Hydrothermal Electrophoretic Deposition Research Articles

Oxidation and thermal cycling behavior of c-AlPO4 and SiC whisker co-modified mullite deposited on SiC-C/SiC composites

A dense and uniform c-AlPO4 and SiC whisker co-modified mullite coating was successfully prepared on SiC-coated C/SiC composites with a thickness of about 70 μm by hydrothermal electrophoretic deposition. The thermal cycling performance of the coating samples was evaluated by thermally cycling between 1773 K and room temperature in a corundum tube furnace. Results show that the addition of SiC whisker (SiCw-mullite coating) significantly improved the thermal cycling resistance of single mullite outer layer on account of the toughening mechanism of SiC whiskers, such as whisker bridging and crack deflection. Then, the addition of c-AlPO4 (c-AlPO4-SiCw-mullite coating, termed ASM coating) further improved the thermal cycling resistance on account of the healing and bonding performances of c-AlPO4 at high temperature. After 40 thermal cycles, the weight loss of ASM coating on SiC-coated C/SiC composites was 4.5% compared to 5.24% for the SiCw-mullite coating. The retention rate of compressive strength of ASM coating on SiC-coated C/SiC matrix was 80.66% compared to 73.65% for the SiCw-mullite coating.

Microstructure evolution and isothermal oxidation properties of c-AlPO4 and SiC whisker co-modified mullite coated SiC-C/SiC composites

An oxidation protective c-AlPO4 and SiC whisker co-modified mullite coating (c-AlPO4-SiCw-mullite) on SiC coated C/SiC composites were manufactured by hydrothermal electrophoretic deposition accompanied by magnetic stirring. Phase composition of c-AlPO4-SiCw-mullite coatings on SiC coated C/SiC composites with different deposition time was detected by X-ray Diffraction (XRD), element distribution and microstructure were investigated by electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). Results show that a crack-free, dense and homogeneous coating was prepared by hydrothermal electrophoretic deposition method. The thickness, homogeneity and antioxidant properties of c-AlPO4-SiCw-mullite coating were improved with the extension of deposition time from 10 min to 30 min. The coating manufactured after deposition of 30 min showed smoothest surface and highest density, which can effectively protect C/SiC composites from oxidation for 160 h at 1773 K in air with a weight loss of 10.02 mg cm−2. Microstructural characterization after oxidation indicated that the failure of the c-AlPO4-SiCw-mullite coating was due to the consecutive formation of penetrative micro-cracks and micro-holes.

A novel oxidation protective SiC-ZrB2-ZrSi2 coating with mosaic structure for carbon/carbon composites

An oxidation protective SiC-ZrB2-ZrSi2 coating with mosaic structure was designed to improve the oxidation resistance of carbon/carbon composites by a combined method of hydrothermal electrophoretic deposition and pack cementation. The phase composition, microstructure, thermal shock resistance and oxidation protective ability of the coating were investigated. Results show that the as-prepared SiC-ZrB2-ZrSi2 coating was dense and crack-free. After 50 thermal cycles between 1773 K and room temperature, the weight gain of the coated samples was 15.2 g m−2. The weight loss of the coated samples was only 15.6 g m−2 after oxidation in air at 1773 K for 580 h. The good thermal shock resistance and oxidation protective ability of the coated samples were attributed to the synergetic effect of the glass layer protection, compressive stress restraint and pinning role of ZrSiO4 inlaid phase.

Effect of the incorporation of SiC nanowire on mullite/SiC protective coating for carbon/carbon composites

An oxidation resistant SiC nanowire-toughened mullite coating for SiC pre-coated carbon/carbon composites (SiCC/C) was prepared by a two-step technique of hydrothermal electrophoretic deposition with a later pulse arc discharge deposition. Sic nanowires could efficiently decrease the size of microcracks and baffle the propagation of the microcracks by various toughening mechanisms, including devitrification, crack deflection, bridging and pull out of SiC nanowire. The results showed that the weight loss of the coated samples was only 0.03% after 50 thermal cycles, and the weight loss of the coated samples was only 107gm−2 after oxidation in air at 1773K for 235h.

