Browsing by Author "Chen, Bo"

Now showing 1 - 7 of 7
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    Accepted Tutorials at The Web Conference 2022
    Tommasini, Riccardo; Basu Roy, Senjuti; Wang, Xuan; Wang, Hongwei; Ji, Heng; Han, Jiawei; Nakov, Preslav; Da San Martino, Giovanni; Alam, Firoj; Schedl, Markus; Lex, Elisabeth; Bharadwaj, Akash; Cormode, Graham; Dojchinovski, Milan; Forberg, Jan; Frey, Johannes; Bonte, Pieter; Balduini, Marco; Belcao, Matteo; Della Valle, Emanuele; Yu, Junliang; Yin, Hongzhi; Chen, Tong; Liu, Haochen; Wang, Yiqi; Fan, Wenqi; Liu, Xiaorui; Dacon, Jamell; Lye, Lingjuan; Tang, Jiliang; Gionis, Aristides; Neumann, Stefan; Ordozgoiti, Bruno; Razniewski, Simon; Arnaout, Hiba; Ghosh, Shrestha; Suchanek, Fabian; Wu, Lingfei; Chen, Yu; Li, Yunyao; Liu, Bang; Ilievski, Filip; Garijo, Daniel; Chalupsky, Hans; Szekely, Pedro; Kanellos, Ilias; Sacharidis, Dimitris; Vergoulis, Thanasis; Choudhary, Nurendra; Rao, Nikhil; Subbian, Karthik; Sengamedu, Srinivasan; Reddy, Chandan; Victor, Friedhelm; Haslhofer, Bernhard; Katsogiannis- Meimarakis, George; Koutrika, Georgia; Jin, Shengmin; Koutra, Danai; Zafarani, Reza; Tsvetkov, Yulia; Balachandran, Vidhisha; Kumar, Sachin; Zhao, Xiangyu; Chen, Bo; Guo, Huifeng; Wang, Yejing; Tang, Ruiming; Zhang, Yang; Wang, Wenjie; Wu, Peng; Feng, Fuli; He, Xiangnan (ACM, 2022-04-25)
    This paper summarizes the content of the 20 tutorials that have been given at The Web Conference 2022: 85% of these tutorials are lecture style, and 15% of these are hands on.
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    Discovery and ramifications of incidental Magnéli phase generation and release from industrial coal-burning
    Yang, Yi; Chen, Bo; Hower, James C.; Schindler, Michael; Winkler, Christopher; Brandt, Jessica E.; Di Giulio, Richard T.; Ge, Jianping; Liu, Min; Fu, Yuhao; Zhang, Lijun; Chen, Yu-ru; Priya, Shashank; Hochella, Michael F. Jr. (Nature Publishing Group, 2017-01-12)
    Coal, as one of the most economic and abundant energy sources, remains the leading fuel for producing electricity worldwide. Yet, burning coal produces more global warming CO2 relative to all other fossil fuels, and it is a major contributor to atmospheric particulate matter known to have a deleterious respiratory and cardiovascular impact in humans, especially in China and India. Here we have discovered that burning coal also produces large quantities of otherwise rare Magneli phases (Ti; x; O2x–1 with 4 ≤ x ≤ 9) from TiO2 minerals naturally present in coal. This provides a new tracer for tracking solid-state emissions worldwide from industrial coal-burning. In its first toxicity testing, we have also shown that nanoscale Magneli phases have potential toxicity pathways that are not photoactive like TiO2 phases, but instead seem to be biologically active without photostimulation. In the future, these phases should be thoroughly tested for their toxicity in the human lung. Solid-state emissions from coal burning remain an environmental concern. Here, the authors have found that TiO2 minerals present in coal are converted into titanium suboxides during burning, and initial biotoxicity screening suggests that further testing is needed to look into human lung consequences.
