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SO2-4/ZrO2-SiO2催化剂的结构及其形成过程 总被引:5,自引:0,他引:5
The structure and the forming process of SO42-/ZrO2-SiO2 catalysts were investigated by TG and DTA. The restraint of silica to the crystallization of the catalysts and the relations of weight loss temperature and loss amount of sulfur oxide bonded to the surface of the catalysts with the contents of zirconia were revealed by experimental results. The forming process of the catalysts was also explored by these techniques, some very important information, which will be useful for understanding the structure and properties of catalysts, were obtained. 相似文献
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采用水热和溶胶-凝胶相结合的方法,制备了具有良好电化学性能的新型多壁碳纳米管-Na3V2(PO4)3(MWCNT-NVP)复合材料(MWCNT的质量分数为8.74%). 通过场发射扫描电子显微镜表征可知,MWCNT分散在NVP纳米颗粒之间,并起到“电子导电线”的作用. 与纯Na3V2(PO4)3相比,MWCNT-NVP具有更高的比容量和更优异的循环性能. 在0.2C(35.2 mA·g-1)的电流密度下,3.0-4.5 V的电压范围内,MWCNT-NVP的初始比容量为82.2 mAh·g-1. 循环100次以后,比容量为72.3 mAh·g-1. 在1.0-3.0 V充放电时,MWCNT-NVP的初始容量为100.6 mAh·g-1. 100次循环以后,其容量保持率高达90%. 同时,交流阻抗测试表明,由于MWCNT的存在,MWCNT-NVP的导电性有了显著的提高. 以上结果表明,MWCNT-NVP是一种良好的锂离子电池电极材料. 相似文献
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CeO2 nanotubes have been synthesized facilely using carbon nanotubes (CNTs) as templates by a liquid phase deposition method. The properties of the CeO2 nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS) as well as thermogravimetry and differential thermal analysis (TG-DTA). The obtained CeO2 nanotubes with a polycrystalline face-centered cubic phase have a uniform diameter ranging from 40 to 50 nm. The CeO2 nanotubes are composed of many tiny interconnected nanocrystallites of about 10 nm in size. The pretreatment of CNTs and calcination temperature were confirmed to be the crucial factors determining the formation of CeO2 nanotubes. A possible formation mechanism has been suggested to explain the formation of CeO2 nanotubes. 相似文献
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Zheng Xiange Wang Zhizhong Feng Jikang Tang Auchin 《Journal of Molecular Structure》1999,469(1-3):115-119
A wide variety of geometrical structures of NLi6 molecule were studied using HF ab initio and BLYP-DFT techniques. Three stationary configurations which take D4h, D3d and D2d configurations were obtained. Their equilibrium geometries and fundamental frequencies were calculated at HF and BLYP-DFT levels. Among the three stable states, the global minimum prefers D3d configuration, which is different from those of CLi6 and OLi6. The D3d isomer of NLi6 is 3.43 and 28.45 kcal/mol lower in energy than the D4h and D2d ones in the DFT calculation, respectively. All calculations were performed with 6-31G* polarized split-valence basis set. 相似文献
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Laura Largo Alvaro Cimas Pilar Redondo Víctor M. Rayn Carmen Barrientos 《Chemical physics》2006,330(3):431-440
A theoretical study of the TiCn (n = 1–8) clusters has been carried out at the B3LYP/6-311+G(d) level. Molecular properties for three different isomers, namely linear, cyclic, and fan species, have been determined. The fan isomers, where the titanium atom is essentially side-bonded to the entire Cn unit, are predicted to be more stable than both linear and cyclic isomers. Only for the largest studied species, TiC8, the cyclic isomer is located lower in energy. An even–odd parity effect in the incremental binding energies is observed for the three isomers, n-even species being in general more stable for linear and fan isomers, whereas for the cyclic species n-odd clusters are favoured. A topological analysis of the electronic charge density shows that all cyclic isomers correspond to true monocyclic rings, whereas for the fan species a variety of different connectivities has been observed. 相似文献
