• Journal of Environmental Health Sciences
• /
• v.45 no.6
• /
• pp.561-568
• /
• 2019

Objectives: The most commonly detected heavy metals in rocks and soils, including Pb, Cd, Cu, Fe, Mn and As, are representative pollutants discharged from abandoned mines and have been listed as potential sources of contamination in drinking water. This study focused on increasing the removal efficiency of heavy metals from drinking water resources by surface modification of natural adsorbents to reduce potential health risks. Methods: Iron oxide coating and graft polymerization with zeolites and talc was conducted for bipolar surface modification to increase the combining capacity of heavy metals for their removal from water. The removal efficiency of heavy metals was measured before and after the surface modification. Results: The removal efficiency of Pb, Cu, and Cd by surface modified zeolite showed 100, 92, and 61.5%, respectively, increases compared to 64, 64, and 38% for non-modified zeolite. This implies that bipolar surface modified natural adsorbents have a good potential use in heavy metal removal. The more interesting finding is the removal increase for As, which has both cation and anion characteristics showing 27% removal efficiency where as non-modified zeolite showed only 2% removal. Conclusions: Zeolite is one of the most widely used adsorptive materials in water treatment processes and bipolar surface modification of zeolite increases its applicability in the removal of heavy metals, especially As.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.1026-1029
• /
• 2002

Outlet of gas has been a big problem in deforming rubber or plastic in pressing mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a produce. In this study, the sintering method is used for making porous metal mold. Porous metal mold has many open pores, which are very small. When Porous metal mold is used for pressing mold, all process would be made short, produce cost would be down, and it would not leave vent marks on the surface of a produce. Porosity varies from sintering and pressing conditions, which are the pressure of compacting powder, the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering temperature condition for the Porous metal mold.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.1
• /
• pp.91-98
• /
• 2003

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• Journal of the Korean Society of Visualization
• /
• v.16 no.1
• /
• pp.54-60
• /
• 2018

It is important to develop more efficient and productive casting processes for an automated high precision molten-metal casting system. Detailed analysis of molten-metal flow in the casting process by the numerical approach will help to optimize the control of a ladle. In this study, the smoothed particle hydrodynamics method was applied to analyze casting flow characteristics with different tilting angular speed and initial molten-metal level. The smoothed particle hydrodynamics technique has advantages to easily handle non-linear free surface behavior with the absence of a computational mesh. We found that tilting angular speed has relatively greater effect on the casting flowrate and that the effect of the initial molten-metal level is only minor. Further extensive study will be necessary to find an optimal condition for high efficient casting system.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.308-311
• /
• 2002

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the Increased cost, the increased number of process. and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of Porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• Journal of the Korean institute of surface engineering
• /
• v.36 no.4
• /
• pp.347-355
• /
• 2003

Roughening of metal surfaces frequently enhances the adhesion strength of metals to polymers by mechanical interlocking. When a failure occurs at a roughened metal/polymer interface, the failure prone to be cohesive. In a previous work, an adhesion study on a roughened metal (oxidized copper-based leadframe)/polymer (Epoxy Molding Compound, EMC) interface was carried out, and the correlation between adhesion strength and failure path was investigated. In the present work, an attempt to interpret the failure path was made under the assumption that microvoids are formed in the EMC as well as near the roots of the CuO needles during compression-molding process. A simple adhesion model developed from the theory of fiber reinforcement of composite materials was introduced to explain the adhesion behavior of the oxidized copper-based leadframe/EMC interface and failure path. It is believed that this adhesion model can be used to explain the adhesion behavior of other similarly roughened metal/polymer interfaces.

