全pH范围内超疏水大面积的微米螺旋炭丝

通过控制催化前驱体(酒石酸铜)的电化学氧化在金属表面形成了铜催化剂,并通过铜催化裂解乙炔在金属表面制备了大面积的微米螺旋炭丝。用SEM, FT-IR,XPS和测接触角对所制制螺旋炭丝进行了表征。发现螺旋炭丝具有非常好的化学稳定性和全PH范围的超疏水性质。这种炭丝被期待用做特殊的界面功能材料。     

High-aligned carbon nanotube film with netlike bulges

High-aligned carbon nanotubes film with netlike bulges made of catalyst particles has been synthesized on a silica wafer by pyrolyzing ferrocene/melamine mixtures. The structure and composition of carbon nanotubes are investigated by scanning electron microscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electron energy-loss spectroscopy (EELS). It is found that these nanotubes have uniform outer diameters of about 25 nm and lengths of about 40 μm. High-resolution TEM images show that each carbon nanotube is composed of graphite-like layers arranged in a stacked-cup-like structure. XPS spectrum shows that the crust covering the tops of the aligned carbon nanotube film consists of carbon, iron and ferric oxide. The EELS spectrum shows that these nanotubes are pure-carbon tubes. The formation mechanism of the netlike bulges has been provided.     

Large‐Scale Synthesis,Annealing, Purification,and Magnetic Properties of Crystalline Helical Carbon Nanotubes with Symmetrical Structures

Crystalline helical carbon nanotubes (HCNTs) are synthesized as the main products in the pyrolysis of acetylene at 450 °C over Fe nanoparticles generated by means of a combined sol–gel/reduction method. Transmission electron microscopy (TEM) images reveal that there are two HCNTs attached to each Fe₃C nanoparticle, and that the two HCNTs are mirror images of each other. Annealing in Ar at 750 °C and purification by immersion in hot (90 °C) HCl solution do not significantly change the structure of the HCNTs, despite the partial removal of Fe nanoparticles by the latter treatment. The magnetic properties of the as‐prepared, annealed, and purified HCNTs have been systematically examined. The annealed sample shows relatively high magnetization due to the ferromagnetic α‐Fe nanoparticles encapsulated in the HCNT nodes. In the case of HCl treatment, relatively pure HCNTs are obtained by the removal of ferromagnetic nanoparticles from the double‐HCNT nodes. The effects of the amount of catalyst used in the synthesis process on the morphology and yield of the carbon products have also been investigated.     

Development and Characterization of C/C-SiC Brake Disc

A new process was developed to produce full-size carbon/carbon-SiC brake discs consisting of two friction layers and a structural layer. Different lengths of chopped carbon fibers were used for the friction layers and structural layer. A preform of each layer was produced by hot-pressing a mixture of resin and carbon fibers. After pyrolyzing the preforms, the layers were joined by hot-pressing. Finally, liquid Si infiltration was performed to obtain a C/C-SiC brake disc. The tensile strength, compressive strength, and bending strength were 40, 46, and 61 MPa, respectively. The density of the disc was 2.1 g/Cm³. The heat transfer coefficient in the vertical direction was 16.5 W/m-°C, and it was 45.9 in the horizontal direction. The friction coefficients obtained under various braking conditions showed stable and suitable values, 0.2–0.6.     

Pyrolysis and combustion kinetics of Fosterton oil using thermogravimetric analysis

Thermogravimetric analysis (TGA) was used to examine the thermal behavior of Fosterton oil mixed with reservoir sand. TGA experiments were performed in nitrogen and air atmospheres at the heating rate of 10 °C/min up to 800 °C. In this study, four sets of TGA runs were performed to examine the thermal behavior of Fosterton whole oil, and the coke sample derived from the whole oil. Similar to previous studies in the literature, we also observed low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO) in the non-isothermal combustion experiment. Higher activation energy values were obtained in reaction regions at higher temperatures. The mean activation energy for whole oil in nitrogen and air atmospheres was 33 and 126 kJ/mol, respectively. Fresh coke samples derived from whole oil were subjected to isothermal combustion at different temperatures from 375 to 500 °C. Arrhenius model was used to obtain the kinetic parameters from the TGA data. From the model, the Arrhenius parameters such as activation energy (E = 127 kJ/mol) and the pre-exponential factor (A = 1.6 × 10⁸/min) were determined for the coke combustion. The results showed a close agreement between the kinetic model and experimental data for different combustion temperatures. It was observed that the apparent order of combustion reaction for different temperatures approach unity.     

A modified model of pyrolysis for charring materials in fire

A modified model of pyrolysis for charring materials in fire has been proposed in this paper. In this model some special factors which show the effect on pyrolysis are considered, i.e., heat loss by convection and radiation caused by surface temperature rise and shrinkage of char surface are considered. Experimental device is designed specially for validating the reliability of the model. Effects of density of materials and heat radiation on pyrolysis of materials have also been investigated.     

Volatilization behavior of fluorine in coal during fluidized-bed pyrolysis and CO2-gasification

The volatilization behavior of fluorine in five Chinese coals was investigated during fluidized-bed pyrolysis and CO₂-gasification at a temperature range of 500-900 °C. The effect of co-existed and added calcium on fluorine volatility during pyrolysis was also determined. With increasing pyrolysis temperature, the volatility of fluorine increases. However, the volatility is greatly dependent on the fluorine chemical forms occurred in coal. Except for Datong and Zhungeer coal, more than 65% of fluorine in other three coals occurs as the steady forms. Fluorapatite is not the major carrier of fluorine in the coals studied. Fluorine volatility is retarded by coexisting calcium during coal pyrolysis, indicating that at least part of the stable forms of fluorine in coal might occur as calcium fluoride or calcium fluoride with complex compounds which are stable even at high pyrolysis temperature. The addition of CaO and limestone can suppress the release of fluorine during pyrolysis. The effect of CaO is better than that of limestone. The volatility of fluorine of coal during CO₂-gasification depends on not only the occurrence mode of fluorine, but also the gasification reactivity of the coal. Compared with N₂ atmosphere, CO₂ is more favorable to the release of fluorine from coal.     

An investigation of the effects of pyrolysis parameters on gas separation properties of carbon materials

A significant extension of an earlier analysis of molecular sieving carbons formed from polymeric precursors is reported for separation of important gas pairs including O₂/N₂, CO₂/CH₄ and C₃H₆/C₃H₈. Previously, it was shown that changing the time or temperature of the pyrolysis protocol for a commercially available polyimide (Matrimid^®) altered the final properties of the carbons produced. Changing the precursor material was shown in this study to also affect the final carbon material obtained for a given final pyrolysis temperature. Analysis of low temperature carbon dioxide adsorption isotherms using density functional theory was employed to characterize the microporosity of the materials. Results are given here for a totally different packing-inhibited polyimide precursor (6FDA/BPDA-DAM). Sorption, permeation and diffusion data are compared with those obtained using the more densely packed commercial polyimide precursor Matrimid^® studied earlier. Thermal soak was also investigated and the effect on permeation properties determined for carbons using both precursors. The results indicate that carbons from both precursors have size-selective ultramicropores as well as larger nonselective micropores that provide high capacity sorption sites for penetrants. High permselectivities, combined with high permeabilities are found for some of the samples when compared with conventional polymer materials. A hypothetical ultramicropore size distribution is shown to be useful to relate transport data to results from more commonly used characterization techniques such as pore size distribution analysis.