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SiC fibers can be obtained by the spinning, curing, and heat treatment of polycarbosilane (PCS); however, the properties of the PCS precursor must be considered to set the correct spinning conditions. Although many studies have focused on the synthesis conditions, the characterization (in particular, the structural characteristics) of PCS fibers, and the polymer itself has limitations. In this study, PCS was prepared in two steps, and the growth of the polymer with respect to the reaction conditions was analyzed. We found that PCS is formed and grown by the rearrangement and subsequent condensation reactions of polydimethylsilane (PDMS). Further, fiber formation was affected by the reaction temperature, time, and pressure. Three types of PCS were obtained under different synthetic conditions, and they were all characterized. Regardless of the structural similarity of the PCS fibers (based on the spectroscopic analysis), the polymers showed different thermal and rheological properties. Our findings will be important in improving the production of PCS fibers (and subsequent SiC fibers) with finely controlled properties.

By iodine curing of polycarbosilane fibers followed by sintering under a controlled atmosphere of carbon monoxide, a unique strategy is developed for the in situ growth of graphene networks inside silicon carbide fibers. In the resulting fibers, three-dimensionally interconnected few-layered graphene sheets are well-dispersed in the nanocrystalline SiC, allowing for fast electron transport through the graphene networks. The roles of iodine and carbon monoxide in fabricating the graphene-network embedded SiC fibers are elucidated. The distinct evolution of graphene structure was observed in the iodine-treated Si(O)C using transmission electron microscopy and Raman spectroscopy. The iodine incorporated in the fibers induces the sp2-hybridization of carbon, generating carbon–carbon double bonds and graphene seeds such as reduced graphene oxide, which are supposed to grow into graphene layers at elevated temperatures. Carbon monoxide is employed as a component of the atmospheric gas mixture during the decomposition of Si(O)C to suppress the evolution of SiO and CO gases, thereby restraining coarsening of SiC nanocrystallites and maintaining the integrity of the graphene network. These processes pave the way for designing graphene structures in polymer-derived ceramic materials for a broad range of applications.

The structural evolution of silicon carbide phase from polycarbosilane fibers cured with iodine in air was investigated using nuclear magnetic resonance (NMR) together with in situ gas analysis up to 1400 °C by thermogravimetry coupled with mass spectroscopy (TG-MS). The investigation with solid-state 1H, 13C, and 29Si NMR analyses showed the influence of the oxygen affinity of Si atoms on the chemical structural changes of the SiOCH system during pyrolysis (up to 800 °C). In particular, the mechanism of phase segregation (SiOC → β-SiC + SiO2 + C) in amorphous SiOC structure at 800–1250 °C was determined. Carbon in the Si–O–C networks is replaced by silicon, forming the Si-O-Si network, while the cleaved carbon atoms, which have unpaired electrons, combine, forming C=C bonds. This mechanism accounts for the structural rearrangement from O2SiC2 to O3SiC to SiO4 (from the silicon-centered standpoint, i.e., SiO2 phase), the growth of β-SiC crystallites, and the carbon clustering.

In this study, we prepared a perfectly ordered nacre-mimetic composite from plate-like alumina particles and epoxy resin using a rolling method. A specific feature of this method is that it progressively aligns the component particles along a single direction regardless of the product thickness at resin contents as low as 25 wt%. The obtained composite exhibited a strength as high as 200 MPa during bending. However, to examine the mechanical properties of artificial nacre, various factors such as the types of initial components and their particle sizes, contents, and orientation degrees must be considered. Hence, this study consists of two parts. The present work (which constitutes the first part) is focused on the orientation effect produced by the plate-like particles and deformation behavior of the composites observed at different orientation degrees. It was found that the obtained composite material with perfectly ordered particles exhibited pull-out behavior similar to that of natural nacre (including the crack propagation route). Further, the fracture toughness of the composite, which was higher than that of alumina, was also affected by its orientation degree.

