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01209 Hydrogen uptake by carbon nanofibers catalyzed by palladium
01 Solid fuels (derived solid fuels) Chars from the co-carbonization of a low-rank coal and olive stones have been used to prepare environmental acceptable smokeless fuel briquettes. The blend was a mixture of char, molasses and H3PO4. This acid was added to favour the polymerization of the binder. The effect of the curing temperature on the physico-chemical features of the briquettes was studied by Fourier Transform Infrared Spectroscopy and Temperature Programmed Decomposition followed by Mass Spectrometry. The presence of H3PO4 as well as the curing process at 200°C of temperature, contribute to the formation of carboxylic acids which lead to the production of briquettes with adequate mechanical properties.
04/01207 Electrolytic, TEM and Raman studies on the production of carbon nanotubes in molten NaCI Kinloch, I. A. et al. Carbon, 2003, 41, (6), 1127-1141. The production of carbon nanotubes (CNTs) by the electrolysis of molten NaC1 was investigated by examining the effect of electrolysis duration, current density and voltage. It was found that as the electrolysis was run for longer periods the cathode eroded, changing the current density and consequently preventing nanotube production. The electrolysis was also inhibited by the anode effect and the formation of a sodium layer on the top of the electrolyte. The cell was modified to avoid these difficulties and then optimized under voltage control. Minimum and optimum voltages and current densities were found for CNT production. However, it was discovered that the percentage of nanotube produce still fell as the electrolysis progressed despite minimizing the variation in the current density. The nanomaterial produced was studied by TEM. In particular, it was observed that half of the nanotubes were coated with amorphous carbon, suggesting a two-stage growth process. No link, though, was established between the growth conditions and the morphology of the nanotubes. Raman spectroscopy showed that the quality of the nanotubes was comparable to those produced by the CVD route. Titration was used to establish the uptake of sodium into the cathodes, providing evidence for the intercalation growth mechanism.
04/01208 Growth of graphite nanofibers from the ironcopper catalyzed decomposition of CO/H2 mixtures Carneiro, O. C. et al. Journal of Physical Chemistry B, 2003, 107, (18), 4237-4244. The formation of graphite nanofibres was investigated, by catalytic decomposition of CO/H2 mixtures over a series of powdered Fe-Cu catalysts at 500-700 ° . The physical and structural characteristics of the nanofibres were established from examination of the materials by a variety of techniques, including transmission electron microscopy, temperature-programmed oxidation, nitrogen surface area measurements, and X-ray diffraction. Addition of Cu to Fe did not exert a significant influence on the amount of solid carbon product formed. On the other hand, examination of the nanofibres by high-resolution transmission electron microscopy (TEM) revealed that the materials generated from Fe-rich Cu bimetallic catalysts were notably more graphitic in nature than those grown from pure Fe. As the reaction temperature was increased, from 600 to 700 °, the structure of the graphite nanoflbres underwent a dramatic change from a 'platelet' to 'tubular' configuration. It is suggested that this transformation is directly associated with the a-Fe to 7-Fe phase change over this temperature range.
04101209 Hydrogen uptake by carbon nanofibers catalyzed by palladium Lupu, D. et al. International Journal of Hydrogen Energy, 2004, 29, (1), 97-102. Carbon nano-fibres of herringbone conformation were obtained by chemical vapour deposition on Pd/La203 catalyst, from ethylenehydrogen mixture. After the removal of La203, samples with various Pd/C ratios were obtained by oxidation in air. The hydrogen sorption capacities measured gravimetrically at 10 MPa in pure hydrogen, for six different batches of samples, show a good correlation with the Pd/C ratio revelling a catalytic effect of Pd, which supplies atomic H. A possible charge transfer might lead to the increasing of the H uptake with the increasing Pd/C ratio. A saturation value of 1.5% H (mass) per carbon is reached at rather high Pd/C mole ratio (,-~1) for nano-fibres with 425-455 mZg 1 BET surface area.
