Design and development of Gallium based liquid metal for electronic components

Gallium (Ga) and its alloys are in a liquid state at room temperature, and their melting points are either lower than, or close to, room temperature, which endows them with additional advantages in comparison to solid metals. For example, they are flexible, stretchable and deformable at room temperature. Also, they display excellent thermal and electrical conductivities with low viscosity and non-toxicity. Therefore, great improvements have been achieved in developing multifunctional devices by using Gabased liquid metals, including actuators, flexible circuits, bio-devices and self-healing superconductors. Nowadays, electronic devices have achieved great impact in modern society, however, electronic devices are small and are usually further subdivided into “integrated circuits”. This miniaturization has been a central background for the booming of modern electronic technology. Micro/nano sized conductive particles have been used for the assembly of electronic devices, but the synthesis procedure for conventional conductive particles is complicated and expensive, so a novel material for electronic assembly has been developed and is described in this Thesis. In this research, we present a facile synthesis method for liquid metal nanoparticles via laser irradiation. Compared with traditional probe sonicator-made particles, the produced size is more uniform by the laser method, and the size can be controlled well by simply controlling the laser energy density. The eutectic EGaInSn alloy particles (EGaInSn) produced in this research were covered by a thin oxide skin, which could be broken by external stimulation. In addition, we reported that the conductive particles in existing anisotropic conductive adhesives could be replaced by EGaInSn nanoparticles (NPs). In such a system, EGaInSn particles remain fluid and soft and the oxide shell can be broken when required by applying mild pressure. By adjusting the concentration of liquid metal, an anisotropic conductive path can be achieved by anisotropic merging of liquid metal droplets. In summary, either bulk material or nanoparticles of Ga based liquid metals display potential for electronic devices fabrication and electronic assembly

High-performance Electrocatalysts Engineering towards Faster Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a critical step for a wide range of energy storage and conversion applications. During the four-electron reactions that constitute the OER, an electrocatalyst is used to decrease the overpotential for water splitting. Conventionally, both heterogeneous and homogenous materials are employed as OER catalysts, but both feature their own benefits and drawbacks. The advantage of homogeneous catalysts is their high utilization of atoms, but their poor stability has limited their performances. In contrast, outstanding stability and recyclability are the benefits of heterogeneous catalysts, but their surface areas are inadequate, resulting in low efficiency for atom utilization. Therefore, two-dimensional (2D) materials and nanosheets have been investigated as electrocatalysts. With high specific surface areas, these materials combine the benefits of both heterogeneous and homogeneous catalysts, which may provide excellent properties to achieve high performance towards the OER. In this thesis, M3GeTe2 (MGT), and Ni5.46GeSe2 (NGS) were each fabricated by a solid-state reaction, and the 2D MGT and NGS nanosheets (NS) were successfully acquired by using a liquid exfoliation reaction. 2D MGT and NGS NS were validated in the electrocatalytic oxygen evolution reaction to demonstrate their catalytic applicability, and the Ni3GeTe2 (NGT) was found to have exceptionally high oxygen evolution activity. The OER performance of MGT was evaluated as a promising novel material for energy-related applications

DeepCollaboration: Collaborative Generative and Discriminative Models for Class Incremental Learning

An important challenge for neural networks is to learn incrementally, i.e., learn new classes without catastrophic forgetting. To overcome this problem, generative replay technique has been suggested, which can generate samples belonging to learned classes while learning new ones. However, such generative models usually suffer from increased distribution mismatch between the generated and original samples along the learning process. In this work, we propose DeepCollaboration (D-Collab), a collaborative framework of deep generative and discriminative models to solve this problem effectively. We develop a discriminative learning model to incrementally update the latent feature space for continual classification. At the same time, a generative model is introduced to achieve conditional generation using the latent feature distribution produced by the discriminative model. Importantly, the generative and discriminative models are connected through bidirectional training to enforce cycle-consistency of mappings between feature and image domains. Furthermore, a domain alignment module is used to eliminate the divergence between the feature distributions of generated images and real ones. This module together with the discriminative model can perform effective sample mining to facilitate incremental learning. Extensive experiments on several visual recognition datasets show that our system can achieve state-of-the-art performance

Recent Progress on Germanene and Functionalized Germanene: Preparation, Characterizations, Applications, and Challenges

