[en] Thermochemical quantities for the formation of Li₂SnO₃(s) have been determined by the third-law treatment on the basis of the reported partial vapor pressures of Li(g), O₂(g), LiO(g), Li₂O(g), and SnO(g) in equilibrium with Li₂SnO₃(s). The enthalpy, Gibbs energy and entropy of formation from the elements are Δ_fH₂₉₈ (Li₂SnO₃,s)=-(1322±13) kJ mol^-1, Δ_fG₂₉₈ (Li₂SnO₃,s)=-(1225±13) kJ mol^-1 and Δ_fS₂₉₈ (Li₂SnO₃,s)=-(326±62) J K^-1mol^-1, respectively. A value for the enthalpy of formation from the constituent oxides Li₂O(s) and SnO₂(s) has also been obtained: Δ_foxH₂₉₈ (Li₂SnO₃,s)=-(143±13) kJ mol^-1. In the Li₂O-SnO₂ system, the thermochemical stability of Li₂SnO₃(s) is probably better than that of Li₈SnO₆(s). Comparison of these results was also made with those of other lithium-containing complex oxides. (orig.)

[en] Aerogels hold 15 titles in the Guinness World Records, i.e. more than any other material. Sometimes aerogels are called “frozen smoke” and derived from aluminum, chromium, tin oxide or carbon in the process of supercritical drying. The composition of aerogels is 99.8% air, which makes it translucent. Aerogels demonstrate properties that make them the most extraordinary insulating materials known. If you have a shield made of aerogels, it will protect you from fire, as well as it will save you from cold. Using this material an insulated and worm dome could be built on the Moon. Aerogels have an incredible surface area of internal fractal structures, i.e. an aerogels cube with an edge of one inch has an internal area equivalent to a football field. The article deals with the concept of aerogels, the most common aerogels, and fields of their application. (paper)

[en] We investigated the gas sensing characteristics of graphene nanosheet (NS)-loaded SnO₂ nanofibers (NFs) that were synthesized by a low-cost facile electrospinning process. The sensing performance was characterized as a function of the graphene content with various gases such as C₆H₆, C₇H₈, CO, CO₂, and H₂S. The loading of graphene NSs significantly improved the gas sensing performances of SnO₂ NFs. The optimal amount of graphene NSs was found to be 0.5 wt%. We proposed a sensing mechanism for the enhanced sensing performance based on the chemical sensitization of graphene NSs and the charge transfer through the heterointerfaces between graphene NSs and SnO₂ nanograins. The results show that graphene NS-loaded SnO₂ NFs are a promising sensing material system that can detect hazardous gaseous species. (paper)

[en] Graphene oxide (GO) has been of particular interest because it provides unique properties due to its high surface area, chemical functionality and ease of mass production. GO is produced by chemical exfoliation of graphite and is decorated with oxygen-containing groups such as phenol hydroxyl, epoxide groups and ionizable carboxylic acid groups. Due to the presence of those functional groups, GO can be utilized as a novel platform for hybrid nanocomposites in chemical synthetic approaches. In this work, GO-SnO₂ nanocomposites have been prepared through the spontaneous formation of molecular hybrids. When SnO₂ precursor solution and GO suspension were simply mixed, Sn²⁺ was spontaneously formed into SnO₂ nanoparticles upon the deoxygenation of GO. Through further chemical reduction by adding hydrazine, reduced GO-SnO₂ hybrid was finally created. Our investigation for the electrocapacitive properties of hybrid electrode showed the enhanced performance (389 F/g), compared with rGO-only electrode (241 F/g). Our approach offers a scalable, robust synthetic route to prepare graphene-based nanocomposites for supercapacitor electrode via spontaneous hybridization

No abstract available

[en] The work described in this thesis is concerned with enhancing the etch rate of fluorine doped tin oxide (SnO₂:F) under Ar/Cl₂ and Ar reactive ion etching conditions. The main project, involved analysing the silylation process for various silylation times, temperatures, and concentrations as a function of the photoresist etch rate in an argon plasma environment. This analysis led to the utilisation of an optimum silylation process (8 minutes at 50 deg. C 15 % Hexamethylcyclotrisilazane, HMCTS) that was found to enhance the resistance of the photoresist to etching by a factor of 12 in the 100% argon and by a factor of 1.8 in the argon chlorine case. The effect of silylation on the etch rate of the photoresist and tin oxide in an 90% Ar/10% Cl₂ plasma environment was investigated. It was found that the etch rate of the photoresist decreased whilst at the same time the etch rate of the tin oxide increased. In the 90% Ar/10% Cl₂ case it was observed that silylation enhanced the tin oxide etch rate by 25% for a 150 W plasma exposure compared to the non silylated case and by ∼ 10% compared to the non silylated case at 250 W and 350 W. A study on the etching of SnO₂:F, the transparent conductive electrode for flat panel displays, using an argon plasma was carried out. Four point probe (FPP) and talystep measurements have been used to monitor changes in the resistivity and the etch rate respectively over a range of etch times and powers (up to 15.5 minutes and 100 - 250W). XPS experiments have been performed in order to analyse the composition of the surface layers whilst optical emission spectroscopy (OES) enabled analysis of the species present in the plasma. The XPS results show a transition from Sn(IV) to Sn(II) and subsequently to metallic Sn. OES of argon plasmas under various pump down regimes have shown the presence of hydrogen in certain conditions and this appears to affect the subsequent modification of the SnO₂:F. In addition a Kelvin probe was used to measure the work function of SnO₂:F, enabling the chemical and physical changes at the surface to be monitored. Essential to this analysis was the calibration of the reference brass probe of the Kelvin probe, which led to establishment of a work function value for brass of 4.53 ± 0.06eV. Once established, utilising this work function value for brass was found to give a work function value for SnO₂:F of 4.73 ± 0.05 eV. The work function of SnO₂:F was then examined during argon etching in the presence of impurities for various etch times and powers. From the data recorded, it was found that the work function of SnO₂:F decreased immediately upon etching, progressing towards that of metallic tin (Sn^o) with increasing etch time and power. The observed decrease in the work function of SnO₂:F was ascribed to a combination of hydrogen adsorption at the surface creating a dipole layer and chemical etching of the constituent tin oxide atoms by reduction reactions producing a Sn excess. The presence of hydrogen in the short pump down (spd) but not in the lpd case indicated that hydrogen was the main species responsible for the change in the work function and resistivity and thus the effects of trace hydrogen impurities are postulated to be of significance in enhancing the etch rate of SnO₂:F. (author)