04/01210 Influence of petrographic and mineral matter composition of coal particles on their combustion reactivity M6ndez, L. B. et al. Fuel, 2003, 82, (15 17), 1875-1882. Combustion at programmed temperature in a thermobalance is a rapid technique, which monitors coal burning characteristics and has shown its utility to classify coals according to their combustion performance. However, combustion profiles are affected by different coal properties and characteristics such as particle size, rank, maceral composition and mineral matter content, whose separate effects are difficult to determine. The objective of this work was to ascertain the influence of coaly and mineral matter composition and distribution on burning
166
Fuel and Energy Abstracts May 2004
profiles as determined by thermogravimetric analysis, by using coals of different rank, and fractions of these coals obtained by density separation. Five coals ranging in rank from lignite to anthracite and with variable mineral matter content and composition were used in this study. Density fractions were separated from each coal to obtain samples with different organic/mineral matter proportions. Some of the factors influencing coal combustion profiles are widely recognized as the negative effect of increasing both rank and inertinite content on the reactivity. The favourable effect of mineral matter content on the reactivity has shown to be related to the maceral size within the density fractions and the intimate association organic/mineral matter that favors the diffusion of the reacting gas. Catalytic effects of the mineral matter could not be demonstrated.
04101211 Purification process for single-wall carbon nanotubes Strong, K. L. et al. Carbon, 2003, 41, (8), 1477-1488. Single-wall carbon nanotubes (SWNTs) have exceptional strength and stiffness and high thermal and electrical conductivity, making them excellent candidates for aerospace structural materials. However, one of the most fundamental challenges is purifying the SWNTs. The purpose of this study was to develop a simple purification process for SWNTs, along with an understanding of the purification process. In addition, uncomplicated analytical methods were sought to screen and compare various purification methods. This study demonstrates an easy method of cleaning SWNTs and evaluating their purity, The cleaning method, which employed oxidative heat treatment followed by acid reflux, was straightforward, inexpensive, and fairly effective. The purification mechanism was determined to be, first, that much of the non-nanotube carbon and iron catalyst was oxidized and, second, that the acid washing removed the iron oxide, leaving relatively pure SWNTS. Also, it was shown that a combination of thermal gravimetric analysis and Raman spectroscopy, both of which take only a few minutes and require little sample preparation, are sufficient as qualitative screening tools to determine the relative purity of SWNTs. Other analytical techniques were used to verify the validity of the screening techniques.
04/01212 Reactivity and characterization of various rank Turkish bituminous coal chars Kizgut, S. et al. Journal of Tbermal Analysis and Calorimetry, 2003, 71, (3), 857 865. A set of seven bituminous coal chars was characterized by IR spectroscopy (FTIR), thermogravimetry (TG) and elemental analysis. FTIR study provided suitable information to establish differences between coal samples according to their chemical compositions. The reactivity of these samples was also studied and correlated with the coal parameters of mean vitrinite reflectance, fuel ratio and H/C ratio. The data suggest that reactivity as detected can be correlated with the mean vitrinite reflectance, fuel ratio and H/C ratio (0.90). The order of reactivity of samples were; Amasra ($1) (Rm=0.65) > Azdavay ($4) (Rm=0.99) ~ Armutcuk ($2) (Rm=0.81) ~ Acenta ($3) (Rm=0.92) > Ac212k ($6) (Rm = 1.11) Cay ($5) (Rm = 1.03) > Sogutozu ($7) (Rm = 2.14).
04•01213
Soot-free synthesis of Cso
Rodgers, R. P. et al. Carbon, 2003, 41, (7), 1469-1475. A new synthetic medium for the production of C60 has been found that does not produce soot. Coo was produced in the liquid phase of an aerosol of precursor soot at 700°C. The precursor soot aerosol, a high temperature stable form of hydrocarbon, was produced by pyrolysis of acetylene at atmospheric pressure in a flow tube reactor. At 700°C, the effluent particles were found to contain PAHs, small hydrocarbons and fullerenes but no observable black material. However, when the reactor temperature was changed to 800°C, soot was also produced in the effluent particles along with PAHs and other small hydrocarbons, and the fullerene product disappeared. These results show a clear competition between the production of fullerenes and other forms of carbon. The filter-collected effluent was shown to be completely soluble in conventional solvents suggesting the possibility of an efficient cyclic synthetic process. Fullerenes were only found in the particle phase implying the first observed liquid phase synthesis of C60.
