Graphitic Carbon Matrix Research Articles

General synthesis of magnetic mesoporous FeNi/graphitic carbon nanocomposites and their application for dye adsorption

A series of magnetic mesoporous FeNi/graphitic carbon nanocomposites have been synthesized through a simple nanocasting method using mesoporous silica SBA-15 as the template. Metal nitrates and natural soybean oil are respectively used as the magnetic particle precursors and carbon source, which can be infiltrated into the silica template after impregnation, grinding mix and heat treatment. X-ray diffraction, nitrogen adsorption–desorption, inductively coupled plasma mass spectrometry, transmission electron microscopy, vibrating-sample magnetometry and thermogravimetric analysis techniques are used to characterize the samples. It is observed that high content of magnetic FeNi alloy nanocrystals with the sizes of about 3–6nm are well homodispersed into the walls of graphitic mesoporous carbon matrix, and the resulting nanocomposites have a uniform mesostructure with a high specific surface area, large pore volume, and high saturation magnetization. Because of these characteristics, the obtained magnetic mesoporous FeNi/graphitic carbon nanocomposites can be used as efficient and recycled adsorbents in the removal of dye from wastewater.

Magnetically-separable hierarchically porous carbon monoliths with partially graphitized structures as excellent adsorbents for dyes

Magnetically-separable hierarchically porous carbon monoliths with partially graphitized structures were synthesized through confinement self-assembly in polyurethane (PU) foam associated with a direct carbonization process from triblock copolymer F127, phenolic resol and ferric nitrate. It was observed that the magnetic Fe nanoparticles were embedded in the walls of graphitic porous carbon matrix, and the resulting materials exhibited hierarchically porous structure with macropores of 100–450 μm, mesopore size of 4.8 nm, BET surface area of 723 m2/g, pore volume of 0.46 cm3/g, and saturation magnetization of 3.1 emu/g. Using methylene blue as model dye pollutant in water, the carbon monolith materials showed high adsorption capacity of 190 mg/g, exhibiting excellent adsorption characteristics desirable for the application in adsorption of dyes and easy separation under an external magnetic field.

Deriving a CO2-permselective carbon membrane from a multilayered matrix of polyion complexes.

A multilayered assembly consisting of polyion complexes was developed over porous ceramic as a unique precursor for a carbon membrane (CM). This specific layer was attained through in situ polymerization of N-methylpyrrole (mPy) over a prime coating layer of poly(4-styrenesulfonic acid) (PSSA) with an embedded oxidant on the ceramic surface. Extensive ion-pair complexation between the sulfonic acid groups of PSSA and the tertiary amine groups of the resulting poly(N-methylpyrrole) (PmPy) sustains this assembly layer. Incorporating cetyltrimethylammonium bromide (CTAB) into the PSSA is critical in facilitating the infiltration of mPy into the PSSA layer and promoting interfacial contact between the two polymers. Upon pyrolysis, the precursor coating was collectively converted into a carbon composite matrix. Such copyrolysis restrains the grain sizes of the carbonized PmPy, thereby halting defects in the resultant carbonaceous matrix. The gas separation performances of the CMs obtained at various graphitization temperatures showed that the least graphitized carbon matrix exhibited the best selectivity of CO2/CH4 = 167 with a CO2 permeability of 7.19 Barrer. This specific feature is attributed to both imine and imide pendant groups that function as selective adsorption sites for CO2 in the carbon skeleton.

Magnetic Nanocomposites Formed by FeNi3 Nanoparticles Embedded in Graphene. Application as Supercapacitors

A general family of magnetic nanocomposites formed by FeNi3 ferromagnetic nanoparticles (NPs) embedded in a graphitized carbon matrix is reported. The soft chemical approach used relies on the catalytic effect of the NPs resulting from the thermal decomposition of the layered double hydroxide precursor, which acts as a multilayered nanoreactor enabling the formation of a range of carbon nanoforms (CNFs). This is followed by acid treatment of the as‐prepared nanocomposites to isolate the different CNFs formed. These range from carbon nano‐onions to graphene depending on the temperature of the thermal decomposition. This synthetic process paves the way for the rational design of metal–carbon nanocomposites with controllable composition as precursors of nanocarbons or even graphene. The coexistence of metal NPs and nanostructured carbon is a major source of applications. As a proof of concept, the electrochemical performance of these metal–carbon hybrid supercapacitors is studied under high discharging current densities and they exhibit high values of specific capacitance and excellent rate capabilities.

Formation of tungsten carbide nanoparticles on graphitized carbon to facilitate the oxygen reduction reaction

Tungsten carbide nanoparticles with the average size less than 5 nm uniformly dispersed on the graphitized carbon matrix have been successfully synthesized by a one-step ion-exchange method. This route is to locally anchor the interested species based on an ionic level exchange process using ion-exchange resin. The advantage of this method is the size control of targeted nanomaterial as well as the graphitization of resin at low temperatures catalyzed by iron salt. The Pt nanoparticles coupled with tungsten carbide nanoparticles on graphitized carbon nanoarchitecture form a stable electrocatalyst (Pt/WC–GC). The typical Pt/WC–GC electrocatalyst gives a Pt-mass activity of 247.7 mA mgPt−1, which is much higher than that of commercial Pt/C electrocatalyst (107.1 mA mgPt−1) for oxygen reduction reaction due to the synergistic effect between Pt and WC. The presented method is simple and could be readily scaled up for mass production of the nanomaterials.

