EBEAM (Electron Beam Emergent Additive Manufacturing)

Permanent URI for this collectionhttp://hdl.handle.net/10084/152646

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Now showing 1 - 11 out of 11 results

Tailoring the Li+ intercalation energy of carbon nanocage anodes via atomic Al-doping for high-performance lithium-ion batteries
(Wiley, 2024) Yu, Xingmiao; Xiang, Jianfei; Shi, Qitao; Li, Luwen; Wang, Jiaqi; Liu, Xiangqi; Zhang, Cheng; Wang, Zhipeng; Zhang, Junjin; Hu, Huimin; Bachmatiuk, Alicja; Trzebicka, Barbara; Chen, Jin; Guo, Tianxiao; Shen, Yanbin; Choi, Jinho; Huang, Cheng; Rümmeli, Mark H.
Graphitic carbon materials are widely used in lithium-ion batteries (LIBs) due to their stability and high conductivity. However, graphite anodes have low specific capacity and degrade over time, limiting their application. To meet advanced energy storage needs, high-performance graphitic carbon materials are required. Enhancing the electrochemical performance of carbon materials can be achieved through boron and nitrogen doping and incorporating 3D structures such as carbon nanocages (CNCs). In this study, aluminum (Al) is introduced into CNC lattices via chemical vapor deposition (CVD). The hollow structure of CNCs enables fast electrolyte penetration. Density functional theory (DFT) calculations show that Al doping lowers the intercalation energy of Li+. The Al-boron (B)-nitrogen (N-doped CNC (AlBN-CNC) anode demonstrates an ultrahigh rate capacity (approximate to 300 mAh g(-1) at 10 A g(-1)) and a prolonged fast-charging lifespan (862.82 mAh g(-1) at 5 A g(-1) after 1000 cycles), surpassing the N-doped or BN-doped CNCs. Al doping improves charging kinetics and structural stability. Surprisingly, AlBN-CNCs exhibit increased capacity upon cycling due to enlarged graphitic interlayer spacing. Characterization of graphitic nanostructures confirms that Al doping effectively tailors and enhances their electrochemical properties, providing a new strategy for high-capacity, fast-charging graphitic carbon anode materials for next-generation LIBs.
Factors controlling the organ-specific T1 contrast effect of silica nanoparticles co-doped with both Mn2+ ions and oleate-coated iron oxides
(Elsevier, 2024) Bochkova, Olga; Stepanov, Alexey; Bebyakina, Anastasiya; Smekalov, Daniil; Kholin, Kirill; Nizameev, Irek; Romashchenko, Alexander; Zavjalov, Evgenii; Lubina, Anna; Voloshina, Alexandra; Tyapkina, Oksana; Tarasov, Maxim; Sultanov, Timur; Rümmeli, Mark H.; Salnikov, Vadim; Budnikova, Yulia; Mustafina, Asiya
The present work introduces the synergistic effect of co-doping of both oleate-coated superparamagnetic iron oxide nanoparticles (SPIONs) and Mn(NO3)(2) into silica nanoparticles (SNs) on the T-1-relaxivity relaxivity of Mn2+ ions. The observed synergism can be attributed to the limited oxidation of Mn(2+ )ions when they are doped into the outer layer of SNs doped with SPIONs, despite the alkaline synthesis conditions. The electrochemical behaviour of the manganese ions inside co-doped SNs corroborates the predominance of their oxidation state (2+). Moreover, the T-1 relaxivities of co-doped SNs have been determined to be 20.0 mM(- 1 )s(- 1 ) and 30.0 mM(- 1 ) s(- 1 ) at 0.47 T. The T-2 relaxivity of co-doped SNs can be tuned by incorporating 6 or 13 nm SPIONs with different saturation magnetizations, which allows the T-2/T-1 2 /T (1) relaxation ratios to be limited to 0.8-5.9. The incorporation of amino groups on the surface of co-doped SNs by substituting silanol groups with propylamino groups reduces T-1 relaxivity to 9.0 mM(- 1) s(- 1) , which is nevertheless sufficient to provide a brightening of the abdominal organs and mouse brain in magnetic resonance imaging at 11.7 T. The preferential localisation of co-doped SNs in the kidneys and intestines compared to the liver is a consequence of the specificity of amino-substituted SNs compared to bare SNs.
