Clemson University

About: Clemson University is a education organization based out in Clemson, South Carolina, United States. It is known for research contribution in the topics: Population & Control theory. The organization has 20556 authors who have published 42518 publications receiving 1170779 citations. The organization is also known as: Clemson Agricultural College of South Carolina.

Zr and Y co-doped perovskite as a stable, high performance cathode for solid oxide fuel cells operating below 500 °C

Abstract: Zr and Y co-doped perovskite BaCo0.4Fe0.4Zr0.1Y0.1O3−δ (BCFZY0.1) was recently developed as a promising new cathode for protonic ceramic fuel cells (PCFCs). Here, it is applied for the first time as a cathode for low-temperature solid oxide fuel cells (LT-SOFCs). It exhibits large lattice parameters, high oxygen reduction reaction (ORR) activity, exceptional low-temperature performance, long-term stability, and excellent chemical compatability with ceria-based SOFC electrolytes. When BCFZY0.1 is used as the cathode in Ce0.8Gd0.2O2−δ (GDC20)-based SOFCs, it enables a peak power density of 0.97 W cm−2 at 500 °C with 2500 hours stable performance and complete recoverability without any degradation after more than 80 fast thermal ramping cycles. Even at 350 °C, peak power density reaches 0.13 W cm−2. It also shows good H2O and CO2 tolerance.

Esterification and transesterification using modified-zirconia catalysts

Abstract: In this paper, modified zirconias (WZ, SZ, and TiZ) have been extensively compared under the same reaction conditions as catalysts for both the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the catalyzed rate of hydrolysis/esterification + transesterification of triglycerides has been quantified and compared to that of the rate of simultaneous esterification of FFAs present in the same reaction mixture. Tricaprylin and caprylic acid were used as representative compounds for the comparison of the catalyst for transesterification and esterification since they give reaction rates related to those of larger TGs and FFAs typically present in vegetable oils and animal fats. For the measurement of the kinetics for the simultaneous reaction of a TG-FFA mixture, the reaction of tricaprylin and oleic acid with ethanol was studied using the most promising of the Zr-based catalysts, WZ. Reaction was carried out in a well-mixed batch reactor under mild conditions (75–120 °C). TiZ, while more active than WZ for transesterification, had by far the lowest activity for esterification. SZ, while the most active catalyst (on a weight basis) for both transesterification and esterification reactions, exhibited significant sulfur loss, which greatly reduced its long term activity. As expected, esterification occurred at a much faster rate than transesterification. However, under simultaneous reaction conditions, by virtue of the water being produced in esterification and hydrolysis of the TG taking place, the conversion of the triglycerides to ester products was greatly increased. The resulting caprylic acid from hydrolysis did not accumulate in the reaction mixture due to its rapid esterification to ethyl caprylate. The activity results for WZ indicate how biodiesel can be efficiently produced from free-fatty-acid-containing feedstocks using a solid-acid-catalyzed pre-esterification step, and how a significant fraction of the triglycerides can also be converted at the same time assisted by initial hydrolysis with byproduct water from esterification.

Proton Conductivity in Nafion® 117 and in a Novel Bis[(perfluoroalkyl)sulfonyl]imide Ionomer Membrane

Abstract: A study of proton conductivity in a commercial sample of Nation® 117 and a structurally similar bis[(perfluoroalkyl)sulfonyl]imide ionomer membrane under variable temperature and humidity conditions is reported. The sulfonyl imide ionomer was synthesized using a novel redox‐initiated emulsion copolymerization method, and conductivities were measured using a galvanostatic four‐point‐probe electrochemical impedance spectroscopy technique. Both materials exhibited a strong dependence of conductivity on temperature and humidity, with conductivity in both cases being strongly diminished with decreasing humidity (at constant temperature) and increasing temperature (at constant water partial pressure). The observed behavior is consistent with a "liquid‐like" mechanism of proton conductivity whereby protons are transported as hydrated hydronium ions through water‐filled pores and channels in the ionomer.

1 The Maternal-Embryonic Relationship in Viviparous Fishes

Abstract: Publisher Summary This chapter discusses the maternal–embryonic relationship in viviparous fishes. Viviparity is a highly successful mode of reproduction that has evolved independently many times and with many variations in widely separated taxonomic groups. It occurs in all classes of vertebrates, except birds, and among many different groups of invertebrates. Initial steps in the evolution of viviparity involved a shift from external to internal fertilization and the retention of fertilized eggs in the female reproductive system. The osmoregulation of early embryos can be accomplished more efficiently and with less expenditure of embryonic energy in a maternally controlled uterine environment, but as development progresses to term, the embryos presumably acquire an increasing degree of osmoregulatory independence. Available evidence suggests that maternal regulation of the osmotic and chemical environment of the embryo also confers a selective advantage on viviparous teleosts. The uterine wall of most viviparous elasmobranchs and the coelocanth both delimits and defines the embryonic environment. The most spectacular maternal specializations for uterine gestation involve the uterine wall and involve (1) the amplification of the surface area in the form of folds, villi, or trophonemata; (2) the production of histotrophe or uterine milk’ (3) the compartmentalization of embryos; and (4) the development of placental attachment sites.