• Journal of the Korean institute of surface engineering
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• v.25 no.4
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• pp.189-206
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• 1992

The effect of activation and electroless nickel plating conditions on contact properties was investi-gated for selective electroless nickel plating of Si wafers in order to obtain an optimum condition of con-tact hole filling. According to RCA prosess, p-type silicon (100) surface was cleaned out and activated. The effects of temperature, DMAB concentration, time, and strirring were investigated for activation of p-type Si(100) surface. The optimal activation condition was 0.2M HF, 1mM PdCl2, 2mM EDTA,$ 70^{\circ}C$, and 90sec under ultrasonic vibration. In electroless nickel plating, the effect of temperature, DMAB concentra-tion, pH, and plating time were studied. The optimal plating condition found was 0.10M NiSO4.H2O, 0.11M Citrate, pH 6.8, $60^{\circ}C$, 30minutes. The contact resistance of films was comparatively low. It took 30minutes to obtain 1$\mu\textrm{m}$ thick film with 8mM DMAB concentration. The film surface roughness was improved with decreasing temperature and decreasing pH of the plating solution. The best quality of the film was obtained at the condition of temperature $60^{\circ}C$ and pH 6.0. The micro-vickers hardness of film was about 800Hv. Plating rate of nickel on the hole pattern was slower than that of nickel on the line pattern.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.445-449
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• 2018

Chromium plating is a common surface treatment technique extensively applied in industry due its excellent properties which include substantial hardness, abrasion resistance, corrosion resistance, surface color, and luster. In this study, the effect of $MoS_2$ particles of the composite coating was investigated. To improve the lubrication of mold, $Cr-P-C/MoS_2$ composite plating was studied by varying the $MoS_2$ content. The current efficiency of the composite plating incorporated $MoS_2$ particles was increased at $MoS_2$ contents of 0.5 and 1.0 g/l due to the incorporation of fine particles. On the other hand, when the content of $MoS_2$ is 1.0 g/l or more, the current efficiency is lowered due to an increase in impact on the cathode surface. In order to evaluate the mechanical properties of Scratch test were conducted. Scratch test confirmed the lubricity and abrasion resistance characteristics revealed that the composite plating with added $MoS_2$ had relatively low surface roughness and uniform surface modification to improve its properties.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.97-103
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• 2006

In this paper, effect of temperature in TiN-coating by arc ion plating on surface characteristics of a TiN coated high speed steel is investigated by experiments. Hardness, surface roughness, TiN-coating thickness and adsorption force are measured in order to evaluate the effects. For evaluation of the experimental data, one-way ANOVA method is used. It is concluded that the furnace temperature in the range $400^[\circ}C\~500^{\circ}C$ in AIP processing has a little influence on the TiN coating of the SKH51 steels.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.609-616
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• 2019

Oxide coatings are formed on die-cast AZ91D Mg alloy through an environmentally friendly plasma electrolytic oxidation(PEO) process using an electrolytic solution of $NaAlO_2$, KOH, and KF. The effects of PEO condition with different duty cycles (10 %, 20 %, and 40 %) and frequencies(500 Hz, 1,000 Hz, and 2,000 Hz) on the crystal phase, composition, microstructure, and micro-hardness properties of the oxide coatings are investigated. The oxide coatings on die-cast AZ91D Mg alloy mainly consist of MgO and $MgAl_2O_4$ phases. The proportion of each crystalline phase depends on various electrical parameters, such as duty cycle and frequency. The surfaces of oxide coatings exhibit as craters of pancake-shaped oxide melting and solidification particles. The pore size and surface roughness of the oxide coating increase considerably with increase in the number of duty cycles, while the densification and thickness of oxide coatings increase progressively. Differences in the growth mechanism may be attributed to differences in oxide growth during PEO treatment that occur because the applied operating voltage is insufficient to reach breakdown voltage at higher frequencies. PEO treatment also results in the oxide coating having strong adhesion properties on the Mg alloy. The micro-hardness at the cross-section of oxide coatings is much higher not only compared to that on the surface but also compared to that of the conventional anodizing oxide coatings. The oxide coatings are found to improve the micro-hardness with the increase in the number of duty cycles, which suggests that various electrical parameters, such as duty cycle and frequency, are among the key factors controlling the structural and physical properties of the oxide coating.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.588-593
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• 2023

The advantage of OTFT technology is that large-area circuits can be manufactured on flexible substrates using a low-cost solution process such as inkjet printing. Compared to silicon-based inorganic semiconductor processes, the process temperature is lower and the process time is shorter, so it can be widely applied to fields that do not require high electron mobility. Materials that have utility as electrode materials include carbon that can be solution-processed, transparent carbon thin films, and metallic nanoparticles, etc. are being studied. Recently, a technology has been developed to facilitate charge injection by coating the surface of the Al electrode with solution-processable titanium oxide (TiOx), which can greatly improve the performance of OTFT. In order to commercialize OTFT technology, an appropriate method is to use a complementary circuit with excellent reliability and stability. For this, insulators and channel semiconductors using organic materials must have stability in the air. In this study, carbon-doped Mo (MoC) thin films were fabricated with different graphite target power densities via unbalanced magnetron sputtering (UBM). The influence of graphite target power density on the structural, surface area, physical, and electrical properties of MoC films was investigated. MoC thin films deposited by the unbalanced magnetron sputtering method exhibited a smooth and uniform surface. However, as the graphite target power density increased, the rms surface roughness of the MoC film increased, and the hardness and elastic modulus of the MoC thin film increased. Additionally, as the graphite target power density increased, the resistivity value of the MoC film increased. In the performance of an organic thin film transistor using a MoC gate electrode, the carrier mobility, threshold voltage, and drain current on/off ratio (I_on/I_off) showed 0.15 cm²/V·s, -5.6 V, and 7.5×10⁴, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.50-56
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• 2015

