Selective doping of pyridinic nitrogen in carbon materials has attracted attention due to its significant properties for various applications such as catalysts and electrodes. However, selective doping of pyridinic nitrogen together with controlling skeletal structure is challenging in the absence of catalysts. In this work, four precursors including four fused aromatic rings and pyridinic nitrogen were simply carbonized in the absence of catalysts in order to attain mass synthesis at low cost and a high percentage of pyridinic nitrogen in carbon materials with controlled edges. Among four precursors, dibenzo[f,h] quinoline (DQ) showed an extremely high percentage of pyridinic nitrogen (96 and 86%) after heat treatment at 923 and 973 K, respectively. Experimental spectroscopic analyses combined with calculated spectroscopic analyses using density functional theory calculations unveiled that the C-H next to the pyridinic nitrogen in DQ generated gulf edge structures with controlled pyridinic nitrogen after carbonization. By comparing the reactivities among the four precursors, three main factors required for maintaining the pyridinic nitrogen in carbon materials with controlled edges, such as (1) high thermal stability of the pyridinic nitrogen, (2) the presence of one pyridinic nitrogen in one ring, and (3) the formation of gulf edges including pyridinic nitrogen to protect the pyridinic nitrogen by the C-H groups on the gulf edges, were revealed.

Cu matrix composites reinforced with chopped carbon fiber (CF), which is cost effective and can be well dispersed, are fabricated using electroless plating and hot pressing, and the effects of content and alignment of CF on the thermal properties of CF/Cu composites are studied. Thermal conductivity of CF/Cu composite increases with CF content in the in-plane direction, but it decreases above 10% CF; this is due to reduction of thermal diffusivity related with phonon scattering by agglomeration of CF. The coefficient of thermal expansion decreases in the in-plane direction and increases in the through-plane direction as the CF content increases. This is because the coefficient of thermal expansion of the long axis of CF is smaller than that of the Cu matrix, and the coefficient of thermal expansion of its short axis is larger than that of the Cu matrix. The thermal conductivity is greatly influenced by the agglomeration of CF in the CF/Cu composite, whereas the coefficient of thermal expansion is more influenced by the alignment of CF than the aggregation of CF.

In this work, the effects of maleic anhydride (MA) content on mechanical properties of chopped carbon fibers (CFs)-reinforced MA-grafted-polypropylene (MAPP) matrix composites. A direct oxyfluorination on CF surfaces was applied to increase the interfacial strength between the CFs and MAPP matrix. The mechanical properties of the CFs/MAPP composites are likely to be different in terms of MA content. Surface characteristics were observed by scanning electron microscope, Fourier transform infrared spectroscopy, and single fiber contact angle method. The mechanical properties of the composites were also measured by a critical stress intensity factor (KIC). From the KIC test results, the KIC values were increased to a maximum value of 3.4 MPa with the 0.1 % of MA in the PP, and then decreased with higher MA content.

This paper investigates the dependency of the critical content for electrical conductivity of carbon powder-filled polymer matrix composites with different matrixes as a function of the carbon powder content (volume fraction) to find the break point of the relationships between the carbon powder content and the electrical conductivity. The electrical conductivity jumps by as much as ten orders of magnitude at the break point. The critical carbon powder content corresponding to the break point in electrical conductivity varies according to the matrix species and tends to increase with an increase in the surface tension of the matrix. In order to explain the dependency of the critical carbon content on the matrix species, a simple equation (Vc* = [1 + 3(γc1/2 − γm1/2)2/(ΔqcR]−1) was derived under some assumptions, the most important of which was that when the interfacial excess energy introduced by particles of carbon powder into the matrix reaches a universal value (Δqc), the particles of carbon powder begin to coagulate so as to avoid any further increase in the energy and to form networks that facilitate electrical conduction. The equation well explains the dependency through surface tension, surface tensions between the particles of carbon powder.

PURPOSES: This study investigates the mechanical performance of carbon-capturing concrete that mainly contains blast furnace slag. METHODS: The mixture variables were considered; these included Portland cement content, which was varied from 10% to 40% of the blast furnace slag by weight. The specimens were exposed to different conditions such as high N2 and O2 concentrations, laboratory conditions and high CO2 conditions. Mechanical performances, including compressive and flexural strengths and carbon-capturing depth, were evaluated. RESULTS : The slump, air content and unit weight were not affected significantly by the variation in cement content. The strength development when the specimens were exposed to high purity air was slightly greater than that when exposed to high CO2. As the cement content increased the compressive and flexural strength increased but not considerably. The carbon-capturing capacity decreased as the cement content increased. The specimens exposed in the field for 70 days had flexural strength greater than 3 MPa. CONCLUSIONS : The results indicate that cement content is not an important parameter in the development of compressive and flexural strengths. However, the carbon-capturing depth was higher for less cement content. Even after field exposure for 70 days, neither any significant damage on the surface nor any decrease in strength was observed.

