Kenneth A. Walz

The Electrochemical Stability of Spinel Electrodes Coated with ZrO2 , Al2 O 3 , and SiO2 from Colloidal Suspensions

Stoichiometric LiMn 2 O 4 and substituted Li 1.05 M 0.05 Mn 1.9 O 4 (M = Al,Ni) spinel electrodes, coated with ZrO 2 , Al 2 O 3 , and SiO 2 from colloidal suspensions, have been evaluated in lithium cells. ZrO 2 -coated Li 1.05 Ni 0.05 Mn 1.9 O 4 electrodes provide the best cycling stability at 50°C. The excellent cycling stability is attributed to a porous network of amphoteric ZrO 2 particles, less than 4 nm in dimension, that protect the spinel surface from acid attack by scavenging HF and H 2 O from the electrolyte, while still allowing access of the electrolyte to the active electrode.

Stabilization of iron(VI) ferrate cathode materials using nanoporous silica coatings

Ferrate salts containing Fe(VI) have received attention as cathode materials in recent years due to their theoretical ability to accept three electrons while being reduced to Fe(III). Unfortunately, ferrate salts are also somewhat unstable, particularly when stored at elevated temperatures or in the presence of an alkaline electrolyte. In this paper, we document the stability of solid barium and potassium ferrate salts under various environmental conditions and report on the use of SiO 2 thin-film coatings to stabilize cathodes composed of solid barium ferrate. The nanoporous coatings are deposited from colloidal silica suspensions using sol-gel techniques. The enhanced stability of coated ferrates is demonstrated, and their discharge performance is characterized relative to uncoated materials. The coating technique employed may be applicable to other nanoparticulate metal oxide chemistries, thus presenting a possible method to modify ferrates and perhaps overcome their stability limitations.

Sensitivity of diesel particulate material emissions and composition to blends of petroleum diesel and biodiesel fuel

A number of investigations have examined the impact of the use of biodiesel on the emissions of carbon dioxide and regulated emissions, but limited information exists on the chemical composition of particulate matter from diesel engines burning biodiesel blends. This study examines the composition of diesel particulate matter (DPM) emissions from a commercial agriculture tractor burning a range of biodiesel blends operating under a load that is controlled by a power take off (PTO) dynamometer. Ultra-low sulfur diesel (ULSD) fuel was blended with soybean and beef tallow based biodiesel to examine fuels containing 0% (B0), 25% (B25), 50% (B50), 75% (B75), and 100% (B100) biodiesel. Samples were then collected using a dilution source sampler to simulate atmospheric dilution. Diluted and aged exhaust was analyzed for particle mass and size distribution, PM2.5 particle mass, PM2.5 organic and elemental carbon, and speciated organic compounds. PM2.5 mass emissions rates for the B25, B50, and B75 soybean oil biodiesel mixtures had 20%–30% lower emissions than the petroleum diesel, but B100 emissions were about 40% higher than the petroleum diesel. The trends in mass emission rates with the increasing biodiesel content can be explained by a significant decrease in elemental carbon (EC) emissions across all blending ranges and increasing organic carbon (OC) emissions with pure biodiesel. Beef tallow biodiesel blends showed similar trends. Nevertheless, it is important to note that the study measurements are based on low dilution rates and the OC emissions changes may be affected by ambient temperature and different dilution conditions spanning micro-environments and atmospheric conditions. The results show that the use of biodiesel fuel for economic or climate change mitigation purposes can lead to reductions in PM emissions and a co-benefit of EC emission reductions. Detailed speciation of the OC emissions were also examined and are presented to understand the sensitivity of OC emissions with respect to biodiesel fuel blends. Copyright 2012 American Association for Aerosol Research

Atmospheric impacts of black carbon emission reductions through the strategic use of biodiesel in California.

The use of biodiesel as a replacement for petroleum-based diesel fuel has gained interest as a strategy for greenhouse gas emission reductions, energy security, and economic advantage. Biodiesel adoption may also reduce particulate elemental carbon (EC) emissions from conventional diesel engines that are not equipped with after-treatment devices. This study examines the impact of biodiesel blends on EC emissions from a commercial off-road diesel engine and simulates the potential public health benefits and climate benefits. EC emissions from the commercial off-road engine decreased by 76% when ultra-low sulfur commercial diesel (ULSD) fuel was replaced by biodiesel. Model calculations predict that reduced EC emissions translate directly into reduced EC concentrations in the atmosphere, but the concentration of secondary particulate matter was not directly affected by this fuel change. Redistribution of secondary particulate matter components to particles emitted from other sources did change the size distribution and therefore deposition rates of those components. Modification of meteorological variables such as water content and temperature influenced secondary particulate matter formation. Simulations with a source-oriented WRF/Chem model (SOWC) for a severe air pollution episode in California that adopted 75% biodiesel blended with ULSD in all non-road diesel engines reduced surface EC concentrations by up to 50% but changed nitrate and total PM2.5 mass concentrations by less than ±5%. These changes in concentrations will have public health benefits but did not significantly affect radiative forcing at the top of the atmosphere. The removal of EC due to the adoption of biodiesel produced larger coatings of secondary particulate matter on other atmospheric particles containing residual EC leading to enhanced absorption associated with those particles. The net effect was a minor change in atmospheric optical properties despite a large change in atmospheric EC concentrations. These results emphasize the importance of considering EC mixing state in climate research.

Teaching-as-research internships: a model for the development of future chemistry faculty and the improvement of teaching in science, technology, engineering, and math

Abstract Over the past decade, the University of Wisconsin-Madison (UW-Madison) and Madison Area Technical College (Madison College) partnered to create an internship pathway for graduate students pursuing careers as future science, technology, engineering and math (STEM) faculty members. Since 2003, 10 doctoral students from the university completed teaching internship appointments with the technical college chemistry department. Interns benefited from a variety of teaching and educational experiences that helped lay the foundations for their future teaching careers. Following completion of their internships, many students secured employment in higher education as new instructors and enthusiastic members of the teaching profession. Intern projects also benefited veteran faculty mentors at Madison College, and the experience provided a rich forum for collaboration that generated curricular and instructional innovations in the classroom. Centered on the three pillars of teaching-as-research, learning community, and learning through diversity, the internship program created at UW-Madison and implemented at Madison College provides a model pathway for preparing future STEM faculty. This approach provides clear benefits not only for the future faculty who are trained, but also for veteran faculty mentors, for the host institution, and for the undergraduate students impacted by the educational innovations. This paper examines the key attributes of this program, with the hope that our experience may be disseminated and replicated to benefit others.