser beams at the target front are susceptible to reconnection,which is one possible mechanism to boost electron *** addition,the resistive magnetic field generated during the transport of the hot electrons in the target bulk tends to improve their *** simulations also indicate that such effects can be further enhanced by overlapping more than two laser beams.

关键词： laser acceleration particle

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Proposed EU legislation to force changes in sewage sludge disposal:A case study

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Frontiers of Chemical Science and Engineering 2018年第4期12卷 660-669页

作者： vojtech Turek Bohuslav Kilkovsky Zdenek Jegla Petr Stehlik Institute of Process Engineering Faculty of Mechanical EngineeringBmo University of Tectmology61669 BmoCzech Republic

The consequences of changes planned in the European Union legislation relevant to the disposal of sewage sludges are discussed. A specific municipal waste water treatment plant is analyzed in terms of drying and subsequent combustion or pyrolysis of the produced stabilized sludge, and the respective net energy balances are carried out. A simplified economic analysis of the two disposal options is presented, which suggest that combustion of the sludge would be economically infeasible while pyrolysis of the sludge in a modular, self-sufficient container unit can bring a small financial benefit due to the selling of the produced phosphorus-rich biochar.

关键词： sewage sludge drying combustion pyrolysis pyrolysis Sewage sludge Combustion Modularity Drying EU legislation Sewage sludge disposal Sewage treatment plants

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Microstructure and mechanical properties of the micrograined hypoeutectic Zn–Mg alloy

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International Journal of Minerals,Metallurgy and Materials 2016年第10期23卷 1167-1176页

作者： J. Kubasek D.vojtech I.Pospisilova A.Michalcova J.Maixner Department of Metals and Corrosion Engineering University of Chemistry and Technology Prague Technicka 5 166 28 Prague 6 Czech Republic Laboratory of RTG Difractometry University of Chemistry and Technology Prague Technicka 5 166 28 Prague 6 Czech Republic

A biodegradable Zn alloy, Zn-1.6Mg, with the potential medical applications as a promising coating material for steel components was studied in this work. The alloy was prepared by three different procedures： gravity casting, hot extrusion, and a combination of rapid solidification and hot extrusion. The samples prepared were characterized by light microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analysis. Vickers hardness, tensile, and compressive tests were performed to determine the samples＇ mechanical properties. Structural examination reveals that the average grain sizes of samples prepared by gravity casting, hot extrusion, and rapid solidification followed by hot extrusion are 35.0, 9.7, and 2.1 μm, respectively. The micrograined sample with the finest grain size exhibits the highest hardness（Hv = 122 MPa）, compressive yield strength（382 MPa）, tensile yield strength（332 MPa）, ultimate tensile strength（370 MPa）, and elongation（9%）. This sample also demonstrates the lowest work hardening in tension and temporary softening in compression among the prepared samples. The mechanical behavior of the samples is discussed in relation to the structural characteristics, Hall-Petch relationship, and deformation mechanisms in fine-grained hexagonal-close-packed metals.

关键词： zinc magnesium alloys extrusion rapid solidification microstructure mechanical properties

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Parallel fluorescence and phosphorescence monitoring of singlet oxygen photosensitization in rats

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Journal of Innovative Optical Health Sciences 2015年第6期8卷 53-66页

作者： Roman Dedic Adam Stibal vojtech Vyklicky Miloslav Franek Antonin Svoboda Jan Hala Faculty of Mathematics and Physics Department of Chemical Physics and Optics Charles University in Prague Ke Karlovu 3 12116 Praha 2Czech Republic Third Faculty of Medicine Department of Normal Pathological and Clinical Physiology Charles University in Prague Ke Karlovu 412000 Praha 2Czech Republic

The time-and spectral-resolved set-up for measurements of weak infrared luminescence of photosensitizers(PSs)and singlet oxygen using optical lightguides was used on skin of laboratory animals in *** rats with abdominal incisions treated by methylis aminolevulinitis(MAL)were used as a model.A control group of animals with abdominal incisions was also *** resolved fluorescence of the PS was acquired during the treatment from the same *** intensity and spectral profile of the fiuorescence signal from the skin can be used to guide the detection setup to the investigated spots in the *** rate of bleaching of Protoporphyrin IX band and appearance of a band of its photoproducts during the treatment can be characterized by the exposition ED,under which the latter becomes dominant feature infiuorescence *** value differs statistically significantly between the normal skin and the lesion treated by *** direct proportionality was found between the fluorescence signal and singlet oxygen ***,the strong fluorescence signal is necessary but not a su±cient condition for higher singlet oxygen production in *** value correlates rather well with production of singlet oxygen,but differently in lesion and normal *** of singlet oxygen differ between spots outside and in the *** triplet state lifetimes exhibit weak di®erence between spots treated and untreated by MAL.

