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Comparative analysis of microstructure,mechanical,and corrosion properties of biodegradable Mg-3Y alloy prepared by selective laser melting and spark plasma sintering

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Journal of Magnesium and Alloys 2024年第4期12卷 1496-1510页

作者： P.Minárik M.Zemková S.Šašek J.Dittrich M.Knapek F.Lukáˇc D.Koutný J.Jaroš R.Král Faculty of Mathematics and Physics Charles UniversityKe Karlovu 5Praha 12116Czech Republic Research Centre University ofŽilinaUniverzitná8215/1Žilina 01026Slovakia Institute of Plasma Physics of the czech Academy of sciences Za Slovankou 1782/318200 Praha 8Czech Republic Institute of Machine and Industrial Design Brno University of TechnologyTechnická2896/2Brno 61669Czech Republic

This work explored possibilities of biodegradable magnesium alloy Mg-3Y preparation by two modern powder metallurgy techniques–spark plasma sintering(SPS)and selective laser melting(SLM).The powder material was consolidated by both methods utilising optimised parameters,which led to very low porosity(∼0.3%)in the SLM material and unmeasurably low porosity in the SPS *** main aim of the study was the thorough microstructure characterisation and interrelation between the microstructure and the functional properties,such as mechanical strength,deformability,and corrosion *** materials showed comparable strength of∼110 MPa in tension and compression and relatively good deformability of∼9%and∼21%for the SLM and SPS materials,*** corrosion resistance of the SPS material in 0.1 M NaCl solution was superior to the SLM one and comparable to the conventional extruded *** digital image correlation during loading and the cross-section analysis of the corrosion layers revealed that the residual porosity and large strained grains have the dominant negative effect on the functional properties of the SLM *** the other hand,one of the primary outcomes of this study is that the SPS consolidation method is very effective in the preparation of the W3 biodegradable alloy,resulting in material with convenient mechanical and degradation properties that might find practical applications.

关键词： Magnesium Yttrium Powder metallurgy Microstructure Mechanical strength Corrosion resistance

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Sustaining forest biodiversity:Exploring the effect of long-term natural disturbance dynamics on contemporary lichen communities in primary forest ecosystems

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Forest Ecosystems 2024年第4期11卷 556-567页

作者： Rhiannon Gloor Marek Svitok Martin Mikolas Jenyk Hofmeister Josef Halda Pavel Janda Francesco Maria Sabatini Lucie Zemanova Arne Buechling Daniel Kozak Matej Ferencik Michal Frankovic Martin Dusatko Miroslav Svoboda Department of Forest Ecology Faculty of Forestry and Wood SciencesCzech University of Life Sciences PragueKamycka 129Praha 6–Suchdol16500Czech Republic Faculty of Ecology and Environmental sciences Technical University in ZvolenT.G.Masaryka 2496001ZvolenSlovakia Institute of Botany Plant Science and Biodiversity CenterSlovak Academy of SciencesDúbravska cesta 984523BratislavaSlovakia PRALES Odtrnovie 56301322RosinaSlovakia Faculty of science University of Hradec KraloveHradecka 1285Hradec KraloveⅢ50003Czech Republic BIOME–Biogeography and Macroecology Department of BiologicalGeological and Environmental Sciences(BIGEA)Alma Mater Studiorum-University of Bolognavia Irnerio 42BolognaItaly

In this era of biodiversity loss and climate change,quantifying the impacts of natural disturbance on forest communities is imperative to improve biodiversity conservation *** and epixylic lichens are effective forest quality bioindicators,as they are generally long-lived organisms supported by continuity of specific forest structures and their associated microclimatic ***,how lichen communities respond to the effects of fluctuating historical disturbances remains *** a dendrochronological approach,this study investigates how natural disturbance dynamics indirectly influence various lichen community metrics in some of Europe's best-preserved primary mixed-beech *** modelling revealed that natural historical disturbance processes have decades-long effects on forest structural attributes,which had both congruent and divergent impacts on lichen community richness and *** species richness indirectly benefited from both historical and recent higher-severity disturbances via increased standing dead tree basal area and canopy openness respectively-likely through the presence of both pioneer and late-successional species associated with these ***-listed species richness showed a dependence on habitat continuity(old trees),and increased with disturbance-related structures(standing dead trees)whilst simultaneously benefiting from periods without severe disturbance events(old trees and reduced deadwood volume).However,if the disturbance occurred over a century in the past,no substantial effect on forest structure was ***,while disturbance-mediated forest structures can promote overall richness,threatened species appear vulnerable to more severe disturbance events-a concern,as disturbances are predicted to intensify with climate ***,the high number of threatened species found reinforce the critical role of primary forest structural attributes for biodiversity ***

