Preparation of Ce1?xFexO2 solid solution and its catalytic performance for oxidation of CH4 and CO

A series of Ce_1−x Fe _x O₂ (0 < x ≤ 0.5) catalysts were prepared by the co-precipitation method, and their catalytic performances were investigated for the total oxidation of CO and CH₄ as model reactions. X-ray diffraction (XRD) and Raman spectroscopy results show that Ce_1−x Fe _x O_2−δ solid solutions are formed with x ≤ 0.2. Ce_0.9Fe_0.1O₂ solid solution presents superior catalytic performance for CH₄ and CO oxidation, while Ce_1−x Fe _x O₂ with x > 0.2 shows less active for CO and CH₄ oxidation. The results of H₂-temperature programmed reduction (H₂-TPR), CH₄-temperature programmed surface reaction (CH₄-TPSR) and CO-TPSR reveal that, the surface oxygen of catalyst is relevant to CO oxidation, which was promoted by the oxygen vacancies formed in Ce–Fe–O solid solution, while the easier lattice oxygen migration property and the favorable reducibility of the catalysts is responsible for the promoted catalytic performance for CH₄ oxidation.     

Preparation and characterization of Y2O3–Sm2O3 co-doped ceria electrolyte for IT-SOFCs

Y₂O₃–Sm₂O₃ co-doped ceria (YSDC) powder was synthesized by a gel-casting method using Ce(NO₃)₃·6H₂O, Sm₂O₃ and Y₂O₃ as raw materials. Phase structure of the synthesized powders was characterized by X-Ray diffraction analysis. Sinterability of the powders was investigated by testing the relative density and observing the microstructure of the sintered YSDC samples. Electrical conductivity of the sintered YSDC samples was measured using impedance spectra method. Single solid oxide fuel cells based on the YSDC electrolyte were also assembled and tested. The results showed that YSDC powders with single-phase fluorite structure can be obtained by calcining the dried gelcasts at temperature above 800 °C. Average particle size of the YSDC powder is 50–100 nm. Relative density of more than 95% of the theoretical can be achieved by sintering the YSDC compacts at temperature above 1400 °C. The sintered YSDC sample has an ionic conductivity of 4.74 × 10⁻² S cm⁻¹ at 800 °C in air. Single fuel cells based on the YSDC electrolyte with 50 μm in thickness were tested using humidified hydrogen as fuel and air as oxidant, and maximum power densities of about 190 and 112 mW cm⁻² were achieved at 700 and 600 °C, respectively.     

Optical properties and structure of R2O–Ga2O3–SiO2 and RO–Ga2O3–SiO2 glasses

Refractive index and molar refraction of Li₂O–, Na₂O–, CaO–, and BaO–Ga₂O₃–SiO₂ glasses have been used to test the validity of a structural model of silicate glasses containing Ga₂O₃ glasses. Ga₂O₃ enters these types of glass in a similar manner as Al₂O₃. It is assumed that, for (SiO₂/Ga₂O₃) >1 and (Ga₂O₃/R₂O) ≤1, Ga₂O₃ associates primarily with modifier oxides to form GaO₄ units. The rest of modifier oxide forms silicate units with non-bridging oxygen ions. Silicate structural units have the same factors as found for binary alkali- and alkaline earth silicate glasses. Differences between experimental and model values suggest another structure for (Ga₂O₃/SiO₂) ≥1.     

Pd/γ-Al2O3复合膜的制备工艺研究

本文研究了采用Sol-Gel法制备用于H     

Structural and dielectric properties of Li2O–ZnO–BaO–B2O3–CuO glasses

Glass samples of the system (15Li₂O–30ZnO–10BaO–(45 − x)B₂O₃–xCuO where x = 0, 5, 10 and 15 mol%) were prepared by using the melt quenching technique. A number of studies, viz. density, differential thermal analysis, FT-IR spectra, a.c. conductivity and dielectric properties (constant εφ, loss tan δ, a.c. conductivity, σ_ac, over a wide range of frequency and temperature) of these glasses were carried out as a function of copper ion concentration. The analysis of the results indicate that the density increases while molar volume decreases with increasing of copper content indicates structural changes of the glass matrix. The glass transition temperature, T _g, and crystallization temperature, T _c, increase with the variation of concentration of CuO referred to the growth in the network connectivity in this concentration range, while glass-forming ability parameter (T _c − T _g) decreases with increasing CuO content, indicates an increasing concentration of copper ions that take part in the network-modifying positions. The FT-IR spectra evidenced that the main structural units are BO₃, BO₄, and ZnO₄. The structural changes observed by varying the CuO content in these glasses and evidenced by FTIR investigation suggest that the CuO plays a network modifier role in these glasses while ZnO plays the role of network formers. The dielectric constant decreased with increase in temperature and CuO content. The variation of a.c. conductivity with the concentration of CuO passes through a maximum at 5 mol%. In the high temperature region, the a.c. conduction seems to be connected with the mixed conduction viz., electronic conduction and ionic conduction.     

