SmCoO3钙钛矿氧化物的高压高温合成及其物性

采用高压高温方法合成钙钛矿型SmCoO₃氧化物, 利用XRD,Raman,电导率和热膨胀测试对样品的结构及性能进行表征. 实验结果表明, 在2.75~4.20 GPa, 1 061 ℃附近, Co₂O₃和 Sm₂O₃发生固相反应形成SmCoO₃, 但反应不完全. 单相SmCoO₃较好的合成条件为3.90 GPa和1 061 ℃左右. 室温Raman谱观察到单相样品中只有SmCoO₃正交相的特征峰. SmCoO₃样品在327 ℃以下为绝缘体, 在327 ℃以上电导率随温度升高而增加. 热膨胀系数在100~800 ℃呈线性变化.      

SmCo5型中熵、高熵金属间化合物的结构与磁性

以SmCo₅为原型,设计了3种中熵金属间化合物(Sm_1/3Ce_1/3Pr_1/3)Co₅、(Sm_1/3Ce_1/3Nd_1/3)Co₅、(Sm_1/3Pr_1/3Nd_1/3)Co₅和1种高熵金属间化合物(Sm_1/4Ce_1/4Pr_1/4Nd_1/4)Co₅,并采用原子半径差和混合焓预测了形成单相结构的可能性. 应用真空电弧熔炼技术成功制备了4种金属间化合物. 采用X射线衍射仪(XRD)、能谱仪(EDS) 和振动样品磁强计(VSM) 表征了样品的物相、成分和磁学性能. 结果表明:4种化合物均为单相,具有六方CaCu₅结构,空间群为P6/mmm,稀土原子占据1a位置;稀土位置上的原子浓度为等原子比;化合物的室温磁化行为遵循Langevin模型,磁化强度依赖于化合物的成分;磁价模型计算证实了化合物(Sm_1/3Ce_1/3Pr_1/3)Co₅、(Sm_1/3Ce_1/3Nd_1/3)Co₅和(Sm_1/4Ce_1/4Pr_1/4Nd_1/4)Co₅中的Ce为+4价,对磁矩没有贡献.     

BaCe0.75Y0.25O3-δ中温电解质的制备及单电池性能

采用溶胶-凝胶法制备掺Y³⁺的BaCeO₃电解质BaCe_0.75Y_0.25O_3-δ. 通过TG\|DTA和烧结曲线测试表明, 样品在1 080 ℃附近开始烧结; XRD谱分析表明, 空气中1 450 ℃烧结10 h的样品已成单相, 为正交钙钛矿结构; 单电池H₂(wet),Ag｜BCY1450｜Ag,Air(dry)测试结果表明, 基于BCY1450电解质的单电池在中温范围具有较高的开路电压.     

金属有机框架衍生的Co3O4/SnO2复合材料制备及其光催化性能

金属有机框架(metal-organic framework,MOF)材料ZIF-67衍生Co₃O₄十二面体纳米块在室温下与SnO₂复合,制备出立方体Co₃O₄/SnO₂复合光催化剂.煅烧后形成的Co₃O₄/SnO₂材料禁带宽度明显降低,荧光淬灭明显,说明Co₃O₄的加入拓展了SnO₂的光响应范围至可见光甚至红外光区域,同时促进了光催化反应过程中光生载流子的分离.以罗丹明B(Rhodamine B,Rh B)为目标反应物,在可见光下考察了MOF衍生的Co₃O₄/SnO₂的光催化降解活性,发现Co₃O₄/SnO₂在60 min内可以降解89.6%的Rh B,分别是纯SnO₂和纯...     