关键词： Mixed-beech forests Species richness Old-growth forests Carpathian mountains Biodiversity conservation Dendroecology Fagus sylvatica

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Sc元素添加对双辊铸轧Al−Cu−Li−Mg−Zr基合金热处理的影响

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Transactions of Nonferrous Metals Society of China 2024年第6期34卷 1759-1773页

作者： Rostislav KRÁLÍK Barbora KŘIVSKÁ Lucia BAJTOŠOVÁ Mykhailo STOLBCHENKO Mirko SCHAPER Olexandr GRYDIN Miroslav CIESLAR Department of Physics of Materials Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 512116PragueCzech Republic Department of Materials science Faculty of Mechanical EngineeringUniversity of PaderbornWarburger Straße 10033098PaderbornGermany

提出制备含Sc的Al−Cu−Li−Mg−Zr基合金带材的工艺方案。即先采用双辊铸轧技术制备近净形状的3 mm厚带材,再对其进行均匀化/固溶处理。研究两种Al−Cu−Li−Mg−Zr基双辊铸轧合金,其中一种添加质量分数为0.17%的Sc,另一种未添加Sc。两种合金... 详细信息

提出制备含Sc的Al−Cu−Li−Mg−Zr基合金带材的工艺方案。即先采用双辊铸轧技术制备近净形状的3 mm厚带材,再对其进行均匀化/固溶处理。研究两种Al−Cu−Li−Mg−Zr基双辊铸轧合金,其中一种添加质量分数为0.17%的Sc,另一种未添加Sc。两种合金均先在300℃下退火30 min,然后在450℃下退火30 min以及530℃下退火30 min,随后进行室温水淬。前两段退火后组织中生成了细小、弥散的Al_(3)Zr/Al_(3)(Sc,Zr)颗粒。最后的退火步骤起到了均匀化/固溶处理的作用。双辊铸轧材料的细小晶粒结构使含有主要合金元素的原始颗粒在较短的退火时间内溶解。缩短保温时间可以限制表面层中Li的耗尽和Al_(3)Zr/Al_(3)(Sc,Zr)弥散相的明显粗化。铸态含Sc材料已经具有明显细小的晶粒结构,而经均匀化/固溶处理后生成的Al_(3)(Sc,Zr)弥散相抑制了晶粒在高温下发生粗化。在后续180℃下时效处理后,形成了θʹ(Al_(2)Cu)、T1(Al_(2)CuLi)和S'(Al_(2)CuMg)强化相。在峰值时效状态下,屈服强度提高了200 MPa,这一数值与类似直接冷却铸造材料的相当,从而证实了所提方案的合理性。

关键词：显微组织力学性能 Al−Cu−Li基合金 Sc合金化双辊铸轧

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Quantification and depth distribution analysis of carbon to nitrogen ratio in forest soils using reflectance spectroscopy

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International Soil and Water Conservation Research 2023年第1期11卷 112-124页

作者： Asa Gholizadeh Mohammadmehdi Saberioon Nastaran Pouladi Eyal Ben-Dor Department of Soil science and Soil Protection Faculty of AgrobiologyFood and Natural ResourcesCzech University of Life Sciences Prague16500PragueCzech Republic Section 1.4 Remote Sensing and Geoinformatics Helmholtz Centre Potsdam GFZ German Research Centre for GeosciencesTelegrafenberg14473Potsdam Germany knoell Germany GmbH Konrad-Zuse-Ring68163MannheimGermany Remote Sensing Laboratoryeparmentof Ggraphy and HumanEnvionmnt Porter Schoolf Evionmntand Earth ScienceTelAvivUniverty 69978TelAvivIsrael

