Synthesis and electrical field-assisted sintering behaviour of yttria-stabilized tetragonal ZrO<Subscript>2</Subscript> nanopowders by polyacrylamide gel method

The tetragonal ZrO₂ nanopowders stabilized with 3 mol% Y₂O₃ (3YSZ) were synthesized using a polyacrylamide gel method. The mean particle size of the 3YSZ nanopowders was found to decrease with increasing molecular ratio of monomer to the precursor salt. The 3YSZ nanopowders with mean particle size of 12 nm can be densified in 1 h at 800^°C, by the application of a d.c. electrical field. Under a constant d.c. electrical field, the current density through the specimen of 3YSZ rose rapidly when the temperature increased to a certain value. In the sintering process, the current density was restricted when the sharp increase occurred. By limiting current density to different values for one hour, it was found that current density was the most important factor in electrical field-assisted sintering process. The grain size of 3YSZ bulk increased with the enhanced current density. The stable stage of electrical field-assisted sintering process can be explained by Joule heating. Corresponding real temperature of specimens is estimated by applying black body radiation theory.     

Facile synthesis of Au/ZnO nanoparticles and their enhanced photocatalytic activity for hydroxylation of benzene

Au/ZnO nanocomposites have been prepared by a simple chemical method. For the first time, the nanocomposites were directly used as photocatalysts for hydroxylation of aromatic hydrocarbons under UV and visible light irradiation. The results show that the as-prepared photocatalysts display high photocatalytic activity for UV and visible catalytic hydroxylation of benzene. Without the assistance of any solvent or additive, high selectivity and high conversion efficiency were still obtained. Different photocatalytic mechanisms were proposed depending on whether excitation happens on ZnO semiconductor or on the surface plasmon band of Au. The former is Au nanoparticles act as electron buffer due to irradiation by UV light and ZnO nanoparticles as reactive sites for hydroxylation of benzene, the latter is that Au nanoparticles act as light harvesters and inject electrons into ZnO conduction band and as photocatalytic sites under visible light irradiation.     

GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized by citric acid assisted high-energy ball milling

Layered LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by a citric acid assisted solid-state method. The structure and electrochemical properties of the LiNi_1/3Co_1/3Mn_1/3O₂ materials were investigated. XRD analysis indicated the as-synthesized LiNi_1/3Co_1/3Mn_1/3O₂ was with the layered α-NaFeO₂ structure. The discharge capacity was about 154 m·Ahg^???1 at 0·1 °C rate in the range of 2·0–4·5 V. The kinetics of the LiNi_1/3Co_1/3Mn_1/3O₂ materials was investigated by the galvanostatic intermittent titration technique (GITT) method. The lithium ion diffusion coefficient of the LiNi_1/3Co_1/3Mn_1/3O₂ was determined in the range of 10^???8??? 10^???9 cm²· s^???1 as a function of voltage of 3·7?4·5 V.     

Ca3Y2(Si3O9)2:Tb3+绿色荧光粉的光谱特性

采用高温固相法制备了Ca₃Y₂(Si₃O₉)₂: Tb³⁺绿色荧光粉,研究了材料的光学性能。X 射线衍射(XRD)结果显示,掺杂少量的Tb³⁺,并未影响Ca₃Y₂(Si₃O₉)₂材料 的晶相结构。Ca₃Y₂(Si₃O₉)₂:Tb³⁺ 荧光粉的激发光谱由较强的4f^75d1宽带吸收(200～300 nm )和较弱的4f-4f电子跃迁吸收 (300～500 nm)构成,主激发峰位于236nm。取波长分别为236、376和482nm的光 作为激发源时,发现样品的主发射峰均位于544 nm,对应Tb³⁺的⁵D 4→⁷F₅跃迁发射。以236nm 紫外光作为激发源,监测544nm主发射峰,随Tb³⁺浓度 的增大,Ca₃Y₂(Si ₃O₉)₂:Tb³⁺的荧光寿命逐渐减小,但在实验范围内并未出现浓度猝灭现象。     

