Investigation of Solid Precipitate that Prevents Etching of Silicon in a Solution of Ethylenediamine and Pyrocatechol

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The effect of the synthesis conditions on structure and photocatalytic activity of Nb2O5 nanostructures

In this work, niobium pentoxide (Nb2O5) nanoparticles of varying sizes and morphology were synthesized using the controlled precipitation method. Ammonium niobate oxylate hydrate (NH4)H2[NbO(C2O4)3] ? 3H2O was used as a niobium precursor and distilled water or acetic acid was used as solvent. The obtained solids were characterized using Fourier transform infrared and Raman spectroscopies, X-ray diffraction and transmission electron microscopy. The as-synthesized solid precipitate was amorphous, but after heat treatment between 500?C and 600?C, the T-Nb2O5 phase was obtained. The size of the primary particles of the niobium pentoxide was nanometric (<100 nm), with agglomerate size of >500 nm, when water was used as a solvent for synthesis. Considering the nature of the process, a possible reaction mechanism of the precursor with the water and NH4OH was proposed, which explains the formation of the solid within an aqueous solution. Considering one potential use of Nb2O5 synthesized in this work, the photo-degradation action of the particles on the organic molecule methylene blue was tested. The sample synthesized in acetic acid at pH ~9.0 and heat treated at 600?C showed the highest photo-degradation capacity, with a degradation of ~60% of the dye for 60 minutes.

On the differing growth mechanisms of black-smoker and Lost City-type hydrothermal vents

Black smokers and Lost City-type springs are varieties of hydrothermal vents on the ocean floors that emit hot, acidic water and cool, alkaline water, respectively. While both produce precipitation structures as the issuing fluid encounters oceanic water, Lost City-type hydrothermal vents in particular have been implicated in the origin of life on the Earth. We present a parallel-velocity flow model for the radius and flow rate of a cylindrical jet of fluid that forms the template for the growth of a tube precipitated about itself and we compare the solution with previous laboratory experimental results from growth of silicate chemical gardens. We show that when the growth of the solid structure is determined by thermal diffusion, fluid flow is slow at the solid–liquid contact. However, in the case of chemical diffusive transport, the fluid jet effectively drags the liquid in the pores of the solid precipitate. These findings suggest a continuum in the diffusive growth rate of hydrothermal vent structures, where Lost City-type hydrothermal vents favour contact between the vent fluid and the external seawater. We explore the implications for the road to life.

In situ monitoring the viscosity change of an electrolyte in a Li–S battery

Li2S2is not a solid precipitate, but an electrolyte–soluble substance.

Análisis espectroscópico del precipitado formado por la mezcla de hipoclorito de sodio y clorhexidina utilizando resonancia magnética nuclear

The aim of this study was to determine the presence of para-chloroaniline (PCA) obtained by the mixture of 5,25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX), evaluated by nuclear magnetic resonance spectroscopy (NMR-H-1) at 600MHz. Initially a commercial sample of 98% PCA (group 1: GPCA) was analyzed by NMRH-1 combining it with dimethylsulfoxide perdeuterated as solvent, in order to obtain the basal spectra. Ten samples were then prepared by combining equal amounts of 5,25%NaOCl and 2%CHX (group 2:GHC) (PROPORTION 1:1 v/v) by manual stirring. Each sample was then spinned for 10 minutes at 25Cº, in order to eliminate the supernatant and to obtain the precipitate, which was prepared at dry vacuum to finally isolate the solid precipitate. The precipitate was again dissolved in d6-DMSO to perform the NMR.H-1 analysis. Commercial PCA showed a distinctive spectra, with a characteristic double sign at 7.02-7.03 ppm and 6.58-6.59 ppm. Experimental samples lack of this distinctive spectra, instead, they all showed a complex combination of signs, which none correspond to pure PCA.

One-pot room-temperature conversion of cyclohexane to adipic acid by ozone and UV light

Nitric acid oxidation of cyclohexane accounts for ~95% of the worldwide adipic acid production and is also responsible for ~5 to 8% of the annual worldwide anthropogenic emission of the ozone-depleting greenhouse gas nitrous oxide (N2O). Here we report a N2O-free process for adipic acid synthesis. Treatment of neat cyclohexane, cyclohexanol, or cyclohexanone with ozone at room temperature and 1 atmosphere of pressure affords adipic acid as a solid precipitate. Addition of acidic water or exposure to ultraviolet (UV) light irradiation (or a combination of both) dramatically enhances the oxidative conversion of cyclohexane to adipic acid.

Profiling Pvp/Ps Homopolymer Interfaces Using Core-Loss Electron Energy-Loss Spectroscopy

Despite the physical and technological significance of polymer interfaces (1), they have not been extensively studied using techniques based on electron scattering. Spontak et al. (2) used digital analysis of bright-field images to study Os-stained polystyrene-polydiene block copolymer interfaces, but work in this area has been lacking largely because of difficulties with staining or uncertainties in the distribution of stain at the nanometer length scales relevant to interfaces. Studies of polymer interfaces are now largely done by neutron scattering (3) This research explores the application of spatially-resolved electron energyloss spectroscopy to measure compositional widths of polymer-polymer interfaces. These first studies focus on blends of poly(2-vinyl pyridine) (PVP) dispersed in poly(styrene) (PS) to establish the various electron-optical, electron-scattering, and specimen-dependent limitations (4) to resolving such an interfacial width. The uncompatibilized PS/PVP interface should be relatively sharp.Blends of PS (M.W. 190,000) and PVP ( M.W. 200,000) were made using a 5wt% solution of polymer in THF with a PS/PVP ratio of 7/3. The solution was cast into methanol. The resulting solid precipitate was removed and annealed under vacuum at 120°C for 36 hours.

Continuous-Melter Vitrification of Fernald Mixed Wastes: Distribution of Contaminants Between Glass, Scrubber Solutions and Off-Gases

ABSTRACTResults are presented from treatability studies on the vitrification of hazardous and low-level radioactive soils and sludges from the Fernald site. The majority of the contaminants of concern are contained in large volumes of sludges accumulated from uranium and thorium production operations that are presently stored in pits at Fernald. These sludges present particular challenges to the vitrification process in that they contain significant amounts of fluorides (mostly magnesium and calcium). In this study, glass formulations used sludges, soils and a minimum amount of additives resulting in waste loadings as high as 94%. Several of these formulations were evaluated by continuous feeding of slurries into a joule-heated vitrification system. Melter off-gases were treated in a two-stage NaOH scrubbing system. HF acid fumes were neutralized, resulting in the formation of a NaF solid precipitate which is removed from the scrubber and recycled to subsequent melter feeds. Elemental and isotope compositions of the glasses, scrubber solutions, NaF precipitate and off-gases show that greater than 99.7% of uranium and thorium, 95% of Pb, Cd, Ni, Sb, Cr, and Hg were retained in the glass. Fluoride and other gaseous emissions from the scrubber system were below regulatory limits, even before HEPA filtration.