We simultaneously conducted reduction and functionalization processes on graphene oxide (GO) in order to obtain functionalized reduced GO (rGO). One of the main barriers to the development of rGO is its poor dispersibility in water and polar solvents. Nevertheless, the rGO synthesized in this study exhibits high dispersibility in water. In this research, we prepared GO by oxidizing graphite using the Hummers method, and it was functionalized by 4-pyridine moiety using 4-hydrazinylpyridine graphene (rGO-4Py). The rGO-4Py was further functionalized by methylation using methylpyridinium iodide, producing reduced graphene oxide (rGO-4Py-MeI). The resulting rGO-4Py-MeI exhibited good dispersion in water due to the effect of the pyridinium. The rGO-4Py-MeI's potential as a nanocomposite filler was evaluated by mixing it into water-soluble poly(vinyl alcohol) (PVA). The tensile strength and modulus of the resulting rGO-4Py-MeI/PVA nanocomposites were measured for different loadings of rGO-4Py-Me. The PVA nanocomposite embedded with 1 wt % of rGO-4Py-MeI showed increases of 69% (88.77 MPa) and 86% (4.36 GPa) in tensile strength and tensile modulus compared to neat PVA, respectively.

Nacre is a natural organic-inorganic hybrid composite, whose hierarchical structure has a complex influence on its high strength. Many structural features have been discovered, which influence the mechanical properties of nacre, and the authors have a particular interest in the role of the asperities and organic-inorganic interactions. In this study, a composite was prepared which mimics the asperity structure using clay minerals. Organic-inorganic bonding was induced with silane treatment. Both factors increased the yield strength of the composites; however, different deformation behavior was exhibited. It was found that asperities improved the strength of the composite, and that composition influences the stiffness of the composite. The organic-inorganic interaction between the resin and the other components of the composite reduced the deformation of the composite and consequently improved strength.

Ash deposition of heat exchange boiler, caused mainly by accumulation of particulate matter, reduces heat transfer of the boiler system. Heat and mass transfer through porous media such as ash deposits mainly depend on the microstructure of deposited ash. Therefore, in this study, we investigated microstructural and thermal properties of the ash deposited on the boiler tube. Samples for this research were obtained from the fuel economizer tube in an industrial waste incinerator. To characterize microstructures of the ash deposit samples, scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD) and BET analysis were employed. The results revealed that it had a porous structure with small particles mostly of less than a few micrometers; the contents of Ca and S were 19.3, 22.6% and 18.5, 18.7%, respectively. Also, the results showed that it consisted mainly of anhydrite (CaSO₄) crystals. - The thermal conductivities of the ash deposit sample obtained from the economizer tube in industrial waste incinerator were measured to be 0.63 and 0.54 W/mK at 200℃, which were about 100 times less than the thermal conductivity (61.32 W/mK) of the boiler tube itself, indicating that ash deposition on the boiler tube was closely related to a decrease in boiler heat transfer.

Foam-type porous silicon carbide (SiC) ceramics without cracks and hollow struts were fabricated using the polymer replica method with polycarbosilane (PCS) and polyurethane (PU) foam as the starting materials. The synthesized porous SiC was analyzed using X-ray diffraction and scanning electron microscopy. The results revealed that a porous SiC ceramic structure was formed with a dense framework at a low temperature of 1200°C. During the heat-treatment process, the PCS experienced an organic–inorganic transformation and then converted to the SiC ceramics. It was determined that the organic–inorganic transformation of PCS, which was the stage of silicon oxycarbide formation, is affected by the curing condition. In this study, the optimum curing condition was determined to be an air atmosphere at 200°C for 7 h.

