Wenming Qiao

Preparation of an activated carbon artifact: oxidative modification of coconut shell-based carbon to improve the strength

Coconut shell-based activated carbon was oxidized in aq. H2SO4, HNO3 and H2O2 to induce surface oxygen functional groups on its surface and to increase the mechanical strength of the resultant activated carbon artifact with PVB as a binder. Although all oxidation was confirmed to significantly increase the strength, aq. H2O2 was found to be most effective, giving strength as high as 6000 kPa, which is believed to be sufficient for the electrode of an electric double layer capacitor (EDLC). The increase of CO2 evolving groups induced on the surface of activated carbon appears to be responsible for the strength increase. There was an optimum extent of oxidation for the strength as well as the performance of the electrode. Too much oxidation reduces the electrical conductivity of the activated carbon. Facile oxidation by aq. H2O2 can be recommended as a practical modification of the surface since it takes place safely below 100°C without releasing any harmful gas.

Catalysts in syntheses of carbon and carbon precursors

Materiais de carbono tem sido aplicados em diferentes campos, devido ao seu desempenho e aplicacao unicos. Naturalmente, as estruturas fisicas e quimicas dos precursores de carbono e materiais de carbono definem as suas propriedades e aplicacoes. Os catalisadores apresentam um papel importante na sintese de precursores de carbono e materiais de carbono, por controlar a quimica composicional e molecular na transformacao de substratos orgânicos em carbono, atraves de intermediarios carbonaceos. Um desempenho maior dos materiais de carbono pode ser obtido, a custos mais baixos, atraves da selecao cuidadosa de catalisadores e processos cataliticos adequados na sintese de fontes de carbono, na carbonizacao, ativacao, grafitizacao, modificacao de precursores de carbono e no crescimento destes materiais de carbono.

Preparation of an activated carbon artifact: factors influencing strength when using a thermoplastic polymer as binder

An activated carbon artifact was prepared through mixing, moulding, curing and carbonizing, using polyvinylbutyral resin (PVB) as the binder, dibutyl phthalate (DBP) as a plasticizing agent and isocyanuric acid ester as a cross-linking agent to clarify influential factors on its strength. Preparation conditions such as moulding pressure, temperature and time of curing, carbonization and the amount of cross-linking agent were varied to find their influences on the strength of the resultant form. The form was observed under SEM of wide scope to find correlations between its morphology and strength. The closed packing of the activated carbon filler and the plastic binder was always favorable to develop the strength of the form. The curing extent of PVB, which was influenced by curing atmosphere, temperature and time, and cross-linking agent, was found to govern the strength of the forms. Air or oxygen is very essential for the curing. The optimum temperature was found to be 200°C and longer curing time is beneficial to improve the strength. The cross-linking agent improved the strength of the form up to 7000 kPa through accelerating the cross-linkage of PVB resin. Sufficient curing allows the rapid heating up to 10°C/min for the development of the strength by maintaining the shape of the form. The thermoplastic powders are highly dispersed onto the surface of activated carbons and are cured sufficiently there to adhere the activated carbon grains. Sufficient curing stabilizes the thermoplastic polymer to be thermosetting, anchoring the grains through the carbon bond for higher strength of the carbonized form. PVB resin is cured into heat-resisting cross-linked chains through oxidative condensation onto the activated carbon surface where the oxygen functional groups appear to play important roles in the curing.