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Ab initio pseudopotential SCF calculations were performed on tetrahedral X4 molecules using double-zeta basis sets with and without d functions. The inclusion of d orbitals shortens the bond lengths, stabilizes the X4 structures and intensifies the electron density inside the tetrahedron. The cubic X8 molecules, calculated without d AOs, are not predicted to be more stable than 2X4. Repulsions between parallel bonds in X8 may compensate the lack of ring strain. 相似文献
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Two new mixed valent Mo(III)/Mo(IV) diphosphates containing lead Pb2(PbO)2Mo8(P2O7)8 and PbK2Mo8(P2O7)8 have been synthesized. The [Mo8P16O56]∞ frameworks of these phosphates are closely related to that of K0.17MoP2O7: the MoO6 octahedra and P2O7 groups form two sorts of large eight-sided tunnels. They are occupied in an ordered way by PbO chains and Pb2+ cations in Pb2(PbO)2Mo8(P2O7)8 and by K+ and Pb2+ cations in PbK2Mo8(P2O7)8. It results in different symmetries of these two structures, which are tetragonal and monoclinic, respectively, showing the great flexibility of these mixed frameworks, susceptible to accommodate various species with different sizes. 相似文献
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I. Sayago H. Santos M. Aleixandre E. Terrado R. Aroz A.M. Benito J. Gutiérrez 《Talanta》2008,77(2):758-764
Networks of different carbon nanotube (CNT) materials were investigated as resistive gas sensors for NO2 detection. Sensor films were fabricated by airbrushing dispersions of double-walled and multi-walled CNTs (DWNTs and MWNTs, respectively) on alumina substrates. Sensors were characterized by resistance measurements from 25 to 250 °C in air atmosphere in order to find the optimum detection temperature. Our results indicate that CNT networks were sensitive to NO2 concentrations as low as 0.1 ppm. All tested sensors provided significantly lower response to interfering gases such as H2, NH3, toluene and octane. We demonstrate that the measured sensitivity upon exposure to NO2 strongly depends on the employed CNT material. The highest sensitivity values were obtained at temperatures ranging between 100 and 200 °C. The best sensor performance, in terms of recovery time, was however achieved at 250 °C. Issues related to the gas detection mechanisms, as well as to CNT network thermal stability in detection experiments performed in air at high operation temperatures are also discussed. 相似文献
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合成了一系列含有羟基的双子表面活性剂:1,3-双(十二烷基二甲基氯化铵)-2-丙醇(12-3OH-12),1,3-双(十四烷基二甲基氯化铵)-2-丙醇(14-3OH-14),1,3-双(十六烷基二甲基氯化铵)-2-丙醇(16-3OH-16)和1,3-双(十八烷基二甲基氯化铵)-2-丙醇(18-3OH-18).采用静态失重法、极化曲线和交流阻抗技术研究了其在H2S/CO2腐蚀环境中对L360钢的缓蚀作用.结果表明,三种研究方法取得的结论是一致的,缓蚀效果为14-3OH-14>12-3OH-12>16-3OH-16>18-3OH-18.其中,12-3OH-12和14-3OH-14都表现出很好的缓蚀效果,在35mg·L-1的较低浓度下缓蚀率就达95%以上.极化曲线测试结果表明n-3OH-n(n=12,14,16,18)型双子表面活性剂是一种以阳极抑制为主的混合型缓蚀剂.除n=18外,其它三种双子表面活性剂n-3OH-n(n=12,14,16)在L360钢表面的吸附服从朗缪尔等温线,并且属于物理和化学混合吸附.提出了一个用来解释双子表面活性剂在H2S/CO2溶液中缓蚀机理的吸附模型. 相似文献
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From C72 to C78, the top 20 low-energy isomers screened out from all isomers of each fullerene are optimized and computed by tight-binding Monte Carlo (TBMC), semi-empirical PM3, and ab initio B3LYP/6-31G*//HF/3-21G methods. The comparison results show that the TBMC method can efficiently optimize the structures and correctly predicate the low energy isomers. The relative energies computed by TBMC are in good agreement with the high-lever B3LYP calculation results. Our TBMC and B3LYP results show that the most energetically favorable structure of C72 is not an isomer satisfying the isolated pentagon rule (IPR), which is different with the result by PM3. The symmetry of the most stable IPR isomer tends to low as the fullerene becomes large and several non-isolated-pentagon structures are found to have low symmetries and low energies close to the most stable isomer. 相似文献
