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  1. Article ; Online: Enhanced Mechanical and Electromechanical Properties of Compositionally Complex Zirconia Zr

    Kabir, Ahsanul / Lemieszek, Bartlomiej / Varenik, Maxim / Buratto Tinti, Victor / Molin, Sebastian / Lubomirsky, Igor / Esposito, Vincenzo / Kern, Frank

    ACS applied materials & interfaces

    2024  Volume 16, Issue 10, Page(s) 12765–12772

    Abstract: Compositionally complex oxides (CCOs) or high-entropy oxides (HEOs) are new multielement oxides with unexplored physical and functional properties. In this work, we report fluorite structure-derived compositionally complex zirconia with composition ... ...

    Abstract Compositionally complex oxides (CCOs) or high-entropy oxides (HEOs) are new multielement oxides with unexplored physical and functional properties. In this work, we report fluorite structure-derived compositionally complex zirconia with composition Zr
    Language English
    Publishing date 2024-03-01
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.3c17501
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Trivalent Dopant Size Influences Electrostrictive Strain in Ceria Solid Solutions.

    Varenik, Maxim / Nino, Juan Claudio / Wachtel, Ellen / Kim, Sangtae / Cohen, Sidney R / Lubomirsky, Igor

    ACS applied materials & interfaces

    2021  Volume 13, Issue 17, Page(s) 20269–20276

    Abstract: The technologically important frequency range for the application of electrostrictors and piezoelectrics is tens of Hz to tens of kHz. ... ...

    Abstract The technologically important frequency range for the application of electrostrictors and piezoelectrics is tens of Hz to tens of kHz. Sm
    Language English
    Publishing date 2021-04-22
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.0c20810
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Lead-free Zr-doped ceria ceramics with low permittivity displaying giant electrostriction.

    Varenik, Maxim / Xu, Boyuan / Li, Junying / Gaver, Elad / Wachtel, Ellen / Ehre, David / Routh, Prahlad K / Khodorov, Sergey / Frenkel, Anatoly I / Qi, Yue / Lubomirsky, Igor

    Nature communications

    2023  Volume 14, Issue 1, Page(s) 7371

    Abstract: Electrostrictors, materials developing mechanical strain proportional to the square of the applied electric field, present many advantages for mechanical actuation as they convert electrical energy into mechanical, but not vice versa. Both high relative ... ...

    Abstract Electrostrictors, materials developing mechanical strain proportional to the square of the applied electric field, present many advantages for mechanical actuation as they convert electrical energy into mechanical, but not vice versa. Both high relative permittivity and reliance on Pb as the key component in commercial electrostrictors pose serious practical and health problems. Here we describe a low relative permittivity (<250) ceramic, Zr
    Language English
    Publishing date 2023-11-15
    Publishing country England
    Document type Journal Article
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-023-43032-5
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Dopant Concentration Controls Quasi-Static Electrostrictive Strain Response of Ceria Ceramics

    Varenik, Maxim / Nino, Juan Claudio / Wachtel, Ellen / Kim, Sangtae / Yeheskel, Ori / Yavo, Nimrod / Lubomirsky, Igor

    ACS applied materials & interfaces. 2020 July 23, v. 12, no. 35

    2020  

    Abstract: Electromechanically active ceramic materials, piezoelectrics and electrostrictors, provide the backbone of a variety of consumer technologies. Gd- and Sm-doped ceria are ion conducting ceramics, finding application in fuel cells, oxygen sensors, and, ... ...

    Abstract Electromechanically active ceramic materials, piezoelectrics and electrostrictors, provide the backbone of a variety of consumer technologies. Gd- and Sm-doped ceria are ion conducting ceramics, finding application in fuel cells, oxygen sensors, and, potentially, as memristor materials. While optimal design of ceria-based devices requires a thorough understanding of their mechanical and electromechanical properties, reports of systematic study of the effect of dopant concentration on the electromechanical behavior of ceria-based ceramics are lacking. Here we report the longitudinal electrostriction strain coefficient (M₃₃) of dense REₓCe₁–ₓO₂–ₓ/₂ (x ≤ 0.25) ceramic pellets, where RE = Gd or Sm, measured under ambient conditions as a function of dopant concentration within the frequency range f = 0.15–350 Hz and electric field amplitude E ≤ 0.5 MV/m. For >100 Hz, all ceramic pellets tested, independent of dopant concentration, exhibit longitudinal electrostriction strain coefficient with magnitude on the order of 10–¹⁸ m²/V². The quasi-static (f < 1 Hz) electrostriction strain coefficient for undoped ceria is comparable in magnitude, while introducing 5 mol % Gd or 5 mol % Sm produces an increase in M₃₃ by up to 2 orders of magnitude. For x ≤ 0.1 (Gd)–0.15 (Sm), the Debye-type relaxation time constant (τ) is in the range 60–300 ms. The inverse relationship between dopant concentration and quasi-static electrostrictive strain parallels the anelasticity and ionic conductivity of Gd- and Sm-doped ceria ceramics, indicating that electrostriction is partially governed by ordering of vacancies and changes in local symmetry.
    Keywords ceramics ; electric field ; fuel cells ; oxygen ; pellets ; thermodynamics
    Language English
    Dates of publication 2020-0723
    Size p. 39381-39387.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021/acsami.0c07799
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: Distinguishing Self-Assembled Pyrene Structures from Exfoliated Graphene

    Varenik, Maxim / Green Micah J / Regev Oren

    Langmuir. 2016 Oct. 18, v. 32, no. 41

    2016  

    Abstract: Sonication-assisted graphene production from graphite is a popular lab-scale approach in which ultrasound energy breaks down graphite sheets into graphene flakes in aqueous medium. Dispersants (surfactant molecules) are incorporated into the solution to ... ...