04•01214 The peculiarities of carbon interaction with catalysts during the synthesis of carbon nanomaterials Yu, S. et al. Carbon, 2003, 41, (7), 1349-1355. Catalysts based on metals of the iron group (Fe, Ni, Co) and their alloys are used in different methods of carbon nanomaterial production. The selection of optimal regimes for these processes calls for fundamental consideration of processes on the catalyst. An investigation of the distribution and thermally activated redistribution of interstitial carbon atoms in the volume and surface of crystalline films has been carried out. These crystals have a b.c.c, lattice and various types of free facets. The kinetic curves of interstitial atom redistribution under changes of temperature have been studied. Correlation has
04/01207 Electrolytic, TEM and Raman studies on the production of carbon nanotubes in molten NaCI Kinloch, I. A. et al. Carbon, 2003, 41, (6), 1127-1141. The production of carbon nanotubes (CNTs) by the electrolysis of molten NaC1 was investigated by examining the effect of electrolysis duration, current density and voltage. It was found that as the electrolysis was run for longer periods the cathode eroded, changing the current density and consequently preventing nanotube production. The electrolysis was also inhibited by the anode effect and the formation of a sodium layer on the top of the electrolyte. The cell was modified to avoid these difficulties and then optimized under voltage control. Minimum and optimum voltages and current densities were found for CNT production. However, it was discovered that the percentage of nanotube produce still fell as the electrolysis progressed despite minimizing the variation in the current density. The nanomaterial produced was studied by TEM. In particular, it was observed that half of the nanotubes were coated with amorphous carbon, suggesting a two-stage growth process. No link, though, was established between the growth conditions and the morphology of the nanotubes. Raman spectroscopy showed that the quality of the nanotubes was comparable to those produced by the CVD route. Titration was used to establish the uptake of sodium into the cathodes, providing evidence for the intercalation growth mechanism.
04/01208 Growth of graphite nanofibers from the ironcopper catalyzed decomposition of CO/H2 mixtures Carneiro, O. C. et al. Journal of Physical Chemistry B, 2003, 107, (18), 4237-4244. The formation of graphite nanofibres was investigated, by catalytic decomposition of CO/H2 mixtures over a series of powdered Fe-Cu catalysts at 500-700 ° . The physical and structural characteristics of the nanofibres were established from examination of the materials by a variety of techniques, including transmission electron microscopy, temperature-programmed oxidation, nitrogen surface area measurements, and X-ray diffraction. Addition of Cu to Fe did not exert a significant influence on the amount of solid carbon product formed. On the other hand, examination of the nanofibres by high-resolution transmission electron microscopy (TEM) revealed that the materials generated from Fe-rich Cu bimetallic catalysts were notably more graphitic in nature than those grown from pure Fe. As the reaction temperature was increased, from 600 to 700 °, the structure of the graphite nanoflbres underwent a dramatic change from a 'platelet' to 'tubular' configuration. It is suggested that this transformation is directly associated with the a-Fe to 7-Fe phase change over this temperature range.
04101209 Hydrogen uptake by carbon nanofibers catalyzed by palladium Lupu, D. et al. International Journal of Hydrogen Energy, 2004, 29, (1), 97-102. Carbon nano-fibres of herringbone conformation were obtained by chemical vapour deposition on Pd/La203 catalyst, from ethylenehydrogen mixture. After the removal of La203, samples with various Pd/C ratios were obtained by oxidation in air. The hydrogen sorption capacities measured gravimetrically at 10 MPa in pure hydrogen, for six different batches of samples, show a good correlation with the Pd/C ratio revelling a catalytic effect of Pd, which supplies atomic H. A possible charge transfer might lead to the increasing of the H uptake with the increasing Pd/C ratio. A saturation value of 1.5% H (mass) per carbon is reached at rather high Pd/C mole ratio (,-~1) for nano-fibres with 425-455 mZg 1 BET surface area.
04/01210 Influence of petrographic and mineral matter composition of coal particles on their combustion reactivity M6ndez, L. B. et al. Fuel, 2003, 82, (15 17), 1875-1882. Combustion at programmed temperature in a thermobalance is a rapid technique, which monitors coal burning characteristics and has shown its utility to classify coals according to their combustion performance. However, combustion profiles are affected by different coal properties and characteristics such as particle size, rank, maceral composition and mineral matter content, whose separate effects are difficult to determine. The objective of this work was to ascertain the influence of coaly and mineral matter composition and distribution on burning
166
Fuel and Energy Abstracts May 2004
profiles as determined by thermogravimetric analysis, by using coals of different rank, and fractions of these coals obtained by density separation. Five coals ranging in rank from lignite to anthracite and with variable mineral matter content and composition were used in this study. Density fractions were separated from each coal to obtain samples with different organic/mineral matter proportions. Some of the factors influencing coal combustion profiles are widely recognized as the negative effect of increasing both rank and inertinite content on the reactivity. The favourable effect of mineral matter content on the reactivity has shown to be related to the maceral size within the density fractions and the intimate association organic/mineral matter that favors the diffusion of the reacting gas. Catalytic effects of the mineral matter could not be demonstrated.
