• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.925-931
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• 2007

We successively fabricated the Ni metal mask by additive method and evaluated the effects of wetting agents addition on the microstructure, hardness, and friction coefficient. In the process, the additive patterns with fine hole and pitch were made by photolithography technique and subsequently Ni plate was electroformed on the patterns. We found that the microstructure and mechanical properties were significantly varied when the different combinations of the wetting agents were used. When the wetting agents of both SF-1 and SF-2 were added, the microstructure consisted of crystal and amorphous phases, the grain size reduced to 5-40 nm, the RMS value decreased to 11.4 nm and the wear resistance improved. In addition, the hardness was as high as 638 Hv which is higher than that of commercial stainless steel mask and this improvement is probably due to the presence of amorphous Phase and fine grain size. The improvement of the wear resistance can provide a higher reliability and a longer service life.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.591-597
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• 2012

This paper presents regularly micro-textured glass surfaces ensuring the superhydrophobic properties in the Cassie-Baxter regime. The proposed surfaces were fabricated simply and efficiently by filling the glass material into a silicon micro-mold with periodic micro-cavities based on a thermal-reflow process, resulting in a successful demonstration of the textured glass surface with periodically-arrayed micro-pillar structures. The static and dynamic wetting properties of the micro-textured glass surfaces were characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH), respectively. In addition, the surface wettability was estimated theoretically based on Wenzel and Cassie-Baxter wetting theories, and compared with the experimental ones. Through the experimental and theoretical observations, it was clearly confirmed that the proposed micro-textured glass surfaces showed the slippery superhydrophobic behaviors in the Cassie-Baxter wetting mode.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.153-167
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• 2022

This study proposes a method to analyze the distribution of coal porosity disturbances after the excavation of ultra-large-diameter water jet boreholes using a coal wetting and softening model. The high-pressure jet is regarded as a short-term high-pressure water injection process. The water injection range is the coal softening range. The time when the reference point of the borehole wall is shocked by the high-pressure water column is equivalent to the time of high-pressure water injection of the coal wall. The influence of roadway excavation with support and borehole diameter on the ultra-large-diameter jet drilling excavation is also studied. The coal core around the borehole is used to measure the gas permeability for determining the porosity disturbance distribution of the coal in the sampling plane to verify the correctness of the simulation results. Results show that the excavation borehole is beneficial to the expansion of the roadway excavation disturbance, and the expansion distance of the roadway excavation disturbance has a quadratic relationship with the borehole diameter. Wetting and softening of the coal around the borehole wall will promote the uniform distribution of the overall porosity disturbance and reduce the amplitude of disturbance fluctuations.

• Journal of Korea Foundry Society
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• v.14 no.3
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• pp.274-284
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• 1994

SiC fibers were coated with Cu, Ag and Ni metallic thin films by magnetron sputtering in order to improve wetting properties between Al matrix and SiC fiber. The wetting behavior of metal coated SiC fiber by pure Al has been studied at $670^{\circ}C{\sim}900^{\circ}C$ range for $10{\sim}90min$. under vacuum atmosphere. Besides, the effect of coated film thickness on the wettability has been investigated. The wetting behavior and interfacial reaction between Al and SiC fibers were analysed with optical microscope and SEM (scanning electron microscope). The wetting behavior of the as-received SiC fiber with Al melt was not uniform, indicated by the contact angles from less than $90^{\circ} to more Al melt was appeared in the initial stage of reation. It was considered that the metallic thin film played an important role in reducing the interfacial free energy and breaking down the aluminum oxide film by eutectic reaction with Al melt. However the wettability of Ni coated SiC fiber was not improved as much as that of Cu or Ag coated SiC fiber. The improvement of wettability by coating thickness is clearly showed in $1{\mu}m$ coated SiC fiber compared with $0.25{\mu}m$ coated SiC.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.606-613
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• 1993

This was studied about aging characteristic of AC4A/$SiC_{w}$ 10-30v/o reinforced composite. Aging hardenability was decreased $SiC_{w}$ 30% > 10% > 20%. Aging hardening of T6 treatmented composite was higher absolute value than AC4A I/M material. And this results indicated initial hardening phenomenon according to increase $SiC_{w}$ volume fraction. Reinforced effect by pressure was the same effect as before aging treatment and the best condition pressure at 75MPa. Similar to reinforced effect according to $SiC_{w}$ volume fraction was 30 % > 10 % > 20 %. In case of pressure is low, whisker is not break the same time press with base metal after wetting. After it is wetting with base metal, a part transformed or wetting part break and whisker maintain original shape or a part transformed on the otherhand, in case of pressure is high, whisker is break in same time it was not against pressure and whisker's shape is near a polygon or spherical shape.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.235-242
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• 2005

