changzeng yan - Academia.edu (original) (raw)
Papers by changzeng yan
2018 19th International Conference on Electronic Packaging Technology (ICEPT), 2018
Herein, carbon supported PdCu alloy is synthesized using copper–based metal-organic frameworks (M... more Herein, carbon supported PdCu alloy is synthesized using copper–based metal-organic frameworks (MOFs) as both precursor and sacrificial template. The PdCu alloy nanoparticles with diameter around 60 nm were evenly distributed on the MOFs derived carbon matrix. The as prepared PdCu/C hybrid exhibits impressive catalytic performance for electroless copper deposition on three different substrates, i.e., epoxy board, polyethylene terephthalate film and tissue paper. Our work suggests that alloying Cu with Pd on carbon matrix is an efficient way to provide cheap and stable catalyst for printed conductive circuit.
C.M. Raghavan, Changzeng Yan, Shashikant. P. Patole, J. B. Yoo, Dae Joon Kang BK 21 Physics Resea... more C.M. Raghavan, Changzeng Yan, Shashikant. P. Patole, J. B. Yoo, Dae Joon Kang BK 21 Physics Research Division, Department of Energy Science, Institute of Basic Sciences, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, South Korea, School of Advanced Materials Science and Engineering, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, South Korea
Journal of Electronic Materials, 2019
Highly crystalline one-dimensional zinc oxide (ZnO) nano-grass was grown on silicon (Si) substrat... more Highly crystalline one-dimensional zinc oxide (ZnO) nano-grass was grown on silicon (Si) substrate by a modified hydrothermal method. A predominantly c-oriented ZnO nano-grass with an average diameter of 40-60 nm and length of 1.5-2.0 lm was obtained. From the photoluminescence (PL) measurement, we observed a defect-free, intense ultraviolet emission of as-grown ZnO nanograss, confirming the absence of singly ionized oxygen vacancies. The absence of green deep-level emission in the PL spectrum further implies a high crystallinity of as-grown ZnO nano-grass. The high-quality ZnO nano-grass has potential applications in single nanowire-based light-emitting diodes, solar cells, themoresistive sensing, photocatalysis, ultraviolet photodetectors, optical switches, waveguides and nano-lasers.
Journal of Applied Polymer Science, 2018
Heat removal via thermal management materials is attracting more and more attention in the electr... more Heat removal via thermal management materials is attracting more and more attention in the electronic industry. Conventional particle/polymer thermal conductive composites require a high filler loading ratio (>30 vol %), which cause severe thermal interfacial resistance and mechanical issue. In this work, we fabricate tellurium nanowires (NWs)/epoxy nanocomposites via a facile bar coating method. According to Agari model and Maxwell-Eucken model, the as-synthesized ultra-long NWs with high aspect ratio (>100) construct the 3D interconnected thermal conductive network better in resin matrix to facilitate the heat transfer process. The results show that at a low loading ratio of 2.4 vol %, this nanocomposite exhibits the out-of-plane and in-plane thermal conductivity of 0.378 and 1.63 W m −1 K −1 , respectively, which is 189 and 715% higher than that of pure epoxy resin. Importantly, good stability, and flexibility of nanocomposites are well maintained.
Nano Research, 2017
We demonstrated the controlled growth of two-dimensional (2D) hexagonal tin disulfide (SnS 2) nan... more We demonstrated the controlled growth of two-dimensional (2D) hexagonal tin disulfide (SnS 2) nanoflakes with stacked monolayer atomic steps. The morphology was similar to flat-topped and step-sided mesa plateaus or step pyramids. The SnS 2 nanoflakes were grown on mica substrates via an atmospheric-pressure chemical vapor deposition process using tin monosulfide and sulfur powder as precursors. Atomic force microscopy (AFM), electron microscopy, and Raman characterizations were performed to investigate the structural features, and a sequential layer-wise epitaxial growth mechanism was revealed. In addition, systematic Raman characterizations were performed on individual SnS 2 nanoflakes with a wide range of thicknesses (1-100 nm), indicating that the A 1g peak intensity and Raman shifts were closely related to the thickness of the SnS 2 nanoflakes. Moreover, photoconductive AFM was performed on the monolayer-stepped SnS 2 nanoflakes, revealing that the flat surface and the edges of the SnS 2 atomic steps had different electrical conductive properties and photoconductive behaviors. This is ascribed to the dangling bonds and defects at the atomic step edges, which caused a height difference of the Schottky barriers formed at the interfaces between the PtIr-coated AFM tip and the step edges or the flat surface of the SnS 2 nanoflakes. The 2D SnS 2 crystals with regular monolayer atomic steps and fast photoresponsivity are promising for novel applications in photodetectors and integrated optoelectronic circuits.
