본 연구에서는 한외여과 polysulfone (PSf) 중공사막에 첨가제를 섞는 방법을 통해 친수성 증가에 따른 분리막 특성 및 성능을 향상하고자 하였다. 15 nm 크기의 fumed silica (FS)를 0.1, 0.3, 0.5 wt%로 방사 용액에 분산시켜 혼합 매트릭스 분리막을 제조하였다. 단면 및 표면상태를 확인하기 위해 SEM 분석을 진행하였으며, FS가 함유될수록 중공사막의 평균 기공 반경이 4 nm 이상 증가하는 것을 확인하였다. 또한, 분리막의 친수성 분석을 위해 접촉각 측정을 진행하였으며, FS 함유로 분리막의 친수성이 높아진 것을 확인하였다. 수투과도의 경우 FS가 섞인 분리막은 91~96 LMH 수준을 보였으며 PSf 분리막보다 5~11%의 증가율을 보였다. 내오염성 평가에서도 친수도가 상승한 FS 혼합 중공사막 표면에 소수성을 띄는 BSA가 흡착되지 못하여 상대 유량 감소율이 PSf 단일막 보다 낮아졌음을 확인하였다.

The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range 0°C and –10°C. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate GIC of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of GIC decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

Synthesis of nano-silica using water glass in a Sol-Gel process is one of several methods to manufacture nano-silica. In nano-silica synthesized from water glass, there are various metal impurities. However, synthesis of nano-silica using water glass in a Sol-Gel process is an interesting method because it is relatively simple and cheap. In this study, nano-silica was synthesized from water glass; we investigated the effect of pH on the synthesis of nano-silica. The morphology of the nanosilica with pH 2 was flat, but the surface of the nano-silica with pH 10 had holes similar to small craters. As a result of ICPOES analysis, the amount of Na in the nano-silica with pH 2 was found to be 170 mg/kg. On the other hand, the amount of Na in the nano-silica with pH 10 was found to be 56,930 mg/kg. After calcination, the crystal structure of the nano-silica with pH 2 was amorphous. The crystal structure of the nano-silica with pH 10 transformed from amorphous to tridymite. This is because elemental Na in the nano-silica had the effect of decreasing the phase transformation temperature

Silica nano-powder (SNP) is an inorganic material able to provide high-performance in various fields because of its multiple functions. Methods used to synthesize high purity SNP, include crushing silica minerals, vapor reaction of silica chloride, and a sol-gel process using TEOS and sodium silicate solution. The sol-gel process is the cheapest method for synthesis of SNP, and was used in this study. First, we investigated the shape and the size of the silica-powder particles in relation to the variation of HCl and sodium silicate concentrations. After drying, the shape of nano-silica powder differed in relation to variations in the HCl concentration. As the pH of the solution increased, so did the density of crosslinking. Initially, there was NaCl in the SNP. To increase its purity, we adopted a washing process that included centrifugation and filtration. After washing, the last of the NaCl was removed using DI water, leaving only amorphous silica powder. The purity of nano-silica powder synthesized using sodium silicate was over 99.6%.

The friction and wear characteristics of the rubber matrix composites filled with nano sized silica particles were investigated at ambient temperature by pin-on-disc friction test. The volume fraction of silica particles was 19%. The cumulative wear volume and wear rate of these materials on counterpart roughness were determined experimentally. The major failure mechanisms were lapping layers, deformation of matrix, ploughing, debonding of particles, fracture of particles and microcracking by scanning electric microscopy photograph of the tested surface. The cumulative wear volume showed a tendency to increase with increase of sliding distance. The wear rate of these composites tested indicated low value as increasing the sliding distance.

The characteristics of abrasive wear of the rubber matrix composites filled with nano sized silica particles were investigated at ambient temperature by pin-on-disc friction test. The range of volume fraction of silica particles tested are between 11% to 25%. The cumulative wear volume and friction coefficient of these materials on particle volume fraction were determined experimentally. The major failure mechanisms were lapping layers, deformation of matrix, ploughing, deboding of particles and microcracking by scanning electric microscopy photograph of the tested surface. The cumulative wear volume showed a tendency to increase nonlinear with increase of sliding distance. As increasing the silica particles of these composites indicated higher friction coefficient.

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and TiO2 for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the TiO2 is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of TiO2.