SiC powders having different purities were prepared by carbothermal reduction under different conditions from traditional process and SiC single crystals were grown by the PVT method from the powders. After crystal growth, boule was cut to wafers and they were polished for chemical and defect analyses. Total impurities including Al, B and Ti which were derived from powders decreased remarkably during crystal growth. The formation of defects including micropipe and dislocations such as TED, TSD and BPD was strongly influenced by impurity content. The effect of impurity seemed to be negligible at below 1ppm level for MPD. On the other hand, dislocations continuously decreased even more when higher purity SiC powder below 1ppm level was used.

Wireless Sensor Networks (WSNs) have been researched to detect various events on sensor fields. A lot of sensor nodes in a specific region called an event region around an event detect it and send reporting data to a sink. To reliably detect an event, reporting data should be reliably delivered to a sink in lossy networks such as WSNs with frequent path breakages. Multipath routing can be one of attractive approaches to cope with the lossy networks. However, if many sensor nodes in an event region construct their own multipaths to a sink and sends their own reporting data through the multipaths to the sink, the data cannot be reliably and energy-efficiently delivered to the sink due to concentration of a large number of data. Therefore, we propose an event-to-sink Multipath Routing protocol with Multiple Sources called MRMS that supports efficient and reliable data delivery from multiple sources in an event region to a sink. MRMS decides the number of multipaths for an event region. The number of multipaths is calculated with the number of sensor nodes in the event region, the data size, and the buffer size. Based on the number of multipath, MRMS divides the event region into sectors and constructs a multipath in each sector. Sensor nodes in each sector uses the multipath in their own sector as the primary path and the multipath in their neighbor sectors as the alternative path. MRMS also provides a multipath reconstruction method against the failure of a multipath. Simulation results conducted in various environments show that the proposed protocol achieves better performance than the well-known previous protocol.

In this study, alumina plates 9~25 μm in size were used as thermal fillers, and epoxy resin was used as a polymer matrix. Oriented alumina plate/epoxy composites were prepared using a rolling method. The effect of ordering alumina plates increased with alumina plate size. The thermal conductivity and flexural strength of the composites were investigated. The horizontal thermal conductivity of the oriented composite was significantly higher than the vertical thermal conductivity. The horizontal thermal conductivity of the 75 wt% alumina content was 8.78 W/mk, although the vertical thermal conductivity was 1.04 W/mk. Ordering of the alumina plate using a rolling method significantly improved the thermal conductivity in the horizontal direction. The flexural strengths of the ordered alumina/epoxy composites prepared at different curing temperatures were measured.

*Energy & Environmental Devision, Korea Institute of Ceramic Engineering and Technology,77 Digital-ro 10 gil, Geumcheon-gu, Seoul 153-801, Korea**Enbion Inc., 841 Tamnip-dong Yuseong-gu, Daejeon 305-501, Korea(Received 15 November 2014; Received in revised form 8 December 2014; accepted 11 December 2014)

Natural materials often have unique mechanical properties, such as the hierarchical structure of nacre formed through mineral bridges or asperities created between an inorganic particle and a natural-layer surface. As these asperities produce an exceptional shear resistance, in this study, we aimed to emulate the natural structure of nacre by synthesizing inorganic asperities and mineral bridges with different temperatures in the range of 1100 - 1300℃ and clay contents from 10 - 50 wt%. Following the infiltration of methyl methacrylate, we measured the mechanical properties to assess whether they were improved by the asperities. It was confirmed that the asperities improved the bending strength by 10%, and the anchoring effect was observed on the fracture surface.

Si(Al)ON precursor was synthesized by formation of new Si-N bond using organoaluminum imine and liquid type poly(phenyl carbosilane). It was decomposed between 200 - 600℃, and the ceramic yield was 51% after pyrolysis. 150 ? 200 ㎚ in thickness of coating film was obtained by spin coating method. The precursor was easily oxidized during process because it was unstable in air. However the oxygen content was limited to 0.5 - 0.7 to silicon in heat treatment step. Even though the content of nitrogen was decreased by pyrolysis, Al-N and Si-N bonds were formed in ammonia atmosphere, and Si(Al)ON film was formed with 0.2 in content to silicon.

