Huaming Hou

Simultaneous 3-dimensional elemental imaging with LIBS and LA-ICP-MS

Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) are used simultaneously for spatially resolved mapping of major and trace elements and isotopes within a Bastnasite rare earth ore sample. The combination of the two techniques provides complementary measurements for elements that are separately unattainable due to low sensitivity and/or strong interferences. Two dimensional (2D) layer-by-layer mapping, 2D cross-sectional imaging and three-dimensional (3D) volume rendering of elements and isotopes in the Bastnasite matrix are presented. These results pave the way for improved 3D elemental imaging through simultaneously acquired LIBS and LA-ICP-MS measurements.

Three-dimensional elemental imaging of Li-ion solid-state electrolytes using fs-laser induced breakdown spectroscopy (LIBS)

Direct chemical imaging is critical to understand and control processes that affect the performance and safety of Li-ion batteries. In this work, femtosecond-Laser Induced Breakdown Spectroscopy (fs-LIBS) is introduced for 3D chemical analysis of Li-ion solid state electrolytes in electrochemical energy storage systems. Spatially resolved chemical maps of major and minor elements in solid-state electrolyte Li7La3Zr2O12 (LLZO) samples are presented, with a depth resolution of 700 nm. We implement newly-developed visualization techniques to chemically image the atomic ratio distributions in a LLZO solid state electrolyte matrix. Statistical analysis, 2D layer-by-layer analysis, 2D cross-sectional imaging and 3D reconstruction of atomic ratios are demonstrated for electrolyte samples prepared under different processing conditions. These results explain the differences in the physical properties of the samples not revealed by conventional characterization techniques, and demonstrate the ability of fs-LIBS for direct 3D elemental imaging of Li-ion battery solid-state electrolytes.

Laser Ablation Molecular Isotopic Spectrometry for Molecules Formation Chemistry in Femtosecond-Laser Ablated Plasmas

Recently, laser ablated molecular isotopic spectrometry (LAMIS) has expanded its capability to explore molecules formation mechanism in laser-induced plasma in addition to isotope analysis. LAMIS is a powerful tool for tracking the origination of atoms that is involved in formation of investigated molecules by labeling atoms with their isotopic substitution. The evolutionary formation pathways of organic molecules, especially of C2 dimers and CN radicals, were frequently reported. However, very little is known about the formation pathways for metallic radicals and heterodimers in laser ablated plasma. This research focuses on elucidating the formation pathways of AlO radicals in femtosecond laser ablated plasma from 18O-labeled Al2O3 pellet. Plasmas expanding with strong forward bias in the direction normal to the sample surface were generated in the wake of a weakly ionized channel created by a femtosecond laser. The formation mechanism of AlO and influence of air were investigated with multiple plasma diagnostic methods such as monochromatic fast gating imaging, spatiotemporal resolved optical emission spectroscopy, and LAMIS. An advanced LAMIS fitting procedure was used to deduce the spatiotemporal distributions of Al18O and Al16O number densities and also their ratios. We found that the Al16O/Al18O number density ratio is higher for plasma portion closer to the sample surface, which suggests that chemical reactions between the plasma plume and ambient air are more intense at the tail of the plasma. The results also reveals that direct association of free Al and O atoms is the main mechanism for the formation of AlO at the early stage of the plasma. To the contrast, chemical reactions between plasma materials and ambient oxygen molecules and the isotope exchange effect are the dominant mechanisms of the formation of AlO and evolution of Al16O/Al18O number density ratio at the late stage of the plasma.

Enhanced lithium ion transport in garnet-type solid state electrolytes

Al-substituted Li7La3Zr2O12 samples processed under argon show enhanced Li-ion transport and interfacial properties in symmetrical cells with lithium electrodes, compared to those prepared in air. In particular, the samples prepared under argon have higher ionic conductivities and lower interfacial impedances in symmetrical lithium cells, and show better DC cycling characteristics. The electronic conductivities are also somewhat higher. Pellets subjected to thermal treatment under the two types of atmospheres have different colors but exhibit similar microstructures. X-ray diffraction experiments suggest that there are slight structural differences between the two types of samples, but few dissimilarities were observed in elemental composition, distribution of ions, oxidation states, or bond lengths using laser-induced breakdown spectroscopy (LIBS), x-ray photoelectron spectroscopy (XPS), and extended x-ray absorption fine structure spectroscopy (EXAFS) to analyze the materials. Additionally, there was no evidence that La or Zr were reduced during the processing under Ar. Possible explanations for the improved electrochemical properties of the sample prepared under Ar compared to the one prepared in air include differences in grain boundary chemistries and conductivities and/or a small concentration of oxygen vacancies in the former.

Femtosecond Filament-Laser Ablation Molecular Isotopic Spectrometry (F 2 -LAMIS) for RemoteIsotope Analysis

LAMIS is an all-optical laser-ablation technique for isotope analysis at atmospheric ambient conditions. In this presentation, the theoretical principles of F2-LAMIS will be overviewed and its application for remote isotopic analysis will be discussed.

3D chemical imaging of Li-ion batteries using femtosecond laser plasma spectroscopy

We introduce the use of femtosecond laser plasma spectroscopy in chemical imaging of Li-ion battery system components. Spatially resolved mapping of major and minor elements of Li-ion batteries is presented and correlated to electrochemical performance.