• 공업화학
• /
• 제10권1호
• /
• pp.98-104
• /
• 1999

본 연구에서는 ECR플라즈마 화학증착법을 이용하여 반응기내 압력의 변화에 따라 수소화된 무정형 실리콘막을 증착하고 박막내 수소의 함량과 결합구조 및 전기적 특성을 조사하였다. 일반적인 CVD에 의해 제조된 a-Si:H막은 증착속도가 증가할수록 광감도는 감소하지만 ECR플라즈마의 경우 증착속도가 증가할수록 광감도가 향상되었다. 마이크로파 출력과 사일렌/수소 희석비, 반응기내 압력등이 동일한 실험 조건에서 증착시간에 따른 막의 두께는 선형적으로 증가하고 막내에 함유된 수소의 농도는 일정하지만, 반응시간이 짧은 경우 막내에 $SiH_2$결합이 SiH결합보다 많이 형성되어 광전도도를 저하시킬 수 있다. 반응기내 압력이 증가함에 따라 박막내에 SiH결합이 증가하여 광학 에너지 갭을 줄여 광전도도를 향상시킬 수 있었으나 암전도도의 증가로 광감도는 감소하였다. 따라서 양질의 박막을 얻기 위해서는 압력이 낮고 수소기체의 양이 적은 조건에서 성장시켜야 한다.

• Journal of the Korean Wood Science and Technology
• /
• 제18권2호
• /
• pp.67-78
• /
• 1990

This study was performed to determine the characteristics of physical and mechanical properties of domestic wood based materials; plywood, particleboard, medium density fiberboard. Main items of tested properties were panel size, moisture content, water absorption, linear expansion and thickness swelling, glue bond shear strength, bending properties(stress at proportional limit, modulus of rupture. modulus of elasticity), tensile strength, screw holding strength, and internal bond as neccessary. the results were discussed mainly with Korean Standards. The obtained conclusions are as follows; 1. Length and width of 3mm thin plywood(3-ply) and 12mm thick plywood(7-ply) were satished with KS-standard, but thicknesses of these panels were not- passed tolerance limit except one of eight makers. 2. Length and width of particleboard and medium density fiberboard were greater than the tolerance limit value of KS standard, but the thicknesses of these panels were passed this value. 3. Moisture contents of 12mm thick and 3mm thin plywood were satisfied with KS-standard except one mill made 3mm thin plywood. 4. Moisture absortion of plywood was not passed tolerance limit of KS-standard but particleboard was satisfied with this standard value. 5. Dry and wet shear strengths in glue bond of 3mm thin plywood were not reached to KS-standard, but those of 12mm thick plywood were sufficiently satisfied with KS standrad. 6. Modulus of ruptures, parallel to grain and perpendicular to grain of plywood, and particleboard and medium density fiberboard were satisfied with KS-standard. 7. Tensile strengths, parallel to grain and perpendicular to grain of plywood were satisfied with allowance stress of US product standard PS 1-74. 8. Screw holding strength of particleboard was not reached to KS standard, but internal bond was satisfied with KS standard.

• 한국도로학회논문집
• /
• 제17권1호
• /
• pp.43-49
• /
• 2015

PURPOSES : The objective of this study is to develop new pothole repair materials using polyurethane-modified asphalt binder, and to evaluate them relative to current pothole repair materials in order to improve the performance of repaired asphalt pavement. METHODS : In the laboratory, polyurethane-modified asphalt binder is developed, and then asphalt binder is added to produce pothole repair materials. In order to evaluate the properties of this new pothole repair material, both an indirect tension strength test and a direct tension strength test are performed to measure the material strength and bond strength, respectively. Additionally, the basic material properties are evaluated using the asphalt cold mix manual. The strength characteristics based on curing times are evaluated using a total of 7 types of materials (3 types of current materials, 2 types of new materials, and 2 types of moisture conditioned new materials). The indirect tension strength tests are conducted at 1, 2, 4, 8, 16, and 32 days of curing time. The bond strength between current HMA(Hot Mix Asphalt) and the new materials is evaluated by the direct tension strength test. RESULTS AND CONCLUSIONS : Overall, the new materials show better properties than current materials. Based on the test results, the new materials demonstrate less susceptibility to moisture, faster curing times, and an improved bond strength between HMA and the new materials. Therefore, the use of the new materials reported in this study may lead to enhanced performance of repairs made to asphalt pavement potholes.

