碳化条件对碳微球结构的影响及其性能评价

以葡萄糖为碳源,直接水热合成法制备碳微球。利用扫描电镜(SEM)和傅里叶变换红外(FT-IR)光谱仪对碳微球进行表征,探究碳化条件对碳微球结构的影响。结果表明,葡萄糖经过碳化由棒状变成球状,碳化温度180℃和碳化时间7 h条件下制备的碳微球结构较均匀,并且含有—OH及—COOH官能团,将制备的催化剂用于纤维素水解时,水解率最高达46. 22%。     

N掺杂TiO2粉体晶体结构与光催化性能的研究

以NH4NO3为氮源,采用溶胶凝胶法制备TiO2粉体.在紫外光的照射下,对有机染料甲基橙进行降解,来评价TiO2粉体的光催化性能.利用场发射扫描电镜和X射线衍射仪对TiO2粉体的晶型和形貌进行表征.结果表明:氮元素的加入不仅能够提高TiO2的光催化性能,同时对TiO2的晶体结构也有影响;氮元素通过改变TiO2晶型和单纯...     

Enhancing the catalytic activity of carbon nanotubes by nitrogen doping in the selective liquid phase oxidation of benzyl alcohol

Nitrogen-doped carbon nanotubes (N-CNTs) were prepared by chemical vapor deposition method and employed as carbon-based catalysts for selective oxidation of benzyl alcohol to benzaldehyde with molecular oxygen as the terminal oxidant under the mild reaction conditions. The results showed that the N-CNTs exhibited much higher activity than the undoped CNTs, and the improved catalytic activity was probably attributed to the introduction of electron-rich nitrogen atoms in the graphitic domains enhanced electron transfer. Moreover, N-CNTs displayed excellent stability without an obvious loss in activity and selectivity for benzyl alcohol oxidation after eight cycling reactions. The results presented herein pave the way for the development of novel carbon catalyst for the liquid-phase oxidation of benzyl alcohol.     

Synthesis of nitrogen incorporated diamond-like carbon thin films using microwave surface-wave plasma CVD

Nitrogenated diamond-like (DLC:N) carbon thin films have been deposited by microwave surface wave plasma chemical vapor deposition on silicon and quartz substrates, using argon gas, camphor dissolved in ethyl alcohol composition and nitrogen as plasma source. The deposited DLC:N films were characterized for their chemical, optical, structural and electrical properties through X-ray photoelectron spectroscopy, UV/VIS/NIR spectroscopy, Raman spectroscopy, atomic force microscope and current–voltage characteristics. Optical band gap decreased (2.7 to 2.4 eV) with increasing Ar gas flow rate. The photovoltaic measurements of DLC:N / p-Si structure show that the open-circuit voltage (V_oc) of 168.8 mV and a short-circuit current density (J_sc) of 8.4 μA/cm² under light illumination (AM 1.5 100 mW/cm²). The energy conversion efficiency and fill factor were found to be 3.4 × 10^{− 4}% and 0.238 respectively.     

Synthesis and in vitro anticoagulation activity of hollow carbon nitride microspheres

Hollow carbon nitride microspheres have been synthesized by a facile templating method through replicating the spherical cavity of the porous silica. Different from the common closed hollow microspheres, the microspheres have one or more small holes on the surface, which may be more convenient for its use as small containers for drug delivery, encapsulation, etc., because the small holes can be used as the entrance for adding drug, proteins, enzymes, etc. The diameters of the hollow carbon nitride microspheres were about 1.8–2.2 μm, and the shell thickness of the hollow carbon nitride microspheres was about 70–100 nm. The composition and structure of the sample were detected by the X-ray powder diffraction (XRD), elemental analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectra (XPS). The in vitro anticoagulation activity of the sample was evaluated by the activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT).     

Effect of carbonization temperature on the structure and microwave absorbing properties of hollow carbon fibres

A series of polyacrylonitrile-based hollow carbon fibres (PAN-HCFs) were prepared by carbonizing polyacrylonitrile (PAN) hollow cured fibres at temperature ranging from 550 to 950 °C for 1 h in nitrogen. The effects of carbonization temperature on the structure, elemental compositions, surface electrical conductivity, electromagnetic parameters and reflectivity of PAN-HCFs were investigated. Results indicate that the obtained PAN-HCFs have not been graphitized and the C content and surface electrical conductivity increases as the carbonization temperature increases. The reflectivity of composites of PAN-HCFs and resin is −7.50 dB at 6.06 GHz and the band of the reflectivity under −5 dB is 6 GHz when the carbonization temperature is 750 °C.     

