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Creators/Authors contains: "Pang, Zhenqian"

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  1. Abstract

    Cellulose nanofibers (NFCs) have emerged as a preferred choice for fabricating nanomaterials with exceptional mechanical properties. At the same time, boron nitride nanotubes (BNNTs) have long been favored in thermal management devices due to their superior thermal conductivity (k). This study uses reverse non-equilibrium molecular dynamics (MD) simulations to investigatekfor a hybrid material based on NFCs and BNNTs. The result is then compared with pure NFC and BNNT-based structures with equivalent total weight content to elucidate how incorporating BNNT fillers enhanceskfor the hybrid system. Furthermore, the fundamental phonon vibration modes responsible for driving thermal transport in NFC-based materials upon incorporating BNNTS are identified by computing the vibrational density of states from the Fourier transform analysis of the averaged mass-weighted velocity autocorrelation function. Additionally, MD simulations demonstrate how both NFCs and BNNTs synergistically improve the constituting hybrid structure’s mechanical properties (e.g. tensile strength and stiffness). The overarching aim is to contribute towards the engineered design of novel functional materials based on nanocellulose that simultaneously improve crucial physical properties pertaining to thermal transport and mechanics.

     
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  2. Abstract

    One possible solution against the accumulation of petrochemical plastics in natural environments is to develop biodegradable plastic substitutes using natural components. However, discovering all-natural alternatives that meet specific properties, such as optical transparency, fire retardancy and mechanical resilience, which have made petrochemical plastics successful, remains challenging. Current approaches still rely on iterative optimization experiments. Here we show an integrated workflow that combines robotics and machine learning to accelerate the discovery of all-natural plastic substitutes with programmable optical, thermal and mechanical properties. First, an automated pipetting robot is commanded to prepare 286 nanocomposite films with various properties to train a support-vector machine classifier. Next, through 14 active learning loops with data augmentation, 135 all-natural nanocomposites are fabricated stagewise, establishing an artificial neural network prediction model. We demonstrate that the prediction model can conduct a two-way design task: (1) predicting the physicochemical properties of an all-natural nanocomposite from its composition and (2) automating the inverse design of biodegradable plastic substitutes that fulfils various user-specific requirements. By harnessing the model’s prediction capabilities, we prepare several all-natural substitutes, that could replace non-biodegradable counterparts as exhibiting analogous properties. Our methodology integrates robot-assisted experiments, machine intelligence and simulation tools to accelerate the discovery and design of eco-friendly plastic substitutes starting from building blocks taken from the generally-recognized-as-safe database.

     
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    Free, publicly-accessible full text available June 1, 2025
  3. Conventional strategies for materials design have long been used by leveraging primary bonding, such as covalent, ionic, and metallic bonds, between constituent atoms. However, bond energy required to break primary bonds is high. Therefore, high temperatures and enormous energy consumption are often required in processing and manufacturing such materials. On the contrary, intermolecular bonds (hydrogen bonds, van der Waals forces, electrostatic interactions, imine bonds, etc.) formed between different molecules and functional groups are relatively weaker than primary bonds. They, thus, require less energy to break and reform. Moreover, intermolecular bonds can form at considerably longer bond lengths between two groups with no constraint on a specific bond angle between them, a feature that primary bonds lack. These features motivate unconventional strategies for the material design by tuning the intermolecular bonding between constituent atoms or groups to achieve superior physical properties. This paper reviews recent development in such strategies that utilize intermolecular bonding and analyzes how such design strategies lead to enhanced thermal stability and mechanical properties of the resulting materials. The applications of the materials designed and fabricated by tuning the intermolecular bonding are also summarized, along with major challenges that remain and future perspectives that call for further attention to maximize the potential of programming material properties by tuning intermolecular bonding. 
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  4. Hydrogels showing strong adhesion to different substrates have garnered significant attention for engineering applications. However, the current development of such hydrogel-based adhesive is predominantly limited to synthetic polymers, owing to their exceptional performance and an extensive array of chemical options. To advance the development of sustainable hydrogel-based adhesives, we successfully create a highly robust all-cellulose hydrogel-based adhesive, which is composed of concentrated dialcohol cellulose nanorods (DCNRs) and relies on enhanced hydrogen bonding interactions between cellulose and the substrate. We implement a sequential oxidization-reduction process to achieve this high-performance all-cellulose hydrogel, which is realized by converting the two secondary hydroxyl groups within an anhydroglucose unit into two primary hydroxyl groups, while simultaneously linearizing the cellulose chains. Such structural and chemical modifications on cellulose chains increase out-of-plane interactions between the DCNRs hydrogel and substrate, as simulations indicate. Additionally, these modifications enhance the flexibility of the cellulose chains, which would otherwise be rigid. The resulting all-cellulose hydrogels demonstrate injectability and strong adhesion capability to a wide range of substrates, including wood, metal, glass, and plastic. This green and sustainable all-cellulose hydrogel-based adhesive holds great promise for future bio-based adhesive design.

     
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    Abstract Direct formation of ultra-small nanoparticles on carbon supports by rapid high temperature synthesis method offers new opportunities for scalable nanomanufacturing and the synthesis of stable multi-elemental nanoparticles. However, the underlying mechanisms affecting the dispersion and stability of nanoparticles on the supports during high temperature processing remain enigmatic. In this work, we report the observation of metallic nanoparticles formation and stabilization on carbon supports through in situ Joule heating method. We find that the formation of metallic nanoparticles is associated with the simultaneous phase transition of amorphous carbon to a highly defective turbostratic graphite (T-graphite). Molecular dynamic (MD) simulations suggest that the defective T-graphite provide numerous nucleation sites for the nanoparticles to form. Furthermore, the nanoparticles partially intercalate and take root on edge planes, leading to high binding energy on support. This interaction between nanoparticles and T-graphite substrate strengthens the anchoring and provides excellent thermal stability to the nanoparticles. These findings provide mechanistic understanding of rapid high temperature synthesis of metal nanoparticles on carbon supports and the origin of their stability. 
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