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乙二醇溶剂热合成的CeO2的可逆氧化还原性及CO2捕获性能 总被引:1,自引:0,他引:1
利用乙二醇的还原性,采用乙二醇溶剂热法制备了表面具有丰富氧空穴的CeO2-GST纳米晶,对其进行了X射线衍射、透射电镜、X射线光电子能谱、原位H2还原-O2氧化循环和CO2原位红外漫反射表征,并研究了其可逆氧化还原性及CO2捕获性能. 结果表明,与CeO2-nanorod和柠檬酸溶胶法合成的CeO2-CA样品相比,CeO2-GST纳米晶具有最好的可逆氧化还原性能和循环稳定性,同时在50 ℃下具有最好的CO2吸附性能(149 μmol/g). 利用原位红外漫反射光谱研究了CO2在还原CeO2表面的吸附情况,发现CO2主要以双齿碳酸盐和桥连碳酸盐两种形式吸附在CeO2表面,其中桥连碳酸盐物种不稳定,He吹扫可脱附. 此外,CO2在CeO2-nanorod上还会生成稳定的甲酸盐和单齿碳酸盐物种. 相似文献
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The discovery of the fullerenes and nanotubes has completely changed our perspective on various aspects of carbon chemistry and materials science in quite fundamental ways. The experiments, which uncovered C60, occurred between 1985 and 1990 and there are lessons to be learned of various kinds over the way scientific advances occur and more importantly the way misconceptions can propagate. For instance much of our received wisdom over the behaviour of carbon, in particular graphite on a microscopic scale, was really quite ill-conceived and certainly misleading. Questions might be asked as to why it took almost till the end of the 20th century for the fact to be uncovered that the elegant C60 molecule had been lurking in the dark shadows of soot chemistry all the time. After all, mass spectrometric techniques were sufficiently advanced for the discovery to have been made in the 1960’s—perhaps even earlier. Some of these issues are addressed here and the discussion gives an insight into the curiously unpredictable way fundamental scientific advances sometimes occur and also highlights the limitations of applied research in this case. 相似文献
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Wei Song Ming Ni Jing Lu Zhengxiang Gao Shigeru Nagase Dapeng Yu Hengqiang Ye Xinwei Zhang 《Journal of Molecular Structure》2005,730(1-3):121-124
Possibility of encapsulations of metallofullerenes inside single-walled boron nitride nanotubes (BNNTs) is studied by using first-principles calculations. We find that both La@C82 and La2@C80 can be exothermically encapsulated inside the (17, 0) and (14, 7) BNNTs. The minimum diameters of exothermically encapsulating both La@C82 and La2@C80 inside BNNTs are predicated to be about 13.4 Å. 相似文献
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首先,借助碳量子点(CQDs)的上转换光致发光(UCPL)特性对ZnIn2S4进行了表面改性,再结合离子交换法制备了复合材料AgIn5S8/CQDs/ZnIn2S4。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射吸收光谱(UV-Vis DRS)、扫描电镜(SEM)、透射电镜(TEM)、氮气吸附-脱附、光致发光(PL)和电化学阻抗(EIS)等测试手段对复合材料的组成、结构、形貌以及表面物理化学性质等进行了表征。结果表明,该复合材料中不同组分间的协同作用导致其呈现宽光谱响应(250~800 nm)。与对比体系相比,复合材料AgIn5S8/CQDs/ZnIn2S4表现出明显增强的光电流密度,更小的电荷转移阻抗,较长的光生载流子寿命。以甲基橙为模型分子,在不同光源作用下进行的光催化活性研究结果显示,AgIn5S8... 相似文献
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Lin Li 《European Polymer Journal》2005,41(7):1613-1622
A new three-component catalytic system, PdCl2/phen/M(CF3SO3)n, was studied in the copolymerization of dicyclopentadiene (DCPD) with CO. It was found that the PdCl2/phen/CF3SO3H catalytic system gave a very low catalytic activity, and the PdCl2/phen/M(CF3SO3)n catalytic system exhibited high activity when M(CF3SO3)n was introduced instead of CF3SO3H. The resultant cooligomer was analyzed using various techniques such as FT-IR, 1H NMR, 13C NMR, DSC and TGA. The results indicated that the copolymer was a polyspiroketal (PS) of CO and DCPD. Due to the tension of the ring of DCPD, the degree of copolymerization is low and the degree of crystallinity is also not high. The effects of ligands, M(CF3SO3)n, solvents, 1,4-benzoquinone/PdCl2 molar ratio, and temperatures on the copolymerization have been discussed in detail. The results showed that this novel catalytic system exhibited highly efficient activity, especially when 1,10-phenanthroline (phen) was used as ligand and Cu(CF3SO3)2 was used as cocatalyst. The corresponding reaction rate was 49 000 g PS/molPd h when the reaction was carried out at 60 °C and 3.0 MPa of CO. The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the resultant cooligomer were 1180 g/mol and 564 g/mol, respectively. 相似文献