CaO/γ-Al2O3吸附剂吸附CO2的性能研究

采用浸渍法制备了以γ-Al2O3为载体的CaO/γ-Al2O3吸附剂,并在自制吸附剂评价装置上,研究了不同CaO负载量对CaO/γ-Al2O3吸附剂吸附性能的影响。利用XRD及BET对CaO/γ-Al2O3吸附剂的物相及结构进行了表征。实验结果表明,CaO/γ-Al2O3吸附剂对CO2有较好的吸附性能,并且CaO/γ-Al2O3吸附剂的比表面积、孔容随着CaO负载量的增大而减小。当CaO的负载量为25%(wt,下同)时,CaO/γ-Al2O3吸附剂的静吸附容量达到最大值,4.95mol/kg。     

Densification and dielectric properties of SrO–Al2O3–B2O3 ceramic bodies

The influence of SrO (0·0–5·0 wt%) on partial substitution of alpha alumina (corundum) in ceramic composition (95 Al₂O₃–5B₂O₃) have been studied by co-precipitated process and their phase composition, microstructure, microchemistry and microwave dielectric properties were studied. Phase composition was revealed by XRD, while microstructure and microchemistry were investigated by electron-probe microanalysis (EPMA). The dielectric properties by means of dielectric constant (ε _r ), quality factor (Q × f) and temperature coefficient of resonant frequency (τ _f ) were measured in the microwave frequency region using a network analyser by the resonance method. The addition of B₂O₃ and SrO significantly reduced the sintering temperature of alumina ceramic bodies to 1600 °C with optimum density (∼ 4g/cm³) as compared with pure alumina powders recycled from Al dross (3·55g/cm³ sintered at 1700 °C).     

Uniform α-Fe2O3 nanotubes fabricated for adsorption and photocatalytic oxidation of naphthalene

Uniform α-Fe₂O₃ nanotubes with small aspect ratio were successfully fabricated by a hydrothermal method. In situ Fourier-transform infrared spectroscopy was used to study the mechanistic details of adsorption and photocatalytic oxidation of naphthalene over theα-Fe₂O₃ nanotubes. A possible degradation mechanism of naphthalene was proposed.     

The interaction of oxygen with high loaded Ru/γ-Al2O3 catalyst

The interaction of oxygen with the Ru/γ-Al₂O₃ catalyst comprising metal particle with sizes of 1-16 nm, was examined over a temperature range 20-400 °C. The catalyst loaded with 10.8 wt.% Ru was prepared by incipient wetness from RuCl₃ precursor. The structure of the Cl-containing catalyst and the catalyst after elimination Cl⁻ ions was characterized using H₂ and O₂ chemisorption, O₂ uptake, BET, XRD and TEM. The Cl⁻ ions in the catalyst decreased the H₂ and O₂ chemisorption capacity of Ru and caused large discrepancies between the mean particle size calculated from gas chemisorption and from TEM. Exposure to O₂ at 100-200 °C caused oxidation of small Ru particles, while larger particles were covered with very thin Ru_xO_y skin (undetected by XRD and TEM). The O/Ru ratio increased up to 200 °C implying high affinity of the small Ru particles to oxygen. Oxidation at 250 °C led to the formation of poorly crystalline RuO₂ particles with a mean size of 4 nm, and coverage of large Ru particles with 1.6 nm thick oxide layer. At 300 and 400 °C crystallization of the RuO₂ phase, as well as significant agglomeration of oxide particles was observed. However, even at 400 °C, metallic Ru was detected by XRD, TEM and SAED suggesting that large metal particles were not fully oxidized under the used conditions. Also, the O₂ uptake at 400 °C was lower than expected for oxidation of Ru metal to RuO₂. For the catalyst after elimination Cl ions the O₂ uptake (O/Ru ratio = 1.50) was higher, than for sample with large amount of Cl ions (O/Ru ratio = 1.34), indicating that the presence of Cl inhibits ruthenium oxidation in the Ru/Al₂O₃ catalyst.     

γ-Al2O3多孔膜的制备与性能研究

以无机盐AlCl3·6H2O为初始原料,采用溶胶-凝胶法通过调节pH值控制溶胶体系的稳定性制备出具有耐高温、耐腐蚀性的γ-Al2O3微孔膜,利用差热、BET和SEM对薄膜的组成、结构和表面形貌进行了分析表征.并对溶胶制备过程中的主要影响因素以及膜制备过程中膜性能的各种影响因素进行了深入探讨.     

