Organic intercalation on layered compound KTiNbO5

Organic intercalations are investigated on HCl treated KTiNbO₅ with a layer structure. The acid treated material is HTiNbO₅ which is a cation exchanged form of KTiNbO₅. It intercalates various kind of amine (B) forming (H⁺) $\text{1?1}\text{m}$ (BH+ $\text{1}\text{m}$ (TiNbO₅^?. When aliphatic amines of the type CH₃(CH₂)_n?1NH₂ are used as intercalants, m=2 in the above mentioned equation and the chain axes of the double layered intercalants are almost perpendicular to the host layer.     

Benzene insertion within the CsC24 graphite intercalation compound: a kinetic neutron diffraction study

The reaction of CsC₂₄ with deuterated benzene (C₆D₆)vapours has been studied in situ by neutron diffraction on a 5 min per spectrum time scale. As in the case of KC₂₄ and RbC₂₄ compounds, we first observed a second-stage ternary CsC₂₄(C₆D₆)y compound (y<2), but it quickly turned into a first-stage ternary CsC₂₄(C₆D₆)₂ compound. Structure model calculations suggest that each Cs⁺ ion is surrounded by two benzene rings, with a tilt angle of 39°, with respect to the c axis.     

聚吡咯包覆FeCl3-石墨层间化合物的制备与电化学储钠性能

以FeCl₃和天然鳞片石墨为原料,通过融盐法制得1阶FeCl₃插层的石墨层间化合物(FeCl₃-GIC)。用原位聚合法对FeCl₃-GIC进行聚吡咯(PPy)包覆改性,形成具有核壳结构的(FeCl₃-GIC)@PPy复合材料。通过多种表征方法研究聚吡咯包覆前后FeCl₃-GIC的表面形貌和微观结构变化。结果表明:聚吡咯均匀致密地包覆在十微米级的FeCl₃-GIC颗粒外部,包覆层厚度为35 nm,经过聚吡咯包覆后(FeCl₃-GIC)@PPy的导电性能显著提高((FeCl₃-GIC)@PPy粉末电阻率2.3×10?3 Ω·cm,FeCl₃-GIC粉末电阻率3.1×10?3 Ω·cm)。采用多种电化学测试探究产物的钠离子存储特性,聚吡咯外壳能够显著提高FeCl₃-GIC作为钠离子电池负极材料的充放电容量、倍率性能和循环性能。在0.1 A·g?1电流密度下循环100次后,FeCl₃-GIC的比容量逐渐衰减到157 mA·h·g?1,而(FeCl₃-GIC)@PPy材料的比容量达到281 mA·h·g?1左右且容量基本保持不变;在电流密度1 A·g?1的条件下循环500次后,(FeCl₃-GIC)@PPy的比容量仍有181 mA·h·g?1,容量保持率约为89%。      

HClO4–graphite intercalation compound and its thermally exfoliated graphite

The aims of this work are to synthesize the HClO₄–graphite intercalation compound (GIC) by chemical method and analyze the effects of processing parameters on the exfoliated volume (EV) of HClO₄–GIC and in the meantime, characterize the structural characteristics of HClO₄–GIC and its exfoliated graphite by using X-ray diffraction. The experimental results show that the optimum condition for preparing the HClO₄–GIC with the maximum EV of 540 cm³/g is that the intercalating reaction temperature, time, the thermally exfoliating temperature and the ratio between natural flake graphite, HClO₄ and HNO₃ are 373 K, 15 min, 1173 K and 1/4/0.15, respectively. The HClO₄–GIC synthesized through the optimum processing condition has EV of 360 cm³/g at 473 K and the natural flake graphite also can be intercalated by HClO₄ at low temperature 258 K in the system.     

Lithium intercalation in TiS2

We report the intercalation of lithium in Li_XTiS₂ corresponding to 0 ≤ x ≤ 3. Intercalation to x = 3 results in a new phase whose charge-discharge behavior displays hysteresis. This is in contrast to the behavior of Li_xTiS₂ for 0 ≤ x ≤ 2.     

Crystal growth and properties of the AgIn5S8 compound

AgIn₅S₈ single crystals were prepared by vapour transport. An improved procedure for a good supersaturation control was obtained by raising source temperature while maintaining growth temperature at a fixed value. Crystals up to 10×5×5 mm³ could be grown. Using X-ray measurements previously reported f.c.c. structure for powdered samples was confirmed. A direct bandgap of about 1.7eV and n-type conductivity was found. Carrier concentration and electron mobility are reported as varying with temperature in the range 100–350°K.     

A new compound K2Cr8O16 with hollandite type structure

A new compound, K₂Cr₈O₁₆ with the hollandite-type structure was synthesized under high temperature-pressure conditions ranging from 1100° to 1250° C and from 55 to 65 kbars. Its crystal structure was classified as C³₂h - C2/m with the lattice parameters a=13.820, b=2.941, c=9.772 A and β=135°. Ferromagnetism was observed in this compound whose Curie temperature was 225 K and magnetic moment was approaximately 18 μ_B.     

Possibilities of atomic hydrogen storage by carbon nanotubes or graphite materials

Atomic hydrogen storage by carbon nanotubes (CNTs) and highly oriented pyrolytic graphite (HOPG) has been studied using a flow catalytic reactor and an ultra-high vacuum surface science apparatus including scanning tunneling microscope (STM), respectively. Defect sites on CNTs as adsorption sites of atomic hydrogen are introduced by oxidation pretreatment using La catalyst. Pd catalysts are then deposited on CNT surfaces for dissociation of H₂ into atomic hydrogen, which spills over to the defect sites. In the best case, 1.5 wt% of hydrogen is stored in the defective CNT with Pd particles at 1 atm and 573 K. In temperature programmed desorption (TPD) experiments, H₂ starts to desorb at 700–900 K depending on the annealing temperatures of CNTs prior to hydrogen storage. On the HOPG surface, hot atomic hydrogen produced by dissociation of H₂ using tungsten wire desorbs from graphite terraces at 400–700 K, which is much lower than that on CNTs. It is possible that one can decrease the desorption temperature by changing the method of H₂ dissociation.     

GexNbSe2 and GexNbS2 intercalation compounds

The structures of two intercalation compounds, Ge_∼0.2NbSe₂ and Ge_∼0.3NbS₂ were investigated by single crystal X-ray diffraction and electron microscopy (selected area electron diffraction (SAED), high resolution electron microscopy (HRTEM) and X-ray microanalysis by energy dispersive spectroscopy (XEDS)). Crystal structure determinations of the average structure of the intercalation compounds 2H-Ge_0.217NbSe₂ and 4H-Ge_0.288NbS₂ are reported: the selenide compound crystallizes in the space group P6₃/mmc with a = 3.4560(9) Å and c = 12.966(3) Å and adopts the 2H-NbSe₂ structure-type, while the sulfide compound crystallizes in the P6₃mc space group, with a = 3.3392(9) Å and c = 25.404(7) Å with a structure-type 4H_c-NbS₂ which it is known for TaSe₂. In both structures the germanium atoms are located in the empty octahedral positions of the van der Waals gap between the NbX₂ (X = S, Se) layers. Electron diffraction patterns from several Ge_xNbSe₂ crystal flakes show different superstructures and exhibit diffracted diffuse intensity: weak satellites corresponding to and 2a₀ × 2a₀ superstructures were observed for x ∼ 0.15 (a₀ is the basal lattice parameter of the host structure). For x ∼ 0.25-0.33, the same type of satellite is observed with a stronger intensity. For x ∼ 0.5 only satellites corresponding to the superstructure were present. In the case of Ge_xNbS₂, with 0.10 < x < 0.25, the germanium atoms are ordered in domains with an superstructure. In some crystals disorder along the c-axis has been observed.     

Photoelectrochemical properties of Re6Se8Cl2 a lamellar transition metal cluster compound

Photoelectrochemical properties of vapor-grown single crystals Re₆Se₈Cl₂ are presented; this Re₆Se₈Cl₂ is a n-type semiconductor with a direct bandgap of about 1.42eV, corresponding to a probable d-d phototransition. The material is not stable under prolonged illumination in aqueous acidic and basic solutions. Addition of a I^?/I^?₃ redox system in acidic solution increases the photopotential (very strongly) to 490mV, shifts 600mV cathodically the onset of the anodic photocurrent and improves considerably the stability of the Re₆Se₈Cl₂ photoanode. This behavior is analysed in relation to the d band semiconductor character of Re₆Se₈Cl₂.     

The intercalation of graphite by uranium hexafluoride

Uranium hexafluoride is shown to react with graphite to yield an intercalation compound of nominal formula “C₁₃UF₆”. Wide line fluorine nuclear magnetic resonance demonstrates the presence not only of uranium (VI) fluoride but also of uranium (IV) fluoride. This assignment is confirmed by the observation of Curie-Weiss Law magnetic susceptibility, indicating approximately 10% of the uranium species to exist as U(IV). The presence of intercalated paramagnetic species, as in “C₁₃UF₆”, “C₁₃CrO₃”, and C₆FeCl₃, can obscure the properties of a fundamental conduction carrier electron spin resonance absorption in graphite/acceptor compounds.     

Crystal structure of Li2 CaUF8

Compound Li₂CaUF₈ is tetragonal. The unit cell, with $\text{a}\text{=5.2290(12)}\text{A}\text{?}$,$\text{c}\text{=11.0130(18)}\text{A}\text{?}$, contains two formula units and the space group is I$\text{bar}\text{?}$m2. The crystal structure has been solved from single crystal diffractometer data by Patterson and Fourier synthesis and refined by a least-squares method. The final value of R is 0.062 for 602 reflections. The cationic distribution is the same as in the scheelite structure, with an additional cationic ordering. Moreover, we observe that the fluorine atoms are randomly distributed at two half occupied sites.     

Low temperature decomposition of PbMo6S8 and Cu2Mo6S8

The reaction of Mo, S and respectively Pb or Cu was studied under hydrothermal conditions. At temperatures below ～500 °C Pb and Cu react readily to give the binary sulfides, while the reaction of Mo is very sluggish. For longer reaction times or higher temperatures the equilibrium three-phase assemblages Cu,MoS₂,Mo and Pb,MoS₂,Mo or Pb,Mo₂S₃,Mo (above ～610 °C) are obtained. The ternary phases PbMo₆S₈ and Cu₂Mo₆S₈ form above 713 and 590 °C, respectively.     

Electronic characterization of alkali ruthenium hollandites: KRu4O8, RbRu4O8 and Cs0.8Li0.2Ru4O8

Transport, specific heat, and magnetic measurements have been performed on three alkali hollandites: KRu₄O₈, RbRu₄O₈, and a newly synthesized Cs analog, Cs_0.8Li_0.2Ru₄O₈, which was determined to have space group I4/m (#87) and lattice parameters, a = 10.0850(4) and c = 3.12180(20). In contrast to the ruthenium perovskites, which display a wide range of electrical and magnetic behavior, the alkali hollandites are simple paramagnetic metals.     

Stability of 8-hydroxyquinoline aluminum films encapsulated by a single Al2O3 barrier deposited by low temperature atomic layer deposition

100 nm thick 8‐AlQ₃ films deposited onto silicon wafers have been encapsulated by mean of low temperature atomic layer deposition of Al₂O₃ (20 nm). Investigation of the film evolution under storage test as harsh as 65 °C/85% RH has been investigated up to ~ 1000 h and no severe degradation could be noticed. The results have been compared to raw AlQ₃ films which deteriorate far faster in the same conditions. For that purpose, fluorescence measurements and atomic force microscopy have been used to monitor the film evolution while transmission electron microscopy has been used to image the interface between AlQ₃ and Al₂O₃. This concept of bilayer AlQ₃/Al₂O₃ barrier films has finally been tested as an encapsulation barrier onto an organic light-emitting diode.     

Production of few-layer graphene by supercritical CO2 exfoliation of graphite

In this study, the authors report a supercritical CO₂ processing technique for intercalating and exfoliating layered graphite. Few-layer graphene is produced by immersing powdered natural graphite in supercritical CO₂ for 30 min followed by rapidly depressurizing the supercritical fluid to expand and exfoliate graphite. The graphene nanosheets are collected by discharging the expanding CO₂ gas directly into a solution containing dispersant sodium dodecyl sulfate (SDS) to avoid restacking. Atomic force microscopy (AFM) shows that the typical graphene sheet contains about 10 atomic layers. This technique offers a low-cost, simple approach to large-scale production of pure graphene sheets without the need for complicated processing steps or chemical treatment.     

载体Al/Si比对Cu-ZnO-ZrO2催化剂上CO2加氢合成甲醇的影响

用直接合成法制备了不同铝硅物质的量比Al-SBA-15(β)(β=n(Al)/n(Si)=0,0.02,0.03,0.05)介孔分子筛,并采用浸渍法制备了金属负载量m=35%的CZZ/Al-SBA-15(β)负载型介孔催化剂,考察了Al/Si比对负载催化剂结构和性能的影响。采用N_2吸附-脱附、X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、CO_2吸附(CO_2-TPD)、NH3吸附(NH3-TPD)和透射电子显微镜(TEM)等手段对样品进行了表征,在固定床反应器上评价了其CO_2加氢合成甲醇的催化性能。实验结果表明,CZZ/Al-SBA-15(β)具有介孔结构,Al的引入不但增加了载体表面酸性位点,同时还提高了催化剂表面铜分散度(DCu%)和铜比表面积(SCu)以及促进了Cu~+-O-Zn活性位的形成,从而大大提高了催化剂的活性。其中CZZ/Al-SBA-15(0.03)催化剂的甲醇选择性达到26%,与不掺铝的CZZ/Al-SBA-15(0)催化剂相比,甲醇选择性提高了11%,但随着掺Al量的继续增加,酸性太强,CO_2吸附能力下降,活性反而降低。     

Improved electrochemical hydrogen storage capacity of Ti45Zr38Ni17 quasicrystal by addition of ZrH2

Ti₄₅Zr₃₈Ni₁₇ + xZrH₂ (x = 5, 10, 15 and 20 wt%) composite materials are produced by ball milling for 20 min. The results of XRD measurement show that the composite materials contain icosahedral quasicrystal phase (I-phase), FCC phase with a Ti₂Ni type crystal and C14 Laves phase. After adding ZrH₂, the composite materials include not only the individual phases mentioned above, but also the ZrH phase. These composite materials are used as the negative electrode material of the nickel-metal hydride batteries. The electrochemical hydrogen storage characteristics of the material after adding ZrH is investigated. The Ti₄₅Zr₃₈Ni₁₇ + xZrH₂ (x = 5, 10, 15 and 20 wt%) composite material has reached the maximum discharge capacity (83.2 mA h/g) when x equals 10. This maximum discharge capacity is much higher than that of Ti₄₅Zr₃₈Ni₁₇ alloy without ZrH. After adding ZrH_2, the high-rate discharge ability and the cycling stability are enhanced simultaneously. The improvement of the electrochemical properties can be attributed to the synergistic effects of ZrH₂, and the synergistic effects in the composite electrodes are probably attributed to the entry of most of hydrogen atoms from weakly bond strength of the Zr-H to the I-phase structure in electrochemical reaction.     

Thin films of In2O3 by atomic layer deposition using In(acac)3

Thin films of indium oxide have been deposited using the atomic layer deposition (ALD) technique using In(acac)₃ (acac = acetylacetonate, pentane-2,4-dione) and either H₂O or O₃ as precursors. Successful growth using In(acac)₃ is contradictory to what has been reported previously in the literature [J.W. Elam, A.B.F. Martinson, M.J. Pellin, J.T. Hupp, Chem. Mater. 18 (2006) 3571.]. Investigation of the dependence of temperature on the deposition shows windows where the growth rates are relatively unaffected by temperature in the ranges 165–200 °C for In(acac)₃ and H₂O, 165–225 °C for In(acac)₃ and O₃. The growth rates obtained are of the order 20 pm/cycle for In(acac)₃ and H₂O, 12 pm/cycle for In(acac)₃.     

Selective CO2 conversion tuned by periodicities in Au8n+4(TBBT)4n+8 nanoclusters

The structure-dependent catalytic behavior is one of the most important issues in catalysis science.However,it has not been fully understood how different types of atom-packing structures of heterogeneous catalysts precisely impact the reaction sites and pathways.Here we investigate a periodic series of Au_8n+4(TBBT)_(4n+8 )nanoclusters with layer-by-layer structural pattern to catalyze CO₂ hydrogenation(where n=3–6 is the number of(001)layers;TBBT=4-tert-butyl-benzenethiolate).An encouraging evolution of CO₂ conversion can be identified:The product selectivity from methanol,formic acid to ethanol can be switched by the structure-dependent deformation from the flattened,perfect,to elongated cuboids in Au_8n+4(TBBT)_4n+8.Through a combined study of experiment and theory,we demonstrate that the variation in structural patterns of catalysts can exclusively tune their adsorption strength with reaction intermediates and further control the CO₂ conversion toward the different products.