• Tribology and Lubricants
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• 제37권2호
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• pp.54-61
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• 2021

The effect of the sand blasting before TiAlN coating in the manufacture of WC hard metal alloy tips have been studied. For four different tips, according to the status of processing of the sand blasting and the coating, residual stress measurement by X-ray diffraction and several tests for mechanical properties have been conducted. The results suggest that there was no difference in static mechanical properties, such as hardness, surface roughness and elastic modulus, between two coatings. Furthermore, compressive residual stress was generated equally on their surfaces. Additionally, the compressive residual stress in substrate WC was found to increase greatly when subjected to sand blasting treatment. However, the compressive residual stress decrease after coating regardless of sand blasting treatment. Nevertheless, it is confirmed that the compressive residual stress generated in the coating after sand blasting is less than that in the non-sandblasting coating. This was attributed to the plastic deformation occurring in the WC substrate during coating after sand blasting. In contrast to the scratch test results, sand blasting was assumed to have a negative effect on the adhesion between the coating and substrate. This is because there is a high possibility of microcracks due to plastic deformation in the WC substrate under the coating after sand blasting.

• 한국양식학회지
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• 제16권2호
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• pp.76-83
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• 2003

본 연구에서는 상향류식 연속 역세여과 연구를 통하여 양어장 순환수 처리 후 박테리아 및 바이러스 등을 효과적으로 처리하는 기술 개발과 여과사에 금속염을 코팅시켜 생물막의 형성을 도모하는 연구를 수행하였다. 여과사를 코팅한 경우 중성 pH에서 zeta potential 양(+)이 됨을 알 수 있었고 zeta potential이 양(+)에 근접할수록 column test에서 바이러스 제거효율이 증가함을 알 수 있었다. 따라서 여과사를 금속염으로 코팅을 하는 경우가 안한 경우 보다 음이온을 띤 부유물 제거에 탁월한 효능이 있음을 보여주었다. pH에 따른 여과재료의 흡착율에서 Al coating과 Al+Fe coating은 반응 시간 30분까지 효과적으로 흡착이 일어나는 것을 볼수 있었고 이 후의 반응시간에서 파과 곡선형태를 보여주었다. 회분식 형태로 운영한 여과재료를 이용한 탈착실험에서 Non, Al, Fe및 Al+Fe coating모두에서 pH 9.95에서 용출(leaching)되는 농도가 가장 높았으며 각각의 농도는 7.47, 4.80, 20.89 및 7.23 mg/L로 각각 나타났다. 이번 연구에서 Al coating의 경우 pH에 따른 영향은 거의 나타나지 않았으며, pH가 증가함에 따라 약간 감소하는 것을 알수 있었고 Fe coating에서는 pH의 영항이 없었으며, Al+Fe coating에서는 pH가 증가함에 따라 탁도도 역시 일정하게 증가하는 것으로 나타났다.

• 대한환경공학회지
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• 제27권7호
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• pp.697-703
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• 2005

본 연구에서는 주문진사 입경, 일차 및 이차 코팅온도, 코팅시간, 및 초기 3가철 주입농도를 변화시키면서 철을 코팅시킨 모래흡착제(Iron-Coated Sand, ICS)를 제조하였다. ICS 제조의 최적조건은 코팅효율, 코팅된 철의 안정성, 및 비소제거능 으로부터 선정하였다. 철코팅 효율은 입경이 작은 모래를 지지체로 사용하고 일차코팅온도를 높여주었을 때 뚜렷이 향상되었다. 철의 코팅효율은 이차코팅온도 및 코팅시간에는 크게 영향을 받지 않았지만 As(V) 흡착능은 이차코팅온도가 증가됨에 따라 크게 감소하는 것으로 나타났다. 이러한 결과들을 고려하여 ICS의 최적 이차코팅 조건을 $150^{\circ}C$ 온도조건과 1시간의 가열시간으로 선정하였다. Fe(III) 주입농도 변화에 따른 철 코팅효율은 0.8 Fe(III) mol/kg sand 될 때 까지는 뚜렷이 증가하였지만 그 이상에서는 큰 차이가 없었다. 기리고 Fe(III) 주입농도를 증가시킬수록 As(V) 흡착능도 증가하였으며 0.8 Fe(III) mol/kg sand 조건에서 최대값을 보여주었다. 이차 코팅온도 및 시간은 ICS 안정성의 주요변수로서 코팅온도를 높이고 코팅시간을 길게 할수록 ICS로 부터 용출되는 철의 양은 감소하였다. ICS에 대한 As(V)의 흡착은 낮은 pH에서 흡착량이 증가하는 전형적인 음이온형 흡착경향을 보여서 ICS는 강한 산성을 띄는 오염수내에 함유된 As(V)를 제거하는데 적용이 가능함을 알 수 있었다.