SMC composites consist of chopped glass fiber as a reinforcements, polyester and mineral fillers. Among them, filler is one of the important factors for improving mechanical and thermal properties of composites, but it has not drawn much attention for SMC composites. In this study, the size effect of calcium carbonate as mineral filler on mechanical properties of SMC composites was discussed using five different sizes of commercial calcium carbonates without chopped fiber reinforcement, to focus on the size effect itself. The SMC process was modified to be suitable for a laboratory scale composed of three steps. The mean sizes of the calcium carbonates were 3 – 20 μm, and the specific surface areas were calculated to be 1 – 5 m2/g by BET. Small size of calcium carbonate having high surface area up to 4 m2/g showed high thermal resistance, and showed higher strength comparing to the large fillers because it affected to form a dense packed microstructure.

$TiO_2-SiO_2$ 나노복합소재는 자체가 화학적으로 안정할 뿐만 아니라 광학적, 열적 특성이 매우 우수하여 광화학센서, 촉매 등 다양한 분야에 적용되고 있다. 이러한 구조를 구현하는 방법으로 티타늄이 첨가된 폴리카보실란(PCS) 혼합용액을 전기방사한 후 이를 적절한 산화분위기에서 열처리하여 부직포상의 $TiO_2-SiO_2$ 나노복합섬유를 만들 수 있는데, 이는 기존의 졸겔공정에 의해 제조되는 섬유보다 더 쉽고 안정적인 방법이다. 공정 중 방사된 섬유를 산화분위기에서 $1200^{\circ}C$ 이상까지 열처리하게 되면 크리스토발라이트 기지조직 내에서 아나타제 나노결정상이 매우 균일하게 형성되었다. 또한, 열처리 후 섬유의 표면과 단면은 매우 치밀하고 매끈하였으며 10~20nm 크기의 아나타제 결정입자들이 내부에 균일하게 분포하였다. 【Nanostructured $TiO_2-SiO_2$ materials have widely been used as anti-reflecting coating, optical-chemical sensors and catalysts because of their superior optical and thermal properties as well as chemical durability. Web type $SiO_2$ microfibers with nano-crystalline $TiO_2$ were prepared by electrospinning of Ti-PCS mixed solution and oxidation controlled heat-treatment, rather simple than sol-gel process. Nano-crystalline anatase phase were formed for the heat-treatment up to $1200^{\circ}C$ and they were finely dispersed in the amorphous $SiO_2$ matrix.】

${\alpha}$ -상 과 ${\beta}$ -상 두 가지 종류의 탄화규소(SiC) 입자 표면에 수열 합성 방법으로 ZSM-5 결정을 형성하였다. SiC는 $50{\mu}m$ 이상이 되는 크기의 입자를 사용하였으며, ZSM-5 결정이 SiC 표면에서부터 성장하도록 유도하기 위하여 합성 단계에 앞서 SiC 표면에 산화층을 형성하였으며, 수열합성 온도와 시간을 변화시켜 보았다. 그 결과 ${\beta}$ -SiC는 $900^{\circ}C$ 조건에서도 산화막이 형성되었으며, 특히 $150^{\circ}C$ 합성 조건에서 ZSM-5가 ${\beta}$ -SiC 표면에서부터 성장하였음이 뚜렷이 관찰되었다. $200^{\circ}C$ 조건에서는 ZSM-5의 결정의 크기가 성장할 뿐 아니라, 시간의 증가에 따라 결정의 형태가 뚜렷해지고 SiC 표면에 도포되는 양이 증가하는 것을 확인할 수 있었다. 【ZSM-5 crystals grew on the surface of ${\alpha}$ -SiC and ${\beta}$ -SiC particles by hydrothermal synthesis method. SiC particles which were > $50{\mu}m$ of size were used, and oxide layer were developed on the surface of the particles to induce growth of ZSM-5 from the surface. Then, synthesis time and temperature condition were considered growing ZSM-5. In this study, oxide layer was formed on ${\beta}$ -SiC at $900^{\circ}C$ in air, and it was controlled to grow ZSM-5 grew from the ${\beta}$ -SiC surface with $150^{\circ}C$ synthesis condition. This is due to Si-O-Si or Si-O-Al bond, which is basic framework of ZSM-5 can be easily formed, from the silicon oxide film on the surface of ${\beta}$ -SiC. When the synthesis temperature was $200^{\circ}C$ , the size of ZSM-5 was increased, and it covered much area of the SiC surface with better crystal shapes with longer synthesis time.】

