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Abstract: Silicon nitride based composites with different amount (1, 3 or 5wt%) of carbon nanotubes have been prepared by using hot isostatic pressing. Composites with 1, 5 or 10wt% carbon black and graphite have been manufactured, in comparison. Optimisation of the manufacturing processes has been performed, providing intact carbon nanotubes during high temperature sintering. In the case of 1 or 3 wt% carbon nanotube addition, the increase of gas pressure during sintering resulted in an increase of bending strength. It was found that microstructure features achieved by properly designed sintering parameters are the main responsible factors for the strength improvements. Scanning electron microscopy showed that carbon nanotubes have a good contact to the surface of silicon nitride grains. The electrical properties of silicon nitride matrices with carbon addition may change essentially. [Copyright &y& Elsevier]

Abstract: The preparation of mesoporous titanium dioxide by using the sol–gel method is described. For the syntheses a triblock copolymer (P-123) surfactant as structure directing agent and titanium isopropoxide as Ti source was employed. In earlier studies the critical synthesis step was found to be the removal of the organic template from the catalyst, which often destroyed the mesostructure and resulted in significant decrease in the specific surface area of the product. Therefore, novel low-temperature surfactant elimination procedures such as ozone treatment at 150°C or solvent extraction combined with ozone treatment have been systematically tested and compared to find how the textural properties of the product can be preserved ensuring the total removal of the block copolymer. The products were characterized by transmission electron microscopic (TEM), Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), thermogravimetry/derivative thermogravimetry/differential thermoanalysis (TG/DTG/DTA) and BET methods. Specific surface areas of over 500m2/g were achieved in the template free materials, and both the pore size and the anatase content were found to depend on the method of template removal and thermal treatment. The subsequent calcination applied to get higher crystallinity and higher photocatalytic activity resulted in structure collapse and surface area reduction. The catalytic performance of the samples was characterized by determining the apparent rate constant of the heterogeneous photocatalytic degradation of phenol and was found to depend not only on the anatase content, but also on the conditions of the synthesis. The characteristics of the samples prepared by us were compared with those of the commercially available Hombikat TiO2 photocatalyst. [Copyright &y& Elsevier]

Abstract: Catalytic hydrodechlorination is an effective and environmentally friendly alternative for the destruction of chlorine-containing organics. Since the byproducts are waste materials (HCl and Cl2), it is important to find and apply inexpensive or natural materials having catalytic activity in hydrodechlorination. A potential catalyst of this type, the calcined “red mud” originated from the alumina process, was studied in comparison with other iron-containing catalysts, such as single (Fe2O3) and mixed oxides (Fe2O3/Al2O3) and modified zeolite (Fe-ZSM5). The red mud is a dangerous waste formed in large amount, nevertheless, it contains catalytically active oxides. The hydrodechlorination reactions were carried out in a fixed-bed flow reactor in the temperature range of 200–400°C using hydrogen as reducing agent. The structure of the catalysts was characterized by XRD, IR and adsorption methods. The metal and chlorine contents of the used samples were also determined. The efficiency of the reductive destruction of 1,2-dichloroethane (DCE), 1,1,2-trichlorethane (TRCE), 1,1,2,2-tetrachloroethane (TCE), trichloroethene (TRCEE) and tetrachloroethene (TCEE) over mixed oxide originating from red mud is comparable to that obtained for synthetic catalysts. The solids used are not only catalysts, but reactants as well in these reactions. Therefore, these processes could be considered as gas–solid reactions. [Copyright &y& Elsevier]

Abstract: Trititanate nanotubes were prepared from anatase TiO2 in 10M Na2S solution kept at 130°C for 2 weeks. On the basis of this reaction, we devised a novel synthesis method which allows the preparation of titanate nanotubes decorated with CdS nanoparticles in one step. The key feature of the suggested method is controlling the rate of CdS formation by introducing Cd2+ ions as a Cd–EDTA complex into the synthesis mixture. The nanotubes obtained are several hundred nm long, tend to aggregate into rod-like structures and are fully covered by CdS nanoparticles with an average diameter of ∼5.3nm. [Copyright &y& Elsevier]

Abstract: Synthesis of carbon nanotubes (CNTs) from the template molecules of the Si-MCM-41 and Al,Si-MCM-41 mesoporous silicates were investigated. The generation of nanotubes was carried out by graphitization, i.e. applying high temperature treatment of the MCM-41 samples in inert gas atmosphere. The as-synthesized and graphitized samples were characterized by several spectroscopic and physico-chemical methods such as IR and MAS NMR spectroscopy, XRD, TEM, and BET. [Copyright &y& Elsevier]