A mullite/SiC oxidation protective coating for carbon/carbon composites

To protect carbon/carbon (C/C) composites against oxidation, a mullite coating was prepared on SiC precoated C/C composites by a hydrothermal electrophoretic deposition process. The phase composition, microstructure and oxidation resistance of the prepared mullite/SiC coatings were investigated. Results show that hydrothermal electrophoretic deposition is an effective route to achieve crack-free mullite coatings. The mullite/SiC coating displays excellent oxidation resistance and can protect C/C composites from oxidation at 1773 K for 322 h with a weight loss rate of only 4.89 × 10 −4 g/cm 2 h. The failure of the multi-layer coatings is considered to be caused by the volatilization of silicate glass layer, the formation of microholes and microcracks on the coating surface and the formation of penetrative holes between the SiC bonding layer and the C/C matrix at 1773 K. The corresponding high temperature oxidation activation energy of the coated C/C composites at 1573–1773 K is calculated to be 111.11 kJ/mol.

Microstructure and oxidation resistance of C-AlPO4–mullite coating prepared by hydrothermal electrophoretic deposition for SiC-C/C composites

Oxidation resistant C-AlPO4–mullite coating for SiC pre-coated carbon/carbon composites (SiC-C/C) was prepared by a novel hydrothermal electrophoretic deposition process. The phase composition, surface and cross-section microstructure of the as-prepared multi-layer coatings were characterized by X-ray Diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of deposition voltage on phase composition, microstructure and oxidation resistance of the as-prepared coatings was particularly investigated. Results show that the outer layer coating mainly composed of C-AlPO4 and mullite phase can be achieved after the hydrothermal electrophoretic deposition. The thickness, density and anti-oxidation property of the C-AlPO4–mullite coating was improved with the increase of deposition voltage from 160V to 200V. The multi-layer coating prepared at a voltage of 200V exhibit excellent anti-oxidation property, which can effectively protect C/C composites from oxidation in air at 1773K for 324h with a weight loss of 1.01%. The failure of the multi-layer coatings is due to the generation of cross-holes in the coating, which cannot be self-cured by the metaphosphate and silicate glass layer after long time oxidation at 1773K.

ZrSiO<sub>4</sub>/SiC Oxidation Protective Coating for Carbon/Carbon Composites Prepared by Hydrothermal Electrophoretic Deposition

In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a ZrSiO4coating on SiC pre-coated C/C composites was prepared by a hydrothermal electrophoretic deposition process. The phase composition, surface and cross-section microstructure, anti-oxidation property of the as-prepared ZrSiO4/SiC coating was investigated. Results show that hydrothermal electrophoretic deposition is an effective route to achieve crack-free ZrSiO4 outer coatings. The ZrSiO4/SiC coating can protect C/C composites from oxidation at 1773 K for 332 h with a weigh loss rate of only 4.83×10-5g/cm2·h.

Preparation and antioxidation properties of glass/yttrium silicates/SiC multilayer coating in both air and combustion atmosphere

Yttrium silicate coating for SiC precoated C/C composite was prepared by a hydrothermal electrophoretic deposition process. The yttrium silicate coating was sealed with a borosilicate glass outer layer. Phase compositions, surface and cross-section microstructures of the as prepared multilayer coatings were characterised by X-ray diffractometer and scanning electron microscopy. The influences of hydrothermal electrophoretic deposition factors on the phase, microstructure and oxidation resistance of the multilayer coated C/C composites were particularly investigated. Results show that the hydrothermal electrophoretic resulting coating is composed of crystallites with a main phase of Y2Si2O7 and Y2SiO5. The thickness and density of the coatings are improved with the increase in deposition voltage and hydrothermal temperature. Compared with the pack cementation SiC monolayer coating, the as prepared multilayer coatings exhibit better antioxidation property. When oxidation in air and combustion atmosphere, the coated C/C composites lose weight by a linear and a parabolic law respectively. The prepared multilayer coating can effectively protect the C/C composites in combustion atmosphere at 1773 K for 85 h. The flexural strength of the coated specimen arrives at the lowest value at about 1123 K in combustion atmosphere.