Coordination-regulated epitaxial growth for 2D/3D perovskite vertical alignment heterostructure
(Elsevier, 2024) Zhao, Guoxiang; Chen, Yuan; Cong, Shan; Li, Lutao; Wang, Chen; Du, Xinyu; Liu, Ruirui; Lu, Jing; Liu, Yu; Chen, Gaoyuan; Zhang, Sihan; Zhang, Liya; Rümmeli, Mark H.; Zou, Guifu
In situ growth of suspended zirconene islets inside graphene pores
(Wiley, 2024) Mendes, Rafael G.; Ta, Huy Quang; Gemming, Thomas; van Gog, Heleen; van Huis, Marijn A.; Bachmatiuk, Alicja; Rümmeli, Mark H.
Experiments using a transmission electron microscope decomposed zirconium acetylacetonate with an electron beam, forming zirconium nanoparticles on graphene. Continued electron irradiation transformed these nanoparticles into atomically thick zirconium islets (zirconene islets) within the graphene lattice. The electron beam caused zirconium atom dislocations and vacancies that are rapidly refilled, a process repeating until the vacancies evolved into zirconium nanoribbons before breaking. This study offers insights into the electron-driven growth and degradation of zirconene islets, showcasing a method to fabricate freestanding zirconenes for use as atomically thin coatings in extreme environments.
High-performance photoelectrochemical hydrogen production using asymmetric quantum dots
(Wiley, 2024) Wang, Kanghong; Wang, Chao; Tao, Yi; Tang, Zikun; Benetti, Daniele; Vidal, François; Liu, Yu; Rümmeli, Mark H.; Zhao, Haiguang; Rosei, Federico; Sun, Xuhui
Solar-driven photoelectrochemical (PEC) reactions using colloidal quantum dots (QDs) as photoabsorbers have shown great potential for the production of clean fuels. However, the low H2 evolution rate, consistent with low values of photocurrent density, and their limited operational stability are still the main obstacles. To address these challenges, the heterostructure engineering of asymmetric capsule-shaped CdSe/CdxZn1-xSe QDs with broad absorption and efficient charge extraction compared to pure-shell QDs is reported. By engineering the shell composition from pure ZnSe shells into CdxZn1-xSe gradient shells, the electron transfer rate increased from 4.0 × 107 s−1 to 32.7 × 107 s−1. Moreover, the capsule-shaped architecture enables more efficient spatial carrier separation, yielding a saturated current density of average of 25.4 mA cm−2 under AM 1.5 G one sun illumination. This value is the highest ever observed for QDs-based devices and comparable to the best-known Si-based devices, perovskite-based devices, and metal oxide-based devices. Furthermore, PEC devices based on heterostructured QDs maintained 96% of the initial current density after 2 h and 82% after 10 h under continuous illumination, respectively. The results represent a breakthrough in hydrogen production using heterostructured asymmetric QDs.
Titanium substitution facilitating oxygen and manganese redox in sodium layered oxide cathode
(Wiley, 2024) Zhou, Junhua; Hu, Huimin; Wang, Jiaqi; Shi, Qitao; Lian, Xueyu; Liu, Lijun; Bachmatiuk, Alicja; Sun, Jingyu; Yang, Ruizhi; Choi, Jin-Ho; Rümmeli, Mark H.
