A method and article of manufacture of amorphous diamond-like carbon. The method involves providi... more A method and article of manufacture of amorphous diamond-like carbon. The method involves providing a substrate in a chamber, providing a mixture of a carbon containing gas and hydrogen gas with the mixture adjusted such that the atomic molar ratio of carbon to hydrogen is less than 0.3, including all carbon atoms and all hydrogen atoms in the mixture. A
The reversible cyclability of Si based composite anodes is greatly improved by optimizing the ato... more The reversible cyclability of Si based composite anodes is greatly improved by optimizing the atomic ratio of Cu/Si in the films fabricated via magnetron sputtering. The galvanostatic test results show that the thin film anode made of 20%at. Cu delivers 1950 mAhg -1 as the initial discharge capacity with 80% coulombic efficiency. Then, after the 50 th cycles 80% of the initial discharge capacity is retained, with 99.5 % coulombic efficiency. This remarkable performance can be explained by small crystalline sizes, amorphous structures of the thin film and its enhanced physical and mechanical properties due to the 20 %at. Cu content. High specific capacities achieved in this study prove that magnetron sputtering deposition might be a good alternative production technique to fabricate high performance anode materials. Furthermore, this one step, environmentally friendly process enables one to control the film composition, structure as well as adhesion which minimizes delamination and p...
Langmuir : the ACS journal of surfaces and colloids, Jan 10, 2015
The oxidized layers at the surface of hydrogenated diamond-like carbon (H-DLC) were studied with ... more The oxidized layers at the surface of hydrogenated diamond-like carbon (H-DLC) were studied with X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, and Raman spectroscopy. The structure of these layers was correlated with the friction and wear behavior observed on H-DLC. H-DLC is well-known for its ultralow friction in inert environments, but the steady superlubricious state is always preceded by a run-in period with a high friction. It was hypothesized that the run-in period is related to the surface oxide layer formed naturally upon exposure of the sample to air. To test this hypothesis, thermal oxide layers were grown, and their structures were analyzed and compared with the native oxide layer on a pristine sample. It was found that the Raman spectra of the surface oxide layers of H-DLC have higher D/G band ratio than the bulk, indicating a larger amount of aromatic clusters compared to the bulk film. Thick oxide layers grown at 300 °C showed a run-in fr...
Abstract We have developed a synchrotron-based x-ray microdiffraction technique for measuring dep... more Abstract We have developed a synchrotron-based x-ray microdiffraction technique for measuring depth-resolved residual stress distribution in nanocrystalline films with submicron resolution [1]. In this study, we further refined this technique and applied it to low-friction ...
ABSTRACT The symposium, `Low Friction Coatings on Glass and Ceramics', was held in Baltim... more ABSTRACT The symposium, `Low Friction Coatings on Glass and Ceramics', was held in Baltimore, MD, in April 2005. This was part of the American Ceramic Society's annual meeting. The symposium was co-organized by Jacqueline A Johnson and Osman L Eryilmaz of Argonne National Laboratory (ANL). They would like to thank all the speakers who participated so enthusiastically in the symposium and the sponsors who kindly contributed to its success: NSF (National Science Foundation) and NIH (National Institutes of Health).
ABSTRACT This paper presents the results of a systematic study demonstrating how controlled or ta... more ABSTRACT This paper presents the results of a systematic study demonstrating how controlled or targeted tribochemistry can lead to super-low friction and wear in diamond-like carbon (DLC) films. Specifically, how hydrogen can lead to dramatic reductions in the friction and wear of hydrogen-free DLC films which otherwise experience high friction and severe wear losses. When sliding tests are performed with a hydrogen-free DLC film in an inert gas (like Ar), the friction coefficients were in the range of 0.4 to 0.7 and it wore out rather quickly. However, when the same tests were run under the 1333 Pa partial pressure of hydrogen, the friction coefficients were reduced by factors of more than 10 and the wear damage became very difficult to quantify. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses provided strong chemical evidence that the sliding contact surfaces of these films underwent tribochemical reactions with hydrogen effectively passivating dangling bonds of surface carbon atoms, which is believed to be responsible for ultralow friction and wear. In an effort to rule out the possibility of contamination and confirm the pivotal role of hydrogen in lubricity of DLC films, we ran similar tests with the same hydrogen-free DLC in deuterium (an isotope of hydrogen) and achieved essentially the same level of reduction in friction. TOF-SIMS clearly confirmed the formation of a deuterium-rich tribofilm on rubbing surfaces thus confirming the critical role of tribochemistry in super-low friction and wear of DLC.