This study is on the evaluation of performance of polymer cement mortar which is used for pre-wetting spray method. Pre-wetting spray method is an epoch-making method to repair concrete structures damaged, which is added a small quantity water preciously to dry mortar to reduce dust and rebound and spray mortar mixed with fixed quantity water at nozzle before spray. The result showed that physical performance such like compressive, flexural and adhesive strength of polymer cement mortar, TS 100 used for pre-wetting spray method was superior to other repair mortar. Also durable performance such as resistance on permeability of chloride ion, carbonation, chemical and freezing-thawing was excellent.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.25-34
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• 2018

The physical properties and unsaturated characteristics of acid sulfate soils were investigated and analyzed. As the results of measuring physical properties of the acid sulfate soils obtained around the Ilkwang mine area, the dry unit weight is $1.246t/m^3$ and this soil is classified into the silty sand (SM) by USCS. Soil Water Characteristics Curves (SWCC) of the drying and wetting paths were measured by the automated SWCC apparatus. Also, Hydraulic Conductivity Functions (HCF) of the drying and wetting paths were estimated by the van Geunchten (1980) model which is the most well-known parameter estimation method. The hydraulic conductivity of acid sulfate soils in the dry path was continuously decreased with increasing the matric suction. However, the hydraulic conductivity in the wetting path was decreased relatively small with increasing matric suction and decreased suddenly just before water entry value of matric suction. Meanwhile, the hysteresis phenomenon was occurred in SWCCs and HCFs during the drying and wetting paths.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.41-47
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• 2007

Geotechnical Phenomena such as landslide, groundwater recharge and groundwater fluctuation due to rainfall can be explain to use a dielectric response and infiltration variation by the movement of a wetting front in the subsurface. The infiltration of a wetting front is infiltrating to the connected pores which are distributed in unsaturated soil. In this study we carried out to laboratory experiment of a vertical infiltration column test using ethanol mix-ing tracer which has same the specific gravity of water. All physical values are detected to use a variation of dielectric constant and calculated to use a dielectric mixing model and tracer test model. This dielectric method measured by each dielectric constant of geological soil porous materials should be of for the geotechnical information and useful a field monitoring technique for detecting the variations of the volumetric water content and the wetting front, which are insignificant the key parameter to understanding the landslide by rainfall.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.35-41
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• 2015

In this study, in order to improve the reliability of ACF interconnections, solder ACF joints were investigated interms of solder joint morphology and solder wetting areas, and evaluated the electrical properties of Flex-on-Board (FOB) interconncections. Solder ACF joints with the ultrasonic bonding method showed excellent solder wetting by broken solder oxide layers on solder surfaces compared with solder joints with remaining solder oxide layer bonded by the conventional thermo-compression (TC) bonding method. When higher target temperature was used, Sn58Bi solder joints showed concave shape due to lower degree of cure of resin at solder MP by higher heating rate. ACFs with epoxy resins and SAC305 solders showed lower degree of resin cure at solder MP due to the slow curing rate resulting in concave shaped solder joints. In terms of solder wetting area, solder ACFs with $25-32{\mu}m$ diameters and 30-40 wt% showed highest wetted solder areas. Solder ACF joints with the concave shape and the highest wetting area showed lower contact resistances and higher reliability in PCT results than conventional ACF joints. These results indicate that solder morphologies and wetting areas of solder ACF joints can be controlled by adjustment of bonding conditions and material properties of solder and polymer resin to improve reliability of ACF joints.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.29-34
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• 2014

In order to examine strength properties depended on climate changes of solidified soil amended by porosity silica which enhance harms of cement, this study conducts a wetting and drying repetition test and then, attempts to verify strength properties before and after solidified soil gets environmental influence. Test pieces for the unconfined compression test changed the mixing ratio of solidified soil compared to mixed soil weigh to 5 %, 10 % and 15 %. For each step, it was created by mixing 0.5 %, 1.0 % and 1.5 % of wood chips, and curing period for 7, 14, and 28 days. Then, the wetting and drying repetition process was repeated 0, 3, 6, and 12 cycles to analyze mechanical properties. To also evaluate changes of relative dynamic elastic modulus before and after the wetting and drying, dynamic elastic modulus tests were conducted when each cycle was completed.