Microporous layers consisting of different ratios of acetylene black and carbon fibers with either a hydrophobic polytetrafluoroethylene (PTFE) or a hydrophilic perfluorosulfonic acid (PFSA) ionomer binder are investigated with regards to oxygen and water transport in PEMFCs. For that, the materials are characterized by scanning electron microscopy and mercury porosimetry, revealing an increase of porosity and pore sizes for an increasing carbon fiber content. MPLs, coated onto a commercial hydrophobized non-woven gas diffusion layer substrate, are examined in H 2 /air fuel cell tests under differential-flow conditions at various dry and humid operating conditions. For both hydrophobic and hydrophilic MPLs in the presence of significant amounts of liquid water in the diffusion layer substrate, the materials with larger pore sizes, i.e. higher carbon fiber contents, perform superior at 0.6 V and show the lowest oxygen transport resistance. However, at the same carbon composition, hydrophilic MPLs have a lower performance compared to the corresponding hydrophobic MPLs, which is explained by the capillary pressure barriers for different pore properties. At operating conditions relevant for automotive applications, a performance enhancement of 48% could be achieved for a purely carbon fiber based MPL compared to a commercial reference.

Lithium-ion batteries are widely used as energy storage devices due to their high energy density and versatile applicability. Key components of lithium-ion batteries are electrically isolated electrodes and a liquid electrolyte solution which enables ion transport between the electrodes. Laser structuring of electrodes is a promising approach to enhance the high-current capability of lithium-ion batteries by reducing cell internal resistances, as a larger contact area of the active material with the electrolyte solution is created. In the work described here, lithium-ion battery anodes were structured by locally ablating small fractions of the coating using femtosecond laser pulses with infrared wavelengths. A study on ablation characteristics depending on different process parameters such as laser fluence and repetition rate was performed. Special focus was on the ablation efficiency, enabling an optimized process design. The influence of the electrode composition was taken into account by studying the ablation behavior at a varying binder content. Evenly distributed micro holes were chosen in order to keep active material removal at a minimum. To evaluate the effect of structured graphite anodes on the electrochemical properties of lithium-ion batteries, test cells were manufactured and galvanostatically cycled at different current rates. Results show improvements in high-current performance which is expressed by an increased discharge capacity yield.

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A simple method for the determination of the earbonyl value of thermally oxidized fats, using hydroxylamine hydrochloride, is described. Normal octyl alcohol containing pyridine was used as a solvent, and the reaction was allowed to proceed at room temperature for 24 hrs. The titrations were carried out with the aid of a pH meter. The method was standardized against aliphatic aldehydes and ketones. The restflts of analyses showed that the different pure compounds reacted to an extent of 98% or better at room temperature.The method has been successfully applied for the deterruination of the earbonyl value of themnally oxidized fats. n-Valeric acid and the fatty acids with higher molecular weight were not found to interfere in the determination of the carbonyl value by the present method.NUIVIBER of analytical procedures for the determination of aldehydes and ketones, based on the use of hydroxylamine hydrochloride, have been reported. The amount of earbonyl oxygen present was quantitatively determined by estimating either the amount of unreaeted hydroxylaminc (1,2) or the amount of water formed during the reaction (3), or by estimating the hydrochloric acid liberated (4,5,6, 7,8). Lappin and Clark (9) have described a procedure which employs 2,4-dinitrophenylhydrazine for determining traces of carbonyls in aqueous or alcoholic solutions. This method with some modifications was employed by Heniek et al. (10) for the determination of carbonyls in rancid fats and foods. These analytical procedures were not found to be reliable for the quantitative determination of carbonyl oxygen in thernmtly oxidized fats because of their limited solubility in all but a few suitable solvents. A method for the determination of the carbonyl content of thermally oxidized fats, using hydroxylamine hydrochloride as a reagent and n-oetyl alcohol as a suitable solvent, is presented in this paper. Experimental ReagentsHydroxylamine Hydrochloride Reagent. Thirtyfive grams of hydroxylamine hydrochloride (reagent grade) were dissolved in 160 ml. of distilled water, and the resulting solution was diluted to 1 liter with 95% earbonyl-free ethyl alcohol.Standard Sodium Hydroxide in Methanol. Twenty grams of sodium hydroxide (analytical reagent) were dissolved in a small amount of water and diluted to 1 liter with absolute methyl alcohol and standardized against standard hydrochloric acid (0.5 N).Pyridinc-octyl Alcohol Solvent. Five ml. of pyridine (analytical reagent) were diluted to 1 liter wth n-octyl alcohol.A Beeknlan ptI meter, Laboratory Model H2, equipped with standard glass electrode and standard calomel electrode, wtcs used in this work. Analytical ProcedureOne gram of the sample to be analyzed was weighed into a 250-ml. glass-stoppered Erlenmeyer flask. Fifty ml. of pyridine-oetyl alcohol solvent were pipetted into it, and, if necessary, the flask was heated on a hot plate until the sample was dissolved. Fifteen ml. of hydroxylamine hydrochloride reagent was then added with a pipette. The flask was stoppered, the contents were mixed we...

Tripalmitin, 1-and 2-1auryl dipalmitin and 1-and 2-oleyl dipalmitin were subjected to thermal oxidation at 200C in the presence of air for various lengths of time. The triglyc-~ showed a loss in weight, and an increase in carbonyl, hydroxyl and acid vMues. The I.V. increased in the ease of saturated triglycerides and decreased in the case of unsaturated triglycerides.Hydrolysis of the ester linkage between glycerol and fatty acid was found to occur during thermal oxidation of the triglycerides. The hydrolysis occurred irrespective of the type and position of the fatty acid in the triglyeeride molecule. The fatty acids released from the triglyceride by hydrolysis were found either to be oxidized further to short chain fatty acids, or were oxygenated with the introduction of a carbonyl or hydroxyl group in the molecule. Moreover, the unsaturated fatty acid in the triglyeeride molecule was found to be oxidized more readily than the saturated fatty acid.A hydroxy fatty acid with a carbon number of 13.5 on a diethylene glycol succinate column was isolated from oxidized tripalmitin and was also found to occur in the free fatty acid fraction of oxidized tripalmitin, 1-1auryl, 2-3 dipalmitin, and 1-oleyl, 2-3 dipalmitin. The presence of lauric or oleie acid in the 2-position of the triglyccride prevented the formation of this acid, which suggested that it is an oxidation product of palmitic acid.