Strong orientational coupling of block copolymer microdomains to smectic layering revealed by magnetic field alignment

We elucidate the roles of the isotropic-nematic (I-N) and nematic-smectic A (N-SmA) transitions in magnetic field directed self-assembly of a liquid crystalline block copolymer (BCP), using \textit{in situ} x-ray scattering. Cooling into the nematic from the disordered melt yields poorly ordered and weakly aligned BCP microdomains. Continued cooling into the SmA however results in an abrupt increase in BCP orientational order with microdomain alignment tightly coupled to the translational order parameter of the smectic layers. These results underscore the significance of the N-SmA transition in generating highly aligned states under magnetic fields in these hierarchically ordered materials

Order-disorder transition and alignment dynamics of a block copolymer under high magnetic fields by in situ x-ray scattering

We present results of temperature resolved scattering studies of a liquid crystalline block copolymer undergoing an order-disorder transition (ODT) in the presence of magnetic fields and time-resolved measurements during isothermal field annealing at sub-ODT temperatures. In each case, field interactions produced strongly textured mesophases with the cylindrical microdomains aligned parallel to the field. We find there is no measurable field-induced shift in the ODT temperature ($T_{ODT}$) which suggests that selective melting does not play a role in mesophase alignment during isothermal experiments. Our data indicate instead that sub-ODT alignment occurs by slow, large scale grain rotation whereas alignment during cooling from the disordered melt is rapid and driven by the nucleation of weakly ordered but preferentially aligned material. We identify an optimum sub-cooling that maximizes alignment during isothermal field annealing. This is corroborated by a simple model incorporating the competing effects of an exponentially decreasing mobility and divergent, increasing magnetic anisotropy on cooling below $T_{ODT}$. The absence of measurable field-effects on $T_{ODT}$ is consistent with rough estimates derived from the relative magnitudes of the free energy due to field interaction and the enthalpy of the isotropic-LC transition.Comment: 5 figures; To appear in Physical Review Letter

HistRED: A Historical Document-Level Relation Extraction Dataset

Despite the extensive applications of relation extraction (RE) tasks in various domains, little has been explored in the historical context, which contains promising data across hundreds and thousands of years. To promote the historical RE research, we present HistRED constructed from Yeonhaengnok. Yeonhaengnok is a collection of records originally written in Hanja, the classical Chinese writing, which has later been translated into Korean. HistRED provides bilingual annotations such that RE can be performed on Korean and Hanja texts. In addition, HistRED supports various self-contained subtexts with different lengths, from a sentence level to a document level, supporting diverse context settings for researchers to evaluate the robustness of their RE models. To demonstrate the usefulness of our dataset, we propose a bilingual RE model that leverages both Korean and Hanja contexts to predict relations between entities. Our model outperforms monolingual baselines on HistRED, showing that employing multiple language contexts supplements the RE predictions. The dataset is publicly available at: https://huggingface.co/datasets/Soyoung/HistRED under CC BY-NC-ND 4.0 license

Laser-based three-dimensional manufacturing technologies for rechargeable batteries

Laser three-dimensional (3D) manufacturing technologies have gained substantial attention to fabricate 3D structured electrochemical rechargeable batteries. Laser 3D manufacturing techniques offer excellent 3D microstructure controllability, good design flexibility, process simplicity, and high energy and cost efficiencies, which are beneficial for rechargeable battery cell manufacturing. In this review, notable progress in development of the rechargeable battery cells via laser 3D manufacturing techniques is introduced and discussed. The basic concepts and remarkable achievements of four representative laser 3D manufacturing techniques such as selective laser sintering (or melting) techniques, direct laser writing for graphene-based electrodes, laser-induced forward transfer technique and laser ablation subtractive manufacturing are highlighted. Finally, major challenges and prospects of the laser 3D manufacturing technologies for battery cell manufacturing will be provided

