Al2O3 has received wide attention with established use as a catalyst and growing application in structural or functional ceramic materials. On the other hand, the boehmite (AlO(OH)) obtained by sol-gel process has exhibited a decrease in surface area during phase transformation due to a decline in surface active site at high temperature. In this work, Al2O3-CuO/ZnO (ACZ) and Al2O3-CuO/CeO (ACC) composite materials were synthesized with aluminum isopropoxide, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate or zinc (II) nitrate hexahydrate. Moreover, the Span 80 as the template block copolymer was added to the ACZ/ACC composition to make nano size particles and to keep increasing the surface area. The ACZ/ACC synthesized powders were characterized by Thermogravimetry-Differential Thermal analysis (TG/DTA), X-ray Diffractometer (XRD), Field-Emmision Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller (BET) surface analysis and thermal electrical conductivity (ZEM-2:M8/L). An enhancement of surface area with the addition to Span 80 surfactant was observed in the ACZ powders from 105 m2/g to 142 m2/g, and the ACC powders from 103 m2/g to 140 m2/g, respectively.

Composites of ceramic powders and an elastomer-based matrix were prepared by mixing CaCO3 powders with polyethylene and polypropylene elastomers, and their mechanical and sound insulation properties were measured. CaCO3 powders with 0.7 μm and 35 μm particle size were added to elastomers up to 80 wt%. Scanning electron microscopy photographs showed uniform distribution of the CaCO3 powders in the matrix. While density and surface hardness increased, melt index, tensile strength and elongation of the composites decreased as the amount of added CaCO3 powders increased. As more CaCO3 powders were added sound transmission loss of the composites increased owing to the increase of density. Addition of 0.7 μm sized CaCO3 powders resulted in a slightly higher transmission loss than the addition of 35 μm sized powders because of the increased interface area between the elastomer matrix and the CaCO3 powders. Composites with a polyethylene matrix showed higher transmission loss than those with a polypropylene matrix because the tensile strength and hardness of the polyethylene-based composites were low and their elongation was high.

In this study, activated carbon (AC) as a carbon source was modified with different concentrations of cobalt chloride (CoCl2) to prepare a Co-AC composite, and it was used for the preparation of Co-AC/TiO2 composites with titanium oxysulfate (TOS) as the titanium precursor. The physicochemical properties of the prepared Co-AC/TiO2 composites were characterized by N2 adsorption at 77 K, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. The photocatalytic treatments of organic dyes were examined under an irradiation of visible light with different irradiation times. N2 adsorption data showed that the composites had decreased surface area compared with the pristine AC, which was 389 m2/g. From the XRD results, the Co-AC/TiO2 composites contained a mixturephase structuresof anatase and rutile, but a cobalt oxide phase was not detected in the XRD pattern. The EDX results of the Co-AC/TiO2 composites confirmed the presence of various elements, namely, C, O, Ti, and Co. Subsequently, the decomposition of methylene orange (MO, C14H14N3NaO3S) and rhodamine B (Rh.B, C28H31ClN2O3) in an aqueous solution, respectively, showed the combined effects of an adsorption effect by AC and the photo degradation effect by TiO2. Especially, the Co particles in the Co-AC/TiO2 composites could enhance the photo degradation behaviors of TiO2 under visible light.

Dispersion of the functionalized multiwalled nanotubes (MWNT) in the polyurethane (PU) matrix and DC conductivity of the MWNT/PU composites are investigated with the oxidation conditions, the kind of surfactants and their content. First, the most optimal surfactant type and its critical micelle concentration in the MWNT suspension are determined as a cationic surfactant, benzalkonium chloride (BKC) of 0.6 wt.% to the MWNT content from DEA and FESEM results. All the MWNT oxidized under several conditions are negatively charged and functionalized with carboxylic group, whereas the degree of damage is different from oxidation conditions. In addition, each MWNT/PU composite derived from several oxidation conditions shows different DC conductivity at a characteristic MWNT content. It is found that in order to enhance DC conductivity of the polymeric composites containing the oxidized MWNT the better dispersion of MWNT should be obtained by effective functionalities and surfactant adsorption with preserving the intrinsic geometry of pristine MWNT.