Nano Energy, 2016
Abstract Although transition metal oxides have attracted considerable attention for their high en... more Abstract Although transition metal oxides have attracted considerable attention for their high energy density as anode materials of lithium-ion batteries, they suffer from large volume expansion during lithiation process, which usually causes fast capacity degradation. Herein, we report a rational design and facile preparation strategy of copper oxide encapsulated mesoporous carbon multi-yolk-shell octahedra, in which multiple CuO nanoparticles are well-confined in the compartments of micro-scale octahedral carbon scaffolds. The advantages of the novel multi-yolk-shell design are that the three-dimensional carbon scaffolds can buffer the volume change and prevent aggregation of CuO nanoparticles during the charge/discharge cycles, provide pathways for electron transport and Li + diffusion, and restrict the thin solid-electrolyte interphase layer to the outer surface of carbon shells. The results demonstrate how the electrochemical properties of anodes can be significantly improved by the multi-yolk-shell nanostructures with greatly enhanced structural stability and electrochemical actuation. Moreover, the micrometer-size CuO@C octahedra reduce the relative quality of SEI, resulting in high Coulombic efficiency and long cycling stability. In Li-ion cells, the CuO@C multi-yolk-shell octahedra anodes deliver a highly-reversible capacity of 598 mA h g −1 at 250 mA g −1 , excellent rate capacity of 365 mA h g −1 at 3000 mA g −1 and exhibit long-term cyclability with a capacity of 512 mA h g −1 after 300 cycles at 500 mA g −1 .
Nano Research, 2018
The ammonia synthesis from nitrogen and water under ambient conditions is one of the most invitin... more The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes. Although nitrogen is abundant in the atmosphere and the ammonia synthesis reaction is exothermic on the thermodynamics, the conversion of N 2 to ammonia is actually hard to proceed owing to the chemical inertness and stability of N 2 molecules. In industry, ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300-500 °C, 20-30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g., CO 2). Recently, a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention, which holds great promise for nitrogen fixation under room temperature and atmospheric pressure. However, the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems. Here we provide an overview of the latest progresses, remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation. Moreover, this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results. We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.
2019 20th International Conference on Electronic Packaging Technology(ICEPT)
As electronic products continue to be miniaturized, the generated heat of the running chip accumu... more As electronic products continue to be miniaturized, the generated heat of the running chip accumulated significantly, thus heat dissipation becomes a crucial issue. According to the previous report, reducing the interface thermal resistance (ITR) and constructing the thermal conductive networking structure can effectively improve the heat transferring property of the polymer based thermal interface materials (TIMs). Here we report a polymer composite loaded with oriented carbon nanofibers which exhibit both high thermal conductivity and excellent flexibility. These nanofibers were prepared by electrospinning technique followed by a high-temperature carbonization process. The obtained well-ordered filler structure not only reduces the ITR but also build the 3D network architecture. Further, when combining with organic matrix to make the thermal gel, the through-plane thermal conductivity along the fiber direction of the composite gel increases greatly, which is as high as 0.847 W m−1 K−1, the strategy of using aligned and networked thermal filler in the TIMs may be a more effective way to enhance the heat dissipation of future 5G communication electronics.
2018 19th International Conference on Electronic Packaging Technology (ICEPT), 2018
MXenes emerged as the new layered 2D semiconductors have exhibited many intriguing electrical, th... more MXenes emerged as the new layered 2D semiconductors have exhibited many intriguing electrical, thermal and optical properties. Therefore, the promising highly thermal conductive property is not yet to be well investigated. Herein, we employ MXenes (Ti<inf>3</inf>C<inf>2</inf>) as thermal filler in epoxy nanocomposites, in which the particulate MXenes is wrapped and interconnected by Ag nanowire. The room-temperature thermal conductivity of Ag/Ti<inf>3</inf>C<inf>2</inf> epoxy nanocomposite is found to be 7.60 W m<sup>−1</sup> K<sup>−1</sup> at a relatively low loading of 15 wt%, which is more than two-fold higher than pure Ti<inf>3</inf>C<inf>2</inf> (3.51 W m<sup>−1</sup> K<sup>−1</sup>). Based on the present investigation, developing MXenes based nanocomposites could be extremely promising for thermal management applications.
2018 20th International Conference on Electronic Materials and Packaging (EMAP), 2018
Modern electronics are seriously limited by heat dissipation. Interfacial thermal resistance and ... more Modern electronics are seriously limited by heat dissipation. Interfacial thermal resistance and constructing thermal conductive network are found to be the key issues. In this work, pine needle-derived carbon (PNDC) was prepared by a simple carbonization method. At optimized condition 50°C for 2 hrs, it shows impressive thermal conductive property. Importantly, the systematic structural characterization indicates that this derived carbon itself has well aligned, interconnected network-like, and channel-shaped microstructure which benefits the interface contact. The resulting Ag @PNDC/epoxy composite films were fabricated via a vacuum infiltration technology, the results show a much enhanced heat transportation (0.537mathrmWm−1mathrmK−1)(0.537 mathrm{Wm}^{-1} \mathrm{K}^{-1})(0.537mathrmWm−1mathrmK−1) as compared to that of pure epoxy resin (0.187mathrmWm−1mathrmK−1)(0.187 mathrm{Wm}^{-1} \mathrm{K}^{-1})(0.187mathrmWm−1mathrmK−1).