A ZrSiO4/SiC oxidation protective coating for carbon/carbon composites

In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a ZrSiO4 coating on SiC pre-coated C/C composites was prepared by a hydrothermal electrophoretic deposition process. Phase compositions and microstructures of the as-prepared ZrSiO4/SiC coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The anti-oxidation property and failure mechanism of the multi-layer coating were investigated. Results show that hydrothermal electrophoretic deposition is an effective route to prepare crack-free ZrSiO4 outer coatings. The multi-layer coating obviously exhibits two-layer structure. The inner layer is composed of SiC phase and the outer layer is composed of ZrSiO4 phase. The bonding strength between the outer layer coatings and C/C–SiC substrate are 30.38MPa. The ZrSiO4/SiC coating displays excellent oxidation resistance and can protect C/C composites from oxidation at 1773K for 332h with a mass loss rate of only 0.48×10−4g/cm2·h. The mechanical properties of the specimens are 84.36MPa before oxidation and 68.29MPa after oxidation. The corresponding high temperature oxidation activation energy of the coated C/C composites at 1573–1773K is calculated to be 119.8kJ/mol. The oxidation process is predominantly controlled by the diffusion rate of oxygen through the ZrSiO4/SiC multi-coating. The failure of the coating is due to the formation of penetrative holes between the SiC bonding layer and the C/C matrix at 1773K.

Preparation and phase composition optimization of yttrium silicates/SiC multilayer coating coated carbon/carbon composites

In order to optimize the phase composition and improve the oxidation resistance of yttrium silicates coating, Y2SiO5-Y2Si2O7-Y4Si3O12 coatings with different phase composition were deposited on the surface of SiC pre-coated carbon/carbon (C/C) composites using a hydrothermal electrophoretic deposition process. The as-prepared multilayer coatings were characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The influence of phase composition on the morphologies and anti-oxidation properties of the multicomposition yttrium silicates coatings were investigated. The phase composition of the coating was optimized. Results show that Y2SiO5/Y2Si2O7/Y4Si3O12 mass ratio has strong effect on the morphology and oxidation resistance of yttrium silicates coatings. It is found that a low thermal expansion coefficient (CTE) district existed in the Y2SiO5-Y2Si2O7-Y4Si3O12 ternary phase diagram. When the optimized phase composition of Y2SiO5/Y2Si2O7/Y4Si3O12 in the low CTE district reaches Y2SiO5 = 20.1 wt%, Y2Si2O7 = 8.3 wt%, and Y4Si3O12 = 71.6 wt%, dense and homogenous yttrium silicates coatings with perfect oxidation resistance are achieved. After 80 h oxidation in 1773 K, weight loss of the coated C/C composites is only 2.17 × 10−3 g.cm−2.

Microstructure and anti-oxidation property of mullite oxidation protective coating prepared by hydrothermal electrophoretic deposition for SiC–C/C composites

Oxidation resistant mullite outer coating for SiC pre-coated carbon/carbon composites (SiC–C/C) was prepared by a novel hydrothermal electrophoretic deposition process using mullite powders, isopropanol and iodine as the start materials, solvent and charging agent, respectively. The phase composition, surface and cross-section microstructure of the as-prepared multilayer coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of hydrothermal deposition temperature on phase composition, microstructure and oxidation resistance of the as-prepared coatings was particularly investigated. Results show that the outer layer coating mainly composed of mullite phase can be achieved by hydrothermal electrophoretic deposition. The thickness, density and anti-oxidation property of the mullite coating were improved with the increase of deposition temperature from 353 K to 393 K. The mullite coating prepared at 393 K exhibits excellent anti-oxidation property, which can effectively protect C/C composites from oxidation in air at 1773 K for 172 h with a weight loss of 1.65%. The failure of the multilayer coatings is considered to be caused by the volatilization of the SiO 2 glass and the formation of microholes and microcracks on the coating surface.