ABSTRACT a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Lithium ion batter... more ABSTRACT a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Lithium ion batteries Anode Helices CuSi thin film Glancing angle deposition Both helical and inclined columnar Si–10 at.% Cu structured thin films were deposited on Cu substrates using glancing angle deposition (GLAD) technique. In order to deposit Cu and Si two evaporation sources were used. Ion assistance was utilized in the first 5 min of the GLAD to enhance the adhesion and the density of the films. These films were characterized by thin film XRD, GDOES, SEM, and EDS. Electrochemical characterizations were made by testing the thin films as anodes in half-cells for 100 cycles. The results showed that the columnar SiCu thin film delivered 2200 mAh g −1 , where the helical one exhibited 2600 mAh g −1 , and, their initial coulom-bic efficiencies were found to be 38%–50% respectively. For the columnar and the helical thin film anodes, sustain-able 520 and 800 mAh g −1 with 90% and 99% coulombic efficiencies were achieved for 100 cycles. These sustainable capacities showed the importance of the thin film structure having nano-sized crystals and amor-phous particles. The higher surface area of the helices increases the capacity of the electrode because the contact area of the thin film anode with Li ions is increased, and the polarization which otherwise forms on the anode surface due to SEI formation is decreased. In addition, because of larger interspaces between the helices the ability of the anode to accommodate the volumetric changes is improved, which results in a higher coulombic efficiency and capacity retention during cycling test.
A method and article of manufacture of amorphous diamond-like carbon. The method involves providi... more A method and article of manufacture of amorphous diamond-like carbon. The method involves providing a substrate in a chamber, providing a mixture of a carbon containing gas and hydrogen gas with the mixture adjusted such that the atomic molar ratio of carbon to hydrogen is less than 0.3, including all carbon atoms and all hydrogen atoms in the mixture. A
The reversible cyclability of Si based composite anodes is greatly improved by optimizing the ato... more The reversible cyclability of Si based composite anodes is greatly improved by optimizing the atomic ratio of Cu/Si in the films fabricated via magnetron sputtering. The galvanostatic test results show that the thin film anode made of 20%at. Cu delivers 1950 mAhg -1 as the initial discharge capacity with 80% coulombic efficiency. Then, after the 50 th cycles 80% of the initial discharge capacity is retained, with 99.5 % coulombic efficiency. This remarkable performance can be explained by small crystalline sizes, amorphous structures of the thin film and its enhanced physical and mechanical properties due to the 20 %at. Cu content. High specific capacities achieved in this study prove that magnetron sputtering deposition might be a good alternative production technique to fabricate high performance anode materials. Furthermore, this one step, environmentally friendly process enables one to control the film composition, structure as well as adhesion which minimizes delamination and p...
Langmuir : the ACS journal of surfaces and colloids, Jan 10, 2015
The oxidized layers at the surface of hydrogenated diamond-like carbon (H-DLC) were studied with ... more The oxidized layers at the surface of hydrogenated diamond-like carbon (H-DLC) were studied with X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, and Raman spectroscopy. The structure of these layers was correlated with the friction and wear behavior observed on H-DLC. H-DLC is well-known for its ultralow friction in inert environments, but the steady superlubricious state is always preceded by a run-in period with a high friction. It was hypothesized that the run-in period is related to the surface oxide layer formed naturally upon exposure of the sample to air. To test this hypothesis, thermal oxide layers were grown, and their structures were analyzed and compared with the native oxide layer on a pristine sample. It was found that the Raman spectra of the surface oxide layers of H-DLC have higher D/G band ratio than the bulk, indicating a larger amount of aromatic clusters compared to the bulk film. Thick oxide layers grown at 300 °C showed a run-in fr...