Electrical conductivity optimization of the Na3AlF6-Al2O3-Sm2O3 molten salts system for Al-Sm intermediate binary alloy production

Metal Sm has been widely used in making Al-Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al-Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant (CVCC) technique was used to measure the conductivity for the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ electrolysis medium in the temperature range from 905 to 1055℃. The temperature (t) and the addition of Al₂O₃ (W(Al₂O₃)), Sm₂O₃ (W(Sm₂O₃)), and a combination of Al₂O₃ and Sm₂O₃ into the basic fluoride system were examined with respect to their effects on the conductivity (κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature (t) and decreases with the addition of Al₂O₃ or Sm₂O₃ or both. We concluded that the optimal operation conditions for Al-Sm intermediate alloy production in the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ system are W(Al₂O₃) + W(Sm₂O₃)=3wt%, W(Al₂O₃):W(Sm₂O₃)=7:3, and a temperature of 965 to 995℃, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.     

异质结g-C3N4/Co3O4复合材料的制备及其丙酮气敏特性研究

为了提升p型半导体金属氧化物Co₃O₄的气敏特性,采用两步法将金属有机骨架衍生的十二面体中空Co₃O₄颗粒与二维石墨相氮化碳(g-C₃N₄)复合制备异质结g-C₃N₄/Co₃O₄复合材料,用于丙酮气体的检测。通过探究该复合物材料的微观结构组成与气敏特性间的构效关系,揭示其气敏机制。结果表明,当g-C₃N₄负载量为0.04 g时获得的g-C₃N₄/Co₃O₄在操作温度为200℃时,对50 mg/L丙酮气体的响应值为140。该复合物对丙酮的检测限为0.7 mg/L,并表现出良好的稳定性和选择性。g-C₃N₄/Co₃O₄复合材料气敏性能的改善源于复合材料比表面...     

外尔半金属Co3Sn2S2薄膜的制备和电磁性质研究

外尔半金属Co₃Sn₂S₂是一种新型的拓扑量子材料，具有独特的拓扑能带结构，被认为是一种非常有潜力的自旋电子材料，而制备电子器件的重要一步是该材料的薄膜化.采用磁控溅射方法分别在Si O₂(300 nm)/Si(100)和Al₂O₃(0001)衬底上生长Co₃Sn₂S₂薄膜.X射线衍射(XRD,X-ray Diffraction)显示Co₃Sn₂S₂薄膜的结构随厚度而变化.在不同衬底上，Co₃Sn₂S₂薄膜的生长情况也不同，较薄的Co₃Sn₂S₂ (<200 nm)适合生长在Al₂O₃(0001)衬底上，而较厚的Co₃Sn     

Light-driven photothermocatalytic performance of the Pt/Co3O4 catalyst for toluene oxidation

Light-driven photothermocatalytic oxidation is a promising method for the elimination of volatile organic compounds(VOCs). The Co₃O₄, 0.46 Pt/Co₃O₄ and 0.97 Pt/Co₃O₄ catalysts were fabricated via the simple molten salt and incipient wetness impregnation method. Compared with Co₃O₄ and 0.46 Pt/Co₃O₄ , the 0.97 Pt/Co₃O₄ catalyst showed higher photothermocatalytic perf...     

复合氧化物Co3O4/Bi2O3对甲苯的光催化作用

采用微乳法制备复合氧化物Co₃O₄/Bi₂O₃纳米粒子， 用TG-DTA， XRD， XPS和FT-IR对其表征， 以甲苯为气相有机污染物研究Co₃O₄/Bi₂O₃的光催化活性. 结果表明， 微乳法制备的Co₃O₄/Bi₂O₃粒子光催化活性优于纯氧化铋； 活性的提高程度与n(Co) ∶n(Bi)有关， 其最佳配比为0.02 ∶1； 光催化活性随焙烧温度升高而增大, 750 ℃焙烧的样品催化活性最好.     