Forest soils have large contents of carbon(C)and total nitrogen(TN),which have significant spatial variability laterally across landscapes and vertically with depth due to decomposition,erosion and ***,the ratio of C to TN contents(C∶N),a crucial indicator of soil quality and health,is also different depending on soil *** attributes can cost-effectively and rapidly be estimated using visible-near infrared-shortwave infrared(VNIR-SWIR)***,the effect of different soil layers,particularly over large scales of highly heterogeneous forest soils,on the perfor-mance of the technique has rarely been *** study evaluated the potential of VNIR-SWIR spectroscopy in quantification and variability analysis of C∶N in soils from different organic and min-eral layers of forested sites of the czech *** each site,we collected samples from the litter(L),fragmented(F)and humus(H)organic layers,and from the A_(1)(depth of 2-10 cm)and A_(2)(depth of 10-40 cm)mineral layers providing a total of 2505 *** vector machine regression(SVMR)was used to train the prediction models of the selected attributes at each individual soil layer and the merged layer(profile).We further produced the spatial distribution maps of C∶N as the target attribute at each soil *** showed that the prediction accuracy based on the profile spectral data was adequate for all ***,F was the most accurately predicted layer,regardless of the soil attribute.C∶N models and maps in the organic layers performed well although in mineral layers,models were poor and maps were reliable only in areas with low and moderate C∶*** the other hand,the study indicated that reflectance spectra could efficiently predict and map organic layers of the forested ***,in mineral layers,high values of C∶N(≥50)were not detectable in the map created based on the reflectance *** general,the study suggests that VNIR-SWIR spectrosc

关键词： Forest soil Soilorganiccarbon C:N Soilhorizons VNIR-SWIRspectroscopy

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Effects of Organic Matter-Rich Amendments on Selenium Mobility in Soils

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Pedosphere 2019年第6期29卷 740-751页

作者： Petra SMAZíKOVá Luká? PRAUS Jirina SZáKOVá Jana TREMLOVá Ale? HANC Pavel TLUSTOS Department of Agro-Environmental Chemistry and Plant Nutrition Faculty of Agrobiology Food and Natural Resources Czech University of Life Sciences Prague

Soil organic matter (SOM) plays an important role in the Se dynamics in soil. The potential effects of vermicompost and digestate as important sources of SOM on selenium (Se) mobility were assessed in this study. Three soils differing in their physicochemical parameters, fluvisol, chernozem, and luvisol, were chosen, and three types of vermicomposts based on various bio-waste materials as digestate (vermicompost 1), kitchen waste with woodchips (vermicompost 2), and garden bio-waste (vermicompost 3) were used due to their high organic matter content. Additionally, digestate samples alone were applied. To evaluate the potential effect of vermicompost application on sorption characteristics of soils, batch sorption experiments were performed. The results showed a predominant effect on Se species in the soils, where selenite sorbed more intensively compared to selenate, regardless of the soil and ameliorative material applied. In the control, the soil sorption ability of selenite tended to decrease in the order: fluvisol > luvisol > chernozem. However, these differences were not significant. Moreover, the effects of the ameliorative materials depended on both soil and amendment used. In fluvisol, all the amendment applications resulted in a decrease in distribution coefficient ( K d values) of Se, whereas in chernozem, this effect was observed only for the digestate-based vermicompost 1. Increasing K d levels were reported in luvisol treated with digestate;the application of garden bio-waste-based vermicompost 3 tended to decrease the K d values. Further studies are required on long-term effects of these amendments on Se mobility in soils and the role of individual organic matter fractions in this context.