Fly ash is one of the aluminosilicate sources used for the synthesis of geopolymers. The particle size distribution of fly ash and the content of unburned carbon residue are known to affect the compressive strength of geopolymers. In this study, the effects of particle size and unburned carbon content of fly ash on the compressive strength of geopolymers have been studied over a compositional range in geopolymer gels. Unburned carbon was effectively separated in the -46μm fraction using an air classifier and the fixed carbon content declined from 3.04 wt% to 0.06 wt%. The mean particle size (d50) decreased from 22.17μm to 10.79μm. Size separation of fly ash by air classification resulted in reduced particle size and carbon residue content with a collateral increase in reactivity with alkali activators. Geopolymers produced from carbon-free ash, which was separated by air classification, developed up to 50 % higher compressive strength compared to geopolymers synthesized from raw ash. It was presumed that porous carbon particles hinder geopolymerization by trapping vitreous spheres in the pores of carbon particles and allowing them to remain intact in spite of alkaline attack. The microstructure of the geopolymers did not vary considerably with compressive strength, but the highest connectivity of the geopolymer gel network was achieved when the Si/Al ratio of the geopolymer gel was 5.0.

In order to investigate the microstructure and mechanical properties of WC-10 wt% Co insert tool alloy fabricated by PIM (Powder Injection Molding) process, the feedstock of WC-10 wt% and wax used as a kind of binder were mixed together by two blade mixer. After injection molding, the debinding process was carried out by two-steps. First, solvent extraction, in which the binder was eliminated by putting the specimen into normal hexane for 24 hrs at , and subsequently thermal debinding which was conducted at and for 6 hrs in the mixed gas of , respectively. Meantime, in order to compensate the decarburization due to hydrogen, 1.2~1.8% of carbon was added to ensure the integrity of the phase. Finally, the specimens were sintered in vacuum under different temperatures, and the relative density of 99.8% and hardness of 2100 Hv can be achieved when sintered at , even the TRS is lower than the conventional sintering process.

We propose an evaluation method of the relative content of single-walled carbon nanotubes (SWCNT) in SWCNT soot synthesized by arc discharge using UV-VIS-NIR absorption spectroscopy. In this method, we consider the absorbance of semiconducting and metallic SWCNTs together to calculate the relative content of SWCNTs with respect to a highly purified reference. Our method provides the more reliable and realistic evaluation of SWCNT content with respect to the whole carbonaceous content than the previously reported method.

We measured the non-carbon content of single-walled carbon nanotubes (SWCNTs) in SWCNT soot using thermogravimetric analysis. The weight increased percentage by the oxidation of metal in the raw soot is well obtained by TGA graph which was confirmed with ICP-AES, XRD, and XPS. This work will be very useful for the purity precise evaluation of SWCNT with UN-vis-NIR spectroscopy.

The dry-milling technique was used for mixing and crushing oxides and graphite powders. The ratio of ball-to-powder was 30:1 and argon gas was filled in jar. The excess carbon was of the stoichiometric amount. The dry-milling was carried for 20 hours. The mixed powders were reduced and carburized at for 3 hours flowing Ar gas in tube furnace. The dry-milled powders showed the wide diffraction patterns of X-ray. The reactions of reduction and carburization were completed in 3 hours at . After the reactions, the mean size of WC particles was about 200 nm. The content of free carbon in WC/Co mixed powders was less as the reaction temperature increased.