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.4
• /
• pp.344-351
• /
• 2002

The purpose of this study is to compare tensile bond strength between Cr-Co alloy and three denture base resins after surface treatment. Following the manufacturer's instructions, 180 bonded specimens were made from three denture base resins (Lucitone 199. Paladent 20. POSS resin) and three surface treatment methods (sandblasting. metal primer. silicoating) 20 samples were made in each group and a half was ther-mocycled 1000 times between $5^{\circ}C$ and $55^{\circ}C$. The tensile bond strength was measured using an Instron with 5mm/min crosshead speed. Data was analyzed with one-way ANOVA, T-test and Duncan test. The results were as follows : 1. Samples with metal primer coating had significantly high tensile bond strength than the other surface treated groups (p<.05). Significantly low tensile bond strength was shown in sand blasted groups (p<.05). 2. No significant difference was observed in metal primer coating groups before and after ther-mocycling (p>.05) 3. Tensile bond strength was decreased in silicoated samples after thermocycling (p<.05). 4. Of the surface treated groups with metal primer, Lucitone 199 had the greatest bond strength and POSS resin and Paladent 20 were followed (p<.05). 5. Of the surface treated groups with silicoating, POSS resin and Lucitone 199 had greater bond strength than Paladent 20 (p<.05).

• The Journal of Advanced Prosthodontics
• /
• v.1 no.2
• /
• pp.68-74
• /
• 2009

STATEMENT OF PROBLEM. When veneering composite resin-metal restoration is prepared, the fact that bond strength between Ti and composite resin is relatively weak should be considered. PURPOSE. The purpose of this study is to evaluate the shear bond strength between the veneering composite resin and commercial pure (CP) Ti / Ti-6Al-4V alloy according to the method of surface treatment. MATERIAL AND METHODS. The disks were cast by two types of metal. Their surfaces were treated by sandblasting, metal conditioner, TiN coating and silicoating respectively. After surface treatment, the disks were veneered by composite resin (Tescera$^{TM}$, Bisco, USA) which is 5 mm in diameter and 3 mm in thickness. The specimens were stored in water at $25^{\circ}C$ for 24 hours, and then evaluated for their shear bond strength by universal testing machine (STM-$5^{(R)}$, United Calibration, USA). These values were statistically analyzed. RESULTS. 1. All methods of surface treatment were used in this study satisfied the requirements of ISO 10477 which is the standard of polymer-based crown and bridge materials. 2. The metal conditioner treated group showed the highest value in shear bond strength of CP Ti, silicoated group, TiN coated group, sandblasted group, in following order. 3. The silicoated group showed the highest value in shear bond strength of Ti-6Al-4V alloy, metal conditioner treated group, sandblasted group, TiN coated group, in following order. CONCLUSION. Within the limitations of this study, all methods of surface treatment used in this study are clinically available.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.3
• /
• pp.34-40
• /
• 2017

In this study, the surface tension of simulant gel propellants was measured by Du $No{\ddot{u}}y$ ring method. The variation of the surface tension was investigated with respect to the amount of the gelling agent, and metal particle addition. Distilled water was used as the base fluid for the preparation of the simulant gel propellant where Carbopol 941 was used as a gelling agent and SUS304 spherical metal particles (mean diameter : 100 nm) as simulant energetic particles. As a result of measurements, surface tension increased with increasing gelling agent concentration while, in the presence of metal particle, different behavior of surface tension has been observed.

• Progress in Medical Physics
• /
• v.10 no.2
• /
• pp.83-88
• /
• 1999

Purpose: TLD experiments were set up to measure the dose distribution and to analyze the influence on dose measurement of thin metal plate and solid water phantom. The aim of the present study was to investigate the build-up effect of metal plate loaded on TLD chip and depth dose in the controlled environment of phantom measurements. Materials and Methods: Measurements were done by using LiF TLD-100 loaded by a thin metal plate with the same surface area (3.2$\times$3.2 $\textrm{mm}^2$) as TLD chip. TLD chips loaded with one metal plate from three different metal plate (Tin, Copper, Gold) of different thicknesses (0.1, 0.15, 0.2, 0.3 mm) were used respectively to measure radiation dose. Using the TLD loaded with one metal plate, surface dose and the depth dose at the build-up maximum region were investigated. Results: Using a metal plate on TLD chip increased the surface dose. Surface dose curve shows the dose build-up against equivalent thickness of metal to water. The values of TL reading obtained by using metal plate at depth of build-up maximum are about 8% to 13% lower than those obtained by normal TLD chip. Conclusion: The metal technique used for TLD dosimetry could provide clinicals information about the build-up of dose up to 4.2mm depth in addition to a depth dose distribution. The results of TLD with a metal plate measurements may help with decisions to boost or bolus certain areas of the skin.