氨基改性MIL-101(Cr)用于CH4/CO2吸附分离的研究

采用浸渍法合成氨基改性金属有机骨架材料MIL-101(Cr),并用XRD、N2吸附和脱附、FT-IR和TG等表征手段考察材料的结构和性能,测试氨基改性MIL-101(Cr)吸附剂在101.3kPa、25℃下的CO2、CH4吸附量。结果表明,氨基改性后的MIL-101(Cr)与CO2作用力显著增强,提高了CO2吸附量和CO2/CH4分离性能。 PEI/MIL-101(Cr)质量比为70的MIL-101-PEI-70吸附剂的CO2吸附量由50.55cm3/g增加到89.43cm3/g,提升76%,而CH4吸附量由10.62cm3/g下降为5.91cm3/g,降低44%,用理想吸附溶液理论预测其CH4/CO2吸附选择性由11增加到255。吸附CO2后的吸附剂可在80℃、真空下再生,脱附条件温和。     

多组分气体吸附平衡预测的探究

为解决由纯组分吸附平衡拟合结果预测多组分气体吸附平衡的问题,在纯组分模型构建时考虑吸附剂表面的不均一性提出了新的双位点吸附模型（Langmuir-Freundlich-Langmuir）,将其吸附行为假设为两类不同吸附位共同作用的结果。在进行双组分的预测时考虑了两类位点的不同排布而导致的两种边界情况,对于每个体系的二元组分吸附平衡的预测都能够很好的满足其中的一种边界情况,三组分气体预测取得良好效果。另外从纯组分模型选取、多组分平衡预测的方程构建方面探讨了影响多组分预测精度的几个因素。     

钢基阳极氧化膜的制备与表征

目的在碳钢表面制备阳极氧化膜,探讨阳极氧化膜的成分组成。方法采用恒电流阳极氧化法在含0.1 mol/dm~3 NH_4F和0.5 mol/dm~3 H_2O的乙二醇电解液中,于45#钢表面制备阳极氧化膜。通过SEM、EDS、XPS、Raman、IR、动电位极化测试等技术手段表征所制备的阳极氧化膜。结果所获阳极氧化膜外观为黄色。电流密度为1 A/dm~2时,氧化膜局部区域出现彩虹色;电流密度为1.5 A/dm~2时,氧化膜颜色较均匀。随着氧化时间的增加,氧化膜颜色变深。阳极氧化膜表面具有特征图案。EDS分析发现,阳极氧化膜中存在Fe、O、C。XPS分析进一步表明,阳极氧化膜中还含有F元素。Fe2p XPS谱的各项数据均与α-Fe_2O_3的较为吻合。拉曼分析表明,电流密度为1.5 A/dm2的阳极氧化膜的拉曼光谱的峰的数量多于电流密度为1 A/dm~2的。所有氧化膜的拉曼光谱均在1400 cm~(-1)附近有峰出现,此峰对应于α-Fe_2O_3。700 cm~(-1)处的峰对应于FeOOH。红外光谱分析表明,所有阳极氧化膜的红外光谱波形一致,在700~400 cm~(-1)之间出现振动,540、514、482 cm~(-1)附近的吸收峰归属于Fe_2O_3的振动带,604、672 cm~(-1)的吸收峰归属于FeOOH。极化测试表明,经阳极氧化处理后,自腐蚀电位上升,自腐蚀电流密度降低。结论碳钢能够在乙二醇体系电解液中生成黄色阳极氧化膜。电流密度和氧化时间对膜的颜色有影响。膜表面具有特征图案。阳极氧化膜主要含Fe、O、F等元素。Fe元素以Fe(Ⅲ)的化学态形式存在于阳极氧化膜中。阳极氧化膜中氧化物主要为α-Fe_2O_3,FeOOH也存在其中。阳极氧化处理后的试样的耐蚀性较处理前有所提升。