    Abstract Sonication-assisted graphene production from graphite is a popular lab-scale approach in which ultrasound energy breaks down graphite sheets into graphene flakes in aqueous medium. Dispersants (surfactant molecules) are incorporated into the solution to prevent individual graphene flakes from reaggregating. However, in solution these dispersants self-assemble into various structures, which can interfere with the characterization of the graphene produced. In this study, we characterized graphene dispersions stabilized by a family of pyrene-based surfactants that facilitate a high exfoliation yield. These surfactants self-assembled to form flakes and ribbonsshapes very similar to those of graphene structures. The dispersant structures were present both in the graphene dispersion and in the precipitate after the solvent had been evaporated and could therefore have been mistakenly identified as graphene by electron microscopy techniques and other characterization techniques, such as Raman and X-ray photoelectron spectroscopy. Contrary to previous reports, we showedby removing the dispersants by filtration and washingthat the surfactants did not affect the shape of the graphene prepared by sonication.
    Keywords X-ray photoelectron spectroscopy ; dispersions ; electron microscopy ; energy ; filtration ; graphene ; solvents ; sonication ; surfactants
    Language English
    Dates of publication 2016-1018
    Size p. 10699-10704.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021%2Facs.langmuir.6b03379
    Database NAL-Catalogue (AGRICOLA)

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  6. Article ; Online: Distinguishing Self-Assembled Pyrene Structures from Exfoliated Graphene.

    Varenik, Maxim / Green, Micah J / Regev, Oren

    Langmuir : the ACS journal of surfaces and colloids

    2016  Volume 32, Issue 41, Page(s) 10699–10704

    Abstract: Sonication-assisted graphene production from graphite is a popular lab-scale approach in which ultrasound energy breaks down graphite sheets into graphene flakes in aqueous medium. Dispersants (surfactant molecules) are incorporated into the solution to ... ...

    Abstract Sonication-assisted graphene production from graphite is a popular lab-scale approach in which ultrasound energy breaks down graphite sheets into graphene flakes in aqueous medium. Dispersants (surfactant molecules) are incorporated into the solution to prevent individual graphene flakes from reaggregating. However, in solution these dispersants self-assemble into various structures, which can interfere with the characterization of the graphene produced. In this study, we characterized graphene dispersions stabilized by a family of pyrene-based surfactants that facilitate a high exfoliation yield. These surfactants self-assembled to form flakes and ribbons-shapes very similar to those of graphene structures. The dispersant structures were present both in the graphene dispersion and in the precipitate after the solvent had been evaporated and could therefore have been mistakenly identified as graphene by electron microscopy techniques and other characterization techniques, such as Raman and X-ray photoelectron spectroscopy. Contrary to previous reports, we showed-by removing the dispersants by filtration and washing-that the surfactants did not affect the shape of the graphene prepared by sonication.
    Language English
    Publishing date 2016-10-10
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021/acs.langmuir.6b03379
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Book ; Online: Electromechanical dopant defect interaction in acceptor doped ceria

    Kabir, Ahsanul / Tintia, Victor Buratto / Varenik, Maxim / Lubomirsky, Igor / Esposito, Vincenzo

    2021  

    Abstract: Oxygen defective cerium oxides exhibits a non classical giant electromechanical response that is superior to lead based electrostrictors. In this work, we report the key role of acceptor dopants, with different size and valence Mg2+, Sc3+, Gd3+, and La3+, ...

    Abstract Oxygen defective cerium oxides exhibits a non classical giant electromechanical response that is superior to lead based electrostrictors. In this work, we report the key role of acceptor dopants, with different size and valence Mg2+, Sc3+, Gd3+, and La3+, on polycrystalline bulk ceria. Different dopants tune the electrostrictive properties by changing the electrosteric dopant defect interactions. We find two distinct electromechanical behaviors when the interaction is weak dopant vacancy binding energy 0.3 eV, electrostriction displays high coefficient, up to 10-17 m2V-2, with strongly time dependent effects. In contrast, we observe no time dependent effects when the interaction becomes strong 0.6 eV.
    Keywords Condensed Matter - Materials Science ; Physics - Chemical Physics
    Publishing date 2021-02-10
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article: Graphene-graphite hybrid epoxy composites with controllable workability for thermal management.