Modern Physics Letters B, 2021
Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of app... more Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of applications in light-emitting devices, semiconductor devices and solar cell devices. However, previous studies usually deposit nanocrystal films on traditional rigid substrates, limiting their applications in large-scale, direct-deposited flexible device fabrication processes, such as roll-to-roll printing process. Here, we report a direct deposition method for lead sulfide (PbS) nanocrystal films on flexible polymer substrates. By adding triethanolamine-coordinated Pb precursors to the reaction system to enhance the adhesion to the substrate and controlling the precursor ratios, we obtained high-quality flexible PbS films. The film is composed of octahedral PbS nanocrystals with preferred (111) orientation. The optical band gap of the nanocrystal films can be tuned from 1.32 eV to 1.60 eV by adjusting the ratio of the precursors, and an ideal band gap of 1.4 eV for single-junction solar c...
Nanotechnology, 2021
Thermal interface material (TIM) is pivotal for the heat dissipation between layers of high-densi... more Thermal interface material (TIM) is pivotal for the heat dissipation between layers of high-density electronic packaging. The most widely used TIMs are particle-filled composite materials, in which highly conductive particulate fillers are added into the polymer matrix to promote heat conduction. The numerical simulation of heat transfer in the composites is essential for the design of TIMs; however, the widely used finite element method (FEM) requires large memory and presents limited computational time for the composites with dense particles. In this work, a numerical homogenization algorithm based on fast Fourier transform was adopted to estimate the thermal conductivity of composites with randomly dispersed particles in 3D space. The unit cell problem is solved by means of a polarization-based iterative scheme, which can accelerate the convergence procedure regardless of the contrast between various components. The algorithm shows good precision and requires dramatically reduced...
Crystals, 2020
This study reports the employment of Co(OH)xF2−x nanosheets, a new material in the sensor field, ... more This study reports the employment of Co(OH)xF2−x nanosheets, a new material in the sensor field, for gas sensor applications. We synthesize Co(OH)xF2−x nanosheets via a hydrothermal route using SiO2 sphere templates. Our material characterization confirms that the material is a densely clustered Co(OH)xF2−x nanosheet with an amorphous microstructure with some short-range ordering. Sensors based on the nanosheets demonstrate a high response of 269% toward 4.5 ppm of acetone gas at an operation temperature of 200 °C and a very low minimum detection limit of 40 ppb. It functions effectively up to a temperature below 300 °C, above which F is found to start to evaporate. Our discussion suggests that an excellent sensor performance arises from the high catalytic function of F incorporated in a high concentration in the material as well as the high specific surface area due to the morphology of densely clustered nanosheets.
ACS Applied Materials & Interfaces, 2020
High-performance thermal management materials are essential in miniaturized, highly integrated, a... more High-performance thermal management materials are essential in miniaturized, highly integrated, and high-power modern electronics for heat dissipation. In this context, the large interface thermal resistance (ITR) that occurs between fillers and the organic matrix in polymer-based nanocomposites greatly limits their thermal conductive performance. Herein, through-plane direction aligned three-dimensional (3D) MXene/silver (Ag) aerogels are designed as heat transferring skeletons for epoxy nanocomposites. Ag nanoparticles (NPs) were in-situ decorated on exfoliated MXene nanosheets to ensure good contact, and subsequent welding of ice-templated MXene/Ag nanofillers at low temperature of ~200 oC reduced contact resistance between individual MXene sheets. Monte Carlo simulations suggest that thermal interficial resistance (R0) of the MXene/Agepoxy nanocomposite was 4.5 × 10-7 m2 W-1 K-1, which was lesser than that of the MXeneepoxy nanocomposite (Rc = 5.2 × 10-7 m2 W-1 K-1). Furthermore, the large-scale atomic/molecular massively parallel simulator was employed to calculate the interfacial resistance. It was found that RMXene=2.4 × 10-9 m2 K W-1, RMXene-Ag=2.0 ×10-9 m2 K W-1, respectively, indicating that the Ag NP enhanced the interfacial heat transport. At a relatively low loading of 15.1 vol%, through-plane thermal conductivity reached a value as high as 2.65 W m-1 K-1, which is 1225 % higher than that of pure epoxy resin. Furthermore, MXene/Agepoxy nanocomposite film exhibit impressive thermal conductive property when applied on a Millet 8 and Dell computer for heat dissipation.
Nanoscale, 2019
Bi2MoO6/OV-BiOBr heterojunctions are synthesized and show good photocatalytic activities for nitr... more Bi2MoO6/OV-BiOBr heterojunctions are synthesized and show good photocatalytic activities for nitrogen reduction to ammonia under ambient conditions.
