Cu-Sn binary metal particle generation by spray pyrolysis

<p>Cu-Sn binary particles were generated via spray pyrolysis from metal salt precursors with ethylene glycol as the co-solvent and reducing agent. The morphology, crystallinity, and elemental distribution of particles were tunable by changing the reaction temperature, residence time, and quench gas flow rate. Hollow porous particles were fabricated with a higher Sn concentration on the particle surface when the furnace set point was 500°C, while solid particles with a lower surface Sn concentration were generated when the furnace set point was 1000°C. Particles with spherical morphologies were obtained at long residence time conditions (4.5 s). Cu-Sn binary particles with irregular structures (e.g., pores on the particle surface, fragmented spherical particles, and lamellar fragments) were formed at short residence time conditions (0.92 s). A possible spray pyrolysis mechanism was proposed that incorporates chemical reaction steps and structural progression. By this mechanism, the metal salts are believed to sequentially undergo hydrolysis to metal hydroxides, decomposition to metal oxides, reduction to metals, and finally diffusion of Sn into the Cu matrix to generate the Cu-Sn solid solution.</p> <p>Copyright © 2017 American Association for Aerosol Research</p

Conductive One- and Two-Dimensional Structures Fabricated Using Oxidation-Resistant Cu–Sn Particles

Cu–Sn powders are promising alternatives to Ag and Au in applications including printed electronics because of their low cost and high oxidation resistance. Further development requires knowledge of the conductivity of their corresponding one- and two-dimensional structures. Herein, CuSn_<i>y</i> (<i>y</i> = atom ratio of Sn/Cu) wires and films were produced by direct printing. In situ measurements of structural resistivities with variation of the temperature from 2 to 400 K in oxygen-free conditions revealed that CuSn_0.1 wires have resistivities comparable to those of Cu wires. Furthermore, CuSn_0.1 films exhibited significantly lower resistivity increases after being heated at 573 K in ambient air, compared with Cu films

Copper–zinc particles with zinc-enriched surfaces generated via spray pyrolysis

<p>Copper is an inexpensive replacement for silver in electronic applications such as solar cell metallization, electromagnetic interference packaging, and printable electronics. However, copper has a characteristically low reduction potential under ambient conditions, favoring formation of non-conducting copper oxides. Here, a spray pyrolysis method of producing oxidation resistant copper particles with surfaces rich in zinc, without need for post-fabrication modifications is described. The effects of precursor and reactor parameters on the particle surface composition with respect to the bulk composition are explored. At reactor temperature conditions of 1000 °C with a precursor containing 90 at% copper–10 at% zinc, the formation of desired morphologies was achieved, smooth dense particles with surfaces enriched in zinc. Increasing the concentration of zinc in the precursor did not improve enrichment, and instead led to the formation of a zinc diamine chloride [Zn(NH₃)₂Cl₂] byproduct.</p> <p>© 2018 American Association for Aerosol Research</p

Biological Templates for Antireflective Current Collectors for Photoelectrochemical Cell Applications

Three-dimensional (3D) structures such as nanowires, nanotubes, and nanorods have the potential to increase surface area, reduce light reflection, and shorten charge carrier transport distances. The assembly of such structures thus holds great promise for enhancing photoelectrochemical solar cell efficiency. In this study, genetically modified <i>Tobacco mosaic virus</i> (TMV1cys) was used to form self-assembling 3D nanorod current collectors and low light-reflecting surfaces. Photoactive CuO was subsequently deposited by sputtering onto these patterned nanostructures, and these structures were examined for photocurrent activity. CuO thicknesses of 520 nm on TMV1cys patterned current collectors produced the highest photocurrent density of 3.15 mA/cm² yet reported for a similar sized CuO system. Reflectivity measurements are in agreement with full-wave electromagnetic simulations, which can be used as a design tool for optimizing the CuO system. Thus the combined effects of reducing charge carrier transport distance, increasing surface area, and the suppression of light reflection make these virus-templated surfaces ideal for photoelectrochemical applications

Expected ozone benefits of reducing nitrogen oxide (NO_x) emissions from coal-fired electricity generating units in the eastern United States

<p>On hot summer days in the eastern United States, electricity demand rises, mainly because of increased use of air conditioning. Power plants must provide this additional energy, emitting additional pollutants when meteorological conditions are primed for poor air quality. To evaluate the impact of summertime NO_x emissions from coal-fired electricity generating units (EGUs) on surface ozone formation, we performed a series of sensitivity modeling forecast scenarios utilizing EPA 2018 version 6.0 emissions (2011 base year) and CMAQ v5.0.2. Coal-fired EGU NO_x emissions were adjusted to match the lowest NO_x rates observed during the ozone seasons (April 1–October 31) of 2005–2012 (Scenario A), where ozone decreased by 3–4 ppb in affected areas. When compared to the highest emissions rates during the same time period (Scenario B), ozone increased ∼4–7 ppb. NO_x emission rates adjusted to match the observed rates from 2011 (Scenario C) increased ozone by ∼4–5 ppb. Finally in Scenario D, the impact of additional NO_x reductions was determined by assuming installation of selective catalytic reduction (SCR) controls on all units lacking postcombustion controls; this decreased ozone by an additional 2–4 ppb relative to Scenario A. Following the announcement of a stricter 8-hour ozone standard, this analysis outlines a strategy that would help bring coastal areas in the mid-Atlantic region closer to attainment, and would also provide profound benefits for upwind states where most of the regional EGU NO_x originates, even if additional capital investments are not made (Scenario A).</p> <p><i>Implications</i>: With the 8-hr maximum ozone National Ambient Air Quality Standard (NAAQS) decreasing from 75 to 70 ppb, modeling results indicate that use of postcombustion controls on coal-fired power plants in 2018 could help keep regions in attainment. By operating already existing nitrogen oxide (NO_x) removal devices to their full potential, ozone could be significantly curtailed, achieving ozone reductions by up to 5 ppb in areas around the source of emission and immediately downwind. Ozone improvements are also significant (1–2 ppb) for areas affected by cross-state transport, especially Mid-Atlantic coast regions that had struggled to meet the 75 ppb standard.</p