Abstract We have developed a synchrotron-based x-ray microdiffraction technique for measuring dep... more Abstract We have developed a synchrotron-based x-ray microdiffraction technique for measuring depth-resolved residual stress distribution in nanocrystalline films with submicron resolution [1]. In this study, we further refined this technique and applied it to low-friction ...
ABSTRACT The symposium, `Low Friction Coatings on Glass and Ceramics', was held in Baltim... more ABSTRACT The symposium, `Low Friction Coatings on Glass and Ceramics', was held in Baltimore, MD, in April 2005. This was part of the American Ceramic Society's annual meeting. The symposium was co-organized by Jacqueline A Johnson and Osman L Eryilmaz of Argonne National Laboratory (ANL). They would like to thank all the speakers who participated so enthusiastically in the symposium and the sponsors who kindly contributed to its success: NSF (National Science Foundation) and NIH (National Institutes of Health).
ABSTRACT This paper presents the results of a systematic study demonstrating how controlled or ta... more ABSTRACT This paper presents the results of a systematic study demonstrating how controlled or targeted tribochemistry can lead to super-low friction and wear in diamond-like carbon (DLC) films. Specifically, how hydrogen can lead to dramatic reductions in the friction and wear of hydrogen-free DLC films which otherwise experience high friction and severe wear losses. When sliding tests are performed with a hydrogen-free DLC film in an inert gas (like Ar), the friction coefficients were in the range of 0.4 to 0.7 and it wore out rather quickly. However, when the same tests were run under the 1333 Pa partial pressure of hydrogen, the friction coefficients were reduced by factors of more than 10 and the wear damage became very difficult to quantify. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses provided strong chemical evidence that the sliding contact surfaces of these films underwent tribochemical reactions with hydrogen effectively passivating dangling bonds of surface carbon atoms, which is believed to be responsible for ultralow friction and wear. In an effort to rule out the possibility of contamination and confirm the pivotal role of hydrogen in lubricity of DLC films, we ran similar tests with the same hydrogen-free DLC in deuterium (an isotope of hydrogen) and achieved essentially the same level of reduction in friction. TOF-SIMS clearly confirmed the formation of a deuterium-rich tribofilm on rubbing surfaces thus confirming the critical role of tribochemistry in super-low friction and wear of DLC.
ABSTRACT a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Lithium ion batter... more ABSTRACT a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Lithium ion batteries Anode Helices CuSi thin film Glancing angle deposition Both helical and inclined columnar Si–10 at.% Cu structured thin films were deposited on Cu substrates using glancing angle deposition (GLAD) technique. In order to deposit Cu and Si two evaporation sources were used. Ion assistance was utilized in the first 5 min of the GLAD to enhance the adhesion and the density of the films. These films were characterized by thin film XRD, GDOES, SEM, and EDS. Electrochemical characterizations were made by testing the thin films as anodes in half-cells for 100 cycles. The results showed that the columnar SiCu thin film delivered 2200 mAh g −1 , where the helical one exhibited 2600 mAh g −1 , and, their initial coulom-bic efficiencies were found to be 38%–50% respectively. For the columnar and the helical thin film anodes, sustain-able 520 and 800 mAh g −1 with 90% and 99% coulombic efficiencies were achieved for 100 cycles. These sustainable capacities showed the importance of the thin film structure having nano-sized crystals and amor-phous particles. The higher surface area of the helices increases the capacity of the electrode because the contact area of the thin film anode with Li ions is increased, and the polarization which otherwise forms on the anode surface due to SEI formation is decreased. In addition, because of larger interspaces between the helices the ability of the anode to accommodate the volumetric changes is improved, which results in a higher coulombic efficiency and capacity retention during cycling test.
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