关键词： PDT dosimetry singlet oxygen Protoporphyrin IX time-resolved luminescence photodiagnosis

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Enhanced macrophage polarization induced by COX-2 inhibitor-loaded Pd octahedral nanozymes for treatment of atherosclerosis

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Chinese Chemical Letters 2023年第1期34卷 262-269页

作者： Min Xu Chuchu Ren Yue Zhou Zbynek Heger Xiaoyang Liang vojtech Adam Nan Li School of Pharmaceutical Science and Technology Tianjin UniversityTainjin 300072China Department of Chemistry and Biochemistry Mendel University in BrnoBrno CZ-61300Czech Republic

Inhibition of foam cell formation is considered a promising treatment method for atherosclerosis,the leading cause of cardiovascular diseases ***,currently available therapeutic strategies have shown unsatisfactory clinical ***,herein,we design aloperine(ALO)-loaded and hyaluronic acid(HA)-modified palladium(Pd)octahedral nanozymes(Pd@HA/ALO)that can synergistically scavenge reactive oxygen species(ROS)and downregulate cyclooxygenase-2(COX-2)expression to induce macrophage polarization,thus inhibiting foam cell formation to attenuate *** to the targeted effect of HA on stabilin-2 and CD44,which are overexpressed in atherosclerotic plaques,Pd@HA/ALO can actively accumulate in atherosclerotic ***,the antioxidative effects of Pd octahedral nanozymes are mediated by their intrinsic superoxide dismutase-and catalase-like activities capable of effective scavenging of *** addition,anti-inflammatory effects are mediated by controlled,on-demand near-infrared-triggered ALO release leading to inhibition of COX-2 ***,the combined therapy can promote the polarization of macrophages to the M2 subtype by upregulating Arg-1 and CD206 expression and downregulating expression of TNF-α,IL-1βand IL-6,thereby inhibiting atherosclerosis-related foam cell *** conclusion,the presented in vitro and in vivo data demonstrate that Pd@HA/ALO enhanced macrophage polarization to reduce plaque formation,identifying an attractive treatment strategy for cardiovascular disease.

关键词： Atherosclerosis COX-2 inhibitor Pd octahedral nanozyme Macrophage polarization Anti-inflammation Antioxidation

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A holistic approach for the investigation of lining response to mechanized tunneling induced construction loadings

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Underground Space 2018年第1期3卷 45-60页

作者： vojtech Ernst Gall Ahmed Marwan Mario Smarslik Markus Obel Peter Mark Gunther Meschke Inustitute for Structural Mechanics Ruhr University BochumBochunGermany Institute of Concrete Structures Ruhr University BochumBochumGermany

Design methods for segmental tunnel linings used in mechanized tunnel constructions typically employ numerical bedded beam mod-els and/or classical analytical solutions for the determination of structural forces(*** and shear and axial forces)and simple load spreading assumptions for the design of the reinforcement in joint *** effcient such methods may be,many physical details are often overlooked and/or oversimpliﬁed in the process of reducing the actual structure to a structural beam model,***-lytically derived loadings are employed,the grouting and ground reactions are reduced to a spring bedding,and the conﬁnement due to grouting at the longitudinal joint is largely not considered in reinforcement *** a design process is not able to account for,or predict,the susceptibility of tunnel linings to often observed damages that,although they may not be structurally relevant,lead to ser-viceability or durability issues,such as crack development or chipping at the segment *** methods,such as the Finite Element Method,provide an opportunity to model the segmental tunnel lining and its response to the entire TBM construction process and to explicitly model the crack development within individual segments using modern methods to model the discontinuities in *** this contribution,a holistic modeling procedure for the representation of the tunnel lining within the tunneling process is pro-posed and compared to traditional lining models.A 3D process oriented Finite Element model is used to calculate the predicted forces on the tunnel lining and the obtained results are compared with those generated by traditional ***,the predicted defor-mations are then transferred to a detailed segment model in which the nonlinear response of the segment at the longitudinal joint is mod-eled using an interface element based approach to simulate concrete cracking.

