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1.
以反式二氯二胺合铂(trans-PtCl2(NH32)为Pt源,溴化亚铜(CuBr)为Cu源,在油胺(OAm)体系中采用一锅法快速制备得到笼状PtCu3空心结构,同时用XRD,TEM,HRTEM和高角环形暗场扫描透射电子显微技术[HAADF-STEM,high angle annular dark field(HAADF)scanning transmissio nelectron microscopy(STEM)]。对产物的结构及形貌进行动态的,多角度的表征,所得PtCu3空心结构对温度敏感,过高的温度会加快原子的扩散速率,导致空心结构坍塌。  相似文献   

2.
以反式二氯二胺合铂(trans-PtCl2(NH3)2)为Pt源,溴化亚铜(CuBr)为Cu源,在油胺(OAm)体系中采用一锅法快速制备得到笼状PtCu3空心结构,同时用XRD,TEM,HRTEM和高角环形暗场扫描透射电子显微技术【HAADF-STEM,high angle annular dark field(HAADF)scanning transmission electron microscopy(STEM)】。对产物的结构及形貌进行动态的,多角度的表征,所得PtCu3空心结构对温度敏感,过高的温度会加快原子的扩散速率,导致空心结构坍塌。  相似文献   

3.
<正>众所周知,纳米材料的尺寸大小、晶型、形貌构型等结构特征对材料的化学物理性能有重要的影响[1],由于特殊形貌的新材料所具有独特、新颖、高效的化学物理等方面的性质以及在众多领域中的潜在应用[2],特别是3D花状空心纳米结构新物质[3-4],新形貌物质的纳米材料的制备方法和应用特性已经吸引了世界上材料领域的广泛兴趣和关注[5]。目前为止,合成3D纳米结构的方法有自组装法、三维导向连接法以及水热法等,即通过使用有  相似文献   

4.
在微波辐射条件下,对CuO/ZnO/Al2O3催化剂的沉淀母液进行老化,通过XRD、TG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂微观结构的进行表征,探讨了CuO/ZnO/Al2O3催化剂前驱体晶相转变过程中微波辐射的作用。结果表明,微波辐射有利于Cu2+取代Zn5(CO3)2(OH)6中Zn2+的同晶取代反应。微波辐射的老化过程中,首先发生Cu2+取代Zn5(CO3)2(OH)6中Zn2+生成(Cu,Zn)5(CO3)2(OH)6的同晶取代反应,并于1.0 h内基本完成;随着老化时间继续延长,主要进行Zn2+取代Cu2(CO3)(OH)2中Cu2+生成(Cu,Zn)2(CO3)(OH)2的同晶取代反应,同时(Cu,Zn)5(CO3)2(OH)6进一步结晶。与常规老化1 h制备的前驱体相比,微波辐射老化1.0 h制备的前驱体含有较多的(Cu,Zn)5(CO3)2(OH)6物相,有助于增强焙烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用,提高表面铜含量,进而提高CuO/ZnO/Al2O3催化剂在浆态床合成甲醇的催化活性和稳定性,在400 h浆态床合成甲醇评价期间,甲醇时空收率最大达318.9 g.kg-1.h-1,失活率仅为0.11%.d-1。  相似文献   

5.
Raman and FTIR spectra of guanidinium zinc sulphate [C(NH2)3]2Zn(SO4)2 are recorded and the spectral bands assignment is carried out in terms of the fundamental modes of vibration of the guanidinium cations and sulphate anions. The analysis of the spectrum reveals distorted SO42− tetrahedra with distinct S–O bonds. The distortion of the sulphate tetrahedra is attributed to Zn–O–S–O–Zn bridging in the structure as well as hydrogen bonding. The CN3 group is planar which is expressed in the twofold symmetry along the C–N (1) vector. Spectral studies also reveal the presence of hydrogen bonds in the sample. The vibrational frequencies of [C(NH2)3]2 and HC(NH2)3 are computed using Gaussian 03 with HF/6-31G* as basis set.  相似文献   