Ceramics International, 2019
A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth... more A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth (CC) was developed; further, free-standing, flexible lithium-ion-battery (LIB) anodes with good electrical contact between current collector and the active substance were prepared. The as-prepared ZnO NFs/CC-based LIB anodes showed a high specific capacity of 1754 mAh g −1 at a current density of 0.1 A g −1 , a capacity retention of almost 52.9% at a current density of 2 A g −1 , as well as high rate capability. Moreover, the anodes demonstrated a high capacity with reversiblity of approximately 1650 mAh g −1 and only 6% capacity fading at a current density of 0.1 A g −1 , even after 100 cycles. These results imply that the synthesized, unique ZnO NFs/CC nanostructures can be employed as high-efficiency anode materials for flexible LIBs.
Advanced Energy Materials, 2019
3833 mAh cm −3 nearly double that of lithium (2062 mAh cm −3), and exhibits a relatively negative... more 3833 mAh cm −3 nearly double that of lithium (2062 mAh cm −3), and exhibits a relatively negative reduction potential of −2.4 V versus standard hydrogen electrode (SHE). [6-9] Despite of these intriguing merits, the practical employment of RMBs is hampered by several main hurdles. First, clumsy Mg 2+ intercalation is the primary limitation for the choice of competent cathode materials, because the strong Coulombic interactions between the divalent Mg 2+ ions and the anions in the host materials often result in sluggish diffusion kinetics and slow interfacial charge transfer. [10-13] Second, to design appropriate electrolytes for Mg plating/ stripping with high Coulombic efficiency, wide electrochemical window, and good compatibility with the cathodic materials is another great challenge. [14,15] Therefore, to develop advanced cathode materials capable of rapid Mg 2+ insertion/extraction in suitable electrolytes for reversible Mg plating/stripping is highly desirable. Since the pioneering work of Chevrel phase compounds (Mo 6 S 8) reported by Aurbach et al. in 2000, [16] tremendous efforts have been devoted to develop cathode materials for RMBs, including transition metal oxides (MnO 2 , V 2 O 5 , Mn 3 O 4 , WO 3 , Co 3 O 4), [17-21] polyanionic compounds (Mg 1.03 Mn 0.97 SiO 4 , MgCoSiO 4), [22,23] and transition metal dichalcogenides (TMDs, such as TiS 2 , MoS 2 , WSe 2). [24-28] However, most oxides and polyanionic compounds suffer from low capacity and poor cycling performance owing to the strong interactions between divalent Mg 2+ and O 2− in the hosts. [25,29] On the contrary, TMDs are deemed to be a class of promising cathode materials with more favorable kinetics, attributing to the relatively weaker MgS or MgSe bonds than MgO bond. [25,28,30] Nevertheless, layered TMDs also suffer from slow Mg 2+ ion diffusion due to the narrow interlayer spacing and the high polarity of Mg 2+. [31] Recently, it was reported that the interlayer distances of TMDs could be expanded by intercalating guest molecules (water or organic molecules), enlarging the dimension of ion diffusion channels and shielding the Coulombic interactions between Mg 2+ and the lattice anions of hosts. 13,27 In addition, the intercalated molecules served as interlayer pillars are conducive to maintain the framework of host materials for prolonged cycles. [32,33] Rechargeable magnesium batteries (RMBs) are attractive candidates for large-scale energy storage owing to the high theoretical specific capacity, rich earth abundance, and good safety characteristics. However, the development of desirable cathode materials for RMBs is constrained by the high polarity and slow intercalation kinetics of Mg 2+ ions. Herein, it is demonstrated that 2-ethylhexylamine pillared vanadium disulfide nanoflowers (expanded VS 2) with enlarged interlayer distances exhibit greatly boosted electrochemical performance as a cathode material in RMBs. Through a one-step solution-phase synthesis and in situ 2-ethylhexylamine intercalation process, VS 2 nanoflowers with ultralarge interlayer spacing are prepared. A series of ex situ characterizations verify that the cathode of expanded VS 2 nanoflowers undergoes a reversible intercalation reaction mechanism, followed by a conversion reaction mechanism. Electrochemical kinetics analysis reveal a relatively fast Mg-ion diffusivity of expanded VS 2 nanoflowers in the order of 10 −11-10 −12 cm 2 s −1 , and the pseudocapacitive contribution is up to 64% for the total capacity at 1 mV s −1. The expanded VS 2 nanoflowers show highly reversible discharge capacity (245 mAh g −1 at 100 mA g −1), good rate capability (103 mAh g −1 at 2000 mA g −1), and stable cycling performance (90 mAh g −1 after 600 cycles at 1000 mA g −1).
Composites Science and Technology, 2019
Improving thermal conductivity through welding boron nitride nanosheets onto silver nanowires via... more Improving thermal conductivity through welding boron nitride nanosheets onto silver nanowires via silver nanoparticles, Composites Science and Technology (2019), doi:
Nanoscale, 2019
Surface plasmon resonance enhanced direct Z-Scheme TiO2/ZnTe/Au nanocorncobs exhibit efficient ph... more Surface plasmon resonance enhanced direct Z-Scheme TiO2/ZnTe/Au nanocorncobs exhibit efficient photocatalytic overall water splitting.