Unidirectional polymer composites were prepared using high-strength carbon fibers as reinforcement and phenolic resin as matrix precursor with keeping fiber volume fraction at 30, 40, 50 and 60% respectively. These composites were carbonized at 1000℃ and graphitised at 2600℃ in the inert atmosphere. The carbonized and graphitised composites were characterized for mechanical properties as well as microstructure. Microscopic studies were carried out of the polished surface of carbonized and graphitised composites after etching by chromic acid, to understand the effect of fiber volume fraction on oxidation at fiber-matrix interface. It is found that the flexural strength in polymer composites increases with fiber volume fraction and so does for the carbonised composites. However, the trend was found to be reversed in graphitised composites. In all the carbonized composites anisotropic region has been observed at fiber-matrix interface which transforms into columnar type microstructure upon graphitisation. The extension of strong and weak columnar type microstructure is function of fiber volume fraction. SEM microscopy of the etched surface of the sample reveal that composites containing 40% fiber volume has minimum oxidation at the interface, revealing a strong interfacial bonding.

시설 오이재배에서 조절가능한 환경요인들, 즉 광도, CO2 농도, 온도 그리고 엽중 질소 농도의 변화에 따른 양액재배 오이 엽의 총광합성 속도를 측정하였다. 광보상점은 10~20μmol.m-2 .s-1 정도로 낮았고 광포화점은 1000μmol.m-2 .s-1 이상이었으며, 오이의 총광합성 속도는 온도가 상승할수록 증가속도는 감소하지만 지속적인 증가를 보였으나 24~32℃ 사이에서 광합성 속도는 큰 차이를 보이지 않아 이 범위가 오이 생육에 대한 적정온도인 것으로 나타났다. CO2 보상점은 20-40μmol.mol-1 사이에 위치하였고 CO2포화점은 1200μmol.mol-1이상으로 나타났으며 엽중은 질소함량의 증가에 따른 잎의 총광합성 속도의 변화는 sigmoid형의 증가추세를 보였다. 요인들간의 상호작용 효과에서는 모든 경우 상승적으로 나타나, 한 요인의 수준이 증가함에 따라 타 요인의 수준의 증가에 따른 총광합성 속도도 상승적을 증가하였다. 각환경요인의 변화와 요인들간의 상호작용에 따른 총광합성 속도의 변화에 대한 수리적 모형을 개발하였다. 이들 모형은 시설 내 환경변이에 따른 오이의 생육 내지는 수량에서의 차이를 밝히는데 이용될 수 있으며 오이의 식물생장 모형이나 더 나아가 경영합리화를 위한 오이 생산 전문가 시스템의 개발에 필요한 기초 자료로 이용될 수 있을 것이다.

The effect of carbon content on the shape of WC grains dispersed in the Co-rich matrix during liquid phase sintering of WC-35%Co hard metals has been determined. The shape of WC grains was observed using SEM stereography after removing cobalt matrix with boiling hydrochloric acid solution. The WC grains changed from hexagonal to trigonal prism as the carbon content increased in the two-phase region of(WC + - Co), while the morphology of WC grains changed from trigonal to hexagonal shape as the carbon content decreased. The morphology of WC grains changes reversibly along with carbon loss or carbon pick-up. Morphology change of WC grains is attributed to crystal structure of WC, which has an asymmetric array of carbon atoms. There are two types of prismatic planes having different numbers of broken W-C bonds in WC grains. It is scrutinized that as the carbon content increases, the high energy prism planes grow fast and the crystals change from hexagonal to trigonal shape. On the other hand, when the carbon content decreases, the high energy prism planes are dissolved accompanying split of (100) plane into (101) and (101) planes.

The effects of the carbon content ranging from 17.5 to 21.0 wt.% in TiC-30vol.% cenmet and the content raging from 0 to 30 wt.% in TiC-20 vol.% cermet were investigated in the relation to the microstures and harbness. The speciment were sintered at 140, 143 and 145 for 60minutes. The results were summarized as follows; 1) The shrinkages and relative densitites of the specimens were incrased up to 20.0 wt.% C and then decreased. 2) The grains of TiC were almost the same size with the different content of carbon. Free carbons were appeared on the microstrures when carbon was added over 20.5 wt.% while TiC and l were formed when carbon was added below 20.0 wt.%; 3) The lattice parameters of the and TiC phases were increased up to 20.5 wt.% C, and then saturated. 4) The hardess was increased up to 20.0 wt.% C, and then decreased. 5) The made the TiC grains fine and the surrounding structure around TiC gains. 6) The micropores were decreased with increasing the binder and the sintering temperature. 7) The lattice parameter of the l ana TiC were almost the samp up to 10 wt.% and then decreased. 8) The hatdness was increased up to 5wt.% and then decreased owing to the micrpores. 9) The more the binder phase, the higher the relative density and the proper amount of cermets were obtained.