The Experts below are selected from a list of 138438 Experts worldwide ranked by ideXlab platform
Steven M George - One of the best experts on this subject based on the ideXlab platform.
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Spatial Molecular Layer Deposition of Ultrathin Polyamide To Stabilize Silicon Anodes in Lithium-Ion Batteries
2019Co-Authors: Jasmine M. Wallas, Steven M George, Brian C. Welch, Yikai Wang, Jun Liu, Simon E. Hafner, Rui Qiao, Taeho Yoon, Yang-tse Cheng, Chunmei BanAbstract:Cycling stability is central to implementing silicon (Si) anodes in next-generation high-energy lithium-ion batteries. However, challenges remain due to the lack of effective strategies to enhance the structural integrity of the anode during electrochemical cycling. Here, we develop a nanoscale polyamide coating, using spatial Molecular Layer deposition (MLD) of m-phenylenediamine and trimesoyl chloride precursors, to preserve the structural integrity of Si anodes. Poly(acrylic acid) (PAA) has been widely used in Si-based anodes as a binding agent due to its effective binding interactions with Si particles. However, the structural integrity of the anode is compromised by thermochemical decomposition of the poly(acrylic acid) binder, which can occur during electrode drying or during electrochemical cycling. Decomposition causes a 62% decrease in the elastic modulus of the Si anode, as measured by nanoindentation in electrolyte-soaked conditions. This study shows that an ultrathin polyamide coating counteracts this structural degradation, increases the elastic modulus of the degraded anode by 345%, and improves cohesion. Electrochemical analysis of polyamide-coated anodes reveals a film thickness dependence in cycling behavior. High overpotentials and fast capacity fading are observed for Si anodes with a 15 nm coating, whereas Si anodes with a 0.5 nm coating demonstrate stable cycling over 150 cycles with a capacity >1400 mAh g–1. Our findings identify polyamide as an effective electrode coating material to enhance structural integrity, leading to excellent cyclability with higher capacity retention. Furthermore, the use of the spatial MLD approach to deposit the coating enables short deposition time and a facile route to scale-up
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Molecular Layer deposition for surface modification of lithium ion battery electrodes
Advanced Materials Interfaces, 2016Co-Authors: Chunmei Ban, Steven M GeorgeAbstract:Inspired by recent successes in applying Molecular Layer deposition (MLD) to stabilize lithium-ion (Li-ion) electrodes, this review presents the MLD process and its outstanding attributes for electrochemical applications. The review discusses various MLD materials and their implementation in Li-ion electrodes. The rationale behind these emerging uses of MLD is examined to motivate future efforts on the fundamental understanding of interphase chemistry and the development of new materials for enhanced electrochemical performance.
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pyrolysis of alucone Molecular Layer deposition films studied using in situ transmission fourier transform infrared spectroscopy
Journal of Physical Chemistry C, 2015Co-Authors: Jaime W Dumont, Steven M GeorgeAbstract:The pyrolysis of alucone Molecular Layer deposition (MLD) films was studied in vacuum using in situ transmission Fourier transform infrared spectroscopy. The initial alucone MLD films were grown using trimethylaluminum (TMA) and either ethylene glycol (EG) (HO–(CH2)2–OH) or hydroquinone (HQ) (HO–C6H4–OH) at 150 °C. The alucone MLD films were then pyrolyzed in vacuum at temperatures ranging from 400 to 750 °C. The absorbance features for the C–H, C–C, and C–O stretching vibrations were observed to be lost at pyrolysis temperatures from 350 to 500 °C. For the alucone films grown using TMA and EG, the loss of these absorbance features was coupled to an increase in carboxylate (R-COO–) absorbance features. The carboxylate absorbance features reached their peak at a pyrolysis temperature of 450 °C and then decreased slowly with higher pyrolysis temperatures. The carboxylate absorbance features are consistent with an Al2O3/carbon composite material with Al3+/COO– species at the interface. In addition, the prese...
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growth of zircone on nanoporous alumina using Molecular Layer deposition
JOM, 2014Co-Authors: Robert A Hall, Steven M George, Yeongae Kim, Woonbong Hwang, Meghan E Samberg, Nancy A Monteiroriviere, Roger J NarayanAbstract:Molecular Layer deposition (MLD) is a sequential and self-limiting process that may be used to create hybrid organic/inorganic thin films from organometallic precursors and organic alcohol precursors. In this study, films of a zirconium-containing hybrid organic/inorganic polymer known as zircone were grown on nanoporous alumina using MLD. Scanning electron microscopy data showed obliteration of the pores in zircone-coated nanoporous alumina. An in vitro cell viability study indicated that the growth of human epidermal keratinocytes was the greatest on zircone-coated nanoporous alumina than on uncoated nanoporous alumina. Our results suggest that MLD may be used to create biocompatible coatings for use in many types of medical devices.
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ultralow thermal conductivity of atomic Molecular Layer deposited hybrid organic inorganic zincone thin films
Nano Letters, 2013Co-Authors: Jun Liu, Steven M George, Byunghoon Yoon, Eli Kuhlmann, Miao Tian, Jie Zhu, Y C Lee, Ronggui YangAbstract:Atomic Layer deposition (ALD) and Molecular Layer deposition (MLD) techniques with atomic level control enable a new class of hybrid organic–inorganic materials with improved functionality. In this work, the cross-plane thermal conductivity and volumetric heat capacity of three types of hybrid organic–inorganic zincone thin films enabled by MLD processes and alternate ALD–MLD processes were measured using the frequency-dependent time-domain thermoreflectance method. We revealed the critical role of backbone flexibility in the structural morphology and thermal conductivity of MLD zincone thin films by comparing the thermal conductivity of MLD zincone films with an aliphatic backbone to that with aromatic backbone. Much lower thermal conductivity values were obtained in ALD/MLD-enabled hybrid organic–inorganic zincone thin films compared to that of the ALD-enabled W/Al2O3 nanolaminates reported by Costescu et al. [Science 2004, 303, 989–990], which suggests that the dramatic material difference between orga...
Byunghoon Yoon - One of the best experts on this subject based on the ideXlab platform.
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ultralow thermal conductivity of atomic Molecular Layer deposited hybrid organic inorganic zincone thin films
Nano Letters, 2013Co-Authors: Jun Liu, Steven M George, Byunghoon Yoon, Eli Kuhlmann, Miao Tian, Jie Zhu, Y C Lee, Ronggui YangAbstract:Atomic Layer deposition (ALD) and Molecular Layer deposition (MLD) techniques with atomic level control enable a new class of hybrid organic–inorganic materials with improved functionality. In this work, the cross-plane thermal conductivity and volumetric heat capacity of three types of hybrid organic–inorganic zincone thin films enabled by MLD processes and alternate ALD–MLD processes were measured using the frequency-dependent time-domain thermoreflectance method. We revealed the critical role of backbone flexibility in the structural morphology and thermal conductivity of MLD zincone thin films by comparing the thermal conductivity of MLD zincone films with an aliphatic backbone to that with aromatic backbone. Much lower thermal conductivity values were obtained in ALD/MLD-enabled hybrid organic–inorganic zincone thin films compared to that of the ALD-enabled W/Al2O3 nanolaminates reported by Costescu et al. [Science 2004, 303, 989–990], which suggests that the dramatic material difference between orga...
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growth and properties of hybrid organic inorganic metalcone films using Molecular Layer deposition techniques
Advanced Functional Materials, 2013Co-Authors: Byoung H Lee, Robert A Hall, Byunghoon Yoon, Aziz I Abdulagatov, Steven M GeorgeAbstract:Molecular Layer deposition (MLD) is a useful technique for fabricating hybrid organic-inorganic thin fi lms. MLD allows for the growth of ultrathin and conformal fi lms using sequential, self-limiting reactions. This article focuses on the MLD of hybrid organic-inorganic fi lms grown using metal precursors and various organic alcohols that yield metal alkoxide fi lms. This family of metal alkoxides can be described as “metalcones”. Many metalcones are possible, such as the “alucones” and “zincones” based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic diols such as ethylene glycol. Alloys of the various metalcones with their parent metal oxide atomic Layer deposition (ALD) fi lms can also be fabricated that have an organic-inorganic composition that can be adjusted by controlling the relative number of ALD and MLD cycles. These metalcone alloys have tunable chemical, optical, mechanical, and electrical properties that may be useful for designing various functional fi lms. The metalcone hybrid organic-inorganic materials offer a new tool set for engineering thin fi lm properties.