Orientation and Morphology Control of Block Copolymers Using External Fields

Self-assembly of soft materials represents a compelling approach to realize a wide variety of useful nanostructured materials. In particular, self-assembly of block copolymers by microphase separation results thermodynamically in the formation of a range of nanostructures including lamellae, cylinders, gyroids and spheres. There is significant potential to use these structures in applications ranging from energy generation to water purification. Despite their significant potential however, the use of block copolymers in the aforementioned areas has been critically limited by general inability to precisely direct their self-assembly, i.e. to control the orientational and positional order of their self-assembled structures over device or application relevant length scales and geometries. In this context, we explore two distinct approaches to attain advanced ability to control the block copolymer microphase. First, this dissertation explores the self-assembly and directed self-assembly of novel liquid crystalline block copolymers. Result are presented from a systematic series of experimental investigations of the phase behavior and directed self-assembly of rationally designed liquid crystalline block copolymers (LC BCPs) under magnetic fields and in the presence of engineered surfaces. We specifically designed a block copolymer platform comprising etchable poly(D,L-lactide) (PLA) with brush architecture and side chain cyanobiphenyl LC block that imparts magnetic anisotropy on the system. Interestingly, this class of brush-like block copolymers behave in accordance with the canonical phase behavior of the conventional linear coil-coil block copolymers. With inclusion of labile mesogen, the magnetic field response of the system was significantly enhanced due to the increased grain size and faster mobility. By adopting cross-linkable mesogen, the LC phase can be readily polymerized and subsequent etching of the PLA produces well-defined nanopores with controlled orientation. At higher blending stoichiometric ratio, the system transforms its morphology from hexagonal cylinders to face-centered cubic (FCC) spheres and, strikingly, we observe the alignment of FCC spheres regardless of the 3 dimensional symmetry of the cubic structure. In the second part, we adopt the use of electrospray deposition and soft-shear laser zone annealing process as tools to direct the self-assembly of structurally complex thin films of block copolymers. Conventionally, block copolymers confined in thin film were examined based on the equilibrium structure as a result of a single annealing process. Here we propose non-equilibrium processing methods that enable us to achieve non-conventional morphologies. Sequential electrospray deposition (ESD) was adopted to form multi-layered BCP thin films which exhibit heterolattice structure that can be precisely tuned by kinetic parameters. We also examine pathway-engineered two-step processing, shear aligning followed by thermal annealing on a neutral substrate, to achieve biaxial alignment of the BCP cylinders array with minimum defect density. Overall, this dissertation provides new insight regarding the self-assembly of LC brush block copolymers and their orientation in the presence of magnetic fields. Further, it establishes a new mechanism for controlling the orientation of these materials in thin films. The results of the research presented here are relevant for the use of block copolymers in lithography and membrane fabrication, among other areas

Torque-Modulated backstepping control for two-dimensional electromagnetic scanners

In this paper, we propose torque-modulated backstepping control for uniform tracking errors in the vertical motion of two-dimensional electromagnetic scanners using only output measurement. Due to manufacturing tolerance, there are parameter uncertainties of two-dimensional electromagnetic scanners so that it is not easy to obtain uniform tracking error performance for the motion control of scanners. In order to resolve the problem, the proposed control law was designed with proportional feedback control with back-stepping approach. We firstly introduce the state-space model of an electromagnetic scanner. The torque-modulated backstepping control was designed for the vertical motion of the mechanical system with only position measurement. Then current tracking controller was implemented with virtual references for the states. We investigated its robust performance via frequency domain analysis with root-locus and sensitivity function. Simulation results are provided to show the effectiveness of the proposed method

LPV H??? Control with Disturbance Estimation for Permanent Magnet Synchronous Motors

This paper presents an H??? controller with an H??? state estimator using a linear parameter-varying (LPV) model of permanent magnet synchronous motor (PMSM). The proposed control method comprises a nonlinear torque modulation, an LPV H??? state estimator, and an LPV H??? state feedback controller. The use of nonlinear torque modulation enables formulation of the electromechanical dynamics of the PMSM in the form of an LPV system. The LPV H??? state estimator is designed to estimate the velocity, currents, and disturbance based solely on position measurement. We introduce a vertex expansion technique to cover all operating points of an LPV system. A velocity tracking controller is designed in the frame work of H??? control to be robust against disturbance. The proposed controller was implemented and validated with a motor generator set consisting of two PMSMs. Experimental results are presented to validate the effectiveness of the proposed method compared to conventional field-oriented control. These results show improved transient responses to velocity reference in the presence of disturbance

Discrete-time nonlinear damping backstepping control with observers for rejection of low and high frequency disturbances