PbZr0.52Ti0.48O3的高压合成

研究使用2种原料进行PbZr_0.52Ti_0.48O₃的高压合成. 实验结果表明, 以PbO,ZrO₂和TiO₂(1:0.52∶0.48)为原料, 在1.5 GPa和3.6 GPa压力, 880~1 061 ℃条件下主要形成PbTiO₃, ZrO₂和Pb三相混合物, 仅在880 ℃附近有少量锆钛酸铅(PZT)相生成. 以Zr_0.52Ti_0.48O₂为B位先驱体, 与PbO混合后进行高压高温合成, 在1.5 GPa, 710~812 ℃条件下形成PbZr_0.52Ti_0.48O₃相, 未发现PbTiO3相. 对高压高温（1.5 GPa, 812 ℃）合成的PbZr_0.52Ti_0.48O₃样品进行变温拉曼测量, 在245 ℃时, 未发生结构相变; 在420 ℃时, 拉曼谱只有177.5,257.7,517 cm^-13个峰, 其结构由铁电相转变为立方顺电相, 因此高压合成的PbZr_0.52Ti_0.48O₃居里温度在420 ℃以下.      

Y掺杂BaZrO3质子导体的常压和高压合成及表征

利用固相反应法和高压高温法研究BaZr_1-xYxO₃(x=0,0.05,0.10,0.15,0.20)的合成. XRD和Raman谱结果表明, 在常压和1 300 ℃进行固相反应不能得到纯立方钙钛矿相BaZr_1-xYxO₃. 对上述样品进行高压（3.6 GPa）再处理, 低掺杂量样品（x=0,0.05）在500 ℃时得到较纯的立方钙钛矿相, 表明增加压力可促进固相反应; 在高掺杂量样品（x≥0.1）中出现少量BaCO₃和m-ZrO₂相, 表明增加压力不利于固相反应. 高压合成样品的晶格常数和晶胞体积均小于常压合成的样品. 保持压力不变, 当温度为1 000 ℃时, 各样品均出现明显的BaO杂相. 表明在500 ℃时, 高压处理可提高BaZr_1-xYxO_{3相似文献}   

Layered La-Ba-Cu mixed oxides with perovskite structure as catalyst for NO reduction by CO

The mixed oxides, including LaBa₂Cu₃O₇, LaBaCu₂O₅, La₄BaCu₅O₁₂ with perovskite structure, were prepared. The catalysts were characterized by means of chemical analysis, XRD, H₂-TPR. It was found that their structures were layered ABO₃ perovskite structure and they were the active catalysts for the NO reduction by CO. The existance of Cu³⁺ is an important factor to give the catalysts a high activity for the NO reduction by CO.     

Synthesis and luminescence properties of Eu3+, Sm3+ doped (YxGd1-x)2O3:Si4+, Mg2+ long-lasting phosphor

A novel red long-lasting phosphor, (Y_1−x Gd _x )₂O₃:Eu³⁺, Sm³⁺, Si⁴⁺, Mg²⁺, was synthesized by the co-precipitation method using oxalate precipitation as the precursor. X-ray diffraction (XRD), scanning electronic microscopy (SEM), integrated thermal analyzer (TG), and photoluminescence spectra (PL) as well as the ST-900PM weak light photometer were used to study the synthesis conditions, morphology, luminescence properties, and the decay time of the phosphor. The XRD results show that the products synthesized at 1400°C for 4 h have good crystallization without any detectable impurity phases. Based on the PL spectra, the optimal conditions are as the following. The molar ratios of Y³⁺ to Gd³⁺ and Eu³⁺ to Sm³⁺ are 2:8 and 3:1, respectively, and the contents of Mg²⁺ and SiO₂ are 5mol% and 3mol%, respectively. The decay time monitored by the ST-900PM weak light photometer is 7200 s, increasing 44% and 100%, respectively, compared with the Eu³⁺ and Sm³⁺ single-doped phosphors. The results indicate that the energy transfer is from Sm³⁺ to Eu³⁺ ion, and Sm³⁺ is a good sensitizer to Eu³⁺.     

