• Title, Summary, Keyword: Environmental barrier coatings

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Fabrication and Characterization of Environmental Barrier Coatings by Spray Drying and Atmospheric Plasma Spraying for Protection of Silicon Carbide Ceramics (분무건조 및 대기 플라즈마 용사에 의한 탄화규소 세라믹스용 내환경 코팅재의 제조 및 평가)

  • Feng, Fan Jie;Moon, Heung Soo;Kwak, Chan Won;Park, Ji Yeon;Lee, Kee Sung
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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    • pp.481-486
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    • 2014
  • Environmental barrier coatings (EBCs) are used to protect SiC-based ceramics or composites from oxidation and corrosion due to reaction with oxygen and water vapour at high temperatures above $1000^{\circ}C$. Mullite ceramics have been studied for environmental barrier coatings for Si-based ceramics. More recently, rare earth silicate ceramics have been identified as more water vapour-resistant materials than mullite for environmental barrier coatings. In this study, we fabricate mullite and yttrium silicate ceramics by an atmospheric plasma spray coating method using spherical granules fabricated by spray drying. As a result, EBCs with thicknesses in the range of $200-300{\mu}m$ are successfully fabricated without any macroscopic cracks or interfacial delamination. Phase and microstructure analysis are conducted, and the basic mechanical properties, such as hardness and indentation load-displacement curves are evaluated.

Anti-Corrosion Characteristics of Steel Structures with Polyaniline Anti-Corrosive Coatings (강 구조물에 대한 폴리아닐린 함유도료의 방청특성)

  • Song, Min-Kyung;Kong, Seung-Dae;Oh, Eun-Ha;Yoon, Hun-Cheol;Kim, Yoon-Shin;Im, Ho-Sub
    • Journal of Environmental Health Sciences
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    • v.36 no.3
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    • pp.236-246
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    • 2010
  • In preparative anti-corrosive coating experiments, polyaniline was obtained by reacting an oxidizing agent with the monomer aniline. Further, the primer coating was prepared using a variety of widely-used materials such as urethane resin. For the top coating, epoxy resin and acrylic urethane resin were used. Characteristics of the coatings were assessed according to KS and ASTM specifications, and the structure of the polyaniline was characterized using FT-IR and TGA. For analysis of anti-corrosive properties in salt-spray experiments, measurements of the oxidation state of iron and surface atomic analysis were conducted using XPS and SEM-EDX. Unlike general anti-corrosive coatings which exhibit anti-corrosive effects only as a primer coating, the anti-corrosive coatings using polyaniline as the anti-corrosive pigment showed a marked synergistic effect with the top coatings. In other words, the top coatings not only produce a fine view effect, but also increase, through interaction with the primer coatings, the resistance to diffusion of corrosive factors from the external environment. It was also found that, unlike the heavy metal oxide-forming layer of the passive barrier alone, the polyaniline anti-corrosive pigment oxidized iron at the interface with the iron substrate to form a passive barrier in the oxidic layer, and itself formed a potential barrier layer with anti-corrosive factors from the external environment. Although the passive layer was damaged, the damaged area did not become completely oxidized iron; on the contrary, it showed a tendency to reduction. This can be interpreted such that a passive layer is formed again on the damaged area, and that at the same time there is a tendency to self-healing.

Effect of Edible Coatings Containing Soy Protein Isolate (SPI) on the Browning and Moisture Content of Cut Fruit and Vegetables

