Browsing by Author "Zhang, Boyu"

Now showing 1 - 4 of 4
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    A Transferable Model for Chromosome Architecture
    (National Academy of Sciences, 2016) Di Pierro, M.; Zhang, Boyu; Aiden, Erez Lieberman; Wolynes, P.G.; Onuchic, José Nelson
    In vivo, the human genome folds into a characteristic ensemble of 3D structures. The mechanism driving the folding process remains unknown. We report a theoretical model for chromatin (Minimal Chromatin Model) that explains the folding of interphase chromosomes and generates chromosome conformations consistent with experimental data. The energy landscape of the model was derived by using the maximum entropy principle and relies on two experimentally derived inputs: a classification of loci into chromatin types and a catalog of the positions of chromatin loops. First, we trained our energy function using the Hi-C contact map of chromosome 10 from human GM12878 lymphoblastoid cells. Then, we used the model to perform molecular dynamics simulations producing an ensemble of 3D structures for all GM12878 autosomes. Finally, we used these 3D structures to generate contact maps. We found that simulated contact maps closely agree with experimental results for all GM12878 autosomes. The ensemble of structures resulting from these simulations exhibited unknotted chromosomes, phase separation of chromatin types, and a tendency for open chromatin to lie at the periphery of chromosome territories.
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    Additive manufacturing and mechanical properties of 2D h-BN reinforced nanocomposite
    (2022-12-02) Zhang, Boyu; Lou, Jun
    Ceramic and inorganic materials have extraordinary physical properties, such as high modulus, high strength, high hardness and heat resistant. However, the low toughness hinders the wide application of ceramic. Although ceramic can withstand high load in the elastic stage, once the crack emerged inside the bulk ceramic, it will propagate fast and cause the dramatic failure of the whole structure. To solve this problem, several toughening mechanisms has been developed, such as bridging mechanism and crack deflection. The main idea is to hinder the crack propagation or increase the energy needed for the crack propagation. One effective way is the add reinforcements in the ceramic to create reinforced ceramic composites. Graphene has been verified to be a promising candidate for reinforcing ceramic matrix composites due to its extremely high elastic modulus (~1 TPa) and intrinsic strength (~130 GPa). However, similar to ceramics, graphene also has brittle fracture behavior, and its fracture toughness is only about 4 MPa·m1/2. h-BN is a kind of 2D material which has a similar lattice structure to graphene, with B and N atoms adjacent to each other. It is well known for it dielectric properties and widely used as dielectric substrate and protective layer. People has found its robustness since it can dramatically increase the sample survival rate if used as protective layer. However, its toughness mechanical property has not been systematically studied since recent years. In this thesis, the mechanical properties of h-BN, interfacial mechanical properties of h-BN/ceramic nanocomposites and additive manufacturing h-BN/silica nanocomposites are shown. The intrinsic toughening mechanism, h-BN/ceramic nanocomposites toughening mechanism are systematically discussed. In chapter 2, the intrinsic toughening fracture behavior of single layer h-BN was firstly introduced and a dual fracture mode (asynchronous and synchronous fracture) of multilayer h-BN caused by interlayer mechanical coupling effect was shown. In chapter 3, by using nanoindentation-assisted micro-mechanical devices integrated with scanning electron microscopy (SEM), the interfacial sliding and failure behaviors between h-BN and PDC were systematically studied. In chapter 4 and 5, 2PP 3D printing technique was developed to create high quality silica and h-BN/silica nanostructures with sub-200 nm. High Q microtoroid resonators and strong photoluminescence of rare earth doped silica nanostructures were demonstrated and mechanical properties of h-BN/silica nanocomposites was studied. Overall, this thesis contributes to the knowledge of toughening mechanism of h-BN and h-BN nanocomposites and shows the advanced way to fabricate inorganic nanocomposites with nanoscale resolution.
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    High-performance 2D electronic devices enabled by strong and tough two-dimensional polymer with ultra-low dielectric constant
    (Springer Nature, 2024) Fang, Qiyi; Yi, Kongyang; Zhai, Tianshu; Luo, Shisong; Lin, Chen-yang; Ai, Qing; Zhu, Yifan; Zhang, Boyu; Alvarez, Gustavo A.; Shao, Yanjie; Zhou, Haolei; Gao, Guanhui; Liu, Yifeng; Xu, Rui; Zhang, Xiang; Wang, Yuzhe; Tian, Xiaoyin; Zhang, Honghu; Han, Yimo; Zhu, Hanyu; Zhao, Yuji; Tian, Zhiting; Zhong, Yu; Liu, Zheng; Lou, Jun; Rice Advanced Materials Institute
    As the feature size of microelectronic circuits is scaling down to nanometer order, the increasing interconnect crosstalk, resistance-capacitance (RC) delay and power consumption can limit the chip performance and reliability. To address these challenges, new low-k dielectric (k < 2) materials need to be developed to replace current silicon dioxide (k = 3.9) or SiCOH, etc. However, existing low-k dielectric materials, such as organosilicate glass or polymeric dielectrics, suffer from poor thermal and mechanical properties. Two-dimensional polymers (2DPs) are considered promising low-k dielectric materials because of their good thermal and mechanical properties, high porosity and designability. Here, we report a chemical-vapor-deposition (CVD) method for growing fluoride rich 2DP-F films on arbitrary substrates. We show that the grown 2DP-F thin films exhibit ultra-low dielectric constant (in plane k = 1.85 and out-of-plane k = 1.82) and remarkable mechanical properties (Young’s modulus > 15 GPa). We also demonstrated the improved performance of monolayer MoS2 field-effect-transistors when utilizing 2DP-F thin films as dielectric substrates.
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    High-surface-area corundum nanoparticles by resistive hotspot-induced phase transformation
    (Springer Nature, 2022) Deng, Bing; Advincula, Paul A.; Luong, Duy Xuan; Zhou, Jingan; Zhang, Boyu; Wang, Zhe; McHugh, Emily A.; Chen, Jinhang; Carter, Robert A.; Kittrell, Carter; Lou, Jun; Zhao, Yuji; Yakobson, Boris I.; Zhao, Yufeng; Tour, James M.; Smalley-Curl Institute; NanoCarbon Center; Welch Institute for Advanced Materials
    High-surface-area α-Al2O3 nanoparticles are used in high-strength ceramics and stable catalyst supports. The production of α-Al2O3 by phase transformation from γ-Al2O3 is hampered by a high activation energy barrier, which usually requires extended high-temperature annealing (~1500 K, > 10 h) and suffers from aggregation. Here, we report the synthesis of dehydrated α-Al2O3 nanoparticles (phase purity ~100%, particle size ~23 nm, surface area ~65 m2 g−1) by a pulsed direct current Joule heating of γ-Al2O3. The phase transformation is completed at a reduced bulk temperature and duration (~573 K, < 1 s) via an intermediate δʹ-Al2O3 phase. Numerical simulations reveal the resistive hotspot-induced local heating in the pulsed current process enables the rapid transformation. Theoretical calculations show the topotactic transition (from γ- to δʹ- to α-Al2O3) is driven by their surface energy differences. The α-Al2O3 nanoparticles are sintered to nanograined ceramics with hardness superior to commercial alumina and approaching that of sapphire.