Poly(acrylic acid)–Poly(ethylene oxide) Comb Polymer Effects on BaTiO3 Nanoparticle Suspension Stability

We have studied the effects of poly(acrylic acid)–poly(ethylene oxide) (PAA–PEO) comb polymers on the stability of aqueous BaTiO₃ nanoparticle suspensions over a wide pH range in the presence and absence of mono- and divalent salt species. The comb polymer architecture consists of charge-neutral PEO teeth attached at random intervals along an ionizable PAA backbone. Potentiometric titrations, light scattering, and turbidity measurements were conducted on pure PAA and PAA–PEO solutions to assess their degree of ionization, radius of hydration, and stability. Adsorption isotherm and rheological measurements were conducted on BaTiO₃ nanoparticle suspensions to determine the effectiveness of both PAA and PAA–PEO dispersants. Our observations indicate that the presence of PEO teeth effectively shield the underlying PAA backbone from ion interactions, e.g., counterion-screening or ion-bridging effects, thereby allowing PAA–PEO dispersants to impart stability to BaTiO₃ nanoparticle suspensions over a wide range of pH, ionic strength, and ion valency conditions where pure PAA fails.     

Detergency studies at low solution concentrations

Summary Tests made with mixtures of Santomerse No. 1 or No. 3 with TSPP at 0.05% (in synthetic sea water) indicate optimum soil removal for combinations of 80% TSPP and 20% Santomerse. At this solution concentration TSPP alone removed more soil than either Santomerse product. Tests made in hard water at 0.075% solution concentration with Santomerse combined with various alkaline soap builders in 1:1 ratios of Santomerse No. 3 to anhydrous alkaline builders permitted arrangement of the alkalies in decreasing order of effectiveness as follows: TSP TSPP TSPP—Orthosilicate (1:1) TSPP—TSP (1:1) Orthosilicate and metasilicate Sodium carbonate Further tests at the same solution concentration were made with hydrous builders on an “as received” basis but with Santomerse No. 1 to builder ratios of 67:33 or 75:25. The order of efficiency of the builders was the same as for the previous tests, and there were negligible differences between the two ratios tested. Detergent testing of several of the alkaline soap builders indicated relatively high soil removal at low solution concentrations in comparison with Santomerse No. 1 and accounts for improved detergency of its mixtures with alkali. Burnt umber peptization values tend to corroborate detergent findings. This paper was presented at the Chicago fall meeting of the American Oil Chemists’ Society, October 25–27.     

A hot-wire probe for thermal measurements of nanowires and nanotubes inside a transmission electron microscope

A hot wire probe has been developed for use inside a transmission electron microscope to measure the thermal resistance of individual nanowires, nanotubes, and their contacts. No microfabrication is involved. The probe is made from a platinum Wollaston wire and is pretensioned to minimize the effects of thermal expansion, intrinsic thermal vibrations, and Lorentz forces. An in situ nanomanipulator is used to select a particular nanowire or nanotube for measurement, and contacts are made with liquid metal droplets or by electron-beam induced deposition. Detailed thermal analysis shows that for best sensitivity, the thermal resistance of the hot-wire probe should be four times that of the sample, but a mismatch of more than two orders of magnitude may be acceptable. Data analysis using the ratio of two ac signals reduces the experimental uncertainty. The range of detectable sample thermal resistances spans from approximately 10(3) to 10(9) KW. The probe can also be adapted for measurements of the electrical conductance and Seebeck coefficient of the same sample. The probe was used to study a multiwalled carbon nanotube with liquid Ga contacts. The measured thermal resistance of 3.3 x 10(7) KW had a noise level of approximately +/-3% and was repeatable to within +/-10% upon breaking and re-making the contact.     

