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  1. Article: Properties of FeAlSi-X-Y Alloys (X,Y=Ni, Mo) Prepared by Mechanical Alloying and Spark Plasma Sintering.

    Průša, Filip / Proshchenko, Olga / Školáková, Andrea / Kučera, Vojtěch / Laufek, František

    Materials (Basel, Switzerland)

    2020  Volume 13, Issue 2

    Abstract: Short-term mechanical alloying and compaction by spark plasma sintering was used for the production of FeAl20Si20Mo20-XNiX (X corresponds to 5-15 wt %) alloy, which showed an ultrafine-grained microstructure with dimensions of phases around 200 nm or ... ...

    Abstract Short-term mechanical alloying and compaction by spark plasma sintering was used for the production of FeAl20Si20Mo20-XNiX (X corresponds to 5-15 wt %) alloy, which showed an ultrafine-grained microstructure with dimensions of phases around 200 nm or smaller. It was found that the addition of Mo and Ni to the FeAl20Si20 alloy results in the formation of the AlMoSi phase compared to the three-phase FeAl20Si20 alloy, which initially contained FeSi, Fe
    Language English
    Publishing date 2020-01-08
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2487261-1
    ISSN 1996-1944
    ISSN 1996-1944
    DOI 10.3390/ma13020292
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  2. Article: Bioprecipitation of As4S4 polymorphs in an abandoned mine adit

    Falteisek, Lukáš / Culka, Adam / Drahota, Petr / Laufek, František / Trubač, Jakub

    Applied geochemistry. 2020 Feb., v. 113

    2020  

    Abstract: Opportunities to study the anthropogenic cementation zones within permanently flooded mine works, where toxic elements accumulate by processes not fully described, are generally very rare. We examined macroscopic arsenic sulfide deposits inside a ... ...

    Abstract Opportunities to study the anthropogenic cementation zones within permanently flooded mine works, where toxic elements accumulate by processes not fully described, are generally very rare. We examined macroscopic arsenic sulfide deposits inside a decomposed timbering of an abandoned mine adit, which had been flooded for 75 years. Bonazziite (β-As4S4) was always the dominant mineral in the deposits (up to 96.5%), while realgar and the ZnS phase were present in minor amounts. These findings differ from near-surface environments, where the most common biogenic As sulfide is realgar and other polymorphs are usually present in trace amounts only. Bonazziite was chemically highly pure with an average As/S molar ratio 0.9. It was 34S depleted compared to both aqueous sulfate and primary sulfides, which is consistent with biogenic sulfur reduction. Sulfide encrustation was confined to individual wood tracheids, indicating the extent of microenvironments that were oversaturated with respect to these minerals. The sulfides were accompanied by older gypsum and younger arsenian schwertmannite indicating complex succession of the redox conditions within the timbering. Authigenic electrum was found in one sample. Analysis of microbial communities revealed the dominance of sulfate reducers and fermenting microorganisms within the timber, similar to realgar-precipitating spots in wetland soils as previously documented. An anoxic environment in the mine water was maintained by autotrophic iron oxidation. The results suggest that a highly reduced microenvironment embedded in anoxic, but relatively oxidized surroundings is the key feature of the realgar and bonazziite-precipitating systems.
    Keywords anaerobic conditions ; arsenic ; geochemistry ; gypsum ; iron ; microbial communities ; microorganisms ; oxidation ; stable isotopes ; sulfates ; sulfur ; toxic substances ; tracheids ; wetland soils ; wood ; zinc sulfide
    Language English
    Dates of publication 2020-02
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 1499242-5
    ISSN 0883-2927
    ISSN 0883-2927
    DOI 10.1016/j.apgeochem.2019.104511
    Database NAL-Catalogue (AGRICOLA)

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  3. Article ; Online: Sizeable net export of base cations from a Carpathian flysch catchment indicates their geogenic origin while the

    Novak, Martin / Kochergina, Yulia V Erban / Andronikov, Alexandre V / Holmden, Chris / Veselovsky, Frantisek / Kachlik, Vaclav / Hruška, Jakub / Laufek, Frantisek / Paces, Tomas / Komarek, Arnost / Sebek, Ondrej / Stepanova, Marketa / Curik, Jan / Prechova, Eva / Fottova, Daniela / Andronikova, Irina E

    Environmental science and pollution research international

    2024  Volume 31, Issue 17, Page(s) 26261–26281

    Abstract: Nutrient imbalances may negatively affect the health status of forests exposed to multiple stress factors, including drought and bark beetle calamities. We studied the origin of base cations in runoff from a small Carpathian catchment underlain by base- ... ...

    Abstract Nutrient imbalances may negatively affect the health status of forests exposed to multiple stress factors, including drought and bark beetle calamities. We studied the origin of base cations in runoff from a small Carpathian catchment underlain by base-poor flysch turbidites using magnesium (Mg), calcium (Ca) and strontium (Sr) isotope composition of 10 ecosystem compartments. Our objective was to constrain conclusions drawn from long-term hydrochemical monitoring of inputs and outputs. Annual export of Mg, Ca and Sr exceeds 5-to-15 times their atmospheric input. Mass budgets per se thus indicate sizeable net leaching of Mg, Ca and Sr from bedrock sandstones and claystones. Surprisingly, δ
    MeSH term(s) Calcium/analysis ; Magnesium/analysis ; Ecosystem ; Environmental Monitoring ; Strontium Isotopes/analysis ; Isotopes ; Cations ; Carbonates
    Chemical Substances Calcium (SY7Q814VUP) ; Magnesium (I38ZP9992A) ; Strontium Isotopes ; Isotopes ; Cations ; Carbonates
    Language English
    Publishing date 2024-03-18
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1178791-0
    ISSN 1614-7499 ; 0944-1344
    ISSN (online) 1614-7499
    ISSN 0944-1344
    DOI 10.1007/s11356-024-32866-1
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  4. Article: Structure and Properties of Alloys Obtained by Aluminothermic Reduction of Deep-Sea Nodules.