2018 19th International Conference on Electronic Packaging Technology (ICEPT), 2018
Herein, carbon supported PdCu alloy is synthesized using copper–based metal-organic frameworks (M... more Herein, carbon supported PdCu alloy is synthesized using copper–based metal-organic frameworks (MOFs) as both precursor and sacrificial template. The PdCu alloy nanoparticles with diameter around 60 nm were evenly distributed on the MOFs derived carbon matrix. The as prepared PdCu/C hybrid exhibits impressive catalytic performance for electroless copper deposition on three different substrates, i.e., epoxy board, polyethylene terephthalate film and tissue paper. Our work suggests that alloying Cu with Pd on carbon matrix is an efficient way to provide cheap and stable catalyst for printed conductive circuit.
C.M. Raghavan, Changzeng Yan, Shashikant. P. Patole, J. B. Yoo, Dae Joon Kang BK 21 Physics Resea... more C.M. Raghavan, Changzeng Yan, Shashikant. P. Patole, J. B. Yoo, Dae Joon Kang BK 21 Physics Research Division, Department of Energy Science, Institute of Basic Sciences, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, South Korea, School of Advanced Materials Science and Engineering, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, South Korea
Journal of Electronic Materials, 2019
Highly crystalline one-dimensional zinc oxide (ZnO) nano-grass was grown on silicon (Si) substrat... more Highly crystalline one-dimensional zinc oxide (ZnO) nano-grass was grown on silicon (Si) substrate by a modified hydrothermal method. A predominantly c-oriented ZnO nano-grass with an average diameter of 40-60 nm and length of 1.5-2.0 lm was obtained. From the photoluminescence (PL) measurement, we observed a defect-free, intense ultraviolet emission of as-grown ZnO nanograss, confirming the absence of singly ionized oxygen vacancies. The absence of green deep-level emission in the PL spectrum further implies a high crystallinity of as-grown ZnO nano-grass. The high-quality ZnO nano-grass has potential applications in single nanowire-based light-emitting diodes, solar cells, themoresistive sensing, photocatalysis, ultraviolet photodetectors, optical switches, waveguides and nano-lasers.
Journal of Applied Polymer Science, 2018
Heat removal via thermal management materials is attracting more and more attention in the electr... more Heat removal via thermal management materials is attracting more and more attention in the electronic industry. Conventional particle/polymer thermal conductive composites require a high filler loading ratio (>30 vol %), which cause severe thermal interfacial resistance and mechanical issue. In this work, we fabricate tellurium nanowires (NWs)/epoxy nanocomposites via a facile bar coating method. According to Agari model and Maxwell-Eucken model, the as-synthesized ultra-long NWs with high aspect ratio (>100) construct the 3D interconnected thermal conductive network better in resin matrix to facilitate the heat transfer process. The results show that at a low loading ratio of 2.4 vol %, this nanocomposite exhibits the out-of-plane and in-plane thermal conductivity of 0.378 and 1.63 W m −1 K −1 , respectively, which is 189 and 715% higher than that of pure epoxy resin. Importantly, good stability, and flexibility of nanocomposites are well maintained.
Nano Research, 2017
We demonstrated the controlled growth of two-dimensional (2D) hexagonal tin disulfide (SnS 2) nan... more We demonstrated the controlled growth of two-dimensional (2D) hexagonal tin disulfide (SnS 2) nanoflakes with stacked monolayer atomic steps. The morphology was similar to flat-topped and step-sided mesa plateaus or step pyramids. The SnS 2 nanoflakes were grown on mica substrates via an atmospheric-pressure chemical vapor deposition process using tin monosulfide and sulfur powder as precursors. Atomic force microscopy (AFM), electron microscopy, and Raman characterizations were performed to investigate the structural features, and a sequential layer-wise epitaxial growth mechanism was revealed. In addition, systematic Raman characterizations were performed on individual SnS 2 nanoflakes with a wide range of thicknesses (1-100 nm), indicating that the A 1g peak intensity and Raman shifts were closely related to the thickness of the SnS 2 nanoflakes. Moreover, photoconductive AFM was performed on the monolayer-stepped SnS 2 nanoflakes, revealing that the flat surface and the edges of the SnS 2 atomic steps had different electrical conductive properties and photoconductive behaviors. This is ascribed to the dangling bonds and defects at the atomic step edges, which caused a height difference of the Schottky barriers formed at the interfaces between the PtIr-coated AFM tip and the step edges or the flat surface of the SnS 2 nanoflakes. The 2D SnS 2 crystals with regular monolayer atomic steps and fast photoresponsivity are promising for novel applications in photodetectors and integrated optoelectronic circuits.
