Polycarbosilane (PCS) fibers have been made using a solvent which is a mixture of N,N-dimethylformamide (DMF) in toluene. Polycarbosilanes (PCS) obtained from NaBond with concentration 1.2 g/ml dissolved in solution toluene and N,N-dimethylformamide (DMF) was stirred gently for 24 h at ambient temperature. DMF was mixed with toluene at ratios 22%, 24%, 26%, 28% and 30%. Electrospinning apparatus (nanoE-Spinning) from NaBond was used. In a vertical electrospinning set up, the solution in a glass syringe delivered to the tip of a 6-gauge (0.5 mm inner diameter) stainless steel needle. The tip to collector distance was adjusted to 100 mm with applied high voltage at 10kV. A stainless steel plate with dimension 100 mm x 100 mm wrapped by aluminum foil was used as collector. The electrospinning non-woven fiber was cured at temperature 200°C (2°C/min), for 1h, 1.5h, and 2h, and fibers with DMF concentration 30% was also pyrolysis at 1000 °C for 3 h in inert atmosphere. The samples were tested and observed with FTIR spectroscopy, and SEM-EDS apparatus. The results showed that PCS fibers can be made from dissolving PCS with toluene with the addition of DMF to increase the polarity of the solvent and the formation of fibers is done by using electrospinning which is supported by the presence of voltage from the outside. Fiber curing is done at 200 °C to evaporate the toluene, the DMF, and resulting stronger fibers than before. The addition concentration of DMF in toluene and curing time will affect the composition of the resulting PCS fiber. Curing time on PCS fibers will affect the composition of solvents such as DMF and Si-H bond on which to assert their PCS fiber cross linking conditions. PCS fiber morphology is known of changes in fiber diameter and fiber uniformity. Smallest PCS fiber average diameter 4.81 μm resulted from 28% DMF with curing time 2 hours and the largest achieved from 22% DMF with curing time 1 hour around 14.22 μm. Composition of pyrolyzed fiber was SiO0.587C0.413, with average density 3.1033 g/cc and average diameter the fiber was 3.06 μm.

Polycarbosilane (PCS) solution was used to form PCS fibers by electrospinning and curing them by thermal process. The cured PCS fibers were then pyrolized under inert atmosphere to obtain silicon oxycarbide (SiOC) fibers. The PCS solution contained 1.2 g/mL PCS with 30% N, N-dimethylformamide (DMF)/70% toluene. The needle inner diameters used for spinning were 0.5 and 0.3 mm and variation for the applied voltage were 10, 12 and 14 kV. The electrospun PCS fibers were cured at 200°C in oxygen atmosphere for 1 hour and then pyrolyzed at 1000°C in inert atmosphere for 1 hour. Nonwoven SiOC fibers diameter ranging between 3 to 8 µm were analyzed by SEM and EDS. The oxygen embodied on the surface of cured PCS fibers arising during the curing process resulted in the SiOC fibers with larger diameters. Rapid solvent evaporation during the pyrolysis caused the SiOC fibers to have ribbon-shapes.

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2014 Nous avons mesuré les dépendances angulaires de la largeur de raie de RPE et du facteur g en bande X et à la température ambiante dans le trichlorure cuivrique de cyclo-hexyl-ammonium (ou CHAC). Nous avons déterminé également la dépendance de la largeur de raie avec la température entre 30 et 300 K.

Single phase samples of Na1-xCaxCo2O4 (with x = 0, 0.1, 0.2 and 0.3) are prepared by utilizing a solid state reaction process, and the Ca2+ substitution effect on thermoelectric properties is then observed. On the samples, the increment of Ca2+ substitution results in the increase of resistivity and thermo power properties. The Ca2+ substitution in NaCo2O4 reduces charge carriers of the samples. This phenomenon indicates that there are many holes in the samples and it is consistent with the positive sign of thermo power. It demonstrates that the Ca2+ substitution is effective to enhance thermoelectric properties.