Precursors For Carbon Materials Research Articles

Structural Evolution of Poly(acrylonitrile-co-itaconic acid) during Thermal Oxidative Stabilization for Carbon Materials

Fourier transform infrared spectroscopy (FT-IR) is employed for the quantitative tracking of the structural evolution of poly(acrylonitrile-co-itaconic acid) (PAI) with different itaconic acid (IA) contents during its thermal oxidative stabilization (TOS). The TOS process includes cyclization, oxidation and tautomerization, as characterized by the evolution of the overlapping peaks of cyclic C═C, C═N, N–H and C═O vibrations in FT-IR. The second derivatives of the spectra facilitate the identification of the position of each contributing structure. The following peak-fitting operations and the determination of the molar absorption coefficients using model compounds allow the quantitative tracking of the extent of the TOS process. PAI containing approximately 3 mol % IA exhibits the most efficient TOS process in terms of cyclization, oxygen uptake and dehydrogenation reactions. A quantitative investigation of the evolution of PAI using FT-IR is an efficient way to determine the optimal structural characteristics of the precursors for carbon materials.

Protic ionic liquids extract asphaltenes from direct coal liquefaction residue at room temperature

Asphaltenes in direct coal liquefaction residue (DCLR) are highly aromatic and polydisperse mixtures, which are important precursors for producing high value-added carbon materials. In this research, a series of protic ionic liquids (PILs) with organic carboxylate anions were synthesized and applied to extract asphaltenes from DCLR at room temperature. The extracts were characterized by elemental analysis, FTIR, 13C-NMR, quinoline insolubles tests and so on. The results show that asphaltenes with the potential of precursors of carbon materials can be separated from DCLR at room temperature using PILs and the solid–liquid separation is carried out facilely due to the lower viscosities of PILs. The influences of PILs structures on extraction yields and atomic ratios of H/C were also investigated. As alkyl chain length of PILs anions increases, extraction yields of asphaltenes increase while H/C ratios decrease. Moreover, extraction yields vary with various cations of PILs and increase according to the order of N-methylimidazolium ([MIM]+)<triethylammonium ([TEtA]+)<3-methylpyridinium ([MPy]+), but H/C ratios decrease following the order of N-methylimidazolium ([MIM]+)>triethylammonium ([TEtA]+)>3-methylpyridinium ( [MPy]+). The asphaltenes extracted from DCLR with PILs have the excellent properties for preparing carbon materials, such as lower H/C ratios, higher aromaticities, lower sulfur contents and nearly no quinoline insolubles.

High carbon yield thermoset resin based on phenolic resin, hyperbranched polyborate, and paraformaldehyde

AbstractHyperbranched polyborate (HBPB) is a new hyperbranched polymer with excellent thermal resistance, which can be used to improve the thermal stability, especially carbon yield, of phenolic resin (PR). In the present paper, thermal properties and curing degrees of the blends of PR and HBPB (PR–HBPB blends) are investigated. It is found that the curing degrees of PR–HBPB blends would be decreased, and the decrease of curing degree can be attributed to the improper ratio of phenol groups of HBPB to hydroxymethyl groups of PR. Paraformaldehyde (PFM) is introduced to remedy the deficiency of hydroxymethyl groups in PR–HBPB blends. The curing degrees of PR–HBPB blends are improved and the carbon yields of the blends of PR, HBPB, and PFM (PR–HBPB–PFM blends) can be up to 75–80% at 800°C in nitrogen. PR–HBPB–PFM blends can be explored as novel precursors for carbon materials with excellent properties, ease of preparation and low cost. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Direct synthesis of a carbonaceous fuel cell catalyst from solid containing small organic molecules and metal salts

In contrast to conventional solid materials used as precursors for carbon materials, which are typically organic polymers and macromolecules, a solid of relatively small organic molecules mixed with metal salts was directly used to form a functional carbon material. Heat treatment of a mixture of 1,4-diamino-2,3-dicyano-9,10-anthraquinone, Fe gluconate, and Mg acetate produced a highly porous carbon material functioning as a noble-metal-free fuel cell cathode catalyst with Fe coordinated by N atoms embedded in the pore surface as the active sites. Its function was confirmed by electricity generation in a polymer electrolyte fuel cell formed using it in the cathode. The high durability of the fuel cell was demonstrated by its continuous operation. This study showed the possibility of forming a wide variety of finely designed functional carbon materials by the proper selection of small organic molecules and metals.

