• Advances in concrete construction
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• 제13권5호
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• pp.349-360
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• 2022

The rising prices of landfills and the lack of cement production are motivating researchers to be more interested in using wastes to produce concrete mixtures materials. The use of waste materials such as eggshell and matakoline waste not only reduces landfill costs and space, but also reduces the cost of cement production for the concrete mixture. However, recycling waste materials has become critical in order to effectively manage environmental sustainability. The purpose of this paper is to investigate the appropriate properties of self-compacting concrete (SCC) by incorporating waste materials such as crushed ceramics as coarse aggregate and nano egg shell (NES) and nanoclay (NC) as cement replacements. Fresh properties of SCC, such as segregation, flow time and diameter, V-funnel, H2/H1 ratio, and fresh unit weight of concrete mixtures, as well as hardened properties, such as 7, 14, and 28 days compressive strength and 28 and 90 days flexural strength, were measured for this purpose. The presence of NC in the SCC mixture enhanced the compressive strength of the concrete when 5% of NES was added or in the case without the addition of NES compared to the control mixture. The flexural strength enhanced with the incorporation of NC in the SCC increased the flexural strength of the concrete compared to the control mixture, but the incorporation of 5% of NES decreased the flexural strength compared to the mixtures with NC. These results prove the possibility of using crushed ceramics as the coarse aggregate, and NES and NC as substitutes for 5, 7, and 10% of the cement in SCC, because the properties of such SCC in hardened and fresh states are satisfactory.

• 한국식품영양과학회지
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• 제44권1호
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• pp.29-34
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• 2015

본 연구에서는 난각 칼슘을 이용하여 분획 공정을 통해 나노칼슘을 제조(입자 크기가 96.5 nm)하였으며 이에 대해 안전성 평가를 위해 OECD guideline에 따라 동물을 이용하여 단회투여의 급성 독성시험과 반복투여의 아급성 독성시험을 실시하였다. 그 결과 급성 및 아급성 독성시험의 모든 암수동물에서 나노 칼슘의 투여에 기인된 사망은 관찰되지 않았으며 나노 칼슘은 모든 암수 rat에 대하여 대조군과 비교하여 유의성 있는 체중 변화를 초래하지 않았다. 또한 나노 칼슘 투여군에서 특이한 임상 증상 및 부검 시 내부 장기의 어떠한 육안적 이상소견도 관찰되지 않았다. 따라서 급성 및 아급성 독성시험의 결과 나노 칼슘은 혈액과 장기 등 평가 지표에 독성으로 인한 영향을 나타내지 않으며 안전한 것으로 판단되었다.

• Advances in nano research
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• 제16권2호
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.

• Advances in nano research
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• 제15권4호
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• pp.315-328
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• 2023

The main goal of the present study was to assess the effects of eggshell powder (ESP) and halloysite nanotubes (HNTs) on the mechanical properties of abaca fiber (AF)-reinforced natural composites. For this purpose, a limited number of indentation tests were first performed on the AF/polypropylene (PP) composites for different HNT and ESP loadings (0 wt.% ~ 6 wt.%), load amplitudes (150, 200, and 250 N), and two types of indenters (Vickers or conical). The Young's modulus, hardness and plasticity index of each specimen were calculated using the indentation test results and Oliver-Pharr method. The accuracy of the experimental results was confirmed by comparing the values of the Young's modulus obtained from the indentation test with the results of the conventional tensile test. Then, a feed-forward shallow artificial neural network (ANN) with high efficiency was trained based on the obtained experimental data. The trained ANN could properly predict the variations of the mentioned mechanical properties of AF/PP composites incorporated with different HNT and ESP loadings. Furthermore, the trained ANN demonstrated that HNTs increase the elastic modulus and hardness of the composite, while the incorporation of ESP reduces these properties. For instance, the Young's modulus of composites incorporated with 3 wt.% of ESP decreased by 30.7% compared with the pure composite, while increasing the weight fraction of ESP up to 6% decreased the Young's modulus by 34.8%. Moreover, the trained ANN indicated that HNTs have a more significant effect on reducing the plasticity index than ESP.

• 한국식품영양과학회지
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• 제43권3호
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• pp.454-458
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• 2014

본 연구에서는 패각에서 유래하는 칼슘의 이용가치를 높이고자 분쇄한 패각 칼슘을 입자 크기별로 제조하여 이온화율과 흡수율을 조사하였다. 패각 칼슘분말 현탁액을 알코올 중에서 비중차이별로 분리하고 입자 크기를 측정하여 4개의 시료군으로 나누었다; NC(일반 패각 칼슘), C-1(1,000 rpm 상등액), C-2(2,000 rpm 상등액), C-3(3,000 rpm 상등액). 이들의 입자 크기는 각각 $2,280.3{\pm}64nm$, $521.3{\pm}83.3nm$, $313.9{\pm}29.5nm$, $280{\pm}3.4nm$를 보였다. 각 칼슘군들을 대상으로 이온화 정도를 측정한 결과 C-3군이 오차범위내에서 다른 군들에 비해 이온화율이 다소 증가했다. In vitro 상에서 dialysis 막을 이용한 나노칼슘의 투과율을 측정한 결과 나노칼슘의 입자 크기가 작을수록 막 투과성이 증대됨을 확인할 수 있었다. 한편 rat의 내장주머니 막(intestinal sac)을 이용하여 장내 환경별 나노칼슘의 투과율을 측정한 결과 C-3군을 제외한 모든 군에서 십이지장(pH 4.2)과 공장(pH 6.2) 환경보다는 회장(pH 7.2)에서의 나노칼슘의 장투과율이 비교적 높게 나타난 반면 C-3군에서는 십이지장 환경에서의 투과율이 다소 높았다. 특히 십이지장 환경에서의 샘플 간 투과율을 비교할 때 C-2와 C-3군이 가장 높은 투과율을 보였고 NC 칼슘이 가장 낮은 투과율을 나타내어 입자 크기가 작을수록 장 투과율이 증가함을 확인할 수 있었다. 위의 결과를 종합해볼 때, 패각에서 유래하는 칼슘을 적절한 가공처리를 거쳐 나노칼슘으로 만들면 칼슘의 이온화율과 장내흡수율을 향상시킬 수 있는 것으로 사료된다.