No abstract

Peptide has recently been demonstrated as a sustainable and smart material for piezoelectric energy conversion. Although the power output was improved compared to other biomaterials, the use of a piezoelectric device alone can only capture the energy from the minute deformation in materials. In comparison, the triboelectric effect can convert mechanical energy from large motion. Consequently, utilizing both piezoelectric and triboelectric effects is of significant research interest due to their complementary energy conversion mechanisms. Here we demonstrated a hybrid nanogenerator that combined a peptide-based piezoelectric nanogenerator with a single-electrode triboelectric nanogenerator. Our device structure enabled the voltage and current outputs of each individual type of nanogenerator to be superposed in the hybrid nanogenerator, producing overall constructive outputs. The design of our device also enabled a simplified configuration of hybrid nanogenerator. This study is important not only for the enhancement of peptide-based piezoelectric device but also for the future design of hybrid piezoelectric and triboelectric nanogenerators.

While X-ray micro-tomography has been in use for some time both in synchrotron and laboratory-based architectures, it has traditionally operated under a single absorption-based contrast mechanism. In this operating mode, an X-ray projection image is formed due to spatially varying density within the sample, resulting in varying attenuation of the incident X-ray beam with reconstruction yielding a 3D map of sample density. This method has been extended by phase contrast methods, using either propagation based phase contrast, through the use of Talbot-Lau interferometer gratings, and Zernike arrangements, to better differentiate low-Z materials or multiple phases of very similar atomic density by enhancing the detection of differences in index of refraction at the boundaries of different phases.However, neither approach can discern the crystallographic information within polycrystalline samples. Knowledge of the grain structure and crystallographic orientation distribution within polycrystalline samples is critical to the understanding of the fracture mechanisms that operate at the length scale of the grains. To address this problem, several years back, a few select synchrotron beamlines began developing methods to not only capture absorption/transmission information, but diffraction signals as well. [1,2]. Since then, the diffraction tomography technique has gained considerable traction over the years as a complementary method to EBSD due to its ability to uniquely obtain bulk, 3D grain structures in a non-destructive fashion, opening the door for large-scale grain structure analysis or time-dependent evolutionary studies. Due to the exclusive presence of the technique at the synchrotron however, its accessibility to the wider research community has been inherently limited.Recently, the adaptation of the method to laboratory-based systems has broadened its user base and impact. In this work, a lab-based adaptation is presented, termed lab diffraction contrast tomography (LabDCT). The LabDCT imaging modality is implemented on the ZEISS Xradia Versa laboratory Xray microscope, and adapted to operate with a polychromatic divergent beam (as opposed to the typically collimated, monochromatic beam at synchrotron beamlines). Mounting a sample in a Laue focusing condition with an equidistant source-sample and sample-detector arrangement, individual grains satisfying the Bragg condition produce diffraction spots on a specialized high resolution detector. The polychromatic beam provides a unique advantage wherein a majority of the grains within a sample simultaneously satisfy the Bragg condition due to the wide spectrum of wavelengths. Rotation of the sample then yields a series of projections with diffraction patterns, which are reconstructed using a dedicated 3D grain reconstruction software (GrainMapper3D, Xnovo Technology ApS, Køge, Denmark) to yield crystallographic information including grain orientation, location of center of mass, and morphology for a large number of grains within the sample. This information can be...

Nano- and micro-scale structural characterization, in 3D, are critical to understanding the structure-property relationships in energy materials.  In solid oxide fuel cells, long-term structural degradation due to such effects as Ni coarsening or oxidation mean that additionally these structures are not static.  Such issues have plagued widespread SOFC adoption, and are inherently difficult to study due to the length and time scales of the heterogeneous material systems.  Recent approaches to the problem have largely employed synchrotron X-ray tomography and FIB-SEM tomography as microstructure characterization techniques.  To date, however, there has been very limited application of laboratory X-ray microscopy which has the potential to offer the combined benefits of round-the-clock access and nondestructive 3D nanoscale imaging.  Recently, simultaneous improvements in X-ray optics and detection have greatly increased the application space of lab nanoscale XRM, which now serves as a viable solution for SOFC characterization. In this work, multiple lab-based imaging techniques are combined in a correlative manner to probe SOFC microstructure.  Specifically, the nondestructive nature of laboratory XRM is combined with the high resolution of FIB-SEM microscopy and EDS to characterize SOFC components through a 4D evolution experiment and spanning the relevant length scales from microns to nanometers. As an initial test, an as-fabricated un-reduced SOFC sample (NiO/YSZ anode) was examined using nanoscale XRM operating at 5.4 keV and 50 nm spatial resolution.  Whereas synchrotron imaging approaches have frequently exploited the tunable nature of the incident beam to perform absorption edge imaging and enhance material contrast, the laboratory-based instrument used in this work operates at a single, fixed beam energy.  Nonetheless, it was found that the 5.4 keV X-rays produced sufficient contrast to discern solid phases of the multiple cell components contained in the sample: NiO/YSZ anode, YSZ electrolyte, and LSM cathode.  Furthermore, additional data collection in phase contrast mode by employing a Zernike phase ring was used to highlight the existence of small features including nanoporosity (defects) in the electrolyte layer. A second SOFC anode sample was sourced, this time in the reduced Ni/YSZ state with small particle sizes characteristic of the active layer of the electrode.  A 3D scan was first performed with the XRM, and an advanced segmentation algorithm based on both grayscale and texture-based contrast was used to segment the Ni, YSZ, and pore phases.  The sample was then mounted in a FIB-SEM instrument which was used to shave a small amount of material from the sample to create a flat, polished surface for EDS mapping.  An EDS map was generated and compared to the corresponding 2D plane of the XRM dataset to validate the XRM capability to accurately characterize the structure. The sample was then degraded by an oxidation process by holding the sample at 700C in ambient air for 1 hour.  A second XRM scan with the same imaging conditions was performed after oxidation.  The before and after datasets were spatially registered and compared to evaluate the effects of Ni oxidation.  Substantial swelling of the Ni upon oxidation, at the expense of the void space, with minimal modification of the YSZ were observed as expected.  Furthermore, it is realized there may be additional modification of the microstructure at a length scale smaller than can be viewed with the XRM (less than 50 nm).  To probe these finer structures, the sample was subsequently brought back to the FIB-SEM, which was used to perform 2D EDS as well as 3D FIB tomography.   Results from the FIB tomography were then correlated back to the 4D before-and-after data set obtained by XRM.

A deep knowledge of the 3D microstructure is essential for optimizing performance in Lithium ion battery electrodes. Tomography methods like focused ion beam-secondary electron microscopy (FIB-SEM) and X-ray tomography are the most frequently used 3D characterization techniques for battery electrodes. While each method has advantages and disadvantages, understanding the complex morphology of electrodes requires a complementary, multi-scale 3D approach. In this work, the possibilities and limitations for both 3D techniques, X-ray and FIB-SEM tomography, are studied using the example of a LiNiCoAlO2-LiCoO2 blend cathode from a commercial cell. The same cathode sample was analyzed with both techniques and moreover with different devices to enable a comparison of the obtained data quality. The material fractions, porosity, surface area and tortuosity are calculated from the different data sets and the results are compared with special emphasis on the differentiation of the different active materials and the carbon-binder phase. The reliable determination of these parameters is essential because they are needed, for example, to compare different electrode structures or to study the influence of the microstructure on the electrode performance to optimize the electrode structure. Figure 1

No abstract