The relative viscosity was measured at different filler loadings for a cycloaliphatic epoxy resin and hexahydro-4-methylphthalic anhydride hardener system filled with micro/nano hybrid silica. Various empirical models were fitted to the experimental data and a fitting parameter such as critical filler fractions (φmax) was estimated. Among the models, the Zhang-Evans model gave the best fit to the viscosity data. For all the silica loadings used, ln (relative viscosity) varied linearly with filler loadings. Using the Zhang-Evans model and the linearity characteristics of the viscosity change, simple methods to predict the relative viscosity below φmax are presented in this work. The predicted viscosity values from the two methods at hybrid silica fractions of φ = 0.086 and 0.1506 were confirmed for a micro:nano = 1:1 hybrid filler. As a result, the difference between measured and predicted values was less than 11%, indicating that the proposed predicting methods are in good agreement with the experiment.

본 연구에서는 졸-겔 공법을 이용하여 가스 차단 특성을 갖는 SiO2/EVOH(에틸렌 비닐알콜 공중합체) 하이브리드 물질을 제조하였다. 제조된 여러 조성의 하이브리드 졸을 표면 처리한 biaxially oriented polypropylene (BOPP) 기지재에 스핀 코팅 방식을 이용하여 코팅하였다. X선 회절 및 DSC 분석에 의해 하이브리드 내의 EVOH 상과 실리카 상 사이의 결합에 따른 결정화 거동의 변화를 조사하였다. 또한 SiO2/EVOH 하이브리드 겔의 모폴로지 관찰을 통하여, 100nm 이하의 실리카 입자들이 균열하게 분산된 매우 치밀한 상 미세구조를 갖는 하이브리드 물질을 제조하기 위해 필요한 Tetraethylorthosilicate (TEOS) 무기전구체의 최적 함량이 존재함을 알 수 있었다. 첨가된 TEOS 함량이 최적 함량보다 낮거나 높은 경우에는 큰 도메인의 입자 클러스터들이 형성되어 매우 불안정한 모폴로지를 나타내는 상분리 현상이 관찰되었다. 이러한 모폴로지 결과는 하이브리드 코팅 필름의 산소 투과도의 변화 결과와 일치하였는데, TEOS 함량이 0.01 - 0.02mol로 첨가되어 제조된 하이브리드로 코팅된 필름의 경우 매우 우수한 산소 차단 특성을 나타냈으며, 0.04mol 이상으로 첨가되었을 때는 상 분리 및 미세 균열 발생으로 인하여 그 차단 특성이 급격하게 감소하는 것으로 나타났다.

본 연구에서는 나노기술을 이용하여 에너지 감쇠 기능을 활용한 감쇠기 개발에 대한 연구를 하였다. 유체 감쇠기를 대체하는 완충역할을 하는 미로구조를 가지는 실리카 겔 입자를 사용하였으며, 입자에 관련한 작동 유체로는 물을 사용하여 그 효과를 검증하였다. 콜로이드 감쇠기를 구현하기 인해서는 형성된 실리카 겔 입자의 표면을 유기 실리콘 매질을 이용한 소수화 코팅 처리를 하였다. 정적 하중 상태에서의 가역적 콜로이드 감쇠기에 대한 실험을 수행하였다. 콜로이드 감쇠기내 다공질 입자의 나노 유로(pore)와 다공성 입자의 직경, 다공성 입자의 구조, 그리고 대기압 상태에서 유체의 출입을 통제하기 위한 코팅처리의 분자 간 길이와 같이 여러 가지 요인의 콜로이드 감쇠기 이력현상에 대한 영향을 평가하였다. 감쇠기의 소산 에너지양과 효율에 대해서도 조사하여 유압 감쇠기 보다 뛰어난 결과를 얻었으며 콜로이드 감쇠기로 사용 가능하다는 사실을 입증하였다.

본 연구에서는 나노기술을 이용하여 에너지 감쇄 기능을 활용한 내진용 감쇄기 개발에 대한 연구를 하였다. 구조물에 사용되는 기존의 유체 감쇄기를 대체하는 무기재료를 이용한 새로운 감쇄기에 대한 기초적 연구를 하였다. 완충역할을 하는 입자로는 미로구조를 가지는 실리카겔을 사용하였으며, 입자에 관련한 작동 유체로는 물을 사용하여 그 효과를 검증하였다. 콜로이드 감쇄기를 구현하기 위해서는 형성된 실리카 겔 입자의 표면을 유기 실리콘 매질을 이용한 소수화 코팅 처리를 하였다. 콜로이드 감쇄기의 이력곡선은 서로 다른 소수화 코팅 처리가 된 입자의 혼합과 소수화 처리시의 분자간 거리에 의해서 조절이 가능함을 알 수 있었다. 콜로이드 감쇄기의 에너지 소산양은 상이한 소수화 처리 정도와 서로 코팅처리량이 서로 다른 재료를 혼합함으로써 제어 할 수 있음을 확인하였다. 기존의 유압 감쇄기에서는 나타나지 않는 이러한 특징은 콜로이드 감쇄기가 충격 흡수 장치로 사용 가능하다는 사실을 입증한다.