• 한국세라믹학회지
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• 제34권5호
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• pp.544-551
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• 1997

We tried to improve the coating capability of the coating material using an additive(hexagonal cystalline graphite) of 2%, 3%, 4% and 6% under various pouring temperature for the easy isolation of sand and coating material from the final product. As a result in case of using a 2% and 3% additive generally no burning state has been occurred under the low pouring temperature, but it has been gradually increased with the pouring temperature. On the other hand in case of using a 4% and 6% additive there has been no burning state through out the whole pouring temperature. From this result we could see that the best state of the final product without sand and coating material could generally be obtained if 4% and/or 6% of the crystalline graphite and the pouring temperature of 140$0^{\circ}C$$\pm$5$^{\circ}C$ would be used.

• 대한환경공학회지
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• 제28권1호
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• pp.54-60
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• 2006

주문진사 및 석영사를 담체로 사용하여 코팅온도, 코팅시간, 및 초기 망간용액 주입농도를 변화시키면서 망간(IV)을 코팅시킨 모래흡착제($MnO_2$-Coated Sand, MCS)를 제조하였으며 As(III)의 산화효율을 비교하였다. MCS 제조의 최적조건은 코팅효율 및 As(III) 산화능으로 부터 선정하였다. 망간 코팅효율은 코팅시간에는 크게 영향을 받지 않았지만 코팅온도가 증가함에 따라 증가하였다. 반면 As(III)의 산화능은 코팅온도가 증가됨에 따라 크게 감소하여 나타났다. 이러한 결과들을 고려하여 MCS의 최적 코팅 조건을 $150^{\circ}C$ 온도조건과 1시간의 가열시간으로 선정할 수 있었다. Mn(II) 주입농도가 늘어남에 따라 망간 코팅효율은 뚜렷이 증가하였지만 As(III)의 산화능은 0.8 Mn(II) mol/kg sand 조건에서 최대값을 보여주었다. MCS로 부터의 망간의 용출은 pH가 감소함에 따라 크게 증가하여 나타났다. 최적 조건에서 제조한 MCS를 사용하여 As(III)의 산화반응 특성을 회분식 실험을 통하여 조사한 결과, MCS의 As(III) 산화특성은 MCS의 농도에 대하여 비례적인 반응속도를 보여주었으며 pH가 감소할수록 As(III)의 산화속도가 증가하였다.

• 한국산업보건학회지
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• 제16권1호
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• pp.27-35
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• 2006

The aim of this study was to identify the sources of benzene detected in airborne of casting workplace where benzene was not used as raw material. We have identified benzene by GC/FID and GC/MSD. In this pilot test, small size iron chamber(diameter 30 cm, height 20 cm) was used. As the raw materials, new sand, recovered sand, and mixed casting sand(new sand + solidifying agent + organic resin + coating material) was tested, respectively. In the new sand benzene was not detected, but in the recovered sand and the mixed casting sand was detected. Xylenesulfonic acid(solidifying agent), one of the mixed casting sand ingredients was thought to product benzene by thermal decomposition above $400^{\circ}$..., but the other raw materials(organic resin and coating material) were thought not to product benzene. In this experiment, the most of benzene by thermal decomposition was produced within 1 hour after pouring the iron solution($1560^{\circ}$...) in small size iron chamber. When the mixed casting sand with coating material was used, the concentration of the produced benzene was average 2.91 ppm(range 1.98~3.72 ppm), and without coating material, benzene concentration was average 0.11 ppm(range 0.08~0.14 ppm).