Abstract: Mesoporous MCM-41-carbon nanocomposites were prepared in several Si:C ratios from amorphous active carbon, graphite and multi-wall carbon nanotube carbon sources. A complete morphological characterization of the samples was performed using XRD, TEM, SEM, N2 adsorption and surface hydrophilicity measurements. Specific surface area, pore size distribution, surface fractal dimension and the dimension of capillary condensation were calculated and the adsorption excess isotherms of the ethanol–cyclohexane system were measured. Our results show that the three carbon types give rise to rather different composite morphological features. On this basis the fine tuning of carbon–silicate composite properties by design appears feasible. [Copyright &y& Elsevier]

Platinum nanoparticles were prepared from colloidal solution in the 5-16 nm range. SBA-15 mesoporous silica was impregnated with particles small enough to enter the 10 nm pores until 0.1 wt% loading was reached. Characterization of the catalysts was carried out by XRD, TEM and BET. Cyclohexene hydrogenation/dehydrogenation was monitored using a reaction cell that permitted infrared spectroscopy monitoring of the gas phase as well as the catalyst surface that was pressed in a wafer and inserted in the reactor. The surface hydroxyl groups on the mesoporous silica show shifts in the 3633-3705 cm-1 range characteristic of the presence of cyclohexene, 1,3- and 1,4-cyclohexadienes. Reaction studies using 10 Torr of cyclohexene and 100 Torr of hydrogen in the 298-473 K range showed that hydrogenation occurs readily at room temperature while dehydrogenation takes place only at higher temperatures as expected. The small platinum nanoparticles carry out reactions at the highest rates while the largest size metal particles of the lowest. There is no apparent change of metal particle size during the reactions. [ABSTRACT FROM AUTHOR]

Abstract: A systematic study on the morphological changes experienced by multi-wall carbon nanotubes during long-time ball milling in a vibrating mill was performed. Samples were collected in the time interval 0–200h and analyzed with TEM and N2 adsorption. The change of the mean nanotube length with time could be approximated with a second-order exponential decay function. The length distribution function changed from the original log-normal to normal after 140h of milling. Specific surface area, surface fractal dimension, the dimension of the capillary condensation and the pore size distribution (PSD) curve were calculated from the N2 adsorption isotherms. These morphological descriptors all experienced characteristic changes after ∼40h of milling: the specific surface area decreased, the fractal dimension increased and the maximum of the PSD curve shifted downwards by ∼0.5nm. Results indicate that ball milling of carbon nanotubes is a rather complex process and that it can cause several morphological changes to samples besides the well-known cutting effect. [Copyright &y& Elsevier]

Abstract: Ion-exchangable titanate nanotubes synthesized by the alkali treatment of TiO2 (anatase) were rendered photochemically active by decorating them with CdS nanoparticles through a simple wet chemical process. HRTEM, Raman and IR observations suggest that the activation could be caused by the strong coupling between the nanotube and the nanoparticles. [Copyright &y& Elsevier]

Multi-walled carbon nanotubes have been shortened by ball milling under ambient conditions. Detailed high-resolution TEM studies of the carbon nanotube ends showed a high-percentage of carbon nanotubes had partially or completely collapsed openings. Their stability was also discussed. Based on the morphology of the broken ends, different mechanisms for carbon nanotubes cleavage under ball milling conditions were proposed. [Copyright &y& Elsevier]

Transition metal containing spherical MCM-41 silicates were prepared and characterized by transmission electron microscopy (TEM), XRD, BET, TPR and IR spectroscopy. Incorporation of aluminum, iron, cobalt, copper ions into the wall of the pores has been established. These ions were almost completely built in into the silicate framework from the synthesis gel. With increasing iron content the ordering of pores decreased, the hydrogen uptake increased, the acidity gained. Only one electron transfer took place (Fe3+ → Fe2+) during the reduction of Fe-MCM-41 samples up to 923 K, which means that iron is stabilized in the mesoporous structure and probably linked with framework via oxygen ions. For cobalt ion containing samples practically no reduction was observed, however, significant Lewis acidity was detected. The copper containing samples behaved different. Two electron transfers took place upon hydrogen treatment proving the reduction of Cu2+ ions to metallic copper, however, a part of the metallic species can be reversible reoxidized to cationic form. The Cu-MCM-41 samples showed also Lewis acidic character. Both Bronsted and Lewis acidic sites could only be observed by IR spectroscopy when aluminum or iron was incorporated into MCM-41. The Fe-MCM-41 samples showed significant catalytic activity in the acid catalyzed alkylation of toluene with benzyl chloride at 333 K. [Copyright &y& Elsevier]