关键词： Mechanized tunneling Segmental tunnel linings Finite element method

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Electrochemical hydriding performance of Mg-TM-Mm (TM=transition metals,Mm=mischmetal) alloys for hydrogen storage

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Transactions of Nonferrous Metals Society of China 2013年第7期23卷 2047-2059页

作者： V.KNOTEK D.vojtech Department of Metals and Corrosion Engineering Institute of Chemical TechnologyPrague Technická 5166 28 Prague 6Czech Republic

Eighteen as-cast binary Mg-Ni, Mg-Mm and ternary Mg-Ni-Mm and Mg-Ni-TM （TM=transition metals （Cu, Zn, Mn and Co）; Mm = mischmetal containing Ce, La, Nd and Pr） alloys were hydrided by an electrochemical process to determine the alloys with the most potential for electrochemical hydrogen storage. The alloys were hydrided in a 6 mol/L KOH solution at 80 °C for 480 min and at 100 A/m2. To assess the electrochemical hydriding performance of alloys, maximum hydrogen concentrations, hydrogen penetration depths and total mass of absorbed hydrogen in the alloys were measured by glow discharge spectrometry. In addition, the structures and phase compositions of the alloys both before and after hydriding were studied by optical and scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction. It was determined that the highest total amount of hydrogen was absorbed by the Mg-25Ni-12Mm and Mg-26Ni （mass fraction, %） alloys. The maximum hydrogen concentrations in the Mg-25Ni-12Mm and Mg-26Ni alloys were 1.0% and 1.6%, respectively. The main hydriding product was the binary MgH2 hydride, and the ternary Mg2NiH4 hydride was also detected in the Mg-25Ni-12Mm alloy. The electrochemical hydriding parameters achieved are discussed in relation to the structures of alloys, alloying elements and hydriding mechanisms.

关键词： hydrogen storage magnesium nickel rare earths electrochemical hydriding

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Microstructure and corrosion resistance of a duplex structured Mg–7.5Li–3Al–1Zn

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Journal of Magnesium and Alloys 2021年第2期9卷 467-477页

作者： Anna Dobkowska Bogusława Adamczyk–Cieslak JiríKubásek Dalibor vojtech Dariusz Kuc Eugeniusz Hadasik Jarosław Mizera Faculty of Materials Science and Engineering Warsaw University of Technology141 Wołoska St02-507 WarsawPoland Chemistry Department Western University of Ontario1151 Richmond StLondonON N6A 5B7Canada Department of Metals and Corrosion Engineering University of Chemistry and TechnologyTechnicka 516628 Prague 6Czechia Institute of Materials Engineering Silesian University of TechnologyKrasinskiego 8St40-019 KatowicePoland

This study describes the corrosion resistance of extruded,and extruded with post-processing annealing,Mg–7.5 Li–3 Al–1 Zn *** results demonstrate that extrusion at 350°C with an extrusion speed 0.5 s^(-1) does not lead to the full recrystallization of the alloy,and the material still exhibits a dendritic *** post-processing annealing triggers the microstructure transformation,and the relative composition of the alloy *** ratio ofβ(Li)toα(Mg)in the extruded alloy was 29–71%;after annealing amount ofβ(Li)increased,and the ratio ofβ(Li)toα(Mg)in the annealed alloy was 35–65%.Corrosion testing shows that in 3.5 wt%Na Cl the extruded alloys immediately undergo strong *** a result of the subsequent annealing,an improvement of corrosion resistance is *** higher amount ofβ(Li)in the annealed alloy reduces the area ratio of cathodic to anodic sites of corrosion,and this makes the annealed alloy more resistive under the analyzed conditions.

关键词： Magnesium-Lithium corrosion Extrusion Annealing

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