• 한국표면공학회지
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• 제27권3호
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• pp.149-157
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• 1994

The formation of spangles on a hot dip galvanized sheet steel by spray cooling the molten zinc coating with air, water and 2.0wt% $NH_4H_2PO_4$ solution has been studied performing laboratory experiments, and their coating properties have been evaluated. Minimized spangles were easily formed by mist spraying the solution for 1 second at the low nozzle spray pressure onto the molten zinc at 420~$422^{\circ}C$ because the solute $NH_4H_2PO_4$ in the sprayed solution imparted a highly rapid cooling effect to the coating through its endothermic de-composition reactions and because the decomposed products acted as numerous nucleation sites for the mini-mized spangles on the coating. Good surface appearances sand sound coating properties were obtained on this coating. Only regular spangles were formed on the coating by the forced convective air cooling. At the high nozzle spray pressure, zero spangles were formed on the coating by the pure water spray cooling. However, the coating had a dull and rough surface with craters sand cracks.

• Advances in concrete construction
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• 제13권4호
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• pp.315-325
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• 2022

Reinforced concrete structures are exposed throughout their lifetime to the phenomenon of carbonation, which considerably influences their durability by causing corrosion of the reinforcements. The fight against this phenomenon is usually ensured by anti-carbonation coatings which have the possibility of limiting the permeability to carbon dioxide or with coatings which absorb the CO₂ present in the air. A coating with good crack-bridging (sealing) capacity will prevent water from entering through existing cracks in concrete. Despite the beneficial effect of these coatings, their durability decreases considerably over time with temperature and humidity. In order to use coatings made from local materials, not presenting any danger, available in abundance in our country, very economical and easy to operate is the main objective of this work. This paper aim is to contribute to the formulation of a corrected dune sand-based mortar as an anti-carbonation coating for concrete. The results obtained show that the cement mortar based on dune sand formulated has a very satisfactory compressive strength, a very low water porosity compared to ordinary cement mortar and that this mortar allows an improvement in the protection of the concrete against the carbonation of 60% compared to ordinary cement mortar based on alluvial sand. Moreover, the formulated cement mortars based on dune sand have good adhesion to the concrete support, their adhesion strengths are greater than 1.5MPa recommended by the standards.

• 한국주조공학회지
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• 제25권4호
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• pp.173-178
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• 2005

The vacuum molding process is one of the clean-foundry molding-processes that can recycle molding sands repeatedly, because molding can be accomplished by introducing vacuum only among dry molding sands in flask. The effects of molding conditions such as sand grain fineness, vacuum pressure and coating thickness on the fluidity of A356 Al alloy were studied and the results was obtained that the fluidity length was decreased as the sand grain fineness number and coating thikness were decreased and the vacuum pressure was increased. A large amount of heat removal from the molten metal resulting from the vacuum suction during the vacuum molding process was the principal cause of this decrease in fluidity.

• 한국세라믹학회지
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• 제53권5호
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• pp.541-547
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• 2016

In developing high temperature molds with advantages of the sand and precision (investment) castings, mechanical properties of the mold were improved through homogeneous coating of starting powders with an inorganic binder and improvement of fabrication process. Beads with mullite composition were employed for properties of the mold under high temperature, which was compared with artificial sands. Precursors of silica and sodium oxide were used as starting materials for an inorganic binder to achieve homogeneous coating on the starting powders. Strength was enhanced by the glass phase converted from the inorganic binder through heat treatment process. Also, two kinds of process, wet and dry processes, were incorporated to prepare mold specimens. Consequently, fabrication process of the mold with superior strength and high temperature applicability, compared with the previous molds for sand casting, could be suggested through control of the starting material and enhancement of the vitrification efficiency.