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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1561-1570 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Formation of titania particles by vapor-phase oxidation of titanium tetrachloride was studied in an aerosol reactor between 1,200 and 1,723 K. The effect of process variables (reactor residence time, temperature, and reactant concentration) on powder size and phase characteristic was investigated using the differential mobility particle sizer, scanning electron microscopy, and X-ray diffraction. Titania particles were primarily anatase though the rutile weight fraction increased with increasing reactor temperature. The geometric number average diameter of the particles was between 0.13 and 0.35 μm, and the geometric standard deviation of the particle size distribution was about 1.4. The average particle size increased with increasing temperature, inlet TiCl4 concentration, and residence time. The observed changes in the particle size distribution were compared with those predicted by solving the aerosol dynamic equation by a sectional method and accounting for coagulation and first-order chemical reaction. While variations in the process variables resulted in discernible changes in the size of the particles, the spread of the distribution remained rather unaffected.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1685-1692 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The formation of submicron crystals of boron carbide (B4C) by coagulation and sintering by the rapid carbothermal reduction of intimately mixed carbon-boron oxide powders in an aerosol flow reactor at temperatures above the boiling point of boron oxide is investigated. High heating rates (105K/s) force rapid evaporation of boron oxide and suboxides from the precursor powder, resulting in its rupture and formation of boron carbide molecular clusters that grow to macroscopic particles by coagulation. Consequently, the formation and growth of B4C particles are described by simultaneous interparticle collision and coalescence using a two-dimensional particle-size distribution model that traces the evolution of both size and shape characteristics of the particles through their volume and surface area. In addition to the coagulation term, the governing population balance equation includes a coalescence contribution based on B4C sintering law. The predicted evolution of the two-dimensional particle-size distribution leads to a direct characterization of morphology as well as the average size and polydispersity of the powders. Furthermore, model predictions of the volume and surface area of boron carbide particles can be directly compared with experimental data of B4C specific surface area and an effective sintering rate of B4C is deduced.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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