    Levy, Idan / Wormser, Eyal Merary / Varenik, Maxim / Buzaglo, Matat / Nadiv, Roey / Regev, Oren

    Beilstein journal of nanotechnology

    2019  Volume 10, Page(s) 95–104

    Abstract: The substantial heat generation in highly dense electronic devices requires the use of materials tailored to facilitate efficient thermal management. The design of such materials may be based on the loading of thermally conductive fillers into the ... ...

    Abstract The substantial heat generation in highly dense electronic devices requires the use of materials tailored to facilitate efficient thermal management. The design of such materials may be based on the loading of thermally conductive fillers into the polymer matrix applied - as a thermal interface material - on the interface between two surfaces to reduce contact resistance. On the one hand, these additives enhance the thermal conductivity of the composite, but on the other hand, they increase the viscosity of the composite and hence impair its workability. This in turn could negatively affect the device-matrix interface. To address this problem, we suggest a tunable composite material comprising a combination of two different carbon-based fillers, graphene nanoplatelets (GNPs) and graphite. By adjusting the GNP:graphite concentration ratio and the total concentration of the fillers, we were able to fine tune the thermal conductivity and the workability of the hybrid polymer composite. To facilitate the optimal design of materials for thermal management, we constructed a 'concentration-thermal conductivity-viscosity phase diagram'. This hybrid approach thus offers solutions for thermal management applications, providing both finely tuned composite thermal properties and workability. We demonstrate the utility of this approach by fabricating a thermal interface material with tunable workability and testing it in a model electronic device.
    Language English
    Publishing date 2019-01-08
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2583584-1
    ISSN 2190-4286
    ISSN 2190-4286
    DOI 10.3762/bjnano.10.9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Optimal nanomaterial concentration: harnessing percolation theory to enhance polymer nanocomposite performance.

    Nadiv, Roey / Shtein, Michael / Shachar, Gal / Varenik, Maxim / Regev, Oren

    Nanotechnology

    2017  Volume 28, Issue 30, Page(s) 305701

    Abstract: A major challenge in nanocomposite research is to predict the optimal nanomaterial concentration (ONC) yielding a maximal reinforcement in a given property. We present a simple approach to identify the ONC based on our finding that it is typically ... ...

    Abstract A major challenge in nanocomposite research is to predict the optimal nanomaterial concentration (ONC) yielding a maximal reinforcement in a given property. We present a simple approach to identify the ONC based on our finding that it is typically located in close proximity to an abrupt increase in polymer matrix viscosity, termed the rheological percolation threshold, and thus may be used as an indicator of the ONC. This premise was validated by rheological and fractography studies of composites loaded by nanomaterials including graphene nanoribbons or carbon or tungsten disulfide nanotubes. The correlation between in situ viscosity, the rheological percolation threshold concentration and the nanocomposite fractography demonstrates the utility of the method.
    Language English
    Publishing date 2017-07-28
    Publishing country England
    Document type Journal Article
    ZDB-ID 1362365-5
    ISSN 1361-6528 ; 0957-4484
    ISSN (online) 1361-6528
    ISSN 0957-4484
    DOI 10.1088/1361-6528/aa793e
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Breaking through the Solid/Liquid Processability Barrier: Thermal Conductivity and Rheology in Hybrid Graphene-Graphite Polymer Composites.

    Varenik, Maxim / Nadiv, Roey / Levy, Idan / Vasilyev, Gleb / Regev, Oren

    ACS applied materials & interfaces

    2017  Volume 9, Issue 8, Page(s) 7556–7564

    Abstract: Thermal conductivity (TC) enhancement of an insulating polymer matrix at low filler concentration is possible through the loading of a high aspect ratio, thermally conductive single filler. Unfortunately, the dispersion of high-aspect-ratio particles ... ...

    Abstract Thermal conductivity (TC) enhancement of an insulating polymer matrix at low filler concentration is possible through the loading of a high aspect ratio, thermally conductive single filler. Unfortunately, the dispersion of high-aspect-ratio particles greatly influences the rheological behavior of the polymer host at relatively low volume fractions, which makes further polymer processing or mixing difficult. A possible remedy is using two (hybrid) fillers, differing in their aspect ratios: (1) a plate-like filler, which sharply increases both viscosity and TC, and (2) an isotropic filler, which gradually increases these properties. We examine this hypothesis in a thermosetting silicone rubber by loading it with different ratios, (1)/(2), of graphene nanoplatelets (GNPs) (1) and graphite powder (2). We constructed a "phase diagram" delineating two composite processability regions: solid-like (moldable) or fluid-like (pourable). This diagram may be employed to tailor the mixture's viscosity to a desired TC value by varying the fillers' volume fraction. The phase diagram highlights the low volume fraction value, above which the composite is solid-like (low processability) for a single high-aspect-ratio nanofiller. By using hybrid filling, one can overcome this limit and prepare a fluid-like composite at a desired TC, not accessible by the single nanofiller. Thus, it provides an indicative tool for polymer processing, especially in applications such as the encapsulation of electronic devices. This approach was demonstrated for a heat source (resistor) potted by silicon rubber graphene-graphite composites, for which a desired TC was obtained in both solid- and liquid-like regions.
    Language English
    Publishing date 2017-03-01
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.6b14568
    Database MEDical Literature Analysis and Retrieval System OnLINE

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