04101211 Purification process for single-wall carbon nanotubes Strong, K. L. et al. Carbon, 2003, 41, (8), 1477-1488. Single-wall carbon nanotubes (SWNTs) have exceptional strength and stiffness and high thermal and electrical conductivity, making them excellent candidates for aerospace structural materials. However, one of the most fundamental challenges is purifying the SWNTs. The purpose of this study was to develop a simple purification process for SWNTs, along with an understanding of the purification process. In addition, uncomplicated analytical methods were sought to screen and compare various purification methods. This study demonstrates an easy method of cleaning SWNTs and evaluating their purity, The cleaning method, which employed oxidative heat treatment followed by acid reflux, was straightforward, inexpensive, and fairly effective. The purification mechanism was determined to be, first, that much of the non-nanotube carbon and iron catalyst was oxidized and, second, that the acid washing removed the iron oxide, leaving relatively pure SWNTS. Also, it was shown that a combination of thermal gravimetric analysis and Raman spectroscopy, both of which take only a few minutes and require little sample preparation, are sufficient as qualitative screening tools to determine the relative purity of SWNTs. Other analytical techniques were used to verify the validity of the screening techniques.
04/01212 Reactivity and characterization of various rank Turkish bituminous coal chars Kizgut, S. et al. Journal of Tbermal Analysis and Calorimetry, 2003, 71, (3), 857 865. A set of seven bituminous coal chars was characterized by IR spectroscopy (FTIR), thermogravimetry (TG) and elemental analysis. FTIR study provided suitable information to establish differences between coal samples according to their chemical compositions. The reactivity of these samples was also studied and correlated with the coal parameters of mean vitrinite reflectance, fuel ratio and H/C ratio. The data suggest that reactivity as detected can be correlated with the mean vitrinite reflectance, fuel ratio and H/C ratio (0.90). The order of reactivity of samples were; Amasra ($1) (Rm=0.65) > Azdavay ($4) (Rm=0.99) ~ Armutcuk ($2) (Rm=0.81) ~ Acenta ($3) (Rm=0.92) > Ac212k ($6) (Rm = 1.11) Cay ($5) (Rm = 1.03) > Sogutozu ($7) (Rm = 2.14).
04•01213
Soot-free synthesis of Cso
Rodgers, R. P. et al. Carbon, 2003, 41, (7), 1469-1475. A new synthetic medium for the production of C60 has been found that does not produce soot. Coo was produced in the liquid phase of an aerosol of precursor soot at 700°C. The precursor soot aerosol, a high temperature stable form of hydrocarbon, was produced by pyrolysis of acetylene at atmospheric pressure in a flow tube reactor. At 700°C, the effluent particles were found to contain PAHs, small hydrocarbons and fullerenes but no observable black material. However, when the reactor temperature was changed to 800°C, soot was also produced in the effluent particles along with PAHs and other small hydrocarbons, and the fullerene product disappeared. These results show a clear competition between the production of fullerenes and other forms of carbon. The filter-collected effluent was shown to be completely soluble in conventional solvents suggesting the possibility of an efficient cyclic synthetic process. Fullerenes were only found in the particle phase implying the first observed liquid phase synthesis of C60.
04•01214 The peculiarities of carbon interaction with catalysts during the synthesis of carbon nanomaterials Yu, S. et al. Carbon, 2003, 41, (7), 1349-1355. Catalysts based on metals of the iron group (Fe, Ni, Co) and their alloys are used in different methods of carbon nanomaterial production. The selection of optimal regimes for these processes calls for fundamental consideration of processes on the catalyst. An investigation of the distribution and thermally activated redistribution of interstitial carbon atoms in the volume and surface of crystalline films has been carried out. These crystals have a b.c.c, lattice and various types of free facets. The kinetic curves of interstitial atom redistribution under changes of temperature have been studied. Correlation has