Growth of Hexagonal Columnar Nanograin Structured SiC Thin Films on Silicon Substrates with Graphene-Graphitic Carbon Nanoflakes Templates from Solid Carbon Sources.

We report a new method for growing hexagonal columnar nanograin structured silicon carbide (SiC) thin films on silicon substrates by using graphene–graphitic carbon nanoflakes (GGNs) templates from solid carbon sources. The growth was carried out in a conventional low pressure chemical vapor deposition system (LPCVD). The GGNs are small plates with lateral sizes of around 100 nm and overlap each other, and are made up of nanosized multilayer graphene and graphitic carbon matrix (GCM). Long and straight SiC nanograins with hexagonal shapes, and with lateral sizes of around 200–400 nm are synthesized on the GGNs, which form compact SiC thin films.

Hierarchically mesostructured TiO2/graphitic carbon composite as a new efficient photocatalyst for the reduction of CO2 under simulated solar irradiation

A hierarchically mesostructured TiO2/graphitic carbon composite photocatalyst with a high content of nanocrystalline TiO2 was prepared using a simple one-step nanocasting route. X-ray diffraction, thermogravimetric analysis, nitrogen adsorption–desorption, transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize this photocatalyst. It was observed that the coexistence of silica and graphitic carbon during the high temperature treatment stabilized the crystalline phase and the size of the anatase TiO2 nanocrystals (5–7 nm in diameter), which were uniformly dispersed in the graphitic carbon matrix after silica removal. The obtained hierarchically mesostructured TiO2/graphitic carbon composite photocatalyst with a high specific surface area and a high surface concentration of hydroxyl groups exhibited considerably higher activity in the photocatalytic reduction of CO2 with H2O under simulated solar irradiation compared to mesostructured anatase TiO2 prepared using a sol–gel method.

A simple solid–liquid grinding/templating route for the synthesis of magnetic iron/graphitic mesoporous carbon composites

Magnetic iron/graphitic mesoporous carbon composites were prepared by a simple one-step solid–liquid grinding/templating route. X-ray diffraction, nitrogen adsorption–desorption, transmission electron microscopy, vibrating-sample magnetometry and thermogravimetric analysis were used to characterize the samples. It was observed that a high content of magnetic iron nanoparticles could be embedded in the walls of graphitic mesoporous carbon matrix, and the resulting materials have a hierarchical mesostructure with a high specific surface area, large pore volume, and high saturation magnetization, giving the materials wide potential applications as catalyst supports and adsorbents.

Layered Graphitic Carbon Host Formation during Liquid-free Solid State Growth of Metal Pyrophosphates

We report a successful ligand- and liquid-free solid state route to form metal pyrophosphates within a layered graphitic carbon matrix through a single step approach involving pyrolysis of previously synthesized organometallic derivatives of a cyclotriphosphazene. In this case, we show how single crystal Mn(2)P(2)O(7) can be formed on either the micro- or the nanoscale in the complete absence of solvents or solutions by an efficient combustion process using rationally designed macromolecular trimer precursors, and present evidence and a mechanism for layered graphite host formation. Using in situ Raman spectroscopy, infrared spectroscopy, X-ray diffraction, high resolution electron microscopy, thermogravimetric and differential scanning calorimetric analysis, and near-edge X-ray absorption fine structure examination, we monitor the formation process of a layered, graphitic carbon in the matrix. The identification of thermally and electrically conductive graphitic carbon host formation is important for the further development of this general ligand-free synthetic approach for inorganic nanocrystal growth in the solid state, and can be extended to form a range of transition metals pyrophosphates. For important energy storage applications, the method gives the ability to form oxide and (pyro)phosphates within a conductive, intercalation possible, graphitic carbon as host-guest composites directly on substrates for high rate Li-ion battery and emerging alternative positive electrode materials.

Laser Ablation Synthesis of Silver Nanoparticles Embedded in Graphitic Carbon Matrix

Laser Ablation Synthesis of Silver Nanoparticles Embedded in Graphitic Carbon Matrix

Template-Free One-Pot Synthesis of Porous Binary and Ternary Metal Nitride@N-Doped Carbon Composites from Ionic Liquids

Herein we present a straightforward synthesis approach toward composites of titanium, vanadium, and titanium–vanadium nitride nanoparticles embedded in nitrogen-doped carbon. These materials can be easily prepared via the heat treatment of mixtures of the corresponding metal precursors TiCl4 or VOCl3 dissolved in the ionic liquid 1-butyl-3-methyl-pyridinium dicyanamide (Bmp-dca) as the nitrogen/carbon source. WAXS diffractograms and TEM pictures of the resulting materials reveal the presence of highly crystalline metal nitride nanoparticles with an average diameter of 5 nm embedded in a graphitic carbon matrix. XPS measurements show that the carbon network is heavily doped with nitrogen; that is, it can be described as a nitrogen-doped carbon. Nitrogen sorption measurements show type I isotherms indicative of mainly microporous composites. The specific BET surface area increases with increasing amount of the metal precursor, and it is also dependent on the respective metal ion used. Under similar syntheti...

