• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.171-177
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• 2002

Metal matrix composites had generated a lot of interest in recent times because of significant in specific properties, it was also highlighted as the material of frontier industry because strength, heat-resistant, corrosion-resistant and wear-resistant were superiored. In recent years, the study of metal matrix composite has increased by aluminum alloy. The study is based on the tribological properties of AC4CH that is a part of the mechanical property of metal matrix composites. Metal matrix composite that is produced from matrix material AC4CH and reinforcement SiO$_2$, Al$_2$O$_3$ and TiO$_2$ are added to the metal matrix composite fur strength so binding among the whisker can take place. Each metal matrix composite is produced using the squeeze casting method. To test for tribe a pin-on-disk machine and lubricant is used without paraffine 8.2CST at room temperature which is 40$\^{C}$. As the results of this study, the tribological properties of each specimen are more improved than AC4CH. The variation of coefficient resistance is more stable at the AC4CH and TiO$_2$, but the variation rates are higher at the inanimate binder.

• Korean Journal of Materials Research
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• v.20 no.4
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• pp.194-198
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• 2010

Cubic boron nitride (c-BN) is a promising material for use in many potential applications because of its outstanding physical properties such as high thermal stability, high abrasive wear resistance, and super hardness. Even though 316L austenitic stainless steel (STS) has poor wear resistance causing it to be toxic in the body due to wear and material chips, 316L STS has been used for implant biomaterials in orthopedics due to its good corrosion resistance and mechanical properties. Therefore, in the present study, c-BN films with a $B_4C$ layer were applied to a 316L STS specimen in order to improve its wear resistance. The deposition of the c-BN films was performed using an r.f. (13.56 MHz) magnetron sputtering system with a $B_4C$ target. The coating layers were characterized using XPS and SEM, and the mechanical properties were investigated using a nanoindenter. The friction coefficient of the c-BN coated 316L STS steel was obtained using a pin-on-disk according to the ASTM G163-99. The thickness of the obtained c-BN and $B_4C$ were about 220 nm and 630 nm, respectively. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of $sp^3$ BN bonds. The hardness and elastic modulus of the c-BN measured by the nanoindenter were 46.8 GPa and 345.7 GPa, respectively. The friction coefficient of the c-BN coated 316L STS was decreased from 3.5 to 1.6. The wear property of the c-BN coated 316L STS was enhanced by a factor of two.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.14-14
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• 2001

Nitride films such as TiN, CrN etc. deposited on glass by PVD processes have been developed for many industrial applications. These nitride films deposited on glass were widely used for not only decorative and optical coatings but also wear and corrosion resistance coatings employed as dies and molds made of glass for the example of lens forming molds. However, the major problem of nitride coatings on glass by PVD process is non-uniform film owing to pin-hole and micro crack. It is estimated that nonuniform coating is influenced by a different surface energy between metal nitrides and glass due to binding states. In this work, therefore, for the evaluation of nucleation and growth mechanism of nitride films on glass TiN and CrN film were synthesized on glass with various nitrogen partial pressure by unbalanced magnetron sputtering. Prior to deposition, for the examination of relationship between surface energy and film microstructure plasma pre-treatment process was carried out with various argon to hydrogen flow rate and substrate bias voltage, duty cycle and frequency by using pulsed DC power supply. Surface energy owing to the different plasma pre-treatment was calculated by the measurement of wetting angle and surface conditions of glass were investigated by X-ray Photoelectron Spectroscopy(XPS) and Atomic Force Microscope(AFM). The microstructure change of nitride films on glass with increase of film thickness were analyzed by X-Ray Diffraction(XRD) and Scanning Electron Microscopy(SEM).

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.207-210
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• 2017

The suspension arrangement of insulators provides flexibility and assists in power transmission in transmission lines. The performance of the insulator string is strongly influenced by the environmental conditions to which it is exposed, its shape and the inherent material properties of suspension-type insulators. The suspension-type insulators are mostly made from glass, porcelain and ceramic material due to their high resistivity. Irregularity in charge distribution throughout the porcelain insulator may lead to accelerated aging and electrical breakdown. A very high and steep lightning impulse voltage may also cause breakdown of suspension-type insulators. We investigated various material characteristics such as alumina addition, surface morphology, x-ray diffraction pattern and relative density of suspension porcelain insulators manufactured in 1989 (36,000 lbs.), 1995 (36,000 lbs.) and 2001 (36,000 lbs.) by the KRI Company for use in 154 kV high power transmission lines. We compared the material characteristics of these porcelain insulators with that of the top-of-the-line porcelain insulators (36,000 lbs.) manufactured by the NGK Company in 2000. These suspension-type porcelain insulators were exposed to arc and flashover tests to examine their electrical and mechanical strength. It was noted that alumina addition (17 wt.%) for K-2001 was one of the major contributors to the enhancement of the performance of the porcelain insulators and to their ability to withstand very high current generation during the arc test. The porcelain insulators manufactured during 2001 also showed the highest relative density of 95.8% as compared to the other insulators manufactured in 1989 and 1995 respectively 94.2% and 91.5%. We also discuss reports of various failure modes of suspension-type porcelain insulators.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.1
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• pp.84-95
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• 2001

Titanium is widely used in dentistry for its low density, high strength, fatigue resistance, corrosion resistance, and biocompatibility. But it has a tendency of surface damage under circumstance of friction and impact for its low hardness of the surface. Coating is one of methods fir increasing surface hardness. Its effect is to improve surface physical characteristics without change of titanium. Diamond-like carbon and titanium nitride are known for its high hardness of the surface. So that this study was aimed at the wear test and the cytotoxicity test of the commercially pure titanium and Ti-6Al-4V alloy which were deposited by diamond-like carbon film or titanium nitride film to acertain improvement of the surface hardness and the biocompatibility. A disk (25mm diameter, 2mm thickness) was made of commercially pure titanium and Ti-6Al-4V alloy and these substrates were deposited by diamond-like carbon film or titanium nitride film. Diamond-like carbon film was deposited by the method of radiofrequency plasma assisted chemical vapor deposition and titanium nitride film was deposited by the method of reactive arc ion plating. Then these substrates were tested about wear characteristics by the pin-on-disk type wear tester in which ruby ball was used as a wear causer under the load of 32N, The fracture cycles were measured by rotating the substrates until their films were fractured. The wear volume was measured after 150 cycles and 3,000 cycles using surface profiler. The cytotoxicity test was peformed by the method of the MTT assay. The results were as follows : 1. In the results of the wear volume test, commercially pure titanium and titanium alloy which were coated by diamond-like carbon film or titanium nitride aim had higher resistance against wear than the substrates which were not coated by any films (P<0.05). 2. In the results of the fracture cycle test and the wear volume test, diamond-like carbon film had higher resistance against wear than titanium nitride film (P<0.05). 3. In both coatings of diamond-like carbon aim and titanium nitride film, Ti-6Al-4V alloy had higher resistance against wear than commercially pure titanium (P<0.05) 4. In the results of the cytotoxicity test, diamond-like carbon film and titanium nitride film had little cytotoxicity as like commercially pure titanium or Ti-6Al-4V alloy (P>0.05).