Catalytic decomposition of acetylene was studied under reduced pressure in a batch reactor over catalyst samples, which previously showed outstanding activity and selectivity in carbon nanotube formation in a fixed-bed flow reactor under atmospheric pressure. It was found that activity depends on the nature of the catalyst sample at lower acetylene pressure. Characterization of the samples was carried out by transmission electron microscopy and X-ray diffraction. Concerning the quality and the graphitization of carbon nanotubes, selectivity showed a strong dependence on the initial pressure. With decreasing pressure the formation of fullerenes was obtained. To detect the amount of fullerenes and polyaromatic hydrocarbons, Soxhlet extraction followed by high pressure liquid chromatography (HPLC) mass spectrometry (MS) analysis was carried out. Certain catalyst samples showed activity in fullerene formation independent of pressure. HPLC results support a mechanism for catalytic C60 formation via polyaromatic hydrocarbons as building blocks. [Copyright &y& Elsevier]

The present text describes an investigation of XPS study of multiwall carbon nanotube (MWNT) synthesis. The aim of the investigation was not only to improve the reaction activity by mixing nickel with vanadium, but also to understand the formation mechanism of the nanotubes. Carbon nanotubes were produced by catalytic chemical vapor deposition (CCVD) of acetylene on transition metal containing catalysts supported on zeolite ZSM-5. The samples were characterized at two different levels. At the nanoscale, they were studied by transmission electron microscopy (TEM), while at macroscopic scale mainly XPS was used to investigate the changes during the reaction. [Copyright &y& Elsevier]

Results concerning the structural consequences of template removal from MCM-41 mesoporous materials are described using ozone, N2O and NO2 as oxidants in comparison with the conventional method applying oxygen. Si, TiSi-, VSi and ZrSi-MCM-41 samples were synthesized by the usual methods. For characterization of the as-synthesized and treated samples XRD, nitrogen adsorption, 29Si MAS NMR-, IR- and UV–Vis spectroscopic methods were used. The catalytic activity of the samples was tested in the Friedel–Crafts alkylation of toluene by benzyl chloride. The comparison of template removal agents showed that ozone was the most active at low temperature (423 K), and the treatment was less destructive than burning off the template in oxygen. Nitrogen oxide treatment (NO2 and N2O) resulted in template removal at relatively low temperature (573–623 K), and structure deterioration was small. Si NMR spectroscopic data and IR spectra taken in the framework vibration range revealed that more original –SiOH groups remained as hydroxyl nests, furthermore, the heteroatom remained in tetrahedral coordination after ozone and nitrogen oxide treatment compared to burning off the template by oxygen. The results proved the advantages of ozone or nitrogen oxide treatments: (i) gentler to heteroatoms situated in the framework of the materials, probably leaves them intact, (ii) does not result in the formation of secondary micropores, which would decrease the uniform arrangement of the original pore systems, (iii) by preserving the active centers in their original coordination more uniform product distribution may be expected in catalytic reactions. [Copyright &y& Elsevier]

The characteristics of In-containing ZSM-5 zeolites prepared by different method have been investigated in the correlation of catalytic activity in the oxidative reaction of pentane and hexane.The zeolite catalysts have been prepared using four different methods: (i) ion-exchange in In(NO3)3 solution; (ii) solid state ion-exchange in oxidative atmosphere; (iii) solid state ion-exchange in reductive atmosphere; (iv) isomorphous substitution of aluminum for indium in the synthesis. The catalysts have been characterized by thermal analytical, XRD, nitrogen adsorption, IR, UV–VIS, 29Si MAS NMR, 27Al MAS NMR spectroscopic methods. Conversion of n-pentane and n-hexane has been studied in a fixed bed flow reactor in the presence or in the absence of dioxygen.High cracking activity is characteristic of the catalysts with high surface Bro¨nsted acidity due to the oxidative treatment, while the catalyst pre-treated in reductive atmosphere having Lewis acidity are effective in the dehydrogenation and aromatization reactions of pentane and hexane. However, the significant increase of aromatic selectivity in the case of the catalyst prepared by solid state ion-exchange could be accounted to rapid dehydrogenation caused by isolated In2O particles formed in reductive atmosphere. Synergism, namely intimate contact between these particles and the framework silicate structure can be assumed as active sites for the dehydrogenation and aromatization of alkenes. [Copyright &y& Elsevier]