Influence of MoSi2 content in suspension on the phase, microstructure and properties of hydrothermal electrophoretic deposited SiC n –MoSi2 coating for SiC pre-coated C/C composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, a nano SiC–MoSi2 (SiCn–MoSi2) coating on SiC pre-coated C/C composites was prepared by hydrothermal electrophoretic deposition. The phase composition, surface and cross-section microstructures of the prepared SiCn–MoSi2 coating deposited with different MoSi2/SiCn mass ratio were characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The influence of MoSi2 content in the hydrothermal electrophoretic deposition suspension on the phase composition, microstructure and high-temperature oxidation resistance of the multi-layer coatings were investigated. Results showed that the content of MoSi2 phase in the prepared coating increases with the increase of MoSi2 content in the suspension. The density and oxidation resistance of the SiCn-MoSi2 coating improve with the increase of MoSi2 mass content from 20 to 60 wt% in the deposition suspension. However, micro-cracks and micro-holes in the coating are found when deposited with 80 wt% MoSi2, and a decrease in oxidation resistance was also detected. The multi-layer coatings deposited with suspension of 60 wt% MoSi2 exhibited the best anti-oxidation ability, which can effectively protect C/C composites from oxidation in air at 1,873 K for 90 h with weight loss of 2.08%.

Influence of Deposition Voltage on the SiC<SUB><I>n</I></SUB>-MoSi<SUB>2</SUB> Coating for C/C Composites Prepared by a Hydrothermal Electrophoretic Deposition Process

Influence of Deposition Voltage on the SiC<SUB><I>n</I></SUB>-MoSi<SUB>2</SUB> Coating for C/C Composites Prepared by a Hydrothermal Electrophoretic Deposition Process

A MoSi 2/SiC oxidation protective coating for carbon/carbon composites

To protect carbon/carbon (C/C) composites against oxidation, a MoSi 2 outer coating was prepared on pack-cementation SiC coated C/C composites by a hydrothermal electrophoretic deposition. The phase composition, microstructure and oxidation resistance of the prepared MoSi 2/SiC coatings were investigated. Results show that hydrothermal electrophoretic deposition is an effective route to achieve crack-free MoSi 2 outer coatings. The MoSi 2/SiC coating can protect C/C composites from oxidation at 1773 K for 346 h with a weight loss of 2.49 mg cm −2 and at 1903 K for 88 h with a weight loss of 5.68 mg cm −2.

M-18 Carbon Nanotube-Reinforced Hydroxyapatite Biocomposite Coatings by Hydrothermal Synthesis and Electrophoretic Deposition (EPD)

M-18 Carbon Nanotube-Reinforced Hydroxyapatite Biocomposite Coatings by Hydrothermal Synthesis and Electrophoretic Deposition (EPD)

Influence of deposition voltage on phase, microstructure and antioxidation property of cristobalite aluminum phosphate coatings

Cristobalite aluminum phosphate (C-AlPO4) coatings were prepared by a hydrothermal electrophoretic deposition process on SiC-coated C/C composites. Phase compositions and microstructures of the as-prepared coatings were characterized by XRD and SEM analyses. The influence of deposition voltage on the phase, microstructure and antioxidation property of the cristobalite aluminum phosphate coatings was investigated. Results show that the as-prepared coatings are composed of cristobalite aluminum phosphate crystallites. The thickness and density of cristobalite aluminum phosphate coatings are improved with the increase of deposition voltage. The deposition amount and bonding strength of the cristobalite aluminum phosphate coatings also increase with the increase of deposition voltage. The deposition mass per unit area of the coatings and the square root of the deposition time at different hydrothermal voltages satisfy linear relationship. The antioxidation property of the coated C/C composites is improved with the increase of deposition voltage. Compared with SiC coatings prepared by pack cementation, the multilayer coatings prepared by pack cementation with a later hydrothermal electrophoretic deposition process exhibit better antioxidation property. The as-prepared multi-coatings can effectively protect C/C composites from oxidation in air at 1 773 K for 37 h with a mass loss rate of 0.53%.