Nano Energy, 2016
Abstract Although transition metal oxides have attracted considerable attention for their high en... more Abstract Although transition metal oxides have attracted considerable attention for their high energy density as anode materials of lithium-ion batteries, they suffer from large volume expansion during lithiation process, which usually causes fast capacity degradation. Herein, we report a rational design and facile preparation strategy of copper oxide encapsulated mesoporous carbon multi-yolk-shell octahedra, in which multiple CuO nanoparticles are well-confined in the compartments of micro-scale octahedral carbon scaffolds. The advantages of the novel multi-yolk-shell design are that the three-dimensional carbon scaffolds can buffer the volume change and prevent aggregation of CuO nanoparticles during the charge/discharge cycles, provide pathways for electron transport and Li + diffusion, and restrict the thin solid-electrolyte interphase layer to the outer surface of carbon shells. The results demonstrate how the electrochemical properties of anodes can be significantly improved by the multi-yolk-shell nanostructures with greatly enhanced structural stability and electrochemical actuation. Moreover, the micrometer-size CuO@C octahedra reduce the relative quality of SEI, resulting in high Coulombic efficiency and long cycling stability. In Li-ion cells, the CuO@C multi-yolk-shell octahedra anodes deliver a highly-reversible capacity of 598 mA h g −1 at 250 mA g −1 , excellent rate capacity of 365 mA h g −1 at 3000 mA g −1 and exhibit long-term cyclability with a capacity of 512 mA h g −1 after 300 cycles at 500 mA g −1 .
Nano Research, 2018
The ammonia synthesis from nitrogen and water under ambient conditions is one of the most invitin... more The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes. Although nitrogen is abundant in the atmosphere and the ammonia synthesis reaction is exothermic on the thermodynamics, the conversion of N 2 to ammonia is actually hard to proceed owing to the chemical inertness and stability of N 2 molecules. In industry, ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300-500 °C, 20-30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g., CO 2). Recently, a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention, which holds great promise for nitrogen fixation under room temperature and atmospheric pressure. However, the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems. Here we provide an overview of the latest progresses, remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation. Moreover, this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results. We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.
2019 20th International Conference on Electronic Packaging Technology(ICEPT)
As electronic products continue to be miniaturized, the generated heat of the running chip accumu... more As electronic products continue to be miniaturized, the generated heat of the running chip accumulated significantly, thus heat dissipation becomes a crucial issue. According to the previous report, reducing the interface thermal resistance (ITR) and constructing the thermal conductive networking structure can effectively improve the heat transferring property of the polymer based thermal interface materials (TIMs). Here we report a polymer composite loaded with oriented carbon nanofibers which exhibit both high thermal conductivity and excellent flexibility. These nanofibers were prepared by electrospinning technique followed by a high-temperature carbonization process. The obtained well-ordered filler structure not only reduces the ITR but also build the 3D network architecture. Further, when combining with organic matrix to make the thermal gel, the through-plane thermal conductivity along the fiber direction of the composite gel increases greatly, which is as high as 0.847 W m−1 K−1, the strategy of using aligned and networked thermal filler in the TIMs may be a more effective way to enhance the heat dissipation of future 5G communication electronics.
2018 19th International Conference on Electronic Packaging Technology (ICEPT), 2018
MXenes emerged as the new layered 2D semiconductors have exhibited many intriguing electrical, th... more MXenes emerged as the new layered 2D semiconductors have exhibited many intriguing electrical, thermal and optical properties. Therefore, the promising highly thermal conductive property is not yet to be well investigated. Herein, we employ MXenes (Ti<inf>3</inf>C<inf>2</inf>) as thermal filler in epoxy nanocomposites, in which the particulate MXenes is wrapped and interconnected by Ag nanowire. The room-temperature thermal conductivity of Ag/Ti<inf>3</inf>C<inf>2</inf> epoxy nanocomposite is found to be 7.60 W m<sup>−1</sup> K<sup>−1</sup> at a relatively low loading of 15 wt%, which is more than two-fold higher than pure Ti<inf>3</inf>C<inf>2</inf> (3.51 W m<sup>−1</sup> K<sup>−1</sup>). Based on the present investigation, developing MXenes based nanocomposites could be extremely promising for thermal management applications.
2018 20th International Conference on Electronic Materials and Packaging (EMAP), 2018
Modern electronics are seriously limited by heat dissipation. Interfacial thermal resistance and ... more Modern electronics are seriously limited by heat dissipation. Interfacial thermal resistance and constructing thermal conductive network are found to be the key issues. In this work, pine needle-derived carbon (PNDC) was prepared by a simple carbonization method. At optimized condition 50°C for 2 hrs, it shows impressive thermal conductive property. Importantly, the systematic structural characterization indicates that this derived carbon itself has well aligned, interconnected network-like, and channel-shaped microstructure which benefits the interface contact. The resulting Ag @PNDC/epoxy composite films were fabricated via a vacuum infiltration technology, the results show a much enhanced heat transportation (0.537mathrmWm−1mathrmK−1)(0.537 mathrm{Wm}^{-1} \mathrm{K}^{-1})(0.537mathrmWm−1mathrmK−1) as compared to that of pure epoxy resin (0.187mathrmWm−1mathrmK−1)(0.187 mathrm{Wm}^{-1} \mathrm{K}^{-1})(0.187mathrmWm−1mathrmK−1).