关键词： Batch sorption experiments Bio-waste material Selenite Selenate Sorption isotherms Vermicompost

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Three-dimensional crystal plasticity and HR-EBSD analysis of the local stress-strain fields induced during twin propagation and thickening in magnesium alloys

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Journal of Magnesium and Alloys 2023年第2期11卷 657-670页

作者： Filip Siska Daria Drozdenko Kristian Mathis Jan Cizek Tingting Guo Matthew Barnett Institute of Physics of Materials The Czech Academy of SciencesZizkova 513/22Brno 61662Czech Republic Department of Physics of Materials Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 5Prague 12116Czech Republic Institute of Plasma Physics The Czech Academy of SciencesZa Slovankou 1782/3Prague 18200Czech Republic Institute for Frontier Materials Deakin UniversityGeelongVictoria 3216Australia

Present work focuses on analysis of the stress and strain fields inside and around the individual {10–12} twin in magnesium alloy. The 3D crystal plasticity model represents twin as an ellipsoidal inclusion surrounded by the matrix. Five different twin thicknesses and three different lateral twin lengths are used for stress/strain analysis. The simulations are complemented with experimental observations using high-resolution electron backscattered diffraction. The simulations and experiments show a similar distribution of the shear stress and the spatial activity of individual slip systems(basal, prismatic, pyramidal). Plasticity induced inside the twin is dominantly caused by the prismatic dislocations slip and does not influence twin back stress which is identical to pure elastic twin. The twin with larger lateral dimension requires lower equilibrium stress which suggests anisotropic twin propagation and increased thickness of such twins. The lateral twin propagation is mostly influenced by prismatic and pyramidal slip in the twin vicinity. The twin thickness can reach a maximal level that is driven by the critical resolved shear stress values for dislocation slip with the significant influence of basal slip.

关键词： Magnesium alloy Twinning FEM Crystal plasticity HR-EBSD

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A new oxidovanadium(Ⅳ) Schiff base complex containing asymmetric tetradentate ONN0O0Schiff base ligand:Synthesis,characterization,crystal structure determination,thermal study and catalytic activity

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Chinese Chemical Letters 2015年第6期26卷 779-784页

作者： Gholamhossein Grivani Abbase Ghavami Vclav Eigner Michal Duek Aliakbar Dehno Khalaji School of Chemistry Damghan University Department of Solid State Chemistry Institute of Chemical TechnologyTechnick Institute of Physics ASCR Department of Chemistry Faculty of ScienceGolestan University

After synthesis of an asymmetric tetradentate ONN＇O＇ Schiff base ligand （H2L） followed by reaction of the synthesized H2L with an equimolar mixture of methanolic solutions of the VO（acac）2, a new oxidovanadium（IV） Schiff base complex （VOL） was synthesized. The Schiff base ligand and its complex were characterized by FT-IR and UV-vis spectra and C, H, N analysis, The crystal structure of VOL was also determined by single crystal X-ray analysis. The VOL complex crystallizes in monoclinic space group Cc. The Schiffbase ligand acts as a tetradentate ligand through its two＇iminic nitrogens and two phenolic and acetylacetonate oxygens. Thermogravimetric analysis of the VOL showed that it decomposes in two steps and converts to mixed vanadium oxides at 477℃. In addition, thermal decomposition of the VOL complex in air at 660 ℃ leads to formation of V2O5 nanoparticles with the average size estimated from XRD 49 nm. The catalytic activity of the VOL complex was investigated in the epoxidation reaction and different reaction parameters were optimized. The results showed that the cyclic alkenes were efficiently converted to the corresponding epoxides, whereas the VOL did not appreciably convert the linear alkenes.

关键词： Oxidovanadium(IV) Scbiff base Crystal structure Nanopartide Epoxidation

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On Scientific Data and Image Compression Based on Adaptive Higher-Order FEM

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Advances in Applied Mathematics and Mechanics 2009年第1期1卷 56-68页

作者： P.Solin D.Andrs Department of Mathematics and Statistics University of NevadaRenoUSA Institute of Thermomechanics PragueCzech Republic

We present a novel compression algorithm for 2D scientific data and images based on exponentially-convergent adaptive higher-order finite element methods(FEM).So far,FEM has been used mainly for the solution of partial differential equations(PDE),but we show that it can be applied to data and image compression *** adaptive compression algorithm is trivial compared to adaptive FEM algorithms for PDE since the error estimation step is not *** method attains extremely high compression rates and is able to compress a data set or an image with any prescribed error *** data and images are stored in the standard FEM format,which makes it possible to analyze them using standard PDE visualization *** examples are *** method is presented in such a way that it can be understood by readers who may not be experts of the finite element method.

