The absorption cross sections of hydrogen peroxide vapor in the wavelength range from 195 to 350 nm were determined at 296 K. The absorption cross sections of neutral aqueous solutions of hydrogen peroxide were also measured in the same wavelength range. The results are compared with those of other workers, and calculated photodissociation coefficients of atmospheric hydrogen peroxide are presented.

Direct methanol fuel cells (DMFCs) in portable applications are expected to provide substantially higher energy density and longer operating times over advanced batteries. The time threshold of advantage of using a fuel cell instead of a battery is almost independent of the power level, and is determined by the power density of the fuel cell and its operating efficiency. The various requirements for portable fuel cells that determine system design are defined with examples. The system design process and analysis methods are illustrated. The characteristics of cells and stacks required for system design are described. The dependence of DMFC stack performance on airflow rate, methanol concentration and temperature are necessary for developing closed loop mathematical models for system design. Such a closed loop system model has been developed and the consequences of varying airflow rate on water recovery, thermal management and overall system performance have been analyzed. Using this model, the effect of crossover rate on the overall efficiency, power density and the operating methanol concentrations have also been investigated. Effect of components on the overall power budget and design issues relating to start‐up and transient response are also discussed.

This paper describes the overall operation of a 15 cm dia. fluidizedbed reactor for silicon production via silane pyrolysis. The fluidized-bed reactor has been characterized by its performance data and parametric effects. A withdrawal system is used to selectively remove big particles. Seed generation is provided by a fluid jet milling device, which avoids metallic grinding contamination. The silicon particle size growth calculated from a scavengingldeposition model agrees with actual size measurements.

Silicon deposition on silicon seed particles by silane pyrolysis in a fluidized bed reactor is being investigated as a low cost, high throughput method to produce high purity polysilicon for solar cell applications. Studies of fines, particles 0.1–10μ diam, initiated from homogeneous decomposition in the reactor were conducted using 2 and 6 in. diam fluidized beds. The studies show functional dependences of fines elutriation on operating parameters such as silane feed concentration, temperature, gas velocity, and bubble size. The observation that the fines elutriation is generally below 10% of the silicon‐in‐silane feed is explained using a concept of scavenging by large particles in an environment of less free space for homogeneous nucleation. Preliminary results suggest that, with proper conditions and distributor design, high silane concentration ( >50%SiH4 in H2 ) feed may be used for silicon production in fluidized bed reactors.

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