In this study, we evaluate different apoproaches to unsupervised classification of cyclic voltammetric data, including Principal Component Analysis (PCA), t-distributed Stochastic Neighbour Embedding (t-SNE), Uniform Manifold Approximation and Projection (UMAP)...

We report a method using scanning tunneling microscope single molecular break junction to simultaneously measure and correlate the single-molecule thermopower and electrical conductance. In contrast to previously reported approaches, it does not require custom-built electronics and takes advantage of a trace-by-trace calibration of the thermal offset at the Au/Au contact, thus greatly facilitating thermoelectric measurements at the single-molecule level. We report measurements of three molecules, 1,4-di(4-(ethynyl(phenylthioacetate))) benzene, 1,8-octanedithiol, and 4,4′-bipyridine, and determine single-molecule Seebeck coefficients of 12(3), 5(2), and −5(2) μV K −1 , respectively. Furthermore, the method statistically correlates the Seebeck voltage offset, electrical conductance, and stretching displacement of the single-molecule junction and allows for direct comparison with current-distance spectroscopy results obtained at constant bias.

Oak Ridge National Laboratory T.O. Box 2008 Oak Ridge. Tennessee 37831-6088 .ABSTRACT,A novel porous carbon material based on carbon fibers has been developed. The material. when activated. develops a significant micro-or mesopore volume dependent upon the carbon tiber type utilked (isonopic pitch or polyacrylonimle). The materials will find applications in the field of fluid separations or aa a catalyst support. Here. the manufacture ana characterization of our porous carbon monoliths are described. NTRODUCTIONA novel adsorbent carbon composite material has been developed'" comprising carbon fibers and a binder. The material. called carbon tiber composite molecular sieve (CFCMS), was developed through a joint research program benveen Oak Ridge Nationai Laboratory (ORNL) and the University of Kentucky, Cznter for Appiied Energy Research (UKCXER).The materials are manufactured from milled carbon fibers and powdered phenolic resin. which are slurried in water ana vacuum molded. The moiding process allows the manufacture of slabs. tubes or more complex geometries with contoured surfaces. The "green" (as molded) artifact is heated at 130°C to cure the phenolic resin and then carbonized at 650°C. Tie resultant monoliths have bulk densities in the range 0.2 -0.4 g~c m and crush strength of 1 -2 MPa. Two carbon fiber types have been utilized in our work to date.First, petroleum-pitch derived isotropic carbon fibers have been fabricated into monoliths and activated in steam or CO. at S50"C. The material develops significant microporosity, with mean pore sizes in the range 0.3 -1.0 run. and micropore volumes in the range 0.2 -0.5 cm'/g. Second monoliths have been manufacrured from polyacrylonimIe (PAN) derived carbon fibers. These materials develop significant mesoporosity in the size range 2-50 nm and mesopore volumes typically exceedins 0.5 cm'/g, making them potential catalyst support materials. In both cases the composites are strong and porous. allowing fluids to easily flow through the material.The isotropic pitch derived carbon fiber porous carbon monolith. when activated. provides a high micropore surface are3 (> 1900 m' ;g) capable o i rapid adsorption and desorption. The activated fiber microDore distribution is very narrow. with mean micropore sizes basis of molecular size and shape. . A potentially large application for our carbon-fiber based porous monoliths is gas separation using the Pressure Swing Adsorption (PSA) process. 1 nm. allowing molecular sieving on the Separation by adsorption is based on the selective accumulation of one or more components of a gas mixture on the surface of a microporous solid. When a gaseous mixture is exposed to an absorbent for sufficient time. an equilibrium is established between the adsorbed phase and the gas phase. The gas phase becomes richer in the less selectively adsorbed component. The amactive forces responsible for adsorption MASTER

Samples of carbon fiber were prepared from polyacrylonitrile (PAN)-based precursors, covering a range of electrical resistivity from 0.9 to 1,000 mΩ cm corresponding to a range of carbonization heat treatment temperatures (HTT) estimated to be between 700 and 2600°C. Experimental gas diffusion media (GDM) were made from these fibers using conventional phenolic resin/carbon fiber construction, prepared at two different carbonization temperatures (950 and 2150°C). GDM thermal and electrical properties displayed similar trends with respect to fiber and paper HTT. Unexpectedly, GDM bending and shear moduli increased with fiber resistivity, possibly due to shortening of the lower resistivity fiber types during GDM production. Results showed that high HTT of either the carbon fiber or the paper was sufficient to enable average (“wet” and “dry”) 5-cm2 fuel cell performance comparable to current state-of-the-art GDM. A proprietary GDM wet-laid production model predicts a potential cost reduction of about 2% at 20 million m2 annual production by reducing the paper HTT.

Portions of this document may be illegible in electronic image products. Images are produced f h m the best available original dOr?umeIIL ABSTRACTThe thermal conductivity of carbon-bonded carbon fiber insulation in vacuum was determined before and after short duration heat treatments to model the effect of varying degrees of graphitization. Specimens of the insulation were heat-treated for 10, 15 and 20 seconds at 2673,2873, 3073, and 3273 K. The dimensions and mass of each specimen was recorded before and after heat treatments. The thermal conductivity of the heat treated specimens was measured as a function of temperature up to 2273 K. These data are compared with previously measured specimens heat treated at the same temperatures for 1 minute and one sample heattreated at 3273 K for 1 h. The thermal conductivity increases with both the heat treatment temperature and time at temperature. The thermal conductivity data has been modeled to obtain equations that predict the thermal conductivity of the insulation as a function of temperature (673 K 6 T 5 3773 K) and heat treatment conditions of time (0 5 t I 2 0 s) and temperature (2673 K to 3773 K).