Pitch-based Carbons Research Articles

Graphitized Pitch-Based Carbons with Ordered Nanopores Synthesized by Using Colloidal Crystals as Templates

A highly graphitized ordered nanoporous carbon (ONC) was synthesized by using commercial mesophase pitch as carbon precursor and siliceous colloidal crystal as template. Since silica colloids of different sizes (above 6 nm) and narrow particle size distribution are commercially available, the pore size tailoring in the resulting ONCs is possible.

Structural evolution of Eucalyptus tar pitch-based carbons during carbonization

Abstract Wood tar pitches are generated as by-products by the charcoal manufacturing industry. They have a macromolecular structure constituted mainly by phenolic, guaiacylic, and siringylic units common to lignin. Due to their characteristics, biopitches are been investigated as precursors of carbon materials such as carbon fibers, bioelectrodes and activated carbons. In the present work the structural evolution of Eucalyptus tar pitches under carbonization is investigated, which is important for the improvement of planning and control of pitch processing and end-product properties during carbon material production. The studies involve X-ray diffraction and infrared analyses, besides helium density, BET surface area and BJH pore volume measurements. The results showed that the conversion of pitch into carbon basically involves three steps: (1) Up to around 600 °C the material has an highly disordered structure, being the release of aliphatic side chains and volatiles the main events taking place. (2) Between 600 °C and 800 °C, condensation of aromatic rings occurs to form bi-dimensional hexagonal networks so that micro- and mesoporosity are developed. The 800 °C-coke is constituted by two phases: one highly disordered and another more crystalline. (3) Over 800 °C, both phases are gradually ordered. As defects are gradually removed, surface area and porosity decrease, approaching zero for the 2100 °C-coke.

Novel pitch-based carbons with bimodal distribution of uniform mesopores

A new method is proposed for the synthesis of pitch-based carbons with bimodal distribution of uniform mesopores formed by co-imprinting of spherical silica colloids and hexagonally ordered mesoporous particles of SBA-15 into mesophase pitch particles and subsequent silica dissolution.

Further carbonization of anisotropic and isotropic pitch-based carbons by microwave irradiation

Isotropic (PFO) and anisotropic (NMP) pitch-based carbon powders thermally carbonized above 600°C were carbonized further by microwave irradiation under inert gases, Ar and N 2. The temperature of the carbon powder during microwave irradiation was measured by an Inconel sheathed thermocouple. The sample under Ar gas showed higher temperature than that under N 2 gas before exhibition of the Ar arc discharge. The temperature increased in the early stage and decreased when the irradiation was continued. The irradiation increased the L c(002) value and electric conductivity with no significant differences in values between isotropic and anisotropic pitch-based carbons. The results were explained on the basis of the mechanism of inductive heating from the material’s resistance to electron movement leading to similar morphological structure with lapse of irradiation time. However, the morphological structural differences between the isotropic and anisotropic carbons reflect on the variations of L c(002) and d (002) values with irradiation time. d (002) of anisotropic carbon showed minimum and maximum behaviors with the increase in L c(002) value indicating stacking in advance and subsequently reduction in d (002) values of the uniformly ordered crystallites. On the other hand, d (002) values of isotropic carbons decreased monotonically with increasing L c(002) values, reflecting the wide distributions of the crystallite sizes in the isotropic carbon. Microwave irradiation for 30 min effectively increased the L c(002) value comparable with the value of NMP-based carbon thermally heat treated at 1500°C for 1 h.

Electron spin resonance behavior of pitch-based carbons in the heat treatment temperature range of 1100–2000 °c

An electron spin resonance (ESR) study in combination with X-ray diffraction has been made on carbons prepared from a coal-tar pitch through heat treatments in the range of 1100–2000 °C. ESR spectra were observed for specimens heat-treated at 1100 °C or less and 1500 °C or higher, but hardly detected for those treated ca 1250 °C unless a high amplification technique was employed. The heat treatment time dependence measurement supports that carbon layer segments formed by the carbonization reaction are combined each other in a large scale at near 1250 °C so as to remove the structural defects carrying unpaired electrons.

Pyrolysed pitch-polysilane blends for use as anode materials in lithium ion batteries

Blends of pitch and silane polymers, (Me 2Si) x (PhMeSi) y , with various pitch/polymer ratios were pyrolysed at 1000 °C. Some of the pyrolysed mixtures demonstrated large reversible capacities for lithium insertion (over 600 mAh/g), small irreversible capacities (150–200 mAh/g) and small hysteresis between charge and discharge cycles. The reversible capacity increases approximately linearly with increased silicon content up to about 30% Si by weight. X-ray diffraction measurements for these materials show patterns similar to those of disordered carbons, suggesting a nanodispersion of silicon atoms in pitch-based carbons. Pyrolysed pitch-polysilane blends are good alternatives to carbons for anode materials in lithium ion batteries.