• Title/Summary/Keyword: Film cracks

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Evaluation of Failure Modes and Adhesion of DLC Films by Scratch Test (스크래치 시험을 통한 DLC 박막 파손과 밀착 특성 평가)

  • Kim, Ju Hee;Park, Chanhyung;Ahn, Hyo Sok
    • Tribology and Lubricants
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    • v.33 no.4
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    • pp.127-133
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    • 2017
  • In order to characterize the adhesive properties and failure mechanisms of diamond-like carbon (DLC) films of two different thicknesses (130 nm and $1.2{\mu}m$), deposited by plasma-enhanced chemical vapor deposition on a Si substrate, scratch testing with a micro-indenter ($12.5{\mu}m$ tip radius) was performed under a linearly increasing load. These scratch tests were conducted under the same test conditions for both films. The critical load of each film was estimated from the scratch test results, based on a sharp increase in the coefficient of friction and a clear distinction of failure modes. The critical load was the basis for evaluating the adhesion strength of the films, and the $1.2{\mu}m-thick$ DLC film had superior adhesion strength. For better understanding of the failure modes, the following analyses were conducted: friction behavior and scratch tracks analysis using scanning electron microscopy, energy-dispersive spectroscopy, and 3-D profilometry. The scratch test results showed that failure modes were related to the thickness of the films. The 130 nm-thick DLC film underwent cohesive failure modes (cracks and chipping) before reaching to a gross failure stage. On the other hand, the thicker DLC film ($1.2{\mu}m-thick$) did not exhibit micro cracks before a sudden gross failure of the film together with the evidence of cracking and chipping of the Si substrate.

Stability and Adhesion of Diamond-like Carbon Film under Micro-tensile Test Condition (미소 인장시험을 통한 다이아몬드상 카본 박막의 안정성 및 접합력 평가)

  • Choi Heon Woong;Lee Kwang-Ryeol;Wang Rizhi;Oh Kyu Hwan
    • Journal of the Korean Vacuum Society
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    • v.13 no.4
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    • pp.175-181
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    • 2004
  • We investigated the stability of the DLC film coated on 304 stainless steel substrate by Radio frequency assisted chemical vapor deposition method. Fracture and spallation behaviour of the coating was observed during micro-tensile test of the fil $m_strate composite. As the tensile deformation progressed, the cracks of the film were observed in the perpendicular direction to the tensile axis. Further deformation resulted in the plastic deformation with $45^{\circ}$ slip bands on the substrate surface. Spallation of the film occurred with the plastic deformation, which was initiated at the cracks of the film and was aligned along the slip directions. We found that both the cracking and the spallation behaviors are strongly dependent on the pre-treatment condition, such as Ar plasma pre-treatment. The spallation of the film was considerably suppressed in an optimized condition of the substrate cleaning by Ar glow discharge. We observed the improved stability with increasing duration of Ar plasma pre-treatment.nt.

Viscoelastic Analysis of Osmotic Blistering Behavior of Coating Film

  • Lee, Sang Soon;Park, Myung Kyu
    • Corrosion Science and Technology
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    • v.8 no.1
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    • pp.11-14
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    • 2009
  • The osmotic blistering behavior of polymeric coating film which is in contact with an aqueous environment has been investigated. In this study, the coating film has been assumed to be linearly viscoelastic. Interfacial stresses induced in a laminate model consisting of the viscoelastic film and the elastic substrate as the film absorbs moisture from the ambient environment have been investigated using the time-domain boundary element method. The overall stress intensity factor for interfacial cracks subjected to a uniform osmotic pressure has been computed using the tractions at the crack tip node. The magnitude of stress intensity factors decreases with time due to viscoelastic relaxation, but remains constant at large times.

Magnetite film on iron (강재의 마그네타이트 피복에 관한 연구)

  • Kim, H. G.;Kang, T.
    • Journal of the Korean institute of surface engineering
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    • v.25 no.2
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    • pp.66-72
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    • 1992
  • Magnetite film on iron surface could be coated in strongly alkaline solution (12M NaH\OH) which contained additives such as NaHCO3, KCl and NaNO2, Iron plate was immersed in boiling solution ($130^{\circ}C$) contained above mentioned additives for 1 hour. There are some microcracks and these cracks proved to be the sites for the initiation of corrosion when immersed in 3% NaCl solution. To improve corrosion resistance of the coated steel plate, chromating was done as a post treatment. Chromate film was formed on magnetite oxide film potentiostatically at-918mV/SCE for five minutes at temperature of $70^{\circ}C$ in the alkaline solution containing 5g/l Na2Cr2O7.2H2O.Cr3O4 was electrodeposited on magnetite oxide film and Cr2O3 was electrodeposited on iron surface which was assumed as surface revealed due to microcracks. Increased corrosion resistance of chromated magnetite oxide film was proved in salt spray test & immersion test.

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Electrochemical Properties of NiO-YSZ Thin Films on 316 Stainless Steel Bipolar Plates Under a Simulated PEMFC Environment

  • Lee, W.G.;Jang, H.
    • Bulletin of the Korean Chemical Society
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    • v.33 no.4
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    • pp.1177-1182
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    • 2012
  • The corrosion resistance of 316L stainless steel coated with NiO-YSZ (Ni added yttria stabilized zirconia) was examined in a proton exchange membrane fuel cell (PEMFC) environment. The NiO-YSZ coating was carried out using a sol-gel dip coating method, and the corrosion resistance and interfacial contact resistance (ICR) were determined by the composition and morphology of the NiO-YSZ film. The corrosion resistance increased with increasing Ni content in the NiO-YSZ film, but rapid corrosion was observed when the YSZ film contained more than 15 wt % Ni due to surface cracks. The polarization resistance was improved by several orders of magnitude when 316L stainless steel was coated with a 15 wt % NiO-YSZ film compared to bare 316L. The ICR of the NiO-YSZ film was decreased to that of bare 316L when the YSZ film contained 25 wt % NiO, suggesting the possible application of NiO-YSZ coated stainless steel for a bipolar plate.