Synthesis,characterization, and electrical properties of nitrogen-doped single-walled carbon nanotubes with different nitrogen content

Nitrogen-doped single walled carbon nanotubes (SWCNTs) have been synthesized via the thermal decomposition of ferrocene using different ratios of acetonitrile/ethanol feedstock mixtures during the chemical vapor deposition process. The experiments were performed at 950 °C and 2 bar. The concentration of acetonitrile in the mixtures was varied from 0% to 100%. High resolution transmission electron microscopy and Raman spectroscopical measurements revealed the formation of SWCNTs for all mixtures. X-ray photoelectron spectroscopical analysis show nitrogen doping levels of up to 2 at.%. The doping levels increase as the acetonitrile concentration increases. The nitrogen incorporation is predominantly in the pyridine form. Electrical conductivity measurements show the dependence of conductivity as a function of nitrogen incorporation in the SWCNTs.     

Synthesis of cuprous oxide using sodium borohydride under microwave irradiation and catalytic effects

Cuprous oxide nanoparticles were synthesized under microwave irradiation for 15 min to use as a catalyst. The product was confirmed by X-ray diffraction and transmission electron microscopy. The catalytic effect of cuprous oxide nanoparticles was investigated for the reduction of 4-nitrophenol to produce 4-aminophenol in the presence of NaBH₄. The above product was confirmed by UV–vis spectroscopy and liquid chromatography–mass spectroscopy.     

Structure, composition, and chemical reactivity of carbon nanotubes by selective nitrogen doping

Carbon nanotubes (CNTs) doped with a range of nitrogen contents (0-10 at.%) were prepared via a floating catalyst CVD method using ferrocene, NH₃, and xylene or pyridine. XPS and Raman microscopy were used to assess quantitatively the compositional and structural properties of the nitrogen-doped carbon nanotubes (N-CNTs). XPS analysis indicates a shift in and broadening of the C 1s spectra track with increasing disorder induced by selective nitrogen doping. N 1s XPS spectra show three principle types of nitrogen coordination (pyridinic, pyrolic, and quaternary), with the pyridinic-like fraction selectively increased from 0.0 to 4.5 at.%. First-order Raman spectra were fit with five peaks that vary in intensity and width with nitrogen content. The ratio of the D and G bands’ integrated intensities scaled linearly with nitrogen content. Iodimetric titrations were used to gauge the number of reducing sites on as-prepared N-CNTs, representing the first report of nitrogen doping as a means to deterministically effect the chemical reactivities of carbon nanotubes. The reported methodology for the regulated growth and selective nitrogen doping of CNTs presents new ways to study systematically the influence of nanocarbon composition and structure on chemical and electrochemical reactivity for a host of applications.     

Impact of nitrogen doping of carbon nanospheres on the nickel-catalyzed hydrogenation of butyronitrile

Three nickel catalysts supported on carbon and nitrogen-doped carbon nanospheres have been prepared by deposition-precipitation (DP) with urea (ca. 2% w/w). The nanospheres were prepared by thermal pyrolysis of benzene (CNS_B), aniline (CNS_A) and nitrobenzene (CNS_N) and characterized by transmission electron microscopy (TEM), N₂ adsorption–desorption, temperature-programmed oxidation (TPO), X-ray diffraction (XRD), elemental (CHN) analysis, X-ray photoelectron spectroscopy (XPS), temperature-programmed decomposition (TPD) and acid/base titrations, revealing different graphitic characteristics and different distribution of nitrogen (when present) functionalities. Upon Ni introduction, the catalysts were characterized by temperature-programmed reduction (TPR), XRD and TEM. Surface area weighted mean Ni particle diameters (post activation at 603 K) were in the range 10.5–18.2 nm. Ni particle size exhibited a big dependence on CNS nitrogen doping, where nitrogen introduction, essentially in the quaternary form, enhanced metal sintering by enriching the surface electron density of the support. The catalysts were tested in the gas phase hydrogenation of butyronitrile (T = 493 K). Extracted specific reaction rates in the steady state followed the sequence: Ni/CNS_B < Ni/CNS_A < Ni/CNS_N. When the active metal was physically mixed with the support, the following sequence was obtained: Ni + CNS_B < Ni + CNS_A < Ni + CNS_N. Our results demonstrate that doping carbon nanospheres with nitrogen strongly impacts on reactant adsorption and metal sintering, both critical aspects in the hydrogenation of nitriles. Selectivity was not sensitive to the support (or the physical mixture) employed and was in all cases close to 100% to the primary amine.     