Sodium layered oxide with anion redox activity (SLO-A) stands out as a promising cathode material for sodium-ion batteries due to its impressive capacity and high voltage resulting from Mn- and O-redox processes. However, the SLO-A faces significant challenges in cycling stability and rate performance, primarily due to the poor reversibility and sluggish kinetics of the O-redox. In this study,a novel Ti-doped material, Na2/3Li2/9Mn53/72Ti1/24O2 (NLMTO), exhibiting remarkable characteristics such as a notable rate capacity (130 mAh g−1 at 3C, where 1C equals 200 mA g−1) and excellent cycling retention (85.4% after 100 cycles at 0.5C) is introduced. Employing electrochemical differential analyses, the contributions to the superior performance arising from the Mn- and O-redox processes are quantitatively delineated. The optimized performance of NLMTO is attributed, in part, to the enhanced stability of both bulk and interface structures. The introduction of Ti through substitution not only contributes to this stability but also allows for the fine-tuning of the material’s electron configurations. This is achieved by augmenting the density of states near the Fermi energy level, as well as elevating the O 2p and Mn 3d orbits. This research advances sodium-ion battery technology
Density functional theory and molecular dynamics study on the growth of graphene by chemical vapor deposition on copper substrate
(AIP Publishing, 2024) Li, Qihang; Luo, Jinping; Li, Zaoyang; Rümmeli, Mark H.; Liu, Lijun
Chemical vapor deposition is an affordable method for producing high-quality graphene. Microscopic defects in graphene grown on copper substrates, such as five- and seven-membered rings, degrade the quality of graphene. Therefore, it is essential to study the growth process and factors affecting the quality of graphene on copper surfaces. In this study, first-principles calculations based on density functional theory show that the four-step dehydrogenation reaction of methane is endothermic, with the energy barrier for the last dehydrogenation step being relatively high. Additionally, CH forms dimers on the copper surface with a lower energy barrier and trimers with a higher energy barrier, indicating that carbon dimers are the primary precursor species for graphene growth in the early stages. Subsequently, in molecular dynamics simulations, the analytical bond-order potential based on quantum mechanics is employed. The results reveal that the growth of graphene on the copper surface involves the diffusion and gradual nucleation of carbon dimers in the early stages, the gradual enlargement of graphene domains in the intermediate stages, and the gradual merging of graphene domain boundaries in the later stages. Moreover, the growth of graphene on the copper substrate follows a self-limiting growth mode. Increasing the deposition interval of carbon atoms and reducing the carbon atom deposition velocity contribute to enhancing the quality of graphene grown on the copper substrate.
Monomolecular membrane-assisted growth of antimony halide perovskite/MoS2 van der Waals epitaxial heterojunctions with long-lived interlayer exciton
(American Chemical Society, 2024) Zhou, Zhicheng; Zhu, Juntong; Li, Lutao; Wang, Chen; Zhang, Changwen; Du, Xinyu; Wang, Xiangyi; Zhao, Guoxiang; Wang, Ruonan; Li, Jiating; Lu, Zheng; Zong, Yi; Sun, Yinghui; Rümmeli, Mark H.; Zou, Guifu
Epitaxial growth stands as a key method for integrating semiconductors into heterostructures, offering a potent avenue to explore the electronic and optoelectronic characteristics of cutting-edge materials, such as transition metal dichalcogenide (TMD) and perovskites. Nevertheless, the layer-by-layer growth atop TMD materials confronts a substantial energy barrier, impeding the adsorption and nucleation of perovskite atoms on the 2D surface. Here, we epitaxially grown an inorganic lead-free perovskite on TMD and formed van der Waals (vdW) heterojunctions. Our work employs a monomolecular membrane-assisted growth strategy that reduces the contact angle and simultaneously diminishing the energy barrier for Cs3Sb2Br9 surface nucleation. By controlling the nucleation temperature, we achieved a reduction in the thickness of the Cs3Sb2Br9 epitaxial layer from 30 to approximately 4 nm. In the realm of inorganic lead-free perovskite and TMD heterojunctions, we observed long-lived interlayer exciton of 9.9 ns, approximately 36 times longer than the intralayer exciton lifetime, which benefited from the excellent interlayer coupling brought by direct epitaxial growth. Our research introduces a monomolecular membrane-assisted growth strategy that expands the diversity of materials attainable through vdW epitaxial growth, potentially contributing to future applications in optoelectronics involving heterojunctions.
Flexible piezoresistive polystyrene composite sensors filled with hollow 3D graphitic shells
(MDPI, 2023) Guzenko, Nataliia; Godzierz, Marcin; Kurtyka, Klaudia; Hercog, Anna; Nocoń-Szmajda, Klaudia; Gawron, Anna; Szeluga, Urszula; Trzebicka, Barbara; Yang, Ruizhi; Rümmeli, Mark H.