微波水热合成γ-AlOOH和γ-Al2O3纳米片

以九水合硝酸铝和尿素为原料,聚乙烯吡咯烷酮为表面活性剂,在180℃微波水热条件下反应30min,制备了γ-AlOOH片状结构产物。此前驱物经600℃热分解2h,得到γ-Al2O3纳米片。采用SEM、TEM、SAED和XRD等方法对样品进行表征,并测试了γ-Al2O3纳米片对刚果红染料的吸附性能。实验结果表明,采用微波水热法可以得到长度约为1μm,厚度为30nm的γ-AlOOH纳米片,该产物经煅烧处理后可以得到微观形貌保持不变的γ-Al2O3纳米片,且片状结构表面存在介孔结构。γ-Al2O3纳米片状结构表现出对废水中刚果红污染物的强吸附性能。     

Electro-codeposition of Al2O3-Y2O3 composite thin film coatings and their high-temperature oxidation resistance on γ-TiAl alloy

In this paper, electro-codeposition based on electrophoretic deposition and electrolytic deposition was developed to prepare Al₂O₃-Y₂O₃ composite thin film coatings on a γ-TiAl based alloy. Scanning electron microscope observations showed that the Al₂O₃-Y₂O₃ composite coatings were very compact and consisted of uniform nano-particles after microwave sintering. Cyclic oxidation at 900 °C indicated that the Al₂O₃-Y₂O₃ composite thin film coatings improved the oxidation and scale spallation resistance of the γ-TiAl alloy significantly. The superior oxidation and spallation resistance of the coatings were attributed to the suppression of outward diffusion of Ti and Al and inward diffusion of O, the promoted selective oxidation of Al in the γ-TiAl alloy, and the improved adhesion of oxide scale induced by the Al₂O₃-Y₂O₃ composite thin film coatings.     

室温离子液体辅助制备中孔γ-Al2O3

液相反应条件下,以薄姆石溶胶为铝源,室温离子液体1-甲基-3-丁基咪唑四氟硼酸盐([BMIM][BF4])存在下制备了晶态结构中孔γ-Al2O3.采用N2物理吸附,X射线衍射,透射电子显微镜,27Al魔角固体核磁共振对所制备的样品进行了结构表征.结果表明:通过调节[BMIM][BF4]的用量,得到了孔道结构呈脚手架状、比表面积较大、平均孔径在12nm左右、孔容在1.0cm3/g以上,孔径分布较宽的介孔氧化铝;[BMIM][BF4]加入能够明显改善氧化铝的孔道结构.     

La2O3/γ-Al2O3复合产物的浸渍-燃烧法制备及表征

采用浸渍-燃烧法制备了La2O3/γ-Al2O3复合产物,原料为La(NO3)3.6H2O(A.R)、一水合柠檬酸和工业级的拟薄水铝石.以六水合硝酸镧和一水合柠檬酸分别为镧源和燃烧剂,柠檬酸与六水硝酸镧的摩尔比为5∶6左右.将拟薄水铝石研磨成粉末并溶于柠檬酸和镧的配合物溶液中,搅拌至凝胶状,110℃干燥2h,再放入马弗炉中焙烧2 h得到产物.采用XRD、BET、XPS进行分析和表征,结果表明La3+的加入提高了γ-Al2O3的热稳定性,随着样品焙烧温度升高,比表面积下降,孔容、孔径变大.随着La3+的量的增加,样品的比表面积增大,孔径尺寸分布变宽.通过控制La3+加入的量以及焙烧温度,可调控多孔γ-Al2O3粉体的比表面积、孔容、孔径大小及孔径分布.     

Effects of copper and Al2O3 particles on characteristics of Cu–Al2O3 composites

High-energy milling was used for production of Cu–Al₂O₃ composites. The inert gas-atomized prealloyed copper powder containing 2 wt.%Al and the mixture of the different sized electrolytic copper powders with 4 wt.% commercial Al₂O₃ powders served as starting materials. Milling of prealloyed copper powders promotes formation of nano-sized Al₂O₃ particles by internal oxidation with oxygen from air. Hot-pressed compacts of composites obtained from 5 and 20 h milled powders were additionally subjected to the high-temperature exposure in argon at 800 °C for 1 and 5 h. Characterization of processed material was performed by optical and scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), microhardness, as well as density and electrical conductivity measurements. Due to nano-sized Al₂O₃ particles microhardness and thermal stability of composite processed from milled prealloyed powders are higher than corresponding properties of composites processed from the milled powder mixtures. The results were discussed in terms of the effects of different size of starting copper powders and Al₂O₃ particles on the structure, strengthening of copper matrix, thermal stability and electrical conductivity of Cu–Al₂O₃ composites.     

