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91.
This paper describes the cylindrical agglomerate model for oxygen/alkali gas diffusion electrodes fabricated from platinum, PTFE and porous nickel. Corrections for the increase in hydroxyl ion concentration with increasing current density have been made to the original model of Brown and Horve. Changes in performance by variation of the bulk structural parameters, e.g. agglomerate radius, porosity and tortuosity, have been studied. Theoretical modes of electrode decay have been explored.List of symbols
Transfer coefficient
-
C
Concentration of O2 in elec trolyte mol cm–3
-
C
i
Concentration of O2 atr = R mol cm–3
-
C
o
Concentration of O2 in electrolyte atr = mol cm–3
-
Diffusion coefficient of O2 in KOH cm2 sec–1
-
Film thickness cm
-
E
Overpotential of the electrode V
-
F
Faraday's constant
-
i
Electrode current density A cm–2
-
i
a
Current per agglomerate A
-
I
1(Z)
First order Bessel function
-
I
0(Z)
Zero order Bessel function
-
j
Local current density A cm–2
-
j
o
Exchange current density A cm–2
-
L
Agglomerate length (catalyst thickness) cm
-
N
Number of electrons in rate determining step
-
N
a
Number of agglomerates per cm2 of electrode
-
Potential drop along ag glomerate V
-
L
Potential drop at La V
-
r
Radial direction
-
R
Radius of agglomerate cm
-
R
o
Gas constant
-
Density of platinum g cm–3
-
S
g
Surface area per gram cm2 g–1
-
Solubility coefficient of O2 mol cm–3
- m
Electrolyte conductivity (ohm cm)–1
-
T
Absolute temperature °K
- a
Axial tortuosity
-
Porosity of platinum in the agglomerate
- r
Aadial tortuosity of the agglomerate
-
W
Catalyst loading g cm–2
-
x
Axial direction 相似文献
92.
The indigo method developed by Bader and Hoigné for aqueous ozone analysis was modified to allow for both gaseous and aqueous ozone determination. Gas or water samples were extracted with a gas-tight syringe containing a known volume of indigo reagent. The modified procedure provided a more consistent basis for gaseous and aqueous ozone determination allowing for more accurate ozone mass balance calculations. Direct gaseous ozone UV absorbance with molar absorptivity of 3,000 M?1cm?1 at 258 nm was used as primary standard to determine the molar absorptivity of the indigo reagent. The molar absorptivity of indigo reagent, assuming a 1:1 stoichiometric ratio for the reaction between indigo and ozone, was determined to be 23,150 ± 80 M?1cm?1, or approximately 16 percent higher than that of 20,000 M?1cm?1 suggested by Bader and Hoigné. An independently calibrated membrane-electrode ozone monitor showed good correlation with indigo method results using the molar absorptivity value determined in this study. The apparent molar absorptivity of aqueous ozone at the wavelength of 258 nm measured by the modified indigo method increased from 2,400 to 3,600 M?1cm?1 in the investigated ozone concentration range of 0.4 to 11.0 mg/L. This variation might have been caused by the inherent interference of unidentified ozone byproducts, which presence was supported with scanning spectra in the wavelength range of 200 to 300 nm. 相似文献
93.
Michael D. Dahlberg Richard L. Rohrer Daniel J. Fauth Richard Sprecher Gregory J. Olson 《Fuel》1993,72(12):1645-1649
A bacterium identified as Arthrobacter sp. was grown on dibenzothiophene (DBT) sulfone as a sole source of sulfur, producing sulfite and sulfate. Sulfur in DBT sulfone (1.0 mM) was nearly quantitatively converted to sulfate by the organism. The organism could also use DBT sulfone as a sole source of carbon and energy. There was evidence for transient accumulation of benzoic acid in the culture medium after growth of the cells slowed. The DBT sulfoxide analogue 9-fluorenone was converted by resting cells to a product identified as 1,10-dihydroxy-1,10-dihydrofluoren-9-one, suggesting that DBT sulfone may be metabolized via an angular hydroxylation resulting in carbon- sulfur bond cleavage. This strain of Arthrobacter showed no ability to desulfurize oxidized Illinois No. 6 coal. 相似文献
94.
Gregory S. Corman 《Journal of the American Ceramic Society》1992,75(12):3421-3424
The compressive creep behavior of single-crystal 6H α-SiC was measured for orientations parallel to and at 45° to [0001]. Deformation of the 45° orientation was dominated by basal slip. Steady-state creep rates above 10-7 /s were measured at temperatures as low as 800°C. An activation energy of 277 kJ/mol and a stress exponent of 3.32 were determined. Creep testing with applied stresses parallel to [0001] was performed at 1650°C to 1850°C, yielding a stress exponent and activation energy of 4.93 and 180 kJ/mol, respectively. The occurrence of basal slip in the [0001] specimens suggested that significant off-axis stresses were present during testing. 相似文献
95.
Unoccupied beaver (Castor canadensis) sites in New York State were for two years experimentally scented with a mixture of beaver castoreum and anal gland secretion. These sites were colonized less often than unscented control sites. The beaver is the first mammal to have been shown experimentally to use intraspecific odor cues when settling in vacant habitat. Territorial pheromones may be useful as repellents for beaver or other rodents. 相似文献
96.
