In situ size sorting in CVD synthesis of Si microspheres

[EN] Silicon microspheres produced in gas-phase by hot-wall CVD offer unique quality in terms of sphericity, surface smoothness, and size. However, the spheres produced are polydisperse in size, which typically range from 0.5 mu m to 5 mu m. In this work we show through experiments and calculations that thermophoretic forces arising from strong temperature gradients inside the reactor volume effectively sort the particles in size along the reactor. These temperature gradients are shown to be produced by a convective gas flow. The results prove that it is possible to select the particle size by collecting them in a particular reactor region, opening new possibilities towards the production by CVD of size-controlled high-quality silicon microspheres.The authors acknowledge financial support from the following projects: ENE2013-49984-EXP, MAT2012-35040, MAT2015-69669-P and ESP2014-54256-C4-2-R of the Spanish Ministry of Economy and Competitiveness (MINECO), and PROMETEOII/2014/026 of the Regional Valencian Government.Garín Escrivá, M.; Fenollosa Esteve, R.; Kowalski, L. (2016). In situ size sorting in CVD synthesis of Si microspheres. Scientific Reports. 6:1-10. https://doi.org/10.1038/srep38719S110

Correlation of publication frequency of newspaper articles with environment and public health issues in fire-prone peatland regions of Riau in Sumatra, Indonesia

Forest fires in peatlands emit pollutants to the atmosphere, affecting public health. Though air quality data and epidemiology information are helpful in the management of the environment and public health, they are not always available. We aimed to reveal the utility of newspaper articles for estimating the public health concerns posed by air pollution. Using the database of a local newspaper, Riau Pos, in Riau Province of Sumatra, Indonesia, we have studied spatiotemporal correlations between publication frequency of newspaper articles mentioning search terms relevant to health issues and Fire Radiation Power (FRP) of peatland fires. FRP from one of the NASA satellite databases has been used as an index of air pollution caused by peatland fires. Visibility data for airport operation were also used as an index of particulate matter concentrations. The study regions are primarily the fire-prone Riau Province and nearby areas in the central area of Sumatra, Indonesia, from 2009 to 2018. Newspaper articles related to public health are found to be associated with FRP and visibility, or regional air pollution

Carbocations generated under stable conditions by ionization of matrix-Isolated radicals: the allyl and benzyl cations

Carbocations are crucial intermediates in many chemical reactions; hence, considerable effort has gone into investigating their structures and properties, for example, in superacids, in salts, or in the gas phase. However, studies of the vibrational structure of carbocations are not abundant, because their infrared spectra are difficult to obtain in superacids or salts (where furthermore the cations may be perturbed by counterions), and the generation of gas-phase carbocations in discharges usually produces several species. We have applied the technique of ionizing neutral compounds by X-irradiation of cryogenic Ar matrices to radicals embedded in such matrices, thus producing closed-shell cations that can be investigated leisurely, and in the absence of counterions or other perturbing effects, by various forms of spectroscopy. This Article describes the first set of results that were obtained by this approach, the IR spectra of the allyl and the benzyl cation. We use the information obtained in this way, together with previously obtained data, to assess the changes in chemical bonding between the allyl and benzyl radicals and cations, respectively