• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.315-323
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• 2021

In general, surface treatments of electroless Ni-P coating are extensively applied in the industry due to their excellent properties for considerable wear resistance, hardness, corrosion resistance. This study aims to determine the effect of ultrasonic conditions on the morphology, alumina content, roughness, hardness, and corrosion resistance of electroless Ni-P-Al₂O₃ composite coatings. The characteristics were analyzed by Energy-dispersive X-ray spectroscopy (EDX), x-ray diffractions (XRD), and atomic force microscopy (AFM), etc. In this study, the effect of ultrasonic condition uniformly distributed alumina within Ni-P solution resulting in a smoother surface, lower surface roughness. Furthermore, the corrosion resistance behavior of the coating was analyzed using tafel polarization curves in a 3.5 wt.% NaCl solution at 25 ℃. Under ultrasonic, Al₂O₃ content in Ni-P composite solution increased from 0.5 to 5.0 g/L, Al₂O₃ content at 3.0 g/L was showed a significantly enhanced corrosion resistance. These results suggested that ultrasonic condition was an effective method to improve the properties of the composite coating.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.393-399
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• 1998

The composition and the properred orientation of Co-Fe-Cr alloy electrodeposits were invesigated according to the electrolysis conditions using sulface bath. The current efficiency and the cathode overpotential decrased noticeably with the increase of Cr content in the bath. As the D.C. current density increased increased, the Cr content in the alloy increasd, while Co content decreased and Fe content remained constant, In the pulse current electrolysis, the Cr content of the alloy increased with the mean current density and off-time and then its content increased mord more noticeably with the peak current density than that of D.C. electrolysis. The preferred orientation of the alloy changed from (220)+(111) to (220) with decreasing cathode overpotential.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.33-40
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• 1991

The decrease in surface roughness of work roll and steel strip in cold rolling of low carbon steel strip has been investigated by working distance, materials, total separating force and total reduction ratio. The main results are as follows; For the same lubricating conditions. 1) The changing of surface roughness of steel strip were similar to work roll. The transcription ratio is in inverse proportion to the carbon content of steel strip. 2) The surface roughness of steel strip is hardly change according to changing of total separating force and total reduction ration. 3) The wear of work rolls surface is more rapid in that case of continuous casted steel strip than ingot casted steel strip. The aluminium content dull powder adhere on the rolls surface, and so. It makes the mirror surface of work roll accelerate.

• Journal of the Korean institute of surface engineering
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• v.45 no.4
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• pp.162-167
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• 2012

Ni-P/C multi-layer was synthesized by electroless plating and paste coating for better corrosion and surface conductance as a metallic bipolar plate. The Ni-P layer could be synthesized with the range of 2.6~22.4 at.% P contents and it's surface morphology and corrosion resistance depend on content of P. Corrosion resistance of the Ni-P layer in sulfuric acid by electrochemical test is similar with pure Ni. Surface resistance of pure Ni after corrosion was increased about 8% compared to pure Ni. On the other hand, that of the Ni-P/C composite with 20% carbon content was increased only 1%.

• Journal of Biosystems Engineering
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• v.27 no.2
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• pp.117-124
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• 2002

This research was conducted to develop a method to remove the effect of surface temperature of Shingo pears for sugar content measurement. Sugar content was measured by a near-infrared spectrum analysis technique. Reflected spectrum and sugar content of a pear were used for developing regression models. For the model development, reflected spectrums having wavelengths in the range of 654 to 1,052nm were used. To remove the effect of surface temperature, special sample preparation techniques and partial least square (PLS) regression models were proposed and tested. 71 Shingo pears stored in a cold storage, which had 2$^{\circ}C$ inside temperature, were taken out and left in a room temperature for a while. Temperature and reflected spectrum of each pear was measured. To increase the temperature distribution of samples, temperature and reflected spectrum of each pear was measured four times with one hour twenty minutes interval. During the experiment, temperature of pears increased up to 17 $^{\circ}C$. The total number of measured spectrum was 284. Three groups of spectrum data were formed according to temperature distribution. First group had surface temperature of 14$^{\circ}C$ and total number of 51. Second group consisted of the first and the fourth experiment data which contained the minimum and the maximum temperatures. Third group consisted of 155 data with normal temperature-distribution. The rest data set were used for model evaluation. Results shelved that PLS model I, which was developed by using the first data group, was inadequate for measuring sugar content of pears which had different surface temperatures from 14$^{\circ}C$. After temperature compensation, sugar content predictions became close to the measured values. Since using many data which had wide range of surface temperatures, PLS model II and III were able to predict sugar content of pears without additional temperature compensation. PLS model IV, which included the surface temperatures as an independent variable. showed slightly improved performance(R$^2$=0.73). Performance of the model could be enhanced by using samples with more wide range of temperatures and sugar contents.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.172-178
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• 2018

