In this paper, we report the effect of growth conditions on the properties of sputtered precursor thin films for CuIn1-xGaxSe2 (CIGS) absorber layers. Specifically, precursor films containing Cu, In, Ga, and Se were deposited via co-sputtering on flexible Mo-coated stainless steel substrates over a wide range of compositions and deposition conditions. The impact on precursor film phase, morphology, and elemental distribution was investigated as a function of precursor Se content, substrate temperature, target type (CIG/CIG vs. In/Cu3Ga), and Na content. Precursor films selenized at high temperature (> 500 degrees C) to form stoichiometric CIGS and completed using a CdS n-type buffer layer and transparent conducting oxide window layers exhibited full-cell efficiencies as high as 11.5%.

In this work, the crosslinking of various thin polyethylene films via electron beam exposure in an inert environment was studied. Increasing Melt Flow Index and polymer density both decreased the insoluble gel fraction resulting from irradiation at a dosage of 800 kGy. The effect of adding low levels of two different polyfunctional monomers was also examined. Trimethylolpropane triacrylate (TMPTA) was found to decrease the dosage necessary to initiate gel formation, and gave higher gel fractions at lower dosages, but showed little effect at higher dosages. A low molecular weight polybutadiene (PBd) resin showed little effect on gel fraction as compared to the neat resin controls.

Sulfur trioxide (SO3) is a highly reactive oxidant, and its reactions with polyethylene fibers in chlorinated solvents can be used to functionalize and stabilize the polyethylene fibers for subsequent carbonization to produce carbon fiber. In this study, the apparent reaction kinetics between SO3 and polyethylene were investigated in various halogenated solvents using in situ Raman spectroscopy with an immersion Raman probe. This work demonstrates the power of in situ Raman spectroscopy to monitor hazardous reactions, and the results show that both solvent and polyethylene properties have a large influence on the reaction kinetics.

A new high-temperature fibre tensile cell is described, developed for use at the Advanced Photon Source at Argonne National Laboratory to enable the investigation of the carbonization and graphitization processes during carbon fibre production. This cell is used to heat precursor fibre bundles to temperatures up to ∼2300°C in a controlled inert atmosphere, while applying tensile stress to facilitate formation of highly oriented graphitic microstructure; evolution of the microstructure as a function of temperature and time during the carbonization and higher-temperature graphitization processes can then be monitored by collecting real-time wide-angle X-ray diffraction (WAXD) patterns. As an example, the carbonization and graphitization behaviour of an oxidized polyacrylonitrile fibre was studied up to a temperature of ∼1750°C. Real-time WAXD revealed the gradual increase in microstructure alignment with the fibre axis with increasing temperature over the temperature range 600-1100°C. Above 1100°C, no further changes in orientation were observed. The overall magnitude of change increased with increasing applied tensile stress during carbonization. As a second example, the high-temperature graphitizability of PAN- and pitch-derived commercial carbon fibres was studied. Here, the magnitude of graphitic microstructure evolution of the pitch-derived fibre far exceeded that of the PAN-derived fibres at temperatures up to ∼2300°C, indicating its facile graphitizability.

Journal Article Lithium Ordering in Next-Generation High-Voltage Lithium-Rich Layered Oxide Cathode Battery Materials Get access Michael Behr, Michael Behr The Dow Chemical Company, Midland, MI, USA Search for other works by this author on: Oxford Academic Google Scholar Michael Lowe, Michael Lowe The Dow Chemical Company, Midland, MI, USA Search for other works by this author on: Oxford Academic Google Scholar Britt Vanchura, Britt Vanchura The Dow Chemical Company, Midland, MI, USA Search for other works by this author on: Oxford Academic Google Scholar Fu Zhou, Fu Zhou The Dow Chemical Company, Midland, MI, USA Search for other works by this author on: Oxford Academic Google Scholar Wenjuan Liu, Wenjuan Liu The Dow Chemical Company, Midland, MI, USA Search for other works by this author on: Oxford Academic Google Scholar Jia Liu Jia Liu The Dow Chemical Company, Midland, MI, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 475–476, https://doi.org/10.1017/S1431927615003177 Published: 23 September 2015

This paper will discuss the structure-property model developed that correlates the tensile modulus to the elastic properties and angular distribution of constituent graphitic layers for carbon fiber derived from a polyethylene precursor. In addition, a high-temperature fiber tensile device was built to enable heating of carbon fiber bundles at a variable rate from 25 °C to greater than ∼2300 °C, while simultaneously applying a tensile stress. This capability combined with synchrotron wide-angle x-ray diffraction (WAXD), enabled observation in situ and in real time of the microstructural transformation from different carbon fiber precursors to high-modulus carbon fiber. Experiments conducted using PAN- and PE-derived fiber precursors reveal stark differences in their carbonization and high-temperature graphitization behavior.

In this report, we successfully demonstrate a novel SiF4 treatment on lithium manganese iron phosphate cathode (LMFP) that can significantly improve its hydrophobic property. The effect of SiF4 treatment on the structure and hydrophobicity of LMFP powder was studied by X-ray diffraction, Fourier transform infra-red spectroscopy, scanning transmission electron microscopy–energy dispersive X-ray spectroscopy, Karl Fisher titration, and thermo-microbalance gravimetric studies. The SiF4 treated LMFP cathode shows a substantial decrease in moisture adsorption by up to half of the untreated LMFP under ambient conditions. The SiF4-treated LMFP also shows excellent cycle life when cycled in lithium-ion full cells, even after exposing the electrodes to ambient conditions for one day, while the untreated LMFP showed a decrease in cycle life after the same exposure.

To develop low-cost carbon fiber, The Dow Chemical Company and others have explored the sulfonation of polyethylene fibers as an alternative to the incumbent poly(acrylonitrile) route. Although the process of polyethylene sulfonation and subsequent thermal carbonization in an inert atmosphere has been known to provide carbonaceous material for over 35years, we have found the chemical understanding of this transformation to be insufficient. Herein, we report a series of studies that have led to our current understanding for both the sulfonation and subsequent thermal treatment steps. Sulfonation of hydrocarbon model compounds yields completely conjugated and functionalized products. Spectroscopic data suggest that sulfonated polyethylene is similar; containing extended conjugated systems with sulfonic acids and various other oxygen-containing functional groups. Near-Edge X-ray Absorption Fine Structure data have identified that between 150 and 200°C the polymer undergoes a cross-linking step, while evolved gas analysis has identified concomitant release of SO2 and H2O. Above 600°C, H2 is produced and a graphenic carbon microstructure is obtained.