• Journal of the Korean Wood Science and Technology
• /
• 제39권6호
• /
• pp.498-504
• /
• 2011

The purpose of this study was to investigate and develop an eco-frendly wood adhesive based on vegetable oil (especially soybean oil), the renewable and sustainable natural resources, using ozonification technology for the chemical structure modification. The waste soybean oil (WSBO) was reacted with $O_3$ at the rate of $450m{\ell}$(acetone) : $50m{\ell}$ (WSBO) for different times, 1, 2, 3 hrs. The investigation of the modified chemical strecture of the ozonied WSBOs were conducted using FT-IR. As ozonification time increased, the peak of the unsaturated double bonds was disappeared especially ozonized-3hrs and aldehyde or carboxyl peak appeared because ozonification broke the oil into small molecules. The plywood were made at $150^{\circ}C$ with 4 minutes hot-press time using the different ozonized 3 hrs WSBO/pMDI adhesives and were tested for the dry, wet, cyclic boil test according to the Korea Industrial Standard F3101 Ordinary plywood. The bond strengths gradually increased until 1 : 0.5~1 : 3, but it decreased 1 : 4, as the contents of pMDI increased. The results of the dry, wet and cyclic bond strengths the equivalent ratio was formed approximately between 1 : 2~1 : 3. And the 1 : 1~1 : 4 strengths met constantly the standard requirement of 7.0kgf/$cm^2$ (KS F3101). From the comprehensive view on the results of above experiment, it could be confirmed that ozonized WSBO/pMDI has characteristics of effective reactivity and wet stability showed as an excellent candidate of wood adhesive applications.

• 한국구조물진단유지관리공학회 논문집
• /
• 제19권4호
• /
• pp.136-143
• /
• 2015

용융아연도금(galvanizing)은 콘크리트 구조물의 철근 부식 문제를 해결하기 위해 사용된다. 용융아연도금 철근 콘크리트 보의 부착강도 영향에 대한 자료는 거의 없는 실정이다. 따라서, 이 연구의 목적은 용융아연도금철근이 콘크리트 보의 부착강도에 미치는 영향을 파악하는데 있다. 용융아연도금철근을 사용한 부재와 일반철근을 사용한 부재의 구조실험을 통하여 겹침이음 거동과 부착강도 특성을 비교하였다. 실험변수로써 철근의 용융아연코팅 유무, 철근 직경과 겹침이음 길이를 고려하였다. 용융아연도금 철근콘크리트 보의 균열 및 파괴 특성을 파악하였다. 용융아연도금철근 콘크리트 보의 겹침이음부 휨 거동특성은 일반철근 콘크리트 보의 겹침이음부 휨거동과 유사한 것으로 나타난다. 또한, 용융아연도금철근의 사용은 일반철근을 사용할 때에 비해 콘크리트 보의 부착강도에 불리한 영향을 미치지는 않는 것으로 나타났다.

• Computers and Concrete
• /
• 제13권6호
• /
• pp.709-737
• /
• 2014

Fibre-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics of hardened concrete as a result of fibre addition. To produce SCC, either the constituent materials or the corresponding mix proportions may notably differ from the conventional concrete (CC). These modifications besides enhance the concrete fresh properties affect the hardened properties of the concrete. Therefore, it is vital to investigate whether all the assumed hypotheses about CC are also valid for SCC structures. In the present paper, the experimental results of short-term flexural load tests on eight reinforced SCC and FRSCC specimens slabs are presented. For this purpose, four SCC mixes - two plain SCC, two steel, two polypropylene, and two hybrid FRSCC slab specimens - are considered in the test program. The tests are conducted to study the development of SCC and FRSCC flexural cracking under increasing short-term loads from first cracking through to flexural failure. The achieved experimental results give the SCC and FRSCC slabs bond shear stresses for short-term crack width calculation. Therefore, the adopted bond shear stress for each mix slab is presented in this study. Crack width, crack patterns, deflections at mid-span, steel strains and concrete surface strains at the steel levels were recorded at each load increment in the post-cracking range.