In this study, AISI M2 powder was selected primarily through various pieces of literature in order to improve the hardness and wear resistance. Among the laser metal deposition parameters, laser power was studied to improve the deposition efficiency in the laser metal deposition using a diode-pumped disk laser. An SKD61 hot work steel plate and AISI M2 powder were used as a substrate and powder for laser metal deposition, respectively. Experiments for the laser metal deposition were carried out by changing the laser power and track layer. The quality of the track surface and cross-section after applying the single-layer method was better than that obtained from applying the multi-layer method. As the laser power increased, the track thickness was increased, and the surface roughness deviation was decreased. In laser power condition of 1.6kW, the maximum hardness of the deposition track was 790Hv. This value was 40% better than the hardness of the SKD61 after heat treatment.

• Transactions of the Society of Information Storage Systems
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• v.3 no.2
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• pp.66-72
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• 2007

Surface finishing using magnetorheological (MR) fluid is useful to finish small but not too small workpieces such as those in a few millimeter scale. However, due to the high surface hardness, this finishing process does not seem to be suit for applying to a hard disk slider. In this work, a preliminary study is performed on the finishing of the hard disk slider surface with a mixture of an MR fluid and diamond powder. During a wheel type MR finishing process, centrifugal force is found to be a major factor to cause a reduction in material remove rate (MRR), which is supported by a theoretical model. To facilitate this founding, the rotational speed of tool is confined to 500rpm while a rectilinear alternating motion with the mean speed, which is equivalent to the rotational speed, is additionally applied to the workpieces. As a consequence, MRR of about 2 times of the sole rotational case is obtained. This paper shows that MR finishing process can be used to polish a hard material in millimeter scale efficiently by controlling the speeds of the tool and the workpiece.

• Design & Manufacturing
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• v.11 no.3
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• pp.8-12
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• 2017

In general, metallic bio-materials is more widely used in solid tissue like bone or tooth than flexible tissue such as skin or muscle. Especially, Cobalt Chrome Molybdenum(Co-Cr-Mo), which is used in tooth surgery, has a great corrosion resistance. Because this bio-material is non-toxic in human body, and has a bio-compatibility that the vital reaction is not occurred with tissue in body. However the chemical reaction is occurred by fatal matter that deteriorate the property of material surface in conventional polishing, and it can affect to fatal disease in human body or decrease the material properties such as hardness, yield strength or bio-compatibility. This surface in poor condition can cause development of corrosion or bacteria. In this study, MR fluid polishing is used to minimize the scratch, pit or surface flaws generated in conventional polishing. Surface roughness is measured according to the polishing condition to obtain fine surface condition.

• Transactions of Materials Processing
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• v.17 no.5
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• pp.343-349
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• 2008

The wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. This study will discuss characteristics of wear between hard and soft piston ring coatings with running surface of cylinder liner. Detailed tribological analysis by using Pin-on-Disk(POD) testing machine describes the lubricity mechanism between piston ring coatings and cylinder liner at different temperature with and without oil. The effect of surface roughness of the cylinder liner on the friction coefficient and wear amount of piston ring coatings will also be analyzed. To simulate scuffing mechanism between piston ring and cylinder liner, accelerated lab testing was performed. This study will provide the data from tribological testing of hard and soft piston ring coatings against cylinder liner. Furthermore, the microstructures and morphological features of the surface and the near-surface materials during wear will be investigated. From the scuffing test by using POD testing machine, scuffing mechanisms for the soft and hard coating will be analyzed and experimentally confirmed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.33-35
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• 2011

Films of CrAlN and CrZrN were deposited on a steel substrate by closed field unbalanced magnetron sputtering, and their oxidation behaviors were investigated. CrAlN films consisted of dense, polycrystalline CrN and AlN fine columns. The formed oxides consisted primarily of crystalline $Cr_2O_3$ incorporated with $Al_2O_3$. The oxide layers were thin and compact so as to make CrAlN films more protective than CrN films. In case of CrZrN films, Zr atoms were dissolved in the CrN phase. Zr atoms advantageously refined the columnar structure, reduced the surface roughness, and increased the micro-hardness. However, the addition of Zr did not increased oxidation resistance, mainly because Zr was not a protective element. All the deposited films displayed relatively good oxidation resistance, owing to the formation of the highly protective $Cr_2O_3$ on their surface. The $Cr_{40}Zr_9N$ and $Cr_{31}Zr_{16}N$ films oxidized to $Cr_2O_3$ as the major phase and ${\alpha}-ZrO_2$ as the minor one, whereas the CrN film oxidized to $Cr_2O_3$.