煤基聚苯胺制掺N碳微纳米管的实验研究

我国煤炭资源丰富,以煤为原料制备碳纳米管,可以实现煤炭资源的高效利用,减少环境污染,为煤炭行业的发展提供新途径。以煤基聚苯胺为碳氮源,分别以乙酸镍或柠檬酸铁为碳源热解催化剂,以二茂镍、乙酸镍或二茂铁为碳管生长催化剂,采用催化热解-化学气相沉积耦合法成功制备出了三种高石墨化程度的掺N碳微纳米管。并对其进行了SEM、TEM、XRD、Raman、XPS等结构测试和甲醇氧化电催化剂载体应用测试,结果发现：三种掺N碳微纳米管的微观形态多样,有直立管、弯曲管、竹节状管等。二茂镍和二茂铁适合生长长而直的碳管,乙酸镍适合生长短而弯的碳管。二茂镍和乙酸镍所长碳管收率相当,约为5.8%（质量）;二茂铁所长碳管收率较高,为21.2%（质量）。N元素主要以石墨型N掺入三种碳微纳米管中,乙酸镍所长碳管的掺N量最高,为1.17%（质量）,且表现出良好的电催化剂载体性能。     

Improving the electrocapacitive properties of mesoporous CMK-5 carbon with carbon nanotubes and nitrogen doping

Nitrogen-containing carbon composite materials composed of mesoporous carbon CMK-5 and carbon nanotubes (CNTs) were prepared by the chemical vapor deposition method with Fe(NO₃)₃-impregnated SBA-15 as template and pyridine as the carbon precursor. The Fe nanoparticles confined in the channels of SBA-15 induced the formation of mesoporous carbon characteristic of CMK-5, whereas Fe particles homogeneously dispersed on the external surface of SBA-15 served as catalysts for CNTs growth. The contents of CNTs, the N doping level and the microstruture of the carbon composite were closely related to the initial Fe/Si atomic ratio in SBA-15 template. Incorporation of CNTs in the composite was found to substantially reduce the electric resistance, leading to the composite materials exhibiting excellent rate-performance. A maximum specific capacitance of 208 F/g and a power density of 10 kW/kg were achieved in 6.0 mol/L KOH aqueous electrolyte when these carbon composites were applied as supercapacitor electrodes. Moreover, the composite electrode also exhibited good electrochemical stability with no capacitance loss after 1000 cycles of galvanostatic charge-discharge process.     

Iridium,carbon and nitrogen multiple-doped TiO2 Nanoparticles with enhanced photocatalytic activity

The aim of this research is to enhance the photocatalytic activity of TiO₂ nanoparticles for the UV–visible light by multiple-doping with Iridium, carbon and nitrogen. The tridoped TiO₂ photocatalyst were prepared by wet chemical method, and characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible light diffuse reflection spectroscopy and room temperature photoluminescence spectroscopy. Besides, the photocatalytic H₂ evolution performance of Ir-C-N tridoped TiO₂ under UV–visible light irradiation was evaluated. It was found that Ir existed as Ir⁴⁺ by substituting Ti in the lattice of TiO₂; meanwhile, C and N were also incorporated into the surface of TiO₂ nanoparticles in interstitial mode. Meanwhile, Ir-C-N tridoping extended the absorption of TiO₂ into the visible light region and narrowed its band gap to ~3.0 eV, resulting in enhanced photocatalytic H₂ evolution under UV–visible light irradiation. This could be attributed to narrow band gap and proper electronic structure of TiO₂ after Ir-C-N tridoping.     