Approximately 20% of couples worldwide are infertile and about half of these couples have male infertility. Therefore, it is important to develop effective strategies for preventing male infertility. In this study, we examined the effects and regulatory mechanisms of curcumin, an active ingredient in the traditional herbal treatment derived from the dietary spice turmeric (Curcuma longa), on exogenous scrotal heat stress-induced testicular injuries in mice. Adult mice were orally administered three different doses of curcumin (20, 40, or 80 mg per kg per day) for 14 consecutive days and then subjected to transient scrotal heat stress at 43 °C for 20 min on day 7. The testes and blood of the mice were collected on day 14. Mice exposed to heat stress showed low testicular weight, severe vacuolization of seminiferous tubules followed by loss of spermatogenic cells, and the appearance of multinucleated giant cells and degenerative Leydig cells. In addition, great changes in oxidative stress (lipid peroxidation, superoxide dismutase (SOD) activity, cytoplasmic SOD, mitochondrial SOD, and phospholipid hydroperoxide glutathione peroxidase mRNAs), apoptosis (B-cell lymphoma-extra large and caspase 3 mRNAs), heat shock reaction (heat shock transcription factor-1 and transforming growth factor-β1 mRNAs) and androgen biosynthesis (testosterone concentration and 3β-hydroxysteroid dehydrogenase mRNA) were observed. However, all these testicular injuries induced by the scrotal hyperthermia were significantly improved by curcumin treatment (20, 40 and 80 mg kg(-1)) in a dose-dependent manner via its antioxidative, anti-apoptotic and androgen synthesis effects, indicating that it has the potential to prevent male infertility.

The reaction of iodine with polycarbosilane (PCS) in air and N2 atmospheres at room temperature was investigated with the goal of limiting oxygen uptake during iodine curing, in order to fabricate SiC fibres with low oxygen contents. The investigation shows that the PCS fibres are well cured by iodisation even at room temperature, regardless of the presence of oxygen in the atmosphere. Although it was previously reported that the amount of oxygen incorporated is affected proportionally by the processing temperature, when PCS fibres were iodised in air at room temperature, they contained significant amounts of oxygen owing to the very long processing time despite the low temperature. On the other hand, when iodised in a N2 atmosphere, the fibres were successfully cured without oxygen uptake, thus demonstrating that iodisation under an oxygen-free atmosphere is a successful curing method for fabricating SiC fibres with low oxygen contents. During the cross-linking process, the iodine causes fragmentation of certain groups from the PCS polymer chains, which mostly contributes to the cross-linking between the chains, but leaves reactive sites that readily allow oxidation in air.

Carbon fibers, which have excellent mechanical and thermal properties, are used in many fields; however, they are very vulnerable to oxidation and have limited service life. Various studies have attempted to address this. In this study, a SiC–C composite material was prepared using a silica sol to coat the carbon surface and improve the oxidation resistance of a carbon-fiber insulator as a material for solar-cell ingot-growing crucibles. The SiC coating was formed on the carbon surface under various conditions by controlling the composition of the silica sol, and its characteristics were examined. Via SiC-conversion coating through a carbothermal reaction, a film of thickness 30–80 nm film was uniformly formed over the entire sample. In addition, the oxidation characteristics were enhanced by a factor of three to five, when compared with conventional carbon materials.

