Formation of oxide phases in the system Fe2O3−Gd2O3

The formation of oxide phases in the system (1 -x) Fe₂O₃ +xGd₂O₃ was investigated for 0 x 1. On the basis of XRD measurements the distribution of oxide phases, -Fe₂O₃, Gd₃Fe₅O₁₂, GdFeO₃ and Gd₂O₃ was determined, as a function ofx. No solid solutions were observed with certainty even at the very ends of the concentration range. This was also confirmed by⁵⁷Fe Mössbauer spectroscopy. New accurate crystallographic data for Gd₃Fe₅O₁₂ are given. The formation of oxide phases in the system Fe₂O₃- Gd₂O₃ is compared with the data for analogous system Fe₂O₃-Eu₂O₃.     

Mechanism of ZrTiO4 Synthesis by Mechanochemical Processing of TiO2 and ZrO2

High-energy ball milling initiates a solid-state reaction in an equimolar mixture of TiO₂ and ZrO₂. The first stage of ball milling induced the transformation of anatase TiO₂ to high-pressure phase TiO₂ (II), isostructural with ZrTiO₄. The formation of solid solutions monoclinic ZrO₂/TiO₂ and TiO₂ (II)/ZrO₂ was observed in the intermediate stage. Afterward, a nanosized ZrTiO₄ phase was formed in the milled product from the TiO₂ (II)/ZrO₂ solid solution. The sintering of the milled product at a temperature <1100°C was examined in situ by Raman spectroscopy. The full solid-state reaction toward ZrTiO₄ ceramic is completed at a temperature considerably lower than reported in the literature.     

Chemical and structural properties of the system Fe2O3-Nd2O3

Chemical and structural properties of the system (1–x)Fe₂O₃ + xNd₂O₃, 0x1, were investigated using X-ray diffraction, ⁵⁷Fe Mössbauer spectroscopy and Fourier transform-infrared (FT-IR) spectroscopy. The samples were prepared by the chemical coprecipitation and thermal treatment of Fe(OH)₃/Nd(OH)₃ coprecipitates. X-ray diffraction showed the presence of oxide phases -Fe₂O₃ + NdFeO₃ in the Fe₂O₃-rich region, and the oxide phases Nd₂O₃ + NdFeO₃ in the Nd₂O₃-rich region. ⁵⁷Fe Mössbauer spectra were characterized with one sextet of spectral lines at room temperature. Mathematical evaluation of the Mössbauer spectra showed distinct regularities in the changes of Mössbauer parameters, thus indicating the presence of two subspectra with very similar spectral behaviour. High sensitivity of the Nd₂O₃ phase to the moisture and atmosphere CO₂ was demonstrated by FT-IR spectroscopy.     

Structural properties of precipitates formed by hydrolysis of Fe3+ ions in Fe2(SO4)3 solutions

The structural properties of the solid phase, formed by the hydrolysis of Fe³⁺ ions in Fe₂(SO₄)₃ solutions at 90 or 120 °C, were investigated using X-ray diffraction,⁵⁷Fe Mössbauer spectroscopy, Fourier transform-infrared spectroscopy (FT—IR) and transmission electron microscopy. The concentration regions of Fe₂(SO₄)₃ were determined for the precipitation of goethite, -FeOOH, or hydronium jarosite, H₃OFe₃(OH)₆(SO₄)₂ as a single phase. Superparamagnetic behaviour of -FeOOH particles was observed. Hydrolysis of Fe³⁺ ions in 0.1 M Fe₂(SO₄)₃ solutions at 120 °C produced H₃OFe₃(OH)₆(SO₄)₂ and basic sulphate, Fe₄(OH)₁₀SO₄. The interpretation of⁵⁷Fe Mössbauer and FT—IR spectra is given.     

Formation of oxide phases in the system Fe2O3-NiO

Mixed metal oxides in the system Fe₂O₃-NiO were prepared by coprecipitation of Fe(OH)₃/Ni(OH)₂ and the thermal treatment of hydroxide coprecipitates up to 800 or 1100°C. X-ray diffraction showed the presence of -Fe₂O₃, NiO and NiFe₂O₄ in samples prepared at 800°C. The oxide phases -Fe₂O₃, NiO, NiFe₂O₄ and a phase with structure similar to NiFe₂O₄ were found in samples prepared at 1100°C. Fourier transform-infrared spectra of oxide phases formed in the system Fe₂O₃-NiO are discussed. Two very strong infrared bands at 553 and 475 cm^–1, a weak intensity infrared band at 383 cm^–1 and two shoulders at 626 and 441 cm^–1 were observed for -Fe₂O₃ prepared at 1100°C. NiFe₂O₄, prepared at the same temperature, showed two broad and very strong infrared bands at 602 and 411 cm^–1, while NiO showed a broad infrared band at 466 cm^–1. Fourier transform infrared spectroscopic results were in agreement with X-ray diffraction.     