In this paper, effects of potassium permanganate, pottasium dichromate, sodium molybdate on lean duplex stainless steel were studied by GDOES, OCP, potentiodynamic curves. The stainless steels were chemically passivated in each nitric acid solutions containing 4wt.% oxidants for 1 hour. As a result, when potassium dichromate or sodium molybdate was added, content of Fe was decreased and content of Cr was increased. Consequently, corrosion resistance of passive film was increased. But in case of potassium permanganate was added, contrastively, content of Fe was increased and content of Cr was decreased. So corrosion resistance was decreased. Adding sodium molybdate in nitric acid for chemical surface treatment process was the most effective among oxidants and also it showed the most stable anti-corrosion in SST.

• Current Photovoltaic Research
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• v.3 no.1
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• pp.27-31
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• 2015

It is known that sulfide at the $Cu(In,Ga)Se_2$ ($CIGSe_2$) surface plays a positive role in $CIGSe_2$ solar cells. We investigated the substitution of S with Se on the $CIGSe_2$ surface in S atmosphere. We observed that the sulfur content in the $CIGSe_2$ films changed according to sulfurization temperature and Cu/(In+Ga) ratio. The sulfur content in the $CIGSe_2$ films increased with increasing the annealing temperature and Cu/(In+Ga) ratio. Also Cu migration toward the surface increased at higher temperature. Since high Cu concentration at the $CIGSe_2$ surface is detrimental role, it is necessary to reduce the S annealing temperature as low as $200^{\circ}C$. The cell performance was improved at $200^{\circ}C$ sulfurization.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.302-314
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• 2016

This study was carried out to confirm the effects of the knife-incising and kerfing pretreatment on the moisture content and surface check occurrence of Douglas-fir heavy timber. In the case of moisture content, the moisture gradient that formed in the inner part of the specimen was observed in all specimens. In addition, the moisture gradient was formed differently from the surface layer to 72 mm depending on the pretreatment conditions, and it was formed gradually in the kerfing than the knife-incising. In addition, it was found that the solid volume should be considered when measuring the average moisture content. In the case of surface check, the surface check occurrence was reduced in the knife-incising, kerfing, and the combination of knife-incising and kerfing than the control. In particular, the kerfing treatment was shown that the expansion of surface check width was effectively suppressed. In the case of knife-incising treatment, although the surface check was less than the control, the preventive effect on the surface check occurrence did not reach the level of the kerfing treatment.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.64-72
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• 2023

Ni-Ti shape memory alloy for dental nerve treatment devices was prepared by adding Mo to Ni-Ti alloy to improve flexibility and fatigue fracture characteristics and simultaneously increase corrosion resistance. Surface properties of the alloy were evaluated. Microstructure analysis of the Ni-Ti-xMo alloy revealed that the amount of needle-like structure increased with increasing Mo content. The shape of the precipitate showed a pattern in which a long needle-like structure gradually disappeared and changed into a small spherical shape. As a result of XRD analysis of the Ni-Ti-xMo alloy, R-phase structure appeared as Mo was added. R-phase and B2 structure were mainly observed. As a result of DSC analysis, phase transformation of the Ti-Ni-Mo alloy showed a two-step phase change of B2-R-B19' transformation with two exothermic peaks and one endothermic peak. As Mo content increased, R-phase formation temperature gradually decreased. As a result of measuring surface hardness of the Ti-Ni-Mo alloy, change in hardness value due to the phase change tended to decrease with increasing Mo content. As a result of the corrosion test, the corrosion potential and pitting potential increased while the current density tended to decrease with increasing Mo content.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.757-762
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• 2002

This study focused on the investigation of durability of latex modified concrete in the points of surface scaling resistance as cement types variated and latex content variated such as 5%, 10%, 15%, and 20%. An increasing the amount of latex produced concrete with increased flexural strength, but with slightly lower compressive strength. The increase in flexural strength might be attributed to the latex films between the hydrated cement and aggregates, and the decrease in compressive strength to the flexibility of the latex component named by Butadiene. The surface scaling resistance test was used to evaluate the durability of latex-modified concretes and rapid setting latex-modified concretes. The surface scaling resistance of LMC was quite good comparing to conventional concrete. Further, surface scaling resistance of RSLMC was improved with increasing the latex content.