  • Shon, Jin-Han;Choi, Yong-Hwa
    • Journal of Applied Biological Chemistry
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    • v.54 no.3
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    • pp.190-196
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    • 2011
  • Effectiveness of edible coatings containing soy protein isolate (SPI), in reducing oxidative browning and moisture loss during storage ($4^{\circ}C$) of cut apples, potatoes, carrots, and onions was investigated. The SPI coatings were shown to have antioxidative activity. Furthermore, addition of carboxymethyl cellulose (CMC) to the formulations significantly improved its antioxidative activity. Oxidative discoloration, as determined by Commission Internationale De I'Eclairage (CIE) lightness ($L^*$), redness ($a^*$), and yellowness ($b^*$) color scale, was significantly reduced (p <0.05) by SPI coating treatments over a storage time of 120 min. Loss of lightness was reduced by SPI coatings with and without CMC. These respectively showed 4.03 and 3.71% change of $L^*$ value compared to 8.56% for control. Browning of the control in cut potatoes was significantly increased by 106.6% in contrast to 34.3 and 35.2% for SPI coatings with and without CMC, respectively. The $b^*$ values also reflected effectiveness of SPI. Moisture barrier effect was significantly better for the treatments, compared to the control. SPI coatings reduced moisture loss in apples and potatoes, respectively, by 21.3 and 29.6% over the control. Cut onions did not show any treatment effect both in terms of browning and moisture loss. SPI coatings prove to be good moisture barrier and antioxidative property.

Inspection of Ceramic Coatings Using Nanoindentation and Frequency Domain Photoacoustic Microscopy

  • Steen, T.L.;Basu, S.N.;Sarin, V.K.;Murray, T.W.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.6
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    • pp.390-402
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    • 2006
  • The elastic properties and thickness of mullite environmental barrier coatings grown through chemical vapor deposition (CVD) on silicon carbide substrates were measured using frequency domain photoacoustic microscopy. In this technique, extremely narrow bandwidth surface acoustic waves are generated with an amplitude modulated laser source. A photorefractive crystal based interferometer is used to detect the resulting surface displacement. The complex displacement field is mapped as a function of source-to-receiver distance in order to extract the wavelength of the surface acoustic wave at a given excitation frequency, and the phase velocity is determined. The coatings tested exhibited spatial variations in thickness and mechanical properties. The measured surface wave dispersion curves were used to extract an effective value for the elastic modulus and the coating thickness. Nanoindentation was used to validate the measurements of the effective elastic modulus. The average elastic modulus measured through the coating thickness using nanoindentation is compared to the effective modulus found using the photoacoustic system. Optical microscopy is used to validate the thickness measurements. The results indicate that the photoacoustic microscopy technique can be used to estimate the effective elastic properties in coatings exhibiting spatial inhomogeneities, potentially providing valuable feedback for the optimization of the CVD growth process.

Effect of Deposition Parameter and Mixing Process of Raw Materials on the Phase and Structure of Ytterbium Silicate Environmental Barrier Coatings by Suspension Plasma Spray Method (서스펜션 플라즈마 스프레이 코팅법으로 제조된 Ytterbium Silicate 환경차폐코팅의 상형성 및 구조에 미치는 증착인자 및 원료혼합 공정의 영향)

  • Ryu, Ho-lim;Choi, Seon-A;Lee, Sung-Min;Han, Yoon-Soo;Choi, Kyun;Nahm, Sahn;Oh, Yoon-Suk
    • Journal of Korean Powder Metallurgy Institute
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    • v.24 no.6
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    • pp.437-443
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    • 2017
  • SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of $1300^{\circ}C$ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. $Yb_2O_3$ and $SiO_2$ are used as the raw starting materials to form ytterbium disilicate ($Yb_2Si_2O_7$). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., $SiO_2$, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

Thermal and Mechanical Evaluation of Environmental Barrier Coatings for SiCf-SiC Composites (SiCf-SiC 복합재료의 내환경 코팅 및 열, 기계적 내구성 평가)