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    Fundamental mechanisms of focused ion beam guided anodization
    Tian, Zhipeng; Lu, Kathy; Chen, Bo (American Institute of Physics, 2010-11-01)
    This paper is focused on understanding the fundamental mechanisms of focused ion beam guided anodization and the unique capabilities of generating new patterns based on such an understanding. By designing proper interpore distance, pore arrangement, and pore shape during focused ion beam patterning, nonspherical pore shape and nonhexagonal patterns can be obtained by further anodization. The electrical field and the mechanical stress field around each focused ion beam patterned concave dictate the pore formation and growth. The oxide barrier layer thickness and shape around the focused ion beam guided pores affect new pore formation and the meshing of different size pores. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3500513]
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    Growth of anodic alumina nanopores and titania nanotubes and their applications
    Chen, Bo (Virginia Tech, 2013-01-07)
    Anodic aluminum oxide (AAO) nanopores are excellent templates to fabricate different nanostructures. However, the pores are limited to a hexagonal arrangement with a domain size of a few micrometers.  In this dissertation, focused ion beam (FIB) is used to create pre-patterned concaves to guide the anodization. Due to the advantage of FIB lithography, highly ordered AAO arrays with different arrangements, alternating diameters, and periodic pore densities are successfully achieved. Anodization window to fabricate ordered AAO is enlarged due to the FIB pre-pattern guidance. AAO has also been successfully used as a template to nanoimprint prepolymer to synthesize vertically aligned and high aspect ratio h-PDMS nanorod arrays with Moiré pattern arrangements. The formation mechanism of anodic TiO2 nanotubes is proposed in this dissertation. Moreover, FIB pre-pattern guided anodization is introduced to synthesize highly ordered TiO₂ nanotubes with different morphologies. The effects of inter-tube distance and arrangement to the structure of TiO₂ nanotubes are investigated. TiO2 nanotubes with branched and bamboo-type structures are achieved by adjusting anodization voltage. The influence of patterned concave depth and surface curvature on the growth of TiO₂ nanotubes and AAO are studied. The efficiency of TiO₂ nanotubes in supercapacitors and photoelectrochemical water splitting are optimized by enlarging surface area and increasing electrical conductivity. Focused ion beam can not only create concave arrays to guide the electrochemical anodization, but also be used for nanoscale sculpting and 3D analysis. When the TiO₂ nanotube surface is bombarded by FIB, there is a mass transfers due to ion-induced viscous flow and sputter milling, thus the TiO₂ nanotubes are selectively closed and opened. By combining FIB cutting and SEM imaging to create a series of 2D cross section SEM images, 3D reconstruction can be obtained by stacking SEM images together. This 3D reconstruction offers an opportunity to directly and quantitatively observe the pore evolution to understand the sintering process.
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    Lead-free epitaxial ferroelectric material integration on semiconducting (100) Nb-doped SrTiO3 for low-power non-volatile memory and efficient ultraviolet ray detection
    Kundu, Souvik; Clavel, Michael B.; Biswas, Pranab; Chen, Bo; Song, Hyun-Cheol; Kumar, Prashant; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Sanghadasa, Mohan; Priya, Shashank (Springer Nature, 2015-07-23)
    We report lead-free ferroelectric based resistive switching non-volatile memory (NVM) devices with epitaxial (1-x)BaTiO3-xBiFeO(3) (x = 0.725) (BT-BFO) film integrated on semiconducting (100) Nb (0.7%) doped SrTiO3 (Nb: STO) substrates. The piezoelectric force microscopy (PFM) measurement at room temperature demonstrated ferroelectricity in the BT-BFO thin film. PFM results also reveal the repeatable polarization inversion by poling, manifesting its potential for read-write operation in NVM devices. The electroforming-free and ferroelectric polarization coupled electrical behaviour demonstrated excellent resistive switching with high retention time, cyclic endurance, and low set/reset voltages. X-ray photoelectron spectroscopy was utilized to determine the band alignment at the BT-BFO and Nb: STO heterojunction, and it exhibited staggered band alignment. This heterojunction is found to behave as an efficient ultraviolet photo-detector with low rise and fall time. The architecture also demonstrates half-wave rectification under low and high input signal frequencies, where the output distortion is minimal. The results provide avenue for an electrical switch that can regulate the pixels in low or high frequency images. Combined this work paves the pathway towards designing future generation low-power ferroelectric based microelectronic devices by merging both electrical and photovoltaic properties of BT-BFO materials.