Modern Physics Letters B, 2021
Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of app... more Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of applications in light-emitting devices, semiconductor devices and solar cell devices. However, previous studies usually deposit nanocrystal films on traditional rigid substrates, limiting their applications in large-scale, direct-deposited flexible device fabrication processes, such as roll-to-roll printing process. Here, we report a direct deposition method for lead sulfide (PbS) nanocrystal films on flexible polymer substrates. By adding triethanolamine-coordinated Pb precursors to the reaction system to enhance the adhesion to the substrate and controlling the precursor ratios, we obtained high-quality flexible PbS films. The film is composed of octahedral PbS nanocrystals with preferred (111) orientation. The optical band gap of the nanocrystal films can be tuned from 1.32 eV to 1.60 eV by adjusting the ratio of the precursors, and an ideal band gap of 1.4 eV for single-junction solar c...
Nanotechnology, 2021
Thermal interface material (TIM) is pivotal for the heat dissipation between layers of high-densi... more Thermal interface material (TIM) is pivotal for the heat dissipation between layers of high-density electronic packaging. The most widely used TIMs are particle-filled composite materials, in which highly conductive particulate fillers are added into the polymer matrix to promote heat conduction. The numerical simulation of heat transfer in the composites is essential for the design of TIMs; however, the widely used finite element method (FEM) requires large memory and presents limited computational time for the composites with dense particles. In this work, a numerical homogenization algorithm based on fast Fourier transform was adopted to estimate the thermal conductivity of composites with randomly dispersed particles in 3D space. The unit cell problem is solved by means of a polarization-based iterative scheme, which can accelerate the convergence procedure regardless of the contrast between various components. The algorithm shows good precision and requires dramatically reduced...
Crystals, 2020
This study reports the employment of Co(OH)xF2−x nanosheets, a new material in the sensor field, ... more This study reports the employment of Co(OH)xF2−x nanosheets, a new material in the sensor field, for gas sensor applications. We synthesize Co(OH)xF2−x nanosheets via a hydrothermal route using SiO2 sphere templates. Our material characterization confirms that the material is a densely clustered Co(OH)xF2−x nanosheet with an amorphous microstructure with some short-range ordering. Sensors based on the nanosheets demonstrate a high response of 269% toward 4.5 ppm of acetone gas at an operation temperature of 200 °C and a very low minimum detection limit of 40 ppb. It functions effectively up to a temperature below 300 °C, above which F is found to start to evaporate. Our discussion suggests that an excellent sensor performance arises from the high catalytic function of F incorporated in a high concentration in the material as well as the high specific surface area due to the morphology of densely clustered nanosheets.
ACS Applied Materials & Interfaces, 2020
High-performance thermal management materials are essential in miniaturized, highly integrated, a... more High-performance thermal management materials are essential in miniaturized, highly integrated, and high-power modern electronics for heat dissipation. In this context, the large interface thermal resistance (ITR) that occurs between fillers and the organic matrix in polymer-based nanocomposites greatly limits their thermal conductive performance. Herein, through-plane direction aligned three-dimensional (3D) MXene/silver (Ag) aerogels are designed as heat transferring skeletons for epoxy nanocomposites. Ag nanoparticles (NPs) were in-situ decorated on exfoliated MXene nanosheets to ensure good contact, and subsequent welding of ice-templated MXene/Ag nanofillers at low temperature of ~200 oC reduced contact resistance between individual MXene sheets. Monte Carlo simulations suggest that thermal interficial resistance (R0) of the MXene/Agepoxy nanocomposite was 4.5 × 10-7 m2 W-1 K-1, which was lesser than that of the MXeneepoxy nanocomposite (Rc = 5.2 × 10-7 m2 W-1 K-1). Furthermore, the large-scale atomic/molecular massively parallel simulator was employed to calculate the interfacial resistance. It was found that RMXene=2.4 × 10-9 m2 K W-1, RMXene-Ag=2.0 ×10-9 m2 K W-1, respectively, indicating that the Ag NP enhanced the interfacial heat transport. At a relatively low loading of 15.1 vol%, through-plane thermal conductivity reached a value as high as 2.65 W m-1 K-1, which is 1225 % higher than that of pure epoxy resin. Furthermore, MXene/Agepoxy nanocomposite film exhibit impressive thermal conductive property when applied on a Millet 8 and Dell computer for heat dissipation.
Nanoscale, 2019
Bi2MoO6/OV-BiOBr heterojunctions are synthesized and show good photocatalytic activities for nitr... more Bi2MoO6/OV-BiOBr heterojunctions are synthesized and show good photocatalytic activities for nitrogen reduction to ammonia under ambient conditions.