Silica hydrogel was synthesized by the reaction of liquid sodium silicate with sulfuric acid. The condensation polymerization of the synthesized hydrogel was carried out via an aging process under the acidic or alkaline conditions. Nano porous silica with the pore size below 3 nm and surface area of , was obtained by the above processes in acidic ranges(pH : 3~5). The pore size and surface area of the silica varied with pH, and in alkaline ranges(pH : 8~10), those were 21 nm and respectively. The characteristics of the silica varied with the thermal treatment which caused the change of surface area, pore volume and pore diameter.

본 연구는 nano-silica solution(NSS)을 배합수 중량치환방법을 사용한 OPC-slag cement의 특성에 관한 연구이다. 새로운 치환방법은 선행연구들보다 높은 NSS 치환율의 시멘트에 대한 거동을 연구하기 위한 기초 단계이다. NSS는 배합수 중량의 10%, 20%, 30%, 40%, 그리고 50% 치환하였다. 그 결과 역학적 및 미세구조적 특성이 향상되는 결과를 보였다. 이는 두 가지 원인으로 요약된다. 첫 번째는 NSS를 배합수 중량 치환하면 나노 실리카 입자의 균질한 분산작용이 향상된다. 이는 초기 수화작용을 촉진한다. 두 번째는 배합수 보다 밀도가 큰 NSS의 치 환은 w/b를 감소시킨다. 이는 치밀한 수화반응물질을 형성시킨다. 새로운 치환방법은 선행연구에서 밝혀진 분말형 나노 실리카 입자를 사용한 결과와 비교하여 역학적과 미세구조 특성의 저하가 나타나지 않았다. 따라서 본 연구에서 사용한 NSS를 배합수 중량 치환한 방법은 OPC-GGBFS cement의 배합에 적용 가능할 것으로 판단된다.

of ordinary Portland cement. Water-cement ratio was 0.40 and cement-sand ratio was 1:3. The content of nano-TiO2 was 3% but the content of nano-SiO2 changed in cement mortars. The content of nano-SiO2 was 0%, 0.5%, 1%, 1.5% and 2% of the binder weight. Mortar prisms and beams were made in specified molds and cured in limewater. Compressive and flexural strengths, porosity and ultrasonic pulse velocity were measured. Then mortars were stored in 6 molar ammonium nitrate (NH4NO3) solution. Leaching depth, variation of mechanical and microstructural properties were measured. Presence of nano-particles decreased the leaching depth and the degradation of mechanical and microstructural properties in mortars.

In this study we propose an effective method, Coating processing methods, which can improve the quality of recycled aggregate relatively easily without new equipment investment and complex treatment process and verify the improved effect using the devised method, Coating processing methods. To attain the research aim we used adequately diluted silicate solution for coating and carried out several property valuation for twelve types of material with different coating method. Also we formed concrete with coated aggregates which showed the best property. In conclusion the aggregates with the method of repeated impregnation in the silicate and drying showed the most excellent quality while other coating methods also resulted in an improvement of aggregate quality but failed to meet the KS Standard. Lastly with the optimal material we could obtain the approved compressive strength from the concrete allowing it to be utilized for road facility of which standard compressive strength of design is under 24MPa.

Sorghum is the fifth most important cereal in the world as one of the staple food. For the use of natural dye, we have done some researches about sorghum red pigments extracted from stalk and leaves on its physiochemical properties, extracting methods and applications. The researches involved maximum extraction of sorghum pigment and analysis of its processing condition. Total polyphenol and tannin contents were measured by varieties and different plant parts. The stabilities of pigment by irradiation and heat treatment for processing were measured by colorimeter and thermal gravimetric analysis (TGA). In addition, hybrid nano-silica composites with sorghum pigment were made by combining with polyvinyl alcohol, polyvinyl acetate and sodium silicate. Water silica hybrids with sorghum pigment were performed by emulsion treatment. Nano-silica particles were identified and measured their size to be about 200 ~ 400 nm by SEM analysis.