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    Pulmonary Exposure to Magnéli Phase Titanium Suboxides Results in Significant Macrophage Abnormalities and Decreased Lung Function
    McDaniel, Dylan K.; Ringel-Scaia, Veronica M.; Morrison, Holly A.; Coutermarsh-Ott, Sheryl; Council-Troche, McAlister; Angle, Jonathan W.; Perry, Justin B.; Davis, Grace; Leng, Weinan; Minarchick, Valerie; Yang, Yi; Chen, Bo; Reece, Sky W.; Brown, David A.; Cecere, Thomas E.; Brown, Jared M.; Gowdy, Kymberly M.; Hochella, Michael F. Jr.; Allen, Irving C. (Frontiers, 2019-11-28)
    Coal is one of the most abundant and economic sources for global energy production. However, the burning of coal is widely recognized as a significant contributor to atmospheric particulate matter linked to deleterious respiratory impacts. Recently, we have discovered that burning coal generates large quantities of otherwise rare Magnéli phase titanium suboxides from TiO2 minerals naturally present in coal. These nanoscale Magnéli phases are biologically active without photostimulation and toxic to airway epithelial cells in vitro and to zebrafish in vivo. Here, we sought to determine the clinical and physiological impact of pulmonary exposure to Magnéli phases using mice as mammalian model organisms. Mice were exposed to the most frequently found Magnéli phases, Ti6O11, at 100 parts per million (ppm) via intratracheal administration. Local and systemic titanium concentrations, lung pathology, and changes in airway mechanics were assessed. Additional mechanistic studies were conducted with primary bone marrow derived macrophages. Our results indicate that macrophages are the cell type most impacted by exposure to these nanoscale particles. Following phagocytosis, macrophages fail to properly eliminate Magnéli phases, resulting in increased oxidative stress, mitochondrial dysfunction, and ultimately apoptosis. In the lungs, these nanoparticles become concentrated in macrophages, resulting in a feedback loop of reactive oxygen species production, cell death, and the initiation of gene expression profiles consistent with lung injury within 6 weeks of exposure. Chronic exposure and accumulation of Magnéli phases ultimately results in significantly reduced lung function impacting airway resistance, compliance, and elastance. Together, these studies demonstrate that Magnéli phases are toxic in the mammalian airway and are likely a significant nanoscale environmental pollutant, especially in geographic regions where coal combustion is a major contributor to atmospheric particulate matter.
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    Self-assembled NaNbO3-Nb2O5 (ferroelectric-semiconductor) heterostructures grown on LaAlO3 substrates
    Wang, Zhiguang; Li, Yanxi; Chen, Bo; Viswan, Ravindranath; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2012-09-01)
    We deposited NaNbO3 (NNO)-Nb2O5 (NO) self-assembled heterostructures on LaAlO3 (LAO) to form ferroelectric-semiconductor vertically integrated nanostructures. The NNO component formed as nanorods embedded in a NO matrix. X-ray diffraction confirmed epitaxial growth of both NNO and NO phases. Phase distribution was detected by scanning electron microscopy. The NNO/NO volume ratio was strongly dependent on the deposition temperature due to the volatility of sodium. Piezoelectric force microscopy revealed a good piezoelectric response in the NNO component with a piezoelectric coefficient of D-33 approximate to 12 pm/V, with SrRuO3 (SRO) acting as bottom electrode. The current-voltage characterization of NNO-NO/SRO-LAO showed a typical diode rectifying behavior. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754713]