Papers by William Desisto
Bioresource technology, 2015
The present study examines the effect of calcium pretreatment on pyrolysis of individual lignocel... more The present study examines the effect of calcium pretreatment on pyrolysis of individual lignocellulosic compounds. Previous work has demonstrated that the incorporation of calcium compounds with the feedstock prior to pyrolysis has a significant effect on the oxygen content and stability of the resulting oil. The aim of this work was to further explore the chemistry of calcium-catalyzed pyrolysis. Bench-scale pyrolysis of biomass constituents, including lignin, cellulose and xylan is performed and compared to the oils produced from pyrolysis of the same components after calcium pretreatment. The resulting oils were analyzed by quantitative GC-MS and SEC. These analyses, together with data collected from previous work provide evidence which was used to develop proposed reaction pathways for pyrolysis of calcium-pretreatment biomass.
Because of its simplicity, fast pyrolysis is an attractive biomass conversion process which is sc... more Because of its simplicity, fast pyrolysis is an attractive biomass conversion process which is scalable from mobile units to thousands of tons per day. However, the utility of the oils produced by fast pyrolysis is limited because of the well-known chemical and physical properties of these highly oxygenated oils. It is possible to improve the quality of the oils by employing catalysts in the pyrolysis reactor and by performing downstream hydrodeoxygenation with additional catalysts and hydrogen. It is important to understand the effects these additional processes have on the technoeconomics and ability to do distributed processing. Also, biomass feedstock composition significantly affects the product distributions and, therefore, the thermal integration within the process. As the most heavily forested state in the country, Maine has a large pulp and paper industry. Along with the 12 million green tons of pulpwood which are harvested annually,[1] there is likely the potential to coll...
Thin Solid Films, 2006
The initial stages of titanium nitride atomic layer deposition using sequential additions of TiCl... more The initial stages of titanium nitride atomic layer deposition using sequential additions of TiCl 4 and NH 3 on fumed silica powder were investigated using in situ Fourier transform infrared spectroscopy techniques. After the first stage, the primary active surface species for the formation of TiN were determined to be TiCl x and Ti 2 NH. After six complete atomic layer deposition cycles the infrared spectrum indicated a strong TiN band that was verified by diffuse reflectance infrared spectroscopy recorded on pure TiN powder. Incomplete surface reactions were also observed.
Applied Physics Letters, 2000
A 1 cm2 area in phosphorus-implanted silicon samples is annealed by irradiation of a much smaller... more A 1 cm2 area in phosphorus-implanted silicon samples is annealed by irradiation of a much smaller 0.002 cm2 area with a single laser pulse. Resistivity of the annealed region is uniform and similar to that measured after thermal annealing. Electrically activated donors did not diffuse into the sample and only slightly towards the sample surface. The process is 100% reproducible.
Bioresource Technology, 2014
Pine sawdust was pretreated with several calcium compounds and then pyrolyzed in a fluidized bed ... more Pine sawdust was pretreated with several calcium compounds and then pyrolyzed in a fluidized bed pyrolysis reactor at 500 °C. The catalytic action of the calcium compounds varies depending on the anion. Analysis of pyrolysis gas, liquid and char yields and compositions demonstrates that calcium sulfate is inert during pyrolysis while calcium formate, carbonate, hydroxide and oxide show significant deoxygenation activity. Of the salts which showed deoxygenation activity, calcium formate had the highest relative yield. This effect is likely attributable to the activity of calcium formate as a hydrogen donor at the pyrolysis temperature.
Microporous and Mesoporous Materials, 2009
The results of a detailed study of the permeation of several light gases through unmodified and m... more The results of a detailed study of the permeation of several light gases through unmodified and modified mesoporous silica membranes are reported. The base membranes which were synthesized by dip-coating multiple layers of a templated silica onto a macroporous alumina support showed relatively high permeances with evidence of both support resistance and a contribution from viscous flow, in addition to
Journal of Power Sources, 2007
Lithium titanate spinel (Li 4 Ti 5 O 12 , or LTS) is receiving consideration as a nanopowder anod... more Lithium titanate spinel (Li 4 Ti 5 O 12 , or LTS) is receiving consideration as a nanopowder anode material for use in lithium-ion batteries. LTS has more positive working potential than traditional graphite anodes, and it does not react with electrolyte components. However, the main drawback of LTS powder is its poor interparticle electronic conductance that reduces the high-rate ability of the electrode. To improve this we have coated the surface of the LTS powder with a titanium nitride layer by atomic layer deposition (ALD). In situ infrared spectroscopy studies were conducted to confirm the attachment of the titanium precursor. The nitrogen content of films was measured by total nitrogen content testing. Transmission electron microscopy (TEM) micrographs confirmed the formation of a thin titanium nitride film around LTS particles by ALD. Finally, lithium cells with electrodes made of original and modified LTS nanopowders were assembled and tested.