Timothy J. Bunning Hong G. Jeon Ajit K. Roy Kristen M. Kearns Barry L. Farmer Walter W. Adams 《应用聚合物科学杂志》2003,87(14):2348-2355
The thermal and mechanical properties of polyurethane‐infiltrated carbon foam of various densities were investigated. By combining the high thermal conductivity of the carbon foam with the mechanical toughness of the pure polyurethane, a mechanically tough composite (relative to the unfilled foam) that could be used at higher temperatures than the polyurethane's degradation was formed. Both the tensile strength and the modulus increased by an order of magnitude for the composites compared to unfilled foam, while the compressive and shear strengths and moduli of the composites approached values exhibited by pure polyurethane. At both 300 and 400°C, the rectangular blocks of pure polyurethane lost their mechanical integrity due to decomposition in air. Thermogravimetric analysis confirms substantial initial weight loss above 290°C. Filled carbon foam blocks, however, maintain their mechanical integrity at both 300 and 400°C indefinitely, although the bulk of the rectangular block mass is polyurethane. Three different carbon foam densities are examined. As expected, the higher density foams show greater heat transfer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2348–2355, 2003 相似文献
97.
The fluid sheet thickness and velocity at the tip of a spray nozzle have previously been identified as being important to the ultimate droplet size distribution. In this investigation both the fluid sheet thickness and the velocity of the top surface just beyond the rim of a splashplate nozzle have been measured as functions of nozzle exit velocity and fluid viscosity. Measurements were made on two Babcock & Wilcox Co. splashplate nozzles, a 12-49 and a 15-52, specifically designed for black liquor, a by-product of wood pulping. Comparisons of the ratio of the sheet velocity to the nozzle velocity are shown to be very similar to previous data for the ratio of droplet velocity to nozzle velocity. Likewise, the dependence of the sheet thickness on nozzle exit velocity closely matches the previously measured dependence of the ultimate median droplet size on nozzle exit velocity. Both of these results are consistent with current theories of droplet formation mechanisms. Analysis of continuity and viscous drag on the splashplate are used to develop correlation equations for the data 相似文献
98.
We have reported that dietary fish oil (FO) rich in n-3 PUFA modulates gut contractility. It was further demonstrated that the gut of spontaneously hypertensive rats (SHR) has a depressed contractility response to prostaglandins (PG) compared with normotensive Wistar-Kyoto (WKY) rats. We investigated whether feeding diets supplemented with n-3 PUFA increased gut contractility and restored the depressed prostanoid response in SHR gut. Thirteen-week-old SHR were fed diets containing fat at 5 g/100 g as coconut oil (CO), lard, canola oil containing 10% (w/w) n-3 FA as alpha-linolenic acid (1 8:3n-3), or FO (as HiDHA, 22:6n-3) for 12 wk. A control WKY group was fed 5 g/100 g CO in the diet. As confirmed, the SHR CO group had a significantly lower gut response to PGE2 and PGF2alpha compared with the WKY CO group. Feeding FO increased the maximal contraction response to acetylcholine in the ileum compared with all diets and in the colon compared with lard, and restored the depressed response to PGE2 and PGF2alpha in the ileum but not the colon of SHR. FO feeding also led to a significant increase in gut total phospholipid n-3 PUFA as DHA (22:6n-3) with lower n-6 PUFA as arachidonic acid (20:4n-6). Canola feeding led to a small increase in ileal EPA (20:5n-3) and DHA and in colonic DHA without affecting contractility. However, there was no change in ileal membrane muscarinic binding properties due to FO feeding. This report confirms that dietary FO increases muscarinic- and eicosanoid receptor-induced contractility in ileum and that the depressed prostanoid response in SHR ileum, but not colon, is restored by tissue incorporation of DHA as the active nutrient. 相似文献
99.
Garrett BC Dixon DA Camaioni DM Chipman DM Johnson MA Jonah CD Kimmel GA Miller JH Rescigno TN Rossky PJ Xantheas SS Colson SD Laufer AH Ray D Barbara PF Bartels DM Becker KH Bowen KH Bradforth SE Carmichael I Coe JV Corrales LR Cowin JP Dupuis M Eisenthal KB Franz JA Gutowski MS Jordan KD Kay BD Laverne JA Lymar SV Madey TE McCurdy CW Meisel D Mukamel S Nilsson AR Orlando TM Petrik NG Pimblott SM Rustad JR Schenter GK Singer SJ Tokmakoff A Wang LS Wettig C Zwier TS 《Chemical reviews》2005,105(1):355-390
100.
Josianne Lefebvre Federico Galli Claudia L. Bianchi Gregory S. Patience Daria C. Boffito 《加拿大化工杂志》2019,97(10):2588-2593
X‐ray photoelectron spectroscopy (XPS) is a quantitative surface analysis technique used to identify the elemental composition, empirical formula, chemical state, and electronic state of an element. The kinetic energy of the electrons escaping from the material surface irradiated by an x‐ray beam produces a spectrum. XPS identifies chemical species and quantifies their content and the interactions between surface species. It is minimally destructive and is sensitive to a depth between 1–10nm. The elemental sensitivity is in the order of 0.1 atomic %. It requires ultra high vacuum ( Pa) in the analysis chamber and measurement time varies from minutes to hours per sample depending on the analyte. XPS dates back 50 years ago. New spectrometers, detectors, and variable size photon beams, reduce analysis time and increase spatial resolution. An XPS bibliometric map of the 10 000 articles indexed by Web of Science[1] identifies five research clusters: (i) nanoparticles, thin films, and surfaces; (ii) catalysis, oxidation, reduction, stability, and oxides; (iii) nanocomposites, graphene, graphite, and electro‐chemistry; (iv) photocatalysis, water, visible light, and ; and (v) adsorption, aqueous solutions, and waste water. 相似文献