In this paper two aspects of the percolation and conductivity of carbon black-filled polyethylene matrix composites will be discussed. Firstly, the percolation behavior, the critical exponent of conductivity of these composites, are discussed based on studying the whole change of resistivity, the relationship between frequency and relative permittivity or ac conductivity. There are two transitions of resistivity for carbon black filling. Below the first transition, resistivity shows an ohmic behavior and its value is almost the same as that of the matrix. Between the first and second transition, the change in resistivity is very sharp, and a non-ohmic electric field dependence of current has been observed. Secondly, the electrical conduction property of the carbon black-filled polyethylene matrix composites below the percolation threshold is discussed with the hopping conduction model. This study investigates the electrical conduction property of the composites below the percolation threshold based on the frequency dependence of conductivity in the range of 20 Hz to 1 MHz. There are two components for the observed ac loss current. One is independent of frequency that becomes prevalent in low frequencies just below the percolation threshold and under a high electrical field. The other is proportional to the frequency of the applied ac voltage in high frequencies and its origin is not clear. These results support the conclusion that the electrical conduction mechanism below the percolation threshold is tunneling.

The fabrication of interconnect from titanium powders and powders is investigated. Corrosion-resistant titanium and are used as reinforcement in order to reveal high heat and corrosion resistance at the elevated temperature. We fabricated the plates for interconnect reinforced with by mixing titanium powders with 10 wt.% of nano-sized . Spark Plasma Sintering (SPS) was chosen for the sintering of these composites. The plate made of titanium powders and powders demonstrates higher corrosion resistance than that of the plate of titanium powders alone. The physical properties of specimens were analyzed by performing hardness test and biaxial strength test. The electrochemical properties, such as corrosion resistance and hydrogen permeability at high temperature, were also investigated. The microstructures of the specimens were investigated by FESEM and profiles of chemical compositions were analyzed by EDX.

Carbon-nanotube-embedded bismuth telluride (CNT/) matrix composites were fabricated by a powder metallurgy process. Composite powders, whereby 5 vol.% of functionalized CNTs were homogeneously mixed with alloying powders, were successfully synthesized by using high-energy ball milling process. The powders were consolidated into bulk CNT/ composites by spark plasma sintering process at for 10 min. The fabricated composites showed the uniform mixing and homogeneous dispersion of CNTs in the matrix. Seebeck coefficient of CNT/ composites reveals that the composite has n-type semiconducting characteristics with values ranging to with increasing temperature. Furthermore, the significant reduction in thermal conductivity has been clearly observed in the composites. The results showed that CNT addition to thermoelectric materials could be useful method to obtain high thermoelectric performance.

It is necessary to develop new methods to prevent catastrophic failure of structural material in order to avoid accidents and conserve natural and energy resources. Design of intelligent materials with a self-diagnosing function to prevent fatal fracture of structural materials was achieved by smart composites consisting of carbon fiber tows or carbon powders with a small value of ultimate elongation and glass fiber tows with a large value of ultimate elongation. The changes in electrical resistance of CF-GFRP/GFRP (carbon fiber and glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased abruptly with increasing strain, and a tremendous change was seen at the transition point where carbon fiber tows were broken. Therefore, the composites were not to monitor damage from the early stage. On the other hand, the change in electrical resistance of CP-GFRP/GFRP (carbon powder dispersed in glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased almost linearly in proportion to strain. CP-GFRP/GFRP composites are superior to CF-GFRP/GFRP composites in terms of their capability to monitor damage by measuring change in electrical resistance from the early stage of damage. However, the former was inferior to the latter as an application because of the difficulties of mass production and high cost. A method based on monitoring damage by measuring changes in the electrical resistance of structural materials is promising for improved reliability of the material.