Fabrication of Piezoelectric PZT Thick Film by Sol-gel Process (Sol-Gel 법에 의한 압전 PZT 후막의 제조)

  • Park, Jong-whan;Bang, Kook-soo;Park, Chan
    • Journal of Ocean Engineering and Technology
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    • v.29 no.1
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    • pp.94-99
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    • 2015
  • Lead zirconate titanate (PZT) thick films with thicknesses of ㎛ were fabricated on silicon substrates using an aerosol deposition method. A PZT powder solution was prepared using a sol-gel process. The average diameters (d50) obtained were 1.67, 1.98, and 2.40μm when the pyrolysis temperatures were 300℃, 350℃, and 450℃ respectively. The as-deposited film had a uniform microstructure without any cracks or pores. The as-deposited films on silicon were annealed at a temperature of 700℃. The 20-㎛-thick PZT film showed good adherence between the PZT film and substrate, with no tearing observed in the conventional solid phase process. This was probably because the presence of pores produced from organic residue during annealing relieved the residual stresses in the deposited film.

Rheology of Slurries and Effects of Polymer Volume Ratio in Aqueous PZT Tape Casting

  • Yoon, Seok-Jin;Shin, Hyo-Soon;Lee, Dong-Kyun;Kang, Chong-Yun;Park, Ji-Won;Kim, Hyun-Jai
    • The Korean Journal of Ceramics
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    • v.7 no.1
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    • pp.16-19
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    • 2001
  • For the fast dry of the aqueous tape, the process which water was reaplaced by organic solvent was proposed. Socalled, it was the solvent washing dry. Three organic solvents (methanol, ethanol and acetone) were selected for the washing solvent. The weight loss of the washed tapes was measured to evaluate the dry rate of the tapes and dried tapes were examined the generation of the cracks with the variations of the organic solvent and the washing time. Methanol, ethanol and acetone were available organic solvents for this method. The tapes washed in methanol, ethanol and acetone were dried rapidly for twenty minutes. After thirty minutes, the weight losses were not found any more, The solvent of the lower surface tension can decreases the crack of dried tape. If solvent substitutes water completely, though it was fast dried, crack can be eliminated.

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Solvent Washing Dry Method for Aqueous Tape Casting

  • Yoon, Seok-Jin;Shin, Hyo-Soon;Park, Ji-Won;Kang, Chong-Yun;Kim, Tae-Song;Kim, Hyun-Jai
    • The Korean Journal of Ceramics
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    • v.7 no.2
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    • pp.55-57
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    • 2001
  • For the fast dry of the aqueous tape, the process which water was replaced by organic solvent was proposed. Socalled, it was the solvent washing dry. Three organic solvents (methanol, ethanol and acetone) were selected for the washing solvent. The weight loss of the washed tapes was measured to evaluate the dry rate of the tapes and dried tapes were examined the generation of the cracks with the variations of the organic solvent and the washing time. Methanol, ethanol and acetone were available organic solvents for this method. The tapes washed in methanol, ethanol and acetone were dried rapidly for twenty minutes. After thirty minutes, the weight losses were not found any more. The solvent of the lower surface tension can decreases the crack of dried tape. If solvent substitutes water completely, though it was fast dried, crack can be eliminated.

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Electrochemical Corrosion Failure of ITO-Coated PET Film for Display Application

  • Farooq, Hina;Kim, Hye-young;Byeon, Jai-Won
    • Journal of Applied Reliability
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    • v.17 no.1
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    • pp.72-77
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    • 2017
  • Purpose: The electrochemical corrosion behavior of tin oxide film coated on PET substrates has been studied under varying concentrations of acrylic acid to investigate possible corrosion in contact with the acidic environment. Method: Potentiodynamic test was performed for a commercial ITO/PET film in 0.1, 0.3, and 0.5 M of acrylic acid. The surface morphology was analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Results: Potentiodynamic test results showed an increase in Icorr and decrease in Ecorr value with increasing concentration of acid. Microscopic evaluation suggested the presence of certain deep cracks on the surface of the film in addition with a severe acidic attack. Conclusion: Exposure of ITO to acrylic acid resulted in the stress corrosion cracking of ITO film due to the mechanical mismatch between brittle inorganic ITO fim and a compliant organic PET substrate leading to the subsequent failure of the film.

Fabrication of piezoelectric PZT thick film by aerosol deposition method (에어로졸 증착법에 의한 압전 PZT 후막의 제조)

  • Kim, Ki-Hoon;Bang, Kook-Soo;Park, Chan
    • Journal of Ocean Engineering and Technology
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    • v.27 no.6
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    • pp.95-99
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    • 2013
  • Lead zirconate titanate (PZT) thick films with a thickness of $10-20{\mu}m$ were fabricated on silicone substrates using an aerosol deposition method. The starting powder, which had diameters of $1-2{\mu}m$, was observed using SEM. The average diameter ($d_{50}$) was $1.1{\mu}m$. An XRD analysis showed a typical perovskite structure, a mixture of the tetragonal phase and rhombohedral phase. The as-deposited film with nano-sized grains had a fairly dense microstructure without any cracks. The deposited film showed a mixture of an amorphous phase and a very fine crystalline phase by diffraction pattern analysis using TEM. The as-deposited films on silicon were annealed at a temperature of $700^{\circ}C$. A 20-${\mu}m$ thick PZT film was torn out as a result of the high compressive stress between the PZT film and substrate.