Journal of Non-Crystalline Solids, 2004
Hemoglobin and myoglobin were encapsulated in silica gels and powders. Protein encapsulated powde... more Hemoglobin and myoglobin were encapsulated in silica gels and powders. Protein encapsulated powders were fabricated via the condensation of silicic acid around the protein, followed by a fast freezing with liquid nitrogen, and subsequent thawing. The fastfreezing technique led to high surface area stable silica encapsulated protein powders. Transmission UV-vis spectroscopy techniques were used to verify that neither protein was damaged during gelling or freezing processes. Both hemoglobin and myoglobin gels and powders retained their biological activity and were able to bind cyano ligands while in the oxidized Fe 3þ state and carbon monoxy ligands while in the reduced Fe 2þ state. Kinetics experiments showed that the rates of binding of CO and CN À to the proteins in the silica gel versus a buffer solution are decreased by 30-45%. This result was likely due to mass transfer effects associated with diffusion through the gel network. Hemoglobin/silica powders were successfully stabilized in the Fe 2þ oxidation state by addition of the amino acid L L -cysteine.
Journal of Crystal Growth, 1997
Real-time UV absorbance of YBCO MOCVD precursors was monitored in-line at the bubbler effluent us... more Real-time UV absorbance of YBCO MOCVD precursors was monitored in-line at the bubbler effluent using a remote fiber-optic based dual-wavelength detection scheme. A SN of 50:1 was obtained by signal averaging detector response over a one second interval. This technique provided a chemical specific measurement of extremely dilute concentrations of MOCVD source materials. In addition, several concentration transients were observed.
Journal of Colloid and Interface Science, 1987
Experimental values of the maximum drop volume that can be sustained on an inclined solid surface... more Experimental values of the maximum drop volume that can be sustained on an inclined solid surface are compared to the theoretical predictions by E. B. Dussan V. (J. Fluid Mech. 151, 1 (1985)). The agreement for both water and glycerol on Teflon substrates is within the measurement error. Thus, critical drop volumes can be predicted upon knowledge of the advancing and receding contact angles, the density and surface tension of the liquid, the gravitational acceleration, and the angle of inclination of the solid--all of which are system material properties or experimental conditions. Although the surface tension of glycerol is far less than that of water, it is held more firmly on the Teflon surface, showing that contact angle hysteresis has a key impact on when a drop will slide on the solid. The validity of the theoretical prediction can be exploited to accurately determine contact angle hysteresis for systems where the difference between the advancing and receding contact angles is small.
The Journal of Chemical Physics, 2008
Mesoporous silica membranes fabricated by the surfactant-templated sol-gel process have received ... more Mesoporous silica membranes fabricated by the surfactant-templated sol-gel process have received attention because of the potential to prepare membranes with a narrow pore size distribution and ordering of the interconnected pores. Potential applications include ultrafiltration, biological separations and drug delivery, and separators in lithium-ion batteries. Despite advancements in synthesis and characterization of these membranes, a quantitative description of the membrane microstructure remains a challenge. Currently the membrane microstructure is characterized by the combination of results from several techniques, i.e., gas permeance testing, x-ray diffraction scanning electron microscopy, transmission electron microscopy, and permporometry. The results from these ensemble methods are then compiled and the data fitted to a particular flow model. Although these methods are very effective in determining membrane performance, general pore size distribution, and defect concentration, they are unable to monitor molecular paths through the membrane and quantitatively measure molecular interactions between the molecular specie and pore network. Single-molecule imaging techniques enable optical measurements that probe materials on nanometer length scales through observation of individual molecules without the influence of averaging. Using single-molecule imaging spectroscopy, we can quantitatively characterize the interaction between the probe molecule and the interior of the pore within mesoporous silica membranes. This approach is radically different from typical membrane characterization methods in that it has the potential to spatially sample the underlying pore structure distribution, the surface energy, and the transport properties. Our hope is that this new fundamental knowledge can be quantitatively linked to both the preparation and the performance of membranes, leading to the advancement of membrane science and technology. Fluorescent molecules, 1,1-dioctadecyl-3,3,3,3-tetramethylindo-carbocyanine perchlorate, used to interrogate the available free volume in their vicinity, were loaded into the mesoporous silica membranes at subnanomolar concentrations. The mesoporous silica films were prepared using a nonionic ethylene oxide-propylene oxide-ethylene oxide triblock copolymer surfactant, Pluronic P123, on single crystal silicon substrates using dip coating of a silica sol. Membranes were prepared resulting in an average pore diameter of approximately 5 nm as measured by helium, nitrogen permeance, and porosimetry. Fluorescent images and time transient experiments were recorded using a custom built single-molecule scanning confocal microscope at differing temperatures (10, 20, 30, 40, and 50 degrees C). Time-dependent polarization anisotropy was used to obtain the enthalpy of adsorption and Henry's law constant of the probe molecule.
Industrial & Engineering Chemistry Research, 2004
... X-ray diffraction techniques and transmission electron microscopy are used to study the textu... more ... X-ray diffraction techniques and transmission electron microscopy are used to study the texture of the prepared layers. Nanoparticle seeding favors the formation of the templating mesophases in the synthesis medium [10]. This ...