A discrete-time backstepping control algorithm is proposed for reference tracking of systems affected by both broadband disturbances at low frequencies and narrow band disturbances at high frequencies. A discrete time DOB, which is constructed based on infinite impulse response filters is applied to compensate for narrow band disturbances at high frequencies. A discrete-time nonlinear damping backstepping controller with an augmented observer is proposed to track the desired output and to compensate for low frequency broadband disturbances along with a disturbance observer, for rejecting narrow band high frequency disturbances. This combination has the merit of simultaneously compensating both broadband disturbances at low frequencies and narrow band disturbances at high frequencies. The performance of the proposed method is validated via experiments

ZiF-8 induced carbon electrodes for selective lithium recovery from aqueous feed water by employing capacitive deionization system

The demand for lithium (Li) will grow from about 500,000 metric tons of lithium carbonate equivalent in 2021 to 3–4 million metric tons in 2030. To meet the Li demand, the separation of Li-mixed monovalent and divalent cations is critical for Li extraction from an aqueous medium. Capacitive deionization (CDI) and membrane capacitive deionization (MCDI) have recently emerged as viable water treatment technologies, yet ion-specific selective recovery using CDI systems is still under-investigated. In this study, the electrode surface of each system was modified to improve Li+ selectivity. Metal-organic frameworks (MOF), particularly zeolitic imidazolate framework-8 (ZiF-8), have shown substantial promise due to their tunable pore size and pore channel chemistry. Through an aqueous medium-based surface modification, we offer a simple technique of synthesizing ZiF-8 on carbon electrodes and underneath the cation exchange membrane (CEM). The bare CDI and MCDI systems initially showed poor selectivity towards Li+ in the mono and divalent ion incorporated simulated solutions. The relative selectivity (ρMLi; (M = metal ions)) in the CDI system was estimated as 0.73, 0.43, 0.67, and 0.58 for Na+, K+, Mg2+, and Ca2+, respectively, which was 0.93, 0.97, 0.39, and 0.30 in the MCDI system. In the case of bare activated carbon (AC) electrodes, the difference of hydration enthalpy played a critical role in Li+ selectivity towards other monovalent ions. However, despite having high hydration enthalpy, the Mg2+ and Ca2+ showed low Li+ selectivity due to the superior charge density of divalent ions. On the other hand, after the modification of AC electrodes with in-situ growth of ZiF-8 on the surface, the Li+ selectivity for monovalent Na+ and K+ was estimated at 3.08 and 1.12, respectively, which is 4.2 and 2.6 times higher than the bare AC electrode, respectively. Besides, compared to Na+, the trade-off between the low dehydration energy of K+ and the rapid ion transit of dehydrated Li+ made separating challenging. Consequently, for divalent Mg2+ and Ca2+, coulombic attraction dominated both in the bare CDI and MCDI systems. This research sheds light on using the newly developed ZiF-8 coating for selective Li recovery.- Qatar National Research Fund (QNRF) - No. NPRP12S-0227-190166 - Australian Research Council (ARC) - No. IH21010000

Chemically Cross-Linked Graphene Oxide as a Selective Layer on Electrospun Polyvinyl Alcohol Nanofiber Membrane for Nanofiltration Application

Graphene oxide (GO) nanosheets were utilized as a selective layer on a highly porous polyvinyl alcohol (PVA) nanofiber support via a pressure-assisted self-assembly technique to synthesize composite nanofiltration membranes. The GO layer was rendered stable by cross-linking the nanosheets (GO-to-GO) and by linking them onto the support surface (GO-to-PVA) using glutaraldehyde (GA). The amounts of GO and GA deposited on the PVA substrate were varied to determine the optimum nanofiltration membrane both in terms of water flux and salt rejection performances. The successful GA cross-linking of GO interlayers and GO-PVA via acetalization was confirmed by FTIR and XPS analyses, which corroborated with other characterization results from contact angle and zeta potential measurements. Morphologies of the most effective membrane (CGOPVA-50) featured a defect-free GA cross-linked GO layer with a thickness of ~67 nm. The best solute rejections of the CGOPVA-50 membrane were 91.01% for Na2SO4 (20 mM), 98.12% for Eosin Y (10 mg/L), 76.92% for Methylene blue (10 mg/L), and 49.62% for NaCl (20 mM). These findings may provide one of the promising approaches in synthesizing mechanically stable GO-based thin-film composite membranes that are effective for solute separation via nanofiltration