Ceramics International, 2019
A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth... more A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth (CC) was developed; further, free-standing, flexible lithium-ion-battery (LIB) anodes with good electrical contact between current collector and the active substance were prepared. The as-prepared ZnO NFs/CC-based LIB anodes showed a high specific capacity of 1754 mAh g −1 at a current density of 0.1 A g −1 , a capacity retention of almost 52.9% at a current density of 2 A g −1 , as well as high rate capability. Moreover, the anodes demonstrated a high capacity with reversiblity of approximately 1650 mAh g −1 and only 6% capacity fading at a current density of 0.1 A g −1 , even after 100 cycles. These results imply that the synthesized, unique ZnO NFs/CC nanostructures can be employed as high-efficiency anode materials for flexible LIBs.
Advanced Energy Materials, 2019
3833 mAh cm −3 nearly double that of lithium (2062 mAh cm −3), and exhibits a relatively negative... more 3833 mAh cm −3 nearly double that of lithium (2062 mAh cm −3), and exhibits a relatively negative reduction potential of −2.4 V versus standard hydrogen electrode (SHE). [6-9] Despite of these intriguing merits, the practical employment of RMBs is hampered by several main hurdles. First, clumsy Mg 2+ intercalation is the primary limitation for the choice of competent cathode materials, because the strong Coulombic interactions between the divalent Mg 2+ ions and the anions in the host materials often result in sluggish diffusion kinetics and slow interfacial charge transfer. [10-13] Second, to design appropriate electrolytes for Mg plating/ stripping with high Coulombic efficiency, wide electrochemical window, and good compatibility with the cathodic materials is another great challenge. [14,15] Therefore, to develop advanced cathode materials capable of rapid Mg 2+ insertion/extraction in suitable electrolytes for reversible Mg plating/stripping is highly desirable. Since the pioneering work of Chevrel phase compounds (Mo 6 S 8) reported by Aurbach et al. in 2000, [16] tremendous efforts have been devoted to develop cathode materials for RMBs, including transition metal oxides (MnO 2 , V 2 O 5 , Mn 3 O 4 , WO 3 , Co 3 O 4), [17-21] polyanionic compounds (Mg 1.03 Mn 0.97 SiO 4 , MgCoSiO 4), [22,23] and transition metal dichalcogenides (TMDs, such as TiS 2 , MoS 2 , WSe 2). [24-28] However, most oxides and polyanionic compounds suffer from low capacity and poor cycling performance owing to the strong interactions between divalent Mg 2+ and O 2− in the hosts. [25,29] On the contrary, TMDs are deemed to be a class of promising cathode materials with more favorable kinetics, attributing to the relatively weaker MgS or MgSe bonds than MgO bond. [25,28,30] Nevertheless, layered TMDs also suffer from slow Mg 2+ ion diffusion due to the narrow interlayer spacing and the high polarity of Mg 2+. [31] Recently, it was reported that the interlayer distances of TMDs could be expanded by intercalating guest molecules (water or organic molecules), enlarging the dimension of ion diffusion channels and shielding the Coulombic interactions between Mg 2+ and the lattice anions of hosts. 13,27 In addition, the intercalated molecules served as interlayer pillars are conducive to maintain the framework of host materials for prolonged cycles. [32,33] Rechargeable magnesium batteries (RMBs) are attractive candidates for large-scale energy storage owing to the high theoretical specific capacity, rich earth abundance, and good safety characteristics. However, the development of desirable cathode materials for RMBs is constrained by the high polarity and slow intercalation kinetics of Mg 2+ ions. Herein, it is demonstrated that 2-ethylhexylamine pillared vanadium disulfide nanoflowers (expanded VS 2) with enlarged interlayer distances exhibit greatly boosted electrochemical performance as a cathode material in RMBs. Through a one-step solution-phase synthesis and in situ 2-ethylhexylamine intercalation process, VS 2 nanoflowers with ultralarge interlayer spacing are prepared. A series of ex situ characterizations verify that the cathode of expanded VS 2 nanoflowers undergoes a reversible intercalation reaction mechanism, followed by a conversion reaction mechanism. Electrochemical kinetics analysis reveal a relatively fast Mg-ion diffusivity of expanded VS 2 nanoflowers in the order of 10 −11-10 −12 cm 2 s −1 , and the pseudocapacitive contribution is up to 64% for the total capacity at 1 mV s −1. The expanded VS 2 nanoflowers show highly reversible discharge capacity (245 mAh g −1 at 100 mA g −1), good rate capability (103 mAh g −1 at 2000 mA g −1), and stable cycling performance (90 mAh g −1 after 600 cycles at 1000 mA g −1).
Composites Science and Technology, 2019
Improving thermal conductivity through welding boron nitride nanosheets onto silver nanowires via... more Improving thermal conductivity through welding boron nitride nanosheets onto silver nanowires via silver nanoparticles, Composites Science and Technology (2019), doi:
Nanoscale, 2019
Surface plasmon resonance enhanced direct Z-Scheme TiO2/ZnTe/Au nanocorncobs exhibit efficient ph... more Surface plasmon resonance enhanced direct Z-Scheme TiO2/ZnTe/Au nanocorncobs exhibit efficient photocatalytic overall water splitting.