The effect of heat-treatment temperature on structure and properties of TiB 2/C composites

Mesocarbon microbeads are an excellent precursor for carbon materials, because of their ability to self-sinter. TiB 2/C composites were prepared from mesocarbon microbeads with TiB 2 additions by pressureless sintering. The effect of heat treatment temperature on microstructure and fracture behavior of the products was investigated. Liquid formation and resultant layered structures were observed when the composite was heat treated at 2800 K or above. Low levels of TiB 2 (5 vol%) addition improved the fracture toughness. At these levels the catalytic effect on graphitization was low and the size of TiB 2 particles decreased significantly because of their interaction with the mesocarbon microbeads. When the content of TiB 2 in the composite was 20% by volume, the mesophase carbon was transformed completely into graphite under the influence of a eutectic liquid, as shown by XRD analysis and fractography, which led to a dramatic decrease in fracture toughness. XRD analysis and laser ablation ICP-MS indicate that boron diffused into the carbon matrix when composites were heat treated above 2700 K. Resistance of the composite materials to crack propagation increased further when finer TiB 2 particles were used, and eventually, TiB 2/C composites with fracture toughness as high as 1.92 MPa m 0.5 were obtained.

05/00592 Supercritical gas extracts from low-quality coals: on the search of new precursors for carbon materials

05/00592 Supercritical gas extracts from low-quality coals: on the search of new precursors for carbon materials

Supercritical gas extracts from low-quality coals: on the search of new precursors for carbon materials

This paper studies the chemical composition of several supercritical gas (SCG) extracts and its influence on the thermal behaviour under carbonisation conditions. The extracts were obtained from a Spanish lignite (Mequinenza), a low-quality coal from the point of view of energy applications. The lignite was treated with toluene, ethanol (EtOH) and tetrahydrofuran (THF) as solvents under different supercritical temperature and pressure conditions. The extracts display high aliphatic nature and enhanced concentrations of oxygen functional groups, aided by the contribution of hydrogenation and oxygen incorporation reactions occurring in the SCG extraction with EtOH and THF. Thiophenic compounds are also present in great concentrations derived from the exceptionally high organic sulphur content of the parent coal. The carbonisation of the extracts renders anisotropic material with fine mosaic texture, as a consequence of the significant thermal reactivity inferred by the aliphatic and oxygenated groups. The size of the mosaic increases with the temperature of the SCG extraction and varies with the supercritical solvent in the order: toluene<EtOH<THF.

Supercritical gas extracts from low-quality coals: on the search of new precursors for carbon materials

This paper studies the chemical composition of several supercritical gas (SCG) extracts and its influence on the thermal behaviour under carbonisation conditions. The extracts were obtained from a Spanish lignite (Mequinenza), a low-quality coal from the point of view of energy applications. The lignite was treated with toluene, ethanol (EtOH) and tetrahydrofuran (THF) as solvents under different supercritical temperature and pressure conditions. The extracts display high aliphatic nature and enhanced concentrations of oxygen functional groups, aided by the contribution of hydrogenation and oxygen incorporation reactions occurring in the SCG extraction with EtOH and THF. Thiophenic compounds are also present in great concentrations derived from the exceptionally high organic sulphur content of the parent coal. The carbonisation of the extracts renders anisotropic material with fine mosaic texture, as a consequence of the significant thermal reactivity inferred by the aliphatic and oxygenated groups. The size of the mosaic increases with the temperature of the SCG extraction and varies with the supercritical solvent in the order: toluene<EtOH<THF.

Preparation of Carbon Materials from Chemically Stabilized Vinyl-type Polymers

Vinyl-type polymers are attractive as precursor for carbon materials because of their high carbon content and good processability. If these polymers are exposed to a carbonization atmosphere, however a large mass loss and fusion usually take place. Thus, some additional treatment for enhancing the thermal stability of the polymers is required prior to carbonization, and this treatment is referred to as stabilization. Since most of vinyl-type polymers are thermally decomposed only at temperatures above their melting points, it is difficult to stabilize them with a low-temperature heat-treatment in air. It is known that the treatments with chemical agents can convert vinyl-type polymers to the thermal resistant polymers. The present authors have developed the novel production processes of carbon materials from various vinyl-type polymers by using a combination of chemical treatment and high-temperature heat-treatment. This paper reviews the structure and properties of viny-type polymer-based carbon materials.