Multi-color long-lasting phosphorescence of rare earth ions in CdSiO<Subscript>3</Subscript> matrix

A series of rare earth ions doped CdSiO3:RE^3 (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,Er, Tin, Yb, Lu) multi-color long-lasting phosphorescence phosphors are prepared by the conventional hightemperature solid-state method. The results of XRD measurement indicate that the products fired under 1050~C for 3h have a good crystallization without any detectable amount of impurity phase. Rare earth ions doped CdSiO3 phosphors possess excellent Inmiuescence properties. When rare earth ions such as Y^3 , La^3 , Gd^3 , Lu^3 , Ce^3 , Nd^3 , Ho^3 , Er^3 ,Tm^3 and Yb^3 are introduced into the CdSiO3 host, one broadband centered at about 420 nm resulting from traps can be observed. In the case of other earth ions such as Pr^3 ,Sm^3 , Eu^3 , Tb^3 and Dy^3 , their characteristic line emitting as well as the -420 nm broadband luminescence can be obtained. The mixture of their characteristic line emitting with the -420 nm broadband Inminescence results in various afterglow color.     

Synthesis and luminescence properties of Ca2SiO4-based red phosphors with Sm3+ doping for white LEDs

Sm³⁺-activated Ca₂SiO₄ red phosphors were prepared by the conventional high-temperature solid-state reaction method, and the effects of sodium (Na⁺) and samarium (Sm³⁺) ions doping concentrations on their crystal structure and luminescent properties were investigated by X-ray diffraction (XRD) and fluorescent spectrofluorometer. XRD patterns demonstrate that a well-crystalline structure forms in the phosphors when they are treated by calcination at 1200°C for 4 h, and the excitation spectra exhibit good absorption in the range between 350 and 420 nm. Under the irradiation of 405 nm near-ultraviolet (NUV) light, the spectra of the phosphors show a main emission peak at 601 nm attributed to the ⁴G_5/2??⁶H_7/2 transition of Sm³⁺ ions, and its intensity is greatly influenced by the concentrations of Sm³⁺ and Na₂CO₃. When the concentrations of Sm³⁺ ions and Na₂CO₃ are 2mol% and 6mol%, respectively, the optimal emission intensity can be obtained. From strong absorption in the near ultraviolet zone, the Na_0.06Sm_0.02Ca_1.92SiO₄ phosphor is a promising red-emitting phosphor for white light emitting diodes (W-LEDs).     

Soft chemical synthesis and luminescence properties of red long-lasting phosphors Y2O2S:Sm3+

Sm³⁺-activated Y₂O₂S red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y₂O₂S:Sm³⁺, Ti⁴⁺, Mg²⁺ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy (SEM) results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y₂O₂S:Sm³⁺ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G_5/2 →6H_5/2, 4G_5/2 →6H_7/2, 4G_5/2 →6H_9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.     

Two distinct roles of Al2Sm and Al11Sm3 phases on the corrosion behavior of the magnesium alloy Mg-5Sm-xAl

The roles of Al₁₁Sm₃ and Al₂Sm phases on microstructure evolution, mechanical properties and corrosion behavior of the Mg-5Sm-xAl system was investigated. The results showed that adding Al to Mg–5Sm binary alloy brought two Al–Sm phases, Al₁₁Sm₃ and Al₂Sm, which had two distinct roles regarding the microstructure evolution, mechanical properties and corrosion behavior of the Mg-Sm-Al alloy. Al₁₁Sm₃ produced a strong galvanic couple with the Mg matrix, and significantly accelerated the corrosion. The Al₂Sm particles promoted heterogeneous nucleation and refined the grains, which increased the tensile strength and ductility. Both types of Al–Sm particles provided strengthening effect for the alloy. With higher Al contents, Al₂Sm formed an Al oxide protective surface layer and increased corrosion resistance.     

Magnetism in Mn and Co doped ZnO bulk samples

Bulk samples with nominal composition Zn0.95Co0.05O and Zn0.92Co0.05Mn0.03O were fabricated by a solid-state reaction method at 600℃.X-ray diffraction experiment showed that the peaks of secondary phase Co3O4 with a cubic structure were visible in both samples,besides the main peaks of wurtzite structure as ZnO.Magnetization measurement indicated that doping Co alone can induce ferromag- netism in ZnO itself,while the introduction of Mn significantly enhances ferromagnetism.However, both samples showed different magnetic behavior at temperatures below 50 K.It was also noted that ferromagnetic coupling interaction was weakened due to the presence of antiferromagnetic Co3O4.