The (1-x)La0.7Sr0.3MnO3(LSMO)/xZnFe2O4(ZFO) (x = 0, 0.01, 0.03, 0.06 and 0.09) composites were prepared by a conventional solid-state reaction method. We investigated the structural properties, magnetic properties and electrical transport properties of (1-x)LSMO/xZFO composites using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-cooled dc magnetization and magnetoresistance (MR) measurements. The XRD and SEM results indicate that LSMO and ZFO coexist in the composites and the ZFO mostly segregates at the grain boundaries of LSMO, which agreed well with the results of the magnetic measurements. The resistivity of the samples increased by the increase of the ZFO doping level. A clear metal-to-insulator (M-I) transition was observed at 360K in pure LSMO. The introduction of ZFO further downshifted the transition temperature (350K-160K) while the transition disappeared in the sample (x = 0.09) and it presented insulating/semiconducting behavior in the measured temperature range (100K to 400K). The MR was measured in the presence of the 10kOe field. Compared with pure LSMO, the enhancement of low-field magnetoresistance (LFMR) was observed in the composites. It was clearly observed that the magnetoresistance effect of x = 0.03 was enhanced at room temperature range. These phenomena can be explained using the double-exchange (DE) mechanism, the grain boundary effect and the intrinsic transport properties together.

Titanium dioxide (TiO2) particles deposited on different quantitative Fe-treated carbon nanotube (CNT) composites with high photocatalytic activity of visible light were prepared by a modified sol-gel method using TNB as a titanium source. The composites were characterized by BET, XRD, SEM, TEM and EDX, which showed that the BET surface area was related to the adsorption capacity for each composite. From TEM images, surface and structural characterization of for the CNT surface had been carried out. The XRD results showed that the Fe-ACF/TiO2 composite mostly contained an anatase structure with a Fe-mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in the Fe-CNT/TiO2 composites. The photocatalytic activity of the composites was examined by degradation of methylene blue (MB) in aqueous solution under visible light, which was found to depend on the amount of CNT. The highest photocatalytic activity among the different composites was related to the optimal content of CNT in the Fe-CNT/TiO2 composites. In particular, the photocatalytic activity of the Fe-CNT/TiO2 composites under visible light was better than that of the CNT/TiO2 composites due to the introduction of Fe particles.

본 논문은 국내에서 최초로 완전 복합신소재 교량을 현장 적용하여， 실제 차량하중 재하실험 및 공용 중 내 하력 평가를 실시 하였고 설계 제작 설치 등을 기술하였다. 현장적용에 앞서 교량상부구조 설계에 대한 검증을 위해 축소모형 교량상부구조를 제작하여 실내실험을 실시 하였다. 실험결과의 타당성을 검증하고자 유한요소해석의 결과와 비교하였다 분석된 자료는 향후 복합신소재 교량의 설계 제작 설치에 대해 기초자료로 제공될 수 있기 를 기대한다. 장기거동 성능에 대한 충분한 데이터가 없지만 복합신소재가 소형 교량에 혁신적인 재료임을 본 연구를 통하여 확인할 수 있다. 그리고 현장재하실험을 통한 공용중인 상태에서 복합신소재 교량의 내하력등급을 통하여 장기 성능실험에 대한 자료를 제공할 수 있었다. 따라서 본 자료는 복합신소재 교량의 장기 성능평가에 자료로 제공 될 수 있다 .