Alumina nano-asperites were grown on plate-like alumina particles of which the surface had been covered with a capping agent to control the asperite formation sites on the particles. Utilized alumina source for asperite was nano sized γ-alumina, which was prepared by calcination of Al(OH)₃ at 600 ℃; silica suspension was used as the capping agent. Plate like alumina particles were covered by silica suspension and continuously heat-treated to 900 ℃ with nano sized γ-alumina, as the source material, under molten-salt atmosphere. Asperite growing site were controlled by the degree of coating of the capping agent; 10-20 nanosize of θ-alumina were formed on the particle surface. On the other hand, alumina particles without capping agent were observed to undergo only step-like crystal growth during heat-treatment.

Aluminum nitride was synthesized using a carbothermal method from mesoporous alumina having a high surface area (> 1,000 ㎡/g) as an aluminum source and CNTs (carbon nano tubes) as a carbon source. In this case the mesoporous alumina was used as the starting material instead of α-Al₂O₃ with the expectation that the mesopores in mesoporous alumina act as channels for N₂ gas and elimination of CO generated as by-product. It is also expected that the synthetic temperature should be lower compared to the use of α- Al₂O₃ as a starting material due to its high surface area. The crystallinity of the produced aluminum nitride was studied by XRD and FTIR, and the microstructure was investigated by FE-SEM. Also the purity of the aluminum nitride was analyzed through N/O determinator and ICP analysis.

Foam type porous silicon carbide ceramics were fabricated by a polymer replica method using polyurethane foam, carbon black, phenol resin, and silicon powder as raw materials. The influence of the C/Si mole ratio of the ceramic slurry and heat treatment temperature on the porous silicon carbide microstructure was investigated. To characterize the microstructure of porous silicon carbide ceramics, BET, bulk density, X-ray Powder Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were employed. The results revealed that the surface area of the porous silicon carbide ceramics decreases with increased heat treatment temperature and carbon content at the 2 nd heat treatment stage. The addition of carbon to the ceramic slurry, which was composed of phenol resin and silicon powder, enhanced the direct carbonization reaction of silicon. This is ascribed to a consequent decrease of the wetting angles of carbon to silicon with increasing heat treatment temperature.

AlN single crystal can be grown by physical vapor transport (PVT) method. The purity and particle size of the source material are important factors for single crystal growth to obtain good quality of AlN single crystal. The aim of this study was purification of AlN powder and growth of its particle size through thermocyclic treatment. The initial particle size was about 1.0 μm and the purity was 98.4% containing 1.6% oxygen and metallic impurities such as Fe, Sn, Ca, Na and Mg etc. which were analyzed based on KSL1612. For purification of AlN powder, it was performed using a thermocycle process with various thermocyclic numbers. After the thermocycle treatment, it is able to obtain large particle size AlN powder as much as 30μm and purity was increased to 99.6% based on chemical analysis.

Drug loaded polyurethane (PU) thin layer was prepared on the silicone tube by electrospinning technique. Microstructure of the PU layer was varied from nanoporous web to dense coating depending on the polymer solution concentration and the amount of drug loaded. It can be easily adjusted the coating thickness and porosity accurately and controlled the drug loading and releasing properties. However, adhesive strength between PU layer and silicone tube was very weak and easily broken away and white turbidity also another important problem. So, surface of silicone tube was atmospheric-pressure plasma (APP) treated for improving the adhesive and removing white turbidity phenomenon.

A hydroxyapatite microsphere was prepared using a spray-drying method. The change in the shape as a function of the slurry concentration and the change in the degree of shrinkage according to the heat-treatment temperatures were observed. To obtain biomaterials with improved bio-stability, CaHPO₄4·2H₂O and Ca(OH)₂ were mixed at a ratio of 6 : 4 and then ball-milled to synthesize hydroxyapatite. The hydroxyapatite microsphere was prepared using 30 wt% ~ 80 wt% hydroxyapatite slurry by a spray-drying method. For concentrations lower than 50 wt% or higher than 80 wt%, doughnut-shaped microspheres were produced. However, perfect microspheres were produced when using slurry concentrations of 50 wt% ~ 70 wt%. A dense microstructure was observed after a heat treatment at temperature higher than 1100℃ and the size was reduced by 24.3% at these temperatures.