The objective of this research was to develop highly effective conductive polymer composite (CPC) materials for flexible piezoresistive sensors, utilizing hollow three-dimensional graphitic shells as a highly conductive particulate component. Polystyrene (PS), a cost-effective and robust polymer widely used in various applications such as household appliances, electronics, automotive parts, packaging, and thermal insulation materials, was chosen as the polymer matrix. The hollow spherical three-dimensional graphitic shells (GS) were synthesized through chemical vapor deposition (CVD) with magnesium oxide (MgO) nanoparticles serving as a support, which was removed post synthesis and employed as the conductive filler. Commercial multi-walled carbon nanotubes (CNTs) were used as a reference one-dimensional graphene material. The main focus of this study was to investigate the impact of the GS on the piezoresistive response of carbon/polymer composite thin films. The distribution and arrangement of GS and CNTs in the polymer matrix were analyzed using techniques such as X-ray diffraction and scanning electron microscopy, while the electrical, thermal, and mechanical properties of the composites were also evaluated. The results revealed that the PS composite films filled with GS exhibited a more pronounced piezoresistive response as compared to the CNT-based composites, despite their lower mechanical and thermal performance.
Effect of growth conditions and reactor configuration on the growth uniformity of large-scale graphene by chemical vapor deposition
(AIP Publishing, 2024) Li, Qihang; Luo, Jinping; Li, Zaoyang; Rümmeli, Mark H.; Liu, Lijun
Chemical vapor deposition (CVD) is an affordable method for the preparation of large-scale and high-quality graphene. With the increase in CVD reactor size, gas mass transfer, flow state, and gas phase dynamics become more complicated. In this study, computational fluid dynamics is used to investigate factors affecting the uniformity of large-scale graphene growth under different growth conditions and reactor configurations. The dimensionless number defined in this paper and the Grashof number are utilized to distinguish the species transfer patterns and the flow states, respectively. A gas-surface dynamics model is established to simulate the graphene growth. Results reveal that the graphene growth rate uniformity is the highest at very low pressure and flow rate due to the flow symmetry and diffusion-dominated species transfer. At an increased pressure of 20 Torr, the uniformity of the graphene growth rate becomes higher axially and lower circumferentially with an increasing inlet mass flow rate. When the flow rate is fixed at 1500 SCCM and pressure is reduced from 20 to 2 Torr, graphene growth uniformity first increases and then decreases due to the influence of gas phase dynamics. Graphene growth rates are analyzed across ordinary reactor configurations and four configurations with inner tubes at 20 Torr pressure and 1500 SCCM flow rate. Comprehensive evaluation suggests that the ordinary reactor configuration performs best under these conditions. This research offers insights into the macroscopic growth mechanism of large-scale graphene and provides guidance for designing growth conditions in large-area graphene production.
Numerical investigation on the effect of gas-phase dynamics on graphene growth in chemical vapor deposition
(AIP Publishing, 2024) Li, Qihang; Luo, Jinping; Li, Zaoyang; Rümmeli, Mark H.; Liu, Lijun
Chemical vapor deposition (CVD) is a crucial technique to prepare high-quality graphene because of its controllability. In the research, we perform a systematic computational fluid dynamics numerical investigation on the effect of gas-phase reaction dynamics on the graphene growth in a horizontal tube CVD reactor. The research results indicate that the gas-phase chemical reactions in the CVD reactor are in a nonequilibrium state, as evidenced by the comparison of species mole fraction distributions during the CVD process and under chemical equilibrium conditions. The effect of gas-phase reaction dynamics on the deposition rate of graphene under different conditions is studied, and our research shows that the main causes of change in graphene growth rates under different conditions are gas-phase reaction dynamics and active species transport. The results of numerical simulation agree well with the experimental phenomena. The research results also indicate that, for methane, the main limiting factor of graphene growth is the surface kinetic reaction rate. Conversely, for active species, the main limiting factor of graphene growth is species transport. Our research suggests that the growth rate of graphene can be regulated from the perspective of the gas reaction mechanism. This method has theoretical guiding significance and can be extended to the preparation of large-area graphene.

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