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Toward Zero Micro/Macro-Scale Wear Using Periodic Nano-Layered Coatings
Penkov, Oleksiy V.,Devizenko, Alexander Yu.,Khadem, Mahdi,Zubarev, Evgeniy N.,Kondratenko, Valeriy V.,Kim, Dae-Eun American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.32
<P>Wear is an important phenomenon that affects the efficiency and life of all moving machines. In this regard, extensive efforts have been devoted to achieve the lowest possible wear in sliding systems. With the advent of novel materials in recent years, technology is moving toward realization of zero wear. Here, we report on the development of new functional coatings comprising periodically stacked nanolayers of amorphous carbon and cobalt that are extremely wear resistant at the micro and macro scale. Because of their unique structure, these coatings simultaneously provide high elasticity and ultrahigh shear strength. As a result, almost zero wear was observed even after one million sliding cycles without any lubrication. The wear rate was reduced by 8–10-fold compared with the best previously reported data on extremely low wear materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-32/acsami.5b05599/production/images/medium/am-2015-05599v_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b05599'>ACS Electronic Supporting Info</A></P>
Self-Healing Phenomenon and Dynamic Hardness of C<sub>60</sub>-Based Nanocomposite Coatings
Penkov, Oleksiy V.,Pukha, Volodymyr E.,Devizenko, Alexander Yu.,Kim, Hae-Jin,Kim, Dae-Eun American Chemical Society 2014 NANO LETTERS Vol.14 No.5
<P>The phenomenon of surface self-healing in C<SUB>60</SUB>-based polymer coatings deposited by ion-beam assisted physical vapor deposition was investigated. Nanoindentation of the coatings led to the formation of a protrusion rather than an indent. This protrusion was accompanied by an abnormal shape of the force–distance curve, where the unloading curve lies above the loading curve due to an additional force applied in pulling the indenter out of the media. The coatings exhibited a nanocomposite structure that was strongly affected by the ratio of C<SUB>60</SUB> ion and C<SUB>60</SUB> molecular beam intensities during deposition. The coatings also demonstrated the dynamic hardness effect, where the effective value of the hardness depends significantly on the indentation speed.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-5/nl500321g/production/images/medium/nl-2014-00321g_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl500321g'>ACS Electronic Supporting Info</A></P>
Hard, Flexible, and Transparent Nanolayered SiN<sub><i>x</i></sub>/BN Periodical Coatings
Penkov, Oleksiy V.,Khadem, Mahdi,Kim, Dae-Eun American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.10
<P>In this study, SiN<SUB><I>x</I></SUB>/BN periodical nanolayered coatings (PNCs) are developed. PNCs were deposited at the room temperature on plastic and glass substrates. They demonstrate the excellent mechanical durability of inorganic materials and optical transparency and flexibility of organic ones. The 150 nm thick PNC shows optical transparency, sapphire-like hardness, high wear protection, and flexibility. Such a coating with a superior combination of optical and mechanical properties has not been reported previously.</P> [FIG OMISSION]</BR>
Highly durable and biocompatible periodical Si/DLC nanocomposite coatings
Penkov, Oleksiy V.,Khadem, Mahdi,Lee, Jung-Seung,Kheradmandfard, Mehdi,Kim, Chang-Lae,Cho, Seung-Woo,Kim, Dae-Eun The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.10
<P>Functional nanocomposite coatings comprised of periodically stacked nanolayers of diamond-like carbon (DLC) and amorphous silicon were developed for biomedical applications. The periodical nanocomposite structure provided high surface durability while silicon aided in reducing the residual stress. The structural, mechanical, tribological, and biomedical properties of the Si/DLC coatings deposited by magnetron sputtering were investigated systematically. The effect of the negative substrate bias on the structure and properties of the coatings was also assessed. The coatings demonstrated high durability and high biocompatibility. The bias voltage and bias mode affected both the hardness and residual stress of the Si/DLC coatings. Particularly, application of 60 V negative bias during the DLC layer deposition resulted in the lowest wear rate. FEM simulations showed that the wear resistance of the coatings was dictated by the hardness as well as the adhesion between the coatings and a chromium sub-layer. The periodical alternation of Si and DLC nanolayers led to a significant improvement of MC3T3 cell adhesion compared to the previously published data for Si-DLC composites.</P>
Tribology of Graphene: A Review
Penkov, Oleksiy,Kim, Hae-Jin,Kim, Hyun-Joon,Kim, Dae-Eun 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.3
Graphene has received significant attention due to its combination of remarkable mechanical, thermal, chemical and electrical properties. Furthermore, due to its superior strength, graphene has great potential for use as an ultra-thin protective coating for various precision components. In this paper, the latest developments in tribological applications of graphene, theoretical simulations of graphene friction and preparation methods are reviewed. It is shown that various graphene coatings can be successfully used to decrease friction and wear in nano-, micro- and macro-mechanical applications. However, the conditions under which graphene serves as an effective protective coating depends on the operating parameters. A comprehensive review is provided with the aim to assess such characteristics of graphene.