Polyimide (PI)-based nanocomposites containing aminophenyl functionalized multiwalled carbon nanotubes (AP-MWCNTs) obtained through a diazonium salt reaction was successfully prepared by in situ polymerization. PI composites with different loadings of AP-MWCNTs were fabricated by the thermal conversion of poly(amic acid) (PAA)/AP-MWCNTs. The mechanical and electrical properties of the AP-MWCNTs/PI composites were improved compared with those of pure PI due to the homogeneous dispersion of AP-MWCNTs and the strong interfacial covalent bonds between AP-MWNTs and the PI matrix. The conductivity of AP-MWNTs/PI composites (5:95 w/w) was 9.32 × 10−1 S/cm which was about 1015 times higher than that of Pure PI. The tensile strength and tensile modules of the AP-MWCNTs/PI composites with 0.5 wt % of AP-MWCNTs were increased by about 77% (316.9 ± 10.5 MPa) and 25% (8.30 ± 1.10 GPa) compared to those of pure PI, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 960–966

Since mesoporous silica such as MCM-41 and SBA-15 was developed, the study of the properties of high-surface area materials was accelerated. Moreover, the mesoporous silica is used as a template to produce high-surface materials by nanocasting technology. The purpose of this paper is the synthesis of a high surface silicon carbide sphere by the nanocasting technology. In this study, KCC-1 silica sphere was used as a template, and polycarbosilane and poly (phenyl carbosilane) were selected for precursor of silicon carbide. Carbosilane polymer gives advantage of synthesis silicon carbide under low temperature, and hollow spheres were produced. In this study, the polycarbosilane was more effective for the synthesis of SiC hollow spheres by inversion of template structure showing a fibrous morphology on the sphere wall. And it was confirmed that the sphere was composed of nanosized SiC crystals, and has high surface area using TEM, XRD and BET analysis.

The influence of a liquid medium duringa wet-milling process in the grinding and oxidation of silicon powder was investigated. Distilled water, dehydrated ethanol and diethylene glycol were used as the liquid media. The applied grinding times were 0.5, 3, and 12 h. Ground silicon powder samples were characterized by means of aparticle size analysis, scanning electron microscopy(SEM), xray powder diffraction (XRD), FT-IR spectroscopy and by a chemical composition analysis. From the results of the characterization process, we found that diethylene glycol is the most efficient liquid medium when silicon powder is ground using a wet-milling process. The FT-IR results show that the Si-O band intensity in an unground silicon powder is quite strongbecause oxygen becomes incorporated with silicon to form SiO₂ in air. By applying deionized water as a liquid medium for the grinding of silicon, the SiO₂ content increased from 4.12% to 31.7%. However, in the cases of dehydrated ethanol and diethylene glycol, it was found that the SiO₂ contents after grinding only changed insignificantly, from 4.12% to 5.91% and 5.28%, respectively.

Nacre is an organic-inorganic composite material; it is composed of CaCO3 platelet and protein. The microstructure of nacre is a matrix that is similar to bricks and mortar. Technology inspired by nature is called biomimetic technology. In this study, to make high thermal conducting ceramic composite materials using biomimetic technology, a porous green body was prepared with BN platelets. PMMA was infiltrated into the porous green body to make a composite. The microstructure of the composite was observed with FESEM, and the thermal properties were measured. The thermal conductivity of the prepared organic ?inorganic composite was 4.19 W/m·K.