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The orthorhombic perovskites, GdAlO3 and GdFeO3, have been studied using single-crystal X-ray diffraction up to 8.52 and 8.13 GPa, respectively, in a diamond anvil cell at 298 K. The evolution of the structures of GdAlO3 and GdFeO3 involves compression of both the GdO12 and the octahedral (AlO6 and FeO6) sites. The compression of the GdO12 site is anisotropic in both perovskites, with the four longest Gd-O distances compressing more than the eight shorter Gd-O bond lengths, resulting in a decrease in the distortion of GdO12 with pressure. In GdAlO3, the GdO12 site is less compressible than the AlO6 site, resulting in an increase of both the interoctahedral Al-O1-Al and Al-O2-Al angles with increasing pressure. Thus GdAlO3 perovskite becomes less distorted with increasing pressure. In GdFeO3, the GdO12 site displays a similar compressibility as the FeO6 site, with little change in the Fe-O2-Fe angle with pressure but an increase of the Fe-O1-Fe tilting angle. Thus GdFeO3 perovskite becomes less distorted with increasing pressure, but the change is not as pronounced as GdAlO3. The high-pressure behavior of GdAlO3 and GdFeO3 is similar to orthorhombic YAlO3 perovskite but contrasts with orthorhombic CaSnO3, which becomes more distorted with increasing pressure. 相似文献
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B. Fidalgo Y. Fernndez A. Domínguez J.J. Pis J.A. Menndez 《Journal of Analytical and Applied Pyrolysis》2008,82(1):158-162
The aim of this work was to study the microwave-assisted pyrolysis of CH4 over an activated carbon, which acted as both microwave receptor and catalyst, and the influence of using different CH4/N2 ratios on the conversion of CH4 to H2. In order to compare the results obtained in the microwave oven, the pyrolysis was also carried out under conventional heating (electric furnace, EF). The effects of N2, which enhanced significantly CH4 conversion, differed depending on the heating device used. Under EF heating, N2 seemed to have an effect similar to distribute the CH4 molecules within the activated carbon bed. Under microwave heating (MW), the N2, as well as distributing the CH4 molecules, favoured the generation of energetic microplasmas, leading to higher conversions. The prevalence of one role over the other depended on the CH4/N2 ratio, the appearance of energetic microplasmas being favoured with high percentages of N2. Consequently, CH4 conversion was higher at low CH4/N2 ratios. Additionally, the formation of carbon nanofibres in experiments where a combination of N2 and MW heating was used is also reported. 相似文献
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Single crystals of the new compounds TM2Cu3Ga8 (TM=V, Mo, W) were synthesised from the elements. Structure determinations of the isotypic compounds (cI104, space group , Z=8; Mo2Cu3Ga8: a=11.9171(10) Å, 613 refl., 23 param., R1(F)=0.022, wR2(F2)=0.047; W2Cu3Ga8: 11.9248(8) Å, 346 refl., 23 param., R1(F)=0.048, wR2(F2)=0.086; V2Cu3Ga8: 11.7861(14) Å, 374 refl., 24 param., R1(F)=0.033, wR2(F2)=0.081) showed a new cubic structure type which can be classified as an ordered defect variant of a bcc packing with a′=4a: [(TM)2(Cu)3(□)3][Ga8]. The coordination polyhedra of the transition metals consist of Ga8-cubes with 3 sides capped by Cu leading to coordination number 11. The arrangement of the TMGa8Cu3-polyhedra is in a way they form itself a 3-fold capped cube. All compositions were confirmed by EDX measurements. 相似文献