Evaluating the Microwave Sintering Behaviors of Binder-jetted Additively Manufactured Alumina

Please click Additional Files below to see the full abstrac

The role of defects in microwave-assisted synthesis of cubic ZrO2

Microwave radiation (MWR) is capable of inducing rapid, low-temperature crystallization and potential non-equilibrium phase formation in ceramic oxide materials.1 However, the mechanisms by which MWR influences phase transitions and atomic ordering are not well understood. Theories to explain the influence of MWR range from purely thermal effects (e.g., rapid heating rate) to purely MWR-driven, non-thermal effects (e.g., enhanced defect generation).2 To take full advantage of the opportunities provided by field-assisted methods, it is necessary to understand the underlying mechanisms. One limiting factor in determining how MWR affects phase formation has been the ability to effectively characterize the effects of an applied field on both long range (crystalline) and short range (amorphous/disordered) atomic order. Here, we utilize synchrotron x-ray pair distribution function (PDF) analysis, coupled with molecular dynamics (MD) and density functional theory (DFT) to explore the role of MWR-induced defects and local atomic disorder on low-temperature cubic phase formation in ZrO2 thin films. PDF analysis is an experimental technique capable of quantitatively characterizing both local and long range atomic order, and thus can characterize the effects of MWR on atomic structure beyond the capabilities of conventional x-ray diffraction. We find the application of MWR can stabilize cubic ZrO2 at temperatures as low as 225°C, about 2000°C lower than conventionally required. Our PDF analysis suggests that distortions in the local atomic structure may be responsible for the stabilization of the cubic phase, and these distortions are consistent with increased oxygen vacancy formation (Fig. 1). Interestingly, higher MWR power levels and faster heating rates do not correspond to more crystalline phase formation, suggesting that thermal effects may not be the sole driving force. To further explore the idea of MWR-induced, defect-mediated phase transitions, we utilize MD and DFT simulations to investigate how oxygen vacancy concentrations affect the relative phase stability of various ZrO2 polymorphs, and compare the resultant simulated structures with our experimental PDF data. Through analysis of both crystalline phase formation and local atomic order, we investigate how defects and local atomic distortions are influenced by MWR exposure, and how these structural effects can impact low-temperature phase transitions. Please click Additional Files below to see the full abstract

Synthesis of Novel Flower-Like Zn(OH)F via a Microwave-Assisted Ionic Liquid Route and Transformation into Nanoporous ZnO by Heat Treatment

Zinc hydroxide fluoride (Zn(OH)F) with novel flower-like morphology has been prepared via a microwave-assisted ionic liquid route. The flower-like Zn(OH)F particle has six petals and every petal is composed of lots of acicular nano-structure. Nanoporous ZnO is obtained by thermal decomposition of as-prepared Zn(OH)F in air, and the flower-like morphology is well retained. In the process of synthesis, ionic liquid 1-Butyl-3-methylimidazolium tetrafluoroborate is used as both the reactant and the template

Battery Charge Curve Prediction via Feature Extraction and Supervised Machine Learning

Abstract Real‐time onboard state monitoring and estimation of a battery over its lifetime is indispensable for the safe and durable operation of battery‐powered devices. In this study, a methodology to predict the entire constant‐current cycling curve with limited input information that can be collected in a short period of time is developed. A total of 10 066 charge curves of LiNiO2‐based batteries at a constant C‐rate are collected. With the combination of a feature extraction step and a multiple linear regression step, the method can accurately predict an entire battery charge curve with an error of < 2% using only 10% of the charge curve as the input information. The method is further validated across other battery chemistries (LiCoO2‐based) using open‐access datasets. The prediction error of the charge curves for the LiCoO2‐based battery is around 2% with only 5% of the charge curve as the input information, indicating the generalization of the developed methodology for predicting battery cycling curves. The developed method paves the way for fast onboard health status monitoring and estimation for batteries during practical applications

Structural characterization and luminescence of porous single crystalline ZnO nanodisks with sponge-like morphology