6.
Microcrystalline samples of Zn(NH3)2Br2 and Ni(NH3)2X2 (X is Cl and Br) have been investigated from 100 to 293 K using X-ray diffraction and IR spectroscopy measurements (range 400–4000 cm) performed with isotopically dilute (5% deuterated) samples. Values of Δν(ND)/ΔT for all compounds hint at the existence of hydrogen bonds. Zn(NH3)2Br2 shows The dynamics of ammonia molecules even at 100 K, and no indications are apparent that dynamic disorder of ammonia molecules takes place in Ni(NH3)2X2 (X is Cl and Br). A comparison between octahedrally coordinated ammoniates [Ni(NH3)6]Br2, Ni(NH3)2Br2 and [Zn(NH3)6]Br2 with tetrahedrally coordinated ones [Zn(NH3)2Br2] leads to the conclusion that the lower coordination number increases the strength of the hydrogen bonds. Because this effect is small, it is not possible to separate the influence of the type of coordinating ions for one coordination number from the influence of the coordination number itself.  相似文献   

7.
SrF2:Eu3+ nanospheres with homogeneous diameter have been synthesized by a microemulsion-mediated hydrothermal method for the first time, in which quaternary microemulsion of CTAB/water/cyclohexane/n-pentanol was used. The possible reaction mechanism and the luminescent properties of SrF2:Eu3+ nanospheres were also investigated in this paper. The morphology and grain sizes of final products were characterized by field emission scanning electron microscopy and transmission electron microscopy, indicating that most of the products were nanospheres with an average diameter of ∼50 nm. Room-temperature emission spectra, recorded under 394-nm excitation, showed that the transition of 5D0 → 7F1 emission be dominating in SrF2:Eu3+ nanospheres. From the dependence of the luminescence intensity on the concentration of Eu3+ ions, the optimal dopant concentration is 2 mol%.  相似文献   

8.
在制备CuO/ZnO/Al2O3催化剂的老化过程中,采用微波辐射老化技术,着重研究了溶剂极性对前躯体物相组成,烧后CuO/ZnO/Al2O3催化剂结构及其在浆态床合成甲醇工艺中催化性能的影响。通过XRD、DTG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂表征表明,沉淀母液在微波辐射条件下进行老化,溶剂的极性对前躯体物相组成及催化剂结构影响显著。随着溶剂极性的增大,Zn2+/Cu2+取代Cu2(CO3)(OH)2/Zn5(CO3)2(OH)6中Cu2+/Zn2+的取代反应增强,使得前躯体中(Cu,Zn)5(CO3)2(OH)6和(Cu,Zn)2(CO3)(OH)2物相的含量增多,结晶度提高,导致烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用增强,且CuO晶粒减小,表面Cu含量增加,催化剂活性和稳定性提高。水溶剂的极性最大,制备的催化剂活性和稳定性最好,甲醇的时空收率(STY)和平均失活率分别为320 mg.g-1.h-1和0.11%.d-1。  相似文献   

9.
The FT IR and FT Raman spectra of Co(en)3Al3P4O16 · 3H2O (compound I) and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O (compound II) are recorded and analysed based on the vibrations of Co(en)33+, Co(NH3)63+, NH4+, Al---O---P, PO3, PO2 and H2O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH2 deformation Fermi resonates with its symmetric stretching vibration. The NH4 ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.  相似文献   

10.
Summary. 2 [Yb2(NH2)2(Pz)4][Yb(NH3)2(Pz)3 PzH], Pz = pyrazolate anion, PzH = pyrazole, C3H4N2 is obtained by the reaction of ytterbium metal with pyrazole in liquid ammonia and subsequent increase of the temperature to 200°C resulting in the formation of colorless single crystals of the compound. The X-ray single crystal analysis reveals that the structure consists of 2 [Yb2(NH2)2(Pz)4] planes with neutral [Yb(NH3)2(Pz)3 PzH] monomeric molecules that are located between the planes and ytterbium is trivalent. This is the first example of a two-dimensional network structure of an organic amine of the rare earth elements that derives from an electride induced synthesis. The product decomposes under release of ammonia outside its sealed reaction vessel, viz. if the NH3 pressure is removed.  相似文献   

11.
2 [Yb2(NH2)2(Pz)4][Yb(NH3)2(Pz)3 PzH], Pz = pyrazolate anion, PzH = pyrazole, C3H4N2 is obtained by the reaction of ytterbium metal with pyrazole in liquid ammonia and subsequent increase of the temperature to 200°C resulting in the formation of colorless single crystals of the compound. The X-ray single crystal analysis reveals that the structure consists of 2 [Yb2(NH2)2(Pz)4] planes with neutral [Yb(NH3)2(Pz)3 PzH] monomeric molecules that are located between the planes and ytterbium is trivalent. This is the first example of a two-dimensional network structure of an organic amine of the rare earth elements that derives from an electride induced synthesis. The product decomposes under release of ammonia outside its sealed reaction vessel, viz. if the NH3 pressure is removed.  相似文献   