Selective preparation of carbon nanoflakes,carbon nanospheres,and carbon nanotubes through carbonization of polymethacrylate by using different catalyst precursors

This work reports the selective preparation of different kinds of carbon nanomaterials through carbonization of polymethacrylate (PMA)/organophilic clay (Oclay) composite by just changing the catalyst precursors. The morphologies and structures of the carbon materials were characterized by Scanning and Transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The result indicated that the catalyst precusors had a strong influence on the morphologies and yields of the obtained products. Carbon nanoflakes were produced when iron oxide was used as the catalyst precursor, cobalt oxide favored the formation of carbon nanospheres, while carbon nanotubes occurred over nickel oxide. The presence of Oclay plallets was determined to prevent the pyrolytic carbon species of PMA in the system from escaping, thus relatively more carbon nanomaterials were obtained. Based on the experimental observations, a possible mechanism was discussed for illustrating the growth process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1029‐1037, 2013     

空心纳米Ni@SiO2复合材料的制备及其催化性能

分别在非离子表面活性剂聚醚L44、聚醚L64、壬基酚聚氧乙烯醚NP-7、脂肪醇聚氧乙烯醚AEO-7、曲拉通X-100和聚乙二醇十六烷基醚(Brij-58)与环己烷构成的反相微乳液体系中,从Ni(NO3)2出发,经水合肼还原、正硅酸四乙酯水解包覆、焙烧、还原,得到不同结构的空心纳米SiO2包覆镍(Ni@SiO2)复合材料...     

空心纳米镍@SiO2复合材料的制备及其催化性能

分别在非离子表面活性剂聚醚 L-44、聚醚 L-64、壬基酚聚氧乙烯醚NP-7、脂肪醇聚氧乙烯醚AEO-7、曲拉通 X-100和聚乙二醇十六烷基醚与环己烷构成的反胶束体系中，从硝酸镍出发，经水合肼还原镍离子、正硅酸四乙酯水解包覆、焙烧、还原，得到不同结构的空心二氧化硅包覆镍复合材料Ni@SiO2，通过TEM、XRD表征材料结构和组成。结果显示，当以聚乙二醇十六烷基醚为模板剂时，制备出球形空心Ni@SiO2；以聚醚 L44、聚醚 L64、NP-7、AEO-7和曲拉通 X-100为模板时，制备出管状空心Ni@SiO2。对空心Ni@SiO2-Brij-58形成机理进行了研究。以催化NaBH4还原对硝基苯酚为模型反应，研究了空心Ni@SiO2-Brij-58的催化性能，结果显示15 min内反应完全，对硝基苯酚转化率97.6%。     

Synthesis,surface characteristics,and electrochemical capacitance of Cu-doped carbon xerogel microspheres

Small-amplitude oscillatory shear tests were used to determine the rheological properties of a copper acetate-doped resorcinol–formaldehyde mixture at between 30 and 40 °C. The apparent activation energy of the sol–gel transition was 76.6 ± 0.6 kJ/mol. Organic gel microspheres were only obtained when the sol was emulsified immediately before the gelation point and not at the gelation point itself, due to the fast gelation kinetics of the copper acetate-doped resorcinol–formaldehyde mixture. The microspherical shape was preserved after carbonization. Cu-doped carbon xerogel microspheres were steam-activated at 840 °C. All samples comprised isolated well-formed microspheres, whose size increased with higher degree of activation. The surface area and porosity varied with the activation degree. Copper was detected as CuO, which acted as gasification catalyst during activation, and its size increased with higher activation degree. Electrochemical measurements were conducted with a three-electrode cell in 1 M H₂SO₄. A very large volumetric capacitance, 146 F/cm³, was found for the 30%-activated Cu-doped activated carbon xerogel, attributable to the high particle density resulting from the very compact packing of the microspheres. This sample also showed the lowest equivalent series resistance, due to its pore texture and high surface Cu content.     

Synthesis of multi-walled carbon nanotube-tungsten carbide composites by the reduction and carbonization process

Multi-walled carbon nanotube-tungsten carbide composites were prepared by the reduction and carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO₃ precursor by molecular level mixing and calcination. The pre-prepared MWCNT-tungsten carbide composites were characterized by scanning electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction. The results showed that the one-dimensional (1D) nanostructure of the MWCNTs was destroyed by the direct carbonization reaction between the MWCNTs and the WO₃ precursor without an additional carbon source. Moreover, pure MWCNT-tungsten carbide composites were difficult to obtain. With the additional carbon source CH₄, pure MWCNT-tungsten carbide composites were prepared, and the 1D nanostructure of the MWCNTs was retained.