• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.9-14
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• 2011

We have investigated the electrical properties of $AlO_x$ thin film device. The device has been fabricated top-bottom electrode structure and its transport properties are measured in order to study the resistance change. Electrical properties with linear voltage sweep on a electrodes are used to show the variation of resistance of $AlO_x$ thin film device. Fabricated $AlO_x$ thin film device with MIM structure is changed from a high conductive On-state to a low conductive Off-state by the external linear voltage sweep. It is found that the initial resistance of the $AlO_x$ thin film is low-resistance On state and reversible switching occurs. Consequently, we believe $AlO_x$ thin film is a promising material for a next-generation nonvolatile memory and other electrical applications.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.386-390
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• 2005

Al film(135.5 nm thick) with Pd film(39.6 nm thick) on the top of it was made by thermal evaporation method. Electrical resistance change due to hydrogen absorption and desorption was measured by four point measurement method. The sample was activated by hydrogen absorption and desorption cycling at room temp. Hydrogen was introduced into the film by increasing hydrogen gas pressure step by step up to 640 torr at room temp. The resistance change ratio was decreased to 12 % with increasing hydrogen pressure in contrast to normal metal behavior. This strange tendency was not understood yet. Further study is needed to find out the mechanism of hydrogen absorption in Al in Al/Pd film.

• Korean Journal of Materials Research
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• v.22 no.12
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• pp.643-649
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• 2012

Coatings composited with alumina and Perfluoro alkoxyalkane (PFA) resin were deposited on stainless steel plate (SUS304) to further improve corrosion resistance. Plate (ca. $10{\mu}m$) and/or nanosize (27~43 nm) alumina used as inorganic additives were mixed in PFA resin to make alumina-fluoro composite coatings. These coatings were deposited on SUS304 plate with wet spray coating and then the film was cured thermally. According to the amount and ratio of the two kinds of alumina having plate morphology and nano size, corrosion resistance of the film was evaluated under strong acids (HF, HCl) and a strong base (NaOH). The film prepared with the addition of 5~10 wt% alumina powders in PFA resin showed corrosion resistance superior to that of pure PFA resin film. However, for the film prepared with alumina content above 10 wt%, the corrosion resistance did not improve with the physical properties, such as surface hardness and adhesion. The film prepared with plate/nanosize (weight ratio = 1/2) alumina especially enhanced the surface hardness and corrosion resistance. This can be explained as showing that the plate and the nanosize alumina dispersed in PFA resin effectively suppressed the penetration of cations and anions due to the long penetration length and fewer defects that accompany the improved surface hardness under a serious environment of 10% HF solution for over 120 hrs.

• Polymer(Korea)
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• v.38 no.5
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• pp.573-579
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• 2014

The effect of synthesis conditions such as carbon nanotube (CNT), 2,2,2-trifluoroethylmethacrylate (3FMA), and composition of organic-inorganic material in ozone resistance and surface characteristics of ultraviolet cured organic-inorganic hybrid coating film has been investigated. Coating solution was prepared using tetraethoxysilane (TEOS), silane coupling agent methacryloyloxypropyltrimethoxysilane (MPTMS), 3FMA, various organic materials with acrylate group, and CNT, then bar-coated on substrates using applicator, and densified by UV-curing. It was found that ozone resistance and adhesion of the coating film were strongly dependent upon contents of TEOS, 3FMA, and CNT. Especially, ozone resistance, adhesion, and surface hardness of coating film with CNT were improved, relatively. Ozone resistance of coating film with a high TEOS content was increased, but adhesion was decreased. In addition, it was also found that ozone resistance of coating film was increased with contents of 3FMA. On the other hand, surface hardness was decreased with increase of 3FMA.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.334-341
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• 2007