2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A new family of single-atom-thick 2D germanium-based materials with graphene-like atomic arrangement, germanene and functionalized germanene, has attracted intensive attention due to their large bandgap and easily tailored electronic properties. Unlike carbon atoms in graphene, germanium atoms tend to adopt mixed sp 2 /sp 3 hybridization in germanene, which makes it chemically active on the surface and allows its electronic states to be easily tuned by chemical functionalization. Impressive achievements in terms of the applications in energy storage and catalysis have been reported by using germanene and functionalized germanene. Herein, the fabrication of epitaxial germanene on different metallic substrates and its unique electronic properties are summarized. Then, the preparation strategies and the fundamental properties of hydrogen-functionalized germanene (germanane or GeH) and other ligand-terminated forms of germanene are presented. Finally, the progress of their applications in energy storage and catalysis, including both experimental results and theoretical predictions, is analyzed

Designing Dendrite-Free Zinc Anodes for Advanced Aqueous Zinc Batteries

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Zn metal has been regarded as the most promising anode for aqueous batteries due to its high capacity, low cost, and environmental benignity. Zn anode still suffers, however, from low Coulombic efficiency due to the side reactions and dendrite growth in slightly acidic electrolytes. Here, the Zn plating/stripping mechanism is thoroughly investigated in 1 m ZnSO4 electrolyte, demonstrating that the poor performance of Zn metal in mild electrolyte should be ascribed to the formation of a porous by-product (Zn4SO4(OH)6·xH2O) layer and serious dendrite growth. To suppress the side reactions and dendrite growth, a highly viscoelastic polyvinyl butyral film, functioning as an artificial solid/electrolyte interphase (SEI), is homogeneously deposited on the Zn surface via a simple spin-coating strategy. This dense artificial SEI film not only effectively blocks water from the Zn surface but also guides the uniform stripping/plating of Zn ions underneath the film due to its good adhesion, hydrophilicity, ionic conductivity, and mechanical strength. Consequently, this side-reaction-free and dendrite-free Zn electrode exhibits high cycling stability and enhanced Coulombic efficiency, which also contributes to enhancement of the full-cell performance when it is coupled with MnO2 and LiFePO4 cathodes

Recent progress on liquid metals and their applications

Gallium-based liquid metals show excellent thermal and electrical conductivities with low viscosity and non-toxicity. Their melting points are either lower than or close to room temperature, which endows them with additional advantages in comparison to the solid metals; for example, they are flexible, stretchable and reformable at room temperature. Recently, great improvements have been achieved in developing multifunctional devices by using Ga-based liquid metals, including actuators, flexible circuits, bio-devices and self-healing superconductors. Here, we review recent research progress on Gallium-based liquid metals, especially on the applications aspects. These applications are mainly based on the unique properties of liquid metals, including low melting point, flexible and stretchable mechanical properties, excellent electrical and thermal conductivities and biocompatibility

Designing Dendrite-Free Zinc Anodes for Advanced Aqueous Zinc Batteries

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Zn metal has been regarded as the most promising anode for aqueous batteries due to its high capacity, low cost, and environmental benignity. Zn anode still suffers, however, from low Coulombic efficiency due to the side reactions and dendrite growth in slightly acidic electrolytes. Here, the Zn plating/stripping mechanism is thoroughly investigated in 1 m ZnSO4 electrolyte, demonstrating that the poor performance of Zn metal in mild electrolyte should be ascribed to the formation of a porous by-product (Zn4SO4(OH)6·xH2O) layer and serious dendrite growth. To suppress the side reactions and dendrite growth, a highly viscoelastic polyvinyl butyral film, functioning as an artificial solid/electrolyte interphase (SEI), is homogeneously deposited on the Zn surface via a simple spin-coating strategy. This dense artificial SEI film not only effectively blocks water from the Zn surface but also guides the uniform stripping/plating of Zn ions underneath the film due to its good adhesion, hydrophilicity, ionic conductivity, and mechanical strength. Consequently, this side-reaction-free and dendrite-free Zn electrode exhibits high cycling stability and enhanced Coulombic efficiency, which also contributes to enhancement of the full-cell performance when it is coupled with MnO2 and LiFePO4 cathodes