12.
Reactions of NH32+ di-cations, observed a few microseconds after formation by electron ionisation of ammonia, have been studied in a double-focusing mass spectrometer using techniques of ion translational energy spectroscopy. Fragmentation reactions occuring under unimolecular conditions correspond to predissociation processes, but lack of knowledge about states of NH32+ precludes any definitive interpretation. A partial tentative interpretation, using arguments by analogy with isoelectronic neutral species, is proposed. Almost all collision-induced fragmentations required electron transfer forming NH3+ as an intermediate step, so the non-dissociative electron transfer processes were also studied. The most unexpected collision-induced fragmentation reaction was that which formed H3+ fragment ions.  相似文献   

13.
Eu3+-doped Gd3PO7 nanospheres with an average diameter of ∼300 nm and a narrow size distribution have been prepared by a facile combustion method and structurally characterized by X-ray diffraction and field emission scanning electron microscopy. The luminescent properties were systemically studied by the measurement of excitation/emission spectra, and emission spectra under different temperatures, as well as by photostability. The strong red-emission intensity peaking at 614 nm originates the 5D07F2 transition and is observed under 254-nm irradiation, indicating that Eu3+ ions in Gd3PO7 mainly occupied non-centrosymmetry sites. The CIE1931 XY chromaticity coordinates of Gd3PO7:Eu3+ nanospheres are (x=0.654, y=0.345) in the red area, which is near the National Television Standard Committee standard chromaticity coordinates for red. Thus, Gd3PO7:Eu3+ nanospheres may be potential red-emitting phosphors for PDP and Xe-based mercury-free lamps.  相似文献   

14.
Phase transitions in MgAl2O4 were examined at 21-27 GPa and 1400-2500 °C using a multianvil apparatus. A mixture of MgO and Al2O3 corundum that are high-pressure dissociation products of MgAl2O4 spinel combines into calcium-ferrite type MgAl2O4 at 26-27 GPa and 1400-2000 °C. At temperature above 2000 °C at pressure below 25.5 GPa, a mixture of Al2O3 corundum and a new phase with Mg2Al2O5 composition is stable. The transition boundary between the two fields has a strongly negative pressure-temperature slope. Structure analysis and Rietveld refinement on the basis of the powder X-ray diffraction profile of the Mg2Al2O5 phase indicated that the phase represented a new structure type with orthorhombic symmetry (Pbam), and the lattice parameters were determined as a=9.3710(6) Å, b=12.1952(6) Å, c=2.7916(2) Å, V=319.03(3) Å3, Z=4. The structure consists of edge-sharing and corner-sharing (Mg, Al)O6 octahedra, and contains chains of edge-sharing octahedra running along the c-axis. A part of Mg atoms are accommodated in six-coordinated trigonal prism sites in tunnels surrounded by the chains of edge-sharing (Mg, Al)O6 octahedra. The structure is related with that of ludwigite (Mg, Fe2+)2(Fe3+, Al)(BO3)O2. The molar volume of the Mg2Al2O5 phase is smaller by 0.18% than sum of molar volumes of 2MgO and Al2O3 corundum. High-pressure dissociation to the mixture of corundum-type phase and the phase with ludwigite-related structure has been found only in MgAl2O4 among various A2+B3+2O4 compounds.  相似文献   