The association of plasma IL-6 levels with functional disability in community-dwelling elderly

BACKGROUND: IL-6 is a multifunctional cytokine that has been shown to increase with age. METHODS: Plasma IL-6 was measured by ELISA in 1,727 community-dwelling elderly subjects whose blood was drawn during the third in-person survey of the Duke Established Populations for Epidemiologic Studies of the Elderly (EPESE). Demographics, functional status (disability), and disease states were determined. Correlations of these factors with IL-6 were analyzed with Spearman's Rho while differences between groups were assessed by Wilcoxon test. RESULTS: IL-6 levels were higher with age (p = .0001) even in this older population (> 70 years). There was a positive correlation between IL-6 and functional disability for each of the functional status measures (p = .0001), as well as a correlation between self-rated health and IL-6. Significantly higher median levels of IL-6 were found in subjects reporting prevalent cancer, heart attack, and high blood pressure, but not diabetes or arthritis. The association between age and functional status with high IL-6 remained when all other variables were controlled, in multivariable analysis. CONCLUSIONS: This association between increased plasma IL-6 levels and functional status suggests that dysregulation of IL-6 may be related to the functional disability seen with aging, and that IL-6 may be useful as a component of an overall marker of health.     

Evaluation of environmental effects on fatigue life of piping

Recent data indicate that the effects of light water reactor environments can significantly reduce the fatigue resistance of materials, and show that design fatigue curves may not be conservative for reactor coolant environments. Using revised fatigue curves developed by Argonne National Laboratory (ANL), the work of this paper calculates the expected probabilities of fatigue failures and associated core damage frequencies at a 40-year and 60-year plant life for a sample of components from five PWR and two BWR plants. These calculations were made possible by the development of an enhanced version of the pc-PRAISE probabilistic fracture mechanics code that has the ability to simulate the initiation of fatigue cracks followed by the linking of these cracks. Results of interim calculations subject to review are presented. Components with the highest probabilities of failure can have predicted frequencies of through-wall cracks in the order of about 5×10⁻² per year. The corresponding maximum contributions to core damage frequencies are in the order of 10⁻⁶ per year. Components with the very high failure rates show essentially no increase in calculated core damage frequency from 40 to 60 years.     

Progress in Metal-Supported Axial-Injection Plasma Sprayed Solid Oxide Fuel Cells Using Nanostructured NiO-Y0.15Zr0.85O1.925 Dry Powder Anode Feedstock

A composite NiO-Y_0.15Zr_0.85O_1.925 (YSZ) agglomerated feedstock having nanoscale NiO and YSZ primary particles was used to fabricate anodes having sub-micrometer structure. These anodes were incorporated into two different metal-supported SOFC architectures, which differ in the order of electrode deposition. The composition of the composite Ni-YSZ anodes is controllable by selection of the agglomerate size fraction and standoff distance, while the porosity is controllable by selection of agglomerate size fraction and addition of a sacrificial pore-forming material. A bi-layer anode was fabricated having a total porosity of 33% for the diffusion layer and 23% porosity for the functional layer. A power density of 630 mW/cm² was obtained at 750 °C in humidified H₂ with cells having the bi-layer anode deposited on the metal support. Cells having the cathode deposited on the metal support showed poor performance due to a significant number of vertical cracks through the electrolyte, allowing excessive gas cross-over between the anode and the cathode compartments.     

Deposition of Composite LSCF-SDC and SSC-SDC Cathodes by Axial-Injection Plasma Spraying

The performance of solid oxide fuel cell cathodes can be improved by increasing the number of electrochemical reaction sites, by controlling microstructures, or by using composite materials that consist of an ionic conductor and a mixed ionic and electronic conductor. LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3???) and SSC (Sm_0.5Sr_0.5CoO₃) cathodes were manufactured by axial-injection atmospheric plasma spraying, and composite cathodes were fabricated by mixing SDC (Ce_0.8Sm_0.2O_1.9) into the feedstock powders. The plasma power was varied by changing the proportion of nitrogen in the plasma gas. The microstructures of cathodes produced with different plasma powers were characterized by scanning electron microscopy and gas permeation measurements. The deposition efficiencies of these cathodes were calculated based on the mass of the sprayed cathode. Particle surface temperatures were measured in-flight to enhance understanding of the relationship between spray parameters, microstructure, and deposition efficiency.