关键词： Data compression image compression adaptive hp-FEM orthogonal projection best approximation problem error control

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Individual effect of Y and Nd on the microstructure formation of Mg-Y-Nd alloys processed by severe plastic deformation and their effect on the subsequent mechanical and corrosion properties

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Journal of Magnesium and Alloys 2023年第2期11卷 509-521页

作者： Maria Zemkova Peter Minarik Jan Dittrich Jan Bohlen Robert Kral Charles University Department of Physics of MaterialsKe Karlovu 512116PragueCzechia University of Zilina Research CentreUniverzitna8215/1Zilina01026Slovakia Institute of Material and Process Design Helmholtz-Zentrum Hereon21502GeesthachtGermany

This work investigated the effect of sole yttrium and neodymium alloying on the microstructure formation during severe plastic deformation by equal channel angular pressing(ECAP) and an impact on the mechanical strength and corrosion resistance of binary Mg-3Y and Mg-3Nd *** results are compared with a ternary Mg-4Y-3Nd alloy,which represents a simplified version of the commercially successful WE43 *** extensive study comprises a thorough microstructural analysis performed by scanning and transmission electron microscopy,including electron backscatter diffraction and texture analysis performed by X-ray *** is shown that the presence of Nd primarily caused precipitation during the processing of the Mg-3Nd alloy,while Y remained dissolved in the magnesium matrix in the Mg-3Y *** difference resulted in a significantly smaller average grain size in the Mg-3Y alloy(~0.77 nm) than in the Mg-3Nd alloy(~1.3 μm) after the final step of the processing and formation of a slightly different ***,the composition and the processing affected the mechanical and corrosion properties of the investigated materials,measured by compression deformation tests,microhardness measurement,and electrochemical impedance *** study shows that the ECAP-processed W3 sample exhibits a surprisingly good combination of ultrafine-grain structure,weak crystallographic texture,high strength,and high corrosion resistance compared with the other investigated *** attributes make this material very interesting for utilisation in the industry and/or medicine.

关键词： Magnesium Rare earth elements Microstructure Texture Mechanical strength Corrosion

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Corrosion and mechanical properties of a novel biomedical WN43magnesium alloy prepared by spark plasma sintering

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Journal of Magnesium and Alloys 2021年第3期9卷 853-865页

作者： Michal Knapek Mária Zemková Adam Gres Eva Jablonská Frantisek Lukác Robert Král Jan Bohlen Peter Minárik Charles University Faculty of Mathematics and PhysicsKe Karlovu 512116 PragueCzech Republic Nuclear Physics Institute of CAS Řež13025068ŘežCzech Republic University of Chemistry and Technology Department of Biochemistry and MicrobiologyTechnická5Prague16628 PragueCzech Republic Institute of Plasma Physics of CAS Za Slovankou 318200 PragueCzech Republic Helmholtz-Zentrum Geesthacht Magnesium Innovation Centre(MagIC)D21502 GeesthachtGermany

Alloying of Mg with rare-earth(RE)elements proved to be beneficial for their in-vitro and in-vivo *** this work,a novel WN43(Mg-4 wt%Y-3 wt%Nd)alloy with a well-defined composition was prepared,where,unlike in the commercial WE43 alloy,the possibly harmful RE mischmetal was substituted by less toxic Nd.A modern spark plasma sintering(SPS)technique was used to effectively produce WN43 samples from atomized *** temperatures of 400℃-550℃ and holding times of 3 or 10 min were used and wellcompacted final materials were successfully *** was shown that a superior combination of corrosion and mechanical properties was attained in the samples sintered at 500℃ and 550℃,while the effect of sintering time was rather *** performance of this material was exceptional within the group of Mg alloys prepared by powder metallurgy and comparable with conventionally prepared ***,it was shown that a great variety of mechanical and corrosion characteristics can be obtained by altering the SPS parameters so as to fulfill case-specific requirements typical of biomedical ***,the novel WN43 alloy prepared by SPS seems to be a particularly suitable material for biomedical use.

关键词： Magnesium Biocompatibility Powder Sintering Corrosion Rare earth element

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