TiO2/γ-Al2O3复相脱硝催化剂载体的制备研究

以二氧化钛、氧化铝和高岭土为主要原料,加入适量的添加剂,通过柱塞式挤压成型设备制得大型蜂窝陶瓷。实验结果表明,2号样品即TiO2和Al2O3的质量分数比为0.27时综合性能最佳,浸渍催化剂后催化活性最高到98.08%。另外,实验还确定了多种干燥方式结合的干燥制度以及最佳烧成制度,样品经850℃煅烧后,BJH脱附平均孔径为51.3nm,BET比表面积为53m2/g,BJH脱附累积孔容为0.14cm3/g,该吸脱附等温线属于Ⅳ型等温线,是介孔物质的吸附类型。     

Synthesis of ZnGa2O4 nanowires with β-Ga2O3 templates and its photoluminescence performance

This paper focuses on a new but much simple approach in synthesizing cubic spinel-structure ZnGa₂O₄ nanowires through the reaction of β-Ga₂O₃ nanowires templates and ZnO vapor at high temperature. Characterization has been achieved by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The length of as-synthesized ZnGa₂O₄ nanowires is scaled over 10 μm and the diameter is 80 nm respectively. It has been noticed that the concentration of ZnO vapor plays an important role for synthesizing ZnGa₂O₄ nanowires. And with different concentration of ZnO vapor, the very nanowires could be compounded in the form of β-Ga₂O₃:ZnGa₂O₄, ZnGa₂O₄ and ZnO:ZnGa₂O₄. The corresponding photoluminescence emission bands centered at 460 nm, 405 nm and 381 nm have also been observed.     

Structure and electrical conductivity relaxation studies of Nb2O5-doped B2O3–Bi2O3–LiF glasses

Glasses with composition (70 − x) B₂O₃·15Bi₂O₃·15LiF·xNb₂O₅ with x = 0–1.0 mol% were prepared by conventional glass-melting technique. The molar volume V _m values decrease and the glass transition temperatures T _g increase with increase of Nb₂O₅ content up to 0.2 mol%, which indicates that Nb⁵⁺ ions act as a glass former. Beyond 0.2 mol% Nb₂O₅ the V _m increases and the T _g decreases, which suggests that Nb⁵⁺ ions act as a glass modifier. The FTIR spectra suggest that Nb⁵⁺ ions are incorporated into the glass network as NbO₆ octahedra, substituting BO₄ groups. The temperature dependence of the dc conductivity follows the Greaves variable range hopping model below 454 K, and follows the small polaron hopping model at temperatures >454 K. σ _dc, σ _ac conductivity and dielectric constant (ε) decrease and activation energy for dc conduction ΔE _dc which increases with increasing Nb₂O₅ content up to 0.2 mol%, whereas σ _dc, σ _ac and (ε) increase and ΔE _dc decreases with increasing Nb₂O₅ content beyond 0.2 mol%. The impedance spectroscopy shows a single semicircle or arcs which indicate only the ionic conduction mechanism. The electric modulus formalism indicates that the conductivity relaxation is occurring at different frequencies exhibit temperature-independent dynamical process. The (FWHM) of the normalized modulus increases with increase in Nb₂O₅ content suggesting that the distribution of relaxation times is associated with the charge carriers Li⁺ or F⁻ ions in the glass network.     

Investigation on the phase stability,sintering and thermal conductivity of Sc2O3–Y2O3–ZrO2 for thermal barrier coating application

Rare earth oxides co-doped zirconia have been developed for application in thermal barrier coating systems to promote the performance and durability of gas turbines. 8 mol%Sc₂O₃, 0.6 mol%Y₂O₃–stabilized ZrO₂ (ScYSZ) powder was synthesized by chemical co-precipitation method. The phase stability, sintering resistance and thermo-physical properties of ScYSZ and 8 wt%Y₂O₃ stabilized ZrO₂ (8YSZ) were investigated. The results indicated that both ScYSZ and 8YSZ show single tetragonal phase before heat treatment. After heat treating at 1500 °C for 300 h, ScYSZ exhibits excellent phase stability with 100% metastable tetragonal (t′) phase, whereas the content of monoclinic phase in 8YSZ reached 49.4 mol%. ScYSZ also exhibits higher sintering resistance and lower thermal conductivity than 8YSZ. ScYSZ can be considered to be explored as candidate material for TBC application.     

K2CO3/γ-Al2O3催化玉米油制备生物柴油成分的定性分析

采用等体积浸渍法制备了负载型固体碱催化剂K2CO3/γ-Al2O3,并将其用于催化玉米油与甲醇酯交换反应制备生物柴油。采用气相色谱质谱联用仪对其成分进行了定性分析。通过分析质谱图的分子离子峰和特征离子峰,确定所制备的生物柴油主要由四种脂肪酸甲酯组成,分别为棕榈酸甲酯、亚油酸甲酯、油酸甲酯和硬脂酸甲酯。