Search Results - (Author, Cooperation:A. W. Weimer)
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1Latest Papers from Table of Contents or Articles in PressC. L. Muhich ; B. W. Evanko ; K. C. Weston ; P. Lichty ; X. Liang ; J. Martinek ; C. B. Musgrave ; A. W. Weimer
American Association for the Advancement of Science (AAAS)
Published 2013Staff ViewPublication Date: 2013-08-03Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Articles: DFG German National LicensesWeimer, A. W. ; Cassiday, J. R. ; Susnitzky, D. W. ; Black, C. K. ; Beamaim, D. R.
Springer
Published 1996Staff ViewISSN: 1573-4803Source: Springer Online Journal Archives 1860-2000Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision MechanicsNotes: Abstract The carbothermal nitridation synthesis of α-Si3N4 was studied using a high-temperature tube furnace to react a precursor, comprised of pyrolysed rice hulls (C/SiO2) and additive “seed” Si3N4, with N2. The experimental design for synthesis was a three-level factorial surface response design for determining the effect of temperature (1300–1380°C) and reaction time (1–5 h) on kinetics. In addition, all precursors were reacted at 1460, 1480 and 1500°G for 5 h in order to ensure high conversion suitable for product powder evaluation (composition and morphology). Following excess carbon removal, the product Si3N4 was 〉95% α-phase and had a surface area of 7.7 m2g−1 with an oxygen content of 3.6 wt% O. The powder was comprised of a bimodal size distribution of submicrometre solid α-Si3N4 crystallites centred at 0.03 and 0.22 μm. No whiskers or high aspect ratio elongated crystallites were found in the powder. The addition of carbon black to the seeded pyrolysed rice hull C/SiO2 mixture had no significant impact on the reaction rate or product powder properties. The reaction was modelled using a nuclei-growth rate expression as $$\begin{gathered} (kt)^{0.58} = - ln(1 --- X) \hfill \\ k = 1.09 \times 10^{10} exp (--- 50502/T) \hfill \\ \end{gathered} $$ k=1.09×1010 exp (−50502/T) where (1573 K〈T〈1653 K), (3600〈t〈18000 s), (0〈X〈1), andk=rate in s−1.Type of Medium: Electronic ResourceURL: -
3Articles: DFG German National LicensesStaff View
ISSN: 0001-1541Keywords: Chemistry ; Chemical EngineeringSource: Wiley InterScience Backfile Collection 1832-2000Topics: Chemistry and PharmacologyProcess Engineering, Biotechnology, Nutrition TechnologyNotes: Particulate expansion and minimum bubbling parameters (n, u′t, umB, εmB) are measured for fine carbon powders (dp = 44 and 112 μm) fluidized with synthesis gas (H2/CO = 0.8) at pressures within the range 2,070 〈 P 〈 12,420 kPa in an industrial, pilot-scale fluidized bed. Deviations between minimum bubbling (umB and εmB) and minimum fluidization (umf and εmf) conditions increase with increasing pressure, P. The expansion index, n, decreases with increasing P and always exceeds values recommended by Richardson and Zaki for solid/liquid systems. Particulate bed expansion for the fine powders is well characterized by the equations of Foscolo et al. and Abrahamsen and Geldart. The theory of Foscolo and Gibilaro adequately estimates the onset of bubbling for both powders at all P, provided that experimentally determined values of n and u′t, are applied. For the dp = 112 μm powder, the theory of Foscolo and Gibilaro is applicable with calculated values of ut and experimental values of n.Additional Material: 10 Ill.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesStaff View
ISSN: 0001-1541Keywords: Chemistry ; Chemical EngineeringSource: Wiley InterScience Backfile Collection 1832-2000Topics: Chemistry and PharmacologyProcess Engineering, Biotechnology, Nutrition TechnologyNotes: Dense phase voidage, εD, dense phase superficial gas velocity, uDo, and absolute bubble rise velocity, uB, were measured at pressures up to 8300 kPa in a pilot-scale, fluidized bed of Group A and boundary Group A/B powders. The mean equivalent bubble diameter, db, near the top of the bed was inferred from uB, and known bed operating conditions. Increased pressure at fixed superficial gas velocity, uo, increased εD and uDo and decreased db for Group A powders. The marked decrease in inferred maximum bubble size, dbmax' with increased pressure could not be explained by a decrease in gas contributing to bubble flow, uBo, but rather appeared to be the result of a bubble instability phenomenon limiting bubble growth.Additional Material: 19 Ill.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesStaff View
ISSN: 0001-1541Keywords: Chemistry ; Chemical EngineeringSource: Wiley InterScience Backfile Collection 1832-2000Topics: Chemistry and PharmacologyProcess Engineering, Biotechnology, Nutrition TechnologyType of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesStaff View
ISSN: 0001-1541Keywords: Chemistry ; Chemical EngineeringSource: Wiley InterScience Backfile Collection 1832-2000Topics: Chemistry and PharmacologyProcess Engineering, Biotechnology, Nutrition TechnologyNotes: An improved bubble velocity equation is developed for gas-solid fluidized beds. Model parameters are evaluated from reported experimental results of bubble flow. Finally, this improved equation is compared to the commonly applied velocity relationship of Davidson and Harrison (1963).Additional Material: 4 Ill.Type of Medium: Electronic ResourceURL: