Showing papers by "Malcolm L. H. Green published in 2005"
TL;DR: The filling of single-walled carbon nanotubes by sublimation of Re2O7 gives rise to encapsulated RexOy clusters that show dynamic behavior under electron beam irradiation and which can be reduced and sintered using hydrogen gas to give enlarged Re metal clusters as mentioned in this paper.
Abstract: The filling of single-walled carbon nanotubes (SWNTs) by sublimation of Re2O7 gives rise to encapsulated RexOy clusters that show dynamic behavior under electron beam irradiation and which can be reduced and sintered using hydrogen gas to give enlarged Re metal clusters.
59 citations
TL;DR: In this article, a controllably grown carbon nanotubes using uniformly distributed cobalt nanoparticles as catalyst were synthesized by chemical reaction and colloidal solutions including the cobalt particles were prepared.
45 citations
TL;DR: A new ferrocenyl- N -heterocyclic carbene ligand precursor 1,1′-bis[(1- tert -butylimidazolium)-3-methyl]ferrocene dichloride has been synthesised and structurally characterised.
38 citations
TL;DR: In this article, an enhanced digital restoration approach of high-resolution transmission electron microscopy (HRTEM) images was used to characterise a carbon nanotubes (SWNT) encapsulation composite.
Abstract: Simple binary solids can be found to adopt unprecedented structures when confined into nanometre-sized cavities, such as the inner cylindrical bore of single-walled carbon nanotubes (SWNT). In the case of the discussed Lal x @SWNT encapsulation composite, the Lal 2 crystal fragment adopts the structure of bulk Lal 3 , with one third of the iodine positions unoccupied. A complete characterisation of the encapsulation composite was achieved using an enhanced digital restoration approach of high-resolution transmission electron microscopy (HRTEM) images. The resulting complex exit surface wave provides information about the precise structural data of both filling material and host SWNT, establishing the SWNT's chirality and thus enabling a prediction of the composite's overall electron-transport properties.
30 citations
TL;DR: In this paper, bimetallic cobalt-molybdenum oxide (CoMoO x ) has been prepared and converted into CoMoN x, CoMoC x and CoMoS x materials by temperature-programmed reactions with ammonia, ethane or hydrogen sulfide, respectively.
Abstract: Bimetallic cobalt–molybdenum oxide (CoMoO x ) has been prepared and converted into CoMoN x , CoMoC x and CoMoS x materials by temperature-programmed reactions with ammonia, ethane or hydrogen sulfide, respectively. These new bimetallic materials have been characterised using X-ray diffraction (XRD) and solid state NMR and tested for pyridine hydrodenitrogenation (HDN) at various temperatures. The initial HDN activity of the catalysts decreases in order CoMoC x ∼ CoMoN x ∼ CoMoO x > CoMoS x . The stability order of the first three of catalysts is CoMoC x > CoMoN x > CoMoO x , and their activities decrease with the time on stream. In contrast the pyridine conversion over CoMoS x is more stable and activity increases with the time on stream, from 30 to over 50%, this is accompanied by the formation of CoMoSC x material. The high catalytic activity of the CoMoC x catalyst may reflect the ability to hydrocrack pyridine to yield methane. The CoMoS x catalyst system has the highest selectivity to the products cyclopentane (35%) and pentane (27%).
28 citations
TL;DR: In this paper, a double-walled carbon nanotube composites MI@DWNTs (M = K, Cs) have been prepared using a melt-phase filling procedure.
Abstract: The alkali-metal iodide double-walled carbon nanotube composites MI@DWNTs (M = K, Cs) have been prepared using a melt-phase filling procedure. The imaging and subsequent structural analysis of the encapsulated metal iodide crystals was performed with a combination of phase restored high-resolution transmission electron microscopy technique, structural modeling, and image simulation. The atomically resolved structures of the MI crystals were seen to contain several lattice defects including interstitials and vacancies as well as distortions of the crystal planes including shearing and rotation.
27 citations
TL;DR: A series of wolframite-type oxides (Co1−xNixWO4) with various compositions was prepared by urea-matrix combustion method and subsequently carburized using a temperature-programmed reaction under a mixture of 10vol% C2H6/H2, from room temperature to 700°C, to obtain a mixed Co, Ni and W carbide catalysts as discussed by the authors.
Abstract: A series of wolframite-type oxides (Co1−xNixWO4) with various compositions was prepared by urea-matrix combustion method and subsequently carburized using a temperature-programmed reaction (1 °C min−1) under a mixture of 10 vol% C2H6/H2, from room temperature to 700 °C, to obtain a mixed Co, Ni and W carbide catalysts The catalytic performance was evaluated in a continuous flow reactor using hydrodenitrogenation of pyridine as model reaction The wolframite-type oxides and the carbide catalysts pre- and post-HDN reaction were characterized using elemental analysis, X-ray diffraction (XRD), laser Raman spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), transmission electron microscopy (TEM) and BET surface area measurements Urea-matrix combustion method is a convenient tool to prepare highly pure wolframite-type oxides, whose composition affects strongly the W-based carbide phase distribution and the HDN catalytic behaviour At Ni compositions lower than Co contents the formation of Co3W3C and β-W2C carbides is favoured, whereas at Ni compositions greater than those of Co the main phases were Ni and α-WC At intermediate composition (Co05Ni05WCx) bimetallic and monometallic carbides were formed The CoWCx bimetallic catalyst showed greater activity in the steady state than Ni-containing catalysts The HDN active phase present in CoWCx is different than that present in the Ni-containing catalysts, that is, carbon–metal bond strength of the bimetallic carbide, for the former, and metal nickel or weak Ni C bond, for the latter, play a very important role in the catalytic process
27 citations
TL;DR: In this article, the hydrogen sorption capacity of arc-synthesized single-walled carbon nanotubes (SWNTs) was studied using a specially built high-pressure rig coupled to a Toepler pump capable of directly measuring the desorbed volumes of gas.
Abstract: The hydrogen sorption capacity of arc-synthesized single-walled carbon nanotubes (SWNTs) was studied using a specially built high-pressure rig coupled to a Toepler pump capable of directly measuring the desorbed volumes of gas. The samples studied were prepared using the arc-evaporation method and were as-produced SWNT material formed at the cathode (collar), as-produced SWNTs deposited in the soot and a purified sample of SWNTs. The three samples had similar diameter ranges, the major difference between them being the concentration of remaining metal particles from the Ni/Y/C catalyst used in the arc-synthesis. The effect of the presence of these residual catalyst metal particles has been analysed and seen to strongly influence the hydrogen storage capacity of the samples.
26 citations
TL;DR: In this paper, the nonenolizable imino-N-heterocyclic carbene ligand precursor [1-t-butylimidazolium-3-{C(Ph) N(Ph)}] chloride has been synthesized.
23 citations
TL;DR: In this paper, neutral and cationic complexes for the Heck coupling of 4-bromoacetophenone with n-butyl acrylate under aerobic conditions were described.
Abstract: New neutral and cationic complexes [NiBr2(L1)] (1), [NiBr2(OPHPh2)(L1)] (2), [NiMe2(L1)] (3), [NiBr(PMe3)(L1)](Br) (4), [Ni(CH3CN)(PMe3)(L1)](BF4)2 (5), [PdBr2(L2)] (6), [PdI2(L1)] (7), [PtMeCl(L1)] (8), [PtMe2(L1)] (9), [Pt(CH3CN)2(L1)](BF4)2 (10), [Pt(L1)2](X)2 [X = Cl (11a), Br (11b)], [PtX(L1)2](X) [X = Cl (12a), Br (12b)], where L1: [Ph2PCH2C(Ph)N(2,6-Me2C6H3)2] and L2: [Ph2PCH2C(Ph)N(2,6-iPr2C6H3)2], have been prepared and characterised. The molecular structures of 1, 2, 6, 7 and 9 have been determined. The complexes [PdBr2(L2)] (6), [PdBr2(L1)] and [PdMeCl(L1)] have been found to catalyse the Heck coupling of 4-bromoacetophenone with n-butyl acrylate under aerobic conditions.
22 citations
TL;DR: In this paper, the treatment of the bulky iminophosphine ligand [Ph 2 PCH 2 C(Ph) N(2,6-Me 2 C 6 H 3 )] (L ) with [M(CH 3 CN) 2 (ligand)] + n, where for M = Pd(II): ligand = η 3 -allyl, n ǫ = 1, and for M ǔ = R ǒ = Rǫ, nǫ= 0, and when M = RH(I): lig
TL;DR: In this paper, a detailed study has been made upon the preparation of γ-Al 2 O 3 -supported Ni-Mo HDS catalyst precursors by urea-matrix combustion (UMxC) method.
Abstract: A detailed study has been made of the different steps involved upon the preparation of γ-Al 2 O 3 -supported Ni-Mo HDS catalyst precursors by urea–matrix combustion (UMxC) method. Catalyst performance was evaluated using a tubular fixed-bed reactor and the hydrodesulfurization of thiophene under normal pressure as a model reaction. The oxidic and sulfurized states of the HDS catalysts were characterized by X-ray diffraction (XRD), laser Raman spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and high resolution transmission electron microscopy (HRTEM) in order to correlate their oxidic and sulfurized properties with the catalytic behaviour. During the UMxC process several consecutive stages such as melting, dissolution and chemical reactions occurred. There was no evidence of residual carbon and well-dispersed Ni- and Mo-oxo-species supported on alumina were formed. Urea employed as fuel not only increases the combustion rate, but also undergoes a decomposition process (endothermic reaction) that could contribute to the reduction of the combustion temperature. The urea–matrix combustion method permit to synthesize highly active γ-Al 2 O 3 -supported Ni-Mo HDS catalysts with a comparable promoter effect than that of corresponding catalyst prepared by impregnation method. In addition, an opposite relation between the activity and the hydrogenation properties was observed indicating that highly active HDS catalyst requires low consumption of hydrogen. Finally, both the ignition temperature and the urea-oxidizer ratio produce no significant changes in the HDS catalytic properties of Ni-Mo-based catalysts.
TL;DR: In this article, a brief review describes the crystallisation behavior of selected lanthanide halides (LnX 3, with Ln = La, Ce, Gd and X = Cl, I), confined to the nanometre-sized inner cavity of single-walled carbon nanotubes.
Abstract: This brief review describes the crystallisation behaviour of selected lanthanide halides (LnX 3 , with Ln = La, Ce, Gd and X = Cl, I), confined to the nanometre-sized inner cavity of single-walled carbon nanotubes. The resulting LnX 3 @SWNT encapsulation composites were characterised using conventional high-resolution transmission electron microscopy techniques, combined with advanced digital image restoration approaches, enabling the complete structural determination of both the encapsulated crystal fragment and the surrounding nanotube. The studies reveal that some encapsulated 1-dimensional lanthanide halide crystal fragments maintain the overall structure of the respective bulk material, while others exhibit unprecedented crystal structure.
TL;DR: The new cobalt (l) acyl compounds, [Co(PMe 3 )(CO) 3 (COMe)] 1, [CoPhMe 2 )( CO) 3 COME)] 2, Co(P(4-Me-C 6 H 4 ) 3 ), [CoPCy 3 ] (Me) 3 ) (CO) 4 (Me)] as discussed by the authors, have been prepared from [Na(Co(Co) 4 )].
TL;DR: Lanthanum iodide was encapsulated within SWNTs and the resulting encapsulation composite was analyzed using energy-dispersive X-ray microanalysis (EDX) and high-resolution transmission electron microscopy (HRTEM) imaging techniques, to reveal a one-dimensional crystal fragment.
Abstract: The novel crystallization properties of nano-materials represent a great challenge to researchers across all disciplines of materials science. Simple binary solids can be found to adopt unprecedented structures, when confined into nanometer-sized cavities, such as the inner cylindrical bore of single-walled carbon nanotubes (SWNT). Lanthanum iodide was encapsulated within SWNTs and the resulting encapsulation composite was analyzed using energy-dispersive X-ray microanalysis (EDX) and high-resolution transmission electron microscopy (HRTEM) imaging techniques, to reveal a one-dimensional crystal fragment, with the stoichiometry of LaI2, crystallizing in the structure of LaI3 with one third of the iodine positions unoccupied. A complete characterization of the encapsulation composite was achieved using an enhanced image restoration technique, which restores the object wave from a focal series of HRTEM images, providing information about the precise structural data of both filling material and host SWNT, and thereby enabling the identification of the SWNT chirality.
TL;DR: In this article, the molybdenum atom is retained in the molecule via a σ-bond between the substituted cyclopentadienyl ring and a basal boron atom in the metallaborane cluster.
TL;DR: In this paper, the first examples of mesostructured materials containing Mo- and W-oxo-sulphur species incorporated into a poorly ordered MCM-41 framework have been prepared under hydrothermal condition and alkaline medium.
TL;DR: In this article, the higher n-alkyl hydrides [W{(η-C5H4)CMe2( ΔηC5D4)CD3)2 (η -C5DH4)2(D4D4)}(R)D], (R = {(CH2)nCH3} (n = 1-4), n = 1−4) and the isotopically labelled analogues [W(θ-C 5D4]C(CD3)-2(δ
Journal Article•
TL;DR: In this article, the catalytic properties of the catalysts for CO oxidation were studied by means of a microreactor-GC system using XRD, H2-TPR, and XPS.
Abstract: CuO/CeO 2 catalysts were prepared via the impregnation of CeO 2 nano-particles derived from sol-gel method with Cu(NO 3 ) 2 solution. The samples were examined using the methods of XRD, H2-TPR, and XPS. The catalytic properties of the catalysts for CO oxidation were studied by means of a microreactor-GC system.
TL;DR: In this article, single walled carbon nanotubes have been filled with a variety of metal oxides and the structural and morphological characteristics of the metal oxide@SWNT composites studied.
Abstract: Single walled carbon nanotubes have been filled with a variety of metal oxides and the structural and morphological characteristics of the metal_oxide@SWNT composites studied. Advanced techniques of software aberrations correction for transmission electron microscopy were used for characterisation. This research shows that, despite their higher reactivity compared to salts such as halides, oxides can be encapsulated within SWNTs with some compounds attaining remarkable filling yields.