Wieslaw J. Suszynski

Reactive boiling of cellulose for integrated catalysis through an intermediate liquid.

Advanced biomass processing technology integrating fast pyrolysis and inorganic catalysis requires an improved understanding of the thermal decomposition of biopolymers in contact with porous catalytic surfaces. High speed photography (1000 frames per second) reveals that direct impingement of microcrystalline cellulose particles (300 μm) with rhodium-based reforming catalysts at high temperature (700 °C) produces an intermediate liquid phase that reactively boils to vapors. The intermediate liquid maintains contact with the porous surface permitting high heat transfer (MW m−2) generating an internal thermal gradient visible within the particle as a propagating wave of solid to liquid conversion. Complete conversion to liquid yields a fluid droplet on the catalyst surface exhibiting a linear decrease in droplet volume with time leaving behind a clean surface absent of solid residue (char). Under specific interfacial conditions, conversion with large cellulosic particles on the length-scale of wood chips (millimeters) occurs continuously as generated liquid and vapors are pushed into the porous surface.

Aerosol generation by reactive boiling ejection of molten cellulose

The generation of primary aerosols from biomass hinders the production of biofuels by pyrolysis, intensifies the environmental impact of forest fires, and exacerbates the health implications associated with cigarette smoking. High speed photography is utilized to elucidate the ejection mechanism of aerosol particles from thermally decomposing cellulose at the timescale of milliseconds. Fluid modeling, based on first principles, and experimental measurement of the ejection phenomenon supports the proposed mechanism of interfacial gas bubble collapse forming a liquid jet which subsequently fragments to form ejected aerosol particles capable of transporting nonvolatile chemicals. Identification of the bubble-collapse/ejection mechanism of intermediate cellulose confirms the transportation of nonvolatile material to the gas phase and provides fundamental understanding for predicting the rate of aerosol generation.

A Raman spectroscopic method to find binder distribution in electrodes during drying

Lithium ion batteries are used extensively in electronic devices as well as hybrid and electric vehicles. The anode electrode layer in the battery can be fabricated by coating an aqueous dispersion of carbon, binder, and additives, and then drying. During manufacturing, the distribution of the binder through the coating thickness can become nonuniform, which compromises the properties and performance of the battery. In this study, a quantitative method to analyze the binder distribution in the electrode during drying was established. A drying apparatus with an integrated analytic balance and surface-temperature measurement was used to prepare specimens. At specific time points during drying, specimens were removed from the apparatus, quickly frozen, and then freeze-dried. Raman spectroscopy was then used to measure the binder concentration at different points through the cross section of the freeze-dried electrode coating. Scanning electron microscopy was also used to explore the changing microstructure qualitatively. Using a model electrode formulation, the method demonstrated different binder distributions for electrodes dried at 150°C under airflow and room temperature, 20°C, with no airflow. The results also showed continued changes in distribution in the interior of the coating as drying continued.

Wettability Contrast Gravure Printing

Silicon gravure patterns are engineered to have cells that are wettable and lands that are not wettable by aqueous inks. This strategy allows excess ink on the lands to be removed without using a doctor blade. Using an aqueous silica ink, continuous lines as narrow as 1.2 μm with 1.5 μm space are gravure printed.

New controlled environment vitrification system for preparing wet samples for cryo-SEM

A new controlled environment vitrification system (CEVS) has been designed and constructed to facilitate examination by cryogenic scanning electron microscopy (Cryo‐SEM) of initial suspension state and of microstructure development in latex, latex–composite and other coatings while they still contain solvent. The new system has a main chamber with provisions for coating as well as drying, and for well‐controlled plunging into cryogen. An added subsidiary chamber holds samples for drying or annealing over minutes to days before they are returned to the main chamber and plunged from it. In the main chamber, samples are blade‐coated on 5 × 7 mm pieces of silicon wafer and held at selected temperature and humidity for successively longer times, either there or after transfer along a rail into the subsidiary chamber. They are then placed in the sample holder mounted on the plunge rod, so as to permit adjustment of the samples attitude when it plunges, at controlled speed, into liquid ethane at its freezing point, to a chosen depth, in order to solidify the sample without significant shear or freezing artifacts. The entries of plunging samples and related sample holders into liquid ethane were recorded with a high‐speed, high‐resolution Photron digital camera. The data were interpreted with a new hypothesis about the width of the band of extremely rapid cooling by deeply subcooled nucleate boiling below the line of entry. Complementary cryo‐SEM images revealed that the freezing rate and surface shearing of a sample need to be balanced by adjusting the plunging attitude.

Reactive Liftoff of Crystalline Cellulose Particles

The condition of heat transfer to lignocellulosic biomass particles during thermal processing at high temperature (>400 °C) dramatically alters the yield and quality of renewable energy and fuels. In this work, crystalline cellulose particles were discovered to lift off heated surfaces by high speed photography similar to the Leidenfrost effect in hot, volatile liquids. Order of magnitude variation in heat transfer rates and cellulose particle lifetimes was observed as intermediate liquid cellulose droplets transitioned from low temperature wetting (500–600 °C) to fully de-wetted, skittering droplets on polished surfaces (>700 °C). Introduction of macroporosity to the heated surface was shown to completely inhibit the cellulose Leidenfrost effect, providing a tunable design parameter to control particle heat transfer rates in industrial biomass reactors.

Water-based coatings for 3D printed parts

Three-dimensional (3D) printing or additive manufacturing is an emerging technology that enables the exploration of new ideas and designs. The process converts a 3D digital model into a 3D object, allowing end users to hold and easily visualize their designs. Since 3D printed parts are built through layer-by-layer deposition, they exhibit limited surface smoothness and surface quality. By applying water-based coatings onto 3D printed parts, surface quality can be improved by reducing surface roughness and by sealing surface gaps without deforming the parts themselves. In this study, water-based coatings were applied to 3D printed parts using a computer-controlled dip coater. Surface profiles of 3D printed parts before and after dip coating were measured using a profilometer and parts were examined with optical microscopy. Two commercial water-based coating systems were evaluated, and the effect of coating speed, drying conditions, and number of coated layers on surface roughness of 3D printed parts was studied. The effect of printing with different print tips and in different orientations on surface roughness before and after coating was also studied. Coating liquids with higher solids loading were found to be most effective at smoothing or planarizing the 3D printed part surface.

Process limits in two-layer reverse roll transfer

Reverse roll coating in which a thin single layer of liquid is applied onto a substrate has been used in industry for decades and has been extensively analyzed in the literature. Modern coatings, however, are often composed of more than one layer to improve the product performance and to reduce the manufacturing cost. Premetered methods such as slot, slide, and curtain coatings are typically used to produce such multilayer coatings. If the caliper of the substrate to be coated is not constant, then the coating gap and consequently the final film thickness deposited on the web will also be nonuniform. In this study, we focused on the use of reverse roll technique with slot die liquid delivery system to produce a uniform thin two-layer coating. The use of this coating technique to produce such a coating has not been previously explored. The liquid film surface as it is transferred from a rigid steel roll to a deformable urethane-covered roll was visualized to find out how the uniformity of the two-layer coating is affected by the speed ratio between two rolls, layers’ wet thicknesses, and liquid viscosities. The effect of these parameters on the ribbing frequency and amplitude was also investigated. The results show that in the two-layer coating, as in the single layer reverse transfer, there is a critical web speed above which ribbing occurs. The critical speed is determined by the bottom layer viscosity.