A quantitative analysis of a trace amount of hydrogen in high temperature heat-treated carbons

A technique to determine a trace amount of hydrogen in carbon materials heat-treated above 1000 °C was developed. Three types of carbons prepared from poly(furfulyl alcohol), poly(vinyl chloride) and mesophase carbon microbeads were heat-treated at various temperatures ranging from 1000 to 1800 °C. Then they were gasified by O₂ in a fixed bed flow reactor, and the H₂O gases formed during the gasification processes were carefully monitored with a Karl Fischer moisture analyzer. As a result, this method makes it possible to determine the hydrogen contents in the carbons down to three places of decimals as a weight percent and can detect even a trace amount of hydrogen as low as 0.002 wt.%. A possible chemical structure of carbon edge sites was also discussed based on the experimentally determined hydrogen contents.     

Preparation of helical carbon and graphite films using morphology-retaining carbonization

Helical carbon and graphite films were prepared from iodine-doped helical polyacetylene (H-PA) film using currently developing morphology-retaining carbonization. It was found from scanning electron microscopy (SEM) observations that the hierarchical helical morphology of the H-PA film remains unchanged even after the carbonization at 800 °C. Besides, the weight loss of the film due to the carbonization was very small, which was only a few percent to the weight of the film before doping. Furthermore, the graphite film prepared by the subsequent heating at 2600 °C still retained the same morphology as those in the original H-PA film and in the helical carbon film prepared at 800 °C. X-ray diffraction (XRD) and Raman scattering measurements were then pursued. The results showed that graphitic crystallization proceeds in the carbon film through the heat treatment at 2600 °C. Transmission electron microscopy (TEM) image of a single helical graphitic fibril was also observed by ultrasonicating the graphite film in ethanol. Carbonization of the H-PA films by way of iodine doping was found to afford helical carbon and graphite films, where spiral morphologies and even helical fibril structures were completely preserved.     

Operation for chronic pulmonary thromboembolism accompanied by thrombophilia in 8 patients

BACKGROUND: Medical therapy for chronic pulmonary thromboembolism is limited, and surgical treatment has become more frequent recently. We have performed pulmonary thromboendarterectomy on 8 patients with chronic pulmonary thromboembolism accompanied by thrombophilia. METHODS: The patients were 6 men and 2 women aged 21 to 56 years (mean, 35 years). Five patients had antiphospholipid syndrome, 2 had protein C deficiency, and 1 had congenital antithrombin III deficiency. The preoperative condition was New York Heart Association functional class III in 5 and class IV in 3. Hypoxemia, marked pulmonary hypertension (mean pulmonary artery pressure, 47+/-6.7 mm Hg), and low cardiac output were observed in all patients. After a median sternotomy, deep hypothermia was induced using a cardiopulmonary bypass, and pulmonary thromboendarterectomy in the bilateral pulmonary arteries was performed under intermittent circulatory arrest. RESULTS: There were no operative deaths. Long-term respiratory management was needed postoperatively by 3 patients. In the remaining 5 patients, no reperfusion injury was observed. The arterial blood oxygen concentration improved, and the mean pulmonary pressure decreased to 16+/-5.5 mm Hg. The cardiac output also increased, and New York Heart Association functional class improved to I in 4 and II in 4 patients. CONCLUSION: Pulmonary thromboendarterectomy under deep hypothermic intermittent circulatory arrest was effective for chronic pulmonary thromboembolism accompanied by thrombophilia for which medical treatment is of limited value.     

Tubular-shaped nanocarbons prepared from polyaniline synthesized by a self-assembly process and their electrical conductivity

A tubular-shaped polyaniline less than 5 microm in length and 170 nm in outer diameter was synthesized by a self-assembly process using D-camphorsulfonic acid as a dopant. A tubular-shaped nanocarbon was prepared from the tubular-shaped polyaniline by means of pyrolysis at 1000 degrees C in argon gas. The structural and electrical properties of the resultant tubular-shaped nanocarbons were investigated using Raman scattering spectrum, X-ray diffraction measurements, scanning and transmission electron microscopes, and a low resistivity meter. The tubular-shaped nanocarbons are very short in length and are an amorphous state. The short length and amorphous tubular-shaped nanocarbon were crystallized to some extent by heat-treatment at 2600 degrees C. The tubular-shaped nanocarbons mentioned in this work are appropriate for mass production, compared to the well-known multi-walled carbon nanotubes. The electrical conductively of the tubular-shaped polyaniline was remarkably improved by the carbonization and was enhanced by the heat-treatment.     

Structural,rheological, and mechanical properties of ternary blends of PEN,PET, and liquid crystalline polymer

Structural, rheological, and mechanical properties of ternary blends of a liquid crystalline copolyester (LCP) composed of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, poly(ehtylene naphthalate)(PEN), and poly(ethylene terephtalate) (PET) were investigated using capillary rheometry, tensile testing, scanning electron microscopy, and X-ray diffraction. Viscosity-shear rate behavior of the ternary blends is very similar to that of pure polymers and their binary blends. The activation energy of flows of the ternary blends was smaller than those of PEN and PET. Tensile modulus and strength of extruded strands of the blends increased with increasing LCP content. The extruded strands of the blends consist of a crystalline and oriented LCP phase and an amorphous and unoriented PEN/PET blended phase. Tensile mechanical properties and structures of the ternary blends were discussed.     

Thermal behavior,morphology, and mechanical properties of blend strands consisting of poly(ethylene terephthalate) and semiaromatic liquid crystalline polymer

Polymer blends of poly(ethylene terephthalate) (PET) and a liquid crystalline polymer (LCP) [random copolymers of the poly(ethylene telephthalate) and poly (hydroxybenzoic acid)] were prepared by using a twin-screw extruder. Strands were extruded from a capillary die. Extruded stands were stretched in an oven at 80°C. DSC and SEM were employed to investigate the structural properties of the strands. Mechanical properties of the strands were evaluated by a sonic propagation method. DSC investigation suggested that LCP phases may act as a nucleating agent of PET and the orientation-induced crystallization of PET was accelerated by the presence of LCP. An SEM micrograph shows that the LCP phases formed finely spherical domains with a diameter of 0.1–1.0 μm in the PET matrix and large parts of LCP spherical droplets were deformed to fibrils. In the case of unstretched strands, sonic moduli increased linearly with increasing LCP content, because PET was reinforced by LCP fibrils as in the case of glass fiber-reinforced PET. The degree of crys-tallization of PET also increased with increasing LCP contents. In the case of stretched strands, sonic moduli increased with an increasing stretching ratio due to the orientation-induced crystallization of PET. A larger increasing of the sonic modulus was shown in LCP-containing strands in the regions of a low stretching ratio (1–5), since the orientation-induced crystallization of PET was accelerated by the presence of LCP phases. © 1996 John Wiley & Sons. Inc.