[en] In the quantitative determination of the tin oxide by Moessbauer effect, the results are dependent on sample granulation, sample composition, calibration etc. In this paper is presented the dependence of the resonance absorbtion on sample granulation and composition, the importance of the calibration curve. The measurements were performed with a AME-20 Moessbauer spectrometer and a Moessbauer analyser of tin oxide. (author)

[en] The process under this invention for making a solution of gallium 68 from germanium 68 involves taking up the germanium 68 on particles of tin dioxide and then eluting the gallium 68 produced by radioactive decay of the germanium 68 taken up on these particles by means of a hydrochloric acid solution. The germanium is advantageously taken up on these tin dioxide particles by causing a solution of hydrochloric acid comprising some germanium 68 to circulate in a column filled with these tin dioxide particles. The hydrochloric acid solution used for taking up the germanium 68 on the tin dioxide particles has a hydrochloric acid concentration of between 0.5 and 4 N. The hydrochloric acid solution employed for extracting the gallium 68 by elution of these particles has a hydrochloric acid concentration of between 1 N and 2 N. Advantageously, the hydrochloric acid solutions employed to take up the germanium 68 and to extract the gallium 68 have the identical hydrochloric acid concentration and preferably one of around 1 N. The process has the particular advantage of leading to the production of a gallium 68 solution in ionic form, which can be used directly for labelling pharmaceutical compositions, for example for labelling microspheres of human albumin serum or for preparing gallium 68 citrate or pyrophosphate

[en] Highlights: • Performances of p-AP redox cycling using different reductants on gold surface are compared. • Background current decreases in order of hydrazine, Na₂SO₃, NaBH₄, NADH, cysteamine, and TCEP. • Chemical reaction rate with QI increases in order of NADH, TCEP, and cysteamine. • NADH, TCEP and cysteamine are suitable for p-AP redox cycling on gold electrode. -- Abstract: p-Aminophenol (p-AP) redox cycling using chemical reductants is one strategy for developing sensitive electrochemical sensors. However, most of the reported reductants are only used on indium-tin oxide (ITO) electrodes but not gold electrodes due to the high background current caused by the oxidation reaction of the reductants on the highly electrocatalytic gold electrodes. Therefore, new strategies and/or reductants are in demand for expanding the application of p-AP redox cycling on gold electrodes. In this work, we compared the performances of several reductants in p-AP redox cycling on self-assembled monolayers (SAMs)-modified gold electrodes. Among the tested reagents, nicotinamide adenine dinucleotide (NADH), tris(2-carboxyethyl)phosphine (TCEP) and cysteamine were demonstrated to be suitable for p-AP redox cycling on the alkanethiol-modified gold electrodes because of their low background current. The rate of chemical reaction between reductants and p-quinone imine (QI, the electrochemically oxidized product of p-AP) increases in the order of NADH < TCEP < cysteamine. The system benefits from the low background current, fast chemical reaction and amenability and sensitivity of the sensor with TCEP or cysteamine as the reductant; these performance enhancements were demonstrated by the detection of microRNA. A detection limit of 2 pmol L⁻¹ was achieved. We believe that our work will be valuable for the development of electrochemical sensors using p-AP redox cycling on gold electrodes

[en] Heat capacities of (Zr_1-ySn_y)O_0.17 and (Zr_1-ySn_y)O_0.28 (y=0-0.07) having α''-ZrO_∼1/6 and α''-ZrO_x type crystal structures, respectively, were measured from 325 to 905 K by using an adiabatic scanning calorimeter. Two kinds of heat capacity anomalies were observed for all samples. The anomaly at lower temperatures is attributed to a nonequilibrium phenomenon. Another anomaly at higher temperatures is assigned to an order-disorder rearrangement of oxygen atoms. The transition temperature, transition enthalpy and entropy changes due to the order-disorder transition decreased with increasing tin content, indicating that arrangement of oxygen atoms in the lower temperature phase may be partially disordered by substituting tin for zirconium. The entropy change due to the order-disorder transition for (Zr_1-ySn_y)O_0.17 and (Zr_1-ySn_y)O_0.28 solid solutions is compared with the theoretical value. The solubility limits of (Zr_1-ySn_y)O_0.17 and (Zr_1-ySn_y)O_0.28 were determined from the variation of lattice constants, transition temperature, transition enthalpy and entropy changes against tin content. (orig.)