Al film(135.5 nm thick) with Pd film(39.6 nm thick) was made by thermal evaporation method. Electrical resistance change by hydrogen absorption and desorption was measured with four point measurement method. Even though Al film(135.5 nm thick) did not absorb any hydrogen at room temperature, Al/Pd film absorbed hydrogen at upto 640 torr pressure. Hydrogen absorption kinetics was monitored by measuring resistance change of the sample in the temperature range from $25^{\circ}C$ to $40^{\circ}C$. Absorption activation energy of Al/Pd film was about 10.7 and 17.7 kcal/mol H for 1st stage and last stage respectively at 1 torr hydrogen pressure. This activation values are bigger than that of Pd film, but are much less than that of Al film. This result indicates there is possibility that Al can be storage material for hydrogen by using Pd film evaporation on it.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.12-13
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• 2012

An environmentally friendly method for in situ growth of Mg-Al hydrotalcite (HT) film on AZ31 magnesium alloy has been developed. The growth processes and corrosion resistance of the HT film were investigated. Then the HT film was surface modified by phytic acid solution to further improve the corrosion resistance. The film formation involves the dissolution of AZ31 substrate, adsorption of the ions from solution, nucleation of the precursor, followed by the dissolution of $Al^{3+}$, exchanging of $OH^-$ by $CO{_3}^{2-}$ and growth of the HT film. The HT film is very compact and acts as a barrier against $Cl^-$ attack in the early stage of corrosion, and then the surface of the film is dissolved gradually. This dense HT film can provide effective protection to the AZ31 alloy. The HT film with surface modification by phytic acid presents a self-healing feature and exhibits better corrosion resistance.

• 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).

• Journal of Biomedical Engineering Research
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• v.14 no.4
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• pp.333-340
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• 1993

The high biocompatibility of titanium is connected with the high corrosion resistance of the surface oxide, its high dielectric constant, and some other specific biochemical properties of the oxide. The corrosion resistance of titanium can be improved with the formation of passive film by anodic oxidation. In other to characterize the titantium oxlde film formed by anodic oxidation, titanium plates were anodized in 0.5M $H_3SO_4$ electrolyte at voltages between 5V and 100v. The oxide film was examined by an X-Ray Diffractometer(XRD) and a Scanning Electron Microscope(SEM). In addition, the corrosion resistance of oxide film was tested by dipping in physiological NaCl,5% HCI,5% $H_3PO_4$ and its biocompatability was evaluated by the fibroblast-like cell culture. The results obtained are as follows : 1. The thickness of surface oxide and micropore are increased with the increase of electrode potential and formed deeply along the grain boundary. 2. The solubilities of titanium in electrolyte solution shows that the anodized titanium has more corrosion resistance than the untreated pure titanium. 3. The biocomatibility of anodized titanium is superior to untreated pure titanium.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.101-110
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• 1997

An experimental study was performed to discover the tribological behaviors of pure silver coated 52100 bearing steel. Pure silver coatings ranging from 80 nm to several micrometers were produced by a thermal evaporation coating method. Experiments using a thrust ball bearing-typed rolling test-rig were performed for the investigations of the influence of coating thickness on the tribological rolling behavior. The existence of optimum film thickness which revealed minimum rolling resistance was discovered. A careful analysis on the contact surfaces for the optimum film thickness has been performed. The contact patches produced by the transferred silver films played an important role for the rolling resistance to keep low.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.676-681
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• 2002

Microstructure, mechanical properties, and oxidation resistance of TiAIN thin films deposited on quenched and tempered STD61 tool steel by arc ion plating were studied using XRD, XPS and micro-balance. The TiAIN film was grown with the (200) orientation. The grain size of TiAIN thin film decreased with increasing Al contents, while chemical binding energy increased with Al contents. When hard coating films were oxidized at $850^{\circ}C$ in air, oxidation resistance of both TiN and TiCN films became relatively lower since the surface of films formed non-protective film such as $TiO_2$. However, oxidation resistance of TiAIN film was excellent because its surface formed protective layer such as $_A12$$O_3$ and $_Al2$$Ti_{7}$$O_{15}$, which suppressed oxygen intrusion.