Influence of synthesis procedure on the morphology of bismuth oxide particles

A modified sol-gel procedure, based on the esterification reaction, was used to prepare the Bi₂O₃ precursor, which was then heated to 400 or 500 °C. β-Bi₂O₃ obtained at 400 °C showed well-shaped plate-like particles. The mixture β-Bi₂O₃/α-Bi₂O₃, obtained by prolonged heating at 400 °C, yielded pseudospherical particles having about 100 nm in size and much larger particles, as found by FE SEM. α-Bi₂O₃ obtained at 500 °C consisted of particles of varying shapes and sizes. Vitrification of α-Bi₂O₃ was also observed. XRD showed a small fraction of unidentified phase(s) in these samples. Different microstructures were obtained when the precipitation from aqueous Bi(NO₃)₃ solution with tetramethylammonium hydroxide at pH ∼ 14 was used. The precipitation at pH ∼ 3.5 yielded cloverleaf-like particles of good uniformity, which were assigned to BiOOH (isomorphous with (La_0.26Bi_0.24)Bi_0.5OOH. It was found that these particles were made up of much smaller primary BiOOH particles.     

雷达维修三维交互式电子技术手册设计研究

针对雷达维修信息种类多、可阅读性差的问题,提出了利用可嵌入式平台将3D技术融入在手册设计的方法,并阐述了3D-IETM设计流程、功能实现及模块组成,开发了三维交互式电子技术手册设计软件。     

A novel route for the synthesis of nanosize particles of metallic palladium

A novel route for the synthesis of metallic palladium consisting of nanosize particles has been reported. The synthesis is based on (a) the addition of tetramethylammonium hydroxide (TMAH) to the aqueous solution of PdCl₂, and (b) autoclaving of this precipitation system at 160 °C. The distribution of the nanosize particles of metallic palladium has its mean value at about 18 nm. The mechanism of the metallic palladium formation is briefly discussed.     

On the Characterisation of Silver Species for SCR of NO x with Ethanol

Reducing of nitrogen oxides (NO _x ) in a lean exhaust gases has become one of the most important environmental concerns. Among the different active phases studied for NO _x reduction reaction, silver-based catalysts supported over alumina show good performances using, as reducing agents, either hydrocarbons or oxygenated compounds. Nevertheless, a good understanding of the mechanism reaction has not been reached yet. This comprehension requires a better characterisation of the silver-based catalysts system. In our study, Ag/Al₂O₃ catalysts showed high efficiency in NO _x reduction using ethanol as reducing agent. The conversion plots, in steady state conditions for the different samples Ag/Al₂O₃ (0.8–3.5% Ag wt), show a great dependance of the activity with the metal loading. The optimal silver loading has been established around 2 wt.% Increasing the silver loading, the temperature of maximal NO _x conversion shifted toward the lower temperatures. According to the literature, a reduced and an oxide phase of silver have been observed by UV–Vis spectroscopy. The ratio between the two phases is changing with the silver loading. However, temperature programmed reduction (TPR) measurements reveal the presence of two types of oxide phases. TPR reveal the coexistence of a silver oxide phase (Ag₂O), according to a production of water in the course of the reaction, and a non-oxygenated phase attributed to isolated Ag⁺ cation. Thus, an original way using TPR measurements has been developed to differentiate the various oxidized phases. The aim of this characterisation is to correlate the catalyst’s activity with the observed silver phases, in order to understand the nature of phase active for NO _x reduction at low temperatures.     

Improved structured light 3D scanner with application to anthropometric parameter estimation

Obtaining accurate anthropometric body segment parameters in a fast and reliable manner is an essential step in biomechanical analysis of human motion. With advance of computer vision, and reduction in cost of electronic components, building a customized computer-vision based measurement device becomes possible. In the paper a novel structured light pattern for 3D structured light scanner is proposed. During development, accuracy and robustness of the proposed system were tested on artificial objects with known surface configurations, after which measurements were performed on human subjects. Simultaneous measurements with standard structured light pattern were achieved and obtained results compared. Volumetric parameters of both artificial object and human body segment obtained by 3D scanning were compared to the immersion method and were found to be in a good agreement and were used for segment mass estimation. Obtained results are presented and analyzed, and conclusions about system performance with possible improvements are discussed.