Influence of Deposition Voltage on Microstructures of Yttrium Silicates Coatings by Hydrothermal Electrophoretic Deposition

Yttrium silicates oxidation resistance coatings were deposited on SiC-C/C composites surface by a hydrothermal electrophoretic deposition process. The influence of deposition voltage on the yttrium silicates coatings and the deposition amount of coatings were particularly investigated. Results show that with the increase of deposition voltage, the deposition amount of coatings increase, the density and uniformity of the coating surface is improved. When the deposition voltage reaches 210V, dense yttrium silicates coatings are achieved. While increase the deposition voltage continually, the uniformity of coatings decrease. When the deposition voltage arrives to 240V, high deposition voltage will result in cracked coatings. There is a parabola relationship between the deposition amount of coatings and time.

Preparation of Hydroxyapatite/Chitosan Biological Coatings on Carbon/Carbon Composites

Hydroxyapatite/Chitosan (HAp/CS) bio-coatings were prepared on the surface of carbon/ carbon (C/C) composites by hydrothermal electrophoretic deposition, using sonochemical process resulted HAp nanoparticles, isopropyl alcohol and chitosan as raw materials. The influences of hydro- thermal conditions and deposition voltage on the microstructures and morphologies of the as-prepared coatings were investigated. It was shown that homogenous and dense HAp/CS coatings on C/C composites are obtained by hydrothermal electrophoretic deposition. With the increase of deposition voltage, density and homogeneity of the as-prepared HAp/CS composite coatings are well improved. Due to the growth of HAp nanoparticles in the hydrothermal condition, the subsequent heat treatment of the HAp/CS coatings is not needed.

Influence of Electrophoretic Deposition Voltage on the Phase, Microstructure and Property of a Nano-SiC Coating

In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a nano-SiC (SiCn) coating for SiC pre-coated C/C was prepared by a hydrothermal electrophoretic deposition process. The phase compositions, surface and cross-section microstructures of the SiCn coatings deposited at different voltages were investigated. XRD and SEM analyses show that SiCn outer layer without penetrative holes and cracks can be achieved at the deposition voltage range from 120 V to 210 V. The thickness and density of the SiCn coatings improve with the increase of deposition voltage. The multi-layer coatings deposited at 210 V can effectively protect C/C composites from oxidation in air at 1773 K for 202 h with a weight loss of 0.79%.

Preparation of a SiC/Cristobalite-AlPO 4 Multi-layer Protective Coating on Carbon/Carbon Composites and Resultant Oxidation Kinetics and Mechanism

In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a SiC/C-AlPO 4 multi-layer coating was fabricated on the C/C composites by a simple and low-cost method. The internal SiC bonding layer was prepared by a two-step pack cementation process and the external C-AlPO 4 coating was deposited by hydrothermal electrophoretic deposition process. Phase compositions and microstructures of the as-prepared multi-layer coating were characterized by X-ray diffraction (XRD), scaning electron microspocy (SEM) and energy dispersive spectrometer (EDS). Anti-oxidation properties, oxidation behavior and the failure behavior of the coated composites were investigated. The results indicate that the multi-layer coating exhibits obviously two-layer structure. The inner layer is composed of β-SiC, α-SiC phase with a scale of silicon phase. The outer layer is composed of cristobalite aluminum phosphate (C-AlPO 4 ) crystallites. The SEM observation shows the good bonding between the inner and outer layers. The multi-layer coating displays an excellent oxidation resistance in air in the temperature range from 1573 to 1773 K, and the corresponding oxidation activation energy of the coated C/C composites is calculated to be 117.2 kJ/mol. The oxidation process is predominantly controlled by the diffusion of O 2 through the C-AlPO 4 coating. The failure of the multi-layer coating results from the generation of the microholes that may be left by the escape of the oxidation gases.