    Novák, Pavel / Vu, Nguyen Hong / Šulcová, Lucie / Kopeček, Jaromír / Laufek, František / Tsepeleva, Alisa / Dvořák, Petr / Michalcová, Alena

    Materials (Basel, Switzerland)

    2021  Volume 14, Issue 3

    Abstract: This paper brings an innovative processing route of manganese deep-sea nodules, which results in completely new grades of alloys. Deep-sea nodules were processed by aluminothermic method without the extraction of individual elements, producing complexly ... ...

    Abstract This paper brings an innovative processing route of manganese deep-sea nodules, which results in completely new grades of alloys. Deep-sea nodules were processed by aluminothermic method without the extraction of individual elements, producing complexly alloyed manganese-based "natural alloys". Three levels of the amount of aluminum were used for the aluminothermic reduction, and hence the alloys differ strongly in the amount of aluminum, which has a significant effect on their phase composition. The alloys have very high wear resistance, comparable with tool steel. The disadvantage of low-aluminum alloy is the susceptibility to local thermal cracking during friction, which occurs especially in the case of a dry sliding wear against the static partner with low thermal conductivity.
    Language English
    Publishing date 2021-01-25
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2487261-1
    ISSN 1996-1944
    ISSN 1996-1944
    DOI 10.3390/ma14030561
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  5. Article: Structure and Properties of Fe-Al-Si Alloy Prepared by Mechanical Alloying.

    Novák, Pavel / Vanka, Tomáš / Nová, Kateřina / Stoulil, Jan / Průša, Filip / Kopeček, Jaromír / Haušild, Petr / Laufek, František

    Materials (Basel, Switzerland)

    2019  Volume 12, Issue 15

    Abstract: Fe-Al-Si alloys have been previously reported as an interesting alternative to common high-temperature materials. This work aimed to improve the properties of FeAl20Si20 alloy (in wt.%) by the application of powder metallurgy process consisting of ... ...

    Abstract Fe-Al-Si alloys have been previously reported as an interesting alternative to common high-temperature materials. This work aimed to improve the properties of FeAl20Si20 alloy (in wt.%) by the application of powder metallurgy process consisting of ultrahigh-energy mechanical alloying and spark plasma sintering. The material consisted of Fe
    Language English
    Publishing date 2019-08-02
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2487261-1
    ISSN 1996-1944
    ISSN 1996-1944
    DOI 10.3390/ma12152463
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  6. Book ; Online: Ferroelectric and Incipient Ferroelectric Properties of a Novel Sr_(9-x)PbxCe2Ti2O36 (x=0-9) Ceramic System

    Kamba, Stanislav / Savinov, Maxim / Laufek, Frantisek / Tkac, Ondrej / Kadlec, Christelle / Veljko, Sergiy / John, Elizabeth J. / Subodh, Ganesanpotti / Sebastian, Mailadil T. / Klementova, Mariana / Bovtun, Viktor / Pokorny, Jan / Goian, Veronica / Petzelt, Jan

    2008  

    Abstract: Sr_(9-x)PbxCe2Ti12O36 system is derived from the perovskite SrTiO3 and its chemical formula can be written as (Sr_(1-y)Pby)0.75Ce0.167TiO3. We investigated dielectric response of Sr_(9-x)PbxCe2Ti12O36 ceramics (x = 0-9) between 100 Hz and 100 THz at ... ...

    Abstract Sr_(9-x)PbxCe2Ti12O36 system is derived from the perovskite SrTiO3 and its chemical formula can be written as (Sr_(1-y)Pby)0.75Ce0.167TiO3. We investigated dielectric response of Sr_(9-x)PbxCe2Ti12O36 ceramics (x = 0-9) between 100 Hz and 100 THz at temperatures from 10 to 700 K using low- and high-frequency dielectric, microwave (MW), THz and infrared spectroscopy. We revealed that Sr9Ce2Ti12O36 is an incipient ferroelectric with the R-3c trigonal structure whose relative permittivity e' increases from 167 at 300 K and saturates near 240 below 30 K. The subsequent substitution of Sr by Pb enhances e' to several thousands and induces a ferroelectric phase transition to monoclinic Cc phase for x>=3. Its critical temperature Tc linearly depends on the Pb concentration and reaches 550 K for x=9. The phase transition is of displacive type. The soft mode frequency follows the Barrett formula in samples with x<=2 (typical for quantum paraelectrics) and the Cochran formula for x>=3. The MW dispersion is lacking and quality factor Q is high in samples with low Pb concentration, although the permittivity is very high in some cases. However, due to the lattice softening, the temperature coefficient of the permittivity is rather high. The best MW quality factor was observed for x=1: Q*f=5800 GHz and e'=250. Concluding, the dielectric properties of Sr_(9- x)PbxCe2Ti12O36 are similar to those of Ba_(1-x)SrxTiO3 so that this system can be presumably used as an alternative for MW devices or capacitors.

    Comment: subm. to Chem. Mater
    Keywords Condensed Matter - Materials Science
    Subject code 600 ; 535
    Publishing date 2008-12-17
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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