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alucone alloys with tunable properties using alucone Molecular Layer deposition and al2o3 atomic Layer deposition
Journal of Physical Chemistry C, 2012Co-Authors: Byoung Hun Lee, Byunghoon Yoon, Virginia R Anderson, Steven M GeorgeAbstract:Ultrathin and conformal hybrid organic–inorganic thin films can be deposited by Molecular Layer deposition (MLD) techniques. By combining the hybrid organic–inorganic MLD process with an inorganic ...
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Molecular Layer deposition of hybrid organic inorganic alucone polymer films using a three step abc reaction sequence
Chemistry of Materials, 2009Co-Authors: Byunghoon Yoon, Dragos Seghete, Andrew S Cavanagh, Steven M GeorgeAbstract:Thin film growth using Molecular Layer deposition (MLD) or atomic Layer deposition (ALD) is based on sequential, self-limiting surface reactions. In this work, MLD is used to grow a hybrid organic−inorganic polymer film based on a three-step ABC reaction sequence using trimethylaluminum (TMA), ethanolamine (EA), and maleic anhydride (MA) as the reactants. This three-step ABC sequence avoids the use of homobifunctional organic precursors by employing a homotrifunctional inorganic reactant (TMA), a heterobifunctional organic reactant (EA), and a ring-opening organic reactant (MA). The resulting hybrid organic−inorganic polymer film is an alucone with an approximate formula of (−AlCH3−OCH2CH2NH−C(O)CHCHCOO−)n. The growth of this ABC alucone film was monitored using in situ Fourier transform infrared (FTIR) measurements at 90−170 °C. The three sequential surface reactions displayed self-limiting growth. The FTIR difference spectra monitored the absorbance from the surface species during the three surface reac...
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Molecular Layer deposition of hybrid organic inorganic polymer films using diethylzinc and ethylene glycol
Chemical Vapor Deposition, 2009Co-Authors: Byunghoon Yoon, Dragos Seghete, Jennifer Opatchen, Andrew Cavanaugh, Steven M GeorgeAbstract:The Molecular Layer deposition (MLD) of a hybrid organic-inorganic polymer based on zinc is demonstrated using sequential exposures of diethyl zinc (DEZ, Zn(CH2CH3)2) and ethylene glycol (EG, HOCH2CH2OH). This polymer is representative of a class of zinc alkoxide polymers with an approximate formula of (� ZnORO� )n that can be called ''zincones''. The film growth and surface chemistry during zincone MLD is studied using in-situ Fourier transform infrared (FTIR) measurements. The absorbance of the infrared features of the zincone film increase progressively versus the number of MLD cycles. The FTIR spectra after the DEZ and EG exposures are consistent with the gain and loss of absorbance from CH, OH, CO, and ZnO stretching vibrations. FTIR studies also confirm the self-limiting nature of the surface reactions and monitor the temperature dependence of the film growth. Transmission electron microscope (TEM) images of ZrO2 nanoparticles show very conformal zincone films and determine that the growth rate varies from 4.0 A u per MLD cycle at 908C to 0.25 A u per MLD cycle at 1708C. Quartz crystal microbalance (QCM) and X-ray reflectivity (XRR) measurements show linear zincone growth versus the number of MLD cycles. XRR studies on silicon wafers are consistent with a growth rate of 0.7 A u per MLD cycle at 1308C. The higher growth rate on the ZrO2 nanoparticles is attributed to the lower gas conductance and possible CVD reactions in the ZrO2 nanoparticles. The reaction mechanism for zincone MLD is dependent on temperature. At higher temperatures, there is evidence for ''double'' reactions of EG because no free hydroxyl groups are observed in the FTIR spectrum after the EG exposures. The zincone film can grow in the absence of free hydroxyl groups if DEZ can diffuse into the zincone film and react during the subsequent EG exposure. The zincone films initially adsorb H2O upon exposure to air and then are very stable with time.
Karteek Popuri - One of the best experts on this subject based on the ideXlab platform.