Synthesis of organic–inorganic hybrids by miniemulsion polymerization and their application for electrochemical energy storage

A general method is reported for creating functional organic–inorganic hybrid materials by copolymerization of organic molecules and inorganic compounds. The approach is based on a miniemulsion polymerization technique followed by a thermal pyrolysis step, and yields nanostructured composites in which nanoparticles are uniformly embedded in a porous, partially graphitic carbon matrix. The method builds upon our previous report disclosing synthesis of organic–inorganic hybrids using miniemulsion polymerization and demonstrates that ex situ engineering of the inorganic phase leads to remarkably improved function. We specifically show that depending upon the chemistry of the starting materials, nanoscale organic–inorganic hybrid materials created using the approach are attractive as anodes and cathodes for next-generation lithium and other rechargeable battery systems. Additionally, we show that the platform is very versatile and through ex situ conversion or utilization of multiple precursors, can be applied to various classes of materials including metal oxides, metals, metal sulfides and alloys. The approach also lends itself to the development of scalable processes for production of nanostructured battery materials.

Fischer−Tropsch Synthesis in a Slurry Reactor Using a Nanoiron Carbide Catalyst Produced by a Plasma Spray Technique

A new catalyst, composed of iron carbide nanoparticles (FeCNPs) and synthesized by plasma-spraying technology, was tested for Fischer−Tropsch synthesis (FTS) in a continuously stirred slurry reactor. The plasma-produced FeCNPs were core−matrix structures (FeC-rich core inside a graphitic carbon matrix) which protected air-sensitive carbides, preventing oxidation during their handling. The reactant used for FTS testing was simulated syngas with a composition similar to that obtained from air gasification of urban waste. This work reports the optimization of a new nanocatalyst reduction/activation protocol aimed at maximizing catalyst activity and a 100-h-long test performed to examine the catalyst’s behavior over time. The catalyst was compared with Nanocat commercial nanoiron powder, and the results showed that its activity and robustness were higher. Conversion with the Nanocat catalyst was slightly but not statistically significantly lower than with the plasma-produced catalyst. However, 6% CH4 selectivity with the plasma-produced catalyst was significantly lower than the 10% obtained with Nanocat.

The effect of precursor system on the resistivity and oxidation susceptibility of C/SiC nanocomposites en route to electronic grade nanomaterials

Presented are results of a study on specific technological properties of affordable C/SiC composite nanomaterials obtained via pyrolysis of several pitch/silicon-bearing precursor systems (elemental Si, silica SiO 2, poly(carbomethylsilane) [–CH 2–Si(H)CH 3–] n , commercial SiC). For pyrolysis at 1300 °C, the formation of nanosized SiC is detected in the systems with elemental Si and poly(carbomethylsilane) while 1650 °C pyrolysis is required for silica to achieve such conversion. In situ formed nano-SiC is homogeneously dispersed in the simultaneously evolving graphitic carbon matrix of the composites. Reactivities vs. CO 2, electrical resistivities, and surface properties of the nanocomposites are determined. Significant differences and patterns in the properties among the materials obtained from these precursor systems and at the selected pyrolysis temperatures are clearly established. Among others, the data suggest potential for carbon removal from the most reactive nanocomposites via reactions with CO 2 to yield unique nano-SiC powder products for further processing towards electronic and ceramic applications.

Silver nanoparticles encapsulated in carbon cages obtained by co-sputtering of the metal and graphite

We have synthesized C–Ag thin films by co-sputtering of a silver–graphite target. The deposition temperature ranged from 77 K to 773 K, the silver concentration varying from 10 to 71 at%. The microstructure of the films has been characterized by transmission electron microscopy (TEM) and small-angle X-ray scattering under grazing incidence (GISAXS) experiments. It is shown that homogeneously distributed silver nanoparticles, having an elongated shape along the direction of the thin film growth, are formed within a more or less graphitized carbon matrix. After liquid nitrogen and room temperature depositions, a preferential crystallographic orientation is observed, dense (111) silver planes being at 90° with respect to the surface layer whereas the carbon matrix is amorphous. A graphitization leading to the encapsulation of the silver nanoparticles in graphite-like carbon has been obtained when the depositions were performed at 773 K for lower silver concentrations without ion-beam assistance and below 573 K for upper silver concentrations with ion-beam assistance. We propose that the demixing of carbon and silver occurs during the co-deposition process by surface diffusion of C and Ag atoms. It is inferred that the presence of silver simply serves as a “catalyst” for the graphitization process at these relatively low temperatures. Furthermore, we have investigated the tribological properties of our C–Ag coatings: a substantial increase in the wear resistance and a significant decrease in friction relative to an austenitic stainless steel substrate is observed.