  • Chae, Yeon-Hwa;Moon, Heung Soo;Kim, Seyoung;Woo, Sang Kuk;Park, Ji-Yeon;Lee, Kee Sung
    • Composites Research
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    • v.30 no.2
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    • pp.84-93
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    • 2017
  • This study investigates thermal and mechanical characterization of environmental barrier coating on the $SiC_f-SiC$ composites. The spherical environmental barrier coating (EBC) powders are prepared using a spray drying process for flowing easily during coating process. The powders consisting of mullite and 12 wt% of Ytterbium silicate are air plasma sprayed on the Si bondcoat on the LSI SiC fiber reinforced SiC composite substrate for protecting the composites from oxidation and water vapor reaction. We vary the process parameter of spray distance during air plasma spray of powders, 100, 120 and 140 mm. After that, we performed the thermal durability tests by thermal annealing test at $1100^{\circ}C$ for 100hr and thermal shock test from $1200^{\circ}C$ for 3000 cycles. As a result, the interface delamination of EBC never occur during thermal durability tests while stable cracks are prominent on the coating layer. The crack density and crack length depend on the spray distance during coating. The post indentation test indicates thermal tests influence on the indentation load-displacement mechanical behavior.

A Study on Chloride Threshold Level of Polymer Inhibitive Coating Containing Calcium Hydroxide (수산화칼슘을 혼입한 폴리머 방청 코팅의 부식 임계치 향상에 대한 연구)

  • Song, Ha-Won;Lee, Chang-Hong;Lee, Kewn-Chu;Ann, Ki-Yong
    • Journal of the Korea Concrete Institute
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    • v.20 no.6
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    • pp.713-719
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    • 2008
  • Various types of coatings have been developed for use as reinforcement in concrete and to resist chloride environment. The most commonly used coatings are inhibited and sealed cement slurry coating, cement polymer compositing coating and epoxy coating. Cement slurry offers passive protection, epoxy coating offers barrier protection whereas polymer coating offers both passive protection and barrier protection. Moreover, damage during handling of the steel may result in disbondment of the epoxy coating, which would increase the risk of localized corrosion. In the present study, inhibiting technique was used to increase the calcium hydroxide content at the interface up to 20%. Calcium hydroxide provides a high buffering capacity that resists a local fall in pH and thus maintains the alkaline environment necessary to prevent chloride corrosion. This study examines the use of a calcium hydroxide coating on the steel surface to enhance the pH buffering capacity of steel-concrete interface. Finally, the chloride threshold level (CTL) of polymer inhibitive coating calcium hydroxide is evaluated.

Characteristics of Percutaneous Absorption for Three Kinds of Phthalate (Phthalate 3종에 대한 경피투과 특성 연구)

  • Jung, Duck-Chae;Yoon, Cheol-Hun;Um, Mi-Sun;Hwang, Hyun-Suk;Baek, Jung-Hun;Choi, Jin-Ho
    • Journal of Environmental Health Sciences
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    • v.39 no.4
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    • pp.360-368
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    • 2013
  • Objectives: Phthalates are used in a large variety of products including as coatings of pharmaceutical tablets, film formers, stabilizers, dispersants, emulsifying agents, and suspending agents. They have been the subject of great public concern in recent years. The extensive uses of this material have attracted attention and issues regarding its safety have been raised. Methods: In this study, three types of phthalate skin permeation were studied using matrixes such as ointments, creams and lotions in vitro. The absorption of phthalate diesters [Dimethyl phthalate (DMP), Di-n-propyl phthalate (DPP) and Di-n-pentyl phthalate (DNPP)] using film former has been measured in vitro through rat skin. Epidermal membranes were set up in Franz diffusion cells and their permeability to PBS measured in order to establish the integrity of the skin before the phthalates were applied to the epidermal surface. Results: Absorption rates for each phthalate ester were determined and permeability assessment made to quantify any irreversible alterations in barrier function due to contact with the esters. Types of phthalate in vitro experimental results quickly appeared in the following order DMP > DPP ${\geq}$ DNPP. Conclusions: In the experimental results, lotion> cream> ointment, and the permeation rate of lotion with a great amount of moisture was the fastest. Skin permeation rate is generally influenced by the chemical characteristics of a given chemical, such as molecular weight and lipophilicity. As the esters became more lipophilic and less hydrophilic, the rate of absorption decreased.