Two kinds of SiC powder having a different impurity contents and particle size were prepared by carbothermal reduction under different conditions from traditional process for controlling the purity of product. SiC single crystal was grown in the RF heating PVT machine at the temperature above 2,100 °C. After crystal growth, boule was cut to wafers in 1mm thickness and fine polished using diamond abrasive slurry. The impurity in the powder and wafer was analyzed using glow discharged mass spectroscopy (GDMS). Major impurities in the SiC wafer were aluminum, boron, iron and titanium which were accorded in the SiC powder and these impurities were decreasing in proportional to those in the powder. However, behavior of each elemental impurity was different from each other during the crystal growth. In case of boron was increased after crystal growth while aluminum decreased. In case of titanium and boron were higher in the wafer than in the powder. It can be explained to other impurity source such as graphite crucible and insulation felt.

A new type of small organic dyes based on the xanthene skeleton are synthesized evaluated for their absorbance and fluorescence properties.

Abalone shell is composed of 95 wt% CaCO 3 platelets and 5 wt% of a protein-rich organic matrix which acts as an adhesive layer, connecting aragonite tablets, thus maintaining the structural integrity of the composite. By mimicking abalone shell, we prepared a silicate plate/polymer nanocomposite by infiltrating PMMA between silicate layers and warm-pressing them at 200 o C for 1 h under 15 tons to make organic-inorganic composite materials. To examine the organic-inorganic composite materials after the warm-pressing procedure, the composite sample was analyzed with FE-SEM and TG. The bending strengths and densities of the composites prepared by a silicate plate and PMMA after the warm-pressing process were ~140 MPa and 1.5, respectively.

Since SiOC was introduced as an anode material for lithium ion batteries, it has been studied with different chemical compositions and microstructures using various silicon based inorganic polymers. Poly(phenyl carbosilane) is a SiOC precursor with a high carbon supply in the form of the phenyl unit, and it has been investigated for film applications. Unlike any other siloxanebased polymers, oxygen atoms must be utilized in an oxidation process, and the amount of oxygen is controllable. In this study, SiOC anodes were prepared using poly(phenyl carbosilane) with different heat treatment conditions, and their electrochemical properties as an anode material for lithium ion batteries were studied. In detail, cyclic voltammetry and charge-discharge cycling behavior were evaluated using a half-cell. A SiOC anode which was prepared under a heat treatment condition at 1200℃ after an oxidation step showed stable cyclic performance with a reversible capacity of 360 mAh/g.

In this study, poly(amic acid) was prepared via a polycondensation reaction of 3,3’-dihydroxybenzidine and pyromellitic dianhydride in an N-methyl-2-pyrrolidone solution; reduced graphene oxide/polybenzoxazole (r-GO/PBO) composite films, which significantly increased the electrical conductivity, were successfully fabricated. GO was prepared from graphite using Brodie’s method. The GO was used as nanofillers for the preparation of r-GO/PBO com posites through an in situ polymerization. The addition of 50 wt% GO led to a significant increase in the electrical conductivity of the composite films by more than sixteen orders of magnitude compared with that of pure PBO films as a result of the electrical percolation networks in the r-GO during the thermal treatment at various temperatures within the films.

SiC hollow fiber was fabricated by curing, dissolution and sintering of Al-PCS fiber, which was melt spun the polyaluminocarbosilane. Al-PCS fiber was thermally oxidized and dissolved in toluene to remove the unoxidized area, the core of the cured fiber. The wall thickness (t wall ) of Al-PCS fiber was monotonically increased with an increasing oxidation curing time. The Al-PCS hollow fiber was heat-treated at the temperature between 1200 and 2000°C to make a SiC hollow fibers having porous structure on the fiber wall. The pore size of the fiber wall was increased with the sintering temperature due to the decomposition of the amorphous SiCxOy matrix and the growth of β-SiC in the matrix. At 1400°C, a nano porous wall with a high specific surface area was obtained. However, nano pores grew with the grain growth after the thermal decomposition of the amorphous matrix. This type of SiC hollow fibers are expected to be used as a substrate for a gas separation membrane.