IEEE Transactions on Appiled Superconductivity, 2000
The material and electrical characteristics of YBa2Cu 3O7 (YBCO) thin films deposited by inverted... more The material and electrical characteristics of YBa2Cu 3O7 (YBCO) thin films deposited by inverted cylindrical magnetron sputtering on (110) SrTiO3 (STO) were investigated. X-ray diffractometry shows the grain orientations to be predominantly the YBCO (110) and (103) with no evidence of c-axis grains, Electron micrographs show the film surface to consist of coupled elongated grains parallel to the (110) STO
Chemical Engineering Science, 2009
Experimental permeance data for several light gases in a mesoporous silica membrane are analyzed ... more Experimental permeance data for several light gases in a mesoporous silica membrane are analyzed in detail and shown to conform closely to the Knudsen diffusion model. The results of this study do not support the conclusions drawn from recent molecular simulations concerning the inadequacy of the Knudsen model.
Applied Surface Science, 2007
While there are numerous studies examining the performance of lithium titanate spinel (LTS) as a ... more While there are numerous studies examining the performance of lithium titanate spinel (LTS) as a lithium-ion battery, little is known about the surface chemistry of this material. In this paper, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy spectroscopy was used to study the type of surface groups present on LTS as a function of temperature. The surface was found to
Applied Physics Letters, 1996
UV spectroscopy has been used as an insitu diagnostic to measure the gas phase concentration of 2... more UV spectroscopy has been used as an insitu diagnostic to measure the gas phase concentration of 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) complexes of Cu and Y in metalorganic chemical vapor deposition (MOCVD) bubbler effluent. These Cu and Y precursors for MOCVD synthesis of YBa2Cu3O7−δ (YBCO) show marked instability in gas phase concentration as a function of time during the initial bubbler purge. The
Applied Physics Letters, 2010
We present a simple fluorescence imaging method for measuring the time-resolved concentration of ... more We present a simple fluorescence imaging method for measuring the time-resolved concentration of a fluorescent molecule diffusing through an anodic alumina membrane with a pore diameter of 20 nm. From the concentration breakthrough curve, the molecular diffusivity of the fluorophore was extracted. The experimentally determined diffusivity was three orders of magnitude lower than reported bulk values. Due to the relative simplicity and ease of use, this method can be applied to provide fundamental information for biomolecular separations applications. One feature of this method is the high sensitivity at intercellular volumes broadening its application to drug delivery and controlled cell growth.
Applied Physics Letters, 1999
Thin films of Ba(1-x)SrxTiO3 (BST) have been deposited by off-axis cosputtering targets of SrTiO3... more Thin films of Ba(1-x)SrxTiO3 (BST) have been deposited by off-axis cosputtering targets of SrTiO3 (STO) and BaTiO3 (BTO). The films were grown on (100) MgO and LaAlO3 substrates at 550 °C at an argon/oxygen gas pressure of 20 Pa. Reaction of the sputtered species in the plasma resulted in the growth of BST films. The film composition was set by
Applied Catalysis A: General, 2010
ABSTRACT Nanocalorimeters based on a micromachined hotplate platform were characterized for poten... more ABSTRACT Nanocalorimeters based on a micromachined hotplate platform were characterized for potential applications in catalyst screening and reaction mechanism studies. The nanocalorimeters were designed to limit heat loss to the surroundings, resulting in a small heat capacity (50 nJ K−1) and thermal time constant (1 ms). This greatly increases the sensitivity of the device, allowing reaction heat flows on the order of <1 μW to be measured in air. The Pt catalyzed combustion of hydrogen in air was used as a model reaction. A relatively-simple heat and mass transfer model was developed which accurately described the data from the microscale system, and the rate-limited and mass transfer-limited regimes of the ignition traces were clearly distinguished. An average activation energy of 48 ± 4 kJ mol−1 was determined for the Pt catalyzed combustion of hydrogen in air. However, unique rapid temperature programmed calorimetry methods convincingly demonstrate that the activation energy is influenced by kinetic phase transitions which also result in reaction rate bistabilities and oscillations.Graphical abstractView high quality image (62K)Research highlights▶ 4-Element nanocalorimeter arrays with 50 nJ/K sensitivity have been evaluated as catalyst screening platforms. ▶ Combined heat and mass transfer models using both a 2-D finite element method and a 1-D mathematical method were used to model calorimeter response to reaction power. ▶ Reaction rate for catalytic hydrogen oxidation was measured using ramped temperature programming and hysteresis and oscillations in reaction rates were observed. ▶ The 1-D model was used to determine model parameters for mass transfer and reaction kinetics for a range of hydrogen concentrations. ▶ Unique millisecond pulsed temperature programming method suggests that the hysteresis and oscillations result from kinetic surface coverage phase transitions. ▶ Results were used to discuss the utility of the method for catalyst screening.
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Papers by William Desisto