15.
以Fe(NO3)3·9H2O和正硅酸乙酯(TEOS)为原料, 通过溶胶-凝胶法和辅助模板法分别制备了纳米α-Fe2O3和SiO2, 并对所合成样品进行了粉末X射线衍射(XRD)和BET表征. 使用自动电位滴定仪测定了α-Fe2O3/SiO2纳米颗粒混合体系的表面酸碱性质. 研究了在不同pH下α-Fe2O3/SiO2混合体系对Cu2+、Pb2+、Zn2+离子的吸附行为. 基于上述实验数据, 用WinSGW软件计算了α-Fe2O3/SiO2混合体系表面酸碱配位常数, 并得出结论: α-Fe2O3/SiO2混合体系表面反应为单一脱质子反应≡XOH ⇔ ≡XO-+ H+(lg K = -8.19±0.15), 明显区别于同时具有加质子和脱质子反应的α-Fe2O3/SiO2/γ-Al2O3, α-Fe2O3/γ-Al2O3和SiO2/γ-Al2O3等纳米颗粒混合体系. 在此基础上拟合得到α-Fe2O3/SiO2混合体系吸附重金属离子Cu2+、Pb2+、Zn2+的表面络合反应平衡常数分别为:
≡XOH + M2+ ⇔ ≡XOM++ H+ [lg K = -3.1, -3.6, -3.8 (M = Cu, Pb, Zn)].
≡XOH+M2++H2O ⇔≡XOMOH+2H+[lg K = -8.8, -8.0, -10.5 (M = Cu, Pb, Zn)]  相似文献   

16.
Different substitutions, i.e. Sr2+, Ba2+, K+, Nb5+ and V5+, have been performed in the triclinic α-La2W2O9 structure in order to stabilise the high temperature and better ionic conductor cubic β-phase. This approach has been used to try to obtain a new series of ionic conductors with LAMOX-type structure without molybdenum and presumably better redox stability compared to β-La2Mo2O9. Nanocrystalline materials obtained by a freeze-drying precursor method at 600 °C exhibit mainly the β-La2W2O9 structure, however, the triclinic α-form is stabilised as the firing temperature increases and the crystallite size grows. Only high levels of Ba2+ and V5+ substitutions retained the cubic form at room temperature after firing above 1100 °C. However, these phases are metastable above 700 °C, exhibiting an irreversible transformation to the low temperature triclinic α-phase. The synthesis, structure, phase stability, kinetic of phase transformation and electrical conductivity of these materials have been studied in the present report.  相似文献   

17.
以浓盐酸为浸出剂,以NaOH和NH4HCO3为沉淀剂,利用Mn2+在碱性条件下的氧化反应改变离子的沉淀次序进而分步回收的方案,探究了浓盐酸酸浸处理三元正极材料LiNi0.8Co0.05Mn0.15O2的最佳条件。在分步沉淀过程中,Mn2+被氧化为不溶于非还原性酸的MnO(OH)2,并在酸性条件下回收。Ni、Co则在碱性条件下利用NaOH回收,而Li则利用NH4HCO3回收。该方法中Mn的回收率达到85.1%,产品纯度达到98.6%; Li的回收率达到95.0%,产品纯度达到99.3%。由回收材料重新合成的三元正极组装的软包电池的首圈放电比容量达到了175 mAh·g-1,可以以超过99.5%的库仑效率稳定循环50圈。  相似文献   

18.
EPR studies of Gd3+ doped in single crystals of Nd2(SO4)3·(NH4)2SO4·8H2O (hereafter referred to as NASO) at room (RT) and liquid nitrogen (LNT) temperatures exhibit that (1) the metal aquo complex has a tetragonal symmetry with abnormally low magnitudes of crystalline field parameters at RT and (2) NASO undergoes a possible phase transition between RT and LNT.  相似文献   

19.
Tao Lin  Wei Li  Maochu Gong  Yao Yu  Bo Du  Yaoqiang Chen   《Acta Physico》2007,23(12):1851-1856
TiO2,ZrO2-TiO2,andZrO2-TiO2-CeO2 were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH3-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H2-TPR). The results showed that ZrO2-TiO2-CeO2 exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V2O5 and 9% (w)WO3 for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O2, and the results of catalytic activity showed that the catalyst used ZrO2-TiO2-CeO2 as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h−1, and it had the best catalytic activity and showed great potential for practical application.  相似文献   

20.
In ground mixtures of In2O3 and NH4Y, incorporation of In+ cations into the zeolitic phase occurs upon thermal treatment by partial reductive solid-state ion exchange associated with oxidation of ammonium ions or released ammonia to N2 and NH2OH. Cationic InO+ species, created in zeolites by reductive solid-state ion exchange of In2O3/NH4-zeolite mixtures in hydrogen atmosphere and subsequent oxidation of the In+ lattice cations by oxygen, do not undergo autoreduction up to 970 K. Reductive solid-state ion exchange easily proceeds in carbon monoxide atmosphere at temperatures between 620 and 770 K. The significance of these observations for the use of indium-containing zeolites as catalysts is discussed.  相似文献   

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