Methylene blue (MB) was degraded by TiO2 and ZnO deposited on an activated carbon fiber (ACF) surface under UV light. The ACF/TiO2 and ACF/ZnO composites were characterized by BET, SEM, XRD, and EDX. The BET surface area was related to the adsorption capacity for composites. The SEM results showed that titanium dioxide and zinc oxide are distributed on the ACF surface. The XRD results showed that the ACF/TiO2 and ACF/ZnO composites contained a unique anatase structure for TiO2 and a typical hexagonal phase for ZnO respectively. These EDX spectra showed the presence of peaks of Ti element on ACF/TiO2 composite and peaks of Zn element on the ACF/ZnO composite. The blank experiments for either illuminating the MB solution or the suspension containing ACF/TiO2 or ACF/ZnO in the dark showed that both illumination and the catalyst were necessary for the mineralization of organic dye. Additionally, the ACF/TiO2 composites proved to be efficient photocatalysts due to degradation of MB at higher reaction rates. The addition of an oxidant ([NH4]2S2O8) led to an increase of the degradation rate of MB for ACF/TiO2 and ACF/ZnO composites.

Temperature dependency of resistivity of the carbon black-polyethylene composites below and above percolation threshold is studied based on the electrical conduction mechanism. Temperature coefficient of resistance of the composites below percolation threshold changed from minus to plus, increasing volume fraction of carbon black; this trend decreased with increasing volume fraction of carbon black. The temperature dependence of resistivity of the composites below percolation threshold can be explained with a tunneling conduction model by incorporating the effect of thermal expansion of the composites into a tunneling gap. Temperature coefficient of resistance of the composites above percolation threshold was positive and its absolute value increased with increasing volume fraction of carbon black. By assuming that the electrical conduction through percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of carbon black, the temperature dependency of the resistivity above percolation threshold has been well explained without violating the universal law of conductivity. The apparent activation energy is estimated to be 0.14 eV.

based composites are candidate materials for ultra-high temperature materials (UHTMs). has become an indispensable ingredient in UHTMs, due to its high melting temperature, relatively low density, and excellent resistance to thermal shock or oxidation. powders are usually synthesized by solid state reactions such as carbothermal, borothermal, or combined carbothermal reaction. SiC is added to this system in order to enhance the oxidation resistance of . In this study, ?based composites were successfully synthesized and densified through two different processing paths. or 25 vol.%SiC was fully synthesized from oxide starting materials with reducing agents after heat treatment at 1400. Besides, ?20 vol.%SiC was fully densified with as a sintering additive after hot pressing at 1900. The synthesis mechanism and the effect of sintering additives on densification of ?SiC composites were also discussed.

Diamond/SiC composites are appropriate candidate materials for heat conduction as well as high temperature abrasive materials because they do not form liquid phase at high temperature. Diamond/SiC composite consists of diamond particles embedded in a SiC binding matrix. SiC is a hard material with strong covalent bonds having similar structure and thermal expansion with diamond. Interfacial reaction plays an important role in diamond/SiC composites. Diamond/SiC composites were fabricated by high temperature and high pressure (HPHT) sintering with different diamond content, single diamond particle size and bi-modal diamond particle size, and also the effects of composition of diamond and silicon on microstructure, mechanical properties and thermal properties of diamond/SiC composite were investigated. The critical factors influencing the dynamics of reaction between diamond and silicon, such as graphitization process and phase composition, were characterized. Key factor to enhance mechanical and thermal properties of diamond/SiC composites is to keep strong interfacial bonding at diamond/SiC composites and homogeneous dispersion of diamond particles in SiC matrix.

We investigated the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with a thin layer of 1 wt% Al-doped ZnO using rf magnetron sputtering deposition. Morphological studies clearly revealed that the ZnO appeared to form beadshaped crystalline nanoparticles with an average diameter as small as 30 nm, attaching to the surface of the nanotubes. It was found that the NO gas sensing properties of the ZnO-CNT layered composites were dramatically improved over Al-doped ZnO thin films. It is reasoned from these observations that an increase in the surface-to-volume ratio associated with the numerous ZnO “nanobeads” on the surface of the CNTs results in the enhancement of the NO gas sensing properties. The ZnO-CNT layered composite sensors exhibited a maximum sensitivity of 13.7 to 2 ppm NO gas at a temperature of 200˚C and a low NO gas detection limit of 0.2 ppm in dry air.