Ion-beam irradiation of DLC-based nanocomposite: Creation of a highly biocompatible surface
Penkov, Oleksiy V.,Kheradmandfard, Mehdi,Khadem, Mahdi,Kharaziha, Mahshid,Mirzaamiri, Rouhollah,Seo, Kuk-Jin,Kim, Dae-Eun Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.469 No.-
<P><B>Abstract</B></P> <P>Ion-beam irradiation of diamond-like carbon (DLC) by He ions was studied. Molecular dynamics simulation was performed to understand the effects of irradiation on the nano-topography and chemical state of the coatings and determine the optimal irradiation conditions. Then, the experiment was conducted to validate the results of the simulation and correlate surface modifications to biomedical properties. It was demonstrated that the irradiation led to the formation of a low-density and low-sp<SUP>3</SUP> content surface layer. The structural and chemical properties of the final surface were nearly independent of the initial sp<SUP>3</SUP> content and irradiation energy. The biocompatibility of DLC-based nanocomposite coatings was significantly improved by ion-beam irradiation. Nanocomposite coatings were irradiated by 1 keV He ions. Irradiation with a dose of 4.2 × 10<SUP>15</SUP> ion/cm<SUP>2</SUP> increased the adhesion of MG63 cells dramatically from 10 to ∼100%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MD models of DLC with various sp<SUP>3</SUP> content were developed. </LI> <LI> MD simulation of ion-beam irradiation of DLC was performed. </LI> <LI> DCL-based nanocomposites were irradiated by He ion beam. </LI> <LI> Effect of the ion-beam irradiation n cell adhesion was assessed. </LI> <LI> Correlations between MD simulation and experiment were established. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Highly wear-resistant and biocompatible carbon nanocomposite coatings for dental implants
Penkov, O.V.,Pukha, V.E.,Starikova, S.L.,Khadem, M.,Starikov, V.V.,Maleev, M.V.,Kim, D.E. IPC Science and Technology Press 2016 Biomaterials Vol.102 No.-
<P>Diamond-like carbon coatings are increasingly used as wear-protective coatings for dental implants, artificial joints, etc. Despite their advantages, they may have several weak points such as high internal stress, poor adhesive properties or high sensitivity to ambient conditions. These weak points could be overcome in the case of a new carbon nanocomposite coating (CNC) deposited by using a C-60 ion beam on a Co/Cr alloy. The structure of the coatings was investigated by Raman and XPS spectroscopy. The wear resistance was assessed by using a reciprocating tribotester under the loads up to 0.4 N in both dry and wet sliding conditions. Biocompatibility of the dental implants was tested in vivo on rabbits. Biocompatibility, bioactivity and mechanical durability of the CNC deposited on a Co/Cr alloy were investigated and compared with those of bulk Co/Cr and Ti alloys. The wear resistance of the CNC was found to be 250-650 fold higher compared to the Co/Cr and Ti alloys. Also, the CNC demonstrated much better biological properties with respect to formation of new tissues and absence of negative morphological parameters such as necrosis and demineralization. Development of the CNC is expected to aid in significant improvement of lifetime and quality of implants for dental applications. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Tribology of Graphene: A Review
Oleksiy Penkov,김대은,김해진,김현준 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
Graphene has received significant attention due to its combination of remarkable mechanical, thermal, chemical and electrical properties. Furthermore, due to its superior strength, graphene has great potential for use as an ultra-thin protective coating for various precision components. In this paper, the latest developments in tribological applications of graphene, theoretical simulations of graphene friction and preparation methods are reviewed. It is shown that various graphene coatings can be successfully used to decrease friction and wear in nano-, micro- and macro-mechanical applications. However, the conditions under which graphene serves as an effective protective coating depends on the operating parameters. A comprehensive review is provided with the aim to assess such characteristics of graphene.