Synthesis of nanorods and mixed shaped copper ferrite and their applications as liquefied petroleum gas sensor

Present paper reports the preparation and characterization of nanorods and mixed shaped (nanospheres/nanocubes) copper ferrite for liquefied petroleum gas (LPG) sensing at room temperature. The structural, surface morphological, optical, electrical as well as LPG sensing properties of the copper ferrite were investigated. Single phase spinel structure of the CuFe₂O₄ was confirmed by XRD data. The minimum crystallite size of copper ferrite was found 25 nm. The stoichiometry was confirmed by elemental analysis and it revealed the presence of oxygen, iron and copper elements with 21.91, 12.39 and 65.70 atomic weight percentages in copper ferrite nanorods. The band gap of copper ferrite was 3.09 and 2.81 eV, respectively for nanospheres/nanocubes and nanorods. The sensing films were made by using screen printing technology and investigated with the exposure of LPG. Our results show that the mixed shaped CuFe₂O₄ had an improved sensing performance over that of the CuFe₂O₄ nanorods, of which a possible sensing mechanism related to a surface reaction process was discussed. Sensor based on mixed shaped copper ferrite is 92% reproducible after one month. The role of PEG in the synthesis for obtaining nanospheres/nanocubes has also been demonstrated.     

Isotopic Assessment of Sources and Processes Affecting Sulfate and Nitrate in Surface Water and Groundwater of Luxembourg

Abstract

Surface water and deep and shallow groundwater samples were taken from selected parts of the Grand-Duchy of Luxembourg to determine the isotopic composition of nitrate and sulfate, in order to identify sources and/or processes affecting these solutes. Deep groundwater had sulfate concentrations between 20 and 40mg/L, δ³⁴S_sulfate values between ?3.0 and ?20.0‰, and δ¹⁸O_sulfate values between +1.5 and +5.0‰ nitrate was characterized by concentrations varying between <0.5 and 10mg/L, δ¹⁵N_nitrate values of ～?0.5‰, and δ¹⁸O_nitrate values ～+3.0‰. In the shallow groundwater, sulfate concentrations ranged from 25 to 30mg/L, δ³⁴S_sulfate values from ?20.0 to +4.5‰, and δ¹⁸O_sulfate values from ～+0.5 to +4.5‰ nitrate concentrations varied between ～10 and 75mg/L, δ¹⁵N_nitrate values between +2.5 and +10.0‰, and δ¹⁸O_nitrate values between +1.0 and +3.0‰. In surface water, sulfate concentrations ranged from 10 to 210mg/L, δ³⁴S_sulfate values varied between ?9.3 and +10.9‰, and δ¹⁸O_sulfate values between +3.0 and +10.7‰ were observed. Nitrate concentrations ranged from 10 to 40mg/L, δ¹⁵N_nitrate values from +6.5 to +12.0‰, and δ¹⁸O_nitrate values from ?0.4 to +4.0‰. Based on these data, three sulfate sources were identified controlling the riverine sulfate load. These are soil sulfate, dissolution of evaporites, and oxidation of reduced S minerals in the bedrock. Both groundwater types were predominantly influenced by sulfate from the two latter lithogenic S sources. The deep groundwater and a couple shallow groundwater samples had nitrate derived mainly from soil nitrification. All other sampling sites were influenced by nitrate originating from sewage and/or manure. A decrease in nitrate concentration observed along one of the rivers was attributed to denitrification. It appears that sulfate within Luxembourg's aquatic ecosystem is mainly of lithogenic origin, whereas nitrate is often derived from anthropogenic activities.     

Star-Configurations in ℙn and the Weak-Lefschetz Property

We find that some union of two star-configurations in ?² has generic Hilbert function. Applying the result, we prove that some Artinian quotients of a coordinate ring of a star-configuration in ?ⁿ satisfy the weak-Lefschetz property. More precisely, let 𝕏 and 𝕐 be star-configurations in ?² of type (2, s) and (2, s + 1) defined by forms F₁,…, F_s, and G₁,…, G_s, L, respectively, with deg(F_i) = deg(G_i) ≤2 for i = 1,…, s and s ≥ 3. If L is a general linear form in R = 𝕜[x₀, x₁, x₂], then R/(I_𝕏 + I_𝕐) has the weak-Lefschetz property with a Lefschetz element L, which extends the result of [21 Shin, Y. S. (2012). Star-configurations in ?² having generic Hilbert functions and the weak-Lefschetz property. Comm. in Algebra 40:2226–2242.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]].     

Characterization and properties of carbon/PMR-15 composites

PMR (polymerization of monomer reactants) -15 was formulated to use as a matrix resin for high performance carbon fiber-reinforced composite materials. Monomers for the PMR-15 were characterized using Fourier transform infrared spectroscopy. Molecular weight change during cure was investigated using gel permeation chromatography. Thermal analysis was carried out to investigate glass transition and thermal degradation. Cure behavior of a glass/PMR-15 prepreg was investigated using a dynamic mechanical analyzer. Flexural strength of a cured carbon/PMR-15 composite was affected by cure temperature and pressure. The morphology of the cured carbon/PMR-15 was affected by cure conditions as well as by the surface conditions of the carbon fibers. A scanning electron micrograph of the composite made of untreated carbon fibers showed a void-trapped morphology.     

痕量汞的光谱分析

本文介绍采用发射光谱法,将粉末样品直接倒入石墨室电极中,以直流电弧为光源,靠电极的热传导使试样缓慢升温,充分利用汞的分馏效应,实现汞与基体元素的有效分离,测定下限达到0.01ppm。单次摄谱RSD为9.7%。对影响汞谱线强度的因素,如样品组成,烘样时间,电流强度,上电极形状等进行了对比试验。发现汞的测定不受样品组分的影响。曾用该法进行了上万个地质、土壤、环保等样品的测定,都获得了比较满意的结果。方法快速、简便、经济,适用于生产中大批量分析任务。