• 대한환경공학회지
• /
• 제22권6호
• /
• pp.1139-1148
• /
• 2000

산업 폐기물 중 다량으로 발생하는 제강슬래그의 재활용을 위하여 -14/+24mesh 정도 크기의 슬래그를 미분말로 분쇄시 최적 조건을 조사하고 경제적인 분쇄조건을 확립하기 위하여 요구되는 동력을 산출하였다. 이를 위한 분쇄조건으로 ball mill의 회전속도, 분쇄시간, ball의 충진량, 시료의 충진량과 크기 등을 선정하였고 이에 대한 분쇄효율을 산출하였다. 본 연구에서는 임계회전속도의 79% 정도에 해당되는 값이 최적의 회전속도인 것으로 조사되었다. 분쇄시간에 따른 분쇄정도는 일반적으로 시간이 증가함에 따라 증가하는 것으로 나타났지만 분쇄 초기에 비해 분쇄가 더 진행될수록 분쇄효율은 감소하는 것으로 나타났다. Ball의 충진율은 mill내부 용량의 50%인 경우에 최척의 분쇄효율을 보였고, 시료의 충진량과 크기에 따른 입도초사 실험 에서는 시료의 충진량이 적고 원시료의 크기가 작을수록 분쇄정도는 증가하였다. 위의 결과에 의해 Bond의 식을 사용하여 동력효율을 계산한 결과 분쇄시간이 길수록 그리고 회전속도가 최적인 조건에서 동력효율이 가장 크게 나타나고 있음이 관찰되었다.

• Restorative Dentistry and Endodontics
• /
• 제48권1호
• /
• pp.8.1-8.8
• /
• 2023

Objectives: This study was designed to evaluate the parameters of bonding performance to root dentin, including push-out bond strength and dentinal tubular biomineralization, of a hydraulic bioceramic root-end filling material premixed with dimethyl sulfoxide (Endocem MTA Premixed) in comparison to a conventional powder-liquid-type cement (ProRoot MTA). Materials and Methods: The root canal of a single-rooted premolar was filled with either ProRoot MTA or Endocem MTA Premixed (n = 15). A slice of dentin was obtained from each root. Using the sliced specimen, the push-out bond strength was measured, and the failure pattern was observed under a stereomicroscope. The apical segment was divided into halves; the split surface was observed under a scanning electron microscope, and intratubular biomineralization was examined by observing the precipitates formed in the dentinal tubule. Then, the chemical characteristics of the precipitates were evaluated with energy-dispersive X-ray spectroscopic (EDS) analysis. The data were analyzed using the Student's t-test followed by the Mann-Whitney U test (p < 0.05). Results: No significant difference was found between the 2 tested groups in push-out bond strength, and cohesive failure was the predominant failure type. In both groups, flake-shaped precipitates were observed along dentinal tubules. The EDS analysis indicated that the mass percentage of calcium and phosphorus in the precipitate was similar to that found in hydroxyapatite. Conclusions: Regarding bonding to root dentin, Endocem MTA Premixed may have potential for use as an acceptable root-end filling material.

• 한국건설순환자원학회논문집
• /
• 제11권1호
• /
• pp.39-47
• /
• 2023

최근 구조물의 장대화로 인하여 고강도 재료의 경량화 요구가 빈번해지고 있는 실정이다. 하지만 현재까지는 압축강도 120 MPa, 단위중량 20 kN/m³ 정도의 고강도 경량 콘크리트를 구조부재에 적용하기 위한 콘크리트와 철근의 부착 특성에 관한 연구가 부족한 실정이다. 따라서 본 논문에서는 압축강도 120 MPa, 단위중량 20 kN/m³ 정도의 고강도 경량 콘크리트 108개의 시편을 제작하여 직접 인발 부착실험을 수행하였고, 실험결과와 현행 설계기준과 비교하여 부착특성을 평가하였다. 솔리드버블은 단위중량 감소에 비해서 압축강도 및 탄성계수 감소효과는 상대적으로 적게 나타나, 초경량화를 위해서는 반드시 적용되어야 할 재료로 판단되며, ACI-408R의 부착강도 산정식과 실험결과는 비교적 유사한 것으로 판단되며, 더 낮은 압축강도, 단위중량의 콘크리트보다 더 큰 슬립 및 매개변수 값을 가지는 것으로 나타났다.

• 한국진공학회지
• /
• 제1권1호
• /
• pp.190-197
• /
• 1992

In this study we have investigated physical and electrical properties of high temperature oxide (HTO) thin film using dichlorosilane (DCS) gas. This film had low etch rate and excellent step coverage, and its characteristics of Si-O bond were similar to those of thermal oxide. I-V curves also showed similar electrical properties to those of thermally grown oxide (SiO2) while time dependent dielectric breakdown (TDDB) results revealed 1/4 value of thermal oxide. However, defect density was measured to be much lower value than that of thermal oxide.