Chemical Engineering @ChemengFiles.Com

Silicon nanoparticle-based floating gate metal-oxide-semiconductor (MOS) field effect devices have potential for terabit [...] density nonvolatile memory applications. Aerosol synthesis of silicon nanoparticles is an important route toward the formation of discontinuous silicon nanoparticle floating gate structures that affords excellent control over particle size and size distribution, particle density, and oxide passivation. We have fabricated nanoparticle memory devices in a conventional MOS ultra-large scale integration (ULSI) process with channel lengths from 0.2 - 10 [...] with a silicon nanoparticle floating gate fabricated by aerosol deposition.

Interest in accurate measurements of the time-dependent Poisson's ratio of polymers arises because it is a component commonly needed in stress analysis and it appears in most theories predicting the behavior of filled materials and composites. Because of the paucity of data and the difficulties in determining [...](t) experimentally, it has been customary in the past to treat [...](t) as a constant. This is unsatisfactory theoretically and inadequate for accurate work.

t is well known that neutral or weakly acid solutions of alkali chlorates show no appreciable oxidizing power. However, it has been observed by K.A. Hofmann (Ber. 45,3329, 1912; 46, 1567, 1913) that, in the presence of very minute amounts of osmium tetroxide, the oxygen becomes readily available. Chlorate solutions activated in this way will, for example, oxidize hydrazine to free nitrogen, potassium iodide to iodine, and arsenic to arsenious acid.

The behavior of the particle size distribution of coagulating dispersions is studied theoretically. If the collision frequency factor is a homogeneous function of particle volume, the partial integro-differential equation describing the coagulation kinetics can be transformed into an ordinary integro-differential equation by a similarity transformation originally proposed by Friedlander. The solution to the resulting equation, called the self-preserving spectrum, is determined for three different collision mechanisms: (1) constant collision frequency factor, (2) Brownian motion, and (3) simultaneous Brownian motion and shear flow, in which the shear rate decreases with time in a particular way. The results of this study indicate that the shape of the self-preserving spectrum is greatly influenced by the collision mechanism.

An electrodynamic balance has been used to measure the water activity as a function of solute concentration at 20 [...]C for eleven single-electrolyte aqueous solutions[...] and three mixed-electrolyte aqueous solutions [...]. The measurements were performed by levitating single, charged, 20-micron diameter droplets of these solutions within the balance and measuring the mass of the particles as a function of the surrounding relative humidity. The deliquescence behavior of the particles was also observed.

An electrodynamic balance has been used to measure the water activity as a function of solute concentration at 20 [...]C for eleven single-electrolyte aqueous solutions[...] and three mixed-electrolyte aqueous solutions [...]. The measurements were performed by levitating single, charged, 20-micron diameter droplets of these solutions within the balance and measuring the mass of the particles as a function of the surrounding relative humidity. The deliquescence behavior of the particles was also observed.

The Orbiting Carbon Observatory (OCO) mission was proposed to deliver the first temporally and spatially resolved global observations of CO2 to improve our understanding of the sources and sinks of CO2. A retrieval algorithm was developed to obtain the column-averaged dry-air mixing ratio of CO2 (XCO2) from spectroscopic measurements of absorption in the 0.76 µm O2 A band and two near-infrared (NIR) bands of CO2 centered at 1.61 µm and 2.06 µm. An aerosol optical-property database was developed to aid with the retrievals. Principal-component analysis was used to speed up radiative transfer (RT) computations. To test the algorithm, column O2 was retrieved from measurements of absorption in the O2 A band over the sea surface. Using a single sounding, the column O2 was retrieved with an error of around 1%. Polarization was shown to have a significant impact on the retrieval-error budget. A new model based on computing two orders of scattering (2OS) was developed to compute polarization in the OCO spectral regions. The multiple-scattering, scalar model Radiant was combined with the 2OS model to create the R-2OS OCO RT model. Tests with simulated backscatter measurements at the OCO validation

This thesis is motivated by the need to improve our understanding of the aerosol indirect effect. The activation of aerosol into cloud droplets has been extensively studied, using a comprehensive numerical cloud droplet activation model. Using this model, the effect of water vapor mass transfer limitations on the cloud droplet activation process was first studied; it was found that mass transfer limitations are important for activation under polluted conditions. The potential effect of (currently unresolved) ``chemical effects' on cloud droplet number (e.g., the presence soluble gases and surface active species) was also assessed. It was seen that small changes in aerosol and gas-phase composition can have a strong effect on cloud droplet number, and should be included in future estimates of the aerosol indirect effect.

The behavior of the particle size distribution of coagulating dispersions is studied theoretically. If the collision frequency factor is a homogeneous function of particle volume, the partial integro-differential equation describing the coagulation kinetics can be transformed into an ordinary integro-differential equation by a similarity transformation originally proposed by Friedlander. The solution to the resulting equation, called the self-preserving spectrum, is determined for three different collision mechanisms: (1) constant collision frequency factor, (2) Brownian motion, and (3) simultaneous Brownian motion and shear flow, in which the shear rate decreases with time in a particular way. The results of this study indicate that the shape of the self-preserving spectrum is greatly influenced by the collision mechanism.

A ballistic piston apparatus is described briefly. The instruments in the apparatus and the associated external measuring circuits are discussed in detail. The differential equations which describe the energy and material transport in the axially-collapsing cylindrical sample-gas chamber are derived and solved numerically. Compressibility factors are calculated for nitrogen gas employing data obtained from two tests made on the ballistic piston apparatus. Temperatures in this investigation range from 2300° to 3300° R, and pressures from 1000 to 6300 pounds per square inch absolute.