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substantially thinner internal granular Layer and reduced Molecular Layer surface in the cerebellar cortex of the tc1 mouse model of down syndrome a comprehensive morphometric analysis with active staining contrast enhanced mri
NeuroImage, 2020Co-Authors: Manuel Jorge Cardoso, Maria A Zuluaga, Marc Modat, Nick M Powell, Frances K Wiseman, Jon O Cleary, Benjamin Sinclair, Ian F Harrison, Bernard Siow, Karteek PopuriAbstract:Down Syndrome is a chromosomal disorder that affects the development of cerebellar cortical lobules. Impaired neurogenesis in the cerebellum varies among different types of neuronal cells and neuronal Layers. In this study, we developed an imaging analysis framework that utilizes gadolinium-enhanced ex vivo mouse brain MRI. We extracted the middle Purkinje Layer of the mouse cerebellar cortex, enabling the estimation of the volume, thickness, and surface area of the entire cerebellar cortex, the internal granular Layer, and the Molecular Layer in the Tc1 mouse model of Down Syndrome. The morphometric analysis of our method revealed that a larger proportion of the cerebellar thinning in this model of Down Syndrome resided in the inner granule cell Layer, while a larger proportion of the surface area shrinkage was in the Molecular Layer.
Bin Zhang - One of the best experts on this subject based on the ideXlab platform.
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wire in tube zno carbon by Molecular Layer deposition accurately tunable electromagnetic parameters and remarkable microwave absorption
Chemical Engineering Journal, 2020Co-Authors: Min Zhang, Shichao Zhao, Bin ZhangAbstract:Abstract Yolk–shell and one-dimensional structures are promising microwave absorption structures due to the microwave multi-reflection and scattering sites of yolk–shell structure, and the conductive network that is easily formed by one-dimensional structure. The wire-in-tube structure may be a more effective microwave absorption structure because it combines the advantages of one-dimensional and yolk–shell structures. However, conventional methods are difficult to realize such a structure because of the weak controllability of the structure, and it is impossible to tune the absorption band or optimize the absorption performance by precisely tailoring the structure. Molecular Layer deposition (MLD), with excellent structure controllability, is an effective strategy to overcome this problem. In this work, a novel wire-in-tube ZnO@carbon nanostructure was realized by polyimide MLD–calcination strategy. The ZnO cores and carbon shells form voids between them by a redox process during calcination, conducive to microwave multi-refection and scattering. More importantaly, by tuning the number of deposition cycles, the carbon shell thickness can be adjusted at the atomic scale so as to modulate the absorption bands effectively. Maximum absorption of −50.05 dB and a bandwidth of 5.68 GHz are simultaneously achieved at a matching thickness of 2.0 mm. The polyimide MLD–calcination strategy not only provides a novel wire-in-tube structure with remarkable microwave absorption performance, but diversifies carbonaceous material fabrication methods, extending the applications to supercapacitors, sensing, catalysis, and the biomedical fields.
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highly efficient microwave absorption of magnetic nanospindle conductive polymer hybrids by Molecular Layer deposition
ACS Applied Materials & Interfaces, 2017Co-Authors: Xixi Wang, Shichao Zhao, Y Li, Bin ZhangAbstract:Oxidative Molecular Layer deposition (oMLD) was applied to fabricate conductive polymer–magnetic material core–shell microwave absorbers in this work. One dimensional Fe3O4–poly(3,4-ethylenedioxythiophene) (PEDOT) nanospindles with controllable PEDOT thickness were successfully synthesized. Their absorption performance was evaluated in the 2–18 GHz frequency range. With the advantage of oMLD, PEDOT shell thicknesses can be controlled precisely. Because the permittivity of Fe3O4–PEDOT nanospindles obviously increases while their permeability decreases slightly with the PEDOT cycles, the properties can be tuned effectively by only adjusting the PEDOT cycle number. With a proper PEDOT shell thickness, excellent reflection characteristics can be obtained. Remarkably high absorption strength (−55.0 dB at 16.2 GHz) and good absorption bandwidth (4.34 GHz less than −10 dB) were realized. Such excellent performance is better than that reported previously for most magnetic material-based absorbers. Considering the...