Catalytically prepared multiwall carbon nanotubes (MWNTs) were cut and functionalised by mechanical and/or chemical methods. Products were characterised by transmission electron microscopy, infrared spectroscopy and BET method. It can be concluded that physical and chemical breaking procedures complete each other very well. With certain MWNT samples containing surface oxides preliminary investigations were done for testing them as catalyst support. [Copyright &y& Elsevier]

We discuss the formation mechanism of titania nanotubes synthesized by the hydrothermal method. On the basis of a comprehensive analysis of TEM, HRTEM, FT-Raman, and N(2) adsorption data, we point out some major shortcomings of the currently accepted trititanate sheet rollup mechanism. We suggest that a novel formation mechanism, oriented nanotube crystal growth from nanoloop seeds, can explain the experimental findings better than the ones proposed so far.

Carbon nanotubes were produced from either a template or the polymer-filled pore systems of mesoporous silicates of various structures and dimensions by heat treatment in the absence of air. Successful synthesis was done when the template molecules contained little or no oxygen. For SBA-15 material, where the structure-directing molecule used for synthesis of mesoporous silicate was polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, no carbon nanostructures were formed. A peculiar carbon nanostructure was generated from the template for pore expanded MCM-41. To demonstrate carbon nanotube formation from polymer in the mesoporous silicates, the mesopores of MCM-41, MCM-48, and SBA-15 silicates were filled with divinyl-benzene polymer and then graphitized at 1300 K. The polymer was successfully transformed into carbon nanotubes for the MCM class silicate but not the SBA-15 silicate.

The species resulting from a typical preparation for metal-substituted hybrids of the Keggin tridecamer, Al 13 or [AlO 4 Al 12 (OH) 24 (OH 2 ) 12 ] 7+ , were examined by performing 27 Al NMR on the solutions during aging and by studying the precipitated sulfate salts via solid state 27 Al NMR and powder X-ray diffraction (XRD). Aqueous mixtures (0.25 mol L -1 ) of AlCl 3 and another metal ion (M), in a 12:1 mole ratio (Al:M), where M = Fe 3+ , Zn 2+ , Ga 3+ , In 3+ , Sn 2+ , La 3+ , and Bi 3+ , were subjected to forced hydrolysis by addition of NaOH (1.0 mol L -1 ) until OH/(Al + M) = 2.25, and the kinetics of Al 13 formation and disappearance with aging at 80 °C was monitored by 27 Al NMR spectroscopy. Al 13 units polymerize on aging with an apparent rate constant (k) of 4.8(8) × 10 -2 h -1 to form a species referred to as AlP 2 . Only the solutions containing Ga 3+ and Sn 2+ exhibited faster Al 13 conversion rates. GaAl 12 forms quickly at 80 °C (k = 0.54 h -1 ) and is more stable than AlP 2 . Sn 2+ apparently promotes AlP 2 formation (k = 0.38 h -1 ). XRD and solid state NMR reveal that only the Ga hybrid can be prepared by this method. No hybrid formation was evidenced using M = Mg 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , In 3+ , La 3+ , or Ce 3+ at 25 °C or M = Co 2+ or La 3+ under reflux conditions. Isostructural (cubic symmetry) single crystals were obtained for the sulfate salts of Al 13 and GaAl 12 . Single-crystal XRD analysis of these two polyoxocations provides the first rigorous comparison between them and shows they have very similar structures. The main crystallographic data for Al 13 and GaAl 12 are as follows:  Na[AlO 4 Al 12 (OH) 24 (H 2 O) 12 ](SO 4 ) 4 ·10H 2 O, cubic, F4̄3m, a = 17.856(2) Å, Z = 4; Na[GaO 4 Al 12 (OH) 24 (H 2 O) 12 ](SO 4 ) 4 ·10H 2 O, cubic, F4̄3m, a = 17.869(3) Å, Z = 4. Thus, the greater thermal stability of GaAl 12 cannot be rationalized in terms of the overall geometric considerations, as suggested by others. Solid state NMR also shows the coordination symmetries of the outer 12 Al nuclei in both clusters to be similar.