We report the synthesis of porous single crystalline ZnO nanodisks with sponge-like morphology through a wet chemical approach. To our best knowledge, this is the first report about highly porous single crystalline nanodisks of ZnO with an average diameter of ∼100 nm. The ZnO nanodisks exhibit strong visible (bluegreen) light emission on UV excitation. Scanning Transmission Electron Microcopy (STEM), High-Resolution Transmission Electron Microscopy (HRTEM), and Selected Area Electron Diffraction (SAED) were performed to confirm that the nanodisks are single crystalline and porous in nature. The porosity of the nanodisks gives them the sponge-like appearance. Energy Dispersive X-ray Spectrometry (EDS) and Electron Energy Loss Spectrometry (EELS) analysis of the nanodisks together with high-resolution electron microscopy and photoluminescence measurements were used to determine the cause of the visible emission and its relation to the sponge-like morphology and growth mechanism. The larger surface area to volume ratio of these sponge-like nanostructures makes them very attractive for applications like biochemical sensors and solar cells. © 2008 American Chemical Society

Structural study of the acute effect of Karwinskia humboldtiana on cerebral motor cortex, hippocampus, and caudate nucleus of the rat

We report the synthesis of porous single crystalline ZnO nanodisks with sponge-like morphology through a wet chemical approach. To our best knowledge, this is the first report about highly porous single crystalline nanodisks of ZnO with an average diameter of ?100 nm. The ZnO nanodisks exhibit strong visible (bluegreen) light emission on UV excitation. Scanning Transmission Electron Microcopy (STEM), High-Resolution Transmission Electron Microscopy (HRTEM), and Selected Area Electron Diffraction (SAED) were performed to confirm that the nanodisks are single crystalline and porous in nature. The porosity of the nanodisks gives them the sponge-like appearance. Energy Dispersive X-ray Spectrometry (EDS) and Electron Energy Loss Spectrometry (EELS) analysis of the nanodisks together with high-resolution electron microscopy and photoluminescence measurements were used to determine the cause of the visible emission and its relation to the sponge-like morphology and growth mechanism. The larger surface area to volume ratio of these sponge-like nanostructures makes them very attractive for applications like biochemical sensors and solar cells. " 2008 American Chemical Society.",,,,,,"10.1021/jp0765704",,,"http://hdl.handle.net/20.500.12104/44787","http://www.scopus.com/inward/record.url?eid=2-s2.0-38549168402&partnerID=40&md5=d46ef308181dc0f331f67ac736078c5

Surface Engineering of a LiMn₂O₄ Electrode Using Nanoscale Polymer Thin Films via Chemical Vapor Deposition Polymerization

Surface engineering is a critical technique for improving the performance of lithium-ion batteries (LIBs). Here, we introduce a novel vapor-based technique, namely, chemical vapor deposition polymerization, that can engineer nanoscale polymer thin films with controllable thickness and composition on the surface of battery electrodes. This technique enables us to, for the first time, systematically compare the effects of a conducting poly­(3,4-ethylenedioxythiophene) (PEDOT) polymer and an insulating poly­(divinylbenzene) (PDVB) polymer on the performance of a LiMn₂O₄ electrode in LIBs. Our results show that conducting PEDOT coatings improve both the rate and the cycling performance of LiMn₂O₄ electrodes, whereas insulating PDVB coatings have little effect on these performances. The PEDOT coating increases 10 C rate capacity by 83% at 25 °C (from 23 to 42 mA h/g) and by 30% at 50 °C (from 64 to 83 mA h/g). Furthermore, the PEDOT coating extends the high-temperature (50 °C) cycling life of LiMn₂O₄ by over 60%. A model is developed, which can precisely describe the capacity degradation exhibited by the different types of cells, based on the aging mechanisms of Mn dissolution and solid-electrolyte interphase growth. Results from X-ray photoelectron spectroscopy suggest that chemical or coordination bonds form between Mn in LiMn₂O₄ and O and S in the PEDOT film. These bonds stabilize the surface of LiMn₂O₄ and thus improve the cycling performance. In contrast, no bonds form between Mn and the elements in the PDVB film. We further demonstrate that this vapor-based technique can be extended to other cathodes for advanced LIBs