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high efficiency cu zno hydrogenation catalyst the tailoring of cu zno interface sites by Molecular Layer deposition
ACS Catalysis, 2015Co-Authors: Bin Zhang, Eckhard Pippel, Yao Chen, Huimin Yang, Zhe Gao, Yong QinAbstract:This paper describes a Molecular Layer deposition (MLD)-assisted route for the preparation of Cu-ZnO catalysts used in the hydrogenation of levulinic acid to produce γ-valerolactone. A Cu precursor supported on multiwalled carbon nanotubes was coated with Zn-polyurea organic–inorganic hybrid films via MLD first, and the catalyst was obtained after calcination and reduction under mild conditions. The produced catalysts exhibited remarkably enhanced selectivity, efficiency, and stability due to the created Cu-ZnO interface sites (Cu0Zn) and the cooperative effect between Cu0Zn and Cu+. The ratio of Cu0Zn sites could be simply modified by changing the MLD cycle number. The correlation between catalytic activity and the ratio of different Cu species (Cu0Zn, Cu0, and Cu+) suggests that Cu0Zn is the main active site and responsible for the remarkably enhancing catalytic activity and low apparent activation energy.
Mato Knez - One of the best experts on this subject based on the ideXlab platform.
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Molecular Layer deposition of hybrid siloxane thin films by ring opening of cyclic trisiloxane v3d3 and azasilane
Chemical Communications, 2020Co-Authors: Mato Knez, Kristina Ashurbekova, Iva Saric, Evgenii Modin, Mladen Petravic, I M Abdulagatov, A I AbdulagatovAbstract:In this work, we report the first ring opening vapor to solid polymerization of cyclotrisiloxane and N-methyl-aza-2,2,4-trimethylsilacyclopentane by Molecular Layer deposition (MLD). This process was studied in situ with a quartz crystal microbalance and the thin film was characterized by X-ray photoelectron spectroscopy, ATR-FTIR and high-resolution transmission electron microscopy.
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Porous Fe2O3 nanotubes with α-γ phase junction for enhanced charge separation and photocatalytic property produced by Molecular Layer deposition
Applied Catalysis B-environmental, 2019Co-Authors: Chaoqiu Chen, Feifei Duan, Wiwat Nuansing, Baiyan Zhang, Weike Wang, Yong Qin, Shichao Zhao, Fan Yang, Mato KnezAbstract:Abstract Constructing nanotubular morphologies and heterojunctions are two effective strategies to enhance the charge separation and transport of α-Fe2O3 for improved photocatalytic performance, while the fabrication of porous α-Fe2O3 nanotubes with precisely tailored wall thickness, pore structure, crystallinity, and junctions still remains a big challenge. Herein, two novel Molecular Layer deposition (MLD) procedures are designed to prepare porous Fe2O3 nanotubes with tunable pore structure and phase junction. The organic fractions of the obtained Fe-hybrid MLD films not only act as soft templates to generate nanopores in nanotube walls but also play a key role in the formation of phase-junction. The porous structure and phase-junction significantly improve the mass diffusion and charge separation efficiency of Fe2O3 nanotubes, leading to a drastically increased photocatalytic activity for photo-Fenton reaction. Especially, the porous α-γ Fe2O3 nanotubes produced by two-step AB MLD from iron tert-butoxide and ethylene glycol exhibit the highest photocatalytic activity, which is more than a 6.5-fold and 20-fold improvement compared with the nonporous pure α-Fe2O3 nanotubes and commercial α-Fe2O3 nanoparticles, respectively. The MLD method provides a new bottom-up approach to develop efficient Fe2O3 based heterostructure porous photocatalysts for waste-water cleaning and water splitting.
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unexpected oxidation behavior of cu nanoparticles embedded in porous alumina films produced by Molecular Layer deposition
Nano Letters, 2011Co-Authors: Yong Qin, Yang Yang, Roland Scholz, Eckhard Pippel, Mato KnezAbstract:This work reports an unexpected oxidation behavior of Cu nanoparticles embedded in porous Al2O3 confinements that are produced by annealing alucone (an organic–inorganic hybrid material) deposited by Molecular Layer deposition. An oxidation of such encapsulated Cu nanoparticles by annealing in air produces Cu oxide nanoparticles attached to the outer surface of the hollow Al2O3 nanostructures, which is in strong contrast to bare or compact, nonporous Al2O3-coated Cu nanoparticles, which result in hollow oxide nanospheres or do not undergo oxidation, respectively. The conversion from encapsulated Cu to supported oxide nanoparticles is explained by a concerted pore-assisted diffusion and oxidation mechanism. The micropores in the films, having diameters of several angstroms, permit a selective out-diffusion of Cu atoms and prevent the inward diffusion of oxygen. The subsequent oxidation occurs at the pore entrances, which work as multiple nucleation sites for the formation of oxide nanoparticles with a smal...
